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  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 AFLBinaryTreeDictionary : public BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> > {
  52  public:
  53   AFLBinaryTreeDictionary(MemRegion mr)
  54       : BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> >(mr) {}
  55 
  56   // Find the list with size "size" in the binary tree and update
  57   // the statistics in the list according to "split" (chunk was
  58   // split or coalesce) and "birth" (chunk was added or removed).
  59   void       dict_census_update(size_t size, bool split, bool birth);
  60   // Return true if the dictionary is overpopulated (more chunks of
  61   // this size than desired) for size "size".
  62   bool       coal_dict_over_populated(size_t size);
  63   // Methods called at the beginning of a sweep to prepare the
  64   // statistics for the sweep.
  65   void       begin_sweep_dict_census(double coalSurplusPercent,
  66                                      float inter_sweep_current,
  67                                      float inter_sweep_estimate,
  68                                      float intra_sweep_estimate);
  69   // Methods called after the end of a sweep to modify the
  70   // statistics for the sweep.
  71   void       end_sweep_dict_census(double splitSurplusPercent);
  72   // Accessors for statistics
  73   void       set_tree_surplus(double splitSurplusPercent);
  74   void       set_tree_hints(void);
  75   // Reset statistics for all the lists in the tree.
  76   void       clear_tree_census(void);
  77   // Print the statistics for all the lists in the tree.  Also may
  78   // print out summaries.
  79   void       print_dict_census(outputStream* st) const;
  80 };
  81 
  82 class LinearAllocBlock {
  83  public:
  84   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
  85     _allocation_size_limit(0) {}
  86   void set(HeapWord* ptr, size_t word_size, size_t refill_size,
  87     size_t allocation_size_limit) {
  88     _ptr = ptr;
  89     _word_size = word_size;
  90     _refillSize = refill_size;
  91     _allocation_size_limit = allocation_size_limit;
  92   }
  93   HeapWord* _ptr;
  94   size_t    _word_size;
  95   size_t    _refillSize;
  96   size_t    _allocation_size_limit;  // Largest size that will be allocated
  97 
  98   void print_on(outputStream* st) const;
  99 };
 100 
 101 // Concrete subclass of CompactibleSpace that implements
 102 // a free list space, such as used in the concurrent mark sweep
 103 // generation.
 104 
 105 class CompactibleFreeListSpace: public CompactibleSpace {
 106   friend class VMStructs;
 107   friend class ConcurrentMarkSweepGeneration;
 108   friend class CMSCollector;
 109   // Local alloc buffer for promotion into this space.
 110   friend class CompactibleFreeListSpaceLAB;
 111   // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
 112 #if INCLUDE_SERIALGC
 113   template <typename SpaceType>
 114   friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
 115   template <typename SpaceType>
 116   friend void CompactibleSpace::scan_and_compact(SpaceType* space);
 117   template <typename SpaceType>
 118   friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
 119   template <typename SpaceType>
 120   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
 121 #endif
 122 
 123   // "Size" of chunks of work (executed during parallel remark phases
 124   // of CMS collection); this probably belongs in CMSCollector, although
 125   // it's cached here because it's used in
 126   // initialize_sequential_subtasks_for_rescan() which modifies
 127   // par_seq_tasks which also lives in Space. XXX
 128   const size_t _rescan_task_size;
 129   const size_t _marking_task_size;
 130 
 131   // Yet another sequential tasks done structure. This supports
 132   // CMS GC, where we have threads dynamically
 133   // claiming sub-tasks from a larger parallel task.
 134   SequentialSubTasksDone _conc_par_seq_tasks;
 135 
 136   BlockOffsetArrayNonContigSpace _bt;
 137 
 138   CMSCollector* _collector;
 139   ConcurrentMarkSweepGeneration* _old_gen;
 140 
 141   // Data structures for free blocks (used during allocation/sweeping)
 142 
 143   // Allocation is done linearly from two different blocks depending on
 144   // whether the request is small or large, in an effort to reduce
 145   // fragmentation. We assume that any locking for allocation is done
 146   // by the containing generation. Thus, none of the methods in this
 147   // space are re-entrant.
