--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Thu Jun 05 15:57:56 2008 -0700
@@ -0,0 +1,1191 @@
+/*
+ * 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.
+ *
+ */
+
+// A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
+// It uses the "Garbage First" heap organization and algorithm, which
+// may combine concurrent marking with parallel, incremental compaction of
+// heap subsets that will yield large amounts of garbage.
+
+class HeapRegion;
+class HeapRegionSeq;
+class HeapRegionList;
+class PermanentGenerationSpec;
+class GenerationSpec;
+class OopsInHeapRegionClosure;
+class G1ScanHeapEvacClosure;
+class ObjectClosure;
+class SpaceClosure;
+class CompactibleSpaceClosure;
+class Space;
+class G1CollectorPolicy;
+class GenRemSet;
+class G1RemSet;
+class HeapRegionRemSetIterator;
+class ConcurrentMark;
+class ConcurrentMarkThread;
+class ConcurrentG1Refine;
+class ConcurrentZFThread;
+
+// If want to accumulate detailed statistics on work queues
+// turn this on.
+#define G1_DETAILED_STATS 0
+
+#if G1_DETAILED_STATS
+#  define IF_G1_DETAILED_STATS(code) code
+#else
+#  define IF_G1_DETAILED_STATS(code)
+#endif
+
+typedef GenericTaskQueue<oop*>    RefToScanQueue;
+typedef GenericTaskQueueSet<oop*> RefToScanQueueSet;
+
+enum G1GCThreadGroups {
+  G1CRGroup = 0,
+  G1ZFGroup = 1,
+  G1CMGroup = 2,
+  G1CLGroup = 3
+};
+
+enum GCAllocPurpose {
+  GCAllocForTenured,
+  GCAllocForSurvived,
+  GCAllocPurposeCount
+};
+
+class YoungList : public CHeapObj {
+private:
+  G1CollectedHeap* _g1h;
+
+  HeapRegion* _head;
+
+  HeapRegion* _scan_only_head;
+  HeapRegion* _scan_only_tail;
+  size_t      _length;
+  size_t      _scan_only_length;
+
+  size_t      _last_sampled_rs_lengths;
+  size_t      _sampled_rs_lengths;
+  HeapRegion* _curr;
+  HeapRegion* _curr_scan_only;
+
+  HeapRegion* _survivor_head;
+  HeapRegion* _survivors_tail;
+  size_t      _survivor_length;
+
+  void          empty_list(HeapRegion* list);
+
+public:
+  YoungList(G1CollectedHeap* g1h);
+
+  void          push_region(HeapRegion* hr);
+  void          add_survivor_region(HeapRegion* hr);
+  HeapRegion*   pop_region();
+  void          empty_list();
+  bool          is_empty() { return _length == 0; }
+  size_t        length() { return _length; }
+  size_t        scan_only_length() { return _scan_only_length; }
+
+  void rs_length_sampling_init();
+  bool rs_length_sampling_more();
+  void rs_length_sampling_next();
+
+  void reset_sampled_info() {
+    _last_sampled_rs_lengths =   0;
+  }
+  size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
+
+  // for development purposes
+  void reset_auxilary_lists();
+  HeapRegion* first_region() { return _head; }
+  HeapRegion* first_scan_only_region() { return _scan_only_head; }
+  HeapRegion* first_survivor_region() { return _survivor_head; }
+  HeapRegion* par_get_next_scan_only_region() {
+    MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
+    HeapRegion* ret = _curr_scan_only;
+    if (ret != NULL)
+      _curr_scan_only = ret->get_next_young_region();
+    return ret;
+  }
+
+  // debugging
+  bool          check_list_well_formed();
+  bool          check_list_empty(bool ignore_scan_only_list,
+                                 bool check_sample = true);
+  void          print();
+};
+
+class RefineCardTableEntryClosure;
+class G1CollectedHeap : public SharedHeap {
+  friend class VM_G1CollectForAllocation;
+  friend class VM_GenCollectForPermanentAllocation;
+  friend class VM_G1CollectFull;
+  friend class VM_G1IncCollectionPause;
+  friend class VM_G1PopRegionCollectionPause;
+  friend class VMStructs;
+
+  // Closures used in implementation.
+  friend class G1ParCopyHelper;
+  friend class G1IsAliveClosure;
+  friend class G1EvacuateFollowersClosure;
+  friend class G1ParScanThreadState;
+  friend class G1ParScanClosureSuper;
+  friend class G1ParEvacuateFollowersClosure;
+  friend class G1ParTask;
+  friend class G1FreeGarbageRegionClosure;
+  friend class RefineCardTableEntryClosure;
+  friend class G1PrepareCompactClosure;
+  friend class RegionSorter;
+  friend class CountRCClosure;
+  friend class EvacPopObjClosure;
+
+  // Other related classes.
+  friend class G1MarkSweep;
+
+private:
+  enum SomePrivateConstants {
+    VeryLargeInBytes = HeapRegion::GrainBytes/2,
+    VeryLargeInWords = VeryLargeInBytes/HeapWordSize,
+    MinHeapDeltaBytes = 10 * HeapRegion::GrainBytes,      // FIXME
+    NumAPIs = HeapRegion::MaxAge
+  };
+
+
+  // The one and only G1CollectedHeap, so static functions can find it.
+  static G1CollectedHeap* _g1h;
+
+  // Storage for the G1 heap (excludes the permanent generation).
+  VirtualSpace _g1_storage;
+  MemRegion    _g1_reserved;
+
+  // The part of _g1_storage that is currently committed.
+  MemRegion _g1_committed;
+
+  // The maximum part of _g1_storage that has ever been committed.
+  MemRegion _g1_max_committed;
+
+  // The number of regions that are completely free.
+  size_t _free_regions;
+
+  // The number of regions we could create by expansion.
+  size_t _expansion_regions;
+
+  // Return the number of free regions in the heap (by direct counting.)
+  size_t count_free_regions();
+  // Return the number of free regions on the free and unclean lists.
+  size_t count_free_regions_list();
+
+  // The block offset table for the G1 heap.
+  G1BlockOffsetSharedArray* _bot_shared;
+
+  // Move all of the regions off the free lists, then rebuild those free
+  // lists, before and after full GC.
+  void tear_down_region_lists();
+  void rebuild_region_lists();
+  // This sets all non-empty regions to need zero-fill (which they will if
+  // they are empty after full collection.)
+  void set_used_regions_to_need_zero_fill();
+
+  // The sequence of all heap regions in the heap.
+  HeapRegionSeq* _hrs;
+
+  // The region from which normal-sized objects are currently being
+  // allocated.  May be NULL.
+  HeapRegion* _cur_alloc_region;
+
+  // Postcondition: cur_alloc_region == NULL.
+  void abandon_cur_alloc_region();
+
+  // The to-space memory regions into which objects are being copied during
+  // a GC.
+  HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
+  uint _gc_alloc_region_counts[GCAllocPurposeCount];
+
+  // A list of the regions that have been set to be alloc regions in the
+  // current collection.
+  HeapRegion* _gc_alloc_region_list;
+
+  // When called by par thread, require par_alloc_during_gc_lock() to be held.
+  void push_gc_alloc_region(HeapRegion* hr);
+
+  // This should only be called single-threaded.  Undeclares all GC alloc
+  // regions.
+  void forget_alloc_region_list();
+
+  // Should be used to set an alloc region, because there's other
+  // associated bookkeeping.
+  void set_gc_alloc_region(int purpose, HeapRegion* r);
+
+  // Check well-formedness of alloc region list.
+  bool check_gc_alloc_regions();
+
+  // Outside of GC pauses, the number of bytes used in all regions other
+  // than the current allocation region.
+  size_t _summary_bytes_used;
+
+  // Summary information about popular objects; method to print it.
+  NumberSeq _pop_obj_rc_at_copy;
+  void print_popularity_summary_info() const;
+
+  unsigned _gc_time_stamp;
+
+  size_t* _surviving_young_words;
+
+  void setup_surviving_young_words();
+  void update_surviving_young_words(size_t* surv_young_words);
+  void cleanup_surviving_young_words();
+
+protected:
+
+  // Returns "true" iff none of the gc alloc regions have any allocations
+  // since the last call to "save_marks".
+  bool all_alloc_regions_no_allocs_since_save_marks();
+  // Calls "note_end_of_copying on all gc alloc_regions.
+  void all_alloc_regions_note_end_of_copying();
+
+  // The number of regions allocated to hold humongous objects.
+  int         _num_humongous_regions;
+  YoungList*  _young_list;
+
+  // The current policy object for the collector.
+  G1CollectorPolicy* _g1_policy;
+
+  // Parallel allocation lock to protect the current allocation region.
+  Mutex  _par_alloc_during_gc_lock;
+  Mutex* par_alloc_during_gc_lock() { return &_par_alloc_during_gc_lock; }
+
+  // If possible/desirable, allocate a new HeapRegion for normal object
+  // allocation sufficient for an allocation of the given "word_size".
+  // If "do_expand" is true, will attempt to expand the heap if necessary
+  // to to satisfy the request.  If "zero_filled" is true, requires a
+  // zero-filled region.
+  // (Returning NULL will trigger a GC.)
+  virtual HeapRegion* newAllocRegion_work(size_t word_size,
+                                          bool do_expand,
+                                          bool zero_filled);
+
+  virtual HeapRegion* newAllocRegion(size_t word_size,
+                                     bool zero_filled = true) {
+    return newAllocRegion_work(word_size, false, zero_filled);
+  }
+  virtual HeapRegion* newAllocRegionWithExpansion(int purpose,
+                                                  size_t word_size,
+                                                  bool zero_filled = true);
+
+  // Attempt to allocate an object of the given (very large) "word_size".
+  // Returns "NULL" on failure.
+  virtual HeapWord* humongousObjAllocate(size_t word_size);
+
+  // If possible, allocate a block of the given word_size, else return "NULL".
+  // Returning NULL will trigger GC or heap expansion.
+  // These two methods have rather awkward pre- and
+  // post-conditions. If they are called outside a safepoint, then
+  // they assume that the caller is holding the heap lock. Upon return
+  // they release the heap lock, if they are returning a non-NULL
+  // value. attempt_allocation_slow() also dirties the cards of a
+  // newly-allocated young region after it releases the heap
+  // lock. This change in interface was the neatest way to achieve
+  // this card dirtying without affecting mem_allocate(), which is a
+  // more frequently called method. We tried two or three different
+  // approaches, but they were even more hacky.
+  HeapWord* attempt_allocation(size_t word_size,
+                               bool permit_collection_pause = true);
+
+  HeapWord* attempt_allocation_slow(size_t word_size,
+                                    bool permit_collection_pause = true);
+
+  // Allocate blocks during garbage collection. Will ensure an
+  // allocation region, either by picking one or expanding the
+  // heap, and then allocate a block of the given size. The block
+  // may not be a humongous - it must fit into a single heap region.
+  HeapWord* allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
+  HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
+
+  HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
+                                    HeapRegion*    alloc_region,
+                                    bool           par,
+                                    size_t         word_size);
+
+  // Ensure that no further allocations can happen in "r", bearing in mind
+  // that parallel threads might be attempting allocations.
+  void par_allocate_remaining_space(HeapRegion* r);
+
+  // Helper function for two callbacks below.
+  // "full", if true, indicates that the GC is for a System.gc() request,
+  // and should collect the entire heap.  If "clear_all_soft_refs" is true,
+  // all soft references are cleared during the GC.  If "full" is false,
+  // "word_size" describes the allocation that the GC should
+  // attempt (at least) to satisfy.
+  void do_collection(bool full, bool clear_all_soft_refs,
+                     size_t word_size);
+
+  // Callback from VM_G1CollectFull operation.
+  // Perform a full collection.
+  void do_full_collection(bool clear_all_soft_refs);
+
+  // Resize the heap if necessary after a full collection.  If this is
+  // after a collect-for allocation, "word_size" is the allocation size,
+  // and will be considered part of the used portion of the heap.
+  void resize_if_necessary_after_full_collection(size_t word_size);
+
+  // Callback from VM_G1CollectForAllocation operation.
+  // This function does everything necessary/possible to satisfy a
+  // failed allocation request (including collection, expansion, etc.)
+  HeapWord* satisfy_failed_allocation(size_t word_size);
+
+  // Attempting to expand the heap sufficiently
+  // to support an allocation of the given "word_size".  If
+  // successful, perform the allocation and return the address of the
+  // allocated block, or else "NULL".
+  virtual HeapWord* expand_and_allocate(size_t word_size);
+
+public:
+  // Expand the garbage-first heap by at least the given size (in bytes!).
+  // (Rounds up to a HeapRegion boundary.)
+  virtual void expand(size_t expand_bytes);
+
+  // Do anything common to GC's.
+  virtual void gc_prologue(bool full);
+  virtual void gc_epilogue(bool full);
+
+protected:
+
+  // Shrink the garbage-first heap by at most the given size (in bytes!).
+  // (Rounds down to a HeapRegion boundary.)
+  virtual void shrink(size_t expand_bytes);
+  void shrink_helper(size_t expand_bytes);
+
+  // Do an incremental collection: identify a collection set, and evacuate
+  // its live objects elsewhere.
+  virtual void do_collection_pause();
+
+  // The guts of the incremental collection pause, executed by the vm
+  // thread.  If "popular_region" is non-NULL, this pause should evacuate
+  // this single region whose remembered set has gotten large, moving
+  // any popular objects to one of the popular regions.
+  virtual void do_collection_pause_at_safepoint(HeapRegion* popular_region);
+
+  // Actually do the work of evacuating the collection set.
+  virtual void evacuate_collection_set();
+
+  // If this is an appropriate right time, do a collection pause.
+  // The "word_size" argument, if non-zero, indicates the size of an
+  // allocation request that is prompting this query.
+  void do_collection_pause_if_appropriate(size_t word_size);
+
+  // The g1 remembered set of the heap.
+  G1RemSet* _g1_rem_set;
+  // And it's mod ref barrier set, used to track updates for the above.
+  ModRefBarrierSet* _mr_bs;
+
+  // The Heap Region Rem Set Iterator.
+  HeapRegionRemSetIterator** _rem_set_iterator;
+
+  // The closure used to refine a single card.
+  RefineCardTableEntryClosure* _refine_cte_cl;
+
+  // A function to check the consistency of dirty card logs.
+  void check_ct_logs_at_safepoint();
+
+  // After a collection pause, make the regions in the CS into free
+  // regions.
+  void free_collection_set(HeapRegion* cs_head);
+
+  // Applies "scan_non_heap_roots" to roots outside the heap,
+  // "scan_rs" to roots inside the heap (having done "set_region" to
+  // indicate the region in which the root resides), and does "scan_perm"
+  // (setting the generation to the perm generation.)  If "scan_rs" is
+  // NULL, then this step is skipped.  The "worker_i"
+  // param is for use with parallel roots processing, and should be
+  // the "i" of the calling parallel worker thread's work(i) function.
+  // In the sequential case this param will be ignored.
+  void g1_process_strong_roots(bool collecting_perm_gen,
+                               SharedHeap::ScanningOption so,
+                               OopClosure* scan_non_heap_roots,
+                               OopsInHeapRegionClosure* scan_rs,
+                               OopsInHeapRegionClosure* scan_so,
+                               OopsInGenClosure* scan_perm,
+                               int worker_i);
+
+  void scan_scan_only_set(OopsInHeapRegionClosure* oc,
+                          int worker_i);
+  void scan_scan_only_region(HeapRegion* hr,
+                             OopsInHeapRegionClosure* oc,
+                             int worker_i);
+
+  // Apply "blk" to all the weak roots of the system.  These include
+  // JNI weak roots, the code cache, system dictionary, symbol table,
+  // string table, and referents of reachable weak refs.
+  void g1_process_weak_roots(OopClosure* root_closure,
+                             OopClosure* non_root_closure);
+
+  // Invoke "save_marks" on all heap regions.
+  void save_marks();
+
+  // Free a heap region.
+  void free_region(HeapRegion* hr);
+  // A component of "free_region", exposed for 'batching'.
+  // All the params after "hr" are out params: the used bytes of the freed
+  // region(s), the number of H regions cleared, the number of regions
+  // freed, and pointers to the head and tail of a list of freed contig
+  // regions, linked throught the "next_on_unclean_list" field.
+  void free_region_work(HeapRegion* hr,
+                        size_t& pre_used,
+                        size_t& cleared_h,
+                        size_t& freed_regions,
+                        UncleanRegionList* list,
+                        bool par = false);
+
+
+  // The concurrent marker (and the thread it runs in.)
+  ConcurrentMark* _cm;
+  ConcurrentMarkThread* _cmThread;
+  bool _mark_in_progress;
+
+  // The concurrent refiner.
+  ConcurrentG1Refine* _cg1r;
+
+  // The concurrent zero-fill thread.
+  ConcurrentZFThread* _czft;
+
+  // The parallel task queues
+  RefToScanQueueSet *_task_queues;
+
+  // True iff a evacuation has failed in the current collection.
+  bool _evacuation_failed;
+
+  // Set the attribute indicating whether evacuation has failed in the
+  // current collection.
+  void set_evacuation_failed(bool b) { _evacuation_failed = b; }
+
+  // Failed evacuations cause some logical from-space objects to have
+  // forwarding pointers to themselves.  Reset them.
+  void remove_self_forwarding_pointers();
+
+  // When one is non-null, so is the other.  Together, they each pair is
+  // an object with a preserved mark, and its mark value.
+  GrowableArray<oop>*     _objs_with_preserved_marks;
+  GrowableArray<markOop>* _preserved_marks_of_objs;
+
+  // Preserve the mark of "obj", if necessary, in preparation for its mark
+  // word being overwritten with a self-forwarding-pointer.
+  void preserve_mark_if_necessary(oop obj, markOop m);
+
+  // The stack of evac-failure objects left to be scanned.
+  GrowableArray<oop>*    _evac_failure_scan_stack;
+  // The closure to apply to evac-failure objects.
+
+  OopsInHeapRegionClosure* _evac_failure_closure;
+  // Set the field above.
+  void
+  set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
+    _evac_failure_closure = evac_failure_closure;
+  }
+
+  // Push "obj" on the scan stack.
+  void push_on_evac_failure_scan_stack(oop obj);
+  // Process scan stack entries until the stack is empty.
+  void drain_evac_failure_scan_stack();
+  // True iff an invocation of "drain_scan_stack" is in progress; to
+  // prevent unnecessary recursion.
+  bool _drain_in_progress;
+
+  // Do any necessary initialization for evacuation-failure handling.
+  // "cl" is the closure that will be used to process evac-failure
+  // objects.
+  void init_for_evac_failure(OopsInHeapRegionClosure* cl);
+  // Do any necessary cleanup for evacuation-failure handling data
+  // structures.
+  void finalize_for_evac_failure();
+
+  // An attempt to evacuate "obj" has failed; take necessary steps.
+  void handle_evacuation_failure(oop obj);
+  oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
+  void handle_evacuation_failure_common(oop obj, markOop m);
+
+
+  // Ensure that the relevant gc_alloc regions are set.
+  void get_gc_alloc_regions();
+  // We're done with GC alloc regions; release them, as appropriate.
+  void release_gc_alloc_regions();
+
+  // ("Weak") Reference processing support
+  ReferenceProcessor* _ref_processor;
+
+  enum G1H_process_strong_roots_tasks {
+    G1H_PS_mark_stack_oops_do,
+    G1H_PS_refProcessor_oops_do,
+    // Leave this one last.
+    G1H_PS_NumElements
+  };
+
+  SubTasksDone* _process_strong_tasks;
+
+  // Allocate space to hold a popular object.  Result is guaranteed below
+  // "popular_object_boundary()".  Note: CURRENTLY halts the system if we
+  // run out of space to hold popular objects.
+  HeapWord* allocate_popular_object(size_t word_size);
+
+  // The boundary between popular and non-popular objects.
+  HeapWord* _popular_object_boundary;
+
+  HeapRegionList* _popular_regions_to_be_evacuated;
+
+  // Compute which objects in "single_region" are popular.  If any are,
+  // evacuate them to a popular region, leaving behind forwarding pointers,
+  // and select "popular_region" as the single collection set region.
+  // Otherwise, leave the collection set null.
+  void popularity_pause_preamble(HeapRegion* populer_region);
+
+  // Compute which objects in "single_region" are popular, and evacuate
+  // them to a popular region, leaving behind forwarding pointers.
+  // Returns "true" if at least one popular object is discovered and
+  // evacuated.  In any case, "*max_rc" is set to the maximum reference
+  // count of an object in the region.
+  bool compute_reference_counts_and_evac_popular(HeapRegion* populer_region,
+                                                 size_t* max_rc);
+  // Subroutines used in the above.
+  bool _rc_region_above;
+  size_t _rc_region_diff;
+  jint* obj_rc_addr(oop obj) {
+    uintptr_t obj_addr = (uintptr_t)obj;
+    if (_rc_region_above) {
+      jint* res = (jint*)(obj_addr + _rc_region_diff);
+      assert((uintptr_t)res > obj_addr, "RC region is above.");
+      return res;
+    } else {
+      jint* res = (jint*)(obj_addr - _rc_region_diff);
+      assert((uintptr_t)res < obj_addr, "RC region is below.");
+      return res;
+    }
+  }
+  jint obj_rc(oop obj) {
+    return *obj_rc_addr(obj);
+  }
+  void inc_obj_rc(oop obj) {
+    (*obj_rc_addr(obj))++;
+  }
+  void atomic_inc_obj_rc(oop obj);
+
+
+  // Number of popular objects and bytes (latter is cheaper!).
+  size_t pop_object_used_objs();
+  size_t pop_object_used_bytes();
+
+  // Index of the popular region in which allocation is currently being
+  // done.
+  int _cur_pop_hr_index;
+
+  // List of regions which require zero filling.
+  UncleanRegionList _unclean_region_list;
+  bool _unclean_regions_coming;
+
+  bool check_age_cohort_well_formed_work(int a, HeapRegion* hr);
+
+public:
+  void set_refine_cte_cl_concurrency(bool concurrent);
+
+  RefToScanQueue *task_queue(int i);
+
+  // Create a G1CollectedHeap with the specified policy.
+  // Must call the initialize method afterwards.
+  // May not return if something goes wrong.
+  G1CollectedHeap(G1CollectorPolicy* policy);
+
+  // Initialize the G1CollectedHeap to have the initial and
+  // maximum sizes, permanent generation, and remembered and barrier sets
+  // specified by the policy object.
+  jint initialize();
+
+  void ref_processing_init();
+
+  void set_par_threads(int t) {
+    SharedHeap::set_par_threads(t);
+    _process_strong_tasks->set_par_threads(t);
+  }
+
+  virtual CollectedHeap::Name kind() const {
+    return CollectedHeap::G1CollectedHeap;
+  }
+
+  // The current policy object for the collector.
+  G1CollectorPolicy* g1_policy() const { return _g1_policy; }
+
+  // Adaptive size policy.  No such thing for g1.
+  virtual AdaptiveSizePolicy* size_policy() { return NULL; }
+
+  // The rem set and barrier set.
+  G1RemSet* g1_rem_set() const { return _g1_rem_set; }
+  ModRefBarrierSet* mr_bs() const { return _mr_bs; }
+
+  // The rem set iterator.
+  HeapRegionRemSetIterator* rem_set_iterator(int i) {
+    return _rem_set_iterator[i];
+  }
+
+  HeapRegionRemSetIterator* rem_set_iterator() {
+    return _rem_set_iterator[0];
+  }
+
+  unsigned get_gc_time_stamp() {
+    return _gc_time_stamp;
+  }
+
+  void reset_gc_time_stamp() {
+    _gc_time_stamp = 0;
+  }
+
+  void iterate_dirty_card_closure(bool concurrent, int worker_i);
+
+  // The shared block offset table array.
+  G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
+
+  // Reference Processing accessor
+  ReferenceProcessor* ref_processor() { return _ref_processor; }
+
+  // Reserved (g1 only; super method includes perm), capacity and the used
+  // portion in bytes.
+  size_t g1_reserved_obj_bytes() { return _g1_reserved.byte_size(); }
+  virtual size_t capacity() const;
+  virtual size_t used() const;
+  size_t recalculate_used() const;
+#ifndef PRODUCT
+  size_t recalculate_used_regions() const;
+#endif // PRODUCT
+
+  // These virtual functions do the actual allocation.
+  virtual HeapWord* mem_allocate(size_t word_size,
+                                 bool   is_noref,
+                                 bool   is_tlab,
+                                 bool* gc_overhead_limit_was_exceeded);
+
+  // Some heaps may offer a contiguous region for shared non-blocking
+  // allocation, via inlined code (by exporting the address of the top and
+  // end fields defining the extent of the contiguous allocation region.)
+  // But G1CollectedHeap doesn't yet support this.
+
+  // Return an estimate of the maximum allocation that could be performed
+  // without triggering any collection or expansion activity.  In a
+  // generational collector, for example, this is probably the largest
+  // allocation that could be supported (without expansion) in the youngest
+  // generation.  It is "unsafe" because no locks are taken; the result
+  // should be treated as an approximation, not a guarantee, for use in
+  // heuristic resizing decisions.
+  virtual size_t unsafe_max_alloc();
+
+  virtual bool is_maximal_no_gc() const {
+    return _g1_storage.uncommitted_size() == 0;
+  }
+
+  // The total number of regions in the heap.
+  size_t n_regions();
+
+  // The number of regions that are completely free.
+  size_t max_regions();
+
+  // The number of regions that are completely free.
+  size_t free_regions();
+
+  // The number of regions that are not completely free.
+  size_t used_regions() { return n_regions() - free_regions(); }
+
+  // True iff the ZF thread should run.
+  bool should_zf();
+
+  // The number of regions available for "regular" expansion.
+  size_t expansion_regions() { return _expansion_regions; }
+
+#ifndef PRODUCT
+  bool regions_accounted_for();
+  bool print_region_accounting_info();
+  void print_region_counts();
+#endif
+
+  HeapRegion* alloc_region_from_unclean_list(bool zero_filled);
+  HeapRegion* alloc_region_from_unclean_list_locked(bool zero_filled);
+
+  void put_region_on_unclean_list(HeapRegion* r);
+  void put_region_on_unclean_list_locked(HeapRegion* r);
+
+  void prepend_region_list_on_unclean_list(UncleanRegionList* list);
+  void prepend_region_list_on_unclean_list_locked(UncleanRegionList* list);
+
+  void set_unclean_regions_coming(bool b);
+  void set_unclean_regions_coming_locked(bool b);
+  // Wait for cleanup to be complete.
+  void wait_for_cleanup_complete();
+  // Like above, but assumes that the calling thread owns the Heap_lock.
+  void wait_for_cleanup_complete_locked();
+
+  // Return the head of the unclean list.
+  HeapRegion* peek_unclean_region_list_locked();
+  // Remove and return the head of the unclean list.
+  HeapRegion* pop_unclean_region_list_locked();
+
+  // List of regions which are zero filled and ready for allocation.
+  HeapRegion* _free_region_list;
+  // Number of elements on the free list.
+  size_t _free_region_list_size;
+
+  // If the head of the unclean list is ZeroFilled, move it to the free
+  // list.
+  bool move_cleaned_region_to_free_list_locked();
+  bool move_cleaned_region_to_free_list();
+
+  void put_free_region_on_list_locked(HeapRegion* r);
+  void put_free_region_on_list(HeapRegion* r);
+
+  // Remove and return the head element of the free list.
+  HeapRegion* pop_free_region_list_locked();
+
+  // If "zero_filled" is true, we first try the free list, then we try the
+  // unclean list, zero-filling the result.  If "zero_filled" is false, we
+  // first try the unclean list, then the zero-filled list.
+  HeapRegion* alloc_free_region_from_lists(bool zero_filled);
+
+  // Verify the integrity of the region lists.
+  void remove_allocated_regions_from_lists();
+  bool verify_region_lists();
+  bool verify_region_lists_locked();
+  size_t unclean_region_list_length();
+  size_t free_region_list_length();
+
+  // Perform a collection of the heap; intended for use in implementing
+  // "System.gc".  This probably implies as full a collection as the
+  // "CollectedHeap" supports.
+  virtual void collect(GCCause::Cause cause);
+
+  // The same as above but assume that the caller holds the Heap_lock.
+  void collect_locked(GCCause::Cause cause);
+
+  // This interface assumes that it's being called by the
+  // vm thread. It collects the heap assuming that the
+  // heap lock is already held and that we are executing in
+  // the context of the vm thread.
+  virtual void collect_as_vm_thread(GCCause::Cause cause);
+
+  // True iff a evacuation has failed in the most-recent collection.
+  bool evacuation_failed() { return _evacuation_failed; }
+
+  // Free a region if it is totally full of garbage.  Returns the number of
+  // bytes freed (0 ==> didn't free it).
+  size_t free_region_if_totally_empty(HeapRegion *hr);
+  void free_region_if_totally_empty_work(HeapRegion *hr,
+                                         size_t& pre_used,
+                                         size_t& cleared_h_regions,
+                                         size_t& freed_regions,
+                                         UncleanRegionList* list,
+                                         bool par = false);
+
+  // If we've done free region work that yields the given changes, update
+  // the relevant global variables.
+  void finish_free_region_work(size_t pre_used,
+                               size_t cleared_h_regions,
+                               size_t freed_regions,
+                               UncleanRegionList* list);
+
+
+  // Returns "TRUE" iff "p" points into the allocated area of the heap.
+  virtual bool is_in(const void* p) const;
+
+  // Return "TRUE" iff the given object address is within the collection
+  // set.
+  inline bool obj_in_cs(oop obj);
+
+  // Return "TRUE" iff the given object address is in the reserved
+  // region of g1 (excluding the permanent generation).
+  bool is_in_g1_reserved(const void* p) const {
+    return _g1_reserved.contains(p);
+  }
+
+  // Returns a MemRegion that corresponds to the space that  has been
+  // committed in the heap
+  MemRegion g1_committed() {
+    return _g1_committed;
+  }
+
+  NOT_PRODUCT( bool is_in_closed_subset(const void* p) const; )
+
+  // Dirty card table entries covering a list of young regions.
+  void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
+
+  // This resets the card table to all zeros.  It is used after
+  // a collection pause which used the card table to claim cards.
+  void cleanUpCardTable();
+
+  // Iteration functions.
+
+  // Iterate over all the ref-containing fields of all objects, calling
+  // "cl.do_oop" on each.
+  virtual void oop_iterate(OopClosure* cl);
+
+  // Same as above, restricted to a memory region.
+  virtual void oop_iterate(MemRegion mr, OopClosure* cl);
+
+  // Iterate over all objects, calling "cl.do_object" on each.
+  virtual void object_iterate(ObjectClosure* cl);
+
+  // Iterate over all objects allocated since the last collection, calling
+  // "cl.do_object" on each.  The heap must have been initialized properly
+  // to support this function, or else this call will fail.
+  virtual void object_iterate_since_last_GC(ObjectClosure* cl);
+
+  // Iterate over all spaces in use in the heap, in ascending address order.
+  virtual void space_iterate(SpaceClosure* cl);
+
+  // Iterate over heap regions, in address order, terminating the
+  // iteration early if the "doHeapRegion" method returns "true".
+  void heap_region_iterate(HeapRegionClosure* blk);
+
+  // Iterate over heap regions starting with r (or the first region if "r"
+  // is NULL), in address order, terminating early if the "doHeapRegion"
+  // method returns "true".
+  void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
+
+  // As above but starting from the region at index idx.
+  void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
+
+  HeapRegion* region_at(size_t idx);
+
+
+  // Divide the heap region sequence into "chunks" of some size (the number
+  // of regions divided by the number of parallel threads times some
+  // overpartition factor, currently 4).  Assumes that this will be called
+  // in parallel by ParallelGCThreads worker threads with discinct worker
+  // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
+  // calls will use the same "claim_value", and that that claim value is
+  // different from the claim_value of any heap region before the start of
+  // the iteration.  Applies "blk->doHeapRegion" to each of the regions, by
+  // attempting to claim the first region in each chunk, and, if
+  // successful, applying the closure to each region in the chunk (and
+  // setting the claim value of the second and subsequent regions of the
+  // chunk.)  For now requires that "doHeapRegion" always returns "false",
+  // i.e., that a closure never attempt to abort a traversal.
+  void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
+                                       int worker,
+                                       jint claim_value);
+
+  // Iterate over the regions (if any) in the current collection set.
+  void collection_set_iterate(HeapRegionClosure* blk);
+
+  // As above but starting from region r
+  void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
+
+  // Returns the first (lowest address) compactible space in the heap.
+  virtual CompactibleSpace* first_compactible_space();
+
+  // A CollectedHeap will contain some number of spaces.  This finds the
+  // space containing a given address, or else returns NULL.
+  virtual Space* space_containing(const void* addr) const;
+
+  // A G1CollectedHeap will contain some number of heap regions.  This
+  // finds the region containing a given address, or else returns NULL.
+  HeapRegion* heap_region_containing(const void* addr) const;
+
+  // Like the above, but requires "addr" to be in the heap (to avoid a
+  // null-check), and unlike the above, may return an continuing humongous
+  // region.
+  HeapRegion* heap_region_containing_raw(const void* addr) const;
+
+  // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
+  // each address in the (reserved) heap is a member of exactly
+  // one block.  The defining characteristic of a block is that it is
+  // possible to find its size, and thus to progress forward to the next
+  // block.  (Blocks may be of different sizes.)  Thus, blocks may
+  // represent Java objects, or they might be free blocks in a
+  // free-list-based heap (or subheap), as long as the two kinds are
+  // distinguishable and the size of each is determinable.
+
+  // Returns the address of the start of the "block" that contains the
+  // address "addr".  We say "blocks" instead of "object" since some heaps
+  // may not pack objects densely; a chunk may either be an object or a
+  // non-object.
+  virtual HeapWord* block_start(const void* addr) const;
+
+  // Requires "addr" to be the start of a chunk, and returns its size.
+  // "addr + size" is required to be the start of a new chunk, or the end
+  // of the active area of the heap.
+  virtual size_t block_size(const HeapWord* addr) const;
+
+  // Requires "addr" to be the start of a block, and returns "TRUE" iff
+  // the block is an object.
+  virtual bool block_is_obj(const HeapWord* addr) const;
+
+  // Does this heap support heap inspection? (+PrintClassHistogram)
+  virtual bool supports_heap_inspection() const { return true; }
+
+  // Section on thread-local allocation buffers (TLABs)
+  // See CollectedHeap for semantics.
+
+  virtual bool supports_tlab_allocation() const;
+  virtual size_t tlab_capacity(Thread* thr) const;
+  virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
+  virtual HeapWord* allocate_new_tlab(size_t size);
+
+  // Can a compiler initialize a new object without store barriers?
+  // This permission only extends from the creation of a new object
+  // via a TLAB up to the first subsequent safepoint.
+  virtual bool can_elide_tlab_store_barriers() const {
+    // Since G1's TLAB's may, on occasion, come from non-young regions
+    // as well. (Is there a flag controlling that? XXX)
+    return false;
+  }
+
+  // Can a compiler elide a store barrier when it writes
+  // a permanent oop into the heap?  Applies when the compiler
+  // is storing x to the heap, where x->is_perm() is true.
+  virtual bool can_elide_permanent_oop_store_barriers() const {
+    // At least until perm gen collection is also G1-ified, at
+    // which point this should return false.
+    return true;
+  }
+
+  virtual bool allocs_are_zero_filled();
+
+  // The boundary between a "large" and "small" array of primitives, in
+  // words.
+  virtual size_t large_typearray_limit();
+
+  // All popular objects are guaranteed to have addresses below this
+  // boundary.
+  HeapWord* popular_object_boundary() {
+    return _popular_object_boundary;
+  }
+
+  // Declare the region as one that should be evacuated because its
+  // remembered set is too large.
+  void schedule_popular_region_evac(HeapRegion* r);
+  // If there is a popular region to evacuate it, remove it from the list
+  // and return it.
+  HeapRegion* popular_region_to_evac();
+  // Evacuate the given popular region.
+  void evac_popular_region(HeapRegion* r);
+
+  // Returns "true" iff the given word_size is "very large".
+  static bool isHumongous(size_t word_size) {
+    return word_size >= VeryLargeInWords;
+  }
+
+  // Update mod union table with the set of dirty cards.
+  void updateModUnion();
+
+  // Set the mod union bits corresponding to the given memRegion.  Note
+  // that this is always a safe operation, since it doesn't clear any
+  // bits.
+  void markModUnionRange(MemRegion mr);
+
+  // Records the fact that a marking phase is no longer in progress.
+  void set_marking_complete() {
+    _mark_in_progress = false;
+  }
+  void set_marking_started() {
+    _mark_in_progress = true;
+  }
+  bool mark_in_progress() {
+    return _mark_in_progress;
+  }
+
+  // Print the maximum heap capacity.
+  virtual size_t max_capacity() const;
+
+  virtual jlong millis_since_last_gc();
+
+  // Perform any cleanup actions necessary before allowing a verification.
+  virtual void prepare_for_verify();
+
+  // Perform verification.
+  virtual void verify(bool allow_dirty, bool silent);
+  virtual void print() const;
+  virtual void print_on(outputStream* st) const;
+
+  virtual void print_gc_threads_on(outputStream* st) const;
+  virtual void gc_threads_do(ThreadClosure* tc) const;
+
+  // Override
+  void print_tracing_info() const;
+
+  // If "addr" is a pointer into the (reserved?) heap, returns a positive
+  // number indicating the "arena" within the heap in which "addr" falls.
+  // Or else returns 0.
+  virtual int addr_to_arena_id(void* addr) const;
+
+  // Convenience function to be used in situations where the heap type can be
+  // asserted to be this type.
+  static G1CollectedHeap* heap();
+
+  void empty_young_list();
+  bool should_set_young_locked();
+
+  void set_region_short_lived_locked(HeapRegion* hr);
+  // add appropriate methods for any other surv rate groups
+
+  void young_list_rs_length_sampling_init() {
+    _young_list->rs_length_sampling_init();
+  }
+  bool young_list_rs_length_sampling_more() {
+    return _young_list->rs_length_sampling_more();
+  }
+  void young_list_rs_length_sampling_next() {
+    _young_list->rs_length_sampling_next();
+  }
+  size_t young_list_sampled_rs_lengths() {
+    return _young_list->sampled_rs_lengths();
+  }
+
+  size_t young_list_length()   { return _young_list->length(); }
+  size_t young_list_scan_only_length() {
+                                      return _young_list->scan_only_length(); }
+
+  HeapRegion* pop_region_from_young_list() {
+    return _young_list->pop_region();
+  }
+
+  HeapRegion* young_list_first_region() {
+    return _young_list->first_region();
+  }
+
+  // debugging
+  bool check_young_list_well_formed() {
+    return _young_list->check_list_well_formed();
+  }
+  bool check_young_list_empty(bool ignore_scan_only_list,
+                              bool check_sample = true);
+
+  // *** Stuff related to concurrent marking.  It's not clear to me that so
+  // many of these need to be public.
+
+  // The functions below are helper functions that a subclass of
+  // "CollectedHeap" can use in the implementation of its virtual
+  // functions.
+  // This performs a concurrent marking of the live objects in a
+  // bitmap off to the side.
+  void doConcurrentMark();
+
+  // This is called from the marksweep collector which then does
+  // a concurrent mark and verifies that the results agree with
+  // the stop the world marking.
+  void checkConcurrentMark();
+  void do_sync_mark();
+
+  bool isMarkedPrev(oop obj) const;
+  bool isMarkedNext(oop obj) const;
+
+  // Determine if an object is dead, given the object and also
+  // the region to which the object belongs. An object is dead
+  // iff a) it was not allocated since the last mark and b) it
+  // is not marked.
+
+  bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
+    return
+      !hr->obj_allocated_since_prev_marking(obj) &&
+      !isMarkedPrev(obj);
+  }
+
+  // This is used when copying an object to survivor space.
+  // If the object is marked live, then we mark the copy live.
+  // If the object is allocated since the start of this mark
+  // cycle, then we mark the copy live.
+  // If the object has been around since the previous mark
+  // phase, and hasn't been marked yet during this phase,
+  // then we don't mark it, we just wait for the
+  // current marking cycle to get to it.
+
+  // This function returns true when an object has been
+  // around since the previous marking and hasn't yet
+  // been marked during this marking.
+
+  bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
+    return
+      !hr->obj_allocated_since_next_marking(obj) &&
+      !isMarkedNext(obj);
+  }
+
+  // Determine if an object is dead, given only the object itself.
+  // This will find the region to which the object belongs and
+  // then call the region version of the same function.
+
+  // Added if it is in permanent gen it isn't dead.
+  // Added if it is NULL it isn't dead.
+
+  bool is_obj_dead(oop obj) {
+    HeapRegion* hr = heap_region_containing(obj);
+    if (hr == NULL) {
+      if (Universe::heap()->is_in_permanent(obj))
+        return false;
+      else if (obj == NULL) return false;
+      else return true;
+    }
+    else return is_obj_dead(obj, hr);
+  }
+
+  bool is_obj_ill(oop obj) {
+    HeapRegion* hr = heap_region_containing(obj);
+    if (hr == NULL) {
+      if (Universe::heap()->is_in_permanent(obj))
+        return false;
+      else if (obj == NULL) return false;
+      else return true;
+    }
+    else return is_obj_ill(obj, hr);
+  }
+
+  // The following is just to alert the verification code
+  // that a full collection has occurred and that the
+  // remembered sets are no longer up to date.
+  bool _full_collection;
+  void set_full_collection() { _full_collection = true;}
+  void clear_full_collection() {_full_collection = false;}
+  bool full_collection() {return _full_collection;}
+
+  ConcurrentMark* concurrent_mark() const { return _cm; }
+  ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
+
+public:
+  void stop_conc_gc_threads();
+
+  // <NEW PREDICTION>
+
+  double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
+  void check_if_region_is_too_expensive(double predicted_time_ms);
+  size_t pending_card_num();
+  size_t max_pending_card_num();
+  size_t cards_scanned();
+
+  // </NEW PREDICTION>
+
+protected:
+  size_t _max_heap_capacity;
+
+//  debug_only(static void check_for_valid_allocation_state();)
+
+public:
+  // Temporary: call to mark things unimplemented for the G1 heap (e.g.,
+  // MemoryService).  In productization, we can make this assert false
+  // to catch such places (as well as searching for calls to this...)
+  static void g1_unimplemented();
+
+};
+
+// Local Variables: ***
+// c-indentation-style: gnu ***
+// End: ***