[PATCH v3 1/2] diffcore-rename: no point trying to find a match better than exact
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From: Elijah Newren via GitGitGadget <hidden>
Date: 2021-02-14 07:36:05
Subsystem:
the rest · Maintainer:
Linus Torvalds
Revision v3 (3 revisions archived).
Revisions (3)
- v1
- v2 [diff against previous]
- v3 current [diff against previous]
From: Elijah Newren <redacted>
diffcore_rename() had some code to avoid having destination paths that
already had an exact rename detected from being re-checked for other
renames. Source paths, however, were re-checked because we wanted to
allow the possibility of detecting copies. But if copy detection isn't
turned on, then this merely amounts to attempting to find a
better-than-exact match, which naturally ends up being an expensive
no-op. In particular, copy detection is never turned on by the merge
machinery.
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: 14.263 s ± 0.053 s 14.119 s ± 0.101 s
mega-renames: 5504.231 s ± 5.150 s 1802.044 s ± 0.828 s
just-one-mega: 158.534 s ± 0.498 s 51.391 s ± 0.028 s
Signed-off-by: Elijah Newren <redacted>
---
diffcore-rename.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 8fe6c9384bcb..8b118628b4ef 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c@@ -463,9 +463,11 @@ void diffcore_rename(struct diff_options *options) struct diff_score *mx; int i, j, rename_count, skip_unmodified = 0; int num_destinations, dst_cnt; + int num_sources, want_copies; struct progress *progress = NULL; trace2_region_enter("diff", "setup", options->repo); + want_copies = (detect_rename == DIFF_DETECT_COPY); if (!minimum_score) minimum_score = DEFAULT_RENAME_SCORE;
@@ -502,7 +504,7 @@ void diffcore_rename(struct diff_options *options) p->one->rename_used++; register_rename_src(p); } - else if (detect_rename == DIFF_DETECT_COPY) { + else if (want_copies) { /* * Increment the "rename_used" score by * one, to indicate ourselves as a user.
@@ -532,12 +534,15 @@ void diffcore_rename(struct diff_options *options) * files still remain as options for rename/copies!) */ num_destinations = (rename_dst_nr - rename_count); + num_sources = rename_src_nr; + if (!want_copies) + num_sources -= rename_count; /* All done? */ - if (!num_destinations) + if (!num_destinations || !num_sources) goto cleanup; - switch (too_many_rename_candidates(num_destinations, rename_src_nr, + switch (too_many_rename_candidates(num_destinations, num_sources, options)) { case 1: goto cleanup;
@@ -553,7 +558,7 @@ void diffcore_rename(struct diff_options *options) if (options->show_rename_progress) { progress = start_delayed_progress( _("Performing inexact rename detection"), - (uint64_t)num_destinations * (uint64_t)rename_src_nr); + (uint64_t)num_destinations * (uint64_t)num_sources); } mx = xcalloc(st_mult(NUM_CANDIDATE_PER_DST, num_destinations),
@@ -573,6 +578,9 @@ void diffcore_rename(struct diff_options *options) struct diff_filespec *one = rename_src[j].p->one; struct diff_score this_src; + if (one->rename_used && !want_copies) + continue; + if (skip_unmodified && diff_unmodified_pair(rename_src[j].p)) continue;
@@ -594,7 +602,7 @@ void diffcore_rename(struct diff_options *options) } dst_cnt++; display_progress(progress, - (uint64_t)dst_cnt * (uint64_t)rename_src_nr); + (uint64_t)dst_cnt * (uint64_t)num_sources); } stop_progress(&progress);
@@ -602,7 +610,7 @@ void diffcore_rename(struct diff_options *options) STABLE_QSORT(mx, dst_cnt * NUM_CANDIDATE_PER_DST, score_compare); rename_count += find_renames(mx, dst_cnt, minimum_score, 0); - if (detect_rename == DIFF_DETECT_COPY) + if (want_copies) rename_count += find_renames(mx, dst_cnt, minimum_score, 1); free(mx); trace2_region_leave("diff", "inexact renames", options->repo);
--
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