1 /* 2 * Copyright (c) 2001, 2014, 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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP 27 28 #include "gc_implementation/g1/g1CollectedHeap.hpp" 29 #include "gc_implementation/g1/heapRegion.hpp" 30 #include "memory/allocation.hpp" 31 #include "memory/cardTableModRefBS.hpp" 32 #include "runtime/mutex.hpp" 33 #include "utilities/globalDefinitions.hpp" 34 35 // Sparse remembered set for a heap region (the "owning" region). Maps 36 // indices of other regions to short sequences of cards in the other region 37 // that might contain pointers into the owner region. 38 39 // These tables only expand while they are accessed in parallel -- 40 // deletions may be done in single-threaded code. This allows us to allow 41 // unsynchronized reads/iterations, as long as expansions caused by 42 // insertions only enqueue old versions for deletions, but do not delete 43 // old versions synchronously. 44 45 class SparsePRTEntry: public CHeapObj<mtGC> { 46 public: 47 enum SomePublicConstants { 48 NullEntry = -1, 49 UnrollFactor = 4 50 }; 51 private: 52 RegionIdx_t _region_ind; 53 int _next_index; 54 CardIdx_t _cards[1]; 55 // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length. 56 // It should always be the last data member. 57 public: 58 // Returns the size of the entry, used for entry allocation. 59 static size_t size() { return sizeof(SparsePRTEntry) + sizeof(CardIdx_t) * (cards_num() - 1); } 60 // Returns the size of the card array. 61 static int cards_num() { 62 // The number of cards should be a multiple of 4, because that's our current 63 // unrolling factor. 64 static const int s = MAX2<int>(G1RSetSparseRegionEntries & ~(UnrollFactor - 1), UnrollFactor); 65 return s; 66 } 67 68 // Set the region_ind to the given value, and delete all cards. 69 inline void init(RegionIdx_t region_ind); 70 71 RegionIdx_t r_ind() const { return _region_ind; } 72 bool valid_entry() const { return r_ind() >= 0; } 73 void set_r_ind(RegionIdx_t rind) { _region_ind = rind; } 74 75 int next_index() const { return _next_index; } 76 int* next_index_addr() { return &_next_index; } 77 void set_next_index(int ni) { _next_index = ni; } 78 79 // Returns "true" iff the entry contains the given card index. 80 inline bool contains_card(CardIdx_t card_index) const; 81 82 // Returns the number of non-NULL card entries. 83 inline int num_valid_cards() const; 84 85 // Requires that the entry not contain the given card index. If there is 86 // space available, add the given card index to the entry and return 87 // "true"; otherwise, return "false" to indicate that the entry is full. 88 enum AddCardResult { 89 overflow, 90 found, 91 added 92 }; 93 inline AddCardResult add_card(CardIdx_t card_index); 94 95 // Copy the current entry's cards into "cards". 96 inline void copy_cards(CardIdx_t* cards) const; 97 // Copy the current entry's cards into the "_card" array of "e." 98 inline void copy_cards(SparsePRTEntry* e) const; 99 100 inline CardIdx_t card(int i) const { return _cards[i]; } 101 }; 102 103 104 class RSHashTable : public CHeapObj<mtGC> { 105 106 friend class RSHashTableIter; 107 108 enum SomePrivateConstants { 109 NullEntry = -1 110 }; 111 112 size_t _capacity; 113 size_t _capacity_mask; 114 size_t _occupied_entries; 115 size_t _occupied_cards; 116 117 SparsePRTEntry* _entries; 118 int* _buckets; 119 int _free_region; 120 int _free_list; 121 122 // Requires that the caller hold a lock preventing parallel modifying 123 // operations, and that the the table be less than completely full. If 124 // an entry for "region_ind" is already in the table, finds it and 125 // returns its address; otherwise allocates, initializes, inserts and 126 // returns a new entry for "region_ind". 127 SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind); 128 129 // Returns the index of the next free entry in "_entries". 130 int alloc_entry(); 131 // Declares the entry "fi" to be free. (It must have already been 132 // deleted from any bucket lists. 133 void free_entry(int fi); 134 135 public: 136 RSHashTable(size_t capacity); 137 ~RSHashTable(); 138 139 // Attempts to ensure that the given card_index in the given region is in 140 // the sparse table. If successful (because the card was already 141 // present, or because it was successfully added) returns "true". 142 // Otherwise, returns "false" to indicate that the addition would 143 // overflow the entry for the region. The caller must transfer these 144 // entries to a larger-capacity representation. 145 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 146 147 bool get_cards(RegionIdx_t region_id, CardIdx_t* cards); 148 149 bool delete_entry(RegionIdx_t region_id); 150 151 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const; 152 153 void add_entry(SparsePRTEntry* e); 154 155 SparsePRTEntry* get_entry(RegionIdx_t region_id) const; 156 157 void clear(); 158 159 size_t capacity() const { return _capacity; } 160 size_t capacity_mask() const { return _capacity_mask; } 161 size_t occupied_entries() const { return _occupied_entries; } 162 size_t occupied_cards() const { return _occupied_cards; } 163 size_t mem_size() const; 164 165 SparsePRTEntry* entry(int i) const { return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); } 166 167 void print(); 168 }; 169 170 // ValueObj because will be embedded in HRRS iterator. 171 class RSHashTableIter VALUE_OBJ_CLASS_SPEC { 172 int _tbl_ind; // [-1, 0.._rsht->_capacity) 173 int _bl_ind; // [-1, 0.._rsht->_capacity) 174 short _card_ind; // [0..SparsePRTEntry::cards_num()) 175 RSHashTable* _rsht; 176 177 // If the bucket list pointed to by _bl_ind contains a card, sets 178 // _bl_ind to the index of that entry, and returns the card. 179 // Otherwise, returns SparseEntry::NullEntry. 180 CardIdx_t find_first_card_in_list(); 181 182 // Computes the proper card index for the card whose offset in the 183 // current region (as indicated by _bl_ind) is "ci". 184 // This is subject to errors when there is iteration concurrent with 185 // modification, but these errors should be benign. 186 size_t compute_card_ind(CardIdx_t ci); 187 188 public: 189 RSHashTableIter(RSHashTable* rsht) : 190 _tbl_ind(RSHashTable::NullEntry), // So that first increment gets to 0. 191 _bl_ind(RSHashTable::NullEntry), 192 _card_ind((SparsePRTEntry::cards_num() - 1)), 193 _rsht(rsht) {} 194 195 bool has_next(size_t& card_index); 196 }; 197 198 // Concurrent access to a SparsePRT must be serialized by some external mutex. 199 200 class SparsePRTIter; 201 class SparsePRTCleanupTask; 202 203 class SparsePRT VALUE_OBJ_CLASS_SPEC { 204 friend class SparsePRTCleanupTask; 205 206 // Iterations are done on the _cur hash table, since they only need to 207 // see entries visible at the start of a collection pause. 208 // All other operations are done using the _next hash table. 209 RSHashTable* _cur; 210 RSHashTable* _next; 211 212 HeapRegion* _hr; 213 214 enum SomeAdditionalPrivateConstants { 215 InitialCapacity = 16 216 }; 217 218 void expand(); 219 220 bool _expanded; 221 222 bool expanded() { return _expanded; } 223 void set_expanded(bool b) { _expanded = b; } 224 225 SparsePRT* _next_expanded; 226 227 SparsePRT* next_expanded() { return _next_expanded; } 228 void set_next_expanded(SparsePRT* nxt) { _next_expanded = nxt; } 229 230 bool should_be_on_expanded_list(); 231 232 static SparsePRT* _head_expanded_list; 233 234 public: 235 SparsePRT(HeapRegion* hr); 236 237 ~SparsePRT(); 238 239 size_t occupied() const { return _next->occupied_cards(); } 240 size_t mem_size() const; 241 242 // Attempts to ensure that the given card_index in the given region is in 243 // the sparse table. If successful (because the card was already 244 // present, or because it was successfully added) returns "true". 245 // Otherwise, returns "false" to indicate that the addition would 246 // overflow the entry for the region. The caller must transfer these 247 // entries to a larger-capacity representation. 248 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 249 250 // If the table hold an entry for "region_ind", Copies its 251 // cards into "cards", which must be an array of length at least 252 // "SparePRTEntry::cards_num()", and returns "true"; otherwise, 253 // returns "false". 254 bool get_cards(RegionIdx_t region_ind, CardIdx_t* cards); 255 256 // Return the pointer to the entry associated with the given region. 257 SparsePRTEntry* get_entry(RegionIdx_t region_ind); 258 259 // If there is an entry for "region_ind", removes it and return "true"; 260 // otherwise returns "false." 261 bool delete_entry(RegionIdx_t region_ind); 262 263 // Clear the table, and reinitialize to initial capacity. 264 void clear(); 265 266 // Ensure that "_cur" and "_next" point to the same table. 267 void cleanup(); 268 269 // Clean up all tables on the expanded list. Called single threaded. 270 static void cleanup_all(); 271 RSHashTable* cur() const { return _cur; } 272 273 static void add_to_expanded_list(SparsePRT* sprt); 274 static SparsePRT* get_from_expanded_list(); 275 276 // The purpose of these three methods is to help the GC workers 277 // during the cleanup pause to recreate the expanded list, purging 278 // any tables from it that belong to regions that are freed during 279 // cleanup (if we don't purge those tables, there is a race that 280 // causes various crashes; see CR 7014261). 281 // 282 // We chose to recreate the expanded list, instead of purging 283 // entries from it by iterating over it, to avoid this serial phase 284 // at the end of the cleanup pause. 285 // 286 // The three methods below work as follows: 287 // * reset_for_cleanup_tasks() : Nulls the expanded list head at the 288 // start of the cleanup pause. 289 // * do_cleanup_work() : Called by the cleanup workers for every 290 // region that is not free / is being freed by the cleanup 291 // pause. It creates a list of expanded tables whose head / tail 292 // are on the thread-local SparsePRTCleanupTask object. 293 // * finish_cleanup_task() : Called by the cleanup workers after 294 // they complete their cleanup task. It adds the local list into 295 // the global expanded list. It assumes that the 296 // ParGCRareEvent_lock is being held to ensure MT-safety. 297 static void reset_for_cleanup_tasks(); 298 void do_cleanup_work(SparsePRTCleanupTask* sprt_cleanup_task); 299 static void finish_cleanup_task(SparsePRTCleanupTask* sprt_cleanup_task); 300 301 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const { 302 return _next->contains_card(region_id, card_index); 303 } 304 }; 305 306 class SparsePRTIter: public RSHashTableIter { 307 public: 308 SparsePRTIter(const SparsePRT* sprt) : 309 RSHashTableIter(sprt->cur()) {} 310 311 bool has_next(size_t& card_index) { 312 return RSHashTableIter::has_next(card_index); 313 } 314 }; 315 316 // This allows each worker during a cleanup pause to create a 317 // thread-local list of sparse tables that have been expanded and need 318 // to be processed at the beginning of the next GC pause. This lists 319 // are concatenated into the single expanded list at the end of the 320 // cleanup pause. 321 class SparsePRTCleanupTask VALUE_OBJ_CLASS_SPEC { 322 private: 323 SparsePRT* _head; 324 SparsePRT* _tail; 325 326 public: 327 SparsePRTCleanupTask() : _head(NULL), _tail(NULL) { } 328 329 void add(SparsePRT* sprt); 330 SparsePRT* head() { return _head; } 331 SparsePRT* tail() { return _tail; } 332 }; 333 334 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_SPARSEPRT_HPP