1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 2 #ifndef _UAPI_LINUX_SCHED_TYPES_H 3 #define _UAPI_LINUX_SCHED_TYPES_H 4 5 #include <linux/types.h> 6 7 struct sched_param { 8 int sched_priority; 9 }; 10 11 #define SCHED_ATTR_SIZE_VER0 48 /* sizeof first published struct */ 12 #define SCHED_ATTR_SIZE_VER1 56 /* add: util_{min,max} */ 13 #define SCHED_ATTR_SIZE_VER2 60 /* add: latency_nice */ 14 15 /* 16 * Extended scheduling parameters data structure. 17 * 18 * This is needed because the original struct sched_param can not be 19 * altered without introducing ABI issues with legacy applications 20 * (e.g., in sched_getparam()). 21 * 22 * However, the possibility of specifying more than just a priority for 23 * the tasks may be useful for a wide variety of application fields, e.g., 24 * multimedia, streaming, automation and control, and many others. 25 * 26 * This variant (sched_attr) allows to define additional attributes to 27 * improve the scheduler knowledge about task requirements. 28 * 29 * Scheduling Class Attributes 30 * =========================== 31 * 32 * A subset of sched_attr attributes specifies the 33 * scheduling policy and relative POSIX attributes: 34 * 35 * @size size of the structure, for fwd/bwd compat. 36 * 37 * @sched_policy task's scheduling policy 38 * @sched_nice task's nice value (SCHED_NORMAL/BATCH) 39 * @sched_priority task's static priority (SCHED_FIFO/RR) 40 * 41 * Certain more advanced scheduling features can be controlled by a 42 * predefined set of flags via the attribute: 43 * 44 * @sched_flags for customizing the scheduler behaviour 45 * 46 * Sporadic Time-Constrained Task Attributes 47 * ========================================= 48 * 49 * A subset of sched_attr attributes allows to describe a so-called 50 * sporadic time-constrained task. 51 * 52 * In such a model a task is specified by: 53 * - the activation period or minimum instance inter-arrival time; 54 * - the maximum (or average, depending on the actual scheduling 55 * discipline) computation time of all instances, a.k.a. runtime; 56 * - the deadline (relative to the actual activation time) of each 57 * instance. 58 * Very briefly, a periodic (sporadic) task asks for the execution of 59 * some specific computation --which is typically called an instance-- 60 * (at most) every period. Moreover, each instance typically lasts no more 61 * than the runtime and must be completed by time instant t equal to 62 * the instance activation time + the deadline. 63 * 64 * This is reflected by the following fields of the sched_attr structure: 65 * 66 * @sched_deadline representative of the task's deadline 67 * @sched_runtime representative of the task's runtime 68 * @sched_period representative of the task's period 69 * 70 * Given this task model, there are a multiplicity of scheduling algorithms 71 * and policies, that can be used to ensure all the tasks will make their 72 * timing constraints. 73 * 74 * As of now, the SCHED_DEADLINE policy (sched_dl scheduling class) is the 75 * only user of this new interface. More information about the algorithm 76 * available in the scheduling class file or in Documentation/. 77 * 78 * Task Utilization Attributes 79 * =========================== 80 * 81 * A subset of sched_attr attributes allows to specify the utilization 82 * expected for a task. These attributes allow to inform the scheduler about 83 * the utilization boundaries within which it should schedule the task. These 84 * boundaries are valuable hints to support scheduler decisions on both task 85 * placement and frequency selection. 86 * 87 * @sched_util_min represents the minimum utilization 88 * @sched_util_max represents the maximum utilization 89 * 90 * Utilization is a value in the range [0..SCHED_CAPACITY_SCALE]. It 91 * represents the percentage of CPU time used by a task when running at the 92 * maximum frequency on the highest capacity CPU of the system. For example, a 93 * 20% utilization task is a task running for 2ms every 10ms at maximum 94 * frequency. 95 * 96 * A task with a min utilization value bigger than 0 is more likely scheduled 97 * on a CPU with a capacity big enough to fit the specified value. 98 * A task with a max utilization value smaller than 1024 is more likely 99 * scheduled on a CPU with no more capacity than the specified value. 100 * 101 * Latency Tolerance Attributes 102 * =========================== 103 * 104 * A subset of sched_attr attributes allows to specify the relative latency 105 * requirements of a task with respect to the other tasks running/queued in the 106 * system. 107 * 108 * @ sched_latency_nice task's latency_nice value 109 * 110 * The latency_nice of a task can have any value in a range of 111 * [MIN_LATENCY_NICE..MAX_LATENCY_NICE]. 112 * 113 * A task with latency_nice with the value of LATENCY_NICE_MIN can be 114 * taken for a task requiring a lower latency as opposed to the task with 115 * higher latency_nice. 116 */ 117 struct sched_attr { 118 __u32 size; 119 120 __u32 sched_policy; 121 __u64 sched_flags; 122 123 /* SCHED_NORMAL, SCHED_BATCH */ 124 __s32 sched_nice; 125 126 /* SCHED_FIFO, SCHED_RR */ 127 __u32 sched_priority; 128 129 /* SCHED_DEADLINE */ 130 __u64 sched_runtime; 131 __u64 sched_deadline; 132 __u64 sched_period; 133 134 /* Utilization hints */ 135 __u32 sched_util_min; 136 __u32 sched_util_max; 137 138 /* latency requirement hints */ 139 __s32 sched_latency_nice; 140 }; 141 142 #endif /* _UAPI_LINUX_SCHED_TYPES_H */ 143