1 /*
2 * Copyright (c) 2023, 2025, 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.
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11 * This code is distributed in the hope that it will be useful, but WITHOUT
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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 *
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26
27 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
28 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP
29
30 #include "gc/shared/collectedHeap.hpp"
31 #include "gc/shared/markBitMap.hpp"
32 #include "gc/shenandoah/mode/shenandoahMode.hpp"
33 #include "gc/shenandoah/shenandoahAllocRate.hpp"
34 #include "gc/shenandoah/shenandoahAllocRequest.hpp"
35 #include "gc/shenandoah/shenandoahAsserts.hpp"
36 #include "gc/shenandoah/shenandoahController.hpp"
37 #include "gc/shenandoah/shenandoahEvacTracker.hpp"
38 #include "gc/shenandoah/shenandoahGenerationType.hpp"
39 #include "gc/shenandoah/shenandoahLock.hpp"
40 #include "gc/shenandoah/shenandoahMmuTracker.hpp"
41 #include "gc/shenandoah/shenandoahPadding.hpp"
42 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
43 #include "gc/shenandoah/shenandoahUnload.hpp"
44 #include "memory/metaspace.hpp"
45 #include "services/memoryManager.hpp"
46 #include "utilities/globalDefinitions.hpp"
47 #include "utilities/stack.hpp"
48
49 class ConcurrentGCTimer;
50 class ObjectIterateScanRootClosure;
51 class ShenandoahCollectorPolicy;
52 class ShenandoahGCSession;
53 class ShenandoahGCStateResetter;
54 class ShenandoahGeneration;
55 class ShenandoahYoungGeneration;
56 class ShenandoahOldGeneration;
57 class ShenandoahHeuristics;
58 class ShenandoahMarkingContext;
59 class ShenandoahMode;
60 class ShenandoahPhaseTimings;
61 class ShenandoahHeap;
62 class ShenandoahHeapRegion;
63 class ShenandoahHeapRegionClosure;
64 class ShenandoahCollectionSet;
65 class ShenandoahFreeSet;
66 class ShenandoahConcurrentMark;
67 class ShenandoahFullGC;
68 class ShenandoahMonitoringSupport;
69 class ShenandoahPacer;
70 class ShenandoahReferenceProcessor;
71 class ShenandoahUncommitThread;
72 class ShenandoahVerifier;
73 class ShenandoahWorkerThreads;
74 class VMStructs;
75
76 // Used for buffering per-region liveness data.
77 // Needed since ShenandoahHeapRegion uses atomics to update liveness.
78 // The ShenandoahHeap array has max-workers elements, each of which is an array of
79 // uint16_t * max_regions. The choice of uint16_t is not accidental:
80 // there is a tradeoff between static/dynamic footprint that translates
81 // into cache pressure (which is already high during marking), and
82 // too many atomic updates. uint32_t is too large, uint8_t is too small.
83 typedef uint16_t ShenandoahLiveData;
84 #define SHENANDOAH_LIVEDATA_MAX ((ShenandoahLiveData)-1)
85
86 class ShenandoahRegionIterator : public StackObj {
87 private:
88 ShenandoahHeap* _heap;
89
90 shenandoah_padding(0);
91 Atomic<size_t> _index;
92 shenandoah_padding(1);
93
94 // No implicit copying: iterators should be passed by reference to capture the state
95 NONCOPYABLE(ShenandoahRegionIterator);
96
97 public:
98 ShenandoahRegionIterator();
99 ShenandoahRegionIterator(ShenandoahHeap* heap);
100
101 // Reset iterator to default state
102 void reset();
103
104 // Returns next region, or null if there are no more regions.
105 // This is multi-thread-safe.
106 inline ShenandoahHeapRegion* next();
107
108 // This is *not* MT safe. However, in the absence of multithreaded access, it
109 // can be used to determine if there is more work to do.
110 bool has_next() const;
111 };
112
113 class ShenandoahHeapRegionClosure : public StackObj {
114 public:
115 virtual void heap_region_do(ShenandoahHeapRegion* r) = 0;
116 virtual size_t parallel_region_stride() { return ShenandoahParallelRegionStride; }
117 virtual bool is_thread_safe() { return false; }
118 };
119
120 typedef ShenandoahLock ShenandoahHeapLock;
121 // ShenandoahHeapLocker implements locker to assure mutually exclusive access to the global heap data structures.
122 // Asserts in the implementation detect potential deadlock usage with regards the rebuild lock that is present
123 // in ShenandoahFreeSet. Whenever both locks are acquired, this lock should be acquired before the
124 // ShenandoahFreeSet rebuild lock.
125 class ShenandoahHeapLocker : public StackObj {
126 private:
127 ShenandoahHeapLock* _lock;
128 public:
129 ShenandoahHeapLocker(ShenandoahHeapLock* lock, bool allow_block_for_safepoint = false);
130
131 ~ShenandoahHeapLocker() {
132 _lock->unlock();
133 }
134 };
135
136 typedef Stack<oop, mtGC> ShenandoahScanObjectStack;
137
138 // Shenandoah GC is low-pause concurrent GC that uses a load reference barrier
139 // for concurent evacuation and a snapshot-at-the-beginning write barrier for
140 // concurrent marking. See ShenandoahControlThread for GC cycle structure.
141 //
142 class ShenandoahHeap : public CollectedHeap {
143 friend class ShenandoahAsserts;
144 friend class VMStructs;
145 friend class ShenandoahGCSession;
146 friend class ShenandoahGCStateResetter;
147 friend class ShenandoahParallelObjectIterator;
148 friend class ShenandoahSafepoint;
149
150 // Supported GC
151 friend class ShenandoahConcurrentGC;
152 friend class ShenandoahOldGC;
153 friend class ShenandoahDegenGC;
154 friend class ShenandoahFullGC;
155 friend class ShenandoahUnload;
156
157 // ---------- Locks that guard important data structures in Heap
158 //
159 private:
160 ShenandoahHeapLock _lock;
161
162 // This is set and cleared by only the VMThread
163 // at each STW pause (safepoint) to the value given to the VM operation.
164 // This allows the value to be always consistently
165 // seen by all mutators as well as all GC worker threads.
166 ShenandoahGeneration* _active_generation;
167
168 protected:
169 void print_tracing_info() const override;
170 void stop() override;
171
172 public:
173 ShenandoahHeapLock* lock() {
174 return &_lock;
175 }
176
177 ShenandoahGeneration* active_generation() const {
178 // value of _active_generation field, see above
179 return _active_generation;
180 }
181
182 // Update the _active_generation field: can only be called at a safepoint by the VMThread.
183 void set_active_generation(ShenandoahGeneration* generation);
184
185 ShenandoahHeuristics* heuristics();
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 virtual void initialize_generations();
199 void initialize_mode();
200 virtual void initialize_heuristics();
201 virtual void post_initialize_heuristics();
202 virtual void print_init_logger() const;
203 void initialize_serviceability() override;
204
205 void print_heap_on(outputStream* st) const override;
206 void print_gc_on(outputStream* st) const override;
207 void print_heap_regions_on(outputStream* st) const;
208
209 // Flushes cycle timings to global timings and prints the phase timings for the last completed cycle.
210 void process_gc_stats() const;
211
212 void prepare_for_verify() override;
213 void verify(VerifyOption vo) override;
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
226 Atomic<size_t> _soft_max_size;
227 shenandoah_padding(0);
228 Atomic<size_t> _committed;
229 shenandoah_padding(1);
230
231 ShenandoahAllocationRate _alloc_rate;
232 ShenandoahDecayAllocRate _alloc_rate_decay;
233
234 public:
235 void increase_committed(size_t bytes);
236 void decrease_committed(size_t bytes);
237
238 size_t min_capacity() const;
239 size_t max_capacity() const override;
240 size_t soft_max_capacity() const;
241 size_t initial_capacity() const;
242 size_t capacity() const override;
243 size_t used() const override;
244 size_t committed() const;
245
246 void set_soft_max_capacity(size_t v);
247
248 ShenandoahAllocationRate& alloc_rate() {
249 return _alloc_rate;
250 }
251
252 // ---------- Periodic Tasks
253 //
254 public:
255 // Notify heuristics and region state change logger that the state of the heap has changed
256 void notify_heap_changed();
257
258 // Force counters to update
259 void set_forced_counters_update(bool value);
260
261 // Update counters if forced flag is set
262 void handle_force_counters_update();
263
264 // ---------- Workers handling
265 //
266 private:
267 uint _max_workers;
268 ShenandoahWorkerThreads* _workers;
269 ShenandoahWorkerThreads* _safepoint_workers;
270
271 virtual void initialize_controller();
272
273 public:
274 uint max_workers();
275 void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
276
277 WorkerThreads* workers() const;
278 WorkerThreads* safepoint_workers() override;
279
280 void gc_threads_do(ThreadClosure* tcl) const override;
281
282 // ---------- Heap regions handling machinery
283 //
284 private:
285 MemRegion _heap_region;
286 bool _heap_region_special;
287 size_t _num_regions;
288 ShenandoahHeapRegion** _regions;
289 uint8_t* _affiliations; // Holds array of enum ShenandoahAffiliation, including FREE status in non-generational mode
290
291 public:
292
293 inline HeapWord* base() const { return _heap_region.start(); }
294 inline HeapWord* end() const { return _heap_region.end(); }
295
296 inline size_t num_regions() const { return _num_regions; }
297 inline bool is_heap_region_special() { return _heap_region_special; }
298
299 inline ShenandoahHeapRegion* heap_region_containing(const void* addr) const;
300 inline size_t heap_region_index_containing(const void* addr) const;
301
302 inline ShenandoahHeapRegion* get_region(size_t region_idx) const;
303
304 void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
305 void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
306 void heap_region_iterator(ShenandoahHeapRegionClosure* blk) const;
307
308 inline ShenandoahMmuTracker* mmu_tracker() { return &_mmu_tracker; };
309
310 // ---------- GC state machinery
311 //
312 // GC state describes the important parts of collector state, that may be
313 // used to make barrier selection decisions in the native and generated code.
314 // Multiple bits can be set at once.
315 //
316 // Important invariant: when GC state is zero, the heap is stable, and no barriers
317 // are required.
318 //
319 public:
320 enum GCStateBitPos {
321 // Heap has forwarded objects: needs LRB barriers.
322 HAS_FORWARDED_BITPOS = 0,
323
324 // Heap is under marking: needs SATB barriers.
325 // For generational mode, it means either young or old marking, or both.
326 MARKING_BITPOS = 1,
327
328 // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
329 EVACUATION_BITPOS = 2,
330
331 // Heap is under updating: needs no additional barriers.
332 UPDATE_REFS_BITPOS = 3,
333
334 // Heap is under weak-reference/roots processing: needs weak-LRB barriers.
335 WEAK_ROOTS_BITPOS = 4,
336
337 // Young regions are under marking, need SATB barriers.
338 YOUNG_MARKING_BITPOS = 5,
339
340 // Old regions are under marking, need SATB barriers.
341 OLD_MARKING_BITPOS = 6
342 };
343
344 enum GCState {
345 STABLE = 0,
346 HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
347 MARKING = 1 << MARKING_BITPOS,
348 EVACUATION = 1 << EVACUATION_BITPOS,
349 UPDATE_REFS = 1 << UPDATE_REFS_BITPOS,
350 WEAK_ROOTS = 1 << WEAK_ROOTS_BITPOS,
351 YOUNG_MARKING = 1 << YOUNG_MARKING_BITPOS,
352 OLD_MARKING = 1 << OLD_MARKING_BITPOS
353 };
354
355 private:
356 bool _gc_state_changed;
357 ShenandoahSharedBitmap _gc_state;
358 ShenandoahSharedFlag _heap_changed;
359 ShenandoahSharedFlag _degenerated_gc_in_progress;
360 ShenandoahSharedFlag _full_gc_in_progress;
361 ShenandoahSharedFlag _full_gc_move_in_progress;
362 ShenandoahSharedFlag _concurrent_strong_root_in_progress;
363
364 Atomic<size_t> _gc_no_progress_count;
365
366 // This updates the singular, global gc state. This call must happen on a safepoint.
367 void set_gc_state_at_safepoint(uint mask, bool value);
368
369 // This also updates the global gc state, but does not need to be called on a safepoint.
370 // Critically, this method will _not_ flag that the global gc state has changed and threads
371 // will continue to use their thread local copy. This is expected to be used in conjunction
372 // with a handshake operation to propagate the new gc state.
373 void set_gc_state_concurrent(uint mask, bool value);
374
375 public:
376 // This returns the raw value of the singular, global gc state.
377 inline char gc_state() const;
378
379 // Compares the given state against either the global gc state, or the thread local state.
380 // The global gc state may change on a safepoint and is the correct value to use until
381 // the global gc state has been propagated to all threads (after which, this method will
382 // compare against the thread local state). The thread local gc state may also be changed
383 // by a handshake operation, in which case, this function continues using the updated thread
384 // local value.
385 inline bool is_gc_state(GCState state) const;
386
387 // This copies the global gc state into a thread local variable for all threads.
388 // The thread local gc state is primarily intended to support quick access at barriers.
389 // All threads are updated because in some cases the control thread or the vm thread may
390 // need to execute the load reference barrier.
391 void propagate_gc_state_to_all_threads();
392
393 // This is public to support assertions that the state hasn't been changed off of
394 // a safepoint and that any changes were propagated to threads after the safepoint.
395 bool has_gc_state_changed() const { return _gc_state_changed; }
396
397 // Returns true if allocations have occurred in new regions or if regions have been
398 // uncommitted since the previous calls. This call will reset the flag to false.
399 bool has_changed() {
400 return _heap_changed.try_unset();
401 }
402
403 virtual void start_idle_span();
404
405 void set_concurrent_young_mark_in_progress(bool in_progress);
406 void set_concurrent_old_mark_in_progress(bool in_progress);
407 void set_evacuation_in_progress(bool in_progress);
408 void set_update_refs_in_progress(bool in_progress);
409 void set_degenerated_gc_in_progress(bool in_progress);
410 void set_full_gc_in_progress(bool in_progress);
411 void set_full_gc_move_in_progress(bool in_progress);
412 void set_has_forwarded_objects(bool cond);
413 void set_concurrent_strong_root_in_progress(bool cond);
414 void set_concurrent_weak_root_in_progress(bool cond);
415
416 inline bool is_idle() const;
417 inline bool is_concurrent_mark_in_progress() const;
418 inline bool is_concurrent_young_mark_in_progress() const;
419 inline bool is_concurrent_old_mark_in_progress() const;
420 inline bool is_update_refs_in_progress() const;
421 inline bool is_evacuation_in_progress() const;
422 inline bool is_degenerated_gc_in_progress() const;
423 inline bool is_full_gc_in_progress() const;
424 inline bool is_full_gc_move_in_progress() const;
425 inline bool has_forwarded_objects() const;
426
427 inline bool is_stw_gc_in_progress() const;
428 inline bool is_concurrent_strong_root_in_progress() const;
429 inline bool is_concurrent_weak_root_in_progress() const;
430 bool is_prepare_for_old_mark_in_progress() const;
431
432 private:
433 void manage_satb_barrier(bool active);
434
435 // Records the time of the first successful cancellation request. This is used to measure
436 // the responsiveness of the heuristic when starting a cycle.
437 double _cancel_requested_time;
438
439 // Indicates the reason the current GC has been cancelled (GCCause::_no_gc means the gc is not cancelled).
440 ShenandoahSharedEnumFlag<GCCause::Cause> _cancelled_gc;
441
442 // Returns true if cancel request was successfully communicated.
443 // Returns false if some other thread already communicated cancel
444 // request. A true return value does not mean GC has been
445 // cancelled, only that the process of cancelling GC has begun.
446 bool try_cancel_gc(GCCause::Cause cause);
447
448 public:
449 // True if gc has been cancelled
450 inline bool cancelled_gc() const;
451
452 // Used by workers in the GC cycle to detect cancellation and honor STS requirements
453 inline bool check_cancelled_gc_and_yield(bool sts_active = true);
454
455 // This indicates the reason the last GC cycle was cancelled.
456 inline GCCause::Cause cancelled_cause() const;
457
458 // Clears the cancellation cause and resets the oom handler
459 inline void clear_cancelled_gc();
460
461 // Clears the cancellation cause iff the current cancellation reason equals the given
462 // expected cancellation cause. Does not reset the oom handler.
463 inline GCCause::Cause clear_cancellation(GCCause::Cause expected);
464
465 void cancel_concurrent_mark();
466
467 // Returns true if and only if this call caused a gc to be cancelled.
468 bool cancel_gc(GCCause::Cause cause);
469
470 // Returns true if the soft maximum heap has been changed using management APIs.
471 bool check_soft_max_changed();
472
473 protected:
474 // This is shared between shConcurrentGC and shDegenerateGC so that degenerated
475 // GC can resume update refs from where the concurrent GC was cancelled. It is
476 // also used in shGenerationalHeap, which uses a different closure for update refs.
477 ShenandoahRegionIterator _update_refs_iterator;
478
479 private:
480 inline void reset_cancellation_time();
481
482 // GC support
483 // Evacuation
484 virtual void evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent);
485 // Concurrent root processing
486 void prepare_concurrent_roots();
487 void finish_concurrent_roots();
488 // Concurrent class unloading support
489 void do_class_unloading();
490 // Reference updating
491 void prepare_update_heap_references();
492
493 // Retires LABs used for evacuation
494 void concurrent_prepare_for_update_refs();
495
496 // Turn off weak roots flag, purge old satb buffers in generational mode
497 void concurrent_final_roots(HandshakeClosure* handshake_closure = nullptr);
498
499 virtual void update_heap_references(ShenandoahGeneration* generation, bool concurrent);
500 // Final update region states
501 void update_heap_region_states(bool concurrent);
502 virtual void final_update_refs_update_region_states();
503
504 void rendezvous_threads(const char* name);
505 void recycle_trash();
506 public:
507 // The following two functions rebuild the free set at the end of GC, in preparation for an idle phase.
508 void rebuild_free_set(bool concurrent);
509 void rebuild_free_set_within_phase();
510 void notify_gc_progress();
511 void notify_gc_no_progress();
512 size_t get_gc_no_progress_count() const;
513
514 // The uncommit thread targets soft max heap, notify this thread when that value has changed.
515 void notify_soft_max_changed();
516
517 // An explicit GC request may have freed regions, notify the uncommit thread.
518 void notify_explicit_gc_requested();
519
520 private:
521 ShenandoahGeneration* _global_generation;
522
523 protected:
524 // The control thread presides over concurrent collection cycles
525 ShenandoahController* _control_thread;
526
527 // The uncommit thread periodically attempts to uncommit regions that have been empty for longer than ShenandoahUncommitDelay
528 ShenandoahUncommitThread* _uncommit_thread;
529
530 ShenandoahYoungGeneration* _young_generation;
531 ShenandoahOldGeneration* _old_generation;
532
533 private:
534 ShenandoahCollectorPolicy* _shenandoah_policy;
535 ShenandoahMode* _gc_mode;
536 ShenandoahFreeSet* _free_set;
537 ShenandoahPacer* _pacer;
538 ShenandoahVerifier* _verifier;
539
540 ShenandoahPhaseTimings* _phase_timings;
541 ShenandoahMmuTracker _mmu_tracker;
542
543 public:
544 ShenandoahController* control_thread() const { return _control_thread; }
545
546 ShenandoahGeneration* global_generation() const { return _global_generation; }
547 ShenandoahYoungGeneration* young_generation() const {
548 assert(mode()->is_generational(), "Young generation requires generational mode");
549 return _young_generation;
550 }
551
552 ShenandoahOldGeneration* old_generation() const {
553 assert(ShenandoahCardBarrier, "Card mark barrier should be on");
554 return _old_generation;
555 }
556
557 ShenandoahGeneration* generation_for(ShenandoahAffiliation affiliation) const;
558
559 ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
560 ShenandoahMode* mode() const { return _gc_mode; }
561 ShenandoahFreeSet* free_set() const { return _free_set; }
562 ShenandoahPacer* pacer() const { return _pacer; }
563
564 ShenandoahPhaseTimings* phase_timings() const { return _phase_timings; }
565
566 ShenandoahEvacuationTracker* evac_tracker() const {
567 return _evac_tracker;
568 }
569
570 void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation, bool is_degenerated, bool is_out_of_cycle);
571 void on_cycle_end(ShenandoahGeneration* generation);
572
573 ShenandoahVerifier* verifier();
574
575 // ---------- VM subsystem bindings
576 //
577 private:
578 ShenandoahMonitoringSupport* _monitoring_support;
579 MemoryPool* _memory_pool;
580 GCMemoryManager _stw_memory_manager;
581 GCMemoryManager _cycle_memory_manager;
582 ConcurrentGCTimer* _gc_timer;
583 // For exporting to SA
584 int _log_min_obj_alignment_in_bytes;
585 public:
586 ShenandoahMonitoringSupport* monitoring_support() const { return _monitoring_support; }
587 GCMemoryManager* cycle_memory_manager() { return &_cycle_memory_manager; }
588 GCMemoryManager* stw_memory_manager() { return &_stw_memory_manager; }
589
590 GrowableArray<GCMemoryManager*> memory_managers() override;
591 GrowableArray<MemoryPool*> memory_pools() override;
592 MemoryUsage memory_usage() override;
593 GCTracer* tracer();
594 ConcurrentGCTimer* gc_timer() const;
595
596 // ---------- Class Unloading
597 //
598 private:
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(ShenandoahGeneration* generation, 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(ShenandoahGeneration* generation, bool full_gc);
613
614 inline void assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
615 ShenandoahAffiliation 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 // Check the pointer is in active part of Java heap.
629 // Use is_in_reserved to check if object is within heap bounds.
630 bool is_in(const void* p) const override;
631
632 // Returns true if the given oop belongs to a generation that is actively being collected.
633 inline bool is_in_active_generation(oop obj) const;
634 inline bool is_in_young(const void* p) const;
635 inline bool is_in_old(const void* p) const;
636
637 // Returns true iff the young generation is being collected and the given pointer
638 // is in the old generation. This is used to prevent the young collection from treating
639 // such an object as unreachable.
640 inline bool is_in_old_during_young_collection(oop obj) const;
641
642 inline ShenandoahAffiliation region_affiliation(const ShenandoahHeapRegion* r) const;
643 inline void set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation);
644
645 inline ShenandoahAffiliation region_affiliation(size_t index) const;
646
647 bool requires_barriers(stackChunkOop obj) const override;
648
649 MemRegion reserved_region() const { return _reserved; }
650 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
651
652 void collect_as_vm_thread(GCCause::Cause cause) override;
653 void collect(GCCause::Cause cause) override;
654 void do_full_collection(bool clear_all_soft_refs) override;
655
656 // Used for parsing heap during error printing
657 HeapWord* block_start(const void* addr) const;
658 bool block_is_obj(const HeapWord* addr) const;
659 bool print_location(outputStream* st, void* addr) const override;
660
661 // Used for native heap walkers: heap dumpers, mostly
662 void object_iterate(ObjectClosure* cl) override;
663 // Parallel heap iteration support
664 ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
665
666 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
667 void keep_alive(oop obj) override;
668
669 // ---------- Safepoint interface hooks
670 //
671 public:
672 void safepoint_synchronize_begin() override;
673 void safepoint_synchronize_end() override;
674
675 // ---------- Code roots handling hooks
676 //
677 public:
678 void register_nmethod(nmethod* nm) override;
679 void unregister_nmethod(nmethod* nm) override;
680 void verify_nmethod(nmethod* nm) override {}
681
682 // ---------- Pinning hooks
683 //
684 public:
685 // Shenandoah supports per-object (per-region) pinning
686 void pin_object(JavaThread* thread, oop obj) override;
687 void unpin_object(JavaThread* thread, oop obj) override;
688
689 void sync_pinned_region_status();
690 void assert_pinned_region_status() const NOT_DEBUG_RETURN;
691 void assert_pinned_region_status(ShenandoahGeneration* generation) const NOT_DEBUG_RETURN;
692
693 // ---------- CDS archive support
694
695 bool can_load_archived_objects() const override { return true; }
696 HeapWord* allocate_loaded_archive_space(size_t size) override;
697 void complete_loaded_archive_space(MemRegion archive_space) override;
698
699 // ---------- Allocation support
700 //
701 protected:
702 inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
703
704 private:
705 HeapWord* allocate_memory_under_lock(ShenandoahAllocRequest& request, bool& in_new_region);
706 HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
707 HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
708
709 // We want to retry an unsuccessful attempt at allocation until at least a full gc.
710 bool should_retry_allocation(size_t original_full_gc_count) const;
711
712 public:
713 HeapWord* allocate_memory(ShenandoahAllocRequest& request);
714 HeapWord* mem_allocate(size_t size) override;
715 oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) override;
716 MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
717 size_t size,
718 Metaspace::MetadataType mdtype) override;
719
720 HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override;
721 size_t tlab_capacity() const override;
722 size_t unsafe_max_tlab_alloc() const override;
723 size_t max_tlab_size() const override;
724 size_t tlab_used() const override;
725
726 void ensure_parsability(bool retire_labs) override;
727
728 void labs_make_parsable();
729 void tlabs_retire(bool resize);
730 void gclabs_retire(bool resize);
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 // Return the marking context regardless of the completeness status.
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 void commit_bitmap_slice(ShenandoahHeapRegion *r);
771 void uncommit_bitmap_slice(ShenandoahHeapRegion *r);
772 bool is_bitmap_region_special() { return _bitmap_region_special; }
773 bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
774
775 // During concurrent reset, the control thread will zero out the mark bitmaps for committed regions.
776 // This cannot happen when the uncommit thread is simultaneously trying to uncommit regions and their bitmaps.
777 // To prevent these threads from working at the same time, we provide these methods for the control thread to
778 // prevent the uncommit thread from working while a collection cycle is in progress.
779
780 // Forbid uncommits (will stop and wait if regions are being uncommitted)
781 void forbid_uncommit();
782
783 // Allow the uncommit thread to process regions
784 void allow_uncommit();
785 #ifdef ASSERT
786 bool is_uncommit_in_progress();
787 #endif
788
789 // Liveness caching support
790 ShenandoahLiveData* get_liveness_cache(uint worker_id);
791 void flush_liveness_cache(uint worker_id);
792
793 size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
794
795 // ---------- Evacuation support
796 //
797 private:
798 ShenandoahCollectionSet* _collection_set;
799
800 oop try_evacuate_object(oop src, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahAffiliation target_gen);
801
802 protected:
803 // Used primarily to look for failed evacuation attempts.
804 ShenandoahEvacuationTracker* _evac_tracker;
805
806 public:
807 static address in_cset_fast_test_addr();
808
809 ShenandoahCollectionSet* collection_set() const { return _collection_set; }
810
811 // Checks if object is in the collection set.
812 inline bool in_collection_set(oop obj) const;
813
814 // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
815 inline bool in_collection_set_loc(void* loc) const;
816
817 // Evacuates or promotes object src. Returns the evacuated object, either evacuated
818 // by this thread, or by some other thread. On allocation failure, installs the
819 // self-forwarded bit on src, flags src's region, and returns src.
820 virtual oop evacuate_object(oop src, Thread* thread);
821
822 // Parallel scan of flagged cset regions to clear self-forwarded bits on live
823 // objects. Must be called at a safepoint; intended for the degenerated and
824 // full GC entry paths.
825 void un_self_forward_cset_regions();
826
827 DEBUG_ONLY(void assert_no_self_forwards() const;)
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 non_conc_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) const;
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 log_heap_status(const char *msg) const;
860
861 private:
862 void trash_cset_regions();
863
864 // ---------- Testing helpers functions
865 //
866 private:
867 ShenandoahSharedFlag _inject_alloc_failure;
868
869 void try_inject_alloc_failure();
870 bool should_inject_alloc_failure();
871 };
872
873 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP