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

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Message-Id: <20090217132039.3504cd3d.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 17 Feb 2009 13:20:39 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	balbir@...ux.vnet.ibm.com, 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)

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 ?

-Kame

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