linux-kernel - Re: [patch v2 3/6] memcg: rework mem_cgroup

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Message-ID: <20121207090135.GC31938@dhcp22.suse.cz>
Date:	Fri, 7 Dec 2012 10:01:35 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Ying Han <yinghan@...gle.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <htejun@...il.com>,
	Glauber Costa <glommer@...allels.com>,
	Li Zefan <lizefan@...wei.com>
Subject: Re: [patch v2 3/6] memcg: rework mem_cgroup_iter to use cgroup
 iterators

On Thu 06-12-12 19:39:41, Ying Han wrote:
[...]
> Michal,
> 
> I got some trouble while running this patch with my test. The test
> creates hundreds of memcgs which each runs some workload to generate
> global pressure. At the last, it removes all the memcgs by rmdir. Then
> the cmd "ls /dev/cgroup/memory/" hangs afterwards.
>
> I studied a bit of the patch, but not spending too much time on it
> yet. Looks like that the v2 has something different from your last
> post, where you replaces the mem_cgroup_get() with css_get() on the
> iter->last_visited. Didn't follow why we made that change, but after
> restoring the behavior a bit seems passed my test.

Hmm, strange. css reference counting should be stronger than mem_cgroup
one because it pins css thus cgroup which in turn keeps memcg alive.

> Here is the patch I applied on top of this one:

[...]
-- 
Michal Hocko
SUSE Labs
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