kernel/sched_features.h

   1 /*
   2  * Disregards a certain amount of sleep time (sched_latency_ns) and
   3  * considers the task to be running during that period. This gives it
   4  * a service deficit on wakeup, allowing it to run sooner.
   5  */
   6 SCHED_FEAT(FAIR_SLEEPERS, 1)
   7
   8 /*
   9  * Only give sleepers 50% of their service deficit. This allows
  10  * them to run sooner, but does not allow tons of sleepers to
  11  * rip the spread apart.
  12  */
  13 SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
  14
  15 /*
  16  * By not normalizing the sleep time, heavy tasks get an effective
  17  * longer period, and lighter task an effective shorter period they
  18  * are considered running.
  19  */
  20 SCHED_FEAT(NORMALIZED_SLEEPER, 0)
  21
  22 /*
  23  * Place new tasks ahead so that they do not starve already running
  24  * tasks
  25  */
  26 SCHED_FEAT(START_DEBIT, 1)
  27
  28 /*
  29  * Should wakeups try to preempt running tasks.
  30  */
  31 SCHED_FEAT(WAKEUP_PREEMPT, 1)
  32
  33 /*
  34  * When converting the wakeup granularity to virtual time, do it such
  35  * that heavier tasks preempting a lighter task have an edge.
  36  */
  37 SCHED_FEAT(ASYM_GRAN, 1)
  38
  39 /*
  40  * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
  41  */
  42 SCHED_FEAT(WAKEUP_SYNC, 0)
  43
  44 /*
  45  * Use the SYNC wakeup hint, pipes and the likes use this to indicate
  46  * the remote end is likely to consume the data we just wrote, and
  47  * therefore has cache benefit from being placed on the same cpu, see
  48  * also AFFINE_WAKEUPS.
  49  */
  50 SCHED_FEAT(SYNC_WAKEUPS, 1)
  51
  52 /*
  53  * Based on load and program behaviour, see if it makes sense to place
  54  * a newly woken task on the same cpu as the task that woke it --
  55  * improve cache locality. Typically used with SYNC wakeups as
  56  * generated by pipes and the like, see also SYNC_WAKEUPS.
  57  */
  58 SCHED_FEAT(AFFINE_WAKEUPS, 1)
  59
  60 /*
  61  * Prefer to schedule the task we woke last (assuming it failed
  62  * wakeup-preemption), since its likely going to consume data we
  63  * touched, increases cache locality.
  64  */
  65 SCHED_FEAT(NEXT_BUDDY, 0)
  66
  67 /*
  68  * Prefer to schedule the task that ran last (when we did
  69  * wake-preempt) as that likely will touch the same data, increases
  70  * cache locality.
  71  */
  72 SCHED_FEAT(LAST_BUDDY, 1)
  73
  74 /*
  75  * Consider buddies to be cache hot, decreases the likelyness of a
  76  * cache buddy being migrated away, increases cache locality.
  77  */
  78 SCHED_FEAT(CACHE_HOT_BUDDY, 1)
  79
  80 /*
  81  * Use arch dependent cpu power functions
  82  */
  83 SCHED_FEAT(ARCH_POWER, 0)
  84
  85 SCHED_FEAT(HRTICK, 0)
  86 SCHED_FEAT(DOUBLE_TICK, 0)
  87 SCHED_FEAT(LB_BIAS, 1)
  88 SCHED_FEAT(LB_SHARES_UPDATE, 1)
  89 SCHED_FEAT(ASYM_EFF_LOAD, 1)
  90
  91 /*
  92  * Spin-wait on mutex acquisition when the mutex owner is running on
  93  * another cpu -- assumes that when the owner is running, it will soon
  94  * release the lock. Decreases scheduling overhead.
  95  */
  96 SCHED_FEAT(OWNER_SPIN, 1)