1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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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/space.hpp"
  32 #include "logging/log.hpp"
  33 #include "memory/binaryTreeDictionary.hpp"
  34 #include "memory/freeList.hpp"
  35 
  36 // Classes in support of keeping track of promotions into a non-Contiguous
  37 // space, in this case a CompactibleFreeListSpace.
  38 
  39 // Forward declarations
  40 class CMSCollector;
  41 class CompactibleFreeListSpace;
  42 class ConcurrentMarkSweepGeneration;
  43 class BlkClosure;
  44 class BlkClosureCareful;
  45 class FreeChunk;
  46 class UpwardsObjectClosure;
  47 class ObjectClosureCareful;
  48 class Klass;
  49 
  50 class LinearAllocBlock VALUE_OBJ_CLASS_SPEC {
  51  public:
  52   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
  53     _allocation_size_limit(0) {}
  54   void set(HeapWord* ptr, size_t word_size, size_t refill_size,
  55     size_t allocation_size_limit) {
  56     _ptr = ptr;
  57     _word_size = word_size;
  58     _refillSize = refill_size;
  59     _allocation_size_limit = allocation_size_limit;
  60   }
  61   HeapWord* _ptr;
  62   size_t    _word_size;
  63   size_t    _refillSize;
  64   size_t    _allocation_size_limit;  // Largest size that will be allocated
  65 
  66   void print_on(outputStream* st) const;
  67 };
  68 
  69 // Concrete subclass of CompactibleSpace that implements
  70 // a free list space, such as used in the concurrent mark sweep
  71 // generation.
  72 
  73 class CompactibleFreeListSpace: public CompactibleSpace {
  74   friend class VMStructs;
  75   friend class ConcurrentMarkSweepGeneration;
  76   friend class CMSCollector;
  77   // Local alloc buffer for promotion into this space.
  78   friend class CompactibleFreeListSpaceLAB;
  79   // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
  80   template <typename SpaceType>
  81   friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
  82   template <typename SpaceType>
  83   friend void CompactibleSpace::scan_and_compact(SpaceType* space);
  84   template <typename SpaceType>
  85   friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
  86   template <typename SpaceType>
  87   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
  88 
  89   // "Size" of chunks of work (executed during parallel remark phases
  90   // of CMS collection); this probably belongs in CMSCollector, although
  91   // it's cached here because it's used in
  92   // initialize_sequential_subtasks_for_rescan() which modifies
  93   // par_seq_tasks which also lives in Space. XXX
  94   const size_t _rescan_task_size;
  95   const size_t _marking_task_size;
  96 
  97   // Yet another sequential tasks done structure. This supports
  98   // CMS GC, where we have threads dynamically
  99   // claiming sub-tasks from a larger parallel task.
 100   SequentialSubTasksDone _conc_par_seq_tasks;
 101 
 102   BlockOffsetArrayNonContigSpace _bt;
 103 
 104   CMSCollector* _collector;
 105   ConcurrentMarkSweepGeneration* _old_gen;
 106 
 107   // Data structures for free blocks (used during allocation/sweeping)
 108 
 109   // Allocation is done linearly from two different blocks depending on
 110   // whether the request is small or large, in an effort to reduce
 111   // fragmentation. We assume that any locking for allocation is done
 112   // by the containing generation. Thus, none of the methods in this
 113   // space are re-entrant.
 114   enum SomeConstants {
 115     SmallForLinearAlloc = 16,        // size < this then use _sLAB
 116     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
 117     IndexSetSize        = SmallForDictionary  // keep this odd-sized
 118   };
 119   static size_t IndexSetStart;
 120   static size_t IndexSetStride;
 121 
 122  private:
 123   enum FitStrategyOptions {
 124     FreeBlockStrategyNone = 0,
 125     FreeBlockBestFitFirst
 126   };
 127 
 128   PromotionInfo _promoInfo;
 129 
 130   // Helps to impose a global total order on freelistLock ranks;
 131   // assumes that CFLSpace's are allocated in global total order
 132   static int   _lockRank;
 133 
 134   // A lock protecting the free lists and free blocks;
 135   // mutable because of ubiquity of locking even for otherwise const methods
 136   mutable Mutex _freelistLock;
 137   // Locking verifier convenience function
 138   void assert_locked() const PRODUCT_RETURN;
 139   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
 140 
 141   // Linear allocation blocks
 142   LinearAllocBlock _smallLinearAllocBlock;
 143 
 144   AFLBinaryTreeDictionary* _dictionary;    // Pointer to dictionary for large size blocks
 145 
 146   // Indexed array for small size blocks
 147   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
 148 
 149   // Allocation strategy
 150   bool _fitStrategy;  // Use best fit strategy
 151 
 152   // This is an address close to the largest free chunk in the heap.
 153   // It is currently assumed to be at the end of the heap.  Free
 154   // chunks with addresses greater than nearLargestChunk are coalesced
 155   // in an effort to maintain a large chunk at the end of the heap.
 156   HeapWord*  _nearLargestChunk;
 157 
 158   // Used to keep track of limit of sweep for the space
 159   HeapWord* _sweep_limit;
 160 
 161   // Used to make the young collector update the mod union table
 162   MemRegionClosure* _preconsumptionDirtyCardClosure;
 163 
 164   // Support for compacting cms
 165   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 166   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
 167 
 168   // Initialization helpers.
 169   void initializeIndexedFreeListArray();
 170 
 171   // Extra stuff to manage promotion parallelism.
 172 
 173   // A lock protecting the dictionary during par promotion allocation.
 174   mutable Mutex _parDictionaryAllocLock;
 175   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
 176 
 177   // Locks protecting the exact lists during par promotion allocation.
 178   Mutex* _indexedFreeListParLocks[IndexSetSize];
 179 
 180   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
 181   // required to be smaller than "IndexSetSize".)  If successful,
 182   // adds them to "fl", which is required to be an empty free list.
 183   // If the count of "fl" is negative, it's absolute value indicates a
 184   // number of free chunks that had been previously "borrowed" from global
 185   // list of size "word_sz", and must now be decremented.
 186   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 187 
 188   // Used by par_get_chunk_of_blocks() for the chunks from the
 189   // indexed_free_lists.
 190   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 191 
 192   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
 193   // evenly splittable into "n" "word_sz" chunks.  Returns that
 194   // evenly splittable chunk.  May split a larger chunk to get the
 195   // evenly splittable chunk.
 196   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
 197 
 198   // Used by par_get_chunk_of_blocks() for the chunks from the
 199   // dictionary.
 200   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
 201 
 202   // Allocation helper functions
 203   // Allocate using a strategy that takes from the indexed free lists
 204   // first.  This allocation strategy assumes a companion sweeping
 205   // strategy that attempts to keep the needed number of chunks in each
 206   // indexed free lists.
 207   HeapWord* allocate_adaptive_freelists(size_t size);
 208 
 209   // Gets a chunk from the linear allocation block (LinAB).  If there
 210   // is not enough space in the LinAB, refills it.
 211   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
 212   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
 213   // Get a chunk from the space remaining in the linear allocation block.  Do
 214   // not attempt to refill if the space is not available, return NULL.  Do the
 215   // repairs on the linear allocation block as appropriate.
 216   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
 217   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
 218 
 219   // Helper function for getChunkFromIndexedFreeList.
 220   // Replenish the indexed free list for this "size".  Do not take from an
 221   // underpopulated size.
 222   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
 223 
 224   // Get a chunk from the indexed free list.  If the indexed free list
 225   // does not have a free chunk, try to replenish the indexed free list
 226   // then get the free chunk from the replenished indexed free list.
 227   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
 228 
 229   // The returned chunk may be larger than requested (or null).
 230   FreeChunk* getChunkFromDictionary(size_t size);
 231   // The returned chunk is the exact size requested (or null).
 232   FreeChunk* getChunkFromDictionaryExact(size_t size);
 233 
 234   // Find a chunk in the indexed free list that is the best
 235   // fit for size "numWords".
 236   FreeChunk* bestFitSmall(size_t numWords);
 237   // For free list "fl" of chunks of size > numWords,
 238   // remove a chunk, split off a chunk of size numWords
 239   // and return it.  The split off remainder is returned to
 240   // the free lists.  The old name for getFromListGreater
 241   // was lookInListGreater.
 242   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
 243   // Get a chunk in the indexed free list or dictionary,
 244   // by considering a larger chunk and splitting it.
 245   FreeChunk* getChunkFromGreater(size_t numWords);
 246   //  Verify that the given chunk is in the indexed free lists.
 247   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
 248   // Remove the specified chunk from the indexed free lists.
 249   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
 250   // Remove the specified chunk from the dictionary.
 251   void       removeChunkFromDictionary(FreeChunk* fc);
 252   // Split a free chunk into a smaller free chunk of size "new_size".
 253   // Return the smaller free chunk and return the remainder to the
 254   // free lists.
 255   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
 256   // Add a chunk to the free lists.
 257   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
 258   // Add a chunk to the free lists, preferring to suffix it
 259   // to the last free chunk at end of space if possible, and
 260   // updating the block census stats as well as block offset table.
 261   // Take any locks as appropriate if we are multithreaded.
 262   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
 263   // Add a free chunk to the indexed free lists.
 264   void       returnChunkToFreeList(FreeChunk* chunk);
 265   // Add a free chunk to the dictionary.
 266   void       returnChunkToDictionary(FreeChunk* chunk);
 267 
 268   // Functions for maintaining the linear allocation buffers (LinAB).
 269   // Repairing a linear allocation block refers to operations
 270   // performed on the remainder of a LinAB after an allocation
 271   // has been made from it.
 272   void       repairLinearAllocationBlocks();
 273   void       repairLinearAllocBlock(LinearAllocBlock* blk);
 274   void       refillLinearAllocBlock(LinearAllocBlock* blk);
 275   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
 276   void       refillLinearAllocBlocksIfNeeded();
 277 
 278   void       verify_objects_initialized() const;
 279 
 280   // Statistics reporting helper functions
 281   void       reportFreeListStatistics(const char* title) const;
 282   void       reportIndexedFreeListStatistics(outputStream* st) const;
 283   size_t     maxChunkSizeInIndexedFreeLists() const;
 284   size_t     numFreeBlocksInIndexedFreeLists() const;
 285   // Accessor
 286   HeapWord* unallocated_block() const {
 287     if (BlockOffsetArrayUseUnallocatedBlock) {
 288       HeapWord* ub = _bt.unallocated_block();
 289       assert(ub >= bottom() &&
 290              ub <= end(), "space invariant");
 291       return ub;
 292     } else {
 293       return end();
 294     }
 295   }
 296   void freed(HeapWord* start, size_t size) {
 297     _bt.freed(start, size);
 298   }
 299 
 300   // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
 301   // See comments for CompactibleSpace for more information.
 302   inline HeapWord* scan_limit() const {
 303     return end();
 304   }
 305 
 306   inline bool scanned_block_is_obj(const HeapWord* addr) const {
 307     return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
 308   }
 309 
 310   inline size_t scanned_block_size(const HeapWord* addr) const {
 311     return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
 312   }
 313 
 314   inline size_t adjust_obj_size(size_t size) const {
 315     return adjustObjectSize(size);
 316   }
 317 
 318   inline size_t obj_size(const HeapWord* addr) const;
 319 
 320  protected:
 321   // Reset the indexed free list to its initial empty condition.
 322   void resetIndexedFreeListArray();
 323   // Reset to an initial state with a single free block described
 324   // by the MemRegion parameter.
 325   void reset(MemRegion mr);
 326   // Return the total number of words in the indexed free lists.
 327   size_t     totalSizeInIndexedFreeLists() const;
 328 
 329  public:
 330   // Constructor
 331   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
 332   // Accessors
 333   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
 334   AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }
 335   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
 336   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
 337 
 338   // Set CMS global values.
 339   static void set_cms_values();
 340 
 341   // Return the free chunk at the end of the space.  If no such
 342   // chunk exists, return NULL.
 343   FreeChunk* find_chunk_at_end();
 344 
 345   void set_collector(CMSCollector* collector) { _collector = collector; }
 346 
 347   // Support for parallelization of rescan and marking.
 348   const size_t rescan_task_size()  const { return _rescan_task_size;  }
 349   const size_t marking_task_size() const { return _marking_task_size; }
 350   // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.
 351   const size_t max_flag_size_for_task_size() const;
 352   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
 353   void initialize_sequential_subtasks_for_rescan(int n_threads);
 354   void initialize_sequential_subtasks_for_marking(int n_threads,
 355          HeapWord* low = NULL);
 356 
 357   virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
 358     return _preconsumptionDirtyCardClosure;
 359   }
 360 
 361   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
 362     _preconsumptionDirtyCardClosure = cl;
 363   }
 364 
 365   // Space enquiries
 366   size_t used() const;
 367   size_t free() const;
 368   size_t max_alloc_in_words() const;
 369   // XXX: should have a less conservative used_region() than that of
 370   // Space; we could consider keeping track of highest allocated
 371   // address and correcting that at each sweep, as the sweeper
 372   // goes through the entire allocated part of the generation. We
 373   // could also use that information to keep the sweeper from
 374   // sweeping more than is necessary. The allocator and sweeper will
 375   // of course need to synchronize on this, since the sweeper will
 376   // try to bump down the address and the allocator will try to bump it up.
 377   // For now, however, we'll just use the default used_region()
 378   // which overestimates the region by returning the entire
 379   // committed region (this is safe, but inefficient).
 380 
 381   // Returns a subregion of the space containing all the objects in
 382   // the space.
 383   MemRegion used_region() const {
 384     return MemRegion(bottom(),
 385                      BlockOffsetArrayUseUnallocatedBlock ?
 386                      unallocated_block() : end());
 387   }
 388 
 389   virtual bool is_free_block(const HeapWord* p) const;
 390 
 391   // Resizing support
 392   void set_end(HeapWord* value);  // override
 393 
 394   // Never mangle CompactibleFreeListSpace
 395   void mangle_unused_area() {}
 396   void mangle_unused_area_complete() {}
 397 
 398   // Mutual exclusion support
 399   Mutex* freelistLock() const { return &_freelistLock; }
 400 
 401   // Iteration support
 402   void oop_iterate(ExtendedOopClosure* cl);
 403 
 404   void object_iterate(ObjectClosure* blk);
 405   // Apply the closure to each object in the space whose references
 406   // point to objects in the heap.  The usage of CompactibleFreeListSpace
 407   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
 408   // objects in the space with references to objects that are no longer
 409   // valid.  For example, an object may reference another object
 410   // that has already been sweep up (collected).  This method uses
 411   // obj_is_alive() to determine whether it is safe to iterate of
 412   // an object.
 413   void safe_object_iterate(ObjectClosure* blk);
 414 
 415   // Iterate over all objects that intersect with mr, calling "cl->do_object"
 416   // on each.  There is an exception to this: if this closure has already
 417   // been invoked on an object, it may skip such objects in some cases.  This is
 418   // Most likely to happen in an "upwards" (ascending address) iteration of
 419   // MemRegions.
 420   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
 421 
 422   // Requires that "mr" be entirely within the space.
 423   // Apply "cl->do_object" to all objects that intersect with "mr".
 424   // If the iteration encounters an unparseable portion of the region,
 425   // terminate the iteration and return the address of the start of the
 426   // subregion that isn't done.  Return of "NULL" indicates that the
 427   // iteration completed.
 428   HeapWord* object_iterate_careful_m(MemRegion mr,
 429                                      ObjectClosureCareful* cl);
 430 
 431   // Override: provides a DCTO_CL specific to this kind of space.
 432   DirtyCardToOopClosure* new_dcto_cl(ExtendedOopClosure* cl,
 433                                      CardTableModRefBS::PrecisionStyle precision,
 434                                      HeapWord* boundary,
 435                                      bool parallel);
 436 
 437   void blk_iterate(BlkClosure* cl);
 438   void blk_iterate_careful(BlkClosureCareful* cl);
 439   HeapWord* block_start_const(const void* p) const;
 440   HeapWord* block_start_careful(const void* p) const;
 441   size_t block_size(const HeapWord* p) const;
 442   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
 443   bool block_is_obj(const HeapWord* p) const;
 444   bool obj_is_alive(const HeapWord* p) const;
 445   size_t block_size_nopar(const HeapWord* p) const;
 446   bool block_is_obj_nopar(const HeapWord* p) const;
 447 
 448   // Iteration support for promotion
 449   void save_marks();
 450   bool no_allocs_since_save_marks();
 451 
 452   // Iteration support for sweeping
 453   void save_sweep_limit() {
 454     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
 455                    unallocated_block() : end();
 456     log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT
 457                                  "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
 458                                  p2i(_sweep_limit), p2i(bottom()), p2i(end()));
 459   }
 460   NOT_PRODUCT(
 461     void clear_sweep_limit() { _sweep_limit = NULL; }
 462   )
 463   HeapWord* sweep_limit() { return _sweep_limit; }
 464 
 465   // Apply "blk->do_oop" to the addresses of all reference fields in objects
 466   // promoted into this generation since the most recent save_marks() call.
 467   // Fields in objects allocated by applications of the closure
 468   // *are* included in the iteration. Thus, when the iteration completes
 469   // there should be no further such objects remaining.
 470   #define CFLS_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 471     void oop_since_save_marks_iterate##nv_suffix(OopClosureType* blk);
 472   ALL_SINCE_SAVE_MARKS_CLOSURES(CFLS_OOP_SINCE_SAVE_MARKS_DECL)
 473   #undef CFLS_OOP_SINCE_SAVE_MARKS_DECL
 474 
 475   // Allocation support
 476   HeapWord* allocate(size_t size);
 477   HeapWord* par_allocate(size_t size);
 478 
 479   oop       promote(oop obj, size_t obj_size);
 480   void      gc_prologue();
 481   void      gc_epilogue();
 482 
 483   // This call is used by a containing CMS generation / collector
 484   // to inform the CFLS space that a sweep has been completed
 485   // and that the space can do any related house-keeping functions.
 486   void      sweep_completed();
 487 
 488   // For an object in this space, the mark-word's two
 489   // LSB's having the value [11] indicates that it has been
 490   // promoted since the most recent call to save_marks() on
 491   // this generation and has not subsequently been iterated
 492   // over (using oop_since_save_marks_iterate() above).
 493   // This property holds only for single-threaded collections,
 494   // and is typically used for Cheney scans; for MT scavenges,
 495   // the property holds for all objects promoted during that
 496   // scavenge for the duration of the scavenge and is used
 497   // by card-scanning to avoid scanning objects (being) promoted
 498   // during that scavenge.
 499   bool obj_allocated_since_save_marks(const oop obj) const {
 500     assert(is_in_reserved(obj), "Wrong space?");
 501     return ((PromotedObject*)obj)->hasPromotedMark();
 502   }
 503 
 504   // A worst-case estimate of the space required (in HeapWords) to expand the
 505   // heap when promoting an obj of size obj_size.
 506   size_t expansionSpaceRequired(size_t obj_size) const;
 507 
 508   FreeChunk* allocateScratch(size_t size);
 509 
 510   // Returns true if either the small or large linear allocation buffer is empty.
 511   bool       linearAllocationWouldFail() const;
 512 
 513   // Adjust the chunk for the minimum size.  This version is called in
 514   // most cases in CompactibleFreeListSpace methods.
 515   inline static size_t adjustObjectSize(size_t size) {
 516     return align_object_size(MAX2(size, (size_t)MinChunkSize));
 517   }
 518   // This is a virtual version of adjustObjectSize() that is called
 519   // only occasionally when the compaction space changes and the type
 520   // of the new compaction space is is only known to be CompactibleSpace.
 521   size_t adjust_object_size_v(size_t size) const {
 522     return adjustObjectSize(size);
 523   }
 524   // Minimum size of a free block.
 525   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
 526   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
 527   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
 528               bool coalesced);
 529 
 530   // Support for compaction.
 531   void prepare_for_compaction(CompactPoint* cp);
 532   void adjust_pointers();
 533   void compact();
 534   // Reset the space to reflect the fact that a compaction of the
 535   // space has been done.
 536   virtual void reset_after_compaction();
 537 
 538   // Debugging support.
 539   void print()                            const;
 540   void print_on(outputStream* st)         const;
 541   void prepare_for_verify();
 542   void verify()                           const;
 543   void verifyFreeLists()                  const PRODUCT_RETURN;
 544   void verifyIndexedFreeLists()           const;
 545   void verifyIndexedFreeList(size_t size) const;
 546   // Verify that the given chunk is in the free lists:
 547   // i.e. either the binary tree dictionary, the indexed free lists
 548   // or the linear allocation block.
 549   bool verify_chunk_in_free_list(FreeChunk* fc) const;
 550   // Verify that the given chunk is the linear allocation block.
 551   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
 552   // Do some basic checks on the the free lists.
 553   void check_free_list_consistency()      const PRODUCT_RETURN;
 554 
 555   // Printing support
 556   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
 557   void print_indexed_free_lists(outputStream* st) const;
 558   void print_dictionary_free_lists(outputStream* st) const;
 559   void print_promo_info_blocks(outputStream* st) const;
 560 
 561   NOT_PRODUCT (
 562     void initializeIndexedFreeListArrayReturnedBytes();
 563     size_t sumIndexedFreeListArrayReturnedBytes();
 564     // Return the total number of chunks in the indexed free lists.
 565     size_t totalCountInIndexedFreeLists() const;
 566     // Return the total number of chunks in the space.
 567     size_t totalCount();
 568   )
 569 
 570   // The census consists of counts of the quantities such as
 571   // the current count of the free chunks, number of chunks
 572   // created as a result of the split of a larger chunk or
 573   // coalescing of smaller chucks, etc.  The counts in the
 574   // census is used to make decisions on splitting and
 575   // coalescing of chunks during the sweep of garbage.
 576 
 577   // Print the statistics for the free lists.
 578   void printFLCensus(size_t sweep_count) const;
 579 
 580   // Statistics functions
 581   // Initialize census for lists before the sweep.
 582   void beginSweepFLCensus(float inter_sweep_current,
 583                           float inter_sweep_estimate,
 584                           float intra_sweep_estimate);
 585   // Set the surplus for each of the free lists.
 586   void setFLSurplus();
 587   // Set the hint for each of the free lists.
 588   void setFLHints();
 589   // Clear the census for each of the free lists.
 590   void clearFLCensus();
 591   // Perform functions for the census after the end of the sweep.
 592   void endSweepFLCensus(size_t sweep_count);
 593   // Return true if the count of free chunks is greater
 594   // than the desired number of free chunks.
 595   bool coalOverPopulated(size_t size);
 596 
 597 // Record (for each size):
 598 //
 599 //   split-births = #chunks added due to splits in (prev-sweep-end,
 600 //      this-sweep-start)
 601 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
 602 //      this-sweep-start)
 603 //   num-curr     = #chunks at start of this sweep
 604 //   num-prev     = #chunks at end of previous sweep
 605 //
 606 // The above are quantities that are measured. Now define:
 607 //
 608 //   num-desired := num-prev + split-births - split-deaths - num-curr
 609 //
 610 // Roughly, num-prev + split-births is the supply,
 611 // split-deaths is demand due to other sizes
 612 // and num-curr is what we have left.
 613 //
 614 // Thus, num-desired is roughly speaking the "legitimate demand"
 615 // for blocks of this size and what we are striving to reach at the
 616 // end of the current sweep.
 617 //
 618 // For a given list, let num-len be its current population.
 619 // Define, for a free list of a given size:
 620 //
 621 //   coal-overpopulated := num-len >= num-desired * coal-surplus
 622 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
 623 // coalescing -- we do not coalesce unless we think that the current
 624 // supply has exceeded the estimated demand by more than 5%).
 625 //
 626 // For the set of sizes in the binary tree, which is neither dense nor
 627 // closed, it may be the case that for a particular size we have never
 628 // had, or do not now have, or did not have at the previous sweep,
 629 // chunks of that size. We need to extend the definition of
 630 // coal-overpopulated to such sizes as well:
 631 //
 632 //   For a chunk in/not in the binary tree, extend coal-overpopulated
 633 //   defined above to include all sizes as follows:
 634 //
 635 //   . a size that is non-existent is coal-overpopulated
 636 //   . a size that has a num-desired <= 0 as defined above is
 637 //     coal-overpopulated.
 638 //
 639 // Also define, for a chunk heap-offset C and mountain heap-offset M:
 640 //
 641 //   close-to-mountain := C >= 0.99 * M
 642 //
 643 // Now, the coalescing strategy is:
 644 //
 645 //    Coalesce left-hand chunk with right-hand chunk if and
 646 //    only if:
 647 //
 648 //      EITHER
 649 //        . left-hand chunk is of a size that is coal-overpopulated
 650 //      OR
 651 //        . right-hand chunk is close-to-mountain
 652   void smallCoalBirth(size_t size);
 653   void smallCoalDeath(size_t size);
 654   void coalBirth(size_t size);
 655   void coalDeath(size_t size);
 656   void smallSplitBirth(size_t size);
 657   void smallSplitDeath(size_t size);
 658   void split_birth(size_t size);
 659   void splitDeath(size_t size);
 660   void split(size_t from, size_t to1);
 661 
 662   double flsFrag() const;
 663 };
 664 
 665 // A parallel-GC-thread-local allocation buffer for allocation into a
 666 // CompactibleFreeListSpace.
 667 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {
 668   // The space that this buffer allocates into.
 669   CompactibleFreeListSpace* _cfls;
 670 
 671   // Our local free lists.
 672   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
 673 
 674   // Initialized from a command-line arg.
 675 
 676   // Allocation statistics in support of dynamic adjustment of
 677   // #blocks to claim per get_from_global_pool() call below.
 678   static AdaptiveWeightedAverage
 679                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
 680   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
 681   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
 682   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
 683 
 684   // Internal work method
 685   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
 686 
 687 public:
 688   static const int _default_dynamic_old_plab_size = 16;
 689   static const int _default_static_old_plab_size  = 50;
 690 
 691   CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);
 692 
 693   // Allocate and return a block of the given size, or else return NULL.
 694   HeapWord* alloc(size_t word_sz);
 695 
 696   // Return any unused portions of the buffer to the global pool.
 697   void retire(int tid);
 698 
 699   // Dynamic OldPLABSize sizing
 700   static void compute_desired_plab_size();
 701   // When the settings are modified from default static initialization
 702   static void modify_initialization(size_t n, unsigned wt);
 703 };
 704 
 705 size_t PromotionInfo::refillSize() const {
 706   const size_t CMSSpoolBlockSize = 256;
 707   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markOop)
 708                                    * CMSSpoolBlockSize);
 709   return CompactibleFreeListSpace::adjustObjectSize(sz);
 710 }
 711 
 712 #endif // SHARE_VM_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP