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/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 
  36 #ifndef SERIALGC
  37 
  38 // A HeapRegion is the smallest piece of a G1CollectedHeap that
  39 // can be collected independently.
  40 
  41 // NOTE: Although a HeapRegion is a Space, its
  42 // Space::initDirtyCardClosure method must not be called.
  43 // The problem is that the existence of this method breaks
  44 // the independence of barrier sets from remembered sets.
  45 // The solution is to remove this method from the definition
  46 // of a Space.
  47 
  48 class CompactibleSpace;
  49 class ContiguousSpace;
  50 class HeapRegionRemSet;
  51 class HeapRegionRemSetIterator;
  52 class HeapRegion;
  53 class HeapRegionSetBase;
  54 
  55 #define HR_FORMAT SIZE_FORMAT":(%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_)->bottom(), (_hr_)->top(), (_hr_)->end()
  60 
  61 // A dirty card to oop closure for heap regions. It
  62 // knows how to get the G1 heap and how to use the bitmap
  63 // in the concurrent marker used by G1 to filter remembered
  64 // sets.
  65 
  66 class HeapRegionDCTOC : public ContiguousSpaceDCTOC {
  67 public:
  68   // Specification of possible DirtyCardToOopClosure filtering.
  69   enum FilterKind {
  70     NoFilterKind,
  71     IntoCSFilterKind,
  72     OutOfRegionFilterKind
  73   };
  74 
  75 protected:
  76   HeapRegion* _hr;
  77   FilterKind _fk;
  78   G1CollectedHeap* _g1;
  79 
  80   void walk_mem_region_with_cl(MemRegion mr,
  81                                HeapWord* bottom, HeapWord* top,
  82                                OopClosure* cl);
  83 
  84   // We don't specialize this for FilteringClosure; filtering is handled by
  85   // the "FilterKind" mechanism.  But we provide this to avoid a compiler
  86   // warning.
  87   void walk_mem_region_with_cl(MemRegion mr,
  88                                HeapWord* bottom, HeapWord* top,
  89                                FilteringClosure* cl) {
  90     HeapRegionDCTOC::walk_mem_region_with_cl(mr, bottom, top,
  91                                                        (OopClosure*)cl);
  92   }
  93 
  94   // Get the actual top of the area on which the closure will
  95   // operate, given where the top is assumed to be (the end of the
  96   // memory region passed to do_MemRegion) and where the object
  97   // at the top is assumed to start. For example, an object may
  98   // start at the top but actually extend past the assumed top,
  99   // in which case the top becomes the end of the object.
 100   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj) {
 101     return ContiguousSpaceDCTOC::get_actual_top(top, top_obj);
 102   }
 103 
 104   // Walk the given memory region from bottom to (actual) top
 105   // looking for objects and applying the oop closure (_cl) to
 106   // them. The base implementation of this treats the area as
 107   // blocks, where a block may or may not be an object. Sub-
 108   // classes should override this to provide more accurate
 109   // or possibly more efficient walking.
 110   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top) {
 111     Filtering_DCTOC::walk_mem_region(mr, bottom, top);
 112   }
 113 
 114 public:
 115   HeapRegionDCTOC(G1CollectedHeap* g1,
 116                   HeapRegion* hr, OopClosure* cl,
 117                   CardTableModRefBS::PrecisionStyle precision,
 118                   FilterKind fk);
 119 };
 120 
 121 // The complicating factor is that BlockOffsetTable diverged
 122 // significantly, and we need functionality that is only in the G1 version.
 123 // So I copied that code, which led to an alternate G1 version of
 124 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could
 125 // be reconciled, then G1OffsetTableContigSpace could go away.
 126 
 127 // The idea behind time stamps is the following. Doing a save_marks on
 128 // all regions at every GC pause is time consuming (if I remember
 129 // well, 10ms or so). So, we would like to do that only for regions
 130 // that are GC alloc regions. To achieve this, we use time
 131 // stamps. For every evacuation pause, G1CollectedHeap generates a
 132 // unique time stamp (essentially a counter that gets
 133 // incremented). Every time we want to call save_marks on a region,
 134 // we set the saved_mark_word to top and also copy the current GC
 135 // time stamp to the time stamp field of the space. Reading the
 136 // saved_mark_word involves checking the time stamp of the
 137 // region. If it is the same as the current GC time stamp, then we
 138 // can safely read the saved_mark_word field, as it is valid. If the
 139 // time stamp of the region is not the same as the current GC time
 140 // stamp, then we instead read top, as the saved_mark_word field is
 141 // invalid. Time stamps (on the regions and also on the
 142 // G1CollectedHeap) are reset at every cleanup (we iterate over
 143 // the regions anyway) and at the end of a Full GC. The current scheme
 144 // that uses sequential unsigned ints will fail only if we have 4b
 145 // evacuation pauses between two cleanups, which is _highly_ unlikely.
 146 
 147 class G1OffsetTableContigSpace: public ContiguousSpace {
 148   friend class VMStructs;
 149  protected:
 150   G1BlockOffsetArrayContigSpace _offsets;
 151   Mutex _par_alloc_lock;
 152   volatile unsigned _gc_time_stamp;
 153   // When we need to retire an allocation region, while other threads
 154   // are also concurrently trying to allocate into it, we typically
 155   // allocate a dummy object at the end of the region to ensure that
 156   // no more allocations can take place in it. However, sometimes we
 157   // want to know where the end of the last "real" object we allocated
 158   // into the region was and this is what this keeps track.
 159   HeapWord* _pre_dummy_top;
 160 
 161  public:
 162   // Constructor.  If "is_zeroed" is true, the MemRegion "mr" may be
 163   // assumed to contain zeros.
 164   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,
 165                            MemRegion mr, bool is_zeroed = false);
 166 
 167   void set_bottom(HeapWord* value);
 168   void set_end(HeapWord* value);
 169 
 170   virtual HeapWord* saved_mark_word() const;
 171   virtual void set_saved_mark();
 172   void reset_gc_time_stamp() { _gc_time_stamp = 0; }
 173 
 174   // See the comment above in the declaration of _pre_dummy_top for an
 175   // explanation of what it is.
 176   void set_pre_dummy_top(HeapWord* pre_dummy_top) {
 177     assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");
 178     _pre_dummy_top = pre_dummy_top;
 179   }
 180   HeapWord* pre_dummy_top() {
 181     return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;
 182   }
 183   void reset_pre_dummy_top() { _pre_dummy_top = NULL; }
 184 
 185   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 186   virtual void clear(bool mangle_space);
 187 
 188   HeapWord* block_start(const void* p);
 189   HeapWord* block_start_const(const void* p) const;
 190 
 191   // Add offset table update.
 192   virtual HeapWord* allocate(size_t word_size);
 193   HeapWord* par_allocate(size_t word_size);
 194 
 195   // MarkSweep support phase3
 196   virtual HeapWord* initialize_threshold();
 197   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
 198 
 199   virtual void print() const;
 200 
 201   void reset_bot() {
 202     _offsets.zero_bottom_entry();
 203     _offsets.initialize_threshold();
 204   }
 205 
 206   void update_bot_for_object(HeapWord* start, size_t word_size) {
 207     _offsets.alloc_block(start, word_size);
 208   }
 209 
 210   void print_bot_on(outputStream* out) {
 211     _offsets.print_on(out);
 212   }
 213 };
 214 
 215 class HeapRegion: public G1OffsetTableContigSpace {
 216   friend class VMStructs;
 217  private:
 218 
 219   enum HumongousType {
 220     NotHumongous = 0,
 221     StartsHumongous,
 222     ContinuesHumongous
 223   };
 224 
 225   // Requires that the region "mr" be dense with objects, and begin and end
 226   // with an object.
 227   void oops_in_mr_iterate(MemRegion mr, OopClosure* cl);
 228 
 229   // The remembered set for this region.
 230   // (Might want to make this "inline" later, to avoid some alloc failure
 231   // issues.)
 232   HeapRegionRemSet* _rem_set;
 233 
 234   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }
 235 
 236  protected:
 237   // The index of this region in the heap region sequence.
 238   size_t  _hrs_index;
 239 
 240   HumongousType _humongous_type;
 241   // For a humongous region, region in which it starts.
 242   HeapRegion* _humongous_start_region;
 243   // For the start region of a humongous sequence, it's original end().
 244   HeapWord* _orig_end;
 245 
 246   // True iff the region is in current collection_set.
 247   bool _in_collection_set;
 248 
 249   // True iff an attempt to evacuate an object in the region failed.
 250   bool _evacuation_failed;
 251 
 252   // A heap region may be a member one of a number of special subsets, each
 253   // represented as linked lists through the field below.  Currently, these
 254   // sets include:
 255   //   The collection set.
 256   //   The set of allocation regions used in a collection pause.
 257   //   Spaces that may contain gray objects.
 258   HeapRegion* _next_in_special_set;
 259 
 260   // next region in the young "generation" region set
 261   HeapRegion* _next_young_region;
 262 
 263   // Next region whose cards need cleaning
 264   HeapRegion* _next_dirty_cards_region;
 265 
 266   // Fields used by the HeapRegionSetBase class and subclasses.
 267   HeapRegion* _next;
 268 #ifdef ASSERT
 269   HeapRegionSetBase* _containing_set;
 270 #endif // ASSERT
 271   bool _pending_removal;
 272 
 273   // For parallel heapRegion traversal.
 274   jint _claimed;
 275 
 276   // We use concurrent marking to determine the amount of live data
 277   // in each heap region.
 278   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.
 279   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.
 280 
 281   // See "sort_index" method.  -1 means is not in the array.
 282   int _sort_index;
 283 
 284   // <PREDICTION>
 285   double _gc_efficiency;
 286   // </PREDICTION>
 287 
 288   enum YoungType {
 289     NotYoung,                   // a region is not young
 290     Young,                      // a region is young
 291     Survivor                    // a region is young and it contains survivors
 292   };
 293 
 294   volatile YoungType _young_type;
 295   int  _young_index_in_cset;
 296   SurvRateGroup* _surv_rate_group;
 297   int  _age_index;
 298 
 299   // The start of the unmarked area. The unmarked area extends from this
 300   // word until the top and/or end of the region, and is the part
 301   // of the region for which no marking was done, i.e. objects may
 302   // have been allocated in this part since the last mark phase.
 303   // "prev" is the top at the start of the last completed marking.
 304   // "next" is the top at the start of the in-progress marking (if any.)
 305   HeapWord* _prev_top_at_mark_start;
 306   HeapWord* _next_top_at_mark_start;
 307   // If a collection pause is in progress, this is the top at the start
 308   // of that pause.
 309 
 310   // We've counted the marked bytes of objects below here.
 311   HeapWord* _top_at_conc_mark_count;
 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     _top_at_conc_mark_count = bot;
 321   }
 322 
 323   void set_young_type(YoungType new_type) {
 324     //assert(_young_type != new_type, "setting the same type" );
 325     // TODO: add more assertions here
 326     _young_type = new_type;
 327   }
 328 
 329   // Cached attributes used in the collection set policy information
 330 
 331   // The RSet length that was added to the total value
 332   // for the collection set.
 333   size_t _recorded_rs_length;
 334 
 335   // The predicted elapsed time that was added to total value
 336   // for the collection set.
 337   double _predicted_elapsed_time_ms;
 338 
 339   // The predicted number of bytes to copy that was added to
 340   // the total value for the collection set.
 341   size_t _predicted_bytes_to_copy;
 342 
 343  public:
 344   // If "is_zeroed" is "true", the region "mr" can be assumed to contain zeros.
 345   HeapRegion(size_t hrs_index,
 346              G1BlockOffsetSharedArray* sharedOffsetArray,
 347              MemRegion mr, bool is_zeroed);
 348 
 349   static int LogOfHRGrainBytes;
 350   static int LogOfHRGrainWords;
 351   // The normal type of these should be size_t. However, they used to
 352   // be members of an enum before and they are assumed by the
 353   // compilers to be ints. To avoid going and fixing all their uses,
 354   // I'm declaring them as ints. I'm not anticipating heap region
 355   // sizes to reach anywhere near 2g, so using an int here is safe.
 356   static int GrainBytes;
 357   static int GrainWords;
 358   static int CardsPerRegion;
 359 
 360   static size_t align_up_to_region_byte_size(size_t sz) {
 361     return (sz + (size_t) GrainBytes - 1) &
 362                                       ~((1 << (size_t) LogOfHRGrainBytes) - 1);
 363   }
 364 
 365   // It sets up the heap region size (GrainBytes / GrainWords), as
 366   // well as other related fields that are based on the heap region
 367   // size (LogOfHRGrainBytes / LogOfHRGrainWords /
 368   // CardsPerRegion). All those fields are considered constant
 369   // throughout the JVM's execution, therefore they should only be set
 370   // up once during initialization time.
 371   static void setup_heap_region_size(uintx min_heap_size);
 372 
 373   enum ClaimValues {
 374     InitialClaimValue     = 0,
 375     FinalCountClaimValue  = 1,
 376     NoteEndClaimValue     = 2,
 377     ScrubRemSetClaimValue = 3,
 378     ParVerifyClaimValue   = 4,
 379     RebuildRSClaimValue   = 5
 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   size_t 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   // An upper bound on the number of live bytes in the region.
 419   size_t max_live_bytes() { return used() - garbage_bytes(); }
 420 
 421   void add_to_marked_bytes(size_t incr_bytes) {
 422     _next_marked_bytes = _next_marked_bytes + incr_bytes;
 423     guarantee( _next_marked_bytes <= used(), "invariant" );
 424   }
 425 
 426   void zero_marked_bytes()      {
 427     _prev_marked_bytes = _next_marked_bytes = 0;
 428   }
 429 
 430   bool isHumongous() const { return _humongous_type != NotHumongous; }
 431   bool startsHumongous() const { return _humongous_type == StartsHumongous; }
 432   bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }
 433   // For a humongous region, region in which it starts.
 434   HeapRegion* humongous_start_region() const {
 435     return _humongous_start_region;
 436   }
 437 
 438   // Makes the current region be a "starts humongous" region, i.e.,
 439   // the first region in a series of one or more contiguous regions
 440   // that will contain a single "humongous" object. The two parameters
 441   // are as follows:
 442   //
 443   // new_top : The new value of the top field of this region which
 444   // points to the end of the humongous object that's being
 445   // allocated. If there is more than one region in the series, top
 446   // will lie beyond this region's original end field and on the last
 447   // region in the series.
 448   //
 449   // new_end : The new value of the end field of this region which
 450   // points to the end of the last region in the series. If there is
 451   // one region in the series (namely: this one) end will be the same
 452   // as the original end of this region.
 453   //
 454   // Updating top and end as described above makes this region look as
 455   // if it spans the entire space taken up by all the regions in the
 456   // series and an single allocation moved its top to new_top. This
 457   // ensures that the space (capacity / allocated) taken up by all
 458   // humongous regions can be calculated by just looking at the
 459   // "starts humongous" regions and by ignoring the "continues
 460   // humongous" regions.
 461   void set_startsHumongous(HeapWord* new_top, HeapWord* new_end);
 462 
 463   // Makes the current region be a "continues humongous'
 464   // region. first_hr is the "start humongous" region of the series
 465   // which this region will be part of.
 466   void set_continuesHumongous(HeapRegion* first_hr);
 467 
 468   // Unsets the humongous-related fields on the region.
 469   void set_notHumongous();
 470 
 471   // If the region has a remembered set, return a pointer to it.
 472   HeapRegionRemSet* rem_set() const {
 473     return _rem_set;
 474   }
 475 
 476   // True iff the region is in current collection_set.
 477   bool in_collection_set() const {
 478     return _in_collection_set;
 479   }
 480   void set_in_collection_set(bool b) {
 481     _in_collection_set = b;
 482   }
 483   HeapRegion* next_in_collection_set() {
 484     assert(in_collection_set(), "should only invoke on member of CS.");
 485     assert(_next_in_special_set == NULL ||
 486            _next_in_special_set->in_collection_set(),
 487            "Malformed CS.");
 488     return _next_in_special_set;
 489   }
 490   void set_next_in_collection_set(HeapRegion* r) {
 491     assert(in_collection_set(), "should only invoke on member of CS.");
 492     assert(r == NULL || r->in_collection_set(), "Malformed CS.");
 493     _next_in_special_set = r;
 494   }
 495 
 496   // Methods used by the HeapRegionSetBase class and subclasses.
 497 
 498   // Getter and setter for the next field used to link regions into
 499   // linked lists.
 500   HeapRegion* next()              { return _next; }
 501 
 502   void set_next(HeapRegion* next) { _next = next; }
 503 
 504   // Every region added to a set is tagged with a reference to that
 505   // set. This is used for doing consistency checking to make sure that
 506   // the contents of a set are as they should be and it's only
 507   // available in non-product builds.
 508 #ifdef ASSERT
 509   void set_containing_set(HeapRegionSetBase* containing_set) {
 510     assert((containing_set == NULL && _containing_set != NULL) ||
 511            (containing_set != NULL && _containing_set == NULL),
 512            err_msg("containing_set: "PTR_FORMAT" "
 513                    "_containing_set: "PTR_FORMAT,
 514                    containing_set, _containing_set));
 515 
 516     _containing_set = containing_set;
 517   }
 518 
 519   HeapRegionSetBase* containing_set() { return _containing_set; }
 520 #else // ASSERT
 521   void set_containing_set(HeapRegionSetBase* containing_set) { }
 522 
 523   // containing_set() is only used in asserts so there's no reason
 524   // to provide a dummy version of it.
 525 #endif // ASSERT
 526 
 527   // If we want to remove regions from a list in bulk we can simply tag
 528   // them with the pending_removal tag and call the
 529   // remove_all_pending() method on the list.
 530 
 531   bool pending_removal() { return _pending_removal; }
 532 
 533   void set_pending_removal(bool pending_removal) {
 534     if (pending_removal) {
 535       assert(!_pending_removal && containing_set() != NULL,
 536              "can only set pending removal to true if it's false and "
 537              "the region belongs to a region set");
 538     } else {
 539       assert( _pending_removal && containing_set() == NULL,
 540               "can only set pending removal to false if it's true and "
 541               "the region does not belong to a region set");
 542     }
 543 
 544     _pending_removal = pending_removal;
 545   }
 546 
 547   HeapRegion* get_next_young_region() { return _next_young_region; }
 548   void set_next_young_region(HeapRegion* hr) {
 549     _next_young_region = hr;
 550   }
 551 
 552   HeapRegion* get_next_dirty_cards_region() const { return _next_dirty_cards_region; }
 553   HeapRegion** next_dirty_cards_region_addr() { return &_next_dirty_cards_region; }
 554   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }
 555   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }
 556 
 557   HeapWord* orig_end() { return _orig_end; }
 558 
 559   // Allows logical separation between objects allocated before and after.
 560   void save_marks();
 561 
 562   // Reset HR stuff to default values.
 563   void hr_clear(bool par, bool clear_space);
 564   void par_clear();
 565 
 566   void initialize(MemRegion mr, bool clear_space, bool mangle_space);
 567 
 568   // Get the start of the unmarked area in this region.
 569   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }
 570   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }
 571 
 572   // Apply "cl->do_oop" to (the addresses of) all reference fields in objects
 573   // allocated in the current region before the last call to "save_mark".
 574   void oop_before_save_marks_iterate(OopClosure* cl);
 575 
 576   DirtyCardToOopClosure*
 577   new_dcto_closure(OopClosure* cl,
 578                    CardTableModRefBS::PrecisionStyle precision,
 579                    HeapRegionDCTOC::FilterKind fk);
 580 
 581   // Note the start or end of marking. This tells the heap region
 582   // that the collector is about to start or has finished (concurrently)
 583   // marking the heap.
 584 
 585   // Note the start of a marking phase. Record the
 586   // start of the unmarked area of the region here.
 587   void note_start_of_marking(bool during_initial_mark) {
 588     init_top_at_conc_mark_count();
 589     _next_marked_bytes = 0;
 590     if (during_initial_mark && is_young() && !is_survivor())
 591       _next_top_at_mark_start = bottom();
 592     else
 593       _next_top_at_mark_start = top();
 594   }
 595 
 596   // Note the end of a marking phase. Install the start of
 597   // the unmarked area that was captured at start of marking.
 598   void note_end_of_marking() {
 599     _prev_top_at_mark_start = _next_top_at_mark_start;
 600     _prev_marked_bytes = _next_marked_bytes;
 601     _next_marked_bytes = 0;
 602 
 603     guarantee(_prev_marked_bytes <=
 604               (size_t) (prev_top_at_mark_start() - bottom()) * HeapWordSize,
 605               "invariant");
 606   }
 607 
 608   // After an evacuation, we need to update _next_top_at_mark_start
 609   // to be the current top.  Note this is only valid if we have only
 610   // ever evacuated into this region.  If we evacuate, allocate, and
 611   // then evacuate we are in deep doodoo.
 612   void note_end_of_copying() {
 613     assert(top() >= _next_top_at_mark_start, "Increase only");
 614     _next_top_at_mark_start = top();
 615   }
 616 
 617   // Returns "false" iff no object in the region was allocated when the
 618   // last mark phase ended.
 619   bool is_marked() { return _prev_top_at_mark_start != bottom(); }
 620 
 621   // If "is_marked()" is true, then this is the index of the region in
 622   // an array constructed at the end of marking of the regions in a
 623   // "desirability" order.
 624   int sort_index() {
 625     return _sort_index;
 626   }
 627   void set_sort_index(int i) {
 628     _sort_index = i;
 629   }
 630 
 631   void init_top_at_conc_mark_count() {
 632     _top_at_conc_mark_count = bottom();
 633   }
 634 
 635   void set_top_at_conc_mark_count(HeapWord *cur) {
 636     assert(bottom() <= cur && cur <= end(), "Sanity.");
 637     _top_at_conc_mark_count = cur;
 638   }
 639 
 640   HeapWord* top_at_conc_mark_count() {
 641     return _top_at_conc_mark_count;
 642   }
 643 
 644   void reset_during_compaction() {
 645     guarantee( isHumongous() && startsHumongous(),
 646                "should only be called for humongous regions");
 647 
 648     zero_marked_bytes();
 649     init_top_at_mark_start();
 650   }
 651 
 652   // <PREDICTION>
 653   void calc_gc_efficiency(void);
 654   double gc_efficiency() { return _gc_efficiency;}
 655   // </PREDICTION>
 656 
 657   bool is_young() const     { return _young_type != NotYoung; }
 658   bool is_survivor() const  { return _young_type == Survivor; }
 659 
 660   int  young_index_in_cset() const { return _young_index_in_cset; }
 661   void set_young_index_in_cset(int index) {
 662     assert( (index == -1) || is_young(), "pre-condition" );
 663     _young_index_in_cset = index;
 664   }
 665 
 666   int age_in_surv_rate_group() {
 667     assert( _surv_rate_group != NULL, "pre-condition" );
 668     assert( _age_index > -1, "pre-condition" );
 669     return _surv_rate_group->age_in_group(_age_index);
 670   }
 671 
 672   void record_surv_words_in_group(size_t words_survived) {
 673     assert( _surv_rate_group != NULL, "pre-condition" );
 674     assert( _age_index > -1, "pre-condition" );
 675     int age_in_group = age_in_surv_rate_group();
 676     _surv_rate_group->record_surviving_words(age_in_group, words_survived);
 677   }
 678 
 679   int age_in_surv_rate_group_cond() {
 680     if (_surv_rate_group != NULL)
 681       return age_in_surv_rate_group();
 682     else
 683       return -1;
 684   }
 685 
 686   SurvRateGroup* surv_rate_group() {
 687     return _surv_rate_group;
 688   }
 689 
 690   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {
 691     assert( surv_rate_group != NULL, "pre-condition" );
 692     assert( _surv_rate_group == NULL, "pre-condition" );
 693     assert( is_young(), "pre-condition" );
 694 
 695     _surv_rate_group = surv_rate_group;
 696     _age_index = surv_rate_group->next_age_index();
 697   }
 698 
 699   void uninstall_surv_rate_group() {
 700     if (_surv_rate_group != NULL) {
 701       assert( _age_index > -1, "pre-condition" );
 702       assert( is_young(), "pre-condition" );
 703 
 704       _surv_rate_group = NULL;
 705       _age_index = -1;
 706     } else {
 707       assert( _age_index == -1, "pre-condition" );
 708     }
 709   }
 710 
 711   void set_young() { set_young_type(Young); }
 712 
 713   void set_survivor() { set_young_type(Survivor); }
 714 
 715   void set_not_young() { set_young_type(NotYoung); }
 716 
 717   // Determine if an object has been allocated since the last
 718   // mark performed by the collector. This returns true iff the object
 719   // is within the unmarked area of the region.
 720   bool obj_allocated_since_prev_marking(oop obj) const {
 721     return (HeapWord *) obj >= prev_top_at_mark_start();
 722   }
 723   bool obj_allocated_since_next_marking(oop obj) const {
 724     return (HeapWord *) obj >= next_top_at_mark_start();
 725   }
 726 
 727   // For parallel heapRegion traversal.
 728   bool claimHeapRegion(int claimValue);
 729   jint claim_value() { return _claimed; }
 730   // Use this carefully: only when you're sure no one is claiming...
 731   void set_claim_value(int claimValue) { _claimed = claimValue; }
 732 
 733   // Returns the "evacuation_failed" property of the region.
 734   bool evacuation_failed() { return _evacuation_failed; }
 735 
 736   // Sets the "evacuation_failed" property of the region.
 737   void set_evacuation_failed(bool b) {
 738     _evacuation_failed = b;
 739 
 740     if (b) {
 741       init_top_at_conc_mark_count();
 742       _next_marked_bytes = 0;
 743     }
 744   }
 745 
 746   // Requires that "mr" be entirely within the region.
 747   // Apply "cl->do_object" to all objects that intersect with "mr".
 748   // If the iteration encounters an unparseable portion of the region,
 749   // or if "cl->abort()" is true after a closure application,
 750   // terminate the iteration and return the address of the start of the
 751   // subregion that isn't done.  (The two can be distinguished by querying
 752   // "cl->abort()".)  Return of "NULL" indicates that the iteration
 753   // completed.
 754   HeapWord*
 755   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);
 756 
 757   // filter_young: if true and the region is a young region then we
 758   // skip the iteration.
 759   // card_ptr: if not NULL, and we decide that the card is not young
 760   // and we iterate over it, we'll clean the card before we start the
 761   // iteration.
 762   HeapWord*
 763   oops_on_card_seq_iterate_careful(MemRegion mr,
 764                                    FilterOutOfRegionClosure* cl,
 765                                    bool filter_young,
 766                                    jbyte* card_ptr);
 767 
 768   // A version of block start that is guaranteed to find *some* block
 769   // boundary at or before "p", but does not object iteration, and may
 770   // therefore be used safely when the heap is unparseable.
 771   HeapWord* block_start_careful(const void* p) const {
 772     return _offsets.block_start_careful(p);
 773   }
 774 
 775   // Requires that "addr" is within the region.  Returns the start of the
 776   // first ("careful") block that starts at or after "addr", or else the
 777   // "end" of the region if there is no such block.
 778   HeapWord* next_block_start_careful(HeapWord* addr);
 779 
 780   size_t recorded_rs_length() const        { return _recorded_rs_length; }
 781   double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }
 782   size_t predicted_bytes_to_copy() const   { return _predicted_bytes_to_copy; }
 783 
 784   void set_recorded_rs_length(size_t rs_length) {
 785     _recorded_rs_length = rs_length;
 786   }
 787 
 788   void set_predicted_elapsed_time_ms(double ms) {
 789     _predicted_elapsed_time_ms = ms;
 790   }
 791 
 792   void set_predicted_bytes_to_copy(size_t bytes) {
 793     _predicted_bytes_to_copy = bytes;
 794   }
 795 
 796 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \
 797   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);
 798   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DECL)
 799 
 800   CompactibleSpace* next_compaction_space() const;
 801 
 802   virtual void reset_after_compaction();
 803 
 804   void print() const;
 805   void print_on(outputStream* st) const;
 806 
 807   // vo == UsePrevMarking  -> use "prev" marking information,
 808   // vo == UseNextMarking -> use "next" marking information
 809   // vo == UseMarkWord    -> use the mark word in the object header
 810   //
 811   // NOTE: Only the "prev" marking information is guaranteed to be
 812   // consistent most of the time, so most calls to this should use
 813   // vo == UsePrevMarking.
 814   // Currently, there is only one case where this is called with
 815   // vo == UseNextMarking, which is to verify the "next" marking
 816   // information at the end of remark.
 817   // Currently there is only one place where this is called with
 818   // vo == UseMarkWord, which is to verify the marking during a
 819   // full GC.
 820   void verify(bool allow_dirty, VerifyOption vo, bool *failures) const;
 821 
 822   // Override; it uses the "prev" marking information
 823   virtual void verify(bool allow_dirty) const;
 824 };
 825 
 826 // HeapRegionClosure is used for iterating over regions.
 827 // Terminates the iteration when the "doHeapRegion" method returns "true".
 828 class HeapRegionClosure : public StackObj {
 829   friend class HeapRegionSeq;
 830   friend class G1CollectedHeap;
 831 
 832   bool _complete;
 833   void incomplete() { _complete = false; }
 834 
 835  public:
 836   HeapRegionClosure(): _complete(true) {}
 837 
 838   // Typically called on each region until it returns true.
 839   virtual bool doHeapRegion(HeapRegion* r) = 0;
 840 
 841   // True after iteration if the closure was applied to all heap regions
 842   // and returned "false" in all cases.
 843   bool complete() { return _complete; }
 844 };
 845 
 846 #endif // SERIALGC
 847 
 848 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP