From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Mon, 26 Mar 2012 20:54:50 +0200 Message-ID: <4F70BB7A.7080808@dlh.net> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203261946.03417.vrozenfe@redhat.com> <20120326175249.GA18465@redhat.com> <201203262036.13472.vrozenfe@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , David Cure , Avi Kivity , kvm@vger.kernel.org To: Vadim Rozenfeld Return-path: Received: from ssl.dlh.net ([91.198.192.8]:33861 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932749Ab2CZSyx (ORCPT ); Mon, 26 Mar 2012 14:54:53 -0400 In-Reply-To: <201203262036.13472.vrozenfe@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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? i will check tomorrow. thanks vadim >> -- >> Gleb.