1 /*
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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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  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/sparsePRT.hpp"
  30 
  31 // Remembered set for a heap region.  Represent a set of "cards" that
  32 // contain pointers into the owner heap region.  Cards are defined somewhat
  33 // abstractly, in terms of what the "BlockOffsetTable" in use can parse.
  34 
  35 class G1CollectedHeap;
  36 class G1BlockOffsetSharedArray;
  37 class HeapRegion;
  38 class HeapRegionRemSetIterator;
  39 class PerRegionTable;
  40 class SparsePRT;
  41 class nmethod;
  42 
  43 // Essentially a wrapper around SparsePRTCleanupTask. See
  44 // sparsePRT.hpp for more details.
  45 class HRRSCleanupTask : public SparsePRTCleanupTask {
  46 };
  47 
  48 // The FromCardCache remembers the most recently processed card on the heap on
  49 // a per-region and per-thread basis.
  50 class FromCardCache : public AllStatic {
  51  private:
  52   // Array of card indices. Indexed by thread X and heap region to minimize
  53   // thread contention.
  54   static int** _cache;
  55   static uint _max_regions;
  56   static size_t _static_mem_size;
  57 
  58  public:
  59   enum {
  60     InvalidCard = -1 // Card value of an invalid card, i.e. a card index not otherwise used.
  61   };
  62 
  63   static void clear(uint region_idx);
  64 
  65   // Returns true if the given card is in the cache at the given location, or
  66   // replaces the card at that location and returns false.
  67   static bool contains_or_replace(uint worker_id, uint region_idx, int card) {
  68     int card_in_cache = at(worker_id, region_idx);
  69     if (card_in_cache == card) {
  70       return true;
  71     } else {
  72       set(worker_id, region_idx, card);
  73       return false;
  74     }
  75   }
  76 
  77   static int at(uint worker_id, uint region_idx) {
  78     return _cache[worker_id][region_idx];
  79   }
  80 
  81   static void set(uint worker_id, uint region_idx, int val) {
  82     _cache[worker_id][region_idx] = val;
  83   }
  84 
  85   static void initialize(uint n_par_rs, uint max_num_regions);
  86 
  87   static void invalidate(uint start_idx, size_t num_regions);
  88 
  89   static void print(outputStream* out = gclog_or_tty) PRODUCT_RETURN;
  90 
  91   static size_t static_mem_size() {
  92     return _static_mem_size;
  93   }
  94 };
  95 
  96 // The "_coarse_map" is a bitmap with one bit for each region, where set
  97 // bits indicate that the corresponding region may contain some pointer
  98 // into the owning region.
  99 
 100 // The "_fine_grain_entries" array is an open hash table of PerRegionTables
 101 // (PRTs), indicating regions for which we're keeping the RS as a set of
 102 // cards.  The strategy is to cap the size of the fine-grain table,
 103 // deleting an entry and setting the corresponding coarse-grained bit when
 104 // we would overflow this cap.
 105 
 106 // We use a mixture of locking and lock-free techniques here.  We allow
 107 // threads to locate PRTs without locking, but threads attempting to alter
 108 // a bucket list obtain a lock.  This means that any failing attempt to
 109 // find a PRT must be retried with the lock.  It might seem dangerous that
 110 // a read can find a PRT that is concurrently deleted.  This is all right,
 111 // because:
 112 //
 113 //   1) We only actually free PRT's at safe points (though we reuse them at
 114 //      other times).
 115 //   2) We find PRT's in an attempt to add entries.  If a PRT is deleted,
 116 //      it's _coarse_map bit is set, so the that we were attempting to add
 117 //      is represented.  If a deleted PRT is re-used, a thread adding a bit,
 118 //      thinking the PRT is for a different region, does no harm.
 119 
 120 class OtherRegionsTable VALUE_OBJ_CLASS_SPEC {
 121   friend class HeapRegionRemSetIterator;
 122 
 123   G1CollectedHeap* _g1h;
 124   Mutex*           _m;
 125   HeapRegion*      _hr;
 126 
 127   // These are protected by "_m".
 128   BitMap      _coarse_map;
 129   size_t      _n_coarse_entries;
 130   static jint _n_coarsenings;
 131 
 132   PerRegionTable** _fine_grain_regions;
 133   size_t           _n_fine_entries;
 134 
 135   // The fine grain remembered sets are doubly linked together using
 136   // their 'next' and 'prev' fields.
 137   // This allows fast bulk freeing of all the fine grain remembered
 138   // set entries, and fast finding of all of them without iterating
 139   // over the _fine_grain_regions table.
 140   PerRegionTable * _first_all_fine_prts;
 141   PerRegionTable * _last_all_fine_prts;
 142 
 143   // Used to sample a subset of the fine grain PRTs to determine which
 144   // PRT to evict and coarsen.
 145   size_t        _fine_eviction_start;
 146   static size_t _fine_eviction_stride;
 147   static size_t _fine_eviction_sample_size;
 148 
 149   SparsePRT   _sparse_table;
 150 
 151   // These are static after init.
 152   static size_t _max_fine_entries;
 153   static size_t _mod_max_fine_entries_mask;
 154 
 155   // Requires "prt" to be the first element of the bucket list appropriate
 156   // for "hr".  If this list contains an entry for "hr", return it,
 157   // otherwise return "NULL".
 158   PerRegionTable* find_region_table(size_t ind, HeapRegion* hr) const;
 159 
 160   // Find, delete, and return a candidate PerRegionTable, if any exists,
 161   // adding the deleted region to the coarse bitmap.  Requires the caller
 162   // to hold _m, and the fine-grain table to be full.
 163   PerRegionTable* delete_region_table();
 164 
 165   // link/add the given fine grain remembered set into the "all" list
 166   void link_to_all(PerRegionTable * prt);
 167   // unlink/remove the given fine grain remembered set into the "all" list
 168   void unlink_from_all(PerRegionTable * prt);
 169 
 170   bool contains_reference_locked(OopOrNarrowOopStar from) const;
 171 
 172   // Clear the from_card_cache entries for this region.
 173   void clear_fcc();
 174 public:
 175   // Create a new remembered set for the given heap region. The given mutex should
 176   // be used to ensure consistency.
 177   OtherRegionsTable(HeapRegion* hr, Mutex* m);
 178 
 179   // For now.  Could "expand" some tables in the future, so that this made
 180   // sense.
 181   void add_reference(OopOrNarrowOopStar from, uint tid);
 182 
 183   // Returns whether the remembered set contains the given reference.
 184   bool contains_reference(OopOrNarrowOopStar from) const;
 185 
 186   // Returns whether this remembered set (and all sub-sets) have an occupancy
 187   // that is less or equal than the given occupancy.
 188   bool occupancy_less_or_equal_than(size_t limit) const;
 189 
 190   // Removes any entries shown by the given bitmaps to contain only dead
 191   // objects. Not thread safe.
 192   // Set bits in the bitmaps indicate that the given region or card is live.
 193   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 194 
 195   // Returns whether this remembered set (and all sub-sets) does not contain any entry.
 196   bool is_empty() const;
 197 
 198   // Returns the number of cards contained in this remembered set.
 199   size_t occupied() const;
 200   size_t occ_fine() const;
 201   size_t occ_coarse() const;
 202   size_t occ_sparse() const;
 203 
 204   static jint n_coarsenings() { return _n_coarsenings; }
 205 
 206   // Returns size of the actual remembered set containers in bytes.
 207   size_t mem_size() const;
 208   // Returns the size of static data in bytes.
 209   static size_t static_mem_size();
 210   // Returns the size of the free list content in bytes.
 211   static size_t fl_mem_size();
 212 
 213   // Clear the entire contents of this remembered set.
 214   void clear();
 215 
 216   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 217 };
 218 
 219 class HeapRegionRemSet : public CHeapObj<mtGC> {
 220   friend class VMStructs;
 221   friend class HeapRegionRemSetIterator;
 222 
 223 private:
 224   G1BlockOffsetSharedArray* _bosa;
 225 
 226   // A set of code blobs (nmethods) whose code contains pointers into
 227   // the region that owns this RSet.
 228   G1CodeRootSet _code_roots;
 229 
 230   Mutex _m;
 231 
 232   OtherRegionsTable _other_regions;
 233 
 234   enum ParIterState { Unclaimed, Claimed, Complete };
 235   volatile ParIterState _iter_state;
 236   volatile size_t _iter_claimed;
 237 
 238 public:
 239   HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr);
 240 
 241   static uint num_par_rem_sets();
 242   static void setup_remset_size();
 243 
 244   bool is_empty() const {
 245     return (strong_code_roots_list_length() == 0) && _other_regions.is_empty();
 246   }
 247 
 248   bool occupancy_less_or_equal_than(size_t occ) const {
 249     return (strong_code_roots_list_length() == 0) && _other_regions.occupancy_less_or_equal_than(occ);
 250   }
 251 
 252   size_t occupied() {
 253     MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
 254     return occupied_locked();
 255   }
 256   size_t occupied_locked() {
 257     return _other_regions.occupied();
 258   }
 259   size_t occ_fine() const {
 260     return _other_regions.occ_fine();
 261   }
 262   size_t occ_coarse() const {
 263     return _other_regions.occ_coarse();
 264   }
 265   size_t occ_sparse() const {
 266     return _other_regions.occ_sparse();
 267   }
 268 
 269   static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); }
 270 
 271   // Used in the sequential case.
 272   void add_reference(OopOrNarrowOopStar from) {
 273     _other_regions.add_reference(from, 0);
 274   }
 275 
 276   // Used in the parallel case.
 277   void add_reference(OopOrNarrowOopStar from, uint tid) {
 278     _other_regions.add_reference(from, tid);
 279   }
 280 
 281   // Removes any entries in the remembered set shown by the given bitmaps to
 282   // contain only dead objects. Not thread safe.
 283   // One bits in the bitmaps indicate that the given region or card is live.
 284   void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm);
 285 
 286   // The region is being reclaimed; clear its remset, and any mention of
 287   // entries for this region in other remsets.
 288   void clear();
 289   void clear_locked();
 290 
 291   // Attempt to claim the region.  Returns true iff this call caused an
 292   // atomic transition from Unclaimed to Claimed.
 293   bool claim_iter();
 294   // Sets the iteration state to "complete".
 295   void set_iter_complete();
 296   // Returns "true" iff the region's iteration is complete.
 297   bool iter_is_complete();
 298 
 299   // Support for claiming blocks of cards during iteration
 300   size_t iter_claimed() const { return _iter_claimed; }
 301   // Claim the next block of cards
 302   size_t iter_claimed_next(size_t step) {
 303     return Atomic::add(step, &_iter_claimed) - step;
 304   }
 305 
 306   void reset_for_par_iteration();
 307 
 308   bool verify_ready_for_par_iteration() {
 309     return (_iter_state == Unclaimed) && (_iter_claimed == 0);
 310   }
 311 
 312   // The actual # of bytes this hr_remset takes up.
 313   // Note also includes the strong code root set.
 314   size_t mem_size() {
 315     MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
 316     return _other_regions.mem_size()
 317       // This correction is necessary because the above includes the second
 318       // part.
 319       + (sizeof(HeapRegionRemSet) - sizeof(OtherRegionsTable))
 320       + strong_code_roots_mem_size();
 321   }
 322 
 323   // Returns the memory occupancy of all static data structures associated
 324   // with remembered sets.
 325   static size_t static_mem_size() {
 326     return OtherRegionsTable::static_mem_size() + G1CodeRootSet::static_mem_size();
 327   }
 328 
 329   // Returns the memory occupancy of all free_list data structures associated
 330   // with remembered sets.
 331   static size_t fl_mem_size() {
 332     return OtherRegionsTable::fl_mem_size();
 333   }
 334 
 335   bool contains_reference(OopOrNarrowOopStar from) const {
 336     return _other_regions.contains_reference(from);
 337   }
 338 
 339   // Routines for managing the list of code roots that point into
 340   // the heap region that owns this RSet.
 341   void add_strong_code_root(nmethod* nm);
 342   void add_strong_code_root_locked(nmethod* nm);
 343   void remove_strong_code_root(nmethod* nm);
 344 
 345   // Applies blk->do_code_blob() to each of the entries in
 346   // the strong code roots list
 347   void strong_code_roots_do(CodeBlobClosure* blk) const;
 348 
 349   void clean_strong_code_roots(HeapRegion* hr);
 350 
 351   // Returns the number of elements in the strong code roots list
 352   size_t strong_code_roots_list_length() const {
 353     return _code_roots.length();
 354   }
 355 
 356   // Returns true if the strong code roots contains the given
 357   // nmethod.
 358   bool strong_code_roots_list_contains(nmethod* nm) {
 359     return _code_roots.contains(nm);
 360   }
 361 
 362   // Returns the amount of memory, in bytes, currently
 363   // consumed by the strong code roots.
 364   size_t strong_code_roots_mem_size();
 365 
 366   void print() PRODUCT_RETURN;
 367 
 368   // Called during a stop-world phase to perform any deferred cleanups.
 369   static void cleanup();
 370 
 371   // Declare the heap size (in # of regions) to the HeapRegionRemSet(s).
 372   // (Uses it to initialize from_card_cache).
 373   static void init_heap(uint max_regions) {
 374     FromCardCache::initialize(num_par_rem_sets(), max_regions);
 375   }
 376 
 377   static void invalidate_from_card_cache(uint start_idx, size_t num_regions) {
 378     FromCardCache::invalidate(start_idx, num_regions);
 379   }
 380 
 381 #ifndef PRODUCT
 382   static void print_from_card_cache() {
 383     FromCardCache::print();
 384   }
 385 #endif
 386 
 387   // These are wrappers for the similarly-named methods on
 388   // SparsePRT. Look at sparsePRT.hpp for more details.
 389   static void reset_for_cleanup_tasks();
 390   void do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task);
 391   static void finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task);
 392 
 393   // Run unit tests.
 394 #ifndef PRODUCT
 395   static void test_prt();
 396   static void test();
 397 #endif
 398 };
 399 
 400 class HeapRegionRemSetIterator : public StackObj {
 401  private:
 402   // The region RSet over which we are iterating.
 403   HeapRegionRemSet* _hrrs;
 404 
 405   // Local caching of HRRS fields.
 406   const BitMap*             _coarse_map;
 407 
 408   G1BlockOffsetSharedArray* _bosa;
 409   G1CollectedHeap*          _g1h;
 410 
 411   // The number of cards yielded since initialization.
 412   size_t _n_yielded_fine;
 413   size_t _n_yielded_coarse;
 414   size_t _n_yielded_sparse;
 415 
 416   // Indicates what granularity of table that we are currently iterating over.
 417   // We start iterating over the sparse table, progress to the fine grain
 418   // table, and then finish with the coarse table.
 419   enum IterState {
 420     Sparse,
 421     Fine,
 422     Coarse
 423   };
 424   IterState _is;
 425 
 426   // For both Coarse and Fine remembered set iteration this contains the
 427   // first card number of the heap region we currently iterate over.
 428   size_t _cur_region_card_offset;
 429 
 430   // Current region index for the Coarse remembered set iteration.
 431   int    _coarse_cur_region_index;
 432   size_t _coarse_cur_region_cur_card;
 433 
 434   bool coarse_has_next(size_t& card_index);
 435 
 436   // The PRT we are currently iterating over.
 437   PerRegionTable* _fine_cur_prt;
 438   // Card offset within the current PRT.
 439   size_t _cur_card_in_prt;
 440 
 441   // Update internal variables when switching to the given PRT.
 442   void switch_to_prt(PerRegionTable* prt);
 443   bool fine_has_next();
 444   bool fine_has_next(size_t& card_index);
 445 
 446   // The Sparse remembered set iterator.
 447   SparsePRTIter _sparse_iter;
 448 
 449  public:
 450   HeapRegionRemSetIterator(HeapRegionRemSet* hrrs);
 451 
 452   // If there remains one or more cards to be yielded, returns true and
 453   // sets "card_index" to one of those cards (which is then considered
 454   // yielded.)   Otherwise, returns false (and leaves "card_index"
 455   // undefined.)
 456   bool has_next(size_t& card_index);
 457 
 458   size_t n_yielded_fine() { return _n_yielded_fine; }
 459   size_t n_yielded_coarse() { return _n_yielded_coarse; }
 460   size_t n_yielded_sparse() { return _n_yielded_sparse; }
 461   size_t n_yielded() {
 462     return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse();
 463   }
 464 };
 465 
 466 #endif // SHARE_VM_GC_G1_HEAPREGIONREMSET_HPP
--- EOF ---