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authorMatthew Wilcox <mawilcox@microsoft.com>2017-07-11 00:51:32 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-11 01:32:34 +0200
commit2a98dc028f911a7c59c87d11d4eed6626be1605b (patch)
tree6ef30a1615e1a374a442c18d1a92015264d32b0f /include
parentbitmap: optimise bitmap_set and bitmap_clear of a single bit (diff)
downloadlinux-2a98dc028f911a7c59c87d11d4eed6626be1605b.tar.xz
linux-2a98dc028f911a7c59c87d11d4eed6626be1605b.zip
include/linux/bitmap.h: turn bitmap_set and bitmap_clear into memset when possible
Several callers have constant 'start' and an 'nbits' that is a multiple of 8, so we can turn them into calls to memset. We don't need the entirety of 'start' and 'nbits' to be constant, we just need to know whether they're divisible by 8. Link: http://lkml.kernel.org/r/20170628153221.11322-4-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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bitmap.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 4e0f0c8167af..c04c9d155e59 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -319,6 +319,9 @@ static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
{
if (__builtin_constant_p(nbits) && nbits == 1)
__set_bit(start, map);
+ else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) &&
+ __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))
+ memset((char *)map + start / 8, 0xff, nbits / 8);
else
__bitmap_set(map, start, nbits);
}
@@ -328,6 +331,9 @@ static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
{
if (__builtin_constant_p(nbits) && nbits == 1)
__clear_bit(start, map);
+ else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) &&
+ __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))
+ memset((char *)map + start / 8, 0, nbits / 8);
else
__bitmap_clear(map, start, nbits);
}