From 39d61db0edb34d60b83c5e0d62d0e906578cc707 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 8 Dec 2006 02:37:52 -0800 Subject: [PATCH] LOG2: Alter get_order() so that it can make use of ilog2() on a constant Alter get_order() so that it can make use of ilog2() on a constant to produce a constant value, retaining the ability for an arch to override it in the non-const case. Signed-off-by: David Howells Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/page.h | 38 ++++++++++++++++++++++++++++++++++---- 1 file changed, 34 insertions(+), 4 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h index a96b5d986b6..b55052ce233 100644 --- a/include/asm-generic/page.h +++ b/include/asm-generic/page.h @@ -4,21 +4,51 @@ #ifdef __KERNEL__ #ifndef __ASSEMBLY__ -#include +#include -/* Pure 2^n version of get_order */ -static __inline__ __attribute_const__ int get_order(unsigned long size) +/* + * non-const pure 2^n version of get_order + * - the arch may override these in asm/bitops.h if they can be implemented + * more efficiently than using the arch log2 routines + * - we use the non-const log2() instead if the arch has defined one suitable + */ +#ifndef ARCH_HAS_GET_ORDER +static inline __attribute__((const)) +int __get_order(unsigned long size, int page_shift) { +#if BITS_PER_LONG == 32 && defined(ARCH_HAS_ILOG2_U32) + int order = __ilog2_u32(size) - page_shift; + return order >= 0 ? order : 0; +#elif BITS_PER_LONG == 64 && defined(ARCH_HAS_ILOG2_U64) + int order = __ilog2_u64(size) - page_shift; + return order >= 0 ? order : 0; +#else int order; - size = (size - 1) >> (PAGE_SHIFT - 1); + size = (size - 1) >> (page_shift - 1); order = -1; do { size >>= 1; order++; } while (size); return order; +#endif } +#endif + +/** + * get_order - calculate log2(pages) to hold a block of the specified size + * @n - size + * + * calculate allocation order based on the current page size + * - this can be used to initialise global variables from constant data + */ +#define get_order(n) \ +( \ + __builtin_constant_p(n) ? \ + ((n < (1UL << PAGE_SHIFT)) ? 0 : ilog2(n) - PAGE_SHIFT) : \ + __get_order(n, PAGE_SHIFT) \ + ) #endif /* __ASSEMBLY__ */ #endif /* __KERNEL__ */ -- cgit v1.2.3-18-g5258