rev 52072 : 8211955: GC abstraction for LAB reserve

   1 /*
   2  * Copyright (c) 2001, 2018, 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.
  22  *
  23  */
  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 "services/memoryUsage.hpp"
  35 #include "utilities/debug.hpp"
  36 #include "utilities/events.hpp"
  37 #include "utilities/formatBuffer.hpp"
  38 #include "utilities/growableArray.hpp"
  39 
  40 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
  41 // is an abstract class: there may be many different kinds of heaps.  This
  42 // class defines the functions that a heap must implement, and contains
  43 // infrastructure common to all heaps.
  44 
  45 class AdaptiveSizePolicy;
  46 class BarrierSet;
  47 class CollectorPolicy;
  48 class GCHeapSummary;
  49 class GCTimer;
  50 class GCTracer;
  51 class GCMemoryManager;
  52 class MemoryPool;
  53 class MetaspaceSummary;
  54 class SoftRefPolicy;
  55 class Thread;
  56 class ThreadClosure;
  57 class VirtualSpaceSummary;
  58 class WorkGang;
  59 class nmethod;
  60 
  61 class GCMessage : public FormatBuffer<1024> {
  62  public:
  63   bool is_before;
  64 
  65  public:
  66   GCMessage() {}
  67 };
  68 
  69 class CollectedHeap;
  70 
  71 class GCHeapLog : public EventLogBase<GCMessage> {
  72  private:
  73   void log_heap(CollectedHeap* heap, bool before);
  74 
  75  public:
  76   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
  77 
  78   void log_heap_before(CollectedHeap* heap) {
  79     log_heap(heap, true);
  80   }
  81   void log_heap_after(CollectedHeap* heap) {
  82     log_heap(heap, false);
  83   }
  84 };
  85 
  86 //
  87 // CollectedHeap
  88 //   GenCollectedHeap
  89 //     SerialHeap
  90 //     CMSHeap
  91 //   G1CollectedHeap
  92 //   ParallelScavengeHeap
  93 //   ZCollectedHeap
  94 //
  95 class CollectedHeap : public CHeapObj<mtInternal> {
  96   friend class VMStructs;
  97   friend class JVMCIVMStructs;
  98   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  99   friend class MemAllocator;
 100 
 101  private:
 102 #ifdef ASSERT
 103   static int       _fire_out_of_memory_count;
 104 #endif
 105 
 106   GCHeapLog* _gc_heap_log;
 107 
 108   MemRegion _reserved;
 109 
 110  protected:
 111   bool _is_gc_active;
 112 
 113   // Used for filler objects (static, but initialized in ctor).
 114   static size_t _filler_array_max_size;
 115 
 116   unsigned int _total_collections;          // ... started
 117   unsigned int _total_full_collections;     // ... started
 118   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 119   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 120 
 121   // Reason for current garbage collection.  Should be set to
 122   // a value reflecting no collection between collections.
 123   GCCause::Cause _gc_cause;
 124   GCCause::Cause _gc_lastcause;
 125   PerfStringVariable* _perf_gc_cause;
 126   PerfStringVariable* _perf_gc_lastcause;
 127 
 128   // Constructor
 129   CollectedHeap();
 130 
 131   // Create a new tlab. All TLAB allocations must go through this.
 132   // To allow more flexible TLAB allocations min_size specifies
 133   // the minimum size needed, while requested_size is the requested
 134   // size based on ergonomics. The actually allocated size will be
 135   // returned in actual_size.
 136   virtual HeapWord* allocate_new_tlab(size_t min_size,
 137                                       size_t requested_size,
 138                                       size_t* actual_size);
 139 
 140   // Reinitialize tlabs before resuming mutators.
 141   virtual void resize_all_tlabs();
 142 
 143   // Raw memory allocation facilities
 144   // The obj and array allocate methods are covers for these methods.
 145   // mem_allocate() should never be
 146   // called to allocate TLABs, only individual objects.
 147   virtual HeapWord* mem_allocate(size_t size,
 148                                  bool* gc_overhead_limit_was_exceeded) = 0;
 149 
 150   // Filler object utilities.
 151   static inline size_t filler_array_hdr_size();
 152   static inline size_t filler_array_min_size();
 153 
 154   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 155   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 156 
 157   // Fill with a single array; caller must ensure filler_array_min_size() <=
 158   // words <= filler_array_max_size().
 159   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 160 
 161   // Fill with a single object (either an int array or a java.lang.Object).
 162   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 163 
 164   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 165 
 166   // Verification functions
 167   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 168     PRODUCT_RETURN;
 169   debug_only(static void check_for_valid_allocation_state();)
 170 
 171  public:
 172   enum Name {
 173     None,
 174     Serial,
 175     Parallel,
 176     CMS,
 177     G1,
 178     Epsilon,
 179     Z
 180   };
 181 
 182   static inline size_t filler_array_max_size() {
 183     return _filler_array_max_size;
 184   }
 185 
 186   virtual Name kind() const = 0;
 187 
 188   virtual const char* name() const = 0;
 189 
 190   /**
 191    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
 192    * and JNI_OK on success.
 193    */
 194   virtual jint initialize() = 0;
 195 
 196   // In many heaps, there will be a need to perform some initialization activities
 197   // after the Universe is fully formed, but before general heap allocation is allowed.
 198   // This is the correct place to place such initialization methods.
 199   virtual void post_initialize();
 200 
 201   // Stop any onging concurrent work and prepare for exit.
 202   virtual void stop() {}
 203 
 204   // Stop and resume concurrent GC threads interfering with safepoint operations
 205   virtual void safepoint_synchronize_begin() {}
 206   virtual void safepoint_synchronize_end() {}
 207 
 208   void initialize_reserved_region(HeapWord *start, HeapWord *end);
 209   MemRegion reserved_region() const { return _reserved; }
 210   address base() const { return (address)reserved_region().start(); }
 211 
 212   virtual size_t capacity() const = 0;
 213   virtual size_t used() const = 0;
 214 
 215   // Return "true" if the part of the heap that allocates Java
 216   // objects has reached the maximal committed limit that it can
 217   // reach, without a garbage collection.
 218   virtual bool is_maximal_no_gc() const = 0;
 219 
 220   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 221   // memory that the vm could make available for storing 'normal' java objects.
 222   // This is based on the reserved address space, but should not include space
 223   // that the vm uses internally for bookkeeping or temporary storage
 224   // (e.g., in the case of the young gen, one of the survivor
 225   // spaces).
 226   virtual size_t max_capacity() const = 0;
 227 
 228   // Returns "TRUE" if "p" points into the reserved area of the heap.
 229   bool is_in_reserved(const void* p) const {
 230     return _reserved.contains(p);
 231   }
 232 
 233   bool is_in_reserved_or_null(const void* p) const {
 234     return p == NULL || is_in_reserved(p);
 235   }
 236 
 237   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 238   // This method can be expensive so avoid using it in performance critical
 239   // code.
 240   virtual bool is_in(const void* p) const = 0;
 241 
 242   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
 243 
 244   // Let's define some terms: a "closed" subset of a heap is one that
 245   //
 246   // 1) contains all currently-allocated objects, and
 247   //
 248   // 2) is closed under reference: no object in the closed subset
 249   //    references one outside the closed subset.
 250   //
 251   // Membership in a heap's closed subset is useful for assertions.
 252   // Clearly, the entire heap is a closed subset, so the default
 253   // implementation is to use "is_in_reserved".  But this may not be too
 254   // liberal to perform useful checking.  Also, the "is_in" predicate
 255   // defines a closed subset, but may be too expensive, since "is_in"
 256   // verifies that its argument points to an object head.  The
 257   // "closed_subset" method allows a heap to define an intermediate
 258   // predicate, allowing more precise checking than "is_in_reserved" at
 259   // lower cost than "is_in."
 260 
 261   // One important case is a heap composed of disjoint contiguous spaces,
 262   // such as the Garbage-First collector.  Such heaps have a convenient
 263   // closed subset consisting of the allocated portions of those
 264   // contiguous spaces.
 265 
 266   // Return "TRUE" iff the given pointer points into the heap's defined
 267   // closed subset (which defaults to the entire heap).
 268   virtual bool is_in_closed_subset(const void* p) const {
 269     return is_in_reserved(p);
 270   }
 271 
 272   bool is_in_closed_subset_or_null(const void* p) const {
 273     return p == NULL || is_in_closed_subset(p);
 274   }
 275 
 276   void set_gc_cause(GCCause::Cause v) {
 277      if (UsePerfData) {
 278        _gc_lastcause = _gc_cause;
 279        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 280        _perf_gc_cause->set_value(GCCause::to_string(v));
 281      }
 282     _gc_cause = v;
 283   }
 284   GCCause::Cause gc_cause() { return _gc_cause; }
 285 
 286   virtual oop obj_allocate(Klass* klass, int size, TRAPS);
 287   virtual oop array_allocate(Klass* klass, int size, int length, bool do_zero, TRAPS);
 288   virtual oop class_allocate(Klass* klass, int size, TRAPS);
 289 
 290   // Utilities for turning raw memory into filler objects.
 291   //
 292   // min_fill_size() is the smallest region that can be filled.
 293   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 294   // multiple objects.  fill_with_object() is for regions known to be smaller
 295   // than the largest array of integers; it uses a single object to fill the
 296   // region and has slightly less overhead.
 297   static size_t min_fill_size() {
 298     return size_t(align_object_size(oopDesc::header_size()));
 299   }
 300 
 301   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 302 
 303   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 304   static void fill_with_object(MemRegion region, bool zap = true) {
 305     fill_with_object(region.start(), region.word_size(), zap);
 306   }
 307   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 308     fill_with_object(start, pointer_delta(end, start), zap);
 309   }
 310 
 311   virtual void fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap);
 312   size_t min_dummy_object_size() const;
 313   size_t tlab_alloc_reserve() const;
 314 
 315   // Return the address "addr" aligned by "alignment_in_bytes" if such
 316   // an address is below "end".  Return NULL otherwise.
 317   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
 318                                                    HeapWord* end,
 319                                                    unsigned short alignment_in_bytes);
 320 
 321   // Some heaps may offer a contiguous region for shared non-blocking
 322   // allocation, via inlined code (by exporting the address of the top and
 323   // end fields defining the extent of the contiguous allocation region.)
 324 
 325   // This function returns "true" iff the heap supports this kind of
 326   // allocation.  (Default is "no".)
 327   virtual bool supports_inline_contig_alloc() const {
 328     return false;
 329   }
 330   // These functions return the addresses of the fields that define the
 331   // boundaries of the contiguous allocation area.  (These fields should be
 332   // physically near to one another.)
 333   virtual HeapWord* volatile* top_addr() const {
 334     guarantee(false, "inline contiguous allocation not supported");
 335     return NULL;
 336   }
 337   virtual HeapWord** end_addr() const {
 338     guarantee(false, "inline contiguous allocation not supported");
 339     return NULL;
 340   }
 341 
 342   // Some heaps may be in an unparseable state at certain times between
 343   // collections. This may be necessary for efficient implementation of
 344   // certain allocation-related activities. Calling this function before
 345   // attempting to parse a heap ensures that the heap is in a parsable
 346   // state (provided other concurrent activity does not introduce
 347   // unparsability). It is normally expected, therefore, that this
 348   // method is invoked with the world stopped.
 349   // NOTE: if you override this method, make sure you call
 350   // super::ensure_parsability so that the non-generational
 351   // part of the work gets done. See implementation of
 352   // CollectedHeap::ensure_parsability and, for instance,
 353   // that of GenCollectedHeap::ensure_parsability().
 354   // The argument "retire_tlabs" controls whether existing TLABs
 355   // are merely filled or also retired, thus preventing further
 356   // allocation from them and necessitating allocation of new TLABs.
 357   virtual void ensure_parsability(bool retire_tlabs);
 358 
 359   // Section on thread-local allocation buffers (TLABs)
 360   // If the heap supports thread-local allocation buffers, it should override
 361   // the following methods:
 362   // Returns "true" iff the heap supports thread-local allocation buffers.
 363   // The default is "no".
 364   virtual bool supports_tlab_allocation() const = 0;
 365 
 366   // The amount of space available for thread-local allocation buffers.
 367   virtual size_t tlab_capacity(Thread *thr) const = 0;
 368 
 369   // The amount of used space for thread-local allocation buffers for the given thread.
 370   virtual size_t tlab_used(Thread *thr) const = 0;
 371 
 372   virtual size_t max_tlab_size() const;
 373 
 374   // An estimate of the maximum allocation that could be performed
 375   // for thread-local allocation buffers without triggering any
 376   // collection or expansion activity.
 377   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 378     guarantee(false, "thread-local allocation buffers not supported");
 379     return 0;
 380   }
 381 
 382   // Perform a collection of the heap; intended for use in implementing
 383   // "System.gc".  This probably implies as full a collection as the
 384   // "CollectedHeap" supports.
 385   virtual void collect(GCCause::Cause cause) = 0;
 386 
 387   // Perform a full collection
 388   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 389 
 390   // This interface assumes that it's being called by the
 391   // vm thread. It collects the heap assuming that the
 392   // heap lock is already held and that we are executing in
 393   // the context of the vm thread.
 394   virtual void collect_as_vm_thread(GCCause::Cause cause);
 395 
 396   virtual MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 397                                                        size_t size,
 398                                                        Metaspace::MetadataType mdtype);
 399 
 400   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 401   // that it should answer "false" for the concurrent part of a concurrent
 402   // collector -- dld).
 403   bool is_gc_active() const { return _is_gc_active; }
 404 
 405   // Total number of GC collections (started)
 406   unsigned int total_collections() const { return _total_collections; }
 407   unsigned int total_full_collections() const { return _total_full_collections;}
 408 
 409   // Increment total number of GC collections (started)
 410   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 411   void increment_total_collections(bool full = false) {
 412     _total_collections++;
 413     if (full) {
 414       increment_total_full_collections();
 415     }
 416   }
 417 
 418   void increment_total_full_collections() { _total_full_collections++; }
 419 
 420   // Return the CollectorPolicy for the heap
 421   virtual CollectorPolicy* collector_policy() const = 0;
 422 
 423   // Return the SoftRefPolicy for the heap;
 424   virtual SoftRefPolicy* soft_ref_policy() = 0;
 425 
 426   virtual MemoryUsage memory_usage();
 427   virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
 428   virtual GrowableArray<MemoryPool*> memory_pools() = 0;
 429 
 430   // Iterate over all objects, calling "cl.do_object" on each.
 431   virtual void object_iterate(ObjectClosure* cl) = 0;
 432 
 433   // Similar to object_iterate() except iterates only
 434   // over live objects.
 435   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 436 
 437   // NOTE! There is no requirement that a collector implement these
 438   // functions.
 439   //
 440   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 441   // each address in the (reserved) heap is a member of exactly
 442   // one block.  The defining characteristic of a block is that it is
 443   // possible to find its size, and thus to progress forward to the next
 444   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 445   // represent Java objects, or they might be free blocks in a
 446   // free-list-based heap (or subheap), as long as the two kinds are
 447   // distinguishable and the size of each is determinable.
 448 
 449   // Returns the address of the start of the "block" that contains the
 450   // address "addr".  We say "blocks" instead of "object" since some heaps
 451   // may not pack objects densely; a chunk may either be an object or a
 452   // non-object.
 453   virtual HeapWord* block_start(const void* addr) const = 0;
 454 
 455   // Requires "addr" to be the start of a chunk, and returns its size.
 456   // "addr + size" is required to be the start of a new chunk, or the end
 457   // of the active area of the heap.
 458   virtual size_t block_size(const HeapWord* addr) const = 0;
 459 
 460   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 461   // the block is an object.
 462   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 463 
 464   // Returns the longest time (in ms) that has elapsed since the last
 465   // time that any part of the heap was examined by a garbage collection.
 466   virtual jlong millis_since_last_gc() = 0;
 467 
 468   // Perform any cleanup actions necessary before allowing a verification.
 469   virtual void prepare_for_verify() = 0;
 470 
 471   // Generate any dumps preceding or following a full gc
 472  private:
 473   void full_gc_dump(GCTimer* timer, bool before);
 474 
 475   virtual void initialize_serviceability() = 0;
 476 
 477  public:
 478   void pre_full_gc_dump(GCTimer* timer);
 479   void post_full_gc_dump(GCTimer* timer);
 480 
 481   virtual VirtualSpaceSummary create_heap_space_summary();
 482   GCHeapSummary create_heap_summary();
 483 
 484   MetaspaceSummary create_metaspace_summary();
 485 
 486   // Print heap information on the given outputStream.
 487   virtual void print_on(outputStream* st) const = 0;
 488   // The default behavior is to call print_on() on tty.
 489   virtual void print() const {
 490     print_on(tty);
 491   }
 492   // Print more detailed heap information on the given
 493   // outputStream. The default behavior is to call print_on(). It is
 494   // up to each subclass to override it and add any additional output
 495   // it needs.
 496   virtual void print_extended_on(outputStream* st) const {
 497     print_on(st);
 498   }
 499 
 500   virtual void print_on_error(outputStream* st) const;
 501 
 502   // Print all GC threads (other than the VM thread)
 503   // used by this heap.
 504   virtual void print_gc_threads_on(outputStream* st) const = 0;
 505   // The default behavior is to call print_gc_threads_on() on tty.
 506   void print_gc_threads() {
 507     print_gc_threads_on(tty);
 508   }
 509   // Iterator for all GC threads (other than VM thread)
 510   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 511 
 512   // Print any relevant tracing info that flags imply.
 513   // Default implementation does nothing.
 514   virtual void print_tracing_info() const = 0;
 515 
 516   void print_heap_before_gc();
 517   void print_heap_after_gc();
 518 
 519   // An object is scavengable if its location may move during a scavenge.
 520   // (A scavenge is a GC which is not a full GC.)
 521   virtual bool is_scavengable(oop obj) = 0;
 522   // Registering and unregistering an nmethod (compiled code) with the heap.
 523   // Override with specific mechanism for each specialized heap type.
 524   virtual void register_nmethod(nmethod* nm) {}
 525   virtual void unregister_nmethod(nmethod* nm) {}
 526   virtual void verify_nmethod(nmethod* nmethod) {}
 527 
 528   void trace_heap_before_gc(const GCTracer* gc_tracer);
 529   void trace_heap_after_gc(const GCTracer* gc_tracer);
 530 
 531   // Heap verification
 532   virtual void verify(VerifyOption option) = 0;
 533 
 534   // Return true if concurrent phase control (via
 535   // request_concurrent_phase_control) is supported by this collector.
 536   // The default implementation returns false.
 537   virtual bool supports_concurrent_phase_control() const;
 538 
 539   // Return a NULL terminated array of concurrent phase names provided
 540   // by this collector.  Supports Whitebox testing.  These are the
 541   // names recognized by request_concurrent_phase(). The default
 542   // implementation returns an array of one NULL element.
 543   virtual const char* const* concurrent_phases() const;
 544 
 545   // Request the collector enter the indicated concurrent phase, and
 546   // wait until it does so.  Supports WhiteBox testing.  Only one
 547   // request may be active at a time.  Phases are designated by name;
 548   // the set of names and their meaning is GC-specific.  Once the
 549   // requested phase has been reached, the collector will attempt to
 550   // avoid transitioning to a new phase until a new request is made.
 551   // [Note: A collector might not be able to remain in a given phase.
 552   // For example, a full collection might cancel an in-progress
 553   // concurrent collection.]
 554   //
 555   // Returns true when the phase is reached.  Returns false for an
 556   // unknown phase.  The default implementation returns false.
 557   virtual bool request_concurrent_phase(const char* phase);
 558 
 559   // Provides a thread pool to SafepointSynchronize to use
 560   // for parallel safepoint cleanup.
 561   // GCs that use a GC worker thread pool may want to share
 562   // it for use during safepoint cleanup. This is only possible
 563   // if the GC can pause and resume concurrent work (e.g. G1
 564   // concurrent marking) for an intermittent non-GC safepoint.
 565   // If this method returns NULL, SafepointSynchronize will
 566   // perform cleanup tasks serially in the VMThread.
 567   virtual WorkGang* get_safepoint_workers() { return NULL; }
 568 
 569   // Support for object pinning. This is used by JNI Get*Critical()
 570   // and Release*Critical() family of functions. If supported, the GC
 571   // must guarantee that pinned objects never move.
 572   virtual bool supports_object_pinning() const;
 573   virtual oop pin_object(JavaThread* thread, oop obj);
 574   virtual void unpin_object(JavaThread* thread, oop obj);
 575 
 576   // Deduplicate the string, iff the GC supports string deduplication.
 577   virtual void deduplicate_string(oop str);
 578 
 579   virtual bool is_oop(oop object) const;
 580 
 581   virtual size_t cell_size(size_t obj_size) const { return obj_size; }
 582 
 583   // Non product verification and debugging.
 584 #ifndef PRODUCT
 585   // Support for PromotionFailureALot.  Return true if it's time to cause a
 586   // promotion failure.  The no-argument version uses
 587   // this->_promotion_failure_alot_count as the counter.
 588   bool promotion_should_fail(volatile size_t* count);
 589   bool promotion_should_fail();
 590 
 591   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 592   // GC in which promotion failure occurred.
 593   void reset_promotion_should_fail(volatile size_t* count);
 594   void reset_promotion_should_fail();
 595 #endif  // #ifndef PRODUCT
 596 
 597 #ifdef ASSERT
 598   static int fired_fake_oom() {
 599     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 600   }
 601 #endif
 602 };
 603 
 604 // Class to set and reset the GC cause for a CollectedHeap.
 605 
 606 class GCCauseSetter : StackObj {
 607   CollectedHeap* _heap;
 608   GCCause::Cause _previous_cause;
 609  public:
 610   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 611     _heap = heap;
 612     _previous_cause = _heap->gc_cause();
 613     _heap->set_gc_cause(cause);
 614   }
 615 
 616   ~GCCauseSetter() {
 617     _heap->set_gc_cause(_previous_cause);
 618   }
 619 };
 620 
 621 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
--- EOF ---