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  24 
  25 #ifndef SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP
  26 #define SHARE_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   template <typename SpaceType>
 113   friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
 114   template <typename SpaceType>
 115   friend void CompactibleSpace::scan_and_compact(SpaceType* space);
 116   template <typename SpaceType>
 117   friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
 118   template <typename SpaceType>
 119   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
 120 
 121   // "Size" of chunks of work (executed during parallel remark phases
 122   // of CMS collection); this probably belongs in CMSCollector, although
 123   // it's cached here because it's used in
 124   // initialize_sequential_subtasks_for_rescan() which modifies
 125   // par_seq_tasks which also lives in Space. XXX
 126   const size_t _rescan_task_size;
 127   const size_t _marking_task_size;
 128 
 129   // Yet another sequential tasks done structure. This supports
 130   // CMS GC, where we have threads dynamically
 131   // claiming sub-tasks from a larger parallel task.
 132   SequentialSubTasksDone _conc_par_seq_tasks;
 133 
 134   BlockOffsetArrayNonContigSpace _bt;
 135 
 136   CMSCollector* _collector;
 137   ConcurrentMarkSweepGeneration* _old_gen;
 138 
 139   // Data structures for free blocks (used during allocation/sweeping)
 140 
 141   // Allocation is done linearly from two different blocks depending on
 142   // whether the request is small or large, in an effort to reduce
 143   // fragmentation. We assume that any locking for allocation is done
 144   // by the containing generation. Thus, none of the methods in this
 145   // space are re-entrant.
 146   enum SomeConstants {
 147     SmallForLinearAlloc = 16,        // size < this then use _sLAB
 148     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
 149     IndexSetSize        = SmallForDictionary  // keep this odd-sized
 150   };
 151   static size_t IndexSetStart;
 152   static size_t IndexSetStride;
 153   static size_t _min_chunk_size_in_bytes;
 154 
 155  private:
 156   enum FitStrategyOptions {
 157     FreeBlockStrategyNone = 0,
 158     FreeBlockBestFitFirst
 159   };
 160 
 161   PromotionInfo _promoInfo;
 162 
 163   // Helps to impose a global total order on freelistLock ranks;
 164   // assumes that CFLSpace's are allocated in global total order
 165   static int   _lockRank;
 166 
 167   // A lock protecting the free lists and free blocks;
 168   // mutable because of ubiquity of locking even for otherwise const methods
 169   mutable Mutex _freelistLock;
 170 
 171   // Locking verifier convenience function
 172   void assert_locked() const PRODUCT_RETURN;
 173   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
 174 
 175   // Linear allocation blocks
 176   LinearAllocBlock _smallLinearAllocBlock;
 177 
 178   AFLBinaryTreeDictionary* _dictionary;    // Pointer to dictionary for large size blocks
 179 
 180   // Indexed array for small size blocks
 181   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
 182 
 183   // Allocation strategy
 184   bool _fitStrategy;  // Use best fit strategy
 185 
 186   // This is an address close to the largest free chunk in the heap.
 187   // It is currently assumed to be at the end of the heap.  Free
 188   // chunks with addresses greater than nearLargestChunk are coalesced
 189   // in an effort to maintain a large chunk at the end of the heap.
 190   HeapWord*  _nearLargestChunk;
 191 
 192   // Used to keep track of limit of sweep for the space
 193   HeapWord* _sweep_limit;
 194 
 195   // Stable value of used().
 196   size_t _used_stable;
 197 
 198   // Used to make the young collector update the mod union table
 199   MemRegionClosure* _preconsumptionDirtyCardClosure;
 200 
 201   // Support for compacting cms
 202   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 203   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
 204 
 205   // Initialization helpers.
 206   void initializeIndexedFreeListArray();
 207 
 208   // Extra stuff to manage promotion parallelism.
 209 
 210   // A lock protecting the dictionary during par promotion allocation.
 211   mutable Mutex _parDictionaryAllocLock;
 212   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
 213 
 214   // Locks protecting the exact lists during par promotion allocation.
 215   Mutex* _indexedFreeListParLocks[IndexSetSize];
 216 
 217   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
 218   // required to be smaller than "IndexSetSize".)  If successful,
 219   // adds them to "fl", which is required to be an empty free list.
 220   // If the count of "fl" is negative, it's absolute value indicates a
 221   // number of free chunks that had been previously "borrowed" from global
 222   // list of size "word_sz", and must now be decremented.
 223   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 224 
 225   // Used by par_get_chunk_of_blocks() for the chunks from the
 226   // indexed_free_lists.
 227   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 228 
 229   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
 230   // evenly splittable into "n" "word_sz" chunks.  Returns that
 231   // evenly splittable chunk.  May split a larger chunk to get the
 232   // evenly splittable chunk.
 233   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
 234 
 235   // Used by par_get_chunk_of_blocks() for the chunks from the
 236   // dictionary.
 237   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 238 
 239   // Allocation helper functions
 240   // Allocate using a strategy that takes from the indexed free lists
 241   // first.  This allocation strategy assumes a companion sweeping
 242   // strategy that attempts to keep the needed number of chunks in each
 243   // indexed free lists.
 244   HeapWord* allocate_adaptive_freelists(size_t size);
 245 
 246   // Gets a chunk from the linear allocation block (LinAB).  If there
 247   // is not enough space in the LinAB, refills it.
 248   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
 249   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
 250   // Get a chunk from the space remaining in the linear allocation block.  Do
 251   // not attempt to refill if the space is not available, return NULL.  Do the
 252   // repairs on the linear allocation block as appropriate.
 253   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
 254   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
 255 
 256   // Helper function for getChunkFromIndexedFreeList.
 257   // Replenish the indexed free list for this "size".  Do not take from an
 258   // underpopulated size.
 259   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
 260 
 261   // Get a chunk from the indexed free list.  If the indexed free list
 262   // does not have a free chunk, try to replenish the indexed free list
 263   // then get the free chunk from the replenished indexed free list.
 264   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
 265 
 266   // The returned chunk may be larger than requested (or null).
 267   FreeChunk* getChunkFromDictionary(size_t size);
 268   // The returned chunk is the exact size requested (or null).
 269   FreeChunk* getChunkFromDictionaryExact(size_t size);
 270 
 271   // Find a chunk in the indexed free list that is the best
 272   // fit for size "numWords".
 273   FreeChunk* bestFitSmall(size_t numWords);
 274   // For free list "fl" of chunks of size > numWords,
 275   // remove a chunk, split off a chunk of size numWords
 276   // and return it.  The split off remainder is returned to
 277   // the free lists.  The old name for getFromListGreater
 278   // was lookInListGreater.
 279   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
 280   // Get a chunk in the indexed free list or dictionary,
 281   // by considering a larger chunk and splitting it.
 282   FreeChunk* getChunkFromGreater(size_t numWords);
 283   //  Verify that the given chunk is in the indexed free lists.
 284   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
 285   // Remove the specified chunk from the indexed free lists.
 286   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
 287   // Remove the specified chunk from the dictionary.
 288   void       removeChunkFromDictionary(FreeChunk* fc);
 289   // Split a free chunk into a smaller free chunk of size "new_size".
 290   // Return the smaller free chunk and return the remainder to the
 291   // free lists.
 292   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
 293   // Add a chunk to the free lists.
 294   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
 295   // Add a chunk to the free lists, preferring to suffix it
 296   // to the last free chunk at end of space if possible, and
 297   // updating the block census stats as well as block offset table.
 298   // Take any locks as appropriate if we are multithreaded.
 299   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
 300   // Add a free chunk to the indexed free lists.
 301   void       returnChunkToFreeList(FreeChunk* chunk);
 302   // Add a free chunk to the dictionary.
 303   void       returnChunkToDictionary(FreeChunk* chunk);
 304 
 305   // Functions for maintaining the linear allocation buffers (LinAB).
 306   // Repairing a linear allocation block refers to operations
 307   // performed on the remainder of a LinAB after an allocation
 308   // has been made from it.
 309   void       repairLinearAllocationBlocks();
 310   void       repairLinearAllocBlock(LinearAllocBlock* blk);
 311   void       refillLinearAllocBlock(LinearAllocBlock* blk);
 312   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
 313   void       refillLinearAllocBlocksIfNeeded();
 314 
 315   void       verify_objects_initialized() const;
 316 
 317   // Statistics reporting helper functions
 318   void       reportFreeListStatistics(const char* title) const;
 319   void       reportIndexedFreeListStatistics(outputStream* st) const;
 320   size_t     maxChunkSizeInIndexedFreeLists() const;
 321   size_t     numFreeBlocksInIndexedFreeLists() const;
 322   // Accessor
 323   HeapWord* unallocated_block() const {
 324     if (BlockOffsetArrayUseUnallocatedBlock) {
 325       HeapWord* ub = _bt.unallocated_block();
 326       assert(ub >= bottom() &&
 327              ub <= end(), "space invariant");
 328       return ub;
 329     } else {
 330       return end();
 331     }
 332   }
 333   void freed(HeapWord* start, size_t size) {
 334     _bt.freed(start, size);
 335   }
 336 
 337   // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
 338   // See comments for CompactibleSpace for more information.
 339   inline HeapWord* scan_limit() const {
 340     return end();
 341   }
 342 
 343   inline bool scanned_block_is_obj(const HeapWord* addr) const {
 344     return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
 345   }
 346 
 347   inline size_t scanned_block_size(const HeapWord* addr) const {
 348     return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
 349   }
 350 
 351   inline size_t adjust_obj_size(size_t size) const {
 352     return adjustObjectSize(size);
 353   }
 354 
 355   inline size_t obj_size(const HeapWord* addr) const;
 356 
 357  protected:
 358   // Reset the indexed free list to its initial empty condition.
 359   void resetIndexedFreeListArray();
 360   // Reset to an initial state with a single free block described
 361   // by the MemRegion parameter.
 362   void reset(MemRegion mr);
 363   // Return the total number of words in the indexed free lists.
 364   size_t     totalSizeInIndexedFreeLists() const;
 365 
 366  public:
 367   // Constructor
 368   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
 369   // Accessors
 370   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
 371   AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }
 372   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
 373   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
 374 
 375   // Set CMS global values.
 376   static void set_cms_values();
 377 
 378   // Return the free chunk at the end of the space.  If no such
 379   // chunk exists, return NULL.
 380   FreeChunk* find_chunk_at_end();
 381 
 382   void set_collector(CMSCollector* collector) { _collector = collector; }
 383 
 384   // Support for parallelization of rescan and marking.
 385   const size_t rescan_task_size()  const { return _rescan_task_size;  }
 386   const size_t marking_task_size() const { return _marking_task_size; }
 387   // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.
 388   const size_t max_flag_size_for_task_size() const;
 389   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
 390   void initialize_sequential_subtasks_for_rescan(int n_threads);
 391   void initialize_sequential_subtasks_for_marking(int n_threads,
 392          HeapWord* low = NULL);
 393 
 394   virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
 395     return _preconsumptionDirtyCardClosure;
 396   }
 397 
 398   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
 399     _preconsumptionDirtyCardClosure = cl;
 400   }
 401 
 402   // Space enquiries
 403   size_t used() const;
 404   size_t free() const;
 405   size_t max_alloc_in_words() const;
 406   // XXX: should have a less conservative used_region() than that of
 407   // Space; we could consider keeping track of highest allocated
 408   // address and correcting that at each sweep, as the sweeper
 409   // goes through the entire allocated part of the generation. We
 410   // could also use that information to keep the sweeper from
 411   // sweeping more than is necessary. The allocator and sweeper will
 412   // of course need to synchronize on this, since the sweeper will
 413   // try to bump down the address and the allocator will try to bump it up.
 414   // For now, however, we'll just use the default used_region()
 415   // which overestimates the region by returning the entire
 416   // committed region (this is safe, but inefficient).
 417 
 418   // Returns monotonically increasing stable used space bytes for CMS.
 419   // This is required for jstat and other memory monitoring tools
 420   // that might otherwise see inconsistent used space values during a garbage
 421   // collection, promotion or allocation into compactibleFreeListSpace.
 422   // The value returned by this function might be smaller than the
 423   // actual value.
 424   size_t used_stable() const;
 425   // Recalculate and cache the current stable used() value. Only to be called
 426   // in places where we can be sure that the result is stable.
 427   void recalculate_used_stable();
 428 
 429   // Returns a subregion of the space containing all the objects in
 430   // the space.
 431   MemRegion used_region() const {
 432     return MemRegion(bottom(),
 433                      BlockOffsetArrayUseUnallocatedBlock ?
 434                      unallocated_block() : end());
 435   }
 436 
 437   virtual bool is_free_block(const HeapWord* p) const;
 438 
 439   // Resizing support
 440   void set_end(HeapWord* value);  // override
 441 
 442   // Never mangle CompactibleFreeListSpace
 443   void mangle_unused_area() {}
 444   void mangle_unused_area_complete() {}
 445 
 446   // Mutual exclusion support
 447   Mutex* freelistLock() const { return &_freelistLock; }
 448 
 449   // Iteration support
 450   void oop_iterate(OopIterateClosure* cl);
 451 
 452   void object_iterate(ObjectClosure* blk);
 453   // Apply the closure to each object in the space whose references
 454   // point to objects in the heap.  The usage of CompactibleFreeListSpace
 455   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
 456   // objects in the space with references to objects that are no longer
 457   // valid.  For example, an object may reference another object
 458   // that has already been sweep up (collected).  This method uses
 459   // obj_is_alive() to determine whether it is safe to iterate of
 460   // an object.
 461   void safe_object_iterate(ObjectClosure* blk);
 462 
 463   // Iterate over all objects that intersect with mr, calling "cl->do_object"
 464   // on each.  There is an exception to this: if this closure has already
 465   // been invoked on an object, it may skip such objects in some cases.  This is
 466   // Most likely to happen in an "upwards" (ascending address) iteration of
 467   // MemRegions.
 468   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 469 
 470   // Requires that "mr" be entirely within the space.
 471   // Apply "cl->do_object" to all objects that intersect with "mr".
 472   // If the iteration encounters an unparseable portion of the region,
 473   // terminate the iteration and return the address of the start of the
 474   // subregion that isn't done.  Return of "NULL" indicates that the
 475   // iteration completed.
 476   HeapWord* object_iterate_careful_m(MemRegion mr,
 477                                      ObjectClosureCareful* cl);
 478 
 479   // Override: provides a DCTO_CL specific to this kind of space.
 480   DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
 481                                      CardTable::PrecisionStyle precision,
 482                                      HeapWord* boundary,
 483                                      bool parallel);
 484 
 485   void blk_iterate(BlkClosure* cl);
 486   void blk_iterate_careful(BlkClosureCareful* cl);
 487   HeapWord* block_start_const(const void* p) const;
 488   HeapWord* block_start_careful(const void* p) const;
 489   size_t block_size(const HeapWord* p) const;
 490   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
 491   bool block_is_obj(const HeapWord* p) const;
 492   bool obj_is_alive(const HeapWord* p) const;
 493   size_t block_size_nopar(const HeapWord* p) const;
 494   bool block_is_obj_nopar(const HeapWord* p) const;
 495 
 496   // Iteration support for promotion
 497   void save_marks();
 498   bool no_allocs_since_save_marks();
 499 
 500   // Iteration support for sweeping
 501   void save_sweep_limit() {
 502     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
 503                    unallocated_block() : end();
 504     log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT
 505                                  "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
 506                                  p2i(_sweep_limit), p2i(bottom()), p2i(end()));
 507   }
 508   NOT_PRODUCT(
 509     void clear_sweep_limit() { _sweep_limit = NULL; }
 510   )
 511   HeapWord* sweep_limit() { return _sweep_limit; }
 512 
 513   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 514   // promoted into this generation since the most recent save_marks() call.
 515   // Fields in objects allocated by applications of the closure
 516   // *are* included in the iteration. Thus, when the iteration completes
 517   // there should be no further such objects remaining.
 518   template <typename OopClosureType>
 519   void oop_since_save_marks_iterate(OopClosureType* blk);
 520 
 521   // Allocation support
 522   HeapWord* allocate(size_t size);
 523   HeapWord* par_allocate(size_t size);
 524 
 525   oop       promote(oop obj, size_t obj_size);
 526   void      gc_prologue();
 527   void      gc_epilogue();
 528 
 529   // This call is used by a containing CMS generation / collector
 530   // to inform the CFLS space that a sweep has been completed
 531   // and that the space can do any related house-keeping functions.
 532   void      sweep_completed();
 533 
 534   // For an object in this space, the mark-word's two
 535   // LSB's having the value [11] indicates that it has been
 536   // promoted since the most recent call to save_marks() on
 537   // this generation and has not subsequently been iterated
 538   // over (using oop_since_save_marks_iterate() above).
 539   // This property holds only for single-threaded collections,
 540   // and is typically used for Cheney scans; for MT scavenges,
 541   // the property holds for all objects promoted during that
 542   // scavenge for the duration of the scavenge and is used
 543   // by card-scanning to avoid scanning objects (being) promoted
 544   // during that scavenge.
 545   bool obj_allocated_since_save_marks(const oop obj) const {
 546     assert(is_in_reserved(obj), "Wrong space?");
 547     return ((PromotedObject*)obj)->hasPromotedMark();
 548   }
 549 
 550   // A worst-case estimate of the space required (in HeapWords) to expand the
 551   // heap when promoting an obj of size obj_size.
 552   size_t expansionSpaceRequired(size_t obj_size) const;
 553 
 554   FreeChunk* allocateScratch(size_t size);
 555 
 556   // Returns true if either the small or large linear allocation buffer is empty.
 557   bool       linearAllocationWouldFail() const;
 558 
 559   // Adjust the chunk for the minimum size.  This version is called in
 560   // most cases in CompactibleFreeListSpace methods.
 561   inline static size_t adjustObjectSize(size_t size) {
 562     return align_object_size(MAX2(size, (size_t)MinChunkSize));
 563   }
 564   // This is a virtual version of adjustObjectSize() that is called
 565   // only occasionally when the compaction space changes and the type
 566   // of the new compaction space is is only known to be CompactibleSpace.
 567   size_t adjust_object_size_v(size_t size) const {
 568     return adjustObjectSize(size);
 569   }
 570   // Minimum size of a free block.
 571   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
 572   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
 573   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
 574               bool coalesced);
 575 
 576   // Support for compaction.
 577   void prepare_for_compaction(CompactPoint* cp);
 578   void adjust_pointers();
 579   void compact();
 580   // Reset the space to reflect the fact that a compaction of the
 581   // space has been done.
 582   virtual void reset_after_compaction();
 583 
 584   // Debugging support.
 585   void print()                            const;
 586   void print_on(outputStream* st)         const;
 587   void prepare_for_verify();
 588   void verify()                           const;
 589   void verifyFreeLists()                  const PRODUCT_RETURN;
 590   void verifyIndexedFreeLists()           const;
 591   void verifyIndexedFreeList(size_t size) const;
 592   // Verify that the given chunk is in the free lists:
 593   // i.e. either the binary tree dictionary, the indexed free lists
 594   // or the linear allocation block.
 595   bool verify_chunk_in_free_list(FreeChunk* fc) const;
 596   // Verify that the given chunk is the linear allocation block.
 597   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
 598   // Do some basic checks on the the free lists.
 599   void check_free_list_consistency()      const PRODUCT_RETURN;
 600 
 601   // Printing support
 602   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
 603   void print_indexed_free_lists(outputStream* st) const;
 604   void print_dictionary_free_lists(outputStream* st) const;
 605   void print_promo_info_blocks(outputStream* st) const;
 606 
 607   NOT_PRODUCT (
 608     void initializeIndexedFreeListArrayReturnedBytes();
 609     size_t sumIndexedFreeListArrayReturnedBytes();
 610     // Return the total number of chunks in the indexed free lists.
 611     size_t totalCountInIndexedFreeLists() const;
 612     // Return the total number of chunks in the space.
 613     size_t totalCount();
 614   )
 615 
 616   // The census consists of counts of the quantities such as
 617   // the current count of the free chunks, number of chunks
 618   // created as a result of the split of a larger chunk or
 619   // coalescing of smaller chucks, etc.  The counts in the
 620   // census is used to make decisions on splitting and
 621   // coalescing of chunks during the sweep of garbage.
 622 
 623   // Print the statistics for the free lists.
 624   void printFLCensus(size_t sweep_count) const;
 625 
 626   // Statistics functions
 627   // Initialize census for lists before the sweep.
 628   void beginSweepFLCensus(float inter_sweep_current,
 629                           float inter_sweep_estimate,
 630                           float intra_sweep_estimate);
 631   // Set the surplus for each of the free lists.
 632   void setFLSurplus();
 633   // Set the hint for each of the free lists.
 634   void setFLHints();
 635   // Clear the census for each of the free lists.
 636   void clearFLCensus();
 637   // Perform functions for the census after the end of the sweep.
 638   void endSweepFLCensus(size_t sweep_count);
 639   // Return true if the count of free chunks is greater
 640   // than the desired number of free chunks.
 641   bool coalOverPopulated(size_t size);
 642 
 643 // Record (for each size):
 644 //
 645 //   split-births = #chunks added due to splits in (prev-sweep-end,
 646 //      this-sweep-start)
 647 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
 648 //      this-sweep-start)
 649 //   num-curr     = #chunks at start of this sweep
 650 //   num-prev     = #chunks at end of previous sweep
 651 //
 652 // The above are quantities that are measured. Now define:
 653 //
 654 //   num-desired := num-prev + split-births - split-deaths - num-curr
 655 //
 656 // Roughly, num-prev + split-births is the supply,
 657 // split-deaths is demand due to other sizes
 658 // and num-curr is what we have left.
 659 //
 660 // Thus, num-desired is roughly speaking the "legitimate demand"
 661 // for blocks of this size and what we are striving to reach at the
 662 // end of the current sweep.
 663 //
 664 // For a given list, let num-len be its current population.
 665 // Define, for a free list of a given size:
 666 //
 667 //   coal-overpopulated := num-len >= num-desired * coal-surplus
 668 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
 669 // coalescing -- we do not coalesce unless we think that the current
 670 // supply has exceeded the estimated demand by more than 5%).
 671 //
 672 // For the set of sizes in the binary tree, which is neither dense nor
 673 // closed, it may be the case that for a particular size we have never
 674 // had, or do not now have, or did not have at the previous sweep,
 675 // chunks of that size. We need to extend the definition of
 676 // coal-overpopulated to such sizes as well:
 677 //
 678 //   For a chunk in/not in the binary tree, extend coal-overpopulated
 679 //   defined above to include all sizes as follows:
 680 //
 681 //   . a size that is non-existent is coal-overpopulated
 682 //   . a size that has a num-desired <= 0 as defined above is
 683 //     coal-overpopulated.
 684 //
 685 // Also define, for a chunk heap-offset C and mountain heap-offset M:
 686 //
 687 //   close-to-mountain := C >= 0.99 * M
 688 //
 689 // Now, the coalescing strategy is:
 690 //
 691 //    Coalesce left-hand chunk with right-hand chunk if and
 692 //    only if:
 693 //
 694 //      EITHER
 695 //        . left-hand chunk is of a size that is coal-overpopulated
 696 //      OR
 697 //        . right-hand chunk is close-to-mountain
 698   void smallCoalBirth(size_t size);
 699   void smallCoalDeath(size_t size);
 700   void coalBirth(size_t size);
 701   void coalDeath(size_t size);
 702   void smallSplitBirth(size_t size);
 703   void smallSplitDeath(size_t size);
 704   void split_birth(size_t size);
 705   void splitDeath(size_t size);
 706   void split(size_t from, size_t to1);
 707 
 708   double flsFrag() const;
 709 };
 710 
 711 // A parallel-GC-thread-local allocation buffer for allocation into a
 712 // CompactibleFreeListSpace.
 713 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {
 714   // The space that this buffer allocates into.
 715   CompactibleFreeListSpace* _cfls;
 716 
 717   // Our local free lists.
 718   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
 719 
 720   // Initialized from a command-line arg.
 721 
 722   // Allocation statistics in support of dynamic adjustment of
 723   // #blocks to claim per get_from_global_pool() call below.
 724   static AdaptiveWeightedAverage
 725                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
 726   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
 727   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
 728   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
 729 
 730   // Internal work method
 731   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
 732 
 733 public:
 734   static const int _default_dynamic_old_plab_size = 16;
 735   static const int _default_static_old_plab_size  = 50;
 736 
 737   CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);
 738 
 739   // Allocate and return a block of the given size, or else return NULL.
 740   HeapWord* alloc(size_t word_sz);
 741 
 742   // Return any unused portions of the buffer to the global pool.
 743   void retire(int tid);
 744 
 745   // Dynamic OldPLABSize sizing
 746   static void compute_desired_plab_size();
 747   // When the settings are modified from default static initialization
 748   static void modify_initialization(size_t n, unsigned wt);
 749 };
 750 
 751 size_t PromotionInfo::refillSize() const {
 752   const size_t CMSSpoolBlockSize = 256;
 753   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markWord)
 754                                    * CMSSpoolBlockSize);
 755   return CompactibleFreeListSpace::adjustObjectSize(sz);
 756 }
 757 
 758 #endif // SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP