linux-kernel - Re: [PATCH] mm: memcontrol: flush percpu vmevents before releasing memcg

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Message-ID: <20190813214731.GB20632@tower.DHCP.thefacebook.com>
Date:   Tue, 13 Aug 2019 21:47:35 +0000
From:   Roman Gushchin <guro@...com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] mm: memcontrol: flush percpu vmevents before releasing
 memcg

On Tue, Aug 13, 2019 at 02:31:17PM -0700, Andrew Morton wrote:
> On Mon, 12 Aug 2019 16:37:54 -0700 Roman Gushchin <guro@...com> wrote:
> 
> > Similar to vmstats, percpu caching of local vmevents leads to an
> > accumulation of errors on non-leaf levels. This happens because
> > some leftovers may remain in percpu caches, so that they are
> > never propagated up by the cgroup tree and just disappear into
> > nonexistence with on releasing of the memory cgroup.
> > 
> > To fix this issue let's accumulate and propagate percpu vmevents
> > values before releasing the memory cgroup similar to what we're
> > doing with vmstats.
> > 
> > Since on cpu hotplug we do flush percpu vmstats anyway, we can
> > iterate only over online cpus.
> > 
> > Fixes: 42a300353577 ("mm: memcontrol: fix recursive statistics correctness & scalabilty")
> 
> No cc:stable?
> 

Here too, cc:stable is definitely missing. Adding now. Thanks!