From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: Dom0 cpu utilisation irregularly distributed Date: Wed, 05 Oct 2011 13:41:52 -0700 Message-ID: <4E8CC110.4010305@goop.org> References: <1317824534750-4872878.post@n5.nabble.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1317824534750-4872878.post@n5.nabble.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Fantu Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 10/05/2011 07:22 AM, Fantu wrote: > On some production servers with dom0 kernel 2.6.32 pvops and xen 4.0 and > domus mainly windows with gplpv I noticed a strange cpu usage by the dom0 > mainly with the use of a single cpu, for example this take from one server: > xm vcpu-list > Name ID VCPU CPU State Time(s) CPU > Affinity > ... > Domain-0 0 0 3 -b- 1043377.5 any cpu > Domain-0 0 1 2 r-- 122083.9 any cpu > Domain-0 0 2 0 -b- 284636.1 any cpu > Domain-0 0 3 1 -b- 80772.9 any cpu > ... > Note the increased utilisation on the vcpu 0 > > Domus cpu utilisation apparently successfully distributed but the dom0 has > always use more of its vcpu 0 > Is this correct or there are bugs on kernel and/or xen? VCPU use is entirely up to the guest kernels. I suspect that cpu0 gets heavier loading because there are a number of things which end up running on cpu 0 by default, such as some kernel threads and interrupts. You can try playing with interrupt migration on dom0 if you like. But balanced CPU use isn't necessarily a good thing. The kernel will generally avoid migrating processes between CPUs needlessly, so unless you're actually starved for CPU time, I would expect some VCPUs to be underused compared to others. It probably just means you've configured dom0 with too many VCPUs. J