linux-kernel - [PATCH v2] sched/fair: fix runnable

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Message-Id: <20200227154115.8332-1-vincent.guittot@linaro.org>
Date:   Thu, 27 Feb 2020 16:41:15 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, linux-kernel@...r.kernel.org
Cc:     pauld@...hat.com, parth@...ux.ibm.com, valentin.schneider@....com,
        hdanton@...a.com, zhout@...aldi.net,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH v2] sched/fair: fix runnable_avg for throttled cfs

When a cfs_rq is throttled, its group entity is dequeued and its running
tasks are removed. We must update runnable_avg with the old h_nr_running
and update group_se->runnable_weight with the new h_nr_running at each
level of the hierarchy.

Fixes: 9f68395333ad ("sched/pelt: Add a new runnable average signal")
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
This patch applies on top of tip/sched/core

Changes since v1:
- update commit message
- add missing {}

 kernel/sched/fair.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fcc968669aea..22d067279269 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4701,8 +4701,13 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 		if (!se->on_rq)
 			break;
 
-		if (dequeue)
+		if (dequeue) {
 			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
+		} else {
+			update_load_avg(qcfs_rq, se, 0);
+			se_update_runnable(se);
+		}
+
 		qcfs_rq->h_nr_running -= task_delta;
 		qcfs_rq->idle_h_nr_running -= idle_task_delta;
 
@@ -4770,8 +4775,13 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 			enqueue = 0;
 
 		cfs_rq = cfs_rq_of(se);
-		if (enqueue)
+		if (enqueue) {
 			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
+		} else {
+			update_load_avg(cfs_rq, se, 0);
+			se_update_runnable(se);
+		}
+
 		cfs_rq->h_nr_running += task_delta;
 		cfs_rq->idle_h_nr_running += idle_task_delta;
 
-- 
2.17.1