Optimize the message queue for many active ports with few messages.

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 5ac23bc98348d1bd1939cea33fdf4a573deeda3f..620b47ee29b3297a8eee4f57a05f58dca7238aac 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -87,6 +87,20 @@ bool IsolateMessageHandler::HandleMessage(Message* message) {
   StackZone zone(isolate_);
   HandleScope handle_scope(isolate_);
 
+  // If the message is in band we lookup the receive port to dispatch to.  If
+  // the receive port is closed, we drop the message without deserializing it.
+  Object& receiver = Object::Handle();

[Ivan Posva, 2012/12/19 07:09:44]

I find the name choice of receiver a bit confusing. How about receive_port?

[Mads Ager (google), 2012/12/19 15:47:57]

Done.

+  if (!message->IsOOB()) {
+    receiver = DartLibraryCalls::LookupReceivePort(message->dest_port());
+    if (receiver.IsError()) {
+      return ProcessUnhandledException(receiver);
+    }
+    if (receiver.IsNull()) {
+      delete message;
+      return true;
+    }
+  }
+
   // Parse the message.
   SnapshotReader reader(message->data(), message->len(),
                         Snapshot::kMessage, Isolate::Current());
@@ -113,8 +127,7 @@ bool IsolateMessageHandler::HandleMessage(Message* message) {
     delete message;
   } else {
     const Object& result = Object::Handle(
-        DartLibraryCalls::HandleMessage(
-            message->dest_port(), message->reply_port(), msg));
+        DartLibraryCalls::HandleMessage(receiver, message->reply_port(), msg));
     delete message;
     if (result.IsError()) {
       return ProcessUnhandledException(result);