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Message-Id: <20201015064846.19809-1-qianjun.kernel@gmail.com>
Date: Thu, 15 Oct 2020 14:48:46 +0800
From: qianjun.kernel@...il.com
To: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, linux-kernel@...r.kernel.org
Cc: jun qian <qianjun.kernel@...il.com>,
Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH 1/1] Sched/fair: Improve the accuracy of sched_stat_wait statistics
From: jun qian <qianjun.kernel@...il.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@...il.com>
Reviewed-by: Yafang Shao <laoar.shao@...il.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
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