On 4/3/08, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
> On Thu, 3 Apr 2008, Fernando Apesteguía wrote:
>
> > On 4/3/08, Robert P. J. Day <rpjday@xxxxxxxxxxxxxx> wrote:
> > >
> > > given that i'm determined to nail down how linux MM works, i'm
> > > perusing the code and some docs from the beginning and, since a lot of
> > > those docs annoyingly disagree with each other in some fundamental
> > > places, i'm going to be asking some annoyingly trivial questions. get
> > > used to it. :-)
> > >
> > > to start, the standard definition of high memory on a 32-bit x86
> > > system is memory above 896M.
> > >
> > > * where is that exact boundary defined?
> >
> > in arch/<architecture>/mm/init.c, e.g:
> >
> > arch/i386/mm/init.c in function zone_size_init
>
> i'm guessing you're looking at an older version of the source tree
> as that arch directory doesn't even exist anymore -- both 32 and 64
> bit versions have been amalgamated under arch/x86 and, as the previous
> poster pointed out, the limit is now in arch/x86/mm/init_32.c, which
> does answer my question. more questions coming shortly.
>
i hav found in zone_sizes_init function under file arch/i386/kernel/setup.c
1168 #ifdef CONFIG_HIGHMEM
1169 zones_size[ZONE_HIGHMEM] = highend_pfn - low;
1170 #endif
At one more place zone_sizes_init(void): arch/i386/mm/discontig.c
380 #ifdef CONFIG_HIGHMEM
381 BUG_ON(start > high);
382 zones_size[ZONE_HIGHMEM] = high - start;
383 #endif
(kernel version 2.6.16.46)
Rgds,
Adil
> rday
>
> p.s. i'm wondering what would happen if you deliberately decided to
> change the defining macro:
>
> unsigned int __VMALLOC_RESERVE = 128 << 20;
>
> --
>
> ========================================================================
> Robert P. J. Day
> Linux Consulting, Training and Annoying Kernel Pedantry:
> Have classroom, will lecture.
>
> http://crashcourse.ca Waterloo, Ontario, CANADA
> ========================================================================
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