linux-stable/include/linux/bitops.h
Alexander van Heukelum 64970b68d2 x86, generic: optimize find_next_(zero_)bit for small constant-size bitmaps
This moves an optimization for searching constant-sized small
bitmaps form x86_64-specific to generic code.

On an i386 defconfig (the x86#testing one), the size of vmlinux hardly
changes with this applied. I have observed only four places where this
optimization avoids a call into find_next_bit:

In the functions return_unused_surplus_pages, alloc_fresh_huge_page,
and adjust_pool_surplus, this patch avoids a call for a 1-bit bitmap.
In __next_cpu a call is avoided for a 32-bit bitmap. That's it.

On x86_64, 52 locations are optimized with a minimal increase in
code size:

Current #testing defconfig:
	146 x bsf, 27 x find_next_*bit
   text    data     bss     dec     hex filename
   5392637  846592  724424 6963653  6a41c5 vmlinux

After removing the x86_64 specific optimization for find_next_*bit:
	94 x bsf, 79 x find_next_*bit
   text    data     bss     dec     hex filename
   5392358  846592  724424 6963374  6a40ae vmlinux

After this patch (making the optimization generic):
	146 x bsf, 27 x find_next_*bit
   text    data     bss     dec     hex filename
   5392396  846592  724424 6963412  6a40d4 vmlinux

[ tglx@linutronix.de: build fixes ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-26 19:21:16 +02:00

192 lines
4.7 KiB
C

#ifndef _LINUX_BITOPS_H
#define _LINUX_BITOPS_H
#include <asm/types.h>
#ifdef __KERNEL__
#define BIT(nr) (1UL << (nr))
#define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_LONG)
#define BITS_PER_BYTE 8
#endif
/*
* Include this here because some architectures need generic_ffs/fls in
* scope
*/
#include <asm/bitops.h>
#define for_each_bit(bit, addr, size) \
for ((bit) = find_first_bit((addr), (size)); \
(bit) < (size); \
(bit) = find_next_bit((addr), (size), (bit) + 1))
static __inline__ int get_bitmask_order(unsigned int count)
{
int order;
order = fls(count);
return order; /* We could be slightly more clever with -1 here... */
}
static __inline__ int get_count_order(unsigned int count)
{
int order;
order = fls(count) - 1;
if (count & (count - 1))
order++;
return order;
}
static inline unsigned long hweight_long(unsigned long w)
{
return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
}
/**
* rol32 - rotate a 32-bit value left
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u32 rol32(__u32 word, unsigned int shift)
{
return (word << shift) | (word >> (32 - shift));
}
/**
* ror32 - rotate a 32-bit value right
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u32 ror32(__u32 word, unsigned int shift)
{
return (word >> shift) | (word << (32 - shift));
}
/**
* rol16 - rotate a 16-bit value left
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u16 rol16(__u16 word, unsigned int shift)
{
return (word << shift) | (word >> (16 - shift));
}
/**
* ror16 - rotate a 16-bit value right
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u16 ror16(__u16 word, unsigned int shift)
{
return (word >> shift) | (word << (16 - shift));
}
/**
* rol8 - rotate an 8-bit value left
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u8 rol8(__u8 word, unsigned int shift)
{
return (word << shift) | (word >> (8 - shift));
}
/**
* ror8 - rotate an 8-bit value right
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u8 ror8(__u8 word, unsigned int shift)
{
return (word >> shift) | (word << (8 - shift));
}
static inline unsigned fls_long(unsigned long l)
{
if (sizeof(l) == 4)
return fls(l);
return fls64(l);
}
#ifdef __KERNEL__
#ifdef CONFIG_GENERIC_FIND_NEXT_BIT
extern unsigned long __find_next_bit(const unsigned long *addr,
unsigned long size, unsigned long offset);
/**
* find_next_bit - find the next set bit in a memory region
* @addr: The address to base the search on
* @offset: The bitnumber to start searching at
* @size: The bitmap size in bits
*/
static __always_inline unsigned long
find_next_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
unsigned long value;
/* Avoid a function call if the bitmap size is a constant */
/* and not bigger than BITS_PER_LONG. */
/* insert a sentinel so that __ffs returns size if there */
/* are no set bits in the bitmap */
if (__builtin_constant_p(size) && (size < BITS_PER_LONG)) {
value = (*addr) & ((~0ul) << offset);
value |= (1ul << size);
return __ffs(value);
}
/* the result of __ffs(0) is undefined, so it needs to be */
/* handled separately */
if (__builtin_constant_p(size) && (size == BITS_PER_LONG)) {
value = (*addr) & ((~0ul) << offset);
return (value == 0) ? BITS_PER_LONG : __ffs(value);
}
/* size is not constant or too big */
return __find_next_bit(addr, size, offset);
}
extern unsigned long __find_next_zero_bit(const unsigned long *addr,
unsigned long size, unsigned long offset);
/**
* find_next_zero_bit - find the next cleared bit in a memory region
* @addr: The address to base the search on
* @offset: The bitnumber to start searching at
* @size: The bitmap size in bits
*/
static __always_inline unsigned long
find_next_zero_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
unsigned long value;
/* Avoid a function call if the bitmap size is a constant */
/* and not bigger than BITS_PER_LONG. */
/* insert a sentinel so that __ffs returns size if there */
/* are no set bits in the bitmap */
if (__builtin_constant_p(size) && (size < BITS_PER_LONG)) {
value = (~(*addr)) & ((~0ul) << offset);
value |= (1ul << size);
return __ffs(value);
}
/* the result of __ffs(0) is undefined, so it needs to be */
/* handled separately */
if (__builtin_constant_p(size) && (size == BITS_PER_LONG)) {
value = (~(*addr)) & ((~0ul) << offset);
return (value == 0) ? BITS_PER_LONG : __ffs(value);
}
/* size is not constant or too big */
return __find_next_zero_bit(addr, size, offset);
}
#endif /* CONFIG_GENERIC_FIND_NEXT_BIT */
#endif /* __KERNEL__ */
#endif