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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP

 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"

 #include "gc_implementation/g1/g1_specialized_oop_closures.hpp"

 #include "gc_implementation/g1/survRateGroup.hpp"

 #include "gc_implementation/shared/ageTable.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "memory/space.inline.hpp"

 #include "memory/watermark.hpp"

 #ifndef SERIALGC

 // A HeapRegion is the smallest piece of a G1CollectedHeap that

 // can be collected independently.

 // NOTE: Although a HeapRegion is a Space, its

 // Space::initDirtyCardClosure method must not be called.

 // The problem is that the existence of this method breaks

 // the independence of barrier sets from remembered sets.

 // The solution is to remove this method from the definition

 // of a Space.

 class CompactibleSpace;

 class ContiguousSpace;

 class HeapRegionRemSet;

 class HeapRegionRemSetIterator;

 class HeapRegion;

 class HeapRegionSetBase;

 #define HR_FORMAT "%d:["PTR_FORMAT","PTR_FORMAT","PTR_FORMAT"]"

 #define HR_FORMAT_PARAMS(_hr_) (_hr_)->hrs_index(), (_hr_)->bottom(), \

                                (_hr_)->top(), (_hr_)->end()

 // A dirty card to oop closure for heap regions. It

 // knows how to get the G1 heap and how to use the bitmap

 // in the concurrent marker used by G1 to filter remembered

 // sets.

 class HeapRegionDCTOC : public ContiguousSpaceDCTOC {

 public:

   // Specification of possible DirtyCardToOopClosure filtering.

   enum FilterKind {

     NoFilterKind,

     IntoCSFilterKind,

     OutOfRegionFilterKind

   };

 protected:

   HeapRegion* _hr;

   FilterKind _fk;

   G1CollectedHeap* _g1;

   void walk_mem_region_with_cl(MemRegion mr,

                                HeapWord* bottom, HeapWord* top,

                                OopClosure* cl);

   // We don't specialize this for FilteringClosure; filtering is handled by

   // the "FilterKind" mechanism.  But we provide this to avoid a compiler

   // warning.

   void walk_mem_region_with_cl(MemRegion mr,

                                HeapWord* bottom, HeapWord* top,

                                FilteringClosure* cl) {

     HeapRegionDCTOC::walk_mem_region_with_cl(mr, bottom, top,

                                                        (OopClosure*)cl);

   }

   // Get the actual top of the area on which the closure will

   // operate, given where the top is assumed to be (the end of the

   // memory region passed to do_MemRegion) and where the object

   // at the top is assumed to start. For example, an object may

   // start at the top but actually extend past the assumed top,

   // in which case the top becomes the end of the object.

   HeapWord* get_actual_top(HeapWord* top, HeapWord* top_obj) {

     return ContiguousSpaceDCTOC::get_actual_top(top, top_obj);

   }

   // Walk the given memory region from bottom to (actual) top

   // looking for objects and applying the oop closure (_cl) to

   // them. The base implementation of this treats the area as

   // blocks, where a block may or may not be an object. Sub-

   // classes should override this to provide more accurate

   // or possibly more efficient walking.

   void walk_mem_region(MemRegion mr, HeapWord* bottom, HeapWord* top) {

     Filtering_DCTOC::walk_mem_region(mr, bottom, top);

   }

 public:

   HeapRegionDCTOC(G1CollectedHeap* g1,

                   HeapRegion* hr, OopClosure* cl,

                   CardTableModRefBS::PrecisionStyle precision,

                   FilterKind fk);

 };

 // The complicating factor is that BlockOffsetTable diverged

 // significantly, and we need functionality that is only in the G1 version.

 // So I copied that code, which led to an alternate G1 version of

 // OffsetTableContigSpace.  If the two versions of BlockOffsetTable could

 // be reconciled, then G1OffsetTableContigSpace could go away.

 // The idea behind time stamps is the following. Doing a save_marks on

 // all regions at every GC pause is time consuming (if I remember

 // well, 10ms or so). So, we would like to do that only for regions

 // that are GC alloc regions. To achieve this, we use time

 // stamps. For every evacuation pause, G1CollectedHeap generates a

 // unique time stamp (essentially a counter that gets

 // incremented). Every time we want to call save_marks on a region,

 // we set the saved_mark_word to top and also copy the current GC

 // time stamp to the time stamp field of the space. Reading the

 // saved_mark_word involves checking the time stamp of the

 // region. If it is the same as the current GC time stamp, then we

 // can safely read the saved_mark_word field, as it is valid. If the

 // time stamp of the region is not the same as the current GC time

 // stamp, then we instead read top, as the saved_mark_word field is

 // invalid. Time stamps (on the regions and also on the

 // G1CollectedHeap) are reset at every cleanup (we iterate over

 // the regions anyway) and at the end of a Full GC. The current scheme

 // that uses sequential unsigned ints will fail only if we have 4b

 // evacuation pauses between two cleanups, which is _highly_ unlikely.

 class G1OffsetTableContigSpace: public ContiguousSpace {

   friend class VMStructs;

  protected:

   G1BlockOffsetArrayContigSpace _offsets;

   Mutex _par_alloc_lock;

   volatile unsigned _gc_time_stamp;

   // When we need to retire an allocation region, while other threads

   // are also concurrently trying to allocate into it, we typically

   // allocate a dummy object at the end of the region to ensure that

   // no more allocations can take place in it. However, sometimes we

   // want to know where the end of the last "real" object we allocated

   // into the region was and this is what this keeps track.

   HeapWord* _pre_dummy_top;

  public:

   // Constructor.  If "is_zeroed" is true, the MemRegion "mr" may be

   // assumed to contain zeros.

   G1OffsetTableContigSpace(G1BlockOffsetSharedArray* sharedOffsetArray,

                            MemRegion mr, bool is_zeroed = false);

   void set_bottom(HeapWord* value);

   void set_end(HeapWord* value);

   virtual HeapWord* saved_mark_word() const;

   virtual void set_saved_mark();

   void reset_gc_time_stamp() { _gc_time_stamp = 0; }

   // See the comment above in the declaration of _pre_dummy_top for an

   // explanation of what it is.

   void set_pre_dummy_top(HeapWord* pre_dummy_top) {

     assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");

     _pre_dummy_top = pre_dummy_top;

   }

   HeapWord* pre_dummy_top() {

     return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;

   }

   void reset_pre_dummy_top() { _pre_dummy_top = NULL; }

   virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);

   virtual void clear(bool mangle_space);

   HeapWord* block_start(const void* p);

   HeapWord* block_start_const(const void* p) const;

   // Add offset table update.

   virtual HeapWord* allocate(size_t word_size);

   HeapWord* par_allocate(size_t word_size);

   // MarkSweep support phase3

   virtual HeapWord* initialize_threshold();

   virtual HeapWord* cross_threshold(HeapWord* start, HeapWord* end);

   virtual void print() const;

   void reset_bot() {

     _offsets.zero_bottom_entry();

     _offsets.initialize_threshold();

   }

   void update_bot_for_object(HeapWord* start, size_t word_size) {

     _offsets.alloc_block(start, word_size);

   }

   void print_bot_on(outputStream* out) {

     _offsets.print_on(out);

   }

 };

 class HeapRegion: public G1OffsetTableContigSpace {

   friend class VMStructs;

  private:

   enum HumongousType {

     NotHumongous = 0,

     StartsHumongous,

     ContinuesHumongous

   };

   // The next filter kind that should be used for a "new_dcto_cl" call with

   // the "traditional" signature.

   HeapRegionDCTOC::FilterKind _next_fk;

   // Requires that the region "mr" be dense with objects, and begin and end

   // with an object.

   void oops_in_mr_iterate(MemRegion mr, OopClosure* cl);

   // The remembered set for this region.

   // (Might want to make this "inline" later, to avoid some alloc failure

   // issues.)

   HeapRegionRemSet* _rem_set;

   G1BlockOffsetArrayContigSpace* offsets() { return &_offsets; }

  protected:

   // If this region is a member of a HeapRegionSeq, the index in that

   // sequence, otherwise -1.

   int  _hrs_index;

   HumongousType _humongous_type;

   // For a humongous region, region in which it starts.

   HeapRegion* _humongous_start_region;

   // For the start region of a humongous sequence, it's original end().

   HeapWord* _orig_end;

   // True iff the region is in current collection_set.

   bool _in_collection_set;

   // Is this or has it been an allocation region in the current collection

   // pause.

   bool _is_gc_alloc_region;

   // True iff an attempt to evacuate an object in the region failed.

   bool _evacuation_failed;

   // A heap region may be a member one of a number of special subsets, each

   // represented as linked lists through the field below.  Currently, these

   // sets include:

   //   The collection set.

   //   The set of allocation regions used in a collection pause.

   //   Spaces that may contain gray objects.

   HeapRegion* _next_in_special_set;

   // next region in the young "generation" region set

   HeapRegion* _next_young_region;

   // Next region whose cards need cleaning

   HeapRegion* _next_dirty_cards_region;

   // Fields used by the HeapRegionSetBase class and subclasses.

   HeapRegion* _next;

 #ifdef ASSERT

   HeapRegionSetBase* _containing_set;

 #endif // ASSERT

   bool _pending_removal;

   // For parallel heapRegion traversal.

   jint _claimed;

   // We use concurrent marking to determine the amount of live data

   // in each heap region.

   size_t _prev_marked_bytes;    // Bytes known to be live via last completed marking.

   size_t _next_marked_bytes;    // Bytes known to be live via in-progress marking.

   // See "sort_index" method.  -1 means is not in the array.

   int _sort_index;

   // <PREDICTION>

   double _gc_efficiency;

   // </PREDICTION>

   enum YoungType {

     NotYoung,                   // a region is not young

     Young,                      // a region is young

     Survivor                    // a region is young and it contains

                                 // survivor

   };

   volatile YoungType _young_type;

   int  _young_index_in_cset;

   SurvRateGroup* _surv_rate_group;

   int  _age_index;

   // The start of the unmarked area. The unmarked area extends from this

   // word until the top and/or end of the region, and is the part

   // of the region for which no marking was done, i.e. objects may

   // have been allocated in this part since the last mark phase.

   // "prev" is the top at the start of the last completed marking.

   // "next" is the top at the start of the in-progress marking (if any.)

   HeapWord* _prev_top_at_mark_start;

   HeapWord* _next_top_at_mark_start;

   // If a collection pause is in progress, this is the top at the start

   // of that pause.

   // We've counted the marked bytes of objects below here.

   HeapWord* _top_at_conc_mark_count;

   void init_top_at_mark_start() {

     assert(_prev_marked_bytes == 0 &&

            _next_marked_bytes == 0,

            "Must be called after zero_marked_bytes.");

     HeapWord* bot = bottom();

     _prev_top_at_mark_start = bot;

     _next_top_at_mark_start = bot;

     _top_at_conc_mark_count = bot;

   }

   void set_young_type(YoungType new_type) {

     //assert(_young_type != new_type, "setting the same type" );

     // TODO: add more assertions here

     _young_type = new_type;

   }

   // Cached attributes used in the collection set policy information

   // The RSet length that was added to the total value

   // for the collection set.

   size_t _recorded_rs_length;

   // The predicted elapsed time that was added to total value

   // for the collection set.

   double _predicted_elapsed_time_ms;

   // The predicted number of bytes to copy that was added to

   // the total value for the collection set.

   size_t _predicted_bytes_to_copy;

  public:

   // If "is_zeroed" is "true", the region "mr" can be assumed to contain zeros.

   HeapRegion(G1BlockOffsetSharedArray* sharedOffsetArray,

              MemRegion mr, bool is_zeroed);

   static int LogOfHRGrainBytes;

   static int LogOfHRGrainWords;

   // The normal type of these should be size_t. However, they used to

   // be members of an enum before and they are assumed by the

   // compilers to be ints. To avoid going and fixing all their uses,

   // I'm declaring them as ints. I'm not anticipating heap region

   // sizes to reach anywhere near 2g, so using an int here is safe.

   static int GrainBytes;

   static int GrainWords;

   static int CardsPerRegion;

   // It sets up the heap region size (GrainBytes / GrainWords), as

   // well as other related fields that are based on the heap region

   // size (LogOfHRGrainBytes / LogOfHRGrainWords /

   // CardsPerRegion). All those fields are considered constant

   // throughout the JVM's execution, therefore they should only be set

   // up once during initialization time.

   static void setup_heap_region_size(uintx min_heap_size);

   enum ClaimValues {

     InitialClaimValue     = 0,

     FinalCountClaimValue  = 1,

     NoteEndClaimValue     = 2,

     ScrubRemSetClaimValue = 3,

     ParVerifyClaimValue   = 4,

     RebuildRSClaimValue   = 5

   };

   inline HeapWord* par_allocate_no_bot_updates(size_t word_size) {

     assert(is_young(), "we can only skip BOT updates on young regions");

     return ContiguousSpace::par_allocate(word_size);

   }

   inline HeapWord* allocate_no_bot_updates(size_t word_size) {

     assert(is_young(), "we can only skip BOT updates on young regions");

     return ContiguousSpace::allocate(word_size);

   }

   // If this region is a member of a HeapRegionSeq, the index in that

   // sequence, otherwise -1.

   int hrs_index() const { return _hrs_index; }

   void set_hrs_index(int index) { _hrs_index = index; }

   // The number of bytes marked live in the region in the last marking phase.

   size_t marked_bytes()    { return _prev_marked_bytes; }

   // The number of bytes counted in the next marking.

   size_t next_marked_bytes() { return _next_marked_bytes; }

   // The number of bytes live wrt the next marking.

   size_t next_live_bytes() {

     return (top() - next_top_at_mark_start())

       * HeapWordSize

       + next_marked_bytes();

   }

   // A lower bound on the amount of garbage bytes in the region.

   size_t garbage_bytes() {

     size_t used_at_mark_start_bytes =

       (prev_top_at_mark_start() - bottom()) * HeapWordSize;

     assert(used_at_mark_start_bytes >= marked_bytes(),

            "Can't mark more than we have.");

     return used_at_mark_start_bytes - marked_bytes();

   }

   // An upper bound on the number of live bytes in the region.

   size_t max_live_bytes() { return used() - garbage_bytes(); }

   void add_to_marked_bytes(size_t incr_bytes) {

     _next_marked_bytes = _next_marked_bytes + incr_bytes;

     guarantee( _next_marked_bytes <= used(), "invariant" );

   }

   void zero_marked_bytes()      {

     _prev_marked_bytes = _next_marked_bytes = 0;

   }

   bool isHumongous() const { return _humongous_type != NotHumongous; }

   bool startsHumongous() const { return _humongous_type == StartsHumongous; }

   bool continuesHumongous() const { return _humongous_type == ContinuesHumongous; }

   // For a humongous region, region in which it starts.

   HeapRegion* humongous_start_region() const {

     return _humongous_start_region;

   }

   // Makes the current region be a "starts humongous" region, i.e.,

   // the first region in a series of one or more contiguous regions

   // that will contain a single "humongous" object. The two parameters

   // are as follows:

   //

   // new_top : The new value of the top field of this region which

   // points to the end of the humongous object that's being

   // allocated. If there is more than one region in the series, top

   // will lie beyond this region's original end field and on the last

   // region in the series.

   //

   // new_end : The new value of the end field of this region which

   // points to the end of the last region in the series. If there is

   // one region in the series (namely: this one) end will be the same

   // as the original end of this region.

   //

   // Updating top and end as described above makes this region look as

   // if it spans the entire space taken up by all the regions in the

   // series and an single allocation moved its top to new_top. This

   // ensures that the space (capacity / allocated) taken up by all

   // humongous regions can be calculated by just looking at the

   // "starts humongous" regions and by ignoring the "continues

   // humongous" regions.

   void set_startsHumongous(HeapWord* new_top, HeapWord* new_end);

   // Makes the current region be a "continues humongous'

   // region. first_hr is the "start humongous" region of the series

   // which this region will be part of.

   void set_continuesHumongous(HeapRegion* first_hr);

   // Unsets the humongous-related fields on the region.

   void set_notHumongous();

   // If the region has a remembered set, return a pointer to it.

   HeapRegionRemSet* rem_set() const {

     return _rem_set;

   }

   // True iff the region is in current collection_set.

   bool in_collection_set() const {

     return _in_collection_set;

   }

   void set_in_collection_set(bool b) {

     _in_collection_set = b;

   }

   HeapRegion* next_in_collection_set() {

     assert(in_collection_set(), "should only invoke on member of CS.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->in_collection_set(),

            "Malformed CS.");

     return _next_in_special_set;

   }

   void set_next_in_collection_set(HeapRegion* r) {

     assert(in_collection_set(), "should only invoke on member of CS.");

     assert(r == NULL || r->in_collection_set(), "Malformed CS.");

     _next_in_special_set = r;

   }

   // True iff it is or has been an allocation region in the current

   // collection pause.

   bool is_gc_alloc_region() const {

     return _is_gc_alloc_region;

   }

   void set_is_gc_alloc_region(bool b) {

     _is_gc_alloc_region = b;

   }

   HeapRegion* next_gc_alloc_region() {

     assert(is_gc_alloc_region(), "should only invoke on member of CS.");

     assert(_next_in_special_set == NULL ||

            _next_in_special_set->is_gc_alloc_region(),

            "Malformed CS.");

     return _next_in_special_set;

   }

   void set_next_gc_alloc_region(HeapRegion* r) {

     assert(is_gc_alloc_region(), "should only invoke on member of CS.");

     assert(r == NULL || r->is_gc_alloc_region(), "Malformed CS.");

     _next_in_special_set = r;

   }

   // Methods used by the HeapRegionSetBase class and subclasses.

   // Getter and setter for the next field used to link regions into

   // linked lists.

   HeapRegion* next()              { return _next; }

   void set_next(HeapRegion* next) { _next = next; }

   // Every region added to a set is tagged with a reference to that

   // set. This is used for doing consistency checking to make sure that

   // the contents of a set are as they should be and it's only

   // available in non-product builds.

 #ifdef ASSERT

   void set_containing_set(HeapRegionSetBase* containing_set) {

     assert((containing_set == NULL && _containing_set != NULL) ||

            (containing_set != NULL && _containing_set == NULL),

            err_msg("containing_set: "PTR_FORMAT" "

                    "_containing_set: "PTR_FORMAT,

                    containing_set, _containing_set));

     _containing_set = containing_set;

   }

   HeapRegionSetBase* containing_set() { return _containing_set; }

 #else // ASSERT

   void set_containing_set(HeapRegionSetBase* containing_set) { }

   // containing_set() is only used in asserts so there's no reason

   // to provide a dummy version of it.

 #endif // ASSERT

   // If we want to remove regions from a list in bulk we can simply tag

   // them with the pending_removal tag and call the

   // remove_all_pending() method on the list.

   bool pending_removal() { return _pending_removal; }

   void set_pending_removal(bool pending_removal) {

     if (pending_removal) {

       assert(!_pending_removal && containing_set() != NULL,

              "can only set pending removal to true if it's false and "

              "the region belongs to a region set");

     } else {

       assert( _pending_removal && containing_set() == NULL,

               "can only set pending removal to false if it's true and "

               "the region does not belong to a region set");

     }

     _pending_removal = pending_removal;

   }

   HeapRegion* get_next_young_region() { return _next_young_region; }

   void set_next_young_region(HeapRegion* hr) {

     _next_young_region = hr;

   }

   HeapRegion* get_next_dirty_cards_region() const { return _next_dirty_cards_region; }

   HeapRegion** next_dirty_cards_region_addr() { return &_next_dirty_cards_region; }

   void set_next_dirty_cards_region(HeapRegion* hr) { _next_dirty_cards_region = hr; }

   bool is_on_dirty_cards_region_list() const { return get_next_dirty_cards_region() != NULL; }

   // Allows logical separation between objects allocated before and after.

   void save_marks();

   // Reset HR stuff to default values.

   void hr_clear(bool par, bool clear_space);

   void initialize(MemRegion mr, bool clear_space, bool mangle_space);

   // Get the start of the unmarked area in this region.

   HeapWord* prev_top_at_mark_start() const { return _prev_top_at_mark_start; }

   HeapWord* next_top_at_mark_start() const { return _next_top_at_mark_start; }

   // Apply "cl->do_oop" to (the addresses of) all reference fields in objects

   // allocated in the current region before the last call to "save_mark".

   void oop_before_save_marks_iterate(OopClosure* cl);

   // This call determines the "filter kind" argument that will be used for

   // the next call to "new_dcto_cl" on this region with the "traditional"

   // signature (i.e., the call below.)  The default, in the absence of a

   // preceding call to this method, is "NoFilterKind", and a call to this

   // method is necessary for each such call, or else it reverts to the

   // default.

   // (This is really ugly, but all other methods I could think of changed a

   // lot of main-line code for G1.)

   void set_next_filter_kind(HeapRegionDCTOC::FilterKind nfk) {

     _next_fk = nfk;

   }

   DirtyCardToOopClosure*

   new_dcto_closure(OopClosure* cl,

                    CardTableModRefBS::PrecisionStyle precision,

                    HeapRegionDCTOC::FilterKind fk);

 #if WHASSUP

   DirtyCardToOopClosure*

   new_dcto_closure(OopClosure* cl,

                    CardTableModRefBS::PrecisionStyle precision,

                    HeapWord* boundary) {

     assert(boundary == NULL, "This arg doesn't make sense here.");

     DirtyCardToOopClosure* res = new_dcto_closure(cl, precision, _next_fk);

     _next_fk = HeapRegionDCTOC::NoFilterKind;

     return res;

   }

 #endif

   //

   // Note the start or end of marking. This tells the heap region

   // that the collector is about to start or has finished (concurrently)

   // marking the heap.

   //

   // Note the start of a marking phase. Record the

   // start of the unmarked area of the region here.

   void note_start_of_marking(bool during_initial_mark) {

     init_top_at_conc_mark_count();

     _next_marked_bytes = 0;

     if (during_initial_mark && is_young() && !is_survivor())

       _next_top_at_mark_start = bottom();

     else

       _next_top_at_mark_start = top();

   }

   // Note the end of a marking phase. Install the start of

   // the unmarked area that was captured at start of marking.

   void note_end_of_marking() {

     _prev_top_at_mark_start = _next_top_at_mark_start;

     _prev_marked_bytes = _next_marked_bytes;

     _next_marked_bytes = 0;

     guarantee(_prev_marked_bytes <=

               (size_t) (prev_top_at_mark_start() - bottom()) * HeapWordSize,

               "invariant");

   }

   // After an evacuation, we need to update _next_top_at_mark_start

   // to be the current top.  Note this is only valid if we have only

   // ever evacuated into this region.  If we evacuate, allocate, and

   // then evacuate we are in deep doodoo.

   void note_end_of_copying() {

     assert(top() >= _next_top_at_mark_start, "Increase only");

     _next_top_at_mark_start = top();

   }

   // Returns "false" iff no object in the region was allocated when the

   // last mark phase ended.

   bool is_marked() { return _prev_top_at_mark_start != bottom(); }

   // If "is_marked()" is true, then this is the index of the region in

   // an array constructed at the end of marking of the regions in a

   // "desirability" order.

   int sort_index() {

     return _sort_index;

   }

   void set_sort_index(int i) {

     _sort_index = i;

   }

   void init_top_at_conc_mark_count() {

     _top_at_conc_mark_count = bottom();

   }

   void set_top_at_conc_mark_count(HeapWord *cur) {

     assert(bottom() <= cur && cur <= end(), "Sanity.");

     _top_at_conc_mark_count = cur;

   }

   HeapWord* top_at_conc_mark_count() {

     return _top_at_conc_mark_count;

   }

   void reset_during_compaction() {

     guarantee( isHumongous() && startsHumongous(),

                "should only be called for humongous regions");

     zero_marked_bytes();

     init_top_at_mark_start();

   }

   // <PREDICTION>

   void calc_gc_efficiency(void);

   double gc_efficiency() { return _gc_efficiency;}

   // </PREDICTION>

   bool is_young() const     { return _young_type != NotYoung; }

   bool is_survivor() const  { return _young_type == Survivor; }

   int  young_index_in_cset() const { return _young_index_in_cset; }

   void set_young_index_in_cset(int index) {

     assert( (index == -1) || is_young(), "pre-condition" );

     _young_index_in_cset = index;

   }

   int age_in_surv_rate_group() {

     assert( _surv_rate_group != NULL, "pre-condition" );

     assert( _age_index > -1, "pre-condition" );

     return _surv_rate_group->age_in_group(_age_index);

   }

   void record_surv_words_in_group(size_t words_survived) {

     assert( _surv_rate_group != NULL, "pre-condition" );

     assert( _age_index > -1, "pre-condition" );

     int age_in_group = age_in_surv_rate_group();

     _surv_rate_group->record_surviving_words(age_in_group, words_survived);

   }

   int age_in_surv_rate_group_cond() {

     if (_surv_rate_group != NULL)

       return age_in_surv_rate_group();

     else

       return -1;

   }

   SurvRateGroup* surv_rate_group() {

     return _surv_rate_group;

   }

   void install_surv_rate_group(SurvRateGroup* surv_rate_group) {

     assert( surv_rate_group != NULL, "pre-condition" );

     assert( _surv_rate_group == NULL, "pre-condition" );

     assert( is_young(), "pre-condition" );

     _surv_rate_group = surv_rate_group;

     _age_index = surv_rate_group->next_age_index();

   }

   void uninstall_surv_rate_group() {

     if (_surv_rate_group != NULL) {

       assert( _age_index > -1, "pre-condition" );

       assert( is_young(), "pre-condition" );

       _surv_rate_group = NULL;

       _age_index = -1;

     } else {

       assert( _age_index == -1, "pre-condition" );

     }

   }

   void set_young() { set_young_type(Young); }

   void set_survivor() { set_young_type(Survivor); }

   void set_not_young() { set_young_type(NotYoung); }

   // Determine if an object has been allocated since the last

   // mark performed by the collector. This returns true iff the object

   // is within the unmarked area of the region.

   bool obj_allocated_since_prev_marking(oop obj) const {

     return (HeapWord *) obj >= prev_top_at_mark_start();

   }

   bool obj_allocated_since_next_marking(oop obj) const {

     return (HeapWord *) obj >= next_top_at_mark_start();

   }

   // For parallel heapRegion traversal.

   bool claimHeapRegion(int claimValue);

   jint claim_value() { return _claimed; }

   // Use this carefully: only when you're sure no one is claiming...

   void set_claim_value(int claimValue) { _claimed = claimValue; }

   // Returns the "evacuation_failed" property of the region.

   bool evacuation_failed() { return _evacuation_failed; }

   // Sets the "evacuation_failed" property of the region.

   void set_evacuation_failed(bool b) {

     _evacuation_failed = b;

     if (b) {

       init_top_at_conc_mark_count();

       _next_marked_bytes = 0;

     }

   }

   // Requires that "mr" be entirely within the region.

   // Apply "cl->do_object" to all objects that intersect with "mr".

   // If the iteration encounters an unparseable portion of the region,

   // or if "cl->abort()" is true after a closure application,

   // terminate the iteration and return the address of the start of the

   // subregion that isn't done.  (The two can be distinguished by querying

   // "cl->abort()".)  Return of "NULL" indicates that the iteration

   // completed.

   HeapWord*

   object_iterate_mem_careful(MemRegion mr, ObjectClosure* cl);

   // In this version - if filter_young is true and the region

   // is a young region then we skip the iteration.

   HeapWord*

   oops_on_card_seq_iterate_careful(MemRegion mr,

                                    FilterOutOfRegionClosure* cl,

                                    bool filter_young);

   // A version of block start that is guaranteed to find *some* block

   // boundary at or before "p", but does not object iteration, and may

   // therefore be used safely when the heap is unparseable.

   HeapWord* block_start_careful(const void* p) const {

     return _offsets.block_start_careful(p);

   }

   // Requires that "addr" is within the region.  Returns the start of the

   // first ("careful") block that starts at or after "addr", or else the

   // "end" of the region if there is no such block.

   HeapWord* next_block_start_careful(HeapWord* addr);

   size_t recorded_rs_length() const        { return _recorded_rs_length; }

   double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }

   size_t predicted_bytes_to_copy() const   { return _predicted_bytes_to_copy; }

   void set_recorded_rs_length(size_t rs_length) {

     _recorded_rs_length = rs_length;

   }

   void set_predicted_elapsed_time_ms(double ms) {

     _predicted_elapsed_time_ms = ms;

   }

   void set_predicted_bytes_to_copy(size_t bytes) {

     _predicted_bytes_to_copy = bytes;

   }

 #define HeapRegion_OOP_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix)  \

   virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl);

   SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(HeapRegion_OOP_SINCE_SAVE_MARKS_DECL)

   CompactibleSpace* next_compaction_space() const;

   virtual void reset_after_compaction();

   void print() const;

   void print_on(outputStream* st) const;

   // use_prev_marking == true  -> use "prev" marking information,

   // use_prev_marking == false -> use "next" marking information

   // NOTE: Only the "prev" marking information is guaranteed to be

   // consistent most of the time, so most calls to this should use

   // use_prev_marking == true. Currently, there is only one case where

   // this is called with use_prev_marking == false, which is to verify

   // the "next" marking information at the end of remark.

   void verify(bool allow_dirty, bool use_prev_marking, bool *failures) const;

   // Override; it uses the "prev" marking information

   virtual void verify(bool allow_dirty) const;

 };

 // HeapRegionClosure is used for iterating over regions.

 // Terminates the iteration when the "doHeapRegion" method returns "true".

 class HeapRegionClosure : public StackObj {

   friend class HeapRegionSeq;

   friend class G1CollectedHeap;

   bool _complete;

   void incomplete() { _complete = false; }

  public:

   HeapRegionClosure(): _complete(true) {}

   // Typically called on each region until it returns true.

   virtual bool doHeapRegion(HeapRegion* r) = 0;

   // True after iteration if the closure was applied to all heap regions

   // and returned "false" in all cases.

   bool complete() { return _complete; }

 };

 #endif // SERIALGC

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_HPP