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

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Message-Id: <20090108132855.77d3d3d4.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 8 Jan 2009 13:28:55 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	balbir@...ux.vnet.ibm.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

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.


> >     Why don't you sort this at memory-reclaim dynamically ?
> >   - Considering above, the look of RB tree can be
> > 
> >                 +30M (an amount over soft limit is 30M)
> >                 /  \
> >              -15M   +60M
> 
> We don't have elements below their soft limit in the tree
> 
> >      ?
> > 
> >     At least, pleease remove the node at uncharge() when the usage goes down.
> >
> 
> We do remove the tree if it goes under its soft limit at commit_charge,
> I thought I had the same code in uncharge(), but clearly that is
> missing. Thanks, I'll add it there.
> 

Ah, ok. I missed it. Thank you for clalification.

Regards,
-Kame

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