@matheusbsbs / matheus-bagliano / commits / e4fd06e7e2

diffcore-rename: avoid doing basename comparisons for irrelevant sources

The basename comparison optimization implemented in find_basename_matches() is very beneficial since it allows a source to sometimes only be compared with one other file instead of N other files. When a match is found, both a source and destination can be removed from the matrix of inexact rename comparisons. In contrast, the irrelevant source optimization only allows us to remove a source from the matrix of inexact rename comparisons...but it has the advantage of allowing a source file to not even be loaded into memory at all and be compared to 0 other files. Generally, not even comparing is a bigger performance win, so when both optimizations could apply, prefer to use the irrelevant-source optimization. For the testcases mentioned in commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2020-10-28), this change improves the performance as follows: Before After no-renames: 5.708 s ± 0.111 s 5.680 s ± 0.096 s mega-renames: 102.171 s ± 0.440 s 13.812 s ± 0.162 s just-one-mega: 3.471 s ± 0.015 s 506.0 ms ± 3.9 ms Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Elijah Newren committed Mar 11, 2021 at 00:38 UTC e4fd06e7e2fa9c433597b76245e38e545eec9ec0
1 file changed +33 -4
diffcore-rename.c
+33 -4
@@ -527,6 +527,7 @@ static void update_dir_rename_counts(struct dir_rename_info *info,
527 }
528
529 static void initialize_dir_rename_info(struct dir_rename_info *info,
530 + struct strset *relevant_sources,
531 struct strset *dirs_removed,
532 struct strmap *dir_rename_count)
533 {
@@ -534,7 +535,7 @@ static void initialize_dir_rename_info(struct dir_rename_info *info,
535 struct strmap_entry *entry;
536 int i;
537
537 - if (!dirs_removed) {
538 + if (!dirs_removed && !relevant_sources) {
539 info->setup = 0;
540 return;
541 }
@@ -549,7 +550,20 @@ static void initialize_dir_rename_info(struct dir_rename_info *info,
550 strmap_init_with_options(&info->dir_rename_guess, NULL, 0);
551
552 /* Setup info->relevant_source_dirs */
552 - info->relevant_source_dirs = dirs_removed;
553 + info->relevant_source_dirs = NULL;
554 + if (dirs_removed || !relevant_sources) {
555 + info->relevant_source_dirs = dirs_removed; /* might be NULL */
556 + } else {
557 + info->relevant_source_dirs = xmalloc(sizeof(struct strintmap));
558 + strset_init(info->relevant_source_dirs);
559 + strset_for_each_entry(relevant_sources, &iter, entry) {
560 + char *dirname = get_dirname(entry->key);
561 + if (!dirs_removed ||
562 + strset_contains(dirs_removed, dirname))
563 + strset_add(info->relevant_source_dirs, dirname);
564 + free(dirname);
565 + }
566 + }
567
568 /*
569 * Loop setting up both info->idx_map, and doing setup of
@@ -627,6 +641,13 @@ static void cleanup_dir_rename_info(struct dir_rename_info *info,
641 /* dir_rename_guess */
642 strmap_clear(&info->dir_rename_guess, 1);
643
644 + /* relevant_source_dirs */
645 + if (info->relevant_source_dirs &&
646 + info->relevant_source_dirs != dirs_removed) {
647 + strset_clear(info->relevant_source_dirs);
648 + FREE_AND_NULL(info->relevant_source_dirs);
649 + }
650 +
651 /* dir_rename_count */
652 if (!keep_dir_rename_count) {
653 partial_clear_dir_rename_count(info->dir_rename_count);
@@ -749,6 +770,7 @@ static int idx_possible_rename(char *filename, struct dir_rename_info *info)
770 static int find_basename_matches(struct diff_options *options,
771 int minimum_score,
772 struct dir_rename_info *info,
773 + struct strset *relevant_sources,
774 struct strset *dirs_removed)
775 {
776 /*
@@ -839,6 +861,11 @@ static int find_basename_matches(struct diff_options *options,
861 intptr_t src_index;
862 intptr_t dst_index;
863
864 + /* Skip irrelevant sources */
865 + if (relevant_sources &&
866 + !strset_contains(relevant_sources, filename))
867 + continue;
868 +
869 /*
870 * If the basename is unique among remaining sources, then
871 * src_index will equal 'i' and we can attempt to match it
@@ -1164,7 +1191,7 @@ void diffcore_rename_extended(struct diff_options *options,
1191
1192 /* Preparation for basename-driven matching. */
1193 trace2_region_enter("diff", "dir rename setup", options->repo);
1167 - initialize_dir_rename_info(&info,
1194 + initialize_dir_rename_info(&info, relevant_sources,
1195 dirs_removed, dir_rename_count);
1196 trace2_region_leave("diff", "dir rename setup", options->repo);
1197
@@ -1172,7 +1199,9 @@ void diffcore_rename_extended(struct diff_options *options,
1199 trace2_region_enter("diff", "basename matches", options->repo);
1200 rename_count += find_basename_matches(options,
1201 min_basename_score,
1175 - &info, dirs_removed);
1202 + &info,
1203 + relevant_sources,
1204 + dirs_removed);
1205 trace2_region_leave("diff", "basename matches", options->repo);
1206
1207 /*