[TUHS] shared memory on Unix

Paul Ruizendaal pnr at planet.nl
Thu Feb 2 09:11:02 AEST 2017


Many thanks to all for that helpful info!

OK, so my vague recollection was more correct than my quick code
inspection...

With CB3 I meant CB Unix 3.0. I had a look at the "pdp11v" code
in the Unix Tree archive and it has a system call "maus". Its implementation
is here:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=pdp11v/usr/src/uts/pdp11/os/maus.c

There is also a CB Unix 2.1 manual and source code listing in the archive.
The manual page for maus says it stands for "multiple access user space"
(http://www.tuhs.org/Archive/PDP-11/Distributions/other/CB_Unix/cbunix_man2_02.pdf)
At first glance 'maus' looks a bit like mmap.

I did not find a print of the maus implementation yet in the source print, but
I haven't exaustively searched yet (it is mentioned in the index, so it
probably is there somewhere).

In any case, the man page for maus is from November 1979, so it goes back at
least as far as that. When was CB Unix 1.0 put together?

--

It will be interesting to see how the BBN and CB approaches compare.

Noel wrote: "Yes, there are two module in 'ken', map_page.c and set_lcba.c
(I was unable to work out what 'LCBA' stood for) which seem to do something with
mapping."

How about "Local Common Block Access"? :^)

Paul


> The so-called Columbus shared memory feature was in their system in the
> mid-1970s, along with a few other things such as semaphores and
> inter-process messages. I seem to recall the acronym MAUG, but I may have a
> letter or two wrong. Something like Multi Access User ____. The much later
> System V features had a completely different API.
> 
> Hey, Doug, do you remember this? In the early 1970s, there were a couple of
> UNIX meetings at Murray Hill, at which various Bell Labs groups presented
> on what they were doing with UNIX, and a group, perhaps Columbus, said that
> UNIX wasn't capable of doing what they wanted, so they had modified it. You
> asked the question, "Why are you using UNIX?"
> 
> To my knowledge, having witnessed another decade or so of groups trying to
> bend UNIX to their will, it was the last time the question was asked.
> 
> --Marc
> 
> 
> > Mary Ann Horton <mah at mhorton.net
> > wrote:
> 
> > > I*'m not sure what you mean by CB3, but these features (shared memory,
> > > semaphores, IPC) were added to CB-UNIX (Bell Labs, Columbus) precisely
> > > because they were needed in real time telco systems and not preset in
> > > the versions from New Jersey.  This would have been in the early 1980s.
> > > When I got there in 1981 I think CB-UNIX was already well established
> > > and had these features.  (These would show up, ironically, in /usr/ucb,
> > > which did not stand for Berkeley.)


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