Re: [Xenomai-help] posix functions for real time and non real time

[Jan Kiszka <jan.kiszka@domain.hid>]

Philippe Gerum wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> On Jan 8, 2008 2:44 PM, Jan Kiszka <jan.kiszka@domain.hid> wrote:
>>>> Gilles Chanteperdrix wrote:
>>>>> When you try to mix up real-time and non real-time threads, it all
>>>>> becomes very complicated. You do not need your complication: just make
>>>>> all your tasks real-time tasks (using priority 0 for low priority
>>>>> tasks) and forget about __real_* calls.
>>>> That can be inefficient in large applications: You don't need the
>>>> (average-case) overhead of Xenomai IPC for pure non-RT interaction. And
>>>> IPC object creation is precisely the critical point, because their type
>>>> cannot be told apart by the wrapping layer based on generic parameters.
>>> The point is that you usually do not care.
>>>
>> My customer does. :)
>>
>> E.g. note that Xenomai IPC does not scale on SMP like glibc/futux-based
>> stuff does (repeating once again: in the average case).
>>
> 
> You mean in the non contended case.

Specifically, but also

 - the potential need to consider the number of non-RT objects in your
   RT system design (specifically if there are a lot of them)

 - scalability limitations of nklock (which would be stressed more
   intensively by contention cases, or when using message queues)

Only when the number of non-RT objects is small, thus negligible, it is
OK to throw them in the same pot as RT objects. Otherwise, it would be
crazy to merge both sets.

Jan

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