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

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Message-Id: <20091215170705.3dca982a.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 15 Dec 2009 17:07:05 +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 Tue, 15 Dec 2009 09:48:09 +0200
"Kirill A. Shutemov" <kirill@...temov.name> wrote:

> On Tue, Dec 15, 2009 at 3:35 AM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@...fujitsu.com> wrote:
> > 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 ?
> 
> I've post some numbers how the patchset affects performance:
> http://article.gmane.org/gmane.linux.kernel.mm/41880
> 
> Do you need any other results?
> 
Ah, sorry. I missed that. The numbers seems good.

(off topic)
multi-fault is too special, It's just a my toy ;)

The test I recommend you is kernel-make on tmpfs.
This is my setup script.
==
#!/bin/sh

mount -t tmpfs none /home/kamezawa/tmpfs
cp /home/kamezawa/linux-2.6.30.tar.bz2 /home/kamezawa/tmpfs
cd /home/kamezawa/tmpfs
mkdir /home/kamezawa/tmpfs/tmp
tar xvpjf linux-2.6.30.tar.bz2
cd linux-2.6.30
make defconfig

and making gcc's tmporarly strage(TMPDIR) on tmpfs.

#make clean; make -j 8 or some.

and check "stime"

But I don't ask you to do this, now.
The whole patch seems attractive to me. Please fix something pointed out.

I stop my patches for memcg's percpu counter rewriting until yours and
Nishimura's patch goes. You can leave your threshold-event-counter as it
is. I'll think of I can do total-rewrite of that counter or not.

Thanks,
-Kame

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