Use just one marking deque.

src/heap/mark-compact.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
@@ skipping 637 matching lines @@
   bool evacuation() const { return evacuation_; }
 
   // Mark the global table which maps weak objects to dependent code without
   // marking its contents.
   void MarkWeakObjectToCodeTable();
 
   // Special case for processing weak references in a full collection. We need
   // to artificially keep AllocationSites alive for a time.
   void MarkAllocationSite(AllocationSite* site);
 
+  MarkingDeque* marking_deque() { return &marking_deque_; }
+
+  void EnsureMarkingDequeIsCommittedAndInitialize();
+
+  void InitializeMarkingDeque();
+
+  void UncommitMarkingDeque();
+
  private:
   class SweeperTask;
 
   explicit MarkCompactCollector(Heap* heap);
   ~MarkCompactCollector();
 
   bool MarkInvalidatedCode();
   bool WillBeDeoptimized(Code* code);
   void RemoveDeadInvalidatedCode();
   void ProcessInvalidatedCode(ObjectVisitor* visitor);
@@ skipping 200 matching lines @@
 
 #ifdef DEBUG
   friend class MarkObjectVisitor;
   static void VisitObject(HeapObject* obj);
 
   friend class UnmarkObjectVisitor;
   static void UnmarkObject(HeapObject* obj);
 #endif
 
   Heap* heap_;
+  base::VirtualMemory* marking_deque_memory_;
+  bool marking_deque_memory_committed_;
   MarkingDeque marking_deque_;
   CodeFlusher* code_flusher_;
   bool have_code_to_deoptimize_;
 
   List<Page*> evacuation_candidates_;
   List<Code*> invalidated_code_;
 
   SmartPointer<FreeList> free_list_old_data_space_;
   SmartPointer<FreeList> free_list_old_pointer_space_;
 
@@ skipping 54 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_H_