1 /*
2 * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
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23 */
24
25 #ifndef SHARE_GC_SHARED_COLLECTEDHEAP_HPP
26 #define SHARE_GC_SHARED_COLLECTEDHEAP_HPP
27
28 #include "gc/shared/gcCause.hpp"
29 #include "gc/shared/gcWhen.hpp"
30 #include "gc/shared/softRefPolicy.hpp"
31 #include "gc/shared/verifyOption.hpp"
32 #include "memory/allocation.hpp"
33 #include "memory/metaspace.hpp"
34 #include "memory/universe.hpp"
35 #include "oops/stackChunkOop.hpp"
36 #include "runtime/handles.hpp"
37 #include "runtime/perfDataTypes.hpp"
38 #include "runtime/safepoint.hpp"
39 #include "services/memoryUsage.hpp"
40 #include "utilities/debug.hpp"
41 #include "utilities/formatBuffer.hpp"
42 #include "utilities/growableArray.hpp"
43
44 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
45 // is an abstract class: there may be many different kinds of heaps. This
46 // class defines the functions that a heap must implement, and contains
47 // infrastructure common to all heaps.
48
49 class WorkerTask;
50 class AdaptiveSizePolicy;
51 class BarrierSet;
52 class GCHeapLog;
53 class GCHeapSummary;
54 class GCTimer;
55 class GCTracer;
56 class GCMemoryManager;
57 class MemoryPool;
58 class MetaspaceSummary;
59 class ReservedHeapSpace;
60 class Thread;
61 class ThreadClosure;
62 class VirtualSpaceSummary;
63 class WorkerThreads;
64 class nmethod;
65
66 class ParallelObjectIteratorImpl : public CHeapObj<mtGC> {
67 public:
68 virtual ~ParallelObjectIteratorImpl() {}
69 virtual void object_iterate(ObjectClosure* cl, uint worker_id) = 0;
70 };
71
72 // User facing parallel object iterator. This is a StackObj, which ensures that
73 // the _impl is allocated and deleted in the scope of this object. This ensures
74 // the life cycle of the implementation is as required by ThreadsListHandle,
75 // which is sometimes used by the root iterators.
76 class ParallelObjectIterator : public StackObj {
77 ParallelObjectIteratorImpl* _impl;
78
79 public:
80 ParallelObjectIterator(uint thread_num);
81 ~ParallelObjectIterator();
82 void object_iterate(ObjectClosure* cl, uint worker_id);
83 };
84
85 //
86 // CollectedHeap
87 // SerialHeap
88 // G1CollectedHeap
89 // ParallelScavengeHeap
90 // ShenandoahHeap
91 // ZCollectedHeap
92 //
93 class CollectedHeap : public CHeapObj<mtGC> {
94 friend class VMStructs;
95 friend class JVMCIVMStructs;
96 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
97 friend class DisableIsGCActiveMark; // Disable current IsGCActiveMark
98 friend class MemAllocator;
99 friend class ParallelObjectIterator;
100
101 private:
102 GCHeapLog* _gc_heap_log;
103
104 // Historic gc information
105 size_t _capacity_at_last_gc;
106 size_t _used_at_last_gc;
107
108 SoftRefPolicy _soft_ref_policy;
109
110 // First, set it to java_lang_Object.
111 // Then, set it to FillerObject after the FillerObject_klass loading is complete.
112 static Klass* _filler_object_klass;
113
114 protected:
115 // Not used by all GCs
116 MemRegion _reserved;
117
118 bool _is_gc_active;
119
120 // (Minimum) Alignment reserve for TLABs and PLABs.
121 static size_t _lab_alignment_reserve;
122 // Used for filler objects (static, but initialized in ctor).
123 static size_t _filler_array_max_size;
124
125 static size_t _stack_chunk_max_size; // 0 for no limit
126
127 // Last time the whole heap has been examined in support of RMI
128 // MaxObjectInspectionAge.
129 // This timestamp must be monotonically non-decreasing to avoid
130 // time-warp warnings.
131 jlong _last_whole_heap_examined_time_ns;
132
133 unsigned int _total_collections; // ... started
134 unsigned int _total_full_collections; // ... started
135 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
136 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
137
138 // Reason for current garbage collection. Should be set to
139 // a value reflecting no collection between collections.
140 GCCause::Cause _gc_cause;
141 GCCause::Cause _gc_lastcause;
142 PerfStringVariable* _perf_gc_cause;
143 PerfStringVariable* _perf_gc_lastcause;
144
145 // Constructor
146 CollectedHeap();
147
148 // Create a new tlab. All TLAB allocations must go through this.
149 // To allow more flexible TLAB allocations min_size specifies
150 // the minimum size needed, while requested_size is the requested
151 // size based on ergonomics. The actually allocated size will be
152 // returned in actual_size.
153 virtual HeapWord* allocate_new_tlab(size_t min_size,
154 size_t requested_size,
155 size_t* actual_size);
156
157 // Reinitialize tlabs before resuming mutators.
158 virtual void resize_all_tlabs();
159
160 // Raw memory allocation facilities
161 // The obj and array allocate methods are covers for these methods.
162 // mem_allocate() should never be
163 // called to allocate TLABs, only individual objects.
164 virtual HeapWord* mem_allocate(size_t size,
165 bool* gc_overhead_limit_was_exceeded) = 0;
166
167 // Filler object utilities.
168 static inline size_t filler_array_hdr_size();
169
170 static size_t filler_array_min_size();
171
172 protected:
173 static inline void zap_filler_array_with(HeapWord* start, size_t words, juint value);
174 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
175 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
176
177 // Fill with a single array; caller must ensure filler_array_min_size() <=
178 // words <= filler_array_max_size().
179 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
180
181 // Fill with a single object (either an int array or a java.lang.Object).
182 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
183
184 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
185
186 // Verification functions
187 debug_only(static void check_for_valid_allocation_state();)
188
189 public:
190 enum Name {
191 None,
192 Serial,
193 Parallel,
194 G1,
195 Epsilon,
196 Z,
197 Shenandoah
198 };
199
200 protected:
201 // Get a pointer to the derived heap object. Used to implement
202 // derived class heap() functions rather than being called directly.
203 template<typename T>
204 static T* named_heap(Name kind) {
205 CollectedHeap* heap = Universe::heap();
206 assert(heap != nullptr, "Uninitialized heap");
207 assert(kind == heap->kind(), "Heap kind %u should be %u",
208 static_cast<uint>(heap->kind()), static_cast<uint>(kind));
209 return static_cast<T*>(heap);
210 }
211
212 public:
213
214 static inline size_t filler_array_max_size() {
215 return _filler_array_max_size;
216 }
217
218 static inline size_t stack_chunk_max_size() {
219 return _stack_chunk_max_size;
220 }
221
222 static inline Klass* filler_object_klass() {
223 return _filler_object_klass;
224 }
225
226 static inline void set_filler_object_klass(Klass* k) {
227 _filler_object_klass = k;
228 }
229
230 virtual Name kind() const = 0;
231
232 virtual const char* name() const = 0;
233
234 /**
235 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
236 * and JNI_OK on success.
237 */
238 virtual jint initialize() = 0;
239
240 // In many heaps, there will be a need to perform some initialization activities
241 // after the Universe is fully formed, but before general heap allocation is allowed.
242 // This is the correct place to place such initialization methods.
243 virtual void post_initialize();
244
245 // Stop any onging concurrent work and prepare for exit.
246 virtual void stop() {}
247
248 // Stop and resume concurrent GC threads interfering with safepoint operations
249 virtual void safepoint_synchronize_begin() {}
250 virtual void safepoint_synchronize_end() {}
251
252 void initialize_reserved_region(const ReservedHeapSpace& rs);
253
254 virtual size_t capacity() const = 0;
255 virtual size_t used() const = 0;
256
257 // Returns unused capacity.
258 virtual size_t unused() const;
259
260 // Historic gc information
261 size_t free_at_last_gc() const { return _capacity_at_last_gc - _used_at_last_gc; }
262 size_t used_at_last_gc() const { return _used_at_last_gc; }
263 void update_capacity_and_used_at_gc();
264
265 // Return "true" if the part of the heap that allocates Java
266 // objects has reached the maximal committed limit that it can
267 // reach, without a garbage collection.
268 virtual bool is_maximal_no_gc() const = 0;
269
270 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
271 // memory that the vm could make available for storing 'normal' java objects.
272 // This is based on the reserved address space, but should not include space
273 // that the vm uses internally for bookkeeping or temporary storage
274 // (e.g., in the case of the young gen, one of the survivor
275 // spaces).
276 virtual size_t max_capacity() const = 0;
277
278 // Returns "TRUE" iff "p" points into the committed areas of the heap.
279 // This method can be expensive so avoid using it in performance critical
280 // code.
281 virtual bool is_in(const void* p) const = 0;
282
283 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == nullptr || is_in(p); })
284
285 void set_gc_cause(GCCause::Cause v);
286 GCCause::Cause gc_cause() { return _gc_cause; }
287
288 oop obj_allocate(Klass* klass, size_t size, TRAPS);
289 oop obj_buffer_allocate(Klass* klass, size_t size, TRAPS); // doesn't clear memory
290 virtual oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS);
291 oop class_allocate(Klass* klass, size_t size, TRAPS);
292
293 // Utilities for turning raw memory into filler objects.
294 //
295 // min_fill_size() is the smallest region that can be filled.
296 // fill_with_objects() can fill arbitrary-sized regions of the heap using
297 // multiple objects. fill_with_object() is for regions known to be smaller
298 // than the largest array of integers; it uses a single object to fill the
299 // region and has slightly less overhead.
300 static size_t min_fill_size() {
301 return size_t(align_object_size(oopDesc::header_size()));
302 }
303
304 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
305
306 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
307 static void fill_with_object(MemRegion region, bool zap = true) {
308 fill_with_object(region.start(), region.word_size(), zap);
309 }
310 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
311 fill_with_object(start, pointer_delta(end, start), zap);
312 }
313
314 virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
315 static constexpr size_t min_dummy_object_size() {
316 return oopDesc::header_size();
317 }
318
319 static size_t lab_alignment_reserve() {
320 assert(_lab_alignment_reserve != SIZE_MAX, "uninitialized");
321 return _lab_alignment_reserve;
322 }
323
324 // Some heaps may be in an unparseable state at certain times between
325 // collections. This may be necessary for efficient implementation of
326 // certain allocation-related activities. Calling this function before
327 // attempting to parse a heap ensures that the heap is in a parsable
328 // state (provided other concurrent activity does not introduce
329 // unparsability). It is normally expected, therefore, that this
330 // method is invoked with the world stopped.
331 // NOTE: if you override this method, make sure you call
332 // super::ensure_parsability so that the non-generational
333 // part of the work gets done. See implementation of
334 // CollectedHeap::ensure_parsability and, for instance,
335 // that of ParallelScavengeHeap::ensure_parsability().
336 // The argument "retire_tlabs" controls whether existing TLABs
337 // are merely filled or also retired, thus preventing further
338 // allocation from them and necessitating allocation of new TLABs.
339 virtual void ensure_parsability(bool retire_tlabs);
340
341 // The amount of space available for thread-local allocation buffers.
342 virtual size_t tlab_capacity(Thread *thr) const = 0;
343
344 // The amount of used space for thread-local allocation buffers for the given thread.
345 virtual size_t tlab_used(Thread *thr) const = 0;
346
347 virtual size_t max_tlab_size() const;
348
349 // An estimate of the maximum allocation that could be performed
350 // for thread-local allocation buffers without triggering any
351 // collection or expansion activity.
352 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
353 guarantee(false, "thread-local allocation buffers not supported");
354 return 0;
355 }
356
357 // If a GC uses a stack watermark barrier, the stack processing is lazy, concurrent,
358 // incremental and cooperative. In order for that to work well, mechanisms that stop
359 // another thread might want to ensure its roots are in a sane state.
360 virtual bool uses_stack_watermark_barrier() const { return false; }
361
362 // Perform a collection of the heap; intended for use in implementing
363 // "System.gc". This probably implies as full a collection as the
364 // "CollectedHeap" supports.
365 virtual void collect(GCCause::Cause cause) = 0;
366
367 // Perform a full collection
368 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
369
370 // This interface assumes that it's being called by the
371 // vm thread. It collects the heap assuming that the
372 // heap lock is already held and that we are executing in
373 // the context of the vm thread.
374 virtual void collect_as_vm_thread(GCCause::Cause cause);
375
376 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
377 size_t size,
378 Metaspace::MetadataType mdtype);
379
380 // Return true, if accesses to the object would require barriers.
381 // This is used by continuations to copy chunks of a thread stack into StackChunk object or out of a StackChunk
382 // object back into the thread stack. These chunks may contain references to objects. It is crucial that
383 // the GC does not attempt to traverse the object while we modify it, because its structure (oopmap) is changed
384 // when stack chunks are stored into it.
385 // StackChunk objects may be reused, the GC must not assume that a StackChunk object is always a freshly
386 // allocated object.
387 virtual bool requires_barriers(stackChunkOop obj) const = 0;
388
389 // Returns "true" iff there is a stop-world GC in progress. (I assume
390 // that it should answer "false" for the concurrent part of a concurrent
391 // collector -- dld).
392 bool is_gc_active() const { return _is_gc_active; }
393
394 // Total number of GC collections (started)
395 unsigned int total_collections() const { return _total_collections; }
396 unsigned int total_full_collections() const { return _total_full_collections;}
397
398 // Increment total number of GC collections (started)
399 void increment_total_collections(bool full = false) {
400 _total_collections++;
401 if (full) {
402 increment_total_full_collections();
403 }
404 }
405
406 void increment_total_full_collections() { _total_full_collections++; }
407
408 // Return the SoftRefPolicy for the heap;
409 SoftRefPolicy* soft_ref_policy() { return &_soft_ref_policy; }
410
411 virtual MemoryUsage memory_usage();
412 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
413 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
414
415 // Iterate over all objects, calling "cl.do_object" on each.
416 virtual void object_iterate(ObjectClosure* cl) = 0;
417
418 protected:
419 virtual ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) {
420 return nullptr;
421 }
422
423 public:
424 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
425 virtual void keep_alive(oop obj) {}
426
427 // Perform any cleanup actions necessary before allowing a verification.
428 virtual void prepare_for_verify() = 0;
429
430 // Returns the longest time (in ms) that has elapsed since the last
431 // time that the whole heap has been examined by a garbage collection.
432 jlong millis_since_last_whole_heap_examined();
433 // GC should call this when the next whole heap analysis has completed to
434 // satisfy above requirement.
435 void record_whole_heap_examined_timestamp();
436
437 private:
438 // Generate any dumps preceding or following a full gc
439 void full_gc_dump(GCTimer* timer, bool before);
440
441 virtual void initialize_serviceability() = 0;
442
443 public:
444 void pre_full_gc_dump(GCTimer* timer);
445 void post_full_gc_dump(GCTimer* timer);
446
447 virtual VirtualSpaceSummary create_heap_space_summary();
448 GCHeapSummary create_heap_summary();
449
450 MetaspaceSummary create_metaspace_summary();
451
452 // GCs are free to represent the bit representation for null differently in memory,
453 // which is typically not observable when using the Access API. However, if for
454 // some reason a context doesn't allow using the Access API, then this function
455 // explicitly checks if the given memory location contains a null value.
456 virtual bool contains_null(const oop* p) const;
457
458 // Print heap information on the given outputStream.
459 virtual void print_on(outputStream* st) const = 0;
460 // The default behavior is to call print_on() on tty.
461 virtual void print() const;
462
463 // Print more detailed heap information on the given
464 // outputStream. The default behavior is to call print_on(). It is
465 // up to each subclass to override it and add any additional output
466 // it needs.
467 virtual void print_extended_on(outputStream* st) const {
468 print_on(st);
469 }
470
471 virtual void print_on_error(outputStream* st) const;
472
473 // Used to print information about locations in the hs_err file.
474 virtual bool print_location(outputStream* st, void* addr) const = 0;
475
476 // Iterator for all GC threads (other than VM thread)
477 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
478
479 // Print any relevant tracing info that flags imply.
480 // Default implementation does nothing.
481 virtual void print_tracing_info() const = 0;
482
483 void print_heap_before_gc();
484 void print_heap_after_gc();
485
486 // Registering and unregistering an nmethod (compiled code) with the heap.
487 virtual void register_nmethod(nmethod* nm) = 0;
488 virtual void unregister_nmethod(nmethod* nm) = 0;
489 virtual void verify_nmethod(nmethod* nm) = 0;
490
491 void trace_heap_before_gc(const GCTracer* gc_tracer);
492 void trace_heap_after_gc(const GCTracer* gc_tracer);
493
494 // Heap verification
495 virtual void verify(VerifyOption option) = 0;
496
497 // Return true if concurrent gc control via WhiteBox is supported by
498 // this collector. The default implementation returns false.
499 virtual bool supports_concurrent_gc_breakpoints() const;
500
501 // Workers used in non-GC safepoints for parallel safepoint cleanup. If this
502 // method returns null, cleanup tasks are done serially in the VMThread. See
503 // `SafepointSynchronize::do_cleanup_tasks` for details.
504 // GCs using a GC worker thread pool inside GC safepoints may opt to share
505 // that pool with non-GC safepoints, avoiding creating extraneous threads.
506 // Such sharing is safe, because GC safepoints and non-GC safepoints never
507 // overlap. For example, `G1CollectedHeap::workers()` (for GC safepoints) and
508 // `G1CollectedHeap::safepoint_workers()` (for non-GC safepoints) return the
509 // same thread-pool.
510 virtual WorkerThreads* safepoint_workers() { return nullptr; }
511
512 // Support for object pinning. This is used by JNI Get*Critical()
513 // and Release*Critical() family of functions. The GC must guarantee
514 // that pinned objects never move and don't get reclaimed as garbage.
515 // These functions are potentially safepointing.
516 virtual void pin_object(JavaThread* thread, oop obj) = 0;
517 virtual void unpin_object(JavaThread* thread, oop obj) = 0;
518
519 // Support for loading objects from CDS archive into the heap
520 // (usually as a snapshot of the old generation).
521 virtual bool can_load_archived_objects() const { return false; }
522 virtual HeapWord* allocate_loaded_archive_space(size_t size) { return nullptr; }
523 virtual void complete_loaded_archive_space(MemRegion archive_space) { }
524
525 virtual bool is_oop(oop object) const;
526 // Non product verification and debugging.
527 #ifndef PRODUCT
528 // Support for PromotionFailureALot. Return true if it's time to cause a
529 // promotion failure. The no-argument version uses
530 // this->_promotion_failure_alot_count as the counter.
531 bool promotion_should_fail(volatile size_t* count);
532 bool promotion_should_fail();
533
534 // Reset the PromotionFailureALot counters. Should be called at the end of a
535 // GC in which promotion failure occurred.
536 void reset_promotion_should_fail(volatile size_t* count);
537 void reset_promotion_should_fail();
538 #endif // #ifndef PRODUCT
539 };
540
541 // Class to set and reset the GC cause for a CollectedHeap.
542
543 class GCCauseSetter : StackObj {
544 CollectedHeap* _heap;
545 GCCause::Cause _previous_cause;
546 public:
547 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
548 _heap = heap;
549 _previous_cause = _heap->gc_cause();
550 _heap->set_gc_cause(cause);
551 }
552
553 ~GCCauseSetter() {
554 _heap->set_gc_cause(_previous_cause);
555 }
556 };
557
558 #endif // SHARE_GC_SHARED_COLLECTEDHEAP_HPP