Re: Ada Microkernel?

["Marin David Condic" <marin.condic.auntie.spam@pacemicro.com>]

The key to it is predictability. Or at least uniformity so you know that
your timing tests are going to be good. One could argue all day about this
OS versus that OS and their relative suitability for realtime work, but I
think that to be a candidate at all, the OS has to provide deterministic
behavior and stability. How compatible is this with the goals of a
"workstation" OS? I don't know. I think that from a requirements viewpoint,
one might insist that a single process should be able to run in some mode
where it can guarantee that its cycle time is 100% consistent. (You could
ask if this is with or without threads within the process - I'd think we
would want that.) As long as the OS will let the process run in a guaranteed
consistent cycle time, the rest is just efficiency and appropriate hardware
to make sure the cycle time is sufficiently fast.

AFAIK, the two things that this would impact the most would be the scheduler
and the device driver model (interrupt handling figuring into the device
driver model as far as I'm concerned.) If you had at the core of your OS
these two things built such that they were suitable for realtime, you'd have
something that could be marketed in a large variety of places. If you could
build a workstation OS on top of that - even if it had to have some
different operation mode - you'd have an environment that was quite valuable
for realtime/embedded development, for reasons that should be obvious.

Can an OS provide at least one "realtime" process and still allow other
processes to run in an acceptable manner? I don't know if this is doable,
but it would certainly be cool if it did exist. I'd even accept some sort of
configuration switch at boot time or OS build time just so you could have
essentially the same OS on your PC as would be used in the realtime/embedded
app. That enables a huge amount of development to occur on the desktop
rather than the lab - at an enormous cost/time savings.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com
Web:      http://www.mcondic.com/


"Ted Dennison" <dennison@telepath.com> wrote in message
news:wG3%6.1950$Kf3.21097@www.newsranger.com...
> In article <9hi6fv$lop$1@nh.pace.co.uk>, Marin David Condic says...
>
> For schedulability analysis, I presume one would handle this either by
adding
> the appropriate multiple of the max scheduling delay (which the OS vendor
would
> hopefully provide), or by showing that the task in question completes in
less
> than one scheduling interval. Being able to provide that max scheduling
delay
> (and have it be a resonable number) is where I think most consumer OS's
would
> have trouble.
>