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Commit 5d5e2b1b authored by Hillf Danton's avatar Hillf Danton Committed by Ingo Molnar
Browse files

sched: Fix CACHE_HOT_BUDY condition 



When computing cache hot, we should check if the migration dst cpu is idle,
instead of the current cpu. Though they are same in normal balancing, that
is false nowadays in nohz idle balancing at least.

Signed-off-by: default avatarHillf Danton <dhillf@gmail.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Mike Galbraith <mgalbraith@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140607090452.4696E301D2@webmail.sinamail.sina.com.cn


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent bb97fc31

kernel/sched/fair.c

+4 −5
Original line number Diff line number Diff line
@@ -5095,8 +5095,7 @@ static void move_task(struct task_struct *p, struct lb_env *env) 
/*

 * Is this task likely cache-hot:

 */

static int

task_hot(struct task_struct *p, u64 now)

static int task_hot(struct task_struct *p, struct lb_env *env)

{

	s64 delta;
@@ -5109,7 +5108,7 @@ task_hot(struct task_struct *p, u64 now) 
	/*

	 * Buddy candidates are cache hot:

	 */

	if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&

	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&

			(&p->se == cfs_rq_of(&p->se)->next ||

			 &p->se == cfs_rq_of(&p->se)->last))

		return 1;
@@ -5119,7 +5118,7 @@ task_hot(struct task_struct *p, u64 now) 
	if (sysctl_sched_migration_cost == 0)

		return 0;



	delta = now - p->se.exec_start;

	delta = rq_clock_task(env->src_rq) - p->se.exec_start;



	return delta < (s64)sysctl_sched_migration_cost;

}
@@ -5273,7 +5272,7 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) 
	 * 2) task is cache cold, or

	 * 3) too many balance attempts have failed.

	 */

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

	tsk_cache_hot = task_hot(p, env);

	if (!tsk_cache_hot)

		tsk_cache_hot = migrate_degrades_locality(p, env);