From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Mon, 26 Mar 2012 19:00:32 +0200 Message-ID: <4F70A0B0.80309@dlh.net> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <201203221048.59643.vrozenfe@redhat.com> <4F6AE85A.1080409@dlh.net> <201203221138.15413.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]:49749 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932724Ab2CZRAg (ORCPT ); Mon, 26 Mar 2012 13:00:36 -0400 In-Reply-To: <201203221138.15413.vrozenfe@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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-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? Peter