1 /*
   2  * Copyright (c) 2001, 2013, 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.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/concurrentMark.hpp"
  29 #include "gc_implementation/g1/evacuationInfo.hpp"
  30 #include "gc_implementation/g1/g1AllocRegion.hpp"
  31 #include "gc_implementation/g1/g1HRPrinter.hpp"
  32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  33 #include "gc_implementation/g1/g1RemSet.hpp"
  34 #include "gc_implementation/g1/g1YCTypes.hpp"
  35 #include "gc_implementation/g1/heapRegionSeq.hpp"
  36 #include "gc_implementation/g1/heapRegionSets.hpp"
  37 #include "gc_implementation/shared/hSpaceCounters.hpp"
  38 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  39 #include "memory/barrierSet.hpp"
  40 #include "memory/memRegion.hpp"
  41 #include "memory/sharedHeap.hpp"
  42 #include "utilities/stack.hpp"
  43 
  44 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  45 // It uses the "Garbage First" heap organization and algorithm, which
  46 // may combine concurrent marking with parallel, incremental compaction of
  47 // heap subsets that will yield large amounts of garbage.
  48 
  49 class HeapRegion;
  50 class HRRSCleanupTask;
  51 class GenerationSpec;
  52 class OopsInHeapRegionClosure;
  53 class G1KlassScanClosure;
  54 class G1ScanHeapEvacClosure;
  55 class ObjectClosure;
  56 class SpaceClosure;
  57 class CompactibleSpaceClosure;
  58 class Space;
  59 class G1CollectorPolicy;
  60 class GenRemSet;
  61 class G1RemSet;
  62 class HeapRegionRemSetIterator;
  63 class ConcurrentMark;
  64 class ConcurrentMarkThread;
  65 class ConcurrentG1Refine;
  66 class ConcurrentGCTimer;
  67 class GenerationCounters;
  68 class STWGCTimer;
  69 class G1NewTracer;
  70 class G1OldTracer;
  71 class EvacuationFailedInfo;
  72 
  73 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  74 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  75 
  76 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  77 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  78 
  79 enum GCAllocPurpose {
  80   GCAllocForTenured,
  81   GCAllocForSurvived,
  82   GCAllocPurposeCount
  83 };
  84 
  85 class YoungList : public CHeapObj<mtGC> {
  86 private:
  87   G1CollectedHeap* _g1h;
  88 
  89   HeapRegion* _head;
  90 
  91   HeapRegion* _survivor_head;
  92   HeapRegion* _survivor_tail;
  93 
  94   HeapRegion* _curr;
  95 
  96   uint        _length;
  97   uint        _survivor_length;
  98 
  99   size_t      _last_sampled_rs_lengths;
 100   size_t      _sampled_rs_lengths;
 101 
 102   void         empty_list(HeapRegion* list);
 103 
 104 public:
 105   YoungList(G1CollectedHeap* g1h);
 106 
 107   void         push_region(HeapRegion* hr);
 108   void         add_survivor_region(HeapRegion* hr);
 109 
 110   void         empty_list();
 111   bool         is_empty() { return _length == 0; }
 112   uint         length() { return _length; }
 113   uint         survivor_length() { return _survivor_length; }
 114 
 115   // Currently we do not keep track of the used byte sum for the
 116   // young list and the survivors and it'd be quite a lot of work to
 117   // do so. When we'll eventually replace the young list with
 118   // instances of HeapRegionLinkedList we'll get that for free. So,
 119   // we'll report the more accurate information then.
 120   size_t       eden_used_bytes() {
 121     assert(length() >= survivor_length(), "invariant");
 122     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 123   }
 124   size_t       survivor_used_bytes() {
 125     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 126   }
 127 
 128   void rs_length_sampling_init();
 129   bool rs_length_sampling_more();
 130   void rs_length_sampling_next();
 131 
 132   void reset_sampled_info() {
 133     _last_sampled_rs_lengths =   0;
 134   }
 135   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 136 
 137   // for development purposes
 138   void reset_auxilary_lists();
 139   void clear() { _head = NULL; _length = 0; }
 140 
 141   void clear_survivors() {
 142     _survivor_head    = NULL;
 143     _survivor_tail    = NULL;
 144     _survivor_length  = 0;
 145   }
 146 
 147   HeapRegion* first_region() { return _head; }
 148   HeapRegion* first_survivor_region() { return _survivor_head; }
 149   HeapRegion* last_survivor_region() { return _survivor_tail; }
 150 
 151   // debugging
 152   bool          check_list_well_formed();
 153   bool          check_list_empty(bool check_sample = true);
 154   void          print();
 155 };
 156 
 157 class MutatorAllocRegion : public G1AllocRegion {
 158 protected:
 159   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 160   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 161 public:
 162   MutatorAllocRegion()
 163     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 164 };
 165 
 166 // The G1 STW is alive closure.
 167 // An instance is embedded into the G1CH and used as the
 168 // (optional) _is_alive_non_header closure in the STW
 169 // reference processor. It is also extensively used during
 170 // reference processing during STW evacuation pauses.
 171 class G1STWIsAliveClosure: public BoolObjectClosure {
 172   G1CollectedHeap* _g1;
 173 public:
 174   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 175   bool do_object_b(oop p);
 176 };
 177 
 178 class SurvivorGCAllocRegion : public G1AllocRegion {
 179 protected:
 180   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 181   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 182 public:
 183   SurvivorGCAllocRegion()
 184   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 185 };
 186 
 187 class OldGCAllocRegion : public G1AllocRegion {
 188 protected:
 189   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 190   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 191 public:
 192   OldGCAllocRegion()
 193   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 194 };
 195 
 196 class RefineCardTableEntryClosure;
 197 
 198 class G1CollectedHeap : public SharedHeap {
 199   friend class VM_G1CollectForAllocation;
 200   friend class VM_G1CollectFull;
 201   friend class VM_G1IncCollectionPause;
 202   friend class VMStructs;
 203   friend class MutatorAllocRegion;
 204   friend class SurvivorGCAllocRegion;
 205   friend class OldGCAllocRegion;
 206 
 207   // Closures used in implementation.
 208   template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
 209   friend class G1ParCopyClosure;
 210   friend class G1IsAliveClosure;
 211   friend class G1EvacuateFollowersClosure;
 212   friend class G1ParScanThreadState;
 213   friend class G1ParScanClosureSuper;
 214   friend class G1ParEvacuateFollowersClosure;
 215   friend class G1ParTask;
 216   friend class G1FreeGarbageRegionClosure;
 217   friend class RefineCardTableEntryClosure;
 218   friend class G1PrepareCompactClosure;
 219   friend class RegionSorter;
 220   friend class RegionResetter;
 221   friend class CountRCClosure;
 222   friend class EvacPopObjClosure;
 223   friend class G1ParCleanupCTTask;
 224 
 225   // Other related classes.
 226   friend class G1MarkSweep;
 227 
 228 private:
 229   // The one and only G1CollectedHeap, so static functions can find it.
 230   static G1CollectedHeap* _g1h;
 231 
 232   static size_t _humongous_object_threshold_in_words;
 233 
 234   // Storage for the G1 heap.
 235   VirtualSpace _g1_storage;
 236   MemRegion    _g1_reserved;
 237 
 238   // The part of _g1_storage that is currently committed.
 239   MemRegion _g1_committed;
 240 
 241   // The master free list. It will satisfy all new region allocations.
 242   MasterFreeRegionList      _free_list;
 243 
 244   // The secondary free list which contains regions that have been
 245   // freed up during the cleanup process. This will be appended to the
 246   // master free list when appropriate.
 247   SecondaryFreeRegionList   _secondary_free_list;
 248 
 249   // It keeps track of the old regions.
 250   MasterOldRegionSet        _old_set;
 251 
 252   // It keeps track of the humongous regions.
 253   MasterHumongousRegionSet  _humongous_set;
 254 
 255   // The number of regions we could create by expansion.
 256   uint _expansion_regions;
 257 
 258   // The block offset table for the G1 heap.
 259   G1BlockOffsetSharedArray* _bot_shared;
 260 
 261   // Tears down the region sets / lists so that they are empty and the
 262   // regions on the heap do not belong to a region set / list. The
 263   // only exception is the humongous set which we leave unaltered. If
 264   // free_list_only is true, it will only tear down the master free
 265   // list. It is called before a Full GC (free_list_only == false) or
 266   // before heap shrinking (free_list_only == true).
 267   void tear_down_region_sets(bool free_list_only);
 268 
 269   // Rebuilds the region sets / lists so that they are repopulated to
 270   // reflect the contents of the heap. The only exception is the
 271   // humongous set which was not torn down in the first place. If
 272   // free_list_only is true, it will only rebuild the master free
 273   // list. It is called after a Full GC (free_list_only == false) or
 274   // after heap shrinking (free_list_only == true).
 275   void rebuild_region_sets(bool free_list_only);
 276 
 277   // The sequence of all heap regions in the heap.
 278   HeapRegionSeq _hrs;
 279 
 280   // Alloc region used to satisfy mutator allocation requests.
 281   MutatorAllocRegion _mutator_alloc_region;
 282 
 283   // Alloc region used to satisfy allocation requests by the GC for
 284   // survivor objects.
 285   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 286 
 287   // PLAB sizing policy for survivors.
 288   PLABStats _survivor_plab_stats;
 289 
 290   // Alloc region used to satisfy allocation requests by the GC for
 291   // old objects.
 292   OldGCAllocRegion _old_gc_alloc_region;
 293 
 294   // PLAB sizing policy for tenured objects.
 295   PLABStats _old_plab_stats;
 296 
 297   PLABStats* stats_for_purpose(GCAllocPurpose purpose) {
 298     PLABStats* stats = NULL;
 299 
 300     switch (purpose) {
 301     case GCAllocForSurvived:
 302       stats = &_survivor_plab_stats;
 303       break;
 304     case GCAllocForTenured:
 305       stats = &_old_plab_stats;
 306       break;
 307     default:
 308       assert(false, "unrecognized GCAllocPurpose");
 309     }
 310 
 311     return stats;
 312   }
 313 
 314   // The last old region we allocated to during the last GC.
 315   // Typically, it is not full so we should re-use it during the next GC.
 316   HeapRegion* _retained_old_gc_alloc_region;
 317 
 318   // It specifies whether we should attempt to expand the heap after a
 319   // region allocation failure. If heap expansion fails we set this to
 320   // false so that we don't re-attempt the heap expansion (it's likely
 321   // that subsequent expansion attempts will also fail if one fails).
 322   // Currently, it is only consulted during GC and it's reset at the
 323   // start of each GC.
 324   bool _expand_heap_after_alloc_failure;
 325 
 326   // It resets the mutator alloc region before new allocations can take place.
 327   void init_mutator_alloc_region();
 328 
 329   // It releases the mutator alloc region.
 330   void release_mutator_alloc_region();
 331 
 332   // It initializes the GC alloc regions at the start of a GC.
 333   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 334 
 335   // It releases the GC alloc regions at the end of a GC.
 336   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 337 
 338   // It does any cleanup that needs to be done on the GC alloc regions
 339   // before a Full GC.
 340   void abandon_gc_alloc_regions();
 341 
 342   // Helper for monitoring and management support.
 343   G1MonitoringSupport* _g1mm;
 344 
 345   // Determines PLAB size for a particular allocation purpose.
 346   size_t desired_plab_sz(GCAllocPurpose purpose);
 347 
 348   // Outside of GC pauses, the number of bytes used in all regions other
 349   // than the current allocation region.
 350   size_t _summary_bytes_used;
 351 
 352   // This is used for a quick test on whether a reference points into
 353   // the collection set or not. Basically, we have an array, with one
 354   // byte per region, and that byte denotes whether the corresponding
 355   // region is in the collection set or not. The entry corresponding
 356   // the bottom of the heap, i.e., region 0, is pointed to by
 357   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 358   // biased so that it actually points to address 0 of the address
 359   // space, to make the test as fast as possible (we can simply shift
 360   // the address to address into it, instead of having to subtract the
 361   // bottom of the heap from the address before shifting it; basically
 362   // it works in the same way the card table works).
 363   bool* _in_cset_fast_test;
 364 
 365   // The allocated array used for the fast test on whether a reference
 366   // points into the collection set or not. This field is also used to
 367   // free the array.
 368   bool* _in_cset_fast_test_base;
 369 
 370   // The length of the _in_cset_fast_test_base array.
 371   uint _in_cset_fast_test_length;
 372 
 373   volatile unsigned _gc_time_stamp;
 374 
 375   size_t* _surviving_young_words;
 376 
 377   G1HRPrinter _hr_printer;
 378 
 379   void setup_surviving_young_words();
 380   void update_surviving_young_words(size_t* surv_young_words);
 381   void cleanup_surviving_young_words();
 382 
 383   // It decides whether an explicit GC should start a concurrent cycle
 384   // instead of doing a STW GC. Currently, a concurrent cycle is
 385   // explicitly started if:
 386   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 387   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 388   // (c) cause == _g1_humongous_allocation
 389   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 390 
 391   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 392   // concurrent cycles) we have started.
 393   volatile unsigned int _old_marking_cycles_started;
 394 
 395   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 396   // concurrent cycles) we have completed.
 397   volatile unsigned int _old_marking_cycles_completed;
 398 
 399   bool _concurrent_cycle_started;
 400 
 401   // This is a non-product method that is helpful for testing. It is
 402   // called at the end of a GC and artificially expands the heap by
 403   // allocating a number of dead regions. This way we can induce very
 404   // frequent marking cycles and stress the cleanup / concurrent
 405   // cleanup code more (as all the regions that will be allocated by
 406   // this method will be found dead by the marking cycle).
 407   void allocate_dummy_regions() PRODUCT_RETURN;
 408 
 409   // Clear RSets after a compaction. It also resets the GC time stamps.
 410   void clear_rsets_post_compaction();
 411 
 412   // If the HR printer is active, dump the state of the regions in the
 413   // heap after a compaction.
 414   void print_hrs_post_compaction();
 415 
 416   double verify(bool guard, const char* msg);
 417   void verify_before_gc();
 418   void verify_after_gc();
 419 
 420   void log_gc_header();
 421   void log_gc_footer(double pause_time_sec);
 422 
 423   // These are macros so that, if the assert fires, we get the correct
 424   // line number, file, etc.
 425 
 426 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 427   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 428           (_extra_message_),                                                  \
 429           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 430           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 431           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 432 
 433 #define assert_heap_locked()                                                  \
 434   do {                                                                        \
 435     assert(Heap_lock->owned_by_self(),                                        \
 436            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 437   } while (0)
 438 
 439 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 440   do {                                                                        \
 441     assert(Heap_lock->owned_by_self() ||                                      \
 442            (SafepointSynchronize::is_at_safepoint() &&                        \
 443              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 444            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 445                                         "should be at a safepoint"));         \
 446   } while (0)
 447 
 448 #define assert_heap_locked_and_not_at_safepoint()                             \
 449   do {                                                                        \
 450     assert(Heap_lock->owned_by_self() &&                                      \
 451                                     !SafepointSynchronize::is_at_safepoint(), \
 452           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 453                                        "should not be at a safepoint"));      \
 454   } while (0)
 455 
 456 #define assert_heap_not_locked()                                              \
 457   do {                                                                        \
 458     assert(!Heap_lock->owned_by_self(),                                       \
 459         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 460   } while (0)
 461 
 462 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 463   do {                                                                        \
 464     assert(!Heap_lock->owned_by_self() &&                                     \
 465                                     !SafepointSynchronize::is_at_safepoint(), \
 466       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 467                                    "should not be at a safepoint"));          \
 468   } while (0)
 469 
 470 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 471   do {                                                                        \
 472     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 473               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 474            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 475   } while (0)
 476 
 477 #define assert_not_at_safepoint()                                             \
 478   do {                                                                        \
 479     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 480            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 481   } while (0)
 482 
 483 protected:
 484 
 485   // The young region list.
 486   YoungList*  _young_list;
 487 
 488   // The current policy object for the collector.
 489   G1CollectorPolicy* _g1_policy;
 490 
 491   // This is the second level of trying to allocate a new region. If
 492   // new_region() didn't find a region on the free_list, this call will
 493   // check whether there's anything available on the
 494   // secondary_free_list and/or wait for more regions to appear on
 495   // that list, if _free_regions_coming is set.
 496   HeapRegion* new_region_try_secondary_free_list();
 497 
 498   // Try to allocate a single non-humongous HeapRegion sufficient for
 499   // an allocation of the given word_size. If do_expand is true,
 500   // attempt to expand the heap if necessary to satisfy the allocation
 501   // request.
 502   HeapRegion* new_region(size_t word_size, bool do_expand);
 503 
 504   // Attempt to satisfy a humongous allocation request of the given
 505   // size by finding a contiguous set of free regions of num_regions
 506   // length and remove them from the master free list. Return the
 507   // index of the first region or G1_NULL_HRS_INDEX if the search
 508   // was unsuccessful.
 509   uint humongous_obj_allocate_find_first(uint num_regions,
 510                                          size_t word_size);
 511 
 512   // Initialize a contiguous set of free regions of length num_regions
 513   // and starting at index first so that they appear as a single
 514   // humongous region.
 515   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 516                                                       uint num_regions,
 517                                                       size_t word_size);
 518 
 519   // Attempt to allocate a humongous object of the given size. Return
 520   // NULL if unsuccessful.
 521   HeapWord* humongous_obj_allocate(size_t word_size);
 522 
 523   // The following two methods, allocate_new_tlab() and
 524   // mem_allocate(), are the two main entry points from the runtime
 525   // into the G1's allocation routines. They have the following
 526   // assumptions:
 527   //
 528   // * They should both be called outside safepoints.
 529   //
 530   // * They should both be called without holding the Heap_lock.
 531   //
 532   // * All allocation requests for new TLABs should go to
 533   //   allocate_new_tlab().
 534   //
 535   // * All non-TLAB allocation requests should go to mem_allocate().
 536   //
 537   // * If either call cannot satisfy the allocation request using the
 538   //   current allocating region, they will try to get a new one. If
 539   //   this fails, they will attempt to do an evacuation pause and
 540   //   retry the allocation.
 541   //
 542   // * If all allocation attempts fail, even after trying to schedule
 543   //   an evacuation pause, allocate_new_tlab() will return NULL,
 544   //   whereas mem_allocate() will attempt a heap expansion and/or
 545   //   schedule a Full GC.
 546   //
 547   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 548   //   should never be called with word_size being humongous. All
 549   //   humongous allocation requests should go to mem_allocate() which
 550   //   will satisfy them with a special path.
 551 
 552   virtual HeapWord* allocate_new_tlab(size_t word_size);
 553 
 554   virtual HeapWord* mem_allocate(size_t word_size,
 555                                  bool*  gc_overhead_limit_was_exceeded);
 556 
 557   // The following three methods take a gc_count_before_ret
 558   // parameter which is used to return the GC count if the method
 559   // returns NULL. Given that we are required to read the GC count
 560   // while holding the Heap_lock, and these paths will take the
 561   // Heap_lock at some point, it's easier to get them to read the GC
 562   // count while holding the Heap_lock before they return NULL instead
 563   // of the caller (namely: mem_allocate()) having to also take the
 564   // Heap_lock just to read the GC count.
 565 
 566   // First-level mutator allocation attempt: try to allocate out of
 567   // the mutator alloc region without taking the Heap_lock. This
 568   // should only be used for non-humongous allocations.
 569   inline HeapWord* attempt_allocation(size_t word_size,
 570                                       unsigned int* gc_count_before_ret,
 571                                       int* gclocker_retry_count_ret);
 572 
 573   // Second-level mutator allocation attempt: take the Heap_lock and
 574   // retry the allocation attempt, potentially scheduling a GC
 575   // pause. This should only be used for non-humongous allocations.
 576   HeapWord* attempt_allocation_slow(size_t word_size,
 577                                     unsigned int* gc_count_before_ret,
 578                                     int* gclocker_retry_count_ret);
 579 
 580   // Takes the Heap_lock and attempts a humongous allocation. It can
 581   // potentially schedule a GC pause.
 582   HeapWord* attempt_allocation_humongous(size_t word_size,
 583                                          unsigned int* gc_count_before_ret,
 584                                          int* gclocker_retry_count_ret);
 585 
 586   // Allocation attempt that should be called during safepoints (e.g.,
 587   // at the end of a successful GC). expect_null_mutator_alloc_region
 588   // specifies whether the mutator alloc region is expected to be NULL
 589   // or not.
 590   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 591                                        bool expect_null_mutator_alloc_region);
 592 
 593   // It dirties the cards that cover the block so that so that the post
 594   // write barrier never queues anything when updating objects on this
 595   // block. It is assumed (and in fact we assert) that the block
 596   // belongs to a young region.
 597   inline void dirty_young_block(HeapWord* start, size_t word_size);
 598 
 599   // Allocate blocks during garbage collection. Will ensure an
 600   // allocation region, either by picking one or expanding the
 601   // heap, and then allocate a block of the given size. The block
 602   // may not be a humongous - it must fit into a single heap region.
 603   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 604 
 605   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 606                                     HeapRegion*    alloc_region,
 607                                     bool           par,
 608                                     size_t         word_size);
 609 
 610   // Ensure that no further allocations can happen in "r", bearing in mind
 611   // that parallel threads might be attempting allocations.
 612   void par_allocate_remaining_space(HeapRegion* r);
 613 
 614   // Allocation attempt during GC for a survivor object / PLAB.
 615   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 616 
 617   // Allocation attempt during GC for an old object / PLAB.
 618   inline HeapWord* old_attempt_allocation(size_t word_size);
 619 
 620   // These methods are the "callbacks" from the G1AllocRegion class.
 621 
 622   // For mutator alloc regions.
 623   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 624   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 625                                    size_t allocated_bytes);
 626 
 627   // For GC alloc regions.
 628   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 629                                   GCAllocPurpose ap);
 630   void retire_gc_alloc_region(HeapRegion* alloc_region,
 631                               size_t allocated_bytes, GCAllocPurpose ap);
 632 
 633   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 634   //   inspection request and should collect the entire heap
 635   // - if clear_all_soft_refs is true, all soft references should be
 636   //   cleared during the GC
 637   // - if explicit_gc is false, word_size describes the allocation that
 638   //   the GC should attempt (at least) to satisfy
 639   // - it returns false if it is unable to do the collection due to the
 640   //   GC locker being active, true otherwise
 641   bool do_collection(bool explicit_gc,
 642                      bool clear_all_soft_refs,
 643                      size_t word_size);
 644 
 645   // Callback from VM_G1CollectFull operation.
 646   // Perform a full collection.
 647   virtual void do_full_collection(bool clear_all_soft_refs);
 648 
 649   // Resize the heap if necessary after a full collection.  If this is
 650   // after a collect-for allocation, "word_size" is the allocation size,
 651   // and will be considered part of the used portion of the heap.
 652   void resize_if_necessary_after_full_collection(size_t word_size);
 653 
 654   // Callback from VM_G1CollectForAllocation operation.
 655   // This function does everything necessary/possible to satisfy a
 656   // failed allocation request (including collection, expansion, etc.)
 657   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 658 
 659   // Attempting to expand the heap sufficiently
 660   // to support an allocation of the given "word_size".  If
 661   // successful, perform the allocation and return the address of the
 662   // allocated block, or else "NULL".
 663   HeapWord* expand_and_allocate(size_t word_size);
 664 
 665   // Process any reference objects discovered during
 666   // an incremental evacuation pause.
 667   void process_discovered_references(uint no_of_gc_workers);
 668 
 669   // Enqueue any remaining discovered references
 670   // after processing.
 671   void enqueue_discovered_references(uint no_of_gc_workers);
 672 
 673 public:
 674 
 675   G1MonitoringSupport* g1mm() {
 676     assert(_g1mm != NULL, "should have been initialized");
 677     return _g1mm;
 678   }
 679 
 680   // Expand the garbage-first heap by at least the given size (in bytes!).
 681   // Returns true if the heap was expanded by the requested amount;
 682   // false otherwise.
 683   // (Rounds up to a HeapRegion boundary.)
 684   bool expand(size_t expand_bytes);
 685 
 686   // Do anything common to GC's.
 687   virtual void gc_prologue(bool full);
 688   virtual void gc_epilogue(bool full);
 689 
 690   // We register a region with the fast "in collection set" test. We
 691   // simply set to true the array slot corresponding to this region.
 692   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 693     assert(_in_cset_fast_test_base != NULL, "sanity");
 694     assert(r->in_collection_set(), "invariant");
 695     uint index = r->hrs_index();
 696     assert(index < _in_cset_fast_test_length, "invariant");
 697     assert(!_in_cset_fast_test_base[index], "invariant");
 698     _in_cset_fast_test_base[index] = true;
 699   }
 700 
 701   // This is a fast test on whether a reference points into the
 702   // collection set or not. It does not assume that the reference
 703   // points into the heap; if it doesn't, it will return false.
 704   bool in_cset_fast_test(oop obj) {
 705     assert(_in_cset_fast_test != NULL, "sanity");
 706     if (_g1_committed.contains((HeapWord*) obj)) {
 707       // no need to subtract the bottom of the heap from obj,
 708       // _in_cset_fast_test is biased
 709       uintx index = (uintx) obj >> HeapRegion::LogOfHRGrainBytes;
 710       bool ret = _in_cset_fast_test[index];
 711       // let's make sure the result is consistent with what the slower
 712       // test returns
 713       assert( ret || !obj_in_cs(obj), "sanity");
 714       assert(!ret ||  obj_in_cs(obj), "sanity");
 715       return ret;
 716     } else {
 717       return false;
 718     }
 719   }
 720 
 721   void clear_cset_fast_test() {
 722     assert(_in_cset_fast_test_base != NULL, "sanity");
 723     memset(_in_cset_fast_test_base, false,
 724            (size_t) _in_cset_fast_test_length * sizeof(bool));
 725   }
 726 
 727   // This is called at the start of either a concurrent cycle or a Full
 728   // GC to update the number of old marking cycles started.
 729   void increment_old_marking_cycles_started();
 730 
 731   // This is called at the end of either a concurrent cycle or a Full
 732   // GC to update the number of old marking cycles completed. Those two
 733   // can happen in a nested fashion, i.e., we start a concurrent
 734   // cycle, a Full GC happens half-way through it which ends first,
 735   // and then the cycle notices that a Full GC happened and ends
 736   // too. The concurrent parameter is a boolean to help us do a bit
 737   // tighter consistency checking in the method. If concurrent is
 738   // false, the caller is the inner caller in the nesting (i.e., the
 739   // Full GC). If concurrent is true, the caller is the outer caller
 740   // in this nesting (i.e., the concurrent cycle). Further nesting is
 741   // not currently supported. The end of this call also notifies
 742   // the FullGCCount_lock in case a Java thread is waiting for a full
 743   // GC to happen (e.g., it called System.gc() with
 744   // +ExplicitGCInvokesConcurrent).
 745   void increment_old_marking_cycles_completed(bool concurrent);
 746 
 747   unsigned int old_marking_cycles_completed() {
 748     return _old_marking_cycles_completed;
 749   }
 750 
 751   void register_concurrent_cycle_start(jlong start_time);
 752   void register_concurrent_cycle_end();
 753   void trace_heap_after_concurrent_cycle();
 754 
 755   G1YCType yc_type();
 756 
 757   G1HRPrinter* hr_printer() { return &_hr_printer; }
 758 
 759 protected:
 760 
 761   // Shrink the garbage-first heap by at most the given size (in bytes!).
 762   // (Rounds down to a HeapRegion boundary.)
 763   virtual void shrink(size_t expand_bytes);
 764   void shrink_helper(size_t expand_bytes);
 765 
 766   #if TASKQUEUE_STATS
 767   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 768   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 769   void reset_taskqueue_stats();
 770   #endif // TASKQUEUE_STATS
 771 
 772   // Schedule the VM operation that will do an evacuation pause to
 773   // satisfy an allocation request of word_size. *succeeded will
 774   // return whether the VM operation was successful (it did do an
 775   // evacuation pause) or not (another thread beat us to it or the GC
 776   // locker was active). Given that we should not be holding the
 777   // Heap_lock when we enter this method, we will pass the
 778   // gc_count_before (i.e., total_collections()) as a parameter since
 779   // it has to be read while holding the Heap_lock. Currently, both
 780   // methods that call do_collection_pause() release the Heap_lock
 781   // before the call, so it's easy to read gc_count_before just before.
 782   HeapWord* do_collection_pause(size_t       word_size,
 783                                 unsigned int gc_count_before,
 784                                 bool*        succeeded);
 785 
 786   // The guts of the incremental collection pause, executed by the vm
 787   // thread. It returns false if it is unable to do the collection due
 788   // to the GC locker being active, true otherwise
 789   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 790 
 791   // Actually do the work of evacuating the collection set.
 792   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 793 
 794   // The g1 remembered set of the heap.
 795   G1RemSet* _g1_rem_set;
 796   // And it's mod ref barrier set, used to track updates for the above.
 797   ModRefBarrierSet* _mr_bs;
 798 
 799   // A set of cards that cover the objects for which the Rsets should be updated
 800   // concurrently after the collection.
 801   DirtyCardQueueSet _dirty_card_queue_set;
 802 
 803   // The closure used to refine a single card.
 804   RefineCardTableEntryClosure* _refine_cte_cl;
 805 
 806   // A function to check the consistency of dirty card logs.
 807   void check_ct_logs_at_safepoint();
 808 
 809   // A DirtyCardQueueSet that is used to hold cards that contain
 810   // references into the current collection set. This is used to
 811   // update the remembered sets of the regions in the collection
 812   // set in the event of an evacuation failure.
 813   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 814 
 815   // After a collection pause, make the regions in the CS into free
 816   // regions.
 817   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 818 
 819   // Abandon the current collection set without recording policy
 820   // statistics or updating free lists.
 821   void abandon_collection_set(HeapRegion* cs_head);
 822 
 823   // Applies "scan_non_heap_roots" to roots outside the heap,
 824   // "scan_rs" to roots inside the heap (having done "set_region" to
 825   // indicate the region in which the root resides),
 826   // and does "scan_metadata" If "scan_rs" is
 827   // NULL, then this step is skipped.  The "worker_i"
 828   // param is for use with parallel roots processing, and should be
 829   // the "i" of the calling parallel worker thread's work(i) function.
 830   // In the sequential case this param will be ignored.
 831   void g1_process_strong_roots(bool is_scavenging,
 832                                ScanningOption so,
 833                                OopClosure* scan_non_heap_roots,
 834                                OopsInHeapRegionClosure* scan_rs,
 835                                G1KlassScanClosure* scan_klasses,
 836                                int worker_i);
 837 
 838   // Apply "blk" to all the weak roots of the system.  These include
 839   // JNI weak roots, the code cache, system dictionary, symbol table,
 840   // string table, and referents of reachable weak refs.
 841   void g1_process_weak_roots(OopClosure* root_closure);
 842 
 843   // Frees a non-humongous region by initializing its contents and
 844   // adding it to the free list that's passed as a parameter (this is
 845   // usually a local list which will be appended to the master free
 846   // list later). The used bytes of freed regions are accumulated in
 847   // pre_used. If par is true, the region's RSet will not be freed
 848   // up. The assumption is that this will be done later.
 849   void free_region(HeapRegion* hr,
 850                    size_t* pre_used,
 851                    FreeRegionList* free_list,
 852                    bool par);
 853 
 854   // Frees a humongous region by collapsing it into individual regions
 855   // and calling free_region() for each of them. The freed regions
 856   // will be added to the free list that's passed as a parameter (this
 857   // is usually a local list which will be appended to the master free
 858   // list later). The used bytes of freed regions are accumulated in
 859   // pre_used. If par is true, the region's RSet will not be freed
 860   // up. The assumption is that this will be done later.
 861   void free_humongous_region(HeapRegion* hr,
 862                              size_t* pre_used,
 863                              FreeRegionList* free_list,
 864                              HumongousRegionSet* humongous_proxy_set,
 865                              bool par);
 866 
 867   // Notifies all the necessary spaces that the committed space has
 868   // been updated (either expanded or shrunk). It should be called
 869   // after _g1_storage is updated.
 870   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 871 
 872   // The concurrent marker (and the thread it runs in.)
 873   ConcurrentMark* _cm;
 874   ConcurrentMarkThread* _cmThread;
 875   bool _mark_in_progress;
 876 
 877   // The concurrent refiner.
 878   ConcurrentG1Refine* _cg1r;
 879 
 880   // The parallel task queues
 881   RefToScanQueueSet *_task_queues;
 882 
 883   // True iff a evacuation has failed in the current collection.
 884   bool _evacuation_failed;
 885 
 886   EvacuationFailedInfo* _evacuation_failed_info_array;
 887 
 888   // Failed evacuations cause some logical from-space objects to have
 889   // forwarding pointers to themselves.  Reset them.
 890   void remove_self_forwarding_pointers();
 891 
 892   // Together, these store an object with a preserved mark, and its mark value.
 893   Stack<oop, mtGC>     _objs_with_preserved_marks;
 894   Stack<markOop, mtGC> _preserved_marks_of_objs;
 895 
 896   // Preserve the mark of "obj", if necessary, in preparation for its mark
 897   // word being overwritten with a self-forwarding-pointer.
 898   void preserve_mark_if_necessary(oop obj, markOop m);
 899 
 900   // The stack of evac-failure objects left to be scanned.
 901   GrowableArray<oop>*    _evac_failure_scan_stack;
 902   // The closure to apply to evac-failure objects.
 903 
 904   OopsInHeapRegionClosure* _evac_failure_closure;
 905   // Set the field above.
 906   void
 907   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 908     _evac_failure_closure = evac_failure_closure;
 909   }
 910 
 911   // Push "obj" on the scan stack.
 912   void push_on_evac_failure_scan_stack(oop obj);
 913   // Process scan stack entries until the stack is empty.
 914   void drain_evac_failure_scan_stack();
 915   // True iff an invocation of "drain_scan_stack" is in progress; to
 916   // prevent unnecessary recursion.
 917   bool _drain_in_progress;
 918 
 919   // Do any necessary initialization for evacuation-failure handling.
 920   // "cl" is the closure that will be used to process evac-failure
 921   // objects.
 922   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 923   // Do any necessary cleanup for evacuation-failure handling data
 924   // structures.
 925   void finalize_for_evac_failure();
 926 
 927   // An attempt to evacuate "obj" has failed; take necessary steps.
 928   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 929   void handle_evacuation_failure_common(oop obj, markOop m);
 930 
 931 #ifndef PRODUCT
 932   // Support for forcing evacuation failures. Analogous to
 933   // PromotionFailureALot for the other collectors.
 934 
 935   // Records whether G1EvacuationFailureALot should be in effect
 936   // for the current GC
 937   bool _evacuation_failure_alot_for_current_gc;
 938 
 939   // Used to record the GC number for interval checking when
 940   // determining whether G1EvaucationFailureALot is in effect
 941   // for the current GC.
 942   size_t _evacuation_failure_alot_gc_number;
 943 
 944   // Count of the number of evacuations between failures.
 945   volatile size_t _evacuation_failure_alot_count;
 946 
 947   // Set whether G1EvacuationFailureALot should be in effect
 948   // for the current GC (based upon the type of GC and which
 949   // command line flags are set);
 950   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 951                                                   bool during_initial_mark,
 952                                                   bool during_marking);
 953 
 954   inline void set_evacuation_failure_alot_for_current_gc();
 955 
 956   // Return true if it's time to cause an evacuation failure.
 957   inline bool evacuation_should_fail();
 958 
 959   // Reset the G1EvacuationFailureALot counters.  Should be called at
 960   // the end of an evacuation pause in which an evacuation failure occurred.
 961   inline void reset_evacuation_should_fail();
 962 #endif // !PRODUCT
 963 
 964   // ("Weak") Reference processing support.
 965   //
 966   // G1 has 2 instances of the reference processor class. One
 967   // (_ref_processor_cm) handles reference object discovery
 968   // and subsequent processing during concurrent marking cycles.
 969   //
 970   // The other (_ref_processor_stw) handles reference object
 971   // discovery and processing during full GCs and incremental
 972   // evacuation pauses.
 973   //
 974   // During an incremental pause, reference discovery will be
 975   // temporarily disabled for _ref_processor_cm and will be
 976   // enabled for _ref_processor_stw. At the end of the evacuation
 977   // pause references discovered by _ref_processor_stw will be
 978   // processed and discovery will be disabled. The previous
 979   // setting for reference object discovery for _ref_processor_cm
 980   // will be re-instated.
 981   //
 982   // At the start of marking:
 983   //  * Discovery by the CM ref processor is verified to be inactive
 984   //    and it's discovered lists are empty.
 985   //  * Discovery by the CM ref processor is then enabled.
 986   //
 987   // At the end of marking:
 988   //  * Any references on the CM ref processor's discovered
 989   //    lists are processed (possibly MT).
 990   //
 991   // At the start of full GC we:
 992   //  * Disable discovery by the CM ref processor and
 993   //    empty CM ref processor's discovered lists
 994   //    (without processing any entries).
 995   //  * Verify that the STW ref processor is inactive and it's
 996   //    discovered lists are empty.
 997   //  * Temporarily set STW ref processor discovery as single threaded.
 998   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 999   //    field.
1000   //  * Finally enable discovery by the STW ref processor.
1001   //
1002   // The STW ref processor is used to record any discovered
1003   // references during the full GC.
1004   //
1005   // At the end of a full GC we:
1006   //  * Enqueue any reference objects discovered by the STW ref processor
1007   //    that have non-live referents. This has the side-effect of
1008   //    making the STW ref processor inactive by disabling discovery.
1009   //  * Verify that the CM ref processor is still inactive
1010   //    and no references have been placed on it's discovered
1011   //    lists (also checked as a precondition during initial marking).
1012 
1013   // The (stw) reference processor...
1014   ReferenceProcessor* _ref_processor_stw;
1015 
1016   STWGCTimer* _gc_timer_stw;
1017   ConcurrentGCTimer* _gc_timer_cm;
1018 
1019   G1OldTracer* _gc_tracer_cm;
1020   G1NewTracer* _gc_tracer_stw;
1021 
1022   // During reference object discovery, the _is_alive_non_header
1023   // closure (if non-null) is applied to the referent object to
1024   // determine whether the referent is live. If so then the
1025   // reference object does not need to be 'discovered' and can
1026   // be treated as a regular oop. This has the benefit of reducing
1027   // the number of 'discovered' reference objects that need to
1028   // be processed.
1029   //
1030   // Instance of the is_alive closure for embedding into the
1031   // STW reference processor as the _is_alive_non_header field.
1032   // Supplying a value for the _is_alive_non_header field is
1033   // optional but doing so prevents unnecessary additions to
1034   // the discovered lists during reference discovery.
1035   G1STWIsAliveClosure _is_alive_closure_stw;
1036 
1037   // The (concurrent marking) reference processor...
1038   ReferenceProcessor* _ref_processor_cm;
1039 
1040   // Instance of the concurrent mark is_alive closure for embedding
1041   // into the Concurrent Marking reference processor as the
1042   // _is_alive_non_header field. Supplying a value for the
1043   // _is_alive_non_header field is optional but doing so prevents
1044   // unnecessary additions to the discovered lists during reference
1045   // discovery.
1046   G1CMIsAliveClosure _is_alive_closure_cm;
1047 
1048   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
1049   HeapRegion** _worker_cset_start_region;
1050 
1051   // Time stamp to validate the regions recorded in the cache
1052   // used by G1CollectedHeap::start_cset_region_for_worker().
1053   // The heap region entry for a given worker is valid iff
1054   // the associated time stamp value matches the current value
1055   // of G1CollectedHeap::_gc_time_stamp.
1056   unsigned int* _worker_cset_start_region_time_stamp;
1057 
1058   enum G1H_process_strong_roots_tasks {
1059     G1H_PS_filter_satb_buffers,
1060     G1H_PS_refProcessor_oops_do,
1061     // Leave this one last.
1062     G1H_PS_NumElements
1063   };
1064 
1065   SubTasksDone* _process_strong_tasks;
1066 
1067   volatile bool _free_regions_coming;
1068 
1069 public:
1070 
1071   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1072 
1073   void set_refine_cte_cl_concurrency(bool concurrent);
1074 
1075   RefToScanQueue *task_queue(int i) const;
1076 
1077   // A set of cards where updates happened during the GC
1078   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1079 
1080   // A DirtyCardQueueSet that is used to hold cards that contain
1081   // references into the current collection set. This is used to
1082   // update the remembered sets of the regions in the collection
1083   // set in the event of an evacuation failure.
1084   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1085         { return _into_cset_dirty_card_queue_set; }
1086 
1087   // Create a G1CollectedHeap with the specified policy.
1088   // Must call the initialize method afterwards.
1089   // May not return if something goes wrong.
1090   G1CollectedHeap(G1CollectorPolicy* policy);
1091 
1092   // Initialize the G1CollectedHeap to have the initial and
1093   // maximum sizes and remembered and barrier sets
1094   // specified by the policy object.
1095   jint initialize();
1096 
1097   // Initialize weak reference processing.
1098   virtual void ref_processing_init();
1099 
1100   void set_par_threads(uint t) {
1101     SharedHeap::set_par_threads(t);
1102     // Done in SharedHeap but oddly there are
1103     // two _process_strong_tasks's in a G1CollectedHeap
1104     // so do it here too.
1105     _process_strong_tasks->set_n_threads(t);
1106   }
1107 
1108   // Set _n_par_threads according to a policy TBD.
1109   void set_par_threads();
1110 
1111   void set_n_termination(int t) {
1112     _process_strong_tasks->set_n_threads(t);
1113   }
1114 
1115   virtual CollectedHeap::Name kind() const {
1116     return CollectedHeap::G1CollectedHeap;
1117   }
1118 
1119   // The current policy object for the collector.
1120   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1121 
1122   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1123 
1124   // Adaptive size policy.  No such thing for g1.
1125   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1126 
1127   // The rem set and barrier set.
1128   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1129   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
1130 
1131   unsigned get_gc_time_stamp() {
1132     return _gc_time_stamp;
1133   }
1134 
1135   void reset_gc_time_stamp() {
1136     _gc_time_stamp = 0;
1137     OrderAccess::fence();
1138     // Clear the cached CSet starting regions and time stamps.
1139     // Their validity is dependent on the GC timestamp.
1140     clear_cset_start_regions();
1141   }
1142 
1143   void check_gc_time_stamps() PRODUCT_RETURN;
1144 
1145   void increment_gc_time_stamp() {
1146     ++_gc_time_stamp;
1147     OrderAccess::fence();
1148   }
1149 
1150   // Reset the given region's GC timestamp. If it's starts humongous,
1151   // also reset the GC timestamp of its corresponding
1152   // continues humongous regions too.
1153   void reset_gc_time_stamps(HeapRegion* hr);
1154 
1155   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1156                                   DirtyCardQueue* into_cset_dcq,
1157                                   bool concurrent, int worker_i);
1158 
1159   // The shared block offset table array.
1160   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1161 
1162   // Reference Processing accessors
1163 
1164   // The STW reference processor....
1165   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1166 
1167   // The Concurrent Marking reference processor...
1168   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1169 
1170   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1171   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1172 
1173   virtual size_t capacity() const;
1174   virtual size_t used() const;
1175   // This should be called when we're not holding the heap lock. The
1176   // result might be a bit inaccurate.
1177   size_t used_unlocked() const;
1178   size_t recalculate_used() const;
1179 
1180   // These virtual functions do the actual allocation.
1181   // Some heaps may offer a contiguous region for shared non-blocking
1182   // allocation, via inlined code (by exporting the address of the top and
1183   // end fields defining the extent of the contiguous allocation region.)
1184   // But G1CollectedHeap doesn't yet support this.
1185 
1186   // Return an estimate of the maximum allocation that could be performed
1187   // without triggering any collection or expansion activity.  In a
1188   // generational collector, for example, this is probably the largest
1189   // allocation that could be supported (without expansion) in the youngest
1190   // generation.  It is "unsafe" because no locks are taken; the result
1191   // should be treated as an approximation, not a guarantee, for use in
1192   // heuristic resizing decisions.
1193   virtual size_t unsafe_max_alloc();
1194 
1195   virtual bool is_maximal_no_gc() const {
1196     return _g1_storage.uncommitted_size() == 0;
1197   }
1198 
1199   // The total number of regions in the heap.
1200   uint n_regions() { return _hrs.length(); }
1201 
1202   // The max number of regions in the heap.
1203   uint max_regions() { return _hrs.max_length(); }
1204 
1205   // The number of regions that are completely free.
1206   uint free_regions() { return _free_list.length(); }
1207 
1208   // The number of regions that are not completely free.
1209   uint used_regions() { return n_regions() - free_regions(); }
1210 
1211   // The number of regions available for "regular" expansion.
1212   uint expansion_regions() { return _expansion_regions; }
1213 
1214   // Factory method for HeapRegion instances. It will return NULL if
1215   // the allocation fails.
1216   HeapRegion* new_heap_region(uint hrs_index, HeapWord* bottom);
1217 
1218   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1219   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1220   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1221   void verify_dirty_young_regions() PRODUCT_RETURN;
1222 
1223   // verify_region_sets() performs verification over the region
1224   // lists. It will be compiled in the product code to be used when
1225   // necessary (i.e., during heap verification).
1226   void verify_region_sets();
1227 
1228   // verify_region_sets_optional() is planted in the code for
1229   // list verification in non-product builds (and it can be enabled in
1230   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1231 #if HEAP_REGION_SET_FORCE_VERIFY
1232   void verify_region_sets_optional() {
1233     verify_region_sets();
1234   }
1235 #else // HEAP_REGION_SET_FORCE_VERIFY
1236   void verify_region_sets_optional() { }
1237 #endif // HEAP_REGION_SET_FORCE_VERIFY
1238 
1239 #ifdef ASSERT
1240   bool is_on_master_free_list(HeapRegion* hr) {
1241     return hr->containing_set() == &_free_list;
1242   }
1243 
1244   bool is_in_humongous_set(HeapRegion* hr) {
1245     return hr->containing_set() == &_humongous_set;
1246   }
1247 #endif // ASSERT
1248 
1249   // Wrapper for the region list operations that can be called from
1250   // methods outside this class.
1251 
1252   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1253     _secondary_free_list.add_as_tail(list);
1254   }
1255 
1256   void append_secondary_free_list() {
1257     _free_list.add_as_head(&_secondary_free_list);
1258   }
1259 
1260   void append_secondary_free_list_if_not_empty_with_lock() {
1261     // If the secondary free list looks empty there's no reason to
1262     // take the lock and then try to append it.
1263     if (!_secondary_free_list.is_empty()) {
1264       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1265       append_secondary_free_list();
1266     }
1267   }
1268 
1269   void old_set_remove(HeapRegion* hr) {
1270     _old_set.remove(hr);
1271   }
1272 
1273   size_t non_young_capacity_bytes() {
1274     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1275   }
1276 
1277   void set_free_regions_coming();
1278   void reset_free_regions_coming();
1279   bool free_regions_coming() { return _free_regions_coming; }
1280   void wait_while_free_regions_coming();
1281 
1282   // Determine whether the given region is one that we are using as an
1283   // old GC alloc region.
1284   bool is_old_gc_alloc_region(HeapRegion* hr) {
1285     return hr == _retained_old_gc_alloc_region;
1286   }
1287 
1288   // Perform a collection of the heap; intended for use in implementing
1289   // "System.gc".  This probably implies as full a collection as the
1290   // "CollectedHeap" supports.
1291   virtual void collect(GCCause::Cause cause);
1292 
1293   // The same as above but assume that the caller holds the Heap_lock.
1294   void collect_locked(GCCause::Cause cause);
1295 
1296   // True iff an evacuation has failed in the most-recent collection.
1297   bool evacuation_failed() { return _evacuation_failed; }
1298 
1299   // It will free a region if it has allocated objects in it that are
1300   // all dead. It calls either free_region() or
1301   // free_humongous_region() depending on the type of the region that
1302   // is passed to it.
1303   void free_region_if_empty(HeapRegion* hr,
1304                             size_t* pre_used,
1305                             FreeRegionList* free_list,
1306                             OldRegionSet* old_proxy_set,
1307                             HumongousRegionSet* humongous_proxy_set,
1308                             HRRSCleanupTask* hrrs_cleanup_task,
1309                             bool par);
1310 
1311   // It appends the free list to the master free list and updates the
1312   // master humongous list according to the contents of the proxy
1313   // list. It also adjusts the total used bytes according to pre_used
1314   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1315   void update_sets_after_freeing_regions(size_t pre_used,
1316                                        FreeRegionList* free_list,
1317                                        OldRegionSet* old_proxy_set,
1318                                        HumongousRegionSet* humongous_proxy_set,
1319                                        bool par);
1320 
1321   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1322   virtual bool is_in(const void* p) const;
1323 
1324   // Return "TRUE" iff the given object address is within the collection
1325   // set.
1326   inline bool obj_in_cs(oop obj);
1327 
1328   // Return "TRUE" iff the given object address is in the reserved
1329   // region of g1.
1330   bool is_in_g1_reserved(const void* p) const {
1331     return _g1_reserved.contains(p);
1332   }
1333 
1334   // Returns a MemRegion that corresponds to the space that has been
1335   // reserved for the heap
1336   MemRegion g1_reserved() {
1337     return _g1_reserved;
1338   }
1339 
1340   // Returns a MemRegion that corresponds to the space that has been
1341   // committed in the heap
1342   MemRegion g1_committed() {
1343     return _g1_committed;
1344   }
1345 
1346   virtual bool is_in_closed_subset(const void* p) const;
1347 
1348   // This resets the card table to all zeros.  It is used after
1349   // a collection pause which used the card table to claim cards.
1350   void cleanUpCardTable();
1351 
1352   // Iteration functions.
1353 
1354   // Iterate over all the ref-containing fields of all objects, calling
1355   // "cl.do_oop" on each.
1356   virtual void oop_iterate(ExtendedOopClosure* cl);
1357 
1358   // Same as above, restricted to a memory region.
1359   void oop_iterate(MemRegion mr, ExtendedOopClosure* cl);
1360 
1361   // Iterate over all objects, calling "cl.do_object" on each.
1362   virtual void object_iterate(ObjectClosure* cl);
1363 
1364   virtual void safe_object_iterate(ObjectClosure* cl) {
1365     object_iterate(cl);
1366   }
1367 
1368   // Iterate over all objects allocated since the last collection, calling
1369   // "cl.do_object" on each.  The heap must have been initialized properly
1370   // to support this function, or else this call will fail.
1371   virtual void object_iterate_since_last_GC(ObjectClosure* cl);
1372 
1373   // Iterate over all spaces in use in the heap, in ascending address order.
1374   virtual void space_iterate(SpaceClosure* cl);
1375 
1376   // Iterate over heap regions, in address order, terminating the
1377   // iteration early if the "doHeapRegion" method returns "true".
1378   void heap_region_iterate(HeapRegionClosure* blk) const;
1379 
1380   // Return the region with the given index. It assumes the index is valid.
1381   HeapRegion* region_at(uint index) const { return _hrs.at(index); }
1382 
1383   // Divide the heap region sequence into "chunks" of some size (the number
1384   // of regions divided by the number of parallel threads times some
1385   // overpartition factor, currently 4).  Assumes that this will be called
1386   // in parallel by ParallelGCThreads worker threads with discinct worker
1387   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1388   // calls will use the same "claim_value", and that that claim value is
1389   // different from the claim_value of any heap region before the start of
1390   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1391   // attempting to claim the first region in each chunk, and, if
1392   // successful, applying the closure to each region in the chunk (and
1393   // setting the claim value of the second and subsequent regions of the
1394   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1395   // i.e., that a closure never attempt to abort a traversal.
1396   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1397                                        uint worker,
1398                                        uint no_of_par_workers,
1399                                        jint claim_value);
1400 
1401   // It resets all the region claim values to the default.
1402   void reset_heap_region_claim_values();
1403 
1404   // Resets the claim values of regions in the current
1405   // collection set to the default.
1406   void reset_cset_heap_region_claim_values();
1407 
1408 #ifdef ASSERT
1409   bool check_heap_region_claim_values(jint claim_value);
1410 
1411   // Same as the routine above but only checks regions in the
1412   // current collection set.
1413   bool check_cset_heap_region_claim_values(jint claim_value);
1414 #endif // ASSERT
1415 
1416   // Clear the cached cset start regions and (more importantly)
1417   // the time stamps. Called when we reset the GC time stamp.
1418   void clear_cset_start_regions();
1419 
1420   // Given the id of a worker, obtain or calculate a suitable
1421   // starting region for iterating over the current collection set.
1422   HeapRegion* start_cset_region_for_worker(int worker_i);
1423 
1424   // This is a convenience method that is used by the
1425   // HeapRegionIterator classes to calculate the starting region for
1426   // each worker so that they do not all start from the same region.
1427   HeapRegion* start_region_for_worker(uint worker_i, uint no_of_par_workers);
1428 
1429   // Iterate over the regions (if any) in the current collection set.
1430   void collection_set_iterate(HeapRegionClosure* blk);
1431 
1432   // As above but starting from region r
1433   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1434 
1435   // Returns the first (lowest address) compactible space in the heap.
1436   virtual CompactibleSpace* first_compactible_space();
1437 
1438   // A CollectedHeap will contain some number of spaces.  This finds the
1439   // space containing a given address, or else returns NULL.
1440   virtual Space* space_containing(const void* addr) const;
1441 
1442   // A G1CollectedHeap will contain some number of heap regions.  This
1443   // finds the region containing a given address, or else returns NULL.
1444   template <class T>
1445   inline HeapRegion* heap_region_containing(const T addr) const;
1446 
1447   // Like the above, but requires "addr" to be in the heap (to avoid a
1448   // null-check), and unlike the above, may return an continuing humongous
1449   // region.
1450   template <class T>
1451   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1452 
1453   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1454   // each address in the (reserved) heap is a member of exactly
1455   // one block.  The defining characteristic of a block is that it is
1456   // possible to find its size, and thus to progress forward to the next
1457   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1458   // represent Java objects, or they might be free blocks in a
1459   // free-list-based heap (or subheap), as long as the two kinds are
1460   // distinguishable and the size of each is determinable.
1461 
1462   // Returns the address of the start of the "block" that contains the
1463   // address "addr".  We say "blocks" instead of "object" since some heaps
1464   // may not pack objects densely; a chunk may either be an object or a
1465   // non-object.
1466   virtual HeapWord* block_start(const void* addr) const;
1467 
1468   // Requires "addr" to be the start of a chunk, and returns its size.
1469   // "addr + size" is required to be the start of a new chunk, or the end
1470   // of the active area of the heap.
1471   virtual size_t block_size(const HeapWord* addr) const;
1472 
1473   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1474   // the block is an object.
1475   virtual bool block_is_obj(const HeapWord* addr) const;
1476 
1477   // Does this heap support heap inspection? (+PrintClassHistogram)
1478   virtual bool supports_heap_inspection() const { return true; }
1479 
1480   // Section on thread-local allocation buffers (TLABs)
1481   // See CollectedHeap for semantics.
1482 
1483   virtual bool supports_tlab_allocation() const;
1484   virtual size_t tlab_capacity(Thread* thr) const;
1485   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1486 
1487   // Can a compiler initialize a new object without store barriers?
1488   // This permission only extends from the creation of a new object
1489   // via a TLAB up to the first subsequent safepoint. If such permission
1490   // is granted for this heap type, the compiler promises to call
1491   // defer_store_barrier() below on any slow path allocation of
1492   // a new object for which such initializing store barriers will
1493   // have been elided. G1, like CMS, allows this, but should be
1494   // ready to provide a compensating write barrier as necessary
1495   // if that storage came out of a non-young region. The efficiency
1496   // of this implementation depends crucially on being able to
1497   // answer very efficiently in constant time whether a piece of
1498   // storage in the heap comes from a young region or not.
1499   // See ReduceInitialCardMarks.
1500   virtual bool can_elide_tlab_store_barriers() const {
1501     return true;
1502   }
1503 
1504   virtual bool card_mark_must_follow_store() const {
1505     return true;
1506   }
1507 
1508   bool is_in_young(const oop obj) {
1509     HeapRegion* hr = heap_region_containing(obj);
1510     return hr != NULL && hr->is_young();
1511   }
1512 
1513 #ifdef ASSERT
1514   virtual bool is_in_partial_collection(const void* p);
1515 #endif
1516 
1517   virtual bool is_scavengable(const void* addr);
1518 
1519   // We don't need barriers for initializing stores to objects
1520   // in the young gen: for the SATB pre-barrier, there is no
1521   // pre-value that needs to be remembered; for the remembered-set
1522   // update logging post-barrier, we don't maintain remembered set
1523   // information for young gen objects.
1524   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1525     return is_in_young(new_obj);
1526   }
1527 
1528   // Returns "true" iff the given word_size is "very large".
1529   static bool isHumongous(size_t word_size) {
1530     // Note this has to be strictly greater-than as the TLABs
1531     // are capped at the humongous thresold and we want to
1532     // ensure that we don't try to allocate a TLAB as
1533     // humongous and that we don't allocate a humongous
1534     // object in a TLAB.
1535     return word_size > _humongous_object_threshold_in_words;
1536   }
1537 
1538   // Update mod union table with the set of dirty cards.
1539   void updateModUnion();
1540 
1541   // Set the mod union bits corresponding to the given memRegion.  Note
1542   // that this is always a safe operation, since it doesn't clear any
1543   // bits.
1544   void markModUnionRange(MemRegion mr);
1545 
1546   // Records the fact that a marking phase is no longer in progress.
1547   void set_marking_complete() {
1548     _mark_in_progress = false;
1549   }
1550   void set_marking_started() {
1551     _mark_in_progress = true;
1552   }
1553   bool mark_in_progress() {
1554     return _mark_in_progress;
1555   }
1556 
1557   // Print the maximum heap capacity.
1558   virtual size_t max_capacity() const;
1559 
1560   virtual jlong millis_since_last_gc();
1561 
1562   // Perform any cleanup actions necessary before allowing a verification.
1563   virtual void prepare_for_verify();
1564 
1565   // Perform verification.
1566 
1567   // vo == UsePrevMarking  -> use "prev" marking information,
1568   // vo == UseNextMarking -> use "next" marking information
1569   // vo == UseMarkWord    -> use the mark word in the object header
1570   //
1571   // NOTE: Only the "prev" marking information is guaranteed to be
1572   // consistent most of the time, so most calls to this should use
1573   // vo == UsePrevMarking.
1574   // Currently, there is only one case where this is called with
1575   // vo == UseNextMarking, which is to verify the "next" marking
1576   // information at the end of remark.
1577   // Currently there is only one place where this is called with
1578   // vo == UseMarkWord, which is to verify the marking during a
1579   // full GC.
1580   void verify(bool silent, VerifyOption vo);
1581 
1582   // Override; it uses the "prev" marking information
1583   virtual void verify(bool silent);
1584 
1585   virtual void print_on(outputStream* st) const;
1586   virtual void print_extended_on(outputStream* st) const;
1587   virtual void print_on_error(outputStream* st) const;
1588 
1589   virtual void print_gc_threads_on(outputStream* st) const;
1590   virtual void gc_threads_do(ThreadClosure* tc) const;
1591 
1592   // Override
1593   void print_tracing_info() const;
1594 
1595   // The following two methods are helpful for debugging RSet issues.
1596   void print_cset_rsets() PRODUCT_RETURN;
1597   void print_all_rsets() PRODUCT_RETURN;
1598 
1599   // Convenience function to be used in situations where the heap type can be
1600   // asserted to be this type.
1601   static G1CollectedHeap* heap();
1602 
1603   void set_region_short_lived_locked(HeapRegion* hr);
1604   // add appropriate methods for any other surv rate groups
1605 
1606   YoungList* young_list() { return _young_list; }
1607 
1608   // debugging
1609   bool check_young_list_well_formed() {
1610     return _young_list->check_list_well_formed();
1611   }
1612 
1613   bool check_young_list_empty(bool check_heap,
1614                               bool check_sample = true);
1615 
1616   // *** Stuff related to concurrent marking.  It's not clear to me that so
1617   // many of these need to be public.
1618 
1619   // The functions below are helper functions that a subclass of
1620   // "CollectedHeap" can use in the implementation of its virtual
1621   // functions.
1622   // This performs a concurrent marking of the live objects in a
1623   // bitmap off to the side.
1624   void doConcurrentMark();
1625 
1626   bool isMarkedPrev(oop obj) const;
1627   bool isMarkedNext(oop obj) const;
1628 
1629   // Determine if an object is dead, given the object and also
1630   // the region to which the object belongs. An object is dead
1631   // iff a) it was not allocated since the last mark and b) it
1632   // is not marked.
1633 
1634   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1635     return
1636       !hr->obj_allocated_since_prev_marking(obj) &&
1637       !isMarkedPrev(obj);
1638   }
1639 
1640   // This function returns true when an object has been
1641   // around since the previous marking and hasn't yet
1642   // been marked during this marking.
1643 
1644   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1645     return
1646       !hr->obj_allocated_since_next_marking(obj) &&
1647       !isMarkedNext(obj);
1648   }
1649 
1650   // Determine if an object is dead, given only the object itself.
1651   // This will find the region to which the object belongs and
1652   // then call the region version of the same function.
1653 
1654   // Added if it is NULL it isn't dead.
1655 
1656   bool is_obj_dead(const oop obj) const {
1657     const HeapRegion* hr = heap_region_containing(obj);
1658     if (hr == NULL) {
1659       if (obj == NULL) return false;
1660       else return true;
1661     }
1662     else return is_obj_dead(obj, hr);
1663   }
1664 
1665   bool is_obj_ill(const oop obj) const {
1666     const HeapRegion* hr = heap_region_containing(obj);
1667     if (hr == NULL) {
1668       if (obj == NULL) return false;
1669       else return true;
1670     }
1671     else return is_obj_ill(obj, hr);
1672   }
1673 
1674   // The methods below are here for convenience and dispatch the
1675   // appropriate method depending on value of the given VerifyOption
1676   // parameter. The options for that parameter are:
1677   //
1678   // vo == UsePrevMarking -> use "prev" marking information,
1679   // vo == UseNextMarking -> use "next" marking information,
1680   // vo == UseMarkWord    -> use mark word from object header
1681 
1682   bool is_obj_dead_cond(const oop obj,
1683                         const HeapRegion* hr,
1684                         const VerifyOption vo) const {
1685     switch (vo) {
1686     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
1687     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
1688     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1689     default:                            ShouldNotReachHere();
1690     }
1691     return false; // keep some compilers happy
1692   }
1693 
1694   bool is_obj_dead_cond(const oop obj,
1695                         const VerifyOption vo) const {
1696     switch (vo) {
1697     case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
1698     case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
1699     case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
1700     default:                            ShouldNotReachHere();
1701     }
1702     return false; // keep some compilers happy
1703   }
1704 
1705   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1706   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1707   bool is_marked(oop obj, VerifyOption vo);
1708   const char* top_at_mark_start_str(VerifyOption vo);
1709 
1710   // The following is just to alert the verification code
1711   // that a full collection has occurred and that the
1712   // remembered sets are no longer up to date.
1713   bool _full_collection;
1714   void set_full_collection() { _full_collection = true;}
1715   void clear_full_collection() {_full_collection = false;}
1716   bool full_collection() {return _full_collection;}
1717 
1718   ConcurrentMark* concurrent_mark() const { return _cm; }
1719   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1720 
1721   // The dirty cards region list is used to record a subset of regions
1722   // whose cards need clearing. The list if populated during the
1723   // remembered set scanning and drained during the card table
1724   // cleanup. Although the methods are reentrant, population/draining
1725   // phases must not overlap. For synchronization purposes the last
1726   // element on the list points to itself.
1727   HeapRegion* _dirty_cards_region_list;
1728   void push_dirty_cards_region(HeapRegion* hr);
1729   HeapRegion* pop_dirty_cards_region();
1730 
1731 public:
1732   void stop_conc_gc_threads();
1733 
1734   size_t pending_card_num();
1735   size_t cards_scanned();
1736 
1737 protected:
1738   size_t _max_heap_capacity;
1739 };
1740 
1741 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1742 private:
1743   bool        _retired;
1744 
1745 public:
1746   G1ParGCAllocBuffer(size_t gclab_word_size);
1747 
1748   void set_buf(HeapWord* buf) {
1749     ParGCAllocBuffer::set_buf(buf);
1750     _retired = false;
1751   }
1752 
1753   void retire(bool end_of_gc, bool retain) {
1754     if (_retired)
1755       return;
1756     ParGCAllocBuffer::retire(end_of_gc, retain);
1757     _retired = true;
1758   }
1759 };
1760 
1761 class G1ParScanThreadState : public StackObj {
1762 protected:
1763   G1CollectedHeap* _g1h;
1764   RefToScanQueue*  _refs;
1765   DirtyCardQueue   _dcq;
1766   CardTableModRefBS* _ct_bs;
1767   G1RemSet* _g1_rem;
1768 
1769   G1ParGCAllocBuffer  _surviving_alloc_buffer;
1770   G1ParGCAllocBuffer  _tenured_alloc_buffer;
1771   G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1772   ageTable            _age_table;
1773 
1774   size_t           _alloc_buffer_waste;
1775   size_t           _undo_waste;
1776 
1777   OopsInHeapRegionClosure*      _evac_failure_cl;
1778   G1ParScanHeapEvacClosure*     _evac_cl;
1779   G1ParScanPartialArrayClosure* _partial_scan_cl;
1780 
1781   int  _hash_seed;
1782   uint _queue_num;
1783 
1784   size_t _term_attempts;
1785 
1786   double _start;
1787   double _start_strong_roots;
1788   double _strong_roots_time;
1789   double _start_term;
1790   double _term_time;
1791 
1792   // Map from young-age-index (0 == not young, 1 is youngest) to
1793   // surviving words. base is what we get back from the malloc call
1794   size_t* _surviving_young_words_base;
1795   // this points into the array, as we use the first few entries for padding
1796   size_t* _surviving_young_words;
1797 
1798 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1799 
1800   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1801 
1802   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1803 
1804   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1805   CardTableModRefBS* ctbs()                      { return _ct_bs; }
1806 
1807   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1808     if (!from->is_survivor()) {
1809       _g1_rem->par_write_ref(from, p, tid);
1810     }
1811   }
1812 
1813   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1814     // If the new value of the field points to the same region or
1815     // is the to-space, we don't need to include it in the Rset updates.
1816     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1817       size_t card_index = ctbs()->index_for(p);
1818       // If the card hasn't been added to the buffer, do it.
1819       if (ctbs()->mark_card_deferred(card_index)) {
1820         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1821       }
1822     }
1823   }
1824 
1825 public:
1826   G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num);
1827 
1828   ~G1ParScanThreadState() {
1829     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC);
1830   }
1831 
1832   RefToScanQueue*   refs()            { return _refs;             }
1833   ageTable*         age_table()       { return &_age_table;       }
1834 
1835   G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1836     return _alloc_buffers[purpose];
1837   }
1838 
1839   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1840   size_t undo_waste() const                      { return _undo_waste; }
1841 
1842 #ifdef ASSERT
1843   bool verify_ref(narrowOop* ref) const;
1844   bool verify_ref(oop* ref) const;
1845   bool verify_task(StarTask ref) const;
1846 #endif // ASSERT
1847 
1848   template <class T> void push_on_queue(T* ref) {
1849     assert(verify_ref(ref), "sanity");
1850     refs()->push(ref);
1851   }
1852 
1853   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1854     if (G1DeferredRSUpdate) {
1855       deferred_rs_update(from, p, tid);
1856     } else {
1857       immediate_rs_update(from, p, tid);
1858     }
1859   }
1860 
1861   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1862     HeapWord* obj = NULL;
1863     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1864     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1865       G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1866       add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1867       alloc_buf->retire(false /* end_of_gc */, false /* retain */);
1868 
1869       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1870       if (buf == NULL) return NULL; // Let caller handle allocation failure.
1871       // Otherwise.
1872       alloc_buf->set_word_size(gclab_word_size);
1873       alloc_buf->set_buf(buf);
1874 
1875       obj = alloc_buf->allocate(word_sz);
1876       assert(obj != NULL, "buffer was definitely big enough...");
1877     } else {
1878       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1879     }
1880     return obj;
1881   }
1882 
1883   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1884     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1885     if (obj != NULL) return obj;
1886     return allocate_slow(purpose, word_sz);
1887   }
1888 
1889   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1890     if (alloc_buffer(purpose)->contains(obj)) {
1891       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1892              "should contain whole object");
1893       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1894     } else {
1895       CollectedHeap::fill_with_object(obj, word_sz);
1896       add_to_undo_waste(word_sz);
1897     }
1898   }
1899 
1900   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1901     _evac_failure_cl = evac_failure_cl;
1902   }
1903   OopsInHeapRegionClosure* evac_failure_closure() {
1904     return _evac_failure_cl;
1905   }
1906 
1907   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1908     _evac_cl = evac_cl;
1909   }
1910 
1911   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1912     _partial_scan_cl = partial_scan_cl;
1913   }
1914 
1915   int* hash_seed() { return &_hash_seed; }
1916   uint queue_num() { return _queue_num; }
1917 
1918   size_t term_attempts() const  { return _term_attempts; }
1919   void note_term_attempt() { _term_attempts++; }
1920 
1921   void start_strong_roots() {
1922     _start_strong_roots = os::elapsedTime();
1923   }
1924   void end_strong_roots() {
1925     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1926   }
1927   double strong_roots_time() const { return _strong_roots_time; }
1928 
1929   void start_term_time() {
1930     note_term_attempt();
1931     _start_term = os::elapsedTime();
1932   }
1933   void end_term_time() {
1934     _term_time += (os::elapsedTime() - _start_term);
1935   }
1936   double term_time() const { return _term_time; }
1937 
1938   double elapsed_time() const {
1939     return os::elapsedTime() - _start;
1940   }
1941 
1942   static void
1943     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1944   void
1945     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1946 
1947   size_t* surviving_young_words() {
1948     // We add on to hide entry 0 which accumulates surviving words for
1949     // age -1 regions (i.e. non-young ones)
1950     return _surviving_young_words;
1951   }
1952 
1953   void retire_alloc_buffers() {
1954     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1955       size_t waste = _alloc_buffers[ap]->words_remaining();
1956       add_to_alloc_buffer_waste(waste);
1957       _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap),
1958                                                  true /* end_of_gc */,
1959                                                  false /* retain */);
1960     }
1961   }
1962 
1963   template <class T> void deal_with_reference(T* ref_to_scan) {
1964     if (has_partial_array_mask(ref_to_scan)) {
1965       _partial_scan_cl->do_oop_nv(ref_to_scan);
1966     } else {
1967       // Note: we can use "raw" versions of "region_containing" because
1968       // "obj_to_scan" is definitely in the heap, and is not in a
1969       // humongous region.
1970       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
1971       _evac_cl->set_region(r);
1972       _evac_cl->do_oop_nv(ref_to_scan);
1973     }
1974   }
1975 
1976   void deal_with_reference(StarTask ref) {
1977     assert(verify_task(ref), "sanity");
1978     if (ref.is_narrow()) {
1979       deal_with_reference((narrowOop*)ref);
1980     } else {
1981       deal_with_reference((oop*)ref);
1982     }
1983   }
1984 
1985   void trim_queue();
1986 };
1987 
1988 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP