1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_GC_G1_SPARSEPRT_HPP
  26 #define SHARE_GC_G1_SPARSEPRT_HPP
  27 
  28 #include "gc/g1/g1CollectedHeap.hpp"
  29 #include "gc/g1/heapRegion.hpp"
  30 #include "gc/shared/cardTableBarrierSet.hpp"
  31 #include "memory/allocation.hpp"
  32 #include "runtime/mutex.hpp"
  33 #include "utilities/align.hpp"
  34 #include "utilities/globalDefinitions.hpp"
  35 
  36 // Sparse remembered set for a heap region (the "owning" region).  Maps
  37 // indices of other regions to short sequences of cards in the other region
  38 // that might contain pointers into the owner region.
  39 
  40 class SparsePRTEntry: public CHeapObj<mtGC> {
  41 private:
  42   // The type of a card entry.
  43   typedef uint16_t card_elem_t;
  44 
  45   // We need to make sizeof(SparsePRTEntry) an even multiple of maximum member size,
  46   // in order to force correct alignment that could otherwise cause SIGBUS errors
  47   // when reading the member variables. This calculates the minimum number of card
  48   // array elements required to get that alignment.
  49   static const size_t card_array_alignment = sizeof(int) / sizeof(card_elem_t);
  50 
  51   RegionIdx_t _region_ind;
  52   int         _next_index;
  53   int         _next_null;
  54   // The actual cards stored in this array.
  55   // WARNING: Don't put any data members beyond this line. Card array has, in fact, variable length.
  56   // It should always be the last data member.
  57   card_elem_t _cards[card_array_alignment];
  58 
  59   // Copy the current entry's cards into "cards".
  60   inline void copy_cards(card_elem_t* cards) const;
  61 public:
  62   // Returns the size of the entry, used for entry allocation.
  63   static size_t size() { return sizeof(SparsePRTEntry) + sizeof(card_elem_t) * (cards_num() - card_array_alignment); }
  64   // Returns the size of the card array.
  65   static int cards_num() {
  66     return align_up((int)G1RSetSparseRegionEntries, (int)card_array_alignment);
  67   }
  68 
  69   // Set the region_ind to the given value, and delete all cards.
  70   inline void init(RegionIdx_t region_ind);
  71 
  72   RegionIdx_t r_ind() const { return _region_ind; }
  73   bool valid_entry() const { return r_ind() >= 0; }
  74   void set_r_ind(RegionIdx_t rind) { _region_ind = rind; }
  75 
  76   int next_index() const { return _next_index; }
  77   int* next_index_addr() { return &_next_index; }
  78   void set_next_index(int ni) { _next_index = ni; }
  79 
  80   // Returns "true" iff the entry contains the given card index.
  81   inline bool contains_card(CardIdx_t card_index) const;
  82 
  83   // Returns the number of non-NULL card entries.
  84   inline int num_valid_cards() const { return _next_null; }
  85 
  86   // Requires that the entry not contain the given card index.  If there is
  87   // space available, add the given card index to the entry and return
  88   // "true"; otherwise, return "false" to indicate that the entry is full.
  89   enum AddCardResult {
  90     overflow,
  91     found,
  92     added
  93   };
  94   inline AddCardResult add_card(CardIdx_t card_index);
  95 
  96   // Copy the current entry's cards into the "_card" array of "e."
  97   inline void copy_cards(SparsePRTEntry* e) const;
  98 
  99   inline CardIdx_t card(int i) const {
 100     assert(i >= 0, "must be nonnegative");
 101     assert(i < cards_num(), "range checking");
 102     return (CardIdx_t)_cards[i];
 103   }
 104 };
 105 
 106 class RSHashTable : public CHeapObj<mtGC> {
 107 
 108   friend class RSHashTableIter;
 109 
 110 
 111   // Inverse maximum hash table occupancy used.
 112   static float TableOccupancyFactor;
 113 
 114   size_t _num_entries;
 115 
 116   size_t _capacity;
 117   size_t _capacity_mask;
 118   size_t _occupied_entries;
 119   size_t _occupied_cards;
 120 
 121   SparsePRTEntry* _entries;
 122   int* _buckets;
 123   int  _free_region;
 124   int  _free_list;
 125 
 126   // Requires that the caller hold a lock preventing parallel modifying
 127   // operations, and that the the table be less than completely full.  If
 128   // an entry for "region_ind" is already in the table, finds it and
 129   // returns its address; otherwise allocates, initializes, inserts and
 130   // returns a new entry for "region_ind".
 131   SparsePRTEntry* entry_for_region_ind_create(RegionIdx_t region_ind);
 132 
 133   // Returns the index of the next free entry in "_entries".
 134   int alloc_entry();
 135   // Declares the entry "fi" to be free.  (It must have already been
 136   // deleted from any bucket lists.
 137   void free_entry(int fi);
 138 
 139 public:
 140   RSHashTable(size_t capacity);
 141   ~RSHashTable();
 142 
 143   static const int NullEntry = -1;
 144 
 145   bool should_expand() const { return _occupied_entries == _num_entries; }
 146 
 147   // Attempts to ensure that the given card_index in the given region is in
 148   // the sparse table.  If successful (because the card was already
 149   // present, or because it was successfully added) returns "true".
 150   // Otherwise, returns "false" to indicate that the addition would
 151   // overflow the entry for the region.  The caller must transfer these
 152   // entries to a larger-capacity representation.
 153   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
 154 
 155   bool delete_entry(RegionIdx_t region_id);
 156 
 157   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const;
 158 
 159   void add_entry(SparsePRTEntry* e);
 160 
 161   SparsePRTEntry* get_entry(RegionIdx_t region_id) const;
 162 
 163   void clear();
 164 
 165   size_t capacity() const      { return _capacity; }
 166   size_t capacity_mask() const { return _capacity_mask;  }
 167   size_t occupied_entries() const { return _occupied_entries; }
 168   size_t occupied_cards() const   { return _occupied_cards; }
 169   size_t mem_size() const;
 170   // The number of SparsePRTEntry instances available.
 171   size_t num_entries() const { return _num_entries; }
 172 
 173   SparsePRTEntry* entry(int i) const {
 174     assert(i >= 0 && (size_t)i < _num_entries, "precondition");
 175     return (SparsePRTEntry*)((char*)_entries + SparsePRTEntry::size() * i);
 176   }
 177 
 178   void print();
 179 };
 180 
 181 // This is embedded in HRRS iterator.
 182 class RSHashTableIter {
 183   // Return value indicating "invalid/no card".
 184   static const int NoCardFound = -1;
 185 
 186   int _tbl_ind;         // [-1, 0.._rsht->_capacity)
 187   int _bl_ind;          // [-1, 0.._rsht->_capacity)
 188   short _card_ind;      // [0..SparsePRTEntry::cards_num())
 189   RSHashTable* _rsht;
 190 
 191   // If the bucket list pointed to by _bl_ind contains a card, sets
 192   // _bl_ind to the index of that entry,
 193   // Returns the card found if there is, otherwise returns InvalidCard.
 194   CardIdx_t find_first_card_in_list();
 195 
 196   // Computes the proper card index for the card whose offset in the
 197   // current region (as indicated by _bl_ind) is "ci".
 198   // This is subject to errors when there is iteration concurrent with
 199   // modification, but these errors should be benign.
 200   size_t compute_card_ind(CardIdx_t ci);
 201 
 202 public:
 203   RSHashTableIter(RSHashTable* rsht) :
 204     _tbl_ind(RSHashTable::NullEntry), // So that first increment gets to 0.
 205     _bl_ind(RSHashTable::NullEntry),
 206     _card_ind((SparsePRTEntry::cards_num() - 1)),
 207     _rsht(rsht) {}
 208 
 209   bool has_next(size_t& card_index);
 210 };
 211 
 212 // Concurrent access to a SparsePRT must be serialized by some external mutex.
 213 
 214 class SparsePRTIter;
 215 
 216 class SparsePRT {
 217   friend class SparsePRTIter;
 218 
 219   RSHashTable* _table;
 220 
 221   static const size_t InitialCapacity = 8;
 222 
 223   void expand();
 224 
 225 public:
 226   SparsePRT();
 227   ~SparsePRT();
 228 
 229   size_t occupied() const { return _table->occupied_cards(); }
 230   size_t mem_size() const;
 231 
 232   // Attempts to ensure that the given card_index in the given region is in
 233   // the sparse table.  If successful (because the card was already
 234   // present, or because it was successfully added) returns "true".
 235   // Otherwise, returns "false" to indicate that the addition would
 236   // overflow the entry for the region.  The caller must transfer these
 237   // entries to a larger-capacity representation.
 238   bool add_card(RegionIdx_t region_id, CardIdx_t card_index);
 239 
 240   // Return the pointer to the entry associated with the given region.
 241   SparsePRTEntry* get_entry(RegionIdx_t region_ind);
 242 
 243   // If there is an entry for "region_ind", removes it and return "true";
 244   // otherwise returns "false."
 245   bool delete_entry(RegionIdx_t region_ind);
 246 
 247   // Clear the table, and reinitialize to initial capacity.
 248   void clear();
 249 
 250   bool contains_card(RegionIdx_t region_id, CardIdx_t card_index) const {
 251     return _table->contains_card(region_id, card_index);
 252   }
 253 };
 254 
 255 class SparsePRTIter: public RSHashTableIter {
 256 public:
 257   SparsePRTIter(const SparsePRT* sprt) :
 258     RSHashTableIter(sprt->_table) { }
 259 
 260   bool has_next(size_t& card_index) {
 261     return RSHashTableIter::has_next(card_index);
 262   }
 263 };
 264 
 265 #endif // SHARE_GC_G1_SPARSEPRT_HPP