From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: slow guest performance with build load, looking for ideas Date: Sun, 14 Jun 2009 12:33:06 +0300 Message-ID: <4A34C3D2.9020009@redhat.com> References: <20090612210443.GA21840@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Erik Jacobson Return-path: Received: from mx2.redhat.com ([66.187.237.31]:33328 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752084AbZFNJdH (ORCPT ); Sun, 14 Jun 2009 05:33:07 -0400 In-Reply-To: <20090612210443.GA21840@sgi.com> Sender: kvm-owner@vger.kernel.org List-ID: Erik Jacobson wrote: > We have been trying to test qemu-kvm virtual machines under an IO load. > The IO load is quite simple: A timed build of the linux kernel and modules. > I have found that virtual machines take more than twice as long to do this > build as the host. It doesn't seem to matter if I use virtio or not, Using > the same device and same filesystem, the host is more than twice as fast. > > We're hoping that we can get some advice on how to address this issue. If > there are any options I should add for our testing, we'd appreciate it. I'm > also game to try development bits to see if they make a difference. If it > turns out "that is just the way it is right now", we'd like to know that > too. > > For these tests, I used Fedora 11 as the virtualization server. I did this > because it has recent bits. I experimented with SLES11 and Fedora11 guests. > > In general, I used virt-manager to do the setup and launching. So the > qemu-kvm command lines are based on that (and this explains why they are > a bit long). I then modified the qemu-kvm command line to perform other > variations of the test. Example command lines can be found at the end of > this message. > > I performed tests on two different systems to be sure it isn't related to > specific hardware. > What is the host cpu type? On pre-Nehalem/Barcelona processors kvm has poor scalability in mmu intensive workloads like kernel builds. -- error compiling committee.c: too many arguments to function