linux-kernel - Re: [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte and mmu notifier to help KSM dirty bit tracking

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Message-ID: <4E01D27F.8080304@redhat.com>
Date:	Wed, 22 Jun 2011 14:31:11 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Izik Eidus <izik.eidus@...ellosystems.com>
CC:	nai.xia@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Chris Wright <chrisw@...s-sol.org>,
	Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH] mmu_notifier, kvm: Introduce dirty bit tracking in spte
 and mmu notifier to help KSM dirty bit tracking

On 06/22/2011 02:28 PM, Avi Kivity wrote:
>
> Actually, this is dangerous.  If we use the dirty bit for other 
> things, we will get data corruption.
>
> For example we might want to map clean host pages as writeable-clean 
> in the spte on a read fault so that we don't get a page fault when 
> they get eventually written.
>

Another example - we can use the dirty bit for dirty page loggging.

So I think we can get away with a conditional tlb flush - only flush if 
the page was dirty.  That should be rare after the first pass, at least 
with small pages.

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

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