[netperf-talk] -s parameter doubt

[Rick Jones]

Otavio Augusto wrote:
> I was reading and test some netperf parameters and I'm doubt with the 
> '-s' or -S'.
> 
> Example:
>  netperf -H 127.0.0.1 -l 2 -- -s 10k -S 10k
> TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 127.0.0.1 
> (127.0.0.1) port 0 AF_INET
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
>  20000  20000  20000    2.00     1977.44
> 
> 
> Why it used the double? I set 10k but it use 20k?
> 
> Thank You.

Linux exposes the "overhead" for the socket buffer not just the actual 
byte count.  So, up to the limit of a couple sysctls, you will see a 
getsockopt() call return 2X what the setsockopt() call requested.  In 
other words, that is a "feature" of linux and is not being done by netperf.

happy benchmarking,

rick jones