Subject: [PATCH v4 0/5] Speed up unpack_trees()

From: Nguyễn Thái Ngọc Duy <[email-masked]>
Date: Sun, 12 Aug 2018 10:15:46 +0200

v4 has a bunch of changes

- 1/5 is a new one to show indented tracing. This way it's less
  misleading to read nested time measurements
- 3/5 now has the switch/restore cache_bottom logic. Junio suggested a
  check instead in his final note, but I think this is safer (yeah I'm
  scared too)
- the old 4/4 is dropped because
  - it assumes n-way logic
  - the visible time saving is not worth the tradeoff
  - Elijah gave me an idea to avoid add_index_entry() that I think
    does not have n-way logic assumptions and gives better saving.
    But it requires some more changes so I'm going to do it later
- 5/5 is also new and should help reduce cache_tree_update() cost.
  I wrote somewhere I was not going to work on this part, but it turns
  out just a couple lines, might as well do it now.

Interdiff

diff --git a/cache-tree.c b/cache-tree.c
index 0dbe10fc85..105f13806f 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -426,7 +426,6 @@ static int update_one(struct cache_tree *it,
 
 int cache_tree_update(struct index_state *istate, int flags)
 {
-	uint64_t start = getnanotime();
 	struct cache_tree *it = istate->cache_tree;
 	struct cache_entry **cache = istate->cache;
 	int entries = istate->cache_nr;
@@ -434,11 +433,12 @@ int cache_tree_update(struct index_state *istate, int flags)
 
 	if (i)
 		return i;
+	trace_performance_enter();
 	i = update_one(it, cache, entries, "", 0, &skip, flags);
+	trace_performance_leave("cache_tree_update");
 	if (i < 0)
 		return i;
 	istate->cache_changed |= CACHE_TREE_CHANGED;
-	trace_performance_since(start, "repair cache-tree");
 	return 0;
 }
 
diff --git a/cache.h b/cache.h
index e6f7ee4b64..8b447652a7 100644
--- a/cache.h
+++ b/cache.h
@@ -673,7 +673,6 @@ extern int index_name_pos(const struct index_state *, const char *name, int name
 #define ADD_CACHE_JUST_APPEND 8		/* Append only; tree.c::read_tree() */
 #define ADD_CACHE_NEW_ONLY 16		/* Do not replace existing ones */
 #define ADD_CACHE_KEEP_CACHE_TREE 32	/* Do not invalidate cache-tree */
-#define ADD_CACHE_SKIP_VERIFY_PATH 64	/* Do not verify path */
 extern int add_index_entry(struct index_state *, struct cache_entry *ce, int option);
 extern void rename_index_entry_at(struct index_state *, int pos, const char *new_name);
 
diff --git a/diff-lib.c b/diff-lib.c
index a9f38eb5a3..1ffa22c882 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -518,8 +518,8 @@ static int diff_cache(struct rev_info *revs,
 int run_diff_index(struct rev_info *revs, int cached)
 {
 	struct object_array_entry *ent;
-	uint64_t start = getnanotime();
 
+	trace_performance_enter();
 	ent = revs->pending.objects;
 	if (diff_cache(revs, &ent->item->oid, ent->name, cached))
 		exit(128);
@@ -528,7 +528,7 @@ int run_diff_index(struct rev_info *revs, int cached)
 	diffcore_fix_diff_index(&revs->diffopt);
 	diffcore_std(&revs->diffopt);
 	diff_flush(&revs->diffopt);
-	trace_performance_since(start, "diff-index");
+	trace_performance_leave("diff-index");
 	return 0;
 }
 
diff --git a/dir.c b/dir.c
index 21e6f2520a..c5e9fc8cea 100644
--- a/dir.c
+++ b/dir.c
@@ -2263,11 +2263,11 @@ int read_directory(struct dir_struct *dir, struct index_state *istate,
 		   const char *path, int len, const struct pathspec *pathspec)
 {
 	struct untracked_cache_dir *untracked;
-	uint64_t start = getnanotime();
 
 	if (has_symlink_leading_path(path, len))
 		return dir->nr;
 
+	trace_performance_enter();
 	untracked = validate_untracked_cache(dir, len, pathspec);
 	if (!untracked)
 		/*
@@ -2302,7 +2302,7 @@ int read_directory(struct dir_struct *dir, struct index_state *istate,
 		dir->nr = i;
 	}
 
-	trace_performance_since(start, "read directory %.*s", len, path);
+	trace_performance_leave("read directory %.*s", len, path);
 	if (dir->untracked) {
 		static int force_untracked_cache = -1;
 		static struct trace_key trace_untracked_stats = TRACE_KEY_INIT(UNTRACKED_STATS);
diff --git a/name-hash.c b/name-hash.c
index 163849831c..1fcda73cb3 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -578,10 +578,10 @@ static void threaded_lazy_init_name_hash(
 
 static void lazy_init_name_hash(struct index_state *istate)
 {
-	uint64_t start = getnanotime();
 
 	if (istate->name_hash_initialized)
 		return;
+	trace_performance_enter();
 	hashmap_init(&istate->name_hash, cache_entry_cmp, NULL, istate->cache_nr);
 	hashmap_init(&istate->dir_hash, dir_entry_cmp, NULL, istate->cache_nr);
 
@@ -602,7 +602,7 @@ static void lazy_init_name_hash(struct index_state *istate)
 	}
 
 	istate->name_hash_initialized = 1;
-	trace_performance_since(start, "initialize name hash");
+	trace_performance_leave("initialize name hash");
 }
 
 /*
diff --git a/preload-index.c b/preload-index.c
index 4d08d44874..d7f7919ba2 100644
--- a/preload-index.c
+++ b/preload-index.c
@@ -78,7 +78,6 @@ static void preload_index(struct index_state *index,
 {
 	int threads, i, work, offset;
 	struct thread_data data[MAX_PARALLEL];
-	uint64_t start = getnanotime();
 
 	if (!core_preload_index)
 		return;
@@ -88,6 +87,7 @@ static void preload_index(struct index_state *index,
 		threads = 2;
 	if (threads < 2)
 		return;
+	trace_performance_enter();
 	if (threads > MAX_PARALLEL)
 		threads = MAX_PARALLEL;
 	offset = 0;
@@ -109,7 +109,7 @@ static void preload_index(struct index_state *index,
 		if (pthread_join(p->pthread, NULL))
 			die("unable to join threaded lstat");
 	}
-	trace_performance_since(start, "preload index");
+	trace_performance_leave("preload index");
 }
 #endif
 
diff --git a/read-cache.c b/read-cache.c
index b0b5df5de7..2b5646ef26 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1170,7 +1170,6 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
 	int ok_to_add = option & ADD_CACHE_OK_TO_ADD;
 	int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 	int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
-	int skip_verify_path = option & ADD_CACHE_SKIP_VERIFY_PATH;
 	int new_only = option & ADD_CACHE_NEW_ONLY;
 
 	if (!(option & ADD_CACHE_KEEP_CACHE_TREE))
@@ -1211,7 +1210,7 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
 
 	if (!ok_to_add)
 		return -1;
-	if (!skip_verify_path && !verify_path(ce->name, ce->ce_mode))
+	if (!verify_path(ce->name, ce->ce_mode))
 		return error("Invalid path '%s'", ce->name);
 
 	if (!skip_df_check &&
@@ -1400,8 +1399,8 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 	const char *typechange_fmt;
 	const char *added_fmt;
 	const char *unmerged_fmt;
-	uint64_t start = getnanotime();
 
+	trace_performance_enter();
 	modified_fmt = (in_porcelain ? "M\t%s\n" : "%s: needs update\n");
 	deleted_fmt = (in_porcelain ? "D\t%s\n" : "%s: needs update\n");
 	typechange_fmt = (in_porcelain ? "T\t%s\n" : "%s needs update\n");
@@ -1471,7 +1470,7 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 
 		replace_index_entry(istate, i, new_entry);
 	}
-	trace_performance_since(start, "refresh index");
+	trace_performance_leave("refresh index");
 	return has_errors;
 }
 
@@ -1902,7 +1901,6 @@ static void freshen_shared_index(const char *shared_index, int warn)
 int read_index_from(struct index_state *istate, const char *path,
 		    const char *gitdir)
 {
-	uint64_t start = getnanotime();
 	struct split_index *split_index;
 	int ret;
 	char *base_oid_hex;
@@ -1912,8 +1910,9 @@ int read_index_from(struct index_state *istate, const char *path,
 	if (istate->initialized)
 		return istate->cache_nr;
 
+	trace_performance_enter();
 	ret = do_read_index(istate, path, 0);
-	trace_performance_since(start, "read cache %s", path);
+	trace_performance_leave("read cache %s", path);
 
 	split_index = istate->split_index;
 	if (!split_index || is_null_oid(&split_index->base_oid)) {
@@ -1921,6 +1920,7 @@ int read_index_from(struct index_state *istate, const char *path,
 		return ret;
 	}
 
+	trace_performance_enter();
 	if (split_index->base)
 		discard_index(split_index->base);
 	else
@@ -1937,8 +1937,8 @@ int read_index_from(struct index_state *istate, const char *path,
 	freshen_shared_index(base_path, 0);
 	merge_base_index(istate);
 	post_read_index_from(istate);
-	trace_performance_since(start, "read cache %s", base_path);
 	free(base_path);
+	trace_performance_leave("read cache %s", base_path);
 	return ret;
 }
 
@@ -2763,4 +2763,6 @@ void move_index_extensions(struct index_state *dst, struct index_state *src)
 {
 	dst->untracked = src->untracked;
 	src->untracked = NULL;
+	dst->cache_tree = src->cache_tree;
+	src->cache_tree = NULL;
 }
diff --git a/trace.c b/trace.c
index fc623e91fd..fa4a2e7120 100644
--- a/trace.c
+++ b/trace.c
@@ -176,10 +176,30 @@ void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
 	strbuf_release(&buf);
 }
 
+static uint64_t perf_start_times[10];
+static int perf_indent;
+
+uint64_t trace_performance_enter(void)
+{
+	uint64_t now;
+
+	if (!trace_want(&trace_perf_key))
+		return 0;
+
+	now = getnanotime();
+	perf_start_times[perf_indent] = now;
+	if (perf_indent + 1 < ARRAY_SIZE(perf_start_times))
+		perf_indent++;
+	else
+		BUG("Too deep indentation");
+	return now;
+}
+
 static void trace_performance_vprintf_fl(const char *file, int line,
 					 uint64_t nanos, const char *format,
 					 va_list ap)
 {
+	static const char space[] = "          ";
 	struct strbuf buf = STRBUF_INIT;
 
 	if (!prepare_trace_line(file, line, &trace_perf_key, &buf))
@@ -188,7 +208,10 @@ static void trace_performance_vprintf_fl(const char *file, int line,
 	strbuf_addf(&buf, "performance: %.9f s", (double) nanos / 1000000000);
 
 	if (format && *format) {
-		strbuf_addstr(&buf, ": ");
+		if (perf_indent >= strlen(space))
+			BUG("Too deep indentation");
+
+		strbuf_addf(&buf, ":%.*s ", perf_indent, space);
 		strbuf_vaddf(&buf, format, ap);
 	}
 
@@ -244,6 +267,24 @@ void trace_performance_since(uint64_t start, const char *format, ...)
 	va_end(ap);
 }
 
+void trace_performance_leave(const char *format, ...)
+{
+	va_list ap;
+	uint64_t since;
+
+	if (perf_indent)
+		perf_indent--;
+
+	if (!format) /* Allow callers to leave without tracing anything */
+		return;
+
+	since = perf_start_times[perf_indent];
+	va_start(ap, format);
+	trace_performance_vprintf_fl(NULL, 0, getnanotime() - since,
+				     format, ap);
+	va_end(ap);
+}
+
 #else
 
 void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
@@ -273,6 +314,24 @@ void trace_performance_fl(const char *file, int line, uint64_t nanos,
 	va_end(ap);
 }
 
+void trace_performance_leave_fl(const char *file, int line,
+				uint64_t nanos, const char *format, ...)
+{
+	va_list ap;
+	uint64_t since;
+
+	if (perf_indent)
+		perf_indent--;
+
+	if (!format) /* Allow callers to leave without tracing anything */
+		return;
+
+	since = perf_start_times[perf_indent];
+	va_start(ap, format);
+	trace_performance_vprintf_fl(file, line, nanos - since, format, ap);
+	va_end(ap);
+}
+
 #endif /* HAVE_VARIADIC_MACROS */

@@ -411,13 +470,11 @@ uint64_t getnanotime(void)
 	}
 }
 
-static uint64_t command_start_time;
 static struct strbuf command_line = STRBUF_INIT;
 
 static void print_command_performance_atexit(void)
 {
-	trace_performance_since(command_start_time, "git command:%s",
-				command_line.buf);
+	trace_performance_leave("git command:%s", command_line.buf);
 }
 
 void trace_command_performance(const char **argv)
@@ -425,10 +482,10 @@ void trace_command_performance(const char **argv)
 	if (!trace_want(&trace_perf_key))
 		return;
 
-	if (!command_start_time)
+	if (!command_line.len)
 		atexit(print_command_performance_atexit);
 
 	strbuf_reset(&command_line);
 	sq_quote_argv_pretty(&command_line, argv);
-	command_start_time = getnanotime();
+	trace_performance_enter();
 }
diff --git a/trace.h b/trace.h
index 2b6a1bc17c..171b256d26 100644
--- a/trace.h
+++ b/trace.h
@@ -23,6 +23,7 @@ extern void trace_disable(struct trace_key *key);
 extern uint64_t getnanotime(void);
 extern void trace_command_performance(const char **argv);
 extern void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
+uint64_t trace_performance_enter(void);
 
 #ifndef HAVE_VARIADIC_MACROS
 
@@ -45,6 +46,9 @@ extern void trace_performance(uint64_t nanos, const char *format, ...);
 __attribute__((format (printf, 2, 3)))
 extern void trace_performance_since(uint64_t start, const char *format, ...);
 
+__attribute__((format (printf, 1, 2)))
+void trace_performance_leave(const char *format, ...);
+
 #else
 
 /*
@@ -118,6 +122,14 @@ extern void trace_performance_since(uint64_t start, const char *format, ...);
 					     __VA_ARGS__);		    \
 	} while (0)
 
+#define trace_performance_leave(...)					    \
+	do {								    \
+		if (trace_pass_fl(&trace_perf_key))			    \
+			trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
+						   getnanotime(),	    \
+						   __VA_ARGS__);	    \
+	} while (0)
+
 /* backend functions, use non-*fl macros instead */
 __attribute__((format (printf, 4, 5)))
 extern void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
@@ -130,6 +142,9 @@ extern void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
 __attribute__((format (printf, 4, 5)))
 extern void trace_performance_fl(const char *file, int line,
 				 uint64_t nanos, const char *fmt, ...);
+__attribute__((format (printf, 4, 5)))
+extern void trace_performance_leave_fl(const char *file, int line,
+				       uint64_t nanos, const char *fmt, ...);
 static inline int trace_pass_fl(struct trace_key *key)
 {
 	return key->fd || !key->initialized;
diff --git a/unpack-trees.c b/unpack-trees.c
index 1438ee1555..d822662c75 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -201,7 +201,6 @@ static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
 
 	ce->ce_flags = (ce->ce_flags & ~clear) | set;
 	return add_index_entry(&o->result, ce,
-			       o->extra_add_index_flags |
 			       ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 }
 
@@ -353,9 +352,9 @@ static int check_updates(struct unpack_trees_options *o)
 	struct progress *progress = NULL;
 	struct index_state *index = &o->result;
 	struct checkout state = CHECKOUT_INIT;
-	uint64_t start = getnanotime();
 	int i;
 
+	trace_performance_enter();
 	state.force = 1;
 	state.quiet = 1;
 	state.refresh_cache = 1;
@@ -425,7 +424,7 @@ static int check_updates(struct unpack_trees_options *o)
 	errs |= finish_delayed_checkout(&state);
 	if (o->update)
 		git_attr_set_direction(GIT_ATTR_CHECKIN, NULL);
-	trace_performance_since(start, "update worktree after a merge");
+	trace_performance_leave("check_updates");
 	return errs != 0;
 }
 
@@ -702,31 +701,13 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
 	if (!o->merge)
 		BUG("We need cache-tree to do this optimization");
 
-	/*
-	 * Try to keep add_index_entry() as fast as possible since
-	 * we're going to do a lot of them.
-	 *
-	 * Skipping verify_path() should totally be safe because these
-	 * paths are from the source index, which must have been
-	 * verified.
-	 *
-	 * Skipping D/F and cache-tree validation checks is trickier
-	 * because it assumes what n-merge code would do when all
-	 * trees and the index are the same. We probably could just
-	 * optimize those code instead (e.g. we don't invalidate that
-	 * many cache-tree, but the searching for them is very
-	 * expensive).
-	 */
-	o->extra_add_index_flags = ADD_CACHE_SKIP_DFCHECK;
-	o->extra_add_index_flags |= ADD_CACHE_SKIP_VERIFY_PATH;
-
 	/*
 	 * Do what unpack_callback() and unpack_nondirectories() normally
 	 * do. But we walk all paths recursively in just one loop instead.
 	 *
-	 * D/F conflicts and staged entries are not a concern because
-	 * cache-tree would be invalidated and we would never get here
-	 * in the first place.
+	 * D/F conflicts and higher stage entries are not a concern
+	 * because cache-tree would be invalidated and we would never
+	 * get here in the first place.
 	 */
 	for (i = 0; i < nr_entries; i++) {
 		int new_ce_len, len, rc;
@@ -761,7 +742,6 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
 
 		mark_ce_used(src[0], o);
 	}
-	o->extra_add_index_flags = 0;
 	free(tree_ce);
 	if (o->debug_unpack)
 		printf("Unpacked %d entries from %s to %s using cache-tree\n",
@@ -791,7 +771,17 @@ static int traverse_trees_recursive(int n, unsigned long dirmask,
 
 		if (!o->merge || df_conflicts)
 			BUG("Wrong condition to get here buddy");
-		return traverse_by_cache_tree(pos, nr_entries, n, names, info);
+
+		/*
+		 * All entries up to 'pos' must have been processed
+		 * (i.e. marked CE_UNPACKED) at this point. But to be safe,
+		 * save and restore cache_bottom anyway to not miss
+		 * unprocessed entries before 'pos'.
+		 */
+		bottom = o->cache_bottom;
+		ret = traverse_by_cache_tree(pos, nr_entries, n, names, info);
+		o->cache_bottom = bottom;
+		return ret;
 	}
 
 	p = names;
@@ -1142,7 +1132,7 @@ static void debug_unpack_callback(int n,
 }
 
 /*
- * Note that traverse_by_cache_tree() duplicates some logic in this funciton
+ * Note that traverse_by_cache_tree() duplicates some logic in this function
  * without actually calling it. If you change the logic here you may need to
  * check and change there as well.
  */
@@ -1425,11 +1415,11 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	int i, ret;
 	static struct cache_entry *dfc;
 	struct exclude_list el;
-	uint64_t start = getnanotime();
 
 	if (len > MAX_UNPACK_TREES)
 		die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
 
+	trace_performance_enter();
 	memset(&el, 0, sizeof(el));
 	if (!core_apply_sparse_checkout || !o->update)
 		o->skip_sparse_checkout = 1;
@@ -1502,7 +1492,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 			}
 		}
 
-		if (traverse_trees(len, t, &info) < 0)
+		trace_performance_enter();
+		ret = traverse_trees(len, t, &info);
+		trace_performance_leave("traverse_trees");
+		if (ret < 0)
 			goto return_failed;
 	}
 
@@ -1574,10 +1567,10 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 			goto done;
 		}
 	}
-	trace_performance_since(start, "unpack trees");
 
 	ret = check_updates(o) ? (-2) : 0;
 	if (o->dst_index) {
+		move_index_extensions(&o->result, o->src_index);
 		if (!ret) {
 			if (!o->result.cache_tree)
 				o->result.cache_tree = cache_tree();
@@ -1586,7 +1579,6 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 						  WRITE_TREE_SILENT |
 						  WRITE_TREE_REPAIR);
 		}
-		move_index_extensions(&o->result, o->src_index);
 		discard_index(o->dst_index);
 		*o->dst_index = o->result;
 	} else {
@@ -1595,6 +1587,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	o->src_index = NULL;
 
 done:
+	trace_performance_leave("unpack_trees");
 	clear_exclude_list(&el);
 	return ret;
 
diff --git a/unpack-trees.h b/unpack-trees.h
index 94e1b14078..c2b434c606 100644
--- a/unpack-trees.h
+++ b/unpack-trees.h
@@ -80,7 +80,6 @@ struct unpack_trees_options {
 	struct index_state result;
 
 	struct exclude_list *el; /* for internal use */
-	unsigned int extra_add_index_flags;
 };
 
 extern int unpack_trees(unsigned n, struct tree_desc *t,

Nguyễn Thái Ngọc Duy (5):
  trace.h: support nested performance tracing
  unpack-trees: add performance tracing
  unpack-trees: optimize walking same trees with cache-tree
  unpack-trees: reduce malloc in cache-tree walk
  unpack-trees: reuse (still valid) cache-tree from src_index

 cache-tree.c    |   2 +
 diff-lib.c      |   4 +-
 dir.c           |   4 +-
 name-hash.c     |   4 +-
 preload-index.c |   4 +-
 read-cache.c    |  13 +++--
 trace.c         |  69 ++++++++++++++++++++--
 trace.h         |  15 +++++
 unpack-trees.c  | 149 +++++++++++++++++++++++++++++++++++++++++++++++-
 9 files changed, 243 insertions(+), 21 deletions(-)

-- 
2.18.0.1004.g6639190530