Port r150 from branches/5.0: Port r19 from innodb-4.1/trunk:

Keep track on unflushed modifications to file spaces.  When there are tens
of thousands of file spaces, flushing all files in fil_flush_file_spaces()
would be very slow.  (Bug #15653)

fil_flush_file_spaces(): Only flush unflushed file spaces.

fil_space_t, fil_system_t: Add a list of unflushed spaces.

fil/fil0fil.c

@@ -181,6 +181,11 @@ struct fil_space_struct {
 	hash_node_t	name_hash;/* hash chain the name_hash table */
 	rw_lock_t	latch;	/* latch protecting the file space storage
 				allocation */
+	UT_LIST_NODE_T(fil_space_t) unflushed_spaces;
+				/* list of spaces with at least one unflushed
+				file we have written to */
+	ibool		is_in_unflushed_spaces; /* TRUE if this space is
+				currently in the list above */
 	UT_LIST_NODE_T(fil_space_t) space_list;
 				/* list of all spaces */
 	ibuf_data_t*	ibuf_data;
@@ -213,6 +218,12 @@ struct fil_system_struct {
 					not put to this list: they are opened
 					after the startup, and kept open until
 					shutdown */
+	UT_LIST_BASE_NODE_T(fil_space_t) unflushed_spaces;
+					/* base node for the list of those
+					tablespaces whose files contain
+					unflushed writes; those spaces have
+					at least one file node where
+					modification_counter > flush_counter */
 	ulint		n_open;		/* number of files currently open */
 	ulint		max_n_open;	/* n_open is not allowed to exceed
 					this */
@@ -389,6 +400,36 @@ fil_space_get_ibuf_data(
 	return(space->ibuf_data);
 }
 
+/**************************************************************************
+Checks if all the file nodes in a space are flushed. The caller must hold
+the fil_system mutex. */
+static
+ibool
+fil_space_is_flushed(
+/*=================*/
+				/* out: TRUE if all are flushed */
+	fil_space_t*	space)	/* in: space */
+{
+	fil_node_t*	node;
+
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(mutex_own(&(fil_system->mutex)));
+#endif /* UNIV_SYNC_DEBUG */
+
+	node = UT_LIST_GET_FIRST(space->chain);
+
+	while (node) {
+		if (node->modification_counter > node->flush_counter) {
+
+			return(FALSE);
+		}
+
+		node = UT_LIST_GET_NEXT(chain, node);
+	}
+
+	return(TRUE);
+}
+
 /***********************************************************************
 Appends a new file to the chain of files of a space. File must be closed. */
 
@@ -841,6 +882,16 @@ fil_node_free(
 
 		node->modification_counter = node->flush_counter;
 
+		if (space->is_in_unflushed_spaces
+		    && fil_space_is_flushed(space)) {
+
+			space->is_in_unflushed_spaces = FALSE;
+
+			UT_LIST_REMOVE(unflushed_spaces,
+					system->unflushed_spaces,
+					space);
+		}
+
 		fil_node_close_file(node, system);
 	}
 
@@ -1004,6 +1055,8 @@ fil_space_create(
 
 	HASH_INSERT(fil_space_t, name_hash, system->name_hash,
 						ut_fold_string(name), space);
+	space->is_in_unflushed_spaces = FALSE;
+
 	UT_LIST_ADD_LAST(space_list, system->space_list, space);
 				
 	mutex_exit(&(system->mutex));
@@ -1099,6 +1152,13 @@ fil_space_free(
 	HASH_DELETE(fil_space_t, name_hash, system->name_hash,
 					   ut_fold_string(space->name), space);
 
+	if (space->is_in_unflushed_spaces) {
+		space->is_in_unflushed_spaces = FALSE;
+
+		UT_LIST_REMOVE(unflushed_spaces, system->unflushed_spaces,
+								space);
+	}
+
 	UT_LIST_REMOVE(space_list, system->space_list, space);
 
 	ut_a(space->magic_n == FIL_SPACE_MAGIC_N);
@@ -1250,6 +1310,7 @@ fil_system_create(
 
 	system->tablespace_version = 0;
 
+	UT_LIST_INIT(system->unflushed_spaces);
 	UT_LIST_INIT(system->space_list);
 
 	return(system);
@@ -3742,6 +3803,14 @@ fil_node_complete_io(
 	if (type == OS_FILE_WRITE) {
 		system->modification_counter++;
 		node->modification_counter = system->modification_counter;
+
+		if (!node->space->is_in_unflushed_spaces) {
+
+			node->space->is_in_unflushed_spaces = TRUE;
+			UT_LIST_ADD_FIRST(unflushed_spaces,
+					system->unflushed_spaces,
+					node->space);
+		}
 	}
 	
 	if (node->n_pending == 0 && node->space->purpose == FIL_TABLESPACE
@@ -4162,6 +4231,16 @@ fil_flush(
 skip_flush:
 			if (node->flush_counter < old_mod_counter) {
 				node->flush_counter = old_mod_counter;
+
+				if (space->is_in_unflushed_spaces
+				    && fil_space_is_flushed(space)) {
+
+					space->is_in_unflushed_spaces = FALSE;
+
+					UT_LIST_REMOVE(unflushed_spaces,
+						system->unflushed_spaces,
+						space);
+				}
 			}
 
 			if (space->purpose == FIL_TABLESPACE) {
@@ -4193,7 +4272,7 @@ fil_flush_file_spaces(
 
 	mutex_enter(&(system->mutex));
 
-	space = UT_LIST_GET_FIRST(system->space_list);
+	space = UT_LIST_GET_FIRST(system->unflushed_spaces);
 
 	while (space) {
 		if (space->purpose == purpose && !space->is_being_deleted) {
@@ -4209,7 +4288,7 @@ fil_flush_file_spaces(
 
 			space->n_pending_flushes--;
 		}
-		space = UT_LIST_GET_NEXT(space_list, space);
+		space = UT_LIST_GET_NEXT(unflushed_spaces, space);
 	}
 	
 	mutex_exit(&(system->mutex));