linux-kernel - Re: [PATCH RFC v2 3/4] memcg: rework usage of stats by soft limit

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Date:	Sat, 12 Dec 2009 21:46:08 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	nishimura@....nes.nec.co.jp
Cc:	containers@...ts.linux-foundation.org, linux-mm@...ck.org,
	Paul Menage <menage@...gle.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Dan Malek <dan@...eddedalley.com>,
	Vladislav Buzov <vbuzov@...eddedalley.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v2 3/4] memcg: rework usage of stats by soft limit

On Sat, Dec 12, 2009 at 4:34 PM, Daisuke Nishimura
<d-nishimura@....biglobe.ne.jp> wrote:
> On Sat, 12 Dec 2009 15:06:52 +0200
> "Kirill A. Shutemov" <kirill@...temov.name> wrote:
>
>> On Sat, Dec 12, 2009 at 5:50 AM, Daisuke Nishimura
>> <d-nishimura@....biglobe.ne.jp> wrote:
>> > And IIUC, it's the same for your threshold feature, right ?
>> > I think it would be better:
>> >
>> > - discard this change.
>> > - in 4/4, rename mem_cgroup_soft_limit_check to mem_cgroup_event_check,
>> >  and instead of adding a new STAT counter, do like:
>> >
>> >        if (mem_cgroup_event_check(mem)) {
>> >                mem_cgroup_update_tree(mem, page);
>> >                mem_cgroup_threshold(mem);
>> >        }
>>
>> I think that mem_cgroup_update_tree() and mem_cgroup_threshold() should be
>> run with different frequency. How to share MEM_CGROUP_STAT_EVENTS
>> between soft limits and thresholds in this case?
>>
> hmm, both softlimit and your threshold count events at the same place(charge and uncharge).
> So, I think those events can be shared.
> Is there any reason they should run in different frequency ?

SOFTLIMIT_EVENTS_THRESH is 1000. If use the same value for thresholds,
a threshold can
be exceed on 1000*nr_cpu_id pages. It's too many. I think, that 100 is
a reasonable value.

mem_cgroup_soft_limit_check() resets MEM_CGROUP_STAT_EVENTS when it reaches
SOFTLIMIT_EVENTS_THRESH. If I will do the same thing for
THRESHOLDS_EVENTS_THRESH
(which is 100) , mem_cgroup_event_check() will never be 'true'. Any
idea how to share
MEM_CGROUP_STAT_EVENTS in this case?
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