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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  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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  20  * or visit www.oracle.com if you need additional information or have any
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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/concurrentMark.hpp"
  29 #include "gc_implementation/g1/evacuationInfo.hpp"
  30 #include "gc_implementation/g1/g1AllocRegion.hpp"
  31 #include "gc_implementation/g1/g1BiasedArray.hpp"
  32 #include "gc_implementation/g1/g1HRPrinter.hpp"
  33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  34 #include "gc_implementation/g1/g1RemSet.hpp"
  35 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  36 #include "gc_implementation/g1/g1YCTypes.hpp"
  37 #include "gc_implementation/g1/heapRegionSeq.hpp"
  38 #include "gc_implementation/g1/heapRegionSet.hpp"
  39 #include "gc_implementation/shared/hSpaceCounters.hpp"
  40 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  41 #include "memory/barrierSet.hpp"
  42 #include "memory/memRegion.hpp"
  43 #include "memory/sharedHeap.hpp"
  44 #include "utilities/stack.hpp"
  45 
  46 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  47 // It uses the "Garbage First" heap organization and algorithm, which
  48 // may combine concurrent marking with parallel, incremental compaction of
  49 // heap subsets that will yield large amounts of garbage.
  50 
  51 // Forward declarations
  52 class HeapRegion;
  53 class HRRSCleanupTask;
  54 class GenerationSpec;
  55 class OopsInHeapRegionClosure;
  56 class G1KlassScanClosure;
  57 class G1ScanHeapEvacClosure;
  58 class ObjectClosure;
  59 class SpaceClosure;
  60 class CompactibleSpaceClosure;
  61 class Space;
  62 class G1CollectorPolicy;
  63 class GenRemSet;
  64 class G1RemSet;
  65 class HeapRegionRemSetIterator;
  66 class ConcurrentMark;
  67 class ConcurrentMarkThread;
  68 class ConcurrentG1Refine;
  69 class ConcurrentGCTimer;
  70 class GenerationCounters;
  71 class STWGCTimer;
  72 class G1NewTracer;
  73 class G1OldTracer;
  74 class EvacuationFailedInfo;
  75 class nmethod;
  76 class Ticks;
  77 
  78 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  79 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  80 
  81 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  82 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  83 
  84 enum GCAllocPurpose {
  85   GCAllocForTenured,
  86   GCAllocForSurvived,
  87   GCAllocPurposeCount
  88 };
  89 
  90 class YoungList : public CHeapObj<mtGC> {
  91 private:
  92   G1CollectedHeap* _g1h;
  93 
  94   HeapRegion* _head;
  95 
  96   HeapRegion* _survivor_head;
  97   HeapRegion* _survivor_tail;
  98 
  99   HeapRegion* _curr;
 100 
 101   uint        _length;
 102   uint        _survivor_length;
 103 
 104   size_t      _last_sampled_rs_lengths;
 105   size_t      _sampled_rs_lengths;
 106 
 107   void         empty_list(HeapRegion* list);
 108 
 109 public:
 110   YoungList(G1CollectedHeap* g1h);
 111 
 112   void         push_region(HeapRegion* hr);
 113   void         add_survivor_region(HeapRegion* hr);
 114 
 115   void         empty_list();
 116   bool         is_empty() { return _length == 0; }
 117   uint         length() { return _length; }
 118   uint         survivor_length() { return _survivor_length; }
 119 
 120   // Currently we do not keep track of the used byte sum for the
 121   // young list and the survivors and it'd be quite a lot of work to
 122   // do so. When we'll eventually replace the young list with
 123   // instances of HeapRegionLinkedList we'll get that for free. So,
 124   // we'll report the more accurate information then.
 125   size_t       eden_used_bytes() {
 126     assert(length() >= survivor_length(), "invariant");
 127     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 128   }
 129   size_t       survivor_used_bytes() {
 130     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 131   }
 132 
 133   void rs_length_sampling_init();
 134   bool rs_length_sampling_more();
 135   void rs_length_sampling_next();
 136 
 137   void reset_sampled_info() {
 138     _last_sampled_rs_lengths =   0;
 139   }
 140   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 141 
 142   // for development purposes
 143   void reset_auxilary_lists();
 144   void clear() { _head = NULL; _length = 0; }
 145 
 146   void clear_survivors() {
 147     _survivor_head    = NULL;
 148     _survivor_tail    = NULL;
 149     _survivor_length  = 0;
 150   }
 151 
 152   HeapRegion* first_region() { return _head; }
 153   HeapRegion* first_survivor_region() { return _survivor_head; }
 154   HeapRegion* last_survivor_region() { return _survivor_tail; }
 155 
 156   // debugging
 157   bool          check_list_well_formed();
 158   bool          check_list_empty(bool check_sample = true);
 159   void          print();
 160 };
 161 
 162 class MutatorAllocRegion : public G1AllocRegion {
 163 protected:
 164   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 165   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 166 public:
 167   MutatorAllocRegion()
 168     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 169 };
 170 
 171 class SurvivorGCAllocRegion : public G1AllocRegion {
 172 protected:
 173   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 174   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 175 public:
 176   SurvivorGCAllocRegion()
 177   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 178 };
 179 
 180 class OldGCAllocRegion : public G1AllocRegion {
 181 protected:
 182   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 183   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 184 public:
 185   OldGCAllocRegion()
 186   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 187 };
 188 
 189 // The G1 STW is alive closure.
 190 // An instance is embedded into the G1CH and used as the
 191 // (optional) _is_alive_non_header closure in the STW
 192 // reference processor. It is also extensively used during
 193 // reference processing during STW evacuation pauses.
 194 class G1STWIsAliveClosure: public BoolObjectClosure {
 195   G1CollectedHeap* _g1;
 196 public:
 197   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 198   bool do_object_b(oop p);
 199 };
 200 
 201 // Instances of this class are used for quick tests on whether a reference points
 202 // into the collection set. Each of the array's elements denotes whether the
 203 // corresponding region is in the collection set.
 204 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<bool> {
 205  protected:
 206   bool default_value() const { return false; }
 207  public:
 208   void clear() { G1BiasedMappedArray<bool>::clear(); }
 209 };
 210 
 211 class RefineCardTableEntryClosure;
 212 
 213 class G1CollectedHeap : public SharedHeap {
 214   friend class VM_G1CollectForAllocation;
 215   friend class VM_G1CollectFull;
 216   friend class VM_G1IncCollectionPause;
 217   friend class VMStructs;
 218   friend class MutatorAllocRegion;
 219   friend class SurvivorGCAllocRegion;
 220   friend class OldGCAllocRegion;
 221 
 222   // Closures used in implementation.
 223   template <G1Barrier barrier, bool do_mark_object>
 224   friend class G1ParCopyClosure;
 225   friend class G1IsAliveClosure;
 226   friend class G1EvacuateFollowersClosure;
 227   friend class G1ParScanThreadState;
 228   friend class G1ParScanClosureSuper;
 229   friend class G1ParEvacuateFollowersClosure;
 230   friend class G1ParTask;
 231   friend class G1FreeGarbageRegionClosure;
 232   friend class RefineCardTableEntryClosure;
 233   friend class G1PrepareCompactClosure;
 234   friend class RegionSorter;
 235   friend class RegionResetter;
 236   friend class CountRCClosure;
 237   friend class EvacPopObjClosure;
 238   friend class G1ParCleanupCTTask;
 239 
 240   // Other related classes.
 241   friend class G1MarkSweep;
 242 
 243 private:
 244   // The one and only G1CollectedHeap, so static functions can find it.
 245   static G1CollectedHeap* _g1h;
 246 
 247   static size_t _humongous_object_threshold_in_words;
 248 
 249   // Storage for the G1 heap.
 250   VirtualSpace _g1_storage;
 251   MemRegion    _g1_reserved;
 252 
 253   // The part of _g1_storage that is currently committed.
 254   MemRegion _g1_committed;
 255 
 256   // The master free list. It will satisfy all new region allocations.
 257   FreeRegionList _free_list;
 258 
 259   // The secondary free list which contains regions that have been
 260   // freed up during the cleanup process. This will be appended to the
 261   // master free list when appropriate.
 262   FreeRegionList _secondary_free_list;
 263 
 264   // It keeps track of the old regions.
 265   HeapRegionSet _old_set;
 266 
 267   // It keeps track of the humongous regions.
 268   HeapRegionSet _humongous_set;
 269 
 270   // The number of regions we could create by expansion.
 271   uint _expansion_regions;
 272 
 273   // The block offset table for the G1 heap.
 274   G1BlockOffsetSharedArray* _bot_shared;
 275 
 276   // Tears down the region sets / lists so that they are empty and the
 277   // regions on the heap do not belong to a region set / list. The
 278   // only exception is the humongous set which we leave unaltered. If
 279   // free_list_only is true, it will only tear down the master free
 280   // list. It is called before a Full GC (free_list_only == false) or
 281   // before heap shrinking (free_list_only == true).
 282   void tear_down_region_sets(bool free_list_only);
 283 
 284   // Rebuilds the region sets / lists so that they are repopulated to
 285   // reflect the contents of the heap. The only exception is the
 286   // humongous set which was not torn down in the first place. If
 287   // free_list_only is true, it will only rebuild the master free
 288   // list. It is called after a Full GC (free_list_only == false) or
 289   // after heap shrinking (free_list_only == true).
 290   void rebuild_region_sets(bool free_list_only);
 291 
 292   // The sequence of all heap regions in the heap.
 293   HeapRegionSeq _hrs;
 294 
 295   // Alloc region used to satisfy mutator allocation requests.
 296   MutatorAllocRegion _mutator_alloc_region;
 297 
 298   // Alloc region used to satisfy allocation requests by the GC for
 299   // survivor objects.
 300   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 301 
 302   // PLAB sizing policy for survivors.
 303   PLABStats _survivor_plab_stats;
 304 
 305   // Alloc region used to satisfy allocation requests by the GC for
 306   // old objects.
 307   OldGCAllocRegion _old_gc_alloc_region;
 308 
 309   // PLAB sizing policy for tenured objects.
 310   PLABStats _old_plab_stats;
 311 
 312   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 313     PLABStats* stats = NULL;
 314 
 315     switch (purpose) {
 316     case GCAllocForSurvived:
 317       stats = &_survivor_plab_stats;
 318       break;
 319     case GCAllocForTenured:
 320       stats = &_old_plab_stats;
 321       break;
 322     default:
 323       assert(false, "unrecognized GCAllocPurpose");
 324     }
 325 
 326     return stats;
 327   }
 328 
 329   // The last old region we allocated to during the last GC.
 330   // Typically, it is not full so we should re-use it during the next GC.
 331   HeapRegion* _retained_old_gc_alloc_region;
 332 
 333   // It specifies whether we should attempt to expand the heap after a
 334   // region allocation failure. If heap expansion fails we set this to
 335   // false so that we don't re-attempt the heap expansion (it's likely
 336   // that subsequent expansion attempts will also fail if one fails).
 337   // Currently, it is only consulted during GC and it's reset at the
 338   // start of each GC.
 339   bool _expand_heap_after_alloc_failure;
 340 
 341   // It resets the mutator alloc region before new allocations can take place.
 342   void init_mutator_alloc_region();
 343 
 344   // It releases the mutator alloc region.
 345   void release_mutator_alloc_region();
 346 
 347   // It initializes the GC alloc regions at the start of a GC.
 348   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 349 
 350   // It releases the GC alloc regions at the end of a GC.
 351   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 352 
 353   // It does any cleanup that needs to be done on the GC alloc regions
 354   // before a Full GC.
 355   void abandon_gc_alloc_regions();
 356 
 357   // Helper for monitoring and management support.
 358   G1MonitoringSupport* _g1mm;
 359 
 360   // Determines PLAB size for a particular allocation purpose.
 361   size_t desired_plab_sz(GCAllocPurpose purpose);
 362 
 363   // Outside of GC pauses, the number of bytes used in all regions other
 364   // than the current allocation region.
 365   size_t _summary_bytes_used;
 366 
 367   // This array is used for a quick test on whether a reference points into
 368   // the collection set or not. Each of the array's elements denotes whether the
 369   // corresponding region is in the collection set or not.
 370   G1FastCSetBiasedMappedArray _in_cset_fast_test;
 371 
 372   volatile unsigned _gc_time_stamp;
 373 
 374   size_t* _surviving_young_words;
 375 
 376   G1HRPrinter _hr_printer;
 377 
 378   void setup_surviving_young_words();
 379   void update_surviving_young_words(size_t* surv_young_words);
 380   void cleanup_surviving_young_words();
 381 
 382   // It decides whether an explicit GC should start a concurrent cycle
 383   // instead of doing a STW GC. Currently, a concurrent cycle is
 384   // explicitly started if:
 385   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 386   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 387   // (c) cause == _g1_humongous_allocation
 388   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 389 
 390   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 391   // concurrent cycles) we have started.
 392   volatile unsigned int _old_marking_cycles_started;
 393 
 394   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 395   // concurrent cycles) we have completed.
 396   volatile unsigned int _old_marking_cycles_completed;
 397 
 398   bool _concurrent_cycle_started;
 399 
 400   // This is a non-product method that is helpful for testing. It is
 401   // called at the end of a GC and artificially expands the heap by
 402   // allocating a number of dead regions. This way we can induce very
 403   // frequent marking cycles and stress the cleanup / concurrent
 404   // cleanup code more (as all the regions that will be allocated by
 405   // this method will be found dead by the marking cycle).
 406   void allocate_dummy_regions() PRODUCT_RETURN;
 407 
 408   // Clear RSets after a compaction. It also resets the GC time stamps.
 409   void clear_rsets_post_compaction();
 410 
 411   // If the HR printer is active, dump the state of the regions in the
 412   // heap after a compaction.
 413   void print_hrs_post_compaction();
 414 
 415   double verify(bool guard, const char* msg);
 416   void verify_before_gc();
 417   void verify_after_gc();
 418 
 419   void log_gc_header();
 420   void log_gc_footer(double pause_time_sec);
 421 
 422   // These are macros so that, if the assert fires, we get the correct
 423   // line number, file, etc.
 424 
 425 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 426   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 427           (_extra_message_),                                                  \
 428           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 429           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 430           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 431 
 432 #define assert_heap_locked()                                                  \
 433   do {                                                                        \
 434     assert(Heap_lock->owned_by_self(),                                        \
 435            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 436   } while (0)
 437 
 438 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 439   do {                                                                        \
 440     assert(Heap_lock->owned_by_self() ||                                      \
 441            (SafepointSynchronize::is_at_safepoint() &&                        \
 442              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 443            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 444                                         "should be at a safepoint"));         \
 445   } while (0)
 446 
 447 #define assert_heap_locked_and_not_at_safepoint()                             \
 448   do {                                                                        \
 449     assert(Heap_lock->owned_by_self() &&                                      \
 450                                     !SafepointSynchronize::is_at_safepoint(), \
 451           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 452                                        "should not be at a safepoint"));      \
 453   } while (0)
 454 
 455 #define assert_heap_not_locked()                                              \
 456   do {                                                                        \
 457     assert(!Heap_lock->owned_by_self(),                                       \
 458         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 459   } while (0)
 460 
 461 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 462   do {                                                                        \
 463     assert(!Heap_lock->owned_by_self() &&                                     \
 464                                     !SafepointSynchronize::is_at_safepoint(), \
 465       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 466                                    "should not be at a safepoint"));          \
 467   } while (0)
 468 
 469 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 470   do {                                                                        \
 471     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 472               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 473            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 474   } while (0)
 475 
 476 #define assert_not_at_safepoint()                                             \
 477   do {                                                                        \
 478     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 479            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 480   } while (0)
 481 
 482 protected:
 483 
 484   // The young region list.
 485   YoungList*  _young_list;
 486 
 487   // The current policy object for the collector.
 488   G1CollectorPolicy* _g1_policy;
 489 
 490   // This is the second level of trying to allocate a new region. If
 491   // new_region() didn't find a region on the free_list, this call will
 492   // check whether there's anything available on the
 493   // secondary_free_list and/or wait for more regions to appear on
 494   // that list, if _free_regions_coming is set.
 495   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 496 
 497   // Try to allocate a single non-humongous HeapRegion sufficient for
 498   // an allocation of the given word_size. If do_expand is true,
 499   // attempt to expand the heap if necessary to satisfy the allocation
 500   // request. If the region is to be used as an old region or for a
 501   // humongous object, set is_old to true. If not, to false.
 502   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 503 
 504   // Attempt to satisfy a humongous allocation request of the given
 505   // size by finding a contiguous set of free regions of num_regions
 506   // length and remove them from the master free list. Return the
 507   // index of the first region or G1_NULL_HRS_INDEX if the search
 508   // was unsuccessful.
 509   uint humongous_obj_allocate_find_first(uint num_regions,
 510                                          size_t word_size);
 511 
 512   // Initialize a contiguous set of free regions of length num_regions
 513   // and starting at index first so that they appear as a single
 514   // humongous region.
 515   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 516                                                       uint num_regions,
 517                                                       size_t word_size);
 518 
 519   // Attempt to allocate a humongous object of the given size. Return
 520   // NULL if unsuccessful.
 521   HeapWord* humongous_obj_allocate(size_t word_size);
 522 
 523   // The following two methods, allocate_new_tlab() and
 524   // mem_allocate(), are the two main entry points from the runtime
 525   // into the G1's allocation routines. They have the following
 526   // assumptions:
 527   //
 528   // * They should both be called outside safepoints.
 529   //
 530   // * They should both be called without holding the Heap_lock.
 531   //
 532   // * All allocation requests for new TLABs should go to
 533   //   allocate_new_tlab().
 534   //
 535   // * All non-TLAB allocation requests should go to mem_allocate().
 536   //
 537   // * If either call cannot satisfy the allocation request using the
 538   //   current allocating region, they will try to get a new one. If
 539   //   this fails, they will attempt to do an evacuation pause and
 540   //   retry the allocation.
 541   //
 542   // * If all allocation attempts fail, even after trying to schedule
 543   //   an evacuation pause, allocate_new_tlab() will return NULL,
 544   //   whereas mem_allocate() will attempt a heap expansion and/or
 545   //   schedule a Full GC.
 546   //
 547   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 548   //   should never be called with word_size being humongous. All
 549   //   humongous allocation requests should go to mem_allocate() which
 550   //   will satisfy them with a special path.
 551 
 552   virtual HeapWord* allocate_new_tlab(size_t word_size);
 553 
 554   virtual HeapWord* mem_allocate(size_t word_size,
 555                                  bool*  gc_overhead_limit_was_exceeded);
 556 
 557   // The following three methods take a gc_count_before_ret
 558   // parameter which is used to return the GC count if the method
 559   // returns NULL. Given that we are required to read the GC count
 560   // while holding the Heap_lock, and these paths will take the
 561   // Heap_lock at some point, it's easier to get them to read the GC
 562   // count while holding the Heap_lock before they return NULL instead
 563   // of the caller (namely: mem_allocate()) having to also take the
 564   // Heap_lock just to read the GC count.
 565 
 566   // First-level mutator allocation attempt: try to allocate out of
 567   // the mutator alloc region without taking the Heap_lock. This
 568   // should only be used for non-humongous allocations.
 569   inline HeapWord* attempt_allocation(size_t word_size,
 570                                       unsigned int* gc_count_before_ret,
 571                                       int* gclocker_retry_count_ret);
 572 
 573   // Second-level mutator allocation attempt: take the Heap_lock and
 574   // retry the allocation attempt, potentially scheduling a GC
 575   // pause. This should only be used for non-humongous allocations.
 576   HeapWord* attempt_allocation_slow(size_t word_size,
 577                                     unsigned int* gc_count_before_ret,
 578                                     int* gclocker_retry_count_ret);
 579 
 580   // Takes the Heap_lock and attempts a humongous allocation. It can
 581   // potentially schedule a GC pause.
 582   HeapWord* attempt_allocation_humongous(size_t word_size,
 583                                          unsigned int* gc_count_before_ret,
 584                                          int* gclocker_retry_count_ret);
 585 
 586   // Allocation attempt that should be called during safepoints (e.g.,
 587   // at the end of a successful GC). expect_null_mutator_alloc_region
 588   // specifies whether the mutator alloc region is expected to be NULL
 589   // or not.
 590   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 591                                        bool expect_null_mutator_alloc_region);
 592 
 593   // It dirties the cards that cover the block so that so that the post
 594   // write barrier never queues anything when updating objects on this
 595   // block. It is assumed (and in fact we assert) that the block
 596   // belongs to a young region.
 597   inline void dirty_young_block(HeapWord* start, size_t word_size);
 598 
 599   // Allocate blocks during garbage collection. Will ensure an
 600   // allocation region, either by picking one or expanding the
 601   // heap, and then allocate a block of the given size. The block
 602   // may not be a humongous - it must fit into a single heap region.
 603   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 604 
 605   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 606                                     HeapRegion*    alloc_region,
 607                                     bool           par,
 608                                     size_t         word_size);
 609 
 610   // Ensure that no further allocations can happen in "r", bearing in mind
 611   // that parallel threads might be attempting allocations.
 612   void par_allocate_remaining_space(HeapRegion* r);
 613 
 614   // Allocation attempt during GC for a survivor object / PLAB.
 615   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 616 
 617   // Allocation attempt during GC for an old object / PLAB.
 618   inline HeapWord* old_attempt_allocation(size_t word_size);
 619 
 620   // These methods are the "callbacks" from the G1AllocRegion class.
 621 
 622   // For mutator alloc regions.
 623   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 624   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 625                                    size_t allocated_bytes);
 626 
 627   // For GC alloc regions.
 628   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 629                                   GCAllocPurpose ap);
 630   void retire_gc_alloc_region(HeapRegion* alloc_region,
 631                               size_t allocated_bytes, GCAllocPurpose ap);
 632 
 633   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 634   //   inspection request and should collect the entire heap
 635   // - if clear_all_soft_refs is true, all soft references should be
 636   //   cleared during the GC
 637   // - if explicit_gc is false, word_size describes the allocation that
 638   //   the GC should attempt (at least) to satisfy
 639   // - it returns false if it is unable to do the collection due to the
 640   //   GC locker being active, true otherwise
 641   bool do_collection(bool explicit_gc,
 642                      bool clear_all_soft_refs,
 643                      size_t word_size);
 644 
 645   // Callback from VM_G1CollectFull operation.
 646   // Perform a full collection.
 647   virtual void do_full_collection(bool clear_all_soft_refs);
 648 
 649   // Resize the heap if necessary after a full collection.  If this is
 650   // after a collect-for allocation, "word_size" is the allocation size,
 651   // and will be considered part of the used portion of the heap.
 652   void resize_if_necessary_after_full_collection(size_t word_size);
 653 
 654   // Callback from VM_G1CollectForAllocation operation.
 655   // This function does everything necessary/possible to satisfy a
 656   // failed allocation request (including collection, expansion, etc.)
 657   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 658 
 659   // Attempting to expand the heap sufficiently
 660   // to support an allocation of the given "word_size".  If
 661   // successful, perform the allocation and return the address of the
 662   // allocated block, or else "NULL".
 663   HeapWord* expand_and_allocate(size_t word_size);
 664 
 665   // Process any reference objects discovered during
 666   // an incremental evacuation pause.
 667   void process_discovered_references(uint no_of_gc_workers);
 668 
 669   // Enqueue any remaining discovered references
 670   // after processing.
 671   void enqueue_discovered_references(uint no_of_gc_workers);
 672 
 673 public:
 674 
 675   G1MonitoringSupport* g1mm() {
 676     assert(_g1mm != NULL, "should have been initialized");
 677     return _g1mm;
 678   }
 679 
 680   // Expand the garbage-first heap by at least the given size (in bytes!).
 681   // Returns true if the heap was expanded by the requested amount;
 682   // false otherwise.
 683   // (Rounds up to a HeapRegion boundary.)
 684   bool expand(size_t expand_bytes);
 685 
 686   // Do anything common to GC's.
 687   virtual void gc_prologue(bool full);
 688   virtual void gc_epilogue(bool full);
 689 
 690   // We register a region with the fast "in collection set" test. We
 691   // simply set to true the array slot corresponding to this region.
 692   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 693     _in_cset_fast_test.set_by_index(r->hrs_index(), true);
 694   }
 695 
 696   // This is a fast test on whether a reference points into the
 697   // collection set or not. Assume that the reference
 698   // points into the heap.
 699   inline bool in_cset_fast_test(oop obj);
 700 
 701   void clear_cset_fast_test() {
 702     _in_cset_fast_test.clear();
 703   }
 704 
 705   // This is called at the start of either a concurrent cycle or a Full
 706   // GC to update the number of old marking cycles started.
 707   void increment_old_marking_cycles_started();
 708 
 709   // This is called at the end of either a concurrent cycle or a Full
 710   // GC to update the number of old marking cycles completed. Those two
 711   // can happen in a nested fashion, i.e., we start a concurrent
 712   // cycle, a Full GC happens half-way through it which ends first,
 713   // and then the cycle notices that a Full GC happened and ends
 714   // too. The concurrent parameter is a boolean to help us do a bit
 715   // tighter consistency checking in the method. If concurrent is
 716   // false, the caller is the inner caller in the nesting (i.e., the
 717   // Full GC). If concurrent is true, the caller is the outer caller
 718   // in this nesting (i.e., the concurrent cycle). Further nesting is
 719   // not currently supported. The end of this call also notifies
 720   // the FullGCCount_lock in case a Java thread is waiting for a full
 721   // GC to happen (e.g., it called System.gc() with
 722   // +ExplicitGCInvokesConcurrent).
 723   void increment_old_marking_cycles_completed(bool concurrent);
 724 
 725   unsigned int old_marking_cycles_completed() {
 726     return _old_marking_cycles_completed;
 727   }
 728 
 729   void register_concurrent_cycle_start(const Ticks& start_time);
 730   void register_concurrent_cycle_end();
 731   void trace_heap_after_concurrent_cycle();
 732 
 733   G1YCType yc_type();
 734 
 735   G1HRPrinter* hr_printer() { return &_hr_printer; }
 736 
 737   // Frees a non-humongous region by initializing its contents and
 738   // adding it to the free list that's passed as a parameter (this is
 739   // usually a local list which will be appended to the master free
 740   // list later). The used bytes of freed regions are accumulated in
 741   // pre_used. If par is true, the region's RSet will not be freed
 742   // up. The assumption is that this will be done later.
 743   // The locked parameter indicates if the caller has already taken
 744   // care of proper synchronization. This may allow some optimizations.
 745   void free_region(HeapRegion* hr,
 746                    FreeRegionList* free_list,
 747                    bool par,
 748                    bool locked = false);
 749 
 750   // Frees a humongous region by collapsing it into individual regions
 751   // and calling free_region() for each of them. The freed regions
 752   // will be added to the free list that's passed as a parameter (this
 753   // is usually a local list which will be appended to the master free
 754   // list later). The used bytes of freed regions are accumulated in
 755   // pre_used. If par is true, the region's RSet will not be freed
 756   // up. The assumption is that this will be done later.
 757   void free_humongous_region(HeapRegion* hr,
 758                              FreeRegionList* free_list,
 759                              bool par);
 760 protected:
 761 
 762   // Shrink the garbage-first heap by at most the given size (in bytes!).
 763   // (Rounds down to a HeapRegion boundary.)
 764   virtual void shrink(size_t expand_bytes);
 765   void shrink_helper(size_t expand_bytes);
 766 
 767   #if TASKQUEUE_STATS
 768   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 769   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 770   void reset_taskqueue_stats();
 771   #endif // TASKQUEUE_STATS
 772 
 773   // Schedule the VM operation that will do an evacuation pause to
 774   // satisfy an allocation request of word_size. *succeeded will
 775   // return whether the VM operation was successful (it did do an
 776   // evacuation pause) or not (another thread beat us to it or the GC
 777   // locker was active). Given that we should not be holding the
 778   // Heap_lock when we enter this method, we will pass the
 779   // gc_count_before (i.e., total_collections()) as a parameter since
 780   // it has to be read while holding the Heap_lock. Currently, both
 781   // methods that call do_collection_pause() release the Heap_lock
 782   // before the call, so it's easy to read gc_count_before just before.
 783   HeapWord* do_collection_pause(size_t         word_size,
 784                                 unsigned int   gc_count_before,
 785                                 bool*          succeeded,
 786                                 GCCause::Cause gc_cause);
 787 
 788   // The guts of the incremental collection pause, executed by the vm
 789   // thread. It returns false if it is unable to do the collection due
 790   // to the GC locker being active, true otherwise
 791   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 792 
 793   // Actually do the work of evacuating the collection set.
 794   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 795 
 796   // The g1 remembered set of the heap.
 797   G1RemSet* _g1_rem_set;
 798 
 799   // A set of cards that cover the objects for which the Rsets should be updated
 800   // concurrently after the collection.
 801   DirtyCardQueueSet _dirty_card_queue_set;
 802 
 803   // The closure used to refine a single card.
 804   RefineCardTableEntryClosure* _refine_cte_cl;
 805 
 806   // A function to check the consistency of dirty card logs.
 807   void check_ct_logs_at_safepoint();
 808 
 809   // A DirtyCardQueueSet that is used to hold cards that contain
 810   // references into the current collection set. This is used to
 811   // update the remembered sets of the regions in the collection
 812   // set in the event of an evacuation failure.
 813   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 814 
 815   // After a collection pause, make the regions in the CS into free
 816   // regions.
 817   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 818 
 819   // Abandon the current collection set without recording policy
 820   // statistics or updating free lists.
 821   void abandon_collection_set(HeapRegion* cs_head);
 822 
 823   // Applies "scan_non_heap_roots" to roots outside the heap,
 824   // "scan_rs" to roots inside the heap (having done "set_region" to
 825   // indicate the region in which the root resides),
 826   // and does "scan_metadata" If "scan_rs" is
 827   // NULL, then this step is skipped.  The "worker_i"
 828   // param is for use with parallel roots processing, and should be
 829   // the "i" of the calling parallel worker thread's work(i) function.
 830   // In the sequential case this param will be ignored.
 831   void g1_process_strong_roots(bool is_scavenging,
 832                                ScanningOption so,
 833                                OopClosure* scan_non_heap_roots,
 834                                OopsInHeapRegionClosure* scan_rs,
 835                                G1KlassScanClosure* scan_klasses,
 836                                uint worker_i);
 837 
 838   // Notifies all the necessary spaces that the committed space has
 839   // been updated (either expanded or shrunk). It should be called
 840   // after _g1_storage is updated.
 841   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 842 
 843   // The concurrent marker (and the thread it runs in.)
 844   ConcurrentMark* _cm;
 845   ConcurrentMarkThread* _cmThread;
 846   bool _mark_in_progress;
 847 
 848   // The concurrent refiner.
 849   ConcurrentG1Refine* _cg1r;
 850 
 851   // The parallel task queues
 852   RefToScanQueueSet *_task_queues;
 853 
 854   // True iff a evacuation has failed in the current collection.
 855   bool _evacuation_failed;
 856 
 857   EvacuationFailedInfo* _evacuation_failed_info_array;
 858 
 859   // Failed evacuations cause some logical from-space objects to have
 860   // forwarding pointers to themselves.  Reset them.
 861   void remove_self_forwarding_pointers();
 862 
 863   // Together, these store an object with a preserved mark, and its mark value.
 864   Stack<oop, mtGC>     _objs_with_preserved_marks;
 865   Stack<markOop, mtGC> _preserved_marks_of_objs;
 866 
 867   // Preserve the mark of "obj", if necessary, in preparation for its mark
 868   // word being overwritten with a self-forwarding-pointer.
 869   void preserve_mark_if_necessary(oop obj, markOop m);
 870 
 871   // The stack of evac-failure objects left to be scanned.
 872   GrowableArray<oop>*    _evac_failure_scan_stack;
 873   // The closure to apply to evac-failure objects.
 874 
 875   OopsInHeapRegionClosure* _evac_failure_closure;
 876   // Set the field above.
 877   void
 878   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 879     _evac_failure_closure = evac_failure_closure;
 880   }
 881 
 882   // Push "obj" on the scan stack.
 883   void push_on_evac_failure_scan_stack(oop obj);
 884   // Process scan stack entries until the stack is empty.
 885   void drain_evac_failure_scan_stack();
 886   // True iff an invocation of "drain_scan_stack" is in progress; to
 887   // prevent unnecessary recursion.
 888   bool _drain_in_progress;
 889 
 890   // Do any necessary initialization for evacuation-failure handling.
 891   // "cl" is the closure that will be used to process evac-failure
 892   // objects.
 893   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 894   // Do any necessary cleanup for evacuation-failure handling data
 895   // structures.
 896   void finalize_for_evac_failure();
 897 
 898   // An attempt to evacuate "obj" has failed; take necessary steps.
 899   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 900   void handle_evacuation_failure_common(oop obj, markOop m);
 901 
 902 #ifndef PRODUCT
 903   // Support for forcing evacuation failures. Analogous to
 904   // PromotionFailureALot for the other collectors.
 905 
 906   // Records whether G1EvacuationFailureALot should be in effect
 907   // for the current GC
 908   bool _evacuation_failure_alot_for_current_gc;
 909 
 910   // Used to record the GC number for interval checking when
 911   // determining whether G1EvaucationFailureALot is in effect
 912   // for the current GC.
 913   size_t _evacuation_failure_alot_gc_number;
 914 
 915   // Count of the number of evacuations between failures.
 916   volatile size_t _evacuation_failure_alot_count;
 917 
 918   // Set whether G1EvacuationFailureALot should be in effect
 919   // for the current GC (based upon the type of GC and which
 920   // command line flags are set);
 921   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 922                                                   bool during_initial_mark,
 923                                                   bool during_marking);
 924 
 925   inline void set_evacuation_failure_alot_for_current_gc();
 926 
 927   // Return true if it's time to cause an evacuation failure.
 928   inline bool evacuation_should_fail();
 929 
 930   // Reset the G1EvacuationFailureALot counters.  Should be called at
 931   // the end of an evacuation pause in which an evacuation failure occurred.
 932   inline void reset_evacuation_should_fail();
 933 #endif // !PRODUCT
 934 
 935   // ("Weak") Reference processing support.
 936   //
 937   // G1 has 2 instances of the reference processor class. One
 938   // (_ref_processor_cm) handles reference object discovery
 939   // and subsequent processing during concurrent marking cycles.
 940   //
 941   // The other (_ref_processor_stw) handles reference object
 942   // discovery and processing during full GCs and incremental
 943   // evacuation pauses.
 944   //
 945   // During an incremental pause, reference discovery will be
 946   // temporarily disabled for _ref_processor_cm and will be
 947   // enabled for _ref_processor_stw. At the end of the evacuation
 948   // pause references discovered by _ref_processor_stw will be
 949   // processed and discovery will be disabled. The previous
 950   // setting for reference object discovery for _ref_processor_cm
 951   // will be re-instated.
 952   //
 953   // At the start of marking:
 954   //  * Discovery by the CM ref processor is verified to be inactive
 955   //    and it's discovered lists are empty.
 956   //  * Discovery by the CM ref processor is then enabled.
 957   //
 958   // At the end of marking:
 959   //  * Any references on the CM ref processor's discovered
 960   //    lists are processed (possibly MT).
 961   //
 962   // At the start of full GC we:
 963   //  * Disable discovery by the CM ref processor and
 964   //    empty CM ref processor's discovered lists
 965   //    (without processing any entries).
 966   //  * Verify that the STW ref processor is inactive and it's
 967   //    discovered lists are empty.
 968   //  * Temporarily set STW ref processor discovery as single threaded.
 969   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 970   //    field.
 971   //  * Finally enable discovery by the STW ref processor.
 972   //
 973   // The STW ref processor is used to record any discovered
 974   // references during the full GC.
 975   //
 976   // At the end of a full GC we:
 977   //  * Enqueue any reference objects discovered by the STW ref processor
 978   //    that have non-live referents. This has the side-effect of
 979   //    making the STW ref processor inactive by disabling discovery.
 980   //  * Verify that the CM ref processor is still inactive
 981   //    and no references have been placed on it's discovered
 982   //    lists (also checked as a precondition during initial marking).
 983 
 984   // The (stw) reference processor...
 985   ReferenceProcessor* _ref_processor_stw;
 986 
 987   STWGCTimer* _gc_timer_stw;
 988   ConcurrentGCTimer* _gc_timer_cm;
 989 
 990   G1OldTracer* _gc_tracer_cm;
 991   G1NewTracer* _gc_tracer_stw;
 992 
 993   // During reference object discovery, the _is_alive_non_header
 994   // closure (if non-null) is applied to the referent object to
 995   // determine whether the referent is live. If so then the
 996   // reference object does not need to be 'discovered' and can
 997   // be treated as a regular oop. This has the benefit of reducing
 998   // the number of 'discovered' reference objects that need to
 999   // be processed.
1000   //
1001   // Instance of the is_alive closure for embedding into the
1002   // STW reference processor as the _is_alive_non_header field.
1003   // Supplying a value for the _is_alive_non_header field is
1004   // optional but doing so prevents unnecessary additions to
1005   // the discovered lists during reference discovery.
1006   G1STWIsAliveClosure _is_alive_closure_stw;
1007 
1008   // The (concurrent marking) reference processor...
1009   ReferenceProcessor* _ref_processor_cm;
1010 
1011   // Instance of the concurrent mark is_alive closure for embedding
1012   // into the Concurrent Marking reference processor as the
1013   // _is_alive_non_header field. Supplying a value for the
1014   // _is_alive_non_header field is optional but doing so prevents
1015   // unnecessary additions to the discovered lists during reference
1016   // discovery.
1017   G1CMIsAliveClosure _is_alive_closure_cm;
1018 
1019   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1020   HeapRegion** _worker_cset_start_region;
1021 
1022   // Time stamp to validate the regions recorded in the cache
1023   // used by G1CollectedHeap::start_cset_region_for_worker().
1024   // The heap region entry for a given worker is valid iff
1025   // the associated time stamp value matches the current value
1026   // of G1CollectedHeap::_gc_time_stamp.
1027   unsigned int* _worker_cset_start_region_time_stamp;
1028 
1029   enum G1H_process_strong_roots_tasks {
1030     G1H_PS_filter_satb_buffers,
1031     G1H_PS_refProcessor_oops_do,
1032     // Leave this one last.
1033     G1H_PS_NumElements
1034   };
1035 
1036   SubTasksDone* _process_strong_tasks;
1037 
1038   volatile bool _free_regions_coming;
1039 
1040 public:
1041 
1042   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1043 
1044   void set_refine_cte_cl_concurrency(bool concurrent);
1045 
1046   RefToScanQueue *task_queue(int i) const;
1047 
1048   // A set of cards where updates happened during the GC
1049   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1050 
1051   // A DirtyCardQueueSet that is used to hold cards that contain
1052   // references into the current collection set. This is used to
1053   // update the remembered sets of the regions in the collection
1054   // set in the event of an evacuation failure.
1055   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1056         { return _into_cset_dirty_card_queue_set; }
1057 
1058   // Create a G1CollectedHeap with the specified policy.
1059   // Must call the initialize method afterwards.
1060   // May not return if something goes wrong.
1061   G1CollectedHeap(G1CollectorPolicy* policy);
1062 
1063   // Initialize the G1CollectedHeap to have the initial and
1064   // maximum sizes and remembered and barrier sets
1065   // specified by the policy object.
1066   jint initialize();
1067 
1068   virtual void stop();
1069 
1070   // Return the (conservative) maximum heap alignment for any G1 heap
1071   static size_t conservative_max_heap_alignment();
1072 
1073   // Initialize weak reference processing.
1074   virtual void ref_processing_init();
1075 
1076   void set_par_threads(uint t) {
1077     SharedHeap::set_par_threads(t);
1078     // Done in SharedHeap but oddly there are
1079     // two _process_strong_tasks's in a G1CollectedHeap
1080     // so do it here too.
1081     _process_strong_tasks->set_n_threads(t);
1082   }
1083 
1084   // Set _n_par_threads according to a policy TBD.
1085   void set_par_threads();
1086 
1087   void set_n_termination(int t) {
1088     _process_strong_tasks->set_n_threads(t);
1089   }
1090 
1091   virtual CollectedHeap::Name kind() const {
1092     return CollectedHeap::G1CollectedHeap;
1093   }
1094 
1095   // The current policy object for the collector.
1096   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1097 
1098   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1099 
1100   // Adaptive size policy.  No such thing for g1.
1101   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1102 
1103   // The rem set and barrier set.
1104   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1105 
1106   unsigned get_gc_time_stamp() {
1107     return _gc_time_stamp;
1108   }
1109 
1110   inline void reset_gc_time_stamp();
1111 
1112   void check_gc_time_stamps() PRODUCT_RETURN;
1113 
1114   inline void increment_gc_time_stamp();
1115 
1116   // Reset the given region's GC timestamp. If it's starts humongous,
1117   // also reset the GC timestamp of its corresponding
1118   // continues humongous regions too.
1119   void reset_gc_time_stamps(HeapRegion* hr);
1120 
1121   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1122                                   DirtyCardQueue* into_cset_dcq,
1123                                   bool concurrent, uint worker_i);
1124 
1125   // The shared block offset table array.
1126   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1127 
1128   // Reference Processing accessors
1129 
1130   // The STW reference processor....
1131   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1132 
1133   // The Concurrent Marking reference processor...
1134   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1135 
1136   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1137   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1138 
1139   virtual size_t capacity() const;
1140   virtual size_t used() const;
1141   // This should be called when we're not holding the heap lock. The
1142   // result might be a bit inaccurate.
1143   size_t used_unlocked() const;
1144   size_t recalculate_used() const;
1145 
1146   // These virtual functions do the actual allocation.
1147   // Some heaps may offer a contiguous region for shared non-blocking
1148   // allocation, via inlined code (by exporting the address of the top and
1149   // end fields defining the extent of the contiguous allocation region.)
1150   // But G1CollectedHeap doesn't yet support this.
1151 
1152   virtual bool is_maximal_no_gc() const {
1153     return _g1_storage.uncommitted_size() == 0;
1154   }
1155 
1156   // The total number of regions in the heap.
1157   uint n_regions() { return _hrs.length(); }
1158 
1159   // The max number of regions in the heap.
1160   uint max_regions() { return _hrs.max_length(); }
1161 
1162   // The number of regions that are completely free.
1163   uint free_regions() { return _free_list.length(); }
1164 
1165   // The number of regions that are not completely free.
1166   uint used_regions() { return n_regions() - free_regions(); }
1167 
1168   // The number of regions available for "regular" expansion.
1169   uint expansion_regions() { return _expansion_regions; }
1170 
1171   // Factory method for HeapRegion instances. It will return NULL if
1172   // the allocation fails.
1173   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1174 
1175   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1176   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1177   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1178   void verify_dirty_young_regions() PRODUCT_RETURN;
1179 
1180 #ifndef PRODUCT
1181   // Make sure that the given bitmap has no marked objects in the
1182   // range [from,limit). If it does, print an error message and return
1183   // false. Otherwise, just return true. bitmap_name should be "prev"
1184   // or "next".
1185   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1186                                 HeapWord* from, HeapWord* limit);
1187 
1188   // Verify that the prev / next bitmap range [tams,end) for the given
1189   // region has no marks. Return true if all is well, false if errors
1190   // are detected.
1191   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1192 #endif // PRODUCT
1193 
1194   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1195   // the given region do not have any spurious marks. If errors are
1196   // detected, print appropriate error messages and crash.
1197   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1198 
1199   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1200   // have any spurious marks. If errors are detected, print
1201   // appropriate error messages and crash.
1202   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1203 
1204   // verify_region_sets() performs verification over the region
1205   // lists. It will be compiled in the product code to be used when
1206   // necessary (i.e., during heap verification).
1207   void verify_region_sets();
1208 
1209   // verify_region_sets_optional() is planted in the code for
1210   // list verification in non-product builds (and it can be enabled in
1211   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1212 #if HEAP_REGION_SET_FORCE_VERIFY
1213   void verify_region_sets_optional() {
1214     verify_region_sets();
1215   }
1216 #else // HEAP_REGION_SET_FORCE_VERIFY
1217   void verify_region_sets_optional() { }
1218 #endif // HEAP_REGION_SET_FORCE_VERIFY
1219 
1220 #ifdef ASSERT
1221   bool is_on_master_free_list(HeapRegion* hr) {
1222     return hr->containing_set() == &_free_list;
1223   }
1224 #endif // ASSERT
1225 
1226   // Wrapper for the region list operations that can be called from
1227   // methods outside this class.
1228 
1229   void secondary_free_list_add(FreeRegionList* list) {
1230     _secondary_free_list.add_ordered(list);
1231   }
1232 
1233   void append_secondary_free_list() {
1234     _free_list.add_ordered(&_secondary_free_list);
1235   }
1236 
1237   void append_secondary_free_list_if_not_empty_with_lock() {
1238     // If the secondary free list looks empty there's no reason to
1239     // take the lock and then try to append it.
1240     if (!_secondary_free_list.is_empty()) {
1241       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1242       append_secondary_free_list();
1243     }
1244   }
1245 
1246   inline void old_set_remove(HeapRegion* hr);
1247 
1248   size_t non_young_capacity_bytes() {
1249     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1250   }
1251 
1252   void set_free_regions_coming();
1253   void reset_free_regions_coming();
1254   bool free_regions_coming() { return _free_regions_coming; }
1255   void wait_while_free_regions_coming();
1256 
1257   // Determine whether the given region is one that we are using as an
1258   // old GC alloc region.
1259   bool is_old_gc_alloc_region(HeapRegion* hr) {
1260     return hr == _retained_old_gc_alloc_region;
1261   }
1262 
1263   // Perform a collection of the heap; intended for use in implementing
1264   // "System.gc".  This probably implies as full a collection as the
1265   // "CollectedHeap" supports.
1266   virtual void collect(GCCause::Cause cause);
1267 
1268   // The same as above but assume that the caller holds the Heap_lock.
1269   void collect_locked(GCCause::Cause cause);
1270 
1271   // True iff an evacuation has failed in the most-recent collection.
1272   bool evacuation_failed() { return _evacuation_failed; }
1273 
1274   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1275   void prepend_to_freelist(FreeRegionList* list);
1276   void decrement_summary_bytes(size_t bytes);
1277 
1278   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1279   virtual bool is_in(const void* p) const;
1280 
1281   // Return "TRUE" iff the given object address is within the collection
1282   // set.
1283   inline bool obj_in_cs(oop obj);
1284 
1285   // Return "TRUE" iff the given object address is in the reserved
1286   // region of g1.
1287   bool is_in_g1_reserved(const void* p) const {
1288     return _g1_reserved.contains(p);
1289   }
1290 
1291   // Returns a MemRegion that corresponds to the space that has been
1292   // reserved for the heap
1293   MemRegion g1_reserved() {
1294     return _g1_reserved;
1295   }
1296 
1297   // Returns a MemRegion that corresponds to the space that has been
1298   // committed in the heap
1299   MemRegion g1_committed() {
1300     return _g1_committed;
1301   }
1302 
1303   virtual bool is_in_closed_subset(const void* p) const;
1304 
1305   G1SATBCardTableModRefBS* g1_barrier_set() {
1306     return (G1SATBCardTableModRefBS*) barrier_set();
1307   }
1308 
1309   // This resets the card table to all zeros.  It is used after
1310   // a collection pause which used the card table to claim cards.
1311   void cleanUpCardTable();
1312 
1313   // Iteration functions.
1314 
1315   // Iterate over all the ref-containing fields of all objects, calling
1316   // "cl.do_oop" on each.
1317   virtual void oop_iterate(ExtendedOopClosure* cl);
1318 
1319   // Same as above, restricted to a memory region.
1320   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1321 
1322   // Iterate over all objects, calling "cl.do_object" on each.
1323   virtual void object_iterate(ObjectClosure* cl);
1324 
1325   virtual void safe_object_iterate(ObjectClosure* cl) {
1326     object_iterate(cl);
1327   }
1328 
1329   // Iterate over all spaces in use in the heap, in ascending address order.
1330   virtual void space_iterate(SpaceClosure* cl);
1331 
1332   // Iterate over heap regions, in address order, terminating the
1333   // iteration early if the "doHeapRegion" method returns "true".
1334   void heap_region_iterate(HeapRegionClosure* blk) const;
1335 
1336   // Return the region with the given index. It assumes the index is valid.
1337   inline HeapRegion* region_at(uint index) const;
1338 
1339   // Divide the heap region sequence into "chunks" of some size (the number
1340   // of regions divided by the number of parallel threads times some
1341   // overpartition factor, currently 4).  Assumes that this will be called
1342   // in parallel by ParallelGCThreads worker threads with distinct worker
1343   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1344   // calls will use the same "claim_value", and that that claim value is
1345   // different from the claim_value of any heap region before the start of
1346   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1347   // attempting to claim the first region in each chunk, and, if
1348   // successful, applying the closure to each region in the chunk (and
1349   // setting the claim value of the second and subsequent regions of the
1350   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1351   // i.e., that a closure never attempt to abort a traversal.
1352   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1353                                        uint worker,
1354                                        uint no_of_par_workers,
1355                                        jint claim_value);
1356 
1357   // It resets all the region claim values to the default.
1358   void reset_heap_region_claim_values();
1359 
1360   // Resets the claim values of regions in the current
1361   // collection set to the default.
1362   void reset_cset_heap_region_claim_values();
1363 
1364 #ifdef ASSERT
1365   bool check_heap_region_claim_values(jint claim_value);
1366 
1367   // Same as the routine above but only checks regions in the
1368   // current collection set.
1369   bool check_cset_heap_region_claim_values(jint claim_value);
1370 #endif // ASSERT
1371 
1372   // Clear the cached cset start regions and (more importantly)
1373   // the time stamps. Called when we reset the GC time stamp.
1374   void clear_cset_start_regions();
1375 
1376   // Given the id of a worker, obtain or calculate a suitable
1377   // starting region for iterating over the current collection set.
1378   HeapRegion* start_cset_region_for_worker(uint worker_i);
1379 
1380   // This is a convenience method that is used by the
1381   // HeapRegionIterator classes to calculate the starting region for
1382   // each worker so that they do not all start from the same region.
1383   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1384 
1385   // Iterate over the regions (if any) in the current collection set.
1386   void collection_set_iterate(HeapRegionClosure* blk);
1387 
1388   // As above but starting from region r
1389   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1390 
1391   // Returns the first (lowest address) compactible space in the heap.
1392   virtual CompactibleSpace* first_compactible_space();
1393 
1394   // A CollectedHeap will contain some number of spaces.  This finds the
1395   // space containing a given address, or else returns NULL.
1396   virtual Space* space_containing(const void* addr) const;
1397 
1398   // Returns the HeapRegion that contains addr. addr must not be NULL.
1399   template <class T>
1400   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1401 
1402   // Returns the HeapRegion that contains addr. addr must not be NULL.
1403   // If addr is within a humongous continues region, it returns its humongous start region.
1404   template <class T>
1405   inline HeapRegion* heap_region_containing(const T addr) const;
1406 
1407   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1408   // each address in the (reserved) heap is a member of exactly
1409   // one block.  The defining characteristic of a block is that it is
1410   // possible to find its size, and thus to progress forward to the next
1411   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1412   // represent Java objects, or they might be free blocks in a
1413   // free-list-based heap (or subheap), as long as the two kinds are
1414   // distinguishable and the size of each is determinable.
1415 
1416   // Returns the address of the start of the "block" that contains the
1417   // address "addr".  We say "blocks" instead of "object" since some heaps
1418   // may not pack objects densely; a chunk may either be an object or a
1419   // non-object.
1420   virtual HeapWord* block_start(const void* addr) const;
1421 
1422   // Requires "addr" to be the start of a chunk, and returns its size.
1423   // "addr + size" is required to be the start of a new chunk, or the end
1424   // of the active area of the heap.
1425   virtual size_t block_size(const HeapWord* addr) const;
1426 
1427   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1428   // the block is an object.
1429   virtual bool block_is_obj(const HeapWord* addr) const;
1430 
1431   // Does this heap support heap inspection? (+PrintClassHistogram)
1432   virtual bool supports_heap_inspection() const { return true; }
1433 
1434   // Section on thread-local allocation buffers (TLABs)
1435   // See CollectedHeap for semantics.
1436 
1437   bool supports_tlab_allocation() const;
1438   size_t tlab_capacity(Thread* ignored) const;
1439   size_t tlab_used(Thread* ignored) const;
1440   size_t max_tlab_size() const;
1441   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1442 
1443   // Can a compiler initialize a new object without store barriers?
1444   // This permission only extends from the creation of a new object
1445   // via a TLAB up to the first subsequent safepoint. If such permission
1446   // is granted for this heap type, the compiler promises to call
1447   // defer_store_barrier() below on any slow path allocation of
1448   // a new object for which such initializing store barriers will
1449   // have been elided. G1, like CMS, allows this, but should be
1450   // ready to provide a compensating write barrier as necessary
1451   // if that storage came out of a non-young region. The efficiency
1452   // of this implementation depends crucially on being able to
1453   // answer very efficiently in constant time whether a piece of
1454   // storage in the heap comes from a young region or not.
1455   // See ReduceInitialCardMarks.
1456   virtual bool can_elide_tlab_store_barriers() const {
1457     return true;
1458   }
1459 
1460   virtual bool card_mark_must_follow_store() const {
1461     return true;
1462   }
1463 
1464   inline bool is_in_young(const oop obj);
1465 
1466 #ifdef ASSERT
1467   virtual bool is_in_partial_collection(const void* p);
1468 #endif
1469 
1470   virtual bool is_scavengable(const void* addr);
1471 
1472   // We don't need barriers for initializing stores to objects
1473   // in the young gen: for the SATB pre-barrier, there is no
1474   // pre-value that needs to be remembered; for the remembered-set
1475   // update logging post-barrier, we don't maintain remembered set
1476   // information for young gen objects.
1477   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1478 
1479   // Returns "true" iff the given word_size is "very large".
1480   static bool isHumongous(size_t word_size) {
1481     // Note this has to be strictly greater-than as the TLABs
1482     // are capped at the humongous threshold and we want to
1483     // ensure that we don't try to allocate a TLAB as
1484     // humongous and that we don't allocate a humongous
1485     // object in a TLAB.
1486     return word_size > _humongous_object_threshold_in_words;
1487   }
1488 
1489   // Update mod union table with the set of dirty cards.
1490   void updateModUnion();
1491 
1492   // Set the mod union bits corresponding to the given memRegion.  Note
1493   // that this is always a safe operation, since it doesn't clear any
1494   // bits.
1495   void markModUnionRange(MemRegion mr);
1496 
1497   // Records the fact that a marking phase is no longer in progress.
1498   void set_marking_complete() {
1499     _mark_in_progress = false;
1500   }
1501   void set_marking_started() {
1502     _mark_in_progress = true;
1503   }
1504   bool mark_in_progress() {
1505     return _mark_in_progress;
1506   }
1507 
1508   // Print the maximum heap capacity.
1509   virtual size_t max_capacity() const;
1510 
1511   virtual jlong millis_since_last_gc();
1512 
1513 
1514   // Convenience function to be used in situations where the heap type can be
1515   // asserted to be this type.
1516   static G1CollectedHeap* heap();
1517 
1518   void set_region_short_lived_locked(HeapRegion* hr);
1519   // add appropriate methods for any other surv rate groups
1520 
1521   YoungList* young_list() const { return _young_list; }
1522 
1523   // debugging
1524   bool check_young_list_well_formed() {
1525     return _young_list->check_list_well_formed();
1526   }
1527 
1528   bool check_young_list_empty(bool check_heap,
1529                               bool check_sample = true);
1530 
1531   // *** Stuff related to concurrent marking.  It's not clear to me that so
1532   // many of these need to be public.
1533 
1534   // The functions below are helper functions that a subclass of
1535   // "CollectedHeap" can use in the implementation of its virtual
1536   // functions.
1537   // This performs a concurrent marking of the live objects in a
1538   // bitmap off to the side.
1539   void doConcurrentMark();
1540 
1541   bool isMarkedPrev(oop obj) const;
1542   bool isMarkedNext(oop obj) const;
1543 
1544   // Determine if an object is dead, given the object and also
1545   // the region to which the object belongs. An object is dead
1546   // iff a) it was not allocated since the last mark and b) it
1547   // is not marked.
1548   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1549     return
1550       !hr->obj_allocated_since_prev_marking(obj) &&
1551       !isMarkedPrev(obj);
1552   }
1553 
1554   // This function returns true when an object has been
1555   // around since the previous marking and hasn't yet
1556   // been marked during this marking.
1557   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1558     return
1559       !hr->obj_allocated_since_next_marking(obj) &&
1560       !isMarkedNext(obj);
1561   }
1562 
1563   // Determine if an object is dead, given only the object itself.
1564   // This will find the region to which the object belongs and
1565   // then call the region version of the same function.
1566 
1567   // Added if it is NULL it isn't dead.
1568 
1569   inline bool is_obj_dead(const oop obj) const;
1570 
1571   inline bool is_obj_ill(const oop obj) const;
1572 
1573   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1574   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1575   bool is_marked(oop obj, VerifyOption vo);
1576   const char* top_at_mark_start_str(VerifyOption vo);
1577 
1578   ConcurrentMark* concurrent_mark() const { return _cm; }
1579 
1580   // Refinement
1581 
1582   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1583 
1584   // The dirty cards region list is used to record a subset of regions
1585   // whose cards need clearing. The list if populated during the
1586   // remembered set scanning and drained during the card table
1587   // cleanup. Although the methods are reentrant, population/draining
1588   // phases must not overlap. For synchronization purposes the last
1589   // element on the list points to itself.
1590   HeapRegion* _dirty_cards_region_list;
1591   void push_dirty_cards_region(HeapRegion* hr);
1592   HeapRegion* pop_dirty_cards_region();
1593 
1594   // Optimized nmethod scanning support routines
1595 
1596   // Register the given nmethod with the G1 heap.
1597   virtual void register_nmethod(nmethod* nm);
1598 
1599   // Unregister the given nmethod from the G1 heap.
1600   virtual void unregister_nmethod(nmethod* nm);
1601 
1602   // Migrate the nmethods in the code root lists of the regions
1603   // in the collection set to regions in to-space. In the event
1604   // of an evacuation failure, nmethods that reference objects
1605   // that were not successfully evacuated are not migrated.
1606   void migrate_strong_code_roots();
1607 
1608   // Free up superfluous code root memory.
1609   void purge_code_root_memory();
1610 
1611   // During an initial mark pause, mark all the code roots that
1612   // point into regions *not* in the collection set.
1613   void mark_strong_code_roots(uint worker_id);
1614 
1615   // Rebuild the strong code root lists for each region
1616   // after a full GC.
1617   void rebuild_strong_code_roots();
1618 
1619   // Delete entries for dead interned string and clean up unreferenced symbols
1620   // in symbol table, possibly in parallel.
1621   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1622 
1623   // Redirty logged cards in the refinement queue.
1624   void redirty_logged_cards();
1625   // Verification
1626 
1627   // The following is just to alert the verification code
1628   // that a full collection has occurred and that the
1629   // remembered sets are no longer up to date.
1630   bool _full_collection;
1631   void set_full_collection() { _full_collection = true;}
1632   void clear_full_collection() {_full_collection = false;}
1633   bool full_collection() {return _full_collection;}
1634 
1635   // Perform any cleanup actions necessary before allowing a verification.
1636   virtual void prepare_for_verify();
1637 
1638   // Perform verification.
1639 
1640   // vo == UsePrevMarking  -> use "prev" marking information,
1641   // vo == UseNextMarking -> use "next" marking information
1642   // vo == UseMarkWord    -> use the mark word in the object header
1643   //
1644   // NOTE: Only the "prev" marking information is guaranteed to be
1645   // consistent most of the time, so most calls to this should use
1646   // vo == UsePrevMarking.
1647   // Currently, there is only one case where this is called with
1648   // vo == UseNextMarking, which is to verify the "next" marking
1649   // information at the end of remark.
1650   // Currently there is only one place where this is called with
1651   // vo == UseMarkWord, which is to verify the marking during a
1652   // full GC.
1653   void verify(bool silent, VerifyOption vo);
1654 
1655   // Override; it uses the "prev" marking information
1656   virtual void verify(bool silent);
1657 
1658   // The methods below are here for convenience and dispatch the
1659   // appropriate method depending on value of the given VerifyOption
1660   // parameter. The values for that parameter, and their meanings,
1661   // are the same as those above.
1662 
1663   bool is_obj_dead_cond(const oop obj,
1664                         const HeapRegion* hr,
1665                         const VerifyOption vo) const;
1666 
1667   bool is_obj_dead_cond(const oop obj,
1668                         const VerifyOption vo) const;
1669 
1670   // Printing
1671 
1672   virtual void print_on(outputStream* st) const;
1673   virtual void print_extended_on(outputStream* st) const;
1674   virtual void print_on_error(outputStream* st) const;
1675 
1676   virtual void print_gc_threads_on(outputStream* st) const;
1677   virtual void gc_threads_do(ThreadClosure* tc) const;
1678 
1679   // Override
1680   void print_tracing_info() const;
1681 
1682   // The following two methods are helpful for debugging RSet issues.
1683   void print_cset_rsets() PRODUCT_RETURN;
1684   void print_all_rsets() PRODUCT_RETURN;
1685 
1686 public:
1687   void stop_conc_gc_threads();
1688 
1689   size_t pending_card_num();
1690   size_t cards_scanned();
1691 
1692 protected:
1693   size_t _max_heap_capacity;
1694 };
1695 
1696 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1697 private:
1698   bool        _retired;
1699 
1700 public:
1701   G1ParGCAllocBuffer(size_t gclab_word_size);
1702   virtual ~G1ParGCAllocBuffer() {
1703     guarantee(_retired, "Allocation buffer has not been retired");
1704   }
1705 
1706   virtual void set_buf(HeapWord* buf) {
1707     ParGCAllocBuffer::set_buf(buf);
1708     _retired = false;
1709   }
1710 
1711   virtual void retire(bool end_of_gc, bool retain) {
1712     if (_retired) {
1713       return;
1714     }
1715     ParGCAllocBuffer::retire(end_of_gc, retain);
1716     _retired = true;
1717   }
1718 };
1719 
1720 class G1ParScanThreadState : public StackObj {
1721 protected:
1722   G1CollectedHeap* _g1h;
1723   RefToScanQueue*  _refs;
1724   DirtyCardQueue   _dcq;
1725   G1SATBCardTableModRefBS* _ct_bs;
1726   G1RemSet* _g1_rem;
1727 
1728   G1ParGCAllocBuffer  _surviving_alloc_buffer;
1729   G1ParGCAllocBuffer  _tenured_alloc_buffer;
1730   G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1731   ageTable            _age_table;
1732 
1733   G1ParScanClosure    _scanner;
1734 
1735   size_t           _alloc_buffer_waste;
1736   size_t           _undo_waste;
1737 
1738   OopsInHeapRegionClosure*      _evac_failure_cl;
1739 
1740   int  _hash_seed;
1741   uint _queue_num;
1742 
1743   size_t _term_attempts;
1744 
1745   double _start;
1746   double _start_strong_roots;
1747   double _strong_roots_time;
1748   double _start_term;
1749   double _term_time;
1750 
1751   // Map from young-age-index (0 == not young, 1 is youngest) to
1752   // surviving words. base is what we get back from the malloc call
1753   size_t* _surviving_young_words_base;
1754   // this points into the array, as we use the first few entries for padding
1755   size_t* _surviving_young_words;
1756 
1757 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1758 
1759   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1760 
1761   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1762 
1763   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1764   G1SATBCardTableModRefBS* ctbs()                { return _ct_bs; }
1765 
1766   template <class T> inline void immediate_rs_update(HeapRegion* from, T* p, int tid);
1767 
1768   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1769     // If the new value of the field points to the same region or
1770     // is the to-space, we don't need to include it in the Rset updates.
1771     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1772       size_t card_index = ctbs()->index_for(p);
1773       // If the card hasn't been added to the buffer, do it.
1774       if (ctbs()->mark_card_deferred(card_index)) {
1775         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1776       }
1777     }
1778   }
1779 
1780 public:
1781   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp);
1782 
1783   ~G1ParScanThreadState() {
1784     retire_alloc_buffers();
1785     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1786   }
1787 
1788   RefToScanQueue*   refs()            { return _refs;             }
1789   ageTable*         age_table()       { return &_age_table;       }
1790 
1791   G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1792     return _alloc_buffers[purpose];
1793   }
1794 
1795   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1796   size_t undo_waste() const                      { return _undo_waste; }
1797 
1798 #ifdef ASSERT
1799   bool verify_ref(narrowOop* ref) const;
1800   bool verify_ref(oop* ref) const;
1801   bool verify_task(StarTask ref) const;
1802 #endif // ASSERT
1803 
1804   template <class T> void push_on_queue(T* ref) {
1805     assert(verify_ref(ref), "sanity");
1806     refs()->push(ref);
1807   }
1808 
1809   template <class T> inline void update_rs(HeapRegion* from, T* p, int tid);
1810 
1811   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1812     HeapWord* obj = NULL;
1813     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1814     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1815       G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1816       add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1817       alloc_buf->retire(false /* end_of_gc */, false /* retain */);
1818 
1819       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1820       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1821       // Otherwise.
1822       alloc_buf->set_word_size(gclab_word_size);
1823       alloc_buf->set_buf(buf);
1824 
1825       obj = alloc_buf->allocate(word_sz);
1826       assert(obj != NULL, "buffer was definitely big enough...");
1827     } else {
1828       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1829     }
1830     return obj;
1831   }
1832 
1833   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1834     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1835     if (obj != NULL) return obj;
1836     return allocate_slow(purpose, word_sz);
1837   }
1838 
1839   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1840     if (alloc_buffer(purpose)->contains(obj)) {
1841       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1842              "should contain whole object");
1843       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1844     } else {
1845       CollectedHeap::fill_with_object(obj, word_sz);
1846       add_to_undo_waste(word_sz);
1847     }
1848   }
1849 
1850   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1851     _evac_failure_cl = evac_failure_cl;
1852   }
1853   OopsInHeapRegionClosure* evac_failure_closure() {
1854     return _evac_failure_cl;
1855   }
1856 
1857   int* hash_seed() { return &_hash_seed; }
1858   uint queue_num() { return _queue_num; }
1859 
1860   size_t term_attempts() const  { return _term_attempts; }
1861   void note_term_attempt() { _term_attempts++; }
1862 
1863   void start_strong_roots() {
1864     _start_strong_roots = os::elapsedTime();
1865   }
1866   void end_strong_roots() {
1867     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1868   }
1869   double strong_roots_time() const { return _strong_roots_time; }
1870 
1871   void start_term_time() {
1872     note_term_attempt();
1873     _start_term = os::elapsedTime();
1874   }
1875   void end_term_time() {
1876     _term_time += (os::elapsedTime() - _start_term);
1877   }
1878   double term_time() const { return _term_time; }
1879 
1880   double elapsed_time() const {
1881     return os::elapsedTime() - _start;
1882   }
1883 
1884   static void
1885     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1886   void
1887     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1888 
1889   size_t* surviving_young_words() {
1890     // We add on to hide entry 0 which accumulates surviving words for
1891     // age -1 regions (i.e. non-young ones)
1892     return _surviving_young_words;
1893   }
1894 
1895 private:
1896   void retire_alloc_buffers() {
1897     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1898       size_t waste = _alloc_buffers[ap]->words_remaining();
1899       add_to_alloc_buffer_waste(waste);
1900       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
1901                                                  true /* end_of_gc */,
1902                                                  false /* retain */);
1903     }
1904   }
1905 
1906 #define G1_PARTIAL_ARRAY_MASK 0x2
1907 
1908   inline bool has_partial_array_mask(oop* ref) const {
1909     return ((uintptr_t)ref & G1_PARTIAL_ARRAY_MASK) == G1_PARTIAL_ARRAY_MASK;
1910   }
1911 
1912   // We never encode partial array oops as narrowOop*, so return false immediately.
1913   // This allows the compiler to create optimized code when popping references from
1914   // the work queue.
1915   inline bool has_partial_array_mask(narrowOop* ref) const {
1916     assert(((uintptr_t)ref & G1_PARTIAL_ARRAY_MASK) != G1_PARTIAL_ARRAY_MASK, "Partial array oop reference encoded as narrowOop*");
1917     return false;
1918   }
1919 
1920   // Only implement set_partial_array_mask() for regular oops, not for narrowOops.
1921   // We always encode partial arrays as regular oop, to allow the
1922   // specialization for has_partial_array_mask() for narrowOops above.
1923   // This means that unintentional use of this method with narrowOops are caught
1924   // by the compiler.
1925   inline oop* set_partial_array_mask(oop obj) const {
1926     assert(((uintptr_t)(void *)obj & G1_PARTIAL_ARRAY_MASK) == 0, "Information loss!");
1927     return (oop*) ((uintptr_t)(void *)obj | G1_PARTIAL_ARRAY_MASK);
1928   }
1929 
1930   inline oop clear_partial_array_mask(oop* ref) const {
1931     return cast_to_oop((intptr_t)ref & ~G1_PARTIAL_ARRAY_MASK);
1932   }
1933 
1934   inline void do_oop_partial_array(oop* p);
1935 
1936   // This method is applied to the fields of the objects that have just been copied.
1937   template <class T> void do_oop_evac(T* p, HeapRegion* from) {
1938     assert(!oopDesc::is_null(oopDesc::load_decode_heap_oop(p)),
1939            "Reference should not be NULL here as such are never pushed to the task queue.");
1940     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
1941 
1942     // Although we never intentionally push references outside of the collection
1943     // set, due to (benign) races in the claim mechanism during RSet scanning more
1944     // than one thread might claim the same card. So the same card may be
1945     // processed multiple times. So redo this check.
1946     if (_g1h->in_cset_fast_test(obj)) {
1947       oop forwardee;
1948       if (obj->is_forwarded()) {
1949         forwardee = obj->forwardee();
1950       } else {
1951         forwardee = copy_to_survivor_space(obj);
1952       }
1953       assert(forwardee != NULL, "forwardee should not be NULL");
1954       oopDesc::encode_store_heap_oop(p, forwardee);
1955     }
1956 
1957     assert(obj != NULL, "Must be");
1958     update_rs(from, p, queue_num());
1959   }
1960 public:
1961 
1962   oop copy_to_survivor_space(oop const obj);
1963 
1964   template <class T> inline void deal_with_reference(T* ref_to_scan);
1965 
1966   inline void deal_with_reference(StarTask ref);
1967 
1968 public:
1969   void trim_queue();
1970 };
1971 
1972 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP