diff -r 000000000000 -r f90c822e73f8 src/share/vm/utilities/intHisto.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/utilities/intHisto.hpp	Wed Apr 27 01:25:04 2016 +0800
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2001, 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_UTILITIES_INTHISTO_HPP
+#define SHARE_VM_UTILITIES_INTHISTO_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/growableArray.hpp"
+
+// This class implements a simple histogram.
+
+// A histogram summarizes a series of "measurements", each of which is
+// assumed (required in this implementation) to have an outcome that is a
+// non-negative integer.  The histogram efficiently maps measurement outcomes
+// to the number of measurements had that outcome.
+
+// To print the results, invoke print() on your Histogram*.
+
+// Note: there is already an existing "Histogram" class, in file
+// histogram.{hpp,cpp}, but to my mind that's not a histogram, it's a table
+// mapping strings to counts.  To be a histogram (IMHO) it needs to map
+// numbers (in fact, integers) to number of occurrences of that number.
+
+// ysr: (i am not sure i agree with the above note.) i suspect we want to have a
+// histogram template that will map an arbitrary type (with a defined order
+// relation) to a count.
+
+
+class IntHistogram : public CHeapObj<mtInternal> {
+ protected:
+  int _max;
+  int _tot;
+  GrowableArray<int>* _elements;
+
+public:
+  // Create a new, empty table.  "est" is an estimate of the maximum outcome
+  // that will be added, and "max" is an outcome such that all outcomes at
+  // least that large will be bundled with it.
+  IntHistogram(int est, int max);
+  // Add a measurement with the given outcome to the sequence.
+  void add_entry(int outcome);
+  // Return the number of entries recorded so far with the given outcome.
+  int  entries_for_outcome(int outcome);
+  // Return the total number of entries recorded so far.
+  int  total_entries() { return _tot; }
+  // Return the number of entries recorded so far with the given outcome as
+  // a fraction of the total number recorded so far.
+  double fraction_for_outcome(int outcome) {
+    return
+      (double)entries_for_outcome(outcome)/
+      (double)total_entries();
+  }
+  // Print the histogram on the given output stream.
+  void print_on(outputStream* st) const;
+};
+
+#endif // SHARE_VM_UTILITIES_INTHISTO_HPP