--- a/hotspot/agent/src/share/classes/sun/jvm/hotspot/oops/ObjectHeap.java	Thu Jan 03 15:03:27 2013 -0800
+++ b/hotspot/agent/src/share/classes/sun/jvm/hotspot/oops/ObjectHeap.java	Tue Jan 29 10:51:33 2013 +0100
@@ -467,7 +467,7 @@
               liveRegions.add(tlab.start());
               liveRegions.add(tlab.start());
               liveRegions.add(tlab.top());
-              liveRegions.add(tlab.end());
+              liveRegions.add(tlab.hardEnd());
             }
           }
         }

--- a/hotspot/agent/src/share/classes/sun/jvm/hotspot/runtime/ThreadLocalAllocBuffer.java	Thu Jan 03 15:03:27 2013 -0800
+++ b/hotspot/agent/src/share/classes/sun/jvm/hotspot/runtime/ThreadLocalAllocBuffer.java	Tue Jan 29 10:51:33 2013 +0100
@@ -27,6 +27,7 @@
 import java.io.*;
 import java.util.*;
 import sun.jvm.hotspot.debugger.*;
+import sun.jvm.hotspot.oops.*;
 import sun.jvm.hotspot.types.*;
 
 /** <P> ThreadLocalAllocBuffer: a descriptor for thread-local storage
@@ -62,9 +63,22 @@
     super(addr);
   }
 
-  public Address start()                        { return startField.getValue(addr); }
-  public Address end()                          { return   endField.getValue(addr); }
-  public Address top()                          { return   topField.getValue(addr); }
+  public Address start()    { return startField.getValue(addr); }
+  public Address end()      { return   endField.getValue(addr); }
+  public Address top()      { return   topField.getValue(addr); }
+  public Address hardEnd()  { return end().addOffsetTo(alignmentReserve()); }
+
+  private long alignmentReserve() {
+    return Oop.alignObjectSize(endReserve());
+  }
+
+  private long endReserve() {
+    long minFillerArraySize = Array.baseOffsetInBytes(BasicType.T_INT);
+    long reserveForAllocationPrefetch = VM.getVM().getReserveForAllocationPrefetch();
+    long heapWordSize = VM.getVM().getHeapWordSize();
+
+    return Math.max(minFillerArraySize, reserveForAllocationPrefetch * heapWordSize);
+  }
 
   /** Support for iteration over heap -- not sure how this will
       interact with GC in reflective system, but necessary for the

--- a/hotspot/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java	Thu Jan 03 15:03:27 2013 -0800
+++ b/hotspot/agent/src/share/classes/sun/jvm/hotspot/runtime/VM.java	Tue Jan 29 10:51:33 2013 +0100
@@ -114,6 +114,7 @@
   private int          invalidOSREntryBCI;
   private ReversePtrs  revPtrs;
   private VMRegImpl    vmregImpl;
+  private int          reserveForAllocationPrefetch;
 
   // System.getProperties from debuggee VM
   private Properties   sysProps;
@@ -293,6 +294,10 @@
        vmRelease = CStringUtilities.getString(releaseAddr);
        Address vmInternalInfoAddr = vmVersion.getAddressField("_s_internal_vm_info_string").getValue();
        vmInternalInfo = CStringUtilities.getString(vmInternalInfoAddr);
+
+       CIntegerType intType = (CIntegerType) db.lookupType("int");
+       CIntegerField reserveForAllocationPrefetchField = vmVersion.getCIntegerField("_reserve_for_allocation_prefetch");
+       reserveForAllocationPrefetch = (int)reserveForAllocationPrefetchField.getCInteger(intType);
     } catch (Exception exp) {
        throw new RuntimeException("can't determine target's VM version : " + exp.getMessage());
     }
@@ -778,6 +783,10 @@
     return vmInternalInfo;
   }
 
+  public int getReserveForAllocationPrefetch() {
+    return reserveForAllocationPrefetch;
+  }
+
   public boolean isSharingEnabled() {
     if (sharingEnabled == null) {
       Flag flag = getCommandLineFlag("UseSharedSpaces");

--- a/hotspot/src/share/vm/runtime/vmStructs.cpp	Thu Jan 03 15:03:27 2013 -0800
+++ b/hotspot/src/share/vm/runtime/vmStructs.cpp	Tue Jan 29 10:51:33 2013 +0100
@@ -1161,6 +1161,7 @@
   static_field(Abstract_VM_Version,            _vm_major_version,                             int)                                   \
   static_field(Abstract_VM_Version,            _vm_minor_version,                             int)                                   \
   static_field(Abstract_VM_Version,            _vm_build_number,                              int)                                   \
+  static_field(Abstract_VM_Version,            _reserve_for_allocation_prefetch,              int)                                   \
                                                                                                                                      \
   static_field(JDK_Version,                    _current,                                      JDK_Version)                           \
   nonstatic_field(JDK_Version,                 _partially_initialized,                        bool)                                  \