20 Dec
2022
20 Dec
'22
9:09 a.m.
On Mon, Dec 19, 2022 at 06:52:47PM -0800, Bakul Shah wrote:
On Dec 19, 2022, at 1:19 PM, Rob Pike
<robpike(a)gmail.com> wrote:
Berkeley didn't really have a good VM system, other than Bill Joy
imagining it and then went on to go to Sun and inspired Joe Moran
to implement it.
FreeBSD took Mach's VM system and while I have respect for what
Mach was trying to do, holy moly, what a mess.
I can't speak to Reiser's code because I haven't seen it, but I
can speak to Joe Moran's code, it was just so clear to see what
he was trying to do. And he did it. And you could understand it,
I did as a year out of grad school.
Reiser and London's Unix, which I greatly admired, died on the vine
for a variety of political reasons, as well as because it had
slightly different semantics in some important cases, and because
of a broad antipathy to virtual memory across the company due to
various people having used VM on inadequate hardware, and of course
then there was Multics. Sandy Fraser was very nervous about
Research adopting the BSD kernel because of his experience with
Atlas. But let it be said: Reiser's VM system was seriously
impressive, cleanly integrated, structurally central, and
wonderfully fast. And Sandy relented but the general warmth of 1127
towards Berkeley led to Research adopting Berkeley Unix as its VAX
VM platform, despite some, including myself, feeling that was
inferior choice.
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) but that is about it.
And it would be interesting to hear why and what you found in
Reiser's VM system that was better than Berkeley's VM system.