At 2023-01-01T00:35:12-0500, Dan Cross wrote:
> On Sun, Jan 1, 2023 at 12:27 AM Warner Losh <imp@bsdimp.com> wrote:
> > On Sat, Dec 31, 2022, 9:38 PM Jonathan Gray <jsg@jsg.id.au> wrote:
> >> [snip]
> >> Bourne's AsiaBSDCon 2016 talk also lists 1976
> >> and goes on to discuss sbrk() use causing problems with ports
> >> https://youtu.be/7tQ2ftt3LO8?t=715
> >
> > And at 5:18 he says he had a vax lab with three vaxen and the Lab's
> > vax port didn't have virtual memory. Bill Joy with 3BSD which had
> > virtual memory. They installed it on the vaxen because they were
> > hitting physical memory limits for some of their programs....
> 
> One wonders what is meant by "virtual memory" in this context. I
> contend that Unix has had "virtual memory" since moving off of the
> PDP-11/20, in the sense of having a virtual address space that was
> mapped onto a (possibly contiguous) physical address space. I think
> all of these references mean demand paging, possibly with page
> reclamation or whole-process swapping under memory pressure.

I apologize if this point is too elementary, but I speculate that one
possible source of confusion comes from a file naming convention: which
of these (multiple) virtual memory or demand-paged VM systems installed
the kernel under the name "vmunix" vs. "unix".

Which ones did and did not?

When I was first learning Unix I asked a local expert why the kernel was
named "vmunix".  They told me that it was because it supported virtual
memory (and explained what that was, because I was even more callow then
than now).

Then I asked where the non-VM kernel was.  I was informed that there
wasn't one--it didn't even exist for modern architectures.  I wondered
then why, if virtual memory was a given, you wouldn't just go back to
using the filename "unix".

I wondered similar things when encountering the "vmlinux" file a couple
of years later.

Reflexive obeisance to traditions has a cost.

Regards,
Branden