diff -r f5e31fb61738 -r 944e56f74fba hotspot/src/share/vm/memory/metachunk.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metachunk.hpp	Tue Sep 18 23:35:42 2012 -0700
@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2012, 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.
+ *
+ */
+#ifndef SHARE_VM_MEMORY_METACHUNK_HPP
+#define SHARE_VM_MEMORY_METACHUNK_HPP
+
+//  Metachunk - Quantum of allocation from a Virtualspace
+//    Metachunks are reused (when freed are put on a global freelist) and
+//    have no permanent association to a SpaceManager.
+
+//            +--------------+ <- end
+//            |              |          --+       ---+
+//            |              |            | free     |
+//            |              |            |          |
+//            |              |            |          | capacity
+//            |              |            |          |
+//            |              | <- top   --+          |
+//            |              |           ---+        |
+//            |              |              | used   |
+//            |              |              |        |
+//            |              |              |        |
+//            +--------------+ <- bottom ---+     ---+
+
+class Metachunk VALUE_OBJ_CLASS_SPEC {
+  // link to support lists of chunks
+  Metachunk* _next;
+  Metachunk* _prev;
+
+  MetaWord* _bottom;
+  MetaWord* _end;
+  MetaWord* _top;
+  size_t _word_size;
+  // Used in a guarantee() so included in the Product builds
+  // even through it is only for debugging.
+  bool _is_free;
+
+  // Metachunks are allocated out of a MetadataVirtualSpace and
+  // and use some of its space to describe itself (plus alignment
+  // considerations).  Metadata is allocated in the rest of the chunk.
+  // This size is the overhead of maintaining the Metachunk within
+  // the space.
+  static size_t _overhead;
+
+  void set_bottom(MetaWord* v) { _bottom = v; }
+  void set_end(MetaWord* v) { _end = v; }
+  void set_top(MetaWord* v) { _top = v; }
+  void set_word_size(size_t v) { _word_size = v; }
+ public:
+#ifdef ASSERT
+  Metachunk() : _bottom(NULL), _end(NULL), _top(NULL), _is_free(false) {}
+#else
+  Metachunk() : _bottom(NULL), _end(NULL), _top(NULL) {}
+#endif
+
+  // Used to add a Metachunk to a list of Metachunks
+  void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
+  void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
+
+  MetaWord* allocate(size_t word_size);
+  static Metachunk* initialize(MetaWord* ptr, size_t word_size);
+
+  // Accessors
+  Metachunk* next() const { return _next; }
+  Metachunk* prev() const { return _prev; }
+  MetaWord* bottom() const { return _bottom; }
+  MetaWord* end() const { return _end; }
+  MetaWord* top() const { return _top; }
+  size_t word_size() const { return _word_size; }
+  size_t size() const volatile { return _word_size; }
+  void set_size(size_t v) { _word_size = v; }
+  bool is_free() { return _is_free; }
+  void set_is_free(bool v) { _is_free = v; }
+  static size_t overhead() { return _overhead; }
+  void clear_next()              { set_next(NULL); }
+  void link_prev(Metachunk* ptr) { set_prev(ptr); }
+  uintptr_t* end()              { return ((uintptr_t*) this) + size(); }
+  bool cantCoalesce() const     { return false; }
+  void link_next(Metachunk* ptr) { set_next(ptr); }
+  void link_after(Metachunk* ptr){
+    link_next(ptr);
+    if (ptr != NULL) ptr->link_prev(this);
+  }
+
+  // Reset top to bottom so chunk can be reused.
+  void reset_empty() { _top = (_bottom + _overhead); }
+  bool is_empty() { return _top == (_bottom + _overhead); }
+
+  // used (has been allocated)
+  // free (available for future allocations)
+  // capacity (total size of chunk)
+  size_t used_word_size();
+  size_t free_word_size();
+  size_t capacity_word_size();
+
+  // Debug support
+#ifdef ASSERT
+  void* prev_addr() const { return (void*)&_prev; }
+  void* next_addr() const { return (void*)&_next; }
+  void* size_addr() const { return (void*)&_word_size; }
+#endif
+  bool verify_chunk_in_free_list(Metachunk* tc) const { return true; }
+  bool verify_par_locked() { return true; }
+
+  void assert_is_mangled() const {/* Don't check "\*/}
+
+#ifdef ASSERT
+  void mangle();
+#endif // ASSERT
+
+  void print_on(outputStream* st) const;
+  void verify();
+};
+#endif  // SHARE_VM_MEMORY_METACHUNK_HPP