- Do not repeatedly allocate and release Monitor objects.

runtime/vm/heap.h

 // 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.
 
 #ifndef VM_HEAP_H_
 #define VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 226 matching lines @@
 
   void PrintToJSONObject(Space space, JSONObject* object) const;
 
   // The heap map contains the sizes and class ids for the objects in each page.
   void PrintHeapMapToJSONStream(Isolate* isolate, JSONStream* stream) {
     return old_space_.PrintHeapMapToJSONStream(isolate, stream);
   }
 
   Isolate* isolate() const { return isolate_; }
 
+  Monitor* barrier() const { return barrier_; }
+  Monitor* barrier_done() const { return barrier_done_; }
+
   bool ShouldPretenure(intptr_t class_id) const;
 
   void SetupExternalPage(void* pointer, uword size, bool is_executable) {
     old_space_.SetupExternalPage(pointer, size, is_executable);
   }
 
  private:
   class GCStats : public ValueObject {
    public:
     GCStats() {}
@@ skipping 65 matching lines @@
   void EndNewSpaceGC();
   bool BeginOldSpaceGC(Thread* thread);
   void EndOldSpaceGC();
 
   // If this heap is non-empty, updates start and end to the smallest range that
   // contains both the original [start, end) and the [lowest, highest) addresses
   // of this heap.
   void GetMergedAddressRange(uword* start, uword* end) const;
 
   Isolate* isolate_;
+  Monitor* barrier_;
+  Monitor* barrier_done_;
 
   // The different spaces used for allocation.
   Scavenger new_space_;
   PageSpace old_space_;
 
   WeakTable* new_weak_tables_[kNumWeakSelectors];
   WeakTable* old_weak_tables_[kNumWeakSelectors];
 
   // GC stats collection.
   GCStats stats_;
@@ skipping 42 matching lines @@
   explicit WritableVMIsolateScope(Thread* thread, bool include_code_pages);
   ~WritableVMIsolateScope();
 
  private:
   bool include_code_pages_;
 };
 
 }  // namespace dart
 
 #endif  // VM_HEAP_H_