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Commit 7a0f3083 authored by Mel Gorman's avatar Mel Gorman Committed by Ingo Molnar
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sched/numa: Resist moving tasks towards nodes with fewer hinting faults 



Just as "sched: Favour moving tasks towards the preferred node" favours
moving tasks towards nodes with a higher number of recorded NUMA hinting
faults, this patch resists moving tasks towards nodes with lower faults.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-24-git-send-email-mgorman@suse.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3a7053b3

kernel/sched/fair.c

+33 −0
Original line number Diff line number Diff line
@@ -4107,12 +4107,43 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env) 


	return false;

}





static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)

{

	int src_nid, dst_nid;



	if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))

		return false;



	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))

		return false;



	src_nid = cpu_to_node(env->src_cpu);

	dst_nid = cpu_to_node(env->dst_cpu);



	if (src_nid == dst_nid ||

	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)

		return false;



	if (p->numa_faults[dst_nid] < p->numa_faults[src_nid])

		return true;



	return false;

}



#else

static inline bool migrate_improves_locality(struct task_struct *p,

					     struct lb_env *env)

{

	return false;

}



static inline bool migrate_degrades_locality(struct task_struct *p,

					     struct lb_env *env)

{

	return false;

}

#endif



/*
@@ -4177,6 +4208,8 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) 
	 * 3) too many balance attempts have failed.

	 */

	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);

	if (!tsk_cache_hot)

		tsk_cache_hot = migrate_degrades_locality(p, env);



	if (migrate_improves_locality(p, env)) {

#ifdef CONFIG_SCHEDSTATS

kernel/sched/features.h

+8 −0
Original line number Diff line number Diff line
@@ -74,4 +74,12 @@ SCHED_FEAT(NUMA, false) 
 * balancing.

 */

SCHED_FEAT(NUMA_FAVOUR_HIGHER, true)



/*

 * NUMA_RESIST_LOWER will resist moving tasks towards nodes where a

 * lower number of hinting faults have been recorded. As this has

 * the potential to prevent a task ever migrating to a new node

 * due to CPU overload it is disabled by default.

 */

SCHED_FEAT(NUMA_RESIST_LOWER, false)

#endif