Date: Wed, 24 Jun 2020 14:31:34 -0400 (EDT)
From: norman(a)oclsc.org (Norman Wilson)
> Reaching outside of UNIX, RSX/11 used external supervisor-mode processes called ACPs (ancillary control processes) to implement file systems. I don't know exactly how they were plugged in, but I do know they were pluggable, so their interface must have constituted a file-system switch of some sort. RSX dates back into the 1970s. At some point in the latter part of the 1980s, Ralph Stamerjohn (a name instantly recognizable in the 16-bit DEC software world) gave a DECUS talk about implementing a remote file system through ACPs: a stub ACP on the client exporting RPCs over the network, a real one at the server end. I remember chatting with him about how that did and didn't resemble the way pjw had done it; interesting architectural comparison.
> Norman Wilson Toronto ON
I am still digesting all the inputs (thanks, all!)
The above post made me realise that the delineation of what is a FSS/VFS or not, is not so easy.
I did a little bit of reading, and the concept of an ACP arrived with RSX11D in May 1973, but only matured in RSX11M in November 1974. As I understand it, originally in RSX11 file system code was closely tied to the low-level device driver for each device. ACP’s separated the file system code from the device driver itself, and became separate processes.
In essence there were two switches: one switch into abstract devices, implemented in ACP code and one kernel switch to deal with hardware interfacing. The first is indeed like a file system switch (although still tied to specific devices).
Looking at this stuff made me realise that my retro machine of choice (the TI990) went through a similar evolution. In the early seventies it had a sort of abstract device switch that linked to individual ‘device service routines’ (drivers). Initially, these modelled batch oriented ‘logical units’ that tied to files at the job control level. Later (late 70’s), the ‘open’ command would carry a file name and the file system was delegated to the device service routine. Still later (say 1983) this was used for networked disks.
As several people have observed in this topic, indeed there appears to be a close relationship between a device switch and a file system switch.
Anybody on the list know much about the provenance of SVr4 and OKIX for the
Okistation 7300 model 30?
http://museum.ipsj.or.jp/en/computer/work/0029.html indicates that OKIX
came later on the model 75, but many years ago as a staff programmer at
Oregon Graduate Institute, a surplus 7300/30 followed me home, but the
sysadmins referred to it as OKIX.
if anybody's interested in the hardware to do some spelunking, email me
off-list.
--
Aaron J. Grier | "Not your ordinary poofy goof." | agrier(a)poofygoof.com
"The price of reliability is the pursuit of the utmost simplicity. It
is a price which the very rich find most hard to pay." -- Tony Hoare
> From: Rob Gingell
> RSEXEC (Resource Sharing EXEC) done on TENEX earlier in the 1970s.
That was associated with the National Software Works project:
https://apps.dtic.mil/dtic/tr/fulltext/u2/a132320.pdf
I think? (It's been four decades since I looked at NSW, so I don't recall
much about it.) Neither was TENEX-specific; e.g. there were Multics
implementations of RSEXEC and NSW.
Noel
> From: Richard Salz
> A web search for "its mldev" finds several things (mostly by Lars
> Brinkhoff it seems)
Yeah, other than the source:
https://github.com/PDP-10/its/blob/master/src/sysen2/mldev.106
there's not a lot on it.
That's typical of a lot of the innovative work done at the AI Lab, LCS, etc;
they built some extraordinary tools, but to them they were just tools they
used to work on their research, their _real_ work. So why bother to write that
stuff up? So people who actually used them remember them, but other than
that...
Welcome to tomorrow, where everything gets re-invented, because everyone is too
busy to waste time learning about the past.
Noel
> From: "Greg A. Woods"
> as Organick said in his 1972 book
A word of warning: i) Organick describes Multics as it was planned, not as it
was actually implemented; and ii) then it changed considerably during its
service life.
Examples of each: i) there was one linkage segment per processs, not per
segment (linkage info was copied across into the shared linkage segment when a
segment was dynamically added to a process' address space); ii) the New Storage
System.
The basic concepts (single level store, dynamic linking etc) are correct in
Organick, but be wary of anything past that. Not his fault, of course; things
just changed.
> As far as I can remember Multics didn't really have the concept of a
> "mount point".
In the original design, no. In 1973-75, with the New Storage System:
https://multicians.org/nss.html
mountable volumes were added (see MTB 229, "Use of Demountable Logical
Volumes", linked from the page above). It was released to customers in
June, 1976.
Noel
Reaching outside of UNIX, RSX/11 used external
supervisor-mode processes called ACPs (ancillary
control processes) to implement file systems.
I don't know exactly how they were plugged in,
but I do know they were pluggable, so their
interface must have constituted a file-system
switch of some sort. RSX dates back into the
1970s.
At some point in the latter part of the 1980s,
Ralph Stamerjohn (a name instantly recognizable
in the 16-bit DEC software world) gave a DECUS
talk about implementing a remote file system
through ACPs: a stub ACP on the client exporting
RPCs over the network, a real one at the server
end. I remember chatting with him about how
that did and didn't resemble the way pjw had
done it; interesting architectural comparison.
Norman Wilson
Toronto ON
> From: Anthony Martin
> wherein they state the following:
> A virtual file system, from the viewpoint of application programs on a
> computer, models the file system functions of other computers. This is
> done in the same way as with virtual terminals, a virtual file system
> consists of a UPP having virtual files (VF), and a UCP which executes
> virtual file system protocols.
> I'd be interested if you find anything earlier.
MLDEV on ITS would, I think, fit under that description.
I don't know if there's a paper on it; it's mid-70's.
Noel
> From: Dave Horsfall <dave(a)horsfall.org>
> Ioctl: the Swiss Army knife of system calls. I thought it was a neat
> idea when it arrived (much better then those primitive stty/gtty calls)
> but now...
Like they say, when the only tool you have is a hammer...
Better syntax than stty/gtty, maybe but I'm not sure the semantics are that
much better. The problem is that, especially with devices, what the I/O
commands do is so widely varied that it's hard to fit them all under a
unified umbrella. Maybe some (e.g. asynchronous I/O), but not all.
Noel
There is an interesting paper that Dennis Ritchie and Dave Presotto wrote, “Interprocess Communication in the Ninth Edition Unix System” (https://www.bell-labs.com/usr/dmr/www/ipcpaper.html <https://www.bell-labs.com/usr/dmr/www/ipcpaper.html>).
This appears to be an update of a paper that they wrote in 1985, “Interprocess Communication in the Eighth Edition Unix System”. This earlier paper is hard to find.
Anybody on this list who has it on hand?
