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linux-next/kernel/sched/features.h
Mel Gorman e6e0dc2d54 sched/fair: Remove SIS_AVG_CPU
SIS_AVG_CPU was introduced as a means of avoiding a search when the
average search cost indicated that the search would likely fail. It was
a blunt instrument and disabled by commit 4c77b18cf8 ("sched/fair: Make
select_idle_cpu() more aggressive") and later replaced with a proportional
search depth by commit 1ad3aaf3fc ("sched/core: Implement new approach
to scale select_idle_cpu()").

While there are corner cases where SIS_AVG_CPU is better, it has now been
disabled for almost three years. As the intent of SIS_PROP is to reduce
the time complexity of select_idle_cpu(), lets drop SIS_AVG_CPU and focus
on SIS_PROP as a throttling mechanism.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210125085909.4600-2-mgorman@techsingularity.net
2021-01-27 17:26:43 +01:00

92 lines
2.4 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
* Only give sleepers 50% of their service deficit. This allows
* them to run sooner, but does not allow tons of sleepers to
* rip the spread apart.
*/
SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
/*
* Place new tasks ahead so that they do not starve already running
* tasks
*/
SCHED_FEAT(START_DEBIT, true)
/*
* 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, false)
/*
* 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, true)
/*
* Consider buddies to be cache hot, decreases the likelyness of a
* cache buddy being migrated away, increases cache locality.
*/
SCHED_FEAT(CACHE_HOT_BUDDY, true)
/*
* Allow wakeup-time preemption of the current task:
*/
SCHED_FEAT(WAKEUP_PREEMPTION, true)
SCHED_FEAT(HRTICK, false)
SCHED_FEAT(DOUBLE_TICK, false)
/*
* Decrement CPU capacity based on time not spent running tasks
*/
SCHED_FEAT(NONTASK_CAPACITY, true)
/*
* Queue remote wakeups on the target CPU and process them
* using the scheduler IPI. Reduces rq->lock contention/bounces.
*/
SCHED_FEAT(TTWU_QUEUE, true)
/*
* When doing wakeups, attempt to limit superfluous scans of the LLC domain.
*/
SCHED_FEAT(SIS_PROP, true)
/*
* Issue a WARN when we do multiple update_rq_clock() calls
* in a single rq->lock section. Default disabled because the
* annotations are not complete.
*/
SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
#ifdef HAVE_RT_PUSH_IPI
/*
* In order to avoid a thundering herd attack of CPUs that are
* lowering their priorities at the same time, and there being
* a single CPU that has an RT task that can migrate and is waiting
* to run, where the other CPUs will try to take that CPUs
* rq lock and possibly create a large contention, sending an
* IPI to that CPU and let that CPU push the RT task to where
* it should go may be a better scenario.
*/
SCHED_FEAT(RT_PUSH_IPI, true)
#endif
SCHED_FEAT(RT_RUNTIME_SHARE, false)
SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(ATTACH_AGE_LOAD, true)
SCHED_FEAT(WA_IDLE, true)
SCHED_FEAT(WA_WEIGHT, true)
SCHED_FEAT(WA_BIAS, true)
/*
* UtilEstimation. Use estimated CPU utilization.
*/
SCHED_FEAT(UTIL_EST, true)
SCHED_FEAT(UTIL_EST_FASTUP, true)