1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
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  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).
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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 || cv == precleaned_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