linux-kernel - Re: [PATCH v2 3/3] mm/memcg: Unify swap and memsw page counters

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Date:   Mon, 14 Sep 2020 08:37:21 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Waiman Long <longman@...hat.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        Chris Down <chris@...isdown.name>,
        Roman Gushchin <guro@...com>,
        Yafang Shao <laoar.shao@...il.com>
Subject: Re: [PATCH v2 3/3] mm/memcg: Unify swap and memsw page counters

On Sun, Sep 13, 2020 at 7:45 PM Waiman Long <longman@...hat.com> wrote:
>
> The swap page counter is v2 only while memsw is v1 only. As v1 and v2
> controllers cannot be active at the same time, there is no point to keep
> both swap and memsw page counters in mem_cgroup. The previous patch has
> made sure that memsw page counter is updated and accessed only when in
> v1 code paths. So it is now safe to alias the v1 memsw page counter to v2
> swap page counter. This saves 14 long's in the size of mem_cgroup. This
> is a saving of 112 bytes for 64-bit archs.
>
> While at it, also document which page counters are used in v1 and/or v2.
>
> Signed-off-by: Waiman Long <longman@...hat.com>

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>