63 строки
1.5 KiB
C
63 строки
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __ASM_GENERIC_GETORDER_H
|
|
#define __ASM_GENERIC_GETORDER_H
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#include <linux/compiler.h>
|
|
#include <linux/log2.h>
|
|
|
|
/*
|
|
* Runtime evaluation of get_order()
|
|
*/
|
|
static inline __attribute_const__
|
|
int __get_order(unsigned long size)
|
|
{
|
|
int order;
|
|
|
|
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 */
|