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 GenerationCounters;
  77 class STWGCTimer;
  78 class G1NewTracer;
  79 class EvacuationFailedInfo;
  80 class nmethod;
  81 class Ticks;
  82 class WorkGang;
  83 class G1Allocator;
  84 class G1ArchiveAllocator;
  85 class G1HeapVerifier;
  86 class G1HeapSizingPolicy;
  87 
  88 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  89 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  90 
  91 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  92 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  93 
  94 // The G1 STW is alive closure.
  95 // An instance is embedded into the G1CH and used as the
  96 // (optional) _is_alive_non_header closure in the STW
  97 // reference processor. It is also extensively used during
  98 // reference processing during STW evacuation pauses.
  99 class G1STWIsAliveClosure: public BoolObjectClosure {
 100   G1CollectedHeap* _g1;
 101 public:
 102   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 103   bool do_object_b(oop p);
 104 };
 105 
 106 class RefineCardTableEntryClosure;
 107 
 108 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 109  private:
 110   void reset_from_card_cache(uint start_idx, size_t num_regions);
 111  public:
 112   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 113 };
 114 
 115 class G1CollectedHeap : public CollectedHeap {
 116   friend class VM_CollectForMetadataAllocation;
 117   friend class VM_G1CollectForAllocation;
 118   friend class VM_G1CollectFull;
 119   friend class VM_G1IncCollectionPause;
 120   friend class VMStructs;
 121   friend class MutatorAllocRegion;
 122   friend class G1GCAllocRegion;
 123   friend class G1HeapVerifier;
 124 
 125   // Closures used in implementation.
 126   friend class G1ParScanThreadState;
 127   friend class G1ParScanThreadStateSet;
 128   friend class G1ParTask;
 129   friend class G1PLABAllocator;
 130   friend class G1PrepareCompactClosure;
 131 
 132   // Other related classes.
 133   friend class HeapRegionClaimer;
 134 
 135   // Testing classes.
 136   friend class G1CheckCSetFastTableClosure;
 137 
 138 private:
 139   WorkGang* _workers;
 140 
 141   static size_t _humongous_object_threshold_in_words;
 142 
 143   // The secondary free list which contains regions that have been
 144   // freed up during the cleanup process. This will be appended to
 145   // the master free list when appropriate.
 146   FreeRegionList _secondary_free_list;
 147 
 148   // It keeps track of the old regions.
 149   HeapRegionSet _old_set;
 150 
 151   // It keeps track of the humongous regions.
 152   HeapRegionSet _humongous_set;
 153 
 154   void eagerly_reclaim_humongous_regions();
 155 
 156   // The number of regions we could create by expansion.
 157   uint _expansion_regions;
 158 
 159   // The block offset table for the G1 heap.
 160   G1BlockOffsetTable* _bot;
 161 
 162   // Tears down the region sets / lists so that they are empty and the
 163   // regions on the heap do not belong to a region set / list. The
 164   // only exception is the humongous set which we leave unaltered. If
 165   // free_list_only is true, it will only tear down the master free
 166   // list. It is called before a Full GC (free_list_only == false) or
 167   // before heap shrinking (free_list_only == true).
 168   void tear_down_region_sets(bool free_list_only);
 169 
 170   // Rebuilds the region sets / lists so that they are repopulated to
 171   // reflect the contents of the heap. The only exception is the
 172   // humongous set which was not torn down in the first place. If
 173   // free_list_only is true, it will only rebuild the master free
 174   // list. It is called after a Full GC (free_list_only == false) or
 175   // after heap shrinking (free_list_only == true).
 176   void rebuild_region_sets(bool free_list_only);
 177 
 178   // Callback for region mapping changed events.
 179   G1RegionMappingChangedListener _listener;
 180 
 181   // The sequence of all heap regions in the heap.
 182   HeapRegionManager _hrm;
 183 
 184   // Manages all allocations with regions except humongous object allocations.
 185   G1Allocator* _allocator;
 186 
 187   // Manages all heap verification.
 188   G1HeapVerifier* _verifier;
 189 
 190   // Outside of GC pauses, the number of bytes used in all regions other
 191   // than the current allocation region(s).
 192   size_t _summary_bytes_used;
 193 
 194   void increase_used(size_t bytes);
 195   void decrease_used(size_t bytes);
 196 
 197   void set_used(size_t bytes);
 198 
 199   // Class that handles archive allocation ranges.
 200   G1ArchiveAllocator* _archive_allocator;
 201 
 202   // Statistics for each allocation context
 203   AllocationContextStats _allocation_context_stats;
 204 
 205   // GC allocation statistics policy for survivors.
 206   G1EvacStats _survivor_evac_stats;
 207 
 208   // GC allocation statistics policy for tenured objects.
 209   G1EvacStats _old_evac_stats;
 210 
 211   // It specifies whether we should attempt to expand the heap after a
 212   // region allocation failure. If heap expansion fails we set this to
 213   // false so that we don't re-attempt the heap expansion (it's likely
 214   // that subsequent expansion attempts will also fail if one fails).
 215   // Currently, it is only consulted during GC and it's reset at the
 216   // start of each GC.
 217   bool _expand_heap_after_alloc_failure;
 218 
 219   // Helper for monitoring and management support.
 220   G1MonitoringSupport* _g1mm;
 221 
 222   // Records whether the region at the given index is (still) a
 223   // candidate for eager reclaim.  Only valid for humongous start
 224   // regions; other regions have unspecified values.  Humongous start
 225   // regions are initialized at start of collection pause, with
 226   // candidates removed from the set as they are found reachable from
 227   // roots or the young generation.
 228   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 229    protected:
 230     bool default_value() const { return false; }
 231    public:
 232     void clear() { G1BiasedMappedArray<bool>::clear(); }
 233     void set_candidate(uint region, bool value) {
 234       set_by_index(region, value);
 235     }
 236     bool is_candidate(uint region) {
 237       return get_by_index(region);
 238     }
 239   };
 240 
 241   HumongousReclaimCandidates _humongous_reclaim_candidates;
 242   // Stores whether during humongous object registration we found candidate regions.
 243   // If not, we can skip a few steps.
 244   bool _has_humongous_reclaim_candidates;
 245 
 246   volatile uint _gc_time_stamp;
 247 
 248   G1HRPrinter _hr_printer;
 249 
 250   // It decides whether an explicit GC should start a concurrent cycle
 251   // instead of doing a STW GC. Currently, a concurrent cycle is
 252   // explicitly started if:
 253   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 254   // (b) cause == _g1_humongous_allocation
 255   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 256   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 257   // (e) cause == _update_allocation_context_stats_inc
 258   // (f) cause == _wb_conc_mark
 259   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 260 
 261   // indicates whether we are in young or mixed GC mode
 262   G1CollectorState _collector_state;
 263 
 264   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 265   // concurrent cycles) we have started.
 266   volatile uint _old_marking_cycles_started;
 267 
 268   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 269   // concurrent cycles) we have completed.
 270   volatile uint _old_marking_cycles_completed;
 271 
 272   // This is a non-product method that is helpful for testing. It is
 273   // called at the end of a GC and artificially expands the heap by
 274   // allocating a number of dead regions. This way we can induce very
 275   // frequent marking cycles and stress the cleanup / concurrent
 276   // cleanup code more (as all the regions that will be allocated by
 277   // this method will be found dead by the marking cycle).
 278   void allocate_dummy_regions() PRODUCT_RETURN;
 279 
 280   // Clear RSets after a compaction. It also resets the GC time stamps.
 281   void clear_rsets_post_compaction();
 282 
 283   // If the HR printer is active, dump the state of the regions in the
 284   // heap after a compaction.
 285   void print_hrm_post_compaction();
 286 
 287   // Create a memory mapper for auxiliary data structures of the given size and
 288   // translation factor.
 289   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 290                                                          size_t size,
 291                                                          size_t translation_factor);
 292 
 293   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 294 
 295   void process_weak_jni_handles();
 296 
 297   // These are macros so that, if the assert fires, we get the correct
 298   // line number, file, etc.
 299 
 300 #define heap_locking_asserts_params(_extra_message_)                          \
 301   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 302   (_extra_message_),                                                          \
 303   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 304   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 305   BOOL_TO_STR(Thread::current()->is_VM_thread())
 306 
 307 #define assert_heap_locked()                                                  \
 308   do {                                                                        \
 309     assert(Heap_lock->owned_by_self(),                                        \
 310            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 311   } while (0)
 312 
 313 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 314   do {                                                                        \
 315     assert(Heap_lock->owned_by_self() ||                                      \
 316            (SafepointSynchronize::is_at_safepoint() &&                        \
 317              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 318            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 319                                         "should be at a safepoint"));         \
 320   } while (0)
 321 
 322 #define assert_heap_locked_and_not_at_safepoint()                             \
 323   do {                                                                        \
 324     assert(Heap_lock->owned_by_self() &&                                      \
 325                                     !SafepointSynchronize::is_at_safepoint(), \
 326           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 327                                        "should not be at a safepoint"));      \
 328   } while (0)
 329 
 330 #define assert_heap_not_locked()                                              \
 331   do {                                                                        \
 332     assert(!Heap_lock->owned_by_self(),                                       \
 333         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 334   } while (0)
 335 
 336 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 337   do {                                                                        \
 338     assert(!Heap_lock->owned_by_self() &&                                     \
 339                                     !SafepointSynchronize::is_at_safepoint(), \
 340       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 341                                    "should not be at a safepoint"));          \
 342   } while (0)
 343 
 344 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 345   do {                                                                        \
 346     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 347               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 348            heap_locking_asserts_params("should be at a safepoint"));          \
 349   } while (0)
 350 
 351 #define assert_not_at_safepoint()                                             \
 352   do {                                                                        \
 353     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 354            heap_locking_asserts_params("should not be at a safepoint"));      \
 355   } while (0)
 356 
 357 protected:
 358 
 359   // The young region list.
 360   YoungList*  _young_list;
 361 
 362   // The current policy object for the collector.
 363   G1CollectorPolicy* _g1_policy;
 364   G1HeapSizingPolicy* _heap_sizing_policy;
 365 
 366   G1CollectionSet _collection_set;
 367 
 368   // This is the second level of trying to allocate a new region. If
 369   // new_region() didn't find a region on the free_list, this call will
 370   // check whether there's anything available on the
 371   // secondary_free_list and/or wait for more regions to appear on
 372   // that list, if _free_regions_coming is set.
 373   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 374 
 375   // Try to allocate a single non-humongous HeapRegion sufficient for
 376   // an allocation of the given word_size. If do_expand is true,
 377   // attempt to expand the heap if necessary to satisfy the allocation
 378   // request. If the region is to be used as an old region or for a
 379   // humongous object, set is_old to true. If not, to false.
 380   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 381 
 382   // Initialize a contiguous set of free regions of length num_regions
 383   // and starting at index first so that they appear as a single
 384   // humongous region.
 385   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 386                                                       uint num_regions,
 387                                                       size_t word_size,
 388                                                       AllocationContext_t context);
 389 
 390   // Attempt to allocate a humongous object of the given size. Return
 391   // NULL if unsuccessful.
 392   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 393 
 394   // The following two methods, allocate_new_tlab() and
 395   // mem_allocate(), are the two main entry points from the runtime
 396   // into the G1's allocation routines. They have the following
 397   // assumptions:
 398   //
 399   // * They should both be called outside safepoints.
 400   //
 401   // * They should both be called without holding the Heap_lock.
 402   //
 403   // * All allocation requests for new TLABs should go to
 404   //   allocate_new_tlab().
 405   //
 406   // * All non-TLAB allocation requests should go to mem_allocate().
 407   //
 408   // * If either call cannot satisfy the allocation request using the
 409   //   current allocating region, they will try to get a new one. If
 410   //   this fails, they will attempt to do an evacuation pause and
 411   //   retry the allocation.
 412   //
 413   // * If all allocation attempts fail, even after trying to schedule
 414   //   an evacuation pause, allocate_new_tlab() will return NULL,
 415   //   whereas mem_allocate() will attempt a heap expansion and/or
 416   //   schedule a Full GC.
 417   //
 418   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 419   //   should never be called with word_size being humongous. All
 420   //   humongous allocation requests should go to mem_allocate() which
 421   //   will satisfy them with a special path.
 422 
 423   virtual HeapWord* allocate_new_tlab(size_t word_size);
 424 
 425   virtual HeapWord* mem_allocate(size_t word_size,
 426                                  bool*  gc_overhead_limit_was_exceeded);
 427 
 428   // The following three methods take a gc_count_before_ret
 429   // parameter which is used to return the GC count if the method
 430   // returns NULL. Given that we are required to read the GC count
 431   // while holding the Heap_lock, and these paths will take the
 432   // Heap_lock at some point, it's easier to get them to read the GC
 433   // count while holding the Heap_lock before they return NULL instead
 434   // of the caller (namely: mem_allocate()) having to also take the
 435   // Heap_lock just to read the GC count.
 436 
 437   // First-level mutator allocation attempt: try to allocate out of
 438   // the mutator alloc region without taking the Heap_lock. This
 439   // should only be used for non-humongous allocations.
 440   inline HeapWord* attempt_allocation(size_t word_size,
 441                                       uint* gc_count_before_ret,
 442                                       uint* gclocker_retry_count_ret);
 443 
 444   // Second-level mutator allocation attempt: take the Heap_lock and
 445   // retry the allocation attempt, potentially scheduling a GC
 446   // pause. This should only be used for non-humongous allocations.
 447   HeapWord* attempt_allocation_slow(size_t word_size,
 448                                     AllocationContext_t context,
 449                                     uint* gc_count_before_ret,
 450                                     uint* gclocker_retry_count_ret);
 451 
 452   // Takes the Heap_lock and attempts a humongous allocation. It can
 453   // potentially schedule a GC pause.
 454   HeapWord* attempt_allocation_humongous(size_t word_size,
 455                                          uint* gc_count_before_ret,
 456                                          uint* gclocker_retry_count_ret);
 457 
 458   // Allocation attempt that should be called during safepoints (e.g.,
 459   // at the end of a successful GC). expect_null_mutator_alloc_region
 460   // specifies whether the mutator alloc region is expected to be NULL
 461   // or not.
 462   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 463                                             AllocationContext_t context,
 464                                             bool expect_null_mutator_alloc_region);
 465 
 466   // These methods are the "callbacks" from the G1AllocRegion class.
 467 
 468   // For mutator alloc regions.
 469   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 470   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 471                                    size_t allocated_bytes);
 472 
 473   // For GC alloc regions.
 474   bool has_more_regions(InCSetState dest);
 475   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 476   void retire_gc_alloc_region(HeapRegion* alloc_region,
 477                               size_t allocated_bytes, InCSetState dest);
 478 
 479   // - if explicit_gc is true, the GC is for a System.gc() etc,
 480   //   otherwise it's for a failed allocation.
 481   // - if clear_all_soft_refs is true, all soft references should be
 482   //   cleared during the GC.
 483   // - it returns false if it is unable to do the collection due to the
 484   //   GC locker being active, true otherwise.
 485   bool do_full_collection(bool explicit_gc,
 486                           bool clear_all_soft_refs);
 487 
 488   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 489   virtual void do_full_collection(bool clear_all_soft_refs);
 490 
 491   // Resize the heap if necessary after a full collection.
 492   void resize_if_necessary_after_full_collection();
 493 
 494   // Callback from VM_G1CollectForAllocation operation.
 495   // This function does everything necessary/possible to satisfy a
 496   // failed allocation request (including collection, expansion, etc.)
 497   HeapWord* satisfy_failed_allocation(size_t word_size,
 498                                       AllocationContext_t context,
 499                                       bool* succeeded);
 500 private:
 501   // Helper method for satisfy_failed_allocation()
 502   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 503                                              AllocationContext_t context,
 504                                              bool do_gc,
 505                                              bool clear_all_soft_refs,
 506                                              bool expect_null_mutator_alloc_region,
 507                                              bool* gc_succeeded);
 508 
 509 protected:
 510   // Attempting to expand the heap sufficiently
 511   // to support an allocation of the given "word_size".  If
 512   // successful, perform the allocation and return the address of the
 513   // allocated block, or else "NULL".
 514   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 515 
 516   // Preserve any referents discovered by concurrent marking that have not yet been
 517   // copied by the STW pause.
 518   void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
 519   // Process any reference objects discovered during
 520   // an incremental evacuation pause.
 521   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 522 
 523   // Enqueue any remaining discovered references
 524   // after processing.
 525   void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 526 
 527   // Merges the information gathered on a per-thread basis for all worker threads
 528   // during GC into global variables.
 529   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 530 public:
 531   WorkGang* workers() const { return _workers; }
 532 
 533   G1Allocator* allocator() {
 534     return _allocator;
 535   }
 536 
 537   G1HeapVerifier* verifier() {
 538     return _verifier;
 539   }
 540 
 541   G1MonitoringSupport* g1mm() {
 542     assert(_g1mm != NULL, "should have been initialized");
 543     return _g1mm;
 544   }
 545 
 546   // Expand the garbage-first heap by at least the given size (in bytes!).
 547   // Returns true if the heap was expanded by the requested amount;
 548   // false otherwise.
 549   // (Rounds up to a HeapRegion boundary.)
 550   bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
 551 
 552   // Returns the PLAB statistics for a given destination.
 553   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 554 
 555   // Determines PLAB size for a given destination.
 556   inline size_t desired_plab_sz(InCSetState dest);
 557 
 558   inline AllocationContextStats& allocation_context_stats();
 559 
 560   // Do anything common to GC's.
 561   void gc_prologue(bool full);
 562   void gc_epilogue(bool full);
 563 
 564   // Modify the reclaim candidate set and test for presence.
 565   // These are only valid for starts_humongous regions.
 566   inline void set_humongous_reclaim_candidate(uint region, bool value);
 567   inline bool is_humongous_reclaim_candidate(uint region);
 568 
 569   // Remove from the reclaim candidate set.  Also remove from the
 570   // collection set so that later encounters avoid the slow path.
 571   inline void set_humongous_is_live(oop obj);
 572 
 573   // Register the given region to be part of the collection set.
 574   inline void register_humongous_region_with_cset(uint index);
 575   // Register regions with humongous objects (actually on the start region) in
 576   // the in_cset_fast_test table.
 577   void register_humongous_regions_with_cset();
 578   // We register a region with the fast "in collection set" test. We
 579   // simply set to true the array slot corresponding to this region.
 580   void register_young_region_with_cset(HeapRegion* r) {
 581     _in_cset_fast_test.set_in_young(r->hrm_index());
 582   }
 583   void register_old_region_with_cset(HeapRegion* r) {
 584     _in_cset_fast_test.set_in_old(r->hrm_index());
 585   }
 586   inline void register_ext_region_with_cset(HeapRegion* r) {
 587     _in_cset_fast_test.set_ext(r->hrm_index());
 588   }
 589   void clear_in_cset(const HeapRegion* hr) {
 590     _in_cset_fast_test.clear(hr);
 591   }
 592 
 593   void clear_cset_fast_test() {
 594     _in_cset_fast_test.clear();
 595   }
 596 
 597   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 598 
 599   // This is called at the start of either a concurrent cycle or a Full
 600   // GC to update the number of old marking cycles started.
 601   void increment_old_marking_cycles_started();
 602 
 603   // This is called at the end of either a concurrent cycle or a Full
 604   // GC to update the number of old marking cycles completed. Those two
 605   // can happen in a nested fashion, i.e., we start a concurrent
 606   // cycle, a Full GC happens half-way through it which ends first,
 607   // and then the cycle notices that a Full GC happened and ends
 608   // too. The concurrent parameter is a boolean to help us do a bit
 609   // tighter consistency checking in the method. If concurrent is
 610   // false, the caller is the inner caller in the nesting (i.e., the
 611   // Full GC). If concurrent is true, the caller is the outer caller
 612   // in this nesting (i.e., the concurrent cycle). Further nesting is
 613   // not currently supported. The end of this call also notifies
 614   // the FullGCCount_lock in case a Java thread is waiting for a full
 615   // GC to happen (e.g., it called System.gc() with
 616   // +ExplicitGCInvokesConcurrent).
 617   void increment_old_marking_cycles_completed(bool concurrent);
 618 
 619   uint old_marking_cycles_completed() {
 620     return _old_marking_cycles_completed;
 621   }
 622 
 623   G1HRPrinter* hr_printer() { return &_hr_printer; }
 624 
 625   // Allocates a new heap region instance.
 626   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 627 
 628   // Allocate the highest free region in the reserved heap. This will commit
 629   // regions as necessary.
 630   HeapRegion* alloc_highest_free_region();
 631 
 632   // Frees a non-humongous region by initializing its contents and
 633   // adding it to the free list that's passed as a parameter (this is
 634   // usually a local list which will be appended to the master free
 635   // list later). The used bytes of freed regions are accumulated in
 636   // pre_used. If par is true, the region's RSet will not be freed
 637   // up. The assumption is that this will be done later.
 638   // The locked parameter indicates if the caller has already taken
 639   // care of proper synchronization. This may allow some optimizations.
 640   void free_region(HeapRegion* hr,
 641                    FreeRegionList* free_list,
 642                    bool par,
 643                    bool locked = false);
 644 
 645   // It dirties the cards that cover the block so that the post
 646   // write barrier never queues anything when updating objects on this
 647   // block. It is assumed (and in fact we assert) that the block
 648   // belongs to a young region.
 649   inline void dirty_young_block(HeapWord* start, size_t word_size);
 650 
 651   // Frees a humongous region by collapsing it into individual regions
 652   // and calling free_region() for each of them. The freed regions
 653   // will be added to the free list that's passed as a parameter (this
 654   // is usually a local list which will be appended to the master free
 655   // list later). The used bytes of freed regions are accumulated in
 656   // pre_used. If par is true, the region's RSet will not be freed
 657   // up. The assumption is that this will be done later.
 658   void free_humongous_region(HeapRegion* hr,
 659                              FreeRegionList* free_list,
 660                              bool par);
 661 
 662   // Facility for allocating in 'archive' regions in high heap memory and
 663   // recording the allocated ranges. These should all be called from the
 664   // VM thread at safepoints, without the heap lock held. They can be used
 665   // to create and archive a set of heap regions which can be mapped at the
 666   // same fixed addresses in a subsequent JVM invocation.
 667   void begin_archive_alloc_range();
 668 
 669   // Check if the requested size would be too large for an archive allocation.
 670   bool is_archive_alloc_too_large(size_t word_size);
 671 
 672   // Allocate memory of the requested size from the archive region. This will
 673   // return NULL if the size is too large or if no memory is available. It
 674   // does not trigger a garbage collection.
 675   HeapWord* archive_mem_allocate(size_t word_size);
 676 
 677   // Optionally aligns the end address and returns the allocated ranges in
 678   // an array of MemRegions in order of ascending addresses.
 679   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 680                                size_t end_alignment_in_bytes = 0);
 681 
 682   // Facility for allocating a fixed range within the heap and marking
 683   // the containing regions as 'archive'. For use at JVM init time, when the
 684   // caller may mmap archived heap data at the specified range(s).
 685   // Verify that the MemRegions specified in the argument array are within the
 686   // reserved heap.
 687   bool check_archive_addresses(MemRegion* range, size_t count);
 688 
 689   // Commit the appropriate G1 regions containing the specified MemRegions
 690   // and mark them as 'archive' regions. The regions in the array must be
 691   // non-overlapping and in order of ascending address.
 692   bool alloc_archive_regions(MemRegion* range, size_t count);
 693 
 694   // Insert any required filler objects in the G1 regions around the specified
 695   // ranges to make the regions parseable. This must be called after
 696   // alloc_archive_regions, and after class loading has occurred.
 697   void fill_archive_regions(MemRegion* range, size_t count);
 698 
 699   // For each of the specified MemRegions, uncommit the containing G1 regions
 700   // which had been allocated by alloc_archive_regions. This should be called
 701   // rather than fill_archive_regions at JVM init time if the archive file
 702   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 703   void dealloc_archive_regions(MemRegion* range, size_t count);
 704 
 705 protected:
 706 
 707   // Shrink the garbage-first heap by at most the given size (in bytes!).
 708   // (Rounds down to a HeapRegion boundary.)
 709   virtual void shrink(size_t expand_bytes);
 710   void shrink_helper(size_t expand_bytes);
 711 
 712   #if TASKQUEUE_STATS
 713   static void print_taskqueue_stats_hdr(outputStream* const st);
 714   void print_taskqueue_stats() const;
 715   void reset_taskqueue_stats();
 716   #endif // TASKQUEUE_STATS
 717 
 718   // Schedule the VM operation that will do an evacuation pause to
 719   // satisfy an allocation request of word_size. *succeeded will
 720   // return whether the VM operation was successful (it did do an
 721   // evacuation pause) or not (another thread beat us to it or the GC
 722   // locker was active). Given that we should not be holding the
 723   // Heap_lock when we enter this method, we will pass the
 724   // gc_count_before (i.e., total_collections()) as a parameter since
 725   // it has to be read while holding the Heap_lock. Currently, both
 726   // methods that call do_collection_pause() release the Heap_lock
 727   // before the call, so it's easy to read gc_count_before just before.
 728   HeapWord* do_collection_pause(size_t         word_size,
 729                                 uint           gc_count_before,
 730                                 bool*          succeeded,
 731                                 GCCause::Cause gc_cause);
 732 
 733   void wait_for_root_region_scanning();
 734 
 735   // The guts of the incremental collection pause, executed by the vm
 736   // thread. It returns false if it is unable to do the collection due
 737   // to the GC locker being active, true otherwise
 738   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 739 
 740   // Actually do the work of evacuating the collection set.
 741   virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
 742 
 743   void pre_evacuate_collection_set();
 744   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 745 
 746   // Print the header for the per-thread termination statistics.
 747   static void print_termination_stats_hdr();
 748   // Print actual per-thread termination statistics.
 749   void print_termination_stats(uint worker_id,
 750                                double elapsed_ms,
 751                                double strong_roots_ms,
 752                                double term_ms,
 753                                size_t term_attempts,
 754                                size_t alloc_buffer_waste,
 755                                size_t undo_waste) const;
 756   // Update object copying statistics.
 757   void record_obj_copy_mem_stats();
 758 
 759   // The g1 remembered set of the heap.
 760   G1RemSet* _g1_rem_set;
 761 
 762   // A set of cards that cover the objects for which the Rsets should be updated
 763   // concurrently after the collection.
 764   DirtyCardQueueSet _dirty_card_queue_set;
 765 
 766   // The closure used to refine a single card.
 767   RefineCardTableEntryClosure* _refine_cte_cl;
 768 
 769   // After a collection pause, make the regions in the CS into free
 770   // regions.
 771   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 772 
 773   // Abandon the current collection set without recording policy
 774   // statistics or updating free lists.
 775   void abandon_collection_set(HeapRegion* cs_head);
 776 
 777   // The concurrent marker (and the thread it runs in.)
 778   G1ConcurrentMark* _cm;
 779   ConcurrentMarkThread* _cmThread;
 780 
 781   // The concurrent refiner.
 782   ConcurrentG1Refine* _cg1r;
 783 
 784   // The parallel task queues
 785   RefToScanQueueSet *_task_queues;
 786 
 787   // True iff a evacuation has failed in the current collection.
 788   bool _evacuation_failed;
 789 
 790   EvacuationFailedInfo* _evacuation_failed_info_array;
 791 
 792   // Failed evacuations cause some logical from-space objects to have
 793   // forwarding pointers to themselves.  Reset them.
 794   void remove_self_forwarding_pointers();
 795 
 796   // Restore the preserved mark words for objects with self-forwarding pointers.
 797   void restore_preserved_marks();
 798 
 799   // Restore the objects in the regions in the collection set after an
 800   // evacuation failure.
 801   void restore_after_evac_failure();
 802 
 803   // Stores marks with the corresponding oop that we need to preserve during evacuation
 804   // failure.
 805   OopAndMarkOopStack*  _preserved_objs;
 806 
 807   // Preserve the mark of "obj", if necessary, in preparation for its mark
 808   // word being overwritten with a self-forwarding-pointer.
 809   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 810 
 811 #ifndef PRODUCT
 812   // Support for forcing evacuation failures. Analogous to
 813   // PromotionFailureALot for the other collectors.
 814 
 815   // Records whether G1EvacuationFailureALot should be in effect
 816   // for the current GC
 817   bool _evacuation_failure_alot_for_current_gc;
 818 
 819   // Used to record the GC number for interval checking when
 820   // determining whether G1EvaucationFailureALot is in effect
 821   // for the current GC.
 822   size_t _evacuation_failure_alot_gc_number;
 823 
 824   // Count of the number of evacuations between failures.
 825   volatile size_t _evacuation_failure_alot_count;
 826 
 827   // Set whether G1EvacuationFailureALot should be in effect
 828   // for the current GC (based upon the type of GC and which
 829   // command line flags are set);
 830   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 831                                                   bool during_initial_mark,
 832                                                   bool during_marking);
 833 
 834   inline void set_evacuation_failure_alot_for_current_gc();
 835 
 836   // Return true if it's time to cause an evacuation failure.
 837   inline bool evacuation_should_fail();
 838 
 839   // Reset the G1EvacuationFailureALot counters.  Should be called at
 840   // the end of an evacuation pause in which an evacuation failure occurred.
 841   inline void reset_evacuation_should_fail();
 842 #endif // !PRODUCT
 843 
 844   // ("Weak") Reference processing support.
 845   //
 846   // G1 has 2 instances of the reference processor class. One
 847   // (_ref_processor_cm) handles reference object discovery
 848   // and subsequent processing during concurrent marking cycles.
 849   //
 850   // The other (_ref_processor_stw) handles reference object
 851   // discovery and processing during full GCs and incremental
 852   // evacuation pauses.
 853   //
 854   // During an incremental pause, reference discovery will be
 855   // temporarily disabled for _ref_processor_cm and will be
 856   // enabled for _ref_processor_stw. At the end of the evacuation
 857   // pause references discovered by _ref_processor_stw will be
 858   // processed and discovery will be disabled. The previous
 859   // setting for reference object discovery for _ref_processor_cm
 860   // will be re-instated.
 861   //
 862   // At the start of marking:
 863   //  * Discovery by the CM ref processor is verified to be inactive
 864   //    and it's discovered lists are empty.
 865   //  * Discovery by the CM ref processor is then enabled.
 866   //
 867   // At the end of marking:
 868   //  * Any references on the CM ref processor's discovered
 869   //    lists are processed (possibly MT).
 870   //
 871   // At the start of full GC we:
 872   //  * Disable discovery by the CM ref processor and
 873   //    empty CM ref processor's discovered lists
 874   //    (without processing any entries).
 875   //  * Verify that the STW ref processor is inactive and it's
 876   //    discovered lists are empty.
 877   //  * Temporarily set STW ref processor discovery as single threaded.
 878   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 879   //    field.
 880   //  * Finally enable discovery by the STW ref processor.
 881   //
 882   // The STW ref processor is used to record any discovered
 883   // references during the full GC.
 884   //
 885   // At the end of a full GC we:
 886   //  * Enqueue any reference objects discovered by the STW ref processor
 887   //    that have non-live referents. This has the side-effect of
 888   //    making the STW ref processor inactive by disabling discovery.
 889   //  * Verify that the CM ref processor is still inactive
 890   //    and no references have been placed on it's discovered
 891   //    lists (also checked as a precondition during initial marking).
 892 
 893   // The (stw) reference processor...
 894   ReferenceProcessor* _ref_processor_stw;
 895 
 896   STWGCTimer* _gc_timer_stw;
 897 
 898   G1NewTracer* _gc_tracer_stw;
 899 
 900   // During reference object discovery, the _is_alive_non_header
 901   // closure (if non-null) is applied to the referent object to
 902   // determine whether the referent is live. If so then the
 903   // reference object does not need to be 'discovered' and can
 904   // be treated as a regular oop. This has the benefit of reducing
 905   // the number of 'discovered' reference objects that need to
 906   // be processed.
 907   //
 908   // Instance of the is_alive closure for embedding into the
 909   // STW reference processor as the _is_alive_non_header field.
 910   // Supplying a value for the _is_alive_non_header field is
 911   // optional but doing so prevents unnecessary additions to
 912   // the discovered lists during reference discovery.
 913   G1STWIsAliveClosure _is_alive_closure_stw;
 914 
 915   // The (concurrent marking) reference processor...
 916   ReferenceProcessor* _ref_processor_cm;
 917 
 918   // Instance of the concurrent mark is_alive closure for embedding
 919   // into the Concurrent Marking reference processor as the
 920   // _is_alive_non_header field. Supplying a value for the
 921   // _is_alive_non_header field is optional but doing so prevents
 922   // unnecessary additions to the discovered lists during reference
 923   // discovery.
 924   G1CMIsAliveClosure _is_alive_closure_cm;
 925 
 926   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 927   HeapRegion** _worker_cset_start_region;
 928 
 929   // Time stamp to validate the regions recorded in the cache
 930   // used by G1CollectedHeap::start_cset_region_for_worker().
 931   // The heap region entry for a given worker is valid iff
 932   // the associated time stamp value matches the current value
 933   // of G1CollectedHeap::_gc_time_stamp.
 934   uint* _worker_cset_start_region_time_stamp;
 935 
 936   volatile bool _free_regions_coming;
 937 
 938 public:
 939 
 940   void set_refine_cte_cl_concurrency(bool concurrent);
 941 
 942   RefToScanQueue *task_queue(uint i) const;
 943 
 944   uint num_task_queues() const;
 945 
 946   // A set of cards where updates happened during the GC
 947   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 948 
 949   // Create a G1CollectedHeap with the specified policy.
 950   // Must call the initialize method afterwards.
 951   // May not return if something goes wrong.
 952   G1CollectedHeap(G1CollectorPolicy* policy);
 953 
 954   // Initialize the G1CollectedHeap to have the initial and
 955   // maximum sizes and remembered and barrier sets
 956   // specified by the policy object.
 957   jint initialize();
 958 
 959   virtual void stop();
 960 
 961   // Return the (conservative) maximum heap alignment for any G1 heap
 962   static size_t conservative_max_heap_alignment();
 963 
 964   // Does operations required after initialization has been done.
 965   void post_initialize();
 966 
 967   // Initialize weak reference processing.
 968   void ref_processing_init();
 969 
 970   virtual Name kind() const {
 971     return CollectedHeap::G1CollectedHeap;
 972   }
 973 
 974   virtual const char* name() const {
 975     return "G1";
 976   }
 977 
 978   const G1CollectorState* collector_state() const { return &_collector_state; }
 979   G1CollectorState* collector_state() { return &_collector_state; }
 980 
 981   // The current policy object for the collector.
 982   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
 983 
 984   const G1CollectionSet* collection_set() const { return &_collection_set; }
 985   G1CollectionSet* collection_set() { return &_collection_set; }
 986 
 987   virtual CollectorPolicy* collector_policy() const;
 988 
 989   // Adaptive size policy.  No such thing for g1.
 990   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
 991 
 992   // The rem set and barrier set.
 993   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
 994 
 995   // Try to minimize the remembered set.
 996   void scrub_rem_set();
 997 
 998   uint get_gc_time_stamp() {
 999     return _gc_time_stamp;
1000   }
1001 
1002   inline void reset_gc_time_stamp();
1003 
1004   void check_gc_time_stamps() PRODUCT_RETURN;
1005 
1006   inline void increment_gc_time_stamp();
1007 
1008   // Reset the given region's GC timestamp. If it's starts humongous,
1009   // also reset the GC timestamp of its corresponding
1010   // continues humongous regions too.
1011   void reset_gc_time_stamps(HeapRegion* hr);
1012 
1013   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1014   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1015 
1016   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1017   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1018 
1019   // The shared block offset table array.
1020   G1BlockOffsetTable* bot() const { return _bot; }
1021 
1022   // Reference Processing accessors
1023 
1024   // The STW reference processor....
1025   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1026 
1027   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1028 
1029   // The Concurrent Marking reference processor...
1030   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1031 
1032   virtual size_t capacity() const;
1033   virtual size_t used() const;
1034   // This should be called when we're not holding the heap lock. The
1035   // result might be a bit inaccurate.
1036   size_t used_unlocked() const;
1037   size_t recalculate_used() const;
1038 
1039   // These virtual functions do the actual allocation.
1040   // Some heaps may offer a contiguous region for shared non-blocking
1041   // allocation, via inlined code (by exporting the address of the top and
1042   // end fields defining the extent of the contiguous allocation region.)
1043   // But G1CollectedHeap doesn't yet support this.
1044 
1045   virtual bool is_maximal_no_gc() const {
1046     return _hrm.available() == 0;
1047   }
1048 
1049   // The current number of regions in the heap.
1050   uint num_regions() const { return _hrm.length(); }
1051 
1052   // The max number of regions in the heap.
1053   uint max_regions() const { return _hrm.max_length(); }
1054 
1055   // The number of regions that are completely free.
1056   uint num_free_regions() const { return _hrm.num_free_regions(); }
1057 
1058   MemoryUsage get_auxiliary_data_memory_usage() const {
1059     return _hrm.get_auxiliary_data_memory_usage();
1060   }
1061 
1062   // The number of regions that are not completely free.
1063   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1064 
1065 #ifdef ASSERT
1066   bool is_on_master_free_list(HeapRegion* hr) {
1067     return _hrm.is_free(hr);
1068   }
1069 #endif // ASSERT
1070 
1071   // Wrapper for the region list operations that can be called from
1072   // methods outside this class.
1073 
1074   void secondary_free_list_add(FreeRegionList* list) {
1075     _secondary_free_list.add_ordered(list);
1076   }
1077 
1078   void append_secondary_free_list() {
1079     _hrm.insert_list_into_free_list(&_secondary_free_list);
1080   }
1081 
1082   void append_secondary_free_list_if_not_empty_with_lock() {
1083     // If the secondary free list looks empty there's no reason to
1084     // take the lock and then try to append it.
1085     if (!_secondary_free_list.is_empty()) {
1086       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1087       append_secondary_free_list();
1088     }
1089   }
1090 
1091   inline void old_set_add(HeapRegion* hr);
1092   inline void old_set_remove(HeapRegion* hr);
1093 
1094   size_t non_young_capacity_bytes() {
1095     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1096   }
1097 
1098   void set_free_regions_coming();
1099   void reset_free_regions_coming();
1100   bool free_regions_coming() { return _free_regions_coming; }
1101   void wait_while_free_regions_coming();
1102 
1103   // Determine whether the given region is one that we are using as an
1104   // old GC alloc region.
1105   bool is_old_gc_alloc_region(HeapRegion* hr);
1106 
1107   // Perform a collection of the heap; intended for use in implementing
1108   // "System.gc".  This probably implies as full a collection as the
1109   // "CollectedHeap" supports.
1110   virtual void collect(GCCause::Cause cause);
1111 
1112   virtual bool copy_allocation_context_stats(const jint* contexts,
1113                                              jlong* totals,
1114                                              jbyte* accuracy,
1115                                              jint len);
1116 
1117   // True iff an evacuation has failed in the most-recent collection.
