linux-kernel - Re: [PATCH 2/4] Memory controller soft limit interface (v3)

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Message-Id: <20090302143518.43f5fcc2.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 2 Mar 2009 14:35:18 +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 2/4] Memory controller soft limit interface (v3)

On Mon, 2 Mar 2009 10:16:31 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:

> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-03-02 11:03:23]:
> 
> > On Sun, 01 Mar 2009 12:00:11 +0530
> > Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> > 
> > > 
> > > From: Balbir Singh <balbir@...ux.vnet.ibm.com>
> > > 
> > > Changelog v2...v1
> > > 1. Add support for res_counter_check_soft_limit_locked. This is used
> > >    by the hierarchy code.
> > > 
> > > Add an interface to allow get/set of soft limits. Soft limits for memory plus
> > > swap controller (memsw) is currently not supported. Resource counters have
> > > been enhanced to support soft limits and new type RES_SOFT_LIMIT has been
> > > added. Unlike hard limits, soft limits can be directly set and do not
> > > need any reclaim or checks before setting them to a newer value.
> > > 
> > > Kamezawa-San raised a question as to whether soft limit should belong
> > > to res_counter. Since all resources understand the basic concepts of
> > > hard and soft limits, it is justified to add soft limits here. Soft limits
> > > are a generic resource usage feature, even file system quotas support
> > > soft limits.
> > > 
> > I don't convice adding more logics to res_counter is a good to do, yet.
> >
> 
> Even though it is extensible and you pay the cost only when soft
> limits is turned on? Can you show me why you are not convinced?
>  
Inserting more codes (like "if") to res_counter itself is not welcome..
I think res_counter is too complex as counter already.

I'm now searching a way to reduce res_counter->lock ping-pong but have no
good idea.

Thanks,
-Kame





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