1 /* 2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_GC_G1_G1SURVRATEGROUP_HPP 26 #define SHARE_GC_G1_G1SURVRATEGROUP_HPP 27 28 #include "gc/g1/g1Predictions.hpp" 29 #include "utilities/numberSeq.hpp" 30 31 // A survivor rate group tracks survival ratios of objects allocated in the 32 // heap regions associated to a set of regions (a "space", i.e. eden or survivor) 33 // on a time basis to predict future survival rates of regions of the same "age". 34 // 35 // Every time a new heap region associated with a survivor rate group is retired 36 // (i.e. the time basis), it gets associated the next "age" entry in that group. 37 // 38 // During garbage collection G1 keeps track how much of total data is copied out 39 // of a heap region (i.e. survives), to update the survivor rate predictor of that age. 40 // 41 // This information is used to predict, given a particular age of a heap region, 42 // how much of its contents will likely survive to determine young generation sizes. 43 // 44 // The age index associated with a heap region is incremented from 0 (retired first) 45 // to N (retired just before the GC). 46 // 47 // To avoid copying around data all the time when the total amount of regions in 48 // a survivor rate group changes, this class organizes the arrays containing the 49 // predictors in reverse chronological order as returned by age_in_group(). I.e. 50 // index 0 contains the rate information for the region retired most recently. 51 class G1SurvRateGroup : public CHeapObj<mtGC> { 52 size_t _stats_arrays_length; 53 double* _accum_surv_rate_pred; 54 double _last_pred; 55 TruncatedSeq** _surv_rate_predictors; 56 57 size_t _num_added_regions; // The number of regions in this survivor rate group. 58 59 void fill_in_last_surv_rates(); 60 void finalize_predictions(const G1Predictions& predictor); 61 62 public: 63 static const int InvalidAgeIndex = -1; 64 static bool is_valid_age_index(int age) { return age >= 0; } 65 66 G1SurvRateGroup(); 67 void reset(); 68 void start_adding_regions(); 69 void stop_adding_regions(); 70 void record_surviving_words(int age_in_group, double surv_rate); 71 void all_surviving_words_recorded(const G1Predictions& predictor, bool update_predictors); 72 73 double accum_surv_rate_pred(int age) const { 74 assert(_stats_arrays_length > 0, "invariant" ); 75 assert(is_valid_age_index(age), "must be"); 76 if ((size_t)age < _stats_arrays_length) 77 return _accum_surv_rate_pred[age]; 78 else { 79 double diff = (double)(age - _stats_arrays_length + 1); 80 return _accum_surv_rate_pred[_stats_arrays_length - 1] + diff * _last_pred; 81 } 82 } 83 84 double surv_rate_pred(G1Predictions const& predictor, int age) const { 85 assert(is_valid_age_index(age), "must be"); 86 87 age = MIN2(age, (int)_stats_arrays_length - 1); 88 89 return predictor.predict_in_unit_interval(_surv_rate_predictors[age]); 90 } 91 92 int next_age_index() { 93 return (int)++_num_added_regions; 94 } 95 96 int age_in_group(int age_index) const { 97 int result = (int)(_num_added_regions - age_index); 98 assert(is_valid_age_index(result), "invariant" ); 99 return result; 100 } 101 }; 102 103 #endif // SHARE_GC_G1_G1SURVRATEGROUP_HPP