From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> Acked-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/bitmap.h | 6 ++++++ 1 file changed, 6 insertions(+) diff -puN include/linux/bitmap.h~turn-bitmap_set-and-bitmap_clear-into-memset-when-possible include/linux/bitmap.h --- a/include/linux/bitmap.h~turn-bitmap_set-and-bitmap_clear-into-memset-when-possible +++ a/include/linux/bitmap.h @@ -319,6 +319,9 @@ static __always_inline void bitmap_set(u { 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 { 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); } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
