tree 9c6bc7d501984fc8a5068935683f50180e08cc46
parent 4f3bd5606a02260274555f41fd7d6368f2bea1d8
author Jeff King <peff@peff.net> 1581704559 -0500
committer Junio C Hamano <gitster@pobox.com> 1581705982 -0800

pack-bitmap: implement BLOB_LIMIT filtering

Just as the previous commit implemented BLOB_NONE, we can support
BLOB_LIMIT filters by looking at the sizes of any blobs in the result
and unsetting their bits as appropriate. This is slightly more expensive
than BLOB_NONE, but still produces a noticeable speedup (these results
are on git.git):

  Test                                         HEAD~2            HEAD
  ------------------------------------------------------------------------------------
  5310.9:  rev-list count with blob:none       1.80(1.77+0.02)   0.22(0.20+0.02) -87.8%
  5310.10: rev-list count with blob:limit=1k   1.99(1.96+0.03)   0.29(0.25+0.03) -85.4%

The implementation is similar to the BLOB_NONE one, with the exception
that we have to go object-by-object while walking the blob-type bitmap
(since we can't mask out the matches, but must look up the size
individually for each blob). The trick with using ctz64() is taken from
show_objects_for_type(), which likewise needs to find individual bits
(but wants to quickly skip over big chunks without blobs).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>