1 /*
   2  * Copyright (c) 2001, 2013, 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
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  24 
  25 #ifndef SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
  26 #define SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP
  27 
  28 #include "gc_interface/gcCause.hpp"
  29 #include "gc_implementation/shared/gcWhen.hpp"
  30 #include "memory/allocation.hpp"
  31 #include "memory/barrierSet.hpp"
  32 #include "runtime/handles.hpp"
  33 #include "runtime/perfData.hpp"
  34 #include "runtime/safepoint.hpp"
  35 #include "utilities/events.hpp"
  36 
  37 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
  38 // is an abstract class: there may be many different kinds of heaps.  This
  39 // class defines the functions that a heap must implement, and contains
  40 // infrastructure common to all heaps.
  41 
  42 class AdaptiveSizePolicy;
  43 class BarrierSet;
  44 class CollectorPolicy;
  45 class GCHeapSummary;
  46 class GCTimer;
  47 class GCTracer;
  48 class MetaspaceSummary;
  49 class Thread;
  50 class ThreadClosure;
  51 class VirtualSpaceSummary;
  52 class nmethod;
  53 
  54 class GCMessage : public FormatBuffer<1024> {
  55  public:
  56   bool is_before;
  57 
  58  public:
  59   GCMessage() {}
  60 };
  61 
  62 class GCHeapLog : public EventLogBase<GCMessage> {
  63  private:
  64   void log_heap(bool before);
  65 
  66  public:
  67   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
  68 
  69   void log_heap_before() {
  70     log_heap(true);
  71   }
  72   void log_heap_after() {
  73     log_heap(false);
  74   }
  75 };
  76 
  77 //
  78 // CollectedHeap
  79 //   SharedHeap
  80 //     GenCollectedHeap
  81 //     G1CollectedHeap
  82 //   ParallelScavengeHeap
  83 //
  84 class CollectedHeap : public CHeapObj<mtInternal> {
  85   friend class VMStructs;
  86   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  87 
  88 #ifdef ASSERT
  89   static int       _fire_out_of_memory_count;
  90 #endif
  91 
  92   // Used for filler objects (static, but initialized in ctor).
  93   static size_t _filler_array_max_size;
  94 
  95   GCHeapLog* _gc_heap_log;
  96 
  97   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
  98   bool _defer_initial_card_mark;
  99 
 100  protected:
 101   MemRegion _reserved;
 102   BarrierSet* _barrier_set;
 103   bool _is_gc_active;
 104   uint _n_par_threads;
 105 
 106   unsigned int _total_collections;          // ... started
 107   unsigned int _total_full_collections;     // ... started
 108   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 109   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 110 
 111   // Reason for current garbage collection.  Should be set to
 112   // a value reflecting no collection between collections.
 113   GCCause::Cause _gc_cause;
 114   GCCause::Cause _gc_lastcause;
 115   PerfStringVariable* _perf_gc_cause;
 116   PerfStringVariable* _perf_gc_lastcause;
 117 
 118   // Constructor
 119   CollectedHeap();
 120 
 121   // Do common initializations that must follow instance construction,
 122   // for example, those needing virtual calls.
 123   // This code could perhaps be moved into initialize() but would
 124   // be slightly more awkward because we want the latter to be a
 125   // pure virtual.
 126   void pre_initialize();
 127 
 128   // Create a new tlab. All TLAB allocations must go through this.
 129   virtual HeapWord* allocate_new_tlab(size_t size);
 130 
 131   // Accumulate statistics on all tlabs.
 132   virtual void accumulate_statistics_all_tlabs();
 133 
 134   // Reinitialize tlabs before resuming mutators.
 135   virtual void resize_all_tlabs();
 136 
 137   // Allocate from the current thread's TLAB, with broken-out slow path.
 138   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
 139   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
 140 
 141   // Allocate an uninitialized block of the given size, or returns NULL if
 142   // this is impossible.
 143   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
 144 
 145   // Like allocate_init, but the block returned by a successful allocation
 146   // is guaranteed initialized to zeros.
 147   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
 148 
 149   // Helper functions for (VM) allocation.
 150   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
 151   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
 152                                                             HeapWord* objPtr);
 153 
 154   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj);
 155 
 156   inline static void post_allocation_setup_array(KlassHandle klass,
 157                                                  HeapWord* obj, int length);
 158 
 159   // Clears an allocated object.
 160   inline static void init_obj(HeapWord* obj, size_t size);
 161 
 162   // Filler object utilities.
 163   static inline size_t filler_array_hdr_size();
 164   static inline size_t filler_array_min_size();
 165 
 166   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 167   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 168 
 169   // Fill with a single array; caller must ensure filler_array_min_size() <=
 170   // words <= filler_array_max_size().
 171   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 172 
 173   // Fill with a single object (either an int array or a java.lang.Object).
 174   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 175 
 176   virtual void trace_heap(GCWhen::Type when, GCTracer* tracer);
 177 
 178   // Verification functions
 179   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 180     PRODUCT_RETURN;
 181   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 182     PRODUCT_RETURN;
 183   debug_only(static void check_for_valid_allocation_state();)
 184 
 185  public:
 186   enum Name {
 187     Abstract,
 188     SharedHeap,
 189     GenCollectedHeap,
 190     ParallelScavengeHeap,
 191     G1CollectedHeap
 192   };
 193 
 194   static inline size_t filler_array_max_size() {
 195     return _filler_array_max_size;
 196   }
 197 
 198   virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
 199 
 200   /**
 201    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
 202    * and JNI_OK on success.
 203    */
 204   virtual jint initialize() = 0;
 205 
 206   // In many heaps, there will be a need to perform some initialization activities
 207   // after the Universe is fully formed, but before general heap allocation is allowed.
 208   // This is the correct place to place such initialization methods.
 209   virtual void post_initialize() = 0;
 210 
 211   MemRegion reserved_region() const { return _reserved; }
 212   address base() const { return (address)reserved_region().start(); }
 213 
 214   virtual size_t capacity() const = 0;
 215   virtual size_t used() const = 0;
 216 
 217   // Return "true" if the part of the heap that allocates Java
 218   // objects has reached the maximal committed limit that it can
 219   // reach, without a garbage collection.
 220   virtual bool is_maximal_no_gc() const = 0;
 221 
 222   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 223   // memory that the vm could make available for storing 'normal' java objects.
 224   // This is based on the reserved address space, but should not include space
 225   // that the vm uses internally for bookkeeping or temporary storage
 226   // (e.g., in the case of the young gen, one of the survivor
 227   // spaces).
 228   virtual size_t max_capacity() const = 0;
 229 
 230   // Returns "TRUE" if "p" points into the reserved area of the heap.
 231   bool is_in_reserved(const void* p) const {
 232     return _reserved.contains(p);
 233   }
 234 
 235   bool is_in_reserved_or_null(const void* p) const {
 236     return p == NULL || is_in_reserved(p);
 237   }
 238 
 239   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 240   // Since this method can be expensive in general, we restrict its
 241   // use to assertion checking only.
 242   virtual bool is_in(const void* p) const = 0;
 243 
 244   bool is_in_or_null(const void* p) const {
 245     return p == NULL || is_in(p);
 246   }
 247 
 248   bool is_in_place(Metadata** p) {
 249     return !Universe::heap()->is_in(p);
 250   }
 251   bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
 252   bool is_in_place(narrowOop* p) {
 253     oop o = oopDesc::load_decode_heap_oop_not_null(p);
 254     return Universe::heap()->is_in((const void*)o);
 255   }
 256 
 257   // Let's define some terms: a "closed" subset of a heap is one that
 258   //
 259   // 1) contains all currently-allocated objects, and
 260   //
 261   // 2) is closed under reference: no object in the closed subset
 262   //    references one outside the closed subset.
 263   //
 264   // Membership in a heap's closed subset is useful for assertions.
 265   // Clearly, the entire heap is a closed subset, so the default
 266   // implementation is to use "is_in_reserved".  But this may not be too
 267   // liberal to perform useful checking.  Also, the "is_in" predicate
 268   // defines a closed subset, but may be too expensive, since "is_in"
 269   // verifies that its argument points to an object head.  The
 270   // "closed_subset" method allows a heap to define an intermediate
 271   // predicate, allowing more precise checking than "is_in_reserved" at
 272   // lower cost than "is_in."
 273 
 274   // One important case is a heap composed of disjoint contiguous spaces,
 275   // such as the Garbage-First collector.  Such heaps have a convenient
 276   // closed subset consisting of the allocated portions of those
 277   // contiguous spaces.
 278 
 279   // Return "TRUE" iff the given pointer points into the heap's defined
 280   // closed subset (which defaults to the entire heap).
 281   virtual bool is_in_closed_subset(const void* p) const {
 282     return is_in_reserved(p);
 283   }
 284 
 285   bool is_in_closed_subset_or_null(const void* p) const {
 286     return p == NULL || is_in_closed_subset(p);
 287   }
 288 
 289 #ifdef ASSERT
 290   // Returns true if "p" is in the part of the
 291   // heap being collected.
 292   virtual bool is_in_partial_collection(const void *p) = 0;
 293 #endif
 294 
 295   // An object is scavengable if its location may move during a scavenge.
 296   // (A scavenge is a GC which is not a full GC.)
 297   virtual bool is_scavengable(const void *p) = 0;
 298 
 299   void set_gc_cause(GCCause::Cause v) {
 300      if (UsePerfData) {
 301        _gc_lastcause = _gc_cause;
 302        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 303        _perf_gc_cause->set_value(GCCause::to_string(v));
 304      }
 305     _gc_cause = v;
 306   }
 307   GCCause::Cause gc_cause() { return _gc_cause; }
 308 
 309   // Number of threads currently working on GC tasks.
 310   uint n_par_threads() { return _n_par_threads; }
 311 
 312   // May be overridden to set additional parallelism.
 313   virtual void set_par_threads(uint t) { _n_par_threads = t; };
 314 
 315   // Allocate and initialize instances of Class
 316   static oop Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS);
 317 
 318   // General obj/array allocation facilities.
 319   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
 320   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
 321   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
 322 
 323   inline static void post_allocation_install_obj_klass(KlassHandle klass,
 324                                                        oop obj);
 325 
 326   // Raw memory allocation facilities
 327   // The obj and array allocate methods are covers for these methods.
 328   // mem_allocate() should never be
 329   // called to allocate TLABs, only individual objects.
 330   virtual HeapWord* mem_allocate(size_t size,
 331                                  bool* gc_overhead_limit_was_exceeded) = 0;
 332 
 333   // Utilities for turning raw memory into filler objects.
 334   //
 335   // min_fill_size() is the smallest region that can be filled.
 336   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 337   // multiple objects.  fill_with_object() is for regions known to be smaller
 338   // than the largest array of integers; it uses a single object to fill the
 339   // region and has slightly less overhead.
 340   static size_t min_fill_size() {
 341     return size_t(align_object_size(oopDesc::header_size()));
 342   }
 343 
 344   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 345 
 346   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 347   static void fill_with_object(MemRegion region, bool zap = true) {
 348     fill_with_object(region.start(), region.word_size(), zap);
 349   }
 350   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 351     fill_with_object(start, pointer_delta(end, start), zap);
 352   }
 353 
 354   // Some heaps may offer a contiguous region for shared non-blocking
 355   // allocation, via inlined code (by exporting the address of the top and
 356   // end fields defining the extent of the contiguous allocation region.)
 357 
 358   // This function returns "true" iff the heap supports this kind of
 359   // allocation.  (Default is "no".)
 360   virtual bool supports_inline_contig_alloc() const {
 361     return false;
 362   }
 363   // These functions return the addresses of the fields that define the
 364   // boundaries of the contiguous allocation area.  (These fields should be
 365   // physically near to one another.)
 366   virtual HeapWord** top_addr() const {
 367     guarantee(false, "inline contiguous allocation not supported");
 368     return NULL;
 369   }
 370   virtual HeapWord** end_addr() const {
 371     guarantee(false, "inline contiguous allocation not supported");
 372     return NULL;
 373   }
 374 
 375   // Some heaps may be in an unparseable state at certain times between
 376   // collections. This may be necessary for efficient implementation of
 377   // certain allocation-related activities. Calling this function before
 378   // attempting to parse a heap ensures that the heap is in a parsable
 379   // state (provided other concurrent activity does not introduce
 380   // unparsability). It is normally expected, therefore, that this
 381   // method is invoked with the world stopped.
 382   // NOTE: if you override this method, make sure you call
 383   // super::ensure_parsability so that the non-generational
 384   // part of the work gets done. See implementation of
 385   // CollectedHeap::ensure_parsability and, for instance,
 386   // that of GenCollectedHeap::ensure_parsability().
 387   // The argument "retire_tlabs" controls whether existing TLABs
 388   // are merely filled or also retired, thus preventing further
 389   // allocation from them and necessitating allocation of new TLABs.
 390   virtual void ensure_parsability(bool retire_tlabs);
 391 
 392   // Return an estimate of the maximum allocation that could be performed
 393   // without triggering any collection or expansion activity.  In a
 394   // generational collector, for example, this is probably the largest
 395   // allocation that could be supported (without expansion) in the youngest
 396   // generation.  It is "unsafe" because no locks are taken; the result
 397   // should be treated as an approximation, not a guarantee, for use in
 398   // heuristic resizing decisions.
 399   virtual size_t unsafe_max_alloc() = 0;
 400 
 401   // Section on thread-local allocation buffers (TLABs)
 402   // If the heap supports thread-local allocation buffers, it should override
 403   // the following methods:
 404   // Returns "true" iff the heap supports thread-local allocation buffers.
 405   // The default is "no".
 406   virtual bool supports_tlab_allocation() const {
 407     return false;
 408   }
 409   // The amount of space available for thread-local allocation buffers.
 410   virtual size_t tlab_capacity(Thread *thr) const {
 411     guarantee(false, "thread-local allocation buffers not supported");
 412     return 0;
 413   }
 414   // An estimate of the maximum allocation that could be performed
 415   // for thread-local allocation buffers without triggering any
 416   // collection or expansion activity.
 417   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 418     guarantee(false, "thread-local allocation buffers not supported");
 419     return 0;
 420   }
 421 
 422   // Can a compiler initialize a new object without store barriers?
 423   // This permission only extends from the creation of a new object
 424   // via a TLAB up to the first subsequent safepoint. If such permission
 425   // is granted for this heap type, the compiler promises to call
 426   // defer_store_barrier() below on any slow path allocation of
 427   // a new object for which such initializing store barriers will
 428   // have been elided.
 429   virtual bool can_elide_tlab_store_barriers() const = 0;
 430 
 431   // If a compiler is eliding store barriers for TLAB-allocated objects,
 432   // there is probably a corresponding slow path which can produce
 433   // an object allocated anywhere.  The compiler's runtime support
 434   // promises to call this function on such a slow-path-allocated
 435   // object before performing initializations that have elided
 436   // store barriers. Returns new_obj, or maybe a safer copy thereof.
 437   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
 438 
 439   // Answers whether an initializing store to a new object currently
 440   // allocated at the given address doesn't need a store
 441   // barrier. Returns "true" if it doesn't need an initializing
 442   // store barrier; answers "false" if it does.
 443   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
 444 
 445   // If a compiler is eliding store barriers for TLAB-allocated objects,
 446   // we will be informed of a slow-path allocation by a call
 447   // to new_store_pre_barrier() above. Such a call precedes the
 448   // initialization of the object itself, and no post-store-barriers will
 449   // be issued. Some heap types require that the barrier strictly follows
 450   // the initializing stores. (This is currently implemented by deferring the
 451   // barrier until the next slow-path allocation or gc-related safepoint.)
 452   // This interface answers whether a particular heap type needs the card
 453   // mark to be thus strictly sequenced after the stores.
 454   virtual bool card_mark_must_follow_store() const = 0;
 455 
 456   // If the CollectedHeap was asked to defer a store barrier above,
 457   // this informs it to flush such a deferred store barrier to the
 458   // remembered set.
 459   virtual void flush_deferred_store_barrier(JavaThread* thread);
 460 
 461   // Does this heap support heap inspection (+PrintClassHistogram?)
 462   virtual bool supports_heap_inspection() const = 0;
 463 
 464   // Perform a collection of the heap; intended for use in implementing
 465   // "System.gc".  This probably implies as full a collection as the
 466   // "CollectedHeap" supports.
 467   virtual void collect(GCCause::Cause cause) = 0;
 468 
 469   // Perform a full collection
 470   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 471 
 472   // This interface assumes that it's being called by the
 473   // vm thread. It collects the heap assuming that the
 474   // heap lock is already held and that we are executing in
 475   // the context of the vm thread.
 476   virtual void collect_as_vm_thread(GCCause::Cause cause);
 477 
 478   // Callback from VM_CollectForMetadataAllocation operation.
 479   MetaWord* satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 480                                                size_t size,
 481                                                Metaspace::MetadataType mdtype);
 482 
 483   // Returns the barrier set for this heap
 484   BarrierSet* barrier_set() { return _barrier_set; }
 485 
 486   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 487   // that it should answer "false" for the concurrent part of a concurrent
 488   // collector -- dld).
 489   bool is_gc_active() const { return _is_gc_active; }
 490 
 491   // Total number of GC collections (started)
 492   unsigned int total_collections() const { return _total_collections; }
 493   unsigned int total_full_collections() const { return _total_full_collections;}
 494 
 495   // Increment total number of GC collections (started)
 496   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 497   void increment_total_collections(bool full = false) {
 498     _total_collections++;
 499     if (full) {
 500       increment_total_full_collections();
 501     }
 502   }
 503 
 504   void increment_total_full_collections() { _total_full_collections++; }
 505 
 506   // Return the AdaptiveSizePolicy for the heap.
 507   virtual AdaptiveSizePolicy* size_policy() = 0;
 508 
 509   // Return the CollectorPolicy for the heap
 510   virtual CollectorPolicy* collector_policy() const = 0;
 511 
 512   void oop_iterate_no_header(OopClosure* cl);
 513 
 514   // Iterate over all the ref-containing fields of all objects, calling
 515   // "cl.do_oop" on each.
 516   virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
 517 
 518   // Iterate over all objects, calling "cl.do_object" on each.
 519   virtual void object_iterate(ObjectClosure* cl) = 0;
 520 
 521   // Similar to object_iterate() except iterates only
 522   // over live objects.
 523   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 524 
 525   // NOTE! There is no requirement that a collector implement these
 526   // functions.
 527   //
 528   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 529   // each address in the (reserved) heap is a member of exactly
 530   // one block.  The defining characteristic of a block is that it is
 531   // possible to find its size, and thus to progress forward to the next
 532   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 533   // represent Java objects, or they might be free blocks in a
 534   // free-list-based heap (or subheap), as long as the two kinds are
 535   // distinguishable and the size of each is determinable.
 536 
 537   // Returns the address of the start of the "block" that contains the
 538   // address "addr".  We say "blocks" instead of "object" since some heaps
 539   // may not pack objects densely; a chunk may either be an object or a
 540   // non-object.
 541   virtual HeapWord* block_start(const void* addr) const = 0;
 542 
 543   // Requires "addr" to be the start of a chunk, and returns its size.
 544   // "addr + size" is required to be the start of a new chunk, or the end
 545   // of the active area of the heap.
 546   virtual size_t block_size(const HeapWord* addr) const = 0;
 547 
 548   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 549   // the block is an object.
 550   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 551 
 552   // Returns the longest time (in ms) that has elapsed since the last
 553   // time that any part of the heap was examined by a garbage collection.
 554   virtual jlong millis_since_last_gc() = 0;
 555 
 556   // Perform any cleanup actions necessary before allowing a verification.
 557   virtual void prepare_for_verify() = 0;
 558 
 559   // Generate any dumps preceding or following a full gc
 560   void pre_full_gc_dump(GCTimer* timer);
 561   void post_full_gc_dump(GCTimer* timer);
 562 
 563   VirtualSpaceSummary create_heap_space_summary();
 564   GCHeapSummary create_heap_summary();
 565 
 566   MetaspaceSummary create_metaspace_summary();
 567 
 568   // Print heap information on the given outputStream.
 569   virtual void print_on(outputStream* st) const = 0;
 570   // The default behavior is to call print_on() on tty.
 571   virtual void print() const {
 572     print_on(tty);
 573   }
 574   // Print more detailed heap information on the given
 575   // outputStream. The default behavior is to call print_on(). It is
 576   // up to each subclass to override it and add any additional output
 577   // it needs.
 578   virtual void print_extended_on(outputStream* st) const {
 579     print_on(st);
 580   }
 581 
 582   virtual void print_on_error(outputStream* st) const {
 583     st->print_cr("Heap:");
 584     print_extended_on(st);
 585     st->cr();
 586 
 587     _barrier_set->print_on(st);
 588   }
 589 
 590   // Print all GC threads (other than the VM thread)
 591   // used by this heap.
 592   virtual void print_gc_threads_on(outputStream* st) const = 0;
 593   // The default behavior is to call print_gc_threads_on() on tty.
 594   void print_gc_threads() {
 595     print_gc_threads_on(tty);
 596   }
 597   // Iterator for all GC threads (other than VM thread)
 598   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 599 
 600   // Print any relevant tracing info that flags imply.
 601   // Default implementation does nothing.
 602   virtual void print_tracing_info() const = 0;
 603 
 604   void print_heap_before_gc();
 605   void print_heap_after_gc();
 606 
 607   // Registering and unregistering an nmethod (compiled code) with the heap.
 608   // Override with specific mechanism for each specialized heap type.
 609   virtual void register_nmethod(nmethod* nm);
 610   virtual void unregister_nmethod(nmethod* nm);
 611 
 612   void trace_heap_before_gc(GCTracer* gc_tracer);
 613   void trace_heap_after_gc(GCTracer* gc_tracer);
 614 
 615   // Heap verification
 616   virtual void verify(bool silent, VerifyOption option) = 0;
 617 
 618   // Non product verification and debugging.
 619 #ifndef PRODUCT
 620   // Support for PromotionFailureALot.  Return true if it's time to cause a
 621   // promotion failure.  The no-argument version uses
 622   // this->_promotion_failure_alot_count as the counter.
 623   inline bool promotion_should_fail(volatile size_t* count);
 624   inline bool promotion_should_fail();
 625 
 626   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 627   // GC in which promotion failure occurred.
 628   inline void reset_promotion_should_fail(volatile size_t* count);
 629   inline void reset_promotion_should_fail();
 630 #endif  // #ifndef PRODUCT
 631 
 632 #ifdef ASSERT
 633   static int fired_fake_oom() {
 634     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 635   }
 636 #endif
 637 
 638  public:
 639   // This is a convenience method that is used in cases where
 640   // the actual number of GC worker threads is not pertinent but
 641   // only whether there more than 0.  Use of this method helps
 642   // reduce the occurrence of ParallelGCThreads to uses where the
 643   // actual number may be germane.
 644   static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
 645 
 646   /////////////// Unit tests ///////////////
 647 
 648   NOT_PRODUCT(static void test_is_in();)
 649 };
 650 
 651 // Class to set and reset the GC cause for a CollectedHeap.
 652 
 653 class GCCauseSetter : StackObj {
 654   CollectedHeap* _heap;
 655   GCCause::Cause _previous_cause;
 656  public:
 657   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 658     assert(SafepointSynchronize::is_at_safepoint(),
 659            "This method manipulates heap state without locking");
 660     _heap = heap;
 661     _previous_cause = _heap->gc_cause();
 662     _heap->set_gc_cause(cause);
 663   }
 664 
 665   ~GCCauseSetter() {
 666     assert(SafepointSynchronize::is_at_safepoint(),
 667           "This method manipulates heap state without locking");
 668     _heap->set_gc_cause(_previous_cause);
 669   }
 670 };
 671 
 672 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP