1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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   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).
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP
  27 
  28 #include "gc_implementation/g1/g1AllocationContext.hpp"
  29 #include "gc_implementation/g1/g1BlockOffsetTable.hpp"
  30 #include "gc_implementation/g1/g1_specialized_oop_closures.hpp"
  31 #include "gc_implementation/g1/heapRegionType.hpp"
  32 #include "gc_implementation/g1/survRateGroup.hpp"
  33 #include "gc_implementation/shared/ageTable.hpp"
  34 #include "gc_implementation/shared/spaceDecorator.hpp"
  35 #include "memory/space.inline.hpp"
  36 #include "memory/watermark.hpp"
  37 #include "utilities/macros.hpp"
  38 
  39 // A HeapRegion is the smallest piece of a G1CollectedHeap that
  40 // can be collected independently.
  41 
  42 // NOTE: Although a HeapRegion is a Space, its
  43 // Space::initDirtyCardClosure method must not be called.
  44 // The problem is that the existence of this method breaks
  45 // the independence of barrier sets from remembered sets.
  46 // The solution is to remove this method from the definition
  47 // of a Space.
  48 
  49 class HeapRegionRemSet;
  50 class HeapRegionRemSetIterator;
  51 class HeapRegion;
  52 class HeapRegionSetBase;
  53 class nmethod;
  54 
  55 #define HR_FORMAT "%u:(%s)["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
  56 #define HR_FORMAT_PARAMS(_hr_) \
  57                 (_hr_)->hrm_index(), \
  58                 (_hr_)->get_short_type_str(), \
  59                 p2i((_hr_)->bottom()), p2i((_hr_)->top()), p2i((_hr_)->end())
  60 
  61 // sentinel value for hrm_index
  62 #define G1_NO_HRM_INDEX ((uint) -1)
  63 
  64 // A dirty card to oop closure for heap regions. It
  65 // knows how to get the G1 heap and how to use the bitmap
  66 // in the concurrent marker used by G1 to filter remembered
  67 // sets.
  68 
  69 class HeapRegionDCTOC : public DirtyCardToOopClosure {
  70 private:
  71   HeapRegion* _hr;
  72   G1ParPushHeapRSClosure* _rs_scan;
  73   G1CollectedHeap* _g1;
  74 
  75   // Walk the given memory region from bottom to (actual) top
  76   // looking for objects and applying the oop closure (_cl) to
  77   // them. The base implementation of this treats the area as
  78   // blocks, where a block may or may not be an object. Sub-
  79   // classes should override this to provide more accurate
  80   // or possibly more efficient walking.
  81   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
  82 
  83 public:
  84   HeapRegionDCTOC(G1CollectedHeap* g1,
  85                   HeapRegion* hr,
  86                   G1ParPushHeapRSClosure* cl,
  87                   CardTableModRefBS::PrecisionStyle precision);
  88 };
  89 
  90 // The complicating factor is that BlockOffsetTable diverged
  91 // significantly, and we need functionality that is only in the G1 version.
  92 // So I copied that code, which led to an alternate G1 version of
  93 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could
  94 // be reconciled, then G1OffsetTableContigSpace could go away.
  95 
  96 // The idea behind time stamps is the following. We want to keep track of
  97 // the highest address where it's safe to scan objects for each region.
  98 // This is only relevant for current GC alloc regions so we keep a time stamp
  99 // per region to determine if the region has been allocated during the current
 100 // GC or not. If the time stamp is current we report a scan_top value which
 101 // was saved at the end of the previous GC for retained alloc regions and which is
 102 // equal to the bottom for all other regions.
 103 // There is a race between card scanners and allocating gc workers where we must ensure
 104 // that card scanners do not read the memory allocated by the gc workers.
 105 // In order to enforce that, we must not return a value of _top which is more recent than the
 106 // time stamp. This is due to the fact that a region may become a gc alloc region at
 107 // some point after we've read the timestamp value as being < the current time stamp.
 108 // The time stamps are re-initialized to zero at cleanup and at Full GCs.
 109 // The current scheme that uses sequential unsigned ints will fail only if we have 4b
 110 // evacuation pauses between two cleanups, which is _highly_ unlikely.
 111 class G1OffsetTableContigSpace: public CompactibleSpace {
 112   friend class VMStructs;
 113   HeapWord* _top;
 114   HeapWord* volatile _scan_top;
 115  protected:
 116   G1BlockOffsetArrayContigSpace _offsets;
 117   Mutex _par_alloc_lock;
 118   volatile unsigned _gc_time_stamp;
 119   // When we need to retire an allocation region, while other threads
 120   // are also concurrently trying to allocate into it, we typically
 121   // allocate a dummy object at the end of the region to ensure that
 122   // no more allocations can take place in it. However, sometimes we
 123   // want to know where the end of the last "real" object we allocated
 124   // into the region was and this is what this keeps track.
 125   HeapWord* _pre_dummy_top;
 126 
 127  public:
 128   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
 129                            MemRegion mr);
 130 
 131   void set_top(HeapWord* value) { _top = value; }
 132   HeapWord* top() const { return _top; }
 133 
 134  protected:
 135   // Reset the G1OffsetTableContigSpace.
 136   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 137 
 138   HeapWord** top_addr() { return &_top; }
 139   // Allocation helpers (return NULL if full).
 140   inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
 141   inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
 142 
 143  public:
 144   void reset_after_compaction() { set_top(compaction_top()); }
 145 
 146   size_t used() const { return byte_size(bottom(), top()); }
 147   size_t free() const { return byte_size(top(), end()); }
 148   bool is_free_block(const HeapWord* p) const { return p >= top(); }
 149 
 150   MemRegion used_region() const { return MemRegion(bottom(), top()); }
 151 
 152   void object_iterate(ObjectClosure* blk);
 153   void safe_object_iterate(ObjectClosure* blk);
 154 
 155   void set_bottom(HeapWord* value);
 156   void set_end(HeapWord* value);
 157 
 158   HeapWord* scan_top() const;
 159   void record_timestamp();
 160   void reset_gc_time_stamp() { _gc_time_stamp = 0; }
 161   unsigned get_gc_time_stamp() { return _gc_time_stamp; }
 162   void record_retained_region();
 163 
 164   // See the comment above in the declaration of _pre_dummy_top for an
 165   // explanation of what it is.
 166   void set_pre_dummy_top(HeapWord* pre_dummy_top) {
 167     assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");
 168     _pre_dummy_top = pre_dummy_top;
 169   }
 170   HeapWord* pre_dummy_top() {
 171     return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;
 172   }
 173   void reset_pre_dummy_top() { _pre_dummy_top = NULL; }
 174 
 175   virtual void clear(bool mangle_space);
 176 
 177   HeapWord* block_start(const void* p);
 178   HeapWord* block_start_const(const void* p) const;
 179 
 180   // Add offset table update.
 181   virtual HeapWord* allocate(size_t word_size);
 182   HeapWord* par_allocate(size_t word_size);
 183 
 184   HeapWord* saved_mark_word() const { ShouldNotReachHere(); return NULL; }
 185 
 186   // MarkSweep support phase3
 187   virtual HeapWord* initialize_threshold();
 188   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 189 
 190   virtual void print() const;
 191 
 192   void reset_bot() {
 193     _offsets.reset_bot();
 194   }
 195 
 196   void print_bot_on(outputStream* out) {
 197     _offsets.print_on(out);
 198   }
 199 };
 200 
 201 class HeapRegion: public G1OffsetTableContigSpace {
 202   friend class VMStructs;
 203   // Allow scan_and_forward to call (private) overrides for auxiliary functions on this class
 204   template <typename SpaceType>
 205   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
 206  private:
 207 
 208   // The remembered set for this region.
 209   // (Might want to make this "inline" later, to avoid some alloc failure
 210   // issues.)
 211   HeapRegionRemSet* _rem_set;
 212 
 213   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
 214 
 215   // Auxiliary functions for scan_and_forward support.
 216   // See comments for CompactibleSpace for more information.
 217   inline HeapWord* scan_limit() const {
 218     return top();
 219   }
 220 
 221   inline bool scanned_block_is_obj(const HeapWord* addr) const {
 222     return true; // Always true, since scan_limit is top
 223   }
 224 
 225   inline size_t scanned_block_size(const HeapWord* addr) const {
 226     return HeapRegion::block_size(addr); // Avoid virtual call
 227   }
 228 
 229  protected:
 230   // The index of this region in the heap region sequence.
 231   uint  _hrm_index;
 232 
 233   AllocationContext_t _allocation_context;
 234 
 235   HeapRegionType _type;
 236 
 237   // For a humongous region, region in which it starts.
 238   HeapRegion* _humongous_start_region;
 239 
 240   // True iff an attempt to evacuate an object in the region failed.
 241   bool _evacuation_failed;
 242 
 243   // A heap region may be a member one of a number of special subsets, each
 244   // represented as linked lists through the field below.  Currently, there
 245   // is only one set:
 246   //   The collection set.
 247   HeapRegion* _next_in_special_set;
 248 
 249   // next region in the young "generation" region set
 250   HeapRegion* _next_young_region;
 251 
 252   // Next region whose cards need cleaning
 253   HeapRegion* _next_dirty_cards_region;
 254 
 255   // Fields used by the HeapRegionSetBase class and subclasses.
 256   HeapRegion* _next;
 257   HeapRegion* _prev;
 258 #ifdef ASSERT
 259   HeapRegionSetBase* _containing_set;
 260 #endif // ASSERT
 261 
 262   // We use concurrent marking to determine the amount of live data
 263   // in each heap region.
 264   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.
 265   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.
 266 
 267   // The calculated GC efficiency of the region.
 268   double _gc_efficiency;
 269 
 270   int  _young_index_in_cset;
 271   SurvRateGroup* _surv_rate_group;
 272   int  _age_index;
 273 
 274   // The start of the unmarked area. The unmarked area extends from this
 275   // word until the top and/or end of the region, and is the part
 276   // of the region for which no marking was done, i.e. objects may
 277   // have been allocated in this part since the last mark phase.
 278   // "prev" is the top at the start of the last completed marking.
 279   // "next" is the top at the start of the in-progress marking (if any.)
 280   HeapWord* _prev_top_at_mark_start;
 281   HeapWord* _next_top_at_mark_start;
 282   // If a collection pause is in progress, this is the top at the start
 283   // of that pause.
 284 
 285   void init_top_at_mark_start() {
 286     assert(_prev_marked_bytes == 0 &&
 287            _next_marked_bytes == 0,
 288            "Must be called after zero_marked_bytes.");
 289     HeapWord* bot = bottom();
 290     _prev_top_at_mark_start = bot;
 291     _next_top_at_mark_start = bot;
 292   }
 293 
 294   // Cached attributes used in the collection set policy information
 295 
 296   // The RSet length that was added to the total value
 297   // for the collection set.
 298   size_t _recorded_rs_length;
 299 
 300   // The predicted elapsed time that was added to total value
 301   // for the collection set.
 302   double _predicted_elapsed_time_ms;
 303 
 304   // The predicted number of bytes to copy that was added to
 305   // the total value for the collection set.
 306   size_t _predicted_bytes_to_copy;
 307 
 308  public:
 309   HeapRegion(uint hrm_index,
 310              G1BlockOffsetSharedArray* sharedOffsetArray,
 311              MemRegion mr);
 312 
 313   // Initializing the HeapRegion not only resets the data structure, but also
 314   // resets the BOT for that heap region.
 315   // The default values for clear_space means that we will do the clearing if
 316   // there's clearing to be done ourselves. We also always mangle the space.
 317   virtual void initialize(MemRegion mr, bool clear_space = false, bool mangle_space = SpaceDecorator::Mangle);
 318 
 319   static int    LogOfHRGrainBytes;
 320   static int    LogOfHRGrainWords;
 321 
 322   static size_t GrainBytes;
 323   static size_t GrainWords;
 324   static size_t CardsPerRegion;
 325 
 326   static size_t align_up_to_region_byte_size(size_t sz) {
 327     return (sz + (size_t) GrainBytes - 1) &
 328                                       ~((1 << (size_t) LogOfHRGrainBytes) - 1);
 329   }
 330 
 331   static size_t max_region_size();
 332 
 333   // It sets up the heap region size (GrainBytes / GrainWords), as
 334   // well as other related fields that are based on the heap region
 335   // size (LogOfHRGrainBytes / LogOfHRGrainWords /
 336   // CardsPerRegion). All those fields are considered constant
 337   // throughout the JVM's execution, therefore they should only be set
 338   // up once during initialization time.
 339   static void setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size);
 340 
 341   // All allocated blocks are occupied by objects in a HeapRegion
 342   bool block_is_obj(const HeapWord* p) const;
 343 
 344   // Returns the object size for all valid block starts
 345   // and the amount of unallocated words if called on top()
 346   size_t block_size(const HeapWord* p) const;
 347 
 348   // Override for scan_and_forward support.
 349   void prepare_for_compaction(CompactPoint* cp);
 350 
 351   inline HeapWord* par_allocate_no_bot_updates(size_t word_size);
 352   inline HeapWord* allocate_no_bot_updates(size_t word_size);
 353 
 354   // If this region is a member of a HeapRegionManager, the index in that
 355   // sequence, otherwise -1.
 356   uint hrm_index() const { return _hrm_index; }
 357 
 358   // The number of bytes marked live in the region in the last marking phase.
 359   size_t marked_bytes()    { return _prev_marked_bytes; }
 360   size_t live_bytes() {
 361     return (top() - prev_top_at_mark_start()) * HeapWordSize + marked_bytes();
 362   }
 363 
 364   // The number of bytes counted in the next marking.
 365   size_t next_marked_bytes() { return _next_marked_bytes; }
 366   // The number of bytes live wrt the next marking.
 367   size_t next_live_bytes() {
 368     return
 369       (top() - next_top_at_mark_start()) * HeapWordSize + next_marked_bytes();
 370   }
 371 
 372   // A lower bound on the amount of garbage bytes in the region.
 373   size_t garbage_bytes() {
 374     size_t used_at_mark_start_bytes =
 375       (prev_top_at_mark_start() - bottom()) * HeapWordSize;
 376     assert(used_at_mark_start_bytes >= marked_bytes(),
 377            "Can't mark more than we have.");
 378     return used_at_mark_start_bytes - marked_bytes();
 379   }
 380 
 381   // Return the amount of bytes we'll reclaim if we collect this
 382   // region. This includes not only the known garbage bytes in the
 383   // region but also any unallocated space in it, i.e., [top, end),
 384   // since it will also be reclaimed if we collect the region.
 385   size_t reclaimable_bytes() {
 386     size_t known_live_bytes = live_bytes();
 387     assert(known_live_bytes <= capacity(), "sanity");
 388     return capacity() - known_live_bytes;
 389   }
 390 
 391   // An upper bound on the number of live bytes in the region.
 392   size_t max_live_bytes() { return used() - garbage_bytes(); }
 393 
 394   void add_to_marked_bytes(size_t incr_bytes) {
 395     _next_marked_bytes = _next_marked_bytes + incr_bytes;
 396     assert(_next_marked_bytes <= used(), "invariant" );
 397   }
 398 
 399   void zero_marked_bytes()      {
 400     _prev_marked_bytes = _next_marked_bytes = 0;
 401   }
 402 
 403   const char* get_type_str() const { return _type.get_str(); }
 404   const char* get_short_type_str() const { return _type.get_short_str(); }
 405 
 406   bool is_free() const { return _type.is_free(); }
 407 
 408   bool is_young()    const { return _type.is_young();    }
 409   bool is_eden()     const { return _type.is_eden();     }
 410   bool is_survivor() const { return _type.is_survivor(); }
 411 
 412   bool is_humongous() const { return _type.is_humongous(); }
 413   bool is_starts_humongous() const { return _type.is_starts_humongous(); }
 414   bool is_continues_humongous() const { return _type.is_continues_humongous();   }
 415 
 416   bool is_old() const { return _type.is_old(); }
 417 
 418   // For a humongous region, region in which it starts.
 419   HeapRegion* humongous_start_region() const {
 420     return _humongous_start_region;
 421   }
 422 
 423   // Return the number of distinct regions that are covered by this region:
 424   // 1 if the region is not humongous, >= 1 if the region is humongous.
 425   uint region_num() const {
 426     if (!is_humongous()) {
 427       return 1U;
 428     } else {
 429       assert(is_starts_humongous(), "doesn't make sense on HC regions");
 430       assert(capacity() % HeapRegion::GrainBytes == 0, "sanity");
 431       return (uint) (capacity() >> HeapRegion::LogOfHRGrainBytes);
 432     }
 433   }
 434 
 435   // Return the index + 1 of the last HC regions that's associated
 436   // with this HS region.
 437   uint last_hc_index() const {
 438     assert(is_starts_humongous(), "don't call this otherwise");
 439     return hrm_index() + region_num();
 440   }
 441 
 442   // Same as Space::is_in_reserved, but will use the original size of the region.
 443   // The original size is different only for start humongous regions. They get
 444   // their _end set up to be the end of the last continues region of the
 445   // corresponding humongous object.
 446   bool is_in_reserved_raw(const void* p) const {
 447     return _bottom <= p && p < orig_end();
 448   }
 449 
 450   // Makes the current region be a "starts humongous" region, i.e.,
 451   // the first region in a series of one or more contiguous regions
 452   // that will contain a single "humongous" object. The two parameters
 453   // are as follows:
 454   //
 455   // new_top : The new value of the top field of this region which
 456   // points to the end of the humongous object that's being
 457   // allocated. If there is more than one region in the series, top
 458   // will lie beyond this region's original end field and on the last
 459   // region in the series.
 460   //
 461   // new_end : The new value of the end field of this region which
 462   // points to the end of the last region in the series. If there is
 463   // one region in the series (namely: this one) end will be the same
 464   // as the original end of this region.
 465   //
 466   // Updating top and end as described above makes this region look as
 467   // if it spans the entire space taken up by all the regions in the
 468   // series and an single allocation moved its top to new_top. This
 469   // ensures that the space (capacity / allocated) taken up by all
 470   // humongous regions can be calculated by just looking at the
 471   // "starts humongous" regions and by ignoring the "continues
 472   // humongous" regions.
 473   void set_starts_humongous(HeapWord* new_top, HeapWord* new_end);
 474 
 475   // Makes the current region be a "continues humongous'
 476   // region. first_hr is the "start humongous" region of the series
 477   // which this region will be part of.
 478   void set_continues_humongous(HeapRegion* first_hr);
 479 
 480   // Unsets the humongous-related fields on the region.
 481   void clear_humongous();
 482 
 483   // If the region has a remembered set, return a pointer to it.
 484   HeapRegionRemSet* rem_set() const {
 485     return _rem_set;
 486   }
 487 
 488   bool in_collection_set() const;
 489 
 490   HeapRegion* next_in_collection_set() {
 491     assert(in_collection_set(), "should only invoke on member of CS.");
 492     assert(_next_in_special_set == NULL ||
 493            _next_in_special_set->in_collection_set(),
 494            "Malformed CS.");
 495     return _next_in_special_set;
 496   }
 497   void set_next_in_collection_set(HeapRegion* r) {
 498     assert(in_collection_set(), "should only invoke on member of CS.");
 499     assert(r == NULL || r->in_collection_set(), "Malformed CS.");
 500     _next_in_special_set = r;
 501   }
 502 
 503   void set_allocation_context(AllocationContext_t context) {
 504     _allocation_context = context;
 505   }
 506 
 507   AllocationContext_t  allocation_context() const {
 508     return _allocation_context;
 509   }
 510 
 511   // Methods used by the HeapRegionSetBase class and subclasses.
 512 
 513   // Getter and setter for the next and prev fields used to link regions into
 514   // linked lists.
 515   HeapRegion* next()              { return _next; }
 516   HeapRegion* prev()              { return _prev; }
 517 
 518   void set_next(HeapRegion* next) { _next = next; }
 519   void set_prev(HeapRegion* prev) { _prev = prev; }
 520 
 521   // Every region added to a set is tagged with a reference to that
 522   // set. This is used for doing consistency checking to make sure that
 523   // the contents of a set are as they should be and it's only
 524   // available in non-product builds.
 525 #ifdef ASSERT
 526   void set_containing_set(HeapRegionSetBase* containing_set) {
 527     assert((containing_set == NULL && _containing_set != NULL) ||
 528            (containing_set != NULL && _containing_set == NULL),
 529            err_msg("containing_set: "PTR_FORMAT" "
 530                    "_containing_set: "PTR_FORMAT,
 531                    p2i(containing_set), p2i(_containing_set)));
 532 
 533     _containing_set = containing_set;
 534   }
 535 
 536   HeapRegionSetBase* containing_set() { return _containing_set; }
 537 #else // ASSERT
 538   void set_containing_set(HeapRegionSetBase* containing_set) { }
 539 
 540   // containing_set() is only used in asserts so there's no reason
 541   // to provide a dummy version of it.
 542 #endif // ASSERT
 543 
 544   HeapRegion* get_next_young_region() { return _next_young_region; }
 545   void set_next_young_region(HeapRegion* hr) {
 546     _next_young_region = hr;
 547   }
 548 
 549   HeapRegion* get_next_dirty_cards_region() const { return _next_dirty_cards_region; }
 550   HeapRegion** next_dirty_cards_region_addr() { return &_next_dirty_cards_region; }
 551   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }
 552   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }
 553 
 554   // For the start region of a humongous sequence, it's original end().
 555   HeapWord* orig_end() const { return _bottom + GrainWords; }
 556 
 557   // Reset HR stuff to default values.
 558   void hr_clear(bool par, bool clear_space, bool locked = false);
 559   void par_clear();
 560 
 561   // Get the start of the unmarked area in this region.
 562   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }
 563   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }
 564 
 565   // Note the start or end of marking. This tells the heap region
 566   // that the collector is about to start or has finished (concurrently)
 567   // marking the heap.
 568 
 569   // Notify the region that concurrent marking is starting. Initialize
 570   // all fields related to the next marking info.
 571   inline void note_start_of_marking();
 572 
 573   // Notify the region that concurrent marking has finished. Copy the
 574   // (now finalized) next marking info fields into the prev marking
 575   // info fields.
 576   inline void note_end_of_marking();
 577 
 578   // Notify the region that it will be used as to-space during a GC
 579   // and we are about to start copying objects into it.
 580   inline void note_start_of_copying(bool during_initial_mark);
 581 
 582   // Notify the region that it ceases being to-space during a GC and
 583   // we will not copy objects into it any more.
 584   inline void note_end_of_copying(bool during_initial_mark);
 585 
 586   // Notify the region that we are about to start processing
 587   // self-forwarded objects during evac failure handling.
 588   void note_self_forwarding_removal_start(bool during_initial_mark,
 589                                           bool during_conc_mark);
 590 
 591   // Notify the region that we have finished processing self-forwarded
 592   // objects during evac failure handling.
 593   void note_self_forwarding_removal_end(bool during_initial_mark,
 594                                         bool during_conc_mark,
 595                                         size_t marked_bytes);
 596 
 597   // Returns "false" iff no object in the region was allocated when the
 598   // last mark phase ended.
 599   bool is_marked() { return _prev_top_at_mark_start != bottom(); }
 600 
 601   void reset_during_compaction() {
 602     assert(is_starts_humongous(),
 603            "should only be called for starts humongous regions");
 604 
 605     zero_marked_bytes();
 606     init_top_at_mark_start();
 607   }
 608 
 609   void calc_gc_efficiency(void);
 610   double gc_efficiency() { return _gc_efficiency;}
 611 
 612   int  young_index_in_cset() const { return _young_index_in_cset; }
 613   void set_young_index_in_cset(int index) {
 614     assert( (index == -1) || is_young(), "pre-condition" );
 615     _young_index_in_cset = index;
 616   }
 617 
 618   int age_in_surv_rate_group() {
 619     assert( _surv_rate_group != NULL, "pre-condition" );
 620     assert( _age_index > -1, "pre-condition" );
 621     return _surv_rate_group->age_in_group(_age_index);
 622   }
 623 
 624   void record_surv_words_in_group(size_t words_survived) {
 625     assert( _surv_rate_group != NULL, "pre-condition" );
 626     assert( _age_index > -1, "pre-condition" );
 627     int age_in_group = age_in_surv_rate_group();
 628     _surv_rate_group->record_surviving_words(age_in_group, words_survived);
 629   }
 630 
 631   int age_in_surv_rate_group_cond() {
 632     if (_surv_rate_group != NULL)
 633       return age_in_surv_rate_group();
 634     else
 635       return -1;
 636   }
 637 
 638   SurvRateGroup* surv_rate_group() {
 639     return _surv_rate_group;
 640   }
 641 
 642   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {
 643     assert( surv_rate_group != NULL, "pre-condition" );
 644     assert( _surv_rate_group == NULL, "pre-condition" );
 645     assert( is_young(), "pre-condition" );
 646 
 647     _surv_rate_group = surv_rate_group;
 648     _age_index = surv_rate_group->next_age_index();
 649   }
 650 
 651   void uninstall_surv_rate_group() {
 652     if (_surv_rate_group != NULL) {
 653       assert( _age_index > -1, "pre-condition" );
 654       assert( is_young(), "pre-condition" );
 655 
 656       _surv_rate_group = NULL;
 657       _age_index = -1;
 658     } else {
 659       assert( _age_index == -1, "pre-condition" );
 660     }
 661   }
 662 
 663   void set_free() { _type.set_free(); }
 664 
 665   void set_eden()        { _type.set_eden();        }
 666   void set_eden_pre_gc() { _type.set_eden_pre_gc(); }
 667   void set_survivor()    { _type.set_survivor();    }
 668 
 669   void set_old() { _type.set_old(); }
 670 
 671   // Determine if an object has been allocated since the last
 672   // mark performed by the collector. This returns true iff the object
 673   // is within the unmarked area of the region.
 674   bool obj_allocated_since_prev_marking(oop obj) const {
 675     return (HeapWord *) obj >= prev_top_at_mark_start();
 676   }
 677   bool obj_allocated_since_next_marking(oop obj) const {
 678     return (HeapWord *) obj >= next_top_at_mark_start();
 679   }
 680 
 681   // Returns the "evacuation_failed" property of the region.
 682   bool evacuation_failed() { return _evacuation_failed; }
 683 
 684   // Sets the "evacuation_failed" property of the region.
 685   void set_evacuation_failed(bool b) {
 686     _evacuation_failed = b;
 687 
 688     if (b) {
 689       _next_marked_bytes = 0;
 690     }
 691   }
 692 
 693   // Requires that "mr" be entirely within the region.
 694   // Apply "cl->do_object" to all objects that intersect with "mr".
 695   // If the iteration encounters an unparseable portion of the region,
 696   // or if "cl->abort()" is true after a closure application,
 697   // terminate the iteration and return the address of the start of the
 698   // subregion that isn't done.  (The two can be distinguished by querying
 699   // "cl->abort()".)  Return of "NULL" indicates that the iteration
 700   // completed.
 701   HeapWord*
 702   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);
 703 
 704   // filter_young: if true and the region is a young region then we
 705   // skip the iteration.
 706   // card_ptr: if not NULL, and we decide that the card is not young
 707   // and we iterate over it, we'll clean the card before we start the
 708   // iteration.
 709   HeapWord*
 710   oops_on_card_seq_iterate_careful(MemRegion mr,
 711                                    FilterOutOfRegionClosure* cl,
 712                                    bool filter_young,
 713                                    jbyte* card_ptr);
 714 
 715   size_t recorded_rs_length() const        { return _recorded_rs_length; }
 716   double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }
 717   size_t predicted_bytes_to_copy() const   { return _predicted_bytes_to_copy; }
 718 
 719   void set_recorded_rs_length(size_t rs_length) {
 720     _recorded_rs_length = rs_length;
 721   }
 722 
 723   void set_predicted_elapsed_time_ms(double ms) {
 724     _predicted_elapsed_time_ms = ms;
 725   }
 726 
 727   void set_predicted_bytes_to_copy(size_t bytes) {
 728     _predicted_bytes_to_copy = bytes;
 729   }
 730 
 731   virtual CompactibleSpace* next_compaction_space() const;
 732 
 733   virtual void reset_after_compaction();
 734 
 735   // Routines for managing a list of code roots (attached to the
 736   // this region's RSet) that point into this heap region.
 737   void add_strong_code_root(nmethod* nm);
 738   void add_strong_code_root_locked(nmethod* nm);
 739   void remove_strong_code_root(nmethod* nm);
 740 
 741   // Applies blk->do_code_blob() to each of the entries in
 742   // the strong code roots list for this region
 743   void strong_code_roots_do(CodeBlobClosure* blk) const;
 744 
 745   // Verify that the entries on the strong code root list for this
 746   // region are live and include at least one pointer into this region.
 747   void verify_strong_code_roots(VerifyOption vo, bool* failures) const;
 748 
 749   void print() const;
 750   void print_on(outputStream* st) const;
 751 
 752   // vo == UsePrevMarking  -> use "prev" marking information,
 753   // vo == UseNextMarking -> use "next" marking information
 754   // vo == UseMarkWord    -> use the mark word in the object header
 755   //
 756   // NOTE: Only the "prev" marking information is guaranteed to be
 757   // consistent most of the time, so most calls to this should use
 758   // vo == UsePrevMarking.
 759   // Currently, there is only one case where this is called with
 760   // vo == UseNextMarking, which is to verify the "next" marking
 761   // information at the end of remark.
 762   // Currently there is only one place where this is called with
 763   // vo == UseMarkWord, which is to verify the marking during a
 764   // full GC.
 765   void verify(VerifyOption vo, bool *failures) const;
 766 
 767   // Override; it uses the "prev" marking information
 768   virtual void verify() const;
 769 };
 770 
 771 // HeapRegionClosure is used for iterating over regions.
 772 // Terminates the iteration when the "doHeapRegion" method returns "true".
 773 class HeapRegionClosure : public StackObj {
 774   friend class HeapRegionManager;
 775   friend class G1CollectedHeap;
 776 
 777   bool _complete;
 778   void incomplete() { _complete = false; }
 779 
 780  public:
 781   HeapRegionClosure(): _complete(true) {}
 782 
 783   // Typically called on each region until it returns true.
 784   virtual bool doHeapRegion(HeapRegion* r) = 0;
 785 
 786   // True after iteration if the closure was applied to all heap regions
 787   // and returned "false" in all cases.
 788   bool complete() { return _complete; }
 789 };
 790 
 791 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP