1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_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/g1CollectorState.hpp"
  35 #include "gc/g1/g1HRPrinter.hpp"
  36 #include "gc/g1/g1InCSetState.hpp"
  37 #include "gc/g1/g1MonitoringSupport.hpp"
  38 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
  39 #include "gc/g1/g1YCTypes.hpp"
  40 #include "gc/g1/hSpaceCounters.hpp"
  41 #include "gc/g1/heapRegionManager.hpp"
  42 #include "gc/g1/heapRegionSet.hpp"
  43 #include "gc/shared/barrierSet.hpp"
  44 #include "gc/shared/collectedHeap.hpp"
  45 #include "memory/memRegion.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 G1ParScanThreadState;
  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 class FlexibleWorkGang;
  80 
  81 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  82 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  83 
  84 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  85 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  86 
  87 class YoungList : public CHeapObj<mtGC> {
  88 private:
  89   G1CollectedHeap* _g1h;
  90 
  91   HeapRegion* _head;
  92 
  93   HeapRegion* _survivor_head;
  94   HeapRegion* _survivor_tail;
  95 
  96   HeapRegion* _curr;
  97 
  98   uint        _length;
  99   uint        _survivor_length;
 100 
 101   size_t      _last_sampled_rs_lengths;
 102   size_t      _sampled_rs_lengths;
 103 
 104   void         empty_list(HeapRegion* list);
 105 
 106 public:
 107   YoungList(G1CollectedHeap* g1h);
 108 
 109   void         push_region(HeapRegion* hr);
 110   void         add_survivor_region(HeapRegion* hr);
 111 
 112   void         empty_list();
 113   bool         is_empty() { return _length == 0; }
 114   uint         length() { return _length; }
 115   uint         eden_length() { return length() - survivor_length(); }
 116   uint         survivor_length() { return _survivor_length; }
 117 
 118   // Currently we do not keep track of the used byte sum for the
 119   // young list and the survivors and it'd be quite a lot of work to
 120   // do so. When we'll eventually replace the young list with
 121   // instances of HeapRegionLinkedList we'll get that for free. So,
 122   // we'll report the more accurate information then.
 123   size_t       eden_used_bytes() {
 124     assert(length() >= survivor_length(), "invariant");
 125     return (size_t) eden_length() * HeapRegion::GrainBytes;
 126   }
 127   size_t       survivor_used_bytes() {
 128     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 129   }
 130 
 131   void rs_length_sampling_init();
 132   bool rs_length_sampling_more();
 133   void rs_length_sampling_next();
 134 
 135   void reset_sampled_info() {
 136     _last_sampled_rs_lengths =   0;
 137   }
 138   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 139 
 140   // for development purposes
 141   void reset_auxilary_lists();
 142   void clear() { _head = NULL; _length = 0; }
 143 
 144   void clear_survivors() {
 145     _survivor_head    = NULL;
 146     _survivor_tail    = NULL;
 147     _survivor_length  = 0;
 148   }
 149 
 150   HeapRegion* first_region() { return _head; }
 151   HeapRegion* first_survivor_region() { return _survivor_head; }
 152   HeapRegion* last_survivor_region() { return _survivor_tail; }
 153 
 154   // debugging
 155   bool          check_list_well_formed();
 156   bool          check_list_empty(bool check_sample = true);
 157   void          print();
 158 };
 159 
 160 // The G1 STW is alive closure.
 161 // An instance is embedded into the G1CH and used as the
 162 // (optional) _is_alive_non_header closure in the STW
 163 // reference processor. It is also extensively used during
 164 // reference processing during STW evacuation pauses.
 165 class G1STWIsAliveClosure: public BoolObjectClosure {
 166   G1CollectedHeap* _g1;
 167 public:
 168   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 169   bool do_object_b(oop p);
 170 };
 171 
 172 class RefineCardTableEntryClosure;
 173 
 174 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 175  private:
 176   void reset_from_card_cache(uint start_idx, size_t num_regions);
 177  public:
 178   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 179 };
 180 
 181 class G1CollectedHeap : public CollectedHeap {
 182   friend class VM_CollectForMetadataAllocation;
 183   friend class VM_G1CollectForAllocation;
 184   friend class VM_G1CollectFull;
 185   friend class VM_G1IncCollectionPause;
 186   friend class VMStructs;
 187   friend class MutatorAllocRegion;
 188   friend class SurvivorGCAllocRegion;
 189   friend class OldGCAllocRegion;
 190   friend class G1Allocator;
 191   friend class G1ArchiveAllocator;
 192 
 193   // Closures used in implementation.
 194   friend class G1ParScanThreadState;
 195   friend class G1ParTask;
 196   friend class G1ParGCAllocator;
 197   friend class G1PrepareCompactClosure;
 198 
 199   // Other related classes.
 200   friend class HeapRegionClaimer;
 201 
 202   // Testing classes.
 203   friend class G1CheckCSetFastTableClosure;
 204 
 205 private:
 206   FlexibleWorkGang* _workers;
 207 
 208   static size_t _humongous_object_threshold_in_words;
 209 
 210   // The secondary free list which contains regions that have been
 211   // freed up during the cleanup process. This will be appended to
 212   // the master free list when appropriate.
 213   FreeRegionList _secondary_free_list;
 214 
 215   // It keeps track of the old regions.
 216   HeapRegionSet _old_set;
 217 
 218   // It keeps track of the humongous regions.
 219   HeapRegionSet _humongous_set;
 220 
 221   void eagerly_reclaim_humongous_regions();
 222 
 223   // The number of regions we could create by expansion.
 224   uint _expansion_regions;
 225 
 226   // The block offset table for the G1 heap.
 227   G1BlockOffsetSharedArray* _bot_shared;
 228 
 229   // Tears down the region sets / lists so that they are empty and the
 230   // regions on the heap do not belong to a region set / list. The
 231   // only exception is the humongous set which we leave unaltered. If
 232   // free_list_only is true, it will only tear down the master free
 233   // list. It is called before a Full GC (free_list_only == false) or
 234   // before heap shrinking (free_list_only == true).
 235   void tear_down_region_sets(bool free_list_only);
 236 
 237   // Rebuilds the region sets / lists so that they are repopulated to
 238   // reflect the contents of the heap. The only exception is the
 239   // humongous set which was not torn down in the first place. If
 240   // free_list_only is true, it will only rebuild the master free
 241   // list. It is called after a Full GC (free_list_only == false) or
 242   // after heap shrinking (free_list_only == true).
 243   void rebuild_region_sets(bool free_list_only);
 244 
 245   // Callback for region mapping changed events.
 246   G1RegionMappingChangedListener _listener;
 247 
 248   // The sequence of all heap regions in the heap.
 249   HeapRegionManager _hrm;
 250 
 251   // Class that handles the different kinds of allocations.
 252   G1Allocator* _allocator;
 253 
 254   // Outside of GC pauses, the number of bytes used in all regions other
 255   // than the current allocation region(s).
 256   size_t _summary_bytes_used;
 257 
 258   void increase_used(size_t bytes);
 259   void decrease_used(size_t bytes);
 260 
 261   void set_used(size_t bytes);
 262 
 263   // Class that handles archive allocation ranges.
 264   G1ArchiveAllocator* _archive_allocator;
 265 
 266   // Statistics for each allocation context
 267   AllocationContextStats _allocation_context_stats;
 268 
 269   // PLAB sizing policy for survivors.
 270   PLABStats _survivor_plab_stats;
 271 
 272   // PLAB sizing policy for tenured objects.
 273   PLABStats _old_plab_stats;
 274 
 275   // It specifies whether we should attempt to expand the heap after a
 276   // region allocation failure. If heap expansion fails we set this to
 277   // false so that we don't re-attempt the heap expansion (it's likely
 278   // that subsequent expansion attempts will also fail if one fails).
 279   // Currently, it is only consulted during GC and it's reset at the
 280   // start of each GC.
 281   bool _expand_heap_after_alloc_failure;
 282 
 283   // It resets the mutator alloc region before new allocations can take place.
 284   void init_mutator_alloc_region();
 285 
 286   // It releases the mutator alloc region.
 287   void release_mutator_alloc_region();
 288 
 289   // It initializes the GC alloc regions at the start of a GC.
 290   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 291 
 292   // It releases the GC alloc regions at the end of a GC.
 293   void release_gc_alloc_regions(EvacuationInfo& evacuation_info);
 294 
 295   // It does any cleanup that needs to be done on the GC alloc regions
 296   // before a Full GC.
 297   void abandon_gc_alloc_regions();
 298 
 299   // Helper for monitoring and management support.
 300   G1MonitoringSupport* _g1mm;
 301 
 302   // Records whether the region at the given index is (still) a
 303   // candidate for eager reclaim.  Only valid for humongous start
 304   // regions; other regions have unspecified values.  Humongous start
 305   // regions are initialized at start of collection pause, with
 306   // candidates removed from the set as they are found reachable from
 307   // roots or the young generation.
 308   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 309    protected:
 310     bool default_value() const { return false; }
 311    public:
 312     void clear() { G1BiasedMappedArray<bool>::clear(); }
 313     void set_candidate(uint region, bool value) {
 314       set_by_index(region, value);
 315     }
 316     bool is_candidate(uint region) {
 317       return get_by_index(region);
 318     }
 319   };
 320 
 321   HumongousReclaimCandidates _humongous_reclaim_candidates;
 322   // Stores whether during humongous object registration we found candidate regions.
 323   // If not, we can skip a few steps.
 324   bool _has_humongous_reclaim_candidates;
 325 
 326   volatile unsigned _gc_time_stamp;
 327 
 328   size_t* _surviving_young_words;
 329 
 330   G1HRPrinter _hr_printer;
 331 
 332   void setup_surviving_young_words();
 333   void update_surviving_young_words(size_t* surv_young_words);
 334   void cleanup_surviving_young_words();
 335 
 336   // It decides whether an explicit GC should start a concurrent cycle
 337   // instead of doing a STW GC. Currently, a concurrent cycle is
 338   // explicitly started if:
 339   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 340   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 341   // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 342   // (d) cause == _g1_humongous_allocation
 343   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 344 
 345   // indicates whether we are in young or mixed GC mode
 346   G1CollectorState _collector_state;
 347 
 348   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 349   // concurrent cycles) we have started.
 350   volatile uint _old_marking_cycles_started;
 351 
 352   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 353   // concurrent cycles) we have completed.
 354   volatile uint _old_marking_cycles_completed;
 355 
 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   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 387 
 388   // These are macros so that, if the assert fires, we get the correct
 389   // line number, file, etc.
 390 
 391 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 392   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 393           (_extra_message_),                                                  \
 394           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 395           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 396           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 397 
 398 #define assert_heap_locked()                                                  \
 399   do {                                                                        \
 400     assert(Heap_lock->owned_by_self(),                                        \
 401            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 402   } while (0)
 403 
 404 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 405   do {                                                                        \
 406     assert(Heap_lock->owned_by_self() ||                                      \
 407            (SafepointSynchronize::is_at_safepoint() &&                        \
 408              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 409            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 410                                         "should be at a safepoint"));         \
 411   } while (0)
 412 
 413 #define assert_heap_locked_and_not_at_safepoint()                             \
 414   do {                                                                        \
 415     assert(Heap_lock->owned_by_self() &&                                      \
 416                                     !SafepointSynchronize::is_at_safepoint(), \
 417           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 418                                        "should not be at a safepoint"));      \
 419   } while (0)
 420 
 421 #define assert_heap_not_locked()                                              \
 422   do {                                                                        \
 423     assert(!Heap_lock->owned_by_self(),                                       \
 424         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 425   } while (0)
 426 
 427 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 428   do {                                                                        \
 429     assert(!Heap_lock->owned_by_self() &&                                     \
 430                                     !SafepointSynchronize::is_at_safepoint(), \
 431       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 432                                    "should not be at a safepoint"));          \
 433   } while (0)
 434 
 435 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 436   do {                                                                        \
 437     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 438               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 439            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 440   } while (0)
 441 
 442 #define assert_not_at_safepoint()                                             \
 443   do {                                                                        \
 444     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 445            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 446   } while (0)
 447 
 448 protected:
 449 
 450   // The young region list.
 451   YoungList*  _young_list;
 452 
 453   // The current policy object for the collector.
 454   G1CollectorPolicy* _g1_policy;
 455 
 456   // This is the second level of trying to allocate a new region. If
 457   // new_region() didn't find a region on the free_list, this call will
 458   // check whether there's anything available on the
 459   // secondary_free_list and/or wait for more regions to appear on
 460   // that list, if _free_regions_coming is set.
 461   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 462 
 463   // Try to allocate a single non-humongous HeapRegion sufficient for
 464   // an allocation of the given word_size. If do_expand is true,
 465   // attempt to expand the heap if necessary to satisfy the allocation
 466   // request. If the region is to be used as an old region or for a
 467   // humongous object, set is_old to true. If not, to false.
 468   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 469 
 470   // Initialize a contiguous set of free regions of length num_regions
 471   // and starting at index first so that they appear as a single
 472   // humongous region.
 473   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 474                                                       uint num_regions,
 475                                                       size_t word_size,
 476                                                       AllocationContext_t context);
 477 
 478   // Attempt to allocate a humongous object of the given size. Return
 479   // NULL if unsuccessful.
 480   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 481 
 482   // The following two methods, allocate_new_tlab() and
 483   // mem_allocate(), are the two main entry points from the runtime
 484   // into the G1's allocation routines. They have the following
 485   // assumptions:
 486   //
 487   // * They should both be called outside safepoints.
 488   //
 489   // * They should both be called without holding the Heap_lock.
 490   //
 491   // * All allocation requests for new TLABs should go to
 492   //   allocate_new_tlab().
 493   //
 494   // * All non-TLAB allocation requests should go to mem_allocate().
 495   //
 496   // * If either call cannot satisfy the allocation request using the
 497   //   current allocating region, they will try to get a new one. If
 498   //   this fails, they will attempt to do an evacuation pause and
 499   //   retry the allocation.
 500   //
 501   // * If all allocation attempts fail, even after trying to schedule
 502   //   an evacuation pause, allocate_new_tlab() will return NULL,
 503   //   whereas mem_allocate() will attempt a heap expansion and/or
 504   //   schedule a Full GC.
 505   //
 506   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 507   //   should never be called with word_size being humongous. All
 508   //   humongous allocation requests should go to mem_allocate() which
 509   //   will satisfy them with a special path.
 510 
 511   virtual HeapWord* allocate_new_tlab(size_t word_size);
 512 
 513   virtual HeapWord* mem_allocate(size_t word_size,
 514                                  bool*  gc_overhead_limit_was_exceeded);
 515 
 516   // The following three methods take a gc_count_before_ret
 517   // parameter which is used to return the GC count if the method
 518   // returns NULL. Given that we are required to read the GC count
 519   // while holding the Heap_lock, and these paths will take the
 520   // Heap_lock at some point, it's easier to get them to read the GC
 521   // count while holding the Heap_lock before they return NULL instead
 522   // of the caller (namely: mem_allocate()) having to also take the
 523   // Heap_lock just to read the GC count.
 524 
 525   // First-level mutator allocation attempt: try to allocate out of
 526   // the mutator alloc region without taking the Heap_lock. This
 527   // should only be used for non-humongous allocations.
 528   inline HeapWord* attempt_allocation(size_t word_size,
 529                                       uint* gc_count_before_ret,
 530                                       uint* gclocker_retry_count_ret);
 531 
 532   // Second-level mutator allocation attempt: take the Heap_lock and
 533   // retry the allocation attempt, potentially scheduling a GC
 534   // pause. This should only be used for non-humongous allocations.
 535   HeapWord* attempt_allocation_slow(size_t word_size,
 536                                     AllocationContext_t context,
 537                                     uint* gc_count_before_ret,
 538                                     uint* gclocker_retry_count_ret);
 539 
 540   // Takes the Heap_lock and attempts a humongous allocation. It can
 541   // potentially schedule a GC pause.
 542   HeapWord* attempt_allocation_humongous(size_t word_size,
 543                                          uint* gc_count_before_ret,
 544                                          uint* gclocker_retry_count_ret);
 545 
 546   // Allocation attempt that should be called during safepoints (e.g.,
 547   // at the end of a successful GC). expect_null_mutator_alloc_region
 548   // specifies whether the mutator alloc region is expected to be NULL
 549   // or not.
 550   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 551                                             AllocationContext_t context,
 552                                             bool expect_null_mutator_alloc_region);
 553 
 554   // It dirties the cards that cover the block so that so that the post
 555   // write barrier never queues anything when updating objects on this
 556   // block. It is assumed (and in fact we assert) that the block
 557   // belongs to a young region.
 558   inline void dirty_young_block(HeapWord* start, size_t word_size);
 559 
 560   // Allocate blocks during garbage collection. Will ensure an
 561   // allocation region, either by picking one or expanding the
 562   // heap, and then allocate a block of the given size. The block
 563   // may not be a humongous - it must fit into a single heap region.
 564   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 565                                           size_t word_size,
 566                                           AllocationContext_t context);
 567   // Ensure that no further allocations can happen in "r", bearing in mind
 568   // that parallel threads might be attempting allocations.
 569   void par_allocate_remaining_space(HeapRegion* r);
 570 
 571   // Allocation attempt during GC for a survivor object / PLAB.
 572   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 573                                                AllocationContext_t context);
 574 
 575   // Allocation attempt during GC for an old object / PLAB.
 576   inline HeapWord* old_attempt_allocation(size_t word_size,
 577                                           AllocationContext_t context);
 578 
 579   // These methods are the "callbacks" from the G1AllocRegion class.
 580 
 581   // For mutator alloc regions.
 582   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 583   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 584                                    size_t allocated_bytes);
 585 
 586   // For GC alloc regions.
 587   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 588                                   InCSetState dest);
 589   void retire_gc_alloc_region(HeapRegion* alloc_region,
 590                               size_t allocated_bytes, InCSetState dest);
 591 
 592   // Allocate the highest free region in the reserved heap. This will commit
 593   // regions as necessary.
 594   HeapRegion* alloc_highest_free_region();
 595 
 596   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 597   //   inspection request and should collect the entire heap
 598   // - if clear_all_soft_refs is true, all soft references should be
 599   //   cleared during the GC
 600   // - if explicit_gc is false, word_size describes the allocation that
 601   //   the GC should attempt (at least) to satisfy
 602   // - it returns false if it is unable to do the collection due to the
 603   //   GC locker being active, true otherwise
 604   bool do_collection(bool explicit_gc,
 605                      bool clear_all_soft_refs,
 606                      size_t word_size);
 607 
 608   // Callback from VM_G1CollectFull operation.
 609   // Perform a full collection.
 610   virtual void do_full_collection(bool clear_all_soft_refs);
 611 
 612   // Resize the heap if necessary after a full collection.  If this is
 613   // after a collect-for allocation, "word_size" is the allocation size,
 614   // and will be considered part of the used portion of the heap.
 615   void resize_if_necessary_after_full_collection(size_t word_size);
 616 
 617   // Callback from VM_G1CollectForAllocation operation.
 618   // This function does everything necessary/possible to satisfy a
 619   // failed allocation request (including collection, expansion, etc.)
 620   HeapWord* satisfy_failed_allocation(size_t word_size,
 621                                       AllocationContext_t context,
 622                                       bool* succeeded);
 623 
 624   // Attempting to expand the heap sufficiently
 625   // to support an allocation of the given "word_size".  If
 626   // successful, perform the allocation and return the address of the
 627   // allocated block, or else "NULL".
 628   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 629 
 630   // Process any reference objects discovered during
 631   // an incremental evacuation pause.
 632   void process_discovered_references();
 633 
 634   // Enqueue any remaining discovered references
 635   // after processing.
 636   void enqueue_discovered_references();
 637 
 638 public:
 639   FlexibleWorkGang* workers() const { return _workers; }
 640 
 641   G1Allocator* allocator() {
 642     return _allocator;
 643   }
 644 
 645   G1MonitoringSupport* g1mm() {
 646     assert(_g1mm != NULL, "should have been initialized");
 647     return _g1mm;
 648   }
 649 
 650   // Expand the garbage-first heap by at least the given size (in bytes!).
 651   // Returns true if the heap was expanded by the requested amount;
 652   // false otherwise.
 653   // (Rounds up to a HeapRegion boundary.)
 654   bool expand(size_t expand_bytes);
 655 
 656   // Returns the PLAB statistics for a given destination.
 657   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 658 
 659   // Determines PLAB size for a given destination.
 660   inline size_t desired_plab_sz(InCSetState dest);
 661 
 662   inline AllocationContextStats& allocation_context_stats();
 663 
 664   // Do anything common to GC's.
 665   void gc_prologue(bool full);
 666   void gc_epilogue(bool full);
 667 
 668   // Modify the reclaim candidate set and test for presence.
 669   // These are only valid for starts_humongous regions.
 670   inline void set_humongous_reclaim_candidate(uint region, bool value);
 671   inline bool is_humongous_reclaim_candidate(uint region);
 672 
 673   // Remove from the reclaim candidate set.  Also remove from the
 674   // collection set so that later encounters avoid the slow path.
 675   inline void set_humongous_is_live(oop obj);
 676 
 677   // Register the given region to be part of the collection set.
 678   inline void register_humongous_region_with_cset(uint index);
 679   // Register regions with humongous objects (actually on the start region) in
 680   // the in_cset_fast_test table.
 681   void register_humongous_regions_with_cset();
 682   // We register a region with the fast "in collection set" test. We
 683   // simply set to true the array slot corresponding to this region.
 684   void register_young_region_with_cset(HeapRegion* r) {
 685     _in_cset_fast_test.set_in_young(r->hrm_index());
 686   }
 687   void register_old_region_with_cset(HeapRegion* r) {
 688     _in_cset_fast_test.set_in_old(r->hrm_index());
 689   }
 690   void clear_in_cset(const HeapRegion* hr) {
 691     _in_cset_fast_test.clear(hr);
 692   }
 693 
 694   void clear_cset_fast_test() {
 695     _in_cset_fast_test.clear();
 696   }
 697 
 698   // This is called at the start of either a concurrent cycle or a Full
 699   // GC to update the number of old marking cycles started.
 700   void increment_old_marking_cycles_started();
 701 
 702   // This is called at the end of either a concurrent cycle or a Full
 703   // GC to update the number of old marking cycles completed. Those two
 704   // can happen in a nested fashion, i.e., we start a concurrent
 705   // cycle, a Full GC happens half-way through it which ends first,
 706   // and then the cycle notices that a Full GC happened and ends
 707   // too. The concurrent parameter is a boolean to help us do a bit
 708   // tighter consistency checking in the method. If concurrent is
 709   // false, the caller is the inner caller in the nesting (i.e., the
 710   // Full GC). If concurrent is true, the caller is the outer caller
 711   // in this nesting (i.e., the concurrent cycle). Further nesting is
 712   // not currently supported. The end of this call also notifies
 713   // the FullGCCount_lock in case a Java thread is waiting for a full
 714   // GC to happen (e.g., it called System.gc() with
 715   // +ExplicitGCInvokesConcurrent).
 716   void increment_old_marking_cycles_completed(bool concurrent);
 717 
 718   uint old_marking_cycles_completed() {
 719     return _old_marking_cycles_completed;
 720   }
 721 
 722   void register_concurrent_cycle_start(const Ticks& start_time);
 723   void register_concurrent_cycle_end();
 724   void trace_heap_after_concurrent_cycle();
 725 
 726   G1HRPrinter* hr_printer() { return &_hr_printer; }
 727 
 728   // Frees a non-humongous region by initializing its contents and
 729   // adding it to the free list that's passed as a parameter (this is
 730   // usually a local list which will be appended to the master free
 731   // list later). The used bytes of freed regions are accumulated in
 732   // pre_used. If par is true, the region's RSet will not be freed
 733   // up. The assumption is that this will be done later.
 734   // The locked parameter indicates if the caller has already taken
 735   // care of proper synchronization. This may allow some optimizations.
 736   void free_region(HeapRegion* hr,
 737                    FreeRegionList* free_list,
 738                    bool par,
 739                    bool locked = false);
 740 
 741   // Frees a humongous region by collapsing it into individual regions
 742   // and calling free_region() for each of them. The freed regions
 743   // will be added to the free list that's passed as a parameter (this
 744   // is usually a local list which will be appended to the master free
 745   // list later). The used bytes of freed regions are accumulated in
 746   // pre_used. If par is true, the region's RSet will not be freed
 747   // up. The assumption is that this will be done later.
 748   void free_humongous_region(HeapRegion* hr,
 749                              FreeRegionList* free_list,
 750                              bool par);
 751 
 752   // Facility for allocating in 'archive' regions in high heap memory and
 753   // recording the allocated ranges. These should all be called from the
 754   // VM thread at safepoints, without the heap lock held. They can be used
 755   // to create and archive a set of heap regions which can be mapped at the
 756   // same fixed addresses in a subsequent JVM invocation.
 757   void begin_archive_alloc_range();
 758 
 759   // Check if the requested size would be too large for an archive allocation.
 760   bool is_archive_alloc_too_large(size_t word_size);
 761 
 762   // Allocate memory of the requested size from the archive region. This will
 763   // return NULL if the size is too large or if no memory is available. It
 764   // does not trigger a garbage collection.
 765   HeapWord* archive_mem_allocate(size_t word_size);
 766 
 767   // Optionally aligns the end address and returns the allocated ranges in
 768   // an array of MemRegions in order of ascending addresses.
 769   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 770                                size_t end_alignment_in_bytes = 0);
 771 
 772   // Facility for allocating a fixed range within the heap and marking
 773   // the containing regions as 'archive'. For use at JVM init time, when the
 774   // caller may mmap archived heap data at the specified range(s).
 775   // Verify that the MemRegions specified in the argument array are within the
 776   // reserved heap.
 777   bool check_archive_addresses(MemRegion* range, size_t count);
 778 
 779   // Commit the appropriate G1 regions containing the specified MemRegions
 780   // and mark them as 'archive' regions. The regions in the array must be
 781   // non-overlapping and in order of ascending address.
 782   bool alloc_archive_regions(MemRegion* range, size_t count);
 783 
 784   // Insert any required filler objects in the G1 regions around the specified
 785   // ranges to make the regions parseable. This must be called after
 786   // alloc_archive_regions, and after class loading has occurred.
 787   void fill_archive_regions(MemRegion* range, size_t count);
 788 
 789   // For each of the specified MemRegions, free the containing G1 regions 
 790   // which had been allocated by alloc_archive_regions. This should be called
 791   // rather than fill_archive_regions at JVM init time if the archive file 
 792   // mapping failed.
 793   void free_archive_regions(MemRegion* range, size_t count);
 794 
 795 protected:
 796 
 797   // Shrink the garbage-first heap by at most the given size (in bytes!).
 798   // (Rounds down to a HeapRegion boundary.)
 799   virtual void shrink(size_t expand_bytes);
 800   void shrink_helper(size_t expand_bytes);
 801 
 802   #if TASKQUEUE_STATS
 803   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 804   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 805   void reset_taskqueue_stats();
 806   #endif // TASKQUEUE_STATS
 807 
 808   // Schedule the VM operation that will do an evacuation pause to
 809   // satisfy an allocation request of word_size. *succeeded will
 810   // return whether the VM operation was successful (it did do an
 811   // evacuation pause) or not (another thread beat us to it or the GC
 812   // locker was active). Given that we should not be holding the
 813   // Heap_lock when we enter this method, we will pass the
 814   // gc_count_before (i.e., total_collections()) as a parameter since
 815   // it has to be read while holding the Heap_lock. Currently, both
 816   // methods that call do_collection_pause() release the Heap_lock
 817   // before the call, so it's easy to read gc_count_before just before.
 818   HeapWord* do_collection_pause(size_t         word_size,
 819                                 uint           gc_count_before,
 820                                 bool*          succeeded,
 821                                 GCCause::Cause gc_cause);
 822 
 823   void wait_for_root_region_scanning();
 824 
 825   // The guts of the incremental collection pause, executed by the vm
 826   // thread. It returns false if it is unable to do the collection due
 827   // to the GC locker being active, true otherwise
 828   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 829 
 830   // Actually do the work of evacuating the collection set.
 831   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 832 
 833   // The g1 remembered set of the heap.
 834   G1RemSet* _g1_rem_set;
 835 
 836   // A set of cards that cover the objects for which the Rsets should be updated
 837   // concurrently after the collection.
 838   DirtyCardQueueSet _dirty_card_queue_set;
 839 
 840   // The closure used to refine a single card.
 841   RefineCardTableEntryClosure* _refine_cte_cl;
 842 
 843   // A DirtyCardQueueSet that is used to hold cards that contain
 844   // references into the current collection set. This is used to
 845   // update the remembered sets of the regions in the collection
 846   // set in the event of an evacuation failure.
 847   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 848 
 849   // After a collection pause, make the regions in the CS into free
 850   // regions.
 851   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 852 
 853   // Abandon the current collection set without recording policy
 854   // statistics or updating free lists.
 855   void abandon_collection_set(HeapRegion* cs_head);
 856 
 857   // The concurrent marker (and the thread it runs in.)
 858   ConcurrentMark* _cm;
 859   ConcurrentMarkThread* _cmThread;
 860 
 861   // The concurrent refiner.
 862   ConcurrentG1Refine* _cg1r;
 863 
 864   // The parallel task queues
 865   RefToScanQueueSet *_task_queues;
 866 
 867   // True iff a evacuation has failed in the current collection.
 868   bool _evacuation_failed;
 869 
 870   EvacuationFailedInfo* _evacuation_failed_info_array;
 871 
 872   // Failed evacuations cause some logical from-space objects to have
 873   // forwarding pointers to themselves.  Reset them.
 874   void remove_self_forwarding_pointers();
 875 
 876   struct OopAndMarkOop {
 877    private:
 878     oop _o;
 879     markOop _m;
 880    public:
 881     OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) {
 882     }
 883 
 884     void set_mark() {
 885       _o->set_mark(_m);
 886     }
 887   };
 888 
 889   typedef Stack<OopAndMarkOop,mtGC> OopAndMarkOopStack;
 890   // Stores marks with the corresponding oop that we need to preserve during evacuation
 891   // failure.
 892   OopAndMarkOopStack*  _preserved_objs;
 893 
 894   // Preserve the mark of "obj", if necessary, in preparation for its mark
 895   // word being overwritten with a self-forwarding-pointer.
 896   void preserve_mark_during_evac_failure(uint queue, oop obj, markOop m);
 897 
 898 #ifndef PRODUCT
 899   // Support for forcing evacuation failures. Analogous to
 900   // PromotionFailureALot for the other collectors.
 901 
 902   // Records whether G1EvacuationFailureALot should be in effect
 903   // for the current GC
 904   bool _evacuation_failure_alot_for_current_gc;
 905 
 906   // Used to record the GC number for interval checking when
 907   // determining whether G1EvaucationFailureALot is in effect
 908   // for the current GC.
 909   size_t _evacuation_failure_alot_gc_number;
 910 
 911   // Count of the number of evacuations between failures.
 912   volatile size_t _evacuation_failure_alot_count;
 913 
 914   // Set whether G1EvacuationFailureALot should be in effect
 915   // for the current GC (based upon the type of GC and which
 916   // command line flags are set);
 917   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 918                                                   bool during_initial_mark,
 919                                                   bool during_marking);
 920 
 921   inline void set_evacuation_failure_alot_for_current_gc();
 922 
 923   // Return true if it's time to cause an evacuation failure.
 924   inline bool evacuation_should_fail();
 925 
 926   // Reset the G1EvacuationFailureALot counters.  Should be called at
 927   // the end of an evacuation pause in which an evacuation failure occurred.
 928   inline void reset_evacuation_should_fail();
 929 #endif // !PRODUCT
 930 
 931   // ("Weak") Reference processing support.
 932   //
 933   // G1 has 2 instances of the reference processor class. One
 934   // (_ref_processor_cm) handles reference object discovery
 935   // and subsequent processing during concurrent marking cycles.
 936   //
 937   // The other (_ref_processor_stw) handles reference object
 938   // discovery and processing during full GCs and incremental
 939   // evacuation pauses.
 940   //
 941   // During an incremental pause, reference discovery will be
 942   // temporarily disabled for _ref_processor_cm and will be
 943   // enabled for _ref_processor_stw. At the end of the evacuation
 944   // pause references discovered by _ref_processor_stw will be
 945   // processed and discovery will be disabled. The previous
 946   // setting for reference object discovery for _ref_processor_cm
 947   // will be re-instated.
 948   //
 949   // At the start of marking:
 950   //  * Discovery by the CM ref processor is verified to be inactive
 951   //    and it's discovered lists are empty.
 952   //  * Discovery by the CM ref processor is then enabled.
 953   //
 954   // At the end of marking:
 955   //  * Any references on the CM ref processor's discovered
 956   //    lists are processed (possibly MT).
 957   //
 958   // At the start of full GC we:
 959   //  * Disable discovery by the CM ref processor and
 960   //    empty CM ref processor's discovered lists
 961   //    (without processing any entries).
 962   //  * Verify that the STW ref processor is inactive and it's
 963   //    discovered lists are empty.
 964   //  * Temporarily set STW ref processor discovery as single threaded.
 965   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 966   //    field.
 967   //  * Finally enable discovery by the STW ref processor.
 968   //
 969   // The STW ref processor is used to record any discovered
 970   // references during the full GC.
 971   //
 972   // At the end of a full GC we:
 973   //  * Enqueue any reference objects discovered by the STW ref processor
 974   //    that have non-live referents. This has the side-effect of
 975   //    making the STW ref processor inactive by disabling discovery.
 976   //  * Verify that the CM ref processor is still inactive
 977   //    and no references have been placed on it's discovered
 978   //    lists (also checked as a precondition during initial marking).
 979 
 980   // The (stw) reference processor...
 981   ReferenceProcessor* _ref_processor_stw;
 982 
 983   STWGCTimer* _gc_timer_stw;
 984   ConcurrentGCTimer* _gc_timer_cm;
 985 
 986   G1OldTracer* _gc_tracer_cm;
 987   G1NewTracer* _gc_tracer_stw;
 988 
 989   // During reference object discovery, the _is_alive_non_header
 990   // closure (if non-null) is applied to the referent object to
 991   // determine whether the referent is live. If so then the
 992   // reference object does not need to be 'discovered' and can
 993   // be treated as a regular oop. This has the benefit of reducing
 994   // the number of 'discovered' reference objects that need to
 995   // be processed.
 996   //
 997   // Instance of the is_alive closure for embedding into the
 998   // STW reference processor as the _is_alive_non_header field.
 999   // Supplying a value for the _is_alive_non_header field is
1000   // optional but doing so prevents unnecessary additions to
1001   // the discovered lists during reference discovery.
1002   G1STWIsAliveClosure _is_alive_closure_stw;
1003 
1004   // The (concurrent marking) reference processor...
1005   ReferenceProcessor* _ref_processor_cm;
1006 
1007   // Instance of the concurrent mark is_alive closure for embedding
1008   // into the Concurrent Marking reference processor as the
1009   // _is_alive_non_header field. Supplying a value for the
1010   // _is_alive_non_header field is optional but doing so prevents
1011   // unnecessary additions to the discovered lists during reference
1012   // discovery.
1013   G1CMIsAliveClosure _is_alive_closure_cm;
1014 
1015   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1016   HeapRegion** _worker_cset_start_region;
1017 
1018   // Time stamp to validate the regions recorded in the cache
1019   // used by G1CollectedHeap::start_cset_region_for_worker().
1020   // The heap region entry for a given worker is valid iff
1021   // the associated time stamp value matches the current value
1022   // of G1CollectedHeap::_gc_time_stamp.
1023   uint* _worker_cset_start_region_time_stamp;
1024 
1025   volatile bool _free_regions_coming;
1026 
1027 public:
1028 
1029   void set_refine_cte_cl_concurrency(bool concurrent);
1030 
1031   RefToScanQueue *task_queue(uint i) const;
1032 
1033   uint num_task_queues() const;
1034 
1035   // A set of cards where updates happened during the GC
1036   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1037 
1038   // A DirtyCardQueueSet that is used to hold cards that contain
1039   // references into the current collection set. This is used to
1040   // update the remembered sets of the regions in the collection
1041   // set in the event of an evacuation failure.
1042   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1043         { return _into_cset_dirty_card_queue_set; }
1044 
1045   // Create a G1CollectedHeap with the specified policy.
1046   // Must call the initialize method afterwards.
1047   // May not return if something goes wrong.
1048   G1CollectedHeap(G1CollectorPolicy* policy);
1049 
1050   // Initialize the G1CollectedHeap to have the initial and
1051   // maximum sizes and remembered and barrier sets
1052   // specified by the policy object.
1053   jint initialize();
1054 
1055   virtual void stop();
1056 
1057   // Return the (conservative) maximum heap alignment for any G1 heap
1058   static size_t conservative_max_heap_alignment();
1059 
1060   // Does operations required after initialization has been done.
1061   void post_initialize();
1062 
1063   // Initialize weak reference processing.
1064   void ref_processing_init();
1065 
1066   virtual Name kind() const {
1067     return CollectedHeap::G1CollectedHeap;
1068   }
1069 
1070   G1CollectorState* collector_state() { return &_collector_state; }
1071 
1072   // The current policy object for the collector.
1073   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1074 
1075   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1076 
1077   // Adaptive size policy.  No such thing for g1.
1078   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1079 
1080   // The rem set and barrier set.
1081   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1082 
1083   unsigned get_gc_time_stamp() {
1084     return _gc_time_stamp;
1085   }
1086 
1087   inline void reset_gc_time_stamp();
1088 
1089   void check_gc_time_stamps() PRODUCT_RETURN;
1090 
1091   inline void increment_gc_time_stamp();
1092 
1093   // Reset the given region's GC timestamp. If it's starts humongous,
1094   // also reset the GC timestamp of its corresponding
1095   // continues humongous regions too.
1096   void reset_gc_time_stamps(HeapRegion* hr);
1097 
1098   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1099                                   DirtyCardQueue* into_cset_dcq,
1100                                   bool concurrent, uint worker_i);
1101 
1102   // The shared block offset table array.
1103   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1104 
1105   // Reference Processing accessors
1106 
1107   // The STW reference processor....
1108   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1109 
1110   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1111 
1112   // The Concurrent Marking reference processor...
1113   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1114 
1115   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1116   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1117 
1118   virtual size_t capacity() const;
1119   virtual size_t used() const;
1120   // This should be called when we're not holding the heap lock. The
1121   // result might be a bit inaccurate.
1122   size_t used_unlocked() const;
1123   size_t recalculate_used() const;
1124 
1125   // These virtual functions do the actual allocation.
1126   // Some heaps may offer a contiguous region for shared non-blocking
1127   // allocation, via inlined code (by exporting the address of the top and
1128   // end fields defining the extent of the contiguous allocation region.)
1129   // But G1CollectedHeap doesn't yet support this.
1130 
1131   virtual bool is_maximal_no_gc() const {
1132     return _hrm.available() == 0;
1133   }
1134 
1135   // The current number of regions in the heap.
1136   uint num_regions() const { return _hrm.length(); }
1137 
1138   // The max number of regions in the heap.
1139   uint max_regions() const { return _hrm.max_length(); }
1140 
1141   // The number of regions that are completely free.
1142   uint num_free_regions() const { return _hrm.num_free_regions(); }
1143 
1144   MemoryUsage get_auxiliary_data_memory_usage() const {
1145     return _hrm.get_auxiliary_data_memory_usage();
1146   }
1147 
1148   // The number of regions that are not completely free.
1149   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1150 
1151   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1152   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1153   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1154   void verify_dirty_young_regions() PRODUCT_RETURN;
1155 
1156 #ifndef PRODUCT
1157   // Make sure that the given bitmap has no marked objects in the
1158   // range [from,limit). If it does, print an error message and return
1159   // false. Otherwise, just return true. bitmap_name should be "prev"
1160   // or "next".
1161   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1162                                 HeapWord* from, HeapWord* limit);
1163 
1164   // Verify that the prev / next bitmap range [tams,end) for the given
1165   // region has no marks. Return true if all is well, false if errors
1166   // are detected.
1167   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1168 #endif // PRODUCT
1169 
1170   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1171   // the given region do not have any spurious marks. If errors are
1172   // detected, print appropriate error messages and crash.
1173   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1174 
1175   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1176   // have any spurious marks. If errors are detected, print
1177   // appropriate error messages and crash.
1178   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1179 
1180   // Do sanity check on the contents of the in-cset fast test table.
1181   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1182 
1183   // verify_region_sets() performs verification over the region
1184   // lists. It will be compiled in the product code to be used when
1185   // necessary (i.e., during heap verification).
1186   void verify_region_sets();
1187 
1188   // verify_region_sets_optional() is planted in the code for
1189   // list verification in non-product builds (and it can be enabled in
1190   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1191 #if HEAP_REGION_SET_FORCE_VERIFY
1192   void verify_region_sets_optional() {
1193     verify_region_sets();
1194   }
1195 #else // HEAP_REGION_SET_FORCE_VERIFY
1196   void verify_region_sets_optional() { }
1197 #endif // HEAP_REGION_SET_FORCE_VERIFY
1198 
1199 #ifdef ASSERT
1200   bool is_on_master_free_list(HeapRegion* hr) {
1201     return _hrm.is_free(hr);
1202   }
1203 #endif // ASSERT
1204 
1205   // Wrapper for the region list operations that can be called from
1206   // methods outside this class.
1207 
1208   void secondary_free_list_add(FreeRegionList* list) {
1209     _secondary_free_list.add_ordered(list);
1210   }
1211 
1212   void append_secondary_free_list() {
1213     _hrm.insert_list_into_free_list(&_secondary_free_list);
1214   }
1215 
1216   void append_secondary_free_list_if_not_empty_with_lock() {
1217     // If the secondary free list looks empty there's no reason to
1218     // take the lock and then try to append it.
1219     if (!_secondary_free_list.is_empty()) {
1220       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1221       append_secondary_free_list();
1222     }
1223   }
1224 
1225   inline void old_set_remove(HeapRegion* hr);
1226 
1227   size_t non_young_capacity_bytes() {
1228     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1229   }
1230 
1231   void set_free_regions_coming();
1232   void reset_free_regions_coming();
1233   bool free_regions_coming() { return _free_regions_coming; }
1234   void wait_while_free_regions_coming();
1235 
1236   // Determine whether the given region is one that we are using as an
1237   // old GC alloc region.
1238   bool is_old_gc_alloc_region(HeapRegion* hr) {
1239     return _allocator->is_retained_old_region(hr);
1240   }
1241 
1242   // Perform a collection of the heap; intended for use in implementing
1243   // "System.gc".  This probably implies as full a collection as the
1244   // "CollectedHeap" supports.
1245   virtual void collect(GCCause::Cause cause);
1246 
1247   // The same as above but assume that the caller holds the Heap_lock.
1248   void collect_locked(GCCause::Cause cause);
1249 
1250   virtual bool copy_allocation_context_stats(const jint* contexts,
1251                                              jlong* totals,
1252                                              jbyte* accuracy,
1253                                              jint len);
1254 
1255   // True iff an evacuation has failed in the most-recent collection.
1256   bool evacuation_failed() { return _evacuation_failed; }
1257 
1258   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1259   void prepend_to_freelist(FreeRegionList* list);
1260   void decrement_summary_bytes(size_t bytes);
1261 
1262   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1263   virtual bool is_in(const void* p) const;
1264 #ifdef ASSERT
1265   // Returns whether p is in one of the available areas of the heap. Slow but
1266   // extensive version.
1267   bool is_in_exact(const void* p) const;
1268 #endif
1269 
1270   // Return "TRUE" iff the given object address is within the collection
1271   // set. Slow implementation.
1272   inline bool obj_in_cs(oop obj);
1273 
1274   inline bool is_in_cset(const HeapRegion *hr);
1275   inline bool is_in_cset(oop obj);
1276 
1277   inline bool is_in_cset_or_humongous(const oop obj);
1278 
1279  private:
1280   // This array is used for a quick test on whether a reference points into
1281   // the collection set or not. Each of the array's elements denotes whether the
1282   // corresponding region is in the collection set or not.
1283   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1284 
1285  public:
1286 
1287   inline InCSetState in_cset_state(const oop obj);
1288 
1289   // Return "TRUE" iff the given object address is in the reserved
1290   // region of g1.
1291   bool is_in_g1_reserved(const void* p) const {
1292     return _hrm.reserved().contains(p);
1293   }
1294 
1295   // Returns a MemRegion that corresponds to the space that has been
1296   // reserved for the heap
1297   MemRegion g1_reserved() const {
1298     return _hrm.reserved();
1299   }
1300 
1301   virtual bool is_in_closed_subset(const void* p) const;
1302 
1303   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1304     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1305   }
1306 
1307   // This resets the card table to all zeros.  It is used after
1308   // a collection pause which used the card table to claim cards.
1309   void cleanUpCardTable();
1310 
1311   // Iteration functions.
1312 
1313   // Iterate over all objects, calling "cl.do_object" on each.
1314   virtual void object_iterate(ObjectClosure* cl);
1315 
1316   virtual void safe_object_iterate(ObjectClosure* cl) {
1317     object_iterate(cl);
1318   }
1319 
1320   // Iterate over heap regions, in address order, terminating the
1321   // iteration early if the "doHeapRegion" method returns "true".
1322   void heap_region_iterate(HeapRegionClosure* blk) const;
1323 
1324   // Return the region with the given index. It assumes the index is valid.
1325   inline HeapRegion* region_at(uint index) const;
1326 
1327   // Calculate the region index of the given address. Given address must be
1328   // within the heap.
1329   inline uint addr_to_region(HeapWord* addr) const;
1330 
1331   inline HeapWord* bottom_addr_for_region(uint index) const;
1332 
1333   // Iterate over the heap regions in parallel. Assumes that this will be called
1334   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1335   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1336   // to each of the regions, by attempting to claim the region using the
1337   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1338   // region. The concurrent argument should be set to true if iteration is
1339   // performed concurrently, during which no assumptions are made for consistent
1340   // attributes of the heap regions (as they might be modified while iterating).
1341   void heap_region_par_iterate(HeapRegionClosure* cl,
1342                                uint worker_id,
1343                                HeapRegionClaimer* hrclaimer,
1344                                bool concurrent = false) const;
1345 
1346   // Clear the cached cset start regions and (more importantly)
1347   // the time stamps. Called when we reset the GC time stamp.
1348   void clear_cset_start_regions();
1349 
1350   // Given the id of a worker, obtain or calculate a suitable
1351   // starting region for iterating over the current collection set.
1352   HeapRegion* start_cset_region_for_worker(uint worker_i);
1353 
1354   // Iterate over the regions (if any) in the current collection set.
1355   void collection_set_iterate(HeapRegionClosure* blk);
1356 
1357   // As above but starting from region r
1358   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1359 
1360   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1361 
1362   // Returns the HeapRegion that contains addr. addr must not be NULL.
1363   template <class T>
1364   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1365 
1366   // Returns the HeapRegion that contains addr. addr must not be NULL.
1367   // If addr is within a humongous continues region, it returns its humongous start region.
1368   template <class T>
1369   inline HeapRegion* heap_region_containing(const T addr) const;
1370 
1371   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1372   // each address in the (reserved) heap is a member of exactly
1373   // one block.  The defining characteristic of a block is that it is
1374   // possible to find its size, and thus to progress forward to the next
1375   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1376   // represent Java objects, or they might be free blocks in a
1377   // free-list-based heap (or subheap), as long as the two kinds are
1378   // distinguishable and the size of each is determinable.
1379 
1380   // Returns the address of the start of the "block" that contains the
1381   // address "addr".  We say "blocks" instead of "object" since some heaps
1382   // may not pack objects densely; a chunk may either be an object or a
1383   // non-object.
1384   virtual HeapWord* block_start(const void* addr) const;
1385 
1386   // Requires "addr" to be the start of a chunk, and returns its size.
1387   // "addr + size" is required to be the start of a new chunk, or the end
1388   // of the active area of the heap.
1389   virtual size_t block_size(const HeapWord* addr) const;
1390 
1391   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1392   // the block is an object.
1393   virtual bool block_is_obj(const HeapWord* addr) const;
1394 
1395   // Section on thread-local allocation buffers (TLABs)
1396   // See CollectedHeap for semantics.
1397 
1398   bool supports_tlab_allocation() const;
1399   size_t tlab_capacity(Thread* ignored) const;
1400   size_t tlab_used(Thread* ignored) const;
1401   size_t max_tlab_size() const;
1402   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1403 
1404   // Can a compiler initialize a new object without store barriers?
1405   // This permission only extends from the creation of a new object
1406   // via a TLAB up to the first subsequent safepoint. If such permission
1407   // is granted for this heap type, the compiler promises to call
1408   // defer_store_barrier() below on any slow path allocation of
1409   // a new object for which such initializing store barriers will
1410   // have been elided. G1, like CMS, allows this, but should be
1411   // ready to provide a compensating write barrier as necessary
1412   // if that storage came out of a non-young region. The efficiency
1413   // of this implementation depends crucially on being able to
1414   // answer very efficiently in constant time whether a piece of
1415   // storage in the heap comes from a young region or not.
1416   // See ReduceInitialCardMarks.
1417   virtual bool can_elide_tlab_store_barriers() const {
1418     return true;
1419   }
1420 
1421   virtual bool card_mark_must_follow_store() const {
1422     return true;
1423   }
1424 
1425   inline bool is_in_young(const oop obj);
1426 
1427   virtual bool is_scavengable(const void* addr);
1428 
1429   // We don't need barriers for initializing stores to objects
1430   // in the young gen: for the SATB pre-barrier, there is no
1431   // pre-value that needs to be remembered; for the remembered-set
1432   // update logging post-barrier, we don't maintain remembered set
1433   // information for young gen objects.
1434   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1435 
1436   // Returns "true" iff the given word_size is "very large".
1437   static bool is_humongous(size_t word_size) {
1438     // Note this has to be strictly greater-than as the TLABs
1439     // are capped at the humongous threshold and we want to
1440     // ensure that we don't try to allocate a TLAB as
1441     // humongous and that we don't allocate a humongous
1442     // object in a TLAB.
1443     return word_size > _humongous_object_threshold_in_words;
1444   }
1445 
1446   // Returns the humongous threshold for a specific region size
1447   static size_t humongous_threshold_for(size_t region_size) {
1448     return (region_size / 2);
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   // Print the maximum heap capacity.
1460   virtual size_t max_capacity() const;
1461 
1462   virtual jlong millis_since_last_gc();
1463 
1464 
1465   // Convenience function to be used in situations where the heap type can be
1466   // asserted to be this type.
1467   static G1CollectedHeap* heap();
1468 
1469   void set_region_short_lived_locked(HeapRegion* hr);
1470   // add appropriate methods for any other surv rate groups
1471 
1472   YoungList* young_list() const { return _young_list; }
1473 
1474   // debugging
1475   bool check_young_list_well_formed() {
1476     return _young_list->check_list_well_formed();
1477   }
1478 
1479   bool check_young_list_empty(bool check_heap,
1480                               bool check_sample = true);
1481 
1482   // *** Stuff related to concurrent marking.  It's not clear to me that so
1483   // many of these need to be public.
1484 
1485   // The functions below are helper functions that a subclass of
1486   // "CollectedHeap" can use in the implementation of its virtual
1487   // functions.
1488   // This performs a concurrent marking of the live objects in a
1489   // bitmap off to the side.
1490   void doConcurrentMark();
1491 
1492   bool isMarkedPrev(oop obj) const;
1493   bool isMarkedNext(oop obj) const;
1494 
1495   // Determine if an object is dead, given the object and also
1496   // the region to which the object belongs. An object is dead
1497   // iff a) it was not allocated since the last mark, b) it
1498   // is not marked, and c) it is not in an archive region.
1499   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1500     return
1501       !hr->obj_allocated_since_prev_marking(obj) &&
1502       !isMarkedPrev(obj) &&
1503       !hr->is_archive();
1504   }
1505 
1506   // This function returns true when an object has been
1507   // around since the previous marking and hasn't yet
1508   // been marked during this marking, and is not in an archive region.
1509   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1510     return
1511       !hr->obj_allocated_since_next_marking(obj) &&
1512       !isMarkedNext(obj) &&
1513       !hr->is_archive();
1514   }
1515 
1516   // Determine if an object is dead, given only the object itself.
1517   // This will find the region to which the object belongs and
1518   // then call the region version of the same function.
1519 
1520   // Added if it is NULL it isn't dead.
1521 
1522   inline bool is_obj_dead(const oop obj) const;
1523 
1524   inline bool is_obj_ill(const oop obj) const;
1525 
1526   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1527   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1528   bool is_marked(oop obj, VerifyOption vo);
1529   const char* top_at_mark_start_str(VerifyOption vo);
1530 
1531   ConcurrentMark* concurrent_mark() const { return _cm; }
1532 
1533   // Refinement
1534 
1535   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1536 
1537   // The dirty cards region list is used to record a subset of regions
1538   // whose cards need clearing. The list if populated during the
1539   // remembered set scanning and drained during the card table
1540   // cleanup. Although the methods are reentrant, population/draining
1541   // phases must not overlap. For synchronization purposes the last
1542   // element on the list points to itself.
1543   HeapRegion* _dirty_cards_region_list;
1544   void push_dirty_cards_region(HeapRegion* hr);
1545   HeapRegion* pop_dirty_cards_region();
1546 
1547   // Optimized nmethod scanning support routines
1548 
1549   // Register the given nmethod with the G1 heap.
1550   virtual void register_nmethod(nmethod* nm);
1551 
1552   // Unregister the given nmethod from the G1 heap.
1553   virtual void unregister_nmethod(nmethod* nm);
1554 
1555   // Free up superfluous code root memory.
1556   void purge_code_root_memory();
1557 
1558   // Rebuild the strong code root lists for each region
1559   // after a full GC.
1560   void rebuild_strong_code_roots();
1561 
1562   // Delete entries for dead interned string and clean up unreferenced symbols
1563   // in symbol table, possibly in parallel.
1564   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1565 
1566   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1567   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1568 
1569   // Redirty logged cards in the refinement queue.
1570   void redirty_logged_cards();
1571   // Verification
1572 
1573   // Perform any cleanup actions necessary before allowing a verification.
1574   virtual void prepare_for_verify();
1575 
1576   // Perform verification.
1577 
1578   // vo == UsePrevMarking  -> use "prev" marking information,
1579   // vo == UseNextMarking -> use "next" marking information
1580   // vo == UseMarkWord    -> use the mark word in the object header
1581   //
1582   // NOTE: Only the "prev" marking information is guaranteed to be
1583   // consistent most of the time, so most calls to this should use
1584   // vo == UsePrevMarking.
1585   // Currently, there is only one case where this is called with
1586   // vo == UseNextMarking, which is to verify the "next" marking
1587   // information at the end of remark.
1588   // Currently there is only one place where this is called with
1589   // vo == UseMarkWord, which is to verify the marking during a
1590   // full GC.
1591   void verify(bool silent, VerifyOption vo);
1592 
1593   // Override; it uses the "prev" marking information
1594   virtual void verify(bool silent);
1595 
1596   // The methods below are here for convenience and dispatch the
1597   // appropriate method depending on value of the given VerifyOption
1598   // parameter. The values for that parameter, and their meanings,
1599   // are the same as those above.
1600 
1601   bool is_obj_dead_cond(const oop obj,
1602                         const HeapRegion* hr,
1603                         const VerifyOption vo) const;
1604 
1605   bool is_obj_dead_cond(const oop obj,
1606                         const VerifyOption vo) const;
1607 
1608   G1HeapSummary create_g1_heap_summary();
1609 
1610   // Printing
1611 
1612   virtual void print_on(outputStream* st) const;
1613   virtual void print_extended_on(outputStream* st) const;
1614   virtual void print_on_error(outputStream* st) const;
1615 
1616   virtual void print_gc_threads_on(outputStream* st) const;
1617   virtual void gc_threads_do(ThreadClosure* tc) const;
1618 
1619   // Override
1620   void print_tracing_info() const;
1621 
1622   // The following two methods are helpful for debugging RSet issues.
1623   void print_cset_rsets() PRODUCT_RETURN;
1624   void print_all_rsets() PRODUCT_RETURN;
1625 
1626 public:
1627   size_t pending_card_num();
1628   size_t cards_scanned();
1629 
1630 protected:
1631   size_t _max_heap_capacity;
1632 };
1633 
1634 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP