Merge pull request #1883 from akka/wip-3720-actor-size-and-speed-regression-master-ban

=act #3720 Optimze actor creation speed and actor size

akka-actor-tests/src/test/scala/akka/TestUtils.scala

@@ -5,9 +5,10 @@
 package akka
 
 import scala.collection.immutable
-import java.net.{ SocketAddress, ServerSocket, DatagramSocket, InetSocketAddress }
+import scala.concurrent.duration.Duration
+import java.net.{ SocketAddress, InetSocketAddress }
 import java.nio.channels.{ DatagramChannel, ServerSocketChannel }
-import akka.actor.{ Terminated, ActorSystem, ActorRef }
+import akka.actor.{ ActorSystem, ActorRef }
 import akka.testkit.TestProbe
 
 object TestUtils {
@@ -33,10 +34,10 @@ object TestUtils {
     } collect { case (socket, address) ⇒ socket.close(); address }
   }
 
-  def verifyActorTermination(actor: ActorRef)(implicit system: ActorSystem): Unit = {
+  def verifyActorTermination(actor: ActorRef, max: Duration = Duration.Undefined)(implicit system: ActorSystem): Unit = {
     val watcher = TestProbe()
     watcher.watch(actor)
-    watcher.expectTerminated(actor)
+    watcher.expectTerminated(actor, max)
   }
 
 }

akka-actor-tests/src/test/scala/akka/actor/ActorPerfSpec.scala

@@ -0,0 +1,150 @@
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package akka.actor
+
+import scala.language.postfixOps
+
+import akka.testkit.{ PerformanceTest, ImplicitSender, AkkaSpec }
+import java.lang.management.ManagementFactory
+import scala.concurrent.duration._
+import akka.TestUtils
+import scala.util.Try
+
+object ActorPerfSpec {
+
+  case class Create(number: Int, props: () ⇒ Props)
+  case object Created
+  case object IsAlive
+  case object Alive
+  case class WaitForChildren(number: Int)
+  case object Waited
+
+  class EmptyActor extends Actor {
+    def receive = {
+      case IsAlive ⇒ sender ! Alive
+    }
+  }
+
+  class EmptyArgsActor(val foo: Int, val bar: Int) extends Actor {
+    def receive = {
+      case IsAlive ⇒ sender ! Alive
+    }
+  }
+
+  class Driver extends Actor {
+
+    def receive = {
+      case IsAlive ⇒
+        sender ! Alive
+      case Create(number, propsCreator) ⇒
+        for (i ← 1 to number) {
+          context.actorOf(propsCreator.apply())
+        }
+        sender ! Created
+      case WaitForChildren(number) ⇒
+        context.children.foreach(_ ! IsAlive)
+        context.become(waiting(number, sender), false)
+    }
+
+    def waiting(number: Int, replyTo: ActorRef): Receive = {
+      var current = number
+
+      {
+        case Alive ⇒
+          current -= 1
+          if (current == 0) {
+            replyTo ! Waited
+            context.unbecome()
+          }
+      }
+    }
+  }
+}
+
+@org.junit.runner.RunWith(classOf[org.scalatest.junit.JUnitRunner])
+class ActorPerfSpec extends AkkaSpec("akka.actor.serialize-messages = off") with ImplicitSender {
+
+  import ActorPerfSpec._
+
+  val warmUp: Int = Integer.getInteger("akka.test.actor.ActorPerfSpec.warmUp", 50000)
+  val numberOfActors: Int = Integer.getInteger("akka.test.actor.ActorPerfSpec.numberOfActors", 100000)
+  val numberOfRepeats: Int = Integer.getInteger("akka.test.actor.ActorPerfSpec.numberOfRepeats", 2)
+
+  def testActorCreation(name: String, propsCreator: () ⇒ Props): Unit = {
+    val actorName = name.replaceAll("[ #\\?/!\\*%\\(\\)\\[\\]]", "_")
+    if (warmUp > 0)
+      measure(s"${actorName}_warmup", warmUp, propsCreator)
+    val results = for (i ← 1 to numberOfRepeats) yield measure(s"${actorName}_driver_$i", numberOfActors, propsCreator)
+    results.foreach {
+      case (duration, memory) ⇒
+        val micros = duration.toMicros
+        val avgMicros = micros.toDouble / numberOfActors
+        val avgMemory = memory.toDouble / numberOfActors
+        println(s"$name Created $numberOfActors");
+        println(s"In $micros us, avg: ${avgMicros}")
+        println(s"Footprint ${memory / 1024} KB, avg: ${avgMemory} B")
+    }
+  }
+
+  def measure(name: String, number: Int, propsCreator: () ⇒ Props): (Duration, Long) = {
+    val memMx = ManagementFactory.getMemoryMXBean()
+    val driver = system.actorOf(Props[Driver], name)
+    driver ! IsAlive
+    expectMsg(Alive)
+    System.gc()
+    val memBefore = memMx.getHeapMemoryUsage
+    val start = System.nanoTime()
+    driver ! Create(number, propsCreator)
+    expectMsgPF(15 seconds, s"$name waiting for Created") { case Created ⇒ }
+    val stop = System.nanoTime()
+    val duration = Duration.fromNanos(stop - start)
+    driver ! WaitForChildren(number)
+    expectMsgPF(15 seconds, s"$name waiting for Waited") { case Waited ⇒ }
+    System.gc()
+    val memAfter = memMx.getHeapMemoryUsage
+    driver ! PoisonPill
+    TestUtils.verifyActorTermination(driver, 15 seconds)
+    (duration, memAfter.getUsed - memBefore.getUsed)
+  }
+
+  "Actor creation with actorFor" must {
+
+    "measure time for Props[EmptyActor] with new Props" taggedAs PerformanceTest in {
+      testActorCreation("Props[EmptyActor] new", () ⇒ { Props[EmptyActor] })
+    }
+
+    "measure time for Props[EmptyActor] with same Props" taggedAs PerformanceTest in {
+      val props = Props[EmptyActor]
+      testActorCreation("Props[EmptyActor] same", () ⇒ { props })
+    }
+
+    "measure time for Props(new EmptyActor) with new Props" taggedAs PerformanceTest in {
+      testActorCreation("Props(new EmptyActor) new", () ⇒ { Props(new EmptyActor) })
+    }
+
+    "measure time for Props(new EmptyActor) with same Props" taggedAs PerformanceTest in {
+      val props = Props(new EmptyActor)
+      testActorCreation("Props(new EmptyActor) same", () ⇒ { props })
+    }
+
+    "measure time for Props(classOf[EmptyArgsActor], ...) with new Props" taggedAs PerformanceTest in {
+      testActorCreation("Props(classOf[EmptyArgsActor], ...) new", () ⇒ { Props(classOf[EmptyArgsActor], 4711, 1729) })
+    }
+
+    "measure time for Props(classOf[EmptyArgsActor], ...) with same Props" taggedAs PerformanceTest in {
+      val props = Props(classOf[EmptyArgsActor], 4711, 1729)
+      testActorCreation("Props(classOf[EmptyArgsActor], ...) same", () ⇒ { props })
+    }
+
+    "measure time for Props(new EmptyArgsActor(...)) with new Props" taggedAs PerformanceTest in {
+      testActorCreation("Props(new EmptyArgsActor(...)) new", () ⇒ { Props(new EmptyArgsActor(4711, 1729)) })
+    }
+
+    "measure time for Props(new EmptyArgsActor(...)) with same Props" taggedAs PerformanceTest in {
+      val props = Props(new EmptyArgsActor(4711, 1729))
+      testActorCreation("Props(new EmptyArgsActor(...)) same", () ⇒ { props })
+    }
+  }
+  override def expectedTestDuration = 2 minutes
+}

akka-actor/src/main/scala/akka/actor/Props.scala

@@ -66,7 +66,7 @@ object Props {
    * Scala API: Returns a Props that has default values except for "creator" which will be a function that creates an instance
    * of the supplied type using the default constructor.
    */
-  def apply[T <: Actor: ClassTag](): Props = apply(defaultDeploy, implicitly[ClassTag[T]].runtimeClass, Vector.empty)
+  def apply[T <: Actor: ClassTag](): Props = apply(defaultDeploy, implicitly[ClassTag[T]].runtimeClass, List.empty)
 
   /**
    * Scala API: Returns a Props that has default values except for "creator" which will be a function that creates an instance
@@ -120,13 +120,13 @@ object Props {
   /**
    * Scala API: create a Props given a class and its constructor arguments.
    */
-  def apply(clazz: Class[_], args: Any*): Props = apply(defaultDeploy, clazz, args.toVector)
+  def apply(clazz: Class[_], args: Any*): Props = apply(defaultDeploy, clazz, args.toList)
 
   /**
    * Java API: create a Props given a class and its constructor arguments.
    */
   @varargs
-  def create(clazz: Class[_], args: AnyRef*): Props = apply(defaultDeploy, clazz, args.toVector)
+  def create(clazz: Class[_], args: AnyRef*): Props = apply(defaultDeploy, clazz, args.toList)
 
   /**
    * Create new Props from the given [[akka.japi.Creator]].
@@ -176,34 +176,28 @@ final case class Props(deploy: Deploy, clazz: Class[_], args: immutable.Seq[Any]
 
   // derived property, does not need to be serialized
   @transient
-  private[this] var _constructor: Constructor[_] = _
+  private[this] var _producer: IndirectActorProducer = _
 
   // derived property, does not need to be serialized
   @transient
   private[this] var _cachedActorClass: Class[_ <: Actor] = _
 
-  private[this] def constructor: Constructor[_] = {
-    if (_constructor eq null)
-      _constructor = Reflect.findConstructor(clazz, args)
+  private[this] def producer: IndirectActorProducer = {
+    if (_producer eq null)
+      _producer = IndirectActorProducer(clazz, args)
 
-    _constructor
+    _producer
   }
 
   private[this] def cachedActorClass: Class[_ <: Actor] = {
     if (_cachedActorClass eq null)
-      _cachedActorClass =
-        if (classOf[IndirectActorProducer].isAssignableFrom(clazz))
-          Reflect.instantiate(constructor, args).asInstanceOf[IndirectActorProducer].actorClass
-        else if (classOf[Actor].isAssignableFrom(clazz))
-          clazz.asInstanceOf[Class[_ <: Actor]]
-        else
-          throw new IllegalArgumentException(s"unknown actor creator [$clazz]")
+      _cachedActorClass = producer.actorClass
 
     _cachedActorClass
   }
 
-  // validate constructor signature; throws IllegalArgumentException if invalid
-  constructor
+  // validate producer constructor signature; throws IllegalArgumentException if invalid
+  producer
 
   /**
    * No-args constructor that sets all the default values.
@@ -211,7 +205,7 @@ final case class Props(deploy: Deploy, clazz: Class[_], args: immutable.Seq[Any]
    * @deprecated use `Props.create(clazz, args ...)` instead
    */
   @deprecated("use Props.create()", "2.2")
-  def this() = this(Props.defaultDeploy, classOf[CreatorFunctionConsumer], Vector(Props.defaultCreator))
+  def this() = this(Props.defaultDeploy, classOf[CreatorFunctionConsumer], List(Props.defaultCreator))
 
   /**
    * Java API: create Props from an [[UntypedActorFactory]]
@@ -222,7 +216,7 @@ final case class Props(deploy: Deploy, clazz: Class[_], args: immutable.Seq[Any]
    *             non-serializable
    */
   @deprecated("use Props.create()", "2.2")
-  def this(factory: UntypedActorFactory) = this(Props.defaultDeploy, classOf[UntypedActorFactoryConsumer], Vector(factory))
+  def this(factory: UntypedActorFactory) = this(Props.defaultDeploy, classOf[UntypedActorFactoryConsumer], List(factory))
 
   /**
    * Java API: create Props from a given [[java.lang.Class]]
@@ -231,7 +225,7 @@ final case class Props(deploy: Deploy, clazz: Class[_], args: immutable.Seq[Any]
    *             another API
    */
   @deprecated("use Props.create()", "2.2")
-  def this(actorClass: Class[_ <: Actor]) = this(Props.defaultDeploy, actorClass, Vector.empty)
+  def this(actorClass: Class[_ <: Actor]) = this(Props.defaultDeploy, actorClass, List.empty)
 
   @deprecated("There is no use-case for this method anymore", "2.2")
   def creator: () ⇒ Actor = newActor
@@ -327,11 +321,7 @@ final case class Props(deploy: Deploy, clazz: Class[_], args: immutable.Seq[Any]
    * used within the implementation of [[IndirectActorProducer#produce]].
    */
   private[akka] def newActor(): Actor = {
-    Reflect.instantiate(constructor, args) match {
-      case a: Actor                 ⇒ a
-      case i: IndirectActorProducer ⇒ i.produce()
-      case _                        ⇒ throw new IllegalArgumentException(s"unknown actor creator [$clazz]")
-    }
+    producer.produce()
   }
 }
 
@@ -362,6 +352,37 @@ trait IndirectActorProducer {
   def actorClass: Class[_ <: Actor]
 }
 
+private[akka] object IndirectActorProducer {
+  val UntypedActorFactoryConsumerClass = classOf[UntypedActorFactoryConsumer]
+  val CreatorFunctionConsumerClass = classOf[CreatorFunctionConsumer]
+  val CreatorConsumerClass = classOf[CreatorConsumer]
+  val TypedCreatorFunctionConsumerClass = classOf[TypedCreatorFunctionConsumer]
+
+  def apply(clazz: Class[_], args: immutable.Seq[Any]): IndirectActorProducer = {
+    if (classOf[IndirectActorProducer].isAssignableFrom(clazz)) {
+      def get1stArg[T]: T = args.head.asInstanceOf[T]
+      def get2ndArg[T]: T = args.tail.head.asInstanceOf[T]
+      // The cost of doing reflection to create these for every props
+      // is rather high, so we match on them and do new instead
+      clazz match {
+        case TypedCreatorFunctionConsumerClass ⇒
+          new TypedCreatorFunctionConsumer(get1stArg, get2ndArg)
+        case UntypedActorFactoryConsumerClass ⇒
+          new UntypedActorFactoryConsumer(get1stArg)
+        case CreatorFunctionConsumerClass ⇒
+          new CreatorFunctionConsumer(get1stArg)
+        case CreatorConsumerClass ⇒
+          new CreatorConsumer(get1stArg, get2ndArg)
+        case _ ⇒
+          Reflect.instantiate(clazz, args).asInstanceOf[IndirectActorProducer]
+      }
+    } else if (classOf[Actor].isAssignableFrom(clazz)) {
+      if (args.isEmpty) new NoArgsReflectConstructor(clazz.asInstanceOf[Class[_ <: Actor]])
+      else new ArgsReflectConstructor(clazz.asInstanceOf[Class[_ <: Actor]], args)
+    } else throw new IllegalArgumentException(s"unknown actor creator [$clazz]")
+  }
+}
+
 /**
  * INTERNAL API
  */
@@ -393,3 +414,21 @@ private[akka] class TypedCreatorFunctionConsumer(clz: Class[_ <: Actor], creator
   override def actorClass = clz
   override def produce() = creator()
 }
+
+/**
+ * INTERNAL API
+ */
+private[akka] class ArgsReflectConstructor(clz: Class[_ <: Actor], args: immutable.Seq[Any]) extends IndirectActorProducer {
+  private[this] val constructor: Constructor[_] = Reflect.findConstructor(clz, args)
+  override def actorClass = clz
+  override def produce() = Reflect.instantiate(constructor, args).asInstanceOf[Actor]
+}
+
+/**
+ * INTERNAL API
+ */
+private[akka] class NoArgsReflectConstructor(clz: Class[_ <: Actor]) extends IndirectActorProducer {
+  Reflect.findConstructor(clz, List.empty)
+  override def actorClass = clz
+  override def produce() = Reflect.instantiate(clz)
+}

akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala

@@ -18,9 +18,6 @@ import scala.concurrent.ExecutionContext
 import scala.concurrent.duration.FiniteDuration
 import scala.util.control.NonFatal
 import scala.util.Try
-import scala.util.Failure
-import akka.util.Reflect
-import java.lang.reflect.ParameterizedType
 
 final case class Envelope private (val message: Any, val sender: ActorRef)
 
@@ -308,7 +305,9 @@ abstract class ExecutorServiceConfigurator(config: Config, prerequisites: Dispat
 /**
  * Base class to be used for hooking in new dispatchers into Dispatchers.
  */
-abstract class MessageDispatcherConfigurator(val config: Config, val prerequisites: DispatcherPrerequisites) {
+abstract class MessageDispatcherConfigurator(_config: Config, val prerequisites: DispatcherPrerequisites) {
+
+  val config: Config = new CachingConfig(_config)
 
   /**
    * Returns an instance of MessageDispatcher given the configuration.

akka-actor/src/main/scala/akka/dispatch/CachingConfig.scala

@@ -0,0 +1,171 @@
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.dispatch
+
+import com.typesafe.config._
+import java.util.concurrent.ConcurrentHashMap
+import scala.util.{ Failure, Success, Try }
+
+/**
+ * INTERNAL API
+ */
+private[akka] object CachingConfig {
+  val emptyConfig = ConfigFactory.empty()
+
+  sealed abstract trait PathEntry {
+    val valid: Boolean
+    val exists: Boolean
+    val config: Config
+  }
+  case class ValuePathEntry(valid: Boolean, exists: Boolean, config: Config = emptyConfig) extends PathEntry
+  case class StringPathEntry(valid: Boolean, exists: Boolean, config: Config, value: String) extends PathEntry
+
+  val invalidPathEntry = ValuePathEntry(false, true)
+  val nonExistingPathEntry = ValuePathEntry(true, false)
+  val emptyPathEntry = ValuePathEntry(true, true)
+}
+
+/**
+ * INTERNAL API
+ *
+ * A CachingConfig is a Config that wraps another Config and is used to cache path lookup and string
+ * retrieval, which we happen to do a lot in some critical paths of the actor creation and mailbox
+ * selection code.
+ *
+ * All other Config operations are delegated to the wrapped Config.
+ */
+private[akka] class CachingConfig(_config: Config) extends Config {
+
+  import CachingConfig._
+
+  private val (config: Config, entryMap: ConcurrentHashMap[String, PathEntry]) = _config match {
+    case cc: CachingConfig ⇒ (cc.config, cc.entryMap)
+    case _                 ⇒ (_config, new ConcurrentHashMap[String, PathEntry])
+  }
+
+  private def getPathEntry(path: String): PathEntry = entryMap.get(path) match {
+    case null ⇒
+      val ne = Try { config.hasPath(path) } match {
+        case Failure(e)     ⇒ invalidPathEntry
+        case Success(false) ⇒ nonExistingPathEntry
+        case _ ⇒
+          Try { config.getValue(path) } match {
+            case Failure(e) ⇒
+              emptyPathEntry
+            case Success(v) ⇒
+              if (v.valueType() == ConfigValueType.STRING)
+                StringPathEntry(true, true, v.atKey("cached"), v.unwrapped().asInstanceOf[String])
+              else
+                ValuePathEntry(true, true, v.atKey("cached"))
+          }
+      }
+
+      entryMap.putIfAbsent(path, ne) match {
+        case null ⇒ ne
+        case e    ⇒ e
+      }
+
+    case e ⇒ e
+  }
+
+  def checkValid(reference: Config, restrictToPaths: String*) {
+    config.checkValid(reference, restrictToPaths: _*)
+  }
+
+  def root() = config.root()
+
+  def origin() = config.origin()
+
+  def withFallback(other: ConfigMergeable) = new CachingConfig(config.withFallback(other))
+
+  def resolve() = resolve(ConfigResolveOptions.defaults())
+
+  def resolve(options: ConfigResolveOptions) = {
+    val resolved = config.resolve(options)
+    if (resolved eq config) this
+    else new CachingConfig(resolved)
+  }
+
+  def hasPath(path: String) = {
+    val entry = getPathEntry(path)
+    if (entry.valid)
+      entry.exists
+    else // run the real code to get proper exceptions
+      config.hasPath(path)
+  }
+
+  def isEmpty = config.isEmpty
+
+  def entrySet() = config.entrySet()
+
+  def getBoolean(path: String) = config.getBoolean(path)
+
+  def getNumber(path: String) = config.getNumber(path)
+
+  def getInt(path: String) = config.getInt(path)
+
+  def getLong(path: String) = config.getLong(path)
+
+  def getDouble(path: String) = config.getDouble(path)
+
+  def getString(path: String) = {
+    getPathEntry(path) match {
+      case StringPathEntry(_, _, _, string) ⇒
+        string
+      case e ⇒ e.config.getString("cached")
+    }
+  }
+
+  def getObject(path: String) = config.getObject(path)
+
+  def getConfig(path: String) = config.getConfig(path)
+
+  def getAnyRef(path: String) = config.getAnyRef(path)
+
+  def getValue(path: String) = config.getValue(path)
+
+  def getBytes(path: String) = config.getBytes(path)
+
+  def getMilliseconds(path: String) = config.getMilliseconds(path)
+
+  def getNanoseconds(path: String) = config.getNanoseconds(path)
+
+  def getList(path: String) = config.getList(path)
+
+  def getBooleanList(path: String) = config.getBooleanList(path)
+
+  def getNumberList(path: String) = config.getNumberList(path)
+
+  def getIntList(path: String) = config.getIntList(path)
+
+  def getLongList(path: String) = config.getLongList(path)
+
+  def getDoubleList(path: String) = config.getDoubleList(path)
+
+  def getStringList(path: String) = config.getStringList(path)
+
+  def getObjectList(path: String) = config.getObjectList(path)
+
+  def getConfigList(path: String) = config.getConfigList(path)
+
+  def getAnyRefList(path: String) = config.getAnyRefList(path)
+
+  def getBytesList(path: String) = config.getBytesList(path)
+
+  def getMillisecondsList(path: String) = config.getMillisecondsList(path)
+
+  def getNanosecondsList(path: String) = config.getNanosecondsList(path)
+
+  def withOnlyPath(path: String) = new CachingConfig(config.withOnlyPath(path))
+
+  def withoutPath(path: String) = new CachingConfig(config.withoutPath(path))
+
+  def atPath(path: String) = new CachingConfig(config.atPath(path))
+
+  def atKey(key: String) = new CachingConfig(config.atKey(key))
+
+  def withValue(path: String, value: ConfigValue) = new CachingConfig(config.withValue(path, value))
+}
+

akka-actor/src/main/scala/akka/dispatch/Dispatchers.scala

@@ -56,6 +56,8 @@ class Dispatchers(val settings: ActorSystem.Settings, val prerequisites: Dispatc
 
   import Dispatchers._
 
+  val cachingConfig = new CachingConfig(settings.config)
+
   val defaultDispatcherConfig: Config =
     idConfig(DefaultDispatcherId).withFallback(settings.config.getConfig(DefaultDispatcherId))
 
@@ -80,7 +82,7 @@ class Dispatchers(val settings: ActorSystem.Settings, val prerequisites: Dispatc
    * using this dispatcher, because the details can only be checked by trying
    * to instantiate it, which might be undesirable when just checking.
    */
-  def hasDispatcher(id: String): Boolean = settings.config.hasPath(id)
+  def hasDispatcher(id: String): Boolean = cachingConfig.hasPath(id)
 
   private def lookupConfigurator(id: String): MessageDispatcherConfigurator = {
     dispatcherConfigurators.get(id) match {
@@ -89,7 +91,7 @@ class Dispatchers(val settings: ActorSystem.Settings, val prerequisites: Dispatc
         // That shouldn't happen often and in case it does the actual ExecutorService isn't
         // created until used, i.e. cheap.
         val newConfigurator =
-          if (settings.config.hasPath(id)) configuratorFrom(config(id))
+          if (cachingConfig.hasPath(id)) configuratorFrom(config(id))
           else throw new ConfigurationException(s"Dispatcher [$id] not configured")
 
         dispatcherConfigurators.putIfAbsent(id, newConfigurator) match {

akka-actor/src/main/scala/akka/util/Reflect.scala

@@ -8,6 +8,7 @@ import scala.collection.immutable
 import java.lang.reflect.Type
 import scala.annotation.tailrec
 import java.lang.reflect.ParameterizedType
+import scala.util.Try
 
 /**
  * Collection of internal reflection utilities which may or may not be
@@ -80,17 +81,30 @@ private[akka] object Reflect {
       val argClasses = args map safeGetClass mkString ", "
       throw new IllegalArgumentException(s"$msg found on $clazz for arguments [$argClasses]")
     }
+
+    val constructor: Constructor[T] =
+      if (args.isEmpty) Try { clazz.getDeclaredConstructor() } getOrElse (null)
+      else {
+        val length = args.length
         val candidates =
-      clazz.getDeclaredConstructors filter (c ⇒
-        c.getParameterTypes.length == args.length &&
-          (c.getParameterTypes zip args forall {
+          clazz.getDeclaredConstructors.asInstanceOf[Array[Constructor[T]]].iterator filter { c ⇒
+            val parameterTypes = c.getParameterTypes
+            parameterTypes.length == length &&
+              (parameterTypes.iterator zip args.iterator forall {
                 case (found, required) ⇒
                   found.isInstance(required) || BoxedType(found).isInstance(required) ||
                     (required == null && !found.isPrimitive)
-          }))
-    if (candidates.size == 1) candidates.head.asInstanceOf[Constructor[T]]
-    else if (candidates.size > 1) error("multiple matching constructors")
-    else error("no matching constructor")
+              })
+          }
+        if (candidates.hasNext) {
+          val cstrtr = candidates.next()
+          if (candidates.hasNext) error("multiple matching constructors")
+          else cstrtr
+        } else null
+      }
+
+    if (constructor == null) error("no matching constructor")
+    else constructor
   }
 
   private def safeGetClass(a: Any): Class[_] =

akka-testkit/src/test/scala/akka/testkit/TestTags.scala

@@ -7,3 +7,4 @@ import org.scalatest.Tag
 
 object TimingTest extends Tag("timing")
 object LongRunningTest extends Tag("long-running")
+object PerformanceTest extends Tag("performance")