1 /*
   2  * Copyright (c) 2001, 2014, 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_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 //   ShenandoahHeap
  84 //
  85 class CollectedHeap : public CHeapObj<mtInternal> {
  86   friend class VMStructs;
  87   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  88 
  89 #ifdef ASSERT
  90   static int       _fire_out_of_memory_count;
  91 #endif
  92 
  93   // Used for filler objects (static, but initialized in ctor).
  94   static size_t _filler_array_max_size;
  95 
  96   GCHeapLog* _gc_heap_log;
  97 
  98   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
  99   bool _defer_initial_card_mark;
 100 
 101  protected:
 102   MemRegion _reserved;
 103   BarrierSet* _barrier_set;
 104   bool _is_gc_active;
 105   uint _n_par_threads;
 106 
 107   unsigned int _total_collections;          // ... started
 108   unsigned int _total_full_collections;     // ... started
 109   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 110   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 111 
 112   // Reason for current garbage collection.  Should be set to
 113   // a value reflecting no collection between collections.
 114   GCCause::Cause _gc_cause;
 115   GCCause::Cause _gc_lastcause;
 116   PerfStringVariable* _perf_gc_cause;
 117   PerfStringVariable* _perf_gc_lastcause;
 118 
 119   // Constructor
 120   CollectedHeap();
 121 
 122   // Do common initializations that must follow instance construction,
 123   // for example, those needing virtual calls.
 124   // This code could perhaps be moved into initialize() but would
 125   // be slightly more awkward because we want the latter to be a
 126   // pure virtual.
 127   void pre_initialize();
 128 
 129   // Create a new tlab. All TLAB allocations must go through this.
 130   virtual HeapWord* allocate_new_tlab(size_t size);
 131 
 132   // Accumulate statistics on all tlabs.
 133   virtual void accumulate_statistics_all_tlabs();
 134 
 135   // Reinitialize tlabs before resuming mutators.
 136   virtual void resize_all_tlabs();
 137 
 138   // Allocate from the current thread's TLAB, with broken-out slow path.
 139   inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
 140   static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
 141 
 142   // Allocate an uninitialized block of the given size, or returns NULL if
 143   // this is impossible.
 144   inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
 145 
 146   // Like allocate_init, but the block returned by a successful allocation
 147   // is guaranteed initialized to zeros.
 148   inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
 149 
 150   // Helper functions for (VM) allocation.
 151   inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
 152   inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
 153                                                             HeapWord* objPtr);
 154 
 155   inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
 156 
 157   inline static void post_allocation_setup_array(KlassHandle klass,
 158                                                  HeapWord* obj, int length);
 159 
 160   // Clears an allocated object.
 161   inline static void init_obj(HeapWord* obj, size_t size);
 162 
 163   // Filler object utilities.
 164   static inline size_t filler_array_hdr_size();
 165   static inline size_t filler_array_min_size();
 166 
 167   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 168   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 169 
 170   // Fill with a single array; caller must ensure filler_array_min_size() <=
 171   // words <= filler_array_max_size().
 172   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 173 
 174   // Fill with a single object (either an int array or a java.lang.Object).
 175   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 176 
 177   virtual void trace_heap(GCWhen::Type when, GCTracer* tracer);
 178 
 179   // Verification functions
 180   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 181     PRODUCT_RETURN;
 182   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 183     PRODUCT_RETURN;
 184   debug_only(static void check_for_valid_allocation_state();)
 185 
 186  public:
 187   enum Name {
 188     Abstract,
 189     SharedHeap,
 190     GenCollectedHeap,
 191     ParallelScavengeHeap,
 192     G1CollectedHeap,
 193     ShenandoahHeap
 194   };
 195 
 196   static inline size_t filler_array_max_size() {
 197     return _filler_array_max_size;
 198   }
 199 
 200   virtual CollectedHeap::Name kind() const { return CollectedHeap::Abstract; }
 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() = 0;
 212 
 213   // Stop any onging concurrent work and prepare for exit.
 214   virtual void stop() {}
 215 
 216   MemRegion reserved_region() const { return _reserved; }
 217   address base() const { return (address)reserved_region().start(); }
 218 
 219   virtual size_t capacity() const = 0;
 220   virtual size_t used() const = 0;
 221 
 222   // Return "true" if the part of the heap that allocates Java
 223   // objects has reached the maximal committed limit that it can
 224   // reach, without a garbage collection.
 225   virtual bool is_maximal_no_gc() const = 0;
 226 
 227   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 228   // memory that the vm could make available for storing 'normal' java objects.
 229   // This is based on the reserved address space, but should not include space
 230   // that the vm uses internally for bookkeeping or temporary storage
 231   // (e.g., in the case of the young gen, one of the survivor
 232   // spaces).
 233   virtual size_t max_capacity() const = 0;
 234 
 235   // Returns "TRUE" if "p" points into the reserved area of the heap.
 236   bool is_in_reserved(const void* p) const {
 237     return _reserved.contains(p);
 238   }
 239 
 240   bool is_in_reserved_or_null(const void* p) const {
 241     return p == NULL || is_in_reserved(p);
 242   }
 243 
 244   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 245   // Since this method can be expensive in general, we restrict its
 246   // use to assertion checking only.
 247   virtual bool is_in(const void* p) const = 0;
 248 
 249   bool is_in_or_null(const void* p) const {
 250     return p == NULL || is_in(p);
 251   }
 252 
 253   bool is_in_place(Metadata** p) {
 254     return !Universe::heap()->is_in(p);
 255   }
 256   bool is_in_place(oop* p) { return Universe::heap()->is_in(p); }
 257   bool is_in_place(narrowOop* p) {
 258     oop o = oopDesc::load_decode_heap_oop_not_null(p);
 259     return Universe::heap()->is_in((const void*)o);
 260   }
 261 
 262   // Let's define some terms: a "closed" subset of a heap is one that
 263   //
 264   // 1) contains all currently-allocated objects, and
 265   //
 266   // 2) is closed under reference: no object in the closed subset
 267   //    references one outside the closed subset.
 268   //
 269   // Membership in a heap's closed subset is useful for assertions.
 270   // Clearly, the entire heap is a closed subset, so the default
 271   // implementation is to use "is_in_reserved".  But this may not be too
 272   // liberal to perform useful checking.  Also, the "is_in" predicate
 273   // defines a closed subset, but may be too expensive, since "is_in"
 274   // verifies that its argument points to an object head.  The
 275   // "closed_subset" method allows a heap to define an intermediate
 276   // predicate, allowing more precise checking than "is_in_reserved" at
 277   // lower cost than "is_in."
 278 
 279   // One important case is a heap composed of disjoint contiguous spaces,
 280   // such as the Garbage-First collector.  Such heaps have a convenient
 281   // closed subset consisting of the allocated portions of those
 282   // contiguous spaces.
 283 
 284   // Return "TRUE" iff the given pointer points into the heap's defined
 285   // closed subset (which defaults to the entire heap).
 286   virtual bool is_in_closed_subset(const void* p) const {
 287     return is_in_reserved(p);
 288   }
 289 
 290   bool is_in_closed_subset_or_null(const void* p) const {
 291     return p == NULL || is_in_closed_subset(p);
 292   }
 293 
 294 #ifdef ASSERT
 295   // Returns true if "p" is in the part of the
 296   // heap being collected.
 297   virtual bool is_in_partial_collection(const void *p) = 0;
 298 #endif
 299 
 300   // An object is scavengable if its location may move during a scavenge.
 301   // (A scavenge is a GC which is not a full GC.)
 302   virtual bool is_scavengable(const void *p) = 0;
 303 
 304   void set_gc_cause(GCCause::Cause v) {
 305      if (UsePerfData) {
 306        _gc_lastcause = _gc_cause;
 307        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 308        _perf_gc_cause->set_value(GCCause::to_string(v));
 309      }
 310     _gc_cause = v;
 311   }
 312   GCCause::Cause gc_cause() { return _gc_cause; }
 313 
 314   // Number of threads currently working on GC tasks.
 315   uint n_par_threads() { return _n_par_threads; }
 316 
 317   // May be overridden to set additional parallelism.
 318   virtual void set_par_threads(uint t) { _n_par_threads = t; };
 319 
 320   // General obj/array allocation facilities.
 321   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
 322   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
 323   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
 324 
 325   inline static void post_allocation_install_obj_klass(KlassHandle klass,
 326                                                        oop obj);
 327 
 328   // Raw memory allocation facilities
 329   // The obj and array allocate methods are covers for these methods.
 330   // mem_allocate() should never be
 331   // called to allocate TLABs, only individual objects.
 332   virtual HeapWord* mem_allocate(size_t size,
 333                                  bool* gc_overhead_limit_was_exceeded) = 0;
 334 
 335   // Utilities for turning raw memory into filler objects.
 336   //
 337   // min_fill_size() is the smallest region that can be filled.
 338   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 339   // multiple objects.  fill_with_object() is for regions known to be smaller
 340   // than the largest array of integers; it uses a single object to fill the
 341   // region and has slightly less overhead.
 342   static size_t min_fill_size() {
 343     return size_t(align_object_size(oopDesc::header_size()));
 344   }
 345 
 346   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 347 
 348   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 349   static void fill_with_object(MemRegion region, bool zap = true) {
 350     fill_with_object(region.start(), region.word_size(), zap);
 351   }
 352   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 353     fill_with_object(start, pointer_delta(end, start), zap);
 354   }
 355 
 356   // Return the address "addr" aligned by "alignment_in_bytes" if such
 357   // an address is below "end".  Return NULL otherwise.
 358   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
 359                                                    HeapWord* end,
 360                                                    unsigned short alignment_in_bytes);
 361 
 362   // Some heaps may offer a contiguous region for shared non-blocking
 363   // allocation, via inlined code (by exporting the address of the top and
 364   // end fields defining the extent of the contiguous allocation region.)
 365 
 366   // This function returns "true" iff the heap supports this kind of
 367   // allocation.  (Default is "no".)
 368   virtual bool supports_inline_contig_alloc() const {
 369     return false;
 370   }
 371   // These functions return the addresses of the fields that define the
 372   // boundaries of the contiguous allocation area.  (These fields should be
 373   // physically near to one another.)
 374   virtual HeapWord** top_addr() const {
 375     guarantee(false, "inline contiguous allocation not supported");
 376     return NULL;
 377   }
 378   virtual HeapWord** end_addr() const {
 379     guarantee(false, "inline contiguous allocation not supported");
 380     return NULL;
 381   }
 382 
 383   // Some heaps may be in an unparseable state at certain times between
 384   // collections. This may be necessary for efficient implementation of
 385   // certain allocation-related activities. Calling this function before
 386   // attempting to parse a heap ensures that the heap is in a parsable
 387   // state (provided other concurrent activity does not introduce
 388   // unparsability). It is normally expected, therefore, that this
 389   // method is invoked with the world stopped.
 390   // NOTE: if you override this method, make sure you call
 391   // super::ensure_parsability so that the non-generational
 392   // part of the work gets done. See implementation of
 393   // CollectedHeap::ensure_parsability and, for instance,
 394   // that of GenCollectedHeap::ensure_parsability().
 395   // The argument "retire_tlabs" controls whether existing TLABs
 396   // are merely filled or also retired, thus preventing further
 397   // allocation from them and necessitating allocation of new TLABs.
 398   virtual void ensure_parsability(bool retire_tlabs);
 399 
 400   // Section on thread-local allocation buffers (TLABs)
 401   // If the heap supports thread-local allocation buffers, it should override
 402   // the following methods:
 403   // Returns "true" iff the heap supports thread-local allocation buffers.
 404   // The default is "no".
 405   virtual bool supports_tlab_allocation() const = 0;
 406 
 407   // The amount of space available for thread-local allocation buffers.
 408   virtual size_t tlab_capacity(Thread *thr) const = 0;
 409 
 410   // The amount of used space for thread-local allocation buffers for the given thread.
 411   virtual size_t tlab_used(Thread *thr) const = 0;
 412 
 413   virtual size_t max_tlab_size() const;
 414 
 415   // An estimate of the maximum allocation that could be performed
 416   // for thread-local allocation buffers without triggering any
 417   // collection or expansion activity.
 418   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 419     guarantee(false, "thread-local allocation buffers not supported");
 420     return 0;
 421   }
 422 
 423   // Can a compiler initialize a new object without store barriers?
 424   // This permission only extends from the creation of a new object
 425   // via a TLAB up to the first subsequent safepoint. If such permission
 426   // is granted for this heap type, the compiler promises to call
 427   // defer_store_barrier() below on any slow path allocation of
 428   // a new object for which such initializing store barriers will
 429   // have been elided.
 430   virtual bool can_elide_tlab_store_barriers() const = 0;
 431 
 432   // If a compiler is eliding store barriers for TLAB-allocated objects,
 433   // there is probably a corresponding slow path which can produce
 434   // an object allocated anywhere.  The compiler's runtime support
 435   // promises to call this function on such a slow-path-allocated
 436   // object before performing initializations that have elided
 437   // store barriers. Returns new_obj, or maybe a safer copy thereof.
 438   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
 439 
 440   // Answers whether an initializing store to a new object currently
 441   // allocated at the given address doesn't need a store
 442   // barrier. Returns "true" if it doesn't need an initializing
 443   // store barrier; answers "false" if it does.
 444   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
 445 
 446   // If a compiler is eliding store barriers for TLAB-allocated objects,
 447   // we will be informed of a slow-path allocation by a call
 448   // to new_store_pre_barrier() above. Such a call precedes the
 449   // initialization of the object itself, and no post-store-barriers will
 450   // be issued. Some heap types require that the barrier strictly follows
 451   // the initializing stores. (This is currently implemented by deferring the
 452   // barrier until the next slow-path allocation or gc-related safepoint.)
 453   // This interface answers whether a particular heap type needs the card
 454   // mark to be thus strictly sequenced after the stores.
 455   virtual bool card_mark_must_follow_store() const = 0;
 456 
 457   // If the CollectedHeap was asked to defer a store barrier above,
 458   // this informs it to flush such a deferred store barrier to the
 459   // remembered set.
 460   virtual void flush_deferred_store_barrier(JavaThread* thread);
 461 
 462   // Does this heap support heap inspection (+PrintClassHistogram?)
 463   virtual bool supports_heap_inspection() const = 0;
 464 
 465   // Perform a collection of the heap; intended for use in implementing
 466   // "System.gc".  This probably implies as full a collection as the
 467   // "CollectedHeap" supports.
 468   virtual void collect(GCCause::Cause cause) = 0;
 469 
 470   // Perform a full collection
 471   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 472 
 473   // This interface assumes that it's being called by the
 474   // vm thread. It collects the heap assuming that the
 475   // heap lock is already held and that we are executing in
 476   // the context of the vm thread.
 477   virtual void collect_as_vm_thread(GCCause::Cause cause);
 478 
 479   // Returns the barrier set for this heap
 480   BarrierSet* barrier_set() { return _barrier_set; }
 481 
 482   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 483   // that it should answer "false" for the concurrent part of a concurrent
 484   // collector -- dld).
 485   bool is_gc_active() const { return _is_gc_active; }
 486 
 487   // Total number of GC collections (started)
 488   unsigned int total_collections() const { return _total_collections; }
 489   unsigned int total_full_collections() const { return _total_full_collections;}
 490 
 491   // Increment total number of GC collections (started)
 492   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 493   void increment_total_collections(bool full = false) {
 494     _total_collections++;
 495     if (full) {
 496       increment_total_full_collections();
 497     }
 498   }
 499 
 500   void increment_total_full_collections() { _total_full_collections++; }
 501 
 502   // Return the AdaptiveSizePolicy for the heap.
 503   virtual AdaptiveSizePolicy* size_policy() = 0;
 504 
 505   // Return the CollectorPolicy for the heap
 506   virtual CollectorPolicy* collector_policy() const = 0;
 507 
 508   void oop_iterate_no_header(OopClosure* cl);
 509 
 510   // Iterate over all the ref-containing fields of all objects, calling
 511   // "cl.do_oop" on each.
 512   virtual void oop_iterate(ExtendedOopClosure* cl) = 0;
 513 
 514   // Iterate over all objects, calling "cl.do_object" on each.
 515   virtual void object_iterate(ObjectClosure* cl) = 0;
 516 
 517   // Similar to object_iterate() except iterates only
 518   // over live objects.
 519   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 520 
 521   // NOTE! There is no requirement that a collector implement these
 522   // functions.
 523   //
 524   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 525   // each address in the (reserved) heap is a member of exactly
 526   // one block.  The defining characteristic of a block is that it is
 527   // possible to find its size, and thus to progress forward to the next
 528   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 529   // represent Java objects, or they might be free blocks in a
 530   // free-list-based heap (or subheap), as long as the two kinds are
 531   // distinguishable and the size of each is determinable.
 532 
 533   // Returns the address of the start of the "block" that contains the
 534   // address "addr".  We say "blocks" instead of "object" since some heaps
 535   // may not pack objects densely; a chunk may either be an object or a
 536   // non-object.
 537   virtual HeapWord* block_start(const void* addr) const = 0;
 538 
 539   // Requires "addr" to be the start of a chunk, and returns its size.
 540   // "addr + size" is required to be the start of a new chunk, or the end
 541   // of the active area of the heap.
 542   virtual size_t block_size(const HeapWord* addr) const = 0;
 543 
 544   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 545   // the block is an object.
 546   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 547 
 548   // Returns the longest time (in ms) that has elapsed since the last
 549   // time that any part of the heap was examined by a garbage collection.
 550   virtual jlong millis_since_last_gc() = 0;
 551 
 552   // Perform any cleanup actions necessary before allowing a verification.
 553   virtual void prepare_for_verify() = 0;
 554 
 555   // Generate any dumps preceding or following a full gc
 556   void pre_full_gc_dump(GCTimer* timer);
 557   void post_full_gc_dump(GCTimer* timer);
 558 
 559   VirtualSpaceSummary create_heap_space_summary();
 560   GCHeapSummary create_heap_summary();
 561 
 562   MetaspaceSummary create_metaspace_summary();
 563 
 564   // Print heap information on the given outputStream.
 565   virtual void print_on(outputStream* st) const = 0;
 566   // The default behavior is to call print_on() on tty.
 567   virtual void print() const {
 568     print_on(tty);
 569   }
 570   // Print more detailed heap information on the given
 571   // outputStream. The default behavior is to call print_on(). It is
 572   // up to each subclass to override it and add any additional output
 573   // it needs.
 574   virtual void print_extended_on(outputStream* st) const {
 575     print_on(st);
 576   }
 577 
 578   virtual void print_on_error(outputStream* st) const {
 579     st->print_cr("Heap:");
 580     print_extended_on(st);
 581     st->cr();
 582 
 583     _barrier_set->print_on(st);
 584   }
 585 
 586   // Print all GC threads (other than the VM thread)
 587   // used by this heap.
 588   virtual void print_gc_threads_on(outputStream* st) const = 0;
 589   // The default behavior is to call print_gc_threads_on() on tty.
 590   void print_gc_threads() {
 591     print_gc_threads_on(tty);
 592   }
 593   // Iterator for all GC threads (other than VM thread)
 594   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 595 
 596   // Print any relevant tracing info that flags imply.
 597   // Default implementation does nothing.
 598   virtual void print_tracing_info() const = 0;
 599 
 600   void print_heap_before_gc();
 601   void print_heap_after_gc();
 602 
 603   // Registering and unregistering an nmethod (compiled code) with the heap.
 604   // Override with specific mechanism for each specialized heap type.
 605   virtual void register_nmethod(nmethod* nm);
 606   virtual void unregister_nmethod(nmethod* nm);
 607 
 608   void trace_heap_before_gc(GCTracer* gc_tracer);
 609   void trace_heap_after_gc(GCTracer* gc_tracer);
 610 
 611   // Heap verification
 612   virtual void verify(bool silent, VerifyOption option) = 0;
 613 
 614   // Shut down all GC workers and other GC related threads.
 615   virtual void shutdown();
 616 
 617   // Accumulate additional statistics from GCLABs.
 618   virtual void accumulate_statistics_all_gclabs();
 619 
 620   // Support for object pinning. This is used by JNI Get*Critical()
 621   // and Release*Critical() family of functions. If supported, the GC
 622   // must guarantee that pinned objects never move.
 623   virtual bool supports_object_pinning() const;
 624   virtual oop pin_object(JavaThread* thread, oop obj);
 625   virtual void unpin_object(JavaThread* thread, oop obj);
 626 
 627   // Non product verification and debugging.
 628 #ifndef PRODUCT
 629   // Support for PromotionFailureALot.  Return true if it's time to cause a
 630   // promotion failure.  The no-argument version uses
 631   // this->_promotion_failure_alot_count as the counter.
 632   inline bool promotion_should_fail(volatile size_t* count);
 633   inline bool promotion_should_fail();
 634 
 635   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 636   // GC in which promotion failure occurred.
 637   inline void reset_promotion_should_fail(volatile size_t* count);
 638   inline void reset_promotion_should_fail();
 639 #endif  // #ifndef PRODUCT
 640 
 641 #ifdef ASSERT
 642   static int fired_fake_oom() {
 643     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 644   }
 645 #endif
 646 
 647  public:
 648   // This is a convenience method that is used in cases where
 649   // the actual number of GC worker threads is not pertinent but
 650   // only whether there more than 0.  Use of this method helps
 651   // reduce the occurrence of ParallelGCThreads to uses where the
 652   // actual number may be germane.
 653   static bool use_parallel_gc_threads() { return ParallelGCThreads > 0; }
 654 
 655   // Copy the current allocation context statistics for the specified contexts.
 656   // For each context in contexts, set the corresponding entries in the totals
 657   // and accuracy arrays to the current values held by the statistics.  Each
 658   // array should be of length len.
 659   // Returns true if there are more stats available.
 660   virtual bool copy_allocation_context_stats(const jint* contexts,
 661                                              jlong* totals,
 662                                              jbyte* accuracy,
 663                                              jint len) {
 664     return false;
 665   }
 666 
 667   /////////////// Unit tests ///////////////
 668 
 669   NOT_PRODUCT(static void test_is_in();)
 670 };
 671 
 672 // Class to set and reset the GC cause for a CollectedHeap.
 673 
 674 class GCCauseSetter : StackObj {
 675   CollectedHeap* _heap;
 676   GCCause::Cause _previous_cause;
 677  public:
 678   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 679     assert(SafepointSynchronize::is_at_safepoint(),
 680            "This method manipulates heap state without locking");
 681     _heap = heap;
 682     _previous_cause = _heap->gc_cause();
 683     _heap->set_gc_cause(cause);
 684   }
 685 
 686   ~GCCauseSetter() {
 687     assert(SafepointSynchronize::is_at_safepoint(),
 688           "This method manipulates heap state without locking");
 689     _heap->set_gc_cause(_previous_cause);
 690   }
 691 };
 692 
 693 #endif // SHARE_VM_GC_INTERFACE_COLLECTEDHEAP_HPP