Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp @ 20304:a22acf6d7598
8048112: G1 Full GC needs to support the case when the very first region is not available
Summary: Refactor preparation for compaction during Full GC so that it lazily initializes the first compaction point. This also avoids problems later when the first region may not be committed. Also reviewed by K. Barrett.
Reviewed-by: brutisso
| author | tschatzl |
|---|---|
| date | Mon, 21 Jul 2014 10:00:31 +0200 |
| parents | 9441d22e429a |
| children | 6701abbc4441 |
| rev | line source |
|---|---|
| 342 | 1 /* |
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2 * Copyright (c) 2001, 2014, 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 G1BlockOffsetSharedArray; | |
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56 class G1OffsetTableContigSpace; |
| 342 | 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 p2i(new_bottom), p2i(_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: " SIZE_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 | |
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160 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset); |
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161 |
| 342 | 162 void set_offset_array(size_t index, u_char offset) { |
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163 check_index(index, "index out of range"); |
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164 check_offset(offset, "offset too large"); |
| 342 | 165 _offset_array[index] = offset; |
| 166 } | |
| 167 | |
| 168 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { | |
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169 check_index(index, "index out of range"); |
| 342 | 170 assert(high >= low, "addresses out of order"); |
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171 check_offset(pointer_delta(high, low), "offset too large"); |
| 342 | 172 _offset_array[index] = (u_char) pointer_delta(high, low); |
| 173 } | |
| 174 | |
| 175 void set_offset_array(size_t left, size_t right, u_char offset) { | |
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176 check_index(right, "right index out of range"); |
| 6610 | 177 assert(left <= right, "indexes out of order"); |
| 342 | 178 size_t num_cards = right - left + 1; |
| 6610 | 179 if (UseMemSetInBOT) { |
| 180 memset(&_offset_array[left], offset, num_cards); | |
| 181 } else { | |
| 182 size_t i = left; | |
| 183 const size_t end = i + num_cards; | |
| 184 for (; i < end; i++) { | |
| 185 _offset_array[i] = offset; | |
| 186 } | |
| 187 } | |
| 342 | 188 } |
| 189 | |
| 190 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
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191 check_index(index, "index out of range"); |
| 342 | 192 assert(high >= low, "addresses out of order"); |
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193 check_offset(pointer_delta(high, low), "offset too large"); |
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194 assert(_offset_array[index] == pointer_delta(high, low), "Wrong offset"); |
| 342 | 195 } |
| 196 | |
| 197 bool is_card_boundary(HeapWord* p) const; | |
| 198 | |
| 199 // Return the number of slots needed for an offset array | |
| 200 // that covers mem_region_words words. | |
| 201 // We always add an extra slot because if an object | |
| 202 // ends on a card boundary we put a 0 in the next | |
| 203 // offset array slot, so we want that slot always | |
| 204 // to be reserved. | |
| 205 | |
| 206 size_t compute_size(size_t mem_region_words) { | |
| 207 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
| 208 return ReservedSpace::page_align_size_up(number_of_slots); | |
| 209 } | |
| 210 | |
| 211 public: | |
| 212 enum SomePublicConstants { | |
| 213 LogN = 9, | |
| 214 LogN_words = LogN - LogHeapWordSize, | |
| 215 N_bytes = 1 << LogN, | |
| 216 N_words = 1 << LogN_words | |
| 217 }; | |
| 218 | |
| 219 // Initialize the table to cover from "base" to (at least) | |
| 220 // "base + init_word_size". In the future, the table may be expanded | |
| 221 // (see "resize" below) up to the size of "_reserved" (which must be at | |
| 222 // least "init_word_size".) The contents of the initial table are | |
| 223 // undefined; it is the responsibility of the constituent | |
| 224 // G1BlockOffsetTable(s) to initialize cards. | |
| 225 G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
| 226 | |
| 227 // Notes a change in the committed size of the region covered by the | |
| 228 // table. The "new_word_size" may not be larger than the size of the | |
| 229 // reserved region this table covers. | |
| 230 void resize(size_t new_word_size); | |
| 231 | |
| 232 void set_bottom(HeapWord* new_bottom); | |
| 233 | |
| 234 // Updates all the BlockOffsetArray's sharing this shared array to | |
| 235 // reflect the current "top"'s of their spaces. | |
| 236 void update_offset_arrays(); | |
| 237 | |
| 238 // Return the appropriate index into "_offset_array" for "p". | |
| 239 inline size_t index_for(const void* p) const; | |
| 240 | |
| 241 // Return the address indicating the start of the region corresponding to | |
| 242 // "index" in "_offset_array". | |
| 243 inline HeapWord* address_for_index(size_t index) const; | |
| 244 }; | |
| 245 | |
| 246 // And here is the G1BlockOffsetTable subtype that uses the array. | |
| 247 | |
| 248 class G1BlockOffsetArray: public G1BlockOffsetTable { | |
| 249 friend class G1BlockOffsetSharedArray; | |
| 250 friend class G1BlockOffsetArrayContigSpace; | |
| 251 friend class VMStructs; | |
| 252 private: | |
| 253 enum SomePrivateConstants { | |
| 254 N_words = G1BlockOffsetSharedArray::N_words, | |
| 255 LogN = G1BlockOffsetSharedArray::LogN | |
| 256 }; | |
| 257 | |
| 258 // The following enums are used by do_block_helper | |
| 259 enum Action { | |
| 260 Action_single, // BOT records a single block (see single_block()) | |
| 261 Action_mark, // BOT marks the start of a block (see mark_block()) | |
| 262 Action_check // Check that BOT records block correctly | |
| 263 // (see verify_single_block()). | |
| 264 }; | |
| 265 | |
| 266 // This is the array, which can be shared by several BlockOffsetArray's | |
| 267 // servicing different | |
| 268 G1BlockOffsetSharedArray* _array; | |
| 269 | |
| 270 // The space that owns this subregion. | |
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271 G1OffsetTableContigSpace* _gsp; |
| 342 | 272 |
| 273 // If true, array entries are initialized to 0; otherwise, they are | |
| 274 // initialized to point backwards to the beginning of the covered region. | |
| 275 bool _init_to_zero; | |
| 276 | |
| 277 // The portion [_unallocated_block, _sp.end()) of the space that | |
| 278 // is a single block known not to contain any objects. | |
| 279 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
| 280 HeapWord* _unallocated_block; | |
| 281 | |
| 282 // Sets the entries | |
| 283 // corresponding to the cards starting at "start" and ending at "end" | |
| 284 // to point back to the card before "start": the interval [start, end) | |
| 285 // is right-open. | |
| 286 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
| 287 // Same as above, except that the args here are a card _index_ interval | |
| 288 // that is closed: [start_index, end_index] | |
| 289 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
| 290 | |
| 291 // A helper function for BOT adjustment/verification work | |
| 292 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
| 293 | |
| 294 protected: | |
| 295 | |
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296 G1OffsetTableContigSpace* gsp() const { return _gsp; } |
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297 |
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298 inline size_t block_size(const HeapWord* p) const; |
| 342 | 299 |
| 300 // Returns the address of a block whose start is at most "addr". | |
| 301 // If "has_max_index" is true, "assumes "max_index" is the last valid one | |
| 302 // in the array. | |
| 303 inline HeapWord* block_at_or_preceding(const void* addr, | |
| 304 bool has_max_index, | |
| 305 size_t max_index) const; | |
| 306 | |
| 307 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
| 308 // next block (or the end of the space.) Return the address of the | |
| 309 // beginning of the block that contains "addr". Does so without side | |
| 310 // effects (see, e.g., spec of block_start.) | |
| 311 inline HeapWord* | |
| 312 forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n, | |
| 313 const void* addr) const; | |
| 314 | |
| 315 // "q" is a block boundary that is <= "addr"; return the address of the | |
| 316 // beginning of the block that contains "addr". May have side effects | |
| 317 // on "this", by updating imprecise entries. | |
| 318 inline HeapWord* forward_to_block_containing_addr(HeapWord* q, | |
| 319 const void* addr); | |
| 320 | |
| 321 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
| 322 // next block (or the end of the space.) Return the address of the | |
| 323 // beginning of the block that contains "addr". May have side effects | |
| 324 // on "this", by updating imprecise entries. | |
| 325 HeapWord* forward_to_block_containing_addr_slow(HeapWord* q, | |
| 326 HeapWord* n, | |
| 327 const void* addr); | |
| 328 | |
| 329 // Requires that "*threshold_" be the first array entry boundary at or | |
| 330 // above "blk_start", and that "*index_" be the corresponding array | |
| 331 // index. If the block starts at or crosses "*threshold_", records | |
| 332 // "blk_start" as the appropriate block start for the array index | |
| 333 // starting at "*threshold_", and for any other indices crossed by the | |
| 334 // block. Updates "*threshold_" and "*index_" to correspond to the first | |
| 335 // index after the block end. | |
| 336 void alloc_block_work2(HeapWord** threshold_, size_t* index_, | |
| 337 HeapWord* blk_start, HeapWord* blk_end); | |
| 338 | |
| 339 public: | |
| 340 // The space may not have it's bottom and top set yet, which is why the | |
| 341 // region is passed as a parameter. If "init_to_zero" is true, the | |
| 342 // elements of the array are initialized to zero. Otherwise, they are | |
| 343 // initialized to point backwards to the beginning. | |
| 344 G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr, | |
| 345 bool init_to_zero); | |
| 346 | |
| 347 // Note: this ought to be part of the constructor, but that would require | |
| 348 // "this" to be passed as a parameter to a member constructor for | |
| 349 // the containing concrete subtype of Space. | |
| 350 // This would be legal C++, but MS VC++ doesn't allow it. | |
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351 void set_space(G1OffsetTableContigSpace* sp); |
| 342 | 352 |
| 353 // Resets the covered region to the given "mr". | |
| 354 void set_region(MemRegion mr); | |
| 355 | |
| 356 // Resets the covered region to one with the same _bottom as before but | |
| 357 // the "new_word_size". | |
| 358 void resize(size_t new_word_size); | |
| 359 | |
| 360 // These must be guaranteed to work properly (i.e., do nothing) | |
| 361 // when "blk_start" ("blk" for second version) is "NULL". | |
| 362 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 363 virtual void alloc_block(HeapWord* blk, size_t size) { | |
| 364 alloc_block(blk, blk + size); | |
| 365 } | |
| 366 | |
| 367 // The following methods are useful and optimized for a | |
| 368 // general, non-contiguous space. | |
| 369 | |
| 370 // Given a block [blk_start, blk_start + full_blk_size), and | |
| 371 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
| 372 // blocks [blk_start, blk_start + left_blk_size) and | |
| 373 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
| 374 // It is assumed (and verified in the non-product VM) that the | |
| 375 // BOT was correct for the original block. | |
| 376 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
| 377 size_t left_blk_size); | |
| 378 | |
| 379 // Adjust the BOT to show that it has a single block in the | |
| 380 // range [blk_start, blk_start + size). All necessary BOT | |
| 381 // cards are adjusted, but _unallocated_block isn't. | |
| 382 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 383 void single_block(HeapWord* blk, size_t size) { | |
| 384 single_block(blk, blk + size); | |
| 385 } | |
| 386 | |
| 387 // Adjust BOT to show that it has a block in the range | |
| 388 // [blk_start, blk_start + size). Only the first card | |
| 389 // of BOT is touched. It is assumed (and verified in the | |
| 390 // non-product VM) that the remaining cards of the block | |
| 391 // are correct. | |
| 392 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 393 void mark_block(HeapWord* blk, size_t size) { | |
| 394 mark_block(blk, blk + size); | |
| 395 } | |
| 396 | |
| 397 // Adjust _unallocated_block to indicate that a particular | |
| 398 // block has been newly allocated or freed. It is assumed (and | |
| 399 // verified in the non-product VM) that the BOT is correct for | |
| 400 // the given block. | |
| 401 inline void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
| 402 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
| 403 verify_single_block(blk_start, blk_end); | |
| 404 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 405 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
| 406 } | |
| 407 } | |
| 408 | |
| 409 inline void allocated(HeapWord* blk, size_t size) { | |
| 410 allocated(blk, blk + size); | |
| 411 } | |
| 412 | |
| 413 inline void freed(HeapWord* blk_start, HeapWord* blk_end); | |
| 414 | |
| 415 inline void freed(HeapWord* blk, size_t size); | |
| 416 | |
| 417 virtual HeapWord* block_start_unsafe(const void* addr); | |
| 418 virtual HeapWord* block_start_unsafe_const(const void* addr) const; | |
| 419 | |
| 420 // Requires "addr" to be the start of a card and returns the | |
| 421 // start of the block that contains the given address. | |
| 422 HeapWord* block_start_careful(const void* addr) const; | |
| 423 | |
| 424 // If true, initialize array slots with no allocated blocks to zero. | |
| 425 // Otherwise, make them point back to the front. | |
| 426 bool init_to_zero() { return _init_to_zero; } | |
| 427 | |
| 428 // Verification & debugging - ensure that the offset table reflects the fact | |
| 429 // that the block [blk_start, blk_end) or [blk, blk + size) is a | |
| 430 // single block of storage. NOTE: can;t const this because of | |
| 431 // call to non-const do_block_internal() below. | |
| 432 inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 433 if (VerifyBlockOffsetArray) { | |
| 434 do_block_internal(blk_start, blk_end, Action_check); | |
| 435 } | |
| 436 } | |
| 437 | |
| 438 inline void verify_single_block(HeapWord* blk, size_t size) { | |
| 439 verify_single_block(blk, blk + size); | |
| 440 } | |
| 441 | |
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442 // Used by region verification. Checks that the contents of the |
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443 // BOT reflect that there's a single object that spans the address |
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444 // range [obj_start, obj_start + word_size); returns true if this is |
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445 // the case, returns false if it's not. |
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446 bool verify_for_object(HeapWord* obj_start, size_t word_size) const; |
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447 |
| 342 | 448 // Verify that the given block is before _unallocated_block |
| 449 inline void verify_not_unallocated(HeapWord* blk_start, | |
| 450 HeapWord* blk_end) const { | |
| 451 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 452 assert(blk_start < blk_end, "Block inconsistency?"); | |
| 453 assert(blk_end <= _unallocated_block, "_unallocated_block problem"); | |
| 454 } | |
| 455 } | |
| 456 | |
| 457 inline void verify_not_unallocated(HeapWord* blk, size_t size) const { | |
| 458 verify_not_unallocated(blk, blk + size); | |
| 459 } | |
| 460 | |
| 461 void check_all_cards(size_t left_card, size_t right_card) const; | |
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462 |
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463 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 464 }; |
| 465 | |
| 466 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 467 // that its underlying space is a ContiguousSpace, so that its "active" | |
| 468 // region can be more efficiently tracked (than for a non-contiguous space). | |
| 469 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray { | |
| 470 friend class VMStructs; | |
| 471 | |
| 472 // allocation boundary at which offset array must be updated | |
| 473 HeapWord* _next_offset_threshold; | |
| 474 size_t _next_offset_index; // index corresponding to that boundary | |
| 475 | |
| 476 // Work function to be called when allocation start crosses the next | |
| 477 // threshold in the contig space. | |
| 478 void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) { | |
| 479 alloc_block_work2(&_next_offset_threshold, &_next_offset_index, | |
| 480 blk_start, blk_end); | |
| 481 } | |
| 482 | |
| 483 public: | |
| 484 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr); | |
| 485 | |
| 486 // Initialize the threshold to reflect the first boundary after the | |
| 487 // bottom of the covered region. | |
| 488 HeapWord* initialize_threshold(); | |
| 489 | |
| 490 // Zero out the entry for _bottom (offset will be zero). | |
| 491 void zero_bottom_entry(); | |
| 492 | |
| 493 // Return the next threshold, the point at which the table should be | |
| 494 // updated. | |
| 495 HeapWord* threshold() const { return _next_offset_threshold; } | |
| 496 | |
| 497 // These must be guaranteed to work properly (i.e., do nothing) | |
| 498 // when "blk_start" ("blk" for second version) is "NULL". In this | |
| 499 // implementation, that's true because NULL is represented as 0, and thus | |
| 500 // never exceeds the "_next_offset_threshold". | |
| 501 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 502 if (blk_end > _next_offset_threshold) | |
| 503 alloc_block_work1(blk_start, blk_end); | |
| 504 } | |
| 505 void alloc_block(HeapWord* blk, size_t size) { | |
| 506 alloc_block(blk, blk+size); | |
| 507 } | |
| 508 | |
| 509 HeapWord* block_start_unsafe(const void* addr); | |
| 510 HeapWord* block_start_unsafe_const(const void* addr) const; | |
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511 |
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512 void set_for_starts_humongous(HeapWord* new_top); |
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513 |
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514 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
| 342 | 515 }; |
| 1972 | 516 |
| 517 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP |