Merge branch 'rs/loose-object-cache-perffix'

The loose object cache used to optimize existence look-up has been
updated.

* rs/loose-object-cache-perffix:
  object-store: retire odb_load_loose_cache()
  object-store: use one oid_array per subdirectory for loose cache
  object-store: factor out odb_clear_loose_cache()
  object-store: factor out odb_loose_cache()

object-store.h

@@ -20,7 +20,7 @@ struct object_directory {
 	 * Be sure to call odb_load_loose_cache() before using.
 	 */
 	char loose_objects_subdir_seen[256];
-	struct oid_array loose_objects_cache;
+	struct oid_array loose_objects_cache[256];
 
 	/*
 	 * Path to the alternative object store. If this is a relative path,
@@ -48,11 +48,14 @@ void add_to_alternates_file(const char *dir);
 void add_to_alternates_memory(const char *dir);
 
 /*
- * Populate an odb's loose object cache for one particular subdirectory (i.e.,
- * the one that corresponds to the first byte of objects you're interested in,
- * from 0 to 255 inclusive).
+ * Populate and return the loose object cache array corresponding to the
+ * given object ID.
  */
-void odb_load_loose_cache(struct object_directory *odb, int subdir_nr);
+struct oid_array *odb_loose_cache(struct object_directory *odb,
+				  const struct object_id *oid);
+
+/* Empty the loose object cache for the specified object directory. */
+void odb_clear_loose_cache(struct object_directory *odb);
 
 struct packed_git {
 	struct packed_git *next;

object.c

@@ -485,7 +485,7 @@ struct raw_object_store *raw_object_store_new(void)
 static void free_object_directory(struct object_directory *odb)
 {
 	free(odb->path);
-	oid_array_clear(&odb->loose_objects_cache);
+	odb_clear_loose_cache(odb);
 	free(odb);
 }
 

packfile.c

@@ -994,11 +994,8 @@ void reprepare_packed_git(struct repository *r)
 {
 	struct object_directory *odb;
 
-	for (odb = r->objects->odb; odb; odb = odb->next) {
-		oid_array_clear(&odb->loose_objects_cache);
-		memset(&odb->loose_objects_subdir_seen, 0,
-		       sizeof(odb->loose_objects_subdir_seen));
-	}
+	for (odb = r->objects->odb; odb; odb = odb->next)
+		odb_clear_loose_cache(odb);
 
 	r->objects->approximate_object_count_valid = 0;
 	r->objects->packed_git_initialized = 0;

sha1-file.c

@@ -924,16 +924,14 @@ static int open_sha1_file(struct repository *r,
 static int quick_has_loose(struct repository *r,
 			   const unsigned char *sha1)
 {
-	int subdir_nr = sha1[0];
 	struct object_id oid;
 	struct object_directory *odb;
 
 	hashcpy(oid.hash, sha1);
 
 	prepare_alt_odb(r);
 	for (odb = r->objects->odb; odb; odb = odb->next) {
-		odb_load_loose_cache(odb, subdir_nr);
-		if (oid_array_lookup(&odb->loose_objects_cache, &oid) >= 0)
+		if (oid_array_lookup(odb_loose_cache(odb, &oid), &oid) >= 0)
 			return 1;
 	}
 	return 0;
@@ -2152,24 +2150,37 @@ static int append_loose_object(const struct object_id *oid, const char *path,
 	return 0;
 }
 
-void odb_load_loose_cache(struct object_directory *odb, int subdir_nr)
+struct oid_array *odb_loose_cache(struct object_directory *odb,
+				  const struct object_id *oid)
 {
+	int subdir_nr = oid->hash[0];
 	struct strbuf buf = STRBUF_INIT;
 
 	if (subdir_nr < 0 ||
 	    subdir_nr >= ARRAY_SIZE(odb->loose_objects_subdir_seen))
 		BUG("subdir_nr out of range");
 
 	if (odb->loose_objects_subdir_seen[subdir_nr])
-		return;
+		return &odb->loose_objects_cache[subdir_nr];
 
 	strbuf_addstr(&buf, odb->path);
 	for_each_file_in_obj_subdir(subdir_nr, &buf,
 				    append_loose_object,
 				    NULL, NULL,
-				    &odb->loose_objects_cache);
+				    &odb->loose_objects_cache[subdir_nr]);
 	odb->loose_objects_subdir_seen[subdir_nr] = 1;
 	strbuf_release(&buf);
+	return &odb->loose_objects_cache[subdir_nr];
+}
+
+void odb_clear_loose_cache(struct object_directory *odb)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(odb->loose_objects_cache); i++)
+		oid_array_clear(&odb->loose_objects_cache[i]);
+	memset(&odb->loose_objects_subdir_seen, 0,
+	       sizeof(odb->loose_objects_subdir_seen));
 }
 
 static int check_stream_sha1(git_zstream *stream,

sha1-name.c

@@ -87,21 +87,21 @@ static int match_sha(unsigned, const unsigned char *, const unsigned char *);
 
 static void find_short_object_filename(struct disambiguate_state *ds)
 {
-	int subdir_nr = ds->bin_pfx.hash[0];
 	struct object_directory *odb;
 
 	for (odb = the_repository->objects->odb;
 	     odb && !ds->ambiguous;
 	     odb = odb->next) {
 		int pos;
+		struct oid_array *loose_objects;
 
-		odb_load_loose_cache(odb, subdir_nr);
-		pos = oid_array_lookup(&odb->loose_objects_cache, &ds->bin_pfx);
+		loose_objects = odb_loose_cache(odb, &ds->bin_pfx);
+		pos = oid_array_lookup(loose_objects, &ds->bin_pfx);
 		if (pos < 0)
 			pos = -1 - pos;
-		while (!ds->ambiguous && pos < odb->loose_objects_cache.nr) {
+		while (!ds->ambiguous && pos < loose_objects->nr) {
 			const struct object_id *oid;
-			oid = odb->loose_objects_cache.oid + pos;
+			oid = loose_objects->oid + pos;
 			if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
 				break;
 			update_candidates(ds, oid);