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