sched: group scheduler wakeup latency fix

group scheduler wakeup latency fix: when checking for preemption
we must check cross-group too, not just intra-group.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 48c69211888f3eca93a14881d55320020b74a916..5384a977c9a7beaa30a1b0269bb708660453bd6d 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -796,7 +796,8 @@ static void yield_task_fair(struct rq *rq)
 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
 {
        struct task_struct *curr = rq->curr;
-       struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+       struct cfs_rq *cfs_rq = task_cfs_rq(curr), *pcfs_rq;
+       struct sched_entity *se = &curr->se, *pse = &p->se;
 
        if (unlikely(rt_prio(p->prio))) {
                update_rq_clock(rq);
@@ -804,11 +805,21 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
                resched_task(curr);
                return;
        }
-       if (is_same_group(curr, p)) {
-               s64 delta = curr->se.vruntime - p->se.vruntime;
 
-               if (delta > (s64)sysctl_sched_wakeup_granularity)
-                       resched_task(curr);
+       for_each_sched_entity(se) {
+               cfs_rq = cfs_rq_of(se);
+               pcfs_rq = cfs_rq_of(pse);
+
+               if (cfs_rq == pcfs_rq) {
+                       s64 delta = se->vruntime - pse->vruntime;
+
+                       if (delta > (s64)sysctl_sched_wakeup_granularity)
+                               resched_task(curr);
+                       break;
+               }
+#ifdef CONFIG_FAIR_GROUP_SCHED
+               pse = pse->parent;
+#endif
        }
 }