1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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
32class DirtyCardToOopClosure;
33class Generation;
34class Space;
35class OopsInGenClosure;
36
37// Helper to remember modified oops in all clds.
38class 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
51class 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
101public:
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 // Override. Might want to devirtualize this in the same fashion as
128 // above. Ensures that the value of the card for field says that it's
129 // a younger card in the current collection.
130 virtual void write_ref_field_gc_par(void* field, oop new_val);
131
132 bool is_aligned(HeapWord* addr) {
133 return is_card_aligned(addr);
134 }
135
136 void verify();
137 void initialize();
138
139 void clear_into_younger(Generation* old_gen);
140
141 void invalidate_or_clear(Generation* old_gen);
142
143 bool is_prev_nonclean_card_val(CardValue v) {
144 return
145 youngergen_card <= v &&
146 v <= cur_youngergen_and_prev_nonclean_card &&
147 v != _cur_youngergen_card_val;
148 }
149
150 static bool youngergen_may_have_been_dirty(CardValue cv) {
151 return cv == CardTableRS::cur_youngergen_and_prev_nonclean_card;
152 }
153
154 // *** Support for parallel card scanning.
155
156 // dirty and precleaned are equivalent wrt younger_refs_iter.
157 static bool card_is_dirty_wrt_gen_iter(CardValue cv) {
158 return cv == dirty_card || cv == precleaned_card;
159 }
160
161 // Returns "true" iff the value "cv" will cause the card containing it
162 // to be scanned in the current traversal. May be overridden by
163 // subtypes.
164 bool card_will_be_scanned(CardValue cv);
165
166 // Returns "true" iff the value "cv" may have represented a dirty card at
167 // some point.
168 bool card_may_have_been_dirty(CardValue cv);
169
170 // Iterate over the portion of the card-table which covers the given
171 // region mr in the given space and apply cl to any dirty sub-regions
172 // of mr. Clears the dirty cards as they are processed.
173 void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,
174 OopsInGenClosure* cl, CardTableRS* ct,
175 uint n_threads);
176
177 // Work method used to implement non_clean_card_iterate_possibly_parallel()
178 // above in the parallel case.
179 virtual void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
180 OopsInGenClosure* cl, CardTableRS* ct,
181 uint n_threads);
182
183 // This is an array, one element per covered region of the card table.
184 // Each entry is itself an array, with one element per chunk in the
185 // covered region. Each entry of these arrays is the lowest non-clean
186 // card of the corresponding chunk containing part of an object from the
187 // previous chunk, or else NULL.
188 typedef CardValue* CardPtr;
189 typedef CardPtr* CardArr;
190 CardArr* _lowest_non_clean;
191 size_t* _lowest_non_clean_chunk_size;
192 uintptr_t* _lowest_non_clean_base_chunk_index;
193 volatile int* _last_LNC_resizing_collection;
194
195 virtual bool is_in_young(oop obj) const;
196};
197
198class ClearNoncleanCardWrapper: public MemRegionClosure {
199 DirtyCardToOopClosure* _dirty_card_closure;
200 CardTableRS* _ct;
201 bool _is_par;
202
203public:
204
205 typedef CardTable::CardValue CardValue;
206private:
207 // Clears the given card, return true if the corresponding card should be
208 // processed.
209 inline bool clear_card(CardValue* entry);
210 // Work methods called by the clear_card()
211 inline bool clear_card_serial(CardValue* entry);
212 inline bool clear_card_parallel(CardValue* entry);
213 // check alignment of pointer
214 bool is_word_aligned(CardValue* entry);
215
216public:
217 ClearNoncleanCardWrapper(DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct, bool is_par);
218 void do_MemRegion(MemRegion mr);
219};
220
221#endif // SHARE_GC_SHARED_CARDTABLERS_HPP
222