On 09/14/2010 10:30 AM, Nikita V. Youshchenko wrote:
anyone can say preempt rt is hard real time?
Hard realtime has something to do with how you define "missing the
deadline". If somebody cuts the cable of your roboter controller in
the factory hall, the system misses the deadline. So it is all about
probabilities: hard realtime systems have a very, very low probability
of missing the deadline. However, in real life systems, it is> 0%.
So yes, if you talk about real world, it is hard realtime.
No. Preempt rt it's not hard realtime.
But most people/companies who think they need hard realtime really
don't. They can live with soft realtime and have a really low
probability of missing deadlines and having long latencies. For these
people, the preempt rt is adequate.
Isn't any case where preempt-rt does not behave as hard reatlime a bug in
preempt-rt, that should be reported to this list and eventually fixed?
That is a philosophical question for the preempt-rt maintainers.
I *believe* that the design goal for the preempt rt code is to minimize
kernel latency. It's not to make the kernel deterministic to support
hard realtime.
So I don't know if I'd call it a bug, but rather on the wish list for
future enhancements.
--
Jeff Angielski
The PTR Group
www.theptrgroup.com
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