In Multics you always mmap'ed files -- that seems crazy to me now that I write asyncio systems inspired by the old mainframe transaction processing systems such as CICS. There is nothing more synchronous, blocking, and dependent on expensive MMU operations than mmap.

MMU operations are a lot more expensive now than they once were.

In particular, one of the most expensive things about mmap today is actually munmap, that trashes the translation lookaside buffer ("TLB"), the cache of memory map lookups, on all the other cores that run threads in the same process. When you had only the one core, that didn't need to happen.

NetBSD used to have "UVM", where they played memory mapping tricks to get "zero-copy" networking. They had to give it up when they went to multiple cores.

Synchronous and blocking is not that bad in timesharing systems, as the computer always has something else to do while it waits for the IO to complete.

As for the expensive MMU operations, as someone pointed out before, they were not always as expensive as we currently have to make them when we need to guard against leaks between processes and multiple CPUs sharing unified memories and caches.

Varnish seems to get good mileage out of that strategy.

> Plan 9 is obviously a joke name too.

Bell Labs replacing the Outer Space in Plan 9 From Outer Space, a schlocky 1959 sci-fi horror film. The subtitle is UNSPEAKABLE HORRORS FROM OUTER SPACE PARALYZE THE LIVING AND RESURRECT THE DEAD.

And riffing off the fact that the previous Bell Labs Unix was version 8.

Do you have a source for that? Bell Labs Unix had version 9 in 1986 and version 10 in 1989. I suppose it's possible that these happened after Plan 9 was named; but as best as I can tell, work on Plan 9 started in 1987[1]; after V9 Unix had been released.

[1]: http://doc.cat-v.org/plan_9/1st_edition/designing_plan_9

Earliest reference to Plan 9 is 1984: http://doc.cat-v.org/unix/unix-before-berkeley/

That 1984 year doesn't seem to be entirely accurate; at a minimum, the article has had additions since 1984 (including the 1998 death of John Lions).

The abstract notes that it was published in DaemonNews in 1999.

I tracked down the DaemonNews publication: https://web.archive.org/web/20000819035036/http://www.daemon...

The copy in DaemonNews includes citations that were elided from the copies on cat-v.org and darwinsys.com. Notably, we see that line change from

> (More recently, much of this work has been consolidated into an operating system called Plan 9 From Bell Laboratories.)

to

> (More recently, much of this work has been consolidated into an operating system called Plan 9 From Bell Laboratories.)[Pike1990a, Pike1995a]

Unfortunately no. I may be wrong.

However I think plan9 started as a skunkworks project well before Unix v9 was released.

[edit - wikipedia maybe supports me ]

> Plan 9 from Bell Labs was originally developed, starting in the mid-1980s,

All of the authoritative sources I've found say that it was started in the "late" 1980s, not "mid" 1980s.

For instance:

> Plan 9 from Bell Labs is a research system developed at Bell Labs starting in the late 1980s.

https://9p.io/plan9/about.html

The Wikipedia's citation on the sentence saying "mid-1980s" is the press release for the 2nd edition of Plan 9 (1995, the first generally available version), which doesn't mention anything of the sort. That is to say: Wikipedia's "mid-1980s" claim isn't well-attributed.

(The 1st edition of Plan 9 (1992) wasn't generally available, and was only made available to universities.)

(My above 1987 citation states that they worked on it in 1987 and implies, but does not explicitly state, that there was no work before that.)