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SubjectRe: 2.4 MM overview?
On Sun, Oct 15, 2000 at 09:45:11PM +0100, Alan Cox wrote:
> > Well, we ain't got these luxuries/complications in VAXland... Hell,
> > we don't even have two-level page tables :-(
> Really. Ugh. I always assumed Vax had at least two levels because mmap on
> 4.2 BSD used to panic on 128K+ blocks. I guess there was a different reason
> for that then

We've kind of got 1.5-level page tables. There are actually 3 page tables.
The system page table maps memory starting at 0x80000000. The P0 process
page table maps from 0x0 up and the P1 process page table maps from
0x7fffffff down.

This means that sparse address spaces are going to be _really_ expensive
on PTEs. I don't know how much of a problem this is going to be yet,
but I'm sure it's going to be fun :-)

You can be sure that the first valid page won't be at 0x08048000...


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