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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