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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  5  *
  6  * This code is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 only, as
  8  * published by the Free Software Foundation.
  9  *
 10  * This code is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 13  * version 2 for more details (a copy is included in the LICENSE file that
 14  * accompanied this code).
 15  *
 16  * You should have received a copy of the GNU General Public License version
 17  * 2 along with this work; if not, write to the Free Software Foundation,
 18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 19  *
 20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 21  * or visit www.oracle.com if you need additional information or have any
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 25 
 26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 27 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
 28 
 29 #include "gc/shared/markBitMap.hpp"
 30 #include "gc/shared/softRefPolicy.hpp"
 31 #include "gc/shared/collectedHeap.hpp"
 32 #include "gc/shenandoah/mode/shenandoahGenerationalMode.hpp"
 33 #include "gc/shenandoah/shenandoahAsserts.hpp"
 34 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
 35 #include "gc/shenandoah/shenandoahLock.hpp"
 36 #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp"
 37 #include "gc/shenandoah/shenandoahEvacTracker.hpp"
 38 #include "gc/shenandoah/shenandoahMmuTracker.hpp"
 39 #include "gc/shenandoah/shenandoahPadding.hpp"
 40 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
 41 #include "gc/shenandoah/shenandoahUnload.hpp"
 42 #include "gc/shenandoah/shenandoahScanRemembered.hpp"
 43 #include "memory/metaspace.hpp"
 44 #include "services/memoryManager.hpp"
 45 #include "utilities/globalDefinitions.hpp"
 46 #include "utilities/stack.hpp"
 47 
 48 class ConcurrentGCTimer;
 49 class ObjectIterateScanRootClosure;
 50 class PLAB;
 51 class ShenandoahCollectorPolicy;
 52 class ShenandoahControlThread;
 53 class ShenandoahRegulatorThread;
 54 class ShenandoahGCSession;
 55 class ShenandoahGCStateResetter;
 56 class ShenandoahGeneration;
 57 class ShenandoahYoungGeneration;
 58 class ShenandoahOldGeneration;
 59 class ShenandoahHeuristics;
 60 class ShenandoahOldHeuristics;
 61 class ShenandoahMarkingContext;
 62 class ShenandoahPhaseTimings;
 63 class ShenandoahHeap;
 64 class ShenandoahHeapRegion;
 65 class ShenandoahHeapRegionClosure;
 66 class ShenandoahCollectionSet;
 67 class ShenandoahFreeSet;
 68 class ShenandoahConcurrentMark;
 69 class ShenandoahFullGC;
 70 class ShenandoahMonitoringSupport;
 71 class ShenandoahPacer;
 72 class ShenandoahReferenceProcessor;
 73 class ShenandoahVerifier;
 74 class ShenandoahWorkerThreads;
 75 class VMStructs;
 76 
 77 // Used for buffering per-region liveness data.
 78 // Needed since ShenandoahHeapRegion uses atomics to update liveness.
 79 // The ShenandoahHeap array has max-workers elements, each of which is an array of
 80 // uint16_t * max_regions. The choice of uint16_t is not accidental:
 81 // there is a tradeoff between static/dynamic footprint that translates
 82 // into cache pressure (which is already high during marking), and
 83 // too many atomic updates. uint32_t is too large, uint8_t is too small.
 84 typedef uint16_t ShenandoahLiveData;
 85 #define SHENANDOAH_LIVEDATA_MAX ((ShenandoahLiveData)-1)
 86 
 87 class ShenandoahRegionIterator : public StackObj {
 88 private:
 89   ShenandoahHeap* _heap;
 90 
 91   shenandoah_padding(0);
 92   volatile size_t _index;
 93   shenandoah_padding(1);
 94 
 95   // No implicit copying: iterators should be passed by reference to capture the state
 96   NONCOPYABLE(ShenandoahRegionIterator);
 97 
 98 public:
 99   ShenandoahRegionIterator();
100   ShenandoahRegionIterator(ShenandoahHeap* heap);
101 
102   // Reset iterator to default state
103   void reset();
104 
105   // Returns next region, or NULL if there are no more regions.
106   // This is multi-thread-safe.
107   inline ShenandoahHeapRegion* next();
108 
109   // This is *not* MT safe. However, in the absence of multithreaded access, it
110   // can be used to determine if there is more work to do.
111   bool has_next() const;
112 };
113 
114 class ShenandoahHeapRegionClosure : public StackObj {
115 public:
116   virtual void heap_region_do(ShenandoahHeapRegion* r) = 0;
117   virtual bool is_thread_safe() { return false; }
118 };
119 
120 template<GenerationMode GENERATION>
121 class ShenandoahGenerationRegionClosure : public ShenandoahHeapRegionClosure {
122  public:
123   explicit ShenandoahGenerationRegionClosure(ShenandoahHeapRegionClosure* cl) : _cl(cl) {}
124   void heap_region_do(ShenandoahHeapRegion* r);
125   virtual bool is_thread_safe() { return _cl->is_thread_safe(); }
126  private:
127   ShenandoahHeapRegionClosure* _cl;
128 };
129 
130 typedef ShenandoahLock    ShenandoahHeapLock;
131 typedef ShenandoahLocker  ShenandoahHeapLocker;
132 typedef Stack<oop, mtGC>  ShenandoahScanObjectStack;
133 
134 // Shenandoah GC is low-pause concurrent GC that uses Brooks forwarding pointers
135 // to encode forwarding data. See BrooksPointer for details on forwarding data encoding.
136 // See ShenandoahControlThread for GC cycle structure.
137 //
138 class ShenandoahHeap : public CollectedHeap {
139   friend class ShenandoahAsserts;
140   friend class VMStructs;
141   friend class ShenandoahGCSession;
142   friend class ShenandoahGCStateResetter;
143   friend class ShenandoahParallelObjectIterator;
144   friend class ShenandoahSafepoint;
145   // Supported GC
146   friend class ShenandoahConcurrentGC;
147   friend class ShenandoahOldGC;
148   friend class ShenandoahDegenGC;
149   friend class ShenandoahFullGC;
150   friend class ShenandoahUnload;
151 
152 // ---------- Locks that guard important data structures in Heap
153 //
154 private:
155   ShenandoahHeapLock _lock;
156   ShenandoahGeneration* _gc_generation;
157 
158   // true iff we are concurrently coalescing and filling old-gen HeapRegions
159   bool _prepare_for_old_mark;
160 
161 public:
162   ShenandoahHeapLock* lock() {
163     return &_lock;
164   }
165 
166   ShenandoahGeneration* active_generation() const {
167     // last or latest generation might be a better name here.
168     return _gc_generation;
169   }
170 
171   void set_gc_generation(ShenandoahGeneration* generation) {
172     _gc_generation = generation;
173   }
174 
175   ShenandoahOldHeuristics* old_heuristics();
176 
177   bool doing_mixed_evacuations();
178   bool is_old_bitmap_stable() const;
179   bool is_gc_generation_young() const;
180 
181 // ---------- Initialization, termination, identification, printing routines
182 //
183 public:
184   static ShenandoahHeap* heap();
185 
186   const char* name()          const override { return "Shenandoah"; }
187   ShenandoahHeap::Name kind() const override { return CollectedHeap::Shenandoah; }
188 
189   ShenandoahHeap(ShenandoahCollectorPolicy* policy);
190   jint initialize() override;
191   void post_initialize() override;
192   void initialize_mode();
193   void initialize_heuristics();
194   void initialize_generations();
195 
196   void initialize_serviceability() override;
197 
198   void print_on(outputStream* st)              const override;
199   void print_extended_on(outputStream *st)     const override;
200   void print_tracing_info()                    const override;
201   void print_heap_regions_on(outputStream* st) const;
202 
203   void stop() override;
204 
205   void prepare_for_verify() override;
206   void verify(VerifyOption vo) override;
207   void verify_rem_set_at_mark();
208   void verify_rem_set_at_update_ref();
209   void verify_rem_set_after_full_gc();
210 
211 // WhiteBox testing support.
212   bool supports_concurrent_gc_breakpoints() const override {
213     return true;
214   }
215 
216 // ---------- Heap counters and metrics
217 //
218 private:
219            size_t _initial_size;
220            size_t _minimum_size;
221   volatile size_t _soft_max_size;
222   shenandoah_padding(0);
223   volatile size_t _used;
224   volatile size_t _committed;
225   shenandoah_padding(1);
226 
227   void help_verify_region_rem_set(ShenandoahHeapRegion* r, ShenandoahMarkingContext* ctx,
228                                   HeapWord* from, HeapWord* top, HeapWord* update_watermark, const char* message);
229 
230 public:
231   void increase_used(size_t bytes);
232   void decrease_used(size_t bytes);
233   void set_used(size_t bytes);
234 
235   void increase_committed(size_t bytes);
236   void decrease_committed(size_t bytes);
237 
238   void reset_bytes_allocated_since_gc_start();
239 
240   size_t min_capacity()      const;
241   size_t max_capacity()      const override;
242   size_t soft_max_capacity() const;
243   size_t initial_capacity()  const;
244   size_t capacity()          const override;
245   size_t used()              const override;
246   size_t committed()         const;
247 
248   void set_soft_max_capacity(size_t v);
249 
250 // ---------- Workers handling
251 //
252 private:
253   uint _max_workers;
254   ShenandoahWorkerThreads* _workers;
255   ShenandoahWorkerThreads* _safepoint_workers;
256 
257 public:
258   uint max_workers();
259   void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
260 
261   WorkerThreads* workers() const;
262   WorkerThreads* safepoint_workers() override;
263 
264   void gc_threads_do(ThreadClosure* tcl) const override;
265 
266 // ---------- Heap regions handling machinery
267 //
268 private:
269   MemRegion _heap_region;
270   bool      _heap_region_special;
271   size_t    _num_regions;
272   ShenandoahHeapRegion** _regions;
273   uint8_t* _affiliations;       // Holds array of enum ShenandoahRegionAffiliation, including FREE status in non-generational mode
274   ShenandoahRegionIterator _update_refs_iterator;
275 
276 public:
277 
278   inline HeapWord* base() const { return _heap_region.start(); }
279 
280   inline size_t num_regions() const { return _num_regions; }
281   inline bool is_heap_region_special() { return _heap_region_special; }
282 
283   inline ShenandoahHeapRegion* const heap_region_containing(const void* addr) const;
284   inline size_t heap_region_index_containing(const void* addr) const;
285 
286   inline ShenandoahHeapRegion* const get_region(size_t region_idx) const;
287 
288   void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
289   void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
290 
291 // ---------- GC state machinery
292 //
293 // GC state describes the important parts of collector state, that may be
294 // used to make barrier selection decisions in the native and generated code.
295 // Multiple bits can be set at once.
296 //
297 // Important invariant: when GC state is zero, the heap is stable, and no barriers
298 // are required.
299 //
300 public:
301   enum GCStateBitPos {
302     // Heap has forwarded objects: needs LRB barriers.
303     HAS_FORWARDED_BITPOS   = 0,
304 
305     // Young regions are under marking: needs SATB barriers.
306     YOUNG_MARKING_BITPOS    = 1,
307 
308     // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
309     EVACUATION_BITPOS = 2,
310 
311     // Heap is under updating: needs no additional barriers.
312     UPDATEREFS_BITPOS = 3,
313 
314     // Heap is under weak-reference/roots processing: needs weak-LRB barriers.
315     WEAK_ROOTS_BITPOS  = 4,
316 
317     // Old regions are under marking, still need SATB barriers.
318     OLD_MARKING_BITPOS = 5
319   };
320 
321   enum GCState {
322     STABLE        = 0,
323     HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
324     YOUNG_MARKING = 1 << YOUNG_MARKING_BITPOS,
325     EVACUATION    = 1 << EVACUATION_BITPOS,
326     UPDATEREFS    = 1 << UPDATEREFS_BITPOS,
327     WEAK_ROOTS    = 1 << WEAK_ROOTS_BITPOS,
328     OLD_MARKING   = 1 << OLD_MARKING_BITPOS
329   };
330 
331 private:
332   ShenandoahSharedBitmap _gc_state;
333   ShenandoahSharedFlag   _degenerated_gc_in_progress;
334   ShenandoahSharedFlag   _full_gc_in_progress;
335   ShenandoahSharedFlag   _full_gc_move_in_progress;
336   ShenandoahSharedFlag   _progress_last_gc;
337   ShenandoahSharedFlag   _concurrent_strong_root_in_progress;
338 
339   // _alloc_supplement_reserve is a supplemental budget for new_memory allocations.  During evacuation and update-references,
340   // mutator allocation requests are "authorized" iff young_gen->available() plus _alloc_supplement_reserve minus
341   // _young_evac_reserve is greater than request size.  The values of _alloc_supplement_reserve and _young_evac_reserve
342   // are zero except during evacuation and update-reference phases of GC.  Both of these values are established at
343   // the start of evacuation, and they remain constant throughout the duration of these two phases of GC.  Since these
344   // two values are constant throughout each GC phases, we introduce a new service into ShenandoahGeneration.  This service
345   // provides adjusted_available() based on an adjusted capacity.  At the start of evacuation, we adjust young capacity by
346   // adding the amount to be borrowed from old-gen and subtracting the _young_evac_reserve, we adjust old capacity by
347   // subtracting the amount to be loaned to young-gen.
348   //
349   // We always use adjusted capacities to determine permission to allocate within young and to promote into old.  Note
350   // that adjusted capacities equal traditional capacities except during evacuation and update refs.
351   //
352   // During evacuation, we assure that _old_evac_expended does not exceed _old_evac_reserve.
353   //
354   // At the end of update references, we perform the following bookkeeping activities:
355   //
356   // 1. Unadjust the capacity within young-gen and old-gen to undo the effects of borrowing memory from old-gen.  Note that
357   //    the entirety of the collection set is now available, so allocation capacity naturally increase at this time.
358   // 2. Clear (reset to zero) _alloc_supplement_reserve, _young_evac_reserve, _old_evac_reserve, and _promoted_reserve
359   //
360   // _young_evac_reserve and _old_evac_reserve are only non-zero during evacuation and update-references.
361   //
362   // Allocation of old GCLABs assures that _old_evac_expended + request-size < _old_evac_reserved.  If the allocation
363   //  is authorized, increment _old_evac_expended by request size.  This allocation ignores old_gen->available().
364   //
365   // Note that the typical total expenditure on evacuation is less than the associated evacuation reserve because we generally
366   // reserve ShenandoahEvacWaste (> 1.0) times the anticipated evacuation need.  In the case that there is an excessive amount
367   // of waste, it may be that one thread fails to grab a new GCLAB, this does not necessarily doom the associated evacuation
368   // effort.  If this happens, the requesting thread blocks until some other thread manages to evacuate the offending object.
369   // Only after "all" threads fail to evacuate an object do we consider the evacuation effort to have failed.
370 
371   intptr_t _alloc_supplement_reserve;  // Bytes reserved for young allocations during evac and update refs
372   size_t _promoted_reserve;            // Bytes reserved within old-gen to hold the results of promotion
373   volatile size_t _promoted_expended;  // Bytes of old-gen memory expended on promotions
374 
375   size_t _old_evac_reserve;            // Bytes reserved within old-gen to hold evacuated objects from old-gen collection set
376   volatile size_t _old_evac_expended;  // Bytes of old-gen memory expended on old-gen evacuations
377 
378   size_t _young_evac_reserve;          // Bytes reserved within young-gen to hold evacuated objects from young-gen collection set
379 
380   size_t _captured_old_usage;          // What was old usage (bytes) when last captured?
381 
382   size_t _previous_promotion;          // Bytes promoted during previous evacuation
383 
384   bool _upgraded_to_full;
385 
386   void set_gc_state_all_threads(char state);
387   void set_gc_state_mask(uint mask, bool value);
388 
389 
390 
391 public:
392   char gc_state() const;
393   static address gc_state_addr();
394 
395   void set_concurrent_young_mark_in_progress(bool in_progress);
396   void set_concurrent_old_mark_in_progress(bool in_progress);
397   void set_evacuation_in_progress(bool in_progress);
398   void set_update_refs_in_progress(bool in_progress);
399   void set_degenerated_gc_in_progress(bool in_progress);
400   void set_full_gc_in_progress(bool in_progress);
401   void set_full_gc_move_in_progress(bool in_progress);
402   void set_has_forwarded_objects(bool cond);
403   void set_concurrent_strong_root_in_progress(bool cond);
404   void set_concurrent_weak_root_in_progress(bool cond);
405   void set_prepare_for_old_mark_in_progress(bool cond);
406   void set_aging_cycle(bool cond);
407 
408   inline bool is_stable() const;
409   inline bool is_idle() const;
410   inline bool is_concurrent_mark_in_progress() const;
411   inline bool is_concurrent_young_mark_in_progress() const;
412   inline bool is_concurrent_old_mark_in_progress() const;
413   inline bool is_update_refs_in_progress() const;
414   inline bool is_evacuation_in_progress() const;
415   inline bool is_degenerated_gc_in_progress() const;
416   inline bool is_full_gc_in_progress() const;
417   inline bool is_full_gc_move_in_progress() const;
418   inline bool has_forwarded_objects() const;
419   inline bool is_gc_in_progress_mask(uint mask) const;
420   inline bool is_stw_gc_in_progress() const;
421   inline bool is_concurrent_strong_root_in_progress() const;
422   inline bool is_concurrent_weak_root_in_progress() const;
423   inline bool is_prepare_for_old_mark_in_progress() const;
424   inline bool is_aging_cycle() const;
425   inline bool upgraded_to_full() { return _upgraded_to_full; }
426   inline void start_conc_gc() { _upgraded_to_full = false; }
427   inline void record_upgrade_to_full() { _upgraded_to_full = true; }
428 
429   inline size_t capture_old_usage(size_t usage);
430   inline void set_previous_promotion(size_t promoted_bytes);
431   inline size_t get_previous_promotion() const;
432 
433   // Returns previous value
434   inline size_t set_promoted_reserve(size_t new_val);
435   inline size_t get_promoted_reserve() const;
436 
437   inline void reset_promoted_expended();
438   inline size_t expend_promoted(size_t increment);
439   inline size_t unexpend_promoted(size_t decrement);
440   inline size_t get_promoted_expended();
441 
442   // Returns previous value
443   inline size_t set_old_evac_reserve(size_t new_val);
444   inline size_t get_old_evac_reserve() const;
445 
446   inline void reset_old_evac_expended();
447   inline size_t expend_old_evac(size_t increment);
448   inline size_t get_old_evac_expended();
449 
450   // Returns previous value
451   inline size_t set_young_evac_reserve(size_t new_val);
452   inline size_t get_young_evac_reserve() const;
453 
454   // Returns previous value.  This is a signed value because it is the amount borrowed minus the amount reserved for
455   // young-gen evacuation.  In case we cannot borrow much, this value might be negative.
456   inline intptr_t set_alloc_supplement_reserve(intptr_t new_val);
457   inline intptr_t get_alloc_supplement_reserve() const;
458 
459 private:
460   void manage_satb_barrier(bool active);
461 
462   enum CancelState {
463     // Normal state. GC has not been cancelled and is open for cancellation.
464     // Worker threads can suspend for safepoint.
465     CANCELLABLE,
466 
467     // GC has been cancelled. Worker threads can not suspend for
468     // safepoint but must finish their work as soon as possible.
469     CANCELLED,
470 
471     // GC has not been cancelled and must not be cancelled. At least
472     // one worker thread checks for pending safepoint and may suspend
473     // if a safepoint is pending.
474     NOT_CANCELLED
475   };
476 
477   double _cancel_requested_time;
478   ShenandoahSharedEnumFlag<CancelState> _cancelled_gc;
479 
480   // Returns true if cancel request was successfully communicated.
481   // Returns false if some other thread already communicated cancel
482   // request.  A true return value does not mean GC has been
483   // cancelled, only that the process of cancelling GC has begun.
484   bool try_cancel_gc();
485 
486 public:
487   inline bool cancelled_gc() const;
488   inline bool check_cancelled_gc_and_yield(bool sts_active = true);
489 
490   inline void clear_cancelled_gc(bool clear_oom_handler = true);
491 
492   void cancel_concurrent_mark();
493   void cancel_gc(GCCause::Cause cause);
494 
495 public:
496   // Elastic heap support
497   void entry_uncommit(double shrink_before, size_t shrink_until);
498   void op_uncommit(double shrink_before, size_t shrink_until);
499 
500 private:
501   // GC support
502   // Evacuation
503   void evacuate_collection_set(bool concurrent);
504   // Concurrent root processing
505   void prepare_concurrent_roots();
506   void finish_concurrent_roots();
507   // Concurrent class unloading support
508   void do_class_unloading();
509   // Reference updating
510   void prepare_update_heap_references(bool concurrent);
511   void update_heap_references(bool concurrent);
512   // Final update region states
513   void update_heap_region_states(bool concurrent);
514   void rebuild_free_set(bool concurrent);
515 
516   void rendezvous_threads();
517   void recycle_trash();
518 public:
519   void notify_gc_progress()    { _progress_last_gc.set();   }
520   void notify_gc_no_progress() { _progress_last_gc.unset(); }
521 
522 //
523 // Mark support
524 private:
525   ShenandoahYoungGeneration* _young_generation;
526   ShenandoahGeneration*      _global_generation;
527   ShenandoahOldGeneration*   _old_generation;
528 
529   ShenandoahControlThread*   _control_thread;
530   ShenandoahRegulatorThread* _regulator_thread;
531   ShenandoahCollectorPolicy* _shenandoah_policy;
532   ShenandoahMode*            _gc_mode;
533   ShenandoahFreeSet*         _free_set;
534   ShenandoahPacer*           _pacer;
535   ShenandoahVerifier*        _verifier;
536 
537   ShenandoahPhaseTimings*       _phase_timings;
538   ShenandoahEvacuationTracker*  _evac_tracker;
539   ShenandoahMmuTracker          _mmu_tracker;
540   ShenandoahGenerationSizer     _generation_sizer;
541 
542   ShenandoahRegulatorThread* regulator_thread()        { return _regulator_thread;  }
543 
544 public:
545   ShenandoahControlThread*   control_thread()          { return _control_thread;    }
546   ShenandoahYoungGeneration* young_generation()  const { return _young_generation;  }
547   ShenandoahGeneration*      global_generation() const { return _global_generation; }
548   ShenandoahOldGeneration*   old_generation()    const { return _old_generation;    }
549   ShenandoahGeneration*      generation_for(ShenandoahRegionAffiliation affiliation) const;
550   const ShenandoahGenerationSizer* generation_sizer()  const { return &_generation_sizer;  }
551 
552   size_t max_size_for(ShenandoahGeneration* generation) const;
553   size_t min_size_for(ShenandoahGeneration* generation) const;
554 
555   ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
556   ShenandoahMode*            mode()              const { return _gc_mode;           }
557   ShenandoahFreeSet*         free_set()          const { return _free_set;          }
558   ShenandoahPacer*           pacer()             const { return _pacer;             }
559 
560   ShenandoahPhaseTimings*      phase_timings()   const { return _phase_timings;     }
561   ShenandoahEvacuationTracker* evac_tracker()    const { return  _evac_tracker;     }
562 
563   void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation);
564   void on_cycle_end(ShenandoahGeneration* generation);
565 
566   ShenandoahVerifier*        verifier();
567 
568 // ---------- VM subsystem bindings
569 //
570 private:
571   ShenandoahMonitoringSupport* _monitoring_support;
572   MemoryPool*                  _memory_pool;
573   MemoryPool*                  _young_gen_memory_pool;
574   MemoryPool*                  _old_gen_memory_pool;
575 
576   GCMemoryManager              _stw_memory_manager;
577   GCMemoryManager              _cycle_memory_manager;
578   ConcurrentGCTimer*           _gc_timer;
579   SoftRefPolicy                _soft_ref_policy;
580 
581   // For exporting to SA
582   int                          _log_min_obj_alignment_in_bytes;
583 public:
584   ShenandoahMonitoringSupport* monitoring_support() const    { return _monitoring_support;    }
585   GCMemoryManager* cycle_memory_manager()                    { return &_cycle_memory_manager; }
586   GCMemoryManager* stw_memory_manager()                      { return &_stw_memory_manager;   }
587   SoftRefPolicy* soft_ref_policy()                  override { return &_soft_ref_policy;      }
588 
589   GrowableArray<GCMemoryManager*> memory_managers() override;
590   GrowableArray<MemoryPool*> memory_pools() override;
591   MemoryUsage memory_usage() override;
592   GCTracer* tracer();
593   ConcurrentGCTimer* gc_timer() const;
594 
595 // ---------- Class Unloading
596 //
597 private:
598   ShenandoahSharedFlag  _is_aging_cycle;
599   ShenandoahSharedFlag _unload_classes;
600   ShenandoahUnload     _unloader;
601 
602 public:
603   void set_unload_classes(bool uc);
604   bool unload_classes() const;
605 
606   // Perform STW class unloading and weak root cleaning
607   void parallel_cleaning(bool full_gc);
608 
609 private:
610   void stw_unload_classes(bool full_gc);
611   void stw_process_weak_roots(bool full_gc);
612   void stw_weak_refs(bool full_gc);
613 
614   inline void assert_lock_for_affiliation(ShenandoahRegionAffiliation orig_affiliation,
615                                           ShenandoahRegionAffiliation new_affiliation);
616 
617   // Heap iteration support
618   void scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops);
619   bool prepare_aux_bitmap_for_iteration();
620   void reclaim_aux_bitmap_for_iteration();
621 
622 // ---------- Generic interface hooks
623 // Minor things that super-interface expects us to implement to play nice with
624 // the rest of runtime. Some of the things here are not required to be implemented,
625 // and can be stubbed out.
626 //
627 public:
628   bool is_maximal_no_gc() const override shenandoah_not_implemented_return(false);
629 
630   inline bool is_in(const void* p) const override;
631 
632   inline bool is_in_active_generation(oop obj) const;
633   inline bool is_in_young(const void* p) const;
634   inline bool is_in_old(const void* p) const;
635   inline bool is_old(oop pobj) const;
636 
637   inline ShenandoahRegionAffiliation region_affiliation(const ShenandoahHeapRegion* r);
638   inline void set_affiliation(ShenandoahHeapRegion* r, ShenandoahRegionAffiliation new_affiliation);
639 
640   inline ShenandoahRegionAffiliation region_affiliation(size_t index);
641   inline void set_affiliation(size_t index, ShenandoahRegionAffiliation new_affiliation);
642 
643   bool requires_barriers(stackChunkOop obj) const override;
644 
645   MemRegion reserved_region() const { return _reserved; }
646   bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
647 
648   void collect(GCCause::Cause cause) override;
649   void do_full_collection(bool clear_all_soft_refs) override;
650 
651   // Used for parsing heap during error printing
652   HeapWord* block_start(const void* addr) const;
653   bool block_is_obj(const HeapWord* addr) const;
654   bool print_location(outputStream* st, void* addr) const override;
655 
656   // Used for native heap walkers: heap dumpers, mostly
657   void object_iterate(ObjectClosure* cl) override;
658   // Parallel heap iteration support
659   ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
660 
661   // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
662   void keep_alive(oop obj) override;
663 
664 // ---------- Safepoint interface hooks
665 //
666 public:
667   void safepoint_synchronize_begin() override;
668   void safepoint_synchronize_end() override;
669 
670 // ---------- Code roots handling hooks
671 //
672 public:
673   void register_nmethod(nmethod* nm) override;
674   void unregister_nmethod(nmethod* nm) override;
675   void verify_nmethod(nmethod* nm) override {}
676 
677 // ---------- Pinning hooks
678 //
679 public:
680   // Shenandoah supports per-object (per-region) pinning
681   void pin_object(JavaThread* thread, oop obj) override;
682   void unpin_object(JavaThread* thread, oop obj) override;
683 
684   void sync_pinned_region_status();
685   void assert_pinned_region_status() NOT_DEBUG_RETURN;
686 
687 // ---------- Concurrent Stack Processing support
688 //
689 public:
690   bool uses_stack_watermark_barrier() const override { return true; }
691 
692 // ---------- Allocation support
693 //
694 private:
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, bool 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   void set_young_lab_region_flags();
727 
728 // ---------- Marking support
729 //
730 private:
731   ShenandoahMarkingContext* _marking_context;
732   MemRegion  _bitmap_region;
733   MemRegion  _aux_bitmap_region;
734   MarkBitMap _verification_bit_map;
735   MarkBitMap _aux_bit_map;
736 
737   size_t _bitmap_size;
738   size_t _bitmap_regions_per_slice;
739   size_t _bitmap_bytes_per_slice;
740 
741   size_t _pretouch_heap_page_size;
742   size_t _pretouch_bitmap_page_size;
743 
744   bool _bitmap_region_special;
745   bool _aux_bitmap_region_special;
746 
747   ShenandoahLiveData** _liveness_cache;
748 
749 public:
750   inline ShenandoahMarkingContext* complete_marking_context() const;
751   inline ShenandoahMarkingContext* marking_context() const;
752 
753   template<class T>
754   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
755 
756   template<class T>
757   inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
758 
759   template<class T>
760   inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
761 
762   // SATB barriers hooks
763   inline bool requires_marking(const void* entry) const;
764 
765   // Support for bitmap uncommits
766   bool commit_bitmap_slice(ShenandoahHeapRegion *r);
767   bool uncommit_bitmap_slice(ShenandoahHeapRegion *r);
768   bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
769 
770   // Liveness caching support
771   ShenandoahLiveData* get_liveness_cache(uint worker_id);
772   void flush_liveness_cache(uint worker_id);
773 
774   size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
775 
776 // ---------- Evacuation support
777 //
778 private:
779   ShenandoahCollectionSet* _collection_set;
780   ShenandoahEvacOOMHandler _oom_evac_handler;
781   ShenandoahSharedFlag _old_gen_oom_evac;
782 
783   inline oop try_evacuate_object(oop src, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahRegionAffiliation target_gen);
784   void handle_old_evacuation(HeapWord* obj, size_t words, bool promotion);
785   void handle_old_evacuation_failure();
786 
787 public:
788   void handle_promotion_failure();
789   void report_promotion_failure(Thread* thread, size_t size);
790 
791   static address in_cset_fast_test_addr();
792 
793   ShenandoahCollectionSet* collection_set() const { return _collection_set; }
794 
795   // Checks if object is in the collection set.
796   inline bool in_collection_set(oop obj) const;
797 
798   // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
799   inline bool in_collection_set_loc(void* loc) const;
800 
801   // Evacuates or promotes object src. Returns the evacuated object, either evacuated
802   // by this thread, or by some other thread.
803   inline oop evacuate_object(oop src, Thread* thread);
804 
805   // Call before/after evacuation.
806   inline void enter_evacuation(Thread* t);
807   inline void leave_evacuation(Thread* t);
808 
809   inline bool clear_old_evacuation_failure();
810 
811 // ---------- Generational support
812 //
813 private:
814   RememberedScanner* _card_scan;
815 
816 public:
817   inline RememberedScanner* card_scan() { return _card_scan; }
818   void clear_cards_for(ShenandoahHeapRegion* region);
819   void dirty_cards(HeapWord* start, HeapWord* end);
820   void clear_cards(HeapWord* start, HeapWord* end);
821   void mark_card_as_dirty(void* location);
822   void retire_plab(PLAB* plab);
823   void retire_plab(PLAB* plab, Thread* thread);
824   void cancel_old_gc();
825   bool is_old_gc_active();
826   void coalesce_and_fill_old_regions();
827   bool adjust_generation_sizes();
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   static inline uint get_object_age(oop obj);
854 
855   void transfer_old_pointers_from_satb();
856 
857   void log_heap_status(const char *msg) const;
858 
859 private:
860   void trash_cset_regions();
861 
862 // ---------- Testing helpers functions
863 //
864 private:
865   ShenandoahSharedFlag _inject_alloc_failure;
866 
867   void try_inject_alloc_failure();
868   bool should_inject_alloc_failure();
869 };
870 
871 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP