On Fri, 2008-08-15 at 10:16 -0700, C Michael Sundius wrote:
> Ah, your right. thanks. "but it's not necessar*il*y a good idea".
> is to say, we don't put
> memory above 2 GiB. No need to make the mem_section array bigger
> need be.
> This gives further credence for it to be a configurable in Kconfig as
I definitely don't want it to be something that users see. It is never
enough overhead to really care. On a 16TB system with 16MB sections,
the mem_section array is still only 16MB!!
So, I'd say to just make it as big as the arch needs in the worst case
(smallest SECTION_SIZE_BITS and largest MAX_PHYSMEM_BITS) and leave it.
We might even want to merge the 32 and 64-bit versions.
For your 32-bit version, we now use:
8 bytes (2 32-bit words) for each mem_section
2GB/128MB sections = 16
So, that's only 512 bytes.
For the 64-bit version, we now use:
16 bytes (2 64-bit words) for each mem_section
32GB/256MB sections = 128
So, that's only 2048 bytes.
If we were to merge the 32 and 64-bit versions to:
#define SECTION_SIZE_BITS 27
#define MAX_PHYSMEM_BITS 35
Your 32-bit version would go to 2048 bytes, and the 64-bit version would
go to 4096 bytes. The 32-bit version would we able to address more
memory, and the 64-bit version would be able to handle smaller memory
holes more efficiently.