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Date: Thu, 19 Jan 2012 14:38:16 +0800
From: Sha <handai.szj@gmail.com>
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To: Michal Hocko <mhocko@suse.cz>
CC: Johannes Weiner <hannes@cmpxchg.org>, Ying Han <yinghan@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Balbir Singh <bsingharora@gmail.com>, cgroups@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 2/2] mm: memcg: hierarchical soft limit reclaim
References: <1326207772-16762-3-git-send-email-hannes@cmpxchg.org> <CALWz4izwNBN_qcSsqg-qYw-Esc9vBL3=4cv3Wsg1jf6001_fWQ@mail.gmail.com> <20120112085904.GG24386@cmpxchg.org> <CALWz4iz3sQX+pCr19rE3_SwV+pRFhDJ7Lq-uJuYBq6u3mRU3AQ@mail.gmail.com> <20120113224424.GC1653@cmpxchg.org> <4F158418.2090509@gmail.com> <20120117145348.GA3144@cmpxchg.org> <CAFj3OHWY2Biw54gaGeH5fkxzgOhxn7NAibeYT_Jmga-_ypNSRg@mail.gmail.com> <20120118092509.GI24386@cmpxchg.org> <4F16AC27.1080906@gmail.com> <20120118152708.GG31112@tiehlicka.suse.cz>
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On 01/18/2012 11:27 PM, Michal Hocko wrote:
> On Wed 18-01-12 19:25:27, Sha wrote:
> [...]
>> Er... I'm even more confused: mem_cgroup_soft_limit_reclaim indeed
>> choses the biggest soft-limit excessor first, but in the succeeding reclaim
>> mem_cgroup_hierarchical_reclaim just selects a child cgroup  by css_id
> mem_cgroup_soft_limit_reclaim picks up the hierarchy root (most
> excessing one) and mem_cgroup_hierarchical_reclaim reclaims from that
> subtree). It doesn't care who exceeds the soft limit under that
> hierarchy it just tries to push the root under its limit as much as it
> can. This is what Johannes tried to explain in the other email in the
> thred.
yeah, I finally twig what  he meant... I'm not quite familiar with this 
part.
Thanks a lot for the explanation. :-)

Sha
>> which has nothing to do with soft limit (see mem_cgroup_select_victim).
>> IMHO, it's not a genuine hierarchical reclaim.
> It is hierarchical because it iterates over hierarchy it is not and
> never was recursively soft-hierarchical...
>