rev 6586 : 8047819: G1 HeapRegionDCTOC does not need to inherit ContiguousSpaceDCTOC
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   1 /*
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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.inline.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 CompactibleSpace;
  50 class ContiguousSpace;
  51 class HeapRegionRemSet;
  52 class HeapRegionRemSetIterator;
  53 class HeapRegion;
  54 class HeapRegionSetBase;
  55 class nmethod;
  56 
  57 #define HR_FORMAT "%u:(%s)["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"
  58 #define HR_FORMAT_PARAMS(_hr_) \
  59                 (_hr_)->hrs_index(), \
  60                 (_hr_)->is_survivor() ? "S" : (_hr_)->is_young() ? "E" : \
  61                 (_hr_)->startsHumongous() ? "HS" : \
  62                 (_hr_)->continuesHumongous() ? "HC" : \
  63                 !(_hr_)->is_empty() ? "O" : "F", \
  64                 p2i((_hr_)->bottom()), p2i((_hr_)->top()), p2i((_hr_)->end())
  65 
  66 // sentinel value for hrs_index
  67 #define G1_NULL_HRS_INDEX ((uint) -1)
  68 
  69 // A dirty card to oop closure for heap regions. It
  70 // knows how to get the G1 heap and how to use the bitmap
  71 // in the concurrent marker used by G1 to filter remembered
  72 // sets.
  73 
  74 class HeapRegionDCTOC : public ContiguousSpaceDCTOC {
  75 public:
  76   // Specification of possible DirtyCardToOopClosure filtering.
  77   enum FilterKind {
  78     NoFilterKind,
  79     IntoCSFilterKind,
  80     OutOfRegionFilterKind
  81   };
  82 
  83 protected:
  84   HeapRegion* _hr;
  85   FilterKind _fk;
  86   G1CollectedHeap* _g1;
  87 
  88   void walk_mem_region_with_cl(MemRegion mr,
  89                                HeapWord* bottom, HeapWord* top,
  90                                ExtendedOopClosure* cl);
  91 
  92   // We don't specialize this for FilteringClosure; filtering is handled by
  93   // the "FilterKind" mechanism.  But we provide this to avoid a compiler
  94   // warning.
  95   void walk_mem_region_with_cl(MemRegion mr,
  96                                HeapWord* bottom, HeapWord* top,
  97                                FilteringClosure* cl) {
  98     HeapRegionDCTOC::walk_mem_region_with_cl(mr, bottom, top,
  99                                              (ExtendedOopClosure*)cl);
 100   }
 101 
 102   // Get the actual top of the area on which the closure will
 103   // operate, given where the top is assumed to be (the end of the
 104   // memory region passed to do_MemRegion) and where the object
 105   // at the top is assumed to start. For example, an object may
 106   // start at the top but actually extend past the assumed top,
 107   // in which case the top becomes the end of the object.
 108   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj) {
 109     return ContiguousSpaceDCTOC::get_actual_top(top, top_obj);
 110   }
 111 
 112   // Walk the given memory region from bottom to (actual) top
 113   // looking for objects and applying the oop closure (_cl) to
 114   // them. The base implementation of this treats the area as
 115   // blocks, where a block may or may not be an object. Sub-
 116   // classes should override this to provide more accurate
 117   // or possibly more efficient walking.
 118   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top) {
 119     Filtering_DCTOC::walk_mem_region(mr, bottom, top);
 120   }
 121 
 122 public:
 123   HeapRegionDCTOC(G1CollectedHeap* g1,
 124                   HeapRegion* hr, ExtendedOopClosure* cl,
 125                   CardTableModRefBS::PrecisionStyle precision,
 126                   FilterKind fk);
 127 };
 128 
 129 // The complicating factor is that BlockOffsetTable diverged
 130 // significantly, and we need functionality that is only in the G1 version.
 131 // So I copied that code, which led to an alternate G1 version of
 132 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could
 133 // be reconciled, then G1OffsetTableContigSpace could go away.
 134 
 135 // The idea behind time stamps is the following. Doing a save_marks on
 136 // all regions at every GC pause is time consuming (if I remember
 137 // well, 10ms or so). So, we would like to do that only for regions
 138 // that are GC alloc regions. To achieve this, we use time
 139 // stamps. For every evacuation pause, G1CollectedHeap generates a
 140 // unique time stamp (essentially a counter that gets
 141 // incremented). Every time we want to call save_marks on a region,
 142 // we set the saved_mark_word to top and also copy the current GC
 143 // time stamp to the time stamp field of the space. Reading the
 144 // saved_mark_word involves checking the time stamp of the
 145 // region. If it is the same as the current GC time stamp, then we
 146 // can safely read the saved_mark_word field, as it is valid. If the
 147 // time stamp of the region is not the same as the current GC time
 148 // stamp, then we instead read top, as the saved_mark_word field is
 149 // invalid. Time stamps (on the regions and also on the
 150 // G1CollectedHeap) are reset at every cleanup (we iterate over
 151 // the regions anyway) and at the end of a Full GC. The current scheme
 152 // that uses sequential unsigned ints will fail only if we have 4b
 153 // evacuation pauses between two cleanups, which is _highly_ unlikely.
 154 
 155 class G1OffsetTableContigSpace: public ContiguousSpace {
 156   friend class VMStructs;
 157  protected:
 158   G1BlockOffsetArrayContigSpace _offsets;
 159   Mutex _par_alloc_lock;
 160   volatile unsigned _gc_time_stamp;
 161   // When we need to retire an allocation region, while other threads
 162   // are also concurrently trying to allocate into it, we typically
 163   // allocate a dummy object at the end of the region to ensure that
 164   // no more allocations can take place in it. However, sometimes we
 165   // want to know where the end of the last "real" object we allocated
 166   // into the region was and this is what this keeps track.
 167   HeapWord* _pre_dummy_top;
 168 
 169  public:
 170   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
 171                            MemRegion mr);
 172 
 173   void set_bottom(HeapWord* value);
 174   void set_end(HeapWord* value);
 175 
 176   virtual HeapWord* saved_mark_word() const;
 177   virtual void set_saved_mark();
 178   void reset_gc_time_stamp() { _gc_time_stamp = 0; }
 179   unsigned get_gc_time_stamp() { return _gc_time_stamp; }
 180 
 181   // See the comment above in the declaration of _pre_dummy_top for an
 182   // explanation of what it is.
 183   void set_pre_dummy_top(HeapWord* pre_dummy_top) {
 184     assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");
 185     _pre_dummy_top = pre_dummy_top;
 186   }
 187   HeapWord* pre_dummy_top() {
 188     return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;
 189   }
 190   void reset_pre_dummy_top() { _pre_dummy_top = NULL; }
 191 
 192   virtual void clear(bool mangle_space);
 193 
 194   HeapWord* block_start(const void* p);
 195   HeapWord* block_start_const(const void* p) const;
 196 
 197   // Add offset table update.
 198   virtual HeapWord* allocate(size_t word_size);
 199   HeapWord* par_allocate(size_t word_size);
 200 
 201   // MarkSweep support phase3
 202   virtual HeapWord* initialize_threshold();
 203   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 204 
 205   virtual void print() const;
 206 
 207   void reset_bot() {
 208     _offsets.zero_bottom_entry();
 209     _offsets.initialize_threshold();
 210   }
 211 
 212   void update_bot_for_object(HeapWord* start, size_t word_size) {
 213     _offsets.alloc_block(start, word_size);
 214   }
 215 
 216   void print_bot_on(outputStream* out) {
 217     _offsets.print_on(out);
 218   }
 219 };
 220 
 221 class HeapRegion: public G1OffsetTableContigSpace {
 222   friend class VMStructs;
 223  private:
 224 
 225   enum HumongousType {
 226     NotHumongous = 0,
 227     StartsHumongous,
 228     ContinuesHumongous
 229   };
 230 
 231   // Requires that the region "mr" be dense with objects, and begin and end
 232   // with an object.
 233   void oops_in_mr_iterate(MemRegion mr, ExtendedOopClosure* cl);
 234 
 235   // The remembered set for this region.
 236   // (Might want to make this "inline" later, to avoid some alloc failure
 237   // issues.)
 238   HeapRegionRemSet* _rem_set;
 239 
 240   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
 241 
 242  protected:
 243   // The index of this region in the heap region sequence.
 244   uint  _hrs_index;
 245 
 246   HumongousType _humongous_type;
 247   // For a humongous region, region in which it starts.
 248   HeapRegion* _humongous_start_region;
 249   // For the start region of a humongous sequence, it's original end().
 250   HeapWord* _orig_end;
 251 
 252   // True iff the region is in current collection_set.
 253   bool _in_collection_set;
 254 
 255   // True iff an attempt to evacuate an object in the region failed.
 256   bool _evacuation_failed;
 257 
 258   // A heap region may be a member one of a number of special subsets, each
 259   // represented as linked lists through the field below.  Currently, these
 260   // sets include:
 261   //   The collection set.
 262   //   The set of allocation regions used in a collection pause.
 263   //   Spaces that may contain gray objects.
 264   HeapRegion* _next_in_special_set;
 265 
 266   // next region in the young "generation" region set
 267   HeapRegion* _next_young_region;
 268 
 269   // Next region whose cards need cleaning
 270   HeapRegion* _next_dirty_cards_region;
 271 
 272   // Fields used by the HeapRegionSetBase class and subclasses.
 273   HeapRegion* _next;
 274   HeapRegion* _prev;
 275 #ifdef ASSERT
 276   HeapRegionSetBase* _containing_set;
 277 #endif // ASSERT
 278   bool _pending_removal;
 279 
 280   // For parallel heapRegion traversal.
 281   jint _claimed;
 282 
 283   // We use concurrent marking to determine the amount of live data
 284   // in each heap region.
 285   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.
 286   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.
 287 
 288   // The calculated GC efficiency of the region.
 289   double _gc_efficiency;
 290 
 291   enum YoungType {
 292     NotYoung,                   // a region is not young
 293     Young,                      // a region is young
 294     Survivor                    // a region is young and it contains survivors
 295   };
 296 
 297   volatile YoungType _young_type;
 298   int  _young_index_in_cset;
 299   SurvRateGroup* _surv_rate_group;
 300   int  _age_index;
 301 
 302   // The start of the unmarked area. The unmarked area extends from this
 303   // word until the top and/or end of the region, and is the part
 304   // of the region for which no marking was done, i.e. objects may
 305   // have been allocated in this part since the last mark phase.
 306   // "prev" is the top at the start of the last completed marking.
 307   // "next" is the top at the start of the in-progress marking (if any.)
 308   HeapWord* _prev_top_at_mark_start;
 309   HeapWord* _next_top_at_mark_start;
 310   // If a collection pause is in progress, this is the top at the start
 311   // of that pause.
 312 
 313   void init_top_at_mark_start() {
 314     assert(_prev_marked_bytes == 0 &&
 315            _next_marked_bytes == 0,
 316            "Must be called after zero_marked_bytes.");
 317     HeapWord* bot = bottom();
 318     _prev_top_at_mark_start = bot;
 319     _next_top_at_mark_start = bot;
 320   }
 321 
 322   void set_young_type(YoungType new_type) {
 323     //assert(_young_type != new_type, "setting the same type" );
 324     // TODO: add more assertions here
 325     _young_type = new_type;
 326   }
 327 
 328   // Cached attributes used in the collection set policy information
 329 
 330   // The RSet length that was added to the total value
 331   // for the collection set.
 332   size_t _recorded_rs_length;
 333 
 334   // The predicted elapsed time that was added to total value
 335   // for the collection set.
 336   double _predicted_elapsed_time_ms;
 337 
 338   // The predicted number of bytes to copy that was added to
 339   // the total value for the collection set.
 340   size_t _predicted_bytes_to_copy;
 341 
 342  public:
 343   HeapRegion(uint hrs_index,
 344              G1BlockOffsetSharedArray* sharedOffsetArray,
 345              MemRegion mr);
 346 
 347   static int    LogOfHRGrainBytes;
 348   static int    LogOfHRGrainWords;
 349 
 350   static size_t GrainBytes;
 351   static size_t GrainWords;
 352   static size_t CardsPerRegion;
 353 
 354   static size_t align_up_to_region_byte_size(size_t sz) {
 355     return (sz + (size_t) GrainBytes - 1) &
 356                                       ~((1 << (size_t) LogOfHRGrainBytes) - 1);
 357   }
 358 
 359   static size_t max_region_size();
 360 
 361   // It sets up the heap region size (GrainBytes / GrainWords), as
 362   // well as other related fields that are based on the heap region
 363   // size (LogOfHRGrainBytes / LogOfHRGrainWords /
 364   // CardsPerRegion). All those fields are considered constant
 365   // throughout the JVM's execution, therefore they should only be set
 366   // up once during initialization time.
 367   static void setup_heap_region_size(size_t initial_heap_size, size_t max_heap_size);
 368 
 369   enum ClaimValues {
 370     InitialClaimValue          = 0,
 371     FinalCountClaimValue       = 1,
 372     NoteEndClaimValue          = 2,
 373     ScrubRemSetClaimValue      = 3,
 374     ParVerifyClaimValue        = 4,
 375     RebuildRSClaimValue        = 5,
 376     ParEvacFailureClaimValue   = 6,
 377     AggregateCountClaimValue   = 7,
 378     VerifyCountClaimValue      = 8,
 379     ParMarkRootClaimValue      = 9
 380   };
 381 
 382   inline HeapWord* par_allocate_no_bot_updates(size_t word_size) {
 383     assert(is_young(), "we can only skip BOT updates on young regions");
 384     return ContiguousSpace::par_allocate(word_size);
 385   }
 386   inline HeapWord* allocate_no_bot_updates(size_t word_size) {
 387     assert(is_young(), "we can only skip BOT updates on young regions");
 388     return ContiguousSpace::allocate(word_size);
 389   }
 390 
 391   // If this region is a member of a HeapRegionSeq, the index in that
 392   // sequence, otherwise -1.
 393   uint hrs_index() const { return _hrs_index; }
 394 
 395   // The number of bytes marked live in the region in the last marking phase.
 396   size_t marked_bytes()    { return _prev_marked_bytes; }
 397   size_t live_bytes() {
 398     return (top() - prev_top_at_mark_start()) * HeapWordSize + marked_bytes();
 399   }
 400 
 401   // The number of bytes counted in the next marking.
 402   size_t next_marked_bytes() { return _next_marked_bytes; }
 403   // The number of bytes live wrt the next marking.
 404   size_t next_live_bytes() {
 405     return
 406       (top() - next_top_at_mark_start()) * HeapWordSize + next_marked_bytes();
 407   }
 408 
 409   // A lower bound on the amount of garbage bytes in the region.
 410   size_t garbage_bytes() {
 411     size_t used_at_mark_start_bytes =
 412       (prev_top_at_mark_start() - bottom()) * HeapWordSize;
 413     assert(used_at_mark_start_bytes >= marked_bytes(),
 414            "Can't mark more than we have.");
 415     return used_at_mark_start_bytes - marked_bytes();
 416   }
 417 
 418   // Return the amount of bytes we'll reclaim if we collect this
 419   // region. This includes not only the known garbage bytes in the
 420   // region but also any unallocated space in it, i.e., [top, end),
 421   // since it will also be reclaimed if we collect the region.
 422   size_t reclaimable_bytes() {
 423     size_t known_live_bytes = live_bytes();
 424     assert(known_live_bytes <= capacity(), "sanity");
 425     return capacity() - known_live_bytes;
 426   }
 427 
 428   // An upper bound on the number of live bytes in the region.
 429   size_t max_live_bytes() { return used() - garbage_bytes(); }
 430 
 431   void add_to_marked_bytes(size_t incr_bytes) {
 432     _next_marked_bytes = _next_marked_bytes + incr_bytes;
 433     assert(_next_marked_bytes <= used(), "invariant" );
 434   }
 435 
 436   void zero_marked_bytes()      {
 437     _prev_marked_bytes = _next_marked_bytes = 0;
 438   }
 439 
 440   bool isHumongous() const { return _humongous_type != NotHumongous; }
 441   bool startsHumongous() const { return _humongous_type == StartsHumongous; }
 442   bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }
 443   // For a humongous region, region in which it starts.
 444   HeapRegion* humongous_start_region() const {
 445     return _humongous_start_region;
 446   }
 447 
 448   // Return the number of distinct regions that are covered by this region:
 449   // 1 if the region is not humongous, >= 1 if the region is humongous.
 450   uint region_num() const {
 451     if (!isHumongous()) {
 452       return 1U;
 453     } else {
 454       assert(startsHumongous(), "doesn't make sense on HC regions");
 455       assert(capacity() % HeapRegion::GrainBytes == 0, "sanity");
 456       return (uint) (capacity() >> HeapRegion::LogOfHRGrainBytes);
 457     }
 458   }
 459 
 460   // Return the index + 1 of the last HC regions that's associated
 461   // with this HS region.
 462   uint last_hc_index() const {
 463     assert(startsHumongous(), "don't call this otherwise");
 464     return hrs_index() + region_num();
 465   }
 466 
 467   // Same as Space::is_in_reserved, but will use the original size of the region.
 468   // The original size is different only for start humongous regions. They get
 469   // their _end set up to be the end of the last continues region of the
 470   // corresponding humongous object.
 471   bool is_in_reserved_raw(const void* p) const {
 472     return _bottom <= p && p < _orig_end;
 473   }
 474 
 475   // Makes the current region be a "starts humongous" region, i.e.,
 476   // the first region in a series of one or more contiguous regions
 477   // that will contain a single "humongous" object. The two parameters
 478   // are as follows:
 479   //
 480   // new_top : The new value of the top field of this region which
 481   // points to the end of the humongous object that's being
 482   // allocated. If there is more than one region in the series, top
 483   // will lie beyond this region's original end field and on the last
 484   // region in the series.
 485   //
 486   // new_end : The new value of the end field of this region which
 487   // points to the end of the last region in the series. If there is
 488   // one region in the series (namely: this one) end will be the same
 489   // as the original end of this region.
 490   //
 491   // Updating top and end as described above makes this region look as
 492   // if it spans the entire space taken up by all the regions in the
 493   // series and an single allocation moved its top to new_top. This
 494   // ensures that the space (capacity / allocated) taken up by all
 495   // humongous regions can be calculated by just looking at the
 496   // "starts humongous" regions and by ignoring the "continues
 497   // humongous" regions.
 498   void set_startsHumongous(HeapWord* new_top, HeapWord* new_end);
 499 
 500   // Makes the current region be a "continues humongous'
 501   // region. first_hr is the "start humongous" region of the series
 502   // which this region will be part of.
 503   void set_continuesHumongous(HeapRegion* first_hr);
 504 
 505   // Unsets the humongous-related fields on the region.
 506   void set_notHumongous();
 507 
 508   // If the region has a remembered set, return a pointer to it.
 509   HeapRegionRemSet* rem_set() const {
 510     return _rem_set;
 511   }
 512 
 513   // True iff the region is in current collection_set.
 514   bool in_collection_set() const {
 515     return _in_collection_set;
 516   }
 517   void set_in_collection_set(bool b) {
 518     _in_collection_set = b;
 519   }
 520   HeapRegion* next_in_collection_set() {
 521     assert(in_collection_set(), "should only invoke on member of CS.");
 522     assert(_next_in_special_set == NULL ||
 523            _next_in_special_set->in_collection_set(),
 524            "Malformed CS.");
 525     return _next_in_special_set;
 526   }
 527   void set_next_in_collection_set(HeapRegion* r) {
 528     assert(in_collection_set(), "should only invoke on member of CS.");
 529     assert(r == NULL || r->in_collection_set(), "Malformed CS.");
 530     _next_in_special_set = r;
 531   }
 532 
 533   // Methods used by the HeapRegionSetBase class and subclasses.
 534 
 535   // Getter and setter for the next and prev fields used to link regions into
 536   // linked lists.
 537   HeapRegion* next()              { return _next; }
 538   HeapRegion* prev()              { return _prev; }
 539 
 540   void set_next(HeapRegion* next) { _next = next; }
 541   void set_prev(HeapRegion* prev) { _prev = prev; }
 542 
 543   // Every region added to a set is tagged with a reference to that
 544   // set. This is used for doing consistency checking to make sure that
 545   // the contents of a set are as they should be and it's only
 546   // available in non-product builds.
 547 #ifdef ASSERT
 548   void set_containing_set(HeapRegionSetBase* containing_set) {
 549     assert((containing_set == NULL && _containing_set != NULL) ||
 550            (containing_set != NULL && _containing_set == NULL),
 551            err_msg("containing_set: "PTR_FORMAT" "
 552                    "_containing_set: "PTR_FORMAT,
 553                    p2i(containing_set), p2i(_containing_set)));
 554 
 555     _containing_set = containing_set;
 556   }
 557 
 558   HeapRegionSetBase* containing_set() { return _containing_set; }
 559 #else // ASSERT
 560   void set_containing_set(HeapRegionSetBase* containing_set) { }
 561 
 562   // containing_set() is only used in asserts so there's no reason
 563   // to provide a dummy version of it.
 564 #endif // ASSERT
 565 
 566   // If we want to remove regions from a list in bulk we can simply tag
 567   // them with the pending_removal tag and call the
 568   // remove_all_pending() method on the list.
 569 
 570   bool pending_removal() { return _pending_removal; }
 571 
 572   void set_pending_removal(bool pending_removal) {
 573     if (pending_removal) {
 574       assert(!_pending_removal && containing_set() != NULL,
 575              "can only set pending removal to true if it's false and "
 576              "the region belongs to a region set");
 577     } else {
 578       assert( _pending_removal && containing_set() == NULL,
 579               "can only set pending removal to false if it's true and "
 580               "the region does not belong to a region set");
 581     }
 582 
 583     _pending_removal = pending_removal;
 584   }
 585 
 586   HeapRegion* get_next_young_region() { return _next_young_region; }
 587   void set_next_young_region(HeapRegion* hr) {
 588     _next_young_region = hr;
 589   }
 590 
 591   HeapRegion* get_next_dirty_cards_region() const { return _next_dirty_cards_region; }
 592   HeapRegion** next_dirty_cards_region_addr() { return &_next_dirty_cards_region; }
 593   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }
 594   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }
 595 
 596   HeapWord* orig_end() { return _orig_end; }
 597 
 598   // Allows logical separation between objects allocated before and after.
 599   void save_marks();
 600 
 601   // Reset HR stuff to default values.
 602   void hr_clear(bool par, bool clear_space, bool locked = false);
 603   void par_clear();
 604 
 605   // Get the start of the unmarked area in this region.
 606   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }
 607   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }
 608 
 609   // Apply "cl->do_oop" to (the addresses of) all reference fields in objects
 610   // allocated in the current region before the last call to "save_mark".
 611   void oop_before_save_marks_iterate(ExtendedOopClosure* cl);
 612 
 613   // Note the start or end of marking. This tells the heap region
 614   // that the collector is about to start or has finished (concurrently)
 615   // marking the heap.
 616 
 617   // Notify the region that concurrent marking is starting. Initialize
 618   // all fields related to the next marking info.
 619   inline void note_start_of_marking();
 620 
 621   // Notify the region that concurrent marking has finished. Copy the
 622   // (now finalized) next marking info fields into the prev marking
 623   // info fields.
 624   inline void note_end_of_marking();
 625 
 626   // Notify the region that it will be used as to-space during a GC
 627   // and we are about to start copying objects into it.
 628   inline void note_start_of_copying(bool during_initial_mark);
 629 
 630   // Notify the region that it ceases being to-space during a GC and
 631   // we will not copy objects into it any more.
 632   inline void note_end_of_copying(bool during_initial_mark);
 633 
 634   // Notify the region that we are about to start processing
 635   // self-forwarded objects during evac failure handling.
 636   void note_self_forwarding_removal_start(bool during_initial_mark,
 637                                           bool during_conc_mark);
 638 
 639   // Notify the region that we have finished processing self-forwarded
 640   // objects during evac failure handling.
 641   void note_self_forwarding_removal_end(bool during_initial_mark,
 642                                         bool during_conc_mark,
 643                                         size_t marked_bytes);
 644 
 645   // Returns "false" iff no object in the region was allocated when the
 646   // last mark phase ended.
 647   bool is_marked() { return _prev_top_at_mark_start != bottom(); }
 648 
 649   void reset_during_compaction() {
 650     assert(isHumongous() && startsHumongous(),
 651            "should only be called for starts humongous regions");
 652 
 653     zero_marked_bytes();
 654     init_top_at_mark_start();
 655   }
 656 
 657   void calc_gc_efficiency(void);
 658   double gc_efficiency() { return _gc_efficiency;}
 659 
 660   bool is_young() const     { return _young_type != NotYoung; }
 661   bool is_survivor() const  { return _young_type == Survivor; }
 662 
 663   int  young_index_in_cset() const { return _young_index_in_cset; }
 664   void set_young_index_in_cset(int index) {
 665     assert( (index == -1) || is_young(), "pre-condition" );
 666     _young_index_in_cset = index;
 667   }
 668 
 669   int age_in_surv_rate_group() {
 670     assert( _surv_rate_group != NULL, "pre-condition" );
 671     assert( _age_index > -1, "pre-condition" );
 672     return _surv_rate_group->age_in_group(_age_index);
 673   }
 674 
 675   void record_surv_words_in_group(size_t words_survived) {
 676     assert( _surv_rate_group != NULL, "pre-condition" );
 677     assert( _age_index > -1, "pre-condition" );
 678     int age_in_group = age_in_surv_rate_group();
 679     _surv_rate_group->record_surviving_words(age_in_group, words_survived);
 680   }
 681 
 682   int age_in_surv_rate_group_cond() {
 683     if (_surv_rate_group != NULL)
 684       return age_in_surv_rate_group();
 685     else
 686       return -1;
 687   }
 688 
 689   SurvRateGroup* surv_rate_group() {
 690     return _surv_rate_group;
 691   }
 692 
 693   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {
 694     assert( surv_rate_group != NULL, "pre-condition" );
 695     assert( _surv_rate_group == NULL, "pre-condition" );
 696     assert( is_young(), "pre-condition" );
 697 
 698     _surv_rate_group = surv_rate_group;
 699     _age_index = surv_rate_group->next_age_index();
 700   }
 701 
 702   void uninstall_surv_rate_group() {
 703     if (_surv_rate_group != NULL) {
 704       assert( _age_index > -1, "pre-condition" );
 705       assert( is_young(), "pre-condition" );
 706 
 707       _surv_rate_group = NULL;
 708       _age_index = -1;
 709     } else {
 710       assert( _age_index == -1, "pre-condition" );
 711     }
 712   }
 713 
 714   void set_young() { set_young_type(Young); }
 715 
 716   void set_survivor() { set_young_type(Survivor); }
 717 
 718   void set_not_young() { set_young_type(NotYoung); }
 719 
 720   // Determine if an object has been allocated since the last
 721   // mark performed by the collector. This returns true iff the object
 722   // is within the unmarked area of the region.
 723   bool obj_allocated_since_prev_marking(oop obj) const {
 724     return (HeapWord *) obj >= prev_top_at_mark_start();
 725   }
 726   bool obj_allocated_since_next_marking(oop obj) const {
 727     return (HeapWord *) obj >= next_top_at_mark_start();
 728   }
 729 
 730   // For parallel heapRegion traversal.
 731   bool claimHeapRegion(int claimValue);
 732   jint claim_value() { return _claimed; }
 733   // Use this carefully: only when you're sure no one is claiming...
 734   void set_claim_value(int claimValue) { _claimed = claimValue; }
 735 
 736   // Returns the "evacuation_failed" property of the region.
 737   bool evacuation_failed() { return _evacuation_failed; }
 738 
 739   // Sets the "evacuation_failed" property of the region.
 740   void set_evacuation_failed(bool b) {
 741     _evacuation_failed = b;
 742 
 743     if (b) {
 744       _next_marked_bytes = 0;
 745     }
 746   }
 747 
 748   // Requires that "mr" be entirely within the region.
 749   // Apply "cl->do_object" to all objects that intersect with "mr".
 750   // If the iteration encounters an unparseable portion of the region,
 751   // or if "cl->abort()" is true after a closure application,
 752   // terminate the iteration and return the address of the start of the
 753   // subregion that isn't done.  (The two can be distinguished by querying
 754   // "cl->abort()".)  Return of "NULL" indicates that the iteration
 755   // completed.
 756   HeapWord*
 757   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);
 758 
 759   // filter_young: if true and the region is a young region then we
 760   // skip the iteration.
 761   // card_ptr: if not NULL, and we decide that the card is not young
 762   // and we iterate over it, we'll clean the card before we start the
 763   // iteration.
 764   HeapWord*
 765   oops_on_card_seq_iterate_careful(MemRegion mr,
 766                                    FilterOutOfRegionClosure* cl,
 767                                    bool filter_young,
 768                                    jbyte* card_ptr);
 769 
 770   // A version of block start that is guaranteed to find *some* block
 771   // boundary at or before "p", but does not object iteration, and may
 772   // therefore be used safely when the heap is unparseable.
 773   HeapWord* block_start_careful(const void* p) const {
 774     return _offsets.block_start_careful(p);
 775   }
 776 
 777   // Requires that "addr" is within the region.  Returns the start of the
 778   // first ("careful") block that starts at or after "addr", or else the
 779   // "end" of the region if there is no such block.
 780   HeapWord* next_block_start_careful(HeapWord* addr);
 781 
 782   size_t recorded_rs_length() const        { return _recorded_rs_length; }
 783   double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }
 784   size_t predicted_bytes_to_copy() const   { return _predicted_bytes_to_copy; }
 785 
 786   void set_recorded_rs_length(size_t rs_length) {
 787     _recorded_rs_length = rs_length;
 788   }
 789 
 790   void set_predicted_elapsed_time_ms(double ms) {
 791     _predicted_elapsed_time_ms = ms;
 792   }
 793 
 794   void set_predicted_bytes_to_copy(size_t bytes) {
 795     _predicted_bytes_to_copy = bytes;
 796   }
 797 
 798 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 799   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
 800   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DECL)
 801 
 802   virtual CompactibleSpace* next_compaction_space() const;
 803 
 804   virtual void reset_after_compaction();
 805 
 806   // Routines for managing a list of code roots (attached to the
 807   // this region's RSet) that point into this heap region.
 808   void add_strong_code_root(nmethod* nm);
 809   void remove_strong_code_root(nmethod* nm);
 810 
 811   // During a collection, migrate the successfully evacuated
 812   // strong code roots that referenced into this region to the
 813   // new regions that they now point into. Unsuccessfully
 814   // evacuated code roots are not migrated.
 815   void migrate_strong_code_roots();
 816 
 817   // Applies blk->do_code_blob() to each of the entries in
 818   // the strong code roots list for this region
 819   void strong_code_roots_do(CodeBlobClosure* blk) const;
 820 
 821   // Verify that the entries on the strong code root list for this
 822   // region are live and include at least one pointer into this region.
 823   void verify_strong_code_roots(VerifyOption vo, bool* failures) const;
 824 
 825   void print() const;
 826   void print_on(outputStream* st) const;
 827 
 828   // vo == UsePrevMarking  -> use "prev" marking information,
 829   // vo == UseNextMarking -> use "next" marking information
 830   // vo == UseMarkWord    -> use the mark word in the object header
 831   //
 832   // NOTE: Only the "prev" marking information is guaranteed to be
 833   // consistent most of the time, so most calls to this should use
 834   // vo == UsePrevMarking.
 835   // Currently, there is only one case where this is called with
 836   // vo == UseNextMarking, which is to verify the "next" marking
 837   // information at the end of remark.
 838   // Currently there is only one place where this is called with
 839   // vo == UseMarkWord, which is to verify the marking during a
 840   // full GC.
 841   void verify(VerifyOption vo, bool *failures) const;
 842 
 843   // Override; it uses the "prev" marking information
 844   virtual void verify() const;
 845 };
 846 
 847 // HeapRegionClosure is used for iterating over regions.
 848 // Terminates the iteration when the "doHeapRegion" method returns "true".
 849 class HeapRegionClosure : public StackObj {
 850   friend class HeapRegionSeq;
 851   friend class G1CollectedHeap;
 852 
 853   bool _complete;
 854   void incomplete() { _complete = false; }
 855 
 856  public:
 857   HeapRegionClosure(): _complete(true) {}
 858 
 859   // Typically called on each region until it returns true.
 860   virtual bool doHeapRegion(HeapRegion* r) = 0;
 861 
 862   // True after iteration if the closure was applied to all heap regions
 863   // and returned "false" in all cases.
 864   bool complete() { return _complete; }
 865 };
 866 
 867 #endif // INCLUDE_ALL_GCS
 868 
 869 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP
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