diff options
Diffstat (limited to 'arch/x86/include/asm/pgtable_32.h')
| -rw-r--r-- | arch/x86/include/asm/pgtable_32.h | 18 |
1 files changed, 6 insertions, 12 deletions
diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h index d7acae4120d5..7c9c968a42ef 100644 --- a/arch/x86/include/asm/pgtable_32.h +++ b/arch/x86/include/asm/pgtable_32.h @@ -57,19 +57,13 @@ do { \ #endif /* - * This is how much memory in addition to the memory covered up to - * and including _end we need mapped initially. - * We need: - * (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE) - * (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE) + * This is used to calculate the .brk reservation for initial pagetables. + * Enough space is reserved to allocate pagetables sufficient to cover all + * of LOWMEM_PAGES, which is an upper bound on the size of the direct map of + * lowmem. * - * Modulo rounding, each megabyte assigned here requires a kilobyte of - * memory, which is currently unreclaimed. - * - * This should be a multiple of a page. - * - * KERNEL_IMAGE_SIZE should be greater than pa(_end) - * and small than max_low_pfn, otherwise will waste some page table entries + * With PAE paging (PTRS_PER_PMD > 1), we allocate PTRS_PER_PGD == 4 pages for + * the PMD's in addition to the pages required for the last level pagetables. */ #if PTRS_PER_PMD > 1 #define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD) |