1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc/g1/evacuationInfo.hpp"
  29 #include "gc/g1/g1AllocationContext.hpp"
  30 #include "gc/g1/g1BiasedArray.hpp"
  31 #include "gc/g1/g1CollectionSet.hpp"
  32 #include "gc/g1/g1CollectorState.hpp"
  33 #include "gc/g1/g1ConcurrentMark.hpp"
  34 #include "gc/g1/g1HRPrinter.hpp"
  35 #include "gc/g1/g1InCSetState.hpp"
  36 #include "gc/g1/g1MonitoringSupport.hpp"
  37 #include "gc/g1/g1EvacFailure.hpp"
  38 #include "gc/g1/g1EvacStats.hpp"
  39 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
  40 #include "gc/g1/g1YCTypes.hpp"
  41 #include "gc/g1/hSpaceCounters.hpp"
  42 #include "gc/g1/heapRegionManager.hpp"
  43 #include "gc/g1/heapRegionSet.hpp"
  44 #include "gc/g1/youngList.hpp"
  45 #include "gc/shared/barrierSet.hpp"
  46 #include "gc/shared/collectedHeap.hpp"
  47 #include "gc/shared/plab.hpp"
  48 #include "memory/memRegion.hpp"
  49 #include "utilities/stack.hpp"
  50 
  51 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  52 // It uses the "Garbage First" heap organization and algorithm, which
  53 // may combine concurrent marking with parallel, incremental compaction of
  54 // heap subsets that will yield large amounts of garbage.
  55 
  56 // Forward declarations
  57 class HeapRegion;
  58 class HRRSCleanupTask;
  59 class GenerationSpec;
  60 class OopsInHeapRegionClosure;
  61 class G1ParScanThreadState;
  62 class G1ParScanThreadStateSet;
  63 class G1KlassScanClosure;
  64 class G1ParScanThreadState;
  65 class ObjectClosure;
  66 class SpaceClosure;
  67 class CompactibleSpaceClosure;
  68 class Space;
  69 class G1CollectionSet;
  70 class G1CollectorPolicy;
  71 class G1RemSet;
  72 class HeapRegionRemSetIterator;
  73 class G1ConcurrentMark;
  74 class ConcurrentMarkThread;
  75 class ConcurrentG1Refine;
  76 class ConcurrentGCTimer;
  77 class GenerationCounters;
  78 class STWGCTimer;
  79 class G1NewTracer;
  80 class G1OldTracer;
  81 class EvacuationFailedInfo;
  82 class nmethod;
  83 class Ticks;
  84 class WorkGang;
  85 class G1Allocator;
  86 class G1ArchiveAllocator;
  87 class G1HeapVerifier;
  88 
  89 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  90 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  91 
  92 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  93 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  94 
  95 // The G1 STW is alive closure.
  96 // An instance is embedded into the G1CH and used as the
  97 // (optional) _is_alive_non_header closure in the STW
  98 // reference processor. It is also extensively used during
  99 // reference processing during STW evacuation pauses.
 100 class G1STWIsAliveClosure: public BoolObjectClosure {
 101   G1CollectedHeap* _g1;
 102 public:
 103   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 104   bool do_object_b(oop p);
 105 };
 106 
 107 class RefineCardTableEntryClosure;
 108 
 109 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 110  private:
 111   void reset_from_card_cache(uint start_idx, size_t num_regions);
 112  public:
 113   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 114 };
 115 
 116 class G1CollectedHeap : public CollectedHeap {
 117   friend class VM_CollectForMetadataAllocation;
 118   friend class VM_G1CollectForAllocation;
 119   friend class VM_G1CollectFull;
 120   friend class VM_G1IncCollectionPause;
 121   friend class VMStructs;
 122   friend class MutatorAllocRegion;
 123   friend class G1GCAllocRegion;
 124   friend class G1HeapVerifier;
 125 
 126   // Closures used in implementation.
 127   friend class G1ParScanThreadState;
 128   friend class G1ParScanThreadStateSet;
 129   friend class G1ParTask;
 130   friend class G1PLABAllocator;
 131   friend class G1PrepareCompactClosure;
 132 
 133   // Other related classes.
 134   friend class HeapRegionClaimer;
 135 
 136   // Testing classes.
 137   friend class G1CheckCSetFastTableClosure;
 138 
 139 private:
 140   WorkGang* _workers;
 141 
 142   static size_t _humongous_object_threshold_in_words;
 143 
 144   // The secondary free list which contains regions that have been
 145   // freed up during the cleanup process. This will be appended to
 146   // the master free list when appropriate.
 147   FreeRegionList _secondary_free_list;
 148 
 149   // It keeps track of the old regions.
 150   HeapRegionSet _old_set;
 151 
 152   // It keeps track of the humongous regions.
 153   HeapRegionSet _humongous_set;
 154 
 155   void eagerly_reclaim_humongous_regions();
 156 
 157   // The number of regions we could create by expansion.
 158   uint _expansion_regions;
 159 
 160   // The block offset table for the G1 heap.
 161   G1BlockOffsetTable* _bot;
 162 
 163   // Tears down the region sets / lists so that they are empty and the
 164   // regions on the heap do not belong to a region set / list. The
 165   // only exception is the humongous set which we leave unaltered. If
 166   // free_list_only is true, it will only tear down the master free
 167   // list. It is called before a Full GC (free_list_only == false) or
 168   // before heap shrinking (free_list_only == true).
 169   void tear_down_region_sets(bool free_list_only);
 170 
 171   // Rebuilds the region sets / lists so that they are repopulated to
 172   // reflect the contents of the heap. The only exception is the
 173   // humongous set which was not torn down in the first place. If
 174   // free_list_only is true, it will only rebuild the master free
 175   // list. It is called after a Full GC (free_list_only == false) or
 176   // after heap shrinking (free_list_only == true).
 177   void rebuild_region_sets(bool free_list_only);
 178 
 179   // Callback for region mapping changed events.
 180   G1RegionMappingChangedListener _listener;
 181 
 182   // The sequence of all heap regions in the heap.
 183   HeapRegionManager _hrm;
 184 
 185   // Manages all allocations with regions except humongous object allocations.
 186   G1Allocator* _allocator;
 187 
 188   // Manages all heap verification.
 189   G1HeapVerifier* _verifier;
 190 
 191   // Outside of GC pauses, the number of bytes used in all regions other
 192   // than the current allocation region(s).
 193   size_t _summary_bytes_used;
 194 
 195   void increase_used(size_t bytes);
 196   void decrease_used(size_t bytes);
 197 
 198   void set_used(size_t bytes);
 199 
 200   // Class that handles archive allocation ranges.
 201   G1ArchiveAllocator* _archive_allocator;
 202 
 203   // Statistics for each allocation context
 204   AllocationContextStats _allocation_context_stats;
 205 
 206   // GC allocation statistics policy for survivors.
 207   G1EvacStats _survivor_evac_stats;
 208 
 209   // GC allocation statistics policy for tenured objects.
 210   G1EvacStats _old_evac_stats;
 211 
 212   // It specifies whether we should attempt to expand the heap after a
 213   // region allocation failure. If heap expansion fails we set this to
 214   // false so that we don't re-attempt the heap expansion (it's likely
 215   // that subsequent expansion attempts will also fail if one fails).
