On Fri, 28 Feb 2003, Chris Friesen wrote: > 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. > Did you also measure throughput? You are overlooking the flexibility that already exists in IP based transports as an advantage; the fact that you can make them distributed instead of localized with a simple addressing change is a very powerful abstraction. > 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. I think you may have something misconfigured. > From > userspace, multicast unix would be *simple* to use, as in totally > transparent. > You could implement the abstraction in user space as a library today by having some server that muxes to several registered clients. > 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. > So whats the addressing scheme for multicast unix? Would it be a reserved path? I am actually indifferent: You could do this in user space for starters. See if it buys you anything. Maybe you could do somethign clever with passing unix file descriptors around to avoid a single server point of failure etc. > Do we agree at least that some form of multicast is the logical solution > to the case of one sender/many listeners? > Thats what mcast definition is. You need to weigh your options; cost is probably worth the flexibility you get with sockets. cheers, jamal - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
