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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/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1Allocator.hpp"
  30 #include "gc_implementation/g1/concurrentMark.hpp"
  31 #include "gc_implementation/g1/evacuationInfo.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.hpp"
  33 #include "gc_implementation/g1/g1BiasedArray.hpp"
  34 #include "gc_implementation/g1/g1HRPrinter.hpp"
  35 #include "gc_implementation/g1/g1InCSetState.hpp"
  36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc_implementation/g1/g1YCTypes.hpp"
  39 #include "gc_implementation/g1/heapRegionManager.hpp"
  40 #include "gc_implementation/g1/heapRegionSet.hpp"

  41 #include "gc_implementation/shared/hSpaceCounters.hpp"
  42 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  43 #include "memory/barrierSet.hpp"
  44 #include "memory/memRegion.hpp"
  45 #include "memory/sharedHeap.hpp"
  46 #include "utilities/stack.hpp"
  47 
  48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  49 // It uses the "Garbage First" heap organization and algorithm, which
  50 // may combine concurrent marking with parallel, incremental compaction of
  51 // heap subsets that will yield large amounts of garbage.
  52 
  53 // Forward declarations
  54 class HeapRegion;
  55 class HRRSCleanupTask;
  56 class GenerationSpec;
  57 class OopsInHeapRegionClosure;
  58 class G1KlassScanClosure;
  59 class G1ScanHeapEvacClosure;
  60 class ObjectClosure;
  61 class SpaceClosure;
  62 class CompactibleSpaceClosure;
  63 class Space;
  64 class G1CollectorPolicy;
  65 class GenRemSet;
  66 class G1RemSet;
  67 class HeapRegionRemSetIterator;
  68 class ConcurrentMark;
  69 class ConcurrentMarkThread;
  70 class ConcurrentG1Refine;
  71 class ConcurrentGCTimer;
  72 class GenerationCounters;
  73 class STWGCTimer;
  74 class G1NewTracer;
  75 class G1OldTracer;
  76 class EvacuationFailedInfo;
  77 class nmethod;
  78 class Ticks;
  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         survivor_length() { return _survivor_length; }
 115 
 116   // Currently we do not keep track of the used byte sum for the
 117   // young list and the survivors and it'd be quite a lot of work to
 118   // do so. When we'll eventually replace the young list with
 119   // instances of HeapRegionLinkedList we'll get that for free. So,
 120   // we'll report the more accurate information then.
 121   size_t       eden_used_bytes() {
 122     assert(length() >= survivor_length(), "invariant");
 123     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 124   }
 125   size_t       survivor_used_bytes() {
 126     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 127   }
 128 
 129   void rs_length_sampling_init();
 130   bool rs_length_sampling_more();
 131   void rs_length_sampling_next();
 132 
 133   void reset_sampled_info() {
 134     _last_sampled_rs_lengths =   0;
 135   }
 136   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 137 
 138   // for development purposes
 139   void reset_auxilary_lists();
 140   void clear() { _head = NULL; _length = 0; }
 141 
 142   void clear_survivors() {
 143     _survivor_head    = NULL;
 144     _survivor_tail    = NULL;
 145     _survivor_length  = 0;
 146   }
 147 
 148   HeapRegion* first_region() { return _head; }
 149   HeapRegion* first_survivor_region() { return _survivor_head; }
 150   HeapRegion* last_survivor_region() { return _survivor_tail; }
 151 
 152   // debugging
 153   bool          check_list_well_formed();
 154   bool          check_list_empty(bool check_sample = true);
 155   void          print();
 156 };
 157 
 158 // The G1 STW is alive closure.
 159 // An instance is embedded into the G1CH and used as the
 160 // (optional) _is_alive_non_header closure in the STW
 161 // reference processor. It is also extensively used during
 162 // reference processing during STW evacuation pauses.
 163 class G1STWIsAliveClosure: public BoolObjectClosure {
 164   G1CollectedHeap* _g1;
 165 public:
 166   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 167   bool do_object_b(oop p);
 168 };
 169 
 170 class RefineCardTableEntryClosure;
 171 
 172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 173  private:
 174   void reset_from_card_cache(uint start_idx, size_t num_regions);
 175  public:
 176   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 177 };
 178 
 179 class G1CollectedHeap : public SharedHeap {
 180   friend class VM_CollectForMetadataAllocation;
 181   friend class VM_G1CollectForAllocation;
 182   friend class VM_G1CollectFull;
 183   friend class VM_G1IncCollectionPause;
 184   friend class VMStructs;
 185   friend class MutatorAllocRegion;
 186   friend class SurvivorGCAllocRegion;
 187   friend class OldGCAllocRegion;
 188   friend class G1Allocator;
 189   friend class G1DefaultAllocator;
 190   friend class G1ResManAllocator;
 191 
 192   // Closures used in implementation.
 193   template <G1Barrier barrier, G1Mark do_mark_object>
 194   friend class G1ParCopyClosure;
 195   friend class G1IsAliveClosure;
 196   friend class G1EvacuateFollowersClosure;
 197   friend class G1ParScanThreadState;
 198   friend class G1ParScanClosureSuper;
 199   friend class G1ParEvacuateFollowersClosure;
 200   friend class G1ParTask;
 201   friend class G1ParGCAllocator;
 202   friend class G1DefaultParGCAllocator;
 203   friend class G1FreeGarbageRegionClosure;
 204   friend class RefineCardTableEntryClosure;
 205   friend class G1PrepareCompactClosure;
 206   friend class RegionSorter;
 207   friend class RegionResetter;
 208   friend class CountRCClosure;
 209   friend class EvacPopObjClosure;
 210   friend class G1ParCleanupCTTask;
 211 
 212   friend class G1FreeHumongousRegionClosure;
 213   // Other related classes.
 214   friend class G1MarkSweep;
 215 
 216   // Testing classes.
 217   friend class G1CheckCSetFastTableClosure;
 218 
 219 private:
 220   // The one and only G1CollectedHeap, so static functions can find it.
 221   static G1CollectedHeap* _g1h;
 222 
 223   static size_t _humongous_object_threshold_in_words;
 224 
 225   // The secondary free list which contains regions that have been
 226   // freed up during the cleanup process. This will be appended to
 227   // the master free list when appropriate.
 228   FreeRegionList _secondary_free_list;
 229 
 230   // It keeps track of the old regions.
 231   HeapRegionSet _old_set;
 232 
 233   // It keeps track of the humongous regions.
 234   HeapRegionSet _humongous_set;
 235 
 236   void eagerly_reclaim_humongous_regions();
 237 
 238   // The number of regions we could create by expansion.
 239   uint _expansion_regions;
 240 
 241   // The block offset table for the G1 heap.
 242   G1BlockOffsetSharedArray* _bot_shared;
 243 
 244   // Tears down the region sets / lists so that they are empty and the
 245   // regions on the heap do not belong to a region set / list. The
 246   // only exception is the humongous set which we leave unaltered. If
 247   // free_list_only is true, it will only tear down the master free
 248   // list. It is called before a Full GC (free_list_only == false) or
 249   // before heap shrinking (free_list_only == true).
 250   void tear_down_region_sets(bool free_list_only);
 251 
 252   // Rebuilds the region sets / lists so that they are repopulated to
 253   // reflect the contents of the heap. The only exception is the
 254   // humongous set which was not torn down in the first place. If
 255   // free_list_only is true, it will only rebuild the master free
 256   // list. It is called after a Full GC (free_list_only == false) or
 257   // after heap shrinking (free_list_only == true).
 258   void rebuild_region_sets(bool free_list_only);
 259 
 260   // Callback for region mapping changed events.
 261   G1RegionMappingChangedListener _listener;
 262 
 263   // The sequence of all heap regions in the heap.
 264   HeapRegionManager _hrm;
 265 
 266   // Class that handles the different kinds of allocations.
 267   G1Allocator* _allocator;
 268 
 269   // Statistics for each allocation context
 270   AllocationContextStats _allocation_context_stats;
 271 
 272   // PLAB sizing policy for survivors.
 273   PLABStats _survivor_plab_stats;
 274 
 275   // PLAB sizing policy for tenured objects.
 276   PLABStats _old_plab_stats;
 277 
 278   // It specifies whether we should attempt to expand the heap after a
 279   // region allocation failure. If heap expansion fails we set this to
 280   // false so that we don't re-attempt the heap expansion (it's likely
 281   // that subsequent expansion attempts will also fail if one fails).
 282   // Currently, it is only consulted during GC and it's reset at the
 283   // start of each GC.
 284   bool _expand_heap_after_alloc_failure;
 285 
 286   // It resets the mutator alloc region before new allocations can take place.
 287   void init_mutator_alloc_region();
 288 
 289   // It releases the mutator alloc region.
 290   void release_mutator_alloc_region();
 291 
 292   // It initializes the GC alloc regions at the start of a GC.
 293   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 294 
 295   // It releases the GC alloc regions at the end of a GC.
 296   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 297 
 298   // It does any cleanup that needs to be done on the GC alloc regions
 299   // before a Full GC.
 300   void abandon_gc_alloc_regions();
 301 
 302   // Helper for monitoring and management support.
 303   G1MonitoringSupport* _g1mm;
 304 
 305   // Records whether the region at the given index is (still) a
 306   // candidate for eager reclaim.  Only valid for humongous start
 307   // regions; other regions have unspecified values.  Humongous start
 308   // regions are initialized at start of collection pause, with
 309   // candidates removed from the set as they are found reachable from
 310   // roots or the young generation.
 311   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 312    protected:
 313     bool default_value() const { return false; }
 314    public:
 315     void clear() { G1BiasedMappedArray<bool>::clear(); }
 316     void set_candidate(uint region, bool value) {
 317       set_by_index(region, value);
 318     }
 319     bool is_candidate(uint region) {
 320       return get_by_index(region);
 321     }
 322   };
 323 
 324   HumongousReclaimCandidates _humongous_reclaim_candidates;
 325   // Stores whether during humongous object registration we found candidate regions.
 326   // If not, we can skip a few steps.
 327   bool _has_humongous_reclaim_candidates;
 328 
 329   volatile unsigned _gc_time_stamp;
 330 
 331   size_t* _surviving_young_words;
 332 
 333   G1HRPrinter _hr_printer;
 334 
 335   void setup_surviving_young_words();
 336   void update_surviving_young_words(size_t* surv_young_words);
 337   void cleanup_surviving_young_words();
 338 
 339   // It decides whether an explicit GC should start a concurrent cycle
 340   // instead of doing a STW GC. Currently, a concurrent cycle is
 341   // explicitly started if:
 342   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 343   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 344   // (c) cause == _g1_humongous_allocation
 345   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 346 
 347   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 348   // concurrent cycles) we have started.
 349   volatile uint _old_marking_cycles_started;
 350 
 351   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 352   // concurrent cycles) we have completed.
 353   volatile uint _old_marking_cycles_completed;
 354 
 355   bool _concurrent_cycle_started;
 356   bool _heap_summary_sent;
 357 
 358   // This is a non-product method that is helpful for testing. It is
 359   // called at the end of a GC and artificially expands the heap by
 360   // allocating a number of dead regions. This way we can induce very
 361   // frequent marking cycles and stress the cleanup / concurrent
 362   // cleanup code more (as all the regions that will be allocated by
 363   // this method will be found dead by the marking cycle).
 364   void allocate_dummy_regions() PRODUCT_RETURN;
 365 
 366   // Clear RSets after a compaction. It also resets the GC time stamps.
 367   void clear_rsets_post_compaction();
 368 
 369   // If the HR printer is active, dump the state of the regions in the
 370   // heap after a compaction.
 371   void print_hrm_post_compaction();
 372 
 373   // Create a memory mapper for auxiliary data structures of the given size and
 374   // translation factor.
 375   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 376                                                          size_t size,
 377                                                          size_t translation_factor);
 378 


 379   double verify(bool guard, const char* msg);
 380   void verify_before_gc();
 381   void verify_after_gc();
 382 
 383   void log_gc_header();
 384   void log_gc_footer(double pause_time_sec);
 385 
 386   // These are macros so that, if the assert fires, we get the correct
 387   // line number, file, etc.
 388 
 389 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 390   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 391           (_extra_message_),                                                  \
 392           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 393           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 394           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 395 
 396 #define assert_heap_locked()                                                  \
 397   do {                                                                        \
 398     assert(Heap_lock->owned_by_self(),                                        \
 399            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 400   } while (0)
 401 
 402 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 403   do {                                                                        \
 404     assert(Heap_lock->owned_by_self() ||                                      \
 405            (SafepointSynchronize::is_at_safepoint() &&                        \
 406              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 407            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 408                                         "should be at a safepoint"));         \
 409   } while (0)
 410 
 411 #define assert_heap_locked_and_not_at_safepoint()                             \
 412   do {                                                                        \
 413     assert(Heap_lock->owned_by_self() &&                                      \
 414                                     !SafepointSynchronize::is_at_safepoint(), \
 415           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 416                                        "should not be at a safepoint"));      \
 417   } while (0)
 418 
 419 #define assert_heap_not_locked()                                              \
 420   do {                                                                        \
 421     assert(!Heap_lock->owned_by_self(),                                       \
 422         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 423   } while (0)
 424 
 425 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 426   do {                                                                        \
 427     assert(!Heap_lock->owned_by_self() &&                                     \
 428                                     !SafepointSynchronize::is_at_safepoint(), \
 429       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 430                                    "should not be at a safepoint"));          \
 431   } while (0)
 432 
 433 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 434   do {                                                                        \
 435     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 436               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 437            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 438   } while (0)
 439 
 440 #define assert_not_at_safepoint()                                             \
 441   do {                                                                        \
 442     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 443            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 444   } while (0)
 445 
 446 protected:
 447 
 448   // The young region list.
 449   YoungList*  _young_list;
 450 
 451   // The current policy object for the collector.
 452   G1CollectorPolicy* _g1_policy;
 453 
 454   // This is the second level of trying to allocate a new region. If
 455   // new_region() didn't find a region on the free_list, this call will
 456   // check whether there's anything available on the
 457   // secondary_free_list and/or wait for more regions to appear on
 458   // that list, if _free_regions_coming is set.
 459   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 460 
 461   // Try to allocate a single non-humongous HeapRegion sufficient for
 462   // an allocation of the given word_size. If do_expand is true,
 463   // attempt to expand the heap if necessary to satisfy the allocation
 464   // request. If the region is to be used as an old region or for a
 465   // humongous object, set is_old to true. If not, to false.
 466   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 467 
 468   // Initialize a contiguous set of free regions of length num_regions
 469   // and starting at index first so that they appear as a single
 470   // humongous region.
 471   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 472                                                       uint num_regions,
 473                                                       size_t word_size,
 474                                                       AllocationContext_t context);
 475 
 476   // Attempt to allocate a humongous object of the given size. Return
 477   // NULL if unsuccessful.
 478   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 479 
 480   // The following two methods, allocate_new_tlab() and
 481   // mem_allocate(), are the two main entry points from the runtime
 482   // into the G1's allocation routines. They have the following
 483   // assumptions:
 484   //
 485   // * They should both be called outside safepoints.
 486   //
 487   // * They should both be called without holding the Heap_lock.
 488   //
 489   // * All allocation requests for new TLABs should go to
 490   //   allocate_new_tlab().
 491   //
 492   // * All non-TLAB allocation requests should go to mem_allocate().
 493   //
 494   // * If either call cannot satisfy the allocation request using the
 495   //   current allocating region, they will try to get a new one. If
 496   //   this fails, they will attempt to do an evacuation pause and
 497   //   retry the allocation.
 498   //
 499   // * If all allocation attempts fail, even after trying to schedule
 500   //   an evacuation pause, allocate_new_tlab() will return NULL,
 501   //   whereas mem_allocate() will attempt a heap expansion and/or
 502   //   schedule a Full GC.
 503   //
 504   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 505   //   should never be called with word_size being humongous. All
 506   //   humongous allocation requests should go to mem_allocate() which
 507   //   will satisfy them with a special path.
 508 
 509   virtual HeapWord* allocate_new_tlab(size_t word_size);
 510 
 511   virtual HeapWord* mem_allocate(size_t word_size,
 512                                  bool*  gc_overhead_limit_was_exceeded);
 513 
 514   // The following three methods take a gc_count_before_ret
 515   // parameter which is used to return the GC count if the method
 516   // returns NULL. Given that we are required to read the GC count
 517   // while holding the Heap_lock, and these paths will take the
 518   // Heap_lock at some point, it's easier to get them to read the GC
 519   // count while holding the Heap_lock before they return NULL instead
 520   // of the caller (namely: mem_allocate()) having to also take the
 521   // Heap_lock just to read the GC count.
 522 
 523   // First-level mutator allocation attempt: try to allocate out of
 524   // the mutator alloc region without taking the Heap_lock. This
 525   // should only be used for non-humongous allocations.
 526   inline HeapWord* attempt_allocation(size_t word_size,
 527                                       uint* gc_count_before_ret,
 528                                       uint* gclocker_retry_count_ret);
 529 
 530   // Second-level mutator allocation attempt: take the Heap_lock and
 531   // retry the allocation attempt, potentially scheduling a GC
 532   // pause. This should only be used for non-humongous allocations.
 533   HeapWord* attempt_allocation_slow(size_t word_size,
 534                                     AllocationContext_t context,
 535                                     uint* gc_count_before_ret,
 536                                     uint* gclocker_retry_count_ret);
 537 
 538   // Takes the Heap_lock and attempts a humongous allocation. It can
 539   // potentially schedule a GC pause.
 540   HeapWord* attempt_allocation_humongous(size_t word_size,
 541                                          uint* gc_count_before_ret,
 542                                          uint* gclocker_retry_count_ret);
 543 
 544   // Allocation attempt that should be called during safepoints (e.g.,
 545   // at the end of a successful GC). expect_null_mutator_alloc_region
 546   // specifies whether the mutator alloc region is expected to be NULL
 547   // or not.
 548   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 549                                             AllocationContext_t context,
 550                                             bool expect_null_mutator_alloc_region);
 551 
 552   // It dirties the cards that cover the block so that so that the post
 553   // write barrier never queues anything when updating objects on this
 554   // block. It is assumed (and in fact we assert) that the block
 555   // belongs to a young region.
 556   inline void dirty_young_block(HeapWord* start, size_t word_size);
 557 
 558   // Allocate blocks during garbage collection. Will ensure an
 559   // allocation region, either by picking one or expanding the
 560   // heap, and then allocate a block of the given size. The block
 561   // may not be a humongous - it must fit into a single heap region.
 562   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 563                                           size_t word_size,
 564                                           AllocationContext_t context);
 565   // Ensure that no further allocations can happen in "r", bearing in mind
 566   // that parallel threads might be attempting allocations.
 567   void par_allocate_remaining_space(HeapRegion* r);
 568 
 569   // Allocation attempt during GC for a survivor object / PLAB.
 570   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 571                                                AllocationContext_t context);
 572 
 573   // Allocation attempt during GC for an old object / PLAB.
 574   inline HeapWord* old_attempt_allocation(size_t word_size,
 575                                           AllocationContext_t context);
 576 
 577   // These methods are the "callbacks" from the G1AllocRegion class.
 578 
 579   // For mutator alloc regions.
 580   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 581   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 582                                    size_t allocated_bytes);
 583 
 584   // For GC alloc regions.
 585   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 586                                   InCSetState dest);
 587   void retire_gc_alloc_region(HeapRegion* alloc_region,
 588                               size_t allocated_bytes, InCSetState dest);
 589 
 590   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 591   //   inspection request and should collect the entire heap
 592   // - if clear_all_soft_refs is true, all soft references should be
 593   //   cleared during the GC
 594   // - if explicit_gc is false, word_size describes the allocation that
 595   //   the GC should attempt (at least) to satisfy
 596   // - it returns false if it is unable to do the collection due to the
 597   //   GC locker being active, true otherwise
 598   bool do_collection(bool explicit_gc,
 599                      bool clear_all_soft_refs,
 600                      size_t word_size);
 601 
 602   // Callback from VM_G1CollectFull operation.
 603   // Perform a full collection.
 604   virtual void do_full_collection(bool clear_all_soft_refs);
 605 
 606   // Resize the heap if necessary after a full collection.  If this is
 607   // after a collect-for allocation, "word_size" is the allocation size,
 608   // and will be considered part of the used portion of the heap.
 609   void resize_if_necessary_after_full_collection(size_t word_size);
 610 
 611   // Callback from VM_G1CollectForAllocation operation.
 612   // This function does everything necessary/possible to satisfy a
 613   // failed allocation request (including collection, expansion, etc.)
 614   HeapWord* satisfy_failed_allocation(size_t word_size,
 615                                       AllocationContext_t context,
 616                                       bool* succeeded);
 617 
 618   // Attempting to expand the heap sufficiently
 619   // to support an allocation of the given "word_size".  If
 620   // successful, perform the allocation and return the address of the
 621   // allocated block, or else "NULL".
 622   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 623 
 624   // Process any reference objects discovered during
 625   // an incremental evacuation pause.
 626   void process_discovered_references(uint no_of_gc_workers);
 627 
 628   // Enqueue any remaining discovered references
 629   // after processing.
 630   void enqueue_discovered_references(uint no_of_gc_workers);
 631 
 632 public:
 633 
 634   G1Allocator* allocator() {
 635     return _allocator;
 636   }
 637 
 638   G1MonitoringSupport* g1mm() {
 639     assert(_g1mm != NULL, "should have been initialized");
 640     return _g1mm;
 641   }
 642 
 643   // Expand the garbage-first heap by at least the given size (in bytes!).
 644   // Returns true if the heap was expanded by the requested amount;
 645   // false otherwise.
 646   // (Rounds up to a HeapRegion boundary.)
 647   bool expand(size_t expand_bytes);
 648 
 649   // Returns the PLAB statistics for a given destination.
 650   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 651 
 652   // Determines PLAB size for a given destination.
 653   inline size_t desired_plab_sz(InCSetState dest);
 654 
 655   inline AllocationContextStats& allocation_context_stats();
 656 
 657   // Do anything common to GC's.
 658   virtual void gc_prologue(bool full);
 659   virtual void gc_epilogue(bool full);
 660 
 661   // Modify the reclaim candidate set and test for presence.
 662   // These are only valid for starts_humongous regions.
 663   inline void set_humongous_reclaim_candidate(uint region, bool value);
 664   inline bool is_humongous_reclaim_candidate(uint region);
 665 
 666   // Remove from the reclaim candidate set.  Also remove from the
 667   // collection set so that later encounters avoid the slow path.
 668   inline void set_humongous_is_live(oop obj);
 669 
 670   // Register the given region to be part of the collection set.
 671   inline void register_humongous_region_with_in_cset_fast_test(uint index);
 672   // Register regions with humongous objects (actually on the start region) in
 673   // the in_cset_fast_test table.
 674   void register_humongous_regions_with_in_cset_fast_test();
 675   // We register a region with the fast "in collection set" test. We
 676   // simply set to true the array slot corresponding to this region.
 677   void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
 678     _in_cset_fast_test.set_in_young(r->hrm_index());
 679   }
 680   void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
 681     _in_cset_fast_test.set_in_old(r->hrm_index());
 682   }
 683 
 684   // This is a fast test on whether a reference points into the
 685   // collection set or not. Assume that the reference
 686   // points into the heap.
 687   inline bool in_cset_fast_test(oop obj);
 688 
 689   void clear_cset_fast_test() {
 690     _in_cset_fast_test.clear();
 691   }
 692 
 693   // This is called at the start of either a concurrent cycle or a Full
 694   // GC to update the number of old marking cycles started.
 695   void increment_old_marking_cycles_started();
 696 
 697   // This is called at the end of either a concurrent cycle or a Full
 698   // GC to update the number of old marking cycles completed. Those two
 699   // can happen in a nested fashion, i.e., we start a concurrent
 700   // cycle, a Full GC happens half-way through it which ends first,
 701   // and then the cycle notices that a Full GC happened and ends
 702   // too. The concurrent parameter is a boolean to help us do a bit
 703   // tighter consistency checking in the method. If concurrent is
 704   // false, the caller is the inner caller in the nesting (i.e., the
 705   // Full GC). If concurrent is true, the caller is the outer caller
 706   // in this nesting (i.e., the concurrent cycle). Further nesting is
 707   // not currently supported. The end of this call also notifies
 708   // the FullGCCount_lock in case a Java thread is waiting for a full
 709   // GC to happen (e.g., it called System.gc() with
 710   // +ExplicitGCInvokesConcurrent).
 711   void increment_old_marking_cycles_completed(bool concurrent);
 712 
 713   uint old_marking_cycles_completed() {
 714     return _old_marking_cycles_completed;
 715   }
 716 
 717   void register_concurrent_cycle_start(const Ticks& start_time);
 718   void register_concurrent_cycle_end();
 719   void trace_heap_after_concurrent_cycle();
 720 
 721   G1YCType yc_type();
 722 
 723   G1HRPrinter* hr_printer() { return &_hr_printer; }
 724 
 725   // Frees a non-humongous region by initializing its contents and
 726   // adding it to the free list that's passed as a parameter (this is
 727   // usually a local list which will be appended to the master free
 728   // list later). The used bytes of freed regions are accumulated in
 729   // pre_used. If par is true, the region's RSet will not be freed
 730   // up. The assumption is that this will be done later.
 731   // The locked parameter indicates if the caller has already taken
 732   // care of proper synchronization. This may allow some optimizations.
 733   void free_region(HeapRegion* hr,
 734                    FreeRegionList* free_list,
 735                    bool par,
 736                    bool locked = false);
 737 
 738   // Frees a humongous region by collapsing it into individual regions
 739   // and calling free_region() for each of them. The freed regions
 740   // will be added to the free list that's passed as a parameter (this
 741   // is usually a local list which will be appended to the master free
 742   // list later). The used bytes of freed regions are accumulated in
 743   // pre_used. If par is true, the region's RSet will not be freed
 744   // up. The assumption is that this will be done later.
 745   void free_humongous_region(HeapRegion* hr,
 746                              FreeRegionList* free_list,
 747                              bool par);
 748 protected:
 749 
 750   // Shrink the garbage-first heap by at most the given size (in bytes!).
 751   // (Rounds down to a HeapRegion boundary.)
 752   virtual void shrink(size_t expand_bytes);
 753   void shrink_helper(size_t expand_bytes);
 754 
 755   #if TASKQUEUE_STATS
 756   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 757   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 758   void reset_taskqueue_stats();
 759   #endif // TASKQUEUE_STATS
 760 
 761   // Schedule the VM operation that will do an evacuation pause to
 762   // satisfy an allocation request of word_size. *succeeded will
 763   // return whether the VM operation was successful (it did do an
 764   // evacuation pause) or not (another thread beat us to it or the GC
 765   // locker was active). Given that we should not be holding the
 766   // Heap_lock when we enter this method, we will pass the
 767   // gc_count_before (i.e., total_collections()) as a parameter since
 768   // it has to be read while holding the Heap_lock. Currently, both
 769   // methods that call do_collection_pause() release the Heap_lock
 770   // before the call, so it's easy to read gc_count_before just before.
 771   HeapWord* do_collection_pause(size_t         word_size,
 772                                 uint           gc_count_before,
 773                                 bool*          succeeded,
 774                                 GCCause::Cause gc_cause);
 775 
 776   // The guts of the incremental collection pause, executed by the vm
 777   // thread. It returns false if it is unable to do the collection due
 778   // to the GC locker being active, true otherwise
 779   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 780 
 781   // Actually do the work of evacuating the collection set.
 782   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 783 
 784   // The g1 remembered set of the heap.
 785   G1RemSet* _g1_rem_set;
 786 
 787   // A set of cards that cover the objects for which the Rsets should be updated
 788   // concurrently after the collection.
 789   DirtyCardQueueSet _dirty_card_queue_set;
 790 
 791   // The closure used to refine a single card.
 792   RefineCardTableEntryClosure* _refine_cte_cl;
 793 
 794   // A function to check the consistency of dirty card logs.
 795   void check_ct_logs_at_safepoint();
 796 
 797   // A DirtyCardQueueSet that is used to hold cards that contain
 798   // references into the current collection set. This is used to
 799   // update the remembered sets of the regions in the collection
 800   // set in the event of an evacuation failure.
 801   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 802 
 803   // After a collection pause, make the regions in the CS into free
 804   // regions.
 805   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 806 
 807   // Abandon the current collection set without recording policy
 808   // statistics or updating free lists.
 809   void abandon_collection_set(HeapRegion* cs_head);
 810 
 811   // The concurrent marker (and the thread it runs in.)
 812   ConcurrentMark* _cm;
 813   ConcurrentMarkThread* _cmThread;
 814   bool _mark_in_progress;
 815 
 816   // The concurrent refiner.
 817   ConcurrentG1Refine* _cg1r;
 818 
 819   // The parallel task queues
 820   RefToScanQueueSet *_task_queues;
 821 
 822   // True iff a evacuation has failed in the current collection.
 823   bool _evacuation_failed;
 824 
 825   EvacuationFailedInfo* _evacuation_failed_info_array;
 826 
 827   // Failed evacuations cause some logical from-space objects to have
 828   // forwarding pointers to themselves.  Reset them.
 829   void remove_self_forwarding_pointers();
 830 
 831   // Together, these store an object with a preserved mark, and its mark value.
 832   Stack<oop, mtGC>     _objs_with_preserved_marks;
 833   Stack<markOop, mtGC> _preserved_marks_of_objs;
 834 
 835   // Preserve the mark of "obj", if necessary, in preparation for its mark
 836   // word being overwritten with a self-forwarding-pointer.
 837   void preserve_mark_if_necessary(oop obj, markOop m);
 838 
 839   // The stack of evac-failure objects left to be scanned.
 840   GrowableArray<oop>*    _evac_failure_scan_stack;
 841   // The closure to apply to evac-failure objects.
 842 
 843   OopsInHeapRegionClosure* _evac_failure_closure;
 844   // Set the field above.
 845   void
 846   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 847     _evac_failure_closure = evac_failure_closure;
 848   }
 849 
 850   // Push "obj" on the scan stack.
 851   void push_on_evac_failure_scan_stack(oop obj);
 852   // Process scan stack entries until the stack is empty.
 853   void drain_evac_failure_scan_stack();
 854   // True iff an invocation of "drain_scan_stack" is in progress; to
 855   // prevent unnecessary recursion.
 856   bool _drain_in_progress;
 857 
 858   // Do any necessary initialization for evacuation-failure handling.
 859   // "cl" is the closure that will be used to process evac-failure
 860   // objects.
 861   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 862   // Do any necessary cleanup for evacuation-failure handling data
 863   // structures.
 864   void finalize_for_evac_failure();
 865 
 866   // An attempt to evacuate "obj" has failed; take necessary steps.
 867   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 868   void handle_evacuation_failure_common(oop obj, markOop m);
 869 
 870 #ifndef PRODUCT
 871   // Support for forcing evacuation failures. Analogous to
 872   // PromotionFailureALot for the other collectors.
 873 
 874   // Records whether G1EvacuationFailureALot should be in effect
 875   // for the current GC
 876   bool _evacuation_failure_alot_for_current_gc;
 877 
 878   // Used to record the GC number for interval checking when
 879   // determining whether G1EvaucationFailureALot is in effect
 880   // for the current GC.
 881   size_t _evacuation_failure_alot_gc_number;
 882 
 883   // Count of the number of evacuations between failures.
 884   volatile size_t _evacuation_failure_alot_count;
 885 
 886   // Set whether G1EvacuationFailureALot should be in effect
 887   // for the current GC (based upon the type of GC and which
 888   // command line flags are set);
 889   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 890                                                   bool during_initial_mark,
 891                                                   bool during_marking);
 892 
 893   inline void set_evacuation_failure_alot_for_current_gc();
 894 
 895   // Return true if it's time to cause an evacuation failure.
 896   inline bool evacuation_should_fail();
 897 
 898   // Reset the G1EvacuationFailureALot counters.  Should be called at
 899   // the end of an evacuation pause in which an evacuation failure occurred.
 900   inline void reset_evacuation_should_fail();
 901 #endif // !PRODUCT
 902 
 903   // ("Weak") Reference processing support.
 904   //
 905   // G1 has 2 instances of the reference processor class. One
 906   // (_ref_processor_cm) handles reference object discovery
 907   // and subsequent processing during concurrent marking cycles.
 908   //
 909   // The other (_ref_processor_stw) handles reference object
 910   // discovery and processing during full GCs and incremental
 911   // evacuation pauses.
 912   //
 913   // During an incremental pause, reference discovery will be
 914   // temporarily disabled for _ref_processor_cm and will be
 915   // enabled for _ref_processor_stw. At the end of the evacuation
 916   // pause references discovered by _ref_processor_stw will be
 917   // processed and discovery will be disabled. The previous
 918   // setting for reference object discovery for _ref_processor_cm
 919   // will be re-instated.
 920   //
 921   // At the start of marking:
 922   //  * Discovery by the CM ref processor is verified to be inactive
 923   //    and it's discovered lists are empty.
 924   //  * Discovery by the CM ref processor is then enabled.
 925   //
 926   // At the end of marking:
 927   //  * Any references on the CM ref processor's discovered
 928   //    lists are processed (possibly MT).
 929   //
 930   // At the start of full GC we:
 931   //  * Disable discovery by the CM ref processor and
 932   //    empty CM ref processor's discovered lists
 933   //    (without processing any entries).
 934   //  * Verify that the STW ref processor is inactive and it's
 935   //    discovered lists are empty.
 936   //  * Temporarily set STW ref processor discovery as single threaded.
 937   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 938   //    field.
 939   //  * Finally enable discovery by the STW ref processor.
 940   //
 941   // The STW ref processor is used to record any discovered
 942   // references during the full GC.
 943   //
 944   // At the end of a full GC we:
 945   //  * Enqueue any reference objects discovered by the STW ref processor
 946   //    that have non-live referents. This has the side-effect of
 947   //    making the STW ref processor inactive by disabling discovery.
 948   //  * Verify that the CM ref processor is still inactive
 949   //    and no references have been placed on it's discovered
 950   //    lists (also checked as a precondition during initial marking).
 951 
 952   // The (stw) reference processor...
 953   ReferenceProcessor* _ref_processor_stw;
 954 
 955   STWGCTimer* _gc_timer_stw;
 956   ConcurrentGCTimer* _gc_timer_cm;
 957 
 958   G1OldTracer* _gc_tracer_cm;
 959   G1NewTracer* _gc_tracer_stw;
 960 
 961   // During reference object discovery, the _is_alive_non_header
 962   // closure (if non-null) is applied to the referent object to
 963   // determine whether the referent is live. If so then the
 964   // reference object does not need to be 'discovered' and can
 965   // be treated as a regular oop. This has the benefit of reducing
 966   // the number of 'discovered' reference objects that need to
 967   // be processed.
 968   //
 969   // Instance of the is_alive closure for embedding into the
 970   // STW reference processor as the _is_alive_non_header field.
 971   // Supplying a value for the _is_alive_non_header field is
 972   // optional but doing so prevents unnecessary additions to
 973   // the discovered lists during reference discovery.
 974   G1STWIsAliveClosure _is_alive_closure_stw;
 975 
 976   // The (concurrent marking) reference processor...
 977   ReferenceProcessor* _ref_processor_cm;
 978 
 979   // Instance of the concurrent mark is_alive closure for embedding
 980   // into the Concurrent Marking reference processor as the
 981   // _is_alive_non_header field. Supplying a value for the
 982   // _is_alive_non_header field is optional but doing so prevents
 983   // unnecessary additions to the discovered lists during reference
 984   // discovery.
 985   G1CMIsAliveClosure _is_alive_closure_cm;
 986 
 987   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 988   HeapRegion** _worker_cset_start_region;
 989 
 990   // Time stamp to validate the regions recorded in the cache
 991   // used by G1CollectedHeap::start_cset_region_for_worker().
 992   // The heap region entry for a given worker is valid iff
 993   // the associated time stamp value matches the current value
 994   // of G1CollectedHeap::_gc_time_stamp.
 995   uint* _worker_cset_start_region_time_stamp;
 996 
 997   volatile bool _free_regions_coming;
 998 
 999 public:
1000 
1001   void set_refine_cte_cl_concurrency(bool concurrent);
1002 
1003   RefToScanQueue *task_queue(int i) const;
1004 
1005   // A set of cards where updates happened during the GC
1006   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1007 
1008   // A DirtyCardQueueSet that is used to hold cards that contain
1009   // references into the current collection set. This is used to
1010   // update the remembered sets of the regions in the collection
1011   // set in the event of an evacuation failure.
1012   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1013         { return _into_cset_dirty_card_queue_set; }
1014 
1015   // Create a G1CollectedHeap with the specified policy.
1016   // Must call the initialize method afterwards.
1017   // May not return if something goes wrong.
1018   G1CollectedHeap(G1CollectorPolicy* policy);
1019 
1020   // Initialize the G1CollectedHeap to have the initial and
1021   // maximum sizes and remembered and barrier sets
1022   // specified by the policy object.
1023   jint initialize();
1024 
1025   virtual void stop();
1026 
1027   // Return the (conservative) maximum heap alignment for any G1 heap
1028   static size_t conservative_max_heap_alignment();
1029 
1030   // Initialize weak reference processing.
1031   virtual void ref_processing_init();
1032 
1033   // Explicitly import set_par_threads into this scope
1034   using SharedHeap::set_par_threads;
1035   // Set _n_par_threads according to a policy TBD.
1036   void set_par_threads();
1037 
1038   virtual CollectedHeap::Name kind() const {
1039     return CollectedHeap::G1CollectedHeap;
1040   }
1041 
1042   // The current policy object for the collector.
1043   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1044 
1045   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1046 
1047   // Adaptive size policy.  No such thing for g1.
1048   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1049 
1050   // The rem set and barrier set.
1051   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1052 
1053   unsigned get_gc_time_stamp() {
1054     return _gc_time_stamp;
1055   }
1056 
1057   inline void reset_gc_time_stamp();
1058 
1059   void check_gc_time_stamps() PRODUCT_RETURN;
1060 
1061   inline void increment_gc_time_stamp();
1062 
1063   // Reset the given region's GC timestamp. If it's starts humongous,
1064   // also reset the GC timestamp of its corresponding
1065   // continues humongous regions too.
1066   void reset_gc_time_stamps(HeapRegion* hr);
1067 
1068   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1069                                   DirtyCardQueue* into_cset_dcq,
1070                                   bool concurrent, uint worker_i);
1071 
1072   // The shared block offset table array.
1073   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1074 
1075   // Reference Processing accessors
1076 
1077   // The STW reference processor....
1078   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1079 
1080   // The Concurrent Marking reference processor...
1081   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1082 
1083   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1084   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1085 
1086   virtual size_t capacity() const;
1087   virtual size_t used() const;
1088   // This should be called when we're not holding the heap lock. The
1089   // result might be a bit inaccurate.
1090   size_t used_unlocked() const;
1091   size_t recalculate_used() const;
1092 
1093   // These virtual functions do the actual allocation.
1094   // Some heaps may offer a contiguous region for shared non-blocking
1095   // allocation, via inlined code (by exporting the address of the top and
1096   // end fields defining the extent of the contiguous allocation region.)
1097   // But G1CollectedHeap doesn't yet support this.
1098 
1099   virtual bool is_maximal_no_gc() const {
1100     return _hrm.available() == 0;
1101   }
1102 
1103   // The current number of regions in the heap.
1104   uint num_regions() const { return _hrm.length(); }
1105 
1106   // The max number of regions in the heap.
1107   uint max_regions() const { return _hrm.max_length(); }
1108 
1109   // The number of regions that are completely free.
1110   uint num_free_regions() const { return _hrm.num_free_regions(); }
1111 
1112   MemoryUsage get_auxiliary_data_memory_usage() const {
1113     return _hrm.get_auxiliary_data_memory_usage();
1114   }
1115 
1116   // The number of regions that are not completely free.
1117   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1118 
1119   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1120   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1121   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1122   void verify_dirty_young_regions() PRODUCT_RETURN;
1123 
1124 #ifndef PRODUCT
1125   // Make sure that the given bitmap has no marked objects in the
1126   // range [from,limit). If it does, print an error message and return
1127   // false. Otherwise, just return true. bitmap_name should be "prev"
1128   // or "next".
1129   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1130                                 HeapWord* from, HeapWord* limit);
1131 
1132   // Verify that the prev / next bitmap range [tams,end) for the given
1133   // region has no marks. Return true if all is well, false if errors
1134   // are detected.
1135   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1136 #endif // PRODUCT
1137 
1138   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1139   // the given region do not have any spurious marks. If errors are
1140   // detected, print appropriate error messages and crash.
1141   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1142 
1143   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1144   // have any spurious marks. If errors are detected, print
1145   // appropriate error messages and crash.
1146   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1147 
1148   // Do sanity check on the contents of the in-cset fast test table.
1149   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1150 
1151   // verify_region_sets() performs verification over the region
1152   // lists. It will be compiled in the product code to be used when
1153   // necessary (i.e., during heap verification).
1154   void verify_region_sets();
1155 
1156   // verify_region_sets_optional() is planted in the code for
1157   // list verification in non-product builds (and it can be enabled in
1158   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1159 #if HEAP_REGION_SET_FORCE_VERIFY
1160   void verify_region_sets_optional() {
1161     verify_region_sets();
1162   }
1163 #else // HEAP_REGION_SET_FORCE_VERIFY
1164   void verify_region_sets_optional() { }
1165 #endif // HEAP_REGION_SET_FORCE_VERIFY
1166 
1167 #ifdef ASSERT
1168   bool is_on_master_free_list(HeapRegion* hr) {
1169     return _hrm.is_free(hr);
1170   }
1171 #endif // ASSERT
1172 
1173   // Wrapper for the region list operations that can be called from
1174   // methods outside this class.
1175 
1176   void secondary_free_list_add(FreeRegionList* list) {
1177     _secondary_free_list.add_ordered(list);
1178   }
1179 
1180   void append_secondary_free_list() {
1181     _hrm.insert_list_into_free_list(&_secondary_free_list);
1182   }
1183 
1184   void append_secondary_free_list_if_not_empty_with_lock() {
1185     // If the secondary free list looks empty there's no reason to
1186     // take the lock and then try to append it.
1187     if (!_secondary_free_list.is_empty()) {
1188       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1189       append_secondary_free_list();
1190     }
1191   }
1192 
1193   inline void old_set_remove(HeapRegion* hr);
1194 
1195   size_t non_young_capacity_bytes() {
1196     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1197   }
1198 
1199   void set_free_regions_coming();
1200   void reset_free_regions_coming();
1201   bool free_regions_coming() { return _free_regions_coming; }
1202   void wait_while_free_regions_coming();
1203 
1204   // Determine whether the given region is one that we are using as an
1205   // old GC alloc region.
1206   bool is_old_gc_alloc_region(HeapRegion* hr) {
1207     return _allocator->is_retained_old_region(hr);
1208   }
1209 
1210   // Perform a collection of the heap; intended for use in implementing
1211   // "System.gc".  This probably implies as full a collection as the
1212   // "CollectedHeap" supports.
1213   virtual void collect(GCCause::Cause cause);
1214 
1215   // The same as above but assume that the caller holds the Heap_lock.
1216   void collect_locked(GCCause::Cause cause);
1217 
1218   virtual bool copy_allocation_context_stats(const jint* contexts,
1219                                              jlong* totals,
1220                                              jbyte* accuracy,
1221                                              jint len);
1222 
1223   // True iff an evacuation has failed in the most-recent collection.
1224   bool evacuation_failed() { return _evacuation_failed; }
1225 
1226   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1227   void prepend_to_freelist(FreeRegionList* list);
1228   void decrement_summary_bytes(size_t bytes);
1229 
1230   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1231   virtual bool is_in(const void* p) const;
1232 #ifdef ASSERT
1233   // Returns whether p is in one of the available areas of the heap. Slow but
1234   // extensive version.
1235   bool is_in_exact(const void* p) const;
1236 #endif
1237 
1238   // Return "TRUE" iff the given object address is within the collection
1239   // set. Slow implementation.
1240   inline bool obj_in_cs(oop obj);
1241 
1242   inline bool is_in_cset(oop obj);
1243 
1244   inline bool is_in_cset_or_humongous(const oop obj);
1245 
1246  private:
1247   // This array is used for a quick test on whether a reference points into
1248   // the collection set or not. Each of the array's elements denotes whether the
1249   // corresponding region is in the collection set or not.
1250   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1251 
1252  public:
1253 
1254   inline InCSetState in_cset_state(const oop obj);
1255 
1256   // Return "TRUE" iff the given object address is in the reserved
1257   // region of g1.
1258   bool is_in_g1_reserved(const void* p) const {
1259     return _hrm.reserved().contains(p);
1260   }
1261 
1262   // Returns a MemRegion that corresponds to the space that has been
1263   // reserved for the heap
1264   MemRegion g1_reserved() const {
1265     return _hrm.reserved();
1266   }
1267 
1268   virtual bool is_in_closed_subset(const void* p) const;
1269 
1270   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1271     return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1272   }
1273 
1274   // This resets the card table to all zeros.  It is used after
1275   // a collection pause which used the card table to claim cards.
1276   void cleanUpCardTable();
1277 
1278   // Iteration functions.
1279 
1280   // Iterate over all the ref-containing fields of all objects, calling
1281   // "cl.do_oop" on each.
1282   virtual void oop_iterate(ExtendedOopClosure* cl);
1283 
1284   // Iterate over all objects, calling "cl.do_object" on each.
1285   virtual void object_iterate(ObjectClosure* cl);
1286 
1287   virtual void safe_object_iterate(ObjectClosure* cl) {
1288     object_iterate(cl);
1289   }
1290 
1291   // Iterate over all spaces in use in the heap, in ascending address order.
1292   virtual void space_iterate(SpaceClosure* cl);
1293 
1294   // Iterate over heap regions, in address order, terminating the
1295   // iteration early if the "doHeapRegion" method returns "true".
1296   void heap_region_iterate(HeapRegionClosure* blk) const;
1297 
1298   // Return the region with the given index. It assumes the index is valid.
1299   inline HeapRegion* region_at(uint index) const;
1300 
1301   // Calculate the region index of the given address. Given address must be
1302   // within the heap.
1303   inline uint addr_to_region(HeapWord* addr) const;
1304 
1305   inline HeapWord* bottom_addr_for_region(uint index) const;
1306 
1307   // Divide the heap region sequence into "chunks" of some size (the number
1308   // of regions divided by the number of parallel threads times some
1309   // overpartition factor, currently 4).  Assumes that this will be called
1310   // in parallel by ParallelGCThreads worker threads with discinct worker
1311   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1312   // calls will use the same "claim_value", and that that claim value is
1313   // different from the claim_value of any heap region before the start of
1314   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1315   // attempting to claim the first region in each chunk, and, if
1316   // successful, applying the closure to each region in the chunk (and
1317   // setting the claim value of the second and subsequent regions of the
1318   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1319   // i.e., that a closure never attempt to abort a traversal.
1320   void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1321                                        uint worker_id,
1322                                        uint num_workers,
1323                                        jint claim_value) const;
1324 
1325   // It resets all the region claim values to the default.
1326   void reset_heap_region_claim_values();
1327 
1328   // Resets the claim values of regions in the current
1329   // collection set to the default.
1330   void reset_cset_heap_region_claim_values();
1331 
1332 #ifdef ASSERT
1333   bool check_heap_region_claim_values(jint claim_value);
1334 
1335   // Same as the routine above but only checks regions in the
1336   // current collection set.
1337   bool check_cset_heap_region_claim_values(jint claim_value);
1338 #endif // ASSERT
1339 
1340   // Clear the cached cset start regions and (more importantly)
1341   // the time stamps. Called when we reset the GC time stamp.
1342   void clear_cset_start_regions();
1343 
1344   // Given the id of a worker, obtain or calculate a suitable
1345   // starting region for iterating over the current collection set.
1346   HeapRegion* start_cset_region_for_worker(uint worker_i);
1347 
1348   // Iterate over the regions (if any) in the current collection set.
1349   void collection_set_iterate(HeapRegionClosure* blk);
1350 
1351   // As above but starting from region r
1352   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1353 
1354   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1355 
1356   // A CollectedHeap will contain some number of spaces.  This finds the
1357   // space containing a given address, or else returns NULL.
1358   virtual Space* space_containing(const void* addr) const;
1359 
1360   // Returns the HeapRegion that contains addr. addr must not be NULL.
1361   template <class T>
1362   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1363 
1364   // Returns the HeapRegion that contains addr. addr must not be NULL.
1365   // If addr is within a humongous continues region, it returns its humongous start region.
1366   template <class T>
1367   inline HeapRegion* heap_region_containing(const T addr) const;
1368 
1369   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1370   // each address in the (reserved) heap is a member of exactly
1371   // one block.  The defining characteristic of a block is that it is
1372   // possible to find its size, and thus to progress forward to the next
1373   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1374   // represent Java objects, or they might be free blocks in a
1375   // free-list-based heap (or subheap), as long as the two kinds are
1376   // distinguishable and the size of each is determinable.
1377 
1378   // Returns the address of the start of the "block" that contains the
1379   // address "addr".  We say "blocks" instead of "object" since some heaps
1380   // may not pack objects densely; a chunk may either be an object or a
1381   // non-object.
1382   virtual HeapWord* block_start(const void* addr) const;
1383 
1384   // Requires "addr" to be the start of a chunk, and returns its size.
1385   // "addr + size" is required to be the start of a new chunk, or the end
1386   // of the active area of the heap.
1387   virtual size_t block_size(const HeapWord* addr) const;
1388 
1389   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1390   // the block is an object.
1391   virtual bool block_is_obj(const HeapWord* addr) const;
1392 
1393   // Does this heap support heap inspection? (+PrintClassHistogram)
1394   virtual bool supports_heap_inspection() const { return true; }
1395 
1396   // Section on thread-local allocation buffers (TLABs)
1397   // See CollectedHeap for semantics.
1398 
1399   bool supports_tlab_allocation() const;
1400   size_t tlab_capacity(Thread* ignored) const;
1401   size_t tlab_used(Thread* ignored) const;
1402   size_t max_tlab_size() const;
1403   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1404 
1405   // Can a compiler initialize a new object without store barriers?
1406   // This permission only extends from the creation of a new object
1407   // via a TLAB up to the first subsequent safepoint. If such permission
1408   // is granted for this heap type, the compiler promises to call
1409   // defer_store_barrier() below on any slow path allocation of
1410   // a new object for which such initializing store barriers will
1411   // have been elided. G1, like CMS, allows this, but should be
1412   // ready to provide a compensating write barrier as necessary
1413   // if that storage came out of a non-young region. The efficiency
1414   // of this implementation depends crucially on being able to
1415   // answer very efficiently in constant time whether a piece of
1416   // storage in the heap comes from a young region or not.
1417   // See ReduceInitialCardMarks.
1418   virtual bool can_elide_tlab_store_barriers() const {
1419     return true;
1420   }
1421 
1422   virtual bool card_mark_must_follow_store() const {
1423     return true;
1424   }
1425 
1426   inline bool is_in_young(const oop obj);
1427 
1428 #ifdef ASSERT
1429   virtual bool is_in_partial_collection(const void* p);
1430 #endif
1431 
1432   virtual bool is_scavengable(const void* addr);
1433 
1434   // We don't need barriers for initializing stores to objects
1435   // in the young gen: for the SATB pre-barrier, there is no
1436   // pre-value that needs to be remembered; for the remembered-set
1437   // update logging post-barrier, we don't maintain remembered set
1438   // information for young gen objects.
1439   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1440 
1441   // Returns "true" iff the given word_size is "very large".
1442   static bool isHumongous(size_t word_size) {
1443     // Note this has to be strictly greater-than as the TLABs
1444     // are capped at the humongous thresold and we want to
1445     // ensure that we don't try to allocate a TLAB as
1446     // humongous and that we don't allocate a humongous
1447     // object in a TLAB.
1448     return word_size > _humongous_object_threshold_in_words;
1449   }
1450 
1451   // Update mod union table with the set of dirty cards.
1452   void updateModUnion();
1453 
1454   // Set the mod union bits corresponding to the given memRegion.  Note
1455   // that this is always a safe operation, since it doesn't clear any
1456   // bits.
1457   void markModUnionRange(MemRegion mr);
1458 
1459   // Records the fact that a marking phase is no longer in progress.
1460   void set_marking_complete() {
1461     _mark_in_progress = false;
1462   }
1463   void set_marking_started() {
1464     _mark_in_progress = true;
1465   }
1466   bool mark_in_progress() {
1467     return _mark_in_progress;
1468   }
1469 
1470   // Print the maximum heap capacity.
1471   virtual size_t max_capacity() const;
1472 
1473   virtual jlong millis_since_last_gc();
1474 
1475 
1476   // Convenience function to be used in situations where the heap type can be
1477   // asserted to be this type.
1478   static G1CollectedHeap* heap();
1479 
1480   void set_region_short_lived_locked(HeapRegion* hr);
1481   // add appropriate methods for any other surv rate groups
1482 
1483   YoungList* young_list() const { return _young_list; }
1484 
1485   // debugging
1486   bool check_young_list_well_formed() {
1487     return _young_list->check_list_well_formed();
1488   }
1489 
1490   bool check_young_list_empty(bool check_heap,
1491                               bool check_sample = true);
1492 
1493   // *** Stuff related to concurrent marking.  It's not clear to me that so
1494   // many of these need to be public.
1495 
1496   // The functions below are helper functions that a subclass of
1497   // "CollectedHeap" can use in the implementation of its virtual
1498   // functions.
1499   // This performs a concurrent marking of the live objects in a
1500   // bitmap off to the side.
1501   void doConcurrentMark();
1502 
1503   bool isMarkedPrev(oop obj) const;
1504   bool isMarkedNext(oop obj) const;
1505 
1506   // Determine if an object is dead, given the object and also
1507   // the region to which the object belongs. An object is dead
1508   // iff a) it was not allocated since the last mark and b) it
1509   // is not marked.
1510   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1511     return
1512       !hr->obj_allocated_since_prev_marking(obj) &&
1513       !isMarkedPrev(obj);
1514   }
1515 
1516   // This function returns true when an object has been
1517   // around since the previous marking and hasn't yet
1518   // been marked during this marking.
1519   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1520     return
1521       !hr->obj_allocated_since_next_marking(obj) &&
1522       !isMarkedNext(obj);
1523   }
1524 
1525   // Determine if an object is dead, given only the object itself.
1526   // This will find the region to which the object belongs and
1527   // then call the region version of the same function.
1528 
1529   // Added if it is NULL it isn't dead.
1530 
1531   inline bool is_obj_dead(const oop obj) const;
1532 
1533   inline bool is_obj_ill(const oop obj) const;
1534 
1535   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1536   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1537   bool is_marked(oop obj, VerifyOption vo);
1538   const char* top_at_mark_start_str(VerifyOption vo);
1539 
1540   ConcurrentMark* concurrent_mark() const { return _cm; }
1541 
1542   // Refinement
1543 
1544   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1545 
1546   // The dirty cards region list is used to record a subset of regions
1547   // whose cards need clearing. The list if populated during the
1548   // remembered set scanning and drained during the card table
1549   // cleanup. Although the methods are reentrant, population/draining
1550   // phases must not overlap. For synchronization purposes the last
1551   // element on the list points to itself.
1552   HeapRegion* _dirty_cards_region_list;
1553   void push_dirty_cards_region(HeapRegion* hr);
1554   HeapRegion* pop_dirty_cards_region();
1555 
1556   // Optimized nmethod scanning support routines
1557 
1558   // Register the given nmethod with the G1 heap
1559   virtual void register_nmethod(nmethod* nm);
1560 
1561   // Unregister the given nmethod from the G1 heap
1562   virtual void unregister_nmethod(nmethod* nm);
1563 
1564   // Free up superfluous code root memory.
1565   void purge_code_root_memory();
1566 
1567   // Rebuild the stong code root lists for each region
1568   // after a full GC
1569   void rebuild_strong_code_roots();
1570 
1571   // Delete entries for dead interned string and clean up unreferenced symbols
1572   // in symbol table, possibly in parallel.
1573   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1574 
1575   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1576   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1577 
1578   // Redirty logged cards in the refinement queue.
1579   void redirty_logged_cards();
1580   // Verification
1581 
1582   // The following is just to alert the verification code
1583   // that a full collection has occurred and that the
1584   // remembered sets are no longer up to date.
1585   bool _full_collection;
1586   void set_full_collection() { _full_collection = true;}
1587   void clear_full_collection() {_full_collection = false;}
1588   bool full_collection() {return _full_collection;}
1589 
1590   // Perform any cleanup actions necessary before allowing a verification.
1591   virtual void prepare_for_verify();
1592 
1593   // Perform verification.
1594 
1595   // vo == UsePrevMarking  -> use "prev" marking information,
1596   // vo == UseNextMarking -> use "next" marking information
1597   // vo == UseMarkWord    -> use the mark word in the object header
1598   //
1599   // NOTE: Only the "prev" marking information is guaranteed to be
1600   // consistent most of the time, so most calls to this should use
1601   // vo == UsePrevMarking.
1602   // Currently, there is only one case where this is called with
1603   // vo == UseNextMarking, which is to verify the "next" marking
1604   // information at the end of remark.
1605   // Currently there is only one place where this is called with
1606   // vo == UseMarkWord, which is to verify the marking during a
1607   // full GC.
1608   void verify(bool silent, VerifyOption vo);
1609 
1610   // Override; it uses the "prev" marking information
1611   virtual void verify(bool silent);
1612 
1613   // The methods below are here for convenience and dispatch the
1614   // appropriate method depending on value of the given VerifyOption
1615   // parameter. The values for that parameter, and their meanings,
1616   // are the same as those above.
1617 
1618   bool is_obj_dead_cond(const oop obj,
1619                         const HeapRegion* hr,
1620                         const VerifyOption vo) const;
1621 
1622   bool is_obj_dead_cond(const oop obj,
1623                         const VerifyOption vo) const;


1624 
1625   // Printing
1626 
1627   virtual void print_on(outputStream* st) const;
1628   virtual void print_extended_on(outputStream* st) const;
1629   virtual void print_on_error(outputStream* st) const;
1630 
1631   virtual void print_gc_threads_on(outputStream* st) const;
1632   virtual void gc_threads_do(ThreadClosure* tc) const;
1633 
1634   // Override
1635   void print_tracing_info() const;
1636 
1637   // The following two methods are helpful for debugging RSet issues.
1638   void print_cset_rsets() PRODUCT_RETURN;
1639   void print_all_rsets() PRODUCT_RETURN;
1640 
1641 public:
1642   size_t pending_card_num();
1643   size_t cards_scanned();
1644 
1645 protected:
1646   size_t _max_heap_capacity;
1647 };
1648 
1649 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---