sched: remove redundant hierarchy walk in check_preempt_wakeup

Impact: micro-optimization

Under group scheduling we traverse up until we are at common siblings
to make the wakeup comparison on.

At this point however, they should have the same parent so continuing
to check up the tree is redundant.

Signed-off-by: Paul Turner <pjt@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <alpine.DEB.1.00.0904081520320.30317@kitami.corp.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3816f217f119ef635cf169f268b5140c6e0f66c6..5f9650e8fe7587938de1bfa71e48cd4a04061d36 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1487,17 +1487,10 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
 
        find_matching_se(&se, &pse);
 
-       while (se) {
-               BUG_ON(!pse);
+       BUG_ON(!pse);
 
-               if (wakeup_preempt_entity(se, pse) == 1) {
-                       resched_task(curr);
-                       break;
-               }
-
-               se = parent_entity(se);
-               pse = parent_entity(pse);
-       }
+       if (wakeup_preempt_entity(se, pse) == 1)
+               resched_task(curr);
 }
 
 static struct task_struct *pick_next_task_fair(struct rq *rq)