Reland https://code.google.com/p/dart/source/detail?r=29315:

runtime/vm/port.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/port.h"
 
 #include "platform/utils.h"
 #include "vm/dart_api_impl.h"
 #include "vm/isolate.h"
 #include "vm/message_handler.h"
@@ skipping 64 matching lines @@
   return result;
 }
 
 
 void PortMap::SetLive(Dart_Port port) {
   MutexLocker ml(mutex_);
   intptr_t index = FindPort(port);
   ASSERT(index >= 0);
   map_[index].live = true;
   map_[index].handler->increment_live_ports();
+  if (FLAG_trace_isolates) {

[Ivan Posva, 2013/10/27 14:33:17]

Added tracing support.

+    OS::Print("[^] Live port: \n"
+              "\thandler:    %s\n"
+              "\tport:       %" Pd64 "\n",
+              map_[index].handler->name(), port);
+  }
 }
 
 
 void PortMap::MaintainInvariants() {
   intptr_t empty = capacity_ - used_ - deleted_;
   if (used_ > ((capacity_ / 4) * 3)) {
     // Grow the port map.
     Rehash(capacity_ * 2);
   } else if (empty < deleted_) {
     // Rehash without growing the table to flush the deleted slots out of the
@@ skipping 35 matching lines @@
   if (map_[index].handler == deleted_entry_) {
     // Consuming a deleted entry.
     deleted_--;
   }
   map_[index] = entry;
 
   // Increment number of used slots and grow if necessary.
   used_++;
   MaintainInvariants();
 
+  if (FLAG_trace_isolates) {

[Ivan Posva, 2013/10/27 14:33:17]

ditto

+    OS::Print("[+] Opening port: \n"
+              "\thandler:    %s\n"
+              "\tport:       %" Pd64 "\n",
+              handler->name(), entry.port);
+  }
+
   return entry.port;
 }
 
 
 bool PortMap::ClosePort(Dart_Port port) {
   MessageHandler* handler = NULL;
   {
     MutexLocker ml(mutex_);
     intptr_t index = FindPort(port);
     if (index < 0) {
@@ skipping 100 matching lines @@
   // TODO(iposva): Verify whether we want to keep exponentially growing.
   ASSERT(Utils::IsPowerOfTwo(kInitialCapacity));
   map_ = new Entry[kInitialCapacity];
   memset(map_, 0, kInitialCapacity * sizeof(Entry));
   capacity_ = kInitialCapacity;
   used_ = 0;
   deleted_ = 0;
 }
 
 }  // namespace dart