1 /*
2 * Pressure stall information for CPU, memory and IO
3 *
4 * Copyright (c) 2018 Facebook, Inc.
5 * Author: Johannes Weiner <hannes@cmpxchg.org>
6 *
7 * Polling support by Suren Baghdasaryan <surenb@google.com>
8 * Copyright (c) 2018 Google, Inc.
9 *
10 * When CPU, memory and IO are contended, tasks experience delays that
11 * reduce throughput and introduce latencies into the workload. Memory
12 * and IO contention, in addition, can cause a full loss of forward
13 * progress in which the CPU goes idle.
14 *
15 * This code aggregates individual task delays into resource pressure
16 * metrics that indicate problems with both workload health and
17 * resource utilization.
18 *
19 * Model
20 *
21 * The time in which a task can execute on a CPU is our baseline for
22 * productivity. Pressure expresses the amount of time in which this
23 * potential cannot be realized due to resource contention.
24 *
25 * This concept of productivity has two components: the workload and
26 * the CPU. To measure the impact of pressure on both, we define two
27 * contention states for a resource: SOME and FULL.
28 *
29 * In the SOME state of a given resource, one or more tasks are
30 * delayed on that resource. This affects the workload's ability to
31 * perform work, but the CPU may still be executing other tasks.
32 *
33 * In the FULL state of a given resource, all non-idle tasks are
34 * delayed on that resource such that nobody is advancing and the CPU
35 * goes idle. This leaves both workload and CPU unproductive.
36 *
37 * (Naturally, the FULL state doesn't exist for the CPU resource.)
38 *
39 * SOME = nr_delayed_tasks != 0
40 * FULL = nr_delayed_tasks != 0 && nr_running_tasks == 0
41 *
42 * The percentage of wallclock time spent in those compound stall
43 * states gives pressure numbers between 0 and 100 for each resource,
44 * where the SOME percentage indicates workload slowdowns and the FULL
45 * percentage indicates reduced CPU utilization:
46 *
47 * %SOME = time(SOME) / period
48 * %FULL = time(FULL) / period
49 *
50 * Multiple CPUs
51 *
52 * The more tasks and available CPUs there are, the more work can be
53 * performed concurrently. This means that the potential that can go
54 * unrealized due to resource contention *also* scales with non-idle
55 * tasks and CPUs.
56 *
57 * Consider a scenario where 257 number crunching tasks are trying to
58 * run concurrently on 256 CPUs. If we simply aggregated the task
59 * states, we would have to conclude a CPU SOME pressure number of
60 * 100%, since *somebody* is waiting on a runqueue at all
61 * times. However, that is clearly not the amount of contention the
62 * workload is experiencing: only one out of 256 possible exceution
63 * threads will be contended at any given time, or about 0.4%.
64 *
65 * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any
66 * given time *one* of the tasks is delayed due to a lack of memory.
67 * Again, looking purely at the task state would yield a memory FULL
68 * pressure number of 0%, since *somebody* is always making forward
69 * progress. But again this wouldn't capture the amount of execution
70 * potential lost, which is 1 out of 4 CPUs, or 25%.
71 *
72 * To calculate wasted potential (pressure) with multiple processors,
73 * we have to base our calculation on the number of non-idle tasks in
74 * conjunction with the number of available CPUs, which is the number
75 * of potential execution threads. SOME becomes then the proportion of
76 * delayed tasks to possibe threads, and FULL is the share of possible
77 * threads that are unproductive due to delays:
78 *
79 * threads = min(nr_nonidle_tasks, nr_cpus)
80 * SOME = min(nr_delayed_tasks / threads, 1)
81 * FULL = (threads - min(nr_running_tasks, threads)) / threads
82 *
83 * For the 257 number crunchers on 256 CPUs, this yields:
84 *
85 * threads = min(257, 256)
86 * SOME = min(1 / 256, 1) = 0.4%
87 * FULL = (256 - min(257, 256)) / 256 = 0%
88 *
89 * For the 1 out of 4 memory-delayed tasks, this yields:
90 *
91 * threads = min(4, 4)
92 * SOME = min(1 / 4, 1) = 25%
93 * FULL = (4 - min(3, 4)) / 4 = 25%
94 *
95 * [ Substitute nr_cpus with 1, and you can see that it's a natural
96 * extension of the single-CPU model. ]
97 *
98 * Implementation
99 *
100 * To assess the precise time spent in each such state, we would have
101 * to freeze the system on task changes and start/stop the state
102 * clocks accordingly. Obviously that doesn't scale in practice.
103 *
104 * Because the scheduler aims to distribute the compute load evenly
105 * among the available CPUs, we can track task state locally to each
106 * CPU and, at much lower frequency, extrapolate the global state for
107 * the cumulative stall times and the running averages.
108 *
109 * For each runqueue, we track:
110 *
111 * tSOME[cpu] = time(nr_delayed_tasks[cpu] != 0)
112 * tFULL[cpu] = time(nr_delayed_tasks[cpu] && !nr_running_tasks[cpu])
113 * tNONIDLE[cpu] = time(nr_nonidle_tasks[cpu] != 0)
114 *
115 * and then periodically aggregate:
116 *
117 * tNONIDLE = sum(tNONIDLE[i])
118 *
119 * tSOME = sum(tSOME[i] * tNONIDLE[i]) / tNONIDLE
120 * tFULL = sum(tFULL[i] * tNONIDLE[i]) / tNONIDLE
121 *
122 * %SOME = tSOME / period
123 * %FULL = tFULL / period
124 *
125 * This gives us an approximation of pressure that is practical
126 * cost-wise, yet way more sensitive and accurate than periodic
127 * sampling of the aggregate task states would be.
128 */
129
130 #include "../workqueue_internal.h"
131 #include <linux/sched/loadavg.h>
132 #include <linux/seq_file.h>
133 #include <linux/proc_fs.h>
134 #include <linux/seqlock.h>
135 #include <linux/uaccess.h>
136 #include <linux/cgroup.h>
137 #include <linux/module.h>
138 #include <linux/sched.h>
139 #include <linux/ctype.h>
140 #include <linux/file.h>
141 #include <linux/poll.h>
142 #include <linux/psi.h>
143 #include "sched.h"
144
145 #include <trace/hooks/psi.h>
146
147 static int psi_bug __read_mostly;
148
149 DEFINE_STATIC_KEY_FALSE(psi_disabled);
150 DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled);
151
152 #ifdef CONFIG_PSI_DEFAULT_DISABLED
153 static bool psi_enable;
154 #else
155 static bool psi_enable = true;
156 #endif
setup_psi(char * str)157 static int __init setup_psi(char *str)
158 {
159 return kstrtobool(str, &psi_enable) == 0;
160 }
161 __setup("psi=", setup_psi);
162
163 /* Running averages - we need to be higher-res than loadavg */
164 #define PSI_FREQ (2*HZ+1) /* 2 sec intervals */
165 #define EXP_10s 1677 /* 1/exp(2s/10s) as fixed-point */
166 #define EXP_60s 1981 /* 1/exp(2s/60s) */
167 #define EXP_300s 2034 /* 1/exp(2s/300s) */
168
169 /* PSI trigger definitions */
170 #define WINDOW_MIN_US 500000 /* Min window size is 500ms */
171 #define WINDOW_MAX_US 10000000 /* Max window size is 10s */
172 #define UPDATES_PER_WINDOW 10 /* 10 updates per window */
173
174 /* Sampling frequency in nanoseconds */
175 static u64 psi_period __read_mostly;
176
177 /* System-level pressure and stall tracking */
178 static DEFINE_PER_CPU(struct psi_group_cpu, system_group_pcpu);
179 struct psi_group psi_system = {
180 .pcpu = &system_group_pcpu,
181 };
182
183 static void psi_avgs_work(struct work_struct *work);
184
185 static void poll_timer_fn(struct timer_list *t);
186
group_init(struct psi_group * group)187 static void group_init(struct psi_group *group)
188 {
189 int cpu;
190
191 for_each_possible_cpu(cpu)
192 seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq);
193 group->avg_last_update = sched_clock();
194 group->avg_next_update = group->avg_last_update + psi_period;
195 INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work);
196 mutex_init(&group->avgs_lock);
197 /* Init trigger-related members */
198 atomic_set(&group->poll_scheduled, 0);
199 mutex_init(&group->trigger_lock);
200 INIT_LIST_HEAD(&group->triggers);
201 memset(group->nr_triggers, 0, sizeof(group->nr_triggers));
202 group->poll_states = 0;
203 group->poll_min_period = U32_MAX;
204 memset(group->polling_total, 0, sizeof(group->polling_total));
205 group->polling_next_update = ULLONG_MAX;
206 group->polling_until = 0;
207 init_waitqueue_head(&group->poll_wait);
208 timer_setup(&group->poll_timer, poll_timer_fn, 0);
209 rcu_assign_pointer(group->poll_task, NULL);
210 }
211
psi_init(void)212 void __init psi_init(void)
213 {
214 if (!psi_enable) {
215 static_branch_enable(&psi_disabled);
216 return;
217 }
218
219 if (!cgroup_psi_enabled())
220 static_branch_disable(&psi_cgroups_enabled);
221
222 psi_period = jiffies_to_nsecs(PSI_FREQ);
223 group_init(&psi_system);
224 }
225
test_state(unsigned int * tasks,enum psi_states state)226 static bool test_state(unsigned int *tasks, enum psi_states state)
227 {
228 switch (state) {
229 case PSI_IO_SOME:
230 return tasks[NR_IOWAIT];
231 case PSI_IO_FULL:
232 return tasks[NR_IOWAIT] && !tasks[NR_RUNNING];
233 case PSI_MEM_SOME:
234 return tasks[NR_MEMSTALL];
235 case PSI_MEM_FULL:
236 return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];
237 case PSI_CPU_SOME:
238 return tasks[NR_RUNNING] > tasks[NR_ONCPU];
239 case PSI_NONIDLE:
240 return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
241 tasks[NR_RUNNING];
242 default:
243 return false;
244 }
245 }
246
get_recent_times(struct psi_group * group,int cpu,enum psi_aggregators aggregator,u32 * times,u32 * pchanged_states)247 static void get_recent_times(struct psi_group *group, int cpu,
248 enum psi_aggregators aggregator, u32 *times,
249 u32 *pchanged_states)
250 {
251 struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
252 u64 now, state_start;
253 enum psi_states s;
254 unsigned int seq;
255 u32 state_mask;
256
257 *pchanged_states = 0;
258
259 /* Snapshot a coherent view of the CPU state */
260 do {
261 seq = read_seqcount_begin(&groupc->seq);
262 now = cpu_clock(cpu);
263 memcpy(times, groupc->times, sizeof(groupc->times));
264 state_mask = groupc->state_mask;
265 state_start = groupc->state_start;
266 } while (read_seqcount_retry(&groupc->seq, seq));
267
268 /* Calculate state time deltas against the previous snapshot */
269 for (s = 0; s < NR_PSI_STATES; s++) {
270 u32 delta;
271 /*
272 * In addition to already concluded states, we also
273 * incorporate currently active states on the CPU,
274 * since states may last for many sampling periods.
275 *
276 * This way we keep our delta sampling buckets small
277 * (u32) and our reported pressure close to what's
278 * actually happening.
279 */
280 if (state_mask & (1 << s))
281 times[s] += now - state_start;
282
283 delta = times[s] - groupc->times_prev[aggregator][s];
284 groupc->times_prev[aggregator][s] = times[s];
285
286 times[s] = delta;
287 if (delta)
288 *pchanged_states |= (1 << s);
289 }
290 }
291
calc_avgs(unsigned long avg[3],int missed_periods,u64 time,u64 period)292 static void calc_avgs(unsigned long avg[3], int missed_periods,
293 u64 time, u64 period)
294 {
295 unsigned long pct;
296
297 /* Fill in zeroes for periods of no activity */
298 if (missed_periods) {
299 avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods);
300 avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods);
301 avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods);
302 }
303
304 /* Sample the most recent active period */
305 pct = div_u64(time * 100, period);
306 pct *= FIXED_1;
307 avg[0] = calc_load(avg[0], EXP_10s, pct);
308 avg[1] = calc_load(avg[1], EXP_60s, pct);
309 avg[2] = calc_load(avg[2], EXP_300s, pct);
310 }
311
collect_percpu_times(struct psi_group * group,enum psi_aggregators aggregator,u32 * pchanged_states)312 static void collect_percpu_times(struct psi_group *group,
313 enum psi_aggregators aggregator,
314 u32 *pchanged_states)
315 {
316 u64 deltas[NR_PSI_STATES - 1] = { 0, };
317 unsigned long nonidle_total = 0;
318 u32 changed_states = 0;
319 int cpu;
320 int s;
321
322 /*
323 * Collect the per-cpu time buckets and average them into a
324 * single time sample that is normalized to wallclock time.
325 *
326 * For averaging, each CPU is weighted by its non-idle time in
327 * the sampling period. This eliminates artifacts from uneven
328 * loading, or even entirely idle CPUs.
329 */
330 for_each_possible_cpu(cpu) {
331 u32 times[NR_PSI_STATES];
332 u32 nonidle;
333 u32 cpu_changed_states;
334
335 get_recent_times(group, cpu, aggregator, times,
336 &cpu_changed_states);
337 changed_states |= cpu_changed_states;
338
339 nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
340 nonidle_total += nonidle;
341
342 for (s = 0; s < PSI_NONIDLE; s++)
343 deltas[s] += (u64)times[s] * nonidle;
344 }
345
346 /*
347 * Integrate the sample into the running statistics that are
348 * reported to userspace: the cumulative stall times and the
349 * decaying averages.
350 *
351 * Pressure percentages are sampled at PSI_FREQ. We might be
352 * called more often when the user polls more frequently than
353 * that; we might be called less often when there is no task
354 * activity, thus no data, and clock ticks are sporadic. The
355 * below handles both.
356 */
357
358 /* total= */
359 for (s = 0; s < NR_PSI_STATES - 1; s++)
360 group->total[aggregator][s] +=
361 div_u64(deltas[s], max(nonidle_total, 1UL));
362
363 if (pchanged_states)
364 *pchanged_states = changed_states;
365 }
366
update_averages(struct psi_group * group,u64 now)367 static u64 update_averages(struct psi_group *group, u64 now)
368 {
369 unsigned long missed_periods = 0;
370 u64 expires, period;
371 u64 avg_next_update;
372 int s;
373
374 /* avgX= */
375 expires = group->avg_next_update;
376 if (now - expires >= psi_period)
377 missed_periods = div_u64(now - expires, psi_period);
378
379 /*
380 * The periodic clock tick can get delayed for various
381 * reasons, especially on loaded systems. To avoid clock
382 * drift, we schedule the clock in fixed psi_period intervals.
383 * But the deltas we sample out of the per-cpu buckets above
384 * are based on the actual time elapsing between clock ticks.
385 */
386 avg_next_update = expires + ((1 + missed_periods) * psi_period);
387 period = now - (group->avg_last_update + (missed_periods * psi_period));
388 group->avg_last_update = now;
389
390 for (s = 0; s < NR_PSI_STATES - 1; s++) {
391 u32 sample;
392
393 sample = group->total[PSI_AVGS][s] - group->avg_total[s];
394 /*
395 * Due to the lockless sampling of the time buckets,
396 * recorded time deltas can slip into the next period,
397 * which under full pressure can result in samples in
398 * excess of the period length.
399 *
400 * We don't want to report non-sensical pressures in
401 * excess of 100%, nor do we want to drop such events
402 * on the floor. Instead we punt any overage into the
403 * future until pressure subsides. By doing this we
404 * don't underreport the occurring pressure curve, we
405 * just report it delayed by one period length.
406 *
407 * The error isn't cumulative. As soon as another
408 * delta slips from a period P to P+1, by definition
409 * it frees up its time T in P.
410 */
411 if (sample > period)
412 sample = period;
413 group->avg_total[s] += sample;
414 calc_avgs(group->avg[s], missed_periods, sample, period);
415 }
416
417 return avg_next_update;
418 }
419
psi_avgs_work(struct work_struct * work)420 static void psi_avgs_work(struct work_struct *work)
421 {
422 struct delayed_work *dwork;
423 struct psi_group *group;
424 u32 changed_states;
425 bool nonidle;
426 u64 now;
427
428 dwork = to_delayed_work(work);
429 group = container_of(dwork, struct psi_group, avgs_work);
430
431 mutex_lock(&group->avgs_lock);
432
433 now = sched_clock();
434
435 collect_percpu_times(group, PSI_AVGS, &changed_states);
436 nonidle = changed_states & (1 << PSI_NONIDLE);
437 /*
438 * If there is task activity, periodically fold the per-cpu
439 * times and feed samples into the running averages. If things
440 * are idle and there is no data to process, stop the clock.
441 * Once restarted, we'll catch up the running averages in one
442 * go - see calc_avgs() and missed_periods.
443 */
444 if (now >= group->avg_next_update)
445 group->avg_next_update = update_averages(group, now);
446
447 if (nonidle) {
448 schedule_delayed_work(dwork, nsecs_to_jiffies(
449 group->avg_next_update - now) + 1);
450 }
451
452 mutex_unlock(&group->avgs_lock);
453 }
454
455 /* Trigger tracking window manupulations */
window_reset(struct psi_window * win,u64 now,u64 value,u64 prev_growth)456 static void window_reset(struct psi_window *win, u64 now, u64 value,
457 u64 prev_growth)
458 {
459 win->start_time = now;
460 win->start_value = value;
461 win->prev_growth = prev_growth;
462 }
463
464 /*
465 * PSI growth tracking window update and growth calculation routine.
466 *
467 * This approximates a sliding tracking window by interpolating
468 * partially elapsed windows using historical growth data from the
469 * previous intervals. This minimizes memory requirements (by not storing
470 * all the intermediate values in the previous window) and simplifies
471 * the calculations. It works well because PSI signal changes only in
472 * positive direction and over relatively small window sizes the growth
473 * is close to linear.
474 */
window_update(struct psi_window * win,u64 now,u64 value)475 static u64 window_update(struct psi_window *win, u64 now, u64 value)
476 {
477 u64 elapsed;
478 u64 growth;
479
480 elapsed = now - win->start_time;
481 growth = value - win->start_value;
482 /*
483 * After each tracking window passes win->start_value and
484 * win->start_time get reset and win->prev_growth stores
485 * the average per-window growth of the previous window.
486 * win->prev_growth is then used to interpolate additional
487 * growth from the previous window assuming it was linear.
488 */
489 if (elapsed > win->size)
490 window_reset(win, now, value, growth);
491 else {
492 u32 remaining;
493
494 remaining = win->size - elapsed;
495 growth += div64_u64(win->prev_growth * remaining, win->size);
496 }
497
498 return growth;
499 }
500
init_triggers(struct psi_group * group,u64 now)501 static void init_triggers(struct psi_group *group, u64 now)
502 {
503 struct psi_trigger *t;
504
505 list_for_each_entry(t, &group->triggers, node)
506 window_reset(&t->win, now,
507 group->total[PSI_POLL][t->state], 0);
508 memcpy(group->polling_total, group->total[PSI_POLL],
509 sizeof(group->polling_total));
510 group->polling_next_update = now + group->poll_min_period;
511 }
512
update_triggers(struct psi_group * group,u64 now)513 static u64 update_triggers(struct psi_group *group, u64 now)
514 {
515 struct psi_trigger *t;
516 bool new_stall = false;
517 u64 *total = group->total[PSI_POLL];
518
519 /*
520 * On subsequent updates, calculate growth deltas and let
521 * watchers know when their specified thresholds are exceeded.
522 */
523 list_for_each_entry(t, &group->triggers, node) {
524 u64 growth;
525
526 /* Check for stall activity */
527 if (group->polling_total[t->state] == total[t->state])
528 continue;
529
530 /*
531 * Multiple triggers might be looking at the same state,
532 * remember to update group->polling_total[] once we've
533 * been through all of them. Also remember to extend the
534 * polling time if we see new stall activity.
535 */
536 new_stall = true;
537
538 /* Calculate growth since last update */
539 growth = window_update(&t->win, now, total[t->state]);
540 if (growth < t->threshold)
541 continue;
542
543 /* Limit event signaling to once per window */
544 if (now < t->last_event_time + t->win.size)
545 continue;
546
547 trace_android_vh_psi_event(t);
548
549 /* Generate an event */
550 if (cmpxchg(&t->event, 0, 1) == 0)
551 wake_up_interruptible(&t->event_wait);
552 t->last_event_time = now;
553 }
554
555 trace_android_vh_psi_group(group);
556
557 if (new_stall)
558 memcpy(group->polling_total, total,
559 sizeof(group->polling_total));
560
561 return now + group->poll_min_period;
562 }
563
564 /* Schedule polling if it's not already scheduled or forced. */
psi_schedule_poll_work(struct psi_group * group,unsigned long delay,bool force)565 static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay,
566 bool force)
567 {
568 struct task_struct *task;
569
570 /*
571 * atomic_xchg should be called even when !force to provide a
572 * full memory barrier (see the comment inside psi_poll_work).
573 */
574 if (atomic_xchg(&group->poll_scheduled, 1) && !force)
575 return;
576
577 rcu_read_lock();
578
579 task = rcu_dereference(group->poll_task);
580 /*
581 * kworker might be NULL in case psi_trigger_destroy races with
582 * psi_task_change (hotpath) which can't use locks
583 */
584 if (likely(task))
585 mod_timer(&group->poll_timer, jiffies + delay);
586 else
587 atomic_set(&group->poll_scheduled, 0);
588
589 rcu_read_unlock();
590 }
591
psi_poll_work(struct psi_group * group)592 static void psi_poll_work(struct psi_group *group)
593 {
594 bool force_reschedule = false;
595 u32 changed_states;
596 u64 now;
597
598 mutex_lock(&group->trigger_lock);
599
600 now = sched_clock();
601
602 if (now > group->polling_until) {
603 /*
604 * We are either about to start or might stop polling if no
605 * state change was recorded. Resetting poll_scheduled leaves
606 * a small window for psi_group_change to sneak in and schedule
607 * an immegiate poll_work before we get to rescheduling. One
608 * potential extra wakeup at the end of the polling window
609 * should be negligible and polling_next_update still keeps
610 * updates correctly on schedule.
611 */
612 atomic_set(&group->poll_scheduled, 0);
613 /*
614 * A task change can race with the poll worker that is supposed to
615 * report on it. To avoid missing events, ensure ordering between
616 * poll_scheduled and the task state accesses, such that if the poll
617 * worker misses the state update, the task change is guaranteed to
618 * reschedule the poll worker:
619 *
620 * poll worker:
621 * atomic_set(poll_scheduled, 0)
622 * smp_mb()
623 * LOAD states
624 *
625 * task change:
626 * STORE states
627 * if atomic_xchg(poll_scheduled, 1) == 0:
628 * schedule poll worker
629 *
630 * The atomic_xchg() implies a full barrier.
631 */
632 smp_mb();
633 } else {
634 /* Polling window is not over, keep rescheduling */
635 force_reschedule = true;
636 }
637
638
639 collect_percpu_times(group, PSI_POLL, &changed_states);
640
641 if (changed_states & group->poll_states) {
642 /* Initialize trigger windows when entering polling mode */
643 if (now > group->polling_until)
644 init_triggers(group, now);
645
646 /*
647 * Keep the monitor active for at least the duration of the
648 * minimum tracking window as long as monitor states are
649 * changing.
650 */
651 group->polling_until = now +
652 group->poll_min_period * UPDATES_PER_WINDOW;
653 }
654
655 if (now > group->polling_until) {
656 group->polling_next_update = ULLONG_MAX;
657 goto out;
658 }
659
660 if (now >= group->polling_next_update)
661 group->polling_next_update = update_triggers(group, now);
662
663 psi_schedule_poll_work(group,
664 nsecs_to_jiffies(group->polling_next_update - now) + 1,
665 force_reschedule);
666
667 out:
668 mutex_unlock(&group->trigger_lock);
669 }
670
psi_poll_worker(void * data)671 static int psi_poll_worker(void *data)
672 {
673 struct psi_group *group = (struct psi_group *)data;
674
675 sched_set_fifo_low(current);
676
677 while (true) {
678 wait_event_interruptible(group->poll_wait,
679 atomic_cmpxchg(&group->poll_wakeup, 1, 0) ||
680 kthread_should_stop());
681 if (kthread_should_stop())
682 break;
683
684 psi_poll_work(group);
685 }
686 return 0;
687 }
688
poll_timer_fn(struct timer_list * t)689 static void poll_timer_fn(struct timer_list *t)
690 {
691 struct psi_group *group = from_timer(group, t, poll_timer);
692
693 atomic_set(&group->poll_wakeup, 1);
694 wake_up_interruptible(&group->poll_wait);
695 }
696
record_times(struct psi_group_cpu * groupc,int cpu,bool memstall_tick)697 static void record_times(struct psi_group_cpu *groupc, int cpu,
698 bool memstall_tick)
699 {
700 u32 delta;
701 u64 now;
702
703 now = cpu_clock(cpu);
704 delta = now - groupc->state_start;
705 groupc->state_start = now;
706
707 if (groupc->state_mask & (1 << PSI_IO_SOME)) {
708 groupc->times[PSI_IO_SOME] += delta;
709 if (groupc->state_mask & (1 << PSI_IO_FULL))
710 groupc->times[PSI_IO_FULL] += delta;
711 }
712
713 if (groupc->state_mask & (1 << PSI_MEM_SOME)) {
714 groupc->times[PSI_MEM_SOME] += delta;
715 if (groupc->state_mask & (1 << PSI_MEM_FULL))
716 groupc->times[PSI_MEM_FULL] += delta;
717 else if (memstall_tick) {
718 u32 sample;
719 /*
720 * Since we care about lost potential, a
721 * memstall is FULL when there are no other
722 * working tasks, but also when the CPU is
723 * actively reclaiming and nothing productive
724 * could run even if it were runnable.
725 *
726 * When the timer tick sees a reclaiming CPU,
727 * regardless of runnable tasks, sample a FULL
728 * tick (or less if it hasn't been a full tick
729 * since the last state change).
730 */
731 sample = min(delta, (u32)jiffies_to_nsecs(1));
732 groupc->times[PSI_MEM_FULL] += sample;
733 }
734 }
735
736 if (groupc->state_mask & (1 << PSI_CPU_SOME))
737 groupc->times[PSI_CPU_SOME] += delta;
738
739 if (groupc->state_mask & (1 << PSI_NONIDLE))
740 groupc->times[PSI_NONIDLE] += delta;
741 }
742
psi_group_change(struct psi_group * group,int cpu,unsigned int clear,unsigned int set,bool wake_clock)743 static void psi_group_change(struct psi_group *group, int cpu,
744 unsigned int clear, unsigned int set,
745 bool wake_clock)
746 {
747 struct psi_group_cpu *groupc;
748 u32 state_mask = 0;
749 unsigned int t, m;
750 enum psi_states s;
751
752 groupc = per_cpu_ptr(group->pcpu, cpu);
753
754 /*
755 * First we assess the aggregate resource states this CPU's
756 * tasks have been in since the last change, and account any
757 * SOME and FULL time these may have resulted in.
758 *
759 * Then we update the task counts according to the state
760 * change requested through the @clear and @set bits.
761 */
762 write_seqcount_begin(&groupc->seq);
763
764 record_times(groupc, cpu, false);
765
766 for (t = 0, m = clear; m; m &= ~(1 << t), t++) {
767 if (!(m & (1 << t)))
768 continue;
769 if (groupc->tasks[t]) {
770 groupc->tasks[t]--;
771 } else if (!psi_bug) {
772 printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n",
773 cpu, t, groupc->tasks[0],
774 groupc->tasks[1], groupc->tasks[2],
775 groupc->tasks[3], clear, set);
776 psi_bug = 1;
777 }
778 }
779
780 for (t = 0; set; set &= ~(1 << t), t++)
781 if (set & (1 << t))
782 groupc->tasks[t]++;
783
784 /* Calculate state mask representing active states */
785 for (s = 0; s < NR_PSI_STATES; s++) {
786 if (test_state(groupc->tasks, s))
787 state_mask |= (1 << s);
788 }
789 groupc->state_mask = state_mask;
790
791 write_seqcount_end(&groupc->seq);
792
793 if (state_mask & group->poll_states)
794 psi_schedule_poll_work(group, 1, false);
795
796 if (wake_clock && !delayed_work_pending(&group->avgs_work))
797 schedule_delayed_work(&group->avgs_work, PSI_FREQ);
798 }
799
iterate_groups(struct task_struct * task,void ** iter)800 static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
801 {
802 if (*iter == &psi_system)
803 return NULL;
804
805 #ifdef CONFIG_CGROUPS
806 if (static_branch_likely(&psi_cgroups_enabled)) {
807 struct cgroup *cgroup = NULL;
808
809 if (!*iter)
810 cgroup = task->cgroups->dfl_cgrp;
811 else
812 cgroup = cgroup_parent(*iter);
813
814 if (cgroup && cgroup_parent(cgroup)) {
815 *iter = cgroup;
816 return cgroup_psi(cgroup);
817 }
818 }
819 #endif
820 *iter = &psi_system;
821 return &psi_system;
822 }
823
psi_flags_change(struct task_struct * task,int clear,int set)824 static void psi_flags_change(struct task_struct *task, int clear, int set)
825 {
826 if (((task->psi_flags & set) ||
827 (task->psi_flags & clear) != clear) &&
828 !psi_bug) {
829 printk_deferred(KERN_ERR "psi: inconsistent task state! task=%d:%s cpu=%d psi_flags=%x clear=%x set=%x\n",
830 task->pid, task->comm, task_cpu(task),
831 task->psi_flags, clear, set);
832 psi_bug = 1;
833 }
834
835 task->psi_flags &= ~clear;
836 task->psi_flags |= set;
837 }
838
psi_task_change(struct task_struct * task,int clear,int set)839 void psi_task_change(struct task_struct *task, int clear, int set)
840 {
841 int cpu = task_cpu(task);
842 struct psi_group *group;
843 bool wake_clock = true;
844 void *iter = NULL;
845
846 if (!task->pid)
847 return;
848
849 psi_flags_change(task, clear, set);
850
851 /*
852 * Periodic aggregation shuts off if there is a period of no
853 * task changes, so we wake it back up if necessary. However,
854 * don't do this if the task change is the aggregation worker
855 * itself going to sleep, or we'll ping-pong forever.
856 */
857 if (unlikely((clear & TSK_RUNNING) &&
858 (task->flags & PF_WQ_WORKER) &&
859 wq_worker_last_func(task) == psi_avgs_work))
860 wake_clock = false;
861
862 while ((group = iterate_groups(task, &iter)))
863 psi_group_change(group, cpu, clear, set, wake_clock);
864 }
865
psi_task_switch(struct task_struct * prev,struct task_struct * next,bool sleep)866 void psi_task_switch(struct task_struct *prev, struct task_struct *next,
867 bool sleep)
868 {
869 struct psi_group *group, *common = NULL;
870 int cpu = task_cpu(prev);
871 void *iter;
872
873 if (next->pid) {
874 psi_flags_change(next, 0, TSK_ONCPU);
875 /*
876 * When moving state between tasks, the group that
877 * contains them both does not change: we can stop
878 * updating the tree once we reach the first common
879 * ancestor. Iterate @next's ancestors until we
880 * encounter @prev's state.
881 */
882 iter = NULL;
883 while ((group = iterate_groups(next, &iter))) {
884 if (per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) {
885 common = group;
886 break;
887 }
888
889 psi_group_change(group, cpu, 0, TSK_ONCPU, true);
890 }
891 }
892
893 /*
894 * If this is a voluntary sleep, dequeue will have taken care
895 * of the outgoing TSK_ONCPU alongside TSK_RUNNING already. We
896 * only need to deal with it during preemption.
897 */
898 if (sleep)
899 return;
900
901 if (prev->pid) {
902 psi_flags_change(prev, TSK_ONCPU, 0);
903
904 iter = NULL;
905 while ((group = iterate_groups(prev, &iter)) && group != common)
906 psi_group_change(group, cpu, TSK_ONCPU, 0, true);
907 }
908 }
909
psi_memstall_tick(struct task_struct * task,int cpu)910 void psi_memstall_tick(struct task_struct *task, int cpu)
911 {
912 struct psi_group *group;
913 void *iter = NULL;
914
915 while ((group = iterate_groups(task, &iter))) {
916 struct psi_group_cpu *groupc;
917
918 groupc = per_cpu_ptr(group->pcpu, cpu);
919 write_seqcount_begin(&groupc->seq);
920 record_times(groupc, cpu, true);
921 write_seqcount_end(&groupc->seq);
922 }
923 }
924
925 /**
926 * psi_memstall_enter - mark the beginning of a memory stall section
927 * @flags: flags to handle nested sections
928 *
929 * Marks the calling task as being stalled due to a lack of memory,
930 * such as waiting for a refault or performing reclaim.
931 */
psi_memstall_enter(unsigned long * flags)932 void psi_memstall_enter(unsigned long *flags)
933 {
934 struct rq_flags rf;
935 struct rq *rq;
936
937 if (static_branch_likely(&psi_disabled))
938 return;
939
940 *flags = current->in_memstall;
941 if (*flags)
942 return;
943 /*
944 * in_memstall setting & accounting needs to be atomic wrt
945 * changes to the task's scheduling state, otherwise we can
946 * race with CPU migration.
947 */
948 rq = this_rq_lock_irq(&rf);
949
950 current->in_memstall = 1;
951 psi_task_change(current, 0, TSK_MEMSTALL);
952
953 rq_unlock_irq(rq, &rf);
954 }
955
956 /**
957 * psi_memstall_leave - mark the end of an memory stall section
958 * @flags: flags to handle nested memdelay sections
959 *
960 * Marks the calling task as no longer stalled due to lack of memory.
961 */
psi_memstall_leave(unsigned long * flags)962 void psi_memstall_leave(unsigned long *flags)
963 {
964 struct rq_flags rf;
965 struct rq *rq;
966
967 if (static_branch_likely(&psi_disabled))
968 return;
969
970 if (*flags)
971 return;
972 /*
973 * in_memstall clearing & accounting needs to be atomic wrt
974 * changes to the task's scheduling state, otherwise we could
975 * race with CPU migration.
976 */
977 rq = this_rq_lock_irq(&rf);
978
979 current->in_memstall = 0;
980 psi_task_change(current, TSK_MEMSTALL, 0);
981
982 rq_unlock_irq(rq, &rf);
983 }
984
985 #ifdef CONFIG_CGROUPS
psi_cgroup_alloc(struct cgroup * cgroup)986 int psi_cgroup_alloc(struct cgroup *cgroup)
987 {
988 if (static_branch_likely(&psi_disabled))
989 return 0;
990
991 cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
992 if (!cgroup->psi.pcpu)
993 return -ENOMEM;
994 group_init(&cgroup->psi);
995 return 0;
996 }
997
psi_cgroup_free(struct cgroup * cgroup)998 void psi_cgroup_free(struct cgroup *cgroup)
999 {
1000 if (static_branch_likely(&psi_disabled))
1001 return;
1002
1003 cancel_delayed_work_sync(&cgroup->psi.avgs_work);
1004 free_percpu(cgroup->psi.pcpu);
1005 /* All triggers must be removed by now */
1006 WARN_ONCE(cgroup->psi.poll_states, "psi: trigger leak\n");
1007 }
1008
1009 /**
1010 * cgroup_move_task - move task to a different cgroup
1011 * @task: the task
1012 * @to: the target css_set
1013 *
1014 * Move task to a new cgroup and safely migrate its associated stall
1015 * state between the different groups.
1016 *
1017 * This function acquires the task's rq lock to lock out concurrent
1018 * changes to the task's scheduling state and - in case the task is
1019 * running - concurrent changes to its stall state.
1020 */
cgroup_move_task(struct task_struct * task,struct css_set * to)1021 void cgroup_move_task(struct task_struct *task, struct css_set *to)
1022 {
1023 unsigned int task_flags;
1024 struct rq_flags rf;
1025 struct rq *rq;
1026
1027 if (static_branch_likely(&psi_disabled)) {
1028 /*
1029 * Lame to do this here, but the scheduler cannot be locked
1030 * from the outside, so we move cgroups from inside sched/.
1031 */
1032 rcu_assign_pointer(task->cgroups, to);
1033 return;
1034 }
1035
1036 rq = task_rq_lock(task, &rf);
1037
1038 /*
1039 * We may race with schedule() dropping the rq lock between
1040 * deactivating prev and switching to next. Because the psi
1041 * updates from the deactivation are deferred to the switch
1042 * callback to save cgroup tree updates, the task's scheduling
1043 * state here is not coherent with its psi state:
1044 *
1045 * schedule() cgroup_move_task()
1046 * rq_lock()
1047 * deactivate_task()
1048 * p->on_rq = 0
1049 * psi_dequeue() // defers TSK_RUNNING & TSK_IOWAIT updates
1050 * pick_next_task()
1051 * rq_unlock()
1052 * rq_lock()
1053 * psi_task_change() // old cgroup
1054 * task->cgroups = to
1055 * psi_task_change() // new cgroup
1056 * rq_unlock()
1057 * rq_lock()
1058 * psi_sched_switch() // does deferred updates in new cgroup
1059 *
1060 * Don't rely on the scheduling state. Use psi_flags instead.
1061 */
1062 task_flags = task->psi_flags;
1063
1064 if (task_flags)
1065 psi_task_change(task, task_flags, 0);
1066
1067 /* See comment above */
1068 rcu_assign_pointer(task->cgroups, to);
1069
1070 if (task_flags)
1071 psi_task_change(task, 0, task_flags);
1072
1073 task_rq_unlock(rq, task, &rf);
1074 }
1075 #endif /* CONFIG_CGROUPS */
1076
psi_show(struct seq_file * m,struct psi_group * group,enum psi_res res)1077 int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
1078 {
1079 int full;
1080 u64 now;
1081
1082 if (static_branch_likely(&psi_disabled))
1083 return -EOPNOTSUPP;
1084
1085 /* Update averages before reporting them */
1086 mutex_lock(&group->avgs_lock);
1087 now = sched_clock();
1088 collect_percpu_times(group, PSI_AVGS, NULL);
1089 if (now >= group->avg_next_update)
1090 group->avg_next_update = update_averages(group, now);
1091 mutex_unlock(&group->avgs_lock);
1092
1093 for (full = 0; full < 2 - (res == PSI_CPU); full++) {
1094 unsigned long avg[3];
1095 u64 total;
1096 int w;
1097
1098 for (w = 0; w < 3; w++)
1099 avg[w] = group->avg[res * 2 + full][w];
1100 total = div_u64(group->total[PSI_AVGS][res * 2 + full],
1101 NSEC_PER_USEC);
1102
1103 seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n",
1104 full ? "full" : "some",
1105 LOAD_INT(avg[0]), LOAD_FRAC(avg[0]),
1106 LOAD_INT(avg[1]), LOAD_FRAC(avg[1]),
1107 LOAD_INT(avg[2]), LOAD_FRAC(avg[2]),
1108 total);
1109 }
1110
1111 return 0;
1112 }
1113
psi_io_show(struct seq_file * m,void * v)1114 static int psi_io_show(struct seq_file *m, void *v)
1115 {
1116 return psi_show(m, &psi_system, PSI_IO);
1117 }
1118
psi_memory_show(struct seq_file * m,void * v)1119 static int psi_memory_show(struct seq_file *m, void *v)
1120 {
1121 return psi_show(m, &psi_system, PSI_MEM);
1122 }
1123
psi_cpu_show(struct seq_file * m,void * v)1124 static int psi_cpu_show(struct seq_file *m, void *v)
1125 {
1126 return psi_show(m, &psi_system, PSI_CPU);
1127 }
1128
psi_io_open(struct inode * inode,struct file * file)1129 static int psi_io_open(struct inode *inode, struct file *file)
1130 {
1131 return single_open(file, psi_io_show, NULL);
1132 }
1133
psi_memory_open(struct inode * inode,struct file * file)1134 static int psi_memory_open(struct inode *inode, struct file *file)
1135 {
1136 return single_open(file, psi_memory_show, NULL);
1137 }
1138
psi_cpu_open(struct inode * inode,struct file * file)1139 static int psi_cpu_open(struct inode *inode, struct file *file)
1140 {
1141 return single_open(file, psi_cpu_show, NULL);
1142 }
1143
psi_trigger_create(struct psi_group * group,char * buf,size_t nbytes,enum psi_res res)1144 struct psi_trigger *psi_trigger_create(struct psi_group *group,
1145 char *buf, size_t nbytes, enum psi_res res)
1146 {
1147 struct psi_trigger *t;
1148 enum psi_states state;
1149 u32 threshold_us;
1150 u32 window_us;
1151
1152 if (static_branch_likely(&psi_disabled))
1153 return ERR_PTR(-EOPNOTSUPP);
1154
1155 if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2)
1156 state = PSI_IO_SOME + res * 2;
1157 else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2)
1158 state = PSI_IO_FULL + res * 2;
1159 else
1160 return ERR_PTR(-EINVAL);
1161
1162 if (state >= PSI_NONIDLE)
1163 return ERR_PTR(-EINVAL);
1164
1165 if (window_us < WINDOW_MIN_US ||
1166 window_us > WINDOW_MAX_US)
1167 return ERR_PTR(-EINVAL);
1168
1169 /* Check threshold */
1170 if (threshold_us == 0 || threshold_us > window_us)
1171 return ERR_PTR(-EINVAL);
1172
1173 t = kmalloc(sizeof(*t), GFP_KERNEL);
1174 if (!t)
1175 return ERR_PTR(-ENOMEM);
1176
1177 t->group = group;
1178 t->state = state;
1179 t->threshold = threshold_us * NSEC_PER_USEC;
1180 t->win.size = window_us * NSEC_PER_USEC;
1181 window_reset(&t->win, 0, 0, 0);
1182
1183 t->event = 0;
1184 t->last_event_time = 0;
1185 init_waitqueue_head(&t->event_wait);
1186
1187 mutex_lock(&group->trigger_lock);
1188
1189 if (!rcu_access_pointer(group->poll_task)) {
1190 struct task_struct *task;
1191
1192 task = kthread_create(psi_poll_worker, group, "psimon");
1193 if (IS_ERR(task)) {
1194 kfree(t);
1195 mutex_unlock(&group->trigger_lock);
1196 return ERR_CAST(task);
1197 }
1198 atomic_set(&group->poll_wakeup, 0);
1199 wake_up_process(task);
1200 rcu_assign_pointer(group->poll_task, task);
1201 }
1202
1203 list_add(&t->node, &group->triggers);
1204 group->poll_min_period = min(group->poll_min_period,
1205 div_u64(t->win.size, UPDATES_PER_WINDOW));
1206 group->nr_triggers[t->state]++;
1207 group->poll_states |= (1 << t->state);
1208
1209 mutex_unlock(&group->trigger_lock);
1210
1211 return t;
1212 }
1213
psi_trigger_destroy(struct psi_trigger * t)1214 void psi_trigger_destroy(struct psi_trigger *t)
1215 {
1216 struct psi_group *group;
1217 struct task_struct *task_to_destroy = NULL;
1218
1219 /*
1220 * We do not check psi_disabled since it might have been disabled after
1221 * the trigger got created.
1222 */
1223 if (!t)
1224 return;
1225
1226 group = t->group;
1227 /*
1228 * Wakeup waiters to stop polling and clear the queue to prevent it from
1229 * being accessed later. Can happen if cgroup is deleted from under a
1230 * polling process.
