kernel/sched/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  */
   7 SCHED_FEAT(PLACE_LAG, true)
   8 /*
   9  * Give new tasks half a slice to ease into the competition.
  10  */
  11 SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
  12 /*
  13  * Preserve relative virtual deadline on 'migration'.
  14  */
  15 SCHED_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  */
  20 SCHED_FEAT(RUN_TO_PARITY, true)
  21 /*
  22  * Allow wakeup of tasks with a shorter slice to cancel RESPECT_SLICE for
  23  * current.
  24  */
  25 SCHED_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  */
  32 SCHED_FEAT(NEXT_BUDDY, false)
  33
  34 /*
  35  * Consider buddies to be cache hot, decreases the likeliness of a
  36  * cache buddy being migrated away, increases cache locality.
  37  */
  38 SCHED_FEAT(CACHE_HOT_BUDDY, true)
  39
  40 /*
  41  * Delay dequeueing tasks until they get selected or woken.
  42  *
  43  * By delaying the dequeue for non-eligible tasks, they remain in the
  44  * competition and can burn off their negative lag. When they get selected
  45  * they'll have positive lag by definition.
  46  *
  47  * DELAY_ZERO clips the lag on dequeue (or wakeup) to 0.
  48  */
  49 SCHED_FEAT(DELAY_DEQUEUE, true)
  50 SCHED_FEAT(DELAY_ZERO, true)
  51
  52 /*
  53  * Allow wakeup-time preemption of the current task:
  54  */
  55 SCHED_FEAT(WAKEUP_PREEMPTION, true)
  56
  57 SCHED_FEAT(HRTICK, false)
  58 SCHED_FEAT(HRTICK_DL, false)
  59 SCHED_FEAT(DOUBLE_TICK, false)
  60
  61 /*
  62  * Decrement CPU capacity based on time not spent running tasks
  63  */
  64 SCHED_FEAT(NONTASK_CAPACITY, true)
  65
  66 #ifdef CONFIG_PREEMPT_RT
  67 SCHED_FEAT(TTWU_QUEUE, false)
  68 #else
  69
  70 /*
  71  * Queue remote wakeups on the target CPU and process them
  72  * using the scheduler IPI. Reduces rq->lock contention/bounces.
  73  */
  74 SCHED_FEAT(TTWU_QUEUE, true)
  75 #endif
  76
  77 /*
  78  * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
  79  */
  80 SCHED_FEAT(SIS_UTIL, true)
  81
  82 /*
  83  * Issue a WARN when we do multiple update_rq_clock() calls
  84  * in a single rq->lock section. Default disabled because the
  85  * annotations are not complete.
  86  */
  87 SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
  88
  89 #ifdef HAVE_RT_PUSH_IPI
  90 /*
  91  * In order to avoid a thundering herd attack of CPUs that are
  92  * lowering their priorities at the same time, and there being
  93  * a single CPU that has an RT task that can migrate and is waiting
  94  * to run, where the other CPUs will try to take that CPUs
  95  * rq lock and possibly create a large contention, sending an
  96  * IPI to that CPU and let that CPU push the RT task to where
  97  * it should go may be a better scenario.
  98  */
  99 SCHED_FEAT(RT_PUSH_IPI, true)
 100 #endif
 101
 102 SCHED_FEAT(RT_RUNTIME_SHARE, false)
 103 SCHED_FEAT(LB_MIN, false)
 104 SCHED_FEAT(ATTACH_AGE_LOAD, true)
 105
 106 SCHED_FEAT(WA_IDLE, true)
 107 SCHED_FEAT(WA_WEIGHT, true)
 108 SCHED_FEAT(WA_BIAS, true)
 109
 110 /*
 111  * UtilEstimation. Use estimated CPU utilization.
 112  */
 113 SCHED_FEAT(UTIL_EST, true)
 114
 115 SCHED_FEAT(LATENCY_WARN, false)