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annotate src/share/vm/memory/blockOffsetTable.hpp @ 1642:0e7d2a08b605
6967423: Hotspot support for modules image
Summary: Add hotspot support for modules image
Reviewed-by: acorn
author | mchung |
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date | Wed, 07 Jul 2010 15:35:58 -0700 |
parents | c18cbe5936b8 |
children | be3f9c242c9d |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2000, 2009, 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 | |
110 // The reserved region covered by the shared array. | |
111 MemRegion _reserved; | |
112 | |
113 // End of the current committed region. | |
114 HeapWord* _end; | |
115 | |
116 // Array for keeping offsets for retrieving object start fast given an | |
117 // address. | |
118 VirtualSpace _vs; | |
119 u_char* _offset_array; // byte array keeping backwards offsets | |
120 | |
121 protected: | |
122 // Bounds checking accessors: | |
123 // For performance these have to devolve to array accesses in product builds. | |
124 u_char offset_array(size_t index) const { | |
125 assert(index < _vs.committed_size(), "index out of range"); | |
126 return _offset_array[index]; | |
127 } | |
128 void set_offset_array(size_t index, u_char offset) { | |
129 assert(index < _vs.committed_size(), "index out of range"); | |
130 _offset_array[index] = offset; | |
131 } | |
132 void set_offset_array(size_t index, HeapWord* high, HeapWord* low) { | |
133 assert(index < _vs.committed_size(), "index out of range"); | |
134 assert(high >= low, "addresses out of order"); | |
135 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
136 _offset_array[index] = (u_char)pointer_delta(high, low); | |
137 } | |
138 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) { | |
139 assert(index_for(right - 1) < _vs.committed_size(), | |
140 "right address out of range"); | |
141 assert(left < right, "Heap addresses out of order"); | |
142 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
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143 |
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144 // Below, we may use an explicit loop instead of memset() |
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145 // because on certain platforms memset() can give concurrent |
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146 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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147 if (UseMemSetInBOT) { |
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148 memset(&_offset_array[index_for(left)], offset, num_cards); |
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149 } else { |
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150 size_t i = index_for(left); |
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151 const size_t end = i + num_cards; |
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152 for (; i < end; i++) { |
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153 _offset_array[i] = offset; |
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154 } |
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155 } |
0 | 156 } |
157 | |
158 void set_offset_array(size_t left, size_t right, u_char offset) { | |
159 assert(right < _vs.committed_size(), "right address out of range"); | |
160 assert(left <= right, "indexes out of order"); | |
161 size_t num_cards = right - left + 1; | |
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162 |
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163 // Below, we may use an explicit loop instead of memset |
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164 // because on certain platforms memset() can give concurrent |
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165 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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166 if (UseMemSetInBOT) { |
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167 memset(&_offset_array[left], offset, num_cards); |
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168 } else { |
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169 size_t i = left; |
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170 const size_t end = i + num_cards; |
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171 for (; i < end; i++) { |
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172 _offset_array[i] = offset; |
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173 } |
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174 } |
0 | 175 } |
176 | |
177 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
178 assert(index < _vs.committed_size(), "index out of range"); | |
179 assert(high >= low, "addresses out of order"); | |
180 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
181 assert(_offset_array[index] == pointer_delta(high, low), | |
182 "Wrong offset"); | |
183 } | |
184 | |
185 bool is_card_boundary(HeapWord* p) const; | |
186 | |
187 // Return the number of slots needed for an offset array | |
188 // that covers mem_region_words words. | |
189 // We always add an extra slot because if an object | |
190 // ends on a card boundary we put a 0 in the next | |
191 // offset array slot, so we want that slot always | |
192 // to be reserved. | |
193 | |
194 size_t compute_size(size_t mem_region_words) { | |
195 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
196 return ReservedSpace::allocation_align_size_up(number_of_slots); | |
197 } | |
198 | |
199 public: | |
200 // Initialize the table to cover from "base" to (at least) | |
201 // "base + init_word_size". In the future, the table may be expanded | |
202 // (see "resize" below) up to the size of "_reserved" (which must be at | |
203 // least "init_word_size".) The contents of the initial table are | |
204 // undefined; it is the responsibility of the constituent | |
205 // BlockOffsetTable(s) to initialize cards. | |
206 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
207 | |
208 // Notes a change in the committed size of the region covered by the | |
209 // table. The "new_word_size" may not be larger than the size of the | |
210 // reserved region this table covers. | |
211 void resize(size_t new_word_size); | |
212 | |
213 void set_bottom(HeapWord* new_bottom); | |
214 | |
215 // Updates all the BlockOffsetArray's sharing this shared array to | |
216 // reflect the current "top"'s of their spaces. | |
217 void update_offset_arrays(); // Not yet implemented! | |
218 | |
219 // Return the appropriate index into "_offset_array" for "p". | |
220 size_t index_for(const void* p) const; | |
221 | |
222 // Return the address indicating the start of the region corresponding to | |
223 // "index" in "_offset_array". | |
224 HeapWord* address_for_index(size_t index) const; | |
225 | |
301
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226 // Return the address "p" incremented by the size of |
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227 // a region. This method does not align the address |
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228 // returned to the start of a region. It is a simple |
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229 // primitive. |
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230 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; } |
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231 |
0 | 232 // Shared space support |
233 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end); | |
234 }; | |
235 | |
236 ////////////////////////////////////////////////////////////////////////// | |
237 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. | |
238 ////////////////////////////////////////////////////////////////////////// | |
239 class BlockOffsetArray: public BlockOffsetTable { | |
240 friend class VMStructs; | |
342 | 241 friend class G1BlockOffsetArray; // temp. until we restructure and cleanup |
0 | 242 protected: |
243 // The following enums are used by do_block_internal() below | |
244 enum Action { | |
245 Action_single, // BOT records a single block (see single_block()) | |
246 Action_mark, // BOT marks the start of a block (see mark_block()) | |
247 Action_check // Check that BOT records block correctly | |
248 // (see verify_single_block()). | |
249 }; | |
250 | |
251 enum SomePrivateConstants { | |
252 N_words = BlockOffsetSharedArray::N_words, | |
253 LogN = BlockOffsetSharedArray::LogN, | |
254 // entries "e" of at least N_words mean "go back by Base^(e-N_words)." | |
255 // All entries are less than "N_words + N_powers". | |
256 LogBase = 4, | |
257 Base = (1 << LogBase), | |
258 N_powers = 14 | |
259 }; | |
260 | |
261 static size_t power_to_cards_back(uint i) { | |
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262 return (size_t)(1 << (LogBase * i)); |
0 | 263 } |
264 static size_t power_to_words_back(uint i) { | |
265 return power_to_cards_back(i) * N_words; | |
266 } | |
267 static size_t entry_to_cards_back(u_char entry) { | |
268 assert(entry >= N_words, "Precondition"); | |
269 return power_to_cards_back(entry - N_words); | |
270 } | |
271 static size_t entry_to_words_back(u_char entry) { | |
272 assert(entry >= N_words, "Precondition"); | |
273 return power_to_words_back(entry - N_words); | |
274 } | |
275 | |
276 // The shared array, which is shared with other BlockOffsetArray's | |
277 // corresponding to different spaces within a generation or span of | |
278 // memory. | |
279 BlockOffsetSharedArray* _array; | |
280 | |
281 // The space that owns this subregion. | |
282 Space* _sp; | |
283 | |
284 // If true, array entries are initialized to 0; otherwise, they are | |
285 // initialized to point backwards to the beginning of the covered region. | |
286 bool _init_to_zero; | |
287 | |
288 // Sets the entries | |
289 // corresponding to the cards starting at "start" and ending at "end" | |
290 // to point back to the card before "start": the interval [start, end) | |
291 // is right-open. | |
292 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
293 // Same as above, except that the args here are a card _index_ interval | |
294 // that is closed: [start_index, end_index] | |
295 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
296 | |
297 // A helper function for BOT adjustment/verification work | |
298 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
299 | |
300 public: | |
301 // The space may not have its bottom and top set yet, which is why the | |
302 // region is passed as a parameter. If "init_to_zero" is true, the | |
303 // elements of the array are initialized to zero. Otherwise, they are | |
304 // initialized to point backwards to the beginning. | |
305 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, | |
306 bool init_to_zero); | |
307 | |
308 // Note: this ought to be part of the constructor, but that would require | |
309 // "this" to be passed as a parameter to a member constructor for | |
310 // the containing concrete subtype of Space. | |
311 // This would be legal C++, but MS VC++ doesn't allow it. | |
312 void set_space(Space* sp) { _sp = sp; } | |
313 | |
314 // Resets the covered region to the given "mr". | |
315 void set_region(MemRegion mr) { | |
316 _bottom = mr.start(); | |
317 _end = mr.end(); | |
318 } | |
319 | |
320 // Note that the committed size of the covered space may have changed, | |
321 // so the table size might also wish to change. | |
322 virtual void resize(size_t new_word_size) { | |
323 HeapWord* new_end = _bottom + new_word_size; | |
324 if (_end < new_end && !init_to_zero()) { | |
325 // verify that the old and new boundaries are also card boundaries | |
326 assert(_array->is_card_boundary(_end), | |
327 "_end not a card boundary"); | |
328 assert(_array->is_card_boundary(new_end), | |
329 "new _end would not be a card boundary"); | |
330 // set all the newly added cards | |
331 _array->set_offset_array(_end, new_end, N_words); | |
332 } | |
333 _end = new_end; // update _end | |
334 } | |
335 | |
336 // Adjust the BOT to show that it has a single block in the | |
337 // range [blk_start, blk_start + size). All necessary BOT | |
338 // cards are adjusted, but _unallocated_block isn't. | |
339 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
340 void single_block(HeapWord* blk, size_t size) { | |
341 single_block(blk, blk + size); | |
342 } | |
343 | |
344 // When the alloc_block() call returns, the block offset table should | |
345 // have enough information such that any subsequent block_start() call | |
346 // with an argument equal to an address that is within the range | |
347 // [blk_start, blk_end) would return the value blk_start, provided | |
348 // there have been no calls in between that reset this information | |
349 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call | |
350 // for an appropriate range covering the said interval). | |
351 // These methods expect to be called with [blk_start, blk_end) | |
352 // representing a block of memory in the heap. | |
353 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
354 void alloc_block(HeapWord* blk, size_t size) { | |
355 alloc_block(blk, blk + size); | |
356 } | |
357 | |
358 // If true, initialize array slots with no allocated blocks to zero. | |
359 // Otherwise, make them point back to the front. | |
360 bool init_to_zero() { return _init_to_zero; } | |
361 | |
362 // Debugging | |
363 // Return the index of the last entry in the "active" region. | |
364 virtual size_t last_active_index() const = 0; | |
365 // Verify the block offset table | |
366 void verify() const; | |
367 void check_all_cards(size_t left_card, size_t right_card) const; | |
368 }; | |
369 | |
370 //////////////////////////////////////////////////////////////////////////// | |
371 // A subtype of BlockOffsetArray that takes advantage of the fact | |
372 // that its underlying space is a NonContiguousSpace, so that some | |
373 // specialized interfaces can be made available for spaces that | |
374 // manipulate the table. | |
375 //////////////////////////////////////////////////////////////////////////// | |
376 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { | |
377 friend class VMStructs; | |
378 private: | |
379 // The portion [_unallocated_block, _sp.end()) of the space that | |
380 // is a single block known not to contain any objects. | |
381 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
382 HeapWord* _unallocated_block; | |
383 | |
384 public: | |
385 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
386 BlockOffsetArray(array, mr, false), | |
387 _unallocated_block(_bottom) { } | |
388 | |
389 // accessor | |
390 HeapWord* unallocated_block() const { | |
391 assert(BlockOffsetArrayUseUnallocatedBlock, | |
392 "_unallocated_block is not being maintained"); | |
393 return _unallocated_block; | |
394 } | |
395 | |
396 void set_unallocated_block(HeapWord* block) { | |
397 assert(BlockOffsetArrayUseUnallocatedBlock, | |
398 "_unallocated_block is not being maintained"); | |
399 assert(block >= _bottom && block <= _end, "out of range"); | |
400 _unallocated_block = block; | |
401 } | |
402 | |
403 // These methods expect to be called with [blk_start, blk_end) | |
404 // representing a block of memory in the heap. | |
405 void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
406 void alloc_block(HeapWord* blk, size_t size) { | |
407 alloc_block(blk, blk + size); | |
408 } | |
409 | |
410 // The following methods are useful and optimized for a | |
411 // non-contiguous space. | |
412 | |
413 // Given a block [blk_start, blk_start + full_blk_size), and | |
414 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
415 // blocks [blk_start, blk_start + left_blk_size) and | |
416 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
417 // It is assumed (and verified in the non-product VM) that the | |
418 // BOT was correct for the original block. | |
419 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
420 size_t left_blk_size); | |
421 | |
422 // Adjust BOT to show that it has a block in the range | |
423 // [blk_start, blk_start + size). Only the first card | |
424 // of BOT is touched. It is assumed (and verified in the | |
425 // non-product VM) that the remaining cards of the block | |
426 // are correct. | |
427 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
428 void mark_block(HeapWord* blk, size_t size) { | |
429 mark_block(blk, blk + size); | |
430 } | |
431 | |
432 // Adjust _unallocated_block to indicate that a particular | |
433 // block has been newly allocated or freed. It is assumed (and | |
434 // verified in the non-product VM) that the BOT is correct for | |
435 // the given block. | |
436 void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
437 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
438 verify_single_block(blk_start, blk_end); | |
439 if (BlockOffsetArrayUseUnallocatedBlock) { | |
440 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
441 } | |
442 } | |
443 | |
444 void allocated(HeapWord* blk, size_t size) { | |
445 allocated(blk, blk + size); | |
446 } | |
447 | |
448 void freed(HeapWord* blk_start, HeapWord* blk_end); | |
449 void freed(HeapWord* blk, size_t size) { | |
450 freed(blk, blk + size); | |
451 } | |
452 | |
453 HeapWord* block_start_unsafe(const void* addr) const; | |
454 | |
455 // Requires "addr" to be the start of a card and returns the | |
456 // start of the block that contains the given address. | |
457 HeapWord* block_start_careful(const void* addr) const; | |
458 | |
459 | |
460 // Verification & debugging: ensure that the offset table reflects | |
461 // the fact that the block [blk_start, blk_end) or [blk, blk + size) | |
462 // is a single block of storage. NOTE: can't const this because of | |
463 // call to non-const do_block_internal() below. | |
464 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) | |
465 PRODUCT_RETURN; | |
466 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; | |
467 | |
468 // Verify that the given block is before _unallocated_block | |
469 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) | |
470 const PRODUCT_RETURN; | |
471 void verify_not_unallocated(HeapWord* blk, size_t size) | |
472 const PRODUCT_RETURN; | |
473 | |
474 // Debugging support | |
475 virtual size_t last_active_index() const; | |
476 }; | |
477 | |
478 //////////////////////////////////////////////////////////////////////////// | |
479 // A subtype of BlockOffsetArray that takes advantage of the fact | |
480 // that its underlying space is a ContiguousSpace, so that its "active" | |
481 // region can be more efficiently tracked (than for a non-contiguous space). | |
482 //////////////////////////////////////////////////////////////////////////// | |
483 class BlockOffsetArrayContigSpace: public BlockOffsetArray { | |
484 friend class VMStructs; | |
485 private: | |
486 // allocation boundary at which offset array must be updated | |
487 HeapWord* _next_offset_threshold; | |
488 size_t _next_offset_index; // index corresponding to that boundary | |
489 | |
490 // Work function when allocation start crosses threshold. | |
491 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); | |
492 | |
493 public: | |
494 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
495 BlockOffsetArray(array, mr, true) { | |
496 _next_offset_threshold = NULL; | |
497 _next_offset_index = 0; | |
498 } | |
499 | |
500 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } | |
501 | |
502 // Initialize the threshold for an empty heap. | |
503 HeapWord* initialize_threshold(); | |
504 // Zero out the entry for _bottom (offset will be zero) | |
505 void zero_bottom_entry(); | |
506 | |
507 // Return the next threshold, the point at which the table should be | |
508 // updated. | |
509 HeapWord* threshold() const { return _next_offset_threshold; } | |
510 | |
511 // In general, these methods expect to be called with | |
512 // [blk_start, blk_end) representing a block of memory in the heap. | |
513 // In this implementation, however, we are OK even if blk_start and/or | |
514 // blk_end are NULL 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_work(blk_start, blk_end); | |
519 } | |
520 } | |
521 void alloc_block(HeapWord* blk, size_t size) { | |
522 alloc_block(blk, blk + size); | |
523 } | |
524 | |
525 HeapWord* block_start_unsafe(const void* addr) const; | |
526 | |
527 void serialize(SerializeOopClosure* soc); | |
528 | |
529 // Debugging support | |
530 virtual size_t last_active_index() const; | |
531 }; |