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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Embedded FreeBSD
Date: 18 Jan 1997 16:01:35 GMT
Organization: Private BSD site, Dresden
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Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch)
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:34180
doug@qnx.com (Doug Santry) wrote:
^^^^^^^
> You should try QNX.
Ah. :-)
> But you can't get around the fact that FreeBSD can spend lots of time
> in the kernel which no amount of scheduler tuning can fix. The kernel
> is not premptable...
Of course, Unix ain't a real-time OS. OTOH, with today's ever faster
CPUs, the question is whether one really needs a real-time OS, or
whether a (basically) timesharing OS is _effectively_ doing the same.
The difference is, of course, that in a timesharing system, you can't
have a _guarantee_ for any timing. It depends from the desired task
whether this is acceptable (or whether you can work around that
problem by putting time-critical parts into a device driver, since the
interrupt routines _can_ preempt other kernel activity) or not. I
love to draw an analogy to the Token Ring vs. Ethernet principles:
while with Token Ring, you get guaranteed response times, you're
paying much more for it (hardware and overhead), and it turns out that
Ethernet can basically get you up & running as well, despite of it
being based on a chaotic principle. Chaos is in fact predictable, as
we have learnt in the past.
Get me right, i don't mind QNX. However, i also realize (and see my
.sig for this :) that many people working in the embedded area are
much happier to also know they have the kernel source, so they can
fiddle whatever part they need to tweak. Even if you don't need this
in the end -- it usually gives you a much warmer feeling to begin
with.
Hint, hint... maybe QNX should also sell the kernel source to its
customers. Of course, this only makes sense if you don't think you
can really sell source code, i.e. sell everything for the same price
as you do now. Nobody is willing to pay N thousand dollars ``just in
case''. I think going this route might really improve your marketing
chances. Don't argument that people might steal your valuable
technology. Everybody who ever tried to `port' a simple device driver
from Linux to BSD knows that even those systems are already different
enough to make this a very time-consuming task. So `stealing'
something from QNX is certainly way out of the question -- and i
didn't ask you to release that source code without an NDA either.
--
cheers, J"org
joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)