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Date:   Thu, 26 May 2022 00:51:46 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     shisiyuan19870131@gmail.com
Cc:     Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cgroup: Return if dst_cgrp equals to src_cgrp
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References: <1653066120-21262-1-git-send-email-shisiyuan@xiaomi.com>
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Hello.

On Sat, May 21, 2022 at 01:02:00AM +0800, shisiyuan <shisiyuan19870131@gmail.com> wrote:
> In function cgroup_migrate_add_src(), if dst_cgrp
> equals to src_cgroup which the tasks link, dont
> go on migrating tasks to another css_set.

Do you have an example which operations lead to this situation?

> This can save the cost of unnecessary migration.

How much are the savings visible?

(Note, I suspect the shortcut on `src_cgrp == dst_cgrp` might not be
always correct when called from cgroup_update_dfl_csses() but not 100%
sure now.)

Thanks,
Michal