linux-kernel - Re: [PATCH v5 0/7] mm: reparent slab memory on cgroup removal

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Message-ID: <20190528070128.GM1658@dhcp22.suse.cz>
Date:   Tue, 28 May 2019 09:01:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Roman Gushchin <guro@...com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Rik van Riel <riel@...riel.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v5 0/7] mm: reparent slab memory on cgroup removal

On Wed 22-05-19 22:23:01, Roman Gushchin wrote:
> On Wed, May 22, 2019 at 02:59:06PM -0700, Andrew Morton wrote:
> > On Wed, 22 May 2019 21:43:54 +0000 Roman Gushchin <guro@...com> wrote:
> > 
> > > Is this patchset good to go? Or do you have any remaining concerns?
> > > 
> > > It has been carefully reviewed by Shakeel; and also Christoph and Waiman
> > > gave some attention to it.
> > > 
> > > Since commit 172b06c32b94 ("mm: slowly shrink slabs with a relatively")
> > > has been reverted, the memcg "leak" problem is open again, and I've heard
> > > from several independent people and companies that it's a real problem
> > > for them. So it will be nice to close it asap.
> > > 
> > > I suspect that the fix is too heavy for stable, unfortunately.
> > > 
> > > Please, let me know if you have any issues that preventing you
> > > from pulling it into the tree.
> > 
> > I looked, and put it on ice for a while, hoping to hear from
> > mhocko/hannes.  Did they look at the earlier versions?
> 
> Johannes has definitely looked at one of early versions of the patchset,
> and one of the outcomes was his own patchset about pushing memcg stats
> up by the tree, which eliminated the need to deal with memcg stats
> on kmem_cache reparenting.
> 
> The problem and the proposed solution have been discussed on latest LSFMM,
> and I didn't hear any opposition. So I assume that Michal is at least
> not against the idea in general. A careful code review is always welcome,
> of course.

I didn't get to review this properly (ETOOBUSY). This is a tricky area
so a careful review is definitely due. I would really appreciate if
Vladimir could have a look. I understand he is busy with other stuff but
a highlevel review from him would be really helpful.
-- 
Michal Hocko
SUSE Labs