[netperf-talk] setting socket size using netperf 2.4.1

[MAHMOUD HANAFI]

So, should I trust the values I passed using the -s and -S options and not use the values reported 
by the output.

-Mahmoud

Rick Jones wrote:
> MAHMOUD HANAFI wrote:
>> When trying to set the send and receive socket size netperf always 
>> doubles it. Is this normal?
> 
> No, it is not normal, and no, it is not netperf doing it.  That is a "we 
> want to be different" linuxism where by what getsockopt() returns is the 
> total overhead limit rather than the "actual byte" limit one sets with 
> setsockopt().  Linux feels compelled to be completely different from all 
> other TCP/IP stacks in this regard.
> 
> As you set the actual byte limit closer and closer to the "soft limits" 
> one can see via sysctl (sysctl -a | grep mem) you will see that it isn't 
> always a doubling.
> 
>>
>> ./netperf -f g -p 32769 -l 10 -H xx.xx.xx.xx -t TCP_STREAM -i 10,2 -I 
>> 99,5 -- -s 16384 -S 16384
>> TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to xx.xx.xx.xx 
>> (xx.xx.xx.xx) port 0 AF_INET : +/-2.5% @ 99% conf.
>> Recv   Send    Send
>> Socket Socket  Message  Elapsed
>> Size   Size    Size     Time     Throughput
>> bytes  bytes   bytes    secs.    10^9bits/sec
>>
>>  87380  32768  32768    10.00       0.90
>>
> 
> Also, notice that it didn't just double the -S option, it had a minimum 
> of 87380.
> 
> If you want to have an explicit send size, add a -m option to your 
> netperf command link.
> 
> happy benchmarking,
> 
> rick jones
>>
>>
>>
>> -Mahmoud
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