1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc/g1/concurrentMark.hpp"
  29 #include "gc/g1/evacuationInfo.hpp"
  30 #include "gc/g1/g1AllocRegion.hpp"
  31 #include "gc/g1/g1AllocationContext.hpp"
  32 #include "gc/g1/g1Allocator.hpp"
  33 #include "gc/g1/g1BiasedArray.hpp"
  34 #include "gc/g1/g1HRPrinter.hpp"
  35 #include "gc/g1/g1InCSetState.hpp"
  36 #include "gc/g1/g1MonitoringSupport.hpp"
  37 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc/g1/g1YCTypes.hpp"
  39 #include "gc/g1/hSpaceCounters.hpp"
  40 #include "gc/g1/heapRegionManager.hpp"
  41 #include "gc/g1/heapRegionSet.hpp"
  42 #include "gc/shared/barrierSet.hpp"
  43 #include "gc/shared/collectedHeap.hpp"
  44 #include "memory/memRegion.hpp"
  45 #include "utilities/stack.hpp"
  46 
  47 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  48 // It uses the "Garbage First" heap organization and algorithm, which
  49 // may combine concurrent marking with parallel, incremental compaction of
  50 // heap subsets that will yield large amounts of garbage.
  51 
  52 // Forward declarations
  53 class HeapRegion;
  54 class HRRSCleanupTask;
  55 class GenerationSpec;
  56 class OopsInHeapRegionClosure;
  57 class G1KlassScanClosure;
  58 class G1ParScanThreadState;
  59 class ObjectClosure;
  60 class SpaceClosure;
  61 class CompactibleSpaceClosure;
  62 class Space;
  63 class G1CollectorPolicy;
  64 class GenRemSet;
  65 class G1RemSet;
  66 class HeapRegionRemSetIterator;
  67 class ConcurrentMark;
  68 class ConcurrentMarkThread;
  69 class ConcurrentG1Refine;
  70 class ConcurrentGCTimer;
  71 class GenerationCounters;
  72 class STWGCTimer;
  73 class G1NewTracer;
  74 class G1OldTracer;
  75 class EvacuationFailedInfo;
  76 class nmethod;
  77 class Ticks;
  78 class FlexibleWorkGang;
  79 
  80 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  82 
  83 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  84 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  85 
  86 class YoungList : public CHeapObj<mtGC> {
  87 private:
  88   G1CollectedHeap* _g1h;
  89 
  90   HeapRegion* _head;
  91 
  92   HeapRegion* _survivor_head;
  93   HeapRegion* _survivor_tail;
  94 
  95   HeapRegion* _curr;
  96 
  97   uint        _length;
  98   uint        _survivor_length;
  99 
 100   size_t      _last_sampled_rs_lengths;
 101   size_t      _sampled_rs_lengths;
 102 
 103   void         empty_list(HeapRegion* list);
 104 
 105 public:
 106   YoungList(G1CollectedHeap* g1h);
 107 
 108   void         push_region(HeapRegion* hr);
 109   void         add_survivor_region(HeapRegion* hr);
 110 
 111   void         empty_list();
 112   bool         is_empty() { return _length == 0; }
 113   uint         length() { return _length; }
 114   uint         eden_length() { return length() - survivor_length(); }
 115   uint         survivor_length() { return _survivor_length; }
 116 
 117   // Currently we do not keep track of the used byte sum for the
 118   // young list and the survivors and it'd be quite a lot of work to
 119   // do so. When we'll eventually replace the young list with
 120   // instances of HeapRegionLinkedList we'll get that for free. So,
 121   // we'll report the more accurate information then.
 122   size_t       eden_used_bytes() {
 123     assert(length() >= survivor_length(), "invariant");
 124     return (size_t) eden_length() * HeapRegion::GrainBytes;
 125   }
 126   size_t       survivor_used_bytes() {
 127     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 128   }
 129 
 130   void rs_length_sampling_init();
 131   bool rs_length_sampling_more();
 132   void rs_length_sampling_next();
 133 
 134   void reset_sampled_info() {
 135     _last_sampled_rs_lengths =   0;
 136   }
 137   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 138 
 139   // for development purposes
 140   void reset_auxilary_lists();
 141   void clear() { _head = NULL; _length = 0; }
 142 
 143   void clear_survivors() {
 144     _survivor_head    = NULL;
 145     _survivor_tail    = NULL;
 146     _survivor_length  = 0;
 147   }
 148 
 149   HeapRegion* first_region() { return _head; }
 150   HeapRegion* first_survivor_region() { return _survivor_head; }
 151   HeapRegion* last_survivor_region() { return _survivor_tail; }
 152 
 153   // debugging
 154   bool          check_list_well_formed();
 155   bool          check_list_empty(bool check_sample = true);
 156   void          print();
 157 };
 158 
 159 // The G1 STW is alive closure.
 160 // An instance is embedded into the G1CH and used as the
 161 // (optional) _is_alive_non_header closure in the STW
 162 // reference processor. It is also extensively used during
 163 // reference processing during STW evacuation pauses.
 164 class G1STWIsAliveClosure: public BoolObjectClosure {
 165   G1CollectedHeap* _g1;
 166 public:
 167   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 168   bool do_object_b(oop p);
 169 };
 170 
 171 class RefineCardTableEntryClosure;
 172 
 173 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 174  private:
 175   void reset_from_card_cache(uint start_idx, size_t num_regions);
 176  public:
 177   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 178 };
 179 
 180 class G1CollectedHeap : public CollectedHeap {
 181   friend class VM_CollectForMetadataAllocation;
 182   friend class VM_G1CollectForAllocation;
 183   friend class VM_G1CollectFull;
 184   friend class VM_G1IncCollectionPause;
 185   friend class VMStructs;
 186   friend class MutatorAllocRegion;
 187   friend class SurvivorGCAllocRegion;
 188   friend class OldGCAllocRegion;
 189   friend class G1Allocator;
 190 
 191   // Closures used in implementation.
 192   friend class G1ParScanThreadState;
 193   friend class G1ParTask;
 194   friend class G1ParGCAllocator;
 195   friend class G1PrepareCompactClosure;
 196 
 197   // Other related classes.
 198   friend class HeapRegionClaimer;
 199 
 200   // Testing classes.
 201   friend class G1CheckCSetFastTableClosure;
 202 
 203 private:
 204   FlexibleWorkGang* _workers;
 205 
 206   static size_t _humongous_object_threshold_in_words;
 207 
 208   // The secondary free list which contains regions that have been
 209   // freed up during the cleanup process. This will be appended to
 210   // the master free list when appropriate.
 211   FreeRegionList _secondary_free_list;
 212 
 213   // It keeps track of the old regions.
 214   HeapRegionSet _old_set;
 215 
 216   // It keeps track of the humongous regions.
 217   HeapRegionSet _humongous_set;
 218 
 219   void eagerly_reclaim_humongous_regions();
 220 
 221   // The number of regions we could create by expansion.
 222   uint _expansion_regions;
 223 
 224   // The block offset table for the G1 heap.
 225   G1BlockOffsetSharedArray* _bot_shared;
 226 
 227   // Tears down the region sets / lists so that they are empty and the
 228   // regions on the heap do not belong to a region set / list. The
 229   // only exception is the humongous set which we leave unaltered. If
 230   // free_list_only is true, it will only tear down the master free
 231   // list. It is called before a Full GC (free_list_only == false) or
 232   // before heap shrinking (free_list_only == true).
 233   void tear_down_region_sets(bool free_list_only);
 234 
 235   // Rebuilds the region sets / lists so that they are repopulated to
 236   // reflect the contents of the heap. The only exception is the
 237   // humongous set which was not torn down in the first place. If
 238   // free_list_only is true, it will only rebuild the master free
 239   // list. It is called after a Full GC (free_list_only == false) or
 240   // after heap shrinking (free_list_only == true).
 241   void rebuild_region_sets(bool free_list_only);
 242 
 243   // Callback for region mapping changed events.
 244   G1RegionMappingChangedListener _listener;
 245 
 246   // The sequence of all heap regions in the heap.
 247   HeapRegionManager _hrm;
 248 
 249   // Class that handles the different kinds of allocations.
 250   G1Allocator* _allocator;
 251 
 252   // Statistics for each allocation context
 253   AllocationContextStats _allocation_context_stats;
 254 
 255   // PLAB sizing policy for survivors.
 256   PLABStats _survivor_plab_stats;
 257 
 258   // PLAB sizing policy for tenured objects.
 259   PLABStats _old_plab_stats;
 260 
 261   // It specifies whether we should attempt to expand the heap after a
 262   // region allocation failure. If heap expansion fails we set this to
 263   // false so that we don't re-attempt the heap expansion (it's likely
 264   // that subsequent expansion attempts will also fail if one fails).
 265   // Currently, it is only consulted during GC and it's reset at the
 266   // start of each GC.
 267   bool _expand_heap_after_alloc_failure;
 268 
 269   // It resets the mutator alloc region before new allocations can take place.
 270   void init_mutator_alloc_region();
 271 
 272   // It releases the mutator alloc region.
 273   void release_mutator_alloc_region();
 274 
 275   // It initializes the GC alloc regions at the start of a GC.
 276   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 277 
 278   // It releases the GC alloc regions at the end of a GC.
 279   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 280 
 281   // It does any cleanup that needs to be done on the GC alloc regions
 282   // before a Full GC.
 283   void abandon_gc_alloc_regions();
 284 
 285   // Helper for monitoring and management support.
 286   G1MonitoringSupport* _g1mm;
 287 
 288   // Records whether the region at the given index is (still) a
 289   // candidate for eager reclaim.  Only valid for humongous start
 290   // regions; other regions have unspecified values.  Humongous start
 291   // regions are initialized at start of collection pause, with
 292   // candidates removed from the set as they are found reachable from
 293   // roots or the young generation.
 294   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 295    protected:
 296     bool default_value() const { return false; }
 297    public:
 298     void clear() { G1BiasedMappedArray<bool>::clear(); }
 299     void set_candidate(uint region, bool value) {
 300       set_by_index(region, value);
 301     }
 302     bool is_candidate(uint region) {
 303       return get_by_index(region);
 304     }
 305   };
 306 
 307   HumongousReclaimCandidates _humongous_reclaim_candidates;
 308   // Stores whether during humongous object registration we found candidate regions.
 309   // If not, we can skip a few steps.
 310   bool _has_humongous_reclaim_candidates;
 311 
 312   volatile unsigned _gc_time_stamp;
 313 
 314   size_t* _surviving_young_words;
 315 
 316   G1HRPrinter _hr_printer;
 317 
 318   void setup_surviving_young_words();
 319   void update_surviving_young_words(size_t* surv_young_words);
 320   void cleanup_surviving_young_words();
 321 
 322   // It decides whether an explicit GC should start a concurrent cycle
 323   // instead of doing a STW GC. Currently, a concurrent cycle is
 324   // explicitly started if:
 325   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 326   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 327   // (c) cause == _g1_humongous_allocation
 328   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 329 
 330   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 331   // concurrent cycles) we have started.
 332   volatile uint _old_marking_cycles_started;
 333 
 334   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 335   // concurrent cycles) we have completed.
 336   volatile uint _old_marking_cycles_completed;
 337 
 338   bool _concurrent_cycle_started;
 339   bool _heap_summary_sent;
 340 
 341   // This is a non-product method that is helpful for testing. It is
 342   // called at the end of a GC and artificially expands the heap by
 343   // allocating a number of dead regions. This way we can induce very
 344   // frequent marking cycles and stress the cleanup / concurrent
 345   // cleanup code more (as all the regions that will be allocated by
 346   // this method will be found dead by the marking cycle).
 347   void allocate_dummy_regions() PRODUCT_RETURN;
 348 
 349   // Clear RSets after a compaction. It also resets the GC time stamps.
 350   void clear_rsets_post_compaction();
 351 
 352   // If the HR printer is active, dump the state of the regions in the
 353   // heap after a compaction.
 354   void print_hrm_post_compaction();
 355 
 356   // Create a memory mapper for auxiliary data structures of the given size and
 357   // translation factor.
 358   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 359                                                          size_t size,
 360                                                          size_t translation_factor);
 361 
 362   double verify(bool guard, const char* msg);
 363   void verify_before_gc();
 364   void verify_after_gc();
 365 
 366   void log_gc_header();
 367   void log_gc_footer(double pause_time_sec);
 368 
 369   // These are macros so that, if the assert fires, we get the correct
 370   // line number, file, etc.
 371 
 372 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 373   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 374           (_extra_message_),                                                  \
 375           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 376           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 377           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 378 
 379 #define assert_heap_locked()                                                  \
 380   do {                                                                        \
 381     assert(Heap_lock->owned_by_self(),                                        \
 382            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 383   } while (0)
 384 
 385 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 386   do {                                                                        \
 387     assert(Heap_lock->owned_by_self() ||                                      \
 388            (SafepointSynchronize::is_at_safepoint() &&                        \
 389              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 390            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 391                                         "should be at a safepoint"));         \
 392   } while (0)
 393 
 394 #define assert_heap_locked_and_not_at_safepoint()                             \
 395   do {                                                                        \
 396     assert(Heap_lock->owned_by_self() &&                                      \
 397                                     !SafepointSynchronize::is_at_safepoint(), \
 398           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 399                                        "should not be at a safepoint"));      \
 400   } while (0)
 401 
 402 #define assert_heap_not_locked()                                              \
 403   do {                                                                        \
 404     assert(!Heap_lock->owned_by_self(),                                       \
 405         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 406   } while (0)
 407 
 408 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 409   do {                                                                        \
 410     assert(!Heap_lock->owned_by_self() &&                                     \
 411                                     !SafepointSynchronize::is_at_safepoint(), \
 412       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 413                                    "should not be at a safepoint"));          \
 414   } while (0)
 415 
 416 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 417   do {                                                                        \
 418     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 419               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 420            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 421   } while (0)
 422 
 423 #define assert_not_at_safepoint()                                             \
 424   do {                                                                        \
 425     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 426            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 427   } while (0)
 428 
 429 protected:
 430 
 431   // The young region list.
 432   YoungList*  _young_list;
 433 
 434   // The current policy object for the collector.
 435   G1CollectorPolicy* _g1_policy;
 436 
 437   // This is the second level of trying to allocate a new region. If
 438   // new_region() didn't find a region on the free_list, this call will
 439   // check whether there's anything available on the
 440   // secondary_free_list and/or wait for more regions to appear on
 441   // that list, if _free_regions_coming is set.
 442   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 443 
 444   // Try to allocate a single non-humongous HeapRegion sufficient for
 445   // an allocation of the given word_size. If do_expand is true,
 446   // attempt to expand the heap if necessary to satisfy the allocation
 447   // request. If the region is to be used as an old region or for a
 448   // humongous object, set is_old to true. If not, to false.
 449   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 450 
 451   // Initialize a contiguous set of free regions of length num_regions
 452   // and starting at index first so that they appear as a single
 453   // humongous region.
 454   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 455                                                       uint num_regions,
 456                                                       size_t word_size,
 457                                                       AllocationContext_t context);
 458 
 459   // Attempt to allocate a humongous object of the given size. Return
 460   // NULL if unsuccessful.
 461   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 462 
 463   // The following two methods, allocate_new_tlab() and
 464   // mem_allocate(), are the two main entry points from the runtime
 465   // into the G1's allocation routines. They have the following
 466   // assumptions:
 467   //
 468   // * They should both be called outside safepoints.
 469   //
 470   // * They should both be called without holding the Heap_lock.
 471   //
 472   // * All allocation requests for new TLABs should go to
 473   //   allocate_new_tlab().
 474   //
 475   // * All non-TLAB allocation requests should go to mem_allocate().
 476   //
 477   // * If either call cannot satisfy the allocation request using the
 478   //   current allocating region, they will try to get a new one. If
 479   //   this fails, they will attempt to do an evacuation pause and
 480   //   retry the allocation.
 481   //
 482   // * If all allocation attempts fail, even after trying to schedule
 483   //   an evacuation pause, allocate_new_tlab() will return NULL,
 484   //   whereas mem_allocate() will attempt a heap expansion and/or
 485   //   schedule a Full GC.
 486   //
 487   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 488   //   should never be called with word_size being humongous. All
 489   //   humongous allocation requests should go to mem_allocate() which
 490   //   will satisfy them with a special path.
 491 
 492   virtual HeapWord* allocate_new_tlab(size_t word_size);
 493 
 494   virtual HeapWord* mem_allocate(size_t word_size,
 495                                  bool*  gc_overhead_limit_was_exceeded);
 496 
 497   // The following three methods take a gc_count_before_ret
 498   // parameter which is used to return the GC count if the method
 499   // returns NULL. Given that we are required to read the GC count
 500   // while holding the Heap_lock, and these paths will take the
 501   // Heap_lock at some point, it's easier to get them to read the GC
 502   // count while holding the Heap_lock before they return NULL instead
 503   // of the caller (namely: mem_allocate()) having to also take the
 504   // Heap_lock just to read the GC count.
 505 
 506   // First-level mutator allocation attempt: try to allocate out of
 507   // the mutator alloc region without taking the Heap_lock. This
 508   // should only be used for non-humongous allocations.
 509   inline HeapWord* attempt_allocation(size_t word_size,
 510                                       uint* gc_count_before_ret,
 511                                       uint* gclocker_retry_count_ret);
 512 
 513   // Second-level mutator allocation attempt: take the Heap_lock and
 514   // retry the allocation attempt, potentially scheduling a GC
 515   // pause. This should only be used for non-humongous allocations.
 516   HeapWord* attempt_allocation_slow(size_t word_size,
 517                                     AllocationContext_t context,
 518                                     uint* gc_count_before_ret,
 519                                     uint* gclocker_retry_count_ret);
 520 
 521   // Takes the Heap_lock and attempts a humongous allocation. It can
 522   // potentially schedule a GC pause.
 523   HeapWord* attempt_allocation_humongous(size_t word_size,
 524                                          uint* gc_count_before_ret,
 525                                          uint* gclocker_retry_count_ret);
 526 
 527   // Allocation attempt that should be called during safepoints (e.g.,
 528   // at the end of a successful GC). expect_null_mutator_alloc_region
 529   // specifies whether the mutator alloc region is expected to be NULL
 530   // or not.
 531   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 532                                             AllocationContext_t context,
 533                                             bool expect_null_mutator_alloc_region);
 534 
 535   // It dirties the cards that cover the block so that so that the post
 536   // write barrier never queues anything when updating objects on this
 537   // block. It is assumed (and in fact we assert) that the block
 538   // belongs to a young region.
 539   inline void dirty_young_block(HeapWord* start, size_t word_size);
 540 
 541   // Allocate blocks during garbage collection. Will ensure an
 542   // allocation region, either by picking one or expanding the
 543   // heap, and then allocate a block of the given size. The block
 544   // may not be a humongous - it must fit into a single heap region.
 545   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 546                                           size_t word_size,
 547                                           AllocationContext_t context);
 548   // Ensure that no further allocations can happen in "r", bearing in mind
 549   // that parallel threads might be attempting allocations.
 550   void par_allocate_remaining_space(HeapRegion* r);
 551 
 552   // Allocation attempt during GC for a survivor object / PLAB.
 553   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 554                                                AllocationContext_t context);
 555 
 556   // Allocation attempt during GC for an old object / PLAB.
 557   inline HeapWord* old_attempt_allocation(size_t word_size,
 558                                           AllocationContext_t context);
 559 
 560   // These methods are the "callbacks" from the G1AllocRegion class.
 561 
 562   // For mutator alloc regions.
 563   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 564   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 565                                    size_t allocated_bytes);
 566 
 567   // For GC alloc regions.
 568   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 569                                   InCSetState dest);
 570   void retire_gc_alloc_region(HeapRegion* alloc_region,
 571                               size_t allocated_bytes, InCSetState dest);
 572 
 573   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 574   //   inspection request and should collect the entire heap
 575   // - if clear_all_soft_refs is true, all soft references should be
 576   //   cleared during the GC
 577   // - if explicit_gc is false, word_size describes the allocation that
 578   //   the GC should attempt (at least) to satisfy
 579   // - it returns false if it is unable to do the collection due to the
 580   //   GC locker being active, true otherwise
 581   bool do_collection(bool explicit_gc,
 582                      bool clear_all_soft_refs,
 583                      size_t word_size);
 584 
 585   // Callback from VM_G1CollectFull operation.
 586   // Perform a full collection.
 587   virtual void do_full_collection(bool clear_all_soft_refs);
 588 
 589   // Resize the heap if necessary after a full collection.  If this is
 590   // after a collect-for allocation, "word_size" is the allocation size,
 591   // and will be considered part of the used portion of the heap.
 592   void resize_if_necessary_after_full_collection(size_t word_size);
 593 
 594   // Callback from VM_G1CollectForAllocation operation.
 595   // This function does everything necessary/possible to satisfy a
 596   // failed allocation request (including collection, expansion, etc.)
 597   HeapWord* satisfy_failed_allocation(size_t word_size,
 598                                       AllocationContext_t context,
 599                                       bool* succeeded);
 600 
 601   // Attempting to expand the heap sufficiently
 602   // to support an allocation of the given "word_size".  If
 603   // successful, perform the allocation and return the address of the
 604   // allocated block, or else "NULL".
 605   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 606 
 607   // Process any reference objects discovered during
 608   // an incremental evacuation pause.
 609   void process_discovered_references(uint no_of_gc_workers);
 610 
 611   // Enqueue any remaining discovered references
 612   // after processing.
 613   void enqueue_discovered_references(uint no_of_gc_workers);
 614 
 615 public:
 616   FlexibleWorkGang* workers() const { return _workers; }
 617 
 618   G1Allocator* allocator() {
 619     return _allocator;
 620   }
 621 
 622   G1MonitoringSupport* g1mm() {
 623     assert(_g1mm != NULL, "should have been initialized");
 624     return _g1mm;
 625   }
 626 
 627   // Expand the garbage-first heap by at least the given size (in bytes!).
 628   // Returns true if the heap was expanded by the requested amount;
 629   // false otherwise.
 630   // (Rounds up to a HeapRegion boundary.)
 631   bool expand(size_t expand_bytes);
 632 
 633   // Returns the PLAB statistics for a given destination.
 634   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 635 
 636   // Determines PLAB size for a given destination.
 637   inline size_t desired_plab_sz(InCSetState dest);
 638 
 639   inline AllocationContextStats& allocation_context_stats();
 640 
 641   // Do anything common to GC's.
 642   void gc_prologue(bool full);
 643   void gc_epilogue(bool full);
 644 
 645   // Modify the reclaim candidate set and test for presence.
 646   // These are only valid for starts_humongous regions.
 647   inline void set_humongous_reclaim_candidate(uint region, bool value);
 648   inline bool is_humongous_reclaim_candidate(uint region);
 649 
 650   // Remove from the reclaim candidate set.  Also remove from the
 651   // collection set so that later encounters avoid the slow path.
 652   inline void set_humongous_is_live(oop obj);
 653 
 654   // Register the given region to be part of the collection set.
 655   inline void register_humongous_region_with_cset(uint index);
 656   // Register regions with humongous objects (actually on the start region) in
 657   // the in_cset_fast_test table.
 658   void register_humongous_regions_with_cset();
 659   // We register a region with the fast "in collection set" test. We
 660   // simply set to true the array slot corresponding to this region.
 661   void register_young_region_with_cset(HeapRegion* r) {
 662     _in_cset_fast_test.set_in_young(r->hrm_index());
 663   }
 664   void register_old_region_with_cset(HeapRegion* r) {
 665     _in_cset_fast_test.set_in_old(r->hrm_index());
 666   }
 667   void clear_in_cset(const HeapRegion* hr) {
 668     _in_cset_fast_test.clear(hr);
 669   }
 670 
 671   void clear_cset_fast_test() {
 672     _in_cset_fast_test.clear();
 673   }
 674 
 675   // This is called at the start of either a concurrent cycle or a Full
 676   // GC to update the number of old marking cycles started.
 677   void increment_old_marking_cycles_started();
 678 
 679   // This is called at the end of either a concurrent cycle or a Full
 680   // GC to update the number of old marking cycles completed. Those two
 681   // can happen in a nested fashion, i.e., we start a concurrent
 682   // cycle, a Full GC happens half-way through it which ends first,
 683   // and then the cycle notices that a Full GC happened and ends
 684   // too. The concurrent parameter is a boolean to help us do a bit
 685   // tighter consistency checking in the method. If concurrent is
 686   // false, the caller is the inner caller in the nesting (i.e., the
 687   // Full GC). If concurrent is true, the caller is the outer caller
 688   // in this nesting (i.e., the concurrent cycle). Further nesting is
 689   // not currently supported. The end of this call also notifies
 690   // the FullGCCount_lock in case a Java thread is waiting for a full
 691   // GC to happen (e.g., it called System.gc() with
 692   // +ExplicitGCInvokesConcurrent).
 693   void increment_old_marking_cycles_completed(bool concurrent);
 694 
 695   uint old_marking_cycles_completed() {
 696     return _old_marking_cycles_completed;
 697   }
 698 
 699   void register_concurrent_cycle_start(const Ticks& start_time);
 700   void register_concurrent_cycle_end();
 701   void trace_heap_after_concurrent_cycle();
 702 
 703   G1YCType yc_type();
 704 
 705   G1HRPrinter* hr_printer() { return &_hr_printer; }
 706 
 707   // Frees a non-humongous region by initializing its contents and
 708   // adding it to the free list that's passed as a parameter (this is
 709   // usually a local list which will be appended to the master free
 710   // list later). The used bytes of freed regions are accumulated in
 711   // pre_used. If par is true, the region's RSet will not be freed
 712   // up. The assumption is that this will be done later.
 713   // The locked parameter indicates if the caller has already taken
 714   // care of proper synchronization. This may allow some optimizations.
 715   void free_region(HeapRegion* hr,
 716                    FreeRegionList* free_list,
 717                    bool par,
 718                    bool locked = false);
 719 
 720   // Frees a humongous region by collapsing it into individual regions
 721   // and calling free_region() for each of them. The freed regions
 722   // will be added to the free list that's passed as a parameter (this
 723   // is usually a local list which will be appended to the master free
 724   // list later). The used bytes of freed regions are accumulated in
 725   // pre_used. If par is true, the region's RSet will not be freed
 726   // up. The assumption is that this will be done later.
 727   void free_humongous_region(HeapRegion* hr,
 728                              FreeRegionList* free_list,
 729                              bool par);
 730 protected:
 731 
 732   // Shrink the garbage-first heap by at most the given size (in bytes!).
 733   // (Rounds down to a HeapRegion boundary.)
 734   virtual void shrink(size_t expand_bytes);
 735   void shrink_helper(size_t expand_bytes);
 736 
 737   #if TASKQUEUE_STATS
 738   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 739   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 740   void reset_taskqueue_stats();
 741   #endif // TASKQUEUE_STATS
 742 
 743   // Schedule the VM operation that will do an evacuation pause to
 744   // satisfy an allocation request of word_size. *succeeded will
 745   // return whether the VM operation was successful (it did do an
 746   // evacuation pause) or not (another thread beat us to it or the GC
 747   // locker was active). Given that we should not be holding the
 748   // Heap_lock when we enter this method, we will pass the
 749   // gc_count_before (i.e., total_collections()) as a parameter since
 750   // it has to be read while holding the Heap_lock. Currently, both
 751   // methods that call do_collection_pause() release the Heap_lock
 752   // before the call, so it's easy to read gc_count_before just before.
 753   HeapWord* do_collection_pause(size_t         word_size,
 754                                 uint           gc_count_before,
 755                                 bool*          succeeded,
 756                                 GCCause::Cause gc_cause);
 757 
 758   // The guts of the incremental collection pause, executed by the vm
 759   // thread. It returns false if it is unable to do the collection due
 760   // to the GC locker being active, true otherwise
 761   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 762 
 763   // Actually do the work of evacuating the collection set.
 764   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 765 
 766   // The g1 remembered set of the heap.
 767   G1RemSet* _g1_rem_set;
 768 
 769   // A set of cards that cover the objects for which the Rsets should be updated
 770   // concurrently after the collection.
 771   DirtyCardQueueSet _dirty_card_queue_set;
 772 
 773   // The closure used to refine a single card.
 774   RefineCardTableEntryClosure* _refine_cte_cl;
 775 
 776   // A DirtyCardQueueSet that is used to hold cards that contain
 777   // references into the current collection set. This is used to
 778   // update the remembered sets of the regions in the collection
 779   // set in the event of an evacuation failure.
 780   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 781 
 782   // After a collection pause, make the regions in the CS into free
 783   // regions.
 784   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 785 
 786   // Abandon the current collection set without recording policy
 787   // statistics or updating free lists.
 788   void abandon_collection_set(HeapRegion* cs_head);
 789 
 790   // The concurrent marker (and the thread it runs in.)
 791   ConcurrentMark* _cm;
 792   ConcurrentMarkThread* _cmThread;
 793   bool _mark_in_progress;
 794 
 795   // The concurrent refiner.
 796   ConcurrentG1Refine* _cg1r;
 797 
 798   // The parallel task queues
 799   RefToScanQueueSet *_task_queues;
 800 
 801   // True iff a evacuation has failed in the current collection.
 802   bool _evacuation_failed;
 803 
 804   EvacuationFailedInfo* _evacuation_failed_info_array;
 805 
 806   // Failed evacuations cause some logical from-space objects to have
 807   // forwarding pointers to themselves.  Reset them.
 808   void remove_self_forwarding_pointers();
 809 
 810   // Together, these store an object with a preserved mark, and its mark value.
 811   Stack<oop, mtGC>     _objs_with_preserved_marks;
 812   Stack<markOop, mtGC> _preserved_marks_of_objs;
 813 
 814   // Preserve the mark of "obj", if necessary, in preparation for its mark
 815   // word being overwritten with a self-forwarding-pointer.
 816   void preserve_mark_if_necessary(oop obj, markOop m);
 817 
 818   // The stack of evac-failure objects left to be scanned.
 819   GrowableArray<oop>*    _evac_failure_scan_stack;
 820   // The closure to apply to evac-failure objects.
 821 
 822   OopsInHeapRegionClosure* _evac_failure_closure;
 823   // Set the field above.
 824   void
 825   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 826     _evac_failure_closure = evac_failure_closure;
 827   }
 828 
 829   // Push "obj" on the scan stack.
 830   void push_on_evac_failure_scan_stack(oop obj);
 831   // Process scan stack entries until the stack is empty.
 832   void drain_evac_failure_scan_stack();
 833   // True iff an invocation of "drain_scan_stack" is in progress; to
 834   // prevent unnecessary recursion.
 835   bool _drain_in_progress;
 836 
 837   // Do any necessary initialization for evacuation-failure handling.
 838   // "cl" is the closure that will be used to process evac-failure
 839   // objects.
 840   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 841   // Do any necessary cleanup for evacuation-failure handling data
 842   // structures.
 843   void finalize_for_evac_failure();
 844 
 845   // An attempt to evacuate "obj" has failed; take necessary steps.
 846   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 847   void handle_evacuation_failure_common(oop obj, markOop m);
 848 
 849 #ifndef PRODUCT
 850   // Support for forcing evacuation failures. Analogous to
 851   // PromotionFailureALot for the other collectors.
 852 
 853   // Records whether G1EvacuationFailureALot should be in effect
 854   // for the current GC
 855   bool _evacuation_failure_alot_for_current_gc;
 856 
 857   // Used to record the GC number for interval checking when
 858   // determining whether G1EvaucationFailureALot is in effect
 859   // for the current GC.
 860   size_t _evacuation_failure_alot_gc_number;
 861 
 862   // Count of the number of evacuations between failures.
 863   volatile size_t _evacuation_failure_alot_count;
 864 
 865   // Set whether G1EvacuationFailureALot should be in effect
 866   // for the current GC (based upon the type of GC and which
 867   // command line flags are set);
 868   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 869                                                   bool during_initial_mark,
 870                                                   bool during_marking);
 871 
 872   inline void set_evacuation_failure_alot_for_current_gc();
 873 
 874   // Return true if it's time to cause an evacuation failure.
 875   inline bool evacuation_should_fail();
 876 
 877   // Reset the G1EvacuationFailureALot counters.  Should be called at
 878   // the end of an evacuation pause in which an evacuation failure occurred.
 879   inline void reset_evacuation_should_fail();
 880 #endif // !PRODUCT
 881 
 882   // ("Weak") Reference processing support.
 883   //
 884   // G1 has 2 instances of the reference processor class. One
 885   // (_ref_processor_cm) handles reference object discovery
 886   // and subsequent processing during concurrent marking cycles.
 887   //
 888   // The other (_ref_processor_stw) handles reference object
 889   // discovery and processing during full GCs and incremental
 890   // evacuation pauses.
 891   //
 892   // During an incremental pause, reference discovery will be
 893   // temporarily disabled for _ref_processor_cm and will be
 894   // enabled for _ref_processor_stw. At the end of the evacuation
 895   // pause references discovered by _ref_processor_stw will be
 896   // processed and discovery will be disabled. The previous
 897   // setting for reference object discovery for _ref_processor_cm
 898   // will be re-instated.
 899   //
 900   // At the start of marking:
 901   //  * Discovery by the CM ref processor is verified to be inactive
 902   //    and it's discovered lists are empty.
 903   //  * Discovery by the CM ref processor is then enabled.
 904   //
 905   // At the end of marking:
 906   //  * Any references on the CM ref processor's discovered
 907   //    lists are processed (possibly MT).
 908   //
 909   // At the start of full GC we:
 910   //  * Disable discovery by the CM ref processor and
 911   //    empty CM ref processor's discovered lists
 912   //    (without processing any entries).
 913   //  * Verify that the STW ref processor is inactive and it's
 914   //    discovered lists are empty.
 915   //  * Temporarily set STW ref processor discovery as single threaded.
 916   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 917   //    field.
 918   //  * Finally enable discovery by the STW ref processor.
 919   //
 920   // The STW ref processor is used to record any discovered
 921   // references during the full GC.
 922   //
 923   // At the end of a full GC we:
 924   //  * Enqueue any reference objects discovered by the STW ref processor
 925   //    that have non-live referents. This has the side-effect of
 926   //    making the STW ref processor inactive by disabling discovery.
 927   //  * Verify that the CM ref processor is still inactive
 928   //    and no references have been placed on it's discovered
 929   //    lists (also checked as a precondition during initial marking).
 930 
 931   // The (stw) reference processor...
 932   ReferenceProcessor* _ref_processor_stw;
 933 
 934   STWGCTimer* _gc_timer_stw;
 935   ConcurrentGCTimer* _gc_timer_cm;
 936 
 937   G1OldTracer* _gc_tracer_cm;
 938   G1NewTracer* _gc_tracer_stw;
 939 
 940   // During reference object discovery, the _is_alive_non_header
 941   // closure (if non-null) is applied to the referent object to
 942   // determine whether the referent is live. If so then the
 943   // reference object does not need to be 'discovered' and can
 944   // be treated as a regular oop. This has the benefit of reducing
 945   // the number of 'discovered' reference objects that need to
 946   // be processed.
 947   //
 948   // Instance of the is_alive closure for embedding into the
 949   // STW reference processor as the _is_alive_non_header field.
 950   // Supplying a value for the _is_alive_non_header field is
 951   // optional but doing so prevents unnecessary additions to
 952   // the discovered lists during reference discovery.
 953   G1STWIsAliveClosure _is_alive_closure_stw;
 954 
 955   // The (concurrent marking) reference processor...
 956   ReferenceProcessor* _ref_processor_cm;
 957 
 958   // Instance of the concurrent mark is_alive closure for embedding
 959   // into the Concurrent Marking reference processor as the
 960   // _is_alive_non_header field. Supplying a value for the
 961   // _is_alive_non_header field is optional but doing so prevents
 962   // unnecessary additions to the discovered lists during reference
 963   // discovery.
 964   G1CMIsAliveClosure _is_alive_closure_cm;
 965 
 966   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 967   HeapRegion** _worker_cset_start_region;
 968 
 969   // Time stamp to validate the regions recorded in the cache
 970   // used by G1CollectedHeap::start_cset_region_for_worker().
 971   // The heap region entry for a given worker is valid iff
 972   // the associated time stamp value matches the current value
 973   // of G1CollectedHeap::_gc_time_stamp.
 974   uint* _worker_cset_start_region_time_stamp;
 975 
 976   volatile bool _free_regions_coming;
 977 
 978 public:
 979 
 980   void set_refine_cte_cl_concurrency(bool concurrent);
 981 
 982   RefToScanQueue *task_queue(uint i) const;
 983 
 984   // A set of cards where updates happened during the GC
 985   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 986 
 987   // A DirtyCardQueueSet that is used to hold cards that contain
 988   // references into the current collection set. This is used to
 989   // update the remembered sets of the regions in the collection
 990   // set in the event of an evacuation failure.
 991   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
 992         { return _into_cset_dirty_card_queue_set; }
 993 
 994   // Create a G1CollectedHeap with the specified policy.
 995   // Must call the initialize method afterwards.
 996   // May not return if something goes wrong.
 997   G1CollectedHeap(G1CollectorPolicy* policy);
 998 
 999   // Initialize the G1CollectedHeap to have the initial and
1000   // maximum sizes and remembered and barrier sets
1001   // specified by the policy object.
1002   jint initialize();
1003 
1004   virtual void stop();
1005 
1006   // Return the (conservative) maximum heap alignment for any G1 heap
1007   static size_t conservative_max_heap_alignment();
1008 
1009   // Does operations required after initialization has been done.
1010   void post_initialize();
1011 
1012   // Initialize weak reference processing.
1013   void ref_processing_init();
1014 
1015   // Explicitly import set_par_threads into this scope
1016   using CollectedHeap::set_par_threads;
1017   // Set _n_par_threads according to a policy TBD.
1018   void set_par_threads();
1019 
1020   virtual Name kind() const {
1021     return CollectedHeap::G1CollectedHeap;
1022   }
1023 
1024   // The current policy object for the collector.
1025   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1026 
1027   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1028 
1029   // Adaptive size policy.  No such thing for g1.
1030   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1031 
1032   // The rem set and barrier set.
1033   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1034 
1035   unsigned get_gc_time_stamp() {
1036     return _gc_time_stamp;
1037   }
1038 
1039   inline void reset_gc_time_stamp();
1040 
1041   void check_gc_time_stamps() PRODUCT_RETURN;
1042 
1043   inline void increment_gc_time_stamp();
1044 
1045   // Reset the given region's GC timestamp. If it's starts humongous,
1046   // also reset the GC timestamp of its corresponding
1047   // continues humongous regions too.
1048   void reset_gc_time_stamps(HeapRegion* hr);
1049 
1050   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1051                                   DirtyCardQueue* into_cset_dcq,
1052                                   bool concurrent, uint worker_i);
1053 
1054   // The shared block offset table array.
1055   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1056 
1057   // Reference Processing accessors
1058 
1059   // The STW reference processor....
1060   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1061 
1062   // The Concurrent Marking reference processor...
1063   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1064 
1065   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1066   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1067 
1068   virtual size_t capacity() const;
1069   virtual size_t used() const;
1070   // This should be called when we're not holding the heap lock. The
1071   // result might be a bit inaccurate.
1072   size_t used_unlocked() const;
1073   size_t recalculate_used() const;
1074 
1075   // These virtual functions do the actual allocation.
1076   // Some heaps may offer a contiguous region for shared non-blocking
1077   // allocation, via inlined code (by exporting the address of the top and
1078   // end fields defining the extent of the contiguous allocation region.)
1079   // But G1CollectedHeap doesn't yet support this.
1080 
1081   virtual bool is_maximal_no_gc() const {
1082     return _hrm.available() == 0;
1083   }
1084 
1085   // The current number of regions in the heap.
1086   uint num_regions() const { return _hrm.length(); }
1087 
1088   // The max number of regions in the heap.
1089   uint max_regions() const { return _hrm.max_length(); }
1090 
1091   // The number of regions that are completely free.
1092   uint num_free_regions() const { return _hrm.num_free_regions(); }
1093 
1094   MemoryUsage get_auxiliary_data_memory_usage() const {
1095     return _hrm.get_auxiliary_data_memory_usage();
1096   }
1097 
1098   // The number of regions that are not completely free.
1099   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1100 
1101   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1102   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1103   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1104   void verify_dirty_young_regions() PRODUCT_RETURN;
1105 
1106 #ifndef PRODUCT
1107   // Make sure that the given bitmap has no marked objects in the
1108   // range [from,limit). If it does, print an error message and return
1109   // false. Otherwise, just return true. bitmap_name should be "prev"
1110   // or "next".
1111   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1112                                 HeapWord* from, HeapWord* limit);
1113 
1114   // Verify that the prev / next bitmap range [tams,end) for the given
1115   // region has no marks. Return true if all is well, false if errors
1116   // are detected.
1117   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1118 #endif // PRODUCT
1119 
1120   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1121   // the given region do not have any spurious marks. If errors are
1122   // detected, print appropriate error messages and crash.
1123   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1124 
1125   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1126   // have any spurious marks. If errors are detected, print
1127   // appropriate error messages and crash.
1128   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1129 
1130   // Do sanity check on the contents of the in-cset fast test table.
1131   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1132 
1133   // verify_region_sets() performs verification over the region
1134   // lists. It will be compiled in the product code to be used when
1135   // necessary (i.e., during heap verification).
1136   void verify_region_sets();
1137 
1138   // verify_region_sets_optional() is planted in the code for
1139   // list verification in non-product builds (and it can be enabled in
1140   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1141 #if HEAP_REGION_SET_FORCE_VERIFY
1142   void verify_region_sets_optional() {
1143     verify_region_sets();
1144   }
1145 #else // HEAP_REGION_SET_FORCE_VERIFY
1146   void verify_region_sets_optional() { }
1147 #endif // HEAP_REGION_SET_FORCE_VERIFY
1148 
1149 #ifdef ASSERT
1150   bool is_on_master_free_list(HeapRegion* hr) {
1151     return _hrm.is_free(hr);
1152   }
1153 #endif // ASSERT
1154 
1155   // Wrapper for the region list operations that can be called from
1156   // methods outside this class.
1157 
1158   void secondary_free_list_add(FreeRegionList* list) {
1159     _secondary_free_list.add_ordered(list);
1160   }
1161 
1162   void append_secondary_free_list() {
1163     _hrm.insert_list_into_free_list(&_secondary_free_list);
1164   }
1165 
1166   void append_secondary_free_list_if_not_empty_with_lock() {
1167     // If the secondary free list looks empty there's no reason to
1168     // take the lock and then try to append it.
1169     if (!_secondary_free_list.is_empty()) {
1170       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1171       append_secondary_free_list();
1172     }
1173   }
1174 
1175   inline void old_set_remove(HeapRegion* hr);
1176 
1177   size_t non_young_capacity_bytes() {
1178     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1179   }
1180 
1181   void set_free_regions_coming();
1182   void reset_free_regions_coming();
1183   bool free_regions_coming() { return _free_regions_coming; }
1184   void wait_while_free_regions_coming();
1185 
1186   // Determine whether the given region is one that we are using as an
1187   // old GC alloc region.
1188   bool is_old_gc_alloc_region(HeapRegion* hr) {
1189     return _allocator->is_retained_old_region(hr);
1190   }
1191 
1192   // Perform a collection of the heap; intended for use in implementing
1193   // "System.gc".  This probably implies as full a collection as the
1194   // "CollectedHeap" supports.
1195   virtual void collect(GCCause::Cause cause);
1196 
1197   // The same as above but assume that the caller holds the Heap_lock.
1198   void collect_locked(GCCause::Cause cause);
1199 
1200   virtual bool copy_allocation_context_stats(const jint* contexts,
1201                                              jlong* totals,
1202                                              jbyte* accuracy,
1203                                              jint len);
1204 
1205   // True iff an evacuation has failed in the most-recent collection.
1206   bool evacuation_failed() { return _evacuation_failed; }
1207 
1208   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1209   void prepend_to_freelist(FreeRegionList* list);
1210   void decrement_summary_bytes(size_t bytes);
1211 
1212   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1213   virtual bool is_in(const void* p) const;
1214 #ifdef ASSERT
1215   // Returns whether p is in one of the available areas of the heap. Slow but
1216   // extensive version.
1217   bool is_in_exact(const void* p) const;
1218 #endif
1219 
1220   // Return "TRUE" iff the given object address is within the collection
1221   // set. Slow implementation.
1222   inline bool obj_in_cs(oop obj);
1223 
1224   inline bool is_in_cset(const HeapRegion *hr);
1225   inline bool is_in_cset(oop obj);
1226 
1227   inline bool is_in_cset_or_humongous(const oop obj);
1228 
1229  private:
1230   // This array is used for a quick test on whether a reference points into
1231   // the collection set or not. Each of the array's elements denotes whether the
1232   // corresponding region is in the collection set or not.
1233   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1234 
1235  public:
1236 
1237   inline InCSetState in_cset_state(const oop obj);
1238 
1239   // Return "TRUE" iff the given object address is in the reserved
1240   // region of g1.
1241   bool is_in_g1_reserved(const void* p) const {
1242     return _hrm.reserved().contains(p);
1243   }
1244 
1245   // Returns a MemRegion that corresponds to the space that has been
1246   // reserved for the heap
1247   MemRegion g1_reserved() const {
1248     return _hrm.reserved();
1249   }
1250 
1251   virtual bool is_in_closed_subset(const void* p) const;
1252 
1253   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1254     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1255   }
1256 
1257   // This resets the card table to all zeros.  It is used after
1258   // a collection pause which used the card table to claim cards.
1259   void cleanUpCardTable();
1260 
1261   // Iteration functions.
1262 
1263   // Iterate over all objects, calling "cl.do_object" on each.
1264   virtual void object_iterate(ObjectClosure* cl);
1265 
1266   virtual void safe_object_iterate(ObjectClosure* cl) {
1267     object_iterate(cl);
1268   }
1269 
1270   // Iterate over heap regions, in address order, terminating the
1271   // iteration early if the "doHeapRegion" method returns "true".
1272   void heap_region_iterate(HeapRegionClosure* blk) const;
1273 
1274   // Return the region with the given index. It assumes the index is valid.
1275   inline HeapRegion* region_at(uint index) const;
1276 
1277   // Calculate the region index of the given address. Given address must be
1278   // within the heap.
1279   inline uint addr_to_region(HeapWord* addr) const;
1280 
1281   inline HeapWord* bottom_addr_for_region(uint index) const;
1282 
1283   // Iterate over the heap regions in parallel. Assumes that this will be called
1284   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1285   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1286   // to each of the regions, by attempting to claim the region using the
1287   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1288   // region. The concurrent argument should be set to true if iteration is
1289   // performed concurrently, during which no assumptions are made for consistent
1290   // attributes of the heap regions (as they might be modified while iterating).
1291   void heap_region_par_iterate(HeapRegionClosure* cl,
1292                                uint worker_id,
1293                                HeapRegionClaimer* hrclaimer,
1294                                bool concurrent = false) const;
1295 
1296   // Clear the cached cset start regions and (more importantly)
1297   // the time stamps. Called when we reset the GC time stamp.
1298   void clear_cset_start_regions();
1299 
1300   // Given the id of a worker, obtain or calculate a suitable
1301   // starting region for iterating over the current collection set.
1302   HeapRegion* start_cset_region_for_worker(uint worker_i);
1303 
1304   // Iterate over the regions (if any) in the current collection set.
1305   void collection_set_iterate(HeapRegionClosure* blk);
1306 
1307   // As above but starting from region r
1308   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1309 
1310   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1311 
1312   // Returns the HeapRegion that contains addr. addr must not be NULL.
1313   template <class T>
1314   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1315 
1316   // Returns the HeapRegion that contains addr. addr must not be NULL.
1317   // If addr is within a humongous continues region, it returns its humongous start region.
1318   template <class T>
1319   inline HeapRegion* heap_region_containing(const T addr) const;
1320 
1321   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1322   // each address in the (reserved) heap is a member of exactly
1323   // one block.  The defining characteristic of a block is that it is
1324   // possible to find its size, and thus to progress forward to the next
1325   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1326   // represent Java objects, or they might be free blocks in a
1327   // free-list-based heap (or subheap), as long as the two kinds are
1328   // distinguishable and the size of each is determinable.
1329 
1330   // Returns the address of the start of the "block" that contains the
1331   // address "addr".  We say "blocks" instead of "object" since some heaps
1332   // may not pack objects densely; a chunk may either be an object or a
1333   // non-object.
1334   virtual HeapWord* block_start(const void* addr) const;
1335 
1336   // Requires "addr" to be the start of a chunk, and returns its size.
1337   // "addr + size" is required to be the start of a new chunk, or the end
1338   // of the active area of the heap.
1339   virtual size_t block_size(const HeapWord* addr) const;
1340 
1341   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1342   // the block is an object.
1343   virtual bool block_is_obj(const HeapWord* addr) const;
1344 
1345   // Section on thread-local allocation buffers (TLABs)
1346   // See CollectedHeap for semantics.
1347 
1348   bool supports_tlab_allocation() const;
1349   size_t tlab_capacity(Thread* ignored) const;
1350   size_t tlab_used(Thread* ignored) const;
1351   size_t max_tlab_size() const;
1352   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1353 
1354   // Can a compiler initialize a new object without store barriers?
1355   // This permission only extends from the creation of a new object
1356   // via a TLAB up to the first subsequent safepoint. If such permission
1357   // is granted for this heap type, the compiler promises to call
1358   // defer_store_barrier() below on any slow path allocation of
1359   // a new object for which such initializing store barriers will
1360   // have been elided. G1, like CMS, allows this, but should be
1361   // ready to provide a compensating write barrier as necessary
1362   // if that storage came out of a non-young region. The efficiency
1363   // of this implementation depends crucially on being able to
1364   // answer very efficiently in constant time whether a piece of
1365   // storage in the heap comes from a young region or not.
1366   // See ReduceInitialCardMarks.
1367   virtual bool can_elide_tlab_store_barriers() const {
1368     return true;
1369   }
1370 
1371   virtual bool card_mark_must_follow_store() const {
1372     return true;
1373   }
1374 
1375   inline bool is_in_young(const oop obj);
1376 
1377   virtual bool is_scavengable(const void* addr);
1378 
1379   // We don't need barriers for initializing stores to objects
1380   // in the young gen: for the SATB pre-barrier, there is no
1381   // pre-value that needs to be remembered; for the remembered-set
1382   // update logging post-barrier, we don't maintain remembered set
1383   // information for young gen objects.
1384   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1385 
1386   // Returns "true" iff the given word_size is "very large".
1387   static bool is_humongous(size_t word_size) {
1388     // Note this has to be strictly greater-than as the TLABs
1389     // are capped at the humongous threshold and we want to
1390     // ensure that we don't try to allocate a TLAB as
1391     // humongous and that we don't allocate a humongous
1392     // object in a TLAB.
1393     return word_size > _humongous_object_threshold_in_words;
1394   }
1395 
1396   // Update mod union table with the set of dirty cards.
1397   void updateModUnion();
1398 
1399   // Set the mod union bits corresponding to the given memRegion.  Note
1400   // that this is always a safe operation, since it doesn't clear any
1401   // bits.
1402   void markModUnionRange(MemRegion mr);
1403 
1404   // Records the fact that a marking phase is no longer in progress.
1405   void set_marking_complete() {
1406     _mark_in_progress = false;
1407   }
1408   void set_marking_started() {
1409     _mark_in_progress = true;
1410   }
1411   bool mark_in_progress() {
1412     return _mark_in_progress;
1413   }
1414 
1415   // Print the maximum heap capacity.
1416   virtual size_t max_capacity() const;
1417 
1418   virtual jlong millis_since_last_gc();
1419 
1420 
1421   // Convenience function to be used in situations where the heap type can be
1422   // asserted to be this type.
1423   static G1CollectedHeap* heap();
1424 
1425   void set_region_short_lived_locked(HeapRegion* hr);
1426   // add appropriate methods for any other surv rate groups
1427 
1428   YoungList* young_list() const { return _young_list; }
1429 
1430   // debugging
1431   bool check_young_list_well_formed() {
1432     return _young_list->check_list_well_formed();
1433   }
1434 
1435   bool check_young_list_empty(bool check_heap,
1436                               bool check_sample = true);
1437 
1438   // *** Stuff related to concurrent marking.  It's not clear to me that so
1439   // many of these need to be public.
1440 
1441   // The functions below are helper functions that a subclass of
1442   // "CollectedHeap" can use in the implementation of its virtual
1443   // functions.
1444   // This performs a concurrent marking of the live objects in a
1445   // bitmap off to the side.
1446   void doConcurrentMark();
1447 
1448   bool isMarkedPrev(oop obj) const;
1449   bool isMarkedNext(oop obj) const;
1450 
1451   // Determine if an object is dead, given the object and also
1452   // the region to which the object belongs. An object is dead
1453   // iff a) it was not allocated since the last mark and b) it
1454   // is not marked.
1455   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1456     return
1457       !hr->obj_allocated_since_prev_marking(obj) &&
1458       !isMarkedPrev(obj);
1459   }
1460 
1461   // This function returns true when an object has been
1462   // around since the previous marking and hasn't yet
1463   // been marked during this marking.
1464   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1465     return
1466       !hr->obj_allocated_since_next_marking(obj) &&
1467       !isMarkedNext(obj);
1468   }
1469 
1470   // Determine if an object is dead, given only the object itself.
1471   // This will find the region to which the object belongs and
1472   // then call the region version of the same function.
1473 
1474   // Added if it is NULL it isn't dead.
1475 
1476   inline bool is_obj_dead(const oop obj) const;
1477 
1478   inline bool is_obj_ill(const oop obj) const;
1479 
1480   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1481   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1482   bool is_marked(oop obj, VerifyOption vo);
1483   const char* top_at_mark_start_str(VerifyOption vo);
1484 
1485   ConcurrentMark* concurrent_mark() const { return _cm; }
1486 
1487   // Refinement
1488 
1489   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1490 
1491   // The dirty cards region list is used to record a subset of regions
1492   // whose cards need clearing. The list if populated during the
1493   // remembered set scanning and drained during the card table
1494   // cleanup. Although the methods are reentrant, population/draining
1495   // phases must not overlap. For synchronization purposes the last
1496   // element on the list points to itself.
1497   HeapRegion* _dirty_cards_region_list;
1498   void push_dirty_cards_region(HeapRegion* hr);
1499   HeapRegion* pop_dirty_cards_region();
1500 
1501   // Optimized nmethod scanning support routines
1502 
1503   // Register the given nmethod with the G1 heap.
1504   virtual void register_nmethod(nmethod* nm);
1505 
1506   // Unregister the given nmethod from the G1 heap.
1507   virtual void unregister_nmethod(nmethod* nm);
1508 
1509   // Free up superfluous code root memory.
1510   void purge_code_root_memory();
1511 
1512   // Rebuild the strong code root lists for each region
1513   // after a full GC.
1514   void rebuild_strong_code_roots();
1515 
1516   // Delete entries for dead interned string and clean up unreferenced symbols
1517   // in symbol table, possibly in parallel.
1518   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1519 
1520   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1521   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1522 
1523   // Redirty logged cards in the refinement queue.
1524   void redirty_logged_cards();
1525   // Verification
1526 
1527   // The following is just to alert the verification code
1528   // that a full collection has occurred and that the
1529   // remembered sets are no longer up to date.
1530   bool _full_collection;
1531   void set_full_collection() { _full_collection = true;}
1532   void clear_full_collection() {_full_collection = false;}
1533   bool full_collection() {return _full_collection;}
1534 
1535   // Perform any cleanup actions necessary before allowing a verification.
1536   virtual void prepare_for_verify();
1537 
1538   // Perform verification.
1539 
1540   // vo == UsePrevMarking  -> use "prev" marking information,
1541   // vo == UseNextMarking -> use "next" marking information
1542   // vo == UseMarkWord    -> use the mark word in the object header
1543   //
1544   // NOTE: Only the "prev" marking information is guaranteed to be
1545   // consistent most of the time, so most calls to this should use
1546   // vo == UsePrevMarking.
1547   // Currently, there is only one case where this is called with
1548   // vo == UseNextMarking, which is to verify the "next" marking
1549   // information at the end of remark.
1550   // Currently there is only one place where this is called with
1551   // vo == UseMarkWord, which is to verify the marking during a
1552   // full GC.
1553   void verify(bool silent, VerifyOption vo);
1554 
1555   // Override; it uses the "prev" marking information
1556   virtual void verify(bool silent);
1557 
1558   // The methods below are here for convenience and dispatch the
1559   // appropriate method depending on value of the given VerifyOption
1560   // parameter. The values for that parameter, and their meanings,
1561   // are the same as those above.
1562 
1563   bool is_obj_dead_cond(const oop obj,
1564                         const HeapRegion* hr,
1565                         const VerifyOption vo) const;
1566 
1567   bool is_obj_dead_cond(const oop obj,
1568                         const VerifyOption vo) const;
1569 
1570   // Printing
1571 
1572   virtual void print_on(outputStream* st) const;
1573   virtual void print_extended_on(outputStream* st) const;
1574   virtual void print_on_error(outputStream* st) const;
1575 
1576   virtual void print_gc_threads_on(outputStream* st) const;
1577   virtual void gc_threads_do(ThreadClosure* tc) const;
1578 
1579   // Override
1580   void print_tracing_info() const;
1581 
1582   // The following two methods are helpful for debugging RSet issues.
1583   void print_cset_rsets() PRODUCT_RETURN;
1584   void print_all_rsets() PRODUCT_RETURN;
1585 
1586 public:
1587   size_t pending_card_num();
1588   size_t cards_scanned();
1589 
1590 protected:
1591   size_t _max_heap_capacity;
1592 };
1593 
1594 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP