diff options
Diffstat (limited to 'include/asm-generic/getorder.h')
| -rw-r--r-- | include/asm-generic/getorder.h | 53 |
1 files changed, 45 insertions, 8 deletions
diff --git a/include/asm-generic/getorder.h b/include/asm-generic/getorder.h index 67e7245dc9b3..65e4468ac53d 100644 --- a/include/asm-generic/getorder.h +++ b/include/asm-generic/getorder.h @@ -4,21 +4,58 @@ #ifndef __ASSEMBLY__ #include <linux/compiler.h> +#include <linux/log2.h> -/* Pure 2^n version of get_order */ -static inline __attribute_const__ int get_order(unsigned long size) +/* + * Runtime evaluation of get_order() + */ +static inline __attribute_const__ +int __get_order(unsigned long size) { int order; - size = (size - 1) >> (PAGE_SHIFT - 1); - order = -1; - do { - size >>= 1; - order++; - } while (size); + size--; + size >>= PAGE_SHIFT; +#if BITS_PER_LONG == 32 + order = fls(size); +#else + order = fls64(size); +#endif return order; } +/** + * get_order - Determine the allocation order of a memory size + * @size: The size for which to get the order + * + * Determine the allocation order of a particular sized block of memory. This + * is on a logarithmic scale, where: + * + * 0 -> 2^0 * PAGE_SIZE and below + * 1 -> 2^1 * PAGE_SIZE to 2^0 * PAGE_SIZE + 1 + * 2 -> 2^2 * PAGE_SIZE to 2^1 * PAGE_SIZE + 1 + * 3 -> 2^3 * PAGE_SIZE to 2^2 * PAGE_SIZE + 1 + * 4 -> 2^4 * PAGE_SIZE to 2^3 * PAGE_SIZE + 1 + * ... + * + * The order returned is used to find the smallest allocation granule required + * to hold an object of the specified size. + * + * The result is undefined if the size is 0. + * + * This function may be used to initialise variables with compile time + * evaluations of constants. + */ +#define get_order(n) \ +( \ + __builtin_constant_p(n) ? ( \ + ((n) == 0UL) ? BITS_PER_LONG - PAGE_SHIFT : \ + (((n) < (1UL << PAGE_SHIFT)) ? 0 : \ + ilog2((n) - 1) - PAGE_SHIFT + 1) \ + ) : \ + __get_order(n) \ +) + #endif /* __ASSEMBLY__ */ #endif /* __ASM_GENERIC_GETORDER_H */ |