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 CollectedHeap;
  62 
  63 class GCHeapLog : public EventLogBase<GCMessage> {
  64  private:
  65   void log_heap(CollectedHeap* heap, bool before);
  66 
  67  public:
  68   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
  69 
  70   void log_heap_before(CollectedHeap* heap) {
  71     log_heap(heap, true);
  72   }
  73   void log_heap_after(CollectedHeap* heap) {
  74     log_heap(heap, false);
  75   }
  76 };
  77 
  78 //
  79 // CollectedHeap
  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  private:
  89 #ifdef ASSERT
  90   static int       _fire_out_of_memory_count;
  91 #endif
  92 
  93   GCHeapLog* _gc_heap_log;
  94 
  95   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
  96   // or INCLUDE_JVMCI 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   // Used for filler objects (static, but initialized in ctor).
 106   static size_t _filler_array_max_size;
 107 
 108   unsigned int _total_collections;          // ... started
 109   unsigned int _total_full_collections;     // ... started
 110   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 111   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 112 
 113   // Reason for current garbage collection.  Should be set to
 114   // a value reflecting no collection between collections.
 115   GCCause::Cause _gc_cause;
 116   GCCause::Cause _gc_lastcause;
 117   PerfStringVariable* _perf_gc_cause;
 118   PerfStringVariable* _perf_gc_lastcause;
 119 
 120   // Constructor
 121   CollectedHeap();
 122 
 123   // Do common initializations that must follow instance construction,
 124   // for example, those needing virtual calls.
 125   // This code could perhaps be moved into initialize() but would
 126   // be slightly more awkward because we want the latter to be a
 127   // pure virtual.
 128   void pre_initialize();
 129 
 130   // Create a new tlab. All TLAB allocations must go through this.
 131   virtual HeapWord* allocate_new_tlab(size_t size);
 132 
 133   // Accumulate statistics on all tlabs.
 134   virtual void accumulate_statistics_all_tlabs();
 135 
 136   // Reinitialize tlabs before resuming mutators.
 137   virtual void resize_all_tlabs();
 138 
 139   // Allocate from the current thread's TLAB, with broken-out slow path.
 140   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
 141   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
 142 
 143   // Allocate an uninitialized block of the given size, or returns NULL if
 144   // this is impossible.
 145   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
 146 
 147   // Like allocate_init, but the block returned by a successful allocation
 148   // is guaranteed initialized to zeros.
 149   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
 150 
 151   // Helper functions for (VM) allocation.
 152   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
 153   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
 154                                                             HeapWord* objPtr);
 155 
 156   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
 157 
 158   inline static void post_allocation_setup_array(KlassHandle klass,
 159                                                  HeapWord* obj, int length);
 160 
 161   // Clears an allocated object.
 162   inline static void init_obj(HeapWord* obj, size_t size);
 163 
 164   // Filler object utilities.
 165   static inline size_t filler_array_hdr_size();
 166   static inline size_t filler_array_min_size();
 167 
 168   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 169   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 170 
 171   // Fill with a single array; caller must ensure filler_array_min_size() <=
 172   // words <= filler_array_max_size().
 173   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 174 
 175   // Fill with a single object (either an int array or a java.lang.Object).
 176   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 177 
 178   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 179 
 180   // Verification functions
 181   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 182     PRODUCT_RETURN;
 183   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 184     PRODUCT_RETURN;
 185   debug_only(static void check_for_valid_allocation_state();)
 186 
 187  public:
 188   enum Name {
 189     GenCollectedHeap,
 190     ParallelScavengeHeap,
 191     G1CollectedHeap
 192   };
 193 
 194   static inline size_t filler_array_max_size() {
 195     return _filler_array_max_size;
 196   }
 197 
 198   virtual Name kind() const = 0;
 199 
 200   virtual const char* name() const = 0;
 201 
 202   /**
 203    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
 204    * and JNI_OK on success.
 205    */
 206   virtual jint initialize() = 0;
 207 
 208   // In many heaps, there will be a need to perform some initialization activities
 209   // after the Universe is fully formed, but before general heap allocation is allowed.
 210   // This is the correct place to place such initialization methods.
 211   virtual void post_initialize();
 212 
 213   // Stop any onging concurrent work and prepare for exit.
 214   virtual void stop() {}
 215 
 216   void initialize_reserved_region(HeapWord *start, HeapWord *end);
 217   MemRegion reserved_region() const { return _reserved; }
 218   address base() const { return (address)reserved_region().start(); }
 219 
 220   virtual size_t capacity() const = 0;
 221   virtual size_t used() const = 0;
 222 
 223   // Return "true" if the part of the heap that allocates Java
 224   // objects has reached the maximal committed limit that it can
 225   // reach, without a garbage collection.
 226   virtual bool is_maximal_no_gc() const = 0;
 227 
 228   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 229   // memory that the vm could make available for storing 'normal' java objects.
 230   // This is based on the reserved address space, but should not include space
 231   // that the vm uses internally for bookkeeping or temporary storage
 232   // (e.g., in the case of the young gen, one of the survivor
 233   // spaces).
 234   virtual size_t max_capacity() const = 0;
 235 
 236   // Returns "TRUE" if "p" points into the reserved area of the heap.
 237   bool is_in_reserved(const void* p) const {
 238     return _reserved.contains(p);
 239   }
 240 
 241   bool is_in_reserved_or_null(const void* p) const {
 242     return p == NULL || is_in_reserved(p);
 243   }
 244 
 245   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 246   // This method can be expensive so avoid using it in performance critical
 247   // code.
 248   virtual bool is_in(const void* p) const = 0;
 249 
 250   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
 251 
 252   // Let's define some terms: a "closed" subset of a heap is one that
 253   //
 254   // 1) contains all currently-allocated objects, and
 255   //
 256   // 2) is closed under reference: no object in the closed subset
 257   //    references one outside the closed subset.
 258   //
 259   // Membership in a heap's closed subset is useful for assertions.
 260   // Clearly, the entire heap is a closed subset, so the default
 261   // implementation is to use "is_in_reserved".  But this may not be too
 262   // liberal to perform useful checking.  Also, the "is_in" predicate
 263   // defines a closed subset, but may be too expensive, since "is_in"
 264   // verifies that its argument points to an object head.  The
 265   // "closed_subset" method allows a heap to define an intermediate
 266   // predicate, allowing more precise checking than "is_in_reserved" at
 267   // lower cost than "is_in."
 268 
 269   // One important case is a heap composed of disjoint contiguous spaces,
 270   // such as the Garbage-First collector.  Such heaps have a convenient
 271   // closed subset consisting of the allocated portions of those
 272   // contiguous spaces.
 273 
 274   // Return "TRUE" iff the given pointer points into the heap's defined
 275   // closed subset (which defaults to the entire heap).
 276   virtual bool is_in_closed_subset(const void* p) const {
 277     return is_in_reserved(p);
 278   }
 279 
 280   bool is_in_closed_subset_or_null(const void* p) const {
 281     return p == NULL || is_in_closed_subset(p);
 282   }
 283 
 284   // An object is scavengable if its location may move during a scavenge.
 285   // (A scavenge is a GC which is not a full GC.)
 286   virtual bool is_scavengable(const void *p) = 0;
 287 
 288   void set_gc_cause(GCCause::Cause v) {
 289      if (UsePerfData) {
 290        _gc_lastcause = _gc_cause;
 291        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 292        _perf_gc_cause->set_value(GCCause::to_string(v));
 293      }
 294     _gc_cause = v;
 295   }
 296   GCCause::Cause gc_cause() { return _gc_cause; }
 297 
 298   // General obj/array allocation facilities.
 299   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
 300   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
 301   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
 302 
 303   inline static void post_allocation_install_obj_klass(KlassHandle klass,
 304                                                        oop obj);
 305 
 306   // Raw memory allocation facilities
 307   // The obj and array allocate methods are covers for these methods.
 308   // mem_allocate() should never be
 309   // called to allocate TLABs, only individual objects.
 310   virtual HeapWord* mem_allocate(size_t size,
 311                                  bool* gc_overhead_limit_was_exceeded) = 0;
 312 
 313   // Utilities for turning raw memory into filler objects.
 314   //
 315   // min_fill_size() is the smallest region that can be filled.
 316   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 317   // multiple objects.  fill_with_object() is for regions known to be smaller
 318   // than the largest array of integers; it uses a single object to fill the
 319   // region and has slightly less overhead.
 320   static size_t min_fill_size() {
 321     return size_t(align_object_size(oopDesc::header_size()));
 322   }
 323 
 324   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 325 
 326   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 327   static void fill_with_object(MemRegion region, bool zap = true) {
 328     fill_with_object(region.start(), region.word_size(), zap);
 329   }
 330   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 331     fill_with_object(start, pointer_delta(end, start), zap);
 332   }
 333 
 334   // Return the address "addr" aligned by "alignment_in_bytes" if such
 335   // an address is below "end".  Return NULL otherwise.
 336   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
 337                                                    HeapWord* end,
 338                                                    unsigned short alignment_in_bytes);
 339 
 340   // Some heaps may offer a contiguous region for shared non-blocking
 341   // allocation, via inlined code (by exporting the address of the top and
 342   // end fields defining the extent of the contiguous allocation region.)
 343 
 344   // This function returns "true" iff the heap supports this kind of
 345   // allocation.  (Default is "no".)
 346   virtual bool supports_inline_contig_alloc() const {
 347     return false;
 348   }
 349   // These functions return the addresses of the fields that define the
 350   // boundaries of the contiguous allocation area.  (These fields should be
 351   // physically near to one another.)
 352   virtual HeapWord** top_addr() const {
 353     guarantee(false, "inline contiguous allocation not supported");
 354     return NULL;
 355   }
 356   virtual HeapWord** end_addr() const {
 357     guarantee(false, "inline contiguous allocation not supported");
 358     return NULL;
 359   }
 360 
 361   // Some heaps may be in an unparseable state at certain times between
 362   // collections. This may be necessary for efficient implementation of
 363   // certain allocation-related activities. Calling this function before
 364   // attempting to parse a heap ensures that the heap is in a parsable
 365   // state (provided other concurrent activity does not introduce
 366   // unparsability). It is normally expected, therefore, that this
 367   // method is invoked with the world stopped.
 368   // NOTE: if you override this method, make sure you call
 369   // super::ensure_parsability so that the non-generational
 370   // part of the work gets done. See implementation of
 371   // CollectedHeap::ensure_parsability and, for instance,
 372   // that of GenCollectedHeap::ensure_parsability().
 373   // The argument "retire_tlabs" controls whether existing TLABs
 374   // are merely filled or also retired, thus preventing further
 375   // allocation from them and necessitating allocation of new TLABs.
 376   virtual void ensure_parsability(bool retire_tlabs);
 377 
 378   // Section on thread-local allocation buffers (TLABs)
 379   // If the heap supports thread-local allocation buffers, it should override
 380   // the following methods:
 381   // Returns "true" iff the heap supports thread-local allocation buffers.
 382   // The default is "no".
 383   virtual bool supports_tlab_allocation() const = 0;
 384 
 385   // The amount of space available for thread-local allocation buffers.
 386   virtual size_t tlab_capacity(Thread *thr) const = 0;
 387 
 388   // The amount of used space for thread-local allocation buffers for the given thread.
 389   virtual size_t tlab_used(Thread *thr) const = 0;
 390 
 391   virtual size_t max_tlab_size() const;
 392 
 393   // An estimate of the maximum allocation that could be performed
 394   // for thread-local allocation buffers without triggering any
 395   // collection or expansion activity.
 396   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 397     guarantee(false, "thread-local allocation buffers not supported");
 398     return 0;
 399   }
 400 
 401   // Can a compiler initialize a new object without store barriers?
 402   // This permission only extends from the creation of a new object
 403   // via a TLAB up to the first subsequent safepoint. If such permission
 404   // is granted for this heap type, the compiler promises to call
 405   // defer_store_barrier() below on any slow path allocation of
 406   // a new object for which such initializing store barriers will
 407   // have been elided.
 408   virtual bool can_elide_tlab_store_barriers() const = 0;
 409 
 410   // If a compiler is eliding store barriers for TLAB-allocated objects,
 411   // there is probably a corresponding slow path which can produce
 412   // an object allocated anywhere.  The compiler's runtime support
 413   // promises to call this function on such a slow-path-allocated
 414   // object before performing initializations that have elided
 415   // store barriers. Returns new_obj, or maybe a safer copy thereof.
 416   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
 417 
 418   // Answers whether an initializing store to a new object currently
 419   // allocated at the given address doesn't need a store
 420   // barrier. Returns "true" if it doesn't need an initializing
 421   // store barrier; answers "false" if it does.
 422   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
 423 
 424   // If a compiler is eliding store barriers for TLAB-allocated objects,
 425   // we will be informed of a slow-path allocation by a call
 426   // to new_store_pre_barrier() above. Such a call precedes the
 427   // initialization of the object itself, and no post-store-barriers will
 428   // be issued. Some heap types require that the barrier strictly follows
 429   // the initializing stores. (This is currently implemented by deferring the
 430   // barrier until the next slow-path allocation or gc-related safepoint.)
 431   // This interface answers whether a particular heap type needs the card
 432   // mark to be thus strictly sequenced after the stores.
 433   virtual bool card_mark_must_follow_store() const = 0;
 434 
 435   // If the CollectedHeap was asked to defer a store barrier above,
 436   // this informs it to flush such a deferred store barrier to the
 437   // remembered set.
 438   virtual void flush_deferred_store_barrier(JavaThread* thread);
 439 
 440   // Perform a collection of the heap; intended for use in implementing
 441   // "System.gc".  This probably implies as full a collection as the
 442   // "CollectedHeap" supports.
 443   virtual void collect(GCCause::Cause cause) = 0;
 444 
 445   // Perform a full collection
 446   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 447 
 448   // This interface assumes that it's being called by the
 449   // vm thread. It collects the heap assuming that the
 450   // heap lock is already held and that we are executing in
 451   // the context of the vm thread.
 452   virtual void collect_as_vm_thread(GCCause::Cause cause);
 453 
 454   // Returns the barrier set for this heap
 455   BarrierSet* barrier_set() { return _barrier_set; }
 456   void set_barrier_set(BarrierSet* barrier_set);
 457 
 458   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 459   // that it should answer "false" for the concurrent part of a concurrent
 460   // collector -- dld).
 461   bool is_gc_active() const { return _is_gc_active; }
 462 
 463   // Total number of GC collections (started)
 464   unsigned int total_collections() const { return _total_collections; }
 465   unsigned int total_full_collections() const { return _total_full_collections;}
 466 
 467   // Increment total number of GC collections (started)
 468   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 469   void increment_total_collections(bool full = false) {
 470     _total_collections++;
 471     if (full) {
 472       increment_total_full_collections();
 473     }
 474   }
 475 
 476   void increment_total_full_collections() { _total_full_collections++; }
 477 
 478   // Return the AdaptiveSizePolicy for the heap.
 479   virtual AdaptiveSizePolicy* size_policy() = 0;
 480 
 481   // Return the CollectorPolicy for the heap
 482   virtual CollectorPolicy* collector_policy() const = 0;
 483 
 484   // Iterate over all objects, calling "cl.do_object" on each.
 485   virtual void object_iterate(ObjectClosure* cl) = 0;
 486 
 487   // Similar to object_iterate() except iterates only
 488   // over live objects.
 489   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 490 
 491   // NOTE! There is no requirement that a collector implement these
 492   // functions.
 493   //
 494   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 495   // each address in the (reserved) heap is a member of exactly
 496   // one block.  The defining characteristic of a block is that it is
 497   // possible to find its size, and thus to progress forward to the next
 498   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 499   // represent Java objects, or they might be free blocks in a
 500   // free-list-based heap (or subheap), as long as the two kinds are
 501   // distinguishable and the size of each is determinable.
 502 
 503   // Returns the address of the start of the "block" that contains the
 504   // address "addr".  We say "blocks" instead of "object" since some heaps
 505   // may not pack objects densely; a chunk may either be an object or a
 506   // non-object.
 507   virtual HeapWord* block_start(const void* addr) const = 0;
 508 
 509   // Requires "addr" to be the start of a chunk, and returns its size.
 510   // "addr + size" is required to be the start of a new chunk, or the end
 511   // of the active area of the heap.
 512   virtual size_t block_size(const HeapWord* addr) const = 0;
 513 
 514   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 515   // the block is an object.
 516   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 517 
 518   // Returns the longest time (in ms) that has elapsed since the last
 519   // time that any part of the heap was examined by a garbage collection.
 520   virtual jlong millis_since_last_gc() = 0;
 521 
 522   // Perform any cleanup actions necessary before allowing a verification.
 523   virtual void prepare_for_verify() = 0;
 524 
 525   // Generate any dumps preceding or following a full gc
 526  private:
 527   void full_gc_dump(GCTimer* timer, const char* when);
 528  public:
 529   void pre_full_gc_dump(GCTimer* timer);
 530   void post_full_gc_dump(GCTimer* timer);
 531 
 532   VirtualSpaceSummary create_heap_space_summary();
 533   GCHeapSummary create_heap_summary();
 534 
 535   MetaspaceSummary create_metaspace_summary();
 536 
 537   // Print heap information on the given outputStream.
 538   virtual void print_on(outputStream* st) const = 0;
 539   // The default behavior is to call print_on() on tty.
 540   virtual void print() const {
 541     print_on(tty);
 542   }
 543   // Print more detailed heap information on the given
 544   // outputStream. The default behavior is to call print_on(). It is
 545   // up to each subclass to override it and add any additional output
 546   // it needs.
 547   virtual void print_extended_on(outputStream* st) const {
 548     print_on(st);
 549   }
 550 
 551   virtual void print_on_error(outputStream* st) const;
 552 
 553   // Print all GC threads (other than the VM thread)
 554   // used by this heap.
 555   virtual void print_gc_threads_on(outputStream* st) const = 0;
 556   // The default behavior is to call print_gc_threads_on() on tty.
 557   void print_gc_threads() {
 558     print_gc_threads_on(tty);
 559   }
 560   // Iterator for all GC threads (other than VM thread)
 561   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 562 
 563   // Print any relevant tracing info that flags imply.
 564   // Default implementation does nothing.
 565   virtual void print_tracing_info() const = 0;
 566 
 567   void print_heap_before_gc();
 568   void print_heap_after_gc();
 569 
 570   // Registering and unregistering an nmethod (compiled code) with the heap.
 571   // Override with specific mechanism for each specialized heap type.
 572   virtual void register_nmethod(nmethod* nm);
 573   virtual void unregister_nmethod(nmethod* nm);
 574 
 575   void trace_heap_before_gc(const GCTracer* gc_tracer);
 576   void trace_heap_after_gc(const GCTracer* gc_tracer);
 577 
 578   // Heap verification
 579   virtual void verify(VerifyOption option) = 0;
 580 
 581   // Non product verification and debugging.
 582 #ifndef PRODUCT
 583   // Support for PromotionFailureALot.  Return true if it's time to cause a
 584   // promotion failure.  The no-argument version uses
 585   // this->_promotion_failure_alot_count as the counter.
 586   inline bool promotion_should_fail(volatile size_t* count);
 587   inline bool promotion_should_fail();
 588 
 589   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 590   // GC in which promotion failure occurred.
 591   inline void reset_promotion_should_fail(volatile size_t* count);
 592   inline void reset_promotion_should_fail();
 593 #endif  // #ifndef PRODUCT
 594 
 595 #ifdef ASSERT
 596   static int fired_fake_oom() {
 597     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 598   }
 599 #endif
 600 
 601  public:
 602   // Copy the current allocation context statistics for the specified contexts.
 603   // For each context in contexts, set the corresponding entries in the totals
 604   // and accuracy arrays to the current values held by the statistics.  Each
 605   // array should be of length len.
 606   // Returns true if there are more stats available.
 607   virtual bool copy_allocation_context_stats(const jint* contexts,
 608                                              jlong* totals,
 609                                              jbyte* accuracy,
 610                                              jint len) {
 611     return false;
 612   }
 613 
 614   /////////////// Unit tests ///////////////
 615 
 616   NOT_PRODUCT(static void test_is_in();)
 617 };
 618 
 619 // Class to set and reset the GC cause for a CollectedHeap.
 620 
 621 class GCCauseSetter : StackObj {
 622   CollectedHeap* _heap;
 623   GCCause::Cause _previous_cause;
 624  public:
 625   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 626     assert(SafepointSynchronize::is_at_safepoint(),
 627            "This method manipulates heap state without locking");
 628     _heap = heap;
 629     _previous_cause = _heap->gc_cause();
 630     _heap->set_gc_cause(cause);
 631   }
 632 
 633   ~GCCauseSetter() {
 634     assert(SafepointSynchronize::is_at_safepoint(),
 635           "This method manipulates heap state without locking");
 636     _heap->set_gc_cause(_previous_cause);
 637   }
 638 };
 639 
 640 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP