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commit-reach: deduplicate queue entries in paint_down_to_common 

paint_down_to_common() can enqueue the same commit multiple times
when it is reached through different parents with different flag
combinations. Add an ENQUEUED flag to track whether a commit is
currently in the priority queue, and skip it if already present.

Introduce prio_queue_put_dedup() and prio_queue_get_dedup()
wrappers that manage the ENQUEUED flag on enqueue and dequeue.

This change is performance-neutral on its own: the O(n)
queue_has_nonstale() scan still dominates the per-iteration cost.
However, the deduplication guarantee (each commit appears in the
queue at most once) is a prerequisite for the next commit, which
replaces that scan with O(1) tracking.

Signed-off-by: Kristofer Karlsson <krka@spotify.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
main
Kristofer Karlsson 2026-05-25 14:28:04 +00:00 committed by Junio C Hamano
parent 85a30b5b26
commit f767dae3e6
2 changed files with 23 additions and 6 deletions
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27
commit-reach.c
View File

@ -17,8 +17,9 @@
#define PARENT2 (1u<<17)
#define STALE (1u<<18)
#define RESULT (1u<<19)
#define ENQUEUED (1u<<20)

static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT | ENQUEUED);

static int compare_commits_by_gen(const void *_a, const void *_b)
{
@ -39,6 +40,22 @@ static int compare_commits_by_gen(const void *_a, const void *_b)
return 0;
}

static void prio_queue_put_dedup(struct prio_queue *queue, struct commit *c)
{
if (c->object.flags & ENQUEUED)
return;
c->object.flags |= ENQUEUED;
prio_queue_put(queue, c);
}

static struct commit *prio_queue_get_dedup(struct prio_queue *queue)
{
struct commit *commit = prio_queue_get(queue);
if (commit)
commit->object.flags &= ~ENQUEUED;
return commit;
}

static int queue_has_nonstale(struct prio_queue *queue)
{
for (size_t i = 0; i < queue->nr; i++) {
@ -70,15 +87,15 @@ static int paint_down_to_common(struct repository *r,
commit_list_append(one, result);
return 0;
}
prio_queue_put(&queue, one);
prio_queue_put_dedup(&queue, one);

for (i = 0; i < n; i++) {
twos[i]->object.flags |= PARENT2;
prio_queue_put(&queue, twos[i]);
prio_queue_put_dedup(&queue, twos[i]);
}

while (queue_has_nonstale(&queue)) {
struct commit *commit = prio_queue_get(&queue);
struct commit *commit = prio_queue_get_dedup(&queue);
struct commit_list *parents;
int flags;
timestamp_t generation = commit_graph_generation(commit);
@ -124,7 +141,7 @@ static int paint_down_to_common(struct repository *r,
oid_to_hex(&p->object.oid));
}
p->object.flags |= flags;
prio_queue_put(&queue, p);
prio_queue_put_dedup(&queue, p);
}
}


2
object.h
View File

@ -75,7 +75,7 @@ void object_array_init(struct object_array *array);
* bundle.c: 16
* http-push.c: 11-----14
* commit-graph.c: 15
* commit-reach.c: 16-----19
* commit-reach.c: 16-------20
* builtin/last-modified.c: 1617
* object-name.c: 20
* list-objects-filter.c: 21