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.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/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/hSpaceCounters.hpp"
  42 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
  43 #include "memory/barrierSet.hpp"
  44 #include "memory/memRegion.hpp"
  45 #include "memory/sharedHeap.hpp"
  46 #include "utilities/stack.hpp"
  47 
  48 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  49 // It uses the "Garbage First" heap organization and algorithm, which
  50 // may combine concurrent marking with parallel, incremental compaction of
  51 // heap subsets that will yield large amounts of garbage.
  52 
  53 // Forward declarations
  54 class HeapRegion;
  55 class HRRSCleanupTask;
  56 class GenerationSpec;
  57 class OopsInHeapRegionClosure;
  58 class G1KlassScanClosure;
  59 class G1ParScanThreadState;
  60 class ObjectClosure;
  61 class SpaceClosure;
  62 class CompactibleSpaceClosure;
  63 class Space;
  64 class G1CollectorPolicy;
  65 class GenRemSet;
  66 class G1RemSet;
  67 class HeapRegionRemSetIterator;
  68 class ConcurrentMark;
  69 class ConcurrentMarkThread;
  70 class ConcurrentG1Refine;
  71 class ConcurrentGCTimer;
  72 class GenerationCounters;
  73 class STWGCTimer;
  74 class G1NewTracer;
  75 class G1OldTracer;
  76 class EvacuationFailedInfo;
  77 class nmethod;
  78 class Ticks;
  79 
  80 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  81 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  82 
  83 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  84 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  85 
  86 class YoungList : public CHeapObj<mtGC> {
  87 private:
  88   G1CollectedHeap* _g1h;
  89 
  90   HeapRegion* _head;
  91 
  92   HeapRegion* _survivor_head;
  93   HeapRegion* _survivor_tail;
  94 
  95   HeapRegion* _curr;
  96 
  97   uint        _length;
  98   uint        _survivor_length;
  99 
 100   size_t      _last_sampled_rs_lengths;
 101   size_t      _sampled_rs_lengths;
 102 
 103   void         empty_list(HeapRegion* list);
 104 
 105 public:
 106   YoungList(G1CollectedHeap* g1h);
 107 
 108   void         push_region(HeapRegion* hr);
 109   void         add_survivor_region(HeapRegion* hr);
 110 
 111   void         empty_list();
 112   bool         is_empty() { return _length == 0; }
 113   uint         length() { return _length; }
 114   uint         eden_length() { return length() - survivor_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) eden_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 
 191   // Closures used in implementation.
 192   friend class G1ParScanThreadState;
 193   friend class G1ParTask;
 194   friend class G1ParGCAllocator;
 195   friend class G1PrepareCompactClosure;
 196 
 197   // Other related classes.
 198   friend class HeapRegionClaimer;
 199 
 200   // Testing classes.
 201   friend class G1CheckCSetFastTableClosure;
 202 
 203 private:
 204   // The one and only G1CollectedHeap, so static functions can find it.
 205   static G1CollectedHeap* _g1h;
 206 
 207   static size_t _humongous_object_threshold_in_words;
 208 
 209   // The secondary free list which contains regions that have been
 210   // freed up during the cleanup process. This will be appended to
 211   // the master free list when appropriate.
 212   FreeRegionList _secondary_free_list;
 213 
 214   // It keeps track of the old regions.
 215   HeapRegionSet _old_set;
 216 
 217   // It keeps track of the humongous regions.
 218   HeapRegionSet _humongous_set;
 219 
 220   void clear_humongous_is_live_table();
 221   void eagerly_reclaim_humongous_regions();
 222 
 223   // The number of regions we could create by expansion.
 224   uint _expansion_regions;
 225 
 226   // The block offset table for the G1 heap.
 227   G1BlockOffsetSharedArray* _bot_shared;
 228 
 229   // Tears down the region sets / lists so that they are empty and the
 230   // regions on the heap do not belong to a region set / list. The
 231   // only exception is the humongous set which we leave unaltered. If
 232   // free_list_only is true, it will only tear down the master free
 233   // list. It is called before a Full GC (free_list_only == false) or
 234   // before heap shrinking (free_list_only == true).
 235   void tear_down_region_sets(bool free_list_only);
 236 
 237   // Rebuilds the region sets / lists so that they are repopulated to
 238   // reflect the contents of the heap. The only exception is the
 239   // humongous set which was not torn down in the first place. If
 240   // free_list_only is true, it will only rebuild the master free
 241   // list. It is called after a Full GC (free_list_only == false) or
 242   // after heap shrinking (free_list_only == true).
 243   void rebuild_region_sets(bool free_list_only);
 244 
 245   // Callback for region mapping changed events.
 246   G1RegionMappingChangedListener _listener;
 247 
 248   // The sequence of all heap regions in the heap.
 249   HeapRegionManager _hrm;
 250 
 251   // Class that handles the different kinds of allocations.
 252   G1Allocator* _allocator;
 253 
 254   // Statistics for each allocation context
 255   AllocationContextStats _allocation_context_stats;
 256 
 257   // PLAB sizing policy for survivors.
 258   PLABStats _survivor_plab_stats;
 259 
 260   // PLAB sizing policy for tenured objects.
 261   PLABStats _old_plab_stats;
 262 
 263   // It specifies whether we should attempt to expand the heap after a
 264   // region allocation failure. If heap expansion fails we set this to
 265   // false so that we don't re-attempt the heap expansion (it's likely
 266   // that subsequent expansion attempts will also fail if one fails).
 267   // Currently, it is only consulted during GC and it's reset at the
 268   // start of each GC.
 269   bool _expand_heap_after_alloc_failure;
 270 
 271   // It resets the mutator alloc region before new allocations can take place.
 272   void init_mutator_alloc_region();
 273 
 274   // It releases the mutator alloc region.
 275   void release_mutator_alloc_region();
 276 
 277   // It initializes the GC alloc regions at the start of a GC.
 278   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 279 
 280   // It releases the GC alloc regions at the end of a GC.
 281   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 282 
 283   // It does any cleanup that needs to be done on the GC alloc regions
 284   // before a Full GC.
 285   void abandon_gc_alloc_regions();
 286 
 287   // Helper for monitoring and management support.
 288   G1MonitoringSupport* _g1mm;
 289 
 290   // Records whether the region at the given index is kept live by roots or
 291   // references from the young generation.
 292   class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
 293    protected:
 294     bool default_value() const { return false; }
 295    public:
 296     void clear() { G1BiasedMappedArray<bool>::clear(); }
 297     void set_live(uint region) {
 298       set_by_index(region, true);
 299     }
 300     bool is_live(uint region) {
 301       return get_by_index(region);
 302     }
 303   };
 304 
 305   HumongousIsLiveBiasedMappedArray _humongous_is_live;
 306   // Stores whether during humongous object registration we found candidate regions.
 307   // If not, we can skip a few steps.
