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 /*

  * Copyright (c) 2001, 2009, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

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  */

 // 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 VALUE_OBJ_CLASS_SPEC {

   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(OopOrNarrowOopStar from, int tid);

   void add_reference(OopOrNarrowOopStar 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(OopOrNarrowOopStar from) const;

   bool contains_reference_locked(OopOrNarrowOopStar 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; }

   OtherRegionsTable _other_regions;

   enum ParIterState { Unclaimed, Claimed, Complete };

   volatile ParIterState _iter_state;

   volatile jlong _iter_claimed;

   // Unused unless G1RecordHRRSOops is true.

   static const int MaxRecorded = 1000000;

   static OopOrNarrowOopStar* _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 void setup_remset_size();

   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. */

   void add_reference(OopOrNarrowOopStar from) {

     _other_regions.add_reference(from);

   }

   /* Used in the parallel case.  Returns "true" iff this addition causes

      the size limit to be reached. */

   void add_reference(OopOrNarrowOopStar from, int tid) {

     _other_regions.add_reference(from, tid);

   }

   // 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();

   // Support for claiming blocks of cards during iteration

   void set_iter_claimed(size_t x) { _iter_claimed = (jlong)x; }

   size_t iter_claimed() const { return (size_t)_iter_claimed; }

   // Claim the next block of cards

   size_t iter_claimed_next(size_t step) {

     size_t current, next;

     do {

       current = iter_claimed();

       next = current + step;

     } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);

     return current;

   }

   // 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(OopOrNarrowOopStar from) const {

     return _other_regions.contains_reference(from);

   }

   void print() const;

   // 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, OopOrNarrowOopStar 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