1 /*
   2  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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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 PosParPRT;
  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   PosParPRT** _fine_grain_regions;
  83   size_t      _n_fine_entries;
  84 
  85 #define SAMPLE_FOR_EVICTION 1
  86 #if SAMPLE_FOR_EVICTION
  87   size_t        _fine_eviction_start;
  88   static size_t _fine_eviction_stride;
  89   static size_t _fine_eviction_sample_size;
  90 #endif
  91 
  92   SparsePRT   _sparse_table;
  93 
  94   // These are static after init.
  95   static size_t _max_fine_entries;
  96   static size_t _mod_max_fine_entries_mask;
  97 
  98   // Requires "prt" to be the first element of the bucket list appropriate
  99   // for "hr".  If this list contains an entry for "hr", return it,
 100   // otherwise return "NULL".
 101   PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const;
 102 
 103   // Find, delete, and return a candidate PosParPRT, if any exists,
 104   // adding the deleted region to the coarse bitmap.  Requires the caller
 105   // to hold _m, and the fine-grain table to be full.
 106   PosParPRT* delete_region_table();
 107 
 108   // If a PRT for "hr" is in the bucket list indicated by "ind" (which must
 109   // be the correct index for "hr"), delete it and return true; else return
 110   // false.
 111   bool del_single_region_table(size_t ind, HeapRegion* hr);
 112 
 113   static jint _cache_probes;
 114   static jint _cache_hits;
 115 
 116   // Indexed by thread X heap region, to minimize thread contention.
 117   static int** _from_card_cache;
 118   static size_t _from_card_cache_max_regions;
 119   static size_t _from_card_cache_mem_size;
 120 
 121 public:
 122   OtherRegionsTable(HeapRegion* hr);
 123 
 124   HeapRegion* hr() const { return _hr; }
 125 
 126   // For now.  Could "expand" some tables in the future, so that this made
 127   // sense.
 128   void add_reference(OopOrNarrowOopStar from, int tid);
 129 
 130   void add_reference(OopOrNarrowOopStar from) {
 131     return add_reference(from, 0);
 132   }
 133 
 134   // Removes any entries shown by the given bitmaps to contain only dead
 135   // objects.
 136   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 137 
 138   // Not const because it takes a lock.
 139   size_t occupied() const;
 140   size_t occ_fine() const;
 141   size_t occ_coarse() const;
 142   size_t occ_sparse() const;
 143 
 144   static jint n_coarsenings() { return _n_coarsenings; }
 145 
 146   // Returns size in bytes.
 147   // Not const because it takes a lock.
 148   size_t mem_size() const;
 149   static size_t static_mem_size();
 150   static size_t fl_mem_size();
 151 
 152   bool contains_reference(OopOrNarrowOopStar from) const;
 153   bool contains_reference_locked(OopOrNarrowOopStar from) const;
 154 
 155   void clear();
 156 
 157   // Specifically clear the from_card_cache.
 158   void clear_fcc();
 159 
 160   // "from_hr" is being cleared; remove any entries from it.
 161   void clear_incoming_entry(HeapRegion* from_hr);
 162 
 163   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 164 
 165   // Declare the heap size (in # of regions) to the OtherRegionsTable.
 166   // (Uses it to initialize from_card_cache).
 167   static void init_from_card_cache(size_t max_regions);
 168 
 169   // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
 170   // Make sure any entries for higher regions are invalid.
 171   static void shrink_from_card_cache(size_t new_n_regs);
 172 
 173   static void print_from_card_cache();
 174 };
 175 
 176 class HeapRegionRemSet : public CHeapObj {
 177   friend class VMStructs;
 178   friend class HeapRegionRemSetIterator;
 179 
 180 public:
 181   enum Event {
 182     Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd
 183   };
 184 
 185 private:
 186   G1BlockOffsetSharedArray* _bosa;
 187   G1BlockOffsetSharedArray* bosa() const { return _bosa; }
 188 
 189   OtherRegionsTable _other_regions;
 190 
 191   enum ParIterState { Unclaimed, Claimed, Complete };
 192   volatile ParIterState _iter_state;
 193   volatile jlong _iter_claimed;
 194 
 195   // Unused unless G1RecordHRRSOops is true.
 196 
 197   static const int MaxRecorded = 1000000;
 198   static OopOrNarrowOopStar* _recorded_oops;
 199   static HeapWord**          _recorded_cards;
 200   static HeapRegion**        _recorded_regions;
 201   static int                 _n_recorded;
 202 
 203   static const int MaxRecordedEvents = 1000;
 204   static Event*       _recorded_events;
 205   static int*         _recorded_event_index;
 206   static int          _n_recorded_events;
 207 
 208   static void print_event(outputStream* str, Event evnt);
 209 
 210 public:
 211   HeapRegionRemSet(G1BlockOffsetSharedArray* bosa,
 212                    HeapRegion* hr);
 213 
 214   static int num_par_rem_sets();
 215   static void setup_remset_size();
 216 
 217   HeapRegion* hr() const {
 218     return _other_regions.hr();
 219   }
 220 
 221   size_t occupied() const {
 222     return _other_regions.occupied();
 223   }
 224   size_t occ_fine() const {
 225     return _other_regions.occ_fine();
 226   }
 227   size_t occ_coarse() const {
 228     return _other_regions.occ_coarse();
 229   }
 230   size_t occ_sparse() const {
 231     return _other_regions.occ_sparse();
 232   }
 233 
 234   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 235 
 236   /* Used in the sequential case.  Returns "true" iff this addition causes
 237      the size limit to be reached. */
 238   void add_reference(OopOrNarrowOopStar from) {
 239     _other_regions.add_reference(from);
 240   }
 241 
 242   /* Used in the parallel case.  Returns "true" iff this addition causes
 243      the size limit to be reached. */
 244   void add_reference(OopOrNarrowOopStar from, int tid) {
 245     _other_regions.add_reference(from, tid);
 246   }
 247 
 248   // Removes any entries shown by the given bitmaps to contain only dead
 249   // objects.
 250   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 251 
 252   // The region is being reclaimed; clear its remset, and any mention of
 253   // entries for this region in other remsets.
 254   void clear();
 255 
 256   // Forget any entries due to pointers from "from_hr".
 257   void clear_incoming_entry(HeapRegion* from_hr) {
 258     _other_regions.clear_incoming_entry(from_hr);
 259   }
 260 
 261 #if 0
 262   virtual void cleanup() = 0;
 263 #endif
 264 
 265   // Attempt to claim the region.  Returns true iff this call caused an
 266   // atomic transition from Unclaimed to Claimed.
 267   bool claim_iter();
 268   // Sets the iteration state to "complete".
 269   void set_iter_complete();
 270   // Returns "true" iff the region's iteration is complete.
 271   bool iter_is_complete();
 272 
 273   // Support for claiming blocks of cards during iteration
 274   size_t iter_claimed() const { return (size_t)_iter_claimed; }
 275   // Claim the next block of cards
 276   size_t iter_claimed_next(size_t step) {
 277     size_t current, next;
 278     do {
 279       current = iter_claimed();
 280       next = current + step;
 281     } while (Atomic::cmpxchg((jlong)next, &_iter_claimed, (jlong)current) != (jlong)current);
 282     return current;
 283   }
 284   void reset_for_par_iteration();
 285 
 286   bool verify_ready_for_par_iteration() {
 287     return (_iter_state == Unclaimed) && (_iter_claimed == 0);
 288   }
 289 
 290   // Initialize the given iterator to iterate over this rem set.
 291   void init_iterator(HeapRegionRemSetIterator* iter) const;
 292 
 293 #if 0
 294   // Apply the "do_card" method to the start address of every card in the
 295   // rem set.  Returns false if some application of the closure aborted.
 296   virtual bool card_iterate(CardClosure* iter) = 0;
 297 #endif
 298 
 299   // The actual # of bytes this hr_remset takes up.
 300   size_t mem_size() {
 301     return _other_regions.mem_size()
 302       // This correction is necessary because the above includes the second
 303       // part.
 304       + sizeof(this) - sizeof(OtherRegionsTable);
 305   }
 306 
 307   // Returns the memory occupancy of all static data structures associated
 308   // with remembered sets.
 309   static size_t static_mem_size() {
 310     return OtherRegionsTable::static_mem_size();
 311   }
 312 
 313   // Returns the memory occupancy of all free_list data structures associated
 314   // with remembered sets.
 315   static size_t fl_mem_size() {
 316     return OtherRegionsTable::fl_mem_size();
 317   }
 318 
 319   bool contains_reference(OopOrNarrowOopStar from) const {
 320     return _other_regions.contains_reference(from);
 321   }
 322   void print() const;
 323 
 324   // Called during a stop-world phase to perform any deferred cleanups.
 325   // The second version may be called by parallel threads after then finish
 326   // collection work.
 327   static void cleanup();
 328   static void par_cleanup();
 329 
 330   // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
 331   // (Uses it to initialize from_card_cache).
 332   static void init_heap(size_t max_regions) {
 333     OtherRegionsTable::init_from_card_cache(max_regions);
 334   }
 335 
 336   // Declares that only regions i s.t. 0 <= i < new_n_regs are in use.
 337   static void shrink_heap(size_t new_n_regs) {
 338     OtherRegionsTable::shrink_from_card_cache(new_n_regs);
 339   }
 340 
 341 #ifndef PRODUCT
 342   static void print_from_card_cache() {
 343     OtherRegionsTable::print_from_card_cache();
 344   }
 345 #endif
 346 
 347   static void record(HeapRegion* hr, OopOrNarrowOopStar f);
 348   static void print_recorded();
 349   static void record_event(Event evnt);
 350 
 351   // These are wrappers for the similarly-named methods on
 352   // SparsePRT. Look at sparsePRT.hpp for more details.
 353   static void reset_for_cleanup_tasks();
 354   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 355   static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
 356 
 357   // Run unit tests.
 358 #ifndef PRODUCT
 359   static void test();
 360 #endif
 361 };
 362 
 363 class HeapRegionRemSetIterator : public CHeapObj {
 364 
 365   // The region over which we're iterating.
 366   const HeapRegionRemSet* _hrrs;
 367 
 368   // Local caching of HRRS fields.
 369   const BitMap*             _coarse_map;
 370   PosParPRT**               _fine_grain_regions;
 371 
 372   G1BlockOffsetSharedArray* _bosa;
 373   G1CollectedHeap*          _g1h;
 374 
 375   // The number yielded since initialization.
 376   size_t _n_yielded_fine;
 377   size_t _n_yielded_coarse;
 378   size_t _n_yielded_sparse;
 379 
 380   // If true we're iterating over the coarse table; if false the fine
 381   // table.
 382   enum IterState {
 383     Sparse,
 384     Fine,
 385     Coarse
 386   };
 387   IterState _is;
 388 
 389   // In both kinds of iteration, heap offset of first card of current
 390   // region.
 391   size_t _cur_region_card_offset;
 392   // Card offset within cur region.
 393   size_t _cur_region_cur_card;
 394 
 395   // Coarse table iteration fields:
 396 
 397   // Current region index;
 398   int    _coarse_cur_region_index;
 399   size_t _coarse_cur_region_cur_card;
 400 
 401   bool coarse_has_next(size_t& card_index);
 402 
 403   // Fine table iteration fields:
 404 
 405   // Index of bucket-list we're working on.
 406   int _fine_array_index;
 407   // Per Region Table we're doing within current bucket list.
 408   PosParPRT* _fine_cur_prt;
 409 
 410   /* SparsePRT::*/ SparsePRTIter _sparse_iter;
 411 
 412   void fine_find_next_non_null_prt();
 413 
 414   bool fine_has_next();
 415   bool fine_has_next(size_t& card_index);
 416 
 417 public:
 418   // We require an iterator to be initialized before use, so the
 419   // constructor does little.
 420   HeapRegionRemSetIterator();
 421 
 422   void initialize(const HeapRegionRemSet* hrrs);
 423 
 424   // If there remains one or more cards to be yielded, returns true and
 425   // sets "card_index" to one of those cards (which is then considered
 426   // yielded.)   Otherwise, returns false (and leaves "card_index"
 427   // undefined.)
 428   bool has_next(size_t& card_index);
 429 
 430   size_t n_yielded_fine() { return _n_yielded_fine; }
 431   size_t n_yielded_coarse() { return _n_yielded_coarse; }
 432   size_t n_yielded_sparse() { return _n_yielded_sparse; }
 433   size_t n_yielded() {
 434     return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
 435   }
 436 };
 437 
 438 #if 0
 439 class CardClosure: public Closure {
 440 public:
 441   virtual void do_card(HeapWord* card_start) = 0;
 442 };
 443 
 444 #endif
 445 
 446 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONREMSET_HPP