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_GC_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_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/g1GCPhaseTimes.hpp"
  39 #include "gc/g1/g1HeapTransition.hpp"
  40 #include "gc/g1/g1HeapVerifier.hpp"
  41 #include "gc/g1/g1HRPrinter.hpp"
  42 #include "gc/g1/g1InCSetState.hpp"
  43 #include "gc/g1/g1MonitoringSupport.hpp"
  44 #include "gc/g1/g1SurvivorRegions.hpp"
  45 #include "gc/g1/g1YCTypes.hpp"
  46 #include "gc/g1/heapRegionManager.hpp"
  47 #include "gc/g1/heapRegionSet.hpp"
  48 #include "gc/g1/heterogeneousHeapRegionManager.hpp"
  49 #include "gc/shared/barrierSet.hpp"
  50 #include "gc/shared/collectedHeap.hpp"
  51 #include "gc/shared/gcHeapSummary.hpp"
  52 #include "gc/shared/plab.hpp"
  53 #include "gc/shared/preservedMarks.hpp"
  54 #include "gc/shared/softRefPolicy.hpp"
  55 #include "memory/memRegion.hpp"
  56 #include "utilities/stack.hpp"
  57 
  58 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  59 // It uses the "Garbage First" heap organization and algorithm, which
  60 // may combine concurrent marking with parallel, incremental compaction of
  61 // heap subsets that will yield large amounts of garbage.
  62 
  63 // Forward declarations
  64 class HeapRegion;
  65 class GenerationSpec;
  66 class G1ParScanThreadState;
  67 class G1ParScanThreadStateSet;
  68 class G1ParScanThreadState;
  69 class MemoryPool;
  70 class MemoryManager;
  71 class ObjectClosure;
  72 class SpaceClosure;
  73 class CompactibleSpaceClosure;
  74 class Space;
  75 class G1CollectionSet;
  76 class G1CollectorPolicy;
  77 class G1Policy;
  78 class G1HotCardCache;
  79 class G1RemSet;
  80 class G1YoungRemSetSamplingThread;
  81 class HeapRegionRemSetIterator;
  82 class G1ConcurrentMark;
  83 class G1ConcurrentMarkThread;
  84 class G1ConcurrentRefine;
  85 class GenerationCounters;
  86 class STWGCTimer;
  87 class G1NewTracer;
  88 class EvacuationFailedInfo;
  89 class nmethod;
  90 class WorkGang;
  91 class G1Allocator;
  92 class G1ArchiveAllocator;
  93 class G1FullGCScope;
  94 class G1HeapVerifier;
  95 class G1HeapSizingPolicy;
  96 class G1HeapSummary;
  97 class G1EvacSummary;
  98 
  99 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
 100 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
 101 
 102 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
 103 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
 104 
 105 // The G1 STW is alive closure.
 106 // An instance is embedded into the G1CH and used as the
 107 // (optional) _is_alive_non_header closure in the STW
 108 // reference processor. It is also extensively used during
 109 // reference processing during STW evacuation pauses.
 110 class G1STWIsAliveClosure : public BoolObjectClosure {
 111   G1CollectedHeap* _g1h;
 112 public:
 113   G1STWIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 114   bool do_object_b(oop p);
 115 };
 116 
 117 class G1STWSubjectToDiscoveryClosure : public BoolObjectClosure {
 118   G1CollectedHeap* _g1h;
 119 public:
 120   G1STWSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 121   bool do_object_b(oop p);
 122 };
 123 
 124 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 125  private:
 126   void reset_from_card_cache(uint start_idx, size_t num_regions);
 127  public:
 128   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 129 };
 130 
 131 class G1CollectedHeap : public CollectedHeap {
 132   friend class G1FreeCollectionSetTask;
 133   friend class VM_CollectForMetadataAllocation;
 134   friend class VM_G1CollectForAllocation;
 135   friend class VM_G1CollectFull;
 136   friend class VMStructs;
 137   friend class MutatorAllocRegion;
 138   friend class G1FullCollector;
 139   friend class G1GCAllocRegion;
 140   friend class G1HeapVerifier;
 141 
 142   // Closures used in implementation.
 143   friend class G1ParScanThreadState;
 144   friend class G1ParScanThreadStateSet;
 145   friend class G1ParTask;
 146   friend class G1PLABAllocator;
 147   friend class G1PrepareCompactClosure;
 148 
 149   // Other related classes.
 150   friend class HeapRegionClaimer;
 151 
 152   // Testing classes.
 153   friend class G1CheckCSetFastTableClosure;
 154 
 155 private:
 156   G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
 157 
 158   WorkGang* _workers;
 159   G1CollectorPolicy* _collector_policy;
 160   G1CardTable* _card_table;
 161 
 162   SoftRefPolicy      _soft_ref_policy;
 163 
 164   static size_t _humongous_object_threshold_in_words;
 165 
 166   // These sets keep track of old, archive and humongous regions respectively.
 167   HeapRegionSet _old_set;
 168   HeapRegionSet _archive_set;
 169   HeapRegionSet _humongous_set;
 170 
 171   void eagerly_reclaim_humongous_regions();
 172   // Start a new incremental collection set for the next pause.
 173   void start_new_collection_set();
 174 
 175   // The block offset table for the G1 heap.
 176   G1BlockOffsetTable* _bot;
 177 
 178   // Tears down the region sets / lists so that they are empty and the
 179   // regions on the heap do not belong to a region set / list. The
 180   // only exception is the humongous set which we leave unaltered. If
 181   // free_list_only is true, it will only tear down the master free
 182   // list. It is called before a Full GC (free_list_only == false) or
 183   // before heap shrinking (free_list_only == true).
 184   void tear_down_region_sets(bool free_list_only);
 185 
 186   // Rebuilds the region sets / lists so that they are repopulated to
 187   // reflect the contents of the heap. The only exception is the
 188   // humongous set which was not torn down in the first place. If
 189   // free_list_only is true, it will only rebuild the master free
 190   // list. It is called after a Full GC (free_list_only == false) or
 191   // after heap shrinking (free_list_only == true).
 192   void rebuild_region_sets(bool free_list_only);
 193 
 194   // Callback for region mapping changed events.
 195   G1RegionMappingChangedListener _listener;
 196 
 197   // The sequence of all heap regions in the heap.
 198   HeapRegionManager* _hrm;
 199 
 200   // Manages all allocations with regions except humongous object allocations.
 201   G1Allocator* _allocator;
 202 
 203   // Manages all heap verification.
 204   G1HeapVerifier* _verifier;
 205 
 206   // Outside of GC pauses, the number of bytes used in all regions other
 207   // than the current allocation region(s).
 208   size_t _summary_bytes_used;
 209 
 210   void increase_used(size_t bytes);
 211   void decrease_used(size_t bytes);
 212 
 213   void set_used(size_t bytes);
 214 
 215   // Class that handles archive allocation ranges.
 216   G1ArchiveAllocator* _archive_allocator;
 217 
 218   // GC allocation statistics policy for survivors.
 219   G1EvacStats _survivor_evac_stats;
 220 
 221   // GC allocation statistics policy for tenured objects.
 222   G1EvacStats _old_evac_stats;
 223 
 224   // It specifies whether we should attempt to expand the heap after a
 225   // region allocation failure. If heap expansion fails we set this to
 226   // false so that we don't re-attempt the heap expansion (it's likely
 227   // that subsequent expansion attempts will also fail if one fails).
 228   // Currently, it is only consulted during GC and it's reset at the
 229   // start of each GC.
 230   bool _expand_heap_after_alloc_failure;
 231 
 232   // Helper for monitoring and management support.
 233   G1MonitoringSupport* _g1mm;
 234 
 235   // Records whether the region at the given index is (still) a
 236   // candidate for eager reclaim.  Only valid for humongous start
 237   // regions; other regions have unspecified values.  Humongous start
 238   // regions are initialized at start of collection pause, with
 239   // candidates removed from the set as they are found reachable from
 240   // roots or the young generation.
 241   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 242    protected:
 243     bool default_value() const { return false; }
 244    public:
 245     void clear() { G1BiasedMappedArray<bool>::clear(); }
 246     void set_candidate(uint region, bool value) {
 247       set_by_index(region, value);
 248     }
 249     bool is_candidate(uint region) {
 250       return get_by_index(region);
 251     }
 252   };
 253 
 254   HumongousReclaimCandidates _humongous_reclaim_candidates;
 255   // Stores whether during humongous object registration we found candidate regions.
 256   // If not, we can skip a few steps.
 257   bool _has_humongous_reclaim_candidates;
 258 
 259   G1HRPrinter _hr_printer;
 260 
 261   // It decides whether an explicit GC should start a concurrent cycle
 262   // instead of doing a STW GC. Currently, a concurrent cycle is
 263   // explicitly started if:
 264   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 265   // (b) cause == _g1_humongous_allocation
 266   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 267   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 268   // (e) cause == _wb_conc_mark
 269   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 270 
 271   // Return true if should upgrade to full gc after an incremental one.
 272   bool should_upgrade_to_full_gc(GCCause::Cause cause);
 273 
 274   // indicates whether we are in young or mixed GC mode
 275   G1CollectorState _collector_state;
 276 
 277   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 278   // concurrent cycles) we have started.
 279   volatile uint _old_marking_cycles_started;
 280 
 281   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 282   // concurrent cycles) we have completed.
 283   volatile uint _old_marking_cycles_completed;
 284 
 285   // This is a non-product method that is helpful for testing. It is
 286   // called at the end of a GC and artificially expands the heap by
 287   // allocating a number of dead regions. This way we can induce very
 288   // frequent marking cycles and stress the cleanup / concurrent
 289   // cleanup code more (as all the regions that will be allocated by
 290   // this method will be found dead by the marking cycle).
 291   void allocate_dummy_regions() PRODUCT_RETURN;
 292 
 293   // If the HR printer is active, dump the state of the regions in the
 294   // heap after a compaction.
 295   void print_hrm_post_compaction();
 296 
 297   // Create a memory mapper for auxiliary data structures of the given size and
 298   // translation factor.
 299   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 300                                                          size_t size,
 301                                                          size_t translation_factor);
 302 
 303   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 304 
 305   // These are macros so that, if the assert fires, we get the correct
 306   // line number, file, etc.
 307 
 308 #define heap_locking_asserts_params(_extra_message_)                          \
 309   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 310   (_extra_message_),                                                          \
 311   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 312   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 313   BOOL_TO_STR(Thread::current()->is_VM_thread())
 314 
 315 #define assert_heap_locked()                                                  \
 316   do {                                                                        \
 317     assert(Heap_lock->owned_by_self(),                                        \
 318            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 319   } while (0)
 320 
 321 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 322   do {                                                                        \
 323     assert(Heap_lock->owned_by_self() ||                                      \
 324            (SafepointSynchronize::is_at_safepoint() &&                        \
 325              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 326            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 327                                         "should be at a safepoint"));         \
 328   } while (0)
 329 
 330 #define assert_heap_locked_and_not_at_safepoint()                             \
 331   do {                                                                        \
 332     assert(Heap_lock->owned_by_self() &&                                      \
 333                                     !SafepointSynchronize::is_at_safepoint(), \
 334           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 335                                        "should not be at a safepoint"));      \
 336   } while (0)
 337 
 338 #define assert_heap_not_locked()                                              \
 339   do {                                                                        \
 340     assert(!Heap_lock->owned_by_self(),                                       \
 341         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 342   } while (0)
 343 
 344 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 345   do {                                                                        \
 346     assert(!Heap_lock->owned_by_self() &&                                     \
 347                                     !SafepointSynchronize::is_at_safepoint(), \
 348       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 349                                    "should not be at a safepoint"));          \
 350   } while (0)
 351 
 352 #define assert_at_safepoint_on_vm_thread()                                    \
 353   do {                                                                        \
 354     assert_at_safepoint();                                                    \
 355     assert(Thread::current_or_null() != NULL, "no current thread");           \
 356     assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \
 357   } while (0)
 358 
 359   // The young region list.
 360   G1EdenRegions _eden;
 361   G1SurvivorRegions _survivor;
 362 
 363   STWGCTimer* _gc_timer_stw;
 364 
 365   G1NewTracer* _gc_tracer_stw;
 366 
 367   // The current policy object for the collector.
 368   G1Policy* _g1_policy;
 369   G1HeapSizingPolicy* _heap_sizing_policy;
 370 
 371   G1CollectionSet _collection_set;
 372 
 373   // Try to allocate a single non-humongous HeapRegion sufficient for
 374   // an allocation of the given word_size. If do_expand is true,
 375   // attempt to expand the heap if necessary to satisfy the allocation
 376   // request. 'type' takes the type of region to be allocated. (Use constants
 377   // Old, Eden, Humongous, Survivor defined in HeapRegionType.)
 378   HeapRegion* new_region(size_t word_size, HeapRegionType type, bool do_expand);
 379 
 380   // Initialize a contiguous set of free regions of length num_regions
 381   // and starting at index first so that they appear as a single
 382   // humongous region.
 383   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 384                                                       uint num_regions,
 385                                                       size_t word_size);
 386 
 387   // Attempt to allocate a humongous object of the given size. Return
 388   // NULL if unsuccessful.
 389   HeapWord* humongous_obj_allocate(size_t word_size);
 390 
 391   // The following two methods, allocate_new_tlab() and
 392   // mem_allocate(), are the two main entry points from the runtime
 393   // into the G1's allocation routines. They have the following
 394   // assumptions:
 395   //
 396   // * They should both be called outside safepoints.
 397   //
 398   // * They should both be called without holding the Heap_lock.
 399   //
 400   // * All allocation requests for new TLABs should go to
 401   //   allocate_new_tlab().
 402   //
 403   // * All non-TLAB allocation requests should go to mem_allocate().
 404   //
 405   // * If either call cannot satisfy the allocation request using the
 406   //   current allocating region, they will try to get a new one. If
 407   //   this fails, they will attempt to do an evacuation pause and
 408   //   retry the allocation.
 409   //
 410   // * If all allocation attempts fail, even after trying to schedule
 411   //   an evacuation pause, allocate_new_tlab() will return NULL,
 412   //   whereas mem_allocate() will attempt a heap expansion and/or
 413   //   schedule a Full GC.
 414   //
 415   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 416   //   should never be called with word_size being humongous. All
 417   //   humongous allocation requests should go to mem_allocate() which
 418   //   will satisfy them with a special path.
 419 
 420   virtual HeapWord* allocate_new_tlab(size_t min_size,
 421                                       size_t requested_size,
 422                                       size_t* actual_size);
 423 
 424   virtual HeapWord* mem_allocate(size_t word_size,
 425                                  bool*  gc_overhead_limit_was_exceeded);
 426 
 427   // First-level mutator allocation attempt: try to allocate out of
 428   // the mutator alloc region without taking the Heap_lock. This
 429   // should only be used for non-humongous allocations.
 430   inline HeapWord* attempt_allocation(size_t min_word_size,
 431                                       size_t desired_word_size,
 432                                       size_t* actual_word_size);
 433 
 434   // Second-level mutator allocation attempt: take the Heap_lock and
 435   // retry the allocation attempt, potentially scheduling a GC
 436   // pause. This should only be used for non-humongous allocations.
 437   HeapWord* attempt_allocation_slow(size_t word_size);
 438 
 439   // Takes the Heap_lock and attempts a humongous allocation. It can
 440   // potentially schedule a GC pause.
 441   HeapWord* attempt_allocation_humongous(size_t word_size);
 442 
 443   // Allocation attempt that should be called during safepoints (e.g.,
 444   // at the end of a successful GC). expect_null_mutator_alloc_region
 445   // specifies whether the mutator alloc region is expected to be NULL
 446   // or not.
 447   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 448                                             bool expect_null_mutator_alloc_region);
 449 
 450   // These methods are the "callbacks" from the G1AllocRegion class.
 451 
 452   // For mutator alloc regions.
 453   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 454   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 455                                    size_t allocated_bytes);
 456 
 457   // For GC alloc regions.
 458   bool has_more_regions(InCSetState dest);
 459   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 460   void retire_gc_alloc_region(HeapRegion* alloc_region,
 461                               size_t allocated_bytes, InCSetState dest);
 462 
 463   // - if explicit_gc is true, the GC is for a System.gc() etc,
 464   //   otherwise it's for a failed allocation.
 465   // - if clear_all_soft_refs is true, all soft references should be
 466   //   cleared during the GC.
 467   // - it returns false if it is unable to do the collection due to the
 468   //   GC locker being active, true otherwise.
 469   bool do_full_collection(bool explicit_gc,
 470                           bool clear_all_soft_refs);
 471 
 472   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 473   virtual void do_full_collection(bool clear_all_soft_refs);
 474 
 475   // Callback from VM_G1CollectForAllocation operation.
 476   // This function does everything necessary/possible to satisfy a
 477   // failed allocation request (including collection, expansion, etc.)
 478   HeapWord* satisfy_failed_allocation(size_t word_size,
 479                                       bool* succeeded);
 480   // Internal helpers used during full GC to split it up to
 481   // increase readability.
 482   void abort_concurrent_cycle();
 483   void verify_before_full_collection(bool explicit_gc);
 484   void prepare_heap_for_full_collection();
 485   void prepare_heap_for_mutators();
 486   void abort_refinement();
 487   void verify_after_full_collection();
 488   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 489 
 490   // Helper method for satisfy_failed_allocation()
 491   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 492                                              bool do_gc,
 493                                              bool clear_all_soft_refs,
 494                                              bool expect_null_mutator_alloc_region,
 495                                              bool* gc_succeeded);
 496 
 497   // Attempting to expand the heap sufficiently
 498   // to support an allocation of the given "word_size".  If
 499   // successful, perform the allocation and return the address of the
 500   // allocated block, or else "NULL".
 501   HeapWord* expand_and_allocate(size_t word_size);
 502 
 503   // Process any reference objects discovered.
 504   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 505 
 506   // If during an initial mark pause we may install a pending list head which is not
 507   // otherwise reachable ensure that it is marked in the bitmap for concurrent marking
 508   // to discover.
 509   void make_pending_list_reachable();
 510 
 511   // Merges the information gathered on a per-thread basis for all worker threads
 512   // during GC into global variables.
 513   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 514 public:
 515   G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
 516 
 517   WorkGang* workers() const { return _workers; }
 518 
 519   G1Allocator* allocator() {
 520     return _allocator;
 521   }
 522 
 523   G1HeapVerifier* verifier() {
 524     return _verifier;
 525   }
 526 
 527   G1MonitoringSupport* g1mm() {
 528     assert(_g1mm != NULL, "should have been initialized");
 529     return _g1mm;
 530   }
 531 
 532   void resize_heap_if_necessary();
 533 
 534   // Expand the garbage-first heap by at least the given size (in bytes!).
 535   // Returns true if the heap was expanded by the requested amount;
 536   // false otherwise.
 537   // (Rounds up to a HeapRegion boundary.)
 538   bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
 539 
 540   // Returns the PLAB statistics for a given destination.
 541   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 542 
 543   // Determines PLAB size for a given destination.
 544   inline size_t desired_plab_sz(InCSetState dest);
 545 
 546   // Do anything common to GC's.
 547   void gc_prologue(bool full);
 548   void gc_epilogue(bool full);
 549 
 550   // Does the given region fulfill remembered set based eager reclaim candidate requirements?
 551   bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
 552 
 553   // Modify the reclaim candidate set and test for presence.
 554   // These are only valid for starts_humongous regions.
 555   inline void set_humongous_reclaim_candidate(uint region, bool value);
 556   inline bool is_humongous_reclaim_candidate(uint region);
 557 
 558   // Remove from the reclaim candidate set.  Also remove from the
 559   // collection set so that later encounters avoid the slow path.
 560   inline void set_humongous_is_live(oop obj);
 561 
 562   // Register the given region to be part of the collection set.
 563   inline void register_humongous_region_with_cset(uint index);
 564   // Register regions with humongous objects (actually on the start region) in
 565   // the in_cset_fast_test table.
 566   void register_humongous_regions_with_cset();
 567   // We register a region with the fast "in collection set" test. We
 568   // simply set to true the array slot corresponding to this region.
 569   void register_young_region_with_cset(HeapRegion* r) {
 570     _in_cset_fast_test.set_in_young(r->hrm_index());
 571   }
 572   void register_old_region_with_cset(HeapRegion* r) {
 573     _in_cset_fast_test.set_in_old(r->hrm_index());
 574   }
 575   void register_optional_region_with_cset(HeapRegion* r) {
 576     _in_cset_fast_test.set_optional(r->hrm_index());
 577   }
 578   void clear_in_cset(const HeapRegion* hr) {
 579     _in_cset_fast_test.clear(hr);
 580   }
 581 
 582   void clear_cset_fast_test() {
 583     _in_cset_fast_test.clear();
 584   }
 585 
 586   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 587 
 588   // This is called at the start of either a concurrent cycle or a Full
 589   // GC to update the number of old marking cycles started.
 590   void increment_old_marking_cycles_started();
 591 
 592   // This is called at the end of either a concurrent cycle or a Full
 593   // GC to update the number of old marking cycles completed. Those two
 594   // can happen in a nested fashion, i.e., we start a concurrent
 595   // cycle, a Full GC happens half-way through it which ends first,
 596   // and then the cycle notices that a Full GC happened and ends
 597   // too. The concurrent parameter is a boolean to help us do a bit
 598   // tighter consistency checking in the method. If concurrent is
 599   // false, the caller is the inner caller in the nesting (i.e., the
 600   // Full GC). If concurrent is true, the caller is the outer caller
 601   // in this nesting (i.e., the concurrent cycle). Further nesting is
 602   // not currently supported. The end of this call also notifies
 603   // the FullGCCount_lock in case a Java thread is waiting for a full
 604   // GC to happen (e.g., it called System.gc() with
 605   // +ExplicitGCInvokesConcurrent).
 606   void increment_old_marking_cycles_completed(bool concurrent);
 607 
 608   uint old_marking_cycles_completed() {
 609     return _old_marking_cycles_completed;
 610   }
 611 
 612   G1HRPrinter* hr_printer() { return &_hr_printer; }
 613 
 614   // Allocates a new heap region instance.
 615   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 616 
 617   // Allocate the highest free region in the reserved heap. This will commit
 618   // regions as necessary.
 619   HeapRegion* alloc_highest_free_region();
 620 
 621   // Frees a non-humongous region by initializing its contents and
 622   // adding it to the free list that's passed as a parameter (this is
 623   // usually a local list which will be appended to the master free
 624   // list later). The used bytes of freed regions are accumulated in
 625   // pre_used. If skip_remset is true, the region's RSet will not be freed
 626   // up. If skip_hot_card_cache is true, the region's hot card cache will not
 627   // be freed up. The assumption is that this will be done later.
 628   // The locked parameter indicates if the caller has already taken
 629   // care of proper synchronization. This may allow some optimizations.
 630   void free_region(HeapRegion* hr,
 631                    FreeRegionList* free_list,
 632                    bool skip_remset,
 633                    bool skip_hot_card_cache = false,
 634                    bool locked = false);
 635 
 636   // It dirties the cards that cover the block so that the post
 637   // write barrier never queues anything when updating objects on this
 638   // block. It is assumed (and in fact we assert) that the block
 639   // belongs to a young region.
 640   inline void dirty_young_block(HeapWord* start, size_t word_size);
 641 
 642   // Frees a humongous region by collapsing it into individual regions
 643   // and calling free_region() for each of them. The freed regions
 644   // will be added to the free list that's passed as a parameter (this
 645   // is usually a local list which will be appended to the master free
 646   // list later).
 647   // The method assumes that only a single thread is ever calling
 648   // this for a particular region at once.
 649   void free_humongous_region(HeapRegion* hr,
 650                              FreeRegionList* free_list);
 651 
 652   // Facility for allocating in 'archive' regions in high heap memory and
 653   // recording the allocated ranges. These should all be called from the
 654   // VM thread at safepoints, without the heap lock held. They can be used
 655   // to create and archive a set of heap regions which can be mapped at the
 656   // same fixed addresses in a subsequent JVM invocation.
 657   void begin_archive_alloc_range(bool open = false);
 658 
 659   // Check if the requested size would be too large for an archive allocation.
 660   bool is_archive_alloc_too_large(size_t word_size);
 661 
 662   // Allocate memory of the requested size from the archive region. This will
 663   // return NULL if the size is too large or if no memory is available. It
 664   // does not trigger a garbage collection.
 665   HeapWord* archive_mem_allocate(size_t word_size);
 666 
 667   // Optionally aligns the end address and returns the allocated ranges in
 668   // an array of MemRegions in order of ascending addresses.
 669   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 670                                size_t end_alignment_in_bytes = 0);
 671 
 672   // Facility for allocating a fixed range within the heap and marking
 673   // the containing regions as 'archive'. For use at JVM init time, when the
 674   // caller may mmap archived heap data at the specified range(s).
 675   // Verify that the MemRegions specified in the argument array are within the
 676   // reserved heap.
 677   bool check_archive_addresses(MemRegion* range, size_t count);
 678 
 679   // Commit the appropriate G1 regions containing the specified MemRegions
 680   // and mark them as 'archive' regions. The regions in the array must be
 681   // non-overlapping and in order of ascending address.
 682   bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
 683 
 684   // Insert any required filler objects in the G1 regions around the specified
 685   // ranges to make the regions parseable. This must be called after
 686   // alloc_archive_regions, and after class loading has occurred.
 687   void fill_archive_regions(MemRegion* range, size_t count);
 688 
 689   // For each of the specified MemRegions, uncommit the containing G1 regions
 690   // which had been allocated by alloc_archive_regions. This should be called
 691   // rather than fill_archive_regions at JVM init time if the archive file
 692   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 693   void dealloc_archive_regions(MemRegion* range, size_t count, bool is_open);
 694 
 695   oop materialize_archived_object(oop obj);
 696 
 697 private:
 698 
 699   // Shrink the garbage-first heap by at most the given size (in bytes!).
 700   // (Rounds down to a HeapRegion boundary.)
 701   void shrink(size_t expand_bytes);
 702   void shrink_helper(size_t expand_bytes);
 703 
 704   #if TASKQUEUE_STATS
 705   static void print_taskqueue_stats_hdr(outputStream* const st);
 706   void print_taskqueue_stats() const;
 707   void reset_taskqueue_stats();
 708   #endif // TASKQUEUE_STATS
 709 
 710   // Schedule the VM operation that will do an evacuation pause to
 711   // satisfy an allocation request of word_size. *succeeded will
 712   // return whether the VM operation was successful (it did do an
 713   // evacuation pause) or not (another thread beat us to it or the GC
 714   // locker was active). Given that we should not be holding the
 715   // Heap_lock when we enter this method, we will pass the
 716   // gc_count_before (i.e., total_collections()) as a parameter since
 717   // it has to be read while holding the Heap_lock. Currently, both
 718   // methods that call do_collection_pause() release the Heap_lock
 719   // before the call, so it's easy to read gc_count_before just before.
 720   HeapWord* do_collection_pause(size_t         word_size,
 721                                 uint           gc_count_before,
 722                                 bool*          succeeded,
 723                                 GCCause::Cause gc_cause);
 724 
 725   void wait_for_root_region_scanning();
 726 
 727   // The guts of the incremental collection pause, executed by the vm
 728   // thread. It returns false if it is unable to do the collection due
 729   // to the GC locker being active, true otherwise
 730   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 731 
 732   // Actually do the work of evacuating the collection set.
 733   void evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states);
 734   void evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states);
 735   void evacuate_optional_regions(G1ParScanThreadStateSet* per_thread_states, G1OptionalCSet* ocset);
 736 
 737   void pre_evacuate_collection_set();
 738   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 739 
 740   // Print the header for the per-thread termination statistics.
 741   static void print_termination_stats_hdr();
 742   // Print actual per-thread termination statistics.
 743   void print_termination_stats(uint worker_id,
 744                                double elapsed_ms,
 745                                double strong_roots_ms,
 746                                double term_ms,
 747                                size_t term_attempts,
 748                                size_t alloc_buffer_waste,
 749                                size_t undo_waste) const;
 750   // Update object copying statistics.
 751   void record_obj_copy_mem_stats();
 752 
 753   // The hot card cache for remembered set insertion optimization.
 754   G1HotCardCache* _hot_card_cache;
 755 
 756   // The g1 remembered set of the heap.
 757   G1RemSet* _g1_rem_set;
 758 
 759   // A set of cards that cover the objects for which the Rsets should be updated
 760   // concurrently after the collection.
 761   DirtyCardQueueSet _dirty_card_queue_set;
 762 
 763   // After a collection pause, convert the regions in the collection set into free
 764   // regions.
 765   void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 766 
 767   // Abandon the current collection set without recording policy
 768   // statistics or updating free lists.
 769   void abandon_collection_set(G1CollectionSet* collection_set);
 770 
 771   // The concurrent marker (and the thread it runs in.)
 772   G1ConcurrentMark* _cm;
 773   G1ConcurrentMarkThread* _cm_thread;
 774 
 775   // The concurrent refiner.
 776   G1ConcurrentRefine* _cr;
 777 
 778   // The parallel task queues
 779   RefToScanQueueSet *_task_queues;
 780 
 781   // True iff a evacuation has failed in the current collection.
 782   bool _evacuation_failed;
 783 
 784   EvacuationFailedInfo* _evacuation_failed_info_array;
 785 
 786   // Failed evacuations cause some logical from-space objects to have
 787   // forwarding pointers to themselves.  Reset them.
 788   void remove_self_forwarding_pointers();
 789 
 790   // Restore the objects in the regions in the collection set after an
 791   // evacuation failure.
 792   void restore_after_evac_failure();
 793 
 794   PreservedMarksSet _preserved_marks_set;
 795 
 796   // Preserve the mark of "obj", if necessary, in preparation for its mark
 797   // word being overwritten with a self-forwarding-pointer.
 798   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 799 
 800 #ifndef PRODUCT
 801   // Support for forcing evacuation failures. Analogous to
 802   // PromotionFailureALot for the other collectors.
 803 
 804   // Records whether G1EvacuationFailureALot should be in effect
 805   // for the current GC
 806   bool _evacuation_failure_alot_for_current_gc;
 807 
 808   // Used to record the GC number for interval checking when
 809   // determining whether G1EvaucationFailureALot is in effect
 810   // for the current GC.
 811   size_t _evacuation_failure_alot_gc_number;
 812 
 813   // Count of the number of evacuations between failures.
 814   volatile size_t _evacuation_failure_alot_count;
 815 
 816   // Set whether G1EvacuationFailureALot should be in effect
 817   // for the current GC (based upon the type of GC and which
 818   // command line flags are set);
 819   inline bool evacuation_failure_alot_for_gc_type(bool for_young_gc,
 820                                                   bool during_initial_mark,
 821                                                   bool mark_or_rebuild_in_progress);
 822 
 823   inline void set_evacuation_failure_alot_for_current_gc();
 824 
 825   // Return true if it's time to cause an evacuation failure.
 826   inline bool evacuation_should_fail();
 827 
 828   // Reset the G1EvacuationFailureALot counters.  Should be called at
 829   // the end of an evacuation pause in which an evacuation failure occurred.
 830   inline void reset_evacuation_should_fail();
 831 #endif // !PRODUCT
 832 
 833   // ("Weak") Reference processing support.
 834   //
 835   // G1 has 2 instances of the reference processor class. One
 836   // (_ref_processor_cm) handles reference object discovery
 837   // and subsequent processing during concurrent marking cycles.
 838   //
 839   // The other (_ref_processor_stw) handles reference object
 840   // discovery and processing during full GCs and incremental
 841   // evacuation pauses.
 842   //
 843   // During an incremental pause, reference discovery will be
 844   // temporarily disabled for _ref_processor_cm and will be
 845   // enabled for _ref_processor_stw. At the end of the evacuation
 846   // pause references discovered by _ref_processor_stw will be
 847   // processed and discovery will be disabled. The previous
 848   // setting for reference object discovery for _ref_processor_cm
 849   // will be re-instated.
 850   //
 851   // At the start of marking:
 852   //  * Discovery by the CM ref processor is verified to be inactive
 853   //    and it's discovered lists are empty.
 854   //  * Discovery by the CM ref processor is then enabled.
 855   //
 856   // At the end of marking:
 857   //  * Any references on the CM ref processor's discovered
 858   //    lists are processed (possibly MT).
 859   //
 860   // At the start of full GC we:
 861   //  * Disable discovery by the CM ref processor and
 862   //    empty CM ref processor's discovered lists
 863   //    (without processing any entries).
 864   //  * Verify that the STW ref processor is inactive and it's
 865   //    discovered lists are empty.
 866   //  * Temporarily set STW ref processor discovery as single threaded.
 867   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 868   //    field.
 869   //  * Finally enable discovery by the STW ref processor.
 870   //
 871   // The STW ref processor is used to record any discovered
 872   // references during the full GC.
 873   //
 874   // At the end of a full GC we:
 875   //  * Enqueue any reference objects discovered by the STW ref processor
 876   //    that have non-live referents. This has the side-effect of
 877   //    making the STW ref processor inactive by disabling discovery.
 878   //  * Verify that the CM ref processor is still inactive
 879   //    and no references have been placed on it's discovered
 880   //    lists (also checked as a precondition during initial marking).
 881 
 882   // The (stw) reference processor...
 883   ReferenceProcessor* _ref_processor_stw;
 884 
 885   // During reference object discovery, the _is_alive_non_header
 886   // closure (if non-null) is applied to the referent object to
 887   // determine whether the referent is live. If so then the
 888   // reference object does not need to be 'discovered' and can
 889   // be treated as a regular oop. This has the benefit of reducing
 890   // the number of 'discovered' reference objects that need to
 891   // be processed.
 892   //
 893   // Instance of the is_alive closure for embedding into the
 894   // STW reference processor as the _is_alive_non_header field.
 895   // Supplying a value for the _is_alive_non_header field is
 896   // optional but doing so prevents unnecessary additions to
 897   // the discovered lists during reference discovery.
 898   G1STWIsAliveClosure _is_alive_closure_stw;
 899 
 900   G1STWSubjectToDiscoveryClosure _is_subject_to_discovery_stw;
 901 
 902   // The (concurrent marking) reference processor...
 903   ReferenceProcessor* _ref_processor_cm;
 904 
 905   // Instance of the concurrent mark is_alive closure for embedding
 906   // into the Concurrent Marking reference processor as the
 907   // _is_alive_non_header field. Supplying a value for the
 908   // _is_alive_non_header field is optional but doing so prevents
 909   // unnecessary additions to the discovered lists during reference
 910   // discovery.
 911   G1CMIsAliveClosure _is_alive_closure_cm;
 912 
 913   G1CMSubjectToDiscoveryClosure _is_subject_to_discovery_cm;
 914 public:
 915 
 916   RefToScanQueue *task_queue(uint i) const;
 917 
 918   uint num_task_queues() const;
 919 
 920   // A set of cards where updates happened during the GC
 921   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 922 
 923   // Create a G1CollectedHeap with the specified policy.
 924   // Must call the initialize method afterwards.
 925   // May not return if something goes wrong.
 926   G1CollectedHeap(G1CollectorPolicy* policy);
 927 
 928 private:
 929   jint initialize_concurrent_refinement();
 930   jint initialize_young_gen_sampling_thread();
 931 public:
 932   // Initialize the G1CollectedHeap to have the initial and
 933   // maximum sizes and remembered and barrier sets
 934   // specified by the policy object.
 935   jint initialize();
 936 
 937   virtual void stop();
 938   virtual void safepoint_synchronize_begin();
 939   virtual void safepoint_synchronize_end();
 940 
 941   // Return the (conservative) maximum heap alignment for any G1 heap
 942   static size_t conservative_max_heap_alignment();
 943 
 944   // Does operations required after initialization has been done.
 945   void post_initialize();
 946 
 947   // Initialize weak reference processing.
 948   void ref_processing_init();
 949 
 950   virtual Name kind() const {
 951     return CollectedHeap::G1;
 952   }
 953 
 954   virtual const char* name() const {
 955     return "G1";
 956   }
 957 
 958   const G1CollectorState* collector_state() const { return &_collector_state; }
 959   G1CollectorState* collector_state() { return &_collector_state; }
 960 
 961   // The current policy object for the collector.
 962   G1Policy* g1_policy() const { return _g1_policy; }
 963 
 964   HeapRegionManager* hrm() const { return _hrm; }
 965 
 966   const G1CollectionSet* collection_set() const { return &_collection_set; }
 967   G1CollectionSet* collection_set() { return &_collection_set; }
 968 
 969   virtual CollectorPolicy* collector_policy() const;
 970   virtual G1CollectorPolicy* g1_collector_policy() const;
 971 
 972   virtual SoftRefPolicy* soft_ref_policy();
 973 
 974   virtual void initialize_serviceability();
 975   virtual MemoryUsage memory_usage();
 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   // Max number of regions that can be comitted.
1034   uint max_expandable_regions() const { return _hrm->max_expandable_length(); }
1035 
1036   // The number of regions that are completely free.
1037   uint num_free_regions() const { return _hrm->num_free_regions(); }
1038 
1039   // The number of regions that can be allocated into.
1040   uint num_free_or_available_regions() const { return num_free_regions() + _hrm->available(); }
1041 
1042   MemoryUsage get_auxiliary_data_memory_usage() const {
1043     return _hrm->get_auxiliary_data_memory_usage();
1044   }
1045 
1046   // The number of regions that are not completely free.
1047   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1048 
1049 #ifdef ASSERT
1050   bool is_on_master_free_list(HeapRegion* hr) {
1051     return _hrm->is_free(hr);
1052   }
1053 #endif // ASSERT
1054 
1055   inline void old_set_add(HeapRegion* hr);
1056   inline void old_set_remove(HeapRegion* hr);
1057 
1058   inline void archive_set_add(HeapRegion* hr);
1059 
1060   size_t non_young_capacity_bytes() {
1061     return (old_regions_count() + _archive_set.length() + humongous_regions_count()) * HeapRegion::GrainBytes;
1062   }
1063 
1064   // Determine whether the given region is one that we are using as an
1065   // old GC alloc region.
1066   bool is_old_gc_alloc_region(HeapRegion* hr);
1067 
1068   // Perform a collection of the heap; intended for use in implementing
1069   // "System.gc".  This probably implies as full a collection as the
1070   // "CollectedHeap" supports.
1071   virtual void collect(GCCause::Cause cause);
1072 
1073   // True iff an evacuation has failed in the most-recent collection.
1074   bool evacuation_failed() { return _evacuation_failed; }
1075 
1076   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1077   void prepend_to_freelist(FreeRegionList* list);
1078   void decrement_summary_bytes(size_t bytes);
1079 
1080   virtual bool is_in(const void* p) const;
1081 #ifdef ASSERT
1082   // Returns whether p is in one of the available areas of the heap. Slow but
1083   // extensive version.
1084   bool is_in_exact(const void* p) const;
1085 #endif
1086 
1087   // Return "TRUE" iff the given object address is within the collection
1088   // set. Assumes that the reference points into the heap.
1089   inline bool is_in_cset(const HeapRegion *hr);
1090   inline bool is_in_cset(oop obj);
1091   inline bool is_in_cset(HeapWord* addr);
1092 
1093   inline bool is_in_cset_or_humongous(const oop obj);
1094 
1095  private:
1096   // This array is used for a quick test on whether a reference points into
1097   // the collection set or not. Each of the array's elements denotes whether the
1098   // corresponding region is in the collection set or not.
1099   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1100 
1101  public:
1102 
1103   inline InCSetState in_cset_state(const oop obj);
1104 
1105   // Return "TRUE" iff the given object address is in the reserved
1106   // region of g1.
1107   bool is_in_g1_reserved(const void* p) const {
1108     return _hrm->reserved().contains(p);
1109   }
1110 
1111   // Returns a MemRegion that corresponds to the space that has been
1112   // reserved for the heap
1113   MemRegion g1_reserved() const {
1114     return _hrm->reserved();
1115   }
1116 
1117   virtual bool is_in_closed_subset(const void* p) const;
1118 
1119   G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1120 
1121   G1CardTable* card_table() const {
1122     return _card_table;
1123   }
1124 
1125   // Iteration functions.
1126 
1127   // Iterate over all objects, calling "cl.do_object" on each.
1128   virtual void object_iterate(ObjectClosure* cl);
1129 
1130   virtual void safe_object_iterate(ObjectClosure* cl) {
1131     object_iterate(cl);
1132   }
1133 
1134   // Iterate over heap regions, in address order, terminating the
1135   // iteration early if the "do_heap_region" method returns "true".
1136   void heap_region_iterate(HeapRegionClosure* blk) const;
1137 
1138   // Return the region with the given index. It assumes the index is valid.
1139   inline HeapRegion* region_at(uint index) const;
1140   inline HeapRegion* region_at_or_null(uint index) const;
1141 
1142   // Return the next region (by index) that is part of the same
1143   // humongous object that hr is part of.
1144   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1145 
1146   // Calculate the region index of the given address. Given address must be
1147   // within the heap.
1148   inline uint addr_to_region(HeapWord* addr) const;
1149 
1150   inline HeapWord* bottom_addr_for_region(uint index) const;
1151 
1152   // Two functions to iterate over the heap regions in parallel. Threads
1153   // compete using the HeapRegionClaimer to claim the regions before
1154   // applying the closure on them.
1155   // The _from_worker_offset version uses the HeapRegionClaimer and
1156   // the worker id to calculate a start offset to prevent all workers to
1157   // start from the point.
1158   void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1159                                                   HeapRegionClaimer* hrclaimer,
1160                                                   uint worker_id) const;
1161 
1162   void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1163                                           HeapRegionClaimer* hrclaimer) const;
1164 
1165   // Iterate over the regions (if any) in the current collection set.
1166   void collection_set_iterate(HeapRegionClosure* blk);
1167 
1168   // Iterate over the regions (if any) in the current collection set. Starts the
1169   // iteration over the entire collection set so that the start regions of a given
1170   // worker id over the set active_workers are evenly spread across the set of
1171   // collection set regions.
1172   void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1173 
1174   // Returns the HeapRegion that contains addr. addr must not be NULL.
1175   template <class T>
1176   inline HeapRegion* heap_region_containing(const T addr) const;
1177 
1178   // Returns the HeapRegion that contains addr, or NULL if that is an uncommitted
1179   // region. addr must not be NULL.
1180   template <class T>
1181   inline HeapRegion* heap_region_containing_or_null(const T addr) const;
1182 
1183   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1184   // each address in the (reserved) heap is a member of exactly
1185   // one block.  The defining characteristic of a block is that it is
1186   // possible to find its size, and thus to progress forward to the next
1187   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1188   // represent Java objects, or they might be free blocks in a
1189   // free-list-based heap (or subheap), as long as the two kinds are
1190   // distinguishable and the size of each is determinable.
1191 
1192   // Returns the address of the start of the "block" that contains the
1193   // address "addr".  We say "blocks" instead of "object" since some heaps
1194   // may not pack objects densely; a chunk may either be an object or a
1195   // non-object.
1196   virtual HeapWord* block_start(const void* addr) const;
1197 
1198   // Requires "addr" to be the start of a chunk, and returns its size.
1199   // "addr + size" is required to be the start of a new chunk, or the end
1200   // of the active area of the heap.
1201   virtual size_t block_size(const HeapWord* addr) const;
1202 
1203   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1204   // the block is an object.
1205   virtual bool block_is_obj(const HeapWord* addr) const;
1206 
1207   // Section on thread-local allocation buffers (TLABs)
1208   // See CollectedHeap for semantics.
1209 
1210   bool supports_tlab_allocation() const;
1211   size_t tlab_capacity(Thread* ignored) const;
1212   size_t tlab_used(Thread* ignored) const;
1213   size_t max_tlab_size() const;
1214   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1215 
1216   inline bool is_in_young(const oop obj);
1217 
1218   // Returns "true" iff the given word_size is "very large".
1219   static bool is_humongous(size_t word_size) {
1220     // Note this has to be strictly greater-than as the TLABs
1221     // are capped at the humongous threshold and we want to
1222     // ensure that we don't try to allocate a TLAB as
1223     // humongous and that we don't allocate a humongous
1224     // object in a TLAB.
1225     return word_size > _humongous_object_threshold_in_words;
1226   }
1227 
1228   // Returns the humongous threshold for a specific region size
1229   static size_t humongous_threshold_for(size_t region_size) {
1230     return (region_size / 2);
1231   }
1232 
1233   // Returns the number of regions the humongous object of the given word size
1234   // requires.
1235   static size_t humongous_obj_size_in_regions(size_t word_size);
1236 
1237   // Print the maximum heap capacity.
1238   virtual size_t max_capacity() const;
1239 
1240   // Return the size of reserved memory. Returns different value than max_capacity() when AllocateOldGenAt is used.
1241   virtual size_t max_reserved_capacity() const;
1242 
1243   virtual jlong millis_since_last_gc();
1244 
1245 
1246   // Convenience function to be used in situations where the heap type can be
1247   // asserted to be this type.
1248   static G1CollectedHeap* heap();
1249 
1250   void set_region_short_lived_locked(HeapRegion* hr);
1251   // add appropriate methods for any other surv rate groups
1252 
1253   const G1SurvivorRegions* survivor() const { return &_survivor; }
1254 
1255   uint eden_regions_count() const { return _eden.length(); }
1256   uint survivor_regions_count() const { return _survivor.length(); }
1257   uint young_regions_count() const { return _eden.length() + _survivor.length(); }
1258   uint old_regions_count() const { return _old_set.length(); }
1259   uint archive_regions_count() const { return _archive_set.length(); }
1260   uint humongous_regions_count() const { return _humongous_set.length(); }
1261 
1262 #ifdef ASSERT
1263   bool check_young_list_empty();
1264 #endif
1265 
1266   // *** Stuff related to concurrent marking.  It's not clear to me that so
1267   // many of these need to be public.
1268 
1269   // The functions below are helper functions that a subclass of
1270   // "CollectedHeap" can use in the implementation of its virtual
1271   // functions.
1272   // This performs a concurrent marking of the live objects in a
1273   // bitmap off to the side.
1274   void do_concurrent_mark();
1275 
1276   bool is_marked_next(oop obj) const;
1277 
1278   // Determine if an object is dead, given the object and also
1279   // the region to which the object belongs. An object is dead
1280   // iff a) it was not allocated since the last mark, b) it
1281   // is not marked, and c) it is not in an archive region.
1282   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1283     return
1284       hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1285       !hr->is_archive();
1286   }
1287 
1288   // This function returns true when an object has been
1289   // around since the previous marking and hasn't yet
1290   // been marked during this marking, and is not in an archive region.
1291   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1292     return
1293       !hr->obj_allocated_since_next_marking(obj) &&
1294       !is_marked_next(obj) &&
1295       !hr->is_archive();
1296   }
1297 
1298   // Determine if an object is dead, given only the object itself.
1299   // This will find the region to which the object belongs and
1300   // then call the region version of the same function.
1301 
1302   // Added if it is NULL it isn't dead.
1303 
1304   inline bool is_obj_dead(const oop obj) const;
1305 
1306   inline bool is_obj_ill(const oop obj) const;
1307 
1308   inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1309   inline bool is_obj_dead_full(const oop obj) const;
1310 
1311   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1312 
1313   // Refinement
1314 
1315   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1316 
1317   // Optimized nmethod scanning support routines
1318 
1319   // Is an oop scavengeable
1320   virtual bool is_scavengable(oop obj);
1321 
1322   // Register the given nmethod with the G1 heap.
1323   virtual void register_nmethod(nmethod* nm);
1324 
1325   // Unregister the given nmethod from the G1 heap.
1326   virtual void unregister_nmethod(nmethod* nm);
1327 
1328   // Free up superfluous code root memory.
1329   void purge_code_root_memory();
1330 
1331   // Rebuild the strong code root lists for each region
1332   // after a full GC.
1333   void rebuild_strong_code_roots();
1334 
1335   // Partial cleaning of VM internal data structures.
1336   // Let the caller choose what structures to clean out:
1337   // - StringDeduplication structures
1338   void partial_cleaning(BoolObjectClosure* is_alive,
1339                         OopClosure* keep_alive,
1340                         bool process_dedup_table,
1341                         G1GCPhaseTimes* phase_times = NULL);
1342 
1343   // Complete cleaning used when class unloading is enabled.
1344   // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1345   void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1346 
1347   // Redirty logged cards in the refinement queue.
1348   void redirty_logged_cards();
1349   // Verification
1350 
1351   // Deduplicate the string
1352   virtual void deduplicate_string(oop str);
1353 
1354   // Perform any cleanup actions necessary before allowing a verification.
1355   virtual void prepare_for_verify();
1356 
1357   // Perform verification.
1358 
1359   // vo == UsePrevMarking -> use "prev" marking information,
1360   // vo == UseNextMarking -> use "next" marking information
1361   // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1362   //
1363   // NOTE: Only the "prev" marking information is guaranteed to be
1364   // consistent most of the time, so most calls to this should use
1365   // vo == UsePrevMarking.
1366   // Currently, there is only one case where this is called with
1367   // vo == UseNextMarking, which is to verify the "next" marking
1368   // information at the end of remark.
1369   // Currently there is only one place where this is called with
1370   // vo == UseFullMarking, which is to verify the marking during a
1371   // full GC.
1372   void verify(VerifyOption vo);
1373 
1374   // WhiteBox testing support.
1375   virtual bool supports_concurrent_phase_control() const;
1376   virtual const char* const* concurrent_phases() const;
1377   virtual bool request_concurrent_phase(const char* phase);
1378 
1379   virtual WorkGang* get_safepoint_workers() { return _workers; }
1380 
1381   // The methods below are here for convenience and dispatch the
1382   // appropriate method depending on value of the given VerifyOption
1383   // parameter. The values for that parameter, and their meanings,
1384   // are the same as those above.
1385 
1386   bool is_obj_dead_cond(const oop obj,
1387                         const HeapRegion* hr,
1388                         const VerifyOption vo) const;
1389 
1390   bool is_obj_dead_cond(const oop obj,
1391                         const VerifyOption vo) const;
1392 
1393   G1HeapSummary create_g1_heap_summary();
1394   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1395 
1396   // Printing
1397 private:
1398   void print_heap_regions() const;
1399   void print_regions_on(outputStream* st) const;
1400 
1401 public:
1402   virtual void print_on(outputStream* st) const;
1403   virtual void print_extended_on(outputStream* st) const;
1404   virtual void print_on_error(outputStream* st) const;
1405 
1406   virtual void print_gc_threads_on(outputStream* st) const;
1407   virtual void gc_threads_do(ThreadClosure* tc) const;
1408 
1409   // Override
1410   void print_tracing_info() const;
1411 
1412   // The following two methods are helpful for debugging RSet issues.
1413   void print_cset_rsets() PRODUCT_RETURN;
1414   void print_all_rsets() PRODUCT_RETURN;
1415 
1416   size_t pending_card_num();
1417 };
1418 
1419 class G1ParEvacuateFollowersClosure : public VoidClosure {
1420 private:
1421   double _start_term;
1422   double _term_time;
1423   size_t _term_attempts;
1424 
1425   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1426   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1427 protected:
1428   G1CollectedHeap*              _g1h;
1429   G1ParScanThreadState*         _par_scan_state;
1430   RefToScanQueueSet*            _queues;
1431   ParallelTaskTerminator*       _terminator;
1432   G1GCPhaseTimes::GCParPhases   _phase;
1433 
1434   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1435   RefToScanQueueSet*      queues()         { return _queues; }
1436   ParallelTaskTerminator* terminator()     { return _terminator; }
1437 
1438 public:
1439   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1440                                 G1ParScanThreadState* par_scan_state,
1441                                 RefToScanQueueSet* queues,
1442                                 ParallelTaskTerminator* terminator,
1443                                 G1GCPhaseTimes::GCParPhases phase)
1444     : _start_term(0.0), _term_time(0.0), _term_attempts(0),
1445       _g1h(g1h), _par_scan_state(par_scan_state),
1446       _queues(queues), _terminator(terminator), _phase(phase) {}
1447 
1448   void do_void();
1449 
1450   double term_time() const { return _term_time; }
1451   size_t term_attempts() const { return _term_attempts; }
1452 
1453 private:
1454   inline bool offer_termination();
1455 };
1456 
1457 #endif // SHARE_GC_G1_G1COLLECTEDHEAP_HPP