126 lines
4.5 KiB
C
126 lines
4.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef _LINUX_SCHED_TYPES_H
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#define _LINUX_SCHED_TYPES_H
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#include <linux/types.h>
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struct sched_param {
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int sched_priority;
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};
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#define SCHED_ATTR_SIZE_VER0 48 /* sizeof first published struct */
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#define SCHED_ATTR_SIZE_VER1 56 /* add: util_{min,max} */
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/*
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* Extended scheduling parameters data structure.
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*
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* This is needed because the original struct sched_param can not be
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* altered without introducing ABI issues with legacy applications
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* (e.g., in sched_getparam()).
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*
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* However, the possibility of specifying more than just a priority for
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* the tasks may be useful for a wide variety of application fields, e.g.,
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* multimedia, streaming, automation and control, and many others.
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*
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* This variant (sched_attr) allows to define additional attributes to
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* improve the scheduler knowledge about task requirements.
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*
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* Scheduling Class Attributes
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* ===========================
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*
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* A subset of sched_attr attributes specifies the
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* scheduling policy and relative POSIX attributes:
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*
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* @size size of the structure, for fwd/bwd compat.
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*
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* @sched_policy task's scheduling policy
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* @sched_nice task's nice value (SCHED_NORMAL/BATCH)
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* @sched_priority task's static priority (SCHED_FIFO/RR)
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*
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* Certain more advanced scheduling features can be controlled by a
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* predefined set of flags via the attribute:
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*
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* @sched_flags for customizing the scheduler behaviour
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*
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* Sporadic Time-Constrained Task Attributes
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* =========================================
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*
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* A subset of sched_attr attributes allows to describe a so-called
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* sporadic time-constrained task.
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*
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* In such a model a task is specified by:
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* - the activation period or minimum instance inter-arrival time;
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* - the maximum (or average, depending on the actual scheduling
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* discipline) computation time of all instances, a.k.a. runtime;
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* - the deadline (relative to the actual activation time) of each
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* instance.
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* Very briefly, a periodic (sporadic) task asks for the execution of
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* some specific computation --which is typically called an instance--
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* (at most) every period. Moreover, each instance typically lasts no more
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* than the runtime and must be completed by time instant t equal to
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* the instance activation time + the deadline.
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*
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* This is reflected by the following fields of the sched_attr structure:
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*
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* @sched_deadline representative of the task's deadline
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* @sched_runtime representative of the task's runtime
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* @sched_period representative of the task's period
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*
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* Given this task model, there are a multiplicity of scheduling algorithms
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* and policies, that can be used to ensure all the tasks will make their
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* timing constraints.
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*
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* As of now, the SCHED_DEADLINE policy (sched_dl scheduling class) is the
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* only user of this new interface. More information about the algorithm
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* available in the scheduling class file or in Documentation/.
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*
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* Task Utilization Attributes
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* ===========================
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*
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* A subset of sched_attr attributes allows to specify the utilization
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* expected for a task. These attributes allow to inform the scheduler about
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* the utilization boundaries within which it should schedule the task. These
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* boundaries are valuable hints to support scheduler decisions on both task
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* placement and frequency selection.
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*
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* @sched_util_min represents the minimum utilization
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* @sched_util_max represents the maximum utilization
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*
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* Utilization is a value in the range [0..SCHED_CAPACITY_SCALE]. It
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* represents the percentage of CPU time used by a task when running at the
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* maximum frequency on the highest capacity CPU of the system. For example, a
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* 20% utilization task is a task running for 2ms every 10ms at maximum
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* frequency.
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*
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* A task with a min utilization value bigger than 0 is more likely scheduled
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* on a CPU with a capacity big enough to fit the specified value.
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* A task with a max utilization value smaller than 1024 is more likely
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* scheduled on a CPU with no more capacity than the specified value.
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*
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* A task utilization boundary can be reset by setting the attribute to -1.
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*/
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struct sched_attr {
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__u32 size;
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__u32 sched_policy;
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__u64 sched_flags;
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/* SCHED_NORMAL, SCHED_BATCH */
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__s32 sched_nice;
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/* SCHED_FIFO, SCHED_RR */
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__u32 sched_priority;
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/* SCHED_DEADLINE */
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__u64 sched_runtime;
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__u64 sched_deadline;
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__u64 sched_period;
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/* Utilization hints */
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__u32 sched_util_min;
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__u32 sched_util_max;
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};
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#endif /* _LINUX_SCHED_TYPES_H */
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