Re: UDP/IP via Ethernet in real time (config-preempt patch)

[M. Koehrer]

Hi, 

> What is your real-time requirement? What's the response time upper 
> bound? I agree with the people who say this may not be right way to go.
I want to close a control loop. The faster it is the better it is...
Well, to tell concrete numbers, I want to have a response within 300 microseconds.
The request and the response amount of data is about 250 byte UDP 
data each (100 MBit full duplex).

Currently, I am using rtnet (http://www.rtnet.org) and the Xenomai real time framework
for Linux. This works fine.
The drawback of this approach is that rtnet supports 
only a limited number of support network adapters. (Special network drivers
are required).
And the preempt patch seems to be closer to standard Linux than a 
a Xenomai patched kernel.
One major problem is that shared interrupts do not really work smoothly with Xenomai...
My goal is to replace the Xenomai/rtnet combination with just the kernel-preempt patch.

> 
> > For this I have a separate network adapter in my PC that is used
> > solely for this UDP Ethernet traffic.
> > However, I think all Ethernet traffic is be handled by
> > the soft IRQ threads [softirq-net-rx] [softirq-net-tx] but I do
> > not see a way to do real time networking via one of the network adapters.
> >
> > How can I get this UDP networking real time capable?
> >
Regards

Mathias

-- 
Mathias Koehrer
mathias_koehrer@xxxxxxxx


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