sched: release buddies on yield

Clear buddies on yield, so that the buddy rules don't schedule them
despite them being placed right-most.

This fixed a performance regression with yield-happy binary JVMs.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Lin Ming <ming.m.lin@intel.com>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 51aa3e1..98345e4 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -716,6 +716,15 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
                __enqueue_entity(cfs_rq, se);
 }
 
+static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+       if (cfs_rq->last == se)
+               cfs_rq->last = NULL;
+
+       if (cfs_rq->next == se)
+               cfs_rq->next = NULL;
+}
+
 static void
 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 {
@@ -738,11 +747,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 #endif
        }
 
-       if (cfs_rq->last == se)
-               cfs_rq->last = NULL;
-
-       if (cfs_rq->next == se)
-               cfs_rq->next = NULL;
+       clear_buddies(cfs_rq, se);
 
        if (se != cfs_rq->curr)
                __dequeue_entity(cfs_rq, se);
@@ -977,6 +982,8 @@ static void yield_task_fair(struct rq *rq)
        if (unlikely(cfs_rq->nr_running == 1))
                return;
 
+       clear_buddies(cfs_rq, se);
+
        if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
                update_rq_clock(rq);
                /*