rev 48000 : [mq]: open.patch
rev 48001 : [mq]: 8191564-diff.patch

   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 #include "utilities/growableArray.hpp"
  38 
  39 // A "CollectedHeap" is an implementation of a java heap for HotSpot.  This
  40 // is an abstract class: there may be many different kinds of heaps.  This
  41 // class defines the functions that a heap must implement, and contains
  42 // infrastructure common to all heaps.
  43 
  44 class AdaptiveSizePolicy;
  45 class BarrierSet;
  46 class CollectorPolicy;
  47 class GCHeapSummary;
  48 class GCTimer;
  49 class GCTracer;
  50 class GCMemoryManager;
  51 class MemoryPool;
  52 class MetaspaceSummary;
  53 class Thread;
  54 class ThreadClosure;
  55 class VirtualSpaceSummary;
  56 class WorkGang;
  57 class nmethod;
  58 
  59 class GCMessage : public FormatBuffer<1024> {
  60  public:
  61   bool is_before;
  62 
  63  public:
  64   GCMessage() {}
  65 };
  66 
  67 class CollectedHeap;
  68 
  69 class GCHeapLog : public EventLogBase<GCMessage> {
  70  private:
  71   void log_heap(CollectedHeap* heap, bool before);
  72 
  73  public:
  74   GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
  75 
  76   void log_heap_before(CollectedHeap* heap) {
  77     log_heap(heap, true);
  78   }
  79   void log_heap_after(CollectedHeap* heap) {
  80     log_heap(heap, false);
  81   }
  82 };
  83 
  84 //
  85 // CollectedHeap
  86 //   GenCollectedHeap
  87 //     SerialHeap
  88 //     CMSHeap
  89 //   G1CollectedHeap
  90 //   ParallelScavengeHeap
  91 //
  92 class CollectedHeap : public CHeapObj<mtInternal> {
  93   friend class VMStructs;
  94   friend class JVMCIVMStructs;
  95   friend class IsGCActiveMark; // Block structured external access to _is_gc_active
  96 
  97  private:
  98 #ifdef ASSERT
  99   static int       _fire_out_of_memory_count;
 100 #endif
 101 
 102   GCHeapLog* _gc_heap_log;
 103 
 104   // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2
 105   // or INCLUDE_JVMCI is being used
 106   bool _defer_initial_card_mark;
 107 
 108   MemRegion _reserved;
 109 
 110  protected:
 111   BarrierSet* _barrier_set;
 112   bool _is_gc_active;
 113 
 114   // Used for filler objects (static, but initialized in ctor).
 115   static size_t _filler_array_max_size;
 116 
 117   unsigned int _total_collections;          // ... started
 118   unsigned int _total_full_collections;     // ... started
 119   NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
 120   NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
 121 
 122   // Reason for current garbage collection.  Should be set to
 123   // a value reflecting no collection between collections.
 124   GCCause::Cause _gc_cause;
 125   GCCause::Cause _gc_lastcause;
 126   PerfStringVariable* _perf_gc_cause;
 127   PerfStringVariable* _perf_gc_lastcause;
 128 
 129   // Constructor
 130   CollectedHeap();
 131 
 132   // Do common initializations that must follow instance construction,
 133   // for example, those needing virtual calls.
 134   // This code could perhaps be moved into initialize() but would
 135   // be slightly more awkward because we want the latter to be a
 136   // pure virtual.
 137   void pre_initialize();
 138 
 139   // Create a new tlab. All TLAB allocations must go through this.
 140   virtual HeapWord* allocate_new_tlab(size_t size);
 141 
 142   // Accumulate statistics on all tlabs.
 143   virtual void accumulate_statistics_all_tlabs();
 144 
 145   // Reinitialize tlabs before resuming mutators.
 146   virtual void resize_all_tlabs();
 147 
 148   // Allocate from the current thread's TLAB, with broken-out slow path.
 149   inline static HeapWord* allocate_from_tlab(Klass* klass, Thread* thread, size_t size);
 150   static HeapWord* allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size);
 151 
 152   // Allocate an uninitialized block of the given size, or returns NULL if
 153   // this is impossible.
 154   inline static HeapWord* common_mem_allocate_noinit(Klass* klass, size_t size, TRAPS);
 155 
 156   // Like allocate_init, but the block returned by a successful allocation
 157   // is guaranteed initialized to zeros.
 158   inline static HeapWord* common_mem_allocate_init(Klass* klass, size_t size, TRAPS);
 159 
 160   // Helper functions for (VM) allocation.
 161   inline static void post_allocation_setup_common(Klass* klass, HeapWord* obj);
 162   inline static void post_allocation_setup_no_klass_install(Klass* klass,
 163                                                             HeapWord* objPtr);
 164 
 165   inline static void post_allocation_setup_obj(Klass* klass, HeapWord* obj, int size);
 166 
 167   inline static void post_allocation_setup_array(Klass* klass,
 168                                                  HeapWord* obj, int length);
 169 
 170   inline static void post_allocation_setup_class(Klass* klass, HeapWord* obj, int size);
 171 
 172   // Clears an allocated object.
 173   inline static void init_obj(HeapWord* obj, size_t size);
 174 
 175   // Filler object utilities.
 176   static inline size_t filler_array_hdr_size();
 177   static inline size_t filler_array_min_size();
 178 
 179   DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
 180   DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
 181 
 182   // Fill with a single array; caller must ensure filler_array_min_size() <=
 183   // words <= filler_array_max_size().
 184   static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
 185 
 186   // Fill with a single object (either an int array or a java.lang.Object).
 187   static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
 188 
 189   virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
 190 
 191   // Verification functions
 192   virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
 193     PRODUCT_RETURN;
 194   virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
 195     PRODUCT_RETURN;
 196   debug_only(static void check_for_valid_allocation_state();)
 197 
 198  public:
 199   enum Name {
 200     SerialHeap,
 201     ParallelScavengeHeap,
 202     G1CollectedHeap,
 203     CMSHeap
 204   };
 205 
 206   static inline size_t filler_array_max_size() {
 207     return _filler_array_max_size;
 208   }
 209 
 210   virtual Name kind() const = 0;
 211 
 212   virtual const char* name() const = 0;
 213 
 214   /**
 215    * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
 216    * and JNI_OK on success.
 217    */
 218   virtual jint initialize() = 0;
 219 
 220   // In many heaps, there will be a need to perform some initialization activities
 221   // after the Universe is fully formed, but before general heap allocation is allowed.
 222   // This is the correct place to place such initialization methods.
 223   virtual void post_initialize() = 0;
 224 
 225   // Stop any onging concurrent work and prepare for exit.
 226   virtual void stop() {}
 227 
 228   // Stop and resume concurrent GC threads interfering with safepoint operations
 229   virtual void safepoint_synchronize_begin() {}
 230   virtual void safepoint_synchronize_end() {}
 231 
 232   void initialize_reserved_region(HeapWord *start, HeapWord *end);
 233   MemRegion reserved_region() const { return _reserved; }
 234   address base() const { return (address)reserved_region().start(); }
 235 
 236   virtual size_t capacity() const = 0;
 237   virtual size_t used() const = 0;
 238 
 239   // Return "true" if the part of the heap that allocates Java
 240   // objects has reached the maximal committed limit that it can
 241   // reach, without a garbage collection.
 242   virtual bool is_maximal_no_gc() const = 0;
 243 
 244   // Support for java.lang.Runtime.maxMemory():  return the maximum amount of
 245   // memory that the vm could make available for storing 'normal' java objects.
 246   // This is based on the reserved address space, but should not include space
 247   // that the vm uses internally for bookkeeping or temporary storage
 248   // (e.g., in the case of the young gen, one of the survivor
 249   // spaces).
 250   virtual size_t max_capacity() const = 0;
 251 
 252   // Returns "TRUE" if "p" points into the reserved area of the heap.
 253   bool is_in_reserved(const void* p) const {
 254     return _reserved.contains(p);
 255   }
 256 
 257   bool is_in_reserved_or_null(const void* p) const {
 258     return p == NULL || is_in_reserved(p);
 259   }
 260 
 261   // Returns "TRUE" iff "p" points into the committed areas of the heap.
 262   // This method can be expensive so avoid using it in performance critical
 263   // code.
 264   virtual bool is_in(const void* p) const = 0;
 265 
 266   DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
 267 
 268   // Let's define some terms: a "closed" subset of a heap is one that
 269   //
 270   // 1) contains all currently-allocated objects, and
 271   //
 272   // 2) is closed under reference: no object in the closed subset
 273   //    references one outside the closed subset.
 274   //
 275   // Membership in a heap's closed subset is useful for assertions.
 276   // Clearly, the entire heap is a closed subset, so the default
 277   // implementation is to use "is_in_reserved".  But this may not be too
 278   // liberal to perform useful checking.  Also, the "is_in" predicate
 279   // defines a closed subset, but may be too expensive, since "is_in"
 280   // verifies that its argument points to an object head.  The
 281   // "closed_subset" method allows a heap to define an intermediate
 282   // predicate, allowing more precise checking than "is_in_reserved" at
 283   // lower cost than "is_in."
 284 
 285   // One important case is a heap composed of disjoint contiguous spaces,
 286   // such as the Garbage-First collector.  Such heaps have a convenient
 287   // closed subset consisting of the allocated portions of those
 288   // contiguous spaces.
 289 
 290   // Return "TRUE" iff the given pointer points into the heap's defined
 291   // closed subset (which defaults to the entire heap).
 292   virtual bool is_in_closed_subset(const void* p) const {
 293     return is_in_reserved(p);
 294   }
 295 
 296   bool is_in_closed_subset_or_null(const void* p) const {
 297     return p == NULL || is_in_closed_subset(p);
 298   }
 299 
 300   void set_gc_cause(GCCause::Cause v) {
 301      if (UsePerfData) {
 302        _gc_lastcause = _gc_cause;
 303        _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
 304        _perf_gc_cause->set_value(GCCause::to_string(v));
 305      }
 306     _gc_cause = v;
 307   }
 308   GCCause::Cause gc_cause() { return _gc_cause; }
 309 
 310   // General obj/array allocation facilities.
 311   inline static oop obj_allocate(Klass* klass, int size, TRAPS);
 312   inline static oop array_allocate(Klass* klass, int size, int length, TRAPS);
 313   inline static oop array_allocate_nozero(Klass* klass, int size, int length, TRAPS);
 314   inline static oop class_allocate(Klass* klass, int size, TRAPS);
 315 
 316   // Raw memory allocation facilities
 317   // The obj and array allocate methods are covers for these methods.
 318   // mem_allocate() should never be
 319   // called to allocate TLABs, only individual objects.
 320   virtual HeapWord* mem_allocate(size_t size,
 321                                  bool* gc_overhead_limit_was_exceeded) = 0;
 322 
 323   // Utilities for turning raw memory into filler objects.
 324   //
 325   // min_fill_size() is the smallest region that can be filled.
 326   // fill_with_objects() can fill arbitrary-sized regions of the heap using
 327   // multiple objects.  fill_with_object() is for regions known to be smaller
 328   // than the largest array of integers; it uses a single object to fill the
 329   // region and has slightly less overhead.
 330   static size_t min_fill_size() {
 331     return size_t(align_object_size(oopDesc::header_size()));
 332   }
 333 
 334   static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
 335 
 336   static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
 337   static void fill_with_object(MemRegion region, bool zap = true) {
 338     fill_with_object(region.start(), region.word_size(), zap);
 339   }
 340   static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
 341     fill_with_object(start, pointer_delta(end, start), zap);
 342   }
 343 
 344   // Return the address "addr" aligned by "alignment_in_bytes" if such
 345   // an address is below "end".  Return NULL otherwise.
 346   inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
 347                                                    HeapWord* end,
 348                                                    unsigned short alignment_in_bytes);
 349 
 350   // Some heaps may offer a contiguous region for shared non-blocking
 351   // allocation, via inlined code (by exporting the address of the top and
 352   // end fields defining the extent of the contiguous allocation region.)
 353 
 354   // This function returns "true" iff the heap supports this kind of
 355   // allocation.  (Default is "no".)
 356   virtual bool supports_inline_contig_alloc() const {
 357     return false;
 358   }
 359   // These functions return the addresses of the fields that define the
 360   // boundaries of the contiguous allocation area.  (These fields should be
 361   // physically near to one another.)
 362   virtual HeapWord* volatile* top_addr() const {
 363     guarantee(false, "inline contiguous allocation not supported");
 364     return NULL;
 365   }
 366   virtual HeapWord** end_addr() const {
 367     guarantee(false, "inline contiguous allocation not supported");
 368     return NULL;
 369   }
 370 
 371   // Some heaps may be in an unparseable state at certain times between
 372   // collections. This may be necessary for efficient implementation of
 373   // certain allocation-related activities. Calling this function before
 374   // attempting to parse a heap ensures that the heap is in a parsable
 375   // state (provided other concurrent activity does not introduce
 376   // unparsability). It is normally expected, therefore, that this
 377   // method is invoked with the world stopped.
 378   // NOTE: if you override this method, make sure you call
 379   // super::ensure_parsability so that the non-generational
 380   // part of the work gets done. See implementation of
 381   // CollectedHeap::ensure_parsability and, for instance,
 382   // that of GenCollectedHeap::ensure_parsability().
 383   // The argument "retire_tlabs" controls whether existing TLABs
 384   // are merely filled or also retired, thus preventing further
 385   // allocation from them and necessitating allocation of new TLABs.
 386   virtual void ensure_parsability(bool retire_tlabs);
 387 
 388   // Section on thread-local allocation buffers (TLABs)
 389   // If the heap supports thread-local allocation buffers, it should override
 390   // the following methods:
 391   // Returns "true" iff the heap supports thread-local allocation buffers.
 392   // The default is "no".
 393   virtual bool supports_tlab_allocation() const = 0;
 394 
 395   // The amount of space available for thread-local allocation buffers.
 396   virtual size_t tlab_capacity(Thread *thr) const = 0;
 397 
 398   // The amount of used space for thread-local allocation buffers for the given thread.
 399   virtual size_t tlab_used(Thread *thr) const = 0;
 400 
 401   virtual size_t max_tlab_size() const;
 402 
 403   // An estimate of the maximum allocation that could be performed
 404   // for thread-local allocation buffers without triggering any
 405   // collection or expansion activity.
 406   virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
 407     guarantee(false, "thread-local allocation buffers not supported");
 408     return 0;
 409   }
 410 
 411   // Can a compiler initialize a new object without store barriers?
 412   // This permission only extends from the creation of a new object
 413   // via a TLAB up to the first subsequent safepoint. If such permission
 414   // is granted for this heap type, the compiler promises to call
 415   // defer_store_barrier() below on any slow path allocation of
 416   // a new object for which such initializing store barriers will
 417   // have been elided.
 418   virtual bool can_elide_tlab_store_barriers() const = 0;
 419 
 420   // If a compiler is eliding store barriers for TLAB-allocated objects,
 421   // there is probably a corresponding slow path which can produce
 422   // an object allocated anywhere.  The compiler's runtime support
 423   // promises to call this function on such a slow-path-allocated
 424   // object before performing initializations that have elided
 425   // store barriers. Returns new_obj, or maybe a safer copy thereof.
 426   virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
 427 
 428   // Answers whether an initializing store to a new object currently
 429   // allocated at the given address doesn't need a store
 430   // barrier. Returns "true" if it doesn't need an initializing
 431   // store barrier; answers "false" if it does.
 432   virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
 433 
 434   // If a compiler is eliding store barriers for TLAB-allocated objects,
 435   // we will be informed of a slow-path allocation by a call
 436   // to new_store_pre_barrier() above. Such a call precedes the
 437   // initialization of the object itself, and no post-store-barriers will
 438   // be issued. Some heap types require that the barrier strictly follows
 439   // the initializing stores. (This is currently implemented by deferring the
 440   // barrier until the next slow-path allocation or gc-related safepoint.)
 441   // This interface answers whether a particular heap type needs the card
 442   // mark to be thus strictly sequenced after the stores.
 443   virtual bool card_mark_must_follow_store() const = 0;
 444 
 445   // If the CollectedHeap was asked to defer a store barrier above,
 446   // this informs it to flush such a deferred store barrier to the
 447   // remembered set.
 448   virtual void flush_deferred_store_barrier(JavaThread* thread);
 449 
 450   // Perform a collection of the heap; intended for use in implementing
 451   // "System.gc".  This probably implies as full a collection as the
 452   // "CollectedHeap" supports.
 453   virtual void collect(GCCause::Cause cause) = 0;
 454 
 455   // Perform a full collection
 456   virtual void do_full_collection(bool clear_all_soft_refs) = 0;
 457 
 458   // This interface assumes that it's being called by the
 459   // vm thread. It collects the heap assuming that the
 460   // heap lock is already held and that we are executing in
 461   // the context of the vm thread.
 462   virtual void collect_as_vm_thread(GCCause::Cause cause);
 463 
 464   // Returns the barrier set for this heap
 465   BarrierSet* barrier_set() { return _barrier_set; }
 466   void set_barrier_set(BarrierSet* barrier_set);
 467 
 468   // Returns "true" iff there is a stop-world GC in progress.  (I assume
 469   // that it should answer "false" for the concurrent part of a concurrent
 470   // collector -- dld).
 471   bool is_gc_active() const { return _is_gc_active; }
 472 
 473   // Total number of GC collections (started)
 474   unsigned int total_collections() const { return _total_collections; }
 475   unsigned int total_full_collections() const { return _total_full_collections;}
 476 
 477   // Increment total number of GC collections (started)
 478   // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
 479   void increment_total_collections(bool full = false) {
 480     _total_collections++;
 481     if (full) {
 482       increment_total_full_collections();
 483     }
 484   }
 485 
 486   void increment_total_full_collections() { _total_full_collections++; }
 487 
 488   // Return the CollectorPolicy for the heap
 489   virtual CollectorPolicy* collector_policy() const = 0;
 490 
 491   virtual GrowableArray<GCMemoryManager*> memory_managers() = 0;
 492   virtual GrowableArray<MemoryPool*> memory_pools() = 0;
 493 
 494   // Iterate over all objects, calling "cl.do_object" on each.
 495   virtual void object_iterate(ObjectClosure* cl) = 0;
 496 
 497   // Similar to object_iterate() except iterates only
 498   // over live objects.
 499   virtual void safe_object_iterate(ObjectClosure* cl) = 0;
 500 
 501   // NOTE! There is no requirement that a collector implement these
 502   // functions.
 503   //
 504   // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
 505   // each address in the (reserved) heap is a member of exactly
 506   // one block.  The defining characteristic of a block is that it is
 507   // possible to find its size, and thus to progress forward to the next
 508   // block.  (Blocks may be of different sizes.)  Thus, blocks may
 509   // represent Java objects, or they might be free blocks in a
 510   // free-list-based heap (or subheap), as long as the two kinds are
 511   // distinguishable and the size of each is determinable.
 512 
 513   // Returns the address of the start of the "block" that contains the
 514   // address "addr".  We say "blocks" instead of "object" since some heaps
 515   // may not pack objects densely; a chunk may either be an object or a
 516   // non-object.
 517   virtual HeapWord* block_start(const void* addr) const = 0;
 518 
 519   // Requires "addr" to be the start of a chunk, and returns its size.
 520   // "addr + size" is required to be the start of a new chunk, or the end
 521   // of the active area of the heap.
 522   virtual size_t block_size(const HeapWord* addr) const = 0;
 523 
 524   // Requires "addr" to be the start of a block, and returns "TRUE" iff
 525   // the block is an object.
 526   virtual bool block_is_obj(const HeapWord* addr) const = 0;
 527 
 528   // Returns the longest time (in ms) that has elapsed since the last
 529   // time that any part of the heap was examined by a garbage collection.
 530   virtual jlong millis_since_last_gc() = 0;
 531 
 532   // Perform any cleanup actions necessary before allowing a verification.
 533   virtual void prepare_for_verify() = 0;
 534 
 535   // Generate any dumps preceding or following a full gc
 536  private:
 537   void full_gc_dump(GCTimer* timer, bool before);



 538  public:
 539   void pre_full_gc_dump(GCTimer* timer);
 540   void post_full_gc_dump(GCTimer* timer);
 541 
 542   VirtualSpaceSummary create_heap_space_summary();
 543   GCHeapSummary create_heap_summary();
 544 
 545   MetaspaceSummary create_metaspace_summary();
 546 
 547   // Print heap information on the given outputStream.
 548   virtual void print_on(outputStream* st) const = 0;
 549   // The default behavior is to call print_on() on tty.
 550   virtual void print() const {
 551     print_on(tty);
 552   }
 553   // Print more detailed heap information on the given
 554   // outputStream. The default behavior is to call print_on(). It is
 555   // up to each subclass to override it and add any additional output
 556   // it needs.
 557   virtual void print_extended_on(outputStream* st) const {
 558     print_on(st);
 559   }
 560 
 561   virtual void print_on_error(outputStream* st) const;
 562 
 563   // Print all GC threads (other than the VM thread)
 564   // used by this heap.
 565   virtual void print_gc_threads_on(outputStream* st) const = 0;
 566   // The default behavior is to call print_gc_threads_on() on tty.
 567   void print_gc_threads() {
 568     print_gc_threads_on(tty);
 569   }
 570   // Iterator for all GC threads (other than VM thread)
 571   virtual void gc_threads_do(ThreadClosure* tc) const = 0;
 572 
 573   // Print any relevant tracing info that flags imply.
 574   // Default implementation does nothing.
 575   virtual void print_tracing_info() const = 0;
 576 
 577   void print_heap_before_gc();
 578   void print_heap_after_gc();
 579 
 580   // An object is scavengable if its location may move during a scavenge.
 581   // (A scavenge is a GC which is not a full GC.)
 582   virtual bool is_scavengable(oop obj) = 0;
 583   // Registering and unregistering an nmethod (compiled code) with the heap.
 584   // Override with specific mechanism for each specialized heap type.
 585   virtual void register_nmethod(nmethod* nm) {}
 586   virtual void unregister_nmethod(nmethod* nm) {}
 587   virtual void verify_nmethod(nmethod* nmethod) {}
 588 
 589   void trace_heap_before_gc(const GCTracer* gc_tracer);
 590   void trace_heap_after_gc(const GCTracer* gc_tracer);
 591 
 592   // Heap verification
 593   virtual void verify(VerifyOption option) = 0;
 594 
 595   // Return true if concurrent phase control (via
 596   // request_concurrent_phase_control) is supported by this collector.
 597   // The default implementation returns false.
 598   virtual bool supports_concurrent_phase_control() const;
 599 
 600   // Return a NULL terminated array of concurrent phase names provided
 601   // by this collector.  Supports Whitebox testing.  These are the
 602   // names recognized by request_concurrent_phase(). The default
 603   // implementation returns an array of one NULL element.
 604   virtual const char* const* concurrent_phases() const;
 605 
 606   // Request the collector enter the indicated concurrent phase, and
 607   // wait until it does so.  Supports WhiteBox testing.  Only one
 608   // request may be active at a time.  Phases are designated by name;
 609   // the set of names and their meaning is GC-specific.  Once the
 610   // requested phase has been reached, the collector will attempt to
 611   // avoid transitioning to a new phase until a new request is made.
 612   // [Note: A collector might not be able to remain in a given phase.
 613   // For example, a full collection might cancel an in-progress
 614   // concurrent collection.]
 615   //
 616   // Returns true when the phase is reached.  Returns false for an
 617   // unknown phase.  The default implementation returns false.
 618   virtual bool request_concurrent_phase(const char* phase);
 619 
 620   // Provides a thread pool to SafepointSynchronize to use
 621   // for parallel safepoint cleanup.
 622   // GCs that use a GC worker thread pool may want to share
 623   // it for use during safepoint cleanup. This is only possible
 624   // if the GC can pause and resume concurrent work (e.g. G1
 625   // concurrent marking) for an intermittent non-GC safepoint.
 626   // If this method returns NULL, SafepointSynchronize will
 627   // perform cleanup tasks serially in the VMThread.
 628   virtual WorkGang* get_safepoint_workers() { return NULL; }
 629 
 630   // Non product verification and debugging.
 631 #ifndef PRODUCT
 632   // Support for PromotionFailureALot.  Return true if it's time to cause a
 633   // promotion failure.  The no-argument version uses
 634   // this->_promotion_failure_alot_count as the counter.
 635   inline bool promotion_should_fail(volatile size_t* count);
 636   inline bool promotion_should_fail();
 637 
 638   // Reset the PromotionFailureALot counters.  Should be called at the end of a
 639   // GC in which promotion failure occurred.
 640   inline void reset_promotion_should_fail(volatile size_t* count);
 641   inline void reset_promotion_should_fail();
 642 #endif  // #ifndef PRODUCT
 643 
 644 #ifdef ASSERT
 645   static int fired_fake_oom() {
 646     return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
 647   }
 648 #endif
 649 
 650  public:
 651   // Copy the current allocation context statistics for the specified contexts.
 652   // For each context in contexts, set the corresponding entries in the totals
 653   // and accuracy arrays to the current values held by the statistics.  Each
 654   // array should be of length len.
 655   // Returns true if there are more stats available.
 656   virtual bool copy_allocation_context_stats(const jint* contexts,
 657                                              jlong* totals,
 658                                              jbyte* accuracy,
 659                                              jint len) {
 660     return false;
 661   }
 662 
 663 };
 664 
 665 // Class to set and reset the GC cause for a CollectedHeap.
 666 
 667 class GCCauseSetter : StackObj {
 668   CollectedHeap* _heap;
 669   GCCause::Cause _previous_cause;
 670  public:
 671   GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
 672     assert(SafepointSynchronize::is_at_safepoint(),
 673            "This method manipulates heap state without locking");
 674     _heap = heap;
 675     _previous_cause = _heap->gc_cause();
 676     _heap->set_gc_cause(cause);
 677   }
 678 
 679   ~GCCauseSetter() {
 680     assert(SafepointSynchronize::is_at_safepoint(),
 681           "This method manipulates heap state without locking");
 682     _heap->set_gc_cause(_previous_cause);
 683   }
 684 };
 685 
 686 #endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
--- EOF ---