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Linux/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 
 72 

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