From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Brook Subject: Re: [Qemu-devel] Re: [PATCH] virtio-blk: add SGI_IO passthru support Date: Wed, 29 Apr 2009 12:29:58 +0100 Message-ID: <200904291229.59766.paul@codesourcery.com> References: <20090427082606.GA32604@lst.de> <200904291211.20374.paul@codesourcery.com> <200904291319.05247.borntraeger@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, Christoph Hellwig , Anthony Liguori , kvm@vger.kernel.org, Rusty Russell , Hannes Reinecke To: Christian Borntraeger Return-path: Received: from mail.codesourcery.com ([65.74.133.4]:51480 "EHLO mail.codesourcery.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965AbZD2LaD (ORCPT ); Wed, 29 Apr 2009 07:30:03 -0400 In-Reply-To: <200904291319.05247.borntraeger@de.ibm.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Wednesday 29 April 2009, Christian Borntraeger wrote: > Am Wednesday 29 April 2009 13:11:19 schrieb Paul Brook: > > On Wednesday 29 April 2009, Christoph Hellwig wrote: > > > On Tue, Apr 28, 2009 at 11:37:01AM -0500, Anthony Liguori wrote: > > > > Ah, excellent. I think that's a great thing to do. So do you think > > > > virtio-scsi would deprecate virtio-blk? > > > > > > I don't think so. If you have an image format or a non-scsi > > > blockdevice underneath virtio-block avoids the encoding into SCSI CDBs > > > and back and should be faster. > > > > Is this actually measurably faster, or just infinitesimally faster in > > theory? > > If the underlying backing is 4k block size and the emulated scsi disk has > 512 byte block size, write performance can be a lot slower. Rubbish. If this is really a problem you can just use a scsi disk with 4k sectors. Paul From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Lz7zL-0007Ev-PD for qemu-devel@nongnu.org; Wed, 29 Apr 2009 07:30:07 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Lz7zH-0007DD-85 for qemu-devel@nongnu.org; Wed, 29 Apr 2009 07:30:07 -0400 Received: from [199.232.76.173] (port=35844 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Lz7zG-0007D3-WB for qemu-devel@nongnu.org; Wed, 29 Apr 2009 07:30:03 -0400 Received: from mx20.gnu.org ([199.232.41.8]:36092) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1Lz7zG-0001o5-Ok for qemu-devel@nongnu.org; Wed, 29 Apr 2009 07:30:02 -0400 Received: from mail.codesourcery.com ([65.74.133.4]) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Lz7zF-0007Oi-SB for qemu-devel@nongnu.org; Wed, 29 Apr 2009 07:30:02 -0400 From: Paul Brook Subject: Re: [Qemu-devel] Re: [PATCH] virtio-blk: add SGI_IO passthru support Date: Wed, 29 Apr 2009 12:29:58 +0100 References: <20090427082606.GA32604@lst.de> <200904291211.20374.paul@codesourcery.com> <200904291319.05247.borntraeger@de.ibm.com> In-Reply-To: <200904291319.05247.borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200904291229.59766.paul@codesourcery.com> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger Cc: kvm@vger.kernel.org, Rusty Russell , qemu-devel@nongnu.org, Hannes Reinecke , Christoph Hellwig On Wednesday 29 April 2009, Christian Borntraeger wrote: > Am Wednesday 29 April 2009 13:11:19 schrieb Paul Brook: > > On Wednesday 29 April 2009, Christoph Hellwig wrote: > > > On Tue, Apr 28, 2009 at 11:37:01AM -0500, Anthony Liguori wrote: > > > > Ah, excellent. I think that's a great thing to do. So do you think > > > > virtio-scsi would deprecate virtio-blk? > > > > > > I don't think so. If you have an image format or a non-scsi > > > blockdevice underneath virtio-block avoids the encoding into SCSI CDBs > > > and back and should be faster. > > > > Is this actually measurably faster, or just infinitesimally faster in > > theory? > > If the underlying backing is 4k block size and the emulated scsi disk has > 512 byte block size, write performance can be a lot slower. Rubbish. If this is really a problem you can just use a scsi disk with 4k sectors. Paul