--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	Wed May 15 22:35:36 2013 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegionRemSet.cpp	Thu May 16 13:02:33 2013 +0200
@@ -706,10 +706,11 @@
   // Cast away const in this case.
   MutexLockerEx x((Mutex*)&_m, Mutex::_no_safepoint_check_flag);
   size_t sum = 0;
-  PerRegionTable * cur = _first_all_fine_prts;
-  while (cur != NULL) {
-    sum += cur->mem_size();
-    cur = cur->next();
+  // all PRTs are of the same size so it is sufficient to query only one of them.
+  if (_first_all_fine_prts != NULL) {
+    assert(_last_all_fine_prts != NULL &&
+      _first_all_fine_prts->mem_size() == _last_all_fine_prts->mem_size(), "check that mem_size() is constant");
+    sum += _first_all_fine_prts->mem_size() * _n_fine_entries;
   }
   sum += (sizeof(PerRegionTable*) * _max_fine_entries);
   sum += (_coarse_map.size_in_words() * HeapWordSize);