Message-ID: <508E8B95.406@parallels.com>
Date: Mon, 29 Oct 2012 17:58:45 +0400
From: Glauber Costa <glommer@parallels.com>
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To: Michal Hocko <mhocko@suse.cz>
CC: <linux-mm@kvack.org>, <cgroups@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>,
        Li Zefan <lizefan@huawei.com>, Johannes Weiner <hannes@cmpxchg.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Balbir Singh <bsingharora@gmail.com>
Subject: Re: [PATCH v3 3/6] memcg: Simplify mem_cgroup_force_empty_list error
 handling
References: <1351251453-6140-1-git-send-email-mhocko@suse.cz> <1351251453-6140-4-git-send-email-mhocko@suse.cz>
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> 
> Changes since v1
> - use kerndoc
> - be more specific about mem_cgroup_move_parent possible failures
> 
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
> Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Glauber Costa <glommer@parallels.com>

> + * move charges to its parent or the root cgroup if the group has no
> + * parent (aka use_hierarchy==0).
> + * Although this might fail (get_page_unless_zero, isolate_lru_page or
> + * mem_cgroup_move_account fails) the failure is always temporary and
> + * it signals a race with a page removal/uncharge or migration. In the
> + * first case the page is on the way out and it will vanish from the LRU
> + * on the next attempt and the call should be retried later.
> + * Isolation from the LRU fails only if page has been isolated from
> + * the LRU since we looked at it and that usually means either global
> + * reclaim or migration going on. The page will either get back to the
> + * LRU or vanish.

I just wonder for how long can it go in the worst case?

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