1 /* 2 * Copyright (c) 2001, 2018, 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_CMS_COMPACTIBLEFREELISTSPACE_HPP 26 #define SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP 27 28 #include "gc/cms/adaptiveFreeList.hpp" 29 #include "gc/cms/promotionInfo.hpp" 30 #include "gc/shared/blockOffsetTable.hpp" 31 #include "gc/shared/cardTable.hpp" 32 #include "gc/shared/space.hpp" 33 #include "logging/log.hpp" 34 #include "memory/binaryTreeDictionary.hpp" 35 #include "memory/freeList.hpp" 36 37 // Classes in support of keeping track of promotions into a non-Contiguous 38 // space, in this case a CompactibleFreeListSpace. 39 40 // Forward declarations 41 class CMSCollector; 42 class CompactibleFreeListSpace; 43 class ConcurrentMarkSweepGeneration; 44 class BlkClosure; 45 class BlkClosureCareful; 46 class FreeChunk; 47 class UpwardsObjectClosure; 48 class ObjectClosureCareful; 49 class Klass; 50 51 class LinearAllocBlock { 52 public: 53 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0), 54 _allocation_size_limit(0) {} 55 void set(HeapWord* ptr, size_t word_size, size_t refill_size, 56 size_t allocation_size_limit) { 57 _ptr = ptr; 58 _word_size = word_size; 59 _refillSize = refill_size; 60 _allocation_size_limit = allocation_size_limit; 61 } 62 HeapWord* _ptr; 63 size_t _word_size; 64 size_t _refillSize; 65 size_t _allocation_size_limit; // Largest size that will be allocated 66 67 void print_on(outputStream* st) const; 68 }; 69 70 // Concrete subclass of CompactibleSpace that implements 71 // a free list space, such as used in the concurrent mark sweep 72 // generation. 73 74 class CompactibleFreeListSpace: public CompactibleSpace { 75 friend class VMStructs; 76 friend class ConcurrentMarkSweepGeneration; 77 friend class CMSCollector; 78 // Local alloc buffer for promotion into this space. 79 friend class CompactibleFreeListSpaceLAB; 80 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class 81 template <typename SpaceType> 82 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space); 83 template <typename SpaceType> 84 friend void CompactibleSpace::scan_and_compact(SpaceType* space); 85 template <typename SpaceType> 86 friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space); 87 template <typename SpaceType> 88 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 89 90 // "Size" of chunks of work (executed during parallel remark phases 91 // of CMS collection); this probably belongs in CMSCollector, although 92 // it's cached here because it's used in 93 // initialize_sequential_subtasks_for_rescan() which modifies 94 // par_seq_tasks which also lives in Space. XXX 95 const size_t _rescan_task_size; 96 const size_t _marking_task_size; 97 98 // Yet another sequential tasks done structure. This supports 99 // CMS GC, where we have threads dynamically 100 // claiming sub-tasks from a larger parallel task. 101 SequentialSubTasksDone _conc_par_seq_tasks; 102 103 BlockOffsetArrayNonContigSpace _bt; 104 105 CMSCollector* _collector; 106 ConcurrentMarkSweepGeneration* _old_gen; 107 108 // Data structures for free blocks (used during allocation/sweeping) 109 110 // Allocation is done linearly from two different blocks depending on 111 // whether the request is small or large, in an effort to reduce 112 // fragmentation. We assume that any locking for allocation is done 113 // by the containing generation. Thus, none of the methods in this 114 // space are re-entrant. 115 enum SomeConstants { 116 SmallForLinearAlloc = 16, // size < this then use _sLAB 117 SmallForDictionary = 257, // size < this then use _indexedFreeList 118 IndexSetSize = SmallForDictionary // keep this odd-sized 119 }; 120 static size_t IndexSetStart; 121 static size_t IndexSetStride; 122 static size_t _min_chunk_size_in_bytes; 123 124 private: 125 enum FitStrategyOptions { 126 FreeBlockStrategyNone = 0, 127 FreeBlockBestFitFirst 128 }; 129 130 PromotionInfo _promoInfo; 131 132 // Helps to impose a global total order on freelistLock ranks; 133 // assumes that CFLSpace's are allocated in global total order 134 static int _lockRank; 135 136 // A lock protecting the free lists and free blocks; 137 // mutable because of ubiquity of locking even for otherwise const methods 138 mutable Mutex _freelistLock; 139 140 // Locking verifier convenience function 141 void assert_locked() const PRODUCT_RETURN; 142 void assert_locked(const Mutex* lock) const PRODUCT_RETURN; 143 144 // Linear allocation blocks 145 LinearAllocBlock _smallLinearAllocBlock; 146 147 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks 148 149 // Indexed array for small size blocks 150 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize]; 151 152 // Allocation strategy 153 bool _fitStrategy; // Use best fit strategy 154 155 // This is an address close to the largest free chunk in the heap. 156 // It is currently assumed to be at the end of the heap. Free 157 // chunks with addresses greater than nearLargestChunk are coalesced 158 // in an effort to maintain a large chunk at the end of the heap. 159 HeapWord* _nearLargestChunk; 160 161 // Used to keep track of limit of sweep for the space 162 HeapWord* _sweep_limit; 163 164 // Used to make the young collector update the mod union table 165 MemRegionClosure* _preconsumptionDirtyCardClosure; 166 167 // Support for compacting cms 168 HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 169 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top); 170 171 // Initialization helpers. 172 void initializeIndexedFreeListArray(); 173 174 // Extra stuff to manage promotion parallelism. 175 176 // A lock protecting the dictionary during par promotion allocation. 177 mutable Mutex _parDictionaryAllocLock; 178 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; } 179 180 // Locks protecting the exact lists during par promotion allocation. 181 Mutex* _indexedFreeListParLocks[IndexSetSize]; 182 183 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is 184 // required to be smaller than "IndexSetSize".) If successful, 185 // adds them to "fl", which is required to be an empty free list. 186 // If the count of "fl" is negative, it's absolute value indicates a 187 // number of free chunks that had been previously "borrowed" from global 188 // list of size "word_sz", and must now be decremented. 189 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 190 191 // Used by par_get_chunk_of_blocks() for the chunks from the 192 // indexed_free_lists. 193 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 194 195 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk 196 // evenly splittable into "n" "word_sz" chunks. Returns that 197 // evenly splittable chunk. May split a larger chunk to get the 198 // evenly splittable chunk. 199 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n); 200 201 // Used by par_get_chunk_of_blocks() for the chunks from the 202 // dictionary. 203 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 204 205 // Allocation helper functions 206 // Allocate using a strategy that takes from the indexed free lists 207 // first. This allocation strategy assumes a companion sweeping 208 // strategy that attempts to keep the needed number of chunks in each 209 // indexed free lists. 210 HeapWord* allocate_adaptive_freelists(size_t size); 211 212 // Gets a chunk from the linear allocation block (LinAB). If there 213 // is not enough space in the LinAB, refills it. 214 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size); 215 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size); 216 // Get a chunk from the space remaining in the linear allocation block. Do 217 // not attempt to refill if the space is not available, return NULL. Do the 218 // repairs on the linear allocation block as appropriate. 219 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size); 220 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size); 221 222 // Helper function for getChunkFromIndexedFreeList. 223 // Replenish the indexed free list for this "size". Do not take from an 224 // underpopulated size. 225 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true); 226 227 // Get a chunk from the indexed free list. If the indexed free list 228 // does not have a free chunk, try to replenish the indexed free list 229 // then get the free chunk from the replenished indexed free list. 230 inline FreeChunk* getChunkFromIndexedFreeList(size_t size); 231 232 // The returned chunk may be larger than requested (or null). 233 FreeChunk* getChunkFromDictionary(size_t size); 234 // The returned chunk is the exact size requested (or null). 235 FreeChunk* getChunkFromDictionaryExact(size_t size); 236 237 // Find a chunk in the indexed free list that is the best 238 // fit for size "numWords". 239 FreeChunk* bestFitSmall(size_t numWords); 240 // For free list "fl" of chunks of size > numWords, 241 // remove a chunk, split off a chunk of size numWords 242 // and return it. The split off remainder is returned to 243 // the free lists. The old name for getFromListGreater 244 // was lookInListGreater. 245 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords); 246 // Get a chunk in the indexed free list or dictionary, 247 // by considering a larger chunk and splitting it. 248 FreeChunk* getChunkFromGreater(size_t numWords); 249 // Verify that the given chunk is in the indexed free lists. 250 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const; 251 // Remove the specified chunk from the indexed free lists. 