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24 
25 #ifndef SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
27 
28 #include "gc_interface/gcCause.hpp"
29 #include "gc_implementation/shared/gcWhen.hpp"
30 #include "memory/allocation.hpp"
31 #include "memory/barrierSet.hpp"
32 #include "runtime/handles.hpp"
33 #include "runtime/perfData.hpp"
34 #include "runtime/safepoint.hpp"
35 #include "utilities/events.hpp"
36 
37 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
38 // is an abstract class: there may be many different kinds of heaps.  This
39 // class defines the functions that a heap must implement, and contains
40 // infrastructure common to all heaps.
41 
42 class AdaptiveSizePolicy;
43 class BarrierSet;
44 class CollectorPolicy;
45 class GCHeapSummary;
46 class GCTimer;
47 class GCTracer;
48 class MetaspaceSummary;
49 class Thread;
50 class ThreadClosure;
51 class VirtualSpaceSummary;
52 class nmethod;
53 
54 class GCMessage : public FormatBuffer<1024> {
55  public:
56   bool is_before;
57 
58  public:
GCMessage()59   GCMessage() {}
60 };
61 
62 class GCHeapLog : public EventLogBase<GCMessage> {
63  private:
64   void log_heap(bool before);
65 
66  public:
GCHeapLog()67   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
68 
log_heap_before()69   void log_heap_before() {
70     log_heap(true);
71   }
log_heap_after()72   void log_heap_after() {
73     log_heap(false);
74   }
75 };
76 
77 //
78 // CollectedHeap
79 //   SharedHeap
80 //     GenCollectedHeap
81 //     G1CollectedHeap
82 //   ParallelScavengeHeap
83 //
84 class CollectedHeap : public CHeapObj<mtInternal> {
85   friend class VMStructs;
86   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
87 
88 #ifdef ASSERT
89   static int       _fire_out_of_memory_count;
90 #endif
91 
92   // Used for filler objects (static, but initialized in ctor).
93   static size_t _filler_array_max_size;
94 
95   GCHeapLog* _gc_heap_log;
96 
97   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
98   bool _defer_initial_card_mark;
99 
100  protected:
101   MemRegion _reserved;
102   BarrierSet* _barrier_set;
103   bool _is_gc_active;
104   uint _n_par_threads;
105 
106   unsigned int _total_collections;          // ... started
107   unsigned int _total_full_collections;     // ... started
108   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
109   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
110 
111   // Reason for current garbage collection.  Should be set to
112   // a value reflecting no collection between collections.
113   GCCause::Cause _gc_cause;
114   GCCause::Cause _gc_lastcause;
115   PerfStringVariable* _perf_gc_cause;
116   PerfStringVariable* _perf_gc_lastcause;
117 
118   // Constructor
119   CollectedHeap();
120 
121   // Do common initializations that must follow instance construction,
122   // for example, those needing virtual calls.
123   // This code could perhaps be moved into initialize() but would
124   // be slightly more awkward because we want the latter to be a
125   // pure virtual.
126   void pre_initialize();
127 
128   // Create a new tlab. All TLAB allocations must go through this.
129   virtual HeapWord* allocate_new_tlab(size_t size);
130 
131   // Accumulate statistics on all tlabs.
132   virtual void accumulate_statistics_all_tlabs();
133 
134   // Reinitialize tlabs before resuming mutators.
135   virtual void resize_all_tlabs();
136 
137   // Allocate from the current thread's TLAB, with broken-out slow path.
138   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
139   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
140 
141   // Allocate an uninitialized block of the given size, or returns NULL if
142   // this is impossible.
143   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
144 
145   // Like allocate_init, but the block returned by a successful allocation
146   // is guaranteed initialized to zeros.
147   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
148 
149   // Helper functions for (VM) allocation.
150   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
151   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
152                                                             HeapWord* objPtr);
153 
154   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
155 
156   inline static void post_allocation_setup_array(KlassHandle klass,
157                                                  HeapWord* obj, int length);
158 
159   // Clears an allocated object.
160   inline static void init_obj(HeapWord* obj, size_t size);
161 
162   // Filler object utilities.
163   static inline size_t filler_array_hdr_size();
164   static inline size_t filler_array_min_size();
165 
166   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
167   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
168 
169   // Fill with a single array; caller must ensure filler_array_min_size() <=
170   // words <= filler_array_max_size().
171   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
172 
173   // Fill with a single object (either an int array or a java.lang.Object).
174   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
175 
176   virtual void trace_heap(GCWhen::Type when, GCTracer* tracer);
177 
178   // Verification functions
179   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
180     PRODUCT_RETURN;
181   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
182     PRODUCT_RETURN;
183   debug_only(static void check_for_valid_allocation_state();)
184 
185  public:
186   enum Name {
187     Abstract,
188     SharedHeap,
189     GenCollectedHeap,
190     ParallelScavengeHeap,
191     G1CollectedHeap
192   };
193 
filler_array_max_size()194   static inline size_t filler_array_max_size() {
195     return _filler_array_max_size;
196   }
197 
kind() const198   virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
199 
200   /**
201    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
202    * and JNI_OK on success.
203    */
204   virtual jint initialize() = 0;
205 
206   // In many heaps, there will be a need to perform some initialization activities
207   // after the Universe is fully formed, but before general heap allocation is allowed.
208   // This is the correct place to place such initialization methods.
209   virtual void post_initialize() = 0;
210 
211   // Stop any onging concurrent work and prepare for exit.
stop()212   virtual void stop() {}
213 
reserved_region() const214   MemRegion reserved_region() const { return _reserved; }
base() const215   address base() const { return (address)reserved_region().start(); }
216 
217   virtual size_t capacity() const = 0;
218   virtual size_t used() const = 0;
219 
220   // Return "true" if the part of the heap that allocates Java
221   // objects has reached the maximal committed limit that it can
222   // reach, without a garbage collection.
223   virtual bool is_maximal_no_gc() const = 0;
224 
225   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
226   // memory that the vm could make available for storing 'normal' java objects.
227   // This is based on the reserved address space, but should not include space
228   // that the vm uses internally for bookkeeping or temporary storage
229   // (e.g., in the case of the young gen, one of the survivor
230   // spaces).
231   virtual size_t max_capacity() const = 0;
232 
233   // Returns "TRUE" if "p" points into the reserved area of the heap.
is_in_reserved(const void * p) const234   bool is_in_reserved(const void* p) const {
235     return _reserved.contains(p);
236   }
237 
is_in_reserved_or_null(const void * p) const238   bool is_in_reserved_or_null(const void* p) const {
239     return p == NULL || is_in_reserved(p);
240   }
241 
242   // Returns "TRUE" iff "p" points into the committed areas of the heap.
243   // Since this method can be expensive in general, we restrict its
244   // use to assertion checking only.
245   virtual bool is_in(const void* p) const = 0;
246 
is_in_or_null(const void * p) const247   bool is_in_or_null(const void* p) const {
248     return p == NULL || is_in(p);
249   }
250 
is_in_place(Metadata ** p)251   bool is_in_place(Metadata** p) {
252     return !Universe::heap()->is_in(p);
253   }
is_in_place(oop * p)254   bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
is_in_place(narrowOop * p)255   bool is_in_place(narrowOop* p) {
256     oop o = oopDesc::load_decode_heap_oop_not_null(p);
257     return Universe::heap()->is_in((const void*)o);
258   }
259 
260   // Let's define some terms: a "closed" subset of a heap is one that
261   //
262   // 1) contains all currently-allocated objects, and
263   //
264   // 2) is closed under reference: no object in the closed subset
265   //    references one outside the closed subset.
266   //
267   // Membership in a heap's closed subset is useful for assertions.
268   // Clearly, the entire heap is a closed subset, so the default
269   // implementation is to use "is_in_reserved".  But this may not be too
270   // liberal to perform useful checking.  Also, the "is_in" predicate
271   // defines a closed subset, but may be too expensive, since "is_in"
272   // verifies that its argument points to an object head.  The
273   // "closed_subset" method allows a heap to define an intermediate
274   // predicate, allowing more precise checking than "is_in_reserved" at
275   // lower cost than "is_in."
276 
277   // One important case is a heap composed of disjoint contiguous spaces,
278   // such as the Garbage-First collector.  Such heaps have a convenient
279   // closed subset consisting of the allocated portions of those
280   // contiguous spaces.
281 
282   // Return "TRUE" iff the given pointer points into the heap's defined
283   // closed subset (which defaults to the entire heap).
is_in_closed_subset(const void * p) const284   virtual bool is_in_closed_subset(const void* p) const {
285     return is_in_reserved(p);
286   }
287 
is_in_closed_subset_or_null(const void * p) const288   bool is_in_closed_subset_or_null(const void* p) const {
289     return p == NULL || is_in_closed_subset(p);
290   }
291 
292 #ifdef ASSERT
293   // Returns true if "p" is in the part of the
294   // heap being collected.
295   virtual bool is_in_partial_collection(const void *p) = 0;
296 #endif
297 
298   // An object is scavengable if its location may move during a scavenge.
299   // (A scavenge is a GC which is not a full GC.)
300   virtual bool is_scavengable(const void *p) = 0;
301 
set_gc_cause(GCCause::Cause v)302   void set_gc_cause(GCCause::Cause v) {
303      if (UsePerfData) {
304        _gc_lastcause = _gc_cause;
305        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
306        _perf_gc_cause->set_value(GCCause::to_string(v));
307      }
308     _gc_cause = v;
309   }
gc_cause()310   GCCause::Cause gc_cause() { return _gc_cause; }
311 
312   // Number of threads currently working on GC tasks.
n_par_threads()313   uint n_par_threads() { return _n_par_threads; }
314 
315   // May be overridden to set additional parallelism.
set_par_threads(uint t)316   virtual void set_par_threads(uint t) { _n_par_threads = t; };
317 
318   // General obj/array allocation facilities.
319   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
320   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
321   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
322 
323   // Raw memory allocation facilities
324   // The obj and array allocate methods are covers for these methods.
325   // mem_allocate() should never be
326   // called to allocate TLABs, only individual objects.
327   virtual HeapWord* mem_allocate(size_t size,
328                                  bool* gc_overhead_limit_was_exceeded) = 0;
329 
330   // Utilities for turning raw memory into filler objects.
331   //
332   // min_fill_size() is the smallest region that can be filled.
333   // fill_with_objects() can fill arbitrary-sized regions of the heap using
334   // multiple objects.  fill_with_object() is for regions known to be smaller
335   // than the largest array of integers; it uses a single object to fill the
336   // region and has slightly less overhead.
min_fill_size()337   static size_t min_fill_size() {
338     return size_t(align_object_size(oopDesc::header_size()));
339   }
340 
341   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
342 
343   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
fill_with_object(MemRegion region,bool zap=true)344   static void fill_with_object(MemRegion region, bool zap = true) {
345     fill_with_object(region.start(), region.word_size(), zap);
346   }
fill_with_object(HeapWord * start,HeapWord * end,bool zap=true)347   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
348     fill_with_object(start, pointer_delta(end, start), zap);
349   }
350 
351   // Return the address "addr" aligned by "alignment_in_bytes" if such
352   // an address is below "end".  Return NULL otherwise.
353   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
354                                                    HeapWord* end,
355                                                    unsigned short alignment_in_bytes);
356 
357   // Some heaps may offer a contiguous region for shared non-blocking
358   // allocation, via inlined code (by exporting the address of the top and
359   // end fields defining the extent of the contiguous allocation region.)
360 
361   // This function returns "true" iff the heap supports this kind of
362   // allocation.  (Default is "no".)
supports_inline_contig_alloc() const363   virtual bool supports_inline_contig_alloc() const {
364     return false;
365   }
366   // These functions return the addresses of the fields that define the
367   // boundaries of the contiguous allocation area.  (These fields should be
368   // physically near to one another.)
top_addr() const369   virtual HeapWord** top_addr() const {
370     guarantee(false, "inline contiguous allocation not supported");
371     return NULL;
372   }
end_addr() const373   virtual HeapWord** end_addr() const {
374     guarantee(false, "inline contiguous allocation not supported");
375     return NULL;
376   }
377 
378   // Some heaps may be in an unparseable state at certain times between
379   // collections. This may be necessary for efficient implementation of
380   // certain allocation-related activities. Calling this function before
381   // attempting to parse a heap ensures that the heap is in a parsable
382   // state (provided other concurrent activity does not introduce
383   // unparsability). It is normally expected, therefore, that this
384   // method is invoked with the world stopped.
385   // NOTE: if you override this method, make sure you call
386   // super::ensure_parsability so that the non-generational
387   // part of the work gets done. See implementation of
388   // CollectedHeap::ensure_parsability and, for instance,
389   // that of GenCollectedHeap::ensure_parsability().
390   // The argument "retire_tlabs" controls whether existing TLABs
391   // are merely filled or also retired, thus preventing further
392   // allocation from them and necessitating allocation of new TLABs.
393   virtual void ensure_parsability(bool retire_tlabs);
394 
395   // Section on thread-local allocation buffers (TLABs)
396   // If the heap supports thread-local allocation buffers, it should override
397   // the following methods:
398   // Returns "true" iff the heap supports thread-local allocation buffers.
399   // The default is "no".
400   virtual bool supports_tlab_allocation() const = 0;
401 
402   // The amount of space available for thread-local allocation buffers.
403   virtual size_t tlab_capacity(Thread *thr) const = 0;
404 
405   // The amount of used space for thread-local allocation buffers for the given thread.
406   virtual size_t tlab_used(Thread *thr) const = 0;
407 
408   virtual size_t max_tlab_size() const;
409 
410   // An estimate of the maximum allocation that could be performed
411   // for thread-local allocation buffers without triggering any
412   // collection or expansion activity.
unsafe_max_tlab_alloc(Thread * thr) const413   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
414     guarantee(false, "thread-local allocation buffers not supported");
415     return 0;
416   }
417 
418   // Can a compiler initialize a new object without store barriers?
419   // This permission only extends from the creation of a new object
420   // via a TLAB up to the first subsequent safepoint. If such permission
421   // is granted for this heap type, the compiler promises to call
422   // defer_store_barrier() below on any slow path allocation of
423   // a new object for which such initializing store barriers will
424   // have been elided.
425   virtual bool can_elide_tlab_store_barriers() const = 0;
426 
427   // If a compiler is eliding store barriers for TLAB-allocated objects,
428   // there is probably a corresponding slow path which can produce
429   // an object allocated anywhere.  The compiler's runtime support
430   // promises to call this function on such a slow-path-allocated
431   // object before performing initializations that have elided
432   // store barriers. Returns new_obj, or maybe a safer copy thereof.
433   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
434 
435   // Answers whether an initializing store to a new object currently
436   // allocated at the given address doesn't need a store
437   // barrier. Returns "true" if it doesn't need an initializing
438   // store barrier; answers "false" if it does.
439   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
440 
441   // If a compiler is eliding store barriers for TLAB-allocated objects,
442   // we will be informed of a slow-path allocation by a call
443   // to new_store_pre_barrier() above. Such a call precedes the
444   // initialization of the object itself, and no post-store-barriers will
445   // be issued. Some heap types require that the barrier strictly follows
446   // the initializing stores. (This is currently implemented by deferring the
447   // barrier until the next slow-path allocation or gc-related safepoint.)
448   // This interface answers whether a particular heap type needs the card
449   // mark to be thus strictly sequenced after the stores.
450   virtual bool card_mark_must_follow_store() const = 0;
451 
452   // If the CollectedHeap was asked to defer a store barrier above,
453   // this informs it to flush such a deferred store barrier to the
454   // remembered set.
455   virtual void flush_deferred_store_barrier(JavaThread* thread);
456 
457   // Does this heap support heap inspection (+PrintClassHistogram?)
458   virtual bool supports_heap_inspection() const = 0;
459 
460   // Perform a collection of the heap; intended for use in implementing
461   // "System.gc".  This probably implies as full a collection as the
462   // "CollectedHeap" supports.
463   virtual void collect(GCCause::Cause cause) = 0;
464 
465   // Perform a full collection
466   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
467 
468   // This interface assumes that it's being called by the
469   // vm thread. It collects the heap assuming that the
470   // heap lock is already held and that we are executing in
471   // the context of the vm thread.
472   virtual void collect_as_vm_thread(GCCause::Cause cause);
473 
474   // Returns the barrier set for this heap
barrier_set()475   BarrierSet* barrier_set() { return _barrier_set; }
476 
477   // Returns "true" iff there is a stop-world GC in progress.  (I assume
478   // that it should answer "false" for the concurrent part of a concurrent
479   // collector -- dld).
is_gc_active() const480   bool is_gc_active() const { return _is_gc_active; }
481 
482   // Total number of GC collections (started)
total_collections() const483   unsigned int total_collections() const { return _total_collections; }
total_full_collections() const484   unsigned int total_full_collections() const { return _total_full_collections;}
485 
486   // Increment total number of GC collections (started)
487   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
increment_total_collections(bool full=false)488   void increment_total_collections(bool full = false) {
489     _total_collections++;
490     if (full) {
491       increment_total_full_collections();
492     }
493   }
494 
increment_total_full_collections()495   void increment_total_full_collections() { _total_full_collections++; }
496 
497   // Return the AdaptiveSizePolicy for the heap.
498   virtual AdaptiveSizePolicy* size_policy() = 0;
499 
500   // Return the CollectorPolicy for the heap
501   virtual CollectorPolicy* collector_policy() const = 0;
502 
503   void oop_iterate_no_header(OopClosure* cl);
504 
505   // Iterate over all the ref-containing fields of all objects, calling
506   // "cl.do_oop" on each.
507   virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
508 
509   // Iterate over all objects, calling "cl.do_object" on each.
510   virtual void object_iterate(ObjectClosure* cl) = 0;
511 
512   // Similar to object_iterate() except iterates only
513   // over live objects.
514   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
515 
516   // NOTE! There is no requirement that a collector implement these
517   // functions.
518   //
519   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
520   // each address in the (reserved) heap is a member of exactly
521   // one block.  The defining characteristic of a block is that it is
522   // possible to find its size, and thus to progress forward to the next
523   // block.  (Blocks may be of different sizes.)  Thus, blocks may
524   // represent Java objects, or they might be free blocks in a
525   // free-list-based heap (or subheap), as long as the two kinds are
526   // distinguishable and the size of each is determinable.
527 
528   // Returns the address of the start of the "block" that contains the
529   // address "addr".  We say "blocks" instead of "object" since some heaps
530   // may not pack objects densely; a chunk may either be an object or a
531   // non-object.
532   virtual HeapWord* block_start(const void* addr) const = 0;
533 
534   // Requires "addr" to be the start of a chunk, and returns its size.
535   // "addr + size" is required to be the start of a new chunk, or the end
536   // of the active area of the heap.
537   virtual size_t block_size(const HeapWord* addr) const = 0;
538 
539   // Requires "addr" to be the start of a block, and returns "TRUE" iff
540   // the block is an object.
541   virtual bool block_is_obj(const HeapWord* addr) const = 0;
542 
543   // Returns the longest time (in ms) that has elapsed since the last
544   // time that any part of the heap was examined by a garbage collection.
545   virtual jlong millis_since_last_gc() = 0;
546 
547   // Perform any cleanup actions necessary before allowing a verification.
548   virtual void prepare_for_verify() = 0;
549 
550   // Generate any dumps preceding or following a full gc
551   void pre_full_gc_dump(GCTimer* timer);
552   void post_full_gc_dump(GCTimer* timer);
553 
554   VirtualSpaceSummary create_heap_space_summary();
555   GCHeapSummary create_heap_summary();
556 
557   MetaspaceSummary create_metaspace_summary();
558 
559   // Print heap information on the given outputStream.
560   virtual void print_on(outputStream* st) const = 0;
561   // The default behavior is to call print_on() on tty.
print() const562   virtual void print() const {
563     print_on(tty);
564   }
565   // Print more detailed heap information on the given
566   // outputStream. The default behavior is to call print_on(). It is
567   // up to each subclass to override it and add any additional output
568   // it needs.
print_extended_on(outputStream * st) const569   virtual void print_extended_on(outputStream* st) const {
570     print_on(st);
571   }
572 
print_on_error(outputStream * st) const573   virtual void print_on_error(outputStream* st) const {
574     st->print_cr("Heap:");
575     print_extended_on(st);
576     st->cr();
577 
578     _barrier_set->print_on(st);
579   }
580 
581   // Print all GC threads (other than the VM thread)
582   // used by this heap.
583   virtual void print_gc_threads_on(outputStream* st) const = 0;
584   // The default behavior is to call print_gc_threads_on() on tty.
print_gc_threads()585   void print_gc_threads() {
586     print_gc_threads_on(tty);
587   }
588   // Iterator for all GC threads (other than VM thread)
589   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
590 
591   // Print any relevant tracing info that flags imply.
592   // Default implementation does nothing.
593   virtual void print_tracing_info() const = 0;
594 
595   void print_heap_before_gc();
596   void print_heap_after_gc();
597 
598   // Registering and unregistering an nmethod (compiled code) with the heap.
599   // Override with specific mechanism for each specialized heap type.
600   virtual void register_nmethod(nmethod* nm);
601   virtual void unregister_nmethod(nmethod* nm);
602 
603   void trace_heap_before_gc(GCTracer* gc_tracer);
604   void trace_heap_after_gc(GCTracer* gc_tracer);
605 
606   // Heap verification
607   virtual void verify(bool silent, VerifyOption option) = 0;
608 
609   // Non product verification and debugging.
610 #ifndef PRODUCT
611   // Support for PromotionFailureALot.  Return true if it's time to cause a
612   // promotion failure.  The no-argument version uses
613   // this->_promotion_failure_alot_count as the counter.
614   inline bool promotion_should_fail(volatile size_t* count);
615   inline bool promotion_should_fail();
616 
617   // Reset the PromotionFailureALot counters.  Should be called at the end of a
618   // GC in which promotion failure occurred.
619   inline void reset_promotion_should_fail(volatile size_t* count);
620   inline void reset_promotion_should_fail();
621 #endif  // #ifndef PRODUCT
622 
623 #ifdef ASSERT
fired_fake_oom()624   static int fired_fake_oom() {
625     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
626   }
627 #endif
628 
629  public:
630   // This is a convenience method that is used in cases where
631   // the actual number of GC worker threads is not pertinent but
632   // only whether there more than 0.  Use of this method helps
633   // reduce the occurrence of ParallelGCThreads to uses where the
634   // actual number may be germane.
use_parallel_gc_threads()635   static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
636 
637   // Copy the current allocation context statistics for the specified contexts.
638   // For each context in contexts, set the corresponding entries in the totals
639   // and accuracy arrays to the current values held by the statistics.  Each
640   // array should be of length len.
641   // Returns true if there are more stats available.
copy_allocation_context_stats(const jint * contexts,jlong * totals,jbyte * accuracy,jint len)642   virtual bool copy_allocation_context_stats(const jint* contexts,
643                                              jlong* totals,
644                                              jbyte* accuracy,
645                                              jint len) {
646     return false;
647   }
648 
649   /////////////// Unit tests ///////////////
650 
651   NOT_PRODUCT(static void test_is_in();)
652 };
653 
654 // Class to set and reset the GC cause for a CollectedHeap.
655 
656 class GCCauseSetter : StackObj {
657   CollectedHeap* _heap;
658   GCCause::Cause _previous_cause;
659  public:
GCCauseSetter(CollectedHeap * heap,GCCause::Cause cause)660   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
661     assert(SafepointSynchronize::is_at_safepoint(),
662            "This method manipulates heap state without locking");
663     _heap = heap;
664     _previous_cause = _heap->gc_cause();
665     _heap->set_gc_cause(cause);
666   }
667 
~GCCauseSetter()668   ~GCCauseSetter() {
669     assert(SafepointSynchronize::is_at_safepoint(),
670           "This method manipulates heap state without locking");
671     _heap->set_gc_cause(_previous_cause);
672   }
673 };
674 
675 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
676