features.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2
  3/*
  4 * Using the avg_vruntime, do the right thing and preserve lag across
  5 * sleep+wake cycles. EEVDF placement strategy #1, #2 if disabled.
  6 */
  7SCHED_FEAT(PLACE_LAG, true)
  8/*
  9 * Give new tasks half a slice to ease into the competition.
 10 */
 11SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 12/*
 13 * Preserve relative virtual deadline on 'migration'.
 14 */
 15SCHED_FEAT(PLACE_REL_DEADLINE, true)
 16/*
 17 * Inhibit (wakeup) preemption until the current task has either matched the
 18 * 0-lag point or until is has exhausted it's slice.
 19 */
 20SCHED_FEAT(RUN_TO_PARITY, true)
 21/*
 22 * Allow wakeup of tasks with a shorter slice to cancel RUN_TO_PARITY for
 23 * current.
 24 */
 25SCHED_FEAT(PREEMPT_SHORT, true)
 26
 27/*
 28 * Prefer to schedule the task we woke last (assuming it failed
 29 * wakeup-preemption), since its likely going to consume data we
 30 * touched, increases cache locality.
 31 */
 32SCHED_FEAT(NEXT_BUDDY, false)
 33
 34/*
 35 * Allow completely ignoring cfs_rq->next; which can be set from various
 36 * places:
 37 *   - NEXT_BUDDY (wakeup preemption)
 38 *   - yield_to_task()
 39 *   - cgroup dequeue / pick
 40 */
 41SCHED_FEAT(PICK_BUDDY, true)
 42
 43/*
 44 * Consider buddies to be cache hot, decreases the likeliness of a
 45 * cache buddy being migrated away, increases cache locality.
 46 */
 47SCHED_FEAT(CACHE_HOT_BUDDY, true)
 48
 49/*
 50 * Delay dequeueing tasks until they get selected or woken.
 51 *
 52 * By delaying the dequeue for non-eligible tasks, they remain in the
 53 * competition and can burn off their negative lag. When they get selected
 54 * they'll have positive lag by definition.
 55 *
 56 * DELAY_ZERO clips the lag on dequeue (or wakeup) to 0.
 57 */
 58SCHED_FEAT(DELAY_DEQUEUE, true)
 59SCHED_FEAT(DELAY_ZERO, true)
 60
 61/*
 62 * Allow wakeup-time preemption of the current task:
 63 */
 64SCHED_FEAT(WAKEUP_PREEMPTION, true)
 65
 66SCHED_FEAT(HRTICK, false)
 67SCHED_FEAT(HRTICK_DL, false)
 68
 69/*
 70 * Decrement CPU capacity based on time not spent running tasks
 71 */
 72SCHED_FEAT(NONTASK_CAPACITY, true)
 73
 74#ifdef CONFIG_PREEMPT_RT
 75SCHED_FEAT(TTWU_QUEUE, false)
 76#else
 77
 78/*
 79 * Queue remote wakeups on the target CPU and process them
 80 * using the scheduler IPI. Reduces rq->lock contention/bounces.
 81 */
 82SCHED_FEAT(TTWU_QUEUE, true)
 83#endif
 84
 85/*
 86 * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
 87 */
 88SCHED_FEAT(SIS_UTIL, true)
 89
 90/*
 91 * Issue a WARN when we do multiple update_rq_clock() calls
 92 * in a single rq->lock section. Default disabled because the
 93 * annotations are not complete.
 94 */
 95SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
 96
 97#ifdef HAVE_RT_PUSH_IPI
 98/*
 99 * In order to avoid a thundering herd attack of CPUs that are
100 * lowering their priorities at the same time, and there being
101 * a single CPU that has an RT task that can migrate and is waiting
102 * to run, where the other CPUs will try to take that CPUs
103 * rq lock and possibly create a large contention, sending an
104 * IPI to that CPU and let that CPU push the RT task to where
105 * it should go may be a better scenario.
106 */
107SCHED_FEAT(RT_PUSH_IPI, true)
108#endif
109
110SCHED_FEAT(RT_RUNTIME_SHARE, false)
111SCHED_FEAT(LB_MIN, false)
112SCHED_FEAT(ATTACH_AGE_LOAD, true)
113
114SCHED_FEAT(WA_IDLE, true)
115SCHED_FEAT(WA_WEIGHT, true)
116SCHED_FEAT(WA_BIAS, true)
117
118/*
119 * UtilEstimation. Use estimated CPU utilization.
120 */
121SCHED_FEAT(UTIL_EST, true)
122
123SCHED_FEAT(LATENCY_WARN, false)
124
125/*
126 * Do newidle balancing proportional to its success rate using randomization.
127 */
128SCHED_FEAT(NI_RANDOM, true)