--- a/src/share/vm/prims/jvmtiTagMap.cpp	Thu Sep 04 18:40:43 2008 -0700
+++ b/src/share/vm/prims/jvmtiTagMap.cpp	Wed Sep 17 16:49:18 2008 +0400
@@ -400,16 +400,28 @@
 
 // get the memory region used for the young generation
 void JvmtiTagMap::get_young_generation() {
-  if (Universe::heap()->kind() == CollectedHeap::GenCollectedHeap) {
-    GenCollectedHeap* gch = GenCollectedHeap::heap();
-    _young_gen = gch->get_gen(0)->reserved();
-  } else {
+  CollectedHeap* ch = Universe::heap();
+  switch (ch->kind()) {
+    case (CollectedHeap::GenCollectedHeap): {
+      _young_gen = ((GenCollectedHeap*)ch)->get_gen(0)->reserved();
+      break;
+    }
 #ifndef SERIALGC
-    ParallelScavengeHeap* psh = ParallelScavengeHeap::heap();
-    _young_gen= psh->young_gen()->reserved();
-#else  // SERIALGC
-    fatal("SerialGC only supported in this configuration.");
-#endif // SERIALGC
+    case (CollectedHeap::ParallelScavengeHeap): {
+      _young_gen = ((ParallelScavengeHeap*)ch)->young_gen()->reserved();
+      break;
+    }
+    case (CollectedHeap::G1CollectedHeap): {
+      // Until a more satisfactory solution is implemented, all
+      // oops in the tag map will require rehash at each gc.
+      // This is a correct, if extremely inefficient solution.
+      // See RFE 6621729 for related commentary.
+      _young_gen = ch->reserved_region();
+      break;
+    }
+#endif  // !SERIALGC
+    default:
+      ShouldNotReachHere();
   }
 }