From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jambunathan K Subject: PCI Passthrough & iperf Throughput Skew Date: Tue, 27 Mar 2007 20:05:38 +0530 Message-ID: <46092BBA.6000105@netxen.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com Cc: Sanjeev Jorapur List-Id: xen-devel@lists.xenproject.org I am seeing a strange behaviour with Xen-3.0.4 which seems to suggest that Dom0 has either higher Scheduling affinity or Interrupt affinity. I am in the initial stages of investigation and it is possible that my hunch is totally wrong. I would like to hear comments or questions from the experts. I have a multifunction NIC card, with one function being used by Dom0 and another one exported to DomU using PCI passthrough Dom0 and DomU have almost the same memory allocated to each (~1.3G). The ports themselves are operating at the same speed and share the same IRQ. iperf (as a client) is started on Dom0 in the same way as it is started on DomU. iperf results are skewed in favour of Dom0 in the ratio 10:1. Given all other things are similar wouldn't it be normal to expect throughputs in the ratio of 1:1. (ps:- The 2 ports on the Xen machine is connected "point-to-point-wise" to 2 ports on another machine running Linux natively) Regards, Jambunathan K.