1 /*
   2  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP
  27 
  28 #include "gc_implementation/concurrentMarkSweep/adaptiveFreeList.hpp"
  29 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
  30 #include "memory/binaryTreeDictionary.hpp"
  31 #include "memory/blockOffsetTable.inline.hpp"
  32 #include "memory/freeList.hpp"
  33 #include "memory/space.hpp"
  34 
  35 // Classes in support of keeping track of promotions into a non-Contiguous
  36 // space, in this case a CompactibleFreeListSpace.
  37 
  38 // Forward declarations
  39 class CompactibleFreeListSpace;
  40 class BlkClosure;
  41 class BlkClosureCareful;
  42 class FreeChunk;
  43 class UpwardsObjectClosure;
  44 class ObjectClosureCareful;
  45 class Klass;
  46 
  47 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
  48  public:
  49   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
  50     _allocation_size_limit(0) {}
  51   void set(HeapWord* ptr, size_t word_size, size_t refill_size,
  52     size_t allocation_size_limit) {
  53     _ptr = ptr;
  54     _word_size = word_size;
  55     _refillSize = refill_size;
  56     _allocation_size_limit = allocation_size_limit;
  57   }
  58   HeapWord* _ptr;
  59   size_t    _word_size;
  60   size_t    _refillSize;
  61   size_t    _allocation_size_limit;  // largest size that will be allocated
  62 
  63   void print_on(outputStream* st) const;
  64 };
  65 
  66 // Concrete subclass of CompactibleSpace that implements
  67 // a free list space, such as used in the concurrent mark sweep
  68 // generation.
  69 
  70 class CompactibleFreeListSpace: public CompactibleSpace {
  71   friend class VMStructs;
  72   friend class ConcurrentMarkSweepGeneration;
  73   friend class ASConcurrentMarkSweepGeneration;
  74   friend class CMSCollector;
  75   // Local alloc buffer for promotion into this space.
  76   friend class CFLS_LAB;
  77 
  78   // "Size" of chunks of work (executed during parallel remark phases
  79   // of CMS collection); this probably belongs in CMSCollector, although
  80   // it's cached here because it's used in
  81   // initialize_sequential_subtasks_for_rescan() which modifies
  82   // par_seq_tasks which also lives in Space. XXX
  83   const size_t _rescan_task_size;
  84   const size_t _marking_task_size;
  85 
  86   // Yet another sequential tasks done structure. This supports
  87   // CMS GC, where we have threads dynamically
  88   // claiming sub-tasks from a larger parallel task.
  89   SequentialSubTasksDone _conc_par_seq_tasks;
  90 
  91   BlockOffsetArrayNonContigSpace _bt;
  92 
  93   CMSCollector* _collector;
  94   ConcurrentMarkSweepGeneration* _gen;
  95 
  96   // Data structures for free blocks (used during allocation/sweeping)
  97 
  98   // Allocation is done linearly from two different blocks depending on
  99   // whether the request is small or large, in an effort to reduce
 100   // fragmentation. We assume that any locking for allocation is done
 101   // by the containing generation. Thus, none of the methods in this
 102   // space are re-entrant.
 103   enum SomeConstants {
 104     SmallForLinearAlloc = 16,        // size < this then use _sLAB
 105     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
 106     IndexSetSize        = SmallForDictionary  // keep this odd-sized
 107   };
 108   static size_t IndexSetStart;
 109   static size_t IndexSetStride;
 110 
 111  private:
 112   enum FitStrategyOptions {
 113     FreeBlockStrategyNone = 0,
 114     FreeBlockBestFitFirst
 115   };
 116 
 117   PromotionInfo _promoInfo;
 118 
 119   // helps to impose a global total order on freelistLock ranks;
 120   // assumes that CFLSpace's are allocated in global total order
 121   static int   _lockRank;
 122 
 123   // a lock protecting the free lists and free blocks;
 124   // mutable because of ubiquity of locking even for otherwise const methods
 125   mutable Mutex _freelistLock;
 126   // locking verifier convenience function
 127   void assert_locked() const PRODUCT_RETURN;
 128   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
 129 
 130   // Linear allocation blocks
 131   LinearAllocBlock _smallLinearAllocBlock;
 132 
 133   FreeBlockDictionary<FreeChunk>::DictionaryChoice _dictionaryChoice;
 134   FreeBlockDictionary<FreeChunk>* _dictionary;    // ptr to dictionary for large size blocks
 135 
 136   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
 137                                        // indexed array for small size blocks
 138   // allocation stategy
 139   bool       _fitStrategy;      // Use best fit strategy.
 140   bool       _adaptive_freelists; // Use adaptive freelists
 141 
 142   // This is an address close to the largest free chunk in the heap.
 143   // It is currently assumed to be at the end of the heap.  Free
 144   // chunks with addresses greater than nearLargestChunk are coalesced
 145   // in an effort to maintain a large chunk at the end of the heap.
 146   HeapWord*  _nearLargestChunk;
 147 
 148   // Used to keep track of limit of sweep for the space
 149   HeapWord* _sweep_limit;
 150 
 151   // Support for compacting cms
 152   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 153   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
 154 
 155   // Initialization helpers.
 156   void initializeIndexedFreeListArray();
 157 
 158   // Extra stuff to manage promotion parallelism.
 159 
 160   // a lock protecting the dictionary during par promotion allocation.
 161   mutable Mutex _parDictionaryAllocLock;
 162   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
 163 
 164   // Locks protecting the exact lists during par promotion allocation.
 165   Mutex* _indexedFreeListParLocks[IndexSetSize];
 166 
 167   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
 168   // required to be smaller than "IndexSetSize".)  If successful,
 169   // adds them to "fl", which is required to be an empty free list.
 170   // If the count of "fl" is negative, it's absolute value indicates a
 171   // number of free chunks that had been previously "borrowed" from global
 172   // list of size "word_sz", and must now be decremented.
 173   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 174 
 175   // Allocation helper functions
 176   // Allocate using a strategy that takes from the indexed free lists
 177   // first.  This allocation strategy assumes a companion sweeping
 178   // strategy that attempts to keep the needed number of chunks in each
 179   // indexed free lists.
 180   HeapWord* allocate_adaptive_freelists(size_t size);
 181   // Allocate from the linear allocation buffers first.  This allocation
 182   // strategy assumes maximal coalescing can maintain chunks large enough
 183   // to be used as linear allocation buffers.
 184   HeapWord* allocate_non_adaptive_freelists(size_t size);
 185 
 186   // Gets a chunk from the linear allocation block (LinAB).  If there
 187   // is not enough space in the LinAB, refills it.
 188   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
 189   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
 190   // Get a chunk from the space remaining in the linear allocation block.  Do
 191   // not attempt to refill if the space is not available, return NULL.  Do the
 192   // repairs on the linear allocation block as appropriate.
 193   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
 194   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
 195 
 196   // Helper function for getChunkFromIndexedFreeList.
 197   // Replenish the indexed free list for this "size".  Do not take from an
 198   // underpopulated size.
 199   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
 200 
 201   // Get a chunk from the indexed free list.  If the indexed free list
 202   // does not have a free chunk, try to replenish the indexed free list
 203   // then get the free chunk from the replenished indexed free list.
 204   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
 205 
 206   // The returned chunk may be larger than requested (or null).
 207   FreeChunk* getChunkFromDictionary(size_t size);
 208   // The returned chunk is the exact size requested (or null).
 209   FreeChunk* getChunkFromDictionaryExact(size_t size);
 210 
 211   // Find a chunk in the indexed free list that is the best
 212   // fit for size "numWords".
 213   FreeChunk* bestFitSmall(size_t numWords);
 214   // For free list "fl" of chunks of size > numWords,
 215   // remove a chunk, split off a chunk of size numWords
 216   // and return it.  The split off remainder is returned to
 217   // the free lists.  The old name for getFromListGreater
 218   // was lookInListGreater.
 219   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
 220   // Get a chunk in the indexed free list or dictionary,
 221   // by considering a larger chunk and splitting it.
 222   FreeChunk* getChunkFromGreater(size_t numWords);
 223   //  Verify that the given chunk is in the indexed free lists.
 224   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
 225   // Remove the specified chunk from the indexed free lists.
 226   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
 227   // Remove the specified chunk from the dictionary.
 228   void       removeChunkFromDictionary(FreeChunk* fc);
 229   // Split a free chunk into a smaller free chunk of size "new_size".
 230   // Return the smaller free chunk and return the remainder to the
 231   // free lists.
 232   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
 233   // Add a chunk to the free lists.
 234   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
 235   // Add a chunk to the free lists, preferring to suffix it
 236   // to the last free chunk at end of space if possible, and
 237   // updating the block census stats as well as block offset table.
 238   // Take any locks as appropriate if we are multithreaded.
 239   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
 240   // Add a free chunk to the indexed free lists.
 241   void       returnChunkToFreeList(FreeChunk* chunk);
 242   // Add a free chunk to the dictionary.
 243   void       returnChunkToDictionary(FreeChunk* chunk);
 244 
 245   // Functions for maintaining the linear allocation buffers (LinAB).
 246   // Repairing a linear allocation block refers to operations
 247   // performed on the remainder of a LinAB after an allocation
 248   // has been made from it.
 249   void       repairLinearAllocationBlocks();
 250   void       repairLinearAllocBlock(LinearAllocBlock* blk);
 251   void       refillLinearAllocBlock(LinearAllocBlock* blk);
 252   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
 253   void       refillLinearAllocBlocksIfNeeded();
 254 
 255   void       verify_objects_initialized() const;
 256 
 257   // Statistics reporting helper functions
 258   void       reportFreeListStatistics() const;
 259   void       reportIndexedFreeListStatistics() const;
 260   size_t     maxChunkSizeInIndexedFreeLists() const;
 261   size_t     numFreeBlocksInIndexedFreeLists() const;
 262   // Accessor
 263   HeapWord* unallocated_block() const {
 264     if (BlockOffsetArrayUseUnallocatedBlock) {
 265       HeapWord* ub = _bt.unallocated_block();
 266       assert(ub >= bottom() &&
 267              ub <= end(), "space invariant");
 268       return ub;
 269     } else {
 270       return end();
 271     }
 272   }
 273   void freed(HeapWord* start, size_t size) {
 274     _bt.freed(start, size);
 275   }
 276 
 277  protected:
 278   // reset the indexed free list to its initial empty condition.
 279   void resetIndexedFreeListArray();
 280   // reset to an initial state with a single free block described
 281   // by the MemRegion parameter.
 282   void reset(MemRegion mr);
 283   // Return the total number of words in the indexed free lists.
 284   size_t     totalSizeInIndexedFreeLists() const;
 285 
 286  public:
 287   // Constructor...
 288   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr,
 289                            bool use_adaptive_freelists,
 290                            FreeBlockDictionary<FreeChunk>::DictionaryChoice);
 291   // accessors
 292   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
 293   FreeBlockDictionary<FreeChunk>* dictionary() const { return _dictionary; }
 294   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
 295   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
 296 
 297   // Set CMS global values
 298   static void set_cms_values();
 299 
 300   // Return the free chunk at the end of the space.  If no such
 301   // chunk exists, return NULL.
 302   FreeChunk* find_chunk_at_end();
 303 
 304   bool adaptive_freelists() const { return _adaptive_freelists; }
 305 
 306   void set_collector(CMSCollector* collector) { _collector = collector; }
 307 
 308   // Support for parallelization of rescan and marking
 309   const size_t rescan_task_size()  const { return _rescan_task_size;  }
 310   const size_t marking_task_size() const { return _marking_task_size; }
 311   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
 312   void initialize_sequential_subtasks_for_rescan(int n_threads);
 313   void initialize_sequential_subtasks_for_marking(int n_threads,
 314          HeapWord* low = NULL);
 315 
 316   // Space enquiries
 317   size_t used() const;
 318   size_t free() const;
 319   size_t max_alloc_in_words() const;
 320   // XXX: should have a less conservative used_region() than that of
 321   // Space; we could consider keeping track of highest allocated
 322   // address and correcting that at each sweep, as the sweeper
 323   // goes through the entire allocated part of the generation. We
 324   // could also use that information to keep the sweeper from
 325   // sweeping more than is necessary. The allocator and sweeper will
 326   // of course need to synchronize on this, since the sweeper will
 327   // try to bump down the address and the allocator will try to bump it up.
 328   // For now, however, we'll just use the default used_region()
 329   // which overestimates the region by returning the entire
 330   // committed region (this is safe, but inefficient).
 331 
 332   // Returns a subregion of the space containing all the objects in
 333   // the space.
 334   MemRegion used_region() const {
 335     return MemRegion(bottom(),
 336                      BlockOffsetArrayUseUnallocatedBlock ?
 337                      unallocated_block() : end());
 338   }
 339 
 340   bool is_in(const void* p) const {
 341     return used_region().contains(p);
 342   }
 343 
 344   virtual bool is_free_block(const HeapWord* p) const;
 345 
 346   // Resizing support
 347   void set_end(HeapWord* value);  // override
 348 
 349   // mutual exclusion support
 350   Mutex* freelistLock() const { return &_freelistLock; }
 351 
 352   // Iteration support
 353   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
 354   void oop_iterate(ExtendedOopClosure* cl);
 355 
 356   void object_iterate(ObjectClosure* blk);
 357   // Apply the closure to each object in the space whose references
 358   // point to objects in the heap.  The usage of CompactibleFreeListSpace
 359   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
 360   // objects in the space with references to objects that are no longer
 361   // valid.  For example, an object may reference another object
 362   // that has already been sweep up (collected).  This method uses
 363   // obj_is_alive() to determine whether it is safe to iterate of
 364   // an object.
 365   void safe_object_iterate(ObjectClosure* blk);
 366   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 367 
 368   // Requires that "mr" be entirely within the space.
 369   // Apply "cl->do_object" to all objects that intersect with "mr".
 370   // If the iteration encounters an unparseable portion of the region,
 371   // terminate the iteration and return the address of the start of the
 372   // subregion that isn't done.  Return of "NULL" indicates that the
 373   // interation completed.
 374   virtual HeapWord*
 375        object_iterate_careful_m(MemRegion mr,
 376                                 ObjectClosureCareful* cl);
 377   virtual HeapWord*
 378        object_iterate_careful(ObjectClosureCareful* cl);
 379 
 380   // Override: provides a DCTO_CL specific to this kind of space.
 381   DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
 382                                      CardTableModRefBS::PrecisionStyle precision,
 383                                      HeapWord* boundary);
 384 
 385   void blk_iterate(BlkClosure* cl);
 386   void blk_iterate_careful(BlkClosureCareful* cl);
 387   HeapWord* block_start_const(const void* p) const;
 388   HeapWord* block_start_careful(const void* p) const;
 389   size_t block_size(const HeapWord* p) const;
 390   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
 391   bool block_is_obj(const HeapWord* p) const;
 392   bool obj_is_alive(const HeapWord* p) const;
 393   size_t block_size_nopar(const HeapWord* p) const;
 394   bool block_is_obj_nopar(const HeapWord* p) const;
 395 
 396   // iteration support for promotion
 397   void save_marks();
 398   bool no_allocs_since_save_marks();
 399   void object_iterate_since_last_GC(ObjectClosure* cl);
 400 
 401   // iteration support for sweeping
 402   void save_sweep_limit() {
 403     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
 404                    unallocated_block() : end();
 405     if (CMSTraceSweeper) {
 406       gclog_or_tty->print_cr(">>>>> Saving sweep limit " PTR_FORMAT
 407                              "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
 408                              _sweep_limit, bottom(), end());
 409     }
 410   }
 411   NOT_PRODUCT(
 412     void clear_sweep_limit() { _sweep_limit = NULL; }
 413   )
 414   HeapWord* sweep_limit() { return _sweep_limit; }
 415 
 416   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 417   // promoted into this generation since the most recent save_marks() call.
 418   // Fields in objects allocated by applications of the closure
 419   // *are* included in the iteration. Thus, when the iteration completes
 420   // there should be no further such objects remaining.
 421   #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 422     void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
 423   ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
 424   #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
 425 
 426   // Allocation support
 427   HeapWord* allocate(size_t size);
 428   HeapWord* par_allocate(size_t size);
 429 
 430   oop       promote(oop obj, size_t obj_size);
 431   void      gc_prologue();
 432   void      gc_epilogue();
 433 
 434   // This call is used by a containing CMS generation / collector
 435   // to inform the CFLS space that a sweep has been completed
 436   // and that the space can do any related house-keeping functions.
 437   void      sweep_completed();
 438 
 439   // For an object in this space, the mark-word's two
 440   // LSB's having the value [11] indicates that it has been
 441   // promoted since the most recent call to save_marks() on
 442   // this generation and has not subsequently been iterated
 443   // over (using oop_since_save_marks_iterate() above).
 444   // This property holds only for single-threaded collections,
 445   // and is typically used for Cheney scans; for MT scavenges,
 446   // the property holds for all objects promoted during that
 447   // scavenge for the duration of the scavenge and is used
 448   // by card-scanning to avoid scanning objects (being) promoted
 449   // during that scavenge.
 450   bool obj_allocated_since_save_marks(const oop obj) const {
 451     assert(is_in_reserved(obj), "Wrong space?");
 452     return ((PromotedObject*)obj)->hasPromotedMark();
 453   }
 454 
 455   // A worst-case estimate of the space required (in HeapWords) to expand the
 456   // heap when promoting an obj of size obj_size.
 457   size_t expansionSpaceRequired(size_t obj_size) const;
 458 
 459   FreeChunk* allocateScratch(size_t size);
 460 
 461   // returns true if either the small or large linear allocation buffer is empty.
 462   bool       linearAllocationWouldFail() const;
 463 
 464   // Adjust the chunk for the minimum size.  This version is called in
 465   // most cases in CompactibleFreeListSpace methods.
 466   inline static size_t adjustObjectSize(size_t size) {
 467     return (size_t) align_object_size(MAX2(size, (size_t)MinChunkSize));
 468   }
 469   // This is a virtual version of adjustObjectSize() that is called
 470   // only occasionally when the compaction space changes and the type
 471   // of the new compaction space is is only known to be CompactibleSpace.
 472   size_t adjust_object_size_v(size_t size) const {
 473     return adjustObjectSize(size);
 474   }
 475   // Minimum size of a free block.
 476   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
 477   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
 478   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
 479               bool coalesced);
 480 
 481   // Support for decisions regarding concurrent collection policy
 482   bool should_concurrent_collect() const;
 483 
 484   // Support for compaction
 485   void prepare_for_compaction(CompactPoint* cp);
 486   void adjust_pointers();
 487   void compact();
 488   // reset the space to reflect the fact that a compaction of the
 489   // space has been done.
 490   virtual void reset_after_compaction();
 491 
 492   // Debugging support
 493   void print()                            const;
 494   void print_on(outputStream* st)         const;
 495   void prepare_for_verify();
 496   void verify()                           const;
 497   void verifyFreeLists()                  const PRODUCT_RETURN;
 498   void verifyIndexedFreeLists()           const;
 499   void verifyIndexedFreeList(size_t size) const;
 500   // Verify that the given chunk is in the free lists:
 501   // i.e. either the binary tree dictionary, the indexed free lists
 502   // or the linear allocation block.
 503   bool verify_chunk_in_free_list(FreeChunk* fc) const;
 504   // Verify that the given chunk is the linear allocation block
 505   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
 506   // Do some basic checks on the the free lists.
 507   void check_free_list_consistency()      const PRODUCT_RETURN;
 508 
 509   // Printing support
 510   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
 511   void print_indexed_free_lists(outputStream* st) const;
 512   void print_dictionary_free_lists(outputStream* st) const;
 513   void print_promo_info_blocks(outputStream* st) const;
 514 
 515   NOT_PRODUCT (
 516     void initializeIndexedFreeListArrayReturnedBytes();
 517     size_t sumIndexedFreeListArrayReturnedBytes();
 518     // Return the total number of chunks in the indexed free lists.
 519     size_t totalCountInIndexedFreeLists() const;
 520     // Return the total numberof chunks in the space.
 521     size_t totalCount();
 522   )
 523 
 524   // The census consists of counts of the quantities such as
 525   // the current count of the free chunks, number of chunks
 526   // created as a result of the split of a larger chunk or
 527   // coalescing of smaller chucks, etc.  The counts in the
 528   // census is used to make decisions on splitting and
 529   // coalescing of chunks during the sweep of garbage.
 530 
 531   // Print the statistics for the free lists.
 532   void printFLCensus(size_t sweep_count) const;
 533 
 534   // Statistics functions
 535   // Initialize census for lists before the sweep.
 536   void beginSweepFLCensus(float inter_sweep_current,
 537                           float inter_sweep_estimate,
 538                           float intra_sweep_estimate);
 539   // Set the surplus for each of the free lists.
 540   void setFLSurplus();
 541   // Set the hint for each of the free lists.
 542   void setFLHints();
 543   // Clear the census for each of the free lists.
 544   void clearFLCensus();
 545   // Perform functions for the census after the end of the sweep.
 546   void endSweepFLCensus(size_t sweep_count);
 547   // Return true if the count of free chunks is greater
 548   // than the desired number of free chunks.
 549   bool coalOverPopulated(size_t size);
 550 
 551 // Record (for each size):
 552 //
 553 //   split-births = #chunks added due to splits in (prev-sweep-end,
 554 //      this-sweep-start)
 555 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
 556 //      this-sweep-start)
 557 //   num-curr     = #chunks at start of this sweep
 558 //   num-prev     = #chunks at end of previous sweep
 559 //
 560 // The above are quantities that are measured. Now define:
 561 //
 562 //   num-desired := num-prev + split-births - split-deaths - num-curr
 563 //
 564 // Roughly, num-prev + split-births is the supply,
 565 // split-deaths is demand due to other sizes
 566 // and num-curr is what we have left.
 567 //
 568 // Thus, num-desired is roughly speaking the "legitimate demand"
 569 // for blocks of this size and what we are striving to reach at the
 570 // end of the current sweep.
 571 //
 572 // For a given list, let num-len be its current population.
 573 // Define, for a free list of a given size:
 574 //
 575 //   coal-overpopulated := num-len >= num-desired * coal-surplus
 576 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
 577 // coalescing -- we do not coalesce unless we think that the current
 578 // supply has exceeded the estimated demand by more than 5%).
 579 //
 580 // For the set of sizes in the binary tree, which is neither dense nor
 581 // closed, it may be the case that for a particular size we have never
 582 // had, or do not now have, or did not have at the previous sweep,
 583 // chunks of that size. We need to extend the definition of
 584 // coal-overpopulated to such sizes as well:
 585 //
 586 //   For a chunk in/not in the binary tree, extend coal-overpopulated
 587 //   defined above to include all sizes as follows:
 588 //
 589 //   . a size that is non-existent is coal-overpopulated
 590 //   . a size that has a num-desired <= 0 as defined above is
 591 //     coal-overpopulated.
 592 //
 593 // Also define, for a chunk heap-offset C and mountain heap-offset M:
 594 //
 595 //   close-to-mountain := C >= 0.99 * M
 596 //
 597 // Now, the coalescing strategy is:
 598 //
 599 //    Coalesce left-hand chunk with right-hand chunk if and
 600 //    only if:
 601 //
 602 //      EITHER
 603 //        . left-hand chunk is of a size that is coal-overpopulated
 604 //      OR
 605 //        . right-hand chunk is close-to-mountain
 606   void smallCoalBirth(size_t size);
 607   void smallCoalDeath(size_t size);
 608   void coalBirth(size_t size);
 609   void coalDeath(size_t size);
 610   void smallSplitBirth(size_t size);
 611   void smallSplitDeath(size_t size);
 612   void split_birth(size_t size);
 613   void splitDeath(size_t size);
 614   void split(size_t from, size_t to1);
 615 
 616   double flsFrag() const;
 617 };
 618 
 619 // A parallel-GC-thread-local allocation buffer for allocation into a
 620 // CompactibleFreeListSpace.
 621 class CFLS_LAB : public CHeapObj<mtGC> {
 622   // The space that this buffer allocates into.
 623   CompactibleFreeListSpace* _cfls;
 624 
 625   // Our local free lists.
 626   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
 627 
 628   // Initialized from a command-line arg.
 629 
 630   // Allocation statistics in support of dynamic adjustment of
 631   // #blocks to claim per get_from_global_pool() call below.
 632   static AdaptiveWeightedAverage
 633                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
 634   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
 635   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
 636   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
 637 
 638   // Internal work method
 639   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
 640 
 641 public:
 642   CFLS_LAB(CompactibleFreeListSpace* cfls);
 643 
 644   // Allocate and return a block of the given size, or else return NULL.
 645   HeapWord* alloc(size_t word_sz);
 646 
 647   // Return any unused portions of the buffer to the global pool.
 648   void retire(int tid);
 649 
 650   // Dynamic OldPLABSize sizing
 651   static void compute_desired_plab_size();
 652   // When the settings are modified from default static initialization
 653   static void modify_initialization(size_t n, unsigned wt);
 654 };
 655 
 656 size_t PromotionInfo::refillSize() const {
 657   const size_t CMSSpoolBlockSize = 256;
 658   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
 659                                    * CMSSpoolBlockSize);
 660   return CompactibleFreeListSpace::adjustObjectSize(sz);
 661 }
 662 
 663 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_COMPACTIBLEFREELISTSPACE_HPP