rev 8024 : imported patch event1
* * *
imported patch event2

   1 /*
   2  * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc_implementation/g1/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1Allocator.hpp"
  30 #include "gc_implementation/g1/concurrentMark.hpp"
  31 #include "gc_implementation/g1/evacuationInfo.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.hpp"
  33 #include "gc_implementation/g1/g1BiasedArray.hpp"
  34 #include "gc_implementation/g1/g1HRPrinter.hpp"
  35 #include "gc_implementation/g1/g1InCSetState.hpp"
  36 #include "gc_implementation/g1/g1MonitoringSupport.hpp"
  37 #include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
  38 #include "gc_implementation/g1/g1YCTypes.hpp"
  39 #include "gc_implementation/g1/heapRegionManager.hpp"
  40 #include "gc_implementation/g1/heapRegionSet.hpp"
  41 #include "gc_implementation/shared/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         eden_length() { return length() - survivor_length(); }
 114   uint         survivor_length() { return _survivor_length; }
 115 
 116   // Currently we do not keep track of the used byte sum for the
 117   // young list and the survivors and it'd be quite a lot of work to
 118   // do so. When we'll eventually replace the young list with
 119   // instances of HeapRegionLinkedList we'll get that for free. So,
 120   // we'll report the more accurate information then.
 121   size_t       eden_used_bytes() {
 122     assert(length() >= survivor_length(), "invariant");
 123     return (size_t) eden_length() * HeapRegion::GrainBytes;
 124   }
 125   size_t       survivor_used_bytes() {
 126     return (size_t) survivor_length() * HeapRegion::GrainBytes;
 127   }
 128 
 129   void rs_length_sampling_init();
 130   bool rs_length_sampling_more();
 131   void rs_length_sampling_next();
 132 
 133   void reset_sampled_info() {
 134     _last_sampled_rs_lengths =   0;
 135   }
 136   size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
 137 
 138   // for development purposes
 139   void reset_auxilary_lists();
 140   void clear() { _head = NULL; _length = 0; }
 141 
 142   void clear_survivors() {
 143     _survivor_head    = NULL;
 144     _survivor_tail    = NULL;
 145     _survivor_length  = 0;
 146   }
 147 
 148   HeapRegion* first_region() { return _head; }
 149   HeapRegion* first_survivor_region() { return _survivor_head; }
 150   HeapRegion* last_survivor_region() { return _survivor_tail; }
 151 
 152   // debugging
 153   bool          check_list_well_formed();
 154   bool          check_list_empty(bool check_sample = true);
 155   void          print();
 156 };
 157 
 158 // The G1 STW is alive closure.
 159 // An instance is embedded into the G1CH and used as the
 160 // (optional) _is_alive_non_header closure in the STW
 161 // reference processor. It is also extensively used during
 162 // reference processing during STW evacuation pauses.
 163 class G1STWIsAliveClosure: public BoolObjectClosure {
 164   G1CollectedHeap* _g1;
 165 public:
 166   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 167   bool do_object_b(oop p);
 168 };
 169 
 170 class RefineCardTableEntryClosure;
 171 
 172 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 173  private:
 174   void reset_from_card_cache(uint start_idx, size_t num_regions);
 175  public:
 176   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 177 };
 178 
 179 class G1CollectedHeap : public SharedHeap {
 180   friend class VM_CollectForMetadataAllocation;
 181   friend class VM_G1CollectForAllocation;
 182   friend class VM_G1CollectFull;
 183   friend class VM_G1IncCollectionPause;
 184   friend class VMStructs;
 185   friend class MutatorAllocRegion;
 186   friend class SurvivorGCAllocRegion;
 187   friend class OldGCAllocRegion;
 188   friend class G1Allocator;
 189 
 190   // Closures used in implementation.
 191   friend class G1ParScanThreadState;
 192   friend class G1ParTask;
 193   friend class G1ParGCAllocator;
 194   friend class G1PrepareCompactClosure;
 195 
 196   // Other related classes.
 197   friend class HeapRegionClaimer;
 198 
 199   // Testing classes.
 200   friend class G1CheckCSetFastTableClosure;
 201 
 202 private:
 203   // The one and only G1CollectedHeap, so static functions can find it.
 204   static G1CollectedHeap* _g1h;
 205 
 206   static size_t _humongous_object_threshold_in_words;
 207 
 208   // The secondary free list which contains regions that have been
 209   // freed up during the cleanup process. This will be appended to
 210   // the master free list when appropriate.
 211   FreeRegionList _secondary_free_list;
 212 
 213   // It keeps track of the old regions.
 214   HeapRegionSet _old_set;
 215 
 216   // It keeps track of the humongous regions.
 217   HeapRegionSet _humongous_set;
 218 
 219   void clear_humongous_is_live_table();
 220   void eagerly_reclaim_humongous_regions();
 221 
 222   // The number of regions we could create by expansion.
 223   uint _expansion_regions;
 224 
 225   // The block offset table for the G1 heap.
 226   G1BlockOffsetSharedArray* _bot_shared;
 227 
 228   // Tears down the region sets / lists so that they are empty and the
 229   // regions on the heap do not belong to a region set / list. The
 230   // only exception is the humongous set which we leave unaltered. If
 231   // free_list_only is true, it will only tear down the master free
 232   // list. It is called before a Full GC (free_list_only == false) or
 233   // before heap shrinking (free_list_only == true).
 234   void tear_down_region_sets(bool free_list_only);
 235 
 236   // Rebuilds the region sets / lists so that they are repopulated to
 237   // reflect the contents of the heap. The only exception is the
 238   // humongous set which was not torn down in the first place. If
 239   // free_list_only is true, it will only rebuild the master free
 240   // list. It is called after a Full GC (free_list_only == false) or
 241   // after heap shrinking (free_list_only == true).
 242   void rebuild_region_sets(bool free_list_only);
 243 
 244   // Callback for region mapping changed events.
 245   G1RegionMappingChangedListener _listener;
 246 
 247   // The sequence of all heap regions in the heap.
 248   HeapRegionManager _hrm;
 249 
 250   // Class that handles the different kinds of allocations.
 251   G1Allocator* _allocator;
 252 
 253   // Statistics for each allocation context
 254   AllocationContextStats _allocation_context_stats;
 255 
 256   // PLAB sizing policy for survivors.
 257   PLABStats _survivor_plab_stats;
 258 
 259   // PLAB sizing policy for tenured objects.
 260   PLABStats _old_plab_stats;
 261 
 262   // It specifies whether we should attempt to expand the heap after a
 263   // region allocation failure. If heap expansion fails we set this to
 264   // false so that we don't re-attempt the heap expansion (it's likely
 265   // that subsequent expansion attempts will also fail if one fails).
 266   // Currently, it is only consulted during GC and it's reset at the
 267   // start of each GC.
 268   bool _expand_heap_after_alloc_failure;
 269 
 270   // It resets the mutator alloc region before new allocations can take place.
 271   void init_mutator_alloc_region();
 272 
 273   // It releases the mutator alloc region.
