xref: /device/soc/rockchip/common/sdk_linux/kernel/sched/fair.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
 */
#include "sched.h"
#include "walt.h"
#include "rtg/rtg.h"

#ifdef CONFIG_SCHED_WALT
static void walt_fixup_sched_stats_fair(struct rq *rq, struct task_struct *p, u16 updated_demand_scaled);
#endif

#if defined(CONFIG_SCHED_WALT) && defined(CONFIG_CFS_BANDWIDTH)
static void walt_init_cfs_rq_stats(struct cfs_rq *cfs_rq);
static void walt_inc_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p);
static void walt_dec_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p);
static void walt_inc_throttled_cfs_rq_stats(struct walt_sched_stats *stats, struct cfs_rq *cfs_rq);
static void walt_dec_throttled_cfs_rq_stats(struct walt_sched_stats *stats, struct cfs_rq *cfs_rq);
#else
static inline void walt_init_cfs_rq_stats(struct cfs_rq *cfs_rq)
{
}
static inline void walt_inc_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p)
{
}
static inline void walt_dec_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p)
{
}

#define walt_inc_throttled_cfs_rq_stats(...)
#define walt_dec_throttled_cfs_rq_stats(...)

#endif

#define FAIR_THREE 3
#define FAIR_FOUR 4
#define FAIR_TWENTY 20
#define FAIR_ONEHUNDRED 100
#define FAIR_TWOHUNDREDFIFTYTHREE 253
#define FAIR_TWOHUNDREDFIFTYSIX 256
#define FAIR_ONETHOUSAND 1000
#define FAIR_SIXTYTHOUSAND 60000

/*
 * Targeted preemption latency for CPU-bound tasks:
 *
 * NOTE: this latency value is not the same as the concept of
 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
 *
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
 *
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
 */
unsigned int sysctl_sched_latency = 6000000ULL;
static unsigned int normalized_sysctl_sched_latency = 6000000ULL;

/*
 * The initial- and re-scaling of tunables is configurable
 *
 * Options are:
 *
 *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
 *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 *
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 */
enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;

/*
 * Minimal preemption granularity for CPU-bound tasks:
 *
 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
 */
unsigned int sysctl_sched_min_granularity = 750000ULL;
EXPORT_SYMBOL_GPL(sysctl_sched_min_granularity);
static unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;

/*
 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
 */
static unsigned int sched_nr_latency = 8;

/*
 * After fork, child runs first. If set to 0 (default) then
 * parent will (try to) run first.
 */
unsigned int sysctl_sched_child_runs_first __read_mostly;

/*
 * SCHED_OTHER wake-up granularity.
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 *
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
 */
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;

const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

int sched_thermal_decay_shift;
static int __init setup_sched_thermal_decay_shift(char *str)
{
    int _shift = 0;

    if (kstrtoint(str, 0, &_shift)) {
        pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
    }

    sched_thermal_decay_shift = clamp(_shift, 0, 10);
    return 1;
}
__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);

#ifdef CONFIG_SMP
/*
 * For asym packing, by default the lower numbered CPU has higher priority.
 */
int __weak arch_asym_cpu_priority(int cpu)
{
    return -cpu;
}

/*
 * The margin used when comparing utilization with CPU capacity.
 *
 * (default: ~20%)
 */
#define fits_capacity(cap, max) ((cap)*1280 < (max)*1024)

#endif

#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
 * (default: 5 msec, units: microseconds)
 */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
    lw->weight += inc;
    lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
    lw->weight -= dec;
    lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
    lw->weight = w;
    lw->inv_weight = 0;
}

/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
static unsigned int get_update_sysctl_factor(void)
{
    unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
    unsigned int factor;

    switch (sysctl_sched_tunable_scaling) {
        case SCHED_TUNABLESCALING_NONE:
            factor = 1;
            break;
        case SCHED_TUNABLESCALING_LINEAR:
            factor = cpus;
            break;
        case SCHED_TUNABLESCALING_LOG:
        default:
            factor = 1 + ilog2(cpus);
            break;
    }

    return factor;
}

static void update_sysctl(void)
{
    unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
    (sysctl_##name = (factor) * normalized_sysctl_##name)
    SET_SYSCTL(sched_min_granularity);
    SET_SYSCTL(sched_latency);
    SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void __init sched_init_granularity(void)
{
    update_sysctl();
}

#define WMULT_CONST (~0U)
#define WMULT_SHIFT 32

static void fair_update_inv_weight(struct load_weight *lw)
{
    unsigned long w;

    if (likely(lw->inv_weight)) {
        return;
    }

    w = scale_load_down(lw->weight);
    if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) {
        lw->inv_weight = 1;
    } else if (unlikely(!w)) {
        lw->inv_weight = WMULT_CONST;
    } else {
        lw->inv_weight = WMULT_CONST / w;
    }
}

/*
 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
 */
static u64 fair_calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
{
    u64 fact = scale_load_down(weight);
    int shift = WMULT_SHIFT;

    fair_update_inv_weight(lw);

    if (unlikely(fact >> 32)) {
        while (fact >> 32) {
            fact >>= 1;
            shift--;
        }
    }

    fact = mul_u32_u32(fact, lw->inv_weight);

    while (fact >> 32) {
        fact >>= 1;
        shift--;
    }

    return mul_u64_u32_shr(delta_exec, fact, shift);
}

const struct sched_class fair_sched_class;

/**************************************************************
 * CFS operations on generic schedulable entities:
 */

#ifdef CONFIG_FAIR_GROUP_SCHED
static inline struct task_struct *task_of(struct sched_entity *se)
{
    SCHED_WARN_ON(!entity_is_task(se));
    return container_of(se, struct task_struct, se);
}

/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
    return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
    return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
    return grp->my_q;
}

static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
{
    if (!path) {
        return;
    }

    if (cfs_rq && task_group_is_autogroup(cfs_rq->tg)) {
        autogroup_path(cfs_rq->tg, path, len);
    } else if (cfs_rq && cfs_rq->tg->css.cgroup) {
        cgroup_path(cfs_rq->tg->css.cgroup, path, len);
    } else {
        strlcpy(path, "(null)", len);
    }
}

static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
    struct rq *rq = rq_of(cfs_rq);
    int cpu = cpu_of(rq);

    if (cfs_rq->on_list) {
        return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
    }

    cfs_rq->on_list = 1;

    /*
     * Ensure we either appear before our parent (if already
     * enqueued) or force our parent to appear after us when it is
     * enqueued. The fact that we always enqueue bottom-up
     * reduces this to two cases and a special case for the root
     * cfs_rq. Furthermore, it also means that we will always reset
     * tmp_alone_branch either when the branch is connected
     * to a tree or when we reach the top of the tree
     */
    if (cfs_rq->tg->parent && cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
        /*
         * If parent is already on the list, we add the child
         * just before. Thanks to circular linked property of
         * the list, this means to put the child at the tail
         * of the list that starts by parent.
         */
        list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
        /*
         * The branch is now connected to its tree so we can
         * reset tmp_alone_branch to the beginning of the
         * list.
         */
        rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
        return true;
    }

    if (!cfs_rq->tg->parent) {
        /*
         * cfs rq without parent should be put
         * at the tail of the list.
         */
        list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
        /*
         * We have reach the top of a tree so we can reset
         * tmp_alone_branch to the beginning of the list.
         */
        rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
        return true;
    }

    /*
     * The parent has not already been added so we want to
     * make sure that it will be put after us.
     * tmp_alone_branch points to the begin of the branch
     * where we will add parent.
     */
    list_add_rcu(&cfs_rq->leaf_cfs_rq_list, rq->tmp_alone_branch);
    /*
     * update tmp_alone_branch to points to the new begin
     * of the branch
     */
    rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
    return false;
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
    if (cfs_rq->on_list) {
        struct rq *rq = rq_of(cfs_rq);

        /*
         * With cfs_rq being unthrottled/throttled during an enqueue,
         * it can happen the tmp_alone_branch points the a leaf that
         * we finally want to del. In this case, tmp_alone_branch moves
         * to the prev element but it will point to rq->leaf_cfs_rq_list
         * at the end of the enqueue.
         */
        if (rq->tmp_alone_branch == &cfs_rq->leaf_cfs_rq_list) {
            rq->tmp_alone_branch = cfs_rq->leaf_cfs_rq_list.prev;
        }

        list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
        cfs_rq->on_list = 0;
    }
}

static inline void assert_list_leaf_cfs_rq(struct rq *rq)
{
    SCHED_WARN_ON(rq->tmp_alone_branch != &rq->leaf_cfs_rq_list);
}

/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)                                                                     \
    list_for_each_entry_safe(cfs_rq, pos, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
static inline struct cfs_rq *is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
    if (se->cfs_rq == pse->cfs_rq) {
        return se->cfs_rq;
    }

    return NULL;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
    return se->parent;
}

static void find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
    int se_depth, pse_depth;

    /*
     * preemption test can be made between sibling entities who are in the
     * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
     * both tasks until we find their ancestors who are siblings of common
     * parent.
     */

    /* First walk up until both entities are at same depth */
    se_depth = (*se)->depth;
    pse_depth = (*pse)->depth;

    while (se_depth > pse_depth) {
        se_depth--;
        *se = parent_entity(*se);
    }

    while (pse_depth > se_depth) {
        pse_depth--;
        *pse = parent_entity(*pse);
    }

    while (!is_same_group(*se, *pse)) {
        *se = parent_entity(*se);
        *pse = parent_entity(*pse);
    }
}

#else /* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
    return container_of(se, struct task_struct, se);
}

#define for_each_sched_entity(se) (for (; se; se = NULL))

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
    return &task_rq(p)->cfs;
}

static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
    struct task_struct *p = task_of(se);
    struct rq *rq = task_rq(p);

    return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
    return NULL;
}

static inline void cfs_rq_tg_path(struct cfs_rq *cfs_rq, char *path, int len)
{
    if (path) {
        strlcpy(path, "(null)", len);
    }
}

static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
    return true;
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void assert_list_leaf_cfs_rq(struct rq *rq)
{
}

#define for_each_leaf_cfs_rq_safe(rq, cfs, pos) (for ((cfs) = &(rq)->cfs, (pos) = NULL; (cfs); (cfs) = (pos)))

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
    return NULL;
}

static inline void find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

#endif /* CONFIG_FAIR_GROUP_SCHED */

static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);

/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
{
    s64 delta = (s64)(vruntime - max_vruntime);
    if (delta > 0) {
        max_vruntime = vruntime;
    }

    return max_vruntime;
}

static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
{
    s64 delta = (s64)(vruntime - min_vruntime);
    if (delta < 0) {
        min_vruntime = vruntime;
    }

    return min_vruntime;
}

static inline int entity_before(struct sched_entity *a, struct sched_entity *b)
{
    return (s64)(a->vruntime - b->vruntime) < 0;
}

static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
    struct sched_entity *curr = cfs_rq->curr;
    struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);

    u64 vruntime = cfs_rq->min_vruntime;

    if (curr) {
        if (curr->on_rq) {
            vruntime = curr->vruntime;
        } else {
            curr = NULL;
        }
    }

    if (leftmost) { /* non-empty tree */
        struct sched_entity *se;
        se = rb_entry(leftmost, struct sched_entity, run_node);

        if (!curr) {
            vruntime = se->vruntime;
        } else {
            vruntime = min_vruntime(vruntime, se->vruntime);
        }
    }

    /* ensure we never gain time by being placed backwards. */
    cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
#ifndef CONFIG_64BIT
    smp_wmb();
    cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
}

/*
 * Enqueue an entity into the rb-tree:
 */
static void fair_enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
    struct rb_node *parent = NULL;
    struct sched_entity *entry;
    bool leftmost = true;

    /*
     * Find the right place in the rbtree:
     */
    while (*link) {
        parent = *link;
        entry = rb_entry(parent, struct sched_entity, run_node);
        /*
         * We dont care about collisions. Nodes with
         * the same key stay together.
         */
        if (entity_before(se, entry)) {
            link = &parent->rb_left;
        } else {
            link = &parent->rb_right;
            leftmost = false;
        }
    }

    rb_link_node(&se->run_node, parent, link);
    rb_insert_color_cached(&se->run_node, &cfs_rq->tasks_timeline, leftmost);
}

static void fair_dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
}

struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
{
    struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);

    if (!left) {
        return NULL;
    }

    return rb_entry(left, struct sched_entity, run_node);
}

static struct sched_entity *fair_pick_next_entity(struct sched_entity *se)
{
    struct rb_node *next = rb_next(&se->run_node);

    if (!next) {
        return NULL;
    }

    return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
    struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);

    if (!last) {
        return NULL;
    }

    return rb_entry(last, struct sched_entity, run_node);
}

/**************************************************************
 * Scheduling class statistics methods
 */

int sched_proc_update_handler(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos)
{
    int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
    unsigned int factor = get_update_sysctl_factor();

    if (ret || !write) {
        return ret;
    }

    sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, sysctl_sched_min_granularity);

#define WRT_SYSCTL(name) (normalized_sysctl_##name = sysctl_##name / (factor))
    WRT_SYSCTL(sched_min_granularity);
    WRT_SYSCTL(sched_latency);
    WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL

    return 0;
}
#endif

/*
 * delta /= w
 */
static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
{
    if (unlikely(se->load.weight != NICE_0_LOAD)) {
        delta = fair_calc_delta(delta, NICE_0_LOAD, &se->load);
    }

    return delta;
}

/*
 * The idea is to set a period in which each task runs once.
 *
 * When there are too many tasks (sched_nr_latency) we have to stretch
 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
static u64 fair_sched_period(unsigned long nr_running)
{
    if (unlikely(nr_running > sched_nr_latency)) {
        return nr_running * sysctl_sched_min_granularity;
    } else {
        return sysctl_sched_latency;
    }
}

/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
 * s = p*P[w/rw]
 */
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    unsigned int nr_running = cfs_rq->nr_running;
    u64 slice;

    if (sched_feat(ALT_PERIOD)) {
        nr_running = rq_of(cfs_rq)->cfs.h_nr_running;
    }

    slice = fair_sched_period(nr_running + !se->on_rq);

    for_each_sched_entity(se) {
        struct load_weight *load;
        struct load_weight lw;

        cfs_rq = cfs_rq_of(se);
        load = &cfs_rq->load;

        if (unlikely(!se->on_rq)) {
            lw = cfs_rq->load;

            update_load_add(&lw, se->load.weight);
            load = &lw;
        }
        slice = fair_calc_delta(slice, se->load.weight, load);
    }

    if (sched_feat(BASE_SLICE)) {
        slice = max(slice, (u64)sysctl_sched_min_granularity);
    }

    return slice;
}

/*
 * We calculate the vruntime slice of a to-be-inserted task.
 *
 * vs = s/w
 */
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    return calc_delta_fair(sched_slice(cfs_rq, se), se);
}

#include "pelt.h"
#ifdef CONFIG_SMP

static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
static unsigned long task_h_load(struct task_struct *p);

/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
{
    struct sched_avg *sa = &se->avg;

    memset(sa, 0, sizeof(*sa));

    /*
     * Tasks are initialized with full load to be seen as heavy tasks until
     * they get a chance to stabilize to their real load level.
     * Group entities are initialized with zero load to reflect the fact that
     * nothing has been attached to the task group yet.
     */
    if (entity_is_task(se)) {
        sa->load_avg = scale_load_down(se->load.weight);
    }

    /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
}

static void attach_entity_cfs_rq(struct sched_entity *se);

/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
 *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task and cpu_scale the CPU capacity.
 *
 * For example, for a CPU with 1024 of capacity, a simplest series from
 * the beginning would be like
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct task_struct *p)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);
    struct sched_avg *sa = &se->avg;
    long cpu_scale = arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)));
    long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;

    if (cap > 0) {
        if (cfs_rq->avg.util_avg != 0) {
            sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
            sa->util_avg /= (cfs_rq->avg.load_avg + 1);

            if (sa->util_avg > cap) {
                sa->util_avg = cap;
            }
        } else {
            sa->util_avg = cap;
        }
    }

    sa->runnable_avg = sa->util_avg;

    if (p->sched_class != &fair_sched_class) {
        /*
         * For !fair tasks do:
         *
        update_cfs_rq_load_avg(now, cfs_rq);
        attach_entity_load_avg(cfs_rq, se);
        switched_from_fair(rq, p);
         *
         * such that the next switched_to_fair() has the
         * expected state.
         */
        se->avg.last_update_time = cfs_rq_clock_pelt(cfs_rq);
        return;
    }

    attach_entity_cfs_rq(se);
}

#else  /* !CONFIG_SMP */
void init_entity_runnable_average(struct sched_entity *se)
{
}
void post_init_entity_util_avg(struct task_struct *p)
{
}
static void update_tg_load_avg(struct cfs_rq *cfs_rq)
{
}
#endif /* CONFIG_SMP */

/*
 * Update the current task's runtime statistics.
 */
static void update_curr(struct cfs_rq *cfs_rq)
{
    struct sched_entity *curr = cfs_rq->curr;
    u64 now = rq_clock_task(rq_of(cfs_rq));
    u64 delta_exec;

    if (unlikely(!curr)) {
        return;
    }

    delta_exec = now - curr->exec_start;
    if (unlikely((s64)delta_exec <= 0)) {
        return;
    }

    curr->exec_start = now;

    schedstat_set(curr->statistics.exec_max, max(delta_exec, curr->statistics.exec_max));

    curr->sum_exec_runtime += delta_exec;
    schedstat_add(cfs_rq->exec_clock, delta_exec);

    curr->vruntime += calc_delta_fair(delta_exec, curr);
    update_min_vruntime(cfs_rq);

    if (entity_is_task(curr)) {
        struct task_struct *curtask = task_of(curr);

        trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
        cgroup_account_cputime(curtask, delta_exec);
        account_group_exec_runtime(curtask, delta_exec);
    }

    account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static void update_curr_fair(struct rq *rq)
{
    update_curr(cfs_rq_of(&rq->curr->se));
}

static inline void update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    u64 wait_start, prev_wait_start;

    if (!schedstat_enabled()) {
        return;
    }

    wait_start = rq_clock(rq_of(cfs_rq));
    prev_wait_start = schedstat_val(se->statistics.wait_start);
    if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) && likely(wait_start > prev_wait_start)) {
        wait_start -= prev_wait_start;
    }

    __schedstat_set(se->statistics.wait_start, wait_start);
}

static inline void update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    struct task_struct *p;
    u64 delta;

    if (!schedstat_enabled()) {
        return;
    }

    delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);

    if (entity_is_task(se)) {
        p = task_of(se);
        if (task_on_rq_migrating(p)) {
            /*
             * Preserve migrating task's wait time so wait_start
             * time stamp can be adjusted to accumulate wait time
             * prior to migration.
             */
            __schedstat_set(se->statistics.wait_start, delta);
            return;
        }
        trace_sched_stat_wait(p, delta);
    }

    __schedstat_set(se->statistics.wait_max, max(schedstat_val(se->statistics.wait_max), delta));
    __schedstat_inc(se->statistics.wait_count);
    __schedstat_add(se->statistics.wait_sum, delta);
    __schedstat_set(se->statistics.wait_start, 0);
}

static inline void update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    struct task_struct *tsk = NULL;
    u64 sleep_start, block_start;

    if (!schedstat_enabled()) {
        return;
    }

    sleep_start = schedstat_val(se->statistics.sleep_start);
    block_start = schedstat_val(se->statistics.block_start);

    if (entity_is_task(se)) {
        tsk = task_of(se);
    }

    if (sleep_start) {
        u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
        if ((s64)delta < 0) {
            delta = 0;
        }

        if (unlikely(delta > schedstat_val(se->statistics.sleep_max))) {
            __schedstat_set(se->statistics.sleep_max, delta);
        }

        __schedstat_set(se->statistics.sleep_start, 0);
        __schedstat_add(se->statistics.sum_sleep_runtime, delta);

        if (tsk) {
            account_scheduler_latency(tsk, delta >> 10, 1);
            trace_sched_stat_sleep(tsk, delta);
        }
    }
    if (block_start) {
        u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
        if ((s64)delta < 0) {
            delta = 0;
        }

        if (unlikely(delta > schedstat_val(se->statistics.block_max))) {
            __schedstat_set(se->statistics.block_max, delta);
        }

        __schedstat_set(se->statistics.block_start, 0);
        __schedstat_add(se->statistics.sum_sleep_runtime, delta);

        if (tsk) {
            if (tsk->in_iowait) {
                __schedstat_add(se->statistics.iowait_sum, delta);
                __schedstat_inc(se->statistics.iowait_count);
                trace_sched_stat_iowait(tsk, delta);
            }

            trace_sched_stat_blocked(tsk, delta);

            /*
             * Blocking time is in units of nanosecs, so shift by
             * 20 to get a milliseconds-range estimation of the
             * amount of time that the task spent sleeping:
             */
            if (unlikely(prof_on == SLEEP_PROFILING)) {
                profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk), delta >> FAIR_TWENTY);
            }
            account_scheduler_latency(tsk, delta >> 10, 0);
        }
    }
}

/*
 * Task is being enqueued - update stats:
 */
static inline void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
    if (!schedstat_enabled()) {
        return;
    }

    /*
     * Are we enqueueing a waiting task? (for current tasks
     * a dequeue/enqueue event is a NOP)
     */
    if (se != cfs_rq->curr) {
        update_stats_wait_start(cfs_rq, se);
    }

    if (flags & ENQUEUE_WAKEUP) {
        update_stats_enqueue_sleeper(cfs_rq, se);
    }
}

static inline void update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
    if (!schedstat_enabled()) {
        return;
    }

    /*
     * Mark the end of the wait period if dequeueing a
     * waiting task:
     */
    if (se != cfs_rq->curr) {
        update_stats_wait_end(cfs_rq, se);
    }

    if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
        struct task_struct *tsk = task_of(se);

        if (tsk->state & TASK_INTERRUPTIBLE) {
            __schedstat_set(se->statistics.sleep_start, rq_clock(rq_of(cfs_rq)));
        }
        if (tsk->state & TASK_UNINTERRUPTIBLE) {
            __schedstat_set(se->statistics.block_start, rq_clock(rq_of(cfs_rq)));
        }
    }
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    /*
     * We are starting a new run period:
     */
    se->exec_start = rq_clock_task(rq_of(cfs_rq));
}

/**************************************************
 * Scheduling class queueing methods:
 */

#ifdef CONFIG_NUMA_BALANCING
/*
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
 */
unsigned int sysctl_numa_balancing_scan_period_min = FAIR_ONETHOUSAND;
unsigned int sysctl_numa_balancing_scan_period_max = FAIR_SIXTYTHOUSAND;

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = FAIR_TWOHUNDREDFIFTYSIX;

/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = FAIR_ONETHOUSAND;

struct numa_group {
    refcount_t refcount;

    spinlock_t lock; /* nr_tasks, tasks */
    int nr_tasks;
    pid_t gid;
    int active_nodes;

    struct rcu_head rcu;
    unsigned long total_faults;
    unsigned long max_faults_cpu;
    /*
     * Faults_cpu is used to decide whether memory should move
     * towards the CPU. As a consequence, these stats are weighted
     * more by CPU use than by memory faults.
     */
    unsigned long *faults_cpu;
    unsigned long faults[];
};

/*
 * For functions that can be called in multiple contexts that permit reading
 * ->numa_group (see struct task_struct for locking rules).
 */
static struct numa_group *deref_task_numa_group(struct task_struct *p)
{
    return rcu_dereference_check(p->numa_group,
                                 p == current || (lockdep_is_held(&task_rq(p)->lock) && !READ_ONCE(p->on_cpu)));
}

static struct numa_group *deref_curr_numa_group(struct task_struct *p)
{
    return rcu_dereference_protected(p->numa_group, p == current);
}

static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);

static unsigned int task_nr_scan_windows(struct task_struct *p)
{
    unsigned long rss = 0;
    unsigned long nr_scan_pages;

    /*
     * Calculations based on RSS as non-present and empty pages are skipped
     * by the PTE scanner and NUMA hinting faults should be trapped based
     * on resident pages
     */
    nr_scan_pages = sysctl_numa_balancing_scan_size << (FAIR_TWENTY - PAGE_SHIFT);
    rss = get_mm_rss(p->mm);
    if (!rss) {
        rss = nr_scan_pages;
    }

    rss = round_up(rss, nr_scan_pages);
    return rss / nr_scan_pages;
}

/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560

static unsigned int task_scan_min(struct task_struct *p)
{
    unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
    unsigned int scan, floor;
    unsigned int windows = 1;

    if (scan_size < MAX_SCAN_WINDOW) {
        windows = MAX_SCAN_WINDOW / scan_size;
    }
    floor = FAIR_ONETHOUSAND / windows;

    scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
    return max_t(unsigned int, floor, scan);
}

static unsigned int task_scan_start(struct task_struct *p)
{
    unsigned long smin = task_scan_min(p);
    unsigned long period = smin;
    struct numa_group *ng;

    /* Scale the maximum scan period with the amount of shared memory. */
    rcu_read_lock();
    ng = rcu_dereference(p->numa_group);
    if (ng) {
        unsigned long shared = group_faults_shared(ng);
        unsigned long private = group_faults_priv(ng);

        period *= refcount_read(&ng->refcount);
        period *= shared + 1;
        period /= private + shared + 1;
    }
    rcu_read_unlock();

    return max(smin, period);
}

static unsigned int task_scan_max(struct task_struct *p)
{
    unsigned long smin = task_scan_min(p);
    unsigned long smax;
    struct numa_group *ng;

    /* Watch for min being lower than max due to floor calculations */
    smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);

    /* Scale the maximum scan period with the amount of shared memory. */
    ng = deref_curr_numa_group(p);
    if (ng) {
        unsigned long shared = group_faults_shared(ng);
        unsigned long private = group_faults_priv(ng);
        unsigned long period = smax;

        period *= refcount_read(&ng->refcount);
        period *= shared + 1;
        period /= private + shared + 1;

        smax = max(smax, period);
    }

    return max(smin, smax);
}

static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
    rq->nr_numa_running += (p->numa_preferred_nid != NUMA_NO_NODE);
    rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
    rq->nr_numa_running -= (p->numa_preferred_nid != NUMA_NO_NODE);
    rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}

/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)

/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)

pid_t task_numa_group_id(struct task_struct *p)
{
    struct numa_group *ng;
    pid_t gid = 0;

    rcu_read_lock();
    ng = rcu_dereference(p->numa_group);
    if (ng) {
        gid = ng->gid;
    }
    rcu_read_unlock();

    return gid;
}

/*
 * The averaged statistics, shared & private, memory & CPU,
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
{
    return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
    if (!p->numa_faults) {
        return 0;
    }

    return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
}

static inline unsigned long group_faults(struct task_struct *p, int nid)
{
    struct numa_group *ng = deref_task_numa_group(p);

    if (!ng) {
        return 0;
    }

    return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] + ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
}

static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
    return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
}

static inline unsigned long group_faults_priv(struct numa_group *ng)
{
    unsigned long faults = 0;
    int node;

    for_each_online_node(node)
    {
        faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
    }

    return faults;
}

static inline unsigned long group_faults_shared(struct numa_group *ng)
{
    unsigned long faults = 0;
    int node;

    for_each_online_node(node)
    {
        faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
    }

    return faults;
}

/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

static bool numa_is_active_node(int nid, struct numa_group *ng)
{
    return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}

/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid, int maxdist, bool task)
{
    unsigned long score = 0;
    int node;

    /*
     * All nodes are directly connected, and the same distance
     * from each other. No need for fancy placement algorithms.
     */
    if (sched_numa_topology_type == NUMA_DIRECT) {
        return 0;
    }

    /*
     * This code is called for each node, introducing N^2 complexity,
     * which should be ok given the number of nodes rarely exceeds 8.
     */
    for_each_online_node(node)
    {
        unsigned long faults;
        int dist = node_distance(nid, node);
        /*
         * The furthest away nodes in the system are not interesting
         * for placement; nid was already counted.
         */
        if (dist == sched_max_numa_distance || node == nid) {
            continue;
        }

        /*
         * On systems with a backplane NUMA topology, compare groups
         * of nodes, and move tasks towards the group with the most
         * memory accesses. When comparing two nodes at distance
         * "hoplimit", only nodes closer by than "hoplimit" are part
         * of each group. Skip other nodes.
         */
        if (sched_numa_topology_type == NUMA_BACKPLANE && dist >= maxdist) {
            continue;
        }

        /* Add up the faults from nearby nodes. */
        if (task) {
            faults = task_faults(p, node);
        } else {
            faults = group_faults(p, node);
        }

        /*
         * On systems with a glueless mesh NUMA topology, there are
         * no fixed "groups of nodes". Instead, nodes that are not
         * directly connected bounce traffic through intermediate
         * nodes; a numa_group can occupy any set of nodes.
         * The further away a node is, the less the faults count.
         * This seems to result in good task placement.
         */
        if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
            faults *= (sched_max_numa_distance - dist);
            faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
        }

        score += faults;
    }

    return score;
}

/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
static inline unsigned long task_weight(struct task_struct *p, int nid, int dist)
{
    unsigned long faults, total_faults;

    if (!p->numa_faults) {
        return 0;
    }

    total_faults = p->total_numa_faults;

    if (!total_faults) {
        return 0;
    }

    faults = task_faults(p, nid);
    faults += score_nearby_nodes(p, nid, dist, true);

    return FAIR_ONETHOUSAND * faults / total_faults;
}

static inline unsigned long group_weight(struct task_struct *p, int nid, int dist)
{
    struct numa_group *ng = deref_task_numa_group(p);
    unsigned long faults, total_faults;

    if (!ng) {
        return 0;
    }

    total_faults = ng->total_faults;

    if (!total_faults) {
        return 0;
    }

    faults = group_faults(p, nid);
    faults += score_nearby_nodes(p, nid, dist, false);

    return FAIR_ONETHOUSAND * faults / total_faults;
}

bool should_numa_migrate_memory(struct task_struct *p, struct page *page, int src_nid, int dst_cpu)
{
    struct numa_group *ng = deref_curr_numa_group(p);
    int dst_nid = cpu_to_node(dst_cpu);
    int last_cpupid, this_cpupid;

    this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
    last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
    /*
     * Allow first faults or private faults to migrate immediately early in
     * the lifetime of a task. The magic number 4 is based on waiting for
     * two full passes of the "multi-stage node selection" test that is
     * executed below.
     */
    if ((p->numa_preferred_nid == NUMA_NO_NODE || p->numa_scan_seq <= FAIR_FOUR) &&
        (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid))) {
        return true;
    }

    /*
     * Multi-stage node selection is used in conjunction with a periodic
     * migration fault to build a temporal task<->page relation. By using
     * a two-stage filter we remove short/unlikely relations.
     *
     * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
     * a task's usage of a particular page (n_p) per total usage of this
     * page (n_t) (in a given time-span) to a probability.
     *
     * Our periodic faults will sample this probability and getting the
     * same result twice in a row, given these samples are fully
     * independent, is then given by P(n)^2, provided our sample period
     * is sufficiently short compared to the usage pattern.
     *
     * This quadric squishes small probabilities, making it less likely we
     * act on an unlikely task<->page relation.
     */
    if (!cpupid_pid_unset(last_cpupid) && cpupid_to_nid(last_cpupid) != dst_nid) {
        return false;
    }

    /* Always allow migrate on private faults */
    if (cpupid_match_pid(p, last_cpupid)) {
        return true;
    }

    /* A shared fault, but p->numa_group has not been set up yet. */
    if (!ng) {
        return true;
    }

    /*
     * Destination node is much more heavily used than the source
     * node? Allow migration.
     */
    if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) * ACTIVE_NODE_FRACTION) {
        return true;
    }

    /*
     * Distribute memory according to CPU & memory use on each node,
     * with 3/4 hysteresis to avoid unnecessary memory migrations:
     *
     * faults_cpu(dst)   3   faults_cpu(src)
     * --------------- * - > ---------------
     * faults_mem(dst)   4   faults_mem(src)
     */
    return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * FAIR_THREE >
           group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * FAIR_FOUR;
}

/*
 * 'numa_type' describes the node at the moment of load balancing.
 */
enum numa_type {
    /* The node has spare capacity that can be used to run more tasks.  */
    node_has_spare = 0,
    /*
     * The node is fully used and the tasks don't compete for more CPU
     * cycles. Nevertheless, some tasks might wait before running.
     */
    node_fully_busy,
    /*
     * The node is overloaded and can't provide expected CPU cycles to all
     * tasks.
     */
    node_overloaded
};

/* Cached statistics for all CPUs within a node */
struct numa_stats {
    unsigned long load;
    unsigned long runnable;
    unsigned long util;
    /* Total compute capacity of CPUs on a node */
    unsigned long compute_capacity;
    unsigned int nr_running;
    unsigned int weight;
    enum numa_type node_type;
    int idle_cpu;
};

static inline bool is_core_idle(int cpu)
{
#ifdef CONFIG_SCHED_SMT
    int sibling;

    for_each_cpu(sibling, cpu_smt_mask(cpu))
    {
        if (cpu == sibling) {
            continue;
        }

        if (!idle_cpu(sibling)) {
            return false;
        }
    }
#endif

    return true;
}

struct task_numa_env {
    struct task_struct *p;

    int src_cpu, src_nid;
    int dst_cpu, dst_nid;

    struct numa_stats src_stats, dst_stats;

    int imbalance_pct;
    int dist;

    struct task_struct *best_task;
    long best_imp;
    int best_cpu;
};

static unsigned long cpu_load(struct rq *rq);
static unsigned long cpu_runnable(struct rq *rq);
static inline long adjust_numa_imbalance(int imbalance, int nr_running);

static inline enum numa_type numa_classify(unsigned int imbalance_pct, struct numa_stats *ns)
{
    if ((ns->nr_running > ns->weight) &&
        (((ns->compute_capacity * FAIR_ONEHUNDRED) < (ns->util * imbalance_pct)) ||
         ((ns->compute_capacity * imbalance_pct) < (ns->runnable * FAIR_ONEHUNDRED)))) {
        return node_overloaded;
    }

    if ((ns->nr_running < ns->weight) ||
        (((ns->compute_capacity * FAIR_ONEHUNDRED) > (ns->util * imbalance_pct)) &&
         ((ns->compute_capacity * imbalance_pct) > (ns->runnable * FAIR_ONEHUNDRED)))) {
        return node_has_spare;
    }

    return node_fully_busy;
}

#ifdef CONFIG_SCHED_SMT
/* Forward declarations of select_idle_sibling helpers */
static inline bool test_idle_cores(int cpu, bool def);
static inline int numa_idle_core(int idle_core, int cpu)
{
    if (!static_branch_likely(&sched_smt_present) || idle_core >= 0 || !test_idle_cores(cpu, false)) {
        return idle_core;
    }

    /*
     * Prefer cores instead of packing HT siblings
     * and triggering future load balancing.
     */
    if (is_core_idle(cpu)) {
        idle_core = cpu;
    }

    return idle_core;
}
#else
static inline int numa_idle_core(int idle_core, int cpu)
{
    return idle_core;
}
#endif

/*
 * Gather all necessary information to make NUMA balancing placement
 * decisions that are compatible with standard load balancer. This
 * borrows code and logic from update_sg_lb_stats but sharing a
 * common implementation is impractical.
 */
static void update_numa_stats(struct task_numa_env *env, struct numa_stats *ns, int nid, bool find_idle)
{
    int cpu, idle_core = -1;

    memset(ns, 0, sizeof(*ns));
    ns->idle_cpu = -1;

    rcu_read_lock();
    for_each_cpu(cpu, cpumask_of_node(nid))
    {
        struct rq *rq = cpu_rq(cpu);

        ns->load += cpu_load(rq);
        ns->runnable += cpu_runnable(rq);
        ns->util += cpu_util(cpu);
        ns->nr_running += rq->cfs.h_nr_running;
        ns->compute_capacity += capacity_of(cpu);

        if (find_idle && !rq->nr_running && idle_cpu(cpu)) {
            if (READ_ONCE(rq->numa_migrate_on) || !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
                continue;
            }

            if (ns->idle_cpu == -1) {
                ns->idle_cpu = cpu;
            }

            idle_core = numa_idle_core(idle_core, cpu);
        }
    }
    rcu_read_unlock();

    ns->weight = cpumask_weight(cpumask_of_node(nid));

    ns->node_type = numa_classify(env->imbalance_pct, ns);

    if (idle_core >= 0) {
        ns->idle_cpu = idle_core;
    }
}

static void task_numa_assign(struct task_numa_env *env, struct task_struct *p, long imp)
{
    struct rq *rq = cpu_rq(env->dst_cpu);

    /* Check if run-queue part of active NUMA balance. */
    if (env->best_cpu != env->dst_cpu && xchg(&rq->numa_migrate_on, 1)) {
        int cpu;
        int start = env->dst_cpu;

        /* Find alternative idle CPU. */
        for_each_cpu_wrap(cpu, cpumask_of_node(env->dst_nid), start)
        {
            if (cpu == env->best_cpu || !idle_cpu(cpu) || !cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
                continue;
            }

            env->dst_cpu = cpu;
            rq = cpu_rq(env->dst_cpu);
            if (!xchg(&rq->numa_migrate_on, 1)) {
                goto assign;
            }
        }

        /* Failed to find an alternative idle CPU */
        return;
    }

assign:
    /*
     * Clear previous best_cpu/rq numa-migrate flag, since task now
     * found a better CPU to move/swap.
     */
    if (env->best_cpu != -1 && env->best_cpu != env->dst_cpu) {
        rq = cpu_rq(env->best_cpu);
        WRITE_ONCE(rq->numa_migrate_on, 0);
    }

    if (env->best_task) {
        put_task_struct(env->best_task);
    }
    if (p) {
        get_task_struct(p);
    }

    env->best_task = p;
    env->best_imp = imp;
    env->best_cpu = env->dst_cpu;
}

static bool load_too_imbalanced(long src_load, long dst_load, struct task_numa_env *env)
{
    long imb, old_imb;
    long orig_src_load, orig_dst_load;
    long src_capacity, dst_capacity;

    /*
     * The load is corrected for the CPU capacity available on each node.
     *
     * src_load        dst_load
     * ------------ vs ---------
     * src_capacity    dst_capacity
     */
    src_capacity = env->src_stats.compute_capacity;
    dst_capacity = env->dst_stats.compute_capacity;

    imb = abs(dst_load * src_capacity - src_load * dst_capacity);

    orig_src_load = env->src_stats.load;
    orig_dst_load = env->dst_stats.load;

    old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);

    /* Would this change make things worse? */
    return (imb > old_imb);
}

/*
 * Maximum NUMA importance can be 1998 (2*999);
 * SMALLIMP @ 30 would be close to 1998/64.
 * Used to deter task migration.
 */
#define SMALLIMP 30

/*
 * This checks if the overall compute and NUMA accesses of the system would
 * be improved if the source tasks was migrated to the target dst_cpu taking
 * into account that it might be best if task running on the dst_cpu should
 * be exchanged with the source task
 */
static bool task_numa_compare(struct task_numa_env *env, long taskimp, long groupimp, bool maymove)
{
    struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
    struct rq *dst_rq = cpu_rq(env->dst_cpu);
    long imp = p_ng ? groupimp : taskimp;
    struct task_struct *cur;
    long src_load, dst_load;
    int dist = env->dist;
    long moveimp = imp;
    long load;
    bool stopsearch = false;

    if (READ_ONCE(dst_rq->numa_migrate_on)) {
        return false;
    }

    rcu_read_lock();
    cur = rcu_dereference(dst_rq->curr);
    if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) {
        cur = NULL;
    }

    /*
     * Because we have preemption enabled we can get migrated around and
     * end try selecting ourselves (current == env->p) as a swap candidate.
     */
    if (cur == env->p) {
        stopsearch = true;
        goto unlock;
    }

    if (!cur) {
        if (maymove && moveimp >= env->best_imp) {
            goto assign;
        } else {
            goto unlock;
        }
    }

    /* Skip this swap candidate if cannot move to the source cpu. */
    if (!cpumask_test_cpu(env->src_cpu, cur->cpus_ptr)) {
        goto unlock;
    }

    /*
     * Skip this swap candidate if it is not moving to its preferred
     * node and the best task is.
     */
    if (env->best_task && env->best_task->numa_preferred_nid == env->src_nid &&
        cur->numa_preferred_nid != env->src_nid) {
        goto unlock;
    }

    /*
     * "imp" is the fault differential for the source task between the
     * source and destination node. Calculate the total differential for
     * the source task and potential destination task. The more negative
     * the value is, the more remote accesses that would be expected to
     * be incurred if the tasks were swapped.
     *
     * If dst and source tasks are in the same NUMA group, or not
     * in any group then look only at task weights.
     */
    cur_ng = rcu_dereference(cur->numa_group);
    if (cur_ng == p_ng) {
        imp = taskimp + task_weight(cur, env->src_nid, dist) - task_weight(cur, env->dst_nid, dist);
        /*
         * Add some hysteresis to prevent swapping the
         * tasks within a group over tiny differences.
         */
        if (cur_ng) {
            imp -= imp / 0x10;
        }
    } else {
        /*
         * Compare the group weights. If a task is all by itself
         * (not part of a group), use the task weight instead.
         */
        if (cur_ng && p_ng) {
            imp += group_weight(cur, env->src_nid, dist) - group_weight(cur, env->dst_nid, dist);
        } else {
            imp += task_weight(cur, env->src_nid, dist) - task_weight(cur, env->dst_nid, dist);
        }
    }

    /* Discourage picking a task already on its preferred node */
    if (cur->numa_preferred_nid == env->dst_nid) {
        imp -= imp / 0x10;
    }

    /*
     * Encourage picking a task that moves to its preferred node.
     * This potentially makes imp larger than it's maximum of
     * 1998 (see SMALLIMP and task_weight for why) but in this
     * case, it does not matter.
     */
    if (cur->numa_preferred_nid == env->src_nid) {
        imp += imp / 0x8;
    }

    if (maymove && moveimp > imp && moveimp > env->best_imp) {
        imp = moveimp;
        cur = NULL;
        goto assign;
    }

    /*
     * Prefer swapping with a task moving to its preferred node over a
     * task that is not.
     */
    if (env->best_task && cur->numa_preferred_nid == env->src_nid &&
        env->best_task->numa_preferred_nid != env->src_nid) {
        goto assign;
    }

    /*
     * If the NUMA importance is less than SMALLIMP,
     * task migration might only result in ping pong
     * of tasks and also hurt performance due to cache
     * misses.
     */
    if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 0x2) {
        goto unlock;
    }

    /*
     * In the overloaded case, try and keep the load balanced.
     */
    load = task_h_load(env->p) - task_h_load(cur);
    if (!load) {
        goto assign;
    }

    dst_load = env->dst_stats.load + load;
    src_load = env->src_stats.load - load;

    if (load_too_imbalanced(src_load, dst_load, env)) {
        goto unlock;
    }

assign:
    /* Evaluate an idle CPU for a task numa move. */
    if (!cur) {
        int cpu = env->dst_stats.idle_cpu;

        /* Nothing cached so current CPU went idle since the search. */
        if (cpu < 0) {
            cpu = env->dst_cpu;
        }

        /*
         * If the CPU is no longer truly idle and the previous best CPU
         * is, keep using it.
         */
        if (!idle_cpu(cpu) && env->best_cpu >= 0 && idle_cpu(env->best_cpu)) {
            cpu = env->best_cpu;
        }

        env->dst_cpu = cpu;
    }

    task_numa_assign(env, cur, imp);

    /*
     * If a move to idle is allowed because there is capacity or load
     * balance improves then stop the search. While a better swap
     * candidate may exist, a search is not free.
     */
    if (maymove && !cur && env->best_cpu >= 0 && idle_cpu(env->best_cpu)) {
        stopsearch = true;
    }

    /*
     * If a swap candidate must be identified and the current best task
     * moves its preferred node then stop the search.
     */
    if (!maymove && env->best_task && env->best_task->numa_preferred_nid == env->src_nid) {
        stopsearch = true;
    }
unlock:
    rcu_read_unlock();

    return stopsearch;
}

static void task_numa_find_cpu(struct task_numa_env *env, long taskimp, long groupimp)
{
    bool maymove = false;
    int cpu;

    /*
     * If dst node has spare capacity, then check if there is an
     * imbalance that would be overruled by the load balancer.
     */
    if (env->dst_stats.node_type == node_has_spare) {
        unsigned int imbalance;
        int src_running, dst_running;

        /*
         * Would movement cause an imbalance? Note that if src has
         * more running tasks that the imbalance is ignored as the
         * move improves the imbalance from the perspective of the
         * CPU load balancer.
         * */
        src_running = env->src_stats.nr_running - 1;
        dst_running = env->dst_stats.nr_running + 1;
        imbalance = max(0, dst_running - src_running);
        imbalance = adjust_numa_imbalance(imbalance, dst_running);
        /* Use idle CPU if there is no imbalance */
        if (!imbalance) {
            maymove = true;
            if (env->dst_stats.idle_cpu >= 0) {
                env->dst_cpu = env->dst_stats.idle_cpu;
                task_numa_assign(env, NULL, 0);
                return;
            }
        }
    } else {
        long src_load, dst_load, load;
        /*
         * If the improvement from just moving env->p direction is better
         * than swapping tasks around, check if a move is possible.
         */
        load = task_h_load(env->p);
        dst_load = env->dst_stats.load + load;
        src_load = env->src_stats.load - load;
        maymove = !load_too_imbalanced(src_load, dst_load, env);
    }

    for_each_cpu(cpu, cpumask_of_node(env->dst_nid))
    {
        /* Skip this CPU if the source task cannot migrate */
        if (!cpumask_test_cpu(cpu, env->p->cpus_ptr)) {
            continue;
        }

        env->dst_cpu = cpu;
        if (task_numa_compare(env, taskimp, groupimp, maymove)) {
            break;
        }
    }
}

static int task_numa_migrate(struct task_struct *p)
{
    struct task_numa_env env = {
        .p = p,

        .src_cpu = task_cpu(p),
        .src_nid = task_node(p),

        .imbalance_pct = 112,

        .best_task = NULL,
        .best_imp = 0,
        .best_cpu = -1,
    };
    unsigned long taskweight, groupweight;
    struct sched_domain *sd;
    long taskimp, groupimp;
    struct numa_group *ng;
    struct rq *best_rq;
    int nid, ret, dist;

    /*
     * Pick the lowest SD_NUMA domain, as that would have the smallest
     * imbalance and would be the first to start moving tasks about.
     *
     * And we want to avoid any moving of tasks about, as that would create
     * random movement of tasks -- counter the numa conditions we're trying
     * to satisfy here.
     */
    rcu_read_lock();
    sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
    if (sd) {
        env.imbalance_pct = FAIR_ONEHUNDRED + (sd->imbalance_pct - FAIR_ONEHUNDRED) / 0x2;
    }
    rcu_read_unlock();

    /*
     * Cpusets can break the scheduler domain tree into smaller
     * balance domains, some of which do not cross NUMA boundaries.
     * Tasks that are "trapped" in such domains cannot be migrated
     * elsewhere, so there is no point in (re)trying.
     */
    if (unlikely(!sd)) {
        sched_setnuma(p, task_node(p));
        return -EINVAL;
    }

    env.dst_nid = p->numa_preferred_nid;
    dist = env.dist = node_distance(env.src_nid, env.dst_nid);
    taskweight = task_weight(p, env.src_nid, dist);
    groupweight = group_weight(p, env.src_nid, dist);
    update_numa_stats(&env, &env.src_stats, env.src_nid, false);
    taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
    groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
    update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);

    /* Try to find a spot on the preferred nid. */
    task_numa_find_cpu(&env, taskimp, groupimp);

    /*
     * Look at other nodes in these cases:
     * - there is no space available on the preferred_nid
     * - the task is part of a numa_group that is interleaved across
     *   multiple NUMA nodes; in order to better consolidate the group,
     *   we need to check other locations.
     */
    ng = deref_curr_numa_group(p);
    if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
        for_each_online_node(nid)
        {
            if (nid == env.src_nid || nid == p->numa_preferred_nid) {
                continue;
            }

            dist = node_distance(env.src_nid, env.dst_nid);
            if (sched_numa_topology_type == NUMA_BACKPLANE && dist != env.dist) {
                taskweight = task_weight(p, env.src_nid, dist);
                groupweight = group_weight(p, env.src_nid, dist);
            }

            /* Only consider nodes where both task and groups benefit */
            taskimp = task_weight(p, nid, dist) - taskweight;
            groupimp = group_weight(p, nid, dist) - groupweight;
            if (taskimp < 0 && groupimp < 0) {
                continue;
            }

            env.dist = dist;
            env.dst_nid = nid;
            update_numa_stats(&env, &env.dst_stats, env.dst_nid, true);
            task_numa_find_cpu(&env, taskimp, groupimp);
        }
    }

    /*
     * If the task is part of a workload that spans multiple NUMA nodes,
     * and is migrating into one of the workload's active nodes, remember
     * this node as the task's preferred numa node, so the workload can
     * settle down.
     * A task that migrated to a second choice node will be better off
     * trying for a better one later. Do not set the preferred node here.
     */
    if (ng) {
        if (env.best_cpu == -1) {
            nid = env.src_nid;
        } else {
            nid = cpu_to_node(env.best_cpu);
        }

        if (nid != p->numa_preferred_nid) {
            sched_setnuma(p, nid);
        }
    }

    /* No better CPU than the current one was found. */
    if (env.best_cpu == -1) {
        trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
        return -EAGAIN;
    }

    best_rq = cpu_rq(env.best_cpu);
    if (env.best_task == NULL) {
        ret = migrate_task_to(p, env.best_cpu);
        WRITE_ONCE(best_rq->numa_migrate_on, 0);
        if (ret != 0) {
            trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
        }
        return ret;
    }

    ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
    WRITE_ONCE(best_rq->numa_migrate_on, 0);

    if (ret != 0) {
        trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
    }
    put_task_struct(env.best_task);
    return ret;
}

/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
    unsigned long interval = HZ;

    /* This task has no NUMA fault statistics yet */
    if (unlikely(p->numa_preferred_nid == NUMA_NO_NODE || !p->numa_faults)) {
        return;
    }

    /* Periodically retry migrating the task to the preferred node */
    interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 0x10);
    p->numa_migrate_retry = jiffies + interval;

    /* Success if task is already running on preferred CPU */
    if (task_node(p) == p->numa_preferred_nid) {
        return;
    }

    /* Otherwise, try migrate to a CPU on the preferred node */
    task_numa_migrate(p);
}

/*
 * Find out how many nodes on the workload is actively running on. Do this by
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 */
static void numa_group_count_active_nodes(struct numa_group *numa_group)
{
    unsigned long faults, max_faults = 0;
    int nid, active_nodes = 0;

    for_each_online_node(nid)
    {
        faults = group_faults_cpu(numa_group, nid);
        if (faults > max_faults) {
            max_faults = faults;
        }
    }

    for_each_online_node(nid)
    {
        faults = group_faults_cpu(numa_group, nid);
        if (faults * ACTIVE_NODE_FRACTION > max_faults) {
            active_nodes++;
        }
    }

    numa_group->max_faults_cpu = max_faults;
    numa_group->active_nodes = active_nodes;
}

/*
 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
 * increments. The more local the fault statistics are, the higher the scan
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
 */
#define NUMA_PERIOD_SLOTS 10
#define NUMA_PERIOD_THRESHOLD 7

/*
 * Increase the scan period (slow down scanning) if the majority of
 * our memory is already on our local node, or if the majority of
 * the page accesses are shared with other processes.
 * Otherwise, decrease the scan period.
 */
static void update_task_scan_period(struct task_struct *p, unsigned long shared, unsigned long private)
{
    unsigned int period_slot;
    int lr_ratio, ps_ratio;
    int diff;

    unsigned long remote = p->numa_faults_locality[0];
    unsigned long local = p->numa_faults_locality[1];

    /*
     * If there were no record hinting faults then either the task is
     * completely idle or all activity is areas that are not of interest
     * to automatic numa balancing. Related to that, if there were failed
     * migration then it implies we are migrating too quickly or the local
     * node is overloaded. In either case, scan slower
     */
    if (local + shared == 0 || p->numa_faults_locality[0x2]) {
        p->numa_scan_period = min(p->numa_scan_period_max, p->numa_scan_period << 1);

        p->mm->numa_next_scan = jiffies + msecs_to_jiffies(p->numa_scan_period);

        return;
    }

    /*
     * Prepare to scale scan period relative to the current period.
     *     == NUMA_PERIOD_THRESHOLD scan period stays the same
     *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
     *     >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
     */
    period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
    lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
    ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);

    if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
        /*
         * Most memory accesses are local. There is no need to
         * do fast NUMA scanning, since memory is already local.
         */
        int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
        if (!slot) {
            slot = 1;
        }
        diff = slot * period_slot;
    } else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
        /*
         * Most memory accesses are shared with other tasks.
         * There is no point in continuing fast NUMA scanning,
         * since other tasks may just move the memory elsewhere.
         */
        int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
        if (!slot) {
            slot = 1;
        }
        diff = slot * period_slot;
    } else {
        /*
         * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
         * yet they are not on the local NUMA node. Speed up
         * NUMA scanning to get the memory moved over.
         */
        int ratio = max(lr_ratio, ps_ratio);
        diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
    }

    p->numa_scan_period = clamp(p->numa_scan_period + diff, task_scan_min(p), task_scan_max(p));
    memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}

/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
    u64 runtime, delta, now;
    /* Use the start of this time slice to avoid calculations. */
    now = p->se.exec_start;
    runtime = p->se.sum_exec_runtime;

    if (p->last_task_numa_placement) {
        delta = runtime - p->last_sum_exec_runtime;
        *period = now - p->last_task_numa_placement;

        /* Avoid time going backwards, prevent potential divide error: */
        if (unlikely((s64)*period < 0)) {
            *period = 0;
        }
    } else {
        delta = p->se.avg.load_sum;
        *period = LOAD_AVG_MAX;
    }

    p->last_sum_exec_runtime = runtime;
    p->last_task_numa_placement = now;

    return delta;
}

/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
    nodemask_t nodes;
    int dist;

    /* Direct connections between all NUMA nodes. */
    if (sched_numa_topology_type == NUMA_DIRECT) {
        return nid;
    }

    /*
     * On a system with glueless mesh NUMA topology, group_weight
     * scores nodes according to the number of NUMA hinting faults on
     * both the node itself, and on nearby nodes.
     */
    if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
        unsigned long score, max_score = 0;
        int node, max_node = nid;

        dist = sched_max_numa_distance;

        for_each_online_node(node)
        {
            score = group_weight(p, node, dist);
            if (score > max_score) {
                max_score = score;
                max_node = node;
            }
        }
        return max_node;
    }

    /*
     * Finding the preferred nid in a system with NUMA backplane
     * interconnect topology is more involved. The goal is to locate
     * tasks from numa_groups near each other in the system, and
     * untangle workloads from different sides of the system. This requires
     * searching down the hierarchy of node groups, recursively searching
     * inside the highest scoring group of nodes. The nodemask tricks
     * keep the complexity of the search down.
     */
    nodes = node_online_map;
    for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
        unsigned long max_faults = 0;
        nodemask_t max_group = NODE_MASK_NONE;
        int a, b;

        /* Are there nodes at this distance from each other? */
        if (!find_numa_distance(dist)) {
            continue;
        }

        for_each_node_mask(a, nodes)
        {
            unsigned long faults = 0;
            nodemask_t this_group;
            nodes_clear(this_group);

            /* Sum group's NUMA faults; includes a==b case. */
            for_each_node_mask(b, nodes)
            {
                if (node_distance(a, b) < dist) {
                    faults += group_faults(p, b);
                    node_set(b, this_group);
                    node_clear(b, nodes);
                }
            }

            /* Remember the top group. */
            if (faults > max_faults) {
                max_faults = faults;
                max_group = this_group;
                /*
                 * subtle: at the smallest distance there is
                 * just one node left in each "group", the
                 * winner is the preferred nid.
                 */
                nid = a;
            }
        }
        /* Next round, evaluate the nodes within max_group. */
        if (!max_faults) {
            break;
        }
        nodes = max_group;
    }
    return nid;
}

static void task_numa_placement(struct task_struct *p)
{
    int seq, nid, max_nid = NUMA_NO_NODE;
    unsigned long max_faults = 0;
    unsigned long fault_types[2] = {0, 0};
    unsigned long total_faults;
    u64 runtime, period;
    spinlock_t *group_lock = NULL;
    struct numa_group *ng;

    /*
     * The p->mm->numa_scan_seq field gets updated without
     * exclusive access. Use READ_ONCE() here to ensure
     * that the field is read in a single access:
     */
    seq = READ_ONCE(p->mm->numa_scan_seq);
    if (p->numa_scan_seq == seq) {
        return;
    }
    p->numa_scan_seq = seq;
    p->numa_scan_period_max = task_scan_max(p);

    total_faults = p->numa_faults_locality[0] + p->numa_faults_locality[1];
    runtime = numa_get_avg_runtime(p, &period);

    /* If the task is part of a group prevent parallel updates to group stats */
    ng = deref_curr_numa_group(p);
    if (ng) {
        group_lock = &ng->lock;
        spin_lock_irq(group_lock);
    }

    /* Find the node with the highest number of faults */
    for_each_online_node(nid)
    {
        /* Keep track of the offsets in numa_faults array */
        int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
        unsigned long faults = 0, group_faults = 0;
        int priv;

        for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
            long diff, f_diff, f_weight;

            mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
            membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
            cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
            cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);

            /* Decay existing window, copy faults since last scan */
            diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 0x2;
            fault_types[priv] += p->numa_faults[membuf_idx];
            p->numa_faults[membuf_idx] = 0;

            /*
             * Normalize the faults_from, so all tasks in a group
             * count according to CPU use, instead of by the raw
             * number of faults. Tasks with little runtime have
             * little over-all impact on throughput, and thus their
             * faults are less important.
             */
            f_weight = div64_u64(runtime << 0x10, period + 1);
            f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / (total_faults + 1);
            f_diff = f_weight - p->numa_faults[cpu_idx] / 0x2;
            p->numa_faults[cpubuf_idx] = 0;

            p->numa_faults[mem_idx] += diff;
            p->numa_faults[cpu_idx] += f_diff;
            faults += p->numa_faults[mem_idx];
            p->total_numa_faults += diff;
            if (ng) {
                /*
                 * safe because we can only change our own group
                 *
                 * mem_idx represents the offset for a given
                 * nid and priv in a specific region because it
                 * is at the beginning of the numa_faults array.
                 */
                ng->faults[mem_idx] += diff;
                ng->faults_cpu[mem_idx] += f_diff;
                ng->total_faults += diff;
                group_faults += ng->faults[mem_idx];
            }
        }

        if (!ng) {
            if (faults > max_faults) {
                max_faults = faults;
                max_nid = nid;
            }
        } else if (group_faults > max_faults) {
            max_faults = group_faults;
            max_nid = nid;
        }
    }

    if (ng) {
        numa_group_count_active_nodes(ng);
        spin_unlock_irq(group_lock);
        max_nid = preferred_group_nid(p, max_nid);
    }

    if (max_faults) {
        /* Set the new preferred node */
        if (max_nid != p->numa_preferred_nid) {
            sched_setnuma(p, max_nid);
        }
    }

    update_task_scan_period(p, fault_types[0], fault_types[1]);
}

static inline int get_numa_group(struct numa_group *grp)
{
    return refcount_inc_not_zero(&grp->refcount);
}

static inline void put_numa_group(struct numa_group *grp)
{
    if (refcount_dec_and_test(&grp->refcount)) {
        kfree_rcu(grp, rcu);
    }
}

static void task_numa_group(struct task_struct *p, int cpupid, int flags, int *priv)
{
    struct numa_group *grp, *my_grp;
    struct task_struct *tsk;
    bool join = false;
    int cpu = cpupid_to_cpu(cpupid);
    int i;

    if (unlikely(!deref_curr_numa_group(p))) {
        unsigned int size = sizeof(struct numa_group) + 0x4 * nr_node_ids * sizeof(unsigned long);

        grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
        if (!grp) {
            return;
        }

        refcount_set(&grp->refcount, 1);
        grp->active_nodes = 1;
        grp->max_faults_cpu = 0;
        spin_lock_init(&grp->lock);
        grp->gid = p->pid;
        /* Second half of the array tracks nids where faults happen */
        grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * nr_node_ids;

        for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
            grp->faults[i] = p->numa_faults[i];
        }

        grp->total_faults = p->total_numa_faults;

        grp->nr_tasks++;
        rcu_assign_pointer(p->numa_group, grp);
    }

    rcu_read_lock();
    tsk = READ_ONCE(cpu_rq(cpu)->curr);
    if (!cpupid_match_pid(tsk, cpupid)) {
        goto no_join;
    }

    grp = rcu_dereference(tsk->numa_group);
    if (!grp) {
        goto no_join;
    }

    my_grp = deref_curr_numa_group(p);
    if (grp == my_grp) {
        goto no_join;
    }

    /*
     * Only join the other group if its bigger; if we're the bigger group,
     * the other task will join us.
     */
    if (my_grp->nr_tasks > grp->nr_tasks) {
        goto no_join;
    }

    /*
     * Tie-break on the grp address.
     */
    if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) {
        goto no_join;
    }

    /* Always join threads in the same process. */
    if (tsk->mm == current->mm) {
        join = true;
    }

    /* Simple filter to avoid false positives due to PID collisions */
    if (flags & TNF_SHARED) {
        join = true;
    }

    /* Update priv based on whether false sharing was detected */
    *priv = !join;

    if (join && !get_numa_group(grp)) {
        goto no_join;
    }

    rcu_read_unlock();

    if (!join) {
        return;
    }

    BUG_ON(irqs_disabled());
    double_lock_irq(&my_grp->lock, &grp->lock);

    for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
        my_grp->faults[i] -= p->numa_faults[i];
        grp->faults[i] += p->numa_faults[i];
    }
    my_grp->total_faults -= p->total_numa_faults;
    grp->total_faults += p->total_numa_faults;

    my_grp->nr_tasks--;
    grp->nr_tasks++;

    spin_unlock(&my_grp->lock);
    spin_unlock_irq(&grp->lock);

    rcu_assign_pointer(p->numa_group, grp);

    put_numa_group(my_grp);
    return;

no_join:
    rcu_read_unlock();
    return;
}

/*
 * Get rid of NUMA staticstics associated with a task (either current or dead).
 * If @final is set, the task is dead and has reached refcount zero, so we can
 * safely free all relevant data structures. Otherwise, there might be
 * concurrent reads from places like load balancing and procfs, and we should
 * reset the data back to default state without freeing ->numa_faults.
 */
void task_numa_free(struct task_struct *p, bool final)
{
    /* safe: p either is current or is being freed by current */
    struct numa_group *grp = rcu_dereference_raw(p->numa_group);
    unsigned long *numa_faults = p->numa_faults;
    unsigned long flags;
    int i;

    if (!numa_faults) {
        return;
    }

    if (grp) {
        spin_lock_irqsave(&grp->lock, flags);
        for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
            grp->faults[i] -= p->numa_faults[i];
        }
        grp->total_faults -= p->total_numa_faults;

        grp->nr_tasks--;
        spin_unlock_irqrestore(&grp->lock, flags);
        RCU_INIT_POINTER(p->numa_group, NULL);
        put_numa_group(grp);
    }

    if (final) {
        p->numa_faults = NULL;
        kfree(numa_faults);
    } else {
        p->total_numa_faults = 0;
        for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
            numa_faults[i] = 0;
        }
    }
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
{
    struct task_struct *p = current;
    bool migrated = flags & TNF_MIGRATED;
    int cpu_node = task_node(current);
    int local = !!(flags & TNF_FAULT_LOCAL);
    struct numa_group *ng;
    int priv;

    if (!static_branch_likely(&sched_numa_balancing)) {
        return;
    }

    /* for example, ksmd faulting in a user's mm */
    if (!p->mm) {
        return;
    }

    /* Allocate buffer to track faults on a per-node basis */
    if (unlikely(!p->numa_faults)) {
        int size = sizeof(*p->numa_faults) * NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;

        p->numa_faults = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
        if (!p->numa_faults) {
            return;
        }

        p->total_numa_faults = 0;
        memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
    }

    /*
     * First accesses are treated as private, otherwise consider accesses
     * to be private if the accessing pid has not changed
     */
    if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
        priv = 1;
    } else {
        priv = cpupid_match_pid(p, last_cpupid);
        if (!priv && !(flags & TNF_NO_GROUP)) {
            task_numa_group(p, last_cpupid, flags, &priv);
        }
    }

    /*
     * If a workload spans multiple NUMA nodes, a shared fault that
     * occurs wholly within the set of nodes that the workload is
     * actively using should be counted as local. This allows the
     * scan rate to slow down when a workload has settled down.
     */
    ng = deref_curr_numa_group(p);
    if (!priv && !local && ng && ng->active_nodes > 1 && numa_is_active_node(cpu_node, ng) &&
        numa_is_active_node(mem_node, ng)) {
        local = 1;
    }

    /*
     * Retry to migrate task to preferred node periodically, in case it
     * previously failed, or the scheduler moved us.
     */
    if (time_after(jiffies, p->numa_migrate_retry)) {
        task_numa_placement(p);
        numa_migrate_preferred(p);
    }

    if (migrated) {
        p->numa_pages_migrated += pages;
    }
    if (flags & TNF_MIGRATE_FAIL) {
        p->numa_faults_locality[0x2] += pages;
    }

    p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
    p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
    p->numa_faults_locality[local] += pages;
}

static void reset_ptenuma_scan(struct task_struct *p)
{
    /*
     * We only did a read acquisition of the mmap sem, so
     * p->mm->numa_scan_seq is written to without exclusive access
     * and the update is not guaranteed to be atomic. That's not
     * much of an issue though, since this is just used for
     * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
     * expensive, to avoid any form of compiler optimizations:
     */
    WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
    p->mm->numa_scan_offset = 0;
}

/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
static void task_numa_work(struct callback_head *work)
{
    unsigned long migrate, next_scan, now = jiffies;
    struct task_struct *p = current;
    struct mm_struct *mm = p->mm;
    u64 runtime = p->se.sum_exec_runtime;
    struct vm_area_struct *vma;
    unsigned long start, end;
    unsigned long nr_pte_updates = 0;
    long pages, virtpages;

    SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));

    work->next = work;
    /*
     * Who cares about NUMA placement when they're dying.
     *
     * NOTE: make sure not to dereference p->mm before this check,
     * exit_task_work() happens _after_ exit_mm() so we could be called
     * without p->mm even though we still had it when we enqueued this
     * work.
     */
    if (p->flags & PF_EXITING) {
        return;
    }

    if (!mm->numa_next_scan) {
        mm->numa_next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
    }

    /*
     * Enforce maximal scan/migration frequency..
     */
    migrate = mm->numa_next_scan;
    if (time_before(now, migrate)) {
        return;
    }

    if (p->numa_scan_period == 0) {
        p->numa_scan_period_max = task_scan_max(p);
        p->numa_scan_period = task_scan_start(p);
    }

    next_scan = now + msecs_to_jiffies(p->numa_scan_period);
    if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) {
        return;
    }

    /*
     * Delay this task enough that another task of this mm will likely win
     * the next time around.
     */
    p->node_stamp += 0x2 * TICK_NSEC;

    start = mm->numa_scan_offset;
    pages = sysctl_numa_balancing_scan_size;
    pages <<= FAIR_TWENTY - PAGE_SHIFT; /* MB in pages */
    virtpages = pages * 0x8;            /* Scan up to this much virtual space */
    if (!pages) {
        return;
    }

    if (!mmap_read_trylock(mm)) {
        return;
    }
    vma = find_vma(mm, start);
    if (!vma) {
        reset_ptenuma_scan(p);
        start = 0;
        vma = mm->mmap;
    }
    for (; vma; vma = vma->vm_next) {
        if (!vma_migratable(vma) || !vma_policy_mof(vma) || is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
            continue;
        }

        /*
         * Shared library pages mapped by multiple processes are not
         * migrated as it is expected they are cache replicated. Avoid
         * hinting faults in read-only file-backed mappings or the vdso
         * as migrating the pages will be of marginal benefit.
         */
        if (!vma->vm_mm || (vma->vm_file && (vma->vm_flags & (VM_READ | VM_WRITE)) == (VM_READ))) {
            continue;
        }

        /*
         * Skip inaccessible VMAs to avoid any confusion between
         * PROT_NONE and NUMA hinting ptes
         */
        if (!vma_is_accessible(vma)) {
            continue;
        }

        do {
            start = max(start, vma->vm_start);
            end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
            end = min(end, vma->vm_end);
            nr_pte_updates = change_prot_numa(vma, start, end);
            /*
             * Try to scan sysctl_numa_balancing_size worth of
             * hpages that have at least one present PTE that
             * is not already pte-numa. If the VMA contains
             * areas that are unused or already full of prot_numa
             * PTEs, scan up to virtpages, to skip through those
             * areas faster.
             */
            if (nr_pte_updates) {
                pages -= (end - start) >> PAGE_SHIFT;
            }
            virtpages -= (end - start) >> PAGE_SHIFT;

            start = end;
            if (pages <= 0 || virtpages <= 0) {
                goto out;
            }

            cond_resched();
        } while (end != vma->vm_end);
    }

out:
    /*
     * It is possible to reach the end of the VMA list but the last few
     * VMAs are not guaranteed to the vma_migratable. If they are not, we
     * would find the !migratable VMA on the next scan but not reset the
     * scanner to the start so check it now.
     */
    if (vma) {
        mm->numa_scan_offset = start;
    } else {
        reset_ptenuma_scan(p);
    }
    mmap_read_unlock(mm);

    /*
     * Make sure tasks use at least 32x as much time to run other code
     * than they used here, to limit NUMA PTE scanning overhead to 3% max.
     * Usually update_task_scan_period slows down scanning enough; on an
     * overloaded system we need to limit overhead on a per task basis.
     */
    if (unlikely(p->se.sum_exec_runtime != runtime)) {
        u64 diff = p->se.sum_exec_runtime - runtime;
        p->node_stamp += 0x20 * diff;
    }
}

void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
    int mm_users = 0;
    struct mm_struct *mm = p->mm;

    if (mm) {
        mm_users = atomic_read(&mm->mm_users);
        if (mm_users == 1) {
            mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
            mm->numa_scan_seq = 0;
        }
    }
    p->node_stamp = 0;
    p->numa_scan_seq = mm ? mm->numa_scan_seq : 0;
    p->numa_scan_period = sysctl_numa_balancing_scan_delay;
    /* Protect against double add, see task_tick_numa and task_numa_work */
    p->numa_work.next = &p->numa_work;
    p->numa_faults = NULL;
    RCU_INIT_POINTER(p->numa_group, NULL);
    p->last_task_numa_placement = 0;
    p->last_sum_exec_runtime = 0;

    init_task_work(&p->numa_work, task_numa_work);

    /* New address space, reset the preferred nid */
    if (!(clone_flags & CLONE_VM)) {
        p->numa_preferred_nid = NUMA_NO_NODE;
        return;
    }

    /*
     * New thread, keep existing numa_preferred_nid which should be copied
     * already by arch_dup_task_struct but stagger when scans start.
     */
    if (mm) {
        unsigned int delay;

        delay = min_t(unsigned int, task_scan_max(current), current->numa_scan_period *mm_users *NSEC_PER_MSEC);
        delay += 0x2 * TICK_NSEC;
        p->node_stamp = delay;
    }
}

/*
 * Drive the periodic memory faults..
 */
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
    struct callback_head *work = &curr->numa_work;
    u64 period, now;

    /*
     * We don't care about NUMA placement if we don't have memory.
     */
    if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work) {
        return;
    }

    /*
     * Using runtime rather than walltime has the dual advantage that
     * we (mostly) drive the selection from busy threads and that the
     * task needs to have done some actual work before we bother with
     * NUMA placement.
     */
    now = curr->se.sum_exec_runtime;
    period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;

    if (now > curr->node_stamp + period) {
        if (!curr->node_stamp) {
            curr->numa_scan_period = task_scan_start(curr);
        }
        curr->node_stamp += period;

        if (!time_before(jiffies, curr->mm->numa_next_scan)) {
            task_work_add(curr, work, TWA_RESUME);
        }
    }
}

static void update_scan_period(struct task_struct *p, int new_cpu)
{
    int src_nid = cpu_to_node(task_cpu(p));
    int dst_nid = cpu_to_node(new_cpu);

    if (!static_branch_likely(&sched_numa_balancing)) {
        return;
    }

    if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING)) {
        return;
    }

    if (src_nid == dst_nid) {
        return;
    }

    /*
     * Allow resets if faults have been trapped before one scan
     * has completed. This is most likely due to a new task that
     * is pulled cross-node due to wakeups or load balancing.
     */
    if (p->numa_scan_seq) {
        /*
         * Avoid scan adjustments if moving to the preferred
         * node or if the task was not previously running on
         * the preferred node.
         */
        if (dst_nid == p->numa_preferred_nid ||
            (p->numa_preferred_nid != NUMA_NO_NODE && src_nid != p->numa_preferred_nid)) {
            return;
        }
    }

    p->numa_scan_period = task_scan_start(p);
}

#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}

static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
}

static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}

static inline void update_scan_period(struct task_struct *p, int new_cpu)
{
}

#endif /* CONFIG_NUMA_BALANCING */

static void account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    update_load_add(&cfs_rq->load, se->load.weight);
#ifdef CONFIG_SMP
    if (entity_is_task(se)) {
        struct rq *rq = rq_of(cfs_rq);

        account_numa_enqueue(rq, task_of(se));
        list_add(&se->group_node, &rq->cfs_tasks);
    }
#endif
    cfs_rq->nr_running++;
}

static void account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    update_load_sub(&cfs_rq->load, se->load.weight);
#ifdef CONFIG_SMP
    if (entity_is_task(se)) {
        account_numa_dequeue(rq_of(cfs_rq), task_of(se));
        list_del_init(&se->group_node);
    }
#endif
    cfs_rq->nr_running--;
}

/*
 * Signed add and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define add_positive(_ptr, _val)                                                                                       \
    do {                                                                                                               \
        typeof(_ptr) ptr = (_ptr);                                                                                     \
        typeof(_val) val = (_val);                                                                                     \
        typeof(*ptr) res, var = READ_ONCE(*ptr);                                                                       \
                                                                                                                       \
        res = var + val;                                                                                               \
                                                                                                                       \
        if (val < 0 && res > var)                                                                                      \
            res = 0;                                                                                                   \
                                                                                                                       \
        WRITE_ONCE(*ptr, res);                                                                                         \
    } while (0)

/*
 * Unsigned subtract and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define sub_positive(_ptr, _val)                                                                                       \
    do {                                                                                                               \
        typeof(_ptr) ptr = (_ptr);                                                                                     \
        typeof(*ptr) val = (_val);                                                                                     \
        typeof(*ptr) res, var = READ_ONCE(*ptr);                                                                       \
        res = var - val;                                                                                               \
        if (res > var)                                                                                                 \
            res = 0;                                                                                                   \
        WRITE_ONCE(*ptr, res);                                                                                         \
    } while (0)

/*
 * Remove and clamp on negative, from a local variable.
 *
 * A variant of sub_positive(), which does not use explicit load-store
 * and is thus optimized for local variable updates.
 */
#define lsub_positive(_ptr, _val)                                                                                      \
    do {                                                                                                               \
        typeof(_ptr) ptr = (_ptr);                                                                                     \
        *ptr -= min_t(typeof(*ptr), *ptr, _val);                                                                       \
    } while (0)

#ifdef CONFIG_SMP
static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    cfs_rq->avg.load_avg += se->avg.load_avg;
    cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
}

static inline void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
    sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
}
#else
static inline void enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}
static inline void dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}
#endif

static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, unsigned long weight)
{
    if (se->on_rq) {
        /* commit outstanding execution time */
        if (cfs_rq->curr == se) {
            update_curr(cfs_rq);
        }
        update_load_sub(&cfs_rq->load, se->load.weight);
    }
    dequeue_load_avg(cfs_rq, se);

    update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
    do {
        u32 divider = get_pelt_divider(&se->avg);

        se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
    } while (0);
#endif

    enqueue_load_avg(cfs_rq, se);
    if (se->on_rq) {
        update_load_add(&cfs_rq->load, se->load.weight);
    }
}

void reweight_task(struct task_struct *p, int prio)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);
    struct load_weight *load = &se->load;
    unsigned long weight = scale_load(sched_prio_to_weight[prio]);

    reweight_entity(cfs_rq, se, weight);
    load->inv_weight = sched_prio_to_wmult[prio];
}

#ifdef CONFIG_FAIR_GROUP_SCHED
#ifdef CONFIG_SMP
/*
 * All this does is approximate the hierarchical proportion which includes that
 * global sum we all love to hate.
 *
 * That is, the weight of a group entity, is the proportional share of the
 * group weight based on the group runqueue weights. That is:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------               (1)
 *                       \Sum grq->load.weight
 *
 * Now, because computing that sum is prohibitively expensive to compute (been
 * there, done that) we approximate it with this average stuff. The average
 * moves slower and therefore the approximation is cheaper and more stable.
 *
 * So instead of the above, we substitute:
 *
 *   grq->load.weight -> grq->avg.load_avg                         (2)
 *
 * which yields the following
 *
 *                     tg->weight * grq->avg.load_avg
 *   ge->load.weight = ------------------------------              (3)
 *                             tg->load_avg
 *
 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
 *
 * That is shares_avg, and it is right (given the approximation (2)).
 *
 * The problem with it is that because the average is slow -- it was designed
 * to be exactly that of course -- this leads to transients in boundary
 * conditions. In specific, the case where the group was idle and we start the
 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
 * yielding bad latency etc..
 *
 * Now, in that special case (1) reduces to:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
 *                         grp->load.weight
 *
 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
 *
 * So what we do is modify our approximation (3) to approach (4) in the (near)
 * UP case, like
 *
 *   ge->load.weight =
 *
 *              tg->weight * grq->load.weight
 *     ---------------------------------------------------         (5)
 *     tg->load_avg - grq->avg.load_avg + grq->load.weight
 *
 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
 * we need to use grq->avg.load_avg as its lower bound, which then gives:
 *
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------           (6)
 *                             tg_load_avg'
 *
 * Where
 *
 *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
 *                  max(grq->load.weight, grq->avg.load_avg)
 *
 * And that is shares_weight and is icky. In the (near) UP case it approaches
 * (4) while in the normal case it approaches (3). It consistently
 * overestimates the ge->load.weight and therefore:
 *
 *   \Sum ge->load.weight >= tg->weight
 *
 * hence icky!
 */
static long calc_group_shares(struct cfs_rq *cfs_rq)
{
    long tg_weight, tg_shares, load, shares;
    struct task_group *tg = cfs_rq->tg;

    tg_shares = READ_ONCE(tg->shares);

    load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);

    tg_weight = atomic_long_read(&tg->load_avg);

    /* Ensure tg_weight >= load */
    tg_weight -= cfs_rq->tg_load_avg_contrib;
    tg_weight += load;

    shares = (tg_shares * load);
    if (tg_weight) {
        shares /= tg_weight;
    }

    /*
     * MIN_SHARES has to be unscaled here to support per-CPU partitioning
     * of a group with small tg->shares value. It is a floor value which is
     * assigned as a minimum load.weight to the sched_entity representing
     * the group on a CPU.
     *
     * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
     * on an 8-core system with 8 tasks each runnable on one CPU shares has
     * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
     * case no task is runnable on a CPU MIN_SHARES=2 should be returned
     * instead of 0.
     */
    return clamp_t(long, shares, MIN_SHARES, tg_shares);
}
#endif /* CONFIG_SMP */

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

/*
 * Recomputes the group entity based on the current state of its group
 * runqueue.
 */
static void update_cfs_group(struct sched_entity *se)
{
    struct cfs_rq *gcfs_rq = group_cfs_rq(se);
    long shares;

    if (!gcfs_rq) {
        return;
    }

    if (throttled_hierarchy(gcfs_rq)) {
        return;
    }

#ifndef CONFIG_SMP
    shares = READ_ONCE(gcfs_rq->tg->shares);
    if (likely(se->load.weight == shares)) {
        return;
    }
#else
    shares = calc_group_shares(gcfs_rq);
#endif

    reweight_entity(cfs_rq_of(se), se, shares);
}

#else  /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_cfs_group(struct sched_entity *se)
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
{
    struct rq *rq = rq_of(cfs_rq);

    if (&rq->cfs == cfs_rq) {
        /*
         * There are a few boundary cases this might miss but it should
         * get called often enough that that should (hopefully) not be
         * a real problem.
         *
         * It will not get called when we go idle, because the idle
         * thread is a different class (!fair), nor will the utilization
         * number include things like RT tasks.
         *
         * As is, the util number is not freq-invariant (we'd have to
         * implement arch_scale_freq_capacity() for that).
         *
         * See cpu_util().
         */
        cpufreq_update_util(rq, flags);
    }
}

#ifdef CONFIG_SMP
#ifdef CONFIG_FAIR_GROUP_SCHED
/**
 * update_tg_load_avg - update the tg's load avg
 * @cfs_rq: the cfs_rq whose avg changed
 *
 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
 * However, because tg->load_avg is a global value there are performance
 * considerations.
 *
 * In order to avoid having to look at the other cfs_rq's, we use a
 * differential update where we store the last value we propagated. This in
 * turn allows skipping updates if the differential is 'small'.
 *
 * Updating tg's load_avg is necessary before update_cfs_share().
 */
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
{
    long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;

    /*
     * No need to update load_avg for root_task_group as it is not used.
     */
    if (cfs_rq->tg == &root_task_group) {
        return;
    }

    if (abs(delta) > cfs_rq->tg_load_avg_contrib / 0x40) {
        atomic_long_add(delta, &cfs_rq->tg->load_avg);
        cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
    }
}

/*
 * Called within set_task_rq() right before setting a task's CPU. The
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se, struct cfs_rq *prev, struct cfs_rq *next)
{
    u64 p_last_update_time;
    u64 n_last_update_time;

    if (!sched_feat(ATTACH_AGE_LOAD)) {
        return;
    }

    /*
     * We are supposed to update the task to "current" time, then its up to
     * date and ready to go to new CPU/cfs_rq. But we have difficulty in
     * getting what current time is, so simply throw away the out-of-date
     * time. This will result in the wakee task is less decayed, but giving
     * the wakee more load sounds not bad.
     */
    if (!(se->avg.last_update_time && prev)) {
        return;
    }

#ifndef CONFIG_64BIT
    {
        u64 p_last_update_time_copy;
        u64 n_last_update_time_copy;

        do {
            p_last_update_time_copy = prev->load_last_update_time_copy;
            n_last_update_time_copy = next->load_last_update_time_copy;

            smp_rmb();

            p_last_update_time = prev->avg.last_update_time;
            n_last_update_time = next->avg.last_update_time;
        } while (p_last_update_time != p_last_update_time_copy || n_last_update_time != n_last_update_time_copy);
    }
#else
    p_last_update_time = prev->avg.last_update_time;
    n_last_update_time = next->avg.last_update_time;
#endif
    __update_load_avg_blocked_se(p_last_update_time, se);
    se->avg.last_update_time = n_last_update_time;
}

/*
 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
 * propagate its contribution. The key to this propagation is the invariant
 * that for each group
 *
 *   ge->avg == grq->avg                        (1)
 *
 * _IFF_ we look at the pure running and runnable sums. Because they
 * represent the very same entity, just at different points in the hierarchy.
 *
 * Per the above update_tg_cfs_util() and update_tg_cfs_runnable() are trivial
 * and simply copies the running/runnable sum over (but still wrong, because
 * the group entity and group rq do not have their PELT windows aligned).
 *
 * However, update_tg_cfs_load() is more complex. So we have:
 *
 *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg        (2)
 *
 * And since, like util, the runnable part should be directly transferable,
 * the following would _appear_ to be the straight forward approach:
 *
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg    (3)
 *
 * And per (1) we have
 *
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
 *
 * Which gives
 *
 *                      ge->load.weight * grq->avg.load_avg
 *   ge->avg.load_avg = -----------------------------------        (4)
 *                               grq->load.weight
 *
 * Except that is wrong!
 *
 * Because while for entities historical weight is not important and we
 * really only care about our future and therefore can consider a pure
 * runnable sum, runqueues can NOT do this.
 *
 * We specifically want runqueues to have a load_avg that includes
 * historical weights. Those represent the blocked load, the load we expect
 * to (shortly) return to us. This only works by keeping the weights as
 * integral part of the sum. We therefore cannot decompose as per (3).
 *
 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
 * runnable section of these tasks overlap (or not). If they were to perfectly
 * align the rq as a whole would be runnable 2/3 of the time. If however we
 * always have at least 1 runnable task, the rq as a whole is always runnable.
 *
 * So we'll have to approximate.. :/
 *
 * Given the constraint
 *
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
 *
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
 *
 * On removal, we'll assume each task is equally runnable; which yields:
 *
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
 *
 * XXX: only do this for the part of runnable > running ?
 *
 */

static inline void update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
    long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
    u32 divider;

    /* Nothing to update */
    if (!delta) {
        return;
    }

    /*
     * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
     * See ___update_load_avg() for details.
     */
    divider = get_pelt_divider(&cfs_rq->avg);

    /* Set new sched_entity's utilization */
    se->avg.util_avg = gcfs_rq->avg.util_avg;
    se->avg.util_sum = se->avg.util_avg * divider;

    /* Update parent cfs_rq utilization */
    add_positive(&cfs_rq->avg.util_avg, delta);
    cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
}

static inline void update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
    long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
    u32 divider;

    /* Nothing to update */
    if (!delta) {
        return;
    }

    /*
     * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
     * See ___update_load_avg() for details.
     */
    divider = get_pelt_divider(&cfs_rq->avg);

    /* Set new sched_entity's runnable */
    se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
    se->avg.runnable_sum = se->avg.runnable_avg * divider;

    /* Update parent cfs_rq runnable */
    add_positive(&cfs_rq->avg.runnable_avg, delta);
    cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
}

static inline void update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
{
    long delta, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
    unsigned long load_avg;
    u64 load_sum = 0;
    u32 divider;

    if (!runnable_sum) {
        return;
    }

    gcfs_rq->prop_runnable_sum = 0;

    /*
     * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
     * See ___update_load_avg() for details.
     */
    divider = get_pelt_divider(&cfs_rq->avg);

    if (runnable_sum >= 0) {
        /*
         * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
         * the CPU is saturated running == runnable.
         */
        runnable_sum += se->avg.load_sum;
        runnable_sum = min_t(long, runnable_sum, divider);
    } else {
        /*
         * Estimate the new unweighted runnable_sum of the gcfs_rq by
         * assuming all tasks are equally runnable.
         */
        if (scale_load_down(gcfs_rq->load.weight)) {
            load_sum = div_s64(gcfs_rq->avg.load_sum, scale_load_down(gcfs_rq->load.weight));
        }

        /* But make sure to not inflate se's runnable */
        runnable_sum = min(se->avg.load_sum, load_sum);
    }

    /*
     * runnable_sum can't be lower than running_sum
     * Rescale running sum to be in the same range as runnable sum
     * running_sum is in [0 : LOAD_AVG_MAX <<  SCHED_CAPACITY_SHIFT]
     * runnable_sum is in [0 : LOAD_AVG_MAX]
     */
    running_sum = se->avg.util_sum >> SCHED_CAPACITY_SHIFT;
    runnable_sum = max(runnable_sum, running_sum);

    load_sum = (s64)se_weight(se) * runnable_sum;
    load_avg = div_s64(load_sum, divider);

    delta = load_avg - se->avg.load_avg;

    se->avg.load_sum = runnable_sum;
    se->avg.load_avg = load_avg;

    add_positive(&cfs_rq->avg.load_avg, delta);
    cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider;
}

static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
{
    cfs_rq->propagate = 1;
    cfs_rq->prop_runnable_sum += runnable_sum;
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq, *gcfs_rq;

    if (entity_is_task(se)) {
        return 0;
    }

    gcfs_rq = group_cfs_rq(se);
    if (!gcfs_rq->propagate) {
        return 0;
    }

    gcfs_rq->propagate = 0;

    cfs_rq = cfs_rq_of(se);

    add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);

    update_tg_cfs_util(cfs_rq, se, gcfs_rq);
    update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
    update_tg_cfs_load(cfs_rq, se, gcfs_rq);

    trace_pelt_cfs_tp(cfs_rq);
    trace_pelt_se_tp(se);

    return 1;
}

/*
 * Check if we need to update the load and the utilization of a blocked
 * group_entity
 */
static inline bool skip_blocked_update(struct sched_entity *se)
{
    struct cfs_rq *gcfs_rq = group_cfs_rq(se);

    /*
     * If sched_entity still have not zero load or utilization, we have to
     * decay it:
     */
    if (se->avg.load_avg || se->avg.util_avg) {
        return false;
    }

    /*
     * If there is a pending propagation, we have to update the load and
     * the utilization of the sched_entity:
     */
    if (gcfs_rq->propagate) {
        return false;
    }

    /*
     * Otherwise, the load and the utilization of the sched_entity is
     * already zero and there is no pending propagation, so it will be a
     * waste of time to try to decay it:
     */
    return true;
}

#else /* CONFIG_FAIR_GROUP_SCHED */

static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
{
}

static inline int propagate_entity_load_avg(struct sched_entity *se)
{
    return 0;
}

static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
{
}

#endif /* CONFIG_FAIR_GROUP_SCHED */

/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_pelt()
 * @cfs_rq: cfs_rq to update
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
 * Returns true if the load decayed or we removed load.
 *
 * Since both these conditions indicate a changed cfs_rq->avg.load we should
 * call update_tg_load_avg() when this function returns true.
 */
static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
{
    unsigned long removed_load = 0, removed_util = 0, removed_runnable = 0;
    struct sched_avg *sa = &cfs_rq->avg;
    int decayed = 0;

    if (cfs_rq->removed.nr) {
        unsigned long r;
        u32 divider = get_pelt_divider(&cfs_rq->avg);

        raw_spin_lock(&cfs_rq->removed.lock);
        swap(cfs_rq->removed.util_avg, removed_util);
        swap(cfs_rq->removed.load_avg, removed_load);
        swap(cfs_rq->removed.runnable_avg, removed_runnable);
        cfs_rq->removed.nr = 0;
        raw_spin_unlock(&cfs_rq->removed.lock);

        r = removed_load;
        sub_positive(&sa->load_avg, r);
        sa->load_sum = sa->load_avg * divider;

        r = removed_util;
        sub_positive(&sa->util_avg, r);
        sub_positive(&sa->util_sum, r * divider);
        /*
         * Because of rounding, se->util_sum might ends up being +1 more than
         * cfs->util_sum. Although this is not a problem by itself, detaching
         * a lot of tasks with the rounding problem between 2 updates of
         * util_avg (~1ms) can make cfs->util_sum becoming null whereas
         * cfs_util_avg is not.
         * Check that util_sum is still above its lower bound for the new
         * util_avg. Given that period_contrib might have moved since the last
         * sync, we are only sure that util_sum must be above or equal to
         *    util_avg * minimum possible divider
         */
        sa->util_sum = max_t(u32, sa->util_sum, sa->util_avg * PELT_MIN_DIVIDER);

        r = removed_runnable;
        sub_positive(&sa->runnable_avg, r);
        sa->runnable_sum = sa->runnable_avg * divider;

        /*
         * removed_runnable is the unweighted version of removed_load so we
         * can use it to estimate removed_load_sum.
         */
        add_tg_cfs_propagate(cfs_rq, -(long)(removed_runnable * divider) >> SCHED_CAPACITY_SHIFT);

        decayed = 1;
    }

    decayed |= __update_load_avg_cfs_rq(now, cfs_rq);

#ifndef CONFIG_64BIT
    smp_wmb();
    cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif

    return decayed;
}

/**
 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
 * @cfs_rq: cfs_rq to attach to
 * @se: sched_entity to attach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    /*
     * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
     * See ___update_load_avg() for details.
     */
    u32 divider = get_pelt_divider(&cfs_rq->avg);

    /*
     * When we attach the @se to the @cfs_rq, we must align the decay
     * window because without that, really weird and wonderful things can
     * happen.
     *
     * XXX illustrate
     */
    se->avg.last_update_time = cfs_rq->avg.last_update_time;
    se->avg.period_contrib = cfs_rq->avg.period_contrib;

    /*
     * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
     * period_contrib. This isn't strictly correct, but since we're
     * entirely outside of the PELT hierarchy, nobody cares if we truncate
     * _sum a little.
     */
    se->avg.util_sum = se->avg.util_avg * divider;

    se->avg.runnable_sum = se->avg.runnable_avg * divider;

    se->avg.load_sum = se->avg.load_avg * divider;
    if (se_weight(se) < se->avg.load_sum)
        se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
    else
        se->avg.load_sum = 1;

    enqueue_load_avg(cfs_rq, se);
    cfs_rq->avg.util_avg += se->avg.util_avg;
    cfs_rq->avg.util_sum += se->avg.util_sum;
    cfs_rq->avg.runnable_avg += se->avg.runnable_avg;
    cfs_rq->avg.runnable_sum += se->avg.runnable_sum;

    add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);

    cfs_rq_util_change(cfs_rq, 0);

    trace_pelt_cfs_tp(cfs_rq);
}

/**
 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
 * @cfs_rq: cfs_rq to detach from
 * @se: sched_entity to detach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    /*
     * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
     * See ___update_load_avg() for details.
     */
    u32 divider = get_pelt_divider(&cfs_rq->avg);

    dequeue_load_avg(cfs_rq, se);
    sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
    cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
    sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
    cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;

    add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);

    cfs_rq_util_change(cfs_rq, 0);

    trace_pelt_cfs_tp(cfs_rq);
}

/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG 0x1
#define SKIP_AGE_LOAD 0x2
#define DO_ATTACH 0x4

/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
    u64 now = cfs_rq_clock_pelt(cfs_rq);
    int decayed;

    /*
     * Track task load average for carrying it to new CPU after migrated, and
     * track group sched_entity load average for task_h_load calc in migration
     */
    if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD)) {
        __update_load_avg_se(now, cfs_rq, se);
    }

    decayed = update_cfs_rq_load_avg(now, cfs_rq);
    decayed |= propagate_entity_load_avg(se);

    if (!se->avg.last_update_time && (flags & DO_ATTACH)) {
        /*
         * DO_ATTACH means we're here from enqueue_entity().
         * !last_update_time means we've passed through
         * migrate_task_rq_fair() indicating we migrated.
         *
         * IOW we're enqueueing a task on a new CPU.
         */
        attach_entity_load_avg(cfs_rq, se);
        update_tg_load_avg(cfs_rq);
    } else if (decayed) {
        cfs_rq_util_change(cfs_rq, 0);

        if (flags & UPDATE_TG) {
            update_tg_load_avg(cfs_rq);
        }
    }
}

#ifndef CONFIG_64BIT
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
    u64 last_update_time_copy;
    u64 last_update_time;

    do {
        last_update_time_copy = cfs_rq->load_last_update_time_copy;
        smp_rmb();
        last_update_time = cfs_rq->avg.last_update_time;
    } while (last_update_time != last_update_time_copy);

    return last_update_time;
}
#else
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
    return cfs_rq->avg.last_update_time;
}
#endif

/*
 * Synchronize entity load avg of dequeued entity without locking
 * the previous rq.
 */
static void sync_entity_load_avg(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq = cfs_rq_of(se);
    u64 last_update_time;

    last_update_time = cfs_rq_last_update_time(cfs_rq);
    __update_load_avg_blocked_se(last_update_time, se);
}

/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
static void remove_entity_load_avg(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq = cfs_rq_of(se);
    unsigned long flags;

    /*
     * tasks cannot exit without having gone through wake_up_new_task() ->
     * post_init_entity_util_avg() which will have added things to the
     * cfs_rq, so we can remove unconditionally.
     */

    sync_entity_load_avg(se);

    raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
    ++cfs_rq->removed.nr;
    cfs_rq->removed.util_avg += se->avg.util_avg;
    cfs_rq->removed.load_avg += se->avg.load_avg;
    cfs_rq->removed.runnable_avg += se->avg.runnable_avg;
    raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
}

static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq)
{
    return cfs_rq->avg.runnable_avg;
}

static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
{
    return cfs_rq->avg.load_avg;
}

static int newidle_balance(struct rq *this_rq, struct rq_flags *rf);

static inline unsigned long task_util(struct task_struct *p)
{
#ifdef CONFIG_SCHED_WALT
    if (likely(!walt_disabled && sysctl_sched_use_walt_task_util)) {
        return p->ravg.demand_scaled;
    }
#endif
    return READ_ONCE(p->se.avg.util_avg);
}

static inline unsigned long _task_util_est(struct task_struct *p)
{
    struct util_est ue = READ_ONCE(p->se.avg.util_est);

    return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED));
}

static inline unsigned long task_util_est(struct task_struct *p)
{
#ifdef CONFIG_SCHED_WALT
    if (likely(!walt_disabled && sysctl_sched_use_walt_task_util)) {
        return p->ravg.demand_scaled;
    }
#endif
    return max(task_util(p), _task_util_est(p));
}

#ifdef CONFIG_UCLAMP_TASK
#ifdef CONFIG_SCHED_RT_CAS
unsigned long uclamp_task_util(struct task_struct *p)
#else
static inline unsigned long uclamp_task_util(struct task_struct *p)
#endif
{
    return clamp(task_util_est(p), uclamp_eff_value(p, UCLAMP_MIN), uclamp_eff_value(p, UCLAMP_MAX));
}
#else
#ifdef CONFIG_SCHED_RT_CAS
unsigned long uclamp_task_util(struct task_struct *p)
#else
static inline unsigned long uclamp_task_util(struct task_struct *p)
#endif
{
    return task_util_est(p);
}
#endif

static inline void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p)
{
    unsigned int enqueued;

    if (!sched_feat(UTIL_EST)) {
        return;
    }

    /* Update root cfs_rq's estimated utilization */
    enqueued = cfs_rq->avg.util_est.enqueued;
    enqueued += _task_util_est(p);
    WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);

    trace_sched_util_est_cfs_tp(cfs_rq);
}

static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p)
{
    unsigned int enqueued;

    if (!sched_feat(UTIL_EST)) {
        return;
    }

    /* Update root cfs_rq's estimated utilization */
    enqueued = cfs_rq->avg.util_est.enqueued;
    enqueued -= min_t(unsigned int, enqueued, _task_util_est(p));
    WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);

    trace_sched_util_est_cfs_tp(cfs_rq);
}

#define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / FAIR_ONEHUNDRED)

/*
 * Check if a (signed) value is within a specified (unsigned) margin,
 * based on the observation that
 *
 *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
 *
 * NOTE: this only works when value + maring < INT_MAX.
 */
static inline bool within_margin(int value, int margin)
{
    return ((unsigned int)(value + margin - 1) < (0x2 * margin - 1));
}

static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
    long last_ewma_diff, last_enqueued_diff;
    struct util_est ue;

    if (!sched_feat(UTIL_EST)) {
        return;
    }

    /*
     * Skip update of task's estimated utilization when the task has not
     * yet completed an activation, e.g. being migrated.
     */
    if (!task_sleep) {
        return;
    }

    /*
     * If the PELT values haven't changed since enqueue time,
     * skip the util_est update.
     */
    ue = p->se.avg.util_est;
    if (ue.enqueued & UTIL_AVG_UNCHANGED) {
        return;
    }

    last_enqueued_diff = ue.enqueued;

    /*
     * Reset EWMA on utilization increases, the moving average is used only
     * to smooth utilization decreases.
     */
    ue.enqueued = task_util(p);
    if (sched_feat(UTIL_EST_FASTUP)) {
        if (ue.ewma < ue.enqueued) {
            ue.ewma = ue.enqueued;
            goto done;
        }
    }

    /*
     * Skip update of task's estimated utilization when its members are
     * already ~1% close to its last activation value.
     */
    last_ewma_diff = ue.enqueued - ue.ewma;
    last_enqueued_diff -= ue.enqueued;
    if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) {
        if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN)) {
            goto done;
        }

        return;
    }

    /*
     * To avoid overestimation of actual task utilization, skip updates if
     * we cannot grant there is idle time in this CPU.
     */
    if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq)))) {
        return;
    }

    /*
     * Update Task's estimated utilization
     *
     * When *p completes an activation we can consolidate another sample
     * of the task size. This is done by storing the current PELT value
     * as ue.enqueued and by using this value to update the Exponential
     * Weighted Moving Average (EWMA):
     *
     *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
     *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
     *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
     *          = w * (      last_ewma_diff            ) +     ewma(t-1)
     *          = w * (last_ewma_diff  +  ewma(t-1) / w)
     *
     * Where 'w' is the weight of new samples, which is configured to be
     * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
     */
    ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
    ue.ewma += last_ewma_diff;
    ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
done:
    ue.enqueued |= UTIL_AVG_UNCHANGED;
    WRITE_ONCE(p->se.avg.util_est, ue);

    trace_sched_util_est_se_tp(&p->se);
}

static inline int task_fits_capacity(struct task_struct *p, long capacity)
{
    return fits_capacity(uclamp_task_util(p), capacity);
}

#ifdef CONFIG_SCHED_RTG
bool task_fits_max(struct task_struct *p, int cpu)
{
    unsigned long capacity = capacity_orig_of(cpu);
    unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity;
    if (capacity == max_capacity) {
        return true;
    }

    return task_fits_capacity(p, capacity);
}
#endif

static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
{
    bool task_fits = false;
#ifdef CONFIG_SCHED_RTG
    int cpu = cpu_of(rq);
    struct cpumask *rtg_target = NULL;
#endif

    if (!static_branch_unlikely(&sched_asym_cpucapacity)) {
        return;
    }

    if (!p || p->nr_cpus_allowed == 1) {
        rq->misfit_task_load = 0;
        return;
    }

#ifdef CONFIG_SCHED_RTG
    rtg_target = find_rtg_target(p);
    if (rtg_target) {
        task_fits = capacity_orig_of(cpu) >= capacity_orig_of(cpumask_first(rtg_target));
    } else {
        task_fits = task_fits_capacity(p, capacity_of(cpu_of(rq)));
    }
#else
    task_fits = task_fits_capacity(p, capacity_of(cpu_of(rq)));
#endif
    if (task_fits) {
        rq->misfit_task_load = 0;
        return;
    }

    /*
     * Make sure that misfit_task_load will not be null even if
     * task_h_load() returns 0.
     */
    rq->misfit_task_load = max_t(unsigned long, task_h_load(p), 1);
}

#else /* CONFIG_SMP */

#define UPDATE_TG 0x0
#define SKIP_AGE_LOAD 0x0
#define DO_ATTACH 0x0

static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
{
    cfs_rq_util_change(cfs_rq, 0);
}

static inline void remove_entity_load_avg(struct sched_entity *se)
{
}

static inline void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}
static inline void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline int newidle_balance(struct rq *rq, struct rq_flags *rf)
{
    return 0;
}

static inline void util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p)
{
}

static inline void util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p)
{
}

static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
}
static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
{
}

#endif /* CONFIG_SMP */

static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
    s64 d = se->vruntime - cfs_rq->min_vruntime;

    if (d < 0) {
        d = -d;
    }

    if (d > 0x3 * sysctl_sched_latency) {
        schedstat_inc(cfs_rq->nr_spread_over);
    }
#endif
}

static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
    u64 vruntime = cfs_rq->min_vruntime;

    /*
     * The 'current' period is already promised to the current tasks,
     * however the extra weight of the new task will slow them down a
     * little, place the new task so that it fits in the slot that
     * stays open at the end.
     */
    if (initial && sched_feat(START_DEBIT)) {
        vruntime += sched_vslice(cfs_rq, se);
    }

    /* sleeps up to a single latency don't count. */
    if (!initial) {
        unsigned long thresh = sysctl_sched_latency;

        /*
         * Halve their sleep time's effect, to allow
         * for a gentler effect of sleepers:
         */
        if (sched_feat(GENTLE_FAIR_SLEEPERS)) {
            thresh >>= 1;
        }

        vruntime -= thresh;
    }

    /* ensure we never gain time by being placed backwards. */
    se->vruntime = max_vruntime(se->vruntime, vruntime);
}

static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
    if (schedstat_enabled()) {
        return;
    }

    /* Force schedstat enabled if a dependent tracepoint is active */
    if (trace_sched_stat_wait_enabled() || trace_sched_stat_sleep_enabled() || trace_sched_stat_iowait_enabled() ||
        trace_sched_stat_blocked_enabled() || trace_sched_stat_runtime_enabled()) {
        printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
                             "stat_blocked and stat_runtime require the "
                             "kernel parameter schedstats=enable or "
                             "kernel.sched_schedstats=1\n");
    }
#endif
}

static inline bool cfs_bandwidth_used(void);

/*
 * MIGRATION
 *
 *    dequeue
 *      update_curr()
 *        update_min_vruntime()
 *      vruntime -= min_vruntime
 *
 *    enqueue
 *      update_curr()
 *        update_min_vruntime()
 *      vruntime += min_vruntime
 *
 * this way the vruntime transition between RQs is done when both
 * min_vruntime are up-to-date.
 *
 * WAKEUP (remote)
 *
 *    ->migrate_task_rq_fair() (p->state == TASK_WAKING)
 *      vruntime -= min_vruntime
 *
 *    enqueue
 *      update_curr()
 *        update_min_vruntime()
 *      vruntime += min_vruntime
 *
 * this way we don't have the most up-to-date min_vruntime on the originating
 * CPU and an up-to-date min_vruntime on the destination CPU.
 */

static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
    bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
    bool curr = cfs_rq->curr == se;

    /*
     * If we're the current task, we must renormalise before calling
     * update_curr().
     */
    if (renorm && curr) {
        se->vruntime += cfs_rq->min_vruntime;
    }

    update_curr(cfs_rq);

    /*
     * Otherwise, renormalise after, such that we're placed at the current
     * moment in time, instead of some random moment in the past. Being
     * placed in the past could significantly boost this task to the
     * fairness detriment of existing tasks.
     */
    if (renorm && !curr) {
        se->vruntime += cfs_rq->min_vruntime;
    }

    /*
     * When enqueuing a sched_entity, we must:
     *   - Update loads to have both entity and cfs_rq synced with now.
     *   - Add its load to cfs_rq->runnable_avg
     *   - For group_entity, update its weight to reflect the new share of
     *     its group cfs_rq
     *   - Add its new weight to cfs_rq->load.weight
     */
    update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
    se_update_runnable(se);
    update_cfs_group(se);
    account_entity_enqueue(cfs_rq, se);

    if (flags & ENQUEUE_WAKEUP) {
        place_entity(cfs_rq, se, 0);
    }

    check_schedstat_required();
    update_stats_enqueue(cfs_rq, se, flags);
    check_spread(cfs_rq, se);
    if (!curr) {
        fair_enqueue_entity(cfs_rq, se);
    }
    se->on_rq = 1;

    /*
     * When bandwidth control is enabled, cfs might have been removed
     * because of a parent been throttled but cfs->nr_running > 1. Try to
     * add it unconditionnally.
     */
    if (cfs_rq->nr_running == 1 || cfs_bandwidth_used()) {
        list_add_leaf_cfs_rq(cfs_rq);
    }

    if (cfs_rq->nr_running == 1) {
        check_enqueue_throttle(cfs_rq);
    }
}

static void fair_clear_buddies_last(struct sched_entity *se)
{
    for_each_sched_entity(se) {
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        if (cfs_rq->last != se) {
            break;
        }

        cfs_rq->last = NULL;
    }
}

static void fair_clear_buddies_next(struct sched_entity *se)
{
    for_each_sched_entity(se) {
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        if (cfs_rq->next != se) {
            break;
        }

        cfs_rq->next = NULL;
    }
}

static void fair_clear_buddies_skip(struct sched_entity *se)
{
    for_each_sched_entity(se) {
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        if (cfs_rq->skip != se) {
            break;
        }

        cfs_rq->skip = NULL;
    }
}

static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    if (cfs_rq->last == se) {
        fair_clear_buddies_last(se);
    }

    if (cfs_rq->next == se) {
        fair_clear_buddies_next(se);
    }

    if (cfs_rq->skip == se) {
        fair_clear_buddies_skip(se);
    }
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
    /*
     * Update run-time statistics of the 'current'.
     */
    update_curr(cfs_rq);

    /*
     * When dequeuing a sched_entity, we must:
     *   - Update loads to have both entity and cfs_rq synced with now.
     *   - Subtract its load from the cfs_rq->runnable_avg.
     *   - Subtract its previous weight from cfs_rq->load.weight.
     *   - For group entity, update its weight to reflect the new share
     *     of its group cfs_rq.
     */
    update_load_avg(cfs_rq, se, UPDATE_TG);
    se_update_runnable(se);

    update_stats_dequeue(cfs_rq, se, flags);

    clear_buddies(cfs_rq, se);

    if (se != cfs_rq->curr) {
        fair_dequeue_entity(cfs_rq, se);
    }
    se->on_rq = 0;
    account_entity_dequeue(cfs_rq, se);

    /*
     * Normalize after update_curr(); which will also have moved
     * min_vruntime if @se is the one holding it back. But before doing
     * update_min_vruntime() again, which will discount @se's position and
     * can move min_vruntime forward still more.
     */
    if (!(flags & DEQUEUE_SLEEP)) {
        se->vruntime -= cfs_rq->min_vruntime;
    }

    /* return excess runtime on last dequeue */
    return_cfs_rq_runtime(cfs_rq);

    update_cfs_group(se);

    /*
     * Now advance min_vruntime if @se was the entity holding it back,
     * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
     * put back on, and if we advance min_vruntime, we'll be placed back
     * further than we started -- ie. we'll be penalized.
     */
    if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE) {
        update_min_vruntime(cfs_rq);
    }
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
    unsigned long ideal_runtime, delta_exec;
    struct sched_entity *se;
    s64 delta;

    ideal_runtime = sched_slice(cfs_rq, curr);
    delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
    if (delta_exec > ideal_runtime) {
        resched_curr(rq_of(cfs_rq));
        /*
         * The current task ran long enough, ensure it doesn't get
         * re-elected due to buddy favours.
         */
        clear_buddies(cfs_rq, curr);
        return;
    }

    /*
     * Ensure that a task that missed wakeup preemption by a
     * narrow margin doesn't have to wait for a full slice.
     * This also mitigates buddy induced latencies under load.
     */
    if (delta_exec < (unsigned long)sysctl_sched_min_granularity) {
        return;
    }

    se = __pick_first_entity(cfs_rq);
    delta = curr->vruntime - se->vruntime;

    if (delta < 0) {
        return;
    }

    if (delta > ideal_runtime) {
        resched_curr(rq_of(cfs_rq));
    }
}

static void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
    /* 'current' is not kept within the tree. */
    if (se->on_rq) {
        /*
         * Any task has to be enqueued before it get to execute on
         * a CPU. So account for the time it spent waiting on the
         * runqueue.
         */
        update_stats_wait_end(cfs_rq, se);
        fair_dequeue_entity(cfs_rq, se);
        update_load_avg(cfs_rq, se, UPDATE_TG);
    }

    update_stats_curr_start(cfs_rq, se);
    cfs_rq->curr = se;

    /*
     * Track our maximum slice length, if the CPU's load is at
     * least twice that of our own weight (i.e. dont track it
     * when there are only lesser-weight tasks around):
     */
    if (schedstat_enabled() && rq_of(cfs_rq)->cfs.load.weight >= 0x2 * se->load.weight) {
        schedstat_set(se->statistics.slice_max, max((u64)schedstat_val(se->statistics.slice_max),
                                                    se->sum_exec_runtime - se->prev_sum_exec_runtime));
    }

    se->prev_sum_exec_runtime = se->sum_exec_runtime;
}

static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

/*
 * Pick the next process, keeping these things in mind, in this order:
 * 1) keep things fair between processes/task groups
 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
    struct sched_entity *left = __pick_first_entity(cfs_rq);
    struct sched_entity *se;

    /*
     * If curr is set we have to see if its left of the leftmost entity
     * still in the tree, provided there was anything in the tree at all.
     */
    if (!left || (curr && entity_before(curr, left))) {
        left = curr;
    }

    se = left; /* ideally we run the leftmost entity */

    /*
     * Avoid running the skip buddy, if running something else can
     * be done without getting too unfair.
     */
    if (cfs_rq->skip == se) {
        struct sched_entity *second;

        if (se == curr) {
            second = __pick_first_entity(cfs_rq);
        } else {
            second = fair_pick_next_entity(se);
            if (!second || (curr && entity_before(curr, second))) {
                second = curr;
            }
        }

        if (second && wakeup_preempt_entity(second, left) < 1) {
            se = second;
        }
    }

    if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) {
        /*
         * Someone really wants this to run. If it's not unfair, run it.
         */
        se = cfs_rq->next;
    } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) {
        /*
         * Prefer last buddy, try to return the CPU to a preempted task.
         */
        se = cfs_rq->last;
    }

    clear_buddies(cfs_rq, se);

    return se;
}

static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
{
    /*
     * If still on the runqueue then deactivate_task()
     * was not called and update_curr() has to be done:
     */
    if (prev->on_rq) {
        update_curr(cfs_rq);
    }

    /* throttle cfs_rqs exceeding runtime */
    check_cfs_rq_runtime(cfs_rq);

    check_spread(cfs_rq, prev);

    if (prev->on_rq) {
        update_stats_wait_start(cfs_rq, prev);
        /* Put 'current' back into the tree. */
        fair_enqueue_entity(cfs_rq, prev);
        /* in !on_rq case, update occurred at dequeue */
        update_load_avg(cfs_rq, prev, 0);
    }
    cfs_rq->curr = NULL;
}

static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
{
    /*
     * Update run-time statistics of the 'current'.
     */
    update_curr(cfs_rq);

    /*
     * Ensure that runnable average is periodically updated.
     */
    update_load_avg(cfs_rq, curr, UPDATE_TG);
    update_cfs_group(curr);

#ifdef CONFIG_SCHED_HRTICK
    /*
     * queued ticks are scheduled to match the slice, so don't bother
     * validating it and just reschedule.
     */
    if (queued) {
        resched_curr(rq_of(cfs_rq));
        return;
    }
    /*
     * don't let the period tick interfere with the hrtick preemption
     */
    if (!sched_feat(DOUBLE_TICK) && hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) {
        return;
    }
#endif

    if (cfs_rq->nr_running > 1) {
        check_preempt_tick(cfs_rq, curr);
    }
}

/**************************************************
 * CFS bandwidth control machinery
 */

#ifdef CONFIG_CFS_BANDWIDTH

#ifdef CONFIG_JUMP_LABEL
static struct static_key fair_cfs_bandwidth_used;

static inline bool cfs_bandwidth_used(void)
{
    return static_key_false(&fair_cfs_bandwidth_used);
}

void cfs_bandwidth_usage_inc(void)
{
    static_key_slow_inc_cpuslocked(&fair_cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
    static_key_slow_dec_cpuslocked(&fair_cfs_bandwidth_used);
}
#else  /* CONFIG_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
    return true;
}

void cfs_bandwidth_usage_inc(void)
{
}
void cfs_bandwidth_usage_dec(void)
{
}
#endif /* CONFIG_JUMP_LABEL */

/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
    return 100000000ULL;
}

static inline u64 sched_cfs_bandwidth_slice(void)
{
    return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

/*
 * Replenish runtime according to assigned quota. We use sched_clock_cpu
 * directly instead of rq->clock to avoid adding additional synchronization
 * around rq->lock.
 *
 * requires cfs_b->lock
 */
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
{
    if (cfs_b->quota != RUNTIME_INF) {
        cfs_b->runtime = cfs_b->quota;
    }
}

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
    return &tg->cfs_bandwidth;
}

/* returns 0 on failure to allocate runtime */
static int fair_assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b, struct cfs_rq *cfs_rq, u64 target_runtime)
{
    u64 min_amount, amount = 0;

    lockdep_assert_held(&cfs_b->lock);

    /* note: this is a positive sum as runtime_remaining <= 0 */
    min_amount = target_runtime - cfs_rq->runtime_remaining;

    if (cfs_b->quota == RUNTIME_INF) {
        amount = min_amount;
    } else {
        start_cfs_bandwidth(cfs_b);

        if (cfs_b->runtime > 0) {
            amount = min(cfs_b->runtime, min_amount);
            cfs_b->runtime -= amount;
            cfs_b->idle = 0;
        }
    }

    cfs_rq->runtime_remaining += amount;

    return cfs_rq->runtime_remaining > 0;
}

/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
    int ret;

    raw_spin_lock(&cfs_b->lock);
    ret = fair_assign_cfs_rq_runtime(cfs_b, cfs_rq, sched_cfs_bandwidth_slice());
    raw_spin_unlock(&cfs_b->lock);

    return ret;
}

static void fair_account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
    /* dock delta_exec before expiring quota (as it could span periods) */
    cfs_rq->runtime_remaining -= delta_exec;

    if (likely(cfs_rq->runtime_remaining > 0)) {
        return;
    }

    if (cfs_rq->throttled) {
        return;
    }
    /*
     * if we're unable to extend our runtime we resched so that the active
     * hierarchy can be throttled
     */
    if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) {
        resched_curr(rq_of(cfs_rq));
    }
}

static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
    if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) {
        return;
    }

    fair_account_cfs_rq_runtime(cfs_rq, delta_exec);
}

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
    return cfs_bandwidth_used() && cfs_rq->throttled;
}

/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
    return cfs_bandwidth_used() && cfs_rq->throttle_count;
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu)
{
    struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

    src_cfs_rq = tg->cfs_rq[src_cpu];
    dest_cfs_rq = tg->cfs_rq[dest_cpu];

    return throttled_hierarchy(src_cfs_rq) || throttled_hierarchy(dest_cfs_rq);
}

static int tg_unthrottle_up(struct task_group *tg, void *data)
{
    struct rq *rq = data;
    struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

    cfs_rq->throttle_count--;
    if (!cfs_rq->throttle_count) {
        cfs_rq->throttled_clock_pelt_time += rq_clock_task(rq) - cfs_rq->throttled_clock_pelt;

        /* Add cfs_rq with already running entity in the list */
        if (cfs_rq->nr_running >= 1) {
            list_add_leaf_cfs_rq(cfs_rq);
        }
    }

    return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
    struct rq *rq = data;
    struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

    /* group is entering throttled state, stop time */
    if (!cfs_rq->throttle_count) {
        cfs_rq->throttled_clock_pelt = rq_clock_task(rq);
        list_del_leaf_cfs_rq(cfs_rq);
    }
    cfs_rq->throttle_count++;

    return 0;
}

static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
{
    struct rq *rq = rq_of(cfs_rq);
    struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
    struct sched_entity *se;
    long task_delta, idle_task_delta, dequeue = 1;

    raw_spin_lock(&cfs_b->lock);
    /* This will start the period timer if necessary */
    if (fair_assign_cfs_rq_runtime(cfs_b, cfs_rq, 1)) {
        /*
         * We have raced with bandwidth becoming available, and if we
         * actually throttled the timer might not unthrottle us for an
         * entire period. We additionally needed to make sure that any
         * subsequent check_cfs_rq_runtime calls agree not to throttle
         * us, as we may commit to do cfs put_prev+pick_next, so we ask
         * for 1ns of runtime rather than just check cfs_b.
         */
        dequeue = 0;
    } else {
        list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
    }
    raw_spin_unlock(&cfs_b->lock);

    if (!dequeue) {
        return false; /* Throttle no longer required. */
    }

    se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

    /* freeze hierarchy runnable averages while throttled */
    rcu_read_lock();
    walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
    rcu_read_unlock();

    task_delta = cfs_rq->h_nr_running;
    idle_task_delta = cfs_rq->idle_h_nr_running;
    for_each_sched_entity(se) {
        struct cfs_rq *qcfs_rq = cfs_rq_of(se);
        /* throttled entity or throttle-on-deactivate */
        if (!se->on_rq) {
            break;
        }

        if (dequeue) {
            dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
        } else {
            update_load_avg(qcfs_rq, se, 0);
            se_update_runnable(se);
        }

        qcfs_rq->h_nr_running -= task_delta;
        qcfs_rq->idle_h_nr_running -= idle_task_delta;
        walt_dec_throttled_cfs_rq_stats(&qcfs_rq->walt_stats, cfs_rq);

        if (qcfs_rq->load.weight) {
            dequeue = 0;
        }
    }

    if (!se) {
        sub_nr_running(rq, task_delta);
        walt_dec_throttled_cfs_rq_stats(&rq->walt_stats, cfs_rq);
    }

    /*
     * Note: distribution will already see us throttled via the
     * throttled-list.  rq->lock protects completion.
     */
    cfs_rq->throttled = 1;
    cfs_rq->throttled_clock = rq_clock(rq);
    return true;
}

void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
{
    struct rq *rq = rq_of(cfs_rq);
    struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
    struct sched_entity *se;
    long task_delta, idle_task_delta;
    struct cfs_rq *tcfs_rq __maybe_unused = cfs_rq;

    se = cfs_rq->tg->se[cpu_of(rq)];

    cfs_rq->throttled = 0;

    update_rq_clock(rq);

    raw_spin_lock(&cfs_b->lock);
    cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
    list_del_rcu(&cfs_rq->throttled_list);
    raw_spin_unlock(&cfs_b->lock);

    /* update hierarchical throttle state */
    walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

    if (!cfs_rq->load.weight) {
        return;
    }

    task_delta = cfs_rq->h_nr_running;
    idle_task_delta = cfs_rq->idle_h_nr_running;
    for_each_sched_entity(se) {
        if (se->on_rq) {
            break;
        }
        cfs_rq = cfs_rq_of(se);
        enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);

        cfs_rq->h_nr_running += task_delta;
        cfs_rq->idle_h_nr_running += idle_task_delta;
        walt_inc_throttled_cfs_rq_stats(&cfs_rq->walt_stats, tcfs_rq);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto unthrottle_throttle;
        }
    }

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);

        update_load_avg(cfs_rq, se, UPDATE_TG);
        se_update_runnable(se);

        cfs_rq->h_nr_running += task_delta;
        cfs_rq->idle_h_nr_running += idle_task_delta;
        walt_inc_throttled_cfs_rq_stats(&cfs_rq->walt_stats, tcfs_rq);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto unthrottle_throttle;
        }

        /*
         * One parent has been throttled and cfs_rq removed from the
         * list. Add it back to not break the leaf list.
         */
        if (throttled_hierarchy(cfs_rq)) {
            list_add_leaf_cfs_rq(cfs_rq);
        }
    }

    /* At this point se is NULL and we are at root level */
    add_nr_running(rq, task_delta);
    walt_inc_throttled_cfs_rq_stats(&rq->walt_stats, tcfs_rq);

unthrottle_throttle:
    /*
     * The cfs_rq_throttled() breaks in the above iteration can result in
     * incomplete leaf list maintenance, resulting in triggering the
     * assertion below.
     */
    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        if (list_add_leaf_cfs_rq(cfs_rq)) {
            break;
        }
    }

    assert_list_leaf_cfs_rq(rq);

    /* Determine whether we need to wake up potentially idle CPU: */
    if (rq->curr == rq->idle && rq->cfs.nr_running) {
        resched_curr(rq);
    }
}

static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
{
    struct cfs_rq *cfs_rq;
    u64 runtime, remaining = 1;

    rcu_read_lock();
    list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, throttled_list)
    {
        struct rq *rq = rq_of(cfs_rq);
        struct rq_flags rf;

        rq_lock_irqsave(rq, &rf);
        if (!cfs_rq_throttled(cfs_rq)) {
            goto next;
        }

        /* By the above check, this should never be true */
        SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);

        raw_spin_lock(&cfs_b->lock);
        runtime = -cfs_rq->runtime_remaining + 1;
        if (runtime > cfs_b->runtime) {
            runtime = cfs_b->runtime;
        }
        cfs_b->runtime -= runtime;
        remaining = cfs_b->runtime;
        raw_spin_unlock(&cfs_b->lock);

        cfs_rq->runtime_remaining += runtime;

        /* we check whether we're throttled above */
        if (cfs_rq->runtime_remaining > 0) {
            unthrottle_cfs_rq(cfs_rq);
        }

    next:
        rq_unlock_irqrestore(rq, &rf);

        if (!remaining) {
            break;
        }
    }
    rcu_read_unlock();
}

/*
 * Responsible for refilling a task_group's bandwidth and unthrottling its
 * cfs_rqs as appropriate. If there has been no activity within the last
 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
 * used to track this state.
 */
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun, unsigned long flags)
{
    int throttled;

    /* no need to continue the timer with no bandwidth constraint */
    if (cfs_b->quota == RUNTIME_INF) {
        goto out_deactivate;
    }

    throttled = !list_empty(&cfs_b->throttled_cfs_rq);
    cfs_b->nr_periods += overrun;

    /*
     * idle depends on !throttled (for the case of a large deficit), and if
     * we're going inactive then everything else can be deferred
     */
    if (cfs_b->idle && !throttled) {
        goto out_deactivate;
    }

    __refill_cfs_bandwidth_runtime(cfs_b);

    if (!throttled) {
        /* mark as potentially idle for the upcoming period */
        cfs_b->idle = 1;
        return 0;
    }

    /* account preceding periods in which throttling occurred */
    cfs_b->nr_throttled += overrun;

    /*
     * This check is repeated as we release cfs_b->lock while we unthrottle.
     */
    while (throttled && cfs_b->runtime > 0) {
        raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
        /* we can't nest cfs_b->lock while distributing bandwidth */
        distribute_cfs_runtime(cfs_b);
        raw_spin_lock_irqsave(&cfs_b->lock, flags);

        throttled = !list_empty(&cfs_b->throttled_cfs_rq);
    }

    /*
     * While we are ensured activity in the period following an
     * unthrottle, this also covers the case in which the new bandwidth is
     * insufficient to cover the existing bandwidth deficit.  (Forcing the
     * timer to remain active while there are any throttled entities.)
     */
    cfs_b->idle = 0;

    return 0;

out_deactivate:
    return 1;
}

/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;

/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
 * hrtimer base being cleared by hrtimer_start. In the case of
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
    struct hrtimer *refresh_timer = &cfs_b->period_timer;
    s64 remaining;

    /* if the call-back is running a quota refresh is already occurring */
    if (hrtimer_callback_running(refresh_timer)) {
        return 1;
    }

    /* is a quota refresh about to occur? */
    remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
    if (remaining < (s64)min_expire) {
        return 1;
    }

    return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
    u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

    /* if there's a quota refresh soon don't bother with slack */
    if (runtime_refresh_within(cfs_b, min_left)) {
        return;
    }

    /* don't push forwards an existing deferred unthrottle */
    if (cfs_b->slack_started) {
        return;
    }
    cfs_b->slack_started = true;

    hrtimer_start(&cfs_b->slack_timer, ns_to_ktime(cfs_bandwidth_slack_period), HRTIMER_MODE_REL);
}

/* we know any runtime found here is valid as update_curr() precedes return */
static void fair_return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
    s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

    if (slack_runtime <= 0) {
        return;
    }

    raw_spin_lock(&cfs_b->lock);
    if (cfs_b->quota != RUNTIME_INF) {
        cfs_b->runtime += slack_runtime;

        /* we are under rq->lock, defer unthrottling using a timer */
        if (cfs_b->runtime > sched_cfs_bandwidth_slice() && !list_empty(&cfs_b->throttled_cfs_rq)) {
            start_cfs_slack_bandwidth(cfs_b);
        }
    }
    raw_spin_unlock(&cfs_b->lock);

    /* even if it's not valid for return we don't want to try again */
    cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    if (!cfs_bandwidth_used()) {
        return;
    }

    if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) {
        return;
    }

    fair_return_cfs_rq_runtime(cfs_rq);
}

/*
 * This is done with a timer (instead of inline with bandwidth return) since
 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
 */
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
    u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
    unsigned long flags;

    /* confirm we're still not at a refresh boundary */
    raw_spin_lock_irqsave(&cfs_b->lock, flags);
    cfs_b->slack_started = false;

    if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
        raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
        return;
    }

    if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
        runtime = cfs_b->runtime;
    }

    raw_spin_unlock_irqrestore(&cfs_b->lock, flags);

    if (!runtime) {
        return;
    }

    distribute_cfs_runtime(cfs_b);

    raw_spin_lock_irqsave(&cfs_b->lock, flags);
    raw_spin_unlock_irqrestore(&cfs_b->lock, flags);
}

/*
 * When a group wakes up we want to make sure that its quota is not already
 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
 * runtime as update_curr() throttling can not not trigger until it's on-rq.
 */
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
    if (!cfs_bandwidth_used()) {
        return;
    }

    /* an active group must be handled by the update_curr()->put() path */
    if (!cfs_rq->runtime_enabled || cfs_rq->curr) {
        return;
    }

    /* ensure the group is not already throttled */
    if (cfs_rq_throttled(cfs_rq)) {
        return;
    }

    /* update runtime allocation */
    account_cfs_rq_runtime(cfs_rq, 0);
    if (cfs_rq->runtime_remaining <= 0) {
        throttle_cfs_rq(cfs_rq);
    }
}

static void sync_throttle(struct task_group *tg, int cpu)
{
    struct cfs_rq *pcfs_rq, *cfs_rq;

    if (!cfs_bandwidth_used()) {
        return;
    }

    if (!tg->parent) {
        return;
    }

    cfs_rq = tg->cfs_rq[cpu];
    pcfs_rq = tg->parent->cfs_rq[cpu];

    cfs_rq->throttle_count = pcfs_rq->throttle_count;
    cfs_rq->throttled_clock_pelt = rq_clock_task(cpu_rq(cpu));
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    if (!cfs_bandwidth_used()) {
        return false;
    }

    if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) {
        return false;
    }

    /*
     * it's possible for a throttled entity to be forced into a running
     * state (e.g. set_curr_task), in this case we're finished.
     */
    if (cfs_rq_throttled(cfs_rq)) {
        return true;
    }

    return throttle_cfs_rq(cfs_rq);
}

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
    struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, slack_timer);

    do_sched_cfs_slack_timer(cfs_b);

    return HRTIMER_NORESTART;
}

static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
    struct cfs_bandwidth *cfs_b = container_of(timer, struct cfs_bandwidth, period_timer);
    unsigned long flags;
    int overrun;
    int idle = 0;
    int count = 0;

    raw_spin_lock_irqsave(&cfs_b->lock, flags);
    for (;;) {
        overrun = hrtimer_forward_now(timer, cfs_b->period);
        if (!overrun) {
            break;
        }

        idle = do_sched_cfs_period_timer(cfs_b, overrun, flags);

        if (++count > 0x3) {
            u64 new, old = ktime_to_ns(cfs_b->period);

            /*
             * Grow period by a factor of 2 to avoid losing precision.
             * Precision loss in the quota/period ratio can cause __cfs_schedulable
             * to fail.
             */
            new = old * 0x2;
            if (new < max_cfs_quota_period) {
                cfs_b->period = ns_to_ktime(new);
                cfs_b->quota *= 0x2;

                pr_warn_ratelimited("cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, "
                                    "cfs_quota_us = %lld)\n",
                                    smp_processor_id(), div_u64(new, NSEC_PER_USEC),
                                    div_u64(cfs_b->quota, NSEC_PER_USEC));
            } else {
                pr_warn_ratelimited("cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing "
                                    "precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
                                    smp_processor_id(), div_u64(old, NSEC_PER_USEC),
                                    div_u64(cfs_b->quota, NSEC_PER_USEC));
            }

            /* reset count so we don't come right back in here */
            count = 0;
        }
    }
    if (idle) {
        cfs_b->period_active = 0;
    }
    raw_spin_unlock_irqrestore(&cfs_b->lock, flags);

    return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
    raw_spin_lock_init(&cfs_b->lock);
    cfs_b->runtime = 0;
    cfs_b->quota = RUNTIME_INF;
    cfs_b->period = ns_to_ktime(default_cfs_period());

    INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
    hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
    cfs_b->period_timer.function = sched_cfs_period_timer;
    hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    cfs_b->slack_timer.function = sched_cfs_slack_timer;
    cfs_b->slack_started = false;
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    cfs_rq->runtime_enabled = 0;
    INIT_LIST_HEAD(&cfs_rq->throttled_list);
    walt_init_cfs_rq_stats(cfs_rq);
}

void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
    lockdep_assert_held(&cfs_b->lock);

    if (cfs_b->period_active) {
        return;
    }

    cfs_b->period_active = 1;
    hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
    hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
    /* init_cfs_bandwidth() was not called */
    if (!cfs_b->throttled_cfs_rq.next) {
        return;
    }

    hrtimer_cancel(&cfs_b->period_timer);
    hrtimer_cancel(&cfs_b->slack_timer);
}

/*
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
    struct task_group *tg;

    lockdep_assert_held(&rq->lock);

    rcu_read_lock();
    list_for_each_entry_rcu(tg, &task_groups, list)
    {
        struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
        struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

        raw_spin_lock(&cfs_b->lock);
        cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
        raw_spin_unlock(&cfs_b->lock);
    }
    rcu_read_unlock();
}

/* cpu offline callback */
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
{
    struct task_group *tg;

    lockdep_assert_held(&rq->lock);

    rcu_read_lock();
    list_for_each_entry_rcu(tg, &task_groups, list)
    {
        struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

        if (!cfs_rq->runtime_enabled) {
            continue;
        }

        /*
         * clock_task is not advancing so we just need to make sure
         * there's some valid quota amount
         */
        cfs_rq->runtime_remaining = 1;
        /*
         * Offline rq is schedulable till CPU is completely disabled
         * in take_cpu_down(), so we prevent new cfs throttling here.
         */
        cfs_rq->runtime_enabled = 0;

        if (cfs_rq_throttled(cfs_rq)) {
            unthrottle_cfs_rq(cfs_rq);
        }
    }
    rcu_read_unlock();
}

#else /* CONFIG_CFS_BANDWIDTH */

static inline bool cfs_bandwidth_used(void)
{
    return false;
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
{
}
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
    return false;
}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
}
static inline void sync_throttle(struct task_group *tg, int cpu)
{
}
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
}

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
    return 0;
}

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
    return 0;
}

static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu)
{
    return 0;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
}
#endif

static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
    return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
}
static inline void update_runtime_enabled(struct rq *rq)
{
}
static inline void unthrottle_offline_cfs_rqs(struct rq *rq)
{
}

#endif /* CONFIG_CFS_BANDWIDTH */

/**************************************************
 * CFS operations on tasks:
 */

#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

    SCHED_WARN_ON(task_rq(p) != rq);

    if (rq->cfs.h_nr_running > 1) {
        u64 slice = sched_slice(cfs_rq, se);
        u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
        s64 delta = slice - ran;

        if (delta < 0) {
            if (rq->curr == p) {
                resched_curr(rq);
            }
            return;
        }
        hrtick_start(rq, delta);
    }
}

/*
 * called from enqueue/dequeue and updates the hrtick when the
 * current task is from our class and nr_running is low enough
 * to matter.
 */
static void hrtick_update(struct rq *rq)
{
    struct task_struct *curr = rq->curr;

    if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) {
        return;
    }

    if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) {
        hrtick_start_fair(rq, curr);
    }
}
#else /* !CONFIG_SCHED_HRTICK */
static inline void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}

static inline void hrtick_update(struct rq *rq)
{
}
#endif

#ifdef CONFIG_SMP
static inline bool cpu_overutilized(int cpu)
{
    return !fits_capacity(cpu_util(cpu), capacity_of(cpu));
}

static inline void update_overutilized_status(struct rq *rq)
{
    if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu)) {
        WRITE_ONCE(rq->rd->overutilized, SG_OVERUTILIZED);
        trace_sched_overutilized_tp(rq->rd, SG_OVERUTILIZED);
    }
}
#else
static inline void update_overutilized_status(struct rq *rq)
{
}
#endif

/* Runqueue only has SCHED_IDLE tasks enqueued */
static int sched_idle_rq(struct rq *rq)
{
    return unlikely(rq->nr_running == rq->cfs.idle_h_nr_running && rq->nr_running);
}

#ifdef CONFIG_SMP
static int sched_idle_cpu(int cpu)
{
    return sched_idle_rq(cpu_rq(cpu));
}
#endif

static void set_next_buddy(struct sched_entity *se);
#ifdef CONFIG_SCHED_LATENCY_NICE
static void check_preempt_from_idle(struct cfs_rq *cfs, struct sched_entity *se)
{
    struct sched_entity *next;
    if (se->latency_weight <= 0)
        return;
    if (cfs->nr_running <= 1)
        return;
    if (cfs->next)
        next = cfs->next;
    else
        next = __pick_first_entity(cfs);
    if (next && wakeup_preempt_entity(next, se) == 1)
        set_next_buddy(se);
}
#endif
/*
 * The enqueue_task method is called before nr_running is
 * increased. Here we update the fair scheduling stats and
 * then put the task into the rbtree:
 */
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &p->se;
    int idle_h_nr_running = task_has_idle_policy(p);
    int task_new = !(flags & ENQUEUE_WAKEUP);

    /*
     * The code below (indirectly) updates schedutil which looks at
     * the cfs_rq utilization to select a frequency.
     * Let's add the task's estimated utilization to the cfs_rq's
     * estimated utilization, before we update schedutil.
     */
    util_est_enqueue(&rq->cfs, p);

    /*
     * If in_iowait is set, the code below may not trigger any cpufreq
     * utilization updates, so do it here explicitly with the IOWAIT flag
     * passed.
     */
    if (p->in_iowait) {
        cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
    }

    for_each_sched_entity(se) {
        if (se->on_rq) {
            break;
        }
        cfs_rq = cfs_rq_of(se);
        enqueue_entity(cfs_rq, se, flags);

        cfs_rq->h_nr_running++;
        cfs_rq->idle_h_nr_running += idle_h_nr_running;
        walt_inc_cfs_rq_stats(cfs_rq, p);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto enqueue_throttle;
        }

        flags = ENQUEUE_WAKEUP;
    }

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);

        update_load_avg(cfs_rq, se, UPDATE_TG);
        se_update_runnable(se);
        update_cfs_group(se);

        cfs_rq->h_nr_running++;
        cfs_rq->idle_h_nr_running += idle_h_nr_running;
        walt_inc_cfs_rq_stats(cfs_rq, p);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto enqueue_throttle;
        }

        /*
         * One parent has been throttled and cfs_rq removed from the
         * list. Add it back to not break the leaf list.
         */
        if (throttled_hierarchy(cfs_rq)) {
            list_add_leaf_cfs_rq(cfs_rq);
        }
    }

    /* At this point se is NULL and we are at root level */
    add_nr_running(rq, 1);
    inc_rq_walt_stats(rq, p);
    /*
     * Since new tasks are assigned an initial util_avg equal to
     * half of the spare capacity of their CPU, tiny tasks have the
     * ability to cross the overutilized threshold, which will
     * result in the load balancer ruining all the task placement
     * done by EAS. As a way to mitigate that effect, do not account
     * for the first enqueue operation of new tasks during the
     * overutilized flag detection.
     *
     * A better way of solving this problem would be to wait for
     * the PELT signals of tasks to converge before taking them
     * into account, but that is not straightforward to implement,
     * and the following generally works well enough in practice.
     */
    if (!task_new) {
        update_overutilized_status(rq);
    }
#ifdef CONFIG_SCHED_LATENCY_NICE
    if (rq->curr == rq->idle)
        check_preempt_from_idle(cfs_rq_of(&p->se), &p->se);
#endif

enqueue_throttle:
    if (cfs_bandwidth_used()) {
        /*
         * When bandwidth control is enabled; the cfs_rq_throttled()
         * breaks in the above iteration can result in incomplete
         * leaf list maintenance, resulting in triggering the assertion
         * below.
         */
        for_each_sched_entity(se) {
            cfs_rq = cfs_rq_of(se);
            if (list_add_leaf_cfs_rq(cfs_rq)) {
                break;
            }
        }
    }

    assert_list_leaf_cfs_rq(rq);

    hrtick_update(rq);
}


/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats
 */
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &p->se;
    int task_sleep = flags & DEQUEUE_SLEEP;
    int idle_h_nr_running = task_has_idle_policy(p);
    bool was_sched_idle = sched_idle_rq(rq);

    util_est_dequeue(&rq->cfs, p);

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        dequeue_entity(cfs_rq, se, flags);

        cfs_rq->h_nr_running--;
        cfs_rq->idle_h_nr_running -= idle_h_nr_running;
        walt_dec_cfs_rq_stats(cfs_rq, p);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto dequeue_throttle;
        }

        /* Don't dequeue parent if it has other entities besides us */
        if (cfs_rq->load.weight) {
            /* Avoid re-evaluating load for this entity: */
            se = parent_entity(se);
            /*
             * Bias pick_next to pick a task from this cfs_rq, as
             * p is sleeping when it is within its sched_slice.
             */
            if (task_sleep && se && !throttled_hierarchy(cfs_rq)) {
                set_next_buddy(se);
            }
            break;
        }
        flags |= DEQUEUE_SLEEP;
    }

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);

        update_load_avg(cfs_rq, se, UPDATE_TG);
        se_update_runnable(se);
        update_cfs_group(se);

        cfs_rq->h_nr_running--;
        cfs_rq->idle_h_nr_running -= idle_h_nr_running;
        walt_dec_cfs_rq_stats(cfs_rq, p);

        /* end evaluation on encountering a throttled cfs_rq */
        if (cfs_rq_throttled(cfs_rq)) {
            goto dequeue_throttle;
        }
    }

    /* At this point se is NULL and we are at root level */
    sub_nr_running(rq, 1);
    dec_rq_walt_stats(rq, p);

    /* balance early to pull high priority tasks */
    if (unlikely(!was_sched_idle && sched_idle_rq(rq))) {
        rq->next_balance = jiffies;
    }

dequeue_throttle:
    util_est_update(&rq->cfs, p, task_sleep);
    hrtick_update(rq);
}

#ifdef CONFIG_SMP

/* Working cpumask for: load_balance, load_balance_newidle. */
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);

#ifdef CONFIG_NO_HZ_COMMON

static struct {
    cpumask_var_t idle_cpus_mask;
    atomic_t nr_cpus;
    int has_blocked;            /* Idle CPUS has blocked load */
    unsigned long next_balance; /* in jiffy units */
    unsigned long next_blocked; /* Next update of blocked load in jiffies */
} nohz ____cacheline_aligned;

#endif /* CONFIG_NO_HZ_COMMON */

static unsigned long cpu_load(struct rq *rq)
{
    return cfs_rq_load_avg(&rq->cfs);
}

/*
 * cpu_load_without - compute CPU load without any contributions from *p
 * @cpu: the CPU which load is requested
 * @p: the task which load should be discounted
 *
 * The load of a CPU is defined by the load of tasks currently enqueued on that
 * CPU as well as tasks which are currently sleeping after an execution on that
 * CPU.
 *
 * This method returns the load of the specified CPU by discounting the load of
 * the specified task, whenever the task is currently contributing to the CPU
 * load.
 */
static unsigned long cpu_load_without(struct rq *rq, struct task_struct *p)
{
    struct cfs_rq *cfs_rq;
    unsigned int load;

    /* Task has no contribution or is new */
    if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) {
        return cpu_load(rq);
    }

    cfs_rq = &rq->cfs;
    load = READ_ONCE(cfs_rq->avg.load_avg);

    /* Discount task's util from CPU's util */
    lsub_positive(&load, task_h_load(p));

    return load;
}

static unsigned long cpu_runnable(struct rq *rq)
{
    return cfs_rq_runnable_avg(&rq->cfs);
}

static unsigned long cpu_runnable_without(struct rq *rq, struct task_struct *p)
{
    struct cfs_rq *cfs_rq;
    unsigned int runnable;

    /* Task has no contribution or is new */
    if (cpu_of(rq) != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) {
        return cpu_runnable(rq);
    }

    cfs_rq = &rq->cfs;
    runnable = READ_ONCE(cfs_rq->avg.runnable_avg);

    /* Discount task's runnable from CPU's runnable */
    lsub_positive(&runnable, p->se.avg.runnable_avg);

    return runnable;
}

static void record_wakee(struct task_struct *p)
{
    /*
     * Only decay a single time; tasks that have less then 1 wakeup per
     * jiffy will not have built up many flips.
     */
    if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
        current->wakee_flips >>= 1;
        current->wakee_flip_decay_ts = jiffies;
    }

    if (current->last_wakee != p) {
        current->last_wakee = p;
        current->wakee_flips++;
    }
}

/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
 *
 * A waker of many should wake a different task than the one last awakened
 * at a frequency roughly N times higher than one of its wakees.
 *
 * In order to determine whether we should let the load spread vs consolidating
 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.
 *
 * With both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.
 *
 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
 * whatever is irrelevant, spread criteria is apparent partner count exceeds
 * socket size.
 */
static int wake_wide(struct task_struct *p)
{
    unsigned int master = current->wakee_flips;
    unsigned int slave = p->wakee_flips;
    int factor = __this_cpu_read(sd_llc_size);

    if (master < slave) {
        swap(master, slave);
    }
    if (slave < factor || master < slave * factor) {
        return 0;
    }
    return 1;
}

/*
 * The purpose of wake_affine() is to quickly determine on which CPU we can run
 * soonest. For the purpose of speed we only consider the waking and previous
 * CPU.
 *
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *            cache-affine and is (or    will be) idle.
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *              scheduling latency of the CPUs. This seems to work
 *              for the overloaded case.
 */
static int wake_affine_idle(int this_cpu, int prev_cpu, int sync)
{
    /*
     * If this_cpu is idle, it implies the wakeup is from interrupt
     * context. Only allow the move if cache is shared. Otherwise an
     * interrupt intensive workload could force all tasks onto one
     * node depending on the IO topology or IRQ affinity settings.
     *
     * If the prev_cpu is idle and cache affine then avoid a migration.
     * There is no guarantee that the cache hot data from an interrupt
     * is more important than cache hot data on the prev_cpu and from
     * a cpufreq perspective, it's better to have higher utilisation
     * on one CPU.
     */
    if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu)) {
        return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
    }

    if (sync && cpu_rq(this_cpu)->nr_running == 1) {
        return this_cpu;
    }

    return nr_cpumask_bits;
}

static int wake_affine_weight(struct sched_domain *sd, struct task_struct *p, int this_cpu, int prev_cpu, int sync)
{
    s64 this_eff_load, prev_eff_load;
    unsigned long task_load;

    this_eff_load = cpu_load(cpu_rq(this_cpu));

    if (sync) {
        unsigned long current_load = task_h_load(current);
        if (current_load > this_eff_load) {
            return this_cpu;
        }

        this_eff_load -= current_load;
    }

    task_load = task_h_load(p);

    this_eff_load += task_load;
    if (sched_feat(WA_BIAS)) {
        this_eff_load *= FAIR_ONEHUNDRED;
    }
    this_eff_load *= capacity_of(prev_cpu);

    prev_eff_load = cpu_load(cpu_rq(prev_cpu));
    prev_eff_load -= task_load;
    if (sched_feat(WA_BIAS)) {
        prev_eff_load *= FAIR_ONEHUNDRED + (sd->imbalance_pct - FAIR_ONEHUNDRED) / 0x2;
    }
    prev_eff_load *= capacity_of(this_cpu);

    /*
     * If sync, adjust the weight of prev_eff_load such that if
     * prev_eff == this_eff that select_idle_sibling() will consider
     * stacking the wakee on top of the waker if no other CPU is
     * idle.
     */
    if (sync) {
        prev_eff_load += 1;
    }

    return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
}

static int wake_affine(struct sched_domain *sd, struct task_struct *p, int this_cpu, int prev_cpu, int sync)
{
    int target = nr_cpumask_bits;

    if (sched_feat(WA_IDLE)) {
        target = wake_affine_idle(this_cpu, prev_cpu, sync);
    }

    if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits) {
        target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
    }

    schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
    if (target == nr_cpumask_bits) {
        return prev_cpu;
    }

    schedstat_inc(sd->ttwu_move_affine);
    schedstat_inc(p->se.statistics.nr_wakeups_affine);
    return target;
}

static struct sched_group *find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu);

/*
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
 */
static int find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
    unsigned long load, min_load = ULONG_MAX;
    unsigned int min_exit_latency = UINT_MAX;
    u64 latest_idle_timestamp = 0;
    int least_loaded_cpu = this_cpu;
    int shallowest_idle_cpu = -1;
    int i;

    /* Check if we have any choice: */
    if (group->group_weight == 1) {
        return cpumask_first(sched_group_span(group));
    }

    /* Traverse only the allowed CPUs */
    for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr)
    {
        if (cpu_isolated(i)) {
            continue;
        }

        if (sched_idle_cpu(i)) {
            return i;
        }

        if (available_idle_cpu(i)) {
            struct rq *rq = cpu_rq(i);
            struct cpuidle_state *idle = idle_get_state(rq);
            if (idle && idle->exit_latency < min_exit_latency) {
                /*
                 * We give priority to a CPU whose idle state
                 * has the smallest exit latency irrespective
                 * of any idle timestamp.
                 */
                min_exit_latency = idle->exit_latency;
                latest_idle_timestamp = rq->idle_stamp;
                shallowest_idle_cpu = i;
            } else if ((!idle || idle->exit_latency == min_exit_latency) && rq->idle_stamp > latest_idle_timestamp) {
                /*
                 * If equal or no active idle state, then
                 * the most recently idled CPU might have
                 * a warmer cache.
                 */
                latest_idle_timestamp = rq->idle_stamp;
                shallowest_idle_cpu = i;
            }
        } else if (shallowest_idle_cpu == -1) {
            load = cpu_load(cpu_rq(i));
            if (load < min_load) {
                min_load = load;
                least_loaded_cpu = i;
            }
        }
    }

    return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
}

static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p, int cpu, int prev_cpu, int sd_flag)
{
    int new_cpu = cpu;

    if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr)) {
        return prev_cpu;
    }

    /*
     * We need task's util for cpu_util_without, sync it up to
     * prev_cpu's last_update_time.
     */
    if (!(sd_flag & SD_BALANCE_FORK)) {
        sync_entity_load_avg(&p->se);
    }

    while (sd) {
        struct sched_group *group;
        struct sched_domain *tmp;
        int weight;

        if (!(sd->flags & sd_flag)) {
            sd = sd->child;
            continue;
        }

        group = find_idlest_group(sd, p, cpu);
        if (!group) {
            sd = sd->child;
            continue;
        }

        new_cpu = find_idlest_group_cpu(group, p, cpu);
        if (new_cpu == cpu) {
            /* Now try balancing at a lower domain level of 'cpu': */
            sd = sd->child;
            continue;
        }

        /* Now try balancing at a lower domain level of 'new_cpu': */
        cpu = new_cpu;
        weight = sd->span_weight;
        sd = NULL;
        for_each_domain(cpu, tmp)
        {
            if (weight <= tmp->span_weight) {
                break;
            }
            if (tmp->flags & sd_flag) {
                sd = tmp;
            }
        }
    }

    return new_cpu;
}

#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);

static inline void set_idle_cores(int cpu, int val)
{
    struct sched_domain_shared *sds;

    sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
    if (sds) {
        WRITE_ONCE(sds->has_idle_cores, val);
    }
}

static inline bool test_idle_cores(int cpu, bool def)
{
    struct sched_domain_shared *sds;

    sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
    if (sds) {
        return READ_ONCE(sds->has_idle_cores);
    }

    return def;
}

/*
 * Scans the local SMT mask to see if the entire core is idle, and records this
 * information in sd_llc_shared->has_idle_cores.
 *
 * Since SMT siblings share all cache levels, inspecting this limited remote
 * state should be fairly cheap.
 */
void fair_update_idle_core(struct rq *rq)
{
    int core = cpu_of(rq);
    int cpu;

    rcu_read_lock();
    if (test_idle_cores(core, true)) {
        goto unlock;
    }

    for_each_cpu(cpu, cpu_smt_mask(core))
    {
        if (cpu == core) {
            continue;
        }

        if (!available_idle_cpu(cpu)) {
            goto unlock;
        }
    }

    set_idle_cores(core, 1);
unlock:
    rcu_read_unlock();
}

/*
 * Scan the entire LLC domain for idle cores; this dynamically switches off if
 * there are no idle cores left in the system; tracked through
 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
 */
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
    struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
    int core, cpu;

    if (!static_branch_likely(&sched_smt_present)) {
        return -1;
    }

    if (!test_idle_cores(target, false)) {
        return -1;
    }

    cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
#ifdef CONFIG_CPU_ISOLATION_OPT
    cpumask_andnot(cpus, cpus, cpu_isolated_mask);
#endif

    for_each_cpu_wrap(core, cpus, target)
    {
        bool idle = true;

        for_each_cpu(cpu, cpu_smt_mask(core))
        {
            if (!available_idle_cpu(cpu)) {
                idle = false;
                break;
            }
        }
        cpumask_andnot(cpus, cpus, cpu_smt_mask(core));

        if (idle) {
            return core;
        }
    }

    /*
     * Failed to find an idle core; stop looking for one.
     */
    set_idle_cores(target, 0);

    return -1;
}

/*
 * Scan the local SMT mask for idle CPUs.
 */
static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
    int cpu;

    if (!static_branch_likely(&sched_smt_present)) {
        return -1;
    }

    for_each_cpu(cpu, cpu_smt_mask(target))
    {
        if (!cpumask_test_cpu(cpu, p->cpus_ptr) || !cpumask_test_cpu(cpu, sched_domain_span(sd))) {
            continue;
        }
        if (cpu_isolated(cpu)) {
            continue;
        }
        if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) {
            return cpu;
        }
    }

    return -1;
}

#else /* CONFIG_SCHED_SMT */

static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
    return -1;
}

static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
    return -1;
}

#endif /* CONFIG_SCHED_SMT */

/*
 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
 * average idle time for this rq (as found in rq->avg_idle).
 */
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
    struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
    struct sched_domain *this_sd;
    u64 avg_cost, avg_idle;
    u64 time;
    int this = smp_processor_id();
    int cpu, nr = INT_MAX;

    this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
    if (!this_sd) {
        return -1;
    }

    /*
     * Due to large variance we need a large fuzz factor; hackbench in
     * particularly is sensitive here.
     */
    avg_idle = this_rq()->avg_idle / 0x200;
    avg_cost = this_sd->avg_scan_cost + 1;

    if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost) {
        return -1;
    }

    if (sched_feat(SIS_PROP)) {
        u64 span_avg = sd->span_weight * avg_idle;
        if (span_avg > 0x4 * avg_cost) {
            nr = div_u64(span_avg, avg_cost);
        } else {
            nr = 0x4;
        }
    }

    time = cpu_clock(this);

    cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);

    for_each_cpu_wrap(cpu, cpus, target)
    {
        if (!--nr) {
            return -1;
        }
        if (cpu_isolated(cpu)) {
            continue;
        }
        if (available_idle_cpu(cpu) || sched_idle_cpu(cpu)) {
            break;
        }
    }

    time = cpu_clock(this) - time;
    update_avg(&this_sd->avg_scan_cost, time);

    return cpu;
}

/*
 * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
 * the task fits. If no CPU is big enough, but there are idle ones, try to
 * maximize capacity.
 */
static int select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
{
    unsigned long task_util, best_cap = 0;
    int cpu, best_cpu = -1;
    struct cpumask *cpus;

    cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
    cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);

    task_util = uclamp_task_util(p);

    for_each_cpu_wrap(cpu, cpus, target)
    {
        unsigned long cpu_cap = capacity_of(cpu);

        if (cpu_isolated(cpu)) {
            continue;
        }

        if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu)) {
            continue;
        }
        if (fits_capacity(task_util, cpu_cap)) {
            return cpu;
        }

        if (cpu_cap > best_cap) {
            best_cap = cpu_cap;
            best_cpu = cpu;
        }
    }

    return best_cpu;
}

static inline bool asym_fits_capacity(int task_util, int cpu)
{
    if (static_branch_unlikely(&sched_asym_cpucapacity)) {
        return fits_capacity(task_util, capacity_of(cpu));
    }

    return true;
}

/*
 * Try and locate an idle core/thread in the LLC cache domain.
 */
static int select_idle_sibling(struct task_struct *p, int prev, int target)
{
    struct sched_domain *sd;
    unsigned long task_util;
    int i, recent_used_cpu;

    /*
     * On asymmetric system, update task utilization because we will check
     * that the task fits with cpu's capacity.
     */
    if (static_branch_unlikely(&sched_asym_cpucapacity)) {
        sync_entity_load_avg(&p->se);
        task_util = uclamp_task_util(p);
    }

    if ((available_idle_cpu(target) || sched_idle_cpu(target)) && !cpu_isolated(target) &&
        asym_fits_capacity(task_util, target)) {
        return target;
    }

    /*
     * If the previous CPU is cache affine and idle, don't be stupid:
     */
    if (prev != target && cpus_share_cache(prev, target) &&
        ((available_idle_cpu(prev) || sched_idle_cpu(prev)) && !cpu_isolated(target) &&
         asym_fits_capacity(task_util, prev))) {
        return prev;
    }

    if (is_per_cpu_kthread(current) &&
        in_task() &&
        prev == smp_processor_id() &&
        this_rq()->nr_running <= 1 &&
        asym_fits_capacity(task_util, prev)) {
        return prev;
    }

    /* Check a recently used CPU as a potential idle candidate: */
    recent_used_cpu = p->recent_used_cpu;
    if (recent_used_cpu != prev && recent_used_cpu != target && cpus_share_cache(recent_used_cpu, target) &&
        (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) &&
        cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) && asym_fits_capacity(task_util, recent_used_cpu)) {
        p->recent_used_cpu = prev;
        return recent_used_cpu;
    }

    if (static_branch_unlikely(&sched_asym_cpucapacity)) {
        sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
        if (sd) {
            i = select_idle_capacity(p, sd, target);
            return ((unsigned)i < nr_cpumask_bits) ? i : target;
        }
    }

    sd = rcu_dereference(per_cpu(sd_llc, target));
    if (!sd) {
        return target;
    }

    i = select_idle_core(p, sd, target);
    if ((unsigned)i < nr_cpumask_bits) {
        return i;
    }

    i = select_idle_cpu(p, sd, target);
    if ((unsigned)i < nr_cpumask_bits) {
        return i;
    }

    i = select_idle_smt(p, sd, target);
    if ((unsigned)i < nr_cpumask_bits) {
        return i;
    }

    return target;
}

/**
 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
 * @cpu: the CPU to get the utilization of
 *
 * The unit of the return value must be the one of capacity so we can compare
 * the utilization with the capacity of the CPU that is available for CFS task
 * (ie cpu_capacity).
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
 * The estimated utilization of a CPU is defined to be the maximum between its
 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
 * currently RUNNABLE on that CPU.
 * This allows to properly represent the expected utilization of a CPU which
 * has just got a big task running since a long sleep period. At the same time
 * however it preserves the benefits of the "blocked utilization" in
 * describing the potential for other tasks waking up on the same CPU.
 *
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
 *
 * Return: the (estimated) utilization for the specified CPU
 */
unsigned long cpu_util(int cpu)
{
    struct cfs_rq *cfs_rq;
    unsigned int util;

#ifdef CONFIG_SCHED_WALT
    if (likely(!walt_disabled && sysctl_sched_use_walt_cpu_util)) {
        u64 walt_cpu_util = cpu_rq(cpu)->walt_stats.cumulative_runnable_avg_scaled;

        return min_t(unsigned long, walt_cpu_util, capacity_orig_of(cpu));
    }
#endif

    cfs_rq = &cpu_rq(cpu)->cfs;
    util = READ_ONCE(cfs_rq->avg.util_avg);

    if (sched_feat(UTIL_EST)) {
        util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
    }

    return min_t(unsigned long, util, capacity_orig_of(cpu));
}

/*
 * cpu_util_without: compute cpu utilization without any contributions from *p
 * @cpu: the CPU which utilization is requested
 * @p: the task which utilization should be discounted
 *
 * The utilization of a CPU is defined by the utilization of tasks currently
 * enqueued on that CPU as well as tasks which are currently sleeping after an
 * execution on that CPU.
 *
 * This method returns the utilization of the specified CPU by discounting the
 * utilization of the specified task, whenever the task is currently
 * contributing to the CPU utilization.
 */
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
{
    struct cfs_rq *cfs_rq;
    unsigned int util;

#ifdef CONFIG_SCHED_WALT
    /*
     * WALT does not decay idle tasks in the same manner
     * as PELT, so it makes little sense to subtract task
     * utilization from cpu utilization. Instead just use
     * cpu_util for this case.
     */
    if (likely(!walt_disabled && sysctl_sched_use_walt_cpu_util) && p->state == TASK_WAKING) {
        return cpu_util(cpu);
    }
#endif

    /* Task has no contribution or is new */
    if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) {
        return cpu_util(cpu);
    }

#ifdef CONFIG_SCHED_WALT
    if (likely(!walt_disabled && sysctl_sched_use_walt_cpu_util)) {
        util = max_t(long, cpu_util(cpu) - task_util(p), 0);
        return min_t(unsigned long, util, capacity_orig_of(cpu));
    }
#endif

    cfs_rq = &cpu_rq(cpu)->cfs;
    util = READ_ONCE(cfs_rq->avg.util_avg);

    /* Discount task's util from CPU's util */
    lsub_positive(&util, task_util(p));

    /*
     * Covered cases:
     *
     * a) if *p is the only task sleeping on this CPU, then:
     *      cpu_util (== task_util) > util_est (== 0)
     *    and thus we return:
     *      cpu_util_without = (cpu_util - task_util) = 0
     *
     * b) if other tasks are SLEEPING on this CPU, which is now exiting
     *    IDLE, then:
     *      cpu_util >= task_util
     *      cpu_util > util_est (== 0)
     *    and thus we discount *p's blocked utilization to return:
     *      cpu_util_without = (cpu_util - task_util) >= 0
     *
     * c) if other tasks are RUNNABLE on that CPU and
     *      util_est > cpu_util
     *    then we use util_est since it returns a more restrictive
     *    estimation of the spare capacity on that CPU, by just
     *    considering the expected utilization of tasks already
     *    runnable on that CPU.
     *
     * Cases a) and b) are covered by the above code, while case c) is
     * covered by the following code when estimated utilization is
     * enabled.
     */
    if (sched_feat(UTIL_EST)) {
        unsigned int estimated = READ_ONCE(cfs_rq->avg.util_est.enqueued);

        /*
         * Despite the following checks we still have a small window
         * for a possible race, when an execl's select_task_rq_fair()
         * races with LB's detach_task():
         *
         *   detach_task()
         *     p->on_rq = TASK_ON_RQ_MIGRATING;
         *     ---------------------------------- A
         *     deactivate_task()                   \
         *       dequeue_task()                     + RaceTime
         *         util_est_dequeue()              /
         *     ---------------------------------- B
         *
         * The additional check on "current == p" it's required to
         * properly fix the execl regression and it helps in further
         * reducing the chances for the above race.
         */
        if (unlikely(task_on_rq_queued(p) || current == p)) {
            lsub_positive(&estimated, _task_util_est(p));
        }

        util = max(util, estimated);
    }

    /*
     * Utilization (estimated) can exceed the CPU capacity, thus let's
     * clamp to the maximum CPU capacity to ensure consistency with
     * the cpu_util call.
     */
    return min_t(unsigned long, util, capacity_orig_of(cpu));
}

#ifdef CONFIG_SCHED_RTG
unsigned long capacity_spare_without(int cpu, struct task_struct *p)
{
    return max_t(long, capacity_of(cpu) - cpu_util_without(cpu, p), 0);
}
#endif
/*
 * Predicts what cpu_util(@cpu) would return if @p was migrated (and enqueued)
 * to @dst_cpu.
 */
static unsigned long cpu_util_next(int cpu, struct task_struct *p, int dst_cpu)
{
    struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
    unsigned long util_est, util = READ_ONCE(cfs_rq->avg.util_avg);

    /*
     * If @p migrates from @cpu to another, remove its contribution. Or,
     * if @p migrates from another CPU to @cpu, add its contribution. In
     * the other cases, @cpu is not impacted by the migration, so the
     * util_avg should already be correct.
     */
    if (task_cpu(p) == cpu && dst_cpu != cpu) {
        sub_positive(&util, task_util(p));
    } else if (task_cpu(p) != cpu && dst_cpu == cpu) {
        util += task_util(p);
    }

    if (sched_feat(UTIL_EST)) {
        util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued);

        /*
         * During wake-up, the task isn't enqueued yet and doesn't
         * appear in the cfs_rq->avg.util_est.enqueued of any rq,
         * so just add it (if needed) to "simulate" what will be
         * cpu_util() after the task has been enqueued.
         */
        if (dst_cpu == cpu) {
            util_est += _task_util_est(p);
        }

        util = max(util, util_est);
    }

    return min(util, capacity_orig_of(cpu));
}

/*
 * Returns the current capacity of cpu after applying both
 * cpu and freq scaling.
 */
unsigned long capacity_curr_of(int cpu)
{
    unsigned long max_cap = cpu_rq(cpu)->cpu_capacity_orig;
    unsigned long scale_freq = arch_scale_freq_capacity(cpu);

    return cap_scale(max_cap, scale_freq);
}

/*
 * compute_energy(): Estimates the energy that @pd would consume if @p was
 * migrated to @dst_cpu. compute_energy() predicts what will be the utilization
 * landscape of @pd's CPUs after the task migration, and uses the Energy Model
 * to compute what would be the energy if we decided to actually migrate that
 * task.
 */
static long compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd)
{
    struct cpumask *pd_mask = perf_domain_span(pd);
    unsigned long cpu_cap = arch_scale_cpu_capacity(cpumask_first(pd_mask));
    unsigned long max_util = 0, sum_util = 0;
    int cpu;

    /*
     * The capacity state of CPUs of the current rd can be driven by CPUs
     * of another rd if they belong to the same pd. So, account for the
     * utilization of these CPUs too by masking pd with cpu_online_mask
     * instead of the rd span.
     *
     * If an entire pd is outside of the current rd, it will not appear in
     * its pd list and will not be accounted by compute_energy().
     */
    for_each_cpu_and(cpu, pd_mask, cpu_online_mask)
    {
        unsigned long cpu_util, util_cfs = cpu_util_next(cpu, p, dst_cpu);
        struct task_struct *tsk = cpu == dst_cpu ? p : NULL;

        /*
         * Busy time computation: utilization clamping is not
         * required since the ratio (sum_util / cpu_capacity)
         * is already enough to scale the EM reported power
         * consumption at the (eventually clamped) cpu_capacity.
         */
        sum_util += schedutil_cpu_util(cpu, util_cfs, cpu_cap, ENERGY_UTIL, NULL);

        /*
         * Performance domain frequency: utilization clamping
         * must be considered since it affects the selection
         * of the performance domain frequency.
         * NOTE: in case RT tasks are running, by default the
         * FREQUENCY_UTIL's utilization can be max OPP.
         */
        cpu_util = schedutil_cpu_util(cpu, util_cfs, cpu_cap, FREQUENCY_UTIL, tsk);
        max_util = max(max_util, cpu_util);
    }

    return em_cpu_energy(pd->em_pd, max_util, sum_util);
}

/*
 * find_energy_efficient_cpu(): Find most energy-efficient target CPU for the
 * waking task. find_energy_efficient_cpu() looks for the CPU with maximum
 * spare capacity in each performance domain and uses it as a potential
 * candidate to execute the task. Then, it uses the Energy Model to figure
 * out which of the CPU candidates is the most energy-efficient.
 *
 * The rationale for this heuristic is as follows. In a performance domain,
 * all the most energy efficient CPU candidates (according to the Energy
 * Model) are those for which we'll request a low frequency. When there are
 * several CPUs for which the frequency request will be the same, we don't
 * have enough data to break the tie between them, because the Energy Model
 * only includes active power costs. With this model, if we assume that
 * frequency requests follow utilization (e.g. using schedutil), the CPU with
 * the maximum spare capacity in a performance domain is guaranteed to be among
 * the best candidates of the performance domain.
 *
 * In practice, it could be preferable from an energy standpoint to pack
 * small tasks on a CPU in order to let other CPUs go in deeper idle states,
 * but that could also hurt our chances to go cluster idle, and we have no
 * ways to tell with the current Energy Model if this is actually a good
 * idea or not. So, find_energy_efficient_cpu() basically favors
 * cluster-packing, and spreading inside a cluster. That should at least be
 * a good thing for latency, and this is consistent with the idea that most
 * of the energy savings of EAS come from the asymmetry of the system, and
 * not so much from breaking the tie between identical CPUs. That's also the
 * reason why EAS is enabled in the topology code only for systems where
 * SD_ASYM_CPUCAPACITY is set.
 *
 * NOTE: Forkees are not accepted in the energy-aware wake-up path because
 * they don't have any useful utilization data yet and it's not possible to
 * forecast their impact on energy consumption. Consequently, they will be
 * placed by find_idlest_cpu() on the least loaded CPU, which might turn out
 * to be energy-inefficient in some use-cases. The alternative would be to
 * bias new tasks towards specific types of CPUs first, or to try to infer
 * their util_avg from the parent task, but those heuristics could hurt
 * other use-cases too. So, until someone finds a better way to solve this,
 * let's keep things simple by re-using the existing slow path.
 */
static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
{
    unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;
    struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
    unsigned long cpu_cap, util, base_energy = 0;
    int cpu, best_energy_cpu = prev_cpu;
    struct sched_domain *sd;
    struct perf_domain *pd;

    rcu_read_lock();
    pd = rcu_dereference(rd->pd);
    if (!pd || READ_ONCE(rd->overutilized)) {
        goto fail;
    }

    /*
     * Energy-aware wake-up happens on the lowest sched_domain starting
     * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
     */
    sd = rcu_dereference(*this_cpu_ptr(&sd_asym_cpucapacity));
    while (sd && !cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) {
        sd = sd->parent;
    }
    if (!sd) {
        goto fail;
    }

    sync_entity_load_avg(&p->se);
    if (!task_util_est(p)) {
        goto unlock;
    }

    for (; pd; pd = pd->next) {
        unsigned long cur_delta, spare_cap, max_spare_cap = 0;
        unsigned long base_energy_pd;
        int max_spare_cap_cpu = -1;

        /* Compute the 'base' energy of the pd, without @p */
        base_energy_pd = compute_energy(p, -1, pd);
        base_energy += base_energy_pd;

        for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd))
        {
            if (!cpumask_test_cpu(cpu, p->cpus_ptr)) {
                continue;
            }

            util = cpu_util_next(cpu, p, cpu);
            cpu_cap = capacity_of(cpu);
            spare_cap = cpu_cap;
            lsub_positive(&spare_cap, util);

            /*
             * Skip CPUs that cannot satisfy the capacity request.
             * IOW, placing the task there would make the CPU
             * overutilized. Take uclamp into account to see how
             * much capacity we can get out of the CPU; this is
             * aligned with schedutil_cpu_util().
             */
            util = uclamp_rq_util_with(cpu_rq(cpu), util, p);
            if (!fits_capacity(util, cpu_cap)) {
                continue;
            }

            /* Always use prev_cpu as a candidate. */
            if (cpu == prev_cpu) {
                prev_delta = compute_energy(p, prev_cpu, pd);
                prev_delta -= base_energy_pd;
                best_delta = min(best_delta, prev_delta);
            }

            /*
             * Find the CPU with the maximum spare capacity in
             * the performance domain
             */
            if (spare_cap > max_spare_cap) {
                max_spare_cap = spare_cap;
                max_spare_cap_cpu = cpu;
            }
        }

        /* Evaluate the energy impact of using this CPU. */
        if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) {
            cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
            cur_delta -= base_energy_pd;
            if (cur_delta < best_delta) {
                best_delta = cur_delta;
                best_energy_cpu = max_spare_cap_cpu;
            }
        }
    }
unlock:
    rcu_read_unlock();

    /*
     * Pick the best CPU if prev_cpu cannot be used, or if it saves at
     * least 6% of the energy used by prev_cpu.
     */
    if (prev_delta == ULONG_MAX) {
        return best_energy_cpu;
    }

    if ((prev_delta - best_delta) > ((prev_delta + base_energy) >> 0x4)) {
        return best_energy_cpu;
    }

    return prev_cpu;

fail:
    rcu_read_unlock();

    return -1;
}

/*
 * select_task_rq_fair: Select target runqueue for the waking task in domains
 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
 *
 * Balances load by selecting the idlest CPU in the idlest group, or under
 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
 *
 * Returns the target CPU number.
 *
 * preempt must be disabled.
 */
static int select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
{
    struct sched_domain *tmp, *sd = NULL;
    int cpu = smp_processor_id();
    int new_cpu = prev_cpu;
    int want_affine = 0;
    int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
#ifdef CONFIG_SCHED_RTG
    int target_cpu = -1;
    target_cpu = find_rtg_cpu(p);
    if (target_cpu >= 0) {
        return target_cpu;
    }
#endif

    if (sd_flag & SD_BALANCE_WAKE) {
        record_wakee(p);

        if (sched_energy_enabled()) {
            new_cpu = find_energy_efficient_cpu(p, prev_cpu);
            if (new_cpu >= 0) {
                return new_cpu;
            }
            new_cpu = prev_cpu;
        }

        want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, p->cpus_ptr);
    }

    rcu_read_lock();
    for_each_domain(cpu, tmp)
    {
        /*
         * If both 'cpu' and 'prev_cpu' are part of this domain,
         * cpu is a valid SD_WAKE_AFFINE target.
         */
        if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
            if (cpu != prev_cpu) {
                new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
            }

            sd = NULL; /* Prefer wake_affine over balance flags */
            break;
        }

        if (tmp->flags & sd_flag) {
            sd = tmp;
        } else if (!want_affine) {
            break;
        }
    }

    if (unlikely(sd)) {
        /* Slow path */
        new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
    } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
        /* Fast path */

        new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);

        if (want_affine) {
            current->recent_used_cpu = cpu;
        }
    }
    rcu_read_unlock();

    return new_cpu;
}

static void detach_entity_cfs_rq(struct sched_entity *se);

/*
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
 */
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
{
    /*
     * As blocked tasks retain absolute vruntime the migration needs to
     * deal with this by subtracting the old and adding the new
     * min_vruntime -- the latter is done by enqueue_entity() when placing
     * the task on the new runqueue.
     */
    if (p->state == TASK_WAKING) {
        struct sched_entity *se = &p->se;
        struct cfs_rq *cfs_rq = cfs_rq_of(se);
        u64 min_vruntime;

#ifndef CONFIG_64BIT
        u64 min_vruntime_copy;

        do {
            min_vruntime_copy = cfs_rq->min_vruntime_copy;
            smp_rmb();
            min_vruntime = cfs_rq->min_vruntime;
        } while (min_vruntime != min_vruntime_copy);
#else
        min_vruntime = cfs_rq->min_vruntime;
#endif

        se->vruntime -= min_vruntime;
    }

    if (p->on_rq == TASK_ON_RQ_MIGRATING) {
        /*
         * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
         * rq->lock and can modify state directly.
         */
        lockdep_assert_held(&task_rq(p)->lock);
        detach_entity_cfs_rq(&p->se);
    } else {
        /*
         * We are supposed to update the task to "current" time, then
         * its up to date and ready to go to new CPU/cfs_rq. But we
         * have difficulty in getting what current time is, so simply
         * throw away the out-of-date time. This will result in the
         * wakee task is less decayed, but giving the wakee more load
         * sounds not bad.
         */
        remove_entity_load_avg(&p->se);
    }

    /* Tell new CPU we are migrated */
    p->se.avg.last_update_time = 0;

    /* We have migrated, no longer consider this task hot */
    p->se.exec_start = 0;

    update_scan_period(p, new_cpu);
}

static void task_dead_fair(struct task_struct *p)
{
    remove_entity_load_avg(&p->se);
}

static int balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
    if (rq->nr_running) {
        return 1;
    }
    return newidle_balance(rq, rf) != 0;
}
#endif /* CONFIG_SMP */

#ifdef CONFIG_SCHED_LATENCY_NICE
static long wakeup_latency_gran(struct sched_entity *curr, struct sched_entity *se)
{
    int latency_weight = se->latency_weight;
    long thresh = sysctl_sched_latency;
    if ((se->latency_weight > 0) || (curr->latency_weight > 0))
        latency_weight -= curr->latency_weight;
    if (!latency_weight)
        return 0;
    if (sched_feat(GENTLE_FAIR_SLEEPERS))
        thresh >>= 1;
    latency_weight = clamp_t(long, latency_weight,
                -1 * NICE_LATENCY_WEIGHT_MAX,
                NICE_LATENCY_WEIGHT_MAX);
    return (thresh * latency_weight) >> NICE_LATENCY_SHIFT;
}
#endif /* CONFIG_SMP */

static unsigned long wakeup_gran(struct sched_entity *se)
{
    unsigned long gran = sysctl_sched_wakeup_granularity;

    /*
     * Since its curr running now, convert the gran from real-time
     * to virtual-time in his units.
     *
     * By using 'se' instead of 'curr' we penalize light tasks, so
     * they get preempted easier. That is, if 'se' < 'curr' then
     * the resulting gran will be larger, therefore penalizing the
     * lighter, if otoh 'se' > 'curr' then the resulting gran will
     * be smaller, again penalizing the lighter task.
     *
     * This is especially important for buddies when the leftmost
     * task is higher priority than the buddy.
     */
    return calc_delta_fair(gran, se);
}

/*
 * Should 'se' preempt 'curr'.
 *
 *             |s1
 *        |s2
 *   |s3
 *         g
 *      |<--->|c
 *
 *  w(c, s1) = -1
 *  w(c, s2) =  0
 *  w(c, s3) =  1
 *
 */
static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
    s64 gran, vdiff = curr->vruntime - se->vruntime;

#ifdef CONFIG_SCHED_LATENCY_NICE
    vdiff += wakeup_latency_gran(curr, se);
#endif
    if (vdiff <= 0) {
        return -1;
    }

    gran = wakeup_gran(se);
    if (vdiff > gran) {
        return 1;
    }

    return 0;
}

static void set_last_buddy(struct sched_entity *se)
{
    if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se)))) {
        return;
    }

    for_each_sched_entity(se) {
        if (SCHED_WARN_ON(!se->on_rq)) {
            return;
        }
        cfs_rq_of(se)->last = se;
    }
}

static void set_next_buddy(struct sched_entity *se)
{
    if (entity_is_task(se) && unlikely(task_has_idle_policy(task_of(se)))) {
        return;
    }

    for_each_sched_entity(se) {
        if (SCHED_WARN_ON(!se->on_rq)) {
            return;
        }
        cfs_rq_of(se)->next = se;
    }
}

static void set_skip_buddy(struct sched_entity *se)
{
    for_each_sched_entity(se) cfs_rq_of(se)->skip = se;
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
    struct task_struct *curr = rq->curr;
    struct sched_entity *se = &curr->se, *pse = &p->se;
    struct cfs_rq *cfs_rq = task_cfs_rq(curr);
    int scale = cfs_rq->nr_running >= sched_nr_latency;
    int next_buddy_marked = 0;

    if (unlikely(se == pse)) {
        return;
    }

    /*
     * This is possible from callers such as attach_tasks(), in which we
     * unconditionally check_prempt_curr() after an enqueue (which may have
     * lead to a throttle).  This both saves work and prevents false
     * next-buddy nomination below.
     */
    if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) {
        return;
    }

    if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
        set_next_buddy(pse);
        next_buddy_marked = 1;
    }

    /*
     * We can come here with TIF_NEED_RESCHED already set from new task
     * wake up path.
     *
     * Note: this also catches the edge-case of curr being in a throttled
     * group (e.g. via set_curr_task), since update_curr() (in the
     * enqueue of curr) will have resulted in resched being set.  This
     * prevents us from potentially nominating it as a false LAST_BUDDY
     * below.
     */
    if (test_tsk_need_resched(curr)) {
        return;
    }

    /* Idle tasks are by definition preempted by non-idle tasks. */
    if (unlikely(task_has_idle_policy(curr)) && likely(!task_has_idle_policy(p))) {
        goto preempt;
    }

    /*
     * Batch and idle tasks do not preempt non-idle tasks (their preemption
     * is driven by the tick):
     */
    if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) {
        return;
    }

    find_matching_se(&se, &pse);
    update_curr(cfs_rq_of(se));
    BUG_ON(!pse);
    if (wakeup_preempt_entity(se, pse) == 1) {
        /*
         * Bias pick_next to pick the sched entity that is
         * triggering this preemption.
         */
        if (!next_buddy_marked) {
            set_next_buddy(pse);
        }
        goto preempt;
    }

    return;

preempt:
    resched_curr(rq);
    /*
     * Only set the backward buddy when the current task is still
     * on the rq. This can happen when a wakeup gets interleaved
     * with schedule on the ->pre_schedule() or idle_balance()
     * point, either of which can * drop the rq lock.
     *
     * Also, during early boot the idle thread is in the fair class,
     * for obvious reasons its a bad idea to schedule back to it.
     */
    if (unlikely(!se->on_rq || curr == rq->idle)) {
        return;
    }

    if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) {
        set_last_buddy(se);
    }
}

struct task_struct *pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
    struct cfs_rq *cfs_rq = &rq->cfs;
    struct sched_entity *se;
    struct task_struct *p;
    int new_tasks;

    while (1) {
        if (!sched_fair_runnable(rq)) {
            goto idle;
        }

#ifdef CONFIG_FAIR_GROUP_SCHED
        if (!prev || prev->sched_class != &fair_sched_class) {
            goto simple;
        }

        /*
         * Because of the set_next_buddy() in dequeue_task_fair() it is rather
         * likely that a next task is from the same cgroup as the current.
         *
         * Therefore attempt to avoid putting and setting the entire cgroup
         * hierarchy, only change the part that actually changes.
         */

        do {
            struct sched_entity *curr = cfs_rq->curr;

            /*
             * Since we got here without doing put_prev_entity() we also
             * have to consider cfs_rq->curr. If it is still a runnable
             * entity, update_curr() will update its vruntime, otherwise
             * forget we've ever seen it.
             */
            if (curr) {
                if (curr->on_rq) {
                    update_curr(cfs_rq);
                } else {
                    curr = NULL;
                }

                /*
                 * This call to check_cfs_rq_runtime() will do the
                 * throttle and dequeue its entity in the parent(s).
                 * Therefore the nr_running test will indeed
                 * be correct.
                 */
                if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
                    cfs_rq = &rq->cfs;

                    if (!cfs_rq->nr_running) {
                        goto idle;
                    }

                    goto simple;
                }
            }

            se = pick_next_entity(cfs_rq, curr);
            cfs_rq = group_cfs_rq(se);
        } while (cfs_rq);

        p = task_of(se);
        /*
         * Since we haven't yet done put_prev_entity and if the selected task
         * is a different task than we started out with, try and touch the
         * least amount of cfs_rqs.
         */
        if (prev != p) {
            struct sched_entity *pse = &prev->se;

            while (!(cfs_rq = is_same_group(se, pse))) {
                int se_depth = se->depth;
                int pse_depth = pse->depth;

                if (se_depth <= pse_depth) {
                    put_prev_entity(cfs_rq_of(pse), pse);
                    pse = parent_entity(pse);
                }
                if (se_depth >= pse_depth) {
                    set_next_entity(cfs_rq_of(se), se);
                    se = parent_entity(se);
                }
            }

            put_prev_entity(cfs_rq, pse);
            set_next_entity(cfs_rq, se);
        }

        goto done;
    simple:
#endif
        if (prev) {
            put_prev_task(rq, prev);
        }

        do {
            se = pick_next_entity(cfs_rq, NULL);
            set_next_entity(cfs_rq, se);
            cfs_rq = group_cfs_rq(se);
        } while (cfs_rq);

        p = task_of(se);

    done:
        __maybe_unused;
#ifdef CONFIG_SMP
        /*
         * Move the next running task to the front of
         * the list, so our cfs_tasks list becomes MRU
         * one.
         */
        list_move(&p->se.group_node, &rq->cfs_tasks);
#endif

        if (hrtick_enabled(rq)) {
            hrtick_start_fair(rq, p);
        }

        update_misfit_status(p, rq);

        return p;

    idle:
        if (!rf) {
            return NULL;
        }

        new_tasks = newidle_balance(rq, rf);
        /*
         * Because newidle_balance() releases (and re-acquires) rq->lock, it is
         * possible for any higher priority task to appear. In that case we
         * must re-start the pick_next_entity() loop.
         */
        if (new_tasks < 0) {
            return RETRY_TASK;
        }

        if (new_tasks > 0) {
            continue;
        }
        break;
    }

    /*
     * rq is about to be idle, check if we need to update the
     * lost_idle_time of clock_pelt
     */
    update_idle_rq_clock_pelt(rq);

    return NULL;
}

static struct task_struct *fair_pick_next_task_fair(struct rq *rq)
{
    return pick_next_task_fair(rq, NULL, NULL);
}

/*
 * Account for a descheduled task
 */
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
{
    struct sched_entity *se = &prev->se;
    struct cfs_rq *cfs_rq;

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        put_prev_entity(cfs_rq, se);
    }
}

/*
 * sched_yield() is very simple
 *
 * The magic of dealing with the ->skip buddy is in pick_next_entity.
 */
static void yield_task_fair(struct rq *rq)
{
    struct task_struct *curr = rq->curr;
    struct cfs_rq *cfs_rq = task_cfs_rq(curr);
    struct sched_entity *se = &curr->se;

    /*
     * Are we the only task in the tree?
     */
    if (unlikely(rq->nr_running == 1)) {
        return;
    }

    clear_buddies(cfs_rq, se);

    if (curr->policy != SCHED_BATCH) {
        update_rq_clock(rq);
        /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);
        /*
         * Tell update_rq_clock() that we've just updated,
         * so we don't do microscopic update in schedule()
         * and double the fastpath cost.
         */
        rq_clock_skip_update(rq);
    }

    set_skip_buddy(se);
}

static bool yield_to_task_fair(struct rq *rq, struct task_struct *p)
{
    struct sched_entity *se = &p->se;

    /* throttled hierarchies are not runnable */
    if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) {
        return false;
    }

    /* Tell the scheduler that we'd really like pse to run next. */
    set_next_buddy(se);

    yield_task_fair(rq);

    return true;
}

#ifdef CONFIG_SMP
/**************************************************
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-CPU scheduler provides, namely provide a proportional amount of compute
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
 * is derived from the nice value as per sched_prio_to_weight[].
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
 * C_i is the compute capacity of CPU i, typically it is the
 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
 * can also include other factors [XXX].
 *
 * To achieve this balance we define a measure of imbalance which follows
 * directly from (1):
 *
 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
 *
 * We them move tasks around to minimize the imbalance. In the continuous
 * function space it is obvious this converges, in the discrete case we get
 * a few fun cases generally called infeasible weight scenarios.
 *
 * [XXX expand on:
 *     - infeasible weights;
 *     - local vs global optima in the discrete case. ]
 *
 *
 * SCHED DOMAINS
 *
 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
 * for all i,j solution, we create a tree of CPUs that follows the hardware
 * topology where each level pairs two lower groups (or better). This results
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
 * tree to only the first of the previous level and we decrease the frequency
 * of load-balance at each level inv. proportional to the number of CPUs in
 * the groups.
 *
 * This yields:
 *
 *     log_2 n     1     n
 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
 *     i = 0      2^i   2^i
 *                               `- size of each group
 *         |         |     `- number of CPUs doing load-balance
 *         |         `- freq
 *         `- sum over all levels
 *
 * Coupled with a limit on how many tasks we can migrate every balance pass,
 * this makes (5) the runtime complexity of the balancer.
 *
 * An important property here is that each CPU is still (indirectly) connected
 * to every other CPU in at most O(log n) steps:
 *
 * The adjacency matrix of the resulting graph is given by:
 *
 *             log_2 n
 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
 *             k = 0
 *
 * And you'll find that:
 *
 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
 *
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
 * The task movement gives a factor of O(m), giving a convergence complexity
 * of:
 *
 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
 *
 *
 * WORK CONSERVING
 *
 * In order to avoid CPUs going idle while there's still work to do, new idle
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
 * tree itself instead of relying on other CPUs to bring it work.
 *
 * This adds some complexity to both (5) and (8) but it reduces the total idle
 * time.
 *
 * [XXX more?]
 *
 *
 * CGROUPS
 *
 * Cgroups make a horror show out of (2), instead of a simple sum we get:
 *
 *                                s_k,i
 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
 *                                 S_k
 *
 * Where
 *
 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
 *
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
 *
 * The big problem is S_k, its a global sum needed to compute a local (W_i)
 * property.
 *
 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
 *      rewrite all of this once again.]
 */

static unsigned long __read_mostly max_load_balance_interval = HZ / 10;

enum fbq_type { regular, remote, all };

/*
 * 'group_type' describes the group of CPUs at the moment of load balancing.
 *
 * The enum is ordered by pulling priority, with the group with lowest priority
 * first so the group_type can simply be compared when selecting the busiest
 * group. See update_sd_pick_busiest().
 */
enum group_type {
    /* The group has spare capacity that can be used to run more tasks.  */
    group_has_spare = 0,
    /*
     * The group is fully used and the tasks don't compete for more CPU
     * cycles. Nevertheless, some tasks might wait before running.
     */
    group_fully_busy,
    /*
     * SD_ASYM_CPUCAPACITY only: One task doesn't fit with CPU's capacity
     * and must be migrated to a more powerful CPU.
     */
    group_misfit_task,
    /*
     * SD_ASYM_PACKING only: One local CPU with higher capacity is available,
     * and the task should be migrated to it instead of running on the
     * current CPU.
     */
    group_asym_packing,
    /*
     * The tasks' affinity constraints previously prevented the scheduler
     * from balancing the load across the system.
     */
    group_imbalanced,
    /*
     * The CPU is overloaded and can't provide expected CPU cycles to all
     * tasks.
     */
    group_overloaded
};

enum migration_type { migrate_load = 0, migrate_util, migrate_task, migrate_misfit };

#define LBF_ALL_PINNED 0x01
#define LBF_NEED_BREAK 0x02
#define LBF_DST_PINNED 0x04
#define LBF_SOME_PINNED 0x08
#define LBF_NOHZ_STATS 0x10
#define LBF_NOHZ_AGAIN 0x20
#define LBF_IGNORE_PREFERRED_CLUSTER_TASKS 0x200

struct lb_env {
    struct sched_domain *sd;

    struct rq *src_rq;
    int src_cpu;

    int dst_cpu;
    struct rq *dst_rq;

    struct cpumask *dst_grpmask;
    int new_dst_cpu;
    enum cpu_idle_type idle;
    long imbalance;
    /* The set of CPUs under consideration for load-balancing */
    struct cpumask *cpus;

    unsigned int flags;

    unsigned int loop;
    unsigned int loop_break;
    unsigned int loop_max;

    enum fbq_type fbq_type;
    enum migration_type migration_type;
    struct list_head tasks;
};

/*
 * Is this task likely cache-hot:
 */
static int task_hot(struct task_struct *p, struct lb_env *env)
{
    s64 delta;

    lockdep_assert_held(&env->src_rq->lock);

    if (p->sched_class != &fair_sched_class) {
        return 0;
    }

    if (unlikely(task_has_idle_policy(p))) {
        return 0;
    }

    /* SMT siblings share cache */
    if (env->sd->flags & SD_SHARE_CPUCAPACITY) {
        return 0;
    }

    /*
     * Buddy candidates are cache hot:
     */
    if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
        (&p->se == cfs_rq_of(&p->se)->next || &p->se == cfs_rq_of(&p->se)->last)) {
        return 1;
    }

    if (sysctl_sched_migration_cost == -1) {
        return 1;
    }
    if (sysctl_sched_migration_cost == 0) {
        return 0;
    }

    delta = rq_clock_task(env->src_rq) - p->se.exec_start;

    return delta < (s64)sysctl_sched_migration_cost;
}

#ifdef CONFIG_NUMA_BALANCING
/*
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
 */
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
    struct numa_group *numa_group = rcu_dereference(p->numa_group);
    unsigned long src_weight, dst_weight;
    int src_nid, dst_nid, dist;

    if (!static_branch_likely(&sched_numa_balancing)) {
        return -1;
    }

    if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) {
        return -1;
    }

    src_nid = cpu_to_node(env->src_cpu);
    dst_nid = cpu_to_node(env->dst_cpu);
    if (src_nid == dst_nid) {
        return -1;
    }

    /* Migrating away from the preferred node is always bad. */
    if (src_nid == p->numa_preferred_nid) {
        if (env->src_rq->nr_running > env->src_rq->nr_preferred_running) {
            return 1;
        } else {
            return -1;
        }
    }

    /* Encourage migration to the preferred node. */
    if (dst_nid == p->numa_preferred_nid) {
        return 0;
    }

    /* Leaving a core idle is often worse than degrading locality. */
    if (env->idle == CPU_IDLE) {
        return -1;
    }

    dist = node_distance(src_nid, dst_nid);
    if (numa_group) {
        src_weight = group_weight(p, src_nid, dist);
        dst_weight = group_weight(p, dst_nid, dist);
    } else {
        src_weight = task_weight(p, src_nid, dist);
        dst_weight = task_weight(p, dst_nid, dist);
    }

    return dst_weight < src_weight;
}

#else
static inline int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
    return -1;
}
#endif

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static int can_migrate_task(struct task_struct *p, struct lb_env *env)
{
    int tsk_cache_hot;

    lockdep_assert_held(&env->src_rq->lock);

    /*
     * We do not migrate tasks that are:
     * 1) throttled_lb_pair, or
     * 2) cannot be migrated to this CPU due to cpus_ptr, or
     * 3) running (obviously), or
     * 4) are cache-hot on their current CPU.
     */
    if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) {
        return 0;
    }

    /* Disregard pcpu kthreads; they are where they need to be. */
    if (kthread_is_per_cpu(p)) {
        return 0;
    }

    if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) {
        int cpu;

        schedstat_inc(p->se.statistics.nr_failed_migrations_affine);

        env->flags |= LBF_SOME_PINNED;

        /*
         * Remember if this task can be migrated to any other CPU in
         * our sched_group. We may want to revisit it if we couldn't
         * meet load balance goals by pulling other tasks on src_cpu.
         *
         * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
         * already computed one in current iteration.
         */
        if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED)) {
            return 0;
        }

        /* Prevent to re-select dst_cpu via env's CPUs: */
        for_each_cpu_and(cpu, env->dst_grpmask, env->cpus)
        {
            if (cpumask_test_cpu(cpu, p->cpus_ptr)) {
                env->flags |= LBF_DST_PINNED;
                env->new_dst_cpu = cpu;
                break;
            }
        }

        return 0;
    }

    /* Record that we found atleast one task that could run on dst_cpu */
    env->flags &= ~LBF_ALL_PINNED;

#ifdef CONFIG_SCHED_RTG
    if (env->flags & LBF_IGNORE_PREFERRED_CLUSTER_TASKS && !preferred_cluster(cpu_rq(env->dst_cpu)->cluster, p)) {
        return 0;
    }
#endif

    if (task_running(env->src_rq, p)) {
        schedstat_inc(p->se.statistics.nr_failed_migrations_running);
        return 0;
    }

    /*
     * Aggressive migration if:
     * 1) destination numa is preferred
     * 2) task is cache cold, or
     * 3) too many balance attempts have failed.
     */
    tsk_cache_hot = migrate_degrades_locality(p, env);
    if (tsk_cache_hot == -1) {
        tsk_cache_hot = task_hot(p, env);
    }

    if (tsk_cache_hot <= 0 || env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
        if (tsk_cache_hot == 1) {
            schedstat_inc(env->sd->lb_hot_gained[env->idle]);
            schedstat_inc(p->se.statistics.nr_forced_migrations);
        }
        return 1;
    }

    schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
    return 0;
}

/*
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
    lockdep_assert_held(&env->src_rq->lock);

    deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
#ifdef CONFIG_SCHED_WALT
    double_lock_balance(env->src_rq, env->dst_rq);
    if (!(env->src_rq->clock_update_flags & RQCF_UPDATED)) {
        update_rq_clock(env->src_rq);
    }
#endif
    set_task_cpu(p, env->dst_cpu);
#ifdef CONFIG_SCHED_WALT
    double_unlock_balance(env->src_rq, env->dst_rq);
#endif
}

/*
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
 * part of active balancing operations within "domain".
 *
 * Returns a task if successful and NULL otherwise.
 */
static struct task_struct *detach_one_task(struct lb_env *env)
{
    struct task_struct *p;

    lockdep_assert_held(&env->src_rq->lock);

    list_for_each_entry_reverse(p, &env->src_rq->cfs_tasks, se.group_node)
    {
        if (!can_migrate_task(p, env)) {
            continue;
        }

        detach_task(p, env);

        /*
         * Right now, this is only the second place where
         * lb_gained[env->idle] is updated (other is detach_tasks)
         * so we can safely collect stats here rather than
         * inside detach_tasks().
         */
        schedstat_inc(env->sd->lb_gained[env->idle]);
        return p;
    }
    return NULL;
}

static const unsigned int sched_nr_migrate_break = 32;

/*
 * detach_tasks() -- tries to detach up to imbalance load/util/tasks from
 * busiest_rq, as part of a balancing operation within domain "sd".
 *
 * Returns number of detached tasks if successful and 0 otherwise.
 */
static int detach_tasks(struct lb_env *env)
{
    struct list_head *tasks = &env->src_rq->cfs_tasks;
    unsigned long util, load;
    struct task_struct *p;
    int detached = 0;
#ifdef CONFIG_SCHED_RTG
    int orig_loop = env->loop;
#endif

    lockdep_assert_held(&env->src_rq->lock);

    if (env->imbalance <= 0) {
        return 0;
    }

#ifdef CONFIG_SCHED_RTG
    if (!same_cluster(env->dst_cpu, env->src_cpu)) {
        env->flags |= LBF_IGNORE_PREFERRED_CLUSTER_TASKS;
    }

redo:
#endif
    while (!list_empty(tasks)) {
        /*
         * We don't want to steal all, otherwise we may be treated likewise,
         * which could at worst lead to a livelock crash.
         */
        if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) {
            break;
        }

        p = list_last_entry(tasks, struct task_struct, se.group_node);

        env->loop++;
        /* We've more or less seen every task there is, call it quits */
        if (env->loop > env->loop_max) {
            break;
        }

        /* take a breather every nr_migrate tasks */
        if (env->loop > env->loop_break) {
            env->loop_break += sched_nr_migrate_break;
            env->flags |= LBF_NEED_BREAK;
            break;
        }

        if (!can_migrate_task(p, env)) {
            goto next;
        }

        switch (env->migration_type) {
            case migrate_load:
                /*
                 * Depending of the number of CPUs and tasks and the
                 * cgroup hierarchy, task_h_load() can return a null
                 * value. Make sure that env->imbalance decreases
                 * otherwise detach_tasks() will stop only after
                 * detaching up to loop_max tasks.
                 */
                load = max_t(unsigned long, task_h_load(p), 1);

                if (sched_feat(LB_MIN) && load < 0x10 && !env->sd->nr_balance_failed) {
                    goto next;
                }

                /*
                 * Make sure that we don't migrate too much load.
                 * Nevertheless, let relax the constraint if
                 * scheduler fails to find a good waiting task to
                 * migrate.
                 */
                if (shr_bound(load, env->sd->nr_balance_failed) > env->imbalance) {
                    goto next;
                }

                env->imbalance -= load;
                break;

            case migrate_util:
                util = task_util_est(p);
                if (util > env->imbalance) {
                    goto next;
                }

                env->imbalance -= util;
                break;

            case migrate_task:
                env->imbalance--;
                break;

            case migrate_misfit:
                /* This is not a misfit task */
                if (task_fits_capacity(p, capacity_of(env->src_cpu))) {
                    goto next;
                }

                env->imbalance = 0;
                break;
        }

        detach_task(p, env);
        list_add(&p->se.group_node, &env->tasks);

        detached++;

#ifdef CONFIG_PREEMPTION
        /*
         * NEWIDLE balancing is a source of latency, so preemptible
         * kernels will stop after the first task is detached to minimize
         * the critical section.
         */
        if (env->idle == CPU_NEWLY_IDLE) {
            break;
        }
#endif

        /*
         * We only want to steal up to the prescribed amount of
         * load/util/tasks.
         */
        if (env->imbalance <= 0) {
            break;
        }

        continue;
    next:
        list_move(&p->se.group_node, tasks);
    }

#ifdef CONFIG_SCHED_RTG
    if (env->flags & LBF_IGNORE_PREFERRED_CLUSTER_TASKS && !detached) {
        tasks = &env->src_rq->cfs_tasks;
        env->flags &= ~LBF_IGNORE_PREFERRED_CLUSTER_TASKS;
        env->loop = orig_loop;
        goto redo;
    }
#endif

    /*
     * Right now, this is one of only two places we collect this stat
     * so we can safely collect detach_one_task() stats here rather
     * than inside detach_one_task().
     */
    schedstat_add(env->sd->lb_gained[env->idle], detached);

    return detached;
}

/*
 * attach_task() -- attach the task detached by detach_task() to its new rq.
 */
static void attach_task(struct rq *rq, struct task_struct *p)
{
    lockdep_assert_held(&rq->lock);

    BUG_ON(task_rq(p) != rq);
    activate_task(rq, p, ENQUEUE_NOCLOCK);
    check_preempt_curr(rq, p, 0);
}

/*
 * attach_one_task() -- attaches the task returned from detach_one_task() to
 * its new rq.
 */
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
    struct rq_flags rf;

    rq_lock(rq, &rf);
    update_rq_clock(rq);
    attach_task(rq, p);
    rq_unlock(rq, &rf);
}

/*
 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
 * new rq.
 */
static void attach_tasks(struct lb_env *env)
{
    struct list_head *tasks = &env->tasks;
    struct task_struct *p;
    struct rq_flags rf;

    rq_lock(env->dst_rq, &rf);
    update_rq_clock(env->dst_rq);

    while (!list_empty(tasks)) {
        p = list_first_entry(tasks, struct task_struct, se.group_node);
        list_del_init(&p->se.group_node);

        attach_task(env->dst_rq, p);
    }

    rq_unlock(env->dst_rq, &rf);
}

#ifdef CONFIG_NO_HZ_COMMON
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
    if (cfs_rq->avg.load_avg) {
        return true;
    }

    if (cfs_rq->avg.util_avg) {
        return true;
    }

    return false;
}

static inline bool others_have_blocked(struct rq *rq)
{
    if (READ_ONCE(rq->avg_rt.util_avg)) {
        return true;
    }

    if (READ_ONCE(rq->avg_dl.util_avg)) {
        return true;
    }

    if (thermal_load_avg(rq)) {
        return true;
    }

#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
    if (READ_ONCE(rq->avg_irq.util_avg)) {
        return true;
    }
#endif

    return false;
}

static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
{
    rq->last_blocked_load_update_tick = jiffies;

    if (!has_blocked) {
        rq->has_blocked_load = 0;
    }
}
#else
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
    return false;
}
static inline bool others_have_blocked(struct rq *rq)
{
    return false;
}
static inline void update_blocked_load_status(struct rq *rq, bool has_blocked)
{
}
#endif

static bool fair_update_blocked_others(struct rq *rq, bool *done)
{
    const struct sched_class *curr_class;
    u64 now = rq_clock_pelt(rq);
    unsigned long thermal_pressure;
    bool decayed;

    /*
     * update_load_avg() can call cpufreq_update_util(). Make sure that RT,
     * DL and IRQ signals have been updated before updating CFS.
     */
    curr_class = rq->curr->sched_class;

    thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));

    decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
              update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
              update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) | update_irq_load_avg(rq, 0);

    if (others_have_blocked(rq)) {
        *done = false;
    }

    return decayed;
}

#ifdef CONFIG_FAIR_GROUP_SCHED

static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
    if (cfs_rq->load.weight) {
        return false;
    }

    if (cfs_rq->avg.load_sum) {
        return false;
    }

    if (cfs_rq->avg.util_sum) {
        return false;
    }

    if (cfs_rq->avg.runnable_sum) {
        return false;
    }

    return true;
}

static bool fair_update_blocked_fair(struct rq *rq, bool *done)
{
    struct cfs_rq *cfs_rq, *pos;
    bool decayed = false;
    int cpu = cpu_of(rq);

    /*
     * Iterates the task_group tree in a bottom up fashion, see
     * list_add_leaf_cfs_rq() for details.
     */
    for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
        struct sched_entity *se;

        if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
            update_tg_load_avg(cfs_rq);

            if (cfs_rq == &rq->cfs) {
                decayed = true;
            }
        }

        /* Propagate pending load changes to the parent, if any: */
        se = cfs_rq->tg->se[cpu];
        if (se && !skip_blocked_update(se)) {
            update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
        }

        /*
         * There can be a lot of idle CPU cgroups.  Don't let fully
         * decayed cfs_rqs linger on the list.
         */
        if (cfs_rq_is_decayed(cfs_rq)) {
            list_del_leaf_cfs_rq(cfs_rq);
        }

        /* Don't need periodic decay once load/util_avg are null */
        if (cfs_rq_has_blocked(cfs_rq)) {
            *done = false;
        }
    }

    return decayed;
}

/*
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
{
    struct rq *rq = rq_of(cfs_rq);
    struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
    unsigned long now = jiffies;
    unsigned long load;

    if (cfs_rq->last_h_load_update == now) {
        return;
    }

    WRITE_ONCE(cfs_rq->h_load_next, NULL);
    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        WRITE_ONCE(cfs_rq->h_load_next, se);
        if (cfs_rq->last_h_load_update == now) {
            break;
        }
    }

    if (!se) {
        cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
        cfs_rq->last_h_load_update = now;
    }

    while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
        load = cfs_rq->h_load;
        load = div64_ul(load * se->avg.load_avg, cfs_rq_load_avg(cfs_rq) + 1);
        cfs_rq = group_cfs_rq(se);
        cfs_rq->h_load = load;
        cfs_rq->last_h_load_update = now;
    }
}

static unsigned long task_h_load(struct task_struct *p)
{
    struct cfs_rq *cfs_rq = task_cfs_rq(p);

    update_cfs_rq_h_load(cfs_rq);
    return div64_ul(p->se.avg.load_avg * cfs_rq->h_load, cfs_rq_load_avg(cfs_rq) + 1);
}
#else
static bool fair_update_blocked_fair(struct rq *rq, bool *done)
{
    struct cfs_rq *cfs_rq = &rq->cfs;
    bool decayed;

    decayed = update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq);
    if (cfs_rq_has_blocked(cfs_rq)) {
        *done = false;
    }

    return decayed;
}

static unsigned long task_h_load(struct task_struct *p)
{
    return p->se.avg.load_avg;
}
#endif

static void update_blocked_averages(int cpu)
{
    bool decayed = false, done = true;
    struct rq *rq = cpu_rq(cpu);
    struct rq_flags rf;

    rq_lock_irqsave(rq, &rf);
    update_rq_clock(rq);

    decayed |= fair_update_blocked_others(rq, &done);
    decayed |= fair_update_blocked_fair(rq, &done);

    update_blocked_load_status(rq, !done);
    if (decayed) {
        cpufreq_update_util(rq, 0);
    }
    rq_unlock_irqrestore(rq, &rf);
}

/********** Helpers for find_busiest_group ************************/

/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
    unsigned long avg_load;   /* Avg load across the CPUs of the group */
    unsigned long group_load; /* Total load over the CPUs of the group */
    unsigned long group_capacity;
    unsigned long group_util;      /* Total utilization over the CPUs of the group */
    unsigned long group_runnable;  /* Total runnable time over the CPUs of the group */
    unsigned int sum_nr_running;   /* Nr of tasks running in the group */
    unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
    unsigned int idle_cpus;
    unsigned int group_weight;
    enum group_type group_type;
    unsigned int group_asym_packing;      /* Tasks should be moved to preferred CPU */
    unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
#ifdef CONFIG_NUMA_BALANCING
    unsigned int nr_numa_running;
    unsigned int nr_preferred_running;
#endif
};

/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *         during load balancing.
 */
struct sd_lb_stats {
    struct sched_group *busiest;  /* Busiest group in this sd */
    struct sched_group *local;    /* Local group in this sd */
    unsigned long total_load;     /* Total load of all groups in sd */
    unsigned long total_capacity; /* Total capacity of all groups in sd */
    unsigned long avg_load;       /* Average load across all groups in sd */
    unsigned int prefer_sibling;  /* tasks should go to sibling first */

    struct sg_lb_stats busiest_stat; /* Statistics of the busiest group */
    struct sg_lb_stats local_stat;   /* Statistics of the local group */
};

static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
    /*
     * Skimp on the clearing to avoid duplicate work. We can avoid clearing
     * local_stat because update_sg_lb_stats() does a full clear/assignment.
     * We must however set busiest_stat::group_type and
     * busiest_stat::idle_cpus to the worst busiest group because
     * update_sd_pick_busiest() reads these before assignment.
     */
    *sds = (struct sd_lb_stats) {
        .busiest = NULL,
        .local = NULL,
        .total_load = 0UL,
        .total_capacity = 0UL,
        .busiest_stat =
            {
                .idle_cpus = UINT_MAX,
                .group_type = group_has_spare,
            },
    };
}

static unsigned long scale_rt_capacity(int cpu)
{
    struct rq *rq = cpu_rq(cpu);
    unsigned long max = arch_scale_cpu_capacity(cpu);
    unsigned long used, free;
    unsigned long irq;

    irq = cpu_util_irq(rq);
    if (unlikely(irq >= max)) {
        return 1;
    }

    /*
     * avg_rt.util_avg and avg_dl.util_avg track binary signals
     * (running and not running) with weights 0 and 1024 respectively.
     * avg_thermal.load_avg tracks thermal pressure and the weighted
     * average uses the actual delta max capacity(load).
     */
    used = READ_ONCE(rq->avg_rt.util_avg);
    used += READ_ONCE(rq->avg_dl.util_avg);
    used += thermal_load_avg(rq);
    if (unlikely(used >= max)) {
        return 1;
    }

    free = max - used;

    return scale_irq_capacity(free, irq, max);
}

static void update_cpu_capacity(struct sched_domain *sd, int cpu)
{
    unsigned long capacity = scale_rt_capacity(cpu);
    struct sched_group *sdg = sd->groups;

    cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(cpu);

    if (!capacity) {
        capacity = 1;
    }

    cpu_rq(cpu)->cpu_capacity = capacity;
    trace_sched_cpu_capacity_tp(cpu_rq(cpu));

    sdg->sgc->capacity = capacity;
    sdg->sgc->min_capacity = capacity;
    sdg->sgc->max_capacity = capacity;
}

void update_group_capacity(struct sched_domain *sd, int cpu)
{
    struct sched_domain *child = sd->child;
    struct sched_group *group, *sdg = sd->groups;
    unsigned long capacity, min_capacity, max_capacity;
    unsigned long interval;

    interval = msecs_to_jiffies(sd->balance_interval);
    interval = clamp(interval, 1UL, max_load_balance_interval);
    sdg->sgc->next_update = jiffies + interval;

    if (!child) {
        update_cpu_capacity(sd, cpu);
        return;
    }

    capacity = 0;
    min_capacity = ULONG_MAX;
    max_capacity = 0;

    if (child->flags & SD_OVERLAP) {
        /*
         * SD_OVERLAP domains cannot assume that child groups
         * span the current group.
         */

        for_each_cpu(cpu, sched_group_span(sdg))
        {
            unsigned long cpu_cap = capacity_of(cpu);

            if (cpu_isolated(cpu)) {
                continue;
            }

            capacity += cpu_cap;
            min_capacity = min(cpu_cap, min_capacity);
            max_capacity = max(cpu_cap, max_capacity);
        }
    } else {
        /*
         * !SD_OVERLAP domains can assume that child groups
         * span the current group.
         */

        group = child->groups;
        do {
            struct sched_group_capacity *sgc = group->sgc;
            __maybe_unused cpumask_t *cpus = sched_group_span(group);

            if (!cpu_isolated(cpumask_first(cpus))) {
                capacity += sgc->capacity;
                min_capacity = min(sgc->min_capacity, min_capacity);
                max_capacity = max(sgc->max_capacity, max_capacity);
            }
            group = group->next;
        } while (group != child->groups);
    }

    sdg->sgc->capacity = capacity;
    sdg->sgc->min_capacity = min_capacity;
    sdg->sgc->max_capacity = max_capacity;
}

/*
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
 */
static inline int check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
{
    return ((rq->cpu_capacity * sd->imbalance_pct) < (rq->cpu_capacity_orig * FAIR_ONEHUNDRED));
}

/*
 * Check whether a rq has a misfit task and if it looks like we can actually
 * help that task: we can migrate the task to a CPU of higher capacity, or
 * the task's current CPU is heavily pressured.
 */
static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
{
    return rq->misfit_task_load && (rq->cpu_capacity_orig < rq->rd->max_cpu_capacity || check_cpu_capacity(rq, sd));
}

/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
 * groups is inadequate due to ->cpus_ptr constraints.
 *
 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
 * Something like
 *
 *    { 0 1 2 3 } { 4 5 6 7 }
 *            *     * * *
 *
 * If we were to balance group-wise we'd place two tasks in the first group and
 * two tasks in the second group. Clearly this is undesired as it will overload
 * cpu 3 and leave one of the CPUs in the second group unused.
 *
 * The current solution to this issue is detecting the skew in the first group
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
 *
 * When this is so detected; this group becomes a candidate for busiest; see
 * update_sd_pick_busiest(). And calculate_imbalance() and
 * find_busiest_group() avoid some of the usual balance conditions to allow it
 * to create an effective group imbalance.
 *
 * This is a somewhat tricky proposition since the next run might not find the
 * group imbalance and decide the groups need to be balanced again. A most
 * subtle and fragile situation.
 */

static inline int sg_imbalanced(struct sched_group *group)
{
    return group->sgc->imbalance;
}

/*
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
 */
static inline bool group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
{
    if (sgs->sum_nr_running < sgs->group_weight) {
        return true;
    }

    if ((sgs->group_capacity * imbalance_pct) < (sgs->group_runnable * FAIR_ONEHUNDRED)) {
        return false;
    }

    if ((sgs->group_capacity * FAIR_ONEHUNDRED) > (sgs->group_util * imbalance_pct)) {
        return true;
    }

    return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
{
    if (sgs->sum_nr_running <= sgs->group_weight) {
        return false;
    }

    if ((sgs->group_capacity * FAIR_ONEHUNDRED) < (sgs->group_util * imbalance_pct)) {
        return true;
    }

    if ((sgs->group_capacity * imbalance_pct) < (sgs->group_runnable * 0x64)) {
        return true;
    }

    return false;
}

/*
 * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
 * per-CPU capacity than sched_group ref.
 */
static inline bool group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
    return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity);
}

/*
 * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
 * per-CPU capacity_orig than sched_group ref.
 */
static inline bool group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
    return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity);
}

static inline enum group_type group_classify(unsigned int imbalance_pct, struct sched_group *group,
                                             struct sg_lb_stats *sgs)
{
    if (group_is_overloaded(imbalance_pct, sgs)) {
        return group_overloaded;
    }

    if (sg_imbalanced(group)) {
        return group_imbalanced;
    }

    if (sgs->group_asym_packing) {
        return group_asym_packing;
    }

    if (sgs->group_misfit_task_load) {
        return group_misfit_task;
    }

    if (!group_has_capacity(imbalance_pct, sgs)) {
        return group_fully_busy;
    }

    return group_has_spare;
}

static bool update_nohz_stats(struct rq *rq, bool force)
{
#ifdef CONFIG_NO_HZ_COMMON
    unsigned int cpu = rq->cpu;

    if (!rq->has_blocked_load) {
        return false;
    }

    if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask)) {
        return false;
    }

    if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick)) {
        return true;
    }

    update_blocked_averages(cpu);

    return rq->has_blocked_load;
#else
    return false;
#endif
}

/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
 * @env: The load balancing environment.
 * @group: sched_group whose statistics are to be updated.
 * @sgs: variable to hold the statistics for this group.
 * @sg_status: Holds flag indicating the status of the sched_group
 */
static inline void update_sg_lb_stats(struct lb_env *env, struct sched_group *group, struct sg_lb_stats *sgs,
                                      int *sg_status)
{
    int i, nr_running, local_group;

    memset(sgs, 0, sizeof(*sgs));

    local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));

    for_each_cpu_and(i, sched_group_span(group), env->cpus)
    {
        struct rq *rq = cpu_rq(i);

        if (cpu_isolated(i)) {
            continue;
        }

        if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false)) {
            env->flags |= LBF_NOHZ_AGAIN;
        }

        sgs->group_load += cpu_load(rq);
        sgs->group_util += cpu_util(i);
        sgs->group_runnable += cpu_runnable(rq);
        sgs->sum_h_nr_running += rq->cfs.h_nr_running;

        nr_running = rq->nr_running;
        sgs->sum_nr_running += nr_running;

        if (nr_running > 1) {
            *sg_status |= SG_OVERLOAD;
        }

        if (cpu_overutilized(i)) {
            *sg_status |= SG_OVERUTILIZED;
        }

#ifdef CONFIG_NUMA_BALANCING
        sgs->nr_numa_running += rq->nr_numa_running;
        sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
        /*
         * No need to call idle_cpu() if nr_running is not 0
         */
        if (!nr_running && idle_cpu(i)) {
            sgs->idle_cpus++;
            /* Idle cpu can't have misfit task */
            continue;
        }

        if (local_group) {
            continue;
        }

        /* Check for a misfit task on the cpu */
        if (env->sd->flags & SD_ASYM_CPUCAPACITY && sgs->group_misfit_task_load < rq->misfit_task_load) {
            sgs->group_misfit_task_load = rq->misfit_task_load;
            *sg_status |= SG_OVERLOAD;
        }
    }

    /* Isolated CPU has no weight */
    if (!group->group_weight) {
        sgs->group_capacity = 0;
        sgs->avg_load = 0;
        sgs->group_type = group_has_spare;
        sgs->group_weight = group->group_weight;
        return;
    }

    /* Check if dst CPU is idle and preferred to this group */
    if (env->sd->flags & SD_ASYM_PACKING && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
        sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
        sgs->group_asym_packing = 1;
    }

    sgs->group_capacity = group->sgc->capacity;

    sgs->group_weight = group->group_weight;

    sgs->group_type = group_classify(env->sd->imbalance_pct, group, sgs);

    /* Computing avg_load makes sense only when group is overloaded */
    if (sgs->group_type == group_overloaded) {
        sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / sgs->group_capacity;
    }
}

/**
 * update_sd_pick_busiest - return 1 on busiest group
 * @env: The load balancing environment.
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
 * @sgs: sched_group statistics
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
 */
static bool update_sd_pick_busiest(struct lb_env *env, struct sd_lb_stats *sds, struct sched_group *sg,
                                   struct sg_lb_stats *sgs)
{
    struct sg_lb_stats *busiest = &sds->busiest_stat;

    /* Make sure that there is at least one task to pull */
    if (!sgs->sum_h_nr_running) {
        return false;
    }

    /*
     * Don't try to pull misfit tasks we can't help.
     * We can use max_capacity here as reduction in capacity on some
     * CPUs in the group should either be possible to resolve
     * internally or be covered by avg_load imbalance (eventually).
     */
    if (sgs->group_type == group_misfit_task &&
        (!group_smaller_max_cpu_capacity(sg, sds->local) || sds->local_stat.group_type != group_has_spare)) {
        return false;
    }

    if (sgs->group_type > busiest->group_type) {
        return true;
    }

    if (sgs->group_type < busiest->group_type) {
        return false;
    }

    /*
     * The candidate and the current busiest group are the same type of
     * group. Let check which one is the busiest according to the type.
     */

    switch (sgs->group_type) {
        case group_overloaded:
            /* Select the overloaded group with highest avg_load. */
            if (sgs->avg_load <= busiest->avg_load) {
                return false;
            }
            break;

        case group_imbalanced:
            /*
             * Select the 1st imbalanced group as we don't have any way to
             * choose one more than another.
             */
            return false;

        case group_asym_packing:
            /* Prefer to move from lowest priority CPU's work */
            if (sched_asym_prefer(sg->asym_prefer_cpu, sds->busiest->asym_prefer_cpu)) {
                return false;
            }
            break;

        case group_misfit_task:
            /*
             * If we have more than one misfit sg go with the biggest
             * misfit.
             */
            if (sgs->group_misfit_task_load < busiest->group_misfit_task_load) {
                return false;
            }
            break;

        case group_fully_busy:
            /*
             * Select the fully busy group with highest avg_load. In
             * theory, there is no need to pull task from such kind of
             * group because tasks have all compute capacity that they need
             * but we can still improve the overall throughput by reducing
             * contention when accessing shared HW resources.
             *
             * XXX for now avg_load is not computed and always 0 so we
             * select the 1st one.
             */
            if (sgs->avg_load <= busiest->avg_load) {
                return false;
            }
            break;

        case group_has_spare:
            /*
             * Select not overloaded group with lowest number of idle cpus
             * and highest number of running tasks. We could also compare
             * the spare capacity which is more stable but it can end up
             * that the group has less spare capacity but finally more idle
             * CPUs which means less opportunity to pull tasks.
             */
            if (sgs->idle_cpus > busiest->idle_cpus) {
                return false;
            } else if ((sgs->idle_cpus == busiest->idle_cpus) && (sgs->sum_nr_running <= busiest->sum_nr_running)) {
                return false;
            }

            break;
    }

    /*
     * Candidate sg has no more than one task per CPU and has higher
     * per-CPU capacity. Migrating tasks to less capable CPUs may harm
     * throughput. Maximize throughput, power/energy consequences are not
     * considered.
     */
    if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && (sgs->group_type <= group_fully_busy) &&
        (group_smaller_min_cpu_capacity(sds->local, sg))) {
        return false;
    }

    return true;
}

#ifdef CONFIG_NUMA_BALANCING
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
    if (sgs->sum_h_nr_running > sgs->nr_numa_running) {
        return regular;
    }
    if (sgs->sum_h_nr_running > sgs->nr_preferred_running) {
        return remote;
    }
    return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
    if (rq->nr_running > rq->nr_numa_running) {
        return regular;
    }
    if (rq->nr_running > rq->nr_preferred_running) {
        return remote;
    }
    return all;
}
#else
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
    return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
    return regular;
}
#endif /* CONFIG_NUMA_BALANCING */

struct sg_lb_stats;

/*
 * task_running_on_cpu - return 1 if @p is running on @cpu.
 */

static unsigned int task_running_on_cpu(int cpu, struct task_struct *p)
{
    /* Task has no contribution or is new */
    if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time)) {
        return 0;
    }

    if (task_on_rq_queued(p)) {
        return 1;
    }

    return 0;
}

/**
 * idle_cpu_without - would a given CPU be idle without p ?
 * @cpu: the processor on which idleness is tested.
 * @p: task which should be ignored.
 *
 * Return: 1 if the CPU would be idle. 0 otherwise.
 */
static int idle_cpu_without(int cpu, struct task_struct *p)
{
    struct rq *rq = cpu_rq(cpu);

    if (rq->curr != rq->idle && rq->curr != p) {
        return 0;
    }

    /*
     * rq->nr_running can't be used but an updated version without the
     * impact of p on cpu must be used instead. The updated nr_running
     * be computed and tested before calling idle_cpu_without().
     */

#ifdef CONFIG_SMP
    if (rq->ttwu_pending) {
        return 0;
    }
#endif

    return 1;
}

/*
 * update_sg_wakeup_stats - Update sched_group's statistics for wakeup.
 * @sd: The sched_domain level to look for idlest group.
 * @group: sched_group whose statistics are to be updated.
 * @sgs: variable to hold the statistics for this group.
 * @p: The task for which we look for the idlest group/CPU.
 */
static inline void update_sg_wakeup_stats(struct sched_domain *sd, struct sched_group *group, struct sg_lb_stats *sgs,
                                          struct task_struct *p)
{
    int i, nr_running;

    memset(sgs, 0, sizeof(*sgs));

    for_each_cpu(i, sched_group_span(group))
    {
        struct rq *rq = cpu_rq(i);
        unsigned int local;

        sgs->group_load += cpu_load_without(rq, p);
        sgs->group_util += cpu_util_without(i, p);
        sgs->group_runnable += cpu_runnable_without(rq, p);
        local = task_running_on_cpu(i, p);
        sgs->sum_h_nr_running += rq->cfs.h_nr_running - local;

        nr_running = rq->nr_running - local;
        sgs->sum_nr_running += nr_running;

        /*
         * No need to call idle_cpu_without() if nr_running is not 0
         */
        if (!nr_running && idle_cpu_without(i, p)) {
            sgs->idle_cpus++;
        }
    }

    /* Check if task fits in the group */
    if (sd->flags & SD_ASYM_CPUCAPACITY && !task_fits_capacity(p, group->sgc->max_capacity)) {
        sgs->group_misfit_task_load = 1;
    }

    sgs->group_capacity = group->sgc->capacity;

    sgs->group_weight = group->group_weight;

    sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);

    /*
     * Computing avg_load makes sense only when group is fully busy or
     * overloaded
     */
    if (sgs->group_type == group_fully_busy || sgs->group_type == group_overloaded) {
        sgs->avg_load = (sgs->group_load * SCHED_CAPACITY_SCALE) / sgs->group_capacity;
    }
}

static bool update_pick_idlest(struct sched_group *idlest, struct sg_lb_stats *idlest_sgs, struct sched_group *group,
                               struct sg_lb_stats *sgs)
{
    if (sgs->group_type < idlest_sgs->group_type) {
        return true;
    }

    if (sgs->group_type > idlest_sgs->group_type) {
        return false;
    }

    /*
     * The candidate and the current idlest group are the same type of
     * group. Let check which one is the idlest according to the type.
     */

    switch (sgs->group_type) {
        case group_overloaded:
        case group_fully_busy:
            /* Select the group with lowest avg_load. */
            if (idlest_sgs->avg_load <= sgs->avg_load) {
                return false;
            }
            break;

        case group_imbalanced:
        case group_asym_packing:
            /* Those types are not used in the slow wakeup path */
            return false;

        case group_misfit_task:
            /* Select group with the highest max capacity */
            if (idlest->sgc->max_capacity >= group->sgc->max_capacity) {
                return false;
            }
            break;

        case group_has_spare:
            /* Select group with most idle CPUs */
            if (idlest_sgs->idle_cpus > sgs->idle_cpus) {
                return false;
            }

            /* Select group with lowest group_util */
            if (idlest_sgs->idle_cpus == sgs->idle_cpus && idlest_sgs->group_util <= sgs->group_util) {
                return false;
            }

            break;
    }

    return true;
}

/*
 * find_idlest_group() finds and returns the least busy CPU group within the
 * domain.
 *
 * Assumes p is allowed on at least one CPU in sd.
 */
static struct sched_group *find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
{
    struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups;
    struct sg_lb_stats local_sgs, tmp_sgs;
    struct sg_lb_stats *sgs;
    unsigned long imbalance;
    struct sg_lb_stats idlest_sgs = {
        .avg_load = UINT_MAX,
        .group_type = group_overloaded,
    };
#ifdef CONFIG_CPU_ISOLATION_OPT
    cpumask_t allowed_cpus;

    cpumask_andnot(&allowed_cpus, p->cpus_ptr, cpu_isolated_mask);
#endif

    imbalance = scale_load_down(NICE_0_LOAD) * (sd->imbalance_pct - FAIR_ONEHUNDRED) / FAIR_ONEHUNDRED;

    do {
        int local_group;

        /* Skip over this group if it has no CPUs allowed */
#ifdef CONFIG_CPU_ISOLATION_OPT
        if (!cpumask_intersects(sched_group_span(group), &allowed_cpus))
#else
        if (!cpumask_intersects(sched_group_span(group), p->cpus_ptr))
#endif
            continue;

        local_group = cpumask_test_cpu(this_cpu, sched_group_span(group));
        if (local_group) {
            sgs = &local_sgs;
            local = group;
        } else {
            sgs = &tmp_sgs;
        }

        update_sg_wakeup_stats(sd, group, sgs, p);

        if (!local_group && update_pick_idlest(idlest, &idlest_sgs, group, sgs)) {
            idlest = group;
            idlest_sgs = *sgs;
        }
    } while (group = group->next, group != sd->groups);

    /* There is no idlest group to push tasks to */
    if (!idlest) {
        return NULL;
    }

    /* The local group has been skipped because of CPU affinity */
    if (!local) {
        return idlest;
    }

    /*
     * If the local group is idler than the selected idlest group
     * don't try and push the task.
     */
    if (local_sgs.group_type < idlest_sgs.group_type) {
        return NULL;
    }

    /*
     * If the local group is busier than the selected idlest group
     * try and push the task.
     */
    if (local_sgs.group_type > idlest_sgs.group_type) {
        return idlest;
    }

    switch (local_sgs.group_type) {
        case group_overloaded:
        case group_fully_busy:
            /*
             * When comparing groups across NUMA domains, it's possible for
             * the local domain to be very lightly loaded relative to the
             * remote domains but "imbalance" skews the comparison making
             * remote CPUs look much more favourable. When considering
             * cross-domain, add imbalance to the load on the remote node
             * and consider staying local.
             */

            if ((sd->flags & SD_NUMA) && ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load)) {
                return NULL;
            }

            /*
             * If the local group is less loaded than the selected
             * idlest group don't try and push any tasks.
             */
            if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance)) {
                return NULL;
            }

            if (FAIR_ONEHUNDRED * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load) {
                return NULL;
            }
            break;

        case group_imbalanced:
        case group_asym_packing:
            /* Those type are not used in the slow wakeup path */
            return NULL;

        case group_misfit_task:
            /* Select group with the highest max capacity */
            if (local->sgc->max_capacity >= idlest->sgc->max_capacity) {
                return NULL;
            }
            break;

        case group_has_spare:
            if (sd->flags & SD_NUMA) {
#ifdef CONFIG_NUMA_BALANCING
                int idlest_cpu;
                /*
                 * If there is spare capacity at NUMA, try to select
                 * the preferred node
                 */
                if (cpu_to_node(this_cpu) == p->numa_preferred_nid) {
                    return NULL;
                }

                idlest_cpu = cpumask_first(sched_group_span(idlest));
                if (cpu_to_node(idlest_cpu) == p->numa_preferred_nid) {
                    return idlest;
                }
#endif
                /*
                 * Otherwise, keep the task on this node to stay close
                 * its wakeup source and improve locality. If there is
                 * a real need of migration, periodic load balance will
                 * take care of it.
                 */
                if (local_sgs.idle_cpus) {
                    return NULL;
                }
            }

            /*
             * Select group with highest number of idle CPUs. We could also
             * compare the utilization which is more stable but it can end
             * up that the group has less spare capacity but finally more
             * idle CPUs which means more opportunity to run task.
             */
            if (local_sgs.idle_cpus >= idlest_sgs.idle_cpus) {
                return NULL;
            }
            break;
    }

    return idlest;
}

/**
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
 * @env: The load balancing environment.
 * @sds: variable to hold the statistics for this sched_domain.
 */

static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
{
    struct sched_domain *child = env->sd->child;
    struct sched_group *sg = env->sd->groups;
    struct sg_lb_stats *local = &sds->local_stat;
    struct sg_lb_stats tmp_sgs;
    int sg_status = 0;

#ifdef CONFIG_NO_HZ_COMMON
    if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked)) {
        env->flags |= LBF_NOHZ_STATS;
    }
#endif

    do {
        struct sg_lb_stats *sgs = &tmp_sgs;
        int local_group;

        local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
        if (local_group) {
            sds->local = sg;
            sgs = local;

            if (env->idle != CPU_NEWLY_IDLE || time_after_eq(jiffies, sg->sgc->next_update)) {
                update_group_capacity(env->sd, env->dst_cpu);
            }
        }

        update_sg_lb_stats(env, sg, sgs, &sg_status);

        if (local_group) {
            goto next_group;
        }

        if (update_sd_pick_busiest(env, sds, sg, sgs)) {
            sds->busiest = sg;
            sds->busiest_stat = *sgs;
        }

    next_group:
        /* Now, start updating sd_lb_stats */
        sds->total_load += sgs->group_load;
        sds->total_capacity += sgs->group_capacity;

        sg = sg->next;
    } while (sg != env->sd->groups);

    /* Tag domain that child domain prefers tasks go to siblings first */
    sds->prefer_sibling = child && child->flags & SD_PREFER_SIBLING;

#ifdef CONFIG_NO_HZ_COMMON
    if ((env->flags & LBF_NOHZ_AGAIN) && cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {
        WRITE_ONCE(nohz.next_blocked, jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
    }
#endif

    if (env->sd->flags & SD_NUMA) {
        env->fbq_type = fbq_classify_group(&sds->busiest_stat);
    }

    if (!env->sd->parent) {
        struct root_domain *rd = env->dst_rq->rd;

        /* update overload indicator if we are at root domain */
        WRITE_ONCE(rd->overload, sg_status & SG_OVERLOAD);

        /* Update over-utilization (tipping point, U >= 0) indicator */
        WRITE_ONCE(rd->overutilized, sg_status & SG_OVERUTILIZED);
        trace_sched_overutilized_tp(rd, sg_status & SG_OVERUTILIZED);
    } else if (sg_status & SG_OVERUTILIZED) {
        struct root_domain *rd = env->dst_rq->rd;

        WRITE_ONCE(rd->overutilized, SG_OVERUTILIZED);
        trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
    }
}

static inline long adjust_numa_imbalance(int imbalance, int nr_running)
{
    unsigned int imbalance_min;

    /*
     * Allow a small imbalance based on a simple pair of communicating
     * tasks that remain local when the source domain is almost idle.
     */
    imbalance_min = 0x2;
    if (nr_running <= imbalance_min) {
        return 0;
    }

    return imbalance;
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *             groups of a given sched_domain during load balance.
 * @env: load balance environment
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
{
    struct sg_lb_stats *local, *busiest;

    local = &sds->local_stat;
    busiest = &sds->busiest_stat;

    if (busiest->group_type == group_misfit_task) {
        /* Set imbalance to allow misfit tasks to be balanced. */
        env->migration_type = migrate_misfit;
        env->imbalance = 1;
        return;
    }

    if (busiest->group_type == group_asym_packing) {
        /*
         * In case of asym capacity, we will try to migrate all load to
         * the preferred CPU.
         */
        env->migration_type = migrate_task;
        env->imbalance = busiest->sum_h_nr_running;
        return;
    }

    if (busiest->group_type == group_imbalanced) {
        /*
         * In the group_imb case we cannot rely on group-wide averages
         * to ensure CPU-load equilibrium, try to move any task to fix
         * the imbalance. The next load balance will take care of
         * balancing back the system.
         */
        env->migration_type = migrate_task;
        env->imbalance = 1;
        return;
    }

    /*
     * Try to use spare capacity of local group without overloading it or
     * emptying busiest.
     */
    if (local->group_type == group_has_spare) {
        if ((busiest->group_type > group_fully_busy) && !(env->sd->flags & SD_SHARE_PKG_RESOURCES)) {
            /*
             * If busiest is overloaded, try to fill spare
             * capacity. This might end up creating spare capacity
             * in busiest or busiest still being overloaded but
             * there is no simple way to directly compute the
             * amount of load to migrate in order to balance the
             * system.
             */
            env->migration_type = migrate_util;
            env->imbalance = max(local->group_capacity, local->group_util) - local->group_util;

            /*
             * In some cases, the group's utilization is max or even
             * higher than capacity because of migrations but the
             * local CPU is (newly) idle. There is at least one
             * waiting task in this overloaded busiest group. Let's
             * try to pull it.
             */
            if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
                env->migration_type = migrate_task;
                env->imbalance = 1;
            }

            return;
        }

        if (busiest->group_weight == 1 || sds->prefer_sibling) {
            unsigned int nr_diff = busiest->sum_nr_running;
            /*
             * When prefer sibling, evenly spread running tasks on
             * groups.
             */
            env->migration_type = migrate_task;
            lsub_positive(&nr_diff, local->sum_nr_running);
            env->imbalance = nr_diff >> 1;
        } else {
            /*
             * If there is no overload, we just want to even the number of
             * idle cpus.
             */
            env->migration_type = migrate_task;
            env->imbalance = max_t(long, 0, (local->idle_cpus - busiest->idle_cpus) >> 1);
        }

        /* Consider allowing a small imbalance between NUMA groups */
        if (env->sd->flags & SD_NUMA) {
            env->imbalance = adjust_numa_imbalance(env->imbalance, busiest->sum_nr_running);
        }

        return;
    }

    /*
     * Local is fully busy but has to take more load to relieve the
     * busiest group
     */
    if (local->group_type < group_overloaded) {
        /*
         * Local will become overloaded so the avg_load metrics are
         * finally needed.
         */

        local->avg_load = (local->group_load * SCHED_CAPACITY_SCALE) / local->group_capacity;

        sds->avg_load = (sds->total_load * SCHED_CAPACITY_SCALE) / sds->total_capacity;
        /*
         * If the local group is more loaded than the selected
         * busiest group don't try to pull any tasks.
         */
        if (local->avg_load >= busiest->avg_load) {
            env->imbalance = 0;
            return;
        }
    }

    /*
     * Both group are or will become overloaded and we're trying to get all
     * the CPUs to the average_load, so we don't want to push ourselves
     * above the average load, nor do we wish to reduce the max loaded CPU
     * below the average load. At the same time, we also don't want to
     * reduce the group load below the group capacity. Thus we look for
     * the minimum possible imbalance.
     */
    env->migration_type = migrate_load;
    env->imbalance = min((busiest->avg_load - sds->avg_load) * busiest->group_capacity,
                         (sds->avg_load - local->avg_load) * local->group_capacity) /
                     SCHED_CAPACITY_SCALE;
}

/******* find_busiest_group() helpers end here *********************/

/*
 * Decision matrix according to the local and busiest group type:
 *
 * busiest \ local has_spare fully_busy misfit asym imbalanced overloaded
 * has_spare        nr_idle   balanced   N/A    N/A  balanced   balanced
 * fully_busy       nr_idle   nr_idle    N/A    N/A  balanced   balanced
 * misfit_task      force     N/A        N/A    N/A  force      force
 * asym_packing     force     force      N/A    N/A  force      force
 * imbalanced       force     force      N/A    N/A  force      force
 * overloaded       force     force      N/A    N/A  force      avg_load
 *
 * N/A :      Not Applicable because already filtered while updating
 *            statistics.
 * balanced : The system is balanced for these 2 groups.
 * force :    Calculate the imbalance as load migration is probably needed.
 * avg_load : Only if imbalance is significant enough.
 * nr_idle :  dst_cpu is not busy and the number of idle CPUs is quite
 *            different in groups.
 */

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
 * if there is an imbalance.
 *
 * Also calculates the amount of runnable load which should be moved
 * to restore balance.
 *
 * @env: The load balancing environment.
 *
 * Return:    - The busiest group if imbalance exists.
 */
static struct sched_group *find_busiest_group(struct lb_env *env)
{
    struct sg_lb_stats *local, *busiest;
    struct sd_lb_stats sds;

    init_sd_lb_stats(&sds);

    /*
     * Compute the various statistics relevant for load balancing at
     * this level.
     */
    update_sd_lb_stats(env, &sds);

    if (sched_energy_enabled()) {
        struct root_domain *rd = env->dst_rq->rd;

        if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized)) {
            goto out_balanced;
        }
    }

    local = &sds.local_stat;
    busiest = &sds.busiest_stat;

    /* There is no busy sibling group to pull tasks from */
    if (!sds.busiest) {
        goto out_balanced;
    }

    /* Misfit tasks should be dealt with regardless of the avg load */
    if (busiest->group_type == group_misfit_task) {
        goto force_balance;
    }

    /* ASYM feature bypasses nice load balance check */
    if (busiest->group_type == group_asym_packing) {
        goto force_balance;
    }

    /*
     * If the busiest group is imbalanced the below checks don't
     * work because they assume all things are equal, which typically
     * isn't true due to cpus_ptr constraints and the like.
     */
    if (busiest->group_type == group_imbalanced) {
        goto force_balance;
    }

    /*
     * If the local group is busier than the selected busiest group
     * don't try and pull any tasks.
     */
    if (local->group_type > busiest->group_type) {
        goto out_balanced;
    }

    /*
     * When groups are overloaded, use the avg_load to ensure fairness
     * between tasks.
     */
    if (local->group_type == group_overloaded) {
        /*
         * If the local group is more loaded than the selected
         * busiest group don't try to pull any tasks.
         */
        if (local->avg_load >= busiest->avg_load) {
            goto out_balanced;
        }

        /* XXX broken for overlapping NUMA groups */
        sds.avg_load = (sds.total_load * SCHED_CAPACITY_SCALE) / sds.total_capacity;

        /*
         * Don't pull any tasks if this group is already above the
         * domain average load.
         */
        if (local->avg_load >= sds.avg_load) {
            goto out_balanced;
        }

        /*
         * If the busiest group is more loaded, use imbalance_pct to be
         * conservative.
         */
        if (FAIR_ONEHUNDRED * busiest->avg_load <= env->sd->imbalance_pct * local->avg_load) {
            goto out_balanced;
        }
    }

    /* Try to move all excess tasks to child's sibling domain */
    if (sds.prefer_sibling && local->group_type == group_has_spare &&
        busiest->sum_nr_running > local->sum_nr_running + 1) {
        goto force_balance;
    }

    if (busiest->group_type != group_overloaded) {
        if (env->idle == CPU_NOT_IDLE) {
            /*
             * If the busiest group is not overloaded (and as a
             * result the local one too) but this CPU is already
             * busy, let another idle CPU try to pull task.
             */
            goto out_balanced;
        }

        if (busiest->group_weight > 1 && local->idle_cpus <= (busiest->idle_cpus + 1)) {
            /*
             * If the busiest group is not overloaded
             * and there is no imbalance between this and busiest
             * group wrt idle CPUs, it is balanced. The imbalance
             * becomes significant if the diff is greater than 1
             * otherwise we might end up to just move the imbalance
             * on another group. Of course this applies only if
             * there is more than 1 CPU per group.
             */
            goto out_balanced;
        }

        if (busiest->sum_h_nr_running == 1) {
            /*
             * busiest doesn't have any tasks waiting to run
             */
            goto out_balanced;
        }
    }

force_balance:
    /* Looks like there is an imbalance. Compute it */
    calculate_imbalance(env, &sds);
    return env->imbalance ? sds.busiest : NULL;

out_balanced:
    env->imbalance = 0;
    return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
 */
static struct rq *find_busiest_queue(struct lb_env *env, struct sched_group *group)
{
    struct rq *busiest = NULL, *rq;
    unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
    unsigned int busiest_nr = 0;
    int i;

    for_each_cpu_and(i, sched_group_span(group), env->cpus)
    {
        unsigned long capacity, load, util;
        unsigned int nr_running;
        enum fbq_type rt;

        rq = cpu_rq(i);
        rt = fbq_classify_rq(rq);
        /*
         * We classify groups/runqueues into three groups:
         *  - regular: there are !numa tasks
         *  - remote:  there are numa tasks that run on the 'wrong' node
         *  - all:     there is no distinction
         *
         * In order to avoid migrating ideally placed numa tasks,
         * ignore those when there's better options.
         *
         * If we ignore the actual busiest queue to migrate another
         * task, the next balance pass can still reduce the busiest
         * queue by moving tasks around inside the node.
         *
         * If we cannot move enough load due to this classification
         * the next pass will adjust the group classification and
         * allow migration of more tasks.
         *
         * Both cases only affect the total convergence complexity.
         */
        if (rt > env->fbq_type) {
            continue;
        }

        if (cpu_isolated(i)) {
            continue;
        }

        capacity = capacity_of(i);
        nr_running = rq->cfs.h_nr_running;

        /*
         * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
         * eventually lead to active_balancing high->low capacity.
         * Higher per-CPU capacity is considered better than balancing
         * average load.
         */
        if (env->sd->flags & SD_ASYM_CPUCAPACITY && capacity_of(env->dst_cpu) < capacity && nr_running == 1) {
            continue;
        }

        switch (env->migration_type) {
            case migrate_load:
                /*
                 * When comparing with load imbalance, use cpu_load()
                 * which is not scaled with the CPU capacity.
                 */
                load = cpu_load(rq);
                if (nr_running == 1 && load > env->imbalance && !check_cpu_capacity(rq, env->sd)) {
                    break;
                }

                /*
                 * For the load comparisons with the other CPUs,
                 * consider the cpu_load() scaled with the CPU
                 * capacity, so that the load can be moved away
                 * from the CPU that is potentially running at a
                 * lower capacity.
                 *
                 * Thus we're looking for max(load_i / capacity_i),
                 * crosswise multiplication to rid ourselves of the
                 * division works out to:
                 * load_i * capacity_j > load_j * capacity_i;
                 * where j is our previous maximum.
                 */
                if (load * busiest_capacity > busiest_load * capacity) {
                    busiest_load = load;
                    busiest_capacity = capacity;
                    busiest = rq;
                }
                break;

            case migrate_util:
                util = cpu_util(cpu_of(rq));

                /*
                 * Don't try to pull utilization from a CPU with one
                 * running task. Whatever its utilization, we will fail
                 * detach the task.
                 */
                if (nr_running <= 1) {
                    continue;
                }

                if (busiest_util < util) {
                    busiest_util = util;
                    busiest = rq;
                }
                break;

            case migrate_task:
                if (busiest_nr < nr_running) {
                    busiest_nr = nr_running;
                    busiest = rq;
                }
                break;

            case migrate_misfit:
                /*
                 * For ASYM_CPUCAPACITY domains with misfit tasks we
                 * simply seek the "biggest" misfit task.
                 */
                if (rq->misfit_task_load > busiest_load) {
                    busiest_load = rq->misfit_task_load;
                    busiest = rq;
                }

                break;
        }
    }

    return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL 512

static inline bool asym_active_balance(struct lb_env *env)
{
    /*
     * ASYM_PACKING needs to force migrate tasks from busy but
     * lower priority CPUs in order to pack all tasks in the
     * highest priority CPUs.
     */
    return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
           sched_asym_prefer(env->dst_cpu, env->src_cpu);
}

static inline bool voluntary_active_balance(struct lb_env *env)
{
    struct sched_domain *sd = env->sd;

    if (asym_active_balance(env)) {
        return 1;
    }

    /*
     * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
     * It's worth migrating the task if the src_cpu's capacity is reduced
     * because of other sched_class or IRQs if more capacity stays
     * available on dst_cpu.
     */
    if ((env->idle != CPU_NOT_IDLE) && (env->src_rq->cfs.h_nr_running == 1)) {
        if ((check_cpu_capacity(env->src_rq, sd)) &&
            (capacity_of(env->src_cpu) * sd->imbalance_pct < capacity_of(env->dst_cpu) * FAIR_ONEHUNDRED)) {
            return 1;
        }
    }

    if (env->migration_type == migrate_misfit) {
        return 1;
    }

    return 0;
}

static int need_active_balance(struct lb_env *env)
{
    struct sched_domain *sd = env->sd;

    if (voluntary_active_balance(env)) {
        return 1;
    }

    return unlikely(sd->nr_balance_failed > sd->cache_nice_tries + 2);
}

#ifdef CONFIG_CPU_ISOLATION_OPT
int group_balance_cpu_not_isolated(struct sched_group *sg)
{
    cpumask_t cpus;

    cpumask_and(&cpus, sched_group_span(sg), group_balance_mask(sg));
    cpumask_andnot(&cpus, &cpus, cpu_isolated_mask);
    return cpumask_first(&cpus);
}
#endif

static int active_load_balance_cpu_stop(void *data);

static int should_we_balance(struct lb_env *env)
{
    struct sched_group *sg = env->sd->groups;
    int cpu;

    /*
     * Ensure the balancing environment is consistent; can happen
     * when the softirq triggers 'during' hotplug.
     */
    if (!cpumask_test_cpu(env->dst_cpu, env->cpus)) {
        return 0;
    }

    /*
     * In the newly idle case, we will allow all the CPUs
     * to do the newly idle load balance.
     */
    if (env->idle == CPU_NEWLY_IDLE) {
        return 1;
    }

    /* Try to find first idle CPU */
    for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus)
    {
        if (!idle_cpu(cpu) || cpu_isolated(cpu)) {
            continue;
        }

        /* Are we the first idle CPU? */
        return cpu == env->dst_cpu;
    }

    /* Are we the first CPU of this group ? */
    return group_balance_cpu_not_isolated(sg) == env->dst_cpu;
}

/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq, struct sched_domain *sd, enum cpu_idle_type idle,
                        int *continue_balancing)
{
    int ld_moved, cur_ld_moved, active_balance = 0;
    struct sched_domain *sd_parent = sd->parent;
    struct sched_group *group;
    struct rq *busiest;
    struct rq_flags rf;
    struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);

    struct lb_env env = {
        .sd = sd,
        .dst_cpu = this_cpu,
        .dst_rq = this_rq,
        .dst_grpmask = sched_group_span(sd->groups),
        .idle = idle,
        .loop_break = sched_nr_migrate_break,
        .cpus = cpus,
        .fbq_type = all,
        .tasks = LIST_HEAD_INIT(env.tasks),
    };

    cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);

    schedstat_inc(sd->lb_count[idle]);

redo:
    if (!should_we_balance(&env)) {
        *continue_balancing = 0;
        goto out_balanced;
    }

    group = find_busiest_group(&env);
    if (!group) {
        schedstat_inc(sd->lb_nobusyg[idle]);
        goto out_balanced;
    }

    busiest = find_busiest_queue(&env, group);
    if (!busiest) {
        schedstat_inc(sd->lb_nobusyq[idle]);
        goto out_balanced;
    }

    BUG_ON(busiest == env.dst_rq);

    schedstat_add(sd->lb_imbalance[idle], env.imbalance);

    env.src_cpu = busiest->cpu;
    env.src_rq = busiest;

    ld_moved = 0;
    if (busiest->nr_running > 1) {
        /*
         * Attempt to move tasks. If find_busiest_group has found
         * an imbalance but busiest->nr_running <= 1, the group is
         * still unbalanced. ld_moved simply stays zero, so it is
         * correctly treated as an imbalance.
         */
        env.flags |= LBF_ALL_PINNED;
        env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);

    more_balance:
        rq_lock_irqsave(busiest, &rf);
        update_rq_clock(busiest);

        /*
         * cur_ld_moved - load moved in current iteration
         * ld_moved     - cumulative load moved across iterations
         */
        cur_ld_moved = detach_tasks(&env);

        /*
         * We've detached some tasks from busiest_rq. Every
         * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
         * unlock busiest->lock, and we are able to be sure
         * that nobody can manipulate the tasks in parallel.
         * See task_rq_lock() family for the details.
         */

        rq_unlock(busiest, &rf);

        if (cur_ld_moved) {
            attach_tasks(&env);
            ld_moved += cur_ld_moved;
        }

        local_irq_restore(rf.flags);

        if (env.flags & LBF_NEED_BREAK) {
            env.flags &= ~LBF_NEED_BREAK;
            goto more_balance;
        }

        /*
         * Revisit (affine) tasks on src_cpu that couldn't be moved to
         * us and move them to an alternate dst_cpu in our sched_group
         * where they can run. The upper limit on how many times we
         * iterate on same src_cpu is dependent on number of CPUs in our
         * sched_group.
         *
         * This changes load balance semantics a bit on who can move
         * load to a given_cpu. In addition to the given_cpu itself
         * (or a ilb_cpu acting on its behalf where given_cpu is
         * nohz-idle), we now have balance_cpu in a position to move
         * load to given_cpu. In rare situations, this may cause
         * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
         * _independently_ and at _same_ time to move some load to
         * given_cpu) causing exceess load to be moved to given_cpu.
         * This however should not happen so much in practice and
         * moreover subsequent load balance cycles should correct the
         * excess load moved.
         */
        if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
            /* Prevent to re-select dst_cpu via env's CPUs */
            __cpumask_clear_cpu(env.dst_cpu, env.cpus);

            env.dst_rq = cpu_rq(env.new_dst_cpu);
            env.dst_cpu = env.new_dst_cpu;
            env.flags &= ~LBF_DST_PINNED;
            env.loop = 0;
            env.loop_break = sched_nr_migrate_break;

            /*
             * Go back to "more_balance" rather than "redo" since we
             * need to continue with same src_cpu.
             */
            goto more_balance;
        }

        /*
         * We failed to reach balance because of affinity.
         */
        if (sd_parent) {
            int *group_imbalance = &sd_parent->groups->sgc->imbalance;

            if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
                *group_imbalance = 1;
            }
        }

        /* All tasks on this runqueue were pinned by CPU affinity */
        if (unlikely(env.flags & LBF_ALL_PINNED)) {
            __cpumask_clear_cpu(cpu_of(busiest), cpus);
            /*
             * Attempting to continue load balancing at the current
             * sched_domain level only makes sense if there are
             * active CPUs remaining as possible busiest CPUs to
             * pull load from which are not contained within the
             * destination group that is receiving any migrated
             * load.
             */
            if (!cpumask_subset(cpus, env.dst_grpmask)) {
                env.loop = 0;
                env.loop_break = sched_nr_migrate_break;
                goto redo;
            }
            goto out_all_pinned;
        }
    }

    if (!ld_moved) {
        schedstat_inc(sd->lb_failed[idle]);
        /*
         * Increment the failure counter only on periodic balance.
         * We do not want newidle balance, which can be very
         * frequent, pollute the failure counter causing
         * excessive cache_hot migrations and active balances.
         */
        if (idle != CPU_NEWLY_IDLE) {
            sd->nr_balance_failed++;
        }

        if (need_active_balance(&env)) {
            unsigned long flags;

            raw_spin_lock_irqsave(&busiest->lock, flags);

            /*
             * Don't kick the active_load_balance_cpu_stop,
             * if the curr task on busiest CPU can't be
             * moved to this_cpu:
             */
            if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
                raw_spin_unlock_irqrestore(&busiest->lock, flags);
                env.flags |= LBF_ALL_PINNED;
                goto out_one_pinned;
            }

            /*
             * ->active_balance synchronizes accesses to
             * ->active_balance_work.  Once set, it's cleared
             * only after active load balance is finished.
             */
            if (!busiest->active_balance && !cpu_isolated(cpu_of(busiest))) {
                busiest->active_balance = 1;
                busiest->push_cpu = this_cpu;
                active_balance = 1;
            }
            raw_spin_unlock_irqrestore(&busiest->lock, flags);

            if (active_balance) {
                stop_one_cpu_nowait(cpu_of(busiest), active_load_balance_cpu_stop, busiest,
                                    &busiest->active_balance_work);
            }

            /* We've kicked active balancing, force task migration. */
            sd->nr_balance_failed = sd->cache_nice_tries + 1;
        }
    } else {
        sd->nr_balance_failed = 0;
    }

    if (likely(!active_balance) || voluntary_active_balance(&env)) {
        /* We were unbalanced, so reset the balancing interval */
        sd->balance_interval = sd->min_interval;
    } else {
        /*
         * If we've begun active balancing, start to back off. This
         * case may not be covered by the all_pinned logic if there
         * is only 1 task on the busy runqueue (because we don't call
         * detach_tasks).
         */
        if (sd->balance_interval < sd->max_interval) {
            sd->balance_interval *= 0x2;
        }
    }

    goto out;

out_balanced:
    /*
     * We reach balance although we may have faced some affinity
     * constraints. Clear the imbalance flag only if other tasks got
     * a chance to move and fix the imbalance.
     */
    if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
        int *group_imbalance = &sd_parent->groups->sgc->imbalance;

        if (*group_imbalance) {
            *group_imbalance = 0;
        }
    }

out_all_pinned:
    /*
     * We reach balance because all tasks are pinned at this level so
     * we can't migrate them. Let the imbalance flag set so parent level
     * can try to migrate them.
     */
    schedstat_inc(sd->lb_balanced[idle]);

    sd->nr_balance_failed = 0;

out_one_pinned:
    ld_moved = 0;

    /*
     * newidle_balance() disregards balance intervals, so we could
     * repeatedly reach this code, which would lead to balance_interval
     * skyrocketting in a short amount of time. Skip the balance_interval
     * increase logic to avoid that.
     */
    if (env.idle == CPU_NEWLY_IDLE) {
        goto out;
    }

    /* tune up the balancing interval */
    if ((env.flags & LBF_ALL_PINNED && sd->balance_interval < MAX_PINNED_INTERVAL) ||
        sd->balance_interval < sd->max_interval) {
        sd->balance_interval *= 0x2;
    }
out:
    return ld_moved;
}

static inline unsigned long get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
    unsigned long interval = sd->balance_interval;

    if (cpu_busy) {
        interval *= sd->busy_factor;
    }

    /* scale ms to jiffies */
    interval = msecs_to_jiffies(interval);

    /*
     * Reduce likelihood of busy balancing at higher domains racing with
     * balancing at lower domains by preventing their balancing periods
     * from being multiples of each other.
     */
    if (cpu_busy) {
        interval -= 1;
    }

    interval = clamp(interval, 1UL, max_load_balance_interval);

    return interval;
}

static inline void update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
{
    unsigned long interval, next;

    /* used by idle balance, so cpu_busy = 0 */
    interval = get_sd_balance_interval(sd, 0);
    next = sd->last_balance + interval;

    if (time_after(*next_balance, next)) {
        *next_balance = next;
    }
}

/*
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
 * running tasks off the busiest CPU onto idle CPUs. It requires at
 * least 1 task to be running on each physical CPU where possible, and
 * avoids physical / logical imbalances.
 */
static int active_load_balance_cpu_stop(void *data)
{
    struct rq *busiest_rq = data;
    int busiest_cpu = cpu_of(busiest_rq);
    int target_cpu = busiest_rq->push_cpu;
    struct rq *target_rq = cpu_rq(target_cpu);
    struct sched_domain *sd = NULL;
    struct task_struct *p = NULL;
    struct rq_flags rf;
#ifdef CONFIG_SCHED_EAS
    struct task_struct *push_task;
    int push_task_detached = 0;
#endif

    rq_lock_irq(busiest_rq, &rf);
    /*
     * Between queueing the stop-work and running it is a hole in which
     * CPUs can become inactive. We should not move tasks from or to
     * inactive CPUs.
     */
    if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu)) {
        goto out_unlock;
    }

    /* Make sure the requested CPU hasn't gone down in the meantime: */
    if (unlikely(busiest_cpu != smp_processor_id() || !busiest_rq->active_balance)) {
        goto out_unlock;
    }

    /* Is there any task to move? */
    if (busiest_rq->nr_running <= 1) {
        goto out_unlock;
    }

    /*
     * This condition is "impossible", if it occurs
     * we need to fix it. Originally reported by
     * Bjorn Helgaas on a 128-CPU setup.
     */
    BUG_ON(busiest_rq == target_rq);

#ifdef CONFIG_SCHED_EAS
    push_task = busiest_rq->push_task;
    target_cpu = busiest_rq->push_cpu;
    if (push_task) {
        struct lb_env env = {
            .sd = sd,
            .dst_cpu = target_cpu,
            .dst_rq = target_rq,
            .src_cpu = busiest_rq->cpu,
            .src_rq = busiest_rq,
            .idle = CPU_IDLE,
            .flags = 0,
            .loop = 0,
        };
        if (task_on_rq_queued(push_task) && push_task->state == TASK_RUNNING && task_cpu(push_task) == busiest_cpu &&
            cpu_online(target_cpu)) {
            update_rq_clock(busiest_rq);
            detach_task(push_task, &env);
            push_task_detached = 1;
        }
        goto out_unlock;
    }
#endif

    /* Search for an sd spanning us and the target CPU. */
    rcu_read_lock();
    for_each_domain(target_cpu, sd)
    {
        if (cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) {
            break;
        }
    }

    if (likely(sd)) {
        struct lb_env env = {
            .sd = sd,
            .dst_cpu = target_cpu,
            .dst_rq = target_rq,
            .src_cpu = busiest_rq->cpu,
            .src_rq = busiest_rq,
            .idle = CPU_IDLE,
            /*
             * can_migrate_task() doesn't need to compute new_dst_cpu
             * for active balancing. Since we have CPU_IDLE, but no
             * @dst_grpmask we need to make that test go away with lying
             * about DST_PINNED.
             */
            .flags = LBF_DST_PINNED,
        };

        schedstat_inc(sd->alb_count);
        update_rq_clock(busiest_rq);

        p = detach_one_task(&env);
        if (p) {
            schedstat_inc(sd->alb_pushed);
            /* Active balancing done, reset the failure counter. */
            sd->nr_balance_failed = 0;
        } else {
            schedstat_inc(sd->alb_failed);
        }
    }
    rcu_read_unlock();
out_unlock:
    busiest_rq->active_balance = 0;

#ifdef CONFIG_SCHED_EAS
    push_task = busiest_rq->push_task;
    if (push_task) {
        busiest_rq->push_task = NULL;
    }
#endif
    rq_unlock(busiest_rq, &rf);

#ifdef CONFIG_SCHED_EAS
    if (push_task) {
        if (push_task_detached) {
            attach_one_task(target_rq, push_task);
        }

        put_task_struct(push_task);
    }
#endif

    if (p) {
        attach_one_task(target_rq, p);
    }

    local_irq_enable();

    return 0;
}

static DEFINE_SPINLOCK(balancing);

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
void update_max_interval(void)
{
    unsigned int available_cpus;
#ifdef CONFIG_CPU_ISOLATION_OPT
    cpumask_t avail_mask;

    cpumask_andnot(&avail_mask, cpu_online_mask, cpu_isolated_mask);
    available_cpus = cpumask_weight(&avail_mask);
#else
    available_cpus = num_online_cpus();
#endif

    max_load_balance_interval = HZ * available_cpus / 0xa;
}

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in init_sched_domains.
 */
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
{
    int continue_balancing = 1;
    int cpu = rq->cpu;
    int busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
    unsigned long interval;
    struct sched_domain *sd;
    /* Earliest time when we have to do rebalance again */
    unsigned long next_balance = jiffies + 60 * HZ;
    int update_next_balance = 0;
    int need_serialize, need_decay = 0;
    u64 max_cost = 0;

    rcu_read_lock();
    for_each_domain(cpu, sd)
    {
        /*
         * Decay the newidle max times here because this is a regular
         * visit to all the domains. Decay ~1% per second.
         */
        if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
            sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * FAIR_TWOHUNDREDFIFTYTHREE) / FAIR_TWOHUNDREDFIFTYSIX;
            sd->next_decay_max_lb_cost = jiffies + HZ;
            need_decay = 1;
        }
        max_cost += sd->max_newidle_lb_cost;

        /*
         * Stop the load balance at this level. There is another
         * CPU in our sched group which is doing load balancing more
         * actively.
         */
        if (!continue_balancing) {
            if (need_decay) {
                continue;
            }
            break;
        }

        interval = get_sd_balance_interval(sd, busy);

        need_serialize = sd->flags & SD_SERIALIZE;
        if (need_serialize) {
            if (!spin_trylock(&balancing)) {
                goto out;
            }
        }

        if (time_after_eq(jiffies, sd->last_balance + interval)) {
            if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
                /*
                 * The LBF_DST_PINNED logic could have changed
                 * env->dst_cpu, so we can't know our idle
                 * state even if we migrated tasks. Update it.
                 */
                idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
                busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
            }
            sd->last_balance = jiffies;
            interval = get_sd_balance_interval(sd, busy);
        }
        if (need_serialize) {
            spin_unlock(&balancing);
        }
    out:
        if (time_after(next_balance, sd->last_balance + interval)) {
            next_balance = sd->last_balance + interval;
            update_next_balance = 1;
        }
    }
    if (need_decay) {
        /*
         * Ensure the rq-wide value also decays but keep it at a
         * reasonable floor to avoid funnies with rq->avg_idle.
         */
        rq->max_idle_balance_cost = max((u64)sysctl_sched_migration_cost, max_cost);
    }
    rcu_read_unlock();

    /*
     * next_balance will be updated only when there is a need.
     * When the cpu is attached to null domain for ex, it will not be
     * updated.
     */
    if (likely(update_next_balance)) {
        rq->next_balance = next_balance;

#ifdef CONFIG_NO_HZ_COMMON
        /*
         * If this CPU has been elected to perform the nohz idle
         * balance. Other idle CPUs have already rebalanced with
         * nohz_idle_balance() and nohz.next_balance has been
         * updated accordingly. This CPU is now running the idle load
         * balance for itself and we need to update the
         * nohz.next_balance accordingly.
         */
        if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance)) {
            nohz.next_balance = rq->next_balance;
        }
#endif
    }
}

static inline int on_null_domain(struct rq *rq)
{
    return unlikely(!rcu_dereference_sched(rq->sd));
}

#ifdef CONFIG_NO_HZ_COMMON
/*
 * idle load balancing details
 * - When one of the busy CPUs notice that there may be an idle rebalancing
 *   needed, they will kick the idle load balancer, which then does idle
 *   load balancing for all the idle CPUs.
 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
 *   anywhere yet.
 */

static inline int find_new_ilb(void)
{
    int ilb;

    for_each_cpu_and(ilb, nohz.idle_cpus_mask, housekeeping_cpumask(HK_FLAG_MISC))
    {
        if (cpu_isolated(ilb)) {
            continue;
        }

        if (idle_cpu(ilb)) {
            return ilb;
        }
    }

    return nr_cpu_ids;
}

/*
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
 */
static void kick_ilb(unsigned int flags)
{
    int ilb_cpu;

    /*
     * Increase nohz.next_balance only when if full ilb is triggered but
     * not if we only update stats.
     */
    if (flags & NOHZ_BALANCE_KICK) {
        nohz.next_balance = jiffies + 1;
    }

    ilb_cpu = find_new_ilb();
    if (ilb_cpu >= nr_cpu_ids) {
        return;
    }

    /*
     * Access to rq::nohz_csd is serialized by NOHZ_KICK_MASK; he who sets
     * the first flag owns it; cleared by nohz_csd_func().
     */
    flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
    if (flags & NOHZ_KICK_MASK) {
        return;
    }

    /*
     * This way we generate an IPI on the target CPU which
     * is idle. And the softirq performing nohz idle load balance
     * will be run before returning from the IPI.
     */
    smp_call_function_single_async(ilb_cpu, &cpu_rq(ilb_cpu)->nohz_csd);
}

/*
 * Current decision point for kicking the idle load balancer in the presence
 * of idle CPUs in the system.
 */
static void nohz_balancer_kick(struct rq *rq)
{
    unsigned long now = jiffies;
    struct sched_domain_shared *sds;
    struct sched_domain *sd;
    int nr_busy, i, cpu = rq->cpu;
    unsigned int flags = 0;
    cpumask_t cpumask;

    if (unlikely(rq->idle_balance)) {
        return;
    }

    /*
     * We may be recently in ticked or tickless idle mode. At the first
     * busy tick after returning from idle, we will update the busy stats.
     */
    nohz_balance_exit_idle(rq);

    /*
     * None are in tickless mode and hence no need for NOHZ idle load
     * balancing.
     */
#ifdef CONFIG_CPU_ISOLATION_OPT
    cpumask_andnot(&cpumask, nohz.idle_cpus_mask, cpu_isolated_mask);
    if (cpumask_empty(&cpumask)) {
        return;
    }
#else
    cpumask_copy(&cpumask, nohz.idle_cpus_mask);
    if (likely(!atomic_read(&nohz.nr_cpus))) {
        return;
    }
#endif

    if (READ_ONCE(nohz.has_blocked) && time_after(now, READ_ONCE(nohz.next_blocked))) {
        flags = NOHZ_STATS_KICK;
    }

    if (time_before(now, nohz.next_balance)) {
        goto out;
    }

    if (rq->nr_running >= 0x2) {
        flags = NOHZ_KICK_MASK;
        goto out;
    }

    rcu_read_lock();

    sd = rcu_dereference(rq->sd);
    if (sd) {
        /*
         * If there's a CFS task and the current CPU has reduced
         * capacity; kick the ILB to see if there's a better CPU to run
         * on.
         */
        if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) {
            flags = NOHZ_KICK_MASK;
            goto unlock;
        }
    }

    sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
    if (sd) {
        /*
         * When ASYM_PACKING; see if there's a more preferred CPU
         * currently idle; in which case, kick the ILB to move tasks
         * around.
         */
        for_each_cpu_and(i, sched_domain_span(sd), &cpumask)
        {
            if (sched_asym_prefer(i, cpu)) {
                flags = NOHZ_KICK_MASK;
                goto unlock;
            }
        }
    }

    sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, cpu));
    if (sd) {
        /*
         * When ASYM_CPUCAPACITY; see if there's a higher capacity CPU
         * to run the misfit task on.
         */
        if (check_misfit_status(rq, sd)) {
            flags = NOHZ_KICK_MASK;
            goto unlock;
        }

        /*
         * For asymmetric systems, we do not want to nicely balance
         * cache use, instead we want to embrace asymmetry and only
         * ensure tasks have enough CPU capacity.
         *
         * Skip the LLC logic because it's not relevant in that case.
         */
        goto unlock;
    }

    sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
    if (sds) {
        /*
         * If there is an imbalance between LLC domains (IOW we could
         * increase the overall cache use), we need some less-loaded LLC
         * domain to pull some load. Likewise, we may need to spread
         * load within the current LLC domain (e.g. packed SMT cores but
         * other CPUs are idle). We can't really know from here how busy
         * the others are - so just get a nohz balance going if it looks
         * like this LLC domain has tasks we could move.
         */
        nr_busy = atomic_read(&sds->nr_busy_cpus);
        if (nr_busy > 1) {
            flags = NOHZ_KICK_MASK;
            goto unlock;
        }
    }
unlock:
    rcu_read_unlock();
out:
    if (flags) {
        kick_ilb(flags);
    }
}

static void set_cpu_sd_state_busy(int cpu)
{
    struct sched_domain *sd;

    rcu_read_lock();
    sd = rcu_dereference(per_cpu(sd_llc, cpu));
    if (!sd || !sd->nohz_idle) {
        goto unlock;
    }
    sd->nohz_idle = 0;

    atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
    rcu_read_unlock();
}

void nohz_balance_exit_idle(struct rq *rq)
{
    SCHED_WARN_ON(rq != this_rq());

    if (likely(!rq->nohz_tick_stopped)) {
        return;
    }

    rq->nohz_tick_stopped = 0;
    cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
    atomic_dec(&nohz.nr_cpus);

    set_cpu_sd_state_busy(rq->cpu);
}

static void set_cpu_sd_state_idle(int cpu)
{
    struct sched_domain *sd;

    rcu_read_lock();
    sd = rcu_dereference(per_cpu(sd_llc, cpu));
    if (!sd || sd->nohz_idle) {
        goto unlock;
    }
    sd->nohz_idle = 1;

    atomic_dec(&sd->shared->nr_busy_cpus);
unlock:
    rcu_read_unlock();
}

/*
 * This routine will record that the CPU is going idle with tick stopped.
 * This info will be used in performing idle load balancing in the future.
 */
void nohz_balance_enter_idle(int cpu)
{
    struct rq *rq = cpu_rq(cpu);

    SCHED_WARN_ON(cpu != smp_processor_id());

    if (!cpu_active(cpu)) {
        /*
         * A CPU can be paused while it is idle with it's tick
         * stopped. nohz_balance_exit_idle() should be called
         * from the local CPU, so it can't be called during
         * pause. This results in paused CPU participating in
         * the nohz idle balance, which should be avoided.
         *
         * When the paused CPU exits idle and enters again,
         * exempt the paused CPU from nohz_balance_exit_idle.
         */
        nohz_balance_exit_idle(rq);
        return;
    }

    /* Spare idle load balancing on CPUs that don't want to be disturbed: */
    if (!housekeeping_cpu(cpu, HK_FLAG_SCHED)) {
        return;
    }

    /*
     * Can be set safely without rq->lock held
     * If a clear happens, it will have evaluated last additions because
     * rq->lock is held during the check and the clear
     */
    rq->has_blocked_load = 1;

    /*
     * The tick is still stopped but load could have been added in the
     * meantime. We set the nohz.has_blocked flag to trig a check of the
     * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
     * of nohz.has_blocked can only happen after checking the new load
     */
    if (rq->nohz_tick_stopped) {
        goto out;
    }

    /* If we're a completely isolated CPU, we don't play: */
    if (on_null_domain(rq)) {
        return;
    }

    rq->nohz_tick_stopped = 1;

    cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
    atomic_inc(&nohz.nr_cpus);

    /*
     * Ensures that if nohz_idle_balance() fails to observe our
     * @idle_cpus_mask store, it must observe the @has_blocked
     * store.
     */
    smp_mb__after_atomic();

    set_cpu_sd_state_idle(cpu);

out:
    /*
     * Each time a cpu enter idle, we assume that it has blocked load and
     * enable the periodic update of the load of idle cpus
     */
    WRITE_ONCE(nohz.has_blocked, 1);
}

/*
 * Internal function that runs load balance for all idle cpus. The load balance
 * can be a simple update of blocked load or a complete load balance with
 * tasks movement depending of flags.
 * The function returns false if the loop has stopped before running
 * through all idle CPUs.
 */
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags, enum cpu_idle_type idle)
{
    /* Earliest time when we have to do rebalance again */
    unsigned long now = jiffies;
    unsigned long next_balance = now + 60 * HZ;
    bool has_blocked_load = false;
    int update_next_balance = 0;
    int this_cpu = this_rq->cpu;
    int balance_cpu;
    int ret = false;
    struct rq *rq;
    cpumask_t cpus;

    SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);

    /*
     * We assume there will be no idle load after this update and clear
     * the has_blocked flag. If a cpu enters idle in the mean time, it will
     * set the has_blocked flag and trig another update of idle load.
     * Because a cpu that becomes idle, is added to idle_cpus_mask before
     * setting the flag, we are sure to not clear the state and not
     * check the load of an idle cpu.
     */
    WRITE_ONCE(nohz.has_blocked, 0);

    /*
     * Ensures that if we miss the CPU, we must see the has_blocked
     * store from nohz_balance_enter_idle().
     */
    smp_mb();

#ifdef CONFIG_CPU_ISOLATION_OPT
    cpumask_andnot(&cpus, nohz.idle_cpus_mask, cpu_isolated_mask);
#else
    cpumask_copy(&cpus, nohz.idle_cpus_mask);
#endif

    for_each_cpu(balance_cpu, &cpus)
    {
        if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) {
            continue;
        }

        /*
         * If this CPU gets work to do, stop the load balancing
         * work being done for other CPUs. Next load
         * balancing owner will pick it up.
         */
        if (need_resched()) {
            has_blocked_load = true;
            goto abort;
        }

        rq = cpu_rq(balance_cpu);

        has_blocked_load |= update_nohz_stats(rq, true);

        /*
         * If time for next balance is due,
         * do the balance.
         */
        if (time_after_eq(jiffies, rq->next_balance)) {
            struct rq_flags rf;

            rq_lock_irqsave(rq, &rf);
            update_rq_clock(rq);
            rq_unlock_irqrestore(rq, &rf);

            if (flags & NOHZ_BALANCE_KICK) {
                rebalance_domains(rq, CPU_IDLE);
            }
        }

        if (time_after(next_balance, rq->next_balance)) {
            next_balance = rq->next_balance;
            update_next_balance = 1;
        }
    }

    /*
     * next_balance will be updated only when there is a need.
     * When the CPU is attached to null domain for ex, it will not be
     * updated.
     */
    if (likely(update_next_balance)) {
        nohz.next_balance = next_balance;
    }

    /* Newly idle CPU doesn't need an update */
    if (idle != CPU_NEWLY_IDLE) {
        update_blocked_averages(this_cpu);
        has_blocked_load |= this_rq->has_blocked_load;
    }

    if (flags & NOHZ_BALANCE_KICK) {
        rebalance_domains(this_rq, CPU_IDLE);
    }

    WRITE_ONCE(nohz.next_blocked, now + msecs_to_jiffies(LOAD_AVG_PERIOD));

    /* The full idle balance loop has been done */
    ret = true;

abort:
    /* There is still blocked load, enable periodic update */
    if (has_blocked_load) {
        WRITE_ONCE(nohz.has_blocked, 1);
    }

    return ret;
}

/*
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
    unsigned int flags = this_rq->nohz_idle_balance;

    if (!flags) {
        return false;
    }

    this_rq->nohz_idle_balance = 0;

    if (idle != CPU_IDLE) {
        return false;
    }

    _nohz_idle_balance(this_rq, flags, idle);

    return true;
}

static void nohz_newidle_balance(struct rq *this_rq)
{
    int this_cpu = this_rq->cpu;

    /*
     * This CPU doesn't want to be disturbed by scheduler
     * housekeeping
     */
    if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED)) {
        return;
    }

    /* Will wake up very soon. No time for doing anything else */
    if (this_rq->avg_idle < sysctl_sched_migration_cost) {
        return;
    }

    /* Don't need to update blocked load of idle CPUs */
    if (!READ_ONCE(nohz.has_blocked) || time_before(jiffies, READ_ONCE(nohz.next_blocked))) {
        return;
    }

    raw_spin_unlock(&this_rq->lock);
    /*
     * This CPU is going to be idle and blocked load of idle CPUs
     * need to be updated. Run the ilb locally as it is a good
     * candidate for ilb instead of waking up another idle CPU.
     * Kick an normal ilb if we failed to do the update.
     */
    if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE)) {
        kick_ilb(NOHZ_STATS_KICK);
    }
    raw_spin_lock(&this_rq->lock);
}

#else  /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq)
{
}

static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
    return false;
}

static inline void nohz_newidle_balance(struct rq *this_rq)
{
}
#endif /* CONFIG_NO_HZ_COMMON */

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 *
 * Returns:
 *   < 0 - we released the lock and there are !fair tasks present
 *     0 - failed, no new tasks
 *   > 0 - success, new (fair) tasks present
 */
static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
{
    unsigned long next_balance = jiffies + HZ;
    int this_cpu = this_rq->cpu;
    struct sched_domain *sd;
    int pulled_task = 0;
    u64 curr_cost = 0;

    if (cpu_isolated(this_cpu)) {
        return 0;
    }

    update_misfit_status(NULL, this_rq);
    /*
     * We must set idle_stamp _before_ calling idle_balance(), such that we
     * measure the duration of idle_balance() as idle time.
     */
    this_rq->idle_stamp = rq_clock(this_rq);

    /*
     * Do not pull tasks towards !active CPUs...
     */
    if (!cpu_active(this_cpu)) {
        return 0;
    }

    /*
     * This is OK, because current is on_cpu, which avoids it being picked
     * for load-balance and preemption/IRQs are still disabled avoiding
     * further scheduler activity on it and we're being very careful to
     * re-start the picking loop.
     */
    rq_unpin_lock(this_rq, rf);

    if (this_rq->avg_idle < sysctl_sched_migration_cost || !READ_ONCE(this_rq->rd->overload)) {
        rcu_read_lock();
        sd = rcu_dereference_check_sched_domain(this_rq->sd);
        if (sd) {
            update_next_balance(sd, &next_balance);
        }
        rcu_read_unlock();

        nohz_newidle_balance(this_rq);

        goto out;
    }

    raw_spin_unlock(&this_rq->lock);

    update_blocked_averages(this_cpu);
    rcu_read_lock();
    for_each_domain(this_cpu, sd)
    {
        int continue_balancing = 1;
        u64 t0, domain_cost;

        if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
            update_next_balance(sd, &next_balance);
            break;
        }

        if (sd->flags & SD_BALANCE_NEWIDLE) {
            t0 = sched_clock_cpu(this_cpu);

            pulled_task = load_balance(this_cpu, this_rq, sd, CPU_NEWLY_IDLE, &continue_balancing);

            domain_cost = sched_clock_cpu(this_cpu) - t0;
            if (domain_cost > sd->max_newidle_lb_cost) {
                sd->max_newidle_lb_cost = domain_cost;
            }

            curr_cost += domain_cost;
        }

        update_next_balance(sd, &next_balance);

        /*
         * Stop searching for tasks to pull if there are
         * now runnable tasks on this rq.
         */
        if (pulled_task || this_rq->nr_running > 0) {
            break;
        }
    }
    rcu_read_unlock();

    raw_spin_lock(&this_rq->lock);

    if (curr_cost > this_rq->max_idle_balance_cost) {
        this_rq->max_idle_balance_cost = curr_cost;
    }

out:
    /*
     * While browsing the domains, we released the rq lock, a task could
     * have been enqueued in the meantime. Since we're not going idle,
     * pretend we pulled a task.
     */
    if (this_rq->cfs.h_nr_running && !pulled_task) {
        pulled_task = 1;
    }

    /* Move the next balance forward */
    if (time_after(this_rq->next_balance, next_balance)) {
        this_rq->next_balance = next_balance;
    }

    /* Is there a task of a high priority class? */
    if (this_rq->nr_running != this_rq->cfs.h_nr_running) {
        pulled_task = -1;
    }

    if (pulled_task) {
        this_rq->idle_stamp = 0;
    }

    rq_repin_lock(this_rq, rf);

    return pulled_task;
}

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
{
    struct rq *this_rq = this_rq();
    enum cpu_idle_type idle = this_rq->idle_balance ? CPU_IDLE : CPU_NOT_IDLE;

    /*
     * Since core isolation doesn't update nohz.idle_cpus_mask, there
     * is a possibility this nohz kicked cpu could be isolated. Hence
     * return if the cpu is isolated.
     */
    if (cpu_isolated(this_rq->cpu)) {
        return;
    }

    /*
     * If this CPU has a pending nohz_balance_kick, then do the
     * balancing on behalf of the other idle CPUs whose ticks are
     * stopped. Do nohz_idle_balance *before* rebalance_domains to
     * give the idle CPUs a chance to load balance. Else we may
     * load balance only within the local sched_domain hierarchy
     * and abort nohz_idle_balance altogether if we pull some load.
     */
    if (nohz_idle_balance(this_rq, idle)) {
        return;
    }

    /* normal load balance */
    update_blocked_averages(this_rq->cpu);
    rebalance_domains(this_rq, idle);
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
void trigger_load_balance(struct rq *rq)
{
    /* Don't need to rebalance while attached to NULL domain or
     * cpu is isolated.
     */
    if (unlikely(on_null_domain(rq)) || cpu_isolated(cpu_of(rq))) {
        return;
    }

    if (time_after_eq(jiffies, rq->next_balance)) {
        raise_softirq(SCHED_SOFTIRQ);
    }

    nohz_balancer_kick(rq);
}

static void rq_online_fair(struct rq *rq)
{
    update_sysctl();

    update_runtime_enabled(rq);
}

static void rq_offline_fair(struct rq *rq)
{
    update_sysctl();

    /* Ensure any throttled groups are reachable by pick_next_task */
    unthrottle_offline_cfs_rqs(rq);
}

#ifdef CONFIG_SCHED_EAS
static inline int kick_active_balance(struct rq *rq, struct task_struct *p, int new_cpu)
{
    unsigned long flags;
    int rc = 0;

    if (cpu_of(rq) == new_cpu) {
        return rc;
    }

    /* Invoke active balance to force migrate currently running task */
    raw_spin_lock_irqsave(&rq->lock, flags);
    if (!rq->active_balance) {
        rq->active_balance = 1;
        rq->push_cpu = new_cpu;
        get_task_struct(p);
        rq->push_task = p;
        rc = 1;
    }
    raw_spin_unlock_irqrestore(&rq->lock, flags);
    return rc;
}

DEFINE_RAW_SPINLOCK(migration_lock);
static void check_for_migration_fair(struct rq *rq, struct task_struct *p)
{
    int active_balance;
    int new_cpu = -1;
    int prev_cpu = task_cpu(p);
    int ret;

#ifdef CONFIG_SCHED_RTG
    bool need_down_migrate = false;
    struct cpumask *rtg_target = find_rtg_target(p);

    if (rtg_target && (capacity_orig_of(prev_cpu) > capacity_orig_of(cpumask_first(rtg_target)))) {
        need_down_migrate = true;
    }
#endif

    if (rq->misfit_task_load) {
        if (rq->curr->state != TASK_RUNNING || rq->curr->nr_cpus_allowed == 1) {
            return;
        }

        raw_spin_lock(&migration_lock);
#ifdef CONFIG_SCHED_RTG
        if (rtg_target) {
            new_cpu = find_rtg_cpu(p);
            if (new_cpu != -1 && need_down_migrate && cpumask_test_cpu(new_cpu, rtg_target) && idle_cpu(new_cpu)) {
                goto do_active_balance;
            }

            if (new_cpu != -1 && capacity_orig_of(new_cpu) > capacity_orig_of(prev_cpu)) {
                goto do_active_balance;
            }

            goto out_unlock;
        }
#endif
        rcu_read_lock();
        new_cpu = find_energy_efficient_cpu(p, prev_cpu);
        rcu_read_unlock();

        if (new_cpu == -1 || capacity_orig_of(new_cpu) <= capacity_orig_of(prev_cpu)) {
            goto out_unlock;
        }
#ifdef CONFIG_SCHED_RTG
    do_active_balance:
#endif
        active_balance = kick_active_balance(rq, p, new_cpu);
        if (active_balance) {
            mark_reserved(new_cpu);
            raw_spin_unlock(&migration_lock);
            ret = stop_one_cpu_nowait(prev_cpu, active_load_balance_cpu_stop, rq, &rq->active_balance_work);
            if (!ret) {
                clear_reserved(new_cpu);
            } else {
                wake_up_if_idle(new_cpu);
            }
            return;
        }
    out_unlock:
        raw_spin_unlock(&migration_lock);
    }
}
#endif /* CONFIG_SCHED_EAS */
#endif /* CONFIG_SMP */

/*
 * scheduler tick hitting a task of our scheduling class.
 *
 * NOTE: This function can be called remotely by the tick offload that
 * goes along full dynticks. Therefore no local assumption can be made
 * and everything must be accessed through the @rq and @curr passed in
 * parameters.
 */
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &curr->se;

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        entity_tick(cfs_rq, se, queued);
    }

    if (static_branch_unlikely(&sched_numa_balancing)) {
        task_tick_numa(rq, curr);
    }

    update_misfit_status(curr, rq);
    update_overutilized_status(task_rq(curr));
}

/*
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
 */
static void task_fork_fair(struct task_struct *p)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &p->se, *curr;
    struct rq *rq = this_rq();
    struct rq_flags rf;

    rq_lock(rq, &rf);
    update_rq_clock(rq);

    cfs_rq = task_cfs_rq(current);
    curr = cfs_rq->curr;
    if (curr) {
        update_curr(cfs_rq);
        se->vruntime = curr->vruntime;
    }
    place_entity(cfs_rq, se, 1);

    if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
        /*
         * Upon rescheduling, sched_class::put_prev_task() will place
         * 'current' within the tree based on its new key value.
         */
        swap(curr->vruntime, se->vruntime);
        resched_curr(rq);
    }

    se->vruntime -= cfs_rq->min_vruntime;
    rq_unlock(rq, &rf);
}

/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
static void prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
{
    if (!task_on_rq_queued(p)) {
        return;
    }

    if (rq->cfs.nr_running == 1) {
        return;
    }

    /*
     * Reschedule if we are currently running on this runqueue and
     * our priority decreased, or if we are not currently running on
     * this runqueue and our priority is higher than the current's
     */
    if (rq->curr == p) {
        if (p->prio > oldprio) {
            resched_curr(rq);
        }
    } else {
        check_preempt_curr(rq, p, 0);
    }
}

static inline bool vruntime_normalized(struct task_struct *p)
{
    struct sched_entity *se = &p->se;

    /*
     * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
     * the dequeue_entity(.flags=0) will already have normalized the
     * vruntime.
     */
    if (p->on_rq) {
        return true;
    }

    /*
     * When !on_rq, vruntime of the task has usually NOT been normalized.
     * But there are some cases where it has already been normalized:
     *
     * - A forked child which is waiting for being woken up by
     *   wake_up_new_task().
     * - A task which has been woken up by try_to_wake_up() and
     *   waiting for actually being woken up by sched_ttwu_pending().
     */
    if (!se->sum_exec_runtime || (p->state == TASK_WAKING && p->sched_remote_wakeup)) {
        return true;
    }

    return false;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * Propagate the changes of the sched_entity across the tg tree to make it
 * visible to the root
 */
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq;

    list_add_leaf_cfs_rq(cfs_rq_of(se));

    /* Start to propagate at parent */
    se = se->parent;

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);
        if (!cfs_rq_throttled(cfs_rq)) {
            update_load_avg(cfs_rq, se, UPDATE_TG);
            list_add_leaf_cfs_rq(cfs_rq);
            continue;
        }

        if (list_add_leaf_cfs_rq(cfs_rq)) {
            break;
        }
    }
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
}
#endif

static void detach_entity_cfs_rq(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

    /* Catch up with the cfs_rq and remove our load when we leave */
    update_load_avg(cfs_rq, se, 0);
    detach_entity_load_avg(cfs_rq, se);
    update_tg_load_avg(cfs_rq);
    propagate_entity_cfs_rq(se);
}

static void attach_entity_cfs_rq(struct sched_entity *se)
{
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

#ifdef CONFIG_FAIR_GROUP_SCHED
    /*
     * Since the real-depth could have been changed (only FAIR
     * class maintain depth value), reset depth properly.
     */
    se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif

    /* Synchronize entity with its cfs_rq */
    update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
    attach_entity_load_avg(cfs_rq, se);
    update_tg_load_avg(cfs_rq);
    propagate_entity_cfs_rq(se);
}

static void detach_task_cfs_rq(struct task_struct *p)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

    if (!vruntime_normalized(p)) {
        /*
         * Fix up our vruntime so that the current sleep doesn't
         * cause 'unlimited' sleep bonus.
         */
        place_entity(cfs_rq, se, 0);
        se->vruntime -= cfs_rq->min_vruntime;
    }

    detach_entity_cfs_rq(se);
}

static void attach_task_cfs_rq(struct task_struct *p)
{
    struct sched_entity *se = &p->se;
    struct cfs_rq *cfs_rq = cfs_rq_of(se);

    attach_entity_cfs_rq(se);

    if (!vruntime_normalized(p)) {
        se->vruntime += cfs_rq->min_vruntime;
    }
}

static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
    detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
    attach_task_cfs_rq(p);

    if (task_on_rq_queued(p)) {
        /*
         * We were most likely switched from sched_rt, so
         * kick off the schedule if running, otherwise just see
         * if we can still preempt the current task.
         */
        if (rq->curr == p) {
            resched_curr(rq);
        } else {
            check_preempt_curr(rq, p, 0);
        }
    }
}

/* Account for a task changing its policy or group.
 *
 * This routine is mostly called to set cfs_rq->curr field when a task
 * migrates between groups/classes.
 */
static void set_next_task_fair(struct rq *rq, struct task_struct *p, bool first)
{
    struct sched_entity *se = &p->se;

#ifdef CONFIG_SMP
    if (task_on_rq_queued(p)) {
        /*
         * Move the next running task to the front of the list, so our
         * cfs_tasks list becomes MRU one.
         */
        list_move(&se->group_node, &rq->cfs_tasks);
    }
#endif

    for_each_sched_entity(se) {
        struct cfs_rq *cfs_rq = cfs_rq_of(se);

        set_next_entity(cfs_rq, se);
        /* ensure bandwidth has been allocated on our new cfs_rq */
        account_cfs_rq_runtime(cfs_rq, 0);
    }
}

void init_cfs_rq(struct cfs_rq *cfs_rq)
{
    cfs_rq->tasks_timeline = RB_ROOT_CACHED;
    cfs_rq->min_vruntime = (u64)(-(1LL << FAIR_TWENTY));
#ifndef CONFIG_64BIT
    cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
#ifdef CONFIG_SMP
    raw_spin_lock_init(&cfs_rq->removed.lock);
#endif
}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void task_set_group_fair(struct task_struct *p)
{
    struct sched_entity *se = &p->se;

    set_task_rq(p, task_cpu(p));
    se->depth = se->parent ? se->parent->depth + 1 : 0;
}

static void task_move_group_fair(struct task_struct *p)
{
    detach_task_cfs_rq(p);
    set_task_rq(p, task_cpu(p));

#ifdef CONFIG_SMP
    /* Tell se's cfs_rq has been changed -- migrated */
    p->se.avg.last_update_time = 0;
#endif
    attach_task_cfs_rq(p);
}

static void task_change_group_fair(struct task_struct *p, int type)
{
    switch (type) {
        case TASK_SET_GROUP:
            task_set_group_fair(p);
            break;

        case TASK_MOVE_GROUP:
            task_move_group_fair(p);
            break;
    }
}

void free_fair_sched_group(struct task_group *tg)
{
    int i;

    destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

    for_each_possible_cpu(i)
    {
        if (tg->cfs_rq) {
            kfree(tg->cfs_rq[i]);
        }
        if (tg->se) {
            kfree(tg->se[i]);
        }
    }

    kfree(tg->cfs_rq);
    kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
    struct sched_entity *se;
    struct cfs_rq *cfs_rq;
    int i;

    tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
    if (!tg->cfs_rq) {
        goto err;
    }
    tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
    if (!tg->se) {
        goto err;
    }

    tg->shares = NICE_0_LOAD;

    init_cfs_bandwidth(tg_cfs_bandwidth(tg));

    for_each_possible_cpu(i)
    {
        cfs_rq = kzalloc_node(sizeof(struct cfs_rq), GFP_KERNEL, cpu_to_node(i));
        if (!cfs_rq) {
            goto err;
        }

        se = kzalloc_node(sizeof(struct sched_entity), GFP_KERNEL, cpu_to_node(i));
        if (!se) {
            goto err_free_rq;
        }

        init_cfs_rq(cfs_rq);
        init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
        init_entity_runnable_average(se);
    }

    return 1;

err_free_rq:
    kfree(cfs_rq);
err:
    return 0;
}

void online_fair_sched_group(struct task_group *tg)
{
    struct sched_entity *se;
    struct rq_flags rf;
    struct rq *rq;
    int i;

    for_each_possible_cpu(i)
    {
        rq = cpu_rq(i);
        se = tg->se[i];
        rq_lock_irq(rq, &rf);
        update_rq_clock(rq);
        attach_entity_cfs_rq(se);
        sync_throttle(tg, i);
        rq_unlock_irq(rq, &rf);
    }
}

void unregister_fair_sched_group(struct task_group *tg)
{
    unsigned long flags;
    struct rq *rq;
    int cpu;

    for_each_possible_cpu(cpu)
    {
        if (tg->se[cpu]) {
            remove_entity_load_avg(tg->se[cpu]);
        }

        /*
         * Only empty task groups can be destroyed; so we can speculatively
         * check on_list without danger of it being re-added.
         */
        if (!tg->cfs_rq[cpu]->on_list) {
            continue;
        }

        rq = cpu_rq(cpu);

        raw_spin_lock_irqsave(&rq->lock, flags);
        list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
        raw_spin_unlock_irqrestore(&rq->lock, flags);
    }
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, struct sched_entity *se, int cpu,
                       struct sched_entity *parent)
{
    struct rq *rq = cpu_rq(cpu);

    cfs_rq->tg = tg;
    cfs_rq->rq = rq;
    init_cfs_rq_runtime(cfs_rq);

    tg->cfs_rq[cpu] = cfs_rq;
    tg->se[cpu] = se;

    /* se could be NULL for root_task_group */
    if (!se) {
        return;
    }

    if (!parent) {
        se->cfs_rq = &rq->cfs;
        se->depth = 0;
    } else {
        se->cfs_rq = parent->my_q;
        se->depth = parent->depth + 1;
    }

    se->my_q = cfs_rq;
    /* guarantee group entities always have weight */
    update_load_set(&se->load, NICE_0_LOAD);
    se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
    int i;

    /*
     * We can't change the weight of the root cgroup.
     */
    if (!tg->se[0]) {
        return -EINVAL;
    }

    shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

    mutex_lock(&shares_mutex);
    if (tg->shares == shares) {
        goto done;
    }

    tg->shares = shares;
    for_each_possible_cpu(i) {
        struct rq *rq = cpu_rq(i);
        struct sched_entity *se = tg->se[i];
        struct rq_flags rf;

        /* Propagate contribution to hierarchy */
        rq_lock_irqsave(rq, &rf);
        update_rq_clock(rq);
        for_each_sched_entity(se) {
            update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
            update_cfs_group(se);
        }
        rq_unlock_irqrestore(rq, &rf);
    }

done:
    mutex_unlock(&shares_mutex);
    return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg)
{
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
    return 1;
}

void online_fair_sched_group(struct task_group *tg)
{
}

void unregister_fair_sched_group(struct task_group *tg)
{
}

#endif /* CONFIG_FAIR_GROUP_SCHED */

static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
{
    struct sched_entity *se = &task->se;
    unsigned int rr_interval = 0;

    /*
     * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
     * idle runqueue:
     */
    if (rq->cfs.load.weight) {
        rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
    }

    return rr_interval;
}

/*
 * All the scheduling class methods:
 */
const struct sched_class fair_sched_class __section("__fair_sched_class") = {
    .enqueue_task = enqueue_task_fair,
    .dequeue_task = dequeue_task_fair,
    .yield_task = yield_task_fair,
    .yield_to_task = yield_to_task_fair,

    .check_preempt_curr = check_preempt_wakeup,

    .pick_next_task = fair_pick_next_task_fair,
    .put_prev_task = put_prev_task_fair,
    .set_next_task = set_next_task_fair,

#ifdef CONFIG_SMP
    .balance = balance_fair,
    .select_task_rq = select_task_rq_fair,
    .migrate_task_rq = migrate_task_rq_fair,

    .rq_online = rq_online_fair,
    .rq_offline = rq_offline_fair,

    .task_dead = task_dead_fair,
    .set_cpus_allowed = set_cpus_allowed_common,
#endif

    .task_tick = task_tick_fair,
    .task_fork = task_fork_fair,

    .prio_changed = prio_changed_fair,
    .switched_from = switched_from_fair,
    .switched_to = switched_to_fair,

    .get_rr_interval = get_rr_interval_fair,

    .update_curr = update_curr_fair,

#ifdef CONFIG_FAIR_GROUP_SCHED
    .task_change_group = task_change_group_fair,
#endif

#ifdef CONFIG_UCLAMP_TASK
    .uclamp_enabled = 1,
#endif
#ifdef CONFIG_SCHED_WALT
    .fixup_walt_sched_stats = walt_fixup_sched_stats_fair,
#endif
#ifdef CONFIG_SCHED_EAS
    .check_for_migration = check_for_migration_fair,
#endif
};

#ifdef CONFIG_SCHED_DEBUG
void print_cfs_stats(struct seq_file *m, int cpu)
{
    struct cfs_rq *cfs_rq, *pos;

    rcu_read_lock();
    for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos) print_cfs_rq(m, cpu, cfs_rq);
    rcu_read_unlock();
}

#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
    int node;
    unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
    struct numa_group *ng;

    rcu_read_lock();
    ng = rcu_dereference(p->numa_group);
    for_each_online_node(node)
    {
        if (p->numa_faults) {
            tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
            tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
        }
        if (ng) {
            gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)], gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
        }
        print_numa_stats(m, node, tsf, tpf, gsf, gpf);
    }
    rcu_read_unlock();
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
    open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

#ifdef CONFIG_NO_HZ_COMMON
    nohz.next_balance = jiffies;
    nohz.next_blocked = jiffies;
    zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */
}

/* WALT sched implementation begins here */
#ifdef CONFIG_SCHED_WALT

#ifdef CONFIG_CFS_BANDWIDTH

static void walt_init_cfs_rq_stats(struct cfs_rq *cfs_rq)
{
    cfs_rq->walt_stats.cumulative_runnable_avg_scaled = 0;
}

static void walt_inc_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p)
{
    fixup_cumulative_runnable_avg(&cfs_rq->walt_stats, p->ravg.demand_scaled);
}

static void walt_dec_cfs_rq_stats(struct cfs_rq *cfs_rq, struct task_struct *p)
{
    fixup_cumulative_runnable_avg(&cfs_rq->walt_stats, -(s64)p->ravg.demand_scaled);
}

static void walt_inc_throttled_cfs_rq_stats(struct walt_sched_stats *stats, struct cfs_rq *tcfs_rq)
{
    struct rq *rq = rq_of(tcfs_rq);

    fixup_cumulative_runnable_avg(stats, tcfs_rq->walt_stats.cumulative_runnable_avg_scaled);

    if (stats == &rq->walt_stats) {
        walt_fixup_cum_window_demand(rq, tcfs_rq->walt_stats.cumulative_runnable_avg_scaled);
    }
}

static void walt_dec_throttled_cfs_rq_stats(struct walt_sched_stats *stats, struct cfs_rq *tcfs_rq)
{
    struct rq *rq = rq_of(tcfs_rq);

    fixup_cumulative_runnable_avg(stats, -tcfs_rq->walt_stats.cumulative_runnable_avg_scaled);

    /*
     * We remove the throttled cfs_rq's tasks's contribution from the
     * cumulative window demand so that the same can be added
     * unconditionally when the cfs_rq is unthrottled.
     */
    if (stats == &rq->walt_stats) {
        walt_fixup_cum_window_demand(rq, -tcfs_rq->walt_stats.cumulative_runnable_avg_scaled);
    }
}

static void walt_fixup_sched_stats_fair(struct rq *rq, struct task_struct *p, u16 updated_demand_scaled)
{
    struct cfs_rq *cfs_rq;
    struct sched_entity *se = &p->se;
    s64 task_load_delta = (s64)updated_demand_scaled - p->ravg.demand_scaled;

    for_each_sched_entity(se) {
        cfs_rq = cfs_rq_of(se);

        fixup_cumulative_runnable_avg(&cfs_rq->walt_stats, task_load_delta);
        if (cfs_rq_throttled(cfs_rq)) {
            break;
        }
    }

    /* Fix up rq->walt_stats only if we didn't find any throttled cfs_rq */
    if (!se) {
        fixup_cumulative_runnable_avg(&rq->walt_stats, task_load_delta);
        walt_fixup_cum_window_demand(rq, task_load_delta);
    }
}

#else  /* CONFIG_CFS_BANDWIDTH */
static void walt_fixup_sched_stats_fair(struct rq *rq, struct task_struct *p, u16 updated_demand_scaled)
{
    fixup_walt_sched_stats_common(rq, p, updated_demand_scaled);
}
#endif /* CONFIG_CFS_BANDWIDTH */
#endif /* CONFIG_SCHED_WALT */

/*
 * Helper functions to facilitate extracting info from tracepoints.
 */

const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq)
{
#ifdef CONFIG_SMP
    return cfs_rq ? &cfs_rq->avg : NULL;
#else
    return NULL;
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_avg);

char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len)
{
    if (!cfs_rq) {
        if (str) {
            strlcpy(str, "(null)", len);
        } else {
            return NULL;
        }
    }

    cfs_rq_tg_path(cfs_rq, str, len);
    return str;
}
EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_path);

int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq)
{
    return cfs_rq ? cpu_of(rq_of(cfs_rq)) : -1;
}
EXPORT_SYMBOL_GPL(sched_trace_cfs_rq_cpu);

const struct sched_avg *sched_trace_rq_avg_rt(struct rq *rq)
{
#ifdef CONFIG_SMP
    return rq ? &rq->avg_rt : NULL;
#else
    return NULL;
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_rq_avg_rt);

const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq)
{
#ifdef CONFIG_SMP
    return rq ? &rq->avg_dl : NULL;
#else
    return NULL;
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_rq_avg_dl);

const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq)
{
#if defined(CONFIG_SMP) && defined(CONFIG_HAVE_SCHED_AVG_IRQ)
    return rq ? &rq->avg_irq : NULL;
#else
    return NULL;
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_rq_avg_irq);

int sched_trace_rq_cpu(struct rq *rq)
{
    return rq ? cpu_of(rq) : -1;
}
EXPORT_SYMBOL_GPL(sched_trace_rq_cpu);

int sched_trace_rq_cpu_capacity(struct rq *rq)
{
    return rq ?
#ifdef CONFIG_SMP
              rq->cpu_capacity
#else
              SCHED_CAPACITY_SCALE
#endif
              : -1;
}
EXPORT_SYMBOL_GPL(sched_trace_rq_cpu_capacity);

const struct cpumask *sched_trace_rd_span(struct root_domain *rd)
{
#ifdef CONFIG_SMP
    return rd ? rd->span : NULL;
#else
    return NULL;
#endif
}
EXPORT_SYMBOL_GPL(sched_trace_rd_span);

int sched_trace_rq_nr_running(struct rq *rq)
{
    return rq ? rq->nr_running : -1;
}
EXPORT_SYMBOL_GPL(sched_trace_rq_nr_running);