types.h

  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 in nanoseconds
 62 *  @sched_runtime	representative of the task's runtime in nanoseconds
 63 *  @sched_period	representative of the task's period in nanoseconds
 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 */
 98struct 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 */