 274   void release_mutator_alloc_region();
 275 
 276   // It initializes the GC alloc regions at the start of a GC.
 277   void init_gc_alloc_regions(EvacuationInfo& evacuation_info);
 278 
 279   // It releases the GC alloc regions at the end of a GC.
 280   void release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info);
 281 
 282   // It does any cleanup that needs to be done on the GC alloc regions
 283   // before a Full GC.
 284   void abandon_gc_alloc_regions();
 285 
 286   // Helper for monitoring and management support.
 287   G1MonitoringSupport* _g1mm;
 288 
 289   // Records whether the region at the given index is kept live by roots or
 290   // references from the young generation.
 291   class HumongousIsLiveBiasedMappedArray : public G1BiasedMappedArray<bool> {
 292    protected:
 293     bool default_value() const { return false; }
 294    public:
 295     void clear() { G1BiasedMappedArray<bool>::clear(); }
 296     void set_live(uint region) {
 297       set_by_index(region, true);
 298     }
 299     bool is_live(uint region) {
 300       return get_by_index(region);
 301     }
 302   };
 303 
 304   HumongousIsLiveBiasedMappedArray _humongous_is_live;
 305   // Stores whether during humongous object registration we found candidate regions.
 306   // If not, we can skip a few steps.
 307   bool _has_humongous_reclaim_candidates;
 308 
 309   volatile unsigned _gc_time_stamp;
 310 
 311   size_t* _surviving_young_words;
 312 
 313   G1HRPrinter _hr_printer;
 314 
 315   void setup_surviving_young_words();
 316   void update_surviving_young_words(size_t* surv_young_words);
 317   void cleanup_surviving_young_words();
 318 
 319   // It decides whether an explicit GC should start a concurrent cycle
 320   // instead of doing a STW GC. Currently, a concurrent cycle is
 321   // explicitly started if:
 322   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 323   // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 324   // (c) cause == _g1_humongous_allocation
 325   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 326 
 327   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 328   // concurrent cycles) we have started.
 329   volatile uint _old_marking_cycles_started;
 330 
 331   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 332   // concurrent cycles) we have completed.
 333   volatile uint _old_marking_cycles_completed;
 334 
 335   bool _concurrent_cycle_started;
 336   bool _heap_summary_sent;
 337 
 338   // This is a non-product method that is helpful for testing. It is
 339   // called at the end of a GC and artificially expands the heap by
 340   // allocating a number of dead regions. This way we can induce very
 341   // frequent marking cycles and stress the cleanup / concurrent
 342   // cleanup code more (as all the regions that will be allocated by
 343   // this method will be found dead by the marking cycle).
 344   void allocate_dummy_regions() PRODUCT_RETURN;
 345 
 346   // Clear RSets after a compaction. It also resets the GC time stamps.
 347   void clear_rsets_post_compaction();
 348 
 349   // If the HR printer is active, dump the state of the regions in the
 350   // heap after a compaction.
 351   void print_hrm_post_compaction();
 352 
 353   double verify(bool guard, const char* msg);
 354   void verify_before_gc();
 355   void verify_after_gc();
 356 
 357   void log_gc_header();
 358   void log_gc_footer(double pause_time_sec);
 359 
 360   // These are macros so that, if the assert fires, we get the correct
 361   // line number, file, etc.
 362 
 363 #define heap_locking_asserts_err_msg(_extra_message_)                         \
 364   err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",    \
 365           (_extra_message_),                                                  \
 366           BOOL_TO_STR(Heap_lock->owned_by_self()),                            \
 367           BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),               \
 368           BOOL_TO_STR(Thread::current()->is_VM_thread()))
 369 
 370 #define assert_heap_locked()                                                  \
 371   do {                                                                        \
 372     assert(Heap_lock->owned_by_self(),                                        \
 373            heap_locking_asserts_err_msg("should be holding the Heap_lock"));  \
 374   } while (0)
 375 
 376 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 377   do {                                                                        \
 378     assert(Heap_lock->owned_by_self() ||                                      \
 379            (SafepointSynchronize::is_at_safepoint() &&                        \
 380              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 381            heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
 382                                         "should be at a safepoint"));         \
 383   } while (0)
 384 
 385 #define assert_heap_locked_and_not_at_safepoint()                             \
 386   do {                                                                        \
 387     assert(Heap_lock->owned_by_self() &&                                      \
 388                                     !SafepointSynchronize::is_at_safepoint(), \
 389           heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
 390                                        "should not be at a safepoint"));      \
 391   } while (0)
 392 
 393 #define assert_heap_not_locked()                                              \
 394   do {                                                                        \
 395     assert(!Heap_lock->owned_by_self(),                                       \
 396         heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
 397   } while (0)
 398 
 399 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 400   do {                                                                        \
 401     assert(!Heap_lock->owned_by_self() &&                                     \
 402                                     !SafepointSynchronize::is_at_safepoint(), \
 403       heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
 404                                    "should not be at a safepoint"));          \
 405   } while (0)
 406 
 407 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 408   do {                                                                        \
 409     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 410               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 411            heap_locking_asserts_err_msg("should be at a safepoint"));         \
 412   } while (0)
 413 
 414 #define assert_not_at_safepoint()                                             \
 415   do {                                                                        \
 416     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 417            heap_locking_asserts_err_msg("should not be at a safepoint"));     \
 418   } while (0)
 419 
 420 protected:
 421 
 422   // The young region list.
 423   YoungList*  _young_list;
 424 
 425   // The current policy object for the collector.
 426   G1CollectorPolicy* _g1_policy;
 427 
 428   // This is the second level of trying to allocate a new region. If
 429   // new_region() didn't find a region on the free_list, this call will
 430   // check whether there's anything available on the
 431   // secondary_free_list and/or wait for more regions to appear on
 432   // that list, if _free_regions_coming is set.
 433   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 434 
 435   // Try to allocate a single non-humongous HeapRegion sufficient for
 436   // an allocation of the given word_size. If do_expand is true,
 437   // attempt to expand the heap if necessary to satisfy the allocation
 438   // request. If the region is to be used as an old region or for a
 439   // humongous object, set is_old to true. If not, to false.
 440   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 441 
 442   // Initialize a contiguous set of free regions of length num_regions
 443   // and starting at index first so that they appear as a single
 444   // humongous region.
 445   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 446                                                       uint num_regions,
 447                                                       size_t word_size,
 448                                                       AllocationContext_t context);
 449 
 450   // Attempt to allocate a humongous object of the given size. Return
 451   // NULL if unsuccessful.
 452   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 453 
 454   // The following two methods, allocate_new_tlab() and
 455   // mem_allocate(), are the two main entry points from the runtime
 456   // into the G1's allocation routines. They have the following
 457   // assumptions:
 458   //
 459   // * They should both be called outside safepoints.
 460   //
 461   // * They should both be called without holding the Heap_lock.
 462   //
 463   // * All allocation requests for new TLABs should go to
 464   //   allocate_new_tlab().
 465   //
 466   // * All non-TLAB allocation requests should go to mem_allocate().
 467   //
 468   // * If either call cannot satisfy the allocation request using the
 469   //   current allocating region, they will try to get a new one. If
 470   //   this fails, they will attempt to do an evacuation pause and
 471   //   retry the allocation.
 472   //
 473   // * If all allocation attempts fail, even after trying to schedule
 474   //   an evacuation pause, allocate_new_tlab() will return NULL,
 475   //   whereas mem_allocate() will attempt a heap expansion and/or
 476   //   schedule a Full GC.
 477   //
 478   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 479   //   should never be called with word_size being humongous. All
 480   //   humongous allocation requests should go to mem_allocate() which
 481   //   will satisfy them with a special path.
 482 
 483   virtual HeapWord* allocate_new_tlab(size_t word_size);
 484 
 485   virtual HeapWord* mem_allocate(size_t word_size,
 486                                  bool*  gc_overhead_limit_was_exceeded);
 487 
 488   // The following three methods take a gc_count_before_ret
 489   // parameter which is used to return the GC count if the method
 490   // returns NULL. Given that we are required to read the GC count
 491   // while holding the Heap_lock, and these paths will take the
 492   // Heap_lock at some point, it's easier to get them to read the GC
 493   // count while holding the Heap_lock before they return NULL instead
 494   // of the caller (namely: mem_allocate()) having to also take the
 495   // Heap_lock just to read the GC count.
 496 
 497   // First-level mutator allocation attempt: try to allocate out of
 498   // the mutator alloc region without taking the Heap_lock. This
 499   // should only be used for non-humongous allocations.
 500   inline HeapWord* attempt_allocation(size_t word_size,
 501                                       uint* gc_count_before_ret,
 502                                       uint* gclocker_retry_count_ret,
 503                                       uint* gc_attempt);
 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                                     uint* gc_attempt);
 513 
 514   // Takes the Heap_lock and attempts a humongous allocation. It can
 515   // potentially schedule a GC pause.
 516   HeapWord* attempt_allocation_humongous(size_t word_size,
 517                                          uint* gc_count_before_ret,
 518                                          uint* gclocker_retry_count_ret,
 519                                          uint* gc_attempt);
 520 
 521   // Allocation attempt that should be called during safepoints (e.g.,
 522   // at the end of a successful GC). expect_null_mutator_alloc_region
 523   // specifies whether the mutator alloc region is expected to be NULL
 524   // or not.
 525   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 526                                             AllocationContext_t context,
 527                                             bool expect_null_mutator_alloc_region);
 528 
 529   // It dirties the cards that cover the block so that so that the post
 530   // write barrier never queues anything when updating objects on this
 531   // block. It is assumed (and in fact we assert) that the block
 532   // belongs to a young region.
 533   inline void dirty_young_block(HeapWord* start, size_t word_size);
 534 
 535   // Allocate blocks during garbage collection. Will ensure an
 536   // allocation region, either by picking one or expanding the
 537   // heap, and then allocate a block of the given size. The block
 538   // may not be a humongous - it must fit into a single heap region.
 539   inline HeapWord* par_allocate_during_gc(InCSetState dest,
 540                                           size_t word_size,
 541                                           AllocationContext_t context);
 542   // Ensure that no further allocations can happen in "r", bearing in mind
 543   // that parallel threads might be attempting allocations.
 544   void par_allocate_remaining_space(HeapRegion* r);
 545 
 546   // Allocation attempt during GC for a survivor object / PLAB.
 547   inline HeapWord* survivor_attempt_allocation(size_t word_size,
 548                                                AllocationContext_t context);
 549 
 550   // Allocation attempt during GC for an old object / PLAB.
 551   inline HeapWord* old_attempt_allocation(size_t word_size,
 552                                           AllocationContext_t context);
 553 
 554   // These methods are the "callbacks" from the G1AllocRegion class.
 555 
 556   // For mutator alloc regions.
 557   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 558   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 559                                    size_t allocated_bytes);
 560 
 561   // For GC alloc regions.
 562   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 563                                   InCSetState dest);
 564   void retire_gc_alloc_region(HeapRegion* alloc_region,
 565                               size_t allocated_bytes, InCSetState dest);
 566 
 567   // - if explicit_gc is true, the GC is for a System.gc() or a heap
 568   //   inspection request and should collect the entire heap
 569   // - if clear_all_soft_refs is true, all soft references should be
 570   //   cleared during the GC
 571   // - if explicit_gc is false, word_size describes the allocation that
 572   //   the GC should attempt (at least) to satisfy
 573   // - it returns false if it is unable to do the collection due to the
 574   //   GC locker being active, true otherwise
 575   bool do_collection(bool explicit_gc,
 576                      bool clear_all_soft_refs,
 577                      size_t word_size);
 578 
 579   // Callback from VM_G1CollectFull operation.
 580   // Perform a full collection.
 581   virtual void do_full_collection(bool clear_all_soft_refs);
 582 
 583   // Resize the heap if necessary after a full collection.  If this is
 584   // after a collect-for allocation, "word_size" is the allocation size,
 585   // and will be considered part of the used portion of the heap.
 586   void resize_if_necessary_after_full_collection(size_t word_size);
 587 
 588   // Callback from VM_G1CollectForAllocation operation.
 589   // This function does everything necessary/possible to satisfy a
 590   // failed allocation request (including collection, expansion, etc.)
 591   HeapWord* satisfy_failed_allocation(size_t word_size,
 592                                       AllocationContext_t context,
 593                                       bool* succeeded);
 594 
 595   // Attempting to expand the heap sufficiently
 596   // to support an allocation of the given "word_size".  If
 597   // successful, perform the allocation and return the address of the
 598   // allocated block, or else "NULL".
 599   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 600 
 601   // Process any reference objects discovered during
 602   // an incremental evacuation pause.
 603   void process_discovered_references(uint no_of_gc_workers);
 604 
 605   // Enqueue any remaining discovered references
 606   // after processing.
 607   void enqueue_discovered_references(uint no_of_gc_workers);
 608 
 609 public:
 610 
 611   G1Allocator* allocator() {
 612     return _allocator;
 613   }
 614 
 615   G1MonitoringSupport* g1mm() {
 616     assert(_g1mm != NULL, "should have been initialized");
 617     return _g1mm;
 618   }
 619 
 620   // Expand the garbage-first heap by at least the given size (in bytes!).
 621   // Returns true if the heap was expanded by the requested amount;
 622   // false otherwise.
 623   // (Rounds up to a HeapRegion boundary.)
 624   bool expand(size_t expand_bytes);
 625 
 626   // Returns the PLAB statistics for a given destination.
 627   inline PLABStats* alloc_buffer_stats(InCSetState dest);
 628 
 629   // Determines PLAB size for a given destination.
 630   inline size_t desired_plab_sz(InCSetState dest);
 631 
 632   inline AllocationContextStats& allocation_context_stats();
 633 
 634   // Do anything common to GC's.
 635   virtual void gc_prologue(bool full);
 636   virtual void gc_epilogue(bool full);
 637 
 638   inline void set_humongous_is_live(oop obj);
 639 
 640   bool humongous_is_live(uint region) {
 641     return _humongous_is_live.is_live(region);
 642   }
 643 
 644   // Returns whether the given region (which must be a humongous (start) region)
 645   // is to be considered conservatively live regardless of any other conditions.
 646   bool humongous_region_is_always_live(uint index);
 647   // Returns whether the given region (which must be a humongous (start) region)
 648   // is considered a candidate for eager reclamation.
 649   bool humongous_region_is_candidate(uint index);
 650   // Register the given region to be part of the collection set.
 651   inline void register_humongous_region_with_cset(uint index);
 652   // Register regions with humongous objects (actually on the start region) in
 653   // the in_cset_fast_test table.
 654   void register_humongous_regions_with_cset();
 655   // We register a region with the fast "in collection set" test. We
 656   // simply set to true the array slot corresponding to this region.
 657   void register_young_region_with_cset(HeapRegion* r) {
 658     _in_cset_fast_test.set_in_young(r->hrm_index());
 659   }
 660   void register_old_region_with_cset(HeapRegion* r) {
 661     _in_cset_fast_test.set_in_old(r->hrm_index());
 662   }
 663   void clear_in_cset(const HeapRegion* hr) {
 664     _in_cset_fast_test.clear(hr);
 665   }
 666 
 667   void clear_cset_fast_test() {
 668     _in_cset_fast_test.clear();
 669   }
 670 
 671   // This is called at the start of either a concurrent cycle or a Full
 672   // GC to update the number of old marking cycles started.
 673   void increment_old_marking_cycles_started();
 674 
 675   // This is called at the end of either a concurrent cycle or a Full
 676   // GC to update the number of old marking cycles completed. Those two
 677   // can happen in a nested fashion, i.e., we start a concurrent
 678   // cycle, a Full GC happens half-way through it which ends first,
 679   // and then the cycle notices that a Full GC happened and ends
 680   // too. The concurrent parameter is a boolean to help us do a bit
 681   // tighter consistency checking in the method. If concurrent is
 682   // false, the caller is the inner caller in the nesting (i.e., the
 683   // Full GC). If concurrent is true, the caller is the outer caller
 684   // in this nesting (i.e., the concurrent cycle). Further nesting is
 685   // not currently supported. The end of this call also notifies
 686   // the FullGCCount_lock in case a Java thread is waiting for a full
 687   // GC to happen (e.g., it called System.gc() with
 688   // +ExplicitGCInvokesConcurrent).
 689   void increment_old_marking_cycles_completed(bool concurrent);
 690 
 691   uint old_marking_cycles_completed() {
 692     return _old_marking_cycles_completed;
 693   }
 694 
 695   void register_concurrent_cycle_start(const Ticks& start_time);
 696   void register_concurrent_cycle_end();
 697   void trace_heap_after_concurrent_cycle();
 698 
 699   G1YCType yc_type();
 700 
 701   G1HRPrinter* hr_printer() { return &_hr_printer; }
 702 
 703   // Frees a non-humongous region by initializing its contents and
 704   // adding it to the free list that's passed as a parameter (this is
 705   // usually a local list which will be appended to the master free
 706   // list later). The used bytes of freed regions are accumulated in
 707   // pre_used. If par is true, the region's RSet will not be freed
 708   // up. The assumption is that this will be done later.
 709   // The locked parameter indicates if the caller has already taken
 710   // care of proper synchronization. This may allow some optimizations.
 711   void free_region(HeapRegion* hr,
 712                    FreeRegionList* free_list,
 713                    bool par,
 714                    bool locked = false);
 715 
 716   // Frees a humongous region by collapsing it into individual regions
 717   // and calling free_region() for each of them. The freed regions
 718   // will be added to the free list that's passed as a parameter (this
 719   // is usually a local list which will be appended to the master free
 720   // list later). The used bytes of freed regions are accumulated in
 721   // pre_used. If par is true, the region's RSet will not be freed
 722   // up. The assumption is that this will be done later.
 723   void free_humongous_region(HeapRegion* hr,
 724                              FreeRegionList* free_list,
 725                              bool par);
 726 protected:
 727 
 728   // Shrink the garbage-first heap by at most the given size (in bytes!).
 729   // (Rounds down to a HeapRegion boundary.)
 730   virtual void shrink(size_t expand_bytes);
 731   void shrink_helper(size_t expand_bytes);
 732 
 733   #if TASKQUEUE_STATS
 734   static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
 735   void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
 736   void reset_taskqueue_stats();
 737   #endif // TASKQUEUE_STATS
 738 
 739   // Schedule the VM operation that will do an evacuation pause to
 740   // satisfy an allocation request of word_size. *succeeded will
 741   // return whether the VM operation was successful (it did do an
 742   // evacuation pause) or not (another thread beat us to it or the GC
 743   // locker was active). Given that we should not be holding the
 744   // Heap_lock when we enter this method, we will pass the
 745   // gc_count_before (i.e., total_collections()) as a parameter since
 746   // it has to be read while holding the Heap_lock. Currently, both
 747   // methods that call do_collection_pause() release the Heap_lock
 748   // before the call, so it's easy to read gc_count_before just before.
 749   HeapWord* do_collection_pause(size_t         word_size,
 750                                 uint           gc_count_before,
 751                                 bool*          succeeded,
 752                                 GCCause::Cause gc_cause,
 753                                 uint           gc_attempt);
 754 
 755   // The guts of the incremental collection pause, executed by the vm
 756   // thread. It returns false if it is unable to do the collection due
 757   // to the GC locker being active, true otherwise
 758   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 759 
 760   // Actually do the work of evacuating the collection set.
 761   void evacuate_collection_set(EvacuationInfo& evacuation_info);
 762 
 763   // The g1 remembered set of the heap.
 764   G1RemSet* _g1_rem_set;
 765 
 766   // A set of cards that cover the objects for which the Rsets should be updated
 767   // concurrently after the collection.
 768   DirtyCardQueueSet _dirty_card_queue_set;
 769 
 770   // The closure used to refine a single card.
 771   RefineCardTableEntryClosure* _refine_cte_cl;
 772 
 773   // A DirtyCardQueueSet that is used to hold cards that contain
 774   // references into the current collection set. This is used to
 775   // update the remembered sets of the regions in the collection
 776   // set in the event of an evacuation failure.
 777   DirtyCardQueueSet _into_cset_dirty_card_queue_set;
 778 
 779   // After a collection pause, make the regions in the CS into free
 780   // regions.
 781   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info);
 782 
 783   // Abandon the current collection set without recording policy
 784   // statistics or updating free lists.
 785   void abandon_collection_set(HeapRegion* cs_head);
 786 
 787   // The concurrent marker (and the thread it runs in.)
 788   ConcurrentMark* _cm;
 789   ConcurrentMarkThread* _cmThread;
 790   bool _mark_in_progress;
 791 
 792   // The concurrent refiner.
 793   ConcurrentG1Refine* _cg1r;
 794 
 795   // The parallel task queues
 796   RefToScanQueueSet *_task_queues;
 797 
 798   // True iff a evacuation has failed in the current collection.
 799   bool _evacuation_failed;
 800 
 801   EvacuationFailedInfo* _evacuation_failed_info_array;
 802 
 803   // Failed evacuations cause some logical from-space objects to have
 804   // forwarding pointers to themselves.  Reset them.
 805   void remove_self_forwarding_pointers();
 806 
 807   // Together, these store an object with a preserved mark, and its mark value.
 808   Stack<oop, mtGC>     _objs_with_preserved_marks;
 809   Stack<markOop, mtGC> _preserved_marks_of_objs;
 810 
 811   // Preserve the mark of "obj", if necessary, in preparation for its mark
 812   // word being overwritten with a self-forwarding-pointer.
 813   void preserve_mark_if_necessary(oop obj, markOop m);
 814 
 815   // The stack of evac-failure objects left to be scanned.
 816   GrowableArray<oop>*    _evac_failure_scan_stack;
 817   // The closure to apply to evac-failure objects.
 818 
 819   OopsInHeapRegionClosure* _evac_failure_closure;
 820   // Set the field above.
 821   void
 822   set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
 823     _evac_failure_closure = evac_failure_closure;
 824   }
 825 
 826   // Push "obj" on the scan stack.
 827   void push_on_evac_failure_scan_stack(oop obj);
 828   // Process scan stack entries until the stack is empty.
 829   void drain_evac_failure_scan_stack();
 830   // True iff an invocation of "drain_scan_stack" is in progress; to
 831   // prevent unnecessary recursion.
 832   bool _drain_in_progress;
 833 
 834   // Do any necessary initialization for evacuation-failure handling.
 835   // "cl" is the closure that will be used to process evac-failure
 836   // objects.
 837   void init_for_evac_failure(OopsInHeapRegionClosure* cl);
 838   // Do any necessary cleanup for evacuation-failure handling data
 839   // structures.
 840   void finalize_for_evac_failure();
 841 
 842   // An attempt to evacuate "obj" has failed; take necessary steps.
 843   oop handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state, oop obj);
 844   void handle_evacuation_failure_common(oop obj, markOop m);
 845 
 846 #ifndef PRODUCT
 847   // Support for forcing evacuation failures. Analogous to
 848   // PromotionFailureALot for the other collectors.
 849 
 850   // Records whether G1EvacuationFailureALot should be in effect
 851   // for the current GC
 852   bool _evacuation_failure_alot_for_current_gc;
 853 
 854   // Used to record the GC number for interval checking when
 855   // determining whether G1EvaucationFailureALot is in effect
 856   // for the current GC.
 857   size_t _evacuation_failure_alot_gc_number;
 858 
 859   // Count of the number of evacuations between failures.
 860   volatile size_t _evacuation_failure_alot_count;
 861 
 862   // Set whether G1EvacuationFailureALot should be in effect
 863   // for the current GC (based upon the type of GC and which
 864   // command line flags are set);
 865   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 866                                                   bool during_initial_mark,
 867                                                   bool during_marking);
 868 
 869   inline void set_evacuation_failure_alot_for_current_gc();
 870 
 871   // Return true if it's time to cause an evacuation failure.
 872   inline bool evacuation_should_fail();
 873 
 874   // Reset the G1EvacuationFailureALot counters.  Should be called at
 875   // the end of an evacuation pause in which an evacuation failure occurred.
 876   inline void reset_evacuation_should_fail();
 877 #endif // !PRODUCT
 878 
 879   // ("Weak") Reference processing support.
 880   //
 881   // G1 has 2 instances of the reference processor class. One
 882   // (_ref_processor_cm) handles reference object discovery
 883   // and subsequent processing during concurrent marking cycles.
 884   //
 885   // The other (_ref_processor_stw) handles reference object
 886   // discovery and processing during full GCs and incremental
 887   // evacuation pauses.
 888   //
 889   // During an incremental pause, reference discovery will be
 890   // temporarily disabled for _ref_processor_cm and will be
 891   // enabled for _ref_processor_stw. At the end of the evacuation
 892   // pause references discovered by _ref_processor_stw will be
 893   // processed and discovery will be disabled. The previous
 894   // setting for reference object discovery for _ref_processor_cm
 895   // will be re-instated.
 896   //
 897   // At the start of marking:
 898   //  * Discovery by the CM ref processor is verified to be inactive
 899   //    and it's discovered lists are empty.
 900   //  * Discovery by the CM ref processor is then enabled.
 901   //
 902   // At the end of marking:
 903   //  * Any references on the CM ref processor's discovered
 904   //    lists are processed (possibly MT).
 905   //
 906   // At the start of full GC we:
 907   //  * Disable discovery by the CM ref processor and
 908   //    empty CM ref processor's discovered lists
 909   //    (without processing any entries).
 910   //  * Verify that the STW ref processor is inactive and it's
 911   //    discovered lists are empty.
 912   //  * Temporarily set STW ref processor discovery as single threaded.
 913   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 914   //    field.
 915   //  * Finally enable discovery by the STW ref processor.
 916   //
 917   // The STW ref processor is used to record any discovered
 918   // references during the full GC.
 919   //
 920   // At the end of a full GC we:
 921   //  * Enqueue any reference objects discovered by the STW ref processor
 922   //    that have non-live referents. This has the side-effect of
 923   //    making the STW ref processor inactive by disabling discovery.
 924   //  * Verify that the CM ref processor is still inactive
 925   //    and no references have been placed on it's discovered
 926   //    lists (also checked as a precondition during initial marking).
 927 
 928   // The (stw) reference processor...
 929   ReferenceProcessor* _ref_processor_stw;
 930 
 931   STWGCTimer* _gc_timer_stw;
 932   ConcurrentGCTimer* _gc_timer_cm;
 933 
 934   G1OldTracer* _gc_tracer_cm;
 935   G1NewTracer* _gc_tracer_stw;
 936 
 937   // During reference object discovery, the _is_alive_non_header
 938   // closure (if non-null) is applied to the referent object to
 939   // determine whether the referent is live. If so then the
 940   // reference object does not need to be 'discovered' and can
 941   // be treated as a regular oop. This has the benefit of reducing
 942   // the number of 'discovered' reference objects that need to
 943   // be processed.
 944   //
 945   // Instance of the is_alive closure for embedding into the
 946   // STW reference processor as the _is_alive_non_header field.
 947   // Supplying a value for the _is_alive_non_header field is
 948   // optional but doing so prevents unnecessary additions to
 949   // the discovered lists during reference discovery.
 950   G1STWIsAliveClosure _is_alive_closure_stw;
 951 
 952   // The (concurrent marking) reference processor...
 953   ReferenceProcessor* _ref_processor_cm;
 954 
 955   // Instance of the concurrent mark is_alive closure for embedding
 956   // into the Concurrent Marking reference processor as the
 957   // _is_alive_non_header field. Supplying a value for the
 958   // _is_alive_non_header field is optional but doing so prevents
 959   // unnecessary additions to the discovered lists during reference
 960   // discovery.
 961   G1CMIsAliveClosure _is_alive_closure_cm;
 962 
 963   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 964   HeapRegion** _worker_cset_start_region;
 965 
 966   // Time stamp to validate the regions recorded in the cache
 967   // used by G1CollectedHeap::start_cset_region_for_worker().
 968   // The heap region entry for a given worker is valid iff
 969   // the associated time stamp value matches the current value
 970   // of G1CollectedHeap::_gc_time_stamp.
 971   uint* _worker_cset_start_region_time_stamp;
 972 
 973   volatile bool _free_regions_coming;
 974 
 975 public:
 976 
 977   void set_refine_cte_cl_concurrency(bool concurrent);
 978 
 979   RefToScanQueue *task_queue(int i) const;
 980 
 981   // A set of cards where updates happened during the GC
 982   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 983 
 984   // A DirtyCardQueueSet that is used to hold cards that contain
 985   // references into the current collection set. This is used to
 986   // update the remembered sets of the regions in the collection
 987   // set in the event of an evacuation failure.
 988   DirtyCardQueueSet& into_cset_dirty_card_queue_set()
 989         { return _into_cset_dirty_card_queue_set; }
 990 
 991   // Create a G1CollectedHeap with the specified policy.
 992   // Must call the initialize method afterwards.
 993   // May not return if something goes wrong.
 994   G1CollectedHeap(G1CollectorPolicy* policy);
 995 
 996   // Initialize the G1CollectedHeap to have the initial and
 997   // maximum sizes and remembered and barrier sets
 998   // specified by the policy object.
 999   jint initialize();
1000 
1001   virtual void stop();
1002 
1003   // Return the (conservative) maximum heap alignment for any G1 heap
1004   static size_t conservative_max_heap_alignment();
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 #endif // PRODUCT
1113 
1114   // If G1VerifyBitmaps is set, verify that the marking bitmaps for
1115   // the given region do not have any spurious marks. If errors are
1116   // detected, print appropriate error messages and crash.
1117   void check_bitmaps(const char* caller, HeapRegion* hr) PRODUCT_RETURN;
1118 
1119   // If G1VerifyBitmaps is set, verify that the marking bitmaps do not
1120   // have any spurious marks. If errors are detected, print
1121   // appropriate error messages and crash.
1122   void check_bitmaps(const char* caller) PRODUCT_RETURN;
1123 
1124   // Do sanity check on the contents of the in-cset fast test table.
1125   bool check_cset_fast_test() PRODUCT_RETURN_( return true; );
1126 
1127   // verify_region_sets() performs verification over the region
1128   // lists. It will be compiled in the product code to be used when
1129   // necessary (i.e., during heap verification).
1130   void verify_region_sets();
1131 
1132   // verify_region_sets_optional() is planted in the code for
1133   // list verification in non-product builds (and it can be enabled in
1134   // product builds by defining HEAP_REGION_SET_FORCE_VERIFY to be 1).
1135 #if HEAP_REGION_SET_FORCE_VERIFY
1136   void verify_region_sets_optional() {
1137     verify_region_sets();
1138   }
1139 #else // HEAP_REGION_SET_FORCE_VERIFY
1140   void verify_region_sets_optional() { }
1141 #endif // HEAP_REGION_SET_FORCE_VERIFY
1142 
1143 #ifdef ASSERT
1144   bool is_on_master_free_list(HeapRegion* hr) {
1145     return _hrm.is_free(hr);
1146   }
1147 #endif // ASSERT
1148 
1149   // Wrapper for the region list operations that can be called from
1150   // methods outside this class.
1151 
1152   void secondary_free_list_add(FreeRegionList* list) {
1153     _secondary_free_list.add_ordered(list);
1154   }
1155 
1156   void append_secondary_free_list() {
1157     _hrm.insert_list_into_free_list(&_secondary_free_list);
1158   }
1159 
1160   void append_secondary_free_list_if_not_empty_with_lock() {
1161     // If the secondary free list looks empty there's no reason to
1162     // take the lock and then try to append it.
1163     if (!_secondary_free_list.is_empty()) {
1164       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1165       append_secondary_free_list();
1166     }
1167   }
1168 
1169   inline void old_set_remove(HeapRegion* hr);
1170 
1171   size_t non_young_capacity_bytes() {
1172     return _old_set.total_capacity_bytes() + _humongous_set.total_capacity_bytes();
1173   }
1174 
1175   void set_free_regions_coming();
1176   void reset_free_regions_coming();
1177   bool free_regions_coming() { return _free_regions_coming; }
1178   void wait_while_free_regions_coming();
1179 
1180   // Determine whether the given region is one that we are using as an
1181   // old GC alloc region.
1182   bool is_old_gc_alloc_region(HeapRegion* hr) {
1183     return _allocator->is_retained_old_region(hr);
1184   }
1185 
1186   // Perform a collection of the heap; intended for use in implementing
1187   // "System.gc".  This probably implies as full a collection as the
1188   // "CollectedHeap" supports.
1189   virtual void collect(GCCause::Cause cause);
1190 
1191   // The same as above but assume that the caller holds the Heap_lock.
1192   void collect_locked(GCCause::Cause cause);
1193 
1194   virtual bool copy_allocation_context_stats(const jint* contexts,
1195                                              jlong* totals,
1196                                              jbyte* accuracy,
1197                                              jint len);
1198 
1199   // True iff an evacuation has failed in the most-recent collection.
1200   bool evacuation_failed() { return _evacuation_failed; }
1201 
1202   void remove_from_old_sets(const HeapRegionSetCount& old_regions_removed, const HeapRegionSetCount& humongous_regions_removed);
1203   void prepend_to_freelist(FreeRegionList* list);
1204   void decrement_summary_bytes(size_t bytes);
1205 
1206   // Returns "TRUE" iff "p" points into the committed areas of the heap.
1207   virtual bool is_in(const void* p) const;
1208 #ifdef ASSERT
1209   // Returns whether p is in one of the available areas of the heap. Slow but
1210   // extensive version.
1211   bool is_in_exact(const void* p) const;
1212 #endif
1213 
1214   // Return "TRUE" iff the given object address is within the collection
1215   // set. Slow implementation.
1216   inline bool obj_in_cs(oop obj);
1217 
1218   inline bool is_in_cset(const HeapRegion *hr);
1219   inline bool is_in_cset(oop obj);
1220 
1221   inline bool is_in_cset_or_humongous(const oop obj);
1222 
1223  private:
1224   // This array is used for a quick test on whether a reference points into
1225   // the collection set or not. Each of the array's elements denotes whether the
1226   // corresponding region is in the collection set or not.
1227   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1228 
1229  public:
1230 
1231   inline InCSetState in_cset_state(const oop obj);
1232 
1233   // Return "TRUE" iff the given object address is in the reserved
1234   // region of g1.
1235   bool is_in_g1_reserved(const void* p) const {
1236     return _hrm.reserved().contains(p);
1237   }
1238 
1239   // Returns a MemRegion that corresponds to the space that has been
1240   // reserved for the heap
1241   MemRegion g1_reserved() const {
1242     return _hrm.reserved();
1243   }
1244 
1245   virtual bool is_in_closed_subset(const void* p) const;
1246 
1247   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1248     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1249   }
1250 
1251   // This resets the card table to all zeros.  It is used after
1252   // a collection pause which used the card table to claim cards.
1253   void cleanUpCardTable();
1254 
1255   // Iteration functions.
1256 
1257   // Iterate over all the ref-containing fields of all objects, calling
1258   // "cl.do_oop" on each.
1259   virtual void oop_iterate(ExtendedOopClosure* cl);
1260 
1261   // Iterate over all objects, calling "cl.do_object" on each.
1262   virtual void object_iterate(ObjectClosure* cl);
1263 
1264   virtual void safe_object_iterate(ObjectClosure* cl) {
1265     object_iterate(cl);
1266   }
1267 
1268   // Iterate over all spaces in use in the heap, in ascending address order.
1269   virtual void space_iterate(SpaceClosure* cl);
1270 
1271   // Iterate over heap regions, in address order, terminating the
1272   // iteration early if the "doHeapRegion" method returns "true".
1273   void heap_region_iterate(HeapRegionClosure* blk) const;
1274 
1275   // Return the region with the given index. It assumes the index is valid.
1276   inline HeapRegion* region_at(uint index) const;
1277 
1278   // Calculate the region index of the given address. Given address must be
1279   // within the heap.
1280   inline uint addr_to_region(HeapWord* addr) const;
1281 
1282   inline HeapWord* bottom_addr_for_region(uint index) const;
1283 
1284   // Iterate over the heap regions in parallel. Assumes that this will be called
1285   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1286   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1287   // to each of the regions, by attempting to claim the region using the
1288   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1289   // region. The concurrent argument should be set to true if iteration is
1290   // performed concurrently, during which no assumptions are made for consistent
1291   // attributes of the heap regions (as they might be modified while iterating).
1292   void heap_region_par_iterate(HeapRegionClosure* cl,
1293                                uint worker_id,
1294                                HeapRegionClaimer* hrclaimer,
1295                                bool concurrent = false) const;
1296 
1297   // Clear the cached cset start regions and (more importantly)
1298   // the time stamps. Called when we reset the GC time stamp.
1299   void clear_cset_start_regions();
1300 
1301   // Given the id of a worker, obtain or calculate a suitable
1302   // starting region for iterating over the current collection set.
1303   HeapRegion* start_cset_region_for_worker(uint worker_i);
1304 
1305   // Iterate over the regions (if any) in the current collection set.
1306   void collection_set_iterate(HeapRegionClosure* blk);
1307 
1308   // As above but starting from region r
1309   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1310 
1311   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1312 
1313   // A CollectedHeap will contain some number of spaces.  This finds the
1314   // space containing a given address, or else returns NULL.
1315   virtual Space* space_containing(const void* addr) const;
1316 
1317   // Returns the HeapRegion that contains addr. addr must not be NULL.
1318   template <class T>
1319   inline HeapRegion* heap_region_containing_raw(const T addr) const;
1320 
1321   // Returns the HeapRegion that contains addr. addr must not be NULL.
1322   // If addr is within a humongous continues region, it returns its humongous start region.
1323   template <class T>
1324   inline HeapRegion* heap_region_containing(const T addr) const;
1325 
1326   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1327   // each address in the (reserved) heap is a member of exactly
1328   // one block.  The defining characteristic of a block is that it is
1329   // possible to find its size, and thus to progress forward to the next
1330   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1331   // represent Java objects, or they might be free blocks in a
1332   // free-list-based heap (or subheap), as long as the two kinds are
1333   // distinguishable and the size of each is determinable.
1334 
1335   // Returns the address of the start of the "block" that contains the
1336   // address "addr".  We say "blocks" instead of "object" since some heaps
1337   // may not pack objects densely; a chunk may either be an object or a
1338   // non-object.
1339   virtual HeapWord* block_start(const void* addr) const;
1340 
1341   // Requires "addr" to be the start of a chunk, and returns its size.
1342   // "addr + size" is required to be the start of a new chunk, or the end
1343   // of the active area of the heap.
1344   virtual size_t block_size(const HeapWord* addr) const;
1345 
1346   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1347   // the block is an object.
1348   virtual bool block_is_obj(const HeapWord* addr) const;
1349 
1350   // Does this heap support heap inspection? (+PrintClassHistogram)
1351   virtual bool supports_heap_inspection() const { return true; }
1352 
1353   // Section on thread-local allocation buffers (TLABs)
1354   // See CollectedHeap for semantics.
1355 
1356   bool supports_tlab_allocation() const;
1357   size_t tlab_capacity(Thread* ignored) const;
1358   size_t tlab_used(Thread* ignored) const;
1359   size_t max_tlab_size() const;
1360   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1361 
1362   // Can a compiler initialize a new object without store barriers?
1363   // This permission only extends from the creation of a new object
1364   // via a TLAB up to the first subsequent safepoint. If such permission
1365   // is granted for this heap type, the compiler promises to call
1366   // defer_store_barrier() below on any slow path allocation of
1367   // a new object for which such initializing store barriers will
1368   // have been elided. G1, like CMS, allows this, but should be
1369   // ready to provide a compensating write barrier as necessary
1370   // if that storage came out of a non-young region. The efficiency
1371   // of this implementation depends crucially on being able to
1372   // answer very efficiently in constant time whether a piece of
1373   // storage in the heap comes from a young region or not.
1374   // See ReduceInitialCardMarks.
1375   virtual bool can_elide_tlab_store_barriers() const {
1376     return true;
1377   }
1378 
1379   virtual bool card_mark_must_follow_store() const {
1380     return true;
1381   }
1382 
1383   inline bool is_in_young(const oop obj);
1384 
1385 #ifdef ASSERT
1386   virtual bool is_in_partial_collection(const void* p);
1387 #endif
1388 
1389   virtual bool is_scavengable(const void* addr);
1390 
1391   // We don't need barriers for initializing stores to objects
1392   // in the young gen: for the SATB pre-barrier, there is no
1393   // pre-value that needs to be remembered; for the remembered-set
1394   // update logging post-barrier, we don't maintain remembered set
1395   // information for young gen objects.
1396   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1397 
1398   // Returns "true" iff the given word_size is "very large".
1399   static bool is_humongous(size_t word_size) {
1400     // Note this has to be strictly greater-than as the TLABs
1401     // are capped at the humongous threshold and we want to
1402     // ensure that we don't try to allocate a TLAB as
1403     // humongous and that we don't allocate a humongous
1404     // object in a TLAB.
1405     return word_size > _humongous_object_threshold_in_words;
1406   }
1407 
1408   // Update mod union table with the set of dirty cards.
1409   void updateModUnion();
1410 
1411   // Set the mod union bits corresponding to the given memRegion.  Note
1412   // that this is always a safe operation, since it doesn't clear any
1413   // bits.
1414   void markModUnionRange(MemRegion mr);
1415 
1416   // Records the fact that a marking phase is no longer in progress.
1417   void set_marking_complete() {
1418     _mark_in_progress = false;
1419   }
1420   void set_marking_started() {
1421     _mark_in_progress = true;
1422   }
1423   bool mark_in_progress() {
1424     return _mark_in_progress;
1425   }
1426 
1427   // Print the maximum heap capacity.
1428   virtual size_t max_capacity() const;
1429 
1430   virtual jlong millis_since_last_gc();
1431 
1432 
1433   // Convenience function to be used in situations where the heap type can be
1434   // asserted to be this type.
1435   static G1CollectedHeap* heap();
1436 
1437   void set_region_short_lived_locked(HeapRegion* hr);
1438   // add appropriate methods for any other surv rate groups
1439 
1440   YoungList* young_list() const { return _young_list; }
1441 
1442   // debugging
1443   bool check_young_list_well_formed() {
1444     return _young_list->check_list_well_formed();
1445   }
1446 
1447   bool check_young_list_empty(bool check_heap,
1448                               bool check_sample = true);
1449 
1450   // *** Stuff related to concurrent marking.  It's not clear to me that so
1451   // many of these need to be public.
1452 
1453   // The functions below are helper functions that a subclass of
1454   // "CollectedHeap" can use in the implementation of its virtual
1455   // functions.
1456   // This performs a concurrent marking of the live objects in a
1457   // bitmap off to the side.
1458   void doConcurrentMark();
1459 
1460   bool isMarkedPrev(oop obj) const;
1461   bool isMarkedNext(oop obj) const;
1462 
1463   // Determine if an object is dead, given the object and also
1464   // the region to which the object belongs. An object is dead
1465   // iff a) it was not allocated since the last mark and b) it
1466   // is not marked.
1467   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1468     return
1469       !hr->obj_allocated_since_prev_marking(obj) &&
1470       !isMarkedPrev(obj);
1471   }
1472 
1473   // This function returns true when an object has been
1474   // around since the previous marking and hasn't yet
1475   // been marked during this marking.
1476   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1477     return
1478       !hr->obj_allocated_since_next_marking(obj) &&
1479       !isMarkedNext(obj);
1480   }
1481 
1482   // Determine if an object is dead, given only the object itself.
1483   // This will find the region to which the object belongs and
1484   // then call the region version of the same function.
1485 
1486   // Added if it is NULL it isn't dead.
1487 
1488   inline bool is_obj_dead(const oop obj) const;
1489 
1490   inline bool is_obj_ill(const oop obj) const;
1491 
1492   bool allocated_since_marking(oop obj, HeapRegion* hr, VerifyOption vo);
1493   HeapWord* top_at_mark_start(HeapRegion* hr, VerifyOption vo);
1494   bool is_marked(oop obj, VerifyOption vo);
1495   const char* top_at_mark_start_str(VerifyOption vo);
1496 
1497   ConcurrentMark* concurrent_mark() const { return _cm; }
1498 
1499   // Refinement
1500 
1501   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1502 
1503   // The dirty cards region list is used to record a subset of regions
1504   // whose cards need clearing. The list if populated during the
1505   // remembered set scanning and drained during the card table
1506   // cleanup. Although the methods are reentrant, population/draining
1507   // phases must not overlap. For synchronization purposes the last
1508   // element on the list points to itself.
1509   HeapRegion* _dirty_cards_region_list;
1510   void push_dirty_cards_region(HeapRegion* hr);
1511   HeapRegion* pop_dirty_cards_region();
1512 
1513   // Optimized nmethod scanning support routines
1514 
1515   // Register the given nmethod with the G1 heap.
1516   virtual void register_nmethod(nmethod* nm);
1517 
1518   // Unregister the given nmethod from the G1 heap.
1519   virtual void unregister_nmethod(nmethod* nm);
1520 
1521   // Free up superfluous code root memory.
1522   void purge_code_root_memory();
1523 
1524   // Rebuild the strong code root lists for each region
1525   // after a full GC.
1526   void rebuild_strong_code_roots();
1527 
1528   // Delete entries for dead interned string and clean up unreferenced symbols
1529   // in symbol table, possibly in parallel.
1530   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1531 
1532   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1533   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1534 
1535   // Redirty logged cards in the refinement queue.
1536   void redirty_logged_cards();
1537   // Verification
1538 
1539   // The following is just to alert the verification code
1540   // that a full collection has occurred and that the
1541   // remembered sets are no longer up to date.
1542   bool _full_collection;
1543   void set_full_collection() { _full_collection = true;}
1544   void clear_full_collection() {_full_collection = false;}
1545   bool full_collection() {return _full_collection;}
1546 
1547   // Perform any cleanup actions necessary before allowing a verification.
1548   virtual void prepare_for_verify();
1549 
1550   // Perform verification.
1551 
1552   // vo == UsePrevMarking  -> use "prev" marking information,
1553   // vo == UseNextMarking -> use "next" marking information
1554   // vo == UseMarkWord    -> use the mark word in the object header
1555   //
1556   // NOTE: Only the "prev" marking information is guaranteed to be
1557   // consistent most of the time, so most calls to this should use
1558   // vo == UsePrevMarking.
1559   // Currently, there is only one case where this is called with
1560   // vo == UseNextMarking, which is to verify the "next" marking
1561   // information at the end of remark.
1562   // Currently there is only one place where this is called with
1563   // vo == UseMarkWord, which is to verify the marking during a
1564   // full GC.
1565   void verify(bool silent, VerifyOption vo);
1566 
1567   // Override; it uses the "prev" marking information
1568   virtual void verify(bool silent);
1569 
1570   // The methods below are here for convenience and dispatch the
1571   // appropriate method depending on value of the given VerifyOption
1572   // parameter. The values for that parameter, and their meanings,
1573   // are the same as those above.
1574 
1575   bool is_obj_dead_cond(const oop obj,
1576                         const HeapRegion* hr,
1577                         const VerifyOption vo) const;
1578 
1579   bool is_obj_dead_cond(const oop obj,
1580                         const VerifyOption vo) const;
1581 
1582   // Printing
1583 
1584   virtual void print_on(outputStream* st) const;
1585   virtual void print_extended_on(outputStream* st) const;
1586   virtual void print_on_error(outputStream* st) const;
1587 
1588   virtual void print_gc_threads_on(outputStream* st) const;
1589   virtual void gc_threads_do(ThreadClosure* tc) const;
1590 
1591   // Override
1592   void print_tracing_info() const;
1593 
1594   // The following two methods are helpful for debugging RSet issues.
1595   void print_cset_rsets() PRODUCT_RETURN;
1596   void print_all_rsets() PRODUCT_RETURN;
1597 
1598 public:
1599   size_t pending_card_num();
1600   size_t cards_scanned();
1601 
1602 protected:
1603   size_t _max_heap_capacity;
1604 };
1605 
1606 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
--- EOF ---