1 /* 2 * Copyright (c) 2001, 2017, 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/space.hpp" 32 #include "logging/log.hpp" 33 #include "memory/binaryTreeDictionary.hpp" 34 #include "memory/freeList.hpp" 35 36 // Classes in support of keeping track of promotions into a non-Contiguous 37 // space, in this case a CompactibleFreeListSpace. 38 39 // Forward declarations 40 class CMSCollector; 41 class CompactibleFreeListSpace; 42 class ConcurrentMarkSweepGeneration; 43 class BlkClosure; 44 class BlkClosureCareful; 45 class FreeChunk; 46 class UpwardsObjectClosure; 47 class ObjectClosureCareful; 48 class Klass; 49 50 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC { 51 public: 52 LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0), 53 _allocation_size_limit(0) {} 54 void set(HeapWord* ptr, size_t word_size, size_t refill_size, 55 size_t allocation_size_limit) { 56 _ptr = ptr; 57 _word_size = word_size; 58 _refillSize = refill_size; 59 _allocation_size_limit = allocation_size_limit; 60 } 61 HeapWord* _ptr; 62 size_t _word_size; 63 size_t _refillSize; 64 size_t _allocation_size_limit; // Largest size that will be allocated 65 66 void print_on(outputStream* st) const; 67 }; 68 69 // Concrete subclass of CompactibleSpace that implements 70 // a free list space, such as used in the concurrent mark sweep 71 // generation. 72 73 class CompactibleFreeListSpace: public CompactibleSpace { 74 friend class VMStructs; 75 friend class ConcurrentMarkSweepGeneration; 76 friend class CMSCollector; 77 // Local alloc buffer for promotion into this space. 78 friend class CompactibleFreeListSpaceLAB; 79 // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class 80 template <typename SpaceType> 81 friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space); 82 template <typename SpaceType> 83 friend void CompactibleSpace::scan_and_compact(SpaceType* space); 84 template <typename SpaceType> 85 friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space); 86 template <typename SpaceType> 87 friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp); 88 89 // "Size" of chunks of work (executed during parallel remark phases 90 // of CMS collection); this probably belongs in CMSCollector, although 91 // it's cached here because it's used in 92 // initialize_sequential_subtasks_for_rescan() which modifies 93 // par_seq_tasks which also lives in Space. XXX 94 const size_t _rescan_task_size; 95 const size_t _marking_task_size; 96 97 // Yet another sequential tasks done structure. This supports 98 // CMS GC, where we have threads dynamically 99 // claiming sub-tasks from a larger parallel task. 100 SequentialSubTasksDone _conc_par_seq_tasks; 101 102 BlockOffsetArrayNonContigSpace _bt; 103 104 CMSCollector* _collector; 105 ConcurrentMarkSweepGeneration* _old_gen; 106 107 // Data structures for free blocks (used during allocation/sweeping) 108 109 // Allocation is done linearly from two different blocks depending on 110 // whether the request is small or large, in an effort to reduce 111 // fragmentation. We assume that any locking for allocation is done 112 // by the containing generation. Thus, none of the methods in this 113 // space are re-entrant. 114 enum SomeConstants { 115 SmallForLinearAlloc = 16, // size < this then use _sLAB 116 SmallForDictionary = 257, // size < this then use _indexedFreeList 117 IndexSetSize = SmallForDictionary // keep this odd-sized 118 }; 119 static size_t IndexSetStart; 120 static size_t IndexSetStride; 121 122 private: 123 enum FitStrategyOptions { 124 FreeBlockStrategyNone = 0, 125 FreeBlockBestFitFirst 126 }; 127 128 PromotionInfo _promoInfo; 129 130 // Helps to impose a global total order on freelistLock ranks; 131 // assumes that CFLSpace's are allocated in global total order 132 static int _lockRank; 133 134 // A lock protecting the free lists and free blocks; 135 // mutable because of ubiquity of locking even for otherwise const methods 136 mutable Mutex _freelistLock; 137 // Locking verifier convenience function 138 void assert_locked() const PRODUCT_RETURN; 139 void assert_locked(const Mutex* lock) const PRODUCT_RETURN; 140 141 // Linear allocation blocks 142 LinearAllocBlock _smallLinearAllocBlock; 143 144 AFLBinaryTreeDictionary* _dictionary; // Pointer to dictionary for large size blocks 145 146 // Indexed array for small size blocks 147 AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize]; 148 149 // Allocation strategy 150 bool _fitStrategy; // Use best fit strategy 151 152 // This is an address close to the largest free chunk in the heap. 153 // It is currently assumed to be at the end of the heap. Free 154 // chunks with addresses greater than nearLargestChunk are coalesced 155 // in an effort to maintain a large chunk at the end of the heap. 156 HeapWord* _nearLargestChunk; 157 158 // Used to keep track of limit of sweep for the space 159 HeapWord* _sweep_limit; 160 161 // Used to make the young collector update the mod union table 162 MemRegionClosure* _preconsumptionDirtyCardClosure; 163 164 // Support for compacting cms 165 HeapWord* cross_threshold(HeapWord* start, HeapWord* end); 166 HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top); 167 168 // Initialization helpers. 169 void initializeIndexedFreeListArray(); 170 171 // Extra stuff to manage promotion parallelism. 172 173 // A lock protecting the dictionary during par promotion allocation. 174 mutable Mutex _parDictionaryAllocLock; 175 Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; } 176 177 // Locks protecting the exact lists during par promotion allocation. 178 Mutex* _indexedFreeListParLocks[IndexSetSize]; 179 180 // Attempt to obtain up to "n" blocks of the size "word_sz" (which is 181 // required to be smaller than "IndexSetSize".) If successful, 182 // adds them to "fl", which is required to be an empty free list. 183 // If the count of "fl" is negative, it's absolute value indicates a 184 // number of free chunks that had been previously "borrowed" from global 185 // list of size "word_sz", and must now be decremented. 186 void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 187 188 // Used by par_get_chunk_of_blocks() for the chunks from the 189 // indexed_free_lists. 190 bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 191 192 // Used by par_get_chunk_of_blocks_dictionary() to get a chunk 193 // evenly splittable into "n" "word_sz" chunks. Returns that 194 // evenly splittable chunk. May split a larger chunk to get the 195 // evenly splittable chunk. 196 FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n); 197 198 // Used by par_get_chunk_of_blocks() for the chunks from the 199 // dictionary. 200 void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl); 201 202 // Allocation helper functions 203 // Allocate using a strategy that takes from the indexed free lists 204 // first. This allocation strategy assumes a companion sweeping 205 // strategy that attempts to keep the needed number of chunks in each 206 // indexed free lists. 207 HeapWord* allocate_adaptive_freelists(size_t size); 208 209 // Gets a chunk from the linear allocation block (LinAB). If there 210 // is not enough space in the LinAB, refills it. 211 HeapWord* getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size); 212 HeapWord* getChunkFromSmallLinearAllocBlock(size_t size); 213 // Get a chunk from the space remaining in the linear allocation block. Do 214 // not attempt to refill if the space is not available, return NULL. Do the 215 // repairs on the linear allocation block as appropriate. 216 HeapWord* getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size); 217 inline HeapWord* getChunkFromSmallLinearAllocBlockRemainder(size_t size); 218 219 // Helper function for getChunkFromIndexedFreeList. 220 // Replenish the indexed free list for this "size". Do not take from an 221 // underpopulated size. 222 FreeChunk* getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true); 223 224 // Get a chunk from the indexed free list. If the indexed free list 225 // does not have a free chunk, try to replenish the indexed free list 226 // then get the free chunk from the replenished indexed free list. 227 inline FreeChunk* getChunkFromIndexedFreeList(size_t size); 228 229 // The returned chunk may be larger than requested (or null). 230 FreeChunk* getChunkFromDictionary(size_t size); 231 // The returned chunk is the exact size requested (or null). 232 FreeChunk* getChunkFromDictionaryExact(size_t size); 233 234 // Find a chunk in the indexed free list that is the best 235 // fit for size "numWords". 236 FreeChunk* bestFitSmall(size_t numWords); 237 // For free list "fl" of chunks of size > numWords, 238 // remove a chunk, split off a chunk of size numWords 239 // and return it. The split off remainder is returned to 240 // the free lists. The old name for getFromListGreater 241 // was lookInListGreater. 242 FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords); 243 // Get a chunk in the indexed free list or dictionary, 244 // by considering a larger chunk and splitting it. 245 FreeChunk* getChunkFromGreater(size_t numWords); 246 // Verify that the given chunk is in the indexed free lists. 247 bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const; 248 // Remove the specified chunk from the indexed free lists. 