1231 */
1232 wake_up_pollfree(&t->event_wait);
1233
1234 mutex_lock(&group->trigger_lock);
1235
1236 if (!list_empty(&t->node)) {
1237 struct psi_trigger *tmp;
1238 u64 period = ULLONG_MAX;
1239
1240 list_del(&t->node);
1241 group->nr_triggers[t->state]--;
1242 if (!group->nr_triggers[t->state])
1243 group->poll_states &= ~(1 << t->state);
1244 /* reset min update period for the remaining triggers */
1245 list_for_each_entry(tmp, &group->triggers, node)
1246 period = min(period, div_u64(tmp->win.size,
1247 UPDATES_PER_WINDOW));
1248 group->poll_min_period = period;
1249 /* Destroy poll_task when the last trigger is destroyed */
1250 if (group->poll_states == 0) {
1251 group->polling_until = 0;
1252 task_to_destroy = rcu_dereference_protected(
1253 group->poll_task,
1254 lockdep_is_held(&group->trigger_lock));
1255 rcu_assign_pointer(group->poll_task, NULL);
1256 del_timer(&group->poll_timer);
1257 }
1258 }
1259
1260 mutex_unlock(&group->trigger_lock);
1261
1262 /*
1263 * Wait for psi_schedule_poll_work RCU to complete its read-side
1264 * critical section before destroying the trigger and optionally the
1265 * poll_task.
1266 */
1267 synchronize_rcu();
1268 /*
1269 * Stop kthread 'psimon' after releasing trigger_lock to prevent a
1270 * deadlock while waiting for psi_poll_work to acquire trigger_lock
1271 */
1272 if (task_to_destroy) {
1273 /*
1274 * After the RCU grace period has expired, the worker
1275 * can no longer be found through group->poll_task.
1276 */
1277 kthread_stop(task_to_destroy);
1278 atomic_set(&group->poll_scheduled, 0);
1279 }
1280 kfree(t);
1281 }
1282
psi_trigger_poll(void ** trigger_ptr,struct file * file,poll_table * wait)1283 __poll_t psi_trigger_poll(void **trigger_ptr,
1284 struct file *file, poll_table *wait)
1285 {
1286 __poll_t ret = DEFAULT_POLLMASK;
1287 struct psi_trigger *t;
1288
1289 if (static_branch_likely(&psi_disabled))
1290 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
1291
1292 t = smp_load_acquire(trigger_ptr);
1293 if (!t)
1294 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
1295
1296 poll_wait(file, &t->event_wait, wait);
1297
1298 if (cmpxchg(&t->event, 1, 0) == 1)
1299 ret |= EPOLLPRI;
1300
1301 return ret;
1302 }
1303
psi_write(struct file * file,const char __user * user_buf,size_t nbytes,enum psi_res res)1304 static ssize_t psi_write(struct file *file, const char __user *user_buf,
1305 size_t nbytes, enum psi_res res)
1306 {
1307 char buf[32];
1308 size_t buf_size;
1309 struct seq_file *seq;
1310 struct psi_trigger *new;
1311
1312 if (static_branch_likely(&psi_disabled))
1313 return -EOPNOTSUPP;
1314
1315 if (!nbytes)
1316 return -EINVAL;
1317
1318 buf_size = min(nbytes, sizeof(buf));
1319 if (copy_from_user(buf, user_buf, buf_size))
1320 return -EFAULT;
1321
1322 buf[buf_size - 1] = '\0';
1323
1324 seq = file->private_data;
1325
1326 /* Take seq->lock to protect seq->private from concurrent writes */
1327 mutex_lock(&seq->lock);
1328
1329 /* Allow only one trigger per file descriptor */
1330 if (seq->private) {
1331 mutex_unlock(&seq->lock);
1332 return -EBUSY;
1333 }
1334
1335 new = psi_trigger_create(&psi_system, buf, nbytes, res);
1336 if (IS_ERR(new)) {
1337 mutex_unlock(&seq->lock);
1338 return PTR_ERR(new);
1339 }
1340
1341 smp_store_release(&seq->private, new);
1342 mutex_unlock(&seq->lock);
1343
1344 return nbytes;
1345 }
1346
psi_io_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1347 static ssize_t psi_io_write(struct file *file, const char __user *user_buf,
1348 size_t nbytes, loff_t *ppos)
1349 {
1350 return psi_write(file, user_buf, nbytes, PSI_IO);
1351 }
1352
psi_memory_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1353 static ssize_t psi_memory_write(struct file *file, const char __user *user_buf,
1354 size_t nbytes, loff_t *ppos)
1355 {
1356 return psi_write(file, user_buf, nbytes, PSI_MEM);
1357 }
1358
psi_cpu_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1359 static ssize_t psi_cpu_write(struct file *file, const char __user *user_buf,
1360 size_t nbytes, loff_t *ppos)
1361 {
1362 return psi_write(file, user_buf, nbytes, PSI_CPU);
1363 }
1364
psi_fop_poll(struct file * file,poll_table * wait)1365 static __poll_t psi_fop_poll(struct file *file, poll_table *wait)
1366 {
1367 struct seq_file *seq = file->private_data;
1368
1369 return psi_trigger_poll(&seq->private, file, wait);
1370 }
1371
psi_fop_release(struct inode * inode,struct file * file)1372 static int psi_fop_release(struct inode *inode, struct file *file)
1373 {
1374 struct seq_file *seq = file->private_data;
1375
1376 psi_trigger_destroy(seq->private);
1377 return single_release(inode, file);
1378 }
1379
1380 static const struct proc_ops psi_io_proc_ops = {
1381 .proc_open = psi_io_open,
1382 .proc_read = seq_read,
1383 .proc_lseek = seq_lseek,
1384 .proc_write = psi_io_write,
1385 .proc_poll = psi_fop_poll,
1386 .proc_release = psi_fop_release,
1387 };
1388
1389 static const struct proc_ops psi_memory_proc_ops = {
1390 .proc_open = psi_memory_open,
1391 .proc_read = seq_read,
1392 .proc_lseek = seq_lseek,
1393 .proc_write = psi_memory_write,
1394 .proc_poll = psi_fop_poll,
1395 .proc_release = psi_fop_release,
1396 };
1397
1398 static const struct proc_ops psi_cpu_proc_ops = {
1399 .proc_open = psi_cpu_open,
1400 .proc_read = seq_read,
1401 .proc_lseek = seq_lseek,
1402 .proc_write = psi_cpu_write,
1403 .proc_poll = psi_fop_poll,
1404 .proc_release = psi_fop_release,
1405 };
1406
psi_proc_init(void)1407 static int __init psi_proc_init(void)
1408 {
1409 if (psi_enable) {
1410 proc_mkdir("pressure", NULL);
1411 proc_create("pressure/io", 0, NULL, &psi_io_proc_ops);
1412 proc_create("pressure/memory", 0, NULL, &psi_memory_proc_ops);
1413 proc_create("pressure/cpu", 0, NULL, &psi_cpu_proc_ops);
1414 }
1415 return 0;
1416 }
1417 module_init(psi_proc_init);
1418