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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  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/g1BiasedArray.hpp"
  30 #include "gc/g1/g1CardTable.hpp"
  31 #include "gc/g1/g1CollectionSet.hpp"
  32 #include "gc/g1/g1CollectorState.hpp"
  33 #include "gc/g1/g1ConcurrentMark.hpp"
  34 #include "gc/g1/g1EdenRegions.hpp"
  35 #include "gc/g1/g1EvacFailure.hpp"
  36 #include "gc/g1/g1EvacStats.hpp"
  37 #include "gc/g1/g1HeapTransition.hpp"
  38 #include "gc/g1/g1HeapVerifier.hpp"
  39 #include "gc/g1/g1HRPrinter.hpp"
  40 #include "gc/g1/g1InCSetState.hpp"
  41 #include "gc/g1/g1MonitoringSupport.hpp"
  42 #include "gc/g1/g1SATBCardTableModRefBS.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 ConcurrentMarkThread;
  83 class G1ConcurrentRefine;
  84 class GenerationCounters;
  85 class STWGCTimer;
  86 class G1NewTracer;
  87 class EvacuationFailedInfo;
  88 class nmethod;
  89 class Ticks;
  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* _g1;
 112 public:
 113   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 114   bool do_object_b(oop p);
 115 };
 116 
 117 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 118  private:
 119   void reset_from_card_cache(uint start_idx, size_t num_regions);
 120  public:
 121   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 122 };
 123 
 124 class G1CollectedHeap : public CollectedHeap {
 125   friend class G1FreeCollectionSetTask;
 126   friend class VM_CollectForMetadataAllocation;
 127   friend class VM_G1CollectForAllocation;
 128   friend class VM_G1CollectFull;
 129   friend class VMStructs;
 130   friend class MutatorAllocRegion;
 131   friend class G1FullCollector;
 132   friend class G1GCAllocRegion;
 133   friend class G1HeapVerifier;
 134 
 135   // Closures used in implementation.
 136   friend class G1ParScanThreadState;
 137   friend class G1ParScanThreadStateSet;
 138   friend class G1ParTask;
 139   friend class G1PLABAllocator;
 140   friend class G1PrepareCompactClosure;
 141 
 142   // Other related classes.
 143   friend class HeapRegionClaimer;
 144 
 145   // Testing classes.
 146   friend class G1CheckCSetFastTableClosure;
 147 
 148 private:
 149   G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
 150 
 151   WorkGang* _workers;
 152   G1CollectorPolicy* _collector_policy;
 153   G1CardTable* _card_table;
 154 
 155   SoftRefPolicy      _soft_ref_policy;
 156 
 157   GCMemoryManager _memory_manager;
 158   GCMemoryManager _full_gc_memory_manager;
 159 
 160   MemoryPool* _eden_pool;
 161   MemoryPool* _survivor_pool;
 162   MemoryPool* _old_pool;
 163 
 164   static size_t _humongous_object_threshold_in_words;
 165 
 166   // The secondary free list which contains regions that have been
 167   // freed up during the cleanup process. This will be appended to
 168   // the master free list when appropriate.
 169   FreeRegionList _secondary_free_list;
 170 
 171   // It keeps track of the old regions.
 172   HeapRegionSet _old_set;
 173 
 174   // It keeps track of the humongous regions.
 175   HeapRegionSet _humongous_set;
 176 
 177   virtual void initialize_serviceability();
 178 
 179   void eagerly_reclaim_humongous_regions();
 180   // Start a new incremental collection set for the next pause.
 181   void start_new_collection_set();
 182 
 183   // The number of regions we could create by expansion.
 184   uint _expansion_regions;
 185 
 186   // The block offset table for the G1 heap.
 187   G1BlockOffsetTable* _bot;
 188 
 189   // Tears down the region sets / lists so that they are empty and the
 190   // regions on the heap do not belong to a region set / list. The
 191   // only exception is the humongous set which we leave unaltered. If
 192   // free_list_only is true, it will only tear down the master free
 193   // list. It is called before a Full GC (free_list_only == false) or
 194   // before heap shrinking (free_list_only == true).
 195   void tear_down_region_sets(bool free_list_only);
 196 
 197   // Rebuilds the region sets / lists so that they are repopulated to
 198   // reflect the contents of the heap. The only exception is the
 199   // humongous set which was not torn down in the first place. If
 200   // free_list_only is true, it will only rebuild the master free
 201   // list. It is called after a Full GC (free_list_only == false) or
 202   // after heap shrinking (free_list_only == true).
 203   void rebuild_region_sets(bool free_list_only);
 204 
 205   // Callback for region mapping changed events.
 206   G1RegionMappingChangedListener _listener;
 207 
 208   // The sequence of all heap regions in the heap.
 209   HeapRegionManager _hrm;
 210 
 211   // Manages all allocations with regions except humongous object allocations.
 212   G1Allocator* _allocator;
 213 
 214   // Manages all heap verification.
 215   G1HeapVerifier* _verifier;
 216 
 217   // Outside of GC pauses, the number of bytes used in all regions other
 218   // than the current allocation region(s).
 219   size_t _summary_bytes_used;
 220 
 221   void increase_used(size_t bytes);
 222   void decrease_used(size_t bytes);
 223 
 224   void set_used(size_t bytes);
 225 
 226   // Class that handles archive allocation ranges.
 227   G1ArchiveAllocator* _archive_allocator;
 228 
 229   // GC allocation statistics policy for survivors.
 230   G1EvacStats _survivor_evac_stats;
 231 
 232   // GC allocation statistics policy for tenured objects.
 233   G1EvacStats _old_evac_stats;
 234 
 235   // It specifies whether we should attempt to expand the heap after a
 236   // region allocation failure. If heap expansion fails we set this to
 237   // false so that we don't re-attempt the heap expansion (it's likely
 238   // that subsequent expansion attempts will also fail if one fails).
 239   // Currently, it is only consulted during GC and it's reset at the
 240   // start of each GC.
 241   bool _expand_heap_after_alloc_failure;
 242 
 243   // Helper for monitoring and management support.
 244   G1MonitoringSupport* _g1mm;
 245 
 246   // Records whether the region at the given index is (still) a
 247   // candidate for eager reclaim.  Only valid for humongous start
 248   // regions; other regions have unspecified values.  Humongous start
 249   // regions are initialized at start of collection pause, with
 250   // candidates removed from the set as they are found reachable from
 251   // roots or the young generation.
 252   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 253    protected:
 254     bool default_value() const { return false; }
 255    public:
 256     void clear() { G1BiasedMappedArray<bool>::clear(); }
 257     void set_candidate(uint region, bool value) {
 258       set_by_index(region, value);
 259     }
 260     bool is_candidate(uint region) {
 261       return get_by_index(region);
 262     }
 263   };
 264 
 265   HumongousReclaimCandidates _humongous_reclaim_candidates;
 266   // Stores whether during humongous object registration we found candidate regions.
 267   // If not, we can skip a few steps.
 268   bool _has_humongous_reclaim_candidates;
 269 
 270   volatile uint _gc_time_stamp;
 271 
 272   G1HRPrinter _hr_printer;
 273 
 274   // It decides whether an explicit GC should start a concurrent cycle
 275   // instead of doing a STW GC. Currently, a concurrent cycle is
 276   // explicitly started if:
 277   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 278   // (b) cause == _g1_humongous_allocation
 279   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 280   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 281   // (e) cause == _wb_conc_mark
 282   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 283 
 284   // indicates whether we are in young or mixed GC mode
 285   G1CollectorState _collector_state;
 286 
 287   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 288   // concurrent cycles) we have started.
 289   volatile uint _old_marking_cycles_started;
 290 
 291   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 292   // concurrent cycles) we have completed.
 293   volatile uint _old_marking_cycles_completed;
 294 
 295   // This is a non-product method that is helpful for testing. It is
 296   // called at the end of a GC and artificially expands the heap by
 297   // allocating a number of dead regions. This way we can induce very
 298   // frequent marking cycles and stress the cleanup / concurrent
 299   // cleanup code more (as all the regions that will be allocated by
 300   // this method will be found dead by the marking cycle).
 301   void allocate_dummy_regions() PRODUCT_RETURN;
 302 
 303   // Clear RSets after a compaction. It also resets the GC time stamps.
 304   void clear_rsets_post_compaction();
 305 
 306   // If the HR printer is active, dump the state of the regions in the
 307   // heap after a compaction.
 308   void print_hrm_post_compaction();
 309 
 310   // Create a memory mapper for auxiliary data structures of the given size and
 311   // translation factor.
 312   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 313                                                          size_t size,
 314                                                          size_t translation_factor);
 315 
 316   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 317 
 318   // These are macros so that, if the assert fires, we get the correct
 319   // line number, file, etc.
 320 
 321 #define heap_locking_asserts_params(_extra_message_)                          \
 322   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 323   (_extra_message_),                                                          \
 324   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 325   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 326   BOOL_TO_STR(Thread::current()->is_VM_thread())
 327 
 328 #define assert_heap_locked()                                                  \
 329   do {                                                                        \
 330     assert(Heap_lock->owned_by_self(),                                        \
 331            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 332   } while (0)
 333 
 334 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 335   do {                                                                        \
 336     assert(Heap_lock->owned_by_self() ||                                      \
 337            (SafepointSynchronize::is_at_safepoint() &&                        \
 338              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 339            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 340                                         "should be at a safepoint"));         \
 341   } while (0)
 342 
 343 #define assert_heap_locked_and_not_at_safepoint()                             \
 344   do {                                                                        \
 345     assert(Heap_lock->owned_by_self() &&                                      \
 346                                     !SafepointSynchronize::is_at_safepoint(), \
 347           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 348                                        "should not be at a safepoint"));      \
 349   } while (0)
 350 
 351 #define assert_heap_not_locked()                                              \
 352   do {                                                                        \
 353     assert(!Heap_lock->owned_by_self(),                                       \
 354         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 355   } while (0)
 356 
 357 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 358   do {                                                                        \
 359     assert(!Heap_lock->owned_by_self() &&                                     \
 360                                     !SafepointSynchronize::is_at_safepoint(), \
 361       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 362                                    "should not be at a safepoint"));          \
 363   } while (0)
 364 
 365 #define assert_at_safepoint_on_vm_thread()                                    \
 366   do {                                                                        \
 367     assert_at_safepoint();                                                    \
 368     assert(Thread::current_or_null() != NULL, "no current thread");           \
 369     assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \
 370   } while (0)
 371 
 372 protected:
 373 
 374   // The young region list.
 375   G1EdenRegions _eden;
 376   G1SurvivorRegions _survivor;
 377 
 378   STWGCTimer* _gc_timer_stw;
 379 
 380   G1NewTracer* _gc_tracer_stw;
 381 
 382   // The current policy object for the collector.
 383   G1Policy* _g1_policy;
 384   G1HeapSizingPolicy* _heap_sizing_policy;
 385 
 386   G1CollectionSet _collection_set;
 387 
 388   // This is the second level of trying to allocate a new region. If
 389   // new_region() didn't find a region on the free_list, this call will
 390   // check whether there's anything available on the
 391   // secondary_free_list and/or wait for more regions to appear on
 392   // that list, if _free_regions_coming is set.
 393   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 394 
 395   // Try to allocate a single non-humongous HeapRegion sufficient for
 396   // an allocation of the given word_size. If do_expand is true,
 397   // attempt to expand the heap if necessary to satisfy the allocation
 398   // request. If the region is to be used as an old region or for a
 399   // humongous object, set is_old to true. If not, to false.
 400   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 401 
 402   // Initialize a contiguous set of free regions of length num_regions
 403   // and starting at index first so that they appear as a single
 404   // humongous region.
 405   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 406                                                       uint num_regions,
 407                                                       size_t word_size);
 408 
 409   // Attempt to allocate a humongous object of the given size. Return
 410   // NULL if unsuccessful.
 411   HeapWord* humongous_obj_allocate(size_t word_size);
 412 
 413   // The following two methods, allocate_new_tlab() and
 414   // mem_allocate(), are the two main entry points from the runtime
 415   // into the G1's allocation routines. They have the following
 416   // assumptions:
 417   //
 418   // * They should both be called outside safepoints.
 419   //
 420   // * They should both be called without holding the Heap_lock.
 421   //
 422   // * All allocation requests for new TLABs should go to
 423   //   allocate_new_tlab().
 424   //
 425   // * All non-TLAB allocation requests should go to mem_allocate().
 426   //
 427   // * If either call cannot satisfy the allocation request using the
 428   //   current allocating region, they will try to get a new one. If
 429   //   this fails, they will attempt to do an evacuation pause and
 430   //   retry the allocation.
 431   //
 432   // * If all allocation attempts fail, even after trying to schedule
 433   //   an evacuation pause, allocate_new_tlab() will return NULL,
 434   //   whereas mem_allocate() will attempt a heap expansion and/or
 435   //   schedule a Full GC.
 436   //
 437   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 438   //   should never be called with word_size being humongous. All
 439   //   humongous allocation requests should go to mem_allocate() which
 440   //   will satisfy them with a special path.
 441 
 442   virtual HeapWord* allocate_new_tlab(size_t word_size);
 443 
 444   virtual HeapWord* mem_allocate(size_t word_size,
 445                                  bool*  gc_overhead_limit_was_exceeded);
 446 
 447   // First-level mutator allocation attempt: try to allocate out of
 448   // the mutator alloc region without taking the Heap_lock. This
 449   // should only be used for non-humongous allocations.
 450   inline HeapWord* attempt_allocation(size_t word_size);
 451 
 452   // Second-level mutator allocation attempt: take the Heap_lock and
 453   // retry the allocation attempt, potentially scheduling a GC
 454   // pause. This should only be used for non-humongous allocations.
 455   HeapWord* attempt_allocation_slow(size_t word_size);
 456 
 457   // Takes the Heap_lock and attempts a humongous allocation. It can
 458   // potentially schedule a GC pause.
 459   HeapWord* attempt_allocation_humongous(size_t word_size);
 460 
 461   // Allocation attempt that should be called during safepoints (e.g.,
 462   // at the end of a successful GC). expect_null_mutator_alloc_region
 463   // specifies whether the mutator alloc region is expected to be NULL
 464   // or not.
 465   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 466                                             bool expect_null_mutator_alloc_region);
 467 
 468   // These methods are the "callbacks" from the G1AllocRegion class.
 469 
 470   // For mutator alloc regions.
 471   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 472   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 473                                    size_t allocated_bytes);
 474 
 475   // For GC alloc regions.
 476   bool has_more_regions(InCSetState dest);
 477   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 478   void retire_gc_alloc_region(HeapRegion* alloc_region,
 479                               size_t allocated_bytes, InCSetState dest);
 480 
 481   // - if explicit_gc is true, the GC is for a System.gc() etc,
 482   //   otherwise it's for a failed allocation.
 483   // - if clear_all_soft_refs is true, all soft references should be
 484   //   cleared during the GC.
 485   // - it returns false if it is unable to do the collection due to the
 486   //   GC locker being active, true otherwise.
 487   bool do_full_collection(bool explicit_gc,
 488                           bool clear_all_soft_refs);
 489 
 490   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 491   virtual void do_full_collection(bool clear_all_soft_refs);
 492 
 493   // Resize the heap if necessary after a full collection.
 494   void resize_if_necessary_after_full_collection();
 495 
 496   // Callback from VM_G1CollectForAllocation operation.
 497   // This function does everything necessary/possible to satisfy a
 498   // failed allocation request (including collection, expansion, etc.)
 499   HeapWord* satisfy_failed_allocation(size_t word_size,
 500                                       bool* succeeded);
 501 private:
 502   // Internal helpers used during full GC to split it up to
 503   // increase readability.
 504   void abort_concurrent_cycle();
 505   void verify_before_full_collection(bool explicit_gc);
 506   void prepare_heap_for_full_collection();
 507   void prepare_heap_for_mutators();
 508   void abort_refinement();
 509   void verify_after_full_collection();
 510   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 511 
 512   // Helper method for satisfy_failed_allocation()
 513   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 514                                              bool do_gc,
 515                                              bool clear_all_soft_refs,
 516                                              bool expect_null_mutator_alloc_region,
 517                                              bool* gc_succeeded);
 518 
 519 protected:
 520   // Attempting to expand the heap sufficiently
 521   // to support an allocation of the given "word_size".  If
 522   // successful, perform the allocation and return the address of the
 523   // allocated block, or else "NULL".
 524   HeapWord* expand_and_allocate(size_t word_size);
 525 
 526   // Preserve any referents discovered by concurrent marking that have not yet been
 527   // copied by the STW pause.
 528   void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
 529   // Process any reference objects discovered during
 530   // an incremental evacuation pause.
 531   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 532 
 533   // Enqueue any remaining discovered references
 534   // after processing.
 535   void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 536 
 537   // Merges the information gathered on a per-thread basis for all worker threads
 538   // during GC into global variables.
 539   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 540 public:
 541   G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
 542 
 543   WorkGang* workers() const { return _workers; }
 544 
 545   G1Allocator* allocator() {
 546     return _allocator;
 547   }
 548 
 549   G1HeapVerifier* verifier() {
 550     return _verifier;
 551   }
 552 
 553   G1MonitoringSupport* g1mm() {
 554     assert(_g1mm != NULL, "should have been initialized");
 555     return _g1mm;
 556   }
 557 
 558   // Expand the garbage-first heap by at least the given size (in bytes!).
 559   // Returns true if the heap was expanded by the requested amount;
 560   // false otherwise.
 561   // (Rounds up to a HeapRegion boundary.)
 562   bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
 563 
 564   // Returns the PLAB statistics for a given destination.
 565   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 566 
 567   // Determines PLAB size for a given destination.
 568   inline size_t desired_plab_sz(InCSetState dest);
 569 
 570   // Do anything common to GC's.
 571   void gc_prologue(bool full);
 572   void gc_epilogue(bool full);
 573 
 574   // Does the given region fulfill remembered set based eager reclaim candidate requirements?
 575   bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
 576 
 577   // Modify the reclaim candidate set and test for presence.
 578   // These are only valid for starts_humongous regions.
 579   inline void set_humongous_reclaim_candidate(uint region, bool value);
 580   inline bool is_humongous_reclaim_candidate(uint region);
 581 
 582   // Remove from the reclaim candidate set.  Also remove from the
 583   // collection set so that later encounters avoid the slow path.
 584   inline void set_humongous_is_live(oop obj);
 585 
 586   // Register the given region to be part of the collection set.
 587   inline void register_humongous_region_with_cset(uint index);
 588   // Register regions with humongous objects (actually on the start region) in
 589   // the in_cset_fast_test table.
 590   void register_humongous_regions_with_cset();
 591   // We register a region with the fast "in collection set" test. We
 592   // simply set to true the array slot corresponding to this region.
 593   void register_young_region_with_cset(HeapRegion* r) {
 594     _in_cset_fast_test.set_in_young(r->hrm_index());
 595   }
 596   void register_old_region_with_cset(HeapRegion* r) {
 597     _in_cset_fast_test.set_in_old(r->hrm_index());
 598   }
 599   void clear_in_cset(const HeapRegion* hr) {
 600     _in_cset_fast_test.clear(hr);
 601   }
 602 
 603   void clear_cset_fast_test() {
 604     _in_cset_fast_test.clear();
 605   }
 606 
 607   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 608 
 609   // This is called at the start of either a concurrent cycle or a Full
 610   // GC to update the number of old marking cycles started.
 611   void increment_old_marking_cycles_started();
 612 
 613   // This is called at the end of either a concurrent cycle or a Full
 614   // GC to update the number of old marking cycles completed. Those two
 615   // can happen in a nested fashion, i.e., we start a concurrent
 616   // cycle, a Full GC happens half-way through it which ends first,
 617   // and then the cycle notices that a Full GC happened and ends
 618   // too. The concurrent parameter is a boolean to help us do a bit
 619   // tighter consistency checking in the method. If concurrent is
 620   // false, the caller is the inner caller in the nesting (i.e., the
 621   // Full GC). If concurrent is true, the caller is the outer caller
 622   // in this nesting (i.e., the concurrent cycle). Further nesting is
 623   // not currently supported. The end of this call also notifies
 624   // the FullGCCount_lock in case a Java thread is waiting for a full
 625   // GC to happen (e.g., it called System.gc() with
 626   // +ExplicitGCInvokesConcurrent).
 627   void increment_old_marking_cycles_completed(bool concurrent);
 628 
 629   uint old_marking_cycles_completed() {
 630     return _old_marking_cycles_completed;
 631   }
 632 
 633   G1HRPrinter* hr_printer() { return &_hr_printer; }
 634 
 635   // Allocates a new heap region instance.
 636   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 637 
 638   // Allocate the highest free region in the reserved heap. This will commit
 639   // regions as necessary.
 640   HeapRegion* alloc_highest_free_region();
 641 
 642   // Frees a non-humongous region by initializing its contents and
 643   // adding it to the free list that's passed as a parameter (this is
 644   // usually a local list which will be appended to the master free
 645   // list later). The used bytes of freed regions are accumulated in
 646   // pre_used. If skip_remset is true, the region's RSet will not be freed
 647   // up. If skip_hot_card_cache is true, the region's hot card cache will not
 648   // be freed up. The assumption is that this will be done later.
 649   // The locked parameter indicates if the caller has already taken
 650   // care of proper synchronization. This may allow some optimizations.
 651   void free_region(HeapRegion* hr,
 652                    FreeRegionList* free_list,
 653                    bool skip_remset,
 654                    bool skip_hot_card_cache = false,
 655                    bool locked = false);
 656 
 657   // It dirties the cards that cover the block so that the post
 658   // write barrier never queues anything when updating objects on this
 659   // block. It is assumed (and in fact we assert) that the block
 660   // belongs to a young region.
 661   inline void dirty_young_block(HeapWord* start, size_t word_size);
 662 
 663   // Frees a humongous region by collapsing it into individual regions
 664   // and calling free_region() for each of them. The freed regions
 665   // will be added to the free list that's passed as a parameter (this
 666   // is usually a local list which will be appended to the master free
 667   // list later). The used bytes of freed regions are accumulated in
 668   // pre_used. If skip_remset is true, the region's RSet will not be freed
 669   // up. The assumption is that this will be done later.
 670   void free_humongous_region(HeapRegion* hr,
 671                              FreeRegionList* free_list,
 672                              bool skip_remset);
 673 
 674   // Facility for allocating in 'archive' regions in high heap memory and
 675   // recording the allocated ranges. These should all be called from the
 676   // VM thread at safepoints, without the heap lock held. They can be used
 677   // to create and archive a set of heap regions which can be mapped at the
 678   // same fixed addresses in a subsequent JVM invocation.
 679   void begin_archive_alloc_range(bool open = false);
 680 
 681   // Check if the requested size would be too large for an archive allocation.
 682   bool is_archive_alloc_too_large(size_t word_size);
 683 
 684   // Allocate memory of the requested size from the archive region. This will
 685   // return NULL if the size is too large or if no memory is available. It
 686   // does not trigger a garbage collection.
 687   HeapWord* archive_mem_allocate(size_t word_size);
 688 
 689   // Optionally aligns the end address and returns the allocated ranges in
 690   // an array of MemRegions in order of ascending addresses.
 691   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 692                                size_t end_alignment_in_bytes = 0);
 693 
 694   // Facility for allocating a fixed range within the heap and marking
 695   // the containing regions as 'archive'. For use at JVM init time, when the
 696   // caller may mmap archived heap data at the specified range(s).
 697   // Verify that the MemRegions specified in the argument array are within the
 698   // reserved heap.
 699   bool check_archive_addresses(MemRegion* range, size_t count);
 700 
 701   // Commit the appropriate G1 regions containing the specified MemRegions
 702   // and mark them as 'archive' regions. The regions in the array must be
 703   // non-overlapping and in order of ascending address.
 704   bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
 705 
 706   // Insert any required filler objects in the G1 regions around the specified
 707   // ranges to make the regions parseable. This must be called after
 708   // alloc_archive_regions, and after class loading has occurred.
 709   void fill_archive_regions(MemRegion* range, size_t count);
 710 
 711   // For each of the specified MemRegions, uncommit the containing G1 regions
 712   // which had been allocated by alloc_archive_regions. This should be called
 713   // rather than fill_archive_regions at JVM init time if the archive file
 714   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 715   void dealloc_archive_regions(MemRegion* range, size_t count);
 716 
 717 protected:
 718 
 719   // Shrink the garbage-first heap by at most the given size (in bytes!).
 720   // (Rounds down to a HeapRegion boundary.)
 721   virtual void shrink(size_t expand_bytes);
 722   void shrink_helper(size_t expand_bytes);
 723 
 724   #if TASKQUEUE_STATS
 725   static void print_taskqueue_stats_hdr(outputStream* const st);
 726   void print_taskqueue_stats() const;
 727   void reset_taskqueue_stats();
 728   #endif // TASKQUEUE_STATS
 729 
 730   // Schedule the VM operation that will do an evacuation pause to
 731   // satisfy an allocation request of word_size. *succeeded will
 732   // return whether the VM operation was successful (it did do an
 733   // evacuation pause) or not (another thread beat us to it or the GC
 734   // locker was active). Given that we should not be holding the
 735   // Heap_lock when we enter this method, we will pass the
 736   // gc_count_before (i.e., total_collections()) as a parameter since
 737   // it has to be read while holding the Heap_lock. Currently, both
 738   // methods that call do_collection_pause() release the Heap_lock
 739   // before the call, so it's easy to read gc_count_before just before.
 740   HeapWord* do_collection_pause(size_t         word_size,
 741                                 uint           gc_count_before,
 742                                 bool*          succeeded,
 743                                 GCCause::Cause gc_cause);
 744 
 745   void wait_for_root_region_scanning();
 746 
 747   // The guts of the incremental collection pause, executed by the vm
 748   // thread. It returns false if it is unable to do the collection due
 749   // to the GC locker being active, true otherwise
 750   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 751 
 752   // Actually do the work of evacuating the collection set.
 753   virtual void evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states);
 754 
 755   void pre_evacuate_collection_set();
 756   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 757 
 758   // Print the header for the per-thread termination statistics.
 759   static void print_termination_stats_hdr();
 760   // Print actual per-thread termination statistics.
 761   void print_termination_stats(uint worker_id,
 762                                double elapsed_ms,
 763                                double strong_roots_ms,
 764                                double term_ms,
 765                                size_t term_attempts,
 766                                size_t alloc_buffer_waste,
 767                                size_t undo_waste) const;
 768   // Update object copying statistics.
 769   void record_obj_copy_mem_stats();
 770 
 771   // The hot card cache for remembered set insertion optimization.
 772   G1HotCardCache* _hot_card_cache;
 773 
 774   // The g1 remembered set of the heap.
 775   G1RemSet* _g1_rem_set;
 776 
 777   // A set of cards that cover the objects for which the Rsets should be updated
 778   // concurrently after the collection.
 779   DirtyCardQueueSet _dirty_card_queue_set;
 780 
 781   // After a collection pause, convert the regions in the collection set into free
 782   // regions.
 783   void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 784 
 785   // Abandon the current collection set without recording policy
 786   // statistics or updating free lists.
 787   void abandon_collection_set(G1CollectionSet* collection_set);
 788 
 789   // The concurrent marker (and the thread it runs in.)
 790   G1ConcurrentMark* _cm;
 791   ConcurrentMarkThread* _cmThread;
 792 
 793   // The concurrent refiner.
 794   G1ConcurrentRefine* _cr;
 795 
 796   // The parallel task queues
 797   RefToScanQueueSet *_task_queues;
 798 
 799   // True iff a evacuation has failed in the current collection.
 800   bool _evacuation_failed;
 801 
 802   EvacuationFailedInfo* _evacuation_failed_info_array;
 803 
 804   // Failed evacuations cause some logical from-space objects to have
 805   // forwarding pointers to themselves.  Reset them.
 806   void remove_self_forwarding_pointers();
 807 
 808   // Restore the objects in the regions in the collection set after an
 809   // evacuation failure.
 810   void restore_after_evac_failure();
 811 
 812   PreservedMarksSet _preserved_marks_set;
 813 
 814   // Preserve the mark of "obj", if necessary, in preparation for its mark
 815   // word being overwritten with a self-forwarding-pointer.
 816   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 817 
 818 #ifndef PRODUCT
 819   // Support for forcing evacuation failures. Analogous to
 820   // PromotionFailureALot for the other collectors.
 821 
 822   // Records whether G1EvacuationFailureALot should be in effect
 823   // for the current GC
 824   bool _evacuation_failure_alot_for_current_gc;
 825 
 826   // Used to record the GC number for interval checking when
 827   // determining whether G1EvaucationFailureALot is in effect
 828   // for the current GC.
 829   size_t _evacuation_failure_alot_gc_number;
 830 
 831   // Count of the number of evacuations between failures.
 832   volatile size_t _evacuation_failure_alot_count;
 833 
 834   // Set whether G1EvacuationFailureALot should be in effect
 835   // for the current GC (based upon the type of GC and which
 836   // command line flags are set);
 837   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 838                                                   bool during_initial_mark,
 839                                                   bool during_marking);
 840 
 841   inline void set_evacuation_failure_alot_for_current_gc();
 842 
 843   // Return true if it's time to cause an evacuation failure.
 844   inline bool evacuation_should_fail();
 845 
 846   // Reset the G1EvacuationFailureALot counters.  Should be called at
 847   // the end of an evacuation pause in which an evacuation failure occurred.
 848   inline void reset_evacuation_should_fail();
 849 #endif // !PRODUCT
 850 
 851   // ("Weak") Reference processing support.
 852   //
 853   // G1 has 2 instances of the reference processor class. One
 854   // (_ref_processor_cm) handles reference object discovery
 855   // and subsequent processing during concurrent marking cycles.
 856   //
 857   // The other (_ref_processor_stw) handles reference object
 858   // discovery and processing during full GCs and incremental
 859   // evacuation pauses.
 860   //
 861   // During an incremental pause, reference discovery will be
 862   // temporarily disabled for _ref_processor_cm and will be
 863   // enabled for _ref_processor_stw. At the end of the evacuation
 864   // pause references discovered by _ref_processor_stw will be
 865   // processed and discovery will be disabled. The previous
 866   // setting for reference object discovery for _ref_processor_cm
 867   // will be re-instated.
 868   //
 869   // At the start of marking:
 870   //  * Discovery by the CM ref processor is verified to be inactive
 871   //    and it's discovered lists are empty.
 872   //  * Discovery by the CM ref processor is then enabled.
 873   //
 874   // At the end of marking:
 875   //  * Any references on the CM ref processor's discovered
 876   //    lists are processed (possibly MT).
 877   //
 878   // At the start of full GC we:
 879   //  * Disable discovery by the CM ref processor and
 880   //    empty CM ref processor's discovered lists
 881   //    (without processing any entries).
 882   //  * Verify that the STW ref processor is inactive and it's
 883   //    discovered lists are empty.
 884   //  * Temporarily set STW ref processor discovery as single threaded.
 885   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 886   //    field.
 887   //  * Finally enable discovery by the STW ref processor.
 888   //
 889   // The STW ref processor is used to record any discovered
 890   // references during the full GC.
 891   //
 892   // At the end of a full GC we:
 893   //  * Enqueue any reference objects discovered by the STW ref processor
 894   //    that have non-live referents. This has the side-effect of
 895   //    making the STW ref processor inactive by disabling discovery.
 896   //  * Verify that the CM ref processor is still inactive
 897   //    and no references have been placed on it's discovered
 898   //    lists (also checked as a precondition during initial marking).
 899 
 900   // The (stw) reference processor...
 901   ReferenceProcessor* _ref_processor_stw;
 902 
 903   // During reference object discovery, the _is_alive_non_header
 904   // closure (if non-null) is applied to the referent object to
 905   // determine whether the referent is live. If so then the
 906   // reference object does not need to be 'discovered' and can
 907   // be treated as a regular oop. This has the benefit of reducing
 908   // the number of 'discovered' reference objects that need to
 909   // be processed.
 910   //
 911   // Instance of the is_alive closure for embedding into the
 912   // STW reference processor as the _is_alive_non_header field.
 913   // Supplying a value for the _is_alive_non_header field is
 914   // optional but doing so prevents unnecessary additions to
 915   // the discovered lists during reference discovery.
 916   G1STWIsAliveClosure _is_alive_closure_stw;
 917 
 918   // The (concurrent marking) reference processor...
 919   ReferenceProcessor* _ref_processor_cm;
 920 
 921   // Instance of the concurrent mark is_alive closure for embedding
 922   // into the Concurrent Marking reference processor as the
 923   // _is_alive_non_header field. Supplying a value for the
 924   // _is_alive_non_header field is optional but doing so prevents
 925   // unnecessary additions to the discovered lists during reference
 926   // discovery.
 927   G1CMIsAliveClosure _is_alive_closure_cm;
 928 
 929   volatile bool _free_regions_coming;
 930 
 931 public:
 932 
 933   RefToScanQueue *task_queue(uint i) const;
 934 
 935   uint num_task_queues() const;
 936 
 937   // A set of cards where updates happened during the GC
 938   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 939 
 940   // Create a G1CollectedHeap with the specified policy.
 941   // Must call the initialize method afterwards.
 942   // May not return if something goes wrong.
 943   G1CollectedHeap(G1CollectorPolicy* policy);
 944 
 945 private:
 946   jint initialize_concurrent_refinement();
 947   jint initialize_young_gen_sampling_thread();
 948 public:
 949   // Initialize the G1CollectedHeap to have the initial and
 950   // maximum sizes and remembered and barrier sets
 951   // specified by the policy object.
 952   jint initialize();
 953 
 954   virtual void stop();
 955   virtual void safepoint_synchronize_begin();
 956   virtual void safepoint_synchronize_end();
 957 
 958   // Return the (conservative) maximum heap alignment for any G1 heap
 959   static size_t conservative_max_heap_alignment();
 960 
 961   // Does operations required after initialization has been done.
 962   void post_initialize();
 963 
 964   // Initialize weak reference processing.
 965   void ref_processing_init();
 966 
 967   virtual Name kind() const {
 968     return CollectedHeap::G1CollectedHeap;
 969   }
 970 
 971   virtual const char* name() const {
 972     return "G1";
 973   }
 974 
 975   const G1CollectorState* collector_state() const { return &_collector_state; }
 976   G1CollectorState* collector_state() { return &_collector_state; }
 977 
 978   // The current policy object for the collector.
 979   G1Policy* g1_policy() const { return _g1_policy; }
 980 
 981   const G1CollectionSet* collection_set() const { return &_collection_set; }
 982   G1CollectionSet* collection_set() { return &_collection_set; }
 983 
 984   virtual CollectorPolicy* collector_policy() const;
 985 
 986   virtual SoftRefPolicy* soft_ref_policy();
 987 
 988   virtual GrowableArray<GCMemoryManager*> memory_managers();
 989   virtual GrowableArray<MemoryPool*> memory_pools();
 990 
 991   // The rem set and barrier set.
 992   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
 993 
 994   // Try to minimize the remembered set.
 995   void scrub_rem_set();
 996 
 997   uint get_gc_time_stamp() {
 998     return _gc_time_stamp;
 999   }
1000 
1001   inline void reset_gc_time_stamp();
1002 
1003   void check_gc_time_stamps() PRODUCT_RETURN;
1004 
1005   inline void increment_gc_time_stamp();
1006 
1007   // Reset the given region's GC timestamp. If it's starts humongous,
1008   // also reset the GC timestamp of its corresponding
1009   // continues humongous regions too.
1010   void reset_gc_time_stamps(HeapRegion* hr);
1011 
1012   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1013   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1014 
1015   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1016   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1017 
1018   // The shared block offset table array.
1019   G1BlockOffsetTable* bot() const { return _bot; }
1020 
1021   // Reference Processing accessors
1022 
1023   // The STW reference processor....
1024   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1025 
1026   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1027 
1028   // The Concurrent Marking reference processor...
1029   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1030 
1031   size_t unused_committed_regions_in_bytes() const;
1032   virtual size_t capacity() const;
1033   virtual size_t used() const;
1034   // This should be called when we're not holding the heap lock. The
1035   // result might be a bit inaccurate.
1036   size_t used_unlocked() const;
1037   size_t recalculate_used() const;
1038 
1039   // These virtual functions do the actual allocation.
1040   // Some heaps may offer a contiguous region for shared non-blocking
1041   // allocation, via inlined code (by exporting the address of the top and
1042   // end fields defining the extent of the contiguous allocation region.)
1043   // But G1CollectedHeap doesn't yet support this.
1044 
1045   virtual bool is_maximal_no_gc() const {
1046     return _hrm.available() == 0;
1047   }
1048 
1049   // Returns whether there are any regions left in the heap for allocation.
1050   bool has_regions_left_for_allocation() const {
1051     return !is_maximal_no_gc() || num_free_regions() != 0;
1052   }
1053 
1054   // The current number of regions in the heap.
1055   uint num_regions() const { return _hrm.length(); }
1056 
1057   // The max number of regions in the heap.
1058   uint max_regions() const { return _hrm.max_length(); }
1059 
1060   // The number of regions that are completely free.
1061   uint num_free_regions() const { return _hrm.num_free_regions(); }
1062 
1063   MemoryUsage get_auxiliary_data_memory_usage() const {
1064     return _hrm.get_auxiliary_data_memory_usage();
1065   }
1066 
1067   // The number of regions that are not completely free.
1068   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1069 
1070 #ifdef ASSERT
1071   bool is_on_master_free_list(HeapRegion* hr) {
1072     return _hrm.is_free(hr);
1073   }
1074 #endif // ASSERT
1075 
1076   // Wrapper for the region list operations that can be called from
1077   // methods outside this class.
1078 
1079   void secondary_free_list_add(FreeRegionList* list) {
1080     _secondary_free_list.add_ordered(list);
1081   }
1082 
1083   void append_secondary_free_list() {
1084     _hrm.insert_list_into_free_list(&_secondary_free_list);
1085   }
1086 
1087   void append_secondary_free_list_if_not_empty_with_lock() {
1088     // If the secondary free list looks empty there's no reason to
1089     // take the lock and then try to append it.
1090     if (!_secondary_free_list.is_empty()) {
1091       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1092       append_secondary_free_list();
1093     }
1094   }
1095 
1096   inline void old_set_add(HeapRegion* hr);
1097   inline void old_set_remove(HeapRegion* hr);
1098 
1099   size_t non_young_capacity_bytes() {
1100     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1101   }
1102 
1103   void set_free_regions_coming();
1104   void reset_free_regions_coming();
1105   bool free_regions_coming() { return _free_regions_coming; }
1106   void wait_while_free_regions_coming();
1107 
1108   // Determine whether the given region is one that we are using as an
1109   // old GC alloc region.
1110   bool is_old_gc_alloc_region(HeapRegion* hr);
1111 
1112   // Perform a collection of the heap; intended for use in implementing
1113   // "System.gc".  This probably implies as full a collection as the
1114   // "CollectedHeap" supports.
1115   virtual void collect(GCCause::Cause cause);
1116 
1117   // True iff an evacuation has failed in the most-recent collection.
1118   bool evacuation_failed() { return _evacuation_failed; }
1119 
1120   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1121   void prepend_to_freelist(FreeRegionList* list);
1122   void decrement_summary_bytes(size_t bytes);
1123 
1124   virtual bool is_in(const void* p) const;
1125 #ifdef ASSERT
1126   // Returns whether p is in one of the available areas of the heap. Slow but
1127   // extensive version.
1128   bool is_in_exact(const void* p) const;
1129 #endif
1130 
1131   // Return "TRUE" iff the given object address is within the collection
1132   // set. Assumes that the reference points into the heap.
1133   inline bool is_in_cset(const HeapRegion *hr);
1134   inline bool is_in_cset(oop obj);
1135   inline bool is_in_cset(HeapWord* addr);
1136 
1137   inline bool is_in_cset_or_humongous(const oop obj);
1138 
1139  private:
1140   // This array is used for a quick test on whether a reference points into
1141   // the collection set or not. Each of the array's elements denotes whether the
1142   // corresponding region is in the collection set or not.
1143   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1144 
1145  public:
1146 
1147   inline InCSetState in_cset_state(const oop obj);
1148 
1149   // Return "TRUE" iff the given object address is in the reserved
1150   // region of g1.
1151   bool is_in_g1_reserved(const void* p) const {
1152     return _hrm.reserved().contains(p);
1153   }
1154 
1155   // Returns a MemRegion that corresponds to the space that has been
1156   // reserved for the heap
1157   MemRegion g1_reserved() const {
1158     return _hrm.reserved();
1159   }
1160 
1161   virtual bool is_in_closed_subset(const void* p) const;
1162 
1163   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1164     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1165   }
1166 
1167   G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1168 
1169   G1CardTable* card_table() const {
1170     return _card_table;
1171   }
1172 
1173   // Iteration functions.
1174 
1175   // Iterate over all objects, calling "cl.do_object" on each.
1176   virtual void object_iterate(ObjectClosure* cl);
1177 
1178   virtual void safe_object_iterate(ObjectClosure* cl) {
1179     object_iterate(cl);
1180   }
1181 
1182   // Iterate over heap regions, in address order, terminating the
1183   // iteration early if the "do_heap_region" method returns "true".
1184   void heap_region_iterate(HeapRegionClosure* blk) const;
1185 
1186   // Return the region with the given index. It assumes the index is valid.
1187   inline HeapRegion* region_at(uint index) const;
1188 
1189   // Return the next region (by index) that is part of the same
1190   // humongous object that hr is part of.
1191   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1192 
1193   // Calculate the region index of the given address. Given address must be
1194   // within the heap.
1195   inline uint addr_to_region(HeapWord* addr) const;
1196 
1197   inline HeapWord* bottom_addr_for_region(uint index) const;
1198 
1199   // Two functions to iterate over the heap regions in parallel. Threads
1200   // compete using the HeapRegionClaimer to claim the regions before
1201   // applying the closure on them.
1202   // The _from_worker_offset version uses the HeapRegionClaimer and
1203   // the worker id to calculate a start offset to prevent all workers to
1204   // start from the point.
1205   void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1206                                                   HeapRegionClaimer* hrclaimer,
1207                                                   uint worker_id) const;
1208 
1209   void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1210                                           HeapRegionClaimer* hrclaimer) const;
1211 
1212   // Iterate over the regions (if any) in the current collection set.
1213   void collection_set_iterate(HeapRegionClosure* blk);
1214 
1215   // Iterate over the regions (if any) in the current collection set. Starts the
1216   // iteration over the entire collection set so that the start regions of a given
1217   // worker id over the set active_workers are evenly spread across the set of
1218   // collection set regions.
1219   void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1220 
1221   // Returns the HeapRegion that contains addr. addr must not be NULL.
1222   template <class T>
1223   inline HeapRegion* heap_region_containing(const T addr) const;
1224 
1225   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1226   // each address in the (reserved) heap is a member of exactly
1227   // one block.  The defining characteristic of a block is that it is
1228   // possible to find its size, and thus to progress forward to the next
1229   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1230   // represent Java objects, or they might be free blocks in a
1231   // free-list-based heap (or subheap), as long as the two kinds are
1232   // distinguishable and the size of each is determinable.
1233 
1234   // Returns the address of the start of the "block" that contains the
1235   // address "addr".  We say "blocks" instead of "object" since some heaps
1236   // may not pack objects densely; a chunk may either be an object or a
1237   // non-object.
1238   virtual HeapWord* block_start(const void* addr) const;
1239 
1240   // Requires "addr" to be the start of a chunk, and returns its size.
1241   // "addr + size" is required to be the start of a new chunk, or the end
1242   // of the active area of the heap.
1243   virtual size_t block_size(const HeapWord* addr) const;
1244 
1245   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1246   // the block is an object.
1247   virtual bool block_is_obj(const HeapWord* addr) const;
1248 
1249   // Section on thread-local allocation buffers (TLABs)
1250   // See CollectedHeap for semantics.
1251 
1252   bool supports_tlab_allocation() const;
1253   size_t tlab_capacity(Thread* ignored) const;
1254   size_t tlab_used(Thread* ignored) const;
1255   size_t max_tlab_size() const;
1256   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1257 
1258   inline bool is_in_young(const oop obj);
1259 
1260   // Returns "true" iff the given word_size is "very large".
1261   static bool is_humongous(size_t word_size) {
1262     // Note this has to be strictly greater-than as the TLABs
1263     // are capped at the humongous threshold and we want to
1264     // ensure that we don't try to allocate a TLAB as
1265     // humongous and that we don't allocate a humongous
1266     // object in a TLAB.
1267     return word_size > _humongous_object_threshold_in_words;
1268   }
1269 
1270   // Returns the humongous threshold for a specific region size
1271   static size_t humongous_threshold_for(size_t region_size) {
1272     return (region_size / 2);
1273   }
1274 
1275   // Returns the number of regions the humongous object of the given word size
1276   // requires.
1277   static size_t humongous_obj_size_in_regions(size_t word_size);
1278 
1279   // Print the maximum heap capacity.
1280   virtual size_t max_capacity() const;
1281 
1282   virtual jlong millis_since_last_gc();
1283 
1284 
1285   // Convenience function to be used in situations where the heap type can be
1286   // asserted to be this type.
1287   static G1CollectedHeap* heap();
1288 
1289   void set_region_short_lived_locked(HeapRegion* hr);
1290   // add appropriate methods for any other surv rate groups
1291 
1292   const G1SurvivorRegions* survivor() const { return &_survivor; }
1293 
1294   uint survivor_regions_count() const {
1295     return _survivor.length();
1296   }
1297 
1298   uint eden_regions_count() const {
1299     return _eden.length();
1300   }
1301 
1302   uint young_regions_count() const {
1303     return _eden.length() + _survivor.length();
1304   }
1305 
1306   uint old_regions_count() const { return _old_set.length(); }
1307 
1308   uint humongous_regions_count() const { return _humongous_set.length(); }
1309 
1310 #ifdef ASSERT
1311   bool check_young_list_empty();
1312 #endif
1313 
1314   // *** Stuff related to concurrent marking.  It's not clear to me that so
1315   // many of these need to be public.
1316 
1317   // The functions below are helper functions that a subclass of
1318   // "CollectedHeap" can use in the implementation of its virtual
1319   // functions.
1320   // This performs a concurrent marking of the live objects in a
1321   // bitmap off to the side.
1322   void doConcurrentMark();
1323 
1324   bool isMarkedNext(oop obj) const;
1325 
1326   // Determine if an object is dead, given the object and also
1327   // the region to which the object belongs. An object is dead
1328   // iff a) it was not allocated since the last mark, b) it
1329   // is not marked, and c) it is not in an archive region.
1330   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1331     return
1332       hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1333       !hr->is_archive();
1334   }
1335 
1336   // This function returns true when an object has been
1337   // around since the previous marking and hasn't yet
1338   // been marked during this marking, and is not in an archive region.
1339   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1340     return
1341       !hr->obj_allocated_since_next_marking(obj) &&
1342       !isMarkedNext(obj) &&
1343       !hr->is_archive();
1344   }
1345 
1346   // Determine if an object is dead, given only the object itself.
1347   // This will find the region to which the object belongs and
1348   // then call the region version of the same function.
1349 
1350   // Added if it is NULL it isn't dead.
1351 
1352   inline bool is_obj_dead(const oop obj) const;
1353 
1354   inline bool is_obj_ill(const oop obj) const;
1355 
1356   inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1357   inline bool is_obj_dead_full(const oop obj) const;
1358 
1359   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1360 
1361   // Refinement
1362 
1363   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1364 
1365   // Optimized nmethod scanning support routines
1366 
1367   // Is an oop scavengeable
1368   virtual bool is_scavengable(oop obj);
1369 
1370   // Register the given nmethod with the G1 heap.
1371   virtual void register_nmethod(nmethod* nm);
1372 
1373   // Unregister the given nmethod from the G1 heap.
1374   virtual void unregister_nmethod(nmethod* nm);
1375 
1376   // Free up superfluous code root memory.
1377   void purge_code_root_memory();
1378 
1379   // Rebuild the strong code root lists for each region
1380   // after a full GC.
1381   void rebuild_strong_code_roots();
1382 
1383   // Partial cleaning used when class unloading is disabled.
1384   // Let the caller choose what structures to clean out:
1385   // - StringTable
1386   // - SymbolTable
1387   // - StringDeduplication structures
1388   void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1389 
1390   // Complete cleaning used when class unloading is enabled.
1391   // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1392   void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1393 
1394   // Redirty logged cards in the refinement queue.
1395   void redirty_logged_cards();
1396   // Verification
1397 
1398   // Perform any cleanup actions necessary before allowing a verification.
1399   virtual void prepare_for_verify();
1400 
1401   // Perform verification.
1402 
1403   // vo == UsePrevMarking -> use "prev" marking information,
1404   // vo == UseNextMarking -> use "next" marking information
1405   // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1406   //
1407   // NOTE: Only the "prev" marking information is guaranteed to be
1408   // consistent most of the time, so most calls to this should use
1409   // vo == UsePrevMarking.
1410   // Currently, there is only one case where this is called with
1411   // vo == UseNextMarking, which is to verify the "next" marking
1412   // information at the end of remark.
1413   // Currently there is only one place where this is called with
1414   // vo == UseFullMarking, which is to verify the marking during a
1415   // full GC.
1416   void verify(VerifyOption vo);
1417 
1418   // WhiteBox testing support.
1419   virtual bool supports_concurrent_phase_control() const;
1420   virtual const char* const* concurrent_phases() const;
1421   virtual bool request_concurrent_phase(const char* phase);
1422 
1423   // The methods below are here for convenience and dispatch the
1424   // appropriate method depending on value of the given VerifyOption
1425   // parameter. The values for that parameter, and their meanings,
1426   // are the same as those above.
1427 
1428   bool is_obj_dead_cond(const oop obj,
1429                         const HeapRegion* hr,
1430                         const VerifyOption vo) const;
1431 
1432   bool is_obj_dead_cond(const oop obj,
1433                         const VerifyOption vo) const;
1434 
1435   G1HeapSummary create_g1_heap_summary();
1436   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1437 
1438   // Printing
1439 private:
1440   void print_heap_regions() const;
1441   void print_regions_on(outputStream* st) const;
1442 
1443 public:
1444   virtual void print_on(outputStream* st) const;
1445   virtual void print_extended_on(outputStream* st) const;
1446   virtual void print_on_error(outputStream* st) const;
1447 
1448   virtual void print_gc_threads_on(outputStream* st) const;
1449   virtual void gc_threads_do(ThreadClosure* tc) const;
1450 
1451   // Override
1452   void print_tracing_info() const;
1453 
1454   // The following two methods are helpful for debugging RSet issues.
1455   void print_cset_rsets() PRODUCT_RETURN;
1456   void print_all_rsets() PRODUCT_RETURN;
1457 
1458 public:
1459   size_t pending_card_num();
1460 
1461 protected:
1462   size_t _max_heap_capacity;
1463 };
1464 
1465 class G1ParEvacuateFollowersClosure : public VoidClosure {
1466 private:
1467   double _start_term;
1468   double _term_time;
1469   size_t _term_attempts;
1470 
1471   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1472   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1473 protected:
1474   G1CollectedHeap*              _g1h;
1475   G1ParScanThreadState*         _par_scan_state;
1476   RefToScanQueueSet*            _queues;
1477   ParallelTaskTerminator*       _terminator;
1478 
1479   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1480   RefToScanQueueSet*      queues()         { return _queues; }
1481   ParallelTaskTerminator* terminator()     { return _terminator; }
1482 
1483 public:
1484   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1485                                 G1ParScanThreadState* par_scan_state,
1486                                 RefToScanQueueSet* queues,
1487                                 ParallelTaskTerminator* terminator)
1488     : _g1h(g1h), _par_scan_state(par_scan_state),
1489       _queues(queues), _terminator(terminator),
1490       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1491 
1492   void do_void();
1493 
1494   double term_time() const { return _term_time; }
1495   size_t term_attempts() const { return _term_attempts; }
1496 
1497 private:
1498   inline bool offer_termination();
1499 };
1500 
1501 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP