Mercurial > hg > truffle
annotate src/share/vm/memory/blockOffsetTable.hpp @ 5274:e72dd6533eb9
documented importance of nmethod::_graal_compiled_method wrt code unloading and GC
author | Doug Simon <doug.simon@oracle.com> |
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date | Mon, 23 Apr 2012 15:42:30 +0200 |
parents | f95d63e2154a |
children | d2a62e0f25eb |
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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 | |
1972 | 25 #ifndef SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP |
26 #define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP | |
27 | |
28 #include "memory/memRegion.hpp" | |
29 #include "runtime/virtualspace.hpp" | |
30 #include "utilities/globalDefinitions.hpp" | |
31 | |
0 | 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 // BlockOffsetTable (abstract) | |
39 // - BlockOffsetArray (abstract) | |
40 // - BlockOffsetArrayNonContigSpace | |
41 // - BlockOffsetArrayContigSpace | |
42 // | |
43 | |
44 class ContiguousSpace; | |
45 class SerializeOopClosure; | |
46 | |
47 ////////////////////////////////////////////////////////////////////////// | |
48 // The BlockOffsetTable "interface" | |
49 ////////////////////////////////////////////////////////////////////////// | |
50 class BlockOffsetTable VALUE_OBJ_CLASS_SPEC { | |
51 friend class VMStructs; | |
52 protected: | |
53 // These members describe the region covered by the table. | |
54 | |
55 // The space this table is covering. | |
56 HeapWord* _bottom; // == reserved.start | |
57 HeapWord* _end; // End of currently allocated region. | |
58 | |
59 public: | |
60 // Initialize the table to cover the given space. | |
61 // The contents of the initial table are undefined. | |
62 BlockOffsetTable(HeapWord* bottom, HeapWord* end): | |
63 _bottom(bottom), _end(end) { | |
64 assert(_bottom <= _end, "arguments out of order"); | |
65 } | |
66 | |
67 // Note that the committed size of the covered space may have changed, | |
68 // so the table size might also wish to change. | |
69 virtual void resize(size_t new_word_size) = 0; | |
70 | |
71 virtual void set_bottom(HeapWord* new_bottom) { | |
72 assert(new_bottom <= _end, "new_bottom > _end"); | |
73 _bottom = new_bottom; | |
74 resize(pointer_delta(_end, _bottom)); | |
75 } | |
76 | |
77 // Requires "addr" to be contained by a block, and returns the address of | |
78 // the start of that block. | |
79 virtual HeapWord* block_start_unsafe(const void* addr) const = 0; | |
80 | |
81 // Returns the address of the start of the block containing "addr", or | |
82 // else "null" if it is covered by no block. | |
83 HeapWord* block_start(const void* addr) const; | |
84 }; | |
85 | |
86 ////////////////////////////////////////////////////////////////////////// | |
87 // One implementation of "BlockOffsetTable," the BlockOffsetArray, | |
88 // divides the covered region into "N"-word subregions (where | |
89 // "N" = 2^"LogN". An array with an entry for each such subregion | |
90 // indicates how far back one must go to find the start of the | |
91 // chunk that includes the first word of the subregion. | |
92 // | |
93 // Each BlockOffsetArray is owned by a Space. However, the actual array | |
94 // may be shared by several BlockOffsetArrays; this is useful | |
95 // when a single resizable area (such as a generation) is divided up into | |
96 // several spaces in which contiguous allocation takes place. (Consider, | |
97 // for example, the garbage-first generation.) | |
98 | |
99 // Here is the shared array type. | |
100 ////////////////////////////////////////////////////////////////////////// | |
101 // BlockOffsetSharedArray | |
102 ////////////////////////////////////////////////////////////////////////// | |
103 class BlockOffsetSharedArray: public CHeapObj { | |
104 friend class BlockOffsetArray; | |
105 friend class BlockOffsetArrayNonContigSpace; | |
106 friend class BlockOffsetArrayContigSpace; | |
107 friend class VMStructs; | |
108 | |
109 private: | |
110 enum SomePrivateConstants { | |
111 LogN = 9, | |
112 LogN_words = LogN - LogHeapWordSize, | |
113 N_bytes = 1 << LogN, | |
114 N_words = 1 << LogN_words | |
115 }; | |
116 | |
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117 bool _init_to_zero; |
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118 |
0 | 119 // The reserved region covered by the shared array. |
120 MemRegion _reserved; | |
121 | |
122 // End of the current committed region. | |
123 HeapWord* _end; | |
124 | |
125 // Array for keeping offsets for retrieving object start fast given an | |
126 // address. | |
127 VirtualSpace _vs; | |
128 u_char* _offset_array; // byte array keeping backwards offsets | |
129 | |
130 protected: | |
131 // Bounds checking accessors: | |
132 // For performance these have to devolve to array accesses in product builds. | |
133 u_char offset_array(size_t index) const { | |
134 assert(index < _vs.committed_size(), "index out of range"); | |
135 return _offset_array[index]; | |
136 } | |
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137 // An assertion-checking helper method for the set_offset_array() methods below. |
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138 void check_reducing_assertion(bool reducing); |
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139 |
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140 void set_offset_array(size_t index, u_char offset, bool reducing = false) { |
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141 check_reducing_assertion(reducing); |
0 | 142 assert(index < _vs.committed_size(), "index out of range"); |
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143 assert(!reducing || _offset_array[index] >= offset, "Not reducing"); |
0 | 144 _offset_array[index] = offset; |
145 } | |
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146 |
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147 void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) { |
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148 check_reducing_assertion(reducing); |
0 | 149 assert(index < _vs.committed_size(), "index out of range"); |
150 assert(high >= low, "addresses out of order"); | |
151 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
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152 assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low), |
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153 "Not reducing"); |
0 | 154 _offset_array[index] = (u_char)pointer_delta(high, low); |
155 } | |
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156 |
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157 void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) { |
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158 check_reducing_assertion(reducing); |
0 | 159 assert(index_for(right - 1) < _vs.committed_size(), |
160 "right address out of range"); | |
161 assert(left < right, "Heap addresses out of order"); | |
162 size_t num_cards = pointer_delta(right, left) >> LogN_words; | |
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163 |
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164 // Below, we may use an explicit loop instead of memset() |
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165 // because on certain platforms memset() can give concurrent |
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166 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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167 if (UseMemSetInBOT) { |
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168 memset(&_offset_array[index_for(left)], offset, num_cards); |
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169 } else { |
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170 size_t i = index_for(left); |
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171 const size_t end = i + num_cards; |
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172 for (; i < end; i++) { |
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173 // Elided until CR 6977974 is fixed properly. |
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174 // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); |
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175 _offset_array[i] = offset; |
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176 } |
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177 } |
0 | 178 } |
179 | |
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180 void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) { |
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181 check_reducing_assertion(reducing); |
0 | 182 assert(right < _vs.committed_size(), "right address out of range"); |
183 assert(left <= right, "indexes out of order"); | |
184 size_t num_cards = right - left + 1; | |
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185 |
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186 // Below, we may use an explicit loop instead of memset |
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187 // because on certain platforms memset() can give concurrent |
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188 // readers "out-of-thin-air," phantom zeros; see 6948537. |
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189 if (UseMemSetInBOT) { |
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190 memset(&_offset_array[left], offset, num_cards); |
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191 } else { |
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192 size_t i = left; |
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193 const size_t end = i + num_cards; |
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194 for (; i < end; i++) { |
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195 // Elided until CR 6977974 is fixed properly. |
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196 // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); |
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197 _offset_array[i] = offset; |
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198 } |
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199 } |
0 | 200 } |
201 | |
202 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { | |
203 assert(index < _vs.committed_size(), "index out of range"); | |
204 assert(high >= low, "addresses out of order"); | |
205 assert(pointer_delta(high, low) <= N_words, "offset too large"); | |
206 assert(_offset_array[index] == pointer_delta(high, low), | |
207 "Wrong offset"); | |
208 } | |
209 | |
210 bool is_card_boundary(HeapWord* p) const; | |
211 | |
212 // Return the number of slots needed for an offset array | |
213 // that covers mem_region_words words. | |
214 // We always add an extra slot because if an object | |
215 // ends on a card boundary we put a 0 in the next | |
216 // offset array slot, so we want that slot always | |
217 // to be reserved. | |
218 | |
219 size_t compute_size(size_t mem_region_words) { | |
220 size_t number_of_slots = (mem_region_words / N_words) + 1; | |
221 return ReservedSpace::allocation_align_size_up(number_of_slots); | |
222 } | |
223 | |
224 public: | |
225 // Initialize the table to cover from "base" to (at least) | |
226 // "base + init_word_size". In the future, the table may be expanded | |
227 // (see "resize" below) up to the size of "_reserved" (which must be at | |
228 // least "init_word_size".) The contents of the initial table are | |
229 // undefined; it is the responsibility of the constituent | |
230 // BlockOffsetTable(s) to initialize cards. | |
231 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); | |
232 | |
233 // Notes a change in the committed size of the region covered by the | |
234 // table. The "new_word_size" may not be larger than the size of the | |
235 // reserved region this table covers. | |
236 void resize(size_t new_word_size); | |
237 | |
238 void set_bottom(HeapWord* new_bottom); | |
239 | |
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240 // Whether entries should be initialized to zero. Used currently only for |
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241 // error checking. |
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242 void set_init_to_zero(bool val) { _init_to_zero = val; } |
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243 bool init_to_zero() { return _init_to_zero; } |
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244 |
0 | 245 // Updates all the BlockOffsetArray's sharing this shared array to |
246 // reflect the current "top"'s of their spaces. | |
247 void update_offset_arrays(); // Not yet implemented! | |
248 | |
249 // Return the appropriate index into "_offset_array" for "p". | |
250 size_t index_for(const void* p) const; | |
251 | |
252 // Return the address indicating the start of the region corresponding to | |
253 // "index" in "_offset_array". | |
254 HeapWord* address_for_index(size_t index) const; | |
255 | |
301
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256 // Return the address "p" incremented by the size of |
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257 // a region. This method does not align the address |
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258 // returned to the start of a region. It is a simple |
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259 // primitive. |
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260 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; } |
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261 |
0 | 262 // Shared space support |
263 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end); | |
264 }; | |
265 | |
266 ////////////////////////////////////////////////////////////////////////// | |
267 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. | |
268 ////////////////////////////////////////////////////////////////////////// | |
269 class BlockOffsetArray: public BlockOffsetTable { | |
270 friend class VMStructs; | |
342 | 271 friend class G1BlockOffsetArray; // temp. until we restructure and cleanup |
0 | 272 protected: |
273 // The following enums are used by do_block_internal() below | |
274 enum Action { | |
275 Action_single, // BOT records a single block (see single_block()) | |
276 Action_mark, // BOT marks the start of a block (see mark_block()) | |
277 Action_check // Check that BOT records block correctly | |
278 // (see verify_single_block()). | |
279 }; | |
280 | |
281 enum SomePrivateConstants { | |
282 N_words = BlockOffsetSharedArray::N_words, | |
283 LogN = BlockOffsetSharedArray::LogN, | |
284 // entries "e" of at least N_words mean "go back by Base^(e-N_words)." | |
285 // All entries are less than "N_words + N_powers". | |
286 LogBase = 4, | |
287 Base = (1 << LogBase), | |
288 N_powers = 14 | |
289 }; | |
290 | |
291 static size_t power_to_cards_back(uint i) { | |
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292 return (size_t)(1 << (LogBase * i)); |
0 | 293 } |
294 static size_t power_to_words_back(uint i) { | |
295 return power_to_cards_back(i) * N_words; | |
296 } | |
297 static size_t entry_to_cards_back(u_char entry) { | |
298 assert(entry >= N_words, "Precondition"); | |
299 return power_to_cards_back(entry - N_words); | |
300 } | |
301 static size_t entry_to_words_back(u_char entry) { | |
302 assert(entry >= N_words, "Precondition"); | |
303 return power_to_words_back(entry - N_words); | |
304 } | |
305 | |
306 // The shared array, which is shared with other BlockOffsetArray's | |
307 // corresponding to different spaces within a generation or span of | |
308 // memory. | |
309 BlockOffsetSharedArray* _array; | |
310 | |
311 // The space that owns this subregion. | |
312 Space* _sp; | |
313 | |
314 // If true, array entries are initialized to 0; otherwise, they are | |
315 // initialized to point backwards to the beginning of the covered region. | |
316 bool _init_to_zero; | |
317 | |
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318 // An assertion-checking helper method for the set_remainder*() methods below. |
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319 void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); } |
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320 |
0 | 321 // Sets the entries |
322 // corresponding to the cards starting at "start" and ending at "end" | |
323 // to point back to the card before "start": the interval [start, end) | |
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324 // is right-open. The last parameter, reducing, indicates whether the |
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325 // updates to individual entries always reduce the entry from a higher |
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326 // to a lower value. (For example this would hold true during a temporal |
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327 // regime during which only block splits were updating the BOT. |
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328 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false); |
0 | 329 // Same as above, except that the args here are a card _index_ interval |
330 // that is closed: [start_index, end_index] | |
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331 void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false); |
0 | 332 |
333 // A helper function for BOT adjustment/verification work | |
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334 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false); |
0 | 335 |
336 public: | |
337 // The space may not have its bottom and top set yet, which is why the | |
338 // region is passed as a parameter. If "init_to_zero" is true, the | |
339 // elements of the array are initialized to zero. Otherwise, they are | |
340 // initialized to point backwards to the beginning. | |
341 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, | |
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342 bool init_to_zero_); |
0 | 343 |
344 // Note: this ought to be part of the constructor, but that would require | |
345 // "this" to be passed as a parameter to a member constructor for | |
346 // the containing concrete subtype of Space. | |
347 // This would be legal C++, but MS VC++ doesn't allow it. | |
348 void set_space(Space* sp) { _sp = sp; } | |
349 | |
350 // Resets the covered region to the given "mr". | |
351 void set_region(MemRegion mr) { | |
352 _bottom = mr.start(); | |
353 _end = mr.end(); | |
354 } | |
355 | |
356 // Note that the committed size of the covered space may have changed, | |
357 // so the table size might also wish to change. | |
358 virtual void resize(size_t new_word_size) { | |
359 HeapWord* new_end = _bottom + new_word_size; | |
360 if (_end < new_end && !init_to_zero()) { | |
361 // verify that the old and new boundaries are also card boundaries | |
362 assert(_array->is_card_boundary(_end), | |
363 "_end not a card boundary"); | |
364 assert(_array->is_card_boundary(new_end), | |
365 "new _end would not be a card boundary"); | |
366 // set all the newly added cards | |
367 _array->set_offset_array(_end, new_end, N_words); | |
368 } | |
369 _end = new_end; // update _end | |
370 } | |
371 | |
372 // Adjust the BOT to show that it has a single block in the | |
373 // range [blk_start, blk_start + size). All necessary BOT | |
374 // cards are adjusted, but _unallocated_block isn't. | |
375 void single_block(HeapWord* blk_start, HeapWord* blk_end); | |
376 void single_block(HeapWord* blk, size_t size) { | |
377 single_block(blk, blk + size); | |
378 } | |
379 | |
380 // When the alloc_block() call returns, the block offset table should | |
381 // have enough information such that any subsequent block_start() call | |
382 // with an argument equal to an address that is within the range | |
383 // [blk_start, blk_end) would return the value blk_start, provided | |
384 // there have been no calls in between that reset this information | |
385 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call | |
386 // for an appropriate range covering the said interval). | |
387 // These methods expect to be called with [blk_start, blk_end) | |
388 // representing a block of memory in the heap. | |
389 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
390 void alloc_block(HeapWord* blk, size_t size) { | |
391 alloc_block(blk, blk + size); | |
392 } | |
393 | |
394 // If true, initialize array slots with no allocated blocks to zero. | |
395 // Otherwise, make them point back to the front. | |
396 bool init_to_zero() { return _init_to_zero; } | |
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397 // Corresponding setter |
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398 void set_init_to_zero(bool val) { |
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399 _init_to_zero = val; |
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400 assert(_array != NULL, "_array should be non-NULL"); |
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401 _array->set_init_to_zero(val); |
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402 } |
0 | 403 |
404 // Debugging | |
405 // Return the index of the last entry in the "active" region. | |
406 virtual size_t last_active_index() const = 0; | |
407 // Verify the block offset table | |
408 void verify() const; | |
409 void check_all_cards(size_t left_card, size_t right_card) const; | |
410 }; | |
411 | |
412 //////////////////////////////////////////////////////////////////////////// | |
413 // A subtype of BlockOffsetArray that takes advantage of the fact | |
414 // that its underlying space is a NonContiguousSpace, so that some | |
415 // specialized interfaces can be made available for spaces that | |
416 // manipulate the table. | |
417 //////////////////////////////////////////////////////////////////////////// | |
418 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { | |
419 friend class VMStructs; | |
420 private: | |
421 // The portion [_unallocated_block, _sp.end()) of the space that | |
422 // is a single block known not to contain any objects. | |
423 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. | |
424 HeapWord* _unallocated_block; | |
425 | |
426 public: | |
427 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
428 BlockOffsetArray(array, mr, false), | |
429 _unallocated_block(_bottom) { } | |
430 | |
431 // accessor | |
432 HeapWord* unallocated_block() const { | |
433 assert(BlockOffsetArrayUseUnallocatedBlock, | |
434 "_unallocated_block is not being maintained"); | |
435 return _unallocated_block; | |
436 } | |
437 | |
438 void set_unallocated_block(HeapWord* block) { | |
439 assert(BlockOffsetArrayUseUnallocatedBlock, | |
440 "_unallocated_block is not being maintained"); | |
441 assert(block >= _bottom && block <= _end, "out of range"); | |
442 _unallocated_block = block; | |
443 } | |
444 | |
445 // These methods expect to be called with [blk_start, blk_end) | |
446 // representing a block of memory in the heap. | |
447 void alloc_block(HeapWord* blk_start, HeapWord* blk_end); | |
448 void alloc_block(HeapWord* blk, size_t size) { | |
449 alloc_block(blk, blk + size); | |
450 } | |
451 | |
452 // The following methods are useful and optimized for a | |
453 // non-contiguous space. | |
454 | |
455 // Given a block [blk_start, blk_start + full_blk_size), and | |
456 // a left_blk_size < full_blk_size, adjust the BOT to show two | |
457 // blocks [blk_start, blk_start + left_blk_size) and | |
458 // [blk_start + left_blk_size, blk_start + full_blk_size). | |
459 // It is assumed (and verified in the non-product VM) that the | |
460 // BOT was correct for the original block. | |
461 void split_block(HeapWord* blk_start, size_t full_blk_size, | |
462 size_t left_blk_size); | |
463 | |
464 // Adjust BOT to show that it has a block in the range | |
465 // [blk_start, blk_start + size). Only the first card | |
466 // of BOT is touched. It is assumed (and verified in the | |
467 // non-product VM) that the remaining cards of the block | |
468 // are correct. | |
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469 void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false); |
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470 void mark_block(HeapWord* blk, size_t size, bool reducing = false) { |
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471 mark_block(blk, blk + size, reducing); |
0 | 472 } |
473 | |
474 // Adjust _unallocated_block to indicate that a particular | |
475 // block has been newly allocated or freed. It is assumed (and | |
476 // verified in the non-product VM) that the BOT is correct for | |
477 // the given block. | |
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478 void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) { |
0 | 479 // Verify that the BOT shows [blk, blk + blk_size) to be one block. |
480 verify_single_block(blk_start, blk_end); | |
481 if (BlockOffsetArrayUseUnallocatedBlock) { | |
482 _unallocated_block = MAX2(_unallocated_block, blk_end); | |
483 } | |
484 } | |
485 | |
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486 void allocated(HeapWord* blk, size_t size, bool reducing = false) { |
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487 allocated(blk, blk + size, reducing); |
0 | 488 } |
489 | |
490 void freed(HeapWord* blk_start, HeapWord* blk_end); | |
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491 void freed(HeapWord* blk, size_t size); |
0 | 492 |
493 HeapWord* block_start_unsafe(const void* addr) const; | |
494 | |
495 // Requires "addr" to be the start of a card and returns the | |
496 // start of the block that contains the given address. | |
497 HeapWord* block_start_careful(const void* addr) const; | |
498 | |
499 // Verification & debugging: ensure that the offset table reflects | |
500 // the fact that the block [blk_start, blk_end) or [blk, blk + size) | |
501 // is a single block of storage. NOTE: can't const this because of | |
502 // call to non-const do_block_internal() below. | |
503 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) | |
504 PRODUCT_RETURN; | |
505 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; | |
506 | |
507 // Verify that the given block is before _unallocated_block | |
508 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) | |
509 const PRODUCT_RETURN; | |
510 void verify_not_unallocated(HeapWord* blk, size_t size) | |
511 const PRODUCT_RETURN; | |
512 | |
513 // Debugging support | |
514 virtual size_t last_active_index() const; | |
515 }; | |
516 | |
517 //////////////////////////////////////////////////////////////////////////// | |
518 // A subtype of BlockOffsetArray that takes advantage of the fact | |
519 // that its underlying space is a ContiguousSpace, so that its "active" | |
520 // region can be more efficiently tracked (than for a non-contiguous space). | |
521 //////////////////////////////////////////////////////////////////////////// | |
522 class BlockOffsetArrayContigSpace: public BlockOffsetArray { | |
523 friend class VMStructs; | |
524 private: | |
525 // allocation boundary at which offset array must be updated | |
526 HeapWord* _next_offset_threshold; | |
527 size_t _next_offset_index; // index corresponding to that boundary | |
528 | |
529 // Work function when allocation start crosses threshold. | |
530 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); | |
531 | |
532 public: | |
533 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): | |
534 BlockOffsetArray(array, mr, true) { | |
535 _next_offset_threshold = NULL; | |
536 _next_offset_index = 0; | |
537 } | |
538 | |
539 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } | |
540 | |
541 // Initialize the threshold for an empty heap. | |
542 HeapWord* initialize_threshold(); | |
543 // Zero out the entry for _bottom (offset will be zero) | |
544 void zero_bottom_entry(); | |
545 | |
546 // Return the next threshold, the point at which the table should be | |
547 // updated. | |
548 HeapWord* threshold() const { return _next_offset_threshold; } | |
549 | |
550 // In general, these methods expect to be called with | |
551 // [blk_start, blk_end) representing a block of memory in the heap. | |
552 // In this implementation, however, we are OK even if blk_start and/or | |
553 // blk_end are NULL because NULL is represented as 0, and thus | |
554 // never exceeds the "_next_offset_threshold". | |
555 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { | |
556 if (blk_end > _next_offset_threshold) { | |
557 alloc_block_work(blk_start, blk_end); | |
558 } | |
559 } | |
560 void alloc_block(HeapWord* blk, size_t size) { | |
561 alloc_block(blk, blk + size); | |
562 } | |
563 | |
564 HeapWord* block_start_unsafe(const void* addr) const; | |
565 | |
566 void serialize(SerializeOopClosure* soc); | |
567 | |
568 // Debugging support | |
569 virtual size_t last_active_index() const; | |
570 }; | |
1972 | 571 |
572 #endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP |