1   /*
   2  * Copyright (c) 2001, 2015, 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
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  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
  21  * questions.
  22  *
  23  */
  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/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1Allocator.hpp"
  30 #include "gc_implementation/g1/concurrentMark.hpp"
  31 #include "gc_implementation/g1/evacuationInfo.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.hpp"
  33 #include "gc_implementation/g1/g1BiasedArray.hpp"
  34 #include "gc_implementation/g1/g1HRPrinter.hpp"
  35 #include "gc_implementation/g1/g1InCSetState.hpp"
  36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc_implementation/g1/g1YCTypes.hpp"
  39 #include "gc_implementation/g1/heapRegionManager.hpp"
  40 #include "gc_implementation/g1/heapRegionSet.hpp"
  41 #include "gc_implementation/shared/gcHeapSummary.hpp"
  42 #include "gc_implementation/shared/hSpaceCounters.hpp"
  43 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  44 #include "memory/barrierSet.hpp"
  45 #include "memory/memRegion.hpp"
  46 #include "memory/sharedHeap.hpp"
  47 #include "utilities/macros.hpp"
  48 #include "utilities/stack.hpp"
  49 
  50 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  51 // It uses the "Garbage First" heap organization and algorithm, which
  52 // may combine concurrent marking with parallel, incremental compaction of
  53 // heap subsets that will yield large amounts of garbage.
  54 
  55 // Forward declarations
  56 class HeapRegion;
  57 class HRRSCleanupTask;
  58 class GenerationSpec;
  59 class OopsInHeapRegionClosure;
  60 class G1KlassScanClosure;
  61 class G1ScanHeapEvacClosure;
  62 class ObjectClosure;
  63 class SpaceClosure;
  64 class CompactibleSpaceClosure;
  65 class Space;
  66 class G1CollectorPolicy;
  67 class GenRemSet;
  68 class G1RemSet;
  69 class HeapRegionRemSetIterator;
  70 class ConcurrentMark;
  71 class ConcurrentMarkThread;
  72 class ConcurrentG1Refine;
  73 class ConcurrentGCTimer;
  74 class GenerationCounters;
  75 class STWGCTimer;
  76 class G1NewTracer;
  77 class G1OldTracer;
  78 class EvacuationFailedInfo;
  79 class nmethod;
  80 
  81 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  82 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  83 
  84 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  85 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  86 
  87 class YoungList : public CHeapObj<mtGC> {
  88 private:
  89   G1CollectedHeap* _g1h;
  90 
  91   HeapRegion* _head;
  92 
  93   HeapRegion* _survivor_head;
  94   HeapRegion* _survivor_tail;
  95 
  96   HeapRegion* _curr;
  97 
  98   uint        _length;
  99   uint        _survivor_length;
 100 
 101   size_t      _last_sampled_rs_lengths;
 102   size_t      _sampled_rs_lengths;
 103 
 104   void         empty_list(HeapRegion* list);
 105 
 106 public:
 107   YoungList(G1CollectedHeap* g1h);
 108 
 109   void         push_region(HeapRegion* hr);
 110   void         add_survivor_region(HeapRegion* hr);
 111 
 112   void         empty_list();
 113   bool         is_empty() { return _length == 0; }
 114   uint         length() { return _length; }
 115   uint         survivor_length() { return _survivor_length; }
 116 
 117   // Currently we do not keep track of the used byte sum for the
 118   // young list and the survivors and it'd be quite a lot of work to
 119   // do so. When we'll eventually replace the young list with
 120   // instances of HeapRegionLinkedList we'll get that for free. So,
 121   // we'll report the more accurate information then.
 122   size_t       eden_used_bytes() {
 123     assert(length() >= survivor_length(), "invariant");
 124     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 125   }
 126   size_t       survivor_used_bytes() {
 127     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 128   }
 129 
 130   void rs_length_sampling_init();
 131   bool rs_length_sampling_more();
 132   void rs_length_sampling_next();
 133 
 134   void reset_sampled_info() {
 135     _last_sampled_rs_lengths =   0;
 136   }
 137   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 138 
 139   // for development purposes
 140   void reset_auxilary_lists();
 141   void clear() { _head = NULL; _length = 0; }
 142 
 143   void clear_survivors() {
 144     _survivor_head    = NULL;
 145     _survivor_tail    = NULL;
 146     _survivor_length  = 0;
 147   }
 148 
 149   HeapRegion* first_region() { return _head; }
 150   HeapRegion* first_survivor_region() { return _survivor_head; }
 151   HeapRegion* last_survivor_region() { return _survivor_tail; }
 152 
 153   // debugging
 154   bool          check_list_well_formed();
 155   bool          check_list_empty(bool check_sample = true);
 156   void          print();
 157 };
 158 
 159 // The G1 STW is alive closure.
 160 // An instance is embedded into the G1CH and used as the
 161 // (optional) _is_alive_non_header closure in the STW
 162 // reference processor. It is also extensively used during
 163 // reference processing during STW evacuation pauses.
 164 class G1STWIsAliveClosure: public BoolObjectClosure {
 165   G1CollectedHeap* _g1;
 166 public:
 167   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 168   bool do_object_b(oop p);
 169 };
 170 
 171 class RefineCardTableEntryClosure;
 172 
 173 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 174  private:
 175   void reset_from_card_cache(uint start_idx, size_t num_regions);
 176  public:
 177   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 178 };
 179 
 180 class G1CollectedHeap : public SharedHeap {
 181   friend class VM_CollectForMetadataAllocation;
 182   friend class VM_G1CollectForAllocation;
 183   friend class VM_G1CollectFull;
 184   friend class VM_G1IncCollectionPause;
 185   friend class VMStructs;
 186   friend class MutatorAllocRegion;
 187   friend class SurvivorGCAllocRegion;
 188   friend class OldGCAllocRegion;
 189   friend class G1Allocator;
 190   friend class G1DefaultAllocator;
 191   friend class G1ResManAllocator;
 192 
 193   // Closures used in implementation.
 194   template <G1Barrier barrier, G1Mark do_mark_object>
 195   friend class G1ParCopyClosure;
 196   friend class G1IsAliveClosure;
 197   friend class G1EvacuateFollowersClosure;
 198   friend class G1ParScanThreadState;
 199   friend class G1ParScanClosureSuper;
 200   friend class G1ParEvacuateFollowersClosure;
 201   friend class G1ParTask;
 202   friend class G1ParGCAllocator;
 203   friend class G1DefaultParGCAllocator;
 204   friend class G1FreeGarbageRegionClosure;
 205   friend class RefineCardTableEntryClosure;
 206   friend class G1PrepareCompactClosure;
 207   friend class RegionSorter;
 208   friend class RegionResetter;
 209   friend class CountRCClosure;
 210   friend class EvacPopObjClosure;
 211   friend class G1ParCleanupCTTask;
 212 
 213   friend class G1FreeHumongousRegionClosure;
 214   // Other related classes.
 215   friend class G1MarkSweep;
 216 
 217   // Testing classes.
 218   friend class G1CheckCSetFastTableClosure;
 219 
 220 private:
 221   // The one and only G1CollectedHeap, so static functions can find it.
 222   static G1CollectedHeap* _g1h;
 223 
 224   static size_t _humongous_object_threshold_in_words;
 225 
 226   // The secondary free list which contains regions that have been
 227   // freed up during the cleanup process. This will be appended to
 228   // the master free list when appropriate.
 229   FreeRegionList _secondary_free_list;
 230 
 231   // It keeps track of the old regions.
 232   HeapRegionSet _old_set;
 233 
 234   // It keeps track of the humongous regions.
 235   HeapRegionSet _humongous_set;
 236 
 237   void eagerly_reclaim_humongous_regions();
 238 
 239   // The number of regions we could create by expansion.
 240   uint _expansion_regions;
 241 
 242   // The block offset table for the G1 heap.
 243   G1BlockOffsetSharedArray* _bot_shared;
 244 
 245   // Tears down the region sets / lists so that they are empty and the
 246   // regions on the heap do not belong to a region set / list. The
 247   // only exception is the humongous set which we leave unaltered. If
 248   // free_list_only is true, it will only tear down the master free
 249   // list. It is called before a Full GC (free_list_only == false) or
 250   // before heap shrinking (free_list_only == true).
 251   void tear_down_region_sets(bool free_list_only);
 252 
 253   // Rebuilds the region sets / lists so that they are repopulated to
 254   // reflect the contents of the heap. The only exception is the
 255   // humongous set which was not torn down in the first place. If
 256   // free_list_only is true, it will only rebuild the master free
 257   // list. It is called after a Full GC (free_list_only == false) or
 258   // after heap shrinking (free_list_only == true).
 259   void rebuild_region_sets(bool free_list_only);
 260 
 261   // Callback for region mapping changed events.
 262   G1RegionMappingChangedListener _listener;
 263 
 264   // The sequence of all heap regions in the heap.
 265   HeapRegionManager _hrm;
 266 
 267   // Class that handles the different kinds of allocations.
 268   G1Allocator* _allocator;
 269 
 270   // Statistics for each allocation context
 271   AllocationContextStats _allocation_context_stats;
 272 
 273   // PLAB sizing policy for survivors.
 274   PLABStats _survivor_plab_stats;
 275 
 276   // PLAB sizing policy for tenured objects.
 277   PLABStats _old_plab_stats;
 278 
 279   // It specifies whether we should attempt to expand the heap after a
 280   // region allocation failure. If heap expansion fails we set this to
 281   // false so that we don't re-attempt the heap expansion (it's likely
 282   // that subsequent expansion attempts will also fail if one fails).
 283   // Currently, it is only consulted during GC and it's reset at the
 284   // start of each GC.
 285   bool _expand_heap_after_alloc_failure;
 286 
 287   // It resets the mutator alloc region before new allocations can take place.
 288   void init_mutator_alloc_region();
 289 
 290   // It releases the mutator alloc region.
 291   void release_mutator_alloc_region();
 292 
 293   // It initializes the GC alloc regions at the start of a GC.
 294   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 295 
 296   // It releases the GC alloc regions at the end of a GC.
 297   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 298 
 299   // It does any cleanup that needs to be done on the GC alloc regions
 300   // before a Full GC.
 301   void abandon_gc_alloc_regions();
 302 
 303   // Helper for monitoring and management support.
 304   G1MonitoringSupport* _g1mm;
 305 
 306   // Records whether the region at the given index is (still) a
 307   // candidate for eager reclaim.  Only valid for humongous start
 308   // regions; other regions have unspecified values.  Humongous start
 309   // regions are initialized at start of collection pause, with
 310   // candidates removed from the set as they are found reachable from
 311   // roots or the young generation.
 312   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 313    protected:
 314     bool default_value() const { return false; }
 315    public:
 316     void clear() { G1BiasedMappedArray<bool>::clear(); }
 317     void set_candidate(uint region, bool value) {
 318       set_by_index(region, value);
 319     }
 320     bool is_candidate(uint region) {
 321       return get_by_index(region);
 322     }
 323   };
 324 
 325   HumongousReclaimCandidates _humongous_reclaim_candidates;
 326   // Stores whether during humongous object registration we found candidate regions.
 327   // If not, we can skip a few steps.
 328   bool _has_humongous_reclaim_candidates;
 329 
 330   volatile unsigned _gc_time_stamp;
 331 
 332   size_t* _surviving_young_words;
 333 
 334   G1HRPrinter _hr_printer;
 335 
 336   void setup_surviving_young_words();
 337   void update_surviving_young_words(size_t* surv_young_words);
 338   void cleanup_surviving_young_words();
 339 
 340   // It decides whether an explicit GC should start a concurrent cycle
 341   // instead of doing a STW GC. Currently, a concurrent cycle is
 342   // explicitly started if:
 343   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 344   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 345   // (c) cause == _g1_humongous_allocation
 346   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 347 
 348   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 349   // concurrent cycles) we have started.
 350   volatile uint _old_marking_cycles_started;
 351 
 352   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 353   // concurrent cycles) we have completed.
 354   volatile uint _old_marking_cycles_completed;
 355 
 356   bool _concurrent_cycle_started;
 357   bool _heap_summary_sent;
 358 
 359   // This is a non-product method that is helpful for testing. It is
 360   // called at the end of a GC and artificially expands the heap by
 361   // allocating a number of dead regions. This way we can induce very
 362   // frequent marking cycles and stress the cleanup / concurrent
 363   // cleanup code more (as all the regions that will be allocated by
 364   // this method will be found dead by the marking cycle).
 365   void allocate_dummy_regions() PRODUCT_RETURN;
 366 
 367   // Clear RSets after a compaction. It also resets the GC time stamps.
 368   void clear_rsets_post_compaction();
 369 
 370   // If the HR printer is active, dump the state of the regions in the
 371   // heap after a compaction.
 372   void print_hrm_post_compaction();
 373 
 374   // Create a memory mapper for auxiliary data structures of the given size and
 375   // translation factor.
 376   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 377                                                          size_t size,
 378                                                          size_t translation_factor);
 379 
 380   void trace_heap(GCWhen::Type when, GCTracer* tracer);
 381 
 382   double verify(bool guard, const char* msg);
 383   void verify_before_gc();
 384   void verify_after_gc();
 385 
 386   void log_gc_header();
 387   void log_gc_footer(double pause_time_sec);
 388 
 389   // These are macros so that, if the assert fires, we get the correct
 390   // line number, file, etc.
 391 
 392 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 393   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 394           (_extra_message_),                                                  \
 395           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 396           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 397           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 398 
 399 #define assert_heap_locked()                                                  \
 400   do {                                                                        \
 401     assert(Heap_lock->owned_by_self(),                                        \
 402            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 403   } while (0)
 404 
 405 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 406   do {                                                                        \
 407     assert(Heap_lock->owned_by_self() ||                                      \
 408            (SafepointSynchronize::is_at_safepoint() &&                        \
 409              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 410            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 411                                         "should be at a safepoint"));         \
 412   } while (0)
 413 
 414 #define assert_heap_locked_and_not_at_safepoint()                             \
 415   do {                                                                        \
 416     assert(Heap_lock->owned_by_self() &&                                      \
 417                                     !SafepointSynchronize::is_at_safepoint(), \
 418           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 419                                        "should not be at a safepoint"));      \
 420   } while (0)
 421 
 422 #define assert_heap_not_locked()                                              \
 423   do {                                                                        \
 424     assert(!Heap_lock->owned_by_self(),                                       \
 425         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 426   } while (0)
 427 
 428 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 429   do {                                                                        \
 430     assert(!Heap_lock->owned_by_self() &&                                     \
 431                                     !SafepointSynchronize::is_at_safepoint(), \
 432       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 433                                    "should not be at a safepoint"));          \
 434   } while (0)
 435 
 436 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 437   do {                                                                        \
 438     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 439               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 440            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 441   } while (0)
 442 
 443 #define assert_not_at_safepoint()                                             \
 444   do {                                                                        \
 445     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 446            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 447   } while (0)
 448 
 449 protected:
 450 
 451   // The young region list.
 452   YoungList*  _young_list;
 453 
 454   // The current policy object for the collector.
