linux-kernel - Re: [RFC][BUGFIX][PATCH 2/2] memcg: fix file mapped underflow at migration (v3)

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Message-Id: <20100420132050.3477a717.nishimura@mxp.nes.nec.co.jp>
Date:	Tue, 20 Apr 2010 13:20:50 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Mel Gorman <mel@....ul.ie>, Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [RFC][BUGFIX][PATCH 2/2] memcg: fix file mapped underflow at
 migration (v3)

> > I have one concern for now. Reading the patch, the flag have influence on
> > only anonymous pages, so we'd better to note it and I feel it strange to
> > set(and clear) the flag of "old page" always(iow, even when !PageAnon)
> > in prepare_migration.
> > 
> 
> Hmm...Checking "Only Anon" is simpler ?
I just thought it was inconsistent that we always set/clear the bit about "old page",
while we set the bit about "new page" only in PageAnon case.

> It will have no meanings for migrating
> file caches, but it may have some meanings for easy debugging. 
> I think "mark it always but it's used only for anonymous page" is reasonable
> (if it causes no bug.)
> 
Anyway, I don't have any strong objection.
It's all right for me as long as it is well documented or commented.


Thanks,
Daisuke Nishimura.
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