linux-kernel - Re: [PATCH v5 2/6] memcg: stop vmscan when enough done.

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Message-ID: <20110818062722.GB23056@tiehlicka.suse.cz>
Date:	Thu, 18 Aug 2011 08:27:22 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"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>,
	"hannes@...xchg.org" <hannes@...xchg.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH v5 2/6]  memcg: stop vmscan when enough done.

On Thu 18-08-11 08:52:33, KAMEZAWA Hiroyuki wrote:
> On Wed, 17 Aug 2011 13:35:50 +0200
> Michal Hocko <mhocko@...e.cz> wrote:
> 
> > On Wed 17-08-11 09:54:05, KAMEZAWA Hiroyuki wrote:
> > > On Thu, 11 Aug 2011 16:50:55 +0200
> > > > - mem_cgroup_force_empty asks for reclaiming all pages. I guess it should be
> > > >   OK but will have to think about it some more.
> > > 
> > > force_empty/rmdir() is allowed to be stopped by Ctrl-C. I think passing res->usage
> > > is overkilling.
> > 
> > So, how many pages should be reclaimed then?
> > 
> 
> How about (1 << (MAX_ORDER-1))/loop ?

Hmm, I am not sure I see any benefit. We want to reclaim all those
pages why shouldn't we do it in one batch? If we use a value based on
MAX_ORDER then we make a bigger chance that force_empty fails for big
cgroups (e.g. with a lot of page cache).
Anyway, if we want to mimic the previous behavior then we should use
something like nr_nodes * SWAP_CLUSTER_MAX (the above value would be
sufficient for up to 32 nodes).

> 
> Thanks,
> -Kame

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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