1 /*
  2  * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
  3  * Copyright (c) 2013, 2021, Red Hat, Inc. All rights reserved.
  4  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
  5  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  6  *
  7  * This code is free software; you can redistribute it and/or modify it
  8  * under the terms of the GNU General Public License version 2 only, as
  9  * published by the Free Software Foundation.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 26 
 27 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 28 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 29 
 30 #include "gc/shared/ageTable.hpp"
 31 #include "gc/shared/markBitMap.hpp"
 32 #include "gc/shared/softRefPolicy.hpp"
 33 #include "gc/shared/collectedHeap.hpp"
 34 #include "gc/shenandoah/shenandoahAgeCensus.hpp"
 35 #include "gc/shenandoah/heuristics/shenandoahSpaceInfo.hpp"
 36 #include "gc/shenandoah/shenandoahAsserts.hpp"
 37 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
 38 #include "gc/shenandoah/shenandoahAsserts.hpp"
 39 #include "gc/shenandoah/shenandoahLock.hpp"
 40 #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp"
 41 #include "gc/shenandoah/shenandoahEvacTracker.hpp"
 42 #include "gc/shenandoah/shenandoahGenerationType.hpp"
 43 #include "gc/shenandoah/shenandoahMmuTracker.hpp"
 44 #include "gc/shenandoah/shenandoahPadding.hpp"
 45 #include "gc/shenandoah/shenandoahScanRemembered.hpp"
 46 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
 47 #include "gc/shenandoah/shenandoahUnload.hpp"
 48 #include "memory/metaspace.hpp"
 49 #include "services/memoryManager.hpp"
 50 #include "utilities/globalDefinitions.hpp"
 51 #include "utilities/stack.hpp"
 52 
 53 class ConcurrentGCTimer;
 54 class ObjectIterateScanRootClosure;
 55 class PLAB;
 56 class ShenandoahCollectorPolicy;
 57 class ShenandoahControlThread;
 58 class ShenandoahRegulatorThread;
 59 class ShenandoahGCSession;
 60 class ShenandoahGCStateResetter;
 61 class ShenandoahGeneration;
 62 class ShenandoahYoungGeneration;
 63 class ShenandoahOldGeneration;
 64 class ShenandoahHeuristics;
 65 class ShenandoahOldHeuristics;
 66 class ShenandoahYoungHeuristics;
 67 class ShenandoahMarkingContext;
 68 class ShenandoahPhaseTimings;
 69 class ShenandoahHeap;
 70 class ShenandoahHeapRegion;
 71 class ShenandoahHeapRegionClosure;
 72 class ShenandoahCollectionSet;
 73 class ShenandoahFreeSet;
 74 class ShenandoahConcurrentMark;
 75 class ShenandoahFullGC;
 76 class ShenandoahMonitoringSupport;
 77 class ShenandoahMode;
 78 class ShenandoahPacer;
 79 class ShenandoahReferenceProcessor;
 80 class ShenandoahVerifier;
 81 class ShenandoahWorkerThreads;
 82 class VMStructs;
 83 
 84 // Used for buffering per-region liveness data.
 85 // Needed since ShenandoahHeapRegion uses atomics to update liveness.
 86 // The ShenandoahHeap array has max-workers elements, each of which is an array of
 87 // uint16_t * max_regions. The choice of uint16_t is not accidental:
 88 // there is a tradeoff between static/dynamic footprint that translates
 89 // into cache pressure (which is already high during marking), and
 90 // too many atomic updates. uint32_t is too large, uint8_t is too small.
 91 typedef uint16_t ShenandoahLiveData;
 92 #define SHENANDOAH_LIVEDATA_MAX ((ShenandoahLiveData)-1)
 93 
 94 class ShenandoahRegionIterator : public StackObj {
 95 private:
 96   ShenandoahHeap* _heap;
 97 
 98   shenandoah_padding(0);
 99   volatile size_t _index;
100   shenandoah_padding(1);
101 
102   // No implicit copying: iterators should be passed by reference to capture the state
103   NONCOPYABLE(ShenandoahRegionIterator);
104 
105 public:
106   ShenandoahRegionIterator();
107   ShenandoahRegionIterator(ShenandoahHeap* heap);
108 
109   // Reset iterator to default state
110   void reset();
111 
112   // Returns next region, or null if there are no more regions.
113   // This is multi-thread-safe.
114   inline ShenandoahHeapRegion* next();
115 
116   // This is *not* MT safe. However, in the absence of multithreaded access, it
117   // can be used to determine if there is more work to do.
118   bool has_next() const;
119 };
120 
121 class ShenandoahHeapRegionClosure : public StackObj {
122 public:
123   virtual void heap_region_do(ShenandoahHeapRegion* r) = 0;
124   virtual bool is_thread_safe() { return false; }
125 };
126 
127 template<ShenandoahGenerationType GENERATION>
128 class ShenandoahGenerationRegionClosure : public ShenandoahHeapRegionClosure {
129  public:
130   explicit ShenandoahGenerationRegionClosure(ShenandoahHeapRegionClosure* cl) : _cl(cl) {}
131   void heap_region_do(ShenandoahHeapRegion* r);
132   virtual bool is_thread_safe() { return _cl->is_thread_safe(); }
133  private:
134   ShenandoahHeapRegionClosure* _cl;
135 };
136 
137 typedef ShenandoahLock    ShenandoahHeapLock;
138 typedef ShenandoahLocker  ShenandoahHeapLocker;
139 typedef Stack<oop, mtGC>  ShenandoahScanObjectStack;
140 
141 // Shenandoah GC is low-pause concurrent GC that uses Brooks forwarding pointers
142 // to encode forwarding data. See BrooksPointer for details on forwarding data encoding.
143 // See ShenandoahControlThread for GC cycle structure.
144 //
145 class ShenandoahHeap : public CollectedHeap {
146   friend class ShenandoahAsserts;
147   friend class VMStructs;
148   friend class ShenandoahGCSession;
149   friend class ShenandoahGCStateResetter;
150   friend class ShenandoahParallelObjectIterator;
151   friend class ShenandoahSafepoint;
152   // Supported GC
153   friend class ShenandoahConcurrentGC;
154   friend class ShenandoahOldGC;
155   friend class ShenandoahDegenGC;
156   friend class ShenandoahFullGC;
157   friend class ShenandoahUnload;
158 
159 // ---------- Locks that guard important data structures in Heap
160 //
161 private:
162   ShenandoahHeapLock _lock;
163   ShenandoahGeneration* _gc_generation;
164 
165 public:
166   ShenandoahHeapLock* lock() {
167     return &_lock;
168   }
169 
170   ShenandoahGeneration* active_generation() const {
171     // last or latest generation might be a better name here.
172     return _gc_generation;
173   }
174 
175   void set_gc_generation(ShenandoahGeneration* generation) {
176     _gc_generation = generation;
177   }
178 
179   ShenandoahHeuristics* heuristics();
180   ShenandoahOldHeuristics* old_heuristics();
181   ShenandoahYoungHeuristics* young_heuristics();
182 
183   bool doing_mixed_evacuations();
184   bool is_old_bitmap_stable() const;
185   bool is_gc_generation_young() const;
186 
187 // ---------- Initialization, termination, identification, printing routines
188 //
189 public:
190   static ShenandoahHeap* heap();
191 
192   const char* name()          const override { return "Shenandoah"; }
193   ShenandoahHeap::Name kind() const override { return CollectedHeap::Shenandoah; }
194 
195   ShenandoahHeap(ShenandoahCollectorPolicy* policy);
196   jint initialize() override;
197   void post_initialize() override;
198   void initialize_heuristics_generations();
199   virtual void print_init_logger() const;
200   void initialize_serviceability() override;
201 
202   void print_on(outputStream* st)              const override;
203   void print_extended_on(outputStream *st)     const override;
204   void print_tracing_info()                    const override;
205   void print_heap_regions_on(outputStream* st) const;
206 
207   void stop() override;
208 
209   void prepare_for_verify() override;
210   void verify(VerifyOption vo) override;
211 
212   bool verify_generation_usage(bool verify_old, size_t old_regions, size_t old_bytes, size_t old_waste,
213                                bool verify_young, size_t young_regions, size_t young_bytes, size_t young_waste);
214 
215 // WhiteBox testing support.
216   bool supports_concurrent_gc_breakpoints() const override {
217     return true;
218   }
219 
220 // ---------- Heap counters and metrics
221 //
222 private:
223   size_t _initial_size;
224   size_t _minimum_size;
225   size_t _promotion_potential;
226   size_t _pad_for_promote_in_place;    // bytes of filler
227   size_t _promotable_humongous_regions;
228   size_t _regular_regions_promoted_in_place;
229 
230   volatile size_t _soft_max_size;
231   shenandoah_padding(0);
232   volatile size_t _committed;
233   shenandoah_padding(1);
234 
235   void increase_used(const ShenandoahAllocRequest& req);
236 
237 public:
238   void increase_used(ShenandoahGeneration* generation, size_t bytes);
239   void decrease_used(ShenandoahGeneration* generation, size_t bytes);
240   void increase_humongous_waste(ShenandoahGeneration* generation, size_t bytes);
241   void decrease_humongous_waste(ShenandoahGeneration* generation, size_t bytes);
242 
243   void increase_committed(size_t bytes);
244   void decrease_committed(size_t bytes);
245 
246   void reset_bytes_allocated_since_gc_start();
247 
248   size_t min_capacity()      const;
249   size_t max_capacity()      const override;
250   size_t soft_max_capacity() const;
251   size_t initial_capacity()  const;
252   size_t capacity()          const override;
253   size_t used()              const override;
254   size_t committed()         const;
255 
256   void set_soft_max_capacity(size_t v);
257 
258 // ---------- Workers handling
259 //
260 private:
261   uint _max_workers;
262   ShenandoahWorkerThreads* _workers;
263   ShenandoahWorkerThreads* _safepoint_workers;
264 
265 public:
266   uint max_workers();
267   void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
268 
269   WorkerThreads* workers() const;
270   WorkerThreads* safepoint_workers() override;
271 
272   void gc_threads_do(ThreadClosure* tcl) const override;
273 
274 // ---------- Heap regions handling machinery
275 //
276 private:
277   MemRegion _heap_region;
278   bool      _heap_region_special;
279   size_t    _num_regions;
280   ShenandoahHeapRegion** _regions;
281   uint8_t* _affiliations;       // Holds array of enum ShenandoahAffiliation, including FREE status in non-generational mode
282   ShenandoahRegionIterator _update_refs_iterator;
283 
284 public:
285 
286   inline HeapWord* base() const { return _heap_region.start(); }
287 
288   inline size_t num_regions() const { return _num_regions; }
289   inline bool is_heap_region_special() { return _heap_region_special; }
290 
291   inline ShenandoahHeapRegion* heap_region_containing(const void* addr) const;
292   inline size_t heap_region_index_containing(const void* addr) const;
293 
294   inline ShenandoahHeapRegion* get_region(size_t region_idx) const;
295 
296   void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
297   void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
298 
299   inline ShenandoahMmuTracker* mmu_tracker() { return &_mmu_tracker; };
300 
301 // ---------- GC state machinery
302 //
303 // GC state describes the important parts of collector state, that may be
304 // used to make barrier selection decisions in the native and generated code.
305 // Multiple bits can be set at once.
306 //
307 // Important invariant: when GC state is zero, the heap is stable, and no barriers
308 // are required.
309 //
310 public:
311   enum GCStateBitPos {
312     // Heap has forwarded objects: needs LRB barriers.
313     HAS_FORWARDED_BITPOS   = 0,
314 
315     // Heap is under marking: needs SATB barriers.
316     // For generational mode, it means either young or old marking, or both.
317     MARKING_BITPOS    = 1,
318 
319     // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
320     EVACUATION_BITPOS = 2,
321 
322     // Heap is under updating: needs no additional barriers.
323     UPDATEREFS_BITPOS = 3,
324 
325     // Heap is under weak-reference/roots processing: needs weak-LRB barriers.
326     WEAK_ROOTS_BITPOS  = 4,
327 
328     // Young regions are under marking, need SATB barriers.
329     YOUNG_MARKING_BITPOS = 5,
330 
331     // Old regions are under marking, need SATB barriers.
332     OLD_MARKING_BITPOS = 6
333   };
334 
335   enum GCState {
336     STABLE        = 0,
337     HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
338     MARKING       = 1 << MARKING_BITPOS,
339     EVACUATION    = 1 << EVACUATION_BITPOS,
340     UPDATEREFS    = 1 << UPDATEREFS_BITPOS,
341     WEAK_ROOTS    = 1 << WEAK_ROOTS_BITPOS,
342     YOUNG_MARKING = 1 << YOUNG_MARKING_BITPOS,
343     OLD_MARKING   = 1 << OLD_MARKING_BITPOS
344   };
345 
346 private:
347   ShenandoahSharedBitmap _gc_state;
348   ShenandoahSharedFlag   _degenerated_gc_in_progress;
349   ShenandoahSharedFlag   _full_gc_in_progress;
350   ShenandoahSharedFlag   _full_gc_move_in_progress;
351   ShenandoahSharedFlag   _concurrent_strong_root_in_progress;
352 
353   size_t _gc_no_progress_count;
354 
355   // TODO: Revisit the following comment.  It may not accurately represent the true behavior when evacuations fail due to
356   // difficulty finding memory to hold evacuated objects.
357   //
358   // Note that the typical total expenditure on evacuation is less than the associated evacuation reserve because we generally
359   // reserve ShenandoahEvacWaste (> 1.0) times the anticipated evacuation need.  In the case that there is an excessive amount
360   // of waste, it may be that one thread fails to grab a new GCLAB, this does not necessarily doom the associated evacuation
361   // effort.  If this happens, the requesting thread blocks until some other thread manages to evacuate the offending object.
362   // Only after "all" threads fail to evacuate an object do we consider the evacuation effort to have failed.
363 
364   size_t _promoted_reserve;            // Bytes reserved within old-gen to hold the results of promotion
365   volatile size_t _promoted_expended;  // Bytes of old-gen memory expended on promotions
366 
367   size_t _old_evac_reserve;            // Bytes reserved within old-gen to hold evacuated objects from old-gen collection set
368   size_t _young_evac_reserve;          // Bytes reserved within young-gen to hold evacuated objects from young-gen collection set
369 
370   ShenandoahAgeCensus* _age_census;    // Age census used for adapting tenuring threshold in generational mode
371 
372   // At the end of final mark, but before we begin evacuating, heuristics calculate how much memory is required to
373   // hold the results of evacuating to young-gen and to old-gen.  These quantitites, stored in _promoted_reserve,
374   // _old_evac_reserve, and _young_evac_reserve, are consulted prior to rebuilding the free set (ShenandoahFreeSet)
375   // in preparation for evacuation.  When the free set is rebuilt, we make sure to reserve sufficient memory in the
376   // collector and old_collector sets to hold if _has_evacuation_reserve_quantities is true.  The other time we
377   // rebuild the freeset is at the end of GC, as we prepare to idle GC until the next trigger.  In this case,
378   // _has_evacuation_reserve_quantities is false because we don't yet know how much memory will need to be evacuated
379   // in the next GC cycle.  When _has_evacuation_reserve_quantities is false, the free set rebuild operation reserves
380   // for the collector and old_collector sets based on alternative mechanisms, such as ShenandoahEvacReserve,
381   // ShenandoahOldEvacReserve, and ShenandoahOldCompactionReserve.  In a future planned enhancement, the reserve
382   // for old_collector set when not _has_evacuation_reserve_quantities is based in part on anticipated promotion as
383   // determined by analysis of live data found during the previous GC pass which is one less than the current tenure age.
384   bool _has_evacuation_reserve_quantities;
385 
386   void set_gc_state_all_threads(char state);
387   void set_gc_state_mask(uint mask, bool value);
388 
389 public:
390   char gc_state() const;
391 
392   void set_evacuation_reserve_quantities(bool is_valid);
393   void set_concurrent_young_mark_in_progress(bool in_progress);
394   void set_concurrent_old_mark_in_progress(bool in_progress);
395   void set_evacuation_in_progress(bool in_progress);
396   void set_update_refs_in_progress(bool in_progress);
397   void set_degenerated_gc_in_progress(bool in_progress);
398   void set_full_gc_in_progress(bool in_progress);
399   void set_full_gc_move_in_progress(bool in_progress);
400   void set_has_forwarded_objects(bool cond);
401   void set_concurrent_strong_root_in_progress(bool cond);
402   void set_concurrent_weak_root_in_progress(bool cond);
403 
404   void set_aging_cycle(bool cond);
405 
406   inline bool is_stable() const;
407   inline bool is_idle() const;
408   inline bool has_evacuation_reserve_quantities() const;
409   inline bool is_concurrent_mark_in_progress() const;
410   inline bool is_concurrent_young_mark_in_progress() const;
411   inline bool is_concurrent_old_mark_in_progress() const;
412   inline bool is_update_refs_in_progress() const;
413   inline bool is_evacuation_in_progress() const;
414   inline bool is_degenerated_gc_in_progress() const;
415   inline bool is_full_gc_in_progress() const;
416   inline bool is_full_gc_move_in_progress() const;
417   inline bool has_forwarded_objects() const;
418 
419   inline bool is_stw_gc_in_progress() const;
420   inline bool is_concurrent_strong_root_in_progress() const;
421   inline bool is_concurrent_weak_root_in_progress() const;
422   bool is_prepare_for_old_mark_in_progress() const;
423   inline bool is_aging_cycle() const;
424 
425   inline void clear_promotion_potential() { _promotion_potential = 0; };
426   inline void set_promotion_potential(size_t val) { _promotion_potential = val; };
427   inline size_t get_promotion_potential() { return _promotion_potential; };
428 
429   inline void set_pad_for_promote_in_place(size_t pad) { _pad_for_promote_in_place = pad; }
430   inline size_t get_pad_for_promote_in_place() { return _pad_for_promote_in_place; }
431 
432   inline void reserve_promotable_humongous_regions(size_t region_count) { _promotable_humongous_regions = region_count; }
433   inline void reserve_promotable_regular_regions(size_t region_count) { _regular_regions_promoted_in_place = region_count; }
434 
435   inline size_t get_promotable_humongous_regions() { return _promotable_humongous_regions; }
436   inline size_t get_regular_regions_promoted_in_place() { return _regular_regions_promoted_in_place; }
437 
438   // Returns previous value
439   inline size_t set_promoted_reserve(size_t new_val);
440   inline size_t get_promoted_reserve() const;
441   inline void augment_promo_reserve(size_t increment);
442 
443   inline void reset_promoted_expended();
444   inline size_t expend_promoted(size_t increment);
445   inline size_t unexpend_promoted(size_t decrement);
446   inline size_t get_promoted_expended();
447 
448   // Returns previous value
449   inline size_t set_old_evac_reserve(size_t new_val);
450   inline size_t get_old_evac_reserve() const;
451   inline void augment_old_evac_reserve(size_t increment);
452 
453   // Returns previous value
454   inline size_t set_young_evac_reserve(size_t new_val);
455   inline size_t get_young_evac_reserve() const;
456 
457   // Return the age census object for young gen (in generational mode)
458   inline ShenandoahAgeCensus* age_census() const;
459 
460 private:
461   void manage_satb_barrier(bool active);
462 
463   enum CancelState {
464     // Normal state. GC has not been cancelled and is open for cancellation.
465     // Worker threads can suspend for safepoint.
466     CANCELLABLE,
467 
468     // GC has been cancelled. Worker threads can not suspend for
469     // safepoint but must finish their work as soon as possible.
470     CANCELLED
471   };
472 
473   double _cancel_requested_time;
474   ShenandoahSharedEnumFlag<CancelState> _cancelled_gc;
475 
476   // Returns true if cancel request was successfully communicated.
477   // Returns false if some other thread already communicated cancel
478   // request.  A true return value does not mean GC has been
479   // cancelled, only that the process of cancelling GC has begun.
480   bool try_cancel_gc();
481 
482 public:
483   inline bool cancelled_gc() const;
484   inline bool check_cancelled_gc_and_yield(bool sts_active = true);
485 
486   inline void clear_cancelled_gc(bool clear_oom_handler = true);
487 
488   void cancel_concurrent_mark();
489   void cancel_gc(GCCause::Cause cause);
490 
491 public:
492   // Elastic heap support
493   void entry_uncommit(double shrink_before, size_t shrink_until);
494   void op_uncommit(double shrink_before, size_t shrink_until);
495 
496 private:
497   // GC support
498   // Evacuation
499   void evacuate_collection_set(bool concurrent);
500   // Concurrent root processing
501   void prepare_concurrent_roots();
502   void finish_concurrent_roots();
503   // Concurrent class unloading support
504   void do_class_unloading();
505   // Reference updating
506   void prepare_update_heap_references(bool concurrent);
507   void update_heap_references(bool concurrent);
508   // Final update region states
509   void update_heap_region_states(bool concurrent);
510 
511   void rendezvous_threads();
512   void recycle_trash();
513 public:
514   void rebuild_free_set(bool concurrent);
515   void notify_gc_progress();
516   void notify_gc_no_progress();
517   size_t get_gc_no_progress_count() const;
518 
519 //
520 // Mark support
521 private:
522   ShenandoahYoungGeneration* _young_generation;
523   ShenandoahGeneration*      _global_generation;
524   ShenandoahOldGeneration*   _old_generation;
525 
526   ShenandoahControlThread*   _control_thread;
527   ShenandoahRegulatorThread* _regulator_thread;
528   ShenandoahCollectorPolicy* _shenandoah_policy;
529   ShenandoahMode*            _gc_mode;
530   ShenandoahFreeSet*         _free_set;
531   ShenandoahPacer*           _pacer;
532   ShenandoahVerifier*        _verifier;
533 
534   ShenandoahPhaseTimings*       _phase_timings;
535   ShenandoahEvacuationTracker*  _evac_tracker;
536   ShenandoahMmuTracker          _mmu_tracker;
537   ShenandoahGenerationSizer     _generation_sizer;
538 
539   ShenandoahRegulatorThread* regulator_thread()        { return _regulator_thread;  }
540 
541 public:
542   ShenandoahControlThread*   control_thread()          { return _control_thread;    }
543   ShenandoahYoungGeneration* young_generation()  const { return _young_generation;  }
544   ShenandoahGeneration*      global_generation() const { return _global_generation; }
545   ShenandoahOldGeneration*   old_generation()    const { return _old_generation;    }
546   ShenandoahGeneration*      generation_for(ShenandoahAffiliation affiliation) const;
547   const ShenandoahGenerationSizer* generation_sizer()  const { return &_generation_sizer;  }
548 
549   size_t max_size_for(ShenandoahGeneration* generation) const;
550   size_t min_size_for(ShenandoahGeneration* generation) const;
551 
552   ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
553   ShenandoahMode*            mode()              const { return _gc_mode;           }
554   ShenandoahFreeSet*         free_set()          const { return _free_set;          }
555   ShenandoahPacer*           pacer()             const { return _pacer;             }
556 
557   ShenandoahPhaseTimings*      phase_timings()   const { return _phase_timings;     }
558   ShenandoahEvacuationTracker* evac_tracker()    const { return  _evac_tracker;     }
559 
560   void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation);
561   void on_cycle_end(ShenandoahGeneration* generation);
562 
563   ShenandoahVerifier*        verifier();
564 
565 // ---------- VM subsystem bindings
566 //
567 private:
568   ShenandoahMonitoringSupport* _monitoring_support;
569   MemoryPool*                  _memory_pool;
570   MemoryPool*                  _young_gen_memory_pool;
571   MemoryPool*                  _old_gen_memory_pool;
572 
573   GCMemoryManager              _stw_memory_manager;
574   GCMemoryManager              _cycle_memory_manager;
575   ConcurrentGCTimer*           _gc_timer;
576   SoftRefPolicy                _soft_ref_policy;
577 
578   // For exporting to SA
579   int                          _log_min_obj_alignment_in_bytes;
580 public:
581   ShenandoahMonitoringSupport* monitoring_support() const    { return _monitoring_support;    }
582   GCMemoryManager* cycle_memory_manager()                    { return &_cycle_memory_manager; }
583   GCMemoryManager* stw_memory_manager()                      { return &_stw_memory_manager;   }
584   SoftRefPolicy* soft_ref_policy()                  override { return &_soft_ref_policy;      }
585 
586   GrowableArray<GCMemoryManager*> memory_managers() override;
587   GrowableArray<MemoryPool*> memory_pools() override;
588   MemoryUsage memory_usage() override;
589   GCTracer* tracer();
590   ConcurrentGCTimer* gc_timer() const;
591 
592 // ---------- Class Unloading
593 //
594 private:
595   ShenandoahSharedFlag  _is_aging_cycle;
596   ShenandoahSharedFlag _unload_classes;
597   ShenandoahUnload     _unloader;
598 
599 public:
600   void set_unload_classes(bool uc);
601   bool unload_classes() const;
602 
603   // Perform STW class unloading and weak root cleaning
604   void parallel_cleaning(bool full_gc);
605 
606 private:
607   void stw_unload_classes(bool full_gc);
608   void stw_process_weak_roots(bool full_gc);
609   void stw_weak_refs(bool full_gc);
610 
611   inline void assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
612                                           ShenandoahAffiliation new_affiliation);
613 
614   // Heap iteration support
615   void scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops);
616   bool prepare_aux_bitmap_for_iteration();
617   void reclaim_aux_bitmap_for_iteration();
618 
619 // ---------- Generic interface hooks
620 // Minor things that super-interface expects us to implement to play nice with
621 // the rest of runtime. Some of the things here are not required to be implemented,
622 // and can be stubbed out.
623 //
624 public:
625   bool is_maximal_no_gc() const override shenandoah_not_implemented_return(false);
626 
627   inline bool is_in(const void* p) const override;
628 
629   inline bool is_in_active_generation(oop obj) const;
630   inline bool is_in_young(const void* p) const;
631   inline bool is_in_old(const void* p) const;
632   inline bool is_old(oop pobj) const;
633 
634   inline ShenandoahAffiliation region_affiliation(const ShenandoahHeapRegion* r);
635   inline void set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation);
636 
637   inline ShenandoahAffiliation region_affiliation(size_t index);
638 
639   bool requires_barriers(stackChunkOop obj) const override;
640 
641   MemRegion reserved_region() const { return _reserved; }
642   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
643 
644   void collect(GCCause::Cause cause) override;
645   void do_full_collection(bool clear_all_soft_refs) override;
646 
647   // Used for parsing heap during error printing
648   HeapWord* block_start(const void* addr) const;
649   bool block_is_obj(const HeapWord* addr) const;
650   bool print_location(outputStream* st, void* addr) const override;
651 
652   // Used for native heap walkers: heap dumpers, mostly
653   void object_iterate(ObjectClosure* cl) override;
654   // Parallel heap iteration support
655   ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
656 
657   // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
658   void keep_alive(oop obj) override;
659 
660 // ---------- Safepoint interface hooks
661 //
662 public:
663   void safepoint_synchronize_begin() override;
664   void safepoint_synchronize_end() override;
665 
666 // ---------- Code roots handling hooks
667 //
668 public:
669   void register_nmethod(nmethod* nm) override;
670   void unregister_nmethod(nmethod* nm) override;
671   void verify_nmethod(nmethod* nm) override {}
672 
673 // ---------- Pinning hooks
674 //
675 public:
676   // Shenandoah supports per-object (per-region) pinning
677   void pin_object(JavaThread* thread, oop obj) override;
678   void unpin_object(JavaThread* thread, oop obj) override;
679 
680   void sync_pinned_region_status();
681   void assert_pinned_region_status() NOT_DEBUG_RETURN;
682 
683 // ---------- Concurrent Stack Processing support
684 //
685 public:
686   bool uses_stack_watermark_barrier() const override { return true; }
687 
688 // ---------- Allocation support
689 //
690 private:
691   // How many bytes to transfer between old and young after we have finished recycling collection set regions?
692   size_t _old_regions_surplus;
693   size_t _old_regions_deficit;
694 
695   HeapWord* allocate_memory_under_lock(ShenandoahAllocRequest& request, bool& in_new_region, bool is_promotion);
696 
697   inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
698   HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
699   HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
700 
701   inline HeapWord* allocate_from_plab(Thread* thread, size_t size, bool is_promotion);
702   HeapWord* allocate_from_plab_slow(Thread* thread, size_t size, bool is_promotion);
703   HeapWord* allocate_new_plab(size_t min_size, size_t word_size, size_t* actual_size);
704 
705 public:
706   HeapWord* allocate_memory(ShenandoahAllocRequest& request, bool is_promotion);
707   HeapWord* mem_allocate(size_t size, bool* what) override;
708   MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
709                                                size_t size,
710                                                Metaspace::MetadataType mdtype) override;
711 
712   void notify_mutator_alloc_words(size_t words, size_t waste);
713 
714   HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override;
715   size_t tlab_capacity(Thread *thr) const override;
716   size_t unsafe_max_tlab_alloc(Thread *thread) const override;
717   size_t max_tlab_size() const override;
718   size_t tlab_used(Thread* ignored) const override;
719 
720   void ensure_parsability(bool retire_labs) override;
721 
722   void labs_make_parsable();
723   void tlabs_retire(bool resize);
724   void gclabs_retire(bool resize);
725 
726   inline void set_old_region_surplus(size_t surplus) { _old_regions_surplus = surplus; };
727   inline void set_old_region_deficit(size_t deficit) { _old_regions_deficit = deficit; };
728 
729   inline size_t get_old_region_surplus() { return _old_regions_surplus; };
730   inline size_t get_old_region_deficit() { return _old_regions_deficit; };
731 
732 // ---------- Marking support
733 //
734 private:
735   ShenandoahMarkingContext* _marking_context;
736   MemRegion  _bitmap_region;
737   MemRegion  _aux_bitmap_region;
738   MarkBitMap _verification_bit_map;
739   MarkBitMap _aux_bit_map;
740 
741   size_t _bitmap_size;
742   size_t _bitmap_regions_per_slice;
743   size_t _bitmap_bytes_per_slice;
744 
745   size_t _pretouch_heap_page_size;
746   size_t _pretouch_bitmap_page_size;
747 
748   bool _bitmap_region_special;
749   bool _aux_bitmap_region_special;
750 
751   ShenandoahLiveData** _liveness_cache;
752 
753 public:
754   inline ShenandoahMarkingContext* complete_marking_context() const;
755   inline ShenandoahMarkingContext* marking_context() const;
756 
757   template<class T>
758   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
759 
760   template<class T>
761   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
762 
763   template<class T>
764   inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
765 
766   // SATB barriers hooks
767   inline bool requires_marking(const void* entry) const;
768 
769   // Support for bitmap uncommits
770   bool commit_bitmap_slice(ShenandoahHeapRegion *r);
771   bool uncommit_bitmap_slice(ShenandoahHeapRegion *r);
772   bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
773 
774   // Liveness caching support
775   ShenandoahLiveData* get_liveness_cache(uint worker_id);
776   void flush_liveness_cache(uint worker_id);
777 
778   size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
779 
780 // ---------- Evacuation support
781 //
782 private:
783   ShenandoahCollectionSet* _collection_set;
784   ShenandoahEvacOOMHandler _oom_evac_handler;
785   ShenandoahSharedFlag _old_gen_oom_evac;
786 
787   inline oop try_evacuate_object(oop src, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahAffiliation target_gen);
788   void handle_old_evacuation(HeapWord* obj, size_t words, bool promotion);
789   void handle_old_evacuation_failure();
790 
791 public:
792   void report_promotion_failure(Thread* thread, size_t size);
793 
794   static address in_cset_fast_test_addr();
795 
796   ShenandoahCollectionSet* collection_set() const { return _collection_set; }
797 
798   // Checks if object is in the collection set.
799   inline bool in_collection_set(oop obj) const;
800 
801   // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
802   inline bool in_collection_set_loc(void* loc) const;
803 
804   // Evacuates or promotes object src. Returns the evacuated object, either evacuated
805   // by this thread, or by some other thread.
806   inline oop evacuate_object(oop src, Thread* thread);
807 
808   // Call before/after evacuation.
809   inline void enter_evacuation(Thread* t);
810   inline void leave_evacuation(Thread* t);
811 
812   inline bool clear_old_evacuation_failure();
813 
814 // ---------- Generational support
815 //
816 private:
817   RememberedScanner* _card_scan;
818 
819 public:
820   inline RememberedScanner* card_scan() { return _card_scan; }
821   void clear_cards_for(ShenandoahHeapRegion* region);
822   void mark_card_as_dirty(void* location);
823   void retire_plab(PLAB* plab);
824   void retire_plab(PLAB* plab, Thread* thread);
825   void cancel_old_gc();
826 
827   void adjust_generation_sizes_for_next_cycle(size_t old_xfer_limit, size_t young_cset_regions, size_t old_cset_regions);
828 
829 // ---------- Helper functions
830 //
831 public:
832   template <class T>
833   inline void conc_update_with_forwarded(T* p);
834 
835   template <class T>
836   inline void update_with_forwarded(T* p);
837 
838   static inline void atomic_update_oop(oop update,       oop* addr,       oop compare);
839   static inline void atomic_update_oop(oop update, narrowOop* addr,       oop compare);
840   static inline void atomic_update_oop(oop update, narrowOop* addr, narrowOop compare);
841 
842   static inline bool atomic_update_oop_check(oop update,       oop* addr,       oop compare);
843   static inline bool atomic_update_oop_check(oop update, narrowOop* addr,       oop compare);
844   static inline bool atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare);
845 
846   static inline void atomic_clear_oop(      oop* addr,       oop compare);
847   static inline void atomic_clear_oop(narrowOop* addr,       oop compare);
848   static inline void atomic_clear_oop(narrowOop* addr, narrowOop compare);
849 
850   size_t trash_humongous_region_at(ShenandoahHeapRegion *r);
851 
852   static inline void increase_object_age(oop obj, uint additional_age);
853 
854   // Return the object's age, or a sentinel value when the age can't
855   // necessarily be determined because of concurrent locking by the
856   // mutator
857   static inline uint get_object_age(oop obj);
858 
859   void transfer_old_pointers_from_satb();
860 
861   void log_heap_status(const char *msg) const;
862 
863 private:
864   void trash_cset_regions();
865 
866 // ---------- Testing helpers functions
867 //
868 private:
869   ShenandoahSharedFlag _inject_alloc_failure;
870 
871   void try_inject_alloc_failure();
872   bool should_inject_alloc_failure();
873 };
874 
875 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP