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 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
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 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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20 * or visit www.oracle.com if you need additional information or have any
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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 IsSTWGCActiveMark; // Block structured external access to _is_stw_gc_active
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 // First, set it to java_lang_Object.
109 // Then, set it to FillerObject after the FillerObject_klass loading is complete.
110 static Klass* _filler_object_klass;
111
112 protected:
113 // Not used by all GCs
114 MemRegion _reserved;
115
116 bool _is_stw_gc_active;
117
118 // (Minimum) Alignment reserve for TLABs and PLABs.
119 static size_t _lab_alignment_reserve;
120 // Used for filler objects (static, but initialized in ctor).
121 static size_t _filler_array_max_size;
122
123 static size_t _stack_chunk_max_size; // 0 for no limit
124
125 // Last time the whole heap has been examined in support of RMI
126 // MaxObjectInspectionAge.
127 // This timestamp must be monotonically non-decreasing to avoid
128 // time-warp warnings.
129 jlong _last_whole_heap_examined_time_ns;
130
131 unsigned int _total_collections; // ... started
132 unsigned int _total_full_collections; // ... started
133 NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
134 NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
135
136 // Reason for current garbage collection. Should be set to
137 // a value reflecting no collection between collections.
138 GCCause::Cause _gc_cause;
139 GCCause::Cause _gc_lastcause;
140 PerfStringVariable* _perf_gc_cause;
141 PerfStringVariable* _perf_gc_lastcause;
142
143 // Constructor
144 CollectedHeap();
145
146 // Create a new tlab. All TLAB allocations must go through this.
147 // To allow more flexible TLAB allocations min_size specifies
148 // the minimum size needed, while requested_size is the requested
149 // size based on ergonomics. The actually allocated size will be
150 // returned in actual_size.
151 virtual HeapWord* allocate_new_tlab(size_t min_size,
152 size_t requested_size,
153 size_t* actual_size);
154
155 // Reinitialize tlabs before resuming mutators.
156 virtual void resize_all_tlabs();
157
158 // Raw memory allocation facilities
159 // The obj and array allocate methods are covers for these methods.
160 // mem_allocate() should never be
161 // called to allocate TLABs, only individual objects.
162 virtual HeapWord* mem_allocate(size_t size,
163 bool* gc_overhead_limit_was_exceeded) = 0;
164
165 // Filler object utilities.
166 static inline size_t filler_array_hdr_size();
167 static inline size_t filler_array_min_size();
168
169 static inline void zap_filler_array_with(HeapWord* start, size_t words, juint value);
170 DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
171 DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
172
173 // Fill with a single array; caller must ensure filler_array_min_size() <=
174 // words <= filler_array_max_size().
175 static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
176
177 // Fill with a single object (either an int array or a java.lang.Object).
178 static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
179
180 virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
181
182 // Verification functions
183 debug_only(static void check_for_valid_allocation_state();)
184
185 public:
186 enum Name {
187 None,
188 Serial,
189 Parallel,
190 G1,
191 Epsilon,
192 Z,
193 Shenandoah
194 };
195
196 protected:
197 // Get a pointer to the derived heap object. Used to implement
198 // derived class heap() functions rather than being called directly.
199 template<typename T>
200 static T* named_heap(Name kind) {
201 CollectedHeap* heap = Universe::heap();
202 assert(heap != nullptr, "Uninitialized heap");
203 assert(kind == heap->kind(), "Heap kind %u should be %u",
204 static_cast<uint>(heap->kind()), static_cast<uint>(kind));
205 return static_cast<T*>(heap);
206 }
207
208 public:
209
210 static inline size_t filler_array_max_size() {
211 return _filler_array_max_size;
212 }
213
214 static inline size_t stack_chunk_max_size() {
215 return _stack_chunk_max_size;
216 }
217
218 static inline Klass* filler_object_klass() {
219 return _filler_object_klass;
220 }
221
222 static inline void set_filler_object_klass(Klass* k) {
223 _filler_object_klass = k;
224 }
225
226 virtual Name kind() const = 0;
227
228 virtual const char* name() const = 0;
229
230 /**
231 * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
232 * and JNI_OK on success.
233 */
234 virtual jint initialize() = 0;
235
236 // In many heaps, there will be a need to perform some initialization activities
237 // after the Universe is fully formed, but before general heap allocation is allowed.
238 // This is the correct place to place such initialization methods.
239 virtual void post_initialize();
240
241 // Stop any onging concurrent work and prepare for exit.
242 virtual void stop() {}
243
244 // Stop and resume concurrent GC threads interfering with safepoint operations
245 virtual void safepoint_synchronize_begin() {}
246 virtual void safepoint_synchronize_end() {}
247
248 void initialize_reserved_region(const ReservedHeapSpace& rs);
249
250 virtual size_t capacity() const = 0;
251 virtual size_t used() const = 0;
252
253 // Returns unused capacity.
254 virtual size_t unused() const;
255
256 // Historic gc information
257 size_t free_at_last_gc() const { return _capacity_at_last_gc - _used_at_last_gc; }
258 size_t used_at_last_gc() const { return _used_at_last_gc; }
259 void update_capacity_and_used_at_gc();
260
261 // Return "true" if the part of the heap that allocates Java
262 // objects has reached the maximal committed limit that it can
263 // reach, without a garbage collection.
264 virtual bool is_maximal_no_gc() const = 0;
265
266 // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
267 // memory that the vm could make available for storing 'normal' java objects.
268 // This is based on the reserved address space, but should not include space
269 // that the vm uses internally for bookkeeping or temporary storage
270 // (e.g., in the case of the young gen, one of the survivor
271 // spaces).
272 virtual size_t max_capacity() const = 0;
273
274 // Returns "TRUE" iff "p" points into the committed areas of the heap.
275 // This method can be expensive so avoid using it in performance critical
276 // code.
277 virtual bool is_in(const void* p) const = 0;
278
279 DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == nullptr || is_in(p); })
280
281 void set_gc_cause(GCCause::Cause v);
282 GCCause::Cause gc_cause() { return _gc_cause; }
283
284 oop obj_allocate(Klass* klass, size_t size, TRAPS);
285 virtual oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS);
286 oop class_allocate(Klass* klass, size_t size, TRAPS);
287
288 // Utilities for turning raw memory into filler objects.
289 //
290 // min_fill_size() is the smallest region that can be filled.
291 // fill_with_objects() can fill arbitrary-sized regions of the heap using
292 // multiple objects. fill_with_object() is for regions known to be smaller
293 // than the largest array of integers; it uses a single object to fill the
294 // region and has slightly less overhead.
295 static size_t min_fill_size() {
296 return size_t(align_object_size(oopDesc::header_size()));
297 }
298
299 static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
300
301 static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
302 static void fill_with_object(MemRegion region, bool zap = true) {
303 fill_with_object(region.start(), region.word_size(), zap);
304 }
305 static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
306 fill_with_object(start, pointer_delta(end, start), zap);
307 }
308
309 virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
310 static size_t min_dummy_object_size() {
311 return oopDesc::header_size();
312 }
313
314 static size_t lab_alignment_reserve() {
315 assert(_lab_alignment_reserve != SIZE_MAX, "uninitialized");
316 return _lab_alignment_reserve;
317 }
318
319 // Some heaps may be in an unparseable state at certain times between
320 // collections. This may be necessary for efficient implementation of
321 // certain allocation-related activities. Calling this function before
322 // attempting to parse a heap ensures that the heap is in a parsable
323 // state (provided other concurrent activity does not introduce
324 // unparsability). It is normally expected, therefore, that this
325 // method is invoked with the world stopped.
326 // NOTE: if you override this method, make sure you call
327 // super::ensure_parsability so that the non-generational
328 // part of the work gets done. See implementation of
329 // CollectedHeap::ensure_parsability and, for instance,
330 // that of GenCollectedHeap::ensure_parsability().
331 // The argument "retire_tlabs" controls whether existing TLABs
332 // are merely filled or also retired, thus preventing further
333 // allocation from them and necessitating allocation of new TLABs.
334 virtual void ensure_parsability(bool retire_tlabs);
335
336 // The amount of space available for thread-local allocation buffers.
337 virtual size_t tlab_capacity(Thread *thr) const = 0;
338
339 // The amount of used space for thread-local allocation buffers for the given thread.
340 virtual size_t tlab_used(Thread *thr) const = 0;
341
342 virtual size_t max_tlab_size() const;
343
344 // An estimate of the maximum allocation that could be performed
345 // for thread-local allocation buffers without triggering any
346 // collection or expansion activity.
347 virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
348 guarantee(false, "thread-local allocation buffers not supported");
349 return 0;
350 }
351
352 // If a GC uses a stack watermark barrier, the stack processing is lazy, concurrent,
353 // incremental and cooperative. In order for that to work well, mechanisms that stop
354 // another thread might want to ensure its roots are in a sane state.
355 virtual bool uses_stack_watermark_barrier() const { return false; }
356
357 // Perform a collection of the heap; intended for use in implementing
358 // "System.gc". This probably implies as full a collection as the
359 // "CollectedHeap" supports.
360 virtual void collect(GCCause::Cause cause) = 0;
361
362 // Perform a full collection
363 virtual void do_full_collection(bool clear_all_soft_refs) = 0;
364
365 // This interface assumes that it's being called by the
366 // vm thread. It collects the heap assuming that the
367 // heap lock is already held and that we are executing in
368 // the context of the vm thread.
369 virtual void collect_as_vm_thread(GCCause::Cause cause);
370
371 virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
372 size_t size,
373 Metaspace::MetadataType mdtype);
374
375 // Return true, if accesses to the object would require barriers.
376 // This is used by continuations to copy chunks of a thread stack into StackChunk object or out of a StackChunk
377 // object back into the thread stack. These chunks may contain references to objects. It is crucial that
378 // the GC does not attempt to traverse the object while we modify it, because its structure (oopmap) is changed
379 // when stack chunks are stored into it.
380 // StackChunk objects may be reused, the GC must not assume that a StackChunk object is always a freshly
381 // allocated object.
382 virtual bool requires_barriers(stackChunkOop obj) const = 0;
383
384 // Returns "true" iff there is a stop-world GC in progress.
385 bool is_stw_gc_active() const { return _is_stw_gc_active; }
386
387 // Total number of GC collections (started)
388 unsigned int total_collections() const { return _total_collections; }
389 unsigned int total_full_collections() const { return _total_full_collections;}
390
391 // Increment total number of GC collections (started)
392 void increment_total_collections(bool full = false) {
393 _total_collections++;
394 if (full) {
395 increment_total_full_collections();
396 }
397 }
398
399 void increment_total_full_collections() { _total_full_collections++; }
400
401 // Return the SoftRefPolicy for the heap;
402 virtual SoftRefPolicy* soft_ref_policy() = 0;
403
404 virtual MemoryUsage memory_usage();
405 virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
406 virtual GrowableArray<MemoryPool*> memory_pools() = 0;
407
408 // Iterate over all objects, calling "cl.do_object" on each.
409 virtual void object_iterate(ObjectClosure* cl) = 0;
410
411 protected:
412 virtual ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) {
413 return nullptr;
414 }
415
416 public:
417 // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
418 virtual void keep_alive(oop obj) {}
419
420 // Perform any cleanup actions necessary before allowing a verification.
421 virtual void prepare_for_verify() = 0;
422
423 // Returns the longest time (in ms) that has elapsed since the last
424 // time that the whole heap has been examined by a garbage collection.
425 jlong millis_since_last_whole_heap_examined();
426 // GC should call this when the next whole heap analysis has completed to
427 // satisfy above requirement.
428 void record_whole_heap_examined_timestamp();
429
430 private:
431 // Generate any dumps preceding or following a full gc
432 void full_gc_dump(GCTimer* timer, bool before);
433
434 virtual void initialize_serviceability() = 0;
435
436 public:
437 void pre_full_gc_dump(GCTimer* timer);
438 void post_full_gc_dump(GCTimer* timer);
439
440 virtual VirtualSpaceSummary create_heap_space_summary();
441 GCHeapSummary create_heap_summary();
442
443 MetaspaceSummary create_metaspace_summary();
444
445 // GCs are free to represent the bit representation for null differently in memory,
446 // which is typically not observable when using the Access API. However, if for
447 // some reason a context doesn't allow using the Access API, then this function
448 // explicitly checks if the given memory location contains a null value.
449 virtual bool contains_null(const oop* p) const;
450
451 // Print heap information on the given outputStream.
452 virtual void print_on(outputStream* st) const = 0;
453 // The default behavior is to call print_on() on tty.
454 virtual void print() const;
455
456 // Print more detailed heap information on the given
457 // outputStream. The default behavior is to call print_on(). It is
458 // up to each subclass to override it and add any additional output
459 // it needs.
460 virtual void print_extended_on(outputStream* st) const {
461 print_on(st);
462 }
463
464 virtual void print_on_error(outputStream* st) const;
465
466 // Used to print information about locations in the hs_err file.
467 virtual bool print_location(outputStream* st, void* addr) const = 0;
468
469 // Iterator for all GC threads (other than VM thread)
470 virtual void gc_threads_do(ThreadClosure* tc) const = 0;
471
472 // Print any relevant tracing info that flags imply.
473 // Default implementation does nothing.
474 virtual void print_tracing_info() const = 0;
475
476 void print_heap_before_gc();
477 void print_heap_after_gc();
478
479 // Registering and unregistering an nmethod (compiled code) with the heap.
480 virtual void register_nmethod(nmethod* nm) = 0;
481 virtual void unregister_nmethod(nmethod* nm) = 0;
482 virtual void verify_nmethod(nmethod* nm) = 0;
483
484 void trace_heap_before_gc(const GCTracer* gc_tracer);
485 void trace_heap_after_gc(const GCTracer* gc_tracer);
486
487 // Heap verification
488 virtual void verify(VerifyOption option) = 0;
489
490 // Return true if concurrent gc control via WhiteBox is supported by
491 // this collector. The default implementation returns false.
492 virtual bool supports_concurrent_gc_breakpoints() const;
493
494 // Workers used in non-GC safepoints for parallel safepoint cleanup. If this
495 // method returns null, cleanup tasks are done serially in the VMThread. See
496 // `SafepointSynchronize::do_cleanup_tasks` for details.
497 // GCs using a GC worker thread pool inside GC safepoints may opt to share
498 // that pool with non-GC safepoints, avoiding creating extraneous threads.
499 // Such sharing is safe, because GC safepoints and non-GC safepoints never
500 // overlap. For example, `G1CollectedHeap::workers()` (for GC safepoints) and
501 // `G1CollectedHeap::safepoint_workers()` (for non-GC safepoints) return the
502 // same thread-pool.
503 virtual WorkerThreads* safepoint_workers() { return nullptr; }
504
505 // Support for object pinning. This is used by JNI Get*Critical()
506 // and Release*Critical() family of functions. The GC must guarantee
507 // that pinned objects never move and don't get reclaimed as garbage.
508 // These functions are potentially safepointing.
509 virtual void pin_object(JavaThread* thread, oop obj) = 0;
510 virtual void unpin_object(JavaThread* thread, oop obj) = 0;
511
512 // Support for loading objects from CDS archive into the heap
513 // (usually as a snapshot of the old generation).
514 virtual bool can_load_archived_objects() const { return false; }
515 virtual HeapWord* allocate_loaded_archive_space(size_t size) { return nullptr; }
516 virtual void complete_loaded_archive_space(MemRegion archive_space) { }
517
518 virtual bool is_oop(oop object) const;
519 // Non product verification and debugging.
520 #ifndef PRODUCT
521 // Support for PromotionFailureALot. Return true if it's time to cause a
522 // promotion failure. The no-argument version uses
523 // this->_promotion_failure_alot_count as the counter.
524 bool promotion_should_fail(volatile size_t* count);
525 bool promotion_should_fail();
526
527 // Reset the PromotionFailureALot counters. Should be called at the end of a
528 // GC in which promotion failure occurred.
529 void reset_promotion_should_fail(volatile size_t* count);
530 void reset_promotion_should_fail();
531 #endif // #ifndef PRODUCT
532 };
533
534 // Class to set and reset the GC cause for a CollectedHeap.
535
536 class GCCauseSetter : StackObj {
537 CollectedHeap* _heap;
538 GCCause::Cause _previous_cause;
539 public:
540 GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
541 _heap = heap;
542 _previous_cause = _heap->gc_cause();
543 _heap->set_gc_cause(cause);
544 }
545
546 ~GCCauseSetter() {
547 _heap->set_gc_cause(_previous_cause);
548 }
549 };
550
551 #endif // SHARE_GC_SHARED_COLLECTEDHEAP_HPP