1118   bool evacuation_failed() { return _evacuation_failed; }
1119 
1120   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1121   void prepend_to_freelist(FreeRegionList* list);
1122   void decrement_summary_bytes(size_t bytes);
1123 
1124   virtual bool is_in(const void* p) const;
1125 #ifdef ASSERT
1126   // Returns whether p is in one of the available areas of the heap. Slow but
1127   // extensive version.
1128   bool is_in_exact(const void* p) const;
1129 #endif
1130 
1131   // Return "TRUE" iff the given object address is within the collection
1132   // set. Slow implementation.
1133   bool obj_in_cs(oop obj);
1134 
1135   inline bool is_in_cset(const HeapRegion *hr);
1136   inline bool is_in_cset(oop obj);
1137 
1138   inline bool is_in_cset_or_humongous(const oop obj);
1139 
1140  private:
1141   // This array is used for a quick test on whether a reference points into
1142   // the collection set or not. Each of the array's elements denotes whether the
1143   // corresponding region is in the collection set or not.
1144   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1145 
1146  public:
1147 
1148   inline InCSetState in_cset_state(const oop obj);
1149 
1150   // Return "TRUE" iff the given object address is in the reserved
1151   // region of g1.
1152   bool is_in_g1_reserved(const void* p) const {
1153     return _hrm.reserved().contains(p);
1154   }
1155 
1156   // Returns a MemRegion that corresponds to the space that has been
1157   // reserved for the heap
1158   MemRegion g1_reserved() const {
1159     return _hrm.reserved();
1160   }
1161 
1162   virtual bool is_in_closed_subset(const void* p) const;
1163 
1164   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1165     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1166   }
1167 
1168   // This resets the card table to all zeros.  It is used after
1169   // a collection pause which used the card table to claim cards.
1170   void cleanUpCardTable();
1171 
1172   // Iteration functions.
1173 
1174   // Iterate over all objects, calling "cl.do_object" on each.
1175   virtual void object_iterate(ObjectClosure* cl);
1176 
1177   virtual void safe_object_iterate(ObjectClosure* cl) {
1178     object_iterate(cl);
1179   }
1180 
1181   // Iterate over heap regions, in address order, terminating the
1182   // iteration early if the "doHeapRegion" method returns "true".
1183   void heap_region_iterate(HeapRegionClosure* blk) const;
1184 
1185   // Return the region with the given index. It assumes the index is valid.
1186   inline HeapRegion* region_at(uint index) const;
1187 
1188   // Return the next region (by index) that is part of the same
1189   // humongous object that hr is part of.
1190   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1191 
1192   // Calculate the region index of the given address. Given address must be
1193   // within the heap.
1194   inline uint addr_to_region(HeapWord* addr) const;
1195 
1196   inline HeapWord* bottom_addr_for_region(uint index) const;
1197 
1198   // Iterate over the heap regions in parallel. Assumes that this will be called
1199   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1200   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1201   // to each of the regions, by attempting to claim the region using the
1202   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1203   // region. The concurrent argument should be set to true if iteration is
1204   // performed concurrently, during which no assumptions are made for consistent
1205   // attributes of the heap regions (as they might be modified while iterating).
1206   void heap_region_par_iterate(HeapRegionClosure* cl,
1207                                uint worker_id,
1208                                HeapRegionClaimer* hrclaimer,
1209                                bool concurrent = false) const;
1210 
1211   // Clear the cached cset start regions and (more importantly)
1212   // the time stamps. Called when we reset the GC time stamp.
1213   void clear_cset_start_regions();
1214 
1215   // Given the id of a worker, obtain or calculate a suitable
1216   // starting region for iterating over the current collection set.
1217   HeapRegion* start_cset_region_for_worker(uint worker_i);
1218 
1219   // Iterate over the regions (if any) in the current collection set.
1220   void collection_set_iterate(HeapRegionClosure* blk);
1221 
1222   // As above but starting from region r
1223   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1224 
1225   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1226 
1227   // Returns the HeapRegion that contains addr. addr must not be NULL.
1228   template <class T>
1229   inline HeapRegion* heap_region_containing(const T addr) const;
1230 
1231   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1232   // each address in the (reserved) heap is a member of exactly
1233   // one block.  The defining characteristic of a block is that it is
1234   // possible to find its size, and thus to progress forward to the next
1235   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1236   // represent Java objects, or they might be free blocks in a
1237   // free-list-based heap (or subheap), as long as the two kinds are
1238   // distinguishable and the size of each is determinable.
1239 
1240   // Returns the address of the start of the "block" that contains the
1241   // address "addr".  We say "blocks" instead of "object" since some heaps
1242   // may not pack objects densely; a chunk may either be an object or a
1243   // non-object.
1244   virtual HeapWord* block_start(const void* addr) const;
1245 
1246   // Requires "addr" to be the start of a chunk, and returns its size.
1247   // "addr + size" is required to be the start of a new chunk, or the end
1248   // of the active area of the heap.
1249   virtual size_t block_size(const HeapWord* addr) const;
1250 
1251   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1252   // the block is an object.
1253   virtual bool block_is_obj(const HeapWord* addr) const;
1254 
1255   // Section on thread-local allocation buffers (TLABs)
1256   // See CollectedHeap for semantics.
1257 
1258   bool supports_tlab_allocation() const;
1259   size_t tlab_capacity(Thread* ignored) const;
1260   size_t tlab_used(Thread* ignored) const;
1261   size_t max_tlab_size() const;
1262   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1263 
1264   // Can a compiler initialize a new object without store barriers?
1265   // This permission only extends from the creation of a new object
1266   // via a TLAB up to the first subsequent safepoint. If such permission
1267   // is granted for this heap type, the compiler promises to call
1268   // defer_store_barrier() below on any slow path allocation of
1269   // a new object for which such initializing store barriers will
1270   // have been elided. G1, like CMS, allows this, but should be
1271   // ready to provide a compensating write barrier as necessary
1272   // if that storage came out of a non-young region. The efficiency
1273   // of this implementation depends crucially on being able to
1274   // answer very efficiently in constant time whether a piece of
1275   // storage in the heap comes from a young region or not.
1276   // See ReduceInitialCardMarks.
1277   virtual bool can_elide_tlab_store_barriers() const {
1278     return true;
1279   }
1280 
1281   virtual bool card_mark_must_follow_store() const {
1282     return true;
1283   }
1284 
1285   // The reference pending list lock is acquired from from the
1286   // ConcurrentMarkThread.
1287   virtual bool needs_reference_pending_list_locker_thread() const {
1288     return true;
1289   }
1290 
1291   inline bool is_in_young(const oop obj);
1292 
1293   virtual bool is_scavengable(const void* addr);
1294 
1295   // We don't need barriers for initializing stores to objects
1296   // in the young gen: for the SATB pre-barrier, there is no
1297   // pre-value that needs to be remembered; for the remembered-set
1298   // update logging post-barrier, we don't maintain remembered set
1299   // information for young gen objects.
1300   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1301 
1302   // Returns "true" iff the given word_size is "very large".
1303   static bool is_humongous(size_t word_size) {
1304     // Note this has to be strictly greater-than as the TLABs
1305     // are capped at the humongous threshold and we want to
1306     // ensure that we don't try to allocate a TLAB as
1307     // humongous and that we don't allocate a humongous
1308     // object in a TLAB.
1309     return word_size > _humongous_object_threshold_in_words;
1310   }
1311 
1312   // Returns the humongous threshold for a specific region size
1313   static size_t humongous_threshold_for(size_t region_size) {
1314     return (region_size / 2);
1315   }
1316 
1317   // Returns the number of regions the humongous object of the given word size
1318   // requires.
1319   static size_t humongous_obj_size_in_regions(size_t word_size);
1320 
1321   // Print the maximum heap capacity.
1322   virtual size_t max_capacity() const;
1323 
1324   virtual jlong millis_since_last_gc();
1325 
1326 
1327   // Convenience function to be used in situations where the heap type can be
1328   // asserted to be this type.
1329   static G1CollectedHeap* heap();
1330 
1331   void set_region_short_lived_locked(HeapRegion* hr);
1332   // add appropriate methods for any other surv rate groups
1333 
1334   YoungList* young_list() const { return _young_list; }
1335 
1336   uint old_regions_count() const { return _old_set.length(); }
1337 
1338   uint humongous_regions_count() const { return _humongous_set.length(); }
1339 
1340   // debugging
1341   bool check_young_list_well_formed() {
1342     return _young_list->check_list_well_formed();
1343   }
1344 
1345   bool check_young_list_empty(bool check_heap);
1346 
1347   // *** Stuff related to concurrent marking.  It's not clear to me that so
1348   // many of these need to be public.
1349 
1350   // The functions below are helper functions that a subclass of
1351   // "CollectedHeap" can use in the implementation of its virtual
1352   // functions.
1353   // This performs a concurrent marking of the live objects in a
1354   // bitmap off to the side.
1355   void doConcurrentMark();
1356 
1357   bool isMarkedPrev(oop obj) const;
1358   bool isMarkedNext(oop obj) const;
1359 
1360   // Determine if an object is dead, given the object and also
1361   // the region to which the object belongs. An object is dead
1362   // iff a) it was not allocated since the last mark, b) it
1363   // is not marked, and c) it is not in an archive region.
1364   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1365     return
1366       !hr->obj_allocated_since_prev_marking(obj) &&
1367       !isMarkedPrev(obj) &&
1368       !hr->is_archive();
1369   }
1370 
1371   // This function returns true when an object has been
1372   // around since the previous marking and hasn't yet
1373   // been marked during this marking, and is not in an archive region.
1374   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1375     return
1376       !hr->obj_allocated_since_next_marking(obj) &&
1377       !isMarkedNext(obj) &&
1378       !hr->is_archive();
1379   }
1380 
1381   // Determine if an object is dead, given only the object itself.
1382   // This will find the region to which the object belongs and
1383   // then call the region version of the same function.
1384 
1385   // Added if it is NULL it isn't dead.
1386 
1387   inline bool is_obj_dead(const oop obj) const;
1388 
1389   inline bool is_obj_ill(const oop obj) const;
1390 
1391   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1392 
1393   // Refinement
1394 
1395   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1396 
1397   // The dirty cards region list is used to record a subset of regions
1398   // whose cards need clearing. The list if populated during the
1399   // remembered set scanning and drained during the card table
1400   // cleanup. Although the methods are reentrant, population/draining
1401   // phases must not overlap. For synchronization purposes the last
1402   // element on the list points to itself.
1403   HeapRegion* _dirty_cards_region_list;
1404   void push_dirty_cards_region(HeapRegion* hr);
1405   HeapRegion* pop_dirty_cards_region();
1406 
1407   // Optimized nmethod scanning support routines
1408 
1409   // Register the given nmethod with the G1 heap.
1410   virtual void register_nmethod(nmethod* nm);
1411 
1412   // Unregister the given nmethod from the G1 heap.
1413   virtual void unregister_nmethod(nmethod* nm);
1414 
1415   // Free up superfluous code root memory.
1416   void purge_code_root_memory();
1417 
1418   // Rebuild the strong code root lists for each region
1419   // after a full GC.
1420   void rebuild_strong_code_roots();
1421 
1422   // Delete entries for dead interned string and clean up unreferenced symbols
1423   // in symbol table, possibly in parallel.
1424   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1425 
1426   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1427   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1428 
1429   // Redirty logged cards in the refinement queue.
1430   void redirty_logged_cards();
1431   // Verification
1432 
1433   // Perform any cleanup actions necessary before allowing a verification.
1434   virtual void prepare_for_verify();
1435 
1436   // Perform verification.
1437 
1438   // vo == UsePrevMarking  -> use "prev" marking information,
1439   // vo == UseNextMarking -> use "next" marking information
1440   // vo == UseMarkWord    -> use the mark word in the object header
1441   //
1442   // NOTE: Only the "prev" marking information is guaranteed to be
1443   // consistent most of the time, so most calls to this should use
1444   // vo == UsePrevMarking.
1445   // Currently, there is only one case where this is called with
1446   // vo == UseNextMarking, which is to verify the "next" marking
1447   // information at the end of remark.
1448   // Currently there is only one place where this is called with
1449   // vo == UseMarkWord, which is to verify the marking during a
1450   // full GC.
1451   void verify(VerifyOption vo);
1452 
1453   // The methods below are here for convenience and dispatch the
1454   // appropriate method depending on value of the given VerifyOption
1455   // parameter. The values for that parameter, and their meanings,
1456   // are the same as those above.
1457 
1458   bool is_obj_dead_cond(const oop obj,
1459                         const HeapRegion* hr,
1460                         const VerifyOption vo) const;
1461 
1462   bool is_obj_dead_cond(const oop obj,
1463                         const VerifyOption vo) const;
1464 
1465   G1HeapSummary create_g1_heap_summary();
1466   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1467 
1468   // Printing
1469 private:
1470   void print_heap_regions() const;
1471   void print_regions_on(outputStream* st) const;
1472 
1473 public:
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