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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 *

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 * 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.

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#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP

#define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP

#include "gc_implementation/g1/g1CodeCacheRemSet.hpp"

#include "gc_implementation/g1/sparsePRT.hpp"

// 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 PerRegionTable;

class SparsePRT;

class nmethod;

// Essentially a wrapper around SparsePRTCleanupTask. See

// sparsePRT.hpp for more details.

class HRRSCleanupTask : public SparsePRTCleanupTask {

};

// 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;

  PerRegionTable** _fine_grain_regions;

  size_t           _n_fine_entries;

  // The fine grain remembered sets are doubly linked together using

  // their 'next' and 'prev' fields.

  // This allows fast bulk freeing of all the fine grain remembered

  // set entries, and fast finding of all of them without iterating

  // over the _fine_grain_regions table.

  PerRegionTable * _first_all_fine_prts;

  PerRegionTable * _last_all_fine_prts;

  // Used to sample a subset of the fine grain PRTs to determine which

  // PRT to evict and coarsen.

  size_t        _fine_eviction_start;

  static size_t _fine_eviction_stride;

  static size_t _fine_eviction_sample_size;

  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".

  PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;

  // Find, delete, and return a candidate PerRegionTable, 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.

  PerRegionTable* 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);

  // Indexed by thread X heap region, to minimize thread contention.

  static int** _from_card_cache;

  static size_t _from_card_cache_mem_size;

  // link/add the given fine grain remembered set into the "all" list

  void link_to_all(PerRegionTable * prt);

  // unlink/remove the given fine grain remembered set into the "all" list

  void unlink_from_all(PerRegionTable * prt);

public:

  OtherRegionsTable(HeapRegion* hr, Mutex* m);

  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);

  // Removes any entries shown by the given bitmaps to contain only dead

  // objects.

  void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);

  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);

  void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);

  // Declare the heap size (in # of regions) to the OtherRegionsTable.

  // (Uses it to initialize from_card_cache).

  // 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 print_from_card_cache();

};

class HeapRegionRemSet : public CHeapObj<mtGC> {

  friend class VMStructs;

  friend class HeapRegionRemSetIterator;

public:

  enum Event {

    Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd

  };

private:

  G1BlockOffsetSharedArray* _bosa;

  G1BlockOffsetSharedArray* bosa() const { return _bosa; }

  // A set of code blobs (nmethods) whose code contains pointers into

  // the region that owns this RSet.

  G1CodeRootSet _code_roots;

  Mutex _m;

  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 void setup_remset_size();

  HeapRegion* hr() const {

    return _other_regions.hr();

  }

  size_t occupied() {

    MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);

    return occupied_locked();

  }

  size_t occupied_locked() {

    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.

  void add_reference(OopOrNarrowOopStar from) {

    _other_regions.add_reference(from, 0);

  }

  // Used in the parallel case.

  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();

  void clear_locked();

  // 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

  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;

  }

  void reset_for_par_iteration();

  bool verify_ready_for_par_iteration() {

    return (_iter_state == Unclaimed) && (_iter_claimed == 0);

  }

  // The actual # of bytes this hr_remset takes up.

  // Note also includes the strong code root set.

  size_t mem_size() {

    MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);

    return _other_regions.mem_size()

      // This correction is necessary because the above includes the second

      // part.

      + (sizeof(this) - sizeof(OtherRegionsTable))

      + strong_code_roots_mem_size();

  }

  // Returns the memory occupancy of all static data structures associated

  // with remembered sets.

  static size_t static_mem_size() {

    return OtherRegionsTable::static_mem_size() + G1CodeRootSet::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() + G1CodeRootSet::fl_mem_size();

  }

  bool contains_reference(OopOrNarrowOopStar from) const {

    return _other_regions.contains_reference(from);

  }

  // Routines for managing the list of code roots that point into

  // the heap region that owns this RSet.

  void add_strong_code_root(nmethod* nm);

  void remove_strong_code_root(nmethod* nm);

  // During a collection, migrate the successfully evacuated strong

  // code roots that referenced into the region that owns this RSet

  // to the RSets of the new regions that they now point into.

  // Unsuccessfully evacuated code roots are not migrated.

  void migrate_strong_code_roots();

  // Applies blk->do_code_blob() to each of the entries in

  // the strong code roots list

  void strong_code_roots_do(CodeBlobClosure* blk) const;

  // Returns the number of elements in the strong code roots list

  size_t strong_code_roots_list_length() {

    return _code_roots.length();

  }

  // Returns true if the strong code roots contains the given

  // nmethod.

  bool strong_code_roots_list_contains(nmethod* nm) {

    return _code_roots.contains(nm);

  }

  // Returns the amount of memory, in bytes, currently

  // consumed by the strong code roots.

  size_t strong_code_roots_mem_size();

  void print() PRODUCT_RETURN;

  // Called during a stop-world phase to perform any deferred cleanups.

  static void cleanup();

  // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).

  // (Uses it to initialize from_card_cache).

  static void init_heap(uint max_regions) {

    G1CodeRootSet::initialize();

  }

  // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.

  static void shrink_heap(uint 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);

  // These are wrappers for the similarly-named methods on

  // SparsePRT. Look at sparsePRT.hpp for more details.

  static void reset_for_cleanup_tasks();

  void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);

  static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);

  // Run unit tests.

#ifndef PRODUCT

  static void test_prt();

  static void test();

#endif

};

class HeapRegionRemSetIterator : public StackObj {

  // The region RSet over which we're iterating.

  HeapRegionRemSet* _hrrs;

  // Local caching of HRRS fields.

  const BitMap*             _coarse_map;

  PerRegionTable**          _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;

  // Indicates what granularity of table that we're currently iterating over.

  // We start iterating over the sparse table, progress to the fine grain

  // table, and then finish with the coarse table.

  // See HeapRegionRemSetIterator::has_next().

  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;

  size_t _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.

  PerRegionTable* _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(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();

  }

};

#endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP