From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vadim Rozenfeld Subject: Re: performance trouble Date: Mon, 26 Mar 2012 22:11:43 +0200 Message-ID: <201203262211.44284.vrozenfe@redhat.com> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203262036.13472.vrozenfe@redhat.com> <4F70BB7A.7080808@dlh.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , David Cure , Avi Kivity , kvm@vger.kernel.org To: Peter Lieven Return-path: Received: from mx1.redhat.com ([209.132.183.28]:30875 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755851Ab2CZULw (ORCPT ); Mon, 26 Mar 2012 16:11:52 -0400 In-Reply-To: <4F70BB7A.7080808@dlh.net> Sender: kvm-owner@vger.kernel.org List-ID: On Monday, March 26, 2012 08:54:50 PM Peter Lieven wrote: > On 26.03.2012 20:36, Vadim Rozenfeld wrote: > > On Monday, March 26, 2012 07:52:49 PM Gleb Natapov wrote: > >> 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.tx > >>>>>>>>>> t.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 > > > > This one is pretty simple to support. Please see attachments for more > > details. I was thinking about synthetic timers > > http://msdn.microsoft.com/en- > > us/library/windows/hardware/ff542758(v=vs.85).aspx > > is this what microsoft qpc uses as clocksource in hyper-v? Yes, it should be enough for Win7 / W2K8R2. Cheers, Vadim. > i will check tomorrow. > > thanks > vadim > > >> -- > >> > >> Gleb.