Re: [Xenomai] a question about ADEOS

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 05/30/2012 07:57 PM, Lennart Sorensen wrote:
> On Wed, May 30, 2012 at 06:53:00PM +0200, Gilles Chanteperdrix wrote:
>> You can see for yourself with the xenomai-forge branch. It is already in
>> a usable state. I do not buy the scheduler argument: the linux scheduler
>> does pretty much the same separation between real-time and non real-time
>> tasks as the separation which happens with xenomai. And the scheduler
>> for real-time tasks is simple, it does not need to know much more than
>> the tasks priorities, I do not see what more you would like to control.
> 
> I have been looking at it a bit.  Maybe I should give it a try soon.
> 
> Based on what I have seen for the real time linux patches, you can set
> priorities of kernel threads as well, which would be nice at times.

I am not sure to get what you mean, Xenomai kernel threads priority are
configurable as well.

> 
> Perhaps our use is just not normal, in that we ahve an application that
> uses realtime, but has some work to do that is very low priority (and
> not in need of realtime) but needs to share memory space and resources
> with the stuff that does have to be real time, which makes it hard to
> make linux tasks run before the less important stuff in the xenomai
> application runs.  It works using an idle priority thread, but it would
> be nice to have better control of it, which I hope the rt patches for
> linux would allow.  Maybe I am hoping for too much.

Starting with Xenomai 2.6, if you create a xenomai thread with
scheduling policy SCHED_OTHER (and priority 0), it returns to secondary
mode as soon as possible, so, is handled by Linux scheduler as a low
priority thread most of the time. If this task is cpu bound, you
probably can even decrease its time slices by using the renice() service.

-- 
					    Gilles.