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_SHENANDOAHHEURISTICS_HPP
27 #define SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHHEURISTICS_HPP
28
29 #include "gc/shenandoah/heuristics/shenandoahSpaceInfo.hpp"
30 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
31 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
32 #include "memory/allocation.hpp"
33 #include "runtime/globals_extension.hpp"
34
35 #define SHENANDOAH_ERGO_DISABLE_FLAG(name) \
36 do { \
37 if (FLAG_IS_DEFAULT(name) && (name)) { \
38 log_info(gc)("Heuristics ergonomically sets -XX:-" #name); \
39 FLAG_SET_DEFAULT(name, false); \
40 } \
41 } while (0)
42
43 #define SHENANDOAH_ERGO_ENABLE_FLAG(name) \
44 do { \
45 if (FLAG_IS_DEFAULT(name) && !(name)) { \
46 log_info(gc)("Heuristics ergonomically sets -XX:+" #name); \
47 FLAG_SET_DEFAULT(name, true); \
48 } \
49 } while (0)
50
51 #define SHENANDOAH_ERGO_OVERRIDE_DEFAULT(name, value) \
52 do { \
53 if (FLAG_IS_DEFAULT(name)) { \
54 log_info(gc)("Heuristics ergonomically sets -XX:" #name "=" #value); \
55 FLAG_SET_DEFAULT(name, value); \
56 } \
57 } while (0)
58
59 class ShenandoahCollectionSet;
60 class ShenandoahHeapRegion;
61
62 /*
63 * Shenandoah heuristics are primarily responsible for deciding when to start
64 * a collection cycle and choosing which regions will be evacuated during the
65 * cycle.
66 */
67 class ShenandoahHeuristics : public CHeapObj<mtGC> {
68 static const intx Concurrent_Adjust = -1; // recover from penalties
69 static const intx Degenerated_Penalty = 10; // how much to penalize average GC duration history on Degenerated GC
70 static const intx Full_Penalty = 20; // how much to penalize average GC duration history on Full GC
71
72 protected:
73 static const uint Moving_Average_Samples = 10; // Number of samples to store in moving averages
74
75 typedef struct {
76 ShenandoahHeapRegion* _region;
77 union {
78 size_t _garbage; // Not used by old-gen heuristics.
79 size_t _live_data; // Only used for old-gen heuristics, which prioritizes retention of _live_data over garbage reclaim
80 } _u;
81 } RegionData;
82
83 // Source of information about the memory space managed by this heuristic
84 ShenandoahSpaceInfo* _space_info;
85
86 // Depending on generation mode, region data represents the results of the relevant
87 // most recently completed marking pass:
88 // - in GLOBAL mode, global marking pass
89 // - in OLD mode, old-gen marking pass
90 // - in YOUNG mode, young-gen marking pass
91 //
92 // Note that there is some redundancy represented in region data because
93 // each instance is an array large enough to hold all regions. However,
94 // any region in young-gen is not in old-gen. And any time we are
95 // making use of the GLOBAL data, there is no need to maintain the
96 // YOUNG or OLD data. Consider this redundancy of data structure to
97 // have negligible cost unless proven otherwise.
98 RegionData* _region_data;
99
100 uint _degenerated_cycles_in_a_row;
101 uint _successful_cycles_in_a_row;
102
103 size_t _guaranteed_gc_interval;
104
105 double _cycle_start;
106 double _last_cycle_end;
107
108 size_t _gc_times_learned;
109 intx _gc_time_penalties;
110 TruncatedSeq* _gc_cycle_time_history;
111
112 // There may be many threads that contend to set this flag
113 ShenandoahSharedFlag _metaspace_oom;
114
115 static int compare_by_garbage(RegionData a, RegionData b);
116
117 // TODO: We need to enhance this API to give visibility to accompanying old-gen evacuation effort.
118 // In the case that the old-gen evacuation effort is small or zero, the young-gen heuristics
119 // should feel free to dedicate increased efforts to young-gen evacuation.
120
121 virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* set,
122 RegionData* data, size_t data_size,
123 size_t free) = 0;
124
125 void adjust_penalty(intx step);
126
127 public:
128 ShenandoahHeuristics(ShenandoahSpaceInfo* space_info);
129 virtual ~ShenandoahHeuristics();
130
131 void record_metaspace_oom() { _metaspace_oom.set(); }
132 void clear_metaspace_oom() { _metaspace_oom.unset(); }
133 bool has_metaspace_oom() const { return _metaspace_oom.is_set(); }
134
135 void set_guaranteed_gc_interval(size_t guaranteed_gc_interval) {
136 _guaranteed_gc_interval = guaranteed_gc_interval;
137 }
138
139 virtual void record_cycle_start();
140
141 virtual void record_cycle_end();
142
143 virtual bool should_start_gc();
144
145 virtual bool should_degenerate_cycle();
146
147 virtual void record_success_concurrent(bool abbreviated);
148
149 virtual void record_success_degenerated();
150
151 virtual void record_success_full();
152
153 virtual void record_allocation_failure_gc();
154
155 virtual void record_requested_gc();
156
157 virtual void choose_collection_set(ShenandoahCollectionSet* collection_set);
158
159 virtual bool can_unload_classes();
160 virtual bool can_unload_classes_normal();
161 virtual bool should_unload_classes();
162
163 virtual const char* name() = 0;
164 virtual bool is_diagnostic() = 0;
165 virtual bool is_experimental() = 0;
166 virtual void initialize();
167
168 double elapsed_cycle_time() const;
169 };
170
171 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHHEURISTICS_HPP