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  */
   7 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
   8
   9 /*
  10  * Place new tasks ahead so that they do not starve already running
  11  * tasks
  12  */
  13 SCHED_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  */
  20 SCHED_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  */
  27 SCHED_FEAT(LAST_BUDDY, true)
  28
  29 /*
  30  * Consider buddies to be cache hot, decreases the likelyness of a
  31  * cache buddy being migrated away, increases cache locality.
  32  */
  33 SCHED_FEAT(CACHE_HOT_BUDDY, true)
  34
  35 /*
  36  * Allow wakeup-time preemption of the current task:
  37  */
  38 SCHED_FEAT(WAKEUP_PREEMPTION, true)
  39
  40 SCHED_FEAT(HRTICK, false)
  41 SCHED_FEAT(DOUBLE_TICK, false)
  42 SCHED_FEAT(LB_BIAS, false)
  43
  44 /*
  45  * Decrement CPU capacity based on time not spent running tasks
  46  */
  47 SCHED_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  */
  53 SCHED_FEAT(TTWU_QUEUE, true)
  54
  55 /*
  56  * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
  57  */
  58 SCHED_FEAT(SIS_AVG_CPU, false)
  59 SCHED_FEAT(SIS_PROP, true)
  60
  61 /*
  62  * Issue a WARN when we do multiple update_rq_clock() calls
  63  * in a single rq->lock section. Default disabled because the
  64  * annotations are not complete.
  65  */
  66 SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
  67
  68 #ifdef HAVE_RT_PUSH_IPI
  69 /*
  70  * In order to avoid a thundering herd attack of CPUs that are
  71  * lowering their priorities at the same time, and there being
  72  * a single CPU that has an RT task that can migrate and is waiting
  73  * to run, where the other CPUs will try to take that CPUs
  74  * rq lock and possibly create a large contention, sending an
  75  * IPI to that CPU and let that CPU push the RT task to where
  76  * it should go may be a better scenario.
  77  */
  78 SCHED_FEAT(RT_PUSH_IPI, true)
  79 #endif
  80
  81 SCHED_FEAT(RT_RUNTIME_SHARE, true)
  82 SCHED_FEAT(LB_MIN, false)
  83 SCHED_FEAT(ATTACH_AGE_LOAD, true)
  84
  85 SCHED_FEAT(WA_IDLE, true)
  86 SCHED_FEAT(WA_WEIGHT, true)
  87 SCHED_FEAT(WA_BIAS, true)
  88
  89 /*
  90  * UtilEstimation. Use estimated CPU utilization.
  91  */
  92 SCHED_FEAT(UTIL_EST, true)