Subject: Re: anyone ever done multicast AF_UNIX sockets?

From: Chris Friesen <[email-masked]>
Date: Mon, 03 Mar 2003 16:32:56 -0500

Terje Eggestad wrote:
> On Mon, 2003-03-03 at 19:56, David S. Miller wrote:

>     TCP bandwidth is slightly faster than AF_UNIX bandwidth on my
>     sparc64 boxes for example.
> 
> I've seen that their are the same on linux.I tried to to do AF_UNIX
> instead of AF_INET internally to boost perf, but to no avail. Makes you
> suspect that the loopback device actually create an AF_UNIX connection
> under the hood ;-)

On my P4 1.8GHz, AF_INET vs AF_UNIX looks like this:

*Local* Communication latencies in microseconds - smaller is better
-------------------------------------------------------------
Host           OS 2p/0K  Pipe AF     UDP  RPC/   TCP  RPC/ TCP
                   ctxsw       UNIX         UDP         TCP conn
--------- ------- ----- ----- ---- ----- ----- ----- ----- ----
pcard0ks. 2.4.18- 1.740  10.4 15.9  20.1  33.1  23.5  44.3 72.7
pcard0ks. 2.4.18- 1.560  10.6 16.0  23.4  38.1  36.1  44.6 77.4

*Local* Communication bandwidths in MB/s - bigger is better
-----------------------------------------------------------
Host          OS  Pipe AF    TCP  File   Mmap  Bcopy  Bcopy  Mem   Mem
                        UNIX      reread reread (libc) (hand) read write
--------- ------- ---- ---- ---- ------ ------ ------ ------ ---- -----
pcard0ks. 2.4.18- 650. 677. 151.  721.9  958.0  290.8  288.8 955. 418.4
pcard0ks. 2.4.18- 379. 701. 163.  714.8  949.5  289.5  288.5 956. 420.5

On this machine at least, UDP latency is 25% worse than AF_UNIX, and TCP 
bandwidth is about 22% that of AF_UNIX.

Chris

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