1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2#ifndef _LINUX_SCHED_TYPES_H
3#define _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 /* _LINUX_SCHED_TYPES_H */
122