From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Byrne Subject: Direct I/O performance: direct interrupts to running domU? Date: Wed, 15 Nov 2006 18:56:22 -0800 Message-ID: <455BD356.5010206@hp.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 List-Id: xen-devel@lists.xenproject.org Hi, I'm testing performance of a NIC assigned directly to a domU. (xen-3.0.3 x86_64) After your help straightening out the problems with my test environment, my netperf throughput numbers were close to base Linux (generally with 0.5%); however, when I did the netperf transaction tests, the numbers on Xen (either dom0 and domU) were 10-20% lower than the base Linux depending on the test parameters. Since this linear transaction test would be very sensitive to the latency/path-length involved in the interrupt delivery, I'm making the assumption, for the moment, that this is the problem without cranking up xenoprof/oprofile to prove it. One of the questions that came up in a discussion was whether it might be technically possible to have interrupts delivered directly to a running domain without the hypervisor overhead. This would presumably involve some additional overhead at the time the hypervisor switched domains, but it might be a worthwhile trade-off. Thanks, John Byrne