1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc/g1/evacuationInfo.hpp"
  29 #include "gc/g1/g1BarrierSet.hpp"
  30 #include "gc/g1/g1BiasedArray.hpp"
  31 #include "gc/g1/g1CardTable.hpp"
  32 #include "gc/g1/g1CollectionSet.hpp"
  33 #include "gc/g1/g1CollectorState.hpp"
  34 #include "gc/g1/g1ConcurrentMark.hpp"
  35 #include "gc/g1/g1EdenRegions.hpp"
  36 #include "gc/g1/g1EvacFailure.hpp"
  37 #include "gc/g1/g1EvacStats.hpp"
  38 #include "gc/g1/g1HeapTransition.hpp"
  39 #include "gc/g1/g1HeapVerifier.hpp"
  40 #include "gc/g1/g1HRPrinter.hpp"
  41 #include "gc/g1/g1InCSetState.hpp"
  42 #include "gc/g1/g1MonitoringSupport.hpp"
  43 #include "gc/g1/g1SurvivorRegions.hpp"
  44 #include "gc/g1/g1YCTypes.hpp"
  45 #include "gc/g1/heapRegionManager.hpp"
  46 #include "gc/g1/heapRegionSet.hpp"
  47 #include "gc/shared/barrierSet.hpp"
  48 #include "gc/shared/collectedHeap.hpp"
  49 #include "gc/shared/gcHeapSummary.hpp"
  50 #include "gc/shared/plab.hpp"
  51 #include "gc/shared/preservedMarks.hpp"
  52 #include "gc/shared/softRefPolicy.hpp"
  53 #include "memory/memRegion.hpp"
  54 #include "services/memoryManager.hpp"
  55 #include "utilities/stack.hpp"
  56 
  57 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  58 // It uses the "Garbage First" heap organization and algorithm, which
  59 // may combine concurrent marking with parallel, incremental compaction of
  60 // heap subsets that will yield large amounts of garbage.
  61 
  62 // Forward declarations
  63 class HeapRegion;
  64 class HRRSCleanupTask;
  65 class GenerationSpec;
  66 class G1ParScanThreadState;
  67 class G1ParScanThreadStateSet;
  68 class G1ParScanThreadState;
  69 class MemoryPool;
  70 class ObjectClosure;
  71 class SpaceClosure;
  72 class CompactibleSpaceClosure;
  73 class Space;
  74 class G1CollectionSet;
  75 class G1CollectorPolicy;
  76 class G1Policy;
  77 class G1HotCardCache;
  78 class G1RemSet;
  79 class G1YoungRemSetSamplingThread;
  80 class HeapRegionRemSetIterator;
  81 class G1ConcurrentMark;
  82 class G1ConcurrentMarkThread;
  83 class G1ConcurrentRefine;
  84 class GenerationCounters;
  85 class STWGCTimer;
  86 class G1NewTracer;
  87 class EvacuationFailedInfo;
  88 class nmethod;
  89 class WorkGang;
  90 class G1Allocator;
  91 class G1ArchiveAllocator;
  92 class G1FullGCScope;
  93 class G1HeapVerifier;
  94 class G1HeapSizingPolicy;
  95 class G1HeapSummary;
  96 class G1EvacSummary;
  97 
  98 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  99 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
 100 
 101 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
 102 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
 103 
 104 // The G1 STW is alive closure.
 105 // An instance is embedded into the G1CH and used as the
 106 // (optional) _is_alive_non_header closure in the STW
 107 // reference processor. It is also extensively used during
 108 // reference processing during STW evacuation pauses.
 109 class G1STWIsAliveClosure : public BoolObjectClosure {
 110   G1CollectedHeap* _g1h;
 111 public:
 112   G1STWIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 113   bool do_object_b(oop p);
 114 };
 115 
 116 class G1STWSubjectToDiscoveryClosure : public BoolObjectClosure {
 117   G1CollectedHeap* _g1h;
 118 public:
 119   G1STWSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 120   bool do_object_b(oop p);
 121 };
 122 
 123 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 124  private:
 125   void reset_from_card_cache(uint start_idx, size_t num_regions);
 126  public:
 127   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 128 };
 129 
 130 class G1CollectedHeap : public CollectedHeap {
 131   friend class G1FreeCollectionSetTask;
 132   friend class VM_CollectForMetadataAllocation;
 133   friend class VM_G1CollectForAllocation;
 134   friend class VM_G1CollectFull;
 135   friend class VMStructs;
 136   friend class MutatorAllocRegion;
 137   friend class G1FullCollector;
 138   friend class G1GCAllocRegion;
 139   friend class G1HeapVerifier;
 140 
 141   // Closures used in implementation.
 142   friend class G1ParScanThreadState;
 143   friend class G1ParScanThreadStateSet;
 144   friend class G1ParTask;
 145   friend class G1PLABAllocator;
 146   friend class G1PrepareCompactClosure;
 147 
 148   // Other related classes.
 149   friend class HeapRegionClaimer;
 150 
 151   // Testing classes.
 152   friend class G1CheckCSetFastTableClosure;
 153 
 154 private:
 155   G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
 156 
 157   WorkGang* _workers;
 158   G1CollectorPolicy* _collector_policy;
 159   G1CardTable* _card_table;
 160 
 161   SoftRefPolicy      _soft_ref_policy;
 162 
 163   GCMemoryManager _memory_manager;
 164   GCMemoryManager _full_gc_memory_manager;
 165 
 166   MemoryPool* _eden_pool;
 167   MemoryPool* _survivor_pool;
 168   MemoryPool* _old_pool;
 169 
 170   static size_t _humongous_object_threshold_in_words;
 171 
 172   // It keeps track of the old regions.
 173   HeapRegionSet _old_set;
 174 
 175   // It keeps track of the humongous regions.
 176   HeapRegionSet _humongous_set;
 177 
 178   virtual void initialize_serviceability();
 179 
 180   void eagerly_reclaim_humongous_regions();
 181   // Start a new incremental collection set for the next pause.
 182   void start_new_collection_set();
 183 
 184   // The number of regions we could create by expansion.
 185   uint _expansion_regions;
 186 
 187   // The block offset table for the G1 heap.
 188   G1BlockOffsetTable* _bot;
 189 
 190   // Tears down the region sets / lists so that they are empty and the
 191   // regions on the heap do not belong to a region set / list. The
 192   // only exception is the humongous set which we leave unaltered. If
 193   // free_list_only is true, it will only tear down the master free
 194   // list. It is called before a Full GC (free_list_only == false) or
 195   // before heap shrinking (free_list_only == true).
 196   void tear_down_region_sets(bool free_list_only);
 197 
 198   // Rebuilds the region sets / lists so that they are repopulated to
 199   // reflect the contents of the heap. The only exception is the
 200   // humongous set which was not torn down in the first place. If
 201   // free_list_only is true, it will only rebuild the master free
 202   // list. It is called after a Full GC (free_list_only == false) or
 203   // after heap shrinking (free_list_only == true).
 204   void rebuild_region_sets(bool free_list_only);
 205 
 206   // Callback for region mapping changed events.
 207   G1RegionMappingChangedListener _listener;
 208 
 209   // The sequence of all heap regions in the heap.
 210   HeapRegionManager _hrm;
 211 
 212   // Manages all allocations with regions except humongous object allocations.
 213   G1Allocator* _allocator;
 214 
 215   // Manages all heap verification.
 216   G1HeapVerifier* _verifier;
 217 
 218   // Outside of GC pauses, the number of bytes used in all regions other
 219   // than the current allocation region(s).
 220   size_t _summary_bytes_used;
 221 
 222   void increase_used(size_t bytes);
 223   void decrease_used(size_t bytes);
 224 
 225   void set_used(size_t bytes);
 226 
 227   // Class that handles archive allocation ranges.
 228   G1ArchiveAllocator* _archive_allocator;
 229 
 230   // GC allocation statistics policy for survivors.
 231   G1EvacStats _survivor_evac_stats;
 232 
 233   // GC allocation statistics policy for tenured objects.
 234   G1EvacStats _old_evac_stats;
 235 
 236   // It specifies whether we should attempt to expand the heap after a
 237   // region allocation failure. If heap expansion fails we set this to
 238   // false so that we don't re-attempt the heap expansion (it's likely
 239   // that subsequent expansion attempts will also fail if one fails).
 240   // Currently, it is only consulted during GC and it's reset at the
 241   // start of each GC.
 242   bool _expand_heap_after_alloc_failure;
 243 
 244   // Helper for monitoring and management support.
 245   G1MonitoringSupport* _g1mm;
 246 
 247   // Records whether the region at the given index is (still) a
 248   // candidate for eager reclaim.  Only valid for humongous start
 249   // regions; other regions have unspecified values.  Humongous start
 250   // regions are initialized at start of collection pause, with
 251   // candidates removed from the set as they are found reachable from
 252   // roots or the young generation.
 253   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 254    protected:
 255     bool default_value() const { return false; }
 256    public:
 257     void clear() { G1BiasedMappedArray<bool>::clear(); }
 258     void set_candidate(uint region, bool value) {
 259       set_by_index(region, value);
 260     }
 261     bool is_candidate(uint region) {
 262       return get_by_index(region);
 263     }
 264   };
 265 
 266   HumongousReclaimCandidates _humongous_reclaim_candidates;
 267   // Stores whether during humongous object registration we found candidate regions.
 268   // If not, we can skip a few steps.
 269   bool _has_humongous_reclaim_candidates;
 270 
 271   G1HRPrinter _hr_printer;
 272 
 273   // It decides whether an explicit GC should start a concurrent cycle
 274   // instead of doing a STW GC. Currently, a concurrent cycle is
 275   // explicitly started if:
 276   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 277   // (b) cause == _g1_humongous_allocation
 278   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 279   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 280   // (e) cause == _wb_conc_mark
 281   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 282 
 283   // indicates whether we are in young or mixed GC mode
 284   G1CollectorState _collector_state;
 285 
 286   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 287   // concurrent cycles) we have started.
 288   volatile uint _old_marking_cycles_started;
 289 
 290   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 291   // concurrent cycles) we have completed.
 292   volatile uint _old_marking_cycles_completed;
 293 
 294   // This is a non-product method that is helpful for testing. It is
 295   // called at the end of a GC and artificially expands the heap by
 296   // allocating a number of dead regions. This way we can induce very
 297   // frequent marking cycles and stress the cleanup / concurrent
 298   // cleanup code more (as all the regions that will be allocated by
 299   // this method will be found dead by the marking cycle).
 300   void allocate_dummy_regions() PRODUCT_RETURN;
 301 
 302   // If the HR printer is active, dump the state of the regions in the
 303   // heap after a compaction.
 304   void print_hrm_post_compaction();
 305 
 306   // Create a memory mapper for auxiliary data structures of the given size and
 307   // translation factor.
 308   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 309                                                          size_t size,
 310                                                          size_t translation_factor);
 311 
 312   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 313 
 314   // These are macros so that, if the assert fires, we get the correct
 315   // line number, file, etc.
 316 
 317 #define heap_locking_asserts_params(_extra_message_)                          \
 318   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 319   (_extra_message_),                                                          \
 320   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 321   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 322   BOOL_TO_STR(Thread::current()->is_VM_thread())
 323 
 324 #define assert_heap_locked()                                                  \
 325   do {                                                                        \
 326     assert(Heap_lock->owned_by_self(),                                        \
 327            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 328   } while (0)
 329 
 330 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 331   do {                                                                        \
 332     assert(Heap_lock->owned_by_self() ||                                      \
 333            (SafepointSynchronize::is_at_safepoint() &&                        \
 334              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 335            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 336                                         "should be at a safepoint"));         \
 337   } while (0)
 338 
 339 #define assert_heap_locked_and_not_at_safepoint()                             \
 340   do {                                                                        \
 341     assert(Heap_lock->owned_by_self() &&                                      \
 342                                     !SafepointSynchronize::is_at_safepoint(), \
 343           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 344                                        "should not be at a safepoint"));      \
 345   } while (0)
 346 
 347 #define assert_heap_not_locked()                                              \
 348   do {                                                                        \
 349     assert(!Heap_lock->owned_by_self(),                                       \
 350         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 351   } while (0)
 352 
 353 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 354   do {                                                                        \
 355     assert(!Heap_lock->owned_by_self() &&                                     \
 356                                     !SafepointSynchronize::is_at_safepoint(), \
 357       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 358                                    "should not be at a safepoint"));          \
 359   } while (0)
 360 
 361 #define assert_at_safepoint_on_vm_thread()                                    \
 362   do {                                                                        \
 363     assert_at_safepoint();                                                    \
 364     assert(Thread::current_or_null() != NULL, "no current thread");           \
 365     assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \
 366   } while (0)
 367 
 368   // The young region list.
 369   G1EdenRegions _eden;
 370   G1SurvivorRegions _survivor;
 371 
 372   STWGCTimer* _gc_timer_stw;
 373 
 374   G1NewTracer* _gc_tracer_stw;
 375 
 376   // The current policy object for the collector.
 377   G1Policy* _g1_policy;
 378   G1HeapSizingPolicy* _heap_sizing_policy;
 379 
 380   G1CollectionSet _collection_set;
 381 
 382   // Try to allocate a single non-humongous HeapRegion sufficient for
 383   // an allocation of the given word_size. If do_expand is true,
 384   // attempt to expand the heap if necessary to satisfy the allocation
 385   // request. If the region is to be used as an old region or for a
 386   // humongous object, set is_old to true. If not, to false.
 387   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 388 
 389   // Initialize a contiguous set of free regions of length num_regions
 390   // and starting at index first so that they appear as a single
 391   // humongous region.
 392   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 393                                                       uint num_regions,
 394                                                       size_t word_size);
 395 
 396   // Attempt to allocate a humongous object of the given size. Return
 397   // NULL if unsuccessful.
 398   HeapWord* humongous_obj_allocate(size_t word_size);
 399 
 400   // The following two methods, allocate_new_tlab() and
 401   // mem_allocate(), are the two main entry points from the runtime
 402   // into the G1's allocation routines. They have the following
 403   // assumptions:
 404   //
 405   // * They should both be called outside safepoints.
 406   //
 407   // * They should both be called without holding the Heap_lock.
 408   //
 409   // * All allocation requests for new TLABs should go to
 410   //   allocate_new_tlab().
 411   //
 412   // * All non-TLAB allocation requests should go to mem_allocate().
 413   //
 414   // * If either call cannot satisfy the allocation request using the
 415   //   current allocating region, they will try to get a new one. If
 416   //   this fails, they will attempt to do an evacuation pause and
 417   //   retry the allocation.
 418   //
 419   // * If all allocation attempts fail, even after trying to schedule
 420   //   an evacuation pause, allocate_new_tlab() will return NULL,
 421   //   whereas mem_allocate() will attempt a heap expansion and/or
 422   //   schedule a Full GC.
 423   //
 424   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 425   //   should never be called with word_size being humongous. All
 426   //   humongous allocation requests should go to mem_allocate() which
 427   //   will satisfy them with a special path.
 428 
 429   virtual HeapWord* allocate_new_tlab(size_t min_size,
 430                                       size_t requested_size,
 431                                       size_t* actual_size);
 432 
 433   virtual HeapWord* mem_allocate(size_t word_size,
 434                                  bool*  gc_overhead_limit_was_exceeded);
 435 
 436   // First-level mutator allocation attempt: try to allocate out of
 437   // the mutator alloc region without taking the Heap_lock. This
 438   // should only be used for non-humongous allocations.
 439   inline HeapWord* attempt_allocation(size_t min_word_size,
 440                                       size_t desired_word_size,
 441                                       size_t* actual_word_size);
 442 
 443   // Second-level mutator allocation attempt: take the Heap_lock and
 444   // retry the allocation attempt, potentially scheduling a GC
 445   // pause. This should only be used for non-humongous allocations.
 446   HeapWord* attempt_allocation_slow(size_t word_size);
 447 
 448   // Takes the Heap_lock and attempts a humongous allocation. It can
 449   // potentially schedule a GC pause.
 450   HeapWord* attempt_allocation_humongous(size_t word_size);
 451 
 452   // Allocation attempt that should be called during safepoints (e.g.,
 453   // at the end of a successful GC). expect_null_mutator_alloc_region
 454   // specifies whether the mutator alloc region is expected to be NULL
 455   // or not.
 456   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 457                                             bool expect_null_mutator_alloc_region);
 458 
 459   // These methods are the "callbacks" from the G1AllocRegion class.
 460 
 461   // For mutator alloc regions.
 462   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 463   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 464                                    size_t allocated_bytes);
 465 
 466   // For GC alloc regions.
 467   bool has_more_regions(InCSetState dest);
 468   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 469   void retire_gc_alloc_region(HeapRegion* alloc_region,
 470                               size_t allocated_bytes, InCSetState dest);
 471 
 472   // - if explicit_gc is true, the GC is for a System.gc() etc,
 473   //   otherwise it's for a failed allocation.
 474   // - if clear_all_soft_refs is true, all soft references should be
 475   //   cleared during the GC.
 476   // - it returns false if it is unable to do the collection due to the
 477   //   GC locker being active, true otherwise.
 478   bool do_full_collection(bool explicit_gc,
 479                           bool clear_all_soft_refs);
 480 
 481   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 482   virtual void do_full_collection(bool clear_all_soft_refs);
 483 
 484   // Resize the heap if necessary after a full collection.
 485   void resize_if_necessary_after_full_collection();
 486 
 487   // Callback from VM_G1CollectForAllocation operation.
 488   // This function does everything necessary/possible to satisfy a
 489   // failed allocation request (including collection, expansion, etc.)
 490   HeapWord* satisfy_failed_allocation(size_t word_size,
 491                                       bool* succeeded);
 492   // Internal helpers used during full GC to split it up to
 493   // increase readability.
 494   void abort_concurrent_cycle();
 495   void verify_before_full_collection(bool explicit_gc);
 496   void prepare_heap_for_full_collection();
 497   void prepare_heap_for_mutators();
 498   void abort_refinement();
 499   void verify_after_full_collection();
 500   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 501 
 502   // Helper method for satisfy_failed_allocation()
 503   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 504                                              bool do_gc,
 505                                              bool clear_all_soft_refs,
 506                                              bool expect_null_mutator_alloc_region,
 507                                              bool* gc_succeeded);
 508 
 509   // Attempting to expand the heap sufficiently
 510   // to support an allocation of the given "word_size".  If
 511   // successful, perform the allocation and return the address of the
 512   // allocated block, or else "NULL".
 513   HeapWord* expand_and_allocate(size_t word_size);
 514 
 515   // Process any reference objects discovered.
 516   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 517 
 518   // If during an initial mark pause we may install a pending list head which is not
 519   // otherwise reachable ensure that it is marked in the bitmap for concurrent marking
 520   // to discover.
 521   void make_pending_list_reachable();
 522 
 523   // Merges the information gathered on a per-thread basis for all worker threads
 524   // during GC into global variables.
 525   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 526 public:
 527   G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
 528 
 529   WorkGang* workers() const { return _workers; }
 530 
 531   G1Allocator* allocator() {
 532     return _allocator;
 533   }
 534 
 535   G1HeapVerifier* verifier() {
 536     return _verifier;
 537   }
 538 
 539   G1MonitoringSupport* g1mm() {
 540     assert(_g1mm != NULL, "should have been initialized");
 541     return _g1mm;
 542   }
 543 
 544   // Expand the garbage-first heap by at least the given size (in bytes!).
 545   // Returns true if the heap was expanded by the requested amount;
 546   // false otherwise.
 547   // (Rounds up to a HeapRegion boundary.)
 548   bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
 549 
 550   // Returns the PLAB statistics for a given destination.
 551   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 552 
 553   // Determines PLAB size for a given destination.
 554   inline size_t desired_plab_sz(InCSetState dest);
 555 
 556   // Do anything common to GC's.
 557   void gc_prologue(bool full);
 558   void gc_epilogue(bool full);
 559 
 560   // Does the given region fulfill remembered set based eager reclaim candidate requirements?
 561   bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
 562 
 563   // Modify the reclaim candidate set and test for presence.
 564   // These are only valid for starts_humongous regions.
 565   inline void set_humongous_reclaim_candidate(uint region, bool value);
 566   inline bool is_humongous_reclaim_candidate(uint region);
 567 
 568   // Remove from the reclaim candidate set.  Also remove from the
 569   // collection set so that later encounters avoid the slow path.
 570   inline void set_humongous_is_live(oop obj);
 571 
 572   // Register the given region to be part of the collection set.
 573   inline void register_humongous_region_with_cset(uint index);
 574   // Register regions with humongous objects (actually on the start region) in
 575   // the in_cset_fast_test table.
 576   void register_humongous_regions_with_cset();
 577   // We register a region with the fast "in collection set" test. We
 578   // simply set to true the array slot corresponding to this region.
 579   void register_young_region_with_cset(HeapRegion* r) {
 580     _in_cset_fast_test.set_in_young(r->hrm_index());
 581   }
 582   void register_old_region_with_cset(HeapRegion* r) {
 583     _in_cset_fast_test.set_in_old(r->hrm_index());
 584   }
 585   void clear_in_cset(const HeapRegion* hr) {
 586     _in_cset_fast_test.clear(hr);
 587   }
 588 
 589   void clear_cset_fast_test() {
 590     _in_cset_fast_test.clear();
 591   }
 592 
 593   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 594 
 595   // This is called at the start of either a concurrent cycle or a Full
 596   // GC to update the number of old marking cycles started.
 597   void increment_old_marking_cycles_started();
 598 
 599   // This is called at the end of either a concurrent cycle or a Full
 600   // GC to update the number of old marking cycles completed. Those two
 601   // can happen in a nested fashion, i.e., we start a concurrent
 602   // cycle, a Full GC happens half-way through it which ends first,
 603   // and then the cycle notices that a Full GC happened and ends
 604   // too. The concurrent parameter is a boolean to help us do a bit
 605   // tighter consistency checking in the method. If concurrent is
 606   // false, the caller is the inner caller in the nesting (i.e., the
 607   // Full GC). If concurrent is true, the caller is the outer caller
 608   // in this nesting (i.e., the concurrent cycle). Further nesting is
 609   // not currently supported. The end of this call also notifies
 610   // the FullGCCount_lock in case a Java thread is waiting for a full
 611   // GC to happen (e.g., it called System.gc() with
 612   // +ExplicitGCInvokesConcurrent).
 613   void increment_old_marking_cycles_completed(bool concurrent);
 614 
 615   uint old_marking_cycles_completed() {
 616     return _old_marking_cycles_completed;
 617   }
 618 
 619   G1HRPrinter* hr_printer() { return &_hr_printer; }
 620 
 621   // Allocates a new heap region instance.
 622   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 623 
 624   // Allocate the highest free region in the reserved heap. This will commit
 625   // regions as necessary.
 626   HeapRegion* alloc_highest_free_region();
 627 
 628   // Frees a non-humongous region by initializing its contents and
 629   // adding it to the free list that's passed as a parameter (this is
 630   // usually a local list which will be appended to the master free
 631   // list later). The used bytes of freed regions are accumulated in
 632   // pre_used. If skip_remset is true, the region's RSet will not be freed
 633   // up. If skip_hot_card_cache is true, the region's hot card cache will not
 634   // be freed up. The assumption is that this will be done later.
 635   // The locked parameter indicates if the caller has already taken
 636   // care of proper synchronization. This may allow some optimizations.
 637   void free_region(HeapRegion* hr,
 638                    FreeRegionList* free_list,
 639                    bool skip_remset,
 640                    bool skip_hot_card_cache = false,
 641                    bool locked = false);
 642 
 643   // It dirties the cards that cover the block so that the post
 644   // write barrier never queues anything when updating objects on this
 645   // block. It is assumed (and in fact we assert) that the block
 646   // belongs to a young region.
 647   inline void dirty_young_block(HeapWord* start, size_t word_size);
 648 
 649   // Frees a humongous region by collapsing it into individual regions
 650   // and calling free_region() for each of them. The freed regions
 651   // will be added to the free list that's passed as a parameter (this
 652   // is usually a local list which will be appended to the master free
 653   // list later).
 654   // The method assumes that only a single thread is ever calling
 655   // this for a particular region at once.
 656   void free_humongous_region(HeapRegion* hr,
 657                              FreeRegionList* free_list);
 658 
 659   // Facility for allocating in 'archive' regions in high heap memory and
 660   // recording the allocated ranges. These should all be called from the
 661   // VM thread at safepoints, without the heap lock held. They can be used
 662   // to create and archive a set of heap regions which can be mapped at the
 663   // same fixed addresses in a subsequent JVM invocation.
 664   void begin_archive_alloc_range(bool open = false);
 665 
 666   // Check if the requested size would be too large for an archive allocation.
 667   bool is_archive_alloc_too_large(size_t word_size);
 668 
 669   // Allocate memory of the requested size from the archive region. This will
 670   // return NULL if the size is too large or if no memory is available. It
 671   // does not trigger a garbage collection.
 672   HeapWord* archive_mem_allocate(size_t word_size);
 673 
 674   // Optionally aligns the end address and returns the allocated ranges in
 675   // an array of MemRegions in order of ascending addresses.
 676   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 677                                size_t end_alignment_in_bytes = 0);
 678 
 679   // Facility for allocating a fixed range within the heap and marking
 680   // the containing regions as 'archive'. For use at JVM init time, when the
 681   // caller may mmap archived heap data at the specified range(s).
 682   // Verify that the MemRegions specified in the argument array are within the
 683   // reserved heap.
 684   bool check_archive_addresses(MemRegion* range, size_t count);
 685 
 686   // Commit the appropriate G1 regions containing the specified MemRegions
 687   // and mark them as 'archive' regions. The regions in the array must be
 688   // non-overlapping and in order of ascending address.
 689   bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
 690 
 691   // Insert any required filler objects in the G1 regions around the specified
 692   // ranges to make the regions parseable. This must be called after
 693   // alloc_archive_regions, and after class loading has occurred.
 694   void fill_archive_regions(MemRegion* range, size_t count);
 695 
 696   // For each of the specified MemRegions, uncommit the containing G1 regions
 697   // which had been allocated by alloc_archive_regions. This should be called
 698   // rather than fill_archive_regions at JVM init time if the archive file
 699   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 700   void dealloc_archive_regions(MemRegion* range, size_t count, bool is_open);
 701 
 702   oop materialize_archived_object(oop obj);
 703 
 704 private:
 705 
 706   // Shrink the garbage-first heap by at most the given size (in bytes!).
 707   // (Rounds down to a HeapRegion boundary.)
 708   void shrink(size_t expand_bytes);
 709   void shrink_helper(size_t expand_bytes);
 710 
 711   #if TASKQUEUE_STATS
 712   static void print_taskqueue_stats_hdr(outputStream* const st);
 713   void print_taskqueue_stats() const;
 714   void reset_taskqueue_stats();
 715   #endif // TASKQUEUE_STATS
 716 
 717   // Schedule the VM operation that will do an evacuation pause to
 718   // satisfy an allocation request of word_size. *succeeded will
 719   // return whether the VM operation was successful (it did do an
 720   // evacuation pause) or not (another thread beat us to it or the GC
 721   // locker was active). Given that we should not be holding the
 722   // Heap_lock when we enter this method, we will pass the
 723   // gc_count_before (i.e., total_collections()) as a parameter since
 724   // it has to be read while holding the Heap_lock. Currently, both
 725   // methods that call do_collection_pause() release the Heap_lock
 726   // before the call, so it's easy to read gc_count_before just before.
 727   HeapWord* do_collection_pause(size_t         word_size,
 728                                 uint           gc_count_before,
 729                                 bool*          succeeded,
 730                                 GCCause::Cause gc_cause);
 731 
 732   void wait_for_root_region_scanning();
 733 
 734   // The guts of the incremental collection pause, executed by the vm
 735   // thread. It returns false if it is unable to do the collection due
 736   // to the GC locker being active, true otherwise
 737   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 738 
 739   // Actually do the work of evacuating the collection set.
 740   void evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states);
 741 
 742   void pre_evacuate_collection_set();
 743   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 744 
 745   // Print the header for the per-thread termination statistics.
 746   static void print_termination_stats_hdr();
 747   // Print actual per-thread termination statistics.
 748   void print_termination_stats(uint worker_id,
 749                                double elapsed_ms,
 750                                double strong_roots_ms,
 751                                double term_ms,
 752                                size_t term_attempts,
 753                                size_t alloc_buffer_waste,
 754                                size_t undo_waste) const;
 755   // Update object copying statistics.
 756   void record_obj_copy_mem_stats();
 757 
 758   // The hot card cache for remembered set insertion optimization.
 759   G1HotCardCache* _hot_card_cache;
 760 
 761   // The g1 remembered set of the heap.
 762   G1RemSet* _g1_rem_set;
 763 
 764   // A set of cards that cover the objects for which the Rsets should be updated
 765   // concurrently after the collection.
 766   DirtyCardQueueSet _dirty_card_queue_set;
 767 
 768   // After a collection pause, convert the regions in the collection set into free
 769   // regions.
 770   void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 771 
 772   // Abandon the current collection set without recording policy
 773   // statistics or updating free lists.
 774   void abandon_collection_set(G1CollectionSet* collection_set);
 775 
 776   // The concurrent marker (and the thread it runs in.)
 777   G1ConcurrentMark* _cm;
 778   G1ConcurrentMarkThread* _cm_thread;
 779 
 780   // The concurrent refiner.
 781   G1ConcurrentRefine* _cr;
 782 
 783   // The parallel task queues
 784   RefToScanQueueSet *_task_queues;
 785 
 786   // True iff a evacuation has failed in the current collection.
 787   bool _evacuation_failed;
 788 
 789   EvacuationFailedInfo* _evacuation_failed_info_array;
 790 
 791   // Failed evacuations cause some logical from-space objects to have
 792   // forwarding pointers to themselves.  Reset them.
 793   void remove_self_forwarding_pointers();
 794 
 795   // Restore the objects in the regions in the collection set after an
 796   // evacuation failure.
 797   void restore_after_evac_failure();
 798 
 799   PreservedMarksSet _preserved_marks_set;
 800 
 801   // Preserve the mark of "obj", if necessary, in preparation for its mark
 802   // word being overwritten with a self-forwarding-pointer.
 803   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 804 
 805 #ifndef PRODUCT
 806   // Support for forcing evacuation failures. Analogous to
 807   // PromotionFailureALot for the other collectors.
 808 
 809   // Records whether G1EvacuationFailureALot should be in effect
 810   // for the current GC
 811   bool _evacuation_failure_alot_for_current_gc;
 812 
 813   // Used to record the GC number for interval checking when
 814   // determining whether G1EvaucationFailureALot is in effect
 815   // for the current GC.
 816   size_t _evacuation_failure_alot_gc_number;
 817 
 818   // Count of the number of evacuations between failures.
 819   volatile size_t _evacuation_failure_alot_count;
 820 
 821   // Set whether G1EvacuationFailureALot should be in effect
 822   // for the current GC (based upon the type of GC and which
 823   // command line flags are set);
 824   inline bool evacuation_failure_alot_for_gc_type(bool for_young_gc,
 825                                                   bool during_initial_mark,
 826                                                   bool mark_or_rebuild_in_progress);
 827 
 828   inline void set_evacuation_failure_alot_for_current_gc();
 829 
 830   // Return true if it's time to cause an evacuation failure.
 831   inline bool evacuation_should_fail();
 832 
 833   // Reset the G1EvacuationFailureALot counters.  Should be called at
 834   // the end of an evacuation pause in which an evacuation failure occurred.
 835   inline void reset_evacuation_should_fail();
 836 #endif // !PRODUCT
 837 
 838   // ("Weak") Reference processing support.
 839   //
 840   // G1 has 2 instances of the reference processor class. One
 841   // (_ref_processor_cm) handles reference object discovery
 842   // and subsequent processing during concurrent marking cycles.
 843   //
 844   // The other (_ref_processor_stw) handles reference object
 845   // discovery and processing during full GCs and incremental
 846   // evacuation pauses.
 847   //
 848   // During an incremental pause, reference discovery will be
 849   // temporarily disabled for _ref_processor_cm and will be
 850   // enabled for _ref_processor_stw. At the end of the evacuation
 851   // pause references discovered by _ref_processor_stw will be
 852   // processed and discovery will be disabled. The previous
 853   // setting for reference object discovery for _ref_processor_cm
 854   // will be re-instated.
 855   //
 856   // At the start of marking:
 857   //  * Discovery by the CM ref processor is verified to be inactive
 858   //    and it's discovered lists are empty.
 859   //  * Discovery by the CM ref processor is then enabled.
 860   //
 861   // At the end of marking:
 862   //  * Any references on the CM ref processor's discovered
 863   //    lists are processed (possibly MT).
 864   //
 865   // At the start of full GC we:
 866   //  * Disable discovery by the CM ref processor and
 867   //    empty CM ref processor's discovered lists
 868   //    (without processing any entries).
 869   //  * Verify that the STW ref processor is inactive and it's
 870   //    discovered lists are empty.
 871   //  * Temporarily set STW ref processor discovery as single threaded.
 872   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 873   //    field.
 874   //  * Finally enable discovery by the STW ref processor.
 875   //
 876   // The STW ref processor is used to record any discovered
 877   // references during the full GC.
 878   //
 879   // At the end of a full GC we:
 880   //  * Enqueue any reference objects discovered by the STW ref processor
 881   //    that have non-live referents. This has the side-effect of
 882   //    making the STW ref processor inactive by disabling discovery.
 883   //  * Verify that the CM ref processor is still inactive
 884   //    and no references have been placed on it's discovered
 885   //    lists (also checked as a precondition during initial marking).
 886 
 887   // The (stw) reference processor...
 888   ReferenceProcessor* _ref_processor_stw;
 889 
 890   // During reference object discovery, the _is_alive_non_header
 891   // closure (if non-null) is applied to the referent object to
 892   // determine whether the referent is live. If so then the
 893   // reference object does not need to be 'discovered' and can
 894   // be treated as a regular oop. This has the benefit of reducing
 895   // the number of 'discovered' reference objects that need to
 896   // be processed.
 897   //
 898   // Instance of the is_alive closure for embedding into the
 899   // STW reference processor as the _is_alive_non_header field.
 900   // Supplying a value for the _is_alive_non_header field is
 901   // optional but doing so prevents unnecessary additions to
 902   // the discovered lists during reference discovery.
 903   G1STWIsAliveClosure _is_alive_closure_stw;
 904 
 905   G1STWSubjectToDiscoveryClosure _is_subject_to_discovery_stw;
 906 
 907   // The (concurrent marking) reference processor...
 908   ReferenceProcessor* _ref_processor_cm;
 909 
 910   // Instance of the concurrent mark is_alive closure for embedding
 911   // into the Concurrent Marking reference processor as the
 912   // _is_alive_non_header field. Supplying a value for the
 913   // _is_alive_non_header field is optional but doing so prevents
 914   // unnecessary additions to the discovered lists during reference
 915   // discovery.
 916   G1CMIsAliveClosure _is_alive_closure_cm;
 917 
 918   G1CMSubjectToDiscoveryClosure _is_subject_to_discovery_cm;
 919 public:
 920 
 921   RefToScanQueue *task_queue(uint i) const;
 922 
 923   uint num_task_queues() const;
 924 
 925   // A set of cards where updates happened during the GC
 926   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 927 
 928   // Create a G1CollectedHeap with the specified policy.
 929   // Must call the initialize method afterwards.
 930   // May not return if something goes wrong.
 931   G1CollectedHeap(G1CollectorPolicy* policy);
 932 
 933 private:
 934   jint initialize_concurrent_refinement();
 935   jint initialize_young_gen_sampling_thread();
 936 public:
 937   // Initialize the G1CollectedHeap to have the initial and
 938   // maximum sizes and remembered and barrier sets
 939   // specified by the policy object.
 940   jint initialize();
 941 
 942   virtual void stop();
 943   virtual void safepoint_synchronize_begin();
 944   virtual void safepoint_synchronize_end();
 945 
 946   // Return the (conservative) maximum heap alignment for any G1 heap
 947   static size_t conservative_max_heap_alignment();
 948 
 949   // Does operations required after initialization has been done.
 950   void post_initialize();
 951 
 952   // Initialize weak reference processing.
 953   void ref_processing_init();
 954 
 955   virtual Name kind() const {
 956     return CollectedHeap::G1;
 957   }
 958 
 959   virtual const char* name() const {
 960     return "G1";
 961   }
 962 
 963   const G1CollectorState* collector_state() const { return &_collector_state; }
 964   G1CollectorState* collector_state() { return &_collector_state; }
 965 
 966   // The current policy object for the collector.
 967   G1Policy* g1_policy() const { return _g1_policy; }
 968 
 969   const G1CollectionSet* collection_set() const { return &_collection_set; }
 970   G1CollectionSet* collection_set() { return &_collection_set; }
 971 
 972   virtual CollectorPolicy* collector_policy() const;
 973 
 974   virtual SoftRefPolicy* soft_ref_policy();
 975 
 976   virtual GrowableArray<GCMemoryManager*> memory_managers();
 977   virtual GrowableArray<MemoryPool*> memory_pools();
 978 
 979   // The rem set and barrier set.
 980   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
 981 
 982   // Try to minimize the remembered set.
 983   void scrub_rem_set();
 984 
 985   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
 986   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
 987 
 988   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
 989   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
 990 
 991   // The shared block offset table array.
 992   G1BlockOffsetTable* bot() const { return _bot; }
 993 
 994   // Reference Processing accessors
 995 
 996   // The STW reference processor....
 997   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
 998 
 999   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1000 
1001   // The Concurrent Marking reference processor...
1002   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1003 
1004   size_t unused_committed_regions_in_bytes() const;
1005   virtual size_t capacity() const;
1006   virtual size_t used() const;
1007   // This should be called when we're not holding the heap lock. The
1008   // result might be a bit inaccurate.
1009   size_t used_unlocked() const;
1010   size_t recalculate_used() const;
1011 
1012   // These virtual functions do the actual allocation.
1013   // Some heaps may offer a contiguous region for shared non-blocking
1014   // allocation, via inlined code (by exporting the address of the top and
1015   // end fields defining the extent of the contiguous allocation region.)
1016   // But G1CollectedHeap doesn't yet support this.
1017 
1018   virtual bool is_maximal_no_gc() const {
1019     return _hrm.available() == 0;
1020   }
1021 
1022   // Returns whether there are any regions left in the heap for allocation.
1023   bool has_regions_left_for_allocation() const {
1024     return !is_maximal_no_gc() || num_free_regions() != 0;
1025   }
1026 
1027   // The current number of regions in the heap.
1028   uint num_regions() const { return _hrm.length(); }
1029 
1030   // The max number of regions in the heap.
1031   uint max_regions() const { return _hrm.max_length(); }
1032 
1033   // The number of regions that are completely free.
1034   uint num_free_regions() const { return _hrm.num_free_regions(); }
1035 
1036   MemoryUsage get_auxiliary_data_memory_usage() const {
1037     return _hrm.get_auxiliary_data_memory_usage();
1038   }
1039 
1040   // The number of regions that are not completely free.
1041   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1042 
1043 #ifdef ASSERT
1044   bool is_on_master_free_list(HeapRegion* hr) {
1045     return _hrm.is_free(hr);
1046   }
1047 #endif // ASSERT
1048 
1049   inline void old_set_add(HeapRegion* hr);
1050   inline void old_set_remove(HeapRegion* hr);
1051 
1052   size_t non_young_capacity_bytes() {
1053     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1054   }
1055 
1056   // Determine whether the given region is one that we are using as an
1057   // old GC alloc region.
1058   bool is_old_gc_alloc_region(HeapRegion* hr);
1059 
1060   // Perform a collection of the heap; intended for use in implementing
1061   // "System.gc".  This probably implies as full a collection as the
1062   // "CollectedHeap" supports.
1063   virtual void collect(GCCause::Cause cause);
1064 
1065   // True iff an evacuation has failed in the most-recent collection.
1066   bool evacuation_failed() { return _evacuation_failed; }
1067 
1068   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1069   void prepend_to_freelist(FreeRegionList* list);
1070   void decrement_summary_bytes(size_t bytes);
1071 
1072   virtual bool is_in(const void* p) const;
1073 #ifdef ASSERT
1074   // Returns whether p is in one of the available areas of the heap. Slow but
1075   // extensive version.
1076   bool is_in_exact(const void* p) const;
1077 #endif
1078 
1079   // Return "TRUE" iff the given object address is within the collection
1080   // set. Assumes that the reference points into the heap.
1081   inline bool is_in_cset(const HeapRegion *hr);
1082   inline bool is_in_cset(oop obj);
1083   inline bool is_in_cset(HeapWord* addr);
1084 
1085   inline bool is_in_cset_or_humongous(const oop obj);
1086 
1087  private:
1088   // This array is used for a quick test on whether a reference points into
1089   // the collection set or not. Each of the array's elements denotes whether the
1090   // corresponding region is in the collection set or not.
1091   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1092 
1093  public:
1094 
1095   inline InCSetState in_cset_state(const oop obj);
1096 
1097   // Return "TRUE" iff the given object address is in the reserved
1098   // region of g1.
1099   bool is_in_g1_reserved(const void* p) const {
1100     return _hrm.reserved().contains(p);
1101   }
1102 
1103   // Returns a MemRegion that corresponds to the space that has been
1104   // reserved for the heap
1105   MemRegion g1_reserved() const {
1106     return _hrm.reserved();
1107   }
1108 
1109   virtual bool is_in_closed_subset(const void* p) const;
1110 
1111   G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1112 
1113   G1CardTable* card_table() const {
1114     return _card_table;
1115   }
1116 
1117   // Iteration functions.
1118 
1119   // Iterate over all objects, calling "cl.do_object" on each.
1120   virtual void object_iterate(ObjectClosure* cl);
1121 
1122   virtual void safe_object_iterate(ObjectClosure* cl) {
1123     object_iterate(cl);
1124   }
1125 
1126   // Iterate over heap regions, in address order, terminating the
1127   // iteration early if the "do_heap_region" method returns "true".
1128   void heap_region_iterate(HeapRegionClosure* blk) const;
1129 
1130   // Return the region with the given index. It assumes the index is valid.
1131   inline HeapRegion* region_at(uint index) const;
1132 
1133   // Return the next region (by index) that is part of the same
1134   // humongous object that hr is part of.
1135   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1136 
1137   // Calculate the region index of the given address. Given address must be
1138   // within the heap.
1139   inline uint addr_to_region(HeapWord* addr) const;
1140 
1141   inline HeapWord* bottom_addr_for_region(uint index) const;
1142 
1143   // Two functions to iterate over the heap regions in parallel. Threads
1144   // compete using the HeapRegionClaimer to claim the regions before
1145   // applying the closure on them.
1146   // The _from_worker_offset version uses the HeapRegionClaimer and
1147   // the worker id to calculate a start offset to prevent all workers to
1148   // start from the point.
1149   void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1150                                                   HeapRegionClaimer* hrclaimer,
1151                                                   uint worker_id) const;
1152 
1153   void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1154                                           HeapRegionClaimer* hrclaimer) const;
1155 
1156   // Iterate over the regions (if any) in the current collection set.
1157   void collection_set_iterate(HeapRegionClosure* blk);
1158 
1159   // Iterate over the regions (if any) in the current collection set. Starts the
1160   // iteration over the entire collection set so that the start regions of a given
1161   // worker id over the set active_workers are evenly spread across the set of
1162   // collection set regions.
1163   void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1164 
1165   // Returns the HeapRegion that contains addr. addr must not be NULL.
1166   template <class T>
1167   inline HeapRegion* heap_region_containing(const T addr) const;
1168 
1169   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1170   // each address in the (reserved) heap is a member of exactly
1171   // one block.  The defining characteristic of a block is that it is
1172   // possible to find its size, and thus to progress forward to the next
1173   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1174   // represent Java objects, or they might be free blocks in a
1175   // free-list-based heap (or subheap), as long as the two kinds are
1176   // distinguishable and the size of each is determinable.
1177 
1178   // Returns the address of the start of the "block" that contains the
1179   // address "addr".  We say "blocks" instead of "object" since some heaps
1180   // may not pack objects densely; a chunk may either be an object or a
1181   // non-object.
1182   virtual HeapWord* block_start(const void* addr) const;
1183 
1184   // Requires "addr" to be the start of a chunk, and returns its size.
1185   // "addr + size" is required to be the start of a new chunk, or the end
1186   // of the active area of the heap.
1187   virtual size_t block_size(const HeapWord* addr) const;
1188 
1189   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1190   // the block is an object.
1191   virtual bool block_is_obj(const HeapWord* addr) const;
1192 
1193   // Section on thread-local allocation buffers (TLABs)
1194   // See CollectedHeap for semantics.
1195 
1196   bool supports_tlab_allocation() const;
1197   size_t tlab_capacity(Thread* ignored) const;
1198   size_t tlab_used(Thread* ignored) const;
1199   size_t max_tlab_size() const;
1200   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1201 
1202   inline bool is_in_young(const oop obj);
1203 
1204   // Returns "true" iff the given word_size is "very large".
1205   static bool is_humongous(size_t word_size) {
1206     // Note this has to be strictly greater-than as the TLABs
1207     // are capped at the humongous threshold and we want to
1208     // ensure that we don't try to allocate a TLAB as
1209     // humongous and that we don't allocate a humongous
1210     // object in a TLAB.
1211     return word_size > _humongous_object_threshold_in_words;
1212   }
1213 
1214   // Returns the humongous threshold for a specific region size
1215   static size_t humongous_threshold_for(size_t region_size) {
1216     return (region_size / 2);
1217   }
1218 
1219   // Returns the number of regions the humongous object of the given word size
1220   // requires.
1221   static size_t humongous_obj_size_in_regions(size_t word_size);
1222 
1223   // Print the maximum heap capacity.
1224   virtual size_t max_capacity() const;
1225 
1226   virtual jlong millis_since_last_gc();
1227 
1228 
1229   // Convenience function to be used in situations where the heap type can be
1230   // asserted to be this type.
1231   static G1CollectedHeap* heap();
1232 
1233   void set_region_short_lived_locked(HeapRegion* hr);
1234   // add appropriate methods for any other surv rate groups
1235 
1236   const G1SurvivorRegions* survivor() const { return &_survivor; }
1237 
1238   uint survivor_regions_count() const {
1239     return _survivor.length();
1240   }
1241 
1242   uint eden_regions_count() const {
1243     return _eden.length();
1244   }
1245 
1246   uint young_regions_count() const {
1247     return _eden.length() + _survivor.length();
1248   }
1249 
1250   uint old_regions_count() const { return _old_set.length(); }
1251 
1252   uint humongous_regions_count() const { return _humongous_set.length(); }
1253 
1254 #ifdef ASSERT
1255   bool check_young_list_empty();
1256 #endif
1257 
1258   // *** Stuff related to concurrent marking.  It's not clear to me that so
1259   // many of these need to be public.
1260 
1261   // The functions below are helper functions that a subclass of
1262   // "CollectedHeap" can use in the implementation of its virtual
1263   // functions.
1264   // This performs a concurrent marking of the live objects in a
1265   // bitmap off to the side.
1266   void do_concurrent_mark();
1267 
1268   bool is_marked_next(oop obj) const;
1269 
1270   // Determine if an object is dead, given the object and also
1271   // the region to which the object belongs. An object is dead
1272   // iff a) it was not allocated since the last mark, b) it
1273   // is not marked, and c) it is not in an archive region.
1274   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1275     return
1276       hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1277       !hr->is_archive();
1278   }
1279 
1280   // This function returns true when an object has been
1281   // around since the previous marking and hasn't yet
1282   // been marked during this marking, and is not in an archive region.
1283   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1284     return
1285       !hr->obj_allocated_since_next_marking(obj) &&
1286       !is_marked_next(obj) &&
1287       !hr->is_archive();
1288   }
1289 
1290   // Determine if an object is dead, given only the object itself.
1291   // This will find the region to which the object belongs and
1292   // then call the region version of the same function.
1293 
1294   // Added if it is NULL it isn't dead.
1295 
1296   inline bool is_obj_dead(const oop obj) const;
1297 
1298   inline bool is_obj_ill(const oop obj) const;
1299 
1300   inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1301   inline bool is_obj_dead_full(const oop obj) const;
1302 
1303   inline bool requires_marking(const void* entry) const;
1304 
1305   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1306 
1307   // Refinement
1308 
1309   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1310 
1311   // Optimized nmethod scanning support routines
1312 
1313   // Is an oop scavengeable
1314   virtual bool is_scavengable(oop obj);
1315 
1316   // Register the given nmethod with the G1 heap.
1317   virtual void register_nmethod(nmethod* nm);
1318 
1319   // Unregister the given nmethod from the G1 heap.
1320   virtual void unregister_nmethod(nmethod* nm);
1321 
1322   // Free up superfluous code root memory.
1323   void purge_code_root_memory();
1324 
1325   // Rebuild the strong code root lists for each region
1326   // after a full GC.
1327   void rebuild_strong_code_roots();
1328 
1329   // Partial cleaning used when class unloading is disabled.
1330   // Let the caller choose what structures to clean out:
1331   // - StringTable
1332   // - SymbolTable
1333   // - StringDeduplication structures
1334   void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1335 
1336   // Complete cleaning used when class unloading is enabled.
1337   // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1338   void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1339 
1340   // Redirty logged cards in the refinement queue.
1341   void redirty_logged_cards();
1342   // Verification
1343 
1344   // Deduplicate the string
1345   virtual void deduplicate_string(oop str);
1346 
1347   // Perform any cleanup actions necessary before allowing a verification.
1348   virtual void prepare_for_verify();
1349 
1350   // Perform verification.
1351 
1352   // vo == UsePrevMarking -> use "prev" marking information,
1353   // vo == UseNextMarking -> use "next" marking information
1354   // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1355   //
1356   // NOTE: Only the "prev" marking information is guaranteed to be
1357   // consistent most of the time, so most calls to this should use
1358   // vo == UsePrevMarking.
1359   // Currently, there is only one case where this is called with
1360   // vo == UseNextMarking, which is to verify the "next" marking
1361   // information at the end of remark.
1362   // Currently there is only one place where this is called with
1363   // vo == UseFullMarking, which is to verify the marking during a
1364   // full GC.
1365   void verify(VerifyOption vo);
1366 
1367   // WhiteBox testing support.
1368   virtual bool supports_concurrent_phase_control() const;
1369   virtual const char* const* concurrent_phases() const;
1370   virtual bool request_concurrent_phase(const char* phase);
1371 
1372   virtual WorkGang* get_safepoint_workers() { return _workers; }
1373 
1374   // The methods below are here for convenience and dispatch the
1375   // appropriate method depending on value of the given VerifyOption
1376   // parameter. The values for that parameter, and their meanings,
1377   // are the same as those above.
1378 
1379   bool is_obj_dead_cond(const oop obj,
1380                         const HeapRegion* hr,
1381                         const VerifyOption vo) const;
1382 
1383   bool is_obj_dead_cond(const oop obj,
1384                         const VerifyOption vo) const;
1385 
1386   G1HeapSummary create_g1_heap_summary();
1387   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1388 
1389   // Printing
1390 private:
1391   void print_heap_regions() const;
1392   void print_regions_on(outputStream* st) const;
1393 
1394 public:
1395   virtual void print_on(outputStream* st) const;
1396   virtual void print_extended_on(outputStream* st) const;
1397   virtual void print_on_error(outputStream* st) const;
1398 
1399   virtual void print_gc_threads_on(outputStream* st) const;
1400   virtual void gc_threads_do(ThreadClosure* tc) const;
1401 
1402   // Override
1403   void print_tracing_info() const;
1404 
1405   // The following two methods are helpful for debugging RSet issues.
1406   void print_cset_rsets() PRODUCT_RETURN;
1407   void print_all_rsets() PRODUCT_RETURN;
1408 
1409 public:
1410   size_t pending_card_num();
1411 
1412 private:
1413   size_t _max_heap_capacity;
1414 };
1415 
1416 class G1ParEvacuateFollowersClosure : public VoidClosure {
1417 private:
1418   double _start_term;
1419   double _term_time;
1420   size_t _term_attempts;
1421 
1422   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1423   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1424 protected:
1425   G1CollectedHeap*              _g1h;
1426   G1ParScanThreadState*         _par_scan_state;
1427   RefToScanQueueSet*            _queues;
1428   ParallelTaskTerminator*       _terminator;
1429 
1430   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1431   RefToScanQueueSet*      queues()         { return _queues; }
1432   ParallelTaskTerminator* terminator()     { return _terminator; }
1433 
1434 public:
1435   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1436                                 G1ParScanThreadState* par_scan_state,
1437                                 RefToScanQueueSet* queues,
1438                                 ParallelTaskTerminator* terminator)
1439     : _g1h(g1h), _par_scan_state(par_scan_state),
1440       _queues(queues), _terminator(terminator),
1441       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1442 
1443   void do_void();
1444 
1445   double term_time() const { return _term_time; }
1446   size_t term_attempts() const { return _term_attempts; }
1447 
1448 private:
1449   inline bool offer_termination();
1450 };
1451 
1452 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP