104 lines
4.0 KiB
C++
104 lines
4.0 KiB
C++
/*
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* Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_GC_G1_G1SURVRATEGROUP_HPP
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#define SHARE_GC_G1_G1SURVRATEGROUP_HPP
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#include "gc/g1/g1Predictions.hpp"
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#include "utilities/numberSeq.hpp"
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// A survivor rate group tracks survival ratios of objects allocated in the
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// heap regions associated to a set of regions (a "space", i.e. eden or survivor)
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// on a time basis to predict future survival rates of regions of the same "age".
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//
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// Every time a new heap region associated with a survivor rate group is retired
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// (i.e. the time basis), it gets associated the next "age" entry in that group.
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//
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// During garbage collection G1 keeps track how much of total data is copied out
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// of a heap region (i.e. survives), to update the survivor rate predictor of that age.
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//
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// This information is used to predict, given a particular age of a heap region,
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// how much of its contents will likely survive to determine young generation sizes.
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//
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// The age index associated with a heap region is incremented from 0 (retired first)
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// to N (retired just before the GC).
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//
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// To avoid copying around data all the time when the total amount of regions in
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// a survivor rate group changes, this class organizes the arrays containing the
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// predictors in reverse chronological order as returned by age_in_group(). I.e.
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// index 0 contains the rate information for the region retired most recently.
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class G1SurvRateGroup : public CHeapObj<mtGC> {
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size_t _stats_arrays_length;
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double* _accum_surv_rate_pred;
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double _last_pred;
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TruncatedSeq** _surv_rate_predictors;
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size_t _num_added_regions; // The number of regions in this survivor rate group.
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void fill_in_last_surv_rates();
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void finalize_predictions(const G1Predictions& predictor);
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public:
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static const int InvalidAgeIndex = -1;
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static bool is_valid_age_index(int age) { return age >= 0; }
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G1SurvRateGroup();
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void reset();
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void start_adding_regions();
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void stop_adding_regions();
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void record_surviving_words(int age_in_group, size_t surv_words);
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void all_surviving_words_recorded(const G1Predictions& predictor, bool update_predictors);
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double accum_surv_rate_pred(int age) const {
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assert(_stats_arrays_length > 0, "invariant" );
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assert(is_valid_age_index(age), "must be");
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if ((size_t)age < _stats_arrays_length)
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return _accum_surv_rate_pred[age];
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else {
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double diff = (double)(age - _stats_arrays_length + 1);
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return _accum_surv_rate_pred[_stats_arrays_length - 1] + diff * _last_pred;
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}
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}
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double surv_rate_pred(G1Predictions const& predictor, int age) const {
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assert(is_valid_age_index(age), "must be");
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age = MIN2(age, (int)_stats_arrays_length - 1);
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return predictor.predict_in_unit_interval(_surv_rate_predictors[age]);
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}
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int next_age_index() {
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return (int)++_num_added_regions;
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}
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int age_in_group(int age_index) const {
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int result = (int)(_num_added_regions - age_index);
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assert(is_valid_age_index(result), "invariant" );
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return result;
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}
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};
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#endif // SHARE_GC_G1_G1SURVRATEGROUP_HPP
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