From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1Lrwqx-0000Rw-G7
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:11:47 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1Lrwqt-0000Ok-QU
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:11:47 -0400
Received: from [199.232.76.173] (port=44724 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Lrwqt-0000Oh-Mf
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:11:43 -0400
Received: from smtp02.citrix.com ([66.165.176.63]:60755)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <Stefano.Stabellini@eu.citrix.com>)
	id 1Lrwqt-0008QE-Dy
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:11:43 -0400
Received: from [10.80.225.184] ([10.80.225.184])
	by smtp01.ad.xensource.com (8.13.1/8.13.1) with ESMTP id n39GBeLi002387
	for <qemu-devel@nongnu.org>; Thu, 9 Apr 2009 09:11:40 -0700
Message-ID: <49DE1E4E.3040509@eu.citrix.com>
Date: Thu, 09 Apr 2009 17:11:58 +0100
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] buffer alignment for block backends
References: <49DCA80A.1020808@eu.citrix.com>	<49DCF2C0.9070704@codemonkey.ws>	<49DDC66F.2000404@eu.citrix.com>	<49DDF3FF.8050706@codemonkey.ws>	<49DDF877.8090805@eu.citrix.com>	<49DDFE1A.9040202@redhat.com>	<20090409152107.GE5457@const.bordeaux.inria.fr>
	<49DE193B.50703@redhat.com>
In-Reply-To: <49DE193B.50703@redhat.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Gerd Hoffmann wrote:

> On 04/09/09 17:21, Samuel Thibault wrote:
>> Gerd Hoffmann, le Thu 09 Apr 2009 15:54:34 +0200, a écrit :
>>> On 04/09/09 15:30, Stefano Stabellini wrote:
>>>> The userspace\kernelspace distinction does not make much sense in
>>>> minios, but yes it provides an interface to communicate with blkback in
>>>> dom0. This interface is used by block-vbd in qemu instead of
>>>> block-raw-posix when run in minios.
>>> Sit back, look again.  Do you really need it being page-aligned?
>> Page aligned is an optimization which comes for free when you can
>> already choose the alignment.
> 
> Ok, so you don't have to.
> 
> Does it have an effect positive actually?  i.e. do you have requests 
> which would fit into one page but actually span two due to the misalignment?


Yep, I can see many here.