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