linux-kernel - Re: Populating multiple ptes at fault time

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Date:	Fri, 26 Sep 2008 12:26:27 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Avi Kivity <avi@...hat.com>, Nick Piggin <nickpiggin@...oo.com.au>,
	Hugh Dickens <hugh@...itas.com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: Populating multiple ptes at fault time

On Thu, 2008-09-25 at 11:32 -0700, Jeremy Fitzhardinge wrote:
> Very few places actually care about the state of the A/D bits; would it
> be expensive to make those places explicitly ask for synchronization
> before testing the bits (or alternatively, have an explicit query
> operation rather than just poking about in the ptes).  Martin, does this
> help with s390's per-page (vs per-pte) A/D state?

With the kvm support the situation on s390 recently has grown a tad more
complicated. We now have dirty bits in the per-page storage key and in
the pgste (page table entry extension) for the kvm guests. For the A/D
bits in the storage key the new pte operations won't help, for the kvm
related bits they could make a difference.

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.


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