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From: Lynn Wheeler <lynn@garlic.com>
Newsgroups: comp.arch
Subject: Re: time-sharing history, Privilege Levels Below User
Date: Wed, 12 Jun 2024 15:19:14 -1000
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Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> I recall CMS was single-user to start with, and the point of running it 
> under “CP” aka “VM” was to offer a multi-user service. Did CMS ever become 
> multi-user in its own right?

over years relying more & more on CP kernel services, no multi-user
.... but did get multitasking
https://www.ibm.com/docs/en/zvm/7.3?topic=cms-application-multitasking
https://www.ibm.com/docs/en/zvm/7.3?topic=programming-zvm-cms-application-multitasking
https://www.vm.ibm.com/pubs/redbooks/sg245164.pdf

original CMS that could run on real hardware support SIO and channel
programs for file i/o ... a CP "diagnose" function for CMS file i/o was
added to CP/67 that ran purely synchronous (didn't return to CMS until
file I/O was completed) ... in transition to VM370, CMS went purely for
CP "diagnose" (and SIO capability was eliminated).

When I joined science center and also saw the virtual memory file
support by MULTICS ... I figured I could do one for CMS ... that scaled
up faster than the normal file I/O operation ... and I claimed I learned
what not to do for a page-mapped filesystem from TSS/360 (part of
TSS/360 was just memory mapped the filesystem then mostly faulted in
pages ... while I did combination of memory mapping and pre-fetching,
read-ahead and write-behind support).

Some of the IBM Future System issues was specifying a TSS/360-like
filesystem ... one of the last nails in the FS coffin was study that
showed if 370/195 applications were ported to FS machine made out of the
fastest available hardware, it would have throughput of 370/145 (about
30 times slowdown ... part of it was serialization of file i/o).

Some existing FS descriptions talk about how FS lived on with S/38 ...
for entry-level business operation ... there was sufficient hardware
performance provide necessary throughput for the s/38 market.

In any case, the FS implosion contributed to memory mapped filesystem
implementations acquiring very bad reputation inside IBM. In 1980s, I
could show that heavily loaded, high-end systems with 3380 (3mbyte/sec
disks) running my page-mapped CMS filesystem had at least three times
the sustained throughput of standard CMS filesystems,

some FS
http://www.jfsowa.com/computer/memo125.htm
https://people.computing.clemson.edu/~mark/fs.html

trivia: my brother was regional Apple rep (largest physical area CONUS)
and when he came into town, I could be invited to business dinners and
argue MAC design (even before MAC announced). He also figured out how to
remotely dial into the S/38 that ran Apple to monitor manufacutring and
delivery schedules.

-- 
virtualization experience starting Jan1968, online at home since Mar1970