From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: Discordant results between UnixBench and nBench Date: Wed, 23 Dec 2009 11:53:15 +0200 Message-ID: <4B31E88B.6020002@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Matthieu Olivier Return-path: Received: from mx1.redhat.com ([209.132.183.28]:4846 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754116AbZLWJxS (ORCPT ); Wed, 23 Dec 2009 04:53:18 -0500 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 12/23/2009 11:43 AM, Matthieu Olivier wrote: > All, > > I am performing a study about KVM. > (Shame on me, I did not check the version of kvm module. All I know is > that I was using the last Red Hat EL 5.4. Anyway). > > I used a DELL server 2950, with: > - 1 processor Xeon L5240 (3 Ghz, 6 Mo cache) > - 8 GB of RAM > - 4 disks SAS 15k in RAID-1 > > I created a procedure consist to launch a benchmark on several > virtual machine at the same time. Each session consist in testing X VM, > where X comes from 1 to 8. With nbench, I collected all results and > extracted an average value of results for each VM. Then, I multiplied > these average values by the number of VM in test, getting one unique > and generic value per session of test. > I did nearly the same with unixbench. > > On the host side, I launched the same tests, except that instead of > running them in separate VM, I just launched several threads at the > same time thanks to a script. > > My main purpose is watching the overhead due to these different > hypervisors, according bechmark results. I am not really in trouble > with KVM itself, but results of my benchmarks: > > -> http://img121.imageshack.us/img121/9279/nbench.png > -> http://img704.imageshack.us/img704/953/unixbench.png > > Indeed, where I have all results growing from 1 VM tested to 8 VM, we > can see the host growing from 1 to 8 VM. which seems good. But KVM > only increases from 1 to 4 VM, and then stays on the same order of > results, without growing anymore. > The situation is inverse on Unixbench, where KVM seems to > follow host's performances. > What does 'top' show for nbench with 8 guests? How about kvm_stat? Are the results different for the 8 guests, or are they all making the same progress? -- error compiling committee.c: too many arguments to function