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References: <20240126203353.1163059-1-tjmercier@google.com> <20240126210642.GK1567330@cmpxchg.org>
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From: "T.J. Mercier" <tjmercier@google.com>
Date: Fri, 26 Jan 2024 13:20:48 -0800
Message-ID: <CABdmKX2mZwVHSvJekT8UNt2a0WiiNnTTW-ZV=ZHvx0D1PoJuhQ@mail.gmail.com>
Subject: Re: [PATCH] mm: memcg: Don't periodically flush stats when memcg is disabled
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>, Roman Gushchin <roman.gushchin@linux.dev>, 
	Shakeel Butt <shakeelb@google.com>, Muchun Song <muchun.song@linux.dev>, 
	Andrew Morton <akpm@linux-foundation.org>, android-mm@google.com, 
	Minchan Kim <minchan@google.com>, cgroups@vger.kernel.org, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org
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On Fri, Jan 26, 2024 at 1:06=E2=80=AFPM Johannes Weiner <hannes@cmpxchg.org=
> wrote:
>
> On Fri, Jan 26, 2024 at 08:33:52PM +0000, T.J. Mercier wrote:
> > The root memcg is onlined even when memcg is disabled. When it's online=
d
> > a 2 second periodic stat flush is started, but no stat flushing is
> > required when memcg is disabled because there can be no child memcgs.
> > Most calls to flush memcg stats are avoided when memcg is disabled as a
> > result of the mem_cgroup_disabled check [1] added in [2], but the
> > periodic flushing started in mem_cgroup_css_online is not. Skip it.
> >
> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/=
tree/mm/memcontrol.c?h=3Dv6.8-rc1#n753
> > [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/=
commit/?id=3D7d7ef0a4686abe43cd76a141b340a348f45ecdf2
> >
> > Fixes: aa48e47e3906 ("memcg: infrastructure to flush memcg stats")
> > Reported-by: Minchan Kim <minchan@google.com>
> > Signed-off-by: T.J. Mercier <tjmercier@google.com>
>
> With what Shakeel pointed out resolved:
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Thanks Shakeel and Johannes. v2 is here, hopefully fixed up correctly:
https://lore.kernel.org/all/20240126211927.1171338-1-tjmercier@google.com/