 308   bool _has_humongous_reclaim_candidates;
 309 
 310   volatile unsigned _gc_time_stamp;
 311 
 312   size_t* _surviving_young_words;
 313 
 314   G1HRPrinter _hr_printer;
 315 
 316   void setup_surviving_young_words();
 317   void update_surviving_young_words(size_t* surv_young_words);
 318   void cleanup_surviving_young_words();
 319 
 320   // It decides whether an explicit GC should start a concurrent cycle
 321   // instead of doing a STW GC. Currently, a concurrent cycle is
 322   // explicitly started if:
 323   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 324   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 325   // (c) cause == _g1_humongous_allocation
 326   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 327 
 328   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 329   // concurrent cycles) we have started.
 330   volatile uint _old_marking_cycles_started;
 331 
 332   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 333   // concurrent cycles) we have completed.
 334   volatile uint _old_marking_cycles_completed;
 335 
 336   bool _concurrent_cycle_started;
 337   bool _heap_summary_sent;
 338 
 339   // This is a non-product method that is helpful for testing. It is
 340   // called at the end of a GC and artificially expands the heap by
 341   // allocating a number of dead regions. This way we can induce very
 342   // frequent marking cycles and stress the cleanup / concurrent
 343   // cleanup code more (as all the regions that will be allocated by
 344   // this method will be found dead by the marking cycle).
 345   void allocate_dummy_regions() PRODUCT_RETURN;
 346 
 347   // Clear RSets after a compaction. It also resets the GC time stamps.
 348   void clear_rsets_post_compaction();
 349 
 350   // If the HR printer is active, dump the state of the regions in the
 351   // heap after a compaction.
 352   void print_hrm_post_compaction();
 353 
 354   double verify(bool guard, const char* msg);
 355   void verify_before_gc();
 356   void verify_after_gc();
 357 
 358   void log_gc_header();
 359   void log_gc_footer(double pause_time_sec);
 360 
 361   // These are macros so that, if the assert fires, we get the correct
 362   // line number, file, etc.
 363 
 364 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 365   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 366           (_extra_message_),                                                  \
 367           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 368           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 369           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 370 
 371 #define assert_heap_locked()                                                  \
 372   do {                                                                        \
 373     assert(Heap_lock->owned_by_self(),                                        \
 374            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 375   } while (0)
 376 
 377 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 378   do {                                                                        \
 379     assert(Heap_lock->owned_by_self() ||                                      \
 380            (SafepointSynchronize::is_at_safepoint() &&                        \
 381              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 382            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 383                                         "should be at a safepoint"));         \
 384   } while (0)
 385 
 386 #define assert_heap_locked_and_not_at_safepoint()                             \
 387   do {                                                                        \
 388     assert(Heap_lock->owned_by_self() &&                                      \
 389                                     !SafepointSynchronize::is_at_safepoint(), \
 390           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 391                                        "should not be at a safepoint"));      \
 392   } while (0)
 393 
 394 #define assert_heap_not_locked()                                              \
 395   do {                                                                        \
 396     assert(!Heap_lock->owned_by_self(),                                       \
 397         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 398   } while (0)
 399 
 400 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 401   do {                                                                        \
 402     assert(!Heap_lock->owned_by_self() &&                                     \
 403                                     !SafepointSynchronize::is_at_safepoint(), \
 404       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 405                                    "should not be at a safepoint"));          \
 406   } while (0)
 407 
 408 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 409   do {                                                                        \
 410     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 411               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 412            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 413   } while (0)
 414 
 415 #define assert_not_at_safepoint()                                             \
 416   do {                                                                        \
 417     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 418            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 419   } while (0)
 420 
 421 protected:
 422 
 423   // The young region list.
 424   YoungList*  _young_list;
 425 
 426   // The current policy object for the collector.
 427   G1CollectorPolicy* _g1_policy;
 428 
 429   // This is the second level of trying to allocate a new region. If
 430   // new_region() didn't find a region on the free_list, this call will
 431   // check whether there's anything available on the
 432   // secondary_free_list and/or wait for more regions to appear on
 433   // that list, if _free_regions_coming is set.
 434   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 435 
 436   // Try to allocate a single non-humongous HeapRegion sufficient for
 437   // an allocation of the given word_size. If do_expand is true,
 438   // attempt to expand the heap if necessary to satisfy the allocation
 439   // request. If the region is to be used as an old region or for a
 440   // humongous object, set is_old to true. If not, to false.
 441   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 442 
 443   // Initialize a contiguous set of free regions of length num_regions
 444   // and starting at index first so that they appear as a single
 445   // humongous region.
 446   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 447                                                       uint num_regions,
 448                                                       size_t word_size,
 449                                                       AllocationContext_t context);
 450 
 451   // Attempt to allocate a humongous object of the given size. Return
 452   // NULL if unsuccessful.
 453   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 454 
 455   // The following two methods, allocate_new_tlab() and
 456   // mem_allocate(), are the two main entry points from the runtime
 457   // into the G1's allocation routines. They have the following
 458   // assumptions:
 459   //
 460   // * They should both be called outside safepoints.
 461   //
 462   // * They should both be called without holding the Heap_lock.
 463   //
 464   // * All allocation requests for new TLABs should go to
 465   //   allocate_new_tlab().
 466   //
 467   // * All non-TLAB allocation requests should go to mem_allocate().
 468   //
 469   // * If either call cannot satisfy the allocation request using the
 470   //   current allocating region, they will try to get a new one. If
 471   //   this fails, they will attempt to do an evacuation pause and
 472   //   retry the allocation.
 473   //
 474   // * If all allocation attempts fail, even after trying to schedule
 475   //   an evacuation pause, allocate_new_tlab() will return NULL,
 476   //   whereas mem_allocate() will attempt a heap expansion and/or
 477   //   schedule a Full GC.
 478   //
 479   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 480   //   should never be called with word_size being humongous. All
 481   //   humongous allocation requests should go to mem_allocate() which
 482   //   will satisfy them with a special path.
 483 
 484   virtual HeapWord* allocate_new_tlab(size_t word_size);
 485 
 486   virtual HeapWord* mem_allocate(size_t word_size,
 487                                  bool*  gc_overhead_limit_was_exceeded);
 488 
 489   // The following three methods take a gc_count_before_ret
 490   // parameter which is used to return the GC count if the method
 491   // returns NULL. Given that we are required to read the GC count
 492   // while holding the Heap_lock, and these paths will take the
 493   // Heap_lock at some point, it's easier to get them to read the GC
 494   // count while holding the Heap_lock before they return NULL instead
 495   // of the caller (namely: mem_allocate()) having to also take the
 496   // Heap_lock just to read the GC count.
 497 
 498   // First-level mutator allocation attempt: try to allocate out of
 499   // the mutator alloc region without taking the Heap_lock. This
 500   // should only be used for non-humongous allocations.
 501   inline HeapWord* attempt_allocation(size_t word_size,
 502                                       uint* gc_count_before_ret,
 503                                       uint* gclocker_retry_count_ret);
 504 
 505   // Second-level mutator allocation attempt: take the Heap_lock and
 506   // retry the allocation attempt, potentially scheduling a GC
 507   // pause. This should only be used for non-humongous allocations.
 508   HeapWord* attempt_allocation_slow(size_t word_size,
 509                                     AllocationContext_t context,
 510                                     uint* gc_count_before_ret,
 511                                     uint* gclocker_retry_count_ret);
 512 
 513   // Takes the Heap_lock and attempts a humongous allocation. It can
 514   // potentially schedule a GC pause.
 515   HeapWord* attempt_allocation_humongous(size_t word_size,
 516                                          uint* gc_count_before_ret,
 517                                          uint* gclocker_retry_count_ret);
 518 
 519   // Allocation attempt that should be called during safepoints (e.g.,
 520   // at the end of a successful GC). expect_null_mutator_alloc_region
 521   // specifies whether the mutator alloc region is expected to be NULL
 522   // or not.
 523   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 524                                             AllocationContext_t context,
 525                                             bool expect_null_mutator_alloc_region);
 526 
 527   // It dirties the cards that cover the block so that so that the post
 528   // write barrier never queues anything when updating objects on this
 529   // block. It is assumed (and in fact we assert) that the block
 530   // belongs to a young region.
 531   inline void dirty_young_block(HeapWord* start, size_t word_size);
 532 
 533   // Allocate blocks during garbage collection. Will ensure an
 534   // allocation region, either by picking one or expanding the
 535   // heap, and then allocate a block of the given size. The block
 536   // may not be a humongous - it must fit into a single heap region.
 537   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 538                                           size_t word_size,
 539                                           AllocationContext_t context);
 540   // Ensure that no further allocations can happen in "r", bearing in mind
 541   // that parallel threads might be attempting allocations.
 542   void par_allocate_remaining_space(HeapRegion* r);
 543 
 544   // Allocation attempt during GC for a survivor object / PLAB.
 545   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 546                                                AllocationContext_t context);
 547 
 548   // Allocation attempt during GC for an old object / PLAB.
 549   inline HeapWord* old_attempt_allocation(size_t word_size,
 550                                           AllocationContext_t context);
 551 
 552   // These methods are the "callbacks" from the G1AllocRegion class.
 553 
 554   // For mutator alloc regions.
 555   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 556   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 557                                    size_t allocated_bytes);
 558 
 559   // For GC alloc regions.
 560   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 561                                   InCSetState dest);
 562   void retire_gc_alloc_region(HeapRegion* alloc_region,
 563                               size_t allocated_bytes, InCSetState dest);
 564 
 565   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 566   //   inspection request and should collect the entire heap
 567   // - if clear_all_soft_refs is true, all soft references should be
 568   //   cleared during the GC
 569   // - if explicit_gc is false, word_size describes the allocation that
 570   //   the GC should attempt (at least) to satisfy
 571   // - it returns false if it is unable to do the collection due to the
 572   //   GC locker being active, true otherwise
 573   bool do_collection(bool explicit_gc,
 574                      bool clear_all_soft_refs,
 575                      size_t word_size);
 576 
 577   // Callback from VM_G1CollectFull operation.
 578   // Perform a full collection.
 579   virtual void do_full_collection(bool clear_all_soft_refs);
 580 
 581   // Resize the heap if necessary after a full collection.  If this is
 582   // after a collect-for allocation, "word_size" is the allocation size,
 583   // and will be considered part of the used portion of the heap.
 584   void resize_if_necessary_after_full_collection(size_t word_size);
 585 
 586   // Callback from VM_G1CollectForAllocation operation.
 587   // This function does everything necessary/possible to satisfy a
 588   // failed allocation request (including collection, expansion, etc.)
 589   HeapWord* satisfy_failed_allocation(size_t word_size,
 590                                       AllocationContext_t context,
 591                                       bool* succeeded);
 592 
 593   // Attempting to expand the heap sufficiently
 594   // to support an allocation of the given "word_size".  If
 595   // successful, perform the allocation and return the address of the
 596   // allocated block, or else "NULL".
 597   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 598 
 599   // Process any reference objects discovered during
 600   // an incremental evacuation pause.
 601   void process_discovered_references(uint no_of_gc_workers);
 602 
 603   // Enqueue any remaining discovered references
 604   // after processing.
 605   void enqueue_discovered_references(uint no_of_gc_workers);
 606 
 607 public:
 608 
 609   G1Allocator* allocator() {
 610     return _allocator;
 611   }
 612 
 613   G1MonitoringSupport* g1mm() {
 614     assert(_g1mm != NULL, "should have been initialized");
 615     return _g1mm;
 616   }
 617 
 618   // Expand the garbage-first heap by at least the given size (in bytes!).
 619   // Returns true if the heap was expanded by the requested amount;
 620   // false otherwise.
 621   // (Rounds up to a HeapRegion boundary.)
 622   bool expand(size_t expand_bytes);
 623 
 624   // Returns the PLAB statistics for a given destination.
 625   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 626 
 627   // Determines PLAB size for a given destination.
 628   inline size_t desired_plab_sz(InCSetState dest);
 629 
 630   inline AllocationContextStats& allocation_context_stats();
 631 
 632   // Do anything common to GC's.
 633   void gc_prologue(bool full);
 634   void gc_epilogue(bool full);
 635 
 636   inline void set_humongous_is_live(oop obj);
 637 
 638   bool humongous_is_live(uint region) {
 639     return _humongous_is_live.is_live(region);
 640   }
 641 
 642   // Returns whether the given region (which must be a humongous (start) region)
 643   // is to be considered conservatively live regardless of any other conditions.
 644   bool humongous_region_is_always_live(uint index);
 645   // Returns whether the given region (which must be a humongous (start) region)
 646   // is considered a candidate for eager reclamation.
 647   bool humongous_region_is_candidate(uint index);
 648   // Register the given region to be part of the collection set.
 649   inline void register_humongous_region_with_cset(uint index);
 650   // Register regions with humongous objects (actually on the start region) in
 651   // the in_cset_fast_test table.
 652   void register_humongous_regions_with_cset();
 653   // We register a region with the fast "in collection set" test. We
 654   // simply set to true the array slot corresponding to this region.
 655   void register_young_region_with_cset(HeapRegion* r) {
 656     _in_cset_fast_test.set_in_young(r->hrm_index());
 657   }
 658   void register_old_region_with_cset(HeapRegion* r) {
 659     _in_cset_fast_test.set_in_old(r->hrm_index());
 660   }
 661   void clear_in_cset(const HeapRegion* hr) {
 662     _in_cset_fast_test.clear(hr);
 663   }
 664 
 665   void clear_cset_fast_test() {
 666     _in_cset_fast_test.clear();
 667   }
 668 
 669   // This is called at the start of either a concurrent cycle or a Full
 670   // GC to update the number of old marking cycles started.
 671   void increment_old_marking_cycles_started();
 672 
 673   // This is called at the end of either a concurrent cycle or a Full
 674   // GC to update the number of old marking cycles completed. Those two
 675   // can happen in a nested fashion, i.e., we start a concurrent
 676   // cycle, a Full GC happens half-way through it which ends first,
 677   // and then the cycle notices that a Full GC happened and ends
 678   // too. The concurrent parameter is a boolean to help us do a bit
 679   // tighter consistency checking in the method. If concurrent is
 680   // false, the caller is the inner caller in the nesting (i.e., the
 681   // Full GC). If concurrent is true, the caller is the outer caller
 682   // in this nesting (i.e., the concurrent cycle). Further nesting is
 683   // not currently supported. The end of this call also notifies
 684   // the FullGCCount_lock in case a Java thread is waiting for a full
 685   // GC to happen (e.g., it called System.gc() with
 686   // +ExplicitGCInvokesConcurrent).
 687   void increment_old_marking_cycles_completed(bool concurrent);
 688 
 689   uint old_marking_cycles_completed() {
 690     return _old_marking_cycles_completed;
 691   }
 692 
 693   void register_concurrent_cycle_start(const Ticks& start_time);
 694   void register_concurrent_cycle_end();
 695   void trace_heap_after_concurrent_cycle();
 696 
 697   G1YCType yc_type();
 698 
 699   G1HRPrinter* hr_printer() { return &_hr_printer; }
 700 
 701   // Frees a non-humongous region by initializing its contents and
 702   // adding it to the free list that's passed as a parameter (this is
 703   // usually a local list which will be appended to the master free
 704   // list later). The used bytes of freed regions are accumulated in
 705   // pre_used. If par is true, the region's RSet will not be freed
 706   // up. The assumption is that this will be done later.
 707   // The locked parameter indicates if the caller has already taken
 708   // care of proper synchronization. This may allow some optimizations.
 709   void free_region(HeapRegion* hr,
 710                    FreeRegionList* free_list,
 711                    bool par,
 712                    bool locked = false);
 713 
 714   // Frees a humongous region by collapsing it into individual regions
 715   // and calling free_region() for each of them. The freed regions
 716   // will be added to the free list that's passed as a parameter (this
 717   // is usually a local list which will be appended to the master free
 718   // list later). The used bytes of freed regions are accumulated in
 719   // pre_used. If par is true, the region's RSet will not be freed
 720   // up. The assumption is that this will be done later.
 721   void free_humongous_region(HeapRegion* hr,
 722                              FreeRegionList* free_list,
 723                              bool par);
 724 protected:
 725 
 726   // Shrink the garbage-first heap by at most the given size (in bytes!).
 727   // (Rounds down to a HeapRegion boundary.)
 728   virtual void shrink(size_t expand_bytes);
 729   void shrink_helper(size_t expand_bytes);
 730 
 731   #if TASKQUEUE_STATS
 732   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 733   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 734   void reset_taskqueue_stats();
 735   #endif // TASKQUEUE_STATS
 736 
 737   // Schedule the VM operation that will do an evacuation pause to
 738   // satisfy an allocation request of word_size. *succeeded will
 739   // return whether the VM operation was successful (it did do an
 740   // evacuation pause) or not (another thread beat us to it or the GC
 741   // locker was active). Given that we should not be holding the
 742   // Heap_lock when we enter this method, we will pass the
 743   // gc_count_before (i.e., total_collections()) as a parameter since
 744   // it has to be read while holding the Heap_lock. Currently, both
 745   // methods that call do_collection_pause() release the Heap_lock
 746   // before the call, so it's easy to read gc_count_before just before.
 747   HeapWord* do_collection_pause(size_t         word_size,
 748                                 uint           gc_count_before,
 749                                 bool*          succeeded,
 750                                 GCCause::Cause gc_cause);
 751 
 752   // The guts of the incremental collection pause, executed by the vm
 753   // thread. It returns false if it is unable to do the collection due
 754   // to the GC locker being active, true otherwise
 755   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 756 
 757   // Actually do the work of evacuating the collection set.
 758   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 759 
 760   // The g1 remembered set of the heap.
 761   G1RemSet* _g1_rem_set;
 762 
 763   // A set of cards that cover the objects for which the Rsets should be updated
 764   // concurrently after the collection.
 765   DirtyCardQueueSet _dirty_card_queue_set;
 766 
 767   // The closure used to refine a single card.
 768   RefineCardTableEntryClosure* _refine_cte_cl;
 769 
 770   // A DirtyCardQueueSet that is used to hold cards that contain
 771   // references into the current collection set. This is used to
 772   // update the remembered sets of the regions in the collection
 773   // set in the event of an evacuation failure.
 774   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 775 
 776   // After a collection pause, make the regions in the CS into free
 777   // regions.
 778   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 779 
 780   // Abandon the current collection set without recording policy
 781   // statistics or updating free lists.
 782   void abandon_collection_set(HeapRegion* cs_head);
 783 
 784   // The concurrent marker (and the thread it runs in.)
 785   ConcurrentMark* _cm;
 786   ConcurrentMarkThread* _cmThread;
 787   bool _mark_in_progress;
 788 
 789   // The concurrent refiner.
 790   ConcurrentG1Refine* _cg1r;
 791 
 792   // The parallel task queues
 793   RefToScanQueueSet *_task_queues;
 794 
 795   // True iff a evacuation has failed in the current collection.
 796   bool _evacuation_failed;
 797 
 798   EvacuationFailedInfo* _evacuation_failed_info_array;
 799 
 800   // Failed evacuations cause some logical from-space objects to have
 801   // forwarding pointers to themselves.  Reset them.
 802   void remove_self_forwarding_pointers();
 803 
 804   // Together, these store an object with a preserved mark, and its mark value.
 805   Stack<oop, mtGC>     _objs_with_preserved_marks;
 806   Stack<markOop, mtGC> _preserved_marks_of_objs;
 807 
 808   // Preserve the mark of "obj", if necessary, in preparation for its mark
 809   // word being overwritten with a self-forwarding-pointer.
 810   void preserve_mark_if_necessary(oop obj, markOop m);
 811 
 812   // The stack of evac-failure objects left to be scanned.
 813   GrowableArray<oop>*    _evac_failure_scan_stack;
 814   // The closure to apply to evac-failure objects.
 815 
 816   OopsInHeapRegionClosure* _evac_failure_closure;
 817   // Set the field above.
 818   void
 819   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 820     _evac_failure_closure = evac_failure_closure;
 821   }
 822 
 823   // Push "obj" on the scan stack.
 824   void push_on_evac_failure_scan_stack(oop obj);
 825   // Process scan stack entries until the stack is empty.
 826   void drain_evac_failure_scan_stack();
 827   // True iff an invocation of "drain_scan_stack" is in progress; to
 828   // prevent unnecessary recursion.
 829   bool _drain_in_progress;
 830 
 831   // Do any necessary initialization for evacuation-failure handling.
 832   // "cl" is the closure that will be used to process evac-failure
 833   // objects.
 834   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 835   // Do any necessary cleanup for evacuation-failure handling data
 836   // structures.
 837   void finalize_for_evac_failure();
 838 
 839   // An attempt to evacuate "obj" has failed; take necessary steps.
 840   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 841   void handle_evacuation_failure_common(oop obj, markOop m);
 842 
 843 #ifndef PRODUCT
 844   // Support for forcing evacuation failures. Analogous to
 845   // PromotionFailureALot for the other collectors.
 846 
 847   // Records whether G1EvacuationFailureALot should be in effect
 848   // for the current GC
 849   bool _evacuation_failure_alot_for_current_gc;
 850 
 851   // Used to record the GC number for interval checking when
 852   // determining whether G1EvaucationFailureALot is in effect
 853   // for the current GC.
 854   size_t _evacuation_failure_alot_gc_number;
 855 
 856   // Count of the number of evacuations between failures.
 857   volatile size_t _evacuation_failure_alot_count;
 858 
 859   // Set whether G1EvacuationFailureALot should be in effect
 860   // for the current GC (based upon the type of GC and which
 861   // command line flags are set);
 862   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 863                                                   bool during_initial_mark,
 864                                                   bool during_marking);
 865 
 866   inline void set_evacuation_failure_alot_for_current_gc();
 867 
 868   // Return true if it's time to cause an evacuation failure.
 869   inline bool evacuation_should_fail();
 870 
 871   // Reset the G1EvacuationFailureALot counters.  Should be called at
 872   // the end of an evacuation pause in which an evacuation failure occurred.
 873   inline void reset_evacuation_should_fail();
 874 #endif // !PRODUCT
 875 
 876   // ("Weak") Reference processing support.
 877   //
 878   // G1 has 2 instances of the reference processor class. One
 879   // (_ref_processor_cm) handles reference object discovery
 880   // and subsequent processing during concurrent marking cycles.
 881   //
 882   // The other (_ref_processor_stw) handles reference object
 883   // discovery and processing during full GCs and incremental
 884   // evacuation pauses.
 885   //
 886   // During an incremental pause, reference discovery will be
 887   // temporarily disabled for _ref_processor_cm and will be
 888   // enabled for _ref_processor_stw. At the end of the evacuation
 889   // pause references discovered by _ref_processor_stw will be
 890   // processed and discovery will be disabled. The previous
 891   // setting for reference object discovery for _ref_processor_cm
 892   // will be re-instated.
 893   //
 894   // At the start of marking:
 895   //  * Discovery by the CM ref processor is verified to be inactive
 896   //    and it's discovered lists are empty.
 897   //  * Discovery by the CM ref processor is then enabled.
 898   //
 899   // At the end of marking:
 900   //  * Any references on the CM ref processor's discovered
 901   //    lists are processed (possibly MT).
 902   //
 903   // At the start of full GC we:
 904   //  * Disable discovery by the CM ref processor and
 905   //    empty CM ref processor's discovered lists
 906   //    (without processing any entries).
 907   //  * Verify that the STW ref processor is inactive and it's
 908   //    discovered lists are empty.
 909   //  * Temporarily set STW ref processor discovery as single threaded.
 910   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 911   //    field.
 912   //  * Finally enable discovery by the STW ref processor.
 913   //
 914   // The STW ref processor is used to record any discovered
 915   // references during the full GC.
 916   //
 917   // At the end of a full GC we:
 918   //  * Enqueue any reference objects discovered by the STW ref processor
 919   //    that have non-live referents. This has the side-effect of
 920   //    making the STW ref processor inactive by disabling discovery.
 921   //  * Verify that the CM ref processor is still inactive
 922   //    and no references have been placed on it's discovered
 923   //    lists (also checked as a precondition during initial marking).
 924 
 925   // The (stw) reference processor...
 926   ReferenceProcessor* _ref_processor_stw;
 927 
 928   STWGCTimer* _gc_timer_stw;
 929   ConcurrentGCTimer* _gc_timer_cm;
 930 
 931   G1OldTracer* _gc_tracer_cm;
 932   G1NewTracer* _gc_tracer_stw;
 933 
 934   // During reference object discovery, the _is_alive_non_header
 935   // closure (if non-null) is applied to the referent object to
 936   // determine whether the referent is live. If so then the
 937   // reference object does not need to be 'discovered' and can
 938   // be treated as a regular oop. This has the benefit of reducing
 939   // the number of 'discovered' reference objects that need to
 940   // be processed.
 941   //
 942   // Instance of the is_alive closure for embedding into the
 943   // STW reference processor as the _is_alive_non_header field.
 944   // Supplying a value for the _is_alive_non_header field is
 945   // optional but doing so prevents unnecessary additions to
 946   // the discovered lists during reference discovery.
 947   G1STWIsAliveClosure _is_alive_closure_stw;
 948 
 949   // The (concurrent marking) reference processor...
 950   ReferenceProcessor* _ref_processor_cm;
 951 
 952   // Instance of the concurrent mark is_alive closure for embedding
 953   // into the Concurrent Marking reference processor as the
 954   // _is_alive_non_header field. Supplying a value for the
 955   // _is_alive_non_header field is optional but doing so prevents
 956   // unnecessary additions to the discovered lists during reference
 957   // discovery.
 958   G1CMIsAliveClosure _is_alive_closure_cm;
 959 
 960   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 961   HeapRegion** _worker_cset_start_region;
 962 
 963   // Time stamp to validate the regions recorded in the cache
 964   // used by G1CollectedHeap::start_cset_region_for_worker().
 965   // The heap region entry for a given worker is valid iff
 966   // the associated time stamp value matches the current value
 967   // of G1CollectedHeap::_gc_time_stamp.
 968   uint* _worker_cset_start_region_time_stamp;
 969 
 970   volatile bool _free_regions_coming;
 971 
 972 public:
 973 
 974   void set_refine_cte_cl_concurrency(bool concurrent);
 975 
 976   RefToScanQueue *task_queue(int i) const;
 977 
 978   // A set of cards where updates happened during the GC
 979   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 980 
 981   // A DirtyCardQueueSet that is used to hold cards that contain
 982   // references into the current collection set. This is used to
 983   // update the remembered sets of the regions in the collection
 984   // set in the event of an evacuation failure.
 985   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
 986         { return _into_cset_dirty_card_queue_set; }
 987 
 988   // Create a G1CollectedHeap with the specified policy.
 989   // Must call the initialize method afterwards.
 990   // May not return if something goes wrong.
 991   G1CollectedHeap(G1CollectorPolicy* policy);
 992 
 993   // Initialize the G1CollectedHeap to have the initial and
 994   // maximum sizes and remembered and barrier sets
 995   // specified by the policy object.
 996   jint initialize();
 997 
 998   virtual void stop();
 999 
1000   // Return the (conservative) maximum heap alignment for any G1 heap
1001   static size_t conservative_max_heap_alignment();
1002 
1003   // Does operations required after initialization has been done.
1004   void post_initialize();
1005 
1006   // Initialize weak reference processing.
1007   virtual void ref_processing_init();
1008 
1009   // Explicitly import set_par_threads into this scope
1010   using SharedHeap::set_par_threads;
1011   // Set _n_par_threads according to a policy TBD.
1012   void set_par_threads();
1013 
1014   virtual CollectedHeap::Name kind() const {
1015     return CollectedHeap::G1CollectedHeap;
1016   }
1017 
1018   // The current policy object for the collector.
1019   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1020 
1021   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1022 
1023   // Adaptive size policy.  No such thing for g1.
1024   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1025 
1026   // The rem set and barrier set.
1027   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1028 
1029   unsigned get_gc_time_stamp() {
1030     return _gc_time_stamp;
1031   }
1032 
1033   inline void reset_gc_time_stamp();
1034 
1035   void check_gc_time_stamps() PRODUCT_RETURN;
1036 
1037   inline void increment_gc_time_stamp();
1038 
1039   // Reset the given region's GC timestamp. If it's starts humongous,
1040   // also reset the GC timestamp of its corresponding
1041   // continues humongous regions too.
1042   void reset_gc_time_stamps(HeapRegion* hr);
1043 
1044   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1045                                   DirtyCardQueue* into_cset_dcq,
1046                                   bool concurrent, uint worker_i);
1047 
1048   // The shared block offset table array.
1049   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1050 
1051   // Reference Processing accessors
1052 
1053   // The STW reference processor....
1054   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1055 
1056   // The Concurrent Marking reference processor...
1057   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1058 
1059   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1060   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1061 
1062   virtual size_t capacity() const;
1063   virtual size_t used() const;
1064   // This should be called when we're not holding the heap lock. The
1065   // result might be a bit inaccurate.
1066   size_t used_unlocked() const;
1067   size_t recalculate_used() const;
1068 
1069   // These virtual functions do the actual allocation.
1070   // Some heaps may offer a contiguous region for shared non-blocking
1071   // allocation, via inlined code (by exporting the address of the top and
1072   // end fields defining the extent of the contiguous allocation region.)
1073   // But G1CollectedHeap doesn't yet support this.
1074 
1075   virtual bool is_maximal_no_gc() const {
1076     return _hrm.available() == 0;
1077   }
1078 
1079   // The current number of regions in the heap.
1080   uint num_regions() const { return _hrm.length(); }
1081 
1082   // The max number of regions in the heap.
1083   uint max_regions() const { return _hrm.max_length(); }
1084 
1085   // The number of regions that are completely free.
1086   uint num_free_regions() const { return _hrm.num_free_regions(); }
1087 
1088   MemoryUsage get_auxiliary_data_memory_usage() const {
1089     return _hrm.get_auxiliary_data_memory_usage();
1090   }
1091 
1092   // The number of regions that are not completely free.
1093   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1094 
1095   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1096   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1097   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1098   void verify_dirty_young_regions() PRODUCT_RETURN;
1099 
1100 #ifndef PRODUCT
1101   // Make sure that the given bitmap has no marked objects in the
1102   // range [from,limit). If it does, print an error message and return
1103   // false. Otherwise, just return true. bitmap_name should be "prev"
1104   // or "next".
1105   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1106                                 HeapWord* from, HeapWord* limit);
1107 
1108   // Verify that the prev / next bitmap range [tams,end) for the given
1109   // region has no marks. Return true if all is well, false if errors
1110   // are detected.
1111   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1112 
1113   // True if the heap_lock is held by the a non-gc thread invoking a gc
1114   // operation.
1115   bool _thread_holds_heap_lock_for_gc;
1116   // Returns true if the calling thread holds the heap lock,
1117   // or the calling thread is a par gc thread and the heap_lock is held
1118   // by the vm thread doing a gc operation.
1119   bool heap_lock_held_for_gc();
1120 
1121   void set_heap_lock_held_for_gc(bool value) { _thread_holds_heap_lock_for_gc = value; }
1122 
1123 #endif // PRODUCT
1124 
1125   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1126   // the given region do not have any spurious marks. If errors are
1127   // detected, print appropriate error messages and crash.
1128   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1129 
1130   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1131   // have any spurious marks. If errors are detected, print
1132   // appropriate error messages and crash.
1133   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1134 
1135   // Do sanity check on the contents of the in-cset fast test table.
1136   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1137 
1138   // verify_region_sets() performs verification over the region
1139   // lists. It will be compiled in the product code to be used when
1140   // necessary (i.e., during heap verification).
1141   void verify_region_sets();
1142 
1143   // verify_region_sets_optional() is planted in the code for
1144   // list verification in non-product builds (and it can be enabled in
1145   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1146 #if HEAP_REGION_SET_FORCE_VERIFY
1147   void verify_region_sets_optional() {
1148     verify_region_sets();
1149   }
1150 #else // HEAP_REGION_SET_FORCE_VERIFY
1151   void verify_region_sets_optional() { }
1152 #endif // HEAP_REGION_SET_FORCE_VERIFY
1153 
1154 #ifdef ASSERT
1155   bool is_on_master_free_list(HeapRegion* hr) {
1156     return _hrm.is_free(hr);
1157   }
1158 #endif // ASSERT
1159 
1160   // Wrapper for the region list operations that can be called from
1161   // methods outside this class.
1162 
1163   void secondary_free_list_add(FreeRegionList* list) {
1164     _secondary_free_list.add_ordered(list);
1165   }
1166 
1167   void append_secondary_free_list() {
1168     _hrm.insert_list_into_free_list(&_secondary_free_list);
1169   }
1170 
1171   void append_secondary_free_list_if_not_empty_with_lock() {
1172     // If the secondary free list looks empty there's no reason to
1173     // take the lock and then try to append it.
1174     if (!_secondary_free_list.is_empty()) {
1175       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1176       append_secondary_free_list();
1177     }
1178   }
1179 
1180   inline void old_set_remove(HeapRegion* hr);
1181 
1182   size_t non_young_capacity_bytes() {
1183     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1184   }
1185 
1186   void set_free_regions_coming();
1187   void reset_free_regions_coming();
1188   bool free_regions_coming() { return _free_regions_coming; }
1189   void wait_while_free_regions_coming();
1190 
1191   // Determine whether the given region is one that we are using as an
1192   // old GC alloc region.
1193   bool is_old_gc_alloc_region(HeapRegion* hr) {
1194     return _allocator->is_retained_old_region(hr);
1195   }
1196 
1197   // Perform a collection of the heap; intended for use in implementing
1198   // "System.gc".  This probably implies as full a collection as the
1199   // "CollectedHeap" supports.
1200   virtual void collect(GCCause::Cause cause);
1201 
1202   // The same as above but assume that the caller holds the Heap_lock.
1203   void collect_locked(GCCause::Cause cause);
1204 
1205   virtual bool copy_allocation_context_stats(const jint* contexts,
1206                                              jlong* totals,
1207                                              jbyte* accuracy,
1208                                              jint len);
1209 
1210   // True iff an evacuation has failed in the most-recent collection.
1211   bool evacuation_failed() { return _evacuation_failed; }
1212 
1213   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1214   void prepend_to_freelist(FreeRegionList* list);
1215   void decrement_summary_bytes(size_t bytes);
1216 
1217   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1218   virtual bool is_in(const void* p) const;
1219 #ifdef ASSERT
1220   // Returns whether p is in one of the available areas of the heap. Slow but
1221   // extensive version.
1222   bool is_in_exact(const void* p) const;
1223 #endif
1224 
1225   // Return "TRUE" iff the given object address is within the collection
1226   // set. Slow implementation.
1227   inline bool obj_in_cs(oop obj);
1228 
1229   inline bool is_in_cset(const HeapRegion *hr);
1230   inline bool is_in_cset(oop obj);
1231 
1232   inline bool is_in_cset_or_humongous(const oop obj);
1233 
1234  private:
1235   // This array is used for a quick test on whether a reference points into
1236   // the collection set or not. Each of the array's elements denotes whether the
1237   // corresponding region is in the collection set or not.
1238   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1239 
1240  public:
1241 
1242   inline InCSetState in_cset_state(const oop obj);
1243 
1244   // Return "TRUE" iff the given object address is in the reserved
1245   // region of g1.
1246   bool is_in_g1_reserved(const void* p) const {
1247     return _hrm.reserved().contains(p);
1248   }
1249 
1250   // Returns a MemRegion that corresponds to the space that has been
1251   // reserved for the heap
1252   MemRegion g1_reserved() const {
1253     return _hrm.reserved();
1254   }
1255 
1256   virtual bool is_in_closed_subset(const void* p) const;
1257 
1258   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1259     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1260   }
1261 
1262   // This resets the card table to all zeros.  It is used after
1263   // a collection pause which used the card table to claim cards.
1264   void cleanUpCardTable();
1265 
1266   // Iteration functions.
1267 
1268   // Iterate over all the ref-containing fields of all objects, calling
1269   // "cl.do_oop" on each.
1270   virtual void oop_iterate(ExtendedOopClosure* cl);
1271 
1272   // Iterate over all objects, calling "cl.do_object" on each.
1273   virtual void object_iterate(ObjectClosure* cl);
1274 
1275   virtual void safe_object_iterate(ObjectClosure* cl) {
1276     object_iterate(cl);
1277   }
1278 
1279   // Iterate over heap regions, in address order, terminating the
1280   // iteration early if the "doHeapRegion" method returns "true".
1281   void heap_region_iterate(HeapRegionClosure* blk) const;
1282 
1283   // Return the region with the given index. It assumes the index is valid.
1284   inline HeapRegion* region_at(uint index) const;
1285 
1286   // Calculate the region index of the given address. Given address must be
1287   // within the heap.
1288   inline uint addr_to_region(HeapWord* addr) const;
1289 
1290   inline HeapWord* bottom_addr_for_region(uint index) const;
1291 
1292   // Iterate over the heap regions in parallel. Assumes that this will be called
1293   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1294   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1295   // to each of the regions, by attempting to claim the region using the
1296   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1297   // region. The concurrent argument should be set to true if iteration is
1298   // performed concurrently, during which no assumptions are made for consistent
1299   // attributes of the heap regions (as they might be modified while iterating).
1300   void heap_region_par_iterate(HeapRegionClosure* cl,
1301                                uint worker_id,
1302                                HeapRegionClaimer* hrclaimer,
1303                                bool concurrent = false) const;
1304 
1305   // Clear the cached cset start regions and (more importantly)
1306   // the time stamps. Called when we reset the GC time stamp.
1307   void clear_cset_start_regions();
1308 
1309   // Given the id of a worker, obtain or calculate a suitable
1310   // starting region for iterating over the current collection set.
1311   HeapRegion* start_cset_region_for_worker(uint worker_i);
1312 
1313   // Iterate over the regions (if any) in the current collection set.
1314   void collection_set_iterate(HeapRegionClosure* blk);
1315 
1316   // As above but starting from region r
1317   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1318 
1319   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1320 
1321   // A CollectedHeap will contain some number of spaces.  This finds the
1322   // space containing a given address, or else returns NULL.
1323   Space* space_containing(const void* addr) const;
1324 
1325   // Returns the HeapRegion that contains addr. addr must not be NULL.
1326   template <class T>
1327   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1328 
1329   // Returns the HeapRegion that contains addr. addr must not be NULL.
1330   // If addr is within a humongous continues region, it returns its humongous start region.
1331   template <class T>
1332   inline HeapRegion* heap_region_containing(const T addr) const;
1333 
1334   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1335   // each address in the (reserved) heap is a member of exactly
1336   // one block.  The defining characteristic of a block is that it is
1337   // possible to find its size, and thus to progress forward to the next
1338   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1339   // represent Java objects, or they might be free blocks in a
1340   // free-list-based heap (or subheap), as long as the two kinds are
1341   // distinguishable and the size of each is determinable.
1342 
1343   // Returns the address of the start of the "block" that contains the
1344   // address "addr".  We say "blocks" instead of "object" since some heaps
1345   // may not pack objects densely; a chunk may either be an object or a
1346   // non-object.
1347   virtual HeapWord* block_start(const void* addr) const;
1348 
1349   // Requires "addr" to be the start of a chunk, and returns its size.
1350   // "addr + size" is required to be the start of a new chunk, or the end
1351   // of the active area of the heap.
1352   virtual size_t block_size(const HeapWord* addr) const;
1353 
1354   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1355   // the block is an object.
1356   virtual bool block_is_obj(const HeapWord* addr) const;
1357 
1358   // Does this heap support heap inspection? (+PrintClassHistogram)
1359   virtual bool supports_heap_inspection() const { return true; }
1360 
1361   // Section on thread-local allocation buffers (TLABs)
1362   // See CollectedHeap for semantics.
1363 
1364   bool supports_tlab_allocation() const;
1365   size_t tlab_capacity(Thread* ignored) const;
1366   size_t tlab_used(Thread* ignored) const;
1367   size_t max_tlab_size() const;
1368   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1369 
1370   // Can a compiler initialize a new object without store barriers?
1371   // This permission only extends from the creation of a new object
1372   // via a TLAB up to the first subsequent safepoint. If such permission
1373   // is granted for this heap type, the compiler promises to call
1374   // defer_store_barrier() below on any slow path allocation of
1375   // a new object for which such initializing store barriers will
1376   // have been elided. G1, like CMS, allows this, but should be
1377   // ready to provide a compensating write barrier as necessary
1378   // if that storage came out of a non-young region. The efficiency
1379   // of this implementation depends crucially on being able to
1380   // answer very efficiently in constant time whether a piece of
1381   // storage in the heap comes from a young region or not.
1382   // See ReduceInitialCardMarks.
1383   virtual bool can_elide_tlab_store_barriers() const {
1384     return true;
1385   }
1386 
1387   virtual bool card_mark_must_follow_store() const {
1388     return true;
1389   }
1390 
1391   inline bool is_in_young(const oop obj);
1392 
1393   virtual bool is_scavengable(const void* addr);
1394 
1395   // We don't need barriers for initializing stores to objects
1396   // in the young gen: for the SATB pre-barrier, there is no
1397   // pre-value that needs to be remembered; for the remembered-set
1398   // update logging post-barrier, we don't maintain remembered set
1399   // information for young gen objects.
1400   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1401 
1402   // Returns "true" iff the given word_size is "very large".
1403   static bool is_humongous(size_t word_size) {
1404     // Note this has to be strictly greater-than as the TLABs
1405     // are capped at the humongous threshold and we want to
1406     // ensure that we don't try to allocate a TLAB as
1407     // humongous and that we don't allocate a humongous
1408     // object in a TLAB.
1409     return word_size > _humongous_object_threshold_in_words;
1410   }
1411 
1412   // Update mod union table with the set of dirty cards.
1413   void updateModUnion();
1414 
1415   // Set the mod union bits corresponding to the given memRegion.  Note
1416   // that this is always a safe operation, since it doesn't clear any
1417   // bits.
1418   void markModUnionRange(MemRegion mr);
1419 
1420   // Records the fact that a marking phase is no longer in progress.
1421   void set_marking_complete() {
1422     _mark_in_progress = false;
1423   }
1424   void set_marking_started() {
1425     _mark_in_progress = true;
1426   }
1427   bool mark_in_progress() {
1428     return _mark_in_progress;
1429   }
1430 
1431   // Print the maximum heap capacity.
1432   virtual size_t max_capacity() const;
1433 
1434   virtual jlong millis_since_last_gc();
1435 
1436 
1437   // Convenience function to be used in situations where the heap type can be
1438   // asserted to be this type.
1439   static G1CollectedHeap* heap();
1440 
1441   void set_region_short_lived_locked(HeapRegion* hr);
1442   // add appropriate methods for any other surv rate groups
1443 
1444   YoungList* young_list() const { return _young_list; }
1445 
1446   // debugging
1447   bool check_young_list_well_formed() {
1448     return _young_list->check_list_well_formed();
1449   }
1450 
1451   bool check_young_list_empty(bool check_heap,
1452                               bool check_sample = true);
1453 
1454   // *** Stuff related to concurrent marking.  It's not clear to me that so
1455   // many of these need to be public.
1456 
1457   // The functions below are helper functions that a subclass of
1458   // "CollectedHeap" can use in the implementation of its virtual
1459   // functions.
1460   // This performs a concurrent marking of the live objects in a
1461   // bitmap off to the side.
1462   void doConcurrentMark();
1463 
1464   bool isMarkedPrev(oop obj) const;
1465   bool isMarkedNext(oop obj) const;
1466 
1467   // Determine if an object is dead, given the object and also
1468   // the region to which the object belongs. An object is dead
1469   // iff a) it was not allocated since the last mark and b) it
1470   // is not marked.
1471   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1472     return
1473       !hr->obj_allocated_since_prev_marking(obj) &&
1474       !isMarkedPrev(obj);
1475   }
1476 
1477   // This function returns true when an object has been
1478   // around since the previous marking and hasn't yet
1479   // been marked during this marking.
1480   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1481     return
1482       !hr->obj_allocated_since_next_marking(obj) &&
1483       !isMarkedNext(obj);
1484   }
1485 
1486   // Determine if an object is dead, given only the object itself.
1487   // This will find the region to which the object belongs and
1488   // then call the region version of the same function.
1489 
1490   // Added if it is NULL it isn't dead.
1491 
1492   inline bool is_obj_dead(const oop obj) const;
1493 
1494   inline bool is_obj_ill(const oop obj) const;
1495 
1496   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1497   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1498   bool is_marked(oop obj, VerifyOption vo);
1499   const char* top_at_mark_start_str(VerifyOption vo);
1500 
1501   ConcurrentMark* concurrent_mark() const { return _cm; }
1502 
1503   // Refinement
1504 
1505   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1506 
1507   // The dirty cards region list is used to record a subset of regions
1508   // whose cards need clearing. The list if populated during the
1509   // remembered set scanning and drained during the card table
1510   // cleanup. Although the methods are reentrant, population/draining
1511   // phases must not overlap. For synchronization purposes the last
1512   // element on the list points to itself.
1513   HeapRegion* _dirty_cards_region_list;
1514   void push_dirty_cards_region(HeapRegion* hr);
1515   HeapRegion* pop_dirty_cards_region();
1516 
1517   // Optimized nmethod scanning support routines
1518 
1519   // Register the given nmethod with the G1 heap.
1520   virtual void register_nmethod(nmethod* nm);
1521 
1522   // Unregister the given nmethod from the G1 heap.
1523   virtual void unregister_nmethod(nmethod* nm);
1524 
1525   // Free up superfluous code root memory.
1526   void purge_code_root_memory();
1527 
1528   // Rebuild the strong code root lists for each region
1529   // after a full GC.
1530   void rebuild_strong_code_roots();
1531 
1532   // Delete entries for dead interned string and clean up unreferenced symbols
1533   // in symbol table, possibly in parallel.
1534   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1535 
1536   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1537   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1538 
1539   // Redirty logged cards in the refinement queue.
1540   void redirty_logged_cards();
1541   // Verification
1542 
1543   // The following is just to alert the verification code
1544   // that a full collection has occurred and that the
1545   // remembered sets are no longer up to date.
1546   bool _full_collection;
1547   void set_full_collection() { _full_collection = true;}
1548   void clear_full_collection() {_full_collection = false;}
1549   bool full_collection() {return _full_collection;}
1550 
1551   // Perform any cleanup actions necessary before allowing a verification.
1552   virtual void prepare_for_verify();
1553 
1554   // Perform verification.
1555 
1556   // vo == UsePrevMarking  -> use "prev" marking information,
1557   // vo == UseNextMarking -> use "next" marking information
1558   // vo == UseMarkWord    -> use the mark word in the object header
1559   //
1560   // NOTE: Only the "prev" marking information is guaranteed to be
1561   // consistent most of the time, so most calls to this should use
1562   // vo == UsePrevMarking.
1563   // Currently, there is only one case where this is called with
1564   // vo == UseNextMarking, which is to verify the "next" marking
1565   // information at the end of remark.
1566   // Currently there is only one place where this is called with
1567   // vo == UseMarkWord, which is to verify the marking during a
1568   // full GC.
1569   void verify(bool silent, VerifyOption vo);
1570 
1571   // Override; it uses the "prev" marking information
1572   virtual void verify(bool silent);
1573 
1574   // The methods below are here for convenience and dispatch the
1575   // appropriate method depending on value of the given VerifyOption
1576   // parameter. The values for that parameter, and their meanings,
1577   // are the same as those above.
1578 
1579   bool is_obj_dead_cond(const oop obj,
1580                         const HeapRegion* hr,
1581                         const VerifyOption vo) const;
1582 
1583   bool is_obj_dead_cond(const oop obj,
1584                         const VerifyOption vo) const;
1585 
1586   // Printing
1587 
1588   virtual void print_on(outputStream* st) const;
1589   virtual void print_extended_on(outputStream* st) const;
1590   virtual void print_on_error(outputStream* st) const;
1591 
1592   virtual void print_gc_threads_on(outputStream* st) const;
1593   virtual void gc_threads_do(ThreadClosure* tc) const;
1594 
1595   // Override
1596   void print_tracing_info() const;
1597 
1598   // The following two methods are helpful for debugging RSet issues.
1599   void print_cset_rsets() PRODUCT_RETURN;
1600   void print_all_rsets() PRODUCT_RETURN;
1601 
1602 public:
1603   size_t pending_card_num();
1604   size_t cards_scanned();
1605 
1606 protected:
1607   size_t _max_heap_capacity;
1608 };
1609 
1610 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP