From: "tip-bot2 for Vincent Guittot" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Odin Ugedal <odin@uged.al>,
Vincent Guittot <vincent.guittot@linaro.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/urgent] sched/fair: Make sure to update tg contrib for blocked load
Date: Mon, 31 May 2021 10:40:51 -0000 [thread overview]
Message-ID: <162245765196.29796.10346723240274549912.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210527122916.27683-3-vincent.guittot@linaro.org>
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 02da26ad5ed6ea8680e5d01f20661439611ed776
Gitweb: https://git.kernel.org/tip/02da26ad5ed6ea8680e5d01f20661439611ed776
Author: Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate: Thu, 27 May 2021 14:29:16 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 31 May 2021 10:14:48 +02:00
sched/fair: Make sure to update tg contrib for blocked load
During the update of fair blocked load (__update_blocked_fair()), we
update the contribution of the cfs in tg->load_avg if cfs_rq's pelt
has decayed. Nevertheless, the pelt values of a cfs_rq could have
been recently updated while propagating the change of a child. In this
case, cfs_rq's pelt will not decayed because it has already been
updated and we don't update tg->load_avg.
__update_blocked_fair
...
for_each_leaf_cfs_rq_safe: child cfs_rq
update cfs_rq_load_avg() for child cfs_rq
...
update_load_avg(cfs_rq_of(se), se, 0)
...
update cfs_rq_load_avg() for parent cfs_rq
-propagation of child's load makes parent cfs_rq->load_sum
becoming null
-UPDATE_TG is not set so it doesn't update parent
cfs_rq->tg_load_avg_contrib
..
for_each_leaf_cfs_rq_safe: parent cfs_rq
update cfs_rq_load_avg() for parent cfs_rq
- nothing to do because parent cfs_rq has already been updated
recently so cfs_rq->tg_load_avg_contrib is not updated
...
parent cfs_rq is decayed
list_del_leaf_cfs_rq parent cfs_rq
- but it still contibutes to tg->load_avg
we must set UPDATE_TG flags when propagting pending load to the parent
Fixes: 039ae8bcf7a5 ("sched/fair: Fix O(nr_cgroups) in the load balancing path")
Reported-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Link: https://lkml.kernel.org/r/20210527122916.27683-3-vincent.guittot@linaro.org
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f4795b8..e7c8277 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8029,7 +8029,7 @@ static bool __update_blocked_fair(struct rq *rq, bool *done)
/* Propagate pending load changes to the parent, if any: */
se = cfs_rq->tg->se[cpu];
if (se && !skip_blocked_update(se))
- update_load_avg(cfs_rq_of(se), se, 0);
+ update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
/*
* There can be a lot of idle CPU cgroups. Don't let fully
next prev parent reply other threads:[~2021-05-31 10:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 12:29 [PATCH 0/2] schd/fair: fix stalled cfs_rq->tg_load_avg_contrib Vincent Guittot
2021-05-27 12:29 ` [PATCH 1/2] sched/fair: keep load_avg and load_sum synced Vincent Guittot
2021-05-27 13:05 ` Peter Zijlstra
2021-05-27 13:18 ` Vincent Guittot
2021-05-27 13:37 ` Peter Zijlstra
2021-05-27 13:40 ` kernel test robot
2021-05-31 10:40 ` [tip: sched/urgent] sched/fair: Keep " tip-bot2 for Vincent Guittot
2021-05-27 12:29 ` [PATCH 2/2] sched/fair: make sure to update tg contrib for blocked load Vincent Guittot
2021-05-31 10:40 ` tip-bot2 for Vincent Guittot [this message]
2021-05-27 14:19 ` [PATCH 0/2] schd/fair: fix stalled cfs_rq->tg_load_avg_contrib Vincent Guittot
2021-05-27 14:24 ` Odin Ugedal
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