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