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.
10 *
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 *
17 * You should have received a copy of the GNU General Public License version
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25 */
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 ShenandoahAllocator;
52 class ShenandoahCollectorPolicy;
53 class ShenandoahGCSession;
54 class ShenandoahGCStateResetter;
55 class ShenandoahGeneration;
56 class ShenandoahYoungGeneration;
57 class ShenandoahOldGeneration;
58 class ShenandoahHeuristics;
59 class ShenandoahMarkingContext;
60 class ShenandoahMode;
61 class ShenandoahPhaseTimings;
62 class ShenandoahHeap;
63 class ShenandoahHeapRegion;
64 class ShenandoahHeapRegionClosure;
65 class ShenandoahCollectionSet;
66 class ShenandoahFreeSet;
67 class ShenandoahConcurrentMark;
68 class ShenandoahFullGC;
69 class ShenandoahMonitoringSupport;
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
497 void op_conc_roots();
498
499 void op_final_roots();
500
501 virtual void update_heap_references(ShenandoahGeneration* generation, bool concurrent);
502 // Final update region states
503 void update_heap_region_states(bool concurrent);
504 virtual void final_update_refs_update_region_states();
505
506 void rendezvous_threads(const char* name);
507 void recycle_trash();
508 public:
509 // The following two functions rebuild the free set at the end of GC, in preparation for an idle phase.
510 void rebuild_free_set(bool concurrent);
511 void rebuild_free_set_within_phase();
512 void notify_gc_progress();
513 void notify_gc_no_progress();
514 size_t get_gc_no_progress_count() const;
515
516 // The uncommit thread targets soft max heap, notify this thread when that value has changed.
517 void notify_soft_max_changed();
518
519 // An explicit GC request may have freed regions, notify the uncommit thread.
520 void notify_explicit_gc_requested();
521
522 private:
523 ShenandoahGeneration* _global_generation;
524
525 protected:
526 // The control thread presides over concurrent collection cycles
527 ShenandoahController* _control_thread;
528
529 // The uncommit thread periodically attempts to uncommit regions that have been empty for longer than ShenandoahUncommitDelay
530 ShenandoahUncommitThread* _uncommit_thread;
531
532 ShenandoahYoungGeneration* _young_generation;
533 ShenandoahOldGeneration* _old_generation;
534
535 private:
536 ShenandoahCollectorPolicy* _shenandoah_policy;
537 ShenandoahMode* _gc_mode;
538 ShenandoahFreeSet* _free_set;
539 ShenandoahAllocator* _allocator;
540 ShenandoahVerifier* _verifier;
541
542 ShenandoahPhaseTimings* _phase_timings;
543 ShenandoahMmuTracker _mmu_tracker;
544
545 public:
546 ShenandoahController* control_thread() const { return _control_thread; }
547
548 ShenandoahGeneration* global_generation() const { return _global_generation; }
549 ShenandoahYoungGeneration* young_generation() const {
550 assert(mode()->is_generational(), "Young generation requires generational mode");
551 return _young_generation;
552 }
553
554 ShenandoahOldGeneration* old_generation() const {
555 assert(ShenandoahCardBarrier, "Card mark barrier should be on");
556 return _old_generation;
557 }
558
559 ShenandoahGeneration* generation_for(ShenandoahAffiliation affiliation) const;
560
561 ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
562 ShenandoahMode* mode() const { return _gc_mode; }
563 ShenandoahFreeSet* free_set() const { return _free_set; }
564 ShenandoahAllocator* allocator() const { return _allocator; }
565
566 ShenandoahPhaseTimings* phase_timings() const { return _phase_timings; }
567
568 ShenandoahEvacuationTracker* evac_tracker() const {
569 return _evac_tracker;
570 }
571
572 void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation, bool is_degenerated, bool is_out_of_cycle);
573 void on_cycle_end(ShenandoahGeneration* generation);
574
575 ShenandoahVerifier* verifier();
576
577 // ---------- VM subsystem bindings
578 //
579 private:
580 ShenandoahMonitoringSupport* _monitoring_support;
581 MemoryPool* _memory_pool;
582 GCMemoryManager _stw_memory_manager;
583 GCMemoryManager _cycle_memory_manager;
584 ConcurrentGCTimer* _gc_timer;
585 // For exporting to SA
586 int _log_min_obj_alignment_in_bytes;
587 public:
588 ShenandoahMonitoringSupport* monitoring_support() const { return _monitoring_support; }
589 GCMemoryManager* cycle_memory_manager() { return &_cycle_memory_manager; }
590 GCMemoryManager* stw_memory_manager() { return &_stw_memory_manager; }
591
592 GrowableArray<GCMemoryManager*> memory_managers() override;
593 GrowableArray<MemoryPool*> memory_pools() override;
594 MemoryUsage memory_usage() override;
595 GCTracer* tracer();
596 ConcurrentGCTimer* gc_timer() const;
597
598 // ---------- Class Unloading
599 //
600 private:
601 ShenandoahSharedFlag _unload_classes;
602 ShenandoahUnload _unloader;
603
604 public:
605 void set_unload_classes(bool uc);
606 bool unload_classes() const;
607
608 // Perform STW class unloading and weak root cleaning
609 void parallel_cleaning(ShenandoahGeneration* generation, bool full_gc);
610
611 private:
612 void stw_unload_classes(bool full_gc);
613 void stw_process_weak_roots(bool full_gc);
614 void stw_weak_refs(ShenandoahGeneration* generation, bool full_gc);
615
616 inline void assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
617 ShenandoahAffiliation new_affiliation);
618
619 // Heap iteration support
620 void scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops);
621 bool prepare_aux_bitmap_for_iteration();
622 void reclaim_aux_bitmap_for_iteration();
623
624 // ---------- Generic interface hooks
625 // Minor things that super-interface expects us to implement to play nice with
626 // the rest of runtime. Some of the things here are not required to be implemented,
627 // and can be stubbed out.
628 //
629 public:
630 // Check the pointer is in active part of Java heap.
631 // Use is_in_reserved to check if object is within heap bounds.
632 bool is_in(const void* p) const override;
633
634 // Returns true if the given oop belongs to a generation that is actively being collected.
635 inline bool is_in_active_generation(oop obj) const;
636 inline bool is_in_young(const void* p) const;
637 inline bool is_in_old(const void* p) const;
638
639 // Returns true iff the young generation is being collected and the given pointer
640 // is in the old generation. This is used to prevent the young collection from treating
641 // such an object as unreachable.
642 inline bool is_in_old_during_young_collection(oop obj) const;
643
644 inline ShenandoahAffiliation region_affiliation(const ShenandoahHeapRegion* r) const;
645 inline void set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation);
646
647 inline ShenandoahAffiliation region_affiliation(size_t index) const;
648
649 bool requires_barriers(stackChunkOop obj) const override;
650
651 MemRegion reserved_region() const { return _reserved; }
652 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
653
654 void collect_as_vm_thread(GCCause::Cause cause) override;
655 void collect(GCCause::Cause cause) override;
656 void do_full_collection(bool clear_all_soft_refs) override;
657
658 // Used for parsing heap during error printing
659 HeapWord* block_start(const void* addr) const;
660 bool block_is_obj(const HeapWord* addr) const;
661 bool print_location(outputStream* st, void* addr) const override;
662
663 // Used for native heap walkers: heap dumpers, mostly
664 void object_iterate(ObjectClosure* cl) override;
665 // Parallel heap iteration support
666 ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
667
668 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
669 void keep_alive(oop obj) override;
670
671 // ---------- Safepoint interface hooks
672 //
673 public:
674 void safepoint_synchronize_begin() override;
675 void safepoint_synchronize_end() override;
676
677 // ---------- Code roots handling hooks
678 //
679 public:
680 void register_nmethod(nmethod* nm) override;
681 void unregister_nmethod(nmethod* nm) override;
682 void verify_nmethod(nmethod* nm) override {}
683
684 // ---------- Pinning hooks
685 //
686 public:
687 // Shenandoah supports per-object (per-region) pinning
688 void pin_object(JavaThread* thread, oop obj) override;
689 void unpin_object(JavaThread* thread, oop obj) override;
690
691 void sync_pinned_region_status();
692 void assert_pinned_region_status() const NOT_DEBUG_RETURN;
693 void assert_pinned_region_status(ShenandoahGeneration* generation) const NOT_DEBUG_RETURN;
694
695 // ---------- CDS archive support
696
697 bool can_load_archived_objects() const override { return true; }
698 HeapWord* allocate_loaded_archive_space(size_t size) override;
699 void complete_loaded_archive_space(MemRegion archive_space) override;
700
701 // ---------- Allocation support
702 //
703 protected:
704 inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
705
706 private:
707 HeapWord* allocate_memory_work(ShenandoahAllocRequest& request, bool& in_new_region);
708 HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
709 HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
710
711 // We want to retry an unsuccessful attempt at allocation until at least a full gc.
712 bool should_retry_allocation(size_t original_full_gc_count) const;
713
714 public:
715 HeapWord* allocate_memory(ShenandoahAllocRequest& request);
716 HeapWord* mem_allocate(size_t size) override;
717 oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS) override;
718 MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
719 size_t size,
720 Metaspace::MetadataType mdtype) override;
721
722 HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override;
723 size_t tlab_capacity() const override;
724 size_t unsafe_max_tlab_alloc() const override;
725 size_t max_tlab_size() const override;
726 size_t tlab_used() const override;
727
728 void ensure_parsability(bool retire_labs) override;
729
730 void labs_make_parsable();
731 void tlabs_retire(bool resize);
732 void gclabs_retire(bool resize);
733
734 // ---------- Marking support
735 //
736 private:
737 ShenandoahMarkingContext* _marking_context;
738 MemRegion _bitmap_region;
739 MemRegion _aux_bitmap_region;
740 MarkBitMap _verification_bit_map;
741 MarkBitMap _aux_bit_map;
742
743 size_t _bitmap_size;
744 size_t _bitmap_regions_per_slice;
745 size_t _bitmap_bytes_per_slice;
746
747 size_t _pretouch_heap_page_size;
748 size_t _pretouch_bitmap_page_size;
749
750 bool _bitmap_region_special;
751 bool _aux_bitmap_region_special;
752
753 ShenandoahLiveData** _liveness_cache;
754
755 public:
756 // Return the marking context regardless of the completeness status.
757 inline ShenandoahMarkingContext* marking_context() const;
758
759 template<class T>
760 inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
761
762 template<class T>
763 inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
764
765 template<class T>
766 inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
767
768 // SATB barriers hooks
769 inline bool requires_marking(const void* entry) const;
770
771 // Support for bitmap uncommits
772 void commit_bitmap_slice(ShenandoahHeapRegion *r);
773 void uncommit_bitmap_slice(ShenandoahHeapRegion *r);
774 bool is_bitmap_region_special() { return _bitmap_region_special; }
775 bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
776
777 // During concurrent reset, the control thread will zero out the mark bitmaps for committed regions.
778 // This cannot happen when the uncommit thread is simultaneously trying to uncommit regions and their bitmaps.
779 // To prevent these threads from working at the same time, we provide these methods for the control thread to
780 // prevent the uncommit thread from working while a collection cycle is in progress.
781
782 // Forbid uncommits (will stop and wait if regions are being uncommitted)
783 void forbid_uncommit();
784
785 // Allow the uncommit thread to process regions
786 void allow_uncommit();
787 #ifdef ASSERT
788 bool is_uncommit_in_progress();
789 #endif
790
791 // Liveness caching support
792 ShenandoahLiveData* get_liveness_cache(uint worker_id);
793 void flush_liveness_cache(uint worker_id);
794
795 size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
796
797 // ---------- Evacuation support
798 //
799 private:
800 ShenandoahCollectionSet* _collection_set;
801
802 oop try_evacuate_object(oop src, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahAffiliation target_gen);
803
804 protected:
805 // Used primarily to look for failed evacuation attempts.
806 ShenandoahEvacuationTracker* _evac_tracker;
807
808 public:
809 static address in_cset_fast_test_addr();
810
811 ShenandoahCollectionSet* collection_set() const { return _collection_set; }
812
813 // Checks if object is in the collection set.
814 inline bool in_collection_set(oop obj) const;
815
816 // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
817 inline bool in_collection_set_loc(void* loc) const;
818
819 // Evacuates or promotes object src. Returns the evacuated object, either evacuated
820 // by this thread, or by some other thread. On allocation failure, installs the
821 // self-forwarded bit on src, flags src's region, and returns src.
822 virtual oop evacuate_object(oop src, Thread* thread);
823
824 // Parallel scan of flagged cset regions to clear self-forwarded bits on live
825 // objects. Must be called at a safepoint; intended for the degenerated and
826 // full GC entry paths.
827 void un_self_forward_cset_regions();
828
829 DEBUG_ONLY(void assert_no_self_forwards() const;)
830
831 // ---------- Helper functions
832 //
833 public:
834 template <class T>
835 inline void conc_update_with_forwarded(T* p);
836
837 template <class T>
838 inline void non_conc_update_with_forwarded(T* p);
839
840 static inline void atomic_update_oop(oop update, oop* addr, oop compare);
841 static inline void atomic_update_oop(oop update, narrowOop* addr, oop compare);
842 static inline void atomic_update_oop(oop update, narrowOop* addr, narrowOop compare);
843
844 static inline bool atomic_update_oop_check(oop update, oop* addr, oop compare);
845 static inline bool atomic_update_oop_check(oop update, narrowOop* addr, oop compare);
846 static inline bool atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare);
847
848 static inline void atomic_clear_oop( oop* addr, oop compare);
849 static inline void atomic_clear_oop(narrowOop* addr, oop compare);
850 static inline void atomic_clear_oop(narrowOop* addr, narrowOop compare);
851
852 size_t trash_humongous_region_at(ShenandoahHeapRegion *r) const;
853
854 static inline void increase_object_age(oop obj, uint additional_age);
855
856 // Return the object's age, or a sentinel value when the age can't
857 // necessarily be determined because of concurrent locking by the
858 // mutator
859 static inline uint get_object_age(oop obj);
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 // Randomly pin a region when ShenandoahPinRegionRate > 0. Pin injection is only called after
875 // the cycle has populated _live_data and runs concurrently on the control thread. Releasing
876 // injected pins is done at the start of every cycle preventing stale pinned region states.
877 void try_inject_pin();
878 void release_injected_pins();
879
880 // Maximum number of regions that can be injected with pins.
881 static const uint MAX_INJECTED_PINS = 32;
882
883 // Tracker for injected pins added by try_inject_pin().
884 size_t _injected_pin_indices[MAX_INJECTED_PINS];
885 uint _injected_pin_count;
886 };
887
888 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP