linux-kernel - Re: [RFC] respect the referenced bit of KVM guest pages?

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Message-ID: <4A79BF55.5090004@redhat.com>
Date:	Wed, 05 Aug 2009 13:20:21 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
CC:	Wu Fengguang <fengguang.wu@...el.com>,
	"Dike, Jeffrey G" <jeffrey.g.dike@...el.com>,
	"Yu, Wilfred" <wilfred.yu@...el.com>,
	"Kleen, Andi" <andi.kleen@...el.com>, Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC] respect the referenced bit of KVM guest pages?

Andrea Arcangeli wrote:
> On Wed, Aug 05, 2009 at 10:40:58AM +0800, Wu Fengguang wrote:
>>  			 */
>> -			if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
>> +			if ((vm_flags & VM_EXEC) || PageAnon(page)) {
>>  				list_add(&page->lru, &l_active);
>>  				continue;
>>  			}
>>
> 
> Please nuke the whole check and do an unconditional list_add;
> continue; there.

That would reinstate the bug that the VM has no pages
available for evicting.  There are very good reasons
that only VM_EXEC file pages get moved to the back of
the active list if they were referenced, and nothing
else.

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