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

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Message-ID: <4A79A468.2020200@redhat.com>
Date:	Wed, 05 Aug 2009 18:25:28 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Rik van Riel <riel@...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>,
	Andrea Arcangeli <aarcange@...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?

On 08/05/2009 06:15 PM, Rik van Riel wrote:
> Avi Kivity wrote:
>
>>> If so, we could unmap them when they get moved from the
>>> active to the inactive list, and soft fault them back in
>>> on access, emulating the referenced bit for EPT pages and
>>> making page replacement on them work like it should.
>>
>> It should be easy to implement via the mmu notifier callback: when 
>> the mm calls clear_flush_young(), mark it as young, and unmap it from 
>> the EPT pagetable.
>
> You mean "mark it as old"?

I meant 'return young, and drop it from the EPT pagetable'.

If we use the present bit as a replacement for the accessed bit, present 
means young, and clear_flush_young means "if present, return young and 
unmap, otherwise return old'.

See kvm_age_rmapp() in arch/x86/kvm/mmu.c.

-- 
error compiling committee.c: too many arguments to function

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