sched: Do not consider SCHED_IDLE tasks to be cache hot

Commit: ef8002f6848236de5adc613063ebeabddea8a6fb upstream

This patch adds a check in task_hot to return if the task has SCHED_IDLE
policy. SCHED_IDLE tasks have very low weight, and when run with regular
workloads, are typically scheduled many milliseconds apart. There is no
need to consider these tasks hot for load balancing.

Signed-off-by: Nikhil Rao <ncrao@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1287173550-30365-2-git-send-email-ncrao@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/sched.c b/kernel/sched.c
index 87e3b2bc4dd4c2c7e4ca755a264a7b4c596557c3..0a1fb240ec377fa161fd146dc7725bb628cf9278 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2014,6 +2014,9 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
        if (p->sched_class != &fair_sched_class)
                return 0;
 
+       if (unlikely(p->policy == SCHED_IDLE))
+               return 0;
+
        /*
         * Buddy candidates are cache hot:
         */