rev 6670 : fast reclaim main patch

   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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  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/g1SATBCardTableModRefBS.hpp"
  35 #include "gc_implementation/g1/g1YCTypes.hpp"
  36 #include "gc_implementation/g1/heapRegionSeq.hpp"
  37 #include "gc_implementation/g1/heapRegionSet.hpp"
  38 #include "gc_implementation/shared/hSpaceCounters.hpp"
  39 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  40 #include "memory/barrierSet.hpp"
  41 #include "memory/memRegion.hpp"
  42 #include "memory/sharedHeap.hpp"
  43 #include "utilities/stack.hpp"
  44 
  45 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  46 // It uses the "Garbage First" heap organization and algorithm, which
  47 // may combine concurrent marking with parallel, incremental compaction of
  48 // heap subsets that will yield large amounts of garbage.
  49 
  50 // Forward declarations
  51 class HeapRegion;
  52 class HRRSCleanupTask;
  53 class GenerationSpec;
  54 class OopsInHeapRegionClosure;
  55 class G1KlassScanClosure;
  56 class G1ScanHeapEvacClosure;
  57 class ObjectClosure;
  58 class SpaceClosure;
  59 class CompactibleSpaceClosure;
  60 class Space;
  61 class G1CollectorPolicy;
  62 class GenRemSet;
  63 class G1RemSet;
  64 class HeapRegionRemSetIterator;
  65 class ConcurrentMark;
  66 class ConcurrentMarkThread;
  67 class ConcurrentG1Refine;
  68 class ConcurrentGCTimer;
  69 class GenerationCounters;
  70 class STWGCTimer;
  71 class G1NewTracer;
  72 class G1OldTracer;
  73 class EvacuationFailedInfo;
  74 class nmethod;
  75 class Ticks;
  76 
  77 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  78 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  79 
  80 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  81 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  82 
  83 enum GCAllocPurpose {
  84   GCAllocForTenured,
  85   GCAllocForSurvived,
  86   GCAllocPurposeCount
  87 };
  88 
  89 class YoungList : public CHeapObj<mtGC> {
  90 private:
  91   G1CollectedHeap* _g1h;
  92 
  93   HeapRegion* _head;
  94 
  95   HeapRegion* _survivor_head;
  96   HeapRegion* _survivor_tail;
  97 
  98   HeapRegion* _curr;
  99 
 100   uint        _length;
 101   uint        _survivor_length;
 102 
 103   size_t      _last_sampled_rs_lengths;
 104   size_t      _sampled_rs_lengths;
 105 
 106   void         empty_list(HeapRegion* list);
 107 
 108 public:
 109   YoungList(G1CollectedHeap* g1h);
 110 
 111   void         push_region(HeapRegion* hr);
 112   void         add_survivor_region(HeapRegion* hr);
 113 
 114   void         empty_list();
 115   bool         is_empty() { return _length == 0; }
 116   uint         length() { return _length; }
 117   uint         survivor_length() { return _survivor_length; }
 118 
 119   // Currently we do not keep track of the used byte sum for the
 120   // young list and the survivors and it'd be quite a lot of work to
 121   // do so. When we'll eventually replace the young list with
 122   // instances of HeapRegionLinkedList we'll get that for free. So,
 123   // we'll report the more accurate information then.
 124   size_t       eden_used_bytes() {
 125     assert(length() >= survivor_length(), "invariant");
 126     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 127   }
 128   size_t       survivor_used_bytes() {
 129     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 130   }
 131 
 132   void rs_length_sampling_init();
 133   bool rs_length_sampling_more();
 134   void rs_length_sampling_next();
 135 
 136   void reset_sampled_info() {
 137     _last_sampled_rs_lengths =   0;
 138   }
 139   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 140 
 141   // for development purposes
 142   void reset_auxilary_lists();
 143   void clear() { _head = NULL; _length = 0; }
 144 
 145   void clear_survivors() {
 146     _survivor_head    = NULL;
 147     _survivor_tail    = NULL;
 148     _survivor_length  = 0;
 149   }
 150 
 151   HeapRegion* first_region() { return _head; }
 152   HeapRegion* first_survivor_region() { return _survivor_head; }
 153   HeapRegion* last_survivor_region() { return _survivor_tail; }
 154 
 155   // debugging
 156   bool          check_list_well_formed();
 157   bool          check_list_empty(bool check_sample = true);
 158   void          print();
 159 };
 160 
 161 class MutatorAllocRegion : public G1AllocRegion {
 162 protected:
 163   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 164   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 165 public:
 166   MutatorAllocRegion()
 167     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 168 };
 169 
 170 class SurvivorGCAllocRegion : public G1AllocRegion {
 171 protected:
 172   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 173   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 174 public:
 175   SurvivorGCAllocRegion()
 176   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 177 };
 178 
 179 class OldGCAllocRegion : public G1AllocRegion {
 180 protected:
 181   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 182   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 183 public:
 184   OldGCAllocRegion()
 185   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 186 };
 187 
 188 // The G1 STW is alive closure.
 189 // An instance is embedded into the G1CH and used as the
 190 // (optional) _is_alive_non_header closure in the STW
 191 // reference processor. It is also extensively used during
 192 // reference processing during STW evacuation pauses.
 193 class G1STWIsAliveClosure: public BoolObjectClosure {
 194   G1CollectedHeap* _g1;
 195 public:
 196   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 197   bool do_object_b(oop p);
 198 };
 199 
 200 // Instances of this class are used for quick tests on whether a reference points
 201 // into the collection set. Each of the array's elements denotes whether the
 202 // corresponding region is in the collection set.
 203 class G1FastCSetBiasedMappedArray : public G1BiasedMappedArray<bool> {















 204  protected:
 205   bool default_value() const { return false; }
 206  public:
 207   void clear() { G1BiasedMappedArray<bool>::clear(); }









 208 };
 209 
 210 class RefineCardTableEntryClosure;
 211 
 212 class G1CollectedHeap : public SharedHeap {
 213   friend class VM_CollectForMetadataAllocation;
 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, G1Mark 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   // Setup the retained old gc alloc region as the currrent old gc alloc region.
 351   void use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info);
 352 
 353   // It releases the GC alloc regions at the end of a GC.
 354   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 355 
 356   // It does any cleanup that needs to be done on the GC alloc regions
 357   // before a Full GC.
 358   void abandon_gc_alloc_regions();
 359 
 360   // Helper for monitoring and management support.
 361   G1MonitoringSupport* _g1mm;
 362 
 363   // Determines PLAB size for a particular allocation purpose.
 364   size_t desired_plab_sz(GCAllocPurpose purpose);
 365 
 366   // Outside of GC pauses, the number of bytes used in all regions other
 367   // than the current allocation region.
 368   size_t _summary_bytes_used;
 369 
 370   // This array is used for a quick test on whether a reference points into
 371   // the collection set or not. Each of the array's elements denotes whether the
 372   // corresponding region is in the collection set or not.
 373   G1FastCSetBiasedMappedArray _in_cset_fast_test;
 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(bool is_old);
 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. If the region is to be used as an old region or for a
 504   // humongous object, set is_old to true. If not, to false.
 505   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 506 
 507   // Attempt to satisfy a humongous allocation request of the given
 508   // size by finding a contiguous set of free regions of num_regions
 509   // length and remove them from the master free list. Return the
 510   // index of the first region or G1_NULL_HRS_INDEX if the search
 511   // was unsuccessful.
 512   uint humongous_obj_allocate_find_first(uint num_regions,
 513                                          size_t word_size);
 514 
 515   // Initialize a contiguous set of free regions of length num_regions
 516   // and starting at index first so that they appear as a single
 517   // humongous region.
 518   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 519                                                       uint num_regions,
 520                                                       size_t word_size);
 521 
 522   // Attempt to allocate a humongous object of the given size. Return
 523   // NULL if unsuccessful.
 524   HeapWord* humongous_obj_allocate(size_t word_size);
 525 
 526   // The following two methods, allocate_new_tlab() and
 527   // mem_allocate(), are the two main entry points from the runtime
 528   // into the G1's allocation routines. They have the following
 529   // assumptions:
 530   //
 531   // * They should both be called outside safepoints.
 532   //
 533   // * They should both be called without holding the Heap_lock.
 534   //
 535   // * All allocation requests for new TLABs should go to
 536   //   allocate_new_tlab().
 537   //
 538   // * All non-TLAB allocation requests should go to mem_allocate().
 539   //
 540   // * If either call cannot satisfy the allocation request using the
 541   //   current allocating region, they will try to get a new one. If
 542   //   this fails, they will attempt to do an evacuation pause and
 543   //   retry the allocation.
 544   //
 545   // * If all allocation attempts fail, even after trying to schedule
 546   //   an evacuation pause, allocate_new_tlab() will return NULL,
 547   //   whereas mem_allocate() will attempt a heap expansion and/or
 548   //   schedule a Full GC.
 549   //
 550   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 551   //   should never be called with word_size being humongous. All
 552   //   humongous allocation requests should go to mem_allocate() which
 553   //   will satisfy them with a special path.
 554 
 555   virtual HeapWord* allocate_new_tlab(size_t word_size);
 556 
 557   virtual HeapWord* mem_allocate(size_t word_size,
 558                                  bool*  gc_overhead_limit_was_exceeded);
 559 
 560   // The following three methods take a gc_count_before_ret
 561   // parameter which is used to return the GC count if the method
 562   // returns NULL. Given that we are required to read the GC count
 563   // while holding the Heap_lock, and these paths will take the
 564   // Heap_lock at some point, it's easier to get them to read the GC
 565   // count while holding the Heap_lock before they return NULL instead
 566   // of the caller (namely: mem_allocate()) having to also take the
 567   // Heap_lock just to read the GC count.
 568 
 569   // First-level mutator allocation attempt: try to allocate out of
 570   // the mutator alloc region without taking the Heap_lock. This
 571   // should only be used for non-humongous allocations.
 572   inline HeapWord* attempt_allocation(size_t word_size,
 573                                       unsigned int* gc_count_before_ret,
 574                                       int* gclocker_retry_count_ret);
 575 
 576   // Second-level mutator allocation attempt: take the Heap_lock and
 577   // retry the allocation attempt, potentially scheduling a GC
 578   // pause. This should only be used for non-humongous allocations.
 579   HeapWord* attempt_allocation_slow(size_t word_size,
 580                                     unsigned int* gc_count_before_ret,
 581                                     int* gclocker_retry_count_ret);
 582 
 583   // Takes the Heap_lock and attempts a humongous allocation. It can
 584   // potentially schedule a GC pause.
 585   HeapWord* attempt_allocation_humongous(size_t word_size,
 586                                          unsigned int* gc_count_before_ret,
 587                                          int* gclocker_retry_count_ret);
 588 
 589   // Allocation attempt that should be called during safepoints (e.g.,
 590   // at the end of a successful GC). expect_null_mutator_alloc_region
 591   // specifies whether the mutator alloc region is expected to be NULL
 592   // or not.
 593   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 594                                        bool expect_null_mutator_alloc_region);
 595 
 596   // It dirties the cards that cover the block so that so that the post
 597   // write barrier never queues anything when updating objects on this
 598   // block. It is assumed (and in fact we assert) that the block
 599   // belongs to a young region.
 600   inline void dirty_young_block(HeapWord* start, size_t word_size);
 601 
 602   // Allocate blocks during garbage collection. Will ensure an
 603   // allocation region, either by picking one or expanding the
 604   // heap, and then allocate a block of the given size. The block
 605   // may not be a humongous - it must fit into a single heap region.
 606   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 607 
 608   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 609                                     HeapRegion*    alloc_region,
 610                                     bool           par,
 611                                     size_t         word_size);
 612 
 613   // Ensure that no further allocations can happen in "r", bearing in mind
 614   // that parallel threads might be attempting allocations.
 615   void par_allocate_remaining_space(HeapRegion* r);
 616 
 617   // Allocation attempt during GC for a survivor object / PLAB.
 618   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 619 
 620   // Allocation attempt during GC for an old object / PLAB.
 621   inline HeapWord* old_attempt_allocation(size_t word_size);
 622 
 623   // These methods are the "callbacks" from the G1AllocRegion class.
 624 
 625   // For mutator alloc regions.
 626   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 627   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 628                                    size_t allocated_bytes);
 629 
 630   // For GC alloc regions.
 631   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 632                                   GCAllocPurpose ap);
 633   void retire_gc_alloc_region(HeapRegion* alloc_region,
 634                               size_t allocated_bytes, GCAllocPurpose ap);
 635 
 636   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 637   //   inspection request and should collect the entire heap
 638   // - if clear_all_soft_refs is true, all soft references should be
 639   //   cleared during the GC
 640   // - if explicit_gc is false, word_size describes the allocation that
 641   //   the GC should attempt (at least) to satisfy
 642   // - it returns false if it is unable to do the collection due to the
 643   //   GC locker being active, true otherwise
 644   bool do_collection(bool explicit_gc,
 645                      bool clear_all_soft_refs,
 646                      size_t word_size);
 647 
 648   // Callback from VM_G1CollectFull operation.
 649   // Perform a full collection.
 650   virtual void do_full_collection(bool clear_all_soft_refs);
 651 
 652   // Resize the heap if necessary after a full collection.  If this is
 653   // after a collect-for allocation, "word_size" is the allocation size,
 654   // and will be considered part of the used portion of the heap.
 655   void resize_if_necessary_after_full_collection(size_t word_size);
 656 
 657   // Callback from VM_G1CollectForAllocation operation.
 658   // This function does everything necessary/possible to satisfy a
 659   // failed allocation request (including collection, expansion, etc.)
 660   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 661 
 662   // Attempting to expand the heap sufficiently
 663   // to support an allocation of the given "word_size".  If
 664   // successful, perform the allocation and return the address of the
 665   // allocated block, or else "NULL".
 666   HeapWord* expand_and_allocate(size_t word_size);
 667 
 668   // Process any reference objects discovered during
 669   // an incremental evacuation pause.
 670   void process_discovered_references(uint no_of_gc_workers);
 671 
 672   // Enqueue any remaining discovered references
 673   // after processing.
 674   void enqueue_discovered_references(uint no_of_gc_workers);
 675 
 676 public:
 677 
 678   G1MonitoringSupport* g1mm() {
 679     assert(_g1mm != NULL, "should have been initialized");
 680     return _g1mm;
 681   }
 682 
 683   // Expand the garbage-first heap by at least the given size (in bytes!).
 684   // Returns true if the heap was expanded by the requested amount;
 685   // false otherwise.
 686   // (Rounds up to a HeapRegion boundary.)
 687   bool expand(size_t expand_bytes);
 688 
 689   // Do anything common to GC's.
 690   virtual void gc_prologue(bool full);
 691   virtual void gc_epilogue(bool full);
 692 














 693   // We register a region with the fast "in collection set" test. We
 694   // simply set to true the array slot corresponding to this region.
 695   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 696     _in_cset_fast_test.set_by_index(r->hrs_index(), true);
 697   }
 698 
 699   // This is a fast test on whether a reference points into the
 700   // collection set or not. Assume that the reference
 701   // points into the heap.
 702   inline bool in_cset_fast_test(oop obj);
 703 
 704   void clear_cset_fast_test() {
 705     _in_cset_fast_test.clear();
 706   }
 707 
 708   // This is called at the start of either a concurrent cycle or a Full
 709   // GC to update the number of old marking cycles started.
 710   void increment_old_marking_cycles_started();
 711 
 712   // This is called at the end of either a concurrent cycle or a Full
 713   // GC to update the number of old marking cycles completed. Those two
 714   // can happen in a nested fashion, i.e., we start a concurrent
 715   // cycle, a Full GC happens half-way through it which ends first,
 716   // and then the cycle notices that a Full GC happened and ends
 717   // too. The concurrent parameter is a boolean to help us do a bit
 718   // tighter consistency checking in the method. If concurrent is
 719   // false, the caller is the inner caller in the nesting (i.e., the
 720   // Full GC). If concurrent is true, the caller is the outer caller
 721   // in this nesting (i.e., the concurrent cycle). Further nesting is
 722   // not currently supported. The end of this call also notifies
 723   // the FullGCCount_lock in case a Java thread is waiting for a full
 724   // GC to happen (e.g., it called System.gc() with
 725   // +ExplicitGCInvokesConcurrent).
 726   void increment_old_marking_cycles_completed(bool concurrent);
 727 
 728   unsigned int old_marking_cycles_completed() {
 729     return _old_marking_cycles_completed;
 730   }
 731 
 732   void register_concurrent_cycle_start(const Ticks& start_time);
 733   void register_concurrent_cycle_end();
 734   void trace_heap_after_concurrent_cycle();
 735 
 736   G1YCType yc_type();
 737 
 738   G1HRPrinter* hr_printer() { return &_hr_printer; }
 739 
 740   // Frees a non-humongous region by initializing its contents and
 741   // adding it to the free list that's passed as a parameter (this is
 742   // usually a local list which will be appended to the master free
 743   // list later). The used bytes of freed regions are accumulated in
 744   // pre_used. If par is true, the region's RSet will not be freed
 745   // up. The assumption is that this will be done later.
 746   // The locked parameter indicates if the caller has already taken
 747   // care of proper synchronization. This may allow some optimizations.
 748   void free_region(HeapRegion* hr,
 749                    FreeRegionList* free_list,
 750                    bool par,
 751                    bool locked = false);
 752 
 753   // Frees a humongous region by collapsing it into individual regions
 754   // and calling free_region() for each of them. The freed regions
 755   // will be added to the free list that's passed as a parameter (this
 756   // is usually a local list which will be appended to the master free
 757   // list later). The used bytes of freed regions are accumulated in
 758   // pre_used. If par is true, the region's RSet will not be freed
 759   // up. The assumption is that this will be done later.
 760   void free_humongous_region(HeapRegion* hr,
 761                              FreeRegionList* free_list,
 762                              bool par);
 763 protected:
 764 
 765   // Shrink the garbage-first heap by at most the given size (in bytes!).
 766   // (Rounds down to a HeapRegion boundary.)
 767   virtual void shrink(size_t expand_bytes);
 768   void shrink_helper(size_t expand_bytes);
 769 
 770   #if TASKQUEUE_STATS
 771   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 772   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 773   void reset_taskqueue_stats();
 774   #endif // TASKQUEUE_STATS
 775 
 776   // Schedule the VM operation that will do an evacuation pause to
 777   // satisfy an allocation request of word_size. *succeeded will
 778   // return whether the VM operation was successful (it did do an
 779   // evacuation pause) or not (another thread beat us to it or the GC
 780   // locker was active). Given that we should not be holding the
 781   // Heap_lock when we enter this method, we will pass the
 782   // gc_count_before (i.e., total_collections()) as a parameter since
 783   // it has to be read while holding the Heap_lock. Currently, both
 784   // methods that call do_collection_pause() release the Heap_lock
 785   // before the call, so it's easy to read gc_count_before just before.
 786   HeapWord* do_collection_pause(size_t         word_size,
 787                                 unsigned int   gc_count_before,
 788                                 bool*          succeeded,
 789                                 GCCause::Cause gc_cause);
 790 
 791   // The guts of the incremental collection pause, executed by the vm
 792   // thread. It returns false if it is unable to do the collection due
 793   // to the GC locker being active, true otherwise
 794   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 795 
 796   // Actually do the work of evacuating the collection set.
 797   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 798 
 799   // The g1 remembered set of the heap.
 800   G1RemSet* _g1_rem_set;
 801 
 802   // A set of cards that cover the objects for which the Rsets should be updated
 803   // concurrently after the collection.
 804   DirtyCardQueueSet _dirty_card_queue_set;
 805 
 806   // The closure used to refine a single card.
 807   RefineCardTableEntryClosure* _refine_cte_cl;
 808 
 809   // A function to check the consistency of dirty card logs.
 810   void check_ct_logs_at_safepoint();
 811 
 812   // A DirtyCardQueueSet that is used to hold cards that contain
 813   // references into the current collection set. This is used to
 814   // update the remembered sets of the regions in the collection
 815   // set in the event of an evacuation failure.
 816   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 817 
 818   // After a collection pause, make the regions in the CS into free
 819   // regions.
 820   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 821 
 822   // Abandon the current collection set without recording policy
 823   // statistics or updating free lists.
 824   void abandon_collection_set(HeapRegion* cs_head);
 825 
 826   // Applies "scan_non_heap_roots" to roots outside the heap,
 827   // "scan_rs" to roots inside the heap (having done "set_region" to
 828   // indicate the region in which the root resides),
 829   // and does "scan_metadata" If "scan_rs" is
 830   // NULL, then this step is skipped.  The "worker_i"
 831   // param is for use with parallel roots processing, and should be
 832   // the "i" of the calling parallel worker thread's work(i) function.
 833   // In the sequential case this param will be ignored.
 834   void g1_process_roots(OopClosure* scan_non_heap_roots,
 835                         OopClosure* scan_non_heap_weak_roots,
 836                         OopsInHeapRegionClosure* scan_rs,
 837                         CLDClosure* scan_strong_clds,
 838                         CLDClosure* scan_weak_clds,
 839                         CodeBlobClosure* scan_strong_code,
 840                         uint worker_i);
 841 
 842   // Notifies all the necessary spaces that the committed space has
 843   // been updated (either expanded or shrunk). It should be called
 844   // after _g1_storage is updated.
 845   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 846 
 847   // The concurrent marker (and the thread it runs in.)
 848   ConcurrentMark* _cm;
 849   ConcurrentMarkThread* _cmThread;
 850   bool _mark_in_progress;
 851 
 852   // The concurrent refiner.
 853   ConcurrentG1Refine* _cg1r;
 854 
 855   // The parallel task queues
 856   RefToScanQueueSet *_task_queues;
 857 
 858   // True iff a evacuation has failed in the current collection.
 859   bool _evacuation_failed;
 860 
 861   EvacuationFailedInfo* _evacuation_failed_info_array;
 862 
 863   // Failed evacuations cause some logical from-space objects to have
 864   // forwarding pointers to themselves.  Reset them.
 865   void remove_self_forwarding_pointers();
 866 
 867   // Together, these store an object with a preserved mark, and its mark value.
 868   Stack<oop, mtGC>     _objs_with_preserved_marks;
 869   Stack<markOop, mtGC> _preserved_marks_of_objs;
 870 
 871   // Preserve the mark of "obj", if necessary, in preparation for its mark
 872   // word being overwritten with a self-forwarding-pointer.
 873   void preserve_mark_if_necessary(oop obj, markOop m);
 874 
 875   // The stack of evac-failure objects left to be scanned.
 876   GrowableArray<oop>*    _evac_failure_scan_stack;
 877   // The closure to apply to evac-failure objects.
 878 
 879   OopsInHeapRegionClosure* _evac_failure_closure;
 880   // Set the field above.
 881   void
 882   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 883     _evac_failure_closure = evac_failure_closure;
 884   }
 885 
 886   // Push "obj" on the scan stack.
 887   void push_on_evac_failure_scan_stack(oop obj);
 888   // Process scan stack entries until the stack is empty.
 889   void drain_evac_failure_scan_stack();
 890   // True iff an invocation of "drain_scan_stack" is in progress; to
 891   // prevent unnecessary recursion.
 892   bool _drain_in_progress;
 893 
 894   // Do any necessary initialization for evacuation-failure handling.
 895   // "cl" is the closure that will be used to process evac-failure
 896   // objects.
 897   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 898   // Do any necessary cleanup for evacuation-failure handling data
 899   // structures.
 900   void finalize_for_evac_failure();
 901 
 902   // An attempt to evacuate "obj" has failed; take necessary steps.
 903   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 904   void handle_evacuation_failure_common(oop obj, markOop m);
 905 
 906 #ifndef PRODUCT
 907   // Support for forcing evacuation failures. Analogous to
 908   // PromotionFailureALot for the other collectors.
 909 
 910   // Records whether G1EvacuationFailureALot should be in effect
 911   // for the current GC
 912   bool _evacuation_failure_alot_for_current_gc;
 913 
 914   // Used to record the GC number for interval checking when
 915   // determining whether G1EvaucationFailureALot is in effect
 916   // for the current GC.
 917   size_t _evacuation_failure_alot_gc_number;
 918 
 919   // Count of the number of evacuations between failures.
 920   volatile size_t _evacuation_failure_alot_count;
 921 
 922   // Set whether G1EvacuationFailureALot should be in effect
 923   // for the current GC (based upon the type of GC and which
 924   // command line flags are set);
 925   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 926                                                   bool during_initial_mark,
 927                                                   bool during_marking);
 928 
 929   inline void set_evacuation_failure_alot_for_current_gc();
 930 
 931   // Return true if it's time to cause an evacuation failure.
 932   inline bool evacuation_should_fail();
 933 
 934   // Reset the G1EvacuationFailureALot counters.  Should be called at
 935   // the end of an evacuation pause in which an evacuation failure occurred.
 936   inline void reset_evacuation_should_fail();
 937 #endif // !PRODUCT
 938 
 939   // ("Weak") Reference processing support.
 940   //
 941   // G1 has 2 instances of the reference processor class. One
 942   // (_ref_processor_cm) handles reference object discovery
 943   // and subsequent processing during concurrent marking cycles.
 944   //
 945   // The other (_ref_processor_stw) handles reference object
 946   // discovery and processing during full GCs and incremental
 947   // evacuation pauses.
 948   //
 949   // During an incremental pause, reference discovery will be
 950   // temporarily disabled for _ref_processor_cm and will be
 951   // enabled for _ref_processor_stw. At the end of the evacuation
 952   // pause references discovered by _ref_processor_stw will be
 953   // processed and discovery will be disabled. The previous
 954   // setting for reference object discovery for _ref_processor_cm
 955   // will be re-instated.
 956   //
 957   // At the start of marking:
 958   //  * Discovery by the CM ref processor is verified to be inactive
 959   //    and it's discovered lists are empty.
 960   //  * Discovery by the CM ref processor is then enabled.
 961   //
 962   // At the end of marking:
 963   //  * Any references on the CM ref processor's discovered
 964   //    lists are processed (possibly MT).
 965   //
 966   // At the start of full GC we:
 967   //  * Disable discovery by the CM ref processor and
 968   //    empty CM ref processor's discovered lists
 969   //    (without processing any entries).
 970   //  * Verify that the STW ref processor is inactive and it's
 971   //    discovered lists are empty.
 972   //  * Temporarily set STW ref processor discovery as single threaded.
 973   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 974   //    field.
 975   //  * Finally enable discovery by the STW ref processor.
 976   //
 977   // The STW ref processor is used to record any discovered
 978   // references during the full GC.
 979   //
 980   // At the end of a full GC we:
 981   //  * Enqueue any reference objects discovered by the STW ref processor
 982   //    that have non-live referents. This has the side-effect of
 983   //    making the STW ref processor inactive by disabling discovery.
 984   //  * Verify that the CM ref processor is still inactive
 985   //    and no references have been placed on it's discovered
 986   //    lists (also checked as a precondition during initial marking).
 987 
 988   // The (stw) reference processor...
 989   ReferenceProcessor* _ref_processor_stw;
 990 
 991   STWGCTimer* _gc_timer_stw;
 992   ConcurrentGCTimer* _gc_timer_cm;
 993 
 994   G1OldTracer* _gc_tracer_cm;
 995   G1NewTracer* _gc_tracer_stw;
 996 
 997   // During reference object discovery, the _is_alive_non_header
 998   // closure (if non-null) is applied to the referent object to
 999   // determine whether the referent is live. If so then the
1000   // reference object does not need to be 'discovered' and can
1001   // be treated as a regular oop. This has the benefit of reducing
1002   // the number of 'discovered' reference objects that need to
1003   // be processed.
1004   //
1005   // Instance of the is_alive closure for embedding into the
1006   // STW reference processor as the _is_alive_non_header field.
1007   // Supplying a value for the _is_alive_non_header field is
1008   // optional but doing so prevents unnecessary additions to
1009   // the discovered lists during reference discovery.
1010   G1STWIsAliveClosure _is_alive_closure_stw;
1011 
1012   // The (concurrent marking) reference processor...
1013   ReferenceProcessor* _ref_processor_cm;
1014 
1015   // Instance of the concurrent mark is_alive closure for embedding
1016   // into the Concurrent Marking reference processor as the
1017   // _is_alive_non_header field. Supplying a value for the
1018   // _is_alive_non_header field is optional but doing so prevents
1019   // unnecessary additions to the discovered lists during reference
1020   // discovery.
1021   G1CMIsAliveClosure _is_alive_closure_cm;
1022 
1023   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1024   HeapRegion** _worker_cset_start_region;
1025 
1026   // Time stamp to validate the regions recorded in the cache
1027   // used by G1CollectedHeap::start_cset_region_for_worker().
1028   // The heap region entry for a given worker is valid iff
1029   // the associated time stamp value matches the current value
1030   // of G1CollectedHeap::_gc_time_stamp.
1031   unsigned int* _worker_cset_start_region_time_stamp;
1032 
1033   enum G1H_process_roots_tasks {
1034     G1H_PS_filter_satb_buffers,
1035     G1H_PS_refProcessor_oops_do,
1036     // Leave this one last.
1037     G1H_PS_NumElements
1038   };
1039 
1040   SubTasksDone* _process_strong_tasks;
1041 
1042   volatile bool _free_regions_coming;
1043 
1044 public:
1045 
1046   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1047 
1048   void set_refine_cte_cl_concurrency(bool concurrent);
1049 
1050   RefToScanQueue *task_queue(int i) const;
1051 
1052   // A set of cards where updates happened during the GC
1053   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1054 
1055   // A DirtyCardQueueSet that is used to hold cards that contain
1056   // references into the current collection set. This is used to
1057   // update the remembered sets of the regions in the collection
1058   // set in the event of an evacuation failure.
1059   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1060         { return _into_cset_dirty_card_queue_set; }
1061 
1062   // Create a G1CollectedHeap with the specified policy.
1063   // Must call the initialize method afterwards.
1064   // May not return if something goes wrong.
1065   G1CollectedHeap(G1CollectorPolicy* policy);
1066 
1067   // Initialize the G1CollectedHeap to have the initial and
1068   // maximum sizes and remembered and barrier sets
1069   // specified by the policy object.
1070   jint initialize();
1071 
1072   virtual void stop();
1073 
1074   // Return the (conservative) maximum heap alignment for any G1 heap
1075   static size_t conservative_max_heap_alignment();
1076 
1077   // Initialize weak reference processing.
1078   virtual void ref_processing_init();
1079 
1080   void set_par_threads(uint t) {
1081     SharedHeap::set_par_threads(t);
1082     // Done in SharedHeap but oddly there are
1083     // two _process_strong_tasks's in a G1CollectedHeap
1084     // so do it here too.
1085     _process_strong_tasks->set_n_threads(t);
1086   }
1087 
1088   // Set _n_par_threads according to a policy TBD.
1089   void set_par_threads();
1090 
1091   void set_n_termination(int t) {
1092     _process_strong_tasks->set_n_threads(t);
1093   }
1094 
1095   virtual CollectedHeap::Name kind() const {
1096     return CollectedHeap::G1CollectedHeap;
1097   }
1098 
1099   // The current policy object for the collector.
1100   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1101 
1102   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1103 
1104   // Adaptive size policy.  No such thing for g1.
1105   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1106 
1107   // The rem set and barrier set.
1108   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1109 
1110   unsigned get_gc_time_stamp() {
1111     return _gc_time_stamp;
1112   }
1113 
1114   inline void reset_gc_time_stamp();
1115 
1116   void check_gc_time_stamps() PRODUCT_RETURN;
1117 
1118   inline void increment_gc_time_stamp();
1119 
1120   // Reset the given region's GC timestamp. If it's starts humongous,
1121   // also reset the GC timestamp of its corresponding
1122   // continues humongous regions too.
1123   void reset_gc_time_stamps(HeapRegion* hr);
1124 
1125   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1126                                   DirtyCardQueue* into_cset_dcq,
1127                                   bool concurrent, uint worker_i);
1128 
1129   // The shared block offset table array.
1130   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1131 
1132   // Reference Processing accessors
1133 
1134   // The STW reference processor....
1135   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1136 
1137   // The Concurrent Marking reference processor...
1138   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1139 
1140   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1141   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1142 
1143   virtual size_t capacity() const;
1144   virtual size_t used() const;
1145   // This should be called when we're not holding the heap lock. The
1146   // result might be a bit inaccurate.
1147   size_t used_unlocked() const;
1148   size_t recalculate_used() const;
1149 
1150   // These virtual functions do the actual allocation.
1151   // Some heaps may offer a contiguous region for shared non-blocking
1152   // allocation, via inlined code (by exporting the address of the top and
1153   // end fields defining the extent of the contiguous allocation region.)
1154   // But G1CollectedHeap doesn't yet support this.
1155 
1156   virtual bool is_maximal_no_gc() const {
1157     return _g1_storage.uncommitted_size() == 0;
1158   }
1159 
1160   // The total number of regions in the heap.
1161   uint n_regions() { return _hrs.length(); }
1162 
1163   // The max number of regions in the heap.
1164   uint max_regions() { return _hrs.max_length(); }
1165 
1166   // The number of regions that are completely free.
1167   uint free_regions() { return _free_list.length(); }
1168 
1169   // The number of regions that are not completely free.
1170   uint used_regions() { return n_regions() - free_regions(); }
1171 
1172   // The number of regions available for "regular" expansion.
1173   uint expansion_regions() { return _expansion_regions; }
1174 
1175   // Factory method for HeapRegion instances. It will return NULL if
1176   // the allocation fails.
1177   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1178 
1179   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1180   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1181   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1182   void verify_dirty_young_regions() PRODUCT_RETURN;
1183 
1184 #ifndef PRODUCT
1185   // Make sure that the given bitmap has no marked objects in the
1186   // range [from,limit). If it does, print an error message and return
1187   // false. Otherwise, just return true. bitmap_name should be "prev"
1188   // or "next".
1189   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1190                                 HeapWord* from, HeapWord* limit);
1191 
1192   // Verify that the prev / next bitmap range [tams,end) for the given
1193   // region has no marks. Return true if all is well, false if errors
1194   // are detected.
1195   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1196 #endif // PRODUCT
1197 
1198   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1199   // the given region do not have any spurious marks. If errors are
1200   // detected, print appropriate error messages and crash.
1201   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1202 
1203   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1204   // have any spurious marks. If errors are detected, print
1205   // appropriate error messages and crash.
1206   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1207 
1208   // verify_region_sets() performs verification over the region
1209   // lists. It will be compiled in the product code to be used when
1210   // necessary (i.e., during heap verification).
1211   void verify_region_sets();
1212 
1213   // verify_region_sets_optional() is planted in the code for
1214   // list verification in non-product builds (and it can be enabled in
1215   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1216 #if HEAP_REGION_SET_FORCE_VERIFY
1217   void verify_region_sets_optional() {
1218     verify_region_sets();
1219   }
1220 #else // HEAP_REGION_SET_FORCE_VERIFY
1221   void verify_region_sets_optional() { }
1222 #endif // HEAP_REGION_SET_FORCE_VERIFY
1223 
1224 #ifdef ASSERT
1225   bool is_on_master_free_list(HeapRegion* hr) {
1226     return hr->containing_set() == &_free_list;
1227   }
1228 #endif // ASSERT
1229 
1230   // Wrapper for the region list operations that can be called from
1231   // methods outside this class.
1232 
1233   void secondary_free_list_add(FreeRegionList* list) {
1234     _secondary_free_list.add_ordered(list);
1235   }
1236 
1237   void append_secondary_free_list() {
1238     _free_list.add_ordered(&_secondary_free_list);
1239   }
1240 
1241   void append_secondary_free_list_if_not_empty_with_lock() {
1242     // If the secondary free list looks empty there's no reason to
1243     // take the lock and then try to append it.
1244     if (!_secondary_free_list.is_empty()) {
1245       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1246       append_secondary_free_list();
1247     }
1248   }
1249 
1250   inline void old_set_remove(HeapRegion* hr);
1251 
1252   size_t non_young_capacity_bytes() {
1253     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1254   }
1255 
1256   void set_free_regions_coming();
1257   void reset_free_regions_coming();
1258   bool free_regions_coming() { return _free_regions_coming; }
1259   void wait_while_free_regions_coming();
1260 
1261   // Determine whether the given region is one that we are using as an
1262   // old GC alloc region.
1263   bool is_old_gc_alloc_region(HeapRegion* hr) {
1264     return hr == _retained_old_gc_alloc_region;
1265   }
1266 
1267   // Perform a collection of the heap; intended for use in implementing
1268   // "System.gc".  This probably implies as full a collection as the
1269   // "CollectedHeap" supports.
1270   virtual void collect(GCCause::Cause cause);
1271 
1272   // The same as above but assume that the caller holds the Heap_lock.
1273   void collect_locked(GCCause::Cause cause);
1274 
1275   // True iff an evacuation has failed in the most-recent collection.
1276   bool evacuation_failed() { return _evacuation_failed; }
1277 
1278   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1279   void prepend_to_freelist(FreeRegionList* list);
1280   void decrement_summary_bytes(size_t bytes);
1281 
1282   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1283   virtual bool is_in(const void* p) const;
1284 
1285   // Return "TRUE" iff the given object address is within the collection
1286   // set.
1287   inline bool obj_in_cs(oop obj);
1288 






1289   // Return "TRUE" iff the given object address is in the reserved
1290   // region of g1.
1291   bool is_in_g1_reserved(const void* p) const {
1292     return _g1_reserved.contains(p);
1293   }
1294 
1295   // Returns a MemRegion that corresponds to the space that has been
1296   // reserved for the heap
1297   MemRegion g1_reserved() {
1298     return _g1_reserved;
1299   }
1300 
1301   // Returns a MemRegion that corresponds to the space that has been
1302   // committed in the heap
1303   MemRegion g1_committed() {
1304     return _g1_committed;
1305   }
1306 
1307   virtual bool is_in_closed_subset(const void* p) const;
1308 
1309   G1SATBCardTableModRefBS* g1_barrier_set() {
1310     return (G1SATBCardTableModRefBS*) barrier_set();
1311   }
1312 
1313   // This resets the card table to all zeros.  It is used after
1314   // a collection pause which used the card table to claim cards.
1315   void cleanUpCardTable();
1316 
1317   // Iteration functions.
1318 
1319   // Iterate over all the ref-containing fields of all objects, calling
1320   // "cl.do_oop" on each.
1321   virtual void oop_iterate(ExtendedOopClosure* cl);
1322 
1323   // Same as above, restricted to a memory region.
1324   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1325 
1326   // Iterate over all objects, calling "cl.do_object" on each.
1327   virtual void object_iterate(ObjectClosure* cl);
1328 
1329   virtual void safe_object_iterate(ObjectClosure* cl) {
1330     object_iterate(cl);
1331   }
1332 
1333   // Iterate over all spaces in use in the heap, in ascending address order.
1334   virtual void space_iterate(SpaceClosure* cl);
1335 
1336   // Iterate over heap regions, in address order, terminating the
1337   // iteration early if the "doHeapRegion" method returns "true".
1338   void heap_region_iterate(HeapRegionClosure* blk) const;
1339 
1340   // Return the region with the given index. It assumes the index is valid.
1341   inline HeapRegion* region_at(uint index) const;
1342 




1343   // Divide the heap region sequence into "chunks" of some size (the number
1344   // of regions divided by the number of parallel threads times some
1345   // overpartition factor, currently 4).  Assumes that this will be called
1346   // in parallel by ParallelGCThreads worker threads with distinct worker
1347   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1348   // calls will use the same "claim_value", and that that claim value is
1349   // different from the claim_value of any heap region before the start of
1350   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1351   // attempting to claim the first region in each chunk, and, if
1352   // successful, applying the closure to each region in the chunk (and
1353   // setting the claim value of the second and subsequent regions of the
1354   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1355   // i.e., that a closure never attempt to abort a traversal.
1356   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1357                                        uint worker,
1358                                        uint no_of_par_workers,
1359                                        jint claim_value);
1360 
1361   // It resets all the region claim values to the default.
1362   void reset_heap_region_claim_values();
1363 
1364   // Resets the claim values of regions in the current
1365   // collection set to the default.
1366   void reset_cset_heap_region_claim_values();
1367 
1368 #ifdef ASSERT
1369   bool check_heap_region_claim_values(jint claim_value);
1370 
1371   // Same as the routine above but only checks regions in the
1372   // current collection set.
1373   bool check_cset_heap_region_claim_values(jint claim_value);
1374 #endif // ASSERT
1375 
1376   // Clear the cached cset start regions and (more importantly)
1377   // the time stamps. Called when we reset the GC time stamp.
1378   void clear_cset_start_regions();
1379 
1380   // Given the id of a worker, obtain or calculate a suitable
1381   // starting region for iterating over the current collection set.
1382   HeapRegion* start_cset_region_for_worker(uint worker_i);
1383 
1384   // This is a convenience method that is used by the
1385   // HeapRegionIterator classes to calculate the starting region for
1386   // each worker so that they do not all start from the same region.
1387   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1388 
1389   // Iterate over the regions (if any) in the current collection set.
1390   void collection_set_iterate(HeapRegionClosure* blk);
1391 
1392   // As above but starting from region r
1393   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1394 
1395   // Returns the first (lowest address) compactible space in the heap.
1396   virtual CompactibleSpace* first_compactible_space();
1397 
1398   // A CollectedHeap will contain some number of spaces.  This finds the
1399   // space containing a given address, or else returns NULL.
1400   virtual Space* space_containing(const void* addr) const;
1401 
1402   // Returns the HeapRegion that contains addr. addr must not be NULL.
1403   template <class T>
1404   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1405 
1406   // Returns the HeapRegion that contains addr. addr must not be NULL.
1407   // If addr is within a humongous continues region, it returns its humongous start region.
1408   template <class T>
1409   inline HeapRegion* heap_region_containing(const T addr) const;
1410 
1411   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1412   // each address in the (reserved) heap is a member of exactly
1413   // one block.  The defining characteristic of a block is that it is
1414   // possible to find its size, and thus to progress forward to the next
1415   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1416   // represent Java objects, or they might be free blocks in a
1417   // free-list-based heap (or subheap), as long as the two kinds are
1418   // distinguishable and the size of each is determinable.
1419 
1420   // Returns the address of the start of the "block" that contains the
1421   // address "addr".  We say "blocks" instead of "object" since some heaps
1422   // may not pack objects densely; a chunk may either be an object or a
1423   // non-object.
1424   virtual HeapWord* block_start(const void* addr) const;
1425 
1426   // Requires "addr" to be the start of a chunk, and returns its size.
1427   // "addr + size" is required to be the start of a new chunk, or the end
1428   // of the active area of the heap.
1429   virtual size_t block_size(const HeapWord* addr) const;
1430 
1431   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1432   // the block is an object.
1433   virtual bool block_is_obj(const HeapWord* addr) const;
1434 
1435   // Does this heap support heap inspection? (+PrintClassHistogram)
1436   virtual bool supports_heap_inspection() const { return true; }
1437 
1438   // Section on thread-local allocation buffers (TLABs)
1439   // See CollectedHeap for semantics.
1440 
1441   bool supports_tlab_allocation() const;
1442   size_t tlab_capacity(Thread* ignored) const;
1443   size_t tlab_used(Thread* ignored) const;
1444   size_t max_tlab_size() const;
1445   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1446 
1447   // Can a compiler initialize a new object without store barriers?
1448   // This permission only extends from the creation of a new object
1449   // via a TLAB up to the first subsequent safepoint. If such permission
1450   // is granted for this heap type, the compiler promises to call
1451   // defer_store_barrier() below on any slow path allocation of
1452   // a new object for which such initializing store barriers will
1453   // have been elided. G1, like CMS, allows this, but should be
1454   // ready to provide a compensating write barrier as necessary
1455   // if that storage came out of a non-young region. The efficiency
1456   // of this implementation depends crucially on being able to
1457   // answer very efficiently in constant time whether a piece of
1458   // storage in the heap comes from a young region or not.
1459   // See ReduceInitialCardMarks.
1460   virtual bool can_elide_tlab_store_barriers() const {
1461     return true;
1462   }
1463 
1464   virtual bool card_mark_must_follow_store() const {
1465     return true;
1466   }
1467 
1468   inline bool is_in_young(const oop obj);
1469 
1470 #ifdef ASSERT
1471   virtual bool is_in_partial_collection(const void* p);
1472 #endif
1473 
1474   virtual bool is_scavengable(const void* addr);
1475 
1476   // We don't need barriers for initializing stores to objects
1477   // in the young gen: for the SATB pre-barrier, there is no
1478   // pre-value that needs to be remembered; for the remembered-set
1479   // update logging post-barrier, we don't maintain remembered set
1480   // information for young gen objects.
1481   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1482 
1483   // Returns "true" iff the given word_size is "very large".
1484   static bool isHumongous(size_t word_size) {
1485     // Note this has to be strictly greater-than as the TLABs
1486     // are capped at the humongous threshold and we want to
1487     // ensure that we don't try to allocate a TLAB as
1488     // humongous and that we don't allocate a humongous
1489     // object in a TLAB.
1490     return word_size > _humongous_object_threshold_in_words;
1491   }
1492 
1493   // Update mod union table with the set of dirty cards.
1494   void updateModUnion();
1495 
1496   // Set the mod union bits corresponding to the given memRegion.  Note
1497   // that this is always a safe operation, since it doesn't clear any
1498   // bits.
1499   void markModUnionRange(MemRegion mr);
1500 
1501   // Records the fact that a marking phase is no longer in progress.
1502   void set_marking_complete() {
1503     _mark_in_progress = false;
1504   }
1505   void set_marking_started() {
1506     _mark_in_progress = true;
1507   }
1508   bool mark_in_progress() {
1509     return _mark_in_progress;
1510   }
1511 
1512   // Print the maximum heap capacity.
1513   virtual size_t max_capacity() const;
1514 
1515   virtual jlong millis_since_last_gc();
1516 
1517 
1518   // Convenience function to be used in situations where the heap type can be
1519   // asserted to be this type.
1520   static G1CollectedHeap* heap();
1521 
1522   void set_region_short_lived_locked(HeapRegion* hr);
1523   // add appropriate methods for any other surv rate groups
1524 
1525   YoungList* young_list() const { return _young_list; }
1526 
1527   // debugging
1528   bool check_young_list_well_formed() {
1529     return _young_list->check_list_well_formed();
1530   }
1531 
1532   bool check_young_list_empty(bool check_heap,
1533                               bool check_sample = true);
1534 
1535   // *** Stuff related to concurrent marking.  It's not clear to me that so
1536   // many of these need to be public.
1537 
1538   // The functions below are helper functions that a subclass of
1539   // "CollectedHeap" can use in the implementation of its virtual
1540   // functions.
1541   // This performs a concurrent marking of the live objects in a
1542   // bitmap off to the side.
1543   void doConcurrentMark();
1544 
1545   bool isMarkedPrev(oop obj) const;
1546   bool isMarkedNext(oop obj) const;
1547 
1548   // Determine if an object is dead, given the object and also
1549   // the region to which the object belongs. An object is dead
1550   // iff a) it was not allocated since the last mark and b) it
1551   // is not marked.
1552   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1553     return
1554       !hr->obj_allocated_since_prev_marking(obj) &&
1555       !isMarkedPrev(obj);
1556   }
1557 
1558   // This function returns true when an object has been
1559   // around since the previous marking and hasn't yet
1560   // been marked during this marking.
1561   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1562     return
1563       !hr->obj_allocated_since_next_marking(obj) &&
1564       !isMarkedNext(obj);
1565   }
1566 
1567   // Determine if an object is dead, given only the object itself.
1568   // This will find the region to which the object belongs and
1569   // then call the region version of the same function.
1570 
1571   // Added if it is NULL it isn't dead.
1572 
1573   inline bool is_obj_dead(const oop obj) const;
1574 
1575   inline bool is_obj_ill(const oop obj) const;
1576 
1577   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1578   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1579   bool is_marked(oop obj, VerifyOption vo);
1580   const char* top_at_mark_start_str(VerifyOption vo);
1581 
1582   ConcurrentMark* concurrent_mark() const { return _cm; }
1583 
1584   // Refinement
1585 
1586   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1587 
1588   // The dirty cards region list is used to record a subset of regions
1589   // whose cards need clearing. The list if populated during the
1590   // remembered set scanning and drained during the card table
1591   // cleanup. Although the methods are reentrant, population/draining
1592   // phases must not overlap. For synchronization purposes the last
1593   // element on the list points to itself.
1594   HeapRegion* _dirty_cards_region_list;
1595   void push_dirty_cards_region(HeapRegion* hr);
1596   HeapRegion* pop_dirty_cards_region();
1597 
1598   // Optimized nmethod scanning support routines
1599 
1600   // Register the given nmethod with the G1 heap.
1601   virtual void register_nmethod(nmethod* nm);
1602 
1603   // Unregister the given nmethod from the G1 heap.
1604   virtual void unregister_nmethod(nmethod* nm);
1605 
1606   // Migrate the nmethods in the code root lists of the regions
1607   // in the collection set to regions in to-space. In the event
1608   // of an evacuation failure, nmethods that reference objects
1609   // that were not successfully evacuated are not migrated.
1610   void migrate_strong_code_roots();
1611 
1612   // Free up superfluous code root memory.
1613   void purge_code_root_memory();
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   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1624   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1625 
1626   // Redirty logged cards in the refinement queue.
1627   void redirty_logged_cards();
1628   // Verification
1629 
1630   // The following is just to alert the verification code
1631   // that a full collection has occurred and that the
1632   // remembered sets are no longer up to date.
1633   bool _full_collection;
1634   void set_full_collection() { _full_collection = true;}
1635   void clear_full_collection() {_full_collection = false;}
1636   bool full_collection() {return _full_collection;}
1637 
1638   // Perform any cleanup actions necessary before allowing a verification.
1639   virtual void prepare_for_verify();
1640 
1641   // Perform verification.
1642 
1643   // vo == UsePrevMarking  -> use "prev" marking information,
1644   // vo == UseNextMarking -> use "next" marking information
1645   // vo == UseMarkWord    -> use the mark word in the object header
1646   //
1647   // NOTE: Only the "prev" marking information is guaranteed to be
1648   // consistent most of the time, so most calls to this should use
1649   // vo == UsePrevMarking.
1650   // Currently, there is only one case where this is called with
1651   // vo == UseNextMarking, which is to verify the "next" marking
1652   // information at the end of remark.
1653   // Currently there is only one place where this is called with
1654   // vo == UseMarkWord, which is to verify the marking during a
1655   // full GC.
1656   void verify(bool silent, VerifyOption vo);
1657 
1658   // Override; it uses the "prev" marking information
1659   virtual void verify(bool silent);
1660 
1661   // The methods below are here for convenience and dispatch the
1662   // appropriate method depending on value of the given VerifyOption
1663   // parameter. The values for that parameter, and their meanings,
1664   // are the same as those above.
1665 
1666   bool is_obj_dead_cond(const oop obj,
1667                         const HeapRegion* hr,
1668                         const VerifyOption vo) const;
1669 
1670   bool is_obj_dead_cond(const oop obj,
1671                         const VerifyOption vo) const;
1672 
1673   // Printing
1674 
1675   virtual void print_on(outputStream* st) const;
1676   virtual void print_extended_on(outputStream* st) const;
1677   virtual void print_on_error(outputStream* st) const;
1678 
1679   virtual void print_gc_threads_on(outputStream* st) const;
1680   virtual void gc_threads_do(ThreadClosure* tc) const;
1681 
1682   // Override
1683   void print_tracing_info() const;
1684 
1685   // The following two methods are helpful for debugging RSet issues.
1686   void print_cset_rsets() PRODUCT_RETURN;
1687   void print_all_rsets() PRODUCT_RETURN;
1688 
1689 public:
1690   size_t pending_card_num();
1691   size_t cards_scanned();
1692 
1693 protected:
1694   size_t _max_heap_capacity;
1695 };
1696 
1697 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1698 private:
1699   bool        _retired;
1700 
1701 public:
1702   G1ParGCAllocBuffer(size_t gclab_word_size);
1703   virtual ~G1ParGCAllocBuffer() {
1704     guarantee(_retired, "Allocation buffer has not been retired");
1705   }
1706 
1707   virtual void set_buf(HeapWord* buf) {
1708     ParGCAllocBuffer::set_buf(buf);
1709     _retired = false;
1710   }
1711 
1712   virtual void retire(bool end_of_gc, bool retain) {
1713     if (_retired) {
1714       return;
1715     }
1716     ParGCAllocBuffer::retire(end_of_gc, retain);
1717     _retired = true;
1718   }
1719 };
1720 
1721 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---