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SubjectRe: is there a limit on bss size?
On Fri, 6 Oct 2000, Philipp Rumpf wrote:

> On Fri, Oct 06, 2000 at 12:32:35PM +0300, Petko Manolov wrote:
> > It is not so difficult as it looks.
>
> I don't see it being difficult at all ...
>
> > The master pgd looking as:
> >
> > .org 0x1000
> > ENTRY(swapper_pg_dir)
> > .long 0x00102007
> > .long 0x00103007
> > .fill BOOT_USER_PGD_PTRS-2,4,0
> > /* default: 766 entries */
> > .long 0x00102007
> > .long 0x00103007
> > /* default: 254 entries */
> > .fill BOOT_KERNEL_PGD_PTRS-2,4,0
> >
> >
> > should become:
> >
> >
> > .org 0x1000
> > ENTRY(swapper_pg_dir)
> > .long 0x00102007
> > .long 0x00103007
> > .... # every entry addresses 4 MB exactly
> > .... # so add as much as you want
> > .long 0x0010X007
> > .fill BOOT_USER_PGD_PTRS-X+2,4,0
>
> I'm unconvinced we need to map more than 4 MB into low virtual addresses;
> nothing seems to break with
>
> ENTRY(swapper_pg_dir)
> .long 0x00102007
> .fill BOOT_USER_PGD_PTRS-1,4,0
>

Hi Phillip,

Ah, _now_ I understand what you are talking about (took me only slightly
over a month ;) and so can answer -- try making a huge bzImage (a few
megs) and boot with it. That was the main reason Werner added the extra
stuff somewhere around 2.3.99-preX.

Having said that, I still don't see why we actually need a specific label
(like pg1) for each successive page worth of pte's if we are filling them
with data starting from pg0 until we hit empty_zero_page (as I asked in my
other message).

Regards,
Tigran

PS. I cc'd the guy who was looking to extend the page tables for booting
with huge bss also...


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