1 /*
   2  * Copyright (c) 2013, 2018, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #ifndef SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
  25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
  26 
  27 #include "gc/shared/markBitMap.hpp"
  28 #include "gc/shared/softRefPolicy.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "gc/shenandoah/shenandoahAsserts.hpp"
  31 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
  32 #include "gc/shenandoah/shenandoahLock.hpp"
  33 #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp"
  34 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
  35 #include "services/memoryManager.hpp"
  36 
  37 class ConcurrentGCTimer;
  38 class ReferenceProcessor;
  39 class ShenandoahAllocTracker;
  40 class ShenandoahCollectorPolicy;
  41 class ShenandoahControlThread;
  42 class ShenandoahGCSession;
  43 class ShenandoahGCStateResetter;
  44 class ShenandoahHeuristics;
  45 class ShenandoahMarkingContext;
  46 class ShenandoahMarkCompact;
  47 class ShenandoahMode;
  48 class ShenandoahPhaseTimings;
  49 class ShenandoahHeap;
  50 class ShenandoahHeapRegion;
  51 class ShenandoahHeapRegionClosure;
  52 class ShenandoahCollectionSet;
  53 class ShenandoahFreeSet;
  54 class ShenandoahConcurrentMark;
  55 class ShenandoahMarkCompact;
  56 class ShenandoahMonitoringSupport;
  57 class ShenandoahPacer;
  58 class ShenandoahTraversalGC;
  59 class ShenandoahVerifier;
  60 class ShenandoahWorkGang;
  61 class VMStructs;
  62 
  63 class ShenandoahRegionIterator : public StackObj {
  64 private:
  65   ShenandoahHeap* _heap;
  66 
  67   DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
  68   volatile size_t _index;
  69   DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
  70 
  71   // No implicit copying: iterators should be passed by reference to capture the state
  72   ShenandoahRegionIterator(const ShenandoahRegionIterator& that);
  73   ShenandoahRegionIterator& operator=(const ShenandoahRegionIterator& o);
  74 
  75 public:
  76   ShenandoahRegionIterator();
  77   ShenandoahRegionIterator(ShenandoahHeap* heap);
  78 
  79   // Reset iterator to default state
  80   void reset();
  81 
  82   // Returns next region, or NULL if there are no more regions.
  83   // This is multi-thread-safe.
  84   inline ShenandoahHeapRegion* next();
  85 
  86   // This is *not* MT safe. However, in the absence of multithreaded access, it
  87   // can be used to determine if there is more work to do.
  88   bool has_next() const;
  89 };
  90 
  91 class ShenandoahHeapRegionClosure : public StackObj {
  92 public:
  93   virtual void heap_region_do(ShenandoahHeapRegion* r) = 0;
  94   virtual bool is_thread_safe() { return false; }
  95 };
  96 
  97 #ifdef ASSERT
  98 class ShenandoahAssertToSpaceClosure : public OopClosure {
  99 private:
 100   template <class T>
 101   void do_oop_work(T* p);
 102 public:
 103   void do_oop(narrowOop* p);
 104   void do_oop(oop* p);
 105 };
 106 #endif
 107 
 108 typedef ShenandoahLock    ShenandoahHeapLock;
 109 typedef ShenandoahLocker  ShenandoahHeapLocker;
 110 
 111 // Shenandoah GC is low-pause concurrent GC that uses Brooks forwarding pointers
 112 // to encode forwarding data. See BrooksPointer for details on forwarding data encoding.
 113 // See ShenandoahControlThread for GC cycle structure.
 114 //
 115 class ShenandoahHeap : public CollectedHeap {
 116   friend class ShenandoahAsserts;
 117   friend class VMStructs;
 118   friend class ShenandoahGCSession;
 119   friend class ShenandoahGCStateResetter;
 120 
 121 // ---------- Locks that guard important data structures in Heap
 122 //
 123 private:
 124   ShenandoahHeapLock _lock;
 125 
 126 public:
 127   ShenandoahHeapLock* lock() {
 128     return &_lock;
 129   }
 130 
 131   void assert_heaplock_owned_by_current_thread()     NOT_DEBUG_RETURN;
 132   void assert_heaplock_not_owned_by_current_thread() NOT_DEBUG_RETURN;
 133   void assert_heaplock_or_safepoint()                NOT_DEBUG_RETURN;
 134 
 135 // ---------- Initialization, termination, identification, printing routines
 136 //
 137 public:
 138   static ShenandoahHeap* heap();
 139   static ShenandoahHeap* heap_no_check();
 140 
 141   const char* name()          const { return "Shenandoah"; }
 142   ShenandoahHeap::Name kind() const { return CollectedHeap::Shenandoah; }
 143 
 144   ShenandoahHeap(ShenandoahCollectorPolicy* policy);
 145   jint initialize();
 146   void post_initialize();
 147   void initialize_heuristics();
 148 
 149   void initialize_serviceability();
 150 
 151   void print_on(outputStream* st)              const;
 152   void print_extended_on(outputStream *st)     const;
 153   void print_tracing_info()                    const;
 154   void print_gc_threads_on(outputStream* st)   const;
 155   void print_heap_regions_on(outputStream* st) const;
 156 
 157   void stop();
 158 
 159   void prepare_for_verify();
 160   void verify(VerifyOption vo);
 161 
 162 // ---------- Heap counters and metrics
 163 //
 164 private:
 165            size_t _initial_size;
 166            size_t _minimum_size;
 167   DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile size_t));
 168   volatile size_t _used;
 169   volatile size_t _committed;
 170   volatile size_t _bytes_allocated_since_gc_start;
 171   DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, 0);
 172 
 173 public:
 174   void increase_used(size_t bytes);
 175   void decrease_used(size_t bytes);
 176   void set_used(size_t bytes);
 177 
 178   void increase_committed(size_t bytes);
 179   void decrease_committed(size_t bytes);
 180   void increase_allocated(size_t bytes);
 181 
 182   size_t bytes_allocated_since_gc_start();
 183   void reset_bytes_allocated_since_gc_start();
 184 
 185   size_t min_capacity()     const;
 186   size_t max_capacity()     const;
 187   size_t initial_capacity() const;
 188   size_t capacity()         const;
 189   size_t used()             const;
 190   size_t committed()        const;
 191 
 192 // ---------- Workers handling
 193 //
 194 private:
 195   uint _max_workers;
 196   ShenandoahWorkGang* _workers;
 197   ShenandoahWorkGang* _safepoint_workers;
 198 
 199 public:
 200   uint max_workers();
 201   void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
 202 
 203   WorkGang* workers() const;
 204   WorkGang* get_safepoint_workers();
 205 
 206   void gc_threads_do(ThreadClosure* tcl) const;
 207 
 208 // ---------- Heap regions handling machinery
 209 //
 210 private:
 211   MemRegion _heap_region;
 212   bool      _heap_region_special;
 213   size_t    _num_regions;
 214   ShenandoahHeapRegion** _regions;
 215   ShenandoahRegionIterator _update_refs_iterator;
 216 
 217 public:
 218   inline size_t num_regions() const { return _num_regions; }
 219   inline bool is_heap_region_special() { return _heap_region_special; }
 220 
 221   inline ShenandoahHeapRegion* const heap_region_containing(const void* addr) const;
 222   inline size_t heap_region_index_containing(const void* addr) const;
 223 
 224   inline ShenandoahHeapRegion* const get_region(size_t region_idx) const;
 225 
 226   void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
 227   void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
 228 
 229 // ---------- GC state machinery
 230 //
 231 // GC state describes the important parts of collector state, that may be
 232 // used to make barrier selection decisions in the native and generated code.
 233 // Multiple bits can be set at once.
 234 //
 235 // Important invariant: when GC state is zero, the heap is stable, and no barriers
 236 // are required.
 237 //
 238 public:
 239   enum GCStateBitPos {
 240     // Heap has forwarded objects: needs LRB barriers.
 241     HAS_FORWARDED_BITPOS   = 0,
 242 
 243     // Heap is under marking: needs SATB barriers.
 244     MARKING_BITPOS    = 1,
 245 
 246     // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
 247     EVACUATION_BITPOS = 2,
 248 
 249     // Heap is under updating: needs no additional barriers.
 250     UPDATEREFS_BITPOS = 3,
 251 
 252     // Heap is under traversal collection
 253     TRAVERSAL_BITPOS  = 4
 254   };
 255 
 256   enum GCState {
 257     STABLE        = 0,
 258     HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
 259     MARKING       = 1 << MARKING_BITPOS,
 260     EVACUATION    = 1 << EVACUATION_BITPOS,
 261     UPDATEREFS    = 1 << UPDATEREFS_BITPOS,
 262     TRAVERSAL     = 1 << TRAVERSAL_BITPOS
 263   };
 264 
 265 private:
 266   ShenandoahSharedBitmap _gc_state;
 267   ShenandoahSharedFlag   _degenerated_gc_in_progress;
 268   ShenandoahSharedFlag   _full_gc_in_progress;
 269   ShenandoahSharedFlag   _full_gc_move_in_progress;
 270   ShenandoahSharedFlag   _progress_last_gc;
 271 
 272   void set_gc_state_all_threads(char state);
 273   void set_gc_state_mask(uint mask, bool value);
 274 
 275 public:
 276   char gc_state() const;
 277   static address gc_state_addr();
 278 
 279   void set_concurrent_mark_in_progress(bool in_progress);
 280   void set_evacuation_in_progress(bool in_progress);
 281   void set_update_refs_in_progress(bool in_progress);
 282   void set_degenerated_gc_in_progress(bool in_progress);
 283   void set_full_gc_in_progress(bool in_progress);
 284   void set_full_gc_move_in_progress(bool in_progress);
 285   void set_concurrent_traversal_in_progress(bool in_progress);
 286   void set_has_forwarded_objects(bool cond);
 287 
 288   inline bool is_stable() const;
 289   inline bool is_idle() const;
 290   inline bool is_concurrent_mark_in_progress() const;
 291   inline bool is_update_refs_in_progress() const;
 292   inline bool is_evacuation_in_progress() const;
 293   inline bool is_degenerated_gc_in_progress() const;
 294   inline bool is_full_gc_in_progress() const;
 295   inline bool is_full_gc_move_in_progress() const;
 296   inline bool is_concurrent_traversal_in_progress() const;
 297   inline bool has_forwarded_objects() const;
 298   inline bool is_gc_in_progress_mask(uint mask) const;
 299 
 300 // ---------- GC cancellation and degeneration machinery
 301 //
 302 // Cancelled GC flag is used to notify concurrent phases that they should terminate.
 303 //
 304 public:
 305   enum ShenandoahDegenPoint {
 306     _degenerated_unset,
 307     _degenerated_traversal,
 308     _degenerated_outside_cycle,
 309     _degenerated_mark,
 310     _degenerated_evac,
 311     _degenerated_updaterefs,
 312     _DEGENERATED_LIMIT
 313   };
 314 
 315   static const char* degen_point_to_string(ShenandoahDegenPoint point) {
 316     switch (point) {
 317       case _degenerated_unset:
 318         return "<UNSET>";
 319       case _degenerated_traversal:
 320         return "Traversal";
 321       case _degenerated_outside_cycle:
 322         return "Outside of Cycle";
 323       case _degenerated_mark:
 324         return "Mark";
 325       case _degenerated_evac:
 326         return "Evacuation";
 327       case _degenerated_updaterefs:
 328         return "Update Refs";
 329       default:
 330         ShouldNotReachHere();
 331         return "ERROR";
 332     }
 333   };
 334 
 335 private:
 336   enum CancelState {
 337     // Normal state. GC has not been cancelled and is open for cancellation.
 338     // Worker threads can suspend for safepoint.
 339     CANCELLABLE,
 340 
 341     // GC has been cancelled. Worker threads can not suspend for
 342     // safepoint but must finish their work as soon as possible.
 343     CANCELLED,
 344 
 345     // GC has not been cancelled and must not be cancelled. At least
 346     // one worker thread checks for pending safepoint and may suspend
 347     // if a safepoint is pending.
 348     NOT_CANCELLED
 349   };
 350 
 351   ShenandoahSharedEnumFlag<CancelState> _cancelled_gc;
 352   inline bool try_cancel_gc();
 353 
 354 public:
 355   static address cancelled_gc_addr();
 356 
 357   inline bool cancelled_gc() const;
 358   inline bool check_cancelled_gc_and_yield(bool sts_active = true);
 359 
 360   inline void clear_cancelled_gc();
 361 
 362   void cancel_gc(GCCause::Cause cause);
 363 
 364 // ---------- GC operations entry points
 365 //
 366 public:
 367   // Entry points to STW GC operations, these cause a related safepoint, that then
 368   // call the entry method below
 369   void vmop_entry_init_mark();
 370   void vmop_entry_final_mark();
 371   void vmop_entry_final_evac();
 372   void vmop_entry_init_updaterefs();
 373   void vmop_entry_final_updaterefs();
 374   void vmop_entry_init_traversal();
 375   void vmop_entry_final_traversal();
 376   void vmop_entry_full(GCCause::Cause cause);
 377   void vmop_degenerated(ShenandoahDegenPoint point);
 378 
 379   // Entry methods to normally STW GC operations. These set up logging, monitoring
 380   // and workers for net VM operation
 381   void entry_init_mark();
 382   void entry_final_mark();
 383   void entry_final_evac();
 384   void entry_init_updaterefs();
 385   void entry_final_updaterefs();
 386   void entry_init_traversal();
 387   void entry_final_traversal();
 388   void entry_full(GCCause::Cause cause);
 389   void entry_degenerated(int point);
 390 
 391   // Entry methods to normally concurrent GC operations. These set up logging, monitoring
 392   // for concurrent operation.
 393   void entry_reset();
 394   void entry_mark();
 395   void entry_preclean();
 396   void entry_cleanup();
 397   void entry_evac();
 398   void entry_updaterefs();
 399   void entry_traversal();
 400   void entry_uncommit(double shrink_before);
 401 
 402 private:
 403   // Actual work for the phases
 404   void op_init_mark();
 405   void op_final_mark();
 406   void op_final_evac();
 407   void op_init_updaterefs();
 408   void op_final_updaterefs();
 409   void op_init_traversal();
 410   void op_final_traversal();
 411   void op_full(GCCause::Cause cause);
 412   void op_degenerated(ShenandoahDegenPoint point);
 413   void op_degenerated_fail();
 414   void op_degenerated_futile();
 415 
 416   void op_reset();
 417   void op_mark();
 418   void op_preclean();
 419   void op_cleanup();
 420   void op_conc_evac();
 421   void op_stw_evac();
 422   void op_updaterefs();
 423   void op_traversal();
 424   void op_uncommit(double shrink_before);
 425 
 426   // Messages for GC trace events, they have to be immortal for
 427   // passing around the logging/tracing systems
 428   const char* init_mark_event_message() const;
 429   const char* final_mark_event_message() const;
 430   const char* conc_mark_event_message() const;
 431   const char* init_traversal_event_message() const;
 432   const char* final_traversal_event_message() const;
 433   const char* conc_traversal_event_message() const;
 434   const char* degen_event_message(ShenandoahDegenPoint point) const;
 435 
 436 // ---------- GC subsystems
 437 //
 438 private:
 439   ShenandoahControlThread*   _control_thread;
 440   ShenandoahCollectorPolicy* _shenandoah_policy;
 441   ShenandoahMode*            _gc_mode;
 442   ShenandoahHeuristics*      _heuristics;
 443   ShenandoahFreeSet*         _free_set;
 444   ShenandoahConcurrentMark*  _scm;
 445   ShenandoahTraversalGC*     _traversal_gc;
 446   ShenandoahMarkCompact*     _full_gc;
 447   ShenandoahPacer*           _pacer;
 448   ShenandoahVerifier*        _verifier;
 449 
 450   ShenandoahAllocTracker*    _alloc_tracker;
 451   ShenandoahPhaseTimings*    _phase_timings;
 452 
 453   ShenandoahControlThread*   control_thread()          { return _control_thread;    }
 454   ShenandoahMarkCompact*     full_gc()                 { return _full_gc;           }
 455 
 456 public:
 457   ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
 458   ShenandoahHeuristics*      heuristics()        const { return _heuristics;        }
 459   ShenandoahFreeSet*         free_set()          const { return _free_set;          }
 460   ShenandoahConcurrentMark*  concurrent_mark()         { return _scm;               }
 461   ShenandoahTraversalGC*     traversal_gc()      const { return _traversal_gc;      }
 462   bool                       is_traversal_mode() const { return _traversal_gc != NULL; }
 463   ShenandoahPacer*           pacer()             const { return _pacer;             }
 464 
 465   ShenandoahPhaseTimings*    phase_timings()     const { return _phase_timings;     }
 466   ShenandoahAllocTracker*    alloc_tracker()     const { return _alloc_tracker;     }
 467 
 468   ShenandoahVerifier*        verifier();
 469 
 470 // ---------- VM subsystem bindings
 471 //
 472 private:
 473   ShenandoahMonitoringSupport* _monitoring_support;
 474   MemoryPool*                  _memory_pool;
 475   GCMemoryManager              _stw_memory_manager;
 476   GCMemoryManager              _cycle_memory_manager;
 477   ConcurrentGCTimer*           _gc_timer;
 478   SoftRefPolicy                _soft_ref_policy;
 479 
 480 public:
 481   ShenandoahMonitoringSupport* monitoring_support() { return _monitoring_support;    }
 482   GCMemoryManager* cycle_memory_manager()           { return &_cycle_memory_manager; }
 483   GCMemoryManager* stw_memory_manager()             { return &_stw_memory_manager;   }
 484   SoftRefPolicy* soft_ref_policy()                  { return &_soft_ref_policy;      }
 485 
 486   GrowableArray<GCMemoryManager*> memory_managers();
 487   GrowableArray<MemoryPool*> memory_pools();
 488   MemoryUsage memory_usage();
 489   GCTracer* tracer();
 490   GCTimer* gc_timer() const;
 491   CollectorPolicy* collector_policy() const;
 492 
 493 // ---------- Reference processing
 494 //
 495 private:
 496   AlwaysTrueClosure    _subject_to_discovery;
 497   ReferenceProcessor*  _ref_processor;
 498   ShenandoahSharedFlag _process_references;
 499 
 500   void ref_processing_init();
 501 
 502 public:
 503   ReferenceProcessor* ref_processor() { return _ref_processor; }
 504   void set_process_references(bool pr);
 505   bool process_references() const;
 506 
 507 // ---------- Class Unloading
 508 //
 509 private:
 510   ShenandoahSharedFlag _unload_classes;
 511 
 512 public:
 513   void set_unload_classes(bool uc);
 514   bool unload_classes() const;
 515 
 516   // Perform STW class unloading and weak root cleaning
 517   void parallel_cleaning(bool full_gc);
 518 
 519 private:
 520   void stw_unload_classes(bool full_gc);
 521   void stw_process_weak_roots(bool full_gc);
 522 
 523 // ---------- Generic interface hooks
 524 // Minor things that super-interface expects us to implement to play nice with
 525 // the rest of runtime. Some of the things here are not required to be implemented,
 526 // and can be stubbed out.
 527 //
 528 public:
 529   AdaptiveSizePolicy* size_policy() shenandoah_not_implemented_return(NULL);
 530   bool is_maximal_no_gc() const shenandoah_not_implemented_return(false);
 531 
 532   bool is_in(const void* p) const;
 533 
 534   // All objects can potentially move
 535   bool is_scavengable(oop obj) { return true; };
 536 
 537   void collect(GCCause::Cause cause);
 538   void do_full_collection(bool clear_all_soft_refs);
 539 
 540   // Used for parsing heap during error printing
 541   HeapWord* block_start(const void* addr) const;
 542   size_t block_size(const HeapWord* addr) const;
 543   bool block_is_obj(const HeapWord* addr) const;
 544 
 545   // Used for native heap walkers: heap dumpers, mostly
 546   void object_iterate(ObjectClosure* cl);
 547   void safe_object_iterate(ObjectClosure* cl);
 548 
 549   // Used by RMI
 550   jlong millis_since_last_gc();
 551 
 552 // ---------- Safepoint interface hooks
 553 //
 554 public:
 555   void safepoint_synchronize_begin();
 556   void safepoint_synchronize_end();
 557 
 558 // ---------- Code roots handling hooks
 559 //
 560 public:
 561   void register_nmethod(nmethod* nm);
 562   void unregister_nmethod(nmethod* nm);
 563 
 564 // ---------- Pinning hooks
 565 //
 566 public:
 567   // Shenandoah supports per-object (per-region) pinning
 568   bool supports_object_pinning() const { return true; }
 569 
 570   oop pin_object(JavaThread* thread, oop obj);
 571   void unpin_object(JavaThread* thread, oop obj);
 572 
 573   void sync_pinned_region_status();
 574   void assert_pinned_region_status() NOT_DEBUG_RETURN;
 575 
 576 // ---------- Allocation support
 577 //
 578 private:
 579   HeapWord* allocate_memory_under_lock(ShenandoahAllocRequest& request, bool& in_new_region);
 580   inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
 581   HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
 582   HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
 583   void retire_and_reset_gclabs();
 584 
 585 public:
 586   HeapWord* allocate_memory(ShenandoahAllocRequest& request);
 587   HeapWord* mem_allocate(size_t size, bool* what);
 588   MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 589                                                size_t size,
 590                                                Metaspace::MetadataType mdtype);
 591 
 592   void notify_mutator_alloc_words(size_t words, bool waste);
 593 
 594   // Shenandoah supports TLAB allocation
 595   bool supports_tlab_allocation() const { return true; }
 596 
 597   HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size);
 598   size_t tlab_capacity(Thread *thr) const;
 599   size_t unsafe_max_tlab_alloc(Thread *thread) const;
 600   size_t max_tlab_size() const;
 601   size_t tlab_used(Thread* ignored) const;
 602 
 603   void accumulate_statistics_tlabs();
 604   void resize_tlabs();
 605 
 606   void ensure_parsability(bool retire_tlabs);
 607   void make_parsable(bool retire_tlabs);
 608 
 609 // ---------- Marking support
 610 //
 611 private:
 612   ShenandoahMarkingContext* _marking_context;
 613   MemRegion  _bitmap_region;
 614   MemRegion  _aux_bitmap_region;
 615   MarkBitMap _verification_bit_map;
 616   MarkBitMap _aux_bit_map;
 617 
 618   size_t _bitmap_size;
 619   size_t _bitmap_regions_per_slice;
 620   size_t _bitmap_bytes_per_slice;
 621 
 622   bool _bitmap_region_special;
 623   bool _aux_bitmap_region_special;
 624 
 625   // Used for buffering per-region liveness data.
 626   // Needed since ShenandoahHeapRegion uses atomics to update liveness.
 627   //
 628   // The array has max-workers elements, each of which is an array of
 629   // jushort * max_regions. The choice of jushort is not accidental:
 630   // there is a tradeoff between static/dynamic footprint that translates
 631   // into cache pressure (which is already high during marking), and
 632   // too many atomic updates. size_t/jint is too large, jbyte is too small.
 633   jushort** _liveness_cache;
 634 
 635 public:
 636   inline ShenandoahMarkingContext* complete_marking_context() const;
 637   inline ShenandoahMarkingContext* marking_context() const;
 638   inline void mark_complete_marking_context();
 639   inline void mark_incomplete_marking_context();
 640 
 641   template<class T>
 642   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
 643 
 644   template<class T>
 645   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
 646 
 647   template<class T>
 648   inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
 649 
 650   void reset_mark_bitmap();
 651 
 652   // SATB barriers hooks
 653   inline bool requires_marking(const void* entry) const;
 654   void force_satb_flush_all_threads();
 655 
 656   // Support for bitmap uncommits
 657   bool commit_bitmap_slice(ShenandoahHeapRegion *r);
 658   bool uncommit_bitmap_slice(ShenandoahHeapRegion *r);
 659   bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
 660 
 661   // Liveness caching support
 662   jushort* get_liveness_cache(uint worker_id);
 663   void flush_liveness_cache(uint worker_id);
 664 
 665 // ---------- Evacuation support
 666 //
 667 private:
 668   ShenandoahCollectionSet* _collection_set;
 669   ShenandoahEvacOOMHandler _oom_evac_handler;
 670 
 671   void evacuate_and_update_roots();
 672 
 673 public:
 674   static address in_cset_fast_test_addr();
 675 
 676   ShenandoahCollectionSet* collection_set() const { return _collection_set; }
 677 
 678   template <class T>
 679   inline bool in_collection_set(T obj) const;
 680 
 681   // Avoid accidentally calling the method above with ShenandoahHeapRegion*, which would be *wrong*.
 682   inline bool in_collection_set(ShenandoahHeapRegion* r) shenandoah_not_implemented_return(false);
 683 
 684   // Evacuates object src. Returns the evacuated object, either evacuated
 685   // by this thread, or by some other thread.
 686   inline oop evacuate_object(oop src, Thread* thread);
 687 
 688   // Call before/after evacuation.
 689   void enter_evacuation();
 690   void leave_evacuation();
 691 
 692 // ---------- Helper functions
 693 //
 694 public:
 695   template <class T>
 696   inline oop evac_update_with_forwarded(T* p);
 697 
 698   template <class T>
 699   inline oop maybe_update_with_forwarded(T* p);
 700 
 701   template <class T>
 702   inline oop maybe_update_with_forwarded_not_null(T* p, oop obj);
 703 
 704   template <class T>
 705   inline oop update_with_forwarded_not_null(T* p, oop obj);
 706 
 707   static inline oop cas_oop(oop n, narrowOop* addr, oop c);
 708   static inline oop cas_oop(oop n, oop* addr, oop c);
 709   static inline oop cas_oop(oop n, narrowOop* addr, narrowOop c);
 710 
 711   void trash_humongous_region_at(ShenandoahHeapRegion *r);
 712 
 713   void deduplicate_string(oop str);
 714 
 715   void stop_concurrent_marking();
 716 
 717 private:
 718   void trash_cset_regions();
 719   void update_heap_references(bool concurrent);
 720 
 721 // ---------- Testing helpers functions
 722 //
 723 private:
 724   ShenandoahSharedFlag _inject_alloc_failure;
 725 
 726   void try_inject_alloc_failure();
 727   bool should_inject_alloc_failure();
 728 };
 729 
 730 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_HPP