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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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP
  27 
  28 #include "gc_implementation/g1/sparsePRT.hpp"
  29 
  30 // Remembered set for a heap region.  Represent a set of "cards" that
  31 // contain pointers into the owner heap region.  Cards are defined somewhat
  32 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
  33 
  34 class G1CollectedHeap;
  35 class G1BlockOffsetSharedArray;
  36 class HeapRegion;
  37 class HeapRegionRemSetIterator;
  38 class PerRegionTable;
  39 class SparsePRT;
  40 
  41 // Essentially a wrapper around SparsePRTCleanupTask. See
  42 // sparsePRT.hpp for more details.
  43 class HRRSCleanupTask : public SparsePRTCleanupTask {
  44 };
  45 
  46 // The "_coarse_map" is a bitmap with one bit for each region, where set
  47 // bits indicate that the corresponding region may contain some pointer
  48 // into the owning region.
  49 
  50 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
  51 // (PRTs), indicating regions for which we're keeping the RS as a set of
  52 // cards.  The strategy is to cap the size of the fine-grain table,
  53 // deleting an entry and setting the corresponding coarse-grained bit when
  54 // we would overflow this cap.
  55 
  56 // We use a mixture of locking and lock-free techniques here.  We allow
  57 // threads to locate PRTs without locking, but threads attempting to alter
  58 // a bucket list obtain a lock.  This means that any failing attempt to
  59 // find a PRT must be retried with the lock.  It might seem dangerous that
  60 // a read can find a PRT that is concurrently deleted.  This is all right,
  61 // because:
  62 //
  63 //   1) We only actually free PRT's at safe points (though we reuse them at
  64 //      other times).
  65 //   2) We find PRT's in an attempt to add entries.  If a PRT is deleted,
  66 //      it's _coarse_map bit is set, so the that we were attempting to add
  67 //      is represented.  If a deleted PRT is re-used, a thread adding a bit,
  68 //      thinking the PRT is for a different region, does no harm.
  69 
  70 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
  71   friend class HeapRegionRemSetIterator;
  72 
  73   G1CollectedHeap* _g1h;
  74   Mutex            _m;
  75   HeapRegion*      _hr;
  76 
  77   // These are protected by "_m".
  78   BitMap      _coarse_map;
  79   size_t      _n_coarse_entries;
  80   static jint _n_coarsenings;
  81 
  82   PerRegionTable** _fine_grain_regions;
  83   size_t           _n_fine_entries;
  84 
  85   // The fine grain remembered sets are doubly linked together using
  86   // their 'next' and 'prev' fields.
  87   // This allows fast bulk freeing of all the fine grain remembered
  88   // set entries, and fast finding of all of them without iterating
  89   // over the _fine_grain_regions table.
  90   PerRegionTable * _first_all_fine_prts;
  91   PerRegionTable * _last_all_fine_prts;
  92 
  93   // Used to sample a subset of the fine grain PRTs to determine which
  94   // PRT to evict and coarsen.
  95   size_t        _fine_eviction_start;
  96   static size_t _fine_eviction_stride;
  97   static size_t _fine_eviction_sample_size;
  98 
  99   SparsePRT   _sparse_table;
 100 
 101   // These are static after init.
 102   static size_t _max_fine_entries;
 103   static size_t _mod_max_fine_entries_mask;
 104 
 105   // Requires "prt" to be the first element of the bucket list appropriate
 106   // for "hr".  If this list contains an entry for "hr", return it,
 107   // otherwise return "NULL".
 108   PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
 109 
 110   // Find, delete, and return a candidate PerRegionTable, if any exists,
 111   // adding the deleted region to the coarse bitmap.  Requires the caller
 112   // to hold _m, and the fine-grain table to be full.
 113   PerRegionTable* delete_region_table();
 114 
 115   // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
 116   // be the correct index for "hr"), delete it and return true; else return
 117   // false.
 118   bool del_single_region_table(size_t ind, HeapRegion* hr);
 119 
 120   // Indexed by thread X heap region, to minimize thread contention.
 121   static int** _from_card_cache;
 122   static size_t _from_card_cache_max_regions;
 123   static size_t _from_card_cache_mem_size;
 124 
 125   // link/add the given fine grain remembered set into the "all" list
 126   void link_to_all(PerRegionTable * prt);
 127   // unlink/remove the given fine grain remembered set into the "all" list
 128   void unlink_from_all(PerRegionTable * prt);
 129 
 130 public:
 131   OtherRegionsTable(HeapRegion* hr);
 132 
 133   HeapRegion* hr() const { return _hr; }
 134 
 135   // For now.  Could "expand" some tables in the future, so that this made
 136   // sense.
 137   void add_reference(OopOrNarrowOopStar from, int tid);
 138 
 139   // Removes any entries shown by the given bitmaps to contain only dead
 140   // objects.
 141   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 142 
 143   // Not const because it takes a lock.
 144   size_t occupied() const;
 145   size_t occ_fine() const;
 146   size_t occ_coarse() const;
 147   size_t occ_sparse() const;
 148 
 149   static jint n_coarsenings() { return _n_coarsenings; }
 150 
 151   // Returns size in bytes.
 152   // Not const because it takes a lock.
 153   size_t mem_size() const;
 154   static size_t static_mem_size();
 155   static size_t fl_mem_size();
 156 
 157   bool contains_reference(OopOrNarrowOopStar from) const;
 158   bool contains_reference_locked(OopOrNarrowOopStar from) const;
 159 
 160   void clear();
 161 
 162   // Specifically clear the from_card_cache.
 163   void clear_fcc();
 164 
 165   // "from_hr" is being cleared; remove any entries from it.
 166   void clear_incoming_entry(HeapRegion* from_hr);
 167 
 168   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 169 
 170   // Declare the heap size (in # of regions) to the OtherRegionsTable.
 171   // (Uses it to initialize from_card_cache).
 172   static void init_from_card_cache(size_t max_regions);
 173 
 174   // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
 175   // Make sure any entries for higher regions are invalid.
 176   static void shrink_from_card_cache(size_t new_n_regs);
 177 
 178   static void print_from_card_cache();
 179 };
 180 
 181 class HeapRegionRemSet : public CHeapObj<mtGC> {
 182   friend class VMStructs;
 183   friend class HeapRegionRemSetIterator;
 184 
 185 public:
 186   enum Event {
 187     Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
 188   };
 189 
 190 private:
 191   G1BlockOffsetSharedArray* _bosa;
 192   G1BlockOffsetSharedArray* bosa() const { return _bosa; }
 193 
 194   OtherRegionsTable _other_regions;
 195 
 196   enum ParIterState { Unclaimed, Claimed, Complete };
 197   volatile ParIterState _iter_state;
 198   volatile jlong _iter_claimed;
 199 
 200   // Unused unless G1RecordHRRSOops is true.
 201 
 202   static const int MaxRecorded = 1000000;
 203   static OopOrNarrowOopStar* _recorded_oops;
 204   static HeapWord**          _recorded_cards;
 205   static HeapRegion**        _recorded_regions;
 206   static int                 _n_recorded;
 207 
 208   static const int MaxRecordedEvents = 1000;
 209   static Event*       _recorded_events;
 210   static int*         _recorded_event_index;
 211   static int          _n_recorded_events;
 212 
 213   static void print_event(outputStream* str, Event evnt);
 214 
 215 public:
 216   HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
 217                    HeapRegion* hr);
 218 
 219   static int num_par_rem_sets();
 220   static void setup_remset_size();
 221 
 222   HeapRegion* hr() const {
 223     return _other_regions.hr();
 224   }
 225 
 226   size_t occupied() const {
 227     return _other_regions.occupied();
 228   }
 229   size_t occ_fine() const {
 230     return _other_regions.occ_fine();
 231   }
 232   size_t occ_coarse() const {
 233     return _other_regions.occ_coarse();
 234   }
 235   size_t occ_sparse() const {
 236     return _other_regions.occ_sparse();
 237   }
 238 
 239   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 240 
 241   // Used in the sequential case.
 242   void add_reference(OopOrNarrowOopStar from) {
 243     _other_regions.add_reference(from, 0);
 244   }
 245 
 246   // Used in the parallel case.
 247   void add_reference(OopOrNarrowOopStar from, int tid) {
 248     _other_regions.add_reference(from, tid);
 249   }
 250 
 251   // Removes any entries shown by the given bitmaps to contain only dead
 252   // objects.
 253   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 254 
 255   // The region is being reclaimed; clear its remset, and any mention of
 256   // entries for this region in other remsets.
 257   void clear();
 258 
 259   // Attempt to claim the region.  Returns true iff this call caused an
 260   // atomic transition from Unclaimed to Claimed.
 261   bool claim_iter();
 262   // Sets the iteration state to "complete".
 263   void set_iter_complete();
 264   // Returns "true" iff the region's iteration is complete.
 265   bool iter_is_complete();
 266 
 267   // Support for claiming blocks of cards during iteration
 268   size_t iter_claimed() const { return (size_t)_iter_claimed; }
 269   // Claim the next block of cards
 270   size_t iter_claimed_next(size_t step) {
 271     size_t current, next;
 272     do {
 273       current = iter_claimed();
 274       next = current + step;
 275     } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
 276     return current;
 277   }
 278   void reset_for_par_iteration();
 279 
 280   bool verify_ready_for_par_iteration() {
 281     return (_iter_state == Unclaimed) && (_iter_claimed == 0);
 282   }
 283 
 284   // The actual # of bytes this hr_remset takes up.
 285   size_t mem_size() {
 286     return _other_regions.mem_size()
 287       // This correction is necessary because the above includes the second
 288       // part.
 289       + sizeof(this) - sizeof(OtherRegionsTable);
 290   }
 291 
 292   // Returns the memory occupancy of all static data structures associated
 293   // with remembered sets.
 294   static size_t static_mem_size() {
 295     return OtherRegionsTable::static_mem_size();
 296   }
 297 
 298   // Returns the memory occupancy of all free_list data structures associated
 299   // with remembered sets.
 300   static size_t fl_mem_size() {
 301     return OtherRegionsTable::fl_mem_size();
 302   }
 303 
 304   bool contains_reference(OopOrNarrowOopStar from) const {
 305     return _other_regions.contains_reference(from);
 306   }
 307   void print() const;
 308 
 309   // Called during a stop-world phase to perform any deferred cleanups.
 310   static void cleanup();
 311 
 312   // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
 313   // (Uses it to initialize from_card_cache).
 314   static void init_heap(uint max_regions) {
 315     OtherRegionsTable::init_from_card_cache((size_t) max_regions);
 316   }
 317 
 318   // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
 319   static void shrink_heap(uint new_n_regs) {
 320     OtherRegionsTable::shrink_from_card_cache((size_t) new_n_regs);
 321   }
 322 
 323 #ifndef PRODUCT
 324   static void print_from_card_cache() {
 325     OtherRegionsTable::print_from_card_cache();
 326   }
 327 #endif
 328 
 329   static void record(HeapRegion* hr, OopOrNarrowOopStar f);
 330   static void print_recorded();
 331   static void record_event(Event evnt);
 332 
 333   // These are wrappers for the similarly-named methods on
 334   // SparsePRT. Look at sparsePRT.hpp for more details.
 335   static void reset_for_cleanup_tasks();
 336   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 337   static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
 338 
 339   // Run unit tests.
 340 #ifndef PRODUCT
 341   static void test_prt();
 342   static void test();
 343 #endif
 344 };
 345 
 346 class HeapRegionRemSetIterator : public StackObj {
 347 
 348   // The region RSet over which we're iterating.
 349   const HeapRegionRemSet* _hrrs;
 350 
 351   // Local caching of HRRS fields.
 352   const BitMap*             _coarse_map;
 353   PerRegionTable**          _fine_grain_regions;
 354 
 355   G1BlockOffsetSharedArray* _bosa;
 356   G1CollectedHeap*          _g1h;
 357 
 358   // The number yielded since initialization.
 359   size_t _n_yielded_fine;
 360   size_t _n_yielded_coarse;
 361   size_t _n_yielded_sparse;
 362 
 363   // Indicates what granularity of table that we're currently iterating over.
 364   // We start iterating over the sparse table, progress to the fine grain
 365   // table, and then finish with the coarse table.
 366   // See HeapRegionRemSetIterator::has_next().
 367   enum IterState {
 368     Sparse,
 369     Fine,
 370     Coarse
 371   };
 372   IterState _is;
 373 
 374   // In both kinds of iteration, heap offset of first card of current
 375   // region.
 376   size_t _cur_region_card_offset;
 377   // Card offset within cur region.
 378   size_t _cur_region_cur_card;
 379 
 380   // Coarse table iteration fields:
 381 
 382   // Current region index;
 383   int    _coarse_cur_region_index;
 384   size_t _coarse_cur_region_cur_card;
 385 
 386   bool coarse_has_next(size_t& card_index);
 387 
 388   // Fine table iteration fields:
 389 
 390   // Index of bucket-list we're working on.
 391   int _fine_array_index;
 392 
 393   // Per Region Table we're doing within current bucket list.
 394   PerRegionTable* _fine_cur_prt;
 395 
 396   /* SparsePRT::*/ SparsePRTIter _sparse_iter;
 397 
 398   void fine_find_next_non_null_prt();
 399 
 400   bool fine_has_next();
 401   bool fine_has_next(size_t& card_index);
 402 
 403 public:
 404   // We require an iterator to be initialized before use, so the
 405   // constructor does little.
 406   HeapRegionRemSetIterator(const HeapRegionRemSet* hrrs);
 407 
 408   // If there remains one or more cards to be yielded, returns true and
 409   // sets "card_index" to one of those cards (which is then considered
 410   // yielded.)   Otherwise, returns false (and leaves "card_index"
 411   // undefined.)
 412   bool has_next(size_t& card_index);
 413 
 414   size_t n_yielded_fine() { return _n_yielded_fine; }
 415   size_t n_yielded_coarse() { return _n_yielded_coarse; }
 416   size_t n_yielded_sparse() { return _n_yielded_sparse; }
 417   size_t n_yielded() {
 418     return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
 419   }
 420 };
 421 
 422 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP