linux-kernel - Re: [PATCHv4] memcg: reclaim memory from node in round-robin

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Message-Id: <20110428110400.2808f50d.nishimura@mxp.nes.nec.co.jp>
Date:	Thu, 28 Apr 2011 11:04:00 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Ying Han <yinghan@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>
Subject: Re: [PATCHv4] memcg: reclaim memory from node in round-robin

On Thu, 28 Apr 2011 10:49:12 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Thu, 28 Apr 2011 10:37:05 +0900
> Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> > > +	if (time_after(mem->next_scan_node_update, jiffies))
> > > +		return;
> > > +
> > Shouldn't it be time_before() or time_after(jiffies, next_scan_node_update) ?
> > 
> > Looks good to me, otherwise.
> > 
> 
> time_after(a, b) returns true when a is after b.....you're right.
> ==
> Now, memory cgroup's direct reclaim frees memory from the current node.
> But this has some troubles. In usual, when a set of threads works in
> cooperative way, they are tend to on the same node. So, if they hit
> limits under memcg, it will reclaim memory from themselves, it may be
> active working set.
> 
> For example, assume 2 node system which has Node 0 and Node 1
> and a memcg which has 1G limit. After some work, file cacne remains and
> and usages are
>    Node 0:  1M
>    Node 1:  998M.
> 
> and run an application on Node 0, it will eats its foot before freeing
> unnecessary file caches.
> 
> This patch adds round-robin for NUMA and adds equal pressure to each
> node. When using cpuset's spread memory feature, this will work very well.
> 
> But yes, better algorithm is appreciated.
> 
> From: Ying Han <yinghan@...gle.com>
> Signed-off-by: Ying Han <yinghan@...gle.com>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
Acked-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
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