linux-kernel - Re: memcg: infrastructure to flush memcg stats

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Message-ID: <CALvZod73acr3zhbGzzQ8YyNGhTOe-6NhUNH6Z6O6FbD+oFoAmw@mail.gmail.com>
Date:   Thu, 16 Sep 2021 14:04:50 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Feng Tang <feng.tang@...el.com>,
        Michael Larabel <Michael@...haellarabel.com>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: memcg: infrastructure to flush memcg stats

On Thu, Sep 16, 2021 at 1:45 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> So the kernel test robot complained about this commit back when it was
> in the -mm tree:
>
>   https://lore.kernel.org/all/20210726022421.GB21872@xsang-OptiPlex-9020/
>
> but I never really saw anything else about it, and left it alone.
>
> However, now Michael Larabel (of phoronix) points to this commit too,
> and says it regresses several of his benchmarks too.
>
> Shakeel, are you looking at this? Based on previous experience,
> Michael is great at running benchmarks on patches that you come up
> with.
>

Yes, I am actively looking into this and the discussion is happening
at https://lore.kernel.org/all/20210905124439.GA15026@xsang-OptiPlex-9020/T/#u

I would definitely take up with Michael on helping with running the benchmarks.

We know the source of the regression which is queue_work() in
__mod_memcg_lruvec_state(). Previously we were doing atomic addition
up the memcg tree. I have to come up with an approach to reduce the
calls to queue_work() in that path.

thanks,
Shakeel