[PATCH 4/5] pack-bitmap.c: avoid repeated `pack_pos_to_offset()` during reuse
- From
Taylor Blau <me@ttaylorr.com>
- Date
- Aug 27, 2024, 21:13 UTC
- Message-ID
- <afa25c8806b0e80f1d3ed46f29eb164cab4583ac.1724793201.git.me@ttaylorr.com>
- In-Reply-To
- <cover.1724793201.git.me@ttaylorr.com>
When calling `try_partial_reuse()`, the (sole) caller from the function `reuse_partial_packfile_from_bitmap_1()` has to translate its bit position to a pack position.
In the MIDX bitmap case, the caller translates from the bit position, to a position in the MIDX's pseudo-pack order (with `pack_pos_to_midx()`), then get a pack offset (with `nth_midxed_offset()`) before finally working backwards to get the pack position in the source pack by calling `offset_to_pack_pos()`.
In the non-MIDX bitmap case, we can use the bit position as the pack position directly (see the comment at the beginning of the `reuse_partial_packfile_from_bitmap_1()` function for why).
In either case, the first thing that `try_partial_reuse()` does after being called is determine the offset of the object at the given pack position by calling `pack_pos_to_offset()`. But we already have that information in the MIDX case!
Avoid re-computing that information by instead passing it in. In the MIDX case, we already have that information stored. In the non-MIDX case, the call to `pack_pos_to_offset()` moves from the function `try_partial_reuse()` to its caller. In total, we'll save one call to `pack_pos_to_offset()` when processing MIDX bitmaps.
(On my machine, there is a slight speed-up on the order of ~2ms, but it is within the margin of error over 10 runs, so I think you'd have to have a truly gigantic repository to confidently measure any significant improvement here).
Signed-off-by: Taylor Blau <me@ttaylorr.com> --- pack-bitmap.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/pack-bitmap.c b/pack-bitmap.c index 218d7ac2eb..9d9b8c4bfb 100644 --- a/pack-bitmap.c +++ b/pack-bitmap.c @@ -2055,17 +2055,18 @@ static int try_partial_reuse(struct bitmap_index *bitmap_git, struct bitmapped_pack *pack, size_t bitmap_pos, uint32_t pack_pos, + off_t offset, struct bitmap *reuse, struct pack_window **w_curs) { - off_t offset, delta_obj_offset; + off_t delta_obj_offset; enum object_type type; unsigned long size; if (pack_pos >= pack->p->num_objects) return -1; /* not actually in the pack */ - offset = delta_obj_offset = pack_pos_to_offset(pack->p, pack_pos); + delta_obj_offset = offset; type = unpack_object_header(pack->p, w_curs, &offset, &size); if (type < 0) return -1; /* broken packfile, punt */ @@ -2184,6 +2185,7 @@ static void reuse_partial_packfile_from_bitmap_1(struct bitmap_index *bitmap_git for (offset = 0; offset < BITS_IN_EWORD; offset++) { size_t bit_pos; uint32_t pack_pos; + off_t ofs; if (word >> offset == 0) break; @@ -2198,7 +2200,6 @@ static void reuse_partial_packfile_from_bitmap_1(struct bitmap_index *bitmap_git if (bitmap_is_midx(bitmap_git)) { uint32_t midx_pos; - off_t ofs; midx_pos = pack_pos_to_midx(bitmap_git->midx, bit_pos); ofs = nth_midxed_offset(bitmap_git->midx, midx_pos); @@ -2213,10 +2214,12 @@ static void reuse_partial_packfile_from_bitmap_1(struct bitmap_index *bitmap_git BUG("advanced beyond the end of pack %s (%"PRIuMAX" > %"PRIu32")", pack_basename(pack->p), (uintmax_t)pack_pos, pack->p->num_objects); + + ofs = pack_pos_to_offset(pack->p, pack_pos); } if (try_partial_reuse(bitmap_git, pack, bit_pos, - pack_pos, reuse, &w_curs) < 0) { + pack_pos, ofs, reuse, &w_curs) < 0) { /* * try_partial_reuse indicated we couldn't reuse * any bits, so there is no point in trying more
-- 2.46.0.426.g82754d92509