----- Original Message -----
From: "Michael Noisternig" <michael.noisternig@xxxxxxxxx>
To: <openbeos@xxxxxxxxxxxxx>
Sent: Monday, June 02, 2003 3:24 PM
Subject: [openbeos] Re: kernel memory limit
> Bruno van Dooren wrote:
> > OK i see what the problem is, but why would they do that?
>
> Because it is easier. You don't have to map/unmap physical pages as
> needed, track their mappings...
>
> > isn't this just a waste of half their address space?
>
> Yes.
>
> >
> > basically this means that they can address byte 0 also at byte 0 + 1G?
> > couldn't they just physical addresses?
>
> *All* memory addresses are translated to physical addresses (on x86, and
> paging turned on). The idea is that behind a (virtual) memory address
> there can be a completely different physical address and this mapping
> can be changed on the fly. So you can do all that crucial stuff like
> presenting continous memory to the programmer (starting at virtual
> address 0), paging, swapping...
>
> So if you address virtual byte 0 + 1G, and that address' page is mapped
> to the physical page starting at address 0, then you access physical byte
0.
> If you address virtual byte 0 then the same translation happens and you
> end at the physical byte that is determined by the page mapping.
>
> >
> > kind regards,
> > Bruno.
>
> Leon Timmermans wrote:
> > Can't this be corrected somewere (is a patch posible)?
> > Or is PHYS_SIZE hardcoded everywhere.
>
> Yes, it is hardcoded by the amount of RAM you have in your system.
> But no, you can change that value by removing some RAM modules from your
> system.
> ;->
I see: I thought PHYS_SIZE == MAX_SIZE.
I should read a little code more before I say stupid things :-)
would the idea make sense if it where about MAX_SIZE??
>
> Michael Noisternig
>
>
>
>
