Commit e5af323c authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

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: default avatarMatthew Wilcox <mawilcox@microsoft.com>
Acked-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3cc78125

include/linux/bitmap.h

+20 −3
Original line number Diff line number Diff line
@@ -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)

{

lib/bitmap.c

+4 −4
Original line number Diff line number Diff line
@@ -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

lib/test_bitmap.c

+0 −3
Original line number Diff line number Diff line
@@ -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);

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