From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: Too much VCPUS makes domU high CPU utiliazation Date: Thu, 19 May 2011 17:21:12 +0100 Message-ID: <1305822072.21026.8514.camel@elijah> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: MaoXiaoyun Cc: George Dunlap , xen devel List-Id: xen-devel@lists.xenproject.org This happens only during boot, is that right? It sounds like maybe Linux is trying to use some kind of barrier synchronization and failing because it's having a hard time getting all 16 vcpus to run at once. If that's the case, I think it's pretty much a Linux kernel issue; not sure what the hypervisor can do about it. -George On Wed, 2011-05-18 at 17:19 +0100, MaoXiaoyun wrote: > HI: > > I have a host with 16 physical CPUS. Dom0 has 4 VCPUS. > > When only start a domU-A(windows 2003 x86 64rc 2) with 16 VCPUS, > it starts quickly and eveything is fine. > > But if I first start domU-B, which has 2VCPUS, domU-C 4VCPUS, and > domU-D 8 VCPUS, later I start DomUA again, > (so we have total 34 VCPUS, plus dom0), it will takes very long time > for domU-A to start ,and during the start, its CPU > utilizaiton is around 800% from xm top, after its start, it response > very slow in VNC, ans CPU utiliazation keeps high. > And right after I destoy other 3 domUs, domUA CPU drops to normal. > > It might relate to CPU schedule, btw, my xen is 4.0.1. > > Any comments? > >