linux-kernel - [RFC PATCH] sched/numa: fix bug in update_task_scan

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Date:   Tue, 11 Aug 2020 16:30:31 +0800
From:   "丁天琛" <tianchen.dingtianc@...baba-inc.com>
To:     "Ingo Molnar" <mingo@...hat.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Juri Lelli" <juri.lelli@...hat.com>,
        "Vincent Guittot" <vincent.guittot@...aro.org>,
        "Dietmar Eggemann" <dietmar.eggemann@....com>,
        "Steven Rostedt" <rostedt@...dmis.org>,
        "Ben Segall" <bsegall@...gle.com>, "Mel Gorman" <mgorman@...e.de>,
        "linux-kernel" <linux-kernel@...r.kernel.org>
Cc:     "王贇" <yun.wang@...ux.alibaba.com>
Subject: [RFC PATCH] sched/numa: fix bug in update_task_scan_period

When p->numa_faults_locality[2] > 0, numa_scan_period is doubled, but
this array will never be cleared, which causes scanning period always
reaching its max value. This patch clears numa_faults_locality after
numa_scan_period being doubled to fix this bug.

Signed-off-by: Tianchen Ding <tianchen.dingtianc@...baba-inc.com>
Signed-off-by: Michael Wang <yun.wang@...ux.alibaba.com>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a0536add..a61ee408202e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2180,6 +2180,8 @@ static void update_task_scan_period(struct task_struct *p,
 		p->mm->numa_next_scan = jiffies +
 			msecs_to_jiffies(p->numa_scan_period);
 
+		memset(p->numa_faults_locality, 0,
+			sizeof(p->numa_faults_locality));
 		return;
 	}
 
-- 
2.25.1