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* [PATCH] sched/fair: fix unthrottle_cfs_rq for leaf_cfs_rq list
@ 2020-05-11 19:13 Vincent Guittot
  2020-05-12 16:03 ` Phil Auld
  2020-05-12 18:59 ` bsegall
  0 siblings, 2 replies; 5+ messages in thread
From: Vincent Guittot @ 2020-05-11 19:13 UTC (permalink / raw)
  To: mingo, peterz, juri.lelli, dietmar.eggemann, rostedt, bsegall,
	mgorman, linux-kernel, pauld, ouwen210
  Cc: Vincent Guittot

Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
are quite close and follow the same sequence for enqueuing an entity in the
cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
enqueue_task_fair(). This fixes a problem already faced with the latter and
add an optimization in the last for_each_sched_entity loop.

Fixes: fe61468b2cb (sched/fair: Fix enqueue_task_fair warning)
Reported-by Tao Zhou <zohooouoto@zoho.com.cn>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---

This path applies on top of 20200507203612.GF19331@lorien.usersys.redhat.com
and fixes similar problem for unthrottle_cfs_rq()

 kernel/sched/fair.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e2450c2e0747..4b73518aa25c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4803,26 +4803,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	idle_task_delta = cfs_rq->idle_h_nr_running;
 	for_each_sched_entity(se) {
 		if (se->on_rq)
-			enqueue = 0;
+			break;
+		cfs_rq = cfs_rq_of(se);
+		enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
 
+		cfs_rq->h_nr_running += task_delta;
+		cfs_rq->idle_h_nr_running += idle_task_delta;
+
+		/* end evaluation on encountering a throttled cfs_rq */
+		if (cfs_rq_throttled(cfs_rq))
+			goto unthrottle_throttle;
+	}
+
+	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
-		if (enqueue) {
-			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
-		} else {
-			update_load_avg(cfs_rq, se, 0);
-			se_update_runnable(se);
-		}
+
+		update_load_avg(cfs_rq, se, UPDATE_TG);
+		se_update_runnable(se);
 
 		cfs_rq->h_nr_running += task_delta;
 		cfs_rq->idle_h_nr_running += idle_task_delta;
 
+
+		/* end evaluation on encountering a throttled cfs_rq */
 		if (cfs_rq_throttled(cfs_rq))
-			break;
+			goto unthrottle_throttle;
+
+		/*
+		 * One parent has been throttled and cfs_rq removed from the
+		 * list. Add it back to not break the leaf list.
+		 */
+		if (throttled_hierarchy(cfs_rq))
+			list_add_leaf_cfs_rq(cfs_rq);
 	}
 
 	if (!se)
 		add_nr_running(rq, task_delta);
 
+unthrottle_throttle:
 	/*
 	 * The cfs_rq_throttled() breaks in the above iteration can result in
 	 * incomplete leaf list maintenance, resulting in triggering the
@@ -4831,7 +4849,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
 
-		list_add_leaf_cfs_rq(cfs_rq);
+		if (list_add_leaf_cfs_rq(cfs_rq))
+			break;
 	}
 
 	assert_list_leaf_cfs_rq(rq);
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2020-05-13 18:22 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2020-05-11 19:13 [PATCH] sched/fair: fix unthrottle_cfs_rq for leaf_cfs_rq list Vincent Guittot
2020-05-12 16:03 ` Phil Auld
2020-05-12 18:59 ` bsegall
2020-05-13  7:11   ` Vincent Guittot
2020-05-13 18:22     ` bsegall

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