linux-kernel - Re: [PATCH] mm: Save soft-dirty bits on swapped pages

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Message-ID: <20130724190453.GJ8508@moon>
Date:	Wed, 24 Jul 2013 23:04:53 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] mm: Save soft-dirty bits on swapped pages

On Wed, Jul 24, 2013 at 10:55:41PM +0400, Pavel Emelyanov wrote:
> > 
> > Well, some part of information already lays in pte (such as 'file' bit,
> > swap entries) so it looks natural i think to work on this level. but
> > letme think if use page struct for that be more convenient...
> 
> It hardly will be. Consider we have a page shared between two tasks,
> then first one "touches" it and soft-dirty is put onto his PTE and,
> subsequently, the page itself. The we go and clear sofr-dirty for the
> 2nd task. What should we do with the soft-dirty bit on the page?

Indeed, this won't help. Well then, bippidy-boppidy-boo, our
pants are metaphorically on fire (c)

> 
> The soft-dirty thing watches changes in the virtual memory, not in
> the physical one.
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