[TUHS] A/UX [was Linux is on-topic]

[Gregg Levine]

Hello!
Larry? I'm surprised. I've worked with QNX a few times. I also grok
that you're one who has mad respect for QNX. Because I'm one also.
It's an interesting OS,
-----
Gregg C Levine gregg.drwho8 at gmail.com
"This signature fought the Time Wars, time and again."

On Mon, Jul 20, 2020 at 9:53 PM Larry McVoy <lm at mcvoy.com> wrote:
>
> On Mon, Jul 20, 2020 at 06:54:40AM -0600, Andrew Warkentin wrote:
> > On 7/20/20, Larry McVoy <lm at mcvoy.com> wrote:
> > > This isn't quite the same but Victor Yodaiken wrote a real time kernel
> > > that ran all of Linux as a user process.  Super cool idea and it worked
> > > great, he would demo it sampling the parallel port while Linux was running
> > > some X11 perf thing, tarring up /usr and untarring on nfs://server/tmp/usr
> > > and doing a ftp transfer.  Basically beating the crap out of Linux as
> > > hard as he could while running a real time sampler and it never missed.
> > >
> > > Clem should pay attention, in my opinion, this is how you do Unix and
> > > real time.  Because Unix is time sharing and throughput, that is the
> > > opposite of what real time is.  Wedging real time into Unix is a mistake.
> > >
> >
> > QNX manages to do realtime fairly decently while still being
> > Unix-like, although it's certainly not a conventional Unix. With a
> > multi-server OS with a properly designed microkernel, it is possible
> > for realtime threads to more or less ignore the fact that they're
> > running on a Unix-like OS (provided that they can access some kind of
> > IPC API that closely matches that of the kernel) since all the OS
> > services other than the microkernel are running beside them at
> > non-realtime priorities, and not underneath them as in a conventional
> > OS. It's kind of doing the same thing as running a Unix kernel as a
> > process under a realtime kernel, but the Unix environment is
> > implemented by servers and libraries instead of a monolithic kernel.
>
> QNX is awesome.
>
> I was friends with Dan Hildebrandt, he was one of the 3 people who were
> allowed to touch the microkernel code.  That kernel could fit easily in
> a 4K instruction cache and leave room for other processes.  They measured
> everything in cache misses, every commit had them thinking about cache
> misses.
>
> I'm definitely a unikernel guy but I had mad respect for QNX, Dan and
> I would talk often about stuff, like how would this work in your world
> and how would it work in my world.  The QNX core team was amazing.
>
> Sadly, we lost Dan to brain cancer (I think) in 1998.
> --
> ---
> Larry McVoy                  lm at mcvoy.com             http://www.mcvoy.com/lm