From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian =?iso-8859-1?q?Borntr=E4ger?= Subject: Re: [PATCH/RFC 8/9] Virtual network host switch support Date: Fri, 11 May 2007 22:50:55 +0200 Message-ID: <200705112250.55801.cborntra@de.ibm.com> References: <1178903957.25135.13.camel@cotte.boeblingen.de.ibm.com> <1178904968.25135.35.camel@cotte.boeblingen.de.ibm.com> <4644D048.7060106@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Martin Schwidefsky To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: In-Reply-To: <4644D048.7060106-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org On Friday 11 May 2007 22:21, Anthony Liguori wrote: > Any feel for the performance relative to the bridging code? The > bridging code is a pretty big bottle neck in guest=>guest communications > in Xen at least. Last time I checked it we had a quite decent guest to guest performance in the gigabits/sec. On the downside the switch is quite aggressive with dropping packages as the inbound buffer of the virtual network adapters has space for 80 packets. (that can be changed) > > > currently tested but not ready yet. We did not use the linux bridging code to > > allow non-root users to create virtual networks between guests. > > > > Is that the primary reason? If so, that seems like a rather large > hammer for something that a userspace suid wrapper could have addressed... Actually there are some reasons why we did not use the bridging code: - One thing is, that a lot of OSA network cards do not support promiscous mode. There is also the issue that a lot of OSA cards are in layer 3 mode (we get IP packets and no ethernet frames) so bridging wont work to the host interface. - non-root switches - the performance of bridging (we copy directly from one guest buffer to another without allocating an skb on the host) - we considered to hook into the qeth driver (for OSA cards) to deal with layer3 mode. The first shot was actually a point-to-point driver (guest netif <--> host netif). We added the switch at a later time. Hmm, if we can make bridging work (with a decent performance) on s390 that would reduce the maintainance work for us as this network switch is far from being complete. cheers Christian ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/