From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Lieven Subject: Re: performance trouble Date: Thu, 22 Mar 2012 09:50:59 +0100 Message-ID: <4F6AE7F3.8020100@dlh.net> References: <20120223083807.GA17505@redhat.com> <20120316101331.GM12293@nfs-rbx.ovh.net> <20120319105134.GA27928@redhat.com> <20120320093220.GS12293@nfs-rbx.ovh.net> <20120320094541.GH22368@redhat.com> <20120320111839.GT12293@nfs-rbx.ovh.net> <20120320123821.GL22368@redhat.com> <20120321111001.GV12293@nfs-rbx.ovh.net> <4F6A1056.1020904@dlh.net> <20120322075345.GA22368@redhat.com> <20120322083357.GX12293@nfs-rbx.ovh.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Avi Kivity , kvm@vger.kernel.org, Vadim Rozenfeld To: David Cure Return-path: Received: from ssl.dlh.net ([91.198.192.8]:42919 "EHLO ssl.dlh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030929Ab2CVIvE (ORCPT ); Thu, 22 Mar 2012 04:51:04 -0400 In-Reply-To: <20120322083357.GX12293@nfs-rbx.ovh.net> Sender: kvm-owner@vger.kernel.org List-ID: On 22.03.2012 09:33, David Cure wrote: > Le Thu, Mar 22, 2012 at 09:53:45AM +0200, Gleb Natapov ecrivait : >> 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! > so if I leave cpu as previous (not defined) and only disable > hpet and use 1 vcpu, it's ok for production ? this is ok, but windows will use pm timer so you will have bad performance. > Is there a workaround for this PM access ? there exists old patches from 2010 for in-kernel pmtimer. they work, but only partly. problem here is windows enables the pmtimer overflow interrupt which this patch did not address (amongst other things). i simply ignored it and windows ran nevertheless. but i would not do this in production because i do not know which side effects it might have. there are to possible solutions: a) a real in-kernel pmtimer implementation (which does also help other systems not only windows) b) hyper-v support in-kernel at least partly (for the timing stuff). this is being worked on by Vadim. Peter > David. >