1 /*
   2  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
   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.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  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/g1AllocRegion.hpp"
  30 #include "gc_implementation/g1/g1HRPrinter.hpp"
  31 #include "gc_implementation/g1/g1RemSet.hpp"
  32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  33 #include "gc_implementation/g1/heapRegionSeq.hpp"
  34 #include "gc_implementation/g1/heapRegionSets.hpp"
  35 #include "gc_implementation/shared/hSpaceCounters.hpp"
  36 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  37 #include "memory/barrierSet.hpp"
  38 #include "memory/memRegion.hpp"
  39 #include "memory/sharedHeap.hpp"
  40 #include "utilities/stack.hpp"
  41 
  42 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  43 // It uses the "Garbage First" heap organization and algorithm, which
  44 // may combine concurrent marking with parallel, incremental compaction of
  45 // heap subsets that will yield large amounts of garbage.
  46 
  47 class HeapRegion;
  48 class HRRSCleanupTask;
  49 class GenerationSpec;
  50 class OopsInHeapRegionClosure;
  51 class G1KlassScanClosure;
  52 class G1ScanHeapEvacClosure;
  53 class ObjectClosure;
  54 class SpaceClosure;
  55 class CompactibleSpaceClosure;
  56 class Space;
  57 class G1CollectorPolicy;
  58 class GenRemSet;
  59 class G1RemSet;
  60 class HeapRegionRemSetIterator;
  61 class ConcurrentMark;
  62 class ConcurrentMarkThread;
  63 class ConcurrentG1Refine;
  64 class GenerationCounters;
  65 
  66 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  67 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  68 
  69 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  70 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  71 
  72 enum GCAllocPurpose {
  73   GCAllocForTenured,
  74   GCAllocForSurvived,
  75   GCAllocPurposeCount
  76 };
  77 
  78 class YoungList : public CHeapObj<mtGC> {
  79 private:
  80   G1CollectedHeap* _g1h;
  81 
  82   HeapRegion* _head;
  83 
  84   HeapRegion* _survivor_head;
  85   HeapRegion* _survivor_tail;
  86 
  87   HeapRegion* _curr;
  88 
  89   uint        _length;
  90   uint        _survivor_length;
  91 
  92   size_t      _last_sampled_rs_lengths;
  93   size_t      _sampled_rs_lengths;
  94 
  95   void         empty_list(HeapRegion* list);
  96 
  97 public:
  98   YoungList(G1CollectedHeap* g1h);
  99 
 100   void         push_region(HeapRegion* hr);
 101   void         add_survivor_region(HeapRegion* hr);
 102 
 103   void         empty_list();
 104   bool         is_empty() { return _length == 0; }
 105   uint         length() { return _length; }
 106   uint         survivor_length() { return _survivor_length; }
 107 
 108   // Currently we do not keep track of the used byte sum for the
 109   // young list and the survivors and it'd be quite a lot of work to
 110   // do so. When we'll eventually replace the young list with
 111   // instances of HeapRegionLinkedList we'll get that for free. So,
 112   // we'll report the more accurate information then.
 113   size_t       eden_used_bytes() {
 114     assert(length() >= survivor_length(), "invariant");
 115     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 116   }
 117   size_t       survivor_used_bytes() {
 118     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 119   }
 120 
 121   void rs_length_sampling_init();
 122   bool rs_length_sampling_more();
 123   void rs_length_sampling_next();
 124 
 125   void reset_sampled_info() {
 126     _last_sampled_rs_lengths =   0;
 127   }
 128   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 129 
 130   // for development purposes
 131   void reset_auxilary_lists();
 132   void clear() { _head = NULL; _length = 0; }
 133 
 134   void clear_survivors() {
 135     _survivor_head    = NULL;
 136     _survivor_tail    = NULL;
 137     _survivor_length  = 0;
 138   }
 139 
 140   HeapRegion* first_region() { return _head; }
 141   HeapRegion* first_survivor_region() { return _survivor_head; }
 142   HeapRegion* last_survivor_region() { return _survivor_tail; }
 143 
 144   // debugging
 145   bool          check_list_well_formed();
 146   bool          check_list_empty(bool check_sample = true);
 147   void          print();
 148 };
 149 
 150 class MutatorAllocRegion : public G1AllocRegion {
 151 protected:
 152   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 153   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 154 public:
 155   MutatorAllocRegion()
 156     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 157 };
 158 
 159 // The G1 STW is alive closure.
 160 // An instance is embedded into the G1CH and used as the
 161 // (optional) _is_alive_non_header closure in the STW
 162 // reference processor. It is also extensively used during
 163 // refence processing during STW evacuation pauses.
 164 class G1STWIsAliveClosure: public BoolObjectClosure {
 165   G1CollectedHeap* _g1;
 166 public:
 167   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 168   bool do_object_b(oop p);
 169 };
 170 
 171 class SurvivorGCAllocRegion : public G1AllocRegion {
 172 protected:
 173   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 174   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 175 public:
 176   SurvivorGCAllocRegion()
 177   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 178 };
 179 
 180 class OldGCAllocRegion : public G1AllocRegion {
 181 protected:
 182   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 183   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 184 public:
 185   OldGCAllocRegion()
 186   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 187 };
 188 
 189 class RefineCardTableEntryClosure;
 190 
 191 class G1CollectedHeap : public SharedHeap {
 192   friend class VM_G1CollectForAllocation;
 193   friend class VM_G1CollectFull;
 194   friend class VM_G1IncCollectionPause;
 195   friend class VMStructs;
 196   friend class MutatorAllocRegion;
 197   friend class SurvivorGCAllocRegion;
 198   friend class OldGCAllocRegion;
 199 
 200   // Closures used in implementation.
 201   template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
 202   friend class G1ParCopyClosure;
 203   friend class G1IsAliveClosure;
 204   friend class G1EvacuateFollowersClosure;
 205   friend class G1ParScanThreadState;
 206   friend class G1ParScanClosureSuper;
 207   friend class G1ParEvacuateFollowersClosure;
 208   friend class G1ParTask;
 209   friend class G1FreeGarbageRegionClosure;
 210   friend class RefineCardTableEntryClosure;
 211   friend class G1PrepareCompactClosure;
 212   friend class RegionSorter;
 213   friend class RegionResetter;
 214   friend class CountRCClosure;
 215   friend class EvacPopObjClosure;
 216   friend class G1ParCleanupCTTask;
 217 
 218   // Other related classes.
 219   friend class G1MarkSweep;
 220 
 221 private:
 222   // The one and only G1CollectedHeap, so static functions can find it.
 223   static G1CollectedHeap* _g1h;
 224 
 225   static size_t _humongous_object_threshold_in_words;
 226 
 227   // Storage for the G1 heap.
 228   VirtualSpace _g1_storage;
 229   MemRegion    _g1_reserved;
 230 
 231   // The part of _g1_storage that is currently committed.
 232   MemRegion _g1_committed;
 233 
 234   // The master free list. It will satisfy all new region allocations.
 235   MasterFreeRegionList      _free_list;
 236 
 237   // The secondary free list which contains regions that have been
 238   // freed up during the cleanup process. This will be appended to the
 239   // master free list when appropriate.
 240   SecondaryFreeRegionList   _secondary_free_list;
 241 
 242   // It keeps track of the old regions.
 243   MasterOldRegionSet        _old_set;
 244 
 245   // It keeps track of the humongous regions.
 246   MasterHumongousRegionSet  _humongous_set;
 247 
 248   // The number of regions we could create by expansion.
 249   uint _expansion_regions;
 250 
 251   // The block offset table for the G1 heap.
 252   G1BlockOffsetSharedArray* _bot_shared;
 253 
 254   // Tears down the region sets / lists so that they are empty and the
 255   // regions on the heap do not belong to a region set / list. The
 256   // only exception is the humongous set which we leave unaltered. If
 257   // free_list_only is true, it will only tear down the master free
 258   // list. It is called before a Full GC (free_list_only == false) or
 259   // before heap shrinking (free_list_only == true).
 260   void tear_down_region_sets(bool free_list_only);
 261 
 262   // Rebuilds the region sets / lists so that they are repopulated to
 263   // reflect the contents of the heap. The only exception is the
 264   // humongous set which was not torn down in the first place. If
 265   // free_list_only is true, it will only rebuild the master free
 266   // list. It is called after a Full GC (free_list_only == false) or
 267   // after heap shrinking (free_list_only == true).
 268   void rebuild_region_sets(bool free_list_only);
 269 
 270   // The sequence of all heap regions in the heap.
 271   HeapRegionSeq _hrs;
 272 
 273   // Alloc region used to satisfy mutator allocation requests.
 274   MutatorAllocRegion _mutator_alloc_region;
 275 
 276   // Alloc region used to satisfy allocation requests by the GC for
 277   // survivor objects.
 278   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 279 
 280   // PLAB sizing policy for survivors.
 281   PLABStats _survivor_plab_stats;
 282 
 283   // Alloc region used to satisfy allocation requests by the GC for
 284   // old objects.
 285   OldGCAllocRegion _old_gc_alloc_region;
 286 
 287   // PLAB sizing policy for tenured objects.
 288   PLABStats _old_plab_stats;
 289 
 290   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 291     PLABStats* stats = NULL;
 292 
 293     switch (purpose) {
 294     case GCAllocForSurvived:
 295       stats = &_survivor_plab_stats;
 296       break;
 297     case GCAllocForTenured:
 298       stats = &_old_plab_stats;
 299       break;
 300     default:
 301       assert(false, "unrecognized GCAllocPurpose");
 302     }
 303 
 304     return stats;
 305   }
 306 
 307   // The last old region we allocated to during the last GC.
 308   // Typically, it is not full so we should re-use it during the next GC.
 309   HeapRegion* _retained_old_gc_alloc_region;
 310 
 311   // It specifies whether we should attempt to expand the heap after a
 312   // region allocation failure. If heap expansion fails we set this to
 313   // false so that we don't re-attempt the heap expansion (it's likely
 314   // that subsequent expansion attempts will also fail if one fails).
 315   // Currently, it is only consulted during GC and it's reset at the
 316   // start of each GC.
 317   bool _expand_heap_after_alloc_failure;
 318 
 319   // It resets the mutator alloc region before new allocations can take place.
 320   void init_mutator_alloc_region();
 321 
 322   // It releases the mutator alloc region.
 323   void release_mutator_alloc_region();
 324 
 325   // It initializes the GC alloc regions at the start of a GC.
 326   void init_gc_alloc_regions();
 327 
 328   // It releases the GC alloc regions at the end of a GC.
 329   void release_gc_alloc_regions(uint no_of_gc_workers);
 330 
 331   // It does any cleanup that needs to be done on the GC alloc regions
 332   // before a Full GC.
 333   void abandon_gc_alloc_regions();
 334 
 335   // Helper for monitoring and management support.
 336   G1MonitoringSupport* _g1mm;
 337 
 338   // Determines PLAB size for a particular allocation purpose.
 339   size_t desired_plab_sz(GCAllocPurpose purpose);
 340 
 341   // Outside of GC pauses, the number of bytes used in all regions other
 342   // than the current allocation region.
 343   size_t _summary_bytes_used;
 344 
 345   // This is used for a quick test on whether a reference points into
 346   // the collection set or not. Basically, we have an array, with one
 347   // byte per region, and that byte denotes whether the corresponding
 348   // region is in the collection set or not. The entry corresponding
 349   // the bottom of the heap, i.e., region 0, is pointed to by
 350   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 351   // biased so that it actually points to address 0 of the address
 352   // space, to make the test as fast as possible (we can simply shift
 353   // the address to address into it, instead of having to subtract the
 354   // bottom of the heap from the address before shifting it; basically
 355   // it works in the same way the card table works).
 356   bool* _in_cset_fast_test;
 357 
 358   // The allocated array used for the fast test on whether a reference
 359   // points into the collection set or not. This field is also used to
 360   // free the array.
 361   bool* _in_cset_fast_test_base;
 362 
 363   // The length of the _in_cset_fast_test_base array.
 364   uint _in_cset_fast_test_length;
 365 
 366   volatile unsigned _gc_time_stamp;
 367 
 368   size_t* _surviving_young_words;
 369 
 370   G1HRPrinter _hr_printer;
 371 
 372   void setup_surviving_young_words();
 373   void update_surviving_young_words(size_t* surv_young_words);
 374   void cleanup_surviving_young_words();
 375 
 376   // It decides whether an explicit GC should start a concurrent cycle
 377   // instead of doing a STW GC. Currently, a concurrent cycle is
 378   // explicitly started if:
 379   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 380   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 381   // (c) cause == _g1_humongous_allocation
 382   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 383 
 384   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 385   // concurrent cycles) we have started.
 386   volatile unsigned int _old_marking_cycles_started;
 387 
 388   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 389   // concurrent cycles) we have completed.
 390   volatile unsigned int _old_marking_cycles_completed;
 391 
 392   // This is a non-product method that is helpful for testing. It is
 393   // called at the end of a GC and artificially expands the heap by
 394   // allocating a number of dead regions. This way we can induce very
 395   // frequent marking cycles and stress the cleanup / concurrent
 396   // cleanup code more (as all the regions that will be allocated by
 397   // this method will be found dead by the marking cycle).
 398   void allocate_dummy_regions() PRODUCT_RETURN;
 399 
 400   // Clear RSets after a compaction. It also resets the GC time stamps.
 401   void clear_rsets_post_compaction();
 402 
 403   // If the HR printer is active, dump the state of the regions in the
 404   // heap after a compaction.
 405   void print_hrs_post_compaction();
 406 
 407   double verify(bool guard, const char* msg);
 408   void verify_before_gc();
 409   void verify_after_gc();
 410 
 411   void log_gc_header();
 412   void log_gc_footer(double pause_time_sec);
 413 
 414   // These are macros so that, if the assert fires, we get the correct
 415   // line number, file, etc.
 416 
 417 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 418   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 419           (_extra_message_),                                                  \
 420           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 421           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 422           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 423 
 424 #define assert_heap_locked()                                                  \
 425   do {                                                                        \
 426     assert(Heap_lock->owned_by_self(),                                        \
 427            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 428   } while (0)
 429 
 430 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 431   do {                                                                        \
 432     assert(Heap_lock->owned_by_self() ||                                      \
 433            (SafepointSynchronize::is_at_safepoint() &&                        \
 434              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 435            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 436                                         "should be at a safepoint"));         \
 437   } while (0)
 438 
 439 #define assert_heap_locked_and_not_at_safepoint()                             \
 440   do {                                                                        \
 441     assert(Heap_lock->owned_by_self() &&                                      \
 442                                     !SafepointSynchronize::is_at_safepoint(), \
 443           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 444                                        "should not be at a safepoint"));      \
 445   } while (0)
 446 
 447 #define assert_heap_not_locked()                                              \
 448   do {                                                                        \
 449     assert(!Heap_lock->owned_by_self(),                                       \
 450         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 451   } while (0)
 452 
 453 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 454   do {                                                                        \
 455     assert(!Heap_lock->owned_by_self() &&                                     \
 456                                     !SafepointSynchronize::is_at_safepoint(), \
 457       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 458                                    "should not be at a safepoint"));          \
 459   } while (0)
 460 
 461 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 462   do {                                                                        \
 463     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 464               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 465            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 466   } while (0)
 467 
 468 #define assert_not_at_safepoint()                                             \
 469   do {                                                                        \
 470     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 471            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 472   } while (0)
 473 
 474 protected:
 475 
 476   // The young region list.
 477   YoungList*  _young_list;
 478 
 479   // The current policy object for the collector.
 480   G1CollectorPolicy* _g1_policy;
 481 
 482   // This is the second level of trying to allocate a new region. If
 483   // new_region() didn't find a region on the free_list, this call will
 484   // check whether there's anything available on the
 485   // secondary_free_list and/or wait for more regions to appear on
 486   // that list, if _free_regions_coming is set.
 487   HeapRegion* new_region_try_secondary_free_list();
 488 
 489   // Try to allocate a single non-humongous HeapRegion sufficient for
 490   // an allocation of the given word_size. If do_expand is true,
 491   // attempt to expand the heap if necessary to satisfy the allocation
 492   // request.
 493   HeapRegion* new_region(size_t word_size, bool do_expand);
 494 
 495   // Attempt to satisfy a humongous allocation request of the given
 496   // size by finding a contiguous set of free regions of num_regions
 497   // length and remove them from the master free list. Return the
 498   // index of the first region or G1_NULL_HRS_INDEX if the search
 499   // was unsuccessful.
 500   uint humongous_obj_allocate_find_first(uint num_regions,
 501                                          size_t word_size);
 502 
 503   // Initialize a contiguous set of free regions of length num_regions
 504   // and starting at index first so that they appear as a single
 505   // humongous region.
 506   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 507                                                       uint num_regions,
 508                                                       size_t word_size);
 509 
 510   // Attempt to allocate a humongous object of the given size. Return
 511   // NULL if unsuccessful.
 512   HeapWord* humongous_obj_allocate(size_t word_size);
 513 
 514   // The following two methods, allocate_new_tlab() and
 515   // mem_allocate(), are the two main entry points from the runtime
 516   // into the G1's allocation routines. They have the following
 517   // assumptions:
 518   //
 519   // * They should both be called outside safepoints.
 520   //
 521   // * They should both be called without holding the Heap_lock.
 522   //
 523   // * All allocation requests for new TLABs should go to
 524   //   allocate_new_tlab().
 525   //
 526   // * All non-TLAB allocation requests should go to mem_allocate().
 527   //
 528   // * If either call cannot satisfy the allocation request using the
 529   //   current allocating region, they will try to get a new one. If
 530   //   this fails, they will attempt to do an evacuation pause and
 531   //   retry the allocation.
 532   //
 533   // * If all allocation attempts fail, even after trying to schedule
 534   //   an evacuation pause, allocate_new_tlab() will return NULL,
 535   //   whereas mem_allocate() will attempt a heap expansion and/or
 536   //   schedule a Full GC.
 537   //
 538   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 539   //   should never be called with word_size being humongous. All
 540   //   humongous allocation requests should go to mem_allocate() which
 541   //   will satisfy them with a special path.
 542 
 543   virtual HeapWord* allocate_new_tlab(size_t word_size);
 544 
 545   virtual HeapWord* mem_allocate(size_t word_size,
 546                                  bool*  gc_overhead_limit_was_exceeded);
 547 
 548   // The following three methods take a gc_count_before_ret
 549   // parameter which is used to return the GC count if the method
 550   // returns NULL. Given that we are required to read the GC count
 551   // while holding the Heap_lock, and these paths will take the
 552   // Heap_lock at some point, it's easier to get them to read the GC
 553   // count while holding the Heap_lock before they return NULL instead
 554   // of the caller (namely: mem_allocate()) having to also take the
 555   // Heap_lock just to read the GC count.
 556 
 557   // First-level mutator allocation attempt: try to allocate out of
 558   // the mutator alloc region without taking the Heap_lock. This
 559   // should only be used for non-humongous allocations.
 560   inline HeapWord* attempt_allocation(size_t word_size,
 561                                       unsigned int* gc_count_before_ret,
 562                                       int* gclocker_retry_count_ret);
 563 
 564   // Second-level mutator allocation attempt: take the Heap_lock and
 565   // retry the allocation attempt, potentially scheduling a GC
 566   // pause. This should only be used for non-humongous allocations.
 567   HeapWord* attempt_allocation_slow(size_t word_size,
 568                                     unsigned int* gc_count_before_ret,
 569                                     int* gclocker_retry_count_ret);
 570 
 571   // Takes the Heap_lock and attempts a humongous allocation. It can
 572   // potentially schedule a GC pause.
 573   HeapWord* attempt_allocation_humongous(size_t word_size,
 574                                          unsigned int* gc_count_before_ret,
 575                                          int* gclocker_retry_count_ret);
 576 
 577   // Allocation attempt that should be called during safepoints (e.g.,
 578   // at the end of a successful GC). expect_null_mutator_alloc_region
 579   // specifies whether the mutator alloc region is expected to be NULL
 580   // or not.
 581   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 582                                        bool expect_null_mutator_alloc_region);
 583 
 584   // It dirties the cards that cover the block so that so that the post
 585   // write barrier never queues anything when updating objects on this
 586   // block. It is assumed (and in fact we assert) that the block
 587   // belongs to a young region.
 588   inline void dirty_young_block(HeapWord* start, size_t word_size);
 589 
 590   // Allocate blocks during garbage collection. Will ensure an
 591   // allocation region, either by picking one or expanding the
 592   // heap, and then allocate a block of the given size. The block
 593   // may not be a humongous - it must fit into a single heap region.
 594   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 595 
 596   // Ensure that no further allocations can happen in "r", bearing in mind
 597   // that parallel threads might be attempting allocations.
 598   void par_allocate_remaining_space(HeapRegion* r);
 599 
 600   // Allocation attempt during GC for a survivor object / PLAB.
 601   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 602 
 603   // Allocation attempt during GC for an old object / PLAB.
 604   inline HeapWord* old_attempt_allocation(size_t word_size);
 605 
 606   // These methods are the "callbacks" from the G1AllocRegion class.
 607 
 608   // For mutator alloc regions.
 609   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 610   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 611                                    size_t allocated_bytes);
 612 
 613   // For GC alloc regions.
 614   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 615                                   GCAllocPurpose ap);
 616   void retire_gc_alloc_region(HeapRegion* alloc_region,
 617                               size_t allocated_bytes, GCAllocPurpose ap);
 618 
 619   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 620   //   inspection request and should collect the entire heap
 621   // - if clear_all_soft_refs is true, all soft references should be
 622   //   cleared during the GC
 623   // - if explicit_gc is false, word_size describes the allocation that
 624   //   the GC should attempt (at least) to satisfy
 625   // - it returns false if it is unable to do the collection due to the
 626   //   GC locker being active, true otherwise
 627   bool do_collection(bool explicit_gc,
 628                      bool clear_all_soft_refs,
 629                      size_t word_size);
 630 
 631   // Callback from VM_G1CollectFull operation.
 632   // Perform a full collection.
 633   virtual void do_full_collection(bool clear_all_soft_refs);
 634 
 635   // Resize the heap if necessary after a full collection.  If this is
 636   // after a collect-for allocation, "word_size" is the allocation size,
 637   // and will be considered part of the used portion of the heap.
 638   void resize_if_necessary_after_full_collection(size_t word_size);
 639 
 640   // Callback from VM_G1CollectForAllocation operation.
 641   // This function does everything necessary/possible to satisfy a
 642   // failed allocation request (including collection, expansion, etc.)
 643   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 644 
 645   // Attempting to expand the heap sufficiently
 646   // to support an allocation of the given "word_size".  If
 647   // successful, perform the allocation and return the address of the
 648   // allocated block, or else "NULL".
 649   HeapWord* expand_and_allocate(size_t word_size);
 650 
 651   // Process any reference objects discovered during
 652   // an incremental evacuation pause.
 653   void process_discovered_references(uint no_of_gc_workers);
 654 
 655   // Enqueue any remaining discovered references
 656   // after processing.
 657   void enqueue_discovered_references(uint no_of_gc_workers);
 658 
 659 public:
 660 
 661   G1MonitoringSupport* g1mm() {
 662     assert(_g1mm != NULL, "should have been initialized");
 663     return _g1mm;
 664   }
 665 
 666   // Expand the garbage-first heap by at least the given size (in bytes!).
 667   // Returns true if the heap was expanded by the requested amount;
 668   // false otherwise.
 669   // (Rounds up to a HeapRegion boundary.)
 670   bool expand(size_t expand_bytes);
 671 
 672   // Do anything common to GC's.
 673   virtual void gc_prologue(bool full);
 674   virtual void gc_epilogue(bool full);
 675 
 676   // We register a region with the fast "in collection set" test. We
 677   // simply set to true the array slot corresponding to this region.
 678   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 679     assert(_in_cset_fast_test_base != NULL, "sanity");
 680     assert(r->in_collection_set(), "invariant");
 681     uint index = r->hrs_index();
 682     assert(index < _in_cset_fast_test_length, "invariant");
 683     assert(!_in_cset_fast_test_base[index], "invariant");
 684     _in_cset_fast_test_base[index] = true;
 685   }
 686 
 687   // This is a fast test on whether a reference points into the
 688   // collection set or not. It does not assume that the reference
 689   // points into the heap; if it doesn't, it will return false.
 690   bool in_cset_fast_test(oop obj) {
 691     assert(_in_cset_fast_test != NULL, "sanity");
 692     if (_g1_committed.contains((HeapWord*) obj)) {
 693       // no need to subtract the bottom of the heap from obj,
 694       // _in_cset_fast_test is biased
 695       uintx index = (uintx) obj >> HeapRegion::LogOfHRGrainBytes;
 696       bool ret = _in_cset_fast_test[index];
 697       // let's make sure the result is consistent with what the slower
 698       // test returns
 699       assert( ret || !obj_in_cs(obj), "sanity");
 700       assert(!ret ||  obj_in_cs(obj), "sanity");
 701       return ret;
 702     } else {
 703       return false;
 704     }
 705   }
 706 
 707   void clear_cset_fast_test() {
 708     assert(_in_cset_fast_test_base != NULL, "sanity");
 709     memset(_in_cset_fast_test_base, false,
 710            (size_t) _in_cset_fast_test_length * sizeof(bool));
 711   }
 712 
 713   // This is called at the start of either a concurrent cycle or a Full
 714   // GC to update the number of old marking cycles started.
 715   void increment_old_marking_cycles_started();
 716 
 717   // This is called at the end of either a concurrent cycle or a Full
 718   // GC to update the number of old marking cycles completed. Those two
 719   // can happen in a nested fashion, i.e., we start a concurrent
 720   // cycle, a Full GC happens half-way through it which ends first,
 721   // and then the cycle notices that a Full GC happened and ends
 722   // too. The concurrent parameter is a boolean to help us do a bit
 723   // tighter consistency checking in the method. If concurrent is
 724   // false, the caller is the inner caller in the nesting (i.e., the
 725   // Full GC). If concurrent is true, the caller is the outer caller
 726   // in this nesting (i.e., the concurrent cycle). Further nesting is
 727   // not currently supported. The end of this call also notifies
 728   // the FullGCCount_lock in case a Java thread is waiting for a full
 729   // GC to happen (e.g., it called System.gc() with
 730   // +ExplicitGCInvokesConcurrent).
 731   void increment_old_marking_cycles_completed(bool concurrent);
 732 
 733   unsigned int old_marking_cycles_completed() {
 734     return _old_marking_cycles_completed;
 735   }
 736 
 737   G1HRPrinter* hr_printer() { return &_hr_printer; }
 738 
 739 protected:
 740 
 741   // Shrink the garbage-first heap by at most the given size (in bytes!).
 742   // (Rounds down to a HeapRegion boundary.)
 743   virtual void shrink(size_t expand_bytes);
 744   void shrink_helper(size_t expand_bytes);
 745 
 746   #if TASKQUEUE_STATS
 747   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 748   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 749   void reset_taskqueue_stats();
 750   #endif // TASKQUEUE_STATS
 751 
 752   // Schedule the VM operation that will do an evacuation pause to
 753   // satisfy an allocation request of word_size. *succeeded will
 754   // return whether the VM operation was successful (it did do an
 755   // evacuation pause) or not (another thread beat us to it or the GC
 756   // locker was active). Given that we should not be holding the
 757   // Heap_lock when we enter this method, we will pass the
 758   // gc_count_before (i.e., total_collections()) as a parameter since
 759   // it has to be read while holding the Heap_lock. Currently, both
 760   // methods that call do_collection_pause() release the Heap_lock
 761   // before the call, so it's easy to read gc_count_before just before.
 762   HeapWord* do_collection_pause(size_t       word_size,
 763                                 unsigned int gc_count_before,
 764                                 bool*        succeeded);
 765 
 766   // The guts of the incremental collection pause, executed by the vm
 767   // thread. It returns false if it is unable to do the collection due
 768   // to the GC locker being active, true otherwise
 769   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 770 
 771   // Actually do the work of evacuating the collection set.
 772   void evacuate_collection_set();
 773 
 774   // The g1 remembered set of the heap.
 775   G1RemSet* _g1_rem_set;
 776   // And it's mod ref barrier set, used to track updates for the above.
 777   ModRefBarrierSet* _mr_bs;
 778 
 779   // A set of cards that cover the objects for which the Rsets should be updated
 780   // concurrently after the collection.
 781   DirtyCardQueueSet _dirty_card_queue_set;
 782 
 783   // The closure used to refine a single card.
 784   RefineCardTableEntryClosure* _refine_cte_cl;
 785 
 786   // A function to check the consistency of dirty card logs.
 787   void check_ct_logs_at_safepoint();
 788 
 789   // A DirtyCardQueueSet that is used to hold cards that contain
 790   // references into the current collection set. This is used to
 791   // update the remembered sets of the regions in the collection
 792   // set in the event of an evacuation failure.
 793   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 794 
 795   // After a collection pause, make the regions in the CS into free
 796   // regions.
 797   void free_collection_set(HeapRegion* cs_head);
 798 
 799   // Abandon the current collection set without recording policy
 800   // statistics or updating free lists.
 801   void abandon_collection_set(HeapRegion* cs_head);
 802 
 803   // Applies "scan_non_heap_roots" to roots outside the heap,
 804   // "scan_rs" to roots inside the heap (having done "set_region" to
 805   // indicate the region in which the root resides),
 806   // and does "scan_metadata" If "scan_rs" is
 807   // NULL, then this step is skipped.  The "worker_i"
 808   // param is for use with parallel roots processing, and should be
 809   // the "i" of the calling parallel worker thread's work(i) function.
 810   // In the sequential case this param will be ignored.
 811   void g1_process_strong_roots(bool is_scavenging,
 812                                ScanningOption so,
 813                                OopClosure* scan_non_heap_roots,
 814                                OopsInHeapRegionClosure* scan_rs,
 815                                G1KlassScanClosure* scan_klasses,
 816                                int worker_i);
 817 
 818   // Apply "blk" to all the weak roots of the system.  These include
 819   // JNI weak roots, the code cache, system dictionary, symbol table,
 820   // string table, and referents of reachable weak refs.
 821   void g1_process_weak_roots(OopClosure* root_closure);
 822 
 823   // Frees a non-humongous region by initializing its contents and
 824   // adding it to the free list that's passed as a parameter (this is
 825   // usually a local list which will be appended to the master free
 826   // list later). The used bytes of freed regions are accumulated in
 827   // pre_used. If par is true, the region's RSet will not be freed
 828   // up. The assumption is that this will be done later.
 829   void free_region(HeapRegion* hr,
 830                    size_t* pre_used,
 831                    FreeRegionList* free_list,
 832                    bool par);
 833 
 834   // Frees a humongous region by collapsing it into individual regions
 835   // and calling free_region() for each of them. The freed regions
 836   // will be added to the free list that's passed as a parameter (this
 837   // is usually a local list which will be appended to the master free
 838   // list later). The used bytes of freed regions are accumulated in
 839   // pre_used. If par is true, the region's RSet will not be freed
 840   // up. The assumption is that this will be done later.
 841   void free_humongous_region(HeapRegion* hr,
 842                              size_t* pre_used,
 843                              FreeRegionList* free_list,
 844                              HumongousRegionSet* humongous_proxy_set,
 845                              bool par);
 846 
 847   // Notifies all the necessary spaces that the committed space has
 848   // been updated (either expanded or shrunk). It should be called
 849   // after _g1_storage is updated.
 850   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 851 
 852   // The concurrent marker (and the thread it runs in.)
 853   ConcurrentMark* _cm;
 854   ConcurrentMarkThread* _cmThread;
 855   bool _mark_in_progress;
 856 
 857   // The concurrent refiner.
 858   ConcurrentG1Refine* _cg1r;
 859 
 860   // The parallel task queues
 861   RefToScanQueueSet *_task_queues;
 862 
 863   // True iff a evacuation has failed in the current collection.
 864   bool _evacuation_failed;
 865 
 866   // Set the attribute indicating whether evacuation has failed in the
 867   // current collection.
 868   void set_evacuation_failed(bool b) { _evacuation_failed = b; }
 869 
 870   // Failed evacuations cause some logical from-space objects to have
 871   // forwarding pointers to themselves.  Reset them.
 872   void remove_self_forwarding_pointers();
 873 
 874   // Together, these store an object with a preserved mark, and its mark value.
 875   Stack<oop, mtGC>     _objs_with_preserved_marks;
 876   Stack<markOop, mtGC> _preserved_marks_of_objs;
 877 
 878   // Preserve the mark of "obj", if necessary, in preparation for its mark
 879   // word being overwritten with a self-forwarding-pointer.
 880   void preserve_mark_if_necessary(oop obj, markOop m);
 881 
 882   // The stack of evac-failure objects left to be scanned.
 883   GrowableArray<oop>*    _evac_failure_scan_stack;
 884   // The closure to apply to evac-failure objects.
 885 
 886   OopsInHeapRegionClosure* _evac_failure_closure;
 887   // Set the field above.
 888   void
 889   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 890     _evac_failure_closure = evac_failure_closure;
 891   }
 892 
 893   // Push "obj" on the scan stack.
 894   void push_on_evac_failure_scan_stack(oop obj);
 895   // Process scan stack entries until the stack is empty.
 896   void drain_evac_failure_scan_stack();
 897   // True iff an invocation of "drain_scan_stack" is in progress; to
 898   // prevent unnecessary recursion.
 899   bool _drain_in_progress;
 900 
 901   // Do any necessary initialization for evacuation-failure handling.
 902   // "cl" is the closure that will be used to process evac-failure
 903   // objects.
 904   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 905   // Do any necessary cleanup for evacuation-failure handling data
 906   // structures.
 907   void finalize_for_evac_failure();
 908 
 909   // An attempt to evacuate "obj" has failed; take necessary steps.
 910   oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
 911   void handle_evacuation_failure_common(oop obj, markOop m);
 912 
 913 #ifndef PRODUCT
 914   // Support for forcing evacuation failures. Analogous to
 915   // PromotionFailureALot for the other collectors.
 916 
 917   // Records whether G1EvacuationFailureALot should be in effect
 918   // for the current GC
 919   bool _evacuation_failure_alot_for_current_gc;
 920 
 921   // Used to record the GC number for interval checking when
 922   // determining whether G1EvaucationFailureALot is in effect
 923   // for the current GC.
 924   size_t _evacuation_failure_alot_gc_number;
 925 
 926   // Count of the number of evacuations between failures.
 927   volatile size_t _evacuation_failure_alot_count;
 928 
 929   // Set whether G1EvacuationFailureALot should be in effect
 930   // for the current GC (based upon the type of GC and which
 931   // command line flags are set);
 932   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 933                                                   bool during_initial_mark,
 934                                                   bool during_marking);
 935 
 936   inline void set_evacuation_failure_alot_for_current_gc();
 937 
 938   // Return true if it's time to cause an evacuation failure.
 939   inline bool evacuation_should_fail();
 940 
 941   // Reset the G1EvacuationFailureALot counters.  Should be called at
 942   // the end of an evacuation pause in which an evacuation failure ocurred.
 943   inline void reset_evacuation_should_fail();
 944 #endif // !PRODUCT
 945 
 946   // ("Weak") Reference processing support.
 947   //
 948   // G1 has 2 instances of the referece processor class. One
 949   // (_ref_processor_cm) handles reference object discovery
 950   // and subsequent processing during concurrent marking cycles.
 951   //
 952   // The other (_ref_processor_stw) handles reference object
 953   // discovery and processing during full GCs and incremental
 954   // evacuation pauses.
 955   //
 956   // During an incremental pause, reference discovery will be
 957   // temporarily disabled for _ref_processor_cm and will be
 958   // enabled for _ref_processor_stw. At the end of the evacuation
 959   // pause references discovered by _ref_processor_stw will be
 960   // processed and discovery will be disabled. The previous
 961   // setting for reference object discovery for _ref_processor_cm
 962   // will be re-instated.
 963   //
 964   // At the start of marking:
 965   //  * Discovery by the CM ref processor is verified to be inactive
 966   //    and it's discovered lists are empty.
 967   //  * Discovery by the CM ref processor is then enabled.
 968   //
 969   // At the end of marking:
 970   //  * Any references on the CM ref processor's discovered
 971   //    lists are processed (possibly MT).
 972   //
 973   // At the start of full GC we:
 974   //  * Disable discovery by the CM ref processor and
 975   //    empty CM ref processor's discovered lists
 976   //    (without processing any entries).
 977   //  * Verify that the STW ref processor is inactive and it's
 978   //    discovered lists are empty.
 979   //  * Temporarily set STW ref processor discovery as single threaded.
 980   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 981   //    field.
 982   //  * Finally enable discovery by the STW ref processor.
 983   //
 984   // The STW ref processor is used to record any discovered
 985   // references during the full GC.
 986   //
 987   // At the end of a full GC we:
 988   //  * Enqueue any reference objects discovered by the STW ref processor
 989   //    that have non-live referents. This has the side-effect of
 990   //    making the STW ref processor inactive by disabling discovery.
 991   //  * Verify that the CM ref processor is still inactive
 992   //    and no references have been placed on it's discovered
 993   //    lists (also checked as a precondition during initial marking).
 994 
 995   // The (stw) reference processor...
 996   ReferenceProcessor* _ref_processor_stw;
 997 
 998   // During reference object discovery, the _is_alive_non_header
 999   // closure (if non-null) is applied to the referent object to
1000   // determine whether the referent is live. If so then the
1001   // reference object does not need to be 'discovered' and can
1002   // be treated as a regular oop. This has the benefit of reducing
1003   // the number of 'discovered' reference objects that need to
1004   // be processed.
1005   //
1006   // Instance of the is_alive closure for embedding into the
1007   // STW reference processor as the _is_alive_non_header field.
1008   // Supplying a value for the _is_alive_non_header field is
1009   // optional but doing so prevents unnecessary additions to
1010   // the discovered lists during reference discovery.
1011   G1STWIsAliveClosure _is_alive_closure_stw;
1012 
1013   // The (concurrent marking) reference processor...
1014   ReferenceProcessor* _ref_processor_cm;
1015 
1016   // Instance of the concurrent mark is_alive closure for embedding
1017   // into the Concurrent Marking reference processor as the
1018   // _is_alive_non_header field. Supplying a value for the
1019   // _is_alive_non_header field is optional but doing so prevents
1020   // unnecessary additions to the discovered lists during reference
1021   // discovery.
1022   G1CMIsAliveClosure _is_alive_closure_cm;
1023 
1024   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1025   HeapRegion** _worker_cset_start_region;
1026 
1027   // Time stamp to validate the regions recorded in the cache
1028   // used by G1CollectedHeap::start_cset_region_for_worker().
1029   // The heap region entry for a given worker is valid iff
1030   // the associated time stamp value matches the current value
1031   // of G1CollectedHeap::_gc_time_stamp.
1032   unsigned int* _worker_cset_start_region_time_stamp;
1033 
1034   enum G1H_process_strong_roots_tasks {
1035     G1H_PS_filter_satb_buffers,
1036     G1H_PS_refProcessor_oops_do,
1037     // Leave this one last.
1038     G1H_PS_NumElements
1039   };
1040 
1041   SubTasksDone* _process_strong_tasks;
1042 
1043   volatile bool _free_regions_coming;
1044 
1045 public:
1046 
1047   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1048 
1049   void set_refine_cte_cl_concurrency(bool concurrent);
1050 
1051   RefToScanQueue *task_queue(int i) const;
1052 
1053   // A set of cards where updates happened during the GC
1054   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1055 
1056   // A DirtyCardQueueSet that is used to hold cards that contain
1057   // references into the current collection set. This is used to
1058   // update the remembered sets of the regions in the collection
1059   // set in the event of an evacuation failure.
1060   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1061         { return _into_cset_dirty_card_queue_set; }
1062 
1063   // Create a G1CollectedHeap with the specified policy.
1064   // Must call the initialize method afterwards.
1065   // May not return if something goes wrong.
1066   G1CollectedHeap(G1CollectorPolicy* policy);
1067 
1068   // Initialize the G1CollectedHeap to have the initial and
1069   // maximum sizes and remembered and barrier sets
1070   // specified by the policy object.
1071   jint initialize();
1072 
1073   // Initialize weak reference processing.
1074   virtual void ref_processing_init();
1075 
1076   void set_par_threads(uint t) {
1077     SharedHeap::set_par_threads(t);
1078     // Done in SharedHeap but oddly there are
1079     // two _process_strong_tasks's in a G1CollectedHeap
1080     // so do it here too.
1081     _process_strong_tasks->set_n_threads(t);
1082   }
1083 
1084   // Set _n_par_threads according to a policy TBD.
1085   void set_par_threads();
1086 
1087   void set_n_termination(int t) {
1088     _process_strong_tasks->set_n_threads(t);
1089   }
1090 
1091   virtual CollectedHeap::Name kind() const {
1092     return CollectedHeap::G1CollectedHeap;
1093   }
1094 
1095   // The current policy object for the collector.
1096   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1097 
1098   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1099 
1100   // Adaptive size policy.  No such thing for g1.
1101   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1102 
1103   // The rem set and barrier set.
1104   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1105   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
1106 
1107   unsigned get_gc_time_stamp() {
1108     return _gc_time_stamp;
1109   }
1110 
1111   void reset_gc_time_stamp() {
1112     _gc_time_stamp = 0;
1113     OrderAccess::fence();
1114     // Clear the cached CSet starting regions and time stamps.
1115     // Their validity is dependent on the GC timestamp.
1116     clear_cset_start_regions();
1117   }
1118 
1119   void check_gc_time_stamps() PRODUCT_RETURN;
1120 
1121   void increment_gc_time_stamp() {
1122     ++_gc_time_stamp;
1123     OrderAccess::fence();
1124   }
1125 
1126   // Reset the given region's GC timestamp. If it's starts humongous,
1127   // also reset the GC timestamp of its corresponding
1128   // continues humongous regions too.
1129   void reset_gc_time_stamps(HeapRegion* hr);
1130 
1131   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1132                                   DirtyCardQueue* into_cset_dcq,
1133                                   bool concurrent, int worker_i);
1134 
1135   // The shared block offset table array.
1136   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1137 
1138   // Reference Processing accessors
1139 
1140   // The STW reference processor....
1141   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1142 
1143   // The Concurent Marking reference processor...
1144   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1145 
1146   virtual size_t capacity() const;
1147   virtual size_t used() const;
1148   // This should be called when we're not holding the heap lock. The
1149   // result might be a bit inaccurate.
1150   size_t used_unlocked() const;
1151   size_t recalculate_used() const;
1152 
1153   // These virtual functions do the actual allocation.
1154   // Some heaps may offer a contiguous region for shared non-blocking
1155   // allocation, via inlined code (by exporting the address of the top and
1156   // end fields defining the extent of the contiguous allocation region.)
1157   // But G1CollectedHeap doesn't yet support this.
1158 
1159   // Return an estimate of the maximum allocation that could be performed
1160   // without triggering any collection or expansion activity.  In a
1161   // generational collector, for example, this is probably the largest
1162   // allocation that could be supported (without expansion) in the youngest
1163   // generation.  It is "unsafe" because no locks are taken; the result
1164   // should be treated as an approximation, not a guarantee, for use in
1165   // heuristic resizing decisions.
1166   virtual size_t unsafe_max_alloc();
1167 
1168   virtual bool is_maximal_no_gc() const {
1169     return _g1_storage.uncommitted_size() == 0;
1170   }
1171 
1172   // The total number of regions in the heap.
1173   uint n_regions() { return _hrs.length(); }
1174 
1175   // The max number of regions in the heap.
1176   uint max_regions() { return _hrs.max_length(); }
1177 
1178   // The number of regions that are completely free.
1179   uint free_regions() { return _free_list.length(); }
1180 
1181   // The number of regions that are not completely free.
1182   uint used_regions() { return n_regions() - free_regions(); }
1183 
1184   // The number of regions available for "regular" expansion.
1185   uint expansion_regions() { return _expansion_regions; }
1186 
1187   // Factory method for HeapRegion instances. It will return NULL if
1188   // the allocation fails.
1189   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1190 
1191   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1192   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1193   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1194   void verify_dirty_young_regions() PRODUCT_RETURN;
1195 
1196   // verify_region_sets() performs verification over the region
1197   // lists. It will be compiled in the product code to be used when
1198   // necessary (i.e., during heap verification).
1199   void verify_region_sets();
1200 
1201   // verify_region_sets_optional() is planted in the code for
1202   // list verification in non-product builds (and it can be enabled in
1203   // product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1).
1204 #if HEAP_REGION_SET_FORCE_VERIFY
1205   void verify_region_sets_optional() {
1206     verify_region_sets();
1207   }
1208 #else // HEAP_REGION_SET_FORCE_VERIFY
1209   void verify_region_sets_optional() { }
1210 #endif // HEAP_REGION_SET_FORCE_VERIFY
1211 
1212 #ifdef ASSERT
1213   bool is_on_master_free_list(HeapRegion* hr) {
1214     return hr->containing_set() == &_free_list;
1215   }
1216 
1217   bool is_in_humongous_set(HeapRegion* hr) {
1218     return hr->containing_set() == &_humongous_set;
1219   }
1220 #endif // ASSERT
1221 
1222   // Wrapper for the region list operations that can be called from
1223   // methods outside this class.
1224 
1225   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1226     _secondary_free_list.add_as_tail(list);
1227   }
1228 
1229   void append_secondary_free_list() {
1230     _free_list.add_as_head(&_secondary_free_list);
1231   }
1232 
1233   void append_secondary_free_list_if_not_empty_with_lock() {
1234     // If the secondary free list looks empty there's no reason to
1235     // take the lock and then try to append it.
1236     if (!_secondary_free_list.is_empty()) {
1237       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1238       append_secondary_free_list();
1239     }
1240   }
1241 
1242   void old_set_remove(HeapRegion* hr) {
1243     _old_set.remove(hr);
1244   }
1245 
1246   size_t non_young_capacity_bytes() {
1247     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1248   }
1249 
1250   void set_free_regions_coming();
1251   void reset_free_regions_coming();
1252   bool free_regions_coming() { return _free_regions_coming; }
1253   void wait_while_free_regions_coming();
1254 
1255   // Determine whether the given region is one that we are using as an
1256   // old GC alloc region.
1257   bool is_old_gc_alloc_region(HeapRegion* hr) {
1258     return hr == _retained_old_gc_alloc_region;
1259   }
1260 
1261   // Perform a collection of the heap; intended for use in implementing
1262   // "System.gc".  This probably implies as full a collection as the
1263   // "CollectedHeap" supports.
1264   virtual void collect(GCCause::Cause cause);
1265 
1266   // The same as above but assume that the caller holds the Heap_lock.
1267   void collect_locked(GCCause::Cause cause);
1268 
1269   // True iff a evacuation has failed in the most-recent collection.
1270   bool evacuation_failed() { return _evacuation_failed; }
1271 
1272   // It will free a region if it has allocated objects in it that are
1273   // all dead. It calls either free_region() or
1274   // free_humongous_region() depending on the type of the region that
1275   // is passed to it.
1276   void free_region_if_empty(HeapRegion* hr,
1277                             size_t* pre_used,
1278                             FreeRegionList* free_list,
1279                             OldRegionSet* old_proxy_set,
1280                             HumongousRegionSet* humongous_proxy_set,
1281                             HRRSCleanupTask* hrrs_cleanup_task,
1282                             bool par);
1283 
1284   // It appends the free list to the master free list and updates the
1285   // master humongous list according to the contents of the proxy
1286   // list. It also adjusts the total used bytes according to pre_used
1287   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1288   void update_sets_after_freeing_regions(size_t pre_used,
1289                                        FreeRegionList* free_list,
1290                                        OldRegionSet* old_proxy_set,
1291                                        HumongousRegionSet* humongous_proxy_set,
1292                                        bool par);
1293 
1294   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1295   virtual bool is_in(const void* p) const;
1296 
1297   // Return "TRUE" iff the given object address is within the collection
1298   // set.
1299   inline bool obj_in_cs(oop obj);
1300 
1301   // Return "TRUE" iff the given object address is in the reserved
1302   // region of g1.
1303   bool is_in_g1_reserved(const void* p) const {
1304     return _g1_reserved.contains(p);
1305   }
1306 
1307   // Returns a MemRegion that corresponds to the space that has been
1308   // reserved for the heap
1309   MemRegion g1_reserved() {
1310     return _g1_reserved;
1311   }
1312 
1313   // Returns a MemRegion that corresponds to the space that has been
1314   // committed in the heap
1315   MemRegion g1_committed() {
1316     return _g1_committed;
1317   }
1318 
1319   virtual bool is_in_closed_subset(const void* p) const;
1320 
1321   // This resets the card table to all zeros.  It is used after
1322   // a collection pause which used the card table to claim cards.
1323   void cleanUpCardTable();
1324 
1325   // Iteration functions.
1326 
1327   // Iterate over all the ref-containing fields of all objects, calling
1328   // "cl.do_oop" on each.
1329   virtual void oop_iterate(ExtendedOopClosure* cl);
1330 
1331   // Same as above, restricted to a memory region.
1332   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1333 
1334   // Iterate over all objects, calling "cl.do_object" on each.
1335   virtual void object_iterate(ObjectClosure* cl);
1336 
1337   virtual void safe_object_iterate(ObjectClosure* cl) {
1338     object_iterate(cl);
1339   }
1340 
1341   // Iterate over all objects allocated since the last collection, calling
1342   // "cl.do_object" on each.  The heap must have been initialized properly
1343   // to support this function, or else this call will fail.
1344   virtual void object_iterate_since_last_GC(ObjectClosure* cl);
1345 
1346   // Iterate over all spaces in use in the heap, in ascending address order.
1347   virtual void space_iterate(SpaceClosure* cl);
1348 
1349   // Iterate over heap regions, in address order, terminating the
1350   // iteration early if the "doHeapRegion" method returns "true".
1351   void heap_region_iterate(HeapRegionClosure* blk) const;
1352 
1353   // Return the region with the given index. It assumes the index is valid.
1354   HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1355 
1356   // Divide the heap region sequence into "chunks" of some size (the number
1357   // of regions divided by the number of parallel threads times some
1358   // overpartition factor, currently 4).  Assumes that this will be called
1359   // in parallel by ParallelGCThreads worker threads with discinct worker
1360   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1361   // calls will use the same "claim_value", and that that claim value is
1362   // different from the claim_value of any heap region before the start of
1363   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1364   // attempting to claim the first region in each chunk, and, if
1365   // successful, applying the closure to each region in the chunk (and
1366   // setting the claim value of the second and subsequent regions of the
1367   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1368   // i.e., that a closure never attempt to abort a traversal.
1369   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1370                                        uint worker,
1371                                        uint no_of_par_workers,
1372                                        jint claim_value);
1373 
1374   // It resets all the region claim values to the default.
1375   void reset_heap_region_claim_values();
1376 
1377   // Resets the claim values of regions in the current
1378   // collection set to the default.
1379   void reset_cset_heap_region_claim_values();
1380 
1381 #ifdef ASSERT
1382   bool check_heap_region_claim_values(jint claim_value);
1383 
1384   // Same as the routine above but only checks regions in the
1385   // current collection set.
1386   bool check_cset_heap_region_claim_values(jint claim_value);
1387 #endif // ASSERT
1388 
1389   // Clear the cached cset start regions and (more importantly)
1390   // the time stamps. Called when we reset the GC time stamp.
1391   void clear_cset_start_regions();
1392 
1393   // Given the id of a worker, obtain or calculate a suitable
1394   // starting region for iterating over the current collection set.
1395   HeapRegion* start_cset_region_for_worker(int worker_i);
1396 
1397   // This is a convenience method that is used by the
1398   // HeapRegionIterator classes to calculate the starting region for
1399   // each worker so that they do not all start from the same region.
1400   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1401 
1402   // Iterate over the regions (if any) in the current collection set.
1403   void collection_set_iterate(HeapRegionClosure* blk);
1404 
1405   // As above but starting from region r
1406   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1407 
1408   // Returns the first (lowest address) compactible space in the heap.
1409   virtual CompactibleSpace* first_compactible_space();
1410 
1411   // A CollectedHeap will contain some number of spaces.  This finds the
1412   // space containing a given address, or else returns NULL.
1413   virtual Space* space_containing(const void* addr) const;
1414 
1415   // A G1CollectedHeap will contain some number of heap regions.  This
1416   // finds the region containing a given address, or else returns NULL.
1417   template <class T>
1418   inline HeapRegion* heap_region_containing(const T addr) const;
1419 
1420   // Like the above, but requires "addr" to be in the heap (to avoid a
1421   // null-check), and unlike the above, may return an continuing humongous
1422   // region.
1423   template <class T>
1424   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1425 
1426   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1427   // each address in the (reserved) heap is a member of exactly
1428   // one block.  The defining characteristic of a block is that it is
1429   // possible to find its size, and thus to progress forward to the next
1430   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1431   // represent Java objects, or they might be free blocks in a
1432   // free-list-based heap (or subheap), as long as the two kinds are
1433   // distinguishable and the size of each is determinable.
1434 
1435   // Returns the address of the start of the "block" that contains the
1436   // address "addr".  We say "blocks" instead of "object" since some heaps
1437   // may not pack objects densely; a chunk may either be an object or a
1438   // non-object.
1439   virtual HeapWord* block_start(const void* addr) const;
1440 
1441   // Requires "addr" to be the start of a chunk, and returns its size.
1442   // "addr + size" is required to be the start of a new chunk, or the end
1443   // of the active area of the heap.
1444   virtual size_t block_size(const HeapWord* addr) const;
1445 
1446   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1447   // the block is an object.
1448   virtual bool block_is_obj(const HeapWord* addr) const;
1449 
1450   // Does this heap support heap inspection? (+PrintClassHistogram)
1451   virtual bool supports_heap_inspection() const { return true; }
1452 
1453   // Section on thread-local allocation buffers (TLABs)
1454   // See CollectedHeap for semantics.
1455 
1456   virtual bool supports_tlab_allocation() const;
1457   virtual size_t tlab_capacity(Thread* thr) const;
1458   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1459 
1460   // Can a compiler initialize a new object without store barriers?
1461   // This permission only extends from the creation of a new object
1462   // via a TLAB up to the first subsequent safepoint. If such permission
1463   // is granted for this heap type, the compiler promises to call
1464   // defer_store_barrier() below on any slow path allocation of
1465   // a new object for which such initializing store barriers will
1466   // have been elided. G1, like CMS, allows this, but should be
1467   // ready to provide a compensating write barrier as necessary
1468   // if that storage came out of a non-young region. The efficiency
1469   // of this implementation depends crucially on being able to
1470   // answer very efficiently in constant time whether a piece of
1471   // storage in the heap comes from a young region or not.
1472   // See ReduceInitialCardMarks.
1473   virtual bool can_elide_tlab_store_barriers() const {
1474     return true;
1475   }
1476 
1477   virtual bool card_mark_must_follow_store() const {
1478     return true;
1479   }
1480 
1481   bool is_in_young(const oop obj) {
1482     HeapRegion* hr = heap_region_containing(obj);
1483     return hr != NULL && hr->is_young();
1484   }
1485 
1486 #ifdef ASSERT
1487   virtual bool is_in_partial_collection(const void* p);
1488 #endif
1489 
1490   virtual bool is_scavengable(const void* addr);
1491 
1492   // We don't need barriers for initializing stores to objects
1493   // in the young gen: for the SATB pre-barrier, there is no
1494   // pre-value that needs to be remembered; for the remembered-set
1495   // update logging post-barrier, we don't maintain remembered set
1496   // information for young gen objects.
1497   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1498     return is_in_young(new_obj);
1499   }
1500 
1501   // Returns "true" iff the given word_size is "very large".
1502   static bool isHumongous(size_t word_size) {
1503     // Note this has to be strictly greater-than as the TLABs
1504     // are capped at the humongous thresold and we want to
1505     // ensure that we don't try to allocate a TLAB as
1506     // humongous and that we don't allocate a humongous
1507     // object in a TLAB.
1508     return word_size > _humongous_object_threshold_in_words;
1509   }
1510 
1511   // Update mod union table with the set of dirty cards.
1512   void updateModUnion();
1513 
1514   // Set the mod union bits corresponding to the given memRegion.  Note
1515   // that this is always a safe operation, since it doesn't clear any
1516   // bits.
1517   void markModUnionRange(MemRegion mr);
1518 
1519   // Records the fact that a marking phase is no longer in progress.
1520   void set_marking_complete() {
1521     _mark_in_progress = false;
1522   }
1523   void set_marking_started() {
1524     _mark_in_progress = true;
1525   }
1526   bool mark_in_progress() {
1527     return _mark_in_progress;
1528   }
1529 
1530   // Print the maximum heap capacity.
1531   virtual size_t max_capacity() const;
1532 
1533   virtual jlong millis_since_last_gc();
1534 
1535   // Perform any cleanup actions necessary before allowing a verification.
1536   virtual void prepare_for_verify();
1537 
1538   // Perform verification.
1539 
1540   // vo == UsePrevMarking  -> use "prev" marking information,
1541   // vo == UseNextMarking -> use "next" marking information
1542   // vo == UseMarkWord    -> use the mark word in the object header
1543   //
1544   // NOTE: Only the "prev" marking information is guaranteed to be
1545   // consistent most of the time, so most calls to this should use
1546   // vo == UsePrevMarking.
1547   // Currently, there is only one case where this is called with
1548   // vo == UseNextMarking, which is to verify the "next" marking
1549   // information at the end of remark.
1550   // Currently there is only one place where this is called with
1551   // vo == UseMarkWord, which is to verify the marking during a
1552   // full GC.
1553   void verify(bool silent, VerifyOption vo);
1554 
1555   // Override; it uses the "prev" marking information
1556   virtual void verify(bool silent);
1557   virtual void print_on(outputStream* st) const;
1558   virtual void print_extended_on(outputStream* st) const;
1559   virtual void print_on_error(outputStream* st) const;
1560 
1561   virtual void print_gc_threads_on(outputStream* st) const;
1562   virtual void gc_threads_do(ThreadClosure* tc) const;
1563 
1564   // Override
1565   void print_tracing_info() const;
1566 
1567   // The following two methods are helpful for debugging RSet issues.
1568   void print_cset_rsets() PRODUCT_RETURN;
1569   void print_all_rsets() PRODUCT_RETURN;
1570 
1571   // Convenience function to be used in situations where the heap type can be
1572   // asserted to be this type.
1573   static G1CollectedHeap* heap();
1574 
1575   void set_region_short_lived_locked(HeapRegion* hr);
1576   // add appropriate methods for any other surv rate groups
1577 
1578   YoungList* young_list() { return _young_list; }
1579 
1580   // debugging
1581   bool check_young_list_well_formed() {
1582     return _young_list->check_list_well_formed();
1583   }
1584 
1585   bool check_young_list_empty(bool check_heap,
1586                               bool check_sample = true);
1587 
1588   // *** Stuff related to concurrent marking.  It's not clear to me that so
1589   // many of these need to be public.
1590 
1591   // The functions below are helper functions that a subclass of
1592   // "CollectedHeap" can use in the implementation of its virtual
1593   // functions.
1594   // This performs a concurrent marking of the live objects in a
1595   // bitmap off to the side.
1596   void doConcurrentMark();
1597 
1598   bool isMarkedPrev(oop obj) const;
1599   bool isMarkedNext(oop obj) const;
1600 
1601   // Determine if an object is dead, given the object and also
1602   // the region to which the object belongs. An object is dead
1603   // iff a) it was not allocated since the last mark and b) it
1604   // is not marked.
1605 
1606   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1607     return
1608       !hr->obj_allocated_since_prev_marking(obj) &&
1609       !isMarkedPrev(obj);
1610   }
1611 
1612   // This function returns true when an object has been
1613   // around since the previous marking and hasn't yet
1614   // been marked during this marking.
1615 
1616   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1617     return
1618       !hr->obj_allocated_since_next_marking(obj) &&
1619       !isMarkedNext(obj);
1620   }
1621 
1622   // Determine if an object is dead, given only the object itself.
1623   // This will find the region to which the object belongs and
1624   // then call the region version of the same function.
1625 
1626   // Added if it is NULL it isn't dead.
1627 
1628   bool is_obj_dead(const oop obj) const {
1629     const HeapRegion* hr = heap_region_containing(obj);
1630     if (hr == NULL) {
1631       if (obj == NULL) return false;
1632       else return true;
1633     }
1634     else return is_obj_dead(obj, hr);
1635   }
1636 
1637   bool is_obj_ill(const oop obj) const {
1638     const HeapRegion* hr = heap_region_containing(obj);
1639     if (hr == NULL) {
1640       if (obj == NULL) return false;
1641       else return true;
1642     }
1643     else return is_obj_ill(obj, hr);
1644   }
1645 
1646   // The methods below are here for convenience and dispatch the
1647   // appropriate method depending on value of the given VerifyOption
1648   // parameter. The options for that parameter are:
1649   //
1650   // vo == UsePrevMarking -> use "prev" marking information,
1651   // vo == UseNextMarking -> use "next" marking information,
1652   // vo == UseMarkWord    -> use mark word from object header
1653 
1654   bool is_obj_dead_cond(const oop obj,
1655                         const HeapRegion* hr,
1656                         const VerifyOption vo) const {
1657     switch (vo) {
1658     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1659     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1660     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1661     default:                            ShouldNotReachHere();
1662     }
1663     return false; // keep some compilers happy
1664   }
1665 
1666   bool is_obj_dead_cond(const oop obj,
1667                         const VerifyOption vo) const {
1668     switch (vo) {
1669     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1670     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1671     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1672     default:                            ShouldNotReachHere();
1673     }
1674     return false; // keep some compilers happy
1675   }
1676 
1677   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1678   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1679   bool is_marked(oop obj, VerifyOption vo);
1680   const char* top_at_mark_start_str(VerifyOption vo);
1681 
1682   // The following is just to alert the verification code
1683   // that a full collection has occurred and that the
1684   // remembered sets are no longer up to date.
1685   bool _full_collection;
1686   void set_full_collection() { _full_collection = true;}
1687   void clear_full_collection() {_full_collection = false;}
1688   bool full_collection() {return _full_collection;}
1689 
1690   ConcurrentMark* concurrent_mark() const { return _cm; }
1691   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1692 
1693   // The dirty cards region list is used to record a subset of regions
1694   // whose cards need clearing. The list if populated during the
1695   // remembered set scanning and drained during the card table
1696   // cleanup. Although the methods are reentrant, population/draining
1697   // phases must not overlap. For synchronization purposes the last
1698   // element on the list points to itself.
1699   HeapRegion* _dirty_cards_region_list;
1700   void push_dirty_cards_region(HeapRegion* hr);
1701   HeapRegion* pop_dirty_cards_region();
1702 
1703 public:
1704   void stop_conc_gc_threads();
1705 
1706   size_t pending_card_num();
1707   size_t cards_scanned();
1708 
1709 protected:
1710   size_t _max_heap_capacity;
1711 };
1712 
1713 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1714 private:
1715   bool        _retired;
1716 
1717 public:
1718   G1ParGCAllocBuffer(size_t gclab_word_size);
1719 
1720   void set_buf(HeapWord* buf) {
1721     ParGCAllocBuffer::set_buf(buf);
1722     _retired = false;
1723   }
1724 
1725   void retire(bool end_of_gc, bool retain) {
1726     if (_retired)
1727       return;
1728     ParGCAllocBuffer::retire(end_of_gc, retain);
1729     _retired = true;
1730   }
1731 
1732   bool is_retired() {
1733     return _retired;
1734   }
1735 };
1736 
1737 class G1ParGCAllocBufferContainer {
1738 protected:
1739   static int const _priority_max = 2;
1740   G1ParGCAllocBuffer* _priority_buffer[_priority_max];
1741 
1742 public:
1743   G1ParGCAllocBufferContainer(size_t gclab_word_size) {
1744     for (int pr = 0; pr < _priority_max; ++pr) {
1745       _priority_buffer[pr] = new G1ParGCAllocBuffer(gclab_word_size);
1746     }
1747   }
1748 
1749   ~G1ParGCAllocBufferContainer() {
1750     for (int pr = 0; pr < _priority_max; ++pr) {
1751       assert(_priority_buffer[pr]->is_retired(), "alloc buffers should all retire at this point.");
1752       delete _priority_buffer[pr];
1753     }
1754   }
1755 
1756   HeapWord* allocate(size_t word_sz) {
1757     HeapWord* obj;
1758     for (int pr = 0; pr < _priority_max; ++pr) {
1759       obj = _priority_buffer[pr]->allocate(word_sz);
1760       if (obj != NULL) return obj;
1761     }
1762     return obj;
1763   }
1764 
1765   bool contains(void* addr) {
1766     for (int pr = 0; pr < _priority_max; ++pr) {
1767       if (_priority_buffer[pr]->contains(addr)) return true;
1768     }
1769     return false;
1770   }
1771 
1772   void undo_allocation(HeapWord* obj, size_t word_sz) {
1773     bool finish_undo;
1774     for (int pr = 0; pr < _priority_max; ++pr) {
1775       if (_priority_buffer[pr]->contains(obj)) {
1776         _priority_buffer[pr]->undo_allocation(obj, word_sz);
1777         finish_undo = true;
1778       }
1779     }
1780     if (!finish_undo) ShouldNotReachHere();
1781   }
1782 
1783   size_t words_remaining() {
1784     size_t result = 0;
1785     for (int pr = 0; pr < _priority_max; ++pr) {
1786       result += _priority_buffer[pr]->words_remaining();
1787     }
1788     return result;
1789   }
1790 
1791   size_t words_remaining_in_retired_buffer() {
1792     G1ParGCAllocBuffer* retired = _priority_buffer[0];
1793     return retired->words_remaining();
1794   }
1795 
1796   void flush_stats_and_retire(PLABStats* stats, bool end_of_gc, bool retain) {
1797     for (int pr = 0; pr < _priority_max; ++pr) {
1798       _priority_buffer[pr]->flush_stats_and_retire(stats, end_of_gc, retain);
1799     }
1800   }
1801 
1802   void update(bool end_of_gc, bool retain, HeapWord* buf, size_t word_sz) {
1803     G1ParGCAllocBuffer* retired_and_set =  _priority_buffer[0];
1804     retired_and_set->retire(end_of_gc, retain);
1805     retired_and_set->set_buf(buf);
1806     retired_and_set->set_word_size(word_sz);
1807     adjust_priority_order();
1808   }
1809 
1810 private:
1811   void adjust_priority_order() {
1812     G1ParGCAllocBuffer* retired_and_set =  _priority_buffer[0];
1813 
1814     int last = _priority_max - 1;
1815     for (int pr = 0; pr < last; ++pr) {
1816       _priority_buffer[pr] = _priority_buffer[pr + 1];
1817     }
1818     _priority_buffer[last] = retired_and_set;
1819   }
1820 };
1821 
1822 class G1ParScanThreadState : public StackObj {
1823 protected:
1824   G1CollectedHeap* _g1h;
1825   RefToScanQueue*  _refs;
1826   DirtyCardQueue   _dcq;
1827   CardTableModRefBS* _ct_bs;
1828   G1RemSet* _g1_rem;
1829 
1830   G1ParGCAllocBufferContainer  _surviving_alloc_buffer;
1831   G1ParGCAllocBufferContainer  _tenured_alloc_buffer;
1832   G1ParGCAllocBufferContainer* _alloc_buffers[GCAllocPurposeCount];
1833   ageTable            _age_table;
1834 
1835   size_t           _alloc_buffer_waste;
1836   size_t           _undo_waste;
1837 
1838   OopsInHeapRegionClosure*      _evac_failure_cl;
1839   G1ParScanHeapEvacClosure*     _evac_cl;
1840   G1ParScanPartialArrayClosure* _partial_scan_cl;
1841 
1842   int _hash_seed;
1843   uint _queue_num;
1844 
1845   size_t _term_attempts;
1846 
1847   double _start;
1848   double _start_strong_roots;
1849   double _strong_roots_time;
1850   double _start_term;
1851   double _term_time;
1852 
1853   // Map from young-age-index (0 == not young, 1 is youngest) to
1854   // surviving words. base is what we get back from the malloc call
1855   size_t* _surviving_young_words_base;
1856   // this points into the array, as we use the first few entries for padding
1857   size_t* _surviving_young_words;
1858 
1859 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1860 
1861   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1862 
1863   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1864 
1865   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1866   CardTableModRefBS* ctbs()                      { return _ct_bs; }
1867 
1868   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1869     if (!from->is_survivor()) {
1870       _g1_rem->par_write_ref(from, p, tid);
1871     }
1872   }
1873 
1874   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1875     // If the new value of the field points to the same region or
1876     // is the to-space, we don't need to include it in the Rset updates.
1877     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1878       size_t card_index = ctbs()->index_for(p);
1879       // If the card hasn't been added to the buffer, do it.
1880       if (ctbs()->mark_card_deferred(card_index)) {
1881         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1882       }
1883     }
1884   }
1885 
1886 public:
1887   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num);
1888 
1889   ~G1ParScanThreadState() {
1890     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1891   }
1892 
1893   RefToScanQueue*   refs()            { return _refs;             }
1894   ageTable*         age_table()       { return &_age_table;       }
1895 
1896   G1ParGCAllocBufferContainer* alloc_buffer(GCAllocPurpose purpose) {
1897     return _alloc_buffers[purpose];
1898   }
1899 
1900   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1901   size_t undo_waste() const                      { return _undo_waste; }
1902 
1903 #ifdef ASSERT
1904   bool verify_ref(narrowOop* ref) const;
1905   bool verify_ref(oop* ref) const;
1906   bool verify_task(StarTask ref) const;
1907 #endif // ASSERT
1908 
1909   template <class T> void push_on_queue(T* ref) {
1910     assert(verify_ref(ref), "sanity");
1911     refs()->push(ref);
1912   }
1913 
1914   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1915     if (G1DeferredRSUpdate) {
1916       deferred_rs_update(from, p, tid);
1917     } else {
1918       immediate_rs_update(from, p, tid);
1919     }
1920   }
1921 
1922   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1923     HeapWord* obj = NULL;
1924     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1925     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1926       G1ParGCAllocBufferContainer* alloc_buf = alloc_buffer(purpose);
1927 
1928       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1929       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1930 
1931       add_to_alloc_buffer_waste(alloc_buf->words_remaining_in_retired_buffer());
1932       alloc_buf->update(false /* end_of_gc */, false /* retain */, buf, gclab_word_size);
1933 
1934       obj = alloc_buf->allocate(word_sz);
1935       assert(obj != NULL, "buffer was definitely big enough...");
1936     } else {
1937       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1938     }
1939     return obj;
1940   }
1941 
1942   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1943     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1944     if (obj != NULL) return obj;
1945     return allocate_slow(purpose, word_sz);
1946   }
1947 
1948   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1949     if (alloc_buffer(purpose)->contains(obj)) {
1950       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1951              "should contain whole object");
1952       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1953     } else {
1954       CollectedHeap::fill_with_object(obj, word_sz);
1955       add_to_undo_waste(word_sz);
1956     }
1957   }
1958 
1959   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1960     _evac_failure_cl = evac_failure_cl;
1961   }
1962   OopsInHeapRegionClosure* evac_failure_closure() {
1963     return _evac_failure_cl;
1964   }
1965 
1966   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1967     _evac_cl = evac_cl;
1968   }
1969 
1970   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1971     _partial_scan_cl = partial_scan_cl;
1972   }
1973 
1974   int* hash_seed() { return &_hash_seed; }
1975   uint queue_num() { return _queue_num; }
1976 
1977   size_t term_attempts() const  { return _term_attempts; }
1978   void note_term_attempt() { _term_attempts++; }
1979 
1980   void start_strong_roots() {
1981     _start_strong_roots = os::elapsedTime();
1982   }
1983   void end_strong_roots() {
1984     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1985   }
1986   double strong_roots_time() const { return _strong_roots_time; }
1987 
1988   void start_term_time() {
1989     note_term_attempt();
1990     _start_term = os::elapsedTime();
1991   }
1992   void end_term_time() {
1993     _term_time += (os::elapsedTime() - _start_term);
1994   }
1995   double term_time() const { return _term_time; }
1996 
1997   double elapsed_time() const {
1998     return os::elapsedTime() - _start;
1999   }
2000 
2001   static void
2002     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
2003   void
2004     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
2005 
2006   size_t* surviving_young_words() {
2007     // We add on to hide entry 0 which accumulates surviving words for
2008     // age -1 regions (i.e. non-young ones)
2009     return _surviving_young_words;
2010   }
2011 
2012   void retire_alloc_buffers() {
2013     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
2014       size_t waste = _alloc_buffers[ap]->words_remaining();
2015       add_to_alloc_buffer_waste(waste);
2016       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
2017                                                  true /* end_of_gc */,
2018                                                  false /* retain */);
2019     }
2020   }
2021 
2022   template <class T> void deal_with_reference(T* ref_to_scan) {
2023     if (has_partial_array_mask(ref_to_scan)) {
2024       _partial_scan_cl->do_oop_nv(ref_to_scan);
2025     } else {
2026       // Note: we can use "raw" versions of "region_containing" because
2027       // "obj_to_scan" is definitely in the heap, and is not in a
2028       // humongous region.
2029       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
2030       _evac_cl->set_region(r);
2031       _evac_cl->do_oop_nv(ref_to_scan);
2032     }
2033   }
2034 
2035   void deal_with_reference(StarTask ref) {
2036     assert(verify_task(ref), "sanity");
2037     if (ref.is_narrow()) {
2038       deal_with_reference((narrowOop*)ref);
2039     } else {
2040       deal_with_reference((oop*)ref);
2041     }
2042   }
2043 
2044   void trim_queue();
2045 };
2046 
2047 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP