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2a1ed24ce9
The current load balancer may not try to prevent a task from moving out of a preferred node to a less preferred node. The reason for this being: - Since sched features NUMA and NUMA_RESIST_LOWER are disabled by default, migrate_degrades_locality() always returns false. - Even if NUMA_RESIST_LOWER were to be enabled, if its cache hot, migrate_degrades_locality() never gets called. The above behaviour can mean that tasks can move out of their preferred node but they may be eventually be brought back to their preferred node by numa balancer (due to higher numa faults). To avoid the above, this commit merges migrate_degrades_locality() and migrate_improves_locality(). It also replaces 3 sched features NUMA, NUMA_FAVOUR_HIGHER and NUMA_RESIST_LOWER by a single sched feature NUMA. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Rik van Riel <riel@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Mike Galbraith <efault@gmx.de> Link: http://lkml.kernel.org/r/1434455762-30857-2-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
91 lines
2.4 KiB
C
91 lines
2.4 KiB
C
/*
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* Only give sleepers 50% of their service deficit. This allows
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* them to run sooner, but does not allow tons of sleepers to
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* rip the spread apart.
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*/
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SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)
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/*
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* Place new tasks ahead so that they do not starve already running
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* tasks
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*/
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SCHED_FEAT(START_DEBIT, true)
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/*
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* Prefer to schedule the task we woke last (assuming it failed
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* wakeup-preemption), since its likely going to consume data we
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* touched, increases cache locality.
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*/
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SCHED_FEAT(NEXT_BUDDY, false)
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/*
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* Prefer to schedule the task that ran last (when we did
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* wake-preempt) as that likely will touch the same data, increases
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* cache locality.
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*/
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SCHED_FEAT(LAST_BUDDY, true)
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/*
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* Consider buddies to be cache hot, decreases the likelyness of a
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* cache buddy being migrated away, increases cache locality.
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*/
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SCHED_FEAT(CACHE_HOT_BUDDY, true)
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/*
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* Allow wakeup-time preemption of the current task:
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*/
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SCHED_FEAT(WAKEUP_PREEMPTION, true)
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/*
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* Use arch dependent cpu capacity functions
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*/
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SCHED_FEAT(ARCH_CAPACITY, true)
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SCHED_FEAT(HRTICK, false)
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SCHED_FEAT(DOUBLE_TICK, false)
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SCHED_FEAT(LB_BIAS, true)
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/*
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* Decrement CPU capacity based on time not spent running tasks
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*/
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SCHED_FEAT(NONTASK_CAPACITY, true)
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/*
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* Queue remote wakeups on the target CPU and process them
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* using the scheduler IPI. Reduces rq->lock contention/bounces.
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*/
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SCHED_FEAT(TTWU_QUEUE, true)
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#ifdef HAVE_RT_PUSH_IPI
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/*
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* In order to avoid a thundering herd attack of CPUs that are
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* lowering their priorities at the same time, and there being
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* a single CPU that has an RT task that can migrate and is waiting
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* to run, where the other CPUs will try to take that CPUs
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* rq lock and possibly create a large contention, sending an
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* IPI to that CPU and let that CPU push the RT task to where
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* it should go may be a better scenario.
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*/
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SCHED_FEAT(RT_PUSH_IPI, true)
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#endif
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SCHED_FEAT(FORCE_SD_OVERLAP, false)
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SCHED_FEAT(RT_RUNTIME_SHARE, true)
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SCHED_FEAT(LB_MIN, false)
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/*
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* Apply the automatic NUMA scheduling policy. Enabled automatically
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* at runtime if running on a NUMA machine. Can be controlled via
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* numa_balancing=
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*/
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#ifdef CONFIG_NUMA_BALANCING
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/*
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* NUMA will favor moving tasks towards nodes where a higher number of
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* hinting faults are recorded during active load balancing. It will
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* resist moving tasks towards nodes where a lower number of hinting
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* faults have been recorded.
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*/
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SCHED_FEAT(NUMA, true)
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#endif
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