From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: virtio performance issue Date: Tue, 16 Sep 2008 09:16:38 -0500 Message-ID: <48CFBFC6.4040405@us.ibm.com> References: <1221574441.26630.19.camel@cluwyn.haifa.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, markmc@redhat.com, Muli Ben-Yehuda To: Ben-Ami Yassour Return-path: Received: from e1.ny.us.ibm.com ([32.97.182.141]:42243 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756006AbYIPORp (ORCPT ); Tue, 16 Sep 2008 10:17:45 -0400 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e1.ny.us.ibm.com (8.13.8/8.13.8) with ESMTP id m8GEHgHv015432 for ; Tue, 16 Sep 2008 10:17:42 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m8GEHgWX194096 for ; Tue, 16 Sep 2008 10:17:42 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m8GEHejb005140 for ; Tue, 16 Sep 2008 10:17:41 -0400 In-Reply-To: <1221574441.26630.19.camel@cluwyn.haifa.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: Ben-Ami Yassour wrote: > I am running virtio with the latest KVM code, and see a significant > performance issue. > > Ping to the host (or any other close machine) reports a 4ms delay. > What kvm version and what host kernel version? It's very easy to mistakenly compile qemu without GSO support too. You have to make sure that the 2.6.27 if_tun.h is being included by QEMU. Regards, Anthony Liguori > In the same setup with an e1000 emulation (just changing model=virtio to > model=e1000 in the KVM command line), ping reports 0.177ms delay. > > BTW, initially I saw that the throughput when using netperf is very low, > even from guest to host, even though the CPU utilization is low. > > What might be the problem? > > Thanks, > Ben > >