linux-kernel - Re: [PATCH] emulate accessed bit for EPT

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Message-ID: <20100204174715.GL5959@random.random>
Date:	Thu, 4 Feb 2010 18:47:15 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	balbir@...ux.vnet.ibm.com, jdike@...toit.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, mtosatti@...hat.com
Subject: Re: [PATCH] emulate accessed bit for EPT

On Thu, Feb 04, 2010 at 08:40:43AM -0500, Rik van Riel wrote:
> I suspect it won't be very many. I have been monitoring
> /proc/meminfo on my system while testing this patch, and
> it is quite typical that the size of the inactive anon
> list does not change for minutes at a time.
> 
> In other words, no pages are moved onto or off of the
> inactive anon list for several minutes. That corresponds
> to a very small number of minor faults introduced by my
> patch.

When there's light VM pressure, ideally there should be zero overhead
caused by the patch. When there is VM pressure this will avoid some
unnecessary I/O which should outweight the minor faults. It should be
a good default behavior.
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