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
   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_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/concurrentMark.hpp"
  29 #include "gc_implementation/g1/evacuationInfo.hpp"
  30 #include "gc_implementation/g1/g1AllocRegion.hpp"
  31 #include "gc_implementation/g1/g1BiasedArray.hpp"
  32 #include "gc_implementation/g1/g1HRPrinter.hpp"
  33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  34 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  35 #include "gc_implementation/g1/g1YCTypes.hpp"
  36 #include "gc_implementation/g1/heapRegionSeq.hpp"
  37 #include "gc_implementation/g1/heapRegionSet.hpp"
  38 #include "gc_implementation/shared/hSpaceCounters.hpp"
  39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  40 #include "memory/barrierSet.hpp"
  41 #include "memory/memRegion.hpp"
  42 #include "memory/sharedHeap.hpp"
  43 #include "utilities/stack.hpp"
  44 
  45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  46 // It uses the "Garbage First" heap organization and algorithm, which
  47 // may combine concurrent marking with parallel, incremental compaction of
  48 // heap subsets that will yield large amounts of garbage.
  49 
  50 // Forward declarations
  51 class HeapRegion;
  52 class HRRSCleanupTask;
  53 class GenerationSpec;
  54 class OopsInHeapRegionClosure;
  55 class G1KlassScanClosure;
  56 class G1ScanHeapEvacClosure;
  57 class ObjectClosure;
  58 class SpaceClosure;
  59 class CompactibleSpaceClosure;
  60 class Space;
  61 class G1CollectorPolicy;
  62 class GenRemSet;
  63 class G1RemSet;
  64 class HeapRegionRemSetIterator;
  65 class ConcurrentMark;
  66 class ConcurrentMarkThread;
  67 class ConcurrentG1Refine;
  68 class ConcurrentGCTimer;
  69 class GenerationCounters;
  70 class STWGCTimer;
  71 class G1NewTracer;
  72 class G1OldTracer;
  73 class EvacuationFailedInfo;
  74 class nmethod;
  75 class Ticks;
  76 
  77 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  79 
  80 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  81 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  82 
  83 enum GCAllocPurpose {
  84   GCAllocForTenured,
  85   GCAllocForSurvived,
  86   GCAllocPurposeCount
  87 };
  88 
  89 class YoungList : public CHeapObj<mtGC> {
  90 private:
  91   G1CollectedHeap* _g1h;
  92 
  93   HeapRegion* _head;
  94 
  95   HeapRegion* _survivor_head;
  96   HeapRegion* _survivor_tail;
  97 
  98   HeapRegion* _curr;
  99 
 100   uint        _length;
 101   uint        _survivor_length;
 102 
 103   size_t      _last_sampled_rs_lengths;
 104   size_t      _sampled_rs_lengths;
 105 
 106   void         empty_list(HeapRegion* list);
 107 
 108 public:
 109   YoungList(G1CollectedHeap* g1h);
 110 
 111   void         push_region(HeapRegion* hr);
 112   void         add_survivor_region(HeapRegion* hr);
 113 
 114   void         empty_list();
 115   bool         is_empty() { return _length == 0; }
 116   uint         length() { return _length; }
 117   uint         survivor_length() { return _survivor_length; }
 118 
 119   // Currently we do not keep track of the used byte sum for the
 120   // young list and the survivors and it'd be quite a lot of work to
 121   // do so. When we'll eventually replace the young list with
 122   // instances of HeapRegionLinkedList we'll get that for free. So,
 123   // we'll report the more accurate information then.
 124   size_t       eden_used_bytes() {
 125     assert(length() >= survivor_length(), "invariant");
 126     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 127   }
 128   size_t       survivor_used_bytes() {
 129     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 130   }
 131 
 132   void rs_length_sampling_init();
 133   bool rs_length_sampling_more();
 134   void rs_length_sampling_next();
 135 
 136   void reset_sampled_info() {
 137     _last_sampled_rs_lengths =   0;
 138   }
 139   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 140 
 141   // for development purposes
 142   void reset_auxilary_lists();
 143   void clear() { _head = NULL; _length = 0; }
 144 
 145   void clear_survivors() {
 146     _survivor_head    = NULL;
 147     _survivor_tail    = NULL;
 148     _survivor_length  = 0;
 149   }
 150 
 151   HeapRegion* first_region() { return _head; }
 152   HeapRegion* first_survivor_region() { return _survivor_head; }
 153   HeapRegion* last_survivor_region() { return _survivor_tail; }
 154 
 155   // debugging
 156   bool          check_list_well_formed();
 157   bool          check_list_empty(bool check_sample = true);
 158   void          print();
 159 };
 160 
 161 class MutatorAllocRegion : public G1AllocRegion {
 162 protected:
 163   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 164   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 165 public:
 166   MutatorAllocRegion()
 167     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 168 };
 169 
 170 class SurvivorGCAllocRegion : public G1AllocRegion {
 171 protected:
 172   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 173   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 174 public:
 175   SurvivorGCAllocRegion()
 176   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 177 };
 178 
 179 class OldGCAllocRegion : public G1AllocRegion {
 180 protected:
 181   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 182   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 183 public:
 184   OldGCAllocRegion()
 185   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 186 };
 187 
 188 // The G1 STW is alive closure.
 189 // An instance is embedded into the G1CH and used as the
 190 // (optional) _is_alive_non_header closure in the STW
 191 // reference processor. It is also extensively used during
 192 // reference processing during STW evacuation pauses.
 193 class G1STWIsAliveClosure: public BoolObjectClosure {
 194   G1CollectedHeap* _g1;
 195 public:
 196   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 197   bool do_object_b(oop p);
 198 };
 199 
 200 // Instances of this class are used for quick tests on whether a reference points
 201 // into the collection set or is a humongous object (points into a humongous
 202 // object).
 203 // Each of the array's elements denotes whether the corresponding region is in
 204 // the collection set or a humongous region.
 205 // We use this to quickly reclaim humongous objects:  by making a humongous region
 206 // succeed this test, we sort-of add it to the collection set which objects are
 207 // supposed to be evacuated. However, since the region is humongous, evacuation
 208 // will automatically fail the test to allocate it into a PLAB. We catch this
 209 // condition (in this slow-path), and mark that region as "live" in a side table.
 210 // At the end of GC, we use this information, among other, to determine whether
 211 // we can reclaim the humongous object or not.
 212 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<char> {
 213  public:
 214   enum in_cset_state_t {
 215    InNeither,           // neither in collection set nor humongous
 216    InCSet,              // region is in collection set only
 217    IsHumongous          // region is a humongous start region
 218   };
 219  protected:
 220   char default_value() const { return InNeither; }
 221  public:
 222   void set_humongous(uintptr_t index) { assert(get_by_index(index) != InCSet, "Should not overwrite InCSet values"); set_by_index(index, IsHumongous); }
 223   void clear_humongous(uintptr_t index) {
 224     set_by_index(index, InNeither);
 225   }
 226   void set_in_cset(uintptr_t index) { assert(get_by_index(index) != IsHumongous, "Should not overwrite IsHumongous value"); set_by_index(index, InCSet); }
 227 
 228   bool is_in_cset_or_humongous(HeapWord* addr) const { return get_by_address(addr) != InNeither; }
 229   bool is_in_cset(HeapWord* addr) const { return get_by_address(addr) == InCSet; }
 230   in_cset_state_t at(HeapWord* addr) const { return (in_cset_state_t)get_by_address(addr); }
 231   void clear() { G1BiasedMappedArray<char>::clear(); }
 232 };
 233 
 234 class RefineCardTableEntryClosure;
 235 
 236 class G1CollectedHeap : public SharedHeap {
 237   friend class VM_CollectForMetadataAllocation;
 238   friend class VM_G1CollectForAllocation;
 239   friend class VM_G1CollectFull;
 240   friend class VM_G1IncCollectionPause;
 241   friend class VMStructs;
 242   friend class MutatorAllocRegion;
 243   friend class SurvivorGCAllocRegion;
 244   friend class OldGCAllocRegion;
 245 
 246   // Closures used in implementation.
