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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1Allocator.hpp"
  30 #include "gc_implementation/g1/concurrentMark.hpp"
  31 #include "gc_implementation/g1/evacuationInfo.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.hpp"
  33 #include "gc_implementation/g1/g1BiasedArray.hpp"
  34 #include "gc_implementation/g1/g1HRPrinter.hpp"
  35 #include "gc_implementation/g1/g1InCSetState.hpp"
  36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc_implementation/g1/g1YCTypes.hpp"
  39 #include "gc_implementation/g1/heapRegionManager.hpp"
  40 #include "gc_implementation/g1/heapRegionSet.hpp"
  41 #include "gc_implementation/shared/gcHeapSummary.hpp"
  42 #include "gc_implementation/shared/hSpaceCounters.hpp"
  43 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  44 #include "memory/barrierSet.hpp"
  45 #include "memory/memRegion.hpp"
  46 #include "memory/sharedHeap.hpp"
  47 #include "utilities/stack.hpp"
  48 
  49 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  50 // It uses the "Garbage First" heap organization and algorithm, which
  51 // may combine concurrent marking with parallel, incremental compaction of
  52 // heap subsets that will yield large amounts of garbage.
  53 
  54 // Forward declarations
  55 class HeapRegion;
  56 class HRRSCleanupTask;
  57 class GenerationSpec;
  58 class OopsInHeapRegionClosure;
  59 class G1KlassScanClosure;
  60 class G1ScanHeapEvacClosure;
  61 class ObjectClosure;
  62 class SpaceClosure;
  63 class CompactibleSpaceClosure;
  64 class Space;
  65 class G1CollectorPolicy;
  66 class GenRemSet;
  67 class G1RemSet;
  68 class HeapRegionRemSetIterator;
  69 class ConcurrentMark;
  70 class ConcurrentMarkThread;
  71 class ConcurrentG1Refine;
  72 class ConcurrentGCTimer;
  73 class GenerationCounters;
  74 class STWGCTimer;
  75 class G1NewTracer;
  76 class G1OldTracer;
  77 class EvacuationFailedInfo;
  78 class nmethod;

  79 
  80 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  82 
  83 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  84 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  85 
  86 class YoungList : public CHeapObj<mtGC> {
  87 private:
  88   G1CollectedHeap* _g1h;
  89 
  90   HeapRegion* _head;
  91 
  92   HeapRegion* _survivor_head;
  93   HeapRegion* _survivor_tail;
  94 
  95   HeapRegion* _curr;
  96 
  97   uint        _length;
  98   uint        _survivor_length;
  99 
 100   size_t      _last_sampled_rs_lengths;
 101   size_t      _sampled_rs_lengths;
 102 
 103   void         empty_list(HeapRegion* list);
 104 
 105 public:
 106   YoungList(G1CollectedHeap* g1h);
 107 
 108   void         push_region(HeapRegion* hr);
 109   void         add_survivor_region(HeapRegion* hr);
 110 
 111   void         empty_list();
 112   bool         is_empty() { return _length == 0; }
 113   uint         length() { return _length; }
 114   uint         survivor_length() { return _survivor_length; }
 115 
 116   // Currently we do not keep track of the used byte sum for the
 117   // young list and the survivors and it'd be quite a lot of work to
 118   // do so. When we'll eventually replace the young list with
 119   // instances of HeapRegionLinkedList we'll get that for free. So,
 120   // we'll report the more accurate information then.
 121   size_t       eden_used_bytes() {
 122     assert(length() >= survivor_length(), "invariant");
 123     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 124   }
 125   size_t       survivor_used_bytes() {
 126     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 127   }
 128 
 129   void rs_length_sampling_init();
 130   bool rs_length_sampling_more();
 131   void rs_length_sampling_next();
 132 
 133   void reset_sampled_info() {
 134     _last_sampled_rs_lengths =   0;
 135   }
 136   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 137 
 138   // for development purposes
 139   void reset_auxilary_lists();
 140   void clear() { _head = NULL; _length = 0; }
 141 
 142   void clear_survivors() {
 143     _survivor_head    = NULL;
 144     _survivor_tail    = NULL;
 145     _survivor_length  = 0;
 146   }
 147 
 148   HeapRegion* first_region() { return _head; }
 149   HeapRegion* first_survivor_region() { return _survivor_head; }
 150   HeapRegion* last_survivor_region() { return _survivor_tail; }
 151 
 152   // debugging
 153   bool          check_list_well_formed();
 154   bool          check_list_empty(bool check_sample = true);
 155   void          print();
 156 };
 157 
 158 // The G1 STW is alive closure.
 159 // An instance is embedded into the G1CH and used as the
 160 // (optional) _is_alive_non_header closure in the STW
 161 // reference processor. It is also extensively used during
 162 // reference processing during STW evacuation pauses.
 163 class G1STWIsAliveClosure: public BoolObjectClosure {
 164   G1CollectedHeap* _g1;
 165 public:
 166   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 167   bool do_object_b(oop p);
 168 };
 169 
 170 class RefineCardTableEntryClosure;
 171 
 172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 173  private:
 174   void reset_from_card_cache(uint start_idx, size_t num_regions);
 175  public:
 176   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 177 };
 178 
 179 class G1CollectedHeap : public SharedHeap {
 180   friend class VM_CollectForMetadataAllocation;
 181   friend class VM_G1CollectForAllocation;
 182   friend class VM_G1CollectFull;
 183   friend class VM_G1IncCollectionPause;
 184   friend class VMStructs;
 185   friend class MutatorAllocRegion;
 186   friend class SurvivorGCAllocRegion;
 187   friend class OldGCAllocRegion;
 188   friend class G1Allocator;
 189   friend class G1DefaultAllocator;
 190   friend class G1ResManAllocator;
 191 
 192   // Closures used in implementation.
 193   template <G1Barrier barrier, G1Mark do_mark_object>
 194   friend class G1ParCopyClosure;
 195   friend class G1IsAliveClosure;
 196   friend class G1EvacuateFollowersClosure;
 197   friend class G1ParScanThreadState;
 198   friend class G1ParScanClosureSuper;
 199   friend class G1ParEvacuateFollowersClosure;
 200   friend class G1ParTask;
 201   friend class G1ParGCAllocator;
 202   friend class G1DefaultParGCAllocator;
 203   friend class G1FreeGarbageRegionClosure;
 204   friend class RefineCardTableEntryClosure;
 205   friend class G1PrepareCompactClosure;
 206   friend class RegionSorter;
 207   friend class RegionResetter;
 208   friend class CountRCClosure;
 209   friend class EvacPopObjClosure;
 210   friend class G1ParCleanupCTTask;
 211 
 212   friend class G1FreeHumongousRegionClosure;
 213   // Other related classes.
 214   friend class G1MarkSweep;
 215 
 216   // Testing classes.
 217   friend class G1CheckCSetFastTableClosure;
 218 
 219 private:
 220   // The one and only G1CollectedHeap, so static functions can find it.
 221   static G1CollectedHeap* _g1h;
 222 
 223   static size_t _humongous_object_threshold_in_words;
 224 
 225   // The secondary free list which contains regions that have been
 226   // freed up during the cleanup process. This will be appended to
 227   // the master free list when appropriate.
 228   FreeRegionList _secondary_free_list;
 229 
 230   // It keeps track of the old regions.
 231   HeapRegionSet _old_set;
 232 
 233   // It keeps track of the humongous regions.
 234   HeapRegionSet _humongous_set;
 235 
 236   void eagerly_reclaim_humongous_regions();
 237 
 238   // The number of regions we could create by expansion.
 239   uint _expansion_regions;
 240 
 241   // The block offset table for the G1 heap.
 242   G1BlockOffsetSharedArray* _bot_shared;
 243 
 244   // Tears down the region sets / lists so that they are empty and the
 245   // regions on the heap do not belong to a region set / list. The
 246   // only exception is the humongous set which we leave unaltered. If
 247   // free_list_only is true, it will only tear down the master free
 248   // list. It is called before a Full GC (free_list_only == false) or
 249   // before heap shrinking (free_list_only == true).
 250   void tear_down_region_sets(bool free_list_only);
 251 
 252   // Rebuilds the region sets / lists so that they are repopulated to
 253   // reflect the contents of the heap. The only exception is the
 254   // humongous set which was not torn down in the first place. If
 255   // free_list_only is true, it will only rebuild the master free
 256   // list. It is called after a Full GC (free_list_only == false) or
 257   // after heap shrinking (free_list_only == true).
 258   void rebuild_region_sets(bool free_list_only);
 259 
 260   // Callback for region mapping changed events.
 261   G1RegionMappingChangedListener _listener;
 262 
 263   // The sequence of all heap regions in the heap.
 264   HeapRegionManager _hrm;
 265 
 266   // Class that handles the different kinds of allocations.
 267   G1Allocator* _allocator;
 268 
 269   // Statistics for each allocation context
 270   AllocationContextStats _allocation_context_stats;
 271 
 272   // PLAB sizing policy for survivors.
 273   PLABStats _survivor_plab_stats;
 274 
 275   // PLAB sizing policy for tenured objects.
 276   PLABStats _old_plab_stats;
 277 
 278   // It specifies whether we should attempt to expand the heap after a
 279   // region allocation failure. If heap expansion fails we set this to
 280   // false so that we don't re-attempt the heap expansion (it's likely
 281   // that subsequent expansion attempts will also fail if one fails).
 282   // Currently, it is only consulted during GC and it's reset at the
 283   // start of each GC.
 284   bool _expand_heap_after_alloc_failure;
 285 
 286   // It resets the mutator alloc region before new allocations can take place.
 287   void init_mutator_alloc_region();
 288 
 289   // It releases the mutator alloc region.
 290   void release_mutator_alloc_region();
 291 
 292   // It initializes the GC alloc regions at the start of a GC.
 293   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 294 
 295   // It releases the GC alloc regions at the end of a GC.
 296   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 297 
 298   // It does any cleanup that needs to be done on the GC alloc regions
 299   // before a Full GC.
 300   void abandon_gc_alloc_regions();
 301 
 302   // Helper for monitoring and management support.
 303   G1MonitoringSupport* _g1mm;
 304 
 305   // Records whether the region at the given index is (still) a
 306   // candidate for eager reclaim.  Only valid for humongous start
 307   // regions; other regions have unspecified values.  Humongous start
 308   // regions are initialized at start of collection pause, with
 309   // candidates removed from the set as they are found reachable from
 310   // roots or the young generation.
 311   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 312    protected:
 313     bool default_value() const { return false; }
 314    public:
 315     void clear() { G1BiasedMappedArray<bool>::clear(); }
 316     void set_candidate(uint region, bool value) {
 317       set_by_index(region, value);
 318     }
 319     bool is_candidate(uint region) {
 320       return get_by_index(region);
 321     }
 322   };
 323 
 324   HumongousReclaimCandidates _humongous_reclaim_candidates;
 325   // Stores whether during humongous object registration we found candidate regions.
 326   // If not, we can skip a few steps.
 327   bool _has_humongous_reclaim_candidates;
 328 
 329   volatile unsigned _gc_time_stamp;
 330 
 331   size_t* _surviving_young_words;
 332 
 333   G1HRPrinter _hr_printer;
 334 
 335   void setup_surviving_young_words();
 336   void update_surviving_young_words(size_t* surv_young_words);
 337   void cleanup_surviving_young_words();
 338 
 339   // It decides whether an explicit GC should start a concurrent cycle
 340   // instead of doing a STW GC. Currently, a concurrent cycle is
 341   // explicitly started if:
 342   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 343   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 344   // (c) cause == _g1_humongous_allocation
 345   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 346 
 347   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 348   // concurrent cycles) we have started.
 349   volatile uint _old_marking_cycles_started;
 350 
 351   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 352   // concurrent cycles) we have completed.
 353   volatile uint _old_marking_cycles_completed;
 354 
 355   bool _concurrent_cycle_started;
 356   bool _heap_summary_sent;
 357 
 358   // This is a non-product method that is helpful for testing. It is
 359   // called at the end of a GC and artificially expands the heap by
 360   // allocating a number of dead regions. This way we can induce very
 361   // frequent marking cycles and stress the cleanup / concurrent
 362   // cleanup code more (as all the regions that will be allocated by
 363   // this method will be found dead by the marking cycle).
 364   void allocate_dummy_regions() PRODUCT_RETURN;
 365 
 366   // Clear RSets after a compaction. It also resets the GC time stamps.
 367   void clear_rsets_post_compaction();
 368 
 369   // If the HR printer is active, dump the state of the regions in the
 370   // heap after a compaction.
 371   void print_hrm_post_compaction();
 372 
 373   // Create a memory mapper for auxiliary data structures of the given size and
 374   // translation factor.
 375   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 376                                                          size_t size,
 377                                                          size_t translation_factor);
 378 
 379   void trace_heap(GCWhen::Type when, GCTracer* tracer);
 380 
 381   double verify(bool guard, const char* msg);
 382   void verify_before_gc();
 383   void verify_after_gc();
 384 
 385   void log_gc_header();
 386   void log_gc_footer(double pause_time_sec);
 387 
 388   // These are macros so that, if the assert fires, we get the correct
 389   // line number, file, etc.
 390 
 391 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 392   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 393           (_extra_message_),                                                  \
 394           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 395           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 396           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 397 
 398 #define assert_heap_locked()                                                  \
 399   do {                                                                        \
 400     assert(Heap_lock->owned_by_self(),                                        \
 401            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 402   } while (0)
 403 
 404 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 405   do {                                                                        \
 406     assert(Heap_lock->owned_by_self() ||                                      \
 407            (SafepointSynchronize::is_at_safepoint() &&                        \
 408              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 409            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 410                                         "should be at a safepoint"));         \
 411   } while (0)
 412 
 413 #define assert_heap_locked_and_not_at_safepoint()                             \
 414   do {                                                                        \
 415     assert(Heap_lock->owned_by_self() &&                                      \
 416                                     !SafepointSynchronize::is_at_safepoint(), \
 417           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 418                                        "should not be at a safepoint"));      \
 419   } while (0)
 420 
 421 #define assert_heap_not_locked()                                              \
 422   do {                                                                        \
 423     assert(!Heap_lock->owned_by_self(),                                       \
 424         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 425   } while (0)
 426 
 427 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 428   do {                                                                        \
 429     assert(!Heap_lock->owned_by_self() &&                                     \
 430                                     !SafepointSynchronize::is_at_safepoint(), \
 431       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 432                                    "should not be at a safepoint"));          \
 433   } while (0)
 434 
 435 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 436   do {                                                                        \
 437     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 438               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 439            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 440   } while (0)
 441 
 442 #define assert_not_at_safepoint()                                             \
 443   do {                                                                        \
 444     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 445            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 446   } while (0)
 447 
 448 protected:
 449 
 450   // The young region list.
 451   YoungList*  _young_list;
 452 
 453   // The current policy object for the collector.
 454   G1CollectorPolicy* _g1_policy;
 455 
 456   // This is the second level of trying to allocate a new region. If
 457   // new_region() didn't find a region on the free_list, this call will
 458   // check whether there's anything available on the
 459   // secondary_free_list and/or wait for more regions to appear on
 460   // that list, if _free_regions_coming is set.
 461   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 462 
 463   // Try to allocate a single non-humongous HeapRegion sufficient for
 464   // an allocation of the given word_size. If do_expand is true,
 465   // attempt to expand the heap if necessary to satisfy the allocation
 466   // request. If the region is to be used as an old region or for a
 467   // humongous object, set is_old to true. If not, to false.
 468   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 469 
 470   // Initialize a contiguous set of free regions of length num_regions
 471   // and starting at index first so that they appear as a single
 472   // humongous region.
 473   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 474                                                       uint num_regions,
 475                                                       size_t word_size,
 476                                                       AllocationContext_t context);
 477 
 478   // Attempt to allocate a humongous object of the given size. Return
 479   // NULL if unsuccessful.
 480   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 481 
 482   // The following two methods, allocate_new_tlab() and
 483   // mem_allocate(), are the two main entry points from the runtime
 484   // into the G1's allocation routines. They have the following
 485   // assumptions:
 486   //
 487   // * They should both be called outside safepoints.
 488   //
 489   // * They should both be called without holding the Heap_lock.
 490   //
 491   // * All allocation requests for new TLABs should go to
 492   //   allocate_new_tlab().
 493   //
 494   // * All non-TLAB allocation requests should go to mem_allocate().
 495   //
 496   // * If either call cannot satisfy the allocation request using the
 497   //   current allocating region, they will try to get a new one. If
 498   //   this fails, they will attempt to do an evacuation pause and
 499   //   retry the allocation.
 500   //
 501   // * If all allocation attempts fail, even after trying to schedule
 502   //   an evacuation pause, allocate_new_tlab() will return NULL,
 503   //   whereas mem_allocate() will attempt a heap expansion and/or
 504   //   schedule a Full GC.
 505   //
 506   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 507   //   should never be called with word_size being humongous. All
 508   //   humongous allocation requests should go to mem_allocate() which
 509   //   will satisfy them with a special path.
 510 
 511   virtual HeapWord* allocate_new_tlab(size_t word_size);
 512 
 513   virtual HeapWord* mem_allocate(size_t word_size,
 514                                  bool*  gc_overhead_limit_was_exceeded);
 515 
 516   // The following three methods take a gc_count_before_ret
 517   // parameter which is used to return the GC count if the method
 518   // returns NULL. Given that we are required to read the GC count
 519   // while holding the Heap_lock, and these paths will take the
 520   // Heap_lock at some point, it's easier to get them to read the GC
 521   // count while holding the Heap_lock before they return NULL instead
 522   // of the caller (namely: mem_allocate()) having to also take the
 523   // Heap_lock just to read the GC count.
 524 
 525   // First-level mutator allocation attempt: try to allocate out of
 526   // the mutator alloc region without taking the Heap_lock. This
 527   // should only be used for non-humongous allocations.
 528   inline HeapWord* attempt_allocation(size_t word_size,
 529                                       uint* gc_count_before_ret,
 530                                       uint* gclocker_retry_count_ret);
 531 
 532   // Second-level mutator allocation attempt: take the Heap_lock and
 533   // retry the allocation attempt, potentially scheduling a GC
 534   // pause. This should only be used for non-humongous allocations.
 535   HeapWord* attempt_allocation_slow(size_t word_size,
 536                                     AllocationContext_t context,
 537                                     uint* gc_count_before_ret,
 538                                     uint* gclocker_retry_count_ret);
 539 
 540   // Takes the Heap_lock and attempts a humongous allocation. It can
 541   // potentially schedule a GC pause.
 542   HeapWord* attempt_allocation_humongous(size_t word_size,
 543                                          uint* gc_count_before_ret,
 544                                          uint* gclocker_retry_count_ret);
 545 
 546   // Allocation attempt that should be called during safepoints (e.g.,
 547   // at the end of a successful GC). expect_null_mutator_alloc_region
 548   // specifies whether the mutator alloc region is expected to be NULL
 549   // or not.
 550   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 551                                             AllocationContext_t context,
 552                                             bool expect_null_mutator_alloc_region);
 553 
 554   // It dirties the cards that cover the block so that so that the post
 555   // write barrier never queues anything when updating objects on this
 556   // block. It is assumed (and in fact we assert) that the block
 557   // belongs to a young region.
 558   inline void dirty_young_block(HeapWord* start, size_t word_size);
 559 
 560   // Allocate blocks during garbage collection. Will ensure an
 561   // allocation region, either by picking one or expanding the
 562   // heap, and then allocate a block of the given size. The block
 563   // may not be a humongous - it must fit into a single heap region.
 564   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 565                                           size_t word_size,
 566                                           AllocationContext_t context);
 567   // Ensure that no further allocations can happen in "r", bearing in mind
 568   // that parallel threads might be attempting allocations.
 569   void par_allocate_remaining_space(HeapRegion* r);
 570 
 571   // Allocation attempt during GC for a survivor object / PLAB.
 572   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 573                                                AllocationContext_t context);
 574 
 575   // Allocation attempt during GC for an old object / PLAB.
 576   inline HeapWord* old_attempt_allocation(size_t word_size,
 577                                           AllocationContext_t context);
 578 
 579   // These methods are the "callbacks" from the G1AllocRegion class.
 580 
 581   // For mutator alloc regions.
 582   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 583   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 584                                    size_t allocated_bytes);
 585 
 586   // For GC alloc regions.
 587   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 588                                   InCSetState dest);
 589   void retire_gc_alloc_region(HeapRegion* alloc_region,
 590                               size_t allocated_bytes, InCSetState dest);
 591 
 592   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 593   //   inspection request and should collect the entire heap
 594   // - if clear_all_soft_refs is true, all soft references should be
 595   //   cleared during the GC
 596   // - if explicit_gc is false, word_size describes the allocation that
 597   //   the GC should attempt (at least) to satisfy
 598   // - it returns false if it is unable to do the collection due to the
 599   //   GC locker being active, true otherwise
 600   bool do_collection(bool explicit_gc,
 601                      bool clear_all_soft_refs,
 602                      size_t word_size);
 603 
 604   // Callback from VM_G1CollectFull operation.
 605   // Perform a full collection.
 606   virtual void do_full_collection(bool clear_all_soft_refs);
 607 
 608   // Resize the heap if necessary after a full collection.  If this is
 609   // after a collect-for allocation, "word_size" is the allocation size,
 610   // and will be considered part of the used portion of the heap.
 611   void resize_if_necessary_after_full_collection(size_t word_size);
 612 
 613   // Callback from VM_G1CollectForAllocation operation.
 614   // This function does everything necessary/possible to satisfy a
 615   // failed allocation request (including collection, expansion, etc.)
 616   HeapWord* satisfy_failed_allocation(size_t word_size,
 617                                       AllocationContext_t context,
 618                                       bool* succeeded);
 619 
 620   // Attempting to expand the heap sufficiently
 621   // to support an allocation of the given "word_size".  If
 622   // successful, perform the allocation and return the address of the
 623   // allocated block, or else "NULL".
 624   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 625 
 626   // Process any reference objects discovered during
 627   // an incremental evacuation pause.
 628   void process_discovered_references(uint no_of_gc_workers);
 629 
 630   // Enqueue any remaining discovered references
 631   // after processing.
 632   void enqueue_discovered_references(uint no_of_gc_workers);
 633 
 634 public:
 635 
 636   G1Allocator* allocator() {
 637     return _allocator;
 638   }
 639 
 640   G1MonitoringSupport* g1mm() {
 641     assert(_g1mm != NULL, "should have been initialized");
 642     return _g1mm;
 643   }
 644 
 645   // Expand the garbage-first heap by at least the given size (in bytes!).
 646   // Returns true if the heap was expanded by the requested amount;
 647   // false otherwise.
 648   // (Rounds up to a HeapRegion boundary.)
 649   bool expand(size_t expand_bytes);
 650 
 651   // Returns the PLAB statistics for a given destination.
 652   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 653 
 654   // Determines PLAB size for a given destination.
 655   inline size_t desired_plab_sz(InCSetState dest);
 656 
 657   inline AllocationContextStats& allocation_context_stats();
 658 
 659   // Do anything common to GC's.
 660   virtual void gc_prologue(bool full);
 661   virtual void gc_epilogue(bool full);
 662 
 663   // Modify the reclaim candidate set and test for presence.
 664   // These are only valid for starts_humongous regions.
 665   inline void set_humongous_reclaim_candidate(uint region, bool value);
 666   inline bool is_humongous_reclaim_candidate(uint region);
 667 
 668   // Remove from the reclaim candidate set.  Also remove from the
 669   // collection set so that later encounters avoid the slow path.
 670   inline void set_humongous_is_live(oop obj);
 671 
 672   // Register the given region to be part of the collection set.
 673   inline void register_humongous_region_with_in_cset_fast_test(uint index);
 674   // Register regions with humongous objects (actually on the start region) in
 675   // the in_cset_fast_test table.
 676   void register_humongous_regions_with_in_cset_fast_test();
 677   // We register a region with the fast "in collection set" test. We
 678   // simply set to true the array slot corresponding to this region.
 679   void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
 680     _in_cset_fast_test.set_in_young(r->hrm_index());
 681   }
 682   void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
 683     _in_cset_fast_test.set_in_old(r->hrm_index());
 684   }
 685 
 686   // This is a fast test on whether a reference points into the
 687   // collection set or not. Assume that the reference
 688   // points into the heap.
 689   inline bool in_cset_fast_test(oop obj);
 690 
 691   void clear_cset_fast_test() {
 692     _in_cset_fast_test.clear();
 693   }
 694 
 695   // This is called at the start of either a concurrent cycle or a Full
 696   // GC to update the number of old marking cycles started.
 697   void increment_old_marking_cycles_started();
 698 
 699   // This is called at the end of either a concurrent cycle or a Full
 700   // GC to update the number of old marking cycles completed. Those two
 701   // can happen in a nested fashion, i.e., we start a concurrent
 702   // cycle, a Full GC happens half-way through it which ends first,
 703   // and then the cycle notices that a Full GC happened and ends
 704   // too. The concurrent parameter is a boolean to help us do a bit
 705   // tighter consistency checking in the method. If concurrent is
 706   // false, the caller is the inner caller in the nesting (i.e., the
 707   // Full GC). If concurrent is true, the caller is the outer caller
 708   // in this nesting (i.e., the concurrent cycle). Further nesting is
 709   // not currently supported. The end of this call also notifies
 710   // the FullGCCount_lock in case a Java thread is waiting for a full
 711   // GC to happen (e.g., it called System.gc() with
 712   // +ExplicitGCInvokesConcurrent).
 713   void increment_old_marking_cycles_completed(bool concurrent);
 714 
 715   uint old_marking_cycles_completed() {
 716     return _old_marking_cycles_completed;
 717   }
 718 
 719   void register_concurrent_cycle_start(const Ticks& start_time);
 720   void register_concurrent_cycle_end();
 721   void trace_heap_after_concurrent_cycle();
 722 
 723   G1YCType yc_type();
 724 
 725   G1HRPrinter* hr_printer() { return &_hr_printer; }
 726 
 727   // Frees a non-humongous region by initializing its contents and
 728   // adding it to the free list that's passed as a parameter (this is
 729   // usually a local list which will be appended to the master free
 730   // list later). The used bytes of freed regions are accumulated in
 731   // pre_used. If par is true, the region's RSet will not be freed
 732   // up. The assumption is that this will be done later.
 733   // The locked parameter indicates if the caller has already taken
 734   // care of proper synchronization. This may allow some optimizations.
 735   void free_region(HeapRegion* hr,
 736                    FreeRegionList* free_list,
 737                    bool par,
 738                    bool locked = false);
 739 
 740   // Frees a humongous region by collapsing it into individual regions
 741   // and calling free_region() for each of them. The freed regions
 742   // will be added to the free list that's passed as a parameter (this
 743   // is usually a local list which will be appended to the master free
 744   // list later). The used bytes of freed regions are accumulated in
 745   // pre_used. If par is true, the region's RSet will not be freed
 746   // up. The assumption is that this will be done later.
 747   void free_humongous_region(HeapRegion* hr,
 748                              FreeRegionList* free_list,
 749                              bool par);
 750 protected:
 751 
 752   // Shrink the garbage-first heap by at most the given size (in bytes!).
 753   // (Rounds down to a HeapRegion boundary.)
 754   virtual void shrink(size_t expand_bytes);
 755   void shrink_helper(size_t expand_bytes);
 756 
 757   #if TASKQUEUE_STATS
 758   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 759   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 760   void reset_taskqueue_stats();
 761   #endif // TASKQUEUE_STATS
 762 
 763   // Schedule the VM operation that will do an evacuation pause to
 764   // satisfy an allocation request of word_size. *succeeded will
 765   // return whether the VM operation was successful (it did do an
 766   // evacuation pause) or not (another thread beat us to it or the GC
 767   // locker was active). Given that we should not be holding the
 768   // Heap_lock when we enter this method, we will pass the
 769   // gc_count_before (i.e., total_collections()) as a parameter since
 770   // it has to be read while holding the Heap_lock. Currently, both
 771   // methods that call do_collection_pause() release the Heap_lock
 772   // before the call, so it's easy to read gc_count_before just before.
 773   HeapWord* do_collection_pause(size_t         word_size,
 774                                 uint           gc_count_before,
 775                                 bool*          succeeded,
 776                                 GCCause::Cause gc_cause);
 777 
 778   // The guts of the incremental collection pause, executed by the vm
 779   // thread. It returns false if it is unable to do the collection due
 780   // to the GC locker being active, true otherwise
 781   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 782 
 783   // Actually do the work of evacuating the collection set.
 784   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 785 
 786   // The g1 remembered set of the heap.
 787   G1RemSet* _g1_rem_set;
 788 
 789   // A set of cards that cover the objects for which the Rsets should be updated
 790   // concurrently after the collection.
 791   DirtyCardQueueSet _dirty_card_queue_set;
 792 
 793   // The closure used to refine a single card.
 794   RefineCardTableEntryClosure* _refine_cte_cl;
 795 
 796   // A function to check the consistency of dirty card logs.
 797   void check_ct_logs_at_safepoint();
 798 
 799   // A DirtyCardQueueSet that is used to hold cards that contain
 800   // references into the current collection set. This is used to
 801   // update the remembered sets of the regions in the collection
 802   // set in the event of an evacuation failure.
 803   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 804 
 805   // After a collection pause, make the regions in the CS into free
 806   // regions.
 807   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 808 
 809   // Abandon the current collection set without recording policy
 810   // statistics or updating free lists.
 811   void abandon_collection_set(HeapRegion* cs_head);
 812 
 813   // The concurrent marker (and the thread it runs in.)
 814   ConcurrentMark* _cm;
 815   ConcurrentMarkThread* _cmThread;
 816   bool _mark_in_progress;
 817 
 818   // The concurrent refiner.
 819   ConcurrentG1Refine* _cg1r;
 820 
 821   // The parallel task queues
 822   RefToScanQueueSet *_task_queues;
 823 
 824   // True iff a evacuation has failed in the current collection.
 825   bool _evacuation_failed;
 826 
 827   EvacuationFailedInfo* _evacuation_failed_info_array;
 828 
 829   // Failed evacuations cause some logical from-space objects to have
 830   // forwarding pointers to themselves.  Reset them.
 831   void remove_self_forwarding_pointers();
 832 
 833   // Together, these store an object with a preserved mark, and its mark value.
 834   Stack<oop, mtGC>     _objs_with_preserved_marks;
 835   Stack<markOop, mtGC> _preserved_marks_of_objs;
 836 
 837   // Preserve the mark of "obj", if necessary, in preparation for its mark
 838   // word being overwritten with a self-forwarding-pointer.
 839   void preserve_mark_if_necessary(oop obj, markOop m);
 840 
 841   // The stack of evac-failure objects left to be scanned.
 842   GrowableArray<oop>*    _evac_failure_scan_stack;
 843   // The closure to apply to evac-failure objects.
 844 
 845   OopsInHeapRegionClosure* _evac_failure_closure;
 846   // Set the field above.
 847   void
 848   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 849     _evac_failure_closure = evac_failure_closure;
 850   }
 851 
 852   // Push "obj" on the scan stack.
 853   void push_on_evac_failure_scan_stack(oop obj);
 854   // Process scan stack entries until the stack is empty.
 855   void drain_evac_failure_scan_stack();
 856   // True iff an invocation of "drain_scan_stack" is in progress; to
 857   // prevent unnecessary recursion.
 858   bool _drain_in_progress;
 859 
 860   // Do any necessary initialization for evacuation-failure handling.
 861   // "cl" is the closure that will be used to process evac-failure
 862   // objects.
 863   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 864   // Do any necessary cleanup for evacuation-failure handling data
 865   // structures.
 866   void finalize_for_evac_failure();
 867 
 868   // An attempt to evacuate "obj" has failed; take necessary steps.
 869   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 870   void handle_evacuation_failure_common(oop obj, markOop m);
 871 
 872 #ifndef PRODUCT
 873   // Support for forcing evacuation failures. Analogous to
 874   // PromotionFailureALot for the other collectors.
 875 
 876   // Records whether G1EvacuationFailureALot should be in effect
 877   // for the current GC
 878   bool _evacuation_failure_alot_for_current_gc;
 879 
 880   // Used to record the GC number for interval checking when
 881   // determining whether G1EvaucationFailureALot is in effect
 882   // for the current GC.
 883   size_t _evacuation_failure_alot_gc_number;
 884 
 885   // Count of the number of evacuations between failures.
 886   volatile size_t _evacuation_failure_alot_count;
 887 
 888   // Set whether G1EvacuationFailureALot should be in effect
 889   // for the current GC (based upon the type of GC and which
 890   // command line flags are set);
 891   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 892                                                   bool during_initial_mark,
 893                                                   bool during_marking);
 894 
 895   inline void set_evacuation_failure_alot_for_current_gc();
 896 
 897   // Return true if it's time to cause an evacuation failure.
 898   inline bool evacuation_should_fail();
 899 
 900   // Reset the G1EvacuationFailureALot counters.  Should be called at
 901   // the end of an evacuation pause in which an evacuation failure occurred.
 902   inline void reset_evacuation_should_fail();
 903 #endif // !PRODUCT
 904 
 905   // ("Weak") Reference processing support.
 906   //
 907   // G1 has 2 instances of the reference processor class. One
 908   // (_ref_processor_cm) handles reference object discovery
 909   // and subsequent processing during concurrent marking cycles.
 910   //
 911   // The other (_ref_processor_stw) handles reference object
 912   // discovery and processing during full GCs and incremental
 913   // evacuation pauses.
 914   //
 915   // During an incremental pause, reference discovery will be
 916   // temporarily disabled for _ref_processor_cm and will be
 917   // enabled for _ref_processor_stw. At the end of the evacuation
 918   // pause references discovered by _ref_processor_stw will be
 919   // processed and discovery will be disabled. The previous
 920   // setting for reference object discovery for _ref_processor_cm
 921   // will be re-instated.
 922   //
 923   // At the start of marking:
 924   //  * Discovery by the CM ref processor is verified to be inactive
 925   //    and it's discovered lists are empty.
 926   //  * Discovery by the CM ref processor is then enabled.
 927   //
 928   // At the end of marking:
 929   //  * Any references on the CM ref processor's discovered
 930   //    lists are processed (possibly MT).
 931   //
 932   // At the start of full GC we:
 933   //  * Disable discovery by the CM ref processor and
 934   //    empty CM ref processor's discovered lists
 935   //    (without processing any entries).
 936   //  * Verify that the STW ref processor is inactive and it's
 937   //    discovered lists are empty.
 938   //  * Temporarily set STW ref processor discovery as single threaded.
 939   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 940   //    field.
 941   //  * Finally enable discovery by the STW ref processor.
 942   //
 943   // The STW ref processor is used to record any discovered
 944   // references during the full GC.
 945   //
 946   // At the end of a full GC we:
 947   //  * Enqueue any reference objects discovered by the STW ref processor
 948   //    that have non-live referents. This has the side-effect of
 949   //    making the STW ref processor inactive by disabling discovery.
 950   //  * Verify that the CM ref processor is still inactive
 951   //    and no references have been placed on it's discovered
 952   //    lists (also checked as a precondition during initial marking).
 953 
 954   // The (stw) reference processor...
 955   ReferenceProcessor* _ref_processor_stw;
 956 
 957   STWGCTimer* _gc_timer_stw;
 958   ConcurrentGCTimer* _gc_timer_cm;
 959 
 960   G1OldTracer* _gc_tracer_cm;
 961   G1NewTracer* _gc_tracer_stw;
 962 
 963   // During reference object discovery, the _is_alive_non_header
 964   // closure (if non-null) is applied to the referent object to
 965   // determine whether the referent is live. If so then the
 966   // reference object does not need to be 'discovered' and can
 967   // be treated as a regular oop. This has the benefit of reducing
 968   // the number of 'discovered' reference objects that need to
 969   // be processed.
 970   //
 971   // Instance of the is_alive closure for embedding into the
 972   // STW reference processor as the _is_alive_non_header field.
 973   // Supplying a value for the _is_alive_non_header field is
 974   // optional but doing so prevents unnecessary additions to
 975   // the discovered lists during reference discovery.
 976   G1STWIsAliveClosure _is_alive_closure_stw;
 977 
 978   // The (concurrent marking) reference processor...
 979   ReferenceProcessor* _ref_processor_cm;
 980 
 981   // Instance of the concurrent mark is_alive closure for embedding
 982   // into the Concurrent Marking reference processor as the
 983   // _is_alive_non_header field. Supplying a value for the
 984   // _is_alive_non_header field is optional but doing so prevents
 985   // unnecessary additions to the discovered lists during reference
 986   // discovery.
 987   G1CMIsAliveClosure _is_alive_closure_cm;
 988 
 989   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 990   HeapRegion** _worker_cset_start_region;
 991 
 992   // Time stamp to validate the regions recorded in the cache
 993   // used by G1CollectedHeap::start_cset_region_for_worker().
 994   // The heap region entry for a given worker is valid iff
 995   // the associated time stamp value matches the current value
 996   // of G1CollectedHeap::_gc_time_stamp.
 997   uint* _worker_cset_start_region_time_stamp;
 998 
 999   volatile bool _free_regions_coming;
1000 
1001 public:
1002 
1003   void set_refine_cte_cl_concurrency(bool concurrent);
1004 
1005   RefToScanQueue *task_queue(int i) const;
1006 
1007   // A set of cards where updates happened during the GC
1008   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1009 
1010   // A DirtyCardQueueSet that is used to hold cards that contain
1011   // references into the current collection set. This is used to
1012   // update the remembered sets of the regions in the collection
1013   // set in the event of an evacuation failure.
1014   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1015         { return _into_cset_dirty_card_queue_set; }
1016 
1017   // Create a G1CollectedHeap with the specified policy.
1018   // Must call the initialize method afterwards.
1019   // May not return if something goes wrong.
1020   G1CollectedHeap(G1CollectorPolicy* policy);
1021 
1022   // Initialize the G1CollectedHeap to have the initial and
1023   // maximum sizes and remembered and barrier sets
1024   // specified by the policy object.
1025   jint initialize();
1026 
1027   virtual void stop();
1028 
1029   // Return the (conservative) maximum heap alignment for any G1 heap
1030   static size_t conservative_max_heap_alignment();
1031 
1032   // Initialize weak reference processing.
1033   virtual void ref_processing_init();
1034 
1035   // Explicitly import set_par_threads into this scope
1036   using SharedHeap::set_par_threads;
1037   // Set _n_par_threads according to a policy TBD.
1038   void set_par_threads();
1039 
1040   virtual CollectedHeap::Name kind() const {
1041     return CollectedHeap::G1CollectedHeap;
1042   }
1043 
1044   // The current policy object for the collector.
1045   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1046 
1047   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1048 
1049   // Adaptive size policy.  No such thing for g1.
1050   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1051 
1052   // The rem set and barrier set.
1053   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1054 
1055   unsigned get_gc_time_stamp() {
1056     return _gc_time_stamp;
1057   }
1058 
1059   inline void reset_gc_time_stamp();
1060 
1061   void check_gc_time_stamps() PRODUCT_RETURN;
1062 
1063   inline void increment_gc_time_stamp();
1064 
1065   // Reset the given region's GC timestamp. If it's starts humongous,
1066   // also reset the GC timestamp of its corresponding
1067   // continues humongous regions too.
1068   void reset_gc_time_stamps(HeapRegion* hr);
1069 
1070   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1071                                   DirtyCardQueue* into_cset_dcq,
1072                                   bool concurrent, uint worker_i);
1073 
1074   // The shared block offset table array.
1075   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1076 
1077   // Reference Processing accessors
1078 
1079   // The STW reference processor....
1080   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1081 
1082   // The Concurrent Marking reference processor...
1083   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1084 
1085   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1086   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1087 
1088   virtual size_t capacity() const;
1089   virtual size_t used() const;
1090   // This should be called when we're not holding the heap lock. The
1091   // result might be a bit inaccurate.
1092   size_t used_unlocked() const;
1093   size_t recalculate_used() const;
1094 
1095   // These virtual functions do the actual allocation.
1096   // Some heaps may offer a contiguous region for shared non-blocking
1097   // allocation, via inlined code (by exporting the address of the top and
1098   // end fields defining the extent of the contiguous allocation region.)
1099   // But G1CollectedHeap doesn't yet support this.
1100 
1101   virtual bool is_maximal_no_gc() const {
1102     return _hrm.available() == 0;
1103   }
1104 
1105   // The current number of regions in the heap.
1106   uint num_regions() const { return _hrm.length(); }
1107 
1108   // The max number of regions in the heap.
1109   uint max_regions() const { return _hrm.max_length(); }
1110 
1111   // The number of regions that are completely free.
1112   uint num_free_regions() const { return _hrm.num_free_regions(); }
1113 
1114   MemoryUsage get_auxiliary_data_memory_usage() const {
1115     return _hrm.get_auxiliary_data_memory_usage();
1116   }
1117 
1118   // The number of regions that are not completely free.
1119   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1120 
1121   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1122   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1123   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1124   void verify_dirty_young_regions() PRODUCT_RETURN;
1125 
1126 #ifndef PRODUCT
1127   // Make sure that the given bitmap has no marked objects in the
1128   // range [from,limit). If it does, print an error message and return
1129   // false. Otherwise, just return true. bitmap_name should be "prev"
1130   // or "next".
1131   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1132                                 HeapWord* from, HeapWord* limit);
1133 
1134   // Verify that the prev / next bitmap range [tams,end) for the given
1135   // region has no marks. Return true if all is well, false if errors
1136   // are detected.
1137   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1138 #endif // PRODUCT
1139 
1140   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1141   // the given region do not have any spurious marks. If errors are
1142   // detected, print appropriate error messages and crash.
1143   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1144 
1145   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1146   // have any spurious marks. If errors are detected, print
1147   // appropriate error messages and crash.
1148   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1149 
1150   // Do sanity check on the contents of the in-cset fast test table.
1151   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1152 
1153   // verify_region_sets() performs verification over the region
1154   // lists. It will be compiled in the product code to be used when
1155   // necessary (i.e., during heap verification).
1156   void verify_region_sets();
1157 
1158   // verify_region_sets_optional() is planted in the code for
1159   // list verification in non-product builds (and it can be enabled in
1160   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1161 #if HEAP_REGION_SET_FORCE_VERIFY
1162   void verify_region_sets_optional() {
1163     verify_region_sets();
1164   }
1165 #else // HEAP_REGION_SET_FORCE_VERIFY
1166   void verify_region_sets_optional() { }
1167 #endif // HEAP_REGION_SET_FORCE_VERIFY
1168 
1169 #ifdef ASSERT
1170   bool is_on_master_free_list(HeapRegion* hr) {
1171     return _hrm.is_free(hr);
1172   }
1173 #endif // ASSERT
1174 
1175   // Wrapper for the region list operations that can be called from
1176   // methods outside this class.
1177 
1178   void secondary_free_list_add(FreeRegionList* list) {
1179     _secondary_free_list.add_ordered(list);
1180   }
1181 
1182   void append_secondary_free_list() {
1183     _hrm.insert_list_into_free_list(&_secondary_free_list);
1184   }
1185 
1186   void append_secondary_free_list_if_not_empty_with_lock() {
1187     // If the secondary free list looks empty there's no reason to
1188     // take the lock and then try to append it.
1189     if (!_secondary_free_list.is_empty()) {
1190       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1191       append_secondary_free_list();
1192     }
1193   }
1194 
1195   inline void old_set_remove(HeapRegion* hr);
1196 
1197   size_t non_young_capacity_bytes() {
1198     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1199   }
1200 
1201   void set_free_regions_coming();
1202   void reset_free_regions_coming();
1203   bool free_regions_coming() { return _free_regions_coming; }
1204   void wait_while_free_regions_coming();
1205 
1206   // Determine whether the given region is one that we are using as an
1207   // old GC alloc region.
1208   bool is_old_gc_alloc_region(HeapRegion* hr) {
1209     return _allocator->is_retained_old_region(hr);
1210   }
1211 
1212   // Perform a collection of the heap; intended for use in implementing
1213   // "System.gc".  This probably implies as full a collection as the
1214   // "CollectedHeap" supports.
1215   virtual void collect(GCCause::Cause cause);
1216 
1217   // The same as above but assume that the caller holds the Heap_lock.
1218   void collect_locked(GCCause::Cause cause);
1219 
1220   virtual bool copy_allocation_context_stats(const jint* contexts,
1221                                              jlong* totals,
1222                                              jbyte* accuracy,
1223                                              jint len);
1224 
1225   // True iff an evacuation has failed in the most-recent collection.
1226   bool evacuation_failed() { return _evacuation_failed; }
1227 
1228   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1229   void prepend_to_freelist(FreeRegionList* list);
1230   void decrement_summary_bytes(size_t bytes);
1231 
1232   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1233   virtual bool is_in(const void* p) const;
1234 #ifdef ASSERT
1235   // Returns whether p is in one of the available areas of the heap. Slow but
1236   // extensive version.
1237   bool is_in_exact(const void* p) const;
1238 #endif
1239 
1240   // Return "TRUE" iff the given object address is within the collection
1241   // set. Slow implementation.
1242   inline bool obj_in_cs(oop obj);
1243 
1244   inline bool is_in_cset(oop obj);
1245 
1246   inline bool is_in_cset_or_humongous(const oop obj);
1247 
1248  private:
1249   // This array is used for a quick test on whether a reference points into
1250   // the collection set or not. Each of the array's elements denotes whether the
1251   // corresponding region is in the collection set or not.
1252   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1253 
1254  public:
1255 
1256   inline InCSetState in_cset_state(const oop obj);
1257 
1258   // Return "TRUE" iff the given object address is in the reserved
1259   // region of g1.
1260   bool is_in_g1_reserved(const void* p) const {
1261     return _hrm.reserved().contains(p);
1262   }
1263 
1264   // Returns a MemRegion that corresponds to the space that has been
1265   // reserved for the heap
1266   MemRegion g1_reserved() const {
1267     return _hrm.reserved();
1268   }
1269 
1270   virtual bool is_in_closed_subset(const void* p) const;
1271 
1272   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1273     return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1274   }
1275 
1276   // This resets the card table to all zeros.  It is used after
1277   // a collection pause which used the card table to claim cards.
1278   void cleanUpCardTable();
1279 
1280   // Iteration functions.
1281 
1282   // Iterate over all the ref-containing fields of all objects, calling
1283   // "cl.do_oop" on each.
1284   virtual void oop_iterate(ExtendedOopClosure* cl);
1285 
1286   // Iterate over all objects, calling "cl.do_object" on each.
1287   virtual void object_iterate(ObjectClosure* cl);
1288 
1289   virtual void safe_object_iterate(ObjectClosure* cl) {
1290     object_iterate(cl);
1291   }
1292 
1293   // Iterate over all spaces in use in the heap, in ascending address order.
1294   virtual void space_iterate(SpaceClosure* cl);
1295 
1296   // Iterate over heap regions, in address order, terminating the
1297   // iteration early if the "doHeapRegion" method returns "true".
1298   void heap_region_iterate(HeapRegionClosure* blk) const;
1299 
1300   // Return the region with the given index. It assumes the index is valid.
1301   inline HeapRegion* region_at(uint index) const;
1302 
1303   // Calculate the region index of the given address. Given address must be
1304   // within the heap.
1305   inline uint addr_to_region(HeapWord* addr) const;
1306 
1307   inline HeapWord* bottom_addr_for_region(uint index) const;
1308 
1309   // Divide the heap region sequence into "chunks" of some size (the number
1310   // of regions divided by the number of parallel threads times some
1311   // overpartition factor, currently 4).  Assumes that this will be called
1312   // in parallel by ParallelGCThreads worker threads with discinct worker
1313   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1314   // calls will use the same "claim_value", and that that claim value is
1315   // different from the claim_value of any heap region before the start of
1316   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1317   // attempting to claim the first region in each chunk, and, if
1318   // successful, applying the closure to each region in the chunk (and
1319   // setting the claim value of the second and subsequent regions of the
1320   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1321   // i.e., that a closure never attempt to abort a traversal.
1322   void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1323                                        uint worker_id,
1324                                        uint num_workers,
1325                                        jint claim_value) const;
1326 
1327   // It resets all the region claim values to the default.
1328   void reset_heap_region_claim_values();
1329 
1330   // Resets the claim values of regions in the current
1331   // collection set to the default.
1332   void reset_cset_heap_region_claim_values();
1333 
1334 #ifdef ASSERT
1335   bool check_heap_region_claim_values(jint claim_value);
1336 
1337   // Same as the routine above but only checks regions in the
1338   // current collection set.
1339   bool check_cset_heap_region_claim_values(jint claim_value);
1340 #endif // ASSERT
1341 
1342   // Clear the cached cset start regions and (more importantly)
1343   // the time stamps. Called when we reset the GC time stamp.
1344   void clear_cset_start_regions();
1345 
1346   // Given the id of a worker, obtain or calculate a suitable
1347   // starting region for iterating over the current collection set.
1348   HeapRegion* start_cset_region_for_worker(uint worker_i);
1349 
1350   // Iterate over the regions (if any) in the current collection set.
1351   void collection_set_iterate(HeapRegionClosure* blk);
1352 
1353   // As above but starting from region r
1354   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1355 
1356   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1357 
1358   // A CollectedHeap will contain some number of spaces.  This finds the
1359   // space containing a given address, or else returns NULL.
1360   virtual Space* space_containing(const void* addr) const;
1361 
1362   // Returns the HeapRegion that contains addr. addr must not be NULL.
1363   template <class T>
1364   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1365 
1366   // Returns the HeapRegion that contains addr. addr must not be NULL.
1367   // If addr is within a humongous continues region, it returns its humongous start region.
1368   template <class T>
1369   inline HeapRegion* heap_region_containing(const T addr) const;
1370 
1371   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1372   // each address in the (reserved) heap is a member of exactly
1373   // one block.  The defining characteristic of a block is that it is
1374   // possible to find its size, and thus to progress forward to the next
1375   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1376   // represent Java objects, or they might be free blocks in a
1377   // free-list-based heap (or subheap), as long as the two kinds are
1378   // distinguishable and the size of each is determinable.
1379 
1380   // Returns the address of the start of the "block" that contains the
1381   // address "addr".  We say "blocks" instead of "object" since some heaps
1382   // may not pack objects densely; a chunk may either be an object or a
1383   // non-object.
1384   virtual HeapWord* block_start(const void* addr) const;
1385 
1386   // Requires "addr" to be the start of a chunk, and returns its size.
1387   // "addr + size" is required to be the start of a new chunk, or the end
1388   // of the active area of the heap.
1389   virtual size_t block_size(const HeapWord* addr) const;
1390 
1391   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1392   // the block is an object.
1393   virtual bool block_is_obj(const HeapWord* addr) const;
1394 
1395   // Does this heap support heap inspection? (+PrintClassHistogram)
1396   virtual bool supports_heap_inspection() const { return true; }
1397 
1398   // Section on thread-local allocation buffers (TLABs)
1399   // See CollectedHeap for semantics.
1400 
1401   bool supports_tlab_allocation() const;
1402   size_t tlab_capacity(Thread* ignored) const;
1403   size_t tlab_used(Thread* ignored) const;
1404   size_t max_tlab_size() const;
1405   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1406 
1407   // Can a compiler initialize a new object without store barriers?
1408   // This permission only extends from the creation of a new object
1409   // via a TLAB up to the first subsequent safepoint. If such permission
1410   // is granted for this heap type, the compiler promises to call
1411   // defer_store_barrier() below on any slow path allocation of
1412   // a new object for which such initializing store barriers will
1413   // have been elided. G1, like CMS, allows this, but should be
1414   // ready to provide a compensating write barrier as necessary
1415   // if that storage came out of a non-young region. The efficiency
1416   // of this implementation depends crucially on being able to
1417   // answer very efficiently in constant time whether a piece of
1418   // storage in the heap comes from a young region or not.
1419   // See ReduceInitialCardMarks.
1420   virtual bool can_elide_tlab_store_barriers() const {
1421     return true;
1422   }
1423 
1424   virtual bool card_mark_must_follow_store() const {
1425     return true;
1426   }
1427 
1428   inline bool is_in_young(const oop obj);
1429 
1430 #ifdef ASSERT
1431   virtual bool is_in_partial_collection(const void* p);
1432 #endif
1433 
1434   virtual bool is_scavengable(const void* addr);
1435 
1436   // We don't need barriers for initializing stores to objects
1437   // in the young gen: for the SATB pre-barrier, there is no
1438   // pre-value that needs to be remembered; for the remembered-set
1439   // update logging post-barrier, we don't maintain remembered set
1440   // information for young gen objects.
1441   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1442 
1443   // Returns "true" iff the given word_size is "very large".
1444   static bool isHumongous(size_t word_size) {
1445     // Note this has to be strictly greater-than as the TLABs
1446     // are capped at the humongous thresold and we want to
1447     // ensure that we don't try to allocate a TLAB as
1448     // humongous and that we don't allocate a humongous
1449     // object in a TLAB.
1450     return word_size > _humongous_object_threshold_in_words;
1451   }
1452 
1453   // Update mod union table with the set of dirty cards.
1454   void updateModUnion();
1455 
1456   // Set the mod union bits corresponding to the given memRegion.  Note
1457   // that this is always a safe operation, since it doesn't clear any
1458   // bits.
1459   void markModUnionRange(MemRegion mr);
1460 
1461   // Records the fact that a marking phase is no longer in progress.
1462   void set_marking_complete() {
1463     _mark_in_progress = false;
1464   }
1465   void set_marking_started() {
1466     _mark_in_progress = true;
1467   }
1468   bool mark_in_progress() {
1469     return _mark_in_progress;
1470   }
1471 
1472   // Print the maximum heap capacity.
1473   virtual size_t max_capacity() const;
1474 
1475   virtual jlong millis_since_last_gc();
1476 
1477 
1478   // Convenience function to be used in situations where the heap type can be
1479   // asserted to be this type.
1480   static G1CollectedHeap* heap();
1481 
1482   void set_region_short_lived_locked(HeapRegion* hr);
1483   // add appropriate methods for any other surv rate groups
1484 
1485   YoungList* young_list() const { return _young_list; }
1486 
1487   // debugging
1488   bool check_young_list_well_formed() {
1489     return _young_list->check_list_well_formed();
1490   }
1491 
1492   bool check_young_list_empty(bool check_heap,
1493                               bool check_sample = true);
1494 
1495   // *** Stuff related to concurrent marking.  It's not clear to me that so
1496   // many of these need to be public.
1497 
1498   // The functions below are helper functions that a subclass of
1499   // "CollectedHeap" can use in the implementation of its virtual
1500   // functions.
1501   // This performs a concurrent marking of the live objects in a
1502   // bitmap off to the side.
1503   void doConcurrentMark();
1504 
1505   bool isMarkedPrev(oop obj) const;
1506   bool isMarkedNext(oop obj) const;
1507 
1508   // Determine if an object is dead, given the object and also
1509   // the region to which the object belongs. An object is dead
1510   // iff a) it was not allocated since the last mark and b) it
1511   // is not marked.
1512   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1513     return
1514       !hr->obj_allocated_since_prev_marking(obj) &&
1515       !isMarkedPrev(obj);
1516   }
1517 
1518   // This function returns true when an object has been
1519   // around since the previous marking and hasn't yet
1520   // been marked during this marking.
1521   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1522     return
1523       !hr->obj_allocated_since_next_marking(obj) &&
1524       !isMarkedNext(obj);
1525   }
1526 
1527   // Determine if an object is dead, given only the object itself.
1528   // This will find the region to which the object belongs and
1529   // then call the region version of the same function.
1530 
1531   // Added if it is NULL it isn't dead.
1532 
1533   inline bool is_obj_dead(const oop obj) const;
1534 
1535   inline bool is_obj_ill(const oop obj) const;
1536 
1537   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1538   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1539   bool is_marked(oop obj, VerifyOption vo);
1540   const char* top_at_mark_start_str(VerifyOption vo);
1541 
1542   ConcurrentMark* concurrent_mark() const { return _cm; }
1543 
1544   // Refinement
1545 
1546   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1547 
1548   // The dirty cards region list is used to record a subset of regions
1549   // whose cards need clearing. The list if populated during the
1550   // remembered set scanning and drained during the card table
1551   // cleanup. Although the methods are reentrant, population/draining
1552   // phases must not overlap. For synchronization purposes the last
1553   // element on the list points to itself.
1554   HeapRegion* _dirty_cards_region_list;
1555   void push_dirty_cards_region(HeapRegion* hr);
1556   HeapRegion* pop_dirty_cards_region();
1557 
1558   // Optimized nmethod scanning support routines
1559 
1560   // Register the given nmethod with the G1 heap
1561   virtual void register_nmethod(nmethod* nm);
1562 
1563   // Unregister the given nmethod from the G1 heap
1564   virtual void unregister_nmethod(nmethod* nm);
1565 
1566   // Free up superfluous code root memory.
1567   void purge_code_root_memory();
1568 
1569   // Rebuild the stong code root lists for each region
1570   // after a full GC
1571   void rebuild_strong_code_roots();
1572 
1573   // Delete entries for dead interned string and clean up unreferenced symbols
1574   // in symbol table, possibly in parallel.
1575   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1576 
1577   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1578   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1579 
1580   // Redirty logged cards in the refinement queue.
1581   void redirty_logged_cards();
1582   // Verification
1583 
1584   // The following is just to alert the verification code
1585   // that a full collection has occurred and that the
1586   // remembered sets are no longer up to date.
1587   bool _full_collection;
1588   void set_full_collection() { _full_collection = true;}
1589   void clear_full_collection() {_full_collection = false;}
1590   bool full_collection() {return _full_collection;}
1591 
1592   // Perform any cleanup actions necessary before allowing a verification.
1593   virtual void prepare_for_verify();
1594 
1595   // Perform verification.
1596 
1597   // vo == UsePrevMarking  -> use "prev" marking information,
1598   // vo == UseNextMarking -> use "next" marking information
1599   // vo == UseMarkWord    -> use the mark word in the object header
1600   //
1601   // NOTE: Only the "prev" marking information is guaranteed to be
1602   // consistent most of the time, so most calls to this should use
1603   // vo == UsePrevMarking.
1604   // Currently, there is only one case where this is called with
1605   // vo == UseNextMarking, which is to verify the "next" marking
1606   // information at the end of remark.
1607   // Currently there is only one place where this is called with
1608   // vo == UseMarkWord, which is to verify the marking during a
1609   // full GC.
1610   void verify(bool silent, VerifyOption vo);
1611 
1612   // Override; it uses the "prev" marking information
1613   virtual void verify(bool silent);
1614 
1615   // The methods below are here for convenience and dispatch the
1616   // appropriate method depending on value of the given VerifyOption
1617   // parameter. The values for that parameter, and their meanings,
1618   // are the same as those above.
1619 
1620   bool is_obj_dead_cond(const oop obj,
1621                         const HeapRegion* hr,
1622                         const VerifyOption vo) const;
1623 
1624   bool is_obj_dead_cond(const oop obj,
1625                         const VerifyOption vo) const;
1626 
1627   G1HeapSummary create_g1_heap_summary();
1628 
1629   // Printing
1630 
1631   virtual void print_on(outputStream* st) const;
1632   virtual void print_extended_on(outputStream* st) const;
1633   virtual void print_on_error(outputStream* st) const;
1634 
1635   virtual void print_gc_threads_on(outputStream* st) const;
1636   virtual void gc_threads_do(ThreadClosure* tc) const;
1637 
1638   // Override
1639   void print_tracing_info() const;
1640 
1641   // The following two methods are helpful for debugging RSet issues.
1642   void print_cset_rsets() PRODUCT_RETURN;
1643   void print_all_rsets() PRODUCT_RETURN;
1644 
1645 public:
1646   size_t pending_card_num();
1647   size_t cards_scanned();
1648 
1649 protected:
1650   size_t _max_heap_capacity;
1651 };
1652 
1653 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---