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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Message-Id: <20080624161903.238eb868.nishimura@mxp.nes.nec.co.jp>
Date:	Tue, 24 Jun 2008 16:19:03 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
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 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.

> Handle that corner case in mem_cgroup_end_migration().
> 
> 


Thanks,
Daisuke Nishimura.
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