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.
8 *
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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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16 * 2 along with this work; if not, write to the Free Software Foundation,
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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 GCHeapLog;
50 class GCHeapSummary;
51 class GCTimer;
52 class GCTracer;
53 class GCMemoryManager;
54 class MemoryPool;
55 class MetaspaceSummary;
56 class ReservedHeapSpace;
57 class Thread;
58 class ThreadClosure;
59 class VirtualSpaceSummary;
60 class WorkerThreads;
61 class nmethod;
62
63 class ParallelObjectIteratorImpl : public CHeapObj<mtGC> {
64 public:
65 virtual ~ParallelObjectIteratorImpl() {}
66 virtual void object_iterate(ObjectClosure* cl, uint worker_id) = 0;
67 };
68
69 // User facing parallel object iterator. This is a StackObj, which ensures that
70 // the _impl is allocated and deleted in the scope of this object. This ensures
71 // the life cycle of the implementation is as required by ThreadsListHandle,
72 // which is sometimes used by the root iterators.
73 class ParallelObjectIterator : public StackObj {
74 ParallelObjectIteratorImpl* _impl;
75
76 public:
77 ParallelObjectIterator(uint thread_num);
78 ~ParallelObjectIterator();
79 void object_iterate(ObjectClosure* cl, uint worker_id);
80 };
81
82 //
83 // CollectedHeap
84 // SerialHeap
85 // G1CollectedHeap
86 // ParallelScavengeHeap
87 // ShenandoahHeap
88 // ZCollectedHeap
89 //
90 class CollectedHeap : public CHeapObj<mtGC> {
91 friend class VMStructs;
92 friend class JVMCIVMStructs;
93 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
94 friend class DisableIsGCActiveMark; // Disable current IsGCActiveMark
95 friend class MemAllocator;
96 friend class ParallelObjectIterator;
97
98 private:
99 GCHeapLog* _gc_heap_log;
100
101 // Historic gc information
102 size_t _capacity_at_last_gc;
103 size_t _used_at_last_gc;
104
105 SoftRefPolicy _soft_ref_policy;
106
107 // First, set it to java_lang_Object.
108 // Then, set it to FillerObject after the FillerObject_klass loading is complete.
109 static Klass* _filler_object_klass;
110
111 protected:
112 // Not used by all GCs
113 MemRegion _reserved;
114
115 bool _is_gc_active;
116
117 // (Minimum) Alignment reserve for TLABs and PLABs.
118 static size_t _lab_alignment_reserve;
119 // Used for filler objects (static, but initialized in ctor).
120 static size_t _filler_array_max_size;
121
122 static size_t _stack_chunk_max_size; // 0 for no limit
123
124 // Last time the whole heap has been examined in support of RMI
125 // MaxObjectInspectionAge.
126 // This timestamp must be monotonically non-decreasing to avoid
127 // time-warp warnings.
128 jlong _last_whole_heap_examined_time_ns;
129
130 unsigned int _total_collections; // ... started
131 unsigned int _total_full_collections; // ... started
132 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
133 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
134
135 // Reason for current garbage collection. Should be set to
136 // a value reflecting no collection between collections.
137 GCCause::Cause _gc_cause;
138 GCCause::Cause _gc_lastcause;
139 PerfStringVariable* _perf_gc_cause;
140 PerfStringVariable* _perf_gc_lastcause;
141
142 // Constructor
143 CollectedHeap();
144
145 // Create a new tlab. All TLAB allocations must go through this.
146 // To allow more flexible TLAB allocations min_size specifies
147 // the minimum size needed, while requested_size is the requested
148 // size based on ergonomics. The actually allocated size will be
149 // returned in actual_size.
150 virtual HeapWord* allocate_new_tlab(size_t min_size,
151 size_t requested_size,
152 size_t* actual_size);
153
154 // Reinitialize tlabs before resuming mutators.
155 virtual void resize_all_tlabs();
156
157 // Raw memory allocation facilities
158 // The obj and array allocate methods are covers for these methods.
159 // mem_allocate() should never be
160 // called to allocate TLABs, only individual objects.
161 virtual HeapWord* mem_allocate(size_t size,
162 bool* gc_overhead_limit_was_exceeded) = 0;
163
164 // Filler object utilities.
165 static inline size_t filler_array_hdr_size();
166
167 static size_t filler_array_min_size();
168
169 protected:
170 static inline void zap_filler_array_with(HeapWord* start, size_t words, juint value);
171 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
172 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
173
174 // Fill with a single array; caller must ensure filler_array_min_size() <=
175 // words <= filler_array_max_size().
176 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
177
178 // Fill with a single object (either an int array or a java.lang.Object).
179 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
180
181 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
182
183 // Verification functions
184 debug_only(static void check_for_valid_allocation_state();)
185
186 public:
187 enum Name {
188 None,
189 Serial,
190 Parallel,
191 G1,
192 Epsilon,
193 Z,
194 Shenandoah
195 };
196
197 protected:
198 // Get a pointer to the derived heap object. Used to implement
199 // derived class heap() functions rather than being called directly.
200 template<typename T>
201 static T* named_heap(Name kind) {
202 CollectedHeap* heap = Universe::heap();
203 assert(heap != nullptr, "Uninitialized heap");
204 assert(kind == heap->kind(), "Heap kind %u should be %u",
205 static_cast<uint>(heap->kind()), static_cast<uint>(kind));
206 return static_cast<T*>(heap);
207 }
208
209 public:
210
211 static inline size_t filler_array_max_size() {
212 return _filler_array_max_size;
213 }
214
215 static inline size_t stack_chunk_max_size() {
216 return _stack_chunk_max_size;
217 }
218
219 static inline Klass* filler_object_klass() {
220 return _filler_object_klass;
221 }
222
223 static inline void set_filler_object_klass(Klass* k) {
224 _filler_object_klass = k;
225 }
226
227 virtual Name kind() const = 0;
228
229 virtual const char* name() const = 0;
230
231 /**
232 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
233 * and JNI_OK on success.
234 */
235 virtual jint initialize() = 0;
236
237 // In many heaps, there will be a need to perform some initialization activities
238 // after the Universe is fully formed, but before general heap allocation is allowed.
239 // This is the correct place to place such initialization methods.
240 virtual void post_initialize();
241
242 // Stop any onging concurrent work and prepare for exit.
243 virtual void stop() {}
244
245 // Stop and resume concurrent GC threads interfering with safepoint operations
246 virtual void safepoint_synchronize_begin() {}
247 virtual void safepoint_synchronize_end() {}
248
249 void initialize_reserved_region(const ReservedHeapSpace& rs);
250
251 virtual size_t capacity() const = 0;
252 virtual size_t used() const = 0;
253
254 // Returns unused capacity.
255 virtual size_t unused() const;
256
257 // Historic gc information
258 size_t free_at_last_gc() const { return _capacity_at_last_gc - _used_at_last_gc; }
259 size_t used_at_last_gc() const { return _used_at_last_gc; }
260 void update_capacity_and_used_at_gc();
261
262 // Return "true" if the part of the heap that allocates Java
263 // objects has reached the maximal committed limit that it can
264 // reach, without a garbage collection.
265 virtual bool is_maximal_no_gc() const = 0;
266
267 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
268 // memory that the vm could make available for storing 'normal' java objects.
269 // This is based on the reserved address space, but should not include space
270 // that the vm uses internally for bookkeeping or temporary storage
271 // (e.g., in the case of the young gen, one of the survivor
272 // spaces).
273 virtual size_t max_capacity() const = 0;
274
275 // Returns "TRUE" iff "p" points into the committed areas of the heap.
276 // This method can be expensive so avoid using it in performance critical
277 // code.
278 virtual bool is_in(const void* p) const = 0;
279
280 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == nullptr || is_in(p); })
281
282 void set_gc_cause(GCCause::Cause v);
283 GCCause::Cause gc_cause() { return _gc_cause; }
284
285 oop obj_allocate(Klass* klass, size_t size, TRAPS);
286 virtual oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS);
287 oop class_allocate(Klass* klass, size_t size, TRAPS);
288
289 // Utilities for turning raw memory into filler objects.
290 //
291 // min_fill_size() is the smallest region that can be filled.
292 // fill_with_objects() can fill arbitrary-sized regions of the heap using
293 // multiple objects. fill_with_object() is for regions known to be smaller
294 // than the largest array of integers; it uses a single object to fill the
295 // region and has slightly less overhead.
296 static size_t min_fill_size() {
297 return size_t(align_object_size(oopDesc::header_size()));
298 }
299
300 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
301
302 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
303 static void fill_with_object(MemRegion region, bool zap = true) {
304 fill_with_object(region.start(), region.word_size(), zap);
305 }
306 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
307 fill_with_object(start, pointer_delta(end, start), zap);
308 }
309
310 virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
311 static constexpr size_t min_dummy_object_size() {
312 return oopDesc::header_size();
313 }
314
315 static size_t lab_alignment_reserve() {
316 assert(_lab_alignment_reserve != SIZE_MAX, "uninitialized");
317 return _lab_alignment_reserve;
318 }
319
320 // Some heaps may be in an unparseable state at certain times between
321 // collections. This may be necessary for efficient implementation of
322 // certain allocation-related activities. Calling this function before
323 // attempting to parse a heap ensures that the heap is in a parsable
324 // state (provided other concurrent activity does not introduce
325 // unparsability). It is normally expected, therefore, that this
326 // method is invoked with the world stopped.
327 // NOTE: if you override this method, make sure you call
328 // super::ensure_parsability so that the non-generational
329 // part of the work gets done. See implementation of
330 // CollectedHeap::ensure_parsability and, for instance,
331 // that of ParallelScavengeHeap::ensure_parsability().
332 // The argument "retire_tlabs" controls whether existing TLABs
333 // are merely filled or also retired, thus preventing further
334 // allocation from them and necessitating allocation of new TLABs.
335 virtual void ensure_parsability(bool retire_tlabs);
336
337 // The amount of space available for thread-local allocation buffers.
338 virtual size_t tlab_capacity(Thread *thr) const = 0;
339
340 // The amount of used space for thread-local allocation buffers for the given thread.
341 virtual size_t tlab_used(Thread *thr) const = 0;
342
343 virtual size_t max_tlab_size() const;
344
345 // An estimate of the maximum allocation that could be performed
346 // for thread-local allocation buffers without triggering any
347 // collection or expansion activity.
348 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
349 guarantee(false, "thread-local allocation buffers not supported");
350 return 0;
351 }
352
353 // If a GC uses a stack watermark barrier, the stack processing is lazy, concurrent,
354 // incremental and cooperative. In order for that to work well, mechanisms that stop
355 // another thread might want to ensure its roots are in a sane state.
356 virtual bool uses_stack_watermark_barrier() const { return false; }
357
358 // Perform a collection of the heap; intended for use in implementing
359 // "System.gc". This probably implies as full a collection as the
360 // "CollectedHeap" supports.
361 virtual void collect(GCCause::Cause cause) = 0;
362
363 // Perform a full collection
364 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
365
366 // This interface assumes that it's being called by the
367 // vm thread. It collects the heap assuming that the
368 // heap lock is already held and that we are executing in
369 // the context of the vm thread.
370 virtual void collect_as_vm_thread(GCCause::Cause cause);
371
372 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
373 size_t size,
374 Metaspace::MetadataType mdtype);
375
376 // Return true, if accesses to the object would require barriers.
377 // This is used by continuations to copy chunks of a thread stack into StackChunk object or out of a StackChunk
378 // object back into the thread stack. These chunks may contain references to objects. It is crucial that
379 // the GC does not attempt to traverse the object while we modify it, because its structure (oopmap) is changed
380 // when stack chunks are stored into it.
381 // StackChunk objects may be reused, the GC must not assume that a StackChunk object is always a freshly
382 // allocated object.
383 virtual bool requires_barriers(stackChunkOop obj) const = 0;
384
385 // Returns "true" iff there is a stop-world GC in progress. (I assume
386 // that it should answer "false" for the concurrent part of a concurrent
387 // collector -- dld).
388 bool is_gc_active() const { return _is_gc_active; }
389
390 // Total number of GC collections (started)
391 unsigned int total_collections() const { return _total_collections; }
392 unsigned int total_full_collections() const { return _total_full_collections;}
393
394 // Increment total number of GC collections (started)
395 void increment_total_collections(bool full = false) {
396 _total_collections++;
397 if (full) {
398 increment_total_full_collections();
399 }
400 }
401
402 void increment_total_full_collections() { _total_full_collections++; }
403
404 // Return the SoftRefPolicy for the heap;
405 SoftRefPolicy* soft_ref_policy() { return &_soft_ref_policy; }
406
407 virtual MemoryUsage memory_usage();
408 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
409 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
410
411 // Iterate over all objects, calling "cl.do_object" on each.
412 virtual void object_iterate(ObjectClosure* cl) = 0;
413
414 protected:
415 virtual ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) {
416 return nullptr;
417 }
418
419 public:
420 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
421 virtual void keep_alive(oop obj) {}
422
423 // Perform any cleanup actions necessary before allowing a verification.
424 virtual void prepare_for_verify() = 0;
425
426 // Returns the longest time (in ms) that has elapsed since the last
427 // time that the whole heap has been examined by a garbage collection.
428 jlong millis_since_last_whole_heap_examined();
429 // GC should call this when the next whole heap analysis has completed to
430 // satisfy above requirement.
431 void record_whole_heap_examined_timestamp();
432
433 private:
434 // Generate any dumps preceding or following a full gc
435 void full_gc_dump(GCTimer* timer, bool before);
436
437 virtual void initialize_serviceability() = 0;
438
439 public:
440 void pre_full_gc_dump(GCTimer* timer);
441 void post_full_gc_dump(GCTimer* timer);
442
443 virtual VirtualSpaceSummary create_heap_space_summary();
444 GCHeapSummary create_heap_summary();
445
446 MetaspaceSummary create_metaspace_summary();
447
448 // GCs are free to represent the bit representation for null differently in memory,
449 // which is typically not observable when using the Access API. However, if for
450 // some reason a context doesn't allow using the Access API, then this function
451 // explicitly checks if the given memory location contains a null value.
452 virtual bool contains_null(const oop* p) const;
453
454 // Print heap information on the given outputStream.
455 virtual void print_on(outputStream* st) const = 0;
456 // The default behavior is to call print_on() on tty.
457 virtual void print() const;
458
459 // Print more detailed heap information on the given
460 // outputStream. The default behavior is to call print_on(). It is
461 // up to each subclass to override it and add any additional output
462 // it needs.
463 virtual void print_extended_on(outputStream* st) const {
464 print_on(st);
465 }
466
467 virtual void print_on_error(outputStream* st) const;
468
469 // Used to print information about locations in the hs_err file.
470 virtual bool print_location(outputStream* st, void* addr) const = 0;
471
472 // Iterator for all GC threads (other than VM thread)
473 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
474
475 // Print any relevant tracing info that flags imply.
476 // Default implementation does nothing.
477 virtual void print_tracing_info() const = 0;
478
479 void print_heap_before_gc();
480 void print_heap_after_gc();
481
482 // Registering and unregistering an nmethod (compiled code) with the heap.
483 virtual void register_nmethod(nmethod* nm) = 0;
484 virtual void unregister_nmethod(nmethod* nm) = 0;
485 virtual void verify_nmethod(nmethod* nm) = 0;
486
487 void trace_heap_before_gc(const GCTracer* gc_tracer);
488 void trace_heap_after_gc(const GCTracer* gc_tracer);
489
490 // Heap verification
491 virtual void verify(VerifyOption option) = 0;
492
493 // Return true if concurrent gc control via WhiteBox is supported by
494 // this collector. The default implementation returns false.
495 virtual bool supports_concurrent_gc_breakpoints() const;
496
497 // Workers used in non-GC safepoints for parallel safepoint cleanup. If this
498 // method returns null, cleanup tasks are done serially in the VMThread. See
499 // `SafepointSynchronize::do_cleanup_tasks` for details.
500 // GCs using a GC worker thread pool inside GC safepoints may opt to share
501 // that pool with non-GC safepoints, avoiding creating extraneous threads.
502 // Such sharing is safe, because GC safepoints and non-GC safepoints never
503 // overlap. For example, `G1CollectedHeap::workers()` (for GC safepoints) and
504 // `G1CollectedHeap::safepoint_workers()` (for non-GC safepoints) return the
505 // same thread-pool.
506 virtual WorkerThreads* safepoint_workers() { return nullptr; }
507
508 // Support for object pinning. This is used by JNI Get*Critical()
509 // and Release*Critical() family of functions. The GC must guarantee
510 // that pinned objects never move and don't get reclaimed as garbage.
511 // These functions are potentially safepointing.
512 virtual void pin_object(JavaThread* thread, oop obj) = 0;
513 virtual void unpin_object(JavaThread* thread, oop obj) = 0;
514
515 // Support for loading objects from CDS archive into the heap
516 // (usually as a snapshot of the old generation).
517 virtual bool can_load_archived_objects() const { return false; }
518 virtual HeapWord* allocate_loaded_archive_space(size_t size) { return nullptr; }
519 virtual void complete_loaded_archive_space(MemRegion archive_space) { }
520
521 virtual bool is_oop(oop object) const;
522 // Non product verification and debugging.
523 #ifndef PRODUCT
524 // Support for PromotionFailureALot. Return true if it's time to cause a
525 // promotion failure. The no-argument version uses
526 // this->_promotion_failure_alot_count as the counter.
527 bool promotion_should_fail(volatile size_t* count);
528 bool promotion_should_fail();
529
530 // Reset the PromotionFailureALot counters. Should be called at the end of a
531 // GC in which promotion failure occurred.
532 void reset_promotion_should_fail(volatile size_t* count);
533 void reset_promotion_should_fail();
534 #endif // #ifndef PRODUCT
535 };
536
537 // Class to set and reset the GC cause for a CollectedHeap.
538
539 class GCCauseSetter : StackObj {
540 CollectedHeap* _heap;
541 GCCause::Cause _previous_cause;
542 public:
543 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
544 _heap = heap;
545 _previous_cause = _heap->gc_cause();
546 _heap->set_gc_cause(cause);
547 }
548
549 ~GCCauseSetter() {
550 _heap->set_gc_cause(_previous_cause);
551 }
552 };
553
554 #endif // SHARE_GC_SHARED_COLLECTEDHEAP_HPP