1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc/g1/evacuationInfo.hpp"
  29 #include "gc/g1/g1AllocationContext.hpp"
  30 #include "gc/g1/g1BiasedArray.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/hSpaceCounters.hpp"
  46 #include "gc/g1/heapRegionManager.hpp"
  47 #include "gc/g1/heapRegionSet.hpp"
  48 #include "gc/shared/barrierSet.hpp"
  49 #include "gc/shared/collectedHeap.hpp"
  50 #include "gc/shared/plab.hpp"
  51 #include "gc/shared/preservedMarks.hpp"
  52 #include "memory/memRegion.hpp"
  53 #include "utilities/stack.hpp"
  54 
  55 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  56 // It uses the "Garbage First" heap organization and algorithm, which
  57 // may combine concurrent marking with parallel, incremental compaction of
  58 // heap subsets that will yield large amounts of garbage.
  59 
  60 // Forward declarations
  61 class HeapRegion;
  62 class HRRSCleanupTask;
  63 class GenerationSpec;
  64 class G1ParScanThreadState;
  65 class G1ParScanThreadStateSet;
  66 class G1ParScanThreadState;
  67 class ObjectClosure;
  68 class SpaceClosure;
  69 class CompactibleSpaceClosure;
  70 class Space;
  71 class G1CollectionSet;
  72 class G1CollectorPolicy;
  73 class G1Policy;
  74 class G1HotCardCache;
  75 class G1RemSet;
  76 class G1YoungRemSetSamplingThread;
  77 class HeapRegionRemSetIterator;
  78 class G1ConcurrentMark;
  79 class ConcurrentMarkThread;
  80 class G1ConcurrentRefine;
  81 class GenerationCounters;
  82 class STWGCTimer;
  83 class G1NewTracer;
  84 class EvacuationFailedInfo;
  85 class nmethod;
  86 class Ticks;
  87 class WorkGang;
  88 class G1Allocator;
  89 class G1ArchiveAllocator;
  90 class G1FullGCScope;
  91 class G1HeapVerifier;
  92 class G1HeapSizingPolicy;
  93 class G1HeapSummary;
  94 class G1EvacSummary;
  95 
  96 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  97 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  98 
  99 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
 100 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
 101 
 102 // The G1 STW is alive closure.
 103 // An instance is embedded into the G1CH and used as the
 104 // (optional) _is_alive_non_header closure in the STW
 105 // reference processor. It is also extensively used during
 106 // reference processing during STW evacuation pauses.
 107 class G1STWIsAliveClosure: public BoolObjectClosure {
 108   G1CollectedHeap* _g1;
 109 public:
 110   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 111   bool do_object_b(oop p);
 112 };
 113 
 114 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 115  private:
 116   void reset_from_card_cache(uint start_idx, size_t num_regions);
 117  public:
 118   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 119 };
 120 
 121 class G1CollectedHeap : public CollectedHeap {
 122   friend class G1FreeCollectionSetTask;
 123   friend class VM_CollectForMetadataAllocation;
 124   friend class VM_G1CollectForAllocation;
 125   friend class VM_G1CollectFull;
 126   friend class VM_G1IncCollectionPause;
 127   friend class VMStructs;
 128   friend class MutatorAllocRegion;
 129   friend class G1FullCollector;
 130   friend class G1GCAllocRegion;
 131   friend class G1HeapVerifier;
 132 
 133   // Closures used in implementation.
 134   friend class G1ParScanThreadState;
 135   friend class G1ParScanThreadStateSet;
 136   friend class G1ParTask;
 137   friend class G1PLABAllocator;
 138   friend class G1PrepareCompactClosure;
 139 
 140   // Other related classes.
 141   friend class HeapRegionClaimer;
 142 
 143   // Testing classes.
 144   friend class G1CheckCSetFastTableClosure;
 145 
 146 private:
 147   G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
 148 
 149   WorkGang* _workers;
 150   G1CollectorPolicy* _collector_policy;
 151 
 152   static size_t _humongous_object_threshold_in_words;
 153 
 154   // The secondary free list which contains regions that have been
 155   // freed up during the cleanup process. This will be appended to
 156   // the master free list when appropriate.
 157   FreeRegionList _secondary_free_list;
 158 
 159   // It keeps track of the old regions.
 160   HeapRegionSet _old_set;
 161 
 162   // It keeps track of the humongous regions.
 163   HeapRegionSet _humongous_set;
 164 
 165   void eagerly_reclaim_humongous_regions();
 166   // Start a new incremental collection set for the next pause.
 167   void start_new_collection_set();
 168 
 169   // The number of regions we could create by expansion.
 170   uint _expansion_regions;
 171 
 172   // The block offset table for the G1 heap.
 173   G1BlockOffsetTable* _bot;
 174 
 175   // Tears down the region sets / lists so that they are empty and the
 176   // regions on the heap do not belong to a region set / list. The
 177   // only exception is the humongous set which we leave unaltered. If
 178   // free_list_only is true, it will only tear down the master free
 179   // list. It is called before a Full GC (free_list_only == false) or
 180   // before heap shrinking (free_list_only == true).
 181   void tear_down_region_sets(bool free_list_only);
 182 
 183   // Rebuilds the region sets / lists so that they are repopulated to
 184   // reflect the contents of the heap. The only exception is the
 185   // humongous set which was not torn down in the first place. If
 186   // free_list_only is true, it will only rebuild the master free
 187   // list. It is called after a Full GC (free_list_only == false) or
 188   // after heap shrinking (free_list_only == true).
 189   void rebuild_region_sets(bool free_list_only);
 190 
 191   // Callback for region mapping changed events.
 192   G1RegionMappingChangedListener _listener;
 193 
 194   // The sequence of all heap regions in the heap.
 195   HeapRegionManager _hrm;
 196 
 197   // Manages all allocations with regions except humongous object allocations.
 198   G1Allocator* _allocator;
 199 
 200   // Manages all heap verification.
 201   G1HeapVerifier* _verifier;
 202 
 203   // Outside of GC pauses, the number of bytes used in all regions other
 204   // than the current allocation region(s).
 205   size_t _summary_bytes_used;
 206 
 207   void increase_used(size_t bytes);
 208   void decrease_used(size_t bytes);
 209 
 210   void set_used(size_t bytes);
 211 
 212   // Class that handles archive allocation ranges.
 213   G1ArchiveAllocator* _archive_allocator;
 214 
 215   // Statistics for each allocation context
 216   AllocationContextStats _allocation_context_stats;
 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   volatile uint _gc_time_stamp;
 260 
 261   G1HRPrinter _hr_printer;
 262 
 263   // It decides whether an explicit GC should start a concurrent cycle
 264   // instead of doing a STW GC. Currently, a concurrent cycle is
 265   // explicitly started if:
 266   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 267   // (b) cause == _g1_humongous_allocation
 268   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 269   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 270   // (e) cause == _update_allocation_context_stats_inc
 271   // (f) cause == _wb_conc_mark
 272   bool should_do_concurrent_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   // Clear RSets after a compaction. It also resets the GC time stamps.
 294   void clear_rsets_post_compaction();
 295 
 296   // If the HR printer is active, dump the state of the regions in the
 297   // heap after a compaction.
 298   void print_hrm_post_compaction();
 299 
 300   // Create a memory mapper for auxiliary data structures of the given size and
 301   // translation factor.
 302   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 303                                                          size_t size,
 304                                                          size_t translation_factor);
 305 
 306   static G1Policy* create_g1_policy(STWGCTimer* gc_timer);
 307 
 308   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 309 
 310   // These are macros so that, if the assert fires, we get the correct
 311   // line number, file, etc.
 312 
 313 #define heap_locking_asserts_params(_extra_message_)                          \
 314   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 315   (_extra_message_),                                                          \
 316   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 317   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 318   BOOL_TO_STR(Thread::current()->is_VM_thread())
 319 
 320 #define assert_heap_locked()                                                  \
 321   do {                                                                        \
 322     assert(Heap_lock->owned_by_self(),                                        \
 323            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 324   } while (0)
 325 
 326 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 327   do {                                                                        \
 328     assert(Heap_lock->owned_by_self() ||                                      \
 329            (SafepointSynchronize::is_at_safepoint() &&                        \
 330              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 331            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 332                                         "should be at a safepoint"));         \
 333   } while (0)
 334 
 335 #define assert_heap_locked_and_not_at_safepoint()                             \
 336   do {                                                                        \
 337     assert(Heap_lock->owned_by_self() &&                                      \
 338                                     !SafepointSynchronize::is_at_safepoint(), \
 339           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 340                                        "should not be at a safepoint"));      \
 341   } while (0)
 342 
 343 #define assert_heap_not_locked()                                              \
 344   do {                                                                        \
 345     assert(!Heap_lock->owned_by_self(),                                       \
 346         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 347   } while (0)
 348 
 349 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 350   do {                                                                        \
 351     assert(!Heap_lock->owned_by_self() &&                                     \
 352                                     !SafepointSynchronize::is_at_safepoint(), \
 353       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 354                                    "should not be at a safepoint"));          \
 355   } while (0)
 356 
 357 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 358   do {                                                                        \
 359     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 360               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 361            heap_locking_asserts_params("should be at a safepoint"));          \
 362   } while (0)
 363 
 364 #define assert_not_at_safepoint()                                             \
 365   do {                                                                        \
 366     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 367            heap_locking_asserts_params("should not be at a safepoint"));      \
 368   } while (0)
 369 
 370 protected:
 371 
 372   // The young region list.
 373   G1EdenRegions _eden;
 374   G1SurvivorRegions _survivor;
 375 
 376   STWGCTimer* _gc_timer_stw;
 377 
 378   G1NewTracer* _gc_tracer_stw;
 379 
 380   // The current policy object for the collector.
 381   G1Policy* _g1_policy;
 382   G1HeapSizingPolicy* _heap_sizing_policy;
 383 
 384   G1CollectionSet _collection_set;
 385 
 386   // This is the second level of trying to allocate a new region. If
 387   // new_region() didn't find a region on the free_list, this call will
 388   // check whether there's anything available on the
 389   // secondary_free_list and/or wait for more regions to appear on
 390   // that list, if _free_regions_coming is set.
 391   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 392 
 393   // Try to allocate a single non-humongous HeapRegion sufficient for
 394   // an allocation of the given word_size. If do_expand is true,
 395   // attempt to expand the heap if necessary to satisfy the allocation
 396   // request. If the region is to be used as an old region or for a
 397   // humongous object, set is_old to true. If not, to false.
 398   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 399 
 400   // Initialize a contiguous set of free regions of length num_regions
 401   // and starting at index first so that they appear as a single
 402   // humongous region.
 403   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 404                                                       uint num_regions,
 405                                                       size_t word_size,
 406                                                       AllocationContext_t context);
 407 
 408   // Attempt to allocate a humongous object of the given size. Return
 409   // NULL if unsuccessful.
 410   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 411 
 412   // The following two methods, allocate_new_tlab() and
 413   // mem_allocate(), are the two main entry points from the runtime
 414   // into the G1's allocation routines. They have the following
 415   // assumptions:
 416   //
 417   // * They should both be called outside safepoints.
 418   //
 419   // * They should both be called without holding the Heap_lock.
 420   //
 421   // * All allocation requests for new TLABs should go to
 422   //   allocate_new_tlab().
 423   //
 424   // * All non-TLAB allocation requests should go to mem_allocate().
 425   //
 426   // * If either call cannot satisfy the allocation request using the
 427   //   current allocating region, they will try to get a new one. If
 428   //   this fails, they will attempt to do an evacuation pause and
 429   //   retry the allocation.
 430   //
 431   // * If all allocation attempts fail, even after trying to schedule
 432   //   an evacuation pause, allocate_new_tlab() will return NULL,
 433   //   whereas mem_allocate() will attempt a heap expansion and/or
 434   //   schedule a Full GC.
 435   //
 436   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 437   //   should never be called with word_size being humongous. All
 438   //   humongous allocation requests should go to mem_allocate() which
 439   //   will satisfy them with a special path.
 440 
 441   virtual HeapWord* allocate_new_tlab(size_t word_size);
 442 
 443   virtual HeapWord* mem_allocate(size_t word_size,
 444                                  bool*  gc_overhead_limit_was_exceeded);
 445 
 446   // The following three methods take a gc_count_before_ret
 447   // parameter which is used to return the GC count if the method
 448   // returns NULL. Given that we are required to read the GC count
 449   // while holding the Heap_lock, and these paths will take the
 450   // Heap_lock at some point, it's easier to get them to read the GC
 451   // count while holding the Heap_lock before they return NULL instead
 452   // of the caller (namely: mem_allocate()) having to also take the
 453   // Heap_lock just to read the GC count.
 454 
 455   // First-level mutator allocation attempt: try to allocate out of
 456   // the mutator alloc region without taking the Heap_lock. This
 457   // should only be used for non-humongous allocations.
 458   inline HeapWord* attempt_allocation(size_t word_size,
 459                                       uint* gc_count_before_ret,
 460                                       uint* gclocker_retry_count_ret);
 461 
 462   // Second-level mutator allocation attempt: take the Heap_lock and
 463   // retry the allocation attempt, potentially scheduling a GC
 464   // pause. This should only be used for non-humongous allocations.
 465   HeapWord* attempt_allocation_slow(size_t word_size,
 466                                     AllocationContext_t context,
 467                                     uint* gc_count_before_ret,
 468                                     uint* gclocker_retry_count_ret);
 469 
 470   // Takes the Heap_lock and attempts a humongous allocation. It can
 471   // potentially schedule a GC pause.
 472   HeapWord* attempt_allocation_humongous(size_t word_size,
 473                                          uint* gc_count_before_ret,
 474                                          uint* gclocker_retry_count_ret);
 475 
 476   // Allocation attempt that should be called during safepoints (e.g.,
 477   // at the end of a successful GC). expect_null_mutator_alloc_region
 478   // specifies whether the mutator alloc region is expected to be NULL
 479   // or not.
 480   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 481                                             AllocationContext_t context,
 482                                             bool expect_null_mutator_alloc_region);
 483 
 484   // These methods are the "callbacks" from the G1AllocRegion class.
 485 
 486   // For mutator alloc regions.
 487   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 488   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 489                                    size_t allocated_bytes);
 490 
 491   // For GC alloc regions.
 492   bool has_more_regions(InCSetState dest);
 493   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 494   void retire_gc_alloc_region(HeapRegion* alloc_region,
 495                               size_t allocated_bytes, InCSetState dest);
 496 
 497   // - if explicit_gc is true, the GC is for a System.gc() etc,
 498   //   otherwise it's for a failed allocation.
 499   // - if clear_all_soft_refs is true, all soft references should be
 500   //   cleared during the GC.
 501   // - it returns false if it is unable to do the collection due to the
 502   //   GC locker being active, true otherwise.
 503   bool do_full_collection(bool explicit_gc,
 504                           bool clear_all_soft_refs);
 505 
 506   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 507   virtual void do_full_collection(bool clear_all_soft_refs);
 508 
 509   // Resize the heap if necessary after a full collection.
 510   void resize_if_necessary_after_full_collection();
 511 
 512   // Callback from VM_G1CollectForAllocation operation.
 513   // This function does everything necessary/possible to satisfy a
 514   // failed allocation request (including collection, expansion, etc.)
 515   HeapWord* satisfy_failed_allocation(size_t word_size,
 516                                       AllocationContext_t context,
 517                                       bool* succeeded);
 518 private:
 519   // Internal helpers used during full GC to split it up to
 520   // increase readability.
 521   void abort_concurrent_cycle();
 522   void verify_before_full_collection(bool explicit_gc);
 523   void prepare_heap_for_full_collection();
 524   void prepare_heap_for_mutators();
 525   void abort_refinement();
 526   void verify_after_full_collection();
 527   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 528 
 529   // Helper method for satisfy_failed_allocation()
 530   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 531                                              AllocationContext_t context,
 532                                              bool do_gc,
 533                                              bool clear_all_soft_refs,
 534                                              bool expect_null_mutator_alloc_region,
 535                                              bool* gc_succeeded);
 536 
 537 protected:
 538   // Attempting to expand the heap sufficiently
 539   // to support an allocation of the given "word_size".  If
 540   // successful, perform the allocation and return the address of the
 541   // allocated block, or else "NULL".
 542   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 543 
 544   // Preserve any referents discovered by concurrent marking that have not yet been
 545   // copied by the STW pause.
 546   void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
 547   // Process any reference objects discovered during
 548   // an incremental evacuation pause.
 549   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 550 
 551   // Enqueue any remaining discovered references
 552   // after processing.
 553   void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 554 
 555   // Merges the information gathered on a per-thread basis for all worker threads
 556   // during GC into global variables.
 557   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 558 public:
 559   G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
 560 
 561   WorkGang* workers() const { return _workers; }
 562 
 563   G1Allocator* allocator() {
 564     return _allocator;
 565   }
 566 
 567   G1HeapVerifier* verifier() {
 568     return _verifier;
 569   }
 570 
 571   G1MonitoringSupport* g1mm() {
 572     assert(_g1mm != NULL, "should have been initialized");
 573     return _g1mm;
 574   }
 575 
 576   // Expand the garbage-first heap by at least the given size (in bytes!).
 577   // Returns true if the heap was expanded by the requested amount;
 578   // false otherwise.
 579   // (Rounds up to a HeapRegion boundary.)
 580   bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
 581 
 582   // Returns the PLAB statistics for a given destination.
 583   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 584 
 585   // Determines PLAB size for a given destination.
 586   inline size_t desired_plab_sz(InCSetState dest);
 587 
 588   inline AllocationContextStats& allocation_context_stats();
 589 
 590   // Do anything common to GC's.
 591   void gc_prologue(bool full);
 592   void gc_epilogue(bool full);
 593 
 594   // Modify the reclaim candidate set and test for presence.
 595   // These are only valid for starts_humongous regions.
 596   inline void set_humongous_reclaim_candidate(uint region, bool value);
 597   inline bool is_humongous_reclaim_candidate(uint region);
 598 
 599   // Remove from the reclaim candidate set.  Also remove from the
 600   // collection set so that later encounters avoid the slow path.
 601   inline void set_humongous_is_live(oop obj);
 602 
 603   // Register the given region to be part of the collection set.
 604   inline void register_humongous_region_with_cset(uint index);
 605   // Register regions with humongous objects (actually on the start region) in
 606   // the in_cset_fast_test table.
 607   void register_humongous_regions_with_cset();
 608   // We register a region with the fast "in collection set" test. We
 609   // simply set to true the array slot corresponding to this region.
 610   void register_young_region_with_cset(HeapRegion* r) {
 611     _in_cset_fast_test.set_in_young(r->hrm_index());
 612   }
 613   void register_old_region_with_cset(HeapRegion* r) {
 614     _in_cset_fast_test.set_in_old(r->hrm_index());
 615   }
 616   inline void register_ext_region_with_cset(HeapRegion* r) {
 617     _in_cset_fast_test.set_ext(r->hrm_index());
 618   }
 619   void clear_in_cset(const HeapRegion* hr) {
 620     _in_cset_fast_test.clear(hr);
 621   }
 622 
 623   void clear_cset_fast_test() {
 624     _in_cset_fast_test.clear();
 625   }
 626 
 627   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 628 
 629   // This is called at the start of either a concurrent cycle or a Full
 630   // GC to update the number of old marking cycles started.
 631   void increment_old_marking_cycles_started();
 632 
 633   // This is called at the end of either a concurrent cycle or a Full
 634   // GC to update the number of old marking cycles completed. Those two
 635   // can happen in a nested fashion, i.e., we start a concurrent
 636   // cycle, a Full GC happens half-way through it which ends first,
 637   // and then the cycle notices that a Full GC happened and ends
 638   // too. The concurrent parameter is a boolean to help us do a bit
 639   // tighter consistency checking in the method. If concurrent is
 640   // false, the caller is the inner caller in the nesting (i.e., the
 641   // Full GC). If concurrent is true, the caller is the outer caller
 642   // in this nesting (i.e., the concurrent cycle). Further nesting is
 643   // not currently supported. The end of this call also notifies
 644   // the FullGCCount_lock in case a Java thread is waiting for a full
 645   // GC to happen (e.g., it called System.gc() with
 646   // +ExplicitGCInvokesConcurrent).
 647   void increment_old_marking_cycles_completed(bool concurrent);
 648 
 649   uint old_marking_cycles_completed() {
 650     return _old_marking_cycles_completed;
 651   }
 652 
 653   G1HRPrinter* hr_printer() { return &_hr_printer; }
 654 
 655   // Allocates a new heap region instance.
 656   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 657 
 658   // Allocate the highest free region in the reserved heap. This will commit
 659   // regions as necessary.
 660   HeapRegion* alloc_highest_free_region();
 661 
 662   // Frees a non-humongous region by initializing its contents and
 663   // adding it to the free list that's passed as a parameter (this is
 664   // usually a local list which will be appended to the master free
 665   // list later). The used bytes of freed regions are accumulated in
 666   // pre_used. If skip_remset is true, the region's RSet will not be freed
 667   // up. If skip_hot_card_cache is true, the region's hot card cache will not
 668   // be freed up. The assumption is that this will be done later.
 669   // The locked parameter indicates if the caller has already taken
 670   // care of proper synchronization. This may allow some optimizations.
 671   void free_region(HeapRegion* hr,
 672                    FreeRegionList* free_list,
 673                    bool skip_remset,
 674                    bool skip_hot_card_cache = false,
 675                    bool locked = false);
 676 
 677   // It dirties the cards that cover the block so that the post
 678   // write barrier never queues anything when updating objects on this
 679   // block. It is assumed (and in fact we assert) that the block
 680   // belongs to a young region.
 681   inline void dirty_young_block(HeapWord* start, size_t word_size);
 682 
 683   // Frees a humongous region by collapsing it into individual regions
 684   // and calling free_region() for each of them. The freed regions
 685   // will be added to the free list that's passed as a parameter (this
 686   // is usually a local list which will be appended to the master free
 687   // list later). The used bytes of freed regions are accumulated in
 688   // pre_used. If skip_remset is true, the region's RSet will not be freed
 689   // up. The assumption is that this will be done later.
 690   void free_humongous_region(HeapRegion* hr,
 691                              FreeRegionList* free_list,
 692                              bool skip_remset);
 693 
 694   // Facility for allocating in 'archive' regions in high heap memory and
 695   // recording the allocated ranges. These should all be called from the
 696   // VM thread at safepoints, without the heap lock held. They can be used
 697   // to create and archive a set of heap regions which can be mapped at the
 698   // same fixed addresses in a subsequent JVM invocation.
 699   void begin_archive_alloc_range(bool open = false);
 700 
 701   // Check if the requested size would be too large for an archive allocation.
 702   bool is_archive_alloc_too_large(size_t word_size);
 703 
 704   // Allocate memory of the requested size from the archive region. This will
 705   // return NULL if the size is too large or if no memory is available. It
 706   // does not trigger a garbage collection.
 707   HeapWord* archive_mem_allocate(size_t word_size);
 708 
 709   // Optionally aligns the end address and returns the allocated ranges in
 710   // an array of MemRegions in order of ascending addresses.
 711   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 712                                size_t end_alignment_in_bytes = 0);
 713 
 714   // Facility for allocating a fixed range within the heap and marking
 715   // the containing regions as 'archive'. For use at JVM init time, when the
 716   // caller may mmap archived heap data at the specified range(s).
 717   // Verify that the MemRegions specified in the argument array are within the
 718   // reserved heap.
 719   bool check_archive_addresses(MemRegion* range, size_t count);
 720 
 721   // Commit the appropriate G1 regions containing the specified MemRegions
 722   // and mark them as 'archive' regions. The regions in the array must be
 723   // non-overlapping and in order of ascending address.
 724   bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
 725 
 726   // Insert any required filler objects in the G1 regions around the specified
 727   // ranges to make the regions parseable. This must be called after
 728   // alloc_archive_regions, and after class loading has occurred.
 729   void fill_archive_regions(MemRegion* range, size_t count);
 730 
 731   // For each of the specified MemRegions, uncommit the containing G1 regions
 732   // which had been allocated by alloc_archive_regions. This should be called
 733   // rather than fill_archive_regions at JVM init time if the archive file
 734   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 735   void dealloc_archive_regions(MemRegion* range, size_t count);
 736 
 737 protected:
 738 
 739   // Shrink the garbage-first heap by at most the given size (in bytes!).
 740   // (Rounds down to a HeapRegion boundary.)
 741   virtual void shrink(size_t expand_bytes);
 742   void shrink_helper(size_t expand_bytes);
 743 
 744   #if TASKQUEUE_STATS
 745   static void print_taskqueue_stats_hdr(outputStream* const st);
 746   void print_taskqueue_stats() const;
 747   void reset_taskqueue_stats();
 748   #endif // TASKQUEUE_STATS
 749 
 750   // Schedule the VM operation that will do an evacuation pause to
 751   // satisfy an allocation request of word_size. *succeeded will
 752   // return whether the VM operation was successful (it did do an
 753   // evacuation pause) or not (another thread beat us to it or the GC
 754   // locker was active). Given that we should not be holding the
 755   // Heap_lock when we enter this method, we will pass the
 756   // gc_count_before (i.e., total_collections()) as a parameter since
 757   // it has to be read while holding the Heap_lock. Currently, both
 758   // methods that call do_collection_pause() release the Heap_lock
 759   // before the call, so it's easy to read gc_count_before just before.
 760   HeapWord* do_collection_pause(size_t         word_size,
 761                                 uint           gc_count_before,
 762                                 bool*          succeeded,
 763                                 GCCause::Cause gc_cause);
 764 
 765   void wait_for_root_region_scanning();
 766 
 767   // The guts of the incremental collection pause, executed by the vm
 768   // thread. It returns false if it is unable to do the collection due
 769   // to the GC locker being active, true otherwise
 770   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 771 
 772   // Actually do the work of evacuating the collection set.
 773   virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
 774 
 775   void pre_evacuate_collection_set();
 776   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 777 
 778   // Print the header for the per-thread termination statistics.
 779   static void print_termination_stats_hdr();
 780   // Print actual per-thread termination statistics.
 781   void print_termination_stats(uint worker_id,
 782                                double elapsed_ms,
 783                                double strong_roots_ms,
 784                                double term_ms,
 785                                size_t term_attempts,
 786                                size_t alloc_buffer_waste,
 787                                size_t undo_waste) const;
 788   // Update object copying statistics.
 789   void record_obj_copy_mem_stats();
 790 
 791   // The hot card cache for remembered set insertion optimization.
