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 23:29:03 +0800
From:	Nai Xia <nai.xia@...il.com>
To:	Izik Eidus <izik.eidus@...ellosystems.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 Monday 28 March 2011 22:59:02 Izik Eidus wrote:
> 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)
> 
> 

Hmm, I will consider these two issues in the next version. Thanks for
input!


Nai
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