Wed, 20 Aug 2008 23:05:04 -0700
6728478: Assertion at parallel promotion from young to old generation
Summary: The fix avoids a call to address_for_index() in this particular situation where it is not known if the passed index is in bounds.
Reviewed-by: tonyp
1 /*
2 * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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23 */
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 //
37 class ContiguousSpace;
38 class SerializeOopClosure;
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.
48 // The space this table is covering.
49 HeapWord* _bottom; // == reserved.start
50 HeapWord* _end; // End of currently allocated region.
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 }
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;
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 }
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;
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 };
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.)
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;
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 };
110 // The reserved region covered by the shared array.
111 MemRegion _reserved;
113 // End of the current committed region.
114 HeapWord* _end;
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
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;
143 memset(&_offset_array[index_for(left)], offset, num_cards);
144 }
146 void set_offset_array(size_t left, size_t right, u_char offset) {
147 assert(right < _vs.committed_size(), "right address out of range");
148 assert(left <= right, "indexes out of order");
149 size_t num_cards = right - left + 1;
150 memset(&_offset_array[left], offset, num_cards);
151 }
153 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
154 assert(index < _vs.committed_size(), "index out of range");
155 assert(high >= low, "addresses out of order");
156 assert(pointer_delta(high, low) <= N_words, "offset too large");
157 assert(_offset_array[index] == pointer_delta(high, low),
158 "Wrong offset");
159 }
161 bool is_card_boundary(HeapWord* p) const;
163 // Return the number of slots needed for an offset array
164 // that covers mem_region_words words.
165 // We always add an extra slot because if an object
166 // ends on a card boundary we put a 0 in the next
167 // offset array slot, so we want that slot always
168 // to be reserved.
170 size_t compute_size(size_t mem_region_words) {
171 size_t number_of_slots = (mem_region_words / N_words) + 1;
172 return ReservedSpace::allocation_align_size_up(number_of_slots);
173 }
175 public:
176 // Initialize the table to cover from "base" to (at least)
177 // "base + init_word_size". In the future, the table may be expanded
178 // (see "resize" below) up to the size of "_reserved" (which must be at
179 // least "init_word_size".) The contents of the initial table are
180 // undefined; it is the responsibility of the constituent
181 // BlockOffsetTable(s) to initialize cards.
182 BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
184 // Notes a change in the committed size of the region covered by the
185 // table. The "new_word_size" may not be larger than the size of the
186 // reserved region this table covers.
187 void resize(size_t new_word_size);
189 void set_bottom(HeapWord* new_bottom);
191 // Updates all the BlockOffsetArray's sharing this shared array to
192 // reflect the current "top"'s of their spaces.
193 void update_offset_arrays(); // Not yet implemented!
195 // Return the appropriate index into "_offset_array" for "p".
196 size_t index_for(const void* p) const;
198 // Return the address indicating the start of the region corresponding to
199 // "index" in "_offset_array".
200 HeapWord* address_for_index(size_t index) const;
202 // Return the address "p" incremented by the size of
203 // a region. This method does not align the address
204 // returned to the start of a region. It is a simple
205 // primitive.
206 HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; }
208 // Shared space support
209 void serialize(SerializeOopClosure* soc, HeapWord* start, HeapWord* end);
210 };
212 //////////////////////////////////////////////////////////////////////////
213 // The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
214 //////////////////////////////////////////////////////////////////////////
215 class BlockOffsetArray: public BlockOffsetTable {
216 friend class VMStructs;
217 protected:
218 // The following enums are used by do_block_internal() below
219 enum Action {
220 Action_single, // BOT records a single block (see single_block())
221 Action_mark, // BOT marks the start of a block (see mark_block())
222 Action_check // Check that BOT records block correctly
223 // (see verify_single_block()).
224 };
226 enum SomePrivateConstants {
227 N_words = BlockOffsetSharedArray::N_words,
228 LogN = BlockOffsetSharedArray::LogN,
229 // entries "e" of at least N_words mean "go back by Base^(e-N_words)."
230 // All entries are less than "N_words + N_powers".
231 LogBase = 4,
232 Base = (1 << LogBase),
233 N_powers = 14
234 };
236 static size_t power_to_cards_back(uint i) {
237 return 1 << (LogBase * i);
238 }
239 static size_t power_to_words_back(uint i) {
240 return power_to_cards_back(i) * N_words;
241 }
242 static size_t entry_to_cards_back(u_char entry) {
243 assert(entry >= N_words, "Precondition");
244 return power_to_cards_back(entry - N_words);
245 }
246 static size_t entry_to_words_back(u_char entry) {
247 assert(entry >= N_words, "Precondition");
248 return power_to_words_back(entry - N_words);
249 }
251 // The shared array, which is shared with other BlockOffsetArray's
252 // corresponding to different spaces within a generation or span of
253 // memory.
254 BlockOffsetSharedArray* _array;
256 // The space that owns this subregion.
257 Space* _sp;
259 // If true, array entries are initialized to 0; otherwise, they are
260 // initialized to point backwards to the beginning of the covered region.
261 bool _init_to_zero;
263 // Sets the entries
264 // corresponding to the cards starting at "start" and ending at "end"
265 // to point back to the card before "start": the interval [start, end)
266 // is right-open.
267 void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
268 // Same as above, except that the args here are a card _index_ interval
269 // that is closed: [start_index, end_index]
270 void set_remainder_to_point_to_start_incl(size_t start, size_t end);
272 // A helper function for BOT adjustment/verification work
273 void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action);
275 public:
276 // The space may not have its bottom and top set yet, which is why the
277 // region is passed as a parameter. If "init_to_zero" is true, the
278 // elements of the array are initialized to zero. Otherwise, they are
279 // initialized to point backwards to the beginning.
280 BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr,
281 bool init_to_zero);
283 // Note: this ought to be part of the constructor, but that would require
284 // "this" to be passed as a parameter to a member constructor for
285 // the containing concrete subtype of Space.
286 // This would be legal C++, but MS VC++ doesn't allow it.
287 void set_space(Space* sp) { _sp = sp; }
289 // Resets the covered region to the given "mr".
290 void set_region(MemRegion mr) {
291 _bottom = mr.start();
292 _end = mr.end();
293 }
295 // Note that the committed size of the covered space may have changed,
296 // so the table size might also wish to change.
297 virtual void resize(size_t new_word_size) {
298 HeapWord* new_end = _bottom + new_word_size;
299 if (_end < new_end && !init_to_zero()) {
300 // verify that the old and new boundaries are also card boundaries
301 assert(_array->is_card_boundary(_end),
302 "_end not a card boundary");
303 assert(_array->is_card_boundary(new_end),
304 "new _end would not be a card boundary");
305 // set all the newly added cards
306 _array->set_offset_array(_end, new_end, N_words);
307 }
308 _end = new_end; // update _end
309 }
311 // Adjust the BOT to show that it has a single block in the
312 // range [blk_start, blk_start + size). All necessary BOT
313 // cards are adjusted, but _unallocated_block isn't.
314 void single_block(HeapWord* blk_start, HeapWord* blk_end);
315 void single_block(HeapWord* blk, size_t size) {
316 single_block(blk, blk + size);
317 }
319 // When the alloc_block() call returns, the block offset table should
320 // have enough information such that any subsequent block_start() call
321 // with an argument equal to an address that is within the range
322 // [blk_start, blk_end) would return the value blk_start, provided
323 // there have been no calls in between that reset this information
324 // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
325 // for an appropriate range covering the said interval).
326 // These methods expect to be called with [blk_start, blk_end)
327 // representing a block of memory in the heap.
328 virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
329 void alloc_block(HeapWord* blk, size_t size) {
330 alloc_block(blk, blk + size);
331 }
333 // If true, initialize array slots with no allocated blocks to zero.
334 // Otherwise, make them point back to the front.
335 bool init_to_zero() { return _init_to_zero; }
337 // Debugging
338 // Return the index of the last entry in the "active" region.
339 virtual size_t last_active_index() const = 0;
340 // Verify the block offset table
341 void verify() const;
342 void check_all_cards(size_t left_card, size_t right_card) const;
343 };
345 ////////////////////////////////////////////////////////////////////////////
346 // A subtype of BlockOffsetArray that takes advantage of the fact
347 // that its underlying space is a NonContiguousSpace, so that some
348 // specialized interfaces can be made available for spaces that
349 // manipulate the table.
350 ////////////////////////////////////////////////////////////////////////////
351 class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
352 friend class VMStructs;
353 private:
354 // The portion [_unallocated_block, _sp.end()) of the space that
355 // is a single block known not to contain any objects.
356 // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
357 HeapWord* _unallocated_block;
359 public:
360 BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
361 BlockOffsetArray(array, mr, false),
362 _unallocated_block(_bottom) { }
364 // accessor
365 HeapWord* unallocated_block() const {
366 assert(BlockOffsetArrayUseUnallocatedBlock,
367 "_unallocated_block is not being maintained");
368 return _unallocated_block;
369 }
371 void set_unallocated_block(HeapWord* block) {
372 assert(BlockOffsetArrayUseUnallocatedBlock,
373 "_unallocated_block is not being maintained");
374 assert(block >= _bottom && block <= _end, "out of range");
375 _unallocated_block = block;
376 }
378 // These methods expect to be called with [blk_start, blk_end)
379 // representing a block of memory in the heap.
380 void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
381 void alloc_block(HeapWord* blk, size_t size) {
382 alloc_block(blk, blk + size);
383 }
385 // The following methods are useful and optimized for a
386 // non-contiguous space.
388 // Given a block [blk_start, blk_start + full_blk_size), and
389 // a left_blk_size < full_blk_size, adjust the BOT to show two
390 // blocks [blk_start, blk_start + left_blk_size) and
391 // [blk_start + left_blk_size, blk_start + full_blk_size).
392 // It is assumed (and verified in the non-product VM) that the
393 // BOT was correct for the original block.
394 void split_block(HeapWord* blk_start, size_t full_blk_size,
395 size_t left_blk_size);
397 // Adjust BOT to show that it has a block in the range
398 // [blk_start, blk_start + size). Only the first card
399 // of BOT is touched. It is assumed (and verified in the
400 // non-product VM) that the remaining cards of the block
401 // are correct.
402 void mark_block(HeapWord* blk_start, HeapWord* blk_end);
403 void mark_block(HeapWord* blk, size_t size) {
404 mark_block(blk, blk + size);
405 }
407 // Adjust _unallocated_block to indicate that a particular
408 // block has been newly allocated or freed. It is assumed (and
409 // verified in the non-product VM) that the BOT is correct for
410 // the given block.
411 void allocated(HeapWord* blk_start, HeapWord* blk_end) {
412 // Verify that the BOT shows [blk, blk + blk_size) to be one block.
413 verify_single_block(blk_start, blk_end);
414 if (BlockOffsetArrayUseUnallocatedBlock) {
415 _unallocated_block = MAX2(_unallocated_block, blk_end);
416 }
417 }
419 void allocated(HeapWord* blk, size_t size) {
420 allocated(blk, blk + size);
421 }
423 void freed(HeapWord* blk_start, HeapWord* blk_end);
424 void freed(HeapWord* blk, size_t size) {
425 freed(blk, blk + size);
426 }
428 HeapWord* block_start_unsafe(const void* addr) const;
430 // Requires "addr" to be the start of a card and returns the
431 // start of the block that contains the given address.
432 HeapWord* block_start_careful(const void* addr) const;
435 // Verification & debugging: ensure that the offset table reflects
436 // the fact that the block [blk_start, blk_end) or [blk, blk + size)
437 // is a single block of storage. NOTE: can't const this because of
438 // call to non-const do_block_internal() below.
439 void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
440 PRODUCT_RETURN;
441 void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
443 // Verify that the given block is before _unallocated_block
444 void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
445 const PRODUCT_RETURN;
446 void verify_not_unallocated(HeapWord* blk, size_t size)
447 const PRODUCT_RETURN;
449 // Debugging support
450 virtual size_t last_active_index() const;
451 };
453 ////////////////////////////////////////////////////////////////////////////
454 // A subtype of BlockOffsetArray that takes advantage of the fact
455 // that its underlying space is a ContiguousSpace, so that its "active"
456 // region can be more efficiently tracked (than for a non-contiguous space).
457 ////////////////////////////////////////////////////////////////////////////
458 class BlockOffsetArrayContigSpace: public BlockOffsetArray {
459 friend class VMStructs;
460 private:
461 // allocation boundary at which offset array must be updated
462 HeapWord* _next_offset_threshold;
463 size_t _next_offset_index; // index corresponding to that boundary
465 // Work function when allocation start crosses threshold.
466 void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
468 public:
469 BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
470 BlockOffsetArray(array, mr, true) {
471 _next_offset_threshold = NULL;
472 _next_offset_index = 0;
473 }
475 void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
477 // Initialize the threshold for an empty heap.
478 HeapWord* initialize_threshold();
479 // Zero out the entry for _bottom (offset will be zero)
480 void zero_bottom_entry();
482 // Return the next threshold, the point at which the table should be
483 // updated.
484 HeapWord* threshold() const { return _next_offset_threshold; }
486 // In general, these methods expect to be called with
487 // [blk_start, blk_end) representing a block of memory in the heap.
488 // In this implementation, however, we are OK even if blk_start and/or
489 // blk_end are NULL because NULL is represented as 0, and thus
490 // never exceeds the "_next_offset_threshold".
491 void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
492 if (blk_end > _next_offset_threshold) {
493 alloc_block_work(blk_start, blk_end);
494 }
495 }
496 void alloc_block(HeapWord* blk, size_t size) {
497 alloc_block(blk, blk + size);
498 }
500 HeapWord* block_start_unsafe(const void* addr) const;
502 void serialize(SerializeOopClosure* soc);
504 // Debugging support
505 virtual size_t last_active_index() const;
506 };