linux-kernel - Re: [PATCH] memcg: don't do cleanup manually if mem_cgroup_css

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Message-ID: <515AE948.1000704@parallels.com>
Date:	Tue, 2 Apr 2013 18:20:56 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH] memcg: don't do cleanup manually if mem_cgroup_css_online()
 fails

On 04/02/2013 06:16 PM, Michal Hocko wrote:
>  mem_cgroup_css_online
>       memcg_init_kmem
>         mem_cgroup_get		# refcnt = 2
>           memcg_update_all_caches
>             memcg_update_cache_size	# fails with ENOMEM

Here is the thing: this one in kmem only happens for kmem enabled
memcgs. For those, we tend to do a get once, and put only when the last
kmem reference is gone.

For non-kmem memcgs, refcnt will be 1 here, and will be balanced out by
the mem_cgroup_put() in css_free.

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