From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758905Ab0CMIVT (ORCPT ); Sat, 13 Mar 2010 03:21:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758877Ab0CMIVR (ORCPT ); Sat, 13 Mar 2010 03:21:17 -0500 Message-ID: <4B9B4AF4.60306@redhat.com> Date: Sat, 13 Mar 2010 10:21:08 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 MIME-Version: 1.0 To: =?UTF-8?B?T3phbiDDh2HEn2xheWFu?= CC: Jeremy Fitzhardinge , "linux-kernel@vger.kernel.org" Subject: Re: Poor KVM guest performance on an HP rack server References: <4B243B2B.806@pardus.org.tr> <4B24856A.4020507@goop.org> <4B24BE17.805@pardus.org.tr> <4B2532A0.2070001@goop.org> <4B9A775D.5070303@pardus.org.tr> In-Reply-To: <4B9A775D.5070303@pardus.org.tr> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/12/2010 07:18 PM, Ozan Çağlayan wrote: > Jeremy Fitzhardinge wrote: > >> On 12/13/09 02:12, Ozan Çağlayan wrote: >> >>> Hmm, that's because we're using/developing a Linux distribution which >>> doesn't have 64-bit support yet. But since the guest will be a >>> compile-farm for our needs, it's worth trying to run an 64-bit distro on >>> the host to see the difference, thanks for the tip but how much should >>> this affect the performance? >>> >> 32-bit PAE is marginal above 4G of memory and the limit is at about 8G. >> Above that, so much lowmem (<~1GB) is occupied by page and other kernel >> structures that there's barely any memory to do any real work. If this >> is what's happening, you'd expect to see poor host performance, and slow >> guest performance would be secondary to that. >> > Updates on the issue after 3 months: > ------------------------------------ > > The host is now running an x86_64 2.6.32.9 kernel with kvm-2.6.32.7 built as an external module. > The guest is 32-bit 2.6.32.9. > You're running an old kvm on a new kernel. It's simpler and better to run the kvm that came with 2.6.32.9. > I've booted the guest with -smp 4 -m 4096 > > and I'm seeing the same slowness that I've mentioned in this thread during CUPS configuration. > I'll try to send kvm_stat output in this week and try the same configure on another guest OS to see if it differs or not. > > I'm also thinking to build an optimized 2.6.33 for that rack server to see if things get better or not. > Better to find out what's wrong first and build kernels later. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.