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commit: add short-circuit to paint_down_to_common()
When running 'git branch --contains', the in_merge_bases_many() method calls paint_down_to_common() to discover if a specific commit is reachable from a set of branches. Commits with lower generation number are not needed to correctly answer the containment query of in_merge_bases_many(). Add a new parameter, min_generation, to paint_down_to_common() that prevents walking commits with generation number strictly less than min_generation. If 0 is given, then there is no functional change. For in_merge_bases_many(), we can pass commit->generation as the cutoff, and this saves time during 'git branch --contains' queries that would otherwise walk "around" the commit we are inspecting. For a copy of the Linux repository, where HEAD is checked out at v4.13~100, we get the following performance improvement for 'git branch --contains' over the previous commit: Before: 0.21s After: 0.13s Rel %: -38% Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
parent
f9b8908b85
commit
d7c1ec3efd
20
commit.c
20
commit.c
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@ -808,11 +808,14 @@ static int queue_has_nonstale(struct prio_queue *queue)
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}
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/* all input commits in one and twos[] must have been parsed! */
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static struct commit_list *paint_down_to_common(struct commit *one, int n, struct commit **twos)
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static struct commit_list *paint_down_to_common(struct commit *one, int n,
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struct commit **twos,
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int min_generation)
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{
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struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
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struct commit_list *result = NULL;
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int i;
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uint32_t last_gen = GENERATION_NUMBER_INFINITY;
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one->object.flags |= PARENT1;
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if (!n) {
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@ -831,6 +834,15 @@ static struct commit_list *paint_down_to_common(struct commit *one, int n, struc
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struct commit_list *parents;
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int flags;
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if (commit->generation > last_gen)
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BUG("bad generation skip %8x > %8x at %s",
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commit->generation, last_gen,
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oid_to_hex(&commit->object.oid));
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last_gen = commit->generation;
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if (commit->generation < min_generation)
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break;
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flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
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if (flags == (PARENT1 | PARENT2)) {
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if (!(commit->object.flags & RESULT)) {
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@ -879,7 +891,7 @@ static struct commit_list *merge_bases_many(struct commit *one, int n, struct co
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return NULL;
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}
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list = paint_down_to_common(one, n, twos);
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list = paint_down_to_common(one, n, twos, 0);
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while (list) {
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struct commit *commit = pop_commit(&list);
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@ -946,7 +958,7 @@ static int remove_redundant(struct commit **array, int cnt)
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filled_index[filled] = j;
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work[filled++] = array[j];
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}
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common = paint_down_to_common(array[i], filled, work);
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common = paint_down_to_common(array[i], filled, work, 0);
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if (array[i]->object.flags & PARENT2)
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redundant[i] = 1;
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for (j = 0; j < filled; j++)
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@ -1070,7 +1082,7 @@ int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit *
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if (commit->generation > min_generation)
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return ret;
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bases = paint_down_to_common(commit, nr_reference, reference);
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bases = paint_down_to_common(commit, nr_reference, reference, commit->generation);
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if (commit->object.flags & PARENT2)
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ret = 1;
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clear_commit_marks(commit, all_flags);
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