1 Jan
2023
1 Jan
'23
11:52 a.m.
At 2023-01-01T00:35:12-0500, Dan Cross wrote:
On Sun, Jan 1, 2023 at 12:27 AM Warner Losh
<imp(a)bsdimp.com> wrote:
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
On Sat, Dec 31, 2022, 9:38 PM Jonathan Gray
<jsg(a)jsg.id.au> wrote:
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. [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....