kernel/sched/features.h

Source file repositories/reference/linux-study-clean/kernel/sched/features.h

File Facts

System
Linux kernel
Corpus path
kernel/sched/features.h
Extension
.h
Size
3790 bytes
Lines
145
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

SCHED_FEAT(PLACE_LAG, true)
/*
 * Give new tasks half a slice to ease into the competition.
 */
SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
/*
 * Preserve relative virtual deadline on 'migration'.
 */
SCHED_FEAT(PLACE_REL_DEADLINE, true)
/*
 * Inhibit (wakeup) preemption until the current task has either matched the
 * 0-lag point or until is has exhausted it's slice.
 */
SCHED_FEAT(RUN_TO_PARITY, true)
/*
 * Allow wakeup of tasks with a shorter slice to cancel RUN_TO_PARITY for
 * current.
 */
SCHED_FEAT(PREEMPT_SHORT, true)

/*
 * Prefer to schedule the task we woke last (assuming it failed
 * wakeup-preemption), since its likely going to consume data we
 * touched, increases cache locality.
 */
SCHED_FEAT(NEXT_BUDDY, false)

/*
 * Allow completely ignoring cfs_rq->next; which can be set from various
 * places:
 *   - NEXT_BUDDY (wakeup preemption)
 *   - yield_to_task()
 *   - cgroup dequeue / pick
 */
SCHED_FEAT(PICK_BUDDY, true)

/*
 * Consider buddies to be cache hot, decreases the likeliness of a
 * cache buddy being migrated away, increases cache locality.
 */
SCHED_FEAT(CACHE_HOT_BUDDY, true)

/*
 * Delay dequeueing tasks until they get selected or woken.
 *
 * By delaying the dequeue for non-eligible tasks, they remain in the
 * competition and can burn off their negative lag. When they get selected
 * they'll have positive lag by definition.
 *
 * DELAY_ZERO clips the lag on dequeue (or wakeup) to 0.
 */
SCHED_FEAT(DELAY_DEQUEUE, true)
SCHED_FEAT(DELAY_ZERO, true)

SCHED_FEAT(PARANOID_AVG, false)

/*
 * Allow wakeup-time preemption of the current task:
 */
SCHED_FEAT(WAKEUP_PREEMPTION, true)

#ifdef CONFIG_HRTIMER_REARM_DEFERRED
SCHED_FEAT(HRTICK, true)
SCHED_FEAT(HRTICK_DL, true)
#else
SCHED_FEAT(HRTICK, false)
SCHED_FEAT(HRTICK_DL, false)
#endif

/*
 * Decrement CPU capacity based on time not spent running tasks
 */
SCHED_FEAT(NONTASK_CAPACITY, true)

#ifdef CONFIG_PREEMPT_RT
SCHED_FEAT(TTWU_QUEUE, false)
#else

/*
 * Queue remote wakeups on the target CPU and process them
 * using the scheduler IPI. Reduces rq->lock contention/bounces.
 */
SCHED_FEAT(TTWU_QUEUE, true)
#endif

/*
 * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
 */
SCHED_FEAT(SIS_UTIL, true)

Annotation

Implementation Notes