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-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
> 
> --
> 			Gleb.