Mercurial > hg > graal-jvmci-8
annotate src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp @ 6610:f99a36499b8c
7192128: G1: Extend fix for 6948537 to G1's BOT
Summary: G1 does not appear to be immune to the issue described in CR 6948537 and increasing the size of old-generation PLABs appears to increase the liklihood of seeing the issue. Extend the fix for 6948537 to G1's BlockOffsetTable.
Reviewed-by: brutisso, jmasa
| author | johnc |
|---|---|
| date | Tue, 21 Aug 2012 10:05:57 -0700 |
| parents | d2a62e0f25eb |
| children | 2fc0334f613a |
| rev | line source |
|---|---|
| 342 | 1 /* |
| 6610 | 2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved. |
| 342 | 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 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 342 | 22 * |
| 23 */ | |
| 24 | |
| 1972 | 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP |
| 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP | |
| 27 | |
| 28 #include "memory/memRegion.hpp" | |
| 29 #include "runtime/virtualspace.hpp" | |
| 30 #include "utilities/globalDefinitions.hpp" | |
| 31 | |
| 342 | 32 // The CollectedHeap type requires subtypes to implement a method |
| 33 // "block_start". For some subtypes, notably generational | |
| 34 // systems using card-table-based write barriers, the efficiency of this | |
| 35 // operation may be important. Implementations of the "BlockOffsetArray" | |
| 36 // class may be useful in providing such efficient implementations. | |
| 37 // | |
| 38 // While generally mirroring the structure of the BOT for GenCollectedHeap, | |
| 39 // the following types are tailored more towards G1's uses; these should, | |
| 40 // however, be merged back into a common BOT to avoid code duplication | |
| 41 // and reduce maintenance overhead. | |
| 42 // | |
| 43 // G1BlockOffsetTable (abstract) | |
| 44 // -- G1BlockOffsetArray (uses G1BlockOffsetSharedArray) | |
| 45 // -- G1BlockOffsetArrayContigSpace | |
| 46 // | |
| 47 // A main impediment to the consolidation of this code might be the | |
| 48 // effect of making some of the block_start*() calls non-const as | |
| 49 // below. Whether that might adversely affect performance optimizations | |
| 50 // that compilers might normally perform in the case of non-G1 | |
| 51 // collectors needs to be carefully investigated prior to any such | |
| 52 // consolidation. | |
| 53 | |
| 54 // Forward declarations | |
| 55 class ContiguousSpace; | |
| 56 class G1BlockOffsetSharedArray; | |
| 57 | |
| 58 class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC { | |
| 59 friend class VMStructs; | |
| 60 protected: | |
| 61 // These members describe the region covered by the table. | |
| 62 | |
| 63 // The space this table is covering. | |
| 64 HeapWord* _bottom; // == reserved.start | |
| 65 HeapWord* _end; // End of currently allocated region. | |
| 66 | |
| 67 public: | |
| 68 // Initialize the table to cover the given space. | |
| 69 // The contents of the initial table are undefined. | |
| 70 G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) : | |
| 71 _bottom(bottom), _end(end) | |
| 72 { | |
| 73 assert(_bottom <= _end, "arguments out of order"); | |
| 74 } | |
| 75 | |
| 76 // Note that the committed size of the covered space may have changed, | |
| 77 // so the table size might also wish to change. | |
| 78 virtual void resize(size_t new_word_size) = 0; | |
| 79 | |
| 80 virtual void set_bottom(HeapWord* new_bottom) { | |
| 81 assert(new_bottom <= _end, "new_bottom > _end"); | |
| 82 _bottom = new_bottom; | |
| 83 resize(pointer_delta(_end, _bottom)); | |
| 84 } | |
| 85 | |
| 86 // Requires "addr" to be contained by a block, and returns the address of | |
| 87 // the start of that block. (May have side effects, namely updating of | |
| 88 // shared array entries that "point" too far backwards. This can occur, | |
| 89 // for example, when LAB allocation is used in a space covered by the | |
| 90 // table.) | |
| 91 virtual HeapWord* block_start_unsafe(const void* addr) = 0; | |
| 92 // Same as above, but does not have any of the possible side effects | |
| 93 // discussed above. | |
| 94 virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0; | |
| 95 | |
| 96 // Returns the address of the start of the block containing "addr", or | |
| 97 // else "null" if it is covered by no block. (May have side effects, | |
| 98 // namely updating of shared array entries that "point" too far | |
| 99 // backwards. This can occur, for example, when lab allocation is used | |
| 100 // in a space covered by the table.) | |
| 101 inline HeapWord* block_start(const void* addr); | |
| 102 // Same as above, but does not have any of the possible side effects | |
| 103 // discussed above. | |
| 104 inline HeapWord* block_start_const(const void* addr) const; | |
| 105 }; | |
| 106 | |
| 107 // This implementation of "G1BlockOffsetTable" divides the covered region | |
| 108 // into "N"-word subregions (where "N" = 2^"LogN". An array with an entry | |
| 109 // for each such subregion indicates how far back one must go to find the | |
| 110 // start of the chunk that includes the first word of the subregion. | |
| 111 // | |
| 112 // Each BlockOffsetArray is owned by a Space. However, the actual array | |
| 113 // may be shared by several BlockOffsetArrays; this is useful | |
| 114 // when a single resizable area (such as a generation) is divided up into | |
| 115 // several spaces in which contiguous allocation takes place, | |
| 116 // such as, for example, in G1 or in the train generation.) | |
| 117 | |
| 118 // Here is the shared array type. | |
| 119 | |
| 6197 | 120 class G1BlockOffsetSharedArray: public CHeapObj<mtGC> { |
| 342 | 121 friend class G1BlockOffsetArray; |
| 122 friend class G1BlockOffsetArrayContigSpace; | |
| 123 friend class VMStructs; | |
| 124 | |
| 125 private: | |
| 126 // The reserved region covered by the shared array. | |
| 127 MemRegion _reserved; | |
| 128 | |
| 129 // End of the current committed region. | |
| 130 HeapWord* _end; | |
| 131 | |
| 132 // Array for keeping offsets for retrieving object start fast given an | |
| 133 // address. | |
| 134 VirtualSpace _vs; | |
| 135 u_char* _offset_array; // byte array keeping backwards offsets | |
| 136 | |
| 137 // Bounds checking accessors: | |
| 138 // For performance these have to devolve to array accesses in product builds. | |
| 139 u_char offset_array(size_t index) const { | |
| 140 assert(index < _vs.committed_size(), "index out of range"); | |
| 141 return _offset_array[index]; | |
| 142 } | |
| 143 | |
| 144 void set_offset_array(size_t index, u_char offset) { | |
| 145 assert(index < _vs.committed_size(), "index out of range"); | |
| 146 assert(offset <= N_words, "offset too large"); | |
| 147 _offset_array[index] = offset; | |
| 148 } | |
| 149 | |
| 150 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { | |
| 151 assert(index < _vs.committed_size(), "index out of range"); | |
| 152 assert(high >= low, "addresses out of order"); | |
| 153 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
| 154 _offset_array[index] = (u_char) pointer_delta(high, low); | |
| 155 } | |
| 156 | |
| 157 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) { | |
| 158 assert(index_for(right - 1) < _vs.committed_size(), | |
| 159 "right address out of range"); | |
| 160 assert(left < right, "Heap addresses out of order"); | |
| 161 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
| 6610 | 162 if (UseMemSetInBOT) { |
| 163 memset(&_offset_array[index_for(left)], offset, num_cards); | |
| 164 } else { | |
| 165 size_t i = index_for(left); | |
| 166 const size_t end = i + num_cards; | |
| 167 for (; i < end; i++) { | |
| 168 _offset_array[i] = offset; | |
| 169 } | |
| 170 } | |
| 342 | 171 } |
| 172 | |
| 173 void set_offset_array(size_t left, size_t right, u_char offset) { | |
| 174 assert(right < _vs.committed_size(), "right address out of range"); | |
| 6610 | 175 assert(left <= right, "indexes out of order"); |
| 342 | 176 size_t num_cards = right - left + 1; |
| 6610 | 177 if (UseMemSetInBOT) { |
| 178 memset(&_offset_array[left], offset, num_cards); | |
| 179 } else { | |
| 180 size_t i = left; | |
| 181 const size_t end = i + num_cards; | |
| 182 for (; i < end; i++) { | |
| 183 _offset_array[i] = offset; | |
| 184 } | |
| 185 } | |
| 342 | 186 } |
| 187 | |
| 188 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
| 189 assert(index < _vs.committed_size(), "index out of range"); | |
| 190 assert(high >= low, "addresses out of order"); | |
| 191 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
| 192 assert(_offset_array[index] == pointer_delta(high, low), | |
| 193 "Wrong offset"); | |
| 194 } | |
| 195 | |
| 196 bool is_card_boundary(HeapWord* p) const; | |
| 197 | |
| 198 // Return the number of slots needed for an offset array | |
| 199 // that covers mem_region_words words. | |
| 200 // We always add an extra slot because if an object | |
| 201 // ends on a card boundary we put a 0 in the next | |
| 202 // offset array slot, so we want that slot always | |
| 203 // to be reserved. | |
| 204 | |
| 205 size_t compute_size(size_t mem_region_words) { | |
| 206 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
| 207 return ReservedSpace::page_align_size_up(number_of_slots); | |
| 208 } | |
| 209 | |
| 210 public: | |
| 211 enum SomePublicConstants { | |
| 212 LogN = 9, | |
| 213 LogN_words = LogN - LogHeapWordSize, | |
| 214 N_bytes = 1 << LogN, | |
| 215 N_words = 1 << LogN_words | |
| 216 }; | |
| 217 | |
| 218 // Initialize the table to cover from "base" to (at least) | |
| 219 // "base + init_word_size". In the future, the table may be expanded | |
| 220 // (see "resize" below) up to the size of "_reserved" (which must be at | |
| 221 // least "init_word_size".) The contents of the initial table are | |
| 222 // undefined; it is the responsibility of the constituent | |
| 223 // G1BlockOffsetTable(s) to initialize cards. | |
| 224 G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
| 225 | |
| 226 // Notes a change in the committed size of the region covered by the | |
| 227 // table. The "new_word_size" may not be larger than the size of the | |
| 228 // reserved region this table covers. | |
| 229 void resize(size_t new_word_size); | |
| 230 | |
| 231 void set_bottom(HeapWord* new_bottom); | |
| 232 | |
| 233 // Updates all the BlockOffsetArray's sharing this shared array to | |
| 234 // reflect the current "top"'s of their spaces. | |
| 235 void update_offset_arrays(); | |
| 236 | |
| 237 // Return the appropriate index into "_offset_array" for "p". | |
| 238 inline size_t index_for(const void* p) const; | |
| 239 | |
| 240 // Return the address indicating the start of the region corresponding to | |
| 241 // "index" in "_offset_array". | |
| 242 inline HeapWord* address_for_index(size_t index) const; | |
| 243 }; | |
| 244 | |
| 245 // And here is the G1BlockOffsetTable subtype that uses the array. | |
| 246 | |
| 247 class G1BlockOffsetArray: public G1BlockOffsetTable { | |
| 248 friend class G1BlockOffsetSharedArray; | |
| 249 friend class G1BlockOffsetArrayContigSpace; | |
| 250 friend class VMStructs; | |
| 251 private: | |
| 252 enum SomePrivateConstants { | |
| 253 N_words = G1BlockOffsetSharedArray::N_words, | |
| 254 LogN = G1BlockOffsetSharedArray::LogN | |
| 255 }; | |
| 256 | |
| 257 // The following enums are used by do_block_helper | |
| 258 enum Action { | |
| 259 Action_single, // BOT records a single block (see single_block()) | |
| 260 Action_mark, // BOT marks the start of a block (see mark_block()) | |
| 261 Action_check // Check that BOT records block correctly | |
| 262 // (see verify_single_block()). | |
| 263 }; | |
| 264 | |
| 265 // This is the array, which can be shared by several BlockOffsetArray's | |
| 266 // servicing different | |
| 267 G1BlockOffsetSharedArray* _array; | |
| 268 | |
| 269 // The space that owns this subregion. | |
| 270 Space* _sp; | |
| 271 | |
| 272 // If "_sp" is a contiguous space, the field below is the view of "_sp" | |
| 273 // as a contiguous space, else NULL. | |
| 274 ContiguousSpace* _csp; | |
| 275 | |
| 276 // If true, array entries are initialized to 0; otherwise, they are | |
| 277 // initialized to point backwards to the beginning of the covered region. | |
| 278 bool _init_to_zero; | |
| 279 | |
| 280 // The portion [_unallocated_block, _sp.end()) of the space that | |
| 281 // is a single block known not to contain any objects. | |
| 282 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
| 283 HeapWord* _unallocated_block; | |
| 284 | |
| 285 // Sets the entries | |
| 286 // corresponding to the cards starting at "start" and ending at "end" | |
| 287 // to point back to the card before "start": the interval [start, end) | |
| 288 // is right-open. | |
| 289 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
| 290 // Same as above, except that the args here are a card _index_ interval | |
| 291 // that is closed: [start_index, end_index] | |
| 292 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
| 293 | |
| 294 // A helper function for BOT adjustment/verification work | |
| 295 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
| 296 | |
| 297 protected: | |
| 298 | |
| 299 ContiguousSpace* csp() const { return _csp; } | |
| 300 | |
| 301 // Returns the address of a block whose start is at most "addr". | |
| 302 // If "has_max_index" is true, "assumes "max_index" is the last valid one | |
| 303 // in the array. | |
| 304 inline HeapWord* block_at_or_preceding(const void* addr, | |
| 305 bool has_max_index, | |
| 306 size_t max_index) const; | |
| 307 | |
| 308 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
| 309 // next block (or the end of the space.) Return the address of the | |
| 310 // beginning of the block that contains "addr". Does so without side | |
| 311 // effects (see, e.g., spec of block_start.) | |
| 312 inline HeapWord* | |
| 313 forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n, | |
| 314 const void* addr) const; | |
| 315 | |
| 316 // "q" is a block boundary that is <= "addr"; return the address of the | |
| 317 // beginning of the block that contains "addr". May have side effects | |
| 318 // on "this", by updating imprecise entries. | |
| 319 inline HeapWord* forward_to_block_containing_addr(HeapWord* q, | |
| 320 const void* addr); | |
| 321 | |
| 322 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
| 323 // next block (or the end of the space.) Return the address of the | |
| 324 // beginning of the block that contains "addr". May have side effects | |
| 325 // on "this", by updating imprecise entries. | |
| 326 HeapWord* forward_to_block_containing_addr_slow(HeapWord* q, | |
| 327 HeapWord* n, | |
| 328 const void* addr); | |
| 329 | |
| 330 // Requires that "*threshold_" be the first array entry boundary at or | |
| 331 // above "blk_start", and that "*index_" be the corresponding array | |
| 332 // index. If the block starts at or crosses "*threshold_", records | |
| 333 // "blk_start" as the appropriate block start for the array index | |
| 334 // starting at "*threshold_", and for any other indices crossed by the | |
| 335 // block. Updates "*threshold_" and "*index_" to correspond to the first | |
| 336 // index after the block end. | |
| 337 void alloc_block_work2(HeapWord** threshold_, size_t* index_, | |
| 338 HeapWord* blk_start, HeapWord* blk_end); | |
| 339 | |
| 340 public: | |
| 341 // The space may not have it's bottom and top set yet, which is why the | |
| 342 // region is passed as a parameter. If "init_to_zero" is true, the | |
| 343 // elements of the array are initialized to zero. Otherwise, they are | |
| 344 // initialized to point backwards to the beginning. | |
| 345 G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr, | |
| 346 bool init_to_zero); | |
| 347 | |
| 348 // Note: this ought to be part of the constructor, but that would require | |
| 349 // "this" to be passed as a parameter to a member constructor for | |
| 350 // the containing concrete subtype of Space. | |
| 351 // This would be legal C++, but MS VC++ doesn't allow it. | |
| 352 void set_space(Space* sp); | |
| 353 | |
| 354 // Resets the covered region to the given "mr". | |
| 355 void set_region(MemRegion mr); | |
| 356 | |
| 357 // Resets the covered region to one with the same _bottom as before but | |
| 358 // the "new_word_size". | |
| 359 void resize(size_t new_word_size); | |
| 360 | |
| 361 // These must be guaranteed to work properly (i.e., do nothing) | |
| 362 // when "blk_start" ("blk" for second version) is "NULL". | |
| 363 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 364 virtual void alloc_block(HeapWord* blk, size_t size) { | |
| 365 alloc_block(blk, blk + size); | |
| 366 } | |
| 367 | |
| 368 // The following methods are useful and optimized for a | |
| 369 // general, non-contiguous space. | |
| 370 | |
| 371 // Given a block [blk_start, blk_start + full_blk_size), and | |
| 372 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
| 373 // blocks [blk_start, blk_start + left_blk_size) and | |
| 374 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
| 375 // It is assumed (and verified in the non-product VM) that the | |
| 376 // BOT was correct for the original block. | |
| 377 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
| 378 size_t left_blk_size); | |
| 379 | |
| 380 // Adjust the BOT to show that it has a single block in the | |
| 381 // range [blk_start, blk_start + size). All necessary BOT | |
| 382 // cards are adjusted, but _unallocated_block isn't. | |
| 383 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 384 void single_block(HeapWord* blk, size_t size) { | |
| 385 single_block(blk, blk + size); | |
| 386 } | |
| 387 | |
| 388 // Adjust BOT to show that it has a block in the range | |
| 389 // [blk_start, blk_start + size). Only the first card | |
| 390 // of BOT is touched. It is assumed (and verified in the | |
| 391 // non-product VM) that the remaining cards of the block | |
| 392 // are correct. | |
| 393 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 394 void mark_block(HeapWord* blk, size_t size) { | |
| 395 mark_block(blk, blk + size); | |
| 396 } | |
| 397 | |
| 398 // Adjust _unallocated_block to indicate that a particular | |
| 399 // block has been newly allocated or freed. It is assumed (and | |
| 400 // verified in the non-product VM) that the BOT is correct for | |
| 401 // the given block. | |
| 402 inline void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
| 403 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
| 404 verify_single_block(blk_start, blk_end); | |
| 405 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 406 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
| 407 } | |
| 408 } | |
| 409 | |
| 410 inline void allocated(HeapWord* blk, size_t size) { | |
| 411 allocated(blk, blk + size); | |
| 412 } | |
| 413 | |
| 414 inline void freed(HeapWord* blk_start, HeapWord* blk_end); | |
| 415 | |
| 416 inline void freed(HeapWord* blk, size_t size); | |
| 417 | |
| 418 virtual HeapWord* block_start_unsafe(const void* addr); | |
| 419 virtual HeapWord* block_start_unsafe_const(const void* addr) const; | |
| 420 | |
| 421 // Requires "addr" to be the start of a card and returns the | |
| 422 // start of the block that contains the given address. | |
| 423 HeapWord* block_start_careful(const void* addr) const; | |
| 424 | |
| 425 // If true, initialize array slots with no allocated blocks to zero. | |
| 426 // Otherwise, make them point back to the front. | |
| 427 bool init_to_zero() { return _init_to_zero; } | |
| 428 | |
| 429 // Verification & debugging - ensure that the offset table reflects the fact | |
| 430 // that the block [blk_start, blk_end) or [blk, blk + size) is a | |
| 431 // single block of storage. NOTE: can;t const this because of | |
| 432 // call to non-const do_block_internal() below. | |
| 433 inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 434 if (VerifyBlockOffsetArray) { | |
| 435 do_block_internal(blk_start, blk_end, Action_check); | |
| 436 } | |
| 437 } | |
| 438 | |
| 439 inline void verify_single_block(HeapWord* blk, size_t size) { | |
| 440 verify_single_block(blk, blk + size); | |
| 441 } | |
| 442 | |
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443 // Used by region verification. Checks that the contents of the |
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444 // BOT reflect that there's a single object that spans the address |
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445 // range [obj_start, obj_start + word_size); returns true if this is |
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446 // the case, returns false if it's not. |
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447 bool verify_for_object(HeapWord* obj_start, size_t word_size) const; |
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448 |
| 342 | 449 // Verify that the given block is before _unallocated_block |
| 450 inline void verify_not_unallocated(HeapWord* blk_start, | |
| 451 HeapWord* blk_end) const { | |
| 452 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 453 assert(blk_start < blk_end, "Block inconsistency?"); | |
| 454 assert(blk_end <= _unallocated_block, "_unallocated_block problem"); | |
| 455 } | |
| 456 } | |
| 457 | |
| 458 inline void verify_not_unallocated(HeapWord* blk, size_t size) const { | |
| 459 verify_not_unallocated(blk, blk + size); | |
| 460 } | |
| 461 | |
| 462 void check_all_cards(size_t left_card, size_t right_card) const; | |
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464 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 465 }; |
| 466 | |
| 467 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 468 // that its underlying space is a ContiguousSpace, so that its "active" | |
| 469 // region can be more efficiently tracked (than for a non-contiguous space). | |
| 470 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray { | |
| 471 friend class VMStructs; | |
| 472 | |
| 473 // allocation boundary at which offset array must be updated | |
| 474 HeapWord* _next_offset_threshold; | |
| 475 size_t _next_offset_index; // index corresponding to that boundary | |
| 476 | |
| 477 // Work function to be called when allocation start crosses the next | |
| 478 // threshold in the contig space. | |
| 479 void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) { | |
| 480 alloc_block_work2(&_next_offset_threshold, &_next_offset_index, | |
| 481 blk_start, blk_end); | |
| 482 } | |
| 483 | |
| 484 | |
| 485 public: | |
| 486 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr); | |
| 487 | |
| 488 // Initialize the threshold to reflect the first boundary after the | |
| 489 // bottom of the covered region. | |
| 490 HeapWord* initialize_threshold(); | |
| 491 | |
| 492 // Zero out the entry for _bottom (offset will be zero). | |
| 493 void zero_bottom_entry(); | |
| 494 | |
| 495 // Return the next threshold, the point at which the table should be | |
| 496 // updated. | |
| 497 HeapWord* threshold() const { return _next_offset_threshold; } | |
| 498 | |
| 499 // These must be guaranteed to work properly (i.e., do nothing) | |
| 500 // when "blk_start" ("blk" for second version) is "NULL". In this | |
| 501 // implementation, that's true because NULL is represented as 0, and thus | |
| 502 // never exceeds the "_next_offset_threshold". | |
| 503 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 504 if (blk_end > _next_offset_threshold) | |
| 505 alloc_block_work1(blk_start, blk_end); | |
| 506 } | |
| 507 void alloc_block(HeapWord* blk, size_t size) { | |
| 508 alloc_block(blk, blk+size); | |
| 509 } | |
| 510 | |
| 511 HeapWord* block_start_unsafe(const void* addr); | |
| 512 HeapWord* block_start_unsafe_const(const void* addr) const; | |
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514 void set_for_starts_humongous(HeapWord* new_top); |
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515 |
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516 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 517 }; |
| 1972 | 518 |
| 519 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP |