[Xenomai] Odp: RtNet and Interrupts

Mariusz Janiak mariuszjaniak at wp.pl
Fri Feb 17 11:45:54 CET 2017


Dnia Piątek, 17 Lutego 2017 11:18 Norbert Lange <nolange79 at gmail.com> napisał(a) 
> Hello,
> 
> I wonder if the Rtnet Stack is driven at packet level, ie. if after
> every one received packet( or even buffer) an IRQ is received.
> I worked on a Project where a similar Problem with Ethernet
> communication had to be solved, and I just queued up enough receive
> buffers and just picked up anything that arrived at the start of a
> timeslot.
> 
> On 100Mbit and a 1ms timeslot, I calculated a max. of 150 received
> pakets. Not that realtime communication can get anywhere close to
> that, but you have to deal with worst cases and guarantee that your
> system aint missing the cpu time spend in IRQs for other things - even
> if you just decide to drop all those packets, the IRQ overhead would
> be there.
> 
> So is Rtnet using "polling" at timeslots, or irqs?

Hi,

As far as I know, RTnet is interrupt driven stack, it means that after reception of each packet the interrupt is generated and handled by the NIC driver. This is one of the reasons why porting of the RT driver  to new NICs is so problematic, especially now when new drivers support NAPI.

> Kind Regards,
> Norbert
> 
> PS.
> Complete unrelated, but are there any big companies using Xenomai /
> Rtnet that can be named?

I know that Universities use it a lot in the field of robotics (eg. SOEM + OROCOS). There is a port of the RTnet stack for microcontrolers if you are interested (RTnet Embedded)

https://bitbucket.org/mariuszjaniak/rtnet-embedded

Best regards,
Mariusz



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