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(NEW_FAIR_SLEEPERS, 0)
   7
   8 /*
   9  * By not normalizing the sleep time, heavy tasks get an effective
  10  * longer period, and lighter task an effective shorter period they
  11  * are considered running.
  12  */
  13 SCHED_FEAT(NORMALIZED_SLEEPER, 0)
  14
  15 /*
  16  * Place new tasks ahead so that they do not starve already running
  17  * tasks
  18  */
  19 SCHED_FEAT(START_DEBIT, 1)
  20
  21 /*
  22  * Should wakeups try to preempt running tasks.
  23  */
  24 SCHED_FEAT(WAKEUP_PREEMPT, 1)
  25
  26 /*
  27  * Compute wakeup_gran based on task behaviour, clipped to
  28  *  [0, sched_wakeup_gran_ns]
  29  */
  30 SCHED_FEAT(ADAPTIVE_GRAN, 1)
  31
  32 /*
  33  * When converting the wakeup granularity to virtual time, do it such
  34  * that heavier tasks preempting a lighter task have an edge.
  35  */
  36 SCHED_FEAT(ASYM_GRAN, 1)
  37
  38 /*
  39  * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
  40  */
  41 SCHED_FEAT(WAKEUP_SYNC, 0)
  42
  43 /*
  44  * Wakeup preempt based on task behaviour. Tasks that do not overlap
  45  * don't get preempted.
  46  */
  47 SCHED_FEAT(WAKEUP_OVERLAP, 0)
  48
  49 /*
  50  * Use the SYNC wakeup hint, pipes and the likes use this to indicate
  51  * the remote end is likely to consume the data we just wrote, and
  52  * therefore has cache benefit from being placed on the same cpu, see
  53  * also AFFINE_WAKEUPS.
  54  */
  55 SCHED_FEAT(SYNC_WAKEUPS, 1)
  56
  57 /*
  58  * Based on load and program behaviour, see if it makes sense to place
  59  * a newly woken task on the same cpu as the task that woke it --
  60  * improve cache locality. Typically used with SYNC wakeups as
  61  * generated by pipes and the like, see also SYNC_WAKEUPS.
  62  */
  63 SCHED_FEAT(AFFINE_WAKEUPS, 1)
  64
  65 /*
  66  * Prefer to schedule the task we woke last (assuming it failed
  67  * wakeup-preemption), since its likely going to consume data we
  68  * touched, increases cache locality.
  69  */
  70 SCHED_FEAT(NEXT_BUDDY, 0)
  71
  72 /*
  73  * Prefer to schedule the task that ran last (when we did
  74  * wake-preempt) as that likely will touch the same data, increases
  75  * cache locality.
  76  */
  77 SCHED_FEAT(LAST_BUDDY, 1)
  78
  79 /*
  80  * Consider buddies to be cache hot, decreases the likelyness of a
  81  * cache buddy being migrated away, increases cache locality.
  82  */
  83 SCHED_FEAT(CACHE_HOT_BUDDY, 1)
  84
  85 SCHED_FEAT(HRTICK, 0)
  86 SCHED_FEAT(DOUBLE_TICK, 0)
  87 SCHED_FEAT(LB_BIAS, 1)
  88 SCHED_FEAT(LB_WAKEUP_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)