 792   G1HotCardCache* _hot_card_cache;
 793 
 794   // The g1 remembered set of the heap.
 795   G1RemSet* _g1_rem_set;
 796 
 797   // A set of cards that cover the objects for which the Rsets should be updated
 798   // concurrently after the collection.
 799   DirtyCardQueueSet _dirty_card_queue_set;
 800 
 801   // After a collection pause, convert the regions in the collection set into free
 802   // regions.
 803   void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 804 
 805   // Abandon the current collection set without recording policy
 806   // statistics or updating free lists.
 807   void abandon_collection_set(G1CollectionSet* collection_set);
 808 
 809   // The concurrent marker (and the thread it runs in.)
 810   G1ConcurrentMark* _cm;
 811   ConcurrentMarkThread* _cmThread;
 812 
 813   // The concurrent refiner.
 814   G1ConcurrentRefine* _cr;
 815 
 816   // The parallel task queues
 817   RefToScanQueueSet *_task_queues;
 818 
 819   // True iff a evacuation has failed in the current collection.
 820   bool _evacuation_failed;
 821 
 822   EvacuationFailedInfo* _evacuation_failed_info_array;
 823 
 824   // Failed evacuations cause some logical from-space objects to have
 825   // forwarding pointers to themselves.  Reset them.
 826   void remove_self_forwarding_pointers();
 827 
 828   // Restore the objects in the regions in the collection set after an
 829   // evacuation failure.
 830   void restore_after_evac_failure();
 831 
 832   PreservedMarksSet _preserved_marks_set;
 833 
 834   // Preserve the mark of "obj", if necessary, in preparation for its mark
 835   // word being overwritten with a self-forwarding-pointer.
 836   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 837 
 838 #ifndef PRODUCT
 839   // Support for forcing evacuation failures. Analogous to
 840   // PromotionFailureALot for the other collectors.
 841 
 842   // Records whether G1EvacuationFailureALot should be in effect
 843   // for the current GC
 844   bool _evacuation_failure_alot_for_current_gc;
 845 
 846   // Used to record the GC number for interval checking when
 847   // determining whether G1EvaucationFailureALot is in effect
 848   // for the current GC.
 849   size_t _evacuation_failure_alot_gc_number;
 850 
 851   // Count of the number of evacuations between failures.
 852   volatile size_t _evacuation_failure_alot_count;
 853 
 854   // Set whether G1EvacuationFailureALot should be in effect
 855   // for the current GC (based upon the type of GC and which
 856   // command line flags are set);
 857   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 858                                                   bool during_initial_mark,
 859                                                   bool during_marking);
 860 
 861   inline void set_evacuation_failure_alot_for_current_gc();
 862 
 863   // Return true if it's time to cause an evacuation failure.
 864   inline bool evacuation_should_fail();
 865 
 866   // Reset the G1EvacuationFailureALot counters.  Should be called at
 867   // the end of an evacuation pause in which an evacuation failure occurred.
 868   inline void reset_evacuation_should_fail();
 869 #endif // !PRODUCT
 870 
 871   // ("Weak") Reference processing support.
 872   //
 873   // G1 has 2 instances of the reference processor class. One
 874   // (_ref_processor_cm) handles reference object discovery
 875   // and subsequent processing during concurrent marking cycles.
 876   //
 877   // The other (_ref_processor_stw) handles reference object
 878   // discovery and processing during full GCs and incremental
 879   // evacuation pauses.
 880   //
 881   // During an incremental pause, reference discovery will be
 882   // temporarily disabled for _ref_processor_cm and will be
 883   // enabled for _ref_processor_stw. At the end of the evacuation
 884   // pause references discovered by _ref_processor_stw will be
 885   // processed and discovery will be disabled. The previous
 886   // setting for reference object discovery for _ref_processor_cm
 887   // will be re-instated.
 888   //
 889   // At the start of marking:
 890   //  * Discovery by the CM ref processor is verified to be inactive
 891   //    and it's discovered lists are empty.
 892   //  * Discovery by the CM ref processor is then enabled.
 893   //
 894   // At the end of marking:
 895   //  * Any references on the CM ref processor's discovered
 896   //    lists are processed (possibly MT).
 897   //
 898   // At the start of full GC we:
 899   //  * Disable discovery by the CM ref processor and
 900   //    empty CM ref processor's discovered lists
 901   //    (without processing any entries).
 902   //  * Verify that the STW ref processor is inactive and it's
 903   //    discovered lists are empty.
 904   //  * Temporarily set STW ref processor discovery as single threaded.
 905   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 906   //    field.
 907   //  * Finally enable discovery by the STW ref processor.
 908   //
 909   // The STW ref processor is used to record any discovered
 910   // references during the full GC.
 911   //
 912   // At the end of a full GC we:
 913   //  * Enqueue any reference objects discovered by the STW ref processor
 914   //    that have non-live referents. This has the side-effect of
 915   //    making the STW ref processor inactive by disabling discovery.
 916   //  * Verify that the CM ref processor is still inactive
 917   //    and no references have been placed on it's discovered
 918   //    lists (also checked as a precondition during initial marking).
 919 
 920   // The (stw) reference processor...
 921   ReferenceProcessor* _ref_processor_stw;
 922 
 923   // During reference object discovery, the _is_alive_non_header
 924   // closure (if non-null) is applied to the referent object to
 925   // determine whether the referent is live. If so then the
 926   // reference object does not need to be 'discovered' and can
 927   // be treated as a regular oop. This has the benefit of reducing
 928   // the number of 'discovered' reference objects that need to
 929   // be processed.
 930   //
 931   // Instance of the is_alive closure for embedding into the
 932   // STW reference processor as the _is_alive_non_header field.
 933   // Supplying a value for the _is_alive_non_header field is
 934   // optional but doing so prevents unnecessary additions to
 935   // the discovered lists during reference discovery.
 936   G1STWIsAliveClosure _is_alive_closure_stw;
 937 
 938   // The (concurrent marking) reference processor...
 939   ReferenceProcessor* _ref_processor_cm;
 940 
 941   // Instance of the concurrent mark is_alive closure for embedding
 942   // into the Concurrent Marking reference processor as the
 943   // _is_alive_non_header field. Supplying a value for the
 944   // _is_alive_non_header field is optional but doing so prevents
 945   // unnecessary additions to the discovered lists during reference
 946   // discovery.
 947   G1CMIsAliveClosure _is_alive_closure_cm;
 948 
 949   volatile bool _free_regions_coming;
 950 
 951 public:
 952 
 953   RefToScanQueue *task_queue(uint i) const;
 954 
 955   uint num_task_queues() const;
 956 
 957   // A set of cards where updates happened during the GC
 958   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 959 
 960   // Create a G1CollectedHeap with the specified policy.
 961   // Must call the initialize method afterwards.
 962   // May not return if something goes wrong.
 963   G1CollectedHeap(G1CollectorPolicy* policy);
 964 
 965 private:
 966   jint initialize_concurrent_refinement();
 967   jint initialize_young_gen_sampling_thread();
 968 public:
 969   // Initialize the G1CollectedHeap to have the initial and
 970   // maximum sizes and remembered and barrier sets
 971   // specified by the policy object.
 972   jint initialize();
 973 
 974   virtual void stop();
 975   virtual void safepoint_synchronize_begin();
 976   virtual void safepoint_synchronize_end();
 977 
 978   // Return the (conservative) maximum heap alignment for any G1 heap
 979   static size_t conservative_max_heap_alignment();
 980 
 981   // Does operations required after initialization has been done.
 982   void post_initialize();
 983 
 984   // Initialize weak reference processing.
 985   void ref_processing_init();
 986 
 987   virtual Name kind() const {
 988     return CollectedHeap::G1CollectedHeap;
 989   }
 990 
 991   virtual const char* name() const {
 992     return "G1";
 993   }
 994 
 995   const G1CollectorState* collector_state() const { return &_collector_state; }
 996   G1CollectorState* collector_state() { return &_collector_state; }
 997 
 998   // The current policy object for the collector.
 999   G1Policy* g1_policy() const { return _g1_policy; }
1000 
1001   const G1CollectionSet* collection_set() const { return &_collection_set; }
1002   G1CollectionSet* collection_set() { return &_collection_set; }
1003 
1004   virtual CollectorPolicy* collector_policy() const;
1005 
1006   // Adaptive size policy.  No such thing for g1.
1007   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1008 
1009   // The rem set and barrier set.
1010   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1011 
1012   // Try to minimize the remembered set.
1013   void scrub_rem_set();
1014 
1015   uint get_gc_time_stamp() {
1016     return _gc_time_stamp;
1017   }
1018 
1019   inline void reset_gc_time_stamp();
1020 
1021   void check_gc_time_stamps() PRODUCT_RETURN;
1022 
1023   inline void increment_gc_time_stamp();
1024 
1025   // Reset the given region's GC timestamp. If it's starts humongous,
1026   // also reset the GC timestamp of its corresponding
1027   // continues humongous regions too.
1028   void reset_gc_time_stamps(HeapRegion* hr);
1029 
1030   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1031   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1032 
1033   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1034   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1035 
1036   // The shared block offset table array.
1037   G1BlockOffsetTable* bot() const { return _bot; }
1038 
1039   // Reference Processing accessors
1040 
1041   // The STW reference processor....
1042   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1043 
1044   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1045 
1046   // The Concurrent Marking reference processor...
1047   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1048 
1049   size_t unused_committed_regions_in_bytes() const;
1050   virtual size_t capacity() const;
1051   virtual size_t used() const;
1052   // This should be called when we're not holding the heap lock. The
1053   // result might be a bit inaccurate.
1054   size_t used_unlocked() const;
1055   size_t recalculate_used() const;
1056 
1057   // These virtual functions do the actual allocation.
1058   // Some heaps may offer a contiguous region for shared non-blocking
1059   // allocation, via inlined code (by exporting the address of the top and
1060   // end fields defining the extent of the contiguous allocation region.)
1061   // But G1CollectedHeap doesn't yet support this.
1062 
1063   virtual bool is_maximal_no_gc() const {
1064     return _hrm.available() == 0;
1065   }
1066 
1067   // The current number of regions in the heap.
1068   uint num_regions() const { return _hrm.length(); }
1069 
1070   // The max number of regions in the heap.
1071   uint max_regions() const { return _hrm.max_length(); }
1072 
1073   // The number of regions that are completely free.
1074   uint num_free_regions() const { return _hrm.num_free_regions(); }
1075 
1076   MemoryUsage get_auxiliary_data_memory_usage() const {
1077     return _hrm.get_auxiliary_data_memory_usage();
1078   }
1079 
1080   // The number of regions that are not completely free.
1081   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1082 
1083 #ifdef ASSERT
1084   bool is_on_master_free_list(HeapRegion* hr) {
1085     return _hrm.is_free(hr);
1086   }
1087 #endif // ASSERT
1088 
1089   // Wrapper for the region list operations that can be called from
1090   // methods outside this class.
1091 
1092   void secondary_free_list_add(FreeRegionList* list) {
1093     _secondary_free_list.add_ordered(list);
1094   }
1095 
1096   void append_secondary_free_list() {
1097     _hrm.insert_list_into_free_list(&_secondary_free_list);
1098   }
1099 
1100   void append_secondary_free_list_if_not_empty_with_lock() {
1101     // If the secondary free list looks empty there's no reason to
1102     // take the lock and then try to append it.
1103     if (!_secondary_free_list.is_empty()) {
1104       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1105       append_secondary_free_list();
1106     }
1107   }
1108 
1109   inline void old_set_add(HeapRegion* hr);
1110   inline void old_set_remove(HeapRegion* hr);
1111 
1112   size_t non_young_capacity_bytes() {
1113     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1114   }
1115 
1116   void set_free_regions_coming();
1117   void reset_free_regions_coming();
1118   bool free_regions_coming() { return _free_regions_coming; }
1119   void wait_while_free_regions_coming();
1120 
1121   // Determine whether the given region is one that we are using as an
1122   // old GC alloc region.
1123   bool is_old_gc_alloc_region(HeapRegion* hr);
1124 
1125   // Perform a collection of the heap; intended for use in implementing
1126   // "System.gc".  This probably implies as full a collection as the
1127   // "CollectedHeap" supports.
1128   virtual void collect(GCCause::Cause cause);
1129 
1130   virtual bool copy_allocation_context_stats(const jint* contexts,
1131                                              jlong* totals,
1132                                              jbyte* accuracy,
1133                                              jint len);
1134 
1135   // True iff an evacuation has failed in the most-recent collection.
1136   bool evacuation_failed() { return _evacuation_failed; }
1137 
1138   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1139   void prepend_to_freelist(FreeRegionList* list);
1140   void decrement_summary_bytes(size_t bytes);
1141 
1142   virtual bool is_in(const void* p) const;
1143 #ifdef ASSERT
1144   // Returns whether p is in one of the available areas of the heap. Slow but
1145   // extensive version.
1146   bool is_in_exact(const void* p) const;
1147 #endif
1148 
1149   // Return "TRUE" iff the given object address is within the collection
1150   // set. Assumes that the reference points into the heap.
1151   inline bool is_in_cset(const HeapRegion *hr);
1152   inline bool is_in_cset(oop obj);
1153   inline bool is_in_cset(HeapWord* addr);
1154 
1155   inline bool is_in_cset_or_humongous(const oop obj);
1156 
1157  private:
1158   // This array is used for a quick test on whether a reference points into
1159   // the collection set or not. Each of the array's elements denotes whether the
1160   // corresponding region is in the collection set or not.
1161   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1162 
1163  public:
1164 
1165   inline InCSetState in_cset_state(const oop obj);
1166 
1167   // Return "TRUE" iff the given object address is in the reserved
1168   // region of g1.
1169   bool is_in_g1_reserved(const void* p) const {
1170     return _hrm.reserved().contains(p);
1171   }
1172 
1173   // Returns a MemRegion that corresponds to the space that has been
1174   // reserved for the heap
1175   MemRegion g1_reserved() const {
1176     return _hrm.reserved();
1177   }
1178 
1179   virtual bool is_in_closed_subset(const void* p) const;
1180 
1181   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1182     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1183   }
1184 
1185   G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1186 
1187   // Iteration functions.
1188 
1189   // Iterate over all objects, calling "cl.do_object" on each.
1190   virtual void object_iterate(ObjectClosure* cl);
1191 
1192   virtual void safe_object_iterate(ObjectClosure* cl) {
1193     object_iterate(cl);
1194   }
1195 
1196   // Iterate over heap regions, in address order, terminating the
1197   // iteration early if the "doHeapRegion" method returns "true".
1198   void heap_region_iterate(HeapRegionClosure* blk) const;
1199 
1200   // Return the region with the given index. It assumes the index is valid.
1201   inline HeapRegion* region_at(uint index) const;
1202 
1203   // Return the next region (by index) that is part of the same
1204   // humongous object that hr is part of.
1205   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1206 
1207   // Calculate the region index of the given address. Given address must be
1208   // within the heap.
1209   inline uint addr_to_region(HeapWord* addr) const;
1210 
1211   inline HeapWord* bottom_addr_for_region(uint index) const;
1212 
1213   // Two functions to iterate over the heap regions in parallel. Threads
1214   // compete using the HeapRegionClaimer to claim the regions before
1215   // applying the closure on them.
1216   // The _from_worker_offset version uses the HeapRegionClaimer and
1217   // the worker id to calculate a start offset to prevent all workers to
1218   // start from the point.
1219   void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1220                                                   HeapRegionClaimer* hrclaimer,
1221                                                   uint worker_id) const;
1222 
1223   void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1224                                           HeapRegionClaimer* hrclaimer) const;
1225 
1226   // Iterate over the regions (if any) in the current collection set.
1227   void collection_set_iterate(HeapRegionClosure* blk);
1228 
1229   // Iterate over the regions (if any) in the current collection set. Starts the
1230   // iteration over the entire collection set so that the start regions of a given
1231   // worker id over the set active_workers are evenly spread across the set of
1232   // collection set regions.
1233   void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1234 
1235   // Returns the HeapRegion that contains addr. addr must not be NULL.
1236   template <class T>
1237   inline HeapRegion* heap_region_containing(const T addr) const;
1238 
1239   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1240   // each address in the (reserved) heap is a member of exactly
1241   // one block.  The defining characteristic of a block is that it is
1242   // possible to find its size, and thus to progress forward to the next
1243   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1244   // represent Java objects, or they might be free blocks in a
1245   // free-list-based heap (or subheap), as long as the two kinds are
1246   // distinguishable and the size of each is determinable.
1247 
1248   // Returns the address of the start of the "block" that contains the
1249   // address "addr".  We say "blocks" instead of "object" since some heaps
1250   // may not pack objects densely; a chunk may either be an object or a
1251   // non-object.
1252   virtual HeapWord* block_start(const void* addr) const;
1253 
1254   // Requires "addr" to be the start of a chunk, and returns its size.
1255   // "addr + size" is required to be the start of a new chunk, or the end
1256   // of the active area of the heap.
1257   virtual size_t block_size(const HeapWord* addr) const;
1258 
1259   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1260   // the block is an object.
1261   virtual bool block_is_obj(const HeapWord* addr) const;
1262 
1263   // Section on thread-local allocation buffers (TLABs)
1264   // See CollectedHeap for semantics.
1265 
1266   bool supports_tlab_allocation() const;
1267   size_t tlab_capacity(Thread* ignored) const;
1268   size_t tlab_used(Thread* ignored) const;
1269   size_t max_tlab_size() const;
1270   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1271 
1272   // Can a compiler initialize a new object without store barriers?
1273   // This permission only extends from the creation of a new object
1274   // via a TLAB up to the first subsequent safepoint. If such permission
1275   // is granted for this heap type, the compiler promises to call
1276   // defer_store_barrier() below on any slow path allocation of
1277   // a new object for which such initializing store barriers will
1278   // have been elided. G1, like CMS, allows this, but should be
1279   // ready to provide a compensating write barrier as necessary
1280   // if that storage came out of a non-young region. The efficiency
1281   // of this implementation depends crucially on being able to
1282   // answer very efficiently in constant time whether a piece of
1283   // storage in the heap comes from a young region or not.
1284   // See ReduceInitialCardMarks.
1285   virtual bool can_elide_tlab_store_barriers() const {
1286     return true;
1287   }
1288 
1289   virtual bool card_mark_must_follow_store() const {
1290     return true;
1291   }
1292 
1293   inline bool is_in_young(const oop obj);
1294 
1295   // We don't need barriers for initializing stores to objects
1296   // in the young gen: for the SATB pre-barrier, there is no
1297   // pre-value that needs to be remembered; for the remembered-set
1298   // update logging post-barrier, we don't maintain remembered set
1299   // information for young gen objects.
1300   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1301 
1302   // Returns "true" iff the given word_size is "very large".
1303   static bool is_humongous(size_t word_size) {
1304     // Note this has to be strictly greater-than as the TLABs
1305     // are capped at the humongous threshold and we want to
1306     // ensure that we don't try to allocate a TLAB as
1307     // humongous and that we don't allocate a humongous
1308     // object in a TLAB.
1309     return word_size > _humongous_object_threshold_in_words;
1310   }
1311 
1312   // Returns the humongous threshold for a specific region size
1313   static size_t humongous_threshold_for(size_t region_size) {
1314     return (region_size / 2);
1315   }
1316 
1317   // Returns the number of regions the humongous object of the given word size
1318   // requires.
1319   static size_t humongous_obj_size_in_regions(size_t word_size);
1320 
1321   // Print the maximum heap capacity.
1322   virtual size_t max_capacity() const;
1323 
1324   virtual jlong millis_since_last_gc();
1325 
1326 
1327   // Convenience function to be used in situations where the heap type can be
1328   // asserted to be this type.
1329   static G1CollectedHeap* heap();
1330 
1331   void set_region_short_lived_locked(HeapRegion* hr);
1332   // add appropriate methods for any other surv rate groups
1333 
1334   const G1SurvivorRegions* survivor() const { return &_survivor; }
1335 
1336   uint survivor_regions_count() const {
1337     return _survivor.length();
1338   }
1339 
1340   uint eden_regions_count() const {
1341     return _eden.length();
1342   }
1343 
1344   uint young_regions_count() const {
1345     return _eden.length() + _survivor.length();
1346   }
1347 
1348   uint old_regions_count() const { return _old_set.length(); }
1349 
1350   uint humongous_regions_count() const { return _humongous_set.length(); }
1351 
1352 #ifdef ASSERT
1353   bool check_young_list_empty();
1354 #endif
1355 
1356   // *** Stuff related to concurrent marking.  It's not clear to me that so
1357   // many of these need to be public.
1358 
1359   // The functions below are helper functions that a subclass of
1360   // "CollectedHeap" can use in the implementation of its virtual
1361   // functions.
1362   // This performs a concurrent marking of the live objects in a
1363   // bitmap off to the side.
1364   void doConcurrentMark();
1365 
1366   bool isMarkedNext(oop obj) const;
1367 
1368   // Determine if an object is dead, given the object and also
1369   // the region to which the object belongs. An object is dead
1370   // iff a) it was not allocated since the last mark, b) it
1371   // is not marked, and c) it is not in an archive region.
1372   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1373     return
1374       hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1375       !hr->is_archive();
1376   }
1377 
1378   // This function returns true when an object has been
1379   // around since the previous marking and hasn't yet
1380   // been marked during this marking, and is not in an archive region.
1381   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1382     return
1383       !hr->obj_allocated_since_next_marking(obj) &&
1384       !isMarkedNext(obj) &&
1385       !hr->is_archive();
1386   }
1387 
1388   // Determine if an object is dead, given only the object itself.
1389   // This will find the region to which the object belongs and
1390   // then call the region version of the same function.
1391 
1392   // Added if it is NULL it isn't dead.
1393 
1394   inline bool is_obj_dead(const oop obj) const;
1395 
1396   inline bool is_obj_ill(const oop obj) const;
1397 
1398   inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1399   inline bool is_obj_dead_full(const oop obj) const;
1400 
1401   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1402 
1403   // Refinement
1404 
1405   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1406 
1407   // Optimized nmethod scanning support routines
1408 
1409   // Is an oop scavengeable
1410   virtual bool is_scavengable(oop obj);
1411 
1412   // Register the given nmethod with the G1 heap.
1413   virtual void register_nmethod(nmethod* nm);
1414 
1415   // Unregister the given nmethod from the G1 heap.
1416   virtual void unregister_nmethod(nmethod* nm);
1417 
1418   // Free up superfluous code root memory.
1419   void purge_code_root_memory();
1420 
1421   // Rebuild the strong code root lists for each region
1422   // after a full GC.
1423   void rebuild_strong_code_roots();
1424 
1425   // Partial cleaning used when class unloading is disabled.
1426   // Let the caller choose what structures to clean out:
1427   // - StringTable
1428   // - SymbolTable
1429   // - StringDeduplication structures
1430   void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1431 
1432   // Complete cleaning used when class unloading is enabled.
1433   // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1434   void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1435 
1436   // Redirty logged cards in the refinement queue.
1437   void redirty_logged_cards();
1438   // Verification
1439 
1440   // Perform any cleanup actions necessary before allowing a verification.
1441   virtual void prepare_for_verify();
1442 
1443   // Perform verification.
1444 
1445   // vo == UsePrevMarking -> use "prev" marking information,
1446   // vo == UseNextMarking -> use "next" marking information
1447   // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1448   //
1449   // NOTE: Only the "prev" marking information is guaranteed to be
1450   // consistent most of the time, so most calls to this should use
1451   // vo == UsePrevMarking.
1452   // Currently, there is only one case where this is called with
1453   // vo == UseNextMarking, which is to verify the "next" marking
1454   // information at the end of remark.
1455   // Currently there is only one place where this is called with
1456   // vo == UseFullMarking, which is to verify the marking during a
1457   // full GC.
1458   void verify(VerifyOption vo);
1459 
1460   // WhiteBox testing support.
1461   virtual bool supports_concurrent_phase_control() const;
1462   virtual const char* const* concurrent_phases() const;
1463   virtual bool request_concurrent_phase(const char* phase);
1464 
1465   // The methods below are here for convenience and dispatch the
1466   // appropriate method depending on value of the given VerifyOption
1467   // parameter. The values for that parameter, and their meanings,
1468   // are the same as those above.
1469 
1470   bool is_obj_dead_cond(const oop obj,
1471                         const HeapRegion* hr,
1472                         const VerifyOption vo) const;
1473 
1474   bool is_obj_dead_cond(const oop obj,
1475                         const VerifyOption vo) const;
1476 
1477   G1HeapSummary create_g1_heap_summary();
1478   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1479 
1480   // Printing
1481 private:
1482   void print_heap_regions() const;
1483   void print_regions_on(outputStream* st) const;
1484 
1485 public:
1486   virtual void print_on(outputStream* st) const;
1487   virtual void print_extended_on(outputStream* st) const;
1488   virtual void print_on_error(outputStream* st) const;
1489 
1490   virtual void print_gc_threads_on(outputStream* st) const;
1491   virtual void gc_threads_do(ThreadClosure* tc) const;
1492 
1493   // Override
1494   void print_tracing_info() const;
1495 
1496   // The following two methods are helpful for debugging RSet issues.
1497   void print_cset_rsets() PRODUCT_RETURN;
1498   void print_all_rsets() PRODUCT_RETURN;
1499 
1500 public:
1501   size_t pending_card_num();
1502 
1503 protected:
1504   size_t _max_heap_capacity;
1505 };
1506 
1507 class G1ParEvacuateFollowersClosure : public VoidClosure {
1508 private:
1509   double _start_term;
1510   double _term_time;
1511   size_t _term_attempts;
1512 
1513   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1514   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1515 protected:
1516   G1CollectedHeap*              _g1h;
1517   G1ParScanThreadState*         _par_scan_state;
1518   RefToScanQueueSet*            _queues;
1519   ParallelTaskTerminator*       _terminator;
1520 
1521   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1522   RefToScanQueueSet*      queues()         { return _queues; }
1523   ParallelTaskTerminator* terminator()     { return _terminator; }
1524 
1525 public:
1526   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1527                                 G1ParScanThreadState* par_scan_state,
1528                                 RefToScanQueueSet* queues,
1529                                 ParallelTaskTerminator* terminator)
1530     : _g1h(g1h), _par_scan_state(par_scan_state),
1531       _queues(queues), _terminator(terminator),
1532       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1533 
1534   void do_void();
1535 
1536   double term_time() const { return _term_time; }
1537   size_t term_attempts() const { return _term_attempts; }
1538 
1539 private:
1540   inline bool offer_termination();
1541 };
1542 
1543 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP