--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Wed Jan 18 09:50:16 2012 -0800
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp	Wed Feb 15 13:06:53 2012 -0500
@@ -415,6 +415,16 @@
     return used_at_mark_start_bytes - marked_bytes();
   }
 
+  // Return the amount of bytes we'll reclaim if we collect this
+  // region. This includes not only the known garbage bytes in the
+  // region but also any unallocated space in it, i.e., [top, end),
+  // since it will also be reclaimed if we collect the region.
+  size_t reclaimable_bytes() {
+    size_t known_live_bytes = live_bytes();
+    assert(known_live_bytes <= capacity(), "sanity");
+    return capacity() - known_live_bytes;
+  }
+
   // An upper bound on the number of live bytes in the region.
   size_t max_live_bytes() { return used() - garbage_bytes(); }
 
@@ -648,10 +658,8 @@
     init_top_at_mark_start();
   }
 
-  // <PREDICTION>
   void calc_gc_efficiency(void);
   double gc_efficiency() { return _gc_efficiency;}
-  // </PREDICTION>
 
   bool is_young() const     { return _young_type != NotYoung; }
   bool is_survivor() const  { return _young_type == Survivor; }