1 /*
   2  * Copyright (c) 2001, 2015, 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
   6  * under the terms of the GNU General Public License version 2 only, as
   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.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
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  24 
  25 #ifndef SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
  27 
  28 #include "gc/shared/gcCause.hpp"
  29 #include "gc/shared/gcWhen.hpp"
  30 #include "memory/allocation.hpp"
  31 #include "runtime/handles.hpp"
  32 #include "runtime/perfData.hpp"
  33 #include "runtime/safepoint.hpp"
  34 #include "utilities/events.hpp"
  35 
  36 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
  37 // is an abstract class: there may be many different kinds of heaps.  This
  38 // class defines the functions that a heap must implement, and contains
  39 // infrastructure common to all heaps.
  40 
  41 class AdaptiveSizePolicy;
  42 class BarrierSet;
  43 class CollectorPolicy;
  44 class GCHeapSummary;
  45 class GCTimer;
  46 class GCTracer;
  47 class MetaspaceSummary;
  48 class Thread;
  49 class ThreadClosure;
  50 class VirtualSpaceSummary;
  51 class nmethod;
  52 
  53 class GCMessage : public FormatBuffer<1024> {
  54  public:
  55   bool is_before;
  56 
  57  public:
  58   GCMessage() {}
  59 };
  60 
  61 class GCHeapLog : public EventLogBase<GCMessage> {
  62  private:
  63   void log_heap(bool before);
  64 
  65  public:
  66   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
  67 
  68   void log_heap_before() {
  69     log_heap(true);
  70   }
  71   void log_heap_after() {
  72     log_heap(false);
  73   }
  74 };
  75 
  76 //
  77 // CollectedHeap
  78 //   GenCollectedHeap
  79 //   G1CollectedHeap
  80 //   ParallelScavengeHeap
  81 //
  82 class CollectedHeap : public CHeapObj<mtInternal> {
  83   friend class VMStructs;
  84   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  85 
  86  private:
  87 #ifdef ASSERT
  88   static int       _fire_out_of_memory_count;
  89 #endif
  90 
  91   // Used for filler objects (static, but initialized in ctor).
  92   static size_t _filler_array_max_size;
  93 
  94   GCHeapLog* _gc_heap_log;
  95 
  96   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
  97   bool _defer_initial_card_mark;
  98 
  99   MemRegion _reserved;
 100 
 101  protected:
 102   BarrierSet* _barrier_set;
 103   bool _is_gc_active;
 104 
 105   unsigned int _total_collections;          // ... started
 106   unsigned int _total_full_collections;     // ... started
 107   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 108   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 109 
 110   // Reason for current garbage collection.  Should be set to
 111   // a value reflecting no collection between collections.
 112   GCCause::Cause _gc_cause;
 113   GCCause::Cause _gc_lastcause;
 114   PerfStringVariable* _perf_gc_cause;
 115   PerfStringVariable* _perf_gc_lastcause;
 116 
 117   // Constructor
 118   CollectedHeap();
 119 
 120   // Do common initializations that must follow instance construction,
 121   // for example, those needing virtual calls.
 122   // This code could perhaps be moved into initialize() but would
 123   // be slightly more awkward because we want the latter to be a
 124   // pure virtual.
 125   void pre_initialize();
 126 
 127   // Create a new tlab. All TLAB allocations must go through this.
 128   virtual HeapWord* allocate_new_tlab(size_t size);
 129 
 130   // Accumulate statistics on all tlabs.
 131   virtual void accumulate_statistics_all_tlabs();
 132 
 133   // Reinitialize tlabs before resuming mutators.
 134   virtual void resize_all_tlabs();
 135 
 136   // Allocate from the current thread's TLAB, with broken-out slow path.
 137   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
 138   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
 139 
 140   // Allocate an uninitialized block of the given size, or returns NULL if
 141   // this is impossible.
 142   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
 143 
 144   // Like allocate_init, but the block returned by a successful allocation
 145   // is guaranteed initialized to zeros.
 146   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
 147 
 148   // Helper functions for (VM) allocation.
 149   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
 150   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
 151                                                             HeapWord* objPtr);
 152 
 153   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
 154 
 155   inline static void post_allocation_setup_array(KlassHandle klass,
 156                                                  HeapWord* obj, int length);
 157 
 158   // Clears an allocated object.
 159   inline static void init_obj(HeapWord* obj, size_t size);
 160 
 161   // Filler object utilities.
 162   static inline size_t filler_array_hdr_size();
 163   static inline size_t filler_array_min_size();
 164 
 165   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 166   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 167 
 168   // Fill with a single array; caller must ensure filler_array_min_size() <=
 169   // words <= filler_array_max_size().
 170   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 171 
 172   // Fill with a single object (either an int array or a java.lang.Object).
 173   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 174 
 175   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 176 
 177   // Verification functions
 178   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 179     PRODUCT_RETURN;
 180   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 181     PRODUCT_RETURN;
 182   debug_only(static void check_for_valid_allocation_state();)
 183 
 184  public:
 185   enum Name {
 186     GenCollectedHeap,
 187     ParallelScavengeHeap,
 188     G1CollectedHeap
 189   };
 190 
 191   static inline size_t filler_array_max_size() {
 192     return _filler_array_max_size;
 193   }
 194 
 195   virtual Name kind() const = 0;
 196 
 197   /**
 198    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
 199    * and JNI_OK on success.
 200    */
 201   virtual jint initialize() = 0;
 202 
 203   // In many heaps, there will be a need to perform some initialization activities
 204   // after the Universe is fully formed, but before general heap allocation is allowed.
 205   // This is the correct place to place such initialization methods.
 206   virtual void post_initialize();
 207 
 208   // Stop any onging concurrent work and prepare for exit.
 209   virtual void stop() {}
 210 
 211   void initialize_reserved_region(HeapWord *start, HeapWord *end);
 212   MemRegion reserved_region() const { return _reserved; }
 213   address base() const { return (address)reserved_region().start(); }
 214 
 215   virtual size_t capacity() const = 0;
 216   virtual size_t used() const = 0;
 217 
 218   // Return "true" if the part of the heap that allocates Java
 219   // objects has reached the maximal committed limit that it can
 220   // reach, without a garbage collection.
 221   virtual bool is_maximal_no_gc() const = 0;
 222 
 223   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 224   // memory that the vm could make available for storing 'normal' java objects.
 225   // This is based on the reserved address space, but should not include space
 226   // that the vm uses internally for bookkeeping or temporary storage
 227   // (e.g., in the case of the young gen, one of the survivor
 228   // spaces).
 229   virtual size_t max_capacity() const = 0;
 230 
 231   // Returns "TRUE" if "p" points into the reserved area of the heap.
 232   bool is_in_reserved(const void* p) const {
 233     return _reserved.contains(p);
 234   }
 235 
 236   bool is_in_reserved_or_null(const void* p) const {
 237     return p == NULL || is_in_reserved(p);
 238   }
 239 
 240   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 241   // This method can be expensive so avoid using it in performance critical
 242   // code.
 243   virtual bool is_in(const void* p) const = 0;
 244 
 245   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
 246 
 247   // Let's define some terms: a "closed" subset of a heap is one that
 248   //
 249   // 1) contains all currently-allocated objects, and
 250   //
 251   // 2) is closed under reference: no object in the closed subset
 252   //    references one outside the closed subset.
 253   //
 254   // Membership in a heap's closed subset is useful for assertions.
 255   // Clearly, the entire heap is a closed subset, so the default
 256   // implementation is to use "is_in_reserved".  But this may not be too
 257   // liberal to perform useful checking.  Also, the "is_in" predicate
 258   // defines a closed subset, but may be too expensive, since "is_in"
 259   // verifies that its argument points to an object head.  The
 260   // "closed_subset" method allows a heap to define an intermediate
 261   // predicate, allowing more precise checking than "is_in_reserved" at
 262   // lower cost than "is_in."
 263 
 264   // One important case is a heap composed of disjoint contiguous spaces,
 265   // such as the Garbage-First collector.  Such heaps have a convenient
 266   // closed subset consisting of the allocated portions of those
 267   // contiguous spaces.
 268 
 269   // Return "TRUE" iff the given pointer points into the heap's defined
 270   // closed subset (which defaults to the entire heap).
 271   virtual bool is_in_closed_subset(const void* p) const {
 272     return is_in_reserved(p);
 273   }
 274 
 275   bool is_in_closed_subset_or_null(const void* p) const {
 276     return p == NULL || is_in_closed_subset(p);
 277   }
 278 
 279   // An object is scavengable if its location may move during a scavenge.
 280   // (A scavenge is a GC which is not a full GC.)
 281   virtual bool is_scavengable(const void *p) = 0;
 282 
 283   void set_gc_cause(GCCause::Cause v) {
 284      if (UsePerfData) {
 285        _gc_lastcause = _gc_cause;
 286        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 287        _perf_gc_cause->set_value(GCCause::to_string(v));
 288      }
 289     _gc_cause = v;
 290   }
 291   GCCause::Cause gc_cause() { return _gc_cause; }
 292 
 293   // May be overridden to set additional parallelism.
 294   virtual void set_par_threads(uint t) { (void)t; };
 295 
 296   // General obj/array allocation facilities.
 297   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
 298   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
 299   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
 300 
 301   inline static void post_allocation_install_obj_klass(KlassHandle klass,
 302                                                        oop obj);
 303 
 304   // Raw memory allocation facilities
 305   // The obj and array allocate methods are covers for these methods.
 306   // mem_allocate() should never be
 307   // called to allocate TLABs, only individual objects.
 308   virtual HeapWord* mem_allocate(size_t size,
 309                                  bool* gc_overhead_limit_was_exceeded) = 0;
 310 
 311   // Utilities for turning raw memory into filler objects.
 312   //
 313   // min_fill_size() is the smallest region that can be filled.
 314   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 315   // multiple objects.  fill_with_object() is for regions known to be smaller
 316   // than the largest array of integers; it uses a single object to fill the
 317   // region and has slightly less overhead.
 318   static size_t min_fill_size() {
 319     return size_t(align_object_size(oopDesc::header_size()));
 320   }
 321 
 322   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 323 
 324   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 325   static void fill_with_object(MemRegion region, bool zap = true) {
 326     fill_with_object(region.start(), region.word_size(), zap);
 327   }
 328   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 329     fill_with_object(start, pointer_delta(end, start), zap);
 330   }
 331 
 332   // Return the address "addr" aligned by "alignment_in_bytes" if such
 333   // an address is below "end".  Return NULL otherwise.
 334   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
 335                                                    HeapWord* end,
 336                                                    unsigned short alignment_in_bytes);
 337 
 338   // Some heaps may offer a contiguous region for shared non-blocking
 339   // allocation, via inlined code (by exporting the address of the top and
 340   // end fields defining the extent of the contiguous allocation region.)
 341 
 342   // This function returns "true" iff the heap supports this kind of
 343   // allocation.  (Default is "no".)
 344   virtual bool supports_inline_contig_alloc() const {
 345     return false;
 346   }
 347   // These functions return the addresses of the fields that define the
 348   // boundaries of the contiguous allocation area.  (These fields should be
 349   // physically near to one another.)
 350   virtual HeapWord** top_addr() const {
 351     guarantee(false, "inline contiguous allocation not supported");
 352     return NULL;
 353   }
 354   virtual HeapWord** end_addr() const {
 355     guarantee(false, "inline contiguous allocation not supported");
 356     return NULL;
 357   }
 358 
 359   // Some heaps may be in an unparseable state at certain times between
 360   // collections. This may be necessary for efficient implementation of
 361   // certain allocation-related activities. Calling this function before
 362   // attempting to parse a heap ensures that the heap is in a parsable
 363   // state (provided other concurrent activity does not introduce
 364   // unparsability). It is normally expected, therefore, that this
 365   // method is invoked with the world stopped.
 366   // NOTE: if you override this method, make sure you call
 367   // super::ensure_parsability so that the non-generational
 368   // part of the work gets done. See implementation of
 369   // CollectedHeap::ensure_parsability and, for instance,
 370   // that of GenCollectedHeap::ensure_parsability().
 371   // The argument "retire_tlabs" controls whether existing TLABs
 372   // are merely filled or also retired, thus preventing further
 373   // allocation from them and necessitating allocation of new TLABs.
 374   virtual void ensure_parsability(bool retire_tlabs);
 375 
 376   // Section on thread-local allocation buffers (TLABs)
 377   // If the heap supports thread-local allocation buffers, it should override
 378   // the following methods:
 379   // Returns "true" iff the heap supports thread-local allocation buffers.
 380   // The default is "no".
 381   virtual bool supports_tlab_allocation() const = 0;
 382 
 383   // The amount of space available for thread-local allocation buffers.
 384   virtual size_t tlab_capacity(Thread *thr) const = 0;
 385 
 386   // The amount of used space for thread-local allocation buffers for the given thread.
 387   virtual size_t tlab_used(Thread *thr) const = 0;
 388 
 389   virtual size_t max_tlab_size() const;
 390 
 391   // An estimate of the maximum allocation that could be performed
 392   // for thread-local allocation buffers without triggering any
 393   // collection or expansion activity.
 394   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 395     guarantee(false, "thread-local allocation buffers not supported");
 396     return 0;
 397   }
 398 
 399   // Can a compiler initialize a new object without store barriers?
 400   // This permission only extends from the creation of a new object
 401   // via a TLAB up to the first subsequent safepoint. If such permission
 402   // is granted for this heap type, the compiler promises to call
 403   // defer_store_barrier() below on any slow path allocation of
 404   // a new object for which such initializing store barriers will
 405   // have been elided.
 406   virtual bool can_elide_tlab_store_barriers() const = 0;
 407 
 408   // If a compiler is eliding store barriers for TLAB-allocated objects,
 409   // there is probably a corresponding slow path which can produce
 410   // an object allocated anywhere.  The compiler's runtime support
 411   // promises to call this function on such a slow-path-allocated
 412   // object before performing initializations that have elided
 413   // store barriers. Returns new_obj, or maybe a safer copy thereof.
 414   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
 415 
 416   // Answers whether an initializing store to a new object currently
 417   // allocated at the given address doesn't need a store
 418   // barrier. Returns "true" if it doesn't need an initializing
 419   // store barrier; answers "false" if it does.
 420   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
 421 
 422   // If a compiler is eliding store barriers for TLAB-allocated objects,
 423   // we will be informed of a slow-path allocation by a call
 424   // to new_store_pre_barrier() above. Such a call precedes the
 425   // initialization of the object itself, and no post-store-barriers will
 426   // be issued. Some heap types require that the barrier strictly follows
 427   // the initializing stores. (This is currently implemented by deferring the
 428   // barrier until the next slow-path allocation or gc-related safepoint.)
 429   // This interface answers whether a particular heap type needs the card
 430   // mark to be thus strictly sequenced after the stores.
 431   virtual bool card_mark_must_follow_store() const = 0;
 432 
 433   // If the CollectedHeap was asked to defer a store barrier above,
 434   // this informs it to flush such a deferred store barrier to the
 435   // remembered set.
 436   virtual void flush_deferred_store_barrier(JavaThread* thread);
 437 
 438   // Perform a collection of the heap; intended for use in implementing
 439   // "System.gc".  This probably implies as full a collection as the
 440   // "CollectedHeap" supports.
 441   virtual void collect(GCCause::Cause cause) = 0;
 442 
 443   // Perform a full collection
 444   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 445 
 446   // This interface assumes that it's being called by the
 447   // vm thread. It collects the heap assuming that the
 448   // heap lock is already held and that we are executing in
 449   // the context of the vm thread.
 450   virtual void collect_as_vm_thread(GCCause::Cause cause);
 451 
 452   // Returns the barrier set for this heap
 453   BarrierSet* barrier_set() { return _barrier_set; }
 454   void set_barrier_set(BarrierSet* barrier_set);
 455 
 456   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 457   // that it should answer "false" for the concurrent part of a concurrent
 458   // collector -- dld).
 459   bool is_gc_active() const { return _is_gc_active; }
 460 
 461   // Total number of GC collections (started)
 462   unsigned int total_collections() const { return _total_collections; }
 463   unsigned int total_full_collections() const { return _total_full_collections;}
 464 
 465   // Increment total number of GC collections (started)
 466   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 467   void increment_total_collections(bool full = false) {
 468     _total_collections++;
 469     if (full) {
 470       increment_total_full_collections();
 471     }
 472   }
 473 
 474   void increment_total_full_collections() { _total_full_collections++; }
 475 
 476   // Return the AdaptiveSizePolicy for the heap.
 477   virtual AdaptiveSizePolicy* size_policy() = 0;
 478 
 479   // Return the CollectorPolicy for the heap
 480   virtual CollectorPolicy* collector_policy() const = 0;
 481 
 482   // Iterate over all objects, calling "cl.do_object" on each.
 483   virtual void object_iterate(ObjectClosure* cl) = 0;
 484 
 485   // Similar to object_iterate() except iterates only
 486   // over live objects.
 487   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 488 
 489   // NOTE! There is no requirement that a collector implement these
 490   // functions.
 491   //
 492   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 493   // each address in the (reserved) heap is a member of exactly
 494   // one block.  The defining characteristic of a block is that it is
 495   // possible to find its size, and thus to progress forward to the next
 496   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 497   // represent Java objects, or they might be free blocks in a
 498   // free-list-based heap (or subheap), as long as the two kinds are
 499   // distinguishable and the size of each is determinable.
 500 
 501   // Returns the address of the start of the "block" that contains the
 502   // address "addr".  We say "blocks" instead of "object" since some heaps
 503   // may not pack objects densely; a chunk may either be an object or a
 504   // non-object.
 505   virtual HeapWord* block_start(const void* addr) const = 0;
 506 
 507   // Requires "addr" to be the start of a chunk, and returns its size.
 508   // "addr + size" is required to be the start of a new chunk, or the end
 509   // of the active area of the heap.
 510   virtual size_t block_size(const HeapWord* addr) const = 0;
 511 
 512   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 513   // the block is an object.
 514   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 515 
 516   // Returns the longest time (in ms) that has elapsed since the last
 517   // time that any part of the heap was examined by a garbage collection.
 518   virtual jlong millis_since_last_gc() = 0;
 519 
 520   // Perform any cleanup actions necessary before allowing a verification.
 521   virtual void prepare_for_verify() = 0;
 522 
 523   // Generate any dumps preceding or following a full gc
 524   void pre_full_gc_dump(GCTimer* timer);
 525   void post_full_gc_dump(GCTimer* timer);
 526 
 527   VirtualSpaceSummary create_heap_space_summary();
 528   GCHeapSummary create_heap_summary();
 529 
 530   MetaspaceSummary create_metaspace_summary();
 531 
 532   // Print heap information on the given outputStream.
 533   virtual void print_on(outputStream* st) const = 0;
 534   // The default behavior is to call print_on() on tty.
 535   virtual void print() const {
 536     print_on(tty);
 537   }
 538   // Print more detailed heap information on the given
 539   // outputStream. The default behavior is to call print_on(). It is
 540   // up to each subclass to override it and add any additional output
 541   // it needs.
 542   virtual void print_extended_on(outputStream* st) const {
 543     print_on(st);
 544   }
 545 
 546   virtual void print_on_error(outputStream* st) const;
 547 
 548   // Print all GC threads (other than the VM thread)
 549   // used by this heap.
 550   virtual void print_gc_threads_on(outputStream* st) const = 0;
 551   // The default behavior is to call print_gc_threads_on() on tty.
 552   void print_gc_threads() {
 553     print_gc_threads_on(tty);
 554   }
 555   // Iterator for all GC threads (other than VM thread)
 556   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 557 
 558   // Print any relevant tracing info that flags imply.
 559   // Default implementation does nothing.
 560   virtual void print_tracing_info() const = 0;
 561 
 562   void print_heap_before_gc();
 563   void print_heap_after_gc();
 564 
 565   // Registering and unregistering an nmethod (compiled code) with the heap.
 566   // Override with specific mechanism for each specialized heap type.
 567   virtual void register_nmethod(nmethod* nm);
 568   virtual void unregister_nmethod(nmethod* nm);
 569 
 570   void trace_heap_before_gc(const GCTracer* gc_tracer);
 571   void trace_heap_after_gc(const GCTracer* gc_tracer);
 572 
 573   // Heap verification
 574   virtual void verify(bool silent, VerifyOption option) = 0;
 575 
 576   // Non product verification and debugging.
 577 #ifndef PRODUCT
 578   // Support for PromotionFailureALot.  Return true if it's time to cause a
 579   // promotion failure.  The no-argument version uses
 580   // this->_promotion_failure_alot_count as the counter.
 581   inline bool promotion_should_fail(volatile size_t* count);
 582   inline bool promotion_should_fail();
 583 
 584   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 585   // GC in which promotion failure occurred.
 586   inline void reset_promotion_should_fail(volatile size_t* count);
 587   inline void reset_promotion_should_fail();
 588 #endif  // #ifndef PRODUCT
 589 
 590 #ifdef ASSERT
 591   static int fired_fake_oom() {
 592     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 593   }
 594 #endif
 595 
 596  public:
 597   // Copy the current allocation context statistics for the specified contexts.
 598   // For each context in contexts, set the corresponding entries in the totals
 599   // and accuracy arrays to the current values held by the statistics.  Each
 600   // array should be of length len.
 601   // Returns true if there are more stats available.
 602   virtual bool copy_allocation_context_stats(const jint* contexts,
 603                                              jlong* totals,
 604                                              jbyte* accuracy,
 605                                              jint len) {
 606     return false;
 607   }
 608 
 609   /////////////// Unit tests ///////////////
 610 
 611   NOT_PRODUCT(static void test_is_in();)
 612 };
 613 
 614 // Class to set and reset the GC cause for a CollectedHeap.
 615 
 616 class GCCauseSetter : StackObj {
 617   CollectedHeap* _heap;
 618   GCCause::Cause _previous_cause;
 619  public:
 620   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 621     assert(SafepointSynchronize::is_at_safepoint(),
 622            "This method manipulates heap state without locking");
 623     _heap = heap;
 624     _previous_cause = _heap->gc_cause();
 625     _heap->set_gc_cause(cause);
 626   }
 627 
 628   ~GCCauseSetter() {
 629     assert(SafepointSynchronize::is_at_safepoint(),
 630           "This method manipulates heap state without locking");
 631     _heap->set_gc_cause(_previous_cause);
 632   }
 633 };
 634 
 635 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP