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@xxxxxxxxxxxxx>
---
commit.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/commit.c b/commit.c
index 3ecdc13356..9875feec01 100644
--- a/commit.c
+++ b/commit.c
@@ -808,11 +808,14 @@ static int queue_has_nonstale(struct prio_queue *queue)
}
/* all input commits in one and twos[] must have been parsed! */
-static struct commit_list *paint_down_to_common(struct commit *one, int n, struct commit **twos)
+static struct commit_list *paint_down_to_common(struct commit *one, int n,
+ struct commit **twos,
+ int min_generation)
{
struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
struct commit_list *result = NULL;
int i;
+ uint32_t last_gen = GENERATION_NUMBER_INFINITY;
one->object.flags |= PARENT1;
if (!n) {
@@ -831,6 +834,15 @@ static struct commit_list *paint_down_to_common(struct commit *one, int n, struc
struct commit_list *parents;
int flags;
+ if (commit->generation > last_gen)
+ BUG("bad generation skip %8x > %8x at %s",
+ commit->generation, last_gen,
+ oid_to_hex(&commit->object.oid));
+ last_gen = commit->generation;
+
+ if (commit->generation < min_generation)
+ break;
+
flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
if (flags == (PARENT1 | PARENT2)) {
if (!(commit->object.flags & RESULT)) {
@@ -879,7 +891,7 @@ static struct commit_list *merge_bases_many(struct commit *one, int n, struct co
return NULL;
}
- list = paint_down_to_common(one, n, twos);
+ list = paint_down_to_common(one, n, twos, 0);
while (list) {
struct commit *commit = pop_commit(&list);
@@ -946,7 +958,7 @@ static int remove_redundant(struct commit **array, int cnt)
filled_index[filled] = j;
work[filled++] = array[j];
}
- common = paint_down_to_common(array[i], filled, work);
+ common = paint_down_to_common(array[i], filled, work, 0);
if (array[i]->object.flags & PARENT2)
redundant[i] = 1;
for (j = 0; j < filled; j++)
@@ -1070,7 +1082,7 @@ int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit *
if (commit->generation > min_generation)
return ret;
- bases = paint_down_to_common(commit, nr_reference, reference);
+ bases = paint_down_to_common(commit, nr_reference, reference, commit->generation);
if (commit->object.flags & PARENT2)
ret = 1;
clear_commit_marks(commit, all_flags);
--
2.17.0.39.g685157f7fb
