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: Luis Henriques <henrix@sapo.pt>
LKML-Reference: <20090316195902.GA6197@hades.domain.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 489e7d926408ebd8bded36ede64075f8ee9f6d8f..d2dfe4c1a225cccd54b23711ca7342caaab58474 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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) ||
-                       sd->nr_balance_failed > sd->cache_nice_tries) {
+       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;
        }