From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: performance trouble Date: Mon, 26 Mar 2012 19:52:49 +0200 Message-ID: <20120326175249.GA18465@redhat.com> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203221138.15413.vrozenfe@redhat.com> <4F70A0B0.80309@dlh.net> <201203261946.03417.vrozenfe@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Lieven , David Cure , Avi Kivity , kvm@vger.kernel.org To: Vadim Rozenfeld Return-path: Received: from mx1.redhat.com ([209.132.183.28]:4950 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933184Ab2CZRw7 (ORCPT ); Mon, 26 Mar 2012 13:52:59 -0400 Content-Disposition: inline In-Reply-To: <201203261946.03417.vrozenfe@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Mar 26, 2012 at 07:46:03PM +0200, Vadim Rozenfeld wrote: > On Monday, March 26, 2012 07:00:32 PM Peter Lieven wrote: > > On 22.03.2012 10:38, Vadim Rozenfeld wrote: > > > On Thursday, March 22, 2012 10:52:42 AM Peter Lieven wrote: > > >> On 22.03.2012 09:48, Vadim Rozenfeld wrote: > > >>> On Thursday, March 22, 2012 09:53:45 AM Gleb Natapov wrote: > > >>>> On Wed, Mar 21, 2012 at 06:31:02PM +0100, Peter Lieven wrote: > > >>>>> On 21.03.2012 12:10, David Cure wrote: > > >>>>>> hello, > > >>>>>> > > >>>>>> Le Tue, Mar 20, 2012 at 02:38:22PM +0200, Gleb Natapov ecrivait : > > >>>>>>> Try to add to cpu > > >>>>>>> definition in XML and check command line. > > >>>>>>> > > >>>>>> ok I try this but I can't use to map the host cpu > > >>>>>> > > >>>>>> (my libvirt is 0.9.8) so I use : > > >>>>>> > > >>>>>> > > >>>>>> Opteron_G3 > > >>>>>> > > >>>>>> > > >>>>>> > > >>>>>> > > >>>>>> (the physical server use Opteron CPU). > > >>>>>> > > >>>>>> The log is here : > > >>>>>> http://www.roullier.net/Report/report-3.2-vhost-net-1vcpu-cpu.txt.gz > > >>>>>> > > >>>>>> And now with only 1 vcpu, the response time is 8.5s, great > > >>>>>> > > >>>>>> improvment. We keep this configuration for production : we check the > > >>>>>> response time when some other users are connected. > > >>>>> > > >>>>> please keep in mind, that setting -hypervisor, disabling hpet and > > >>>>> only one vcpu > > >>>>> makes windows use tsc as clocksource. you have to make sure, that > > >>>>> your vm is not switching between physical sockets on your system and > > >>>>> that you have constant_tsc feature to have a stable tsc between the > > >>>>> cores in the same socket. its also likely that the vm will crash > > >>>>> when live migrated. > > >>>> > > >>>> All true. I asked to try -hypervisor only to verify where we loose > > >>>> performance. Since you get good result with it frequent access to PM > > >>>> timer is probably the reason. I do not recommend using -hypervisor for > > >>>> production! > > >>>> > > >>>>> @gleb: do you know whats the state of in-kernel hyper-v timers? > > >>>> > > >>>> Vadim is working on it. I'll let him answer. > > >>> > > >>> It would be nice to have synthetic timers supported. But, at the > > >>> moment, I'm only researching this feature. > > >> > > >> So it will take months at least? > > > > > > I would say weeks. > > > > Is there a way, we could contribute and help you with this? > Hi Peter, > You are welcome to add an appropriate handler. I think Vadim refers to this HV MSR http://msdn.microsoft.com/en-us/library/windows/hardware/ff542633%28v=vs.85%29.aspx -- Gleb.