linux-kernel - Re: [BUG]: mm/vmscan.c: shrink_slab does not work correctly with memcg disabled via commandline

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Date:   Thu, 1 Aug 2019 17:54:34 +0200
From:   Jan Hadrava <had@....mff.cuni.cz>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        wizards@....mff.cuni.cz, Kirill Tkhai <ktkhai@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [BUG]: mm/vmscan.c: shrink_slab does not work correctly with
 memcg disabled via commandline

On Thu, Aug 01, 2019 at 04:06:10PM +0200, Michal Hocko wrote:
> On Thu 01-08-19 15:42:50, Jan Hadrava wrote:
> > There seems to be a bug in mm/vmscan.c shrink_slab function when kernel is
> > compilled with CONFIG_MEMCG=y and it is then disabled at boot with commandline
> > parameter cgroup_disable=memory. SLABs are then not getting shrinked if the
> > system memory is consumed by userspace.
> 
> This looks similar to http://lkml.kernel.org/r/1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com
> although the culprit commit has been identified to be different. Could
> you try it out please? Maybe we need more fixes.

Yes, it is same. So my report is duplicate and I'm just bad in searching the
archives, sorry.

Just to be sure, i run my tests and patch proposed in the original thread
solves my issue in all four affected stable releases:

> > This issue is present in linux-stable 4.19 and all newer lines.
> >     (tested on git tags v5.3-rc2 v5.2.5 v5.1.21 v4.19.63)

And culprit commit is in fact also the same: b0dedc49a2da introduces one issue
in one place and aeed1d325d42 (culprit according to original thread) moves it
few lines up:

> > Git bisect is pointing to commit:
> > 	b0dedc49a2daa0f44ddc51fbf686b2ef012fccbf
(...)
> > Following commit aeed1d325d429ac9699c4bf62d17156d60905519
> > deletes conditional continue (and so it fixes the problem). But it is creating
> > similar issue few lines earlier: