From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Mueller Subject: Re: qcow2 slowdown in kvm-78,79 Date: Wed, 19 Nov 2008 19:49:24 +0000 (UTC) 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=UTF-8 Content-Transfer-Encoding: 8bit To: kvm@vger.kernel.org Return-path: Received: from main.gmane.org ([80.91.229.2]:49195 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752348AbYKSTtf (ORCPT ); Wed, 19 Nov 2008 14:49:35 -0500 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1L2t3L-00078m-7Q for kvm@vger.kernel.org; Wed, 19 Nov 2008 19:49:31 +0000 Received: from 77-58-232-244.dclient.hispeed.ch ([77.58.232.244]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 19 Nov 2008 19:49:31 +0000 Received: from thomas by 77-58-232-244.dclient.hispeed.ch with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 19 Nov 2008 19:49:31 +0000 Sender: kvm-owner@vger.kernel.org List-ID: On Wed, 19 Nov 2008 12:26:41 -0600, 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. this was it. cache=writeback and the throughput goes from 10mb/s to 80/mb/ s with if=scsi thanks. - Thomas