rev 7854 : imported patch 8027962-per-phase-timing-measurements-for-strong-roots-processing
rev 7855 : [mq]: 8027962-bengt-suggestions

   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.
  18  *
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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 ObjectClosure;
  60 class SpaceClosure;
  61 class CompactibleSpaceClosure;
  62 class Space;
  63 class G1CollectorPolicy;
  64 class GenRemSet;
  65 class G1RemSet;
  66 class HeapRegionRemSetIterator;
  67 class ConcurrentMark;
  68 class ConcurrentMarkThread;
  69 class ConcurrentG1Refine;
  70 class ConcurrentGCTimer;
  71 class GenerationCounters;
  72 class STWGCTimer;
  73 class G1NewTracer;
  74 class G1OldTracer;
  75 class EvacuationFailedInfo;
  76 class nmethod;
  77 class Ticks;
  78 
  79 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  80 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  81 
  82 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  83 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  84 
  85 class YoungList : public CHeapObj<mtGC> {
  86 private:
  87   G1CollectedHeap* _g1h;
  88 
  89   HeapRegion* _head;
  90 
  91   HeapRegion* _survivor_head;
  92   HeapRegion* _survivor_tail;
  93 
  94   HeapRegion* _curr;
  95 
  96   uint        _length;
  97   uint        _survivor_length;
  98 
  99   size_t      _last_sampled_rs_lengths;
 100   size_t      _sampled_rs_lengths;
 101 
 102   void         empty_list(HeapRegion* list);
 103 
 104 public:
 105   YoungList(G1CollectedHeap* g1h);
 106 
 107   void         push_region(HeapRegion* hr);
 108   void         add_survivor_region(HeapRegion* hr);
 109 
 110   void         empty_list();
 111   bool         is_empty() { return _length == 0; }
 112   uint         length() { return _length; }
 113   uint         survivor_length() { return _survivor_length; }
 114 
 115   // Currently we do not keep track of the used byte sum for the
 116   // young list and the survivors and it'd be quite a lot of work to
 117   // do so. When we'll eventually replace the young list with
 118   // instances of HeapRegionLinkedList we'll get that for free. So,
 119   // we'll report the more accurate information then.
 120   size_t       eden_used_bytes() {
 121     assert(length() >= survivor_length(), "invariant");
 122     return (size_t) (length() - survivor_length()) * HeapRegion::GrainBytes;
 123   }
 124   size_t       survivor_used_bytes() {
 125     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 126   }
 127 
 128   void rs_length_sampling_init();
 129   bool rs_length_sampling_more();
 130   void rs_length_sampling_next();
 131 
 132   void reset_sampled_info() {
 133     _last_sampled_rs_lengths =   0;
 134   }
 135   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 136 
 137   // for development purposes
 138   void reset_auxilary_lists();
 139   void clear() { _head = NULL; _length = 0; }
 140 
 141   void clear_survivors() {
 142     _survivor_head    = NULL;
 143     _survivor_tail    = NULL;
 144     _survivor_length  = 0;
 145   }
 146 
 147   HeapRegion* first_region() { return _head; }
 148   HeapRegion* first_survivor_region() { return _survivor_head; }
 149   HeapRegion* last_survivor_region() { return _survivor_tail; }
 150 
 151   // debugging
 152   bool          check_list_well_formed();
 153   bool          check_list_empty(bool check_sample = true);
 154   void          print();
 155 };
 156 
 157 // The G1 STW is alive closure.
 158 // An instance is embedded into the G1CH and used as the
 159 // (optional) _is_alive_non_header closure in the STW
 160 // reference processor. It is also extensively used during
 161 // reference processing during STW evacuation pauses.
 162 class G1STWIsAliveClosure: public BoolObjectClosure {
 163   G1CollectedHeap* _g1;
 164 public:
 165   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 166   bool do_object_b(oop p);
 167 };
 168 
 169 class RefineCardTableEntryClosure;
 170 
 171 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 172  private:
 173   void reset_from_card_cache(uint start_idx, size_t num_regions);
 174  public:
 175   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 176 };
 177 
 178 class G1CollectedHeap : public SharedHeap {
 179   friend class VM_CollectForMetadataAllocation;
 180   friend class VM_G1CollectForAllocation;
 181   friend class VM_G1CollectFull;
 182   friend class VM_G1IncCollectionPause;
 183   friend class VMStructs;
 184   friend class MutatorAllocRegion;
 185   friend class SurvivorGCAllocRegion;
 186   friend class OldGCAllocRegion;
 187   friend class G1Allocator;
 188 
 189   // Closures used in implementation.
 190   friend class G1ParScanThreadState;
 191   friend class G1ParTask;
 192   friend class G1ParGCAllocator;
 193   friend class G1PrepareCompactClosure;
 194 
 195   // Other related classes.
 196   friend class HeapRegionClaimer;
 197 
 198   // Testing classes.
 199   friend class G1CheckCSetFastTableClosure;
 200 
 201 private:
 202   // The one and only G1CollectedHeap, so static functions can find it.
 203   static G1CollectedHeap* _g1h;
 204 
 205   static size_t _humongous_object_threshold_in_words;
 206 
 207   // The secondary free list which contains regions that have been
 208   // freed up during the cleanup process. This will be appended to
 209   // the master free list when appropriate.
 210   FreeRegionList _secondary_free_list;
 211 
 212   // It keeps track of the old regions.
 213   HeapRegionSet _old_set;
 214 
 215   // It keeps track of the humongous regions.
 216   HeapRegionSet _humongous_set;
 217 
 218   void clear_humongous_is_live_table();
 219   void eagerly_reclaim_humongous_regions();
 220 
 221   // The number of regions we could create by expansion.
 222   uint _expansion_regions;
 223 
 224   // The block offset table for the G1 heap.
 225   G1BlockOffsetSharedArray* _bot_shared;
 226 
 227   // Tears down the region sets / lists so that they are empty and the
 228   // regions on the heap do not belong to a region set / list. The
 229   // only exception is the humongous set which we leave unaltered. If
 230   // free_list_only is true, it will only tear down the master free
 231   // list. It is called before a Full GC (free_list_only == false) or
 232   // before heap shrinking (free_list_only == true).
 233   void tear_down_region_sets(bool free_list_only);
 234 
 235   // Rebuilds the region sets / lists so that they are repopulated to
 236   // reflect the contents of the heap. The only exception is the
 237   // humongous set which was not torn down in the first place. If
 238   // free_list_only is true, it will only rebuild the master free
 239   // list. It is called after a Full GC (free_list_only == false) or
 240   // after heap shrinking (free_list_only == true).
 241   void rebuild_region_sets(bool free_list_only);
 242 
 243   // Callback for region mapping changed events.
 244   G1RegionMappingChangedListener _listener;
 245 
 246   // The sequence of all heap regions in the heap.
 247   HeapRegionManager _hrm;
 248 
 249   // Class that handles the different kinds of allocations.
