[zeromq-dev] ZMQ_RATE

[Steven McCoy]

On 3 October 2011 12:02, Emmanuel TAUREL <taurel at esrf.fr> wrote:

>  On 03/10/2011 17:53, Steven McCoy wrote:
>
> On 3 October 2011 11:18, Emmanuel TAUREL <taurel at esrf.fr> wrote:
>
>>   On 03/10/2011 17:02, Steven McCoy wrote:
>>
>> 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
>>
>>
>>  Thank's for your answer.
>> I am using zmq 3.
>>
>>
>  So this might be a regression on setting the rate limit on the PGM
> socket.  I would suggest comparing operation with version 2.  I'm only
> looking at v2 for bug fixes and v4 for enhancements so additional awareness
> is required for the v3 branch.
>
>
> I am sorry but I am lost. In our application, we would like to use either
> TCP transport either PGM transport.
> With ZMQ 3, we have the nice event subscription feature and this is why we
> are using it.
> Do you mean that PGM is not supported with ZMQ 3?
>
>
Well it means I haven't reviewed it, I think Martin is still listed as the
official maintainer.

A quick look at 3.0.1 it would appear that v3 does not set any rate limiting
at all.

2.1: Sets PGM_ODATA_MAX_RTE PGM socket option.

https://github.com/zeromq/zeromq2-1/blob/master/src/pgm_socket.cpp#L251

The lines are dropped in 3.0:

https://github.com/zeromq/zeromq3-0/blob/master/src/pgm_socket.cpp#L238

-- 
Steve-o
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