Merge branch 'mt/parallel-checkout-part-1' into seen

Parallel checkout.

* mt/parallel-checkout-part-1:
  ci: run test round with parallel-checkout enabled
  parallel-checkout: add tests related to .gitattributes
  parallel-checkout: add tests related to clone collisions
  parallel-checkout: add tests for basic operations
  checkout-index: add parallel checkout support
  builtin/checkout.c: complete parallel checkout support
  make_transient_cache_entry(): optionally alloc from mem_pool
  parallel-checkout: support progress displaying
  parallel-checkout: make it truly parallel
  unpack-trees: add basic support for parallel checkout
  entry: add checkout_entry_ca() which takes preloaded conv_attrs
  entry: move conv_attrs lookup up to checkout_entry()
  entry: extract cache_entry update from write_entry()
  entry: make fstat_output() and read_blob_entry() public
  entry: extract a header file for entry.c functions
  convert: add conv_attrs classification
  convert: add get_stream_filter_ca() variant
  convert: add [async_]convert_to_working_tree_ca() variants
  convert: make convert_attrs() and convert structs public

Author: gitster

.gitignore

@@ -33,6 +33,7 @@
 /git-check-mailmap
 /git-check-ref-format
 /git-checkout
+/git-checkout--helper
 /git-checkout-index
 /git-cherry
 /git-cherry-pick

Documentation/config/checkout.txt

@@ -16,3 +16,24 @@ will checkout the '<something>' branch on another remote,
 and by linkgit:git-worktree[1] when 'git worktree add' refers to a
 remote branch. This setting might be used for other checkout-like
 commands or functionality in the future.
+
+checkout.workers::
+	The number of parallel workers to use when updating the working tree.
+	The default is one, i.e. sequential execution. If set to a value less
+	than one, Git will use as many workers as the number of logical cores
+	available. This setting and checkout.thresholdForParallelism affect all
+	commands that perform checkout. E.g. checkout, switch, clone, reset,
+	sparse-checkout, read-tree, etc.
++
+Note: parallel checkout usually delivers better performance for repositories
+located on SSDs or over NFS. For repositories on spinning disks and/or machines
+with a small number of cores, the default sequential checkout often performs
+better. The size and compression level of a repository might also influence how
+well the parallel version performs.
+
+checkout.thresholdForParallelism::
+	When running parallel checkout with a small number of files, the cost
+	of subprocess spawning and inter-process communication might outweigh
+	the parallelization gains. This setting allows to define the minimum
+	number of files for which parallel checkout should be attempted. The
+	default is 100.

Makefile

@@ -950,6 +950,7 @@ LIB_OBJS += pack-revindex.o
 LIB_OBJS += pack-write.o
 LIB_OBJS += packfile.o
 LIB_OBJS += pager.o
+LIB_OBJS += parallel-checkout.o
 LIB_OBJS += parse-options-cb.o
 LIB_OBJS += parse-options.o
 LIB_OBJS += patch-delta.o
@@ -1068,6 +1069,7 @@ BUILTIN_OBJS += builtin/check-attr.o
 BUILTIN_OBJS += builtin/check-ignore.o
 BUILTIN_OBJS += builtin/check-mailmap.o
 BUILTIN_OBJS += builtin/check-ref-format.o
+BUILTIN_OBJS += builtin/checkout--helper.o
 BUILTIN_OBJS += builtin/checkout-index.o
 BUILTIN_OBJS += builtin/checkout.o
 BUILTIN_OBJS += builtin/clean.o

apply.c

@@ -21,6 +21,7 @@
 #include "quote.h"
 #include "rerere.h"
 #include "apply.h"
+#include "entry.h"
 
 struct gitdiff_data {
 	struct strbuf *root;

builtin.h

@@ -123,6 +123,7 @@ int cmd_bugreport(int argc, const char **argv, const char *prefix);
 int cmd_bundle(int argc, const char **argv, const char *prefix);
 int cmd_cat_file(int argc, const char **argv, const char *prefix);
 int cmd_checkout(int argc, const char **argv, const char *prefix);
+int cmd_checkout__helper(int argc, const char **argv, const char *prefix);
 int cmd_checkout_index(int argc, const char **argv, const char *prefix);
 int cmd_check_attr(int argc, const char **argv, const char *prefix);
 int cmd_check_ignore(int argc, const char **argv, const char *prefix);

builtin/checkout--helper.c

@@ -0,0 +1,142 @@
+#include "builtin.h"
+#include "config.h"
+#include "entry.h"
+#include "parallel-checkout.h"
+#include "parse-options.h"
+#include "pkt-line.h"
+
+static void packet_to_pc_item(char *line, int len,
+			      struct parallel_checkout_item *pc_item)
+{
+	struct pc_item_fixed_portion *fixed_portion;
+	char *encoding, *variant;
+
+	if (len < sizeof(struct pc_item_fixed_portion))
+		BUG("checkout worker received too short item (got %dB, exp %dB)",
+		    len, (int)sizeof(struct pc_item_fixed_portion));
+
+	fixed_portion = (struct pc_item_fixed_portion *)line;
+
+	if (len - sizeof(struct pc_item_fixed_portion) !=
+		fixed_portion->name_len + fixed_portion->working_tree_encoding_len)
+		BUG("checkout worker received corrupted item");
+
+	variant = line + sizeof(struct pc_item_fixed_portion);
+
+	/*
+	 * Note: the main process uses zero length to communicate that the
+	 * encoding is NULL. There is no use case in actually sending an empty
+	 * string since it's considered as NULL when ca.working_tree_encoding
+	 * is set at git_path_check_encoding().
+	 */
+	if (fixed_portion->working_tree_encoding_len) {
+		encoding = xmemdupz(variant,
+				    fixed_portion->working_tree_encoding_len);
+		variant += fixed_portion->working_tree_encoding_len;
+	} else {
+		encoding = NULL;
+	}
+
+	memset(pc_item, 0, sizeof(*pc_item));
+	pc_item->ce = make_empty_transient_cache_entry(fixed_portion->name_len, NULL);
+	pc_item->ce->ce_namelen = fixed_portion->name_len;
+	pc_item->ce->ce_mode = fixed_portion->ce_mode;
+	memcpy(pc_item->ce->name, variant, pc_item->ce->ce_namelen);
+	oidcpy(&pc_item->ce->oid, &fixed_portion->oid);
+
+	pc_item->id = fixed_portion->id;
+	pc_item->ca.crlf_action = fixed_portion->crlf_action;
+	pc_item->ca.ident = fixed_portion->ident;
+	pc_item->ca.working_tree_encoding = encoding;
+}
+
+static void report_result(struct parallel_checkout_item *pc_item)
+{
+	struct pc_item_result res = { 0 };
+	size_t size;
+
+	res.id = pc_item->id;
+	res.status = pc_item->status;
+
+	if (pc_item->status == PC_ITEM_WRITTEN) {
+		res.st = pc_item->st;
+		size = sizeof(res);
+	} else {
+		size = PC_ITEM_RESULT_BASE_SIZE;
+	}
+
+	packet_write(1, (const char *)&res, size);
+}
+
+/* Free the worker-side malloced data, but not pc_item itself. */
+static void release_pc_item_data(struct parallel_checkout_item *pc_item)
+{
+	free((char *)pc_item->ca.working_tree_encoding);
+	discard_cache_entry(pc_item->ce);
+}
+
+static void worker_loop(struct checkout *state)
+{
+	struct parallel_checkout_item *items = NULL;
+	size_t i, nr = 0, alloc = 0;
+
+	while (1) {
+		int len;
+		char *line = packet_read_line(0, &len);
+
+		if (!line)
+			break;
+
+		ALLOC_GROW(items, nr + 1, alloc);
+		packet_to_pc_item(line, len, &items[nr++]);
+	}
+
+	for (i = 0; i < nr; ++i) {
+		struct parallel_checkout_item *pc_item = &items[i];
+		write_pc_item(pc_item, state);
+		report_result(pc_item);
+		release_pc_item_data(pc_item);
+	}
+
+	packet_flush(1);
+
+	free(items);
+}
+
+static const char * const checkout_helper_usage[] = {
+	N_("git checkout--helper [<options>]"),
+	NULL
+};
+
+int cmd_checkout__helper(int argc, const char **argv, const char *prefix)
+{
+	struct checkout state = CHECKOUT_INIT;
+	struct option checkout_helper_options[] = {
+		OPT_STRING(0, "prefix", &state.base_dir, N_("string"),
+			N_("when creating files, prepend <string>")),
+		OPT_END()
+	};
+
+	if (argc == 2 && !strcmp(argv[1], "-h"))
+		usage_with_options(checkout_helper_usage,
+				   checkout_helper_options);
+
+	git_config(git_default_config, NULL);
+	argc = parse_options(argc, argv, prefix, checkout_helper_options,
+			     checkout_helper_usage, 0);
+	if (argc > 0)
+		usage_with_options(checkout_helper_usage, checkout_helper_options);
+
+	if (state.base_dir)
+		state.base_dir_len = strlen(state.base_dir);
+
+	/*
+	 * Setting this on worker won't actually update the index. We just need
+	 * to pretend so to induce the checkout machinery to stat() the written
+	 * entries.
+	 */
+	state.refresh_cache = 1;
+
+	worker_loop(&state);
+	return 0;
+}

builtin/checkout-index.c

@@ -11,6 +11,8 @@
 #include "quote.h"
 #include "cache-tree.h"
 #include "parse-options.h"
+#include "entry.h"
+#include "parallel-checkout.h"
 
 #define CHECKOUT_ALL 4
 static int nul_term_line;
@@ -159,6 +161,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	int prefix_length;
 	int force = 0, quiet = 0, not_new = 0;
 	int index_opt = 0;
+	int pc_workers, pc_threshold;
 	struct option builtin_checkout_index_options[] = {
 		OPT_BOOL('a', "all", &all,
 			N_("check out all files in the index")),
@@ -213,6 +216,14 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 		hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
 	}
 
+	if (!to_tempfile)
+		get_parallel_checkout_configs(&pc_workers, &pc_threshold);
+	else
+		pc_workers = 1;
+
+	if (pc_workers > 1)
+		init_parallel_checkout();
+
 	/* Check out named files first */
 	for (i = 0; i < argc; i++) {
 		const char *arg = argv[i];
@@ -255,6 +266,12 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	if (all)
 		checkout_all(prefix, prefix_length);
 
+	if (pc_workers > 1) {
+		/* Errors were already reported */
+		run_parallel_checkout(&state, pc_workers, pc_threshold,
+				      NULL, NULL);
+	}
+
 	if (is_lock_file_locked(&lock_file) &&
 	    write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 		die("Unable to write new index file");

builtin/checkout.c

@@ -26,6 +26,8 @@
 #include "unpack-trees.h"
 #include "wt-status.h"
 #include "xdiff-interface.h"
+#include "entry.h"
+#include "parallel-checkout.h"
 
 static const char * const checkout_usage[] = {
 	N_("git checkout [<options>] <branch>"),
@@ -229,7 +231,8 @@ static int checkout_stage(int stage, const struct cache_entry *ce, int pos,
 		return error(_("path '%s' does not have their version"), ce->name);
 }
 
-static int checkout_merged(int pos, const struct checkout *state, int *nr_checkouts)
+static int checkout_merged(int pos, const struct checkout *state,
+			   int *nr_checkouts, struct mem_pool *ce_mem_pool)
 {
 	struct cache_entry *ce = active_cache[pos];
 	const char *path = ce->name;
@@ -290,11 +293,10 @@ static int checkout_merged(int pos, const struct checkout *state, int *nr_checko
 	if (write_object_file(result_buf.ptr, result_buf.size, blob_type, &oid))
 		die(_("Unable to add merge result for '%s'"), path);
 	free(result_buf.ptr);
-	ce = make_transient_cache_entry(mode, &oid, path, 2);
+	ce = make_transient_cache_entry(mode, &oid, path, 2, ce_mem_pool);
 	if (!ce)
 		die(_("make_cache_entry failed for path '%s'"), path);
 	status = checkout_entry(ce, state, NULL, nr_checkouts);
-	discard_cache_entry(ce);
 	return status;
 }
 
@@ -358,16 +360,22 @@ static int checkout_worktree(const struct checkout_opts *opts,
 	int nr_checkouts = 0, nr_unmerged = 0;
 	int errs = 0;
 	int pos;
+	int pc_workers, pc_threshold;
+	struct mem_pool ce_mem_pool;
 
 	state.force = 1;
 	state.refresh_cache = 1;
 	state.istate = &the_index;
 
+	mem_pool_init(&ce_mem_pool, 0);
+	get_parallel_checkout_configs(&pc_workers, &pc_threshold);
 	init_checkout_metadata(&state.meta, info->refname,
 			       info->commit ? &info->commit->object.oid : &info->oid,
 			       NULL);
 
 	enable_delayed_checkout(&state);
+	if (pc_workers > 1)
+		init_parallel_checkout();
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
 		if (ce->ce_flags & CE_MATCHED) {
@@ -383,10 +391,15 @@ static int checkout_worktree(const struct checkout_opts *opts,
 						       &nr_checkouts, opts->overlay_mode);
 			else if (opts->merge)
 				errs |= checkout_merged(pos, &state,
-							&nr_unmerged);
+							&nr_unmerged,
+							&ce_mem_pool);
 			pos = skip_same_name(ce, pos) - 1;
 		}
 	}
+	if (pc_workers > 1)
+		errs |= run_parallel_checkout(&state, pc_workers, pc_threshold,
+					      NULL, NULL);
+	mem_pool_discard(&ce_mem_pool, should_validate_cache_entries());
 	remove_marked_cache_entries(&the_index, 1);
 	remove_scheduled_dirs();
 	errs |= finish_delayed_checkout(&state, &nr_checkouts);

builtin/difftool.c

@@ -23,6 +23,7 @@
 #include "lockfile.h"
 #include "object-store.h"
 #include "dir.h"
+#include "entry.h"
 
 static int trust_exit_code;
 
@@ -322,7 +323,7 @@ static int checkout_path(unsigned mode, struct object_id *oid,
 	struct cache_entry *ce;
 	int ret;
 
-	ce = make_transient_cache_entry(mode, oid, path, 0);
+	ce = make_transient_cache_entry(mode, oid, path, 0, NULL);
 	ret = checkout_entry(ce, state, NULL, NULL);
 
 	discard_cache_entry(ce);

cache.h

@@ -355,16 +355,16 @@ struct cache_entry *make_empty_cache_entry(struct index_state *istate,
 					   size_t name_len);
 
 /*
- * Create a cache_entry that is not intended to be added to an index.
- * Caller is responsible for discarding the cache_entry
- * with `discard_cache_entry`.
+ * Create a cache_entry that is not intended to be added to an index. If mp is
+ * not NULL, the entry is allocated within the given memory pool. Caller is
+ * responsible for discarding the cache_entry with `discard_cache_entry`.
  */
 struct cache_entry *make_transient_cache_entry(unsigned int mode,
 					       const struct object_id *oid,
 					       const char *path,
-					       int stage);
+					       int stage, struct mem_pool *mp);
 
-struct cache_entry *make_empty_transient_cache_entry(size_t name_len);
+struct cache_entry *make_empty_transient_cache_entry(size_t len, struct mem_pool *mp);
 
 /*
  * Discard cache entry.
@@ -1705,30 +1705,6 @@ const char *show_ident_date(const struct ident_split *id,
  */
 int ident_cmp(const struct ident_split *, const struct ident_split *);
 
-struct checkout {
-	struct index_state *istate;
-	const char *base_dir;
-	int base_dir_len;
-	struct delayed_checkout *delayed_checkout;
-	struct checkout_metadata meta;
-	unsigned force:1,
-		 quiet:1,
-		 not_new:1,
-		 clone:1,
-		 refresh_cache:1;
-};
-#define CHECKOUT_INIT { NULL, "" }
-
-#define TEMPORARY_FILENAME_LENGTH 25
-int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath, int *nr_checkouts);
-void enable_delayed_checkout(struct checkout *state);
-int finish_delayed_checkout(struct checkout *state, int *nr_checkouts);
-/*
- * Unlink the last component and schedule the leading directories for
- * removal, such that empty directories get removed.
- */
-void unlink_entry(const struct cache_entry *ce);
-
 struct cache_def {
 	struct strbuf path;
 	int flags;