--- old/agent/src/share/classes/sun/jvm/hotspot/gc_implementation/g1/G1CollectedHeap.java	2015-03-06 20:51:39.407304979 +0100
+++ new/agent/src/share/classes/sun/jvm/hotspot/gc_implementation/g1/G1CollectedHeap.java	2015-03-06 20:51:39.347303230 +0100
@@ -36,6 +36,7 @@
 import sun.jvm.hotspot.runtime.VM;
 import sun.jvm.hotspot.runtime.VMObjectFactory;
 import sun.jvm.hotspot.types.AddressField;
+import sun.jvm.hotspot.types.CIntegerField;
 import sun.jvm.hotspot.types.Type;
 import sun.jvm.hotspot.types.TypeDataBase;
 
@@ -46,14 +47,14 @@
     static private long hrmFieldOffset;
     // MemRegion _g1_reserved;
     static private long g1ReservedFieldOffset;
-    // G1Allocator* _allocator
-    static private AddressField g1Allocator;
     // G1MonitoringSupport* _g1mm;
     static private AddressField g1mmField;
     // HeapRegionSet _old_set;
     static private long oldSetFieldOffset;
     // HeapRegionSet _humongous_set;
     static private long humongousSetFieldOffset;
+    // size_t _summary_bytes_used;
+    static private CIntegerField summaryBytesUsedField;
 
     static {
         VM.registerVMInitializedObserver(new Observer() {
@@ -67,10 +68,10 @@
         Type type = db.lookupType("G1CollectedHeap");
 
         hrmFieldOffset = type.getField("_hrm").getOffset();
-        g1Allocator = type.getAddressField("_allocator");
         g1mmField = type.getAddressField("_g1mm");
         oldSetFieldOffset = type.getField("_old_set").getOffset();
         humongousSetFieldOffset = type.getField("_humongous_set").getOffset();
+        summaryBytesUsedField = type.getCIntegerField("_summary_bytes_used");
     }
 
     public long capacity() {
@@ -78,7 +79,7 @@
     }
 
     public long used() {
-        return allocator().getSummaryBytes();
+        return summaryBytesUsedField.getValue(addr);
     }
 
     public long n_regions() {
@@ -96,11 +97,6 @@
         return (G1MonitoringSupport) VMObjectFactory.newObject(G1MonitoringSupport.class, g1mmAddr);
     }
 
-    public G1Allocator allocator() {
-        Address g1AllocatorAddr = g1Allocator.getValue(addr);
-        return (G1Allocator) VMObjectFactory.newObject(G1Allocator.class, g1AllocatorAddr);
-    }
-
     public HeapRegionSetBase oldSet() {
         Address oldSetAddr = addr.addOffsetTo(oldSetFieldOffset);
         return (HeapRegionSetBase) VMObjectFactory.newObject(HeapRegionSetBase.class,