[zeromq-dev] ZEROMQ WITH RTNET

Steven McCoy steven.mccoy at miru.hk
Fri Sep 23 14:52:24 CEST 2011


On 23 September 2011 04:39, Sentenac Daniel <daniel.sentenac at ego-gw.it>wrote:

> Hi,
> I am interested in the ZeroMQ performances under real time conditions. I
> saw the paper on "Tests on Linux Real-Time Kernel" on SUSE Linux
> Enterprise Real Time kernel. I would like to achieve the same using RTAI
> kernel.
> I think it would need the use of RTnet hard real-time network protocol
> to be implemented in libzmq.
> Has anybody thought about doing so ? Or is there any other way to
> achieve real time performances using RTAI ?
>

RTnet is a bit confusing and it looks dead.  It appear to be only targeting
UDP with "minimal TCP" in their latest 2010 release.

The important distinction to be made is that RTAI appears to be offering
real hard deadlines whilst "real time Linux" which is a continuing branch of
mainline Linux concentrates on breaking larger locks and implementing full
pre-emption to user-space.

Real time Linux, via SuSe, RHEL, or even Ubuntu is more about bringing
deterministic timers to the application as it is barely relevant to 0MQ
itself.  It does affect OpenPGM, the PGM protocol within 0MQ as it
implements a network protocol in user-space.  Extensive testing on latency
with different kernels show that performance becomes more deterministic at
the cost of being slower, a bit opposite to many on first look.

http://openpgmdev.blogspot.com/2011/04/real-time-linux.html

-- 
Steve-o
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