1 /*
2 * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #ifndef SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP
27 #define SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP
28
29 #include "runtime/globals_extension.hpp"
30 #include "memory/allocation.hpp"
31 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
32 #include "gc/shenandoah/heuristics/shenandoahSpaceInfo.hpp"
33 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
34 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
35 #include "utilities/numberSeq.hpp"
36
37 class ShenandoahAllocationRate : public CHeapObj<mtGC> {
38 public:
39 explicit ShenandoahAllocationRate();
40 void allocation_counter_reset();
41
42 double sample(size_t allocated);
43
44 double upper_bound(double sds) const;
45 bool is_spiking(double rate, double threshold) const;
46 private:
47
48 double instantaneous_rate(double time, size_t allocated) const;
49
50 double _last_sample_time;
51 size_t _last_sample_value;
52 double _interval_sec;
53 TruncatedSeq _rate;
54 TruncatedSeq _rate_avg;
55 };
56
57 /*
58 * The adaptive heuristic tracks the allocation behavior and average cycle
59 * time of the application. It attempts to start a cycle with enough time
60 * to complete before the available memory is exhausted. It errors on the
61 * side of starting cycles early to avoid allocation failures (degenerated
62 * cycles).
63 *
64 * This heuristic limits the number of regions for evacuation such that the
65 * evacuation reserve is respected. This helps it avoid allocation failures
66 * during evacuation. It preferentially selects regions with the most garbage.
67 */
68 class ShenandoahAdaptiveHeuristics : public ShenandoahHeuristics {
69 public:
70 ShenandoahAdaptiveHeuristics(ShenandoahSpaceInfo* space_info);
71
72 virtual ~ShenandoahAdaptiveHeuristics();
73
74 virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
75 RegionData* data, size_t size,
76 size_t actual_free);
77
78 void record_cycle_start();
79 void record_success_concurrent(bool abbreviated);
80 void record_success_degenerated();
81 void record_success_full();
82
83 virtual bool should_start_gc();
84
85 virtual const char* name() { return "Adaptive"; }
86 virtual bool is_diagnostic() { return false; }
87 virtual bool is_experimental() { return false; }
88
89 private:
90 // These are used to adjust the margin of error and the spike threshold
91 // in response to GC cycle outcomes. These values are shared, but the
92 // margin of error and spike threshold trend in opposite directions.
93 const static double FULL_PENALTY_SD;
94 const static double DEGENERATE_PENALTY_SD;
95
96 const static double MINIMUM_CONFIDENCE;
97 const static double MAXIMUM_CONFIDENCE;
98
99 const static double LOWEST_EXPECTED_AVAILABLE_AT_END;
100 const static double HIGHEST_EXPECTED_AVAILABLE_AT_END;
101
102 friend class ShenandoahAllocationRate;
103
104 // Used to record the last trigger that signaled to start a GC.
105 // This itself is used to decide whether or not to adjust the margin of
106 // error for the average cycle time and allocation rate or the allocation
107 // spike detection threshold.
108 enum Trigger {
109 SPIKE, RATE, OTHER
110 };
111
112 void adjust_last_trigger_parameters(double amount);
113 void adjust_margin_of_error(double amount);
114 void adjust_spike_threshold(double amount);
115
116 protected:
117 ShenandoahAllocationRate _allocation_rate;
118
119 // The margin of error expressed in standard deviations to add to our
120 // average cycle time and allocation rate. As this value increases we
121 // tend to overestimate the rate at which mutators will deplete the
122 // heap. In other words, erring on the side of caution will trigger more
123 // concurrent GCs.
124 double _margin_of_error_sd;
125
126 // The allocation spike threshold is expressed in standard deviations.
127 // If the standard deviation of the most recent sample of the allocation
128 // rate exceeds this threshold, a GC cycle is started. As this value
129 // decreases the sensitivity to allocation spikes increases. In other
130 // words, lowering the spike threshold will tend to increase the number
131 // of concurrent GCs.
132 double _spike_threshold_sd;
133
134 // Remember which trigger is responsible for the last GC cycle. When the
135 // outcome of the cycle is evaluated we will adjust the parameters for the
136 // corresponding triggers. Note that successful outcomes will raise
137 // the spike threshold and lower the margin of error.
138 Trigger _last_trigger;
139
140 // Keep track of the available memory at the end of a GC cycle. This
141 // establishes what is 'normal' for the application and is used as a
142 // source of feedback to adjust trigger parameters.
143 TruncatedSeq _available;
144
145 size_t min_free_threshold();
146 };
147
148 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP