1 /* 2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP 27 28 #include "gc_implementation/concurrentMarkSweep/adaptiveFreeList.hpp" 29 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp" 30 #include "memory/binaryTreeDictionary.hpp" 31 #include "memory/blockOffsetTable.inline.hpp" 32 #include "memory/freeList.hpp" 33 #include "memory/space.hpp" 34 35 // Classes in support of keeping track of promotions into a non-Contiguous 36 // space, in this case a CompactibleFreeListSpace. 37 38 // Forward declarations 39 class CompactibleFreeListSpace; 40 class BlkClosure; 41 class BlkClosureCareful; 42 class FreeChunk; 43 class UpwardsObjectClosure; 44 class ObjectClosureCareful; 45 class Klass; 46 47 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC { 48 public: 49 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0), 50 _allocation_size_limit(0) {} 51 void set(HeapWord* ptr, size_t word_size, size_t refill_size, 52 size_t allocation_size_limit) { 53 _ptr = ptr; 54 _word_size = word_size; 55 _refillSize = refill_size; 56 _allocation_size_limit = allocation_size_limit; 57 } 58 HeapWord* _ptr; 59 size_t _word_size; 60 size_t _refillSize; 61 size_t _allocation_size_limit; // Largest size that will be allocated 62 63 void print_on(outputStream* st) const; 64 }; 65 66 // Concrete subclass of CompactibleSpace that implements 67 // a free list space, such as used in the concurrent mark sweep 68 // generation. 69 70 class CompactibleFreeListSpace: public CompactibleSpace { 71 friend class VMStructs; 72 friend class ConcurrentMarkSweepGeneration; 73 friend class CMSCollector; 74 // Local alloc buffer for promotion into this space. 75 friend class CFLS_LAB; 76 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class 77 template <typename SpaceType> 78 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space); 79 template <typename SpaceType> 80 friend void CompactibleSpace::scan_and_compact(SpaceType* space); 81 template <typename SpaceType> 82 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 83 84 // "Size" of chunks of work (executed during parallel remark phases 85 // of CMS collection); this probably belongs in CMSCollector, although 86 // it's cached here because it's used in 87 // initialize_sequential_subtasks_for_rescan() which modifies 88 // par_seq_tasks which also lives in Space. XXX 89 const size_t _rescan_task_size; 90 const size_t _marking_task_size; 91 92 // Yet another sequential tasks done structure. This supports 93 // CMS GC, where we have threads dynamically 94 // claiming sub-tasks from a larger parallel task. 95 SequentialSubTasksDone _conc_par_seq_tasks; 96 97 BlockOffsetArrayNonContigSpace _bt; 98 99 CMSCollector* _collector; 100 ConcurrentMarkSweepGeneration* _gen; 101 102 // Data structures for free blocks (used during allocation/sweeping) 103 104 // Allocation is done linearly from two different blocks depending on 105 // whether the request is small or large, in an effort to reduce 106 // fragmentation. We assume that any locking for allocation is done 107 // by the containing generation. Thus, none of the methods in this 108 // space are re-entrant. 109 enum SomeConstants { 110 SmallForLinearAlloc = 16, // size < this then use _sLAB 111 SmallForDictionary = 257, // size < this then use _indexedFreeList 112 IndexSetSize = SmallForDictionary // keep this odd-sized 113 }; 114 static size_t IndexSetStart; 115 static size_t IndexSetStride; 116 117 private: 118 enum FitStrategyOptions { 119 FreeBlockStrategyNone = 0, 120 FreeBlockBestFitFirst 121 }; 122 123 PromotionInfo _promoInfo; 124 125 // Helps to impose a global total order on freelistLock ranks; 126 // assumes that CFLSpace's are allocated in global total order 127 static int _lockRank; 128 129 // A lock protecting the free lists and free blocks; 130 // mutable because of ubiquity of locking even for otherwise const methods 131 mutable Mutex _freelistLock; 132 // Locking verifier convenience function 133 void assert_locked() const PRODUCT_RETURN; 134 void assert_locked(const Mutex* lock) const PRODUCT_RETURN; 135 136 // Linear allocation blocks 137 LinearAllocBlock _smallLinearAllocBlock; 138 139 FreeBlockDictionary<FreeChunk>::DictionaryChoice _dictionaryChoice; 140 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks 141 142 // Indexed array for small size blocks 143 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize]; 144 145 // Allocation strategy 146 bool _fitStrategy; // Use best fit strategy 147 bool _adaptive_freelists; // Use adaptive freelists 148 149 // This is an address close to the largest free chunk in the heap. 150 // It is currently assumed to be at the end of the heap. Free 151 // chunks with addresses greater than nearLargestChunk are coalesced 152 // in an effort to maintain a large chunk at the end of the heap. 153 HeapWord* _nearLargestChunk; 154 155 // Used to keep track of limit of sweep for the space 156 HeapWord* _sweep_limit; 157 158 // Used to make the young collector update the mod union table 159 MemRegionClosure* _preconsumptionDirtyCardClosure; 160 161 // Support for compacting cms 162 HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 163 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top); 164 165 // Initialization helpers. 166 void initializeIndexedFreeListArray(); 167 168 // Extra stuff to manage promotion parallelism. 169 170 // A lock protecting the dictionary during par promotion allocation. 171 mutable Mutex _parDictionaryAllocLock; 172 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; } 173 174 // Locks protecting the exact lists during par promotion allocation. 175 Mutex* _indexedFreeListParLocks[IndexSetSize]; 176 177 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is 178 // required to be smaller than "IndexSetSize".) If successful, 179 // adds them to "fl", which is required to be an empty free list. 180 // If the count of "fl" is negative, it's absolute value indicates a 181 // number of free chunks that had been previously "borrowed" from global 182 // list of size "word_sz", and must now be decremented. 183 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 184 185 // Used by par_get_chunk_of_blocks() for the chunks from the 186 // indexed_free_lists. 187 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 188 189 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk 190 // evenly splittable into "n" "word_sz" chunks. Returns that 191 // evenly splittable chunk. May split a larger chunk to get the 192 // evenly splittable chunk. 193 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n); 194 195 // Used by par_get_chunk_of_blocks() for the chunks from the 196 // dictionary. 197 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 198 199 // Allocation helper functions 200 // Allocate using a strategy that takes from the indexed free lists 201 // first. This allocation strategy assumes a companion sweeping 202 // strategy that attempts to keep the needed number of chunks in each 203 // indexed free lists. 204 HeapWord* allocate_adaptive_freelists(size_t size); 205 // Allocate from the linear allocation buffers first. This allocation 206 // strategy assumes maximal coalescing can maintain chunks large enough 207 // to be used as linear allocation buffers. 208 HeapWord* allocate_non_adaptive_freelists(size_t size); 209 210 // Gets a chunk from the linear allocation block (LinAB). If there 211 // is not enough space in the LinAB, refills it. 212 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size); 213 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size); 214 // Get a chunk from the space remaining in the linear allocation block. Do 215 // not attempt to refill if the space is not available, return NULL. Do the 216 // repairs on the linear allocation block as appropriate. 217 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size); 218 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size); 219 220 // Helper function for getChunkFromIndexedFreeList. 221 // Replenish the indexed free list for this "size". Do not take from an 222 // underpopulated size. 223 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true); 224 225 // Get a chunk from the indexed free list. If the indexed free list 226 // does not have a free chunk, try to replenish the indexed free list 227 // then get the free chunk from the replenished indexed free list. 228 inline FreeChunk* getChunkFromIndexedFreeList(size_t size); 229 230 // The returned chunk may be larger than requested (or null). 231 FreeChunk* getChunkFromDictionary(size_t size); 232 // The returned chunk is the exact size requested (or null). 233 FreeChunk* getChunkFromDictionaryExact(size_t size); 234 235 // Find a chunk in the indexed free list that is the best 236 // fit for size "numWords". 237 FreeChunk* bestFitSmall(size_t numWords); 238 // For free list "fl" of chunks of size > numWords, 239 // remove a chunk, split off a chunk of size numWords 240 // and return it. The split off remainder is returned to 241 // the free lists. The old name for getFromListGreater 242 // was lookInListGreater. 243 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords); 244 // Get a chunk in the indexed free list or dictionary, 245 // by considering a larger chunk and splitting it. 246 FreeChunk* getChunkFromGreater(size_t numWords); 247 // Verify that the given chunk is in the indexed free lists. 248 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const; 249 // Remove the specified chunk from the indexed free lists. 250 void removeChunkFromIndexedFreeList(FreeChunk* fc); 251 // Remove the specified chunk from the dictionary. 252 void removeChunkFromDictionary(FreeChunk* fc); 253 // Split a free chunk into a smaller free chunk of size "new_size". 254 // Return the smaller free chunk and return the remainder to the 255 // free lists. 256 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size); 257 // Add a chunk to the free lists. 258 void addChunkToFreeLists(HeapWord* chunk, size_t size); 259 // Add a chunk to the free lists, preferring to suffix it 260 // to the last free chunk at end of space if possible, and 261 // updating the block census stats as well as block offset table. 262 // Take any locks as appropriate if we are multithreaded. 263 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size); 264 // Add a free chunk to the indexed free lists. 265 void returnChunkToFreeList(FreeChunk* chunk); 266 // Add a free chunk to the dictionary. 267 void returnChunkToDictionary(FreeChunk* chunk); 268 269 // Functions for maintaining the linear allocation buffers (LinAB). 270 // Repairing a linear allocation block refers to operations 271 // performed on the remainder of a LinAB after an allocation 272 // has been made from it. 273 void repairLinearAllocationBlocks(); 274 void repairLinearAllocBlock(LinearAllocBlock* blk); 275 void refillLinearAllocBlock(LinearAllocBlock* blk); 276 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk); 277 void refillLinearAllocBlocksIfNeeded(); 278 279 void verify_objects_initialized() const; 280 281 // Statistics reporting helper functions 282 void reportFreeListStatistics() const; 283 void reportIndexedFreeListStatistics() const; 284 size_t maxChunkSizeInIndexedFreeLists() const; 285 size_t numFreeBlocksInIndexedFreeLists() const; 286 // Accessor 287 HeapWord* unallocated_block() const { 288 if (BlockOffsetArrayUseUnallocatedBlock) { 289 HeapWord* ub = _bt.unallocated_block(); 290 assert(ub >= bottom() && 291 ub <= end(), "space invariant"); 292 return ub; 293 } else { 294 return end(); 295 } 296 } 297 void freed(HeapWord* start, size_t size) { 298 _bt.freed(start, size); 299 } 300 301 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 302 // See comments for CompactibleSpace for more information. 303 inline HeapWord* scan_limit() const { 304 return end(); 305 } 306 307 inline bool scanned_block_is_obj(const HeapWord* addr) const { 308 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call 309 } 310 311 inline size_t scanned_block_size(const HeapWord* addr) const { 312 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call 313 } 314 315 inline size_t adjust_obj_size(size_t size) const { 316 return adjustObjectSize(size); 317 } 318 319 inline size_t obj_size(const HeapWord* addr) const { 320 return adjustObjectSize(oop(addr)->size()); 321 } 322 323 protected: 324 // Reset the indexed free list to its initial empty condition. 325 void resetIndexedFreeListArray(); 326 // Reset to an initial state with a single free block described 327 // by the MemRegion parameter. 328 void reset(MemRegion mr); 329 // Return the total number of words in the indexed free lists. 330 size_t totalSizeInIndexedFreeLists() const; 331 332 public: 333 // Constructor 334 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr, 335 bool use_adaptive_freelists, 336 FreeBlockDictionary<FreeChunk>::DictionaryChoice); 337 // Accessors 338 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; } 339 FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; } 340 HeapWord* nearLargestChunk() const { return _nearLargestChunk; } 341 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; } 342 343 // Set CMS global values. 344 static void set_cms_values(); 345 346 // Return the free chunk at the end of the space. If no such 347 // chunk exists, return NULL. 348 FreeChunk* find_chunk_at_end(); 349 350 bool adaptive_freelists() const { return _adaptive_freelists; } 351 352 void set_collector(CMSCollector* collector) { _collector = collector; } 353 354 // Support for parallelization of rescan and marking. 355 const size_t rescan_task_size() const { return _rescan_task_size; } 356 const size_t marking_task_size() const { return _marking_task_size; } 357 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; } 358 void initialize_sequential_subtasks_for_rescan(int n_threads); 359 void initialize_sequential_subtasks_for_marking(int n_threads, 360 HeapWord* low = NULL); 361 362 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 363 return _preconsumptionDirtyCardClosure; 364 } 365 366 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) { 367 _preconsumptionDirtyCardClosure = cl; 368 } 369 370 // Space enquiries 371 size_t used() const; 372 size_t free() const; 373 size_t max_alloc_in_words() const; 374 // XXX: should have a less conservative used_region() than that of 375 // Space; we could consider keeping track of highest allocated 376 // address and correcting that at each sweep, as the sweeper 377 // goes through the entire allocated part of the generation. We 378 // could also use that information to keep the sweeper from 379 // sweeping more than is necessary. The allocator and sweeper will 380 // of course need to synchronize on this, since the sweeper will 381 // try to bump down the address and the allocator will try to bump it up. 382 // For now, however, we'll just use the default used_region() 383 // which overestimates the region by returning the entire 384 // committed region (this is safe, but inefficient). 385 386 // Returns a subregion of the space containing all the objects in 387 // the space. 388 MemRegion used_region() const { 389 return MemRegion(bottom(), 390 BlockOffsetArrayUseUnallocatedBlock ? 391 unallocated_block() : end()); 392 } 393 394 virtual bool is_free_block(const HeapWord* p) const; 395 396 // Resizing support 397 void set_end(HeapWord* value); // override 398 399 // Mutual exclusion support 400 Mutex* freelistLock() const { return &_freelistLock; } 401 402 // Iteration support 403 void oop_iterate(ExtendedOopClosure* cl); 404 405 void object_iterate(ObjectClosure* blk); 406 // Apply the closure to each object in the space whose references 407 // point to objects in the heap. The usage of CompactibleFreeListSpace 408 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows 409 // objects in the space with references to objects that are no longer 410 // valid. For example, an object may reference another object 411 // that has already been sweep up (collected). This method uses 412 // obj_is_alive() to determine whether it is safe to iterate of 413 // an object. 414 void safe_object_iterate(ObjectClosure* blk); 415 416 // Iterate over all objects that intersect with mr, calling "cl->do_object" 417 // on each. There is an exception to this: if this closure has already 418 // been invoked on an object, it may skip such objects in some cases. This is 419 // Most likely to happen in an "upwards" (ascending address) iteration of 420 // MemRegions. 421 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 422 423 // Requires that "mr" be entirely within the space. 424 // Apply "cl->do_object" to all objects that intersect with "mr". 425 // If the iteration encounters an unparseable portion of the region, 426 // terminate the iteration and return the address of the start of the 427 // subregion that isn't done. Return of "NULL" indicates that the 428 // iteration completed. 429 HeapWord* object_iterate_careful_m(MemRegion mr, 430 ObjectClosureCareful* cl); 431 432 // Override: provides a DCTO_CL specific to this kind of space. 433 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 434 CardTableModRefBS::PrecisionStyle precision, 435 HeapWord* boundary); 436 437 void blk_iterate(BlkClosure* cl); 438 void blk_iterate_careful(BlkClosureCareful* cl); 439 HeapWord* block_start_const(const void* p) const; 440 HeapWord* block_start_careful(const void* p) const; 441 size_t block_size(const HeapWord* p) const; 442 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const; 443 bool block_is_obj(const HeapWord* p) const; 444 bool obj_is_alive(const HeapWord* p) const; 445 size_t block_size_nopar(const HeapWord* p) const; 446 bool block_is_obj_nopar(const HeapWord* p) const; 447 448 // Iteration support for promotion 449 void save_marks(); 450 bool no_allocs_since_save_marks(); 451 452 // Iteration support for sweeping 453 void save_sweep_limit() { 454 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ? 455 unallocated_block() : end(); 456 if (CMSTraceSweeper) { 457 gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT 458 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<", 459 p2i(_sweep_limit), p2i(bottom()), p2i(end())); 460 } 461 } 462 NOT_PRODUCT( 463 void clear_sweep_limit() { _sweep_limit = NULL; } 464 ) 465 HeapWord* sweep_limit() { return _sweep_limit; } 466 467 // Apply "blk->do_oop" to the addresses of all reference fields in objects 468 // promoted into this generation since the most recent save_marks() call. 469 // Fields in objects allocated by applications of the closure 470 // *are* included in the iteration. Thus, when the iteration completes 471 // there should be no further such objects remaining. 472 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 473 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 474 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL) 475 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL 476 477 // Allocation support 478 HeapWord* allocate(size_t size); 479 HeapWord* par_allocate(size_t size); 480 481 oop promote(oop obj, size_t obj_size); 482 void gc_prologue(); 483 void gc_epilogue(); 484 485 // This call is used by a containing CMS generation / collector 486 // to inform the CFLS space that a sweep has been completed 487 // and that the space can do any related house-keeping functions. 488 void sweep_completed(); 489 490 // For an object in this space, the mark-word's two 491 // LSB's having the value [11] indicates that it has been 492 // promoted since the most recent call to save_marks() on 493 // this generation and has not subsequently been iterated 494 // over (using oop_since_save_marks_iterate() above). 495 // This property holds only for single-threaded collections, 496 // and is typically used for Cheney scans; for MT scavenges, 497 // the property holds for all objects promoted during that 498 // scavenge for the duration of the scavenge and is used 499 // by card-scanning to avoid scanning objects (being) promoted 500 // during that scavenge. 501 bool obj_allocated_since_save_marks(const oop obj) const { 502 assert(is_in_reserved(obj), "Wrong space?"); 503 return ((PromotedObject*)obj)->hasPromotedMark(); 504 } 505 506 // A worst-case estimate of the space required (in HeapWords) to expand the 507 // heap when promoting an obj of size obj_size. 508 size_t expansionSpaceRequired(size_t obj_size) const; 509 510 FreeChunk* allocateScratch(size_t size); 511 512 // Returns true if either the small or large linear allocation buffer is empty. 513 bool linearAllocationWouldFail() const; 514 515 // Adjust the chunk for the minimum size. This version is called in 516 // most cases in CompactibleFreeListSpace methods. 517 inline static size_t adjustObjectSize(size_t size) { 518 return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize)); 519 } 520 // This is a virtual version of adjustObjectSize() that is called 521 // only occasionally when the compaction space changes and the type 522 // of the new compaction space is is only known to be CompactibleSpace. 523 size_t adjust_object_size_v(size_t size) const { 524 return adjustObjectSize(size); 525 } 526 // Minimum size of a free block. 527 virtual size_t minimum_free_block_size() const { return MinChunkSize; } 528 void removeFreeChunkFromFreeLists(FreeChunk* chunk); 529 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size, 530 bool coalesced); 531 532 // Support for decisions regarding concurrent collection policy. 533 bool should_concurrent_collect() const; 534 535 // Support for compaction. 536 void prepare_for_compaction(CompactPoint* cp); 537 void adjust_pointers(); 538 void compact(); 539 // Reset the space to reflect the fact that a compaction of the 540 // space has been done. 541 virtual void reset_after_compaction(); 542 543 // Debugging support. 544 void print() const; 545 void print_on(outputStream* st) const; 546 void prepare_for_verify(); 547 void verify() const; 548 void verifyFreeLists() const PRODUCT_RETURN; 549 void verifyIndexedFreeLists() const; 550 void verifyIndexedFreeList(size_t size) const; 551 // Verify that the given chunk is in the free lists: 552 // i.e. either the binary tree dictionary, the indexed free lists 553 // or the linear allocation block. 554 bool verify_chunk_in_free_list(FreeChunk* fc) const; 555 // Verify that the given chunk is the linear allocation block. 556 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const; 557 // Do some basic checks on the the free lists. 558 void check_free_list_consistency() const PRODUCT_RETURN; 559 560 // Printing support 561 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st); 562 void print_indexed_free_lists(outputStream* st) const; 563 void print_dictionary_free_lists(outputStream* st) const; 564 void print_promo_info_blocks(outputStream* st) const; 565 566 NOT_PRODUCT ( 567 void initializeIndexedFreeListArrayReturnedBytes(); 568 size_t sumIndexedFreeListArrayReturnedBytes(); 569 // Return the total number of chunks in the indexed free lists. 570 size_t totalCountInIndexedFreeLists() const; 571 // Return the total number of chunks in the space. 572 size_t totalCount(); 573 ) 574 575 // The census consists of counts of the quantities such as 576 // the current count of the free chunks, number of chunks 577 // created as a result of the split of a larger chunk or 578 // coalescing of smaller chucks, etc. The counts in the 579 // census is used to make decisions on splitting and 580 // coalescing of chunks during the sweep of garbage. 581 582 // Print the statistics for the free lists. 583 void printFLCensus(size_t sweep_count) const; 584 585 // Statistics functions 586 // Initialize census for lists before the sweep. 587 void beginSweepFLCensus(float inter_sweep_current, 588 float inter_sweep_estimate, 589 float intra_sweep_estimate); 590 // Set the surplus for each of the free lists. 591 void setFLSurplus(); 592 // Set the hint for each of the free lists. 593 void setFLHints(); 594 // Clear the census for each of the free lists. 595 void clearFLCensus(); 596 // Perform functions for the census after the end of the sweep. 597 void endSweepFLCensus(size_t sweep_count); 598 // Return true if the count of free chunks is greater 599 // than the desired number of free chunks. 600 bool coalOverPopulated(size_t size); 601 602 // Record (for each size): 603 // 604 // split-births = #chunks added due to splits in (prev-sweep-end, 605 // this-sweep-start) 606 // split-deaths = #chunks removed for splits in (prev-sweep-end, 607 // this-sweep-start) 608 // num-curr = #chunks at start of this sweep 609 // num-prev = #chunks at end of previous sweep 610 // 611 // The above are quantities that are measured. Now define: 612 // 613 // num-desired := num-prev + split-births - split-deaths - num-curr 614 // 615 // Roughly, num-prev + split-births is the supply, 616 // split-deaths is demand due to other sizes 617 // and num-curr is what we have left. 618 // 619 // Thus, num-desired is roughly speaking the "legitimate demand" 620 // for blocks of this size and what we are striving to reach at the 621 // end of the current sweep. 622 // 623 // For a given list, let num-len be its current population. 624 // Define, for a free list of a given size: 625 // 626 // coal-overpopulated := num-len >= num-desired * coal-surplus 627 // (coal-surplus is set to 1.05, i.e. we allow a little slop when 628 // coalescing -- we do not coalesce unless we think that the current 629 // supply has exceeded the estimated demand by more than 5%). 630 // 631 // For the set of sizes in the binary tree, which is neither dense nor 632 // closed, it may be the case that for a particular size we have never 633 // had, or do not now have, or did not have at the previous sweep, 634 // chunks of that size. We need to extend the definition of 635 // coal-overpopulated to such sizes as well: 636 // 637 // For a chunk in/not in the binary tree, extend coal-overpopulated 638 // defined above to include all sizes as follows: 639 // 640 // . a size that is non-existent is coal-overpopulated 641 // . a size that has a num-desired <= 0 as defined above is 642 // coal-overpopulated. 643 // 644 // Also define, for a chunk heap-offset C and mountain heap-offset M: 645 // 646 // close-to-mountain := C >= 0.99 * M 647 // 648 // Now, the coalescing strategy is: 649 // 650 // Coalesce left-hand chunk with right-hand chunk if and 651 // only if: 652 // 653 // EITHER 654 // . left-hand chunk is of a size that is coal-overpopulated 655 // OR 656 // . right-hand chunk is close-to-mountain 657 void smallCoalBirth(size_t size); 658 void smallCoalDeath(size_t size); 659 void coalBirth(size_t size); 660 void coalDeath(size_t size); 661 void smallSplitBirth(size_t size); 662 void smallSplitDeath(size_t size); 663 void split_birth(size_t size); 664 void splitDeath(size_t size); 665 void split(size_t from, size_t to1); 666 667 double flsFrag() const; 668 }; 669 670 // A parallel-GC-thread-local allocation buffer for allocation into a 671 // CompactibleFreeListSpace. 672 class CFLS_LAB : public CHeapObj<mtGC> { 673 // The space that this buffer allocates into. 674 CompactibleFreeListSpace* _cfls; 675 676 // Our local free lists. 677 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize]; 678 679 // Initialized from a command-line arg. 680 681 // Allocation statistics in support of dynamic adjustment of 682 // #blocks to claim per get_from_global_pool() call below. 683 static AdaptiveWeightedAverage 684 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize]; 685 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize]; 686 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize]; 687 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize]; 688 689 // Internal work method 690 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl); 691 692 public: 693 static const int _default_dynamic_old_plab_size = 16; 694 static const int _default_static_old_plab_size = 50; 695 696 CFLS_LAB(CompactibleFreeListSpace* cfls); 697 698 // Allocate and return a block of the given size, or else return NULL. 699 HeapWord* alloc(size_t word_sz); 700 701 // Return any unused portions of the buffer to the global pool. 702 void retire(int tid); 703 704 // Dynamic OldPLABSize sizing 705 static void compute_desired_plab_size(); 706 // When the settings are modified from default static initialization 707 static void modify_initialization(size_t n, unsigned wt); 708 }; 709 710 size_t PromotionInfo::refillSize() const { 711 const size_t CMSSpoolBlockSize = 256; 712 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop) 713 * CMSSpoolBlockSize); 714 return CompactibleFreeListSpace::adjustObjectSize(sz); 715 } 716 717 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP