File: getorder.h

package info (click to toggle)
linux 3.16.7-ckt2-1
  • links: PTS, VCS
  • area: main
  • in suites: jessie
  • size: 734,120 kB
  • ctags: 2,369,605
  • sloc: ansic: 12,212,866; asm: 277,256; perl: 53,999; xml: 47,771; makefile: 30,481; sh: 8,035; python: 6,583; cpp: 5,121; yacc: 4,254; lex: 2,215; awk: 741; pascal: 231; lisp: 218; sed: 30
file content (61 lines) | stat: -rw-r--r-- 1,448 bytes parent folder | download | duplicates (26)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
#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 */