/*

 * 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.

  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