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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-05-25 09:32:20 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-06-13 15:58:21 +0200 |
| commit | 7dd968163f7c12bcb2132792bf873133b397a2d2 (patch) | |
| tree | da3208182cf31c4dbee7863c908bc6e5a7e78251 | |
| parent | s390/mm: fix vunmap vs finish_arch_post_lock_switch (diff) | |
| download | linux-7dd968163f7c12bcb2132792bf873133b397a2d2.tar.xz linux-7dd968163f7c12bcb2132792bf873133b397a2d2.zip | |
bitmap: bitmap_equal memcmp optimization
The bitmap_equal function has optimized code for small bitmaps with less
than BITS_PER_LONG bits. For larger bitmaps the out-of-line function
__bitmap_equal is called.
For a constant number of bits divisible by BITS_PER_LONG the memcmp
function can be used. For s390 gcc knows how to optimize this function,
memcmp calls with up to 256 bytes / 2048 bits are translated into a
single instruction.
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| -rw-r--r-- | include/linux/bitmap.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index e9b0b9ab07e5..27bfc0b631a9 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -267,6 +267,10 @@ static inline int bitmap_equal(const unsigned long *src1, { if (small_const_nbits(nbits)) return ! ((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)); +#ifdef CONFIG_S390 + else if (__builtin_constant_p(nbits) && (nbits % BITS_PER_LONG) == 0) + return !memcmp(src1, src2, nbits / 8); +#endif else return __bitmap_equal(src1, src2, nbits); } |