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).
  14  *
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  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/g1MonitoringSupport.hpp"
  32 #include "gc_implementation/g1/g1PreserveMarkQueue.hpp"
  33 #include "gc_implementation/g1/g1RemSet.hpp"
  34 #include "gc_implementation/g1/heapRegionSeq.hpp"
  35 #include "gc_implementation/g1/heapRegionSets.hpp"
  36 #include "gc_implementation/shared/hSpaceCounters.hpp"
  37 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  38 #include "memory/barrierSet.hpp"
  39 #include "memory/memRegion.hpp"
  40 #include "memory/sharedHeap.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   void do_object(oop p) { assert(false, "Do not call."); }
 169   bool do_object_b(oop p);
 170 };
 171 
 172 class SurvivorGCAllocRegion : public G1AllocRegion {
 173 protected:
 174   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 175   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 176 public:
 177   SurvivorGCAllocRegion()
 178   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 179 };
 180 
 181 class OldGCAllocRegion : public G1AllocRegion {
 182 protected:
 183   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 184   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 185 public:
 186   OldGCAllocRegion()
 187   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 188 };
 189 
 190 class RefineCardTableEntryClosure;
 191 
 192 class G1CollectedHeap : public SharedHeap {
 193   friend class VM_G1CollectForAllocation;
 194   friend class VM_G1CollectFull;
 195   friend class VM_G1IncCollectionPause;
 196   friend class VMStructs;
 197   friend class MutatorAllocRegion;
 198   friend class SurvivorGCAllocRegion;
 199   friend class OldGCAllocRegion;
 200 
 201   // Closures used in implementation.
 202   template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
 203   friend class G1ParCopyClosure;
 204   friend class G1IsAliveClosure;
 205   friend class G1EvacuateFollowersClosure;
 206   friend class G1ParScanThreadState;
 207   friend class G1ParScanClosureSuper;
 208   friend class G1ParEvacuateFollowersClosure;
 209   friend class G1ParTask;
 210   friend class G1FreeGarbageRegionClosure;
 211   friend class RefineCardTableEntryClosure;
 212   friend class G1PrepareCompactClosure;
 213   friend class RegionSorter;
 214   friend class RegionResetter;
 215   friend class CountRCClosure;
 216   friend class EvacPopObjClosure;
 217   friend class G1ParCleanupCTTask;
 218 
 219   // Other related classes.
 220   friend class G1MarkSweep;
 221 
 222 private:
 223   // The one and only G1CollectedHeap, so static functions can find it.
 224   static G1CollectedHeap* _g1h;
 225 
 226   static size_t _humongous_object_threshold_in_words;
 227 
 228   // Storage for the G1 heap.
 229   VirtualSpace _g1_storage;
 230   MemRegion    _g1_reserved;
 231 
 232   // The part of _g1_storage that is currently committed.
 233   MemRegion _g1_committed;
 234 
 235   // The master free list. It will satisfy all new region allocations.
 236   MasterFreeRegionList      _free_list;
 237 
 238   // The secondary free list which contains regions that have been
 239   // freed up during the cleanup process. This will be appended to the
 240   // master free list when appropriate.
 241   SecondaryFreeRegionList   _secondary_free_list;
 242 
 243   // It keeps track of the old regions.
 244   MasterOldRegionSet        _old_set;
 245 
 246   // It keeps track of the humongous regions.
 247   MasterHumongousRegionSet  _humongous_set;
 248 
 249   // The number of regions we could create by expansion.
 250   uint _expansion_regions;
 251 
 252   // The block offset table for the G1 heap.
 253   G1BlockOffsetSharedArray* _bot_shared;
 254 
 255   // Tears down the region sets / lists so that they are empty and the
 256   // regions on the heap do not belong to a region set / list. The
 257   // only exception is the humongous set which we leave unaltered. If
 258   // free_list_only is true, it will only tear down the master free
 259   // list. It is called before a Full GC (free_list_only == false) or
 260   // before heap shrinking (free_list_only == true).
 261   void tear_down_region_sets(bool free_list_only);
 262 
 263   // Rebuilds the region sets / lists so that they are repopulated to
 264   // reflect the contents of the heap. The only exception is the
 265   // humongous set which was not torn down in the first place. If
 266   // free_list_only is true, it will only rebuild the master free
 267   // list. It is called after a Full GC (free_list_only == false) or
 268   // after heap shrinking (free_list_only == true).
 269   void rebuild_region_sets(bool free_list_only);
 270 
 271   // The sequence of all heap regions in the heap.
 272   HeapRegionSeq _hrs;
 273 
 274   // Alloc region used to satisfy mutator allocation requests.
 275   MutatorAllocRegion _mutator_alloc_region;
 276 
 277   // Alloc region used to satisfy allocation requests by the GC for
 278   // survivor objects.
 279   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 280 
 281   // PLAB sizing policy for survivors.
 282   PLABStats _survivor_plab_stats;
 283 
 284   // Alloc region used to satisfy allocation requests by the GC for
 285   // old objects.
 286   OldGCAllocRegion _old_gc_alloc_region;
 287 
 288   // PLAB sizing policy for tenured objects.
 289   PLABStats _old_plab_stats;
 290 
 291   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 292     PLABStats* stats = NULL;
 293 
 294     switch (purpose) {
 295     case GCAllocForSurvived:
 296       stats = &_survivor_plab_stats;
 297       break;
 298     case GCAllocForTenured:
 299       stats = &_old_plab_stats;
 300       break;
 301     default:
 302       assert(false, "unrecognized GCAllocPurpose");
 303     }
 304 
 305     return stats;
 306   }
 307 
 308   // The last old region we allocated to during the last GC.
 309   // Typically, it is not full so we should re-use it during the next GC.
 310   HeapRegion* _retained_old_gc_alloc_region;
 311 
 312   // It specifies whether we should attempt to expand the heap after a
 313   // region allocation failure. If heap expansion fails we set this to
 314   // false so that we don't re-attempt the heap expansion (it's likely
 315   // that subsequent expansion attempts will also fail if one fails).
 316   // Currently, it is only consulted during GC and it's reset at the
 317   // start of each GC.
 318   bool _expand_heap_after_alloc_failure;
 319 
 320   // It resets the mutator alloc region before new allocations can take place.
 321   void init_mutator_alloc_region();
 322 
 323   // It releases the mutator alloc region.
 324   void release_mutator_alloc_region();
 325 
 326   // It initializes the GC alloc regions at the start of a GC.
 327   void init_gc_alloc_regions();
 328 
 329   // It releases the GC alloc regions at the end of a GC.
 330   void release_gc_alloc_regions(uint no_of_gc_workers);
 331 
 332   // It does any cleanup that needs to be done on the GC alloc regions
 333   // before a Full GC.
 334   void abandon_gc_alloc_regions();
 335 
 336   // Helper for monitoring and management support.
 337   G1MonitoringSupport* _g1mm;
 338 
 339   // Determines PLAB size for a particular allocation purpose.
 340   size_t desired_plab_sz(GCAllocPurpose purpose);
 341 
 342   // Outside of GC pauses, the number of bytes used in all regions other
 343   // than the current allocation region.
 344   size_t _summary_bytes_used;
 345 
 346   // This is used for a quick test on whether a reference points into
 347   // the collection set or not. Basically, we have an array, with one
 348   // byte per region, and that byte denotes whether the corresponding
 349   // region is in the collection set or not. The entry corresponding
 350   // the bottom of the heap, i.e., region 0, is pointed to by
 351   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 352   // biased so that it actually points to address 0 of the address
 353   // space, to make the test as fast as possible (we can simply shift
 354   // the address to address into it, instead of having to subtract the
 355   // bottom of the heap from the address before shifting it; basically
 356   // it works in the same way the card table works).
 357   bool* _in_cset_fast_test;
 358 
 359   // The allocated array used for the fast test on whether a reference
 360   // points into the collection set or not. This field is also used to
 361   // free the array.
 362   bool* _in_cset_fast_test_base;
 363 
 364   // The length of the _in_cset_fast_test_base array.
 365   uint _in_cset_fast_test_length;
 366 
 367   volatile unsigned _gc_time_stamp;
 368 
 369   size_t* _surviving_young_words;
 370 
 371   G1HRPrinter _hr_printer;
 372 
 373   void setup_surviving_young_words();
 374   void update_surviving_young_words(size_t* surv_young_words);
 375   void cleanup_surviving_young_words();
 376 
 377   // It decides whether an explicit GC should start a concurrent cycle
 378   // instead of doing a STW GC. Currently, a concurrent cycle is
 379   // explicitly started if:
 380   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 381   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 382   // (c) cause == _g1_humongous_allocation
 383   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 384 
 385   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 386   // concurrent cycles) we have started.
 387   volatile unsigned int _old_marking_cycles_started;
 388 
 389   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 390   // concurrent cycles) we have completed.
 391   volatile unsigned int _old_marking_cycles_completed;
 392 
 393   // This is a non-product method that is helpful for testing. It is
 394   // called at the end of a GC and artificially expands the heap by
 395   // allocating a number of dead regions. This way we can induce very
 396   // frequent marking cycles and stress the cleanup / concurrent
 397   // cleanup code more (as all the regions that will be allocated by
 398   // this method will be found dead by the marking cycle).
 399   void allocate_dummy_regions() PRODUCT_RETURN;
 400 
 401   // Clear RSets after a compaction. It also resets the GC time stamps.
 402   void clear_rsets_post_compaction();
 403 
 404   // If the HR printer is active, dump the state of the regions in the
 405   // heap after a compaction.
 406   void print_hrs_post_compaction();
 407 
 408   double verify(bool guard, const char* msg);
 409   void verify_before_gc();
 410   void verify_after_gc();
 411 
 412   void log_gc_header();
 413   void log_gc_footer(double pause_time_sec);
 414 
 415   // These are macros so that, if the assert fires, we get the correct
 416   // line number, file, etc.
 417 
 418 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 419   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 420           (_extra_message_),                                                  \
 421           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 422           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 423           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 424 
 425 #define assert_heap_locked()                                                  \
 426   do {                                                                        \
 427     assert(Heap_lock->owned_by_self(),                                        \
 428            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 429   } while (0)
 430 
 431 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 432   do {                                                                        \
 433     assert(Heap_lock->owned_by_self() ||                                      \
 434            (SafepointSynchronize::is_at_safepoint() &&                        \
 435              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 436            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 437                                         "should be at a safepoint"));         \
 438   } while (0)
 439 
 440 #define assert_heap_locked_and_not_at_safepoint()                             \
 441   do {                                                                        \
 442     assert(Heap_lock->owned_by_self() &&                                      \
 443                                     !SafepointSynchronize::is_at_safepoint(), \
 444           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 445                                        "should not be at a safepoint"));      \
 446   } while (0)
 447 
 448 #define assert_heap_not_locked()                                              \
 449   do {                                                                        \
 450     assert(!Heap_lock->owned_by_self(),                                       \
 451         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 452   } while (0)
 453 
 454 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 455   do {                                                                        \
 456     assert(!Heap_lock->owned_by_self() &&                                     \
 457                                     !SafepointSynchronize::is_at_safepoint(), \
 458       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 459                                    "should not be at a safepoint"));          \
 460   } while (0)
 461 
 462 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 463   do {                                                                        \
 464     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 465               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 466            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 467   } while (0)
 468 
 469 #define assert_not_at_safepoint()                                             \
 470   do {                                                                        \
 471     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 472            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 473   } while (0)
 474 
 475 protected:
 476 
 477   // The young region list.
 478   YoungList*  _young_list;
 479 
 480   // The current policy object for the collector.
 481   G1CollectorPolicy* _g1_policy;
 482 
 483   // This is the second level of trying to allocate a new region. If
 484   // new_region() didn't find a region on the free_list, this call will
 485   // check whether there's anything available on the
 486   // secondary_free_list and/or wait for more regions to appear on
 487   // that list, if _free_regions_coming is set.
 488   HeapRegion* new_region_try_secondary_free_list();
 489 
 490   // Try to allocate a single non-humongous HeapRegion sufficient for
 491   // an allocation of the given word_size. If do_expand is true,
 492   // attempt to expand the heap if necessary to satisfy the allocation
 493   // request.
 494   HeapRegion* new_region(size_t word_size, bool do_expand);
 495 
 496   // Attempt to satisfy a humongous allocation request of the given
 497   // size by finding a contiguous set of free regions of num_regions
 498   // length and remove them from the master free list. Return the
 499   // index of the first region or G1_NULL_HRS_INDEX if the search
 500   // was unsuccessful.
 501   uint humongous_obj_allocate_find_first(uint num_regions,
 502                                          size_t word_size);
 503 
 504   // Initialize a contiguous set of free regions of length num_regions
 505   // and starting at index first so that they appear as a single
 506   // humongous region.
 507   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 508                                                       uint num_regions,
 509                                                       size_t word_size);
 510 
 511   // Attempt to allocate a humongous object of the given size. Return
 512   // NULL if unsuccessful.
 513   HeapWord* humongous_obj_allocate(size_t word_size);
 514 
 515   // The following two methods, allocate_new_tlab() and
 516   // mem_allocate(), are the two main entry points from the runtime
 517   // into the G1's allocation routines. They have the following
 518   // assumptions:
 519   //
 520   // * They should both be called outside safepoints.
 521   //
 522   // * They should both be called without holding the Heap_lock.
 523   //
 524   // * All allocation requests for new TLABs should go to
 525   //   allocate_new_tlab().
 526   //
 527   // * All non-TLAB allocation requests should go to mem_allocate().
 528   //
 529   // * If either call cannot satisfy the allocation request using the
 530   //   current allocating region, they will try to get a new one. If
 531   //   this fails, they will attempt to do an evacuation pause and
 532   //   retry the allocation.
 533   //
 534   // * If all allocation attempts fail, even after trying to schedule
 535   //   an evacuation pause, allocate_new_tlab() will return NULL,
 536   //   whereas mem_allocate() will attempt a heap expansion and/or
 537   //   schedule a Full GC.
 538   //
 539   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 540   //   should never be called with word_size being humongous. All
 541   //   humongous allocation requests should go to mem_allocate() which
 542   //   will satisfy them with a special path.
 543 
 544   virtual HeapWord* allocate_new_tlab(size_t word_size);
 545 
 546   virtual HeapWord* mem_allocate(size_t word_size,
 547                                  bool*  gc_overhead_limit_was_exceeded);
 548 
 549   // The following three methods take a gc_count_before_ret
 550   // parameter which is used to return the GC count if the method
 551   // returns NULL. Given that we are required to read the GC count
 552   // while holding the Heap_lock, and these paths will take the
 553   // Heap_lock at some point, it's easier to get them to read the GC
 554   // count while holding the Heap_lock before they return NULL instead
 555   // of the caller (namely: mem_allocate()) having to also take the
 556   // Heap_lock just to read the GC count.
 557 
 558   // First-level mutator allocation attempt: try to allocate out of
 559   // the mutator alloc region without taking the Heap_lock. This
 560   // should only be used for non-humongous allocations.
 561   inline HeapWord* attempt_allocation(size_t word_size,
 562                                       unsigned int* gc_count_before_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 
 570   // Takes the Heap_lock and attempts a humongous allocation. It can
 571   // potentially schedule a GC pause.
 572   HeapWord* attempt_allocation_humongous(size_t word_size,
 573                                          unsigned int* gc_count_before_ret);
 574 
 575   // Allocation attempt that should be called during safepoints (e.g.,
 576   // at the end of a successful GC). expect_null_mutator_alloc_region
 577   // specifies whether the mutator alloc region is expected to be NULL
 578   // or not.
 579   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 580                                        bool expect_null_mutator_alloc_region);
 581 
 582   // It dirties the cards that cover the block so that so that the post
 583   // write barrier never queues anything when updating objects on this
 584   // block. It is assumed (and in fact we assert) that the block
 585   // belongs to a young region.
 586   inline void dirty_young_block(HeapWord* start, size_t word_size);
 587 
 588   // Allocate blocks during garbage collection. Will ensure an
 589   // allocation region, either by picking one or expanding the
 590   // heap, and then allocate a block of the given size. The block
 591   // may not be a humongous - it must fit into a single heap region.
 592   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 593 
 594   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 595                                     HeapRegion*    alloc_region,
 596                                     bool           par,
 597                                     size_t         word_size);
 598 
 599   // Ensure that no further allocations can happen in "r", bearing in mind
 600   // that parallel threads might be attempting allocations.
 601   void par_allocate_remaining_space(HeapRegion* r);
 602 
 603   // Allocation attempt during GC for a survivor object / PLAB.
 604   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 605 
 606   // Allocation attempt during GC for an old object / PLAB.
 607   inline HeapWord* old_attempt_allocation(size_t word_size);
 608 
 609   // These methods are the "callbacks" from the G1AllocRegion class.
 610 
 611   // For mutator alloc regions.
 612   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 613   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 614                                    size_t allocated_bytes);
 615 
 616   // For GC alloc regions.
 617   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 618                                   GCAllocPurpose ap);
 619   void retire_gc_alloc_region(HeapRegion* alloc_region,
 620                               size_t allocated_bytes, GCAllocPurpose ap);
 621 
 622   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 623   //   inspection request and should collect the entire heap
 624   // - if clear_all_soft_refs is true, all soft references should be
 625   //   cleared during the GC
 626   // - if explicit_gc is false, word_size describes the allocation that
 627   //   the GC should attempt (at least) to satisfy
 628   // - it returns false if it is unable to do the collection due to the
 629   //   GC locker being active, true otherwise
 630   bool do_collection(bool explicit_gc,
 631                      bool clear_all_soft_refs,
 632                      size_t word_size);
 633 
 634   // Callback from VM_G1CollectFull operation.
 635   // Perform a full collection.
 636   virtual void do_full_collection(bool clear_all_soft_refs);
 637 
 638   // Resize the heap if necessary after a full collection.  If this is
 639   // after a collect-for allocation, "word_size" is the allocation size,
 640   // and will be considered part of the used portion of the heap.
 641   void resize_if_necessary_after_full_collection(size_t word_size);
 642 
 643   // Callback from VM_G1CollectForAllocation operation.
 644   // This function does everything necessary/possible to satisfy a
 645   // failed allocation request (including collection, expansion, etc.)
 646   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 647 
 648   // Attempting to expand the heap sufficiently
 649   // to support an allocation of the given "word_size".  If
 650   // successful, perform the allocation and return the address of the
 651   // allocated block, or else "NULL".
 652   HeapWord* expand_and_allocate(size_t word_size);
 653 
 654   // Process any reference objects discovered during
 655   // an incremental evacuation pause.
 656   void process_discovered_references(uint no_of_gc_workers);
 657 
 658   // Enqueue any remaining discovered references
 659   // after processing.
 660   void enqueue_discovered_references(uint no_of_gc_workers);
 661 
 662 public:
 663 
 664   G1MonitoringSupport* g1mm() {
 665     assert(_g1mm != NULL, "should have been initialized");
 666     return _g1mm;
 667   }
 668 
 669   // Expand the garbage-first heap by at least the given size (in bytes!).
 670   // Returns true if the heap was expanded by the requested amount;
 671   // false otherwise.
 672   // (Rounds up to a HeapRegion boundary.)
 673   bool expand(size_t expand_bytes);
 674 
 675   // Do anything common to GC's.
 676   virtual void gc_prologue(bool full);
 677   virtual void gc_epilogue(bool full);
 678 
 679   // We register a region with the fast "in collection set" test. We
 680   // simply set to true the array slot corresponding to this region.
 681   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 682     assert(_in_cset_fast_test_base != NULL, "sanity");
 683     assert(r->in_collection_set(), "invariant");
 684     uint index = r->hrs_index();
 685     assert(index < _in_cset_fast_test_length, "invariant");
 686     assert(!_in_cset_fast_test_base[index], "invariant");
 687     _in_cset_fast_test_base[index] = true;
 688   }
 689 
 690   // This is a fast test on whether a reference points into the
 691   // collection set or not. It does not assume that the reference
 692   // points into the heap; if it doesn't, it will return false.
 693   bool in_cset_fast_test(oop obj) {
 694     assert(_in_cset_fast_test != NULL, "sanity");
 695     if (_g1_committed.contains((HeapWord*) obj)) {
 696       // no need to subtract the bottom of the heap from obj,
 697       // _in_cset_fast_test is biased
 698       uintx index = (uintx) obj >> HeapRegion::LogOfHRGrainBytes;
 699       bool ret = _in_cset_fast_test[index];
 700       // let's make sure the result is consistent with what the slower
 701       // test returns
 702       assert( ret || !obj_in_cs(obj), "sanity");
 703       assert(!ret ||  obj_in_cs(obj), "sanity");
 704       return ret;
 705     } else {
 706       return false;
 707     }
 708   }
 709 
 710   void clear_cset_fast_test() {
 711     assert(_in_cset_fast_test_base != NULL, "sanity");
 712     memset(_in_cset_fast_test_base, false,
 713            (size_t) _in_cset_fast_test_length * sizeof(bool));
 714   }
 715 
 716   // This is called at the start of either a concurrent cycle or a Full
 717   // GC to update the number of old marking cycles started.
 718   void increment_old_marking_cycles_started();
 719 
 720   // This is called at the end of either a concurrent cycle or a Full
 721   // GC to update the number of old marking cycles completed. Those two
 722   // can happen in a nested fashion, i.e., we start a concurrent
 723   // cycle, a Full GC happens half-way through it which ends first,
 724   // and then the cycle notices that a Full GC happened and ends
 725   // too. The concurrent parameter is a boolean to help us do a bit
 726   // tighter consistency checking in the method. If concurrent is
 727   // false, the caller is the inner caller in the nesting (i.e., the
 728   // Full GC). If concurrent is true, the caller is the outer caller
 729   // in this nesting (i.e., the concurrent cycle). Further nesting is
 730   // not currently supported. The end of this call also notifies
 731   // the FullGCCount_lock in case a Java thread is waiting for a full
 732   // GC to happen (e.g., it called System.gc() with
 733   // +ExplicitGCInvokesConcurrent).
 734   void increment_old_marking_cycles_completed(bool concurrent);
 735 
 736   unsigned int old_marking_cycles_completed() {
 737     return _old_marking_cycles_completed;
 738   }
 739 
 740   G1HRPrinter* hr_printer() { return &_hr_printer; }
 741 
 742 protected:
 743 
 744   // Shrink the garbage-first heap by at most the given size (in bytes!).
 745   // (Rounds down to a HeapRegion boundary.)
 746   virtual void shrink(size_t expand_bytes);
 747   void shrink_helper(size_t expand_bytes);
 748 
 749   #if TASKQUEUE_STATS
 750   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 751   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 752   void reset_taskqueue_stats();
 753   #endif // TASKQUEUE_STATS
 754 
 755   // Schedule the VM operation that will do an evacuation pause to
 756   // satisfy an allocation request of word_size. *succeeded will
 757   // return whether the VM operation was successful (it did do an
 758   // evacuation pause) or not (another thread beat us to it or the GC
 759   // locker was active). Given that we should not be holding the
 760   // Heap_lock when we enter this method, we will pass the
 761   // gc_count_before (i.e., total_collections()) as a parameter since
 762   // it has to be read while holding the Heap_lock. Currently, both
 763   // methods that call do_collection_pause() release the Heap_lock
 764   // before the call, so it's easy to read gc_count_before just before.
 765   HeapWord* do_collection_pause(size_t       word_size,
 766                                 unsigned int gc_count_before,
 767                                 bool*        succeeded);
 768 
 769   // The guts of the incremental collection pause, executed by the vm
 770   // thread. It returns false if it is unable to do the collection due
 771   // to the GC locker being active, true otherwise
 772   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 773 
 774   // Actually do the work of evacuating the collection set.
 775   void evacuate_collection_set();
 776 
 777   // The g1 remembered set of the heap.
 778   G1RemSet* _g1_rem_set;
 779   // And it's mod ref barrier set, used to track updates for the above.
 780   ModRefBarrierSet* _mr_bs;
 781 
 782   // A set of cards that cover the objects for which the Rsets should be updated
 783   // concurrently after the collection.
 784   DirtyCardQueueSet _dirty_card_queue_set;
 785 
 786   // The Heap Region Rem Set Iterator.
 787   HeapRegionRemSetIterator** _rem_set_iterator;
 788 
 789   // The closure used to refine a single card.
 790   RefineCardTableEntryClosure* _refine_cte_cl;
 791 
 792   // A function to check the consistency of dirty card logs.
 793   void check_ct_logs_at_safepoint();
 794 
 795   // A DirtyCardQueueSet that is used to hold cards that contain
 796   // references into the current collection set. This is used to
 797   // update the remembered sets of the regions in the collection
 798   // set in the event of an evacuation failure.
 799   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 800 
 801   // After a collection pause, make the regions in the CS into free
 802   // regions.
 803   void free_collection_set(HeapRegion* cs_head);
 804 
 805   // Abandon the current collection set without recording policy
 806   // statistics or updating free lists.
 807   void abandon_collection_set(HeapRegion* cs_head);
 808 
 809   // Applies "scan_non_heap_roots" to roots outside the heap,
 810   // "scan_rs" to roots inside the heap (having done "set_region" to
 811   // indicate the region in which the root resides),
 812   // and does "scan_metadata" If "scan_rs" is
 813   // NULL, then this step is skipped.  The "worker_i"
 814   // param is for use with parallel roots processing, and should be
 815   // the "i" of the calling parallel worker thread's work(i) function.
 816   // In the sequential case this param will be ignored.
 817   void g1_process_strong_roots(bool is_scavenging,
 818                                ScanningOption so,
 819                                OopClosure* scan_non_heap_roots,
 820                                OopsInHeapRegionClosure* scan_rs,
 821                                G1KlassScanClosure* scan_klasses,
 822                                int worker_i);
 823 
 824   // Apply "blk" to all the weak roots of the system.  These include
 825   // JNI weak roots, the code cache, system dictionary, symbol table,
 826   // string table, and referents of reachable weak refs.
 827   void g1_process_weak_roots(OopClosure* root_closure,
 828                              OopClosure* non_root_closure);
 829 
 830   // Frees a non-humongous region by initializing its contents and
 831   // adding it to the free list that's passed as a parameter (this is
 832   // usually a local list which will be appended to the master free
 833   // list later). The used bytes of freed regions are accumulated in
 834   // pre_used. If par is true, the region's RSet will not be freed
 835   // up. The assumption is that this will be done later.
 836   void free_region(HeapRegion* hr,
 837                    size_t* pre_used,
 838                    FreeRegionList* free_list,
 839                    bool par);
 840 
 841   // Frees a humongous region by collapsing it into individual regions
 842   // and calling free_region() for each of them. The freed regions
 843   // will be added to the free list that's passed as a parameter (this
 844   // is usually a local list which will be appended to the master free
 845   // list later). The used bytes of freed regions are accumulated in
 846   // pre_used. If par is true, the region's RSet will not be freed
 847   // up. The assumption is that this will be done later.
 848   void free_humongous_region(HeapRegion* hr,
 849                              size_t* pre_used,
 850                              FreeRegionList* free_list,
 851                              HumongousRegionSet* humongous_proxy_set,
 852                              bool par);
 853 
 854   // Notifies all the necessary spaces that the committed space has
 855   // been updated (either expanded or shrunk). It should be called
 856   // after _g1_storage is updated.
 857   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 858 
 859   // The concurrent marker (and the thread it runs in.)
 860   ConcurrentMark* _cm;
 861   ConcurrentMarkThread* _cmThread;
 862   bool _mark_in_progress;
 863 
 864   // The concurrent refiner.
 865   ConcurrentG1Refine* _cg1r;
 866 
 867   // The parallel task queues
 868   RefToScanQueueSet *_task_queues;
 869 
 870   // True iff a evacuation has failed in the current collection.
 871   bool _evacuation_failed;
 872 
 873   // Set the attribute indicating whether evacuation has failed in the
 874   // current collection.
 875   void set_evacuation_failed(bool b) { _evacuation_failed = b; }
 876 
 877   // Failed evacuations cause some logical from-space objects to have
 878   // forwarding pointers to themselves.  Reset them.
 879   void remove_self_forwarding_pointers();
 880 
 881   // Objects with a preserved mark, and its mark value.
 882   G1PreserveMarkQueue _preserved_marks;


 883 
 884   // Preserve the mark of "obj", if necessary, in preparation for its mark
 885   // word being overwritten with a self-forwarding-pointer.
 886   void preserve_mark_if_necessary(oop obj, markOop m);
 887 
 888   // The stack of evac-failure objects left to be scanned.
 889   GrowableArray<oop>*    _evac_failure_scan_stack;
 890   // The closure to apply to evac-failure objects.
 891 
 892   OopsInHeapRegionClosure* _evac_failure_closure;
 893   // Set the field above.
 894   void
 895   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 896     _evac_failure_closure = evac_failure_closure;
 897   }
 898 
 899   // Push "obj" on the scan stack.
 900   void push_on_evac_failure_scan_stack(oop obj);
 901   // Process scan stack entries until the stack is empty.
 902   void drain_evac_failure_scan_stack();
 903   // True iff an invocation of "drain_scan_stack" is in progress; to
 904   // prevent unnecessary recursion.
 905   bool _drain_in_progress;
 906 
 907   // Do any necessary initialization for evacuation-failure handling.
 908   // "cl" is the closure that will be used to process evac-failure
 909   // objects.
 910   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 911   // Do any necessary cleanup for evacuation-failure handling data
 912   // structures.
 913   void finalize_for_evac_failure();
 914 
 915   // An attempt to evacuate "obj" has failed; take necessary steps.
 916   oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
 917   void handle_evacuation_failure_common(oop obj, markOop m);
 918 
 919 #ifndef PRODUCT
 920   // Support for forcing evacuation failures. Analogous to
 921   // PromotionFailureALot for the other collectors.
 922 
 923   // Records whether G1EvacuationFailureALot should be in effect
 924   // for the current GC
 925   bool _evacuation_failure_alot_for_current_gc;
 926 
 927   // Used to record the GC number for interval checking when
 928   // determining whether G1EvaucationFailureALot is in effect
 929   // for the current GC.
 930   size_t _evacuation_failure_alot_gc_number;
 931 
 932   // Count of the number of evacuations between failures.
 933   volatile size_t _evacuation_failure_alot_count;
 934 
 935   // Set whether G1EvacuationFailureALot should be in effect
 936   // for the current GC (based upon the type of GC and which
 937   // command line flags are set);
 938   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 939                                                   bool during_initial_mark,
 940                                                   bool during_marking);
 941 
 942   inline void set_evacuation_failure_alot_for_current_gc();
 943 
 944   // Return true if it's time to cause an evacuation failure.
 945   inline bool evacuation_should_fail();
 946 
 947   // Reset the G1EvacuationFailureALot counters.  Should be called at
 948   // the end of an evacuation pause in which an evacuation failure ocurred.
 949   inline void reset_evacuation_should_fail();
 950 #endif // !PRODUCT
 951 
 952   // ("Weak") Reference processing support.
 953   //
 954   // G1 has 2 instances of the referece processor class. One
 955   // (_ref_processor_cm) handles reference object discovery
 956   // and subsequent processing during concurrent marking cycles.
 957   //
 958   // The other (_ref_processor_stw) handles reference object
 959   // discovery and processing during full GCs and incremental
 960   // evacuation pauses.
 961   //
 962   // During an incremental pause, reference discovery will be
 963   // temporarily disabled for _ref_processor_cm and will be
 964   // enabled for _ref_processor_stw. At the end of the evacuation
 965   // pause references discovered by _ref_processor_stw will be
 966   // processed and discovery will be disabled. The previous
 967   // setting for reference object discovery for _ref_processor_cm
 968   // will be re-instated.
 969   //
 970   // At the start of marking:
 971   //  * Discovery by the CM ref processor is verified to be inactive
 972   //    and it's discovered lists are empty.
 973   //  * Discovery by the CM ref processor is then enabled.
 974   //
 975   // At the end of marking:
 976   //  * Any references on the CM ref processor's discovered
 977   //    lists are processed (possibly MT).
 978   //
 979   // At the start of full GC we:
 980   //  * Disable discovery by the CM ref processor and
 981   //    empty CM ref processor's discovered lists
 982   //    (without processing any entries).
 983   //  * Verify that the STW ref processor is inactive and it's
 984   //    discovered lists are empty.
 985   //  * Temporarily set STW ref processor discovery as single threaded.
 986   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 987   //    field.
 988   //  * Finally enable discovery by the STW ref processor.
 989   //
 990   // The STW ref processor is used to record any discovered
 991   // references during the full GC.
 992   //
 993   // At the end of a full GC we:
 994   //  * Enqueue any reference objects discovered by the STW ref processor
 995   //    that have non-live referents. This has the side-effect of
 996   //    making the STW ref processor inactive by disabling discovery.
 997   //  * Verify that the CM ref processor is still inactive
 998   //    and no references have been placed on it's discovered
 999   //    lists (also checked as a precondition during initial marking).
1000 
1001   // The (stw) reference processor...
1002   ReferenceProcessor* _ref_processor_stw;
1003 
1004   // During reference object discovery, the _is_alive_non_header
1005   // closure (if non-null) is applied to the referent object to
1006   // determine whether the referent is live. If so then the
1007   // reference object does not need to be 'discovered' and can
1008   // be treated as a regular oop. This has the benefit of reducing
1009   // the number of 'discovered' reference objects that need to
1010   // be processed.
1011   //
1012   // Instance of the is_alive closure for embedding into the
1013   // STW reference processor as the _is_alive_non_header field.
1014   // Supplying a value for the _is_alive_non_header field is
1015   // optional but doing so prevents unnecessary additions to
1016   // the discovered lists during reference discovery.
1017   G1STWIsAliveClosure _is_alive_closure_stw;
1018 
1019   // The (concurrent marking) reference processor...
1020   ReferenceProcessor* _ref_processor_cm;
1021 
1022   // Instance of the concurrent mark is_alive closure for embedding
1023   // into the Concurrent Marking reference processor as the
1024   // _is_alive_non_header field. Supplying a value for the
1025   // _is_alive_non_header field is optional but doing so prevents
1026   // unnecessary additions to the discovered lists during reference
1027   // discovery.
1028   G1CMIsAliveClosure _is_alive_closure_cm;
1029 
1030   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1031   HeapRegion** _worker_cset_start_region;
1032 
1033   // Time stamp to validate the regions recorded in the cache
1034   // used by G1CollectedHeap::start_cset_region_for_worker().
1035   // The heap region entry for a given worker is valid iff
1036   // the associated time stamp value matches the current value
1037   // of G1CollectedHeap::_gc_time_stamp.
1038   unsigned int* _worker_cset_start_region_time_stamp;
1039 
1040   enum G1H_process_strong_roots_tasks {
1041     G1H_PS_filter_satb_buffers,
1042     G1H_PS_refProcessor_oops_do,
1043     // Leave this one last.
1044     G1H_PS_NumElements
1045   };
1046 
1047   SubTasksDone* _process_strong_tasks;
1048 
1049   volatile bool _free_regions_coming;
1050 
1051 public:
1052 
1053   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1054 
1055   void set_refine_cte_cl_concurrency(bool concurrent);
1056 
1057   RefToScanQueue *task_queue(int i) const;
1058 
1059   // A set of cards where updates happened during the GC
1060   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1061 
1062   // A DirtyCardQueueSet that is used to hold cards that contain
1063   // references into the current collection set. This is used to
1064   // update the remembered sets of the regions in the collection
1065   // set in the event of an evacuation failure.
1066   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1067         { return _into_cset_dirty_card_queue_set; }
1068 
1069   // Create a G1CollectedHeap with the specified policy.
1070   // Must call the initialize method afterwards.
1071   // May not return if something goes wrong.
1072   G1CollectedHeap(G1CollectorPolicy* policy);
1073 
1074   // Initialize the G1CollectedHeap to have the initial and
1075   // maximum sizes and remembered and barrier sets
1076   // specified by the policy object.
1077   jint initialize();
1078 
1079   // Initialize weak reference processing.
1080   virtual void ref_processing_init();
1081 
1082   void set_par_threads(uint t) {
1083     SharedHeap::set_par_threads(t);
1084     // Done in SharedHeap but oddly there are
1085     // two _process_strong_tasks's in a G1CollectedHeap
1086     // so do it here too.
1087     _process_strong_tasks->set_n_threads(t);
1088   }
1089 
1090   // Set _n_par_threads according to a policy TBD.
1091   void set_par_threads();
1092 
1093   void set_n_termination(int t) {
1094     _process_strong_tasks->set_n_threads(t);
1095   }
1096 
1097   virtual CollectedHeap::Name kind() const {
1098     return CollectedHeap::G1CollectedHeap;
1099   }
1100 
1101   // The current policy object for the collector.
1102   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1103 
1104   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1105 
1106   // Adaptive size policy.  No such thing for g1.
1107   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1108 
1109   // The rem set and barrier set.
1110   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1111   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
1112 
1113   // The rem set iterator.
1114   HeapRegionRemSetIterator* rem_set_iterator(int i) {
1115     return _rem_set_iterator[i];
1116   }
1117 
1118   HeapRegionRemSetIterator* rem_set_iterator() {
1119     return _rem_set_iterator[0];
1120   }
1121 
1122   unsigned get_gc_time_stamp() {
1123     return _gc_time_stamp;
1124   }
1125 
1126   void reset_gc_time_stamp() {
1127     _gc_time_stamp = 0;
1128     OrderAccess::fence();
1129     // Clear the cached CSet starting regions and time stamps.
1130     // Their validity is dependent on the GC timestamp.
1131     clear_cset_start_regions();
1132   }
1133 
1134   void check_gc_time_stamps() PRODUCT_RETURN;
1135 
1136   void increment_gc_time_stamp() {
1137     ++_gc_time_stamp;
1138     OrderAccess::fence();
1139   }
1140 
1141   // Reset the given region's GC timestamp. If it's starts humongous,
1142   // also reset the GC timestamp of its corresponding
1143   // continues humongous regions too.
1144   void reset_gc_time_stamps(HeapRegion* hr);
1145 
1146   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1147                                   DirtyCardQueue* into_cset_dcq,
1148                                   bool concurrent, int worker_i);
1149 
1150   // The shared block offset table array.
1151   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1152 
1153   // Reference Processing accessors
1154 
1155   // The STW reference processor....
1156   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1157 
1158   // The Concurent Marking reference processor...
1159   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1160 
1161   virtual size_t capacity() const;
1162   virtual size_t used() const;
1163   // This should be called when we're not holding the heap lock. The
1164   // result might be a bit inaccurate.
1165   size_t used_unlocked() const;
1166   size_t recalculate_used() const;
1167 
1168   // These virtual functions do the actual allocation.
1169   // Some heaps may offer a contiguous region for shared non-blocking
1170   // allocation, via inlined code (by exporting the address of the top and
1171   // end fields defining the extent of the contiguous allocation region.)
1172   // But G1CollectedHeap doesn't yet support this.
1173 
1174   // Return an estimate of the maximum allocation that could be performed
1175   // without triggering any collection or expansion activity.  In a
1176   // generational collector, for example, this is probably the largest
1177   // allocation that could be supported (without expansion) in the youngest
1178   // generation.  It is "unsafe" because no locks are taken; the result
1179   // should be treated as an approximation, not a guarantee, for use in
1180   // heuristic resizing decisions.
1181   virtual size_t unsafe_max_alloc();
1182 
1183   virtual bool is_maximal_no_gc() const {
1184     return _g1_storage.uncommitted_size() == 0;
1185   }
1186 
1187   // The total number of regions in the heap.
1188   uint n_regions() { return _hrs.length(); }
1189 
1190   // The max number of regions in the heap.
1191   uint max_regions() { return _hrs.max_length(); }
1192 
1193   // The number of regions that are completely free.
1194   uint free_regions() { return _free_list.length(); }
1195 
1196   // The number of regions that are not completely free.
1197   uint used_regions() { return n_regions() - free_regions(); }
1198 
1199   // The number of regions available for "regular" expansion.
1200   uint expansion_regions() { return _expansion_regions; }
1201 
1202   // Factory method for HeapRegion instances. It will return NULL if
1203   // the allocation fails.
1204   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1205 
1206   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1207   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1208   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1209   void verify_dirty_young_regions() PRODUCT_RETURN;
1210 
1211   // verify_region_sets() performs verification over the region
1212   // lists. It will be compiled in the product code to be used when
1213   // necessary (i.e., during heap verification).
1214   void verify_region_sets();
1215 
1216   // verify_region_sets_optional() is planted in the code for
1217   // list verification in non-product builds (and it can be enabled in
1218   // product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1).
1219 #if HEAP_REGION_SET_FORCE_VERIFY
1220   void verify_region_sets_optional() {
1221     verify_region_sets();
1222   }
1223 #else // HEAP_REGION_SET_FORCE_VERIFY
1224   void verify_region_sets_optional() { }
1225 #endif // HEAP_REGION_SET_FORCE_VERIFY
1226 
1227 #ifdef ASSERT
1228   bool is_on_master_free_list(HeapRegion* hr) {
1229     return hr->containing_set() == &_free_list;
1230   }
1231 
1232   bool is_in_humongous_set(HeapRegion* hr) {
1233     return hr->containing_set() == &_humongous_set;
1234   }
1235 #endif // ASSERT
1236 
1237   // Wrapper for the region list operations that can be called from
1238   // methods outside this class.
1239 
1240   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1241     _secondary_free_list.add_as_tail(list);
1242   }
1243 
1244   void append_secondary_free_list() {
1245     _free_list.add_as_head(&_secondary_free_list);
1246   }
1247 
1248   void append_secondary_free_list_if_not_empty_with_lock() {
1249     // If the secondary free list looks empty there's no reason to
1250     // take the lock and then try to append it.
1251     if (!_secondary_free_list.is_empty()) {
1252       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1253       append_secondary_free_list();
1254     }
1255   }
1256 
1257   void old_set_remove(HeapRegion* hr) {
1258     _old_set.remove(hr);
1259   }
1260 
1261   size_t non_young_capacity_bytes() {
1262     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1263   }
1264 
1265   void set_free_regions_coming();
1266   void reset_free_regions_coming();
1267   bool free_regions_coming() { return _free_regions_coming; }
1268   void wait_while_free_regions_coming();
1269 
1270   // Determine whether the given region is one that we are using as an
1271   // old GC alloc region.
1272   bool is_old_gc_alloc_region(HeapRegion* hr) {
1273     return hr == _retained_old_gc_alloc_region;
1274   }
1275 
1276   // Perform a collection of the heap; intended for use in implementing
1277   // "System.gc".  This probably implies as full a collection as the
1278   // "CollectedHeap" supports.
1279   virtual void collect(GCCause::Cause cause);
1280 
1281   // The same as above but assume that the caller holds the Heap_lock.
1282   void collect_locked(GCCause::Cause cause);
1283 
1284   // True iff a evacuation has failed in the most-recent collection.
1285   bool evacuation_failed() { return _evacuation_failed; }
1286 
1287   // It will free a region if it has allocated objects in it that are
1288   // all dead. It calls either free_region() or
1289   // free_humongous_region() depending on the type of the region that
1290   // is passed to it.
1291   void free_region_if_empty(HeapRegion* hr,
1292                             size_t* pre_used,
1293                             FreeRegionList* free_list,
1294                             OldRegionSet* old_proxy_set,
1295                             HumongousRegionSet* humongous_proxy_set,
1296                             HRRSCleanupTask* hrrs_cleanup_task,
1297                             bool par);
1298 
1299   // It appends the free list to the master free list and updates the
1300   // master humongous list according to the contents of the proxy
1301   // list. It also adjusts the total used bytes according to pre_used
1302   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1303   void update_sets_after_freeing_regions(size_t pre_used,
1304                                        FreeRegionList* free_list,
1305                                        OldRegionSet* old_proxy_set,
1306                                        HumongousRegionSet* humongous_proxy_set,
1307                                        bool par);
1308 
1309   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1310   virtual bool is_in(const void* p) const;
1311 
1312   // Return "TRUE" iff the given object address is within the collection
1313   // set.
1314   inline bool obj_in_cs(oop obj);
1315 
1316   // Return "TRUE" iff the given object address is in the reserved
1317   // region of g1.
1318   bool is_in_g1_reserved(const void* p) const {
1319     return _g1_reserved.contains(p);
1320   }
1321 
1322   // Returns a MemRegion that corresponds to the space that has been
1323   // reserved for the heap
1324   MemRegion g1_reserved() {
1325     return _g1_reserved;
1326   }
1327 
1328   // Returns a MemRegion that corresponds to the space that has been
1329   // committed in the heap
1330   MemRegion g1_committed() {
1331     return _g1_committed;
1332   }
1333 
1334   virtual bool is_in_closed_subset(const void* p) const;
1335 
1336   // This resets the card table to all zeros.  It is used after
1337   // a collection pause which used the card table to claim cards.
1338   void cleanUpCardTable();
1339 
1340   // Iteration functions.
1341 
1342   // Iterate over all the ref-containing fields of all objects, calling
1343   // "cl.do_oop" on each.
1344   virtual void oop_iterate(ExtendedOopClosure* cl);
1345 
1346   // Same as above, restricted to a memory region.
1347   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1348 
1349   // Iterate over all objects, calling "cl.do_object" on each.
1350   virtual void object_iterate(ObjectClosure* cl);
1351 
1352   virtual void safe_object_iterate(ObjectClosure* cl) {
1353     object_iterate(cl);
1354   }
1355 
1356   // Iterate over all objects allocated since the last collection, calling
1357   // "cl.do_object" on each.  The heap must have been initialized properly
1358   // to support this function, or else this call will fail.
1359   virtual void object_iterate_since_last_GC(ObjectClosure* cl);
1360 
1361   // Iterate over all spaces in use in the heap, in ascending address order.
1362   virtual void space_iterate(SpaceClosure* cl);
1363 
1364   // Iterate over heap regions, in address order, terminating the
1365   // iteration early if the "doHeapRegion" method returns "true".
1366   void heap_region_iterate(HeapRegionClosure* blk) const;
1367 
1368   // Return the region with the given index. It assumes the index is valid.
1369   HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1370 
1371   // Divide the heap region sequence into "chunks" of some size (the number
1372   // of regions divided by the number of parallel threads times some
1373   // overpartition factor, currently 4).  Assumes that this will be called
1374   // in parallel by ParallelGCThreads worker threads with discinct worker
1375   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1376   // calls will use the same "claim_value", and that that claim value is
1377   // different from the claim_value of any heap region before the start of
1378   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1379   // attempting to claim the first region in each chunk, and, if
1380   // successful, applying the closure to each region in the chunk (and
1381   // setting the claim value of the second and subsequent regions of the
1382   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1383   // i.e., that a closure never attempt to abort a traversal.
1384   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1385                                        uint worker,
1386                                        uint no_of_par_workers,
1387                                        jint claim_value);
1388 
1389   // It resets all the region claim values to the default.
1390   void reset_heap_region_claim_values();
1391 
1392   // Resets the claim values of regions in the current
1393   // collection set to the default.
1394   void reset_cset_heap_region_claim_values();
1395 
1396 #ifdef ASSERT
1397   bool check_heap_region_claim_values(jint claim_value);
1398 
1399   // Same as the routine above but only checks regions in the
1400   // current collection set.
1401   bool check_cset_heap_region_claim_values(jint claim_value);
1402 #endif // ASSERT
1403 
1404   // Clear the cached cset start regions and (more importantly)
1405   // the time stamps. Called when we reset the GC time stamp.
1406   void clear_cset_start_regions();
1407 
1408   // Given the id of a worker, obtain or calculate a suitable
1409   // starting region for iterating over the current collection set.
1410   HeapRegion* start_cset_region_for_worker(int worker_i);
1411 
1412   // This is a convenience method that is used by the
1413   // HeapRegionIterator classes to calculate the starting region for
1414   // each worker so that they do not all start from the same region.
1415   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1416 
1417   // Iterate over the regions (if any) in the current collection set.
1418   void collection_set_iterate(HeapRegionClosure* blk);
1419 
1420   // As above but starting from region r
1421   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1422 
1423   // Returns the first (lowest address) compactible space in the heap.
1424   virtual CompactibleSpace* first_compactible_space();
1425 
1426   // A CollectedHeap will contain some number of spaces.  This finds the
1427   // space containing a given address, or else returns NULL.
1428   virtual Space* space_containing(const void* addr) const;
1429 
1430   // A G1CollectedHeap will contain some number of heap regions.  This
1431   // finds the region containing a given address, or else returns NULL.
1432   template <class T>
1433   inline HeapRegion* heap_region_containing(const T addr) const;
1434 
1435   // Like the above, but requires "addr" to be in the heap (to avoid a
1436   // null-check), and unlike the above, may return an continuing humongous
1437   // region.
1438   template <class T>
1439   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1440 
1441   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1442   // each address in the (reserved) heap is a member of exactly
1443   // one block.  The defining characteristic of a block is that it is
1444   // possible to find its size, and thus to progress forward to the next
1445   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1446   // represent Java objects, or they might be free blocks in a
1447   // free-list-based heap (or subheap), as long as the two kinds are
1448   // distinguishable and the size of each is determinable.
1449 
1450   // Returns the address of the start of the "block" that contains the
1451   // address "addr".  We say "blocks" instead of "object" since some heaps
1452   // may not pack objects densely; a chunk may either be an object or a
1453   // non-object.
1454   virtual HeapWord* block_start(const void* addr) const;
1455 
1456   // Requires "addr" to be the start of a chunk, and returns its size.
1457   // "addr + size" is required to be the start of a new chunk, or the end
1458   // of the active area of the heap.
1459   virtual size_t block_size(const HeapWord* addr) const;
1460 
1461   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1462   // the block is an object.
1463   virtual bool block_is_obj(const HeapWord* addr) const;
1464 
1465   // Does this heap support heap inspection? (+PrintClassHistogram)
1466   virtual bool supports_heap_inspection() const { return true; }
1467 
1468   // Section on thread-local allocation buffers (TLABs)
1469   // See CollectedHeap for semantics.
1470 
1471   virtual bool supports_tlab_allocation() const;
1472   virtual size_t tlab_capacity(Thread* thr) const;
1473   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1474 
1475   // Can a compiler initialize a new object without store barriers?
1476   // This permission only extends from the creation of a new object
1477   // via a TLAB up to the first subsequent safepoint. If such permission
1478   // is granted for this heap type, the compiler promises to call
1479   // defer_store_barrier() below on any slow path allocation of
1480   // a new object for which such initializing store barriers will
1481   // have been elided. G1, like CMS, allows this, but should be
1482   // ready to provide a compensating write barrier as necessary
1483   // if that storage came out of a non-young region. The efficiency
1484   // of this implementation depends crucially on being able to
1485   // answer very efficiently in constant time whether a piece of
1486   // storage in the heap comes from a young region or not.
1487   // See ReduceInitialCardMarks.
1488   virtual bool can_elide_tlab_store_barriers() const {
1489     return true;
1490   }
1491 
1492   virtual bool card_mark_must_follow_store() const {
1493     return true;
1494   }
1495 
1496   bool is_in_young(const oop obj) {
1497     HeapRegion* hr = heap_region_containing(obj);
1498     return hr != NULL && hr->is_young();
1499   }
1500 
1501 #ifdef ASSERT
1502   virtual bool is_in_partial_collection(const void* p);
1503 #endif
1504 
1505   virtual bool is_scavengable(const void* addr);
1506 
1507   // We don't need barriers for initializing stores to objects
1508   // in the young gen: for the SATB pre-barrier, there is no
1509   // pre-value that needs to be remembered; for the remembered-set
1510   // update logging post-barrier, we don't maintain remembered set
1511   // information for young gen objects.
1512   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1513     return is_in_young(new_obj);
1514   }
1515 
1516   // Returns "true" iff the given word_size is "very large".
1517   static bool isHumongous(size_t word_size) {
1518     // Note this has to be strictly greater-than as the TLABs
1519     // are capped at the humongous thresold and we want to
1520     // ensure that we don't try to allocate a TLAB as
1521     // humongous and that we don't allocate a humongous
1522     // object in a TLAB.
1523     return word_size > _humongous_object_threshold_in_words;
1524   }
1525 
1526   // Update mod union table with the set of dirty cards.
1527   void updateModUnion();
1528 
1529   // Set the mod union bits corresponding to the given memRegion.  Note
1530   // that this is always a safe operation, since it doesn't clear any
1531   // bits.
1532   void markModUnionRange(MemRegion mr);
1533 
1534   // Records the fact that a marking phase is no longer in progress.
1535   void set_marking_complete() {
1536     _mark_in_progress = false;
1537   }
1538   void set_marking_started() {
1539     _mark_in_progress = true;
1540   }
1541   bool mark_in_progress() {
1542     return _mark_in_progress;
1543   }
1544 
1545   // Print the maximum heap capacity.
1546   virtual size_t max_capacity() const;
1547 
1548   virtual jlong millis_since_last_gc();
1549 
1550   // Perform any cleanup actions necessary before allowing a verification.
1551   virtual void prepare_for_verify();
1552 
1553   // Perform verification.
1554 
1555   // vo == UsePrevMarking  -> use "prev" marking information,
1556   // vo == UseNextMarking -> use "next" marking information
1557   // vo == UseMarkWord    -> use the mark word in the object header
1558   //
1559   // NOTE: Only the "prev" marking information is guaranteed to be
1560   // consistent most of the time, so most calls to this should use
1561   // vo == UsePrevMarking.
1562   // Currently, there is only one case where this is called with
1563   // vo == UseNextMarking, which is to verify the "next" marking
1564   // information at the end of remark.
1565   // Currently there is only one place where this is called with
1566   // vo == UseMarkWord, which is to verify the marking during a
1567   // full GC.
1568   void verify(bool silent, VerifyOption vo);
1569 
1570   // Override; it uses the "prev" marking information
1571   virtual void verify(bool silent);
1572   virtual void print_on(outputStream* st) const;
1573   virtual void print_extended_on(outputStream* st) const;
1574 
1575   virtual void print_gc_threads_on(outputStream* st) const;
1576   virtual void gc_threads_do(ThreadClosure* tc) const;
1577 
1578   // Override
1579   void print_tracing_info() const;
1580 
1581   // The following two methods are helpful for debugging RSet issues.
1582   void print_cset_rsets() PRODUCT_RETURN;
1583   void print_all_rsets() PRODUCT_RETURN;
1584 
1585   // Convenience function to be used in situations where the heap type can be
1586   // asserted to be this type.
1587   static G1CollectedHeap* heap();
1588 
1589   void set_region_short_lived_locked(HeapRegion* hr);
1590   // add appropriate methods for any other surv rate groups
1591 
1592   YoungList* young_list() { return _young_list; }
1593 
1594   // debugging
1595   bool check_young_list_well_formed() {
1596     return _young_list->check_list_well_formed();
1597   }
1598 
1599   bool check_young_list_empty(bool check_heap,
1600                               bool check_sample = true);
1601 
1602   // *** Stuff related to concurrent marking.  It's not clear to me that so
1603   // many of these need to be public.
1604 
1605   // The functions below are helper functions that a subclass of
1606   // "CollectedHeap" can use in the implementation of its virtual
1607   // functions.
1608   // This performs a concurrent marking of the live objects in a
1609   // bitmap off to the side.
1610   void doConcurrentMark();
1611 
1612   bool isMarkedPrev(oop obj) const;
1613   bool isMarkedNext(oop obj) const;
1614 
1615   // Determine if an object is dead, given the object and also
1616   // the region to which the object belongs. An object is dead
1617   // iff a) it was not allocated since the last mark and b) it
1618   // is not marked.
1619 
1620   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1621     return
1622       !hr->obj_allocated_since_prev_marking(obj) &&
1623       !isMarkedPrev(obj);
1624   }
1625 
1626   // This function returns true when an object has been
1627   // around since the previous marking and hasn't yet
1628   // been marked during this marking.
1629 
1630   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1631     return
1632       !hr->obj_allocated_since_next_marking(obj) &&
1633       !isMarkedNext(obj);
1634   }
1635 
1636   // Determine if an object is dead, given only the object itself.
1637   // This will find the region to which the object belongs and
1638   // then call the region version of the same function.
1639 
1640   // Added if it is NULL it isn't dead.
1641 
1642   bool is_obj_dead(const oop obj) const {
1643     const HeapRegion* hr = heap_region_containing(obj);
1644     if (hr == NULL) {
1645       if (obj == NULL) return false;
1646       else return true;
1647     }
1648     else return is_obj_dead(obj, hr);
1649   }
1650 
1651   bool is_obj_ill(const oop obj) const {
1652     const HeapRegion* hr = heap_region_containing(obj);
1653     if (hr == NULL) {
1654       if (obj == NULL) return false;
1655       else return true;
1656     }
1657     else return is_obj_ill(obj, hr);
1658   }
1659 
1660   // The methods below are here for convenience and dispatch the
1661   // appropriate method depending on value of the given VerifyOption
1662   // parameter. The options for that parameter are:
1663   //
1664   // vo == UsePrevMarking -> use "prev" marking information,
1665   // vo == UseNextMarking -> use "next" marking information,
1666   // vo == UseMarkWord    -> use mark word from object header
1667 
1668   bool is_obj_dead_cond(const oop obj,
1669                         const HeapRegion* hr,
1670                         const VerifyOption vo) const {
1671     switch (vo) {
1672     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1673     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1674     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1675     default:                            ShouldNotReachHere();
1676     }
1677     return false; // keep some compilers happy
1678   }
1679 
1680   bool is_obj_dead_cond(const oop obj,
1681                         const VerifyOption vo) const {
1682     switch (vo) {
1683     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1684     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1685     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1686     default:                            ShouldNotReachHere();
1687     }
1688     return false; // keep some compilers happy
1689   }
1690 
1691   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1692   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1693   bool is_marked(oop obj, VerifyOption vo);
1694   const char* top_at_mark_start_str(VerifyOption vo);
1695 
1696   // The following is just to alert the verification code
1697   // that a full collection has occurred and that the
1698   // remembered sets are no longer up to date.
1699   bool _full_collection;
1700   void set_full_collection() { _full_collection = true;}
1701   void clear_full_collection() {_full_collection = false;}
1702   bool full_collection() {return _full_collection;}
1703 
1704   ConcurrentMark* concurrent_mark() const { return _cm; }
1705   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1706 
1707   // The dirty cards region list is used to record a subset of regions
1708   // whose cards need clearing. The list if populated during the
1709   // remembered set scanning and drained during the card table
1710   // cleanup. Although the methods are reentrant, population/draining
1711   // phases must not overlap. For synchronization purposes the last
1712   // element on the list points to itself.
1713   HeapRegion* _dirty_cards_region_list;
1714   void push_dirty_cards_region(HeapRegion* hr);
1715   HeapRegion* pop_dirty_cards_region();
1716 
1717 public:
1718   void stop_conc_gc_threads();
1719 
1720   size_t pending_card_num();
1721   size_t cards_scanned();
1722 
1723 protected:
1724   size_t _max_heap_capacity;
1725 };
1726 
1727 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1728 private:
1729   bool        _retired;
1730 
1731 public:
1732   G1ParGCAllocBuffer(size_t gclab_word_size);
1733 
1734   void set_buf(HeapWord* buf) {
1735     ParGCAllocBuffer::set_buf(buf);
1736     _retired = false;
1737   }
1738 
1739   void retire(bool end_of_gc, bool retain) {
1740     if (_retired)
1741       return;
1742     ParGCAllocBuffer::retire(end_of_gc, retain);
1743     _retired = true;
1744   }
1745 };
1746 
1747 class G1ParScanThreadState : public StackObj {
1748 protected:
1749   G1CollectedHeap* _g1h;
1750   RefToScanQueue*  _refs;
1751   DirtyCardQueue   _dcq;
1752   CardTableModRefBS* _ct_bs;
1753   G1RemSet* _g1_rem;
1754 
1755   G1ParGCAllocBuffer  _surviving_alloc_buffer;
1756   G1ParGCAllocBuffer  _tenured_alloc_buffer;
1757   G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1758   ageTable            _age_table;
1759 
1760   size_t           _alloc_buffer_waste;
1761   size_t           _undo_waste;
1762 
1763   OopsInHeapRegionClosure*      _evac_failure_cl;
1764   G1ParScanHeapEvacClosure*     _evac_cl;
1765   G1ParScanPartialArrayClosure* _partial_scan_cl;
1766 
1767   int _hash_seed;
1768   uint _queue_num;
1769 
1770   size_t _term_attempts;
1771 
1772   double _start;
1773   double _start_strong_roots;
1774   double _strong_roots_time;
1775   double _start_term;
1776   double _term_time;
1777 
1778   // Map from young-age-index (0 == not young, 1 is youngest) to
1779   // surviving words. base is what we get back from the malloc call
1780   size_t* _surviving_young_words_base;
1781   // this points into the array, as we use the first few entries for padding
1782   size_t* _surviving_young_words;
1783 
1784 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1785 
1786   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1787 
1788   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1789 
1790   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1791   CardTableModRefBS* ctbs()                      { return _ct_bs; }
1792 
1793   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1794     if (!from->is_survivor()) {
1795       _g1_rem->par_write_ref(from, p, tid);
1796     }
1797   }
1798 
1799   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1800     // If the new value of the field points to the same region or
1801     // is the to-space, we don't need to include it in the Rset updates.
1802     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1803       size_t card_index = ctbs()->index_for(p);
1804       // If the card hasn't been added to the buffer, do it.
1805       if (ctbs()->mark_card_deferred(card_index)) {
1806         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1807       }
1808     }
1809   }
1810 
1811 public:
1812   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num);
1813 
1814   ~G1ParScanThreadState() {
1815     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1816   }
1817 
1818   RefToScanQueue*   refs()            { return _refs;             }
1819   ageTable*         age_table()       { return &_age_table;       }
1820 
1821   G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1822     return _alloc_buffers[purpose];
1823   }
1824 
1825   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1826   size_t undo_waste() const                      { return _undo_waste; }
1827 
1828 #ifdef ASSERT
1829   bool verify_ref(narrowOop* ref) const;
1830   bool verify_ref(oop* ref) const;
1831   bool verify_task(StarTask ref) const;
1832 #endif // ASSERT
1833 
1834   template <class T> void push_on_queue(T* ref) {
1835     assert(verify_ref(ref), "sanity");
1836     refs()->push(ref);
1837   }
1838 
1839   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1840     if (G1DeferredRSUpdate) {
1841       deferred_rs_update(from, p, tid);
1842     } else {
1843       immediate_rs_update(from, p, tid);
1844     }
1845   }
1846 
1847   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1848     HeapWord* obj = NULL;
1849     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1850     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1851       G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1852       add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1853       alloc_buf->retire(false /* end_of_gc */, false /* retain */);
1854 
1855       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1856       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1857       // Otherwise.
1858       alloc_buf->set_word_size(gclab_word_size);
1859       alloc_buf->set_buf(buf);
1860 
1861       obj = alloc_buf->allocate(word_sz);
1862       assert(obj != NULL, "buffer was definitely big enough...");
1863     } else {
1864       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1865     }
1866     return obj;
1867   }
1868 
1869   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1870     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1871     if (obj != NULL) return obj;
1872     return allocate_slow(purpose, word_sz);
1873   }
1874 
1875   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1876     if (alloc_buffer(purpose)->contains(obj)) {
1877       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1878              "should contain whole object");
1879       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1880     } else {
1881       CollectedHeap::fill_with_object(obj, word_sz);
1882       add_to_undo_waste(word_sz);
1883     }
1884   }
1885 
1886   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1887     _evac_failure_cl = evac_failure_cl;
1888   }
1889   OopsInHeapRegionClosure* evac_failure_closure() {
1890     return _evac_failure_cl;
1891   }
1892 
1893   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1894     _evac_cl = evac_cl;
1895   }
1896 
1897   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1898     _partial_scan_cl = partial_scan_cl;
1899   }
1900 
1901   int* hash_seed() { return &_hash_seed; }
1902   uint queue_num() { return _queue_num; }
1903 
1904   size_t term_attempts() const  { return _term_attempts; }
1905   void note_term_attempt() { _term_attempts++; }
1906 
1907   void start_strong_roots() {
1908     _start_strong_roots = os::elapsedTime();
1909   }
1910   void end_strong_roots() {
1911     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1912   }
1913   double strong_roots_time() const { return _strong_roots_time; }
1914 
1915   void start_term_time() {
1916     note_term_attempt();
1917     _start_term = os::elapsedTime();
1918   }
1919   void end_term_time() {
1920     _term_time += (os::elapsedTime() - _start_term);
1921   }
1922   double term_time() const { return _term_time; }
1923 
1924   double elapsed_time() const {
1925     return os::elapsedTime() - _start;
1926   }
1927 
1928   static void
1929     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1930   void
1931     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1932 
1933   size_t* surviving_young_words() {
1934     // We add on to hide entry 0 which accumulates surviving words for
1935     // age -1 regions (i.e. non-young ones)
1936     return _surviving_young_words;
1937   }
1938 
1939   void retire_alloc_buffers() {
1940     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1941       size_t waste = _alloc_buffers[ap]->words_remaining();
1942       add_to_alloc_buffer_waste(waste);
1943       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
1944                                                  true /* end_of_gc */,
1945                                                  false /* retain */);
1946     }
1947   }
1948 
1949   template <class T> void deal_with_reference(T* ref_to_scan) {
1950     if (has_partial_array_mask(ref_to_scan)) {
1951       _partial_scan_cl->do_oop_nv(ref_to_scan);
1952     } else {
1953       // Note: we can use "raw" versions of "region_containing" because
1954       // "obj_to_scan" is definitely in the heap, and is not in a
1955       // humongous region.
1956       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
1957       _evac_cl->set_region(r);
1958       _evac_cl->do_oop_nv(ref_to_scan);
1959     }
1960   }
1961 
1962   void deal_with_reference(StarTask ref) {
1963     assert(verify_task(ref), "sanity");
1964     if (ref.is_narrow()) {
1965       deal_with_reference((narrowOop*)ref);
1966     } else {
1967       deal_with_reference((oop*)ref);
1968     }
1969   }
1970 
1971 public:
1972   void trim_queue();
1973 };
1974 
1975 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---