Mercurial > hg > graal-compiler
annotate src/share/vm/memory/blockOffsetTable.hpp @ 1732:52f2bc645da5
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Reviewed-by: jcoomes, jmasa, tonyp
| author | ysr |
|---|---|
| date | Thu, 19 Aug 2010 12:02:10 -0700 |
| parents | be3f9c242c9d |
| children | f95d63e2154a |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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. |
| 0 | 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 | |
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110 bool _init_to_zero; |
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111 |
| 0 | 112 // The reserved region covered by the shared array. |
| 113 MemRegion _reserved; | |
| 114 | |
| 115 // End of the current committed region. | |
| 116 HeapWord* _end; | |
| 117 | |
| 118 // Array for keeping offsets for retrieving object start fast given an | |
| 119 // address. | |
| 120 VirtualSpace _vs; | |
| 121 u_char* _offset_array; // byte array keeping backwards offsets | |
| 122 | |
| 123 protected: | |
| 124 // Bounds checking accessors: | |
| 125 // For performance these have to devolve to array accesses in product builds. | |
| 126 u_char offset_array(size_t index) const { | |
| 127 assert(index < _vs.committed_size(), "index out of range"); | |
| 128 return _offset_array[index]; | |
| 129 } | |
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130 // An assertion-checking helper method for the set_offset_array() methods below. |
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131 void check_reducing_assertion(bool reducing); |
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132 |
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133 void set_offset_array(size_t index, u_char offset, bool reducing = false) { |
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134 check_reducing_assertion(reducing); |
| 0 | 135 assert(index < _vs.committed_size(), "index out of range"); |
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136 assert(!reducing || _offset_array[index] >= offset, "Not reducing"); |
| 0 | 137 _offset_array[index] = offset; |
| 138 } | |
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139 |
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140 void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) { |
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141 check_reducing_assertion(reducing); |
| 0 | 142 assert(index < _vs.committed_size(), "index out of range"); |
| 143 assert(high >= low, "addresses out of order"); | |
| 144 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
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145 assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low), |
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146 "Not reducing"); |
| 0 | 147 _offset_array[index] = (u_char)pointer_delta(high, low); |
| 148 } | |
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149 |
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150 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) { |
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151 check_reducing_assertion(reducing); |
| 0 | 152 assert(index_for(right - 1) < _vs.committed_size(), |
| 153 "right address out of range"); | |
| 154 assert(left < right, "Heap addresses out of order"); | |
| 155 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
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156 |
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157 // Below, we may use an explicit loop instead of memset() |
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158 // because on certain platforms memset() can give concurrent |
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159 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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160 if (UseMemSetInBOT) { |
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161 memset(&_offset_array[index_for(left)], offset, num_cards); |
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162 } else { |
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163 size_t i = index_for(left); |
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164 const size_t end = i + num_cards; |
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165 for (; i < end; i++) { |
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166 // Elided until CR 6977974 is fixed properly. |
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167 // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); |
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168 _offset_array[i] = offset; |
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169 } |
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170 } |
| 0 | 171 } |
| 172 | |
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173 void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) { |
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174 check_reducing_assertion(reducing); |
| 0 | 175 assert(right < _vs.committed_size(), "right address out of range"); |
| 176 assert(left <= right, "indexes out of order"); | |
| 177 size_t num_cards = right - left + 1; | |
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178 |
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179 // Below, we may use an explicit loop instead of memset |
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180 // because on certain platforms memset() can give concurrent |
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181 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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182 if (UseMemSetInBOT) { |
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183 memset(&_offset_array[left], offset, num_cards); |
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184 } else { |
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185 size_t i = left; |
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186 const size_t end = i + num_cards; |
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187 for (; i < end; i++) { |
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188 // Elided until CR 6977974 is fixed properly. |
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189 // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); |
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190 _offset_array[i] = offset; |
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191 } |
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192 } |
| 0 | 193 } |
| 194 | |
| 195 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
| 196 assert(index < _vs.committed_size(), "index out of range"); | |
| 197 assert(high >= low, "addresses out of order"); | |
| 198 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
| 199 assert(_offset_array[index] == pointer_delta(high, low), | |
| 200 "Wrong offset"); | |
| 201 } | |
| 202 | |
| 203 bool is_card_boundary(HeapWord* p) const; | |
| 204 | |
| 205 // Return the number of slots needed for an offset array | |
| 206 // that covers mem_region_words words. | |
| 207 // We always add an extra slot because if an object | |
| 208 // ends on a card boundary we put a 0 in the next | |
| 209 // offset array slot, so we want that slot always | |
| 210 // to be reserved. | |
| 211 | |
| 212 size_t compute_size(size_t mem_region_words) { | |
| 213 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
| 214 return ReservedSpace::allocation_align_size_up(number_of_slots); | |
| 215 } | |
| 216 | |
| 217 public: | |
| 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 // BlockOffsetTable(s) to initialize cards. | |
| 224 BlockOffsetSharedArray(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 | |
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233 // Whether entries should be initialized to zero. Used currently only for |
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234 // error checking. |
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235 void set_init_to_zero(bool val) { _init_to_zero = val; } |
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236 bool init_to_zero() { return _init_to_zero; } |
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237 |
| 0 | 238 // Updates all the BlockOffsetArray's sharing this shared array to |
| 239 // reflect the current "top"'s of their spaces. | |
| 240 void update_offset_arrays(); // Not yet implemented! | |
| 241 | |
| 242 // Return the appropriate index into "_offset_array" for "p". | |
| 243 size_t index_for(const void* p) const; | |
| 244 | |
| 245 // Return the address indicating the start of the region corresponding to | |
| 246 // "index" in "_offset_array". | |
| 247 HeapWord* address_for_index(size_t index) const; | |
| 248 | |
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249 // Return the address "p" incremented by the size of |
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250 // a region. This method does not align the address |
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251 // returned to the start of a region. It is a simple |
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252 // primitive. |
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253 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; } |
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254 |
| 0 | 255 // Shared space support |
| 256 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end); | |
| 257 }; | |
| 258 | |
| 259 ////////////////////////////////////////////////////////////////////////// | |
| 260 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. | |
| 261 ////////////////////////////////////////////////////////////////////////// | |
| 262 class BlockOffsetArray: public BlockOffsetTable { | |
| 263 friend class VMStructs; | |
| 342 | 264 friend class G1BlockOffsetArray; // temp. until we restructure and cleanup |
| 0 | 265 protected: |
| 266 // The following enums are used by do_block_internal() below | |
| 267 enum Action { | |
| 268 Action_single, // BOT records a single block (see single_block()) | |
| 269 Action_mark, // BOT marks the start of a block (see mark_block()) | |
| 270 Action_check // Check that BOT records block correctly | |
| 271 // (see verify_single_block()). | |
| 272 }; | |
| 273 | |
| 274 enum SomePrivateConstants { | |
| 275 N_words = BlockOffsetSharedArray::N_words, | |
| 276 LogN = BlockOffsetSharedArray::LogN, | |
| 277 // entries "e" of at least N_words mean "go back by Base^(e-N_words)." | |
| 278 // All entries are less than "N_words + N_powers". | |
| 279 LogBase = 4, | |
| 280 Base = (1 << LogBase), | |
| 281 N_powers = 14 | |
| 282 }; | |
| 283 | |
| 284 static size_t power_to_cards_back(uint i) { | |
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285 return (size_t)(1 << (LogBase * i)); |
| 0 | 286 } |
| 287 static size_t power_to_words_back(uint i) { | |
| 288 return power_to_cards_back(i) * N_words; | |
| 289 } | |
| 290 static size_t entry_to_cards_back(u_char entry) { | |
| 291 assert(entry >= N_words, "Precondition"); | |
| 292 return power_to_cards_back(entry - N_words); | |
| 293 } | |
| 294 static size_t entry_to_words_back(u_char entry) { | |
| 295 assert(entry >= N_words, "Precondition"); | |
| 296 return power_to_words_back(entry - N_words); | |
| 297 } | |
| 298 | |
| 299 // The shared array, which is shared with other BlockOffsetArray's | |
| 300 // corresponding to different spaces within a generation or span of | |
| 301 // memory. | |
| 302 BlockOffsetSharedArray* _array; | |
| 303 | |
| 304 // The space that owns this subregion. | |
| 305 Space* _sp; | |
| 306 | |
| 307 // If true, array entries are initialized to 0; otherwise, they are | |
| 308 // initialized to point backwards to the beginning of the covered region. | |
| 309 bool _init_to_zero; | |
| 310 | |
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311 // An assertion-checking helper method for the set_remainder*() methods below. |
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312 void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); } |
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313 |
| 0 | 314 // Sets the entries |
| 315 // corresponding to the cards starting at "start" and ending at "end" | |
| 316 // to point back to the card before "start": the interval [start, end) | |
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317 // is right-open. The last parameter, reducing, indicates whether the |
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318 // updates to individual entries always reduce the entry from a higher |
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319 // to a lower value. (For example this would hold true during a temporal |
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320 // regime during which only block splits were updating the BOT. |
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321 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false); |
| 0 | 322 // Same as above, except that the args here are a card _index_ interval |
| 323 // that is closed: [start_index, end_index] | |
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324 void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false); |
| 0 | 325 |
| 326 // A helper function for BOT adjustment/verification work | |
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327 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false); |
| 0 | 328 |
| 329 public: | |
| 330 // The space may not have its bottom and top set yet, which is why the | |
| 331 // region is passed as a parameter. If "init_to_zero" is true, the | |
| 332 // elements of the array are initialized to zero. Otherwise, they are | |
| 333 // initialized to point backwards to the beginning. | |
| 334 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, | |
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335 bool init_to_zero_); |
| 0 | 336 |
| 337 // Note: this ought to be part of the constructor, but that would require | |
| 338 // "this" to be passed as a parameter to a member constructor for | |
| 339 // the containing concrete subtype of Space. | |
| 340 // This would be legal C++, but MS VC++ doesn't allow it. | |
| 341 void set_space(Space* sp) { _sp = sp; } | |
| 342 | |
| 343 // Resets the covered region to the given "mr". | |
| 344 void set_region(MemRegion mr) { | |
| 345 _bottom = mr.start(); | |
| 346 _end = mr.end(); | |
| 347 } | |
| 348 | |
| 349 // Note that the committed size of the covered space may have changed, | |
| 350 // so the table size might also wish to change. | |
| 351 virtual void resize(size_t new_word_size) { | |
| 352 HeapWord* new_end = _bottom + new_word_size; | |
| 353 if (_end < new_end && !init_to_zero()) { | |
| 354 // verify that the old and new boundaries are also card boundaries | |
| 355 assert(_array->is_card_boundary(_end), | |
| 356 "_end not a card boundary"); | |
| 357 assert(_array->is_card_boundary(new_end), | |
| 358 "new _end would not be a card boundary"); | |
| 359 // set all the newly added cards | |
| 360 _array->set_offset_array(_end, new_end, N_words); | |
| 361 } | |
| 362 _end = new_end; // update _end | |
| 363 } | |
| 364 | |
| 365 // Adjust the BOT to show that it has a single block in the | |
| 366 // range [blk_start, blk_start + size). All necessary BOT | |
| 367 // cards are adjusted, but _unallocated_block isn't. | |
| 368 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 369 void single_block(HeapWord* blk, size_t size) { | |
| 370 single_block(blk, blk + size); | |
| 371 } | |
| 372 | |
| 373 // When the alloc_block() call returns, the block offset table should | |
| 374 // have enough information such that any subsequent block_start() call | |
| 375 // with an argument equal to an address that is within the range | |
| 376 // [blk_start, blk_end) would return the value blk_start, provided | |
| 377 // there have been no calls in between that reset this information | |
| 378 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call | |
| 379 // for an appropriate range covering the said interval). | |
| 380 // These methods expect to be called with [blk_start, blk_end) | |
| 381 // representing a block of memory in the heap. | |
| 382 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 383 void alloc_block(HeapWord* blk, size_t size) { | |
| 384 alloc_block(blk, blk + size); | |
| 385 } | |
| 386 | |
| 387 // If true, initialize array slots with no allocated blocks to zero. | |
| 388 // Otherwise, make them point back to the front. | |
| 389 bool init_to_zero() { return _init_to_zero; } | |
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390 // Corresponding setter |
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391 void set_init_to_zero(bool val) { |
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392 _init_to_zero = val; |
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393 assert(_array != NULL, "_array should be non-NULL"); |
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394 _array->set_init_to_zero(val); |
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395 } |
| 0 | 396 |
| 397 // Debugging | |
| 398 // Return the index of the last entry in the "active" region. | |
| 399 virtual size_t last_active_index() const = 0; | |
| 400 // Verify the block offset table | |
| 401 void verify() const; | |
| 402 void check_all_cards(size_t left_card, size_t right_card) const; | |
| 403 }; | |
| 404 | |
| 405 //////////////////////////////////////////////////////////////////////////// | |
| 406 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 407 // that its underlying space is a NonContiguousSpace, so that some | |
| 408 // specialized interfaces can be made available for spaces that | |
| 409 // manipulate the table. | |
| 410 //////////////////////////////////////////////////////////////////////////// | |
| 411 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { | |
| 412 friend class VMStructs; | |
| 413 private: | |
| 414 // The portion [_unallocated_block, _sp.end()) of the space that | |
| 415 // is a single block known not to contain any objects. | |
| 416 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
| 417 HeapWord* _unallocated_block; | |
| 418 | |
| 419 public: | |
| 420 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
| 421 BlockOffsetArray(array, mr, false), | |
| 422 _unallocated_block(_bottom) { } | |
| 423 | |
| 424 // accessor | |
| 425 HeapWord* unallocated_block() const { | |
| 426 assert(BlockOffsetArrayUseUnallocatedBlock, | |
| 427 "_unallocated_block is not being maintained"); | |
| 428 return _unallocated_block; | |
| 429 } | |
| 430 | |
| 431 void set_unallocated_block(HeapWord* block) { | |
| 432 assert(BlockOffsetArrayUseUnallocatedBlock, | |
| 433 "_unallocated_block is not being maintained"); | |
| 434 assert(block >= _bottom && block <= _end, "out of range"); | |
| 435 _unallocated_block = block; | |
| 436 } | |
| 437 | |
| 438 // These methods expect to be called with [blk_start, blk_end) | |
| 439 // representing a block of memory in the heap. | |
| 440 void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
| 441 void alloc_block(HeapWord* blk, size_t size) { | |
| 442 alloc_block(blk, blk + size); | |
| 443 } | |
| 444 | |
| 445 // The following methods are useful and optimized for a | |
| 446 // non-contiguous space. | |
| 447 | |
| 448 // Given a block [blk_start, blk_start + full_blk_size), and | |
| 449 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
| 450 // blocks [blk_start, blk_start + left_blk_size) and | |
| 451 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
| 452 // It is assumed (and verified in the non-product VM) that the | |
| 453 // BOT was correct for the original block. | |
| 454 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
| 455 size_t left_blk_size); | |
| 456 | |
| 457 // Adjust BOT to show that it has a block in the range | |
| 458 // [blk_start, blk_start + size). Only the first card | |
| 459 // of BOT is touched. It is assumed (and verified in the | |
| 460 // non-product VM) that the remaining cards of the block | |
| 461 // are correct. | |
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462 void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false); |
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463 void mark_block(HeapWord* blk, size_t size, bool reducing = false) { |
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464 mark_block(blk, blk + size, reducing); |
| 0 | 465 } |
| 466 | |
| 467 // Adjust _unallocated_block to indicate that a particular | |
| 468 // block has been newly allocated or freed. It is assumed (and | |
| 469 // verified in the non-product VM) that the BOT is correct for | |
| 470 // the given block. | |
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471 void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) { |
| 0 | 472 // Verify that the BOT shows [blk, blk + blk_size) to be one block. |
| 473 verify_single_block(blk_start, blk_end); | |
| 474 if (BlockOffsetArrayUseUnallocatedBlock) { | |
| 475 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
| 476 } | |
| 477 } | |
| 478 | |
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479 void allocated(HeapWord* blk, size_t size, bool reducing = false) { |
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480 allocated(blk, blk + size, reducing); |
| 0 | 481 } |
| 482 | |
| 483 void freed(HeapWord* blk_start, HeapWord* blk_end); | |
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484 void freed(HeapWord* blk, size_t size); |
| 0 | 485 |
| 486 HeapWord* block_start_unsafe(const void* addr) const; | |
| 487 | |
| 488 // Requires "addr" to be the start of a card and returns the | |
| 489 // start of the block that contains the given address. | |
| 490 HeapWord* block_start_careful(const void* addr) const; | |
| 491 | |
| 492 // Verification & debugging: ensure that the offset table reflects | |
| 493 // the fact that the block [blk_start, blk_end) or [blk, blk + size) | |
| 494 // is a single block of storage. NOTE: can't const this because of | |
| 495 // call to non-const do_block_internal() below. | |
| 496 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) | |
| 497 PRODUCT_RETURN; | |
| 498 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; | |
| 499 | |
| 500 // Verify that the given block is before _unallocated_block | |
| 501 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) | |
| 502 const PRODUCT_RETURN; | |
| 503 void verify_not_unallocated(HeapWord* blk, size_t size) | |
| 504 const PRODUCT_RETURN; | |
| 505 | |
| 506 // Debugging support | |
| 507 virtual size_t last_active_index() const; | |
| 508 }; | |
| 509 | |
| 510 //////////////////////////////////////////////////////////////////////////// | |
| 511 // A subtype of BlockOffsetArray that takes advantage of the fact | |
| 512 // that its underlying space is a ContiguousSpace, so that its "active" | |
| 513 // region can be more efficiently tracked (than for a non-contiguous space). | |
| 514 //////////////////////////////////////////////////////////////////////////// | |
| 515 class BlockOffsetArrayContigSpace: public BlockOffsetArray { | |
| 516 friend class VMStructs; | |
| 517 private: | |
| 518 // allocation boundary at which offset array must be updated | |
| 519 HeapWord* _next_offset_threshold; | |
| 520 size_t _next_offset_index; // index corresponding to that boundary | |
| 521 | |
| 522 // Work function when allocation start crosses threshold. | |
| 523 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); | |
| 524 | |
| 525 public: | |
| 526 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
| 527 BlockOffsetArray(array, mr, true) { | |
| 528 _next_offset_threshold = NULL; | |
| 529 _next_offset_index = 0; | |
| 530 } | |
| 531 | |
| 532 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } | |
| 533 | |
| 534 // Initialize the threshold for an empty heap. | |
| 535 HeapWord* initialize_threshold(); | |
| 536 // Zero out the entry for _bottom (offset will be zero) | |
| 537 void zero_bottom_entry(); | |
| 538 | |
| 539 // Return the next threshold, the point at which the table should be | |
| 540 // updated. | |
| 541 HeapWord* threshold() const { return _next_offset_threshold; } | |
| 542 | |
| 543 // In general, these methods expect to be called with | |
| 544 // [blk_start, blk_end) representing a block of memory in the heap. | |
| 545 // In this implementation, however, we are OK even if blk_start and/or | |
| 546 // blk_end are NULL because NULL is represented as 0, and thus | |
| 547 // never exceeds the "_next_offset_threshold". | |
| 548 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
| 549 if (blk_end > _next_offset_threshold) { | |
| 550 alloc_block_work(blk_start, blk_end); | |
| 551 } | |
| 552 } | |
| 553 void alloc_block(HeapWord* blk, size_t size) { | |
| 554 alloc_block(blk, blk + size); | |
| 555 } | |
| 556 | |
| 557 HeapWord* block_start_unsafe(const void* addr) const; | |
| 558 | |
| 559 void serialize(SerializeOopClosure* soc); | |
| 560 | |
| 561 // Debugging support | |
| 562 virtual size_t last_active_index() const; | |
| 563 }; |