--- old/src/share/vm/gc/shenandoah/shenandoahHeap.hpp	2017-10-05 21:08:02.206145753 +0200
+++ new/src/share/vm/gc/shenandoah/shenandoahHeap.hpp	2017-10-05 21:08:02.093145478 +0200
@@ -135,8 +135,7 @@
   size_t _bitmap_size;
   size_t _bitmap_words_per_region;
   MemRegion _heap_region;
-  MemRegion _bitmap0_region;
-  MemRegion _bitmap1_region;
+  MemRegion _bitmap_region;
 
   // Sortable array of regions
   ShenandoahHeapRegionSet* _ordered_regions;
@@ -165,16 +164,12 @@
   volatile size_t _committed;
 
   MarkBitMap _verification_bit_map;
-  MarkBitMap _mark_bit_map0;
-  MarkBitMap _mark_bit_map1;
-  MarkBitMap* _complete_mark_bit_map;
-  MarkBitMap* _next_mark_bit_map;
+  MarkBitMap __mark_bit_map;
+  MarkBitMap* _mark_bit_map;
+  bool _bitmap_valid;
 
-  HeapWord** _complete_top_at_mark_starts;
-  HeapWord** _complete_top_at_mark_starts_base;
-
-  HeapWord** _next_top_at_mark_starts;
-  HeapWord** _next_top_at_mark_starts_base;
+  HeapWord** _top_at_mark_starts;
+  HeapWord** _top_at_mark_starts_base;
 
   volatile jbyte _cancelled_concgc;
 
@@ -190,7 +185,7 @@
 
   unsigned int _evacuation_in_progress;
   bool _need_update_refs;
-  bool _need_reset_bitmaps;
+  bool _need_reset_bitmap;
 
   ReferenceProcessor* _ref_processor;
 
@@ -340,13 +335,9 @@
   template <class T>
   inline bool in_collection_set(T obj) const;
 
-  inline bool allocated_after_next_mark_start(HeapWord* addr) const;
-  void set_next_top_at_mark_start(HeapWord* region_base, HeapWord* addr);
-  HeapWord* next_top_at_mark_start(HeapWord* region_base);
-
-  inline bool allocated_after_complete_mark_start(HeapWord* addr) const;
-  void set_complete_top_at_mark_start(HeapWord* region_base, HeapWord* addr);
-  HeapWord* complete_top_at_mark_start(HeapWord* region_base);
+  inline bool allocated_after_mark_start(HeapWord* addr) const;
+  void set_top_at_mark_start(HeapWord* region_base, HeapWord* addr);
+  HeapWord* top_at_mark_start(HeapWord* region_base);
 
   // Evacuates object src. Returns the evacuated object if this thread
   // succeeded, otherwise rolls back the evacuation and returns the
@@ -378,17 +369,16 @@
 
   size_t garbage();
 
-  void reset_next_mark_bitmap(WorkGang* gang);
-  void reset_complete_mark_bitmap(WorkGang* gang);
+  void reset_mark_bitmap(WorkGang* gang);
+
+  MarkBitMap* mark_bit_map();
+  inline bool is_marked(oop obj) const;
+  inline bool mark(oop obj) const;
+  bool is_bitmap_clear();
+  bool is_bitmap_clear_range(HeapWord* start, HeapWord* end);
 
-  MarkBitMap* complete_mark_bit_map();
-  MarkBitMap* next_mark_bit_map();
-  inline bool is_marked_complete(oop obj) const;
-  inline bool mark_next(oop obj) const;
-  inline bool is_marked_next(oop obj) const;
-  bool is_next_bitmap_clear();
-  bool is_next_bitmap_clear_range(HeapWord* start, HeapWord* end);
-  bool is_complete_bitmap_clear_range(HeapWord* start, HeapWord* end);
+  bool is_bitmap_valid() const { return _bitmap_valid; }
+  void set_bitmap_valid(bool valid) { _bitmap_valid = valid; }
 
   bool commit_bitmaps(ShenandoahHeapRegion* r);
   bool uncommit_bitmaps(ShenandoahHeapRegion* r);
@@ -454,8 +444,6 @@
 
   GCTimer* gc_timer() const;
 
-  void swap_mark_bitmaps();
-
   void cancel_concgc(GCCause::Cause cause);
   void cancel_concgc(ShenandoahCancelCause cause);
 
@@ -502,7 +490,7 @@
 
   ShenandoahConcurrentThread* concurrent_thread() { return _concurrent_gc_thread; }
 
-  inline bool mark_next_no_checks(oop obj) const;
+  inline bool mark_no_checks(oop obj) const;
 
 public:
   inline oop atomic_compare_exchange_oop(oop n, narrowOop* addr, oop c);