Re: [Xenomai-core] rtdm timers

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

Steven Seeger wrote:
> Gilles believes he's on the track of our FPU issue when using kernel  
> threads. Would using an RTDM timer to accomplish our need have the  
> same issue? We would not use the FPU in the timer of course, because  
> it is not allowed.
> 
> I just don't want to spend the time converting things if it won't  
> help. Does the list think it would be a worthwhile effort?

We can not say for sure as long as we know what the bug is. But if it
is, as I suspect, a bug in the FPU switching logic for non-fxsr x86_32
cpus, you will not have it with a timer: when the timer fires, there is
no context switch and because of that you should have a lower latency
and a lower overhead of the driver using the timer (the downside, of
course, is that you can not call a function which sleeps). I do not know
however if it makes much difference on x86, to have an idea, compare the
output of klatency -t 1 and klatency -t 2.

-- 
					    Gilles.