--- old/src/share/vm/gc/shared/threadLocalAllocBuffer.hpp	2017-06-12 10:25:12.666255648 -0700
+++ new/src/share/vm/gc/shared/threadLocalAllocBuffer.hpp	2017-06-12 10:25:12.590255944 -0700
@@ -45,6 +45,7 @@
   HeapWord* _top;                                // address after last allocation
   HeapWord* _pf_top;                             // allocation prefetch watermark
   HeapWord* _end;                                // allocation end (excluding alignment_reserve)
+  HeapWord* _actual_end;                         // allocation actual_end (excluding alignment_reserve)
   size_t    _desired_size;                       // desired size   (including alignment_reserve)
   size_t    _refill_waste_limit;                 // hold onto tlab if free() is larger than this
   size_t    _allocated_before_last_gc;           // total bytes allocated up until the last gc
@@ -52,6 +53,8 @@
   static size_t   _max_size;                          // maximum size of any TLAB
   static int      _reserve_for_allocation_prefetch;   // Reserve at the end of the TLAB
   static unsigned _target_refills;                    // expected number of refills between GCs
+  size_t _bytes_until_sample;                         // bytes until sample.
+  size_t _extra_space;                                // extra space due to sampling logic.
 
   unsigned  _number_of_refills;
   unsigned  _fast_refill_waste;
@@ -66,10 +69,12 @@
 
   void set_start(HeapWord* start)                { _start = start; }
   void set_end(HeapWord* end)                    { _end = end; }
+  void set_actual_end(HeapWord* actual_end)      { _actual_end = actual_end; }
   void set_top(HeapWord* top)                    { _top = top; }
   void set_pf_top(HeapWord* pf_top)              { _pf_top = pf_top; }
   void set_desired_size(size_t desired_size)     { _desired_size = desired_size; }
   void set_refill_waste_limit(size_t waste)      { _refill_waste_limit = waste;  }
+  void set_bytes_until_sample(size_t bytes)      { _bytes_until_sample = bytes;  }
 
   size_t initial_refill_waste_limit()            { return desired_size() / TLABRefillWasteFraction; }
 
@@ -115,13 +120,14 @@
 
   HeapWord* start() const                        { return _start; }
   HeapWord* end() const                          { return _end; }
-  HeapWord* hard_end() const                     { return _end + alignment_reserve(); }
+  HeapWord* hard_end() const                     { return _actual_end + alignment_reserve(); }
   HeapWord* top() const                          { return _top; }
   HeapWord* pf_top() const                       { return _pf_top; }
   size_t desired_size() const                    { return _desired_size; }
   size_t used() const                            { return pointer_delta(top(), start()); }
   size_t used_bytes() const                      { return pointer_delta(top(), start(), 1); }
   size_t free() const                            { return pointer_delta(end(), top()); }
+
   // Don't discard tlab if remaining space is larger than this.
   size_t refill_waste_limit() const              { return _refill_waste_limit; }
 
@@ -159,14 +165,22 @@
   // Resize tlabs for all threads
   static void resize_all_tlabs();
 
+  void set_back_actual_end() { _end = _actual_end; }
   void fill(HeapWord* start, HeapWord* top, size_t new_size);
   void initialize();
 
+  void pick_next_sample();
+  void handle_sample(Thread* thread, HeapWord* result, size_t size);
+  size_t bytes_until_sample() { return _bytes_until_sample; }
+  size_t *bytes_until_sample_addr() { return &_bytes_until_sample; }
+  bool should_sample() { return bytes_until_sample() == 0; }
+
   static size_t refill_waste_limit_increment()   { return TLABWasteIncrement; }
 
   // Code generation support
   static ByteSize start_offset()                 { return byte_offset_of(ThreadLocalAllocBuffer, _start); }
   static ByteSize end_offset()                   { return byte_offset_of(ThreadLocalAllocBuffer, _end  ); }
+  static ByteSize actual_end_offset()            { return byte_offset_of(ThreadLocalAllocBuffer, _actual_end  ); }
   static ByteSize top_offset()                   { return byte_offset_of(ThreadLocalAllocBuffer, _top  ); }
   static ByteSize pf_top_offset()                { return byte_offset_of(ThreadLocalAllocBuffer, _pf_top  ); }
   static ByteSize size_offset()                  { return byte_offset_of(ThreadLocalAllocBuffer, _desired_size ); }