linux-kernel - Re: [PATCH 0/4] Memory controller soft limit patches (v3)

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Message-Id: <20090306085323.a96cfb01.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 6 Mar 2009 08:53:23 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.com
Cc:	linux-mm@...ck.org, Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	Bharata B Rao <bharata@...ibm.com>,
	Paul Menage <menage@...gle.com>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelianov <xemul@...nvz.org>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3)

On Thu, 5 Mar 2009 20:56:42 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-03-05 18:04:10]:
> 
> > On Tue, 3 Mar 2009 16:42:44 +0530
> > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > 
> > > > I wrote
> > > > ==
> > > >  if (victim is not over soft-limit)
> > > > ==
> > > > ....Maybe this discussion style is bad and I should explain my approach in patch.
> > > > (I can't write code today, sorry.)
> > > > 
> > 
> > This is an example of my direction, " do it lazy" softlimit.
> > 
> > Maybe this is not perfect but this addresses almost all my concern.
> > I hope this will be an input for you.
> > I didn't divide patch into small pieces intentionally to show a big picture.
> > Thanks,
> > -Kame
> > ==
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> > 
> > An example patch. Don't trust me, this patch may have bugs.
> >
> 
> Well this is not do it lazy, all memcg's are scanned tree is built everytime
> kswapd invokes soft limit reclaim. 
tree is built ? no. there are not tree. And this is lazy. No impact until
kswapd runs.

> With 100 cgroups and 5 nodes, we'll
> end up scanning cgroups 500 times.
No. 100 cgroups. (kswapd works per node and all kswapd doesn't work at once.)

> There is no ordering of selected victims, 
I don't think this is necessary but if you want you can add it easily.

> so the largest victim might still be running unaffected.
> 
No problem from my point of view.

"Soft limit" is a hint from the user to show "if usage is larger than this,
recalaim from this cgroup is appropriate"

Thanks,
-Kame






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