1 /* 2 * Copyright (c) 2001, 2018, 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_G1_SPARSEPRT_HPP 26 #define SHARE_VM_GC_G1_SPARSEPRT_HPP 27 28 #include "gc/g1/g1CollectedHeap.hpp" 29 #include "gc/g1/heapRegion.hpp" 30 #include "gc/shared/cardTableBarrierSet.hpp" 31 #include "memory/allocation.hpp" 32 #include "runtime/mutex.hpp" 33 #include "utilities/align.hpp" 34 #include "utilities/globalDefinitions.hpp" 35 36 // Sparse remembered set for a heap region (the "owning" region). Maps 37 // indices of other regions to short sequences of cards in the other region 38 // that might contain pointers into the owner region. 39 40 class SparsePRTEntry: public CHeapObj<mtGC> { 41 private: 42 // The type of a card entry. 43 typedef uint16_t card_elem_t; 44 45 // We need to make sizeof(SparsePRTEntry) an even multiple of maximum member size, 46 // in order to force correct alignment that could otherwise cause SIGBUS errors 47 // when reading the member variables. This calculates the minimum number of card 48 // array elements required to get that alignment. 49 static const size_t card_array_alignment = sizeof(int) / sizeof(card_elem_t); 50 51 RegionIdx_t _region_ind; 52 int _next_index; 53 int _next_null; 54 // The actual cards stored in this array. 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 card_elem_t _cards[card_array_alignment]; 58 59 // Copy the current entry's cards into "cards". 60 inline void copy_cards(card_elem_t* cards) const; 61 public: 62 // Returns the size of the entry, used for entry allocation. 63 static size_t size() { return sizeof(SparsePRTEntry) + sizeof(card_elem_t) * (cards_num() - card_array_alignment); } 64 // Returns the size of the card array. 65 static int cards_num() { 66 return align_up((int)G1RSetSparseRegionEntries, (int)card_array_alignment); 67 } 68 69 // Set the region_ind to the given value, and delete all cards. 70 inline void init(RegionIdx_t region_ind); 71 72 RegionIdx_t r_ind() const { return _region_ind; } 73 bool valid_entry() const { return r_ind() >= 0; } 74 void set_r_ind(RegionIdx_t rind) { _region_ind = rind; } 75 76 int next_index() const { return _next_index; } 77 int* next_index_addr() { return &_next_index; } 78 void set_next_index(int ni) { _next_index = ni; } 79 80 // Returns "true" iff the entry contains the given card index. 81 inline bool contains_card(CardIdx_t card_index) const; 82 83 // Returns the number of non-NULL card entries. 84 inline int num_valid_cards() const { return _next_null; } 85 86 // Requires that the entry not contain the given card index. If there is 87 // space available, add the given card index to the entry and return 88 // "true"; otherwise, return "false" to indicate that the entry is full. 89 enum AddCardResult { 90 overflow, 91 found, 92 added 93 }; 94 inline AddCardResult add_card(CardIdx_t card_index); 95 96 // Copy the current entry's cards into the "_card" array of "e." 97 inline void copy_cards(SparsePRTEntry* e) const; 98 99 inline CardIdx_t card(int i) const { 100 assert(i >= 0, "must be nonnegative"); 101 assert(i < cards_num(), "range checking"); 102 return (CardIdx_t)_cards[i]; 103 } 104 }; 105 106 class RSHashTable : public CHeapObj<mtGC> { 107 108 friend class RSHashTableIter; 109 110 111 // Inverse maximum hash table occupancy used. 112 static float TableOccupancyFactor; 113 114 size_t _num_entries; 115 116 size_t _capacity; 117 size_t _capacity_mask; 118 size_t _occupied_entries; 119 size_t _occupied_cards; 120 121 SparsePRTEntry* _entries; 122 int* _buckets; 123 int _free_region; 124 int _free_list; 125 126 // Requires that the caller hold a lock preventing parallel modifying 127 // operations, and that the the table be less than completely full. If 128 // an entry for "region_ind" is already in the table, finds it and 129 // returns its address; otherwise allocates, initializes, inserts and 130 // returns a new entry for "region_ind". 131 SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind); 132 133 // Returns the index of the next free entry in "_entries". 134 int alloc_entry(); 135 // Declares the entry "fi" to be free. (It must have already been 136 // deleted from any bucket lists. 137 void free_entry(int fi); 138 139 public: 140 RSHashTable(size_t capacity); 141 ~RSHashTable(); 142 143 static const int NullEntry = -1; 144 145 bool should_expand() const { return _occupied_entries == _num_entries; } 146 147 // Attempts to ensure that the given card_index in the given region is in 148 // the sparse table. If successful (because the card was already 149 // present, or because it was successfully added) returns "true". 150 // Otherwise, returns "false" to indicate that the addition would 151 // overflow the entry for the region. The caller must transfer these 152 // entries to a larger-capacity representation. 153 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 154 155 bool delete_entry(RegionIdx_t region_id); 156 157 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const; 158 159 void add_entry(SparsePRTEntry* e); 160 161 SparsePRTEntry* get_entry(RegionIdx_t region_id) const; 162 163 void clear(); 164 165 size_t capacity() const { return _capacity; } 166 size_t capacity_mask() const { return _capacity_mask; } 167 size_t occupied_entries() const { return _occupied_entries; } 168 size_t occupied_cards() const { return _occupied_cards; } 169 size_t mem_size() const; 170 // The number of SparsePRTEntry instances available. 171 size_t num_entries() const { return _num_entries; } 172 173 SparsePRTEntry* entry(int i) const { 174 assert(i >= 0 && (size_t)i < _num_entries, "precondition"); 175 return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i); 176 } 177 178 void print(); 179 }; 180 181 // This is embedded in HRRS iterator. 182 class RSHashTableIter { 183 // Return value indicating "invalid/no card". 184 static const int NoCardFound = -1; 185 186 int _tbl_ind; // [-1, 0.._rsht->_capacity) 187 int _bl_ind; // [-1, 0.._rsht->_capacity) 188 short _card_ind; // [0..SparsePRTEntry::cards_num()) 189 RSHashTable* _rsht; 190 191 // If the bucket list pointed to by _bl_ind contains a card, sets 192 // _bl_ind to the index of that entry, 193 // Returns the card found if there is, otherwise returns InvalidCard. 194 CardIdx_t find_first_card_in_list(); 195 196 // Computes the proper card index for the card whose offset in the 197 // current region (as indicated by _bl_ind) is "ci". 198 // This is subject to errors when there is iteration concurrent with 199 // modification, but these errors should be benign. 200 size_t compute_card_ind(CardIdx_t ci); 201 202 public: 203 RSHashTableIter(RSHashTable* rsht) : 204 _tbl_ind(RSHashTable::NullEntry), // So that first increment gets to 0. 205 _bl_ind(RSHashTable::NullEntry), 206 _card_ind((SparsePRTEntry::cards_num() - 1)), 207 _rsht(rsht) {} 208 209 bool has_next(size_t& card_index); 210 }; 211 212 // Concurrent access to a SparsePRT must be serialized by some external mutex. 213 214 class SparsePRTIter; 215 216 class SparsePRT { 217 friend class SparsePRTIter; 218 219 RSHashTable* _table; 220 221 enum SomeAdditionalPrivateConstants { 222 InitialCapacity = 16 223 }; 224 225 void expand(); 226 227 public: 228 SparsePRT(); 229 ~SparsePRT(); 230 231 size_t occupied() const { return _table->occupied_cards(); } 232 size_t mem_size() const; 233 234 // Attempts to ensure that the given card_index in the given region is in 235 // the sparse table. If successful (because the card was already 236 // present, or because it was successfully added) returns "true". 237 // Otherwise, returns "false" to indicate that the addition would 238 // overflow the entry for the region. The caller must transfer these 239 // entries to a larger-capacity representation. 240 bool add_card(RegionIdx_t region_id, CardIdx_t card_index); 241 242 // Return the pointer to the entry associated with the given region. 243 SparsePRTEntry* get_entry(RegionIdx_t region_ind); 244 245 // If there is an entry for "region_ind", removes it and return "true"; 246 // otherwise returns "false." 247 bool delete_entry(RegionIdx_t region_ind); 248 249 // Clear the table, and reinitialize to initial capacity. 250 void clear(); 251 252 bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const { 253 return _table->contains_card(region_id, card_index); 254 } 255 }; 256 257 class SparsePRTIter: public RSHashTableIter { 258 public: 259 SparsePRTIter(const SparsePRT* sprt) : 260 RSHashTableIter(sprt->_table) { } 261 262 bool has_next(size_t& card_index) { 263 return RSHashTableIter::has_next(card_index); 264 } 265 }; 266 267 #endif // SHARE_VM_GC_G1_SPARSEPRT_HPP