kernel/sched/features.h

   1 /*
   2  * Only give sleepers 50% of their service deficit. This allows
   3  * them to run sooner, but does not allow tons of sleepers to
   4  * rip the spread apart.
   5  */
   6 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
   7
   8 /*
   9  * Place new tasks ahead so that they do not starve already running
  10  * tasks
  11  */
  12 SCHED_FEAT(START_DEBIT, true)
  13
  14 /*
  15  * Prefer to schedule the task we woke last (assuming it failed
  16  * wakeup-preemption), since its likely going to consume data we
  17  * touched, increases cache locality.
  18  */
  19 SCHED_FEAT(NEXT_BUDDY, false)
  20
  21 /*
  22  * Prefer to schedule the task that ran last (when we did
  23  * wake-preempt) as that likely will touch the same data, increases
  24  * cache locality.
  25  */
  26 SCHED_FEAT(LAST_BUDDY, true)
  27
  28 /*
  29  * Consider buddies to be cache hot, decreases the likelyness of a
  30  * cache buddy being migrated away, increases cache locality.
  31  */
  32 SCHED_FEAT(CACHE_HOT_BUDDY, true)
  33
  34 /*
  35  * Allow wakeup-time preemption of the current task:
  36  */
  37 SCHED_FEAT(WAKEUP_PREEMPTION, true)
  38
  39 SCHED_FEAT(HRTICK, false)
  40 SCHED_FEAT(DOUBLE_TICK, false)
  41 SCHED_FEAT(LB_BIAS, true)
  42
  43 /*
  44  * Decrement CPU capacity based on time not spent running tasks
  45  */
  46 SCHED_FEAT(NONTASK_CAPACITY, true)
  47
  48 /*
  49  * Queue remote wakeups on the target CPU and process them
  50  * using the scheduler IPI. Reduces rq->lock contention/bounces.
  51  */
  52 SCHED_FEAT(TTWU_QUEUE, true)
  53
  54 #ifdef HAVE_RT_PUSH_IPI
  55 /*
  56  * In order to avoid a thundering herd attack of CPUs that are
  57  * lowering their priorities at the same time, and there being
  58  * a single CPU that has an RT task that can migrate and is waiting
  59  * to run, where the other CPUs will try to take that CPUs
  60  * rq lock and possibly create a large contention, sending an
  61  * IPI to that CPU and let that CPU push the RT task to where
  62  * it should go may be a better scenario.
  63  */
  64 SCHED_FEAT(RT_PUSH_IPI, true)
  65 #endif
  66
  67 SCHED_FEAT(FORCE_SD_OVERLAP, false)
  68 SCHED_FEAT(RT_RUNTIME_SHARE, true)
  69 SCHED_FEAT(LB_MIN, false)
  70 SCHED_FEAT(ATTACH_AGE_LOAD, true)
  71