249 void removeChunkFromIndexedFreeList(FreeChunk* fc); 250 // Remove the specified chunk from the dictionary. 251 void removeChunkFromDictionary(FreeChunk* fc); 252 // Split a free chunk into a smaller free chunk of size "new_size". 253 // Return the smaller free chunk and return the remainder to the 254 // free lists. 255 FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size); 256 // Add a chunk to the free lists. 257 void addChunkToFreeLists(HeapWord* chunk, size_t size); 258 // Add a chunk to the free lists, preferring to suffix it 259 // to the last free chunk at end of space if possible, and 260 // updating the block census stats as well as block offset table. 261 // Take any locks as appropriate if we are multithreaded. 262 void addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size); 263 // Add a free chunk to the indexed free lists. 264 void returnChunkToFreeList(FreeChunk* chunk); 265 // Add a free chunk to the dictionary. 266 void returnChunkToDictionary(FreeChunk* chunk); 267 268 // Functions for maintaining the linear allocation buffers (LinAB). 269 // Repairing a linear allocation block refers to operations 270 // performed on the remainder of a LinAB after an allocation 271 // has been made from it. 272 void repairLinearAllocationBlocks(); 273 void repairLinearAllocBlock(LinearAllocBlock* blk); 274 void refillLinearAllocBlock(LinearAllocBlock* blk); 275 void refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk); 276 void refillLinearAllocBlocksIfNeeded(); 277 278 void verify_objects_initialized() const; 279 280 // Statistics reporting helper functions 281 void reportFreeListStatistics(const char* title) const; 282 void reportIndexedFreeListStatistics(outputStream* st) const; 283 size_t maxChunkSizeInIndexedFreeLists() const; 284 size_t numFreeBlocksInIndexedFreeLists() const; 285 // Accessor 286 HeapWord* unallocated_block() const { 287 if (BlockOffsetArrayUseUnallocatedBlock) { 288 HeapWord* ub = _bt.unallocated_block(); 289 assert(ub >= bottom() && 290 ub <= end(), "space invariant"); 291 return ub; 292 } else { 293 return end(); 294 } 295 } 296 void freed(HeapWord* start, size_t size) { 297 _bt.freed(start, size); 298 } 299 300 // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support. 301 // See comments for CompactibleSpace for more information. 302 inline HeapWord* scan_limit() const { 303 return end(); 304 } 305 306 inline bool scanned_block_is_obj(const HeapWord* addr) const { 307 return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call 308 } 309 310 inline size_t scanned_block_size(const HeapWord* addr) const { 311 return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call 312 } 313 314 inline size_t adjust_obj_size(size_t size) const { 315 return adjustObjectSize(size); 316 } 317 318 inline size_t obj_size(const HeapWord* addr) const; 319 320 protected: 321 // Reset the indexed free list to its initial empty condition. 322 void resetIndexedFreeListArray(); 323 // Reset to an initial state with a single free block described 324 // by the MemRegion parameter. 325 void reset(MemRegion mr); 326 // Return the total number of words in the indexed free lists. 327 size_t totalSizeInIndexedFreeLists() const; 328 329 public: 330 // Constructor 331 CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr); 332 // Accessors 333 bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; } 334 AFLBinaryTreeDictionary* dictionary() const { return _dictionary; } 335 HeapWord* nearLargestChunk() const { return _nearLargestChunk; } 336 void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; } 337 338 // Set CMS global values. 339 static void set_cms_values(); 340 341 // Return the free chunk at the end of the space. If no such 342 // chunk exists, return NULL. 343 FreeChunk* find_chunk_at_end(); 344 345 void set_collector(CMSCollector* collector) { _collector = collector; } 346 347 // Support for parallelization of rescan and marking. 348 const size_t rescan_task_size() const { return _rescan_task_size; } 349 const size_t marking_task_size() const { return _marking_task_size; } 350 // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple. 351 const size_t max_flag_size_for_task_size() const; 352 SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; } 353 void initialize_sequential_subtasks_for_rescan(int n_threads); 354 void initialize_sequential_subtasks_for_marking(int n_threads, 355 HeapWord* low = NULL); 356 357 virtual MemRegionClosure* preconsumptionDirtyCardClosure() const { 358 return _preconsumptionDirtyCardClosure; 359 } 360 361 void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) { 362 _preconsumptionDirtyCardClosure = cl; 