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  24 
  25 #ifndef SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
  26 #define SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP
  27 
  28 #include "gc/cms/cmsOopClosures.hpp"
  29 #include "gc/cms/gSpaceCounters.hpp"
  30 #include "gc/cms/yieldingWorkgroup.hpp"
  31 #include "gc/shared/cardGeneration.hpp"
  32 #include "gc/shared/gcHeapSummary.hpp"
  33 #include "gc/shared/gcStats.hpp"
  34 #include "gc/shared/gcWhen.hpp"
  35 #include "gc/shared/generationCounters.hpp"
  36 #include "gc/shared/space.hpp"
  37 #include "gc/shared/taskqueue.hpp"
  38 #include "memory/freeBlockDictionary.hpp"
  39 #include "memory/iterator.hpp"
  40 #include "memory/virtualspace.hpp"
  41 #include "runtime/mutexLocker.hpp"
  42 #include "services/memoryService.hpp"
  43 #include "utilities/bitMap.hpp"
  44 #include "utilities/stack.hpp"
  45 
  46 // ConcurrentMarkSweepGeneration is in support of a concurrent
  47 // mark-sweep old generation in the Detlefs-Printezis--Boehm-Demers-Schenker
  48 // style. We assume, for now, that this generation is always the
  49 // seniormost generation and for simplicity
  50 // in the first implementation, that this generation is a single compactible
  51 // space. Neither of these restrictions appears essential, and will be
  52 // relaxed in the future when more time is available to implement the
  53 // greater generality (and there's a need for it).
  54 //
  55 // Concurrent mode failures are currently handled by
  56 // means of a sliding mark-compact.
  57 
  58 class AdaptiveSizePolicy;
  59 class CMSCollector;
  60 class CMSConcMarkingTask;
  61 class CMSGCAdaptivePolicyCounters;
  62 class CMSTracer;
  63 class ConcurrentGCTimer;
  64 class ConcurrentMarkSweepGeneration;
  65 class ConcurrentMarkSweepPolicy;
  66 class ConcurrentMarkSweepThread;
  67 class CompactibleFreeListSpace;
  68 class FreeChunk;
  69 class ParNewGeneration;
  70 class PromotionInfo;
  71 class ScanMarkedObjectsAgainCarefullyClosure;
  72 class TenuredGeneration;
  73 class SerialOldTracer;
  74 
  75 // A generic CMS bit map. It's the basis for both the CMS marking bit map
  76 // as well as for the mod union table (in each case only a subset of the
  77 // methods are used). This is essentially a wrapper around the BitMap class,
  78 // with one bit per (1<<_shifter) HeapWords. (i.e. for the marking bit map,
  79 // we have _shifter == 0. and for the mod union table we have
  80 // shifter == CardTableModRefBS::card_shift - LogHeapWordSize.)
  81 // XXX 64-bit issues in BitMap?
  82 class CMSBitMap VALUE_OBJ_CLASS_SPEC {
  83   friend class VMStructs;
  84 
  85   HeapWord* _bmStartWord;   // base address of range covered by map
  86   size_t    _bmWordSize;    // map size (in #HeapWords covered)
  87   const int _shifter;       // shifts to convert HeapWord to bit position
  88   VirtualSpace _virtual_space; // underlying the bit map
  89   BitMap    _bm;            // the bit map itself
  90  public:
  91   Mutex* const _lock;       // mutex protecting _bm;
  92 
  93  public:
  94   // constructor
  95   CMSBitMap(int shifter, int mutex_rank, const char* mutex_name);
  96 
  97   // allocates the actual storage for the map
  98   bool allocate(MemRegion mr);
  99   // field getter
 100   Mutex* lock() const { return _lock; }
 101   // locking verifier convenience function
 102   void assert_locked() const PRODUCT_RETURN;
 103 
 104   // inquiries
 105   HeapWord* startWord()   const { return _bmStartWord; }
 106   size_t    sizeInWords() const { return _bmWordSize;  }
 107   size_t    sizeInBits()  const { return _bm.size();   }
 108   // the following is one past the last word in space
 109   HeapWord* endWord()     const { return _bmStartWord + _bmWordSize; }
 110 
 111   // reading marks
 112   bool isMarked(HeapWord* addr) const;
 113   bool par_isMarked(HeapWord* addr) const; // do not lock checks
 114   bool isUnmarked(HeapWord* addr) const;
 115   bool isAllClear() const;
 116 
 117   // writing marks
 118   void mark(HeapWord* addr);
 119   // For marking by parallel GC threads;
 120   // returns true if we did, false if another thread did
 121   bool par_mark(HeapWord* addr);
 122 
 123   void mark_range(MemRegion mr);
 124   void par_mark_range(MemRegion mr);
 125   void mark_large_range(MemRegion mr);
 126   void par_mark_large_range(MemRegion mr);
 127   void par_clear(HeapWord* addr); // For unmarking by parallel GC threads.
 128   void clear_range(MemRegion mr);
 129   void par_clear_range(MemRegion mr);
 130   void clear_large_range(MemRegion mr);
 131   void par_clear_large_range(MemRegion mr);
 132   void clear_all();
 133   void clear_all_incrementally();  // Not yet implemented!!
 134 
 135   NOT_PRODUCT(
 136     // checks the memory region for validity
 137     void region_invariant(MemRegion mr);
 138   )
 139 
 140   // iteration
 141   void iterate(BitMapClosure* cl) {
 142     _bm.iterate(cl);
 143   }
 144   void iterate(BitMapClosure* cl, HeapWord* left, HeapWord* right);
 145   void dirty_range_iterate_clear(MemRegionClosure* cl);
 146   void dirty_range_iterate_clear(MemRegion mr, MemRegionClosure* cl);
 147 
 148   // auxiliary support for iteration
 149   HeapWord* getNextMarkedWordAddress(HeapWord* addr) const;
 150   HeapWord* getNextMarkedWordAddress(HeapWord* start_addr,
 151                                             HeapWord* end_addr) const;
 152   HeapWord* getNextUnmarkedWordAddress(HeapWord* addr) const;
 153   HeapWord* getNextUnmarkedWordAddress(HeapWord* start_addr,
 154                                               HeapWord* end_addr) const;
 155   MemRegion getAndClearMarkedRegion(HeapWord* addr);
 156   MemRegion getAndClearMarkedRegion(HeapWord* start_addr,
 157                                            HeapWord* end_addr);
 158 
 159   // conversion utilities
 160   HeapWord* offsetToHeapWord(size_t offset) const;
 161   size_t    heapWordToOffset(HeapWord* addr) const;
 162   size_t    heapWordDiffToOffsetDiff(size_t diff) const;
 163 
 164   void print_on_error(outputStream* st, const char* prefix) const;
 165 
 166   // debugging
 167   // is this address range covered by the bit-map?
 168   NOT_PRODUCT(
 169     bool covers(MemRegion mr) const;
 170     bool covers(HeapWord* start, size_t size = 0) const;
 171   )
 172   void verifyNoOneBitsInRange(HeapWord* left, HeapWord* right) PRODUCT_RETURN;
 173 };
 174 
 175 // Represents a marking stack used by the CMS collector.
 176 // Ideally this should be GrowableArray<> just like MSC's marking stack(s).
 177 class CMSMarkStack: public CHeapObj<mtGC>  {
 178   friend class CMSCollector;   // To get at expansion stats further below.
 179 
 180   VirtualSpace _virtual_space;  // Space for the stack
 181   oop*   _base;      // Bottom of stack
 182   size_t _index;     // One more than last occupied index
 183   size_t _capacity;  // Max #elements
 184   Mutex  _par_lock;  // An advisory lock used in case of parallel access
 185   NOT_PRODUCT(size_t _max_depth;)  // Max depth plumbed during run
 186 
 187  protected:
 188   size_t _hit_limit;      // We hit max stack size limit
 189   size_t _failed_double;  // We failed expansion before hitting limit
 190 
 191  public:
 192   CMSMarkStack():
 193     _par_lock(Mutex::event, "CMSMarkStack._par_lock", true,
 194               Monitor::_safepoint_check_never),
 195     _hit_limit(0),
 196     _failed_double(0) {}
 197 
 198   bool allocate(size_t size);
 199 
 200   size_t capacity() const { return _capacity; }
 201 
 202   oop pop() {
 203     if (!isEmpty()) {
 204       return _base[--_index] ;
 205     }
 206     return NULL;
 207   }
 208 
 209   bool push(oop ptr) {
 210     if (isFull()) {
 211       return false;
 212     } else {
 213       _base[_index++] = ptr;
 214       NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
 215       return true;
 216     }
 217   }
 218 
 219   bool isEmpty() const { return _index == 0; }
 220   bool isFull()  const {
 221     assert(_index <= _capacity, "buffer overflow");
 222     return _index == _capacity;
 223   }
 224 
 225   size_t length() { return _index; }
 226 
 227   // "Parallel versions" of some of the above
 228   oop par_pop() {
 229     // lock and pop
 230     MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
 231     return pop();
 232   }
 233 
 234   bool par_push(oop ptr) {
 235     // lock and push
 236     MutexLockerEx x(&_par_lock, Mutex::_no_safepoint_check_flag);
 237     return push(ptr);
 238   }
 239 
 240   // Forcibly reset the stack, losing all of its contents.
 241   void reset() {
 242     _index = 0;
 243   }
 244 
 245   // Expand the stack, typically in response to an overflow condition.
 246   void expand();
 247 
 248   // Compute the least valued stack element.
 249   oop least_value(HeapWord* low) {
 250      oop least = (oop)low;
 251      for (size_t i = 0; i < _index; i++) {
 252        least = MIN2(least, _base[i]);
 253      }
 254      return least;
 255   }
 256 
 257   // Exposed here to allow stack expansion in || case.
 258   Mutex* par_lock() { return &_par_lock; }
 259 };
 260 
 261 class CardTableRS;
 262 class CMSParGCThreadState;
 263 
 264 class ModUnionClosure: public MemRegionClosure {
 265  protected:
 266   CMSBitMap* _t;
 267  public:
 268   ModUnionClosure(CMSBitMap* t): _t(t) { }
 269   void do_MemRegion(MemRegion mr);
 270 };
 271 
 272 class ModUnionClosurePar: public ModUnionClosure {
 273  public:
 274   ModUnionClosurePar(CMSBitMap* t): ModUnionClosure(t) { }
 275   void do_MemRegion(MemRegion mr);
 276 };
 277 
 278 // Survivor Chunk Array in support of parallelization of
 279 // Survivor Space rescan.
 280 class ChunkArray: public CHeapObj<mtGC> {
 281   size_t _index;
 282   size_t _capacity;
 283   size_t _overflows;
 284   HeapWord** _array;   // storage for array
 285 
 286  public:
 287   ChunkArray() : _index(0), _capacity(0), _overflows(0), _array(NULL) {}
 288   ChunkArray(HeapWord** a, size_t c):
 289     _index(0), _capacity(c), _overflows(0), _array(a) {}
 290 
 291   HeapWord** array() { return _array; }
 292   void set_array(HeapWord** a) { _array = a; }
 293 
 294   size_t capacity() { return _capacity; }
 295   void set_capacity(size_t c) { _capacity = c; }
 296 
 297   size_t end() {
 298     assert(_index <= capacity(),
 299            err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT "): out of bounds",
 300                    _index, _capacity));
 301     return _index;
 302   }  // exclusive
 303 
 304   HeapWord* nth(size_t n) {
 305     assert(n < end(), "Out of bounds access");
 306     return _array[n];
 307   }
 308 
 309   void reset() {
 310     _index = 0;
 311     if (_overflows > 0 && PrintCMSStatistics > 1) {
 312       warning("CMS: ChunkArray[" SIZE_FORMAT "] overflowed " SIZE_FORMAT " times",
 313               _capacity, _overflows);
 314     }
 315     _overflows = 0;
 316   }
 317 
 318   void record_sample(HeapWord* p, size_t sz) {
 319     // For now we do not do anything with the size
 320     if (_index < _capacity) {
 321       _array[_index++] = p;
 322     } else {
 323       ++_overflows;
 324       assert(_index == _capacity,
 325              err_msg("_index (" SIZE_FORMAT ") > _capacity (" SIZE_FORMAT
 326                      "): out of bounds at overflow#" SIZE_FORMAT,
 327                      _index, _capacity, _overflows));
 328     }
 329   }
 330 };
 331 
 332 //
 333 // Timing, allocation and promotion statistics for gc scheduling and incremental
 334 // mode pacing.  Most statistics are exponential averages.
 335 //
 336 class CMSStats VALUE_OBJ_CLASS_SPEC {
 337  private:
 338   ConcurrentMarkSweepGeneration* const _cms_gen;   // The cms (old) gen.
 339 
 340   // The following are exponential averages with factor alpha:
 341   //   avg = (100 - alpha) * avg + alpha * cur_sample
 342   //
 343   //   The durations measure:  end_time[n] - start_time[n]
 344   //   The periods measure:    start_time[n] - start_time[n-1]
 345   //
 346   // The cms period and duration include only concurrent collections; time spent
 347   // in foreground cms collections due to System.gc() or because of a failure to
 348   // keep up are not included.
 349   //
 350   // There are 3 alphas to "bootstrap" the statistics.  The _saved_alpha is the
 351   // real value, but is used only after the first period.  A value of 100 is
 352   // used for the first sample so it gets the entire weight.
 353   unsigned int _saved_alpha; // 0-100
 354   unsigned int _gc0_alpha;
 355   unsigned int _cms_alpha;
 356 
 357   double _gc0_duration;
 358   double _gc0_period;
 359   size_t _gc0_promoted;         // bytes promoted per gc0
 360   double _cms_duration;
 361   double _cms_duration_pre_sweep; // time from initiation to start of sweep
 362   double _cms_period;
 363   size_t _cms_allocated;        // bytes of direct allocation per gc0 period
 364 
 365   // Timers.
 366   elapsedTimer _cms_timer;
 367   TimeStamp    _gc0_begin_time;
 368   TimeStamp    _cms_begin_time;
 369   TimeStamp    _cms_end_time;
 370 
 371   // Snapshots of the amount used in the CMS generation.
 372   size_t _cms_used_at_gc0_begin;
 373   size_t _cms_used_at_gc0_end;
 374   size_t _cms_used_at_cms_begin;
 375 
 376   // Used to prevent the duty cycle from being reduced in the middle of a cms
 377   // cycle.
 378   bool _allow_duty_cycle_reduction;
 379 
 380   enum {
 381     _GC0_VALID = 0x1,
 382     _CMS_VALID = 0x2,
 383     _ALL_VALID = _GC0_VALID | _CMS_VALID
 384   };
 385 
 386   unsigned int _valid_bits;
 387 
 388  protected:
 389   // In support of adjusting of cms trigger ratios based on history
 390   // of concurrent mode failure.
 391   double cms_free_adjustment_factor(size_t free) const;
 392   void   adjust_cms_free_adjustment_factor(bool fail, size_t free);
 393 
 394  public:
 395   CMSStats(ConcurrentMarkSweepGeneration* cms_gen,
 396            unsigned int alpha = CMSExpAvgFactor);
 397 
 398   // Whether or not the statistics contain valid data; higher level statistics
 399   // cannot be called until this returns true (they require at least one young
 400   // gen and one cms cycle to have completed).
 401   bool valid() const;
 402 
 403   // Record statistics.
 404   void record_gc0_begin();
 405   void record_gc0_end(size_t cms_gen_bytes_used);
 406   void record_cms_begin();
 407   void record_cms_end();
 408 
 409   // Allow management of the cms timer, which must be stopped/started around
 410   // yield points.
 411   elapsedTimer& cms_timer()     { return _cms_timer; }
 412   void start_cms_timer()        { _cms_timer.start(); }
 413   void stop_cms_timer()         { _cms_timer.stop(); }
 414 
 415   // Basic statistics; units are seconds or bytes.
 416   double gc0_period() const     { return _gc0_period; }
 417   double gc0_duration() const   { return _gc0_duration; }
 418   size_t gc0_promoted() const   { return _gc0_promoted; }
 419   double cms_period() const          { return _cms_period; }
 420   double cms_duration() const        { return _cms_duration; }
 421   size_t cms_allocated() const       { return _cms_allocated; }
 422 
 423   size_t cms_used_at_gc0_end() const { return _cms_used_at_gc0_end;}
 424 
 425   // Seconds since the last background cms cycle began or ended.
 426   double cms_time_since_begin() const;
 427   double cms_time_since_end() const;
 428 
 429   // Higher level statistics--caller must check that valid() returns true before
 430   // calling.
 431 
 432   // Returns bytes promoted per second of wall clock time.
 433   double promotion_rate() const;
 434 
 435   // Returns bytes directly allocated per second of wall clock time.
 436   double cms_allocation_rate() const;
 437 
 438   // Rate at which space in the cms generation is being consumed (sum of the
 439   // above two).
 440   double cms_consumption_rate() const;
 441 
 442   // Returns an estimate of the number of seconds until the cms generation will
 443   // fill up, assuming no collection work is done.
 444   double time_until_cms_gen_full() const;
 445 
 446   // Returns an estimate of the number of seconds remaining until
 447   // the cms generation collection should start.
 448   double time_until_cms_start() const;
 449 
 450   // End of higher level statistics.
 451 
 452   // Debugging.
 453   void print_on(outputStream* st) const PRODUCT_RETURN;
 454   void print() const { print_on(gclog_or_tty); }
 455 };
 456 
 457 // A closure related to weak references processing which
 458 // we embed in the CMSCollector, since we need to pass
 459 // it to the reference processor for secondary filtering
 460 // of references based on reachability of referent;
 461 // see role of _is_alive_non_header closure in the
 462 // ReferenceProcessor class.
 463 // For objects in the CMS generation, this closure checks
 464 // if the object is "live" (reachable). Used in weak
 465 // reference processing.
 466 class CMSIsAliveClosure: public BoolObjectClosure {
 467   const MemRegion  _span;
 468   const CMSBitMap* _bit_map;
 469 
 470   friend class CMSCollector;
 471  public:
 472   CMSIsAliveClosure(MemRegion span,
 473                     CMSBitMap* bit_map):
 474     _span(span),
 475     _bit_map(bit_map) {
 476     assert(!span.is_empty(), "Empty span could spell trouble");
 477   }
 478 
 479   bool do_object_b(oop obj);
 480 };
 481 
 482 
 483 // Implements AbstractRefProcTaskExecutor for CMS.
 484 class CMSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 485 public:
 486 
 487   CMSRefProcTaskExecutor(CMSCollector& collector)
 488     : _collector(collector)
 489   { }
 490 
 491   // Executes a task using worker threads.
 492   virtual void execute(ProcessTask& task);
 493   virtual void execute(EnqueueTask& task);
 494 private:
 495   CMSCollector& _collector;
 496 };
 497 
 498 
 499 class CMSCollector: public CHeapObj<mtGC> {
 500   friend class VMStructs;
 501   friend class ConcurrentMarkSweepThread;
 502   friend class ConcurrentMarkSweepGeneration;
 503   friend class CompactibleFreeListSpace;
 504   friend class CMSParMarkTask;
 505   friend class CMSParInitialMarkTask;
 506   friend class CMSParRemarkTask;
 507   friend class CMSConcMarkingTask;
 508   friend class CMSRefProcTaskProxy;
 509   friend class CMSRefProcTaskExecutor;
 510   friend class ScanMarkedObjectsAgainCarefullyClosure;  // for sampling eden
 511   friend class SurvivorSpacePrecleanClosure;            // --- ditto -------
 512   friend class PushOrMarkClosure;             // to access _restart_addr
 513   friend class Par_PushOrMarkClosure;             // to access _restart_addr
 514   friend class MarkFromRootsClosure;          //  -- ditto --
 515                                               // ... and for clearing cards
 516   friend class Par_MarkFromRootsClosure;      //  to access _restart_addr
 517                                               // ... and for clearing cards
 518   friend class Par_ConcMarkingClosure;        //  to access _restart_addr etc.
 519   friend class MarkFromRootsVerifyClosure;    // to access _restart_addr
 520   friend class PushAndMarkVerifyClosure;      //  -- ditto --
 521   friend class MarkRefsIntoAndScanClosure;    // to access _overflow_list
 522   friend class PushAndMarkClosure;            //  -- ditto --
 523   friend class Par_PushAndMarkClosure;        //  -- ditto --
 524   friend class CMSKeepAliveClosure;           //  -- ditto --
 525   friend class CMSDrainMarkingStackClosure;   //  -- ditto --
 526   friend class CMSInnerParMarkAndPushClosure; //  -- ditto --
 527   NOT_PRODUCT(friend class ScanMarkedObjectsAgainClosure;) //  assertion on _overflow_list
 528   friend class ReleaseForegroundGC;  // to access _foregroundGCShouldWait
 529   friend class VM_CMS_Operation;
 530   friend class VM_CMS_Initial_Mark;
 531   friend class VM_CMS_Final_Remark;
 532   friend class TraceCMSMemoryManagerStats;
 533 
 534  private:
 535   jlong _time_of_last_gc;
 536   void update_time_of_last_gc(jlong now) {
 537     _time_of_last_gc = now;
 538   }
 539 
 540   OopTaskQueueSet* _task_queues;
 541 
 542   // Overflow list of grey objects, threaded through mark-word
 543   // Manipulated with CAS in the parallel/multi-threaded case.
 544   oop _overflow_list;
 545   // The following array-pair keeps track of mark words
 546   // displaced for accommodating overflow list above.
 547   // This code will likely be revisited under RFE#4922830.
 548   Stack<oop, mtGC>     _preserved_oop_stack;
 549   Stack<markOop, mtGC> _preserved_mark_stack;
 550 
 551   int*             _hash_seed;
 552 
 553   // In support of multi-threaded concurrent phases
 554   YieldingFlexibleWorkGang* _conc_workers;
 555 
 556   // Performance Counters
 557   CollectorCounters* _gc_counters;
 558 
 559   // Initialization Errors
 560   bool _completed_initialization;
 561 
 562   // In support of ExplicitGCInvokesConcurrent
 563   static bool _full_gc_requested;
 564   static GCCause::Cause _full_gc_cause;
 565   unsigned int _collection_count_start;
 566 
 567   // Should we unload classes this concurrent cycle?
 568   bool _should_unload_classes;
 569   unsigned int  _concurrent_cycles_since_last_unload;
 570   unsigned int concurrent_cycles_since_last_unload() const {
 571     return _concurrent_cycles_since_last_unload;
 572   }
 573   // Did we (allow) unload classes in the previous concurrent cycle?
 574   bool unloaded_classes_last_cycle() const {
 575     return concurrent_cycles_since_last_unload() == 0;
 576   }
 577   // Root scanning options for perm gen
 578   int _roots_scanning_options;
 579   int roots_scanning_options() const      { return _roots_scanning_options; }
 580   void add_root_scanning_option(int o)    { _roots_scanning_options |= o;   }
 581   void remove_root_scanning_option(int o) { _roots_scanning_options &= ~o;  }
 582 
 583   // Verification support
 584   CMSBitMap     _verification_mark_bm;
 585   void verify_after_remark_work_1();
 586   void verify_after_remark_work_2();
 587 
 588   // True if any verification flag is on.
 589   bool _verifying;
 590   bool verifying() const { return _verifying; }
 591   void set_verifying(bool v) { _verifying = v; }
 592 
 593   // Collector policy
 594   ConcurrentMarkSweepPolicy* _collector_policy;
 595   ConcurrentMarkSweepPolicy* collector_policy() { return _collector_policy; }
 596 
 597   void set_did_compact(bool v);
 598 
 599   // XXX Move these to CMSStats ??? FIX ME !!!
 600   elapsedTimer _inter_sweep_timer;   // Time between sweeps
 601   elapsedTimer _intra_sweep_timer;   // Time _in_ sweeps
 602   // Padded decaying average estimates of the above
 603   AdaptivePaddedAverage _inter_sweep_estimate;
 604   AdaptivePaddedAverage _intra_sweep_estimate;
 605 
 606   CMSTracer* _gc_tracer_cm;
 607   ConcurrentGCTimer* _gc_timer_cm;
 608 
 609   bool _cms_start_registered;
 610 
 611   GCHeapSummary _last_heap_summary;
 612   MetaspaceSummary _last_metaspace_summary;
 613 
 614   void register_gc_start(GCCause::Cause cause);
 615   void register_gc_end();
 616   void save_heap_summary();
 617   void report_heap_summary(GCWhen::Type when);
 618 
 619  protected:
 620   ConcurrentMarkSweepGeneration* _cmsGen;  // Old gen (CMS)
 621   MemRegion                      _span;    // Span covering above two
 622   CardTableRS*                   _ct;      // Card table
 623 
 624   // CMS marking support structures
 625   CMSBitMap     _markBitMap;
 626   CMSBitMap     _modUnionTable;
 627   CMSMarkStack  _markStack;
 628 
 629   HeapWord*     _restart_addr; // In support of marking stack overflow
 630   void          lower_restart_addr(HeapWord* low);
 631 
 632   // Counters in support of marking stack / work queue overflow handling:
 633   // a non-zero value indicates certain types of overflow events during
 634   // the current CMS cycle and could lead to stack resizing efforts at
 635   // an opportune future time.
 636   size_t        _ser_pmc_preclean_ovflw;
 637   size_t        _ser_pmc_remark_ovflw;
 638   size_t        _par_pmc_remark_ovflw;
 639   size_t        _ser_kac_preclean_ovflw;
 640   size_t        _ser_kac_ovflw;
 641   size_t        _par_kac_ovflw;
 642   NOT_PRODUCT(ssize_t _num_par_pushes;)
 643 
 644   // ("Weak") Reference processing support.
 645   ReferenceProcessor*            _ref_processor;
 646   CMSIsAliveClosure              _is_alive_closure;
 647   // Keep this textually after _markBitMap and _span; c'tor dependency.
 648 
 649   ConcurrentMarkSweepThread*     _cmsThread;   // The thread doing the work
 650   ModUnionClosurePar _modUnionClosurePar;
 651 
 652   // CMS abstract state machine
 653   // initial_state: Idling
 654   // next_state(Idling)            = {Marking}
 655   // next_state(Marking)           = {Precleaning, Sweeping}
 656   // next_state(Precleaning)       = {AbortablePreclean, FinalMarking}
 657   // next_state(AbortablePreclean) = {FinalMarking}
 658   // next_state(FinalMarking)      = {Sweeping}
 659   // next_state(Sweeping)          = {Resizing}
 660   // next_state(Resizing)          = {Resetting}
 661   // next_state(Resetting)         = {Idling}
 662   // The numeric values below are chosen so that:
 663   // . _collectorState <= Idling ==  post-sweep && pre-mark
 664   // . _collectorState in (Idling, Sweeping) == {initial,final}marking ||
 665   //                                            precleaning || abortablePrecleanb
 666  public:
 667   enum CollectorState {
 668     Resizing            = 0,
 669     Resetting           = 1,
 670     Idling              = 2,
 671     InitialMarking      = 3,
 672     Marking             = 4,
 673     Precleaning         = 5,
 674     AbortablePreclean   = 6,
 675     FinalMarking        = 7,
 676     Sweeping            = 8
 677   };
 678  protected:
 679   static CollectorState _collectorState;
 680 
 681   // State related to prologue/epilogue invocation for my generations
 682   bool _between_prologue_and_epilogue;
 683 
 684   // Signaling/State related to coordination between fore- and background GC
 685   // Note: When the baton has been passed from background GC to foreground GC,
 686   // _foregroundGCIsActive is true and _foregroundGCShouldWait is false.
 687   static bool _foregroundGCIsActive;    // true iff foreground collector is active or
 688                                  // wants to go active
 689   static bool _foregroundGCShouldWait;  // true iff background GC is active and has not
 690                                  // yet passed the baton to the foreground GC
 691 
 692   // Support for CMSScheduleRemark (abortable preclean)
 693   bool _abort_preclean;
 694   bool _start_sampling;
 695 
 696   int    _numYields;
 697   size_t _numDirtyCards;
 698   size_t _sweep_count;
 699 
 700   // Occupancy used for bootstrapping stats
 701   double _bootstrap_occupancy;
 702 
 703   // Timer
 704   elapsedTimer _timer;
 705 
 706   // Timing, allocation and promotion statistics, used for scheduling.
 707   CMSStats      _stats;
 708 
 709   enum CMS_op_type {
 710     CMS_op_checkpointRootsInitial,
 711     CMS_op_checkpointRootsFinal
 712   };
 713 
 714   void do_CMS_operation(CMS_op_type op, GCCause::Cause gc_cause);
 715   bool stop_world_and_do(CMS_op_type op);
 716 
 717   OopTaskQueueSet* task_queues() { return _task_queues; }
 718   int*             hash_seed(int i) { return &_hash_seed[i]; }
 719   YieldingFlexibleWorkGang* conc_workers() { return _conc_workers; }
 720 
 721   // Support for parallelizing Eden rescan in CMS remark phase
 722   void sample_eden(); // ... sample Eden space top
 723 
 724  private:
 725   // Support for parallelizing young gen rescan in CMS remark phase
 726   ParNewGeneration* _young_gen;
 727 
 728   HeapWord** _top_addr;    // ... Top of Eden
 729   HeapWord** _end_addr;    // ... End of Eden
 730   Mutex*     _eden_chunk_lock;
 731   HeapWord** _eden_chunk_array; // ... Eden partitioning array
 732   size_t     _eden_chunk_index; // ... top (exclusive) of array
 733   size_t     _eden_chunk_capacity;  // ... max entries in array
 734 
 735   // Support for parallelizing survivor space rescan
 736   HeapWord** _survivor_chunk_array;
 737   size_t     _survivor_chunk_index;
 738   size_t     _survivor_chunk_capacity;
 739   size_t*    _cursor;
 740   ChunkArray* _survivor_plab_array;
 741 
 742   // Support for marking stack overflow handling
 743   bool take_from_overflow_list(size_t num, CMSMarkStack* to_stack);
 744   bool par_take_from_overflow_list(size_t num,
 745                                    OopTaskQueue* to_work_q,
 746                                    int no_of_gc_threads);
 747   void push_on_overflow_list(oop p);
 748   void par_push_on_overflow_list(oop p);
 749   // The following is, obviously, not, in general, "MT-stable"
 750   bool overflow_list_is_empty() const;
 751 
 752   void preserve_mark_if_necessary(oop p);
 753   void par_preserve_mark_if_necessary(oop p);
 754   void preserve_mark_work(oop p, markOop m);
 755   void restore_preserved_marks_if_any();
 756   NOT_PRODUCT(bool no_preserved_marks() const;)
 757   // In support of testing overflow code
 758   NOT_PRODUCT(int _overflow_counter;)
 759   NOT_PRODUCT(bool simulate_overflow();)       // Sequential
 760   NOT_PRODUCT(bool par_simulate_overflow();)   // MT version
 761 
 762   // CMS work methods
 763   void checkpointRootsInitialWork(); // Initial checkpoint work
 764 
 765   // A return value of false indicates failure due to stack overflow
 766   bool markFromRootsWork();  // Concurrent marking work
 767 
 768  public:   // FIX ME!!! only for testing
 769   bool do_marking_st();      // Single-threaded marking
 770   bool do_marking_mt();      // Multi-threaded  marking
 771 
 772  private:
 773 
 774   // Concurrent precleaning work
 775   size_t preclean_mod_union_table(ConcurrentMarkSweepGeneration* old_gen,
 776                                   ScanMarkedObjectsAgainCarefullyClosure* cl);
 777   size_t preclean_card_table(ConcurrentMarkSweepGeneration* old_gen,
 778                              ScanMarkedObjectsAgainCarefullyClosure* cl);
 779   // Does precleaning work, returning a quantity indicative of
 780   // the amount of "useful work" done.
 781   size_t preclean_work(bool clean_refs, bool clean_survivors);
 782   void preclean_klasses(MarkRefsIntoAndScanClosure* cl, Mutex* freelistLock);
 783   void abortable_preclean(); // Preclean while looking for possible abort
 784   void initialize_sequential_subtasks_for_young_gen_rescan(int i);
 785   // Helper function for above; merge-sorts the per-thread plab samples
 786   void merge_survivor_plab_arrays(ContiguousSpace* surv, int no_of_gc_threads);
 787   // Resets (i.e. clears) the per-thread plab sample vectors
 788   void reset_survivor_plab_arrays();
 789 
 790   // Final (second) checkpoint work
 791   void checkpointRootsFinalWork();
 792   // Work routine for parallel version of remark
 793   void do_remark_parallel();
 794   // Work routine for non-parallel version of remark
 795   void do_remark_non_parallel();
 796   // Reference processing work routine (during second checkpoint)
 797   void refProcessingWork();
 798 
 799   // Concurrent sweeping work
 800   void sweepWork(ConcurrentMarkSweepGeneration* old_gen);
 801 
 802   // (Concurrent) resetting of support data structures
 803   void reset(bool concurrent);
 804 
 805   // Clear _expansion_cause fields of constituent generations
 806   void clear_expansion_cause();
 807 
 808   // An auxiliary method used to record the ends of
 809   // used regions of each generation to limit the extent of sweep
 810   void save_sweep_limits();
 811 
 812   // A work method used by the foreground collector to do
 813   // a mark-sweep-compact.
 814   void do_compaction_work(bool clear_all_soft_refs);
 815 
 816   // Work methods for reporting concurrent mode interruption or failure
 817   bool is_external_interruption();
 818   void report_concurrent_mode_interruption();
 819 
 820   // If the background GC is active, acquire control from the background
 821   // GC and do the collection.
 822   void acquire_control_and_collect(bool   full, bool clear_all_soft_refs);
 823 
 824   // For synchronizing passing of control from background to foreground
 825   // GC.  waitForForegroundGC() is called by the background
 826   // collector.  It if had to wait for a foreground collection,
 827   // it returns true and the background collection should assume
 828   // that the collection was finished by the foreground
 829   // collector.
 830   bool waitForForegroundGC();
 831 
 832   size_t block_size_using_printezis_bits(HeapWord* addr) const;
 833   size_t block_size_if_printezis_bits(HeapWord* addr) const;
 834   HeapWord* next_card_start_after_block(HeapWord* addr) const;
 835 
 836   void setup_cms_unloading_and_verification_state();
 837  public:
 838   CMSCollector(ConcurrentMarkSweepGeneration* cmsGen,
 839                CardTableRS*                   ct,
 840                ConcurrentMarkSweepPolicy*     cp);
 841   ConcurrentMarkSweepThread* cmsThread() { return _cmsThread; }
 842 
 843   ReferenceProcessor* ref_processor() { return _ref_processor; }
 844   void ref_processor_init();
 845 
 846   Mutex* bitMapLock()        const { return _markBitMap.lock();    }
 847   static CollectorState abstract_state() { return _collectorState;  }
 848 
 849   bool should_abort_preclean() const; // Whether preclean should be aborted.
 850   size_t get_eden_used() const;
 851   size_t get_eden_capacity() const;
 852 
 853   ConcurrentMarkSweepGeneration* cmsGen() { return _cmsGen; }
 854 
 855   // Locking checks
 856   NOT_PRODUCT(static bool have_cms_token();)
 857 
 858   bool shouldConcurrentCollect();
 859 
 860   void collect(bool   full,
 861                bool   clear_all_soft_refs,
 862                size_t size,
 863                bool   tlab);
 864   void collect_in_background(GCCause::Cause cause);
 865 
 866   // In support of ExplicitGCInvokesConcurrent
 867   static void request_full_gc(unsigned int full_gc_count, GCCause::Cause cause);
 868   // Should we unload classes in a particular concurrent cycle?
 869   bool should_unload_classes() const {
 870     return _should_unload_classes;
 871   }
 872   void update_should_unload_classes();
 873 
 874   void direct_allocated(HeapWord* start, size_t size);
 875 
 876   // Object is dead if not marked and current phase is sweeping.
 877   bool is_dead_obj(oop obj) const;
 878 
 879   // After a promotion (of "start"), do any necessary marking.
 880   // If "par", then it's being done by a parallel GC thread.
 881   // The last two args indicate if we need precise marking
 882   // and if so the size of the object so it can be dirtied
 883   // in its entirety.
 884   void promoted(bool par, HeapWord* start,
 885                 bool is_obj_array, size_t obj_size);
 886 
 887   void getFreelistLocks() const;
 888   void releaseFreelistLocks() const;
 889   bool haveFreelistLocks() const;
 890 
 891   // Adjust size of underlying generation
 892   void compute_new_size();
 893 
 894   // GC prologue and epilogue
 895   void gc_prologue(bool full);
 896   void gc_epilogue(bool full);
 897 
 898   jlong time_of_last_gc(jlong now) {
 899     if (_collectorState <= Idling) {
 900       // gc not in progress
 901       return _time_of_last_gc;
 902     } else {
 903       // collection in progress
 904       return now;
 905     }
 906   }
 907 
 908   // Support for parallel remark of survivor space
 909   void* get_data_recorder(int thr_num);
 910   void sample_eden_chunk();
 911 
 912   CMSBitMap* markBitMap()  { return &_markBitMap; }
 913   void directAllocated(HeapWord* start, size_t size);
 914 
 915   // Main CMS steps and related support
 916   void checkpointRootsInitial();
 917   bool markFromRoots();  // a return value of false indicates failure
 918                          // due to stack overflow
 919   void preclean();
 920   void checkpointRootsFinal();
 921   void sweep();
 922 
 923   // Check that the currently executing thread is the expected
 924   // one (foreground collector or background collector).
 925   static void check_correct_thread_executing() PRODUCT_RETURN;
 926 
 927   bool is_cms_reachable(HeapWord* addr);
 928 
 929   // Performance Counter Support
 930   CollectorCounters* counters()    { return _gc_counters; }
 931 
 932   // Timer stuff
 933   void    startTimer() { assert(!_timer.is_active(), "Error"); _timer.start();   }
 934   void    stopTimer()  { assert( _timer.is_active(), "Error"); _timer.stop();    }
 935   void    resetTimer() { assert(!_timer.is_active(), "Error"); _timer.reset();   }
 936   double  timerValue() { assert(!_timer.is_active(), "Error"); return _timer.seconds(); }
 937 
 938   int  yields()          { return _numYields; }
 939   void resetYields()     { _numYields = 0;    }
 940   void incrementYields() { _numYields++;      }
 941   void resetNumDirtyCards()               { _numDirtyCards = 0; }
 942   void incrementNumDirtyCards(size_t num) { _numDirtyCards += num; }
 943   size_t  numDirtyCards()                 { return _numDirtyCards; }
 944 
 945   static bool foregroundGCShouldWait() { return _foregroundGCShouldWait; }
 946   static void set_foregroundGCShouldWait(bool v) { _foregroundGCShouldWait = v; }
 947   static bool foregroundGCIsActive() { return _foregroundGCIsActive; }
 948   static void set_foregroundGCIsActive(bool v) { _foregroundGCIsActive = v; }
 949   size_t sweep_count() const             { return _sweep_count; }
 950   void   increment_sweep_count()         { _sweep_count++; }
 951 
 952   // Timers/stats for gc scheduling and incremental mode pacing.
 953   CMSStats& stats() { return _stats; }
 954 
 955   // Adaptive size policy
 956   AdaptiveSizePolicy* size_policy();
 957 
 958   static void print_on_error(outputStream* st);
 959 
 960   // Debugging
 961   void verify();
 962   bool verify_after_remark(bool silent = VerifySilently);
 963   void verify_ok_to_terminate() const PRODUCT_RETURN;
 964   void verify_work_stacks_empty() const PRODUCT_RETURN;
 965   void verify_overflow_empty() const PRODUCT_RETURN;
 966 
 967   // Convenience methods in support of debugging
 968   static const size_t skip_header_HeapWords() PRODUCT_RETURN0;
 969   HeapWord* block_start(const void* p) const PRODUCT_RETURN0;
 970 
 971   // Accessors
 972   CMSMarkStack* verification_mark_stack() { return &_markStack; }
 973   CMSBitMap*    verification_mark_bm()    { return &_verification_mark_bm; }
 974 
 975   // Initialization errors
 976   bool completed_initialization() { return _completed_initialization; }
 977 
 978   void print_eden_and_survivor_chunk_arrays();
 979 };
 980 
 981 class CMSExpansionCause : public AllStatic  {
 982  public:
 983   enum Cause {
 984     _no_expansion,
 985     _satisfy_free_ratio,
 986     _satisfy_promotion,
 987     _satisfy_allocation,
 988     _allocate_par_lab,
 989     _allocate_par_spooling_space,
 990     _adaptive_size_policy
 991   };
 992   // Return a string describing the cause of the expansion.
 993   static const char* to_string(CMSExpansionCause::Cause cause);
 994 };
 995 
 996 class ConcurrentMarkSweepGeneration: public CardGeneration {
 997   friend class VMStructs;
 998   friend class ConcurrentMarkSweepThread;
 999   friend class ConcurrentMarkSweep;
1000   friend class CMSCollector;
1001  protected:
1002   static CMSCollector*       _collector; // the collector that collects us
1003   CompactibleFreeListSpace*  _cmsSpace;  // underlying space (only one for now)
1004 
1005   // Performance Counters
1006   GenerationCounters*      _gen_counters;
1007   GSpaceCounters*          _space_counters;
1008 
1009   // Words directly allocated, used by CMSStats.
1010   size_t _direct_allocated_words;
1011 
1012   // Non-product stat counters
1013   NOT_PRODUCT(
1014     size_t _numObjectsPromoted;
1015     size_t _numWordsPromoted;
1016     size_t _numObjectsAllocated;
1017     size_t _numWordsAllocated;
1018   )
1019 
1020   // Used for sizing decisions
1021   bool _incremental_collection_failed;
1022   bool incremental_collection_failed() {
1023     return _incremental_collection_failed;
1024   }
1025   void set_incremental_collection_failed() {
1026     _incremental_collection_failed = true;
1027   }
1028   void clear_incremental_collection_failed() {
1029     _incremental_collection_failed = false;
1030   }
1031 
1032   // accessors
1033   void set_expansion_cause(CMSExpansionCause::Cause v) { _expansion_cause = v;}
1034   CMSExpansionCause::Cause expansion_cause() const { return _expansion_cause; }
1035 
1036   // Accessing spaces
1037   CompactibleSpace* space() const { return (CompactibleSpace*)_cmsSpace; }
1038 
1039  private:
1040   // For parallel young-gen GC support.
1041   CMSParGCThreadState** _par_gc_thread_states;
1042 
1043   // Reason generation was expanded
1044   CMSExpansionCause::Cause _expansion_cause;
1045 
1046   // In support of MinChunkSize being larger than min object size
1047   const double _dilatation_factor;
1048 
1049   // True if a compacting collection was done.
1050   bool _did_compact;
1051   bool did_compact() { return _did_compact; }
1052 
1053   // Fraction of current occupancy at which to start a CMS collection which
1054   // will collect this generation (at least).
1055   double _initiating_occupancy;
1056 
1057  protected:
1058   // Shrink generation by specified size (returns false if unable to shrink)
1059   void shrink_free_list_by(size_t bytes);
1060 
1061   // Update statistics for GC
1062   virtual void update_gc_stats(Generation* current_generation, bool full);
1063 
1064   // Maximum available space in the generation (including uncommitted)
1065   // space.
1066   size_t max_available() const;
1067 
1068   // getter and initializer for _initiating_occupancy field.
1069   double initiating_occupancy() const { return _initiating_occupancy; }
1070   void   init_initiating_occupancy(intx io, uintx tr);
1071 
1072   void expand_for_gc_cause(size_t bytes, size_t expand_bytes, CMSExpansionCause::Cause cause);
1073 
1074   void assert_correct_size_change_locking();
1075 
1076  public:
1077   ConcurrentMarkSweepGeneration(ReservedSpace rs, size_t initial_byte_size,
1078                                 CardTableRS* ct,
1079                                 bool use_adaptive_freelists,
1080                                 FreeBlockDictionary<FreeChunk>::DictionaryChoice);
1081 
1082   // Accessors
1083   CMSCollector* collector() const { return _collector; }
1084   static void set_collector(CMSCollector* collector) {
1085     assert(_collector == NULL, "already set");
1086     _collector = collector;
1087   }
1088   CompactibleFreeListSpace*  cmsSpace() const { return _cmsSpace;  }
1089 
1090   Mutex* freelistLock() const;
1091 
1092   virtual Generation::Name kind() { return Generation::ConcurrentMarkSweep; }
1093 
1094   void set_did_compact(bool v) { _did_compact = v; }
1095 
1096   bool refs_discovery_is_atomic() const { return false; }
1097   bool refs_discovery_is_mt()     const {
1098     // Note: CMS does MT-discovery during the parallel-remark
1099     // phases. Use ReferenceProcessorMTMutator to make refs
1100     // discovery MT-safe during such phases or other parallel
1101     // discovery phases in the future. This may all go away
1102     // if/when we decide that refs discovery is sufficiently
1103     // rare that the cost of the CAS's involved is in the
1104     // noise. That's a measurement that should be done, and
1105     // the code simplified if that turns out to be the case.
1106     return ConcGCThreads > 1;
1107   }
1108 
1109   // Override
1110   virtual void ref_processor_init();
1111 
1112   void clear_expansion_cause() { _expansion_cause = CMSExpansionCause::_no_expansion; }
1113 
1114   // Space enquiries
1115   double occupancy() const { return ((double)used())/((double)capacity()); }
1116   size_t contiguous_available() const;
1117   size_t unsafe_max_alloc_nogc() const;
1118 
1119   // over-rides
1120   MemRegion used_region_at_save_marks() const;
1121 
1122   // Does a "full" (forced) collection invoked on this generation collect
1123   // the young generation as well?
1124   virtual bool full_collects_young_generation() const {
1125     return !ScavengeBeforeFullGC;
1126   }
1127 
1128   // Adjust quantities in the generation affected by
1129   // the compaction.
1130   void reset_after_compaction();
1131 
1132   // Allocation support
1133   HeapWord* allocate(size_t size, bool tlab);
1134   HeapWord* have_lock_and_allocate(size_t size, bool tlab);
1135   oop       promote(oop obj, size_t obj_size);
1136   HeapWord* par_allocate(size_t size, bool tlab) {
1137     return allocate(size, tlab);
1138   }
1139 
1140 
1141   // Used by CMSStats to track direct allocation.  The value is sampled and
1142   // reset after each young gen collection.
1143   size_t direct_allocated_words() const { return _direct_allocated_words; }
1144   void reset_direct_allocated_words()   { _direct_allocated_words = 0; }
1145 
1146   // Overrides for parallel promotion.
1147   virtual oop par_promote(int thread_num,
1148                           oop obj, markOop m, size_t word_sz);
1149   virtual void par_promote_alloc_done(int thread_num);
1150   virtual void par_oop_since_save_marks_iterate_done(int thread_num);
1151 
1152   virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes) const;
1153 
1154   // Inform this (old) generation that a promotion failure was
1155   // encountered during a collection of the young generation.
1156   virtual void promotion_failure_occurred();
1157 
1158   bool should_collect(bool full, size_t size, bool tlab);
1159   virtual bool should_concurrent_collect() const;
1160   virtual bool is_too_full() const;
1161   void collect(bool   full,
1162                bool   clear_all_soft_refs,
1163                size_t size,
1164                bool   tlab);
1165 
1166   HeapWord* expand_and_allocate(size_t word_size,
1167                                 bool tlab,
1168                                 bool parallel = false);
1169 
1170   // GC prologue and epilogue
1171   void gc_prologue(bool full);
1172   void gc_prologue_work(bool full, bool registerClosure,
1173                         ModUnionClosure* modUnionClosure);
1174   void gc_epilogue(bool full);
1175   void gc_epilogue_work(bool full);
1176 
1177   // Time since last GC of this generation
1178   jlong time_of_last_gc(jlong now) {
1179     return collector()->time_of_last_gc(now);
1180   }
1181   void update_time_of_last_gc(jlong now) {
1182     collector()-> update_time_of_last_gc(now);
1183   }
1184 
1185   // Allocation failure
1186   void shrink(size_t bytes);
1187   HeapWord* expand_and_par_lab_allocate(CMSParGCThreadState* ps, size_t word_sz);
1188   bool expand_and_ensure_spooling_space(PromotionInfo* promo);
1189 
1190   // Iteration support and related enquiries
1191   void save_marks();
1192   bool no_allocs_since_save_marks();
1193 
1194   // Iteration support specific to CMS generations
1195   void save_sweep_limit();
1196 
1197   // More iteration support
1198   virtual void oop_iterate(ExtendedOopClosure* cl);
1199   virtual void safe_object_iterate(ObjectClosure* cl);
1200   virtual void object_iterate(ObjectClosure* cl);
1201 
1202   // Need to declare the full complement of closures, whether we'll
1203   // override them or not, or get message from the compiler:
1204   //   oop_since_save_marks_iterate_nv hides virtual function...
1205   #define CMS_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \
1206     void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
1207   ALL_SINCE_SAVE_MARKS_CLOSURES(CMS_SINCE_SAVE_MARKS_DECL)
1208 
1209   // Smart allocation  XXX -- move to CFLSpace?
1210   void setNearLargestChunk();
1211   bool isNearLargestChunk(HeapWord* addr);
1212 
1213   // Get the chunk at the end of the space.  Delegates to
1214   // the space.
1215   FreeChunk* find_chunk_at_end();
1216 
1217   void post_compact();
1218 
1219   // Debugging
1220   void prepare_for_verify();
1221   void verify();
1222   void print_statistics()               PRODUCT_RETURN;
1223 
1224   // Performance Counters support
1225   virtual void update_counters();
1226   virtual void update_counters(size_t used);
1227   void initialize_performance_counters();
1228   CollectorCounters* counters()  { return collector()->counters(); }
1229 
1230   // Support for parallel remark of survivor space
1231   void* get_data_recorder(int thr_num) {
1232     //Delegate to collector
1233     return collector()->get_data_recorder(thr_num);
1234   }
1235   void sample_eden_chunk() {
1236     //Delegate to collector
1237     return collector()->sample_eden_chunk();
1238   }
1239 
1240   // Printing
1241   const char* name() const;
1242   virtual const char* short_name() const { return "CMS"; }
1243   void        print() const;
1244   void printOccupancy(const char* s);
1245 
1246   // Resize the generation after a compacting GC.  The
1247   // generation can be treated as a contiguous space
1248   // after the compaction.
1249   virtual void compute_new_size();
1250   // Resize the generation after a non-compacting
1251   // collection.
1252   void compute_new_size_free_list();
1253 };
1254 
1255 //
1256 // Closures of various sorts used by CMS to accomplish its work
1257 //
1258 
1259 // This closure is used to do concurrent marking from the roots
1260 // following the first checkpoint.
1261 class MarkFromRootsClosure: public BitMapClosure {
1262   CMSCollector*  _collector;
1263   MemRegion      _span;
1264   CMSBitMap*     _bitMap;
1265   CMSBitMap*     _mut;
1266   CMSMarkStack*  _markStack;
1267   bool           _yield;
1268   int            _skipBits;
1269   HeapWord*      _finger;
1270   HeapWord*      _threshold;
1271   DEBUG_ONLY(bool _verifying;)
1272 
1273  public:
1274   MarkFromRootsClosure(CMSCollector* collector, MemRegion span,
1275                        CMSBitMap* bitMap,
1276                        CMSMarkStack*  markStack,
1277                        bool should_yield, bool verifying = false);
1278   bool do_bit(size_t offset);
1279   void reset(HeapWord* addr);
1280   inline void do_yield_check();
1281 
1282  private:
1283   void scanOopsInOop(HeapWord* ptr);
1284   void do_yield_work();
1285 };
1286 
1287 // This closure is used to do concurrent multi-threaded
1288 // marking from the roots following the first checkpoint.
1289 // XXX This should really be a subclass of The serial version
1290 // above, but i have not had the time to refactor things cleanly.
1291 class Par_MarkFromRootsClosure: public BitMapClosure {
1292   CMSCollector*  _collector;
1293   MemRegion      _whole_span;
1294   MemRegion      _span;
1295   CMSBitMap*     _bit_map;
1296   CMSBitMap*     _mut;
1297   OopTaskQueue*  _work_queue;
1298   CMSMarkStack*  _overflow_stack;
1299   int            _skip_bits;
1300   HeapWord*      _finger;
1301   HeapWord*      _threshold;
1302   CMSConcMarkingTask* _task;
1303  public:
1304   Par_MarkFromRootsClosure(CMSConcMarkingTask* task, CMSCollector* collector,
1305                        MemRegion span,
1306                        CMSBitMap* bit_map,
1307                        OopTaskQueue* work_queue,
1308                        CMSMarkStack*  overflow_stack);
1309   bool do_bit(size_t offset);
1310   inline void do_yield_check();
1311 
1312  private:
1313   void scan_oops_in_oop(HeapWord* ptr);
1314   void do_yield_work();
1315   bool get_work_from_overflow_stack();
1316 };
1317 
1318 // The following closures are used to do certain kinds of verification of
1319 // CMS marking.
1320 class PushAndMarkVerifyClosure: public MetadataAwareOopClosure {
1321   CMSCollector*    _collector;
1322   MemRegion        _span;
1323   CMSBitMap*       _verification_bm;
1324   CMSBitMap*       _cms_bm;
1325   CMSMarkStack*    _mark_stack;
1326  protected:
1327   void do_oop(oop p);
1328   template <class T> inline void do_oop_work(T *p) {
1329     oop obj = oopDesc::load_decode_heap_oop(p);
1330     do_oop(obj);
1331   }
1332  public:
1333   PushAndMarkVerifyClosure(CMSCollector* cms_collector,
1334                            MemRegion span,
1335                            CMSBitMap* verification_bm,
1336                            CMSBitMap* cms_bm,
1337                            CMSMarkStack*  mark_stack);
1338   void do_oop(oop* p);
1339   void do_oop(narrowOop* p);
1340 
1341   // Deal with a stack overflow condition
1342   void handle_stack_overflow(HeapWord* lost);
1343 };
1344 
1345 class MarkFromRootsVerifyClosure: public BitMapClosure {
1346   CMSCollector*  _collector;
1347   MemRegion      _span;
1348   CMSBitMap*     _verification_bm;
1349   CMSBitMap*     _cms_bm;
1350   CMSMarkStack*  _mark_stack;
1351   HeapWord*      _finger;
1352   PushAndMarkVerifyClosure _pam_verify_closure;
1353  public:
1354   MarkFromRootsVerifyClosure(CMSCollector* collector, MemRegion span,
1355                              CMSBitMap* verification_bm,
1356                              CMSBitMap* cms_bm,
1357                              CMSMarkStack*  mark_stack);
1358   bool do_bit(size_t offset);
1359   void reset(HeapWord* addr);
1360 };
1361 
1362 
1363 // This closure is used to check that a certain set of bits is
1364 // "empty" (i.e. the bit vector doesn't have any 1-bits).
1365 class FalseBitMapClosure: public BitMapClosure {
1366  public:
1367   bool do_bit(size_t offset) {
1368     guarantee(false, "Should not have a 1 bit");
1369     return true;
1370   }
1371 };
1372 
1373 // A version of ObjectClosure with "memory" (see _previous_address below)
1374 class UpwardsObjectClosure: public BoolObjectClosure {
1375   HeapWord* _previous_address;
1376  public:
1377   UpwardsObjectClosure() : _previous_address(NULL) { }
1378   void set_previous(HeapWord* addr) { _previous_address = addr; }
1379   HeapWord* previous()              { return _previous_address; }
1380   // A return value of "true" can be used by the caller to decide
1381   // if this object's end should *NOT* be recorded in
1382   // _previous_address above.
1383   virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
1384 };
1385 
1386 // This closure is used during the second checkpointing phase
1387 // to rescan the marked objects on the dirty cards in the mod
1388 // union table and the card table proper. It's invoked via
1389 // MarkFromDirtyCardsClosure below. It uses either
1390 // [Par_]MarkRefsIntoAndScanClosure (Par_ in the parallel case)
1391 // declared in genOopClosures.hpp to accomplish some of its work.
1392 // In the parallel case the bitMap is shared, so access to
1393 // it needs to be suitably synchronized for updates by embedded
1394 // closures that update it; however, this closure itself only
1395 // reads the bit_map and because it is idempotent, is immune to
1396 // reading stale values.
1397 class ScanMarkedObjectsAgainClosure: public UpwardsObjectClosure {
1398   #ifdef ASSERT
1399     CMSCollector*          _collector;
1400     MemRegion              _span;
1401     union {
1402       CMSMarkStack*        _mark_stack;
1403       OopTaskQueue*        _work_queue;
1404     };
1405   #endif // ASSERT
1406   bool                       _parallel;
1407   CMSBitMap*                 _bit_map;
1408   union {
1409     MarkRefsIntoAndScanClosure*     _scan_closure;
1410     Par_MarkRefsIntoAndScanClosure* _par_scan_closure;
1411   };
1412 
1413  public:
1414   ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1415                                 MemRegion span,
1416                                 ReferenceProcessor* rp,
1417                                 CMSBitMap* bit_map,
1418                                 CMSMarkStack*  mark_stack,
1419                                 MarkRefsIntoAndScanClosure* cl):
1420     #ifdef ASSERT
1421       _collector(collector),
1422       _span(span),
1423       _mark_stack(mark_stack),
1424     #endif // ASSERT
1425     _parallel(false),
1426     _bit_map(bit_map),
1427     _scan_closure(cl) { }
1428 
1429   ScanMarkedObjectsAgainClosure(CMSCollector* collector,
1430                                 MemRegion span,
1431                                 ReferenceProcessor* rp,
1432                                 CMSBitMap* bit_map,
1433                                 OopTaskQueue* work_queue,
1434                                 Par_MarkRefsIntoAndScanClosure* cl):
1435     #ifdef ASSERT
1436       _collector(collector),
1437       _span(span),
1438       _work_queue(work_queue),
1439     #endif // ASSERT
1440     _parallel(true),
1441     _bit_map(bit_map),
1442     _par_scan_closure(cl) { }
1443 
1444   bool do_object_b(oop obj) {
1445     guarantee(false, "Call do_object_b(oop, MemRegion) form instead");
1446     return false;
1447   }
1448   bool do_object_bm(oop p, MemRegion mr);
1449 };
1450 
1451 // This closure is used during the second checkpointing phase
1452 // to rescan the marked objects on the dirty cards in the mod
1453 // union table and the card table proper. It invokes
1454 // ScanMarkedObjectsAgainClosure above to accomplish much of its work.
1455 // In the parallel case, the bit map is shared and requires
1456 // synchronized access.
1457 class MarkFromDirtyCardsClosure: public MemRegionClosure {
1458   CompactibleFreeListSpace*      _space;
1459   ScanMarkedObjectsAgainClosure  _scan_cl;
1460   size_t                         _num_dirty_cards;
1461 
1462  public:
1463   MarkFromDirtyCardsClosure(CMSCollector* collector,
1464                             MemRegion span,
1465                             CompactibleFreeListSpace* space,
1466                             CMSBitMap* bit_map,
1467                             CMSMarkStack* mark_stack,
1468                             MarkRefsIntoAndScanClosure* cl):
1469     _space(space),
1470     _num_dirty_cards(0),
1471     _scan_cl(collector, span, collector->ref_processor(), bit_map,
1472                  mark_stack, cl) { }
1473 
1474   MarkFromDirtyCardsClosure(CMSCollector* collector,
1475                             MemRegion span,
1476                             CompactibleFreeListSpace* space,
1477                             CMSBitMap* bit_map,
1478                             OopTaskQueue* work_queue,
1479                             Par_MarkRefsIntoAndScanClosure* cl):
1480     _space(space),
1481     _num_dirty_cards(0),
1482     _scan_cl(collector, span, collector->ref_processor(), bit_map,
1483              work_queue, cl) { }
1484 
1485   void do_MemRegion(MemRegion mr);
1486   void set_space(CompactibleFreeListSpace* space) { _space = space; }
1487   size_t num_dirty_cards() { return _num_dirty_cards; }
1488 };
1489 
1490 // This closure is used in the non-product build to check
1491 // that there are no MemRegions with a certain property.
1492 class FalseMemRegionClosure: public MemRegionClosure {
1493   void do_MemRegion(MemRegion mr) {
1494     guarantee(!mr.is_empty(), "Shouldn't be empty");
1495     guarantee(false, "Should never be here");
1496   }
1497 };
1498 
1499 // This closure is used during the precleaning phase
1500 // to "carefully" rescan marked objects on dirty cards.
1501 // It uses MarkRefsIntoAndScanClosure declared in genOopClosures.hpp
1502 // to accomplish some of its work.
1503 class ScanMarkedObjectsAgainCarefullyClosure: public ObjectClosureCareful {
1504   CMSCollector*                  _collector;
1505   MemRegion                      _span;
1506   bool                           _yield;
1507   Mutex*                         _freelistLock;
1508   CMSBitMap*                     _bitMap;
1509   CMSMarkStack*                  _markStack;
1510   MarkRefsIntoAndScanClosure*    _scanningClosure;
1511 
1512  public:
1513   ScanMarkedObjectsAgainCarefullyClosure(CMSCollector* collector,
1514                                          MemRegion     span,
1515                                          CMSBitMap* bitMap,
1516                                          CMSMarkStack*  markStack,
1517                                          MarkRefsIntoAndScanClosure* cl,
1518                                          bool should_yield):
1519     _collector(collector),
1520     _span(span),
1521     _yield(should_yield),
1522     _bitMap(bitMap),
1523     _markStack(markStack),
1524     _scanningClosure(cl) {
1525   }
1526 
1527   void do_object(oop p) {
1528     guarantee(false, "call do_object_careful instead");
1529   }
1530 
1531   size_t      do_object_careful(oop p) {
1532     guarantee(false, "Unexpected caller");
1533     return 0;
1534   }
1535 
1536   size_t      do_object_careful_m(oop p, MemRegion mr);
1537 
1538   void setFreelistLock(Mutex* m) {
1539     _freelistLock = m;
1540     _scanningClosure->set_freelistLock(m);
1541   }
1542 
1543  private:
1544   inline bool do_yield_check();
1545 
1546   void do_yield_work();
1547 };
1548 
1549 class SurvivorSpacePrecleanClosure: public ObjectClosureCareful {
1550   CMSCollector*                  _collector;
1551   MemRegion                      _span;
1552   bool                           _yield;
1553   CMSBitMap*                     _bit_map;
1554   CMSMarkStack*                  _mark_stack;
1555   PushAndMarkClosure*            _scanning_closure;
1556   unsigned int                   _before_count;
1557 
1558  public:
1559   SurvivorSpacePrecleanClosure(CMSCollector* collector,
1560                                MemRegion     span,
1561                                CMSBitMap*    bit_map,
1562                                CMSMarkStack* mark_stack,
1563                                PushAndMarkClosure* cl,
1564                                unsigned int  before_count,
1565                                bool          should_yield):
1566     _collector(collector),
1567     _span(span),
1568     _yield(should_yield),
1569     _bit_map(bit_map),
1570     _mark_stack(mark_stack),
1571     _scanning_closure(cl),
1572     _before_count(before_count)
1573   { }
1574 
1575   void do_object(oop p) {
1576     guarantee(false, "call do_object_careful instead");
1577   }
1578 
1579   size_t      do_object_careful(oop p);
1580 
1581   size_t      do_object_careful_m(oop p, MemRegion mr) {
1582     guarantee(false, "Unexpected caller");
1583     return 0;
1584   }
1585 
1586  private:
1587   inline void do_yield_check();
1588   void do_yield_work();
1589 };
1590 
1591 // This closure is used to accomplish the sweeping work
1592 // after the second checkpoint but before the concurrent reset
1593 // phase.
1594 //
1595 // Terminology
1596 //   left hand chunk (LHC) - block of one or more chunks currently being
1597 //     coalesced.  The LHC is available for coalescing with a new chunk.
1598 //   right hand chunk (RHC) - block that is currently being swept that is
1599 //     free or garbage that can be coalesced with the LHC.
1600 // _inFreeRange is true if there is currently a LHC
1601 // _lastFreeRangeCoalesced is true if the LHC consists of more than one chunk.
1602 // _freeRangeInFreeLists is true if the LHC is in the free lists.
1603 // _freeFinger is the address of the current LHC
1604 class SweepClosure: public BlkClosureCareful {
1605   CMSCollector*                  _collector;  // collector doing the work
1606   ConcurrentMarkSweepGeneration* _g;    // Generation being swept
1607   CompactibleFreeListSpace*      _sp;   // Space being swept
1608   HeapWord*                      _limit;// the address at or above which the sweep should stop
1609                                         // because we do not expect newly garbage blocks
1610                                         // eligible for sweeping past that address.
1611   Mutex*                         _freelistLock; // Free list lock (in space)
1612   CMSBitMap*                     _bitMap;       // Marking bit map (in
1613                                                 // generation)
1614   bool                           _inFreeRange;  // Indicates if we are in the
1615                                                 // midst of a free run
1616   bool                           _freeRangeInFreeLists;
1617                                         // Often, we have just found
1618                                         // a free chunk and started
1619                                         // a new free range; we do not
1620                                         // eagerly remove this chunk from
1621                                         // the free lists unless there is
1622                                         // a possibility of coalescing.
1623                                         // When true, this flag indicates
1624                                         // that the _freeFinger below
1625                                         // points to a potentially free chunk
1626                                         // that may still be in the free lists
1627   bool                           _lastFreeRangeCoalesced;
1628                                         // free range contains chunks
1629                                         // coalesced
1630   bool                           _yield;
1631                                         // Whether sweeping should be
1632                                         // done with yields. For instance
1633                                         // when done by the foreground
1634                                         // collector we shouldn't yield.
1635   HeapWord*                      _freeFinger;   // When _inFreeRange is set, the
1636                                                 // pointer to the "left hand
1637                                                 // chunk"
1638   size_t                         _freeRangeSize;
1639                                         // When _inFreeRange is set, this
1640                                         // indicates the accumulated size
1641                                         // of the "left hand chunk"
1642   NOT_PRODUCT(
1643     size_t                       _numObjectsFreed;
1644     size_t                       _numWordsFreed;
1645     size_t                       _numObjectsLive;
1646     size_t                       _numWordsLive;
1647     size_t                       _numObjectsAlreadyFree;
1648     size_t                       _numWordsAlreadyFree;
1649     FreeChunk*                   _last_fc;
1650   )
1651  private:
1652   // Code that is common to a free chunk or garbage when
1653   // encountered during sweeping.
1654   void do_post_free_or_garbage_chunk(FreeChunk *fc, size_t chunkSize);
1655   // Process a free chunk during sweeping.
1656   void do_already_free_chunk(FreeChunk *fc);
1657   // Work method called when processing an already free or a
1658   // freshly garbage chunk to do a lookahead and possibly a
1659   // preemptive flush if crossing over _limit.
1660   void lookahead_and_flush(FreeChunk* fc, size_t chunkSize);
1661   // Process a garbage chunk during sweeping.
1662   size_t do_garbage_chunk(FreeChunk *fc);
1663   // Process a live chunk during sweeping.
1664   size_t do_live_chunk(FreeChunk* fc);
1665 
1666   // Accessors.
1667   HeapWord* freeFinger() const          { return _freeFinger; }
1668   void set_freeFinger(HeapWord* v)      { _freeFinger = v; }
1669   bool inFreeRange()    const           { return _inFreeRange; }
1670   void set_inFreeRange(bool v)          { _inFreeRange = v; }
1671   bool lastFreeRangeCoalesced() const    { return _lastFreeRangeCoalesced; }
1672   void set_lastFreeRangeCoalesced(bool v) { _lastFreeRangeCoalesced = v; }
1673   bool freeRangeInFreeLists() const     { return _freeRangeInFreeLists; }
1674   void set_freeRangeInFreeLists(bool v) { _freeRangeInFreeLists = v; }
1675 
1676   // Initialize a free range.
1677   void initialize_free_range(HeapWord* freeFinger, bool freeRangeInFreeLists);
1678   // Return this chunk to the free lists.
1679   void flush_cur_free_chunk(HeapWord* chunk, size_t size);
1680 
1681   // Check if we should yield and do so when necessary.
1682   inline void do_yield_check(HeapWord* addr);
1683 
1684   // Yield
1685   void do_yield_work(HeapWord* addr);
1686 
1687   // Debugging/Printing
1688   void print_free_block_coalesced(FreeChunk* fc) const;
1689 
1690  public:
1691   SweepClosure(CMSCollector* collector, ConcurrentMarkSweepGeneration* g,
1692                CMSBitMap* bitMap, bool should_yield);
1693   ~SweepClosure() PRODUCT_RETURN;
1694 
1695   size_t       do_blk_careful(HeapWord* addr);
1696   void         print() const { print_on(tty); }
1697   void         print_on(outputStream *st) const;
1698 };
1699 
1700 // Closures related to weak references processing
1701 
1702 // During CMS' weak reference processing, this is a
1703 // work-routine/closure used to complete transitive
1704 // marking of objects as live after a certain point
1705 // in which an initial set has been completely accumulated.
1706 // This closure is currently used both during the final
1707 // remark stop-world phase, as well as during the concurrent
1708 // precleaning of the discovered reference lists.
1709 class CMSDrainMarkingStackClosure: public VoidClosure {
1710   CMSCollector*        _collector;
1711   MemRegion            _span;
1712   CMSMarkStack*        _mark_stack;
1713   CMSBitMap*           _bit_map;
1714   CMSKeepAliveClosure* _keep_alive;
1715   bool                 _concurrent_precleaning;
1716  public:
1717   CMSDrainMarkingStackClosure(CMSCollector* collector, MemRegion span,
1718                       CMSBitMap* bit_map, CMSMarkStack* mark_stack,
1719                       CMSKeepAliveClosure* keep_alive,
1720                       bool cpc):
1721     _collector(collector),
1722     _span(span),
1723     _bit_map(bit_map),
1724     _mark_stack(mark_stack),
1725     _keep_alive(keep_alive),
1726     _concurrent_precleaning(cpc) {
1727     assert(_concurrent_precleaning == _keep_alive->concurrent_precleaning(),
1728            "Mismatch");
1729   }
1730 
1731   void do_void();
1732 };
1733 
1734 // A parallel version of CMSDrainMarkingStackClosure above.
1735 class CMSParDrainMarkingStackClosure: public VoidClosure {
1736   CMSCollector*           _collector;
1737   MemRegion               _span;
1738   OopTaskQueue*           _work_queue;
1739   CMSBitMap*              _bit_map;
1740   CMSInnerParMarkAndPushClosure _mark_and_push;
1741 
1742  public:
1743   CMSParDrainMarkingStackClosure(CMSCollector* collector,
1744                                  MemRegion span, CMSBitMap* bit_map,
1745                                  OopTaskQueue* work_queue):
1746     _collector(collector),
1747     _span(span),
1748     _bit_map(bit_map),
1749     _work_queue(work_queue),
1750     _mark_and_push(collector, span, bit_map, work_queue) { }
1751 
1752  public:
1753   void trim_queue(uint max);
1754   void do_void();
1755 };
1756 
1757 // Allow yielding or short-circuiting of reference list
1758 // precleaning work.
1759 class CMSPrecleanRefsYieldClosure: public YieldClosure {
1760   CMSCollector* _collector;
1761   void do_yield_work();
1762  public:
1763   CMSPrecleanRefsYieldClosure(CMSCollector* collector):
1764     _collector(collector) {}
1765   virtual bool should_return();
1766 };
1767 
1768 
1769 // Convenience class that locks free list locks for given CMS collector
1770 class FreelistLocker: public StackObj {
1771  private:
1772   CMSCollector* _collector;
1773  public:
1774   FreelistLocker(CMSCollector* collector):
1775     _collector(collector) {
1776     _collector->getFreelistLocks();
1777   }
1778 
1779   ~FreelistLocker() {
1780     _collector->releaseFreelistLocks();
1781   }
1782 };
1783 
1784 // Mark all dead objects in a given space.
1785 class MarkDeadObjectsClosure: public BlkClosure {
1786   const CMSCollector*             _collector;
1787   const CompactibleFreeListSpace* _sp;
1788   CMSBitMap*                      _live_bit_map;
1789   CMSBitMap*                      _dead_bit_map;
1790 public:
1791   MarkDeadObjectsClosure(const CMSCollector* collector,
1792                          const CompactibleFreeListSpace* sp,
1793                          CMSBitMap *live_bit_map,
1794                          CMSBitMap *dead_bit_map) :
1795     _collector(collector),
1796     _sp(sp),
1797     _live_bit_map(live_bit_map),
1798     _dead_bit_map(dead_bit_map) {}
1799   size_t do_blk(HeapWord* addr);
1800 };
1801 
1802 class TraceCMSMemoryManagerStats : public TraceMemoryManagerStats {
1803 
1804  public:
1805   TraceCMSMemoryManagerStats(CMSCollector::CollectorState phase, GCCause::Cause cause);
1806 };
1807 
1808 
1809 #endif // SHARE_VM_GC_CMS_CONCURRENTMARKSWEEPGENERATION_HPP