 455   G1CollectorPolicy* _g1_policy;
 456 
 457   // This is the second level of trying to allocate a new region. If
 458   // new_region() didn't find a region on the free_list, this call will
 459   // check whether there's anything available on the
 460   // secondary_free_list and/or wait for more regions to appear on
 461   // that list, if _free_regions_coming is set.
 462   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 463 
 464   // Try to allocate a single non-humongous HeapRegion sufficient for
 465   // an allocation of the given word_size. If do_expand is true,
 466   // attempt to expand the heap if necessary to satisfy the allocation
 467   // request. If the region is to be used as an old region or for a
 468   // humongous object, set is_old to true. If not, to false.
 469   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 470 
 471   // Initialize a contiguous set of free regions of length num_regions
 472   // and starting at index first so that they appear as a single
 473   // humongous region.
 474   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 475                                                       uint num_regions,
 476                                                       size_t word_size,
 477                                                       AllocationContext_t context);
 478 
 479   // Attempt to allocate a humongous object of the given size. Return
 480   // NULL if unsuccessful.
 481   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 482 
 483   // The following two methods, allocate_new_tlab() and
 484   // mem_allocate(), are the two main entry points from the runtime
 485   // into the G1's allocation routines. They have the following
 486   // assumptions:
 487   //
 488   // * They should both be called outside safepoints.
 489   //
 490   // * They should both be called without holding the Heap_lock.
 491   //
 492   // * All allocation requests for new TLABs should go to
 493   //   allocate_new_tlab().
 494   //
 495   // * All non-TLAB allocation requests should go to mem_allocate().
 496   //
 497   // * If either call cannot satisfy the allocation request using the
 498   //   current allocating region, they will try to get a new one. If
 499   //   this fails, they will attempt to do an evacuation pause and
 500   //   retry the allocation.
 501   //
 502   // * If all allocation attempts fail, even after trying to schedule
 503   //   an evacuation pause, allocate_new_tlab() will return NULL,
 504   //   whereas mem_allocate() will attempt a heap expansion and/or
 505   //   schedule a Full GC.
 506   //
 507   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 508   //   should never be called with word_size being humongous. All
 509   //   humongous allocation requests should go to mem_allocate() which
 510   //   will satisfy them with a special path.
 511 
 512   virtual HeapWord* allocate_new_tlab(size_t word_size);
 513 
 514   virtual HeapWord* mem_allocate(size_t word_size,
 515                                  bool*  gc_overhead_limit_was_exceeded);
 516 
 517   // The following three methods take a gc_count_before_ret
 518   // parameter which is used to return the GC count if the method
 519   // returns NULL. Given that we are required to read the GC count
 520   // while holding the Heap_lock, and these paths will take the
 521   // Heap_lock at some point, it's easier to get them to read the GC
 522   // count while holding the Heap_lock before they return NULL instead
 523   // of the caller (namely: mem_allocate()) having to also take the
 524   // Heap_lock just to read the GC count.
 525 
 526   // First-level mutator allocation attempt: try to allocate out of
 527   // the mutator alloc region without taking the Heap_lock. This
 528   // should only be used for non-humongous allocations.
 529   inline HeapWord* attempt_allocation(size_t word_size,
 530                                       uint* gc_count_before_ret,
 531                                       uint* gclocker_retry_count_ret);
 532 
 533   // Second-level mutator allocation attempt: take the Heap_lock and
 534   // retry the allocation attempt, potentially scheduling a GC
 535   // pause. This should only be used for non-humongous allocations.
 536   HeapWord* attempt_allocation_slow(size_t word_size,
 537                                     AllocationContext_t context,
 538                                     uint* gc_count_before_ret,
 539                                     uint* gclocker_retry_count_ret);
 540 
 541   // Takes the Heap_lock and attempts a humongous allocation. It can
 542   // potentially schedule a GC pause.
 543   HeapWord* attempt_allocation_humongous(size_t word_size,
 544                                          uint* gc_count_before_ret,
 545                                          uint* gclocker_retry_count_ret);
 546 
 547   // Allocation attempt that should be called during safepoints (e.g.,
 548   // at the end of a successful GC). expect_null_mutator_alloc_region
 549   // specifies whether the mutator alloc region is expected to be NULL
 550   // or not.
 551   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 552                                             AllocationContext_t context,
 553                                             bool expect_null_mutator_alloc_region);
 554 
 555   // It dirties the cards that cover the block so that so that the post
 556   // write barrier never queues anything when updating objects on this
 557   // block. It is assumed (and in fact we assert) that the block
 558   // belongs to a young region.
 559   inline void dirty_young_block(HeapWord* start, size_t word_size);
 560 
 561   // Allocate blocks during garbage collection. Will ensure an
 562   // allocation region, either by picking one or expanding the
 563   // heap, and then allocate a block of the given size. The block
 564   // may not be a humongous - it must fit into a single heap region.
 565   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 566                                           size_t word_size,
 567                                           AllocationContext_t context);
 568   // Ensure that no further allocations can happen in "r", bearing in mind
 569   // that parallel threads might be attempting allocations.
 570   void par_allocate_remaining_space(HeapRegion* r);
 571 
 572   // Allocation attempt during GC for a survivor object / PLAB.
 573   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 574                                                AllocationContext_t context);
 575 
 576   // Allocation attempt during GC for an old object / PLAB.
 577   inline HeapWord* old_attempt_allocation(size_t word_size,
 578                                           AllocationContext_t context);
 579 
 580   // These methods are the "callbacks" from the G1AllocRegion class.
 581 
 582   // For mutator alloc regions.
 583   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 584   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 585                                    size_t allocated_bytes);
 586 
 587   // For GC alloc regions.
 588   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 589                                   InCSetState dest);
 590   void retire_gc_alloc_region(HeapRegion* alloc_region,
 591                               size_t allocated_bytes, InCSetState dest);
 592 
 593   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 594   //   inspection request and should collect the entire heap
 595   // - if clear_all_soft_refs is true, all soft references should be
 596   //   cleared during the GC
 597   // - if explicit_gc is false, word_size describes the allocation that
 598   //   the GC should attempt (at least) to satisfy
 599   // - it returns false if it is unable to do the collection due to the
 600   //   GC locker being active, true otherwise
 601   bool do_collection(bool explicit_gc,
 602                      bool clear_all_soft_refs,
 603                      size_t word_size);
 604 
 605   // Callback from VM_G1CollectFull operation.
 606   // Perform a full collection.
 607   virtual void do_full_collection(bool clear_all_soft_refs);
 608 
 609   // Resize the heap if necessary after a full collection.  If this is
 610   // after a collect-for allocation, "word_size" is the allocation size,
 611   // and will be considered part of the used portion of the heap.
 612   void resize_if_necessary_after_full_collection(size_t word_size);
 613 
 614   // Callback from VM_G1CollectForAllocation operation.
 615   // This function does everything necessary/possible to satisfy a
 616   // failed allocation request (including collection, expansion, etc.)
 617   HeapWord* satisfy_failed_allocation(size_t word_size,
 618                                       AllocationContext_t context,
 619                                       bool* succeeded);
 620 
 621   // Attempting to expand the heap sufficiently
 622   // to support an allocation of the given "word_size".  If
 623   // successful, perform the allocation and return the address of the
 624   // allocated block, or else "NULL".
 625   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 626 
 627   // Process any reference objects discovered during
 628   // an incremental evacuation pause.
 629   void process_discovered_references(uint no_of_gc_workers);
 630 
 631   // Enqueue any remaining discovered references
 632   // after processing.
 633   void enqueue_discovered_references(uint no_of_gc_workers);
 634 
 635 public:
 636 
 637   G1Allocator* allocator() {
 638     return _allocator;
 639   }
 640 
 641   G1MonitoringSupport* g1mm() {
 642     assert(_g1mm != NULL, "should have been initialized");
 643     return _g1mm;
 644   }
 645 
 646   // Expand the garbage-first heap by at least the given size (in bytes!).
 647   // Returns true if the heap was expanded by the requested amount;
 648   // false otherwise.
 649   // (Rounds up to a HeapRegion boundary.)
 650   bool expand(size_t expand_bytes);
 651 
 652   // Returns the PLAB statistics for a given destination.
 653   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 654 
 655   // Determines PLAB size for a given destination.
 656   inline size_t desired_plab_sz(InCSetState dest);
 657 
 658   inline AllocationContextStats& allocation_context_stats();
 659 
 660   // Do anything common to GC's.
 661   virtual void gc_prologue(bool full);
 662   virtual void gc_epilogue(bool full);
 663 
 664   // Modify the reclaim candidate set and test for presence.
 665   // These are only valid for starts_humongous regions.
 666   inline void set_humongous_reclaim_candidate(uint region, bool value);
 667   inline bool is_humongous_reclaim_candidate(uint region);
 668 
 669   // Remove from the reclaim candidate set.  Also remove from the
 670   // collection set so that later encounters avoid the slow path.
 671   inline void set_humongous_is_live(oop obj);
 672 
 673   // Register the given region to be part of the collection set.
 674   inline void register_humongous_region_with_in_cset_fast_test(uint index);
 675   // Register regions with humongous objects (actually on the start region) in
 676   // the in_cset_fast_test table.
 677   void register_humongous_regions_with_in_cset_fast_test();
 678   // We register a region with the fast "in collection set" test. We
 679   // simply set to true the array slot corresponding to this region.
 680   void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
 681     _in_cset_fast_test.set_in_young(r->hrm_index());
 682   }
 683   void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
 684     _in_cset_fast_test.set_in_old(r->hrm_index());
 685   }
 686 
 687   // This is a fast test on whether a reference points into the
 688   // collection set or not. Assume that the reference
 689   // points into the heap.
 690   inline bool in_cset_fast_test(oop obj);
 691 
 692   void clear_cset_fast_test() {
 693     _in_cset_fast_test.clear();
 694   }
 695 
 696   // This is called at the start of either a concurrent cycle or a Full
 697   // GC to update the number of old marking cycles started.
 698   void increment_old_marking_cycles_started();
 699 
 700   // This is called at the end of either a concurrent cycle or a Full
 701   // GC to update the number of old marking cycles completed. Those two
 702   // can happen in a nested fashion, i.e., we start a concurrent
 703   // cycle, a Full GC happens half-way through it which ends first,
 704   // and then the cycle notices that a Full GC happened and ends
 705   // too. The concurrent parameter is a boolean to help us do a bit
 706   // tighter consistency checking in the method. If concurrent is
 707   // false, the caller is the inner caller in the nesting (i.e., the
 708   // Full GC). If concurrent is true, the caller is the outer caller
 709   // in this nesting (i.e., the concurrent cycle). Further nesting is
 710   // not currently supported. The end of this call also notifies
 711   // the FullGCCount_lock in case a Java thread is waiting for a full
 712   // GC to happen (e.g., it called System.gc() with
 713   // +ExplicitGCInvokesConcurrent).
 714   void increment_old_marking_cycles_completed(bool concurrent);
 715 
 716   uint old_marking_cycles_completed() {
 717     return _old_marking_cycles_completed;
 718   }
 719 
 720   void register_concurrent_cycle_start(const Ticks& start_time);
 721   void register_concurrent_cycle_end();
 722   void trace_heap_after_concurrent_cycle();
 723 
 724   G1YCType yc_type();
 725 
 726   G1HRPrinter* hr_printer() { return &_hr_printer; }
 727 
 728   // Frees a non-humongous region by initializing its contents and
 729   // adding it to the free list that's passed as a parameter (this is
 730   // usually a local list which will be appended to the master free
 731   // list later). The used bytes of freed regions are accumulated in
 732   // pre_used. If par is true, the region's RSet will not be freed
 733   // up. The assumption is that this will be done later.
 734   // The locked parameter indicates if the caller has already taken
 735   // care of proper synchronization. This may allow some optimizations.
 736   void free_region(HeapRegion* hr,
 737                    FreeRegionList* free_list,
 738                    bool par,
 739                    bool locked = false);
 740 
 741   // Frees a humongous region by collapsing it into individual regions
 742   // and calling free_region() for each of them. The freed regions
 743   // will be added to the free list that's passed as a parameter (this
 744   // is usually a local list which will be appended to the master free
 745   // list later). The used bytes of freed regions are accumulated in
 746   // pre_used. If par is true, the region's RSet will not be freed
 747   // up. The assumption is that this will be done later.
 748   void free_humongous_region(HeapRegion* hr,
 749                              FreeRegionList* free_list,
 750                              bool par);
 751 protected:
 752 
 753   // Shrink the garbage-first heap by at most the given size (in bytes!).
 754   // (Rounds down to a HeapRegion boundary.)
 755   virtual void shrink(size_t expand_bytes);
 756   void shrink_helper(size_t expand_bytes);
 757 
 758   #if TASKQUEUE_STATS
 759   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 760   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 761   void reset_taskqueue_stats();
 762   #endif // TASKQUEUE_STATS
 763 
 764   // Schedule the VM operation that will do an evacuation pause to
 765   // satisfy an allocation request of word_size. *succeeded will
 766   // return whether the VM operation was successful (it did do an
 767   // evacuation pause) or not (another thread beat us to it or the GC
 768   // locker was active). Given that we should not be holding the
 769   // Heap_lock when we enter this method, we will pass the
 770   // gc_count_before (i.e., total_collections()) as a parameter since
 771   // it has to be read while holding the Heap_lock. Currently, both
 772   // methods that call do_collection_pause() release the Heap_lock
 773   // before the call, so it's easy to read gc_count_before just before.
 774   HeapWord* do_collection_pause(size_t         word_size,
 775                                 uint           gc_count_before,
 776                                 bool*          succeeded,
 777                                 GCCause::Cause gc_cause);
 778 
 779   // The guts of the incremental collection pause, executed by the vm
 780   // thread. It returns false if it is unable to do the collection due
 781   // to the GC locker being active, true otherwise
 782   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 783 
 784   // Actually do the work of evacuating the collection set.
 785   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 786 
 787   // The g1 remembered set of the heap.
 788   G1RemSet* _g1_rem_set;
 789 
 790   // A set of cards that cover the objects for which the Rsets should be updated
 791   // concurrently after the collection.
 792   DirtyCardQueueSet _dirty_card_queue_set;
 793 
 794   // The closure used to refine a single card.
 795   RefineCardTableEntryClosure* _refine_cte_cl;
 796 
 797   // A function to check the consistency of dirty card logs.
 798   void check_ct_logs_at_safepoint();
 799 
 800   // A DirtyCardQueueSet that is used to hold cards that contain
 801   // references into the current collection set. This is used to
 802   // update the remembered sets of the regions in the collection
 803   // set in the event of an evacuation failure.
 804   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 805 
 806   // After a collection pause, make the regions in the CS into free
 807   // regions.
 808   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 809 
 810   // Abandon the current collection set without recording policy
 811   // statistics or updating free lists.
 812   void abandon_collection_set(HeapRegion* cs_head);
 813 
 814   // The concurrent marker (and the thread it runs in.)
 815   ConcurrentMark* _cm;
 816   ConcurrentMarkThread* _cmThread;
 817   bool _mark_in_progress;
 818 
 819   // The concurrent refiner.
 820   ConcurrentG1Refine* _cg1r;
 821 
 822   // The parallel task queues
 823   RefToScanQueueSet *_task_queues;
 824 
 825   // True iff a evacuation has failed in the current collection.
 826   bool _evacuation_failed;
 827 
 828   EvacuationFailedInfo* _evacuation_failed_info_array;
 829 
 830   // Failed evacuations cause some logical from-space objects to have
 831   // forwarding pointers to themselves.  Reset them.
 832   void remove_self_forwarding_pointers();
 833 
 834   // Together, these store an object with a preserved mark, and its mark value.
 835   Stack<oop, mtGC>     _objs_with_preserved_marks;
 836   Stack<markOop, mtGC> _preserved_marks_of_objs;
 837 
 838   // Preserve the mark of "obj", if necessary, in preparation for its mark
 839   // word being overwritten with a self-forwarding-pointer.
 840   void preserve_mark_if_necessary(oop obj, markOop m);
 841 
 842   // The stack of evac-failure objects left to be scanned.
 843   GrowableArray<oop>*    _evac_failure_scan_stack;
 844   // The closure to apply to evac-failure objects.
 845 
 846   OopsInHeapRegionClosure* _evac_failure_closure;
 847   // Set the field above.
 848   void
 849   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 850     _evac_failure_closure = evac_failure_closure;
 851   }
 852 
 853   // Push "obj" on the scan stack.
 854   void push_on_evac_failure_scan_stack(oop obj);
 855   // Process scan stack entries until the stack is empty.
 856   void drain_evac_failure_scan_stack();
 857   // True iff an invocation of "drain_scan_stack" is in progress; to
 858   // prevent unnecessary recursion.
 859   bool _drain_in_progress;
 860 
 861   // Do any necessary initialization for evacuation-failure handling.
 862   // "cl" is the closure that will be used to process evac-failure
 863   // objects.
 864   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 865   // Do any necessary cleanup for evacuation-failure handling data
 866   // structures.
 867   void finalize_for_evac_failure();
 868 
 869   // An attempt to evacuate "obj" has failed; take necessary steps.
 870   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 871   void handle_evacuation_failure_common(oop obj, markOop m);
 872 
 873 #ifndef PRODUCT
 874   // Support for forcing evacuation failures. Analogous to
 875   // PromotionFailureALot for the other collectors.
 876 
 877   // Records whether G1EvacuationFailureALot should be in effect
 878   // for the current GC
 879   bool _evacuation_failure_alot_for_current_gc;
 880 
 881   // Used to record the GC number for interval checking when
 882   // determining whether G1EvaucationFailureALot is in effect
 883   // for the current GC.
 884   size_t _evacuation_failure_alot_gc_number;
 885 
 886   // Count of the number of evacuations between failures.
 887   volatile size_t _evacuation_failure_alot_count;
 888 
 889   // Set whether G1EvacuationFailureALot should be in effect
 890   // for the current GC (based upon the type of GC and which
 891   // command line flags are set);
 892   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 893                                                   bool during_initial_mark,
 894                                                   bool during_marking);
 895 
 896   inline void set_evacuation_failure_alot_for_current_gc();
 897 
 898   // Return true if it's time to cause an evacuation failure.
 899   inline bool evacuation_should_fail();
 900 
 901   // Reset the G1EvacuationFailureALot counters.  Should be called at
 902   // the end of an evacuation pause in which an evacuation failure occurred.
 903   inline void reset_evacuation_should_fail();
 904 #endif // !PRODUCT
 905 
 906   // ("Weak") Reference processing support.
 907   //
 908   // G1 has 2 instances of the reference processor class. One
 909   // (_ref_processor_cm) handles reference object discovery
 910   // and subsequent processing during concurrent marking cycles.
 911   //
 912   // The other (_ref_processor_stw) handles reference object
 913   // discovery and processing during full GCs and incremental
 914   // evacuation pauses.
 915   //
 916   // During an incremental pause, reference discovery will be
 917   // temporarily disabled for _ref_processor_cm and will be
 918   // enabled for _ref_processor_stw. At the end of the evacuation
 919   // pause references discovered by _ref_processor_stw will be
 920   // processed and discovery will be disabled. The previous
 921   // setting for reference object discovery for _ref_processor_cm
 922   // will be re-instated.
 923   //
 924   // At the start of marking:
 925   //  * Discovery by the CM ref processor is verified to be inactive
 926   //    and it's discovered lists are empty.
 927   //  * Discovery by the CM ref processor is then enabled.
 928   //
 929   // At the end of marking:
 930   //  * Any references on the CM ref processor's discovered
 931   //    lists are processed (possibly MT).
 932   //
 933   // At the start of full GC we:
 934   //  * Disable discovery by the CM ref processor and
 935   //    empty CM ref processor's discovered lists
 936   //    (without processing any entries).
 937   //  * Verify that the STW ref processor is inactive and it's
 938   //    discovered lists are empty.
 939   //  * Temporarily set STW ref processor discovery as single threaded.
 940   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 941   //    field.
 942   //  * Finally enable discovery by the STW ref processor.
 943   //
 944   // The STW ref processor is used to record any discovered
 945   // references during the full GC.
 946   //
 947   // At the end of a full GC we:
 948   //  * Enqueue any reference objects discovered by the STW ref processor
 949   //    that have non-live referents. This has the side-effect of
 950   //    making the STW ref processor inactive by disabling discovery.
 951   //  * Verify that the CM ref processor is still inactive
 952   //    and no references have been placed on it's discovered
 953   //    lists (also checked as a precondition during initial marking).
 954 
 955   // The (stw) reference processor...
 956   ReferenceProcessor* _ref_processor_stw;
 957 
 958   STWGCTimer* _gc_timer_stw;
 959   ConcurrentGCTimer* _gc_timer_cm;
 960 
 961   G1OldTracer* _gc_tracer_cm;
 962   G1NewTracer* _gc_tracer_stw;
 963 
 964   // During reference object discovery, the _is_alive_non_header
 965   // closure (if non-null) is applied to the referent object to
 966   // determine whether the referent is live. If so then the
 967   // reference object does not need to be 'discovered' and can
 968   // be treated as a regular oop. This has the benefit of reducing
 969   // the number of 'discovered' reference objects that need to
 970   // be processed.
 971   //
 972   // Instance of the is_alive closure for embedding into the
 973   // STW reference processor as the _is_alive_non_header field.
 974   // Supplying a value for the _is_alive_non_header field is
 975   // optional but doing so prevents unnecessary additions to
 976   // the discovered lists during reference discovery.
 977   G1STWIsAliveClosure _is_alive_closure_stw;
 978 
 979   // The (concurrent marking) reference processor...
 980   ReferenceProcessor* _ref_processor_cm;
 981 
 982   // Instance of the concurrent mark is_alive closure for embedding
 983   // into the Concurrent Marking reference processor as the
 984   // _is_alive_non_header field. Supplying a value for the
 985   // _is_alive_non_header field is optional but doing so prevents
 986   // unnecessary additions to the discovered lists during reference
 987   // discovery.
 988   G1CMIsAliveClosure _is_alive_closure_cm;
 989 
 990   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 991   HeapRegion** _worker_cset_start_region;
 992 
 993   // Time stamp to validate the regions recorded in the cache
 994   // used by G1CollectedHeap::start_cset_region_for_worker().
 995   // The heap region entry for a given worker is valid iff
 996   // the associated time stamp value matches the current value
 997   // of G1CollectedHeap::_gc_time_stamp.
 998   uint* _worker_cset_start_region_time_stamp;
 999 
1000   volatile bool _free_regions_coming;
1001 
1002 public:
1003 
1004   void set_refine_cte_cl_concurrency(bool concurrent);
1005 
1006   RefToScanQueue *task_queue(int i) const;
1007 
1008   // A set of cards where updates happened during the GC
1009   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1010 
1011   // A DirtyCardQueueSet that is used to hold cards that contain
1012   // references into the current collection set. This is used to
1013   // update the remembered sets of the regions in the collection
1014   // set in the event of an evacuation failure.
1015   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1016         { return _into_cset_dirty_card_queue_set; }
1017 
1018   // Create a G1CollectedHeap with the specified policy.
1019   // Must call the initialize method afterwards.
1020   // May not return if something goes wrong.
1021   G1CollectedHeap(G1CollectorPolicy* policy);
1022 
1023   // Initialize the G1CollectedHeap to have the initial and
1024   // maximum sizes and remembered and barrier sets
1025   // specified by the policy object.
1026   jint initialize();
1027 
1028   virtual void stop();
1029 
1030   // Return the (conservative) maximum heap alignment for any G1 heap
1031   static size_t conservative_max_heap_alignment();
1032 
1033   // Initialize weak reference processing.
1034   virtual void ref_processing_init();
1035 
1036   // Explicitly import set_par_threads into this scope
1037   using SharedHeap::set_par_threads;
1038   // Set _n_par_threads according to a policy TBD.
1039   void set_par_threads();
1040 
1041   virtual CollectedHeap::Name kind() const {
1042     return CollectedHeap::G1CollectedHeap;
1043   }
1044 
1045   // The current policy object for the collector.
1046   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1047 
1048   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1049 
1050   // Adaptive size policy.  No such thing for g1.
1051   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1052 
1053   // The rem set and barrier set.
1054   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1055 
1056   unsigned get_gc_time_stamp() {
1057     return _gc_time_stamp;
1058   }
1059 
1060   inline void reset_gc_time_stamp();
1061 
1062   void check_gc_time_stamps() PRODUCT_RETURN;
1063 
1064   inline void increment_gc_time_stamp();
1065 
1066   // Reset the given region's GC timestamp. If it's starts humongous,
1067   // also reset the GC timestamp of its corresponding
1068   // continues humongous regions too.
1069   void reset_gc_time_stamps(HeapRegion* hr);
1070 
1071   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1072                                   DirtyCardQueue* into_cset_dcq,
1073                                   bool concurrent, uint worker_i);
1074 
1075   // The shared block offset table array.
1076   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1077 
1078   // Reference Processing accessors
1079 
1080   // The STW reference processor....
1081   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1082 
1083   // The Concurrent Marking reference processor...
1084   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1085 
1086   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1087   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1088 
1089   virtual size_t capacity() const;
1090   virtual size_t used() const;
1091   // This should be called when we're not holding the heap lock. The
1092   // result might be a bit inaccurate.
1093   size_t used_unlocked() const;
1094   size_t recalculate_used() const;
1095 
1096   // These virtual functions do the actual allocation.
1097   // Some heaps may offer a contiguous region for shared non-blocking
1098   // allocation, via inlined code (by exporting the address of the top and
1099   // end fields defining the extent of the contiguous allocation region.)
1100   // But G1CollectedHeap doesn't yet support this.
1101 
1102   virtual bool is_maximal_no_gc() const {
1103     return _hrm.available() == 0;
1104   }
1105 
1106   // The current number of regions in the heap.
1107   uint num_regions() const { return _hrm.length(); }
1108 
1109   // The max number of regions in the heap.
1110   uint max_regions() const { return _hrm.max_length(); }
1111 
1112   // The number of regions that are completely free.
1113   uint num_free_regions() const { return _hrm.num_free_regions(); }
1114 
1115   MemoryUsage get_auxiliary_data_memory_usage() const {
1116     return _hrm.get_auxiliary_data_memory_usage();
1117   }
1118 
1119   // The number of regions that are not completely free.
1120   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1121 
1122   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1123   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1124   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1125   void verify_dirty_young_regions() PRODUCT_RETURN;
1126 
1127 #ifndef PRODUCT
1128   // Make sure that the given bitmap has no marked objects in the
1129   // range [from,limit). If it does, print an error message and return
1130   // false. Otherwise, just return true. bitmap_name should be "prev"
1131   // or "next".
1132   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1133                                 HeapWord* from, HeapWord* limit);
1134 
1135   // Verify that the prev / next bitmap range [tams,end) for the given
1136   // region has no marks. Return true if all is well, false if errors
1137   // are detected.
1138   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1139 #endif // PRODUCT
1140 
1141   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1142   // the given region do not have any spurious marks. If errors are
1143   // detected, print appropriate error messages and crash.
1144   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1145 
1146   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1147   // have any spurious marks. If errors are detected, print
1148   // appropriate error messages and crash.
1149   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1150 
1151   // Do sanity check on the contents of the in-cset fast test table.
1152   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1153 
1154   void verify_region_sets();
1155 
1156   // verify_region_sets_optional() is planted in the code for
1157   // list verification in debug builds.
1158   void verify_region_sets_optional() { DEBUG_ONLY(verify_region_sets();) }
1159 
1160 #ifdef ASSERT
1161   bool is_on_master_free_list(HeapRegion* hr) {
1162     return _hrm.is_free(hr);
1163   }
1164 #endif // ASSERT
1165 
1166   // Wrapper for the region list operations that can be called from
1167   // methods outside this class.
1168 
1169   void secondary_free_list_add(FreeRegionList* list) {
1170     _secondary_free_list.add_ordered(list);
1171   }
1172 
1173   void append_secondary_free_list() {
1174     _hrm.insert_list_into_free_list(&_secondary_free_list);
1175   }
1176 
1177   void append_secondary_free_list_if_not_empty_with_lock() {
1178     // If the secondary free list looks empty there's no reason to
1179     // take the lock and then try to append it.
1180     if (!_secondary_free_list.is_empty()) {
1181       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1182       append_secondary_free_list();
1183     }
1184   }
1185 
1186   inline void old_set_remove(HeapRegion* hr);
1187 
1188   size_t non_young_capacity_bytes() {
1189     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1190   }
1191 
1192   void set_free_regions_coming();
1193   void reset_free_regions_coming();
1194   bool free_regions_coming() { return _free_regions_coming; }
1195   void wait_while_free_regions_coming();
1196 
1197   // Determine whether the given region is one that we are using as an
1198   // old GC alloc region.
1199   bool is_old_gc_alloc_region(HeapRegion* hr) {
1200     return _allocator->is_retained_old_region(hr);
1201   }
1202 
1203   // Perform a collection of the heap; intended for use in implementing
1204   // "System.gc".  This probably implies as full a collection as the
1205   // "CollectedHeap" supports.
1206   virtual void collect(GCCause::Cause cause);
1207 
1208   // The same as above but assume that the caller holds the Heap_lock.
1209   void collect_locked(GCCause::Cause cause);
1210 
1211   virtual bool copy_allocation_context_stats(const jint* contexts,
1212                                              jlong* totals,
1213                                              jbyte* accuracy,
1214                                              jint len);
1215 
1216   // True iff an evacuation has failed in the most-recent collection.
1217   bool evacuation_failed() { return _evacuation_failed; }
1218 
1219   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1220   void prepend_to_freelist(FreeRegionList* list);
1221   void decrement_summary_bytes(size_t bytes);
1222 
1223   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1224   virtual bool is_in(const void* p) const;
1225 #ifdef ASSERT
1226   // Returns whether p is in one of the available areas of the heap. Slow but
1227   // extensive version.
1228   bool is_in_exact(const void* p) const;
1229 #endif
1230 
1231   // Return "TRUE" iff the given object address is within the collection
1232   // set. Slow implementation.
