From: René Scharfe Date: Fri, 18 Jul 2025 09:39:06 +0000 (+0200) Subject: commit: convert pop_most_recent_commit() to prio_queue X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d6ec08788e667d4f556e9c2d97bbd7adb7e582be;p=thirdparty%2Fgit.git commit: convert pop_most_recent_commit() to prio_queue pop_most_recent_commit() calls commit_list_insert_by_date() for parent commits, which is itself called in a loop. This can lead to quadratic complexity if there are many merges. Replace the commit_list with a prio_queue to ensure logarithmic worst case complexity and convert all three users. Add a performance test that exercises one of them using a pathological history that consists of 50% merges and 50% root commits to demonstrate the speedup: Test v2.50.1 HEAD ---------------------------------------------------------------------- 1501.2: rev-parse ':/65535' 2.48(2.47+0.00) 0.20(0.19+0.00) -91.9% Alas, sane histories don't benefit from the conversion much, and traversing Git's own history takes a 1% performance hit on my machine: $ hyperfine -w3 -L git ./git_2.50.1,./git '{git} rev-parse :/^Initial.revision' Benchmark 1: ./git_2.50.1 rev-parse :/^Initial.revision Time (mean ± σ): 1.071 s ± 0.004 s [User: 1.052 s, System: 0.017 s] Range (min … max): 1.067 s … 1.078 s 10 runs Benchmark 2: ./git rev-parse :/^Initial.revision Time (mean ± σ): 1.079 s ± 0.003 s [User: 1.060 s, System: 0.017 s] Range (min … max): 1.074 s … 1.083 s 10 runs Summary ./git_2.50.1 rev-parse :/^Initial.revision ran 1.01 ± 0.00 times faster than ./git rev-parse :/^Initial.revision Signed-off-by: René Scharfe Signed-off-by: Junio C Hamano --- diff --git a/commit.c b/commit.c index e915b2b9a1..0200759aaa 100644 --- a/commit.c +++ b/commit.c @@ -31,6 +31,7 @@ #include "parse.h" #include "object-file.h" #include "object-file-convert.h" +#include "prio-queue.h" static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **); @@ -738,17 +739,17 @@ void commit_list_sort_by_date(struct commit_list **list) commit_list_sort(list, commit_list_compare_by_date); } -struct commit *pop_most_recent_commit(struct commit_list **list, +struct commit *pop_most_recent_commit(struct prio_queue *queue, unsigned int mark) { - struct commit *ret = pop_commit(list); + struct commit *ret = prio_queue_get(queue); struct commit_list *parents = ret->parents; while (parents) { struct commit *commit = parents->item; if (!repo_parse_commit(the_repository, commit) && !(commit->object.flags & mark)) { commit->object.flags |= mark; - commit_list_insert_by_date(commit, list); + prio_queue_put(queue, commit); } parents = parents->next; } diff --git a/commit.h b/commit.h index 70c870dae4..9630c076d6 100644 --- a/commit.h +++ b/commit.h @@ -201,10 +201,10 @@ const char *repo_logmsg_reencode(struct repository *r, const char *skip_blank_lines(const char *msg); -/** Removes the first commit from a list sorted by date, and adds all - * of its parents. - **/ -struct commit *pop_most_recent_commit(struct commit_list **list, +struct prio_queue; + +/* Removes the first commit from a prio_queue and adds its parents. */ +struct commit *pop_most_recent_commit(struct prio_queue *queue, unsigned int mark); struct commit *pop_commit(struct commit_list **stack); diff --git a/fetch-pack.c b/fetch-pack.c index fa4231fee7..6afe2f964e 100644 --- a/fetch-pack.c +++ b/fetch-pack.c @@ -34,6 +34,7 @@ #include "commit-graph.h" #include "sigchain.h" #include "mergesort.h" +#include "prio-queue.h" static int transfer_unpack_limit = -1; static int fetch_unpack_limit = -1; @@ -600,7 +601,7 @@ done: return count ? retval : 0; } -static struct commit_list *complete; +static struct prio_queue complete = { compare_commits_by_commit_date }; static int mark_complete(const struct object_id *oid) { @@ -608,7 +609,7 @@ static int mark_complete(const struct object_id *oid) if (commit && !(commit->object.flags & COMPLETE)) { commit->object.flags |= COMPLETE; - commit_list_insert(commit, &complete); + prio_queue_put(&complete, commit); } return 0; } @@ -625,9 +626,12 @@ static int mark_complete_oid(const char *refname UNUSED, static void mark_recent_complete_commits(struct fetch_pack_args *args, timestamp_t cutoff) { - while (complete && cutoff <= complete->item->date) { + while (complete.nr) { + struct commit *item = prio_queue_peek(&complete); + if (item->date < cutoff) + break; print_verbose(args, _("Marking %s as complete"), - oid_to_hex(&complete->item->object.oid)); + oid_to_hex(&item->object.oid)); pop_most_recent_commit(&complete, COMPLETE); } } @@ -797,7 +801,6 @@ static void mark_complete_and_common_ref(struct fetch_negotiator *negotiator, refs_for_each_rawref(get_main_ref_store(the_repository), mark_complete_oid, NULL); for_each_cached_alternate(NULL, mark_alternate_complete); - commit_list_sort_by_date(&complete); if (cutoff) mark_recent_complete_commits(args, cutoff); } diff --git a/object-name.c b/object-name.c index 9288b2dd24..8a787b3ff3 100644 --- a/object-name.c +++ b/object-name.c @@ -28,6 +28,7 @@ #include "commit-reach.h" #include "date.h" #include "object-file-convert.h" +#include "prio-queue.h" static int get_oid_oneline(struct repository *r, const char *, struct object_id *, const struct commit_list *); @@ -1457,7 +1458,7 @@ static int get_oid_oneline(struct repository *r, const char *prefix, struct object_id *oid, const struct commit_list *list) { - struct commit_list *copy = NULL, **copy_tail = © + struct prio_queue copy = { compare_commits_by_commit_date }; const struct commit_list *l; int found = 0; int negative = 0; @@ -1479,9 +1480,9 @@ static int get_oid_oneline(struct repository *r, for (l = list; l; l = l->next) { l->item->object.flags |= ONELINE_SEEN; - copy_tail = &commit_list_insert(l->item, copy_tail)->next; + prio_queue_put(©, l->item); } - while (copy) { + while (copy.nr) { const char *p, *buf; struct commit *commit; int matches; @@ -1503,7 +1504,7 @@ static int get_oid_oneline(struct repository *r, regfree(®ex); for (l = list; l; l = l->next) clear_commit_marks(l->item, ONELINE_SEEN); - free_commit_list(copy); + clear_prio_queue(©); return found ? 0 : -1; } @@ -2057,7 +2058,6 @@ static enum get_oid_result get_oid_with_context_1(struct repository *repo, cb.list = &list; refs_for_each_ref(get_main_ref_store(repo), handle_one_ref, &cb); refs_head_ref(get_main_ref_store(repo), handle_one_ref, &cb); - commit_list_sort_by_date(&list); ret = get_oid_oneline(repo, name + 2, oid, list); free_commit_list(list); diff --git a/t/meson.build b/t/meson.build index d052fc3e23..b39f6d008d 100644 --- a/t/meson.build +++ b/t/meson.build @@ -1117,6 +1117,7 @@ benchmarks = [ 'perf/p1450-fsck.sh', 'perf/p1451-fsck-skip-list.sh', 'perf/p1500-graph-walks.sh', + 'perf/p1501-rev-parse-oneline.sh', 'perf/p2000-sparse-operations.sh', 'perf/p3400-rebase.sh', 'perf/p3404-rebase-interactive.sh', diff --git a/t/perf/p1501-rev-parse-oneline.sh b/t/perf/p1501-rev-parse-oneline.sh new file mode 100755 index 0000000000..538fa9c404 --- /dev/null +++ b/t/perf/p1501-rev-parse-oneline.sh @@ -0,0 +1,71 @@ +#!/bin/sh + +test_description='Test :/ object name notation' + +. ./perf-lib.sh + +test_perf_fresh_repo + +# +# Creates lots of merges to make history traversal costly. In +# particular it creates 2^($max_level-1)-1 2-way merges on top of +# 2^($max_level-1) root commits. E.g., the commit history looks like +# this for a $max_level of 3: +# +# _1_ +# / \ +# 2 3 +# / \ / \ +# 4 5 6 7 +# +# The numbers are the fast-import marks, which also are the commit +# messages. 1 is the HEAD commit and a merge, 2 and 3 are also merges, +# 4-7 are the root commits. +# +build_history () { + local max_level="$1" && + local level="${2:-1}" && + local mark="${3:-1}" && + if test $level -eq $max_level + then + echo "reset refs/heads/master" && + echo "from $ZERO_OID" && + echo "commit refs/heads/master" && + echo "mark :$mark" && + echo "committer C 1234567890 +0000" && + echo "data < 1234567890 +0000" && + echo "data <commits && + sed -n -e "s/ .*$//p" -e "q" expect && + sed -n -e "s/^.* //p" -e "q" needle +' + +test_perf "rev-parse :/$(cat needle)" ' + git rev-parse :/$(cat needle) >actual +' + +test_expect_success 'verify result' ' + test_cmp expect actual +' + +test_done diff --git a/walker.c b/walker.c index b470d43e54..c6d0e20c72 100644 --- a/walker.c +++ b/walker.c @@ -14,6 +14,7 @@ #include "blob.h" #include "refs.h" #include "progress.h" +#include "prio-queue.h" static struct object_id current_commit_oid; @@ -78,7 +79,7 @@ static int process_tree(struct walker *walker, struct tree *tree) #define SEEN (1U << 1) #define TO_SCAN (1U << 2) -static struct commit_list *complete = NULL; +static struct prio_queue complete = { compare_commits_by_commit_date }; static int process_commit(struct walker *walker, struct commit *commit) { @@ -87,7 +88,10 @@ static int process_commit(struct walker *walker, struct commit *commit) if (repo_parse_commit(the_repository, commit)) return -1; - while (complete && complete->item->date >= commit->date) { + while (complete.nr) { + struct commit *item = prio_queue_peek(&complete); + if (item->date < commit->date) + break; pop_most_recent_commit(&complete, COMPLETE); } @@ -233,7 +237,7 @@ static int mark_complete(const char *path UNUSED, if (commit) { commit->object.flags |= COMPLETE; - commit_list_insert(commit, &complete); + prio_queue_put(&complete, commit); } return 0; } @@ -302,7 +306,6 @@ int walker_fetch(struct walker *walker, int targets, char **target, if (!walker->get_recover) { refs_for_each_ref(get_main_ref_store(the_repository), mark_complete, NULL); - commit_list_sort_by_date(&complete); } for (i = 0; i < targets; i++) {