1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   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.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  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/g1BarrierSet.hpp"
  30 #include "gc/g1/g1BiasedArray.hpp"
  31 #include "gc/g1/g1CardTable.hpp"
  32 #include "gc/g1/g1CollectionSet.hpp"
  33 #include "gc/g1/g1CollectorState.hpp"
  34 #include "gc/g1/g1ConcurrentMark.hpp"
  35 #include "gc/g1/g1EdenRegions.hpp"
  36 #include "gc/g1/g1EvacFailure.hpp"
  37 #include "gc/g1/g1EvacStats.hpp"
  38 #include "gc/g1/g1HeapTransition.hpp"
  39 #include "gc/g1/g1HeapVerifier.hpp"
  40 #include "gc/g1/g1HRPrinter.hpp"
  41 #include "gc/g1/g1InCSetState.hpp"
  42 #include "gc/g1/g1MonitoringSupport.hpp"
  43 #include "gc/g1/g1SurvivorRegions.hpp"
  44 #include "gc/g1/g1YCTypes.hpp"
  45 #include "gc/g1/heapRegionManager.hpp"
  46 #include "gc/g1/heapRegionSet.hpp"
  47 #include "gc/shared/barrierSet.hpp"
  48 #include "gc/shared/collectedHeap.hpp"
  49 #include "gc/shared/gcHeapSummary.hpp"
  50 #include "gc/shared/plab.hpp"
  51 #include "gc/shared/preservedMarks.hpp"
  52 #include "gc/shared/softRefPolicy.hpp"
  53 #include "memory/memRegion.hpp"
  54 #include "services/memoryManager.hpp"
  55 #include "utilities/stack.hpp"
  56 
  57 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  58 // It uses the "Garbage First" heap organization and algorithm, which
  59 // may combine concurrent marking with parallel, incremental compaction of
  60 // heap subsets that will yield large amounts of garbage.
  61 
  62 // Forward declarations
  63 class HeapRegion;
  64 class HRRSCleanupTask;
  65 class GenerationSpec;
  66 class G1ParScanThreadState;
  67 class G1ParScanThreadStateSet;
  68 class G1ParScanThreadState;
  69 class MemoryPool;
  70 class ObjectClosure;
  71 class SpaceClosure;
  72 class CompactibleSpaceClosure;
  73 class Space;
  74 class G1CollectionSet;
  75 class G1CollectorPolicy;
  76 class G1Policy;
  77 class G1HotCardCache;
  78 class G1RemSet;
  79 class G1YoungRemSetSamplingThread;
  80 class HeapRegionRemSetIterator;
  81 class G1ConcurrentMark;
  82 class G1ConcurrentMarkThread;
  83 class G1ConcurrentRefine;
  84 class GenerationCounters;
  85 class STWGCTimer;
  86 class G1NewTracer;
  87 class EvacuationFailedInfo;
  88 class nmethod;
  89 class Ticks;
  90 class WorkGang;
  91 class G1Allocator;
  92 class G1ArchiveAllocator;
  93 class G1FullGCScope;
  94 class G1HeapVerifier;
  95 class G1HeapSizingPolicy;
  96 class G1HeapSummary;
  97 class G1EvacSummary;
  98 
  99 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
 100 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
 101 
 102 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
 103 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
 104 
 105 // The G1 STW is alive closure.
 106 // An instance is embedded into the G1CH and used as the
 107 // (optional) _is_alive_non_header closure in the STW
 108 // reference processor. It is also extensively used during
 109 // reference processing during STW evacuation pauses.
 110 class G1STWIsAliveClosure : public BoolObjectClosure {
 111   G1CollectedHeap* _g1h;
 112 public:
 113   G1STWIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 114   bool do_object_b(oop p);
 115 };
 116 
 117 class G1STWSubjectToDiscoveryClosure : public BoolObjectClosure {
 118   G1CollectedHeap* _g1h;
 119 public:
 120   G1STWSubjectToDiscoveryClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
 121   bool do_object_b(oop p);
 122 };
 123 
 124 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 125  private:
 126   void reset_from_card_cache(uint start_idx, size_t num_regions);
 127  public:
 128   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 129 };
 130 
 131 class G1CollectedHeap : public CollectedHeap {
 132   friend class G1FreeCollectionSetTask;
 133   friend class VM_CollectForMetadataAllocation;
 134   friend class VM_G1CollectForAllocation;
 135   friend class VM_G1CollectFull;
 136   friend class VMStructs;
 137   friend class MutatorAllocRegion;
 138   friend class G1FullCollector;
 139   friend class G1GCAllocRegion;
 140   friend class G1HeapVerifier;
 141 
 142   // Closures used in implementation.
 143   friend class G1ParScanThreadState;
 144   friend class G1ParScanThreadStateSet;
 145   friend class G1ParTask;
 146   friend class G1PLABAllocator;
 147   friend class G1PrepareCompactClosure;
 148 
 149   // Other related classes.
 150   friend class HeapRegionClaimer;
 151 
 152   // Testing classes.
 153   friend class G1CheckCSetFastTableClosure;
 154 
 155 private:
 156   G1YoungRemSetSamplingThread* _young_gen_sampling_thread;
 157 
 158   WorkGang* _workers;
 159   G1CollectorPolicy* _collector_policy;
 160   G1CardTable* _card_table;
 161 
 162   SoftRefPolicy      _soft_ref_policy;
 163 
 164   GCMemoryManager _memory_manager;
 165   GCMemoryManager _full_gc_memory_manager;
 166 
 167   MemoryPool* _eden_pool;
 168   MemoryPool* _survivor_pool;
 169   MemoryPool* _old_pool;
 170 
 171   static size_t _humongous_object_threshold_in_words;
 172 
 173   // It keeps track of the old regions.
 174   HeapRegionSet _old_set;
 175 
 176   // It keeps track of the humongous regions.
 177   HeapRegionSet _humongous_set;
 178 
 179   virtual void initialize_serviceability();
 180 
 181   void eagerly_reclaim_humongous_regions();
 182   // Start a new incremental collection set for the next pause.
 183   void start_new_collection_set();
 184 
 185   // The number of regions we could create by expansion.
 186   uint _expansion_regions;
 187 
 188   // The block offset table for the G1 heap.
 189   G1BlockOffsetTable* _bot;
 190 
 191   // Tears down the region sets / lists so that they are empty and the
 192   // regions on the heap do not belong to a region set / list. The
 193   // only exception is the humongous set which we leave unaltered. If
 194   // free_list_only is true, it will only tear down the master free
 195   // list. It is called before a Full GC (free_list_only == false) or
 196   // before heap shrinking (free_list_only == true).
 197   void tear_down_region_sets(bool free_list_only);
 198 
 199   // Rebuilds the region sets / lists so that they are repopulated to
 200   // reflect the contents of the heap. The only exception is the
 201   // humongous set which was not torn down in the first place. If
 202   // free_list_only is true, it will only rebuild the master free
 203   // list. It is called after a Full GC (free_list_only == false) or
 204   // after heap shrinking (free_list_only == true).
 205   void rebuild_region_sets(bool free_list_only);
 206 
 207   // Callback for region mapping changed events.
 208   G1RegionMappingChangedListener _listener;
 209 
 210   // The sequence of all heap regions in the heap.
 211   HeapRegionManager _hrm;
 212 
 213   // Manages all allocations with regions except humongous object allocations.
 214   G1Allocator* _allocator;
 215 
 216   // Manages all heap verification.
 217   G1HeapVerifier* _verifier;
 218 
 219   // Outside of GC pauses, the number of bytes used in all regions other
 220   // than the current allocation region(s).
 221   size_t _summary_bytes_used;
 222 
 223   void increase_used(size_t bytes);
 224   void decrease_used(size_t bytes);
 225 
 226   void set_used(size_t bytes);
 227 
 228   // Class that handles archive allocation ranges.
 229   G1ArchiveAllocator* _archive_allocator;
 230 
 231   // GC allocation statistics policy for survivors.
 232   G1EvacStats _survivor_evac_stats;
 233 
 234   // GC allocation statistics policy for tenured objects.
 235   G1EvacStats _old_evac_stats;
 236 
 237   // It specifies whether we should attempt to expand the heap after a
 238   // region allocation failure. If heap expansion fails we set this to
 239   // false so that we don't re-attempt the heap expansion (it's likely
 240   // that subsequent expansion attempts will also fail if one fails).
 241   // Currently, it is only consulted during GC and it's reset at the
 242   // start of each GC.
 243   bool _expand_heap_after_alloc_failure;
 244 
 245   // Helper for monitoring and management support.
 246   G1MonitoringSupport* _g1mm;
 247 
 248   // Records whether the region at the given index is (still) a
 249   // candidate for eager reclaim.  Only valid for humongous start
 250   // regions; other regions have unspecified values.  Humongous start
 251   // regions are initialized at start of collection pause, with
 252   // candidates removed from the set as they are found reachable from
 253   // roots or the young generation.
 254   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 255    protected:
 256     bool default_value() const { return false; }
 257    public:
 258     void clear() { G1BiasedMappedArray<bool>::clear(); }
 259     void set_candidate(uint region, bool value) {
 260       set_by_index(region, value);
 261     }
 262     bool is_candidate(uint region) {
 263       return get_by_index(region);
 264     }
 265   };
 266 
 267   HumongousReclaimCandidates _humongous_reclaim_candidates;
 268   // Stores whether during humongous object registration we found candidate regions.
 269   // If not, we can skip a few steps.
 270   bool _has_humongous_reclaim_candidates;
 271 
 272   G1HRPrinter _hr_printer;
 273 
 274   // It decides whether an explicit GC should start a concurrent cycle
 275   // instead of doing a STW GC. Currently, a concurrent cycle is
 276   // explicitly started if:
 277   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 278   // (b) cause == _g1_humongous_allocation
 279   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 280   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 281   // (e) cause == _wb_conc_mark
 282   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 283 
 284   // indicates whether we are in young or mixed GC mode
 285   G1CollectorState _collector_state;
 286 
 287   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 288   // concurrent cycles) we have started.
 289   volatile uint _old_marking_cycles_started;
 290 
 291   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 292   // concurrent cycles) we have completed.
 293   volatile uint _old_marking_cycles_completed;
 294 
 295   // This is a non-product method that is helpful for testing. It is
 296   // called at the end of a GC and artificially expands the heap by
 297   // allocating a number of dead regions. This way we can induce very
 298   // frequent marking cycles and stress the cleanup / concurrent
 299   // cleanup code more (as all the regions that will be allocated by
 300   // this method will be found dead by the marking cycle).
 301   void allocate_dummy_regions() PRODUCT_RETURN;
 302 
 303   // If the HR printer is active, dump the state of the regions in the
 304   // heap after a compaction.
 305   void print_hrm_post_compaction();
 306 
 307   // Create a memory mapper for auxiliary data structures of the given size and
 308   // translation factor.
 309   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 310                                                          size_t size,
 311                                                          size_t translation_factor);
 312 
 313   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 314 
 315   // These are macros so that, if the assert fires, we get the correct
 316   // line number, file, etc.
 317 
 318 #define heap_locking_asserts_params(_extra_message_)                          \
 319   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 320   (_extra_message_),                                                          \
 321   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 322   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 323   BOOL_TO_STR(Thread::current()->is_VM_thread())
 324 
 325 #define assert_heap_locked()                                                  \
 326   do {                                                                        \
 327     assert(Heap_lock->owned_by_self(),                                        \
 328            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 329   } while (0)
 330 
 331 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 332   do {                                                                        \
 333     assert(Heap_lock->owned_by_self() ||                                      \
 334            (SafepointSynchronize::is_at_safepoint() &&                        \
 335              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 336            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 337                                         "should be at a safepoint"));         \
 338   } while (0)
 339 
 340 #define assert_heap_locked_and_not_at_safepoint()                             \
 341   do {                                                                        \
 342     assert(Heap_lock->owned_by_self() &&                                      \
 343                                     !SafepointSynchronize::is_at_safepoint(), \
 344           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 345                                        "should not be at a safepoint"));      \
 346   } while (0)
 347 
 348 #define assert_heap_not_locked()                                              \
 349   do {                                                                        \
 350     assert(!Heap_lock->owned_by_self(),                                       \
 351         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 352   } while (0)
 353 
 354 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 355   do {                                                                        \
 356     assert(!Heap_lock->owned_by_self() &&                                     \
 357                                     !SafepointSynchronize::is_at_safepoint(), \
 358       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 359                                    "should not be at a safepoint"));          \
 360   } while (0)
 361 
 362 #define assert_at_safepoint_on_vm_thread()                                    \
 363   do {                                                                        \
 364     assert_at_safepoint();                                                    \
 365     assert(Thread::current_or_null() != NULL, "no current thread");           \
 366     assert(Thread::current()->is_VM_thread(), "current thread is not VM thread"); \
 367   } while (0)
 368 
 369   // The young region list.
 370   G1EdenRegions _eden;
 371   G1SurvivorRegions _survivor;
 372 
 373   STWGCTimer* _gc_timer_stw;
 374 
 375   G1NewTracer* _gc_tracer_stw;
 376 
 377   // The current policy object for the collector.
 378   G1Policy* _g1_policy;
 379   G1HeapSizingPolicy* _heap_sizing_policy;
 380 
 381   G1CollectionSet _collection_set;
 382 
 383   // Try to allocate a single non-humongous HeapRegion sufficient for
 384   // an allocation of the given word_size. If do_expand is true,
 385   // attempt to expand the heap if necessary to satisfy the allocation
 386   // request. If the region is to be used as an old region or for a
 387   // humongous object, set is_old to true. If not, to false.
 388   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 389 
 390   // Initialize a contiguous set of free regions of length num_regions
 391   // and starting at index first so that they appear as a single
 392   // humongous region.
 393   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 394                                                       uint num_regions,
 395                                                       size_t word_size);
 396 
 397   // Attempt to allocate a humongous object of the given size. Return
 398   // NULL if unsuccessful.
 399   HeapWord* humongous_obj_allocate(size_t word_size);
 400 
 401   // The following two methods, allocate_new_tlab() and
 402   // mem_allocate(), are the two main entry points from the runtime
 403   // into the G1's allocation routines. They have the following
 404   // assumptions:
 405   //
 406   // * They should both be called outside safepoints.
 407   //
 408   // * They should both be called without holding the Heap_lock.
 409   //
 410   // * All allocation requests for new TLABs should go to
 411   //   allocate_new_tlab().
 412   //
 413   // * All non-TLAB allocation requests should go to mem_allocate().
 414   //
 415   // * If either call cannot satisfy the allocation request using the
 416   //   current allocating region, they will try to get a new one. If
 417   //   this fails, they will attempt to do an evacuation pause and
 418   //   retry the allocation.
 419   //
 420   // * If all allocation attempts fail, even after trying to schedule
 421   //   an evacuation pause, allocate_new_tlab() will return NULL,
 422   //   whereas mem_allocate() will attempt a heap expansion and/or
 423   //   schedule a Full GC.
 424   //
 425   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 426   //   should never be called with word_size being humongous. All
 427   //   humongous allocation requests should go to mem_allocate() which
 428   //   will satisfy them with a special path.
 429 
 430   virtual HeapWord* allocate_new_tlab(size_t min_size,
 431                                       size_t requested_size,
 432                                       size_t* actual_size);
 433 
 434   virtual HeapWord* mem_allocate(size_t word_size,
 435                                  bool*  gc_overhead_limit_was_exceeded);
 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 min_word_size,
 441                                       size_t desired_word_size,
 442                                       size_t* actual_word_size);
 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 
 449   // Takes the Heap_lock and attempts a humongous allocation. It can
 450   // potentially schedule a GC pause.
 451   HeapWord* attempt_allocation_humongous(size_t word_size);
 452 
 453   // Allocation attempt that should be called during safepoints (e.g.,
 454   // at the end of a successful GC). expect_null_mutator_alloc_region
 455   // specifies whether the mutator alloc region is expected to be NULL
 456   // or not.
 457   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 458                                             bool expect_null_mutator_alloc_region);
 459 
 460   // These methods are the "callbacks" from the G1AllocRegion class.
 461 
 462   // For mutator alloc regions.
 463   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 464   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 465                                    size_t allocated_bytes);
 466 
 467   // For GC alloc regions.
 468   bool has_more_regions(InCSetState dest);
 469   HeapRegion* new_gc_alloc_region(size_t word_size, InCSetState dest);
 470   void retire_gc_alloc_region(HeapRegion* alloc_region,
 471                               size_t allocated_bytes, InCSetState dest);
 472 
 473   // - if explicit_gc is true, the GC is for a System.gc() etc,
 474   //   otherwise it's for a failed allocation.
 475   // - if clear_all_soft_refs is true, all soft references should be
 476   //   cleared during the GC.
 477   // - it returns false if it is unable to do the collection due to the
 478   //   GC locker being active, true otherwise.
 479   bool do_full_collection(bool explicit_gc,
 480                           bool clear_all_soft_refs);
 481 
 482   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 483   virtual void do_full_collection(bool clear_all_soft_refs);
 484 
 485   // Resize the heap if necessary after a full collection.
 486   void resize_if_necessary_after_full_collection();
 487 
 488   // Callback from VM_G1CollectForAllocation operation.
 489   // This function does everything necessary/possible to satisfy a
 490   // failed allocation request (including collection, expansion, etc.)
 491   HeapWord* satisfy_failed_allocation(size_t word_size,
 492                                       bool* succeeded);
 493   // Internal helpers used during full GC to split it up to
 494   // increase readability.
 495   void abort_concurrent_cycle();
 496   void verify_before_full_collection(bool explicit_gc);
 497   void prepare_heap_for_full_collection();
 498   void prepare_heap_for_mutators();
 499   void abort_refinement();
 500   void verify_after_full_collection();
 501   void print_heap_after_full_collection(G1HeapTransition* heap_transition);
 502 
 503   // Helper method for satisfy_failed_allocation()
 504   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 505                                              bool do_gc,
 506                                              bool clear_all_soft_refs,
 507                                              bool expect_null_mutator_alloc_region,
 508                                              bool* gc_succeeded);
 509 
 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);
 515 
 516   // Process any reference objects discovered.
 517   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 518 
 519   // If during an initial mark pause we may install a pending list head which is not
 520   // otherwise reachable ensure that it is marked in the bitmap for concurrent marking
 521   // to discover.
 522   void make_pending_list_reachable();
 523 
 524   // Merges the information gathered on a per-thread basis for all worker threads
 525   // during GC into global variables.
 526   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 527 public:
 528   G1YoungRemSetSamplingThread* sampling_thread() const { return _young_gen_sampling_thread; }
 529 
 530   WorkGang* workers() const { return _workers; }
 531 
 532   G1Allocator* allocator() {
 533     return _allocator;
 534   }
 535 
 536   G1HeapVerifier* verifier() {
 537     return _verifier;
 538   }
 539 
 540   G1MonitoringSupport* g1mm() {
 541     assert(_g1mm != NULL, "should have been initialized");
 542     return _g1mm;
 543   }
 544 
 545   // Expand the garbage-first heap by at least the given size (in bytes!).
 546   // Returns true if the heap was expanded by the requested amount;
 547   // false otherwise.
 548   // (Rounds up to a HeapRegion boundary.)
 549   bool expand(size_t expand_bytes, WorkGang* pretouch_workers = NULL, double* expand_time_ms = NULL);
 550 
 551   // Returns the PLAB statistics for a given destination.
 552   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 553 
 554   // Determines PLAB size for a given destination.
 555   inline size_t desired_plab_sz(InCSetState dest);
 556 
 557   // Do anything common to GC's.
 558   void gc_prologue(bool full);
 559   void gc_epilogue(bool full);
 560 
 561   // Does the given region fulfill remembered set based eager reclaim candidate requirements?
 562   bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
 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   void clear_in_cset(const HeapRegion* hr) {
 587     _in_cset_fast_test.clear(hr);
 588   }
 589 
 590   void clear_cset_fast_test() {
 591     _in_cset_fast_test.clear();
 592   }
 593 
 594   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 595 
 596   // This is called at the start of either a concurrent cycle or a Full
 597   // GC to update the number of old marking cycles started.
 598   void increment_old_marking_cycles_started();
 599 
 600   // This is called at the end of either a concurrent cycle or a Full
 601   // GC to update the number of old marking cycles completed. Those two
 602   // can happen in a nested fashion, i.e., we start a concurrent
 603   // cycle, a Full GC happens half-way through it which ends first,
 604   // and then the cycle notices that a Full GC happened and ends
 605   // too. The concurrent parameter is a boolean to help us do a bit
 606   // tighter consistency checking in the method. If concurrent is
 607   // false, the caller is the inner caller in the nesting (i.e., the
 608   // Full GC). If concurrent is true, the caller is the outer caller
 609   // in this nesting (i.e., the concurrent cycle). Further nesting is
 610   // not currently supported. The end of this call also notifies
 611   // the FullGCCount_lock in case a Java thread is waiting for a full
 612   // GC to happen (e.g., it called System.gc() with
 613   // +ExplicitGCInvokesConcurrent).
 614   void increment_old_marking_cycles_completed(bool concurrent);
 615 
 616   uint old_marking_cycles_completed() {
 617     return _old_marking_cycles_completed;
 618   }
 619 
 620   G1HRPrinter* hr_printer() { return &_hr_printer; }
 621 
 622   // Allocates a new heap region instance.
 623   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 624 
 625   // Allocate the highest free region in the reserved heap. This will commit
 626   // regions as necessary.
 627   HeapRegion* alloc_highest_free_region();
 628 
 629   // Frees a non-humongous region by initializing its contents and
 630   // adding it to the free list that's passed as a parameter (this is
 631   // usually a local list which will be appended to the master free
 632   // list later). The used bytes of freed regions are accumulated in
 633   // pre_used. If skip_remset is true, the region's RSet will not be freed
 634   // up. If skip_hot_card_cache is true, the region's hot card cache will not
 635   // be freed up. The assumption is that this will be done later.
 636   // The locked parameter indicates if the caller has already taken
 637   // care of proper synchronization. This may allow some optimizations.
 638   void free_region(HeapRegion* hr,
 639                    FreeRegionList* free_list,
 640                    bool skip_remset,
 641                    bool skip_hot_card_cache = false,
 642                    bool locked = false);
 643 
 644   // It dirties the cards that cover the block so that the post
 645   // write barrier never queues anything when updating objects on this
 646   // block. It is assumed (and in fact we assert) that the block
 647   // belongs to a young region.
 648   inline void dirty_young_block(HeapWord* start, size_t word_size);
 649 
 650   // Frees a humongous region by collapsing it into individual regions
 651   // and calling free_region() for each of them. The freed regions
 652   // will be added to the free list that's passed as a parameter (this
 653   // is usually a local list which will be appended to the master free
 654   // list later).
 655   // The method assumes that only a single thread is ever calling
 656   // this for a particular region at once.
 657   void free_humongous_region(HeapRegion* hr,
 658                              FreeRegionList* free_list);
 659 
 660   // Facility for allocating in 'archive' regions in high heap memory and
 661   // recording the allocated ranges. These should all be called from the
 662   // VM thread at safepoints, without the heap lock held. They can be used
 663   // to create and archive a set of heap regions which can be mapped at the
 664   // same fixed addresses in a subsequent JVM invocation.
 665   void begin_archive_alloc_range(bool open = false);
 666 
 667   // Check if the requested size would be too large for an archive allocation.
 668   bool is_archive_alloc_too_large(size_t word_size);
 669 
 670   // Allocate memory of the requested size from the archive region. This will
 671   // return NULL if the size is too large or if no memory is available. It
 672   // does not trigger a garbage collection.
 673   HeapWord* archive_mem_allocate(size_t word_size);
 674 
 675   // Optionally aligns the end address and returns the allocated ranges in
 676   // an array of MemRegions in order of ascending addresses.
 677   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 678                                size_t end_alignment_in_bytes = 0);
 679 
 680   // Facility for allocating a fixed range within the heap and marking
 681   // the containing regions as 'archive'. For use at JVM init time, when the
 682   // caller may mmap archived heap data at the specified range(s).
 683   // Verify that the MemRegions specified in the argument array are within the
 684   // reserved heap.
 685   bool check_archive_addresses(MemRegion* range, size_t count);
 686 
 687   // Commit the appropriate G1 regions containing the specified MemRegions
 688   // and mark them as 'archive' regions. The regions in the array must be
 689   // non-overlapping and in order of ascending address.
 690   bool alloc_archive_regions(MemRegion* range, size_t count, bool open);
 691 
 692   // Insert any required filler objects in the G1 regions around the specified
 693   // ranges to make the regions parseable. This must be called after
 694   // alloc_archive_regions, and after class loading has occurred.
 695   void fill_archive_regions(MemRegion* range, size_t count);
 696 
 697   // For each of the specified MemRegions, uncommit the containing G1 regions
 698   // which had been allocated by alloc_archive_regions. This should be called
 699   // rather than fill_archive_regions at JVM init time if the archive file
 700   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 701   void dealloc_archive_regions(MemRegion* range, size_t count);
 702 
 703 private:
 704 
 705   // Shrink the garbage-first heap by at most the given size (in bytes!).
 706   // (Rounds down to a HeapRegion boundary.)
 707   void shrink(size_t expand_bytes);
 708   void shrink_helper(size_t expand_bytes);
 709 
 710   #if TASKQUEUE_STATS
 711   static void print_taskqueue_stats_hdr(outputStream* const st);
 712   void print_taskqueue_stats() const;
 713   void reset_taskqueue_stats();
 714   #endif // TASKQUEUE_STATS
 715 
 716   // Schedule the VM operation that will do an evacuation pause to
 717   // satisfy an allocation request of word_size. *succeeded will
 718   // return whether the VM operation was successful (it did do an
 719   // evacuation pause) or not (another thread beat us to it or the GC
 720   // locker was active). Given that we should not be holding the
 721   // Heap_lock when we enter this method, we will pass the
 722   // gc_count_before (i.e., total_collections()) as a parameter since
 723   // it has to be read while holding the Heap_lock. Currently, both
 724   // methods that call do_collection_pause() release the Heap_lock
 725   // before the call, so it's easy to read gc_count_before just before.
 726   HeapWord* do_collection_pause(size_t         word_size,
 727                                 uint           gc_count_before,
 728                                 bool*          succeeded,
 729                                 GCCause::Cause gc_cause);
 730 
 731   void wait_for_root_region_scanning();
 732 
 733   // The guts of the incremental collection pause, executed by the vm
 734   // thread. It returns false if it is unable to do the collection due
 735   // to the GC locker being active, true otherwise
 736   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 737 
 738   // Actually do the work of evacuating the collection set.
 739   void evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states);
 740 
 741   void pre_evacuate_collection_set();
 742   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 743 
 744   // Print the header for the per-thread termination statistics.
 745   static void print_termination_stats_hdr();
 746   // Print actual per-thread termination statistics.
 747   void print_termination_stats(uint worker_id,
 748                                double elapsed_ms,
 749                                double strong_roots_ms,
 750                                double term_ms,
 751                                size_t term_attempts,
 752                                size_t alloc_buffer_waste,
 753                                size_t undo_waste) const;
 754   // Update object copying statistics.
 755   void record_obj_copy_mem_stats();
 756 
 757   // The hot card cache for remembered set insertion optimization.
 758   G1HotCardCache* _hot_card_cache;
 759 
 760   // The g1 remembered set of the heap.
 761   G1RemSet* _g1_rem_set;
 762 
 763   // A set of cards that cover the objects for which the Rsets should be updated
 764   // concurrently after the collection.
 765   DirtyCardQueueSet _dirty_card_queue_set;
 766 
 767   // After a collection pause, convert the regions in the collection set into free
 768   // regions.
 769   void free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 770 
 771   // Abandon the current collection set without recording policy
 772   // statistics or updating free lists.
 773   void abandon_collection_set(G1CollectionSet* collection_set);
 774 
 775   // The concurrent marker (and the thread it runs in.)
 776   G1ConcurrentMark* _cm;
 777   G1ConcurrentMarkThread* _cm_thread;
 778 
 779   // The concurrent refiner.
 780   G1ConcurrentRefine* _cr;
 781 
 782   // The parallel task queues
 783   RefToScanQueueSet *_task_queues;
 784 
 785   // True iff a evacuation has failed in the current collection.
 786   bool _evacuation_failed;
 787 
 788   EvacuationFailedInfo* _evacuation_failed_info_array;
 789 
 790   // Failed evacuations cause some logical from-space objects to have
 791   // forwarding pointers to themselves.  Reset them.
 792   void remove_self_forwarding_pointers();
 793 
 794   // Restore the objects in the regions in the collection set after an
 795   // evacuation failure.
 796   void restore_after_evac_failure();
 797 
 798   PreservedMarksSet _preserved_marks_set;
 799 
 800   // Preserve the mark of "obj", if necessary, in preparation for its mark
 801   // word being overwritten with a self-forwarding-pointer.
 802   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 803 
 804 #ifndef PRODUCT
 805   // Support for forcing evacuation failures. Analogous to
 806   // PromotionFailureALot for the other collectors.
 807 
 808   // Records whether G1EvacuationFailureALot should be in effect
 809   // for the current GC
 810   bool _evacuation_failure_alot_for_current_gc;
 811 
 812   // Used to record the GC number for interval checking when
 813   // determining whether G1EvaucationFailureALot is in effect
 814   // for the current GC.
 815   size_t _evacuation_failure_alot_gc_number;
 816 
 817   // Count of the number of evacuations between failures.
 818   volatile size_t _evacuation_failure_alot_count;
 819 
 820   // Set whether G1EvacuationFailureALot should be in effect
 821   // for the current GC (based upon the type of GC and which
 822   // command line flags are set);
 823   inline bool evacuation_failure_alot_for_gc_type(bool for_young_gc,
 824                                                   bool during_initial_mark,
 825                                                   bool mark_or_rebuild_in_progress);
 826 
 827   inline void set_evacuation_failure_alot_for_current_gc();
 828 
 829   // Return true if it's time to cause an evacuation failure.
 830   inline bool evacuation_should_fail();
 831 
 832   // Reset the G1EvacuationFailureALot counters.  Should be called at
 833   // the end of an evacuation pause in which an evacuation failure occurred.
 834   inline void reset_evacuation_should_fail();
 835 #endif // !PRODUCT
 836 
 837   // ("Weak") Reference processing support.
 838   //
 839   // G1 has 2 instances of the reference processor class. One
 840   // (_ref_processor_cm) handles reference object discovery
 841   // and subsequent processing during concurrent marking cycles.
 842   //
 843   // The other (_ref_processor_stw) handles reference object
 844   // discovery and processing during full GCs and incremental
 845   // evacuation pauses.
 846   //
 847   // During an incremental pause, reference discovery will be
 848   // temporarily disabled for _ref_processor_cm and will be
 849   // enabled for _ref_processor_stw. At the end of the evacuation
 850   // pause references discovered by _ref_processor_stw will be
 851   // processed and discovery will be disabled. The previous
 852   // setting for reference object discovery for _ref_processor_cm
 853   // will be re-instated.
 854   //
 855   // At the start of marking:
 856   //  * Discovery by the CM ref processor is verified to be inactive
 857   //    and it's discovered lists are empty.
 858   //  * Discovery by the CM ref processor is then enabled.
 859   //
 860   // At the end of marking:
 861   //  * Any references on the CM ref processor's discovered
 862   //    lists are processed (possibly MT).
 863   //
 864   // At the start of full GC we:
 865   //  * Disable discovery by the CM ref processor and
 866   //    empty CM ref processor's discovered lists
 867   //    (without processing any entries).
 868   //  * Verify that the STW ref processor is inactive and it's
 869   //    discovered lists are empty.
 870   //  * Temporarily set STW ref processor discovery as single threaded.
 871   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 872   //    field.
 873   //  * Finally enable discovery by the STW ref processor.
 874   //
 875   // The STW ref processor is used to record any discovered
 876   // references during the full GC.
 877   //
 878   // At the end of a full GC we:
 879   //  * Enqueue any reference objects discovered by the STW ref processor
 880   //    that have non-live referents. This has the side-effect of
 881   //    making the STW ref processor inactive by disabling discovery.
 882   //  * Verify that the CM ref processor is still inactive
 883   //    and no references have been placed on it's discovered
 884   //    lists (also checked as a precondition during initial marking).
 885 
 886   // The (stw) reference processor...
 887   ReferenceProcessor* _ref_processor_stw;
 888 
 889   // During reference object discovery, the _is_alive_non_header
 890   // closure (if non-null) is applied to the referent object to
 891   // determine whether the referent is live. If so then the
 892   // reference object does not need to be 'discovered' and can
 893   // be treated as a regular oop. This has the benefit of reducing
 894   // the number of 'discovered' reference objects that need to
 895   // be processed.
 896   //
 897   // Instance of the is_alive closure for embedding into the
 898   // STW reference processor as the _is_alive_non_header field.
 899   // Supplying a value for the _is_alive_non_header field is
 900   // optional but doing so prevents unnecessary additions to
 901   // the discovered lists during reference discovery.
 902   G1STWIsAliveClosure _is_alive_closure_stw;
 903 
 904   G1STWSubjectToDiscoveryClosure _is_subject_to_discovery_stw;
 905 
 906   // The (concurrent marking) reference processor...
 907   ReferenceProcessor* _ref_processor_cm;
 908 
 909   // Instance of the concurrent mark is_alive closure for embedding
 910   // into the Concurrent Marking reference processor as the
 911   // _is_alive_non_header field. Supplying a value for the
 912   // _is_alive_non_header field is optional but doing so prevents
 913   // unnecessary additions to the discovered lists during reference
 914   // discovery.
 915   G1CMIsAliveClosure _is_alive_closure_cm;
 916 
 917   G1CMSubjectToDiscoveryClosure _is_subject_to_discovery_cm;
 918 public:
 919 
 920   RefToScanQueue *task_queue(uint i) const;
 921 
 922   uint num_task_queues() const;
 923 
 924   // A set of cards where updates happened during the GC
 925   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 926 
 927   // Create a G1CollectedHeap with the specified policy.
 928   // Must call the initialize method afterwards.
 929   // May not return if something goes wrong.
 930   G1CollectedHeap(G1CollectorPolicy* policy);
 931 
 932 private:
 933   jint initialize_concurrent_refinement();
 934   jint initialize_young_gen_sampling_thread();
 935 public:
 936   // Initialize the G1CollectedHeap to have the initial and
 937   // maximum sizes and remembered and barrier sets
 938   // specified by the policy object.
 939   jint initialize();
 940 
 941   virtual void stop();
 942   virtual void safepoint_synchronize_begin();
 943   virtual void safepoint_synchronize_end();
 944 
 945   // Return the (conservative) maximum heap alignment for any G1 heap
 946   static size_t conservative_max_heap_alignment();
 947 
 948   // Does operations required after initialization has been done.
 949   void post_initialize();
 950 
 951   // Initialize weak reference processing.
 952   void ref_processing_init();
 953 
 954   virtual Name kind() const {
 955     return CollectedHeap::G1;
 956   }
 957 
 958   virtual const char* name() const {
 959     return "G1";
 960   }
 961 
 962   const G1CollectorState* collector_state() const { return &_collector_state; }
 963   G1CollectorState* collector_state() { return &_collector_state; }
 964 
 965   // The current policy object for the collector.
 966   G1Policy* g1_policy() const { return _g1_policy; }
 967 
 968   const G1CollectionSet* collection_set() const { return &_collection_set; }
 969   G1CollectionSet* collection_set() { return &_collection_set; }
 970 
 971   virtual CollectorPolicy* collector_policy() const;
 972 
 973   virtual SoftRefPolicy* soft_ref_policy();
 974 
 975   virtual GrowableArray<GCMemoryManager*> memory_managers();
 976   virtual GrowableArray<MemoryPool*> memory_pools();
 977 
 978   // The rem set and barrier set.
 979   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
 980 
 981   // Try to minimize the remembered set.
 982   void scrub_rem_set();
 983 
 984   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
 985   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
 986 
 987   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
 988   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
 989 
 990   // The shared block offset table array.
 991   G1BlockOffsetTable* bot() const { return _bot; }
 992 
 993   // Reference Processing accessors
 994 
 995   // The STW reference processor....
 996   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
 997 
 998   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
 999 
1000   // The Concurrent Marking reference processor...
1001   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1002 
1003   size_t unused_committed_regions_in_bytes() const;
1004   virtual size_t capacity() const;
1005   virtual size_t used() const;
1006   // This should be called when we're not holding the heap lock. The
1007   // result might be a bit inaccurate.
1008   size_t used_unlocked() const;
1009   size_t recalculate_used() const;
1010 
1011   // These virtual functions do the actual allocation.
1012   // Some heaps may offer a contiguous region for shared non-blocking
1013   // allocation, via inlined code (by exporting the address of the top and
1014   // end fields defining the extent of the contiguous allocation region.)
1015   // But G1CollectedHeap doesn't yet support this.
1016 
1017   virtual bool is_maximal_no_gc() const {
1018     return _hrm.available() == 0;
1019   }
1020 
1021   // Returns whether there are any regions left in the heap for allocation.
1022   bool has_regions_left_for_allocation() const {
1023     return !is_maximal_no_gc() || num_free_regions() != 0;
1024   }
1025 
1026   // The current number of regions in the heap.
1027   uint num_regions() const { return _hrm.length(); }
1028 
1029   // The max number of regions in the heap.
1030   uint max_regions() const { return _hrm.max_length(); }
1031 
1032   // The number of regions that are completely free.
1033   uint num_free_regions() const { return _hrm.num_free_regions(); }
1034 
1035   MemoryUsage get_auxiliary_data_memory_usage() const {
1036     return _hrm.get_auxiliary_data_memory_usage();
1037   }
1038 
1039   // The number of regions that are not completely free.
1040   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1041 
1042 #ifdef ASSERT
1043   bool is_on_master_free_list(HeapRegion* hr) {
1044     return _hrm.is_free(hr);
1045   }
1046 #endif // ASSERT
1047 
1048   inline void old_set_add(HeapRegion* hr);
1049   inline void old_set_remove(HeapRegion* hr);
1050 
1051   size_t non_young_capacity_bytes() {
1052     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1053   }
1054 
1055   // Determine whether the given region is one that we are using as an
1056   // old GC alloc region.
1057   bool is_old_gc_alloc_region(HeapRegion* hr);
1058 
1059   // Perform a collection of the heap; intended for use in implementing
1060   // "System.gc".  This probably implies as full a collection as the
1061   // "CollectedHeap" supports.
1062   virtual void collect(GCCause::Cause cause);
1063 
1064   // True iff an evacuation has failed in the most-recent collection.
1065   bool evacuation_failed() { return _evacuation_failed; }
1066 
1067   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1068   void prepend_to_freelist(FreeRegionList* list);
1069   void decrement_summary_bytes(size_t bytes);
1070 
1071   virtual bool is_in(const void* p) const;
1072 #ifdef ASSERT
1073   // Returns whether p is in one of the available areas of the heap. Slow but
1074   // extensive version.
1075   bool is_in_exact(const void* p) const;
1076 #endif
1077 
1078   // Return "TRUE" iff the given object address is within the collection
1079   // set. Assumes that the reference points into the heap.
1080   inline bool is_in_cset(const HeapRegion *hr);
1081   inline bool is_in_cset(oop obj);
1082   inline bool is_in_cset(HeapWord* addr);
1083 
1084   inline bool is_in_cset_or_humongous(const oop obj);
1085 
1086  private:
1087   // This array is used for a quick test on whether a reference points into
1088   // the collection set or not. Each of the array's elements denotes whether the
1089   // corresponding region is in the collection set or not.
1090   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1091 
1092  public:
1093 
1094   inline InCSetState in_cset_state(const oop obj);
1095 
1096   // Return "TRUE" iff the given object address is in the reserved
1097   // region of g1.
1098   bool is_in_g1_reserved(const void* p) const {
1099     return _hrm.reserved().contains(p);
1100   }
1101 
1102   // Returns a MemRegion that corresponds to the space that has been
1103   // reserved for the heap
1104   MemRegion g1_reserved() const {
1105     return _hrm.reserved();
1106   }
1107 
1108   virtual bool is_in_closed_subset(const void* p) const;
1109 
1110   G1HotCardCache* g1_hot_card_cache() const { return _hot_card_cache; }
1111 
1112   G1CardTable* card_table() const {
1113     return _card_table;
1114   }
1115 
1116   // Iteration functions.
1117 
1118   // Iterate over all objects, calling "cl.do_object" on each.
1119   virtual void object_iterate(ObjectClosure* cl);
1120 
1121   virtual void safe_object_iterate(ObjectClosure* cl) {
1122     object_iterate(cl);
1123   }
1124 
1125   // Iterate over heap regions, in address order, terminating the
1126   // iteration early if the "do_heap_region" method returns "true".
1127   void heap_region_iterate(HeapRegionClosure* blk) const;
1128 
1129   // Return the region with the given index. It assumes the index is valid.
1130   inline HeapRegion* region_at(uint index) const;
1131 
1132   // Return the next region (by index) that is part of the same
1133   // humongous object that hr is part of.
1134   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1135 
1136   // Calculate the region index of the given address. Given address must be
1137   // within the heap.
1138   inline uint addr_to_region(HeapWord* addr) const;
1139 
1140   inline HeapWord* bottom_addr_for_region(uint index) const;
1141 
1142   // Two functions to iterate over the heap regions in parallel. Threads
1143   // compete using the HeapRegionClaimer to claim the regions before
1144   // applying the closure on them.
1145   // The _from_worker_offset version uses the HeapRegionClaimer and
1146   // the worker id to calculate a start offset to prevent all workers to
1147   // start from the point.
1148   void heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1149                                                   HeapRegionClaimer* hrclaimer,
1150                                                   uint worker_id) const;
1151 
1152   void heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1153                                           HeapRegionClaimer* hrclaimer) const;
1154 
1155   // Iterate over the regions (if any) in the current collection set.
1156   void collection_set_iterate(HeapRegionClosure* blk);
1157 
1158   // Iterate over the regions (if any) in the current collection set. Starts the
1159   // iteration over the entire collection set so that the start regions of a given
1160   // worker id over the set active_workers are evenly spread across the set of
1161   // collection set regions.
1162   void collection_set_iterate_from(HeapRegionClosure *blk, uint worker_id);
1163 
1164   // Returns the HeapRegion that contains addr. addr must not be NULL.
1165   template <class T>
1166   inline HeapRegion* heap_region_containing(const T addr) const;
1167 
1168   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1169   // each address in the (reserved) heap is a member of exactly
1170   // one block.  The defining characteristic of a block is that it is
1171   // possible to find its size, and thus to progress forward to the next
1172   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1173   // represent Java objects, or they might be free blocks in a
1174   // free-list-based heap (or subheap), as long as the two kinds are
1175   // distinguishable and the size of each is determinable.
1176 
1177   // Returns the address of the start of the "block" that contains the
1178   // address "addr".  We say "blocks" instead of "object" since some heaps
1179   // may not pack objects densely; a chunk may either be an object or a
1180   // non-object.
1181   virtual HeapWord* block_start(const void* addr) const;
1182 
1183   // Requires "addr" to be the start of a chunk, and returns its size.
1184   // "addr + size" is required to be the start of a new chunk, or the end
1185   // of the active area of the heap.
1186   virtual size_t block_size(const HeapWord* addr) const;
1187 
1188   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1189   // the block is an object.
1190   virtual bool block_is_obj(const HeapWord* addr) const;
1191 
1192   // Section on thread-local allocation buffers (TLABs)
1193   // See CollectedHeap for semantics.
1194 
1195   bool supports_tlab_allocation() const;
1196   size_t tlab_capacity(Thread* ignored) const;
1197   size_t tlab_used(Thread* ignored) const;
1198   size_t max_tlab_size() const;
1199   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1200 
1201   inline bool is_in_young(const oop obj);
1202 
1203   // Returns "true" iff the given word_size is "very large".
1204   static bool is_humongous(size_t word_size) {
1205     // Note this has to be strictly greater-than as the TLABs
1206     // are capped at the humongous threshold and we want to
1207     // ensure that we don't try to allocate a TLAB as
1208     // humongous and that we don't allocate a humongous
1209     // object in a TLAB.
1210     return word_size > _humongous_object_threshold_in_words;
1211   }
1212 
1213   // Returns the humongous threshold for a specific region size
1214   static size_t humongous_threshold_for(size_t region_size) {
1215     return (region_size / 2);
1216   }
1217 
1218   // Returns the number of regions the humongous object of the given word size
1219   // requires.
1220   static size_t humongous_obj_size_in_regions(size_t word_size);
1221 
1222   // Print the maximum heap capacity.
1223   virtual size_t max_capacity() const;
1224 
1225   virtual jlong millis_since_last_gc();
1226 
1227 
1228   // Convenience function to be used in situations where the heap type can be
1229   // asserted to be this type.
1230   static G1CollectedHeap* heap();
1231 
1232   void set_region_short_lived_locked(HeapRegion* hr);
1233   // add appropriate methods for any other surv rate groups
1234 
1235   const G1SurvivorRegions* survivor() const { return &_survivor; }
1236 
1237   uint survivor_regions_count() const {
1238     return _survivor.length();
1239   }
1240 
1241   uint eden_regions_count() const {
1242     return _eden.length();
1243   }
1244 
1245   uint young_regions_count() const {
1246     return _eden.length() + _survivor.length();
1247   }
1248 
1249   uint old_regions_count() const { return _old_set.length(); }
1250 
1251   uint humongous_regions_count() const { return _humongous_set.length(); }
1252 
1253 #ifdef ASSERT
1254   bool check_young_list_empty();
1255 #endif
1256 
1257   // *** Stuff related to concurrent marking.  It's not clear to me that so
1258   // many of these need to be public.
1259 
1260   // The functions below are helper functions that a subclass of
1261   // "CollectedHeap" can use in the implementation of its virtual
1262   // functions.
1263   // This performs a concurrent marking of the live objects in a
1264   // bitmap off to the side.
1265   void do_concurrent_mark();
1266 
1267   bool is_marked_next(oop obj) const;
1268 
1269   // Determine if an object is dead, given the object and also
1270   // the region to which the object belongs. An object is dead
1271   // iff a) it was not allocated since the last mark, b) it
1272   // is not marked, and c) it is not in an archive region.
1273   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1274     return
1275       hr->is_obj_dead(obj, _cm->prev_mark_bitmap()) &&
1276       !hr->is_archive();
1277   }
1278 
1279   // This function returns true when an object has been
1280   // around since the previous marking and hasn't yet
1281   // been marked during this marking, and is not in an archive region.
1282   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1283     return
1284       !hr->obj_allocated_since_next_marking(obj) &&
1285       !is_marked_next(obj) &&
1286       !hr->is_archive();
1287   }
1288 
1289   // Determine if an object is dead, given only the object itself.
1290   // This will find the region to which the object belongs and
1291   // then call the region version of the same function.
1292 
1293   // Added if it is NULL it isn't dead.
1294 
1295   inline bool is_obj_dead(const oop obj) const;
1296 
1297   inline bool is_obj_ill(const oop obj) const;
1298 
1299   inline bool is_obj_dead_full(const oop obj, const HeapRegion* hr) const;
1300   inline bool is_obj_dead_full(const oop obj) const;
1301 
1302   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1303 
1304   // Refinement
1305 
1306   G1ConcurrentRefine* concurrent_refine() const { return _cr; }
1307 
1308   // Optimized nmethod scanning support routines
1309 
1310   // Is an oop scavengeable
1311   virtual bool is_scavengable(oop obj);
1312 
1313   // Register the given nmethod with the G1 heap.
1314   virtual void register_nmethod(nmethod* nm);
1315 
1316   // Unregister the given nmethod from the G1 heap.
1317   virtual void unregister_nmethod(nmethod* nm);
1318 
1319   // Free up superfluous code root memory.
1320   void purge_code_root_memory();
1321 
1322   // Rebuild the strong code root lists for each region
1323   // after a full GC.
1324   void rebuild_strong_code_roots();
1325 
1326   // Partial cleaning used when class unloading is disabled.
1327   // Let the caller choose what structures to clean out:
1328   // - StringTable
1329   // - SymbolTable
1330   // - StringDeduplication structures
1331   void partial_cleaning(BoolObjectClosure* is_alive, bool unlink_strings, bool unlink_symbols, bool unlink_string_dedup);
1332 
1333   // Complete cleaning used when class unloading is enabled.
1334   // Cleans out all structures handled by partial_cleaning and also the CodeCache.
1335   void complete_cleaning(BoolObjectClosure* is_alive, bool class_unloading_occurred);
1336 
1337   // Redirty logged cards in the refinement queue.
1338   void redirty_logged_cards();
1339   // Verification
1340 
1341   // Perform any cleanup actions necessary before allowing a verification.
1342   virtual void prepare_for_verify();
1343 
1344   // Perform verification.
1345 
1346   // vo == UsePrevMarking -> use "prev" marking information,
1347   // vo == UseNextMarking -> use "next" marking information
1348   // vo == UseFullMarking -> use "next" marking bitmap but no TAMS
1349   //
1350   // NOTE: Only the "prev" marking information is guaranteed to be
1351   // consistent most of the time, so most calls to this should use
1352   // vo == UsePrevMarking.
1353   // Currently, there is only one case where this is called with
1354   // vo == UseNextMarking, which is to verify the "next" marking
1355   // information at the end of remark.
1356   // Currently there is only one place where this is called with
1357   // vo == UseFullMarking, which is to verify the marking during a
1358   // full GC.
1359   void verify(VerifyOption vo);
1360 
1361   // WhiteBox testing support.
1362   virtual bool supports_concurrent_phase_control() const;
1363   virtual const char* const* concurrent_phases() const;
1364   virtual bool request_concurrent_phase(const char* phase);
1365 
1366   // The methods below are here for convenience and dispatch the
1367   // appropriate method depending on value of the given VerifyOption
1368   // parameter. The values for that parameter, and their meanings,
1369   // are the same as those above.
1370 
1371   bool is_obj_dead_cond(const oop obj,
1372                         const HeapRegion* hr,
1373                         const VerifyOption vo) const;
1374 
1375   bool is_obj_dead_cond(const oop obj,
1376                         const VerifyOption vo) const;
1377 
1378   G1HeapSummary create_g1_heap_summary();
1379   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1380 
1381   // Printing
1382 private:
1383   void print_heap_regions() const;
1384   void print_regions_on(outputStream* st) const;
1385 
1386 public:
1387   virtual void print_on(outputStream* st) const;
1388   virtual void print_extended_on(outputStream* st) const;
1389   virtual void print_on_error(outputStream* st) const;
1390 
1391   virtual void print_gc_threads_on(outputStream* st) const;
1392   virtual void gc_threads_do(ThreadClosure* tc) const;
1393 
1394   // Override
1395   void print_tracing_info() const;
1396 
1397   // The following two methods are helpful for debugging RSet issues.
1398   void print_cset_rsets() PRODUCT_RETURN;
1399   void print_all_rsets() PRODUCT_RETURN;
1400 
1401 public:
1402   size_t pending_card_num();
1403 
1404 private:
1405   size_t _max_heap_capacity;
1406 };
1407 
1408 class G1ParEvacuateFollowersClosure : public VoidClosure {
1409 private:
1410   double _start_term;
1411   double _term_time;
1412   size_t _term_attempts;
1413 
1414   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1415   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1416 protected:
1417   G1CollectedHeap*              _g1h;
1418   G1ParScanThreadState*         _par_scan_state;
1419   RefToScanQueueSet*            _queues;
1420   ParallelTaskTerminator*       _terminator;
1421 
1422   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1423   RefToScanQueueSet*      queues()         { return _queues; }
1424   ParallelTaskTerminator* terminator()     { return _terminator; }
1425 
1426 public:
1427   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1428                                 G1ParScanThreadState* par_scan_state,
1429                                 RefToScanQueueSet* queues,
1430                                 ParallelTaskTerminator* terminator)
1431     : _g1h(g1h), _par_scan_state(par_scan_state),
1432       _queues(queues), _terminator(terminator),
1433       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1434 
1435   void do_void();
1436 
1437   double term_time() const { return _term_time; }
1438   size_t term_attempts() const { return _term_attempts; }
1439 
1440 private:
1441   inline bool offer_termination();
1442 };
1443 
1444 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP