From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: SMP/DRBVD issues ... Date: Sun, 06 Dec 2009 14:35:05 +0200 Message-ID: <4B1BA4F9.9020006@redhat.com> References: <11227160.23151260098914825.JavaMail.root@zimbra> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Gareth Bult Return-path: Received: from mx1.redhat.com ([209.132.183.28]:61862 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753971AbZLFMfs (ORCPT ); Sun, 6 Dec 2009 07:35:48 -0500 In-Reply-To: <11227160.23151260098914825.JavaMail.root@zimbra> Sender: kvm-owner@vger.kernel.org List-ID: On 12/06/2009 01:28 PM, Gareth Bult wrote: > Hi, > > Specific example of SMP slowdowns; > > Two hosts (A), (B) running Ubuntu 9.10. > One guest on (B) running Ubuntu 9.10 on two cores. > > VPN connection (OpenVPN) between host (A) and Guest. > Copy file over VPN from host (A) to Guest over VPN. > > Copy seems slow. > > Guest CPU usage is around 25% using "top" inside guest. > Host A usage is minimal (5-10%). > Host B CPU usage is around 160%. > > I'm expecting Host (B) usage to be ~ 30% ish - this is a huge discrepancy. > > I'm also noticing during lots of disk/network IO (virtio driver) whereas client / VM load averages tend to be up around the 1.0 mark, looking at the host the load average is showing 10+. (not a specific problem, but curious and concerning) > > In real terms, if I do a raw copy (not via the VPN, so it's all IO and no CPU) the copy (scp) runs through at around 40Mb/sec. Via the VPN, I'm getting ~ 6Mb/sec. If I reduce the VM to 1 core, I get 12Mb/sec .. so doubling the cores on the VM halves the speed! > > Is the time reported on the host user time or system time? Please post a kvm_stat report when the slowdown occurs. -- error compiling committee.c: too many arguments to function