linux-kernel - Re: [PATCH] cgroup/cpuset: Avoid memory migration when nodemasks match

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Message-ID: <YSZ1fgJgJfWmvaC4@slm.duckdns.org>
Date:   Wed, 25 Aug 2021 06:53:18 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Nicolas Saenz Julienne <nsaenzju@...hat.com>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        lizefan.x@...edance.com, hannes@...xchg.org, mtosatti@...hat.com,
        nilal@...hat.com, frederic@...nel.org, longman@...hat.com
Subject: Re: [PATCH] cgroup/cpuset: Avoid memory migration when nodemasks
 match

On Wed, Aug 25, 2021 at 12:54:15PM +0200, Nicolas Saenz Julienne wrote:
> With the introduction of ee9707e8593d ("cgroup/cpuset: Enable memory
> migration for cpuset v2") attaching a process to a different cgroup will
> trigger a memory migration regardless of whether it's really needed.
> Memory migration is an expensive operation, so bypass it if the
> nodemasks passed to cpuset_migrate_mm() are equal.
> 
> Note that we're not only avoiding the migration work itself, but also a
> call to lru_cache_disable(), which triggers and flushes an LRU drain
> work on every online CPU.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenzju@...hat.com>

Applied to cgroup/for-5.15.

Thanks.

-- 
tejun