1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
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  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  *
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 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 GCMemoryManager;
 52 class GCMetaspaceLog;
 53 class GCTimer;
 54 class GCTracer;
 55 class MemoryPool;
 56 class MetaspaceSummary;
 57 class ReservedHeapSpace;
 58 class Thread;
 59 class ThreadClosure;
 60 class VirtualSpaceSummary;
 61 class WorkerThreads;
 62 class nmethod;
 63 
 64 class ParallelObjectIteratorImpl : public CHeapObj<mtGC> {
 65 public:
 66   virtual ~ParallelObjectIteratorImpl() {}
 67   virtual void object_iterate(ObjectClosure* cl, uint worker_id) = 0;
 68 };
 69 
 70 // User facing parallel object iterator. This is a StackObj, which ensures that
 71 // the _impl is allocated and deleted in the scope of this object. This ensures
 72 // the life cycle of the implementation is as required by ThreadsListHandle,
 73 // which is sometimes used by the root iterators.
 74 class ParallelObjectIterator : public StackObj {
 75   ParallelObjectIteratorImpl* _impl;
 76 
 77 public:
 78   ParallelObjectIterator(uint thread_num);
 79   ~ParallelObjectIterator();
 80   void object_iterate(ObjectClosure* cl, uint worker_id);
 81 };
 82 
 83 //
 84 // CollectedHeap
 85 //   SerialHeap
 86 //   G1CollectedHeap
 87 //   ParallelScavengeHeap
 88 //   ShenandoahHeap
 89 //   ZCollectedHeap
 90 //
 91 class CollectedHeap : public CHeapObj<mtGC> {
 92   friend class VMStructs;
 93   friend class JVMCIVMStructs;
 94   friend class IsSTWGCActiveMark; // Block structured external access to _is_stw_gc_active
 95   friend class MemAllocator;
 96 
 97  private:
 98   GCHeapLog*      _heap_log;
 99   GCMetaspaceLog* _metaspace_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_stw_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   jlong _vmthread_cpu_time;
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) = 0;
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   // Print any relevant tracing info that flags imply.
212   // Default implementation does nothing.
213   virtual void print_tracing_info() const = 0;
214 
215   // Stop any onging concurrent work and prepare for exit.
216   virtual void stop() = 0;
217 
218  public:
219 
220   static inline size_t filler_array_max_size() {
221     return _filler_array_max_size;
222   }
223 
224   static inline size_t stack_chunk_max_size() {
225     return _stack_chunk_max_size;
226   }
227 
228   static inline Klass* filler_object_klass() {
229     return _filler_object_klass;
230   }
231 
232   static inline void set_filler_object_klass(Klass* k) {
233     _filler_object_klass = k;
234   }
235 
236   virtual Name kind() const = 0;
237 
238   virtual const char* name() const = 0;
239 
240   /**
241    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
242    * and JNI_OK on success.
243    */
244   virtual jint initialize() = 0;
245 
246   // In many heaps, there will be a need to perform some initialization activities
247   // after the Universe is fully formed, but before general heap allocation is allowed.
248   // This is the correct place to place such initialization methods.
249   virtual void post_initialize();
250 
251   void before_exit();
252 
253   // Stop and resume concurrent GC threads interfering with safepoint operations
254   virtual void safepoint_synchronize_begin() {}
255   virtual void safepoint_synchronize_end() {}
256 
257   void add_vmthread_cpu_time(jlong time);
258 
259   void initialize_reserved_region(const ReservedHeapSpace& rs);
260 
261   virtual size_t capacity() const = 0;
262   virtual size_t used() const = 0;
263 
264   // Returns unused capacity.
265   virtual size_t unused() const;
266 
267   // Historic gc information
268   size_t free_at_last_gc() const { return _capacity_at_last_gc - _used_at_last_gc; }
269   size_t used_at_last_gc() const { return _used_at_last_gc; }
270   void update_capacity_and_used_at_gc();
271 
272   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
273   // memory that the vm could make available for storing 'normal' java objects.
274   // This is based on the reserved address space, but should not include space
275   // that the vm uses internally for bookkeeping or temporary storage
276   // (e.g., in the case of the young gen, one of the survivor
277   // spaces).
278   virtual size_t max_capacity() const = 0;
279 
280   // Returns "TRUE" iff "p" points into the committed areas of the heap.
281   // This method can be expensive so avoid using it in performance critical
282   // code.
283   virtual bool is_in(const void* p) const = 0;
284 
285   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == nullptr || is_in(p); })
286 
287   void set_gc_cause(GCCause::Cause v);
288   GCCause::Cause gc_cause() { return _gc_cause; }
289 
290   oop obj_allocate(Klass* klass, size_t size, TRAPS);
291   virtual oop array_allocate(Klass* klass, size_t size, int length, bool do_zero, TRAPS);
292   oop class_allocate(Klass* klass, size_t size, size_t base_size, TRAPS);
293 
294   // Utilities for turning raw memory into filler objects.
295   //
296   // min_fill_size() is the smallest region that can be filled.
297   // fill_with_objects() can fill arbitrary-sized regions of the heap using
298   // multiple objects.  fill_with_object() is for regions known to be smaller
299   // than the largest array of integers; it uses a single object to fill the
300   // region and has slightly less overhead.
301   static size_t min_fill_size() {
302     return size_t(align_object_size(oopDesc::header_size()));
303   }
304 
305   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
306 
307   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
308   static void fill_with_object(MemRegion region, bool zap = true) {
309     fill_with_object(region.start(), region.word_size(), zap);
310   }
311   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
312     fill_with_object(start, pointer_delta(end, start), zap);
313   }
314 
315   virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
316   static size_t min_dummy_object_size() {
317     return oopDesc::header_size();
318   }
319 
320   static size_t lab_alignment_reserve() {
321     assert(_lab_alignment_reserve != SIZE_MAX, "uninitialized");
322     return _lab_alignment_reserve;
323   }
324 
325   // Some heaps may be in an unparseable state at certain times between
326   // collections. This may be necessary for efficient implementation of
327   // certain allocation-related activities. Calling this function before
328   // attempting to parse a heap ensures that the heap is in a parsable
329   // state (provided other concurrent activity does not introduce
330   // unparsability). It is normally expected, therefore, that this
331   // method is invoked with the world stopped.
332   // NOTE: if you override this method, make sure you call
333   // super::ensure_parsability so that the non-generational
334   // part of the work gets done. See implementation of
335   // CollectedHeap::ensure_parsability and, for instance,
336   // that of ParallelScavengeHeap::ensure_parsability().
337   // The argument "retire_tlabs" controls whether existing TLABs
338   // are merely filled or also retired, thus preventing further
339   // allocation from them and necessitating allocation of new TLABs.
340   virtual void ensure_parsability(bool retire_tlabs);
341 
342   // The amount of space available for thread-local allocation buffers.
343   virtual size_t tlab_capacity(Thread *thr) const = 0;
344 
345   // The amount of used space for thread-local allocation buffers for the given thread.
346   virtual size_t tlab_used(Thread *thr) const = 0;
347 
348   virtual size_t max_tlab_size() const;
349 
350   // An estimate of the maximum allocation that could be performed
351   // for thread-local allocation buffers without triggering any
352   // collection or expansion activity.
353   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const = 0;
354 
355   // Perform a collection of the heap; intended for use in implementing
356   // "System.gc".  This probably implies as full a collection as the
357   // "CollectedHeap" supports.
358   virtual void collect(GCCause::Cause cause) = 0;
359 
360   // Perform a full collection
361   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
362 
363   // This interface assumes that it's being called by the
364   // vm thread. It collects the heap assuming that the
365   // heap lock is already held and that we are executing in
366   // the context of the vm thread.
367   virtual void collect_as_vm_thread(GCCause::Cause cause);
368 
369   virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
370                                                        size_t size,
371                                                        Metaspace::MetadataType mdtype);
372 
373   // Return true, if accesses to the object would require barriers.
374   // This is used by continuations to copy chunks of a thread stack into StackChunk object or out of a StackChunk
375   // object back into the thread stack. These chunks may contain references to objects. It is crucial that
376   // the GC does not attempt to traverse the object while we modify it, because its structure (oopmap) is changed
377   // when stack chunks are stored into it.
378   // StackChunk objects may be reused, the GC must not assume that a StackChunk object is always a freshly
379   // allocated object.
380   virtual bool requires_barriers(stackChunkOop obj) const = 0;
381 
382   // Returns "true" iff there is a stop-world GC in progress.
383   bool is_stw_gc_active() const { return _is_stw_gc_active; }
384 
385   // Total number of GC collections (started)
386   unsigned int total_collections() const { return _total_collections; }
387   unsigned int total_full_collections() const { return _total_full_collections;}
388 
389   // Increment total number of GC collections (started)
390   void increment_total_collections(bool full = false) {
391     _total_collections++;
392     if (full) {
393       _total_full_collections++;
394     }
395   }
396 
397   // Return the SoftRefPolicy for the heap;
398   SoftRefPolicy* soft_ref_policy() { return &_soft_ref_policy; }
399 
400   virtual MemoryUsage memory_usage();
401   virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
402   virtual GrowableArray<MemoryPool*> memory_pools() = 0;
403 
404   // Iterate over all objects, calling "cl.do_object" on each.
405   virtual void object_iterate(ObjectClosure* cl) = 0;
406 
407   virtual ParallelObjectIteratorImpl* parallel_object_iterator(uint thread_num) {
408     return nullptr;
409   }
410 
411   // Keep alive an object that was loaded with AS_NO_KEEPALIVE.
412   virtual void keep_alive(oop obj) {}
413 
414   // Perform any cleanup actions necessary before allowing a verification.
415   virtual void prepare_for_verify() = 0;
416 
417   // Returns the longest time (in ms) that has elapsed since the last
418   // time that the whole heap has been examined by a garbage collection.
419   jlong millis_since_last_whole_heap_examined();
420   // GC should call this when the next whole heap analysis has completed to
421   // satisfy above requirement.
422   void record_whole_heap_examined_timestamp();
423 
424  private:
425   // Generate any dumps preceding or following a full gc
426   void full_gc_dump(GCTimer* timer, bool before);
427 
428   virtual void initialize_serviceability() = 0;
429 
430   void print_relative_to_gc(GCWhen::Type when) const;
431 
432   void log_gc_cpu_time() const;
433 
434  public:
435   void pre_full_gc_dump(GCTimer* timer);
436   void post_full_gc_dump(GCTimer* timer);
437 
438   virtual VirtualSpaceSummary create_heap_space_summary();
439   GCHeapSummary create_heap_summary();
440 
441   MetaspaceSummary create_metaspace_summary();
442 
443   // GCs are free to represent the bit representation for null differently in memory,
444   // which is typically not observable when using the Access API. However, if for
445   // some reason a context doesn't allow using the Access API, then this function
446   // explicitly checks if the given memory location contains a null value.
447   virtual bool contains_null(const oop* p) const;
448 
449   void print_invocation_on(outputStream* st, const char* type, GCWhen::Type when) const;
450 
451   // Print heap information.
452   virtual void print_heap_on(outputStream* st) const = 0;
453 
454   // Print additional information about the GC that is not included in print_heap_on().
455   virtual void print_gc_on(outputStream* st) const = 0;
456 
457   // The default behavior is to call print_heap_on() and print_gc_on() on tty.
458   virtual void print() const;
459 
460   // Used to print information about locations in the hs_err file.
461   virtual bool print_location(outputStream* st, void* addr) const = 0;
462 
463   // Iterator for all GC threads (other than VM thread)
464   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
465 
466   double elapsed_gc_cpu_time() const;
467 
468   void print_before_gc() const;
469   void print_after_gc() const;
470 
471   // Registering and unregistering an nmethod (compiled code) with the heap.
472   virtual void register_nmethod(nmethod* nm) = 0;
473   virtual void unregister_nmethod(nmethod* nm) = 0;
474   virtual void verify_nmethod(nmethod* nm) = 0;
475 
476   void trace_heap_before_gc(const GCTracer* gc_tracer);
477   void trace_heap_after_gc(const GCTracer* gc_tracer);
478 
479   // Heap verification
480   virtual void verify(VerifyOption option) = 0;
481 
482   // Return true if concurrent gc control via WhiteBox is supported by
483   // this collector.  The default implementation returns false.
484   virtual bool supports_concurrent_gc_breakpoints() const;
485 
486   // Workers used in non-GC safepoints for parallel safepoint cleanup. If this
487   // method returns null, cleanup tasks are done serially in the VMThread. See
488   // `SafepointSynchronize::do_cleanup_tasks` for details.
489   // GCs using a GC worker thread pool inside GC safepoints may opt to share
490   // that pool with non-GC safepoints, avoiding creating extraneous threads.
491   // Such sharing is safe, because GC safepoints and non-GC safepoints never
492   // overlap. For example, `G1CollectedHeap::workers()` (for GC safepoints) and
493   // `G1CollectedHeap::safepoint_workers()` (for non-GC safepoints) return the
494   // same thread-pool.
495   virtual WorkerThreads* safepoint_workers() { return nullptr; }
496 
497   // Support for object pinning. This is used by JNI Get*Critical()
498   // and Release*Critical() family of functions. The GC must guarantee
499   // that pinned objects never move and don't get reclaimed as garbage.
500   // These functions are potentially safepointing.
501   virtual void pin_object(JavaThread* thread, oop obj) = 0;
502   virtual void unpin_object(JavaThread* thread, oop obj) = 0;
503 
504   // Support for loading objects from CDS archive into the heap
505   // (usually as a snapshot of the old generation).
506   virtual bool can_load_archived_objects() const { return false; }
507   virtual HeapWord* allocate_loaded_archive_space(size_t size) { return nullptr; }
508   virtual void complete_loaded_archive_space(MemRegion archive_space) { }
509 
510   virtual bool is_oop(oop object) const;
511   // Non product verification and debugging.
512 #ifndef PRODUCT
513   // Support for PromotionFailureALot.  Return true if it's time to cause a
514   // promotion failure.  The no-argument version uses
515   // this->_promotion_failure_alot_count as the counter.
516   bool promotion_should_fail(volatile size_t* count);
517   bool promotion_should_fail();
518 
519   // Reset the PromotionFailureALot counters.  Should be called at the end of a
520   // GC in which promotion failure occurred.
521   void reset_promotion_should_fail(volatile size_t* count);
522   void reset_promotion_should_fail();
523 #endif  // #ifndef PRODUCT
524 };
525 
526 // Class to set and reset the GC cause for a CollectedHeap.
527 
528 class GCCauseSetter : StackObj {
529   CollectedHeap* _heap;
530   GCCause::Cause _previous_cause;
531  public:
532   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
533     _heap = heap;
534     _previous_cause = _heap->gc_cause();
535     _heap->set_gc_cause(cause);
536   }
537 
538   ~GCCauseSetter() {
539     _heap->set_gc_cause(_previous_cause);
540   }
541 };
542 
543 #endif // SHARE_GC_SHARED_COLLECTEDHEAP_HPP