linux-kernel - Re: [PATCH 0/2] ksm: take dirty bit as reference to avoid volatile pages

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Date:	Mon, 28 Mar 2011 16:59:02 +0200
From:	Izik Eidus <izik.eidus@...ellosystems.com>
To:	nai.xia@...il.com
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH 0/2] ksm: take dirty bit as reference to avoid volatile
 pages

On 03/28/2011 04:14 PM, Nai Xia wrote:
> Currently, ksm uses page checksum to detect volatile pages. Izik Eidus
> suggested that we could use pte dirty bit to optimize. This patch series
> adds this new logic.
>

Hi,

One small note:
When kvm will use ksm on intel cpu with extended page tables support, 
the cpu won`t track
dirty bit, therefore the calc_hash() logic should be used in such cases
(untill intel will fadd this support in their cpus)...

Moreover I think that even though that AMD nested page tables does 
update dirty bit, you still need
to sync it with the host page table using mmu notifiers ?

(Not that on regular application use case of ksm any of this should be 
an issue)

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