From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Tue, 27 Mar 2012 14:28:04 +0200 Message-ID: <4F71B254.807@dlh.net> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203262211.44284.vrozenfe@redhat.com> <20120327085604.GQ22368@redhat.com> <201203271123.33524.vrozenfe@redhat.com> <4F7187C5.4080607@dlh.net> <20120327100034.GT22368@redhat.com> <4F71B087.8060008@dlh.net> <20120327122645.GW22368@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Vadim Rozenfeld , David Cure , Avi Kivity , kvm@vger.kernel.org To: Gleb Natapov Return-path: Received: from ssl.dlh.net ([91.198.192.8]:48640 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752132Ab2C0M2G (ORCPT ); Tue, 27 Mar 2012 08:28:06 -0400 In-Reply-To: <20120327122645.GW22368@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 27.03.2012 14:26, Gleb Natapov wrote: > On Tue, Mar 27, 2012 at 02:20:23PM +0200, Peter Lieven wrote: >> On 27.03.2012 12:00, Gleb Natapov wrote: >>> On Tue, Mar 27, 2012 at 11:26:29AM +0200, Peter Lieven wrote: >>>> 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? >>>> >>> No, they are for kernel. >> i meant the qemu.diff file. >> > Yes, I missed the second attachment. > >> if i understand correctly i have to pass -cpu host,+hv_refcnt to qemu? >> > Looks like it. ok, so it would be interesting if it helps to avoid the pmtimer reads we observed earlier. right? peter > -- > Gleb. > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html