From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Thu, 22 Mar 2012 09:52:42 +0100 Message-ID: <4F6AE85A.1080409@dlh.net> References: <20120222163356.GE26955@nfs-rbx.ovh.net> <4F6A1056.1020904@dlh.net> <20120322075345.GA22368@redhat.com> <201203221048.59643.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]:53926 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755708Ab2CVIwn (ORCPT ); Thu, 22 Mar 2012 04:52:43 -0400 In-Reply-To: <201203221048.59643.vrozenfe@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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? What do the others think, would it be feasible to make a proper in-kernel pmtimer solution in the meantime. I think Windows guest performance is very important for the success of KVM. Peter >>> peter >>> >>>> David. >>>> >>>> -- >>>> 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 >> -- >> Gleb.