1 /*
   2  * Copyright (c) 2001, 2011, 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  *
  15  * You should have received a copy of the GNU General Public License version
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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/g1RemSet.hpp"
  32 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  33 #include "gc_implementation/g1/heapRegionSeq.hpp"
  34 #include "gc_implementation/g1/heapRegionSets.hpp"
  35 #include "gc_implementation/shared/hSpaceCounters.hpp"
  36 #include "gc_implementation/parNew/parGCAllocBuffer.hpp"
  37 #include "memory/barrierSet.hpp"
  38 #include "memory/memRegion.hpp"
  39 #include "memory/sharedHeap.hpp"
  40 
  41 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  42 // It uses the "Garbage First" heap organization and algorithm, which
  43 // may combine concurrent marking with parallel, incremental compaction of
  44 // heap subsets that will yield large amounts of garbage.
  45 
  46 class HeapRegion;
  47 class HRRSCleanupTask;
  48 class PermanentGenerationSpec;
  49 class GenerationSpec;
  50 class OopsInHeapRegionClosure;
  51 class G1ScanHeapEvacClosure;
  52 class ObjectClosure;
  53 class SpaceClosure;
  54 class CompactibleSpaceClosure;
  55 class Space;
  56 class G1CollectorPolicy;
  57 class GenRemSet;
  58 class G1RemSet;
  59 class HeapRegionRemSetIterator;
  60 class ConcurrentMark;
  61 class ConcurrentMarkThread;
  62 class ConcurrentG1Refine;
  63 class GenerationCounters;
  64 
  65 typedef OverflowTaskQueue<StarTask>         RefToScanQueue;
  66 typedef GenericTaskQueueSet<RefToScanQueue> RefToScanQueueSet;
  67 
  68 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  69 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  70 
  71 enum GCAllocPurpose {
  72   GCAllocForTenured,
  73   GCAllocForSurvived,
  74   GCAllocPurposeCount
  75 };
  76 
  77 class YoungList : public CHeapObj {
  78 private:
  79   G1CollectedHeap* _g1h;
  80 
  81   HeapRegion* _head;
  82 
  83   HeapRegion* _survivor_head;
  84   HeapRegion* _survivor_tail;
  85 
  86   HeapRegion* _curr;
  87 
  88   size_t      _length;
  89   size_t      _survivor_length;
  90 
  91   size_t      _last_sampled_rs_lengths;
  92   size_t      _sampled_rs_lengths;
  93 
  94   void         empty_list(HeapRegion* list);
  95 
  96 public:
  97   YoungList(G1CollectedHeap* g1h);
  98 
  99   void         push_region(HeapRegion* hr);
 100   void         add_survivor_region(HeapRegion* hr);
 101 
 102   void         empty_list();
 103   bool         is_empty() { return _length == 0; }
 104   size_t       length() { return _length; }
 105   size_t       survivor_length() { return _survivor_length; }
 106 
 107   // Currently we do not keep track of the used byte sum for the
 108   // young list and the survivors and it'd be quite a lot of work to
 109   // do so. When we'll eventually replace the young list with
 110   // instances of HeapRegionLinkedList we'll get that for free. So,
 111   // we'll report the more accurate information then.
 112   size_t       eden_used_bytes() {
 113     assert(length() >= survivor_length(), "invariant");
 114     return (length() - survivor_length()) * HeapRegion::GrainBytes;
 115   }
 116   size_t       survivor_used_bytes() {
 117     return survivor_length() * HeapRegion::GrainBytes;
 118   }
 119 
 120   void rs_length_sampling_init();
 121   bool rs_length_sampling_more();
 122   void rs_length_sampling_next();
 123 
 124   void reset_sampled_info() {
 125     _last_sampled_rs_lengths =   0;
 126   }
 127   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 128 
 129   // for development purposes
 130   void reset_auxilary_lists();
 131   void clear() { _head = NULL; _length = 0; }
 132 
 133   void clear_survivors() {
 134     _survivor_head    = NULL;
 135     _survivor_tail    = NULL;
 136     _survivor_length  = 0;
 137   }
 138 
 139   HeapRegion* first_region() { return _head; }
 140   HeapRegion* first_survivor_region() { return _survivor_head; }
 141   HeapRegion* last_survivor_region() { return _survivor_tail; }
 142 
 143   // debugging
 144   bool          check_list_well_formed();
 145   bool          check_list_empty(bool check_sample = true);
 146   void          print();
 147 };
 148 
 149 class MutatorAllocRegion : public G1AllocRegion {
 150 protected:
 151   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 152   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 153 public:
 154   MutatorAllocRegion()
 155     : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
 156 };
 157 
 158 // The G1 STW is alive closure.
 159 // An instance is embedded into the G1CH and used as the
 160 // (optional) _is_alive_non_header closure in the STW
 161 // reference processor. It is also extensively used during
 162 // refence processing during STW evacuation pauses.
 163 class G1STWIsAliveClosure: public BoolObjectClosure {
 164   G1CollectedHeap* _g1;
 165 public:
 166   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 167   void do_object(oop p) { assert(false, "Do not call."); }
 168   bool do_object_b(oop p);
 169 };
 170 
 171 class SurvivorGCAllocRegion : public G1AllocRegion {
 172 protected:
 173   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 174   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 175 public:
 176   SurvivorGCAllocRegion()
 177   : G1AllocRegion("Survivor GC Alloc Region", false /* bot_updates */) { }
 178 };
 179 
 180 class OldGCAllocRegion : public G1AllocRegion {
 181 protected:
 182   virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
 183   virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
 184 public:
 185   OldGCAllocRegion()
 186   : G1AllocRegion("Old GC Alloc Region", true /* bot_updates */) { }
 187 };
 188 
 189 class RefineCardTableEntryClosure;
 190 
 191 class G1CollectedHeap : public SharedHeap {
 192   friend class VM_G1CollectForAllocation;
 193   friend class VM_GenCollectForPermanentAllocation;
 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   friend class G1ParCopyHelper;
 203   friend class G1IsAliveClosure;
 204   friend class G1EvacuateFollowersClosure;
 205   friend class G1ParScanThreadState;
 206   friend class G1ParScanClosureSuper;
 207   friend class G1ParEvacuateFollowersClosure;
 208   friend class G1ParTask;
 209   friend class G1FreeGarbageRegionClosure;
 210   friend class RefineCardTableEntryClosure;
 211   friend class G1PrepareCompactClosure;
 212   friend class RegionSorter;
 213   friend class RegionResetter;
 214   friend class CountRCClosure;
 215   friend class EvacPopObjClosure;
 216   friend class G1ParCleanupCTTask;
 217 
 218   // Other related classes.
 219   friend class G1MarkSweep;
 220 
 221 private:
 222   // The one and only G1CollectedHeap, so static functions can find it.
 223   static G1CollectedHeap* _g1h;
 224 
 225   static size_t _humongous_object_threshold_in_words;
 226 
 227   // Storage for the G1 heap (excludes the permanent generation).
 228   VirtualSpace _g1_storage;
 229   MemRegion    _g1_reserved;
 230 
 231   // The part of _g1_storage that is currently committed.
 232   MemRegion _g1_committed;
 233 
 234   // The master free list. It will satisfy all new region allocations.
 235   MasterFreeRegionList      _free_list;
 236 
 237   // The secondary free list which contains regions that have been
 238   // freed up during the cleanup process. This will be appended to the
 239   // master free list when appropriate.
 240   SecondaryFreeRegionList   _secondary_free_list;
 241 
 242   // It keeps track of the old regions.
 243   MasterOldRegionSet        _old_set;
 244 
 245   // It keeps track of the humongous regions.
 246   MasterHumongousRegionSet  _humongous_set;
 247 
 248   // The number of regions we could create by expansion.
 249   size_t _expansion_regions;
 250 
 251   // The block offset table for the G1 heap.
 252   G1BlockOffsetSharedArray* _bot_shared;
 253 
 254   // Tears down the region sets / lists so that they are empty and the
 255   // regions on the heap do not belong to a region set / list. The
 256   // only exception is the humongous set which we leave unaltered. If
 257   // free_list_only is true, it will only tear down the master free
 258   // list. It is called before a Full GC (free_list_only == false) or
 259   // before heap shrinking (free_list_only == true).
 260   void tear_down_region_sets(bool free_list_only);
 261 
 262   // Rebuilds the region sets / lists so that they are repopulated to
 263   // reflect the contents of the heap. The only exception is the
 264   // humongous set which was not torn down in the first place. If
 265   // free_list_only is true, it will only rebuild the master free
 266   // list. It is called after a Full GC (free_list_only == false) or
 267   // after heap shrinking (free_list_only == true).
 268   void rebuild_region_sets(bool free_list_only);
 269 
 270   // The sequence of all heap regions in the heap.
 271   HeapRegionSeq _hrs;
 272 
 273   // Alloc region used to satisfy mutator allocation requests.
 274   MutatorAllocRegion _mutator_alloc_region;
 275 
 276   // Alloc region used to satisfy allocation requests by the GC for
 277   // survivor objects.
 278   SurvivorGCAllocRegion _survivor_gc_alloc_region;
 279 
 280   // Alloc region used to satisfy allocation requests by the GC for
 281   // old objects.
 282   OldGCAllocRegion _old_gc_alloc_region;
 283 
 284   // The last old region we allocated to during the last GC.
 285   // Typically, it is not full so we should re-use it during the next GC.
 286   HeapRegion* _retained_old_gc_alloc_region;
 287 
 288   // It resets the mutator alloc region before new allocations can take place.
 289   void init_mutator_alloc_region();
 290 
 291   // It releases the mutator alloc region.
 292   void release_mutator_alloc_region();
 293 
 294   // It initializes the GC alloc regions at the start of a GC.
 295   void init_gc_alloc_regions();
 296 
 297   // It releases the GC alloc regions at the end of a GC.
