[zeromq-dev] ZMQ_RATE

[Emmanuel TAUREL]

On 03/10/2011 17:02, Steven McCoy wrote:
> On 3 October 2011 10:19, Emmanuel TAUREL <taurel at esrf.fr 
> <mailto:taurel at esrf.fr>> wrote:
>
>     Hello all,
>
>     I am experimenting PUB/SUB sockets with PGM protocol.
>     I am actually using with the ZMQ_RATE socket option.
>     My understanding of this parameter was that it is the maximum rate for
>     sending/receiving data and thus limits the network bandwidth used
>     by PGM.
>     In my test, the publisher sends messages as fast as it can.
>     I have tried different value for the ZMQ_RATE parameter: 100 which
>     means
>     100 kbits/sec (the default) and 80000 which means 80Mbit/sec.
>     I capture network packets using wireshark. When I look at its IO graph
>     after the capture, there is no difference between the two runs.
>     During the PGM transmission, I always have a network usage close
>     to 100
>     Mbit/sec which is my network bandwidth between the pub and sub hosts.
>
>     Where is my error?
>     Do I have to understand that ZMQ_RATE limits the data rate in the
>     process but not on the network (meaning buffering required in case of
>     slow ZMQ_RATE)?
>
>
> Correct but the differences are going to be only latent.
>
> The default for ZMQ_RATE is now 40*1000, 40mbit/s, because you cannot 
> really do any testing with 100kbit/s as it is way too slow.  This does 
> suggest you are on an older version and you may wish to retry with at 
> least 2.1.9.
>
> You can compare with the local_thr and remote_thr performance test 
> programs which work correctly.
>
> There may be a problem with timer accuracy on your platform, you may 
> try setting the environment variable PGM_TIMER to GETTIMEOFDAY, TSC, 
> or CLOCK_GETTIME for different methods:
>
> http://code.google.com/p/openpgm/wiki/OpenPgmCReferenceRunWithTheseCapabilities
>

Thank's for your answer.
I am using zmq 3.
In fact the man page is wrong. In the zmq_setsockopt man page, it is 
still written that the default value for ZMQ_RATE is 100 kilobits/sec!

Regards

Emmanuel
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