1 /*
2 * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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
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24
25 #ifndef SHARE_GC_SHARED_CARDTABLERS_HPP
26 #define SHARE_GC_SHARED_CARDTABLERS_HPP
27
28 #include "gc/shared/cardTable.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/oop.hpp"
31
32 class DirtyCardToOopClosure;
33 class Generation;
34 class Space;
35 class OopsInGenClosure;
36
37 // Helper to remember modified oops in all clds.
38 class CLDRemSet {
39 bool _accumulate_modified_oops;
40 public:
41 CLDRemSet() : _accumulate_modified_oops(false) {}
42 void set_accumulate_modified_oops(bool value) { _accumulate_modified_oops = value; }
43 bool accumulate_modified_oops() { return _accumulate_modified_oops; }
44 bool mod_union_is_clear();
45 void clear_mod_union();
46 };
47
48 // This RemSet uses a card table both as shared data structure
49 // for a mod ref barrier set and for the rem set information.
50
51 class CardTableRS: public CardTable {
52 friend class VMStructs;
53 // Below are private classes used in impl.
54 friend class VerifyCTSpaceClosure;
55 friend class ClearNoncleanCardWrapper;
56
57 CLDRemSet _cld_rem_set;
58
59 void verify_space(Space* s, HeapWord* gen_start);
60
61 enum ExtendedCardValue {
62 youngergen_card = CT_MR_BS_last_reserved + 1,
63 // These are for parallel collection.
64 // There are three P (parallel) youngergen card values. In general, this
65 // needs to be more than the number of generations (including the perm
66 // gen) that might have younger_refs_do invoked on them separately. So
67 // if we add more gens, we have to add more values.
68 youngergenP1_card = CT_MR_BS_last_reserved + 2,
69 youngergenP2_card = CT_MR_BS_last_reserved + 3,
70 youngergenP3_card = CT_MR_BS_last_reserved + 4,
71 cur_youngergen_and_prev_nonclean_card =
72 CT_MR_BS_last_reserved + 5
73 };
74
75 // An array that contains, for each generation, the card table value last
76 // used as the current value for a younger_refs_do iteration of that
77 // portion of the table. The perm gen is index 0. The young gen is index 1,
78 // but will always have the value "clean_card". The old gen is index 2.
79 CardValue* _last_cur_val_in_gen;
80
81 CardValue _cur_youngergen_card_val;
82
83 // Number of generations, plus one for lingering PermGen issues in CardTableRS.
84 static const int _regions_to_iterate = 3;
85
86 CardValue cur_youngergen_card_val() {
87 return _cur_youngergen_card_val;
88 }
89 void set_cur_youngergen_card_val(CardValue v) {
90 _cur_youngergen_card_val = v;
91 }
92 bool is_prev_youngergen_card_val(CardValue v) {
93 return
94 youngergen_card <= v &&
95 v < cur_youngergen_and_prev_nonclean_card &&
96 v != _cur_youngergen_card_val;
97 }
98 // Return a youngergen_card_value that is not currently in use.
99 CardValue find_unused_youngergenP_card_value();
100
101 public:
102 CardTableRS(MemRegion whole_heap, bool scanned_concurrently);
103 ~CardTableRS();
104
105 CLDRemSet* cld_rem_set() { return &_cld_rem_set; }
106
107 void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl, uint n_threads);
108
109 virtual void verify_used_region_at_save_marks(Space* sp) const NOT_DEBUG_RETURN;
110
111 // Override.
112 void prepare_for_younger_refs_iterate(bool parallel);
113
114 // Card table entries are cleared before application; "blk" is
115 // responsible for dirtying if the oop is still older-to-younger after
116 // closure application.
117 void younger_refs_iterate(Generation* g, OopsInGenClosure* blk, uint n_threads);
118
119 void inline_write_ref_field_gc(void* field, oop new_val) {
120 CardValue* byte = byte_for(field);
121 *byte = youngergen_card;
122 }
123 void write_ref_field_gc_work(void* field, oop new_val) {
124 inline_write_ref_field_gc(field, new_val);
125 }
126
127 bool is_aligned(HeapWord* addr) {
128 return is_card_aligned(addr);
129 }
130
131 void verify();
132 void initialize();
133
134 void clear_into_younger(Generation* old_gen);
135
136 void invalidate_or_clear(Generation* old_gen);
137
138 bool is_prev_nonclean_card_val(CardValue v) {
139 return
140 youngergen_card <= v &&
141 v <= cur_youngergen_and_prev_nonclean_card &&
142 v != _cur_youngergen_card_val;
143 }
144
145 static bool youngergen_may_have_been_dirty(CardValue cv) {
146 return cv == CardTableRS::cur_youngergen_and_prev_nonclean_card;
147 }
148
149 // *** Support for parallel card scanning.
150
151 // dirty and precleaned are equivalent wrt younger_refs_iter.
152 static bool card_is_dirty_wrt_gen_iter(CardValue cv) {
153 return cv == dirty_card;
154 }
155
156 // Returns "true" iff the value "cv" will cause the card containing it
157 // to be scanned in the current traversal. May be overridden by
158 // subtypes.
159 bool card_will_be_scanned(CardValue cv);
160
161 // Returns "true" iff the value "cv" may have represented a dirty card at
162 // some point.
163 bool card_may_have_been_dirty(CardValue cv);
164
165 // Iterate over the portion of the card-table which covers the given
166 // region mr in the given space and apply cl to any dirty sub-regions
167 // of mr. Clears the dirty cards as they are processed.
168 void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,
169 OopsInGenClosure* cl, CardTableRS* ct,
170 uint n_threads);
171
172 // Work method used to implement non_clean_card_iterate_possibly_parallel()
173 // above in the parallel case.
174 virtual void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
175 OopsInGenClosure* cl, CardTableRS* ct,
176 uint n_threads);
177
178 // This is an array, one element per covered region of the card table.
179 // Each entry is itself an array, with one element per chunk in the
180 // covered region. Each entry of these arrays is the lowest non-clean
181 // card of the corresponding chunk containing part of an object from the
182 // previous chunk, or else NULL.
183 typedef CardValue* CardPtr;
184 typedef CardPtr* CardArr;
185 CardArr* _lowest_non_clean;
186 size_t* _lowest_non_clean_chunk_size;
187 uintptr_t* _lowest_non_clean_base_chunk_index;
188 volatile int* _last_LNC_resizing_collection;
189
190 virtual bool is_in_young(oop obj) const;
191 };
192
193 class ClearNoncleanCardWrapper: public MemRegionClosure {
194 DirtyCardToOopClosure* _dirty_card_closure;
195 CardTableRS* _ct;
196 bool _is_par;
197
198 public:
199
200 typedef CardTable::CardValue CardValue;
201 private:
202 // Clears the given card, return true if the corresponding card should be
203 // processed.
204 inline bool clear_card(CardValue* entry);
205 // Work methods called by the clear_card()
206 inline bool clear_card_serial(CardValue* entry);
207 inline bool clear_card_parallel(CardValue* entry);
208 // check alignment of pointer
209 bool is_word_aligned(CardValue* entry);
210
211 public:
212 ClearNoncleanCardWrapper(DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct, bool is_par);
213 void do_MemRegion(MemRegion mr);
214 };
215
216 #endif // SHARE_GC_SHARED_CARDTABLERS_HPP