[netperf-talk] Netperf Doc about internal processes and UDP packet loss

[Rick Jones]

cmanko at mpifr-bonn.mpg.de wrote:
> Hello,
> 
> I am writing my final thesis about a 10Gbit/s Ethernet connection. I have two 
> identical PCs each with a Myricon 10GBASE SR NIC. I am trying to optimize the 
> connection for a special project.
> 
> 1. Does a documentation exist about the exact function of netperf (internal 
> processes, data generation, memory usage and so on)? Unfortunately I do not 
> have much time left. And I would appreciate if somebody could spare me 
> studying the netperf source codes. Any doc would help.

There really isn't much written-up about netperf internals.  I suppose 
there are bits and pieces in the manual:

http://www.netperf.org/svn/netperf2/trunk/doc/netperf.html

but there really isn't much there.

> 
> 2. I am using also the UDP_STREAM  test. On the transceiver site, I always get 
> a throughput about 9910 Mbit/s, but on the receiver site I only get a 
> throughput around 8700 Mbit/s.
> I tested different setup and optimized the configurations.
> 
> MSI=1
> WC=1
> wcfifo=0 
> timestamps=0
> interrupt coalescing=75us
> 
> command: netperf -H host -C -c -l 60 -t UDP_STREAM -- -m 8972 -s 1M -S 1M
> 
> Has somebody an explanation for the packet loss?

99 times out of ten that would be UDP socket buffer overflow on the 
reciever.  It can/will happen even with 1M socket buffers.  UDP as I 
suspect you know has no flow-control, and netperf does not add any of 
its own - unless :)  you configure --enable-intervals, at which point 
you get two new options -  -b and -w for burst size and interburst interval.

hth,

rick jones

> Thank you very much!!
> 
> Christian Manko
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