--- old/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.cpp	2015-02-17 09:29:58.042898596 +0100
+++ new/src/share/vm/gc_implementation/g1/g1RegionToSpaceMapper.cpp	2015-02-17 09:29:57.978896738 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,6 +31,7 @@
 #include "utilities/bitMap.inline.hpp"
 
 G1RegionToSpaceMapper::G1RegionToSpaceMapper(ReservedSpace rs,
+                                             size_t actual_size,
                                              size_t commit_granularity,
                                              size_t region_granularity,
                                              MemoryType type) :
@@ -41,7 +42,7 @@
   _commit_map() {
   guarantee(is_power_of_2(commit_granularity), "must be");
   guarantee(is_power_of_2(region_granularity), "must be");
-  _storage.initialize_with_granularity(rs, commit_granularity);
+  _storage.initialize_with_granularity(rs, actual_size, commit_granularity);
 
   MemTracker::record_virtual_memory_type((address)rs.base(), type);
 }
@@ -55,11 +56,12 @@
 
  public:
   G1RegionsLargerThanCommitSizeMapper(ReservedSpace rs,
+                                      size_t actual_size,
                                       size_t os_commit_granularity,
                                       size_t alloc_granularity,
                                       size_t commit_factor,
                                       MemoryType type) :
-     G1RegionToSpaceMapper(rs, os_commit_granularity, alloc_granularity, type),
+    G1RegionToSpaceMapper(rs, actual_size, os_commit_granularity, alloc_granularity, type),
     _pages_per_region(alloc_granularity / (os_commit_granularity * commit_factor)) {
 
     guarantee(alloc_granularity >= os_commit_granularity, "allocation granularity smaller than commit granularity");
@@ -98,15 +100,16 @@
 
  public:
   G1RegionsSmallerThanCommitSizeMapper(ReservedSpace rs,
+                                       size_t actual_size,
                                        size_t os_commit_granularity,
                                        size_t alloc_granularity,
                                        size_t commit_factor,
                                        MemoryType type) :
-     G1RegionToSpaceMapper(rs, os_commit_granularity, alloc_granularity, type),
+    G1RegionToSpaceMapper(rs, actual_size, os_commit_granularity, alloc_granularity, type),
     _regions_per_page((os_commit_granularity * commit_factor) / alloc_granularity), _refcounts() {
 
     guarantee((os_commit_granularity * commit_factor) >= alloc_granularity, "allocation granularity smaller than commit granularity");
-    _refcounts.initialize((HeapWord*)rs.base(), (HeapWord*)(rs.base() + rs.size()), os_commit_granularity);
+    _refcounts.initialize((HeapWord*)rs.base(), (HeapWord*)(rs.base() + align_size_up(rs.size(), os_commit_granularity)), os_commit_granularity);
     _commit_map.resize(rs.size() * commit_factor / alloc_granularity, /* in_resource_area */ false);
   }
 
@@ -147,14 +150,15 @@
 }
 
 G1RegionToSpaceMapper* G1RegionToSpaceMapper::create_mapper(ReservedSpace rs,
+                                                            size_t actual_size,
                                                             size_t os_commit_granularity,
                                                             size_t region_granularity,
                                                             size_t commit_factor,
                                                             MemoryType type) {
 
   if (region_granularity >= (os_commit_granularity * commit_factor)) {
-    return new G1RegionsLargerThanCommitSizeMapper(rs, os_commit_granularity, region_granularity, commit_factor, type);
+    return new G1RegionsLargerThanCommitSizeMapper(rs, actual_size, os_commit_granularity, region_granularity, commit_factor, type);
   } else {
-    return new G1RegionsSmallerThanCommitSizeMapper(rs, os_commit_granularity, region_granularity, commit_factor, type);
+    return new G1RegionsSmallerThanCommitSizeMapper(rs, actual_size, os_commit_granularity, region_granularity, commit_factor, type);
   }
 }