From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:50177) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Qlenw-0000mM-Md for qemu-devel@nongnu.org; Tue, 26 Jul 2011 06:24:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Qlenv-00057a-Fi for qemu-devel@nongnu.org; Tue, 26 Jul 2011 06:24:00 -0400 Received: from cantor2.suse.de ([195.135.220.15]:51055 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Qlenv-00057T-B5 for qemu-devel@nongnu.org; Tue, 26 Jul 2011 06:23:59 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.221.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx2.suse.de (Postfix) with ESMTP id 629568F0D1 for ; Tue, 26 Jul 2011 12:23:58 +0200 (CEST) Message-ID: <4E2E95BE.2070005@suse.de> Date: Tue, 26 Jul 2011 12:23:58 +0200 From: Hannes Reinecke MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] idea: non-ethernet paravirtual network device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On 07/26/2011 08:04 AM, Stefan Hajnoczi wrote: > On Mon, Jul 25, 2011 at 4:53 PM, Sassan Panahinejad wrote: >> Here's a thought, could we improve network performance by creating a >> paravirtual network device which doesn't emulate ethernet? It shouldn'= t be >> too hard to just whack IP packets pretty much directly over a virtio l= ink. >> This should improve performance when using a "user" host connection an= d we >> could introduce a tun host connection instead of tap for this setup. >> >> Does anyone have any thoughts on how worthwhile this would be? Would t= he >> performance improvement justify the effort involved? > > My guess is no noticable impact (if you ignore ARP requests). > > The Ethernet header is only 14 bytes or so. We don't calculate any > checksums at that level. There's probably not much of a win. > Only lots of pain to be had. Mainframe used to do this. But abandoned it not, thankfully. Problem is that you need to patch each and every tool looking at the=20 packets to _not_ expecting an Ethernet header. And patching up DHCP is _not_ trivial. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)