@matheusbsbs / matheus-bagliano / commits / abf05d856f

show-branch: use prio_queue

Building a list using commit_list_insert_by_date() has quadratic worst case complexity. Avoid it by using prio_queue. Use prio_queue_peek()+prio_queue_replace() instead of prio_queue_get()+ prio_queue_put() if possible, as the former only rebalance the prio_queue heap once instead of twice. In sane repositories this won't make much of a difference because the number of items in the list or queue won't be very high: Benchmark 1: ./git_v2.52.0 show-branch origin/main origin/next origin/seen origin/todo Time (mean ± σ): 538.2 ms ± 0.8 ms [User: 527.6 ms, System: 9.6 ms] Range (min … max): 537.0 ms … 539.2 ms 10 runs Benchmark 2: ./git show-branch origin/main origin/next origin/seen origin/todo Time (mean ± σ): 530.6 ms ± 0.4 ms [User: 519.8 ms, System: 9.8 ms] Range (min … max): 530.1 ms … 531.3 ms 10 runs Summary ./git show-branch origin/main origin/next origin/seen origin/todo ran 1.01 ± 0.00 times faster than ./git_v2.52.0 show-branch origin/main origin/next origin/seen origin/todo That number is not limited, though, and in pathological cases like the one in p6010 we see a sizable improvement: Test v2.52.0 HEAD ------------------------------------------------------------------ 6010.4: git show-branch 2.19(2.19+0.00) 0.03(0.02+0.00) -98.6% Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

René Scharfe committed Dec 26, 2025 at 08:44 UTC abf05d856f50fbd8f0390b31e7187d78930dbaf5

2 files changed +27 -15

builtin/show-branch.c

+21 -13

@@ -18,6 +18,7 @@

18 #include "commit-slab.h"

19 #include "date.h"

20 #include "wildmatch.h"

21 +#include "prio-queue.h"

23 static const char*const show_branch_usage[] = {

24 N_("git show-branch [-a | --all] [-r | --remotes] [--topo-order | --date-order]\n"

@@ -59,11 +60,10 @@ static const char *get_color_reset_code(void)

60 return "";

61 }

62 -static struct commit *interesting(struct commit_list *list)

63 +static struct commit *interesting(struct prio_queue *queue)

64 {

64 - while (list) {

65 - struct commit *commit = list->item;

66 - list = list->next;

65 + for (size_t i = 0; i < queue->nr; i++) {

66 + struct commit *commit = queue->array[i].data;

67 if (commit->object.flags & UNINTERESTING)

68 continue;

69 return commit;

@@ -222,17 +222,18 @@ static int mark_seen(struct commit *commit, struct commit_list **seen_p)

222 return 0;

223 }

224

225 -static void join_revs(struct commit_list **list_p,

225 +static void join_revs(struct prio_queue *queue,

226 struct commit_list **seen_p,

227 int num_rev, int extra)

228 {

229 int all_mask = ((1u << (REV_SHIFT + num_rev)) - 1);

230 int all_revs = all_mask & ~((1u << REV_SHIFT) - 1);

231

232 - while (*list_p) {

232 + while (queue->nr) {

233 struct commit_list *parents;

234 - int still_interesting = !!interesting(*list_p);

235 - struct commit *commit = pop_commit(list_p);

234 + int still_interesting = !!interesting(queue);

235 + struct commit *commit = prio_queue_peek(queue);

236 + bool get_pending = true;

237 int flags = commit->object.flags & all_mask;

238

239 if (!still_interesting && extra <= 0)

@@ -253,8 +254,14 @@ static void join_revs(struct commit_list **list_p,

254 if (mark_seen(p, seen_p) && !still_interesting)

255 extra--;

256 p->object.flags |= flags;

256 - commit_list_insert_by_date(p, list_p);

257 + if (get_pending)

258 + prio_queue_replace(queue, p);

259 + else

260 + prio_queue_put(queue, p);

261 + get_pending = false;

262 }

263 + if (get_pending)

264 + prio_queue_get(queue);

265 }

266

267 /*

@@ -642,7 +649,8 @@ int cmd_show_branch(int ac,

649 {

650 struct commit *rev[MAX_REVS], *commit;

651 char *reflog_msg[MAX_REVS] = {0};

645 - struct commit_list *list = NULL, *seen = NULL;

652 + struct commit_list *seen = NULL;

653 + struct prio_queue queue = { compare_commits_by_commit_date };

654 unsigned int rev_mask[MAX_REVS];

655 int num_rev, i, extra = 0;

656 int all_heads = 0, all_remotes = 0;

@@ -886,14 +894,14 @@ int cmd_show_branch(int ac,

894 */

895 commit->object.flags |= flag;

896 if (commit->object.flags == flag)

889 - commit_list_insert_by_date(commit, &list);

897 + prio_queue_put(&queue, commit);

898 rev[num_rev] = commit;

899 }

900 for (i = 0; i < num_rev; i++)

901 rev_mask[i] = rev[i]->object.flags;

902

903 if (0 <= extra)

896 - join_revs(&list, &seen, num_rev, extra);

904 + join_revs(&queue, &seen, num_rev, extra);

905

906 commit_list_sort_by_date(&seen);

907

@@ -1004,7 +1012,7 @@ out:

1012 for (size_t i = 0; i < ARRAY_SIZE(reflog_msg); i++)

1013 free(reflog_msg[i]);

1014 free_commit_list(seen);

1007 - free_commit_list(list);

1015 + clear_prio_queue(&queue);

1016 free(args_copy);

1017 free(head);

1018 return ret;

t/perf/p6010-merge-base.sh

+6 -2

@@ -83,9 +83,9 @@ build_history2 () {

83 test_expect_success 'setup' '

84 max_level=15 &&

85 build_history $max_level | git fast-import --export-marks=marks &&

86 - git tag one &&

86 + git branch one &&

87 build_history2 $max_level | git fast-import --import-marks=marks --force &&

88 - git tag two &&

88 + git branch two &&

89 git gc &&

90 git log --format=%H --no-merges >expect

91 '

@@ -98,4 +98,8 @@ test_expect_success 'verify result' '

98 test_cmp expect actual

99 '

100

101 +test_perf 'git show-branch' '

102 + git show-branch one two

103 +'

104 +

105 test_done