From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Mailand Subject: Re: virtio-blk performance regression and qemu-kvm Date: Mon, 05 Mar 2012 17:13:20 +0100 Message-ID: <4F54E620.8060400@tuxadero.com> References: <20120210143639.GA17883@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, stefanha@gmail.com To: Dongsu Park Return-path: Received: from einhorn.in-berlin.de ([192.109.42.8]:57011 "EHLO einhorn.in-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754438Ab2CEQNc (ORCPT ); Mon, 5 Mar 2012 11:13:32 -0500 In-Reply-To: <20120210143639.GA17883@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: Am 10.02.2012 15:36, schrieb Dongsu Park: > 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. Hi, I think I found the problem, there is no regression in the code. I think the problem is, that qmeu-kvm with the IO-Thread enabled doesn't produce enough cpu load to get the core to a higher cpu frequency, because the load is distributed to two threads. If I change the cpu governor to "performance" the result from the master branch is better than from the v0.14.1 branch. I get the same results on a serversystem without powermanagment activated. @Dongsu Could you confirm those findings? 1. Test on i7 Laptop with Cpu governor "ondemand". v0.14.1 bw=63492KB/s iops=15873 bw=63221KB/s iops=15805 v1.0 bw=36696KB/s iops=9173 bw=37404KB/s iops=9350 master bw=36396KB/s iops=9099 bw=34182KB/s iops=8545 Change the Cpu governor to "performance" master bw=81756KB/s iops=20393 bw=81453KB/s iops=20257 2. Test on AMD Istanbul without powermanagement activated. v0.14.1 bw=53167KB/s iops=13291 bw=61386KB/s iops=15346 v1.0 bw=43599KB/s iops=10899 bw=46288KB/s iops=11572 master bw=60678KB/s iops=15169 bw=62733KB/s iops=15683 -martin