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
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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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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP
  26 #define SHARE_VM_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 public:
 121   // Create a new remembered set. The given mutex is used to ensure consistency.
 122   OtherRegionsTable(Mutex* m);
 123 
 124   // Returns the card index of the given within_region pointer relative to the bottom
 125   // of the given heap region.
 126   static CardIdx_t card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr);
 127   // Adds the reference from "from to this remembered set.
 128   void add_reference(OopOrNarrowOopStar from, uint tid);
 129 
 130   // Returns whether the remembered set contains the given reference.
 131   bool contains_reference(OopOrNarrowOopStar from) const;
 132 
 133   // Returns whether this remembered set (and all sub-sets) have an occupancy
 134   // that is less or equal than the given occupancy.
 135   bool occupancy_less_or_equal_than(size_t limit) const;
 136 
 137   // Returns whether this remembered set (and all sub-sets) does not contain any entry.
 138   bool is_empty() const;
 139 
 140   // Returns the number of cards contained in this remembered set.
 141   size_t occupied() const;
 142   size_t occ_fine() const;
 143   size_t occ_coarse() const;
 144   size_t occ_sparse() const;
 145 
 146   static jint n_coarsenings() { return _n_coarsenings; }
 147 
 148   // Returns size of the actual remembered set containers in bytes.
 149   size_t mem_size() const;
 150   // Returns the size of static data in bytes.
 151   static size_t static_mem_size();
 152   // Returns the size of the free list content in bytes.
 153   static size_t fl_mem_size();
 154 
 155   // Clear the entire contents of this remembered set.
 156   void clear();
 157 };
 158 
 159 class HeapRegionRemSet : public CHeapObj<mtGC> {
 160   friend class VMStructs;
 161   friend class HeapRegionRemSetIterator;
 162 
 163 private:
 164   G1BlockOffsetTable* _bot;
 165 
 166   // A set of code blobs (nmethods) whose code contains pointers into
 167   // the region that owns this RSet.
 168   G1CodeRootSet _code_roots;
 169 
 170   Mutex _m;
 171 
 172   OtherRegionsTable _other_regions;
 173 
 174   HeapRegion* _hr;
 175 
 176   void clear_fcc();
 177 
 178 public:
 179   HeapRegionRemSet(G1BlockOffsetTable* bot, HeapRegion* hr);
 180 
 181   static void setup_remset_size();
 182 
 183   bool cardset_is_empty() const {
 184     return _other_regions.is_empty();
 185   }
 186 
 187   bool is_empty() const {
 188     return (strong_code_roots_list_length() == 0) && cardset_is_empty();
 189   }
 190 
 191   bool occupancy_less_or_equal_than(size_t occ) const {
 192     return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
 193   }
 194 
 195   size_t occupied() {
 196     MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
 197     return occupied_locked();
 198   }
 199   size_t occupied_locked() {
 200     return _other_regions.occupied();
 201   }
 202   size_t occ_fine() const {
 203     return _other_regions.occ_fine();
 204   }
 205   size_t occ_coarse() const {
 206     return _other_regions.occ_coarse();
 207   }
 208   size_t occ_sparse() const {
 209     return _other_regions.occ_sparse();
 210   }
 211 
 212   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 213 
 214 private:
 215   enum RemSetState {
 216     Untracked,
 217     Updating,
 218     Complete
 219   };
 220 
 221   RemSetState _state;
 222 
 223   static const char* _state_strings[];
 224   static const char* _short_state_strings[];
 225 public:
 226 
 227   const char* get_state_str() const { return _state_strings[_state]; }
 228   const char* get_short_state_str() const { return _short_state_strings[_state]; }
 229 
 230   bool is_tracked() { return _state != Untracked; }
 231   bool is_updating() { return _state == Updating; }
 232   bool is_complete() { return _state == Complete; }
 233 
 234   void set_state_empty() {
 235     guarantee(SafepointSynchronize::is_at_safepoint() || !is_tracked(), "Should only set to Untracked during safepoint but is %s.", get_state_str());
 236     if (_state == Untracked) {
 237       return;
 238     }
 239     clear_fcc();
 240     _state = Untracked;
 241   }
 242 
 243   void set_state_updating() {
 244     guarantee(SafepointSynchronize::is_at_safepoint() && !is_tracked(), "Should only set to Updating from Untracked during safepoint but is %s", get_state_str());
 245     clear_fcc();
 246     _state = Updating;
 247   }
 248 
 249   void set_state_complete() {
 250     clear_fcc();
 251     _state = Complete;
 252   }
 253 
 254   // Used in the sequential case.
 255   void add_reference(OopOrNarrowOopStar from) {
 256     add_reference(from, 0);
 257   }
 258 
 259   // Used in the parallel case.
 260   void add_reference(OopOrNarrowOopStar from, uint tid) {
 261     RemSetState state = _state;
 262     if (state == Untracked) {
 263       return;
 264     }
 265 
 266     uint cur_idx = _hr->hrm_index();
 267     uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
 268 
 269     if (G1FromCardCache::contains_or_replace(tid, cur_idx, from_card)) {
 270       assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
 271       return;
 272     }
 273 
 274     _other_regions.add_reference(from, tid);
 275   }
 276 
 277   // The region is being reclaimed; clear its remset, and any mention of
 278   // entries for this region in other remsets.
 279   void clear(bool only_cardset = false);
 280   void clear_locked(bool only_cardset = false);
 281 
 282   // The actual # of bytes this hr_remset takes up.
 283   // Note also includes the strong code root set.
 284   size_t mem_size() {
 285     MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
 286     return _other_regions.mem_size()
 287       // This correction is necessary because the above includes the second
 288       // part.
 289       + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
 290       + strong_code_roots_mem_size();
 291   }
 292 
 293   // Returns the memory occupancy of all static data structures associated
 294   // with remembered sets.
 295   static size_t static_mem_size() {
 296     return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
 297   }
 298 
 299   // Returns the memory occupancy of all free_list data structures associated
 300   // with remembered sets.
 301   static size_t fl_mem_size() {
 302     return OtherRegionsTable::fl_mem_size();
 303   }
 304 
 305   bool contains_reference(OopOrNarrowOopStar from) const {
 306     return _other_regions.contains_reference(from);
 307   }
 308 
 309   // Routines for managing the list of code roots that point into
 310   // the heap region that owns this RSet.
 311   void add_strong_code_root(nmethod* nm);
 312   void add_strong_code_root_locked(nmethod* nm);
 313   void remove_strong_code_root(nmethod* nm);
 314 
 315   // Applies blk->do_code_blob() to each of the entries in
 316   // the strong code roots list
 317   void strong_code_roots_do(CodeBlobClosure* blk) const;
 318 
 319   void clean_strong_code_roots(HeapRegion* hr);
 320 
 321   // Returns the number of elements in the strong code roots list
 322   size_t strong_code_roots_list_length() const {
 323     return _code_roots.length();
 324   }
 325 
 326   // Returns true if the strong code roots contains the given
 327   // nmethod.
 328   bool strong_code_roots_list_contains(nmethod* nm) {
 329     return _code_roots.contains(nm);
 330   }
 331 
 332   // Returns the amount of memory, in bytes, currently
 333   // consumed by the strong code roots.
 334   size_t strong_code_roots_mem_size();
 335 
 336   static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
 337     G1FromCardCache::invalidate(start_idx, num_regions);
 338   }
 339 
 340 #ifndef PRODUCT
 341   static void print_from_card_cache() {
 342     G1FromCardCache::print();
 343   }
 344 
 345   static void test();
 346 #endif
 347 };
 348 
 349 class HeapRegionRemSetIterator : public StackObj {
 350 private:
 351   // The region RSet over which we are iterating.
 352   HeapRegionRemSet* _hrrs;
 353 
 354   // Local caching of HRRS fields.
 355   const BitMap*             _coarse_map;
 356 
 357   G1BlockOffsetTable*       _bot;
 358   G1CollectedHeap*          _g1h;
 359 
 360   // The number of cards yielded since initialization.
 361   size_t _n_yielded_fine;
 362   size_t _n_yielded_coarse;
 363   size_t _n_yielded_sparse;
 364 
 365   // Indicates what granularity of table that we are currently iterating over.
 366   // We start iterating over the sparse table, progress to the fine grain
 367   // table, and then finish with the coarse table.
 368   enum IterState {
 369     Sparse,
 370     Fine,
 371     Coarse
 372   };
 373   IterState _is;
 374 
 375   // For both Coarse and Fine remembered set iteration this contains the
 376   // first card number of the heap region we currently iterate over.
 377   size_t _cur_region_card_offset;
 378 
 379   // Current region index for the Coarse remembered set iteration.
 380   int    _coarse_cur_region_index;
 381   size_t _coarse_cur_region_cur_card;
 382 
 383   bool coarse_has_next(size_t& card_index);
 384 
 385   // The PRT we are currently iterating over.
 386   PerRegionTable* _fine_cur_prt;
 387   // Card offset within the current PRT.
 388   size_t _cur_card_in_prt;
 389 
 390   // Update internal variables when switching to the given PRT.
 391   void switch_to_prt(PerRegionTable* prt);
 392   bool fine_has_next();
 393   bool fine_has_next(size_t& card_index);
 394 
 395   // The Sparse remembered set iterator.
 396   SparsePRTIter _sparse_iter;
 397 
 398 public:
 399   HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
 400 
 401   // If there remains one or more cards to be yielded, returns true and
 402   // sets "card_index" to one of those cards (which is then considered
 403   // yielded.)   Otherwise, returns false (and leaves "card_index"
 404   // undefined.)
 405   bool has_next(size_t& card_index);
 406 
 407   size_t n_yielded_fine() { return _n_yielded_fine; }
 408   size_t n_yielded_coarse() { return _n_yielded_coarse; }
 409   size_t n_yielded_sparse() { return _n_yielded_sparse; }
 410   size_t n_yielded() {
 411     return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
 412   }
 413 };
 414 
 415 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP