From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH 4/5] kvm: qemu: Use vringfd to eliminate copies Date: Mon, 16 Jun 2008 12:10:57 +1000 Message-ID: <200806161210.57926.rusty@rustcorp.com.au> References: <1213365481-23460-1-git-send-email-markmc@redhat.com> <1213365481-23460-5-git-send-email-markmc@redhat.com> <48545422.1040109@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Mark McLoughlin , Avi Kivity , kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from ozlabs.org ([203.10.76.45]:35462 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751267AbYFPDOl (ORCPT ); Sun, 15 Jun 2008 23:14:41 -0400 In-Reply-To: <48545422.1040109@us.ibm.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Sunday 15 June 2008 09:28:34 Anthony Liguori wrote: > Have you benchmarked the driver? I wasn't seeing great performance > myself although I think that was due to some bugs in the vringfd code. Yeah, every time I get close to benchmarking I find another bug :( But I've spent some time optimising the normal lguest net device, so we'll have a fair comparison. In theory vringfd will get us zero copy from guest sendfile out to external machines. For anything else we're doing a copy anyway, so avoiding copying has no great benefit. The interface is still worthwhile to provide zero-copy receive on intelligent or bound NICs, but that's science fiction at the moment... Cheers, Rusty.