1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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/g1HRPrinter.hpp"
  32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  33 #include "gc_implementation/g1/g1RemSet.hpp"
  34 #include "gc_implementation/g1/g1YCTypes.hpp"
  35 #include "gc_implementation/g1/heapRegionSeq.hpp"
  36 #include "gc_implementation/g1/heapRegionSets.hpp"
  37 #include "gc_implementation/shared/hSpaceCounters.hpp"
  38 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  39 #include "memory/barrierSet.hpp"
  40 #include "memory/memRegion.hpp"
  41 #include "memory/sharedHeap.hpp"
  42 #include "utilities/stack.hpp"
  43 
  44 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  45 // It uses the "Garbage First" heap organization and algorithm, which
  46 // may combine concurrent marking with parallel, incremental compaction of
  47 // heap subsets that will yield large amounts of garbage.
  48 
  49 // Forward declarations
  50 class HeapRegion;
  51 class HRRSCleanupTask;
  52 class GenerationSpec;
  53 class OopsInHeapRegionClosure;
  54 class G1KlassScanClosure;
  55 class G1ScanHeapEvacClosure;
  56 class ObjectClosure;
  57 class SpaceClosure;
  58 class CompactibleSpaceClosure;
  59 class Space;
  60 class G1CollectorPolicy;
  61 class GenRemSet;
  62 class G1RemSet;
  63 class HeapRegionRemSetIterator;
  64 class ConcurrentMark;
  65 class ConcurrentMarkThread;
  66 class ConcurrentG1Refine;
  67 class ConcurrentGCTimer;
  68 class GenerationCounters;
  69 class STWGCTimer;
  70 class G1NewTracer;
  71 class G1OldTracer;
  72 class EvacuationFailedInfo;
  73 class nmethod;
  74 
  75 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  76 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  77 
  78 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  79 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  80 
  81 enum GCAllocPurpose {
  82   GCAllocForTenured,
  83   GCAllocForSurvived,
  84   GCAllocPurposeCount
  85 };
  86 
  87 class YoungList : public CHeapObj<mtGC> {
  88 private:
  89   G1CollectedHeap* _g1h;
  90 
  91   HeapRegion* _head;
  92 
  93   HeapRegion* _survivor_head;
  94   HeapRegion* _survivor_tail;
  95 
  96   HeapRegion* _curr;
  97 
  98   uint        _length;
  99   uint        _survivor_length;
 100 
 101   size_t      _last_sampled_rs_lengths;
 102   size_t      _sampled_rs_lengths;
 103 
 104   void         empty_list(HeapRegion* list);
 105 
 106 public:
 107   YoungList(G1CollectedHeap* g1h);
 108 
 109   void         push_region(HeapRegion* hr);
 110   void         add_survivor_region(HeapRegion* hr);
 111 
 112   void         empty_list();
 113   bool         is_empty() { return _length == 0; }
 114   uint         length() { return _length; }
 115   uint         survivor_length() { return _survivor_length; }
 116 
 117   // Currently we do not keep track of the used byte sum for the
 118   // young list and the survivors and it'd be quite a lot of work to
 119   // do so. When we'll eventually replace the young list with
 120   // instances of HeapRegionLinkedList we'll get that for free. So,
 121   // we'll report the more accurate information then.
 122   size_t       eden_used_bytes() {
 123     assert(length() >= survivor_length(), "invariant");
 124     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 125   }
 126   size_t       survivor_used_bytes() {
 127     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 128   }
 129 
 130   void rs_length_sampling_init();
 131   bool rs_length_sampling_more();
 132   void rs_length_sampling_next();
 133 
 134   void reset_sampled_info() {
 135     _last_sampled_rs_lengths =   0;
 136   }
 137   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 138 
 139   // for development purposes
 140   void reset_auxilary_lists();
 141   void clear() { _head = NULL; _length = 0; }
 142 
 143   void clear_survivors() {
 144     _survivor_head    = NULL;
 145     _survivor_tail    = NULL;
 146     _survivor_length  = 0;
 147   }
 148 
 149   HeapRegion* first_region() { return _head; }
 150   HeapRegion* first_survivor_region() { return _survivor_head; }
 151   HeapRegion* last_survivor_region() { return _survivor_tail; }
 152 
 153   // debugging
 154   bool          check_list_well_formed();
 155   bool          check_list_empty(bool check_sample = true);
 156   void          print();
 157 };
 158 
 159 class MutatorAllocRegion : public G1AllocRegion {
 160 protected:
 161   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 162   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 163 public:
 164   MutatorAllocRegion()
 165     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 166 };
 167 
 168 class SurvivorGCAllocRegion : public G1AllocRegion {
 169 protected:
 170   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 171   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 172 public:
 173   SurvivorGCAllocRegion()
 174   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 175 };
 176 
 177 class OldGCAllocRegion : public G1AllocRegion {
 178 protected:
 179   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 180   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 181 public:
 182   OldGCAllocRegion()
 183   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 184 };
 185 
 186 // The G1 STW is alive closure.
 187 // An instance is embedded into the G1CH and used as the
 188 // (optional) _is_alive_non_header closure in the STW
 189 // reference processor. It is also extensively used during
 190 // reference processing during STW evacuation pauses.
 191 class G1STWIsAliveClosure: public BoolObjectClosure {
 192   G1CollectedHeap* _g1;
 193 public:
 194   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 195   bool do_object_b(oop p);
 196 };
 197 
 198 class RefineCardTableEntryClosure;
 199 
 200 class G1CollectedHeap : public SharedHeap {
 201   friend class VM_G1CollectForAllocation;
 202   friend class VM_G1CollectFull;
 203   friend class VM_G1IncCollectionPause;
 204   friend class VMStructs;
 205   friend class MutatorAllocRegion;
 206   friend class SurvivorGCAllocRegion;
 207   friend class OldGCAllocRegion;
 208 
 209   // Closures used in implementation.
 210   template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
 211   friend class G1ParCopyClosure;
 212   friend class G1IsAliveClosure;
 213   friend class G1EvacuateFollowersClosure;
 214   friend class G1ParScanThreadState;
 215   friend class G1ParScanClosureSuper;
 216   friend class G1ParEvacuateFollowersClosure;
 217   friend class G1ParTask;
 218   friend class G1FreeGarbageRegionClosure;
 219   friend class RefineCardTableEntryClosure;
 220   friend class G1PrepareCompactClosure;
 221   friend class RegionSorter;
 222   friend class RegionResetter;
 223   friend class CountRCClosure;
 224   friend class EvacPopObjClosure;
 225   friend class G1ParCleanupCTTask;
 226 
 227   // Other related classes.
 228   friend class G1MarkSweep;
 229 
 230 private:
 231   // The one and only G1CollectedHeap, so static functions can find it.
 232   static G1CollectedHeap* _g1h;
 233 
 234   static size_t _humongous_object_threshold_in_words;
 235 
 236   // Storage for the G1 heap.
 237   VirtualSpace _g1_storage;
 238   MemRegion    _g1_reserved;
 239 
 240   // The part of _g1_storage that is currently committed.
 241   MemRegion _g1_committed;
 242 
 243   // The master free list. It will satisfy all new region allocations.
 244   MasterFreeRegionList      _free_list;
 245 
 246   // The secondary free list which contains regions that have been
 247   // freed up during the cleanup process. This will be appended to the
 248   // master free list when appropriate.
 249   SecondaryFreeRegionList   _secondary_free_list;
 250 
 251   // It keeps track of the old regions.
 252   MasterOldRegionSet        _old_set;
 253 
 254   // It keeps track of the humongous regions.
 255   MasterHumongousRegionSet  _humongous_set;
 256 
 257   // The number of regions we could create by expansion.
 258   uint _expansion_regions;
 259 
 260   // The block offset table for the G1 heap.
 261   G1BlockOffsetSharedArray* _bot_shared;
 262 
 263   // Tears down the region sets / lists so that they are empty and the
 264   // regions on the heap do not belong to a region set / list. The
 265   // only exception is the humongous set which we leave unaltered. If
 266   // free_list_only is true, it will only tear down the master free
 267   // list. It is called before a Full GC (free_list_only == false) or
 268   // before heap shrinking (free_list_only == true).
 269   void tear_down_region_sets(bool free_list_only);
 270 
 271   // Rebuilds the region sets / lists so that they are repopulated to
 272   // reflect the contents of the heap. The only exception is the
 273   // humongous set which was not torn down in the first place. If
 274   // free_list_only is true, it will only rebuild the master free
 275   // list. It is called after a Full GC (free_list_only == false) or
 276   // after heap shrinking (free_list_only == true).
 277   void rebuild_region_sets(bool free_list_only);
 278 
 279   // The sequence of all heap regions in the heap.
 280   HeapRegionSeq _hrs;
 281 
 282   // Alloc region used to satisfy mutator allocation requests.
 283   MutatorAllocRegion _mutator_alloc_region;
 284 
 285   // Alloc region used to satisfy allocation requests by the GC for
 286   // survivor objects.
 287   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 288 
 289   // PLAB sizing policy for survivors.
 290   PLABStats _survivor_plab_stats;
 291 
 292   // Alloc region used to satisfy allocation requests by the GC for
 293   // old objects.
 294   OldGCAllocRegion _old_gc_alloc_region;
 295 
 296   // PLAB sizing policy for tenured objects.
 297   PLABStats _old_plab_stats;
 298 
 299   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 300     PLABStats* stats = NULL;
 301 
 302     switch (purpose) {
 303     case GCAllocForSurvived:
 304       stats = &_survivor_plab_stats;
 305       break;
 306     case GCAllocForTenured:
 307       stats = &_old_plab_stats;
 308       break;
 309     default:
 310       assert(false, "unrecognized GCAllocPurpose");
 311     }
 312 
 313     return stats;
 314   }
 315 
 316   // The last old region we allocated to during the last GC.
 317   // Typically, it is not full so we should re-use it during the next GC.
 318   HeapRegion* _retained_old_gc_alloc_region;
 319 
 320   // It specifies whether we should attempt to expand the heap after a
 321   // region allocation failure. If heap expansion fails we set this to
 322   // false so that we don't re-attempt the heap expansion (it's likely
 323   // that subsequent expansion attempts will also fail if one fails).
 324   // Currently, it is only consulted during GC and it's reset at the
 325   // start of each GC.
 326   bool _expand_heap_after_alloc_failure;
 327 
 328   // It resets the mutator alloc region before new allocations can take place.
 329   void init_mutator_alloc_region();
 330 
 331   // It releases the mutator alloc region.
 332   void release_mutator_alloc_region();
 333 
 334   // It initializes the GC alloc regions at the start of a GC.
 335   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 336 
 337   // It releases the GC alloc regions at the end of a GC.
 338   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 339 
 340   // It does any cleanup that needs to be done on the GC alloc regions
 341   // before a Full GC.
 342   void abandon_gc_alloc_regions();
 343 
 344   // Helper for monitoring and management support.
 345   G1MonitoringSupport* _g1mm;
 346 
 347   // Determines PLAB size for a particular allocation purpose.
 348   size_t desired_plab_sz(GCAllocPurpose purpose);
 349 
 350   // Outside of GC pauses, the number of bytes used in all regions other
 351   // than the current allocation region.
 352   size_t _summary_bytes_used;
 353 
 354   // This is used for a quick test on whether a reference points into
 355   // the collection set or not. Basically, we have an array, with one
 356   // byte per region, and that byte denotes whether the corresponding
 357   // region is in the collection set or not. The entry corresponding
 358   // the bottom of the heap, i.e., region 0, is pointed to by
 359   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 360   // biased so that it actually points to address 0 of the address
 361   // space, to make the test as fast as possible (we can simply shift
 362   // the address to address into it, instead of having to subtract the
 363   // bottom of the heap from the address before shifting it; basically
 364   // it works in the same way the card table works).
 365   bool* _in_cset_fast_test;
 366 
 367   // The allocated array used for the fast test on whether a reference
 368   // points into the collection set or not. This field is also used to
 369   // free the array.
 370   bool* _in_cset_fast_test_base;
 371 
 372   // The length of the _in_cset_fast_test_base array.
 373   uint _in_cset_fast_test_length;
 374 
 375   volatile unsigned _gc_time_stamp;
 376 
 377   size_t* _surviving_young_words;
 378 
 379   G1HRPrinter _hr_printer;
 380 
 381   void setup_surviving_young_words();
 382   void update_surviving_young_words(size_t* surv_young_words);
 383   void cleanup_surviving_young_words();
 384 
 385   // It decides whether an explicit GC should start a concurrent cycle
 386   // instead of doing a STW GC. Currently, a concurrent cycle is
 387   // explicitly started if:
 388   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 389   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 390   // (c) cause == _g1_humongous_allocation
 391   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 392 
 393   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 394   // concurrent cycles) we have started.
 395   volatile unsigned int _old_marking_cycles_started;
 396 
 397   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 398   // concurrent cycles) we have completed.
 399   volatile unsigned int _old_marking_cycles_completed;
 400 
 401   bool _concurrent_cycle_started;
 402 
 403   // This is a non-product method that is helpful for testing. It is
 404   // called at the end of a GC and artificially expands the heap by
 405   // allocating a number of dead regions. This way we can induce very
 406   // frequent marking cycles and stress the cleanup / concurrent
 407   // cleanup code more (as all the regions that will be allocated by
 408   // this method will be found dead by the marking cycle).
 409   void allocate_dummy_regions() PRODUCT_RETURN;
 410 
 411   // Clear RSets after a compaction. It also resets the GC time stamps.
 412   void clear_rsets_post_compaction();
 413 
 414   // If the HR printer is active, dump the state of the regions in the
 415   // heap after a compaction.
 416   void print_hrs_post_compaction();
 417 
 418   double verify(bool guard, const char* msg);
 419   void verify_before_gc();
 420   void verify_after_gc();
 421 
 422   void log_gc_header();
 423   void log_gc_footer(double pause_time_sec);
 424 
 425   // These are macros so that, if the assert fires, we get the correct
 426   // line number, file, etc.
 427 
 428 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 429   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 430           (_extra_message_),                                                  \
 431           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 432           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 433           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 434 
 435 #define assert_heap_locked()                                                  \
 436   do {                                                                        \
 437     assert(Heap_lock->owned_by_self(),                                        \
 438            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 439   } while (0)
 440 
 441 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 442   do {                                                                        \
 443     assert(Heap_lock->owned_by_self() ||                                      \
 444            (SafepointSynchronize::is_at_safepoint() &&                        \
 445              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 446            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 447                                         "should be at a safepoint"));         \
 448   } while (0)
 449 
 450 #define assert_heap_locked_and_not_at_safepoint()                             \
 451   do {                                                                        \
 452     assert(Heap_lock->owned_by_self() &&                                      \
 453                                     !SafepointSynchronize::is_at_safepoint(), \
 454           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 455                                        "should not be at a safepoint"));      \
 456   } while (0)
 457 
 458 #define assert_heap_not_locked()                                              \
 459   do {                                                                        \
 460     assert(!Heap_lock->owned_by_self(),                                       \
 461         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 462   } while (0)
 463 
 464 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 465   do {                                                                        \
 466     assert(!Heap_lock->owned_by_self() &&                                     \
 467                                     !SafepointSynchronize::is_at_safepoint(), \
 468       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 469                                    "should not be at a safepoint"));          \
 470   } while (0)
 471 
 472 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 473   do {                                                                        \
 474     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 475               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 476            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 477   } while (0)
 478 
 479 #define assert_not_at_safepoint()                                             \
 480   do {                                                                        \
 481     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 482            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 483   } while (0)
 484 
 485 protected:
 486 
 487   // The young region list.
 488   YoungList*  _young_list;
 489 
 490   // The current policy object for the collector.
 491   G1CollectorPolicy* _g1_policy;
 492 
 493   // This is the second level of trying to allocate a new region. If
 494   // new_region() didn't find a region on the free_list, this call will
 495   // check whether there's anything available on the
 496   // secondary_free_list and/or wait for more regions to appear on
 497   // that list, if _free_regions_coming is set.
 498   HeapRegion* new_region_try_secondary_free_list();
 499 
 500   // Try to allocate a single non-humongous HeapRegion sufficient for
 501   // an allocation of the given word_size. If do_expand is true,
 502   // attempt to expand the heap if necessary to satisfy the allocation
 503   // request.
 504   HeapRegion* new_region(size_t word_size, bool do_expand);
 505 
 506   // Attempt to satisfy a humongous allocation request of the given
 507   // size by finding a contiguous set of free regions of num_regions
 508   // length and remove them from the master free list. Return the
 509   // index of the first region or G1_NULL_HRS_INDEX if the search
 510   // was unsuccessful.
 511   uint humongous_obj_allocate_find_first(uint num_regions,
 512                                          size_t word_size);
 513 
 514   // Initialize a contiguous set of free regions of length num_regions
 515   // and starting at index first so that they appear as a single
 516   // humongous region.
 517   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 518                                                       uint num_regions,
 519                                                       size_t word_size);
 520 
 521   // Attempt to allocate a humongous object of the given size. Return
 522   // NULL if unsuccessful.
 523   HeapWord* humongous_obj_allocate(size_t word_size);
 524 
 525   // The following two methods, allocate_new_tlab() and
 526   // mem_allocate(), are the two main entry points from the runtime
 527   // into the G1's allocation routines. They have the following
 528   // assumptions:
 529   //
 530   // * They should both be called outside safepoints.
 531   //
 532   // * They should both be called without holding the Heap_lock.
 533   //
 534   // * All allocation requests for new TLABs should go to
 535   //   allocate_new_tlab().
 536   //
 537   // * All non-TLAB allocation requests should go to mem_allocate().
 538   //
 539   // * If either call cannot satisfy the allocation request using the
 540   //   current allocating region, they will try to get a new one. If
 541   //   this fails, they will attempt to do an evacuation pause and
 542   //   retry the allocation.
 543   //
 544   // * If all allocation attempts fail, even after trying to schedule
 545   //   an evacuation pause, allocate_new_tlab() will return NULL,
 546   //   whereas mem_allocate() will attempt a heap expansion and/or
 547   //   schedule a Full GC.
 548   //
 549   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 550   //   should never be called with word_size being humongous. All
 551   //   humongous allocation requests should go to mem_allocate() which
 552   //   will satisfy them with a special path.
 553 
 554   virtual HeapWord* allocate_new_tlab(size_t word_size);
 555 
 556   virtual HeapWord* mem_allocate(size_t word_size,
 557                                  bool*  gc_overhead_limit_was_exceeded);
 558 
 559   // The following three methods take a gc_count_before_ret
 560   // parameter which is used to return the GC count if the method
 561   // returns NULL. Given that we are required to read the GC count
 562   // while holding the Heap_lock, and these paths will take the
 563   // Heap_lock at some point, it's easier to get them to read the GC
 564   // count while holding the Heap_lock before they return NULL instead
 565   // of the caller (namely: mem_allocate()) having to also take the
 566   // Heap_lock just to read the GC count.
 567 
 568   // First-level mutator allocation attempt: try to allocate out of
 569   // the mutator alloc region without taking the Heap_lock. This
 570   // should only be used for non-humongous allocations.
 571   inline HeapWord* attempt_allocation(size_t word_size,
 572                                       unsigned int* gc_count_before_ret,
 573                                       int* gclocker_retry_count_ret);
 574 
 575   // Second-level mutator allocation attempt: take the Heap_lock and
 576   // retry the allocation attempt, potentially scheduling a GC
 577   // pause. This should only be used for non-humongous allocations.
 578   HeapWord* attempt_allocation_slow(size_t word_size,
 579                                     unsigned int* gc_count_before_ret,
 580                                     int* gclocker_retry_count_ret);
 581 
 582   // Takes the Heap_lock and attempts a humongous allocation. It can
 583   // potentially schedule a GC pause.
 584   HeapWord* attempt_allocation_humongous(size_t word_size,
 585                                          unsigned int* gc_count_before_ret,
 586                                          int* gclocker_retry_count_ret);
 587 
 588   // Allocation attempt that should be called during safepoints (e.g.,
 589   // at the end of a successful GC). expect_null_mutator_alloc_region
 590   // specifies whether the mutator alloc region is expected to be NULL
 591   // or not.
 592   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 593                                        bool expect_null_mutator_alloc_region);
 594 
 595   // It dirties the cards that cover the block so that so that the post
 596   // write barrier never queues anything when updating objects on this
 597   // block. It is assumed (and in fact we assert) that the block
 598   // belongs to a young region.
 599   inline void dirty_young_block(HeapWord* start, size_t word_size);
 600 
 601   // Allocate blocks during garbage collection. Will ensure an
 602   // allocation region, either by picking one or expanding the
 603   // heap, and then allocate a block of the given size. The block
 604   // may not be a humongous - it must fit into a single heap region.
 605   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 606 
 607   // Ensure that no further allocations can happen in "r", bearing in mind
 608   // that parallel threads might be attempting allocations.
 609   void par_allocate_remaining_space(HeapRegion* r);
 610 
 611   // Allocation attempt during GC for a survivor object / PLAB.
 612   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 613 
 614   // Allocation attempt during GC for an old object / PLAB.
 615   inline HeapWord* old_attempt_allocation(size_t word_size);
 616 
 617   // These methods are the "callbacks" from the G1AllocRegion class.
 618 
 619   // For mutator alloc regions.
 620   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 621   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 622                                    size_t allocated_bytes);
 623 
 624   // For GC alloc regions.
 625   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 626                                   GCAllocPurpose ap);
 627   void retire_gc_alloc_region(HeapRegion* alloc_region,
 628                               size_t allocated_bytes, GCAllocPurpose ap);
 629 
 630   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 631   //   inspection request and should collect the entire heap
 632   // - if clear_all_soft_refs is true, all soft references should be
 633   //   cleared during the GC
 634   // - if explicit_gc is false, word_size describes the allocation that
 635   //   the GC should attempt (at least) to satisfy
 636   // - it returns false if it is unable to do the collection due to the
 637   //   GC locker being active, true otherwise
 638   bool do_collection(bool explicit_gc,
 639                      bool clear_all_soft_refs,
 640                      size_t word_size);
 641 
 642   // Callback from VM_G1CollectFull operation.
 643   // Perform a full collection.
 644   virtual void do_full_collection(bool clear_all_soft_refs);
 645 
 646   // Resize the heap if necessary after a full collection.  If this is
 647   // after a collect-for allocation, "word_size" is the allocation size,
 648   // and will be considered part of the used portion of the heap.
 649   void resize_if_necessary_after_full_collection(size_t word_size);
 650 
 651   // Callback from VM_G1CollectForAllocation operation.
 652   // This function does everything necessary/possible to satisfy a
 653   // failed allocation request (including collection, expansion, etc.)
 654   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 655 
 656   // Attempting to expand the heap sufficiently
 657   // to support an allocation of the given "word_size".  If
 658   // successful, perform the allocation and return the address of the
 659   // allocated block, or else "NULL".
 660   HeapWord* expand_and_allocate(size_t word_size);
 661 
 662   // Process any reference objects discovered during
 663   // an incremental evacuation pause.
 664   void process_discovered_references(uint no_of_gc_workers);
 665 
 666   // Enqueue any remaining discovered references
 667   // after processing.
 668   void enqueue_discovered_references(uint no_of_gc_workers);
 669 
 670 public:
 671 
 672   G1MonitoringSupport* g1mm() {
 673     assert(_g1mm != NULL, "should have been initialized");
 674     return _g1mm;
 675   }
 676 
 677   // Expand the garbage-first heap by at least the given size (in bytes!).
 678   // Returns true if the heap was expanded by the requested amount;
 679   // false otherwise.
 680   // (Rounds up to a HeapRegion boundary.)
 681   bool expand(size_t expand_bytes);
 682 
 683   // Do anything common to GC's.
 684   virtual void gc_prologue(bool full);
 685   virtual void gc_epilogue(bool full);
 686 
 687   // We register a region with the fast "in collection set" test. We
 688   // simply set to true the array slot corresponding to this region.
 689   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 690     assert(_in_cset_fast_test_base != NULL, "sanity");
 691     assert(r->in_collection_set(), "invariant");
 692     uint index = r->hrs_index();
 693     assert(index < _in_cset_fast_test_length, "invariant");
 694     assert(!_in_cset_fast_test_base[index], "invariant");
 695     _in_cset_fast_test_base[index] = true;
 696   }
 697 
 698   // This is a fast test on whether a reference points into the
 699   // collection set or not. It does not assume that the reference
 700   // points into the heap; if it doesn't, it will return false.
 701   bool in_cset_fast_test(oop obj) {
 702     assert(_in_cset_fast_test != NULL, "sanity");
 703     if (_g1_committed.contains((HeapWord*) obj)) {
 704       // no need to subtract the bottom of the heap from obj,
 705       // _in_cset_fast_test is biased
 706       uintx index = (uintx) obj >> HeapRegion::LogOfHRGrainBytes;
 707       bool ret = _in_cset_fast_test[index];
 708       // let's make sure the result is consistent with what the slower
 709       // test returns
 710       assert( ret || !obj_in_cs(obj), "sanity");
 711       assert(!ret ||  obj_in_cs(obj), "sanity");
 712       return ret;
 713     } else {
 714       return false;
 715     }
 716   }
 717 
 718   void clear_cset_fast_test() {
 719     assert(_in_cset_fast_test_base != NULL, "sanity");
 720     memset(_in_cset_fast_test_base, false,
 721            (size_t) _in_cset_fast_test_length * sizeof(bool));
 722   }
 723 
 724   // This is called at the start of either a concurrent cycle or a Full
 725   // GC to update the number of old marking cycles started.
 726   void increment_old_marking_cycles_started();
 727 
 728   // This is called at the end of either a concurrent cycle or a Full
 729   // GC to update the number of old marking cycles completed. Those two
 730   // can happen in a nested fashion, i.e., we start a concurrent
 731   // cycle, a Full GC happens half-way through it which ends first,
 732   // and then the cycle notices that a Full GC happened and ends
 733   // too. The concurrent parameter is a boolean to help us do a bit
 734   // tighter consistency checking in the method. If concurrent is
 735   // false, the caller is the inner caller in the nesting (i.e., the
 736   // Full GC). If concurrent is true, the caller is the outer caller
 737   // in this nesting (i.e., the concurrent cycle). Further nesting is
 738   // not currently supported. The end of this call also notifies
 739   // the FullGCCount_lock in case a Java thread is waiting for a full
 740   // GC to happen (e.g., it called System.gc() with
 741   // +ExplicitGCInvokesConcurrent).
 742   void increment_old_marking_cycles_completed(bool concurrent);
 743 
 744   unsigned int old_marking_cycles_completed() {
 745     return _old_marking_cycles_completed;
 746   }
 747 
 748   void register_concurrent_cycle_start(jlong start_time);
 749   void register_concurrent_cycle_end();
 750   void trace_heap_after_concurrent_cycle();
 751 
 752   G1YCType yc_type();
 753 
 754   G1HRPrinter* hr_printer() { return &_hr_printer; }
 755 
 756 protected:
 757 
 758   // Shrink the garbage-first heap by at most the given size (in bytes!).
 759   // (Rounds down to a HeapRegion boundary.)
 760   virtual void shrink(size_t expand_bytes);
 761   void shrink_helper(size_t expand_bytes);
 762 
 763   #if TASKQUEUE_STATS
 764   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 765   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 766   void reset_taskqueue_stats();
 767   #endif // TASKQUEUE_STATS
 768 
 769   // Schedule the VM operation that will do an evacuation pause to
 770   // satisfy an allocation request of word_size. *succeeded will
 771   // return whether the VM operation was successful (it did do an
 772   // evacuation pause) or not (another thread beat us to it or the GC
 773   // locker was active). Given that we should not be holding the
 774   // Heap_lock when we enter this method, we will pass the
 775   // gc_count_before (i.e., total_collections()) as a parameter since
 776   // it has to be read while holding the Heap_lock. Currently, both
 777   // methods that call do_collection_pause() release the Heap_lock
 778   // before the call, so it's easy to read gc_count_before just before.
 779   HeapWord* do_collection_pause(size_t         word_size,
 780                                 unsigned int   gc_count_before,
 781                                 bool*          succeeded,
 782                                 GCCause::Cause gc_cause);
 783 
 784   // The guts of the incremental collection pause, executed by the vm
 785   // thread. It returns false if it is unable to do the collection due
 786   // to the GC locker being active, true otherwise
 787   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 788 
 789   // Actually do the work of evacuating the collection set.
