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