On Thu, Jun 22, 2006 at 04:54:06PM +0100, Mel Gorman wrote:
> On Thu, 22 Jun 2006, Franck Bui-Huu wrote:
> >It's the default value (see memory_model.h). It means that pfn start
> >for node 0 is 0, therefore your physical memory address starts at 0.
>
> I know, but what I'm getting at is that ARCH_PFN_OFFSET may be unnecessary
> with flatmem-relax-requirement-for-memory-to-start-at-pfn-0.patch applied.
> ARCH_PFN_OFFSET is used as
>
> #define page_to_pfn(page) ((unsigned long)((page) - mem_map) + \
> ARCH_PFN_OFFSET)
>
> because it knew that the map may not start at PFN 0. With
> flatmem-relax-requirement-for-memory-to-start-at-pfn-0.patch, the map will
> start at PFN 0 even if physical memory does not start until later.
Doesn't that result in a massive array of struct pages if your memory
starts a 3GB physical and has 4K pages? If you have only 32MB in that
scenario, and that was correct, you'd gobble 25MB of that just to
store that array. Ouch.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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