From cf8937acdedc80e636587f5fc2f495ea38bd5fe0 Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Sat, 23 Jan 2021 22:01:10 -0800 Subject: merge-ort: fix massive leak When a series of merges was performed (such as for a rebase or series of cherry-picks), only the data structures allocated by the final merge operation were being freed. The problem was that while picking out pieces of merge-ort to upstream, I previously misread a certain section of merge_start() and assumed it was associated with a later optimization. Include that section now, which ensures that if there was a previous merge operation, that we clear out result->priv and then re-use it for opt->priv, and otherwise we allocate opt->priv. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano --- merge-ort.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/merge-ort.c b/merge-ort.c index 05c6b2e0dc..b5845ff6e9 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -3227,11 +3227,28 @@ static void merge_start(struct merge_options *opt, struct merge_result *result) assert(opt->obuf.len == 0); assert(opt->priv == NULL); + if (result->priv) { + opt->priv = result->priv; + result->priv = NULL; + /* + * opt->priv non-NULL means we had results from a previous + * run; do a few sanity checks that user didn't mess with + * it in an obvious fashion. + */ + assert(opt->priv->call_depth == 0); + assert(!opt->priv->toplevel_dir || + 0 == strlen(opt->priv->toplevel_dir)); + } /* Default to histogram diff. Actually, just hardcode it...for now. */ opt->xdl_opts = DIFF_WITH_ALG(opt, HISTOGRAM_DIFF); /* Initialization of opt->priv, our internal merge data */ + if (opt->priv) { + clear_or_reinit_internal_opts(opt->priv, 1); + trace2_region_leave("merge", "allocate/init", opt->repo); + return; + } opt->priv = xcalloc(1, sizeof(*opt->priv)); /* Initialization of various renames fields */ -- cgit v1.2.3 From 5ced7c3da009090c5a926e3123a71314c7f28d42 Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Sat, 23 Jan 2021 22:01:11 -0800 Subject: merge-ort: ignore the directory rename split conflict for now get_provisional_directory_renames() has code to detect directories being evenly split between different locations. However, as noted previously, if there are no new files added to that directory that was split evenly, our inability to determine where the directory was renamed to doesn't matter since there are no new files to try to move into the new location. Unfortunately, that code is unaware of whether there are new files under the directory in question and we just ignore that, causing us to fail t6423 test 2b but pass test 2a; turn off the error for now, swapping which tests pass and fail. The motivating reason for switching this off as a temporary measure is that as we add optimizations, we'll start looking at only subsets of renames, and subsets of renames can start switching the result we get when this error is (wrongly) on. Once we get enough optimizations, however, we can prevent that code from even running when there are no new files added to the relevant directory, at which point we can revert this commit and then both testcases 2a and 2b will pass simultaneously. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano --- merge-ort.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/merge-ort.c b/merge-ort.c index b5845ff6e9..f04fab96d7 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -1439,7 +1439,18 @@ static void get_provisional_directory_renames(struct merge_options *opt, "no destination getting a majority of the " "files."), source_dir); - *clean = 0; + /* + * We should mark this as unclean IF something attempts + * to use this rename. We do not yet have the logic + * in place to detect if this directory rename is being + * used, and optimizations that reduce the number of + * renames cause this to falsely trigger. For now, + * just disable it, causing t6423 testcase 2a to break. + * We'll later fix the detection, and when we do we + * will re-enable setting *clean to 0 (and thereby fix + * t6423 testcase 2a). + */ + /* *clean = 0; */ } else { strmap_put(&renames->dir_renames[side], source_dir, (void*)best); -- cgit v1.2.3 From 557ac0350d9efa1f59c708779ca3fb3aee121131 Mon Sep 17 00:00:00 2001 From: Elijah Newren Date: Sat, 23 Jan 2021 22:01:12 -0800 Subject: merge-ort: begin performance work; instrument with trace2_region_* calls MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add some timing instrumentation for both merge-ort and diffcore-rename; I used these to measure and optimize performance in both, and several future patch series will build on these to reduce the timings of some select testcases. === Setup === The primary testcase I used involved rebasing a random topic in the linux kernel (consisting of 35 patches) against an older version. I added two variants, one where I rename a toplevel directory, and another where I only rebase one patch instead of the whole topic. The setup is as follows: $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git $ git branch hwmon-updates fd8bdb23b91876ac1e624337bb88dc1dcc21d67e $ git branch hwmon-just-one fd8bdb23b91876ac1e624337bb88dc1dcc21d67e~34 $ git branch base 4703d9119972bf586d2cca76ec6438f819ffa30e $ git switch -c 5.4-renames v5.4 $ git mv drivers pilots # Introduce over 26,000 renames $ git commit -m "Rename drivers/ to pilots/" $ git config merge.renameLimit 30000 $ git config merge.directoryRenames true === Testcases === Now with REBASE standing for either "git rebase [--merge]" (using merge-recursive) or "test-tool fast-rebase" (using merge-ort), the testcases are: Testcase #1: no-renames $ git checkout v5.4^0 $ REBASE --onto HEAD base hwmon-updates Note: technically the name is misleading; there are some renames, but very few. Rename detection only takes about half the overall time. Testcase #2: mega-renames $ git checkout 5.4-renames^0 $ REBASE --onto HEAD base hwmon-updates Testcase #3: just-one-mega $ git checkout 5.4-renames^0 $ REBASE --onto HEAD base hwmon-just-one === Timing results === Overall timings, using hyperfine (1 warmup run, 3 runs for mega-renames, 10 runs for the other two cases): merge-recursive merge-ort no-renames: 18.912 s ± 0.174 s 14.263 s ± 0.053 s mega-renames: 5964.031 s ± 10.459 s 5504.231 s ± 5.150 s just-one-mega: 149.583 s ± 0.751 s 158.534 s ± 0.498 s A single re-run of each with some breakdowns: --- no-renames --- merge-recursive merge-ort overall runtime: 19.302 s 14.257 s inexact rename detection: 7.603 s 7.906 s everything else: 11.699 s 6.351 s --- mega-renames --- merge-recursive merge-ort overall runtime: 5950.195 s 5499.672 s inexact rename detection: 5746.309 s 5487.120 s everything else: 203.886 s 17.552 s --- just-one-mega --- merge-recursive merge-ort overall runtime: 151.001 s 158.582 s inexact rename detection: 143.448 s 157.835 s everything else: 7.553 s 0.747 s === Timing observations === 0) Maximum speedup The "everything else" row represents the maximum speedup we could achieve if we were to somehow infinitely parallelize inexact rename detection, but leave everything else alone. The fact that this is so much smaller than the real runtime (even in the case with virtually no renames) makes it clear just how overwhelmingly large the time spent on rename detection can be. 1) no-renames 1a) merge-ort is faster than merge-recursive, which is nice. However, this still should not be considered good enough. Although the "merge" backend to rebase (merge-recursive) is sometimes faster than the "apply" backend, this is one of those cases where it is not. In fact, even merge-ort is slower. The "apply" backend can complete this testcase in 6.940 s ± 0.485 s which is about 2x faster than merge-ort and 3x faster than merge-recursive. One goal of the merge-ort performance work will be to make it faster than git-am on this (and similar) testcases. 2) mega-renames 2a) Obviously rename detection is a huge cost; it's where most the time is spent. We need to cut that down. If we could somehow infinitely parallelize it and drive its time to 0, the merge-recursive time would drop to about 204s, and the merge-ort time would drop to about 17s. I think this particular stat shows I've subtly baked a couple performance improvements into merge-ort and into fast-rebase already. 3) just-one-mega 3a) not much to say here, it just gives some flavor for how rebasing only one patch compares to rebasing 35. === Goals === This patch is obviously just the beginning. Here are some of my goals that this measurement will help us achieve: * Drive the cost of rename detection down considerably for merges * After the above has been achieved, see if there are other slowness factors (which would have previously been overshadowed by rename detection costs) which we can then focus on and also optimize. * Ensure our rebase testcase that requires little rename detection is noticeably faster with merge-ort than with apply-based rebase. Signed-off-by: Elijah Newren Acked-by: Taylor Blau Signed-off-by: Junio C Hamano --- diffcore-rename.c | 8 ++++++++ merge-ort.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 65 insertions(+) diff --git a/diffcore-rename.c b/diffcore-rename.c index 90db9ebd6d..8fe6c9384b 100644 --- a/diffcore-rename.c +++ b/diffcore-rename.c @@ -465,6 +465,7 @@ void diffcore_rename(struct diff_options *options) int num_destinations, dst_cnt; struct progress *progress = NULL; + trace2_region_enter("diff", "setup", options->repo); if (!minimum_score) minimum_score = DEFAULT_RENAME_SCORE; @@ -510,14 +511,17 @@ void diffcore_rename(struct diff_options *options) register_rename_src(p); } } + trace2_region_leave("diff", "setup", options->repo); if (rename_dst_nr == 0 || rename_src_nr == 0) goto cleanup; /* nothing to do */ + trace2_region_enter("diff", "exact renames", options->repo); /* * We really want to cull the candidates list early * with cheap tests in order to avoid doing deltas. */ rename_count = find_exact_renames(options); + trace2_region_leave("diff", "exact renames", options->repo); /* Did we only want exact renames? */ if (minimum_score == MAX_SCORE) @@ -545,6 +549,7 @@ void diffcore_rename(struct diff_options *options) break; } + trace2_region_enter("diff", "inexact renames", options->repo); if (options->show_rename_progress) { progress = start_delayed_progress( _("Performing inexact rename detection"), @@ -600,11 +605,13 @@ void diffcore_rename(struct diff_options *options) if (detect_rename == DIFF_DETECT_COPY) rename_count += find_renames(mx, dst_cnt, minimum_score, 1); free(mx); + trace2_region_leave("diff", "inexact renames", options->repo); cleanup: /* At this point, we have found some renames and copies and they * are recorded in rename_dst. The original list is still in *q. */ + trace2_region_enter("diff", "write back to queue", options->repo); DIFF_QUEUE_CLEAR(&outq); for (i = 0; i < q->nr; i++) { struct diff_filepair *p = q->queue[i]; @@ -680,5 +687,6 @@ void diffcore_rename(struct diff_options *options) strintmap_clear(break_idx); FREE_AND_NULL(break_idx); } + trace2_region_leave("diff", "write back to queue", options->repo); return; } diff --git a/merge-ort.c b/merge-ort.c index f04fab96d7..931b91438c 100644 --- a/merge-ort.c +++ b/merge-ort.c @@ -752,7 +752,9 @@ static int collect_merge_info(struct merge_options *opt, init_tree_desc(t + 1, side1->buffer, side1->size); init_tree_desc(t + 2, side2->buffer, side2->size); + trace2_region_enter("merge", "traverse_trees", opt->repo); ret = traverse_trees(NULL, 3, t, &info); + trace2_region_leave("merge", "traverse_trees", opt->repo); return ret; } @@ -2105,9 +2107,12 @@ static void detect_regular_renames(struct merge_options *opt, diff_opts.show_rename_progress = opt->show_rename_progress; diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT; diff_setup_done(&diff_opts); + + trace2_region_enter("diff", "diffcore_rename", opt->repo); diff_tree_oid(&merge_base->object.oid, &side->object.oid, "", &diff_opts); diffcore_std(&diff_opts); + trace2_region_leave("diff", "diffcore_rename", opt->repo); if (diff_opts.needed_rename_limit > renames->needed_limit) renames->needed_limit = diff_opts.needed_rename_limit; @@ -2206,9 +2211,12 @@ static int detect_and_process_renames(struct merge_options *opt, memset(&combined, 0, sizeof(combined)); + trace2_region_enter("merge", "regular renames", opt->repo); detect_regular_renames(opt, merge_base, side1, MERGE_SIDE1); detect_regular_renames(opt, merge_base, side2, MERGE_SIDE2); + trace2_region_leave("merge", "regular renames", opt->repo); + trace2_region_enter("merge", "directory renames", opt->repo); need_dir_renames = !opt->priv->call_depth && (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE || @@ -2230,8 +2238,11 @@ static int detect_and_process_renames(struct merge_options *opt, &renames->dir_renames[1], &renames->dir_renames[2]); QSORT(combined.queue, combined.nr, compare_pairs); + trace2_region_leave("merge", "directory renames", opt->repo); + trace2_region_enter("merge", "process renames", opt->repo); clean &= process_renames(opt, &combined); + trace2_region_leave("merge", "process renames", opt->repo); /* Free memory for renames->pairs[] and combined */ for (s = MERGE_SIDE1; s <= MERGE_SIDE2; s++) { @@ -2913,20 +2924,30 @@ static void process_entries(struct merge_options *opt, STRING_LIST_INIT_NODUP, NULL, 0 }; + trace2_region_enter("merge", "process_entries setup", opt->repo); if (strmap_empty(&opt->priv->paths)) { oidcpy(result_oid, opt->repo->hash_algo->empty_tree); return; } /* Hack to pre-allocate plist to the desired size */ + trace2_region_enter("merge", "plist grow", opt->repo); ALLOC_GROW(plist.items, strmap_get_size(&opt->priv->paths), plist.alloc); + trace2_region_leave("merge", "plist grow", opt->repo); /* Put every entry from paths into plist, then sort */ + trace2_region_enter("merge", "plist copy", opt->repo); strmap_for_each_entry(&opt->priv->paths, &iter, e) { string_list_append(&plist, e->key)->util = e->value; } + trace2_region_leave("merge", "plist copy", opt->repo); + + trace2_region_enter("merge", "plist special sort", opt->repo); plist.cmp = string_list_df_name_compare; string_list_sort(&plist); + trace2_region_leave("merge", "plist special sort", opt->repo); + + trace2_region_leave("merge", "process_entries setup", opt->repo); /* * Iterate over the items in reverse order, so we can handle paths @@ -2937,6 +2958,7 @@ static void process_entries(struct merge_options *opt, * (because it allows us to know whether the directory is still in * the way when it is time to process the file at the same path). */ + trace2_region_enter("merge", "processing", opt->repo); for (entry = &plist.items[plist.nr-1]; entry >= plist.items; --entry) { char *path = entry->string; /* @@ -2955,7 +2977,9 @@ static void process_entries(struct merge_options *opt, process_entry(opt, path, ci, &dir_metadata); } } + trace2_region_leave("merge", "processing", opt->repo); + trace2_region_enter("merge", "process_entries cleanup", opt->repo); if (dir_metadata.offsets.nr != 1 || (uintptr_t)dir_metadata.offsets.items[0].util != 0) { printf("dir_metadata.offsets.nr = %d (should be 1)\n", @@ -2970,6 +2994,7 @@ static void process_entries(struct merge_options *opt, string_list_clear(&plist, 0); string_list_clear(&dir_metadata.versions, 0); string_list_clear(&dir_metadata.offsets, 0); + trace2_region_leave("merge", "process_entries cleanup", opt->repo); } /*** Function Grouping: functions related to merge_switch_to_result() ***/ @@ -3128,12 +3153,15 @@ void merge_switch_to_result(struct merge_options *opt, if (result->clean >= 0 && update_worktree_and_index) { struct merge_options_internal *opti = result->priv; + trace2_region_enter("merge", "checkout", opt->repo); if (checkout(opt, head, result->tree)) { /* failure to function */ result->clean = -1; return; } + trace2_region_leave("merge", "checkout", opt->repo); + trace2_region_enter("merge", "record_conflicted", opt->repo); if (record_conflicted_index_entries(opt, opt->repo->index, &opti->paths, &opti->conflicted)) { @@ -3141,6 +3169,7 @@ void merge_switch_to_result(struct merge_options *opt, result->clean = -1; return; } + trace2_region_leave("merge", "record_conflicted", opt->repo); } if (display_update_msgs) { @@ -3150,6 +3179,8 @@ void merge_switch_to_result(struct merge_options *opt, struct string_list olist = STRING_LIST_INIT_NODUP; int i; + trace2_region_enter("merge", "display messages", opt->repo); + /* Hack to pre-allocate olist to the desired size */ ALLOC_GROW(olist.items, strmap_get_size(&opti->output), olist.alloc); @@ -3171,6 +3202,8 @@ void merge_switch_to_result(struct merge_options *opt, /* Also include needed rename limit adjustment now */ diff_warn_rename_limit("merge.renamelimit", opti->renames.needed_limit, 0); + + trace2_region_leave("merge", "display messages", opt->repo); } merge_finalize(opt, result); @@ -3212,6 +3245,7 @@ static void merge_start(struct merge_options *opt, struct merge_result *result) int i; /* Sanity checks on opt */ + trace2_region_enter("merge", "sanity checks", opt->repo); assert(opt->repo); assert(opt->branch1 && opt->branch2); @@ -3250,11 +3284,13 @@ static void merge_start(struct merge_options *opt, struct merge_result *result) assert(!opt->priv->toplevel_dir || 0 == strlen(opt->priv->toplevel_dir)); } + trace2_region_leave("merge", "sanity checks", opt->repo); /* Default to histogram diff. Actually, just hardcode it...for now. */ opt->xdl_opts = DIFF_WITH_ALG(opt, HISTOGRAM_DIFF); /* Initialization of opt->priv, our internal merge data */ + trace2_region_enter("merge", "allocate/init", opt->repo); if (opt->priv) { clear_or_reinit_internal_opts(opt->priv, 1); trace2_region_leave("merge", "allocate/init", opt->repo); @@ -3292,6 +3328,8 @@ static void merge_start(struct merge_options *opt, struct merge_result *result) * subset of the overall paths that have special output. */ strmap_init(&opt->priv->output); + + trace2_region_leave("merge", "allocate/init", opt->repo); } /*** Function Grouping: merge_incore_*() and their internal variants ***/ @@ -3307,6 +3345,7 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt, { struct object_id working_tree_oid; + trace2_region_enter("merge", "collect_merge_info", opt->repo); if (collect_merge_info(opt, merge_base, side1, side2) != 0) { /* * TRANSLATORS: The %s arguments are: 1) tree hash of a merge @@ -3319,10 +3358,16 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt, result->clean = -1; return; } + trace2_region_leave("merge", "collect_merge_info", opt->repo); + trace2_region_enter("merge", "renames", opt->repo); result->clean = detect_and_process_renames(opt, merge_base, side1, side2); + trace2_region_leave("merge", "renames", opt->repo); + + trace2_region_enter("merge", "process_entries", opt->repo); process_entries(opt, &working_tree_oid); + trace2_region_leave("merge", "process_entries", opt->repo); /* Set return values */ result->tree = parse_tree_indirect(&working_tree_oid); @@ -3423,9 +3468,15 @@ void merge_incore_nonrecursive(struct merge_options *opt, struct tree *side2, struct merge_result *result) { + trace2_region_enter("merge", "incore_nonrecursive", opt->repo); + + trace2_region_enter("merge", "merge_start", opt->repo); assert(opt->ancestor != NULL); merge_start(opt, result); + trace2_region_leave("merge", "merge_start", opt->repo); + merge_ort_nonrecursive_internal(opt, merge_base, side1, side2, result); + trace2_region_leave("merge", "incore_nonrecursive", opt->repo); } void merge_incore_recursive(struct merge_options *opt, @@ -3434,9 +3485,15 @@ void merge_incore_recursive(struct merge_options *opt, struct commit *side2, struct merge_result *result) { + trace2_region_enter("merge", "incore_recursive", opt->repo); + /* We set the ancestor label based on the merge_bases */ assert(opt->ancestor == NULL); + trace2_region_enter("merge", "merge_start", opt->repo); merge_start(opt, result); + trace2_region_leave("merge", "merge_start", opt->repo); + merge_ort_internal(opt, merge_bases, side1, side2, result); + trace2_region_leave("merge", "incore_recursive", opt->repo); } -- cgit v1.2.3