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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  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_HEAPREGIONREMSET_HPP
  26 #define SHARE_GC_G1_HEAPREGIONREMSET_HPP
  27 
  28 #include "gc/g1/g1CodeCacheRemSet.hpp"
  29 #include "gc/g1/g1FromCardCache.hpp"
  30 #include "gc/g1/sparsePRT.hpp"
  31 
  32 // Remembered set for a heap region.  Represent a set of "cards" that
  33 // contain pointers into the owner heap region.  Cards are defined somewhat
  34 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
  35 
  36 class G1CollectedHeap;
  37 class G1BlockOffsetTable;
  38 class G1CardLiveData;
  39 class HeapRegion;
  40 class HeapRegionRemSetIterator;
  41 class PerRegionTable;
  42 class SparsePRT;
  43 class nmethod;
  44 
  45 // The "_coarse_map" is a bitmap with one bit for each region, where set
  46 // bits indicate that the corresponding region may contain some pointer
  47 // into the owning region.
  48 
  49 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
  50 // (PRTs), indicating regions for which we're keeping the RS as a set of
  51 // cards.  The strategy is to cap the size of the fine-grain table,
  52 // deleting an entry and setting the corresponding coarse-grained bit when
  53 // we would overflow this cap.
  54 
  55 // We use a mixture of locking and lock-free techniques here.  We allow
  56 // threads to locate PRTs without locking, but threads attempting to alter
  57 // a bucket list obtain a lock.  This means that any failing attempt to
  58 // find a PRT must be retried with the lock.  It might seem dangerous that
  59 // a read can find a PRT that is concurrently deleted.  This is all right,
  60 // because:
  61 //
  62 //   1) We only actually free PRT's at safe points (though we reuse them at
  63 //      other times).
  64 //   2) We find PRT's in an attempt to add entries.  If a PRT is deleted,
  65 //      it's _coarse_map bit is set, so the that we were attempting to add
  66 //      is represented.  If a deleted PRT is re-used, a thread adding a bit,
  67 //      thinking the PRT is for a different region, does no harm.
  68 
  69 class OtherRegionsTable {
  70   friend class HeapRegionRemSetIterator;
  71 
  72   G1CollectedHeap* _g1h;
  73   Mutex*           _m;
  74 
  75   // These are protected by "_m".
  76   CHeapBitMap _coarse_map;
  77   size_t      _n_coarse_entries;
  78   static jint _n_coarsenings;
  79 
  80   PerRegionTable** _fine_grain_regions;
  81   size_t           _n_fine_entries;
  82 
  83   // The fine grain remembered sets are doubly linked together using
  84   // their 'next' and 'prev' fields.
  85   // This allows fast bulk freeing of all the fine grain remembered
  86   // set entries, and fast finding of all of them without iterating
  87   // over the _fine_grain_regions table.
  88   PerRegionTable * _first_all_fine_prts;
  89   PerRegionTable * _last_all_fine_prts;
  90 
  91   // Used to sample a subset of the fine grain PRTs to determine which
  92   // PRT to evict and coarsen.
  93   size_t        _fine_eviction_start;
  94   static size_t _fine_eviction_stride;
  95   static size_t _fine_eviction_sample_size;
  96 
  97   SparsePRT   _sparse_table;
  98 
  99   // These are static after init.
 100   static size_t _max_fine_entries;
 101   static size_t _mod_max_fine_entries_mask;
 102 
 103   // Requires "prt" to be the first element of the bucket list appropriate
 104   // for "hr".  If this list contains an entry for "hr", return it,
 105   // otherwise return "NULL".
 106   PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
 107 
 108   // Find, delete, and return a candidate PerRegionTable, if any exists,
 109   // adding the deleted region to the coarse bitmap.  Requires the caller
 110   // to hold _m, and the fine-grain table to be full.
 111   PerRegionTable* delete_region_table();
 112 
 113   // link/add the given fine grain remembered set into the "all" list
 114   void link_to_all(PerRegionTable * prt);
 115   // unlink/remove the given fine grain remembered set into the "all" list
 116   void unlink_from_all(PerRegionTable * prt);
 117 
 118   bool contains_reference_locked(OopOrNarrowOopStar from) const;
 119 
 120   size_t occ_fine() const;
 121   size_t occ_coarse() const;
 122   size_t occ_sparse() const;
 123 
 124 public:
 125   // Create a new remembered set. The given mutex is used to ensure consistency.
 126   OtherRegionsTable(Mutex* m);
 127 
 128   // Returns the card index of the given within_region pointer relative to the bottom
 129   // of the given heap region.
 130   static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
 131   // Adds the reference from "from to this remembered set.
 132   void add_reference(OopOrNarrowOopStar from, uint tid);
 133 
 134   // Returns whether the remembered set contains the given reference.
 135   bool contains_reference(OopOrNarrowOopStar from) const;
 136 
 137   // Returns whether this remembered set (and all sub-sets) have an occupancy
 138   // that is less or equal than the given occupancy.
 139   bool occupancy_less_or_equal_than(size_t limit) const;
 140 
 141   // Returns whether this remembered set (and all sub-sets) does not contain any entry.
 142   bool is_empty() const;
 143 
 144   // Returns the number of cards contained in this remembered set.
 145   size_t occupied() const;
 146 
 147   static jint n_coarsenings() { return _n_coarsenings; }
 148 
 149   // Returns size of the actual remembered set containers in bytes.
 150   size_t mem_size() const;
 151   // Returns the size of static data in bytes.
 152   static size_t static_mem_size();
 153   // Returns the size of the free list content in bytes.
 154   static size_t fl_mem_size();
 155 
 156   // Clear the entire contents of this remembered set.
 157   void clear();
 158 };
 159 
 160 class HeapRegionRemSet : public CHeapObj<mtGC> {
 161   friend class VMStructs;
 162   friend class HeapRegionRemSetIterator;
 163 
 164 private:
 165   G1BlockOffsetTable* _bot;
 166 
 167   // A set of code blobs (nmethods) whose code contains pointers into
 168   // the region that owns this RSet.
 169   G1CodeRootSet _code_roots;
 170 
 171   Mutex _m;
 172 
 173   OtherRegionsTable _other_regions;
 174 
 175   HeapRegion* _hr;
 176 
 177   void clear_fcc();
 178 
 179 public:
 180   HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
 181 
 182   // Setup sparse and fine-grain tables sizes.
 183   static void setup_remset_size();
 184 
 185   bool cardset_is_empty() const {
 186     return _other_regions.is_empty();
 187   }
 188 
 189   bool is_empty() const {
 190     return (strong_code_roots_list_length() == 0) && cardset_is_empty();
 191   }
 192 
 193   bool occupancy_less_or_equal_than(size_t occ) const {
 194     return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
 195   }
 196 
 197   size_t occupied() {
 198     MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
 199     return occupied_locked();
 200   }
 201   size_t occupied_locked() {
 202     return _other_regions.occupied();
 203   }
 204 
 205   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 206 
 207 private:
 208   enum RemSetState {
 209     Untracked,
 210     Updating,
 211     Complete
 212   };
 213 
 214   RemSetState _state;
 215 
 216   static const char* _state_strings[];
 217   static const char* _short_state_strings[];
 218 public:
 219 
 220   const char* get_state_str() const { return _state_strings[_state]; }
 221   const char* get_short_state_str() const { return _short_state_strings[_state]; }
 222 
 223   bool is_tracked() { return _state != Untracked; }
 224   bool is_updating() { return _state == Updating; }
 225   bool is_complete() { return _state == Complete; }
 226 
 227   void set_state_empty() {
 228     guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
 229     if (_state == Untracked) {
 230       return;
 231     }
 232     clear_fcc();
 233     _state = Untracked;
 234   }
 235 
 236   void set_state_updating() {
 237     guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
 238     clear_fcc();
 239     _state = Updating;
 240   }
 241 
 242   void set_state_complete() {
 243     clear_fcc();
 244     _state = Complete;
 245   }
 246 
 247   // Used in the sequential case.
 248   void add_reference(OopOrNarrowOopStar from) {
 249     add_reference(from, 0);
 250   }
 251 
 252   // Used in the parallel case.
 253   void add_reference(OopOrNarrowOopStar from, uint tid) {
 254     RemSetState state = _state;
 255     if (state == Untracked) {
 256       return;
 257     }
 258 
 259     uint cur_idx = _hr->hrm_index();
 260     uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
 261 
 262     if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
 263       assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
 264       return;
 265     }
 266 
 267     _other_regions.add_reference(from, tid);
 268   }
 269 
 270   // The region is being reclaimed; clear its remset, and any mention of
 271   // entries for this region in other remsets.
 272   void clear(bool only_cardset = false);
 273   void clear_locked(bool only_cardset = false);
 274 
 275   // The actual # of bytes this hr_remset takes up.
 276   // Note also includes the strong code root set.
 277   size_t mem_size() {
 278     MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
 279     return _other_regions.mem_size()
 280       // This correction is necessary because the above includes the second
 281       // part.
 282       + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
 283       + strong_code_roots_mem_size();
 284   }
 285 
 286   // Returns the memory occupancy of all static data structures associated
 287   // with remembered sets.
 288   static size_t static_mem_size() {
 289     return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
 290   }
 291 
 292   // Returns the memory occupancy of all free_list data structures associated
 293   // with remembered sets.
 294   static size_t fl_mem_size() {
 295     return OtherRegionsTable::fl_mem_size();
 296   }
 297 
 298   bool contains_reference(OopOrNarrowOopStar from) const {
 299     return _other_regions.contains_reference(from);
 300   }
 301 
 302   // Routines for managing the list of code roots that point into
 303   // the heap region that owns this RSet.
 304   void add_strong_code_root(nmethod* nm);
 305   void add_strong_code_root_locked(nmethod* nm);
 306   void remove_strong_code_root(nmethod* nm);
 307 
 308   // Applies blk->do_code_blob() to each of the entries in
 309   // the strong code roots list
 310   void strong_code_roots_do(CodeBlobClosure* blk) const;
 311 
 312   void clean_strong_code_roots(HeapRegion* hr);
 313 
 314   // Returns the number of elements in the strong code roots list
 315   size_t strong_code_roots_list_length() const {
 316     return _code_roots.length();
 317   }
 318 
 319   // Returns true if the strong code roots contains the given
 320   // nmethod.
 321   bool strong_code_roots_list_contains(nmethod* nm) {
 322     return _code_roots.contains(nm);
 323   }
 324 
 325   // Returns the amount of memory, in bytes, currently
 326   // consumed by the strong code roots.
 327   size_t strong_code_roots_mem_size();
 328 
 329   static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
 330     G1FromCardCache::invalidate(start_idx, num_regions);
 331   }
 332 
 333 #ifndef PRODUCT
 334   static void print_from_card_cache() {
 335     G1FromCardCache::print();
 336   }
 337 
 338   static void test();
 339 #endif
 340 };
 341 
 342 class HeapRegionRemSetIterator : public StackObj {
 343 private:
 344   // The region RSet over which we are iterating.
 345   HeapRegionRemSet* _hrrs;
 346 
 347   // Local caching of HRRS fields.
 348   const BitMap*             _coarse_map;
 349 
 350   G1BlockOffsetTable*       _bot;
 351   G1CollectedHeap*          _g1h;
 352 
 353   // The number of cards yielded since initialization.
 354   size_t _n_yielded_fine;
 355   size_t _n_yielded_coarse;
 356   size_t _n_yielded_sparse;
 357 
 358   // Indicates what granularity of table that we are currently iterating over.
 359   // We start iterating over the sparse table, progress to the fine grain
 360   // table, and then finish with the coarse table.
 361   enum IterState {
 362     Sparse,
 363     Fine,
 364     Coarse
 365   };
 366   IterState _is;
 367 
 368   // For both Coarse and Fine remembered set iteration this contains the
 369   // first card number of the heap region we currently iterate over.
 370   size_t _cur_region_card_offset;
 371 
 372   // Current region index for the Coarse remembered set iteration.
 373   int    _coarse_cur_region_index;
 374   size_t _coarse_cur_region_cur_card;
 375 
 376   bool coarse_has_next(size_t& card_index);
 377 
 378   // The PRT we are currently iterating over.
 379   PerRegionTable* _fine_cur_prt;
 380   // Card offset within the current PRT.
 381   size_t _cur_card_in_prt;
 382 
 383   // Update internal variables when switching to the given PRT.
 384   void switch_to_prt(PerRegionTable* prt);
 385   bool fine_has_next();
 386   bool fine_has_next(size_t& card_index);
 387 
 388   // The Sparse remembered set iterator.
 389   SparsePRTIter _sparse_iter;
 390 
 391 public:
 392   HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
 393 
 394   // If there remains one or more cards to be yielded, returns true and
 395   // sets "card_index" to one of those cards (which is then considered
 396   // yielded.)   Otherwise, returns false (and leaves "card_index"
 397   // undefined.)
 398   bool has_next(size_t& card_index);
 399 
 400   size_t n_yielded_fine() { return _n_yielded_fine; }
 401   size_t n_yielded_coarse() { return _n_yielded_coarse; }
 402   size_t n_yielded_sparse() { return _n_yielded_sparse; }
 403   size_t n_yielded() {
 404     return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
 405   }
 406 };
 407 
 408 #endif // SHARE_GC_G1_HEAPREGIONREMSET_HPP