1233   inline bool obj_in_cs(oop obj);
1234 
1235   inline bool is_in_cset(oop obj);
1236 
1237   inline bool is_in_cset_or_humongous(const oop obj);
1238 
1239  private:
1240   // This array is used for a quick test on whether a reference points into
1241   // the collection set or not. Each of the array's elements denotes whether the
1242   // corresponding region is in the collection set or not.
1243   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1244 
1245  public:
1246 
1247   inline InCSetState in_cset_state(const oop obj);
1248 
1249   // Return "TRUE" iff the given object address is in the reserved
1250   // region of g1.
1251   bool is_in_g1_reserved(const void* p) const {
1252     return _hrm.reserved().contains(p);
1253   }
1254 
1255   // Returns a MemRegion that corresponds to the space that has been
1256   // reserved for the heap
1257   MemRegion g1_reserved() const {
1258     return _hrm.reserved();
1259   }
1260 
1261   virtual bool is_in_closed_subset(const void* p) const;
1262 
1263   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1264     return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1265   }
1266 
1267   // This resets the card table to all zeros.  It is used after
1268   // a collection pause which used the card table to claim cards.
1269   void cleanUpCardTable();
1270 
1271   // Iteration functions.
1272 
1273   // Iterate over all the ref-containing fields of all objects, calling
1274   // "cl.do_oop" on each.
1275   virtual void oop_iterate(ExtendedOopClosure* cl);
1276 
1277   // Iterate over all objects, calling "cl.do_object" on each.
1278   virtual void object_iterate(ObjectClosure* cl);
1279 
1280   virtual void safe_object_iterate(ObjectClosure* cl) {
1281     object_iterate(cl);
1282   }
1283 
1284   // Iterate over all spaces in use in the heap, in ascending address order.
1285   virtual void space_iterate(SpaceClosure* cl);
1286 
1287   // Iterate over heap regions, in address order, terminating the
1288   // iteration early if the "doHeapRegion" method returns "true".
1289   void heap_region_iterate(HeapRegionClosure* blk) const;
1290 
1291   // Return the region with the given index. It assumes the index is valid.
1292   inline HeapRegion* region_at(uint index) const;
1293 
1294   // Calculate the region index of the given address. Given address must be
1295   // within the heap.
1296   inline uint addr_to_region(HeapWord* addr) const;
1297 
1298   inline HeapWord* bottom_addr_for_region(uint index) const;
1299 
1300   // Divide the heap region sequence into "chunks" of some size (the number
1301   // of regions divided by the number of parallel threads times some
1302   // overpartition factor, currently 4).  Assumes that this will be called
1303   // in parallel by ParallelGCThreads worker threads with discinct worker
1304   // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1305   // calls will use the same "claim_value", and that that claim value is
1306   // different from the claim_value of any heap region before the start of
1307   // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
1308   // attempting to claim the first region in each chunk, and, if
1309   // successful, applying the closure to each region in the chunk (and
1310   // setting the claim value of the second and subsequent regions of the
1311   // chunk.)  For now requires that "doHeapRegion" always returns "false",
1312   // i.e., that a closure never attempt to abort a traversal.
1313   void heap_region_par_iterate_chunked(HeapRegionClosure* cl,
1314                                        uint worker_id,
1315                                        uint num_workers,
1316                                        jint claim_value) const;
1317 
1318   // It resets all the region claim values to the default.
1319   void reset_heap_region_claim_values();
1320 
1321   // Resets the claim values of regions in the current
1322   // collection set to the default.
1323   void reset_cset_heap_region_claim_values();
1324 
1325 #ifdef ASSERT
1326   bool check_heap_region_claim_values(jint claim_value);
1327 
1328   // Same as the routine above but only checks regions in the
1329   // current collection set.
1330   bool check_cset_heap_region_claim_values(jint claim_value);
1331 #endif // ASSERT
1332 
1333   // Clear the cached cset start regions and (more importantly)
1334   // the time stamps. Called when we reset the GC time stamp.
1335   void clear_cset_start_regions();
1336 
1337   // Given the id of a worker, obtain or calculate a suitable
1338   // starting region for iterating over the current collection set.
1339   HeapRegion* start_cset_region_for_worker(uint worker_i);
1340 
1341   // Iterate over the regions (if any) in the current collection set.
1342   void collection_set_iterate(HeapRegionClosure* blk);
1343 
1344   // As above but starting from region r
1345   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1346 
1347   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1348 
1349   // A CollectedHeap will contain some number of spaces.  This finds the
1350   // space containing a given address, or else returns NULL.
1351   virtual Space* space_containing(const void* addr) const;
1352 
1353   // Returns the HeapRegion that contains addr. addr must not be NULL.
1354   template <class T>
1355   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1356 
1357   // Returns the HeapRegion that contains addr. addr must not be NULL.
1358   // If addr is within a humongous continues region, it returns its humongous start region.
1359   template <class T>
1360   inline HeapRegion* heap_region_containing(const T addr) const;
1361 
1362   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1363   // each address in the (reserved) heap is a member of exactly
1364   // one block.  The defining characteristic of a block is that it is
1365   // possible to find its size, and thus to progress forward to the next
1366   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1367   // represent Java objects, or they might be free blocks in a
1368   // free-list-based heap (or subheap), as long as the two kinds are
1369   // distinguishable and the size of each is determinable.
1370 
1371   // Returns the address of the start of the "block" that contains the
1372   // address "addr".  We say "blocks" instead of "object" since some heaps
1373   // may not pack objects densely; a chunk may either be an object or a
1374   // non-object.
1375   virtual HeapWord* block_start(const void* addr) const;
1376 
1377   // Requires "addr" to be the start of a chunk, and returns its size.
1378   // "addr + size" is required to be the start of a new chunk, or the end
1379   // of the active area of the heap.
1380   virtual size_t block_size(const HeapWord* addr) const;
1381 
1382   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1383   // the block is an object.
1384   virtual bool block_is_obj(const HeapWord* addr) const;
1385 
1386   // Does this heap support heap inspection? (+PrintClassHistogram)
1387   virtual bool supports_heap_inspection() const { return true; }
1388 
1389   // Section on thread-local allocation buffers (TLABs)
1390   // See CollectedHeap for semantics.
1391 
1392   bool supports_tlab_allocation() const;
1393   size_t tlab_capacity(Thread* ignored) const;
1394   size_t tlab_used(Thread* ignored) const;
1395   size_t max_tlab_size() const;
1396   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1397 
1398   // Can a compiler initialize a new object without store barriers?
1399   // This permission only extends from the creation of a new object
1400   // via a TLAB up to the first subsequent safepoint. If such permission
1401   // is granted for this heap type, the compiler promises to call
1402   // defer_store_barrier() below on any slow path allocation of
1403   // a new object for which such initializing store barriers will
1404   // have been elided. G1, like CMS, allows this, but should be
1405   // ready to provide a compensating write barrier as necessary
1406   // if that storage came out of a non-young region. The efficiency
1407   // of this implementation depends crucially on being able to
1408   // answer very efficiently in constant time whether a piece of
1409   // storage in the heap comes from a young region or not.
1410   // See ReduceInitialCardMarks.
1411   virtual bool can_elide_tlab_store_barriers() const {
1412     return true;
1413   }
1414 
1415   virtual bool card_mark_must_follow_store() const {
1416     return true;
1417   }
1418 
1419   inline bool is_in_young(const oop obj);
1420 
1421 #ifdef ASSERT
1422   virtual bool is_in_partial_collection(const void* p);
1423 #endif
1424 
1425   virtual bool is_scavengable(const void* addr);
1426 
1427   // We don't need barriers for initializing stores to objects
1428   // in the young gen: for the SATB pre-barrier, there is no
1429   // pre-value that needs to be remembered; for the remembered-set
1430   // update logging post-barrier, we don't maintain remembered set
1431   // information for young gen objects.
1432   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1433 
1434   // Returns "true" iff the given word_size is "very large".
1435   static bool isHumongous(size_t word_size) {
1436     // Note this has to be strictly greater-than as the TLABs
1437     // are capped at the humongous thresold and we want to
1438     // ensure that we don't try to allocate a TLAB as
1439     // humongous and that we don't allocate a humongous
1440     // object in a TLAB.
1441     return word_size > _humongous_object_threshold_in_words;
1442   }
1443 
1444   // Update mod union table with the set of dirty cards.
1445   void updateModUnion();
1446 
1447   // Set the mod union bits corresponding to the given memRegion.  Note
1448   // that this is always a safe operation, since it doesn't clear any
1449   // bits.
1450   void markModUnionRange(MemRegion mr);
1451 
1452   // Records the fact that a marking phase is no longer in progress.
1453   void set_marking_complete() {
1454     _mark_in_progress = false;
1455   }
1456   void set_marking_started() {
1457     _mark_in_progress = true;
1458   }
1459   bool mark_in_progress() {
1460     return _mark_in_progress;
1461   }
1462 
1463   // Print the maximum heap capacity.
1464   virtual size_t max_capacity() const;
1465 
1466   virtual jlong millis_since_last_gc();
1467 
1468 
1469   // Convenience function to be used in situations where the heap type can be
1470   // asserted to be this type.
1471   static G1CollectedHeap* heap();
1472 
1473   void set_region_short_lived_locked(HeapRegion* hr);
1474   // add appropriate methods for any other surv rate groups
1475 
1476   YoungList* young_list() const { return _young_list; }
1477 
1478   // debugging
1479   bool check_young_list_well_formed() {
1480     return _young_list->check_list_well_formed();
1481   }
1482 
1483   bool check_young_list_empty(bool check_heap,
1484                               bool check_sample = true);
1485 
1486   // *** Stuff related to concurrent marking.  It's not clear to me that so
1487   // many of these need to be public.
1488 
1489   // The functions below are helper functions that a subclass of
1490   // "CollectedHeap" can use in the implementation of its virtual
1491   // functions.
1492   // This performs a concurrent marking of the live objects in a
1493   // bitmap off to the side.
1494   void doConcurrentMark();
1495 
1496   bool isMarkedPrev(oop obj) const;
1497   bool isMarkedNext(oop obj) const;
1498 
1499   // Determine if an object is dead, given the object and also
1500   // the region to which the object belongs. An object is dead
1501   // iff a) it was not allocated since the last mark and b) it
1502   // is not marked.
1503   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1504     return
1505       !hr->obj_allocated_since_prev_marking(obj) &&
1506       !isMarkedPrev(obj);
1507   }
1508 
1509   // This function returns true when an object has been
1510   // around since the previous marking and hasn't yet
1511   // been marked during this marking.
1512   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1513     return
1514       !hr->obj_allocated_since_next_marking(obj) &&
1515       !isMarkedNext(obj);
1516   }
1517 
1518   // Determine if an object is dead, given only the object itself.
1519   // This will find the region to which the object belongs and
1520   // then call the region version of the same function.
1521 
1522   // Added if it is NULL it isn't dead.
1523 
1524   inline bool is_obj_dead(const oop obj) const;
1525 
1526   inline bool is_obj_ill(const oop obj) const;
1527 
1528   inline bool requires_marking(const void* entry) const;
1529 
1530   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1531   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1532   bool is_marked(oop obj, VerifyOption vo);
1533   const char* top_at_mark_start_str(VerifyOption vo);
1534 
1535   ConcurrentMark* concurrent_mark() const { return _cm; }
1536 
1537   // Refinement
1538 
1539   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1540 
1541   // The dirty cards region list is used to record a subset of regions
1542   // whose cards need clearing. The list if populated during the
1543   // remembered set scanning and drained during the card table
1544   // cleanup. Although the methods are reentrant, population/draining
1545   // phases must not overlap. For synchronization purposes the last
1546   // element on the list points to itself.
1547   HeapRegion* _dirty_cards_region_list;
1548   void push_dirty_cards_region(HeapRegion* hr);
1549   HeapRegion* pop_dirty_cards_region();
1550 
1551   // Optimized nmethod scanning support routines
1552 
1553   // Register the given nmethod with the G1 heap
1554   virtual void register_nmethod(nmethod* nm);
1555 
1556   // Unregister the given nmethod from the G1 heap
1557   virtual void unregister_nmethod(nmethod* nm);
1558 
1559   // Free up superfluous code root memory.
1560   void purge_code_root_memory();
1561 
1562   // Rebuild the stong code root lists for each region
1563   // after a full GC
1564   void rebuild_strong_code_roots();
1565 
1566   // Delete entries for dead interned string and clean up unreferenced symbols
1567   // in symbol table, possibly in parallel.
1568   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1569 
1570   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1571   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1572 
1573   // Redirty logged cards in the refinement queue.
1574   void redirty_logged_cards();
1575   // Verification
1576 
1577   // The following is just to alert the verification code
1578   // that a full collection has occurred and that the
1579   // remembered sets are no longer up to date.
1580   bool _full_collection;
1581   void set_full_collection() { _full_collection = true;}
1582   void clear_full_collection() {_full_collection = false;}
1583   bool full_collection() {return _full_collection;}
1584 
1585   // Perform any cleanup actions necessary before allowing a verification.
1586   virtual void prepare_for_verify();
1587 
1588   // Perform verification.
1589 
1590   // vo == UsePrevMarking  -> use "prev" marking information,
1591   // vo == UseNextMarking -> use "next" marking information
1592   // vo == UseMarkWord    -> use the mark word in the object header
1593   //
1594   // NOTE: Only the "prev" marking information is guaranteed to be
1595   // consistent most of the time, so most calls to this should use
1596   // vo == UsePrevMarking.
1597   // Currently, there is only one case where this is called with
1598   // vo == UseNextMarking, which is to verify the "next" marking
1599   // information at the end of remark.
1600   // Currently there is only one place where this is called with
1601   // vo == UseMarkWord, which is to verify the marking during a
1602   // full GC.
1603   void verify(bool silent, VerifyOption vo);
1604 
1605   // Override; it uses the "prev" marking information
1606   virtual void verify(bool silent);
1607 
1608   // The methods below are here for convenience and dispatch the
1609   // appropriate method depending on value of the given VerifyOption
1610   // parameter. The values for that parameter, and their meanings,
1611   // are the same as those above.
1612 
1613   bool is_obj_dead_cond(const oop obj,
1614                         const HeapRegion* hr,
1615                         const VerifyOption vo) const;
1616 
1617   bool is_obj_dead_cond(const oop obj,
1618                         const VerifyOption vo) const;
1619 
1620   G1HeapSummary create_g1_heap_summary();
1621 
1622   // Printing
1623 
1624   virtual void print_on(outputStream* st) const;
1625   virtual void print_extended_on(outputStream* st) const;
1626   virtual void print_on_error(outputStream* st) const;
1627 
1628   virtual void print_gc_threads_on(outputStream* st) const;
1629   virtual void gc_threads_do(ThreadClosure* tc) const;
1630 
1631   // Override
1632   void print_tracing_info() const;
1633 
1634   // The following two methods are helpful for debugging RSet issues.
1635   void print_cset_rsets() PRODUCT_RETURN;
1636   void print_all_rsets() PRODUCT_RETURN;
1637 
1638 public:
1639   size_t pending_card_num();
1640   size_t cards_scanned();
1641 
1642 protected:
1643   size_t _max_heap_capacity;
1644 };
1645 
1646 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP