1 /*
   2  * Copyright (c) 2001, 2016, 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_G1_G1COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP
  27 
  28 #include "gc/g1/evacuationInfo.hpp"
  29 #include "gc/g1/g1AllocationContext.hpp"
  30 #include "gc/g1/g1BiasedArray.hpp"
  31 #include "gc/g1/g1CollectionSet.hpp"
  32 #include "gc/g1/g1CollectorState.hpp"
  33 #include "gc/g1/g1ConcurrentMark.hpp"
  34 #include "gc/g1/g1HRPrinter.hpp"
  35 #include "gc/g1/g1InCSetState.hpp"
  36 #include "gc/g1/g1MonitoringSupport.hpp"
  37 #include "gc/g1/g1EvacFailure.hpp"
  38 #include "gc/g1/g1EvacStats.hpp"
  39 #include "gc/g1/g1SATBCardTableModRefBS.hpp"
  40 #include "gc/g1/g1YCTypes.hpp"
  41 #include "gc/g1/hSpaceCounters.hpp"
  42 #include "gc/g1/heapRegionManager.hpp"
  43 #include "gc/g1/heapRegionSet.hpp"
  44 #include "gc/g1/youngList.hpp"
  45 #include "gc/shared/barrierSet.hpp"
  46 #include "gc/shared/collectedHeap.hpp"
  47 #include "gc/shared/plab.hpp"
  48 #include "memory/memRegion.hpp"
  49 #include "utilities/stack.hpp"
  50 
  51 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
  52 // It uses the "Garbage First" heap organization and algorithm, which
  53 // may combine concurrent marking with parallel, incremental compaction of
  54 // heap subsets that will yield large amounts of garbage.
  55 
  56 // Forward declarations
  57 class HeapRegion;
  58 class HRRSCleanupTask;
  59 class GenerationSpec;
  60 class OopsInHeapRegionClosure;
  61 class G1ParScanThreadState;
  62 class G1ParScanThreadStateSet;
  63 class G1KlassScanClosure;
  64 class G1ParScanThreadState;
  65 class ObjectClosure;
  66 class SpaceClosure;
  67 class CompactibleSpaceClosure;
  68 class Space;
  69 class G1CollectionSet;
  70 class G1CollectorPolicy;
  71 class G1RemSet;
  72 class HeapRegionRemSetIterator;
  73 class G1ConcurrentMark;
  74 class ConcurrentMarkThread;
  75 class ConcurrentG1Refine;
  76 class ConcurrentGCTimer;
  77 class GenerationCounters;
  78 class STWGCTimer;
  79 class G1NewTracer;
  80 class G1OldTracer;
  81 class EvacuationFailedInfo;
  82 class nmethod;
  83 class Ticks;
  84 class WorkGang;
  85 class G1Allocator;
  86 class G1ArchiveAllocator;
  87 class G1HeapVerifier;
  88 class G1HeapSizingPolicy;
  89 
  90 typedef OverflowTaskQueue<StarTask, mtGC>         RefToScanQueue;
  91 typedef GenericTaskQueueSet<RefToScanQueue, mtGC> RefToScanQueueSet;
  92 
  93 typedef int RegionIdx_t;   // needs to hold [ 0..max_regions() )
  94 typedef int CardIdx_t;     // needs to hold [ 0..CardsPerRegion )
  95 
  96 // The G1 STW is alive closure.
  97 // An instance is embedded into the G1CH and used as the
  98 // (optional) _is_alive_non_header closure in the STW
  99 // reference processor. It is also extensively used during
 100 // reference processing during STW evacuation pauses.
 101 class G1STWIsAliveClosure: public BoolObjectClosure {
 102   G1CollectedHeap* _g1;
 103 public:
 104   G1STWIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
 105   bool do_object_b(oop p);
 106 };
 107 
 108 class RefineCardTableEntryClosure;
 109 
 110 class G1RegionMappingChangedListener : public G1MappingChangedListener {
 111  private:
 112   void reset_from_card_cache(uint start_idx, size_t num_regions);
 113  public:
 114   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 115 };
 116 
 117 class G1CollectedHeap : public CollectedHeap {
 118   friend class VM_CollectForMetadataAllocation;
 119   friend class VM_G1CollectForAllocation;
 120   friend class VM_G1CollectFull;
 121   friend class VM_G1IncCollectionPause;
 122   friend class VMStructs;
 123   friend class MutatorAllocRegion;
 124   friend class G1GCAllocRegion;
 125   friend class G1HeapVerifier;
 126 
 127   // Closures used in implementation.
 128   friend class G1ParScanThreadState;
 129   friend class G1ParScanThreadStateSet;
 130   friend class G1ParTask;
 131   friend class G1PLABAllocator;
 132   friend class G1PrepareCompactClosure;
 133 
 134   // Other related classes.
 135   friend class HeapRegionClaimer;
 136 
 137   // Testing classes.
 138   friend class G1CheckCSetFastTableClosure;
 139 
 140 private:
 141   WorkGang* _workers;
 142 
 143   static size_t _humongous_object_threshold_in_words;
 144 
 145   // The secondary free list which contains regions that have been
 146   // freed up during the cleanup process. This will be appended to
 147   // the master free list when appropriate.
 148   FreeRegionList _secondary_free_list;
 149 
 150   // It keeps track of the old regions.
 151   HeapRegionSet _old_set;
 152 
 153   // It keeps track of the humongous regions.
 154   HeapRegionSet _humongous_set;
 155 
 156   void eagerly_reclaim_humongous_regions();
 157 
 158   // The number of regions we could create by expansion.
 159   uint _expansion_regions;
 160 
 161   // The block offset table for the G1 heap.
 162   G1BlockOffsetTable* _bot;
 163 
 164   // Tears down the region sets / lists so that they are empty and the
 165   // regions on the heap do not belong to a region set / list. The
 166   // only exception is the humongous set which we leave unaltered. If
 167   // free_list_only is true, it will only tear down the master free
 168   // list. It is called before a Full GC (free_list_only == false) or
 169   // before heap shrinking (free_list_only == true).
 170   void tear_down_region_sets(bool free_list_only);
 171 
 172   // Rebuilds the region sets / lists so that they are repopulated to
 173   // reflect the contents of the heap. The only exception is the
 174   // humongous set which was not torn down in the first place. If
 175   // free_list_only is true, it will only rebuild the master free
 176   // list. It is called after a Full GC (free_list_only == false) or
 177   // after heap shrinking (free_list_only == true).
 178   void rebuild_region_sets(bool free_list_only);
 179 
 180   // Callback for region mapping changed events.
 181   G1RegionMappingChangedListener _listener;
 182 
 183   // The sequence of all heap regions in the heap.
 184   HeapRegionManager _hrm;
 185 
 186   // Manages all allocations with regions except humongous object allocations.
 187   G1Allocator* _allocator;
 188 
 189   // Manages all heap verification.
 190   G1HeapVerifier* _verifier;
 191 
 192   // Outside of GC pauses, the number of bytes used in all regions other
 193   // than the current allocation region(s).
 194   size_t _summary_bytes_used;
 195 
 196   void increase_used(size_t bytes);
 197   void decrease_used(size_t bytes);
 198 
 199   void set_used(size_t bytes);
 200 
 201   // Class that handles archive allocation ranges.
 202   G1ArchiveAllocator* _archive_allocator;
 203 
 204   // Statistics for each allocation context
 205   AllocationContextStats _allocation_context_stats;
 206 
 207   // GC allocation statistics policy for survivors.
 208   G1EvacStats _survivor_evac_stats;
 209 
 210   // GC allocation statistics policy for tenured objects.
 211   G1EvacStats _old_evac_stats;
 212 
 213   // It specifies whether we should attempt to expand the heap after a
 214   // region allocation failure. If heap expansion fails we set this to
 215   // false so that we don't re-attempt the heap expansion (it's likely
 216   // that subsequent expansion attempts will also fail if one fails).
 217   // Currently, it is only consulted during GC and it's reset at the
 218   // start of each GC.
 219   bool _expand_heap_after_alloc_failure;
 220 
 221   // Helper for monitoring and management support.
 222   G1MonitoringSupport* _g1mm;
 223 
 224   // Records whether the region at the given index is (still) a
 225   // candidate for eager reclaim.  Only valid for humongous start
 226   // regions; other regions have unspecified values.  Humongous start
 227   // regions are initialized at start of collection pause, with
 228   // candidates removed from the set as they are found reachable from
 229   // roots or the young generation.
 230   class HumongousReclaimCandidates : public G1BiasedMappedArray<bool> {
 231    protected:
 232     bool default_value() const { return false; }
 233    public:
 234     void clear() { G1BiasedMappedArray<bool>::clear(); }
 235     void set_candidate(uint region, bool value) {
 236       set_by_index(region, value);
 237     }
 238     bool is_candidate(uint region) {
 239       return get_by_index(region);
 240     }
 241   };
 242 
 243   HumongousReclaimCandidates _humongous_reclaim_candidates;
 244   // Stores whether during humongous object registration we found candidate regions.
 245   // If not, we can skip a few steps.
 246   bool _has_humongous_reclaim_candidates;
 247 
 248   volatile unsigned _gc_time_stamp;
 249 
 250   G1HRPrinter _hr_printer;
 251 
 252   // It decides whether an explicit GC should start a concurrent cycle
 253   // instead of doing a STW GC. Currently, a concurrent cycle is
 254   // explicitly started if:
 255   // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
 256   // (b) cause == _g1_humongous_allocation
 257   // (c) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
 258   // (d) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent.
 259   // (e) cause == _update_allocation_context_stats_inc
 260   // (f) cause == _wb_conc_mark
 261   bool should_do_concurrent_full_gc(GCCause::Cause cause);
 262 
 263   // indicates whether we are in young or mixed GC mode
 264   G1CollectorState _collector_state;
 265 
 266   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 267   // concurrent cycles) we have started.
 268   volatile uint _old_marking_cycles_started;
 269 
 270   // Keeps track of how many "old marking cycles" (i.e., Full GCs or
 271   // concurrent cycles) we have completed.
 272   volatile uint _old_marking_cycles_completed;
 273 
 274   bool _heap_summary_sent;
 275 
 276   // This is a non-product method that is helpful for testing. It is
 277   // called at the end of a GC and artificially expands the heap by
 278   // allocating a number of dead regions. This way we can induce very
 279   // frequent marking cycles and stress the cleanup / concurrent
 280   // cleanup code more (as all the regions that will be allocated by
 281   // this method will be found dead by the marking cycle).
 282   void allocate_dummy_regions() PRODUCT_RETURN;
 283 
 284   // Clear RSets after a compaction. It also resets the GC time stamps.
 285   void clear_rsets_post_compaction();
 286 
 287   // If the HR printer is active, dump the state of the regions in the
 288   // heap after a compaction.
 289   void print_hrm_post_compaction();
 290 
 291   // Create a memory mapper for auxiliary data structures of the given size and
 292   // translation factor.
 293   static G1RegionToSpaceMapper* create_aux_memory_mapper(const char* description,
 294                                                          size_t size,
 295                                                          size_t translation_factor);
 296 
 297   void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 298 
 299   void process_weak_jni_handles();
 300 
 301   // These are macros so that, if the assert fires, we get the correct
 302   // line number, file, etc.
 303 
 304 #define heap_locking_asserts_params(_extra_message_)                          \
 305   "%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s",            \
 306   (_extra_message_),                                                          \
 307   BOOL_TO_STR(Heap_lock->owned_by_self()),                                    \
 308   BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),                       \
 309   BOOL_TO_STR(Thread::current()->is_VM_thread())
 310 
 311 #define assert_heap_locked()                                                  \
 312   do {                                                                        \
 313     assert(Heap_lock->owned_by_self(),                                        \
 314            heap_locking_asserts_params("should be holding the Heap_lock"));   \
 315   } while (0)
 316 
 317 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_)             \
 318   do {                                                                        \
 319     assert(Heap_lock->owned_by_self() ||                                      \
 320            (SafepointSynchronize::is_at_safepoint() &&                        \
 321              ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
 322            heap_locking_asserts_params("should be holding the Heap_lock or "  \
 323                                         "should be at a safepoint"));         \
 324   } while (0)
 325 
 326 #define assert_heap_locked_and_not_at_safepoint()                             \
 327   do {                                                                        \
 328     assert(Heap_lock->owned_by_self() &&                                      \
 329                                     !SafepointSynchronize::is_at_safepoint(), \
 330           heap_locking_asserts_params("should be holding the Heap_lock and "  \
 331                                        "should not be at a safepoint"));      \
 332   } while (0)
 333 
 334 #define assert_heap_not_locked()                                              \
 335   do {                                                                        \
 336     assert(!Heap_lock->owned_by_self(),                                       \
 337         heap_locking_asserts_params("should not be holding the Heap_lock"));  \
 338   } while (0)
 339 
 340 #define assert_heap_not_locked_and_not_at_safepoint()                         \
 341   do {                                                                        \
 342     assert(!Heap_lock->owned_by_self() &&                                     \
 343                                     !SafepointSynchronize::is_at_safepoint(), \
 344       heap_locking_asserts_params("should not be holding the Heap_lock and "  \
 345                                    "should not be at a safepoint"));          \
 346   } while (0)
 347 
 348 #define assert_at_safepoint(_should_be_vm_thread_)                            \
 349   do {                                                                        \
 350     assert(SafepointSynchronize::is_at_safepoint() &&                         \
 351               ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
 352            heap_locking_asserts_params("should be at a safepoint"));          \
 353   } while (0)
 354 
 355 #define assert_not_at_safepoint()                                             \
 356   do {                                                                        \
 357     assert(!SafepointSynchronize::is_at_safepoint(),                          \
 358            heap_locking_asserts_params("should not be at a safepoint"));      \
 359   } while (0)
 360 
 361 protected:
 362 
 363   // The young region list.
 364   YoungList*  _young_list;
 365 
 366   // The current policy object for the collector.
 367   G1CollectorPolicy* _g1_policy;
 368   G1HeapSizingPolicy* _heap_sizing_policy;
 369 
 370   G1CollectionSet _collection_set;
 371 
 372   // This is the second level of trying to allocate a new region. If
 373   // new_region() didn't find a region on the free_list, this call will
 374   // check whether there's anything available on the
 375   // secondary_free_list and/or wait for more regions to appear on
 376   // that list, if _free_regions_coming is set.
 377   HeapRegion* new_region_try_secondary_free_list(bool is_old);
 378 
 379   // Try to allocate a single non-humongous HeapRegion sufficient for
 380   // an allocation of the given word_size. If do_expand is true,
 381   // attempt to expand the heap if necessary to satisfy the allocation
 382   // request. If the region is to be used as an old region or for a
 383   // humongous object, set is_old to true. If not, to false.
 384   HeapRegion* new_region(size_t word_size, bool is_old, bool do_expand);
 385 
 386   // Initialize a contiguous set of free regions of length num_regions
 387   // and starting at index first so that they appear as a single
 388   // humongous region.
 389   HeapWord* humongous_obj_allocate_initialize_regions(uint first,
 390                                                       uint num_regions,
 391                                                       size_t word_size,
 392                                                       AllocationContext_t context);
 393 
 394   // Attempt to allocate a humongous object of the given size. Return
 395   // NULL if unsuccessful.
 396   HeapWord* humongous_obj_allocate(size_t word_size, AllocationContext_t context);
 397 
 398   // The following two methods, allocate_new_tlab() and
 399   // mem_allocate(), are the two main entry points from the runtime
 400   // into the G1's allocation routines. They have the following
 401   // assumptions:
 402   //
 403   // * They should both be called outside safepoints.
 404   //
 405   // * They should both be called without holding the Heap_lock.
 406   //
 407   // * All allocation requests for new TLABs should go to
 408   //   allocate_new_tlab().
 409   //
 410   // * All non-TLAB allocation requests should go to mem_allocate().
 411   //
 412   // * If either call cannot satisfy the allocation request using the
 413   //   current allocating region, they will try to get a new one. If
 414   //   this fails, they will attempt to do an evacuation pause and
 415   //   retry the allocation.
 416   //
 417   // * If all allocation attempts fail, even after trying to schedule
 418   //   an evacuation pause, allocate_new_tlab() will return NULL,
 419   //   whereas mem_allocate() will attempt a heap expansion and/or
 420   //   schedule a Full GC.
 421   //
 422   // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
 423   //   should never be called with word_size being humongous. All
 424   //   humongous allocation requests should go to mem_allocate() which
 425   //   will satisfy them with a special path.
 426 
 427   virtual HeapWord* allocate_new_tlab(size_t word_size);
 428 
 429   virtual HeapWord* mem_allocate(size_t word_size,
 430                                  bool*  gc_overhead_limit_was_exceeded);
 431 
 432   // The following three methods take a gc_count_before_ret
 433   // parameter which is used to return the GC count if the method
 434   // returns NULL. Given that we are required to read the GC count
 435   // while holding the Heap_lock, and these paths will take the
 436   // Heap_lock at some point, it's easier to get them to read the GC
 437   // count while holding the Heap_lock before they return NULL instead
 438   // of the caller (namely: mem_allocate()) having to also take the
 439   // Heap_lock just to read the GC count.
 440 
 441   // First-level mutator allocation attempt: try to allocate out of
 442   // the mutator alloc region without taking the Heap_lock. This
 443   // should only be used for non-humongous allocations.
 444   inline HeapWord* attempt_allocation(size_t word_size,
 445                                       uint* gc_count_before_ret,
 446                                       uint* gclocker_retry_count_ret);
 447 
 448   // Second-level mutator allocation attempt: take the Heap_lock and
 449   // retry the allocation attempt, potentially scheduling a GC
 450   // pause. This should only be used for non-humongous allocations.
 451   HeapWord* attempt_allocation_slow(size_t word_size,
 452                                     AllocationContext_t context,
 453                                     uint* gc_count_before_ret,
 454                                     uint* gclocker_retry_count_ret);
 455 
 456   // Takes the Heap_lock and attempts a humongous allocation. It can
 457   // potentially schedule a GC pause.
 458   HeapWord* attempt_allocation_humongous(size_t word_size,
 459                                          uint* gc_count_before_ret,
 460                                          uint* gclocker_retry_count_ret);
 461 
 462   // Allocation attempt that should be called during safepoints (e.g.,
 463   // at the end of a successful GC). expect_null_mutator_alloc_region
 464   // specifies whether the mutator alloc region is expected to be NULL
 465   // or not.
 466   HeapWord* attempt_allocation_at_safepoint(size_t word_size,
 467                                             AllocationContext_t context,
 468                                             bool expect_null_mutator_alloc_region);
 469 
 470   // These methods are the "callbacks" from the G1AllocRegion class.
 471 
 472   // For mutator alloc regions.
 473   HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
 474   void retire_mutator_alloc_region(HeapRegion* alloc_region,
 475                                    size_t allocated_bytes);
 476 
 477   // For GC alloc regions.
 478   HeapRegion* new_gc_alloc_region(size_t word_size, uint count,
 479                                   InCSetState dest);
 480   void retire_gc_alloc_region(HeapRegion* alloc_region,
 481                               size_t allocated_bytes, InCSetState dest);
 482 
 483   // - if explicit_gc is true, the GC is for a System.gc() etc,
 484   //   otherwise it's for a failed allocation.
 485   // - if clear_all_soft_refs is true, all soft references should be
 486   //   cleared during the GC.
 487   // - it returns false if it is unable to do the collection due to the
 488   //   GC locker being active, true otherwise.
 489   bool do_full_collection(bool explicit_gc,
 490                           bool clear_all_soft_refs);
 491 
 492   // Callback from VM_G1CollectFull operation, or collect_as_vm_thread.
 493   virtual void do_full_collection(bool clear_all_soft_refs);
 494 
 495   // Resize the heap if necessary after a full collection.
 496   void resize_if_necessary_after_full_collection();
 497 
 498   // Callback from VM_G1CollectForAllocation operation.
 499   // This function does everything necessary/possible to satisfy a
 500   // failed allocation request (including collection, expansion, etc.)
 501   HeapWord* satisfy_failed_allocation(size_t word_size,
 502                                       AllocationContext_t context,
 503                                       bool* succeeded);
 504 private:
 505   // Helper method for satisfy_failed_allocation()
 506   HeapWord* satisfy_failed_allocation_helper(size_t word_size,
 507                                              AllocationContext_t context,
 508                                              bool do_gc,
 509                                              bool clear_all_soft_refs,
 510                                              bool expect_null_mutator_alloc_region,
 511                                              bool* gc_succeeded);
 512 
 513 protected:
 514   // Attempting to expand the heap sufficiently
 515   // to support an allocation of the given "word_size".  If
 516   // successful, perform the allocation and return the address of the
 517   // allocated block, or else "NULL".
 518   HeapWord* expand_and_allocate(size_t word_size, AllocationContext_t context);
 519 
 520   // Preserve any referents discovered by concurrent marking that have not yet been
 521   // copied by the STW pause.
 522   void preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states);
 523   // Process any reference objects discovered during
 524   // an incremental evacuation pause.
 525   void process_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 526 
 527   // Enqueue any remaining discovered references
 528   // after processing.
 529   void enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states);
 530 
 531   // Merges the information gathered on a per-thread basis for all worker threads
 532   // during GC into global variables.
 533   void merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states);
 534 public:
 535   WorkGang* workers() const { return _workers; }
 536 
 537   G1Allocator* allocator() {
 538     return _allocator;
 539   }
 540 
 541   G1HeapVerifier* verifier() {
 542     return _verifier;
 543   }
 544 
 545   G1MonitoringSupport* g1mm() {
 546     assert(_g1mm != NULL, "should have been initialized");
 547     return _g1mm;
 548   }
 549 
 550   // Expand the garbage-first heap by at least the given size (in bytes!).
 551   // Returns true if the heap was expanded by the requested amount;
 552   // false otherwise.
 553   // (Rounds up to a HeapRegion boundary.)
 554   bool expand(size_t expand_bytes, double* expand_time_ms = NULL);
 555 
 556   // Returns the PLAB statistics for a given destination.
 557   inline G1EvacStats* alloc_buffer_stats(InCSetState dest);
 558 
 559   // Determines PLAB size for a given destination.
 560   inline size_t desired_plab_sz(InCSetState dest);
 561 
 562   inline AllocationContextStats& allocation_context_stats();
 563 
 564   // Do anything common to GC's.
 565   void gc_prologue(bool full);
 566   void gc_epilogue(bool full);
 567 
 568   // Modify the reclaim candidate set and test for presence.
 569   // These are only valid for starts_humongous regions.
 570   inline void set_humongous_reclaim_candidate(uint region, bool value);
 571   inline bool is_humongous_reclaim_candidate(uint region);
 572 
 573   // Remove from the reclaim candidate set.  Also remove from the
 574   // collection set so that later encounters avoid the slow path.
 575   inline void set_humongous_is_live(oop obj);
 576 
 577   // Register the given region to be part of the collection set.
 578   inline void register_humongous_region_with_cset(uint index);
 579   // Register regions with humongous objects (actually on the start region) in
 580   // the in_cset_fast_test table.
 581   void register_humongous_regions_with_cset();
 582   // We register a region with the fast "in collection set" test. We
 583   // simply set to true the array slot corresponding to this region.
 584   void register_young_region_with_cset(HeapRegion* r) {
 585     _in_cset_fast_test.set_in_young(r->hrm_index());
 586   }
 587   void register_old_region_with_cset(HeapRegion* r) {
 588     _in_cset_fast_test.set_in_old(r->hrm_index());
 589   }
 590   inline void register_ext_region_with_cset(HeapRegion* r) {
 591     _in_cset_fast_test.set_ext(r->hrm_index());
 592   }
 593   void clear_in_cset(const HeapRegion* hr) {
 594     _in_cset_fast_test.clear(hr);
 595   }
 596 
 597   void clear_cset_fast_test() {
 598     _in_cset_fast_test.clear();
 599   }
 600 
 601   bool is_user_requested_concurrent_full_gc(GCCause::Cause cause);
 602 
 603   // This is called at the start of either a concurrent cycle or a Full
 604   // GC to update the number of old marking cycles started.
 605   void increment_old_marking_cycles_started();
 606 
 607   // This is called at the end of either a concurrent cycle or a Full
 608   // GC to update the number of old marking cycles completed. Those two
 609   // can happen in a nested fashion, i.e., we start a concurrent
 610   // cycle, a Full GC happens half-way through it which ends first,
 611   // and then the cycle notices that a Full GC happened and ends
 612   // too. The concurrent parameter is a boolean to help us do a bit
 613   // tighter consistency checking in the method. If concurrent is
 614   // false, the caller is the inner caller in the nesting (i.e., the
 615   // Full GC). If concurrent is true, the caller is the outer caller
 616   // in this nesting (i.e., the concurrent cycle). Further nesting is
 617   // not currently supported. The end of this call also notifies
 618   // the FullGCCount_lock in case a Java thread is waiting for a full
 619   // GC to happen (e.g., it called System.gc() with
 620   // +ExplicitGCInvokesConcurrent).
 621   void increment_old_marking_cycles_completed(bool concurrent);
 622 
 623   uint old_marking_cycles_completed() {
 624     return _old_marking_cycles_completed;
 625   }
 626 
 627   void register_concurrent_cycle_start(const Ticks& start_time);
 628   void register_concurrent_cycle_end();
 629   void trace_heap_after_concurrent_cycle();
 630 
 631   G1HRPrinter* hr_printer() { return &_hr_printer; }
 632 
 633   // Allocates a new heap region instance.
 634   HeapRegion* new_heap_region(uint hrs_index, MemRegion mr);
 635 
 636   // Allocate the highest free region in the reserved heap. This will commit
 637   // regions as necessary.
 638   HeapRegion* alloc_highest_free_region();
 639 
 640   // Frees a non-humongous region by initializing its contents and
 641   // adding it to the free list that's passed as a parameter (this is
 642   // usually a local list which will be appended to the master free
 643   // list later). The used bytes of freed regions are accumulated in
 644   // pre_used. If par is true, the region's RSet will not be freed
 645   // up. The assumption is that this will be done later.
 646   // The locked parameter indicates if the caller has already taken
 647   // care of proper synchronization. This may allow some optimizations.
 648   void free_region(HeapRegion* hr,
 649                    FreeRegionList* free_list,
 650                    bool par,
 651                    bool locked = false);
 652 
 653   // It dirties the cards that cover the block so that the post
 654   // write barrier never queues anything when updating objects on this
 655   // block. It is assumed (and in fact we assert) that the block
 656   // belongs to a young region.
 657   inline void dirty_young_block(HeapWord* start, size_t word_size);
 658 
 659   // Frees a humongous region by collapsing it into individual regions
 660   // and calling free_region() for each of them. The freed regions
 661   // will be added to the free list that's passed as a parameter (this
 662   // is usually a local list which will be appended to the master free
 663   // list later). The used bytes of freed regions are accumulated in
 664   // pre_used. If par is true, the region's RSet will not be freed
 665   // up. The assumption is that this will be done later.
 666   void free_humongous_region(HeapRegion* hr,
 667                              FreeRegionList* free_list,
 668                              bool par);
 669 
 670   // Facility for allocating in 'archive' regions in high heap memory and
 671   // recording the allocated ranges. These should all be called from the
 672   // VM thread at safepoints, without the heap lock held. They can be used
 673   // to create and archive a set of heap regions which can be mapped at the
 674   // same fixed addresses in a subsequent JVM invocation.
 675   void begin_archive_alloc_range();
 676 
 677   // Check if the requested size would be too large for an archive allocation.
 678   bool is_archive_alloc_too_large(size_t word_size);
 679 
 680   // Allocate memory of the requested size from the archive region. This will
 681   // return NULL if the size is too large or if no memory is available. It
 682   // does not trigger a garbage collection.
 683   HeapWord* archive_mem_allocate(size_t word_size);
 684 
 685   // Optionally aligns the end address and returns the allocated ranges in
 686   // an array of MemRegions in order of ascending addresses.
 687   void end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 688                                size_t end_alignment_in_bytes = 0);
 689 
 690   // Facility for allocating a fixed range within the heap and marking
 691   // the containing regions as 'archive'. For use at JVM init time, when the
 692   // caller may mmap archived heap data at the specified range(s).
 693   // Verify that the MemRegions specified in the argument array are within the
 694   // reserved heap.
 695   bool check_archive_addresses(MemRegion* range, size_t count);
 696 
 697   // Commit the appropriate G1 regions containing the specified MemRegions
 698   // and mark them as 'archive' regions. The regions in the array must be
 699   // non-overlapping and in order of ascending address.
 700   bool alloc_archive_regions(MemRegion* range, size_t count);
 701 
 702   // Insert any required filler objects in the G1 regions around the specified
 703   // ranges to make the regions parseable. This must be called after
 704   // alloc_archive_regions, and after class loading has occurred.
 705   void fill_archive_regions(MemRegion* range, size_t count);
 706 
 707   // For each of the specified MemRegions, uncommit the containing G1 regions
 708   // which had been allocated by alloc_archive_regions. This should be called
 709   // rather than fill_archive_regions at JVM init time if the archive file
 710   // mapping failed, with the same non-overlapping and sorted MemRegion array.
 711   void dealloc_archive_regions(MemRegion* range, size_t count);
 712 
 713 protected:
 714 
 715   // Shrink the garbage-first heap by at most the given size (in bytes!).
 716   // (Rounds down to a HeapRegion boundary.)
 717   virtual void shrink(size_t expand_bytes);
 718   void shrink_helper(size_t expand_bytes);
 719 
 720   #if TASKQUEUE_STATS
 721   static void print_taskqueue_stats_hdr(outputStream* const st);
 722   void print_taskqueue_stats() const;
 723   void reset_taskqueue_stats();
 724   #endif // TASKQUEUE_STATS
 725 
 726   // Schedule the VM operation that will do an evacuation pause to
 727   // satisfy an allocation request of word_size. *succeeded will
 728   // return whether the VM operation was successful (it did do an
 729   // evacuation pause) or not (another thread beat us to it or the GC
 730   // locker was active). Given that we should not be holding the
 731   // Heap_lock when we enter this method, we will pass the
 732   // gc_count_before (i.e., total_collections()) as a parameter since
 733   // it has to be read while holding the Heap_lock. Currently, both
 734   // methods that call do_collection_pause() release the Heap_lock
 735   // before the call, so it's easy to read gc_count_before just before.
 736   HeapWord* do_collection_pause(size_t         word_size,
 737                                 uint           gc_count_before,
 738                                 bool*          succeeded,
 739                                 GCCause::Cause gc_cause);
 740 
 741   void wait_for_root_region_scanning();
 742 
 743   // The guts of the incremental collection pause, executed by the vm
 744   // thread. It returns false if it is unable to do the collection due
 745   // to the GC locker being active, true otherwise
 746   bool do_collection_pause_at_safepoint(double target_pause_time_ms);
 747 
 748   // Actually do the work of evacuating the collection set.
 749   virtual void evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states);
 750 
 751   void pre_evacuate_collection_set();
 752   void post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* pss);
 753 
 754   // Print the header for the per-thread termination statistics.
 755   static void print_termination_stats_hdr();
 756   // Print actual per-thread termination statistics.
 757   void print_termination_stats(uint worker_id,
 758                                double elapsed_ms,
 759                                double strong_roots_ms,
 760                                double term_ms,
 761                                size_t term_attempts,
 762                                size_t alloc_buffer_waste,
 763                                size_t undo_waste) const;
 764   // Update object copying statistics.
 765   void record_obj_copy_mem_stats();
 766 
 767   // The g1 remembered set of the heap.
 768   G1RemSet* _g1_rem_set;
 769 
 770   // A set of cards that cover the objects for which the Rsets should be updated
 771   // concurrently after the collection.
 772   DirtyCardQueueSet _dirty_card_queue_set;
 773 
 774   // The closure used to refine a single card.
 775   RefineCardTableEntryClosure* _refine_cte_cl;
 776 
 777   // After a collection pause, make the regions in the CS into free
 778   // regions.
 779   void free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words);
 780 
 781   // Abandon the current collection set without recording policy
 782   // statistics or updating free lists.
 783   void abandon_collection_set(HeapRegion* cs_head);
 784 
 785   // The concurrent marker (and the thread it runs in.)
 786   G1ConcurrentMark* _cm;
 787   ConcurrentMarkThread* _cmThread;
 788 
 789   // The concurrent refiner.
 790   ConcurrentG1Refine* _cg1r;
 791 
 792   // The parallel task queues
 793   RefToScanQueueSet *_task_queues;
 794 
 795   // True iff a evacuation has failed in the current collection.
 796   bool _evacuation_failed;
 797 
 798   EvacuationFailedInfo* _evacuation_failed_info_array;
 799 
 800   // Failed evacuations cause some logical from-space objects to have
 801   // forwarding pointers to themselves.  Reset them.
 802   void remove_self_forwarding_pointers();
 803 
 804   // Restore the preserved mark words for objects with self-forwarding pointers.
 805   void restore_preserved_marks();
 806 
 807   // Restore the objects in the regions in the collection set after an
 808   // evacuation failure.
 809   void restore_after_evac_failure();
 810 
 811   // Stores marks with the corresponding oop that we need to preserve during evacuation
 812   // failure.
 813   OopAndMarkOopStack*  _preserved_objs;
 814 
 815   // Preserve the mark of "obj", if necessary, in preparation for its mark
 816   // word being overwritten with a self-forwarding-pointer.
 817   void preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m);
 818 
 819 #ifndef PRODUCT
 820   // Support for forcing evacuation failures. Analogous to
 821   // PromotionFailureALot for the other collectors.
 822 
 823   // Records whether G1EvacuationFailureALot should be in effect
 824   // for the current GC
 825   bool _evacuation_failure_alot_for_current_gc;
 826 
 827   // Used to record the GC number for interval checking when
 828   // determining whether G1EvaucationFailureALot is in effect
 829   // for the current GC.
 830   size_t _evacuation_failure_alot_gc_number;
 831 
 832   // Count of the number of evacuations between failures.
 833   volatile size_t _evacuation_failure_alot_count;
 834 
 835   // Set whether G1EvacuationFailureALot should be in effect
 836   // for the current GC (based upon the type of GC and which
 837   // command line flags are set);
 838   inline bool evacuation_failure_alot_for_gc_type(bool gcs_are_young,
 839                                                   bool during_initial_mark,
 840                                                   bool during_marking);
 841 
 842   inline void set_evacuation_failure_alot_for_current_gc();
 843 
 844   // Return true if it's time to cause an evacuation failure.
 845   inline bool evacuation_should_fail();
 846 
 847   // Reset the G1EvacuationFailureALot counters.  Should be called at
 848   // the end of an evacuation pause in which an evacuation failure occurred.
 849   inline void reset_evacuation_should_fail();
 850 #endif // !PRODUCT
 851 
 852   // ("Weak") Reference processing support.
 853   //
 854   // G1 has 2 instances of the reference processor class. One
 855   // (_ref_processor_cm) handles reference object discovery
 856   // and subsequent processing during concurrent marking cycles.
 857   //
 858   // The other (_ref_processor_stw) handles reference object
 859   // discovery and processing during full GCs and incremental
 860   // evacuation pauses.
 861   //
 862   // During an incremental pause, reference discovery will be
 863   // temporarily disabled for _ref_processor_cm and will be
 864   // enabled for _ref_processor_stw. At the end of the evacuation
 865   // pause references discovered by _ref_processor_stw will be
 866   // processed and discovery will be disabled. The previous
 867   // setting for reference object discovery for _ref_processor_cm
 868   // will be re-instated.
 869   //
 870   // At the start of marking:
 871   //  * Discovery by the CM ref processor is verified to be inactive
 872   //    and it's discovered lists are empty.
 873   //  * Discovery by the CM ref processor is then enabled.
 874   //
 875   // At the end of marking:
 876   //  * Any references on the CM ref processor's discovered
 877   //    lists are processed (possibly MT).
 878   //
 879   // At the start of full GC we:
 880   //  * Disable discovery by the CM ref processor and
 881   //    empty CM ref processor's discovered lists
 882   //    (without processing any entries).
 883   //  * Verify that the STW ref processor is inactive and it's
 884   //    discovered lists are empty.
 885   //  * Temporarily set STW ref processor discovery as single threaded.
 886   //  * Temporarily clear the STW ref processor's _is_alive_non_header
 887   //    field.
 888   //  * Finally enable discovery by the STW ref processor.
 889   //
 890   // The STW ref processor is used to record any discovered
 891   // references during the full GC.
 892   //
 893   // At the end of a full GC we:
 894   //  * Enqueue any reference objects discovered by the STW ref processor
 895   //    that have non-live referents. This has the side-effect of
 896   //    making the STW ref processor inactive by disabling discovery.
 897   //  * Verify that the CM ref processor is still inactive
 898   //    and no references have been placed on it's discovered
 899   //    lists (also checked as a precondition during initial marking).
 900 
 901   // The (stw) reference processor...
 902   ReferenceProcessor* _ref_processor_stw;
 903 
 904   STWGCTimer* _gc_timer_stw;
 905   ConcurrentGCTimer* _gc_timer_cm;
 906 
 907   G1OldTracer* _gc_tracer_cm;
 908   G1NewTracer* _gc_tracer_stw;
 909 
 910   // During reference object discovery, the _is_alive_non_header
 911   // closure (if non-null) is applied to the referent object to
 912   // determine whether the referent is live. If so then the
 913   // reference object does not need to be 'discovered' and can
 914   // be treated as a regular oop. This has the benefit of reducing
 915   // the number of 'discovered' reference objects that need to
 916   // be processed.
 917   //
 918   // Instance of the is_alive closure for embedding into the
 919   // STW reference processor as the _is_alive_non_header field.
 920   // Supplying a value for the _is_alive_non_header field is
 921   // optional but doing so prevents unnecessary additions to
 922   // the discovered lists during reference discovery.
 923   G1STWIsAliveClosure _is_alive_closure_stw;
 924 
 925   // The (concurrent marking) reference processor...
 926   ReferenceProcessor* _ref_processor_cm;
 927 
 928   // Instance of the concurrent mark is_alive closure for embedding
 929   // into the Concurrent Marking reference processor as the
 930   // _is_alive_non_header field. Supplying a value for the
 931   // _is_alive_non_header field is optional but doing so prevents
 932   // unnecessary additions to the discovered lists during reference
 933   // discovery.
 934   G1CMIsAliveClosure _is_alive_closure_cm;
 935 
 936   // Cache used by G1CollectedHeap::start_cset_region_for_worker().
 937   HeapRegion** _worker_cset_start_region;
 938 
 939   // Time stamp to validate the regions recorded in the cache
 940   // used by G1CollectedHeap::start_cset_region_for_worker().
 941   // The heap region entry for a given worker is valid iff
 942   // the associated time stamp value matches the current value
 943   // of G1CollectedHeap::_gc_time_stamp.
 944   uint* _worker_cset_start_region_time_stamp;
 945 
 946   volatile bool _free_regions_coming;
 947 
 948 public:
 949 
 950   void set_refine_cte_cl_concurrency(bool concurrent);
 951 
 952   RefToScanQueue *task_queue(uint i) const;
 953 
 954   uint num_task_queues() const;
 955 
 956   // A set of cards where updates happened during the GC
 957   DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
 958 
 959   // Create a G1CollectedHeap with the specified policy.
 960   // Must call the initialize method afterwards.
 961   // May not return if something goes wrong.
 962   G1CollectedHeap(G1CollectorPolicy* policy);
 963 
 964   // Initialize the G1CollectedHeap to have the initial and
 965   // maximum sizes and remembered and barrier sets
 966   // specified by the policy object.
 967   jint initialize();
 968 
 969   virtual void stop();
 970 
 971   // Return the (conservative) maximum heap alignment for any G1 heap
 972   static size_t conservative_max_heap_alignment();
 973 
 974   // Does operations required after initialization has been done.
 975   void post_initialize();
 976 
 977   // Initialize weak reference processing.
 978   void ref_processing_init();
 979 
 980   virtual Name kind() const {
 981     return CollectedHeap::G1CollectedHeap;
 982   }
 983 
 984   virtual const char* name() const {
 985     return "G1";
 986   }
 987 
 988   const G1CollectorState* collector_state() const { return &_collector_state; }
 989   G1CollectorState* collector_state() { return &_collector_state; }
 990 
 991   // The current policy object for the collector.
 992   G1CollectorPolicy* g1_policy() const { return _g1_policy; }
 993 
 994   const G1CollectionSet* collection_set() const { return &_collection_set; }
 995   G1CollectionSet* collection_set() { return &_collection_set; }
 996 
 997   virtual CollectorPolicy* collector_policy() const;
 998 
 999   // Adaptive size policy.  No such thing for g1.
1000   virtual AdaptiveSizePolicy* size_policy() { return NULL; }
1001 
1002   // The rem set and barrier set.
1003   G1RemSet* g1_rem_set() const { return _g1_rem_set; }
1004 
1005   void scrub_rem_set(BitMap* region_bm, BitMap* card_bm);
1006 
1007   unsigned get_gc_time_stamp() {
1008     return _gc_time_stamp;
1009   }
1010 
1011   inline void reset_gc_time_stamp();
1012 
1013   void check_gc_time_stamps() PRODUCT_RETURN;
1014 
1015   inline void increment_gc_time_stamp();
1016 
1017   // Reset the given region's GC timestamp. If it's starts humongous,
1018   // also reset the GC timestamp of its corresponding
1019   // continues humongous regions too.
1020   void reset_gc_time_stamps(HeapRegion* hr);
1021 
1022   // Apply the given closure on all cards in the Hot Card Cache, emptying it.
1023   void iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i);
1024 
1025   // Apply the given closure on all cards in the Dirty Card Queue Set, emptying it.
1026   void iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i);
1027 
1028   // The shared block offset table array.
1029   G1BlockOffsetTable* bot() const { return _bot; }
1030 
1031   // Reference Processing accessors
1032 
1033   // The STW reference processor....
1034   ReferenceProcessor* ref_processor_stw() const { return _ref_processor_stw; }
1035 
1036   G1NewTracer* gc_tracer_stw() const { return _gc_tracer_stw; }
1037 
1038   // The Concurrent Marking reference processor...
1039   ReferenceProcessor* ref_processor_cm() const { return _ref_processor_cm; }
1040 
1041   ConcurrentGCTimer* gc_timer_cm() const { return _gc_timer_cm; }
1042   G1OldTracer* gc_tracer_cm() const { return _gc_tracer_cm; }
1043 
1044   virtual size_t capacity() const;
1045   virtual size_t used() const;
1046   // This should be called when we're not holding the heap lock. The
1047   // result might be a bit inaccurate.
1048   size_t used_unlocked() const;
1049   size_t recalculate_used() const;
1050 
1051   // These virtual functions do the actual allocation.
1052   // Some heaps may offer a contiguous region for shared non-blocking
1053   // allocation, via inlined code (by exporting the address of the top and
1054   // end fields defining the extent of the contiguous allocation region.)
1055   // But G1CollectedHeap doesn't yet support this.
1056 
1057   virtual bool is_maximal_no_gc() const {
1058     return _hrm.available() == 0;
1059   }
1060 
1061   // The current number of regions in the heap.
1062   uint num_regions() const { return _hrm.length(); }
1063 
1064   // The max number of regions in the heap.
1065   uint max_regions() const { return _hrm.max_length(); }
1066 
1067   // The number of regions that are completely free.
1068   uint num_free_regions() const { return _hrm.num_free_regions(); }
1069 
1070   MemoryUsage get_auxiliary_data_memory_usage() const {
1071     return _hrm.get_auxiliary_data_memory_usage();
1072   }
1073 
1074   // The number of regions that are not completely free.
1075   uint num_used_regions() const { return num_regions() - num_free_regions(); }
1076 
1077 #ifdef ASSERT
1078   bool is_on_master_free_list(HeapRegion* hr) {
1079     return _hrm.is_free(hr);
1080   }
1081 #endif // ASSERT
1082 
1083   // Wrapper for the region list operations that can be called from
1084   // methods outside this class.
1085 
1086   void secondary_free_list_add(FreeRegionList* list) {
1087     _secondary_free_list.add_ordered(list);
1088   }
1089 
1090   void append_secondary_free_list() {
1091     _hrm.insert_list_into_free_list(&_secondary_free_list);
1092   }
1093 
1094   void append_secondary_free_list_if_not_empty_with_lock() {
1095     // If the secondary free list looks empty there's no reason to
1096     // take the lock and then try to append it.
1097     if (!_secondary_free_list.is_empty()) {
1098       MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1099       append_secondary_free_list();
1100     }
1101   }
1102 
1103   inline void old_set_add(HeapRegion* hr);
1104   inline void old_set_remove(HeapRegion* hr);
1105 
1106   size_t non_young_capacity_bytes() {
1107     return (_old_set.length() + _humongous_set.length()) * HeapRegion::GrainBytes;
1108   }
1109 
1110   void set_free_regions_coming();
1111   void reset_free_regions_coming();
1112   bool free_regions_coming() { return _free_regions_coming; }
1113   void wait_while_free_regions_coming();
1114 
1115   // Determine whether the given region is one that we are using as an
1116   // old GC alloc region.
1117   bool is_old_gc_alloc_region(HeapRegion* hr);
1118 
1119   // Perform a collection of the heap; intended for use in implementing
1120   // "System.gc".  This probably implies as full a collection as the
1121   // "CollectedHeap" supports.
1122   virtual void collect(GCCause::Cause cause);
1123 
1124   virtual bool copy_allocation_context_stats(const jint* contexts,
1125                                              jlong* totals,
1126                                              jbyte* accuracy,
1127                                              jint len);
1128 
1129   // True iff an evacuation has failed in the most-recent collection.
1130   bool evacuation_failed() { return _evacuation_failed; }
1131 
1132   void remove_from_old_sets(const uint old_regions_removed, const uint humongous_regions_removed);
1133   void prepend_to_freelist(FreeRegionList* list);
1134   void decrement_summary_bytes(size_t bytes);
1135 
1136   virtual bool is_in(const void* p) const;
1137 #ifdef ASSERT
1138   // Returns whether p is in one of the available areas of the heap. Slow but
1139   // extensive version.
1140   bool is_in_exact(const void* p) const;
1141 #endif
1142 
1143   // Return "TRUE" iff the given object address is within the collection
1144   // set. Slow implementation.
1145   bool obj_in_cs(oop obj);
1146 
1147   inline bool is_in_cset(const HeapRegion *hr);
1148   inline bool is_in_cset(oop obj);
1149 
1150   inline bool is_in_cset_or_humongous(const oop obj);
1151 
1152  private:
1153   // This array is used for a quick test on whether a reference points into
1154   // the collection set or not. Each of the array's elements denotes whether the
1155   // corresponding region is in the collection set or not.
1156   G1InCSetStateFastTestBiasedMappedArray _in_cset_fast_test;
1157 
1158  public:
1159 
1160   inline InCSetState in_cset_state(const oop obj);
1161 
1162   // Return "TRUE" iff the given object address is in the reserved
1163   // region of g1.
1164   bool is_in_g1_reserved(const void* p) const {
1165     return _hrm.reserved().contains(p);
1166   }
1167 
1168   // Returns a MemRegion that corresponds to the space that has been
1169   // reserved for the heap
1170   MemRegion g1_reserved() const {
1171     return _hrm.reserved();
1172   }
1173 
1174   virtual bool is_in_closed_subset(const void* p) const;
1175 
1176   G1SATBCardTableLoggingModRefBS* g1_barrier_set() {
1177     return barrier_set_cast<G1SATBCardTableLoggingModRefBS>(barrier_set());
1178   }
1179 
1180   // This resets the card table to all zeros.  It is used after
1181   // a collection pause which used the card table to claim cards.
1182   void cleanUpCardTable();
1183 
1184   // Iteration functions.
1185 
1186   // Iterate over all objects, calling "cl.do_object" on each.
1187   virtual void object_iterate(ObjectClosure* cl);
1188 
1189   virtual void safe_object_iterate(ObjectClosure* cl) {
1190     object_iterate(cl);
1191   }
1192 
1193   // Iterate over heap regions, in address order, terminating the
1194   // iteration early if the "doHeapRegion" method returns "true".
1195   void heap_region_iterate(HeapRegionClosure* blk) const;
1196 
1197   // Return the region with the given index. It assumes the index is valid.
1198   inline HeapRegion* region_at(uint index) const;
1199 
1200   // Return the next region (by index) that is part of the same
1201   // humongous object that hr is part of.
1202   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
1203 
1204   // Calculate the region index of the given address. Given address must be
1205   // within the heap.
1206   inline uint addr_to_region(HeapWord* addr) const;
1207 
1208   inline HeapWord* bottom_addr_for_region(uint index) const;
1209 
1210   // Iterate over the heap regions in parallel. Assumes that this will be called
1211   // in parallel by ParallelGCThreads worker threads with distinct worker ids
1212   // in the range [0..max(ParallelGCThreads-1, 1)]. Applies "blk->doHeapRegion"
1213   // to each of the regions, by attempting to claim the region using the
1214   // HeapRegionClaimer and, if successful, applying the closure to the claimed
1215   // region. The concurrent argument should be set to true if iteration is
1216   // performed concurrently, during which no assumptions are made for consistent
1217   // attributes of the heap regions (as they might be modified while iterating).
1218   void heap_region_par_iterate(HeapRegionClosure* cl,
1219                                uint worker_id,
1220                                HeapRegionClaimer* hrclaimer,
1221                                bool concurrent = false) const;
1222 
1223   // Clear the cached cset start regions and (more importantly)
1224   // the time stamps. Called when we reset the GC time stamp.
1225   void clear_cset_start_regions();
1226 
1227   // Given the id of a worker, obtain or calculate a suitable
1228   // starting region for iterating over the current collection set.
1229   HeapRegion* start_cset_region_for_worker(uint worker_i);
1230 
1231   // Iterate over the regions (if any) in the current collection set.
1232   void collection_set_iterate(HeapRegionClosure* blk);
1233 
1234   // As above but starting from region r
1235   void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1236 
1237   HeapRegion* next_compaction_region(const HeapRegion* from) const;
1238 
1239   // Returns the HeapRegion that contains addr. addr must not be NULL.
1240   template <class T>
1241   inline HeapRegion* heap_region_containing(const T addr) const;
1242 
1243   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1244   // each address in the (reserved) heap is a member of exactly
1245   // one block.  The defining characteristic of a block is that it is
1246   // possible to find its size, and thus to progress forward to the next
1247   // block.  (Blocks may be of different sizes.)  Thus, blocks may
1248   // represent Java objects, or they might be free blocks in a
1249   // free-list-based heap (or subheap), as long as the two kinds are
1250   // distinguishable and the size of each is determinable.
1251 
1252   // Returns the address of the start of the "block" that contains the
1253   // address "addr".  We say "blocks" instead of "object" since some heaps
1254   // may not pack objects densely; a chunk may either be an object or a
1255   // non-object.
1256   virtual HeapWord* block_start(const void* addr) const;
1257 
1258   // Requires "addr" to be the start of a chunk, and returns its size.
1259   // "addr + size" is required to be the start of a new chunk, or the end
1260   // of the active area of the heap.
1261   virtual size_t block_size(const HeapWord* addr) const;
1262 
1263   // Requires "addr" to be the start of a block, and returns "TRUE" iff
1264   // the block is an object.
1265   virtual bool block_is_obj(const HeapWord* addr) const;
1266 
1267   // Section on thread-local allocation buffers (TLABs)
1268   // See CollectedHeap for semantics.
1269 
1270   bool supports_tlab_allocation() const;
1271   size_t tlab_capacity(Thread* ignored) const;
1272   size_t tlab_used(Thread* ignored) const;
1273   size_t max_tlab_size() const;
1274   size_t unsafe_max_tlab_alloc(Thread* ignored) const;
1275 
1276   // Can a compiler initialize a new object without store barriers?
1277   // This permission only extends from the creation of a new object
1278   // via a TLAB up to the first subsequent safepoint. If such permission
1279   // is granted for this heap type, the compiler promises to call
1280   // defer_store_barrier() below on any slow path allocation of
1281   // a new object for which such initializing store barriers will
1282   // have been elided. G1, like CMS, allows this, but should be
1283   // ready to provide a compensating write barrier as necessary
1284   // if that storage came out of a non-young region. The efficiency
1285   // of this implementation depends crucially on being able to
1286   // answer very efficiently in constant time whether a piece of
1287   // storage in the heap comes from a young region or not.
1288   // See ReduceInitialCardMarks.
1289   virtual bool can_elide_tlab_store_barriers() const {
1290     return true;
1291   }
1292 
1293   virtual bool card_mark_must_follow_store() const {
1294     return true;
1295   }
1296 
1297   inline bool is_in_young(const oop obj);
1298 
1299   virtual bool is_scavengable(const void* addr);
1300 
1301   // We don't need barriers for initializing stores to objects
1302   // in the young gen: for the SATB pre-barrier, there is no
1303   // pre-value that needs to be remembered; for the remembered-set
1304   // update logging post-barrier, we don't maintain remembered set
1305   // information for young gen objects.
1306   virtual inline bool can_elide_initializing_store_barrier(oop new_obj);
1307 
1308   // Returns "true" iff the given word_size is "very large".
1309   static bool is_humongous(size_t word_size) {
1310     // Note this has to be strictly greater-than as the TLABs
1311     // are capped at the humongous threshold and we want to
1312     // ensure that we don't try to allocate a TLAB as
1313     // humongous and that we don't allocate a humongous
1314     // object in a TLAB.
1315     return word_size > _humongous_object_threshold_in_words;
1316   }
1317 
1318   // Returns the humongous threshold for a specific region size
1319   static size_t humongous_threshold_for(size_t region_size) {
1320     return (region_size / 2);
1321   }
1322 
1323   // Returns the number of regions the humongous object of the given word size
1324   // requires.
1325   static size_t humongous_obj_size_in_regions(size_t word_size);
1326 
1327   // Print the maximum heap capacity.
1328   virtual size_t max_capacity() const;
1329 
1330   virtual jlong millis_since_last_gc();
1331 
1332 
1333   // Convenience function to be used in situations where the heap type can be
1334   // asserted to be this type.
1335   static G1CollectedHeap* heap();
1336 
1337   void set_region_short_lived_locked(HeapRegion* hr);
1338   // add appropriate methods for any other surv rate groups
1339 
1340   YoungList* young_list() const { return _young_list; }
1341 
1342   uint old_regions_count() const { return _old_set.length(); }
1343 
1344   uint humongous_regions_count() const { return _humongous_set.length(); }
1345 
1346   // debugging
1347   bool check_young_list_well_formed() {
1348     return _young_list->check_list_well_formed();
1349   }
1350 
1351   bool check_young_list_empty(bool check_heap);
1352 
1353   // *** Stuff related to concurrent marking.  It's not clear to me that so
1354   // many of these need to be public.
1355 
1356   // The functions below are helper functions that a subclass of
1357   // "CollectedHeap" can use in the implementation of its virtual
1358   // functions.
1359   // This performs a concurrent marking of the live objects in a
1360   // bitmap off to the side.
1361   void doConcurrentMark();
1362 
1363   bool isMarkedPrev(oop obj) const;
1364   bool isMarkedNext(oop obj) const;
1365 
1366   // Determine if an object is dead, given the object and also
1367   // the region to which the object belongs. An object is dead
1368   // iff a) it was not allocated since the last mark, b) it
1369   // is not marked, and c) it is not in an archive region.
1370   bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1371     return
1372       !hr->obj_allocated_since_prev_marking(obj) &&
1373       !isMarkedPrev(obj) &&
1374       !hr->is_archive();
1375   }
1376 
1377   // This function returns true when an object has been
1378   // around since the previous marking and hasn't yet
1379   // been marked during this marking, and is not in an archive region.
1380   bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1381     return
1382       !hr->obj_allocated_since_next_marking(obj) &&
1383       !isMarkedNext(obj) &&
1384       !hr->is_archive();
1385   }
1386 
1387   // Determine if an object is dead, given only the object itself.
1388   // This will find the region to which the object belongs and
1389   // then call the region version of the same function.
1390 
1391   // Added if it is NULL it isn't dead.
1392 
1393   inline bool is_obj_dead(const oop obj) const;
1394 
1395   inline bool is_obj_ill(const oop obj) const;
1396 
1397   G1ConcurrentMark* concurrent_mark() const { return _cm; }
1398 
1399   // Refinement
1400 
1401   ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1402 
1403   // The dirty cards region list is used to record a subset of regions
1404   // whose cards need clearing. The list if populated during the
1405   // remembered set scanning and drained during the card table
1406   // cleanup. Although the methods are reentrant, population/draining
1407   // phases must not overlap. For synchronization purposes the last
1408   // element on the list points to itself.
1409   HeapRegion* _dirty_cards_region_list;
1410   void push_dirty_cards_region(HeapRegion* hr);
1411   HeapRegion* pop_dirty_cards_region();
1412 
1413   // Optimized nmethod scanning support routines
1414 
1415   // Register the given nmethod with the G1 heap.
1416   virtual void register_nmethod(nmethod* nm);
1417 
1418   // Unregister the given nmethod from the G1 heap.
1419   virtual void unregister_nmethod(nmethod* nm);
1420 
1421   // Free up superfluous code root memory.
1422   void purge_code_root_memory();
1423 
1424   // Rebuild the strong code root lists for each region
1425   // after a full GC.
1426   void rebuild_strong_code_roots();
1427 
1428   // Delete entries for dead interned string and clean up unreferenced symbols
1429   // in symbol table, possibly in parallel.
1430   void unlink_string_and_symbol_table(BoolObjectClosure* is_alive, bool unlink_strings = true, bool unlink_symbols = true);
1431 
1432   // Parallel phase of unloading/cleaning after G1 concurrent mark.
1433   void parallel_cleaning(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool class_unloading_occurred);
1434 
1435   // Redirty logged cards in the refinement queue.
1436   void redirty_logged_cards();
1437   // Verification
1438 
1439   // Perform any cleanup actions necessary before allowing a verification.
1440   virtual void prepare_for_verify();
1441 
1442   // Perform verification.
1443 
1444   // vo == UsePrevMarking  -> use "prev" marking information,
1445   // vo == UseNextMarking -> use "next" marking information
1446   // vo == UseMarkWord    -> use the mark word in the object header
1447   //
1448   // NOTE: Only the "prev" marking information is guaranteed to be
1449   // consistent most of the time, so most calls to this should use
1450   // vo == UsePrevMarking.
1451   // Currently, there is only one case where this is called with
1452   // vo == UseNextMarking, which is to verify the "next" marking
1453   // information at the end of remark.
1454   // Currently there is only one place where this is called with
1455   // vo == UseMarkWord, which is to verify the marking during a
1456   // full GC.
1457   void verify(VerifyOption vo);
1458 
1459   // The methods below are here for convenience and dispatch the
1460   // appropriate method depending on value of the given VerifyOption
1461   // parameter. The values for that parameter, and their meanings,
1462   // are the same as those above.
1463 
1464   bool is_obj_dead_cond(const oop obj,
1465                         const HeapRegion* hr,
1466                         const VerifyOption vo) const;
1467 
1468   bool is_obj_dead_cond(const oop obj,
1469                         const VerifyOption vo) const;
1470 
1471   G1HeapSummary create_g1_heap_summary();
1472   G1EvacSummary create_g1_evac_summary(G1EvacStats* stats);
1473 
1474   // Printing
1475 
1476   virtual void print_on(outputStream* st) const;
1477   virtual void print_extended_on(outputStream* st) const;
1478   virtual void print_on_error(outputStream* st) const;
1479 
1480   virtual void print_gc_threads_on(outputStream* st) const;
1481   virtual void gc_threads_do(ThreadClosure* tc) const;
1482 
1483   // Override
1484   void print_tracing_info() const;
1485 
1486   // The following two methods are helpful for debugging RSet issues.
1487   void print_cset_rsets() PRODUCT_RETURN;
1488   void print_all_rsets() PRODUCT_RETURN;
1489 
1490 public:
1491   size_t pending_card_num();
1492 
1493 protected:
1494   size_t _max_heap_capacity;
1495 };
1496 
1497 class G1ParEvacuateFollowersClosure : public VoidClosure {
1498 private:
1499   double _start_term;
1500   double _term_time;
1501   size_t _term_attempts;
1502 
1503   void start_term_time() { _term_attempts++; _start_term = os::elapsedTime(); }
1504   void end_term_time() { _term_time += os::elapsedTime() - _start_term; }
1505 protected:
1506   G1CollectedHeap*              _g1h;
1507   G1ParScanThreadState*         _par_scan_state;
1508   RefToScanQueueSet*            _queues;
1509   ParallelTaskTerminator*       _terminator;
1510 
1511   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
1512   RefToScanQueueSet*      queues()         { return _queues; }
1513   ParallelTaskTerminator* terminator()     { return _terminator; }
1514 
1515 public:
1516   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
1517                                 G1ParScanThreadState* par_scan_state,
1518                                 RefToScanQueueSet* queues,
1519                                 ParallelTaskTerminator* terminator)
1520     : _g1h(g1h), _par_scan_state(par_scan_state),
1521       _queues(queues), _terminator(terminator),
1522       _start_term(0.0), _term_time(0.0), _term_attempts(0) {}
1523 
1524   void do_void();
1525 
1526   double term_time() const { return _term_time; }
1527   size_t term_attempts() const { return _term_attempts; }
1528 
1529 private:
1530   inline bool offer_termination();
1531 };
1532 
1533 #endif // SHARE_VM_GC_G1_G1COLLECTEDHEAP_HPP