Redo of Message Queue

* Functionality moved to a base class CallQueue, which will be used for inter-thread communication within the scene.
* MessageQueue now uses growing pages, starts from a single 4k page.
* Limit still exists, but because its not allocated by default, it can be much higher.

core/object/message_queue.cpp

@@ -35,94 +35,55 @@
 #include "core/object/class_db.h"
 #include "core/object/script_language.h"
 
-MessageQueue *MessageQueue::singleton = nullptr;
+void CallQueue::_add_page() {
-
+	if (pages_used == page_messages.size()) {
-MessageQueue *MessageQueue::get_singleton() {
+		pages.push_back(allocator->alloc());
-	return singleton;
+		page_messages.push_back(0);
+	}
+	page_messages[pages_used] = 0;
+	pages_used++;
+	page_offset = 0;
 }
 
-Error MessageQueue::push_callp(ObjectID p_id, const StringName &p_method, const Variant **p_args, int p_argcount, bool p_show_error) {
+Error CallQueue::push_callp(ObjectID p_id, const StringName &p_method, const Variant **p_args, int p_argcount, bool p_show_error) {
 	return push_callablep(Callable(p_id, p_method), p_args, p_argcount, p_show_error);
 }
 
-Error MessageQueue::push_set(ObjectID p_id, const StringName &p_prop, const Variant &p_value) {
+Error CallQueue::push_callp(Object *p_object, const StringName &p_method, const Variant **p_args, int p_argcount, bool p_show_error) {
-	_THREAD_SAFE_METHOD_
-
-	uint8_t room_needed = sizeof(Message) + sizeof(Variant);
-
-	if ((buffer_end + room_needed) >= buffer_size) {
-		String type;
-		if (ObjectDB::get_instance(p_id)) {
-			type = ObjectDB::get_instance(p_id)->get_class();
-		}
-		ERR_PRINT("Failed set: " + type + ":" + p_prop + " target ID: " + itos(p_id) + ". Message queue out of memory. Try increasing \"memory/limits/message_queue/max_size_kb\" in project settings.");
-		statistics();
-		return ERR_OUT_OF_MEMORY;
-	}
-
-	Message *msg = memnew_placement(&buffer[buffer_end], Message);
-	msg->args = 1;
-	msg->callable = Callable(p_id, p_prop);
-	msg->type = TYPE_SET;
-
-	buffer_end += sizeof(Message);
-
-	Variant *v = memnew_placement(&buffer[buffer_end], Variant);
-	buffer_end += sizeof(Variant);
-	*v = p_value;
-
-	return OK;
-}
-
-Error MessageQueue::push_notification(ObjectID p_id, int p_notification) {
-	_THREAD_SAFE_METHOD_
-
-	ERR_FAIL_COND_V(p_notification < 0, ERR_INVALID_PARAMETER);
-
-	uint8_t room_needed = sizeof(Message);
-
-	if ((buffer_end + room_needed) >= buffer_size) {
-		ERR_PRINT("Failed notification: " + itos(p_notification) + " target ID: " + itos(p_id) + ". Message queue out of memory. Try increasing \"memory/limits/message_queue/max_size_kb\" in project settings.");
-		statistics();
-		return ERR_OUT_OF_MEMORY;
-	}
-
-	Message *msg = memnew_placement(&buffer[buffer_end], Message);
-
-	msg->type = TYPE_NOTIFICATION;
-	msg->callable = Callable(p_id, CoreStringNames::get_singleton()->notification); //name is meaningless but callable needs it
-	//msg->target;
-	msg->notification = p_notification;
-
-	buffer_end += sizeof(Message);
-
-	return OK;
-}
-
-Error MessageQueue::push_callp(Object *p_object, const StringName &p_method, const Variant **p_args, int p_argcount, bool p_show_error) {
 	return push_callp(p_object->get_instance_id(), p_method, p_args, p_argcount, p_show_error);
 }
 
-Error MessageQueue::push_notification(Object *p_object, int p_notification) {
+Error CallQueue::push_notification(Object *p_object, int p_notification) {
 	return push_notification(p_object->get_instance_id(), p_notification);
 }
 
-Error MessageQueue::push_set(Object *p_object, const StringName &p_prop, const Variant &p_value) {
+Error CallQueue::push_set(Object *p_object, const StringName &p_prop, const Variant &p_value) {
 	return push_set(p_object->get_instance_id(), p_prop, p_value);
 }
 
-Error MessageQueue::push_callablep(const Callable &p_callable, const Variant **p_args, int p_argcount, bool p_show_error) {
+Error CallQueue::push_callablep(const Callable &p_callable, const Variant **p_args, int p_argcount, bool p_show_error) {
-	_THREAD_SAFE_METHOD_
+	mutex.lock();
+	uint32_t room_needed = sizeof(Message) + sizeof(Variant) * p_argcount;
 
-	int room_needed = sizeof(Message) + sizeof(Variant) * p_argcount;
+	ERR_FAIL_COND_V_MSG(room_needed > uint32_t(PAGE_SIZE_BYTES), ERR_INVALID_PARAMETER, "Message is too large to fit on a page (" + itos(PAGE_SIZE_BYTES) + " bytes), consider passing less arguments.");
 
-	if ((buffer_end + room_needed) >= buffer_size) {
+	_ensure_first_page();
-		ERR_PRINT("Failed method: " + p_callable + ". Message queue out of memory. Try increasing \"memory/limits/message_queue/max_size_kb\" in project settings.");
+
-		statistics();
+	if ((page_offset + room_needed) > uint32_t(PAGE_SIZE_BYTES)) {
-		return ERR_OUT_OF_MEMORY;
+		if (room_needed > uint32_t(PAGE_SIZE_BYTES) || pages_used == max_pages) {
+			ERR_PRINT("Failed method: " + p_callable + ". Message queue out of memory. " + error_text);
+			statistics();
+			mutex.unlock();
+			return ERR_OUT_OF_MEMORY;
+		}
+		_add_page();
 	}
 
-	Message *msg = memnew_placement(&buffer[buffer_end], Message);
+	Page *page = pages[pages_used - 1];
+
+	uint8_t *buffer_end = &page->data[page_offset];
+
+	Message *msg = memnew_placement(buffer_end, Message);
 	msg->args = p_argcount;
 	msg->callable = p_callable;
 	msg->type = TYPE_CALL;
@@ -133,89 +94,95 @@ Error MessageQueue::push_callablep(const Callable &p_callable, const Variant **p
 	buffer_end += sizeof(Message);
 
 	for (int i = 0; i < p_argcount; i++) {
-		Variant *v = memnew_placement(&buffer[buffer_end], Variant);
+		Variant *v = memnew_placement(buffer_end, Variant);
 		buffer_end += sizeof(Variant);
 		*v = *p_args[i];
 	}
 
+	page_messages[pages_used - 1]++;
+	page_offset += room_needed;
+
+	mutex.unlock();
+
 	return OK;
 }
 
-void MessageQueue::statistics() {
+Error CallQueue::push_set(ObjectID p_id, const StringName &p_prop, const Variant &p_value) {
-	HashMap<StringName, int> set_count;
+	mutex.lock();
-	HashMap<int, int> notify_count;
+	uint32_t room_needed = sizeof(Message) + sizeof(Variant);
-	HashMap<Callable, int> call_count;
-	int null_count = 0;
 
-	uint32_t read_pos = 0;
+	_ensure_first_page();
-	while (read_pos < buffer_end) {
-		Message *message = (Message *)&buffer[read_pos];
 
-		Object *target = message->callable.get_object();
+	if ((page_offset + room_needed) > uint32_t(PAGE_SIZE_BYTES)) {
-
+		if (pages_used == max_pages) {
-		if (target != nullptr) {
+			String type;
-			switch (message->type & FLAG_MASK) {
+			if (ObjectDB::get_instance(p_id)) {
-				case TYPE_CALL: {
+				type = ObjectDB::get_instance(p_id)->get_class();
-					if (!call_count.has(message->callable)) {
-						call_count[message->callable] = 0;
-					}
-
-					call_count[message->callable]++;
-
-				} break;
-				case TYPE_NOTIFICATION: {
-					if (!notify_count.has(message->notification)) {
-						notify_count[message->notification] = 0;
-					}
-
-					notify_count[message->notification]++;
-
-				} break;
-				case TYPE_SET: {
-					StringName t = message->callable.get_method();
-					if (!set_count.has(t)) {
-						set_count[t] = 0;
-					}
-
-					set_count[t]++;
-
-				} break;
 			}
+			ERR_PRINT("Failed set: " + type + ":" + p_prop + " target ID: " + itos(p_id) + ". Message queue out of memory. " + error_text);
+			statistics();
 
-		} else {
+			mutex.unlock();
-			//object was deleted
+			return ERR_OUT_OF_MEMORY;
-			print_line("Object was deleted while awaiting a callback");
-
-			null_count++;
-		}
-
-		read_pos += sizeof(Message);
-		if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
-			read_pos += sizeof(Variant) * message->args;
 		}
+		_add_page();
 	}
 
-	print_line("TOTAL BYTES: " + itos(buffer_end));
+	Page *page = pages[pages_used - 1];
-	print_line("NULL count: " + itos(null_count));
+	uint8_t *buffer_end = &page->data[page_offset];
 
-	for (const KeyValue<StringName, int> &E : set_count) {
+	Message *msg = memnew_placement(buffer_end, Message);
-		print_line("SET " + E.key + ": " + itos(E.value));
+	msg->args = 1;
-	}
+	msg->callable = Callable(p_id, p_prop);
+	msg->type = TYPE_SET;
 
-	for (const KeyValue<Callable, int> &E : call_count) {
+	buffer_end += sizeof(Message);
-		print_line("CALL " + E.key + ": " + itos(E.value));
-	}
 
-	for (const KeyValue<int, int> &E : notify_count) {
+	Variant *v = memnew_placement(buffer_end, Variant);
-		print_line("NOTIFY " + itos(E.key) + ": " + itos(E.value));
+	*v = p_value;
-	}
+
+	page_messages[pages_used - 1]++;
+	page_offset += room_needed;
+	mutex.unlock();
+
+	return OK;
 }
 
-int MessageQueue::get_max_buffer_usage() const {
+Error CallQueue::push_notification(ObjectID p_id, int p_notification) {
-	return buffer_max_used;
+	ERR_FAIL_COND_V(p_notification < 0, ERR_INVALID_PARAMETER);
+	mutex.lock();
+	uint32_t room_needed = sizeof(Message);
+
+	_ensure_first_page();
+
+	if ((page_offset + room_needed) > uint32_t(PAGE_SIZE_BYTES)) {
+		if (pages_used == max_pages) {
+			ERR_PRINT("Failed notification: " + itos(p_notification) + " target ID: " + itos(p_id) + ". Message queue out of memory. " + error_text);
+			statistics();
+			mutex.unlock();
+			return ERR_OUT_OF_MEMORY;
+		}
+		_add_page();
+	}
+
+	Page *page = pages[pages_used - 1];
+	uint8_t *buffer_end = &page->data[page_offset];
+
+	Message *msg = memnew_placement(buffer_end, Message);
+
+	msg->type = TYPE_NOTIFICATION;
+	msg->callable = Callable(p_id, CoreStringNames::get_singleton()->notification); //name is meaningless but callable needs it
+	//msg->target;
+	msg->notification = p_notification;
+
+	page_messages[pages_used - 1]++;
+	page_offset += room_needed;
+	mutex.unlock();
+
+	return OK;
 }
 
-void MessageQueue::_call_function(const Callable &p_callable, const Variant *p_args, int p_argcount, bool p_show_error) {
+void CallQueue::_call_function(const Callable &p_callable, const Variant *p_args, int p_argcount, bool p_show_error) {
 	const Variant **argptrs = nullptr;
 	if (p_argcount) {
 		argptrs = (const Variant **)alloca(sizeof(Variant *) * p_argcount);
@@ -232,26 +199,32 @@ void MessageQueue::_call_function(const Callable &p_callable, const Variant *p_a
 	}
 }
 
-void MessageQueue::flush() {
+Error CallQueue::flush() {
-	if (buffer_end > buffer_max_used) {
+	mutex.lock();
-		buffer_max_used = buffer_end;
+
+	if (pages.size() == 0) {
+		// Never allocated
+		mutex.unlock();
+		return OK; // Do nothing.
 	}
 
-	uint32_t read_pos = 0;
-
-	//using reverse locking strategy
-	_THREAD_SAFE_LOCK_
-
 	if (flushing) {
-		_THREAD_SAFE_UNLOCK_
+		mutex.unlock();
-		ERR_FAIL_COND(flushing); //already flushing, you did something odd
+		return ERR_BUSY;
 	}
+
 	flushing = true;
 
-	while (read_pos < buffer_end) {
+	uint32_t i = 0;
+	uint32_t j = 0;
+	uint32_t offset = 0;
+
+	while (i < pages_used && j < page_messages[i]) {
+		Page *page = pages[i];
+
 		//lock on each iteration, so a call can re-add itself to the message queue
 
-		Message *message = (Message *)&buffer[read_pos];
+		Message *message = (Message *)&page->data[offset];
 
 		uint32_t advance = sizeof(Message);
 		if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
@@ -259,12 +232,12 @@ void MessageQueue::flush() {
 		}
 
 		//pre-advance so this function is reentrant
-		read_pos += advance;
+		offset += advance;
-
-		_THREAD_SAFE_UNLOCK_
 
 		Object *target = message->callable.get_object();
 
+		mutex.unlock();
+
 		if (target != nullptr) {
 			switch (message->type & FLAG_MASK) {
 				case TYPE_CALL: {
@@ -291,54 +264,208 @@ void MessageQueue::flush() {
 
 		if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
 			Variant *args = (Variant *)(message + 1);
-			for (int i = 0; i < message->args; i++) {
+			for (int k = 0; k < message->args; k++) {
-				args[i].~Variant();
+				args[k].~Variant();
 			}
 		}
 
 		message->~Message();
 
-		_THREAD_SAFE_LOCK_
+		mutex.lock();
+		j++;
+		if (j == page_messages[i]) {
+			j = 0;
+			i++;
+			offset = 0;
+		}
 	}
 
-	buffer_end = 0; // reset buffer
+	page_messages[0] = 0;
+	page_offset = 0;
+	pages_used = 1;
+
 	flushing = false;
-	_THREAD_SAFE_UNLOCK_
+	mutex.unlock();
+	return OK;
 }
 
-bool MessageQueue::is_flushing() const {
+void CallQueue::clear() {
+	mutex.lock();
+
+	if (pages.size() == 0) {
+		mutex.unlock();
+		return; // Nothing to clear.
+	}
+
+	for (uint32_t i = 0; i < pages_used; i++) {
+		uint32_t offset = 0;
+		for (uint32_t j = 0; j < page_messages[i]; j++) {
+			Page *page = pages[i];
+
+			//lock on each iteration, so a call can re-add itself to the message queue
+
+			Message *message = (Message *)&page->data[offset];
+
+			uint32_t advance = sizeof(Message);
+			if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
+				advance += sizeof(Variant) * message->args;
+			}
+
+			//pre-advance so this function is reentrant
+			offset += advance;
+
+			if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
+				Variant *args = (Variant *)(message + 1);
+				for (int k = 0; k < message->args; k++) {
+					args[k].~Variant();
+				}
+			}
+
+			message->~Message();
+		}
+	}
+
+	pages_used = 1;
+	page_offset = 0;
+	page_messages[0] = 0;
+
+	mutex.unlock();
+}
+
+void CallQueue::statistics() {
+	mutex.lock();
+	HashMap<StringName, int> set_count;
+	HashMap<int, int> notify_count;
+	HashMap<Callable, int> call_count;
+	int null_count = 0;
+
+	for (uint32_t i = 0; i < pages_used; i++) {
+		uint32_t offset = 0;
+		for (uint32_t j = 0; j < page_messages[i]; j++) {
+			Page *page = pages[i];
+
+			//lock on each iteration, so a call can re-add itself to the message queue
+
+			Message *message = (Message *)&page->data[offset];
+
+			uint32_t advance = sizeof(Message);
+			if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
+				advance += sizeof(Variant) * message->args;
+			}
+
+			Object *target = message->callable.get_object();
+
+			if (target != nullptr) {
+				switch (message->type & FLAG_MASK) {
+					case TYPE_CALL: {
+						if (!call_count.has(message->callable)) {
+							call_count[message->callable] = 0;
+						}
+
+						call_count[message->callable]++;
+
+					} break;
+					case TYPE_NOTIFICATION: {
+						if (!notify_count.has(message->notification)) {
+							notify_count[message->notification] = 0;
+						}
+
+						notify_count[message->notification]++;
+
+					} break;
+					case TYPE_SET: {
+						StringName t = message->callable.get_method();
+						if (!set_count.has(t)) {
+							set_count[t] = 0;
+						}
+
+						set_count[t]++;
+
+					} break;
+				}
+
+			} else {
+				//object was deleted
+				print_line("Object was deleted while awaiting a callback");
+
+				null_count++;
+			}
+
+			//pre-advance so this function is reentrant
+			offset += advance;
+
+			if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
+				Variant *args = (Variant *)(message + 1);
+				for (int k = 0; k < message->args; k++) {
+					args[k].~Variant();
+				}
+			}
+
+			message->~Message();
+		}
+	}
+
+	print_line("TOTAL PAGES: " + itos(pages_used) + " (" + itos(pages_used * PAGE_SIZE_BYTES) + " bytes).");
+	print_line("NULL count: " + itos(null_count));
+
+	for (const KeyValue<StringName, int> &E : set_count) {
+		print_line("SET " + E.key + ": " + itos(E.value));
+	}
+
+	for (const KeyValue<Callable, int> &E : call_count) {
+		print_line("CALL " + E.key + ": " + itos(E.value));
+	}
+
+	for (const KeyValue<int, int> &E : notify_count) {
+		print_line("NOTIFY " + itos(E.key) + ": " + itos(E.value));
+	}
+
+	mutex.unlock();
+}
+
+bool CallQueue::is_flushing() const {
 	return flushing;
 }
 
-MessageQueue::MessageQueue() {
+int CallQueue::get_max_buffer_usage() const {
+	return pages.size() * PAGE_SIZE_BYTES;
+}
+
+CallQueue::CallQueue(Allocator *p_custom_allocator, uint32_t p_max_pages, const String &p_error_text) {
+	if (p_custom_allocator) {
+		allocator = p_custom_allocator;
+		allocator_is_custom = true;
+	} else {
+		allocator = memnew(Allocator(16)); // 16 elements per allocator page, 64kb per allocator page. Anything small will do, though.
+		allocator_is_custom = false;
+	}
+	max_pages = p_max_pages;
+	error_text = p_error_text;
+}
+
+CallQueue::~CallQueue() {
+	clear();
+	// Let go of pages.
+	for (uint32_t i = 0; i < pages.size(); i++) {
+		allocator->free(pages[i]);
+	}
+	if (!allocator_is_custom) {
+		memdelete(allocator);
+	}
+}
+
+//////////////////////
+
+MessageQueue *MessageQueue::singleton = nullptr;
+
+MessageQueue::MessageQueue() :
+		CallQueue(nullptr,
+				int(GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "memory/limits/message_queue/max_size_mb", PROPERTY_HINT_RANGE, "1,512,1,or_greater"), 32)) * 1024 * 1024 / PAGE_SIZE_BYTES,
+				"Message queue out of memory. Try increasing 'memory/limits/message_queue/max_size_mb' in project settings.") {
 	ERR_FAIL_COND_MSG(singleton != nullptr, "A MessageQueue singleton already exists.");
 	singleton = this;
-
-	buffer_size = GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "memory/limits/message_queue/max_size_kb", PROPERTY_HINT_RANGE, "1024,4096,1,or_greater"), DEFAULT_QUEUE_SIZE_KB);
-	buffer_size *= 1024;
-	buffer = memnew_arr(uint8_t, buffer_size);
 }
 
 MessageQueue::~MessageQueue() {
-	uint32_t read_pos = 0;
-
-	while (read_pos < buffer_end) {
-		Message *message = (Message *)&buffer[read_pos];
-		Variant *args = (Variant *)(message + 1);
-		int argc = message->args;
-		if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
-			for (int i = 0; i < argc; i++) {
-				args[i].~Variant();
-			}
-		}
-		message->~Message();
-
-		read_pos += sizeof(Message);
-		if ((message->type & FLAG_MASK) != TYPE_NOTIFICATION) {
-			read_pos += sizeof(Variant) * message->args;
-		}
-	}
-
 	singleton = nullptr;
-	memdelete_arr(buffer);
 }

core/object/message_queue.h

@@ -33,26 +33,45 @@
 
 #include "core/object/object_id.h"
 #include "core/os/thread_safe.h"
+#include "core/templates/local_vector.h"
+#include "core/templates/paged_allocator.h"
 #include "core/variant/variant.h"
 
 class Object;
 
-class MessageQueue {
+class CallQueue {
-	_THREAD_SAFE_CLASS_
+public:
-
 	enum {
-		DEFAULT_QUEUE_SIZE_KB = 4096
+		PAGE_SIZE_BYTES = 4096
 	};
 
+private:
 	enum {
 		TYPE_CALL,
 		TYPE_NOTIFICATION,
 		TYPE_SET,
+		TYPE_END, // End marker.
 		FLAG_SHOW_ERROR = 1 << 14,
-		FLAG_MASK = FLAG_SHOW_ERROR - 1
+		FLAG_MASK = FLAG_SHOW_ERROR - 1,
-
 	};
 
+	struct Page {
+		uint8_t data[PAGE_SIZE_BYTES];
+	};
+
+	Mutex mutex;
+	typedef PagedAllocator<Page, true> Allocator;
+
+	Allocator *allocator = nullptr;
+	bool allocator_is_custom = false;
+
+	LocalVector<Page *> pages;
+	LocalVector<uint32_t> page_messages;
+	uint32_t max_pages = 0;
+	uint32_t pages_used = 0;
+	uint32_t page_offset = 0;
+	bool flushing = false;
+
 	struct Message {
 		Callable callable;
 		int16_t type;
@@ -62,20 +81,21 @@ class MessageQueue {
 		};
 	};
 
-	uint8_t *buffer = nullptr;
+	_FORCE_INLINE_ void _ensure_first_page() {
-	uint32_t buffer_end = 0;
+		if (unlikely(pages.is_empty())) {
-	uint32_t buffer_max_used = 0;
+			pages.push_back(allocator->alloc());
-	uint32_t buffer_size = 0;
+			page_messages.push_back(0);
+			pages_used = 1;
+		}
+	}
+
+	void _add_page();
 
 	void _call_function(const Callable &p_callable, const Variant *p_args, int p_argcount, bool p_show_error);
 
-	static MessageQueue *singleton;
+	String error_text;
-
-	bool flushing = false;
 
 public:
-	static MessageQueue *get_singleton();
-
 	Error push_callp(ObjectID p_id, const StringName &p_method, const Variant **p_args, int p_argcount, bool p_show_error = false);
 	template <typename... VarArgs>
 	Error push_call(ObjectID p_id, const StringName &p_method, VarArgs... p_args) {
@@ -87,9 +107,9 @@ public:
 		return push_callp(p_id, p_method, sizeof...(p_args) == 0 ? nullptr : (const Variant **)argptrs, sizeof...(p_args));
 	}
 
-	Error push_notification(ObjectID p_id, int p_notification);
-	Error push_set(ObjectID p_id, const StringName &p_prop, const Variant &p_value);
 	Error push_callablep(const Callable &p_callable, const Variant **p_args, int p_argcount, bool p_show_error = false);
+	Error push_set(ObjectID p_id, const StringName &p_prop, const Variant &p_value);
+	Error push_notification(ObjectID p_id, int p_notification);
 
 	template <typename... VarArgs>
 	Error push_callable(const Callable &p_callable, VarArgs... p_args) {
@@ -115,13 +135,22 @@ public:
 	Error push_notification(Object *p_object, int p_notification);
 	Error push_set(Object *p_object, const StringName &p_prop, const Variant &p_value);
 
+	Error flush();
+	void clear();
 	void statistics();
-	void flush();
 
 	bool is_flushing() const;
-
 	int get_max_buffer_usage() const;
 
+	CallQueue(Allocator *p_custom_allocator = 0, uint32_t p_max_pages = 8192, const String &p_error_text = String());
+	virtual ~CallQueue();
+};
+
+class MessageQueue : public CallQueue {
+	static MessageQueue *singleton;
+
+public:
+	_FORCE_INLINE_ static MessageQueue *get_singleton() { return singleton; }
 	MessageQueue();
 	~MessageQueue();
 };

doc/classes/ProjectSettings.xml

@@ -1739,7 +1739,7 @@
 		<member name="layer_names/3d_render/layer_9" type="String" setter="" getter="" default="&quot;&quot;">
 			Optional name for the 3D render layer 9. If left empty, the layer will display as "Layer 9".
 		</member>
-		<member name="memory/limits/message_queue/max_size_kb" type="int" setter="" getter="" default="4096">
+		<member name="memory/limits/message_queue/max_size_mb" type="int" setter="" getter="" default="32">
 			Godot uses a message queue to defer some function calls. If you run out of space on it (you will see an error), you can increase the size here.
 		</member>
 		<member name="memory/limits/multithreaded_server/rid_pool_prealloc" type="int" setter="" getter="" default="60">