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