--- a/hotspot/src/share/vm/gc_implementation/parallelScavenge/psCompactionManager.hpp	Tue Nov 22 04:47:10 2011 -0500
+++ b/hotspot/src/share/vm/gc_implementation/parallelScavenge/psCompactionManager.hpp	Tue Aug 09 10:16:01 2011 -0700
@@ -48,6 +48,7 @@
   friend class StealRegionCompactionTask;
   friend class UpdateAndFillClosure;
   friend class RefProcTaskExecutor;
+  friend class IdleGCTask;
 
  public:
 
@@ -85,7 +86,31 @@
   // Is there a way to reuse the _marking_stack for the
   // saving empty regions?  For now just create a different
   // type of TaskQueue.
-  RegionTaskQueue               _region_stack;
+  RegionTaskQueue*             _region_stack;
+
+  static RegionTaskQueue**     _region_list;
+  // Index in _region_list for current _region_stack.
+  uint _region_stack_index;
+
+  // Indexes of recycled region stacks/overflow stacks
+  // Stacks of regions to be compacted are embedded in the tasks doing
+  // the compaction.  A thread that executes the task extracts the
+  // region stack and drains it.  These threads keep these region
+  // stacks for use during compaction task stealing.  If a thread
+  // gets a second draining task, it pushed its current region stack
+  // index into the array _recycled_stack_index and gets a new
+  // region stack from the task.  A thread that is executing a
+  // compaction stealing task without ever having executing a
+  // draining task, will get a region stack from _recycled_stack_index.
+  //
+  // Array of indexes into the array of region stacks.
+  static uint*                    _recycled_stack_index;
+  // The index into _recycled_stack_index of the last region stack index
+  // pushed.  If -1, there are no entries into _recycled_stack_index.
+  static int                      _recycled_top;
+  // The index into _recycled_stack_index of the last region stack index
+  // popped.  If -1, there has not been any entry popped.
+  static int                      _recycled_bottom;
 
   Stack<Klass*>                 _revisit_klass_stack;
   Stack<DataLayout*>            _revisit_mdo_stack;
@@ -104,7 +129,6 @@
   // Array of tasks.  Needed by the ParallelTaskTerminator.
   static RegionTaskQueueSet* region_array()      { return _region_array; }
   OverflowTaskQueue<oop>*  marking_stack()       { return &_marking_stack; }
-  RegionTaskQueue* region_stack()                { return &_region_stack; }
 
   // Pushes onto the marking stack.  If the marking stack is full,
   // pushes onto the overflow stack.
@@ -116,10 +140,33 @@
   Action action() { return _action; }
   void set_action(Action v) { _action = v; }
 
+  RegionTaskQueue* region_stack()                { return _region_stack; }
+  void set_region_stack(RegionTaskQueue* v)       { _region_stack = v; }
+
   inline static ParCompactionManager* manager_array(int index);
 
+  inline static RegionTaskQueue* region_list(int index) {
+    return _region_list[index];
+  }
+
+  uint region_stack_index() { return _region_stack_index; }
+  void set_region_stack_index(uint v) { _region_stack_index = v; }
+
+  // Pop and push unique reusable stack index
+  static int pop_recycled_stack_index();
+  static void push_recycled_stack_index(uint v);
+  static void reset_recycled_stack_index() {
+    _recycled_bottom = _recycled_top = -1;
+  }
+
   ParCompactionManager();
+  ~ParCompactionManager();
 
+  // Pushes onto the region stack at the given index.  If the
+  // region stack is full,
+  // pushes onto the region overflow stack.
+  static void region_list_push(uint stack_index, size_t region_index);
+  static void verify_region_list_empty(uint stack_index);
   ParMarkBitMap* mark_bitmap() { return _mark_bitmap; }
 
   // Take actions in preparation for a compaction.