[TUHS] Re: UNIX on (not quite bare) System/370

[Bakul Shah <bakul@iitbombay.org>]

> On Dec 20, 2022, at 2:25 PM, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> 
>> From: Bakul Shah
> 
>> Is there a publicly available description of Reiser's VM system?  I
>> found "A Unix operating system for the DEC VAX 11/780 Computer" by
>> London & Reiser which includes a long paragraph on VM (included below)
> 
> That para is basically all about the VAX paging hardware; it doesn't say
> anything about how that (any :-) Unix actually uses it.

You are right! Mea culpa.

There is a further para:

    Like the UNIX system for the PDP-11, the current
    implementation for the VAX-11/780 maintains each process
    in contiguous physical memory and swaps processes to disk
    when there is not enough physical memory to contain them
    all.  Reducing external memory fragmentation to zero by
    utilizing the VAX- 11/780 memory mapping hardware for
    scatter loading is high on the list of things to do in
    the second imple- mentation pass. To simplify kernel
    memory allocation, the size of the user-segment memory
    map is an assembly parameter which currently allows three
    pages of page table or 192K bytes total for text, data,
    and stack. This also deserves to be rewritten, both to
    allow varying process size, and to allow processes larger
    than physical memory through demand paging. Dynamic page
    table size would mean dynamic u area size if the page
    table remained part of the u area.

This seems like a minimal "bring up" port of V7. Later they
must have implemented demand paging?