 148   enum SomeConstants {
 149     SmallForLinearAlloc = 16,        // size < this then use _sLAB
 150     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
 151     IndexSetSize        = SmallForDictionary  // keep this odd-sized
 152   };
 153   static size_t IndexSetStart;
 154   static size_t IndexSetStride;
 155   static size_t _min_chunk_size_in_bytes;
 156 
 157  private:
 158   enum FitStrategyOptions {
 159     FreeBlockStrategyNone = 0,
 160     FreeBlockBestFitFirst
 161   };
 162 
 163   PromotionInfo _promoInfo;
 164 
 165   // Helps to impose a global total order on freelistLock ranks;
 166   // assumes that CFLSpace's are allocated in global total order
 167   static int   _lockRank;
 168 
 169   // A lock protecting the free lists and free blocks;
 170   // mutable because of ubiquity of locking even for otherwise const methods
 171   mutable Mutex _freelistLock;
 172 
 173   // Locking verifier convenience function
 174   void assert_locked() const PRODUCT_RETURN;
 175   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
 176 
 177   // Linear allocation blocks
 178   LinearAllocBlock _smallLinearAllocBlock;
 179 
 180   AFLBinaryTreeDictionary* _dictionary;    // Pointer to dictionary for large size blocks
 181 
 182   // Indexed array for small size blocks
 183   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
 184 
 185   // Allocation strategy
 186   bool _fitStrategy;  // Use best fit strategy
 187 
 188   // This is an address close to the largest free chunk in the heap.
 189   // It is currently assumed to be at the end of the heap.  Free
 190   // chunks with addresses greater than nearLargestChunk are coalesced
 191   // in an effort to maintain a large chunk at the end of the heap.
 192   HeapWord*  _nearLargestChunk;
 193 
 194   // Used to keep track of limit of sweep for the space
 195   HeapWord* _sweep_limit;
 196 
 197   // Used to make the young collector update the mod union table
 198   MemRegionClosure* _preconsumptionDirtyCardClosure;
 199 
 200   // Support for compacting cms
 201   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 202   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
 203 
 204   // Initialization helpers.
 205   void initializeIndexedFreeListArray();
 206 
 207   // Extra stuff to manage promotion parallelism.
 208 
 209   // A lock protecting the dictionary during par promotion allocation.
 210   mutable Mutex _parDictionaryAllocLock;
 211   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
 212 
 213   // Locks protecting the exact lists during par promotion allocation.
 214   Mutex* _indexedFreeListParLocks[IndexSetSize];
 215 
 216   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
 217   // required to be smaller than "IndexSetSize".)  If successful,
 218   // adds them to "fl", which is required to be an empty free list.
 219   // If the count of "fl" is negative, it's absolute value indicates a
 220   // number of free chunks that had been previously "borrowed" from global
 221   // list of size "word_sz", and must now be decremented.
 222   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 223 
 224   // Used by par_get_chunk_of_blocks() for the chunks from the
 225   // indexed_free_lists.
 226   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 227 
 228   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
 229   // evenly splittable into "n" "word_sz" chunks.  Returns that
 230   // evenly splittable chunk.  May split a larger chunk to get the
 231   // evenly splittable chunk.
 232   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
 233 
 234   // Used by par_get_chunk_of_blocks() for the chunks from the
 235   // dictionary.
 236   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 237 
 238   // Allocation helper functions
 239   // Allocate using a strategy that takes from the indexed free lists
 240   // first.  This allocation strategy assumes a companion sweeping
 241   // strategy that attempts to keep the needed number of chunks in each
 242   // indexed free lists.
 243   HeapWord* allocate_adaptive_freelists(size_t size);
 244 
 245   // Gets a chunk from the linear allocation block (LinAB).  If there
 246   // is not enough space in the LinAB, refills it.
 247   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
 248   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
 249   // Get a chunk from the space remaining in the linear allocation block.  Do
 250   // not attempt to refill if the space is not available, return NULL.  Do the
 251   // repairs on the linear allocation block as appropriate.
 252   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
 253   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
 254 
 255   // Helper function for getChunkFromIndexedFreeList.
 256   // Replenish the indexed free list for this "size".  Do not take from an
 257   // underpopulated size.
 258   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
 259 
 260   // Get a chunk from the indexed free list.  If the indexed free list
 261   // does not have a free chunk, try to replenish the indexed free list
 262   // then get the free chunk from the replenished indexed free list.
 263   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
 264 
 265   // The returned chunk may be larger than requested (or null).
 266   FreeChunk* getChunkFromDictionary(size_t size);
 267   // The returned chunk is the exact size requested (or null).
 268   FreeChunk* getChunkFromDictionaryExact(size_t size);
 269 
 270   // Find a chunk in the indexed free list that is the best
 271   // fit for size "numWords".
 272   FreeChunk* bestFitSmall(size_t numWords);
 273   // For free list "fl" of chunks of size > numWords,
 274   // remove a chunk, split off a chunk of size numWords
 275   // and return it.  The split off remainder is returned to
 276   // the free lists.  The old name for getFromListGreater
 277   // was lookInListGreater.
 278   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
 279   // Get a chunk in the indexed free list or dictionary,
 280   // by considering a larger chunk and splitting it.
 281   FreeChunk* getChunkFromGreater(size_t numWords);
 282   //  Verify that the given chunk is in the indexed free lists.
 283   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
 284   // Remove the specified chunk from the indexed free lists.
 285   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
 286   // Remove the specified chunk from the dictionary.
 287   void       removeChunkFromDictionary(FreeChunk* fc);
 288   // Split a free chunk into a smaller free chunk of size "new_size".
 289   // Return the smaller free chunk and return the remainder to the
 290   // free lists.
 291   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
 292   // Add a chunk to the free lists.
 293   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
 294   // Add a chunk to the free lists, preferring to suffix it
 295   // to the last free chunk at end of space if possible, and
 296   // updating the block census stats as well as block offset table.
 297   // Take any locks as appropriate if we are multithreaded.
 298   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
 299   // Add a free chunk to the indexed free lists.
 300   void       returnChunkToFreeList(FreeChunk* chunk);
 301   // Add a free chunk to the dictionary.
 302   void       returnChunkToDictionary(FreeChunk* chunk);
 303 
 304   // Functions for maintaining the linear allocation buffers (LinAB).
 305   // Repairing a linear allocation block refers to operations
 306   // performed on the remainder of a LinAB after an allocation
 307   // has been made from it.
 308   void       repairLinearAllocationBlocks();
 309   void       repairLinearAllocBlock(LinearAllocBlock* blk);
 310   void       refillLinearAllocBlock(LinearAllocBlock* blk);
 311   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
 312   void       refillLinearAllocBlocksIfNeeded();
 313 
 314   void       verify_objects_initialized() const;
 315 
 316   // Statistics reporting helper functions
 317   void       reportFreeListStatistics(const char* title) const;
 318   void       reportIndexedFreeListStatistics(outputStream* st) const;
 319   size_t     maxChunkSizeInIndexedFreeLists() const;
 320   size_t     numFreeBlocksInIndexedFreeLists() const;
 321   // Accessor
 322   HeapWord* unallocated_block() const {
 323     if (BlockOffsetArrayUseUnallocatedBlock) {
 324       HeapWord* ub = _bt.unallocated_block();
 325       assert(ub >= bottom() &&
 326              ub <= end(), "space invariant");
 327       return ub;
 328     } else {
 329       return end();
 330     }
 331   }
 332   void freed(HeapWord* start, size_t size) {
 333     _bt.freed(start, size);
 334   }
 335 
 336   // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
 337   // See comments for CompactibleSpace for more information.
