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From: Shakeel Butt <shakeelb@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Thelen <gthelen@google.com>, Roman Gushchin <guro@fb.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>, Linux MM <linux-mm@kvack.org>,
	Cgroups <cgroups@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com
Subject: Re: [PATCH] mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node()
Date: Tue, 29 Oct 2019 18:15:45 -0700	[thread overview]
Message-ID: <CALvZod6DB0h93bDoTFdY9bU8fnxjBJphpf+AWr_u5r2SBo_isA@mail.gmail.com> (raw)
In-Reply-To: <20191029175459.b3bfed9326559e69acdd2e35@linux-foundation.org>

On Tue, Oct 29, 2019 at 5:55 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue, 29 Oct 2019 16:47:53 -0700 Shakeel Butt <shakeelb@google.com> wrote:
>
> > Since commit 1ba6fc9af35b ("mm: vmscan: do not share cgroup iteration
> > between reclaimers"), the memcg reclaim does not bail out earlier based
> > on sc->nr_reclaimed and will traverse all the nodes. All the reclaimable
> > pages of the memcg on all the nodes will be scanned relative to the
> > reclaim priority. So, there is no need to maintain state regarding which
> > node to start the memcg reclaim from. Also KCSAN complains data races in
> > the code maintaining the state.
> >
> > This patch effectively reverts the commit 889976dbcb12 ("memcg: reclaim
> > memory from nodes in round-robin order") and the commit 453a9bf347f1
> > ("memcg: fix numa scan information update to be triggered by memory
> > event").
> >
> > Signed-off-by: Shakeel Butt <shakeelb@google.com>
> > Reported-by: <syzbot+13f93c99c06988391efe@syzkaller.appspotmail.com>
>
> I can't find the original sysbot email.  Help?
>
> iirc the incidentally-fixed issue is a rather theoretical data race and
> the patch isn't a high priority thing?
>

Let me check why the link is not working. However you are right that
the fix is for a theoretical data race and no need to be backported to
stable trees.

Shakeel

  reply	other threads:[~2019-10-30  1:15 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-29 23:47 [PATCH] mm: vmscan: memcontrol: remove mem_cgroup_select_victim_node() Shakeel Butt
2019-10-29 23:47 ` Shakeel Butt
2019-10-29 23:51 ` Roman Gushchin
2019-10-29 23:51   ` Roman Gushchin
2019-10-30  0:47 ` Andrew Morton
2019-10-30  0:54 ` Andrew Morton
2019-10-30  1:15   ` Shakeel Butt [this message]
2019-10-30  1:15     ` Shakeel Butt
2019-10-30 11:49 ` Michal Hocko
2019-10-30 17:44 ` Johannes Weiner
2019-10-30 17:53   ` Michal Hocko
2019-10-30 18:06     ` Johannes Weiner

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