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