 338   inline HeapWord* scan_limit() const {
 339     return end();
 340   }
 341 
 342   inline bool scanned_block_is_obj(const HeapWord* addr) const {
 343     return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
 344   }
 345 
 346   inline size_t scanned_block_size(const HeapWord* addr) const {
 347     return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
 348   }
 349 
 350   inline size_t adjust_obj_size(size_t size) const {
 351     return adjustObjectSize(size);
 352   }
 353 
 354   inline size_t obj_size(const HeapWord* addr) const;
 355 
 356  protected:
 357   // Reset the indexed free list to its initial empty condition.
 358   void resetIndexedFreeListArray();
 359   // Reset to an initial state with a single free block described
 360   // by the MemRegion parameter.
 361   void reset(MemRegion mr);
 362   // Return the total number of words in the indexed free lists.
 363   size_t     totalSizeInIndexedFreeLists() const;
 364 
 365  public:
 366   // Constructor
 367   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
 368   // Accessors
 369   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
 370   AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }
 371   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
 372   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
 373 
 374   // Set CMS global values.
 375   static void set_cms_values();
 376 
 377   // Return the free chunk at the end of the space.  If no such
 378   // chunk exists, return NULL.
 379   FreeChunk* find_chunk_at_end();
 380 
 381   void set_collector(CMSCollector* collector) { _collector = collector; }
 382 
 383   // Support for parallelization of rescan and marking.
 384   const size_t rescan_task_size()  const { return _rescan_task_size;  }
 385   const size_t marking_task_size() const { return _marking_task_size; }
 386   // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.
 387   const size_t max_flag_size_for_task_size() const;
 388   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
 389   void initialize_sequential_subtasks_for_rescan(int n_threads);
 390   void initialize_sequential_subtasks_for_marking(int n_threads,
 391          HeapWord* low = NULL);
 392 
 393   virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
 394     return _preconsumptionDirtyCardClosure;
 395   }
 396 
 397   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
 398     _preconsumptionDirtyCardClosure = cl;
 399   }
 400 
 401   // Space enquiries
 402   size_t used() const;
 403   size_t free() const;
 404   size_t max_alloc_in_words() const;
 405   // XXX: should have a less conservative used_region() than that of
 406   // Space; we could consider keeping track of highest allocated
 407   // address and correcting that at each sweep, as the sweeper
 408   // goes through the entire allocated part of the generation. We
 409   // could also use that information to keep the sweeper from
 410   // sweeping more than is necessary. The allocator and sweeper will
 411   // of course need to synchronize on this, since the sweeper will
 412   // try to bump down the address and the allocator will try to bump it up.
 413   // For now, however, we'll just use the default used_region()
 414   // which overestimates the region by returning the entire
 415   // committed region (this is safe, but inefficient).
 416 
 417   // Returns a subregion of the space containing all the objects in
 418   // the space.
 419   MemRegion used_region() const {
 420     return MemRegion(bottom(),
 421                      BlockOffsetArrayUseUnallocatedBlock ?
 422                      unallocated_block() : end());
 423   }
 424 
 425   virtual bool is_free_block(const HeapWord* p) const;
 426 
 427   // Resizing support
 428   void set_end(HeapWord* value);  // override
 429 
 430   // Never mangle CompactibleFreeListSpace
 431   void mangle_unused_area() {}
 432   void mangle_unused_area_complete() {}
 433 
 434   // Mutual exclusion support
 435   Mutex* freelistLock() const { return &_freelistLock; }
 436 
 437   // Iteration support
 438   void oop_iterate(OopIterateClosure* cl);
 439 
 440   void object_iterate(ObjectClosure* blk);
 441   // Apply the closure to each object in the space whose references
 442   // point to objects in the heap.  The usage of CompactibleFreeListSpace
 443   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
 444   // objects in the space with references to objects that are no longer
 445   // valid.  For example, an object may reference another object
 446   // that has already been sweep up (collected).  This method uses
 447   // obj_is_alive() to determine whether it is safe to iterate of
 448   // an object.
 449   void safe_object_iterate(ObjectClosure* blk);
 450 
 451   // Iterate over all objects that intersect with mr, calling "cl->do_object"
 452   // on each.  There is an exception to this: if this closure has already
 453   // been invoked on an object, it may skip such objects in some cases.  This is
 454   // Most likely to happen in an "upwards" (ascending address) iteration of
 455   // MemRegions.
 456   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 457 
 458   // Requires that "mr" be entirely within the space.
 459   // Apply "cl->do_object" to all objects that intersect with "mr".
 460   // If the iteration encounters an unparseable portion of the region,
 461   // terminate the iteration and return the address of the start of the
 462   // subregion that isn't done.  Return of "NULL" indicates that the
 463   // iteration completed.
 464   HeapWord* object_iterate_careful_m(MemRegion mr,
 465                                      ObjectClosureCareful* cl);
 466 
 467   // Override: provides a DCTO_CL specific to this kind of space.
 468   DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
 469                                      CardTable::PrecisionStyle precision,
 470                                      HeapWord* boundary,
 471                                      bool parallel);
 472 
 473   void blk_iterate(BlkClosure* cl);
 474   void blk_iterate_careful(BlkClosureCareful* cl);
 475   HeapWord* block_start_const(const void* p) const;
 476   HeapWord* block_start_careful(const void* p) const;
 477   size_t block_size(const HeapWord* p) const;
 478   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
 479   bool block_is_obj(const HeapWord* p) const;
 480   bool obj_is_alive(const HeapWord* p) const;
 481   size_t block_size_nopar(const HeapWord* p) const;
 482   bool block_is_obj_nopar(const HeapWord* p) const;
 483 
 484   // Iteration support for promotion
 485   void save_marks();
 486   bool no_allocs_since_save_marks();
 487 
 488   // Iteration support for sweeping
 489   void save_sweep_limit() {
 490     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
 491                    unallocated_block() : end();
 492     log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT
 493                                  "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
 494                                  p2i(_sweep_limit), p2i(bottom()), p2i(end()));
 495   }
 496   NOT_PRODUCT(
 497     void clear_sweep_limit() { _sweep_limit = NULL; }
 498   )
 499   HeapWord* sweep_limit() { return _sweep_limit; }
 500 
 501   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 502   // promoted into this generation since the most recent save_marks() call.
 503   // Fields in objects allocated by applications of the closure
 504   // *are* included in the iteration. Thus, when the iteration completes
 505   // there should be no further such objects remaining.
 506   template <typename OopClosureType>
 507   void oop_since_save_marks_iterate(OopClosureType* blk);
 508 
 509   // Allocation support
 510   HeapWord* allocate(size_t size);
 511   HeapWord* par_allocate(size_t size);
 512 
 513   oop       promote(oop obj, size_t obj_size);
 514   void      gc_prologue();
 515   void      gc_epilogue();
 516 
 517   // This call is used by a containing CMS generation / collector
 518   // to inform the CFLS space that a sweep has been completed
 519   // and that the space can do any related house-keeping functions.
 520   void      sweep_completed();
 521 
 522   // For an object in this space, the mark-word's two
 523   // LSB's having the value [11] indicates that it has been
 524   // promoted since the most recent call to save_marks() on
 525   // this generation and has not subsequently been iterated
 526   // over (using oop_since_save_marks_iterate() above).
 527   // This property holds only for single-threaded collections,
 528   // and is typically used for Cheney scans; for MT scavenges,
 529   // the property holds for all objects promoted during that
 530   // scavenge for the duration of the scavenge and is used
 531   // by card-scanning to avoid scanning objects (being) promoted
 532   // during that scavenge.
 533   bool obj_allocated_since_save_marks(const oop obj) const {
 534     assert(is_in_reserved(obj), "Wrong space?");
 535     return ((PromotedObject*)obj)->hasPromotedMark();
 536   }
 537 
 538   // A worst-case estimate of the space required (in HeapWords) to expand the
 539   // heap when promoting an obj of size obj_size.
 540   size_t expansionSpaceRequired(size_t obj_size) const;
 541 
 542   FreeChunk* allocateScratch(size_t size);
 543 
 544   // Returns true if either the small or large linear allocation buffer is empty.
 545   bool       linearAllocationWouldFail() const;
 546 
 547   // Adjust the chunk for the minimum size.  This version is called in
 548   // most cases in CompactibleFreeListSpace methods.
 549   inline static size_t adjustObjectSize(size_t size) {
 550     return align_object_size(MAX2(size, (size_t)MinChunkSize));
 551   }
 552   // This is a virtual version of adjustObjectSize() that is called
 553   // only occasionally when the compaction space changes and the type
 554   // of the new compaction space is is only known to be CompactibleSpace.
 555   size_t adjust_object_size_v(size_t size) const {
 556     return adjustObjectSize(size);
 557   }
 558   // Minimum size of a free block.
 559   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
 560   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
 561   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
 562               bool coalesced);
 563 
 564   // Support for compaction.
 565   void prepare_for_compaction(CompactPoint* cp);
 566   void adjust_pointers();
 567   void compact();
 568   // Reset the space to reflect the fact that a compaction of the
 569   // space has been done.
 570   virtual void reset_after_compaction();
 571 
 572   // Debugging support.
 573   void print()                            const;
 574   void print_on(outputStream* st)         const;
 575   void prepare_for_verify();
 576   void verify()                           const;
 577   void verifyFreeLists()                  const PRODUCT_RETURN;
 578   void verifyIndexedFreeLists()           const;
 579   void verifyIndexedFreeList(size_t size) const;
 580   // Verify that the given chunk is in the free lists:
 581   // i.e. either the binary tree dictionary, the indexed free lists
 582   // or the linear allocation block.
 583   bool verify_chunk_in_free_list(FreeChunk* fc) const;
 584   // Verify that the given chunk is the linear allocation block.
 585   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
 586   // Do some basic checks on the the free lists.
 587   void check_free_list_consistency()      const PRODUCT_RETURN;
 588 
 589   // Printing support
 590   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
 591   void print_indexed_free_lists(outputStream* st) const;
 592   void print_dictionary_free_lists(outputStream* st) const;
 593   void print_promo_info_blocks(outputStream* st) const;
 594 
 595   NOT_PRODUCT (
 596     void initializeIndexedFreeListArrayReturnedBytes();
 597     size_t sumIndexedFreeListArrayReturnedBytes();
 598     // Return the total number of chunks in the indexed free lists.
 599     size_t totalCountInIndexedFreeLists() const;
 600     // Return the total number of chunks in the space.
 601     size_t totalCount();
 602   )
 603 
 604   // The census consists of counts of the quantities such as
 605   // the current count of the free chunks, number of chunks
 606   // created as a result of the split of a larger chunk or
 607   // coalescing of smaller chucks, etc.  The counts in the
 608   // census is used to make decisions on splitting and
 609   // coalescing of chunks during the sweep of garbage.
 610 
 611   // Print the statistics for the free lists.
 612   void printFLCensus(size_t sweep_count) const;
 613 
 614   // Statistics functions
 615   // Initialize census for lists before the sweep.
 616   void beginSweepFLCensus(float inter_sweep_current,
 617                           float inter_sweep_estimate,
 618                           float intra_sweep_estimate);
 619   // Set the surplus for each of the free lists.
 620   void setFLSurplus();
 621   // Set the hint for each of the free lists.
 622   void setFLHints();
 623   // Clear the census for each of the free lists.
 624   void clearFLCensus();
 625   // Perform functions for the census after the end of the sweep.
 626   void endSweepFLCensus(size_t sweep_count);
 627   // Return true if the count of free chunks is greater
 628   // than the desired number of free chunks.
 629   bool coalOverPopulated(size_t size);
 630 
 631 // Record (for each size):
 632 //
 633 //   split-births = #chunks added due to splits in (prev-sweep-end,
 634 //      this-sweep-start)
 635 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
 636 //      this-sweep-start)
 637 //   num-curr     = #chunks at start of this sweep
 638 //   num-prev     = #chunks at end of previous sweep
 639 //
 640 // The above are quantities that are measured. Now define:
 641 //
 642 //   num-desired := num-prev + split-births - split-deaths - num-curr
 643 //
 644 // Roughly, num-prev + split-births is the supply,
 645 // split-deaths is demand due to other sizes
 646 // and num-curr is what we have left.
 647 //
 648 // Thus, num-desired is roughly speaking the "legitimate demand"
 649 // for blocks of this size and what we are striving to reach at the
 650 // end of the current sweep.
 651 //
 652 // For a given list, let num-len be its current population.
 653 // Define, for a free list of a given size:
 654 //
 655 //   coal-overpopulated := num-len >= num-desired * coal-surplus
 656 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
 657 // coalescing -- we do not coalesce unless we think that the current
 658 // supply has exceeded the estimated demand by more than 5%).
 659 //
 660 // For the set of sizes in the binary tree, which is neither dense nor
 661 // closed, it may be the case that for a particular size we have never
 662 // had, or do not now have, or did not have at the previous sweep,
 663 // chunks of that size. We need to extend the definition of
 664 // coal-overpopulated to such sizes as well:
 665 //
 666 //   For a chunk in/not in the binary tree, extend coal-overpopulated
 667 //   defined above to include all sizes as follows:
 668 //
 669 //   . a size that is non-existent is coal-overpopulated
 670 //   . a size that has a num-desired <= 0 as defined above is
 671 //     coal-overpopulated.
 672 //
 673 // Also define, for a chunk heap-offset C and mountain heap-offset M:
 674 //
 675 //   close-to-mountain := C >= 0.99 * M
 676 //
 677 // Now, the coalescing strategy is:
 678 //
 679 //    Coalesce left-hand chunk with right-hand chunk if and
 680 //    only if:
 681 //
 682 //      EITHER
 683 //        . left-hand chunk is of a size that is coal-overpopulated
 684 //      OR
 685 //        . right-hand chunk is close-to-mountain
 686   void smallCoalBirth(size_t size);
 687   void smallCoalDeath(size_t size);
 688   void coalBirth(size_t size);
 689   void coalDeath(size_t size);
 690   void smallSplitBirth(size_t size);
 691   void smallSplitDeath(size_t size);
 692   void split_birth(size_t size);
 693   void splitDeath(size_t size);
 694   void split(size_t from, size_t to1);
 695 
 696   double flsFrag() const;
 697 };
 698 
 699 // A parallel-GC-thread-local allocation buffer for allocation into a
 700 // CompactibleFreeListSpace.
 701 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {
 702   // The space that this buffer allocates into.
 703   CompactibleFreeListSpace* _cfls;
 704 
 705   // Our local free lists.
 706   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
 707 
 708   // Initialized from a command-line arg.
 709 
 710   // Allocation statistics in support of dynamic adjustment of
 711   // #blocks to claim per get_from_global_pool() call below.
 712   static AdaptiveWeightedAverage
 713                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
 714   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
 715   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
 716   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
 717 
 718   // Internal work method
 719   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
 720 
 721 public:
 722   static const int _default_dynamic_old_plab_size = 16;
 723   static const int _default_static_old_plab_size  = 50;
 724 
 725   CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);
 726 
 727   // Allocate and return a block of the given size, or else return NULL.
 728   HeapWord* alloc(size_t word_sz);
 729 
 730   // Return any unused portions of the buffer to the global pool.
 731   void retire(int tid);
 732 
 733   // Dynamic OldPLABSize sizing
 734   static void compute_desired_plab_size();
 735   // When the settings are modified from default static initialization
 736   static void modify_initialization(size_t n, unsigned wt);
 737 };
 738 
 739 size_t PromotionInfo::refillSize() const {
 740   const size_t CMSSpoolBlockSize = 256;
 741   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
 742                                    * CMSSpoolBlockSize);
 743   return CompactibleFreeListSpace::adjustObjectSize(sz);
 744 }
 745 
 746 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP