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Commit 708dc512 authored by Luis Henriques's avatar Luis Henriques Committed by Ingo Molnar
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sched: small optimisation of can_migrate_task() 



There were 3 invocations of task_hot() in can_migrate_task().

Replace these 3 invocations by only one invocation, cached in
a local variable.

Signed-off-by: default avatarLuis Henriques <henrix@sapo.pt>
LKML-Reference: <20090316195902.GA6197@hades.domain.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 80dd99b3

kernel/sched.c

+6 −4
Original line number Diff line number Diff line
@@ -3002,6 +3002,7 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, 
		     struct sched_domain *sd, enum cpu_idle_type idle,

		     int *all_pinned)

{

	int tsk_cache_hot = 0;

	/*

	 * We do not migrate tasks that are:

	 * 1) running (obviously), or
@@ -3025,10 +3026,11 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, 
	 * 2) too many balance attempts have failed.

	 */



	if (!task_hot(p, rq->clock, sd) ||

	tsk_cache_hot = task_hot(p, rq->clock, sd);

	if (!tsk_cache_hot ||

		sd->nr_balance_failed > sd->cache_nice_tries) {

#ifdef CONFIG_SCHEDSTATS

		if (task_hot(p, rq->clock, sd)) {

		if (tsk_cache_hot) {

			schedstat_inc(sd, lb_hot_gained[idle]);

			schedstat_inc(p, se.nr_forced_migrations);

		}
@@ -3036,7 +3038,7 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, 
		return 1;

	}



	if (task_hot(p, rq->clock, sd)) {

	if (tsk_cache_hot) {

		schedstat_inc(p, se.nr_failed_migrations_hot);

		return 0;

	}