[netperf-talk] Urgent UDP_Stream question

[Andrew Gallatin]

> UDP_STREAM test:
> Socket Size, bytes 	Message Size, bytes 	Elapsed Time, secs 	Messages
> Throughput, 10^6bits/sec
> Okay 	Errors
> 112640 	65507 	60.00 	57408 	0 	501.42
> 112640 		60.00 	94 		0.82

A big part of the problem here is that netperf has been asked
(implicitly) to send 64KB datagrams.  Assuming a standard 1500b
MTU, these will get fragmented into around 40 separate IP
fragments per datagram.  If even just a single fragment is
dropped, then the entire message is lost.


I'd suggest re-trying the test with a datagram size small enough
to fit into the network MTU.  Assuming a 1500b MTU with IPv4,
that will be 1472 (1500 - 20 byte IP header - 8 byte UDP hdr).
So you'd run netperf using the -- -m <message size> argument.  Eg:

netperf -tUDP_STREAM -Hserver -- -m 1472

Note the "--" preceding -m 1472 is required.  You should get a more
accurate picture of how much traffic is making it to the client.

Drew