diff --git a/src/pocketmine/MemoryManager.php b/src/pocketmine/MemoryManager.php
index 3fd444d7c..0bf70c333 100644
--- a/src/pocketmine/MemoryManager.php
+++ b/src/pocketmine/MemoryManager.php
@@ -54,6 +54,13 @@ class MemoryManager{
 	private $chunkCache;
 	private $cacheTrigger;
 
+	/** @var \WeakRef[] */
+	private $leakWatch = [];
+
+	private $leakInfo = [];
+
+	private $leakSeed = 0;
+
 	public function __construct(Server $server){
 		$this->server = $server;
 
@@ -172,4 +179,85 @@ class MemoryManager{
 
 		return $cycles;
 	}
+
+	/**
+	 * @param object $object
+	 *
+	 * @return string Object identifier for future checks
+	 */
+	public function addObjectWatcher($object){
+		if(!is_object($object)){
+			throw new \InvalidArgumentException("Not an object!");
+		}
+
+
+		$identifier = spl_object_hash($object) . ":" . get_class($object);
+
+		if(isset($this->leakInfo[$identifier])){
+			return $this->leakInfo["id"];
+		}
+
+		$this->leakInfo[$identifier] = [
+			"id" => $id = Utils::dataToUUID($identifier . ":" . $this->leakSeed++),
+			"class" => get_class($object),
+			"hash" => $identifier
+		];
+		$this->leakInfo[$id] = $this->leakInfo[$identifier];
+
+		$this->leakWatch[$id] = new \WeakRef($object);
+
+		return $id;
+	}
+
+	public function isObjectAlive($id){
+		if(isset($this->leakWatch[$id])){
+			return $this->leakWatch[$id]->valid();
+		}
+
+		return false;
+	}
+
+	public function removeObjectWatch($id){
+		if(!isset($this->leakWatch[$id])){
+			return;
+		}
+		unset($this->leakInfo[$this->leakInfo[$id]["hash"]]);
+		unset($this->leakInfo[$id]);
+		unset($this->leakWatch[$id]);
+	}
+
+	public function doObjectCleanup(){
+		foreach($this->leakWatch as $id => $w){
+			if(!$w->valid()){
+				$this->removeObjectWatch($id);
+			}
+		}
+	}
+
+	public function getObjectInformation($id, $includeObject = false){
+		if(!isset($this->leakWatch[$id])){
+			return null;
+		}
+
+		$valid = false;
+		$references = 0;
+		$object = null;
+
+		if($this->leakWatch[$id]->acquire()){
+			$object = $this->leakWatch[$id]->get();
+			$this->leakWatch[$id]->release();
+
+			$valid = true;
+			$references = getReferenceCount($object, false);
+		}
+
+		return [
+			"id" => $id,
+			"class" => $this->leakInfo[$id]["class"],
+			"hash" => $this->leakInfo[$id]["hash"],
+			"valid" => $valid,
+			"references" => $references,
+			"object" => $includeObject ? $object : null
+		];
+	}
 }
\ No newline at end of file
diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index 129b60aec..7c6054d72 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -176,6 +176,8 @@ class Player extends Human implements CommandSender, InventoryHolder, IPlayer{
 	 */
 	public $loginData = [];
 
+	public $creationTime = 0;
+
 	protected $randomClientId;
 	protected $uuid;
 
@@ -499,6 +501,8 @@ class Player extends Human implements CommandSender, InventoryHolder, IPlayer{
 		$this->boundingBox = new AxisAlignedBB(0, 0, 0, 0, 0, 0);
 
 		$this->uuid = Utils::dataToUUID($ip, $port, $clientID);
+
+		$this->creationTime = microtime(true);
 	}
 
 	/**
@@ -2703,7 +2707,10 @@ class Player extends Human implements CommandSender, InventoryHolder, IPlayer{
 			unset($this->buffer);
 		}
 
-		$this->perm->clearPermissions();
+		if($this->perm !== null){
+			$this->perm->clearPermissions();
+		}
+
 		$this->server->removePlayer($this);
 	}
 
diff --git a/src/pocketmine/PocketMine.php b/src/pocketmine/PocketMine.php
index d108f67f1..8ba486dd9 100644
--- a/src/pocketmine/PocketMine.php
+++ b/src/pocketmine/PocketMine.php
@@ -465,21 +465,8 @@ namespace pocketmine {
 	$logger->info("Stopping other threads");
 
 	foreach(ThreadManager::getInstance()->getAll() as $id => $thread){
-		if($thread->isRunning()){
-			$logger->debug("Killing " . (new \ReflectionClass($thread))->getShortName() . " thread");
-			$thread->kill();
-			sleep(1);
-			$thread->detach();
-		}elseif(!$thread->isJoined()){
-			if(!$thread->isTerminated()){
-				$logger->debug("Joining " . (new \ReflectionClass($thread))->getShortName() . " thread");
-				$thread->join();
-			}else{
-				$logger->debug("Killing " . (new \ReflectionClass($thread))->getShortName() . " thread");
-				$thread->kill();
-				$thread->detach();
-			}
-		}
+		$logger->debug("Stopping " . (new \ReflectionClass($thread))->getShortName() . " thread");
+		$thread->quit();
 	}
 
 	$logger->shutdown();
diff --git a/src/pocketmine/Server.php b/src/pocketmine/Server.php
index ad1bd5f6b..97f01bd55 100644
--- a/src/pocketmine/Server.php
+++ b/src/pocketmine/Server.php
@@ -1570,10 +1570,10 @@ class Server{
 
 		if(($poolSize = $this->getProperty("settings.async-workers", "auto")) === "auto"){
 			$poolSize = ServerScheduler::$WORKERS;
-			$processors = Utils::getCoreCount();
+			$processors = Utils::getCoreCount() - 2;
 
 			if($processors > 0){
-				$poolSize = max(2, $processors);
+				$poolSize = max(1, $processors);
 			}
 		}
 
@@ -1957,8 +1957,10 @@ class Server{
 		$this->reloadWhitelist();
 		$this->operators->reload();
 
+		$this->memoryManager->doObjectCleanup();
+
 		foreach($this->getIPBans()->getEntries() as $entry){
-			$this->blockAddress($entry->getName(), -1);
+			$this->getNetwork()->blockAddress($entry->getName(), -1);
 		}
 
 		$this->pluginManager->registerInterface(PharPluginLoader::class);
@@ -2024,6 +2026,8 @@ class Server{
 				$interface->shutdown();
 				$this->network->unregisterInterface($interface);
 			}
+
+			$this->memoryManager->doObjectCleanup();
 		}catch(\Exception $e){
 			$this->logger->emergency("Crashed while crashing, killing process");
 			@kill(getmypid());
diff --git a/src/pocketmine/Thread.php b/src/pocketmine/Thread.php
index d8f1ec5e4..a79385ad1 100644
--- a/src/pocketmine/Thread.php
+++ b/src/pocketmine/Thread.php
@@ -63,4 +63,25 @@ abstract class Thread extends \Thread{
 
 		return false;
 	}
+
+	/**
+	 * Stops the thread using the best way possible. Try to stop it yourself before calling this.
+	 */
+	public function quit(){
+		if($this->isRunning()){
+			$this->kill();
+			$this->detach();
+		}elseif(!$this->isJoined()){
+			if(!$this->isTerminated()){
+				$this->join();
+			}else{
+				$this->kill();
+				$this->detach();
+			}
+		}else{
+			$this->detach();
+		}
+
+		ThreadManager::getInstance()->remove($this);
+	}
 }
\ No newline at end of file
diff --git a/src/pocketmine/Worker.php b/src/pocketmine/Worker.php
index 58ec885ec..4f8603ff9 100644
--- a/src/pocketmine/Worker.php
+++ b/src/pocketmine/Worker.php
@@ -63,4 +63,26 @@ abstract class Worker extends \Worker{
 
 		return false;
 	}
+
+	/**
+	 * Stops the thread using the best way possible. Try to stop it yourself before calling this.
+	 */
+	public function quit(){
+		if($this->isRunning()){
+			$this->unstack();
+			$this->kill();
+			$this->detach();
+		}elseif(!$this->isJoined()){
+			if(!$this->isTerminated()){
+				$this->join();
+			}else{
+				$this->kill();
+				$this->detach();
+			}
+		}else{
+			$this->detach();
+		}
+
+		ThreadManager::getInstance()->remove($this);
+	}
 }
\ No newline at end of file
diff --git a/src/pocketmine/entity/Entity.php b/src/pocketmine/entity/Entity.php
index ea105e62f..8918bd84d 100644
--- a/src/pocketmine/entity/Entity.php
+++ b/src/pocketmine/entity/Entity.php
@@ -82,7 +82,7 @@ abstract class Entity extends Location implements Metadatable{
 	const DATA_AIR = 1;
 	const DATA_SHOW_NAMETAG = 3;
 	const DATA_POTION_COLOR = 7;
-	const DATA_POTION_VISIBLE = 8;
+	const DATA_POTION_AMBIENT = 8;
     const DATA_NO_AI = 15;
 
 
@@ -337,10 +337,10 @@ abstract class Entity extends Location implements Metadatable{
 			$b = ($color[2] / $count) & 0xff;
 
 			$this->setDataProperty(Entity::DATA_POTION_COLOR, Entity::DATA_TYPE_INT, ($r << 16) + ($g << 8) + $b);
-			$this->setDataProperty(Entity::DATA_POTION_VISIBLE, Entity::DATA_TYPE_BYTE, $ambient ? 1 : 0);
+			$this->setDataProperty(Entity::DATA_POTION_AMBIENT, Entity::DATA_TYPE_BYTE, $ambient ? 1 : 0);
 		}else{
 			$this->setDataProperty(Entity::DATA_POTION_COLOR, Entity::DATA_TYPE_INT, 0);
-			$this->setDataProperty(Entity::DATA_POTION_VISIBLE, Entity::DATA_TYPE_BYTE, 0);
+			$this->setDataProperty(Entity::DATA_POTION_AMBIENT, Entity::DATA_TYPE_BYTE, 0);
 		}
 	}
 
diff --git a/src/pocketmine/network/RakLibInterface.php b/src/pocketmine/network/RakLibInterface.php
index ff02619bb..000fb912d 100644
--- a/src/pocketmine/network/RakLibInterface.php
+++ b/src/pocketmine/network/RakLibInterface.php
@@ -98,9 +98,7 @@ class RakLibInterface implements ServerInstance, AdvancedSourceInterface{
 			$this->identifiers->detach($player);
 			unset($this->players[$identifier]);
 			unset($this->identifiersACK[$identifier]);
-			if(!$player->closed){
-				$player->close($player->getLeaveMessage(), $reason);
-			}
+			$player->close($player->getLeaveMessage(), $reason);
 		}
 	}
 
diff --git a/src/pocketmine/plugin/PluginManager.php b/src/pocketmine/plugin/PluginManager.php
index 168f93d0d..c01cc6aaf 100644
--- a/src/pocketmine/plugin/PluginManager.php
+++ b/src/pocketmine/plugin/PluginManager.php
@@ -459,8 +459,9 @@ class PluginManager{
 			$subs = [];
 			foreach($this->permSubs[$permission] as $k => $perm){
 				/** @var \WeakRef $perm */
-				if($perm->valid()){
+				if($perm->acquire()){
 					$subs[] = $perm->get();
+					$perm->release();
 				}else{
 					unset($this->permSubs[$permission][$k]);
 				}
@@ -507,8 +508,9 @@ class PluginManager{
 		if($op === true){
 			foreach($this->defSubsOp as $k => $perm){
 				/** @var \WeakRef $perm */
-				if($perm->valid()){
+				if($perm->acquire()){
 					$subs[] = $perm->get();
+					$perm->release();
 				}else{
 					unset($this->defSubsOp[$k]);
 				}
@@ -516,8 +518,9 @@ class PluginManager{
 		}else{
 			foreach($this->defSubs as $k => $perm){
 				/** @var \WeakRef $perm */
-				if($perm->valid()){
+				if($perm->acquire()){
 					$subs[] = $perm->get();
+					$perm->release();
 				}else{
 					unset($this->defSubs[$k]);
 				}
diff --git a/src/pocketmine/scheduler/AsyncPool.php b/src/pocketmine/scheduler/AsyncPool.php
index ad7dcdabb..20b3e3216 100644
--- a/src/pocketmine/scheduler/AsyncPool.php
+++ b/src/pocketmine/scheduler/AsyncPool.php
@@ -117,8 +117,6 @@ class AsyncPool{
 		unset($this->taskWorkers[$task->getTaskId()]);
 
 		$task->cleanObject();
-
-		unset($task);
 	}
 
 	public function removeTasks(){