From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [Qemu-devel] buffer alignment for block backends
Date: Thu, 9 Apr 2009 16:38:51 +0100 [thread overview]
Message-ID: <200904091638.51737.paul@codesourcery.com> (raw)
In-Reply-To: <20090409151944.GD5457@const.bordeaux.inria.fr>
On Thursday 09 April 2009, Samuel Thibault wrote:
> Anthony Liguori, le Thu 09 Apr 2009 08:11:27 -0500, a écrit :
> > >- ide.c:ide_init2
> >
> > This buffer is only used when not doing DMA. When doing DMA, we are
> > able to do zero-copy IO so the alignment of the request depends on how
> > the guest aligned the request. I suspect you'll find a lot of guests
> > that, in practice, do not align requests at 4k boundaries.
>
> Eeeeerrr, why shoudn't they? Guests usually work on pages, which are
> already aligned on 4k boundaries.
Assuming that page == 4k is going to get you into all sorts of trouble.
Paul
next prev parent reply other threads:[~2009-04-09 15:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-08 13:35 [Qemu-devel] buffer alignment for block backends Stefano Stabellini
2009-04-08 18:53 ` Anthony Liguori
2009-04-09 9:57 ` Stefano Stabellini
2009-04-09 13:11 ` Anthony Liguori
2009-04-09 13:30 ` Stefano Stabellini
2009-04-09 13:54 ` Gerd Hoffmann
2009-04-09 15:21 ` Samuel Thibault
2009-04-09 15:46 ` Stefano Stabellini
2009-04-09 15:50 ` Gerd Hoffmann
2009-04-09 16:11 ` Stefano Stabellini
2009-04-09 16:13 ` Samuel Thibault
2009-04-09 16:28 ` Anthony Liguori
2009-04-09 15:55 ` Jamie Lokier
2009-04-09 16:15 ` Samuel Thibault
2009-04-09 17:29 ` Lennart Sorensen
2009-04-09 13:33 ` Stefano Stabellini
2009-04-09 15:19 ` Samuel Thibault
2009-04-09 15:38 ` Paul Brook [this message]
2009-04-09 15:40 ` Samuel Thibault
2009-04-09 15:56 ` Anthony Liguori
2009-04-09 16:19 ` Samuel Thibault
2009-04-09 10:07 ` Stefano Stabellini
2009-04-09 13:14 ` Anthony Liguori
2009-04-09 13:30 ` Stefano Stabellini
2009-04-09 13:19 ` Christoph Hellwig
2009-04-09 13:30 ` Stefano Stabellini
2009-04-09 15:31 ` Christoph Hellwig
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