 790   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 791 
 792   // The g1 remembered set of the heap.
 793   G1RemSet* _g1_rem_set;
 794   // And it's mod ref barrier set, used to track updates for the above.
 795   ModRefBarrierSet* _mr_bs;
 796 
 797   // A set of cards that cover the objects for which the Rsets should be updated
 798   // concurrently after the collection.
 799   DirtyCardQueueSet _dirty_card_queue_set;
 800 
 801   // The closure used to refine a single card.
 802   RefineCardTableEntryClosure* _refine_cte_cl;
 803 
 804   // A function to check the consistency of dirty card logs.
 805   void check_ct_logs_at_safepoint();
 806 
 807   // A DirtyCardQueueSet that is used to hold cards that contain
 808   // references into the current collection set. This is used to
 809   // update the remembered sets of the regions in the collection
 810   // set in the event of an evacuation failure.
 811   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 812 
 813   // After a collection pause, make the regions in the CS into free
 814   // regions.
 815   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 816 
 817   // Abandon the current collection set without recording policy
 818   // statistics or updating free lists.
 819   void abandon_collection_set(HeapRegion* cs_head);
 820 
 821   // Applies "scan_non_heap_roots" to roots outside the heap,
 822   // "scan_rs" to roots inside the heap (having done "set_region" to
 823   // indicate the region in which the root resides),
 824   // and does "scan_metadata" If "scan_rs" is
 825   // NULL, then this step is skipped.  The "worker_i"
 826   // param is for use with parallel roots processing, and should be
 827   // the "i" of the calling parallel worker thread's work(i) function.
 828   // In the sequential case this param will be ignored.
 829   void g1_process_strong_roots(bool is_scavenging,
 830                                ScanningOption so,
 831                                OopClosure* scan_non_heap_roots,
 832                                OopsInHeapRegionClosure* scan_rs,
 833                                G1KlassScanClosure* scan_klasses,
 834                                int worker_i);
 835 
 836   // Apply "blk" to all the weak roots of the system.  These include
 837   // JNI weak roots, the code cache, system dictionary, symbol table,
 838   // string table, and referents of reachable weak refs.
 839   void g1_process_weak_roots(OopClosure* root_closure);
 840 
 841   // Frees a non-humongous region by initializing its contents and
 842   // adding it to the free list that's passed as a parameter (this is
 843   // usually a local list which will be appended to the master free
 844   // list later). The used bytes of freed regions are accumulated in
 845   // pre_used. If par is true, the region's RSet will not be freed
 846   // up. The assumption is that this will be done later.
 847   void free_region(HeapRegion* hr,
 848                    size_t* pre_used,
 849                    FreeRegionList* free_list,
 850                    bool par);
 851 
 852   // Frees a humongous region by collapsing it into individual regions
 853   // and calling free_region() for each of them. The freed regions
 854   // will be added to the free list that's passed as a parameter (this
 855   // is usually a local list which will be appended to the master free
 856   // list later). The used bytes of freed regions are accumulated in
 857   // pre_used. If par is true, the region's RSet will not be freed
 858   // up. The assumption is that this will be done later.
 859   void free_humongous_region(HeapRegion* hr,
 860                              size_t* pre_used,
 861                              FreeRegionList* free_list,
 862                              HumongousRegionSet* humongous_proxy_set,
 863                              bool par);
 864 
 865   // Notifies all the necessary spaces that the committed space has
 866   // been updated (either expanded or shrunk). It should be called
 867   // after _g1_storage is updated.
 868   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 869 
 870   // The concurrent marker (and the thread it runs in.)
 871   ConcurrentMark* _cm;
 872   ConcurrentMarkThread* _cmThread;
 873   bool _mark_in_progress;
 874 
 875   // The concurrent refiner.
 876   ConcurrentG1Refine* _cg1r;
 877 
 878   // The parallel task queues
 879   RefToScanQueueSet *_task_queues;
 880 
 881   // True iff a evacuation has failed in the current collection.
 882   bool _evacuation_failed;
 883 
 884   EvacuationFailedInfo* _evacuation_failed_info_array;
 885 
 886   // Failed evacuations cause some logical from-space objects to have
 887   // forwarding pointers to themselves.  Reset them.
 888   void remove_self_forwarding_pointers();
 889 
 890   // Together, these store an object with a preserved mark, and its mark value.
 891   Stack<oop, mtGC>     _objs_with_preserved_marks;
 892   Stack<markOop, mtGC> _preserved_marks_of_objs;
 893 
 894   // Preserve the mark of "obj", if necessary, in preparation for its mark
 895   // word being overwritten with a self-forwarding-pointer.
 896   void preserve_mark_if_necessary(oop obj, markOop m);
 897 
 898   // The stack of evac-failure objects left to be scanned.
 899   GrowableArray<oop>*    _evac_failure_scan_stack;
 900   // The closure to apply to evac-failure objects.
 901 
 902   OopsInHeapRegionClosure* _evac_failure_closure;
 903   // Set the field above.
 904   void
 905   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 906     _evac_failure_closure = evac_failure_closure;
 907   }
 908 
 909   // Push "obj" on the scan stack.
 910   void push_on_evac_failure_scan_stack(oop obj);
 911   // Process scan stack entries until the stack is empty.
 912   void drain_evac_failure_scan_stack();
 913   // True iff an invocation of "drain_scan_stack" is in progress; to
 914   // prevent unnecessary recursion.
 915   bool _drain_in_progress;
 916 
 917   // Do any necessary initialization for evacuation-failure handling.
 918   // "cl" is the closure that will be used to process evac-failure
 919   // objects.
 920   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 921   // Do any necessary cleanup for evacuation-failure handling data
 922   // structures.
 923   void finalize_for_evac_failure();
 924 
 925   // An attempt to evacuate "obj" has failed; take necessary steps.
 926   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 927   void handle_evacuation_failure_common(oop obj, markOop m);
 928 
 929 #ifndef PRODUCT
 930   // Support for forcing evacuation failures. Analogous to
 931   // PromotionFailureALot for the other collectors.
 932 
 933   // Records whether G1EvacuationFailureALot should be in effect
 934   // for the current GC
 935   bool _evacuation_failure_alot_for_current_gc;
 936 
 937   // Used to record the GC number for interval checking when
 938   // determining whether G1EvaucationFailureALot is in effect
 939   // for the current GC.
 940   size_t _evacuation_failure_alot_gc_number;
 941 
 942   // Count of the number of evacuations between failures.
 943   volatile size_t _evacuation_failure_alot_count;
 944 
 945   // Set whether G1EvacuationFailureALot should be in effect
 946   // for the current GC (based upon the type of GC and which
 947   // command line flags are set);
 948   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 949                                                   bool during_initial_mark,
 950                                                   bool during_marking);
 951 
 952   inline void set_evacuation_failure_alot_for_current_gc();
 953 
 954   // Return true if it's time to cause an evacuation failure.
 955   inline bool evacuation_should_fail();
 956 
 957   // Reset the G1EvacuationFailureALot counters.  Should be called at
 958   // the end of an evacuation pause in which an evacuation failure occurred.
 959   inline void reset_evacuation_should_fail();
 960 #endif // !PRODUCT
 961 
 962   // ("Weak") Reference processing support.
 963   //
 964   // G1 has 2 instances of the reference processor class. One
 965   // (_ref_processor_cm) handles reference object discovery
 966   // and subsequent processing during concurrent marking cycles.
 967   //
 968   // The other (_ref_processor_stw) handles reference object
 969   // discovery and processing during full GCs and incremental
 970   // evacuation pauses.
 971   //
 972   // During an incremental pause, reference discovery will be
 973   // temporarily disabled for _ref_processor_cm and will be
 974   // enabled for _ref_processor_stw. At the end of the evacuation
 975   // pause references discovered by _ref_processor_stw will be
 976   // processed and discovery will be disabled. The previous
 977   // setting for reference object discovery for _ref_processor_cm
 978   // will be re-instated.
 979   //
 980   // At the start of marking:
 981   //  * Discovery by the CM ref processor is verified to be inactive
 982   //    and it's discovered lists are empty.
 983   //  * Discovery by the CM ref processor is then enabled.
 984   //
 985   // At the end of marking:
 986   //  * Any references on the CM ref processor's discovered
 987   //    lists are processed (possibly MT).
 988   //
 989   // At the start of full GC we:
 990   //  * Disable discovery by the CM ref processor and
 991   //    empty CM ref processor's discovered lists
 992   //    (without processing any entries).
 993   //  * Verify that the STW ref processor is inactive and it's
 994   //    discovered lists are empty.
 995   //  * Temporarily set STW ref processor discovery as single threaded.
 996   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 997   //    field.
 998   //  * Finally enable discovery by the STW ref processor.
 999   //
1000   // The STW ref processor is used to record any discovered
1001   // references during the full GC.
1002   //
1003   // At the end of a full GC we:
1004   //  * Enqueue any reference objects discovered by the STW ref processor
1005   //    that have non-live referents. This has the side-effect of
1006   //    making the STW ref processor inactive by disabling discovery.
1007   //  * Verify that the CM ref processor is still inactive
1008   //    and no references have been placed on it's discovered
1009   //    lists (also checked as a precondition during initial marking).
1010 
1011   // The (stw) reference processor...
1012   ReferenceProcessor* _ref_processor_stw;
1013 
1014   STWGCTimer* _gc_timer_stw;
1015   ConcurrentGCTimer* _gc_timer_cm;
1016 
1017   G1OldTracer* _gc_tracer_cm;
1018   G1NewTracer* _gc_tracer_stw;
1019 
1020   // During reference object discovery, the _is_alive_non_header
1021   // closure (if non-null) is applied to the referent object to
1022   // determine whether the referent is live. If so then the
1023   // reference object does not need to be 'discovered' and can
1024   // be treated as a regular oop. This has the benefit of reducing
1025   // the number of 'discovered' reference objects that need to
1026   // be processed.
1027   //
1028   // Instance of the is_alive closure for embedding into the
1029   // STW reference processor as the _is_alive_non_header field.
1030   // Supplying a value for the _is_alive_non_header field is
1031   // optional but doing so prevents unnecessary additions to
1032   // the discovered lists during reference discovery.
1033   G1STWIsAliveClosure _is_alive_closure_stw;
1034 
1035   // The (concurrent marking) reference processor...
1036   ReferenceProcessor* _ref_processor_cm;
1037 
1038   // Instance of the concurrent mark is_alive closure for embedding
1039   // into the Concurrent Marking reference processor as the
1040   // _is_alive_non_header field. Supplying a value for the
1041   // _is_alive_non_header field is optional but doing so prevents
1042   // unnecessary additions to the discovered lists during reference
1043   // discovery.
1044   G1CMIsAliveClosure _is_alive_closure_cm;
1045 
1046   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1047   HeapRegion** _worker_cset_start_region;
1048 
1049   // Time stamp to validate the regions recorded in the cache
1050   // used by G1CollectedHeap::start_cset_region_for_worker().
1051   // The heap region entry for a given worker is valid iff
1052   // the associated time stamp value matches the current value
1053   // of G1CollectedHeap::_gc_time_stamp.
1054   unsigned int* _worker_cset_start_region_time_stamp;
1055 
1056   enum G1H_process_strong_roots_tasks {
1057     G1H_PS_filter_satb_buffers,
1058     G1H_PS_refProcessor_oops_do,
1059     // Leave this one last.
1060     G1H_PS_NumElements
1061   };
1062 
1063   SubTasksDone* _process_strong_tasks;
1064 
1065   volatile bool _free_regions_coming;
1066 
1067 public:
1068 
1069   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1070 
1071   void set_refine_cte_cl_concurrency(bool concurrent);
1072 
1073   RefToScanQueue *task_queue(int i) const;
1074 
1075   // A set of cards where updates happened during the GC
1076   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1077 
1078   // A DirtyCardQueueSet that is used to hold cards that contain
1079   // references into the current collection set. This is used to
1080   // update the remembered sets of the regions in the collection
1081   // set in the event of an evacuation failure.
1082   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1083         { return _into_cset_dirty_card_queue_set; }
1084 
1085   // Create a G1CollectedHeap with the specified policy.
1086   // Must call the initialize method afterwards.
1087   // May not return if something goes wrong.
1088   G1CollectedHeap(G1CollectorPolicy* policy);
1089 
1090   // Initialize the G1CollectedHeap to have the initial and
1091   // maximum sizes and remembered and barrier sets
1092   // specified by the policy object.
1093   jint initialize();
1094 
1095   // Return the (conservative) maximum heap alignment for any G1 heap
1096   static size_t conservative_max_heap_alignment();
1097 
1098   // Initialize weak reference processing.
1099   virtual void ref_processing_init();
1100 
1101   void set_par_threads(uint t) {
1102     SharedHeap::set_par_threads(t);
1103     // Done in SharedHeap but oddly there are
1104     // two _process_strong_tasks's in a G1CollectedHeap
1105     // so do it here too.
1106     _process_strong_tasks->set_n_threads(t);
1107   }
1108 
1109   // Set _n_par_threads according to a policy TBD.
1110   void set_par_threads();
1111 
1112   void set_n_termination(int t) {
1113     _process_strong_tasks->set_n_threads(t);
1114   }
1115 
1116   virtual CollectedHeap::Name kind() const {
1117     return CollectedHeap::G1CollectedHeap;
1118   }
1119 
1120   // The current policy object for the collector.
1121   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1122 
1123   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1124 
1125   // Adaptive size policy.  No such thing for g1.
1126   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1127 
1128   // The rem set and barrier set.
1129   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1130   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
1131 
1132   unsigned get_gc_time_stamp() {
1133     return _gc_time_stamp;
1134   }
1135 
1136   void reset_gc_time_stamp() {
1137     _gc_time_stamp = 0;
1138     OrderAccess::fence();
1139     // Clear the cached CSet starting regions and time stamps.
1140     // Their validity is dependent on the GC timestamp.
1141     clear_cset_start_regions();
1142   }
1143 
1144   void check_gc_time_stamps() PRODUCT_RETURN;
1145 
1146   void increment_gc_time_stamp() {
1147     ++_gc_time_stamp;
1148     OrderAccess::fence();
1149   }
1150 
1151   // Reset the given region's GC timestamp. If it's starts humongous,
1152   // also reset the GC timestamp of its corresponding
1153   // continues humongous regions too.
1154   void reset_gc_time_stamps(HeapRegion* hr);
1155 
1156   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1157                                   DirtyCardQueue* into_cset_dcq,
1158                                   bool concurrent, int worker_i);
1159 
1160   // The shared block offset table array.
1161   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1162 
1163   // Reference Processing accessors
1164 
1165   // The STW reference processor....
1166   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1167 
1168   // The Concurrent Marking reference processor...
1169   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1170 
1171   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1172   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1173 
1174   virtual size_t capacity() const;
1175   virtual size_t used() const;
1176   // This should be called when we're not holding the heap lock. The
1177   // result might be a bit inaccurate.
1178   size_t used_unlocked() const;
1179   size_t recalculate_used() const;
1180 
1181   // These virtual functions do the actual allocation.
1182   // Some heaps may offer a contiguous region for shared non-blocking
1183   // allocation, via inlined code (by exporting the address of the top and
1184   // end fields defining the extent of the contiguous allocation region.)
1185   // But G1CollectedHeap doesn't yet support this.
1186 
1187   // Return an estimate of the maximum allocation that could be performed
1188   // without triggering any collection or expansion activity.  In a
1189   // generational collector, for example, this is probably the largest
1190   // allocation that could be supported (without expansion) in the youngest
1191   // generation.  It is "unsafe" because no locks are taken; the result
1192   // should be treated as an approximation, not a guarantee, for use in
1193   // heuristic resizing decisions.
1194   virtual size_t unsafe_max_alloc();
1195 
1196   virtual bool is_maximal_no_gc() const {
1197     return _g1_storage.uncommitted_size() == 0;
1198   }
1199 
1200   // The total number of regions in the heap.
1201   uint n_regions() { return _hrs.length(); }
1202 
1203   // The max number of regions in the heap.
1204   uint max_regions() { return _hrs.max_length(); }
1205 
1206   // The number of regions that are completely free.
1207   uint free_regions() { return _free_list.length(); }
1208 
1209   // The number of regions that are not completely free.
1210   uint used_regions() { return n_regions() - free_regions(); }
1211 
1212   // The number of regions available for "regular" expansion.
1213   uint expansion_regions() { return _expansion_regions; }
1214 
1215   // Factory method for HeapRegion instances. It will return NULL if
1216   // the allocation fails.
1217   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1218 
1219   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1220   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1221   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1222   void verify_dirty_young_regions() PRODUCT_RETURN;
1223 
1224   // verify_region_sets() performs verification over the region
1225   // lists. It will be compiled in the product code to be used when
1226   // necessary (i.e., during heap verification).
1227   void verify_region_sets();
1228 
1229   // verify_region_sets_optional() is planted in the code for
1230   // list verification in non-product builds (and it can be enabled in
1231   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1232 #if HEAP_REGION_SET_FORCE_VERIFY
1233   void verify_region_sets_optional() {
1234     verify_region_sets();
1235   }
1236 #else // HEAP_REGION_SET_FORCE_VERIFY
1237   void verify_region_sets_optional() { }
1238 #endif // HEAP_REGION_SET_FORCE_VERIFY
1239 
1240 #ifdef ASSERT
1241   bool is_on_master_free_list(HeapRegion* hr) {
1242     return hr->containing_set() == &_free_list;
1243   }
1244 
1245   bool is_in_humongous_set(HeapRegion* hr) {
1246     return hr->containing_set() == &_humongous_set;
1247   }
1248 #endif // ASSERT
1249 
1250   // Wrapper for the region list operations that can be called from
1251   // methods outside this class.
1252 
1253   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1254     _secondary_free_list.add_as_tail(list);
1255   }
1256 
1257   void append_secondary_free_list() {
1258     _free_list.add_as_head(&_secondary_free_list);
1259   }
1260 
1261   void append_secondary_free_list_if_not_empty_with_lock() {
1262     // If the secondary free list looks empty there's no reason to
1263     // take the lock and then try to append it.
1264     if (!_secondary_free_list.is_empty()) {
1265       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1266       append_secondary_free_list();
1267     }
1268   }
1269 
1270   void old_set_remove(HeapRegion* hr) {
1271     _old_set.remove(hr);
1272   }
1273 
1274   size_t non_young_capacity_bytes() {
1275     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1276   }
1277 
1278   void set_free_regions_coming();
1279   void reset_free_regions_coming();
1280   bool free_regions_coming() { return _free_regions_coming; }
1281   void wait_while_free_regions_coming();
1282 
1283   // Determine whether the given region is one that we are using as an
1284   // old GC alloc region.
1285   bool is_old_gc_alloc_region(HeapRegion* hr) {
1286     return hr == _retained_old_gc_alloc_region;
1287   }
1288 
1289   // Perform a collection of the heap; intended for use in implementing
1290   // "System.gc".  This probably implies as full a collection as the
1291   // "CollectedHeap" supports.
1292   virtual void collect(GCCause::Cause cause);
1293 
1294   // The same as above but assume that the caller holds the Heap_lock.
1295   void collect_locked(GCCause::Cause cause);
1296 
1297   // True iff an evacuation has failed in the most-recent collection.
1298   bool evacuation_failed() { return _evacuation_failed; }
1299 
1300   // It will free a region if it has allocated objects in it that are
1301   // all dead. It calls either free_region() or
1302   // free_humongous_region() depending on the type of the region that
1303   // is passed to it.
1304   void free_region_if_empty(HeapRegion* hr,
1305                             size_t* pre_used,
1306                             FreeRegionList* free_list,
1307                             OldRegionSet* old_proxy_set,
1308                             HumongousRegionSet* humongous_proxy_set,
1309                             HRRSCleanupTask* hrrs_cleanup_task,
1310                             bool par);
1311 
1312   // It appends the free list to the master free list and updates the
1313   // master humongous list according to the contents of the proxy
1314   // list. It also adjusts the total used bytes according to pre_used
1315   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1316   void update_sets_after_freeing_regions(size_t pre_used,
1317                                        FreeRegionList* free_list,
1318                                        OldRegionSet* old_proxy_set,
1319                                        HumongousRegionSet* humongous_proxy_set,
1320                                        bool par);
1321 
1322   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1323   virtual bool is_in(const void* p) const;
1324 
1325   // Return "TRUE" iff the given object address is within the collection
1326   // set.
1327   inline bool obj_in_cs(oop obj);
1328 
1329   // Return "TRUE" iff the given object address is in the reserved
1330   // region of g1.
1331   bool is_in_g1_reserved(const void* p) const {
1332     return _g1_reserved.contains(p);
1333   }
1334 
1335   // Returns a MemRegion that corresponds to the space that has been
1336   // reserved for the heap
1337   MemRegion g1_reserved() {
1338     return _g1_reserved;
1339   }
1340 
1341   // Returns a MemRegion that corresponds to the space that has been
1342   // committed in the heap
1343   MemRegion g1_committed() {
1344     return _g1_committed;
1345   }
1346 
1347   virtual bool is_in_closed_subset(const void* p) const;
1348 
1349   // This resets the card table to all zeros.  It is used after
1350   // a collection pause which used the card table to claim cards.
1351   void cleanUpCardTable();
1352 
1353   // Iteration functions.
1354 
1355   // Iterate over all the ref-containing fields of all objects, calling
1356   // "cl.do_oop" on each.
1357   virtual void oop_iterate(ExtendedOopClosure* cl);
1358 
1359   // Same as above, restricted to a memory region.
1360   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1361 
1362   // Iterate over all objects, calling "cl.do_object" on each.
1363   virtual void object_iterate(ObjectClosure* cl);
1364 
1365   virtual void safe_object_iterate(ObjectClosure* cl) {
1366     object_iterate(cl);
1367   }
1368 
1369   // Iterate over all spaces in use in the heap, in ascending address order.
1370   virtual void space_iterate(SpaceClosure* cl);
1371 
1372   // Iterate over heap regions, in address order, terminating the
1373   // iteration early if the "doHeapRegion" method returns "true".
1374   void heap_region_iterate(HeapRegionClosure* blk) const;
1375 
1376   // Return the region with the given index. It assumes the index is valid.
1377   HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1378 
1379   // Divide the heap region sequence into "chunks" of some size (the number
1380   // of regions divided by the number of parallel threads times some
1381   // overpartition factor, currently 4).  Assumes that this will be called
1382   // in parallel by ParallelGCThreads worker threads with discinct worker
1383   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1384   // calls will use the same "claim_value", and that that claim value is
1385   // different from the claim_value of any heap region before the start of
1386   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1387   // attempting to claim the first region in each chunk, and, if
1388   // successful, applying the closure to each region in the chunk (and
1389   // setting the claim value of the second and subsequent regions of the
1390   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1391   // i.e., that a closure never attempt to abort a traversal.
1392   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1393                                        uint worker,
1394                                        uint no_of_par_workers,
1395                                        jint claim_value);
1396 
1397   // It resets all the region claim values to the default.
1398   void reset_heap_region_claim_values();
1399 
1400   // Resets the claim values of regions in the current
1401   // collection set to the default.
1402   void reset_cset_heap_region_claim_values();
1403 
1404 #ifdef ASSERT
1405   bool check_heap_region_claim_values(jint claim_value);
1406 
1407   // Same as the routine above but only checks regions in the
1408   // current collection set.
1409   bool check_cset_heap_region_claim_values(jint claim_value);
1410 #endif // ASSERT
1411 
1412   // Clear the cached cset start regions and (more importantly)
1413   // the time stamps. Called when we reset the GC time stamp.
1414   void clear_cset_start_regions();
1415 
1416   // Given the id of a worker, obtain or calculate a suitable
1417   // starting region for iterating over the current collection set.
1418   HeapRegion* start_cset_region_for_worker(int worker_i);
1419 
1420   // This is a convenience method that is used by the
1421   // HeapRegionIterator classes to calculate the starting region for
1422   // each worker so that they do not all start from the same region.
1423   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1424 
1425   // Iterate over the regions (if any) in the current collection set.
1426   void collection_set_iterate(HeapRegionClosure* blk);
1427 
1428   // As above but starting from region r
1429   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1430 
1431   // Returns the first (lowest address) compactible space in the heap.
1432   virtual CompactibleSpace* first_compactible_space();
1433 
1434   // A CollectedHeap will contain some number of spaces.  This finds the
1435   // space containing a given address, or else returns NULL.
1436   virtual Space* space_containing(const void* addr) const;
1437 
1438   // A G1CollectedHeap will contain some number of heap regions.  This
1439   // finds the region containing a given address, or else returns NULL.
1440   template <class T>
1441   inline HeapRegion* heap_region_containing(const T addr) const;
1442 
1443   // Like the above, but requires "addr" to be in the heap (to avoid a
1444   // null-check), and unlike the above, may return an continuing humongous
1445   // region.
1446   template <class T>
1447   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1448 
1449   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1450   // each address in the (reserved) heap is a member of exactly
1451   // one block.  The defining characteristic of a block is that it is
1452   // possible to find its size, and thus to progress forward to the next
1453   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1454   // represent Java objects, or they might be free blocks in a
1455   // free-list-based heap (or subheap), as long as the two kinds are
1456   // distinguishable and the size of each is determinable.
1457 
1458   // Returns the address of the start of the "block" that contains the
1459   // address "addr".  We say "blocks" instead of "object" since some heaps
1460   // may not pack objects densely; a chunk may either be an object or a
1461   // non-object.
1462   virtual HeapWord* block_start(const void* addr) const;
1463 
1464   // Requires "addr" to be the start of a chunk, and returns its size.
1465   // "addr + size" is required to be the start of a new chunk, or the end
1466   // of the active area of the heap.
1467   virtual size_t block_size(const HeapWord* addr) const;
1468 
1469   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1470   // the block is an object.
1471   virtual bool block_is_obj(const HeapWord* addr) const;
1472 
1473   // Does this heap support heap inspection? (+PrintClassHistogram)
1474   virtual bool supports_heap_inspection() const { return true; }
1475 
1476   // Section on thread-local allocation buffers (TLABs)
1477   // See CollectedHeap for semantics.
1478 
1479   virtual bool supports_tlab_allocation() const;
1480   virtual size_t tlab_capacity(Thread* thr) const;
1481   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1482 
1483   // Can a compiler initialize a new object without store barriers?
1484   // This permission only extends from the creation of a new object
1485   // via a TLAB up to the first subsequent safepoint. If such permission
1486   // is granted for this heap type, the compiler promises to call
1487   // defer_store_barrier() below on any slow path allocation of
1488   // a new object for which such initializing store barriers will
1489   // have been elided. G1, like CMS, allows this, but should be
1490   // ready to provide a compensating write barrier as necessary
1491   // if that storage came out of a non-young region. The efficiency
1492   // of this implementation depends crucially on being able to
1493   // answer very efficiently in constant time whether a piece of
1494   // storage in the heap comes from a young region or not.
1495   // See ReduceInitialCardMarks.
1496   virtual bool can_elide_tlab_store_barriers() const {
1497     return true;
1498   }
1499 
1500   virtual bool card_mark_must_follow_store() const {
1501     return true;
1502   }
1503 
1504   bool is_in_young(const oop obj) {
1505     HeapRegion* hr = heap_region_containing(obj);
1506     return hr != NULL && hr->is_young();
1507   }
1508 
1509 #ifdef ASSERT
1510   virtual bool is_in_partial_collection(const void* p);
1511 #endif
1512 
1513   virtual bool is_scavengable(const void* addr);
1514 
1515   // We don't need barriers for initializing stores to objects
1516   // in the young gen: for the SATB pre-barrier, there is no
1517   // pre-value that needs to be remembered; for the remembered-set
1518   // update logging post-barrier, we don't maintain remembered set
1519   // information for young gen objects.
1520   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1521     return is_in_young(new_obj);
1522   }
1523 
1524   // Returns "true" iff the given word_size is "very large".
1525   static bool isHumongous(size_t word_size) {
1526     // Note this has to be strictly greater-than as the TLABs
1527     // are capped at the humongous thresold and we want to
1528     // ensure that we don't try to allocate a TLAB as
1529     // humongous and that we don't allocate a humongous
1530     // object in a TLAB.
1531     return word_size > _humongous_object_threshold_in_words;
1532   }
1533 
1534   // Update mod union table with the set of dirty cards.
1535   void updateModUnion();
1536 
1537   // Set the mod union bits corresponding to the given memRegion.  Note
1538   // that this is always a safe operation, since it doesn't clear any
1539   // bits.
1540   void markModUnionRange(MemRegion mr);
1541 
1542   // Records the fact that a marking phase is no longer in progress.
1543   void set_marking_complete() {
1544     _mark_in_progress = false;
1545   }
1546   void set_marking_started() {
1547     _mark_in_progress = true;
1548   }
1549   bool mark_in_progress() {
1550     return _mark_in_progress;
1551   }
1552 
1553   // Print the maximum heap capacity.
1554   virtual size_t max_capacity() const;
1555 
1556   virtual jlong millis_since_last_gc();
1557 
1558 
1559   // Convenience function to be used in situations where the heap type can be
1560   // asserted to be this type.
1561   static G1CollectedHeap* heap();
1562 
1563   void set_region_short_lived_locked(HeapRegion* hr);
1564   // add appropriate methods for any other surv rate groups
1565 
1566   YoungList* young_list() { return _young_list; }
1567 
1568   // debugging
1569   bool check_young_list_well_formed() {
1570     return _young_list->check_list_well_formed();
1571   }
1572 
1573   bool check_young_list_empty(bool check_heap,
1574                               bool check_sample = true);
1575 
1576   // *** Stuff related to concurrent marking.  It's not clear to me that so
1577   // many of these need to be public.
1578 
1579   // The functions below are helper functions that a subclass of
1580   // "CollectedHeap" can use in the implementation of its virtual
1581   // functions.
1582   // This performs a concurrent marking of the live objects in a
1583   // bitmap off to the side.
1584   void doConcurrentMark();
1585 
1586   bool isMarkedPrev(oop obj) const;
1587   bool isMarkedNext(oop obj) const;
1588 
1589   // Determine if an object is dead, given the object and also
1590   // the region to which the object belongs. An object is dead
1591   // iff a) it was not allocated since the last mark and b) it
1592   // is not marked.
1593 
1594   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1595     return
1596       !hr->obj_allocated_since_prev_marking(obj) &&
1597       !isMarkedPrev(obj);
1598   }
1599 
1600   // This function returns true when an object has been
1601   // around since the previous marking and hasn't yet
1602   // been marked during this marking.
1603 
1604   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1605     return
1606       !hr->obj_allocated_since_next_marking(obj) &&
1607       !isMarkedNext(obj);
1608   }
1609 
1610   // Determine if an object is dead, given only the object itself.
1611   // This will find the region to which the object belongs and
1612   // then call the region version of the same function.
1613 
1614   // Added if it is NULL it isn't dead.
1615 
1616   bool is_obj_dead(const oop obj) const {
1617     const HeapRegion* hr = heap_region_containing(obj);
1618     if (hr == NULL) {
1619       if (obj == NULL) return false;
1620       else return true;
1621     }
1622     else return is_obj_dead(obj, hr);
1623   }
1624 
1625   bool is_obj_ill(const oop obj) const {
1626     const HeapRegion* hr = heap_region_containing(obj);
1627     if (hr == NULL) {
1628       if (obj == NULL) return false;
1629       else return true;
1630     }
1631     else return is_obj_ill(obj, hr);
1632   }
1633 
1634   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1635   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1636   bool is_marked(oop obj, VerifyOption vo);
1637   const char* top_at_mark_start_str(VerifyOption vo);
1638 
1639   ConcurrentMark* concurrent_mark() const { return _cm; }
1640 
1641   // Refinement
1642 
1643   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1644 
1645   // The dirty cards region list is used to record a subset of regions
1646   // whose cards need clearing. The list if populated during the
1647   // remembered set scanning and drained during the card table
1648   // cleanup. Although the methods are reentrant, population/draining
1649   // phases must not overlap. For synchronization purposes the last
1650   // element on the list points to itself.
1651   HeapRegion* _dirty_cards_region_list;
1652   void push_dirty_cards_region(HeapRegion* hr);
1653   HeapRegion* pop_dirty_cards_region();
1654 
1655   // Optimized nmethod scanning support routines
1656 
1657   // Register the given nmethod with the G1 heap
1658   virtual void register_nmethod(nmethod* nm);
1659 
1660   // Unregister the given nmethod from the G1 heap
1661   virtual void unregister_nmethod(nmethod* nm);
1662 
1663   // Migrate the nmethods in the code root lists of the regions
1664   // in the collection set to regions in to-space. In the event
1665   // of an evacuation failure, nmethods that reference objects
1666   // that were not successfullly evacuated are not migrated.
1667   void migrate_strong_code_roots();
1668 
1669   // During an initial mark pause, mark all the code roots that
1670   // point into regions *not* in the collection set.
1671   void mark_strong_code_roots(uint worker_id);
1672 
1673   // Rebuild the stong code root lists for each region
1674   // after a full GC
1675   void rebuild_strong_code_roots();
1676 
1677   // Verification
1678 
1679   // The following is just to alert the verification code
1680   // that a full collection has occurred and that the
1681   // remembered sets are no longer up to date.
1682   bool _full_collection;
1683   void set_full_collection() { _full_collection = true;}
1684   void clear_full_collection() {_full_collection = false;}
1685   bool full_collection() {return _full_collection;}
1686 
1687   // Perform any cleanup actions necessary before allowing a verification.
1688   virtual void prepare_for_verify();
1689 
1690   // Perform verification.
1691 
1692   // vo == UsePrevMarking  -> use "prev" marking information,
1693   // vo == UseNextMarking -> use "next" marking information
1694   // vo == UseMarkWord    -> use the mark word in the object header
1695   //
1696   // NOTE: Only the "prev" marking information is guaranteed to be
1697   // consistent most of the time, so most calls to this should use
1698   // vo == UsePrevMarking.
1699   // Currently, there is only one case where this is called with
1700   // vo == UseNextMarking, which is to verify the "next" marking
1701   // information at the end of remark.
1702   // Currently there is only one place where this is called with
1703   // vo == UseMarkWord, which is to verify the marking during a
1704   // full GC.
1705   void verify(bool silent, VerifyOption vo);
1706 
1707   // Override; it uses the "prev" marking information
1708   virtual void verify(bool silent);
1709 
1710   // The methods below are here for convenience and dispatch the
1711   // appropriate method depending on value of the given VerifyOption
1712   // parameter. The values for that parameter, and their meanings,
1713   // are the same as those above.
1714 
1715   bool is_obj_dead_cond(const oop obj,
1716                         const HeapRegion* hr,
1717                         const VerifyOption vo) const {
1718     switch (vo) {
1719     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1720     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1721     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1722     default:                            ShouldNotReachHere();
1723     }
1724     return false; // keep some compilers happy
1725   }
1726 
1727   bool is_obj_dead_cond(const oop obj,
1728                         const VerifyOption vo) const {
1729     switch (vo) {
1730     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1731     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1732     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1733     default:                            ShouldNotReachHere();
1734     }
1735     return false; // keep some compilers happy
1736   }
1737 
1738   // Printing
1739 
1740   virtual void print_on(outputStream* st) const;
1741   virtual void print_extended_on(outputStream* st) const;
1742   virtual void print_on_error(outputStream* st) const;
1743 
1744   virtual void print_gc_threads_on(outputStream* st) const;
1745   virtual void gc_threads_do(ThreadClosure* tc) const;
1746 
1747   // Override
1748   void print_tracing_info() const;
1749 
1750   // The following two methods are helpful for debugging RSet issues.
1751   void print_cset_rsets() PRODUCT_RETURN;
1752   void print_all_rsets() PRODUCT_RETURN;
1753 
1754 public:
1755   void stop_conc_gc_threads();
1756 
1757   size_t pending_card_num();
1758   size_t cards_scanned();
1759 
1760 protected:
1761   size_t _max_heap_capacity;
1762 };
1763 
1764 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1765 private:
1766   bool        _retired;
1767 
1768 public:
1769   G1ParGCAllocBuffer(size_t gclab_word_size);
1770 
1771   void set_buf(HeapWord* buf) {
1772     ParGCAllocBuffer::set_buf(buf);
1773     _retired = false;
1774   }
1775 
1776   void retire(bool end_of_gc, bool retain) {
1777     if (_retired)
1778       return;
1779     ParGCAllocBuffer::retire(end_of_gc, retain);
1780     _retired = true;
1781   }
1782 
1783   bool is_retired() {
1784     return _retired;
1785   }
1786 };
1787 
1788 class G1ParGCAllocBufferContainer {
1789 protected:
1790   static int const _priority_max = 2;
1791   G1ParGCAllocBuffer* _priority_buffer[_priority_max];
1792 
1793 public:
1794   G1ParGCAllocBufferContainer(size_t gclab_word_size) {
1795     for (int pr = 0; pr < _priority_max; ++pr) {
1796       _priority_buffer[pr] = new G1ParGCAllocBuffer(gclab_word_size);
1797     }
1798   }
1799 
1800   ~G1ParGCAllocBufferContainer() {
1801     for (int pr = 0; pr < _priority_max; ++pr) {
1802       assert(_priority_buffer[pr]->is_retired(), "alloc buffers should all retire at this point.");
1803       delete _priority_buffer[pr];
1804     }
1805   }
1806 
1807   HeapWord* allocate(size_t word_sz) {
1808     HeapWord* obj;
1809     for (int pr = 0; pr < _priority_max; ++pr) {
1810       obj = _priority_buffer[pr]->allocate(word_sz);
1811       if (obj != NULL) return obj;
1812     }
1813     return obj;
1814   }
1815 
1816   bool contains(void* addr) {
1817     for (int pr = 0; pr < _priority_max; ++pr) {
1818       if (_priority_buffer[pr]->contains(addr)) return true;
1819     }
1820     return false;
1821   }
1822 
1823   void undo_allocation(HeapWord* obj, size_t word_sz) {
1824     bool finish_undo;
1825     for (int pr = 0; pr < _priority_max; ++pr) {
1826       if (_priority_buffer[pr]->contains(obj)) {
1827         _priority_buffer[pr]->undo_allocation(obj, word_sz);
1828         finish_undo = true;
1829       }
1830     }
1831     if (!finish_undo) ShouldNotReachHere();
1832   }
1833 
1834   size_t words_remaining() {
1835     size_t result = 0;
1836     for (int pr = 0; pr < _priority_max; ++pr) {
1837       result += _priority_buffer[pr]->words_remaining();
1838     }
1839     return result;
1840   }
1841 
1842   size_t words_remaining_in_retired_buffer() {
1843     G1ParGCAllocBuffer* retired = _priority_buffer[0];
1844     return retired->words_remaining();
1845   }
1846 
1847   void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) {
1848     for (int pr = 0; pr < _priority_max; ++pr) {
1849       _priority_buffer[pr]->flush_stats_and_retire(stats, end_of_gc, retain);
1850     }
1851   }
1852 
1853   void update(bool end_of_gc, bool retain, HeapWord* buf, size_t word_sz) {
1854     G1ParGCAllocBuffer* retired_and_set = _priority_buffer[0];
1855     retired_and_set->retire(end_of_gc, retain);
1856     retired_and_set->set_buf(buf);
1857     retired_and_set->set_word_size(word_sz);
1858     adjust_priority_order();
1859   }
1860 
1861 private:
1862   void adjust_priority_order() {
1863     G1ParGCAllocBuffer* retired_and_set = _priority_buffer[0];
1864 
1865     int last = _priority_max - 1;
1866     for (int pr = 0; pr < last; ++pr) {
1867       _priority_buffer[pr] = _priority_buffer[pr + 1];
1868     }
1869     _priority_buffer[last] = retired_and_set;
1870   }
1871 };
1872 
1873 class G1ParScanThreadState : public StackObj {
1874 protected:
1875   G1CollectedHeap* _g1h;
1876   RefToScanQueue*  _refs;
1877   DirtyCardQueue   _dcq;
1878   CardTableModRefBS* _ct_bs;
1879   G1RemSet* _g1_rem;
1880 
1881   G1ParGCAllocBufferContainer  _surviving_alloc_buffer;
1882   G1ParGCAllocBufferContainer  _tenured_alloc_buffer;
1883   G1ParGCAllocBufferContainer* _alloc_buffers[GCAllocPurposeCount];
1884   ageTable            _age_table;
1885 
1886   size_t           _alloc_buffer_waste;
1887   size_t           _undo_waste;
1888 
1889   OopsInHeapRegionClosure*      _evac_failure_cl;
1890   G1ParScanHeapEvacClosure*     _evac_cl;
1891   G1ParScanPartialArrayClosure* _partial_scan_cl;
1892 
1893   int  _hash_seed;
1894   uint _queue_num;
1895 
1896   size_t _term_attempts;
1897 
1898   double _start;
1899   double _start_strong_roots;
1900   double _strong_roots_time;
1901   double _start_term;
1902   double _term_time;
1903 
1904   // Map from young-age-index (0 == not young, 1 is youngest) to
1905   // surviving words. base is what we get back from the malloc call
1906   size_t* _surviving_young_words_base;
1907   // this points into the array, as we use the first few entries for padding
1908   size_t* _surviving_young_words;
1909 
1910 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1911 
1912   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1913 
1914   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1915 
1916   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1917   CardTableModRefBS* ctbs()                      { return _ct_bs; }
1918 
1919   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1920     if (!from->is_survivor()) {
1921       _g1_rem->par_write_ref(from, p, tid);
1922     }
1923   }
1924 
1925   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1926     // If the new value of the field points to the same region or
1927     // is the to-space, we don't need to include it in the Rset updates.
1928     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1929       size_t card_index = ctbs()->index_for(p);
1930       // If the card hasn't been added to the buffer, do it.
1931       if (ctbs()->mark_card_deferred(card_index)) {
1932         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1933       }
1934     }
1935   }
1936 
1937 public:
1938   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num);
1939 
1940   ~G1ParScanThreadState() {
1941     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1942   }
1943 
1944   RefToScanQueue*   refs()            { return _refs;             }
1945   ageTable*         age_table()       { return &_age_table;       }
1946 
1947   G1ParGCAllocBufferContainer* alloc_buffer(GCAllocPurpose purpose) {
1948     return _alloc_buffers[purpose];
1949   }
1950 
1951   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1952   size_t undo_waste() const                      { return _undo_waste; }
1953 
1954 #ifdef ASSERT
1955   bool verify_ref(narrowOop* ref) const;
1956   bool verify_ref(oop* ref) const;
1957   bool verify_task(StarTask ref) const;
1958 #endif // ASSERT
1959 
1960   template <class T> void push_on_queue(T* ref) {
1961     assert(verify_ref(ref), "sanity");
1962     refs()->push(ref);
1963   }
1964 
1965   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1966     if (G1DeferredRSUpdate) {
1967       deferred_rs_update(from, p, tid);
1968     } else {
1969       immediate_rs_update(from, p, tid);
1970     }
1971   }
1972 
1973   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1974     HeapWord* obj = NULL;
1975     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1976     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1977       G1ParGCAllocBufferContainer* alloc_buf = alloc_buffer(purpose);
1978 
1979       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1980       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1981 
1982       add_to_alloc_buffer_waste(alloc_buf->words_remaining_in_retired_buffer());
1983       alloc_buf->update(false /* end_of_gc */, false /* retain */, buf, gclab_word_size);
1984 
1985       obj = alloc_buf->allocate(word_sz);
1986       assert(obj != NULL, "buffer was definitely big enough...");
1987     } else {
1988       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1989     }
1990     return obj;
1991   }
1992 
1993   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1994     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1995     if (obj != NULL) return obj;
1996     return allocate_slow(purpose, word_sz);
1997   }
1998 
1999   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
2000     if (alloc_buffer(purpose)->contains(obj)) {
2001       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
2002              "should contain whole object");
2003       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
2004     } else {
2005       CollectedHeap::fill_with_object(obj, word_sz);
2006       add_to_undo_waste(word_sz);
2007     }
2008   }
2009 
2010   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
2011     _evac_failure_cl = evac_failure_cl;
2012   }
2013   OopsInHeapRegionClosure* evac_failure_closure() {
2014     return _evac_failure_cl;
2015   }
2016 
2017   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
2018     _evac_cl = evac_cl;
2019   }
2020 
2021   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
2022     _partial_scan_cl = partial_scan_cl;
2023   }
2024 
2025   int* hash_seed() { return &_hash_seed; }
2026   uint queue_num() { return _queue_num; }
2027 
2028   size_t term_attempts() const  { return _term_attempts; }
2029   void note_term_attempt() { _term_attempts++; }
2030 
2031   void start_strong_roots() {
2032     _start_strong_roots = os::elapsedTime();
2033   }
2034   void end_strong_roots() {
2035     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
2036   }
2037   double strong_roots_time() const { return _strong_roots_time; }
2038 
2039   void start_term_time() {
2040     note_term_attempt();
2041     _start_term = os::elapsedTime();
2042   }
2043   void end_term_time() {
2044     _term_time += (os::elapsedTime() - _start_term);
2045   }
2046   double term_time() const { return _term_time; }
2047 
2048   double elapsed_time() const {
2049     return os::elapsedTime() - _start;
2050   }
2051 
2052   static void
2053     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
2054   void
2055     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
2056 
2057   size_t* surviving_young_words() {
2058     // We add on to hide entry 0 which accumulates surviving words for
2059     // age -1 regions (i.e. non-young ones)
2060     return _surviving_young_words;
2061   }
2062 
2063   void retire_alloc_buffers() {
2064     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
2065       size_t waste = _alloc_buffers[ap]->words_remaining();
2066       add_to_alloc_buffer_waste(waste);
2067       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
2068                                                  true /* end_of_gc */,
2069                                                  false /* retain */);
2070     }
2071   }
2072 
2073   template <class T> void deal_with_reference(T* ref_to_scan) {
2074     if (has_partial_array_mask(ref_to_scan)) {
2075       _partial_scan_cl->do_oop_nv(ref_to_scan);
2076     } else {
2077       // Note: we can use "raw" versions of "region_containing" because
2078       // "obj_to_scan" is definitely in the heap, and is not in a
2079       // humongous region.
2080       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
2081       _evac_cl->set_region(r);
2082       _evac_cl->do_oop_nv(ref_to_scan);
2083     }
2084   }
2085 
2086   void deal_with_reference(StarTask ref) {
2087     assert(verify_task(ref), "sanity");
2088     if (ref.is_narrow()) {
2089       deal_with_reference((narrowOop*)ref);
2090     } else {
2091       deal_with_reference((oop*)ref);
2092     }
2093   }
2094 
2095   void trim_queue();
2096 };
2097 
2098 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP