| Message ID | 1363881457-14814-5-git-send-email-pl@kamp.de |
|---|---|
| State | New |
| Headers | show |
On 03/21/2013 09:57 AM, 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> > --- > util/bitops.c | 22 +++++++++++++++++++--- > 1 file changed, 19 insertions(+), 3 deletions(-) Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/util/bitops.c b/util/bitops.c index e72237a..8ea79ae 100644 --- a/util/bitops.c +++ b/util/bitops.c @@ -42,10 +42,26 @@ 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) { + if ((tmp = *p)) { + 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) { + if ((tmp = *p)) { + goto found_middle; + } + } } + p++; result += BITS_PER_LONG; size -= BITS_PER_LONG; }
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> --- util/bitops.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-)