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

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Date:   Fri, 28 Jan 2022 07:40:19 -0000
From:   "tip-bot2 for Honglei Wang" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Honglei Wang <wanghonglei@...ichuxing.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/numa: initialize numa statistics when forking
 new task

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     12bf8a7eb84e4d3547ebfd89bb0a9255a0f2acc7
Gitweb:        https://git.kernel.org/tip/12bf8a7eb84e4d3547ebfd89bb0a9255a0f2acc7
Author:        Honglei Wang <wanghonglei@...ichuxing.com>
AuthorDate:    Thu, 13 Jan 2022 21:39:20 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 27 Jan 2022 12:57:18 +01:00

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Mel Gorman <mgorman@...e.de>
Link: https://lore.kernel.org/r/20220113133920.49900-1-wanghonglei@didichuxing.com
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 095b0aa..5dca13f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2825,6 +2825,8 @@ 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;