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authorLibravatar Junio C Hamano <gitster@pobox.com>2021-08-04 13:28:54 -0700
committerLibravatar Junio C Hamano <gitster@pobox.com>2021-08-04 13:28:54 -0700
commit1a6fb019d6c09f5e7e2b76fab2a6ad50a8506461 (patch)
treeb2fe947618c9af0df5becfd1d58ff91f14b0c37b
parentMerge branch 'ds/commit-and-checkout-with-sparse-index' (diff)
parentmerge-ort: restart merge with cached renames to reduce process entry cost (diff)
downloadtgif-1a6fb019d6c09f5e7e2b76fab2a6ad50a8506461.tar.xz
Merge branch 'en/ort-perf-batch-14'
Further optimization on "merge -sort" backend. * en/ort-perf-batch-14: merge-ort: restart merge with cached renames to reduce process entry cost merge-ort: avoid recursing into directories when we don't need to merge-ort: defer recursing into directories when merge base is matched merge-ort: add a handle_deferred_entries() helper function merge-ort: add data structures for allowable trivial directory resolves merge-ort: add some more explanations in collect_merge_info_callback() merge-ort: resolve paths early when we have sufficient information
-rw-r--r--merge-ort.c399
-rwxr-xr-xt/t6423-merge-rename-directories.sh2
2 files changed, 389 insertions, 12 deletions
diff --git a/merge-ort.c b/merge-ort.c
index ec0c590421..6eb910d6f0 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -62,6 +62,53 @@ struct traversal_callback_data {
struct name_entry names[3];
};
+struct deferred_traversal_data {
+ /*
+ * possible_trivial_merges: directories to be explored only when needed
+ *
+ * possible_trivial_merges is a map of directory names to
+ * dir_rename_mask. When we detect that a directory is unchanged on
+ * one side, we can sometimes resolve the directory without recursing
+ * into it. Renames are the only things that can prevent such an
+ * optimization. However, for rename sources:
+ * - If no parent directory needed directory rename detection, then
+ * no path under such a directory can be a relevant_source.
+ * and for rename destinations:
+ * - If no cached rename has a target path under the directory AND
+ * - If there are no unpaired relevant_sources elsewhere in the
+ * repository
+ * then we don't need any path under this directory for a rename
+ * destination. The only way to know the last item above is to defer
+ * handling such directories until the end of collect_merge_info(),
+ * in handle_deferred_entries().
+ *
+ * For each we store dir_rename_mask, since that's the only bit of
+ * information we need, other than the path, to resume the recursive
+ * traversal.
+ */
+ struct strintmap possible_trivial_merges;
+
+ /*
+ * trivial_merges_okay: if trivial directory merges are okay
+ *
+ * See possible_trivial_merges above. The "no unpaired
+ * relevant_sources elsewhere in the repository" is a single boolean
+ * per merge side, which we store here. Note that while 0 means no,
+ * 1 only means "maybe" rather than "yes"; we optimistically set it
+ * to 1 initially and only clear when we determine it is unsafe to
+ * do trivial directory merges.
+ */
+ unsigned trivial_merges_okay;
+
+ /*
+ * target_dirs: ancestor directories of rename targets
+ *
+ * target_dirs contains all directory names that are an ancestor of
+ * any rename destination.
+ */
+ struct strset target_dirs;
+};
+
struct rename_info {
/*
* All variables that are arrays of size 3 correspond to data tracked
@@ -119,6 +166,8 @@ struct rename_info {
*/
struct strintmap relevant_sources[3];
+ struct deferred_traversal_data deferred[3];
+
/*
* dir_rename_mask:
* 0: optimization removing unmodified potential rename source okay
@@ -164,6 +213,7 @@ struct rename_info {
* MERGE_SIDE2: cached data from side2 can be reused
* MERGE_SIDE1: cached data from side1 can be reused
* 0: no cached data can be reused
+ * -1: See redo_after_renames; both sides can be reused.
*/
int cached_pairs_valid_side;
@@ -210,6 +260,28 @@ struct rename_info {
struct strset cached_irrelevant[3];
/*
+ * redo_after_renames: optimization flag for "restarting" the merge
+ *
+ * Sometimes it pays to detect renames, cache them, and then
+ * restart the merge operation from the beginning. The reason for
+ * this is that when we know where all the renames are, we know
+ * whether a certain directory has any paths under it affected --
+ * and if a directory is not affected then it permits us to do
+ * trivial tree merging in more cases. Doing trivial tree merging
+ * prevents the need to run process_entry() on every path
+ * underneath trees that can be trivially merged, and
+ * process_entry() is more expensive than collect_merge_info() --
+ * plus, the second collect_merge_info() will be much faster since
+ * it doesn't have to recurse into the relevant trees.