 216   // Currently, it is only consulted during GC and it's reset at the
 217   // start of each GC.
 218   bool _expand_heap_after_alloc_failure;
 219 
 220   // Helper for monitoring and management support.
 221   G1MonitoringSupport* _g1mm;
 222 
 223   // Records whether the region at the given index is (still) a
 224   // candidate for eager reclaim.  Only valid for humongous start
 225   // regions; other regions have unspecified values.  Humongous start
 226   // regions are initialized at start of collection pause, with
 227   // candidates removed from the set as they are found reachable from
 228   // roots or the young generation.
 229   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 230    protected:
 231     bool default_value() const { return false; }
 232    public:
 233     void clear() { G1BiasedMappedArray<bool>::clear(); }
 234     void set_candidate(uint region, bool value) {
 235       set_by_index(region, value);
 236     }
 237     bool is_candidate(uint region) {
 238       return get_by_index(region);
 239     }
 240   };
 241 
 242   HumongousReclaimCandidates _humongous_reclaim_candidates;
 243   // Stores whether during humongous object registration we found candidate regions.
 244   // If not, we can skip a few steps.
 245   bool _has_humongous_reclaim_candidates;
 246 
 247   volatile unsigned _gc_time_stamp;
 248 
 249   G1HRPrinter _hr_printer;
 250 
 251   // It decides whether an explicit GC should start a concurrent cycle
 252   // instead of doing a STW GC. Currently, a concurrent cycle is
 253   // explicitly started if:
 254   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 255   // (b) cause == _g1_humongous_allocation
 256   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 257   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 258   // (e) cause == _update_allocation_context_stats_inc
 259   // (f) cause == _wb_conc_mark
 260   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 261 
 262   // indicates whether we are in young or mixed GC mode
 263   G1CollectorState _collector_state;
 264 
 265   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 266   // concurrent cycles) we have started.
 267   volatile uint _old_marking_cycles_started;
 268 
 269   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 270   // concurrent cycles) we have completed.
 271   volatile uint _old_marking_cycles_completed;
 272 
 273   bool _heap_summary_sent;
 274 
 275   // This is a non-product method that is helpful for testing. It is
 276   // called at the end of a GC and artificially expands the heap by
 277   // allocating a number of dead regions. This way we can induce very
 278   // frequent marking cycles and stress the cleanup / concurrent
 279   // cleanup code more (as all the regions that will be allocated by
 280   // this method will be found dead by the marking cycle).
 281   void allocate_dummy_regions() PRODUCT_RETURN;
 282 
 283   // Clear RSets after a compaction. It also resets the GC time stamps.
 284   void clear_rsets_post_compaction();
 285 
 286   // If the HR printer is active, dump the state of the regions in the
 287   // heap after a compaction.
 288   void print_hrm_post_compaction();
 289 
 290   // Create a memory mapper for auxiliary data structures of the given size and
 291   // translation factor.
 292   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 293                                                          size_t size,
 294                                                          size_t translation_factor);
 295 
 296   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 297 
 298   void process_weak_jni_handles();
 299 
 300   // These are macros so that, if the assert fires, we get the correct
 301   // line number, file, etc.
 302 
 303 #define heap_locking_asserts_params(_extra_message_)                          \
 304   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 305   (_extra_message_),                                                          \
 306   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 307   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 308   BOOL_TO_STR(Thread::current()->is_VM_thread())
 309 
 310 #define assert_heap_locked()                                                  \
 311   do {                                                                        \
 312     assert(Heap_lock->owned_by_self(),                                        \
 313            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 314   } while (0)
 315 
 316 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 317   do {                                                                        \
 318     assert(Heap_lock->owned_by_self() ||                                      \
 319            (SafepointSynchronize::is_at_safepoint() &&                        \
 320              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 321            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 322                                         "should be at a safepoint"));         \
 323   } while (0)
 324 
 325 #define assert_heap_locked_and_not_at_safepoint()                             \
 326   do {                                                                        \
 327     assert(Heap_lock->owned_by_self() &&                                      \
 328                                     !SafepointSynchronize::is_at_safepoint(), \
 329           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 330                                        "should not be at a safepoint"));      \
 331   } while (0)
 332 
 333 #define assert_heap_not_locked()                                              \
 334   do {                                                                        \
 335     assert(!Heap_lock->owned_by_self(),                                       \
 336         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 337   } while (0)
 338 
 339 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 340   do {                                                                        \
 341     assert(!Heap_lock->owned_by_self() &&                                     \
 342                                     !SafepointSynchronize::is_at_safepoint(), \
 343       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 344                                    "should not be at a safepoint"));          \
 345   } while (0)
 346 
 347 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 348   do {                                                                        \
 349     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 350               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 351            heap_locking_asserts_params("should be at a safepoint"));          \
 352   } while (0)
 353 
 354 #define assert_not_at_safepoint()                                             \
 355   do {                                                                        \
 356     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 357            heap_locking_asserts_params("should not be at a safepoint"));      \
 358   } while (0)
 359 
 360 protected:
 361 
 362   // The young region list.
 363   YoungList*  _young_list;
 364 
 365   // The current policy object for the collector.
 366   G1CollectorPolicy* _g1_policy;
 367 
 368   G1CollectionSet _collection_set;
 369 
 370   // This is the second level of trying to allocate a new region. If
 371   // new_region() didn't find a region on the free_list, this call will
 372   // check whether there's anything available on the
 373   // secondary_free_list and/or wait for more regions to appear on
 374   // that list, if _free_regions_coming is set.
 375   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 376 
 377   // Try to allocate a single non-humongous HeapRegion sufficient for
 378   // an allocation of the given word_size. If do_expand is true,
 379   // attempt to expand the heap if necessary to satisfy the allocation
 380   // request. If the region is to be used as an old region or for a
 381   // humongous object, set is_old to true. If not, to false.
 382   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 383 
 384   // Initialize a contiguous set of free regions of length num_regions
 385   // and starting at index first so that they appear as a single
 386   // humongous region.
 387   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 388                                                       uint num_regions,
 389                                                       size_t word_size,
 390                                                       AllocationContext_t context);
 391 
 392   // Attempt to allocate a humongous object of the given size. Return
 393   // NULL if unsuccessful.
 394   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 395 
 396   // The following two methods, allocate_new_tlab() and
 397   // mem_allocate(), are the two main entry points from the runtime
 398   // into the G1's allocation routines. They have the following
 399   // assumptions:
 400   //
 401   // * They should both be called outside safepoints.
 402   //
 403   // * They should both be called without holding the Heap_lock.
 404   //
 405   // * All allocation requests for new TLABs should go to
 406   //   allocate_new_tlab().
 407   //
 408   // * All non-TLAB allocation requests should go to mem_allocate().
 409   //
 410   // * If either call cannot satisfy the allocation request using the
 411   //   current allocating region, they will try to get a new one. If
 412   //   this fails, they will attempt to do an evacuation pause and
 413   //   retry the allocation.
 414   //
 415   // * If all allocation attempts fail, even after trying to schedule
 416   //   an evacuation pause, allocate_new_tlab() will return NULL,
 417   //   whereas mem_allocate() will attempt a heap expansion and/or
 418   //   schedule a Full GC.
 419   //
 420   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 421   //   should never be called with word_size being humongous. All
 422   //   humongous allocation requests should go to mem_allocate() which
 423   //   will satisfy them with a special path.
 424 
 425   virtual HeapWord* allocate_new_tlab(size_t word_size);
 426 
 427   virtual HeapWord* mem_allocate(size_t word_size,
 428                                  bool*  gc_overhead_limit_was_exceeded);
 429 
 430   // The following three methods take a gc_count_before_ret
 431   // parameter which is used to return the GC count if the method
 432   // returns NULL. Given that we are required to read the GC count
 433   // while holding the Heap_lock, and these paths will take the
 434   // Heap_lock at some point, it's easier to get them to read the GC
 435   // count while holding the Heap_lock before they return NULL instead
 436   // of the caller (namely: mem_allocate()) having to also take the
 437   // Heap_lock just to read the GC count.
 438 
 439   // First-level mutator allocation attempt: try to allocate out of
 440   // the mutator alloc region without taking the Heap_lock. This
 441   // should only be used for non-humongous allocations.
 442   inline HeapWord* attempt_allocation(size_t word_size,
 443                                       uint* gc_count_before_ret,
 444                                       uint* gclocker_retry_count_ret);
 445 
 446   // Second-level mutator allocation attempt: take the Heap_lock and
 447   // retry the allocation attempt, potentially scheduling a GC
 448   // pause. This should only be used for non-humongous allocations.
 449   HeapWord* attempt_allocation_slow(size_t word_size,
 450                                     AllocationContext_t context,
 451                                     uint* gc_count_before_ret,
 452                                     uint* gclocker_retry_count_ret);
 453 
 454   // Takes the Heap_lock and attempts a humongous allocation. It can
 455   // potentially schedule a GC pause.
 456   HeapWord* attempt_allocation_humongous(size_t word_size,
 457                                          uint* gc_count_before_ret,
 458                                          uint* gclocker_retry_count_ret);
 459 
 460   // Allocation attempt that should be called during safepoints (e.g.,
 461   // at the end of a successful GC). expect_null_mutator_alloc_region
 462   // specifies whether the mutator alloc region is expected to be NULL
 463   // or not.
 464   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 465                                             AllocationContext_t context,
 466                                             bool expect_null_mutator_alloc_region);
 467 
 468   // These methods are the "callbacks" from the G1AllocRegion class.
 469 
 470   // For mutator alloc regions.
 471   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 472   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 473                                    size_t allocated_bytes);
 474 
 475   // For GC alloc regions.
 476   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 477                                   InCSetState dest);
 478   void retire_gc_alloc_region(HeapRegion* alloc_region,
 479                               size_t allocated_bytes, InCSetState dest);
 480 
 481   // - if explicit_gc is true, the GC is for a System.gc() etc,
 482   //   otherwise it's for a failed allocation.
 483   // - if clear_all_soft_refs is true, all soft references should be
 484   //   cleared during the GC.
 485   // - it returns false if it is unable to do the collection due to the
 486   //   GC locker being active, true otherwise.
 487   bool do_full_collection(bool explicit_gc,
 488                           bool clear_all_soft_refs);
 489 
 490   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 491   virtual void do_full_collection(bool clear_all_soft_refs);
 492 
 493   // Resize the heap if necessary after a full collection.
 494   void resize_if_necessary_after_full_collection();
 495 
 496   // Callback from VM_G1CollectForAllocation operation.
 497   // This function does everything necessary/possible to satisfy a
 498   // failed allocation request (including collection, expansion, etc.)
 499   HeapWord* satisfy_failed_allocation(size_t word_size,
 500                                       AllocationContext_t context,
 501                                       bool* succeeded);
 502 private:
 503   // Helper method for satisfy_failed_allocation()
 504   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 505                                              AllocationContext_t context,
 506                                              bool do_gc,
 507                                              bool clear_all_soft_refs,
 508                                              bool expect_null_mutator_alloc_region,
 509                                              bool* gc_succeeded);
 510 
 511 protected:
 512   // Attempting to expand the heap sufficiently
 513   // to support an allocation of the given "word_size".  If
 514   // successful, perform the allocation and return the address of the
 515   // allocated block, or else "NULL".
 516   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 517 
 518   // Preserve any referents discovered by concurrent marking that have not yet been
 519   // copied by the STW pause.
 520   void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
 521   // Process any reference objects discovered during
 522   // an incremental evacuation pause.
 523   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 524 
 525   // Enqueue any remaining discovered references
 526   // after processing.
 527   void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 528 
 529   // Merges the information gathered on a per-thread basis for all worker threads
 530   // during GC into global variables.
 531   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 532 public:
 533   WorkGang* workers() const { return _workers; }
 534 
 535   G1Allocator* allocator() {
 536     return _allocator;
 537   }
 538 
 539   G1HeapVerifier* verifier() {
 540     return _verifier;
 541   }
 542 
 543   G1MonitoringSupport* g1mm() {
 544     assert(_g1mm != NULL, "should have been initialized");
 545     return _g1mm;
 546   }
 547 
 548   // Expand the garbage-first heap by at least the given size (in bytes!).
 549   // Returns true if the heap was expanded by the requested amount;
 550   // false otherwise.
 551   // (Rounds up to a HeapRegion boundary.)
 552   bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
 553 
 554   // Returns the PLAB statistics for a given destination.
 555   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 556 
 557   // Determines PLAB size for a given destination.
 558   inline size_t desired_plab_sz(InCSetState dest);
 559 
 560   inline AllocationContextStats& allocation_context_stats();
 561 
 562   // Do anything common to GC's.
 563   void gc_prologue(bool full);
 564   void gc_epilogue(bool full);
 565 
 566   // Modify the reclaim candidate set and test for presence.
 567   // These are only valid for starts_humongous regions.
 568   inline void set_humongous_reclaim_candidate(uint region, bool value);
 569   inline bool is_humongous_reclaim_candidate(uint region);
 570 
 571   // Remove from the reclaim candidate set.  Also remove from the
 572   // collection set so that later encounters avoid the slow path.
 573   inline void set_humongous_is_live(oop obj);
 574 
 575   // Register the given region to be part of the collection set.
 576   inline void register_humongous_region_with_cset(uint index);
 577   // Register regions with humongous objects (actually on the start region) in
 578   // the in_cset_fast_test table.
 579   void register_humongous_regions_with_cset();
 580   // We register a region with the fast "in collection set" test. We
 581   // simply set to true the array slot corresponding to this region.
 582   void register_young_region_with_cset(HeapRegion* r) {
 583     _in_cset_fast_test.set_in_young(r->hrm_index());
 584   }
 585   void register_old_region_with_cset(HeapRegion* r) {
 586     _in_cset_fast_test.set_in_old(r->hrm_index());
 587   }
 588   inline void register_ext_region_with_cset(HeapRegion* r) {
 589     _in_cset_fast_test.set_ext(r->hrm_index());
 590   }
 591   void clear_in_cset(const HeapRegion* hr) {
 592     _in_cset_fast_test.clear(hr);
 593   }
 594 
 595   void clear_cset_fast_test() {
 596     _in_cset_fast_test.clear();
 597   }
 598 
 599   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 600 
 601   // This is called at the start of either a concurrent cycle or a Full
 602   // GC to update the number of old marking cycles started.
 603   void increment_old_marking_cycles_started();
 604 
 605   // This is called at the end of either a concurrent cycle or a Full
 606   // GC to update the number of old marking cycles completed. Those two
 607   // can happen in a nested fashion, i.e., we start a concurrent
 608   // cycle, a Full GC happens half-way through it which ends first,
 609   // and then the cycle notices that a Full GC happened and ends
 610   // too. The concurrent parameter is a boolean to help us do a bit
 611   // tighter consistency checking in the method. If concurrent is
 612   // false, the caller is the inner caller in the nesting (i.e., the
 613   // Full GC). If concurrent is true, the caller is the outer caller
 614   // in this nesting (i.e., the concurrent cycle). Further nesting is
 615   // not currently supported. The end of this call also notifies
 616   // the FullGCCount_lock in case a Java thread is waiting for a full
 617   // GC to happen (e.g., it called System.gc() with
 618   // +ExplicitGCInvokesConcurrent).
 619   void increment_old_marking_cycles_completed(bool concurrent);
 620 
 621   uint old_marking_cycles_completed() {
 622     return _old_marking_cycles_completed;
 623   }
 624 
 625   void register_concurrent_cycle_start(const Ticks& start_time);
 626   void register_concurrent_cycle_end();
 627   void trace_heap_after_concurrent_cycle();
 628 
 629   G1HRPrinter* hr_printer() { return &_hr_printer; }
 630 
 631   // Allocates a new heap region instance.
 632   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 633 
 634   // Allocate the highest free region in the reserved heap. This will commit
 635   // regions as necessary.
 636   HeapRegion* alloc_highest_free_region();
 637 
 638   // Frees a non-humongous region by initializing its contents and
 639   // adding it to the free list that's passed as a parameter (this is
 640   // usually a local list which will be appended to the master free
 641   // list later). The used bytes of freed regions are accumulated in
 642   // pre_used. If par is true, the region's RSet will not be freed
 643   // up. The assumption is that this will be done later.
 644   // The locked parameter indicates if the caller has already taken
 645   // care of proper synchronization. This may allow some optimizations.
 646   void free_region(HeapRegion* hr,
 647                    FreeRegionList* free_list,
 648                    bool par,
 649                    bool locked = false);
 650 
 651   // It dirties the cards that cover the block so that the post
 652   // write barrier never queues anything when updating objects on this
 653   // block. It is assumed (and in fact we assert) that the block
 654   // belongs to a young region.
 655   inline void dirty_young_block(HeapWord* start, size_t word_size);
 656 
 657   // Frees a humongous region by collapsing it into individual regions
 658   // and calling free_region() for each of them. The freed regions
 659   // will be added to the free list that's passed as a parameter (this
 660   // is usually a local list which will be appended to the master free
 661   // list later). The used bytes of freed regions are accumulated in
 662   // pre_used. If par is true, the region's RSet will not be freed
 663   // up. The assumption is that this will be done later.
 664   void free_humongous_region(HeapRegion* hr,
 665                              FreeRegionList* free_list,
 666                              bool par);
 667 
 668   // Facility for allocating in 'archive' regions in high heap memory and
 669   // recording the allocated ranges. These should all be called from the
 670   // VM thread at safepoints, without the heap lock held. They can be used
 671   // to create and archive a set of heap regions which can be mapped at the
 672   // same fixed addresses in a subsequent JVM invocation.
 673   void begin_archive_alloc_range();
 674 
 675   // Check if the requested size would be too large for an archive allocation.
 676   bool is_archive_alloc_too_large(size_t word_size);
 677 
 678   // Allocate memory of the requested size from the archive region. This will
 679   // return NULL if the size is too large or if no memory is available. It
 680   // does not trigger a garbage collection.
 681   HeapWord* archive_mem_allocate(size_t word_size);
 682 
 683   // Optionally aligns the end address and returns the allocated ranges in
 684   // an array of MemRegions in order of ascending addresses.
 685   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 686                                size_t end_alignment_in_bytes = 0);
 687 
 688   // Facility for allocating a fixed range within the heap and marking
 689   // the containing regions as 'archive'. For use at JVM init time, when the
 690   // caller may mmap archived heap data at the specified range(s).
 691   // Verify that the MemRegions specified in the argument array are within the
 692   // reserved heap.
 693   bool check_archive_addresses(MemRegion* range, size_t count);
 694 
 695   // Commit the appropriate G1 regions containing the specified MemRegions
 696   // and mark them as 'archive' regions. The regions in the array must be
 697   // non-overlapping and in order of ascending address.
 698   bool alloc_archive_regions(MemRegion* range, size_t count);
 699 
 700   // Insert any required filler objects in the G1 regions around the specified
 701   // ranges to make the regions parseable. This must be called after
 702   // alloc_archive_regions, and after class loading has occurred.
 703   void fill_archive_regions(MemRegion* range, size_t count);
 704 
 705   // For each of the specified MemRegions, uncommit the containing G1 regions
 706   // which had been allocated by alloc_archive_regions. This should be called
 707   // rather than fill_archive_regions at JVM init time if the archive file
 708   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 709   void dealloc_archive_regions(MemRegion* range, size_t count);
 710 
 711 protected:
 712 
 713   // Shrink the garbage-first heap by at most the given size (in bytes!).
 714   // (Rounds down to a HeapRegion boundary.)
 715   virtual void shrink(size_t expand_bytes);
 716   void shrink_helper(size_t expand_bytes);
 717 
 718   #if TASKQUEUE_STATS
 719   static void print_taskqueue_stats_hdr(outputStream* const st);
 720   void print_taskqueue_stats() const;
 721   void reset_taskqueue_stats();
 722   #endif // TASKQUEUE_STATS
 723 
 724   // Schedule the VM operation that will do an evacuation pause to
 725   // satisfy an allocation request of word_size. *succeeded will
 726   // return whether the VM operation was successful (it did do an
 727   // evacuation pause) or not (another thread beat us to it or the GC
 728   // locker was active). Given that we should not be holding the
 729   // Heap_lock when we enter this method, we will pass the
 730   // gc_count_before (i.e., total_collections()) as a parameter since
 731   // it has to be read while holding the Heap_lock. Currently, both
 732   // methods that call do_collection_pause() release the Heap_lock
 733   // before the call, so it's easy to read gc_count_before just before.
 734   HeapWord* do_collection_pause(size_t         word_size,
 735                                 uint           gc_count_before,
 736                                 bool*          succeeded,
 737                                 GCCause::Cause gc_cause);
 738 
 739   void wait_for_root_region_scanning();
 740 
 741   // The guts of the incremental collection pause, executed by the vm
 742   // thread. It returns false if it is unable to do the collection due
 743   // to the GC locker being active, true otherwise
 744   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 745 
 746   // Actually do the work of evacuating the collection set.
 747   virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
 748 
 749   void pre_evacuate_collection_set();
 750   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 751 
 752   // Print the header for the per-thread termination statistics.
 753   static void print_termination_stats_hdr();
 754   // Print actual per-thread termination statistics.
 755   void print_termination_stats(uint worker_id,
 756                                double elapsed_ms,
 757                                double strong_roots_ms,
 758                                double term_ms,
 759                                size_t term_attempts,
 760                                size_t alloc_buffer_waste,
 761                                size_t undo_waste) const;
 762   // Update object copying statistics.
 763   void record_obj_copy_mem_stats();
 764 
 765   // The g1 remembered set of the heap.
 766   G1RemSet* _g1_rem_set;
 767 
 768   // A set of cards that cover the objects for which the Rsets should be updated
 769   // concurrently after the collection.
 770   DirtyCardQueueSet _dirty_card_queue_set;
 771 
 772   // The closure used to refine a single card.
 773   RefineCardTableEntryClosure* _refine_cte_cl;
 774 
 775   // After a collection pause, make the regions in the CS into free
 776   // regions.
 777   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 778 
 779   // Abandon the current collection set without recording policy
 780   // statistics or updating free lists.
 781   void abandon_collection_set(HeapRegion* cs_head);
 782 
 783   // The concurrent marker (and the thread it runs in.)
 784   G1ConcurrentMark* _cm;
 785   ConcurrentMarkThread* _cmThread;
 786 
 787   // The concurrent refiner.
 788   ConcurrentG1Refine* _cg1r;
 789 
 790   // The parallel task queues
 791   RefToScanQueueSet *_task_queues;
 792 
 793   // True iff a evacuation has failed in the current collection.
 794   bool _evacuation_failed;
 795 
 796   EvacuationFailedInfo* _evacuation_failed_info_array;
 797 
 798   // Failed evacuations cause some logical from-space objects to have
 799   // forwarding pointers to themselves.  Reset them.
 800   void remove_self_forwarding_pointers();
 801 
 802   // Restore the preserved mark words for objects with self-forwarding pointers.
 803   void restore_preserved_marks();
 804 
 805   // Restore the objects in the regions in the collection set after an
 806   // evacuation failure.
 807   void restore_after_evac_failure();
 808 
 809   // Stores marks with the corresponding oop that we need to preserve during evacuation
 810   // failure.
 811   OopAndMarkOopStack*  _preserved_objs;
 812 
 813   // Preserve the mark of "obj", if necessary, in preparation for its mark
 814   // word being overwritten with a self-forwarding-pointer.
 815   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 816 
 817 #ifndef PRODUCT
 818   // Support for forcing evacuation failures. Analogous to
 819   // PromotionFailureALot for the other collectors.
 820 
 821   // Records whether G1EvacuationFailureALot should be in effect
 822   // for the current GC
 823   bool _evacuation_failure_alot_for_current_gc;
 824 
 825   // Used to record the GC number for interval checking when
 826   // determining whether G1EvaucationFailureALot is in effect
 827   // for the current GC.
 828   size_t _evacuation_failure_alot_gc_number;
 829 
 830   // Count of the number of evacuations between failures.
 831   volatile size_t _evacuation_failure_alot_count;
 832 
 833   // Set whether G1EvacuationFailureALot should be in effect
 834   // for the current GC (based upon the type of GC and which
 835   // command line flags are set);
 836   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 837                                                   bool during_initial_mark,
 838                                                   bool during_marking);
 839 
 840   inline void set_evacuation_failure_alot_for_current_gc();
 841 
 842   // Return true if it's time to cause an evacuation failure.
 843   inline bool evacuation_should_fail();
 844 
 845   // Reset the G1EvacuationFailureALot counters.  Should be called at
 846   // the end of an evacuation pause in which an evacuation failure occurred.
 847   inline void reset_evacuation_should_fail();
 848 #endif // !PRODUCT
 849 
 850   // ("Weak") Reference processing support.
 851   //
 852   // G1 has 2 instances of the reference processor class. One
 853   // (_ref_processor_cm) handles reference object discovery
 854   // and subsequent processing during concurrent marking cycles.
 855   //
 856   // The other (_ref_processor_stw) handles reference object
 857   // discovery and processing during full GCs and incremental
 858   // evacuation pauses.
 859   //
 860   // During an incremental pause, reference discovery will be
 861   // temporarily disabled for _ref_processor_cm and will be
 862   // enabled for _ref_processor_stw. At the end of the evacuation
 863   // pause references discovered by _ref_processor_stw will be
 864   // processed and discovery will be disabled. The previous
 865   // setting for reference object discovery for _ref_processor_cm
 866   // will be re-instated.
 867   //
 868   // At the start of marking:
 869   //  * Discovery by the CM ref processor is verified to be inactive
 870   //    and it's discovered lists are empty.
 871   //  * Discovery by the CM ref processor is then enabled.
 872   //
 873   // At the end of marking:
 874   //  * Any references on the CM ref processor's discovered
 875   //    lists are processed (possibly MT).
 876   //
 877   // At the start of full GC we:
 878   //  * Disable discovery by the CM ref processor and
 879   //    empty CM ref processor's discovered lists
 880   //    (without processing any entries).
 881   //  * Verify that the STW ref processor is inactive and it's
 882   //    discovered lists are empty.
 883   //  * Temporarily set STW ref processor discovery as single threaded.
 884   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 885   //    field.
 886   //  * Finally enable discovery by the STW ref processor.
 887   //
 888   // The STW ref processor is used to record any discovered
 889   // references during the full GC.
 890   //
 891   // At the end of a full GC we:
 892   //  * Enqueue any reference objects discovered by the STW ref processor
 893   //    that have non-live referents. This has the side-effect of
 894   //    making the STW ref processor inactive by disabling discovery.
 895   //  * Verify that the CM ref processor is still inactive
 896   //    and no references have been placed on it's discovered
 897   //    lists (also checked as a precondition during initial marking).
 898 
 899   // The (stw) reference processor...
 900   ReferenceProcessor* _ref_processor_stw;
 901 
 902   STWGCTimer* _gc_timer_stw;
 903   ConcurrentGCTimer* _gc_timer_cm;
 904 
 905   G1OldTracer* _gc_tracer_cm;
 906   G1NewTracer* _gc_tracer_stw;
 907 
 908   // During reference object discovery, the _is_alive_non_header
 909   // closure (if non-null) is applied to the referent object to
 910   // determine whether the referent is live. If so then the
 911   // reference object does not need to be 'discovered' and can
 912   // be treated as a regular oop. This has the benefit of reducing
 913   // the number of 'discovered' reference objects that need to
 914   // be processed.
 915   //
 916   // Instance of the is_alive closure for embedding into the
 917   // STW reference processor as the _is_alive_non_header field.
 918   // Supplying a value for the _is_alive_non_header field is
 919   // optional but doing so prevents unnecessary additions to
 920   // the discovered lists during reference discovery.
 921   G1STWIsAliveClosure _is_alive_closure_stw;
 922 
 923   // The (concurrent marking) reference processor...
 924   ReferenceProcessor* _ref_processor_cm;
 925 
 926   // Instance of the concurrent mark is_alive closure for embedding
 927   // into the Concurrent Marking reference processor as the
 928   // _is_alive_non_header field. Supplying a value for the
 929   // _is_alive_non_header field is optional but doing so prevents
 930   // unnecessary additions to the discovered lists during reference
 931   // discovery.
 932   G1CMIsAliveClosure _is_alive_closure_cm;
 933 
 934   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 935   HeapRegion** _worker_cset_start_region;
 936 
 937   // Time stamp to validate the regions recorded in the cache
 938   // used by G1CollectedHeap::start_cset_region_for_worker().
 939   // The heap region entry for a given worker is valid iff
 940   // the associated time stamp value matches the current value
 941   // of G1CollectedHeap::_gc_time_stamp.
 942   uint* _worker_cset_start_region_time_stamp;
 943 
 944   volatile bool _free_regions_coming;
 945 
 946 public:
 947 
 948   void set_refine_cte_cl_concurrency(bool concurrent);
 949 
 950   RefToScanQueue *task_queue(uint i) const;
 951 
 952   uint num_task_queues() const;
 953 
 954   // A set of cards where updates happened during the GC
 955   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 956 
 957   // Create a G1CollectedHeap with the specified policy.
 958   // Must call the initialize method afterwards.
 959   // May not return if something goes wrong.
 960   G1CollectedHeap(G1CollectorPolicy* policy);
 961 
 962   // Initialize the G1CollectedHeap to have the initial and
 963   // maximum sizes and remembered and barrier sets
 964   // specified by the policy object.
 965   jint initialize();
 966 
 967   virtual void stop();
 968 
 969   // Return the (conservative) maximum heap alignment for any G1 heap
 970   static size_t conservative_max_heap_alignment();
 971 
 972   // Does operations required after initialization has been done.
 973   void post_initialize();
 974 
 975   // Initialize weak reference processing.
 976   void ref_processing_init();
 977 
 978   virtual Name kind() const {
 979     return CollectedHeap::G1CollectedHeap;
 980   }
 981 
 982   virtual const char* name() const {
 983     return "G1";
 984   }
 985 
 986   const G1CollectorState* collector_state() const { return &_collector_state; }
 987   G1CollectorState* collector_state() { return &_collector_state; }
 988 
 989   // The current policy object for the collector.
 990   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
 991 
 992   const G1CollectionSet* collection_set() const { return &_collection_set; }
 993   G1CollectionSet* collection_set() { return &_collection_set; }
 994 
 995   virtual CollectorPolicy* collector_policy() const;
 996 
 997   // Adaptive size policy.  No such thing for g1.
 998   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
 999 
1000   // The rem set and barrier set.
1001   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1002 
1003   void scrub_rem_set(BitMap* region_bm, BitMap* card_bm);
1004 
1005   unsigned get_gc_time_stamp() {
1006     return _gc_time_stamp;
1007   }
1008 
1009   inline void reset_gc_time_stamp();
1010 
1011   void check_gc_time_stamps() PRODUCT_RETURN;
1012 
1013   inline void increment_gc_time_stamp();
1014 
1015   // Reset the given region's GC timestamp. If it's starts humongous,
1016   // also reset the GC timestamp of its corresponding
1017   // continues humongous regions too.
1018   void reset_gc_time_stamps(HeapRegion* hr);
1019 
1020   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1021   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1022 
1023   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1024   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1025 
1026   // The shared block offset table array.
1027   G1BlockOffsetTable* bot() const { return _bot; }
1028 
1029   // Reference Processing accessors
1030 
1031   // The STW reference processor....
1032   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1033 
1034   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1035 
1036   // The Concurrent Marking reference processor...
1037   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1038 
1039   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1040   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1041 
1042   virtual size_t capacity() const;
1043   virtual size_t used() const;
1044   // This should be called when we're not holding the heap lock. The
1045   // result might be a bit inaccurate.
1046   size_t used_unlocked() const;
1047   size_t recalculate_used() const;
1048 
1049   // These virtual functions do the actual allocation.
1050   // Some heaps may offer a contiguous region for shared non-blocking
1051   // allocation, via inlined code (by exporting the address of the top and
1052   // end fields defining the extent of the contiguous allocation region.)
1053   // But G1CollectedHeap doesn't yet support this.
1054 
1055   virtual bool is_maximal_no_gc() const {
1056     return _hrm.available() == 0;
1057   }
1058 
1059   // The current number of regions in the heap.
1060   uint num_regions() const { return _hrm.length(); }
1061 
1062   // The max number of regions in the heap.
1063   uint max_regions() const { return _hrm.max_length(); }
1064 
1065   // The number of regions that are completely free.
1066   uint num_free_regions() const { return _hrm.num_free_regions(); }
1067 
1068   MemoryUsage get_auxiliary_data_memory_usage() const {
1069     return _hrm.get_auxiliary_data_memory_usage();
1070   }
1071 
1072   // The number of regions that are not completely free.
1073   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1074 
1075 #ifdef ASSERT
1076   bool is_on_master_free_list(HeapRegion* hr) {
1077     return _hrm.is_free(hr);
1078   }
1079 #endif // ASSERT
1080 
1081   // Wrapper for the region list operations that can be called from
1082   // methods outside this class.
1083 
1084   void secondary_free_list_add(FreeRegionList* list) {
1085     _secondary_free_list.add_ordered(list);
1086   }
1087 
1088   void append_secondary_free_list() {
1089     _hrm.insert_list_into_free_list(&_secondary_free_list);
1090   }
1091 
1092   void append_secondary_free_list_if_not_empty_with_lock() {
1093     // If the secondary free list looks empty there's no reason to
1094     // take the lock and then try to append it.
1095     if (!_secondary_free_list.is_empty()) {
1096       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1097       append_secondary_free_list();
1098     }
1099   }
1100 
1101   inline void old_set_add(HeapRegion* hr);
1102   inline void old_set_remove(HeapRegion* hr);
1103 
1104   size_t non_young_capacity_bytes() {
1105     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1106   }
1107 
1108   void set_free_regions_coming();
1109   void reset_free_regions_coming();
1110   bool free_regions_coming() { return _free_regions_coming; }
1111   void wait_while_free_regions_coming();
1112 
1113   // Determine whether the given region is one that we are using as an
1114   // old GC alloc region.
1115   bool is_old_gc_alloc_region(HeapRegion* hr);
1116 
1117   // Perform a collection of the heap; intended for use in implementing
1118   // "System.gc".  This probably implies as full a collection as the
1119   // "CollectedHeap" supports.
1120   virtual void collect(GCCause::Cause cause);
1121 
1122   virtual bool copy_allocation_context_stats(const jint* contexts,
1123                                              jlong* totals,
1124                                              jbyte* accuracy,
1125                                              jint len);
1126 
1127   // True iff an evacuation has failed in the most-recent collection.
1128   bool evacuation_failed() { return _evacuation_failed; }
1129 
1130   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1131   void prepend_to_freelist(FreeRegionList* list);
1132   void decrement_summary_bytes(size_t bytes);
1133 
1134   virtual bool is_in(const void* p) const;
1135 #ifdef ASSERT
1136   // Returns whether p is in one of the available areas of the heap. Slow but
1137   // extensive version.
1138   bool is_in_exact(const void* p) const;
1139 #endif
1140 
1141   // Return "TRUE" iff the given object address is within the collection
1142   // set. Slow implementation.
1143   bool obj_in_cs(oop obj);
1144 
1145   inline bool is_in_cset(const HeapRegion *hr);
1146   inline bool is_in_cset(oop obj);
1147 
1148   inline bool is_in_cset_or_humongous(const oop obj);
1149 
1150  private:
1151   // This array is used for a quick test on whether a reference points into
1152   // the collection set or not. Each of the array's elements denotes whether the
1153   // corresponding region is in the collection set or not.
1154   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1155 
1156  public:
1157 
1158   inline InCSetState in_cset_state(const oop obj);
1159 
1160   // Return "TRUE" iff the given object address is in the reserved
1161   // region of g1.
1162   bool is_in_g1_reserved(const void* p) const {
1163     return _hrm.reserved().contains(p);
1164   }
1165 
1166   // Returns a MemRegion that corresponds to the space that has been
1167   // reserved for the heap
1168   MemRegion g1_reserved() const {
1169     return _hrm.reserved();
1170   }
1171 
1172   virtual bool is_in_closed_subset(const void* p) const;
1173 
1174   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1175     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1176   }
1177 
1178   // This resets the card table to all zeros.  It is used after
1179   // a collection pause which used the card table to claim cards.
1180   void cleanUpCardTable();
1181 
1182   // Iteration functions.
1183 
1184   // Iterate over all objects, calling "cl.do_object" on each.
1185   virtual void object_iterate(ObjectClosure* cl);
1186 
1187   virtual void safe_object_iterate(ObjectClosure* cl) {
1188     object_iterate(cl);
1189   }
1190 
1191   // Iterate over heap regions, in address order, terminating the
1192   // iteration early if the "doHeapRegion" method returns "true".
1193   void heap_region_iterate(HeapRegionClosure* blk) const;
1194 
1195   // Return the region with the given index. It assumes the index is valid.
1196   inline HeapRegion* region_at(uint index) const;
1197 
1198   // Return the next region (by index) that is part of the same
1199   // humongous object that hr is part of.
1200   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1201 
1202   // Calculate the region index of the given address. Given address must be
1203   // within the heap.
1204   inline uint addr_to_region(HeapWord* addr) const;
1205 
1206   inline HeapWord* bottom_addr_for_region(uint index) const;
1207 
1208   // Iterate over the heap regions in parallel. Assumes that this will be called
1209   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1210   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1211   // to each of the regions, by attempting to claim the region using the
1212   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1213   // region. The concurrent argument should be set to true if iteration is
1214   // performed concurrently, during which no assumptions are made for consistent
1215   // attributes of the heap regions (as they might be modified while iterating).
1216   void heap_region_par_iterate(HeapRegionClosure* cl,
1217                                uint worker_id,
1218                                HeapRegionClaimer* hrclaimer,
1219                                bool concurrent = false) const;
1220 
1221   // Clear the cached cset start regions and (more importantly)
1222   // the time stamps. Called when we reset the GC time stamp.
1223   void clear_cset_start_regions();
1224 
1225   // Given the id of a worker, obtain or calculate a suitable
1226   // starting region for iterating over the current collection set.
1227   HeapRegion* start_cset_region_for_worker(uint worker_i);
1228 
1229   // Iterate over the regions (if any) in the current collection set.
1230   void collection_set_iterate(HeapRegionClosure* blk);
1231 
1232   // As above but starting from region r
1233   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1234 
1235   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1236 
1237   // Returns the HeapRegion that contains addr. addr must not be NULL.
1238   template <class T>
1239   inline HeapRegion* heap_region_containing(const T addr) const;
1240 
1241   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1242   // each address in the (reserved) heap is a member of exactly
1243   // one block.  The defining characteristic of a block is that it is
1244   // possible to find its size, and thus to progress forward to the next
1245   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1246   // represent Java objects, or they might be free blocks in a
1247   // free-list-based heap (or subheap), as long as the two kinds are
1248   // distinguishable and the size of each is determinable.
1249 
1250   // Returns the address of the start of the "block" that contains the
1251   // address "addr".  We say "blocks" instead of "object" since some heaps
1252   // may not pack objects densely; a chunk may either be an object or a
1253   // non-object.
1254   virtual HeapWord* block_start(const void* addr) const;
1255 
1256   // Requires "addr" to be the start of a chunk, and returns its size.
1257   // "addr + size" is required to be the start of a new chunk, or the end
1258   // of the active area of the heap.
1259   virtual size_t block_size(const HeapWord* addr) const;
1260 
1261   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1262   // the block is an object.
1263   virtual bool block_is_obj(const HeapWord* addr) const;
1264 
1265   // Section on thread-local allocation buffers (TLABs)
1266   // See CollectedHeap for semantics.
1267 
1268   bool supports_tlab_allocation() const;
1269   size_t tlab_capacity(Thread* ignored) const;
1270   size_t tlab_used(Thread* ignored) const;
1271   size_t max_tlab_size() const;
1272   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1273 
1274   // Can a compiler initialize a new object without store barriers?
1275   // This permission only extends from the creation of a new object
1276   // via a TLAB up to the first subsequent safepoint. If such permission
1277   // is granted for this heap type, the compiler promises to call
1278   // defer_store_barrier() below on any slow path allocation of
1279   // a new object for which such initializing store barriers will
1280   // have been elided. G1, like CMS, allows this, but should be
1281   // ready to provide a compensating write barrier as necessary
1282   // if that storage came out of a non-young region. The efficiency
1283   // of this implementation depends crucially on being able to
1284   // answer very efficiently in constant time whether a piece of
1285   // storage in the heap comes from a young region or not.
1286   // See ReduceInitialCardMarks.
1287   virtual bool can_elide_tlab_store_barriers() const {
1288     return true;
1289   }
1290 
1291   virtual bool card_mark_must_follow_store() const {
1292     return true;
1293   }
1294 
1295   inline bool is_in_young(const oop obj);
1296 
1297   virtual bool is_scavengable(const void* addr);
1298 
1299   // We don't need barriers for initializing stores to objects
1300   // in the young gen: for the SATB pre-barrier, there is no
1301   // pre-value that needs to be remembered; for the remembered-set
1302   // update logging post-barrier, we don't maintain remembered set
1303   // information for young gen objects.
1304   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1305 
1306   // Returns "true" iff the given word_size is "very large".
1307   static bool is_humongous(size_t word_size) {
1308     // Note this has to be strictly greater-than as the TLABs
1309     // are capped at the humongous threshold and we want to
1310     // ensure that we don't try to allocate a TLAB as
1311     // humongous and that we don't allocate a humongous
1312     // object in a TLAB.
1313     return word_size > _humongous_object_threshold_in_words;
1314   }
1315 
1316   // Returns the humongous threshold for a specific region size
1317   static size_t humongous_threshold_for(size_t region_size) {
1318     return (region_size / 2);
1319   }
1320 
1321   // Returns the number of regions the humongous object of the given word size
1322   // requires.
1323   static size_t humongous_obj_size_in_regions(size_t word_size);
1324 
1325   // Print the maximum heap capacity.
1326   virtual size_t max_capacity() const;
1327 
1328   virtual jlong millis_since_last_gc();
1329 
1330 
1331   // Convenience function to be used in situations where the heap type can be
1332   // asserted to be this type.
1333   static G1CollectedHeap* heap();
1334 
1335   void set_region_short_lived_locked(HeapRegion* hr);
1336   // add appropriate methods for any other surv rate groups
1337 
1338   YoungList* young_list() const { return _young_list; }
1339 
1340   uint old_regions_count() const { return _old_set.length(); }
1341 
1342   uint humongous_regions_count() const { return _humongous_set.length(); }
1343 
1344   // debugging
1345   bool check_young_list_well_formed() {
1346     return _young_list->check_list_well_formed();
1347   }
1348 
1349   bool check_young_list_empty(bool check_heap);
1350 
1351   // *** Stuff related to concurrent marking.  It's not clear to me that so
1352   // many of these need to be public.
1353 
1354   // The functions below are helper functions that a subclass of
1355   // "CollectedHeap" can use in the implementation of its virtual
1356   // functions.
1357   // This performs a concurrent marking of the live objects in a
1358   // bitmap off to the side.
1359   void doConcurrentMark();
1360 
1361   bool isMarkedPrev(oop obj) const;
1362   bool isMarkedNext(oop obj) const;
1363 
1364   // Determine if an object is dead, given the object and also
1365   // the region to which the object belongs. An object is dead
1366   // iff a) it was not allocated since the last mark, b) it
1367   // is not marked, and c) it is not in an archive region.
1368   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1369     return
1370       !hr->obj_allocated_since_prev_marking(obj) &&
1371       !isMarkedPrev(obj) &&
1372       !hr->is_archive();
1373   }
1374 
1375   // This function returns true when an object has been
1376   // around since the previous marking and hasn't yet
1377   // been marked during this marking, and is not in an archive region.
1378   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1379     return
1380       !hr->obj_allocated_since_next_marking(obj) &&
1381       !isMarkedNext(obj) &&
1382       !hr->is_archive();
1383   }
1384 
1385   // Determine if an object is dead, given only the object itself.
1386   // This will find the region to which the object belongs and
1387   // then call the region version of the same function.
1388 
1389   // Added if it is NULL it isn't dead.
1390 
1391   inline bool is_obj_dead(const oop obj) const;
1392 
1393   inline bool is_obj_ill(const oop obj) const;
1394 
1395   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1396 
1397   // Refinement
1398 
1399   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1400 
1401   // The dirty cards region list is used to record a subset of regions
1402   // whose cards need clearing. The list if populated during the
1403   // remembered set scanning and drained during the card table
1404   // cleanup. Although the methods are reentrant, population/draining
1405   // phases must not overlap. For synchronization purposes the last
1406   // element on the list points to itself.
1407   HeapRegion* _dirty_cards_region_list;
1408   void push_dirty_cards_region(HeapRegion* hr);
1409   HeapRegion* pop_dirty_cards_region();
1410 
1411   // Optimized nmethod scanning support routines
1412 
1413   // Register the given nmethod with the G1 heap.
1414   virtual void register_nmethod(nmethod* nm);
1415 
1416   // Unregister the given nmethod from the G1 heap.
1417   virtual void unregister_nmethod(nmethod* nm);
1418 
1419   // Free up superfluous code root memory.
1420   void purge_code_root_memory();
1421 
1422   // Rebuild the strong code root lists for each region
1423   // after a full GC.
1424   void rebuild_strong_code_roots();
1425 
1426   // Delete entries for dead interned string and clean up unreferenced symbols
1427   // in symbol table, possibly in parallel.
1428   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1429 
1430   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1431   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1432 
1433   // Redirty logged cards in the refinement queue.
1434   void redirty_logged_cards();
1435   // Verification
1436 
1437   // Perform any cleanup actions necessary before allowing a verification.
1438   virtual void prepare_for_verify();
1439 
1440   // Perform verification.
1441 
1442   // vo == UsePrevMarking  -> use "prev" marking information,
1443   // vo == UseNextMarking -> use "next" marking information
1444   // vo == UseMarkWord    -> use the mark word in the object header
1445   //
1446   // NOTE: Only the "prev" marking information is guaranteed to be
1447   // consistent most of the time, so most calls to this should use
1448   // vo == UsePrevMarking.
1449   // Currently, there is only one case where this is called with
1450   // vo == UseNextMarking, which is to verify the "next" marking
1451   // information at the end of remark.
1452   // Currently there is only one place where this is called with
1453   // vo == UseMarkWord, which is to verify the marking during a
1454   // full GC.
1455   void verify(VerifyOption vo);
1456 
1457   // The methods below are here for convenience and dispatch the
1458   // appropriate method depending on value of the given VerifyOption
1459   // parameter. The values for that parameter, and their meanings,
1460   // are the same as those above.
1461 
1462   bool is_obj_dead_cond(const oop obj,
1463                         const HeapRegion* hr,
1464                         const VerifyOption vo) const;
1465 
1466   bool is_obj_dead_cond(const oop obj,
1467                         const VerifyOption vo) const;
1468 
1469   G1HeapSummary create_g1_heap_summary();
1470   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1471 
1472   // Printing
1473 
1474   virtual void print_on(outputStream* st) const;
1475   virtual void print_extended_on(outputStream* st) const;
1476   virtual void print_on_error(outputStream* st) const;
1477 
1478   virtual void print_gc_threads_on(outputStream* st) const;
1479   virtual void gc_threads_do(ThreadClosure* tc) const;
1480 
1481   // Override
1482   void print_tracing_info() const;
1483 
1484   // The following two methods are helpful for debugging RSet issues.
1485   void print_cset_rsets() PRODUCT_RETURN;
1486   void print_all_rsets() PRODUCT_RETURN;
1487 
1488 public:
1489   size_t pending_card_num();
1490 
1491 protected:
1492   size_t _max_heap_capacity;
1493 };
1494 
1495 class G1ParEvacuateFollowersClosure : public VoidClosure {
1496 private:
1497   double _start_term;
1498   double _term_time;
1499   size_t _term_attempts;
1500 
1501   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1502   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1503 protected:
1504   G1CollectedHeap*              _g1h;
1505   G1ParScanThreadState*         _par_scan_state;
1506   RefToScanQueueSet*            _queues;
1507   ParallelTaskTerminator*       _terminator;
1508 
1509   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1510   RefToScanQueueSet*      queues()         { return _queues; }
1511   ParallelTaskTerminator* terminator()     { return _terminator; }
1512 
1513 public:
1514   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1515                                 G1ParScanThreadState* par_scan_state,
1516                                 RefToScanQueueSet* queues,
1517                                 ParallelTaskTerminator* terminator)
1518     : _g1h(g1h), _par_scan_state(par_scan_state),
1519       _queues(queues), _terminator(terminator),
1520       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1521 
1522   void do_void();
1523 
1524   double term_time() const { return _term_time; }
1525   size_t term_attempts() const { return _term_attempts; }
1526 
1527 private:
1528   inline bool offer_termination();
1529 };
1530 
1531 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP