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From:   Shakeel Butt <shakeelb@google.com>
Date:   Tue, 16 Aug 2022 15:06:15 -0700
Message-ID: <CALvZod5t7Qo1NQ040pRyWco+nJGn3hSrxZyuFQ0UBi31Ni6=_g@mail.gmail.com>
Subject: Re: [PATCH] mm: memcg: export workingset refault stats for cgroup v1
To:     Yang Shi <shy828301@gmail.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Muchun Song <songmuchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Cgroups <cgroups@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Yosry Ahmed <yosryahmed@google.com>
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On Tue, Aug 16, 2022 at 11:58 AM Yang Shi <shy828301@gmail.com> wrote:
>
> Workingset refault stats are important and usefule metrics to measure
> how well reclaimer and swapping work and how healthy the services are,
> but they are just available for cgroup v2.  There are still plenty users
> with cgroup v1, export the stats for cgroup v1.
>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
> I do understand the development of cgroup v1 is actually stalled and
> the community is reluctant to accept new features for v1.  However
> the workingset refault stats are really quite useful and exporting
> two new stats, which have been supported by v2, seems ok IMHO.  So
> hopefully this patch could be considered.  Thanks.
>

Is just workingset refault good enough for your use-case? What about
the other workingset stats? I don't have a strong opinion against
adding these to v1 and I think these specific stats should be fine.
(There is subtlety in exposing objcg based stats (i.e. reparenting) in
v1 due to non-hierarchical stats in v1. I remember Yosry and Muchun
were looking into that.)