@matheusbsbs / matheus-bagliano / commits / f9b8908b85

commit: use generation numbers for in_merge_bases()

The containment algorithm for 'git branch --contains' is different from that for 'git tag --contains' in that it uses is_descendant_of() instead of contains_tag_algo(). The expensive portion of the branch algorithm is computing merge bases. When a commit-graph file exists with generation numbers computed, we can avoid this merge-base calculation when the target commit has a larger generation number than the initial commits. Performance tests were run on a copy of the Linux repository where HEAD is contained in v4.13 but no earlier tag. Also, all tags were copied to branches and 'git branch --contains' was tested: Before: 60.0s After: 0.4s Rel %: -99.3% Reported-by: Jeff King <peff@peff.net> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Derrick Stolee committed May 1, 2018 at 12:47 UTC f9b8908b85247ef60001a683c281af0080e9ee77

1 file changed +8 -1

commit.c

+8 -1

@@ -1056,12 +1056,19 @@ int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit *

1056 {

1057 struct commit_list *bases;

1058 int ret = 0, i;

1059 + uint32_t min_generation = GENERATION_NUMBER_INFINITY;

1060

1061 if (parse_commit(commit))

1062 return ret;

1062 - for (i = 0; i < nr_reference; i++)

1063 + for (i = 0; i < nr_reference; i++) {

1064 if (parse_commit(reference[i]))

1065 return ret;

1066 + if (reference[i]->generation < min_generation)

1067 + min_generation = reference[i]->generation;

1068 + }

1069 +

1070 + if (commit->generation > min_generation)

1071 + return ret;

1072

1073 bases = paint_down_to_common(commit, nr_reference, reference);

1074 if (commit->object.flags & PARENT2)