4793241be4
Impact: improve/change/fix wakeup-buddy scheduling Currently we only have a forward looking buddy, that is, we prefer to schedule to the task we last woke up, under the presumption that its going to consume the data we just produced, and therefore will have cache hot benefits. This allows co-waking producer/consumer task pairs to run ahead of the pack for a little while, keeping their cache warm. Without this, we would interleave all pairs, utterly trashing the cache. This patch introduces a backward looking buddy, that is, suppose that in the above scenario, the consumer preempts the producer before it can go to sleep, we will therefore miss the wakeup from consumer to producer (its already running, after all), breaking the cycle and reverting to the cache-trashing interleaved schedule pattern. The backward buddy will try to schedule back to the task that woke us up in case the forward buddy is not available, under the assumption that the last task will be the one with the most cache hot task around barring current. This will basically allow a task to continue after it got preempted. In order to avoid starvation, we allow either buddy to get wakeup_gran ahead of the pack. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
16 lines
427 B
C
16 lines
427 B
C
SCHED_FEAT(NEW_FAIR_SLEEPERS, 1)
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SCHED_FEAT(NORMALIZED_SLEEPER, 1)
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SCHED_FEAT(WAKEUP_PREEMPT, 1)
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SCHED_FEAT(START_DEBIT, 1)
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SCHED_FEAT(AFFINE_WAKEUPS, 1)
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SCHED_FEAT(CACHE_HOT_BUDDY, 1)
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SCHED_FEAT(SYNC_WAKEUPS, 1)
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SCHED_FEAT(HRTICK, 0)
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SCHED_FEAT(DOUBLE_TICK, 0)
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SCHED_FEAT(ASYM_GRAN, 1)
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SCHED_FEAT(LB_BIAS, 1)
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SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
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SCHED_FEAT(ASYM_EFF_LOAD, 1)
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SCHED_FEAT(WAKEUP_OVERLAP, 0)
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SCHED_FEAT(LAST_BUDDY, 1)
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