linux-kernel - Re: Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use

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Message-ID: <87wqnehapu.fsf@tassilo.jf.intel.com>
Date:	Wed, 21 Aug 2013 16:42:53 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, Xen-devel@...ts.xen.org,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Jan Beulich <jbeulich@...e.com>
Subject: Re: Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use

Cyrill Gorcunov <gorcunov@...il.com> writes:
>
> Hi all, I worked on patch which would not touch PSE bit for dirty page
> tracking and the result is not that good:
>
>  - 2level pages now always page dirty if page is swapped in and out, because
>    there is no space left in PTE (other than PSE bit)

Maybe just don't support soft dirty for 2 level page tables?

2 level page tables should be really on the way out anyways, as they
have severe limits and do not support NX. With 3 levels there is enough
space.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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