 298   void release_gc_alloc_regions();
 299 
 300   // It does any cleanup that needs to be done on the GC alloc regions
 301   // before a Full GC.
 302   void abandon_gc_alloc_regions();
 303 
 304   // Helper for monitoring and management support.
 305   G1MonitoringSupport* _g1mm;
 306 
 307   // Determines PLAB size for a particular allocation purpose.
 308   static size_t desired_plab_sz(GCAllocPurpose purpose);
 309 
 310   // Outside of GC pauses, the number of bytes used in all regions other
 311   // than the current allocation region.
 312   size_t _summary_bytes_used;
 313 
 314   // This is used for a quick test on whether a reference points into
 315   // the collection set or not. Basically, we have an array, with one
 316   // byte per region, and that byte denotes whether the corresponding
 317   // region is in the collection set or not. The entry corresponding
 318   // the bottom of the heap, i.e., region 0, is pointed to by
 319   // _in_cset_fast_test_base.  The _in_cset_fast_test field has been
 320   // biased so that it actually points to address 0 of the address
 321   // space, to make the test as fast as possible (we can simply shift
 322   // the address to address into it, instead of having to subtract the
 323   // bottom of the heap from the address before shifting it; basically
 324   // it works in the same way the card table works).
 325   bool* _in_cset_fast_test;
 326 
 327   // The allocated array used for the fast test on whether a reference
 328   // points into the collection set or not. This field is also used to
 329   // free the array.
 330   bool* _in_cset_fast_test_base;
 331 
 332   // The length of the _in_cset_fast_test_base array.
 333   size_t _in_cset_fast_test_length;
 334 
 335   volatile unsigned _gc_time_stamp;
 336 
 337   size_t* _surviving_young_words;
 338 
 339   G1HRPrinter _hr_printer;
 340 
 341   void setup_surviving_young_words();
 342   void update_surviving_young_words(size_t* surv_young_words);
 343   void cleanup_surviving_young_words();
 344 
 345   // It decides whether an explicit GC should start a concurrent cycle
 346   // instead of doing a STW GC. Currently, a concurrent cycle is
 347   // explicitly started if:
 348   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 349   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 350   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 351 
 352   // Keeps track of how many "full collections" (i.e., Full GCs or
 353   // concurrent cycles) we have completed. The number of them we have
 354   // started is maintained in _total_full_collections in CollectedHeap.
 355   volatile unsigned int _full_collections_completed;
 356 
 357   // This is a non-product method that is helpful for testing. It is
 358   // called at the end of a GC and artificially expands the heap by
 359   // allocating a number of dead regions. This way we can induce very
 360   // frequent marking cycles and stress the cleanup / concurrent
 361   // cleanup code more (as all the regions that will be allocated by
 362   // this method will be found dead by the marking cycle).
 363   void allocate_dummy_regions() PRODUCT_RETURN;
 364 
 365   // These are macros so that, if the assert fires, we get the correct
 366   // line number, file, etc.
 367 
 368 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 369   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 370           (_extra_message_),                                                  \
 371           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 372           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 373           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 374 
 375 #define assert_heap_locked()                                                  \
 376   do {                                                                        \
 377     assert(Heap_lock->owned_by_self(),                                        \
 378            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 379   } while (0)
 380 
 381 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 382   do {                                                                        \
 383     assert(Heap_lock->owned_by_self() ||                                      \
 384            (SafepointSynchronize::is_at_safepoint() &&                        \
 385              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 386            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 387                                         "should be at a safepoint"));         \
 388   } while (0)
 389 
 390 #define assert_heap_locked_and_not_at_safepoint()                             \
 391   do {                                                                        \
 392     assert(Heap_lock->owned_by_self() &&                                      \
 393                                     !SafepointSynchronize::is_at_safepoint(), \
 394           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 395                                        "should not be at a safepoint"));      \
 396   } while (0)
 397 
 398 #define assert_heap_not_locked()                                              \
 399   do {                                                                        \
 400     assert(!Heap_lock->owned_by_self(),                                       \
 401         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 402   } while (0)
 403 
 404 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 405   do {                                                                        \
 406     assert(!Heap_lock->owned_by_self() &&                                     \
 407                                     !SafepointSynchronize::is_at_safepoint(), \
 408       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 409                                    "should not be at a safepoint"));          \
 410   } while (0)
 411 
 412 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 413   do {                                                                        \
 414     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 415               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 416            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 417   } while (0)
 418 
 419 #define assert_not_at_safepoint()                                             \
 420   do {                                                                        \
 421     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 422            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 423   } while (0)
 424 
 425 protected:
 426 
 427   // The young region list.
 428   YoungList*  _young_list;
 429 
 430   // The current policy object for the collector.
 431   G1CollectorPolicy* _g1_policy;
 432 
 433   // This is the second level of trying to allocate a new region. If
 434   // new_region() didn't find a region on the free_list, this call will
 435   // check whether there's anything available on the
 436   // secondary_free_list and/or wait for more regions to appear on
 437   // that list, if _free_regions_coming is set.
 438   HeapRegion* new_region_try_secondary_free_list();
 439 
 440   // Try to allocate a single non-humongous HeapRegion sufficient for
 441   // an allocation of the given word_size. If do_expand is true,
 442   // attempt to expand the heap if necessary to satisfy the allocation
 443   // request.
 444   HeapRegion* new_region(size_t word_size, bool do_expand);
 445 
 446   // Attempt to satisfy a humongous allocation request of the given
 447   // size by finding a contiguous set of free regions of num_regions
 448   // length and remove them from the master free list. Return the
 449   // index of the first region or G1_NULL_HRS_INDEX if the search
 450   // was unsuccessful.
 451   size_t humongous_obj_allocate_find_first(size_t num_regions,
 452                                            size_t word_size);
 453 
 454   // Initialize a contiguous set of free regions of length num_regions
 455   // and starting at index first so that they appear as a single
 456   // humongous region.
 457   HeapWord* humongous_obj_allocate_initialize_regions(size_t first,
 458                                                       size_t num_regions,
 459                                                       size_t word_size);
 460 
 461   // Attempt to allocate a humongous object of the given size. Return
 462   // NULL if unsuccessful.
 463   HeapWord* humongous_obj_allocate(size_t word_size);
 464 
 465   // The following two methods, allocate_new_tlab() and
 466   // mem_allocate(), are the two main entry points from the runtime
 467   // into the G1's allocation routines. They have the following
 468   // assumptions:
 469   //
 470   // * They should both be called outside safepoints.
 471   //
 472   // * They should both be called without holding the Heap_lock.
 473   //
 474   // * All allocation requests for new TLABs should go to
 475   //   allocate_new_tlab().
 476   //
 477   // * All non-TLAB allocation requests should go to mem_allocate().
 478   //
 479   // * If either call cannot satisfy the allocation request using the
 480   //   current allocating region, they will try to get a new one. If
 481   //   this fails, they will attempt to do an evacuation pause and
 482   //   retry the allocation.
 483   //
 484   // * If all allocation attempts fail, even after trying to schedule
 485   //   an evacuation pause, allocate_new_tlab() will return NULL,
 486   //   whereas mem_allocate() will attempt a heap expansion and/or
 487   //   schedule a Full GC.
 488   //
 489   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 490   //   should never be called with word_size being humongous. All
 491   //   humongous allocation requests should go to mem_allocate() which
 492   //   will satisfy them with a special path.
 493 
 494   virtual HeapWord* allocate_new_tlab(size_t word_size);
 495 
 496   virtual HeapWord* mem_allocate(size_t word_size,
 497                                  bool*  gc_overhead_limit_was_exceeded);
 498 
 499   // The following three methods take a gc_count_before_ret
 500   // parameter which is used to return the GC count if the method
 501   // returns NULL. Given that we are required to read the GC count
 502   // while holding the Heap_lock, and these paths will take the
 503   // Heap_lock at some point, it's easier to get them to read the GC
 504   // count while holding the Heap_lock before they return NULL instead
 505   // of the caller (namely: mem_allocate()) having to also take the
 506   // Heap_lock just to read the GC count.
 507 
 508   // First-level mutator allocation attempt: try to allocate out of
 509   // the mutator alloc region without taking the Heap_lock. This
 510   // should only be used for non-humongous allocations.
 511   inline HeapWord* attempt_allocation(size_t word_size,
 512                                       unsigned int* gc_count_before_ret);
 513 
 514   // Second-level mutator allocation attempt: take the Heap_lock and
 515   // retry the allocation attempt, potentially scheduling a GC
 516   // pause. This should only be used for non-humongous allocations.
 517   HeapWord* attempt_allocation_slow(size_t word_size,
 518                                     unsigned int* gc_count_before_ret);
 519 
 520   // Takes the Heap_lock and attempts a humongous allocation. It can
 521   // potentially schedule a GC pause.
 522   HeapWord* attempt_allocation_humongous(size_t word_size,
 523                                          unsigned int* gc_count_before_ret);
 524 
 525   // Allocation attempt that should be called during safepoints (e.g.,
 526   // at the end of a successful GC). expect_null_mutator_alloc_region
 527   // specifies whether the mutator alloc region is expected to be NULL
 528   // or not.
 529   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 530                                        bool expect_null_mutator_alloc_region);
 531 
 532   // It dirties the cards that cover the block so that so that the post
 533   // write barrier never queues anything when updating objects on this
 534   // block. It is assumed (and in fact we assert) that the block
 535   // belongs to a young region.
 536   inline void dirty_young_block(HeapWord* start, size_t word_size);
 537 
 538   // Allocate blocks during garbage collection. Will ensure an
 539   // allocation region, either by picking one or expanding the
 540   // heap, and then allocate a block of the given size. The block
 541   // may not be a humongous - it must fit into a single heap region.
 542   HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
 543 
 544   HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
 545                                     HeapRegion*    alloc_region,
 546                                     bool           par,
 547                                     size_t         word_size);
 548 
 549   // Ensure that no further allocations can happen in "r", bearing in mind
 550   // that parallel threads might be attempting allocations.
 551   void par_allocate_remaining_space(HeapRegion* r);
 552 
 553   // Allocation attempt during GC for a survivor object / PLAB.
 554   inline HeapWord* survivor_attempt_allocation(size_t word_size);
 555 
 556   // Allocation attempt during GC for an old object / PLAB.
 557   inline HeapWord* old_attempt_allocation(size_t word_size);
 558 
 559   // These methods are the "callbacks" from the G1AllocRegion class.
 560 
 561   // For mutator alloc regions.
 562   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 563   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 564                                    size_t allocated_bytes);
 565 
 566   // For GC alloc regions.
 567   HeapRegion* new_gc_alloc_region(size_t word_size, size_t count,
 568                                   GCAllocPurpose ap);
 569   void retire_gc_alloc_region(HeapRegion* alloc_region,
 570                               size_t allocated_bytes, GCAllocPurpose ap);
 571 
 572   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 573   //   inspection request and should collect the entire heap
 574   // - if clear_all_soft_refs is true, all soft references should be
 575   //   cleared during the GC
 576   // - if explicit_gc is false, word_size describes the allocation that
 577   //   the GC should attempt (at least) to satisfy
 578   // - it returns false if it is unable to do the collection due to the
 579   //   GC locker being active, true otherwise
 580   bool do_collection(bool explicit_gc,
 581                      bool clear_all_soft_refs,
 582                      size_t word_size);
 583 
 584   // Callback from VM_G1CollectFull operation.
 585   // Perform a full collection.
 586   void do_full_collection(bool clear_all_soft_refs);
 587 
 588   // Resize the heap if necessary after a full collection.  If this is
 589   // after a collect-for allocation, "word_size" is the allocation size,
 590   // and will be considered part of the used portion of the heap.
 591   void resize_if_necessary_after_full_collection(size_t word_size);
 592 
 593   // Callback from VM_G1CollectForAllocation operation.
 594   // This function does everything necessary/possible to satisfy a
 595   // failed allocation request (including collection, expansion, etc.)
 596   HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
 597 
 598   // Attempting to expand the heap sufficiently
 599   // to support an allocation of the given "word_size".  If
 600   // successful, perform the allocation and return the address of the
 601   // allocated block, or else "NULL".
 602   HeapWord* expand_and_allocate(size_t word_size);
 603 
 604   // Process any reference objects discovered during
 605   // an incremental evacuation pause.
 606   void process_discovered_references();
 607 
 608   // Enqueue any remaining discovered references
 609   // after processing.
 610   void enqueue_discovered_references();
 611 
 612 public:
 613 
 614   G1MonitoringSupport* g1mm() {
 615     assert(_g1mm != NULL, "should have been initialized");
 616     return _g1mm;
 617   }
 618 
 619   // Expand the garbage-first heap by at least the given size (in bytes!).
 620   // Returns true if the heap was expanded by the requested amount;
 621   // false otherwise.
 622   // (Rounds up to a HeapRegion boundary.)
 623   bool expand(size_t expand_bytes);
 624 
 625   // Do anything common to GC's.
 626   virtual void gc_prologue(bool full);
 627   virtual void gc_epilogue(bool full);
 628 
 629   // We register a region with the fast "in collection set" test. We
 630   // simply set to true the array slot corresponding to this region.
 631   void register_region_with_in_cset_fast_test(HeapRegion* r) {
 632     assert(_in_cset_fast_test_base != NULL, "sanity");
 633     assert(r->in_collection_set(), "invariant");
 634     size_t index = r->hrs_index();
 635     assert(index < _in_cset_fast_test_length, "invariant");
 636     assert(!_in_cset_fast_test_base[index], "invariant");
 637     _in_cset_fast_test_base[index] = true;
 638   }
 639 
 640   // This is a fast test on whether a reference points into the
 641   // collection set or not. It does not assume that the reference
 642   // points into the heap; if it doesn't, it will return false.
 643   bool in_cset_fast_test(oop obj) {
 644     assert(_in_cset_fast_test != NULL, "sanity");
 645     if (_g1_committed.contains((HeapWord*) obj)) {
 646       // no need to subtract the bottom of the heap from obj,
 647       // _in_cset_fast_test is biased
 648       size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
 649       bool ret = _in_cset_fast_test[index];
 650       // let's make sure the result is consistent with what the slower
 651       // test returns
 652       assert( ret || !obj_in_cs(obj), "sanity");
 653       assert(!ret ||  obj_in_cs(obj), "sanity");
 654       return ret;
 655     } else {
 656       return false;
 657     }
 658   }
 659 
 660   void clear_cset_fast_test() {
 661     assert(_in_cset_fast_test_base != NULL, "sanity");
 662     memset(_in_cset_fast_test_base, false,
 663         _in_cset_fast_test_length * sizeof(bool));
 664   }
 665 
 666   // This is called at the end of either a concurrent cycle or a Full
 667   // GC to update the number of full collections completed. Those two
 668   // can happen in a nested fashion, i.e., we start a concurrent
 669   // cycle, a Full GC happens half-way through it which ends first,
 670   // and then the cycle notices that a Full GC happened and ends
 671   // too. The concurrent parameter is a boolean to help us do a bit
 672   // tighter consistency checking in the method. If concurrent is
 673   // false, the caller is the inner caller in the nesting (i.e., the
 674   // Full GC). If concurrent is true, the caller is the outer caller
 675   // in this nesting (i.e., the concurrent cycle). Further nesting is
 676   // not currently supported. The end of the this call also notifies
 677   // the FullGCCount_lock in case a Java thread is waiting for a full
 678   // GC to happen (e.g., it called System.gc() with
 679   // +ExplicitGCInvokesConcurrent).
 680   void increment_full_collections_completed(bool concurrent);
 681 
 682   unsigned int full_collections_completed() {
 683     return _full_collections_completed;
 684   }
 685 
 686   G1HRPrinter* hr_printer() { return &_hr_printer; }
 687 
 688 protected:
 689 
 690   // Shrink the garbage-first heap by at most the given size (in bytes!).
 691   // (Rounds down to a HeapRegion boundary.)
 692   virtual void shrink(size_t expand_bytes);
 693   void shrink_helper(size_t expand_bytes);
 694 
 695   #if TASKQUEUE_STATS
 696   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 697   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 698   void reset_taskqueue_stats();
 699   #endif // TASKQUEUE_STATS
 700 
 701   // Schedule the VM operation that will do an evacuation pause to
 702   // satisfy an allocation request of word_size. *succeeded will
 703   // return whether the VM operation was successful (it did do an
 704   // evacuation pause) or not (another thread beat us to it or the GC
 705   // locker was active). Given that we should not be holding the
 706   // Heap_lock when we enter this method, we will pass the
 707   // gc_count_before (i.e., total_collections()) as a parameter since
 708   // it has to be read while holding the Heap_lock. Currently, both
 709   // methods that call do_collection_pause() release the Heap_lock
 710   // before the call, so it's easy to read gc_count_before just before.
 711   HeapWord* do_collection_pause(size_t       word_size,
 712                                 unsigned int gc_count_before,
 713                                 bool*        succeeded);
 714 
 715   // The guts of the incremental collection pause, executed by the vm
 716   // thread. It returns false if it is unable to do the collection due
 717   // to the GC locker being active, true otherwise
 718   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 719 
 720   // Actually do the work of evacuating the collection set.
 721   void evacuate_collection_set();
 722 
 723   // The g1 remembered set of the heap.
 724   G1RemSet* _g1_rem_set;
 725   // And it's mod ref barrier set, used to track updates for the above.
 726   ModRefBarrierSet* _mr_bs;
 727 
 728   // A set of cards that cover the objects for which the Rsets should be updated
 729   // concurrently after the collection.
 730   DirtyCardQueueSet _dirty_card_queue_set;
 731 
 732   // The Heap Region Rem Set Iterator.
 733   HeapRegionRemSetIterator** _rem_set_iterator;
 734 
 735   // The closure used to refine a single card.
 736   RefineCardTableEntryClosure* _refine_cte_cl;
 737 
 738   // A function to check the consistency of dirty card logs.
 739   void check_ct_logs_at_safepoint();
 740 
 741   // A DirtyCardQueueSet that is used to hold cards that contain
 742   // references into the current collection set. This is used to
 743   // update the remembered sets of the regions in the collection
 744   // set in the event of an evacuation failure.
 745   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 746 
 747   // After a collection pause, make the regions in the CS into free
 748   // regions.
 749   void free_collection_set(HeapRegion* cs_head);
 750 
 751   // Abandon the current collection set without recording policy
 752   // statistics or updating free lists.
 753   void abandon_collection_set(HeapRegion* cs_head);
 754 
 755   // Applies "scan_non_heap_roots" to roots outside the heap,
 756   // "scan_rs" to roots inside the heap (having done "set_region" to
 757   // indicate the region in which the root resides), and does "scan_perm"
 758   // (setting the generation to the perm generation.)  If "scan_rs" is
 759   // NULL, then this step is skipped.  The "worker_i"
 760   // param is for use with parallel roots processing, and should be
 761   // the "i" of the calling parallel worker thread's work(i) function.
 762   // In the sequential case this param will be ignored.
 763   void g1_process_strong_roots(bool collecting_perm_gen,
 764                                SharedHeap::ScanningOption so,
 765                                OopClosure* scan_non_heap_roots,
 766                                OopsInHeapRegionClosure* scan_rs,
 767                                OopsInGenClosure* scan_perm,
 768                                int worker_i);
 769 
 770   // Apply "blk" to all the weak roots of the system.  These include
 771   // JNI weak roots, the code cache, system dictionary, symbol table,
 772   // string table, and referents of reachable weak refs.
 773   void g1_process_weak_roots(OopClosure* root_closure,
 774                              OopClosure* non_root_closure);
 775 
 776   // Frees a non-humongous region by initializing its contents and
 777   // adding it to the free list that's passed as a parameter (this is
 778   // usually a local list which will be appended to the master free
 779   // list later). The used bytes of freed regions are accumulated in
 780   // pre_used. If par is true, the region's RSet will not be freed
 781   // up. The assumption is that this will be done later.
 782   void free_region(HeapRegion* hr,
 783                    size_t* pre_used,
 784                    FreeRegionList* free_list,
 785                    bool par);
 786 
 787   // Frees a humongous region by collapsing it into individual regions
 788   // and calling free_region() for each of them. The freed regions
 789   // will be added to the free list that's passed as a parameter (this
 790   // is usually a local list which will be appended to the master free
 791   // list later). The used bytes of freed regions are accumulated in
 792   // pre_used. If par is true, the region's RSet will not be freed
 793   // up. The assumption is that this will be done later.
 794   void free_humongous_region(HeapRegion* hr,
 795                              size_t* pre_used,
 796                              FreeRegionList* free_list,
 797                              HumongousRegionSet* humongous_proxy_set,
 798                              bool par);
 799 
 800   // Notifies all the necessary spaces that the committed space has
 801   // been updated (either expanded or shrunk). It should be called
 802   // after _g1_storage is updated.
 803   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 804 
 805   // The concurrent marker (and the thread it runs in.)
 806   ConcurrentMark* _cm;
 807   ConcurrentMarkThread* _cmThread;
 808   bool _mark_in_progress;
 809 
 810   // The concurrent refiner.
 811   ConcurrentG1Refine* _cg1r;
 812 
 813   // The parallel task queues
 814   RefToScanQueueSet *_task_queues;
 815 
 816   // True iff a evacuation has failed in the current collection.
 817   bool _evacuation_failed;
 818 
 819   // Set the attribute indicating whether evacuation has failed in the
 820   // current collection.
 821   void set_evacuation_failed(bool b) { _evacuation_failed = b; }
 822 
 823   // Failed evacuations cause some logical from-space objects to have
 824   // forwarding pointers to themselves.  Reset them.
 825   void remove_self_forwarding_pointers();
 826 
 827   // When one is non-null, so is the other.  Together, they each pair is
 828   // an object with a preserved mark, and its mark value.
 829   GrowableArray<oop>*     _objs_with_preserved_marks;
 830   GrowableArray<markOop>* _preserved_marks_of_objs;
 831 
 832   // Preserve the mark of "obj", if necessary, in preparation for its mark
 833   // word being overwritten with a self-forwarding-pointer.
 834   void preserve_mark_if_necessary(oop obj, markOop m);
 835 
 836   // The stack of evac-failure objects left to be scanned.
 837   GrowableArray<oop>*    _evac_failure_scan_stack;
 838   // The closure to apply to evac-failure objects.
 839 
 840   OopsInHeapRegionClosure* _evac_failure_closure;
 841   // Set the field above.
 842   void
 843   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 844     _evac_failure_closure = evac_failure_closure;
 845   }
 846 
 847   // Push "obj" on the scan stack.
 848   void push_on_evac_failure_scan_stack(oop obj);
 849   // Process scan stack entries until the stack is empty.
 850   void drain_evac_failure_scan_stack();
 851   // True iff an invocation of "drain_scan_stack" is in progress; to
 852   // prevent unnecessary recursion.
 853   bool _drain_in_progress;
 854 
 855   // Do any necessary initialization for evacuation-failure handling.
 856   // "cl" is the closure that will be used to process evac-failure
 857   // objects.
 858   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 859   // Do any necessary cleanup for evacuation-failure handling data
 860   // structures.
 861   void finalize_for_evac_failure();
 862 
 863   // An attempt to evacuate "obj" has failed; take necessary steps.
 864   oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj,
 865                                     bool should_mark_root);
 866   void handle_evacuation_failure_common(oop obj, markOop m);
 867 
 868   // ("Weak") Reference processing support.
 869   //
 870   // G1 has 2 instances of the referece processor class. One
 871   // (_ref_processor_cm) handles reference object discovery
 872   // and subsequent processing during concurrent marking cycles.
 873   //
 874   // The other (_ref_processor_stw) handles reference object
 875   // discovery and processing during full GCs and incremental
 876   // evacuation pauses.
 877   //
 878   // During an incremental pause, reference discovery will be
 879   // temporarily disabled for _ref_processor_cm and will be
 880   // enabled for _ref_processor_stw. At the end of the evacuation
 881   // pause references discovered by _ref_processor_stw will be
 882   // processed and discovery will be disabled. The previous
 883   // setting for reference object discovery for _ref_processor_cm
 884   // will be re-instated.
 885   //
 886   // At the start of marking:
 887   //  * Discovery by the CM ref processor is verified to be inactive
 888   //    and it's discovered lists are empty.
 889   //  * Discovery by the CM ref processor is then enabled.
 890   //
 891   // At the end of marking:
 892   //  * Any references on the CM ref processor's discovered
 893   //    lists are processed (possibly MT).
 894   //
 895   // At the start of full GC we:
 896   //  * Disable discovery by the CM ref processor and
 897   //    empty CM ref processor's discovered lists
 898   //    (without processing any entries).
 899   //  * Verify that the STW ref processor is inactive and it's
 900   //    discovered lists are empty.
 901   //  * Temporarily set STW ref processor discovery as single threaded.
 902   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 903   //    field.
 904   //  * Finally enable discovery by the STW ref processor.
 905   //
 906   // The STW ref processor is used to record any discovered
 907   // references during the full GC.
 908   //
 909   // At the end of a full GC we:
 910   //  * Enqueue any reference objects discovered by the STW ref processor
 911   //    that have non-live referents. This has the side-effect of
 912   //    making the STW ref processor inactive by disabling discovery.
 913   //  * Verify that the CM ref processor is still inactive
 914   //    and no references have been placed on it's discovered
 915   //    lists (also checked as a precondition during initial marking).
 916 
 917   // The (stw) reference processor...
 918   ReferenceProcessor* _ref_processor_stw;
 919 
 920   // During reference object discovery, the _is_alive_non_header
 921   // closure (if non-null) is applied to the referent object to
 922   // determine whether the referent is live. If so then the
 923   // reference object does not need to be 'discovered' and can
 924   // be treated as a regular oop. This has the benefit of reducing
 925   // the number of 'discovered' reference objects that need to
 926   // be processed.
 927   //
 928   // Instance of the is_alive closure for embedding into the
 929   // STW reference processor as the _is_alive_non_header field.
 930   // Supplying a value for the _is_alive_non_header field is
 931   // optional but doing so prevents unnecessary additions to
 932   // the discovered lists during reference discovery.
 933   G1STWIsAliveClosure _is_alive_closure_stw;
 934 
 935   // The (concurrent marking) reference processor...
 936   ReferenceProcessor* _ref_processor_cm;
 937 
 938   // Instance of the concurrent mark is_alive closure for embedding
 939   // into the Concurrent Marking reference processor as the
 940   // _is_alive_non_header field. Supplying a value for the
 941   // _is_alive_non_header field is optional but doing so prevents
 942   // unnecessary additions to the discovered lists during reference
 943   // discovery.
 944   G1CMIsAliveClosure _is_alive_closure_cm;
 945 
 946   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 947   HeapRegion** _worker_cset_start_region;
 948 
 949   // Time stamp to validate the regions recorded in the cache
 950   // used by G1CollectedHeap::start_cset_region_for_worker().
 951   // The heap region entry for a given worker is valid iff
 952   // the associated time stamp value matches the current value
 953   // of G1CollectedHeap::_gc_time_stamp.
 954   unsigned int* _worker_cset_start_region_time_stamp;
 955 
 956   enum G1H_process_strong_roots_tasks {
 957     G1H_PS_mark_stack_oops_do,
 958     G1H_PS_refProcessor_oops_do,
 959     // Leave this one last.
 960     G1H_PS_NumElements
 961   };
 962 
 963   SubTasksDone* _process_strong_tasks;
 964 
 965   volatile bool _free_regions_coming;
 966 
 967 public:
 968 
 969   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
 970 
 971   void set_refine_cte_cl_concurrency(bool concurrent);
 972 
 973   RefToScanQueue *task_queue(int i) const;
 974 
 975   // A set of cards where updates happened during the GC
 976   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 977 
 978   // A DirtyCardQueueSet that is used to hold cards that contain
 979   // references into the current collection set. This is used to
 980   // update the remembered sets of the regions in the collection
 981   // set in the event of an evacuation failure.
 982   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
 983         { return _into_cset_dirty_card_queue_set; }
 984 
 985   // Create a G1CollectedHeap with the specified policy.
 986   // Must call the initialize method afterwards.
 987   // May not return if something goes wrong.
 988   G1CollectedHeap(G1CollectorPolicy* policy);
 989 
 990   // Initialize the G1CollectedHeap to have the initial and
 991   // maximum sizes, permanent generation, and remembered and barrier sets
 992   // specified by the policy object.
 993   jint initialize();
 994 
 995   // Initialize weak reference processing.
 996   virtual void ref_processing_init();
 997 
 998   void set_par_threads(int t) {
 999     SharedHeap::set_par_threads(t);
1000     // Done in SharedHeap but oddly there are
1001     // two _process_strong_tasks's in a G1CollectedHeap
1002     // so do it here too.
1003     _process_strong_tasks->set_n_threads(t);
1004   }
1005 
1006   // Set _n_par_threads according to a policy TBD.
1007   void set_par_threads();
1008 
1009   void set_n_termination(int t) {
1010     _process_strong_tasks->set_n_threads(t);
1011   }
1012 
1013   virtual CollectedHeap::Name kind() const {
1014     return CollectedHeap::G1CollectedHeap;
1015   }
1016 
1017   // The current policy object for the collector.
1018   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1019 
1020   // Adaptive size policy.  No such thing for g1.
1021   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1022 
1023   // The rem set and barrier set.
1024   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1025   ModRefBarrierSet* mr_bs() const { return _mr_bs; }
1026 
1027   // The rem set iterator.
1028   HeapRegionRemSetIterator* rem_set_iterator(int i) {
1029     return _rem_set_iterator[i];
1030   }
1031 
1032   HeapRegionRemSetIterator* rem_set_iterator() {
1033     return _rem_set_iterator[0];
1034   }
1035 
1036   unsigned get_gc_time_stamp() {
1037     return _gc_time_stamp;
1038   }
1039 
1040   void reset_gc_time_stamp() {
1041     _gc_time_stamp = 0;
1042     OrderAccess::fence();
1043     // Clear the cached CSet starting regions and time stamps.
1044     // Their validity is dependent on the GC timestamp.
1045     clear_cset_start_regions();
1046   }
1047 
1048   void increment_gc_time_stamp() {
1049     ++_gc_time_stamp;
1050     OrderAccess::fence();
1051   }
1052 
1053   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1054                                   DirtyCardQueue* into_cset_dcq,
1055                                   bool concurrent, int worker_i);
1056 
1057   // The shared block offset table array.
1058   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1059 
1060   // Reference Processing accessors
1061 
1062   // The STW reference processor....
1063   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1064 
1065   // The Concurent Marking reference processor...
1066   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1067 
1068   virtual size_t capacity() const;
1069   virtual size_t used() const;
1070   // This should be called when we're not holding the heap lock. The
1071   // result might be a bit inaccurate.
1072   size_t used_unlocked() const;
1073   size_t recalculate_used() const;
1074 
1075   // These virtual functions do the actual allocation.
1076   // Some heaps may offer a contiguous region for shared non-blocking
1077   // allocation, via inlined code (by exporting the address of the top and
1078   // end fields defining the extent of the contiguous allocation region.)
1079   // But G1CollectedHeap doesn't yet support this.
1080 
1081   // Return an estimate of the maximum allocation that could be performed
1082   // without triggering any collection or expansion activity.  In a
1083   // generational collector, for example, this is probably the largest
1084   // allocation that could be supported (without expansion) in the youngest
1085   // generation.  It is "unsafe" because no locks are taken; the result
1086   // should be treated as an approximation, not a guarantee, for use in
1087   // heuristic resizing decisions.
1088   virtual size_t unsafe_max_alloc();
1089 
1090   virtual bool is_maximal_no_gc() const {
1091     return _g1_storage.uncommitted_size() == 0;
1092   }
1093 
1094   // The total number of regions in the heap.
1095   size_t n_regions() { return _hrs.length(); }
1096 
1097   // The max number of regions in the heap.
1098   size_t max_regions() { return _hrs.max_length(); }
1099 
1100   // The number of regions that are completely free.
1101   size_t free_regions() { return _free_list.length(); }
1102 
1103   // The number of regions that are not completely free.
1104   size_t used_regions() { return n_regions() - free_regions(); }
1105 
1106   // The number of regions available for "regular" expansion.
1107   size_t expansion_regions() { return _expansion_regions; }
1108 
1109   // Factory method for HeapRegion instances. It will return NULL if
1110   // the allocation fails.
1111   HeapRegion* new_heap_region(size_t hrs_index, HeapWord* bottom);
1112 
1113   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1114   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1115   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1116   void verify_dirty_young_regions() PRODUCT_RETURN;
1117 
1118   // verify_region_sets() performs verification over the region
1119   // lists. It will be compiled in the product code to be used when
1120   // necessary (i.e., during heap verification).
1121   void verify_region_sets();
1122 
1123   // verify_region_sets_optional() is planted in the code for
1124   // list verification in non-product builds (and it can be enabled in
1125   // product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1).
1126 #if HEAP_REGION_SET_FORCE_VERIFY
1127   void verify_region_sets_optional() {
1128     verify_region_sets();
1129   }
1130 #else // HEAP_REGION_SET_FORCE_VERIFY
1131   void verify_region_sets_optional() { }
1132 #endif // HEAP_REGION_SET_FORCE_VERIFY
1133 
1134 #ifdef ASSERT
1135   bool is_on_master_free_list(HeapRegion* hr) {
1136     return hr->containing_set() == &_free_list;
1137   }
1138 
1139   bool is_in_humongous_set(HeapRegion* hr) {
1140     return hr->containing_set() == &_humongous_set;
1141   }
1142 #endif // ASSERT
1143 
1144   // Wrapper for the region list operations that can be called from
1145   // methods outside this class.
1146 
1147   void secondary_free_list_add_as_tail(FreeRegionList* list) {
1148     _secondary_free_list.add_as_tail(list);
1149   }
1150 
1151   void append_secondary_free_list() {
1152     _free_list.add_as_head(&_secondary_free_list);
1153   }
1154 
1155   void append_secondary_free_list_if_not_empty_with_lock() {
1156     // If the secondary free list looks empty there's no reason to
1157     // take the lock and then try to append it.
1158     if (!_secondary_free_list.is_empty()) {
1159       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1160       append_secondary_free_list();
1161     }
1162   }
1163 
1164   void old_set_remove(HeapRegion* hr) {
1165     _old_set.remove(hr);
1166   }
1167 
1168   void set_free_regions_coming();
1169   void reset_free_regions_coming();
1170   bool free_regions_coming() { return _free_regions_coming; }
1171   void wait_while_free_regions_coming();
1172 
1173   // Perform a collection of the heap; intended for use in implementing
1174   // "System.gc".  This probably implies as full a collection as the
1175   // "CollectedHeap" supports.
1176   virtual void collect(GCCause::Cause cause);
1177 
1178   // The same as above but assume that the caller holds the Heap_lock.
1179   void collect_locked(GCCause::Cause cause);
1180 
1181   // This interface assumes that it's being called by the
1182   // vm thread. It collects the heap assuming that the
1183   // heap lock is already held and that we are executing in
1184   // the context of the vm thread.
1185   virtual void collect_as_vm_thread(GCCause::Cause cause);
1186 
1187   // True iff a evacuation has failed in the most-recent collection.
1188   bool evacuation_failed() { return _evacuation_failed; }
1189 
1190   // It will free a region if it has allocated objects in it that are
1191   // all dead. It calls either free_region() or
1192   // free_humongous_region() depending on the type of the region that
1193   // is passed to it.
1194   void free_region_if_empty(HeapRegion* hr,
1195                             size_t* pre_used,
1196                             FreeRegionList* free_list,
1197                             OldRegionSet* old_proxy_set,
1198                             HumongousRegionSet* humongous_proxy_set,
1199                             HRRSCleanupTask* hrrs_cleanup_task,
1200                             bool par);
1201 
1202   // It appends the free list to the master free list and updates the
1203   // master humongous list according to the contents of the proxy
1204   // list. It also adjusts the total used bytes according to pre_used
1205   // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1206   void update_sets_after_freeing_regions(size_t pre_used,
1207                                        FreeRegionList* free_list,
1208                                        OldRegionSet* old_proxy_set,
1209                                        HumongousRegionSet* humongous_proxy_set,
1210                                        bool par);
1211 
1212   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1213   virtual bool is_in(const void* p) const;
1214 
1215   // Return "TRUE" iff the given object address is within the collection
1216   // set.
1217   inline bool obj_in_cs(oop obj);
1218 
1219   // Return "TRUE" iff the given object address is in the reserved
1220   // region of g1 (excluding the permanent generation).
1221   bool is_in_g1_reserved(const void* p) const {
1222     return _g1_reserved.contains(p);
1223   }
1224 
1225   // Returns a MemRegion that corresponds to the space that has been
1226   // reserved for the heap
1227   MemRegion g1_reserved() {
1228     return _g1_reserved;
1229   }
1230 
1231   // Returns a MemRegion that corresponds to the space that has been
1232   // committed in the heap
1233   MemRegion g1_committed() {
1234     return _g1_committed;
1235   }
1236 
1237   virtual bool is_in_closed_subset(const void* p) const;
1238 
1239   // This resets the card table to all zeros.  It is used after
1240   // a collection pause which used the card table to claim cards.
1241   void cleanUpCardTable();
1242 
1243   // Iteration functions.
1244 
1245   // Iterate over all the ref-containing fields of all objects, calling
1246   // "cl.do_oop" on each.
1247   virtual void oop_iterate(OopClosure* cl) {
1248     oop_iterate(cl, true);
1249   }
1250   void oop_iterate(OopClosure* cl, bool do_perm);
1251 
1252   // Same as above, restricted to a memory region.
1253   virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
1254     oop_iterate(mr, cl, true);
1255   }
1256   void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
1257 
1258   // Iterate over all objects, calling "cl.do_object" on each.
1259   virtual void object_iterate(ObjectClosure* cl) {
1260     object_iterate(cl, true);
1261   }
1262   virtual void safe_object_iterate(ObjectClosure* cl) {
1263     object_iterate(cl, true);
1264   }
1265   void object_iterate(ObjectClosure* cl, bool do_perm);
1266 
1267   // Iterate over all objects allocated since the last collection, calling
1268   // "cl.do_object" on each.  The heap must have been initialized properly
1269   // to support this function, or else this call will fail.
1270   virtual void object_iterate_since_last_GC(ObjectClosure* cl);
1271 
1272   // Iterate over all spaces in use in the heap, in ascending address order.
1273   virtual void space_iterate(SpaceClosure* cl);
1274 
1275   // Iterate over heap regions, in address order, terminating the
1276   // iteration early if the "doHeapRegion" method returns "true".
1277   void heap_region_iterate(HeapRegionClosure* blk) const;
1278 
1279   // Iterate over heap regions starting with r (or the first region if "r"
1280   // is NULL), in address order, terminating early if the "doHeapRegion"
1281   // method returns "true".
1282   void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk) const;
1283 
1284   // Return the region with the given index. It assumes the index is valid.
1285   HeapRegion* region_at(size_t index) const { return _hrs.at(index); }
1286 
1287   // Divide the heap region sequence into "chunks" of some size (the number
1288   // of regions divided by the number of parallel threads times some
1289   // overpartition factor, currently 4).  Assumes that this will be called
1290   // in parallel by ParallelGCThreads worker threads with discinct worker
1291   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1292   // calls will use the same "claim_value", and that that claim value is
1293   // different from the claim_value of any heap region before the start of
1294   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1295   // attempting to claim the first region in each chunk, and, if
1296   // successful, applying the closure to each region in the chunk (and
1297   // setting the claim value of the second and subsequent regions of the
1298   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1299   // i.e., that a closure never attempt to abort a traversal.
1300   void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1301                                        int worker,
1302                                        int no_of_par_workers,
1303                                        jint claim_value);
1304 
1305   // It resets all the region claim values to the default.
1306   void reset_heap_region_claim_values();
1307 
1308 #ifdef ASSERT
1309   bool check_heap_region_claim_values(jint claim_value);
1310 
1311   // Same as the routine above but only checks regions in the
1312   // current collection set.
1313   bool check_cset_heap_region_claim_values(jint claim_value);
1314 #endif // ASSERT
1315 
1316   // Clear the cached cset start regions and (more importantly)
1317   // the time stamps. Called when we reset the GC time stamp.
1318   void clear_cset_start_regions();
1319 
1320   // Given the id of a worker, obtain or calculate a suitable
1321   // starting region for iterating over the current collection set.
1322   HeapRegion* start_cset_region_for_worker(int worker_i);
1323 
1324   // Iterate over the regions (if any) in the current collection set.
1325   void collection_set_iterate(HeapRegionClosure* blk);
1326 
1327   // As above but starting from region r
1328   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1329 
1330   // Returns the first (lowest address) compactible space in the heap.
1331   virtual CompactibleSpace* first_compactible_space();
1332 
1333   // A CollectedHeap will contain some number of spaces.  This finds the
1334   // space containing a given address, or else returns NULL.
1335   virtual Space* space_containing(const void* addr) const;
1336 
1337   // A G1CollectedHeap will contain some number of heap regions.  This
1338   // finds the region containing a given address, or else returns NULL.
1339   template <class T>
1340   inline HeapRegion* heap_region_containing(const T addr) const;
1341 
1342   // Like the above, but requires "addr" to be in the heap (to avoid a
1343   // null-check), and unlike the above, may return an continuing humongous
1344   // region.
1345   template <class T>
1346   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1347 
1348   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1349   // each address in the (reserved) heap is a member of exactly
1350   // one block.  The defining characteristic of a block is that it is
1351   // possible to find its size, and thus to progress forward to the next
1352   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1353   // represent Java objects, or they might be free blocks in a
1354   // free-list-based heap (or subheap), as long as the two kinds are
1355   // distinguishable and the size of each is determinable.
1356 
1357   // Returns the address of the start of the "block" that contains the
1358   // address "addr".  We say "blocks" instead of "object" since some heaps
1359   // may not pack objects densely; a chunk may either be an object or a
1360   // non-object.
1361   virtual HeapWord* block_start(const void* addr) const;
1362 
1363   // Requires "addr" to be the start of a chunk, and returns its size.
1364   // "addr + size" is required to be the start of a new chunk, or the end
1365   // of the active area of the heap.
1366   virtual size_t block_size(const HeapWord* addr) const;
1367 
1368   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1369   // the block is an object.
1370   virtual bool block_is_obj(const HeapWord* addr) const;
1371 
1372   // Does this heap support heap inspection? (+PrintClassHistogram)
1373   virtual bool supports_heap_inspection() const { return true; }
1374 
1375   // Section on thread-local allocation buffers (TLABs)
1376   // See CollectedHeap for semantics.
1377 
1378   virtual bool supports_tlab_allocation() const;
1379   virtual size_t tlab_capacity(Thread* thr) const;
1380   virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1381 
1382   // Can a compiler initialize a new object without store barriers?
1383   // This permission only extends from the creation of a new object
1384   // via a TLAB up to the first subsequent safepoint. If such permission
1385   // is granted for this heap type, the compiler promises to call
1386   // defer_store_barrier() below on any slow path allocation of
1387   // a new object for which such initializing store barriers will
1388   // have been elided. G1, like CMS, allows this, but should be
1389   // ready to provide a compensating write barrier as necessary
1390   // if that storage came out of a non-young region. The efficiency
1391   // of this implementation depends crucially on being able to
1392   // answer very efficiently in constant time whether a piece of
1393   // storage in the heap comes from a young region or not.
1394   // See ReduceInitialCardMarks.
1395   virtual bool can_elide_tlab_store_barriers() const {
1396     return true;
1397   }
1398 
1399   virtual bool card_mark_must_follow_store() const {
1400     return true;
1401   }
1402 
1403   bool is_in_young(const oop obj) {
1404     HeapRegion* hr = heap_region_containing(obj);
1405     return hr != NULL && hr->is_young();
1406   }
1407 
1408 #ifdef ASSERT
1409   virtual bool is_in_partial_collection(const void* p);
1410 #endif
1411 
1412   virtual bool is_scavengable(const void* addr);
1413 
1414   // We don't need barriers for initializing stores to objects
1415   // in the young gen: for the SATB pre-barrier, there is no
1416   // pre-value that needs to be remembered; for the remembered-set
1417   // update logging post-barrier, we don't maintain remembered set
1418   // information for young gen objects.
1419   virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1420     return is_in_young(new_obj);
1421   }
1422 
1423   // Can a compiler elide a store barrier when it writes
1424   // a permanent oop into the heap?  Applies when the compiler
1425   // is storing x to the heap, where x->is_perm() is true.
1426   virtual bool can_elide_permanent_oop_store_barriers() const {
1427     // At least until perm gen collection is also G1-ified, at
1428     // which point this should return false.
1429     return true;
1430   }
1431 
1432   // Returns "true" iff the given word_size is "very large".
1433   static bool isHumongous(size_t word_size) {
1434     // Note this has to be strictly greater-than as the TLABs
1435     // are capped at the humongous thresold and we want to
1436     // ensure that we don't try to allocate a TLAB as
1437     // humongous and that we don't allocate a humongous
1438     // object in a TLAB.
1439     return word_size > _humongous_object_threshold_in_words;
1440   }
1441 
1442   // Update mod union table with the set of dirty cards.
1443   void updateModUnion();
1444 
1445   // Set the mod union bits corresponding to the given memRegion.  Note
1446   // that this is always a safe operation, since it doesn't clear any
1447   // bits.
1448   void markModUnionRange(MemRegion mr);
1449 
1450   // Records the fact that a marking phase is no longer in progress.
1451   void set_marking_complete() {
1452     _mark_in_progress = false;
1453   }
1454   void set_marking_started() {
1455     _mark_in_progress = true;
1456   }
1457   bool mark_in_progress() {
1458     return _mark_in_progress;
1459   }
1460 
1461   // Print the maximum heap capacity.
1462   virtual size_t max_capacity() const;
1463 
1464   virtual jlong millis_since_last_gc();
1465 
1466   // Perform any cleanup actions necessary before allowing a verification.
1467   virtual void prepare_for_verify();
1468 
1469   // Perform verification.
1470 
1471   // vo == UsePrevMarking  -> use "prev" marking information,
1472   // vo == UseNextMarking -> use "next" marking information
1473   // vo == UseMarkWord    -> use the mark word in the object header
1474   //
1475   // NOTE: Only the "prev" marking information is guaranteed to be
1476   // consistent most of the time, so most calls to this should use
1477   // vo == UsePrevMarking.
1478   // Currently, there is only one case where this is called with
1479   // vo == UseNextMarking, which is to verify the "next" marking
1480   // information at the end of remark.
1481   // Currently there is only one place where this is called with
1482   // vo == UseMarkWord, which is to verify the marking during a
1483   // full GC.
1484   void verify(bool allow_dirty, bool silent, VerifyOption vo);
1485 
1486   // Override; it uses the "prev" marking information
1487   virtual void verify(bool allow_dirty, bool silent);
1488   virtual void print_on(outputStream* st) const;
1489   virtual void print_extended_on(outputStream* st) const;
1490 
1491   virtual void print_gc_threads_on(outputStream* st) const;
1492   virtual void gc_threads_do(ThreadClosure* tc) const;
1493 
1494   // Override
1495   void print_tracing_info() const;
1496 
1497   // The following two methods are helpful for debugging RSet issues.
1498   void print_cset_rsets() PRODUCT_RETURN;
1499   void print_all_rsets() PRODUCT_RETURN;
1500 
1501   // Convenience function to be used in situations where the heap type can be
1502   // asserted to be this type.
1503   static G1CollectedHeap* heap();
1504 
1505   void set_region_short_lived_locked(HeapRegion* hr);
1506   // add appropriate methods for any other surv rate groups
1507 
1508   YoungList* young_list() { return _young_list; }
1509 
1510   // debugging
1511   bool check_young_list_well_formed() {
1512     return _young_list->check_list_well_formed();
1513   }
1514 
1515   bool check_young_list_empty(bool check_heap,
1516                               bool check_sample = true);
1517 
1518   // *** Stuff related to concurrent marking.  It's not clear to me that so
1519   // many of these need to be public.
1520 
1521   // The functions below are helper functions that a subclass of
1522   // "CollectedHeap" can use in the implementation of its virtual
1523   // functions.
1524   // This performs a concurrent marking of the live objects in a
1525   // bitmap off to the side.
1526   void doConcurrentMark();
1527 
1528   bool isMarkedPrev(oop obj) const;
1529   bool isMarkedNext(oop obj) const;
1530 
1531   // vo == UsePrevMarking -> use "prev" marking information,
1532   // vo == UseNextMarking -> use "next" marking information,
1533   // vo == UseMarkWord    -> use mark word from object header
1534   bool is_obj_dead_cond(const oop obj,
1535                         const HeapRegion* hr,
1536                         const VerifyOption vo) const {
1537 
1538     switch (vo) {
1539       case VerifyOption_G1UsePrevMarking:
1540         return is_obj_dead(obj, hr);
1541       case VerifyOption_G1UseNextMarking:
1542         return is_obj_ill(obj, hr);
1543       default:
1544         assert(vo == VerifyOption_G1UseMarkWord, "must be");
1545         return !obj->is_gc_marked();
1546     }
1547   }
1548 
1549   // Determine if an object is dead, given the object and also
1550   // the region to which the object belongs. An object is dead
1551   // iff a) it was not allocated since the last mark and b) it
1552   // is not marked.
1553 
1554   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1555     return
1556       !hr->obj_allocated_since_prev_marking(obj) &&
1557       !isMarkedPrev(obj);
1558   }
1559 
1560   // This is used when copying an object to survivor space.
1561   // If the object is marked live, then we mark the copy live.
1562   // If the object is allocated since the start of this mark
1563   // cycle, then we mark the copy live.
1564   // If the object has been around since the previous mark
1565   // phase, and hasn't been marked yet during this phase,
1566   // then we don't mark it, we just wait for the
1567   // current marking cycle to get to it.
1568 
1569   // This function returns true when an object has been
1570   // around since the previous marking and hasn't yet
1571   // been marked during this marking.
1572 
1573   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1574     return
1575       !hr->obj_allocated_since_next_marking(obj) &&
1576       !isMarkedNext(obj);
1577   }
1578 
1579   // Determine if an object is dead, given only the object itself.
1580   // This will find the region to which the object belongs and
1581   // then call the region version of the same function.
1582 
1583   // Added if it is in permanent gen it isn't dead.
1584   // Added if it is NULL it isn't dead.
1585 
1586   // vo == UsePrevMarking -> use "prev" marking information,
1587   // vo == UseNextMarking -> use "next" marking information,
1588   // vo == UseMarkWord    -> use mark word from object header
1589   bool is_obj_dead_cond(const oop obj,
1590                         const VerifyOption vo) const {
1591 
1592     switch (vo) {
1593       case VerifyOption_G1UsePrevMarking:
1594         return is_obj_dead(obj);
1595       case VerifyOption_G1UseNextMarking:
1596         return is_obj_ill(obj);
1597       default:
1598         assert(vo == VerifyOption_G1UseMarkWord, "must be");
1599         return !obj->is_gc_marked();
1600     }
1601   }
1602 
1603   bool is_obj_dead(const oop obj) const {
1604     const HeapRegion* hr = heap_region_containing(obj);
1605     if (hr == NULL) {
1606       if (Universe::heap()->is_in_permanent(obj))
1607         return false;
1608       else if (obj == NULL) return false;
1609       else return true;
1610     }
1611     else return is_obj_dead(obj, hr);
1612   }
1613 
1614   bool is_obj_ill(const oop obj) const {
1615     const HeapRegion* hr = heap_region_containing(obj);
1616     if (hr == NULL) {
1617       if (Universe::heap()->is_in_permanent(obj))
1618         return false;
1619       else if (obj == NULL) return false;
1620       else return true;
1621     }
1622     else return is_obj_ill(obj, hr);
1623   }
1624 
1625   // The following is just to alert the verification code
1626   // that a full collection has occurred and that the
1627   // remembered sets are no longer up to date.
1628   bool _full_collection;
1629   void set_full_collection() { _full_collection = true;}
1630   void clear_full_collection() {_full_collection = false;}
1631   bool full_collection() {return _full_collection;}
1632 
1633   ConcurrentMark* concurrent_mark() const { return _cm; }
1634   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1635 
1636   // The dirty cards region list is used to record a subset of regions
1637   // whose cards need clearing. The list if populated during the
1638   // remembered set scanning and drained during the card table
1639   // cleanup. Although the methods are reentrant, population/draining
1640   // phases must not overlap. For synchronization purposes the last
1641   // element on the list points to itself.
1642   HeapRegion* _dirty_cards_region_list;
1643   void push_dirty_cards_region(HeapRegion* hr);
1644   HeapRegion* pop_dirty_cards_region();
1645 
1646 public:
1647   void stop_conc_gc_threads();
1648 
1649   double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
1650   void check_if_region_is_too_expensive(double predicted_time_ms);
1651   size_t pending_card_num();
1652   size_t max_pending_card_num();
1653   size_t cards_scanned();
1654 
1655 protected:
1656   size_t _max_heap_capacity;
1657 };
1658 
1659 #define use_local_bitmaps         1
1660 #define verify_local_bitmaps      0
1661 #define oop_buffer_length       256
1662 
1663 #ifndef PRODUCT
1664 class GCLabBitMap;
1665 class GCLabBitMapClosure: public BitMapClosure {
1666 private:
1667   ConcurrentMark* _cm;
1668   GCLabBitMap*    _bitmap;
1669 
1670 public:
1671   GCLabBitMapClosure(ConcurrentMark* cm,
1672                      GCLabBitMap* bitmap) {
1673     _cm     = cm;
1674     _bitmap = bitmap;
1675   }
1676 
1677   virtual bool do_bit(size_t offset);
1678 };
1679 #endif // !PRODUCT
1680 
1681 class GCLabBitMap: public BitMap {
1682 private:
1683   ConcurrentMark* _cm;
1684 
1685   int       _shifter;
1686   size_t    _bitmap_word_covers_words;
1687 
1688   // beginning of the heap
1689   HeapWord* _heap_start;
1690 
1691   // this is the actual start of the GCLab
1692   HeapWord* _real_start_word;
1693 
1694   // this is the actual end of the GCLab
1695   HeapWord* _real_end_word;
1696 
1697   // this is the first word, possibly located before the actual start
1698   // of the GCLab, that corresponds to the first bit of the bitmap
1699   HeapWord* _start_word;
1700 
1701   // size of a GCLab in words
1702   size_t _gclab_word_size;
1703 
1704   static int shifter() {
1705     return MinObjAlignment - 1;
1706   }
1707 
1708   // how many heap words does a single bitmap word corresponds to?
1709   static size_t bitmap_word_covers_words() {
1710     return BitsPerWord << shifter();
1711   }
1712 
1713   size_t gclab_word_size() const {
1714     return _gclab_word_size;
1715   }
1716 
1717   // Calculates actual GCLab size in words
1718   size_t gclab_real_word_size() const {
1719     return bitmap_size_in_bits(pointer_delta(_real_end_word, _start_word))
1720            / BitsPerWord;
1721   }
1722 
1723   static size_t bitmap_size_in_bits(size_t gclab_word_size) {
1724     size_t bits_in_bitmap = gclab_word_size >> shifter();
1725     // We are going to ensure that the beginning of a word in this
1726     // bitmap also corresponds to the beginning of a word in the
1727     // global marking bitmap. To handle the case where a GCLab
1728     // starts from the middle of the bitmap, we need to add enough
1729     // space (i.e. up to a bitmap word) to ensure that we have
1730     // enough bits in the bitmap.
1731     return bits_in_bitmap + BitsPerWord - 1;
1732   }
1733 public:
1734   GCLabBitMap(HeapWord* heap_start, size_t gclab_word_size)
1735     : BitMap(bitmap_size_in_bits(gclab_word_size)),
1736       _cm(G1CollectedHeap::heap()->concurrent_mark()),
1737       _shifter(shifter()),
1738       _bitmap_word_covers_words(bitmap_word_covers_words()),
1739       _heap_start(heap_start),
1740       _gclab_word_size(gclab_word_size),
1741       _real_start_word(NULL),
1742       _real_end_word(NULL),
1743       _start_word(NULL)
1744   {
1745     guarantee( size_in_words() >= bitmap_size_in_words(),
1746                "just making sure");
1747   }
1748 
1749   inline unsigned heapWordToOffset(HeapWord* addr) {
1750     unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
1751     assert(offset < size(), "offset should be within bounds");
1752     return offset;
1753   }
1754 
1755   inline HeapWord* offsetToHeapWord(size_t offset) {
1756     HeapWord* addr =  _start_word + (offset << _shifter);
1757     assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
1758     return addr;
1759   }
1760 
1761   bool fields_well_formed() {
1762     bool ret1 = (_real_start_word == NULL) &&
1763                 (_real_end_word == NULL) &&
1764                 (_start_word == NULL);
1765     if (ret1)
1766       return true;
1767 
1768     bool ret2 = _real_start_word >= _start_word &&
1769       _start_word < _real_end_word &&
1770       (_real_start_word + _gclab_word_size) == _real_end_word &&
1771       (_start_word + _gclab_word_size + _bitmap_word_covers_words)
1772                                                               > _real_end_word;
1773     return ret2;
1774   }
1775 
1776   inline bool mark(HeapWord* addr) {
1777     guarantee(use_local_bitmaps, "invariant");
1778     assert(fields_well_formed(), "invariant");
1779 
1780     if (addr >= _real_start_word && addr < _real_end_word) {
1781       assert(!isMarked(addr), "should not have already been marked");
1782 
1783       // first mark it on the bitmap
1784       at_put(heapWordToOffset(addr), true);
1785 
1786       return true;
1787     } else {
1788       return false;
1789     }
1790   }
1791 
1792   inline bool isMarked(HeapWord* addr) {
1793     guarantee(use_local_bitmaps, "invariant");
1794     assert(fields_well_formed(), "invariant");
1795 
1796     return at(heapWordToOffset(addr));
1797   }
1798 
1799   void set_buffer(HeapWord* start) {
1800     guarantee(use_local_bitmaps, "invariant");
1801     clear();
1802 
1803     assert(start != NULL, "invariant");
1804     _real_start_word = start;
1805     _real_end_word   = start + _gclab_word_size;
1806 
1807     size_t diff =
1808       pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
1809     _start_word = start - diff;
1810 
1811     assert(fields_well_formed(), "invariant");
1812   }
1813 
1814 #ifndef PRODUCT
1815   void verify() {
1816     // verify that the marks have been propagated
1817     GCLabBitMapClosure cl(_cm, this);
1818     iterate(&cl);
1819   }
1820 #endif // PRODUCT
1821 
1822   void retire() {
1823     guarantee(use_local_bitmaps, "invariant");
1824     assert(fields_well_formed(), "invariant");
1825 
1826     if (_start_word != NULL) {
1827       CMBitMap*       mark_bitmap = _cm->nextMarkBitMap();
1828 
1829       // this means that the bitmap was set up for the GCLab
1830       assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
1831 
1832       mark_bitmap->mostly_disjoint_range_union(this,
1833                                 0, // always start from the start of the bitmap
1834                                 _start_word,
1835                                 gclab_real_word_size());
1836       _cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
1837 
1838 #ifndef PRODUCT
1839       if (use_local_bitmaps && verify_local_bitmaps)
1840         verify();
1841 #endif // PRODUCT
1842     } else {
1843       assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
1844     }
1845   }
1846 
1847   size_t bitmap_size_in_words() const {
1848     return (bitmap_size_in_bits(gclab_word_size()) + BitsPerWord - 1) / BitsPerWord;
1849   }
1850 
1851 };
1852 
1853 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1854 private:
1855   bool        _retired;
1856   bool        _should_mark_objects;
1857   GCLabBitMap _bitmap;
1858 
1859 public:
1860   G1ParGCAllocBuffer(size_t gclab_word_size);
1861 
1862   inline bool mark(HeapWord* addr) {
1863     guarantee(use_local_bitmaps, "invariant");
1864     assert(_should_mark_objects, "invariant");
1865     return _bitmap.mark(addr);
1866   }
1867 
1868   inline void set_buf(HeapWord* buf) {
1869     if (use_local_bitmaps && _should_mark_objects) {
1870       _bitmap.set_buffer(buf);
1871     }
1872     ParGCAllocBuffer::set_buf(buf);
1873     _retired = false;
1874   }
1875 
1876   inline void retire(bool end_of_gc, bool retain) {
1877     if (_retired)
1878       return;
1879     if (use_local_bitmaps && _should_mark_objects) {
1880       _bitmap.retire();
1881     }
1882     ParGCAllocBuffer::retire(end_of_gc, retain);
1883     _retired = true;
1884   }
1885 };
1886 
1887 class G1ParScanThreadState : public StackObj {
1888 protected:
1889   G1CollectedHeap* _g1h;
1890   RefToScanQueue*  _refs;
1891   DirtyCardQueue   _dcq;
1892   CardTableModRefBS* _ct_bs;
1893   G1RemSet* _g1_rem;
1894 
1895   G1ParGCAllocBuffer  _surviving_alloc_buffer;
1896   G1ParGCAllocBuffer  _tenured_alloc_buffer;
1897   G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1898   ageTable            _age_table;
1899 
1900   size_t           _alloc_buffer_waste;
1901   size_t           _undo_waste;
1902 
1903   OopsInHeapRegionClosure*      _evac_failure_cl;
1904   G1ParScanHeapEvacClosure*     _evac_cl;
1905   G1ParScanPartialArrayClosure* _partial_scan_cl;
1906 
1907   int _hash_seed;
1908   int _queue_num;
1909 
1910   size_t _term_attempts;
1911 
1912   double _start;
1913   double _start_strong_roots;
1914   double _strong_roots_time;
1915   double _start_term;
1916   double _term_time;
1917 
1918   // Map from young-age-index (0 == not young, 1 is youngest) to
1919   // surviving words. base is what we get back from the malloc call
1920   size_t* _surviving_young_words_base;
1921   // this points into the array, as we use the first few entries for padding
1922   size_t* _surviving_young_words;
1923 
1924 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1925 
1926   void   add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1927 
1928   void   add_to_undo_waste(size_t waste)         { _undo_waste += waste; }
1929 
1930   DirtyCardQueue& dirty_card_queue()             { return _dcq;  }
1931   CardTableModRefBS* ctbs()                      { return _ct_bs; }
1932 
1933   template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1934     if (!from->is_survivor()) {
1935       _g1_rem->par_write_ref(from, p, tid);
1936     }
1937   }
1938 
1939   template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1940     // If the new value of the field points to the same region or
1941     // is the to-space, we don't need to include it in the Rset updates.
1942     if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1943       size_t card_index = ctbs()->index_for(p);
1944       // If the card hasn't been added to the buffer, do it.
1945       if (ctbs()->mark_card_deferred(card_index)) {
1946         dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1947       }
1948     }
1949   }
1950 
1951 public:
1952   G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
1953 
1954   ~G1ParScanThreadState() {
1955     FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
1956   }
1957 
1958   RefToScanQueue*   refs()            { return _refs;             }
1959   ageTable*         age_table()       { return &_age_table;       }
1960 
1961   G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1962     return _alloc_buffers[purpose];
1963   }
1964 
1965   size_t alloc_buffer_waste() const              { return _alloc_buffer_waste; }
1966   size_t undo_waste() const                      { return _undo_waste; }
1967 
1968 #ifdef ASSERT
1969   bool verify_ref(narrowOop* ref) const;
1970   bool verify_ref(oop* ref) const;
1971   bool verify_task(StarTask ref) const;
1972 #endif // ASSERT
1973 
1974   template <class T> void push_on_queue(T* ref) {
1975     assert(verify_ref(ref), "sanity");
1976     refs()->push(ref);
1977   }
1978 
1979   template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1980     if (G1DeferredRSUpdate) {
1981       deferred_rs_update(from, p, tid);
1982     } else {
1983       immediate_rs_update(from, p, tid);
1984     }
1985   }
1986 
1987   HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1988 
1989     HeapWord* obj = NULL;
1990     size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1991     if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1992       G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1993       assert(gclab_word_size == alloc_buf->word_sz(),
1994              "dynamic resizing is not supported");
1995       add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1996       alloc_buf->retire(false, false);
1997 
1998       HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1999       if (buf == NULL) return NULL; // Let caller handle allocation failure.
2000       // Otherwise.
2001       alloc_buf->set_buf(buf);
2002 
2003       obj = alloc_buf->allocate(word_sz);
2004       assert(obj != NULL, "buffer was definitely big enough...");
2005     } else {
2006       obj = _g1h->par_allocate_during_gc(purpose, word_sz);
2007     }
2008     return obj;
2009   }
2010 
2011   HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
2012     HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
2013     if (obj != NULL) return obj;
2014     return allocate_slow(purpose, word_sz);
2015   }
2016 
2017   void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
2018     if (alloc_buffer(purpose)->contains(obj)) {
2019       assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
2020              "should contain whole object");
2021       alloc_buffer(purpose)->undo_allocation(obj, word_sz);
2022     } else {
2023       CollectedHeap::fill_with_object(obj, word_sz);
2024       add_to_undo_waste(word_sz);
2025     }
2026   }
2027 
2028   void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
2029     _evac_failure_cl = evac_failure_cl;
2030   }
2031   OopsInHeapRegionClosure* evac_failure_closure() {
2032     return _evac_failure_cl;
2033   }
2034 
2035   void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
2036     _evac_cl = evac_cl;
2037   }
2038 
2039   void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
2040     _partial_scan_cl = partial_scan_cl;
2041   }
2042 
2043   int* hash_seed() { return &_hash_seed; }
2044   int  queue_num() { return _queue_num; }
2045 
2046   size_t term_attempts() const  { return _term_attempts; }
2047   void note_term_attempt() { _term_attempts++; }
2048 
2049   void start_strong_roots() {
2050     _start_strong_roots = os::elapsedTime();
2051   }
2052   void end_strong_roots() {
2053     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
2054   }
2055   double strong_roots_time() const { return _strong_roots_time; }
2056 
2057   void start_term_time() {
2058     note_term_attempt();
2059     _start_term = os::elapsedTime();
2060   }
2061   void end_term_time() {
2062     _term_time += (os::elapsedTime() - _start_term);
2063   }
2064   double term_time() const { return _term_time; }
2065 
2066   double elapsed_time() const {
2067     return os::elapsedTime() - _start;
2068   }
2069 
2070   static void
2071     print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
2072   void
2073     print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
2074 
2075   size_t* surviving_young_words() {
2076     // We add on to hide entry 0 which accumulates surviving words for
2077     // age -1 regions (i.e. non-young ones)
2078     return _surviving_young_words;
2079   }
2080 
2081   void retire_alloc_buffers() {
2082     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
2083       size_t waste = _alloc_buffers[ap]->words_remaining();
2084       add_to_alloc_buffer_waste(waste);
2085       _alloc_buffers[ap]->retire(true, false);
2086     }
2087   }
2088 
2089   template <class T> void deal_with_reference(T* ref_to_scan) {
2090     if (has_partial_array_mask(ref_to_scan)) {
2091       _partial_scan_cl->do_oop_nv(ref_to_scan);
2092     } else {
2093       // Note: we can use "raw" versions of "region_containing" because
2094       // "obj_to_scan" is definitely in the heap, and is not in a
2095       // humongous region.
2096       HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
2097       _evac_cl->set_region(r);
2098       _evac_cl->do_oop_nv(ref_to_scan);
2099     }
2100   }
2101 
2102   void deal_with_reference(StarTask ref) {
2103     assert(verify_task(ref), "sanity");
2104     if (ref.is_narrow()) {
2105       deal_with_reference((narrowOop*)ref);
2106     } else {
2107       deal_with_reference((oop*)ref);
2108     }
2109   }
2110 
2111 public:
2112   void trim_queue();
2113 };
2114 
2115 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP