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

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Date:	Thu, 13 Aug 2009 11:46:45 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.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>,
	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?

Wu Fengguang wrote:
> On Wed, Aug 12, 2009 at 10:31:41PM +0800, Rik van Riel wrote:

>> For zones it is a fixed value, which is available in
>> /proc/zoneinfo
> 
> On my 64bit desktop with 4GB memory:
> 
>         DMA     inactive_ratio:    1
>         DMA32   inactive_ratio:    4
>         Normal  inactive_ratio:    1
> 
> The biggest zone DMA32 has inactive_ratio=4. But I guess the
> referenced bit should not be ignored on this typical desktop
> configuration?

We need to ignore the referenced bit on active anon pages
on very large systems, but it could indeed be helpful to
respect the referenced bit on smaller systems.

I have no idea where the cut-off between them would be.

Maybe at inactive_ratio <= 4 ?

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