Re: performance trouble

[Peter Lieven <pl@dlh.net>]

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<feature policy='disable' name='hypervisor'/>
>>>>>>>>>>>>>>> to cpu definition in XML and check command line.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>> 	ok I try this but I can't use<cpu model>      to map the
>>>>>>>>>>>>>> 	host cpu
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> (my libvirt is 0.9.8) so I use :
>>>>>>>>>>>>>>       <cpu match='exact'>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>         <model>Opteron_G3</model>
>>>>>>>>>>>>>>         <feature policy='disable' name='hypervisor'/>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>       </cpu>
>>>>>>>>>>>>>> 	
>>>>>>>>>>>>>> 	(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.