| Message ID | 1343318468-10412-3-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Jul 26, 2012 at 05:01:08PM +0100, Will Deacon wrote: > Page migration encodes the pfn in the offset field of a swp_entry_t. > For LPAE, we support physical addresses of up to 36 bits (due to > sparsemem limitations with the size of page flags), requiring 24 bits > to represent a pfn. A further 3 bits are used to encode a swp_entry into > a pte, leaving 5 bits for the type field. Furthermore, the core code > defines MAX_SWAPFILES_SHIFT as 5, so the additional type bit does not > get used. > > This patch reduces the width of the type field to 5 bits, allowing us > to create up to 31 swapfiles of 64GB each. > > Signed-off-by: Will Deacon <will.deacon@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h index d88f9f0..41dc31f 100644 --- a/arch/arm/include/asm/pgtable.h +++ b/arch/arm/include/asm/pgtable.h @@ -253,13 +253,13 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) * * 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 * 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 - * <--------------- offset --------------------> <- type --> 0 0 0 + * <--------------- offset ----------------------> < type -> 0 0 0 * - * This gives us up to 63 swap files and 32GB per swap file. Note that + * This gives us up to 31 swap files and 64GB per swap file. Note that * the offset field is always non-zero. */ #define __SWP_TYPE_SHIFT 3 -#define __SWP_TYPE_BITS 6 +#define __SWP_TYPE_BITS 5 #define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1) #define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT)
Page migration encodes the pfn in the offset field of a swp_entry_t. For LPAE, we support physical addresses of up to 36 bits (due to sparsemem limitations with the size of page flags), requiring 24 bits to represent a pfn. A further 3 bits are used to encode a swp_entry into a pte, leaving 5 bits for the type field. Furthermore, the core code defines MAX_SWAPFILES_SHIFT as 5, so the additional type bit does not get used. This patch reduces the width of the type field to 5 bits, allowing us to create up to 31 swapfiles of 64GB each. Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm/include/asm/pgtable.h | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)