linux-kernel - [RFC PATCH 4/4] sched/numa: Don't update mm->numa_next

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Date:   Mon, 4 Oct 2021 16:27:06 +0530
From:   Bharata B Rao <bharata@....com>
To:     <linux-kernel@...r.kernel.org>
CC:     <mingo@...hat.com>, <peterz@...radead.org>, <mgorman@...e.de>,
        <riel@...hat.com>, Bharata B Rao <bharata@....com>
Subject: [RFC PATCH 4/4] sched/numa: Don't update mm->numa_next_scan from fault path

p->numa_scan_period is typically scaled up or down from
the fault path and mm->numa_next_scan is updated during
scanning from the task_work context using cmpxchg.

However there is one case where the scan period is increased
in the fault path, but mm->numa_next_scan

 - is immediately updated and
 - updated without using cmpxchg

Both of the above don't seem intended and hence remove
the updation of mm->numa_next_scan from the fault path
Updation should happen from task_work context subsequently.

Signed-off-by: Bharata B Rao <bharata@....com>
---
 kernel/sched/fair.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ceadb43e927b..3e420e73e265 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2180,9 +2180,6 @@ static void update_task_scan_period(struct task_struct *p,
 		p->numa_scan_period = min(p->numa_scan_period_max,
 			p->numa_scan_period << 1);
 
-		p->mm->numa_next_scan = jiffies +
-			msecs_to_jiffies(p->numa_scan_period);
-
 		return;
 	}
 
-- 
2.25.1