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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-09-11 10:31:23 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-09-15 14:01:03 (GMT) |
commit | e26af0e8b2c9916f1e8a12ddaf52057bbe8ff600 (patch) | |
tree | 0e885c5891b8d43af27d00a5702600ee15d113d3 /kernel/sched_features.h | |
parent | 3cb63d527f76e25dbccce4f577f21aecfa2abac7 (diff) | |
download | linux-e26af0e8b2c9916f1e8a12ddaf52057bbe8ff600.tar.xz |
sched: Add come comments to the sched features
Add text...
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_features.h')
-rw-r--r-- | kernel/sched_features.h | 93 |
1 files changed, 85 insertions, 8 deletions
diff --git a/kernel/sched_features.h b/kernel/sched_features.h index 6174c12..891ea0f 100644 --- a/kernel/sched_features.h +++ b/kernel/sched_features.h @@ -1,19 +1,96 @@ +/* + * Disregards a certain amount of sleep time (sched_latency_ns) and + * considers the task to be running during that period. This gives it + * a service deficit on wakeup, allowing it to run sooner. + */ SCHED_FEAT(NEW_FAIR_SLEEPERS, 0) + +/* + * By not normalizing the sleep time, heavy tasks get an effective + * longer period, and lighter task an effective shorter period they + * are considered running. + */ SCHED_FEAT(NORMALIZED_SLEEPER, 0) -SCHED_FEAT(ADAPTIVE_GRAN, 1) -SCHED_FEAT(WAKEUP_PREEMPT, 1) + +/* + * Place new tasks ahead so that they do not starve already running + * tasks + */ SCHED_FEAT(START_DEBIT, 1) + +/* + * Should wakeups try to preempt running tasks. + */ +SCHED_FEAT(WAKEUP_PREEMPT, 1) + +/* + * Compute wakeup_gran based on task behaviour, clipped to + * [0, sched_wakeup_gran_ns] + */ +SCHED_FEAT(ADAPTIVE_GRAN, 1) + +/* + * When converting the wakeup granularity to virtual time, do it such + * that heavier tasks preempting a lighter task have an edge. + */ +SCHED_FEAT(ASYM_GRAN, 1) + +/* + * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS. + */ +SCHED_FEAT(WAKEUP_SYNC, 0) + +/* + * Wakeup preempt based on task behaviour. Tasks that do not overlap + * don't get preempted. + */ +SCHED_FEAT(WAKEUP_OVERLAP, 0) + +/* + * Use the SYNC wakeup hint, pipes and the likes use this to indicate + * the remote end is likely to consume the data we just wrote, and + * therefore has cache benefit from being placed on the same cpu, see + * also AFFINE_WAKEUPS. + */ +SCHED_FEAT(SYNC_WAKEUPS, 1) + +/* + * Based on load and program behaviour, see if it makes sense to place + * a newly woken task on the same cpu as the task that woke it -- + * improve cache locality. Typically used with SYNC wakeups as + * generated by pipes and the like, see also SYNC_WAKEUPS. + */ SCHED_FEAT(AFFINE_WAKEUPS, 1) + +/* + * Prefer to schedule the task we woke last (assuming it failed + * wakeup-preemption), since its likely going to consume data we + * touched, increases cache locality. + */ +SCHED_FEAT(NEXT_BUDDY, 1) + +/* + * Prefer to schedule the task that ran last (when we did + * wake-preempt) as that likely will touch the same data, increases + * cache locality. + */ +SCHED_FEAT(LAST_BUDDY, 1) + +/* + * Consider buddies to be cache hot, decreases the likelyness of a + * cache buddy being migrated away, increases cache locality. + */ SCHED_FEAT(CACHE_HOT_BUDDY, 1) -SCHED_FEAT(SYNC_WAKEUPS, 1) + SCHED_FEAT(HRTICK, 0) SCHED_FEAT(DOUBLE_TICK, 0) -SCHED_FEAT(ASYM_GRAN, 1) SCHED_FEAT(LB_BIAS, 1) SCHED_FEAT(LB_WAKEUP_UPDATE, 1) SCHED_FEAT(ASYM_EFF_LOAD, 1) -SCHED_FEAT(WAKEUP_SYNC, 0) -SCHED_FEAT(WAKEUP_OVERLAP, 0) -SCHED_FEAT(NEXT_BUDDY, 1) -SCHED_FEAT(LAST_BUDDY, 1) + +/* + * Spin-wait on mutex acquisition when the mutex owner is running on + * another cpu -- assumes that when the owner is running, it will soon + * release the lock. Decreases scheduling overhead. + */ SCHED_FEAT(OWNER_SPIN, 1) |