1 /* 2 * Copyright (c) 2018, 2019, Red Hat, Inc. 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_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP 26 #define SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP 27 28 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp" 29 #include "gc/shenandoah/shenandoahPhaseTimings.hpp" 30 #include "utilities/numberSeq.hpp" 31 32 class ShenandoahAllocationRate : public CHeapObj<mtGC> { 33 public: 34 explicit ShenandoahAllocationRate(); 35 void allocation_counter_reset(); 36 37 double sample(size_t allocated); 38 39 double instantaneous_rate(size_t allocated) const; 40 double upper_bound(double sds) const; 41 bool is_spiking(double rate, double threshold) const; 42 43 private: 44 45 double instantaneous_rate(double time, size_t allocated) const; 46 47 double _last_sample_time; 48 size_t _last_sample_value; 49 double _interval_sec; 50 TruncatedSeq _rate; 51 TruncatedSeq _rate_avg; 52 }; 53 54 class ShenandoahAdaptiveHeuristics : public ShenandoahHeuristics { 55 public: 56 ShenandoahAdaptiveHeuristics(); 57 58 virtual ~ShenandoahAdaptiveHeuristics(); 59 60 virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset, 61 RegionData* data, size_t size, 62 size_t actual_free); 63 64 void record_cycle_start(); 65 void record_success_concurrent(); 66 void record_success_degenerated(); 67 void record_success_full(); 68 69 virtual bool should_start_gc(); 70 71 virtual const char* name() { return "Adaptive"; } 72 virtual bool is_diagnostic() { return false; } 73 virtual bool is_experimental() { return false; } 74 75 private: 76 // These are used to adjust the margin of error and the spike threshold 77 // in response to GC cycle outcomes. These values are shared, but the 78 // margin of error and spike threshold trend in opposite directions. 79 const static double FULL_PENALTY_SD; 80 const static double DEGENERATE_PENALTY_SD; 81 82 const static double MINIMUM_CONFIDENCE; 83 const static double MAXIMUM_CONFIDENCE; 84 85 const static double LOWEST_EXPECTED_AVAILABLE_AT_END; 86 const static double HIGHEST_EXPECTED_AVAILABLE_AT_END; 87 88 friend class ShenandoahAllocationRate; 89 90 // Used to record the last trigger that signaled to start a GC. 91 // This itself is used to decide whether or not to adjust the margin of 92 // error for the average cycle time and allocation rate or the allocation 93 // spike detection threshold. 94 enum Trigger { 95 SPIKE, RATE, OTHER 96 }; 97 98 void adjust_last_trigger_parameters(double amount); 99 void adjust_margin_of_error(double amount); 100 void adjust_spike_threshold(double amount); 101 102 ShenandoahAllocationRate _allocation_rate; 103 104 // The margin of error expressed in standard deviations to add to our 105 // average cycle time and allocation rate. As this value increases we 106 // tend to over estimate the rate at which mutators will deplete the 107 // heap. In other words, erring on the side of caution will trigger more 108 // concurrent GCs. 109 double _margin_of_error_sd; 110 111 // The allocation spike threshold is expressed in standard deviations. 112 // If the standard deviation of the most recent sample of the allocation 113 // rate exceeds this threshold, a GC cycle is started. As this value 114 // decreases the sensitivity to allocation spikes increases. In other 115 // words, lowering the spike threshold will tend to increase the number 116 // of concurrent GCs. 117 double _spike_threshold_sd; 118 119 // Remember which trigger is responsible for the last GC cycle. When the 120 // outcome of the cycle is evaluated we will adjust the parameters for the 121 // corresponding triggers. Note that successful outcomes will raise 122 // the spike threshold and lower the margin of error. 123 Trigger _last_trigger; 124 125 // Keep track of the available memory at the end of a GC cycle. This 126 // establishes what is 'normal' for the application and is used as a 127 // source of feedback to adjust trigger parameters. 128 TruncatedSeq _available; 129 }; 130 131 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP