Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp @ 20337:1f1d373cd044
8038423: G1: Decommit memory within heap
Summary: Allow G1 to decommit memory of arbitrary regions within the heap and their associated auxiliary data structures card table, BOT, hot card cache, and mark bitmaps.
Reviewed-by: mgerdin, brutisso, jwilhelm
author | tschatzl |
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date | Thu, 21 Aug 2014 11:47:10 +0200 |
parents | 6701abbc4441 |
children | 0fcaab91d485 |
rev | line source |
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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 | |
20337 | 28 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp" |
1972 | 29 #include "memory/memRegion.hpp" |
30 #include "runtime/virtualspace.hpp" | |
31 #include "utilities/globalDefinitions.hpp" | |
32 | |
342 | 33 // The CollectedHeap type requires subtypes to implement a method |
34 // "block_start". For some subtypes, notably generational | |
35 // systems using card-table-based write barriers, the efficiency of this | |
36 // operation may be important. Implementations of the "BlockOffsetArray" | |
37 // class may be useful in providing such efficient implementations. | |
38 // | |
39 // While generally mirroring the structure of the BOT for GenCollectedHeap, | |
40 // the following types are tailored more towards G1's uses; these should, | |
41 // however, be merged back into a common BOT to avoid code duplication | |
42 // and reduce maintenance overhead. | |
43 // | |
44 // G1BlockOffsetTable (abstract) | |
45 // -- G1BlockOffsetArray (uses G1BlockOffsetSharedArray) | |
46 // -- G1BlockOffsetArrayContigSpace | |
47 // | |
48 // A main impediment to the consolidation of this code might be the | |
49 // effect of making some of the block_start*() calls non-const as | |
50 // below. Whether that might adversely affect performance optimizations | |
51 // that compilers might normally perform in the case of non-G1 | |
52 // collectors needs to be carefully investigated prior to any such | |
53 // consolidation. | |
54 | |
55 // Forward declarations | |
56 class G1BlockOffsetSharedArray; | |
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57 class G1OffsetTableContigSpace; |
342 | 58 |
59 class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC { | |
60 friend class VMStructs; | |
61 protected: | |
62 // These members describe the region covered by the table. | |
63 | |
64 // The space this table is covering. | |
65 HeapWord* _bottom; // == reserved.start | |
66 HeapWord* _end; // End of currently allocated region. | |
67 | |
68 public: | |
69 // Initialize the table to cover the given space. | |
70 // The contents of the initial table are undefined. | |
71 G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) : | |
72 _bottom(bottom), _end(end) | |
73 { | |
74 assert(_bottom <= _end, "arguments out of order"); | |
75 } | |
76 | |
77 // Note that the committed size of the covered space may have changed, | |
78 // so the table size might also wish to change. | |
79 virtual void resize(size_t new_word_size) = 0; | |
80 | |
81 virtual void set_bottom(HeapWord* new_bottom) { | |
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82 assert(new_bottom <= _end, |
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83 err_msg("new_bottom (" PTR_FORMAT ") > _end (" PTR_FORMAT ")", |
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84 p2i(new_bottom), p2i(_end))); |
342 | 85 _bottom = new_bottom; |
86 resize(pointer_delta(_end, _bottom)); | |
87 } | |
88 | |
89 // Requires "addr" to be contained by a block, and returns the address of | |
90 // the start of that block. (May have side effects, namely updating of | |
91 // shared array entries that "point" too far backwards. This can occur, | |
92 // for example, when LAB allocation is used in a space covered by the | |
93 // table.) | |
94 virtual HeapWord* block_start_unsafe(const void* addr) = 0; | |
95 // Same as above, but does not have any of the possible side effects | |
96 // discussed above. | |
97 virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0; | |
98 | |
99 // Returns the address of the start of the block containing "addr", or | |
100 // else "null" if it is covered by no block. (May have side effects, | |
101 // namely updating of shared array entries that "point" too far | |
102 // backwards. This can occur, for example, when lab allocation is used | |
103 // in a space covered by the table.) | |
104 inline HeapWord* block_start(const void* addr); | |
105 // Same as above, but does not have any of the possible side effects | |
106 // discussed above. | |
107 inline HeapWord* block_start_const(const void* addr) const; | |
108 }; | |
109 | |
20337 | 110 class G1BlockOffsetSharedArrayMappingChangedListener : public G1MappingChangedListener { |
111 public: | |
112 virtual void on_commit(uint start_idx, size_t num_regions); | |
113 }; | |
114 | |
342 | 115 // This implementation of "G1BlockOffsetTable" divides the covered region |
116 // into "N"-word subregions (where "N" = 2^"LogN". An array with an entry | |
117 // for each such subregion indicates how far back one must go to find the | |
118 // start of the chunk that includes the first word of the subregion. | |
119 // | |
120 // Each BlockOffsetArray is owned by a Space. However, the actual array | |
121 // may be shared by several BlockOffsetArrays; this is useful | |
122 // when a single resizable area (such as a generation) is divided up into | |
123 // several spaces in which contiguous allocation takes place, | |
124 // such as, for example, in G1 or in the train generation.) | |
125 | |
126 // Here is the shared array type. | |
127 | |
6197 | 128 class G1BlockOffsetSharedArray: public CHeapObj<mtGC> { |
342 | 129 friend class G1BlockOffsetArray; |
130 friend class G1BlockOffsetArrayContigSpace; | |
131 friend class VMStructs; | |
132 | |
133 private: | |
20337 | 134 G1BlockOffsetSharedArrayMappingChangedListener _listener; |
342 | 135 // The reserved region covered by the shared array. |
136 MemRegion _reserved; | |
137 | |
138 // End of the current committed region. | |
139 HeapWord* _end; | |
140 | |
141 // Array for keeping offsets for retrieving object start fast given an | |
142 // address. | |
143 u_char* _offset_array; // byte array keeping backwards offsets | |
144 | |
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145 void check_offset(size_t offset, const char* msg) const { |
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146 assert(offset <= N_words, |
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147 err_msg("%s - " |
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148 "offset: " SIZE_FORMAT ", N_words: " UINT32_FORMAT, |
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149 msg, offset, N_words)); |
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150 } |
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151 |
342 | 152 // Bounds checking accessors: |
153 // For performance these have to devolve to array accesses in product builds. | |
20337 | 154 inline u_char offset_array(size_t index) const; |
342 | 155 |
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156 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset); |
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157 |
20337 | 158 void set_offset_array_raw(size_t index, u_char offset) { |
342 | 159 _offset_array[index] = offset; |
160 } | |
161 | |
20337 | 162 inline void set_offset_array(size_t index, u_char offset); |
163 | |
164 inline void set_offset_array(size_t index, HeapWord* high, HeapWord* low); | |
342 | 165 |
20337 | 166 inline void set_offset_array(size_t left, size_t right, u_char offset); |
342 | 167 |
20337 | 168 inline void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const; |
342 | 169 |
170 bool is_card_boundary(HeapWord* p) const; | |
171 | |
20337 | 172 public: |
173 | |
342 | 174 // Return the number of slots needed for an offset array |
175 // that covers mem_region_words words. | |
20337 | 176 static size_t compute_size(size_t mem_region_words) { |
177 size_t number_of_slots = (mem_region_words / N_words); | |
178 return ReservedSpace::allocation_align_size_up(number_of_slots); | |
342 | 179 } |
180 | |
181 enum SomePublicConstants { | |
182 LogN = 9, | |
183 LogN_words = LogN - LogHeapWordSize, | |
184 N_bytes = 1 << LogN, | |
185 N_words = 1 << LogN_words | |
186 }; | |
187 | |
188 // Initialize the table to cover from "base" to (at least) | |
189 // "base + init_word_size". In the future, the table may be expanded | |
190 // (see "resize" below) up to the size of "_reserved" (which must be at | |
191 // least "init_word_size".) The contents of the initial table are | |
192 // undefined; it is the responsibility of the constituent | |
193 // G1BlockOffsetTable(s) to initialize cards. | |
20337 | 194 G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage); |
342 | 195 |
196 void set_bottom(HeapWord* new_bottom); | |
197 | |
198 // Return the appropriate index into "_offset_array" for "p". | |
199 inline size_t index_for(const void* p) const; | |
20337 | 200 inline size_t index_for_raw(const void* p) const; |
342 | 201 |
202 // Return the address indicating the start of the region corresponding to | |
203 // "index" in "_offset_array". | |
204 inline HeapWord* address_for_index(size_t index) const; | |
20337 | 205 // Variant of address_for_index that does not check the index for validity. |
206 inline HeapWord* address_for_index_raw(size_t index) const { | |
207 return _reserved.start() + (index << LogN_words); | |
208 } | |
342 | 209 }; |
210 | |
211 // And here is the G1BlockOffsetTable subtype that uses the array. | |
212 | |
213 class G1BlockOffsetArray: public G1BlockOffsetTable { | |
214 friend class G1BlockOffsetSharedArray; | |
215 friend class G1BlockOffsetArrayContigSpace; | |
216 friend class VMStructs; | |
217 private: | |
218 enum SomePrivateConstants { | |
219 N_words = G1BlockOffsetSharedArray::N_words, | |
220 LogN = G1BlockOffsetSharedArray::LogN | |
221 }; | |
222 | |
223 // The following enums are used by do_block_helper | |
224 enum Action { | |
225 Action_single, // BOT records a single block (see single_block()) | |
226 Action_mark, // BOT marks the start of a block (see mark_block()) | |
227 Action_check // Check that BOT records block correctly | |
228 // (see verify_single_block()). | |
229 }; | |
230 | |
231 // This is the array, which can be shared by several BlockOffsetArray's | |
232 // servicing different | |
233 G1BlockOffsetSharedArray* _array; | |
234 | |
235 // The space that owns this subregion. | |
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236 G1OffsetTableContigSpace* _gsp; |
342 | 237 |
238 // If true, array entries are initialized to 0; otherwise, they are | |
239 // initialized to point backwards to the beginning of the covered region. | |
240 bool _init_to_zero; | |
241 | |
242 // The portion [_unallocated_block, _sp.end()) of the space that | |
243 // is a single block known not to contain any objects. | |
244 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
245 HeapWord* _unallocated_block; | |
246 | |
247 // Sets the entries | |
248 // corresponding to the cards starting at "start" and ending at "end" | |
249 // to point back to the card before "start": the interval [start, end) | |
250 // is right-open. | |
251 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end); | |
252 // Same as above, except that the args here are a card _index_ interval | |
253 // that is closed: [start_index, end_index] | |
254 void set_remainder_to_point_to_start_incl(size_t start, size_t end); | |
255 | |
256 // A helper function for BOT adjustment/verification work | |
257 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action); | |
258 | |
259 protected: | |
260 | |
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261 G1OffsetTableContigSpace* gsp() const { return _gsp; } |
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262 |
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263 inline size_t block_size(const HeapWord* p) const; |
342 | 264 |
265 // Returns the address of a block whose start is at most "addr". | |
266 // If "has_max_index" is true, "assumes "max_index" is the last valid one | |
267 // in the array. | |
268 inline HeapWord* block_at_or_preceding(const void* addr, | |
269 bool has_max_index, | |
270 size_t max_index) const; | |
271 | |
272 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
273 // next block (or the end of the space.) Return the address of the | |
274 // beginning of the block that contains "addr". Does so without side | |
275 // effects (see, e.g., spec of block_start.) | |
276 inline HeapWord* | |
277 forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n, | |
278 const void* addr) const; | |
279 | |
280 // "q" is a block boundary that is <= "addr"; return the address of the | |
281 // beginning of the block that contains "addr". May have side effects | |
282 // on "this", by updating imprecise entries. | |
283 inline HeapWord* forward_to_block_containing_addr(HeapWord* q, | |
284 const void* addr); | |
285 | |
286 // "q" is a block boundary that is <= "addr"; "n" is the address of the | |
287 // next block (or the end of the space.) Return the address of the | |
288 // beginning of the block that contains "addr". May have side effects | |
289 // on "this", by updating imprecise entries. | |
290 HeapWord* forward_to_block_containing_addr_slow(HeapWord* q, | |
291 HeapWord* n, | |
292 const void* addr); | |
293 | |
294 // Requires that "*threshold_" be the first array entry boundary at or | |
295 // above "blk_start", and that "*index_" be the corresponding array | |
296 // index. If the block starts at or crosses "*threshold_", records | |
297 // "blk_start" as the appropriate block start for the array index | |
298 // starting at "*threshold_", and for any other indices crossed by the | |
299 // block. Updates "*threshold_" and "*index_" to correspond to the first | |
300 // index after the block end. | |
301 void alloc_block_work2(HeapWord** threshold_, size_t* index_, | |
302 HeapWord* blk_start, HeapWord* blk_end); | |
303 | |
304 public: | |
305 // The space may not have it's bottom and top set yet, which is why the | |
306 // region is passed as a parameter. If "init_to_zero" is true, the | |
307 // elements of the array are initialized to zero. Otherwise, they are | |
308 // initialized to point backwards to the beginning. | |
309 G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr, | |
310 bool init_to_zero); | |
311 | |
312 // Note: this ought to be part of the constructor, but that would require | |
313 // "this" to be passed as a parameter to a member constructor for | |
314 // the containing concrete subtype of Space. | |
315 // This would be legal C++, but MS VC++ doesn't allow it. | |
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316 void set_space(G1OffsetTableContigSpace* sp); |
342 | 317 |
318 // Resets the covered region to the given "mr". | |
319 void set_region(MemRegion mr); | |
320 | |
321 // Resets the covered region to one with the same _bottom as before but | |
322 // the "new_word_size". | |
323 void resize(size_t new_word_size); | |
324 | |
325 // These must be guaranteed to work properly (i.e., do nothing) | |
326 // when "blk_start" ("blk" for second version) is "NULL". | |
327 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
328 virtual void alloc_block(HeapWord* blk, size_t size) { | |
329 alloc_block(blk, blk + size); | |
330 } | |
331 | |
332 // The following methods are useful and optimized for a | |
333 // general, non-contiguous space. | |
334 | |
335 // Given a block [blk_start, blk_start + full_blk_size), and | |
336 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
337 // blocks [blk_start, blk_start + left_blk_size) and | |
338 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
339 // It is assumed (and verified in the non-product VM) that the | |
340 // BOT was correct for the original block. | |
341 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
342 size_t left_blk_size); | |
343 | |
344 // Adjust the BOT to show that it has a single block in the | |
345 // range [blk_start, blk_start + size). All necessary BOT | |
346 // cards are adjusted, but _unallocated_block isn't. | |
347 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
348 void single_block(HeapWord* blk, size_t size) { | |
349 single_block(blk, blk + size); | |
350 } | |
351 | |
352 // Adjust BOT to show that it has a block in the range | |
353 // [blk_start, blk_start + size). Only the first card | |
354 // of BOT is touched. It is assumed (and verified in the | |
355 // non-product VM) that the remaining cards of the block | |
356 // are correct. | |
357 void mark_block(HeapWord* blk_start, HeapWord* blk_end); | |
358 void mark_block(HeapWord* blk, size_t size) { | |
359 mark_block(blk, blk + size); | |
360 } | |
361 | |
362 // Adjust _unallocated_block to indicate that a particular | |
363 // block has been newly allocated or freed. It is assumed (and | |
364 // verified in the non-product VM) that the BOT is correct for | |
365 // the given block. | |
366 inline void allocated(HeapWord* blk_start, HeapWord* blk_end) { | |
367 // Verify that the BOT shows [blk, blk + blk_size) to be one block. | |
368 verify_single_block(blk_start, blk_end); | |
369 if (BlockOffsetArrayUseUnallocatedBlock) { | |
370 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
371 } | |
372 } | |
373 | |
374 inline void allocated(HeapWord* blk, size_t size) { | |
375 allocated(blk, blk + size); | |
376 } | |
377 | |
378 inline void freed(HeapWord* blk_start, HeapWord* blk_end); | |
379 | |
380 inline void freed(HeapWord* blk, size_t size); | |
381 | |
382 virtual HeapWord* block_start_unsafe(const void* addr); | |
383 virtual HeapWord* block_start_unsafe_const(const void* addr) const; | |
384 | |
385 // Requires "addr" to be the start of a card and returns the | |
386 // start of the block that contains the given address. | |
387 HeapWord* block_start_careful(const void* addr) const; | |
388 | |
389 // If true, initialize array slots with no allocated blocks to zero. | |
390 // Otherwise, make them point back to the front. | |
391 bool init_to_zero() { return _init_to_zero; } | |
392 | |
393 // Verification & debugging - ensure that the offset table reflects the fact | |
394 // that the block [blk_start, blk_end) or [blk, blk + size) is a | |
395 // single block of storage. NOTE: can;t const this because of | |
396 // call to non-const do_block_internal() below. | |
397 inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) { | |
398 if (VerifyBlockOffsetArray) { | |
399 do_block_internal(blk_start, blk_end, Action_check); | |
400 } | |
401 } | |
402 | |
403 inline void verify_single_block(HeapWord* blk, size_t size) { | |
404 verify_single_block(blk, blk + size); | |
405 } | |
406 | |
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407 // Used by region verification. Checks that the contents of the |
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408 // BOT reflect that there's a single object that spans the address |
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409 // range [obj_start, obj_start + word_size); returns true if this is |
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410 // the case, returns false if it's not. |
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411 bool verify_for_object(HeapWord* obj_start, size_t word_size) const; |
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412 |
342 | 413 // Verify that the given block is before _unallocated_block |
414 inline void verify_not_unallocated(HeapWord* blk_start, | |
415 HeapWord* blk_end) const { | |
416 if (BlockOffsetArrayUseUnallocatedBlock) { | |
417 assert(blk_start < blk_end, "Block inconsistency?"); | |
418 assert(blk_end <= _unallocated_block, "_unallocated_block problem"); | |
419 } | |
420 } | |
421 | |
422 inline void verify_not_unallocated(HeapWord* blk, size_t size) const { | |
423 verify_not_unallocated(blk, blk + size); | |
424 } | |
425 | |
426 void check_all_cards(size_t left_card, size_t right_card) const; | |
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428 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
342 | 429 }; |
430 | |
431 // A subtype of BlockOffsetArray that takes advantage of the fact | |
432 // that its underlying space is a ContiguousSpace, so that its "active" | |
433 // region can be more efficiently tracked (than for a non-contiguous space). | |
434 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray { | |
435 friend class VMStructs; | |
436 | |
437 // allocation boundary at which offset array must be updated | |
438 HeapWord* _next_offset_threshold; | |
439 size_t _next_offset_index; // index corresponding to that boundary | |
440 | |
441 // Work function to be called when allocation start crosses the next | |
442 // threshold in the contig space. | |
443 void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) { | |
444 alloc_block_work2(&_next_offset_threshold, &_next_offset_index, | |
445 blk_start, blk_end); | |
446 } | |
447 | |
20337 | 448 // Variant of zero_bottom_entry that does not check for availability of the |
449 // memory first. | |
450 void zero_bottom_entry_raw(); | |
451 // Variant of initialize_threshold that does not check for availability of the | |
452 // memory first. | |
453 HeapWord* initialize_threshold_raw(); | |
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454 // Zero out the entry for _bottom (offset will be zero). |
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455 void zero_bottom_entry(); |
342 | 456 public: |
457 G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr); | |
458 | |
459 // Initialize the threshold to reflect the first boundary after the | |
460 // bottom of the covered region. | |
461 HeapWord* initialize_threshold(); | |
462 | |
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463 void reset_bot() { |
20337 | 464 zero_bottom_entry_raw(); |
465 initialize_threshold_raw(); | |
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466 } |
342 | 467 |
468 // Return the next threshold, the point at which the table should be | |
469 // updated. | |
470 HeapWord* threshold() const { return _next_offset_threshold; } | |
471 | |
472 // These must be guaranteed to work properly (i.e., do nothing) | |
473 // when "blk_start" ("blk" for second version) is "NULL". In this | |
474 // implementation, that's true because NULL is represented as 0, and thus | |
475 // never exceeds the "_next_offset_threshold". | |
476 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
477 if (blk_end > _next_offset_threshold) | |
478 alloc_block_work1(blk_start, blk_end); | |
479 } | |
480 void alloc_block(HeapWord* blk, size_t size) { | |
481 alloc_block(blk, blk+size); | |
482 } | |
483 | |
484 HeapWord* block_start_unsafe(const void* addr); | |
485 HeapWord* block_start_unsafe_const(const void* addr) const; | |
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487 void set_for_starts_humongous(HeapWord* new_top); |
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488 |
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489 virtual void print_on(outputStream* out) PRODUCT_RETURN; |
342 | 490 }; |
1972 | 491 |
492 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP |