From mboxrd@z Thu Jan 1 00:00:00 1970 From: Reeted Subject: Re: [Qemu-devel] virtio-blk performance regression and qemu-kvm Date: Tue, 06 Mar 2012 23:07:40 +0100 Message-ID: <4F568AAC.6060206@shiftmail.org> References: <20120210143639.GA17883@gmail.com> <4F54E620.8060400@tuxadero.com> <4F54ED84.7030601@tuxadero.com> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org To: Stefan Hajnoczi , Martin Mailand , Dongsu Park Return-path: Received: from blade3.isti.cnr.it ([194.119.192.19]:2474 "EHLO blade3.isti.cnr.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754648Ab2CFWHb (ORCPT ); Tue, 6 Mar 2012 17:07:31 -0500 Received: from [10.0.55.100] ([94.36.81.210]) by mx.isti.cnr.it (PMDF V6.5-x6 #31988) with ESMTPSA id <01OCT9K8FFD4KUGT11@mx.isti.cnr.it> for kvm@vger.kernel.org; Tue, 06 Mar 2012 23:07:16 +0100 (MET) In-reply-to: Sender: kvm-owner@vger.kernel.org List-ID: On 03/06/12 13:59, Stefan Hajnoczi wrote: > On Mon, Mar 5, 2012 at 4:44 PM, Martin Mailand wrote: >> Am 05.03.2012 17:35, schrieb Stefan Hajnoczi: >> >>>> 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 >>> Interesting finding. Did you show the 0.14.1 results with >>> "performance" governor? >> >> >> Hi Stefan, >> all results are with "ondemand" except the one where I changed it to >> "performance" >> >> Do you want a v0.14.1 test with the governor on "performance"? > Yes, the reason why that would be interesting is because it allows us > to put the performance gain with master+"performance" into > perspective. We could see how much of a change we get. Me too, I would be interested in seeing 0.14.1 being tested with performance governor so to compare it to master with performance governor, to make sure that this is not a regression. BTW, I'll take the opportunity to say that 15.8 or 20.3 k IOPS are very low figures compared to what I'd instinctively expect from a paravirtualized block driver. There are now PCIe SSD cards that do 240 k IOPS (e.g. "OCZ RevoDrive 3 x2 max iops") which is 12-15 times higher, for something that has to go through a real driver and a real PCI-express bus, and can't use zero-copy techniques. The IOPS we can give to a VM is currently less than half that of a single SSD SATA drive (60 k IOPS or so, these days). That's why I consider this topic of virtio-blk performances very important. I hope there can be improvements in this sector... Thanks for your time R.