linux-kernel - Re: [RFC][PATCH 3/4] Memory controller soft limit organize cgroups

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Message-ID: <20090108044108.GG7294@balbir.in.ibm.com>
Date:	Thu, 8 Jan 2009 10:11:08 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
	YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
	Paul Menage <menage@...gle.com>, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Rientjes <rientjes@...gle.com>,
	Pavel Emelianov <xemul@...nvz.org>
Subject: Re: [RFC][PATCH 3/4] Memory controller soft limit organize cgroups

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-01-08 13:28:55]:

> On Thu, 8 Jan 2009 09:55:58 +0530
> Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> 
> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-01-08 10:11:48]:
> > > Hmm,  Could you clarify following ?
> > >   
> > >   - Usage of memory at insertsion and usage of memory at reclaim is different.
> > >     So, this *sorted* order by RB-tree isn't the best order in general.
> > 
> > True, but we frequently update the tree at an interval of HZ/4.
> > Updating at every page fault sounded like an overkill and building the
> > entire tree at reclaim is an overkill too.
> > 
> "sort" is not necessary.
> If this feature is implemented as background daemon,
> just select the worst one at each iteration is enough.

OK, definitely an alternative worth considering, but the trade-off is
lazy building (your suggestion), which involves actively seeing the
usage of all cgroups (and if they are large, O(c), c is number of
cgroups can be quite a bit) versus building the tree as and when the
fault occurs and controlled by some interval.

-- 
	Balbir
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