1 /* 2 * Copyright (c) 2000, 2016, 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_SHARED_CARDTABLEMODREFBS_HPP 26 #define SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP 27 28 #include "gc/shared/modRefBarrierSet.hpp" 29 #include "oops/oop.hpp" 30 31 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and 32 // enumerate ref fields that have been modified (since the last 33 // enumeration.) 34 35 // As it currently stands, this barrier is *imprecise*: when a ref field in 36 // an object "o" is modified, the card table entry for the card containing 37 // the head of "o" is dirtied, not necessarily the card containing the 38 // modified field itself. For object arrays, however, the barrier *is* 39 // precise; only the card containing the modified element is dirtied. 40 // Closures used to scan dirty cards should take these 41 // considerations into account. 42 43 class CardTableModRefBS: public ModRefBarrierSet { 44 // Some classes get to look at some private stuff. 45 friend class VMStructs; 46 protected: 47 48 enum CardValues { 49 clean_card = -1, 50 // The mask contains zeros in places for all other values. 51 clean_card_mask = clean_card - 31, 52 53 dirty_card = 0, 54 precleaned_card = 1, 55 claimed_card = 2, 56 deferred_card = 4, 57 last_card = 8, 58 CT_MR_BS_last_reserved = 16 59 }; 60 61 // a word's worth (row) of clean card values 62 static const intptr_t clean_card_row = (intptr_t)(-1); 63 64 // The declaration order of these const fields is important; see the 65 // constructor before changing. 66 const MemRegion _whole_heap; // the region covered by the card table 67 size_t _guard_index; // index of very last element in the card 68 // table; it is set to a guard value 69 // (last_card) and should never be modified 70 size_t _last_valid_index; // index of the last valid element 71 const size_t _page_size; // page size used when mapping _byte_map 72 size_t _byte_map_size; // in bytes 73 jbyte* _byte_map; // the card marking array 74 75 int _cur_covered_regions; 76 // The covered regions should be in address order. 77 MemRegion* _covered; 78 // The committed regions correspond one-to-one to the covered regions. 79 // They represent the card-table memory that has been committed to service 80 // the corresponding covered region. It may be that committed region for 81 // one covered region corresponds to a larger region because of page-size 82 // roundings. Thus, a committed region for one covered region may 83 // actually extend onto the card-table space for the next covered region. 84 MemRegion* _committed; 85 86 // The last card is a guard card, and we commit the page for it so 87 // we can use the card for verification purposes. We make sure we never 88 // uncommit the MemRegion for that page. 89 MemRegion _guard_region; 90 91 protected: 92 inline size_t compute_byte_map_size(); 93 94 // Finds and return the index of the region, if any, to which the given 95 // region would be contiguous. If none exists, assign a new region and 96 // returns its index. Requires that no more than the maximum number of 97 // covered regions defined in the constructor are ever in use. 98 int find_covering_region_by_base(HeapWord* base); 99 100 // Same as above, but finds the region containing the given address 101 // instead of starting at a given base address. 102 int find_covering_region_containing(HeapWord* addr); 103 104 // Resize one of the regions covered by the remembered set. 105 virtual void resize_covered_region(MemRegion new_region); 106 107 // Returns the leftmost end of a committed region corresponding to a 108 // covered region before covered region "ind", or else "NULL" if "ind" is 109 // the first covered region. 110 HeapWord* largest_prev_committed_end(int ind) const; 111 112 // Returns the part of the region mr that doesn't intersect with 113 // any committed region other than self. Used to prevent uncommitting 114 // regions that are also committed by other regions. Also protects 115 // against uncommitting the guard region. 116 MemRegion committed_unique_to_self(int self, MemRegion mr) const; 117 118 // Mapping from address to card marking array entry 119 jbyte* byte_for(const void* p) const { 120 assert(_whole_heap.contains(p), 121 "Attempt to access p = " PTR_FORMAT " out of bounds of " 122 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 123 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 124 jbyte* result = &byte_map_base[uintptr_t(p) >> card_shift]; 125 assert(result >= _byte_map && result < _byte_map + _byte_map_size, 126 "out of bounds accessor for card marking array"); 127 return result; 128 } 129 130 // The card table byte one after the card marking array 131 // entry for argument address. Typically used for higher bounds 132 // for loops iterating through the card table. 133 jbyte* byte_after(const void* p) const { 134 return byte_for(p) + 1; 135 } 136 137 protected: 138 // Dirty the bytes corresponding to "mr" (not all of which must be 139 // covered.) 140 void dirty_MemRegion(MemRegion mr); 141 142 // Clear (to clean_card) the bytes entirely contained within "mr" (not 143 // all of which must be covered.) 144 void clear_MemRegion(MemRegion mr); 145 146 public: 147 // Constants 148 enum SomePublicConstants { 149 card_shift = 9, 150 card_size = 1 << card_shift, 151 card_size_in_words = card_size / sizeof(HeapWord) 152 }; 153 154 static int clean_card_val() { return clean_card; } 155 static int clean_card_mask_val() { return clean_card_mask; } 156 static int dirty_card_val() { return dirty_card; } 157 static int claimed_card_val() { return claimed_card; } 158 static int precleaned_card_val() { return precleaned_card; } 159 static int deferred_card_val() { return deferred_card; } 160 161 virtual void initialize(); 162 163 // *** Barrier set functions. 164 165 bool has_write_ref_pre_barrier() { return false; } 166 167 // Initialization utilities; covered_words is the size of the covered region 168 // in, um, words. 169 inline size_t cards_required(size_t covered_words) { 170 // Add one for a guard card, used to detect errors. 171 const size_t words = align_up(covered_words, card_size_in_words); 172 return words / card_size_in_words + 1; 173 } 174 175 protected: 176 177 CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti); 178 ~CardTableModRefBS(); 179 180 // Record a reference update. Note that these versions are precise! 181 // The scanning code has to handle the fact that the write barrier may be 182 // either precise or imprecise. We make non-virtual inline variants of 183 // these functions here for performance. 184 185 void write_ref_field_work(oop obj, size_t offset, oop newVal); 186 virtual void write_ref_field_work(void* field, oop newVal, bool release); 187 public: 188 189 bool has_write_ref_array_opt() { return true; } 190 bool has_write_region_opt() { return true; } 191 192 inline void inline_write_region(MemRegion mr) { 193 dirty_MemRegion(mr); 194 } 195 protected: 196 void write_region_work(MemRegion mr) { 197 inline_write_region(mr); 198 } 199 public: 200 201 inline void inline_write_ref_array(MemRegion mr) { 202 dirty_MemRegion(mr); 203 } 204 protected: 205 void write_ref_array_work(MemRegion mr) { 206 inline_write_ref_array(mr); 207 } 208 public: 209 210 bool is_aligned(HeapWord* addr) { 211 return is_card_aligned(addr); 212 } 213 214 // *** Card-table-barrier-specific things. 215 216 template <class T> inline void inline_write_ref_field_pre(T* field, oop newVal) {} 217 218 template <class T> inline void inline_write_ref_field(T* field, oop newVal, bool release); 219 220 // These are used by G1, when it uses the card table as a temporary data 221 // structure for card claiming. 222 bool is_card_dirty(size_t card_index) { 223 return _byte_map[card_index] == dirty_card_val(); 224 } 225 226 void mark_card_dirty(size_t card_index) { 227 _byte_map[card_index] = dirty_card_val(); 228 } 229 230 bool is_card_clean(size_t card_index) { 231 return _byte_map[card_index] == clean_card_val(); 232 } 233 234 // Card marking array base (adjusted for heap low boundary) 235 // This would be the 0th element of _byte_map, if the heap started at 0x0. 236 // But since the heap starts at some higher address, this points to somewhere 237 // before the beginning of the actual _byte_map. 238 jbyte* byte_map_base; 239 240 // Return true if "p" is at the start of a card. 241 bool is_card_aligned(HeapWord* p) { 242 jbyte* pcard = byte_for(p); 243 return (addr_for(pcard) == p); 244 } 245 246 HeapWord* align_to_card_boundary(HeapWord* p) { 247 jbyte* pcard = byte_for(p + card_size_in_words - 1); 248 return addr_for(pcard); 249 } 250 251 // The kinds of precision a CardTableModRefBS may offer. 252 enum PrecisionStyle { 253 Precise, 254 ObjHeadPreciseArray 255 }; 256 257 // Tells what style of precision this card table offers. 258 PrecisionStyle precision() { 259 return ObjHeadPreciseArray; // Only one supported for now. 260 } 261 262 // ModRefBS functions. 263 virtual void invalidate(MemRegion mr); 264 void clear(MemRegion mr); 265 void dirty(MemRegion mr); 266 267 // *** Card-table-RemSet-specific things. 268 269 static uintx ct_max_alignment_constraint(); 270 271 // Apply closure "cl" to the dirty cards containing some part of 272 // MemRegion "mr". 273 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl); 274 275 // Return the MemRegion corresponding to the first maximal run 276 // of dirty cards lying completely within MemRegion mr. 277 // If reset is "true", then sets those card table entries to the given 278 // value. 279 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset, 280 int reset_val); 281 282 // Provide read-only access to the card table array. 283 const jbyte* byte_for_const(const void* p) const { 284 return byte_for(p); 285 } 286 const jbyte* byte_after_const(const void* p) const { 287 return byte_after(p); 288 } 289 290 // Mapping from card marking array entry to address of first word 291 HeapWord* addr_for(const jbyte* p) const { 292 assert(p >= _byte_map && p < _byte_map + _byte_map_size, 293 "out of bounds access to card marking array. p: " PTR_FORMAT 294 " _byte_map: " PTR_FORMAT " _byte_map + _byte_map_size: " PTR_FORMAT, 295 p2i(p), p2i(_byte_map), p2i(_byte_map + _byte_map_size)); 296 size_t delta = pointer_delta(p, byte_map_base, sizeof(jbyte)); 297 HeapWord* result = (HeapWord*) (delta << card_shift); 298 assert(_whole_heap.contains(result), 299 "Returning result = " PTR_FORMAT " out of bounds of " 300 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 301 p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 302 return result; 303 } 304 305 // Mapping from address to card marking array index. 306 size_t index_for(void* p) { 307 assert(_whole_heap.contains(p), 308 "Attempt to access p = " PTR_FORMAT " out of bounds of " 309 " card marking array's _whole_heap = [" PTR_FORMAT "," PTR_FORMAT ")", 310 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())); 311 return byte_for(p) - _byte_map; 312 } 313 314 const jbyte* byte_for_index(const size_t card_index) const { 315 return _byte_map + card_index; 316 } 317 318 // Print a description of the memory for the barrier set 319 virtual void print_on(outputStream* st) const; 320 321 void verify(); 322 void verify_guard(); 323 324 // val_equals -> it will check that all cards covered by mr equal val 325 // !val_equals -> it will check that all cards covered by mr do not equal val 326 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN; 327 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN; 328 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN; 329 }; 330 331 template<> 332 struct BarrierSet::GetName<CardTableModRefBS> { 333 static const BarrierSet::Name value = BarrierSet::CardTableModRef; 334 }; 335 336 337 #endif // SHARE_VM_GC_SHARED_CARDTABLEMODREFBS_HPP