diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/ThreadLocalAllocBuffer.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/ThreadLocalAllocBuffer.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+package sun.jvm.hotspot.runtime;
+
+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
+    used by the threads for allocation. </P>
+
+    <P> It is thread-private at any time, but maybe multiplexed over
+    time across multiple threads. </P> */
+
+public class ThreadLocalAllocBuffer extends VMObject {
+  private static AddressField  startField;
+  private static AddressField  topField;
+  private static AddressField  endField;
+  private static CIntegerField desired_sizeField;
+
+  static {
+    VM.registerVMInitializedObserver(new Observer() {
+        public void update(Observable o, Object data) {
+          initialize(VM.getVM().getTypeDataBase());
+        }
+      });
+  }
+
+  private static synchronized void initialize(TypeDataBase db) {
+    Type type = db.lookupType("ThreadLocalAllocBuffer");
+
+    startField         = type.getAddressField("_start");
+    topField           = type.getAddressField("_top");
+    endField           = type.getAddressField("_end");
+    desired_sizeField          = type.getCIntegerField("_desired_size");
+  }
+
+  public ThreadLocalAllocBuffer(Address addr) {
+    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 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
+      debugging mechanism */
+  public OopHandle startAsOopHandle() {
+    return startField.getOopHandle(addr);
+  }
+
+  /** Support for iteration over heap -- not sure how this will
+      interact with GC in reflective system, but necessary for the
+      debugging mechanism */
+  public OopHandle nextOopHandle(OopHandle handle, long size) {
+    return handle.addOffsetToAsOopHandle(size);
+  }
+
+  //  public int     size();           // FIXME: must adjust this to be in bytes
+  //  public int     availableSize();  // FIXME: must adjust this to be in bytes
+  public void print() {
+    printOn(System.out);
+  }
+
+  public boolean contains(Address p) {
+    if (top() == null) {
+      return false;
+    }
+    return (start().lessThanOrEqual(p) && top().greaterThan(p));
+  }
+
+  public void printOn(PrintStream tty) {
+    tty.println(" [" + start() + "," +
+                top() + "," + end() + ",{" + hardEnd() + "})");
+  }
+}