Release 4.7 include/asm-generic/getorder.h

#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;
}

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david howells
david howells
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stephen rothwell
stephen rothwell
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1
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linus torvalds
linus torvalds
8
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1
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arnd bergmann
arnd bergmann
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48
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/**
 * 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 */
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david howells
david howells
35
44.30%
2
33.33%
stephen rothwell
stephen rothwell
30
37.97%
1
16.67%
linus torvalds
linus torvalds
9
11.39%
1
16.67%
arnd bergmann
arnd bergmann
4
5.06%
1
16.67%
joerg roedel
joerg roedel
1
1.27%
1
16.67%
Total
79
100.00%
6
100.00%
  
Directory: include/asm-generic

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