linux-kernel - Re: [PATCH] memcg: end migration fix (was [bad page] memcg: another bad page at page migration (2.6.26-rc5-mm3 + patch collection))

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Date:	Tue, 24 Jun 2008 16:30:24 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	linux-mm@...ck.org, balbir@...ux.vnet.ibm.com, xemul@...nvz.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memcg: end migration fix (was  [bad page] memcg:
 another bad page at page migration (2.6.26-rc5-mm3 + patch collection))

On Tue, 24 Jun 2008 16:19:03 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> On Tue, 24 Jun 2008 14:51:27 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> > Hi, Nishimura-san. thank you for all your help. 
> > 
> > I think this one is......hopefully.
> > 
> I hope so too :)
> 
> I think the corner case that this patch fixes is likely
> in my case(there may be other cases though..).
> 
> I'm testing this one now.
> 
> > ==
> > 
> > In general, mem_cgroup's charge on ANON page is removed when page_remove_rmap()
> > is called.
> > 
> > At migration, the newpage is remapped again by remove_migration_ptes(). But
> > pte may be already changed (by task exits).
> > It is charged at page allocation but have no chance to be uncharged in that
> > case because it is never added to rmap.
> > 
> I think "charged by mem_cgroup_prepare_migration()" is more precise.
> 
Thanks, will rewrite.

Regards,
-Kame


> > Handle that corner case in mem_cgroup_end_migration().
> > 
> > 
> 
> 
> Thanks,
> Daisuke Nishimura.
> 

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