diff -r fdd9909928ae -r 6a3c85b8111c hotspot/src/share/vm/memory/metablock.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metablock.cpp	Thu Nov 29 10:09:04 2012 -0800
@@ -0,0 +1,75 @@
+/*
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "memory/allocation.hpp"
+#include "memory/metablock.hpp"
+#include "utilities/copy.hpp"
+#include "utilities/debug.hpp"
+
+// Blocks of space for metadata are allocated out of Metachunks.
+//
+// Metachunk are allocated out of MetadataVirtualspaces and once
+// allocated there is no explicit link between a Metachunk and
+// the MetadataVirtualspaces from which it was allocated.
+//
+// Each SpaceManager maintains a
+// list of the chunks it is using and the current chunk.  The current
+// chunk is the chunk from which allocations are done.  Space freed in
+// a chunk is placed on the free list of blocks (BlockFreelist) and
+// reused from there.
+//
+// Future modification
+//
+// The Metachunk can conceivable be replaced by the Chunk in
+// allocation.hpp.  Note that the latter Chunk is the space for
+// allocation (allocations from the chunk are out of the space in
+// the Chunk after the header for the Chunk) where as Metachunks
+// point to space in a VirtualSpace.  To replace Metachunks with
+// Chunks, change Chunks so that they can be allocated out of a VirtualSpace.
+size_t Metablock::_min_block_byte_size = sizeof(Metablock);
+
+#ifdef ASSERT
+size_t Metablock::_overhead =
+  Chunk::aligned_overhead_size(sizeof(Metablock)) / BytesPerWord;
+#else
+size_t Metablock::_overhead = 0;
+#endif
+
+// New blocks returned by the Metaspace are zero initialized.
+// We should fix the constructors to not assume this instead.
+Metablock* Metablock::initialize(MetaWord* p, size_t word_size) {
+  if (p == NULL) {
+    return NULL;
+  }
+
+  Metablock* result = (Metablock*) p;
+
+  // Clear the memory
+  Copy::fill_to_aligned_words((HeapWord*)result, word_size);
+#ifdef ASSERT
+  result->set_word_size(word_size);
+#endif
+  return result;
+}