+ *
+ * Values for this flag:
+ * 0 = don't bother, not worth it (or conditions not yet checked)
+ * 1 = conditions for optimization met, optimization worthwhile
+ * 2 = we already did it (don't restart merge yet again)
+ */
+ unsigned redo_after_renames;
+
+ /*
* needed_limit: value needed for inexact rename detection to run
*
* If the current rename limit wasn't high enough for inexact
@@ -492,7 +564,8 @@ static void clear_or_reinit_internal_opts(struct merge_options_internal *opti,
strintmap_func(&renames->relevant_sources[i]);
if (!reinitialize)
assert(renames->cached_pairs_valid_side == 0);
- if (i != renames->cached_pairs_valid_side) {
+ if (i != renames->cached_pairs_valid_side &&
+ -1 != renames->cached_pairs_valid_side) {
strset_func(&renames->cached_target_names[i]);
strmap_func(&renames->cached_pairs[i], 1);
strset_func(&renames->cached_irrelevant[i]);
@@ -501,6 +574,11 @@ static void clear_or_reinit_internal_opts(struct merge_options_internal *opti,
strmap_clear(&renames->dir_rename_count[i], 1);
}
}
+ for (i = MERGE_SIDE1; i <= MERGE_SIDE2; ++i) {
+ strintmap_func(&renames->deferred[i].possible_trivial_merges);
+ strset_func(&renames->deferred[i].target_dirs);
+ renames->deferred[i].trivial_merges_okay = 1; /* 1 == maybe */
+ }
renames->cached_pairs_valid_side = 0;
renames->dir_rename_mask = 0;
@@ -1019,20 +1097,67 @@ static int collect_merge_info_callback(int n,
if (side1_matches_mbase && side2_matches_mbase) {
/* mbase, side1, & side2 all match; use mbase as resolution */
setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
- names, names+0, mbase_null, 0,
+ names, names+0, mbase_null, 0 /* df_conflict */,
+ filemask, dirmask, 1 /* resolved */);
+ return mask;
+ }
+
+ /*
+ * If the sides match, and all three paths are present and are
+ * files, then we can take either as the resolution. We can't do
+ * this with trees, because there may be rename sources from the
+ * merge_base.
+ */
+ if (sides_match && filemask == 0x07) {
+ /* use side1 (== side2) version as resolution */
+ setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+ names, names+1, side1_null, 0,
+ filemask, dirmask, 1);
+ return mask;
+ }
+
+ /*
+ * If side1 matches mbase and all three paths are present and are
+ * files, then we can use side2 as the resolution. We cannot
+ * necessarily do so this for trees, because there may be rename
+ * destinations within side2.
+ */
+ if (side1_matches_mbase && filemask == 0x07) {
+ /* use side2 version as resolution */
+ setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+ names, names+2, side2_null, 0,
+ filemask, dirmask, 1);
+ return mask;
+ }
+
+ /* Similar to above but swapping sides 1 and 2 */
+ if (side2_matches_mbase && filemask == 0x07) {
+ /* use side1 version as resolution */
+ setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+ names, names+1, side1_null, 0,
filemask, dirmask, 1);
return mask;
}
/*
- * Gather additional information used in rename detection.
+ * Sometimes we can tell that a source path need not be included in
+ * rename detection -- namely, whenever either
+ * side1_matches_mbase && side2_null
+ * or
+ * side2_matches_mbase && side1_null
+ * However, we call collect_rename_info() even in those cases,
+ * because exact renames are cheap and would let us remove both a
+ * source and destination path. We'll cull the unneeded sources
+ * later.
*/
collect_rename_info(opt, names, dirname, fullpath,
filemask, dirmask, match_mask);
/*
- * Record information about the path so we can resolve later in
- * process_entries.
+ * None of the special cases above matched, so we have a
+ * provisional conflict. (Rename detection might allow us to
+ * unconflict some more cases, but that comes later so all we can
+ * do now is record the different non-null file hashes.)
*/
setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
names, NULL, 0, df_conflict, filemask, dirmask, 0);
@@ -1047,8 +1172,36 @@ static int collect_merge_info_callback(int n,
struct tree_desc t[3];
void *buf[3] = {NULL, NULL, NULL};
const char *original_dir_name;
- int i, ret;
+ int i, ret, side;
+ /*
+ * Check for whether we can avoid recursing due to one side
+ * matching the merge base. The side that does NOT match is
+ * the one that might have a rename destination we need.
+ */
+ assert(!side1_matches_mbase || !side2_matches_mbase);
+ side = side1_matches_mbase ? MERGE_SIDE2 :
+ side2_matches_mbase ? MERGE_SIDE1 : MERGE_BASE;
+ if (filemask == 0 && (dirmask == 2 || dirmask == 4)) {
+ /*
+ * Also defer recursing into new directories; set up a
+ * few variables to let us do so.
+ */
+ ci->match_mask = (7 - dirmask);
+ side = dirmask / 2;
+ }
+ if (renames->dir_rename_mask != 0x07 &&
+ side != MERGE_BASE &&
+ renames->deferred[side].trivial_merges_okay &&
+ !strset_contains(&renames->deferred[side].target_dirs,
+ pi.string)) {
+ strintmap_set(&renames->deferred[side].possible_trivial_merges,
+ pi.string, renames->dir_rename_mask);
+ renames->dir_rename_mask = prev_dir_rename_mask;
+ return mask;
+ }
+
+ /* We need to recurse */
ci->match_mask &= filemask;
newinfo = *info;
newinfo.prev = info;
@@ -1102,6 +1255,192 @@ static int collect_merge_info_callback(int n,
return mask;
}
+static void resolve_trivial_directory_merge(struct conflict_info *ci, int side)
+{
+ VERIFY_CI(ci);
+ assert((side == 1 && ci->match_mask == 5) ||
+ (side == 2 && ci->match_mask == 3));
+ oidcpy(&ci->merged.result.oid, &ci->stages[side].oid);
+ ci->merged.result.mode = ci->stages[side].mode;
+ ci->merged.is_null = is_null_oid(&ci->stages[side].oid);
+ ci->match_mask = 0;
+ ci->merged.clean = 1; /* (ci->filemask == 0); */
+}
+
+static int handle_deferred_entries(struct merge_options *opt,
+ struct traverse_info *info)
+{
+ struct rename_info *renames = &opt->priv->renames;
+ struct hashmap_iter iter;
+ struct strmap_entry *entry;
+ int side, ret = 0;
+ int path_count_before, path_count_after = 0;
+
+ path_count_before = strmap_get_size(&opt->priv->paths);
+ for (side = MERGE_SIDE1; side <= MERGE_SIDE2; side++) {
+ unsigned optimization_okay = 1;
+ struct strintmap copy;
+
+ /* Loop over the set of paths we need to know rename info for */
+ strset_for_each_entry(&renames->relevant_sources[side],
+ &iter, entry) {
+ char *rename_target, *dir, *dir_marker;
+ struct strmap_entry *e;
+
+ /*
+ * If we don't know delete/rename info for this path,
+ * then we need to recurse into all trees to get all
+ * adds to make sure we have it.
+ */
+ if (strset_contains(&renames->cached_irrelevant[side],
+ entry->key))
+ continue;
+ e = strmap_get_entry(&renames->cached_pairs[side],
+ entry->key);
+ if (!e) {
+ optimization_okay = 0;
+ break;
+ }
+
+ /* If this is a delete, we have enough info already */
+ rename_target = e->value;
+ if (!rename_target)
+ continue;
+
+ /* If we already walked the rename target, we're good */
+ if (strmap_contains(&opt->priv->paths, rename_target))
+ continue;
+
+ /*
+ * Otherwise, we need to get a list of directories that
+ * will need to be recursed into to get this
+ * rename_target.
+ */
+ dir = xstrdup(rename_target);
+ while ((dir_marker = strrchr(dir, '/'))) {
+ *dir_marker = '\0';
+ if (strset_contains(&renames->deferred[side].target_dirs,
+ dir))
+ break;
+ strset_add(&renames->deferred[side].target_dirs,
+ dir);
+ }
+ free(dir);
+ }
+ renames->deferred[side].trivial_merges_okay = optimization_okay;
+ /*
+ * We need to recurse into any directories in
+ * possible_trivial_merges[side] found in target_dirs[side].
+ * But when we recurse, we may need to queue up some of the
+ * subdirectories for possible_trivial_merges[side]. Since
+ * we can't safely iterate through a hashmap while also adding
+ * entries, move the entries into 'copy', iterate over 'copy',
+ * and then we'll also iterate anything added into
+ * possible_trivial_merges[side] once this loop is done.
+ */
+ copy = renames->deferred[side].possible_trivial_merges;
+ strintmap_init_with_options(&renames->deferred[side].possible_trivial_merges,
+ 0,
+ NULL,
+ 0);
+ strintmap_for_each_entry(&copy, &iter, entry) {
+ const char *path = entry->key;
+ unsigned dir_rename_mask = (intptr_t)entry->value;
+ struct conflict_info *ci;
+ unsigned dirmask;
+ struct tree_desc t[3];
+ void *buf[3] = {NULL,};
+ int i;
+
+ ci = strmap_get(&opt->priv->paths, path);
+ VERIFY_CI(ci);
+ dirmask = ci->dirmask;
+
+ if (optimization_okay &&
+ !strset_contains(&renames->deferred[side].target_dirs,
+ path)) {
+ resolve_trivial_directory_merge(ci, side);
+ continue;
+ }
+
+ info->name = path;
+ info->namelen = strlen(path);
+ info->pathlen = info->namelen + 1;
+
+ for (i = 0; i < 3; i++, dirmask >>= 1) {
+ if (i == 1 && ci->match_mask == 3)
+ t[1] = t[0];
+ else if (i == 2 && ci->match_mask == 5)
+ t[2] = t[0];
+ else if (i == 2 && ci->match_mask == 6)
+ t[2] = t[1];
+ else {
+ const struct object_id *oid = NULL;
+ if (dirmask & 1)
+ oid = &ci->stages[i].oid;
+ buf[i] = fill_tree_descriptor(opt->repo,
+ t+i, oid);
+ }
+ }
+
+ ci->match_mask &= ci->filemask;
+ opt->priv->current_dir_name = path;
+ renames->dir_rename_mask = dir_rename_mask;
+ if (renames->dir_rename_mask == 0 ||
+ renames->dir_rename_mask == 0x07)
+ ret = traverse_trees(NULL, 3, t, info);
+ else
+ ret = traverse_trees_wrapper(NULL, 3, t, info);
+
+ for (i = MERGE_BASE; i <= MERGE_SIDE2; i++)
+ free(buf[i]);
+
+ if (ret < 0)
+ return ret;
+ }
+ strintmap_clear(&copy);
+ strintmap_for_each_entry(&renames->deferred[side].possible_trivial_merges,
+ &iter, entry) {
+ const char *path = entry->key;
+ struct conflict_info *ci;
+
+ ci = strmap_get(&opt->priv->paths, path);
+ VERIFY_CI(ci);
+
+ assert(renames->deferred[side].trivial_merges_okay &&
+ !strset_contains(&renames->deferred[side].target_dirs,
+ path));
+ resolve_trivial_directory_merge(ci, side);
+ }
+ if (!optimization_okay || path_count_after)
+ path_count_after = strmap_get_size(&opt->priv->paths);
+ }
+ if (path_count_after) {
+ /*
+ * The choice of wanted_factor here does not affect
+ * correctness, only performance. When the
+ * path_count_after / path_count_before
+ * ratio is high, redoing after renames is a big
+ * performance boost. I suspect that redoing is a wash
+ * somewhere near a value of 2, and below that redoing will
+ * slow things down. I applied a fudge factor and picked
+ * 3; see the commit message when this was introduced for
+ * back of the envelope calculations for this ratio.
+ */
+ const int wanted_factor = 3;
+
+ /* We should only redo collect_merge_info one time */
+ assert(renames->redo_after_renames == 0);
+
+ if (path_count_after / path_count_before >= wanted_factor) {
+ renames->redo_after_renames = 1;
+ renames->cached_pairs_valid_side = -1;
+ }
+ } else if (renames->redo_after_renames == 2)
+ renames->redo_after_renames = 0;
+ return ret;
+}
+
static int collect_merge_info(struct merge_options *opt,
struct tree *merge_base,
struct tree *side1,
@@ -1127,6 +1466,8 @@ static int collect_merge_info(struct merge_options *opt,
trace2_region_enter("merge", "traverse_trees", opt->repo);
ret = traverse_trees(NULL, 3, t, &info);
+ if (ret == 0)
+ ret = handle_deferred_entries(opt, &info);
trace2_region_leave("merge", "traverse_trees", opt->repo);
return ret;
@@ -2539,8 +2880,8 @@ static int compare_pairs(const void *a_, const void *b_)
}
/* Call diffcore_rename() to update deleted/added pairs into rename pairs */
-static void detect_regular_renames(struct merge_options *opt,
- unsigned side_index)
+static int detect_regular_renames(struct merge_options *opt,
+ unsigned side_index)
{
struct diff_options diff_opts;
struct rename_info *renames = &opt->priv->renames;
@@ -2553,7 +2894,7 @@ static void detect_regular_renames(struct merge_options *opt,
* side had directory renames.
*/
resolve_diffpair_statuses(&renames->pairs[side_index]);
- return;
+ return 0;
}
partial_clear_dir_rename_count(&renames->dir_rename_count[side_index]);
@@ -2579,6 +2920,8 @@ static void detect_regular_renames(struct merge_options *opt,
trace2_region_leave("diff", "diffcore_rename", opt->repo);
resolve_diffpair_statuses(&diff_queued_diff);
+ if (diff_opts.needed_rename_limit > 0)
+ renames->redo_after_renames = 0;
if (diff_opts.needed_rename_limit > renames->needed_limit)
renames->needed_limit = diff_opts.needed_rename_limit;
@@ -2588,6 +2931,8 @@ static void detect_regular_renames(struct merge_options *opt,
diff_queued_diff.nr = 0;
diff_queued_diff.queue = NULL;
diff_flush(&diff_opts);
+
+ return 1;
}
/*
@@ -2677,14 +3022,32 @@ static int detect_and_process_renames(struct merge_options *opt,
struct diff_queue_struct combined;
struct rename_info *renames = &opt->priv->renames;
int need_dir_renames, s, clean = 1;
+ unsigned detection_run = 0;
memset(&combined, 0, sizeof(combined));
if (!possible_renames(renames))
goto cleanup;
trace2_region_enter("merge", "regular renames", opt->repo);
- detect_regular_renames(opt, MERGE_SIDE1);
- detect_regular_renames(opt, MERGE_SIDE2);
+ detection_run |= detect_regular_renames(opt, MERGE_SIDE1);
+ detection_run |= detect_regular_renames(opt, MERGE_SIDE2);
+ if (renames->redo_after_renames && detection_run) {
+ int i, side;
+ struct diff_filepair *p;
+
+ /* Cache the renames, we found */
+ for (side = MERGE_SIDE1; side <= MERGE_SIDE2; side++) {
+ for (i = 0; i < renames->pairs[side].nr; ++i) {
+ p = renames->pairs[side].queue[i];
+ possibly_cache_new_pair(renames, p, side, NULL);
+ }
+ }
+
+ /* Restart the merge with the cached renames */
+ renames->redo_after_renames = 2;
+ trace2_region_leave("merge", "regular renames", opt->repo);
+ goto cleanup;
+ }
use_cached_pairs(opt, &renames->cached_pairs[1], &renames->pairs[1]);
use_cached_pairs(opt, &renames->cached_pairs[2], &renames->pairs[2]);
trace2_region_leave("merge", "regular renames", opt->repo);
@@ -4019,6 +4382,13 @@ static void merge_start(struct merge_options *opt, struct merge_result *result)
strset_init_with_options(&renames->cached_target_names[i],
NULL, 0);
}
+ for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
+ strintmap_init_with_options(&renames->deferred[i].possible_trivial_merges,
+ 0, NULL, 0);
+ strset_init_with_options(&renames->deferred[i].target_dirs,
+ NULL, 1);
+ renames->deferred[i].trivial_merges_okay = 1; /* 1 == maybe */
+ }
/*
* Although we initialize opt->priv->paths with strdup_strings=0,
@@ -4107,6 +4477,7 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt,
opt->subtree_shift);
}
+redo:
trace2_region_enter("merge", "collect_merge_info", opt->repo);
if (collect_merge_info(opt, merge_base, side1, side2) != 0) {
/*
@@ -4126,6 +4497,12 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt,
result->clean = detect_and_process_renames(opt, merge_base,
side1, side2);
trace2_region_leave("merge", "renames", opt->repo);
+ if (opt->priv->renames.redo_after_renames == 2) {
+ trace2_region_enter("merge", "reset_maps", opt->repo);
+ clear_or_reinit_internal_opts(opt->priv, 1);
+ trace2_region_leave("merge", "reset_maps", opt->repo);
+ goto redo;
+ }
trace2_region_enter("merge", "process_entries", opt->repo);
process_entries(opt, &working_tree_oid);
diff --git a/t/t6423-merge-rename-directories.sh b/t/t6423-merge-rename-directories.sh
index 4af4fb0038..5b81a130e9 100755
--- a/t/t6423-merge-rename-directories.sh
+++ b/t/t6423-merge-rename-directories.sh
@@ -4797,7 +4797,7 @@ test_setup_12f () {
)
}
-test_expect_merge_algorithm failure failure '12f: Trivial directory resolve, caching, all kinds of fun' '
+test_expect_merge_algorithm failure success '12f: Trivial directory resolve, caching, all kinds of fun' '
test_setup_12f &&
(
cd 12f &&