From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Tue, 27 Mar 2012 11:26:29 +0200 Message-ID: <4F7187C5.4080607@dlh.net> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203262211.44284.vrozenfe@redhat.com> <20120327085604.GQ22368@redhat.com> <201203271123.33524.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]:47084 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757611Ab2C0J0b (ORCPT ); Tue, 27 Mar 2012 05:26:31 -0400 In-Reply-To: <201203271123.33524.vrozenfe@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 27.03.2012 11:23, Vadim Rozenfeld wrote: > On Tuesday, March 27, 2012 10:56:05 AM Gleb Natapov wrote: >> On Mon, Mar 26, 2012 at 10:11:43PM +0200, Vadim Rozenfeld wrote: >>> 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-cp >>>>>>>>>>>>>> u.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%28 >>>>>> v=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. >> To clarify the thing that microsoft qpc uses is what is implemented by >> the patch Vadim attached to his previous email. But I believe that >> additional qemu patch is needed for Windows to actually use it. > You are right. > bits 1 and 9 must be set to on in leaf 0x40000003 and HPET > should be completely removed from ACPI. could you advise how to do this and/or make a patch? the stuff you send yesterday is for qemu, right? would it be possible to use it in qemu-kvm also? peter >> -- >> Gleb.