Mercurial > hg > truffle
annotate src/share/vm/memory/blockOffsetTable.hpp @ 301:387a62b4be60
6728478: Assertion at parallel promotion from young to old generation
Summary: The fix avoids a call to address_for_index() in this particular situation where it is not known if the passed index is in bounds.
Reviewed-by: tonyp
| author | jmasa |
|---|---|
| date | Wed, 20 Aug 2008 23:05:04 -0700 |
| parents | a61af66fc99e |
| children | 9ee9cf798b59 2564c620fa42 |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
| 20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
| 21 * have any questions. | |
| 22 * | |
| 23 */ | |
| 24 | |
| 25 // The CollectedHeap type requires subtypes to implement a method | |
| 26 // "block_start". For some subtypes, notably generational | |
| 27 // systems using card-table-based write barriers, the efficiency of this | |
| 28 // operation may be important. Implementations of the "BlockOffsetArray" | |
| 29 // class may be useful in providing such efficient implementations. | |
| 30 // | |
| 31 // BlockOffsetTable (abstract) | |
| 32 // - BlockOffsetArray (abstract) | |
| 33 // - BlockOffsetArrayNonContigSpace | |
| 34 // - BlockOffsetArrayContigSpace | |
| 35 // | |
| 36 | |
| 37 class ContiguousSpace; | |
| 38 class SerializeOopClosure; | |
| 39 | |
| 40 ////////////////////////////////////////////////////////////////////////// | |
| 41 // The BlockOffsetTable "interface" | |
| 42 ////////////////////////////////////////////////////////////////////////// | |
| 43 class BlockOffsetTable VALUE_OBJ_CLASS_SPEC { | |
| 44 friend class VMStructs; | |
| 45 protected: | |
| 46 // These members describe the region covered by the table. | |
| 47 | |
| 48 // The space this table is covering. | |
| 49 HeapWord* _bottom; // == reserved.start | |
| 50 HeapWord* _end; // End of currently allocated region. | |
| 51 | |
| 52 public: | |
| 53 // Initialize the table to cover the given space. | |
| 54 // The contents of the initial table are undefined. | |
| 55 BlockOffsetTable(HeapWord* bottom, HeapWord* end): | |
| 56 _bottom(bottom), _end(end) { | |
| 57 assert(_bottom <= _end, "arguments out of order"); | |
| 58 } | |
| 59 | |
| 60 // Note that the committed size of the covered space may have changed, | |
| 61 // so the table size might also wish to change. | |
| 62 virtual void resize(size_t new_word_size) = 0; | |
| 63 | |
| 64 virtual void set_bottom(HeapWord* new_bottom) { | |
| 65 assert(new_bottom <= _end, "new_bottom > _end"); | |
| 66 _bottom = new_bottom; | |
| 67 resize(pointer_delta(_end, _bottom)); | |
| 68 } | |
| 69 | |
| 70 // Requires "addr" to be contained by a block, and returns the address of | |
| 71 // the start of that block. | |
| 72 virtual HeapWord* block_start_unsafe(const void* addr) const = 0; | |
| 73 | |
| 74 // Returns the address of the start of the block containing "addr", or | |
| 75 // else "null" if it is covered by no block. | |
| 76 HeapWord* block_start(const void* addr) const; | |
| 77 }; | |
| 78 | |
| 79 ////////////////////////////////////////////////////////////////////////// | |
| 80 // One implementation of "BlockOffsetTable," the BlockOffsetArray, | |
| 81 // divides the covered region into "N"-word subregions (where | |
| 82 // "N" = 2^"LogN". An array with an entry for each such subregion | |
| 83 // indicates how far back one must go to find the start of the | |
| 84 // chunk that includes the first word of the subregion. | |
| 85 // | |
| 86 // Each BlockOffsetArray is owned by a Space. However, the actual array | |
| 87 // may be shared by several BlockOffsetArrays; this is useful | |
| 88 // when a single resizable area (such as a generation) is divided up into | |
| 89 // several spaces in which contiguous allocation takes place. (Consider, | |
| 90 // for example, the garbage-first generation.) | |
| 91 | |
| 92 // Here is the shared array type. | |
| 93 ////////////////////////////////////////////////////////////////////////// | |
| 94 // BlockOffsetSharedArray | |
| 95 ////////////////////////////////////////////////////////////////////////// | |
| 96 class BlockOffsetSharedArray: public CHeapObj { | |
| 97 friend class BlockOffsetArray; | |
| 98 friend class BlockOffsetArrayNonContigSpace; | |
| 99 friend class BlockOffsetArrayContigSpace; | |
| 100 friend class VMStructs; | |
| 101 | |
| 102 private: | |
| 103 enum SomePrivateConstants { | |
| 104 LogN = 9, | |
| 105 LogN_words = LogN - LogHeapWordSize, | |
| 106 N_bytes = 1 << LogN, | |
| 107 N_words = 1 << LogN_words | |
| 108 }; | |
| 109 | |
| 110 // The reserved region covered by the shared array. | |
| 111 MemRegion _reserved; | |
| 112 | |
| 113 // End of the current committed region. | |
| 114 HeapWord* _end; | |
| 115 | |
| 116 // Array for keeping offsets for retrieving object start fast given an | |
| 117 // address. | |
| 118 VirtualSpace _vs; | |
| 119 u_char* _offset_array; // byte array keeping backwards offsets | |
| 120 | |
| 121 protected: | |
| 122 // Bounds checking accessors: | |
| 123 // For performance these have to devolve to array accesses in product builds. | |
| 124 u_char offset_array(size_t index) const { | |
| 125 assert(index < _vs.committed_size(), "index out of range"); | |
| 126 return _offset_array[index]; | |
| 127 } | |
| 128 void set_offset_array(size_t index, u_char offset) { | |
| 129 assert(index < _vs.committed_size(), "index out of range"); | |
| 130 _offset_array[index] = offset; | |
| 131 } | |
| 132 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { | |
| 133 assert(index < _vs.committed_size(), "index out of range"); | |
| 134 assert(high >= low, "addresses out of order"); | |
| 135 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
| 136 _offset_array[index] = (u_char)pointer_delta(high, low); | |
| 137 } | |
| 138 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) { | |
| 139 assert(index_for(right - 1) < _vs.committed_size(), | |
| 140 "right address out of range"); | |
| 141 assert(left < right, "Heap addresses out of order"); | |
| 142 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
| 143 memset(&_offset_array[index_for(left)], offset, num_cards); | |
| 144 } | |
| 145 | |
| 146 void set_offset_array(size_t left, size_t right, u_char offset) { | |
| 147 assert(right < _vs.committed_size(), "right address out of range"); | |
| 148 assert(left <= right, "indexes out of order"); | |
| 149 size_t num_cards = right - left + 1; | |
| 150 memset(&_offset_array[left], offset, num_cards); | |
| 151 } | |
| 152 | |
| 153 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
| 154 assert(index < _vs.committed_size(), "index out of range"); | |
| 155 assert(high >= low, "addresses out of order"); | |
| 156 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
| 157 assert(_offset_array[index] == pointer_delta(high, low), | |
| 158 "Wrong offset"); | |
| 159 } | |
| 160 | |
| 161 bool is_card_boundary(HeapWord* p) const; | |
| 162 | |
| 163 // Return the number of slots needed for an offset array | |
| 164 // that covers mem_region_words words. | |
| 165 // We always add an extra slot because if an object | |
| 166 // ends on a card boundary we put a 0 in the next | |
| 167 // offset array slot, so we want that slot always | |
| 168 // to be reserved. | |
| 169 | |
| 170 size_t compute_size(size_t mem_region_words) { | |
| 171 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
| 172 return ReservedSpace::allocation_align_size_up(number_of_slots); | |
| 173 } | |
| 174 | |
| 175 public: | |
| 176 // Initialize the table to cover from "base" to (at least) | |
| 177 // "base + init_word_size". In the future, the table may be expanded | |
| 178 // (see "resize" below) up to the size of "_reserved" (which must be at | |
| 179 // least "init_word_size".) The contents of the initial table are | |
| 180 // undefined; it is the responsibility of the constituent | |
| 181 // BlockOffsetTable(s) to initialize cards. | |
| 182 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
| 183 | |
| 184 // Notes a change in the committed size of the region covered by the | |
| 185 // table. The "new_word_size" may not be larger than the size of the | |
| 186 // reserved region this table covers. | |
| 187 void resize(size_t new_word_size); | |
| 188 | |
| 189 void set_bottom(HeapWord* new_bottom); | |
| 190 | |
| 191 // Updates all the BlockOffsetArray's sharing this shared array to | |
| 192 // reflect the current "top"'s of their spaces. | |
| 193 void update_offset_arrays(); // Not yet implemented! | |
| 194 | |
| 195 // Return the appropriate index into "_offset_array" for "p". | |
| 196 size_t index_for(const void* p) const; | |
| 197 | |
| 198 // Return the address indicating the start of the region corresponding to | |
| 199 // "index" in "_offset_array". | |
| 200 HeapWord* address_for_index(size_t index) const; | |
| 201 | |
|
301
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202 // Return the address "p" incremented by the size of |
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203 // a region. This method does not align the address |
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204 // returned to the start of a region. It is a simple |
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205 // primitive. |
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206 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; } |
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207 |
| 0 | 208 // Shared space support |
| 209 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end); | |
| 210 }; | |
| 211 | |
| 212 ////////////////////////////////////////////////////////////////////////// | |
| 213 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. | |
| 214 ////////////////////////////////////////////////////////////////////////// | |
| 215 class BlockOffsetArray: public BlockOffsetTable { | |
| 216 friend class VMStructs; | |
| 217 protected: | |
| 218 // The following enums are used by do_block_internal() below | |
| 219 enum Action { | |
| 220 Action_single, // BOT records a single block (see single_block()) | |
| 221 Action_mark, // BOT marks the start of a block (see mark_block()) | |
| 222 Action_check // Check that BOT records block correctly | |
| 223 // (see verify_single_block()). | |
| 224 }; | |
| 225 | |
| 226 enum SomePrivateConstants { | |
| 227 N_words = BlockOffsetSharedArray::N_words, | |
| 228 LogN = BlockOffsetSharedArray::LogN, | |
| 229 // entries "e" of at least N_words mean "go back by Base^(e-N_words)." | |
| 230 // All entries are less than "N_words + N_powers". | |
| 231 LogBase = 4, | |
| 232 Base = (1 << LogBase), | |
| 233 N_powers = 14 | |
| 234 }; | |
| 235 | |
| 236 static size_t power_to_cards_back(uint i) { | |
| 237 return 1 << (LogBase * i); | |
| 238 } | |
| 239 static size_t power_to_words_back(uint i) { | |
| 240 return power_to_cards_back(i) * N_words; | |
| 241 } | |
| 242 static size_t entry_to_cards_back(u_char entry) { | |
| 243 assert(entry >= N_words, "Precondition"); | |
| 244 return power_to_cards_back(entry - N_words); | |
| 245 } | |
| 246 static size_t entry_to_words_back(u_char entry) { | |
| 247 assert(entry >= N_words, "Precondition"); | |
| 248 return power_to_words_back(entry - N_words); | |
| 249 } | |
| 250 | |
| 251 // The shared array, which is shared with other BlockOffsetArray's | |
| 252 // corresponding to different spaces within a generation or span of | |
| 253 // memory. | |
| 254 BlockOffsetSharedArray* _array; | |
| 255 | |
| 256 // The space that owns this subregion. | |
| 257 Space* _sp; | |
| 258 | |
| 259 // If true, array entries are initialized to 0; otherwise, they are | |
| 260 // initialized to point backwards to the beginning of the covered region. | |
| 261 bool _init_to_zero; | |
| 262 | |
| 263 // Sets the entries | |
| 264 // corresponding to the cards starting at "start" and ending at "end" | |
| 265 // to point back to the card before "start": the interval [start, end) | |
| 266 // is right-open. | |
| 267 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
| 268 // Same as above, except that the args here are a card _index_ interval | |
| 269 // that is closed: [start_index, end_index] | |
| 270 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
| 271 | |
| 272 // A helper function for BOT adjustment/verification work | |
| 273 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
| 274 | |
| 275 public: | |
| 276 // The space may not have its bottom and top set yet, which is why the | |
| 277 // region is passed as a parameter. If "init_to_zero" is true, the | |
| 278 // elements of the array are initialized to zero. Otherwise, they are | |
| 279 // initialized to point backwards to the beginning. | |
| 280 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, | |
| 281 bool init_to_zero); | |
| 282 | |
| 283 // Note: this ought to be part of the constructor, but that would require | |
| 284 // "this" to be passed as a parameter to a member constructor for | |
| 285 // the containing concrete subtype of Space. | |
| 286 // This would be legal C++, but MS VC++ doesn't allow it. | |
| 287 void set_space(Space* sp) { _sp = sp; } | |
| 288 | |
| 289 // Resets the covered region to the given "mr". | |
| 290 void set_region(MemRegion mr) { | |
| 291 _bottom = mr.start(); | |
| 292 _end = mr.end(); | |
| 293 } | |
| 294 | |
| 295 // Note that the committed size of the covered space may have changed, | |
| 296 // so the table size might also wish to change. | |
| 297 virtual void resize(size_t new_word_size) { | |
| 298 HeapWord* new_end = _bottom + new_word_size; | |
| 299 if (_end < new_end && !init_to_zero()) { | |
| 300 // verify that the old and new boundaries are also card boundaries | |
| 301 assert(_array->is_card_boundary(_end), | |
| 302 "_end not a card boundary"); | |
| 303 assert(_array->is_card_boundary(new_end), | |
| 304 "new _end would not be a card boundary"); | |
| 305 // set all the newly added cards | |
| 306 _array->set_offset_array(_end, new_end, N_words); | |
| 307 } | |
| 308 _end = new_end; // update _end | |
| 309 } | |
| 310 | |
| 311 // Adjust the BOT to show that it has a single block in the | |
| 312 // range [blk_start, blk_start + size). All necessary BOT | |
| 313 // cards are adjusted, but _unallocated_block isn't. | |
| 314 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 315 void single_block(HeapWord* blk, size_t size) { | |
| 316 single_block(blk, blk + size); | |
| 317 } | |
| 318 | |
| 319 // When the alloc_block() call returns, the block offset table should | |
| 320 // have enough information such that any subsequent block_start() call | |
| 321 // with an argument equal to an address that is within the range | |
| 322 // [blk_start, blk_end) would return the value blk_start, provided | |
| 323 // there have been no calls in between that reset this information | |
| 324 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call | |
| 325 // for an appropriate range covering the said interval). | |
| 326 // These methods expect to be called with [blk_start, blk_end) | |
| 327 // representing a block of memory in the heap. | |
| 328 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 329 void alloc_block(HeapWord* blk, size_t size) { | |
| 330 alloc_block(blk, blk + size); | |
| 331 } | |
| 332 | |
| 333 // If true, initialize array slots with no allocated blocks to zero. | |
| 334 // Otherwise, make them point back to the front. | |
| 335 bool init_to_zero() { return _init_to_zero; } | |
| 336 | |
| 337 // Debugging | |
| 338 // Return the index of the last entry in the "active" region. | |
| 339 virtual size_t last_active_index() const = 0; | |
| 340 // Verify the block offset table | |
| 341 void verify() const; | |
| 342 void check_all_cards(size_t left_card, size_t right_card) const; | |
| 343 }; | |
| 344 | |
| 345 //////////////////////////////////////////////////////////////////////////// | |
| 346 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 347 // that its underlying space is a NonContiguousSpace, so that some | |
| 348 // specialized interfaces can be made available for spaces that | |
| 349 // manipulate the table. | |
| 350 //////////////////////////////////////////////////////////////////////////// | |
| 351 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { | |
| 352 friend class VMStructs; | |
| 353 private: | |
| 354 // The portion [_unallocated_block, _sp.end()) of the space that | |
| 355 // is a single block known not to contain any objects. | |
| 356 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
| 357 HeapWord* _unallocated_block; | |
| 358 | |
| 359 public: | |
| 360 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
| 361 BlockOffsetArray(array, mr, false), | |
| 362 _unallocated_block(_bottom) { } | |
| 363 | |
| 364 // accessor | |
| 365 HeapWord* unallocated_block() const { | |
| 366 assert(BlockOffsetArrayUseUnallocatedBlock, | |
| 367 "_unallocated_block is not being maintained"); | |
| 368 return _unallocated_block; | |
| 369 } | |
| 370 | |
| 371 void set_unallocated_block(HeapWord* block) { | |
| 372 assert(BlockOffsetArrayUseUnallocatedBlock, | |
| 373 "_unallocated_block is not being maintained"); | |
| 374 assert(block >= _bottom && block <= _end, "out of range"); | |
| 375 _unallocated_block = block; | |
| 376 } | |
| 377 | |
| 378 // These methods expect to be called with [blk_start, blk_end) | |
| 379 // representing a block of memory in the heap. | |
| 380 void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 381 void alloc_block(HeapWord* blk, size_t size) { | |
| 382 alloc_block(blk, blk + size); | |
| 383 } | |
| 384 | |
| 385 // The following methods are useful and optimized for a | |
| 386 // non-contiguous space. | |
| 387 | |
| 388 // Given a block [blk_start, blk_start + full_blk_size), and | |
| 389 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
| 390 // blocks [blk_start, blk_start + left_blk_size) and | |
| 391 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
| 392 // It is assumed (and verified in the non-product VM) that the | |
| 393 // BOT was correct for the original block. | |
| 394 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
| 395 size_t left_blk_size); | |
| 396 | |
| 397 // Adjust BOT to show that it has a block in the range | |
| 398 // [blk_start, blk_start + size). Only the first card | |
| 399 // of BOT is touched. It is assumed (and verified in the | |
| 400 // non-product VM) that the remaining cards of the block | |
| 401 // are correct. | |
| 402 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 403 void mark_block(HeapWord* blk, size_t size) { | |
| 404 mark_block(blk, blk + size); | |
| 405 } | |
| 406 | |
| 407 // Adjust _unallocated_block to indicate that a particular | |
| 408 // block has been newly allocated or freed. It is assumed (and | |
| 409 // verified in the non-product VM) that the BOT is correct for | |
| 410 // the given block. | |
| 411 void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
| 412 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
| 413 verify_single_block(blk_start, blk_end); | |
| 414 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 415 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
| 416 } | |
| 417 } | |
| 418 | |
| 419 void allocated(HeapWord* blk, size_t size) { | |
| 420 allocated(blk, blk + size); | |
| 421 } | |
| 422 | |
| 423 void freed(HeapWord* blk_start, HeapWord* blk_end); | |
| 424 void freed(HeapWord* blk, size_t size) { | |
| 425 freed(blk, blk + size); | |
| 426 } | |
| 427 | |
| 428 HeapWord* block_start_unsafe(const void* addr) const; | |
| 429 | |
| 430 // Requires "addr" to be the start of a card and returns the | |
| 431 // start of the block that contains the given address. | |
| 432 HeapWord* block_start_careful(const void* addr) const; | |
| 433 | |
| 434 | |
| 435 // Verification & debugging: ensure that the offset table reflects | |
| 436 // the fact that the block [blk_start, blk_end) or [blk, blk + size) | |
| 437 // is a single block of storage. NOTE: can't const this because of | |
| 438 // call to non-const do_block_internal() below. | |
| 439 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) | |
| 440 PRODUCT_RETURN; | |
| 441 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; | |
| 442 | |
| 443 // Verify that the given block is before _unallocated_block | |
| 444 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) | |
| 445 const PRODUCT_RETURN; | |
| 446 void verify_not_unallocated(HeapWord* blk, size_t size) | |
| 447 const PRODUCT_RETURN; | |
| 448 | |
| 449 // Debugging support | |
| 450 virtual size_t last_active_index() const; | |
| 451 }; | |
| 452 | |
| 453 //////////////////////////////////////////////////////////////////////////// | |
| 454 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 455 // that its underlying space is a ContiguousSpace, so that its "active" | |
| 456 // region can be more efficiently tracked (than for a non-contiguous space). | |
| 457 //////////////////////////////////////////////////////////////////////////// | |
| 458 class BlockOffsetArrayContigSpace: public BlockOffsetArray { | |
| 459 friend class VMStructs; | |
| 460 private: | |
| 461 // allocation boundary at which offset array must be updated | |
| 462 HeapWord* _next_offset_threshold; | |
| 463 size_t _next_offset_index; // index corresponding to that boundary | |
| 464 | |
| 465 // Work function when allocation start crosses threshold. | |
| 466 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); | |
| 467 | |
| 468 public: | |
| 469 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
| 470 BlockOffsetArray(array, mr, true) { | |
| 471 _next_offset_threshold = NULL; | |
| 472 _next_offset_index = 0; | |
| 473 } | |
| 474 | |
| 475 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } | |
| 476 | |
| 477 // Initialize the threshold for an empty heap. | |
| 478 HeapWord* initialize_threshold(); | |
| 479 // Zero out the entry for _bottom (offset will be zero) | |
| 480 void zero_bottom_entry(); | |
| 481 | |
| 482 // Return the next threshold, the point at which the table should be | |
| 483 // updated. | |
| 484 HeapWord* threshold() const { return _next_offset_threshold; } | |
| 485 | |
| 486 // In general, these methods expect to be called with | |
| 487 // [blk_start, blk_end) representing a block of memory in the heap. | |
| 488 // In this implementation, however, we are OK even if blk_start and/or | |
| 489 // blk_end are NULL because NULL is represented as 0, and thus | |
| 490 // never exceeds the "_next_offset_threshold". | |
| 491 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 492 if (blk_end > _next_offset_threshold) { | |
| 493 alloc_block_work(blk_start, blk_end); | |
| 494 } | |
| 495 } | |
| 496 void alloc_block(HeapWord* blk, size_t size) { | |
| 497 alloc_block(blk, blk + size); | |
| 498 } | |
| 499 | |
| 500 HeapWord* block_start_unsafe(const void* addr) const; | |
| 501 | |
| 502 void serialize(SerializeOopClosure* soc); | |
| 503 | |
| 504 // Debugging support | |
| 505 virtual size_t last_active_index() const; | |
| 506 }; |