--- old/src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.cpp	2015-02-03 11:17:52.043666200 +0100
+++ new/src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.cpp	2015-02-03 11:17:51.973664179 +0100
@@ -72,10 +72,10 @@
   _commit_size = commit_size;
 
   assert(_committed.size() == 0, "virtual space initialized more than once");
-  BitMap::idx_t size_in_pages = align_size_up(rs.size(), commit_size) / commit_size;
-  _committed.resize(size_in_pages, /* in_resource_area */ false);
+  BitMap::idx_t size_in_commit_pages = round_to(rs.size(), commit_size);
+  _committed.resize(size_in_commit_pages, /* in_resource_area */ false);
   if (_special) {
-    _dirty.resize(size_in_pages, /* in_resource_area */ false);
+    _dirty.resize(size_in_commit_pages, /* in_resource_area */ false);
   }
 
   return true;
@@ -140,7 +140,7 @@
   return _high_boundary;
 }
 
-void G1PageBasedVirtualSpace::commit_int(char* start, char* end) {
+void G1PageBasedVirtualSpace::commit_internal(char* start, char* end) {
   guarantee(start >= _low_boundary && start < _high_boundary,
             err_msg("Start address " PTR_FORMAT" is outside of reserved space.", p2i(start)));
   guarantee(is_ptr_aligned(start, _commit_size),
@@ -187,7 +187,7 @@
       _dirty.clear_range(start, end);
     }
   } else {
-    commit_int(page_start(start), page_end(end - 1));
+    commit_internal(page_start(start), page_end(end - 1));
   }
   _committed.set_range(start, end);
 
@@ -197,7 +197,7 @@
   return zero_filled;
 }
 
-void G1PageBasedVirtualSpace::uncommit_int(char* start, char* end) {
+void G1PageBasedVirtualSpace::uncommit_internal(char* start, char* end) {
   os::uncommit_memory(start, pointer_delta(end, start, sizeof(char)));
 }
 
@@ -210,7 +210,7 @@
     // need to be cleared explicitly.
     _dirty.set_range(start, end);
   } else {
-    uncommit_int(page_start(start), page_end(end - 1));
+    uncommit_internal(page_start(start), page_end(end - 1));
   }
 
   _committed.clear_range(start, end);
--- old/src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.hpp	2015-02-03 11:17:52.425677231 +0100
+++ new/src/share/vm/gc_implementation/g1/g1PageBasedVirtualSpace.hpp	2015-02-03 11:17:52.355675209 +0100
@@ -34,11 +34,12 @@
 // granularity.
 // (De-)Allocation requests are always OS page aligned by passing a page index
 // and multiples of pages.
-// We only support reservations which base address is aligned to a given commit
-// size. The length of the area managed need not commit size aligned (but OS default
-// page size aligned) because some OSes cannot provide a an os_commit_size aligned
-// reservation without also being size-aligned. Any tail area is committed using OS
-// small pages.
+// For systems that only commits of memory in a given size (always greater than
+// page size) the base address is required to be aligned to that commit size.
+// The actual size requested need not be aligned to the commit size, but the size
+// of the reservation passed may be rounded up to the commit size. Any fragment
+// (less than the commit size) of the actual size at the tail of the request will
+// be committed using OS small pages.
 // The implementation gives an error when trying to commit or uncommit pages that
 // have already been committed or uncommitted.
 class G1PageBasedVirtualSpace VALUE_OBJ_CLASS_SPEC {
@@ -70,15 +71,16 @@
   // Commit the given memory range by using _commit_size pages as much as possible
   // and the remainder with small sized pages. The start address must be _commit_size
   // aligned.
-  void commit_int(char* start, char* end);
+  void commit_internal(char* start, char* end);
   // Uncommit the given memory range.
-  void uncommit_int(char* start, char* end);
+  void uncommit_internal(char* start, char* end);
 
   // Returns the index of the page which contains the given address.
   uintptr_t  addr_to_page_index(char* addr) const;
   // Returns the address of the given page index.
   char*  page_start(uintptr_t index);
-  // Returns the address of the given page index ranging from 0..size_in_pages-1.
+  // Returns the address of the end of the page given the page index ranging
+  // from 0..size_in_pages-2. For the last page, return _high_boundary.
   char*  page_end(uintptr_t index);
 
   // Returns true if the entire area is backed by committed memory.