6711316: Open source the Garbage-First garbage collector

First mercurial integration of the code for the Garbage-First garbage collector.

Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr

hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp

@@ -0,0 +1,924 @@
+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * 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).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+#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;
+
+// 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;
+
+ 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; }
+
+  virtual void initialize(MemRegion mr, bool clear_space);
+  virtual void clear();
+
+  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;
+};
+
+class HeapRegion: public G1OffsetTableContigSpace {
+  friend class VMStructs;
+ private:
+
+  // 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;
+
+  bool _humongous;         // starts or continues a humongous object
+  bool _humongous_start;   // starts a humongous object
+  // 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;
+
+    // True iff the region is on the unclean list, waiting to be zero filled.
+  bool _is_on_unclean_list;
+
+  // True iff the region is on the free list, ready for allocation.
+  bool _is_on_free_list;
+
+  // 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;
+
+  // 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;
+
+  // Means it has (or at least had) a very large RS, and should not be
+  // considered for membership in a collection set.
+  enum PopularityState {
+    NotPopular,
+    PopularPending,
+    Popular
+  };
+  PopularityState _popularity;
+
+  // <PREDICTION>
+  double _gc_efficiency;
+  // </PREDICTION>
+
+  enum YoungType {
+    NotYoung,                   // a region is not young
+    ScanOnly,                   // a region is young and scan-only
+    Young,                      // a region is young
+    Survivor                    // a region is young and it contains
+                                // survivor
+  };
+
+  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;
+  }
+
+  jint _zfs;  // A member of ZeroFillState.  Protected by ZF_lock.
+  Thread* _zero_filler; // If _zfs is ZeroFilling, the thread that (last)
+                        // made it so.
+
+  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;
+  }
+
+ public:
+  // If "is_zeroed" is "true", the region "mr" can be assumed to contain zeros.
+  HeapRegion(G1BlockOffsetSharedArray* sharedOffsetArray,
+             MemRegion mr, bool is_zeroed);
+
+  enum SomePublicConstants {
+    // HeapRegions are GrainBytes-aligned
+    // and have sizes that are multiples of GrainBytes.
+    LogOfHRGrainBytes = 20,
+    LogOfHRGrainWords = LogOfHRGrainBytes - LogHeapWordSize,
+    GrainBytes = 1 << LogOfHRGrainBytes,
+    GrainWords = 1 <<LogOfHRGrainWords,
+    MaxAge = 2, NoOfAges = MaxAge+1
+  };
+
+  // Concurrent refinement requires contiguous heap regions (in which TLABs
+  // might be allocated) to be zero-filled.  Each region therefore has a
+  // zero-fill-state.
+  enum ZeroFillState {
+    NotZeroFilled,
+    ZeroFilling,
+    ZeroFilled,
+    Allocated
+  };
+
+  // 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; }
+  bool startsHumongous() const { return _humongous_start; }
+  bool continuesHumongous() const { return _humongous && ! _humongous_start; }
+  // For a humongous region, region in which it starts.
+  HeapRegion* humongous_start_region() const {
+    return _humongous_start_region;
+  }
+
+  // Causes the current region to represent a humongous object spanning "n"
+  // regions.
+  virtual void set_startsHumongous();
+
+  // The regions that continue a humongous sequence should be added using
+  // this method, in increasing address order.
+  void set_continuesHumongous(HeapRegion* start);
+
+  void add_continuingHumongousRegion(HeapRegion* cont);
+
+  // 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;
+  }
+
+  bool is_reserved() {
+    return popular();
+  }
+
+  bool is_on_free_list() {
+    return _is_on_free_list;
+  }
+
+  void set_on_free_list(bool b) {
+    _is_on_free_list = b;
+  }
+
+  HeapRegion* next_from_free_list() {
+    assert(is_on_free_list(),
+           "Should only invoke on free space.");
+    assert(_next_in_special_set == NULL ||
+           _next_in_special_set->is_on_free_list(),
+           "Malformed Free List.");
+    return _next_in_special_set;
+  }
+
+  void set_next_on_free_list(HeapRegion* r) {
+    assert(r == NULL || r->is_on_free_list(), "Malformed free list.");
+    _next_in_special_set = r;
+  }
+
+  bool is_on_unclean_list() {
+    return _is_on_unclean_list;
+  }
+
+  void set_on_unclean_list(bool b);
+
+  HeapRegion* next_from_unclean_list() {
+    assert(is_on_unclean_list(),
+           "Should only invoke on unclean space.");
+    assert(_next_in_special_set == NULL ||
+           _next_in_special_set->is_on_unclean_list(),
+           "Malformed unclean List.");
+    return _next_in_special_set;
+  }
+
+  void set_next_on_unclean_list(HeapRegion* r);
+
+  HeapRegion* get_next_young_region() { return _next_young_region; }
+  void set_next_young_region(HeapRegion* hr) {
+    _next_young_region = hr;
+  }
+
+  // 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);
+
+  // Ensure that "this" is zero-filled.
+  void ensure_zero_filled();
+  // This one requires that the calling thread holds ZF_mon.
+  void ensure_zero_filled_locked();
+
+  // 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();
+  }
+
+  bool popular() { return _popularity == Popular; }
+  void set_popular(bool b) {
+    if (b) {
+      _popularity = Popular;
+    } else {
+      _popularity = NotPopular;
+    }
+  }
+  bool popular_pending() { return _popularity == PopularPending; }
+  void set_popular_pending(bool b) {
+    if (b) {
+      _popularity = PopularPending;
+    } else {
+      _popularity = NotPopular;
+    }
+  }
+
+  // <PREDICTION>
+  void calc_gc_efficiency(void);
+  double gc_efficiency() { return _gc_efficiency;}
+  // </PREDICTION>
+
+  bool is_young() const     { return _young_type != NotYoung; }
+  bool is_scan_only() const { return _young_type == ScanOnly; }
+  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 recalculate_age_in_surv_rate_group() {
+    assert( _surv_rate_group != NULL, "pre-condition" );
+    assert( _age_index > -1, "pre-condition" );
+    _age_index = _surv_rate_group->recalculate_age_index(_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_scan_only() { set_young_type(ScanOnly); }
+
+  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);
+
+  HeapWord*
+  oops_on_card_seq_iterate_careful(MemRegion mr,
+                                   FilterOutOfRegionClosure* cl);
+
+  // The region "mr" is entirely in "this", and starts and ends at block
+  // boundaries. The caller declares that all the contained blocks are
+  // coalesced into one.
+  void declare_filled_region_to_BOT(MemRegion mr) {
+    _offsets.single_block(mr.start(), mr.end());
+  }
+
+  // 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);
+
+  // Returns the zero-fill-state of the current region.
+  ZeroFillState zero_fill_state() { return (ZeroFillState)_zfs; }
+  bool zero_fill_is_allocated() { return _zfs == Allocated; }
+  Thread* zero_filler() { return _zero_filler; }
+
+  // Indicate that the contents of the region are unknown, and therefore
+  // might require zero-filling.
+  void set_zero_fill_needed() {
+    set_zero_fill_state_work(NotZeroFilled);
+  }
+  void set_zero_fill_in_progress(Thread* t) {
+    set_zero_fill_state_work(ZeroFilling);
+    _zero_filler = t;
+  }
+  void set_zero_fill_complete();
+  void set_zero_fill_allocated() {
+    set_zero_fill_state_work(Allocated);
+  }
+
+  void set_zero_fill_state_work(ZeroFillState zfs);
+
+  // This is called when a full collection shrinks the heap.
+  // We want to set the heap region to a value which says
+  // it is no longer part of the heap.  For now, we'll let "NotZF" fill
+  // that role.
+  void reset_zero_fill() {
+    set_zero_fill_state_work(NotZeroFilled);
+    _zero_filler = NULL;
+  }
+
+#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;
+
+  // Override
+  virtual void verify(bool allow_dirty) const;
+
+#ifdef DEBUG
+  HeapWord* allocate(size_t size);
+#endif
+};
+
+// 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; }
+};
+
+// A linked lists of heap regions.  It leaves the "next" field
+// unspecified; that's up to subtypes.
+class RegionList {
+protected:
+  virtual HeapRegion* get_next(HeapRegion* chr) = 0;
+  virtual void set_next(HeapRegion* chr,
+                        HeapRegion* new_next) = 0;
+
+  HeapRegion* _hd;
+  HeapRegion* _tl;
+  size_t _sz;
+
+  // Protected constructor because this type is only meaningful
+  // when the _get/_set next functions are defined.
+  RegionList() : _hd(NULL), _tl(NULL), _sz(0) {}
+public:
+  void reset() {
+    _hd = NULL;
+    _tl = NULL;
+    _sz = 0;
+  }
+  HeapRegion* hd() { return _hd; }
+  HeapRegion* tl() { return _tl; }
+  size_t sz() { return _sz; }
+  size_t length();
+
+  bool well_formed() {
+    return
+      ((hd() == NULL && tl() == NULL && sz() == 0)
+       || (hd() != NULL && tl() != NULL && sz() > 0))
+      && (sz() == length());
+  }
+  virtual void insert_before_head(HeapRegion* r);
+  void prepend_list(RegionList* new_list);
+  virtual HeapRegion* pop();
+  void dec_sz() { _sz--; }
+  // Requires that "r" is an element of the list, and is not the tail.
+  void delete_after(HeapRegion* r);
+};
+
+class EmptyNonHRegionList: public RegionList {
+protected:
+  // Protected constructor because this type is only meaningful
+  // when the _get/_set next functions are defined.
+  EmptyNonHRegionList() : RegionList() {}
+
+public:
+  void insert_before_head(HeapRegion* r) {
+    //    assert(r->is_empty(), "Better be empty");
+    assert(!r->isHumongous(), "Better not be humongous.");
+    RegionList::insert_before_head(r);
+  }
+  void prepend_list(EmptyNonHRegionList* new_list) {
+    //    assert(new_list->hd() == NULL || new_list->hd()->is_empty(),
+    //     "Better be empty");
+    assert(new_list->hd() == NULL || !new_list->hd()->isHumongous(),
+           "Better not be humongous.");
+    //    assert(new_list->tl() == NULL || new_list->tl()->is_empty(),
+    //     "Better be empty");
+    assert(new_list->tl() == NULL || !new_list->tl()->isHumongous(),
+           "Better not be humongous.");
+    RegionList::prepend_list(new_list);
+  }
+};
+
+class UncleanRegionList: public EmptyNonHRegionList {
+public:
+  HeapRegion* get_next(HeapRegion* hr) {
+    return hr->next_from_unclean_list();
+  }
+  void set_next(HeapRegion* hr, HeapRegion* new_next) {
+    hr->set_next_on_unclean_list(new_next);
+  }
+
+  UncleanRegionList() : EmptyNonHRegionList() {}
+
+  void insert_before_head(HeapRegion* r) {
+    assert(!r->is_on_free_list(),
+           "Better not already be on free list");
+    assert(!r->is_on_unclean_list(),
+           "Better not already be on unclean list");
+    r->set_zero_fill_needed();
+    r->set_on_unclean_list(true);
+    EmptyNonHRegionList::insert_before_head(r);
+  }
+  void prepend_list(UncleanRegionList* new_list) {
+    assert(new_list->tl() == NULL || !new_list->tl()->is_on_free_list(),
+           "Better not already be on free list");
+    assert(new_list->tl() == NULL || new_list->tl()->is_on_unclean_list(),
+           "Better already be marked as on unclean list");
+    assert(new_list->hd() == NULL || !new_list->hd()->is_on_free_list(),
+           "Better not already be on free list");
+    assert(new_list->hd() == NULL || new_list->hd()->is_on_unclean_list(),
+           "Better already be marked as on unclean list");
+    EmptyNonHRegionList::prepend_list(new_list);
+  }
+  HeapRegion* pop() {
+    HeapRegion* res = RegionList::pop();
+    if (res != NULL) res->set_on_unclean_list(false);
+    return res;
+  }
+};
+
+// Local Variables: ***
+// c-indentation-style: gnu ***
+// End: ***
+
+#endif // SERIALGC