[TUHS] A few comments on porting the Bourne shell

[Warner Losh]

On Sat, Dec 31, 2022, 10:35 PM Dan Cross <crossd at gmail.com> wrote:

> On Sun, Jan 1, 2023 at 12:27 AM Warner Losh <imp at bsdimp.com> wrote:
> > On Sat, Dec 31, 2022, 9:38 PM Jonathan Gray <jsg at 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.
>

It's clear from context it's demand paging and that unlocks processes
larger than physical memory. Imho.

Warner

>
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