On Fri, 2008-08-15 at 10:03 +0200, Thomas Bogendoerfer wrote: > On Thu, Aug 14, 2008 at 04:52:34PM -0700, C Michael Sundius wrote: > > + > > +#ifndef CONFIG_64BIT > > +#define SECTION_SIZE_BITS 27 /* 128 MiB */ > > +#define MAX_PHYSMEM_BITS 31 /* 2 GiB */ > > +#else > > #define SECTION_SIZE_BITS 28 > > #define MAX_PHYSMEM_BITS 35 > > +#endif > > why is this needed ? I'm sure Michael can speak to the specifics. But, in general, making SECTION_SIZE_BITS smaller is good if you have lots of small holes in memory. It does this at the cost if increasing the size of the mem_section[] array. MAX_PHYSMEM_BITS should be as as small as possible, but not so small that it restricts the amount of RAM that your systems support. Increasing it has the effect of increasing the size of the mem_section[] array. My guess would be that Michael knew that his 32-bit MIPS platform only ever has 2GB of memory. He also knew that its holes (or RAM) come in 128MB sections. This configuration lets him save the most amount of memory with SPARSEMEM. Michael, I *guess* you could also include a wee bit on how you chose your numbers in the documentation. Not a big deal, though. -- Dave
