Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp @ 12343:d55c004e1d4d
8025305: Cleanup CardTableModRefBS usage in G1
Summary: Move some G1 specific code from CardTableModRefBS to G1SATBCardTableModRefBS.
Reviewed-by: brutisso, tschatzl, ehelin
| author | mgerdin |
|---|---|
| date | Tue, 24 Sep 2013 14:46:29 +0200 |
| parents | 2fc0334f613a |
| children | 78bbf4d43a14 |
| 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) { | |
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81 assert(new_bottom <= _end, |
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82 err_msg("new_bottom (" PTR_FORMAT ") > _end (" PTR_FORMAT ")", |
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83 new_bottom, _end)); |
| 342 | 84 _bottom = new_bottom; |
| 85 resize(pointer_delta(_end, _bottom)); | |
| 86 } | |
| 87 | |
| 88 // Requires "addr" to be contained by a block, and returns the address of | |
| 89 // the start of that block. (May have side effects, namely updating of | |
| 90 // shared array entries that "point" too far backwards. This can occur, | |
| 91 // for example, when LAB allocation is used in a space covered by the | |
| 92 // table.) | |
| 93 virtual HeapWord* block_start_unsafe(const void* addr) = 0; | |
| 94 // Same as above, but does not have any of the possible side effects | |
| 95 // discussed above. | |
| 96 virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0; | |
| 97 | |
| 98 // Returns the address of the start of the block containing "addr", or | |
| 99 // else "null" if it is covered by no block. (May have side effects, | |
| 100 // namely updating of shared array entries that "point" too far | |
| 101 // backwards. This can occur, for example, when lab allocation is used | |
| 102 // in a space covered by the table.) | |
| 103 inline HeapWord* block_start(const void* addr); | |
| 104 // Same as above, but does not have any of the possible side effects | |
| 105 // discussed above. | |
| 106 inline HeapWord* block_start_const(const void* addr) const; | |
| 107 }; | |
| 108 | |
| 109 // This implementation of "G1BlockOffsetTable" divides the covered region | |
| 110 // into "N"-word subregions (where "N" = 2^"LogN". An array with an entry | |
| 111 // for each such subregion indicates how far back one must go to find the | |
| 112 // start of the chunk that includes the first word of the subregion. | |
| 113 // | |
| 114 // Each BlockOffsetArray is owned by a Space. However, the actual array | |
| 115 // may be shared by several BlockOffsetArrays; this is useful | |
| 116 // when a single resizable area (such as a generation) is divided up into | |
| 117 // several spaces in which contiguous allocation takes place, | |
| 118 // such as, for example, in G1 or in the train generation.) | |
| 119 | |
| 120 // Here is the shared array type. | |
| 121 | |
| 6197 | 122 class G1BlockOffsetSharedArray: public CHeapObj<mtGC> { |
| 342 | 123 friend class G1BlockOffsetArray; |
| 124 friend class G1BlockOffsetArrayContigSpace; | |
| 125 friend class VMStructs; | |
| 126 | |
| 127 private: | |
| 128 // The reserved region covered by the shared array. | |
| 129 MemRegion _reserved; | |
| 130 | |
| 131 // End of the current committed region. | |
| 132 HeapWord* _end; | |
| 133 | |
| 134 // Array for keeping offsets for retrieving object start fast given an | |
| 135 // address. | |
| 136 VirtualSpace _vs; | |
| 137 u_char* _offset_array; // byte array keeping backwards offsets | |
| 138 | |
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139 void check_index(size_t index, const char* msg) const { |
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140 assert(index < _vs.committed_size(), |
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141 err_msg("%s - " |
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142 "index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT, |
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143 msg, index, _vs.committed_size())); |
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144 } |
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145 |
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146 void check_offset(size_t offset, const char* msg) const { |
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147 assert(offset <= N_words, |
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148 err_msg("%s - " |
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149 "offset: " UINT32_FORMAT", N_words: " UINT32_FORMAT, |
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150 msg, offset, N_words)); |
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151 } |
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152 |
| 342 | 153 // Bounds checking accessors: |
| 154 // For performance these have to devolve to array accesses in product builds. | |
| 155 u_char offset_array(size_t index) const { | |
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156 check_index(index, "index out of range"); |
| 342 | 157 return _offset_array[index]; |
| 158 } | |
| 159 | |
| 160 void set_offset_array(size_t index, u_char offset) { | |
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161 check_index(index, "index out of range"); |
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162 check_offset(offset, "offset too large"); |
| 342 | 163 _offset_array[index] = offset; |
| 164 } | |
| 165 | |
| 166 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { | |
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167 check_index(index, "index out of range"); |
| 342 | 168 assert(high >= low, "addresses out of order"); |
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169 check_offset(pointer_delta(high, low), "offset too large"); |
| 342 | 170 _offset_array[index] = (u_char) pointer_delta(high, low); |
| 171 } | |
| 172 | |
| 173 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) { | |
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174 check_index(index_for(right - 1), "right address out of range"); |
| 342 | 175 assert(left < right, "Heap addresses out of order"); |
| 176 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
| 6610 | 177 if (UseMemSetInBOT) { |
| 178 memset(&_offset_array[index_for(left)], offset, num_cards); | |
| 179 } else { | |
| 180 size_t i = index_for(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 set_offset_array(size_t left, size_t right, u_char offset) { | |
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189 check_index(right, "right index out of range"); |
| 6610 | 190 assert(left <= right, "indexes out of order"); |
| 342 | 191 size_t num_cards = right - left + 1; |
| 6610 | 192 if (UseMemSetInBOT) { |
| 193 memset(&_offset_array[left], offset, num_cards); | |
| 194 } else { | |
| 195 size_t i = left; | |
| 196 const size_t end = i + num_cards; | |
| 197 for (; i < end; i++) { | |
| 198 _offset_array[i] = offset; | |
| 199 } | |
| 200 } | |
| 342 | 201 } |
| 202 | |
| 203 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
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204 check_index(index, "index out of range"); |
| 342 | 205 assert(high >= low, "addresses out of order"); |
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206 check_offset(pointer_delta(high, low), "offset too large"); |
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207 assert(_offset_array[index] == pointer_delta(high, low), "Wrong offset"); |
| 342 | 208 } |
| 209 | |
| 210 bool is_card_boundary(HeapWord* p) const; | |
| 211 | |
| 212 // Return the number of slots needed for an offset array | |
| 213 // that covers mem_region_words words. | |
| 214 // We always add an extra slot because if an object | |
| 215 // ends on a card boundary we put a 0 in the next | |
| 216 // offset array slot, so we want that slot always | |
| 217 // to be reserved. | |
| 218 | |
| 219 size_t compute_size(size_t mem_region_words) { | |
| 220 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
| 221 return ReservedSpace::page_align_size_up(number_of_slots); | |
| 222 } | |
| 223 | |
| 224 public: | |
| 225 enum SomePublicConstants { | |
| 226 LogN = 9, | |
| 227 LogN_words = LogN - LogHeapWordSize, | |
| 228 N_bytes = 1 << LogN, | |
| 229 N_words = 1 << LogN_words | |
| 230 }; | |
| 231 | |
| 232 // Initialize the table to cover from "base" to (at least) | |
| 233 // "base + init_word_size". In the future, the table may be expanded | |
| 234 // (see "resize" below) up to the size of "_reserved" (which must be at | |
| 235 // least "init_word_size".) The contents of the initial table are | |
| 236 // undefined; it is the responsibility of the constituent | |
| 237 // G1BlockOffsetTable(s) to initialize cards. | |
| 238 G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
| 239 | |
| 240 // Notes a change in the committed size of the region covered by the | |
| 241 // table. The "new_word_size" may not be larger than the size of the | |
| 242 // reserved region this table covers. | |
| 243 void resize(size_t new_word_size); | |
| 244 | |
| 245 void set_bottom(HeapWord* new_bottom); | |
| 246 | |
| 247 // Updates all the BlockOffsetArray's sharing this shared array to | |
| 248 // reflect the current "top"'s of their spaces. | |
| 249 void update_offset_arrays(); | |
| 250 | |
| 251 // Return the appropriate index into "_offset_array" for "p". | |
| 252 inline size_t index_for(const void* p) const; | |
| 253 | |
| 254 // Return the address indicating the start of the region corresponding to | |
| 255 // "index" in "_offset_array". | |
| 256 inline HeapWord* address_for_index(size_t index) const; | |
| 257 }; | |
| 258 | |
| 259 // And here is the G1BlockOffsetTable subtype that uses the array. | |
| 260 | |
| 261 class G1BlockOffsetArray: public G1BlockOffsetTable { | |
| 262 friend class G1BlockOffsetSharedArray; | |
| 263 friend class G1BlockOffsetArrayContigSpace; | |
| 264 friend class VMStructs; | |
| 265 private: | |
| 266 enum SomePrivateConstants { | |
| 267 N_words = G1BlockOffsetSharedArray::N_words, | |
| 268 LogN = G1BlockOffsetSharedArray::LogN | |
| 269 }; | |
| 270 | |
| 271 // The following enums are used by do_block_helper | |
| 272 enum Action { | |
| 273 Action_single, // BOT records a single block (see single_block()) | |
| 274 Action_mark, // BOT marks the start of a block (see mark_block()) | |
| 275 Action_check // Check that BOT records block correctly | |
| 276 // (see verify_single_block()). | |
| 277 }; | |
| 278 | |
| 279 // This is the array, which can be shared by several BlockOffsetArray's | |
| 280 // servicing different | |
| 281 G1BlockOffsetSharedArray* _array; | |
| 282 | |
| 283 // The space that owns this subregion. | |
| 284 Space* _sp; | |
| 285 | |
| 286 // If "_sp" is a contiguous space, the field below is the view of "_sp" | |
| 287 // as a contiguous space, else NULL. | |
| 288 ContiguousSpace* _csp; | |
| 289 | |
| 290 // If true, array entries are initialized to 0; otherwise, they are | |
| 291 // initialized to point backwards to the beginning of the covered region. | |
| 292 bool _init_to_zero; | |
| 293 | |
| 294 // The portion [_unallocated_block, _sp.end()) of the space that | |
| 295 // is a single block known not to contain any objects. | |
| 296 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
| 297 HeapWord* _unallocated_block; | |
| 298 | |
| 299 // Sets the entries | |
| 300 // corresponding to the cards starting at "start" and ending at "end" | |
| 301 // to point back to the card before "start": the interval [start, end) | |
| 302 // is right-open. | |
| 303 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
| 304 // Same as above, except that the args here are a card _index_ interval | |
| 305 // that is closed: [start_index, end_index] | |
| 306 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
| 307 | |
| 308 // A helper function for BOT adjustment/verification work | |
| 309 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
| 310 | |
| 311 protected: | |
| 312 | |
| 313 ContiguousSpace* csp() const { return _csp; } | |
| 314 | |
| 315 // Returns the address of a block whose start is at most "addr". | |
| 316 // If "has_max_index" is true, "assumes "max_index" is the last valid one | |
| 317 // in the array. | |
| 318 inline HeapWord* block_at_or_preceding(const void* addr, | |
| 319 bool has_max_index, | |
| 320 size_t max_index) const; | |
| 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". Does so without side | |
| 325 // effects (see, e.g., spec of block_start.) | |
| 326 inline HeapWord* | |
| 327 forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n, | |
| 328 const void* addr) const; | |
| 329 | |
| 330 // "q" is a block boundary that is <= "addr"; return the address of the | |
| 331 // beginning of the block that contains "addr". May have side effects | |
| 332 // on "this", by updating imprecise entries. | |
| 333 inline HeapWord* forward_to_block_containing_addr(HeapWord* q, | |
| 334 const void* addr); | |
| 335 | |
| 336 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
| 337 // next block (or the end of the space.) Return the address of the | |
| 338 // beginning of the block that contains "addr". May have side effects | |
| 339 // on "this", by updating imprecise entries. | |
| 340 HeapWord* forward_to_block_containing_addr_slow(HeapWord* q, | |
| 341 HeapWord* n, | |
| 342 const void* addr); | |
| 343 | |
| 344 // Requires that "*threshold_" be the first array entry boundary at or | |
| 345 // above "blk_start", and that "*index_" be the corresponding array | |
| 346 // index. If the block starts at or crosses "*threshold_", records | |
| 347 // "blk_start" as the appropriate block start for the array index | |
| 348 // starting at "*threshold_", and for any other indices crossed by the | |
| 349 // block. Updates "*threshold_" and "*index_" to correspond to the first | |
| 350 // index after the block end. | |
| 351 void alloc_block_work2(HeapWord** threshold_, size_t* index_, | |
| 352 HeapWord* blk_start, HeapWord* blk_end); | |
| 353 | |
| 354 public: | |
| 355 // The space may not have it's bottom and top set yet, which is why the | |
| 356 // region is passed as a parameter. If "init_to_zero" is true, the | |
| 357 // elements of the array are initialized to zero. Otherwise, they are | |
| 358 // initialized to point backwards to the beginning. | |
| 359 G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr, | |
| 360 bool init_to_zero); | |
| 361 | |
| 362 // Note: this ought to be part of the constructor, but that would require | |
| 363 // "this" to be passed as a parameter to a member constructor for | |
| 364 // the containing concrete subtype of Space. | |
| 365 // This would be legal C++, but MS VC++ doesn't allow it. | |
| 366 void set_space(Space* sp); | |
| 367 | |
| 368 // Resets the covered region to the given "mr". | |
| 369 void set_region(MemRegion mr); | |
| 370 | |
| 371 // Resets the covered region to one with the same _bottom as before but | |
| 372 // the "new_word_size". | |
| 373 void resize(size_t new_word_size); | |
| 374 | |
| 375 // These must be guaranteed to work properly (i.e., do nothing) | |
| 376 // when "blk_start" ("blk" for second version) is "NULL". | |
| 377 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 378 virtual void alloc_block(HeapWord* blk, size_t size) { | |
| 379 alloc_block(blk, blk + size); | |
| 380 } | |
| 381 | |
| 382 // The following methods are useful and optimized for a | |
| 383 // general, non-contiguous space. | |
| 384 | |
| 385 // Given a block [blk_start, blk_start + full_blk_size), and | |
| 386 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
| 387 // blocks [blk_start, blk_start + left_blk_size) and | |
| 388 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
| 389 // It is assumed (and verified in the non-product VM) that the | |
| 390 // BOT was correct for the original block. | |
| 391 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
| 392 size_t left_blk_size); | |
| 393 | |
| 394 // Adjust the BOT to show that it has a single block in the | |
| 395 // range [blk_start, blk_start + size). All necessary BOT | |
| 396 // cards are adjusted, but _unallocated_block isn't. | |
| 397 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 398 void single_block(HeapWord* blk, size_t size) { | |
| 399 single_block(blk, blk + size); | |
| 400 } | |
| 401 | |
| 402 // Adjust BOT to show that it has a block in the range | |
| 403 // [blk_start, blk_start + size). Only the first card | |
| 404 // of BOT is touched. It is assumed (and verified in the | |
| 405 // non-product VM) that the remaining cards of the block | |
| 406 // are correct. | |
| 407 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 408 void mark_block(HeapWord* blk, size_t size) { | |
| 409 mark_block(blk, blk + size); | |
| 410 } | |
| 411 | |
| 412 // Adjust _unallocated_block to indicate that a particular | |
| 413 // block has been newly allocated or freed. It is assumed (and | |
| 414 // verified in the non-product VM) that the BOT is correct for | |
| 415 // the given block. | |
| 416 inline void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
| 417 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
| 418 verify_single_block(blk_start, blk_end); | |
| 419 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 420 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
| 421 } | |
| 422 } | |
| 423 | |
| 424 inline void allocated(HeapWord* blk, size_t size) { | |
| 425 allocated(blk, blk + size); | |
| 426 } | |
| 427 | |
| 428 inline void freed(HeapWord* blk_start, HeapWord* blk_end); | |
| 429 | |
| 430 inline void freed(HeapWord* blk, size_t size); | |
| 431 | |
| 432 virtual HeapWord* block_start_unsafe(const void* addr); | |
| 433 virtual HeapWord* block_start_unsafe_const(const void* addr) const; | |
| 434 | |
| 435 // Requires "addr" to be the start of a card and returns the | |
| 436 // start of the block that contains the given address. | |
| 437 HeapWord* block_start_careful(const void* addr) const; | |
| 438 | |
| 439 // If true, initialize array slots with no allocated blocks to zero. | |
| 440 // Otherwise, make them point back to the front. | |
| 441 bool init_to_zero() { return _init_to_zero; } | |
| 442 | |
| 443 // Verification & debugging - ensure that the offset table reflects the fact | |
| 444 // that the block [blk_start, blk_end) or [blk, blk + size) is a | |
| 445 // single block of storage. NOTE: can;t const this because of | |
| 446 // call to non-const do_block_internal() below. | |
| 447 inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 448 if (VerifyBlockOffsetArray) { | |
| 449 do_block_internal(blk_start, blk_end, Action_check); | |
| 450 } | |
| 451 } | |
| 452 | |
| 453 inline void verify_single_block(HeapWord* blk, size_t size) { | |
| 454 verify_single_block(blk, blk + size); | |
| 455 } | |
| 456 | |
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457 // Used by region verification. Checks that the contents of the |
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458 // BOT reflect that there's a single object that spans the address |
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459 // range [obj_start, obj_start + word_size); returns true if this is |
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460 // the case, returns false if it's not. |
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461 bool verify_for_object(HeapWord* obj_start, size_t word_size) const; |
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462 |
| 342 | 463 // Verify that the given block is before _unallocated_block |
| 464 inline void verify_not_unallocated(HeapWord* blk_start, | |
| 465 HeapWord* blk_end) const { | |
| 466 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 467 assert(blk_start < blk_end, "Block inconsistency?"); | |
| 468 assert(blk_end <= _unallocated_block, "_unallocated_block problem"); | |
| 469 } | |
| 470 } | |
| 471 | |
| 472 inline void verify_not_unallocated(HeapWord* blk, size_t size) const { | |
| 473 verify_not_unallocated(blk, blk + size); | |
| 474 } | |
| 475 | |
| 476 void check_all_cards(size_t left_card, size_t right_card) const; | |
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477 |
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478 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 479 }; |
| 480 | |
| 481 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 482 // that its underlying space is a ContiguousSpace, so that its "active" | |
| 483 // region can be more efficiently tracked (than for a non-contiguous space). | |
| 484 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray { | |
| 485 friend class VMStructs; | |
| 486 | |
| 487 // allocation boundary at which offset array must be updated | |
| 488 HeapWord* _next_offset_threshold; | |
| 489 size_t _next_offset_index; // index corresponding to that boundary | |
| 490 | |
| 491 // Work function to be called when allocation start crosses the next | |
| 492 // threshold in the contig space. | |
| 493 void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) { | |
| 494 alloc_block_work2(&_next_offset_threshold, &_next_offset_index, | |
| 495 blk_start, blk_end); | |
| 496 } | |
| 497 | |
| 498 public: | |
| 499 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr); | |
| 500 | |
| 501 // Initialize the threshold to reflect the first boundary after the | |
| 502 // bottom of the covered region. | |
| 503 HeapWord* initialize_threshold(); | |
| 504 | |
| 505 // Zero out the entry for _bottom (offset will be zero). | |
| 506 void zero_bottom_entry(); | |
| 507 | |
| 508 // Return the next threshold, the point at which the table should be | |
| 509 // updated. | |
| 510 HeapWord* threshold() const { return _next_offset_threshold; } | |
| 511 | |
| 512 // These must be guaranteed to work properly (i.e., do nothing) | |
| 513 // when "blk_start" ("blk" for second version) is "NULL". In this | |
| 514 // implementation, that's true because NULL is represented as 0, and thus | |
| 515 // never exceeds the "_next_offset_threshold". | |
| 516 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 517 if (blk_end > _next_offset_threshold) | |
| 518 alloc_block_work1(blk_start, blk_end); | |
| 519 } | |
| 520 void alloc_block(HeapWord* blk, size_t size) { | |
| 521 alloc_block(blk, blk+size); | |
| 522 } | |
| 523 | |
| 524 HeapWord* block_start_unsafe(const void* addr); | |
| 525 HeapWord* block_start_unsafe_const(const void* addr) const; | |
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526 |
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527 void set_for_starts_humongous(HeapWord* new_top); |
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528 |
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529 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 530 }; |
| 1972 | 531 |
| 532 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP |