From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=41919 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OghA5-0006LW-Nb for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:49:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OghA4-0005a1-K6 for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:49:49 -0400 Received: from mail-qy0-f173.google.com ([209.85.216.173]:48446) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OghA4-0005Zu-Fp for qemu-devel@nongnu.org; Wed, 04 Aug 2010 12:49:48 -0400 Received: by qyk35 with SMTP id 35so2046167qyk.4 for ; Wed, 04 Aug 2010 09:49:48 -0700 (PDT) Message-ID: <4C599A27.9000602@codemonkey.ws> Date: Wed, 04 Aug 2010 11:49:43 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? References: <4C5847CD.9080107@codemonkey.ws> <4C5848C7.3090806@redhat.com> <4C584982.5000108@codemonkey.ws> <4C584B66.5070404@redhat.com> <4C5854F1.3000905@codemonkey.ws> <4C5858B2.9090801@redhat.com> <4C585F5B.5070502@codemonkey.ws> <4C58635B.7020407@redhat.com> <20100803191346.GA28523@amd.home.annexia.org> <4C586C6E.9030002@redhat.com> <20100803200057.GB28523@amd.home.annexia.org> <4C5880BC.2080802@codemonkey.ws> <4C588685.8070509@redhat.com> <4C588B7D.5040902@codemonkey.ws> <4C591D87.5020809@redhat.com> <4C5962DA.4090108@codemonkey.ws> <4C5998EB.2050804@redhat.com> <4C59996A.9010402@codemonkey.ws> <58DD5B14-F1A9-408C-982A-A29E0A7FACF2@suse.de> In-Reply-To: <58DD5B14-F1A9-408C-982A-A29E0A7FACF2@suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Gleb Natapov , kvm@vger.kernel.org, qemu-devel@nongnu.org, "Richard W.M. Jones" , Avi Kivity , Paolo Bonzini On 08/04/2010 11:48 AM, Alexander Graf wrote: > On 04.08.2010, at 18:46, Anthony Liguori wrote: > > >> On 08/04/2010 11:44 AM, Avi Kivity wrote: >> >>> On 08/04/2010 03:53 PM, Anthony Liguori wrote: >>> >>>> So how do we enable support for more than 20 disks? I think a virtio-scsi is inevitable.. >>>> >>> Not only for large numbers of disks, also for JBOD performance. If you have one queue per disk you'll have low queue depths and high interrupt rates. Aggregating many spindles into a single queue is important for reducing overhead. >>> >> Right, the only question is, to you inject your own bus or do you just reuse SCSI. On the surface, it seems like reusing SCSI has a significant number of advantages. For instance, without changing the guest's drivers, we can implement PV cdroms or PC tape drivers. >> > What exactly would keep us from doing that with virtio-blk? I thought that supports scsi commands already. > I think the toughest change would be making it appear as a scsi device within the guest. You could do that to virtio-blk but it would be a flag day as reasonable configured guests will break. Having virtio-blk device show up as /dev/vdX was a big mistake. It's been nothing but a giant PITA. There is an amazing amount of software that only looks at /dev/sd* and /dev/hd*. Regards, Anthony Liguori > Alex > >