linux-kernel - Re: [RFC][PATCH 0/4] Memory controller soft limit patches (v2)

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Message-ID: <20090217044222.GE20958@balbir.in.ibm.com>
Date:	Tue, 17 Feb 2009 10:12:22 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.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: [RFC][PATCH 0/4] Memory controller soft limit patches (v2)

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-02-17 13:20:39]:

> On Tue, 17 Feb 2009 13:03:52 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > > > 2. I don't like to change usual direct-memory-reclaim path. It will be obstacles
> > > >    for VM-maintaners to improve memory reclaim. memcg's LRU is designed for
> > > >    shrinking memory usage and not for avoiding memory shortage. IOW, it's slow routine
> > > >    for reclaiming memory for memory shortage.
> > > 
> > > I don't think I agree here. Direct reclaim is the first indication of
> > > shortage and if order 0 pages are short, memcg's above their soft
> > > limit can be targetted first.
> > > 
> > My "slow" means "the overhead seems to be big". The latency will increase.
> > 
> > About 0-order
> > In patch 4/4
> > +	did_some_progress = mem_cgroup_soft_limit_reclaim(gfp_mask);
> > +	/*
> > should be
> >         if (!order)
> >             did_some_progress = mem....
> above is wrong.
> 
> if (!order && (gfp_mask & GFP_MOVABLE)) ....Hmm, but this is not correct.
> I have no good idea to avoid unnecessary works.
> 
> BTW,  why don't you call soft_limit_reclaim from kswapd's path ?
>

I think it has to be both kswapd and pdflush path, I can consider that
option as well. That needs more thought on the design.
 

-- 
	Balbir
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