Re: preempt rt in commercial use

[Patrice Kadionik <kadionik@enseirb-matmeca.fr>]

  Le 15/09/2010 15:51, Nivedita Singhvi a écrit :
> Patrice Kadionik wrote:
>
>
>> Hi Nivedita;
>>> I would go further and say people need to stop using the terms
>>> "hard" and "soft". There isn't a binary yes/no answer to the real-time
>>> requirements spectrum.
>>>
>> I don't agree with that.
>> We are all OK to say that the application or the process to control 
>> fixes the timing constraints to the overall HW/SW system.
>>
>> If the application can NEVER miss an event or a deadline because it 
>> will be catastrophic, we MUST use a hard RTOS.
>> If the application supports to miss (from time to time) an event or a 
>> deadline without catastrophic consequence, we can use a soft RTOS (or 
>> a hard RTOS if we want).
>
> No, not really. The consequences may not be catastrophic, but people
> still want performance, latency, determinism, etc. For the majority
> of applications out there, this is true.  And they have specific
> requirements. So they _do_ need to ask, specifically, "can your OS
> do this?".
>
>
>> Not thinking hard nor soft realtime can have dramatic consequences.
>
> I think you missed my point. That's sort of exactly what I'm saying:
oops,

Sorry. I've misunderstood.

Cheers,

Patrice
>
> That customers/users need to think *VERY CAREFULLY* about their
> _specific_ requirements.
>
> i.e., it is never enough to ask "Is it a hard RTOS or soft"?
>
> If you have any specific requirements, the question needs to be:
>
> "can it do xxx in yyy when running zzz in ppp" etc.
>
> Followed by a whole heap of actual testing.
>
> i.e., the answer you get to the first question provides little
> value if you don't know how it is being defined, or worse, it's
> silently being defined differently than what you define it to be.
>
>
>> Until now, PREEMPT-RT is a nice solution as soft RTOS and offers no 
>> guaranty on an very big latency appeared in a particular case. 
>> Thinking that PREEMPT-RT is a hard RTOS is false.
>
> I'm not sure what this means, because most people I know are
> not making any kind of specific claims about PREEMPT_RT.
>
> thanks,
> Nivedita
>


-- 
Patrice Kadionik. F6KQH / F4CUQ
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