From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dongsu Park Subject: Re: virtio-blk performance regression and qemu-kvm Date: Tue, 21 Feb 2012 17:45:08 +0100 Message-ID: <20120221164508.GB950@gmail.com> References: <20120210143639.GA17883@gmail.com> <87sjifd2sw.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org To: Rusty Russell Return-path: Received: from mail-ey0-f174.google.com ([209.85.215.174]:60222 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719Ab2BUQpO (ORCPT ); Tue, 21 Feb 2012 11:45:14 -0500 Received: by eaah12 with SMTP id h12so2730862eaa.19 for ; Tue, 21 Feb 2012 08:45:12 -0800 (PST) Content-Disposition: inline In-Reply-To: <87sjifd2sw.fsf@rustcorp.com.au> Sender: kvm-owner@vger.kernel.org List-ID: Hi Rusty, On 13.02.2012 10:25, Rusty Russell wrote: > On Fri, 10 Feb 2012 15:36:39 +0100, Dongsu Park wrote: > > Hi, > > > > Recently I observed performance regression regarding virtio-blk, > > especially different IO bandwidths between qemu-kvm 0.14.1 and 1.0. > > So I want to share the benchmark results, and ask you what the reason > > would be. > > Interesting. There are two obvious possibilities here. One is that > qemu has regressed, the other is that virtio_blk has regressed; the new > qemu may negotiate new features. Please do the following in the guest > with old and new qemus: > > cat /sys/class/block/vdb/device/features > > (eg, here that gives: 0010101101100000000000000000100e0). I did that on guest VM, using both qemu-kvm 0.14.1 and 1.0. (cat /sys/class/block/vdb/device/features) using qemu-kvm 0.14.1: 0010101101100000000000000000100000000000000000000000000000000000 using qemu-kvm 1.0: 0010101101100000000000000000110000000000000000000000000000000000 >>From my understanding, both of them have the same virtio features. Please correct me if I'm wrong. Regards, Dongsu