Experimental Physics and
Industrial Control System

<[email protected]> · Tue, 31 May 2011 16:28:50 +0000

Dirk,

While not the same thing, we have looked briefly at porting EPICS to the Linux RT_PREEMPT kernel. EPICS will, of course, work with the RT_PREEMPT kernel, but this is not the same as saying it works as you would expect if you set the EPICS threads to real-time priorities. In fact, we know its behaviour is not ideal for a realtime system and, as a result, there is a Launchpad blueprint to add Posix realtime support for osdMessageQueue, which is the biggest problem we spotted (there may be more). Other than this, we found the RT_PREEMPT kernel worked well, with minimal pain to us.

So I think, with a general movement away from specialist real-time systems, I think we need to look at the EPICS behaviour with real-time Linux kernels, and possibly try and recommend one more than others. I am not sure how many of these problems are common to all Linux real-time kernel implementations and how many are specific to one implementation. Anyway, looking at this issue sounds a good codeathon task.

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Andrew Johnson
> Sent: 31 May 2011 16:24
> To: Dirk Zimoch
> Cc: [email protected]
> Subject: Re: Xenomai Linux
> 
> Hi Dirk,
> 
> On 2011-05-30 Dirk Zimoch wrote:
> >
> > Has anyone considered porting EPICS to Xenomai real-time Linux?
> > Maybe even started working on this issue?
> 
> I had not heard of Xenomai before, and I'm not aware of anyone doing such a
> port so if you get no other responses the floor is all yours.
> 
> Xenomai looks interesting, do you have specific hardware that is already
> running it?  Which skin are you looking at?  I would guess the native one, but
> I've not looked at the others very closely.
> 
> - Andrew
> --
> Optimization is the process of taking something that works and
> replacing it with something that almost works, but costs less.
> -- Roger Needham

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System