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bitmap: optimise bitmap_set and bitmap_clear of a single bit 

We have eight users calling bitmap_clear for a single bit and seventeen
calling bitmap_set for a single bit.  Rather than fix all of them to
call __clear_bit or __set_bit, turn bitmap_clear and bitmap_set into
inline functions and make this special case efficient.

Link: http://lkml.kernel.org/r/20170628153221.11322-3-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2017-07-10 15:51:29 -07:00 committed by Linus Torvalds
parent 3cc78125a0
commit e5af323c9b
3 changed files with 24 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
include/linux/bitmap.h
View File

@ -112,9 +112,8 @@ extern int __bitmap_intersects(const unsigned long *bitmap1,
extern int __bitmap_subset(const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
extern int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
extern void bitmap_set(unsigned long *map, unsigned int start, int len);
extern void bitmap_clear(unsigned long *map, unsigned int start, int len);
extern void __bitmap_set(unsigned long *map, unsigned int start, int len);
extern void __bitmap_clear(unsigned long *map, unsigned int start, int len);
extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
unsigned long size,
@ -315,6 +314,24 @@ static __always_inline int bitmap_weight(const unsigned long *src, unsigned int
return __bitmap_weight(src, nbits);
}
static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
unsigned int nbits)
{
if (__builtin_constant_p(nbits) && nbits == 1)
__set_bit(start, map);
else
__bitmap_set(map, start, nbits);
}
static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
unsigned int nbits)
{
if (__builtin_constant_p(nbits) && nbits == 1)
__clear_bit(start, map);
else
__bitmap_clear(map, start, nbits);
}
static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *src,
unsigned int shift, int nbits)
{

8
lib/bitmap.c
View File

@ -251,7 +251,7 @@ int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
}
EXPORT_SYMBOL(__bitmap_weight);
void bitmap_set(unsigned long *map, unsigned int start, int len)
void __bitmap_set(unsigned long *map, unsigned int start, int len)
{
unsigned long *p = map + BIT_WORD(start);
const unsigned int size = start + len;
@ -270,9 +270,9 @@ void bitmap_set(unsigned long *map, unsigned int start, int len)
*p |= mask_to_set;
}
}
EXPORT_SYMBOL(bitmap_set);
EXPORT_SYMBOL(__bitmap_set);
void bitmap_clear(unsigned long *map, unsigned int start, int len)
void __bitmap_clear(unsigned long *map, unsigned int start, int len)
{
unsigned long *p = map + BIT_WORD(start);
const unsigned int size = start + len;
@ -291,7 +291,7 @@ void bitmap_clear(unsigned long *map, unsigned int start, int len)
*p &= ~mask_to_clear;
}
}
EXPORT_SYMBOL(bitmap_clear);
EXPORT_SYMBOL(__bitmap_clear);
/**
* bitmap_find_next_zero_area_off - find a contiguous aligned zero area

3
lib/test_bitmap.c
View File

@ -333,9 +333,6 @@ static void __init test_bitmap_u32_array_conversions(void)
}
}
#define __bitmap_set(a, b, c) bitmap_set(a, b, c)
#define __bitmap_clear(a, b, c) bitmap_clear(a, b, c)
static void noinline __init test_mem_optimisations(void)
{
DECLARE_BITMAP(bmap1, 1024);