1 /*
2 * Copyright (c) 2001, 2023, 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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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/verifyOption.hpp"
31 #include "memory/allocation.hpp"
32 #include "memory/metaspace.hpp"
33 #include "memory/universe.hpp"
34 #include "oops/stackChunkOop.hpp"
35 #include "runtime/handles.hpp"
36 #include "runtime/perfDataTypes.hpp"
37 #include "runtime/safepoint.hpp"
38 #include "services/memoryUsage.hpp"
39 #include "utilities/debug.hpp"
40 #include "utilities/formatBuffer.hpp"
41 #include "utilities/growableArray.hpp"
42
43 // A "CollectedHeap" is an implementation of a java heap for HotSpot. This
44 // is an abstract class: there may be many different kinds of heaps. This
45 // class defines the functions that a heap must implement, and contains
46 // infrastructure common to all heaps.
47
48 class WorkerTask;
49 class AdaptiveSizePolicy;
50 class BarrierSet;
51 class GCHeapLog;
52 class GCHeapSummary;
53 class GCTimer;
54 class GCTracer;
55 class GCMemoryManager;
56 class MemoryPool;
57 class MetaspaceSummary;
58 class ReservedHeapSpace;
59 class SoftRefPolicy;
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 // GenCollectedHeap
88 // SerialHeap
89 // G1CollectedHeap
90 // ParallelScavengeHeap
91 // ShenandoahHeap
92 // ZCollectedHeap
93 //
94 class CollectedHeap : public CHeapObj<mtGC> {
95 friend class VMStructs;
96 friend class JVMCIVMStructs;
97 friend class IsGCActiveMark; // Block structured external access to _is_gc_active
98 friend class DisableIsGCActiveMark; // Disable current IsGCActiveMark
99 friend class MemAllocator;
100 friend class ParallelObjectIterator;
101
102 private:
103 GCHeapLog* _gc_heap_log;
104
105 // Historic gc information
106 size_t _capacity_at_last_gc;
107 size_t _used_at_last_gc;
108
109 // First, set it to java_lang_Object.
110 // Then, set it to FillerObject after the FillerObject_klass loading is complete.
111 static Klass* _filler_object_klass;
112
113 protected:
114 // Not used by all GCs
115 MemRegion _reserved;
116
117 bool _is_gc_active;
118
119 // (Minimum) Alignment reserve for TLABs and PLABs.
120 static size_t _lab_alignment_reserve;
121 // Used for filler objects (static, but initialized in ctor).
122 static size_t _filler_array_max_size;
123
124 static size_t _stack_chunk_max_size; // 0 for no limit
125
126 // Last time the whole heap has been examined in support of RMI
127 // MaxObjectInspectionAge.
128 // This timestamp must be monotonically non-decreasing to avoid
129 // time-warp warnings.
130 jlong _last_whole_heap_examined_time_ns;
131
132 unsigned int _total_collections; // ... started
133 unsigned int _total_full_collections; // ... started
134 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
135 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
136
137 // Reason for current garbage collection. Should be set to
138 // a value reflecting no collection between collections.
139 GCCause::Cause _gc_cause;
140 GCCause::Cause _gc_lastcause;
141 PerfStringVariable* _perf_gc_cause;
142 PerfStringVariable* _perf_gc_lastcause;
143
144 // Constructor
145 CollectedHeap();
146
147 // Create a new tlab. All TLAB allocations must go through this.
148 // To allow more flexible TLAB allocations min_size specifies
149 // the minimum size needed, while requested_size is the requested
150 // size based on ergonomics. The actually allocated size will be
151 // returned in actual_size.
152 virtual HeapWord* allocate_new_tlab(size_t min_size,
153 size_t requested_size,
154 size_t* actual_size);
155
156 // Reinitialize tlabs before resuming mutators.
157 virtual void resize_all_tlabs();
158
159 // Raw memory allocation facilities
160 // The obj and array allocate methods are covers for these methods.
161 // mem_allocate() should never be
162 // called to allocate TLABs, only individual objects.
163 virtual HeapWord* mem_allocate(size_t size,
164 bool* gc_overhead_limit_was_exceeded) = 0;
165
166 // Filler object utilities.
167 static inline size_t filler_array_hdr_size();
168
169 static size_t filler_array_min_size();
170
171 protected:
172 static inline void zap_filler_array_with(HeapWord* start, size_t words, juint value);
173 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
174 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
175
176 // Fill with a single array; caller must ensure filler_array_min_size() <=
177 // words <= filler_array_max_size().
178 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
179
180 // Fill with a single object (either an int array or a java.lang.Object).
181 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
182
183 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
184
185 // Verification functions
186 debug_only(static void check_for_valid_allocation_state();)
187
188 public:
189 enum Name {
190 None,
191 Serial,
192 Parallel,
193 G1,
194 Epsilon,
195 Z,
196 Shenandoah
197 };
198
199 protected:
200 // Get a pointer to the derived heap object. Used to implement
201 // derived class heap() functions rather than being called directly.
202 template<typename T>
203 static T* named_heap(Name kind) {
204 CollectedHeap* heap = Universe::heap();
205 assert(heap != nullptr, "Uninitialized heap");
206 assert(kind == heap->kind(), "Heap kind %u should be %u",
207 static_cast<uint>(heap->kind()), static_cast<uint>(kind));
208 return static_cast<T*>(heap);
209 }
210
211 public:
212
213 static inline size_t filler_array_max_size() {
214 return _filler_array_max_size;
215 }
216
217 static inline size_t stack_chunk_max_size() {
218 return _stack_chunk_max_size;
219 }
220
221 static inline Klass* filler_object_klass() {
222 return _filler_object_klass;
223 }
224
225 static inline void set_filler_object_klass(Klass* k) {
226 _filler_object_klass = k;
227 }
228
229 virtual Name kind() const = 0;
230
231 virtual const char* name() const = 0;
232
233 /**
234 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
235 * and JNI_OK on success.
236 */
237 virtual jint initialize() = 0;
238
239 // In many heaps, there will be a need to perform some initialization activities
240 // after the Universe is fully formed, but before general heap allocation is allowed.
241 // This is the correct place to place such initialization methods.
242 virtual void post_initialize();
243
244 // Stop any onging concurrent work and prepare for exit.
245 virtual void stop() {}
246
247 // Stop and resume concurrent GC threads interfering with safepoint operations
248 virtual void safepoint_synchronize_begin() {}
249 virtual void safepoint_synchronize_end() {}
250
251 void initialize_reserved_region(const ReservedHeapSpace& rs);
252
253 virtual size_t capacity() const = 0;
254 virtual size_t used() const = 0;
255
256 // Returns unused capacity.
257 virtual size_t unused() const;
258
259 // Historic gc information
260 size_t free_at_last_gc() const { return _capacity_at_last_gc - _used_at_last_gc; }
261 size_t used_at_last_gc() const { return _used_at_last_gc; }
262 void update_capacity_and_used_at_gc();
263
264 // Return "true" if the part of the heap that allocates Java
265 // objects has reached the maximal committed limit that it can
266 // reach, without a garbage collection.
267 virtual bool is_maximal_no_gc() const = 0;
268
269 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
270 // memory that the vm could make available for storing 'normal' java objects.
271 // This is based on the reserved address space, but should not include space
272 // that the vm uses internally for bookkeeping or temporary storage
273 // (e.g., in the case of the young gen, one of the survivor
274 // spaces).
275 virtual size_t max_capacity() const = 0;
276
277 // Returns "TRUE" iff "p" points into the committed areas of the heap.
278 // This method can be expensive so avoid using it in performance critical
279 // code.
280 virtual bool is_in(const void* p) const = 0;
281
282 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == nullptr || is_in(p); })
283
284 void set_gc_cause(GCCause::Cause v);
285 GCCause::Cause gc_cause() { return _gc_cause; }
286
287 oop obj_allocate(Klass* klass, size_t size, TRAPS);
288 virtual oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS);
289 oop class_allocate(Klass* klass, size_t size, TRAPS);
290
291 // Utilities for turning raw memory into filler objects.
292 //
293 // min_fill_size() is the smallest region that can be filled.
294 // fill_with_objects() can fill arbitrary-sized regions of the heap using
295 // multiple objects. fill_with_object() is for regions known to be smaller
296 // than the largest array of integers; it uses a single object to fill the
297 // region and has slightly less overhead.
298 static size_t min_fill_size() {
299 return size_t(align_object_size(oopDesc::header_size()));
300 }
301
302 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
303
304 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
305 static void fill_with_object(MemRegion region, bool zap = true) {
306 fill_with_object(region.start(), region.word_size(), zap);
307 }
308 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
309 fill_with_object(start, pointer_delta(end, start), zap);
310 }
311
312 virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
313 static constexpr size_t min_dummy_object_size() {
314 return oopDesc::header_size();
315 }
316
317 static size_t lab_alignment_reserve() {
318 assert(_lab_alignment_reserve != SIZE_MAX, "uninitialized");
319 return _lab_alignment_reserve;
320 }
321
322 // Some heaps may be in an unparseable state at certain times between
323 // collections. This may be necessary for efficient implementation of
324 // certain allocation-related activities. Calling this function before
325 // attempting to parse a heap ensures that the heap is in a parsable
326 // state (provided other concurrent activity does not introduce
327 // unparsability). It is normally expected, therefore, that this
328 // method is invoked with the world stopped.
329 // NOTE: if you override this method, make sure you call
330 // super::ensure_parsability so that the non-generational
331 // part of the work gets done. See implementation of
332 // CollectedHeap::ensure_parsability and, for instance,
333 // that of ParallelScavengeHeap::ensure_parsability().
334 // The argument "retire_tlabs" controls whether existing TLABs
335 // are merely filled or also retired, thus preventing further
336 // allocation from them and necessitating allocation of new TLABs.
337 virtual void ensure_parsability(bool retire_tlabs);
338
339 // The amount of space available for thread-local allocation buffers.
340 virtual size_t tlab_capacity(Thread *thr) const = 0;
341
342 // The amount of used space for thread-local allocation buffers for the given thread.
343 virtual size_t tlab_used(Thread *thr) const = 0;
344
345 virtual size_t max_tlab_size() const;
346
347 // An estimate of the maximum allocation that could be performed
348 // for thread-local allocation buffers without triggering any
349 // collection or expansion activity.
350 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
351 guarantee(false, "thread-local allocation buffers not supported");
352 return 0;
353 }
354
355 // If a GC uses a stack watermark barrier, the stack processing is lazy, concurrent,
356 // incremental and cooperative. In order for that to work well, mechanisms that stop
357 // another thread might want to ensure its roots are in a sane state.
358 virtual bool uses_stack_watermark_barrier() const { return false; }
359
360 // Perform a collection of the heap; intended for use in implementing
361 // "System.gc". This probably implies as full a collection as the
362 // "CollectedHeap" supports.
363 virtual void collect(GCCause::Cause cause) = 0;
364
365 // Perform a full collection
366 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
367
368 // This interface assumes that it's being called by the
369 // vm thread. It collects the heap assuming that the
370 // heap lock is already held and that we are executing in
371 // the context of the vm thread.
372 virtual void collect_as_vm_thread(GCCause::Cause cause);
373
374 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
375 size_t size,
376 Metaspace::MetadataType mdtype);
377
378 // Return true, if accesses to the object would require barriers.
379 // This is used by continuations to copy chunks of a thread stack into StackChunk object or out of a StackChunk
380 // object back into the thread stack. These chunks may contain references to objects. It is crucial that
381 // the GC does not attempt to traverse the object while we modify it, because its structure (oopmap) is changed
382 // when stack chunks are stored into it.
383 // StackChunk objects may be reused, the GC must not assume that a StackChunk object is always a freshly
384 // allocated object.
385 virtual bool requires_barriers(stackChunkOop obj) const = 0;
386
387 // Returns "true" iff there is a stop-world GC in progress. (I assume
388 // that it should answer "false" for the concurrent part of a concurrent
389 // collector -- dld).
390 bool is_gc_active() const { return _is_gc_active; }
391
392 // Total number of GC collections (started)
393 unsigned int total_collections() const { return _total_collections; }
394 unsigned int total_full_collections() const { return _total_full_collections;}
395
396 // Increment total number of GC collections (started)
397 void increment_total_collections(bool full = false) {
398 _total_collections++;
399 if (full) {
400 increment_total_full_collections();
401 }
402 }
403
404 void increment_total_full_collections() { _total_full_collections++; }
405
406 // Return the SoftRefPolicy for the heap;
407 virtual SoftRefPolicy* soft_ref_policy() = 0;
408
409 virtual MemoryUsage memory_usage();
410 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
411 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
412
413 // Iterate over all objects, calling "cl.do_object" on each.
414 virtual void object_iterate(ObjectClosure* cl) = 0;
415
416 protected:
417 virtual ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) {
418 return nullptr;
419 }
420
421 public:
422 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
423 virtual void keep_alive(oop obj) {}
424
425 // Perform any cleanup actions necessary before allowing a verification.
426 virtual void prepare_for_verify() = 0;
427
428 // Returns the longest time (in ms) that has elapsed since the last
429 // time that the whole heap has been examined by a garbage collection.
430 jlong millis_since_last_whole_heap_examined();
431 // GC should call this when the next whole heap analysis has completed to
432 // satisfy above requirement.
433 void record_whole_heap_examined_timestamp();
434
435 private:
436 // Generate any dumps preceding or following a full gc
437 void full_gc_dump(GCTimer* timer, bool before);
438
439 virtual void initialize_serviceability() = 0;
440
441 public:
442 void pre_full_gc_dump(GCTimer* timer);
443 void post_full_gc_dump(GCTimer* timer);
444
445 virtual VirtualSpaceSummary create_heap_space_summary();
446 GCHeapSummary create_heap_summary();
447
448 MetaspaceSummary create_metaspace_summary();
449
450 // GCs are free to represent the bit representation for null differently in memory,
451 // which is typically not observable when using the Access API. However, if for
452 // some reason a context doesn't allow using the Access API, then this function
453 // explicitly checks if the given memory location contains a null value.
454 virtual bool contains_null(const oop* p) const;
455
456 // Print heap information on the given outputStream.
457 virtual void print_on(outputStream* st) const = 0;
458 // The default behavior is to call print_on() on tty.
459 virtual void print() const;
460
461 // Print more detailed heap information on the given
462 // outputStream. The default behavior is to call print_on(). It is
463 // up to each subclass to override it and add any additional output
464 // it needs.
465 virtual void print_extended_on(outputStream* st) const {
466 print_on(st);
467 }
468
469 virtual void print_on_error(outputStream* st) const;
470
471 // Used to print information about locations in the hs_err file.
472 virtual bool print_location(outputStream* st, void* addr) const = 0;
473
474 // Iterator for all GC threads (other than VM thread)
475 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
476
477 // Print any relevant tracing info that flags imply.
478 // Default implementation does nothing.
479 virtual void print_tracing_info() const = 0;
480
481 void print_heap_before_gc();
482 void print_heap_after_gc();
483
484 // Registering and unregistering an nmethod (compiled code) with the heap.
485 virtual void register_nmethod(nmethod* nm) = 0;
486 virtual void unregister_nmethod(nmethod* nm) = 0;
487 virtual void verify_nmethod(nmethod* nm) = 0;
488
489 void trace_heap_before_gc(const GCTracer* gc_tracer);
490 void trace_heap_after_gc(const GCTracer* gc_tracer);
491
492 // Heap verification
493 virtual void verify(VerifyOption option) = 0;
494
495 // Return true if concurrent gc control via WhiteBox is supported by
496 // this collector. The default implementation returns false.
497 virtual bool supports_concurrent_gc_breakpoints() const;
498
499 // Workers used in non-GC safepoints for parallel safepoint cleanup. If this
500 // method returns null, cleanup tasks are done serially in the VMThread. See
501 // `SafepointSynchronize::do_cleanup_tasks` for details.
502 // GCs using a GC worker thread pool inside GC safepoints may opt to share
503 // that pool with non-GC safepoints, avoiding creating extraneous threads.
504 // Such sharing is safe, because GC safepoints and non-GC safepoints never
505 // overlap. For example, `G1CollectedHeap::workers()` (for GC safepoints) and
506 // `G1CollectedHeap::safepoint_workers()` (for non-GC safepoints) return the
507 // same thread-pool.
508 virtual WorkerThreads* safepoint_workers() { return nullptr; }
509
510 // Support for object pinning. This is used by JNI Get*Critical()
511 // and Release*Critical() family of functions. The GC must guarantee
512 // that pinned objects never move and don't get reclaimed as garbage.
513 // These functions are potentially safepointing.
514 virtual void pin_object(JavaThread* thread, oop obj) = 0;
515 virtual void unpin_object(JavaThread* thread, oop obj) = 0;
516
517 // Support for loading objects from CDS archive into the heap
518 // (usually as a snapshot of the old generation).
519 virtual bool can_load_archived_objects() const { return false; }
520 virtual HeapWord* allocate_loaded_archive_space(size_t size) { return nullptr; }
521 virtual void complete_loaded_archive_space(MemRegion archive_space) { }
522
523 virtual bool is_oop(oop object) const;
524 // Non product verification and debugging.
525 #ifndef PRODUCT
526 // Support for PromotionFailureALot. Return true if it's time to cause a
527 // promotion failure. The no-argument version uses
528 // this->_promotion_failure_alot_count as the counter.
529 bool promotion_should_fail(volatile size_t* count);
530 bool promotion_should_fail();
531
532 // Reset the PromotionFailureALot counters. Should be called at the end of a
533 // GC in which promotion failure occurred.
534 void reset_promotion_should_fail(volatile size_t* count);
535 void reset_promotion_should_fail();
536 #endif // #ifndef PRODUCT
537 };
538
539 // Class to set and reset the GC cause for a CollectedHeap.
540
541 class GCCauseSetter : StackObj {
542 CollectedHeap* _heap;
543 GCCause::Cause _previous_cause;
544 public:
545 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
546 _heap = heap;
547 _previous_cause = _heap->gc_cause();
548 _heap->set_gc_cause(cause);
549 }
550
551 ~GCCauseSetter() {
552 _heap->set_gc_cause(_previous_cause);
553 }
554 };
555
556 #endif // SHARE_GC_SHARED_COLLECTEDHEAP_HPP