LXR linux/kernel/sched/features.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * Only give sleepers 50% of their service deficit. This allows
   4 * them to run sooner, but does not allow tons of sleepers to
   5 * rip the spread apart.
   6 */
   7SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
   8
   9/*
  10 * Place new tasks ahead so that they do not starve already running
  11 * tasks
  12 */
  13SCHED_FEAT(START_DEBIT, true)
  14
  15/*
  16 * Prefer to schedule the task we woke last (assuming it failed
  17 * wakeup-preemption), since its likely going to consume data we
  18 * touched, increases cache locality.
  19 */
  20SCHED_FEAT(NEXT_BUDDY, false)
  21
  22/*
  23 * Prefer to schedule the task that ran last (when we did
  24 * wake-preempt) as that likely will touch the same data, increases
  25 * cache locality.
  26 */
  27SCHED_FEAT(LAST_BUDDY, true)
  28
  29/*
  30 * Consider buddies to be cache hot, decreases the likeliness of a
  31 * cache buddy being migrated away, increases cache locality.
  32 */
  33SCHED_FEAT(CACHE_HOT_BUDDY, true)
  34
  35/*
  36 * Allow wakeup-time preemption of the current task:
  37 */
  38SCHED_FEAT(WAKEUP_PREEMPTION, true)
  39
  40SCHED_FEAT(HRTICK, false)
  41SCHED_FEAT(HRTICK_DL, false)
  42SCHED_FEAT(DOUBLE_TICK, false)
  43
  44/*
  45 * Decrement CPU capacity based on time not spent running tasks
  46 */
  47SCHED_FEAT(NONTASK_CAPACITY, true)
  48
  49/*
  50 * Queue remote wakeups on the target CPU and process them
  51 * using the scheduler IPI. Reduces rq->lock contention/bounces.
  52 */
  53SCHED_FEAT(TTWU_QUEUE, true)
  54
  55/*
  56 * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
  57 */
  58SCHED_FEAT(SIS_PROP, true)
  59
  60/*
  61 * Issue a WARN when we do multiple update_rq_clock() calls
  62 * in a single rq->lock section. Default disabled because the
  63 * annotations are not complete.
  64 */
  65SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
  66
  67#ifdef HAVE_RT_PUSH_IPI
  68/*
  69 * In order to avoid a thundering herd attack of CPUs that are
  70 * lowering their priorities at the same time, and there being
  71 * a single CPU that has an RT task that can migrate and is waiting
  72 * to run, where the other CPUs will try to take that CPUs
  73 * rq lock and possibly create a large contention, sending an
  74 * IPI to that CPU and let that CPU push the RT task to where
  75 * it should go may be a better scenario.
  76 */
  77SCHED_FEAT(RT_PUSH_IPI, true)
  78#endif
  79
  80SCHED_FEAT(RT_RUNTIME_SHARE, false)
  81SCHED_FEAT(LB_MIN, false)
  82SCHED_FEAT(ATTACH_AGE_LOAD, true)
  83
  84SCHED_FEAT(WA_IDLE, true)
  85SCHED_FEAT(WA_WEIGHT, true)
  86SCHED_FEAT(WA_BIAS, true)
  87
  88/*
  89 * UtilEstimation. Use estimated CPU utilization.
  90 */
  91SCHED_FEAT(UTIL_EST, true)
  92SCHED_FEAT(UTIL_EST_FASTUP, true)
  93
  94SCHED_FEAT(LATENCY_WARN, false)
  95
  96SCHED_FEAT(ALT_PERIOD, true)
  97SCHED_FEAT(BASE_SLICE, true)
  98