Messages in this thread |  | | Date | Mon, 16 Oct 2000 12:33:49 +0100 | From | Philipp Rumpf <> | Subject | Re: 2.4 MM overview? |
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On Sun, Oct 15, 2000 at 11:35:23PM +0100, Kenn Humborg wrote: > 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.
And they have to be physically contiguous I guess ?
> 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 :-)
512 byte pages, 4 bytes per pte ? Ouch. Can you fill the TLB manually ?
OTOH, I think mapping all physical memory makes sense with the three page table setup.
Philipp Rumpf - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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