[netperf-talk] -s parameter doubt

[Frank Schuster]

Ok, but what value is used default for the sender and receiver buffer?
My sysctl on ubuntu 9.10 with kernel 2.6.33 shows:
net.sctp.sctp_mem = 47616	63488	95232
net.sctp.sctp_rmem = 4096	277500	2031616
net.sctp.sctp_wmem = 4096	16384	2031616
this output.

netperf -H 192.168.1.101 -t SCTP_STREAM -l 1
SCTP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 192.168.1.101 (192.168.1.101) port 0 AF_INET
Recv   Send    Send                          
Socket Socket  Message  Elapsed              
Size   Size    Size     Time     Throughput  
bytes  bytes   bytes    secs.    10^6bits/sec  

233016 112640 112640    1.01       85.89

So, the recv socket is ok, because it is to another system and there is in sysctl exactly this value. But the send socket size 112640 Byte (the half is 61320) but I have no value for this in sysctl. How this value will be calculated?

Regards
Frank

> 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
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