1 /* 2 * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved. 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 * 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 // Classes in support of keeping track of promotions into a non-Contiguous 26 // space, in this case a CompactibleFreeListSpace. 27 28 #define CFLS_LAB_REFILL_STATS 0 29 30 // Forward declarations 31 class CompactibleFreeListSpace; 32 class BlkClosure; 33 class BlkClosureCareful; 34 class UpwardsObjectClosure; 35 class ObjectClosureCareful; 36 class Klass; 37 38 class PromotedObject VALUE_OBJ_CLASS_SPEC { 39 private: 40 enum { 41 promoted_mask = right_n_bits(2), // i.e. 0x3 42 displaced_mark = nth_bit(2), // i.e. 0x4 43 next_mask = ~(right_n_bits(3)) // i.e. ~(0x7) 44 }; 45 intptr_t _next; 46 public: 47 inline PromotedObject* next() const { 48 return (PromotedObject*)(_next & next_mask); 49 } 50 inline void setNext(PromotedObject* x) { 51 assert(((intptr_t)x & ~next_mask) == 0, 52 "Conflict in bit usage, " 53 " or insufficient alignment of objects"); 54 _next |= (intptr_t)x; 55 } 56 inline void setPromotedMark() { 57 _next |= promoted_mask; 58 } 59 inline bool hasPromotedMark() const { 60 return (_next & promoted_mask) == promoted_mask; 61 } 62 inline void setDisplacedMark() { 63 _next |= displaced_mark; 64 } 65 inline bool hasDisplacedMark() const { 66 return (_next & displaced_mark) != 0; 67 } 68 inline void clearNext() { _next = 0; } 69 debug_only(void *next_addr() { return (void *) &_next; }) 70 }; 71 72 class SpoolBlock: public FreeChunk { 73 friend class PromotionInfo; 74 protected: 75 SpoolBlock* nextSpoolBlock; 76 size_t bufferSize; // number of usable words in this block 77 markOop* displacedHdr; // the displaced headers start here 78 79 // Note about bufferSize: it denotes the number of entries available plus 1; 80 // legal indices range from 1 through BufferSize - 1. See the verification 81 // code verify() that counts the number of displaced headers spooled. 82 size_t computeBufferSize() { 83 return (size() * sizeof(HeapWord) - sizeof(*this)) / sizeof(markOop); 84 } 85 86 public: 87 void init() { 88 bufferSize = computeBufferSize(); 89 displacedHdr = (markOop*)&displacedHdr; 90 nextSpoolBlock = NULL; 91 } 92 }; 93 94 class PromotionInfo VALUE_OBJ_CLASS_SPEC { 95 bool _tracking; // set if tracking 96 CompactibleFreeListSpace* _space; // the space to which this belongs 97 PromotedObject* _promoHead; // head of list of promoted objects 98 PromotedObject* _promoTail; // tail of list of promoted objects 99 SpoolBlock* _spoolHead; // first spooling block 100 SpoolBlock* _spoolTail; // last non-full spooling block or null 101 SpoolBlock* _splice_point; // when _spoolTail is null, holds list tail 102 SpoolBlock* _spareSpool; // free spool buffer 103 size_t _firstIndex; // first active index in 104 // first spooling block (_spoolHead) 105 size_t _nextIndex; // last active index + 1 in last 106 // spooling block (_spoolTail) 107 private: 108 // ensure that spooling space exists; return true if there is spooling space 109 bool ensure_spooling_space_work(); 110 111 public: 112 PromotionInfo() : 113 _tracking(0), _space(NULL), 114 _promoHead(NULL), _promoTail(NULL), 115 _spoolHead(NULL), _spoolTail(NULL), 116 _spareSpool(NULL), _firstIndex(1), 117 _nextIndex(1) {} 118 119 bool noPromotions() const { 120 assert(_promoHead != NULL || _promoTail == NULL, "list inconsistency"); 121 return _promoHead == NULL; 122 } 123 void startTrackingPromotions(); 124 void stopTrackingPromotions(); 125 bool tracking() const { return _tracking; } 126 void track(PromotedObject* trackOop); // keep track of a promoted oop 127 // The following variant must be used when trackOop is not fully 128 // initialized and has a NULL klass: 129 void track(PromotedObject* trackOop, klassOop klassOfOop); // keep track of a promoted oop 130 void setSpace(CompactibleFreeListSpace* sp) { _space = sp; } 131 CompactibleFreeListSpace* space() const { return _space; } 132 markOop nextDisplacedHeader(); // get next header & forward spool pointer 133 void saveDisplacedHeader(markOop hdr); 134 // save header and forward spool 135 136 inline size_t refillSize() const; 137 138 SpoolBlock* getSpoolBlock(); // return a free spooling block 139 inline bool has_spooling_space() { 140 return _spoolTail != NULL && _spoolTail->bufferSize > _nextIndex; 141 } 142 // ensure that spooling space exists 143 bool ensure_spooling_space() { 144 return has_spooling_space() || ensure_spooling_space_work(); 145 } 146 #define PROMOTED_OOPS_ITERATE_DECL(OopClosureType, nv_suffix) \ 147 void promoted_oops_iterate##nv_suffix(OopClosureType* cl); 148 ALL_SINCE_SAVE_MARKS_CLOSURES(PROMOTED_OOPS_ITERATE_DECL) 149 #undef PROMOTED_OOPS_ITERATE_DECL 150 void promoted_oops_iterate(OopsInGenClosure* cl) { 151 promoted_oops_iterate_v(cl); 152 } 153 void verify() const; 154 void reset() { 155 _promoHead = NULL; 156 _promoTail = NULL; 157 _spoolHead = NULL; 158 _spoolTail = NULL; 159 _spareSpool = NULL; 160 _firstIndex = 0; 161 _nextIndex = 0; 162 163 } 164 }; 165 166 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC { 167 public: 168 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0), 169 _allocation_size_limit(0) {} 170 void set(HeapWord* ptr, size_t word_size, size_t refill_size, 171 size_t allocation_size_limit) { 172 _ptr = ptr; 173 _word_size = word_size; 174 _refillSize = refill_size; 175 _allocation_size_limit = allocation_size_limit; 176 } 177 HeapWord* _ptr; 178 size_t _word_size; 179 size_t _refillSize; 180 size_t _allocation_size_limit; // largest size that will be allocated 181 }; 182 183 // Concrete subclass of CompactibleSpace that implements 184 // a free list space, such as used in the concurrent mark sweep 185 // generation. 186 187 class CompactibleFreeListSpace: public CompactibleSpace { 188 friend class VMStructs; 189 friend class ConcurrentMarkSweepGeneration; 190 friend class ASConcurrentMarkSweepGeneration; 191 friend class CMSCollector; 192 friend class CMSPermGenGen; 193 // Local alloc buffer for promotion into this space. 194 friend class CFLS_LAB; 195 196 // "Size" of chunks of work (executed during parallel remark phases 197 // of CMS collection); this probably belongs in CMSCollector, although 198 // it's cached here because it's used in 199 // initialize_sequential_subtasks_for_rescan() which modifies 200 // par_seq_tasks which also lives in Space. XXX 201 const size_t _rescan_task_size; 202 const size_t _marking_task_size; 203 204 // Yet another sequential tasks done structure. This supports 205 // CMS GC, where we have threads dynamically 206 // claiming sub-tasks from a larger parallel task. 207 SequentialSubTasksDone _conc_par_seq_tasks; 208 209 BlockOffsetArrayNonContigSpace _bt; 210 211 CMSCollector* _collector; 212 ConcurrentMarkSweepGeneration* _gen; 213 214 // Data structures for free blocks (used during allocation/sweeping) 215 216 // Allocation is done linearly from two different blocks depending on 217 // whether the request is small or large, in an effort to reduce 218 // fragmentation. We assume that any locking for allocation is done 219 // by the containing generation. Thus, none of the methods in this 220 // space are re-entrant. 221 enum SomeConstants { 222 SmallForLinearAlloc = 16, // size < this then use _sLAB 223 SmallForDictionary = 257, // size < this then use _indexedFreeList 224 IndexSetSize = SmallForDictionary, // keep this odd-sized 225 IndexSetStart = MinObjAlignment, 226 IndexSetStride = MinObjAlignment 227 }; 228 229 private: 230 enum FitStrategyOptions { 231 FreeBlockStrategyNone = 0, 232 FreeBlockBestFitFirst 233 }; 234 235 PromotionInfo _promoInfo; 236 237 // helps to impose a global total order on freelistLock ranks; 238 // assumes that CFLSpace's are allocated in global total order 239 static int _lockRank; 240 241 // a lock protecting the free lists and free blocks; 242 // mutable because of ubiquity of locking even for otherwise const methods 243 mutable Mutex _freelistLock; 244 // locking verifier convenience function 245 void assert_locked() const PRODUCT_RETURN; 246 247 // Linear allocation blocks 248 LinearAllocBlock _smallLinearAllocBlock; 249 250 FreeBlockDictionary::DictionaryChoice _dictionaryChoice; 251 FreeBlockDictionary* _dictionary; // ptr to dictionary for large size blocks 252 253 FreeList _indexedFreeList[IndexSetSize]; 254 // indexed array for small size blocks 255 // allocation stategy 256 bool _fitStrategy; // Use best fit strategy. 257 bool _adaptive_freelists; // Use adaptive freelists 258 259 // This is an address close to the largest free chunk in the heap. 260 // It is currently assumed to be at the end of the heap. Free 261 // chunks with addresses greater than nearLargestChunk are coalesced 262 // in an effort to maintain a large chunk at the end of the heap. 263 HeapWord* _nearLargestChunk; 264 265 // Used to keep track of limit of sweep for the space 266 HeapWord* _sweep_limit; 267 268 // Support for compacting cms 269 HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 270 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top); 271 272 // Initialization helpers. 273 void initializeIndexedFreeListArray(); 274 275 // Extra stuff to manage promotion parallelism. 276 277 // a lock protecting the dictionary during par promotion allocation. 278 mutable Mutex _parDictionaryAllocLock; 279 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; } 280 281 // Locks protecting the exact lists during par promotion allocation. 282 Mutex* _indexedFreeListParLocks[IndexSetSize]; 283 284 #if CFLS_LAB_REFILL_STATS 285 // Some statistics. 286 jint _par_get_chunk_from_small; 287 jint _par_get_chunk_from_large; 288 #endif 289 290 291 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is 292 // required to be smaller than "IndexSetSize".) If successful, 293 // adds them to "fl", which is required to be an empty free list. 294 // If the count of "fl" is negative, it's absolute value indicates a 295 // number of free chunks that had been previously "borrowed" from global 296 // list of size "word_sz", and must now be decremented. 297 void par_get_chunk_of_blocks(size_t word_sz, size_t n, FreeList* fl); 298 299 // Allocation helper functions 300 // Allocate using a strategy that takes from the indexed free lists 301 // first. This allocation strategy assumes a companion sweeping 302 // strategy that attempts to keep the needed number of chunks in each 303 // indexed free lists. 304 HeapWord* allocate_adaptive_freelists(size_t size); 305 // Allocate from the linear allocation buffers first. This allocation 306 // strategy assumes maximal coalescing can maintain chunks large enough 307 // to be used as linear allocation buffers. 308 HeapWord* allocate_non_adaptive_freelists(size_t size); 309 310 // Gets a chunk from the linear allocation block (LinAB). If there 311 // is not enough space in the LinAB, refills it. 312 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size); 313 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size); 314 // Get a chunk from the space remaining in the linear allocation block. Do 315 // not attempt to refill if the space is not available, return NULL. Do the 316 // repairs on the linear allocation block as appropriate. 317 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size); 318 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size); 319 320 // Helper function for getChunkFromIndexedFreeList. 321 // Replenish the indexed free list for this "size". Do not take from an 322 // underpopulated size. 323 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size); 324 325 // Get a chunk from the indexed free list. If the indexed free list 326 // does not have a free chunk, try to replenish the indexed free list 327 // then get the free chunk from the replenished indexed free list. 328 inline FreeChunk* getChunkFromIndexedFreeList(size_t size); 329 330 // The returned chunk may be larger than requested (or null). 331 FreeChunk* getChunkFromDictionary(size_t size); 332 // The returned chunk is the exact size requested (or null). 333 FreeChunk* getChunkFromDictionaryExact(size_t size); 334 335 // Find a chunk in the indexed free list that is the best 336 // fit for size "numWords". 337 FreeChunk* bestFitSmall(size_t numWords); 338 // For free list "fl" of chunks of size > numWords, 339 // remove a chunk, split off a chunk of size numWords 340 // and return it. The split off remainder is returned to 341 // the free lists. The old name for getFromListGreater 342 // was lookInListGreater. 343 FreeChunk* getFromListGreater(FreeList* fl, size_t numWords); 344 // Get a chunk in the indexed free list or dictionary, 345 // by considering a larger chunk and splitting it. 346 FreeChunk* getChunkFromGreater(size_t numWords); 347 // Verify that the given chunk is in the indexed free lists. 348 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const; 349 // Remove the specified chunk from the indexed free lists. 350 void removeChunkFromIndexedFreeList(FreeChunk* fc); 351 // Remove the specified chunk from the dictionary. 352 void removeChunkFromDictionary(FreeChunk* fc); 353 // Split a free chunk into a smaller free chunk of size "new_size". 354 // Return the smaller free chunk and return the remainder to the 355 // free lists. 356 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size); 357 // Add a chunk to the free lists. 358 void addChunkToFreeLists(HeapWord* chunk, size_t size); 359 // Add a chunk to the free lists, preferring to suffix it 360 // to the last free chunk at end of space if possible, and 361 // updating the block census stats as well as block offset table. 362 // Take any locks as appropriate if we are multithreaded. 363 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size); 364 // Add a free chunk to the indexed free lists. 365 void returnChunkToFreeList(FreeChunk* chunk); 366 // Add a free chunk to the dictionary. 367 void returnChunkToDictionary(FreeChunk* chunk); 368 369 // Functions for maintaining the linear allocation buffers (LinAB). 370 // Repairing a linear allocation block refers to operations 371 // performed on the remainder of a LinAB after an allocation 372 // has been made from it. 373 void repairLinearAllocationBlocks(); 374 void repairLinearAllocBlock(LinearAllocBlock* blk); 375 void refillLinearAllocBlock(LinearAllocBlock* blk); 376 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk); 377 void refillLinearAllocBlocksIfNeeded(); 378 379 void verify_objects_initialized() const; 380 381 // Statistics reporting helper functions 382 void reportFreeListStatistics() const; 383 void reportIndexedFreeListStatistics() const; 384 size_t maxChunkSizeInIndexedFreeLists() const; 385 size_t numFreeBlocksInIndexedFreeLists() const; 386 // Accessor 387 HeapWord* unallocated_block() const { 388 HeapWord* ub = _bt.unallocated_block(); 389 assert(ub >= bottom() && 390 ub <= end(), "space invariant"); 391 return ub; 392 } 393 void freed(HeapWord* start, size_t size) { 394 _bt.freed(start, size); 395 } 396 397 protected: 398 // reset the indexed free list to its initial empty condition. 399 void resetIndexedFreeListArray(); 400 // reset to an initial state with a single free block described 401 // by the MemRegion parameter. 402 void reset(MemRegion mr); 403 // Return the total number of words in the indexed free lists. 404 size_t totalSizeInIndexedFreeLists() const; 405 406 public: 407 // Constructor... 408 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr, 409 bool use_adaptive_freelists, 410 FreeBlockDictionary::DictionaryChoice); 411 // accessors 412 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; } 413 FreeBlockDictionary* dictionary() const { return _dictionary; } 414 HeapWord* nearLargestChunk() const { return _nearLargestChunk; } 415 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; } 416 417 // Return the free chunk at the end of the space. If no such 418 // chunk exists, return NULL. 419 FreeChunk* find_chunk_at_end(); 420 421 bool adaptive_freelists() const { return _adaptive_freelists; } 422 423 void set_collector(CMSCollector* collector) { _collector = collector; } 424 425 // Support for parallelization of rescan and marking 426 const size_t rescan_task_size() const { return _rescan_task_size; } 427 const size_t marking_task_size() const { return _marking_task_size; } 428 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; } 429 void initialize_sequential_subtasks_for_rescan(int n_threads); 430 void initialize_sequential_subtasks_for_marking(int n_threads, 431 HeapWord* low = NULL); 432 433 #if CFLS_LAB_REFILL_STATS 434 void print_par_alloc_stats(); 435 #endif 436 437 // Space enquiries 438 size_t used() const; 439 size_t free() const; 440 size_t max_alloc_in_words() const; 441 // XXX: should have a less conservative used_region() than that of 442 // Space; we could consider keeping track of highest allocated 443 // address and correcting that at each sweep, as the sweeper 444 // goes through the entire allocated part of the generation. We 445 // could also use that information to keep the sweeper from 446 // sweeping more than is necessary. The allocator and sweeper will 447 // of course need to synchronize on this, since the sweeper will 448 // try to bump down the address and the allocator will try to bump it up. 449 // For now, however, we'll just use the default used_region() 450 // which overestimates the region by returning the entire 451 // committed region (this is safe, but inefficient). 452 453 // Returns a subregion of the space containing all the objects in 454 // the space. 455 MemRegion used_region() const { 456 return MemRegion(bottom(), 457 BlockOffsetArrayUseUnallocatedBlock ? 458 unallocated_block() : end()); 459 } 460 461 // This is needed because the default implementation uses block_start() 462 // which can;t be used at certain times (for example phase 3 of mark-sweep). 463 // A better fix is to change the assertions in phase 3 of mark-sweep to 464 // use is_in_reserved(), but that is deferred since the is_in() assertions 465 // are buried through several layers of callers and are used elsewhere 466 // as well. 467 bool is_in(const void* p) const { 468 return used_region().contains(p); 469 } 470 471 virtual bool is_free_block(const HeapWord* p) const; 472 473 // Resizing support 474 void set_end(HeapWord* value); // override 475 476 // mutual exclusion support 477 Mutex* freelistLock() const { return &_freelistLock; } 478 479 // Iteration support 480 void oop_iterate(MemRegion mr, OopClosure* cl); 481 void oop_iterate(OopClosure* cl); 482 483 void object_iterate(ObjectClosure* blk); 484 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 485 486 // Requires that "mr" be entirely within the space. 487 // Apply "cl->do_object" to all objects that intersect with "mr". 488 // If the iteration encounters an unparseable portion of the region, 489 // terminate the iteration and return the address of the start of the 490 // subregion that isn't done. Return of "NULL" indicates that the 491 // interation completed. 492 virtual HeapWord* 493 object_iterate_careful_m(MemRegion mr, 494 ObjectClosureCareful* cl); 495 virtual HeapWord* 496 object_iterate_careful(ObjectClosureCareful* cl); 497 498 // Override: provides a DCTO_CL specific to this kind of space. 499 DirtyCardToOopClosure* new_dcto_cl(OopClosure* cl, 500 CardTableModRefBS::PrecisionStyle precision, 501 HeapWord* boundary); 502 503 void blk_iterate(BlkClosure* cl); 504 void blk_iterate_careful(BlkClosureCareful* cl); 505 HeapWord* block_start(const void* p) const; 506 HeapWord* block_start_careful(const void* p) const; 507 size_t block_size(const HeapWord* p) const; 508 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const; 509 bool block_is_obj(const HeapWord* p) const; 510 bool obj_is_alive(const HeapWord* p) const; 511 size_t block_size_nopar(const HeapWord* p) const; 512 bool block_is_obj_nopar(const HeapWord* p) const; 513 514 // iteration support for promotion 515 void save_marks(); 516 bool no_allocs_since_save_marks(); 517 void object_iterate_since_last_GC(ObjectClosure* cl); 518 519 // iteration support for sweeping 520 void save_sweep_limit() { 521 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ? 522 unallocated_block() : end(); 523 } 524 NOT_PRODUCT( 525 void clear_sweep_limit() { _sweep_limit = NULL; } 526 ) 527 HeapWord* sweep_limit() { return _sweep_limit; } 528 529 // Apply "blk->do_oop" to the addresses of all reference fields in objects 530 // promoted into this generation since the most recent save_marks() call. 531 // Fields in objects allocated by applications of the closure 532 // *are* included in the iteration. Thus, when the iteration completes 533 // there should be no further such objects remaining. 534 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 535 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 536 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL) 537 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL 538 539 // Allocation support 540 HeapWord* allocate(size_t size); 541 HeapWord* par_allocate(size_t size); 542 543 oop promote(oop obj, size_t obj_size, oop* ref); 544 void gc_prologue(); 545 void gc_epilogue(); 546 547 // This call is used by a containing CMS generation / collector 548 // to inform the CFLS space that a sweep has been completed 549 // and that the space can do any related house-keeping functions. 550 void sweep_completed(); 551 552 // For an object in this space, the mark-word's two 553 // LSB's having the value [11] indicates that it has been 554 // promoted since the most recent call to save_marks() on 555 // this generation and has not subsequently been iterated 556 // over (using oop_since_save_marks_iterate() above). 557 bool obj_allocated_since_save_marks(const oop obj) const { 558 assert(is_in_reserved(obj), "Wrong space?"); 559 return ((PromotedObject*)obj)->hasPromotedMark(); 560 } 561 562 // A worst-case estimate of the space required (in HeapWords) to expand the 563 // heap when promoting an obj of size obj_size. 564 size_t expansionSpaceRequired(size_t obj_size) const; 565 566 FreeChunk* allocateScratch(size_t size); 567 568 // returns true if either the small or large linear allocation buffer is empty. 569 bool linearAllocationWouldFail() const; 570 571 // Adjust the chunk for the minimum size. This version is called in 572 // most cases in CompactibleFreeListSpace methods. 573 inline static size_t adjustObjectSize(size_t size) { 574 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize)); 575 } 576 // This is a virtual version of adjustObjectSize() that is called 577 // only occasionally when the compaction space changes and the type 578 // of the new compaction space is is only known to be CompactibleSpace. 579 size_t adjust_object_size_v(size_t size) const { 580 return adjustObjectSize(size); 581 } 582 // Minimum size of a free block. 583 virtual size_t minimum_free_block_size() const { return MinChunkSize; } 584 void removeFreeChunkFromFreeLists(FreeChunk* chunk); 585 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size, 586 bool coalesced); 587 588 // Support for decisions regarding concurrent collection policy 589 bool should_concurrent_collect() const; 590 591 // Support for compaction 592 void prepare_for_compaction(CompactPoint* cp); 593 void adjust_pointers(); 594 void compact(); 595 // reset the space to reflect the fact that a compaction of the 596 // space has been done. 597 virtual void reset_after_compaction(); 598 599 // Debugging support 600 void print() const; 601 void prepare_for_verify(); 602 void verify(bool allow_dirty) const; 603 void verifyFreeLists() const PRODUCT_RETURN; 604 void verifyIndexedFreeLists() const; 605 void verifyIndexedFreeList(size_t size) const; 606 // verify that the given chunk is in the free lists. 607 bool verifyChunkInFreeLists(FreeChunk* fc) const; 608 // Do some basic checks on the the free lists. 609 void checkFreeListConsistency() const PRODUCT_RETURN; 610 611 NOT_PRODUCT ( 612 void initializeIndexedFreeListArrayReturnedBytes(); 613 size_t sumIndexedFreeListArrayReturnedBytes(); 614 // Return the total number of chunks in the indexed free lists. 615 size_t totalCountInIndexedFreeLists() const; 616 // Return the total numberof chunks in the space. 617 size_t totalCount(); 618 ) 619 620 // The census consists of counts of the quantities such as 621 // the current count of the free chunks, number of chunks 622 // created as a result of the split of a larger chunk or 623 // coalescing of smaller chucks, etc. The counts in the 624 // census is used to make decisions on splitting and 625 // coalescing of chunks during the sweep of garbage. 626 627 // Print the statistics for the free lists. 628 void printFLCensus(size_t sweep_count) const; 629 630 // Statistics functions 631 // Initialize census for lists before the sweep. 632 void beginSweepFLCensus(float sweep_current, 633 float sweep_estimate); 634 // Set the surplus for each of the free lists. 635 void setFLSurplus(); 636 // Set the hint for each of the free lists. 637 void setFLHints(); 638 // Clear the census for each of the free lists. 639 void clearFLCensus(); 640 // Perform functions for the census after the end of the sweep. 641 void endSweepFLCensus(size_t sweep_count); 642 // Return true if the count of free chunks is greater 643 // than the desired number of free chunks. 644 bool coalOverPopulated(size_t size); 645 646 // Record (for each size): 647 // 648 // split-births = #chunks added due to splits in (prev-sweep-end, 649 // this-sweep-start) 650 // split-deaths = #chunks removed for splits in (prev-sweep-end, 651 // this-sweep-start) 652 // num-curr = #chunks at start of this sweep 653 // num-prev = #chunks at end of previous sweep 654 // 655 // The above are quantities that are measured. Now define: 656 // 657 // num-desired := num-prev + split-births - split-deaths - num-curr 658 // 659 // Roughly, num-prev + split-births is the supply, 660 // split-deaths is demand due to other sizes 661 // and num-curr is what we have left. 662 // 663 // Thus, num-desired is roughly speaking the "legitimate demand" 664 // for blocks of this size and what we are striving to reach at the 665 // end of the current sweep. 666 // 667 // For a given list, let num-len be its current population. 668 // Define, for a free list of a given size: 669 // 670 // coal-overpopulated := num-len >= num-desired * coal-surplus 671 // (coal-surplus is set to 1.05, i.e. we allow a little slop when 672 // coalescing -- we do not coalesce unless we think that the current 673 // supply has exceeded the estimated demand by more than 5%). 674 // 675 // For the set of sizes in the binary tree, which is neither dense nor 676 // closed, it may be the case that for a particular size we have never 677 // had, or do not now have, or did not have at the previous sweep, 678 // chunks of that size. We need to extend the definition of 679 // coal-overpopulated to such sizes as well: 680 // 681 // For a chunk in/not in the binary tree, extend coal-overpopulated 682 // defined above to include all sizes as follows: 683 // 684 // . a size that is non-existent is coal-overpopulated 685 // . a size that has a num-desired <= 0 as defined above is 686 // coal-overpopulated. 687 // 688 // Also define, for a chunk heap-offset C and mountain heap-offset M: 689 // 690 // close-to-mountain := C >= 0.99 * M 691 // 692 // Now, the coalescing strategy is: 693 // 694 // Coalesce left-hand chunk with right-hand chunk if and 695 // only if: 696 // 697 // EITHER 698 // . left-hand chunk is of a size that is coal-overpopulated 699 // OR 700 // . right-hand chunk is close-to-mountain 701 void smallCoalBirth(size_t size); 702 void smallCoalDeath(size_t size); 703 void coalBirth(size_t size); 704 void coalDeath(size_t size); 705 void smallSplitBirth(size_t size); 706 void smallSplitDeath(size_t size); 707 void splitBirth(size_t size); 708 void splitDeath(size_t size); 709 void split(size_t from, size_t to1); 710 711 double flsFrag() const; 712 }; 713 714 // A parallel-GC-thread-local allocation buffer for allocation into a 715 // CompactibleFreeListSpace. 716 class CFLS_LAB : public CHeapObj { 717 // The space that this buffer allocates into. 718 CompactibleFreeListSpace* _cfls; 719 720 // Our local free lists. 721 FreeList _indexedFreeList[CompactibleFreeListSpace::IndexSetSize]; 722 723 // Initialized from a command-line arg. 724 size_t _blocks_to_claim; 725 726 #if CFLS_LAB_REFILL_STATS 727 // Some statistics. 728 int _refills; 729 int _blocksTaken; 730 static int _tot_refills; 731 static int _tot_blocksTaken; 732 static int _next_threshold; 733 #endif 734 735 public: 736 CFLS_LAB(CompactibleFreeListSpace* cfls); 737 738 // Allocate and return a block of the given size, or else return NULL. 739 HeapWord* alloc(size_t word_sz); 740 741 // Return any unused portions of the buffer to the global pool. 742 void retire(); 743 }; 744 745 size_t PromotionInfo::refillSize() const { 746 const size_t CMSSpoolBlockSize = 256; 747 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop) 748 * CMSSpoolBlockSize); 749 return CompactibleFreeListSpace::adjustObjectSize(sz); 750 } --- EOF ---