--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp	Thu Jun 05 15:57:56 2008 -0700
@@ -0,0 +1,470 @@
+/*
+ * 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.
+ *
+ */
+
+// Remembered set for a heap region.  Represent a set of "cards" that
+// contain pointers into the owner heap region.  Cards are defined somewhat
+// abstractly, in terms of what the "BlockOffsetTable" in use can parse.
+
+class G1CollectedHeap;
+class G1BlockOffsetSharedArray;
+class HeapRegion;
+class HeapRegionRemSetIterator;
+class PosParPRT;
+class SparsePRT;
+
+
+// The "_coarse_map" is a bitmap with one bit for each region, where set
+// bits indicate that the corresponding region may contain some pointer
+// into the owning region.
+
+// The "_fine_grain_entries" array is an open hash table of PerRegionTables
+// (PRTs), indicating regions for which we're keeping the RS as a set of
+// cards.  The strategy is to cap the size of the fine-grain table,
+// deleting an entry and setting the corresponding coarse-grained bit when
+// we would overflow this cap.
+
+// We use a mixture of locking and lock-free techniques here.  We allow
+// threads to locate PRTs without locking, but threads attempting to alter
+// a bucket list obtain a lock.  This means that any failing attempt to
+// find a PRT must be retried with the lock.  It might seem dangerous that
+// a read can find a PRT that is concurrently deleted.  This is all right,
+// because:
+//
+//   1) We only actually free PRT's at safe points (though we reuse them at
+//      other times).
+//   2) We find PRT's in an attempt to add entries.  If a PRT is deleted,
+//      it's _coarse_map bit is set, so the that we were attempting to add
+//      is represented.  If a deleted PRT is re-used, a thread adding a bit,
+//      thinking the PRT is for a different region, does no harm.
+
+class OtherRegionsTable: public CHeapObj {
+  friend class HeapRegionRemSetIterator;
+
+  G1CollectedHeap* _g1h;
+  Mutex            _m;
+  HeapRegion*      _hr;
+
+  // These are protected by "_m".
+  BitMap      _coarse_map;
+  size_t      _n_coarse_entries;
+  static jint _n_coarsenings;
+
+  PosParPRT** _fine_grain_regions;
+  size_t      _n_fine_entries;
+
+#define SAMPLE_FOR_EVICTION 1
+#if SAMPLE_FOR_EVICTION
+  size_t        _fine_eviction_start;
+  static size_t _fine_eviction_stride;
+  static size_t _fine_eviction_sample_size;
+#endif
+
+  SparsePRT   _sparse_table;
+
+  // These are static after init.
+  static size_t _max_fine_entries;
+  static size_t _mod_max_fine_entries_mask;
+
+  // Requires "prt" to be the first element of the bucket list appropriate
+  // for "hr".  If this list contains an entry for "hr", return it,
+  // otherwise return "NULL".
+  PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
+
+  // Find, delete, and return a candidate PosParPRT, if any exists,
+  // adding the deleted region to the coarse bitmap.  Requires the caller
+  // to hold _m, and the fine-grain table to be full.
+  PosParPRT* delete_region_table();
+
+  // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
+  // be the correct index for "hr"), delete it and return true; else return
+  // false.
+  bool del_single_region_table(size_t ind, HeapRegion* hr);
+
+  static jint _cache_probes;
+  static jint _cache_hits;
+
+  // Indexed by thread X heap region, to minimize thread contention.
+  static int** _from_card_cache;
+  static size_t _from_card_cache_max_regions;
+  static size_t _from_card_cache_mem_size;
+
+public:
+  OtherRegionsTable(HeapRegion* hr);
+
+  HeapRegion* hr() const { return _hr; }
+
+  // For now.  Could "expand" some tables in the future, so that this made
+  // sense.
+  void add_reference(oop* from, int tid);
+
+  void add_reference(oop* from) {
+    return add_reference(from, 0);
+  }
+
+  // Removes any entries shown by the given bitmaps to contain only dead
+  // objects.
+  void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
+
+  // Not const because it takes a lock.
+  size_t occupied() const;
+  size_t occ_fine() const;
+  size_t occ_coarse() const;
+  size_t occ_sparse() const;
+
+  static jint n_coarsenings() { return _n_coarsenings; }
+
+  // Returns size in bytes.
+  // Not const because it takes a lock.
+  size_t mem_size() const;
+  static size_t static_mem_size();
+  static size_t fl_mem_size();
+
+  bool contains_reference(oop* from) const;
+  bool contains_reference_locked(oop* from) const;
+
+  void clear();
+
+  // Specifically clear the from_card_cache.
+  void clear_fcc();
+
+  // "from_hr" is being cleared; remove any entries from it.
+  void clear_incoming_entry(HeapRegion* from_hr);
+
+  // Declare the heap size (in # of regions) to the OtherRegionsTable.
+  // (Uses it to initialize from_card_cache).
+  static void init_from_card_cache(size_t max_regions);
+
+  // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
+  // Make sure any entries for higher regions are invalid.
+  static void shrink_from_card_cache(size_t new_n_regs);
+
+  static void print_from_card_cache();
+
+};
+
+
+class HeapRegionRemSet : public CHeapObj {
+  friend class VMStructs;
+  friend class HeapRegionRemSetIterator;
+
+public:
+  enum Event {
+    Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
+  };
+
+private:
+  G1BlockOffsetSharedArray* _bosa;
+  G1BlockOffsetSharedArray* bosa() const { return _bosa; }
+
+  static bool _par_traversal;
+
+  OtherRegionsTable _other_regions;
+
+  // One set bit for every region that has an entry for this one.
+  BitMap _outgoing_region_map;
+
+  // Clear entries for the current region in any rem sets named in
+  // the _outgoing_region_map.
+  void clear_outgoing_entries();
+
+#if MAYBE
+  // Audit the given card index.
+  void audit_card(size_t card_num, HeapRegion* hr, u2* rc_arr,
+                  HeapRegionRemSet* empty_cards, size_t* one_obj_cards);
+
+  // Assumes that "audit_stage1" has been called for "hr", to set up
+  // "shadow" and "new_rs" appropriately.  Identifies individual popular
+  // objects; returns "true" if any are found.
+  bool audit_find_pop(HeapRegion* hr, u2* rc_arr);
+
+  // Assumes that "audit_stage1" has been called for "hr", to set up
+  // "shadow" and "new_rs" appropriately.  Identifies individual popular
+  // objects, and determines the number of entries in "new_rs" if any such
+  // popular objects are ignored.  If this is sufficiently small, returns
+  // "false" to indicate that a constraint should not be introduced.
+  // Otherwise, returns "true" to indicate that we should go ahead with
+  // adding the constraint.
+  bool audit_stag(HeapRegion* hr, u2* rc_arr);
+
+
+  u2* alloc_rc_array();
+
+  SeqHeapRegionRemSet* audit_post(u2* rc_arr, size_t multi_obj_crds,
+                                  SeqHeapRegionRemSet* empty_cards);
+#endif
+
+  enum ParIterState { Unclaimed, Claimed, Complete };
+  ParIterState _iter_state;
+
+  // Unused unless G1RecordHRRSOops is true.
+
+  static const int MaxRecorded = 1000000;
+  static oop**        _recorded_oops;
+  static HeapWord**   _recorded_cards;
+  static HeapRegion** _recorded_regions;
+  static int          _n_recorded;
+
+  static const int MaxRecordedEvents = 1000;
+  static Event*       _recorded_events;
+  static int*         _recorded_event_index;
+  static int          _n_recorded_events;
+
+  static void print_event(outputStream* str, Event evnt);
+
+public:
+  HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
+                   HeapRegion* hr);
+
+  static int num_par_rem_sets();
+  static bool par_traversal() { return _par_traversal; }
+  static void set_par_traversal(bool b);
+
+  HeapRegion* hr() const {
+    return _other_regions.hr();
+  }
+
+  size_t occupied() const {
+    return _other_regions.occupied();
+  }
+  size_t occ_fine() const {
+    return _other_regions.occ_fine();
+  }
+  size_t occ_coarse() const {
+    return _other_regions.occ_coarse();
+  }
+  size_t occ_sparse() const {
+    return _other_regions.occ_sparse();
+  }
+
+  static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
+
+  /* Used in the sequential case.  Returns "true" iff this addition causes
+     the size limit to be reached. */
+  bool add_reference(oop* from) {
+    _other_regions.add_reference(from);
+    return false;
+  }
+
+  /* Used in the parallel case.  Returns "true" iff this addition causes
+     the size limit to be reached. */
+  bool add_reference(oop* from, int tid) {
+    _other_regions.add_reference(from, tid);
+    return false;
+  }
+
+  // Records the fact that the current region contains an outgoing
+  // reference into "to_hr".
+  void add_outgoing_reference(HeapRegion* to_hr);
+
+  // Removes any entries shown by the given bitmaps to contain only dead
+  // objects.
+  void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
+
+  // The region is being reclaimed; clear its remset, and any mention of
+  // entries for this region in other remsets.
+  void clear();
+
+  // Forget any entries due to pointers from "from_hr".
+  void clear_incoming_entry(HeapRegion* from_hr) {
+    _other_regions.clear_incoming_entry(from_hr);
+  }
+
+#if 0
+  virtual void cleanup() = 0;
+#endif
+
+  // Should be called from single-threaded code.
+  void init_for_par_iteration();
+  // Attempt to claim the region.  Returns true iff this call caused an
+  // atomic transition from Unclaimed to Claimed.
+  bool claim_iter();
+  // Sets the iteration state to "complete".
+  void set_iter_complete();
+  // Returns "true" iff the region's iteration is complete.
+  bool iter_is_complete();
+
+  // Initialize the given iterator to iterate over this rem set.
+  void init_iterator(HeapRegionRemSetIterator* iter) const;
+
+#if 0
+  // Apply the "do_card" method to the start address of every card in the
+  // rem set.  Returns false if some application of the closure aborted.
+  virtual bool card_iterate(CardClosure* iter) = 0;
+#endif
+
+  // The actual # of bytes this hr_remset takes up.
+  size_t mem_size() {
+    return _other_regions.mem_size()
+      // This correction is necessary because the above includes the second
+      // part.
+      + sizeof(this) - sizeof(OtherRegionsTable);
+  }
+
+  // Returns the memory occupancy of all static data structures associated
+  // with remembered sets.
+  static size_t static_mem_size() {
+    return OtherRegionsTable::static_mem_size();
+  }
+
+  // Returns the memory occupancy of all free_list data structures associated
+  // with remembered sets.
+  static size_t fl_mem_size() {
+    return OtherRegionsTable::fl_mem_size();
+  }
+
+  bool contains_reference(oop* from) const {
+    return _other_regions.contains_reference(from);
+  }
+  void print() const;
+
+#if MAYBE
+  // We are about to introduce a constraint, requiring the collection time
+  // of the region owning this RS to be <= "hr", and forgetting pointers
+  // from the owning region to "hr."  Before doing so, examines this rem
+  // set for pointers to "hr", possibly identifying some popular objects.,
+  // and possibly finding some cards to no longer contain pointers to "hr",
+  //
+  // These steps may prevent the the constraint from being necessary; in
+  // which case returns a set of cards now thought to contain no pointers
+  // into HR.  In the normal (I assume) case, returns NULL, indicating that
+  // we should go ahead and add the constraint.
+  virtual SeqHeapRegionRemSet* audit(HeapRegion* hr) = 0;
+#endif
+
+  // Called during a stop-world phase to perform any deferred cleanups.
+  // The second version may be called by parallel threads after then finish
+  // collection work.
+  static void cleanup();
+  static void par_cleanup();
+
+  // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
+  // (Uses it to initialize from_card_cache).
+  static void init_heap(size_t max_regions) {
+    OtherRegionsTable::init_from_card_cache(max_regions);
+  }
+
+  // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
+  static void shrink_heap(size_t new_n_regs) {
+    OtherRegionsTable::shrink_from_card_cache(new_n_regs);
+  }
+
+#ifndef PRODUCT
+  static void print_from_card_cache() {
+    OtherRegionsTable::print_from_card_cache();
+  }
+#endif
+
+  static void record(HeapRegion* hr, oop* f);
+  static void print_recorded();
+  static void record_event(Event evnt);
+
+  // Run unit tests.
+#ifndef PRODUCT
+  static void test();
+#endif
+
+};
+
+class HeapRegionRemSetIterator : public CHeapObj {
+
+  // The region over which we're iterating.
+  const HeapRegionRemSet* _hrrs;
+
+  // Local caching of HRRS fields.
+  const BitMap*             _coarse_map;
+  PosParPRT**               _fine_grain_regions;
+
+  G1BlockOffsetSharedArray* _bosa;
+  G1CollectedHeap*          _g1h;
+
+  // The number yielded since initialization.
+  size_t _n_yielded_fine;
+  size_t _n_yielded_coarse;
+  size_t _n_yielded_sparse;
+
+  // If true we're iterating over the coarse table; if false the fine
+  // table.
+  enum IterState {
+    Sparse,
+    Fine,
+    Coarse
+  };
+  IterState _is;
+
+  // In both kinds of iteration, heap offset of first card of current
+  // region.
+  size_t _cur_region_card_offset;
+  // Card offset within cur region.
+  size_t _cur_region_cur_card;
+
+  // Coarse table iteration fields:
+
+  // Current region index;
+  int _coarse_cur_region_index;
+  int _coarse_cur_region_cur_card;
+
+  bool coarse_has_next(size_t& card_index);
+
+  // Fine table iteration fields:
+
+  // Index of bucket-list we're working on.
+  int _fine_array_index;
+  // Per Region Table we're doing within current bucket list.
+  PosParPRT* _fine_cur_prt;
+
+  /* SparsePRT::*/ SparsePRTIter _sparse_iter;
+
+  void fine_find_next_non_null_prt();
+
+  bool fine_has_next();
+  bool fine_has_next(size_t& card_index);
+
+public:
+  // We require an iterator to be initialized before use, so the
+  // constructor does little.
+  HeapRegionRemSetIterator();
+
+  void initialize(const HeapRegionRemSet* hrrs);
+
+  // If there remains one or more cards to be yielded, returns true and
+  // sets "card_index" to one of those cards (which is then considered
+  // yielded.)   Otherwise, returns false (and leaves "card_index"
+  // undefined.)
+  bool has_next(size_t& card_index);
+
+  size_t n_yielded_fine() { return _n_yielded_fine; }
+  size_t n_yielded_coarse() { return _n_yielded_coarse; }
+  size_t n_yielded_sparse() { return _n_yielded_sparse; }
+  size_t n_yielded() {
+    return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
+  }
+};
+
+#if 0
+class CardClosure: public Closure {
+public:
+  virtual void do_card(HeapWord* card_start) = 0;
+};
+
+#endif