--- old/src/share/vm/gc/g1/g1CollectionSet.hpp	2016-06-28 14:13:05.515439009 +0200
+++ new/src/share/vm/gc/g1/g1CollectionSet.hpp	2016-06-28 14:13:05.426436328 +0200
@@ -26,7 +26,6 @@
 #define SHARE_VM_GC_G1_G1COLLECTIONSET_HPP
 
 #include "gc/g1/collectionSetChooser.hpp"
-#include "gc/g1/g1FixedSizeStack.hpp"
 #include "memory/allocation.hpp"
 #include "utilities/debug.hpp"
 #include "utilities/globalDefinitions.hpp"
@@ -49,7 +48,9 @@
   uint _old_region_length;
 
   // The actual collection set as a set of region indices.
-  G1FixedSizeStack<uint> _collection_set_regions;
+  uint* _collection_set_regions;
+  volatile size_t _collection_set_cur_length;
+  size_t _collection_set_max_length;
 
   // The number of bytes in the collection set before the pause. Set from
   // the incrementally built collection set at the start of an evacuation
@@ -127,7 +128,7 @@
   uint survivor_region_length() const { return _survivor_region_length; }
   uint old_region_length() const      { return _old_region_length;      }
 
-  // Incremental collection set Support
+  // Incremental collection set support
 
   // Initialize incremental collection set info.
   void start_incremental_building();
@@ -137,12 +138,12 @@
   void finalize_incremental_building();
 
   // Reset the contents of the collection set.
-  void clear() {
-    _collection_set_regions.clear();
-  }
+  void clear();
 
   // Iterate over the collection set, applying the given HeapRegionClosure on all of them.
-  void iterate(HeapRegionClosure* cl);
+  // If may_be_aborted is true, iteration may be aborted using the return value of the
+  // called closure method.
+  void iterate(HeapRegionClosure* cl, bool may_be_aborted = false);
 
   // Iterate over the collection set, applying the given HeapRegionClosure on all of them,
   // trying to optimally spread out starting position of total_workers workers given the