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From: qianjun.kernel@gmail.com
To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org
Cc: linux-kernel@vger.kernel.org, jun qian <qianjun.kernel@gmail.com>,
	Yafang Shao <laoar.shao@gmail.com>
Subject: [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics
Date: Fri,  9 Oct 2020 17:25:30 +0800	[thread overview]
Message-ID: <20201009092530.223-1-qianjun.kernel@gmail.com> (raw)

From: jun qian <qianjun.kernel@gmail.com>

When the sched_schedstat changes from 0 to 1, some sched se maybe
already in the runqueue, the se->statistics.wait_start will be 0.
So it will let the (rq_of(cfs_rq)) - se->statistics.wait_start)
wrong. We need to avoid this scenario.

Signed-off-by: jun qian <qianjun.kernel@gmail.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/sched/fair.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a05..6f8ca0c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -906,6 +906,15 @@ static void update_curr_fair(struct rq *rq)
 	if (!schedstat_enabled())
 		return;
 
+	/*
+	 * When the sched_schedstat changes from 0 to 1, some sched se
+	 * maybe already in the runqueue, the se->statistics.wait_start
+	 * will be 0.So it will let the delta wrong. We need to avoid this
+	 * scenario.
+	 */
+	if (unlikely(!schedstat_val(se->statistics.wait_start)))
+		return;
+
 	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
 
 	if (entity_is_task(se)) {
-- 
1.8.3.1


             reply	other threads:[~2020-10-09  9:25 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09  9:25 qianjun.kernel [this message]
2020-10-14 13:19 ` [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics Peter Zijlstra
2020-10-15  6:06   ` Yafang Shao
2020-10-15  6:48 qianjun.kernel
2020-10-15 11:02 ` Peter Zijlstra

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