1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/concurrentMark.hpp"
  29 #include "gc_implementation/g1/evacuationInfo.hpp"
  30 #include "gc_implementation/g1/g1AllocRegion.hpp"
  31 #include "gc_implementation/g1/g1BiasedArray.hpp"
  32 #include "gc_implementation/g1/g1HRPrinter.hpp"
  33 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  34 #include "gc_implementation/g1/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_G1CollectForAllocation;
 214   friend class VM_G1CollectFull;
 215   friend class VM_G1IncCollectionPause;
 216   friend class VMStructs;
 217   friend class MutatorAllocRegion;
 218   friend class SurvivorGCAllocRegion;
 219   friend class OldGCAllocRegion;
 220 
 221   // Closures used in implementation.
 222   template <G1Barrier barrier, bool do_mark_object>
 223   friend class G1ParCopyClosure;
 224   friend class G1IsAliveClosure;
 225   friend class G1EvacuateFollowersClosure;
 226   friend class G1ParScanThreadState;
 227   friend class G1ParScanClosureSuper;
 228   friend class G1ParEvacuateFollowersClosure;
 229   friend class G1ParTask;
 230   friend class G1FreeGarbageRegionClosure;
 231   friend class RefineCardTableEntryClosure;
 232   friend class G1PrepareCompactClosure;
 233   friend class RegionSorter;
 234   friend class RegionResetter;
 235   friend class CountRCClosure;
 236   friend class EvacPopObjClosure;
 237   friend class G1ParCleanupCTTask;
 238 
 239   // Other related classes.
 240   friend class G1MarkSweep;
 241 
 242 private:
 243   // The one and only G1CollectedHeap, so static functions can find it.
 244   static G1CollectedHeap* _g1h;
 245 
 246   static size_t _humongous_object_threshold_in_words;
 247 
 248   // Storage for the G1 heap.
 249   VirtualSpace _g1_storage;
 250   MemRegion    _g1_reserved;
 251 
 252   // The part of _g1_storage that is currently committed.
 253   MemRegion _g1_committed;
 254 
 255   // The master free list. It will satisfy all new region allocations.
 256   FreeRegionList _free_list;
 257 
 258   // The secondary free list which contains regions that have been
 259   // freed up during the cleanup process. This will be appended to the
 260   // master free list when appropriate.
 261   FreeRegionList _secondary_free_list;
 262 
 263   // It keeps track of the old regions.
 264   HeapRegionSet _old_set;
 265 
 266   // It keeps track of the humongous regions.
 267   HeapRegionSet _humongous_set;
 268 
 269   // The number of regions we could create by expansion.
 270   uint _expansion_regions;
 271 
 272   // The block offset table for the G1 heap.
 273   G1BlockOffsetSharedArray* _bot_shared;
 274 
 275   // Tears down the region sets / lists so that they are empty and the
 276   // regions on the heap do not belong to a region set / list. The
 277   // only exception is the humongous set which we leave unaltered. If
 278   // free_list_only is true, it will only tear down the master free
 279   // list. It is called before a Full GC (free_list_only == false) or
 280   // before heap shrinking (free_list_only == true).
 281   void tear_down_region_sets(bool free_list_only);
 282 
 283   // Rebuilds the region sets / lists so that they are repopulated to
 284   // reflect the contents of the heap. The only exception is the
 285   // humongous set which was not torn down in the first place. If
 286   // free_list_only is true, it will only rebuild the master free
 287   // list. It is called after a Full GC (free_list_only == false) or
 288   // after heap shrinking (free_list_only == true).
 289   void rebuild_region_sets(bool free_list_only);
 290 
 291   // The sequence of all heap regions in the heap.
 292   HeapRegionSeq _hrs;
 293 
 294   // Alloc region used to satisfy mutator allocation requests.
 295   MutatorAllocRegion _mutator_alloc_region;
 296 
 297   // Alloc region used to satisfy allocation requests by the GC for
 298   // survivor objects.
 299   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 300 
 301   // PLAB sizing policy for survivors.
 302   PLABStats _survivor_plab_stats;
 303 
 304   // Alloc region used to satisfy allocation requests by the GC for
 305   // old objects.
 306   OldGCAllocRegion _old_gc_alloc_region;
 307 
 308   // PLAB sizing policy for tenured objects.
 309   PLABStats _old_plab_stats;
 310 
 311   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 312     PLABStats* stats = NULL;
 313 
 314     switch (purpose) {
 315     case GCAllocForSurvived:
 316       stats = &_survivor_plab_stats;
 317       break;
 318     case GCAllocForTenured:
 319       stats = &_old_plab_stats;
 320       break;
 321     default:
 322       assert(false, "unrecognized GCAllocPurpose");
 323     }
 324 
 325     return stats;
 326   }
 327 
 328   // The last old region we allocated to during the last GC.
 329   // Typically, it is not full so we should re-use it during the next GC.
 330   HeapRegion* _retained_old_gc_alloc_region;
 331 
 332   // It specifies whether we should attempt to expand the heap after a
 333   // region allocation failure. If heap expansion fails we set this to
 334   // false so that we don't re-attempt the heap expansion (it's likely
 335   // that subsequent expansion attempts will also fail if one fails).
 336   // Currently, it is only consulted during GC and it's reset at the
 337   // start of each GC.
 338   bool _expand_heap_after_alloc_failure;
 339 
 340   // It resets the mutator alloc region before new allocations can take place.
 341   void init_mutator_alloc_region();
 342 
 343   // It releases the mutator alloc region.
 344   void release_mutator_alloc_region();
 345 
 346   // It initializes the GC alloc regions at the start of a GC.
 347   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 348 
 349   // It releases the GC alloc regions at the end of a GC.
 350   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 351 
 352   // It does any cleanup that needs to be done on the GC alloc regions
 353   // before a Full GC.
 354   void abandon_gc_alloc_regions();
 355 
 356   // Helper for monitoring and management support.
 357   G1MonitoringSupport* _g1mm;
 358 
 359   // Determines PLAB size for a particular allocation purpose.
 360   size_t desired_plab_sz(GCAllocPurpose purpose);
 361 
 362   // Outside of GC pauses, the number of bytes used in all regions other
 363   // than the current allocation region.
 364   size_t _summary_bytes_used;
 365 
 366   // This array is used for a quick test on whether a reference points into
 367   // the collection set or not. Each of the array's elements denotes whether the
 368   // corresponding region is in the collection set or not.
 369   G1FastCSetBiasedMappedArray _in_cset_fast_test;
 370 
 371   volatile unsigned _gc_time_stamp;
 372 
 373   size_t* _surviving_young_words;
 374 
 375   G1HRPrinter _hr_printer;
 376 
 377   void setup_surviving_young_words();
 378   void update_surviving_young_words(size_t* surv_young_words);
 379   void cleanup_surviving_young_words();
 380 
 381   // It decides whether an explicit GC should start a concurrent cycle
 382   // instead of doing a STW GC. Currently, a concurrent cycle is
 383   // explicitly started if:
 384   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 385   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 386   // (c) cause == _g1_humongous_allocation
 387   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 388 
 389   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 390   // concurrent cycles) we have started.
 391   volatile unsigned int _old_marking_cycles_started;
 392 
 393   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 394   // concurrent cycles) we have completed.
 395   volatile unsigned int _old_marking_cycles_completed;
 396 
 397   bool _concurrent_cycle_started;
 398 
 399   // This is a non-product method that is helpful for testing. It is
 400   // called at the end of a GC and artificially expands the heap by
 401   // allocating a number of dead regions. This way we can induce very
 402   // frequent marking cycles and stress the cleanup / concurrent
 403   // cleanup code more (as all the regions that will be allocated by
 404   // this method will be found dead by the marking cycle).
 405   void allocate_dummy_regions() PRODUCT_RETURN;
 406 
 407   // Clear RSets after a compaction. It also resets the GC time stamps.
 408   void clear_rsets_post_compaction();
 409 
 410   // If the HR printer is active, dump the state of the regions in the
 411   // heap after a compaction.
 412   void print_hrs_post_compaction();
 413 
 414   double verify(bool guard, const char* msg);
 415   void verify_before_gc();
 416   void verify_after_gc();
 417 
 418   void log_gc_header();
 419   void log_gc_footer(double pause_time_sec);
 420 
 421   // These are macros so that, if the assert fires, we get the correct
 422   // line number, file, etc.
 423 
 424 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 425   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 426           (_extra_message_),                                                  \
 427           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 428           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 429           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 430 
 431 #define assert_heap_locked()                                                  \
 432   do {                                                                        \
 433     assert(Heap_lock->owned_by_self(),                                        \
 434            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 435   } while (0)
 436 
 437 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 438   do {                                                                        \
 439     assert(Heap_lock->owned_by_self() ||                                      \
 440            (SafepointSynchronize::is_at_safepoint() &&                        \
 441              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 442            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 443                                         "should be at a safepoint"));         \
 444   } while (0)
 445 
 446 #define assert_heap_locked_and_not_at_safepoint()                             \
 447   do {                                                                        \
 448     assert(Heap_lock->owned_by_self() &&                                      \
 449                                     !SafepointSynchronize::is_at_safepoint(), \
 450           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 451                                        "should not be at a safepoint"));      \
 452   } while (0)
 453 
 454 #define assert_heap_not_locked()                                              \
 455   do {                                                                        \
 456     assert(!Heap_lock->owned_by_self(),                                       \
 457         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 458   } while (0)
 459 
 460 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 461   do {                                                                        \
 462     assert(!Heap_lock->owned_by_self() &&                                     \
 463                                     !SafepointSynchronize::is_at_safepoint(), \
 464       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 465                                    "should not be at a safepoint"));          \
 466   } while (0)
 467 
 468 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 469   do {                                                                        \
 470     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 471               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 472            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 473   } while (0)
 474 
 475 #define assert_not_at_safepoint()                                             \
 476   do {                                                                        \
 477     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 478            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 479   } while (0)
 480 
 481 protected:
 482 
 483   // The young region list.
 484   YoungList*  _young_list;
 485 
 486   // The current policy object for the collector.
 487   G1CollectorPolicy* _g1_policy;
 488 
 489   // This is the second level of trying to allocate a new region. If
 490   // new_region() didn't find a region on the free_list, this call will
 491   // check whether there's anything available on the
 492   // secondary_free_list and/or wait for more regions to appear on
 493   // that list, if _free_regions_coming is set.
 494   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 495 
 496   // Try to allocate a single non-humongous HeapRegion sufficient for
 497   // an allocation of the given word_size. If do_expand is true,
 498   // attempt to expand the heap if necessary to satisfy the allocation
 499   // request. If the region is to be used as an old region or for a
 500   // humongous object, set is_old to true. If not, to false.
 501   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 502 
 503   // Attempt to satisfy a humongous allocation request of the given
 504   // size by finding a contiguous set of free regions of num_regions
 505   // length and remove them from the master free list. Return the
 506   // index of the first region or G1_NULL_HRS_INDEX if the search
 507   // was unsuccessful.
 508   uint humongous_obj_allocate_find_first(uint num_regions,
 509                                          size_t word_size);
 510 
 511   // Initialize a contiguous set of free regions of length num_regions
 512   // and starting at index first so that they appear as a single
 513   // humongous region.
 514   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 515                                                       uint num_regions,
 516                                                       size_t word_size);
 517 
 518   // Attempt to allocate a humongous object of the given size. Return
 519   // NULL if unsuccessful.
 520   HeapWord* humongous_obj_allocate(size_t word_size);
 521 
 522   // The following two methods, allocate_new_tlab() and
 523   // mem_allocate(), are the two main entry points from the runtime
 524   // into the G1's allocation routines. They have the following
 525   // assumptions:
 526   //
 527   // * They should both be called outside safepoints.
 528   //
 529   // * They should both be called without holding the Heap_lock.
 530   //
 531   // * All allocation requests for new TLABs should go to
 532   //   allocate_new_tlab().
 533   //
 534   // * All non-TLAB allocation requests should go to mem_allocate().
 535   //
 536   // * If either call cannot satisfy the allocation request using the
 537   //   current allocating region, they will try to get a new one. If
 538   //   this fails, they will attempt to do an evacuation pause and
 539   //   retry the allocation.
 540   //
 541   // * If all allocation attempts fail, even after trying to schedule
 542   //   an evacuation pause, allocate_new_tlab() will return NULL,
 543   //   whereas mem_allocate() will attempt a heap expansion and/or
 544   //   schedule a Full GC.
 545   //
 546   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 547   //   should never be called with word_size being humongous. All
 548   //   humongous allocation requests should go to mem_allocate() which
 549   //   will satisfy them with a special path.
 550 
 551   virtual HeapWord* allocate_new_tlab(size_t word_size);
 552 
 553   virtual HeapWord* mem_allocate(size_t word_size,
 554                                  bool*  gc_overhead_limit_was_exceeded);
 555 
 556   // The following three methods take a gc_count_before_ret
 557   // parameter which is used to return the GC count if the method
 558   // returns NULL. Given that we are required to read the GC count
 559   // while holding the Heap_lock, and these paths will take the
 560   // Heap_lock at some point, it's easier to get them to read the GC
 561   // count while holding the Heap_lock before they return NULL instead
 562   // of the caller (namely: mem_allocate()) having to also take the
 563   // Heap_lock just to read the GC count.
 564 
 565   // First-level mutator allocation attempt: try to allocate out of
 566   // the mutator alloc region without taking the Heap_lock. This
 567   // should only be used for non-humongous allocations.
 568   inline HeapWord* attempt_allocation(size_t word_size,
 569                                       unsigned int* gc_count_before_ret,
 570                                       int* gclocker_retry_count_ret);
 571 
 572   // Second-level mutator allocation attempt: take the Heap_lock and
 573   // retry the allocation attempt, potentially scheduling a GC
 574   // pause. This should only be used for non-humongous allocations.
 575   HeapWord* attempt_allocation_slow(size_t word_size,
 576                                     unsigned int* gc_count_before_ret,
 577                                     int* gclocker_retry_count_ret);
 578 
 579   // Takes the Heap_lock and attempts a humongous allocation. It can
 580   // potentially schedule a GC pause.
 581   HeapWord* attempt_allocation_humongous(size_t word_size,
 582                                          unsigned int* gc_count_before_ret,
 583                                          int* gclocker_retry_count_ret);
 584 
 585   // Allocation attempt that should be called during safepoints (e.g.,
 586   // at the end of a successful GC). expect_null_mutator_alloc_region
 587   // specifies whether the mutator alloc region is expected to be NULL
 588   // or not.
 589   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 590                                        bool expect_null_mutator_alloc_region);
 591 
 592   // It dirties the cards that cover the block so that so that the post
 593   // write barrier never queues anything when updating objects on this
 594   // block. It is assumed (and in fact we assert) that the block
 595   // belongs to a young region.
 596   inline void dirty_young_block(HeapWord* start, size_t word_size);
 597 
 598   // Allocate blocks during garbage collection. Will ensure an
 599   // allocation region, either by picking one or expanding the
 600   // heap, and then allocate a block of the given size. The block
 601   // may not be a humongous - it must fit into a single heap region.
 602   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 603 
 604   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 605                                     HeapRegion*    alloc_region,
 606                                     bool           par,
 607                                     size_t         word_size);
 608 
 609   // Ensure that no further allocations can happen in "r", bearing in mind
 610   // that parallel threads might be attempting allocations.
 611   void par_allocate_remaining_space(HeapRegion* r);
 612 
 613   // Allocation attempt during GC for a survivor object / PLAB.
 614   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 615 
 616   // Allocation attempt during GC for an old object / PLAB.
 617   inline HeapWord* old_attempt_allocation(size_t word_size);
 618 
 619   // These methods are the "callbacks" from the G1AllocRegion class.
 620 
 621   // For mutator alloc regions.
 622   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 623   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 624                                    size_t allocated_bytes);
 625 
 626   // For GC alloc regions.
 627   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 628                                   GCAllocPurpose ap);
 629   void retire_gc_alloc_region(HeapRegion* alloc_region,
 630                               size_t allocated_bytes, GCAllocPurpose ap);
 631 
 632   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 633   //   inspection request and should collect the entire heap
 634   // - if clear_all_soft_refs is true, all soft references should be
 635   //   cleared during the GC
 636   // - if explicit_gc is false, word_size describes the allocation that
 637   //   the GC should attempt (at least) to satisfy
 638   // - it returns false if it is unable to do the collection due to the
 639   //   GC locker being active, true otherwise
 640   bool do_collection(bool explicit_gc,
 641                      bool clear_all_soft_refs,
 642                      size_t word_size);
 643 
 644   // Callback from VM_G1CollectFull operation.
 645   // Perform a full collection.
 646   virtual void do_full_collection(bool clear_all_soft_refs);
 647 
 648   // Resize the heap if necessary after a full collection.  If this is
 649   // after a collect-for allocation, "word_size" is the allocation size,
 650   // and will be considered part of the used portion of the heap.
 651   void resize_if_necessary_after_full_collection(size_t word_size);
 652 
 653   // Callback from VM_G1CollectForAllocation operation.
 654   // This function does everything necessary/possible to satisfy a
 655   // failed allocation request (including collection, expansion, etc.)
 656   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 657 
 658   // Attempting to expand the heap sufficiently
 659   // to support an allocation of the given "word_size".  If
 660   // successful, perform the allocation and return the address of the
 661   // allocated block, or else "NULL".
 662   HeapWord* expand_and_allocate(size_t word_size);
 663 
 664   // Process any reference objects discovered during
 665   // an incremental evacuation pause.
 666   void process_discovered_references(uint no_of_gc_workers);
 667 
 668   // Enqueue any remaining discovered references
 669   // after processing.
 670   void enqueue_discovered_references(uint no_of_gc_workers);
 671 
 672 public:
 673 
 674   G1MonitoringSupport* g1mm() {
 675     assert(_g1mm != NULL, "should have been initialized");
 676     return _g1mm;
 677   }
 678 
 679   // Expand the garbage-first heap by at least the given size (in bytes!).
 680   // Returns true if the heap was expanded by the requested amount;
 681   // false otherwise.
 682   // (Rounds up to a HeapRegion boundary.)
 683   bool expand(size_t expand_bytes);
 684 
 685   // Do anything common to GC's.
 686   virtual void gc_prologue(bool full);
 687   virtual void gc_epilogue(bool full);
 688 
 689   // We register a region with the fast "in collection set" test. We
 690   // simply set to true the array slot corresponding to this region.
 691   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 692     _in_cset_fast_test.set_by_index(r->hrs_index(), true);
 693   }
 694 
 695   // This is a fast test on whether a reference points into the
 696   // collection set or not. Assume that the reference
 697   // points into the heap.
 698   inline bool in_cset_fast_test(oop obj);
 699 
 700   void clear_cset_fast_test() {
 701     _in_cset_fast_test.clear();
 702   }
 703 
 704   // This is called at the start of either a concurrent cycle or a Full
 705   // GC to update the number of old marking cycles started.
 706   void increment_old_marking_cycles_started();
 707 
 708   // This is called at the end of either a concurrent cycle or a Full
 709   // GC to update the number of old marking cycles completed. Those two
 710   // can happen in a nested fashion, i.e., we start a concurrent
 711   // cycle, a Full GC happens half-way through it which ends first,
 712   // and then the cycle notices that a Full GC happened and ends
 713   // too. The concurrent parameter is a boolean to help us do a bit
 714   // tighter consistency checking in the method. If concurrent is
 715   // false, the caller is the inner caller in the nesting (i.e., the
 716   // Full GC). If concurrent is true, the caller is the outer caller
 717   // in this nesting (i.e., the concurrent cycle). Further nesting is
 718   // not currently supported. The end of this call also notifies
 719   // the FullGCCount_lock in case a Java thread is waiting for a full
 720   // GC to happen (e.g., it called System.gc() with
 721   // +ExplicitGCInvokesConcurrent).
 722   void increment_old_marking_cycles_completed(bool concurrent);
 723 
 724   unsigned int old_marking_cycles_completed() {
 725     return _old_marking_cycles_completed;
 726   }
 727 
 728   void register_concurrent_cycle_start(const Ticks& start_time);
 729   void register_concurrent_cycle_end();
 730   void trace_heap_after_concurrent_cycle();
 731 
 732   G1YCType yc_type();
 733 
 734   G1HRPrinter* hr_printer() { return &_hr_printer; }
 735 
 736   // Frees a non-humongous region by initializing its contents and
 737   // adding it to the free list that's passed as a parameter (this is
 738   // usually a local list which will be appended to the master free
 739   // list later). The used bytes of freed regions are accumulated in
 740   // pre_used. If par is true, the region's RSet will not be freed
 741   // up. The assumption is that this will be done later.
 742   // The locked parameter indicates if the caller has already taken
 743   // care of proper synchronization. This may allow some optimizations.
 744   void free_region(HeapRegion* hr,
 745                    FreeRegionList* free_list,
 746                    bool par,
 747                    bool locked = false);
 748 
 749   // Frees a humongous region by collapsing it into individual regions
 750   // and calling free_region() for each of them. The freed regions
 751   // will be added to the free list that's passed as a parameter (this
 752   // is usually a local list which will be appended to the master free
 753   // list later). The used bytes of freed regions are accumulated in
 754   // pre_used. If par is true, the region's RSet will not be freed
 755   // up. The assumption is that this will be done later.
 756   void free_humongous_region(HeapRegion* hr,
 757                              FreeRegionList* free_list,
 758                              bool par);
 759 protected:
 760 
 761   // Shrink the garbage-first heap by at most the given size (in bytes!).
 762   // (Rounds down to a HeapRegion boundary.)
 763   virtual void shrink(size_t expand_bytes);
 764   void shrink_helper(size_t expand_bytes);
 765 
 766   #if TASKQUEUE_STATS
 767   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 768   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 769   void reset_taskqueue_stats();
 770   #endif // TASKQUEUE_STATS
 771 
 772   // Schedule the VM operation that will do an evacuation pause to
 773   // satisfy an allocation request of word_size. *succeeded will
 774   // return whether the VM operation was successful (it did do an
 775   // evacuation pause) or not (another thread beat us to it or the GC
 776   // locker was active). Given that we should not be holding the
 777   // Heap_lock when we enter this method, we will pass the
 778   // gc_count_before (i.e., total_collections()) as a parameter since
 779   // it has to be read while holding the Heap_lock. Currently, both
 780   // methods that call do_collection_pause() release the Heap_lock
 781   // before the call, so it's easy to read gc_count_before just before.
 782   HeapWord* do_collection_pause(size_t         word_size,
 783                                 unsigned int   gc_count_before,
 784                                 bool*          succeeded,
 785                                 GCCause::Cause gc_cause);
 786 
 787   // The guts of the incremental collection pause, executed by the vm
 788   // thread. It returns false if it is unable to do the collection due
 789   // to the GC locker being active, true otherwise
 790   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 791 
 792   // Actually do the work of evacuating the collection set.
 793   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 794 
 795   // The g1 remembered set of the heap.
 796   G1RemSet* _g1_rem_set;
 797 
 798   // A set of cards that cover the objects for which the Rsets should be updated
 799   // concurrently after the collection.
 800   DirtyCardQueueSet _dirty_card_queue_set;
 801 
 802   // The closure used to refine a single card.
 803   RefineCardTableEntryClosure* _refine_cte_cl;
 804 
 805   // A function to check the consistency of dirty card logs.
 806   void check_ct_logs_at_safepoint();
 807 
 808   // A DirtyCardQueueSet that is used to hold cards that contain
 809   // references into the current collection set. This is used to
 810   // update the remembered sets of the regions in the collection
 811   // set in the event of an evacuation failure.
 812   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 813 
 814   // After a collection pause, make the regions in the CS into free
 815   // regions.
 816   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 817 
 818   // Abandon the current collection set without recording policy
 819   // statistics or updating free lists.
 820   void abandon_collection_set(HeapRegion* cs_head);
 821 
 822   // Applies "scan_non_heap_roots" to roots outside the heap,
 823   // "scan_rs" to roots inside the heap (having done "set_region" to
 824   // indicate the region in which the root resides),
 825   // and does "scan_metadata" If "scan_rs" is
 826   // NULL, then this step is skipped.  The "worker_i"
 827   // param is for use with parallel roots processing, and should be
 828   // the "i" of the calling parallel worker thread's work(i) function.
 829   // In the sequential case this param will be ignored.
 830   void g1_process_strong_roots(bool is_scavenging,
 831                                ScanningOption so,
 832                                OopClosure* scan_non_heap_roots,
 833                                OopsInHeapRegionClosure* scan_rs,
 834                                G1KlassScanClosure* scan_klasses,
 835                                uint worker_i);
 836 
 837   // Notifies all the necessary spaces that the committed space has
 838   // been updated (either expanded or shrunk). It should be called
 839   // after _g1_storage is updated.
 840   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 841 
 842   // The concurrent marker (and the thread it runs in.)
 843   ConcurrentMark* _cm;
 844   ConcurrentMarkThread* _cmThread;
 845   bool _mark_in_progress;
 846 
 847   // The concurrent refiner.
 848   ConcurrentG1Refine* _cg1r;
 849 
 850   // The parallel task queues
 851   RefToScanQueueSet *_task_queues;
 852 
 853   // True iff a evacuation has failed in the current collection.
 854   bool _evacuation_failed;
 855 
 856   EvacuationFailedInfo* _evacuation_failed_info_array;
 857 
 858   // Failed evacuations cause some logical from-space objects to have
 859   // forwarding pointers to themselves.  Reset them.
 860   void remove_self_forwarding_pointers();
 861 
 862   // Together, these store an object with a preserved mark, and its mark value.
 863   Stack<oop, mtGC>     _objs_with_preserved_marks;
 864   Stack<markOop, mtGC> _preserved_marks_of_objs;
 865 
 866   // Preserve the mark of "obj", if necessary, in preparation for its mark
 867   // word being overwritten with a self-forwarding-pointer.
 868   void preserve_mark_if_necessary(oop obj, markOop m);
 869 
 870   // The stack of evac-failure objects left to be scanned.
 871   GrowableArray<oop>*    _evac_failure_scan_stack;
 872   // The closure to apply to evac-failure objects.
 873 
 874   OopsInHeapRegionClosure* _evac_failure_closure;
 875   // Set the field above.
 876   void
 877   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 878     _evac_failure_closure = evac_failure_closure;
 879   }
 880 
 881   // Push "obj" on the scan stack.
 882   void push_on_evac_failure_scan_stack(oop obj);
 883   // Process scan stack entries until the stack is empty.
 884   void drain_evac_failure_scan_stack();
 885   // True iff an invocation of "drain_scan_stack" is in progress; to
 886   // prevent unnecessary recursion.
 887   bool _drain_in_progress;
 888 
 889   // Do any necessary initialization for evacuation-failure handling.
 890   // "cl" is the closure that will be used to process evac-failure
 891   // objects.
 892   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 893   // Do any necessary cleanup for evacuation-failure handling data
 894   // structures.
 895   void finalize_for_evac_failure();
 896 
 897   // An attempt to evacuate "obj" has failed; take necessary steps.
 898   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 899   void handle_evacuation_failure_common(oop obj, markOop m);
 900 
 901 #ifndef PRODUCT
 902   // Support for forcing evacuation failures. Analogous to
 903   // PromotionFailureALot for the other collectors.
 904 
 905   // Records whether G1EvacuationFailureALot should be in effect
 906   // for the current GC
 907   bool _evacuation_failure_alot_for_current_gc;
 908 
 909   // Used to record the GC number for interval checking when
 910   // determining whether G1EvaucationFailureALot is in effect
 911   // for the current GC.
 912   size_t _evacuation_failure_alot_gc_number;
 913 
 914   // Count of the number of evacuations between failures.
 915   volatile size_t _evacuation_failure_alot_count;
 916 
 917   // Set whether G1EvacuationFailureALot should be in effect
 918   // for the current GC (based upon the type of GC and which
 919   // command line flags are set);
 920   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 921                                                   bool during_initial_mark,
 922                                                   bool during_marking);
 923 
 924   inline void set_evacuation_failure_alot_for_current_gc();
 925 
 926   // Return true if it's time to cause an evacuation failure.
 927   inline bool evacuation_should_fail();
 928 
 929   // Reset the G1EvacuationFailureALot counters.  Should be called at
 930   // the end of an evacuation pause in which an evacuation failure occurred.
 931   inline void reset_evacuation_should_fail();
 932 #endif // !PRODUCT
 933 
 934   // ("Weak") Reference processing support.
 935   //
 936   // G1 has 2 instances of the reference processor class. One
 937   // (_ref_processor_cm) handles reference object discovery
 938   // and subsequent processing during concurrent marking cycles.
 939   //
 940   // The other (_ref_processor_stw) handles reference object
 941   // discovery and processing during full GCs and incremental
 942   // evacuation pauses.
 943   //
 944   // During an incremental pause, reference discovery will be
 945   // temporarily disabled for _ref_processor_cm and will be
 946   // enabled for _ref_processor_stw. At the end of the evacuation
 947   // pause references discovered by _ref_processor_stw will be
 948   // processed and discovery will be disabled. The previous
 949   // setting for reference object discovery for _ref_processor_cm
 950   // will be re-instated.
 951   //
 952   // At the start of marking:
 953   //  * Discovery by the CM ref processor is verified to be inactive
 954   //    and it's discovered lists are empty.
 955   //  * Discovery by the CM ref processor is then enabled.
 956   //
 957   // At the end of marking:
 958   //  * Any references on the CM ref processor's discovered
 959   //    lists are processed (possibly MT).
 960   //
 961   // At the start of full GC we:
 962   //  * Disable discovery by the CM ref processor and
 963   //    empty CM ref processor's discovered lists
 964   //    (without processing any entries).
 965   //  * Verify that the STW ref processor is inactive and it's
 966   //    discovered lists are empty.
 967   //  * Temporarily set STW ref processor discovery as single threaded.
 968   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 969   //    field.
 970   //  * Finally enable discovery by the STW ref processor.
 971   //
 972   // The STW ref processor is used to record any discovered
 973   // references during the full GC.
 974   //
 975   // At the end of a full GC we:
 976   //  * Enqueue any reference objects discovered by the STW ref processor
 977   //    that have non-live referents. This has the side-effect of
 978   //    making the STW ref processor inactive by disabling discovery.
 979   //  * Verify that the CM ref processor is still inactive
 980   //    and no references have been placed on it's discovered
 981   //    lists (also checked as a precondition during initial marking).
 982 
 983   // The (stw) reference processor...
 984   ReferenceProcessor* _ref_processor_stw;
 985 
 986   STWGCTimer* _gc_timer_stw;
 987   ConcurrentGCTimer* _gc_timer_cm;
 988 
 989   G1OldTracer* _gc_tracer_cm;
 990   G1NewTracer* _gc_tracer_stw;
 991 
 992   // During reference object discovery, the _is_alive_non_header
 993   // closure (if non-null) is applied to the referent object to
 994   // determine whether the referent is live. If so then the
 995   // reference object does not need to be 'discovered' and can
 996   // be treated as a regular oop. This has the benefit of reducing
 997   // the number of 'discovered' reference objects that need to
 998   // be processed.
 999   //
1000   // Instance of the is_alive closure for embedding into the
1001   // STW reference processor as the _is_alive_non_header field.
1002   // Supplying a value for the _is_alive_non_header field is
1003   // optional but doing so prevents unnecessary additions to
1004   // the discovered lists during reference discovery.
1005   G1STWIsAliveClosure _is_alive_closure_stw;
1006 
1007   // The (concurrent marking) reference processor...
1008   ReferenceProcessor* _ref_processor_cm;
1009 
1010   // Instance of the concurrent mark is_alive closure for embedding
1011   // into the Concurrent Marking reference processor as the
1012   // _is_alive_non_header field. Supplying a value for the
1013   // _is_alive_non_header field is optional but doing so prevents
1014   // unnecessary additions to the discovered lists during reference
1015   // discovery.
1016   G1CMIsAliveClosure _is_alive_closure_cm;
1017 
1018   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1019   HeapRegion** _worker_cset_start_region;
1020 
1021   // Time stamp to validate the regions recorded in the cache
1022   // used by G1CollectedHeap::start_cset_region_for_worker().
1023   // The heap region entry for a given worker is valid iff
1024   // the associated time stamp value matches the current value
1025   // of G1CollectedHeap::_gc_time_stamp.
1026   unsigned int* _worker_cset_start_region_time_stamp;
1027 
1028   enum G1H_process_strong_roots_tasks {
1029     G1H_PS_filter_satb_buffers,
1030     G1H_PS_refProcessor_oops_do,
1031     // Leave this one last.
1032     G1H_PS_NumElements
1033   };
1034 
1035   SubTasksDone* _process_strong_tasks;
1036 
1037   volatile bool _free_regions_coming;
1038 
1039 public:
1040 
1041   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1042 
1043   void set_refine_cte_cl_concurrency(bool concurrent);
1044 
1045   RefToScanQueue *task_queue(int i) const;
1046 
1047   // A set of cards where updates happened during the GC
1048   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1049 
1050   // A DirtyCardQueueSet that is used to hold cards that contain
1051   // references into the current collection set. This is used to
1052   // update the remembered sets of the regions in the collection
1053   // set in the event of an evacuation failure.
1054   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1055         { return _into_cset_dirty_card_queue_set; }
1056 
1057   // Create a G1CollectedHeap with the specified policy.
1058   // Must call the initialize method afterwards.
1059   // May not return if something goes wrong.
1060   G1CollectedHeap(G1CollectorPolicy* policy);
1061 
1062   // Initialize the G1CollectedHeap to have the initial and
1063   // maximum sizes and remembered and barrier sets
1064   // specified by the policy object.
1065   jint initialize();
1066 
1067   virtual void stop();
1068 
1069   // Return the (conservative) maximum heap alignment for any G1 heap
1070   static size_t conservative_max_heap_alignment();
1071 
1072   // Initialize weak reference processing.
1073   virtual void ref_processing_init();
1074 
1075   void set_par_threads(uint t) {
1076     SharedHeap::set_par_threads(t);
1077     // Done in SharedHeap but oddly there are
1078     // two _process_strong_tasks's in a G1CollectedHeap
1079     // so do it here too.
1080     _process_strong_tasks->set_n_threads(t);
1081   }
1082 
1083   // Set _n_par_threads according to a policy TBD.
1084   void set_par_threads();
1085 
1086   void set_n_termination(int t) {
1087     _process_strong_tasks->set_n_threads(t);
1088   }
1089 
1090   virtual CollectedHeap::Name kind() const {
1091     return CollectedHeap::G1CollectedHeap;
1092   }
1093 
1094   // The current policy object for the collector.
1095   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1096 
1097   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1098 
1099   // Adaptive size policy.  No such thing for g1.
1100   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1101 
1102   // The rem set and barrier set.
1103   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1104 
1105   unsigned get_gc_time_stamp() {
1106     return _gc_time_stamp;
1107   }
1108 
1109   inline void reset_gc_time_stamp();
1110 
1111   void check_gc_time_stamps() PRODUCT_RETURN;
1112 
1113   inline void increment_gc_time_stamp();
1114 
1115   // Reset the given region's GC timestamp. If it's starts humongous,
1116   // also reset the GC timestamp of its corresponding
1117   // continues humongous regions too.
1118   void reset_gc_time_stamps(HeapRegion* hr);
1119 
1120   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1121                                   DirtyCardQueue* into_cset_dcq,
1122                                   bool concurrent, uint worker_i);
1123 
1124   // The shared block offset table array.
1125   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1126 
1127   // Reference Processing accessors
1128 
1129   // The STW reference processor....
1130   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1131 
1132   // The Concurrent Marking reference processor...
1133   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1134 
1135   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1136   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1137 
1138   virtual size_t capacity() const;
1139   virtual size_t used() const;
1140   // This should be called when we're not holding the heap lock. The
1141   // result might be a bit inaccurate.
1142   size_t used_unlocked() const;
1143   size_t recalculate_used() const;
1144 
1145   // These virtual functions do the actual allocation.
1146   // Some heaps may offer a contiguous region for shared non-blocking
1147   // allocation, via inlined code (by exporting the address of the top and
1148   // end fields defining the extent of the contiguous allocation region.)
1149   // But G1CollectedHeap doesn't yet support this.
1150 
1151   virtual bool is_maximal_no_gc() const {
1152     return _g1_storage.uncommitted_size() == 0;
1153   }
1154 
1155   // The total number of regions in the heap.
1156   uint n_regions() { return _hrs.length(); }
1157 
1158   // The max number of regions in the heap.
1159   uint max_regions() { return _hrs.max_length(); }
1160 
1161   // The number of regions that are completely free.
1162   uint free_regions() { return _free_list.length(); }
1163 
1164   // The number of regions that are not completely free.
1165   uint used_regions() { return n_regions() - free_regions(); }
1166 
1167   // The number of regions available for "regular" expansion.
1168   uint expansion_regions() { return _expansion_regions; }
1169 
1170   // Factory method for HeapRegion instances. It will return NULL if
1171   // the allocation fails.
1172   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1173 
1174   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1175   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1176   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1177   void verify_dirty_young_regions() PRODUCT_RETURN;
1178 
1179 #ifndef PRODUCT
1180   // Make sure that the given bitmap has no marked objects in the
1181   // range [from,limit). If it does, print an error message and return
1182   // false. Otherwise, just return true. bitmap_name should be "prev"
1183   // or "next".
1184   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1185                                 HeapWord* from, HeapWord* limit);
1186 
1187   // Verify that the prev / next bitmap range [tams,end) for the given
1188   // region has no marks. Return true if all is well, false if errors
1189   // are detected.
1190   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1191 #endif // PRODUCT
1192 
1193   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1194   // the given region do not have any spurious marks. If errors are
1195   // detected, print appropriate error messages and crash.
1196   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1197 
1198   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1199   // have any spurious marks. If errors are detected, print
1200   // appropriate error messages and crash.
1201   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1202 
1203   // verify_region_sets() performs verification over the region
1204   // lists. It will be compiled in the product code to be used when
1205   // necessary (i.e., during heap verification).
1206   void verify_region_sets();
1207 
1208   // verify_region_sets_optional() is planted in the code for
1209   // list verification in non-product builds (and it can be enabled in
1210   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1211 #if HEAP_REGION_SET_FORCE_VERIFY
1212   void verify_region_sets_optional() {
1213     verify_region_sets();
1214   }
1215 #else // HEAP_REGION_SET_FORCE_VERIFY
1216   void verify_region_sets_optional() { }
1217 #endif // HEAP_REGION_SET_FORCE_VERIFY
1218 
1219 #ifdef ASSERT
1220   bool is_on_master_free_list(HeapRegion* hr) {
1221     return hr->containing_set() == &_free_list;
1222   }
1223 #endif // ASSERT
1224 
1225   // Wrapper for the region list operations that can be called from
1226   // methods outside this class.
1227 
1228   void secondary_free_list_add(FreeRegionList* list) {
1229     _secondary_free_list.add_ordered(list);
1230   }
1231 
1232   void append_secondary_free_list() {
1233     _free_list.add_ordered(&_secondary_free_list);
1234   }
1235 
1236   void append_secondary_free_list_if_not_empty_with_lock() {
1237     // If the secondary free list looks empty there's no reason to
1238     // take the lock and then try to append it.
1239     if (!_secondary_free_list.is_empty()) {
1240       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1241       append_secondary_free_list();
1242     }
1243   }
1244 
1245   inline void old_set_remove(HeapRegion* hr);
1246 
1247   size_t non_young_capacity_bytes() {
1248     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1249   }
1250 
1251   void set_free_regions_coming();
1252   void reset_free_regions_coming();
1253   bool free_regions_coming() { return _free_regions_coming; }
1254   void wait_while_free_regions_coming();
1255 
1256   // Determine whether the given region is one that we are using as an
1257   // old GC alloc region.
1258   bool is_old_gc_alloc_region(HeapRegion* hr) {
1259     return hr == _retained_old_gc_alloc_region;
1260   }
1261 
1262   // Perform a collection of the heap; intended for use in implementing
1263   // "System.gc".  This probably implies as full a collection as the
1264   // "CollectedHeap" supports.
1265   virtual void collect(GCCause::Cause cause);
1266 
1267   // The same as above but assume that the caller holds the Heap_lock.
1268   void collect_locked(GCCause::Cause cause);
1269 
1270   // True iff an evacuation has failed in the most-recent collection.
1271   bool evacuation_failed() { return _evacuation_failed; }
1272 
1273   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1274   void prepend_to_freelist(FreeRegionList* list);
1275   void decrement_summary_bytes(size_t bytes);
1276 
1277   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1278   virtual bool is_in(const void* p) const;
1279 
1280   // Return "TRUE" iff the given object address is within the collection
1281   // set.
1282   inline bool obj_in_cs(oop obj);
1283 
1284   // Return "TRUE" iff the given object address is in the reserved
1285   // region of g1.
1286   bool is_in_g1_reserved(const void* p) const {
1287     return _g1_reserved.contains(p);
1288   }
1289 
1290   // Returns a MemRegion that corresponds to the space that has been
1291   // reserved for the heap
1292   MemRegion g1_reserved() {
1293     return _g1_reserved;
1294   }
1295 
1296   // Returns a MemRegion that corresponds to the space that has been
1297   // committed in the heap
1298   MemRegion g1_committed() {
1299     return _g1_committed;
1300   }
1301 
1302   virtual bool is_in_closed_subset(const void* p) const;
1303 
1304   G1SATBCardTableModRefBS* g1_barrier_set() {
1305     return (G1SATBCardTableModRefBS*) barrier_set();
1306   }
1307 
1308   // This resets the card table to all zeros.  It is used after
1309   // a collection pause which used the card table to claim cards.
1310   void cleanUpCardTable();
1311 
1312   // Iteration functions.
1313 
1314   // Iterate over all the ref-containing fields of all objects, calling
1315   // "cl.do_oop" on each.
1316   virtual void oop_iterate(ExtendedOopClosure* cl);
1317 
1318   // Same as above, restricted to a memory region.
1319   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1320 
1321   // Iterate over all objects, calling "cl.do_object" on each.
1322   virtual void object_iterate(ObjectClosure* cl);
1323 
1324   virtual void safe_object_iterate(ObjectClosure* cl) {
1325     object_iterate(cl);
1326   }
1327 
1328   // Iterate over all spaces in use in the heap, in ascending address order.
1329   virtual void space_iterate(SpaceClosure* cl);
1330 
1331   // Iterate over heap regions, in address order, terminating the
1332   // iteration early if the "doHeapRegion" method returns "true".
1333   void heap_region_iterate(HeapRegionClosure* blk) const;
1334 
1335   // Return the region with the given index. It assumes the index is valid.
1336   inline HeapRegion* region_at(uint index) const;
1337 
1338   // Divide the heap region sequence into "chunks" of some size (the number
1339   // of regions divided by the number of parallel threads times some
1340   // overpartition factor, currently 4).  Assumes that this will be called
1341   // in parallel by ParallelGCThreads worker threads with distinct worker
1342   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1343   // calls will use the same "claim_value", and that that claim value is
1344   // different from the claim_value of any heap region before the start of
1345   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1346   // attempting to claim the first region in each chunk, and, if
1347   // successful, applying the closure to each region in the chunk (and
1348   // setting the claim value of the second and subsequent regions of the
1349   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1350   // i.e., that a closure never attempt to abort a traversal.
1351   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1352                                        uint worker,
1353                                        uint no_of_par_workers,
1354                                        jint claim_value);
1355 
1356   // It resets all the region claim values to the default.
1357   void reset_heap_region_claim_values();
1358 
1359   // Resets the claim values of regions in the current
1360   // collection set to the default.
1361   void reset_cset_heap_region_claim_values();
1362 
1363 #ifdef ASSERT
1364   bool check_heap_region_claim_values(jint claim_value);
1365 
1366   // Same as the routine above but only checks regions in the
1367   // current collection set.
1368   bool check_cset_heap_region_claim_values(jint claim_value);
1369 #endif // ASSERT
1370 
1371   // Clear the cached cset start regions and (more importantly)
1372   // the time stamps. Called when we reset the GC time stamp.
1373   void clear_cset_start_regions();
1374 
1375   // Given the id of a worker, obtain or calculate a suitable
1376   // starting region for iterating over the current collection set.
1377   HeapRegion* start_cset_region_for_worker(uint worker_i);
1378 
1379   // This is a convenience method that is used by the
1380   // HeapRegionIterator classes to calculate the starting region for
1381   // each worker so that they do not all start from the same region.
1382   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1383 
1384   // Iterate over the regions (if any) in the current collection set.
1385   void collection_set_iterate(HeapRegionClosure* blk);
1386 
1387   // As above but starting from region r
1388   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1389 
1390   // Returns the first (lowest address) compactible space in the heap.
1391   virtual CompactibleSpace* first_compactible_space();
1392 
1393   // A CollectedHeap will contain some number of spaces.  This finds the
1394   // space containing a given address, or else returns NULL.
1395   virtual Space* space_containing(const void* addr) const;
1396 
1397   // Returns the HeapRegion that contains addr. addr must not be NULL.
1398   template <class T>
1399   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1400 
1401   // Returns the HeapRegion that contains addr. addr must not be NULL.
1402   // If addr is within a humongous continues region, it returns its humongous start region.
1403   template <class T>
1404   inline HeapRegion* heap_region_containing(const T addr) const;
1405 
1406   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1407   // each address in the (reserved) heap is a member of exactly
1408   // one block.  The defining characteristic of a block is that it is
1409   // possible to find its size, and thus to progress forward to the next
1410   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1411   // represent Java objects, or they might be free blocks in a
1412   // free-list-based heap (or subheap), as long as the two kinds are
1413   // distinguishable and the size of each is determinable.
1414 
1415   // Returns the address of the start of the "block" that contains the
1416   // address "addr".  We say "blocks" instead of "object" since some heaps
1417   // may not pack objects densely; a chunk may either be an object or a
1418   // non-object.
1419   virtual HeapWord* block_start(const void* addr) const;
1420 
1421   // Requires "addr" to be the start of a chunk, and returns its size.
1422   // "addr + size" is required to be the start of a new chunk, or the end
1423   // of the active area of the heap.
1424   virtual size_t block_size(const HeapWord* addr) const;
1425 
1426   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1427   // the block is an object.
1428   virtual bool block_is_obj(const HeapWord* addr) const;
1429 
1430   // Does this heap support heap inspection? (+PrintClassHistogram)
1431   virtual bool supports_heap_inspection() const { return true; }
1432 
1433   // Section on thread-local allocation buffers (TLABs)
1434   // See CollectedHeap for semantics.
1435 
1436   bool supports_tlab_allocation() const;
1437   size_t tlab_capacity(Thread* ignored) const;
1438   size_t tlab_used(Thread* ignored) const;
1439   size_t max_tlab_size() const;
1440   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1441 
1442   // Can a compiler initialize a new object without store barriers?
1443   // This permission only extends from the creation of a new object
1444   // via a TLAB up to the first subsequent safepoint. If such permission
1445   // is granted for this heap type, the compiler promises to call
1446   // defer_store_barrier() below on any slow path allocation of
1447   // a new object for which such initializing store barriers will
1448   // have been elided. G1, like CMS, allows this, but should be
1449   // ready to provide a compensating write barrier as necessary
1450   // if that storage came out of a non-young region. The efficiency
1451   // of this implementation depends crucially on being able to
1452   // answer very efficiently in constant time whether a piece of
1453   // storage in the heap comes from a young region or not.
1454   // See ReduceInitialCardMarks.
1455   virtual bool can_elide_tlab_store_barriers() const {
1456     return true;
1457   }
1458 
1459   virtual bool card_mark_must_follow_store() const {
1460     return true;
1461   }
1462 
1463   inline bool is_in_young(const oop obj);
1464 
1465 #ifdef ASSERT
1466   virtual bool is_in_partial_collection(const void* p);
1467 #endif
1468 
1469   virtual bool is_scavengable(const void* addr);
1470 
1471   // We don't need barriers for initializing stores to objects
1472   // in the young gen: for the SATB pre-barrier, there is no
1473   // pre-value that needs to be remembered; for the remembered-set
1474   // update logging post-barrier, we don't maintain remembered set
1475   // information for young gen objects.
1476   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1477 
1478   // Returns "true" iff the given word_size is "very large".
1479   static bool isHumongous(size_t word_size) {
1480     // Note this has to be strictly greater-than as the TLABs
1481     // are capped at the humongous threshold and we want to
1482     // ensure that we don't try to allocate a TLAB as
1483     // humongous and that we don't allocate a humongous
1484     // object in a TLAB.
1485     return word_size > _humongous_object_threshold_in_words;
1486   }
1487 
1488   // Update mod union table with the set of dirty cards.
1489   void updateModUnion();
1490 
1491   // Set the mod union bits corresponding to the given memRegion.  Note
1492   // that this is always a safe operation, since it doesn't clear any
1493   // bits.
1494   void markModUnionRange(MemRegion mr);
1495 
1496   // Records the fact that a marking phase is no longer in progress.
1497   void set_marking_complete() {
1498     _mark_in_progress = false;
1499   }
1500   void set_marking_started() {
1501     _mark_in_progress = true;
1502   }
1503   bool mark_in_progress() {
1504     return _mark_in_progress;
1505   }
1506 
1507   // Print the maximum heap capacity.
1508   virtual size_t max_capacity() const;
1509 
1510   virtual jlong millis_since_last_gc();
1511 
1512 
1513   // Convenience function to be used in situations where the heap type can be
1514   // asserted to be this type.
1515   static G1CollectedHeap* heap();
1516 
1517   void set_region_short_lived_locked(HeapRegion* hr);
1518   // add appropriate methods for any other surv rate groups
1519 
1520   YoungList* young_list() const { return _young_list; }
1521 
1522   // debugging
1523   bool check_young_list_well_formed() {
1524     return _young_list->check_list_well_formed();
1525   }
1526 
1527   bool check_young_list_empty(bool check_heap,
1528                               bool check_sample = true);
1529 
1530   // *** Stuff related to concurrent marking.  It's not clear to me that so
1531   // many of these need to be public.
1532 
1533   // The functions below are helper functions that a subclass of
1534   // "CollectedHeap" can use in the implementation of its virtual
1535   // functions.
1536   // This performs a concurrent marking of the live objects in a
1537   // bitmap off to the side.
1538   void doConcurrentMark();
1539 
1540   bool isMarkedPrev(oop obj) const;
1541   bool isMarkedNext(oop obj) const;
1542 
1543   // Determine if an object is dead, given the object and also
1544   // the region to which the object belongs. An object is dead
1545   // iff a) it was not allocated since the last mark and b) it
1546   // is not marked.
1547   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1548     return
1549       !hr->obj_allocated_since_prev_marking(obj) &&
1550       !isMarkedPrev(obj);
1551   }
1552 
1553   // This function returns true when an object has been
1554   // around since the previous marking and hasn't yet
1555   // been marked during this marking.
1556   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1557     return
1558       !hr->obj_allocated_since_next_marking(obj) &&
1559       !isMarkedNext(obj);
1560   }
1561 
1562   // Determine if an object is dead, given only the object itself.
1563   // This will find the region to which the object belongs and
1564   // then call the region version of the same function.
1565 
1566   // Added if it is NULL it isn't dead.
1567 
1568   inline bool is_obj_dead(const oop obj) const;
1569 
1570   inline bool is_obj_ill(const oop obj) const;
1571 
1572   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1573   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1574   bool is_marked(oop obj, VerifyOption vo);
1575   const char* top_at_mark_start_str(VerifyOption vo);
1576 
1577   ConcurrentMark* concurrent_mark() const { return _cm; }
1578 
1579   // Refinement
1580 
1581   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1582 
1583   // The dirty cards region list is used to record a subset of regions
1584   // whose cards need clearing. The list if populated during the
1585   // remembered set scanning and drained during the card table
1586   // cleanup. Although the methods are reentrant, population/draining
1587   // phases must not overlap. For synchronization purposes the last
1588   // element on the list points to itself.
1589   HeapRegion* _dirty_cards_region_list;
1590   void push_dirty_cards_region(HeapRegion* hr);
1591   HeapRegion* pop_dirty_cards_region();
1592 
1593   // Optimized nmethod scanning support routines
1594 
1595   // Register the given nmethod with the G1 heap.
1596   virtual void register_nmethod(nmethod* nm);
1597 
1598   // Unregister the given nmethod from the G1 heap.
1599   virtual void unregister_nmethod(nmethod* nm);
1600 
1601   // Migrate the nmethods in the code root lists of the regions
1602   // in the collection set to regions in to-space. In the event
1603   // of an evacuation failure, nmethods that reference objects
1604   // that were not successfully evacuated are not migrated.
1605   void migrate_strong_code_roots();
1606 
1607   // Free up superfluous code root memory.
1608   void purge_code_root_memory();
1609 
1610   // During an initial mark pause, mark all the code roots that
1611   // point into regions *not* in the collection set.
1612   void mark_strong_code_roots(uint worker_id);
1613 
1614   // Rebuild the strong code root lists for each region
1615   // after a full GC.
1616   void rebuild_strong_code_roots();
1617 
1618   // Delete entries for dead interned string and clean up unreferenced symbols
1619   // in symbol table, possibly in parallel.
1620   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1621 
1622   // Redirty logged cards in the refinement queue.
1623   void redirty_logged_cards();
1624   // Verification
1625 
1626   // The following is just to alert the verification code
1627   // that a full collection has occurred and that the
1628   // remembered sets are no longer up to date.
1629   bool _full_collection;
1630   void set_full_collection() { _full_collection = true;}
1631   void clear_full_collection() {_full_collection = false;}
1632   bool full_collection() {return _full_collection;}
1633 
1634   // Perform any cleanup actions necessary before allowing a verification.
1635   virtual void prepare_for_verify();
1636 
1637   // Perform verification.
1638 
1639   // vo == UsePrevMarking  -> use "prev" marking information,
1640   // vo == UseNextMarking -> use "next" marking information
1641   // vo == UseMarkWord    -> use the mark word in the object header
1642   //
1643   // NOTE: Only the "prev" marking information is guaranteed to be
1644   // consistent most of the time, so most calls to this should use
1645   // vo == UsePrevMarking.
1646   // Currently, there is only one case where this is called with
1647   // vo == UseNextMarking, which is to verify the "next" marking
1648   // information at the end of remark.
1649   // Currently there is only one place where this is called with
1650   // vo == UseMarkWord, which is to verify the marking during a
1651   // full GC.
1652   void verify(bool silent, VerifyOption vo);
1653 
1654   // Override; it uses the "prev" marking information
1655   virtual void verify(bool silent);
1656 
1657   // The methods below are here for convenience and dispatch the
1658   // appropriate method depending on value of the given VerifyOption
1659   // parameter. The values for that parameter, and their meanings,
1660   // are the same as those above.
1661 
1662   bool is_obj_dead_cond(const oop obj,
1663                         const HeapRegion* hr,
1664                         const VerifyOption vo) const;
1665 
1666   bool is_obj_dead_cond(const oop obj,
1667                         const VerifyOption vo) const;
1668 
1669   // Printing
1670 
1671   virtual void print_on(outputStream* st) const;
1672   virtual void print_extended_on(outputStream* st) const;
1673   virtual void print_on_error(outputStream* st) const;
1674 
1675   virtual void print_gc_threads_on(outputStream* st) const;
1676   virtual void gc_threads_do(ThreadClosure* tc) const;
1677 
1678   // Override
1679   void print_tracing_info() const;
1680 
1681   // The following two methods are helpful for debugging RSet issues.
1682   void print_cset_rsets() PRODUCT_RETURN;
1683   void print_all_rsets() PRODUCT_RETURN;
1684 
1685 public:
1686   size_t pending_card_num();
1687   size_t cards_scanned();
1688 
1689 protected:
1690   size_t _max_heap_capacity;
1691 };
1692 
1693 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1694 private:
1695   bool        _retired;
1696 
1697 public:
1698   G1ParGCAllocBuffer(size_t gclab_word_size);
1699   virtual ~G1ParGCAllocBuffer() {
1700     guarantee(_retired, "Allocation buffer has not been retired");
1701   }
1702 
1703   virtual void set_buf(HeapWord* buf) {
1704     ParGCAllocBuffer::set_buf(buf);
1705     _retired = false;
1706   }
1707 
1708   virtual void retire(bool end_of_gc, bool retain) {
1709     if (_retired) {
1710       return;
1711     }
1712     ParGCAllocBuffer::retire(end_of_gc, retain);
1713     _retired = true;
1714   }
1715 };
1716 
1717 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP