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 "memory/allocation.hpp"
30 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
31 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
32 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
33 #include "utilities/numberSeq.hpp"
34
35 class ShenandoahAllocationRate : public CHeapObj<mtGC> {
36 public:
37 explicit ShenandoahAllocationRate();
38 void allocation_counter_reset();
39
40 double sample(size_t allocated);
41
42 double upper_bound(double sds) const;
43 bool is_spiking(double rate, double threshold) const;
44 private:
45
46 double instantaneous_rate(double time, size_t allocated) const;
47
48 double _last_sample_time;
49 size_t _last_sample_value;
50 double _interval_sec;
51 TruncatedSeq _rate;
52 TruncatedSeq _rate_avg;
53 };
54
55 /*
56 * The adaptive heuristic tracks the allocation behavior and average cycle
57 * time of the application. It attempts to start a cycle with enough time
58 * to complete before the available memory is exhausted. It errors on the
59 * side of starting cycles early to avoid allocation failures (degenerated
60 * cycles).
61 *
62 * This heuristic limits the number of regions for evacuation such that the
63 * evacuation reserve is respected. This helps it avoid allocation failures
64 * during evacuation. It preferentially selects regions with the most garbage.
65 */
66 class ShenandoahAdaptiveHeuristics : public ShenandoahHeuristics {
67 public:
68 ShenandoahAdaptiveHeuristics(ShenandoahSpaceInfo* space_info);
69
70 virtual ~ShenandoahAdaptiveHeuristics();
71
72 virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
73 RegionData* data, size_t size,
74 size_t actual_free);
75
76 void record_cycle_start();
77 void record_success_concurrent();
78 void record_success_degenerated();
79 void record_success_full();
80
81 virtual bool should_start_gc();
82
83 virtual const char* name() { return "Adaptive"; }
84 virtual bool is_diagnostic() { return false; }
85 virtual bool is_experimental() { return false; }
86
87 private:
88 // These are used to adjust the margin of error and the spike threshold
89 // in response to GC cycle outcomes. These values are shared, but the
90 // margin of error and spike threshold trend in opposite directions.
91 const static double FULL_PENALTY_SD;
92 const static double DEGENERATE_PENALTY_SD;
93
94 const static double MINIMUM_CONFIDENCE;
95 const static double MAXIMUM_CONFIDENCE;
96
97 const static double LOWEST_EXPECTED_AVAILABLE_AT_END;
98 const static double HIGHEST_EXPECTED_AVAILABLE_AT_END;
99
100 friend class ShenandoahAllocationRate;
101
102 // Used to record the last trigger that signaled to start a GC.
103 // This itself is used to decide whether or not to adjust the margin of
104 // error for the average cycle time and allocation rate or the allocation
105 // spike detection threshold.
106 enum Trigger {
107 SPIKE, RATE, OTHER
108 };
109
110 void adjust_last_trigger_parameters(double amount);
111 void adjust_margin_of_error(double amount);
112 void adjust_spike_threshold(double amount);
113
114 protected:
115 ShenandoahAllocationRate _allocation_rate;
116
117 // The margin of error expressed in standard deviations to add to our
118 // average cycle time and allocation rate. As this value increases we
119 // tend to overestimate the rate at which mutators will deplete the
120 // heap. In other words, erring on the side of caution will trigger more
121 // concurrent GCs.
122 double _margin_of_error_sd;
123
124 // The allocation spike threshold is expressed in standard deviations.
125 // If the standard deviation of the most recent sample of the allocation
126 // rate exceeds this threshold, a GC cycle is started. As this value
127 // decreases the sensitivity to allocation spikes increases. In other
128 // words, lowering the spike threshold will tend to increase the number
129 // of concurrent GCs.
130 double _spike_threshold_sd;
131
132 // Remember which trigger is responsible for the last GC cycle. When the
133 // outcome of the cycle is evaluated we will adjust the parameters for the
134 // corresponding triggers. Note that successful outcomes will raise
135 // the spike threshold and lower the margin of error.
136 Trigger _last_trigger;
137
138 // Keep track of the available memory at the end of a GC cycle. This
139 // establishes what is 'normal' for the application and is used as a
140 // source of feedback to adjust trigger parameters.
141 TruncatedSeq _available;
142
143 // A conservative minimum threshold of free space that we'll try to maintain when possible.
144 // For example, we might trigger a concurrent gc if we are likely to drop below
145 // this threshold, or we might consider this when dynamically resizing generations
146 // in the generational case. Controlled by global flag ShenandoahMinFreeThreshold.
147 size_t min_free_threshold();
148 };
149
150 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHADAPTIVEHEURISTICS_HPP