From mboxrd@z Thu Jan 1 00:00:00 1970 From: Farkas Levente Subject: Re: Benchmarking on CentOS 5 Date: Wed, 28 May 2008 22:27:08 +0200 Message-ID: <483DC01C.5090603@bppiac.hu> References: <483D9AE5.6040509@cs.ualberta.ca> <20080528183352.GE8086@duo.random> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Cam Macdonell , kvm@vger.kernel.org To: Andrea Arcangeli Return-path: Received: from portal.bppiac.hu ([213.253.216.130]:46737 "EHLO portal.bppiac.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752655AbYE1U1K (ORCPT ); Wed, 28 May 2008 16:27:10 -0400 In-Reply-To: <20080528183352.GE8086@duo.random> Sender: kvm-owner@vger.kernel.org List-ID: Andrea Arcangeli wrote: > On Wed, May 28, 2008 at 11:48:21AM -0600, Cam Macdonell wrote: >> Hi, >> >> I wanted to some benchmarking on a CentOS 5 host. However, the warning in >> dmesg about preempt notifiers indicates I shouldn't benchmark. Is there a >> workaround (aside from updating the kernel) that handles the issue? > > The problem is that the preempt notifier emulation through hardware > breakpoints is worse at optimizing lightweight vm exists than the real > preempt notifiers supported by recent kernels. If you benchmark > without upgrading the kernel, it has to be clear it is running slower > than it would on a recent optimized host kernel. If you decide to > upgrade and compile the host kernel yourself, you need to configure it > with CONFIG_KVM=m to be sure the preempt notifiers are enabled in the > host kernel and in turn the printk will go away. ok. so what is qumranet recommendation? the just released latest rhel 5.2 kernel is kernel-2.6.18-92.el5 is it good enough for kvm host os? or its' better to change some other distro eg: fedora 9? until now we try to use the latest rhel/centos on all of our servers while we use fedora (currently 8 but may be upgrade in a few weeks if 9 become stable) on desktops. but now it seems probably then for a kvm host rhel/centos is not enough:-( -- Levente "Si vis pacem para bellum!"