From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: "Nick Piggin" <nickpiggin@yahoo.com.au>,
"David Chinner" <dgc@sgi.com>,
"Jeremy Fitzhardinge" <jeremy@goop.org>,
xfs@oss.sgi.com, Xen-devel <xen-devel@lists.xensource.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Mark Williamson" <mark.williamson@cl.cam.ac.uk>,
"Morten Bøgeskov" <xen-users@morten.bogeskov.dk>,
xfs-masters@oss.sgi.com
Subject: Re: Interaction between Xen and XFS: stray RW mappings
Date: Mon, 22 Oct 2007 08:16:01 +1000 [thread overview]
Message-ID: <1193004961.6745.42.camel@pasglop> (raw)
In-Reply-To: <20071015110735.GA11748@one.firstfloor.org>
On Mon, 2007-10-15 at 13:07 +0200, Andi Kleen wrote:
> On Tue, Oct 16, 2007 at 12:56:46AM +1000, Nick Piggin wrote:
> > Is this true even if you don't write through those old mappings?
>
> I think it happened for reads too. It is a little counter intuitive
> because in theory the CPU doesn't need to write back non dirty lines,
> but in the one case which took so long to debug exactly this happened
> somehow.
The problem exist also on ppc, and afaik, is due to the line being in
the cache at all (either dirty (write) or not (read)), thus causing the
snoop logic to hit, that is what's causing the problem vs. non cached
accesses.
Also, on some processors, the simple fact of having the page mapped can
cause the CPU to prefetch from it even if it's not actually accessed
(speculative prefetch can cross page boundaries if things are mapped).
Ben.
next prev parent reply other threads:[~2007-10-21 22:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-12 16:58 Interaction between Xen and XFS: stray RW mappings Jeremy Fitzhardinge
2007-10-12 17:08 ` Jeremy Fitzhardinge
2007-10-14 22:56 ` David Chinner
2007-10-14 23:12 ` Jeremy Fitzhardinge
2007-10-14 23:33 ` David Chinner
2007-10-15 4:15 ` Nick Piggin
2007-10-15 0:57 ` Jeremy Fitzhardinge
2007-10-15 7:26 ` Nick Piggin
2007-10-15 3:42 ` Jeremy Fitzhardinge
2007-10-15 4:11 ` David Chinner
2007-10-15 4:18 ` Jeremy Fitzhardinge
2007-10-15 4:25 ` David Chinner
2007-10-15 8:31 ` [xfs-masters] " Christoph Hellwig
2007-10-22 3:18 ` dean gaudet
2007-10-22 3:34 ` Jeremy Fitzhardinge
2007-10-22 4:28 ` dean gaudet
2007-10-22 4:39 ` Nick Piggin
2007-10-22 18:37 ` Jeremy Fitzhardinge
2007-10-22 18:32 ` Jeremy Fitzhardinge
2007-10-22 13:47 ` Andi Kleen
2007-10-22 18:40 ` Jeremy Fitzhardinge
2007-10-22 19:07 ` Andi Kleen
2007-10-22 19:11 ` Jeremy Fitzhardinge
2007-10-22 22:32 ` David Chinner
2007-10-22 23:35 ` Andi Kleen
2007-10-23 0:16 ` Zachary Amsden
2007-10-23 0:36 ` David Chinner
2007-10-23 7:04 ` [patch] " David Chinner
2007-10-23 9:30 ` Andi Kleen
2007-10-23 12:41 ` David Chinner
2007-10-23 14:33 ` Jeremy Fitzhardinge
2007-10-24 4:36 ` [PATCH] Allow lazy unmapping by taking extra page references V2 David Chinner
2007-10-24 5:08 ` Jeremy Fitzhardinge
2007-10-24 21:48 ` [PATCH] Allow lazy unmapping by taking extra page references V3 David Chinner
2007-10-24 22:46 ` Jeremy Fitzhardinge
2007-10-24 23:21 ` David Chinner
2007-10-23 9:28 ` Interaction between Xen and XFS: stray RW mappings Andi Kleen
2007-10-15 9:36 ` Andi Kleen
2007-10-15 14:56 ` Nick Piggin
2007-10-15 11:07 ` Andi Kleen
2007-10-15 11:28 ` Nick Piggin
2007-10-15 12:54 ` Andi Kleen
2007-10-21 12:17 ` Dave Airlie
2007-10-21 22:16 ` Benjamin Herrenschmidt [this message]
2007-10-22 9:49 ` Andi Kleen
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