1 /* 2 * Copyright (c) 2001, 2009, Oracle and/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. 22 * 23 */ 24 25 // Sparse remembered set for a heap region (the "owning" region). Maps 26 // indices of other regions to short sequences of cards in the other region 27 // that might contain pointers into the owner region. 28 29 // These tables only expand while they are accessed in parallel -- 30 // deletions may be done in single-threaded code. This allows us to allow 31 // unsynchronized reads/iterations, as long as expansions caused by 32 // insertions only enqueue old versions for deletions, but do not delete 33 // old versions synchronously. 34 35 class SparsePRTEntry: public CHeapObj { 36 public: 37 enum SomePublicConstants { 38 NullEntry = -1, 39 UnrollFactor = 4 40 }; 41 private: 42 RegionIdx_t _region_ind; 43 int _next_index; 44 CardIdx_t _cards[1]; 45 // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length. 46 // It should always be the last data member. 47 public: 48 // Returns the size of the entry, used for entry allocation. 49 static size_t size() { return sizeof(SparsePRTEntry) + sizeof(CardIdx_t) * (cards_num() - 1); } 50 // Returns the size of the card array. 51 static int cards_num() { 52 // The number of cards should be a multiple of 4, because that's our current 53 // unrolling factor. 54 static const int s = MAX2<int>(G1RSetSparseRegionEntries & ~(UnrollFactor - 1), UnrollFactor); 55 return s; 56 } 57 58 // Set the region_ind to the given value, and delete all cards. 59 inline void init(RegionIdx_t region_ind); 60 61 RegionIdx_t r_ind() const { return _region_ind; } 62 bool valid_entry() const { return r_ind() >= 0; } 63 void set_r_ind(RegionIdx_t rind) { _region_ind = rind; } 64 65 int next_index() const { return _next_index; } 66 int* next_index_addr() { return &_next_index; } 67 void set_next_index(int ni) { _next_index = ni; } 68 69 // Returns "true" iff the entry contains the given card index. 70 inline bool contains_card(CardIdx_t card_index) const; 71 72 // Returns the number of non-NULL card entries. 73 inline int num_valid_cards() const; 74 75 // Requires that the entry not contain the given card index. If there is 76 // space available, add the given card index to the entry and return 77 // "true"; otherwise, return "false" to indicate that the entry is full. 78 enum AddCardResult { 79 overflow, 80 found, 81 added 82 }; 83 inline AddCardResult add_card(CardIdx_t card_index); 84 85 // Copy the current entry's cards into "cards". 86 inline void copy_cards(CardIdx_t* cards) const; 87 // Copy the current entry's cards into the "_card" array of "e." 88 inline void copy_cards(SparsePRTEntry* e) const; 89 90 inline CardIdx_t card(int i) const { return _cards[i]; } 91 }; 92 93 94 class RSHashTable : public CHeapObj { 95 96 friend class RSHashTableIter; 97 98 enum SomePrivateConstants { 99 NullEntry = -1 100 }; 101 102 size_t _capacity; 103 size_t _capacity_mask; 104 size_t _occupied_entries; 105 size_t _occupied_cards; 106 107 SparsePRTEntry* _entries; 108 int* _buckets; 109 int _free_region; 110 int _free_list; 111 112 // Requires that the caller hold a lock preventing parallel modifying 113 // operations, and that the the table be less than completely full. If 114 // an entry for "region_ind" is already in the table, finds it and 115 // returns its address; otherwise returns "NULL." 116 SparsePRTEntry* entry_for_region_ind(RegionIdx_t region_ind) const; 117 118 // Requires that the caller hold a lock preventing parallel modifying 119 // operations, and that the the table be less than completely full. If 120 // an entry for "region_ind" is already in the table, finds it and 121 // returns its address; otherwise allocates, initializes, inserts and 122 // returns a new entry for "region_ind". 123 SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind); 124 125 // Returns the index of the next free entry in "_entries". 126 int alloc_entry(); 127 // Declares the entry "fi" to be free. (It must have already been 128 // deleted from any bucket lists. 129 void free_entry(int fi); 130 131 public: 132 RSHashTable(size_t capacity); 133 ~RSHashTable(); 134 135 // Attempts to ensure that the given card_index in the given region is in 136 // the sparse table. If successful (because the card was already 137 // present, or because it was successfullly added) returns "true". 138 // Otherwise, returns "false" to indicate that the addition would 139 // overflow the entry for the region. The caller must transfer these 140 // entries to a larger-capacity representation. 141 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 142 143 bool get_cards(RegionIdx_t region_id, CardIdx_t* cards); 144 145 bool delete_entry(RegionIdx_t region_id); 146 147 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const; 148 149 void add_entry(SparsePRTEntry* e); 150 151 SparsePRTEntry* get_entry(RegionIdx_t region_id); 152 153 void clear(); 154 155 size_t capacity() const { return _capacity; } 156 size_t capacity_mask() const { return _capacity_mask; } 157 size_t occupied_entries() const { return _occupied_entries; } 158 size_t occupied_cards() const { return _occupied_cards; } 159 size_t mem_size() const; 160 161 SparsePRTEntry* entry(int i) const { return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); } 162 163 void print(); 164 }; 165 166 // ValueObj because will be embedded in HRRS iterator. 167 class RSHashTableIter VALUE_OBJ_CLASS_SPEC { 168 int _tbl_ind; // [-1, 0.._rsht->_capacity) 169 int _bl_ind; // [-1, 0.._rsht->_capacity) 170 short _card_ind; // [0..SparsePRTEntry::cards_num()) 171 RSHashTable* _rsht; 172 size_t _heap_bot_card_ind; 173 174 // If the bucket list pointed to by _bl_ind contains a card, sets 175 // _bl_ind to the index of that entry, and returns the card. 176 // Otherwise, returns SparseEntry::NullEntry. 177 CardIdx_t find_first_card_in_list(); 178 179 // Computes the proper card index for the card whose offset in the 180 // current region (as indicated by _bl_ind) is "ci". 181 // This is subject to errors when there is iteration concurrent with 182 // modification, but these errors should be benign. 183 size_t compute_card_ind(CardIdx_t ci); 184 185 public: 186 RSHashTableIter(size_t heap_bot_card_ind) : 187 _tbl_ind(RSHashTable::NullEntry), 188 _bl_ind(RSHashTable::NullEntry), 189 _card_ind((SparsePRTEntry::cards_num() - 1)), 190 _rsht(NULL), 191 _heap_bot_card_ind(heap_bot_card_ind) 192 {} 193 194 void init(RSHashTable* rsht) { 195 _rsht = rsht; 196 _tbl_ind = -1; // So that first increment gets to 0. 197 _bl_ind = RSHashTable::NullEntry; 198 _card_ind = (SparsePRTEntry::cards_num() - 1); 199 } 200 201 bool has_next(size_t& card_index); 202 }; 203 204 // Concurrent accesss to a SparsePRT must be serialized by some external 205 // mutex. 206 207 class SparsePRTIter; 208 209 class SparsePRT VALUE_OBJ_CLASS_SPEC { 210 // Iterations are done on the _cur hash table, since they only need to 211 // see entries visible at the start of a collection pause. 212 // All other operations are done using the _next hash table. 213 RSHashTable* _cur; 214 RSHashTable* _next; 215 216 HeapRegion* _hr; 217 218 enum SomeAdditionalPrivateConstants { 219 InitialCapacity = 16 220 }; 221 222 void expand(); 223 224 bool _expanded; 225 226 bool expanded() { return _expanded; } 227 void set_expanded(bool b) { _expanded = b; } 228 229 SparsePRT* _next_expanded; 230 231 SparsePRT* next_expanded() { return _next_expanded; } 232 void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; } 233 234 static SparsePRT* _head_expanded_list; 235 236 public: 237 SparsePRT(HeapRegion* hr); 238 239 ~SparsePRT(); 240 241 size_t occupied() const { return _next->occupied_cards(); } 242 size_t mem_size() const; 243 244 // Attempts to ensure that the given card_index in the given region is in 245 // the sparse table. If successful (because the card was already 246 // present, or because it was successfullly added) returns "true". 247 // Otherwise, returns "false" to indicate that the addition would 248 // overflow the entry for the region. The caller must transfer these 249 // entries to a larger-capacity representation. 250 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 251 252 // If the table hold an entry for "region_ind", Copies its 253 // cards into "cards", which must be an array of length at least 254 // "SparePRTEntry::cards_num()", and returns "true"; otherwise, 255 // returns "false". 256 bool get_cards(RegionIdx_t region_ind, CardIdx_t* cards); 257 258 // Return the pointer to the entry associated with the given region. 259 SparsePRTEntry* get_entry(RegionIdx_t region_ind); 260 261 // If there is an entry for "region_ind", removes it and return "true"; 262 // otherwise returns "false." 263 bool delete_entry(RegionIdx_t region_ind); 264 265 // Clear the table, and reinitialize to initial capacity. 266 void clear(); 267 268 // Ensure that "_cur" and "_next" point to the same table. 269 void cleanup(); 270 271 // Clean up all tables on the expanded list. Called single threaded. 272 static void cleanup_all(); 273 RSHashTable* cur() const { return _cur; } 274 275 void init_iterator(SparsePRTIter* sprt_iter); 276 277 static void add_to_expanded_list(SparsePRT* sprt); 278 static SparsePRT* get_from_expanded_list(); 279 280 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const { 281 return _next->contains_card(region_id, card_index); 282 } 283 284 #if 0 285 void verify_is_cleared(); 286 void print(); 287 #endif 288 }; 289 290 291 class SparsePRTIter: public /* RSHashTable:: */RSHashTableIter { 292 public: 293 SparsePRTIter(size_t heap_bot_card_ind) : 294 /* RSHashTable:: */RSHashTableIter(heap_bot_card_ind) 295 {} 296 297 void init(const SparsePRT* sprt) { 298 RSHashTableIter::init(sprt->cur()); 299 } 300 bool has_next(size_t& card_index) { 301 return RSHashTableIter::has_next(card_index); 302 } 303 };