1 /*
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   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.
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   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).
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1Allocator.hpp"
  30 #include "gc_implementation/g1/concurrentMark.hpp"
  31 #include "gc_implementation/g1/evacuationInfo.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.hpp"
  33 #include "gc_implementation/g1/g1BiasedArray.hpp"
  34 #include "gc_implementation/g1/g1HRPrinter.hpp"
  35 #include "gc_implementation/g1/g1InCSetState.hpp"
  36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc_implementation/g1/g1YCTypes.hpp"
  39 #include "gc_implementation/g1/heapRegionManager.hpp"
  40 #include "gc_implementation/g1/heapRegionSet.hpp"
  41 #include "gc_implementation/shared/hSpaceCounters.hpp"
  42 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  43 #include "memory/barrierSet.hpp"
  44 #include "memory/memRegion.hpp"
  45 #include "memory/sharedHeap.hpp"
  46 #include "utilities/stack.hpp"
  47 
  48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  49 // It uses the "Garbage First" heap organization and algorithm, which
  50 // may combine concurrent marking with parallel, incremental compaction of
  51 // heap subsets that will yield large amounts of garbage.
  52 
  53 // Forward declarations
  54 class HeapRegion;
  55 class HRRSCleanupTask;
  56 class GenerationSpec;
  57 class OopsInHeapRegionClosure;
  58 class G1KlassScanClosure;
  59 class G1ParScanThreadState;
  60 class ObjectClosure;
  61 class SpaceClosure;
  62 class CompactibleSpaceClosure;
  63 class Space;
  64 class G1CollectorPolicy;
  65 class GenRemSet;
  66 class G1RemSet;
  67 class HeapRegionRemSetIterator;
  68 class ConcurrentMark;
  69 class ConcurrentMarkThread;
  70 class ConcurrentG1Refine;
  71 class ConcurrentGCTimer;
  72 class GenerationCounters;
  73 class STWGCTimer;
  74 class G1NewTracer;
  75 class G1OldTracer;
  76 class EvacuationFailedInfo;
  77 class nmethod;
  78 class Ticks;
  79 class FlexibleWorkGang;
  80 
  81 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  82 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  83 
  84 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  85 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  86 
  87 class YoungList : public CHeapObj<mtGC> {
  88 private:
  89   G1CollectedHeap* _g1h;
  90 
  91   HeapRegion* _head;
  92 
  93   HeapRegion* _survivor_head;
  94   HeapRegion* _survivor_tail;
  95 
  96   HeapRegion* _curr;
  97 
  98   uint        _length;
  99   uint        _survivor_length;
 100 
 101   size_t      _last_sampled_rs_lengths;
 102   size_t      _sampled_rs_lengths;
 103 
 104   void         empty_list(HeapRegion* list);
 105 
 106 public:
 107   YoungList(G1CollectedHeap* g1h);
 108 
 109   void         push_region(HeapRegion* hr);
 110   void         add_survivor_region(HeapRegion* hr);
 111 
 112   void         empty_list();
 113   bool         is_empty() { return _length == 0; }
 114   uint         length() { return _length; }
 115   uint         eden_length() { return length() - survivor_length(); }
 116   uint         survivor_length() { return _survivor_length; }
 117 
 118   // Currently we do not keep track of the used byte sum for the
 119   // young list and the survivors and it'd be quite a lot of work to
 120   // do so. When we'll eventually replace the young list with
 121   // instances of HeapRegionLinkedList we'll get that for free. So,
 122   // we'll report the more accurate information then.
 123   size_t       eden_used_bytes() {
 124     assert(length() >= survivor_length(), "invariant");
 125     return (size_t) eden_length() * HeapRegion::GrainBytes;
 126   }
 127   size_t       survivor_used_bytes() {
 128     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 129   }
 130 
 131   void rs_length_sampling_init();
 132   bool rs_length_sampling_more();
 133   void rs_length_sampling_next();
 134 
 135   void reset_sampled_info() {
 136     _last_sampled_rs_lengths =   0;
 137   }
 138   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 139 
 140   // for development purposes
 141   void reset_auxilary_lists();
 142   void clear() { _head = NULL; _length = 0; }
 143 
 144   void clear_survivors() {
 145     _survivor_head    = NULL;
 146     _survivor_tail    = NULL;
 147     _survivor_length  = 0;
 148   }
 149 
 150   HeapRegion* first_region() { return _head; }
 151   HeapRegion* first_survivor_region() { return _survivor_head; }
 152   HeapRegion* last_survivor_region() { return _survivor_tail; }
 153 
 154   // debugging
 155   bool          check_list_well_formed();
 156   bool          check_list_empty(bool check_sample = true);
 157   void          print();
 158 };
 159 
 160 // The G1 STW is alive closure.
 161 // An instance is embedded into the G1CH and used as the
 162 // (optional) _is_alive_non_header closure in the STW
 163 // reference processor. It is also extensively used during
 164 // reference processing during STW evacuation pauses.
 165 class G1STWIsAliveClosure: public BoolObjectClosure {
 166   G1CollectedHeap* _g1;
 167 public:
 168   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 169   bool do_object_b(oop p);
 170 };
 171 
 172 class RefineCardTableEntryClosure;
 173 
 174 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 175  private:
 176   void reset_from_card_cache(uint start_idx, size_t num_regions);
 177  public:
 178   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 179 };
 180 
 181 class G1CollectedHeap : public SharedHeap {
 182   friend class VM_CollectForMetadataAllocation;
 183   friend class VM_G1CollectForAllocation;
 184   friend class VM_G1CollectFull;
 185   friend class VM_G1IncCollectionPause;
 186   friend class VMStructs;
 187   friend class MutatorAllocRegion;
 188   friend class SurvivorGCAllocRegion;
 189   friend class OldGCAllocRegion;
 190   friend class G1Allocator;
 191 
 192   // Closures used in implementation.
 193   friend class G1ParScanThreadState;
 194   friend class G1ParTask;
 195   friend class G1ParGCAllocator;
 196   friend class G1PrepareCompactClosure;
 197 
 198   // Other related classes.
 199   friend class HeapRegionClaimer;
 200 
 201   // Testing classes.
 202   friend class G1CheckCSetFastTableClosure;
 203 
 204 private:
 205   // The one and only G1CollectedHeap, so static functions can find it.
 206   static G1CollectedHeap* _g1h;
 207 
 208   FlexibleWorkGang* _workers;
 209 
 210   static size_t _humongous_object_threshold_in_words;
 211 
 212   // The secondary free list which contains regions that have been
 213   // freed up during the cleanup process. This will be appended to
 214   // the master free list when appropriate.
 215   FreeRegionList _secondary_free_list;
 216 
 217   // It keeps track of the old regions.
 218   HeapRegionSet _old_set;
 219 
 220   // It keeps track of the humongous regions.
 221   HeapRegionSet _humongous_set;
 222 
 223   void clear_humongous_is_live_table();
 224   void eagerly_reclaim_humongous_regions();
 225 
 226   // The number of regions we could create by expansion.
 227   uint _expansion_regions;
 228 
 229   // The block offset table for the G1 heap.
 230   G1BlockOffsetSharedArray* _bot_shared;
 231 
 232   // Tears down the region sets / lists so that they are empty and the
 233   // regions on the heap do not belong to a region set / list. The
 234   // only exception is the humongous set which we leave unaltered. If
 235   // free_list_only is true, it will only tear down the master free
 236   // list. It is called before a Full GC (free_list_only == false) or
 237   // before heap shrinking (free_list_only == true).
 238   void tear_down_region_sets(bool free_list_only);
 239 
 240   // Rebuilds the region sets / lists so that they are repopulated to
 241   // reflect the contents of the heap. The only exception is the
 242   // humongous set which was not torn down in the first place. If
 243   // free_list_only is true, it will only rebuild the master free
 244   // list. It is called after a Full GC (free_list_only == false) or
 245   // after heap shrinking (free_list_only == true).
 246   void rebuild_region_sets(bool free_list_only);
 247 
 248   // Callback for region mapping changed events.
 249   G1RegionMappingChangedListener _listener;
 250 
 251   // The sequence of all heap regions in the heap.
 252   HeapRegionManager _hrm;
 253 
 254   // Class that handles the different kinds of allocations.
 255   G1Allocator* _allocator;
 256 
 257   // Statistics for each allocation context
 258   AllocationContextStats _allocation_context_stats;
 259 
 260   // PLAB sizing policy for survivors.
 261   PLABStats _survivor_plab_stats;
 262 
 263   // PLAB sizing policy for tenured objects.
 264   PLABStats _old_plab_stats;
 265 
 266   // It specifies whether we should attempt to expand the heap after a
 267   // region allocation failure. If heap expansion fails we set this to
 268   // false so that we don't re-attempt the heap expansion (it's likely
 269   // that subsequent expansion attempts will also fail if one fails).
 270   // Currently, it is only consulted during GC and it's reset at the
 271   // start of each GC.
 272   bool _expand_heap_after_alloc_failure;
 273 
 274   // It resets the mutator alloc region before new allocations can take place.
 275   void init_mutator_alloc_region();
 276 
 277   // It releases the mutator alloc region.
 278   void release_mutator_alloc_region();
 279 
 280   // It initializes the GC alloc regions at the start of a GC.
 281   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 282 
 283   // It releases the GC alloc regions at the end of a GC.
 284   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 285 
 286   // It does any cleanup that needs to be done on the GC alloc regions
 287   // before a Full GC.
 288   void abandon_gc_alloc_regions();
 289 
 290   // Helper for monitoring and management support.
 291   G1MonitoringSupport* _g1mm;
 292 
 293   // Records whether the region at the given index is kept live by roots or
 294   // references from the young generation.
 295   class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
 296    protected:
 297     bool default_value() const { return false; }
 298    public:
 299     void clear() { G1BiasedMappedArray<bool>::clear(); }
 300     void set_live(uint region) {
 301       set_by_index(region, true);
 302     }
 303     bool is_live(uint region) {
 304       return get_by_index(region);
 305     }
 306   };
 307 
 308   HumongousIsLiveBiasedMappedArray _humongous_is_live;
 309   // Stores whether during humongous object registration we found candidate regions.
 310   // If not, we can skip a few steps.
 311   bool _has_humongous_reclaim_candidates;
 312 
 313   volatile unsigned _gc_time_stamp;
 314 
 315   size_t* _surviving_young_words;
 316 
 317   G1HRPrinter _hr_printer;
 318 
 319   void setup_surviving_young_words();
 320   void update_surviving_young_words(size_t* surv_young_words);
 321   void cleanup_surviving_young_words();
 322 
 323   // It decides whether an explicit GC should start a concurrent cycle
 324   // instead of doing a STW GC. Currently, a concurrent cycle is
 325   // explicitly started if:
 326   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 327   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 328   // (c) cause == _g1_humongous_allocation
 329   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 330 
 331   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 332   // concurrent cycles) we have started.
 333   volatile uint _old_marking_cycles_started;
 334 
 335   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 336   // concurrent cycles) we have completed.
 337   volatile uint _old_marking_cycles_completed;
 338 
 339   bool _concurrent_cycle_started;
 340   bool _heap_summary_sent;
 341 
 342   // This is a non-product method that is helpful for testing. It is
 343   // called at the end of a GC and artificially expands the heap by
 344   // allocating a number of dead regions. This way we can induce very
 345   // frequent marking cycles and stress the cleanup / concurrent
 346   // cleanup code more (as all the regions that will be allocated by
 347   // this method will be found dead by the marking cycle).
 348   void allocate_dummy_regions() PRODUCT_RETURN;
 349 
 350   // Clear RSets after a compaction. It also resets the GC time stamps.
 351   void clear_rsets_post_compaction();
 352 
 353   // If the HR printer is active, dump the state of the regions in the
 354   // heap after a compaction.
 355   void print_hrm_post_compaction();
 356 
 357   double verify(bool guard, const char* msg);
 358   void verify_before_gc();
 359   void verify_after_gc();
 360 
 361   void log_gc_header();
 362   void log_gc_footer(double pause_time_sec);
 363 
 364   // These are macros so that, if the assert fires, we get the correct
 365   // line number, file, etc.
 366 
 367 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 368   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 369           (_extra_message_),                                                  \
 370           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 371           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 372           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 373 
 374 #define assert_heap_locked()                                                  \
 375   do {                                                                        \
 376     assert(Heap_lock->owned_by_self(),                                        \
 377            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 378   } while (0)
 379 
 380 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 381   do {                                                                        \
 382     assert(Heap_lock->owned_by_self() ||                                      \
 383            (SafepointSynchronize::is_at_safepoint() &&                        \
 384              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 385            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 386                                         "should be at a safepoint"));         \
 387   } while (0)
 388 
 389 #define assert_heap_locked_and_not_at_safepoint()                             \
 390   do {                                                                        \
 391     assert(Heap_lock->owned_by_self() &&                                      \
 392                                     !SafepointSynchronize::is_at_safepoint(), \
 393           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 394                                        "should not be at a safepoint"));      \
 395   } while (0)
 396 
 397 #define assert_heap_not_locked()                                              \
 398   do {                                                                        \
 399     assert(!Heap_lock->owned_by_self(),                                       \
 400         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 401   } while (0)
 402 
 403 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 404   do {                                                                        \
 405     assert(!Heap_lock->owned_by_self() &&                                     \
 406                                     !SafepointSynchronize::is_at_safepoint(), \
 407       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 408                                    "should not be at a safepoint"));          \
 409   } while (0)
 410 
 411 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 412   do {                                                                        \
 413     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 414               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 415            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 416   } while (0)
 417 
 418 #define assert_not_at_safepoint()                                             \
 419   do {                                                                        \
 420     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 421            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 422   } while (0)
 423 
 424 protected:
 425 
 426   // The young region list.
 427   YoungList*  _young_list;
 428 
 429   // The current policy object for the collector.
 430   G1CollectorPolicy* _g1_policy;
 431 
 432   // This is the second level of trying to allocate a new region. If
 433   // new_region() didn't find a region on the free_list, this call will
 434   // check whether there's anything available on the
 435   // secondary_free_list and/or wait for more regions to appear on
 436   // that list, if _free_regions_coming is set.
 437   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 438 
 439   // Try to allocate a single non-humongous HeapRegion sufficient for
 440   // an allocation of the given word_size. If do_expand is true,
 441   // attempt to expand the heap if necessary to satisfy the allocation
 442   // request. If the region is to be used as an old region or for a
 443   // humongous object, set is_old to true. If not, to false.
 444   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 445 
 446   // Initialize a contiguous set of free regions of length num_regions
 447   // and starting at index first so that they appear as a single
 448   // humongous region.
 449   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 450                                                       uint num_regions,
 451                                                       size_t word_size,
 452                                                       AllocationContext_t context);
 453 
 454   // Attempt to allocate a humongous object of the given size. Return
 455   // NULL if unsuccessful.
 456   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 457 
 458   // The following two methods, allocate_new_tlab() and
 459   // mem_allocate(), are the two main entry points from the runtime
 460   // into the G1's allocation routines. They have the following
 461   // assumptions:
 462   //
 463   // * They should both be called outside safepoints.
 464   //
 465   // * They should both be called without holding the Heap_lock.
 466   //
 467   // * All allocation requests for new TLABs should go to
 468   //   allocate_new_tlab().
 469   //
 470   // * All non-TLAB allocation requests should go to mem_allocate().
 471   //
 472   // * If either call cannot satisfy the allocation request using the
 473   //   current allocating region, they will try to get a new one. If
 474   //   this fails, they will attempt to do an evacuation pause and
 475   //   retry the allocation.
 476   //
 477   // * If all allocation attempts fail, even after trying to schedule
 478   //   an evacuation pause, allocate_new_tlab() will return NULL,
 479   //   whereas mem_allocate() will attempt a heap expansion and/or
 480   //   schedule a Full GC.
 481   //
 482   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 483   //   should never be called with word_size being humongous. All
 484   //   humongous allocation requests should go to mem_allocate() which
 485   //   will satisfy them with a special path.
 486 
 487   virtual HeapWord* allocate_new_tlab(size_t word_size);
 488 
 489   virtual HeapWord* mem_allocate(size_t word_size,
 490                                  bool*  gc_overhead_limit_was_exceeded);
 491 
 492   // The following three methods take a gc_count_before_ret
 493   // parameter which is used to return the GC count if the method
 494   // returns NULL. Given that we are required to read the GC count
 495   // while holding the Heap_lock, and these paths will take the
 496   // Heap_lock at some point, it's easier to get them to read the GC
 497   // count while holding the Heap_lock before they return NULL instead
 498   // of the caller (namely: mem_allocate()) having to also take the
 499   // Heap_lock just to read the GC count.
 500 
 501   // First-level mutator allocation attempt: try to allocate out of
 502   // the mutator alloc region without taking the Heap_lock. This
 503   // should only be used for non-humongous allocations.
 504   inline HeapWord* attempt_allocation(size_t word_size,
 505                                       uint* gc_count_before_ret,
 506                                       uint* gclocker_retry_count_ret);
 507 
 508   // Second-level mutator allocation attempt: take the Heap_lock and
 509   // retry the allocation attempt, potentially scheduling a GC
 510   // pause. This should only be used for non-humongous allocations.
 511   HeapWord* attempt_allocation_slow(size_t word_size,
 512                                     AllocationContext_t context,
 513                                     uint* gc_count_before_ret,
 514                                     uint* gclocker_retry_count_ret);
 515 
 516   // Takes the Heap_lock and attempts a humongous allocation. It can
 517   // potentially schedule a GC pause.
 518   HeapWord* attempt_allocation_humongous(size_t word_size,
 519                                          uint* gc_count_before_ret,
 520                                          uint* gclocker_retry_count_ret);
 521 
 522   // Allocation attempt that should be called during safepoints (e.g.,
 523   // at the end of a successful GC). expect_null_mutator_alloc_region
 524   // specifies whether the mutator alloc region is expected to be NULL
 525   // or not.
 526   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 527                                             AllocationContext_t context,
 528                                             bool expect_null_mutator_alloc_region);
 529 
 530   // It dirties the cards that cover the block so that so that the post
 531   // write barrier never queues anything when updating objects on this
 532   // block. It is assumed (and in fact we assert) that the block
 533   // belongs to a young region.
 534   inline void dirty_young_block(HeapWord* start, size_t word_size);
 535 
 536   // Allocate blocks during garbage collection. Will ensure an
 537   // allocation region, either by picking one or expanding the
 538   // heap, and then allocate a block of the given size. The block
 539   // may not be a humongous - it must fit into a single heap region.
 540   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 541                                           size_t word_size,
 542                                           AllocationContext_t context);
 543   // Ensure that no further allocations can happen in "r", bearing in mind
 544   // that parallel threads might be attempting allocations.
 545   void par_allocate_remaining_space(HeapRegion* r);
 546 
 547   // Allocation attempt during GC for a survivor object / PLAB.
 548   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 549                                                AllocationContext_t context);
 550 
 551   // Allocation attempt during GC for an old object / PLAB.
 552   inline HeapWord* old_attempt_allocation(size_t word_size,
 553                                           AllocationContext_t context);
 554 
 555   // These methods are the "callbacks" from the G1AllocRegion class.
 556 
 557   // For mutator alloc regions.
 558   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 559   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 560                                    size_t allocated_bytes);
 561 
 562   // For GC alloc regions.
 563   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 564                                   InCSetState dest);
 565   void retire_gc_alloc_region(HeapRegion* alloc_region,
 566                               size_t allocated_bytes, InCSetState dest);
 567 
 568   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 569   //   inspection request and should collect the entire heap
 570   // - if clear_all_soft_refs is true, all soft references should be
 571   //   cleared during the GC
 572   // - if explicit_gc is false, word_size describes the allocation that
 573   //   the GC should attempt (at least) to satisfy
 574   // - it returns false if it is unable to do the collection due to the
 575   //   GC locker being active, true otherwise
 576   bool do_collection(bool explicit_gc,
 577                      bool clear_all_soft_refs,
 578                      size_t word_size);
 579 
 580   // Callback from VM_G1CollectFull operation.
 581   // Perform a full collection.
 582   virtual void do_full_collection(bool clear_all_soft_refs);
 583 
 584   // Resize the heap if necessary after a full collection.  If this is
 585   // after a collect-for allocation, "word_size" is the allocation size,
 586   // and will be considered part of the used portion of the heap.
 587   void resize_if_necessary_after_full_collection(size_t word_size);
 588 
 589   // Callback from VM_G1CollectForAllocation operation.
 590   // This function does everything necessary/possible to satisfy a
 591   // failed allocation request (including collection, expansion, etc.)
 592   HeapWord* satisfy_failed_allocation(size_t word_size,
 593                                       AllocationContext_t context,
 594                                       bool* succeeded);
 595 
 596   // Attempting to expand the heap sufficiently
 597   // to support an allocation of the given "word_size".  If
 598   // successful, perform the allocation and return the address of the
 599   // allocated block, or else "NULL".
 600   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 601 
 602   // Process any reference objects discovered during
 603   // an incremental evacuation pause.
 604   void process_discovered_references(uint no_of_gc_workers);
 605 
 606   // Enqueue any remaining discovered references
 607   // after processing.
 608   void enqueue_discovered_references(uint no_of_gc_workers);
 609 
 610 public:
 611   FlexibleWorkGang* workers() const { return _workers; }
 612 
 613   G1Allocator* allocator() {
 614     return _allocator;
 615   }
 616 
 617   G1MonitoringSupport* g1mm() {
 618     assert(_g1mm != NULL, "should have been initialized");
 619     return _g1mm;
 620   }
 621 
 622   // Expand the garbage-first heap by at least the given size (in bytes!).
 623   // Returns true if the heap was expanded by the requested amount;
 624   // false otherwise.
 625   // (Rounds up to a HeapRegion boundary.)
 626   bool expand(size_t expand_bytes);
 627 
 628   // Returns the PLAB statistics for a given destination.
 629   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 630 
 631   // Determines PLAB size for a given destination.
 632   inline size_t desired_plab_sz(InCSetState dest);
 633 
 634   inline AllocationContextStats& allocation_context_stats();
 635 
 636   // Do anything common to GC's.
 637   void gc_prologue(bool full);
 638   void gc_epilogue(bool full);
 639 
 640   inline void set_humongous_is_live(oop obj);
 641 
 642   bool humongous_is_live(uint region) {
 643     return _humongous_is_live.is_live(region);
 644   }
 645 
 646   // Returns whether the given region (which must be a humongous (start) region)
 647   // is to be considered conservatively live regardless of any other conditions.
 648   bool humongous_region_is_always_live(uint index);
 649   // Returns whether the given region (which must be a humongous (start) region)
 650   // is considered a candidate for eager reclamation.
 651   bool humongous_region_is_candidate(uint index);
 652   // Register the given region to be part of the collection set.
 653   inline void register_humongous_region_with_cset(uint index);
 654   // Register regions with humongous objects (actually on the start region) in
 655   // the in_cset_fast_test table.
 656   void register_humongous_regions_with_cset();
 657   // We register a region with the fast "in collection set" test. We
 658   // simply set to true the array slot corresponding to this region.
 659   void register_young_region_with_cset(HeapRegion* r) {
 660     _in_cset_fast_test.set_in_young(r->hrm_index());
 661   }
 662   void register_old_region_with_cset(HeapRegion* r) {
 663     _in_cset_fast_test.set_in_old(r->hrm_index());
 664   }
 665   void clear_in_cset(const HeapRegion* hr) {
 666     _in_cset_fast_test.clear(hr);
 667   }
 668 
 669   void clear_cset_fast_test() {
 670     _in_cset_fast_test.clear();
 671   }
 672 
 673   // This is called at the start of either a concurrent cycle or a Full
 674   // GC to update the number of old marking cycles started.
 675   void increment_old_marking_cycles_started();
 676 
 677   // This is called at the end of either a concurrent cycle or a Full
 678   // GC to update the number of old marking cycles completed. Those two
 679   // can happen in a nested fashion, i.e., we start a concurrent
 680   // cycle, a Full GC happens half-way through it which ends first,
 681   // and then the cycle notices that a Full GC happened and ends
 682   // too. The concurrent parameter is a boolean to help us do a bit
 683   // tighter consistency checking in the method. If concurrent is
 684   // false, the caller is the inner caller in the nesting (i.e., the
 685   // Full GC). If concurrent is true, the caller is the outer caller
 686   // in this nesting (i.e., the concurrent cycle). Further nesting is
 687   // not currently supported. The end of this call also notifies
 688   // the FullGCCount_lock in case a Java thread is waiting for a full
 689   // GC to happen (e.g., it called System.gc() with
 690   // +ExplicitGCInvokesConcurrent).
 691   void increment_old_marking_cycles_completed(bool concurrent);
 692 
 693   uint old_marking_cycles_completed() {
 694     return _old_marking_cycles_completed;
 695   }
 696 
 697   void register_concurrent_cycle_start(const Ticks& start_time);
 698   void register_concurrent_cycle_end();
 699   void trace_heap_after_concurrent_cycle();
 700 
 701   G1YCType yc_type();
 702 
 703   G1HRPrinter* hr_printer() { return &_hr_printer; }
 704 
 705   // Frees a non-humongous region by initializing its contents and
 706   // adding it to the free list that's passed as a parameter (this is
 707   // usually a local list which will be appended to the master free
 708   // list later). The used bytes of freed regions are accumulated in
 709   // pre_used. If par is true, the region's RSet will not be freed
 710   // up. The assumption is that this will be done later.
 711   // The locked parameter indicates if the caller has already taken
 712   // care of proper synchronization. This may allow some optimizations.
 713   void free_region(HeapRegion* hr,
 714                    FreeRegionList* free_list,
 715                    bool par,
 716                    bool locked = false);
 717 
 718   // Frees a humongous region by collapsing it into individual regions
 719   // and calling free_region() for each of them. The freed regions
 720   // will be added to the free list that's passed as a parameter (this
 721   // is usually a local list which will be appended to the master free
 722   // list later). The used bytes of freed regions are accumulated in
 723   // pre_used. If par is true, the region's RSet will not be freed
 724   // up. The assumption is that this will be done later.
 725   void free_humongous_region(HeapRegion* hr,
 726                              FreeRegionList* free_list,
 727                              bool par);
 728 protected:
 729 
 730   // Shrink the garbage-first heap by at most the given size (in bytes!).
 731   // (Rounds down to a HeapRegion boundary.)
 732   virtual void shrink(size_t expand_bytes);
 733   void shrink_helper(size_t expand_bytes);
 734 
 735   #if TASKQUEUE_STATS
 736   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 737   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 738   void reset_taskqueue_stats();
 739   #endif // TASKQUEUE_STATS
 740 
 741   // Schedule the VM operation that will do an evacuation pause to
 742   // satisfy an allocation request of word_size. *succeeded will
 743   // return whether the VM operation was successful (it did do an
 744   // evacuation pause) or not (another thread beat us to it or the GC
 745   // locker was active). Given that we should not be holding the
 746   // Heap_lock when we enter this method, we will pass the
 747   // gc_count_before (i.e., total_collections()) as a parameter since
 748   // it has to be read while holding the Heap_lock. Currently, both
 749   // methods that call do_collection_pause() release the Heap_lock
 750   // before the call, so it's easy to read gc_count_before just before.
 751   HeapWord* do_collection_pause(size_t         word_size,
 752                                 uint           gc_count_before,
 753                                 bool*          succeeded,
 754                                 GCCause::Cause gc_cause);
 755 
 756   // The guts of the incremental collection pause, executed by the vm
 757   // thread. It returns false if it is unable to do the collection due
 758   // to the GC locker being active, true otherwise
 759   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 760 
 761   // Actually do the work of evacuating the collection set.
 762   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 763 
 764   // The g1 remembered set of the heap.
 765   G1RemSet* _g1_rem_set;
 766 
 767   // A set of cards that cover the objects for which the Rsets should be updated
 768   // concurrently after the collection.
 769   DirtyCardQueueSet _dirty_card_queue_set;
 770 
 771   // The closure used to refine a single card.
 772   RefineCardTableEntryClosure* _refine_cte_cl;
 773 
 774   // A DirtyCardQueueSet that is used to hold cards that contain
 775   // references into the current collection set. This is used to
 776   // update the remembered sets of the regions in the collection
 777   // set in the event of an evacuation failure.
 778   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 779 
 780   // After a collection pause, make the regions in the CS into free
 781   // regions.
 782   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 783 
 784   // Abandon the current collection set without recording policy
 785   // statistics or updating free lists.
 786   void abandon_collection_set(HeapRegion* cs_head);
 787 
 788   // The concurrent marker (and the thread it runs in.)
 789   ConcurrentMark* _cm;
 790   ConcurrentMarkThread* _cmThread;
 791   bool _mark_in_progress;
 792 
 793   // The concurrent refiner.
 794   ConcurrentG1Refine* _cg1r;
 795 
 796   // The parallel task queues
 797   RefToScanQueueSet *_task_queues;
 798 
 799   // True iff a evacuation has failed in the current collection.
 800   bool _evacuation_failed;
 801 
 802   EvacuationFailedInfo* _evacuation_failed_info_array;
 803 
 804   // Failed evacuations cause some logical from-space objects to have
 805   // forwarding pointers to themselves.  Reset them.
 806   void remove_self_forwarding_pointers();
 807 
 808   // Together, these store an object with a preserved mark, and its mark value.
 809   Stack<oop, mtGC>     _objs_with_preserved_marks;
 810   Stack<markOop, mtGC> _preserved_marks_of_objs;
 811 
 812   // Preserve the mark of "obj", if necessary, in preparation for its mark
 813   // word being overwritten with a self-forwarding-pointer.
 814   void preserve_mark_if_necessary(oop obj, markOop m);
 815 
 816   // The stack of evac-failure objects left to be scanned.
 817   GrowableArray<oop>*    _evac_failure_scan_stack;
 818   // The closure to apply to evac-failure objects.
 819 
 820   OopsInHeapRegionClosure* _evac_failure_closure;
 821   // Set the field above.
 822   void
 823   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 824     _evac_failure_closure = evac_failure_closure;
 825   }
 826 
 827   // Push "obj" on the scan stack.
 828   void push_on_evac_failure_scan_stack(oop obj);
 829   // Process scan stack entries until the stack is empty.
 830   void drain_evac_failure_scan_stack();
 831   // True iff an invocation of "drain_scan_stack" is in progress; to
 832   // prevent unnecessary recursion.
 833   bool _drain_in_progress;
 834 
 835   // Do any necessary initialization for evacuation-failure handling.
 836   // "cl" is the closure that will be used to process evac-failure
 837   // objects.
 838   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 839   // Do any necessary cleanup for evacuation-failure handling data
 840   // structures.
 841   void finalize_for_evac_failure();
 842 
 843   // An attempt to evacuate "obj" has failed; take necessary steps.
 844   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 845   void handle_evacuation_failure_common(oop obj, markOop m);
 846 
 847 #ifndef PRODUCT
 848   // Support for forcing evacuation failures. Analogous to
 849   // PromotionFailureALot for the other collectors.
 850 
 851   // Records whether G1EvacuationFailureALot should be in effect
 852   // for the current GC
 853   bool _evacuation_failure_alot_for_current_gc;
 854 
 855   // Used to record the GC number for interval checking when
 856   // determining whether G1EvaucationFailureALot is in effect
 857   // for the current GC.
 858   size_t _evacuation_failure_alot_gc_number;
 859 
 860   // Count of the number of evacuations between failures.
 861   volatile size_t _evacuation_failure_alot_count;
 862 
 863   // Set whether G1EvacuationFailureALot should be in effect
 864   // for the current GC (based upon the type of GC and which
 865   // command line flags are set);
 866   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 867                                                   bool during_initial_mark,
 868                                                   bool during_marking);
 869 
 870   inline void set_evacuation_failure_alot_for_current_gc();
 871 
 872   // Return true if it's time to cause an evacuation failure.
 873   inline bool evacuation_should_fail();
 874 
 875   // Reset the G1EvacuationFailureALot counters.  Should be called at
 876   // the end of an evacuation pause in which an evacuation failure occurred.
 877   inline void reset_evacuation_should_fail();
 878 #endif // !PRODUCT
 879 
 880   // ("Weak") Reference processing support.
 881   //
 882   // G1 has 2 instances of the reference processor class. One
 883   // (_ref_processor_cm) handles reference object discovery
 884   // and subsequent processing during concurrent marking cycles.
 885   //
 886   // The other (_ref_processor_stw) handles reference object
 887   // discovery and processing during full GCs and incremental
 888   // evacuation pauses.
 889   //
 890   // During an incremental pause, reference discovery will be
 891   // temporarily disabled for _ref_processor_cm and will be
 892   // enabled for _ref_processor_stw. At the end of the evacuation
 893   // pause references discovered by _ref_processor_stw will be
 894   // processed and discovery will be disabled. The previous
 895   // setting for reference object discovery for _ref_processor_cm
 896   // will be re-instated.
 897   //
 898   // At the start of marking:
 899   //  * Discovery by the CM ref processor is verified to be inactive
 900   //    and it's discovered lists are empty.
 901   //  * Discovery by the CM ref processor is then enabled.
 902   //
 903   // At the end of marking:
 904   //  * Any references on the CM ref processor's discovered
 905   //    lists are processed (possibly MT).
 906   //
 907   // At the start of full GC we:
 908   //  * Disable discovery by the CM ref processor and
 909   //    empty CM ref processor's discovered lists
 910   //    (without processing any entries).
 911   //  * Verify that the STW ref processor is inactive and it's
 912   //    discovered lists are empty.
 913   //  * Temporarily set STW ref processor discovery as single threaded.
 914   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 915   //    field.
 916   //  * Finally enable discovery by the STW ref processor.
 917   //
 918   // The STW ref processor is used to record any discovered
 919   // references during the full GC.
 920   //
 921   // At the end of a full GC we:
 922   //  * Enqueue any reference objects discovered by the STW ref processor
 923   //    that have non-live referents. This has the side-effect of
 924   //    making the STW ref processor inactive by disabling discovery.
 925   //  * Verify that the CM ref processor is still inactive
 926   //    and no references have been placed on it's discovered
 927   //    lists (also checked as a precondition during initial marking).
 928 
 929   // The (stw) reference processor...
 930   ReferenceProcessor* _ref_processor_stw;
 931 
 932   STWGCTimer* _gc_timer_stw;
 933   ConcurrentGCTimer* _gc_timer_cm;
 934 
 935   G1OldTracer* _gc_tracer_cm;
 936   G1NewTracer* _gc_tracer_stw;
 937 
 938   // During reference object discovery, the _is_alive_non_header
 939   // closure (if non-null) is applied to the referent object to
 940   // determine whether the referent is live. If so then the
 941   // reference object does not need to be 'discovered' and can
 942   // be treated as a regular oop. This has the benefit of reducing
 943   // the number of 'discovered' reference objects that need to
 944   // be processed.
 945   //
 946   // Instance of the is_alive closure for embedding into the
 947   // STW reference processor as the _is_alive_non_header field.
 948   // Supplying a value for the _is_alive_non_header field is
 949   // optional but doing so prevents unnecessary additions to
 950   // the discovered lists during reference discovery.
 951   G1STWIsAliveClosure _is_alive_closure_stw;
 952 
 953   // The (concurrent marking) reference processor...
 954   ReferenceProcessor* _ref_processor_cm;
 955 
 956   // Instance of the concurrent mark is_alive closure for embedding
 957   // into the Concurrent Marking reference processor as the
 958   // _is_alive_non_header field. Supplying a value for the
 959   // _is_alive_non_header field is optional but doing so prevents
 960   // unnecessary additions to the discovered lists during reference
 961   // discovery.
 962   G1CMIsAliveClosure _is_alive_closure_cm;
 963 
 964   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 965   HeapRegion** _worker_cset_start_region;
 966 
 967   // Time stamp to validate the regions recorded in the cache
 968   // used by G1CollectedHeap::start_cset_region_for_worker().
 969   // The heap region entry for a given worker is valid iff
 970   // the associated time stamp value matches the current value
 971   // of G1CollectedHeap::_gc_time_stamp.
 972   uint* _worker_cset_start_region_time_stamp;
 973 
 974   volatile bool _free_regions_coming;
 975 
 976 public:
 977 
 978   void set_refine_cte_cl_concurrency(bool concurrent);
 979 
 980   RefToScanQueue *task_queue(int i) const;
 981 
 982   // A set of cards where updates happened during the GC
 983   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 984 
 985   // A DirtyCardQueueSet that is used to hold cards that contain
 986   // references into the current collection set. This is used to
 987   // update the remembered sets of the regions in the collection
 988   // set in the event of an evacuation failure.
 989   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
 990         { return _into_cset_dirty_card_queue_set; }
 991 
 992   // Create a G1CollectedHeap with the specified policy.
 993   // Must call the initialize method afterwards.
 994   // May not return if something goes wrong.
 995   G1CollectedHeap(G1CollectorPolicy* policy);
 996 
 997   // Initialize the G1CollectedHeap to have the initial and
 998   // maximum sizes and remembered and barrier sets
 999   // specified by the policy object.
1000   jint initialize();
1001 
1002   virtual void stop();
1003 
1004   // Return the (conservative) maximum heap alignment for any G1 heap
1005   static size_t conservative_max_heap_alignment();
1006 
1007   // Does operations required after initialization has been done.
1008   void post_initialize();
1009 
1010   // Initialize weak reference processing.
1011   void ref_processing_init();
1012 
1013   // Explicitly import set_par_threads into this scope
1014   using SharedHeap::set_par_threads;
1015   // Set _n_par_threads according to a policy TBD.
1016   void set_par_threads();
1017 
1018   virtual Name kind() const {
1019     return CollectedHeap::G1CollectedHeap;
1020   }
1021 
1022   // The current policy object for the collector.
1023   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1024 
1025   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1026 
1027   // Adaptive size policy.  No such thing for g1.
1028   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1029 
1030   // The rem set and barrier set.
1031   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1032 
1033   unsigned get_gc_time_stamp() {
1034     return _gc_time_stamp;
1035   }
1036 
1037   inline void reset_gc_time_stamp();
1038 
1039   void check_gc_time_stamps() PRODUCT_RETURN;
1040 
1041   inline void increment_gc_time_stamp();
1042 
1043   // Reset the given region's GC timestamp. If it's starts humongous,
1044   // also reset the GC timestamp of its corresponding
1045   // continues humongous regions too.
1046   void reset_gc_time_stamps(HeapRegion* hr);
1047 
1048   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1049                                   DirtyCardQueue* into_cset_dcq,
1050                                   bool concurrent, uint worker_i);
1051 
1052   // The shared block offset table array.
1053   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1054 
1055   // Reference Processing accessors
1056 
1057   // The STW reference processor....
1058   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1059 
1060   // The Concurrent Marking reference processor...
1061   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1062 
1063   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1064   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1065 
1066   virtual size_t capacity() const;
1067   virtual size_t used() const;
1068   // This should be called when we're not holding the heap lock. The
1069   // result might be a bit inaccurate.
1070   size_t used_unlocked() const;
1071   size_t recalculate_used() const;
1072 
1073   // These virtual functions do the actual allocation.
1074   // Some heaps may offer a contiguous region for shared non-blocking
1075   // allocation, via inlined code (by exporting the address of the top and
1076   // end fields defining the extent of the contiguous allocation region.)
1077   // But G1CollectedHeap doesn't yet support this.
1078 
1079   virtual bool is_maximal_no_gc() const {
1080     return _hrm.available() == 0;
1081   }
1082 
1083   // The current number of regions in the heap.
1084   uint num_regions() const { return _hrm.length(); }
1085 
1086   // The max number of regions in the heap.
1087   uint max_regions() const { return _hrm.max_length(); }
1088 
1089   // The number of regions that are completely free.
1090   uint num_free_regions() const { return _hrm.num_free_regions(); }
1091 
1092   MemoryUsage get_auxiliary_data_memory_usage() const {
1093     return _hrm.get_auxiliary_data_memory_usage();
1094   }
1095 
1096   // The number of regions that are not completely free.
1097   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1098 
1099   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1100   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1101   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1102   void verify_dirty_young_regions() PRODUCT_RETURN;
1103 
1104 #ifndef PRODUCT
1105   // Make sure that the given bitmap has no marked objects in the
1106   // range [from,limit). If it does, print an error message and return
1107   // false. Otherwise, just return true. bitmap_name should be "prev"
1108   // or "next".
1109   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1110                                 HeapWord* from, HeapWord* limit);
1111 
1112   // Verify that the prev / next bitmap range [tams,end) for the given
1113   // region has no marks. Return true if all is well, false if errors
1114   // are detected.
1115   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1116 #endif // PRODUCT
1117 
1118   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1119   // the given region do not have any spurious marks. If errors are
1120   // detected, print appropriate error messages and crash.
1121   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1122 
1123   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1124   // have any spurious marks. If errors are detected, print
1125   // appropriate error messages and crash.
1126   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1127 
1128   // Do sanity check on the contents of the in-cset fast test table.
1129   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1130 
1131   // verify_region_sets() performs verification over the region
1132   // lists. It will be compiled in the product code to be used when
1133   // necessary (i.e., during heap verification).
1134   void verify_region_sets();
1135 
1136   // verify_region_sets_optional() is planted in the code for
1137   // list verification in non-product builds (and it can be enabled in
1138   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1139 #if HEAP_REGION_SET_FORCE_VERIFY
1140   void verify_region_sets_optional() {
1141     verify_region_sets();
1142   }
1143 #else // HEAP_REGION_SET_FORCE_VERIFY
1144   void verify_region_sets_optional() { }
1145 #endif // HEAP_REGION_SET_FORCE_VERIFY
1146 
1147 #ifdef ASSERT
1148   bool is_on_master_free_list(HeapRegion* hr) {
1149     return _hrm.is_free(hr);
1150   }
1151 #endif // ASSERT
1152 
1153   // Wrapper for the region list operations that can be called from
1154   // methods outside this class.
1155 
1156   void secondary_free_list_add(FreeRegionList* list) {
1157     _secondary_free_list.add_ordered(list);
1158   }
1159 
1160   void append_secondary_free_list() {
1161     _hrm.insert_list_into_free_list(&_secondary_free_list);
1162   }
1163 
1164   void append_secondary_free_list_if_not_empty_with_lock() {
1165     // If the secondary free list looks empty there's no reason to
1166     // take the lock and then try to append it.
1167     if (!_secondary_free_list.is_empty()) {
1168       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1169       append_secondary_free_list();
1170     }
1171   }
1172 
1173   inline void old_set_remove(HeapRegion* hr);
1174 
1175   size_t non_young_capacity_bytes() {
1176     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1177   }
1178 
1179   void set_free_regions_coming();
1180   void reset_free_regions_coming();
1181   bool free_regions_coming() { return _free_regions_coming; }
1182   void wait_while_free_regions_coming();
1183 
1184   // Determine whether the given region is one that we are using as an
1185   // old GC alloc region.
1186   bool is_old_gc_alloc_region(HeapRegion* hr) {
1187     return _allocator->is_retained_old_region(hr);
1188   }
1189 
1190   // Perform a collection of the heap; intended for use in implementing
1191   // "System.gc".  This probably implies as full a collection as the
1192   // "CollectedHeap" supports.
1193   virtual void collect(GCCause::Cause cause);
1194 
1195   // The same as above but assume that the caller holds the Heap_lock.
1196   void collect_locked(GCCause::Cause cause);
1197 
1198   virtual bool copy_allocation_context_stats(const jint* contexts,
1199                                              jlong* totals,
1200                                              jbyte* accuracy,
1201                                              jint len);
1202 
1203   // True iff an evacuation has failed in the most-recent collection.
1204   bool evacuation_failed() { return _evacuation_failed; }
1205 
1206   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1207   void prepend_to_freelist(FreeRegionList* list);
1208   void decrement_summary_bytes(size_t bytes);
1209 
1210   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1211   virtual bool is_in(const void* p) const;
1212 #ifdef ASSERT
1213   // Returns whether p is in one of the available areas of the heap. Slow but
1214   // extensive version.
1215   bool is_in_exact(const void* p) const;
1216 #endif
1217 
1218   // Return "TRUE" iff the given object address is within the collection
1219   // set. Slow implementation.
1220   inline bool obj_in_cs(oop obj);
1221 
1222   inline bool is_in_cset(const HeapRegion *hr);
1223   inline bool is_in_cset(oop obj);
1224 
1225   inline bool is_in_cset_or_humongous(const oop obj);
1226 
1227  private:
1228   // This array is used for a quick test on whether a reference points into
1229   // the collection set or not. Each of the array's elements denotes whether the
1230   // corresponding region is in the collection set or not.
1231   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1232 
1233  public:
1234 
1235   inline InCSetState in_cset_state(const oop obj);
1236 
1237   // Return "TRUE" iff the given object address is in the reserved
1238   // region of g1.
1239   bool is_in_g1_reserved(const void* p) const {
1240     return _hrm.reserved().contains(p);
1241   }
1242 
1243   // Returns a MemRegion that corresponds to the space that has been
1244   // reserved for the heap
1245   MemRegion g1_reserved() const {
1246     return _hrm.reserved();
1247   }
1248 
1249   virtual bool is_in_closed_subset(const void* p) const;
1250 
1251   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1252     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1253   }
1254 
1255   // This resets the card table to all zeros.  It is used after
1256   // a collection pause which used the card table to claim cards.
1257   void cleanUpCardTable();
1258 
1259   // Iteration functions.
1260 
1261   // Iterate over all objects, calling "cl.do_object" on each.
1262   virtual void object_iterate(ObjectClosure* cl);
1263 
1264   virtual void safe_object_iterate(ObjectClosure* cl) {
1265     object_iterate(cl);
1266   }
1267 
1268   // Iterate over heap regions, in address order, terminating the
1269   // iteration early if the "doHeapRegion" method returns "true".
1270   void heap_region_iterate(HeapRegionClosure* blk) const;
1271 
1272   // Return the region with the given index. It assumes the index is valid.
1273   inline HeapRegion* region_at(uint index) const;
1274 
1275   // Calculate the region index of the given address. Given address must be
1276   // within the heap.
1277   inline uint addr_to_region(HeapWord* addr) const;
1278 
1279   inline HeapWord* bottom_addr_for_region(uint index) const;
1280 
1281   // Iterate over the heap regions in parallel. Assumes that this will be called
1282   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1283   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1284   // to each of the regions, by attempting to claim the region using the
1285   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1286   // region. The concurrent argument should be set to true if iteration is
1287   // performed concurrently, during which no assumptions are made for consistent
1288   // attributes of the heap regions (as they might be modified while iterating).
1289   void heap_region_par_iterate(HeapRegionClosure* cl,
1290                                uint worker_id,
1291                                HeapRegionClaimer* hrclaimer,
1292                                bool concurrent = false) const;
1293 
1294   // Clear the cached cset start regions and (more importantly)
1295   // the time stamps. Called when we reset the GC time stamp.
1296   void clear_cset_start_regions();
1297 
1298   // Given the id of a worker, obtain or calculate a suitable
1299   // starting region for iterating over the current collection set.
1300   HeapRegion* start_cset_region_for_worker(uint worker_i);
1301 
1302   // Iterate over the regions (if any) in the current collection set.
1303   void collection_set_iterate(HeapRegionClosure* blk);
1304 
1305   // As above but starting from region r
1306   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1307 
1308   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1309 
1310   // Returns the HeapRegion that contains addr. addr must not be NULL.
1311   template <class T>
1312   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1313 
1314   // Returns the HeapRegion that contains addr. addr must not be NULL.
1315   // If addr is within a humongous continues region, it returns its humongous start region.
1316   template <class T>
1317   inline HeapRegion* heap_region_containing(const T addr) const;
1318 
1319   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1320   // each address in the (reserved) heap is a member of exactly
1321   // one block.  The defining characteristic of a block is that it is
1322   // possible to find its size, and thus to progress forward to the next
1323   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1324   // represent Java objects, or they might be free blocks in a
1325   // free-list-based heap (or subheap), as long as the two kinds are
1326   // distinguishable and the size of each is determinable.
1327 
1328   // Returns the address of the start of the "block" that contains the
1329   // address "addr".  We say "blocks" instead of "object" since some heaps
1330   // may not pack objects densely; a chunk may either be an object or a
1331   // non-object.
1332   virtual HeapWord* block_start(const void* addr) const;
1333 
1334   // Requires "addr" to be the start of a chunk, and returns its size.
1335   // "addr + size" is required to be the start of a new chunk, or the end
1336   // of the active area of the heap.
1337   virtual size_t block_size(const HeapWord* addr) const;
1338 
1339   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1340   // the block is an object.
1341   virtual bool block_is_obj(const HeapWord* addr) const;
1342 
1343   // Does this heap support heap inspection? (+PrintClassHistogram)
1344   virtual bool supports_heap_inspection() const { return true; }
1345 
1346   // Section on thread-local allocation buffers (TLABs)
1347   // See CollectedHeap for semantics.
1348 
1349   bool supports_tlab_allocation() const;
1350   size_t tlab_capacity(Thread* ignored) const;
1351   size_t tlab_used(Thread* ignored) const;
1352   size_t max_tlab_size() const;
1353   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1354 
1355   // Can a compiler initialize a new object without store barriers?
1356   // This permission only extends from the creation of a new object
1357   // via a TLAB up to the first subsequent safepoint. If such permission
1358   // is granted for this heap type, the compiler promises to call
1359   // defer_store_barrier() below on any slow path allocation of
1360   // a new object for which such initializing store barriers will
1361   // have been elided. G1, like CMS, allows this, but should be
1362   // ready to provide a compensating write barrier as necessary
1363   // if that storage came out of a non-young region. The efficiency
1364   // of this implementation depends crucially on being able to
1365   // answer very efficiently in constant time whether a piece of
1366   // storage in the heap comes from a young region or not.
1367   // See ReduceInitialCardMarks.
1368   virtual bool can_elide_tlab_store_barriers() const {
1369     return true;
1370   }
1371 
1372   virtual bool card_mark_must_follow_store() const {
1373     return true;
1374   }
1375 
1376   inline bool is_in_young(const oop obj);
1377 
1378   virtual bool is_scavengable(const void* addr);
1379 
1380   // We don't need barriers for initializing stores to objects
1381   // in the young gen: for the SATB pre-barrier, there is no
1382   // pre-value that needs to be remembered; for the remembered-set
1383   // update logging post-barrier, we don't maintain remembered set
1384   // information for young gen objects.
1385   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1386 
1387   // Returns "true" iff the given word_size is "very large".
