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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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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/shenandoahAllocRequest.hpp"
34 #include "gc/shenandoah/shenandoahAsserts.hpp"
35 #include "gc/shenandoah/shenandoahController.hpp"
36 #include "gc/shenandoah/shenandoahEvacOOMHandler.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 typedef ShenandoahLocker ShenandoahHeapLocker;
122 typedef Stack<oop, mtGC> ShenandoahScanObjectStack;
123
124 // Shenandoah GC is low-pause concurrent GC that uses a load reference barrier
125 // for concurent evacuation and a snapshot-at-the-beginning write barrier for
126 // concurrent marking. See ShenandoahControlThread for GC cycle structure.
127 //
128 class ShenandoahHeap : public CollectedHeap {
129 friend class ShenandoahAsserts;
130 friend class VMStructs;
131 friend class ShenandoahGCSession;
132 friend class ShenandoahGCStateResetter;
133 friend class ShenandoahParallelObjectIterator;
134 friend class ShenandoahSafepoint;
135
136 // Supported GC
137 friend class ShenandoahConcurrentGC;
138 friend class ShenandoahOldGC;
139 friend class ShenandoahDegenGC;
140 friend class ShenandoahFullGC;
141 friend class ShenandoahUnload;
142
143 // ---------- Locks that guard important data structures in Heap
144 //
145 private:
146 ShenandoahHeapLock _lock;
147
148 // This is set and cleared by only the VMThread
149 // at each STW pause (safepoint) to the value given to the VM operation.
150 // This allows the value to be always consistently
151 // seen by all mutators as well as all GC worker threads.
152 ShenandoahGeneration* _active_generation;
153
154 protected:
155 void print_tracing_info() const override;
156 void stop() override;
157
158 public:
159 ShenandoahHeapLock* lock() {
160 return &_lock;
161 }
162
163 ShenandoahGeneration* active_generation() const {
164 // value of _active_generation field, see above
165 return _active_generation;
166 }
167
168 // Update the _active_generation field: can only be called at a safepoint by the VMThread.
169 void set_active_generation(ShenandoahGeneration* generation);
170
171 ShenandoahHeuristics* heuristics();
172
173 // ---------- Initialization, termination, identification, printing routines
174 //
175 public:
176 static ShenandoahHeap* heap();
177
178 const char* name() const override { return "Shenandoah"; }
179 ShenandoahHeap::Name kind() const override { return CollectedHeap::Shenandoah; }
180
181 ShenandoahHeap(ShenandoahCollectorPolicy* policy);
182 jint initialize() override;
183 void post_initialize() override;
184 void initialize_mode();
185 virtual void initialize_heuristics();
186 virtual void post_initialize_heuristics();
187 virtual void print_init_logger() const;
188 void initialize_serviceability() override;
189
190 void print_heap_on(outputStream* st) const override;
191 void print_gc_on(outputStream* st) const override;
192 void print_heap_regions_on(outputStream* st) const;
193
194 // Flushes cycle timings to global timings and prints the phase timings for the last completed cycle.
195 void process_gc_stats() const;
196
197 void prepare_for_verify() override;
198 void verify(VerifyOption vo) override;
199
200 // WhiteBox testing support.
201 bool supports_concurrent_gc_breakpoints() const override {
202 return true;
203 }
204
205 // ---------- Heap counters and metrics
206 //
207 private:
208 size_t _initial_size;
209 size_t _minimum_size;
210
211 Atomic<size_t> _soft_max_size;
212 shenandoah_padding(0);
213 Atomic<size_t> _committed;
214 shenandoah_padding(1);
215
216 public:
217 void increase_committed(size_t bytes);
218 void decrease_committed(size_t bytes);
219
220 void reset_bytes_allocated_since_gc_start();
221
222 size_t min_capacity() const;
223 size_t max_capacity() const override;
224 size_t soft_max_capacity() const;
225 size_t initial_capacity() const;
226 size_t capacity() const override;
227 size_t used() const override;
228 size_t committed() const;
229
230 void set_soft_max_capacity(size_t v);
231
232 // ---------- Periodic Tasks
233 //
234 public:
235 // Notify heuristics and region state change logger that the state of the heap has changed
236 void notify_heap_changed();
237
238 // Force counters to update
239 void set_forced_counters_update(bool value);
240
241 // Update counters if forced flag is set
242 void handle_force_counters_update();
243
244 // ---------- Workers handling
245 //
246 private:
247 uint _max_workers;
248 ShenandoahWorkerThreads* _workers;
249 ShenandoahWorkerThreads* _safepoint_workers;
250
251 virtual void initialize_controller();
252
253 public:
254 uint max_workers();
255 void assert_gc_workers(uint nworker) NOT_DEBUG_RETURN;
256
257 WorkerThreads* workers() const;
258 WorkerThreads* safepoint_workers() override;
259
260 void gc_threads_do(ThreadClosure* tcl) const override;
261
262 // ---------- Heap regions handling machinery
263 //
264 private:
265 MemRegion _heap_region;
266 bool _heap_region_special;
267 size_t _num_regions;
268 ShenandoahHeapRegion** _regions;
269 uint8_t* _affiliations; // Holds array of enum ShenandoahAffiliation, including FREE status in non-generational mode
270
271 public:
272
273 inline HeapWord* base() const { return _heap_region.start(); }
274 inline HeapWord* end() const { return _heap_region.end(); }
275
276 inline size_t num_regions() const { return _num_regions; }
277 inline bool is_heap_region_special() { return _heap_region_special; }
278
279 inline ShenandoahHeapRegion* heap_region_containing(const void* addr) const;
280 inline size_t heap_region_index_containing(const void* addr) const;
281
282 inline ShenandoahHeapRegion* get_region(size_t region_idx) const;
283
284 void heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
285 void parallel_heap_region_iterate(ShenandoahHeapRegionClosure* blk) const;
286
287 inline ShenandoahMmuTracker* mmu_tracker() { return &_mmu_tracker; };
288
289 // ---------- GC state machinery
290 //
291 // GC state describes the important parts of collector state, that may be
292 // used to make barrier selection decisions in the native and generated code.
293 // Multiple bits can be set at once.
294 //
295 // Important invariant: when GC state is zero, the heap is stable, and no barriers
296 // are required.
297 //
298 public:
299 enum GCStateBitPos {
300 // Heap has forwarded objects: needs LRB barriers.
301 HAS_FORWARDED_BITPOS = 0,
302
303 // Heap is under marking: needs SATB barriers.
304 // For generational mode, it means either young or old marking, or both.
305 MARKING_BITPOS = 1,
306
307 // Heap is under evacuation: needs LRB barriers. (Set together with HAS_FORWARDED)
308 EVACUATION_BITPOS = 2,
309
310 // Heap is under updating: needs no additional barriers.
311 UPDATE_REFS_BITPOS = 3,
312
313 // Heap is under weak-reference/roots processing: needs weak-LRB barriers.
314 WEAK_ROOTS_BITPOS = 4,
315
316 // Young regions are under marking, need SATB barriers.
317 YOUNG_MARKING_BITPOS = 5,
318
319 // Old regions are under marking, need SATB barriers.
320 OLD_MARKING_BITPOS = 6
321 };
322
323 enum GCState {
324 STABLE = 0,
325 HAS_FORWARDED = 1 << HAS_FORWARDED_BITPOS,
326 MARKING = 1 << MARKING_BITPOS,
327 EVACUATION = 1 << EVACUATION_BITPOS,
328 UPDATE_REFS = 1 << UPDATE_REFS_BITPOS,
329 WEAK_ROOTS = 1 << WEAK_ROOTS_BITPOS,
330 YOUNG_MARKING = 1 << YOUNG_MARKING_BITPOS,
331 OLD_MARKING = 1 << OLD_MARKING_BITPOS
332 };
333
334 private:
335 bool _gc_state_changed;
336 ShenandoahSharedBitmap _gc_state;
337 ShenandoahSharedFlag _heap_changed;
338 ShenandoahSharedFlag _degenerated_gc_in_progress;
339 ShenandoahSharedFlag _full_gc_in_progress;
340 ShenandoahSharedFlag _full_gc_move_in_progress;
341 ShenandoahSharedFlag _concurrent_strong_root_in_progress;
342
343 Atomic<size_t> _gc_no_progress_count;
344
345 // This updates the singular, global gc state. This call must happen on a safepoint.
346 void set_gc_state_at_safepoint(uint mask, bool value);
347
348 // This also updates the global gc state, but does not need to be called on a safepoint.
349 // Critically, this method will _not_ flag that the global gc state has changed and threads
350 // will continue to use their thread local copy. This is expected to be used in conjunction
351 // with a handshake operation to propagate the new gc state.
352 void set_gc_state_concurrent(uint mask, bool value);
353
354 public:
355 // This returns the raw value of the singular, global gc state.
356 inline char gc_state() const;
357
358 // Compares the given state against either the global gc state, or the thread local state.
359 // The global gc state may change on a safepoint and is the correct value to use until
360 // the global gc state has been propagated to all threads (after which, this method will
361 // compare against the thread local state). The thread local gc state may also be changed
362 // by a handshake operation, in which case, this function continues using the updated thread
363 // local value.
364 inline bool is_gc_state(GCState state) const;
365
366 // This copies the global gc state into a thread local variable for all threads.
367 // The thread local gc state is primarily intended to support quick access at barriers.
368 // All threads are updated because in some cases the control thread or the vm thread may
369 // need to execute the load reference barrier.
370 void propagate_gc_state_to_all_threads();
371
372 // This is public to support assertions that the state hasn't been changed off of
373 // a safepoint and that any changes were propagated to threads after the safepoint.
374 bool has_gc_state_changed() const { return _gc_state_changed; }
375
376 // Returns true if allocations have occurred in new regions or if regions have been
377 // uncommitted since the previous calls. This call will reset the flag to false.
378 bool has_changed() {
379 return _heap_changed.try_unset();
380 }
381
382 void set_concurrent_young_mark_in_progress(bool in_progress);
383 void set_concurrent_old_mark_in_progress(bool in_progress);
384 void set_evacuation_in_progress(bool in_progress);
385 void set_update_refs_in_progress(bool in_progress);
386 void set_degenerated_gc_in_progress(bool in_progress);
387 void set_full_gc_in_progress(bool in_progress);
388 void set_full_gc_move_in_progress(bool in_progress);
389 void set_has_forwarded_objects(bool cond);
390 void set_concurrent_strong_root_in_progress(bool cond);
391 void set_concurrent_weak_root_in_progress(bool cond);
392
393 inline bool is_idle() const;
394 inline bool is_concurrent_mark_in_progress() const;
395 inline bool is_concurrent_young_mark_in_progress() const;
396 inline bool is_concurrent_old_mark_in_progress() const;
397 inline bool is_update_refs_in_progress() const;
398 inline bool is_evacuation_in_progress() const;
399 inline bool is_degenerated_gc_in_progress() const;
400 inline bool is_full_gc_in_progress() const;
401 inline bool is_full_gc_move_in_progress() const;
402 inline bool has_forwarded_objects() const;
403
404 inline bool is_stw_gc_in_progress() const;
405 inline bool is_concurrent_strong_root_in_progress() const;
406 inline bool is_concurrent_weak_root_in_progress() const;
407 bool is_prepare_for_old_mark_in_progress() const;
408
409 private:
410 void manage_satb_barrier(bool active);
411
412 // Records the time of the first successful cancellation request. This is used to measure
413 // the responsiveness of the heuristic when starting a cycle.
414 double _cancel_requested_time;
415
416 // Indicates the reason the current GC has been cancelled (GCCause::_no_gc means the gc is not cancelled).
417 ShenandoahSharedEnumFlag<GCCause::Cause> _cancelled_gc;
418
419 // Returns true if cancel request was successfully communicated.
420 // Returns false if some other thread already communicated cancel
421 // request. A true return value does not mean GC has been
422 // cancelled, only that the process of cancelling GC has begun.
423 bool try_cancel_gc(GCCause::Cause cause);
424
425 public:
426 // True if gc has been cancelled
427 inline bool cancelled_gc() const;
428
429 // Used by workers in the GC cycle to detect cancellation and honor STS requirements
430 inline bool check_cancelled_gc_and_yield(bool sts_active = true);
431
432 // This indicates the reason the last GC cycle was cancelled.
433 inline GCCause::Cause cancelled_cause() const;
434
435 // Clears the cancellation cause and resets the oom handler
436 inline void clear_cancelled_gc();
437
438 // Clears the cancellation cause iff the current cancellation reason equals the given
439 // expected cancellation cause. Does not reset the oom handler.
440 inline GCCause::Cause clear_cancellation(GCCause::Cause expected);
441
442 void cancel_concurrent_mark();
443
444 // Returns true if and only if this call caused a gc to be cancelled.
445 bool cancel_gc(GCCause::Cause cause);
446
447 // Returns true if the soft maximum heap has been changed using management APIs.
448 bool check_soft_max_changed();
449
450 protected:
451 // This is shared between shConcurrentGC and shDegenerateGC so that degenerated
452 // GC can resume update refs from where the concurrent GC was cancelled. It is
453 // also used in shGenerationalHeap, which uses a different closure for update refs.
454 ShenandoahRegionIterator _update_refs_iterator;
455
456 private:
457 inline void reset_cancellation_time();
458
459 // GC support
460 // Evacuation
461 virtual void evacuate_collection_set(ShenandoahGeneration* generation, bool concurrent);
462 // Concurrent root processing
463 void prepare_concurrent_roots();
464 void finish_concurrent_roots();
465 // Concurrent class unloading support
466 void do_class_unloading();
467 // Reference updating
468 void prepare_update_heap_references();
469
470 // Retires LABs used for evacuation
471 void concurrent_prepare_for_update_refs();
472
473 // Turn off weak roots flag, purge old satb buffers in generational mode
474 void concurrent_final_roots(HandshakeClosure* handshake_closure = nullptr);
475
476 virtual void update_heap_references(ShenandoahGeneration* generation, bool concurrent);
477 // Final update region states
478 void update_heap_region_states(bool concurrent);
479 virtual void final_update_refs_update_region_states();
480
481 void rendezvous_threads(const char* name);
482 void recycle_trash();
483 public:
484 // The following two functions rebuild the free set at the end of GC, in preparation for an idle phase.
485 void rebuild_free_set(bool concurrent);
486 void rebuild_free_set_within_phase();
487 void notify_gc_progress();
488 void notify_gc_no_progress();
489 size_t get_gc_no_progress_count() const;
490
491 // The uncommit thread targets soft max heap, notify this thread when that value has changed.
492 void notify_soft_max_changed();
493
494 // An explicit GC request may have freed regions, notify the uncommit thread.
495 void notify_explicit_gc_requested();
496
497 private:
498 ShenandoahGeneration* _global_generation;
499
500 protected:
501 // The control thread presides over concurrent collection cycles
502 ShenandoahController* _control_thread;
503
504 // The uncommit thread periodically attempts to uncommit regions that have been empty for longer than ShenandoahUncommitDelay
505 ShenandoahUncommitThread* _uncommit_thread;
506
507 ShenandoahYoungGeneration* _young_generation;
508 ShenandoahOldGeneration* _old_generation;
509
510 private:
511 ShenandoahCollectorPolicy* _shenandoah_policy;
512 ShenandoahMode* _gc_mode;
513 ShenandoahFreeSet* _free_set;
514 ShenandoahPacer* _pacer;
515 ShenandoahVerifier* _verifier;
516
517 ShenandoahPhaseTimings* _phase_timings;
518 ShenandoahMmuTracker _mmu_tracker;
519
520 public:
521 ShenandoahController* control_thread() const { return _control_thread; }
522
523 ShenandoahGeneration* global_generation() const { return _global_generation; }
524 ShenandoahYoungGeneration* young_generation() const {
525 assert(mode()->is_generational(), "Young generation requires generational mode");
526 return _young_generation;
527 }
528
529 ShenandoahOldGeneration* old_generation() const {
530 assert(ShenandoahCardBarrier, "Card mark barrier should be on");
531 return _old_generation;
532 }
533
534 ShenandoahGeneration* generation_for(ShenandoahAffiliation affiliation) const;
535
536 ShenandoahCollectorPolicy* shenandoah_policy() const { return _shenandoah_policy; }
537 ShenandoahMode* mode() const { return _gc_mode; }
538 ShenandoahFreeSet* free_set() const { return _free_set; }
539 ShenandoahPacer* pacer() const { return _pacer; }
540
541 ShenandoahPhaseTimings* phase_timings() const { return _phase_timings; }
542
543 ShenandoahEvacOOMHandler* oom_evac_handler() { return &_oom_evac_handler; }
544
545 ShenandoahEvacuationTracker* evac_tracker() const {
546 return _evac_tracker;
547 }
548
549 void on_cycle_start(GCCause::Cause cause, ShenandoahGeneration* generation);
550 void on_cycle_end(ShenandoahGeneration* generation);
551
552 ShenandoahVerifier* verifier();
553
554 // ---------- VM subsystem bindings
555 //
556 private:
557 ShenandoahMonitoringSupport* _monitoring_support;
558 MemoryPool* _memory_pool;
559 GCMemoryManager _stw_memory_manager;
560 GCMemoryManager _cycle_memory_manager;
561 ConcurrentGCTimer* _gc_timer;
562 // For exporting to SA
563 int _log_min_obj_alignment_in_bytes;
564 public:
565 ShenandoahMonitoringSupport* monitoring_support() const { return _monitoring_support; }
566 GCMemoryManager* cycle_memory_manager() { return &_cycle_memory_manager; }
567 GCMemoryManager* stw_memory_manager() { return &_stw_memory_manager; }
568
569 GrowableArray<GCMemoryManager*> memory_managers() override;
570 GrowableArray<MemoryPool*> memory_pools() override;
571 MemoryUsage memory_usage() override;
572 GCTracer* tracer();
573 ConcurrentGCTimer* gc_timer() const;
574
575 // ---------- Class Unloading
576 //
577 private:
578 ShenandoahSharedFlag _unload_classes;
579 ShenandoahUnload _unloader;
580
581 public:
582 void set_unload_classes(bool uc);
583 bool unload_classes() const;
584
585 // Perform STW class unloading and weak root cleaning
586 void parallel_cleaning(ShenandoahGeneration* generation, bool full_gc);
587
588 private:
589 void stw_unload_classes(bool full_gc);
590 void stw_process_weak_roots(bool full_gc);
591 void stw_weak_refs(ShenandoahGeneration* generation, bool full_gc);
592
593 inline void assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
594 ShenandoahAffiliation new_affiliation);
595
596 // Heap iteration support
597 void scan_roots_for_iteration(ShenandoahScanObjectStack* oop_stack, ObjectIterateScanRootClosure* oops);
598 bool prepare_aux_bitmap_for_iteration();
599 void reclaim_aux_bitmap_for_iteration();
600
601 // ---------- Generic interface hooks
602 // Minor things that super-interface expects us to implement to play nice with
603 // the rest of runtime. Some of the things here are not required to be implemented,
604 // and can be stubbed out.
605 //
606 public:
607 // Check the pointer is in active part of Java heap.
608 // Use is_in_reserved to check if object is within heap bounds.
609 bool is_in(const void* p) const override;
610
611 // Returns true if the given oop belongs to a generation that is actively being collected.
612 inline bool is_in_active_generation(oop obj) const;
613 inline bool is_in_young(const void* p) const;
614 inline bool is_in_old(const void* p) const;
615
616 // Returns true iff the young generation is being collected and the given pointer
617 // is in the old generation. This is used to prevent the young collection from treating
618 // such an object as unreachable.
619 inline bool is_in_old_during_young_collection(oop obj) const;
620
621 inline ShenandoahAffiliation region_affiliation(const ShenandoahHeapRegion* r) const;
622 inline void set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation);
623
624 inline ShenandoahAffiliation region_affiliation(size_t index) const;
625
626 bool requires_barriers(stackChunkOop obj) const override;
627
628 MemRegion reserved_region() const { return _reserved; }
629 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
630
631 void collect_as_vm_thread(GCCause::Cause cause) override;
632 void collect(GCCause::Cause cause) override;
633 void do_full_collection(bool clear_all_soft_refs) override;
634
635 // Used for parsing heap during error printing
636 HeapWord* block_start(const void* addr) const;
637 bool block_is_obj(const HeapWord* addr) const;
638 bool print_location(outputStream* st, void* addr) const override;
639
640 // Used for native heap walkers: heap dumpers, mostly
641 void object_iterate(ObjectClosure* cl) override;
642 // Parallel heap iteration support
643 ParallelObjectIteratorImpl* parallel_object_iterator(uint workers) override;
644
645 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
646 void keep_alive(oop obj) override;
647
648 // ---------- Safepoint interface hooks
649 //
650 public:
651 void safepoint_synchronize_begin() override;
652 void safepoint_synchronize_end() override;
653
654 // ---------- Code roots handling hooks
655 //
656 public:
657 void register_nmethod(nmethod* nm) override;
658 void unregister_nmethod(nmethod* nm) override;
659 void verify_nmethod(nmethod* nm) override {}
660
661 // ---------- Pinning hooks
662 //
663 public:
664 // Shenandoah supports per-object (per-region) pinning
665 void pin_object(JavaThread* thread, oop obj) override;
666 void unpin_object(JavaThread* thread, oop obj) override;
667
668 void sync_pinned_region_status();
669 void assert_pinned_region_status() const NOT_DEBUG_RETURN;
670 void assert_pinned_region_status(ShenandoahGeneration* generation) const NOT_DEBUG_RETURN;
671
672 // ---------- CDS archive support
673
674 bool can_load_archived_objects() const override { return true; }
675 HeapWord* allocate_loaded_archive_space(size_t size) override;
676 void complete_loaded_archive_space(MemRegion archive_space) override;
677
678 // ---------- Allocation support
679 //
680 protected:
681 inline HeapWord* allocate_from_gclab(Thread* thread, size_t size);
682
683 private:
684 HeapWord* allocate_memory_under_lock(ShenandoahAllocRequest& request, bool& in_new_region);
685 HeapWord* allocate_from_gclab_slow(Thread* thread, size_t size);
686 HeapWord* allocate_new_gclab(size_t min_size, size_t word_size, size_t* actual_size);
687
688 // We want to retry an unsuccessful attempt at allocation until at least a full gc.
689 bool should_retry_allocation(size_t original_full_gc_count) const;
690
691 public:
692 HeapWord* allocate_memory(ShenandoahAllocRequest& request);
693 HeapWord* mem_allocate(size_t size) override;
694 MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
695 size_t size,
696 Metaspace::MetadataType mdtype) override;
697
698 HeapWord* allocate_new_tlab(size_t min_size, size_t requested_size, size_t* actual_size) override;
699 size_t tlab_capacity() const override;
700 size_t unsafe_max_tlab_alloc() const override;
701 size_t max_tlab_size() const override;
702 size_t tlab_used() const override;
703
704 void ensure_parsability(bool retire_labs) override;
705
706 void labs_make_parsable();
707 void tlabs_retire(bool resize);
708 void gclabs_retire(bool resize);
709
710 // ---------- Marking support
711 //
712 private:
713 ShenandoahMarkingContext* _marking_context;
714 MemRegion _bitmap_region;
715 MemRegion _aux_bitmap_region;
716 MarkBitMap _verification_bit_map;
717 MarkBitMap _aux_bit_map;
718
719 size_t _bitmap_size;
720 size_t _bitmap_regions_per_slice;
721 size_t _bitmap_bytes_per_slice;
722
723 size_t _pretouch_heap_page_size;
724 size_t _pretouch_bitmap_page_size;
725
726 bool _bitmap_region_special;
727 bool _aux_bitmap_region_special;
728
729 ShenandoahLiveData** _liveness_cache;
730
731 public:
732 // Return the marking context regardless of the completeness status.
733 inline ShenandoahMarkingContext* marking_context() const;
734
735 template<class T>
736 inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl);
737
738 template<class T>
739 inline void marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
740
741 template<class T>
742 inline void marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit);
743
744 // SATB barriers hooks
745 inline bool requires_marking(const void* entry) const;
746
747 // Support for bitmap uncommits
748 void commit_bitmap_slice(ShenandoahHeapRegion *r);
749 void uncommit_bitmap_slice(ShenandoahHeapRegion *r);
750 bool is_bitmap_region_special() { return _bitmap_region_special; }
751 bool is_bitmap_slice_committed(ShenandoahHeapRegion* r, bool skip_self = false);
752
753 // During concurrent reset, the control thread will zero out the mark bitmaps for committed regions.
754 // This cannot happen when the uncommit thread is simultaneously trying to uncommit regions and their bitmaps.
755 // To prevent these threads from working at the same time, we provide these methods for the control thread to
756 // prevent the uncommit thread from working while a collection cycle is in progress.
757
758 // Forbid uncommits (will stop and wait if regions are being uncommitted)
759 void forbid_uncommit();
760
761 // Allow the uncommit thread to process regions
762 void allow_uncommit();
763 #ifdef ASSERT
764 bool is_uncommit_in_progress();
765 #endif
766
767 // Liveness caching support
768 ShenandoahLiveData* get_liveness_cache(uint worker_id);
769 void flush_liveness_cache(uint worker_id);
770
771 size_t pretouch_heap_page_size() { return _pretouch_heap_page_size; }
772
773 // ---------- Evacuation support
774 //
775 private:
776 ShenandoahCollectionSet* _collection_set;
777 ShenandoahEvacOOMHandler _oom_evac_handler;
778
779 oop try_evacuate_object(oop src, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahAffiliation target_gen);
780
781 protected:
782 // Used primarily to look for failed evacuation attempts.
783 ShenandoahEvacuationTracker* _evac_tracker;
784
785 public:
786 static address in_cset_fast_test_addr();
787
788 ShenandoahCollectionSet* collection_set() const { return _collection_set; }
789
790 // Checks if object is in the collection set.
791 inline bool in_collection_set(oop obj) const;
792
793 // Checks if location is in the collection set. Can be interior pointer, not the oop itself.
794 inline bool in_collection_set_loc(void* loc) const;
795
796 // Evacuates or promotes object src. Returns the evacuated object, either evacuated
797 // by this thread, or by some other thread.
798 virtual oop evacuate_object(oop src, Thread* thread);
799
800 // Call before/after evacuation.
801 inline void enter_evacuation(Thread* t);
802 inline void leave_evacuation(Thread* t);
803
804 // ---------- Helper functions
805 //
806 public:
807 template <class T>
808 inline void conc_update_with_forwarded(T* p);
809
810 template <class T>
811 inline void non_conc_update_with_forwarded(T* p);
812
813 static inline void atomic_update_oop(oop update, oop* addr, oop compare);
814 static inline void atomic_update_oop(oop update, narrowOop* addr, oop compare);
815 static inline void atomic_update_oop(oop update, narrowOop* addr, narrowOop compare);
816
817 static inline bool atomic_update_oop_check(oop update, oop* addr, oop compare);
818 static inline bool atomic_update_oop_check(oop update, narrowOop* addr, oop compare);
819 static inline bool atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare);
820
821 static inline void atomic_clear_oop( oop* addr, oop compare);
822 static inline void atomic_clear_oop(narrowOop* addr, oop compare);
823 static inline void atomic_clear_oop(narrowOop* addr, narrowOop compare);
824
825 size_t trash_humongous_region_at(ShenandoahHeapRegion *r) const;
826
827 static inline void increase_object_age(oop obj, uint additional_age);
828
829 // Return the object's age, or a sentinel value when the age can't
830 // necessarily be determined because of concurrent locking by the
831 // mutator
832 static inline uint get_object_age(oop obj);
833
834 void log_heap_status(const char *msg) const;
835
836 private:
837 void trash_cset_regions();
838
839 // ---------- Testing helpers functions
840 //
841 private:
842 ShenandoahSharedFlag _inject_alloc_failure;
843
844 void try_inject_alloc_failure();
845 bool should_inject_alloc_failure();
846 };
847
848 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_HPP