From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [evb] RE: [PATCH][RFC] net/bridge: add basic VEPA support Date: Mon, 10 Aug 2009 21:18:49 +0200 Message-ID: <200908102118.49253.arnd@arndb.de> References: <0199E0D51A61344794750DC57738F58E6D6AE99884@GVW1118EXC.americas.hpqcorp.net> <20090810095118.125fe966@nehalam> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , "Fischer, Anna" , "Paul Congdon \(UC Davis\)" , "evb@yahoogroups.com" , "netdev@vger.kernel.org" , "bridge@lists.linux-foundation.org" , "adobriyan@gmail.com" , "davem@davemloft.net" To: virtualization@lists.linux-foundation.org Return-path: Received: from moutng.kundenserver.de ([212.227.126.188]:63223 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797AbZHJTSy (ORCPT ); Mon, 10 Aug 2009 15:18:54 -0400 In-Reply-To: <20090810095118.125fe966@nehalam> Sender: netdev-owner@vger.kernel.org List-ID: On Monday 10 August 2009, Stephen Hemminger wrote: > On Mon, 10 Aug 2009 16:32:01, "Fischer, Anna" wrote: > > How would this work though, if the OS inside the guest wants to register > > to a particular multicast address? Is this propagated through the backend > > drivers to the macvlan/macvtap interface? > > Sure filtering is better, but multicast performance with large number > of guests is really a corner case, not the real performance issue. Well, right now, qemu does not care at all about this, it essentially leaves the tun device in ALLMULTI state. I should check whether macvtap at this stage can receive multicast frames at all, but if it does, it will get them all ;-). If we want to implement this with kvm, we would have to start with the qemu virtio-net implementation, to move the receive filter into the tap device. With tun/tap that will mean less copying to user space, with macvtap (after implementing TUNSETTXFILTER) we get already pretty far because we no longer need to have the external interface in ALLMULTI state. Once that is in place, we can start thinking about filtering per virtual device. Arnd <><