1 /*
   2  * Copyright (c) 2001, 2016, 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 JVMCIVMStructs;
  87   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  88 
  89  private:
  90 #ifdef ASSERT
  91   static int       _fire_out_of_memory_count;
  92 #endif
  93 
  94   GCHeapLog* _gc_heap_log;
  95 
  96   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
  97   // or INCLUDE_JVMCI is being used
  98   bool _defer_initial_card_mark;
  99 
 100   MemRegion _reserved;
 101 
 102  protected:
 103   BarrierSet* _barrier_set;
 104   bool _is_gc_active;
 105 
 106   // Used for filler objects (static, but initialized in ctor).
 107   static size_t _filler_array_max_size;
 108 
 109   unsigned int _total_collections;          // ... started
 110   unsigned int _total_full_collections;     // ... started
 111   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 112   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 113 
 114   // Reason for current garbage collection.  Should be set to
 115   // a value reflecting no collection between collections.
 116   GCCause::Cause _gc_cause;
 117   GCCause::Cause _gc_lastcause;
 118   PerfStringVariable* _perf_gc_cause;
 119   PerfStringVariable* _perf_gc_lastcause;
 120 
 121   // Constructor
 122   CollectedHeap();
 123 
 124   // Do common initializations that must follow instance construction,
 125   // for example, those needing virtual calls.
 126   // This code could perhaps be moved into initialize() but would
 127   // be slightly more awkward because we want the latter to be a
 128   // pure virtual.
 129   void pre_initialize();
 130 
 131   // Create a new tlab. All TLAB allocations must go through this.
 132   virtual HeapWord* allocate_new_tlab(size_t size);
 133 
 134   // Accumulate statistics on all tlabs.
 135   virtual void accumulate_statistics_all_tlabs();
 136 
 137   // Reinitialize tlabs before resuming mutators.
 138   virtual void resize_all_tlabs();
 139 
 140   // Allocate from the current thread's TLAB, with broken-out slow path.
 141   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
 142   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
 143 
 144   // Allocate an uninitialized block of the given size, or returns NULL if
 145   // this is impossible.
 146   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
 147 
 148   // Like allocate_init, but the block returned by a successful allocation
 149   // is guaranteed initialized to zeros.
 150   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
 151 
 152   // Helper functions for (VM) allocation.
 153   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
 154   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
 155                                                             HeapWord* objPtr);
 156 
 157   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
 158 
 159   inline static void post_allocation_setup_array(KlassHandle klass,
 160                                                  HeapWord* obj, int length);
 161 
 162   inline static void post_allocation_setup_class(KlassHandle klass, HeapWord* obj, int size);
 163 
 164   // Clears an allocated object.
 165   inline static void init_obj(HeapWord* obj, size_t size);
 166 
 167   // Filler object utilities.
 168   static inline size_t filler_array_hdr_size();
 169   static inline size_t filler_array_min_size();
 170 
 171   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 172   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 173 
 174   // Fill with a single array; caller must ensure filler_array_min_size() <=
 175   // words <= filler_array_max_size().
 176   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 177 
 178   // Fill with a single object (either an int array or a java.lang.Object).
 179   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 180 
 181   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 182 
 183   // Verification functions
 184   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 185     PRODUCT_RETURN;
 186   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 187     PRODUCT_RETURN;
 188   debug_only(static void check_for_valid_allocation_state();)
 189 
 190  public:
 191   enum Name {
 192     GenCollectedHeap,
 193     ParallelScavengeHeap,
 194     G1CollectedHeap

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