1 /*

     2  * Copyright (c) 2001, 2017, 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/debug.hpp"

    35 #include "utilities/events.hpp"

    36 #include "utilities/formatBuffer.hpp"

    37 

    38 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This

    39 // is an abstract class: there may be many different kinds of heaps.  This

    40 // class defines the functions that a heap must implement, and contains

    41 // infrastructure common to all heaps.

    42 

    43 class AdaptiveSizePolicy;

    44 class BarrierSet;

    45 class CollectorPolicy;

    46 class GCHeapSummary;

    47 class GCTimer;

    48 class GCTracer;

    49 class MetaspaceSummary;

    50 class Thread;

    51 class ThreadClosure;

    52 class VirtualSpaceSummary;

    53 class WorkGang;

    54 class nmethod;

    55 

    56 class GCMessage : public FormatBuffer<1024> {

    57  public:

    58   bool is_before;

    59 

    60  public:

    61   GCMessage() {}

    62 };

    63 

    64 class CollectedHeap;

    65 

    66 class GCHeapLog : public EventLogBase<GCMessage> {

    67  private:

    68   void log_heap(CollectedHeap* heap, bool before);

    69 

    70  public:

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

    72 

    73   void log_heap_before(CollectedHeap* heap) {

    74     log_heap(heap, true);

    75   }

    76   void log_heap_after(CollectedHeap* heap) {

    77     log_heap(heap, false);

    78   }

    79 };

    80 

    81 //

    82 // CollectedHeap

    83 //   GenCollectedHeap

    84 //   G1CollectedHeap

    85 //   ParallelScavengeHeap

    86 //

    87 class CollectedHeap : public CHeapObj<mtInternal> {

    88   friend class VMStructs;

    89   friend class JVMCIVMStructs;

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

    91 

    92  private:

    93 #ifdef ASSERT

    94   static int       _fire_out_of_memory_count;

    95 #endif

    96 

    97   GCHeapLog* _gc_heap_log;

    98 

    99   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2

   100   // or INCLUDE_JVMCI is being used

   101   bool _defer_initial_card_mark;

   102 

   103   MemRegion _reserved;

   104 

   105  protected:

   106   BarrierSet* _barrier_set;

   107   bool _is_gc_active;

   108 

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

   110   static size_t _filler_array_max_size;

   111 

   112   unsigned int _total_collections;          // ... started

   113   unsigned int _total_full_collections;     // ... started

   114   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)

   115   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)

   116 

   117   // Reason for current garbage collection.  Should be set to

   118   // a value reflecting no collection between collections.

   119   GCCause::Cause _gc_cause;

   120   GCCause::Cause _gc_lastcause;

   121   PerfStringVariable* _perf_gc_cause;

   122   PerfStringVariable* _perf_gc_lastcause;

   123 

   124   // Constructor

   125   CollectedHeap();

   126 

   127   // Do common initializations that must follow instance construction,

   128   // for example, those needing virtual calls.

   129   // This code could perhaps be moved into initialize() but would

   130   // be slightly more awkward because we want the latter to be a

   131   // pure virtual.

   132   void pre_initialize();

   133 

   134   // Create a new tlab. All TLAB allocations must go through this.

   135   virtual HeapWord* allocate_new_tlab(size_t size);

   136 

   137   // Accumulate statistics on all tlabs.

   138   virtual void accumulate_statistics_all_tlabs();

   139 

   140   // Reinitialize tlabs before resuming mutators.

   141   virtual void resize_all_tlabs();

   142 

   143   // Allocate from the current thread's TLAB, with broken-out slow path.

   144   inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size);

   145   static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size);

   146 

   147   // Allocate an uninitialized block of the given size, or returns NULL if

   148   // this is impossible.

   149   inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);

   150 

   151   // Like allocate_init, but the block returned by a successful allocation

   152   // is guaranteed initialized to zeros.

   153   inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);

   154 

   155   // Helper functions for (VM) allocation.

   156   inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);

   157   inline static void post_allocation_setup_no_klass_install(Klass* klass,

   158                                                             HeapWord* objPtr);

   159 

   160   inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);

   161 

   162   inline static void post_allocation_setup_array(Klass* klass,

   163                                                  HeapWord* obj, int length);

   164 

   165   inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);

   166 

   167   // Clears an allocated object.

   168   inline static void init_obj(HeapWord* obj, size_t size);

   169 

   170   // Filler object utilities.

   171   static inline size_t filler_array_hdr_size();

   172   static inline size_t filler_array_min_size();

   173 

   174   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)

   175   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)

   176 

   177   // Fill with a single array; caller must ensure filler_array_min_size() <=

   178   // words <= filler_array_max_size().

   179   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);

   180 

   181   // Fill with a single object (either an int array or a java.lang.Object).

   182   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);

   183 

   184   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);

   185 

   186   // Verification functions

   187   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)

   188     PRODUCT_RETURN;

   189   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)

   190     PRODUCT_RETURN;

   191   debug_only(static void check_for_valid_allocation_state();)

   192 

   193  public:

   194   enum Name {

   195     GenCollectedHeap,

   196     ParallelScavengeHeap,

   197     G1CollectedHeap

   198   };

   199 

   200   static inline size_t filler_array_max_size() {

   201     return _filler_array_max_size;

   202   }

   203 

   204   virtual Name kind() const = 0;

   205 

   206   virtual const char* name() const = 0;

   207 

   208   /**

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

   210    * and JNI_OK on success.

   211    */

   212   virtual jint initialize() = 0;

   213 

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

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

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

   217   virtual void post_initialize() = 0;

   218 

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

   220   virtual void stop() {}

   221 

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

   223   MemRegion reserved_region() const { return _reserved; }

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

   225 

   226   virtual size_t capacity() const = 0;

   227   virtual size_t used() const = 0;

   228 

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

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

   231   // reach, without a garbage collection.

   232   virtual bool is_maximal_no_gc() const = 0;

   233 

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

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

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

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

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

   239   // spaces).

   240   virtual size_t max_capacity() const = 0;

   241 

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

   243   bool is_in_reserved(const void* p) const {

   244     return _reserved.contains(p);

   245   }

   246 

   247   bool is_in_reserved_or_null(const void* p) const {

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

   249   }

   250 

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

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

   253   // code.

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

   255 

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

   257 

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

   259   //

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

   261   //

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

   263   //    references one outside the closed subset.

   264   //

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

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

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

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

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

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

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

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

   273   // lower cost than "is_in."

   274 

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

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

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

   278   // contiguous spaces.

   279 

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

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

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

   283     return is_in_reserved(p);

   284   }

   285 

   286   bool is_in_closed_subset_or_null(const void* p) const {

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

   288   }

   289 

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

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

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

   293 

   294   void set_gc_cause(GCCause::Cause v) {

   295      if (UsePerfData) {

   296        _gc_lastcause = _gc_cause;

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

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

   299      }

   300     _gc_cause = v;

   301   }

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

   303 

   304   // General obj/array allocation facilities.

   305   inline static oop obj_allocate(Klass* klass, int size, TRAPS);

   306   inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);

   307   inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);

   308   inline static oop class_allocate(Klass* klass, int size, TRAPS);

   309 

   310   // Raw memory allocation facilities

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

   312   // mem_allocate() should never be

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

   314   virtual HeapWord* mem_allocate(size_t size,

   315                                  bool* gc_overhead_limit_was_exceeded) = 0;

   316 

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

   318   //

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

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

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

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

   323   // region and has slightly less overhead.

   324   static size_t min_fill_size() {

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

   326   }

   327 

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

   329 

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

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

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

   333   }

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

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

   336   }

   337 

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

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

   340   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,

   341                                                    HeapWord* end,

   342                                                    unsigned short alignment_in_bytes);

   343 

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

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

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

   347 

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

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

   350   virtual bool supports_inline_contig_alloc() const {

   351     return false;

   352   }

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

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

   355   // physically near to one another.)

   356   virtual HeapWord* volatile* top_addr() const {

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

   358     return NULL;

   359   }

   360   virtual HeapWord** end_addr() const {

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

   362     return NULL;

   363   }

   364 

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

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

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

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

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

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

   371   // method is invoked with the world stopped.

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

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

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

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

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

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

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

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

   380   virtual void ensure_parsability(bool retire_tlabs);

   381 

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

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

   384   // the following methods:

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

   386   // The default is "no".

   387   virtual bool supports_tlab_allocation() const = 0;

   388 

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

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

   391 

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

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

   394 

   395   virtual size_t max_tlab_size() const;

   396 

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

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

   399   // collection or expansion activity.

   400   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {

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

   402     return 0;

   403   }

   404 

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

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

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

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

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

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

   411   // have been elided.

   412   virtual bool can_elide_tlab_store_barriers() const = 0;

   413 

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

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

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

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

   418   // object before performing initializations that have elided

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

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

   421 

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

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

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

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

   426   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;

   427 

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

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

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

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

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

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

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

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

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

   437   virtual bool card_mark_must_follow_store() const = 0;

   438 

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

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

   441   // remembered set.

   442   virtual void flush_deferred_store_barrier(JavaThread* thread);

   443 

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

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

   446   // "CollectedHeap" supports.

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

   448 

   449   // Perform a full collection

   450   virtual void do_full_collection(bool clear_all_soft_refs) = 0;

   451 

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

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

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

   455   // the context of the vm thread.

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

   457 

   458   // Returns the barrier set for this heap

   459   BarrierSet* barrier_set() { return _barrier_set; }

   460   void set_barrier_set(BarrierSet* barrier_set);

   461 

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

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

   464   // collector -- dld).

   465   bool is_gc_active() const { return _is_gc_active; }

   466 

   467   // Total number of GC collections (started)

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

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

   470 

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

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

   473   void increment_total_collections(bool full = false) {

   474     _total_collections++;

   475     if (full) {

   476       increment_total_full_collections();

   477     }

   478   }

   479 

   480   void increment_total_full_collections() { _total_full_collections++; }

   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   // Return true if concurrent phase control (via

   583   // request_concurrent_phase_control) is supported by this collector.

   584   // The default implementation returns false.

   585   virtual bool supports_concurrent_phase_control() const;

   586 

   587   // Return a NULL terminated array of concurrent phase names provided

   588   // by this collector.  Supports Whitebox testing.  These are the

   589   // names recognized by request_concurrent_phase(). The default

   590   // implementation returns an array of one NULL element.

   591   virtual const char* const* concurrent_phases() const;

   592 

   593   // Request the collector enter the indicated concurrent phase, and

   594   // wait until it does so.  Supports WhiteBox testing.  Only one

   595   // request may be active at a time.  Phases are designated by name;

   596   // the set of names and their meaning is GC-specific.  Once the

   597   // requested phase has been reached, the collector will attempt to

   598   // avoid transitioning to a new phase until a new request is made.

   599   // [Note: A collector might not be able to remain in a given phase.

   600   // For example, a full collection might cancel an in-progress

   601   // concurrent collection.]

   602   //

   603   // Returns true when the phase is reached.  Returns false for an

   604   // unknown phase.  The default implementation returns false.

   605   virtual bool request_concurrent_phase(const char* phase);

   606 

   607   // Provides a thread pool to SafepointSynchronize to use

   608   // for parallel safepoint cleanup.

   609   // GCs that use a GC worker thread pool may want to share

   610   // it for use during safepoint cleanup. This is only possible

   611   // if the GC can pause and resume concurrent work (e.g. G1

   612   // concurrent marking) for an intermittent non-GC safepoint.

   613   // If this method returns NULL, SafepointSynchronize will

   614   // perform cleanup tasks serially in the VMThread.

   615   virtual WorkGang* get_safepoint_workers() { return NULL; }

   616 

   617   // Non product verification and debugging.

   618 #ifndef PRODUCT

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

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

   621   // this->_promotion_failure_alot_count as the counter.

   622   inline bool promotion_should_fail(volatile size_t* count);

   623   inline bool promotion_should_fail();

   624 

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

   626   // GC in which promotion failure occurred.

   627   inline void reset_promotion_should_fail(volatile size_t* count);

   628   inline void reset_promotion_should_fail();

   629 #endif  // #ifndef PRODUCT

   630 

   631 #ifdef ASSERT

   632   static int fired_fake_oom() {

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

   634   }

   635 #endif

   636 

   637  public:

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

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

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

   641   // array should be of length len.

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

   643   virtual bool copy_allocation_context_stats(const jint* contexts,

   644                                              jlong* totals,

   645                                              jbyte* accuracy,

   646                                              jint len) {

   647     return false;

   648   }

   649 

   650 };

   651 

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

   653 

   654 class GCCauseSetter : StackObj {

   655   CollectedHeap* _heap;

   656   GCCause::Cause _previous_cause;

   657  public:

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

   659     assert(SafepointSynchronize::is_at_safepoint(),

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

   661     _heap = heap;

   662     _previous_cause = _heap->gc_cause();

   663     _heap->set_gc_cause(cause);

   664   }

   665 

   666   ~GCCauseSetter() {

   667     assert(SafepointSynchronize::is_at_safepoint(),

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

   669     _heap->set_gc_cause(_previous_cause);

   670   }

   671 };

   672 

   673 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP