Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 28 Feb 2003 09:29:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 28 Feb 2003 09:29:44 -0500 Received: from zcars04e.nortelnetworks.com ([47.129.242.56]:58065 "EHLO zcars04e.nortelnetworks.com") by vger.kernel.org with ESMTP id ; Fri, 28 Feb 2003 09:29:38 -0500 Message-ID: <3E5F748E.2080605@nortelnetworks.com> Date: Fri, 28 Feb 2003 09:39:10 -0500 X-Sybari-Space: 00000000 00000000 00000000 From: Chris Friesen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.8) Gecko/20020204 X-Accept-Language: en-us MIME-Version: 1.0 To: jamal Cc: linux-kernel@vger.kernel.org, netdev@oss.sgi.com, linux-net@vger.kernel.org Subject: Re: anyone ever done multicast AF_UNIX sockets? References: <3E5E7081.6020704@nortelnetworks.com> <20030228083009.Y53276@shell.cyberus.ca> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3166 Lines: 78 jamal wrote: > > On Thu, 27 Feb 2003, Chris Friesen wrote: >>It is fairly common to want to distribute information between a single >>sender and multiple receivers on a single box. >>Multicast IP sockets are one possibility, but then you have additional >>overhead in the IP stack. > I think this is a _very weak_ reason. > Without addressing any of your other arguements, can you describe what > such painful overhead you are talking about? Did you do any measurements > and under what circumstances are unix sockets vs say localhost bound > udp sockets are different? I am not looking for hand waving reason of > "but theres an IP stack". From lmbench local communication tests: This is a multiproc 1GHz G4 Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP ctxsw UNIX UDP TCP conn --------- ------------- ----- ----- ---- ----- ----- ----- ----- ---- pcary0z0. Linux 2.4.18- 0.600 3.756 6.58 10.2 26.4 13.8 36.9 599K pcary0z0. Linux 2.4.18- 0.590 3.766 6.43 10.1 26.7 13.9 37.2 59.1 This is a 400MHz uniproc G4 Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP ctxsw UNIX UDP TCP conn --------- ------------- ----- ----- ---- ----- ----- ----- ----- ---- zcarm0pd. Linux 2.2.17- 1.710 9.888 21.3 26.4 59.4 43.0 105.4 146. zcarm0pd. Linux 2.2.17- 1.740 9.866 22.2 26.3 60.4 43.1 106.7 147. This is a 1.8GHz P4 Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP ctxsw UNIX UDP TCP conn --------- ------------- ----- ----- ---- ----- ----- ----- ----- ---- pcard0ks. Linux 2.4.18- 1.740 10.4 15.9 20.1 33.1 23.5 44.3 72.7 pcard0ks. Linux 2.4.18- 10.3 16.1 19.8 36.3 22.8 43.6 74.1 pcard0ks. Linux 2.4.18- 1.560 10.6 16.0 23.4 38.1 36.1 44.6 77.4 From these numbers, UDP has 18%-44% higher latency than AF_UNIX, with the difference going up as the machine speed goes up. Aside from that, IP multicast doesn't seem to work properly. I enabled multicast on lo and disabled it on eth0, and a ping to 224.0.0.1 still got responses from all the multicast-capable hosts on the network. From userspace, multicast unix would be *simple* to use, as in totally transparent. The other reason why I would like to see this happen is that it just makes *sense*, at least to me. We've got multicast IP, so multicast unix for local machine access is a logical extension in my books. Do we agree at least that some form of multicast is the logical solution to the case of one sender/many listeners? Thanks for your thoughts, Chris -- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/