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Date: Fri, 6 Mar 2009 08:53:23 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: balbir@linux.vnet.ibm.com
Cc: linux-mm@kvack.org, Sudhir Kumar <skumar@linux.vnet.ibm.com>,
       YAMAMOTO Takashi <yamamoto@valinux.co.jp>,
       Bharata B Rao <bharata@in.ibm.com>, Paul Menage <menage@google.com>,
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       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       Rik van Riel <riel@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/4] Memory controller soft limit patches (v3)
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On Thu, 5 Mar 2009 20:56:42 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-03-05 18:04:10]:
> 
> > On Tue, 3 Mar 2009 16:42:44 +0530
> > Balbir Singh <balbir@linux.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@jp.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