linux-kernel - Re: [PATCH 1/2] mm, memcg: Avoid stale protection values when cgroup is above protection

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Message-ID: <CALOAHbAzZUwGq3mnEtOcSetvAAm+m=X_KnQ2eS9U0QQVHggWYg@mail.gmail.com>
Date:   Thu, 30 Apr 2020 09:49:46 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Chris Down <chris@...isdown.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>,
        Linux MM <linux-mm@...ck.org>,
        Cgroups <cgroups@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mm, memcg: Avoid stale protection values when cgroup
 is above protection

On Thu, Apr 30, 2020 at 9:46 AM Chris Down <chris@...isdown.name> wrote:
>
> Yafang Shao writes:
> >My concern is why we add these barriers to memcg protection
> >specifically but don't add these barriers to the other memebers like
> >memcg->oom_group which has the same issue ?
> >What is the difference between these members and that members ?
>
> There are certainly more missing cases -- I didn't look at oom_group
> specifically, but it sounds likely if there's not other mitigating factors.
> Most of us have just been busy and haven't had time to comprehensively fix all
> the potential store and load tears.
>
> Tearing is another case of something that would be nice to fix once and for all
> in the memcg code, but isn't causing any significant issues for the timebeing.
> We should certainly aim to avoid introducing any new tearing opportunities,
> though :-)
>
> So the answer is just that improvement is incremental and we've not had the
> time to track down and fix them all. If you find more cases, feel free to send
> out the patches and I'll be happy to take a look.

Thanks for your suggestion.
I'm planning to add these barriers all over the memory cgroup code.

-- 
Thanks
Yafang