1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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/g1BlockOffsetTable.hpp"
  29 #include "gc_implementation/g1/g1_specialized_oop_closures.hpp"
  30 #include "gc_implementation/g1/survRateGroup.hpp"
  31 #include "gc_implementation/shared/ageTable.hpp"
  32 #include "gc_implementation/shared/spaceDecorator.hpp"
  33 #include "memory/space.inline.hpp"
  34 #include "memory/watermark.hpp"
  35 #include "utilities/macros.hpp"
  36 
  37 #if INCLUDE_ALL_GCS
  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_)->hrs_index(), \
  58                 (_hr_)->is_survivor() ? "S" : (_hr_)->is_young() ? "E" : \
  59                 (_hr_)->startsHumongous() ? "HS" : \
  60                 (_hr_)->continuesHumongous() ? "HC" : \
  61                 !(_hr_)->is_empty() ? "O" : "F", \
  62                 p2i((_hr_)->bottom()), p2i((_hr_)->top()), p2i((_hr_)->end())
  63 
  64 // sentinel value for hrs_index
  65 #define G1_NO_HRS_INDEX ((uint) -1)
  66 
  67 // A dirty card to oop closure for heap regions. It
  68 // knows how to get the G1 heap and how to use the bitmap
  69 // in the concurrent marker used by G1 to filter remembered
  70 // sets.
  71 
  72 class HeapRegionDCTOC : public DirtyCardToOopClosure {
  73 public:
  74   // Specification of possible DirtyCardToOopClosure filtering.
  75   enum FilterKind {
  76     NoFilterKind,
  77     IntoCSFilterKind,
  78     OutOfRegionFilterKind
  79   };
  80 
  81 protected:
  82   HeapRegion* _hr;
  83   FilterKind _fk;
  84   G1CollectedHeap* _g1;
  85 
  86   // Walk the given memory region from bottom to (actual) top
  87   // looking for objects and applying the oop closure (_cl) to
  88   // them. The base implementation of this treats the area as
  89   // blocks, where a block may or may not be an object. Sub-
  90   // classes should override this to provide more accurate
  91   // or possibly more efficient walking.
  92   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top);
  93 
  94 public:
  95   HeapRegionDCTOC(G1CollectedHeap* g1,
  96                   HeapRegion* hr, ExtendedOopClosure* cl,
  97                   CardTableModRefBS::PrecisionStyle precision,
  98                   FilterKind fk);
  99 };
 100 
 101 // The complicating factor is that BlockOffsetTable diverged
 102 // significantly, and we need functionality that is only in the G1 version.
 103 // So I copied that code, which led to an alternate G1 version of
 104 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could
 105 // be reconciled, then G1OffsetTableContigSpace could go away.
 106 
 107 // The idea behind time stamps is the following. Doing a save_marks on
 108 // all regions at every GC pause is time consuming (if I remember
 109 // well, 10ms or so). So, we would like to do that only for regions
 110 // that are GC alloc regions. To achieve this, we use time
 111 // stamps. For every evacuation pause, G1CollectedHeap generates a
 112 // unique time stamp (essentially a counter that gets
 113 // incremented). Every time we want to call save_marks on a region,
 114 // we set the saved_mark_word to top and also copy the current GC
 115 // time stamp to the time stamp field of the space. Reading the
 116 // saved_mark_word involves checking the time stamp of the
 117 // region. If it is the same as the current GC time stamp, then we
 118 // can safely read the saved_mark_word field, as it is valid. If the
 119 // time stamp of the region is not the same as the current GC time
 120 // stamp, then we instead read top, as the saved_mark_word field is
 121 // invalid. Time stamps (on the regions and also on the
 122 // G1CollectedHeap) are reset at every cleanup (we iterate over
 123 // the regions anyway) and at the end of a Full GC. The current scheme
 124 // that uses sequential unsigned ints will fail only if we have 4b
 125 // evacuation pauses between two cleanups, which is _highly_ unlikely.
