| /* |
| * 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 |