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