From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vadim Rozenfeld <vrozenfe@redhat.com>
Subject: Re: performance trouble
Date: Mon, 26 Mar 2012 19:46:03 +0200
Message-ID: <201203261946.03417.vrozenfe@redhat.com>
References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203221138.15413.vrozenfe@redhat.com> <4F70A0B0.80309@dlh.net>
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Cc: Gleb Natapov <gleb@redhat.com>, David Cure <kvm@cure.nom.fr>,
	Avi Kivity <avi@redhat.com>, kvm@vger.kernel.org
To: Peter Lieven <pl@dlh.net>
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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.txt.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.
Best regards,
Vadim.
> 
> Peter