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