--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1Predictions.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2015, 2016, 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_GC_G1_G1PREDICTIONS_HPP
+#define SHARE_VM_GC_G1_G1PREDICTIONS_HPP
+
+#include "utilities/numberSeq.hpp"
+
+// Utility class containing various helper methods for prediction.
+class G1Predictions VALUE_OBJ_CLASS_SPEC {
+ private:
+  double _sigma;
+
+  // This function is used to estimate the stddev of sample sets. There is some
+  // special consideration of small sample sets: the actual stddev for them is
+  // not very useful, so we calculate some value based on the sample average.
+  // Five or more samples yields zero (at that point we use the stddev); fewer
+  // scale the sample set average linearly from two times the average to 0.5 times
+  // it.
+  double stddev_estimate(TruncatedSeq const* seq) const {
+    double estimate = seq->dsd();
+    int const samples = seq->num();
+    if (samples < 5) {
+      estimate = MAX2(seq->davg() * (5 - samples) / 2.0, estimate);
+    }
+    return estimate;
+  }
+ public:
+  G1Predictions(double sigma) : _sigma(sigma) {
+    assert(sigma >= 0.0, "Confidence must be larger than or equal to zero");
+  }
+
+  // Confidence factor.
+  double sigma() const { return _sigma; }
+
+  double get_new_prediction(TruncatedSeq const* seq) const {
+    return seq->davg() + _sigma * stddev_estimate(seq);
+  }
+};
+
+#endif // SHARE_VM_GC_G1_G1PREDICTIONS_HPP