252 void removeChunkFromIndexedFreeList(FreeChunk* fc); 253 // Remove the specified chunk from the dictionary. 254 void removeChunkFromDictionary(FreeChunk* fc); 255 // Split a free chunk into a smaller free chunk of size "new_size". 256 // Return the smaller free chunk and return the remainder to the 257 // free lists. 258 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size); 259 // Add a chunk to the free lists. 260 void addChunkToFreeLists(HeapWord* chunk, size_t size); 261 // Add a chunk to the free lists, preferring to suffix it 262 // to the last free chunk at end of space if possible, and 263 // updating the block census stats as well as block offset table. 264 // Take any locks as appropriate if we are multithreaded. 265 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size); 266 // Add a free chunk to the indexed free lists. 267 void returnChunkToFreeList(FreeChunk* chunk); 268 // Add a free chunk to the dictionary. 269 void returnChunkToDictionary(FreeChunk* chunk); 270 271 // Functions for maintaining the linear allocation buffers (LinAB). 272 // Repairing a linear allocation block refers to operations 273 // performed on the remainder of a LinAB after an allocation 274 // has been made from it. 275 void repairLinearAllocationBlocks(); 276 void repairLinearAllocBlock(LinearAllocBlock* blk); 277 void refillLinearAllocBlock(LinearAllocBlock* blk); 278 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk); 279 void refillLinearAllocBlocksIfNeeded(); 280 281 void verify_objects_initialized() const; 282 283 // Statistics reporting helper functions 284 void reportFreeListStatistics(const char* title) const; 285 void reportIndexedFreeListStatistics(outputStream* st) const; 286 size_t maxChunkSizeInIndexedFreeLists() const; 287 size_t numFreeBlocksInIndexedFreeLists() const; 288 // Accessor 289 HeapWord* unallocated_block() const { 290 if (BlockOffsetArrayUseUnallocatedBlock) { 291 HeapWord* ub = _bt.unallocated_block(); 292 assert(ub >= bottom() && 293 ub <= end(), "space invariant"); 294 return ub; 295 } else { 296 return end(); 297 } 298 } 299 void freed(HeapWord* start, size_t size) { 300 _bt.freed(start, size); 301 } 302 303 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 304 // See comments for CompactibleSpace for more information. 305 inline HeapWord* scan_limit() const { 306 return end(); 307 } 308 309 inline bool scanned_block_is_obj(const HeapWord* addr) const { 310 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call 311 } 312 313 inline size_t scanned_block_size(const HeapWord* addr) const { 314 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call 315 } 316 317 inline size_t adjust_obj_size(size_t size) const { 318 return adjustObjectSize(size); 319 } 320 321 inline size_t obj_size(const HeapWord* addr) const; 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 // Accessors 336 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; } 337 AFLBinaryTreeDictionary* dictionary() const { return _dictionary; } 338 HeapWord* nearLargestChunk() const { return _nearLargestChunk; } 339 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; } 340 341 // Set CMS global values. 342 static void set_cms_values(); 343 344 // Return the free chunk at the end of the space. If no such 345 // chunk exists, return NULL. 346 FreeChunk* find_chunk_at_end(); 347 348 void set_collector(CMSCollector* collector) { _collector = collector; } 349 350 // Support for parallelization of rescan and marking. 351 const size_t rescan_task_size() const { return _rescan_task_size; } 352 const size_t marking_task_size() const { return _marking_task_size; } 353 // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple. 354 const size_t max_flag_size_for_task_size() const; 355 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; } 356 void initialize_sequential_subtasks_for_rescan(int n_threads); 357 void initialize_sequential_subtasks_for_marking(int n_threads, 358 HeapWord* low = NULL); 359 360 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 361 return _preconsumptionDirtyCardClosure; 362 } 363 364 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) { 365 _preconsumptionDirtyCardClosure = cl; 366 } 367 368 // Space enquiries 369 size_t used() const; 370 size_t free() const; 371 size_t max_alloc_in_words() const; 372 // XXX: should have a less conservative used_region() than that of 373 // Space; we could consider keeping track of highest allocated 374 // address and correcting that at each sweep, as the sweeper 375 // goes through the entire allocated part of the generation. We 376 // could also use that information to keep the sweeper from 377 // sweeping more than is necessary. The allocator and sweeper will 378 // of course need to synchronize on this, since the sweeper will 379 // try to bump down the address and the allocator will try to bump it up. 380 // For now, however, we'll just use the default used_region() 381 // which overestimates the region by returning the entire 382 // committed region (this is safe, but inefficient). 383 384 // Returns a subregion of the space containing all the objects in 385 // the space. 386 MemRegion used_region() const { 387 return MemRegion(bottom(), 388 BlockOffsetArrayUseUnallocatedBlock ? 389 unallocated_block() : end()); 390 } 391 392 virtual bool is_free_block(const HeapWord* p) const; 393 394 // Resizing support 395 void set_end(HeapWord* value); // override 396 397 // Never mangle CompactibleFreeListSpace 398 void mangle_unused_area() {} 399 void mangle_unused_area_complete() {} 400 401 // Mutual exclusion support 402 Mutex* freelistLock() const { return &_freelistLock; } 403 404 // Iteration support 405 void oop_iterate(ExtendedOopClosure* cl); 406 407 void object_iterate(ObjectClosure* blk); 408 // Apply the closure to each object in the space whose references 409 // point to objects in the heap. The usage of CompactibleFreeListSpace 410 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows 411 // objects in the space with references to objects that are no longer 412 // valid. For example, an object may reference another object 413 // that has already been sweep up (collected). This method uses 414 // obj_is_alive() to determine whether it is safe to iterate of 415 // an object. 416 void safe_object_iterate(ObjectClosure* blk); 417 418 // Iterate over all objects that intersect with mr, calling "cl->do_object" 419 // on each. There is an exception to this: if this closure has already 420 // been invoked on an object, it may skip such objects in some cases. This is 421 // Most likely to happen in an "upwards" (ascending address) iteration of 422 // MemRegions. 423 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 424 425 // Requires that "mr" be entirely within the space. 426 // Apply "cl->do_object" to all objects that intersect with "mr". 427 // If the iteration encounters an unparseable portion of the region, 428 // terminate the iteration and return the address of the start of the 429 // subregion that isn't done. Return of "NULL" indicates that the 430 // iteration completed. 431 HeapWord* object_iterate_careful_m(MemRegion mr, 432 ObjectClosureCareful* cl); 433 434 // Override: provides a DCTO_CL specific to this kind of space. 435 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 436 CardTable::PrecisionStyle precision, 437 HeapWord* boundary, 438 bool parallel); 439 440 void blk_iterate(BlkClosure* cl); 441 void blk_iterate_careful(BlkClosureCareful* cl); 442 HeapWord* block_start_const(const void* p) const; 443 HeapWord* block_start_careful(const void* p) const; 444 size_t block_size(const HeapWord* p) const; 445 size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const; 446 bool block_is_obj(const HeapWord* p) const; 447 bool obj_is_alive(const HeapWord* p) const; 448 size_t block_size_nopar(const HeapWord* p) const; 449 bool block_is_obj_nopar(const HeapWord* p) const; 450 451 // Iteration support for promotion 452 void save_marks(); 453 bool no_allocs_since_save_marks(); 454 455 // Iteration support for sweeping 456 void save_sweep_limit() { 457 _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ? 458 unallocated_block() : end(); 459 log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT 460 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<", 461 p2i(_sweep_limit), p2i(bottom()), p2i(end())); 462 } 463 NOT_PRODUCT( 464 void clear_sweep_limit() { _sweep_limit = NULL; } 465 ) 466 HeapWord* sweep_limit() { return _sweep_limit; } 467 468 // Apply "blk->do_oop" to the addresses of all reference fields in objects 469 // promoted into this generation since the most recent save_marks() call. 470 // Fields in objects allocated by applications of the closure 471 // *are* included in the iteration. Thus, when the iteration completes 472 // there should be no further such objects remaining. 473 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 474 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 475 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL) 476 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL 477 478 // Allocation support 479 HeapWord* allocate(size_t size); 480 HeapWord* par_allocate(size_t size); 481 482 oop promote(oop obj, size_t obj_size); 483 void gc_prologue(); 484 void gc_epilogue(); 485 486 // This call is used by a containing CMS generation / collector 487 // to inform the CFLS space that a sweep has been completed 488 // and that the space can do any related house-keeping functions. 489 void sweep_completed(); 490 491 // For an object in this space, the mark-word's two 492 // LSB's having the value [11] indicates that it has been 493 // promoted since the most recent call to save_marks() on 494 // this generation and has not subsequently been iterated 495 // over (using oop_since_save_marks_iterate() above). 496 // This property holds only for single-threaded collections, 497 // and is typically used for Cheney scans; for MT scavenges, 498 // the property holds for all objects promoted during that 499 // scavenge for the duration of the scavenge and is used 500 // by card-scanning to avoid scanning objects (being) promoted 501 // during that scavenge. 502 bool obj_allocated_since_save_marks(const oop obj) const { 503 assert(is_in_reserved(obj), "Wrong space?"); 504 return ((PromotedObject*)obj)->hasPromotedMark(); 505 } 506 507 // A worst-case estimate of the space required (in HeapWords) to expand the 508 // heap when promoting an obj of size obj_size. 509 size_t expansionSpaceRequired(size_t obj_size) const; 510 511 FreeChunk* allocateScratch(size_t size); 512 513 // Returns true if either the small or large linear allocation buffer is empty. 514 bool linearAllocationWouldFail() const; 515 516 // Adjust the chunk for the minimum size. This version is called in 517 // most cases in CompactibleFreeListSpace methods. 518 inline static size_t adjustObjectSize(size_t size) { 519 return align_object_size(MAX2(size, (size_t)MinChunkSize)); 520 } 521 // This is a virtual version of adjustObjectSize() that is called 522 // only occasionally when the compaction space changes and the type 523 // of the new compaction space is is only known to be CompactibleSpace. 524 size_t adjust_object_size_v(size_t size) const { 525 return adjustObjectSize(size); 526 } 527 // Minimum size of a free block. 528 virtual size_t minimum_free_block_size() const { return MinChunkSize; } 529 void removeFreeChunkFromFreeLists(FreeChunk* chunk); 530 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size, 531 bool coalesced); 532 533 // Support for compaction. 534 void prepare_for_compaction(CompactPoint* cp); 535 void adjust_pointers(); 536 void compact(); 537 // Reset the space to reflect the fact that a compaction of the 538 // space has been done. 539 virtual void reset_after_compaction(); 540 541 // Debugging support. 542 void print() const; 543 void print_on(outputStream* st) const; 544 void prepare_for_verify(); 545 void verify() const; 546 void verifyFreeLists() const PRODUCT_RETURN; 547 void verifyIndexedFreeLists() const; 548 void verifyIndexedFreeList(size_t size) const; 549 // Verify that the given chunk is in the free lists: 550 // i.e. either the binary tree dictionary, the indexed free lists 551 // or the linear allocation block. 552 bool verify_chunk_in_free_list(FreeChunk* fc) const; 553 // Verify that the given chunk is the linear allocation block. 554 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const; 555 // Do some basic checks on the the free lists. 556 void check_free_list_consistency() const PRODUCT_RETURN; 557 558 // Printing support 559 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st); 560 void print_indexed_free_lists(outputStream* st) const; 561 void print_dictionary_free_lists(outputStream* st) const; 562 void print_promo_info_blocks(outputStream* st) const; 563 564 NOT_PRODUCT ( 565 void initializeIndexedFreeListArrayReturnedBytes(); 566 size_t sumIndexedFreeListArrayReturnedBytes(); 567 // Return the total number of chunks in the indexed free lists. 568 size_t totalCountInIndexedFreeLists() const; 569 // Return the total number of chunks in the space. 570 size_t totalCount(); 571 ) 572 573 // The census consists of counts of the quantities such as 574 // the current count of the free chunks, number of chunks 575 // created as a result of the split of a larger chunk or 576 // coalescing of smaller chucks, etc. The counts in the 577 // census is used to make decisions on splitting and 578 // coalescing of chunks during the sweep of garbage. 579 580 // Print the statistics for the free lists. 581 void printFLCensus(size_t sweep_count) const; 582 583 // Statistics functions 584 // Initialize census for lists before the sweep. 585 void beginSweepFLCensus(float inter_sweep_current, 586 float inter_sweep_estimate, 587 float intra_sweep_estimate); 588 // Set the surplus for each of the free lists. 589 void setFLSurplus(); 590 // Set the hint for each of the free lists. 591 void setFLHints(); 592 // Clear the census for each of the free lists. 593 void clearFLCensus(); 594 // Perform functions for the census after the end of the sweep. 595 void endSweepFLCensus(size_t sweep_count); 596 // Return true if the count of free chunks is greater 597 // than the desired number of free chunks. 598 bool coalOverPopulated(size_t size); 599 600 // Record (for each size): 601 // 602 // split-births = #chunks added due to splits in (prev-sweep-end, 603 // this-sweep-start) 604 // split-deaths = #chunks removed for splits in (prev-sweep-end, 605 // this-sweep-start) 606 // num-curr = #chunks at start of this sweep 607 // num-prev = #chunks at end of previous sweep 608 // 609 // The above are quantities that are measured. Now define: 610 // 611 // num-desired := num-prev + split-births - split-deaths - num-curr 612 // 613 // Roughly, num-prev + split-births is the supply, 614 // split-deaths is demand due to other sizes 615 // and num-curr is what we have left. 616 // 617 // Thus, num-desired is roughly speaking the "legitimate demand" 618 // for blocks of this size and what we are striving to reach at the 619 // end of the current sweep. 620 // 621 // For a given list, let num-len be its current population. 622 // Define, for a free list of a given size: 623 // 624 // coal-overpopulated := num-len >= num-desired * coal-surplus 625 // (coal-surplus is set to 1.05, i.e. we allow a little slop when 626 // coalescing -- we do not coalesce unless we think that the current 627 // supply has exceeded the estimated demand by more than 5%). 628 // 629 // For the set of sizes in the binary tree, which is neither dense nor 630 // closed, it may be the case that for a particular size we have never 631 // had, or do not now have, or did not have at the previous sweep, 632 // chunks of that size. We need to extend the definition of 633 // coal-overpopulated to such sizes as well: 634 // 635 // For a chunk in/not in the binary tree, extend coal-overpopulated 636 // defined above to include all sizes as follows: 637 // 638 // . a size that is non-existent is coal-overpopulated 639 // . a size that has a num-desired <= 0 as defined above is 640 // coal-overpopulated. 641 // 642 // Also define, for a chunk heap-offset C and mountain heap-offset M: 643 // 644 // close-to-mountain := C >= 0.99 * M 645 // 646 // Now, the coalescing strategy is: 647 // 648 // Coalesce left-hand chunk with right-hand chunk if and 649 // only if: 650 // 651 // EITHER 652 // . left-hand chunk is of a size that is coal-overpopulated 653 // OR 654 // . right-hand chunk is close-to-mountain 655 void smallCoalBirth(size_t size); 656 void smallCoalDeath(size_t size); 657 void coalBirth(size_t size); 658 void coalDeath(size_t size); 659 void smallSplitBirth(size_t size); 660 void smallSplitDeath(size_t size); 661 void split_birth(size_t size); 662 void splitDeath(size_t size); 663 void split(size_t from, size_t to1); 664 665 double flsFrag() const; 666 }; 667 668 // A parallel-GC-thread-local allocation buffer for allocation into a 669 // CompactibleFreeListSpace. 670 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> { 671 // The space that this buffer allocates into. 672 CompactibleFreeListSpace* _cfls; 673 674 // Our local free lists. 675 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize]; 676 677 // Initialized from a command-line arg. 678 679 // Allocation statistics in support of dynamic adjustment of 680 // #blocks to claim per get_from_global_pool() call below. 681 static AdaptiveWeightedAverage 682 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize]; 683 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize]; 684 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize]; 685 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize]; 686 687 // Internal work method 688 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl); 689 690 public: 691 static const int _default_dynamic_old_plab_size = 16; 692 static const int _default_static_old_plab_size = 50; 693 694 CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls); 695 696 // Allocate and return a block of the given size, or else return NULL. 697 HeapWord* alloc(size_t word_sz); 698 699 // Return any unused portions of the buffer to the global pool. 700 void retire(int tid); 701 702 // Dynamic OldPLABSize sizing 703 static void compute_desired_plab_size(); 704 // When the settings are modified from default static initialization 705 static void modify_initialization(size_t n, unsigned wt); 706 }; 707 708 size_t PromotionInfo::refillSize() const { 709 const size_t CMSSpoolBlockSize = 256; 710 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop) 711 * CMSSpoolBlockSize); 712 return CompactibleFreeListSpace::adjustObjectSize(sz); 713 } 714 715 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP