| Message ID | 513F4F4E.1060009@dlhnet.de |
|---|---|
| State | New |
| Headers | show |
On 03/12/2013 09:52 AM, Peter Lieven wrote: > this patch adds the usage of buffer_find_nonzero_offset() > to skip large areas of zeroes. > > compared to loop unrolling this adds another 50% performance > benefit for skipping large areas of zeroes. > > Signed-off-by: Peter Lieven <pl@kamp.de> > --- > util/bitops.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > + if (((uintptr_t) p) % sizeof(VECTYPE) == 0 > + && size >= BITS_PER_BYTE*8*sizeof(VECTYPE)) { Spaces around binary operators. CHAR_BITS instead of magic 8. > + unsigned long tmp2 = > + buffer_find_nonzero_offset(p, ((size/BITS_PER_BYTE) & > ~(8*sizeof(VECTYPE)-1))); Spaces around binary operators.
diff --git a/util/bitops.c b/util/bitops.c index e72237a..0a056ff 100644 --- a/util/bitops.c +++ b/util/bitops.c @@ -42,10 +42,27 @@ 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 (((uintptr_t) p) % sizeof(VECTYPE) == 0 + && size >= BITS_PER_BYTE*8*sizeof(VECTYPE)) { + unsigned long tmp2 = + buffer_find_nonzero_offset(p, ((size/BITS_PER_BYTE) & ~(8*sizeof(VECTYPE)-1))); + 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 this adds another 50% performance benefit for skipping large areas of zeroes. Signed-off-by: Peter Lieven <pl@kamp.de> --- util/bitops.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)