[zeromq-dev] ZMQ_RATE

[Steven McCoy]

On 3 October 2011 10:19, Emmanuel TAUREL <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

-- 
Steve-o
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