From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43410) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4vQw-00022P-9d for qemu-devel@nongnu.org; Tue, 06 Mar 2012 09:32:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S4vQu-0006Sk-Fr for qemu-devel@nongnu.org; Tue, 06 Mar 2012 09:32:09 -0500 Received: from mail-ee0-f45.google.com ([74.125.83.45]:61047) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4vQu-0006SN-9e for qemu-devel@nongnu.org; Tue, 06 Mar 2012 09:32:08 -0500 Received: by eeit10 with SMTP id t10so2212029eei.4 for ; Tue, 06 Mar 2012 06:32:05 -0800 (PST) Date: Tue, 6 Mar 2012 15:32:00 +0100 From: Dongsu Park Message-ID: <20120306143200.GB4053@gmail.com> References: <20120210143639.GA17883@gmail.com> <4F54E620.8060400@tuxadero.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4F54E620.8060400@tuxadero.com> Subject: Re: [Qemu-devel] virtio-blk performance regression and qemu-kvm List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Martin Mailand Cc: stefanha@gmail.com, qemu-devel@nongnu.org, kvm@vger.kernel.org Hi Martin, On 05.03.2012 17:13, Martin Mailand wrote: > 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? Yes, I can confirm that. I just tested with different CPU governor configs, "ondemand" and "performance". (qemu-kvm 1.0, AMD Phenom II X4 955) The result is more or less like yours. Bandwidth with "performance" gets more than 100% better than that with "ondemand". That looks definitely one of the reasons of regressions I experienced. Actually I had always tested with "ondemand", which I haven't noticed. Good catch, thanks! Dongsu > 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