From: "tip-bot2 for Rik van Riel" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Sachin Sant <sachinp@linux.vnet.ibm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Rik van Riel <riel@surriel.com>, Ingo Molnar <mingo@kernel.org>,
Odin Ugedal <odin@uged.al>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/urgent] sched/fair: Ensure that the CFS parent is added after unthrottling
Date: Tue, 22 Jun 2021 12:27:07 -0000 [thread overview]
Message-ID: <162436482704.395.4620107137029173552.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210621174330.11258-1-vincent.guittot@linaro.org>
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: fdaba61ef8a268d4136d0a113d153f7a89eb9984
Gitweb: https://git.kernel.org/tip/fdaba61ef8a268d4136d0a113d153f7a89eb9984
Author: Rik van Riel <riel@surriel.com>
AuthorDate: Mon, 21 Jun 2021 19:43:30 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 22 Jun 2021 14:06:57 +02:00
sched/fair: Ensure that the CFS parent is added after unthrottling
Ensure that a CFS parent will be in the list whenever one of its children is also
in the list.
A warning on rq->tmp_alone_branch != &rq->leaf_cfs_rq_list has been
reported while running LTP test cfs_bandwidth01.
Odin Ugedal found the root cause:
$ tree /sys/fs/cgroup/ltp/ -d --charset=ascii
/sys/fs/cgroup/ltp/
|-- drain
`-- test-6851
`-- level2
|-- level3a
| |-- worker1
| `-- worker2
`-- level3b
`-- worker3
Timeline (ish):
- worker3 gets throttled
- level3b is decayed, since it has no more load
- level2 get throttled
- worker3 get unthrottled
- level2 get unthrottled
- worker3 is added to list
- level3b is not added to list, since nr_running==0 and is decayed
[ Vincent Guittot: Rebased and updated to fix for the reported warning. ]
Fixes: a7b359fc6a37 ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Acked-by: Odin Ugedal <odin@uged.al>
Link: https://lore.kernel.org/r/20210621174330.11258-1-vincent.guittot@linaro.org
---
kernel/sched/fair.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bfaa6e1..2366331 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3298,6 +3298,31 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
#ifdef CONFIG_SMP
#ifdef CONFIG_FAIR_GROUP_SCHED
+/*
+ * Because list_add_leaf_cfs_rq always places a child cfs_rq on the list
+ * immediately before a parent cfs_rq, and cfs_rqs are removed from the list
+ * bottom-up, we only have to test whether the cfs_rq before us on the list
+ * is our child.
+ * If cfs_rq is not on the list, test whether a child needs its to be added to
+ * connect a branch to the tree * (see list_add_leaf_cfs_rq() for details).
+ */
+static inline bool child_cfs_rq_on_list(struct cfs_rq *cfs_rq)
+{
+ struct cfs_rq *prev_cfs_rq;
+ struct list_head *prev;
+
+ if (cfs_rq->on_list) {
+ prev = cfs_rq->leaf_cfs_rq_list.prev;
+ } else {
+ struct rq *rq = rq_of(cfs_rq);
+
+ prev = rq->tmp_alone_branch;
+ }
+
+ prev_cfs_rq = container_of(prev, struct cfs_rq, leaf_cfs_rq_list);
+
+ return (prev_cfs_rq->tg->parent == cfs_rq->tg);
+}
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
@@ -3313,6 +3338,9 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
if (cfs_rq->avg.runnable_sum)
return false;
+ if (child_cfs_rq_on_list(cfs_rq))
+ return false;
+
return true;
}
prev parent reply other threads:[~2021-06-22 12:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 17:43 [PATCH] sched/fair: Ensure that the cfs parent is added after unthrottling Vincent Guittot
2021-06-22 12:03 ` [tip: sched/urgent] sched/fair: Ensure that the CFS " tip-bot2 for Rik van Riel
2021-06-22 12:27 ` tip-bot2 for Rik van Riel [this message]
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