1 /*
2 * Copyright (c) 2021, Amazon.com, Inc. or its affiliates. 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.
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23 */
24
25 #ifndef SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHOLDHEURISTICS_HPP
26 #define SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHOLDHEURISTICS_HPP
27
28 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
29 #include "gc/shenandoah/shenandoahGeneration.hpp"
30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
31 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
32 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
33
34 class ShenandoahOldHeuristics : public ShenandoahHeuristics {
35
36 private:
37
38 // if (_generation->generation_mode() == OLD) _old_collection_candidates
39 // represent the number of regions selected for collection following the
40 // most recently completed old-gen mark that have not yet been selected
41 // for evacuation and _next_collection_candidate is the index within
42 // _region_data of the next candidate region to be selected for evacuation.
43 // if (_generation->generation_mode() != OLD) these two variables are
44 // not used.
45 uint _old_collection_candidates;
46 uint _next_old_collection_candidate;
47
48 // At the time we select the old-gen collection set, _hidden_old_collection_candidates
49 // and _hidden_next_old_collection_candidates are set to remember the intended old-gen
50 // collection set. After all old-gen regions not in the old-gen collection set have been
51 // coalesced and filled, the content of these variables is copied to _old_collection_candidates
52 // and _next_old_collection_candidates so that evacuations can begin evacuating these regions.
53 uint _hidden_old_collection_candidates;
54 uint _hidden_next_old_collection_candidate;
55
56 // if (_generation->generation_mode() == OLD)
57 // _old_coalesce_and_fill_candidates represents the number of regions
58 // that were chosen for the garbage contained therein to be coalesced
59 // and filled and _first_coalesce_and_fill_candidate represents the
60 // the index of the first such region within the _region_data array.
61 // if (_generation->generation_mode() != OLD) these two variables are
62 // not used.
63 uint _old_coalesce_and_fill_candidates;
64 uint _first_coalesce_and_fill_candidate;
65
66 // This can be the 'static' or 'adaptive' heuristic.
67 ShenandoahHeuristics* _trigger_heuristic;
68
69 // Flag is set when promotion failure is detected (by gc thread), cleared when old generation collection begins (by control thread)
70 volatile bool _promotion_failed;
71
72 // Prepare for evacuation of old-gen regions by capturing the mark results of a recently completed concurrent mark pass.
73 void prepare_for_old_collections();
74
75 protected:
76 virtual void choose_collection_set_from_regiondata(ShenandoahCollectionSet* set, RegionData* data, size_t data_size,
77 size_t free) override;
78
79 public:
80 ShenandoahOldHeuristics(ShenandoahGeneration* generation, ShenandoahHeuristics* trigger_heuristic);
81
82 // Return true iff chosen collection set includes at least one old-gen HeapRegion.
83 virtual bool choose_collection_set(ShenandoahCollectionSet* collection_set, ShenandoahOldHeuristics* old_heuristics) override;
84
85 // Return true iff the collection set is primed with at least one old-gen region.
86 bool prime_collection_set(ShenandoahCollectionSet* set);
87
88 // Having coalesced and filled all old-gen heap regions that are not part of the old-gen collection set, begin
89 // evacuating the collection set.
90 void start_old_evacuations();
91
92 // How many old-collection candidates have not yet been processed?
93 uint unprocessed_old_collection_candidates();
94
95 // How many old or hidden collection candidates have not yet been processed?
96 uint unprocessed_old_or_hidden_collection_candidates();
97
98 // Return the next old-collection candidate in order of decreasing amounts of garbage. (We process most-garbage regions
99 // first.) This does not consume the candidate. If the candidate is selected for inclusion in a collection set, then
100 // the candidate is consumed by invoking consume_old_collection_candidate().
101 ShenandoahHeapRegion* next_old_collection_candidate();
102
103 // Adjust internal state to reflect that one fewer old-collection candidate remains to be processed.
104 void consume_old_collection_candidate();
105
106 // How many old-collection regions were identified at the end of the most recent old-gen mark to require their
107 // unmarked objects to be coalesced and filled?
108 uint old_coalesce_and_fill_candidates();
109
110 // Fill in buffer with all of the old-collection regions that were identified at the end of the most recent old-gen
111 // mark to require their unmarked objects to be coalesced and filled. The buffer array must have at least
112 // old_coalesce_and_fill_candidates() entries, or memory may be corrupted when this function overwrites the
113 // end of the array.
114 void get_coalesce_and_fill_candidates(ShenandoahHeapRegion** buffer);
115
116 // If a GLOBAL gc occurs, it will collect the entire heap which invalidates any collection candidates being
117 // held by this heuristic for supplying mixed collections.
118 void abandon_collection_candidates();
119
120 // Notify the heuristic of promotion failures. The promotion attempt will be skipped and the object will
121 // be evacuated into the young generation. The collection should complete normally, but we want to schedule
122 // an old collection as soon as possible.
123 void handle_promotion_failure();
124
125 virtual void record_cycle_start() override;
126
127 virtual void record_cycle_end() override;
128
129 virtual bool should_start_gc() override;
130
131 virtual bool should_degenerate_cycle() override;
132
133 virtual void record_success_concurrent() override;
134
135 virtual void record_success_degenerated() override;
136
137 virtual void record_success_full() override;
138
139 virtual void record_allocation_failure_gc() override;
140
141 virtual void record_requested_gc() override;
142
143 virtual bool can_unload_classes() override;
144
145 virtual bool can_unload_classes_normal() override;
146
147 virtual bool should_unload_classes() override;
148
149 virtual const char* name() override;
150
151 virtual bool is_diagnostic() override;
152
153 virtual bool is_experimental() override;
154
155 };
156
157 #endif // SHARE_GC_SHENANDOAH_HEURISTICS_SHENANDOAHOLDHEURISTICS_HPP