rev 7993 : [mq]: fix

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_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 ObjectClosure;
  60 class SpaceClosure;
  61 class CompactibleSpaceClosure;
  62 class Space;
  63 class G1CollectorPolicy;
  64 class GenRemSet;
  65 class G1RemSet;
  66 class HeapRegionRemSetIterator;
  67 class ConcurrentMark;
  68 class ConcurrentMarkThread;
  69 class ConcurrentG1Refine;
  70 class ConcurrentGCTimer;
  71 class GenerationCounters;
  72 class STWGCTimer;
  73 class G1NewTracer;
  74 class G1OldTracer;
  75 class EvacuationFailedInfo;
  76 class nmethod;
  77 class Ticks;
  78 
  79 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  81 
  82 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  83 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  84 
  85 class YoungList : public CHeapObj<mtGC> {
  86 private:
  87   G1CollectedHeap* _g1h;
  88 
  89   HeapRegion* _head;
  90 
  91   HeapRegion* _survivor_head;
  92   HeapRegion* _survivor_tail;
  93 
  94   HeapRegion* _curr;
  95 
  96   uint        _length;
  97   uint        _survivor_length;
  98 
  99   size_t      _last_sampled_rs_lengths;
 100   size_t      _sampled_rs_lengths;
 101 
 102   void         empty_list(HeapRegion* list);
 103 
 104 public:
 105   YoungList(G1CollectedHeap* g1h);
 106 
 107   void         push_region(HeapRegion* hr);
 108   void         add_survivor_region(HeapRegion* hr);
 109 
 110   void         empty_list();
 111   bool         is_empty() { return _length == 0; }
 112   uint         length() { return _length; }
 113   uint         eden_length() { return length() - survivor_length(); }
 114   uint         survivor_length() { return _survivor_length; }
 115 
 116   // Currently we do not keep track of the used byte sum for the
 117   // young list and the survivors and it'd be quite a lot of work to
 118   // do so. When we'll eventually replace the young list with
 119   // instances of HeapRegionLinkedList we'll get that for free. So,
 120   // we'll report the more accurate information then.
 121   size_t       eden_used_bytes() {
 122     assert(length() >= survivor_length(), "invariant");
 123     return (size_t) eden_length() * HeapRegion::GrainBytes;
 124   }
 125   size_t       survivor_used_bytes() {
 126     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 127   }
 128 
 129   void rs_length_sampling_init();
 130   bool rs_length_sampling_more();
 131   void rs_length_sampling_next();
 132 
 133   void reset_sampled_info() {
 134     _last_sampled_rs_lengths =   0;
 135   }
 136   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 137 
 138   // for development purposes
 139   void reset_auxilary_lists();
 140   void clear() { _head = NULL; _length = 0; }
 141 
 142   void clear_survivors() {
 143     _survivor_head    = NULL;
 144     _survivor_tail    = NULL;
 145     _survivor_length  = 0;
 146   }
 147 
 148   HeapRegion* first_region() { return _head; }
 149   HeapRegion* first_survivor_region() { return _survivor_head; }
 150   HeapRegion* last_survivor_region() { return _survivor_tail; }
 151 
 152   // debugging
 153   bool          check_list_well_formed();
 154   bool          check_list_empty(bool check_sample = true);
 155   void          print();
 156 };
 157 
 158 // The G1 STW is alive closure.
 159 // An instance is embedded into the G1CH and used as the
 160 // (optional) _is_alive_non_header closure in the STW
 161 // reference processor. It is also extensively used during
 162 // reference processing during STW evacuation pauses.
 163 class G1STWIsAliveClosure: public BoolObjectClosure {
 164   G1CollectedHeap* _g1;
 165 public:
 166   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 167   bool do_object_b(oop p);
 168 };
 169 
 170 class RefineCardTableEntryClosure;
 171 
 172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 173  private:
 174   void reset_from_card_cache(uint start_idx, size_t num_regions);
 175  public:
 176   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 177 };
 178 
 179 class G1CollectedHeap : public SharedHeap {
 180   friend class VM_CollectForMetadataAllocation;
 181   friend class VM_G1CollectForAllocation;
 182   friend class VM_G1CollectFull;
 183   friend class VM_G1IncCollectionPause;
 184   friend class VMStructs;
 185   friend class MutatorAllocRegion;
 186   friend class SurvivorGCAllocRegion;
 187   friend class OldGCAllocRegion;
 188   friend class G1Allocator;
 189 
 190   // Closures used in implementation.
 191   friend class G1ParScanThreadState;
 192   friend class G1ParTask;
 193   friend class G1ParGCAllocator;
 194   friend class G1PrepareCompactClosure;
 195 
 196   // Other related classes.
 197   friend class HeapRegionClaimer;
 198 
 199   // Testing classes.
 200   friend class G1CheckCSetFastTableClosure;
 201 
 202 private:
 203   // The one and only G1CollectedHeap, so static functions can find it.
 204   static G1CollectedHeap* _g1h;
 205 
 206   static size_t _humongous_object_threshold_in_words;
 207 
 208   // The secondary free list which contains regions that have been
 209   // freed up during the cleanup process. This will be appended to
 210   // the master free list when appropriate.
 211   FreeRegionList _secondary_free_list;
 212 
 213   // It keeps track of the old regions.
 214   HeapRegionSet _old_set;
 215 
 216   // It keeps track of the humongous regions.
 217   HeapRegionSet _humongous_set;
 218 

 219   void eagerly_reclaim_humongous_regions();
 220 
 221   // The number of regions we could create by expansion.
 222   uint _expansion_regions;
 223 
 224   // The block offset table for the G1 heap.
 225   G1BlockOffsetSharedArray* _bot_shared;
 226 
 227   // Tears down the region sets / lists so that they are empty and the
 228   // regions on the heap do not belong to a region set / list. The
 229   // only exception is the humongous set which we leave unaltered. If
 230   // free_list_only is true, it will only tear down the master free
 231   // list. It is called before a Full GC (free_list_only == false) or
 232   // before heap shrinking (free_list_only == true).
 233   void tear_down_region_sets(bool free_list_only);
 234 
 235   // Rebuilds the region sets / lists so that they are repopulated to
 236   // reflect the contents of the heap. The only exception is the
 237   // humongous set which was not torn down in the first place. If
 238   // free_list_only is true, it will only rebuild the master free
 239   // list. It is called after a Full GC (free_list_only == false) or
 240   // after heap shrinking (free_list_only == true).
 241   void rebuild_region_sets(bool free_list_only);
 242 
 243   // Callback for region mapping changed events.
 244   G1RegionMappingChangedListener _listener;
 245 
 246   // The sequence of all heap regions in the heap.
 247   HeapRegionManager _hrm;
 248 
 249   // Class that handles the different kinds of allocations.
 250   G1Allocator* _allocator;
 251 
 252   // Statistics for each allocation context
 253   AllocationContextStats _allocation_context_stats;
 254 
 255   // PLAB sizing policy for survivors.
 256   PLABStats _survivor_plab_stats;
 257 
 258   // PLAB sizing policy for tenured objects.
 259   PLABStats _old_plab_stats;
 260 
 261   // It specifies whether we should attempt to expand the heap after a
 262   // region allocation failure. If heap expansion fails we set this to
 263   // false so that we don't re-attempt the heap expansion (it's likely
 264   // that subsequent expansion attempts will also fail if one fails).
 265   // Currently, it is only consulted during GC and it's reset at the
 266   // start of each GC.
 267   bool _expand_heap_after_alloc_failure;
 268 
 269   // It resets the mutator alloc region before new allocations can take place.
 270   void init_mutator_alloc_region();
 271 
 272   // It releases the mutator alloc region.
 273   void release_mutator_alloc_region();
 274 
 275   // It initializes the GC alloc regions at the start of a GC.
 276   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 277 
 278   // It releases the GC alloc regions at the end of a GC.
 279   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 280 
 281   // It does any cleanup that needs to be done on the GC alloc regions
 282   // before a Full GC.
 283   void abandon_gc_alloc_regions();
 284 
 285   // Helper for monitoring and management support.
 286   G1MonitoringSupport* _g1mm;
 287 
 288   // Records whether the region at the given index is (still) a
 289   // candidate for eager reclaim.  Only valid for humongous start
 290   // regions; other regions have unspecified values.  Initialized at
 291   // start of collection pause, with candidates removed as they are
 292   // found reachable from roots or the young generation.
 293   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 294    protected:
 295     bool default_value() const { return false; }
 296    public:
 297     void clear() { G1BiasedMappedArray<bool>::clear(); }
 298     void add_candidate(uint region) {
 299       set_by_index(region, true);
 300     }
 301     void remove_candidate(uint region) {
 302       set_by_index(region, false);
 303     }
 304     bool is_candidate(uint region) {
 305       return get_by_index(region);
 306     }
 307   };
 308 
 309   HumongousReclaimCandidates _humongous_reclaim_candidates;
 310   // Stores whether during humongous object registration we found candidate regions.
 311   // If not, we can skip a few steps.
 312   bool _has_humongous_reclaim_candidates;
 313 
 314   volatile unsigned _gc_time_stamp;
 315 
 316   size_t* _surviving_young_words;
 317 
 318   G1HRPrinter _hr_printer;
 319 
 320   void setup_surviving_young_words();
 321   void update_surviving_young_words(size_t* surv_young_words);
 322   void cleanup_surviving_young_words();
 323 
 324   // It decides whether an explicit GC should start a concurrent cycle
 325   // instead of doing a STW GC. Currently, a concurrent cycle is
 326   // explicitly started if:
 327   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 328   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 329   // (c) cause == _g1_humongous_allocation
 330   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 331 
 332   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 333   // concurrent cycles) we have started.
 334   volatile uint _old_marking_cycles_started;
 335 
 336   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 337   // concurrent cycles) we have completed.
 338   volatile uint _old_marking_cycles_completed;
 339 
 340   bool _concurrent_cycle_started;
 341   bool _heap_summary_sent;
 342 
 343   // This is a non-product method that is helpful for testing. It is
 344   // called at the end of a GC and artificially expands the heap by
 345   // allocating a number of dead regions. This way we can induce very
 346   // frequent marking cycles and stress the cleanup / concurrent
 347   // cleanup code more (as all the regions that will be allocated by
 348   // this method will be found dead by the marking cycle).
 349   void allocate_dummy_regions() PRODUCT_RETURN;
 350 
 351   // Clear RSets after a compaction. It also resets the GC time stamps.
 352   void clear_rsets_post_compaction();
 353 
 354   // If the HR printer is active, dump the state of the regions in the
 355   // heap after a compaction.
 356   void print_hrm_post_compaction();
 357 
 358   double verify(bool guard, const char* msg);
 359   void verify_before_gc();
 360   void verify_after_gc();
 361 
 362   void log_gc_header();
 363   void log_gc_footer(double pause_time_sec);
 364 
 365   // These are macros so that, if the assert fires, we get the correct
 366   // line number, file, etc.
 367 
 368 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 369   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 370           (_extra_message_),                                                  \
 371           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 372           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 373           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 374 
 375 #define assert_heap_locked()                                                  \
 376   do {                                                                        \
 377     assert(Heap_lock->owned_by_self(),                                        \
 378            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 379   } while (0)
 380 
 381 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 382   do {                                                                        \
 383     assert(Heap_lock->owned_by_self() ||                                      \
 384            (SafepointSynchronize::is_at_safepoint() &&                        \
 385              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 386            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 387                                         "should be at a safepoint"));         \
 388   } while (0)
 389 
 390 #define assert_heap_locked_and_not_at_safepoint()                             \
 391   do {                                                                        \
 392     assert(Heap_lock->owned_by_self() &&                                      \
 393                                     !SafepointSynchronize::is_at_safepoint(), \
 394           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 395                                        "should not be at a safepoint"));      \
 396   } while (0)
 397 
 398 #define assert_heap_not_locked()                                              \
 399   do {                                                                        \
 400     assert(!Heap_lock->owned_by_self(),                                       \
 401         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 402   } while (0)
 403 
 404 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 405   do {                                                                        \
 406     assert(!Heap_lock->owned_by_self() &&                                     \
 407                                     !SafepointSynchronize::is_at_safepoint(), \
 408       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 409                                    "should not be at a safepoint"));          \
 410   } while (0)
 411 
 412 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 413   do {                                                                        \
 414     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 415               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 416            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 417   } while (0)
 418 
 419 #define assert_not_at_safepoint()                                             \
 420   do {                                                                        \
 421     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 422            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 423   } while (0)
 424 
 425 protected:
 426 
 427   // The young region list.
 428   YoungList*  _young_list;
 429 
 430   // The current policy object for the collector.
 431   G1CollectorPolicy* _g1_policy;
 432 
 433   // This is the second level of trying to allocate a new region. If
 434   // new_region() didn't find a region on the free_list, this call will
 435   // check whether there's anything available on the
 436   // secondary_free_list and/or wait for more regions to appear on
 437   // that list, if _free_regions_coming is set.
 438   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 439 
 440   // Try to allocate a single non-humongous HeapRegion sufficient for
 441   // an allocation of the given word_size. If do_expand is true,
 442   // attempt to expand the heap if necessary to satisfy the allocation
 443   // request. If the region is to be used as an old region or for a
 444   // humongous object, set is_old to true. If not, to false.
 445   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 446 
 447   // Initialize a contiguous set of free regions of length num_regions
 448   // and starting at index first so that they appear as a single
 449   // humongous region.
 450   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 451                                                       uint num_regions,
 452                                                       size_t word_size,
 453                                                       AllocationContext_t context);
 454 
 455   // Attempt to allocate a humongous object of the given size. Return
 456   // NULL if unsuccessful.
 457   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 458 
 459   // The following two methods, allocate_new_tlab() and
 460   // mem_allocate(), are the two main entry points from the runtime
 461   // into the G1's allocation routines. They have the following
 462   // assumptions:
 463   //
 464   // * They should both be called outside safepoints.
 465   //
 466   // * They should both be called without holding the Heap_lock.
 467   //
 468   // * All allocation requests for new TLABs should go to
 469   //   allocate_new_tlab().
 470   //
 471   // * All non-TLAB allocation requests should go to mem_allocate().
 472   //
 473   // * If either call cannot satisfy the allocation request using the
 474   //   current allocating region, they will try to get a new one. If
 475   //   this fails, they will attempt to do an evacuation pause and
 476   //   retry the allocation.
 477   //
 478   // * If all allocation attempts fail, even after trying to schedule
 479   //   an evacuation pause, allocate_new_tlab() will return NULL,
 480   //   whereas mem_allocate() will attempt a heap expansion and/or
 481   //   schedule a Full GC.
 482   //
 483   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 484   //   should never be called with word_size being humongous. All
 485   //   humongous allocation requests should go to mem_allocate() which
 486   //   will satisfy them with a special path.
 487 
 488   virtual HeapWord* allocate_new_tlab(size_t word_size);
 489 
 490   virtual HeapWord* mem_allocate(size_t word_size,
 491                                  bool*  gc_overhead_limit_was_exceeded);
 492 
 493   // The following three methods take a gc_count_before_ret
 494   // parameter which is used to return the GC count if the method
 495   // returns NULL. Given that we are required to read the GC count
 496   // while holding the Heap_lock, and these paths will take the
 497   // Heap_lock at some point, it's easier to get them to read the GC
 498   // count while holding the Heap_lock before they return NULL instead
 499   // of the caller (namely: mem_allocate()) having to also take the
 500   // Heap_lock just to read the GC count.
 501 
 502   // First-level mutator allocation attempt: try to allocate out of
 503   // the mutator alloc region without taking the Heap_lock. This
 504   // should only be used for non-humongous allocations.
 505   inline HeapWord* attempt_allocation(size_t word_size,
 506                                       uint* gc_count_before_ret,
 507                                       uint* gclocker_retry_count_ret);
 508 
 509   // Second-level mutator allocation attempt: take the Heap_lock and
 510   // retry the allocation attempt, potentially scheduling a GC
 511   // pause. This should only be used for non-humongous allocations.
 512   HeapWord* attempt_allocation_slow(size_t word_size,
 513                                     AllocationContext_t context,
 514                                     uint* gc_count_before_ret,
 515                                     uint* gclocker_retry_count_ret);
 516 
 517   // Takes the Heap_lock and attempts a humongous allocation. It can
 518   // potentially schedule a GC pause.
 519   HeapWord* attempt_allocation_humongous(size_t word_size,
 520                                          uint* gc_count_before_ret,
 521                                          uint* gclocker_retry_count_ret);
 522 
 523   // Allocation attempt that should be called during safepoints (e.g.,
 524   // at the end of a successful GC). expect_null_mutator_alloc_region
 525   // specifies whether the mutator alloc region is expected to be NULL
 526   // or not.
 527   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 528                                             AllocationContext_t context,
 529                                             bool expect_null_mutator_alloc_region);
 530 
 531   // It dirties the cards that cover the block so that so that the post
 532   // write barrier never queues anything when updating objects on this
 533   // block. It is assumed (and in fact we assert) that the block
 534   // belongs to a young region.
 535   inline void dirty_young_block(HeapWord* start, size_t word_size);
 536 
 537   // Allocate blocks during garbage collection. Will ensure an
 538   // allocation region, either by picking one or expanding the
 539   // heap, and then allocate a block of the given size. The block
 540   // may not be a humongous - it must fit into a single heap region.
 541   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 542                                           size_t word_size,
 543                                           AllocationContext_t context);
 544   // Ensure that no further allocations can happen in "r", bearing in mind
 545   // that parallel threads might be attempting allocations.
 546   void par_allocate_remaining_space(HeapRegion* r);
 547 
 548   // Allocation attempt during GC for a survivor object / PLAB.
 549   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 550                                                AllocationContext_t context);
 551 
 552   // Allocation attempt during GC for an old object / PLAB.
 553   inline HeapWord* old_attempt_allocation(size_t word_size,
 554                                           AllocationContext_t context);
 555 
 556   // These methods are the "callbacks" from the G1AllocRegion class.
 557 
 558   // For mutator alloc regions.
 559   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 560   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 561                                    size_t allocated_bytes);
 562 
 563   // For GC alloc regions.
 564   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 565                                   InCSetState dest);
 566   void retire_gc_alloc_region(HeapRegion* alloc_region,
 567                               size_t allocated_bytes, InCSetState dest);
 568 
 569   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 570   //   inspection request and should collect the entire heap
 571   // - if clear_all_soft_refs is true, all soft references should be
 572   //   cleared during the GC
 573   // - if explicit_gc is false, word_size describes the allocation that
 574   //   the GC should attempt (at least) to satisfy
 575   // - it returns false if it is unable to do the collection due to the
 576   //   GC locker being active, true otherwise
 577   bool do_collection(bool explicit_gc,
 578                      bool clear_all_soft_refs,
 579                      size_t word_size);
 580 
 581   // Callback from VM_G1CollectFull operation.
 582   // Perform a full collection.
 583   virtual void do_full_collection(bool clear_all_soft_refs);
 584 
 585   // Resize the heap if necessary after a full collection.  If this is
 586   // after a collect-for allocation, "word_size" is the allocation size,
 587   // and will be considered part of the used portion of the heap.
 588   void resize_if_necessary_after_full_collection(size_t word_size);
 589 
 590   // Callback from VM_G1CollectForAllocation operation.
 591   // This function does everything necessary/possible to satisfy a
 592   // failed allocation request (including collection, expansion, etc.)
 593   HeapWord* satisfy_failed_allocation(size_t word_size,
 594                                       AllocationContext_t context,
 595                                       bool* succeeded);
 596 
 597   // Attempting to expand the heap sufficiently
 598   // to support an allocation of the given "word_size".  If
 599   // successful, perform the allocation and return the address of the
 600   // allocated block, or else "NULL".
 601   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 602 
 603   // Process any reference objects discovered during
 604   // an incremental evacuation pause.
 605   void process_discovered_references(uint no_of_gc_workers);
 606 
 607   // Enqueue any remaining discovered references
 608   // after processing.
 609   void enqueue_discovered_references(uint no_of_gc_workers);
 610 
 611 public:
 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   virtual void gc_prologue(bool full);
 638   virtual void gc_epilogue(bool full);
 639 
 640   inline void set_humongous_is_live(oop obj);
 641 
 642   void add_humongous_reclaim_candidate(uint region) {
 643     assert(_hrm.at(region)->is_starts_humongous(), "Must start a humongous object");
 644     _humongous_reclaim_candidates.add_candidate(region);
 645   }
 646 
 647   void remove_humongous_reclaim_candidate(uint region) {
 648     assert(_hrm.at(region)->is_starts_humongous(), "Must start a humongous object");
 649     _humongous_reclaim_candidates.remove_candidate(region);
 650   }
 651 
 652   bool is_humongous_reclaim_candidate(uint region) {
 653     assert(_hrm.at(region)->is_starts_humongous(), "Must start a humongous object");
 654     return _humongous_reclaim_candidates.is_candidate(region);
 655   }
 656 






 657   // Register the given region to be part of the collection set.
 658   inline void register_humongous_region_with_cset(uint index);
 659   // Register regions with humongous objects (actually on the start region) in
 660   // the in_cset_fast_test table.
 661   void register_humongous_regions_with_cset();
 662   // We register a region with the fast "in collection set" test. We
 663   // simply set to true the array slot corresponding to this region.
 664   void register_young_region_with_cset(HeapRegion* r) {
 665     _in_cset_fast_test.set_in_young(r->hrm_index());
 666   }
 667   void register_old_region_with_cset(HeapRegion* r) {
 668     _in_cset_fast_test.set_in_old(r->hrm_index());
 669   }
 670   void clear_in_cset(const HeapRegion* hr) {
 671     _in_cset_fast_test.clear(hr);
 672   }
 673 
 674   void clear_cset_fast_test() {
 675     _in_cset_fast_test.clear();
 676   }
 677 
 678   // This is called at the start of either a concurrent cycle or a Full
 679   // GC to update the number of old marking cycles started.
 680   void increment_old_marking_cycles_started();
 681 
 682   // This is called at the end of either a concurrent cycle or a Full
 683   // GC to update the number of old marking cycles completed. Those two
 684   // can happen in a nested fashion, i.e., we start a concurrent
 685   // cycle, a Full GC happens half-way through it which ends first,
 686   // and then the cycle notices that a Full GC happened and ends
 687   // too. The concurrent parameter is a boolean to help us do a bit
 688   // tighter consistency checking in the method. If concurrent is
 689   // false, the caller is the inner caller in the nesting (i.e., the
 690   // Full GC). If concurrent is true, the caller is the outer caller
 691   // in this nesting (i.e., the concurrent cycle). Further nesting is
 692   // not currently supported. The end of this call also notifies
 693   // the FullGCCount_lock in case a Java thread is waiting for a full
 694   // GC to happen (e.g., it called System.gc() with
 695   // +ExplicitGCInvokesConcurrent).
 696   void increment_old_marking_cycles_completed(bool concurrent);
 697 
 698   uint old_marking_cycles_completed() {
 699     return _old_marking_cycles_completed;
 700   }
 701 
 702   void register_concurrent_cycle_start(const Ticks& start_time);
 703   void register_concurrent_cycle_end();
 704   void trace_heap_after_concurrent_cycle();
 705 
 706   G1YCType yc_type();
 707 
 708   G1HRPrinter* hr_printer() { return &_hr_printer; }
 709 
 710   // Frees a non-humongous region by initializing its contents and
 711   // adding it to the free list that's passed as a parameter (this is
 712   // usually a local list which will be appended to the master free
 713   // list later). The used bytes of freed regions are accumulated in
 714   // pre_used. If par is true, the region's RSet will not be freed
 715   // up. The assumption is that this will be done later.
 716   // The locked parameter indicates if the caller has already taken
 717   // care of proper synchronization. This may allow some optimizations.
 718   void free_region(HeapRegion* hr,
 719                    FreeRegionList* free_list,
 720                    bool par,
 721                    bool locked = false);
 722 
 723   // Frees a humongous region by collapsing it into individual regions
 724   // and calling free_region() for each of them. The freed regions
 725   // will be added to the free list that's passed as a parameter (this
 726   // is usually a local list which will be appended to the master free
 727   // list later). The used bytes of freed regions are accumulated in
 728   // pre_used. If par is true, the region's RSet will not be freed
 729   // up. The assumption is that this will be done later.
 730   void free_humongous_region(HeapRegion* hr,
 731                              FreeRegionList* free_list,
 732                              bool par);
 733 protected:
 734 
 735   // Shrink the garbage-first heap by at most the given size (in bytes!).
 736   // (Rounds down to a HeapRegion boundary.)
 737   virtual void shrink(size_t expand_bytes);
 738   void shrink_helper(size_t expand_bytes);
 739 
 740   #if TASKQUEUE_STATS
 741   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 742   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 743   void reset_taskqueue_stats();
 744   #endif // TASKQUEUE_STATS
 745 
 746   // Schedule the VM operation that will do an evacuation pause to
 747   // satisfy an allocation request of word_size. *succeeded will
 748   // return whether the VM operation was successful (it did do an
 749   // evacuation pause) or not (another thread beat us to it or the GC
 750   // locker was active). Given that we should not be holding the
 751   // Heap_lock when we enter this method, we will pass the
 752   // gc_count_before (i.e., total_collections()) as a parameter since
 753   // it has to be read while holding the Heap_lock. Currently, both
 754   // methods that call do_collection_pause() release the Heap_lock
 755   // before the call, so it's easy to read gc_count_before just before.
 756   HeapWord* do_collection_pause(size_t         word_size,
 757                                 uint           gc_count_before,
 758                                 bool*          succeeded,
 759                                 GCCause::Cause gc_cause);
 760 
 761   // The guts of the incremental collection pause, executed by the vm
 762   // thread. It returns false if it is unable to do the collection due
 763   // to the GC locker being active, true otherwise
 764   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 765 
 766   // Actually do the work of evacuating the collection set.
 767   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 768 
 769   // The g1 remembered set of the heap.
 770   G1RemSet* _g1_rem_set;
 771 
 772   // A set of cards that cover the objects for which the Rsets should be updated
 773   // concurrently after the collection.
 774   DirtyCardQueueSet _dirty_card_queue_set;
 775 
 776   // The closure used to refine a single card.
 777   RefineCardTableEntryClosure* _refine_cte_cl;
 778 
 779   // A DirtyCardQueueSet that is used to hold cards that contain
 780   // references into the current collection set. This is used to
 781   // update the remembered sets of the regions in the collection
 782   // set in the event of an evacuation failure.
 783   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 784 
 785   // After a collection pause, make the regions in the CS into free
 786   // regions.
 787   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 788 
 789   // Abandon the current collection set without recording policy
 790   // statistics or updating free lists.
 791   void abandon_collection_set(HeapRegion* cs_head);
 792 
 793   // Applies "scan_non_heap_roots" to roots outside the heap,
 794   // "scan_rs" to roots inside the heap (having done "set_region" to
 795   // indicate the region in which the root resides),
 796   // and does "scan_metadata" If "scan_rs" is
 797   // NULL, then this step is skipped.  The "worker_i"
 798   // param is for use with parallel roots processing, and should be
 799   // the "i" of the calling parallel worker thread's work(i) function.
 800   // In the sequential case this param will be ignored.
 801   void g1_process_roots(OopClosure* scan_non_heap_roots,
 802                         OopClosure* scan_non_heap_weak_roots,
 803                         G1ParPushHeapRSClosure* scan_rs,
 804                         CLDClosure* scan_strong_clds,
 805                         CLDClosure* scan_weak_clds,
 806                         CodeBlobClosure* scan_strong_code,
 807                         uint worker_i);
 808 
 809   // The concurrent marker (and the thread it runs in.)
 810   ConcurrentMark* _cm;
 811   ConcurrentMarkThread* _cmThread;
 812   bool _mark_in_progress;
 813 
 814   // The concurrent refiner.
 815   ConcurrentG1Refine* _cg1r;
 816 
 817   // The parallel task queues
 818   RefToScanQueueSet *_task_queues;
 819 
 820   // True iff a evacuation has failed in the current collection.
 821   bool _evacuation_failed;
 822 
 823   EvacuationFailedInfo* _evacuation_failed_info_array;
 824 
 825   // Failed evacuations cause some logical from-space objects to have
 826   // forwarding pointers to themselves.  Reset them.
 827   void remove_self_forwarding_pointers();
 828 
 829   // Together, these store an object with a preserved mark, and its mark value.
 830   Stack<oop, mtGC>     _objs_with_preserved_marks;
 831   Stack<markOop, mtGC> _preserved_marks_of_objs;
 832 
 833   // Preserve the mark of "obj", if necessary, in preparation for its mark
 834   // word being overwritten with a self-forwarding-pointer.
 835   void preserve_mark_if_necessary(oop obj, markOop m);
 836 
 837   // The stack of evac-failure objects left to be scanned.
 838   GrowableArray<oop>*    _evac_failure_scan_stack;
 839   // The closure to apply to evac-failure objects.
 840 
 841   OopsInHeapRegionClosure* _evac_failure_closure;
 842   // Set the field above.
 843   void
 844   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 845     _evac_failure_closure = evac_failure_closure;
 846   }
 847 
 848   // Push "obj" on the scan stack.
 849   void push_on_evac_failure_scan_stack(oop obj);
 850   // Process scan stack entries until the stack is empty.
 851   void drain_evac_failure_scan_stack();
 852   // True iff an invocation of "drain_scan_stack" is in progress; to
 853   // prevent unnecessary recursion.
 854   bool _drain_in_progress;
 855 
 856   // Do any necessary initialization for evacuation-failure handling.
 857   // "cl" is the closure that will be used to process evac-failure
 858   // objects.
 859   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 860   // Do any necessary cleanup for evacuation-failure handling data
 861   // structures.
 862   void finalize_for_evac_failure();
 863 
 864   // An attempt to evacuate "obj" has failed; take necessary steps.
 865   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 866   void handle_evacuation_failure_common(oop obj, markOop m);
 867 
 868 #ifndef PRODUCT
 869   // Support for forcing evacuation failures. Analogous to
 870   // PromotionFailureALot for the other collectors.
 871 
 872   // Records whether G1EvacuationFailureALot should be in effect
 873   // for the current GC
 874   bool _evacuation_failure_alot_for_current_gc;
 875 
 876   // Used to record the GC number for interval checking when
 877   // determining whether G1EvaucationFailureALot is in effect
 878   // for the current GC.
 879   size_t _evacuation_failure_alot_gc_number;
 880 
 881   // Count of the number of evacuations between failures.
 882   volatile size_t _evacuation_failure_alot_count;
 883 
 884   // Set whether G1EvacuationFailureALot should be in effect
 885   // for the current GC (based upon the type of GC and which
 886   // command line flags are set);
 887   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 888                                                   bool during_initial_mark,
 889                                                   bool during_marking);
 890 
 891   inline void set_evacuation_failure_alot_for_current_gc();
 892 
 893   // Return true if it's time to cause an evacuation failure.
 894   inline bool evacuation_should_fail();
 895 
 896   // Reset the G1EvacuationFailureALot counters.  Should be called at
 897   // the end of an evacuation pause in which an evacuation failure occurred.
 898   inline void reset_evacuation_should_fail();
 899 #endif // !PRODUCT
 900 
 901   // ("Weak") Reference processing support.
 902   //
 903   // G1 has 2 instances of the reference processor class. One
 904   // (_ref_processor_cm) handles reference object discovery
 905   // and subsequent processing during concurrent marking cycles.
 906   //
 907   // The other (_ref_processor_stw) handles reference object
 908   // discovery and processing during full GCs and incremental
 909   // evacuation pauses.
 910   //
 911   // During an incremental pause, reference discovery will be
 912   // temporarily disabled for _ref_processor_cm and will be
 913   // enabled for _ref_processor_stw. At the end of the evacuation
 914   // pause references discovered by _ref_processor_stw will be
 915   // processed and discovery will be disabled. The previous
 916   // setting for reference object discovery for _ref_processor_cm
 917   // will be re-instated.
 918   //
 919   // At the start of marking:
 920   //  * Discovery by the CM ref processor is verified to be inactive
 921   //    and it's discovered lists are empty.
 922   //  * Discovery by the CM ref processor is then enabled.
 923   //
 924   // At the end of marking:
 925   //  * Any references on the CM ref processor's discovered
 926   //    lists are processed (possibly MT).
 927   //
 928   // At the start of full GC we:
 929   //  * Disable discovery by the CM ref processor and
 930   //    empty CM ref processor's discovered lists
 931   //    (without processing any entries).
 932   //  * Verify that the STW ref processor is inactive and it's
 933   //    discovered lists are empty.
 934   //  * Temporarily set STW ref processor discovery as single threaded.
 935   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 936   //    field.
 937   //  * Finally enable discovery by the STW ref processor.
 938   //
 939   // The STW ref processor is used to record any discovered
 940   // references during the full GC.
 941   //
 942   // At the end of a full GC we:
 943   //  * Enqueue any reference objects discovered by the STW ref processor
 944   //    that have non-live referents. This has the side-effect of
 945   //    making the STW ref processor inactive by disabling discovery.
 946   //  * Verify that the CM ref processor is still inactive
 947   //    and no references have been placed on it's discovered
 948   //    lists (also checked as a precondition during initial marking).
 949 
 950   // The (stw) reference processor...
 951   ReferenceProcessor* _ref_processor_stw;
 952 
 953   STWGCTimer* _gc_timer_stw;
 954   ConcurrentGCTimer* _gc_timer_cm;
 955 
 956   G1OldTracer* _gc_tracer_cm;
 957   G1NewTracer* _gc_tracer_stw;
 958 
 959   // During reference object discovery, the _is_alive_non_header
 960   // closure (if non-null) is applied to the referent object to
 961   // determine whether the referent is live. If so then the
 962   // reference object does not need to be 'discovered' and can
 963   // be treated as a regular oop. This has the benefit of reducing
 964   // the number of 'discovered' reference objects that need to
 965   // be processed.
 966   //
 967   // Instance of the is_alive closure for embedding into the
 968   // STW reference processor as the _is_alive_non_header field.
 969   // Supplying a value for the _is_alive_non_header field is
 970   // optional but doing so prevents unnecessary additions to
 971   // the discovered lists during reference discovery.
 972   G1STWIsAliveClosure _is_alive_closure_stw;
 973 
 974   // The (concurrent marking) reference processor...
 975   ReferenceProcessor* _ref_processor_cm;
 976 
 977   // Instance of the concurrent mark is_alive closure for embedding
 978   // into the Concurrent Marking reference processor as the
 979   // _is_alive_non_header field. Supplying a value for the
 980   // _is_alive_non_header field is optional but doing so prevents
 981   // unnecessary additions to the discovered lists during reference
 982   // discovery.
 983   G1CMIsAliveClosure _is_alive_closure_cm;
 984 
 985   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 986   HeapRegion** _worker_cset_start_region;
 987 
 988   // Time stamp to validate the regions recorded in the cache
 989   // used by G1CollectedHeap::start_cset_region_for_worker().
 990   // The heap region entry for a given worker is valid iff
 991   // the associated time stamp value matches the current value
 992   // of G1CollectedHeap::_gc_time_stamp.
 993   uint* _worker_cset_start_region_time_stamp;
 994 
 995   enum G1H_process_roots_tasks {
 996     G1H_PS_filter_satb_buffers,
 997     G1H_PS_refProcessor_oops_do,
 998     // Leave this one last.
 999     G1H_PS_NumElements
1000   };
1001 
1002   SubTasksDone* _process_strong_tasks;
1003 
1004   volatile bool _free_regions_coming;
1005 
1006 public:
1007 
1008   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1009 
1010   void set_refine_cte_cl_concurrency(bool concurrent);
1011 
1012   RefToScanQueue *task_queue(int i) const;
1013 
1014   // A set of cards where updates happened during the GC
1015   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1016 
1017   // A DirtyCardQueueSet that is used to hold cards that contain
1018   // references into the current collection set. This is used to
1019   // update the remembered sets of the regions in the collection
1020   // set in the event of an evacuation failure.
1021   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1022         { return _into_cset_dirty_card_queue_set; }
1023 
1024   // Create a G1CollectedHeap with the specified policy.
1025   // Must call the initialize method afterwards.
1026   // May not return if something goes wrong.
1027   G1CollectedHeap(G1CollectorPolicy* policy);
1028 
1029   // Initialize the G1CollectedHeap to have the initial and
1030   // maximum sizes and remembered and barrier sets
1031   // specified by the policy object.
1032   jint initialize();
1033 
1034   virtual void stop();
1035 
1036   // Return the (conservative) maximum heap alignment for any G1 heap
1037   static size_t conservative_max_heap_alignment();
1038 
1039   // Initialize weak reference processing.
1040   virtual void ref_processing_init();
1041 
1042   void set_par_threads(uint t) {
1043     SharedHeap::set_par_threads(t);
1044     // Done in SharedHeap but oddly there are
1045     // two _process_strong_tasks's in a G1CollectedHeap
1046     // so do it here too.
1047     _process_strong_tasks->set_n_threads(t);
1048   }
1049 
1050   // Set _n_par_threads according to a policy TBD.
1051   void set_par_threads();
1052 
1053   void set_n_termination(int t) {
1054     _process_strong_tasks->set_n_threads(t);
1055   }
1056 
1057   virtual CollectedHeap::Name kind() const {
1058     return CollectedHeap::G1CollectedHeap;
1059   }
1060 
1061   // The current policy object for the collector.
1062   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1063 
1064   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1065 
1066   // Adaptive size policy.  No such thing for g1.
1067   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1068 
1069   // The rem set and barrier set.
1070   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1071 
1072   unsigned get_gc_time_stamp() {
1073     return _gc_time_stamp;
1074   }
1075 
1076   inline void reset_gc_time_stamp();
1077 
1078   void check_gc_time_stamps() PRODUCT_RETURN;
1079 
1080   inline void increment_gc_time_stamp();
1081 
1082   // Reset the given region's GC timestamp. If it's starts humongous,
1083   // also reset the GC timestamp of its corresponding
1084   // continues humongous regions too.
1085   void reset_gc_time_stamps(HeapRegion* hr);
1086 
1087   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1088                                   DirtyCardQueue* into_cset_dcq,
1089                                   bool concurrent, uint worker_i);
1090 
1091   // The shared block offset table array.
1092   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1093 
1094   // Reference Processing accessors
1095 
1096   // The STW reference processor....
1097   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1098 
1099   // The Concurrent Marking reference processor...
1100   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1101 
1102   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1103   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1104 
1105   virtual size_t capacity() const;
1106   virtual size_t used() const;
1107   // This should be called when we're not holding the heap lock. The
1108   // result might be a bit inaccurate.
1109   size_t used_unlocked() const;
1110   size_t recalculate_used() const;
1111 
1112   // These virtual functions do the actual allocation.
1113   // Some heaps may offer a contiguous region for shared non-blocking
1114   // allocation, via inlined code (by exporting the address of the top and
1115   // end fields defining the extent of the contiguous allocation region.)
1116   // But G1CollectedHeap doesn't yet support this.
1117 
1118   virtual bool is_maximal_no_gc() const {
1119     return _hrm.available() == 0;
1120   }
1121 
1122   // The current number of regions in the heap.
1123   uint num_regions() const { return _hrm.length(); }
1124 
1125   // The max number of regions in the heap.
1126   uint max_regions() const { return _hrm.max_length(); }
1127 
1128   // The number of regions that are completely free.
1129   uint num_free_regions() const { return _hrm.num_free_regions(); }
1130 
1131   MemoryUsage get_auxiliary_data_memory_usage() const {
1132     return _hrm.get_auxiliary_data_memory_usage();
1133   }
1134 
1135   // The number of regions that are not completely free.
1136   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1137 
1138   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1139   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1140   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1141   void verify_dirty_young_regions() PRODUCT_RETURN;
1142 
1143 #ifndef PRODUCT
1144   // Make sure that the given bitmap has no marked objects in the
1145   // range [from,limit). If it does, print an error message and return
1146   // false. Otherwise, just return true. bitmap_name should be "prev"
1147   // or "next".
1148   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1149                                 HeapWord* from, HeapWord* limit);
1150 
1151   // Verify that the prev / next bitmap range [tams,end) for the given
1152   // region has no marks. Return true if all is well, false if errors
1153   // are detected.
1154   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1155 #endif // PRODUCT
1156 
1157   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1158   // the given region do not have any spurious marks. If errors are
1159   // detected, print appropriate error messages and crash.
1160   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1161 
1162   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1163   // have any spurious marks. If errors are detected, print
1164   // appropriate error messages and crash.
1165   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1166 
1167   // Do sanity check on the contents of the in-cset fast test table.
1168   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1169 
1170   // verify_region_sets() performs verification over the region
1171   // lists. It will be compiled in the product code to be used when
1172   // necessary (i.e., during heap verification).
1173   void verify_region_sets();
1174 
1175   // verify_region_sets_optional() is planted in the code for
1176   // list verification in non-product builds (and it can be enabled in
1177   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1178 #if HEAP_REGION_SET_FORCE_VERIFY
1179   void verify_region_sets_optional() {
1180     verify_region_sets();
1181   }
1182 #else // HEAP_REGION_SET_FORCE_VERIFY
1183   void verify_region_sets_optional() { }
1184 #endif // HEAP_REGION_SET_FORCE_VERIFY
1185 
1186 #ifdef ASSERT
1187   bool is_on_master_free_list(HeapRegion* hr) {
1188     return _hrm.is_free(hr);
1189   }
1190 #endif // ASSERT
1191 
1192   // Wrapper for the region list operations that can be called from
1193   // methods outside this class.
1194 
1195   void secondary_free_list_add(FreeRegionList* list) {
1196     _secondary_free_list.add_ordered(list);
1197   }
1198 
1199   void append_secondary_free_list() {
1200     _hrm.insert_list_into_free_list(&_secondary_free_list);
1201   }
1202 
1203   void append_secondary_free_list_if_not_empty_with_lock() {
1204     // If the secondary free list looks empty there's no reason to
1205     // take the lock and then try to append it.
1206     if (!_secondary_free_list.is_empty()) {
1207       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1208       append_secondary_free_list();
1209     }
1210   }
1211 
1212   inline void old_set_remove(HeapRegion* hr);
1213 
1214   size_t non_young_capacity_bytes() {
1215     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1216   }
1217 
1218   void set_free_regions_coming();
1219   void reset_free_regions_coming();
1220   bool free_regions_coming() { return _free_regions_coming; }
1221   void wait_while_free_regions_coming();
1222 
1223   // Determine whether the given region is one that we are using as an
1224   // old GC alloc region.
1225   bool is_old_gc_alloc_region(HeapRegion* hr) {
1226     return _allocator->is_retained_old_region(hr);
1227   }
1228 
1229   // Perform a collection of the heap; intended for use in implementing
1230   // "System.gc".  This probably implies as full a collection as the
1231   // "CollectedHeap" supports.
1232   virtual void collect(GCCause::Cause cause);
1233 
1234   // The same as above but assume that the caller holds the Heap_lock.
1235   void collect_locked(GCCause::Cause cause);
1236 
1237   virtual bool copy_allocation_context_stats(const jint* contexts,
1238                                              jlong* totals,
1239                                              jbyte* accuracy,
1240                                              jint len);
1241 
1242   // True iff an evacuation has failed in the most-recent collection.
1243   bool evacuation_failed() { return _evacuation_failed; }
1244 
1245   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1246   void prepend_to_freelist(FreeRegionList* list);
1247   void decrement_summary_bytes(size_t bytes);
1248 
1249   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1250   virtual bool is_in(const void* p) const;
1251 #ifdef ASSERT
1252   // Returns whether p is in one of the available areas of the heap. Slow but
1253   // extensive version.
1254   bool is_in_exact(const void* p) const;
1255 #endif
1256 
1257   // Return "TRUE" iff the given object address is within the collection
1258   // set. Slow implementation.
1259   inline bool obj_in_cs(oop obj);
1260 
1261   inline bool is_in_cset(const HeapRegion *hr);
1262   inline bool is_in_cset(oop obj);
1263 
1264   inline bool is_in_cset_or_humongous(const oop obj);
1265 
1266  private:
1267   // This array is used for a quick test on whether a reference points into
1268   // the collection set or not. Each of the array's elements denotes whether the
1269   // corresponding region is in the collection set or not.
1270   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1271 
1272  public:
1273 
1274   inline InCSetState in_cset_state(const oop obj);
1275 
1276   // Return "TRUE" iff the given object address is in the reserved
1277   // region of g1.
1278   bool is_in_g1_reserved(const void* p) const {
1279     return _hrm.reserved().contains(p);
1280   }
1281 
1282   // Returns a MemRegion that corresponds to the space that has been
1283   // reserved for the heap
1284   MemRegion g1_reserved() const {
1285     return _hrm.reserved();
1286   }
1287 
1288   virtual bool is_in_closed_subset(const void* p) const;
1289 
1290   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1291     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1292   }
1293 
1294   // This resets the card table to all zeros.  It is used after
1295   // a collection pause which used the card table to claim cards.
1296   void cleanUpCardTable();
1297 
1298   // Iteration functions.
1299 
1300   // Iterate over all the ref-containing fields of all objects, calling
1301   // "cl.do_oop" on each.
1302   virtual void oop_iterate(ExtendedOopClosure* cl);
1303 
1304   // Iterate over all objects, calling "cl.do_object" on each.
1305   virtual void object_iterate(ObjectClosure* cl);
1306 
1307   virtual void safe_object_iterate(ObjectClosure* cl) {
1308     object_iterate(cl);
1309   }
1310 
1311   // Iterate over all spaces in use in the heap, in ascending address order.
1312   virtual void space_iterate(SpaceClosure* cl);
1313 
1314   // Iterate over heap regions, in address order, terminating the
1315   // iteration early if the "doHeapRegion" method returns "true".
1316   void heap_region_iterate(HeapRegionClosure* blk) const;
1317 
1318   // Return the region with the given index. It assumes the index is valid.
1319   inline HeapRegion* region_at(uint index) const;
1320 
1321   // Calculate the region index of the given address. Given address must be
1322   // within the heap.
1323   inline uint addr_to_region(HeapWord* addr) const;
1324 
1325   inline HeapWord* bottom_addr_for_region(uint index) const;
1326 
1327   // Iterate over the heap regions in parallel. Assumes that this will be called
1328   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1329   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1330   // to each of the regions, by attempting to claim the region using the
1331   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1332   // region. The concurrent argument should be set to true if iteration is
1333   // performed concurrently, during which no assumptions are made for consistent
1334   // attributes of the heap regions (as they might be modified while iterating).
1335   void heap_region_par_iterate(HeapRegionClosure* cl,
1336                                uint worker_id,
1337                                HeapRegionClaimer* hrclaimer,
1338                                bool concurrent = false) const;
1339 
1340   // Clear the cached cset start regions and (more importantly)
1341   // the time stamps. Called when we reset the GC time stamp.
1342   void clear_cset_start_regions();
1343 
1344   // Given the id of a worker, obtain or calculate a suitable
1345   // starting region for iterating over the current collection set.
1346   HeapRegion* start_cset_region_for_worker(uint worker_i);
1347 
1348   // Iterate over the regions (if any) in the current collection set.
1349   void collection_set_iterate(HeapRegionClosure* blk);
1350 
1351   // As above but starting from region r
1352   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1353 
1354   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1355 
1356   // A CollectedHeap will contain some number of spaces.  This finds the
1357   // space containing a given address, or else returns NULL.
1358   virtual Space* space_containing(const void* addr) const;
1359 
1360   // Returns the HeapRegion that contains addr. addr must not be NULL.
1361   template <class T>
1362   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1363 
1364   // Returns the HeapRegion that contains addr. addr must not be NULL.
1365   // If addr is within a humongous continues region, it returns its humongous start region.
1366   template <class T>
1367   inline HeapRegion* heap_region_containing(const T addr) const;
1368 
1369   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1370   // each address in the (reserved) heap is a member of exactly
1371   // one block.  The defining characteristic of a block is that it is
1372   // possible to find its size, and thus to progress forward to the next
1373   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1374   // represent Java objects, or they might be free blocks in a
1375   // free-list-based heap (or subheap), as long as the two kinds are
1376   // distinguishable and the size of each is determinable.
1377 
1378   // Returns the address of the start of the "block" that contains the
1379   // address "addr".  We say "blocks" instead of "object" since some heaps
1380   // may not pack objects densely; a chunk may either be an object or a
1381   // non-object.
1382   virtual HeapWord* block_start(const void* addr) const;
1383 
1384   // Requires "addr" to be the start of a chunk, and returns its size.
1385   // "addr + size" is required to be the start of a new chunk, or the end
1386   // of the active area of the heap.
1387   virtual size_t block_size(const HeapWord* addr) const;
1388 
1389   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1390   // the block is an object.
1391   virtual bool block_is_obj(const HeapWord* addr) const;
1392 
1393   // Does this heap support heap inspection? (+PrintClassHistogram)
1394   virtual bool supports_heap_inspection() const { return true; }
1395 
1396   // Section on thread-local allocation buffers (TLABs)
1397   // See CollectedHeap for semantics.
1398 
1399   bool supports_tlab_allocation() const;
1400   size_t tlab_capacity(Thread* ignored) const;
1401   size_t tlab_used(Thread* ignored) const;
1402   size_t max_tlab_size() const;
1403   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1404 
1405   // Can a compiler initialize a new object without store barriers?
1406   // This permission only extends from the creation of a new object
1407   // via a TLAB up to the first subsequent safepoint. If such permission
1408   // is granted for this heap type, the compiler promises to call
1409   // defer_store_barrier() below on any slow path allocation of
1410   // a new object for which such initializing store barriers will
1411   // have been elided. G1, like CMS, allows this, but should be
1412   // ready to provide a compensating write barrier as necessary
1413   // if that storage came out of a non-young region. The efficiency
1414   // of this implementation depends crucially on being able to
1415   // answer very efficiently in constant time whether a piece of
1416   // storage in the heap comes from a young region or not.
1417   // See ReduceInitialCardMarks.
1418   virtual bool can_elide_tlab_store_barriers() const {
1419     return true;
1420   }
1421 
1422   virtual bool card_mark_must_follow_store() const {
1423     return true;
1424   }
1425 
1426   inline bool is_in_young(const oop obj);
1427 
1428 #ifdef ASSERT
1429   virtual bool is_in_partial_collection(const void* p);
1430 #endif
1431 
1432   virtual bool is_scavengable(const void* addr);
1433 
1434   // We don't need barriers for initializing stores to objects
1435   // in the young gen: for the SATB pre-barrier, there is no
1436   // pre-value that needs to be remembered; for the remembered-set
1437   // update logging post-barrier, we don't maintain remembered set
1438   // information for young gen objects.
1439   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1440 
1441   // Returns "true" iff the given word_size is "very large".
1442   static bool is_humongous(size_t word_size) {
1443     // Note this has to be strictly greater-than as the TLABs
1444     // are capped at the humongous threshold and we want to
1445     // ensure that we don't try to allocate a TLAB as
1446     // humongous and that we don't allocate a humongous
1447     // object in a TLAB.
1448     return word_size > _humongous_object_threshold_in_words;
1449   }
1450 
1451   // Update mod union table with the set of dirty cards.
1452   void updateModUnion();
1453 
1454   // Set the mod union bits corresponding to the given memRegion.  Note
1455   // that this is always a safe operation, since it doesn't clear any
1456   // bits.
1457   void markModUnionRange(MemRegion mr);
1458 
1459   // Records the fact that a marking phase is no longer in progress.
1460   void set_marking_complete() {
1461     _mark_in_progress = false;
1462   }
1463   void set_marking_started() {
1464     _mark_in_progress = true;
1465   }
1466   bool mark_in_progress() {
1467     return _mark_in_progress;
1468   }
1469 
1470   // Print the maximum heap capacity.
1471   virtual size_t max_capacity() const;
1472 
1473   virtual jlong millis_since_last_gc();
1474 
1475 
1476   // Convenience function to be used in situations where the heap type can be
1477   // asserted to be this type.
1478   static G1CollectedHeap* heap();
1479 
1480   void set_region_short_lived_locked(HeapRegion* hr);
1481   // add appropriate methods for any other surv rate groups
1482 
1483   YoungList* young_list() const { return _young_list; }
1484 
1485   // debugging
1486   bool check_young_list_well_formed() {
1487     return _young_list->check_list_well_formed();
1488   }
1489 
1490   bool check_young_list_empty(bool check_heap,
1491                               bool check_sample = true);
1492 
1493   // *** Stuff related to concurrent marking.  It's not clear to me that so
1494   // many of these need to be public.
1495 
1496   // The functions below are helper functions that a subclass of
1497   // "CollectedHeap" can use in the implementation of its virtual
1498   // functions.
1499   // This performs a concurrent marking of the live objects in a
1500   // bitmap off to the side.
1501   void doConcurrentMark();
1502 
1503   bool isMarkedPrev(oop obj) const;
1504   bool isMarkedNext(oop obj) const;
1505 
1506   // Determine if an object is dead, given the object and also
1507   // the region to which the object belongs. An object is dead
1508   // iff a) it was not allocated since the last mark and b) it
1509   // is not marked.
1510   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1511     return
1512       !hr->obj_allocated_since_prev_marking(obj) &&
1513       !isMarkedPrev(obj);
1514   }
1515 
1516   // This function returns true when an object has been
1517   // around since the previous marking and hasn't yet
1518   // been marked during this marking.
1519   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1520     return
1521       !hr->obj_allocated_since_next_marking(obj) &&
1522       !isMarkedNext(obj);
1523   }
1524 
1525   // Determine if an object is dead, given only the object itself.
1526   // This will find the region to which the object belongs and
1527   // then call the region version of the same function.
1528 
1529   // Added if it is NULL it isn't dead.
1530 
1531   inline bool is_obj_dead(const oop obj) const;
1532 
1533   inline bool is_obj_ill(const oop obj) const;
1534 
1535   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1536   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1537   bool is_marked(oop obj, VerifyOption vo);
1538   const char* top_at_mark_start_str(VerifyOption vo);
1539 
1540   ConcurrentMark* concurrent_mark() const { return _cm; }
1541 
1542   // Refinement
1543 
1544   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1545 
1546   // The dirty cards region list is used to record a subset of regions
1547   // whose cards need clearing. The list if populated during the
1548   // remembered set scanning and drained during the card table
1549   // cleanup. Although the methods are reentrant, population/draining
1550   // phases must not overlap. For synchronization purposes the last
1551   // element on the list points to itself.
1552   HeapRegion* _dirty_cards_region_list;
1553   void push_dirty_cards_region(HeapRegion* hr);
1554   HeapRegion* pop_dirty_cards_region();
1555 
1556   // Optimized nmethod scanning support routines
1557 
1558   // Register the given nmethod with the G1 heap.
1559   virtual void register_nmethod(nmethod* nm);
1560 
1561   // Unregister the given nmethod from the G1 heap.
1562   virtual void unregister_nmethod(nmethod* nm);
1563 
1564   // Free up superfluous code root memory.
1565   void purge_code_root_memory();
1566 
1567   // Rebuild the strong code root lists for each region
1568   // after a full GC.
1569   void rebuild_strong_code_roots();
1570 
1571   // Delete entries for dead interned string and clean up unreferenced symbols
1572   // in symbol table, possibly in parallel.
1573   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1574 
1575   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1576   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1577 
1578   // Redirty logged cards in the refinement queue.
1579   void redirty_logged_cards();
1580   // Verification
1581 
1582   // The following is just to alert the verification code
1583   // that a full collection has occurred and that the
1584   // remembered sets are no longer up to date.
1585   bool _full_collection;
1586   void set_full_collection() { _full_collection = true;}
1587   void clear_full_collection() {_full_collection = false;}
1588   bool full_collection() {return _full_collection;}
1589 
1590   // Perform any cleanup actions necessary before allowing a verification.
1591   virtual void prepare_for_verify();
1592 
1593   // Perform verification.
1594 
1595   // vo == UsePrevMarking  -> use "prev" marking information,
1596   // vo == UseNextMarking -> use "next" marking information
1597   // vo == UseMarkWord    -> use the mark word in the object header
1598   //
1599   // NOTE: Only the "prev" marking information is guaranteed to be
1600   // consistent most of the time, so most calls to this should use
1601   // vo == UsePrevMarking.
1602   // Currently, there is only one case where this is called with
1603   // vo == UseNextMarking, which is to verify the "next" marking
1604   // information at the end of remark.
1605   // Currently there is only one place where this is called with
1606   // vo == UseMarkWord, which is to verify the marking during a
1607   // full GC.
1608   void verify(bool silent, VerifyOption vo);
1609 
1610   // Override; it uses the "prev" marking information
1611   virtual void verify(bool silent);
1612 
1613   // The methods below are here for convenience and dispatch the
1614   // appropriate method depending on value of the given VerifyOption
1615   // parameter. The values for that parameter, and their meanings,
1616   // are the same as those above.
1617 
1618   bool is_obj_dead_cond(const oop obj,
1619                         const HeapRegion* hr,
1620                         const VerifyOption vo) const;
1621 
1622   bool is_obj_dead_cond(const oop obj,
1623                         const VerifyOption vo) const;
1624 
1625   // Printing
1626 
1627   virtual void print_on(outputStream* st) const;
1628   virtual void print_extended_on(outputStream* st) const;
1629   virtual void print_on_error(outputStream* st) const;
1630 
1631   virtual void print_gc_threads_on(outputStream* st) const;
1632   virtual void gc_threads_do(ThreadClosure* tc) const;
1633 
1634   // Override
1635   void print_tracing_info() const;
1636 
1637   // The following two methods are helpful for debugging RSet issues.
1638   void print_cset_rsets() PRODUCT_RETURN;
1639   void print_all_rsets() PRODUCT_RETURN;
1640 
1641 public:
1642   size_t pending_card_num();
1643   size_t cards_scanned();
1644 
1645 protected:
1646   size_t _max_heap_capacity;
1647 };
1648 
1649 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---