sched: only try to push a task on wakeup if it is migratable

There is no sense in wasting time trying to push a task away that
cannot move anywhere else.  We gain no benefit from trying to push
other tasks at this point, so if the task being woken up is non
migratable, just skip the whole operation.  This reduces overhead
in the wakeup path for certain tasks.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index d047f288c411d536fe05dd78e04dc4b3da5ecc1c..8d33843cb2c4cc0b42afd0945b6c206a917345d1 100644 (file)
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1314,7 +1314,8 @@ static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
 {
        if (!task_running(rq, p) &&
            !test_tsk_need_resched(rq->curr) &&
-           rq->rt.overloaded)
+           rq->rt.overloaded &&
+           p->rt.nr_cpus_allowed > 1)
                push_rt_tasks(rq);
 }