 126 class G1OffsetTableContigSpace: public CompactibleSpace {
 127   friend class VMStructs;
 128   HeapWord* _top;
 129  protected:
 130   G1BlockOffsetArrayContigSpace _offsets;
 131   Mutex _par_alloc_lock;
 132   volatile unsigned _gc_time_stamp;
 133   // When we need to retire an allocation region, while other threads
 134   // are also concurrently trying to allocate into it, we typically
 135   // allocate a dummy object at the end of the region to ensure that
 136   // no more allocations can take place in it. However, sometimes we
 137   // want to know where the end of the last "real" object we allocated
 138   // into the region was and this is what this keeps track.
 139   HeapWord* _pre_dummy_top;
 140 
 141  public:
 142   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
 143                            MemRegion mr);
 144 
 145   void set_top(HeapWord* value) { _top = value; }
 146   HeapWord* top() const { return _top; }
 147 
 148  protected:
 149   // Reset the G1OffsetTableContigSpace.
 150   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 151 
 152   HeapWord** top_addr() { return &_top; }
 153   // Allocation helpers (return NULL if full).
 154   inline HeapWord* allocate_impl(size_t word_size, HeapWord* end_value);
 155   inline HeapWord* par_allocate_impl(size_t word_size, HeapWord* end_value);
 156 
 157  public:
 158   void reset_after_compaction() { set_top(compaction_top()); }
 159 
 160   size_t used() const { return byte_size(bottom(), top()); }
 161   size_t free() const { return byte_size(top(), end()); }
 162   bool is_free_block(const HeapWord* p) const { return p >= top(); }
 163 
 164   MemRegion used_region() const { return MemRegion(bottom(), top()); }
 165 
 166   void object_iterate(ObjectClosure* blk);
 167   void safe_object_iterate(ObjectClosure* blk);
 168 
 169   void set_bottom(HeapWord* value);
 170   void set_end(HeapWord* value);
 171 
 172   virtual HeapWord* saved_mark_word() const;
 173   void record_top_and_timestamp();
 174   void reset_gc_time_stamp() { _gc_time_stamp = 0; }
 175   unsigned get_gc_time_stamp() { return _gc_time_stamp; }
 176 
 177   // See the comment above in the declaration of _pre_dummy_top for an
 178   // explanation of what it is.
 179   void set_pre_dummy_top(HeapWord* pre_dummy_top) {
 180     assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");
 181     _pre_dummy_top = pre_dummy_top;
 182   }
 183   HeapWord* pre_dummy_top() {
 184     return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;
 185   }
 186   void reset_pre_dummy_top() { _pre_dummy_top = NULL; }
 187 
 188   virtual void clear(bool mangle_space);
 189 
 190   HeapWord* block_start(const void* p);
 191   HeapWord* block_start_const(const void* p) const;
 192 
 193   void prepare_for_compaction(CompactPoint* cp);
 194 
 195   // Add offset table update.
 196   virtual HeapWord* allocate(size_t word_size);
 197   HeapWord* par_allocate(size_t word_size);
 198 
 199   // MarkSweep support phase3
 200   virtual HeapWord* initialize_threshold();
 201   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 202 
 203   virtual void print() const;
 204 
 205   void reset_bot() {
 206     _offsets.reset_bot();
 207   }
 208 
 209   void update_bot_for_object(HeapWord* start, size_t word_size) {
 210     _offsets.alloc_block(start, word_size);
 211   }
 212 
 213   void print_bot_on(outputStream* out) {
 214     _offsets.print_on(out);
 215   }
 216 };
 217 
 218 class HeapRegion: public G1OffsetTableContigSpace {
 219   friend class VMStructs;
 220  private:
 221 
 222   enum HumongousType {
 223     NotHumongous = 0,
 224     StartsHumongous,
 225     ContinuesHumongous
 226   };
 227 
 228   // The remembered set for this region.
 229   // (Might want to make this "inline" later, to avoid some alloc failure
 230   // issues.)
 231   HeapRegionRemSet* _rem_set;
 232 
 233   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
 234 
 235  protected:
 236   // The index of this region in the heap region sequence.
 237   uint  _hrs_index;
 238 
 239   HumongousType _humongous_type;
 240   // For a humongous region, region in which it starts.
 241   HeapRegion* _humongous_start_region;
 242   // For the start region of a humongous sequence, it's original end().
 243   HeapWord* _orig_end;
 244 
 245   // True iff the region is in current collection_set.
 246   bool _in_collection_set;
 247 
 248   // True iff an attempt to evacuate an object in the region failed.
 249   bool _evacuation_failed;
 250 
 251   // A heap region may be a member one of a number of special subsets, each
 252   // represented as linked lists through the field below.  Currently, there
 253   // is only one set:
 254   //   The collection set.
 255   HeapRegion* _next_in_special_set;
 256 
 257   // next region in the young "generation" region set
 258   HeapRegion* _next_young_region;
 259 
 260   // Next region whose cards need cleaning
 261   HeapRegion* _next_dirty_cards_region;
 262 
 263   // Fields used by the HeapRegionSetBase class and subclasses.
 264   HeapRegion* _next;
 265   HeapRegion* _prev;
 266 #ifdef ASSERT
 267   HeapRegionSetBase* _containing_set;
 268 #endif // ASSERT
 269 
 270   // For parallel heapRegion traversal.
 271   jint _claimed;
 272 
 273   // We use concurrent marking to determine the amount of live data
 274   // in each heap region.
 275   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.
 276   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.
 277 
 278   // The calculated GC efficiency of the region.
 279   double _gc_efficiency;
 280 
 281   enum YoungType {
 282     NotYoung,                   // a region is not young
 283     Young,                      // a region is young
 284     Survivor                    // a region is young and it contains survivors
 285   };
 286 
 287   volatile YoungType _young_type;
 288   int  _young_index_in_cset;
 289   SurvRateGroup* _surv_rate_group;
 290   int  _age_index;
 291 
 292   // The start of the unmarked area. The unmarked area extends from this
 293   // word until the top and/or end of the region, and is the part
 294   // of the region for which no marking was done, i.e. objects may
 295   // have been allocated in this part since the last mark phase.
 296   // "prev" is the top at the start of the last completed marking.
 297   // "next" is the top at the start of the in-progress marking (if any.)
 298   HeapWord* _prev_top_at_mark_start;
 299   HeapWord* _next_top_at_mark_start;
 300   // If a collection pause is in progress, this is the top at the start
 301   // of that pause.
 302 
 303   void init_top_at_mark_start() {
 304     assert(_prev_marked_bytes == 0 &&
 305            _next_marked_bytes == 0,
 306            "Must be called after zero_marked_bytes.");
 307     HeapWord* bot = bottom();
 308     _prev_top_at_mark_start = bot;
 309     _next_top_at_mark_start = bot;
 310   }
 311 
 312   void set_young_type(YoungType new_type) {
 313     //assert(_young_type != new_type, "setting the same type" );
 314     // TODO: add more assertions here
 315     _young_type = new_type;
 316   }
 317 
 318   // Cached attributes used in the collection set policy information
 319 
 320   // The RSet length that was added to the total value
 321   // for the collection set.
 322   size_t _recorded_rs_length;
 323 
 324   // The predicted elapsed time that was added to total value
 325   // for the collection set.
 326   double _predicted_elapsed_time_ms;
 327 
 328   // The predicted number of bytes to copy that was added to
 329   // the total value for the collection set.
 330   size_t _predicted_bytes_to_copy;
 331 
 332  public:
 333   HeapRegion(uint hrs_index,
 334              G1BlockOffsetSharedArray* sharedOffsetArray,
 335              MemRegion mr);
 336 
 337   // Initializing the HeapRegion not only resets the data structure, but also
 338   // resets the BOT for that heap region.
 339   // The default values for clear_space means that we will do the clearing if
 340   // there's clearing to be done ourselves. We also always mangle the space.
 341   virtual void initialize(MemRegion mr, bool clear_space = false, bool mangle_space = SpaceDecorator::Mangle);
 342 
 343   static int    LogOfHRGrainBytes;
 344   static int    LogOfHRGrainWords;
 345 
 346   static size_t GrainBytes;
 347   static size_t GrainWords;
 348   static size_t CardsPerRegion;
 349 
 350   static size_t align_up_to_region_byte_size(size_t sz) {
 351     return (sz + (size_t) GrainBytes - 1) &
 352                                       ~((1 << (size_t) LogOfHRGrainBytes) - 1);
 353   }
 354 
 355   static size_t max_region_size();
 356 
 357   // It sets up the heap region size (GrainBytes / GrainWords), as
 358   // well as other related fields that are based on the heap region
 359   // size (LogOfHRGrainBytes / LogOfHRGrainWords /
 360   // CardsPerRegion). All those fields are considered constant
 361   // throughout the JVM's execution, therefore they should only be set
 362   // up once during initialization time.
 363   static void setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size);
 364 
 365   enum ClaimValues {
 366     InitialClaimValue          = 0,
 367     FinalCountClaimValue       = 1,
 368     NoteEndClaimValue          = 2,
 369     ScrubRemSetClaimValue      = 3,
 370     ParVerifyClaimValue        = 4,
 371     RebuildRSClaimValue        = 5,
 372     ParEvacFailureClaimValue   = 6,
 373     AggregateCountClaimValue   = 7,
 374     VerifyCountClaimValue      = 8,
 375     ParMarkRootClaimValue      = 9
 376   };
 377 
 378   // All allocated blocks are occupied by objects in a HeapRegion
 379   bool block_is_obj(const HeapWord* p) const;
 380 
 381   // Returns the object size for all valid block starts
 382   // and the amount of unallocated words if called on top()
 383   size_t block_size(const HeapWord* p) const;
 384 
 385   inline HeapWord* par_allocate_no_bot_updates(size_t word_size);
 386   inline HeapWord* allocate_no_bot_updates(size_t word_size);
 387 
 388   // If this region is a member of a HeapRegionSeq, the index in that
 389   // sequence, otherwise -1.
 390   uint hrs_index() const { return _hrs_index; }
 391 
 392   // The number of bytes marked live in the region in the last marking phase.
 393   size_t marked_bytes()    { return _prev_marked_bytes; }
 394   size_t live_bytes() {
 395     return (top() - prev_top_at_mark_start()) * HeapWordSize + marked_bytes();
 396   }
 397 
 398   // The number of bytes counted in the next marking.
 399   size_t next_marked_bytes() { return _next_marked_bytes; }
 400   // The number of bytes live wrt the next marking.
 401   size_t next_live_bytes() {
 402     return
 403       (top() - next_top_at_mark_start()) * HeapWordSize + next_marked_bytes();
 404   }
 405 
 406   // A lower bound on the amount of garbage bytes in the region.
 407   size_t garbage_bytes() {
 408     size_t used_at_mark_start_bytes =
 409       (prev_top_at_mark_start() - bottom()) * HeapWordSize;
 410     assert(used_at_mark_start_bytes >= marked_bytes(),
 411            "Can't mark more than we have.");
 412     return used_at_mark_start_bytes - marked_bytes();
 413   }
 414 
 415   // Return the amount of bytes we'll reclaim if we collect this
 416   // region. This includes not only the known garbage bytes in the
 417   // region but also any unallocated space in it, i.e., [top, end),
 418   // since it will also be reclaimed if we collect the region.
 419   size_t reclaimable_bytes() {
 420     size_t known_live_bytes = live_bytes();
 421     assert(known_live_bytes <= capacity(), "sanity");
 422     return capacity() - known_live_bytes;
 423   }
 424 
 425   // An upper bound on the number of live bytes in the region.
 426   size_t max_live_bytes() { return used() - garbage_bytes(); }
 427 
 428   void add_to_marked_bytes(size_t incr_bytes) {
 429     _next_marked_bytes = _next_marked_bytes + incr_bytes;
 430     assert(_next_marked_bytes <= used(), "invariant" );
 431   }
 432 
 433   void zero_marked_bytes()      {
 434     _prev_marked_bytes = _next_marked_bytes = 0;
 435   }
 436 
 437   bool isHumongous() const { return _humongous_type != NotHumongous; }
 438   bool startsHumongous() const { return _humongous_type == StartsHumongous; }
 439   bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }
 440   // For a humongous region, region in which it starts.
 441   HeapRegion* humongous_start_region() const {
 442     return _humongous_start_region;
 443   }
 444 
 445   // Return the number of distinct regions that are covered by this region:
 446   // 1 if the region is not humongous, >= 1 if the region is humongous.
 447   uint region_num() const {
 448     if (!isHumongous()) {
 449       return 1U;
 450     } else {
 451       assert(startsHumongous(), "doesn't make sense on HC regions");
 452       assert(capacity() % HeapRegion::GrainBytes == 0, "sanity");
 453       return (uint) (capacity() >> HeapRegion::LogOfHRGrainBytes);
 454     }
 455   }
 456 
 457   // Return the index + 1 of the last HC regions that's associated
 458   // with this HS region.
 459   uint last_hc_index() const {
 460     assert(startsHumongous(), "don't call this otherwise");
 461     return hrs_index() + region_num();
 462   }
 463 
 464   // Same as Space::is_in_reserved, but will use the original size of the region.
 465   // The original size is different only for start humongous regions. They get
 466   // their _end set up to be the end of the last continues region of the
 467   // corresponding humongous object.
 468   bool is_in_reserved_raw(const void* p) const {
 469     return _bottom <= p && p < _orig_end;
 470   }
 471 
 472   // Makes the current region be a "starts humongous" region, i.e.,
 473   // the first region in a series of one or more contiguous regions
 474   // that will contain a single "humongous" object. The two parameters
 475   // are as follows:
 476   //
 477   // new_top : The new value of the top field of this region which
 478   // points to the end of the humongous object that's being
 479   // allocated. If there is more than one region in the series, top
 480   // will lie beyond this region's original end field and on the last
 481   // region in the series.
 482   //
 483   // new_end : The new value of the end field of this region which
 484   // points to the end of the last region in the series. If there is
 485   // one region in the series (namely: this one) end will be the same
 486   // as the original end of this region.
 487   //
 488   // Updating top and end as described above makes this region look as
 489   // if it spans the entire space taken up by all the regions in the
 490   // series and an single allocation moved its top to new_top. This
 491   // ensures that the space (capacity / allocated) taken up by all
 492   // humongous regions can be calculated by just looking at the
 493   // "starts humongous" regions and by ignoring the "continues
 494   // humongous" regions.
 495   void set_startsHumongous(HeapWord* new_top, HeapWord* new_end);
 496 
 497   // Makes the current region be a "continues humongous'
 498   // region. first_hr is the "start humongous" region of the series
 499   // which this region will be part of.
 500   void set_continuesHumongous(HeapRegion* first_hr);
 501 
 502   // Unsets the humongous-related fields on the region.
 503   void set_notHumongous();
 504 
 505   // If the region has a remembered set, return a pointer to it.
 506   HeapRegionRemSet* rem_set() const {
 507     return _rem_set;
 508   }
 509 
 510   // True iff the region is in current collection_set.
 511   bool in_collection_set() const {
 512     return _in_collection_set;
 513   }
 514   void set_in_collection_set(bool b) {
 515     _in_collection_set = b;
 516   }
 517   HeapRegion* next_in_collection_set() {
 518     assert(in_collection_set(), "should only invoke on member of CS.");
 519     assert(_next_in_special_set == NULL ||
 520            _next_in_special_set->in_collection_set(),
 521            "Malformed CS.");
 522     return _next_in_special_set;
 523   }
 524   void set_next_in_collection_set(HeapRegion* r) {
 525     assert(in_collection_set(), "should only invoke on member of CS.");
 526     assert(r == NULL || r->in_collection_set(), "Malformed CS.");
 527     _next_in_special_set = r;
 528   }
 529 
 530   // Methods used by the HeapRegionSetBase class and subclasses.
 531 
 532   // Getter and setter for the next and prev fields used to link regions into
 533   // linked lists.
 534   HeapRegion* next()              { return _next; }
 535   HeapRegion* prev()              { return _prev; }
 536 
 537   void set_next(HeapRegion* next) { _next = next; }
 538   void set_prev(HeapRegion* prev) { _prev = prev; }
 539 
 540   // Every region added to a set is tagged with a reference to that
 541   // set. This is used for doing consistency checking to make sure that
 542   // the contents of a set are as they should be and it's only
 543   // available in non-product builds.
 544 #ifdef ASSERT
 545   void set_containing_set(HeapRegionSetBase* containing_set) {
 546     assert((containing_set == NULL && _containing_set != NULL) ||
 547            (containing_set != NULL && _containing_set == NULL),
 548            err_msg("containing_set: "PTR_FORMAT" "
 549                    "_containing_set: "PTR_FORMAT,
 550                    p2i(containing_set), p2i(_containing_set)));
 551 
 552     _containing_set = containing_set;
 553   }
 554 
 555   HeapRegionSetBase* containing_set() { return _containing_set; }
 556 #else // ASSERT
 557   void set_containing_set(HeapRegionSetBase* containing_set) { }
 558 
 559   // containing_set() is only used in asserts so there's no reason
 560   // to provide a dummy version of it.
 561 #endif // ASSERT
 562 
 563   HeapRegion* get_next_young_region() { return _next_young_region; }
 564   void set_next_young_region(HeapRegion* hr) {
 565     _next_young_region = hr;
 566   }
 567 
 568   HeapRegion* get_next_dirty_cards_region() const { return _next_dirty_cards_region; }
 569   HeapRegion** next_dirty_cards_region_addr() { return &_next_dirty_cards_region; }
 570   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }
 571   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }
 572 
 573   HeapWord* orig_end() { return _orig_end; }
 574 
 575   // Reset HR stuff to default values.
 576   void hr_clear(bool par, bool clear_space, bool locked = false);
 577   void par_clear();
 578 
 579   // Get the start of the unmarked area in this region.
 580   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }
 581   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }
 582 
 583   // Note the start or end of marking. This tells the heap region
 584   // that the collector is about to start or has finished (concurrently)
 585   // marking the heap.
 586 
 587   // Notify the region that concurrent marking is starting. Initialize
 588   // all fields related to the next marking info.
 589   inline void note_start_of_marking();
 590 
 591   // Notify the region that concurrent marking has finished. Copy the
 592   // (now finalized) next marking info fields into the prev marking
 593   // info fields.
 594   inline void note_end_of_marking();
 595 
 596   // Notify the region that it will be used as to-space during a GC
 597   // and we are about to start copying objects into it.
 598   inline void note_start_of_copying(bool during_initial_mark);
 599 
 600   // Notify the region that it ceases being to-space during a GC and
 601   // we will not copy objects into it any more.
 602   inline void note_end_of_copying(bool during_initial_mark);
 603 
 604   // Notify the region that we are about to start processing
 605   // self-forwarded objects during evac failure handling.
 606   void note_self_forwarding_removal_start(bool during_initial_mark,
 607                                           bool during_conc_mark);
 608 
 609   // Notify the region that we have finished processing self-forwarded
 610   // objects during evac failure handling.
 611   void note_self_forwarding_removal_end(bool during_initial_mark,
 612                                         bool during_conc_mark,
 613                                         size_t marked_bytes);
 614 
 615   // Returns "false" iff no object in the region was allocated when the
 616   // last mark phase ended.
 617   bool is_marked() { return _prev_top_at_mark_start != bottom(); }
 618 
 619   void reset_during_compaction() {
 620     assert(isHumongous() && startsHumongous(),
 621            "should only be called for starts humongous regions");
 622 
 623     zero_marked_bytes();
 624     init_top_at_mark_start();
 625   }
 626 
 627   void calc_gc_efficiency(void);
 628   double gc_efficiency() { return _gc_efficiency;}
 629 
 630   bool is_young() const     { return _young_type != NotYoung; }
 631   bool is_survivor() const  { return _young_type == Survivor; }
 632 
 633   int  young_index_in_cset() const { return _young_index_in_cset; }
 634   void set_young_index_in_cset(int index) {
 635     assert( (index == -1) || is_young(), "pre-condition" );
 636     _young_index_in_cset = index;
 637   }
 638 
 639   int age_in_surv_rate_group() {
 640     assert( _surv_rate_group != NULL, "pre-condition" );
 641     assert( _age_index > -1, "pre-condition" );
 642     return _surv_rate_group->age_in_group(_age_index);
 643   }
 644 
 645   void record_surv_words_in_group(size_t words_survived) {
 646     assert( _surv_rate_group != NULL, "pre-condition" );
 647     assert( _age_index > -1, "pre-condition" );
 648     int age_in_group = age_in_surv_rate_group();
 649     _surv_rate_group->record_surviving_words(age_in_group, words_survived);
 650   }
 651 
 652   int age_in_surv_rate_group_cond() {
 653     if (_surv_rate_group != NULL)
 654       return age_in_surv_rate_group();
 655     else
 656       return -1;
 657   }
 658 
 659   SurvRateGroup* surv_rate_group() {
 660     return _surv_rate_group;
 661   }
 662 
 663   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {
 664     assert( surv_rate_group != NULL, "pre-condition" );
 665     assert( _surv_rate_group == NULL, "pre-condition" );
 666     assert( is_young(), "pre-condition" );
 667 
 668     _surv_rate_group = surv_rate_group;
 669     _age_index = surv_rate_group->next_age_index();
 670   }
 671 
 672   void uninstall_surv_rate_group() {
 673     if (_surv_rate_group != NULL) {
 674       assert( _age_index > -1, "pre-condition" );
 675       assert( is_young(), "pre-condition" );
 676 
 677       _surv_rate_group = NULL;
 678       _age_index = -1;
 679     } else {
 680       assert( _age_index == -1, "pre-condition" );
 681     }
 682   }
 683 
 684   void set_young() { set_young_type(Young); }
 685 
 686   void set_survivor() { set_young_type(Survivor); }
 687 
 688   void set_not_young() { set_young_type(NotYoung); }
 689 
 690   // Determine if an object has been allocated since the last
 691   // mark performed by the collector. This returns true iff the object
 692   // is within the unmarked area of the region.
 693   bool obj_allocated_since_prev_marking(oop obj) const {
 694     return (HeapWord *) obj >= prev_top_at_mark_start();
 695   }
 696   bool obj_allocated_since_next_marking(oop obj) const {
 697     return (HeapWord *) obj >= next_top_at_mark_start();
 698   }
 699 
 700   // For parallel heapRegion traversal.
 701   bool claimHeapRegion(int claimValue);
 702   jint claim_value() { return _claimed; }
 703   // Use this carefully: only when you're sure no one is claiming...
 704   void set_claim_value(int claimValue) { _claimed = claimValue; }
 705 
 706   // Returns the "evacuation_failed" property of the region.
 707   bool evacuation_failed() { return _evacuation_failed; }
 708 
 709   // Sets the "evacuation_failed" property of the region.
 710   void set_evacuation_failed(bool b) {
 711     _evacuation_failed = b;
 712 
 713     if (b) {
 714       _next_marked_bytes = 0;
 715     }
 716   }
 717 
 718   // Requires that "mr" be entirely within the region.
 719   // Apply "cl->do_object" to all objects that intersect with "mr".
 720   // If the iteration encounters an unparseable portion of the region,
 721   // or if "cl->abort()" is true after a closure application,
 722   // terminate the iteration and return the address of the start of the
 723   // subregion that isn't done.  (The two can be distinguished by querying
 724   // "cl->abort()".)  Return of "NULL" indicates that the iteration
 725   // completed.
 726   HeapWord*
 727   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);
 728 
 729   // filter_young: if true and the region is a young region then we
 730   // skip the iteration.
 731   // card_ptr: if not NULL, and we decide that the card is not young
 732   // and we iterate over it, we'll clean the card before we start the
 733   // iteration.
 734   HeapWord*
 735   oops_on_card_seq_iterate_careful(MemRegion mr,
 736                                    FilterOutOfRegionClosure* cl,
 737                                    bool filter_young,
 738                                    jbyte* card_ptr);
 739 
 740   // A version of block start that is guaranteed to find *some* block
 741   // boundary at or before "p", but does not object iteration, and may
 742   // therefore be used safely when the heap is unparseable.
 743   HeapWord* block_start_careful(const void* p) const {
 744     return _offsets.block_start_careful(p);
 745   }
 746 
 747   // Requires that "addr" is within the region.  Returns the start of the
 748   // first ("careful") block that starts at or after "addr", or else the
 749   // "end" of the region if there is no such block.
 750   HeapWord* next_block_start_careful(HeapWord* addr);
 751 
 752   size_t recorded_rs_length() const        { return _recorded_rs_length; }
 753   double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }
 754   size_t predicted_bytes_to_copy() const   { return _predicted_bytes_to_copy; }
 755 
 756   void set_recorded_rs_length(size_t rs_length) {
 757     _recorded_rs_length = rs_length;
 758   }
 759 
 760   void set_predicted_elapsed_time_ms(double ms) {
 761     _predicted_elapsed_time_ms = ms;
 762   }
 763 
 764   void set_predicted_bytes_to_copy(size_t bytes) {
 765     _predicted_bytes_to_copy = bytes;
 766   }
 767 
 768   virtual CompactibleSpace* next_compaction_space() const;
 769 
 770   virtual void reset_after_compaction();
 771 
 772   // Routines for managing a list of code roots (attached to the
 773   // this region's RSet) that point into this heap region.
 774   void add_strong_code_root(nmethod* nm);
 775   void remove_strong_code_root(nmethod* nm);
 776 
 777   // During a collection, migrate the successfully evacuated
 778   // strong code roots that referenced into this region to the
 779   // new regions that they now point into. Unsuccessfully
 780   // evacuated code roots are not migrated.
 781   void migrate_strong_code_roots();
 782 
 783   // Applies blk->do_code_blob() to each of the entries in
 784   // the strong code roots list for this region
 785   void strong_code_roots_do(CodeBlobClosure* blk) const;
 786 
 787   // Verify that the entries on the strong code root list for this
 788   // region are live and include at least one pointer into this region.
 789   void verify_strong_code_roots(VerifyOption vo, bool* failures) const;
 790 
 791   void print() const;
 792   void print_on(outputStream* st) const;
 793 
 794   // vo == UsePrevMarking  -> use "prev" marking information,
 795   // vo == UseNextMarking -> use "next" marking information
 796   // vo == UseMarkWord    -> use the mark word in the object header
 797   //
 798   // NOTE: Only the "prev" marking information is guaranteed to be
 799   // consistent most of the time, so most calls to this should use
 800   // vo == UsePrevMarking.
 801   // Currently, there is only one case where this is called with
 802   // vo == UseNextMarking, which is to verify the "next" marking
 803   // information at the end of remark.
 804   // Currently there is only one place where this is called with
 805   // vo == UseMarkWord, which is to verify the marking during a
 806   // full GC.
 807   void verify(VerifyOption vo, bool *failures) const;
 808 
 809   // Override; it uses the "prev" marking information
 810   virtual void verify() const;
 811 };
 812 
 813 // HeapRegionClosure is used for iterating over regions.
 814 // Terminates the iteration when the "doHeapRegion" method returns "true".
 815 class HeapRegionClosure : public StackObj {
 816   friend class HeapRegionSeq;
 817   friend class G1CollectedHeap;
 818 
 819   bool _complete;
 820   void incomplete() { _complete = false; }
 821 
 822  public:
 823   HeapRegionClosure(): _complete(true) {}
 824 
 825   // Typically called on each region until it returns true.
 826   virtual bool doHeapRegion(HeapRegion* r) = 0;
 827 
 828   // True after iteration if the closure was applied to all heap regions
 829   // and returned "false" in all cases.
 830   bool complete() { return _complete; }
 831 };
 832 
 833 #endif // INCLUDE_ALL_GCS
 834 
 835 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP