Re: [PATCH] 16K page size in 32 bit kernel

[Songmao Tian <tiansm@lemote.com>]

Thanks Dajie:)

With 22 PGDIR_SHIFT, 15 extra page tables is populated when a whole 64M 
address space is accessed, the patch can save memory quite a bit:)

Dajie Tan wrote:
> 32-bit Kernel for loongson2e currently use 16KB page size to avoid
> cache alias problem.So, the definiton of PGDIR_SHIFT muse be 12+14.
>
> Using 22 in 16K page size do not lead to a serious problem but the number
> of pages allocated for page table is more than previous. (cat
> /proc/vmstat | grep nr_page_table_pages)
>
> It's been tested on FuLong mini PC(loongson2e inside).
>
>
> Signed-off-by: Dajie Tan <jiankemeng@gmail.com>
> ---
>  include/asm-mips/pgtable-32.h |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/include/asm-mips/pgtable-32.h b/include/asm-mips/pgtable-32.h
> index 2fbd47e..8d34ebf 100644
> --- a/include/asm-mips/pgtable-32.h
> +++ b/include/asm-mips/pgtable-32.h
> @@ -46,7 +46,7 @@ extern int add_temporary_entry(unsigned long entrylo0, unsigned long entrylo1,
>  #ifdef CONFIG_64BIT_PHYS_ADDR
>  #define PGDIR_SHIFT	21
>  #else
> -#define PGDIR_SHIFT	22
> +#define PGDIR_SHIFT	(PAGE_SHIFT + (PAGE_SHIFT + PTE_ORDER - 2))
>  #endif
>  #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
>  #define PGDIR_MASK	(~(PGDIR_SIZE-1))
>
>
>
>
>