 247   template <G1Barrier barrier, G1Mark do_mark_object>
 248   friend class G1ParCopyClosure;
 249   friend class G1IsAliveClosure;
 250   friend class G1EvacuateFollowersClosure;
 251   friend class G1ParScanThreadState;
 252   friend class G1ParScanClosureSuper;
 253   friend class G1ParEvacuateFollowersClosure;
 254   friend class G1ParTask;
 255   friend class G1FreeGarbageRegionClosure;
 256   friend class RefineCardTableEntryClosure;
 257   friend class G1PrepareCompactClosure;
 258   friend class RegionSorter;
 259   friend class RegionResetter;
 260   friend class CountRCClosure;
 261   friend class EvacPopObjClosure;
 262   friend class G1ParCleanupCTTask;
 263 
 264   friend class G1FreeHumongousRegionClosure;
 265   // Other related classes.
 266   friend class G1MarkSweep;
 267 
 268 private:
 269   // The one and only G1CollectedHeap, so static functions can find it.
 270   static G1CollectedHeap* _g1h;
 271 
 272   static size_t _humongous_object_threshold_in_words;
 273 
 274   // Storage for the G1 heap.
 275   VirtualSpace _g1_storage;
 276   MemRegion    _g1_reserved;
 277 
 278   // The part of _g1_storage that is currently committed.
 279   MemRegion _g1_committed;
 280 
 281   // The master free list. It will satisfy all new region allocations.
 282   FreeRegionList _free_list;
 283 
 284   // The secondary free list which contains regions that have been
 285   // freed up during the cleanup process. This will be appended to the
 286   // master free list when appropriate.
 287   FreeRegionList _secondary_free_list;
 288 
 289   // It keeps track of the old regions.
 290   HeapRegionSet _old_set;
 291 
 292   // It keeps track of the humongous regions.
 293   HeapRegionSet _humongous_set;
 294 
 295   void clear_humongous_is_live_table();
 296   void eagerly_reclaim_humongous_regions();
 297 
 298   // The number of regions we could create by expansion.
 299   uint _expansion_regions;
 300 
 301   // The block offset table for the G1 heap.
 302   G1BlockOffsetSharedArray* _bot_shared;
 303 
 304   // Tears down the region sets / lists so that they are empty and the
 305   // regions on the heap do not belong to a region set / list. The
 306   // only exception is the humongous set which we leave unaltered. If
 307   // free_list_only is true, it will only tear down the master free
 308   // list. It is called before a Full GC (free_list_only == false) or
 309   // before heap shrinking (free_list_only == true).
 310   void tear_down_region_sets(bool free_list_only);
 311 
 312   // Rebuilds the region sets / lists so that they are repopulated to
 313   // reflect the contents of the heap. The only exception is the
 314   // humongous set which was not torn down in the first place. If
 315   // free_list_only is true, it will only rebuild the master free
 316   // list. It is called after a Full GC (free_list_only == false) or
 317   // after heap shrinking (free_list_only == true).
 318   void rebuild_region_sets(bool free_list_only);
 319 
 320   // The sequence of all heap regions in the heap.
 321   HeapRegionSeq _hrs;
 322 
 323   // Alloc region used to satisfy mutator allocation requests.
 324   MutatorAllocRegion _mutator_alloc_region;
 325 
 326   // Alloc region used to satisfy allocation requests by the GC for
 327   // survivor objects.
 328   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 329 
 330   // PLAB sizing policy for survivors.
 331   PLABStats _survivor_plab_stats;
 332 
 333   // Alloc region used to satisfy allocation requests by the GC for
 334   // old objects.
 335   OldGCAllocRegion _old_gc_alloc_region;
 336 
 337   // PLAB sizing policy for tenured objects.
 338   PLABStats _old_plab_stats;
 339 
 340   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 341     PLABStats* stats = NULL;
 342 
 343     switch (purpose) {
 344     case GCAllocForSurvived:
 345       stats = &_survivor_plab_stats;
 346       break;
 347     case GCAllocForTenured:
 348       stats = &_old_plab_stats;
 349       break;
 350     default:
 351       assert(false, "unrecognized GCAllocPurpose");
 352     }
 353 
 354     return stats;
 355   }
 356 
 357   // The last old region we allocated to during the last GC.
 358   // Typically, it is not full so we should re-use it during the next GC.
 359   HeapRegion* _retained_old_gc_alloc_region;
 360 
 361   // It specifies whether we should attempt to expand the heap after a
 362   // region allocation failure. If heap expansion fails we set this to
 363   // false so that we don't re-attempt the heap expansion (it's likely
 364   // that subsequent expansion attempts will also fail if one fails).
 365   // Currently, it is only consulted during GC and it's reset at the
 366   // start of each GC.
 367   bool _expand_heap_after_alloc_failure;
 368 
 369   // It resets the mutator alloc region before new allocations can take place.
 370   void init_mutator_alloc_region();
 371 
 372   // It releases the mutator alloc region.
 373   void release_mutator_alloc_region();
 374 
 375   // It initializes the GC alloc regions at the start of a GC.
 376   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 377 
 378   // Setup the retained old gc alloc region as the currrent old gc alloc region.
 379   void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
 380 
 381   // It releases the GC alloc regions at the end of a GC.
 382   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 383 
 384   // It does any cleanup that needs to be done on the GC alloc regions
 385   // before a Full GC.
 386   void abandon_gc_alloc_regions();
 387 
 388   // Helper for monitoring and management support.
 389   G1MonitoringSupport* _g1mm;
 390 
 391   // Determines PLAB size for a particular allocation purpose.
 392   size_t desired_plab_sz(GCAllocPurpose purpose);
 393 
 394   // Outside of GC pauses, the number of bytes used in all regions other
 395   // than the current allocation region.
 396   size_t _summary_bytes_used;
 397 
 398   // This array is used for a quick test on whether a reference points into
 399   // the collection set or not. Each of the array's elements denotes whether the
 400   // corresponding region is in the collection set or not.
 401   G1FastCSetBiasedMappedArray _in_cset_fast_test;
 402 
 403   // Records whether the region at the given index is kept live by roots or
 404   // references from the young generation.
 405   class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
 406    protected:
 407     bool default_value() const { return false; }
 408    public:
 409     void clear() { G1BiasedMappedArray<bool>::clear(); }
 410     void set_live(uint region) {
 411       set_by_index(region, true);
 412     }
 413     bool is_live(uint region) {
 414       return get_by_index(region);
 415     }
 416   };
 417 
 418   HumongousIsLiveBiasedMappedArray _humongous_is_live;
 419   // Stores whether during humongous object registration we found candidate regions.
 420   // If not, we can skip a few steps.
 421   bool _has_humongous_reclaim_candidates;
 422 
 423   volatile unsigned _gc_time_stamp;
 424 
 425   size_t* _surviving_young_words;
 426 
 427   G1HRPrinter _hr_printer;
 428 
 429   void setup_surviving_young_words();
 430   void update_surviving_young_words(size_t* surv_young_words);
 431   void cleanup_surviving_young_words();
 432 
 433   // It decides whether an explicit GC should start a concurrent cycle
 434   // instead of doing a STW GC. Currently, a concurrent cycle is
 435   // explicitly started if:
 436   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 437   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 438   // (c) cause == _g1_humongous_allocation
 439   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 440 
 441   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 442   // concurrent cycles) we have started.
 443   volatile unsigned int _old_marking_cycles_started;
 444 
 445   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 446   // concurrent cycles) we have completed.
 447   volatile unsigned int _old_marking_cycles_completed;
 448 
 449   bool _concurrent_cycle_started;
 450 
 451   // This is a non-product method that is helpful for testing. It is
 452   // called at the end of a GC and artificially expands the heap by
 453   // allocating a number of dead regions. This way we can induce very
 454   // frequent marking cycles and stress the cleanup / concurrent
 455   // cleanup code more (as all the regions that will be allocated by
 456   // this method will be found dead by the marking cycle).
 457   void allocate_dummy_regions() PRODUCT_RETURN;
 458 
 459   // Clear RSets after a compaction. It also resets the GC time stamps.
 460   void clear_rsets_post_compaction();
 461 
 462   // If the HR printer is active, dump the state of the regions in the
 463   // heap after a compaction.
 464   void print_hrs_post_compaction();
 465 
 466   double verify(bool guard, const char* msg);
 467   void verify_before_gc();
 468   void verify_after_gc();
 469 
 470   void log_gc_header();
 471   void log_gc_footer(double pause_time_sec);
 472 
 473   // These are macros so that, if the assert fires, we get the correct
 474   // line number, file, etc.
 475 
 476 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 477   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 478           (_extra_message_),                                                  \
 479           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 480           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 481           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 482 
 483 #define assert_heap_locked()                                                  \
 484   do {                                                                        \
 485     assert(Heap_lock->owned_by_self(),                                        \
 486            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 487   } while (0)
 488 
 489 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 490   do {                                                                        \
 491     assert(Heap_lock->owned_by_self() ||                                      \
 492            (SafepointSynchronize::is_at_safepoint() &&                        \
 493              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 494            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 495                                         "should be at a safepoint"));         \
 496   } while (0)
 497 
 498 #define assert_heap_locked_and_not_at_safepoint()                             \
 499   do {                                                                        \
 500     assert(Heap_lock->owned_by_self() &&                                      \
 501                                     !SafepointSynchronize::is_at_safepoint(), \
 502           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 503                                        "should not be at a safepoint"));      \
 504   } while (0)
 505 
 506 #define assert_heap_not_locked()                                              \
 507   do {                                                                        \
 508     assert(!Heap_lock->owned_by_self(),                                       \
 509         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 510   } while (0)
 511 
 512 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 513   do {                                                                        \
 514     assert(!Heap_lock->owned_by_self() &&                                     \
 515                                     !SafepointSynchronize::is_at_safepoint(), \
 516       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 517                                    "should not be at a safepoint"));          \
 518   } while (0)
 519 
 520 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 521   do {                                                                        \
 522     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 523               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 524            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 525   } while (0)
 526 
 527 #define assert_not_at_safepoint()                                             \
 528   do {                                                                        \
 529     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 530            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 531   } while (0)
 532 
 533 protected:
 534 
 535   // The young region list.
 536   YoungList*  _young_list;
 537 
 538   // The current policy object for the collector.
 539   G1CollectorPolicy* _g1_policy;
 540 
 541   // This is the second level of trying to allocate a new region. If
 542   // new_region() didn't find a region on the free_list, this call will
 543   // check whether there's anything available on the
 544   // secondary_free_list and/or wait for more regions to appear on
 545   // that list, if _free_regions_coming is set.
 546   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 547 
 548   // Try to allocate a single non-humongous HeapRegion sufficient for
 549   // an allocation of the given word_size. If do_expand is true,
 550   // attempt to expand the heap if necessary to satisfy the allocation
 551   // request. If the region is to be used as an old region or for a
 552   // humongous object, set is_old to true. If not, to false.
 553   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 554 
 555   // Attempt to satisfy a humongous allocation request of the given
 556   // size by finding a contiguous set of free regions of num_regions
 557   // length and remove them from the master free list. Return the
 558   // index of the first region or G1_NULL_HRS_INDEX if the search
 559   // was unsuccessful.
 560   uint humongous_obj_allocate_find_first(uint num_regions,
 561                                          size_t word_size);
 562 
 563   // Initialize a contiguous set of free regions of length num_regions
 564   // and starting at index first so that they appear as a single
 565   // humongous region.
 566   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 567                                                       uint num_regions,
 568                                                       size_t word_size);
 569 
 570   // Attempt to allocate a humongous object of the given size. Return
 571   // NULL if unsuccessful.
 572   HeapWord* humongous_obj_allocate(size_t word_size);
 573 
 574   // The following two methods, allocate_new_tlab() and
 575   // mem_allocate(), are the two main entry points from the runtime
 576   // into the G1's allocation routines. They have the following
 577   // assumptions:
 578   //
 579   // * They should both be called outside safepoints.
 580   //
 581   // * They should both be called without holding the Heap_lock.
 582   //
 583   // * All allocation requests for new TLABs should go to
 584   //   allocate_new_tlab().
 585   //
 586   // * All non-TLAB allocation requests should go to mem_allocate().
 587   //
 588   // * If either call cannot satisfy the allocation request using the
 589   //   current allocating region, they will try to get a new one. If
 590   //   this fails, they will attempt to do an evacuation pause and
 591   //   retry the allocation.
 592   //
 593   // * If all allocation attempts fail, even after trying to schedule
 594   //   an evacuation pause, allocate_new_tlab() will return NULL,
 595   //   whereas mem_allocate() will attempt a heap expansion and/or
 596   //   schedule a Full GC.
 597   //
 598   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 599   //   should never be called with word_size being humongous. All
 600   //   humongous allocation requests should go to mem_allocate() which
 601   //   will satisfy them with a special path.
 602 
 603   virtual HeapWord* allocate_new_tlab(size_t word_size);
 604 
 605   virtual HeapWord* mem_allocate(size_t word_size,
 606                                  bool*  gc_overhead_limit_was_exceeded);
 607 
 608   // The following three methods take a gc_count_before_ret
 609   // parameter which is used to return the GC count if the method
 610   // returns NULL. Given that we are required to read the GC count
 611   // while holding the Heap_lock, and these paths will take the
 612   // Heap_lock at some point, it's easier to get them to read the GC
 613   // count while holding the Heap_lock before they return NULL instead
 614   // of the caller (namely: mem_allocate()) having to also take the
 615   // Heap_lock just to read the GC count.
 616 
 617   // First-level mutator allocation attempt: try to allocate out of
 618   // the mutator alloc region without taking the Heap_lock. This
 619   // should only be used for non-humongous allocations.
 620   inline HeapWord* attempt_allocation(size_t word_size,
 621                                       unsigned int* gc_count_before_ret,
 622                                       int* gclocker_retry_count_ret);
 623 
 624   // Second-level mutator allocation attempt: take the Heap_lock and
 625   // retry the allocation attempt, potentially scheduling a GC
 626   // pause. This should only be used for non-humongous allocations.
 627   HeapWord* attempt_allocation_slow(size_t word_size,
 628                                     unsigned int* gc_count_before_ret,
 629                                     int* gclocker_retry_count_ret);
 630 
 631   // Takes the Heap_lock and attempts a humongous allocation. It can
 632   // potentially schedule a GC pause.
 633   HeapWord* attempt_allocation_humongous(size_t word_size,
 634                                          unsigned int* gc_count_before_ret,
 635                                          int* gclocker_retry_count_ret);
 636 
 637   // Allocation attempt that should be called during safepoints (e.g.,
 638   // at the end of a successful GC). expect_null_mutator_alloc_region
 639   // specifies whether the mutator alloc region is expected to be NULL
 640   // or not.
 641   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 642                                        bool expect_null_mutator_alloc_region);
 643 
 644   // It dirties the cards that cover the block so that so that the post
 645   // write barrier never queues anything when updating objects on this
 646   // block. It is assumed (and in fact we assert) that the block
 647   // belongs to a young region.
 648   inline void dirty_young_block(HeapWord* start, size_t word_size);
 649 
 650   // Allocate blocks during garbage collection. Will ensure an
 651   // allocation region, either by picking one or expanding the
 652   // heap, and then allocate a block of the given size. The block
 653   // may not be a humongous - it must fit into a single heap region.
 654   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 655 
 656   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 657                                     HeapRegion*    alloc_region,
 658                                     bool           par,
 659                                     size_t         word_size);
 660 
 661   // Ensure that no further allocations can happen in "r", bearing in mind
 662   // that parallel threads might be attempting allocations.
 663   void par_allocate_remaining_space(HeapRegion* r);
 664 
 665   // Allocation attempt during GC for a survivor object / PLAB.
 666   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 667 
 668   // Allocation attempt during GC for an old object / PLAB.
 669   inline HeapWord* old_attempt_allocation(size_t word_size);
 670 
 671   // These methods are the "callbacks" from the G1AllocRegion class.
 672 
 673   // For mutator alloc regions.
 674   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 675   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 676                                    size_t allocated_bytes);
 677 
 678   // For GC alloc regions.
 679   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 680                                   GCAllocPurpose ap);
 681   void retire_gc_alloc_region(HeapRegion* alloc_region,
 682                               size_t allocated_bytes, GCAllocPurpose ap);
 683 
 684   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 685   //   inspection request and should collect the entire heap
 686   // - if clear_all_soft_refs is true, all soft references should be
 687   //   cleared during the GC
 688   // - if explicit_gc is false, word_size describes the allocation that
 689   //   the GC should attempt (at least) to satisfy
 690   // - it returns false if it is unable to do the collection due to the
 691   //   GC locker being active, true otherwise
 692   bool do_collection(bool explicit_gc,
 693                      bool clear_all_soft_refs,
 694                      size_t word_size);
 695 
 696   // Callback from VM_G1CollectFull operation.
 697   // Perform a full collection.
 698   virtual void do_full_collection(bool clear_all_soft_refs);
 699 
 700   // Resize the heap if necessary after a full collection.  If this is
 701   // after a collect-for allocation, "word_size" is the allocation size,
 702   // and will be considered part of the used portion of the heap.
 703   void resize_if_necessary_after_full_collection(size_t word_size);
 704 
 705   // Callback from VM_G1CollectForAllocation operation.
 706   // This function does everything necessary/possible to satisfy a
 707   // failed allocation request (including collection, expansion, etc.)
 708   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 709 
 710   // Attempting to expand the heap sufficiently
 711   // to support an allocation of the given "word_size".  If
 712   // successful, perform the allocation and return the address of the
 713   // allocated block, or else "NULL".
 714   HeapWord* expand_and_allocate(size_t word_size);
 715 
 716   // Process any reference objects discovered during
 717   // an incremental evacuation pause.
 718   void process_discovered_references(uint no_of_gc_workers);
 719 
 720   // Enqueue any remaining discovered references
 721   // after processing.
 722   void enqueue_discovered_references(uint no_of_gc_workers);
 723 
 724 public:
 725 
 726   G1MonitoringSupport* g1mm() {
 727     assert(_g1mm != NULL, "should have been initialized");
 728     return _g1mm;
 729   }
 730 
 731   // Expand the garbage-first heap by at least the given size (in bytes!).
 732   // Returns true if the heap was expanded by the requested amount;
 733   // false otherwise.
 734   // (Rounds up to a HeapRegion boundary.)
 735   bool expand(size_t expand_bytes);
 736 
 737   // Do anything common to GC's.
 738   virtual void gc_prologue(bool full);
 739   virtual void gc_epilogue(bool full);
 740 
 741   inline void set_humongous_is_live(oop obj);
 742 
 743   bool humongous_is_live(uint region) {
 744     return _humongous_is_live.is_live(region);
 745   }
 746 
 747   // Returns whether the given region (which must be a humongous (start) region)
 748   // is to be considered conservatively live regardless of any other conditions.
 749   bool humongous_region_is_always_live(uint index);
 750   // Register the given region to be part of the collection set.
 751   inline void register_humongous_region_with_in_cset_fast_test(uint index);
 752   // Register regions with humongous objects (actually on the start region) in
 753   // the in_cset_fast_test table.
 754   void register_humongous_regions_with_in_cset_fast_test();
 755   // We register a region with the fast "in collection set" test. We
 756   // simply set to true the array slot corresponding to this region.
 757   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 758     _in_cset_fast_test.set_in_cset(r->hrs_index());
 759   }
 760 
 761   // This is a fast test on whether a reference points into the
 762   // collection set or not. Assume that the reference
 763   // points into the heap.
 764   inline bool in_cset_fast_test(oop obj);
 765 
 766   void clear_cset_fast_test() {
 767     _in_cset_fast_test.clear();
 768   }
 769 
 770   // This is called at the start of either a concurrent cycle or a Full
 771   // GC to update the number of old marking cycles started.
 772   void increment_old_marking_cycles_started();
 773 
 774   // This is called at the end of either a concurrent cycle or a Full
 775   // GC to update the number of old marking cycles completed. Those two
 776   // can happen in a nested fashion, i.e., we start a concurrent
 777   // cycle, a Full GC happens half-way through it which ends first,
 778   // and then the cycle notices that a Full GC happened and ends
 779   // too. The concurrent parameter is a boolean to help us do a bit
 780   // tighter consistency checking in the method. If concurrent is
 781   // false, the caller is the inner caller in the nesting (i.e., the
 782   // Full GC). If concurrent is true, the caller is the outer caller
 783   // in this nesting (i.e., the concurrent cycle). Further nesting is
 784   // not currently supported. The end of this call also notifies
 785   // the FullGCCount_lock in case a Java thread is waiting for a full
 786   // GC to happen (e.g., it called System.gc() with
 787   // +ExplicitGCInvokesConcurrent).
 788   void increment_old_marking_cycles_completed(bool concurrent);
 789 
 790   unsigned int old_marking_cycles_completed() {
 791     return _old_marking_cycles_completed;
 792   }
 793 
 794   void register_concurrent_cycle_start(const Ticks& start_time);
 795   void register_concurrent_cycle_end();
 796   void trace_heap_after_concurrent_cycle();
 797 
 798   G1YCType yc_type();
 799 
 800   G1HRPrinter* hr_printer() { return &_hr_printer; }
 801 
 802   // Frees a non-humongous region by initializing its contents and
 803   // adding it to the free list that's passed as a parameter (this is
 804   // usually a local list which will be appended to the master free
 805   // list later). The used bytes of freed regions are accumulated in
 806   // pre_used. If par is true, the region's RSet will not be freed
 807   // up. The assumption is that this will be done later.
 808   // The locked parameter indicates if the caller has already taken
 809   // care of proper synchronization. This may allow some optimizations.
 810   void free_region(HeapRegion* hr,
 811                    FreeRegionList* free_list,
 812                    bool par,
 813                    bool locked = false);
 814 
 815   // Frees a humongous region by collapsing it into individual regions
 816   // and calling free_region() for each of them. The freed regions
 817   // will be added to the free list that's passed as a parameter (this
 818   // is usually a local list which will be appended to the master free
 819   // list later). The used bytes of freed regions are accumulated in
 820   // pre_used. If par is true, the region's RSet will not be freed
 821   // up. The assumption is that this will be done later.
 822   void free_humongous_region(HeapRegion* hr,
 823                              FreeRegionList* free_list,
 824                              bool par);
 825 protected:
 826 
 827   // Shrink the garbage-first heap by at most the given size (in bytes!).
 828   // (Rounds down to a HeapRegion boundary.)
 829   virtual void shrink(size_t expand_bytes);
 830   void shrink_helper(size_t expand_bytes);
 831 
 832   #if TASKQUEUE_STATS
 833   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 834   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 835   void reset_taskqueue_stats();
 836   #endif // TASKQUEUE_STATS
 837 
 838   // Schedule the VM operation that will do an evacuation pause to
 839   // satisfy an allocation request of word_size. *succeeded will
 840   // return whether the VM operation was successful (it did do an
 841   // evacuation pause) or not (another thread beat us to it or the GC
 842   // locker was active). Given that we should not be holding the
 843   // Heap_lock when we enter this method, we will pass the
 844   // gc_count_before (i.e., total_collections()) as a parameter since
 845   // it has to be read while holding the Heap_lock. Currently, both
 846   // methods that call do_collection_pause() release the Heap_lock
 847   // before the call, so it's easy to read gc_count_before just before.
 848   HeapWord* do_collection_pause(size_t         word_size,
 849                                 unsigned int   gc_count_before,
 850                                 bool*          succeeded,
 851                                 GCCause::Cause gc_cause);
 852 
 853   // The guts of the incremental collection pause, executed by the vm
 854   // thread. It returns false if it is unable to do the collection due
 855   // to the GC locker being active, true otherwise
 856   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 857 
 858   // Actually do the work of evacuating the collection set.
 859   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 860 
 861   // The g1 remembered set of the heap.
 862   G1RemSet* _g1_rem_set;
 863 
 864   // A set of cards that cover the objects for which the Rsets should be updated
 865   // concurrently after the collection.
 866   DirtyCardQueueSet _dirty_card_queue_set;
 867 
 868   // The closure used to refine a single card.
 869   RefineCardTableEntryClosure* _refine_cte_cl;
 870 
 871   // A function to check the consistency of dirty card logs.
 872   void check_ct_logs_at_safepoint();
 873 
 874   // A DirtyCardQueueSet that is used to hold cards that contain
 875   // references into the current collection set. This is used to
 876   // update the remembered sets of the regions in the collection
 877   // set in the event of an evacuation failure.
 878   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 879 
 880   // After a collection pause, make the regions in the CS into free
 881   // regions.
 882   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 883 
 884   // Abandon the current collection set without recording policy
 885   // statistics or updating free lists.
 886   void abandon_collection_set(HeapRegion* cs_head);
 887 
 888   // Applies "scan_non_heap_roots" to roots outside the heap,
 889   // "scan_rs" to roots inside the heap (having done "set_region" to
 890   // indicate the region in which the root resides),
 891   // and does "scan_metadata" If "scan_rs" is
 892   // NULL, then this step is skipped.  The "worker_i"
 893   // param is for use with parallel roots processing, and should be
 894   // the "i" of the calling parallel worker thread's work(i) function.
 895   // In the sequential case this param will be ignored.
 896   void g1_process_roots(OopClosure* scan_non_heap_roots,
 897                         OopClosure* scan_non_heap_weak_roots,
 898                         OopsInHeapRegionClosure* scan_rs,
 899                         CLDClosure* scan_strong_clds,
 900                         CLDClosure* scan_weak_clds,
 901                         CodeBlobClosure* scan_strong_code,
 902                         uint worker_i);
 903 
 904   // Notifies all the necessary spaces that the committed space has
 905   // been updated (either expanded or shrunk). It should be called
 906   // after _g1_storage is updated.
 907   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 908 
 909   // The concurrent marker (and the thread it runs in.)
 910   ConcurrentMark* _cm;
 911   ConcurrentMarkThread* _cmThread;
 912   bool _mark_in_progress;
 913 
 914   // The concurrent refiner.
 915   ConcurrentG1Refine* _cg1r;
 916 
 917   // The parallel task queues
 918   RefToScanQueueSet *_task_queues;
 919 
 920   // True iff a evacuation has failed in the current collection.
 921   bool _evacuation_failed;
 922 
 923   EvacuationFailedInfo* _evacuation_failed_info_array;
 924 
 925   // Failed evacuations cause some logical from-space objects to have
 926   // forwarding pointers to themselves.  Reset them.
 927   void remove_self_forwarding_pointers();
 928 
 929   // Together, these store an object with a preserved mark, and its mark value.
 930   Stack<oop, mtGC>     _objs_with_preserved_marks;
 931   Stack<markOop, mtGC> _preserved_marks_of_objs;
 932 
 933   // Preserve the mark of "obj", if necessary, in preparation for its mark
 934   // word being overwritten with a self-forwarding-pointer.
 935   void preserve_mark_if_necessary(oop obj, markOop m);
 936 
 937   // The stack of evac-failure objects left to be scanned.
 938   GrowableArray<oop>*    _evac_failure_scan_stack;
 939   // The closure to apply to evac-failure objects.
 940 
 941   OopsInHeapRegionClosure* _evac_failure_closure;
 942   // Set the field above.
 943   void
 944   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 945     _evac_failure_closure = evac_failure_closure;
 946   }
 947 
 948   // Push "obj" on the scan stack.
 949   void push_on_evac_failure_scan_stack(oop obj);
 950   // Process scan stack entries until the stack is empty.
 951   void drain_evac_failure_scan_stack();
 952   // True iff an invocation of "drain_scan_stack" is in progress; to
 953   // prevent unnecessary recursion.
 954   bool _drain_in_progress;
 955 
 956   // Do any necessary initialization for evacuation-failure handling.
 957   // "cl" is the closure that will be used to process evac-failure
 958   // objects.
 959   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 960   // Do any necessary cleanup for evacuation-failure handling data
 961   // structures.
 962   void finalize_for_evac_failure();
 963 
 964   // An attempt to evacuate "obj" has failed; take necessary steps.
 965   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 966   void handle_evacuation_failure_common(oop obj, markOop m);
 967 
 968 #ifndef PRODUCT
 969   // Support for forcing evacuation failures. Analogous to
 970   // PromotionFailureALot for the other collectors.
 971 
 972   // Records whether G1EvacuationFailureALot should be in effect
 973   // for the current GC
 974   bool _evacuation_failure_alot_for_current_gc;
 975 
 976   // Used to record the GC number for interval checking when
 977   // determining whether G1EvaucationFailureALot is in effect
 978   // for the current GC.
 979   size_t _evacuation_failure_alot_gc_number;
 980 
 981   // Count of the number of evacuations between failures.
 982   volatile size_t _evacuation_failure_alot_count;
 983 
 984   // Set whether G1EvacuationFailureALot should be in effect
 985   // for the current GC (based upon the type of GC and which
 986   // command line flags are set);
 987   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 988                                                   bool during_initial_mark,
 989                                                   bool during_marking);
 990 
 991   inline void set_evacuation_failure_alot_for_current_gc();
 992 
 993   // Return true if it's time to cause an evacuation failure.
 994   inline bool evacuation_should_fail();
 995 
 996   // Reset the G1EvacuationFailureALot counters.  Should be called at
 997   // the end of an evacuation pause in which an evacuation failure occurred.
 998   inline void reset_evacuation_should_fail();
 999 #endif // !PRODUCT
1000 
1001   // ("Weak") Reference processing support.
1002   //
1003   // G1 has 2 instances of the reference processor class. One
1004   // (_ref_processor_cm) handles reference object discovery
1005   // and subsequent processing during concurrent marking cycles.
1006   //
1007   // The other (_ref_processor_stw) handles reference object
1008   // discovery and processing during full GCs and incremental
1009   // evacuation pauses.
1010   //
1011   // During an incremental pause, reference discovery will be
1012   // temporarily disabled for _ref_processor_cm and will be
1013   // enabled for _ref_processor_stw. At the end of the evacuation
1014   // pause references discovered by _ref_processor_stw will be
1015   // processed and discovery will be disabled. The previous
1016   // setting for reference object discovery for _ref_processor_cm
1017   // will be re-instated.
1018   //
1019   // At the start of marking:
1020   //  * Discovery by the CM ref processor is verified to be inactive
1021   //    and it's discovered lists are empty.
1022   //  * Discovery by the CM ref processor is then enabled.
1023   //
1024   // At the end of marking:
1025   //  * Any references on the CM ref processor's discovered
1026   //    lists are processed (possibly MT).
1027   //
1028   // At the start of full GC we:
1029   //  * Disable discovery by the CM ref processor and
1030   //    empty CM ref processor's discovered lists
1031   //    (without processing any entries).
1032   //  * Verify that the STW ref processor is inactive and it's
1033   //    discovered lists are empty.
1034   //  * Temporarily set STW ref processor discovery as single threaded.
1035   //  * Temporarily clear the STW ref processor's _is_alive_non_header
1036   //    field.
1037   //  * Finally enable discovery by the STW ref processor.
1038   //
1039   // The STW ref processor is used to record any discovered
1040   // references during the full GC.
1041   //
1042   // At the end of a full GC we:
1043   //  * Enqueue any reference objects discovered by the STW ref processor
1044   //    that have non-live referents. This has the side-effect of
1045   //    making the STW ref processor inactive by disabling discovery.
1046   //  * Verify that the CM ref processor is still inactive
1047   //    and no references have been placed on it's discovered
1048   //    lists (also checked as a precondition during initial marking).
1049 
1050   // The (stw) reference processor...
1051   ReferenceProcessor* _ref_processor_stw;
1052 
1053   STWGCTimer* _gc_timer_stw;
1054   ConcurrentGCTimer* _gc_timer_cm;
1055 
1056   G1OldTracer* _gc_tracer_cm;
1057   G1NewTracer* _gc_tracer_stw;
1058 
1059   // During reference object discovery, the _is_alive_non_header
1060   // closure (if non-null) is applied to the referent object to
1061   // determine whether the referent is live. If so then the
1062   // reference object does not need to be 'discovered' and can
1063   // be treated as a regular oop. This has the benefit of reducing
1064   // the number of 'discovered' reference objects that need to
1065   // be processed.
1066   //
1067   // Instance of the is_alive closure for embedding into the
1068   // STW reference processor as the _is_alive_non_header field.
1069   // Supplying a value for the _is_alive_non_header field is
1070   // optional but doing so prevents unnecessary additions to
1071   // the discovered lists during reference discovery.
1072   G1STWIsAliveClosure _is_alive_closure_stw;
1073 
1074   // The (concurrent marking) reference processor...
1075   ReferenceProcessor* _ref_processor_cm;
1076 
1077   // Instance of the concurrent mark is_alive closure for embedding
1078   // into the Concurrent Marking reference processor as the
1079   // _is_alive_non_header field. Supplying a value for the
1080   // _is_alive_non_header field is optional but doing so prevents
1081   // unnecessary additions to the discovered lists during reference
1082   // discovery.
1083   G1CMIsAliveClosure _is_alive_closure_cm;
1084 
1085   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1086   HeapRegion** _worker_cset_start_region;
1087 
1088   // Time stamp to validate the regions recorded in the cache
1089   // used by G1CollectedHeap::start_cset_region_for_worker().
1090   // The heap region entry for a given worker is valid iff
1091   // the associated time stamp value matches the current value
1092   // of G1CollectedHeap::_gc_time_stamp.
1093   unsigned int* _worker_cset_start_region_time_stamp;
1094 
1095   enum G1H_process_roots_tasks {
1096     G1H_PS_filter_satb_buffers,
1097     G1H_PS_refProcessor_oops_do,
1098     // Leave this one last.
1099     G1H_PS_NumElements
1100   };
1101 
1102   SubTasksDone* _process_strong_tasks;
1103 
1104   volatile bool _free_regions_coming;
1105 
1106 public:
1107 
1108   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1109 
1110   void set_refine_cte_cl_concurrency(bool concurrent);
1111 
1112   RefToScanQueue *task_queue(int i) const;
1113 
1114   // A set of cards where updates happened during the GC
1115   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1116 
1117   // A DirtyCardQueueSet that is used to hold cards that contain
1118   // references into the current collection set. This is used to
1119   // update the remembered sets of the regions in the collection
1120   // set in the event of an evacuation failure.
1121   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1122         { return _into_cset_dirty_card_queue_set; }
1123 
1124   // Create a G1CollectedHeap with the specified policy.
1125   // Must call the initialize method afterwards.
1126   // May not return if something goes wrong.
1127   G1CollectedHeap(G1CollectorPolicy* policy);
1128 
1129   // Initialize the G1CollectedHeap to have the initial and
1130   // maximum sizes and remembered and barrier sets
1131   // specified by the policy object.
1132   jint initialize();
1133 
1134   virtual void stop();
1135 
1136   // Return the (conservative) maximum heap alignment for any G1 heap
1137   static size_t conservative_max_heap_alignment();
1138 
1139   // Initialize weak reference processing.
1140   virtual void ref_processing_init();
1141 
1142   void set_par_threads(uint t) {
1143     SharedHeap::set_par_threads(t);
1144     // Done in SharedHeap but oddly there are
1145     // two _process_strong_tasks's in a G1CollectedHeap
1146     // so do it here too.
1147     _process_strong_tasks->set_n_threads(t);
1148   }
1149 
1150   // Set _n_par_threads according to a policy TBD.
1151   void set_par_threads();
1152 
1153   void set_n_termination(int t) {
1154     _process_strong_tasks->set_n_threads(t);
1155   }
1156 
1157   virtual CollectedHeap::Name kind() const {
1158     return CollectedHeap::G1CollectedHeap;
1159   }
1160 
1161   // The current policy object for the collector.
1162   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1163 
1164   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1165 
1166   // Adaptive size policy.  No such thing for g1.
1167   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1168 
1169   // The rem set and barrier set.
1170   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1171 
1172   unsigned get_gc_time_stamp() {
1173     return _gc_time_stamp;
1174   }
1175 
1176   inline void reset_gc_time_stamp();
1177 
1178   void check_gc_time_stamps() PRODUCT_RETURN;
1179 
1180   inline void increment_gc_time_stamp();
1181 
1182   // Reset the given region's GC timestamp. If it's starts humongous,
1183   // also reset the GC timestamp of its corresponding
1184   // continues humongous regions too.
1185   void reset_gc_time_stamps(HeapRegion* hr);
1186 
1187   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1188                                   DirtyCardQueue* into_cset_dcq,
1189                                   bool concurrent, uint worker_i);
1190 
1191   // The shared block offset table array.
1192   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1193 
1194   // Reference Processing accessors
1195 
1196   // The STW reference processor....
1197   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1198 
1199   // The Concurrent Marking reference processor...
1200   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1201 
1202   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1203   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1204 
1205   virtual size_t capacity() const;
1206   virtual size_t used() const;
1207   // This should be called when we're not holding the heap lock. The
1208   // result might be a bit inaccurate.
1209   size_t used_unlocked() const;
1210   size_t recalculate_used() const;
1211 
1212   // These virtual functions do the actual allocation.
1213   // Some heaps may offer a contiguous region for shared non-blocking
1214   // allocation, via inlined code (by exporting the address of the top and
1215   // end fields defining the extent of the contiguous allocation region.)
1216   // But G1CollectedHeap doesn't yet support this.
1217 
1218   virtual bool is_maximal_no_gc() const {
1219     return _g1_storage.uncommitted_size() == 0;
1220   }
1221 
1222   // The total number of regions in the heap.
1223   uint n_regions() { return _hrs.length(); }
1224 
1225   // The max number of regions in the heap.
1226   uint max_regions() { return _hrs.max_length(); }
1227 
1228   // The number of regions that are completely free.
1229   uint free_regions() { return _free_list.length(); }
1230 
1231   // The number of regions that are not completely free.
1232   uint used_regions() { return n_regions() - free_regions(); }
1233 
1234   // The number of regions available for "regular" expansion.
1235   uint expansion_regions() { return _expansion_regions; }
1236 
1237   // Factory method for HeapRegion instances. It will return NULL if
1238   // the allocation fails.
1239   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1240 
1241   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1242   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1243   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1244   void verify_dirty_young_regions() PRODUCT_RETURN;
1245 
1246 #ifndef PRODUCT
1247   // Make sure that the given bitmap has no marked objects in the
1248   // range [from,limit). If it does, print an error message and return
1249   // false. Otherwise, just return true. bitmap_name should be "prev"
1250   // or "next".
1251   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1252                                 HeapWord* from, HeapWord* limit);
1253 
1254   // Verify that the prev / next bitmap range [tams,end) for the given
1255   // region has no marks. Return true if all is well, false if errors
1256   // are detected.
1257   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1258 #endif // PRODUCT
1259 
1260   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1261   // the given region do not have any spurious marks. If errors are
1262   // detected, print appropriate error messages and crash.
1263   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1264 
1265   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1266   // have any spurious marks. If errors are detected, print
1267   // appropriate error messages and crash.
1268   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1269 
1270   // verify_region_sets() performs verification over the region
1271   // lists. It will be compiled in the product code to be used when
1272   // necessary (i.e., during heap verification).
1273   void verify_region_sets();
1274 
1275   // verify_region_sets_optional() is planted in the code for
1276   // list verification in non-product builds (and it can be enabled in
1277   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1278 #if HEAP_REGION_SET_FORCE_VERIFY
1279   void verify_region_sets_optional() {
1280     verify_region_sets();
1281   }
1282 #else // HEAP_REGION_SET_FORCE_VERIFY
1283   void verify_region_sets_optional() { }
1284 #endif // HEAP_REGION_SET_FORCE_VERIFY
1285 
1286 #ifdef ASSERT
1287   bool is_on_master_free_list(HeapRegion* hr) {
1288     return hr->containing_set() == &_free_list;
1289   }
1290 #endif // ASSERT
1291 
1292   // Wrapper for the region list operations that can be called from
1293   // methods outside this class.
1294 
1295   void secondary_free_list_add(FreeRegionList* list) {
1296     _secondary_free_list.add_ordered(list);
1297   }
1298 
1299   void append_secondary_free_list() {
1300     _free_list.add_ordered(&_secondary_free_list);
1301   }
1302 
1303   void append_secondary_free_list_if_not_empty_with_lock() {
1304     // If the secondary free list looks empty there's no reason to
1305     // take the lock and then try to append it.
1306     if (!_secondary_free_list.is_empty()) {
1307       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1308       append_secondary_free_list();
1309     }
1310   }
1311 
1312   inline void old_set_remove(HeapRegion* hr);
1313 
1314   size_t non_young_capacity_bytes() {
1315     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1316   }
1317 
1318   void set_free_regions_coming();
1319   void reset_free_regions_coming();
1320   bool free_regions_coming() { return _free_regions_coming; }
1321   void wait_while_free_regions_coming();
1322 
1323   // Determine whether the given region is one that we are using as an
1324   // old GC alloc region.
1325   bool is_old_gc_alloc_region(HeapRegion* hr) {
1326     return hr == _retained_old_gc_alloc_region;
1327   }
1328 
1329   // Perform a collection of the heap; intended for use in implementing
1330   // "System.gc".  This probably implies as full a collection as the
1331   // "CollectedHeap" supports.
1332   virtual void collect(GCCause::Cause cause);
1333 
1334   // The same as above but assume that the caller holds the Heap_lock.
1335   void collect_locked(GCCause::Cause cause);
1336 
1337   // True iff an evacuation has failed in the most-recent collection.
1338   bool evacuation_failed() { return _evacuation_failed; }
1339 
1340   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1341   void prepend_to_freelist(FreeRegionList* list);
1342   void decrement_summary_bytes(size_t bytes);
1343 
1344   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1345   virtual bool is_in(const void* p) const;
1346 
1347   // Return "TRUE" iff the given object address is within the collection
1348   // set. Slow implementation.
1349   inline bool obj_in_cs(oop obj);
1350 
1351   inline bool is_in_cset(oop obj);
1352 
1353   inline bool is_in_cset_or_humongous(const oop obj);
1354 
1355   inline G1FastCSetBiasedMappedArray::in_cset_state_t in_cset_state(const oop obj);
1356 
1357   // Return "TRUE" iff the given object address is in the reserved
1358   // region of g1.
1359   bool is_in_g1_reserved(const void* p) const {
1360     return _g1_reserved.contains(p);
1361   }
1362 
1363   // Returns a MemRegion that corresponds to the space that has been
1364   // reserved for the heap
1365   MemRegion g1_reserved() {
1366     return _g1_reserved;
1367   }
1368 
1369   // Returns a MemRegion that corresponds to the space that has been
1370   // committed in the heap
1371   MemRegion g1_committed() {
1372     return _g1_committed;
1373   }
1374 
1375   virtual bool is_in_closed_subset(const void* p) const;
1376 
1377   G1SATBCardTableModRefBS* g1_barrier_set() {
1378     return (G1SATBCardTableModRefBS*) barrier_set();
1379   }
1380 
1381   // This resets the card table to all zeros.  It is used after
1382   // a collection pause which used the card table to claim cards.
1383   void cleanUpCardTable();
1384 
1385   // Iteration functions.
1386 
1387   // Iterate over all the ref-containing fields of all objects, calling
1388   // "cl.do_oop" on each.
1389   virtual void oop_iterate(ExtendedOopClosure* cl);
1390 
1391   // Same as above, restricted to a memory region.
1392   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1393 
1394   // Iterate over all objects, calling "cl.do_object" on each.
1395   virtual void object_iterate(ObjectClosure* cl);
1396 
1397   virtual void safe_object_iterate(ObjectClosure* cl) {
1398     object_iterate(cl);
1399   }
1400 
1401   // Iterate over all spaces in use in the heap, in ascending address order.
1402   virtual void space_iterate(SpaceClosure* cl);
1403 
1404   // Iterate over heap regions, in address order, terminating the
1405   // iteration early if the "doHeapRegion" method returns "true".
1406   void heap_region_iterate(HeapRegionClosure* blk) const;
1407 
1408   // Return the region with the given index. It assumes the index is valid.
1409   inline HeapRegion* region_at(uint index) const;
1410 
1411   // Calculate the region index of the given address. Given address must be
1412   // within the heap.
1413   inline uint addr_to_region(HeapWord* addr) const;
1414 
1415   // Divide the heap region sequence into "chunks" of some size (the number
1416   // of regions divided by the number of parallel threads times some
1417   // overpartition factor, currently 4).  Assumes that this will be called
1418   // in parallel by ParallelGCThreads worker threads with distinct worker
1419   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1420   // calls will use the same "claim_value", and that that claim value is
1421   // different from the claim_value of any heap region before the start of
1422   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1423   // attempting to claim the first region in each chunk, and, if
1424   // successful, applying the closure to each region in the chunk (and
1425   // setting the claim value of the second and subsequent regions of the
1426   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1427   // i.e., that a closure never attempt to abort a traversal.
1428   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1429                                        uint worker,
1430                                        uint no_of_par_workers,
1431                                        jint claim_value);
1432 
1433   // It resets all the region claim values to the default.
1434   void reset_heap_region_claim_values();
1435 
1436   // Resets the claim values of regions in the current
1437   // collection set to the default.
1438   void reset_cset_heap_region_claim_values();
1439 
1440 #ifdef ASSERT
1441   bool check_heap_region_claim_values(jint claim_value);
1442 
1443   // Same as the routine above but only checks regions in the
1444   // current collection set.
1445   bool check_cset_heap_region_claim_values(jint claim_value);
1446 #endif // ASSERT
1447 
1448   // Clear the cached cset start regions and (more importantly)
1449   // the time stamps. Called when we reset the GC time stamp.
1450   void clear_cset_start_regions();
1451 
1452   // Given the id of a worker, obtain or calculate a suitable
1453   // starting region for iterating over the current collection set.
1454   HeapRegion* start_cset_region_for_worker(uint worker_i);
1455 
1456   // This is a convenience method that is used by the
1457   // HeapRegionIterator classes to calculate the starting region for
1458   // each worker so that they do not all start from the same region.
1459   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1460 
1461   // Iterate over the regions (if any) in the current collection set.
1462   void collection_set_iterate(HeapRegionClosure* blk);
1463 
1464   // As above but starting from region r
1465   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1466 
1467   // Returns the first (lowest address) compactible space in the heap.
1468   virtual CompactibleSpace* first_compactible_space();
1469 
1470   // A CollectedHeap will contain some number of spaces.  This finds the
1471   // space containing a given address, or else returns NULL.
1472   virtual Space* space_containing(const void* addr) const;
1473 
1474   // Returns the HeapRegion that contains addr. addr must not be NULL.
1475   template <class T>
1476   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1477 
1478   // Returns the HeapRegion that contains addr. addr must not be NULL.
1479   // If addr is within a humongous continues region, it returns its humongous start region.
1480   template <class T>
1481   inline HeapRegion* heap_region_containing(const T addr) const;
1482 
1483   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1484   // each address in the (reserved) heap is a member of exactly
1485   // one block.  The defining characteristic of a block is that it is
1486   // possible to find its size, and thus to progress forward to the next
1487   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1488   // represent Java objects, or they might be free blocks in a
1489   // free-list-based heap (or subheap), as long as the two kinds are
1490   // distinguishable and the size of each is determinable.
1491 
1492   // Returns the address of the start of the "block" that contains the
1493   // address "addr".  We say "blocks" instead of "object" since some heaps
1494   // may not pack objects densely; a chunk may either be an object or a
1495   // non-object.
1496   virtual HeapWord* block_start(const void* addr) const;
1497 
1498   // Requires "addr" to be the start of a chunk, and returns its size.
1499   // "addr + size" is required to be the start of a new chunk, or the end
1500   // of the active area of the heap.
1501   virtual size_t block_size(const HeapWord* addr) const;
1502 
1503   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1504   // the block is an object.
1505   virtual bool block_is_obj(const HeapWord* addr) const;
1506 
1507   // Does this heap support heap inspection? (+PrintClassHistogram)
1508   virtual bool supports_heap_inspection() const { return true; }
1509 
1510   // Section on thread-local allocation buffers (TLABs)
1511   // See CollectedHeap for semantics.
1512 
1513   bool supports_tlab_allocation() const;
1514   size_t tlab_capacity(Thread* ignored) const;
1515   size_t tlab_used(Thread* ignored) const;
1516   size_t max_tlab_size() const;
1517   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1518 
1519   // Can a compiler initialize a new object without store barriers?
1520   // This permission only extends from the creation of a new object
1521   // via a TLAB up to the first subsequent safepoint. If such permission
1522   // is granted for this heap type, the compiler promises to call
1523   // defer_store_barrier() below on any slow path allocation of
1524   // a new object for which such initializing store barriers will
1525   // have been elided. G1, like CMS, allows this, but should be
1526   // ready to provide a compensating write barrier as necessary
1527   // if that storage came out of a non-young region. The efficiency
1528   // of this implementation depends crucially on being able to
1529   // answer very efficiently in constant time whether a piece of
1530   // storage in the heap comes from a young region or not.
1531   // See ReduceInitialCardMarks.
1532   virtual bool can_elide_tlab_store_barriers() const {
1533     return true;
1534   }
1535 
1536   virtual bool card_mark_must_follow_store() const {
1537     return true;
1538   }
1539 
1540   inline bool is_in_young(const oop obj);
1541 
1542 #ifdef ASSERT
1543   virtual bool is_in_partial_collection(const void* p);
1544 #endif
1545 
1546   virtual bool is_scavengable(const void* addr);
1547 
1548   // We don't need barriers for initializing stores to objects
1549   // in the young gen: for the SATB pre-barrier, there is no
1550   // pre-value that needs to be remembered; for the remembered-set
1551   // update logging post-barrier, we don't maintain remembered set
1552   // information for young gen objects.
1553   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1554 
1555   // Returns "true" iff the given word_size is "very large".
1556   static bool isHumongous(size_t word_size) {
1557     // Note this has to be strictly greater-than as the TLABs
1558     // are capped at the humongous threshold and we want to
1559     // ensure that we don't try to allocate a TLAB as
1560     // humongous and that we don't allocate a humongous
1561     // object in a TLAB.
1562     return word_size > _humongous_object_threshold_in_words;
1563   }
1564 
1565   // Update mod union table with the set of dirty cards.
1566   void updateModUnion();
1567 
1568   // Set the mod union bits corresponding to the given memRegion.  Note
1569   // that this is always a safe operation, since it doesn't clear any
1570   // bits.
1571   void markModUnionRange(MemRegion mr);
1572 
1573   // Records the fact that a marking phase is no longer in progress.
1574   void set_marking_complete() {
1575     _mark_in_progress = false;
1576   }
1577   void set_marking_started() {
1578     _mark_in_progress = true;
1579   }
1580   bool mark_in_progress() {
1581     return _mark_in_progress;
1582   }
1583 
1584   // Print the maximum heap capacity.
1585   virtual size_t max_capacity() const;
1586 
1587   virtual jlong millis_since_last_gc();
1588 
1589 
1590   // Convenience function to be used in situations where the heap type can be
1591   // asserted to be this type.
1592   static G1CollectedHeap* heap();
1593 
1594   void set_region_short_lived_locked(HeapRegion* hr);
1595   // add appropriate methods for any other surv rate groups
1596 
1597   YoungList* young_list() const { return _young_list; }
1598 
1599   // debugging
1600   bool check_young_list_well_formed() {
1601     return _young_list->check_list_well_formed();
1602   }
1603 
1604   bool check_young_list_empty(bool check_heap,
1605                               bool check_sample = true);
1606 
1607   // *** Stuff related to concurrent marking.  It's not clear to me that so
1608   // many of these need to be public.
1609 
1610   // The functions below are helper functions that a subclass of
1611   // "CollectedHeap" can use in the implementation of its virtual
1612   // functions.
1613   // This performs a concurrent marking of the live objects in a
1614   // bitmap off to the side.
1615   void doConcurrentMark();
1616 
1617   bool isMarkedPrev(oop obj) const;
1618   bool isMarkedNext(oop obj) const;
1619 
1620   // Determine if an object is dead, given the object and also
1621   // the region to which the object belongs. An object is dead
1622   // iff a) it was not allocated since the last mark and b) it
1623   // is not marked.
1624   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1625     return
1626       !hr->obj_allocated_since_prev_marking(obj) &&
1627       !isMarkedPrev(obj);
1628   }
1629 
1630   // This function returns true when an object has been
1631   // around since the previous marking and hasn't yet
1632   // been marked during this marking.
1633   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1634     return
1635       !hr->obj_allocated_since_next_marking(obj) &&
1636       !isMarkedNext(obj);
1637   }
1638 
1639   // Determine if an object is dead, given only the object itself.
1640   // This will find the region to which the object belongs and
1641   // then call the region version of the same function.
1642 
1643   // Added if it is NULL it isn't dead.
1644 
1645   inline bool is_obj_dead(const oop obj) const;
1646 
1647   inline bool is_obj_ill(const oop obj) const;
1648 
1649   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1650   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1651   bool is_marked(oop obj, VerifyOption vo);
1652   const char* top_at_mark_start_str(VerifyOption vo);
1653 
1654   ConcurrentMark* concurrent_mark() const { return _cm; }
1655 
1656   // Refinement
1657 
1658   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1659 
1660   // The dirty cards region list is used to record a subset of regions
1661   // whose cards need clearing. The list if populated during the
1662   // remembered set scanning and drained during the card table
1663   // cleanup. Although the methods are reentrant, population/draining
1664   // phases must not overlap. For synchronization purposes the last
1665   // element on the list points to itself.
1666   HeapRegion* _dirty_cards_region_list;
1667   void push_dirty_cards_region(HeapRegion* hr);
1668   HeapRegion* pop_dirty_cards_region();
1669 
1670   // Optimized nmethod scanning support routines
1671 
1672   // Register the given nmethod with the G1 heap.
1673   virtual void register_nmethod(nmethod* nm);
1674 
1675   // Unregister the given nmethod from the G1 heap.
1676   virtual void unregister_nmethod(nmethod* nm);
1677 
1678   // Migrate the nmethods in the code root lists of the regions
1679   // in the collection set to regions in to-space. In the event
1680   // of an evacuation failure, nmethods that reference objects
1681   // that were not successfully evacuated are not migrated.
1682   void migrate_strong_code_roots();
1683 
1684   // Free up superfluous code root memory.
1685   void purge_code_root_memory();
1686 
1687   // Rebuild the strong code root lists for each region
1688   // after a full GC.
1689   void rebuild_strong_code_roots();
1690 
1691   // Delete entries for dead interned string and clean up unreferenced symbols
1692   // in symbol table, possibly in parallel.
1693   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1694 
1695   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1696   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1697 
1698   // Redirty logged cards in the refinement queue.
1699   void redirty_logged_cards();
1700   // Verification
1701 
1702   // The following is just to alert the verification code
1703   // that a full collection has occurred and that the
1704   // remembered sets are no longer up to date.
1705   bool _full_collection;
1706   void set_full_collection() { _full_collection = true;}
1707   void clear_full_collection() {_full_collection = false;}
1708   bool full_collection() {return _full_collection;}
1709 
1710   // Perform any cleanup actions necessary before allowing a verification.
1711   virtual void prepare_for_verify();
1712 
1713   // Perform verification.
1714 
1715   // vo == UsePrevMarking  -> use "prev" marking information,
1716   // vo == UseNextMarking -> use "next" marking information
1717   // vo == UseMarkWord    -> use the mark word in the object header
1718   //
1719   // NOTE: Only the "prev" marking information is guaranteed to be
1720   // consistent most of the time, so most calls to this should use
1721   // vo == UsePrevMarking.
1722   // Currently, there is only one case where this is called with
1723   // vo == UseNextMarking, which is to verify the "next" marking
1724   // information at the end of remark.
1725   // Currently there is only one place where this is called with
1726   // vo == UseMarkWord, which is to verify the marking during a
1727   // full GC.
1728   void verify(bool silent, VerifyOption vo);
1729 
1730   // Override; it uses the "prev" marking information
1731   virtual void verify(bool silent);
1732 
1733   // The methods below are here for convenience and dispatch the
1734   // appropriate method depending on value of the given VerifyOption
1735   // parameter. The values for that parameter, and their meanings,
1736   // are the same as those above.
1737 
1738   bool is_obj_dead_cond(const oop obj,
1739                         const HeapRegion* hr,
1740                         const VerifyOption vo) const;
1741 
1742   bool is_obj_dead_cond(const oop obj,
1743                         const VerifyOption vo) const;
1744 
1745   // Printing
1746 
1747   virtual void print_on(outputStream* st) const;
1748   virtual void print_extended_on(outputStream* st) const;
1749   virtual void print_on_error(outputStream* st) const;
1750 
1751   virtual void print_gc_threads_on(outputStream* st) const;
1752   virtual void gc_threads_do(ThreadClosure* tc) const;
1753 
1754   // Override
1755   void print_tracing_info() const;
1756 
1757   // The following two methods are helpful for debugging RSet issues.
1758   void print_cset_rsets() PRODUCT_RETURN;
1759   void print_all_rsets() PRODUCT_RETURN;
1760 
1761 public:
1762   size_t pending_card_num();
1763   size_t cards_scanned();
1764 
1765 protected:
1766   size_t _max_heap_capacity;
1767 };
1768 
1769 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1770 private:
1771   bool        _retired;
1772 
1773 public:
1774   G1ParGCAllocBuffer(size_t gclab_word_size);
1775   virtual ~G1ParGCAllocBuffer() {
1776     guarantee(_retired, "Allocation buffer has not been retired");
1777   }
1778 
1779   virtual void set_buf(HeapWord* buf) {
1780     ParGCAllocBuffer::set_buf(buf);
1781     _retired = false;
1782   }
1783 
1784   virtual void retire(bool end_of_gc, bool retain) {
1785     if (_retired) {
1786       return;
1787     }
1788     ParGCAllocBuffer::retire(end_of_gc, retain);
1789     _retired = true;
1790   }
1791 };
1792 
1793 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP