Subject: Re: The VM system
To: None <tech-kern@NetBSD.ORG>
From: Frank van der Linden <>
List: tech-kern
Date: 11/20/1995 13:39:39
Quoting Tim Liddelow,

> > I'd like to humbly suggest that a slightly more important project,
> > both from a PR and a reliability/performance point of view, would be
> > fixing the VM subsystem once and for all.

> What I think is a shame is
> that John Dyson et. al. have put in a lot of hard work with FreeBSD
> that is going to be duplicated (albeit in a NetBSD way - whatever that
> is).

I don't think we should 'just reintegrate' the FreeBSD stuff; the VM system
is too important to do that without maybe understanding the details of
John Dyson's implementation. In a recent message Gordon Ross indicated that
he had done some research into VM designs, and from his words gather that
he was inclined to go for the SVR4 approach (at least, with regard
to the VOP_{GET,PUT}PAGE interface). I've done some looking as well, and
do think this is the best way to go. How this should be integrated is
another thing. Sometimes, when looking at the VM code, I wonder if only
leaving the pmap interface intact and redoing the MI code would be
appropriate.. The VM code seems to be an example of something that looks
good in concept, but the implementation got more and more complex as time
went on. Oh, I believe that the FreeBSD code is also going towards the
VOP_XXXPAGE interface (if it hasn't already), but did it slightly different
originally. I haven't looked at their code for a while though.

I hope there'll be a fruitful discussion on this when Gordon presents
his views, as he indicated he would.

> > I also volunteer to buy the implementation team for a new VM system a
> > bottle of very fine single malt Scotch whiskey (say, The Macallan), or
> > the comparable award of their choice.

Hey, now there's an idea. The NetBSD Foundation should give away liquor
to stimulate people to write new code. Not _during_ the development mind you..
Ever coded something while not being completely sober and looked at it the
next day? ;-)

I'll stop before this thread gets too alcoholic..

- Frank