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

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 *

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#ifndef SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP

#define SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP

#include "gc/g1/g1CodeCacheRemSet.hpp"

#include "gc/g1/g1FromCardCache.hpp"

#include "gc/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 G1BlockOffsetTable;

class G1CardLiveData;

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".

  CHeapBitMap _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();

  // 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);

  bool contains_reference_locked(OopOrNarrowOopStar from) const;

  // Clear the from_card_cache entries for this region.

  void clear_fcc();

public:

  // Create a new remembered set for the given heap region. The given mutex should

  // be used to ensure consistency.

  OtherRegionsTable(HeapRegion* hr, Mutex* m);

  // For now.  Could "expand" some tables in the future, so that this made

  // sense.

  void add_reference(OopOrNarrowOopStar from, uint tid);

  // Returns whether the remembered set contains the given reference.

  bool contains_reference(OopOrNarrowOopStar from) const;

  // Returns whether this remembered set (and all sub-sets) have an occupancy

  // that is less or equal than the given occupancy.

  bool occupancy_less_or_equal_than(size_t limit) const;

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

  // objects. Not thread safe.

  // Set bits in the bitmaps indicate that the given region or card is live.

  void scrub(G1CardLiveData* live_data);

  // Returns whether this remembered set (and all sub-sets) does not contain any entry.

  bool is_empty() const;

  // Returns the number of cards contained in this remembered set.

  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 of the actual remembered set containers in bytes.

  size_t mem_size() const;

  // Returns the size of static data in bytes.

  static size_t static_mem_size();

  // Returns the size of the free list content in bytes.

  static size_t fl_mem_size();

  // Clear the entire contents of this remembered set.

  void clear();

  void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);

};

class HeapRegionRemSet : public CHeapObj<mtGC> {

  friend class VMStructs;

  friend class HeapRegionRemSetIterator;

private:

  G1BlockOffsetTable* _bot;

  // 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;

public:

  HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);

  static void setup_remset_size();

  bool is_empty() const {

    return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();

  }

  bool occupancy_less_or_equal_than(size_t occ) const {

    return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);

  }

  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, uint tid) {

    _other_regions.add_reference(from, tid);

  }

  // Removes any entries in the remembered set shown by the given card live data to

  // contain only dead objects. Not thread safe.

  void scrub(G1CardLiveData* live_data);

  // The region is being reclaimed; clear its remset, and any mention of

  // entries for this region in other remsets.

  void clear();

  void clear_locked();

  // 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(HeapRegionRemSet) - 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();

  }

  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 add_strong_code_root_locked(nmethod* nm);

  void remove_strong_code_root(nmethod* nm);

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

  // the strong code roots list

  void strong_code_roots_do(CodeBlobClosure* blk) const;

  void clean_strong_code_roots(HeapRegion* hr);

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

  size_t strong_code_roots_list_length() const {

    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();

  static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {

    G1FromCardCache::invalidate(start_idx, num_regions);

  }

#ifndef PRODUCT

  static void print_from_card_cache() {

    G1FromCardCache::print();

  }

#endif

  // 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();

#endif

};

class HeapRegionRemSetIterator : public StackObj {

 private:

  // The region RSet over which we are iterating.

  HeapRegionRemSet* _hrrs;

  // Local caching of HRRS fields.

  const BitMap*             _coarse_map;

  G1BlockOffsetTable*       _bot;

  G1CollectedHeap*          _g1h;

  // The number of cards 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 are currently iterating over.

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

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

  enum IterState {

    Sparse,

    Fine,

    Coarse

  };

  IterState _is;

  // For both Coarse and Fine remembered set iteration this contains the

  // first card number of the heap region we currently iterate over.

  size_t _cur_region_card_offset;

  // Current region index for the Coarse remembered set iteration.

  int    _coarse_cur_region_index;

  size_t _coarse_cur_region_cur_card;

  bool coarse_has_next(size_t& card_index);

  // The PRT we are currently iterating over.

  PerRegionTable* _fine_cur_prt;

  // Card offset within the current PRT.

  size_t _cur_card_in_prt;

  // Update internal variables when switching to the given PRT.

  void switch_to_prt(PerRegionTable* prt);

  bool fine_has_next();

  bool fine_has_next(size_t& card_index);

  // The Sparse remembered set iterator.

  SparsePRTIter _sparse_iter;

 public:

  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_G1_HEAPREGIONREMSET_HPP