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replace ConcurrentLinkedQueue with single-linked list for Mailbox.systemQueue

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cost zero when empty, non-blocking, shave off 84 bytes per actor
This commit is contained in:
Roland 2011-10-18 18:06:17 +02:00
parent 01efcd7b50
commit 5c823ad50d
5 changed files with 116 additions and 41 deletions
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60
akka-actor/src/main/scala/akka/dispatch/AbstractDispatcher.scala
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@ -12,6 +12,7 @@ import akka.util.{ Duration, Switch, ReentrantGuard }
import java.util.concurrent.ThreadPoolExecutor.{ AbortPolicy, CallerRunsPolicy, DiscardOldestPolicy, DiscardPolicy }
import akka.actor._
import akka.AkkaApplication
import scala.annotation.tailrec
/**
* @author <a href="http://jonasboner.com">Jonas Bon&#233;r</a>
@ -24,17 +25,45 @@ final case class Envelope(val receiver: ActorCell, val message: Any, val channel
}
}
sealed trait SystemMessage extends PossiblyHarmful {
def next: SystemMessage
object SystemMessage {
@tailrec
final def size(list: SystemMessage, acc: Int = 0): Int = {
if (list eq null) acc else size(list.next, acc + 1)
}
@tailrec
final def reverse(list: SystemMessage, acc: SystemMessage = null): SystemMessage = {
if (list eq null) acc else {
val next = list.next
list.next = acc
reverse(next, list)
}
}
}
case class Create(next: SystemMessage = null) extends SystemMessage
case class Recreate(cause: Throwable, next: SystemMessage = null) extends SystemMessage
case class Suspend(next: SystemMessage = null) extends SystemMessage
case class Resume(next: SystemMessage = null) extends SystemMessage
case class Terminate(next: SystemMessage = null) extends SystemMessage
case class Supervise(child: ActorRef, next: SystemMessage = null) extends SystemMessage
case class Link(subject: ActorRef, next: SystemMessage = null) extends SystemMessage
case class Unlink(subject: ActorRef, next: SystemMessage = null) extends SystemMessage
/**
* System messages are handled specially: they form their own queue within
* each actor’s mailbox. This queue is encoded in the messages themselves to
* avoid extra allocations and overhead. The next pointer is a normal var, and
* it does not need to be volatile because in the enqueuing method its update
* is immediately succeeded by a volatile write and all reads happen after the
* volatile read in the dequeuing thread. Afterwards, the obtained list of
* system messages is handled in a single thread only and not ever passed around,
* hence no further synchronization is needed.
*
* ➡➡➡ NEVER SEND THE SAME SYSTEM MESSAGE OBJECT TO TWO ACTORS ⬅⬅⬅
*/
sealed trait SystemMessage extends PossiblyHarmful {
var next: SystemMessage = _
}
case class Create() extends SystemMessage
case class Recreate(cause: Throwable) extends SystemMessage
case class Suspend() extends SystemMessage
case class Resume() extends SystemMessage
case class Terminate() extends SystemMessage
case class Supervise(child: ActorRef) extends SystemMessage
case class Link(subject: ActorRef) extends SystemMessage
case class Unlink(subject: ActorRef) extends SystemMessage
final case class TaskInvocation(app: AkkaApplication, function: () ⇒ Unit, cleanup: () ⇒ Unit) extends Runnable {
def run() {
@ -85,7 +114,7 @@ abstract class MessageDispatcher(val app: AkkaApplication) extends Serializable
override def enqueue(envelope: Envelope) { envelope.channel sendException new ActorKilledException("Actor has been stopped") }
override def dequeue() = null
override def systemEnqueue(handle: SystemMessage): Unit = ()
override def systemDequeue(): SystemMessage = null
override def systemDrain(): SystemMessage = null
override def hasMessages = false
override def hasSystemMessages = false
override def numberOfMessages = 0
@ -172,6 +201,7 @@ abstract class MessageDispatcher(val app: AkkaApplication) extends Serializable
*/
protected[akka] def register(actor: ActorCell) {
_actors.incrementAndGet()
// ➡➡➡ NEVER SEND THE SAME SYSTEM MESSAGE OBJECT TO TWO ACTORS ⬅⬅⬅
systemDispatch(actor, Create()) //FIXME should this be here or moved into ActorCell.start perhaps?
}
@ -194,10 +224,10 @@ abstract class MessageDispatcher(val app: AkkaApplication) extends Serializable
protected def cleanUpMailboxFor(actor: ActorCell, mailBox: Mailbox) {
if (mailBox.hasSystemMessages) {
var envelope = mailBox.systemDequeue()
while (envelope ne null) {
deadLetterMailbox.systemEnqueue(envelope)
envelope = mailBox.systemDequeue()
var message = mailBox.systemDrain()
while (message ne null) {
deadLetterMailbox.systemEnqueue(message)
message = message.next
}
}