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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_GC_G1_HEAPREGIONREMSET_HPP

#define SHARE_GC_G1_HEAPREGIONREMSET_HPP

#include "gc/g1/g1CodeCacheRemSet.hpp"

#include "gc/g1/g1FromCardCache.hpp"

#include "gc/g1/sparsePRT.hpp"

#include "utilities/bitMap.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 PerRegionTable;

class SparsePRT;

class nmethod;

// 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 {

  G1CollectedHeap* _g1h;

  Mutex*           _m;

  // 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;

  size_t occ_fine() const;

  size_t occ_coarse() const;

  size_t occ_sparse() const;

public:

  // Create a new remembered set. The given mutex is used to ensure consistency.

  OtherRegionsTable(Mutex* m);

  template <class Closure>

  void iterate(Closure& v);

  // Returns the card index of the given within_region pointer relative to the bottom

  // of the given heap region.

  static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);

  // Adds the reference from "from to this remembered set.

  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;

  // 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;

  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();

};

class PerRegionTable: public CHeapObj<mtGC> {

  friend class OtherRegionsTable;

  HeapRegion*     _hr;

  CHeapBitMap     _bm;

  jint            _occupied;

  // next pointer for free/allocated 'all' list

  PerRegionTable* _next;

  // prev pointer for the allocated 'all' list

  PerRegionTable* _prev;

  // next pointer in collision list

  PerRegionTable * _collision_list_next;

  // Global free list of PRTs

  static PerRegionTable* volatile _free_list;

protected:

  PerRegionTable(HeapRegion* hr) :

    _hr(hr),

    _bm(HeapRegion::CardsPerRegion, mtGC),

    _occupied(0),

    _next(NULL), _prev(NULL),

    _collision_list_next(NULL)

  {}

public:

  // We need access in order to union things into the base table.

  BitMap* bm() { return &_bm; }

  jint occupied() const {

    // Overkill, but if we ever need it...

    // guarantee(_occupied == _bm.count_one_bits(), "Check");

    return _occupied;

  }

  void init(HeapRegion* hr, bool clear_links_to_all_list);

  inline void add_reference(OopOrNarrowOopStar from);

  inline void add_card(CardIdx_t from_card_index);

  // (Destructively) union the bitmap of the current table into the given

  // bitmap (which is assumed to be of the same size.)

  void union_bitmap_into(BitMap* bm) {

    bm->set_union(_bm);

  }

  // Mem size in bytes.

  size_t mem_size() const {

    return sizeof(PerRegionTable) + _bm.size_in_words() * HeapWordSize;

  }

  // Requires "from" to be in "hr()".

  bool contains_reference(OopOrNarrowOopStar from) const {

    assert(hr()->is_in_reserved(from), "Precondition.");

    size_t card_ind = pointer_delta(from, hr()->bottom(),

                                    G1CardTable::card_size);

    return _bm.at(card_ind);

  }

  // Bulk-free the PRTs from prt to last, assumes that they are

  // linked together using their _next field.

  static void bulk_free(PerRegionTable* prt, PerRegionTable* last) {

    while (true) {

      PerRegionTable* fl = _free_list;

      last->set_next(fl);

      PerRegionTable* res = Atomic::cmpxchg(prt, &_free_list, fl);

      if (res == fl) {

        return;

      }

    }

    ShouldNotReachHere();

  }

  static void free(PerRegionTable* prt) {

    bulk_free(prt, prt);

  }

  // Returns an initialized PerRegionTable instance.

  static PerRegionTable* alloc(HeapRegion* hr);

  PerRegionTable* next() const { return _next; }

  void set_next(PerRegionTable* next) { _next = next; }

  PerRegionTable* prev() const { return _prev; }

  void set_prev(PerRegionTable* prev) { _prev = prev; }

  // Accessor and Modification routines for the pointer for the

  // singly linked collision list that links the PRTs within the

  // OtherRegionsTable::_fine_grain_regions hash table.

  //

  // It might be useful to also make the collision list doubly linked

  // to avoid iteration over the collisions list during scrubbing/deletion.

  // OTOH there might not be many collisions.

  PerRegionTable* collision_list_next() const {

    return _collision_list_next;

  }

  void set_collision_list_next(PerRegionTable* next) {

    _collision_list_next = next;

  }

  PerRegionTable** collision_list_next_addr() {

    return &_collision_list_next;

  }

  static size_t fl_mem_size() {

    PerRegionTable* cur = _free_list;

    size_t res = 0;

    while (cur != NULL) {

      res += cur->mem_size();

      cur = cur->next();

    }

    return res;

  }

  static void test_fl_mem_size();

};

class HeapRegionRemSet : public CHeapObj<mtGC> {

  friend class VMStructs;

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;

  HeapRegion* _hr;

  void clear_fcc();

public:

  HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);

  // Setup sparse and fine-grain tables sizes.

  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);

  }

  // For each PRT in the card (remembered) set call one of the following methods

  // of the given closure:

  //

  // set_full_region_dirty(uint region_idx) - pass the region index for coarse PRTs

  // set_bitmap_dirty(uint region_idx, BitMap* bitmap) - pass the region index and bitmap for fine PRTs

  // set_cards_dirty(uint region_idx, elem_t* cards, uint num_cards) - pass region index and cards for sparse PRTs

  template <class Closure>

  inline void iterate_prts(Closure& cl);

  size_t occupied() {

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

    return occupied_locked();

  }

  size_t occupied_locked() {

    return _other_regions.occupied();

  }

  static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }

private:

  enum RemSetState {

    Untracked,

    Updating,

    Complete

  };

  RemSetState _state;

  static const char* _state_strings[];

  static const char* _short_state_strings[];

public:

  const char* get_state_str() const { return _state_strings[_state]; }

  const char* get_short_state_str() const { return _short_state_strings[_state]; }

  bool is_tracked() { return _state != Untracked; }

  bool is_updating() { return _state == Updating; }

  bool is_complete() { return _state == Complete; }

  void set_state_empty() {

    guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());

    if (_state == Untracked) {

      return;

    }

    clear_fcc();

    _state = Untracked;

  }

  void set_state_updating() {

    guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());

    clear_fcc();

    _state = Updating;

  }

  void set_state_complete() {

    clear_fcc();

    _state = Complete;

  }

  void add_reference(OopOrNarrowOopStar from, uint tid) {

    RemSetState state = _state;

    if (state == Untracked) {

      return;

    }

    uint cur_idx = _hr->hrm_index();

    uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;

    if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {

      assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));

      return;

    }

    _other_regions.add_reference(from, tid);

  }

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

  // entries for this region in other remsets.

  void clear(bool only_cardset = false);

  void clear_locked(bool only_cardset = false);

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

  // Note also includes the strong code root set.

  size_t mem_size() {

    MutexLocker 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();

  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();

  }

  static void test();

#endif

};

#endif // SHARE_GC_G1_HEAPREGIONREMSET_HPP