--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Thu Apr 02 16:42:24 2015 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp	Tue Apr 07 10:53:51 2015 +0200
@@ -116,7 +116,7 @@
 }
 
 size_t CMBitMap::compute_size(size_t heap_size) {
-  return heap_size / mark_distance();
+  return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
 }
 
 size_t CMBitMap::mark_distance() {