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

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Message-Id: <20091215103517.75645536.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 15 Dec 2009 10:35:17 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	nishimura@....nes.nec.co.jp, 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>,
	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, 12 Dec 2009 21:46:08 +0200
"Kirill A. Shutemov" <kirill@...temov.name> wrote:

> 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.
> 

Hmm, then what amount of costs does this code add ?

Do you have benchmark result ?

Thanks,
-Kame

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