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  * Compute wakeup_gran based on task behaviour, clipped to
  35  *  [0, sched_wakeup_gran_ns]
  36  */
  37 SCHED_FEAT(ADAPTIVE_GRAN, 1)
  38
  39 /*
  40  * When converting the wakeup granularity to virtual time, do it such
  41  * that heavier tasks preempting a lighter task have an edge.
  42  */
  43 SCHED_FEAT(ASYM_GRAN, 1)
  44
  45 /*
  46  * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
  47  */
  48 SCHED_FEAT(WAKEUP_SYNC, 0)
  49
  50 /*
  51  * Wakeup preempt based on task behaviour. Tasks that do not overlap
  52  * don't get preempted.
  53  */
  54 SCHED_FEAT(WAKEUP_OVERLAP, 0)
  55
  56 /*
  57  * Wakeup preemption towards tasks that run short
  58  */
  59 SCHED_FEAT(WAKEUP_RUNNING, 0)
  60
  61 /*
  62  * Use the SYNC wakeup hint, pipes and the likes use this to indicate
  63  * the remote end is likely to consume the data we just wrote, and
  64  * therefore has cache benefit from being placed on the same cpu, see
  65  * also AFFINE_WAKEUPS.
  66  */
  67 SCHED_FEAT(SYNC_WAKEUPS, 1)
  68
  69 /*
  70  * Based on load and program behaviour, see if it makes sense to place
  71  * a newly woken task on the same cpu as the task that woke it --
  72  * improve cache locality. Typically used with SYNC wakeups as
  73  * generated by pipes and the like, see also SYNC_WAKEUPS.
  74  */
  75 SCHED_FEAT(AFFINE_WAKEUPS, 1)
  76
  77 /*
  78  * Weaken SYNC hint based on overlap
  79  */
  80 SCHED_FEAT(SYNC_LESS, 1)
  81
  82 /*
  83  * Add SYNC hint based on overlap
  84  */
  85 SCHED_FEAT(SYNC_MORE, 0)
  86
  87 /*
  88  * Prefer to schedule the task we woke last (assuming it failed
  89  * wakeup-preemption), since its likely going to consume data we
  90  * touched, increases cache locality.
  91  */
  92 SCHED_FEAT(NEXT_BUDDY, 0)
  93
  94 /*
  95  * Prefer to schedule the task that ran last (when we did
  96  * wake-preempt) as that likely will touch the same data, increases
  97  * cache locality.
  98  */
  99 SCHED_FEAT(LAST_BUDDY, 1)
 100
 101 /*
 102  * Consider buddies to be cache hot, decreases the likelyness of a
 103  * cache buddy being migrated away, increases cache locality.
 104  */
 105 SCHED_FEAT(CACHE_HOT_BUDDY, 1)
 106
 107 /*
 108  * Use arch dependent cpu power functions
 109  */
 110 SCHED_FEAT(ARCH_POWER, 0)
 111
 112 SCHED_FEAT(HRTICK, 0)
 113 SCHED_FEAT(DOUBLE_TICK, 0)
 114 SCHED_FEAT(LB_BIAS, 1)
 115 SCHED_FEAT(LB_SHARES_UPDATE, 1)
 116 SCHED_FEAT(ASYM_EFF_LOAD, 1)
 117
 118 /*
 119  * Spin-wait on mutex acquisition when the mutex owner is running on
 120  * another cpu -- assumes that when the owner is running, it will soon
 121  * release the lock. Decreases scheduling overhead.
 122  */
 123 SCHED_FEAT(OWNER_SPIN, 1)