1388   static bool is_humongous(size_t word_size) {
1389     // Note this has to be strictly greater-than as the TLABs
1390     // are capped at the humongous threshold and we want to
1391     // ensure that we don't try to allocate a TLAB as
1392     // humongous and that we don't allocate a humongous
1393     // object in a TLAB.
1394     return word_size > _humongous_object_threshold_in_words;
1395   }
1396 
1397   // Update mod union table with the set of dirty cards.
1398   void updateModUnion();
1399 
1400   // Set the mod union bits corresponding to the given memRegion.  Note
1401   // that this is always a safe operation, since it doesn't clear any
1402   // bits.
1403   void markModUnionRange(MemRegion mr);
1404 
1405   // Records the fact that a marking phase is no longer in progress.
1406   void set_marking_complete() {
1407     _mark_in_progress = false;
1408   }
1409   void set_marking_started() {
1410     _mark_in_progress = true;
1411   }
1412   bool mark_in_progress() {
1413     return _mark_in_progress;
1414   }
1415 
1416   // Print the maximum heap capacity.
1417   virtual size_t max_capacity() const;
1418 
1419   virtual jlong millis_since_last_gc();
1420 
1421 
1422   // Convenience function to be used in situations where the heap type can be
1423   // asserted to be this type.
1424   static G1CollectedHeap* heap();
1425 
1426   void set_region_short_lived_locked(HeapRegion* hr);
1427   // add appropriate methods for any other surv rate groups
1428 
1429   YoungList* young_list() const { return _young_list; }
1430 
1431   // debugging
1432   bool check_young_list_well_formed() {
1433     return _young_list->check_list_well_formed();
1434   }
1435 
1436   bool check_young_list_empty(bool check_heap,
1437                               bool check_sample = true);
1438 
1439   // *** Stuff related to concurrent marking.  It's not clear to me that so
1440   // many of these need to be public.
1441 
1442   // The functions below are helper functions that a subclass of
1443   // "CollectedHeap" can use in the implementation of its virtual
1444   // functions.
1445   // This performs a concurrent marking of the live objects in a
1446   // bitmap off to the side.
1447   void doConcurrentMark();
1448 
1449   bool isMarkedPrev(oop obj) const;
1450   bool isMarkedNext(oop obj) const;
1451 
1452   // Determine if an object is dead, given the object and also
1453   // the region to which the object belongs. An object is dead
1454   // iff a) it was not allocated since the last mark and b) it
1455   // is not marked.
1456   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1457     return
1458       !hr->obj_allocated_since_prev_marking(obj) &&
1459       !isMarkedPrev(obj);
1460   }
1461 
1462   // This function returns true when an object has been
1463   // around since the previous marking and hasn't yet
1464   // been marked during this marking.
1465   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1466     return
1467       !hr->obj_allocated_since_next_marking(obj) &&
1468       !isMarkedNext(obj);
1469   }
1470 
1471   // Determine if an object is dead, given only the object itself.
1472   // This will find the region to which the object belongs and
1473   // then call the region version of the same function.
1474 
1475   // Added if it is NULL it isn't dead.
1476 
1477   inline bool is_obj_dead(const oop obj) const;
1478 
1479   inline bool is_obj_ill(const oop obj) const;
1480 
1481   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1482   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1483   bool is_marked(oop obj, VerifyOption vo);
1484   const char* top_at_mark_start_str(VerifyOption vo);
1485 
1486   ConcurrentMark* concurrent_mark() const { return _cm; }
1487 
1488   // Refinement
1489 
1490   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1491 
1492   // The dirty cards region list is used to record a subset of regions
1493   // whose cards need clearing. The list if populated during the
1494   // remembered set scanning and drained during the card table
1495   // cleanup. Although the methods are reentrant, population/draining
1496   // phases must not overlap. For synchronization purposes the last
1497   // element on the list points to itself.
1498   HeapRegion* _dirty_cards_region_list;
1499   void push_dirty_cards_region(HeapRegion* hr);
1500   HeapRegion* pop_dirty_cards_region();
1501 
1502   // Optimized nmethod scanning support routines
1503 
1504   // Register the given nmethod with the G1 heap.
1505   virtual void register_nmethod(nmethod* nm);
1506 
1507   // Unregister the given nmethod from the G1 heap.
1508   virtual void unregister_nmethod(nmethod* nm);
1509 
1510   // Free up superfluous code root memory.
1511   void purge_code_root_memory();
1512 
1513   // Rebuild the strong code root lists for each region
1514   // after a full GC.
1515   void rebuild_strong_code_roots();
1516 
1517   // Delete entries for dead interned string and clean up unreferenced symbols
1518   // in symbol table, possibly in parallel.
1519   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1520 
1521   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1522   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1523 
1524   // Redirty logged cards in the refinement queue.
1525   void redirty_logged_cards();
1526   // Verification
1527 
1528   // The following is just to alert the verification code
1529   // that a full collection has occurred and that the
1530   // remembered sets are no longer up to date.
1531   bool _full_collection;
1532   void set_full_collection() { _full_collection = true;}
1533   void clear_full_collection() {_full_collection = false;}
1534   bool full_collection() {return _full_collection;}
1535 
1536   // Perform any cleanup actions necessary before allowing a verification.
1537   virtual void prepare_for_verify();
1538 
1539   // Perform verification.
1540 
1541   // vo == UsePrevMarking  -> use "prev" marking information,
1542   // vo == UseNextMarking -> use "next" marking information
1543   // vo == UseMarkWord    -> use the mark word in the object header
1544   //
1545   // NOTE: Only the "prev" marking information is guaranteed to be
1546   // consistent most of the time, so most calls to this should use
1547   // vo == UsePrevMarking.
1548   // Currently, there is only one case where this is called with
1549   // vo == UseNextMarking, which is to verify the "next" marking
1550   // information at the end of remark.
1551   // Currently there is only one place where this is called with
1552   // vo == UseMarkWord, which is to verify the marking during a
1553   // full GC.
1554   void verify(bool silent, VerifyOption vo);
1555 
1556   // Override; it uses the "prev" marking information
1557   virtual void verify(bool silent);
1558 
1559   // The methods below are here for convenience and dispatch the
1560   // appropriate method depending on value of the given VerifyOption
1561   // parameter. The values for that parameter, and their meanings,
1562   // are the same as those above.
1563 
1564   bool is_obj_dead_cond(const oop obj,
1565                         const HeapRegion* hr,
1566                         const VerifyOption vo) const;
1567 
1568   bool is_obj_dead_cond(const oop obj,
1569                         const VerifyOption vo) const;
1570 
1571   // Printing
1572 
1573   virtual void print_on(outputStream* st) const;
1574   virtual void print_extended_on(outputStream* st) const;
1575   virtual void print_on_error(outputStream* st) const;
1576 
1577   virtual void print_gc_threads_on(outputStream* st) const;
1578   virtual void gc_threads_do(ThreadClosure* tc) const;
1579 
1580   // Override
1581   void print_tracing_info() const;
1582 
1583   // The following two methods are helpful for debugging RSet issues.
1584   void print_cset_rsets() PRODUCT_RETURN;
1585   void print_all_rsets() PRODUCT_RETURN;
1586 
1587 public:
1588   size_t pending_card_num();
1589   size_t cards_scanned();
1590 
1591 protected:
1592   size_t _max_heap_capacity;
1593 };
1594 
1595 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP