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.

    22  *

    23  */

    24 

    25 #ifndef SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP

    26 #define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP

    27 

    28 #include "gc/shared/gcCause.hpp"

    29 #include "gc/shared/gcWhen.hpp"

    30 #include "memory/allocation.hpp"

    31 #include "runtime/handles.hpp"

    32 #include "runtime/perfData.hpp"

    33 #include "runtime/safepoint.hpp"

    34 #include "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 GCHeapLog : public EventLogBase<GCMessage> {

    62  private:

    63   void log_heap(bool before);

    64 

    65  public:

    66   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}

    67 

    68   void log_heap_before() {

    69     log_heap(true);

    70   }

    71   void log_heap_after() {

    72     log_heap(false);

    73   }

    74 };

    75 

    76 //

    77 // CollectedHeap

    78 //   GenCollectedHeap

    79 //   G1CollectedHeap

    80 //   ParallelScavengeHeap

    81 //

    82 class CollectedHeap : public CHeapObj<mtInternal> {

    83   friend class VMStructs;

    84   friend class IsGCActiveMark; // Block structured external access to _is_gc_active

    85 

    86  private:

    87 #ifdef ASSERT

    88   static int       _fire_out_of_memory_count;

    89 #endif

    90 

    91   // Used for filler objects (static, but initialized in ctor).

    92   static size_t _filler_array_max_size;

    93 

    94   GCHeapLog* _gc_heap_log;

    95 

    96   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 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   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, int size);

   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, const 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     GenCollectedHeap,

   188     ParallelScavengeHeap,

   189     G1CollectedHeap

   190   };

   191 

   192   static inline size_t filler_array_max_size() {

   193     return _filler_array_max_size;

   194   }

   195 

   196   virtual Name kind() const = 0;

   197 

   198   /**

   199    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,

   200    * and JNI_OK on success.

   201    */

   202   virtual jint initialize() = 0;

   203 

   204   // In many heaps, there will be a need to perform some initialization activities

   205   // after the Universe is fully formed, but before general heap allocation is allowed.

   206   // This is the correct place to place such initialization methods.

   207   virtual void post_initialize();

   208 

   209   // Stop any onging concurrent work and prepare for exit.

   210   virtual void stop() {}

   211 

   212   void initialize_reserved_region(HeapWord *start, HeapWord *end);

   213   MemRegion reserved_region() const { return _reserved; }

   214   address base() const { return (address)reserved_region().start(); }

   215 

   216   virtual size_t capacity() const = 0;

   217   virtual size_t used() const = 0;

   218 

   219   // Return "true" if the part of the heap that allocates Java

   220   // objects has reached the maximal committed limit that it can

   221   // reach, without a garbage collection.

   222   virtual bool is_maximal_no_gc() const = 0;

   223 

   224   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of

   225   // memory that the vm could make available for storing 'normal' java objects.

   226   // This is based on the reserved address space, but should not include space

   227   // that the vm uses internally for bookkeeping or temporary storage

   228   // (e.g., in the case of the young gen, one of the survivor

   229   // spaces).

   230   virtual size_t max_capacity() const = 0;

   231 

   232   // Returns "TRUE" if "p" points into the reserved area of the heap.

   233   bool is_in_reserved(const void* p) const {

   234     return _reserved.contains(p);

   235   }

   236 

   237   bool is_in_reserved_or_null(const void* p) const {

   238     return p == NULL || is_in_reserved(p);

   239   }

   240 

   241   // Returns "TRUE" iff "p" points into the committed areas of the heap.

   242   // This method can be expensive so avoid using it in performance critical

   243   // code.

   244   virtual bool is_in(const void* p) const = 0;

   245 

   246   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })

   247 

   248   // Let's define some terms: a "closed" subset of a heap is one that

   249   //

   250   // 1) contains all currently-allocated objects, and

   251   //

   252   // 2) is closed under reference: no object in the closed subset

   253   //    references one outside the closed subset.

   254   //

   255   // Membership in a heap's closed subset is useful for assertions.

   256   // Clearly, the entire heap is a closed subset, so the default

   257   // implementation is to use "is_in_reserved".  But this may not be too

   258   // liberal to perform useful checking.  Also, the "is_in" predicate

   259   // defines a closed subset, but may be too expensive, since "is_in"

   260   // verifies that its argument points to an object head.  The

   261   // "closed_subset" method allows a heap to define an intermediate

   262   // predicate, allowing more precise checking than "is_in_reserved" at

   263   // lower cost than "is_in."

   264 

   265   // One important case is a heap composed of disjoint contiguous spaces,

   266   // such as the Garbage-First collector.  Such heaps have a convenient

   267   // closed subset consisting of the allocated portions of those

   268   // contiguous spaces.

   269 

   270   // Return "TRUE" iff the given pointer points into the heap's defined

   271   // closed subset (which defaults to the entire heap).

   272   virtual bool is_in_closed_subset(const void* p) const {

   273     return is_in_reserved(p);

   274   }

   275 

   276   bool is_in_closed_subset_or_null(const void* p) const {

   277     return p == NULL || is_in_closed_subset(p);

   278   }

   279 

   280   // An object is scavengable if its location may move during a scavenge.

   281   // (A scavenge is a GC which is not a full GC.)

   282   virtual bool is_scavengable(const void *p) = 0;

   283 

   284   void set_gc_cause(GCCause::Cause v) {

   285      if (UsePerfData) {

   286        _gc_lastcause = _gc_cause;

   287        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));

   288        _perf_gc_cause->set_value(GCCause::to_string(v));

   289      }

   290     _gc_cause = v;

   291   }

   292   GCCause::Cause gc_cause() { return _gc_cause; }

   293 

   294   // Number of threads currently working on GC tasks.

   295   uint n_par_threads() { return _n_par_threads; }

   296 

   297   // May be overridden to set additional parallelism.

   298   virtual void set_par_threads(uint t) { _n_par_threads = t; };

   299 

   300   // General obj/array allocation facilities.

   301   inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);

   302   inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);

   303   inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);

   304 

   305   inline static void post_allocation_install_obj_klass(KlassHandle klass,

   306                                                        oop obj);

   307 

   308   // Raw memory allocation facilities

   309   // The obj and array allocate methods are covers for these methods.

   310   // mem_allocate() should never be

   311   // called to allocate TLABs, only individual objects.

   312   virtual HeapWord* mem_allocate(size_t size,

   313                                  bool* gc_overhead_limit_was_exceeded) = 0;

   314 

   315   // Utilities for turning raw memory into filler objects.

   316   //

   317   // min_fill_size() is the smallest region that can be filled.

   318   // fill_with_objects() can fill arbitrary-sized regions of the heap using

   319   // multiple objects.  fill_with_object() is for regions known to be smaller

   320   // than the largest array of integers; it uses a single object to fill the

   321   // region and has slightly less overhead.

   322   static size_t min_fill_size() {

   323     return size_t(align_object_size(oopDesc::header_size()));

   324   }

   325 

   326   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);

   327 

   328   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);

   329   static void fill_with_object(MemRegion region, bool zap = true) {

   330     fill_with_object(region.start(), region.word_size(), zap);

   331   }

   332   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {

   333     fill_with_object(start, pointer_delta(end, start), zap);

   334   }

   335 

   336   // Return the address "addr" aligned by "alignment_in_bytes" if such

   337   // an address is below "end".  Return NULL otherwise.

   338   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,

   339                                                    HeapWord* end,

   340                                                    unsigned short alignment_in_bytes);

   341 

   342   // Some heaps may offer a contiguous region for shared non-blocking

   343   // allocation, via inlined code (by exporting the address of the top and

   344   // end fields defining the extent of the contiguous allocation region.)

   345 

   346   // This function returns "true" iff the heap supports this kind of

   347   // allocation.  (Default is "no".)

   348   virtual bool supports_inline_contig_alloc() const {

   349     return false;

   350   }

   351   // These functions return the addresses of the fields that define the

   352   // boundaries of the contiguous allocation area.  (These fields should be

   353   // physically near to one another.)

   354   virtual HeapWord** top_addr() const {

   355     guarantee(false, "inline contiguous allocation not supported");

   356     return NULL;

   357   }

   358   virtual HeapWord** end_addr() const {

   359     guarantee(false, "inline contiguous allocation not supported");

   360     return NULL;

   361   }

   362 

   363   // Some heaps may be in an unparseable state at certain times between

   364   // collections. This may be necessary for efficient implementation of

   365   // certain allocation-related activities. Calling this function before

   366   // attempting to parse a heap ensures that the heap is in a parsable

   367   // state (provided other concurrent activity does not introduce

   368   // unparsability). It is normally expected, therefore, that this

   369   // method is invoked with the world stopped.

   370   // NOTE: if you override this method, make sure you call

   371   // super::ensure_parsability so that the non-generational

   372   // part of the work gets done. See implementation of

   373   // CollectedHeap::ensure_parsability and, for instance,

   374   // that of GenCollectedHeap::ensure_parsability().

   375   // The argument "retire_tlabs" controls whether existing TLABs

   376   // are merely filled or also retired, thus preventing further

   377   // allocation from them and necessitating allocation of new TLABs.

   378   virtual void ensure_parsability(bool retire_tlabs);

   379 

   380   // Section on thread-local allocation buffers (TLABs)

   381   // If the heap supports thread-local allocation buffers, it should override

   382   // the following methods:

   383   // Returns "true" iff the heap supports thread-local allocation buffers.

   384   // The default is "no".

   385   virtual bool supports_tlab_allocation() const = 0;

   386 

   387   // The amount of space available for thread-local allocation buffers.

   388   virtual size_t tlab_capacity(Thread *thr) const = 0;

   389 

   390   // The amount of used space for thread-local allocation buffers for the given thread.

   391   virtual size_t tlab_used(Thread *thr) const = 0;

   392 

   393   virtual size_t max_tlab_size() const;

   394 

   395   // An estimate of the maximum allocation that could be performed

   396   // for thread-local allocation buffers without triggering any

   397   // collection or expansion activity.

   398   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {

   399     guarantee(false, "thread-local allocation buffers not supported");

   400     return 0;

   401   }

   402 

   403   // Can a compiler initialize a new object without store barriers?

   404   // This permission only extends from the creation of a new object

   405   // via a TLAB up to the first subsequent safepoint. If such permission

   406   // is granted for this heap type, the compiler promises to call

   407   // defer_store_barrier() below on any slow path allocation of

   408   // a new object for which such initializing store barriers will

   409   // have been elided.

   410   virtual bool can_elide_tlab_store_barriers() const = 0;

   411 

   412   // If a compiler is eliding store barriers for TLAB-allocated objects,

   413   // there is probably a corresponding slow path which can produce

   414   // an object allocated anywhere.  The compiler's runtime support

   415   // promises to call this function on such a slow-path-allocated

   416   // object before performing initializations that have elided

   417   // store barriers. Returns new_obj, or maybe a safer copy thereof.

   418   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);

   419 

   420   // Answers whether an initializing store to a new object currently

   421   // allocated at the given address doesn't need a store

   422   // barrier. Returns "true" if it doesn't need an initializing

   423   // store barrier; answers "false" if it does.

   424   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;

   425 

   426   // If a compiler is eliding store barriers for TLAB-allocated objects,

   427   // we will be informed of a slow-path allocation by a call

   428   // to new_store_pre_barrier() above. Such a call precedes the

   429   // initialization of the object itself, and no post-store-barriers will

   430   // be issued. Some heap types require that the barrier strictly follows

   431   // the initializing stores. (This is currently implemented by deferring the

   432   // barrier until the next slow-path allocation or gc-related safepoint.)

   433   // This interface answers whether a particular heap type needs the card

   434   // mark to be thus strictly sequenced after the stores.

   435   virtual bool card_mark_must_follow_store() const = 0;

   436 

   437   // If the CollectedHeap was asked to defer a store barrier above,

   438   // this informs it to flush such a deferred store barrier to the

   439   // remembered set.

   440   virtual void flush_deferred_store_barrier(JavaThread* thread);

   441 

   442   // Perform a collection of the heap; intended for use in implementing

   443   // "System.gc".  This probably implies as full a collection as the

   444   // "CollectedHeap" supports.

   445   virtual void collect(GCCause::Cause cause) = 0;

   446 

   447   // Perform a full collection

   448   virtual void do_full_collection(bool clear_all_soft_refs) = 0;

   449 

   450   // This interface assumes that it's being called by the

   451   // vm thread. It collects the heap assuming that the

   452   // heap lock is already held and that we are executing in

   453   // the context of the vm thread.

   454   virtual void collect_as_vm_thread(GCCause::Cause cause);

   455 

   456   // Returns the barrier set for this heap

   457   BarrierSet* barrier_set() { return _barrier_set; }

   458   void set_barrier_set(BarrierSet* barrier_set);

   459 

   460   // Returns "true" iff there is a stop-world GC in progress.  (I assume

   461   // that it should answer "false" for the concurrent part of a concurrent

   462   // collector -- dld).

   463   bool is_gc_active() const { return _is_gc_active; }

   464 

   465   // Total number of GC collections (started)

   466   unsigned int total_collections() const { return _total_collections; }

   467   unsigned int total_full_collections() const { return _total_full_collections;}

   468 

   469   // Increment total number of GC collections (started)

   470   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2

   471   void increment_total_collections(bool full = false) {

   472     _total_collections++;

   473     if (full) {

   474       increment_total_full_collections();

   475     }

   476   }

   477 

   478   void increment_total_full_collections() { _total_full_collections++; }

   479 

   480   // Return the AdaptiveSizePolicy for the heap.

   481   virtual AdaptiveSizePolicy* size_policy() = 0;

   482 

   483   // Return the CollectorPolicy for the heap

   484   virtual CollectorPolicy* collector_policy() const = 0;

   485 

   486   // Iterate over all objects, calling "cl.do_object" on each.

   487   virtual void object_iterate(ObjectClosure* cl) = 0;

   488 

   489   // Similar to object_iterate() except iterates only

   490   // over live objects.

   491   virtual void safe_object_iterate(ObjectClosure* cl) = 0;

   492 

   493   // NOTE! There is no requirement that a collector implement these

   494   // functions.

   495   //

   496   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,

   497   // each address in the (reserved) heap is a member of exactly

   498   // one block.  The defining characteristic of a block is that it is

   499   // possible to find its size, and thus to progress forward to the next

   500   // block.  (Blocks may be of different sizes.)  Thus, blocks may

   501   // represent Java objects, or they might be free blocks in a

   502   // free-list-based heap (or subheap), as long as the two kinds are

   503   // distinguishable and the size of each is determinable.

   504 

   505   // Returns the address of the start of the "block" that contains the

   506   // address "addr".  We say "blocks" instead of "object" since some heaps

   507   // may not pack objects densely; a chunk may either be an object or a

   508   // non-object.

   509   virtual HeapWord* block_start(const void* addr) const = 0;

   510 

   511   // Requires "addr" to be the start of a chunk, and returns its size.

   512   // "addr + size" is required to be the start of a new chunk, or the end

   513   // of the active area of the heap.

   514   virtual size_t block_size(const HeapWord* addr) const = 0;

   515 

   516   // Requires "addr" to be the start of a block, and returns "TRUE" iff

   517   // the block is an object.

   518   virtual bool block_is_obj(const HeapWord* addr) const = 0;

   519 

   520   // Returns the longest time (in ms) that has elapsed since the last

   521   // time that any part of the heap was examined by a garbage collection.

   522   virtual jlong millis_since_last_gc() = 0;

   523 

   524   // Perform any cleanup actions necessary before allowing a verification.

   525   virtual void prepare_for_verify() = 0;

   526 

   527   // Generate any dumps preceding or following a full gc

   528   void pre_full_gc_dump(GCTimer* timer);

   529   void post_full_gc_dump(GCTimer* timer);

   530 

   531   VirtualSpaceSummary create_heap_space_summary();

   532   GCHeapSummary create_heap_summary();

   533 

   534   MetaspaceSummary create_metaspace_summary();

   535 

   536   // Print heap information on the given outputStream.

   537   virtual void print_on(outputStream* st) const = 0;

   538   // The default behavior is to call print_on() on tty.

   539   virtual void print() const {

   540     print_on(tty);

   541   }

   542   // Print more detailed heap information on the given

   543   // outputStream. The default behavior is to call print_on(). It is

   544   // up to each subclass to override it and add any additional output

   545   // it needs.

   546   virtual void print_extended_on(outputStream* st) const {

   547     print_on(st);

   548   }

   549 

   550   virtual void print_on_error(outputStream* st) const;

   551 

   552   // Print all GC threads (other than the VM thread)

   553   // used by this heap.

   554   virtual void print_gc_threads_on(outputStream* st) const = 0;

   555   // The default behavior is to call print_gc_threads_on() on tty.

   556   void print_gc_threads() {

   557     print_gc_threads_on(tty);

   558   }

   559   // Iterator for all GC threads (other than VM thread)

   560   virtual void gc_threads_do(ThreadClosure* tc) const = 0;

   561 

   562   // Print any relevant tracing info that flags imply.

   563   // Default implementation does nothing.

   564   virtual void print_tracing_info() const = 0;

   565 

   566   void print_heap_before_gc();

   567   void print_heap_after_gc();

   568 

   569   // Registering and unregistering an nmethod (compiled code) with the heap.

   570   // Override with specific mechanism for each specialized heap type.

   571   virtual void register_nmethod(nmethod* nm);

   572   virtual void unregister_nmethod(nmethod* nm);

   573 

   574   void trace_heap_before_gc(const GCTracer* gc_tracer);

   575   void trace_heap_after_gc(const GCTracer* gc_tracer);

   576 

   577   // Heap verification

   578   virtual void verify(bool silent, VerifyOption option) = 0;

   579 

   580   // Non product verification and debugging.

   581 #ifndef PRODUCT

   582   // Support for PromotionFailureALot.  Return true if it's time to cause a

   583   // promotion failure.  The no-argument version uses

   584   // this->_promotion_failure_alot_count as the counter.

   585   inline bool promotion_should_fail(volatile size_t* count);

   586   inline bool promotion_should_fail();

   587 

   588   // Reset the PromotionFailureALot counters.  Should be called at the end of a

   589   // GC in which promotion failure occurred.

   590   inline void reset_promotion_should_fail(volatile size_t* count);

   591   inline void reset_promotion_should_fail();

   592 #endif  // #ifndef PRODUCT

   593 

   594 #ifdef ASSERT

   595   static int fired_fake_oom() {

   596     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);

   597   }

   598 #endif

   599 

   600  public:

   601   // Copy the current allocation context statistics for the specified contexts.

   602   // For each context in contexts, set the corresponding entries in the totals

   603   // and accuracy arrays to the current values held by the statistics.  Each

   604   // array should be of length len.

   605   // Returns true if there are more stats available.

   606   virtual bool copy_allocation_context_stats(const jint* contexts,

   607                                              jlong* totals,

   608                                              jbyte* accuracy,

   609                                              jint len) {

   610     return false;

   611   }

   612 

   613   /////////////// Unit tests ///////////////

   614 

   615   NOT_PRODUCT(static void test_is_in();)

   616 };

   617 

   618 // Class to set and reset the GC cause for a CollectedHeap.

   619 

   620 class GCCauseSetter : StackObj {

   621   CollectedHeap* _heap;

   622   GCCause::Cause _previous_cause;

   623  public:

   624   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {

   625     assert(SafepointSynchronize::is_at_safepoint(),

   626            "This method manipulates heap state without locking");

   627     _heap = heap;

   628     _previous_cause = _heap->gc_cause();

   629     _heap->set_gc_cause(cause);

   630   }

   631 

   632   ~GCCauseSetter() {

   633     assert(SafepointSynchronize::is_at_safepoint(),

   634           "This method manipulates heap state without locking");

   635     _heap->set_gc_cause(_previous_cause);

   636   }

   637 };

   638 

   639 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP