From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Feng Wang" Subject: So strange, time becomes skew when VM is running Date: Mon, 22 Oct 2007 17:55:37 +0800 Message-ID: <393046937.11701@ustc.edu.cn> Reply-To: Feng Wang Content-Type: multipart/mixed; boundary="===============1046347658==" To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org --===============1046347658== Content-Type: text/plain When I started up two KVM VMs upon SLES 10 OS based on a multi-core hardware platform and ran some computing-intensive tasks (e.g. SPECjbb2005) within each VM, I found that something confusing me very much. The VM which is first started is running as well as it runs without other VMs, but the system time of the subsequent started one is skew. E.g. VM1 and VM2 are both started at 10:00am, and then I execute the same one computing-intensive task in each VM at nearly same time, i.e. 10:15am. Then you will see that the execution of task in VM2 is much slowly than VM1 (There are enough computing resource for VMs, e.g. the hardware platform have 8 CPUs, and each VM is configured by supporting 1 CPUs). When the task in VM1 is finished, the system times of VM1 and Host are both 10:30am, this means the execution of task needs nearly 15 minutes. But when the task in VM2 is finished, the system time of Host is 10:40am, the system time of VM2 is 10:30am, so the system time of VM2 is slower than the Host's. Why? Additionally, I found that the CPU¡¯s ¡°bogomips¡± feature listed in /proc/cpuinfo of each VM is different. I guess this maybe results from the CPU emulation of QEMU because I found the similar phenomenon when I used KVM VM with the ¡°-no-kvm¡± option. I don¡¯t know if this is the reason for the problems described above, but according to my experiment results I found that the bogomips feature has few relations with the execution performance of VM. I don¡¯t know if this can demonstrate the performance conflict between two VMs, so I need your help. Thank you very much. --===============1046347658== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ --===============1046347658== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ kvm-devel mailing list kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/kvm-devel --===============1046347658==--