linux-kernel - [PATCH] sched/numa: initialize numa statistics when forking new task

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Date:   Thu, 13 Jan 2022 21:39:20 +0800
From:   Honglei Wang <wanghonglei@...ichuxing.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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        <linux-kernel@...r.kernel.org>
CC:     Honglei Wang <jameshongleiwang@....com>
Subject: [PATCH] sched/numa: initialize numa statistics when forking new task

The child processes will inherit numa_pages_migrated and
total_numa_faults from the parent. It means even if there is no numa
fault happen on the child, the statistics in /proc/$pid of the child
process might show huge amount. This is a bit weird. Let's initialize
them when do fork.

Signed-off-by: Honglei Wang <wanghonglei@...ichuxing.com>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6e476f6d9435..1aa0ec123a4b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2826,6 +2826,8 @@ void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
 	/* Protect against double add, see task_tick_numa and task_numa_work */
 	p->numa_work.next		= &p->numa_work;
 	p->numa_faults			= NULL;
+	p->numa_pages_migrated		= 0;
+	p->total_numa_faults		= 0;
 	RCU_INIT_POINTER(p->numa_group, NULL);
 	p->last_task_numa_placement	= 0;
 	p->last_sum_exec_runtime	= 0;
-- 
2.14.1