Subject: [PATCH v3 0/7] pack-bitmap: permute existing namehash values

From: Taylor Blau <[email-masked]>
Date: Fri, 17 Sep 2021 17:21:11 -0400

Here is a very small reroll of my series to permute values from an existing
hash-cache when generating multi-pack reachability bitmaps.

The only changes since last time are a slightly modified version of the
performance tests which don't time generating the pack-bitmap. And the new test
in t5326 no longer has a redundant `git config pack.writeBitmapHashCache` since
it is true by default.

It is based on the `tb/multi-pack-bitmaps` topic, which graduated to master.
Thanks in advance for your review on this hopefully-final iteration :-).

Taylor Blau (7):
  t/helper/test-bitmap.c: add 'dump-hashes' mode
  pack-bitmap.c: propagate namehash values from existing bitmaps
  midx.c: respect 'pack.writeBitmapHashcache' when writing bitmaps
  p5326: create missing 'perf-tag' tag
  p5326: don't set core.multiPackIndex unnecessarily
  p5326: generate pack bitmaps before writing the MIDX bitmap
  t5326: test propagating hashcache values

 Documentation/config/pack.txt      |  4 +++
 builtin/multi-pack-index.c         | 21 +++++++++++++++
 midx.c                             |  6 ++++-
 midx.h                             |  1 +
 pack-bitmap.c                      | 41 +++++++++++++++++++++++++-----
 pack-bitmap.h                      |  1 +
 t/helper/test-bitmap.c             | 10 +++++++-
 t/perf/p5326-multi-pack-bitmaps.sh | 15 ++++++++---
 t/t5326-multi-pack-bitmaps.sh      | 30 ++++++++++++++++++++++
 9 files changed, 118 insertions(+), 11 deletions(-)

Range-diff against v2:
1:  4f2b8d9530 = 1:  4f2b8d9530 t/helper/test-bitmap.c: add 'dump-hashes' mode
2:  2cd2f3aa5e = 2:  2cd2f3aa5e pack-bitmap.c: propagate namehash values from existing bitmaps
3:  f0d8f106c2 = 3:  f0d8f106c2 midx.c: respect 'pack.writeBitmapHashcache' when writing bitmaps
4:  a8c6e845ad = 4:  a8c6e845ad p5326: create missing 'perf-tag' tag
5:  191922c8f2 = 5:  191922c8f2 p5326: don't set core.multiPackIndex unnecessarily
6:  040bb40548 ! 6:  59b6914ef8 p5326: generate pack bitmaps before writing the MIDX bitmap
    @@ Commit message
         we have to rely on a single-pack bitmap to generate those values for us.

         Therefore, generate a pack bitmap before the MIDX one in order to ensure
    -    that the MIDX bitmap has entries in its hash-cache.
    +    that the MIDX bitmap has entries in its hash-cache. Since we don't want
    +    to time generating the pack bitmap, move that to a non-perf test run
    +    before we try to generate the MIDX bitmap.
    +
    +    Likewise, get rid of the pack bitmap afterwords, to make certain that we
    +    are not accidentally using it in the performance tests run later on.

         Signed-off-by: Taylor Blau <[email-masked]>

      ## t/perf/p5326-multi-pack-bitmaps.sh ##
     @@ t/perf/p5326-multi-pack-bitmaps.sh: test_expect_success 'create tags' '
    + 	git tag --message="tag pointing to HEAD" perf-tag HEAD
      '

    ++test_expect_success 'start with bitmapped pack' '
    ++	git repack -adb
    ++'
    ++
      test_perf 'setup multi-pack index' '
     -	git repack -ad &&
    -+	git repack -adb &&
      	git multi-pack-index write --bitmap
      '

    ++test_expect_success 'drop pack bitmap' '
    ++	rm -f .git/objects/pack/pack-*.bitmap
    ++'
    ++
    + test_full_bitmap
    +
    + test_expect_success 'create partial bitmap state' '
7:  fdf71432b3 ! 7:  bb16125915 t5326: test propagating hashcache values
    @@ t/t5326-multi-pack-bitmaps.sh: test_expect_success 'pack.preferBitmapTips' '
     +	(
     +		cd repo &&
     +
    -+		git config pack.writeBitmapHashCache true &&
    -+
     +		test_commit base &&
     +		test_commit base2 &&
     +		git repack -adb &&
--
2.33.0.96.g73915697e6