> Mike wrote..
>
>Aren't there some time based schedulers for ChorusOS? Chorus is still
>used by Alcatel, Lucent, and several other big telecom companies on
>existing products, and is being re-packaged by Sun as a real-time
>platform for embedded Java.
I looked up the website for ChorusOS and their whitepaper. It says you can
modify the scheduler modules, but didnt seem to mention a time based
scheduler available.
>On Tue, 27 Jul 1999, Paul Koning wrote:
> I'm not sure what "time based scheduling" is, so I don't know if what
> I described is or isn't that.
>
> The system I've settled on as most desirable -- which is what I'm
> using at the moment -- is a single priority design, with all tasks
> running to completion (or explicit reschedule), and no interrupts,
> just I/O polling.
>
Ok, but then you are completely bypassing the OS. your application itself
manages the tasks. That would definitely make it highly non-portable.
Instead, an RTOS could be designed to provide QoS in terms of time, where
each task requests a QoS in terms of period, compute time and deadline.
That would certainly make it efforless to port an application to the
ever changing hardware platforms.
It seems most Embedded application programmers, do all the scheduling in
the back of their minds and assign priorities/ design calendars. And
certainly if those guys can do it, a well designed OS should be able to
schedule tasks just as well. Yet no RTOS is designed to take this load off
the application writers.
> So it isn't scheduling in terms of deadlines or other time based
> notions, but rather just round robin scheduling of active tasks. So
> long as you know the time bounds it's trivial to analyze, and even if
> you don't know hard time bounds, you still obviously have guaranteed
> progress on all tasks. For networking boxes (which is what we do) it
> turns out guaranteed liveness is what you look for; trying to come up
> with hard time bounds as you might do in a process control environment
> is usually more effort than it's worth.
>
> paul
>
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