 250   G1Allocator* _allocator;
 251 
 252   // Statistics for each allocation context
 253   AllocationContextStats _allocation_context_stats;
 254 
 255   // PLAB sizing policy for survivors.
 256   PLABStats _survivor_plab_stats;
 257 
 258   // PLAB sizing policy for tenured objects.
 259   PLABStats _old_plab_stats;
 260 
 261   // It specifies whether we should attempt to expand the heap after a
 262   // region allocation failure. If heap expansion fails we set this to
 263   // false so that we don't re-attempt the heap expansion (it's likely
 264   // that subsequent expansion attempts will also fail if one fails).
 265   // Currently, it is only consulted during GC and it's reset at the
 266   // start of each GC.
 267   bool _expand_heap_after_alloc_failure;
 268 
 269   // It resets the mutator alloc region before new allocations can take place.
 270   void init_mutator_alloc_region();
 271 
 272   // It releases the mutator alloc region.
 273   void release_mutator_alloc_region();
 274 
 275   // It initializes the GC alloc regions at the start of a GC.
 276   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 277 
 278   // It releases the GC alloc regions at the end of a GC.
 279   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 280 
 281   // It does any cleanup that needs to be done on the GC alloc regions
 282   // before a Full GC.
 283   void abandon_gc_alloc_regions();
 284 
 285   // Helper for monitoring and management support.
 286   G1MonitoringSupport* _g1mm;
 287 
 288   // Records whether the region at the given index is kept live by roots or
 289   // references from the young generation.
 290   class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
 291    protected:
 292     bool default_value() const { return false; }
 293    public:
 294     void clear() { G1BiasedMappedArray<bool>::clear(); }
 295     void set_live(uint region) {
 296       set_by_index(region, true);
 297     }
 298     bool is_live(uint region) {
 299       return get_by_index(region);
 300     }
 301   };
 302 
 303   HumongousIsLiveBiasedMappedArray _humongous_is_live;
 304   // Stores whether during humongous object registration we found candidate regions.
 305   // If not, we can skip a few steps.
 306   bool _has_humongous_reclaim_candidates;
 307 
 308   volatile unsigned _gc_time_stamp;
 309 
 310   size_t* _surviving_young_words;
 311 
 312   G1HRPrinter _hr_printer;
 313 
 314   void setup_surviving_young_words();
 315   void update_surviving_young_words(size_t* surv_young_words);
 316   void cleanup_surviving_young_words();
 317 
 318   // It decides whether an explicit GC should start a concurrent cycle
 319   // instead of doing a STW GC. Currently, a concurrent cycle is
 320   // explicitly started if:
 321   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 322   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 323   // (c) cause == _g1_humongous_allocation
 324   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 325 
 326   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 327   // concurrent cycles) we have started.
 328   volatile uint _old_marking_cycles_started;
 329 
 330   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 331   // concurrent cycles) we have completed.
 332   volatile uint _old_marking_cycles_completed;
 333 
 334   bool _concurrent_cycle_started;
 335   bool _heap_summary_sent;
 336 
 337   // This is a non-product method that is helpful for testing. It is
 338   // called at the end of a GC and artificially expands the heap by
 339   // allocating a number of dead regions. This way we can induce very
 340   // frequent marking cycles and stress the cleanup / concurrent
 341   // cleanup code more (as all the regions that will be allocated by
 342   // this method will be found dead by the marking cycle).
 343   void allocate_dummy_regions() PRODUCT_RETURN;
 344 
 345   // Clear RSets after a compaction. It also resets the GC time stamps.
 346   void clear_rsets_post_compaction();
 347 
 348   // If the HR printer is active, dump the state of the regions in the
 349   // heap after a compaction.
 350   void print_hrm_post_compaction();
 351 
 352   double verify(bool guard, const char* msg);
 353   void verify_before_gc();
 354   void verify_after_gc();
 355 
 356   void log_gc_header();
 357   void log_gc_footer(double pause_time_sec);
 358 
 359   // These are macros so that, if the assert fires, we get the correct
 360   // line number, file, etc.
 361 
 362 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 363   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 364           (_extra_message_),                                                  \
 365           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 366           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 367           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 368 
 369 #define assert_heap_locked()                                                  \
 370   do {                                                                        \
 371     assert(Heap_lock->owned_by_self(),                                        \
 372            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 373   } while (0)
 374 
 375 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 376   do {                                                                        \
 377     assert(Heap_lock->owned_by_self() ||                                      \
 378            (SafepointSynchronize::is_at_safepoint() &&                        \
 379              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 380            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 381                                         "should be at a safepoint"));         \
 382   } while (0)
 383 
 384 #define assert_heap_locked_and_not_at_safepoint()                             \
 385   do {                                                                        \
 386     assert(Heap_lock->owned_by_self() &&                                      \
 387                                     !SafepointSynchronize::is_at_safepoint(), \
 388           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 389                                        "should not be at a safepoint"));      \
 390   } while (0)
 391 
 392 #define assert_heap_not_locked()                                              \
 393   do {                                                                        \
 394     assert(!Heap_lock->owned_by_self(),                                       \
 395         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 396   } while (0)
 397 
 398 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 399   do {                                                                        \
 400     assert(!Heap_lock->owned_by_self() &&                                     \
 401                                     !SafepointSynchronize::is_at_safepoint(), \
 402       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 403                                    "should not be at a safepoint"));          \
 404   } while (0)
 405 
 406 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 407   do {                                                                        \
 408     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 409               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 410            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 411   } while (0)
 412 
 413 #define assert_not_at_safepoint()                                             \
 414   do {                                                                        \
 415     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 416            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 417   } while (0)
 418 
 419 protected:
 420 
 421   // The young region list.
 422   YoungList*  _young_list;
 423 
 424   // The current policy object for the collector.
 425   G1CollectorPolicy* _g1_policy;
 426 
 427   // This is the second level of trying to allocate a new region. If
 428   // new_region() didn't find a region on the free_list, this call will
 429   // check whether there's anything available on the
 430   // secondary_free_list and/or wait for more regions to appear on
 431   // that list, if _free_regions_coming is set.
 432   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 433 
 434   // Try to allocate a single non-humongous HeapRegion sufficient for
 435   // an allocation of the given word_size. If do_expand is true,
 436   // attempt to expand the heap if necessary to satisfy the allocation
 437   // request. If the region is to be used as an old region or for a
 438   // humongous object, set is_old to true. If not, to false.
 439   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 440 
 441   // Initialize a contiguous set of free regions of length num_regions
 442   // and starting at index first so that they appear as a single
 443   // humongous region.
 444   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 445                                                       uint num_regions,
 446                                                       size_t word_size,
 447                                                       AllocationContext_t context);
 448 
 449   // Attempt to allocate a humongous object of the given size. Return
 450   // NULL if unsuccessful.
 451   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 452 
 453   // The following two methods, allocate_new_tlab() and
 454   // mem_allocate(), are the two main entry points from the runtime
 455   // into the G1's allocation routines. They have the following
 456   // assumptions:
 457   //
 458   // * They should both be called outside safepoints.
 459   //
 460   // * They should both be called without holding the Heap_lock.
 461   //
 462   // * All allocation requests for new TLABs should go to
 463   //   allocate_new_tlab().
 464   //
 465   // * All non-TLAB allocation requests should go to mem_allocate().
 466   //
 467   // * If either call cannot satisfy the allocation request using the
 468   //   current allocating region, they will try to get a new one. If
 469   //   this fails, they will attempt to do an evacuation pause and
 470   //   retry the allocation.
 471   //
 472   // * If all allocation attempts fail, even after trying to schedule
 473   //   an evacuation pause, allocate_new_tlab() will return NULL,
 474   //   whereas mem_allocate() will attempt a heap expansion and/or
 475   //   schedule a Full GC.
 476   //
 477   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 478   //   should never be called with word_size being humongous. All
 479   //   humongous allocation requests should go to mem_allocate() which
 480   //   will satisfy them with a special path.
 481 
 482   virtual HeapWord* allocate_new_tlab(size_t word_size);
 483 
 484   virtual HeapWord* mem_allocate(size_t word_size,
 485                                  bool*  gc_overhead_limit_was_exceeded);
 486 
 487   // The following three methods take a gc_count_before_ret
 488   // parameter which is used to return the GC count if the method
 489   // returns NULL. Given that we are required to read the GC count
 490   // while holding the Heap_lock, and these paths will take the
 491   // Heap_lock at some point, it's easier to get them to read the GC
 492   // count while holding the Heap_lock before they return NULL instead
 493   // of the caller (namely: mem_allocate()) having to also take the
 494   // Heap_lock just to read the GC count.
 495 
 496   // First-level mutator allocation attempt: try to allocate out of
 497   // the mutator alloc region without taking the Heap_lock. This
 498   // should only be used for non-humongous allocations.
 499   inline HeapWord* attempt_allocation(size_t word_size,
 500                                       uint* gc_count_before_ret,
 501                                       uint* gclocker_retry_count_ret);
 502 
 503   // Second-level mutator allocation attempt: take the Heap_lock and
 504   // retry the allocation attempt, potentially scheduling a GC
 505   // pause. This should only be used for non-humongous allocations.
 506   HeapWord* attempt_allocation_slow(size_t word_size,
 507                                     AllocationContext_t context,
 508                                     uint* gc_count_before_ret,
 509                                     uint* gclocker_retry_count_ret);
 510 
 511   // Takes the Heap_lock and attempts a humongous allocation. It can
 512   // potentially schedule a GC pause.
 513   HeapWord* attempt_allocation_humongous(size_t word_size,
 514                                          uint* gc_count_before_ret,
 515                                          uint* gclocker_retry_count_ret);
 516 
 517   // Allocation attempt that should be called during safepoints (e.g.,
 518   // at the end of a successful GC). expect_null_mutator_alloc_region
 519   // specifies whether the mutator alloc region is expected to be NULL
 520   // or not.
 521   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 522                                             AllocationContext_t context,
 523                                             bool expect_null_mutator_alloc_region);
 524 
 525   // It dirties the cards that cover the block so that so that the post
 526   // write barrier never queues anything when updating objects on this
 527   // block. It is assumed (and in fact we assert) that the block
 528   // belongs to a young region.
 529   inline void dirty_young_block(HeapWord* start, size_t word_size);
 530 
 531   // Allocate blocks during garbage collection. Will ensure an
 532   // allocation region, either by picking one or expanding the
 533   // heap, and then allocate a block of the given size. The block
 534   // may not be a humongous - it must fit into a single heap region.
 535   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 536                                           size_t word_size,
 537                                           AllocationContext_t context);
 538   // Ensure that no further allocations can happen in "r", bearing in mind
 539   // that parallel threads might be attempting allocations.
 540   void par_allocate_remaining_space(HeapRegion* r);
 541 
 542   // Allocation attempt during GC for a survivor object / PLAB.
 543   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 544                                                AllocationContext_t context);
 545 
 546   // Allocation attempt during GC for an old object / PLAB.
 547   inline HeapWord* old_attempt_allocation(size_t word_size,
 548                                           AllocationContext_t context);
 549 
 550   // These methods are the "callbacks" from the G1AllocRegion class.
 551 
 552   // For mutator alloc regions.
 553   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 554   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 555                                    size_t allocated_bytes);
 556 
 557   // For GC alloc regions.
 558   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 559                                   InCSetState dest);
 560   void retire_gc_alloc_region(HeapRegion* alloc_region,
 561                               size_t allocated_bytes, InCSetState dest);
 562 
 563   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 564   //   inspection request and should collect the entire heap
 565   // - if clear_all_soft_refs is true, all soft references should be
 566   //   cleared during the GC
 567   // - if explicit_gc is false, word_size describes the allocation that
 568   //   the GC should attempt (at least) to satisfy
 569   // - it returns false if it is unable to do the collection due to the
 570   //   GC locker being active, true otherwise
 571   bool do_collection(bool explicit_gc,
 572                      bool clear_all_soft_refs,
 573                      size_t word_size);
 574 
 575   // Callback from VM_G1CollectFull operation.
 576   // Perform a full collection.
 577   virtual void do_full_collection(bool clear_all_soft_refs);
 578 
 579   // Resize the heap if necessary after a full collection.  If this is
 580   // after a collect-for allocation, "word_size" is the allocation size,
 581   // and will be considered part of the used portion of the heap.
 582   void resize_if_necessary_after_full_collection(size_t word_size);
 583 
 584   // Callback from VM_G1CollectForAllocation operation.
 585   // This function does everything necessary/possible to satisfy a
 586   // failed allocation request (including collection, expansion, etc.)
 587   HeapWord* satisfy_failed_allocation(size_t word_size,
 588                                       AllocationContext_t context,
 589                                       bool* succeeded);
 590 
 591   // Attempting to expand the heap sufficiently
 592   // to support an allocation of the given "word_size".  If
 593   // successful, perform the allocation and return the address of the
 594   // allocated block, or else "NULL".
 595   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 596 
 597   // Process any reference objects discovered during
 598   // an incremental evacuation pause.
 599   void process_discovered_references(uint no_of_gc_workers);
 600 
 601   // Enqueue any remaining discovered references
 602   // after processing.
 603   void enqueue_discovered_references(uint no_of_gc_workers);
 604 
 605 public:
 606 
 607   G1Allocator* allocator() {
 608     return _allocator;
 609   }
 610 
 611   G1MonitoringSupport* g1mm() {
 612     assert(_g1mm != NULL, "should have been initialized");
 613     return _g1mm;
 614   }
 615 
 616   // Expand the garbage-first heap by at least the given size (in bytes!).
 617   // Returns true if the heap was expanded by the requested amount;
 618   // false otherwise.
 619   // (Rounds up to a HeapRegion boundary.)
 620   bool expand(size_t expand_bytes);
 621 
 622   // Returns the PLAB statistics for a given destination.
 623   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 624 
 625   // Determines PLAB size for a given destination.
 626   inline size_t desired_plab_sz(InCSetState dest);
 627 
 628   inline AllocationContextStats& allocation_context_stats();
 629 
 630   // Do anything common to GC's.
 631   virtual void gc_prologue(bool full);
 632   virtual void gc_epilogue(bool full);
 633 
 634   inline void set_humongous_is_live(oop obj);
 635 
 636   bool humongous_is_live(uint region) {
 637     return _humongous_is_live.is_live(region);
 638   }
 639 
 640   // Returns whether the given region (which must be a humongous (start) region)
 641   // is to be considered conservatively live regardless of any other conditions.
 642   bool humongous_region_is_always_live(uint index);
 643   // Returns whether the given region (which must be a humongous (start) region)
 644   // is considered a candidate for eager reclamation.
 645   bool humongous_region_is_candidate(uint index);
 646   // Register the given region to be part of the collection set.
 647   inline void register_humongous_region_with_in_cset_fast_test(uint index);
 648   // Register regions with humongous objects (actually on the start region) in
 649   // the in_cset_fast_test table.
 650   void register_humongous_regions_with_in_cset_fast_test();
 651   // We register a region with the fast "in collection set" test. We
 652   // simply set to true the array slot corresponding to this region.
 653   void register_young_region_with_in_cset_fast_test(HeapRegion* r) {
 654     _in_cset_fast_test.set_in_young(r->hrm_index());
 655   }
 656   void register_old_region_with_in_cset_fast_test(HeapRegion* r) {
 657     _in_cset_fast_test.set_in_old(r->hrm_index());
 658   }
 659 
 660   // This is a fast test on whether a reference points into the
 661   // collection set or not. Assume that the reference
 662   // points into the heap.
 663   inline bool in_cset_fast_test(oop obj);
 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   // Applies "scan_non_heap_roots" to roots outside the heap,
 785   // "scan_rs" to roots inside the heap (having done "set_region" to
 786   // indicate the region in which the root resides),
 787   // and does "scan_metadata" If "scan_rs" is
 788   // NULL, then this step is skipped.  The "worker_i"
 789   // param is for use with parallel roots processing, and should be
 790   // the "i" of the calling parallel worker thread's work(i) function.
 791   // In the sequential case this param will be ignored.
 792   void g1_process_roots(OopClosure* scan_non_heap_roots,
 793                         OopClosure* scan_non_heap_weak_roots,
 794                         G1ParPushHeapRSClosure* scan_rs,
 795                         CLDClosure* scan_strong_clds,
 796                         CLDClosure* scan_weak_clds,
 797                         CodeBlobClosure* scan_strong_code,
 798                         uint worker_i);

 799 
 800   // The concurrent marker (and the thread it runs in.)
 801   ConcurrentMark* _cm;
 802   ConcurrentMarkThread* _cmThread;
 803   bool _mark_in_progress;
 804 
 805   // The concurrent refiner.
 806   ConcurrentG1Refine* _cg1r;
 807 
 808   // The parallel task queues
 809   RefToScanQueueSet *_task_queues;
 810 
 811   // True iff a evacuation has failed in the current collection.
 812   bool _evacuation_failed;
 813 
 814   EvacuationFailedInfo* _evacuation_failed_info_array;
 815 
 816   // Failed evacuations cause some logical from-space objects to have
 817   // forwarding pointers to themselves.  Reset them.
 818   void remove_self_forwarding_pointers();
 819 
 820   // Together, these store an object with a preserved mark, and its mark value.
 821   Stack<oop, mtGC>     _objs_with_preserved_marks;
 822   Stack<markOop, mtGC> _preserved_marks_of_objs;
 823 
 824   // Preserve the mark of "obj", if necessary, in preparation for its mark
 825   // word being overwritten with a self-forwarding-pointer.
 826   void preserve_mark_if_necessary(oop obj, markOop m);
 827 
 828   // The stack of evac-failure objects left to be scanned.
 829   GrowableArray<oop>*    _evac_failure_scan_stack;
 830   // The closure to apply to evac-failure objects.
 831 
 832   OopsInHeapRegionClosure* _evac_failure_closure;
 833   // Set the field above.
 834   void
 835   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 836     _evac_failure_closure = evac_failure_closure;
 837   }
 838 
 839   // Push "obj" on the scan stack.
 840   void push_on_evac_failure_scan_stack(oop obj);
 841   // Process scan stack entries until the stack is empty.
 842   void drain_evac_failure_scan_stack();
 843   // True iff an invocation of "drain_scan_stack" is in progress; to
 844   // prevent unnecessary recursion.
 845   bool _drain_in_progress;
 846 
 847   // Do any necessary initialization for evacuation-failure handling.
 848   // "cl" is the closure that will be used to process evac-failure
 849   // objects.
 850   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 851   // Do any necessary cleanup for evacuation-failure handling data
 852   // structures.
 853   void finalize_for_evac_failure();
 854 
 855   // An attempt to evacuate "obj" has failed; take necessary steps.
 856   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 857   void handle_evacuation_failure_common(oop obj, markOop m);
 858 
 859 #ifndef PRODUCT
 860   // Support for forcing evacuation failures. Analogous to
 861   // PromotionFailureALot for the other collectors.
 862 
 863   // Records whether G1EvacuationFailureALot should be in effect
 864   // for the current GC
 865   bool _evacuation_failure_alot_for_current_gc;
 866 
 867   // Used to record the GC number for interval checking when
 868   // determining whether G1EvaucationFailureALot is in effect
 869   // for the current GC.
 870   size_t _evacuation_failure_alot_gc_number;
 871 
 872   // Count of the number of evacuations between failures.
 873   volatile size_t _evacuation_failure_alot_count;
 874 
 875   // Set whether G1EvacuationFailureALot should be in effect
 876   // for the current GC (based upon the type of GC and which
 877   // command line flags are set);
 878   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 879                                                   bool during_initial_mark,
 880                                                   bool during_marking);
 881 
 882   inline void set_evacuation_failure_alot_for_current_gc();
 883 
 884   // Return true if it's time to cause an evacuation failure.
 885   inline bool evacuation_should_fail();
 886 
 887   // Reset the G1EvacuationFailureALot counters.  Should be called at
 888   // the end of an evacuation pause in which an evacuation failure occurred.
 889   inline void reset_evacuation_should_fail();
 890 #endif // !PRODUCT
 891 
 892   // ("Weak") Reference processing support.
 893   //
 894   // G1 has 2 instances of the reference processor class. One
 895   // (_ref_processor_cm) handles reference object discovery
 896   // and subsequent processing during concurrent marking cycles.
 897   //
 898   // The other (_ref_processor_stw) handles reference object
 899   // discovery and processing during full GCs and incremental
 900   // evacuation pauses.
 901   //
 902   // During an incremental pause, reference discovery will be
 903   // temporarily disabled for _ref_processor_cm and will be
 904   // enabled for _ref_processor_stw. At the end of the evacuation
 905   // pause references discovered by _ref_processor_stw will be
 906   // processed and discovery will be disabled. The previous
 907   // setting for reference object discovery for _ref_processor_cm
 908   // will be re-instated.
 909   //
 910   // At the start of marking:
 911   //  * Discovery by the CM ref processor is verified to be inactive
 912   //    and it's discovered lists are empty.
 913   //  * Discovery by the CM ref processor is then enabled.
 914   //
 915   // At the end of marking:
 916   //  * Any references on the CM ref processor's discovered
 917   //    lists are processed (possibly MT).
 918   //
 919   // At the start of full GC we:
 920   //  * Disable discovery by the CM ref processor and
 921   //    empty CM ref processor's discovered lists
 922   //    (without processing any entries).
 923   //  * Verify that the STW ref processor is inactive and it's
 924   //    discovered lists are empty.
 925   //  * Temporarily set STW ref processor discovery as single threaded.
 926   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 927   //    field.
 928   //  * Finally enable discovery by the STW ref processor.
 929   //
 930   // The STW ref processor is used to record any discovered
 931   // references during the full GC.
 932   //
 933   // At the end of a full GC we:
 934   //  * Enqueue any reference objects discovered by the STW ref processor
 935   //    that have non-live referents. This has the side-effect of
 936   //    making the STW ref processor inactive by disabling discovery.
 937   //  * Verify that the CM ref processor is still inactive
 938   //    and no references have been placed on it's discovered
 939   //    lists (also checked as a precondition during initial marking).
 940 
 941   // The (stw) reference processor...
 942   ReferenceProcessor* _ref_processor_stw;
 943 
 944   STWGCTimer* _gc_timer_stw;
 945   ConcurrentGCTimer* _gc_timer_cm;
 946 
 947   G1OldTracer* _gc_tracer_cm;
 948   G1NewTracer* _gc_tracer_stw;
 949 
 950   // During reference object discovery, the _is_alive_non_header
 951   // closure (if non-null) is applied to the referent object to
 952   // determine whether the referent is live. If so then the
 953   // reference object does not need to be 'discovered' and can
 954   // be treated as a regular oop. This has the benefit of reducing
 955   // the number of 'discovered' reference objects that need to
 956   // be processed.
 957   //
 958   // Instance of the is_alive closure for embedding into the
 959   // STW reference processor as the _is_alive_non_header field.
 960   // Supplying a value for the _is_alive_non_header field is
 961   // optional but doing so prevents unnecessary additions to
 962   // the discovered lists during reference discovery.
 963   G1STWIsAliveClosure _is_alive_closure_stw;
 964 
 965   // The (concurrent marking) reference processor...
 966   ReferenceProcessor* _ref_processor_cm;
 967 
 968   // Instance of the concurrent mark is_alive closure for embedding
 969   // into the Concurrent Marking reference processor as the
 970   // _is_alive_non_header field. Supplying a value for the
 971   // _is_alive_non_header field is optional but doing so prevents
 972   // unnecessary additions to the discovered lists during reference
 973   // discovery.
 974   G1CMIsAliveClosure _is_alive_closure_cm;
 975 
 976   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 977   HeapRegion** _worker_cset_start_region;
 978 
 979   // Time stamp to validate the regions recorded in the cache
 980   // used by G1CollectedHeap::start_cset_region_for_worker().
 981   // The heap region entry for a given worker is valid iff
 982   // the associated time stamp value matches the current value
 983   // of G1CollectedHeap::_gc_time_stamp.
 984   uint* _worker_cset_start_region_time_stamp;
 985 






 986   enum G1H_process_roots_tasks {
 987     G1H_PS_filter_satb_buffers,

 988     G1H_PS_refProcessor_oops_do,


 989     // Leave this one last.
 990     G1H_PS_NumElements
 991   };
 992 
 993   SubTasksDone* _process_strong_tasks;
 994 
 995   volatile bool _free_regions_coming;
 996 
 997 public:
 998 
 999   SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
1000 
1001   void set_refine_cte_cl_concurrency(bool concurrent);
1002 
1003   RefToScanQueue *task_queue(int i) const;
1004 
1005   // A set of cards where updates happened during the GC
1006   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
1007 
1008   // A DirtyCardQueueSet that is used to hold cards that contain
1009   // references into the current collection set. This is used to
1010   // update the remembered sets of the regions in the collection
1011   // set in the event of an evacuation failure.
1012   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
1013         { return _into_cset_dirty_card_queue_set; }
1014 
1015   // Create a G1CollectedHeap with the specified policy.
1016   // Must call the initialize method afterwards.
1017   // May not return if something goes wrong.
1018   G1CollectedHeap(G1CollectorPolicy* policy);
1019 
1020   // Initialize the G1CollectedHeap to have the initial and
1021   // maximum sizes and remembered and barrier sets
1022   // specified by the policy object.
1023   jint initialize();
1024 
1025   virtual void stop();
1026 
1027   // Return the (conservative) maximum heap alignment for any G1 heap
1028   static size_t conservative_max_heap_alignment();
1029 
1030   // Initialize weak reference processing.
1031   virtual void ref_processing_init();
1032 
1033   void set_par_threads(uint t) {
1034     SharedHeap::set_par_threads(t);
1035     // Done in SharedHeap but oddly there are
1036     // two _process_strong_tasks's in a G1CollectedHeap
1037     // so do it here too.
1038     _process_strong_tasks->set_n_threads(t);
1039   }
1040 
1041   // Set _n_par_threads according to a policy TBD.
1042   void set_par_threads();
1043 
1044   void set_n_termination(int t) {
1045     _process_strong_tasks->set_n_threads(t);
1046   }
1047 
1048   virtual CollectedHeap::Name kind() const {
1049     return CollectedHeap::G1CollectedHeap;
1050   }
1051 
1052   // The current policy object for the collector.
1053   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
1054 
1055   virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) g1_policy(); }
1056 
1057   // Adaptive size policy.  No such thing for g1.
1058   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1059 
1060   // The rem set and barrier set.
1061   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1062 
1063   unsigned get_gc_time_stamp() {
1064     return _gc_time_stamp;
1065   }
1066 
1067   inline void reset_gc_time_stamp();
1068 
1069   void check_gc_time_stamps() PRODUCT_RETURN;
1070 
1071   inline void increment_gc_time_stamp();
1072 
1073   // Reset the given region's GC timestamp. If it's starts humongous,
1074   // also reset the GC timestamp of its corresponding
1075   // continues humongous regions too.
1076   void reset_gc_time_stamps(HeapRegion* hr);
1077 
1078   void iterate_dirty_card_closure(CardTableEntryClosure* cl,
1079                                   DirtyCardQueue* into_cset_dcq,
1080                                   bool concurrent, uint worker_i);
1081 
1082   // The shared block offset table array.
1083   G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
1084 
1085   // Reference Processing accessors
1086 
1087   // The STW reference processor....
1088   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1089 
1090   // The Concurrent Marking reference processor...
1091   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1092 
1093   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1094   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1095 
1096   virtual size_t capacity() const;
1097   virtual size_t used() const;
1098   // This should be called when we're not holding the heap lock. The
1099   // result might be a bit inaccurate.
1100   size_t used_unlocked() const;
1101   size_t recalculate_used() const;
1102 
1103   // These virtual functions do the actual allocation.
1104   // Some heaps may offer a contiguous region for shared non-blocking
1105   // allocation, via inlined code (by exporting the address of the top and
1106   // end fields defining the extent of the contiguous allocation region.)
1107   // But G1CollectedHeap doesn't yet support this.
1108 
1109   virtual bool is_maximal_no_gc() const {
1110     return _hrm.available() == 0;
1111   }
1112 
1113   // The current number of regions in the heap.
1114   uint num_regions() const { return _hrm.length(); }
1115 
1116   // The max number of regions in the heap.
1117   uint max_regions() const { return _hrm.max_length(); }
1118 
1119   // The number of regions that are completely free.
1120   uint num_free_regions() const { return _hrm.num_free_regions(); }
1121 
1122   // The number of regions that are not completely free.
1123   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1124 
1125   void verify_not_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1126   void verify_dirty_region(HeapRegion* hr) PRODUCT_RETURN;
1127   void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
1128   void verify_dirty_young_regions() PRODUCT_RETURN;
1129 
1130 #ifndef PRODUCT
1131   // Make sure that the given bitmap has no marked objects in the
1132   // range [from,limit). If it does, print an error message and return
1133   // false. Otherwise, just return true. bitmap_name should be "prev"
1134   // or "next".
1135   bool verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
1136                                 HeapWord* from, HeapWord* limit);
1137 
1138   // Verify that the prev / next bitmap range [tams,end) for the given
1139   // region has no marks. Return true if all is well, false if errors
1140   // are detected.
1141   bool verify_bitmaps(const char* caller, HeapRegion* hr);
1142 #endif // PRODUCT
1143 
1144   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1145   // the given region do not have any spurious marks. If errors are
1146   // detected, print appropriate error messages and crash.
1147   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1148 
1149   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1150   // have any spurious marks. If errors are detected, print
1151   // appropriate error messages and crash.
1152   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1153 
1154   // Do sanity check on the contents of the in-cset fast test table.
1155   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1156 
1157   // verify_region_sets() performs verification over the region
1158   // lists. It will be compiled in the product code to be used when
1159   // necessary (i.e., during heap verification).
1160   void verify_region_sets();
1161 
1162   // verify_region_sets_optional() is planted in the code for
1163   // list verification in non-product builds (and it can be enabled in
1164   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1165 #if HEAP_REGION_SET_FORCE_VERIFY
1166   void verify_region_sets_optional() {
1167     verify_region_sets();
1168   }
1169 #else // HEAP_REGION_SET_FORCE_VERIFY
1170   void verify_region_sets_optional() { }
1171 #endif // HEAP_REGION_SET_FORCE_VERIFY
1172 
1173 #ifdef ASSERT
1174   bool is_on_master_free_list(HeapRegion* hr) {
1175     return _hrm.is_free(hr);
1176   }
1177 #endif // ASSERT
1178 
1179   // Wrapper for the region list operations that can be called from
1180   // methods outside this class.
1181 
1182   void secondary_free_list_add(FreeRegionList* list) {
1183     _secondary_free_list.add_ordered(list);
1184   }
1185 
1186   void append_secondary_free_list() {
1187     _hrm.insert_list_into_free_list(&_secondary_free_list);
1188   }
1189 
1190   void append_secondary_free_list_if_not_empty_with_lock() {
1191     // If the secondary free list looks empty there's no reason to
1192     // take the lock and then try to append it.
1193     if (!_secondary_free_list.is_empty()) {
1194       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1195       append_secondary_free_list();
1196     }
1197   }
1198 
1199   inline void old_set_remove(HeapRegion* hr);
1200 
1201   size_t non_young_capacity_bytes() {
1202     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1203   }
1204 
1205   void set_free_regions_coming();
1206   void reset_free_regions_coming();
1207   bool free_regions_coming() { return _free_regions_coming; }
1208   void wait_while_free_regions_coming();
1209 
1210   // Determine whether the given region is one that we are using as an
1211   // old GC alloc region.
1212   bool is_old_gc_alloc_region(HeapRegion* hr) {
1213     return _allocator->is_retained_old_region(hr);
1214   }
1215 
1216   // Perform a collection of the heap; intended for use in implementing
1217   // "System.gc".  This probably implies as full a collection as the
1218   // "CollectedHeap" supports.
1219   virtual void collect(GCCause::Cause cause);
1220 
1221   // The same as above but assume that the caller holds the Heap_lock.
1222   void collect_locked(GCCause::Cause cause);
1223 
1224   virtual bool copy_allocation_context_stats(const jint* contexts,
1225                                              jlong* totals,
1226                                              jbyte* accuracy,
1227                                              jint len);
1228 
1229   // True iff an evacuation has failed in the most-recent collection.
1230   bool evacuation_failed() { return _evacuation_failed; }
1231 
1232   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1233   void prepend_to_freelist(FreeRegionList* list);
1234   void decrement_summary_bytes(size_t bytes);
1235 
1236   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1237   virtual bool is_in(const void* p) const;
1238 #ifdef ASSERT
1239   // Returns whether p is in one of the available areas of the heap. Slow but
1240   // extensive version.
1241   bool is_in_exact(const void* p) const;
1242 #endif
1243 
1244   // Return "TRUE" iff the given object address is within the collection
1245   // set. Slow implementation.
1246   inline bool obj_in_cs(oop obj);
1247 
1248   inline bool is_in_cset(oop obj);
1249 
1250   inline bool is_in_cset_or_humongous(const oop obj);
1251 
1252  private:
1253   // This array is used for a quick test on whether a reference points into
1254   // the collection set or not. Each of the array's elements denotes whether the
1255   // corresponding region is in the collection set or not.
1256   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1257 
1258  public:
1259 
1260   inline InCSetState in_cset_state(const oop obj);
1261 
1262   // Return "TRUE" iff the given object address is in the reserved
1263   // region of g1.
1264   bool is_in_g1_reserved(const void* p) const {
1265     return _hrm.reserved().contains(p);
1266   }
1267 
1268   // Returns a MemRegion that corresponds to the space that has been
1269   // reserved for the heap
1270   MemRegion g1_reserved() const {
1271     return _hrm.reserved();
1272   }
1273 
1274   virtual bool is_in_closed_subset(const void* p) const;
1275 
1276   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1277     return (G1SATBCardTableLoggingModRefBS*) barrier_set();
1278   }
1279 
1280   // This resets the card table to all zeros.  It is used after
1281   // a collection pause which used the card table to claim cards.
1282   void cleanUpCardTable();
1283 
1284   // Iteration functions.
1285 
1286   // Iterate over all the ref-containing fields of all objects, calling
1287   // "cl.do_oop" on each.
1288   virtual void oop_iterate(ExtendedOopClosure* cl);
1289 
1290   // Iterate over all objects, calling "cl.do_object" on each.
1291   virtual void object_iterate(ObjectClosure* cl);
1292 
1293   virtual void safe_object_iterate(ObjectClosure* cl) {
1294     object_iterate(cl);
1295   }
1296 
1297   // Iterate over all spaces in use in the heap, in ascending address order.
1298   virtual void space_iterate(SpaceClosure* cl);
1299 
1300   // Iterate over heap regions, in address order, terminating the
1301   // iteration early if the "doHeapRegion" method returns "true".
1302   void heap_region_iterate(HeapRegionClosure* blk) const;
1303 
1304   // Return the region with the given index. It assumes the index is valid.
1305   inline HeapRegion* region_at(uint index) const;
1306 
1307   // Calculate the region index of the given address. Given address must be
1308   // within the heap.
1309   inline uint addr_to_region(HeapWord* addr) const;
1310 
1311   inline HeapWord* bottom_addr_for_region(uint index) const;
1312 
1313   // Iterate over the heap regions in parallel. Assumes that this will be called
1314   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1315   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1316   // to each of the regions, by attempting to claim the region using the
1317   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1318   // region. The concurrent argument should be set to true if iteration is
1319   // performed concurrently, during which no assumptions are made for consistent
1320   // attributes of the heap regions (as they might be modified while iterating).
1321   void heap_region_par_iterate(HeapRegionClosure* cl,
1322                                uint worker_id,
1323                                HeapRegionClaimer* hrclaimer,
1324                                bool concurrent = false) const;
1325 
1326   // Clear the cached cset start regions and (more importantly)
1327   // the time stamps. Called when we reset the GC time stamp.
1328   void clear_cset_start_regions();
1329 
1330   // Given the id of a worker, obtain or calculate a suitable
1331   // starting region for iterating over the current collection set.
1332   HeapRegion* start_cset_region_for_worker(uint worker_i);
1333 
1334   // Iterate over the regions (if any) in the current collection set.
1335   void collection_set_iterate(HeapRegionClosure* blk);
1336 
1337   // As above but starting from region r
1338   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1339 
1340   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1341 
1342   // A CollectedHeap will contain some number of spaces.  This finds the
1343   // space containing a given address, or else returns NULL.
1344   virtual Space* space_containing(const void* addr) const;
1345 
1346   // Returns the HeapRegion that contains addr. addr must not be NULL.
1347   template <class T>
1348   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1349 
1350   // Returns the HeapRegion that contains addr. addr must not be NULL.
1351   // If addr is within a humongous continues region, it returns its humongous start region.
1352   template <class T>
1353   inline HeapRegion* heap_region_containing(const T addr) const;
1354 
1355   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1356   // each address in the (reserved) heap is a member of exactly
1357   // one block.  The defining characteristic of a block is that it is
1358   // possible to find its size, and thus to progress forward to the next
1359   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1360   // represent Java objects, or they might be free blocks in a
1361   // free-list-based heap (or subheap), as long as the two kinds are
1362   // distinguishable and the size of each is determinable.
1363 
1364   // Returns the address of the start of the "block" that contains the
1365   // address "addr".  We say "blocks" instead of "object" since some heaps
1366   // may not pack objects densely; a chunk may either be an object or a
1367   // non-object.
1368   virtual HeapWord* block_start(const void* addr) const;
1369 
1370   // Requires "addr" to be the start of a chunk, and returns its size.
1371   // "addr + size" is required to be the start of a new chunk, or the end
1372   // of the active area of the heap.
1373   virtual size_t block_size(const HeapWord* addr) const;
1374 
1375   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1376   // the block is an object.
1377   virtual bool block_is_obj(const HeapWord* addr) const;
1378 
1379   // Does this heap support heap inspection? (+PrintClassHistogram)
1380   virtual bool supports_heap_inspection() const { return true; }
1381 
1382   // Section on thread-local allocation buffers (TLABs)
1383   // See CollectedHeap for semantics.
1384 
1385   bool supports_tlab_allocation() const;
1386   size_t tlab_capacity(Thread* ignored) const;
1387   size_t tlab_used(Thread* ignored) const;
1388   size_t max_tlab_size() const;
1389   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1390 
1391   // Can a compiler initialize a new object without store barriers?
1392   // This permission only extends from the creation of a new object
1393   // via a TLAB up to the first subsequent safepoint. If such permission
1394   // is granted for this heap type, the compiler promises to call
1395   // defer_store_barrier() below on any slow path allocation of
1396   // a new object for which such initializing store barriers will
1397   // have been elided. G1, like CMS, allows this, but should be
1398   // ready to provide a compensating write barrier as necessary
1399   // if that storage came out of a non-young region. The efficiency
1400   // of this implementation depends crucially on being able to
1401   // answer very efficiently in constant time whether a piece of
1402   // storage in the heap comes from a young region or not.
1403   // See ReduceInitialCardMarks.
1404   virtual bool can_elide_tlab_store_barriers() const {
1405     return true;
1406   }
1407 
1408   virtual bool card_mark_must_follow_store() const {
1409     return true;
1410   }
1411 
1412   inline bool is_in_young(const oop obj);
1413 
1414 #ifdef ASSERT
1415   virtual bool is_in_partial_collection(const void* p);
1416 #endif
1417 
1418   virtual bool is_scavengable(const void* addr);
1419 
1420   // We don't need barriers for initializing stores to objects
1421   // in the young gen: for the SATB pre-barrier, there is no
1422   // pre-value that needs to be remembered; for the remembered-set
1423   // update logging post-barrier, we don't maintain remembered set
1424   // information for young gen objects.
1425   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1426 
1427   // Returns "true" iff the given word_size is "very large".
1428   static bool is_humongous(size_t word_size) {
1429     // Note this has to be strictly greater-than as the TLABs
1430     // are capped at the humongous threshold and we want to
1431     // ensure that we don't try to allocate a TLAB as
1432     // humongous and that we don't allocate a humongous
1433     // object in a TLAB.
1434     return word_size > _humongous_object_threshold_in_words;
1435   }
1436 
1437   // Update mod union table with the set of dirty cards.
1438   void updateModUnion();
1439 
1440   // Set the mod union bits corresponding to the given memRegion.  Note
1441   // that this is always a safe operation, since it doesn't clear any
1442   // bits.
1443   void markModUnionRange(MemRegion mr);
1444 
1445   // Records the fact that a marking phase is no longer in progress.
1446   void set_marking_complete() {
1447     _mark_in_progress = false;
1448   }
1449   void set_marking_started() {
1450     _mark_in_progress = true;
1451   }
1452   bool mark_in_progress() {
1453     return _mark_in_progress;
1454   }
1455 
1456   // Print the maximum heap capacity.
1457   virtual size_t max_capacity() const;
1458 
1459   virtual jlong millis_since_last_gc();
1460 
1461 
1462   // Convenience function to be used in situations where the heap type can be
1463   // asserted to be this type.
1464   static G1CollectedHeap* heap();
1465 
1466   void set_region_short_lived_locked(HeapRegion* hr);
1467   // add appropriate methods for any other surv rate groups
1468 
1469   YoungList* young_list() const { return _young_list; }
1470 
1471   // debugging
1472   bool check_young_list_well_formed() {
1473     return _young_list->check_list_well_formed();
1474   }
1475 
1476   bool check_young_list_empty(bool check_heap,
1477                               bool check_sample = true);
1478 
1479   // *** Stuff related to concurrent marking.  It's not clear to me that so
1480   // many of these need to be public.
1481 
1482   // The functions below are helper functions that a subclass of
1483   // "CollectedHeap" can use in the implementation of its virtual
1484   // functions.
1485   // This performs a concurrent marking of the live objects in a
1486   // bitmap off to the side.
1487   void doConcurrentMark();
1488 
1489   bool isMarkedPrev(oop obj) const;
1490   bool isMarkedNext(oop obj) const;
1491 
1492   // Determine if an object is dead, given the object and also
1493   // the region to which the object belongs. An object is dead
1494   // iff a) it was not allocated since the last mark and b) it
1495   // is not marked.
1496   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1497     return
1498       !hr->obj_allocated_since_prev_marking(obj) &&
1499       !isMarkedPrev(obj);
1500   }
1501 
1502   // This function returns true when an object has been
1503   // around since the previous marking and hasn't yet
1504   // been marked during this marking.
1505   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1506     return
1507       !hr->obj_allocated_since_next_marking(obj) &&
1508       !isMarkedNext(obj);
1509   }
1510 
1511   // Determine if an object is dead, given only the object itself.
1512   // This will find the region to which the object belongs and
1513   // then call the region version of the same function.
1514 
1515   // Added if it is NULL it isn't dead.
1516 
1517   inline bool is_obj_dead(const oop obj) const;
1518 
1519   inline bool is_obj_ill(const oop obj) const;
1520 
1521   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1522   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1523   bool is_marked(oop obj, VerifyOption vo);
1524   const char* top_at_mark_start_str(VerifyOption vo);
1525 
1526   ConcurrentMark* concurrent_mark() const { return _cm; }
1527 
1528   // Refinement
1529 
1530   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1531 
1532   // The dirty cards region list is used to record a subset of regions
1533   // whose cards need clearing. The list if populated during the
1534   // remembered set scanning and drained during the card table
1535   // cleanup. Although the methods are reentrant, population/draining
1536   // phases must not overlap. For synchronization purposes the last
1537   // element on the list points to itself.
1538   HeapRegion* _dirty_cards_region_list;
1539   void push_dirty_cards_region(HeapRegion* hr);
1540   HeapRegion* pop_dirty_cards_region();
1541 
1542   // Optimized nmethod scanning support routines
1543 
1544   // Register the given nmethod with the G1 heap.
1545   virtual void register_nmethod(nmethod* nm);
1546 
1547   // Unregister the given nmethod from the G1 heap.
1548   virtual void unregister_nmethod(nmethod* nm);
1549 
1550   // Free up superfluous code root memory.
1551   void purge_code_root_memory();
1552 
1553   // Rebuild the strong code root lists for each region
1554   // after a full GC.
1555   void rebuild_strong_code_roots();
1556 
1557   // Delete entries for dead interned string and clean up unreferenced symbols
1558   // in symbol table, possibly in parallel.
1559   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1560 
1561   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1562   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1563 
1564   // Redirty logged cards in the refinement queue.
1565   void redirty_logged_cards();
1566   // Verification
1567 
1568   // The following is just to alert the verification code
1569   // that a full collection has occurred and that the
1570   // remembered sets are no longer up to date.
1571   bool _full_collection;
1572   void set_full_collection() { _full_collection = true;}
1573   void clear_full_collection() {_full_collection = false;}
1574   bool full_collection() {return _full_collection;}
1575 
1576   // Perform any cleanup actions necessary before allowing a verification.
1577   virtual void prepare_for_verify();
1578 
1579   // Perform verification.
1580 
1581   // vo == UsePrevMarking  -> use "prev" marking information,
1582   // vo == UseNextMarking -> use "next" marking information
1583   // vo == UseMarkWord    -> use the mark word in the object header
1584   //
1585   // NOTE: Only the "prev" marking information is guaranteed to be
1586   // consistent most of the time, so most calls to this should use
1587   // vo == UsePrevMarking.
1588   // Currently, there is only one case where this is called with
1589   // vo == UseNextMarking, which is to verify the "next" marking
1590   // information at the end of remark.
1591   // Currently there is only one place where this is called with
1592   // vo == UseMarkWord, which is to verify the marking during a
1593   // full GC.
1594   void verify(bool silent, VerifyOption vo);
1595 
1596   // Override; it uses the "prev" marking information
1597   virtual void verify(bool silent);
1598 
1599   // The methods below are here for convenience and dispatch the
1600   // appropriate method depending on value of the given VerifyOption
1601   // parameter. The values for that parameter, and their meanings,
1602   // are the same as those above.
1603 
1604   bool is_obj_dead_cond(const oop obj,
1605                         const HeapRegion* hr,
1606                         const VerifyOption vo) const;
1607 
1608   bool is_obj_dead_cond(const oop obj,
1609                         const VerifyOption vo) const;
1610 
1611   // Printing
1612 
1613   virtual void print_on(outputStream* st) const;
1614   virtual void print_extended_on(outputStream* st) const;
1615   virtual void print_on_error(outputStream* st) const;
1616 
1617   virtual void print_gc_threads_on(outputStream* st) const;
1618   virtual void gc_threads_do(ThreadClosure* tc) const;
1619 
1620   // Override
1621   void print_tracing_info() const;
1622 
1623   // The following two methods are helpful for debugging RSet issues.
1624   void print_cset_rsets() PRODUCT_RETURN;
1625   void print_all_rsets() PRODUCT_RETURN;
1626 
1627 public:
1628   size_t pending_card_num();
1629   size_t cards_scanned();
1630 
1631 protected:
1632   size_t _max_heap_capacity;
1633 };
1634 
1635 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---