From mboxrd@z Thu Jan 1 00:00:00 1970 From: walt Subject: Re: qcow2 slowdown in kvm-78,79 Date: Wed, 19 Nov 2008 15:47:33 -0800 Message-ID: References: <1227019192.22098.4.camel@henrik-desktop> <20081119182317.GA31893@us.ibm.com> <49245A61.9050504@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from main.gmane.org ([80.91.229.2]:56096 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752141AbYKSXro (ORCPT ); Wed, 19 Nov 2008 18:47:44 -0500 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1L2wlp-0007jB-Fm for kvm@vger.kernel.org; Wed, 19 Nov 2008 23:47:41 +0000 Received: from adsl-69-234-183-8.dsl.irvnca.pacbell.net ([69.234.183.8]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 19 Nov 2008 23:47:41 +0000 Received: from w41ter by adsl-69-234-183-8.dsl.irvnca.pacbell.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 19 Nov 2008 23:47:41 +0000 In-Reply-To: <49245A61.9050504@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: Anthony Liguori wrote: > Ryan Harper wrote: >> * Henrik Holst [2008-11-18 08:42]: >>> The bundled qemu in kvm-78 and kvm-79 slows down disk i/o with qcow2 >>> images by an order of 10. If one got 60MB/s before, one gets around >>> 6MB/s with 78 and 79 (measured with dd) >> >> dd command? >> >> what's your -drive parameters look like, specifically, what if type? >> ide, scsi, virtio? > > This is probably the change to cache=writethrough. I bet if you set > cache=writeback then you'll see this go away. Would this affect 'qemu-img commit'? It took over an hour to commit a fresh install of Vista on a qcow2 virtual disk. (The base image expanded from 3GB to 11GB, which is a lot of committing, though.)