Message ID | 1363956370-23681-5-git-send-email-pl@kamp.de |
---|---|
State | New |
Headers | show |
On 03/22/2013 02:46 PM, Peter Lieven wrote: > this patch adds the usage of buffer_find_nonzero_offset() > to skip large areas of zeroes. > > compared to loop unrolling presented in an earlier > patch this adds another 50% performance benefit for > skipping large areas of zeroes. loop unrolling alone > added close to 100% speedup. > > Signed-off-by: Peter Lieven <pl@kamp.de> > Reviewed-by: Eric Blake <eblake@redhat.com> > --- > util/bitops.c | 24 +++++++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > diff --git a/util/bitops.c b/util/bitops.c > index e72237a..9bb61ff 100644 > --- a/util/bitops.c > +++ b/util/bitops.c > @@ -42,10 +42,28 @@ unsigned long find_next_bit(const unsigned long *addr, unsigned long size, > size -= BITS_PER_LONG; > result += BITS_PER_LONG; > } > - while (size & ~(BITS_PER_LONG-1)) { > - if ((tmp = *(p++))) { > - goto found_middle; > + while (size >= BITS_PER_LONG) { > + tmp = *p; > + if (tmp) { > + goto found_middle; > + } > + if (can_use_buffer_find_nonzero_offset(p, size / BITS_PER_BYTE)) { > + size_t tmp2 = > + buffer_find_nonzero_offset(p, size / BITS_PER_BYTE); > + result += tmp2 * BITS_PER_BYTE; > + size -= tmp2 * BITS_PER_BYTE; > + p += tmp2 / sizeof(unsigned long); > + if (!size) { > + return result; > + } > + if (tmp2) { > + tmp = *p; > + if (tmp) { > + goto found_middle; > + } > + } > } > + p++; > result += BITS_PER_LONG; > size -= BITS_PER_LONG; > } > Reviewed-by: Orit Wasserman <owasserm@redhat.com>
diff --git a/util/bitops.c b/util/bitops.c index e72237a..9bb61ff 100644 --- a/util/bitops.c +++ b/util/bitops.c @@ -42,10 +42,28 @@ unsigned long find_next_bit(const unsigned long *addr, unsigned long size, size -= BITS_PER_LONG; result += BITS_PER_LONG; } - while (size & ~(BITS_PER_LONG-1)) { - if ((tmp = *(p++))) { - goto found_middle; + while (size >= BITS_PER_LONG) { + tmp = *p; + if (tmp) { + goto found_middle; + } + if (can_use_buffer_find_nonzero_offset(p, size / BITS_PER_BYTE)) { + size_t tmp2 = + buffer_find_nonzero_offset(p, size / BITS_PER_BYTE); + result += tmp2 * BITS_PER_BYTE; + size -= tmp2 * BITS_PER_BYTE; + p += tmp2 / sizeof(unsigned long); + if (!size) { + return result; + } + if (tmp2) { + tmp = *p; + if (tmp) { + goto found_middle; + } + } } + p++; result += BITS_PER_LONG; size -= BITS_PER_LONG; }