363 } 364 365 // Space enquiries 366 size_t used() const; 367 size_t free() const; 368 size_t max_alloc_in_words() const; 369 // XXX: should have a less conservative used_region() than that of 370 // Space; we could consider keeping track of highest allocated 371 // address and correcting that at each sweep, as the sweeper 372 // goes through the entire allocated part of the generation. We 373 // could also use that information to keep the sweeper from 374 // sweeping more than is necessary. The allocator and sweeper will 375 // of course need to synchronize on this, since the sweeper will 376 // try to bump down the address and the allocator will try to bump it up. 377 // For now, however, we'll just use the default used_region() 378 // which overestimates the region by returning the entire 379 // committed region (this is safe, but inefficient). 380 381 // Returns a subregion of the space containing all the objects in 382 // the space. 383 MemRegion used_region() const { 384 return MemRegion(bottom(), 385 BlockOffsetArrayUseUnallocatedBlock ? 386 unallocated_block() : end()); 387 } 388 389 virtual bool is_free_block(const HeapWord* p) const; 390 391 // Resizing support 392 void set_end(HeapWord* value); // override 393 394 // Never mangle CompactibleFreeListSpace 395 void mangle_unused_area() {} 396 void mangle_unused_area_complete() {} 397 398 // Mutual exclusion support 399 Mutex* freelistLock() const { return &_freelistLock; } 400 401 // Iteration support 402 void oop_iterate(ExtendedOopClosure* cl); 403 404 void object_iterate(ObjectClosure* blk); 405 // Apply the closure to each object in the space whose references 406 // point to objects in the heap. The usage of CompactibleFreeListSpace 407 // by the ConcurrentMarkSweepGeneration for concurrent GC's allows 408 // objects in the space with references to objects that are no longer 409 // valid. For example, an object may reference another object 410 // that has already been sweep up (collected). This method uses 411 // obj_is_alive() to determine whether it is safe to iterate of 412 // an object. 413 void safe_object_iterate(ObjectClosure* blk); 414 415 // Iterate over all objects that intersect with mr, calling "cl->do_object" 416 // on each. There is an exception to this: if this closure has already 417 // been invoked on an object, it may skip such objects in some cases. This is 418 // Most likely to happen in an "upwards" (ascending address) iteration of 419 // MemRegions. 420 void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl); 421 422 // Requires that "mr" be entirely within the space. 423 // Apply "cl->do_object" to all objects that intersect with "mr". 424 // If the iteration encounters an unparseable portion of the region, 425 // terminate the iteration and return the address of the start of the 426 // subregion that isn't done. Return of "NULL" indicates that the 427 // iteration completed. 428 HeapWord* object_iterate_careful_m(MemRegion mr, 429 ObjectClosureCareful* cl); 430 431 // Override: provides a DCTO_CL specific to this kind of space. 432 DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl, 433 CardTableModRefBS::PrecisionStyle precision, 434 HeapWord* boundary, 435 bool parallel); 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 log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT 457 " for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<", 458 p2i(_sweep_limit), p2i(bottom()), p2i(end())); 459 } 460 NOT_PRODUCT( 461 void clear_sweep_limit() { _sweep_limit = NULL; } 462 ) 463 HeapWord* sweep_limit() { return _sweep_limit; } 464 465 // Apply "blk->do_oop" to the addresses of all reference fields in objects 466 // promoted into this generation since the most recent save_marks() call. 467 // Fields in objects allocated by applications of the closure 468 // *are* included in the iteration. Thus, when the iteration completes 469 // there should be no further such objects remaining. 470 #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ 471 void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk); 472 ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL) 473 #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL 474 475 // Allocation support 476 HeapWord* allocate(size_t size); 477 HeapWord* par_allocate(size_t size); 478 479 oop promote(oop obj, size_t obj_size); 480 void gc_prologue(); 481 void gc_epilogue(); 482 483 // This call is used by a containing CMS generation / collector 484 // to inform the CFLS space that a sweep has been completed 485 // and that the space can do any related house-keeping functions. 486 void sweep_completed(); 487 488 // For an object in this space, the mark-word's two 489 // LSB's having the value [11] indicates that it has been 490 // promoted since the most recent call to save_marks() on 491 // this generation and has not subsequently been iterated 492 // over (using oop_since_save_marks_iterate() above). 493 // This property holds only for single-threaded collections, 494 // and is typically used for Cheney scans; for MT scavenges, 495 // the property holds for all objects promoted during that 496 // scavenge for the duration of the scavenge and is used 497 // by card-scanning to avoid scanning objects (being) promoted 498 // during that scavenge. 499 bool obj_allocated_since_save_marks(const oop obj) const { 500 assert(is_in_reserved(obj), "Wrong space?"); 501 return ((PromotedObject*)obj)->hasPromotedMark(); 502 } 503 504 // A worst-case estimate of the space required (in HeapWords) to expand the 505 // heap when promoting an obj of size obj_size. 506 size_t expansionSpaceRequired(size_t obj_size) const; 507 508 FreeChunk* allocateScratch(size_t size); 509 510 // Returns true if either the small or large linear allocation buffer is empty. 511 bool linearAllocationWouldFail() const; 512 513 // Adjust the chunk for the minimum size. This version is called in 514 // most cases in CompactibleFreeListSpace methods. 515 inline static size_t adjustObjectSize(size_t size) { 516 return align_object_size(MAX2(size, (size_t)MinChunkSize)); 517 } 518 // This is a virtual version of adjustObjectSize() that is called 519 // only occasionally when the compaction space changes and the type 520 // of the new compaction space is is only known to be CompactibleSpace. 521 size_t adjust_object_size_v(size_t size) const { 522 return adjustObjectSize(size); 523 } 524 // Minimum size of a free block. 525 virtual size_t minimum_free_block_size() const { return MinChunkSize; } 526 void removeFreeChunkFromFreeLists(FreeChunk* chunk); 527 void addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size, 528 bool coalesced); 529 530 // Support for compaction. 531 void prepare_for_compaction(CompactPoint* cp); 532 void adjust_pointers(); 533 void compact(); 534 // Reset the space to reflect the fact that a compaction of the 535 // space has been done. 536 virtual void reset_after_compaction(); 537 538 // Debugging support. 539 void print() const; 540 void print_on(outputStream* st) const; 541 void prepare_for_verify(); 542 void verify() const; 543 void verifyFreeLists() const PRODUCT_RETURN; 544 void verifyIndexedFreeLists() const; 545 void verifyIndexedFreeList(size_t size) const; 546 // Verify that the given chunk is in the free lists: 547 // i.e. either the binary tree dictionary, the indexed free lists 548 // or the linear allocation block. 549 bool verify_chunk_in_free_list(FreeChunk* fc) const; 550 // Verify that the given chunk is the linear allocation block. 551 bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const; 552 // Do some basic checks on the the free lists. 553 void check_free_list_consistency() const PRODUCT_RETURN; 554 555 // Printing support 556 void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st); 557 void print_indexed_free_lists(outputStream* st) const; 558 void print_dictionary_free_lists(outputStream* st) const; 559 void print_promo_info_blocks(outputStream* st) const; 560 561 NOT_PRODUCT ( 562 void initializeIndexedFreeListArrayReturnedBytes(); 563 size_t sumIndexedFreeListArrayReturnedBytes(); 564 // Return the total number of chunks in the indexed free lists. 565 size_t totalCountInIndexedFreeLists() const; 566 // Return the total number of chunks in the space. 567 size_t totalCount(); 568 ) 569 570 // The census consists of counts of the quantities such as 571 // the current count of the free chunks, number of chunks 572 // created as a result of the split of a larger chunk or 573 // coalescing of smaller chucks, etc. The counts in the 574 // census is used to make decisions on splitting and 575 // coalescing of chunks during the sweep of garbage. 576 577 // Print the statistics for the free lists. 578 void printFLCensus(size_t sweep_count) const; 579 580 // Statistics functions 581 // Initialize census for lists before the sweep. 582 void beginSweepFLCensus(float inter_sweep_current, 583 float inter_sweep_estimate, 584 float intra_sweep_estimate); 585 // Set the surplus for each of the free lists. 586 void setFLSurplus(); 587 // Set the hint for each of the free lists. 588 void setFLHints(); 589 // Clear the census for each of the free lists. 590 void clearFLCensus(); 591 // Perform functions for the census after the end of the sweep. 592 void endSweepFLCensus(size_t sweep_count); 593 // Return true if the count of free chunks is greater 594 // than the desired number of free chunks. 595 bool coalOverPopulated(size_t size); 596 597 // Record (for each size): 598 // 599 // split-births = #chunks added due to splits in (prev-sweep-end, 600 // this-sweep-start) 601 // split-deaths = #chunks removed for splits in (prev-sweep-end, 602 // this-sweep-start) 603 // num-curr = #chunks at start of this sweep 604 // num-prev = #chunks at end of previous sweep 605 // 606 // The above are quantities that are measured. Now define: 607 // 608 // num-desired := num-prev + split-births - split-deaths - num-curr 609 // 610 // Roughly, num-prev + split-births is the supply, 611 // split-deaths is demand due to other sizes 612 // and num-curr is what we have left. 613 // 614 // Thus, num-desired is roughly speaking the "legitimate demand" 615 // for blocks of this size and what we are striving to reach at the 616 // end of the current sweep. 617 // 618 // For a given list, let num-len be its current population. 619 // Define, for a free list of a given size: 620 // 621 // coal-overpopulated := num-len >= num-desired * coal-surplus 622 // (coal-surplus is set to 1.05, i.e. we allow a little slop when 623 // coalescing -- we do not coalesce unless we think that the current 624 // supply has exceeded the estimated demand by more than 5%). 625 // 626 // For the set of sizes in the binary tree, which is neither dense nor 627 // closed, it may be the case that for a particular size we have never 628 // had, or do not now have, or did not have at the previous sweep, 629 // chunks of that size. We need to extend the definition of 630 // coal-overpopulated to such sizes as well: 631 // 632 // For a chunk in/not in the binary tree, extend coal-overpopulated 633 // defined above to include all sizes as follows: 634 // 635 // . a size that is non-existent is coal-overpopulated 636 // . a size that has a num-desired <= 0 as defined above is 637 // coal-overpopulated. 638 // 639 // Also define, for a chunk heap-offset C and mountain heap-offset M: 640 // 641 // close-to-mountain := C >= 0.99 * M 642 // 643 // Now, the coalescing strategy is: 644 // 645 // Coalesce left-hand chunk with right-hand chunk if and 646 // only if: 647 // 648 // EITHER 649 // . left-hand chunk is of a size that is coal-overpopulated 650 // OR 651 // . right-hand chunk is close-to-mountain 652 void smallCoalBirth(size_t size); 653 void smallCoalDeath(size_t size); 654 void coalBirth(size_t size); 655 void coalDeath(size_t size); 656 void smallSplitBirth(size_t size); 657 void smallSplitDeath(size_t size); 658 void split_birth(size_t size); 659 void splitDeath(size_t size); 660 void split(size_t from, size_t to1); 661 662 double flsFrag() const; 663 }; 664 665 // A parallel-GC-thread-local allocation buffer for allocation into a 666 // CompactibleFreeListSpace. 667 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> { 668 // The space that this buffer allocates into. 669 CompactibleFreeListSpace* _cfls; 670 671 // Our local free lists. 672 AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize]; 673 674 // Initialized from a command-line arg. 675 676 // Allocation statistics in support of dynamic adjustment of 677 // #blocks to claim per get_from_global_pool() call below. 678 static AdaptiveWeightedAverage 679 _blocks_to_claim [CompactibleFreeListSpace::IndexSetSize]; 680 static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize]; 681 static uint _global_num_workers[CompactibleFreeListSpace::IndexSetSize]; 682 size_t _num_blocks [CompactibleFreeListSpace::IndexSetSize]; 683 684 // Internal work method 685 void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl); 686 687 public: 688 static const int _default_dynamic_old_plab_size = 16; 689 static const int _default_static_old_plab_size = 50; 690 691 CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls); 692 693 // Allocate and return a block of the given size, or else return NULL. 694 HeapWord* alloc(size_t word_sz); 695 696 // Return any unused portions of the buffer to the global pool. 697 void retire(int tid); 698 699 // Dynamic OldPLABSize sizing 700 static void compute_desired_plab_size(); 701 // When the settings are modified from default static initialization 702 static void modify_initialization(size_t n, unsigned wt); 703 }; 704 705 size_t PromotionInfo::refillSize() const { 706 const size_t CMSSpoolBlockSize = 256; 707 const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop) 708 * CMSSpoolBlockSize); 709 return CompactibleFreeListSpace::adjustObjectSize(sz); 710 } 711 712 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP