1 /*
   2  * Copyright (c) 2001, 2018, 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
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  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
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1ConcurrentRefine.hpp"
  29 #include "gc/g1/heapRegionManager.inline.hpp"
  30 #include "gc/g1/heapRegionRemSet.hpp"
  31 #include "gc/shared/space.inline.hpp"
  32 #include "memory/allocation.hpp"
  33 #include "memory/padded.inline.hpp"
  34 #include "oops/oop.inline.hpp"
  35 #include "runtime/atomic.hpp"
  36 #include "utilities/bitMap.inline.hpp"
  37 #include "utilities/debug.hpp"
  38 #include "utilities/formatBuffer.hpp"
  39 #include "utilities/globalDefinitions.hpp"
  40 #include "utilities/growableArray.hpp"
  41 
  42 const char* HeapRegionRemSet::_state_strings[] =  {"Untracked", "Updating", "Complete"};
  43 const char* HeapRegionRemSet::_short_state_strings[] =  {"UNTRA", "UPDAT", "CMPLT"};
  44 
  45 class PerRegionTable: public CHeapObj<mtGC> {
  46   friend class OtherRegionsTable;
  47   friend class HeapRegionRemSetIterator;
  48 
  49   HeapRegion*     _hr;
  50   CHeapBitMap     _bm;
  51   jint            _occupied;
  52 
  53   // next pointer for free/allocated 'all' list
  54   PerRegionTable* _next;
  55 
  56   // prev pointer for the allocated 'all' list
  57   PerRegionTable* _prev;
  58 
  59   // next pointer in collision list
  60   PerRegionTable * _collision_list_next;
  61 
  62   // Global free list of PRTs
  63   static PerRegionTable* volatile _free_list;
  64 
  65 protected:
  66   // We need access in order to union things into the base table.
  67   BitMap* bm() { return &_bm; }
  68 
  69   PerRegionTable(HeapRegion* hr) :
  70     _hr(hr),
  71     _bm(HeapRegion::CardsPerRegion, mtGC),
  72     _occupied(0),
  73     _next(NULL), _prev(NULL),
  74     _collision_list_next(NULL)
  75   {}
  76 
  77   void add_card_work(CardIdx_t from_card, bool par) {
  78     if (!_bm.at(from_card)) {
  79       if (par) {
  80         if (_bm.par_at_put(from_card, 1)) {
  81           Atomic::inc(&_occupied);
  82         }
  83       } else {
  84         _bm.at_put(from_card, 1);
  85         _occupied++;
  86       }
  87     }
  88   }
  89 
  90   void add_reference_work(OopOrNarrowOopStar from, bool par) {
  91     // Must make this robust in case "from" is not in "_hr", because of
  92     // concurrency.
  93 
  94     HeapRegion* loc_hr = hr();
  95     // If the test below fails, then this table was reused concurrently
  96     // with this operation.  This is OK, since the old table was coarsened,
  97     // and adding a bit to the new table is never incorrect.
  98     if (loc_hr->is_in_reserved(from)) {
  99       CardIdx_t from_card = OtherRegionsTable::card_within_region(from, loc_hr);
 100       add_card_work(from_card, par);
 101     }
 102   }
 103 
 104 public:
 105 
 106   HeapRegion* hr() const { return OrderAccess::load_acquire(&_hr); }
 107 
 108   jint occupied() const {
 109     // Overkill, but if we ever need it...
 110     // guarantee(_occupied == _bm.count_one_bits(), "Check");
 111     return _occupied;
 112   }
 113 
 114   void init(HeapRegion* hr, bool clear_links_to_all_list) {
 115     if (clear_links_to_all_list) {
 116       set_next(NULL);
 117       set_prev(NULL);
 118     }
 119     _collision_list_next = NULL;
 120     _occupied = 0;
 121     _bm.clear();
 122     // Make sure that the bitmap clearing above has been finished before publishing
 123     // this PRT to concurrent threads.
 124     OrderAccess::release_store(&_hr, hr);
 125   }
 126 
 127   void add_reference(OopOrNarrowOopStar from) {
 128     add_reference_work(from, /*parallel*/ true);
 129   }
 130 
 131   void seq_add_reference(OopOrNarrowOopStar from) {
 132     add_reference_work(from, /*parallel*/ false);
 133   }
 134 
 135   void add_card(CardIdx_t from_card_index) {
 136     add_card_work(from_card_index, /*parallel*/ true);
 137   }
 138 
 139   void seq_add_card(CardIdx_t from_card_index) {
 140     add_card_work(from_card_index, /*parallel*/ false);
 141   }
 142 
 143   // (Destructively) union the bitmap of the current table into the given
 144   // bitmap (which is assumed to be of the same size.)
 145   void union_bitmap_into(BitMap* bm) {
 146     bm->set_union(_bm);
 147   }
 148 
 149   // Mem size in bytes.
 150   size_t mem_size() const {
 151     return sizeof(PerRegionTable) + _bm.size_in_words() * HeapWordSize;
 152   }
 153 
 154   // Requires "from" to be in "hr()".
 155   bool contains_reference(OopOrNarrowOopStar from) const {
 156     assert(hr()->is_in_reserved(from), "Precondition.");
 157     size_t card_ind = pointer_delta(from, hr()->bottom(),
 158                                     G1CardTable::card_size);
 159     return _bm.at(card_ind);
 160   }
 161 
 162   // Bulk-free the PRTs from prt to last, assumes that they are
 163   // linked together using their _next field.
 164   static void bulk_free(PerRegionTable* prt, PerRegionTable* last) {
 165     while (true) {
 166       PerRegionTable* fl = _free_list;
 167       last->set_next(fl);
 168       PerRegionTable* res = Atomic::cmpxchg(prt, &_free_list, fl);
 169       if (res == fl) {
 170         return;
 171       }
 172     }
 173     ShouldNotReachHere();
 174   }
 175 
 176   static void free(PerRegionTable* prt) {
 177     bulk_free(prt, prt);
 178   }
 179 
 180   // Returns an initialized PerRegionTable instance.
 181   static PerRegionTable* alloc(HeapRegion* hr) {
 182     PerRegionTable* fl = _free_list;
 183     while (fl != NULL) {
 184       PerRegionTable* nxt = fl->next();
 185       PerRegionTable* res = Atomic::cmpxchg(nxt, &_free_list, fl);
 186       if (res == fl) {
 187         fl->init(hr, true);
 188         return fl;
 189       } else {
 190         fl = _free_list;
 191       }
 192     }
 193     assert(fl == NULL, "Loop condition.");
 194     return new PerRegionTable(hr);
 195   }
 196 
 197   PerRegionTable* next() const { return _next; }
 198   void set_next(PerRegionTable* next) { _next = next; }
 199   PerRegionTable* prev() const { return _prev; }
 200   void set_prev(PerRegionTable* prev) { _prev = prev; }
 201 
 202   // Accessor and Modification routines for the pointer for the
 203   // singly linked collision list that links the PRTs within the
 204   // OtherRegionsTable::_fine_grain_regions hash table.
 205   //
 206   // It might be useful to also make the collision list doubly linked
 207   // to avoid iteration over the collisions list during scrubbing/deletion.
 208   // OTOH there might not be many collisions.
 209 
 210   PerRegionTable* collision_list_next() const {
 211     return _collision_list_next;
 212   }
 213 
 214   void set_collision_list_next(PerRegionTable* next) {
 215     _collision_list_next = next;
 216   }
 217 
 218   PerRegionTable** collision_list_next_addr() {
 219     return &_collision_list_next;
 220   }
 221 
 222   static size_t fl_mem_size() {
 223     PerRegionTable* cur = _free_list;
 224     size_t res = 0;
 225     while (cur != NULL) {
 226       res += cur->mem_size();
 227       cur = cur->next();
 228     }
 229     return res;
 230   }
 231 
 232   static void test_fl_mem_size();
 233 };
 234 
 235 PerRegionTable* volatile PerRegionTable::_free_list = NULL;
 236 
 237 size_t OtherRegionsTable::_max_fine_entries = 0;
 238 size_t OtherRegionsTable::_mod_max_fine_entries_mask = 0;
 239 size_t OtherRegionsTable::_fine_eviction_stride = 0;
 240 size_t OtherRegionsTable::_fine_eviction_sample_size = 0;
 241 
 242 OtherRegionsTable::OtherRegionsTable(HeapRegion* hr, Mutex* m) :
 243   _g1h(G1CollectedHeap::heap()),
 244   _m(m),
 245   _hr(hr),
 246   _coarse_map(G1CollectedHeap::heap()->max_regions(), mtGC),
 247   _n_coarse_entries(0),
 248   _fine_grain_regions(NULL),
 249   _n_fine_entries(0),
 250   _first_all_fine_prts(NULL),
 251   _last_all_fine_prts(NULL),
 252   _fine_eviction_start(0),
 253   _sparse_table(hr)
 254 {
 255   typedef PerRegionTable* PerRegionTablePtr;
 256 
 257   if (_max_fine_entries == 0) {
 258     assert(_mod_max_fine_entries_mask == 0, "Both or none.");
 259     size_t max_entries_log = (size_t)log2_long((jlong)G1RSetRegionEntries);
 260     _max_fine_entries = (size_t)1 << max_entries_log;
 261     _mod_max_fine_entries_mask = _max_fine_entries - 1;
 262 
 263     assert(_fine_eviction_sample_size == 0
 264            && _fine_eviction_stride == 0, "All init at same time.");
 265     _fine_eviction_sample_size = MAX2((size_t)4, max_entries_log);
 266     _fine_eviction_stride = _max_fine_entries / _fine_eviction_sample_size;
 267   }
 268 
 269   _fine_grain_regions = NEW_C_HEAP_ARRAY3(PerRegionTablePtr, _max_fine_entries,
 270                         mtGC, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 271 
 272   if (_fine_grain_regions == NULL) {
 273     vm_exit_out_of_memory(sizeof(void*)*_max_fine_entries, OOM_MALLOC_ERROR,
 274                           "Failed to allocate _fine_grain_entries.");
 275   }
 276 
 277   for (size_t i = 0; i < _max_fine_entries; i++) {
 278     _fine_grain_regions[i] = NULL;
 279   }
 280 }
 281 
 282 void OtherRegionsTable::link_to_all(PerRegionTable* prt) {
 283   // We always append to the beginning of the list for convenience;
 284   // the order of entries in this list does not matter.
 285   if (_first_all_fine_prts != NULL) {
 286     assert(_first_all_fine_prts->prev() == NULL, "invariant");
 287     _first_all_fine_prts->set_prev(prt);
 288     prt->set_next(_first_all_fine_prts);
 289   } else {
 290     // this is the first element we insert. Adjust the "last" pointer
 291     _last_all_fine_prts = prt;
 292     assert(prt->next() == NULL, "just checking");
 293   }
 294   // the new element is always the first element without a predecessor
 295   prt->set_prev(NULL);
 296   _first_all_fine_prts = prt;
 297 
 298   assert(prt->prev() == NULL, "just checking");
 299   assert(_first_all_fine_prts == prt, "just checking");
 300   assert((_first_all_fine_prts == NULL && _last_all_fine_prts == NULL) ||
 301          (_first_all_fine_prts != NULL && _last_all_fine_prts != NULL),
 302          "just checking");
 303   assert(_last_all_fine_prts == NULL || _last_all_fine_prts->next() == NULL,
 304          "just checking");
 305   assert(_first_all_fine_prts == NULL || _first_all_fine_prts->prev() == NULL,
 306          "just checking");
 307 }
 308 
 309 void OtherRegionsTable::unlink_from_all(PerRegionTable* prt) {
 310   if (prt->prev() != NULL) {
 311     assert(_first_all_fine_prts != prt, "just checking");
 312     prt->prev()->set_next(prt->next());
 313     // removing the last element in the list?
 314     if (_last_all_fine_prts == prt) {
 315       _last_all_fine_prts = prt->prev();
 316     }
 317   } else {
 318     assert(_first_all_fine_prts == prt, "just checking");
 319     _first_all_fine_prts = prt->next();
 320     // list is empty now?
 321     if (_first_all_fine_prts == NULL) {
 322       _last_all_fine_prts = NULL;
 323     }
 324   }
 325 
 326   if (prt->next() != NULL) {
 327     prt->next()->set_prev(prt->prev());
 328   }
 329 
 330   prt->set_next(NULL);
 331   prt->set_prev(NULL);
 332 
 333   assert((_first_all_fine_prts == NULL && _last_all_fine_prts == NULL) ||
 334          (_first_all_fine_prts != NULL && _last_all_fine_prts != NULL),
 335          "just checking");
 336   assert(_last_all_fine_prts == NULL || _last_all_fine_prts->next() == NULL,
 337          "just checking");
 338   assert(_first_all_fine_prts == NULL || _first_all_fine_prts->prev() == NULL,
 339          "just checking");
 340 }
 341 
 342 CardIdx_t OtherRegionsTable::card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr) {
 343   assert(hr->is_in_reserved(within_region),
 344          "HeapWord " PTR_FORMAT " is outside of region %u [" PTR_FORMAT ", " PTR_FORMAT ")",
 345          p2i(within_region), hr->hrm_index(), p2i(hr->bottom()), p2i(hr->end()));
 346   CardIdx_t result = (CardIdx_t)(pointer_delta((HeapWord*)within_region, hr->bottom()) >> (CardTable::card_shift - LogHeapWordSize));
 347   return result;
 348 }
 349 
 350 void OtherRegionsTable::add_reference(OopOrNarrowOopStar from, uint tid) {
 351   uint cur_hrm_ind = _hr->hrm_index();
 352 
 353   uintptr_t from_card = uintptr_t(from) >> CardTable::card_shift;
 354 
 355   if (G1FromCardCache::contains_or_replace(tid, cur_hrm_ind, from_card)) {
 356     assert(contains_reference(from), "We just found " PTR_FORMAT " in the FromCardCache", p2i(from));
 357     return;
 358   }
 359 
 360   // Note that this may be a continued H region.
 361   HeapRegion* from_hr = _g1h->heap_region_containing(from);
 362   RegionIdx_t from_hrm_ind = (RegionIdx_t) from_hr->hrm_index();
 363 
 364   // If the region is already coarsened, return.
 365   if (_coarse_map.at(from_hrm_ind)) {
 366     assert(contains_reference(from), "We just found " PTR_FORMAT " in the Coarse table", p2i(from));
 367     return;
 368   }
 369 
 370   // Otherwise find a per-region table to add it to.
 371   size_t ind = from_hrm_ind & _mod_max_fine_entries_mask;
 372   PerRegionTable* prt = find_region_table(ind, from_hr);
 373   if (prt == NULL) {
 374     MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
 375     // Confirm that it's really not there...
 376     prt = find_region_table(ind, from_hr);
 377     if (prt == NULL) {
 378 
 379       CardIdx_t card_index = card_within_region(from, from_hr);
 380 
 381       if (G1HRRSUseSparseTable &&
 382           _sparse_table.add_card(from_hrm_ind, card_index)) {
 383         assert(contains_reference_locked(from), "We just added " PTR_FORMAT " to the Sparse table", p2i(from));
 384         return;
 385       }
 386 
 387       if (_n_fine_entries == _max_fine_entries) {
 388         prt = delete_region_table();
 389         // There is no need to clear the links to the 'all' list here:
 390         // prt will be reused immediately, i.e. remain in the 'all' list.
 391         prt->init(from_hr, false /* clear_links_to_all_list */);
 392       } else {
 393         prt = PerRegionTable::alloc(from_hr);
 394         link_to_all(prt);
 395       }
 396 
 397       PerRegionTable* first_prt = _fine_grain_regions[ind];
 398       prt->set_collision_list_next(first_prt);
 399       // The assignment into _fine_grain_regions allows the prt to
 400       // start being used concurrently. In addition to
 401       // collision_list_next which must be visible (else concurrent
 402       // parsing of the list, if any, may fail to see other entries),
 403       // the content of the prt must be visible (else for instance
 404       // some mark bits may not yet seem cleared or a 'later' update
 405       // performed by a concurrent thread could be undone when the
 406       // zeroing becomes visible). This requires store ordering.
 407       OrderAccess::release_store(&_fine_grain_regions[ind], prt);
 408       _n_fine_entries++;
 409 
 410       if (G1HRRSUseSparseTable) {
 411         // Transfer from sparse to fine-grain.
 412         SparsePRTEntry *sprt_entry = _sparse_table.get_entry(from_hrm_ind);
 413         assert(sprt_entry != NULL, "There should have been an entry");
 414         for (int i = 0; i < sprt_entry->num_valid_cards(); i++) {
 415           CardIdx_t c = sprt_entry->card(i);
 416           prt->add_card(c);
 417         }
 418         // Now we can delete the sparse entry.
 419         bool res = _sparse_table.delete_entry(from_hrm_ind);
 420         assert(res, "It should have been there.");
 421       }
 422     }
 423     assert(prt != NULL && prt->hr() == from_hr, "consequence");
 424   }
 425   // Note that we can't assert "prt->hr() == from_hr", because of the
 426   // possibility of concurrent reuse.  But see head comment of
 427   // OtherRegionsTable for why this is OK.
 428   assert(prt != NULL, "Inv");
 429 
 430   prt->add_reference(from);
 431   assert(contains_reference(from), "We just added " PTR_FORMAT " to the PRT (%d)", p2i(from), prt->contains_reference(from));
 432 }
 433 
 434 PerRegionTable*
 435 OtherRegionsTable::find_region_table(size_t ind, HeapRegion* hr) const {
 436   assert(ind < _max_fine_entries, "Preconditions.");
 437   PerRegionTable* prt = _fine_grain_regions[ind];
 438   while (prt != NULL && prt->hr() != hr) {
 439     prt = prt->collision_list_next();
 440   }
 441   // Loop postcondition is the method postcondition.
 442   return prt;
 443 }
 444 
 445 jint OtherRegionsTable::_n_coarsenings = 0;
 446 
 447 PerRegionTable* OtherRegionsTable::delete_region_table() {
 448   assert(_m->owned_by_self(), "Precondition");
 449   assert(_n_fine_entries == _max_fine_entries, "Precondition");
 450   PerRegionTable* max = NULL;
 451   jint max_occ = 0;
 452   PerRegionTable** max_prev = NULL;
 453   size_t max_ind;
 454 
 455   size_t i = _fine_eviction_start;
 456   for (size_t k = 0; k < _fine_eviction_sample_size; k++) {
 457     size_t ii = i;
 458     // Make sure we get a non-NULL sample.
 459     while (_fine_grain_regions[ii] == NULL) {
 460       ii++;
 461       if (ii == _max_fine_entries) ii = 0;
 462       guarantee(ii != i, "We must find one.");
 463     }
 464     PerRegionTable** prev = &_fine_grain_regions[ii];
 465     PerRegionTable* cur = *prev;
 466     while (cur != NULL) {
 467       jint cur_occ = cur->occupied();
 468       if (max == NULL || cur_occ > max_occ) {
 469         max = cur;
 470         max_prev = prev;
 471         max_ind = i;
 472         max_occ = cur_occ;
 473       }
 474       prev = cur->collision_list_next_addr();
 475       cur = cur->collision_list_next();
 476     }
 477     i = i + _fine_eviction_stride;
 478     if (i >= _n_fine_entries) i = i - _n_fine_entries;
 479   }
 480 
 481   _fine_eviction_start++;
 482 
 483   if (_fine_eviction_start >= _n_fine_entries) {
 484     _fine_eviction_start -= _n_fine_entries;
 485   }
 486 
 487   guarantee(max != NULL, "Since _n_fine_entries > 0");
 488   guarantee(max_prev != NULL, "Since max != NULL.");
 489 
 490   // Set the corresponding coarse bit.
 491   size_t max_hrm_index = (size_t) max->hr()->hrm_index();
 492   if (!_coarse_map.at(max_hrm_index)) {
 493     _coarse_map.at_put(max_hrm_index, true);
 494     _n_coarse_entries++;
 495   }
 496 
 497   // Unsplice.
 498   *max_prev = max->collision_list_next();
 499   Atomic::inc(&_n_coarsenings);
 500   _n_fine_entries--;
 501   return max;
 502 }
 503 
 504 bool OtherRegionsTable::occupancy_less_or_equal_than(size_t limit) const {
 505   if (limit <= (size_t)G1RSetSparseRegionEntries) {
 506     return occ_coarse() == 0 && _first_all_fine_prts == NULL && occ_sparse() <= limit;
 507   } else {
 508     // Current uses of this method may only use values less than G1RSetSparseRegionEntries
 509     // for the limit. The solution, comparing against occupied() would be too slow
 510     // at this time.
 511     Unimplemented();
 512     return false;
 513   }
 514 }
 515 
 516 bool OtherRegionsTable::is_empty() const {
 517   return occ_sparse() == 0 && occ_coarse() == 0 && _first_all_fine_prts == NULL;
 518 }
 519 
 520 size_t OtherRegionsTable::occupied() const {
 521   size_t sum = occ_fine();
 522   sum += occ_sparse();
 523   sum += occ_coarse();
 524   return sum;
 525 }
 526 
 527 size_t OtherRegionsTable::occ_fine() const {
 528   size_t sum = 0;
 529 
 530   size_t num = 0;
 531   PerRegionTable * cur = _first_all_fine_prts;
 532   while (cur != NULL) {
 533     sum += cur->occupied();
 534     cur = cur->next();
 535     num++;
 536   }
 537   guarantee(num == _n_fine_entries, "just checking");
 538   return sum;
 539 }
 540 
 541 size_t OtherRegionsTable::occ_coarse() const {
 542   return (_n_coarse_entries * HeapRegion::CardsPerRegion);
 543 }
 544 
 545 size_t OtherRegionsTable::occ_sparse() const {
 546   return _sparse_table.occupied();
 547 }
 548 
 549 size_t OtherRegionsTable::mem_size() const {
 550   size_t sum = 0;
 551   // all PRTs are of the same size so it is sufficient to query only one of them.
 552   if (_first_all_fine_prts != NULL) {
 553     assert(_last_all_fine_prts != NULL &&
 554       _first_all_fine_prts->mem_size() == _last_all_fine_prts->mem_size(), "check that mem_size() is constant");
 555     sum += _first_all_fine_prts->mem_size() * _n_fine_entries;
 556   }
 557   sum += (sizeof(PerRegionTable*) * _max_fine_entries);
 558   sum += (_coarse_map.size_in_words() * HeapWordSize);
 559   sum += (_sparse_table.mem_size());
 560   sum += sizeof(OtherRegionsTable) - sizeof(_sparse_table); // Avoid double counting above.
 561   return sum;
 562 }
 563 
 564 size_t OtherRegionsTable::static_mem_size() {
 565   return G1FromCardCache::static_mem_size();
 566 }
 567 
 568 size_t OtherRegionsTable::fl_mem_size() {
 569   return PerRegionTable::fl_mem_size();
 570 }
 571 
 572 void OtherRegionsTable::clear_fcc() {
 573   G1FromCardCache::clear(_hr->hrm_index());
 574 }
 575 
 576 void OtherRegionsTable::clear() {
 577   // if there are no entries, skip this step
 578   if (_first_all_fine_prts != NULL) {
 579     guarantee(_first_all_fine_prts != NULL && _last_all_fine_prts != NULL, "just checking");
 580     PerRegionTable::bulk_free(_first_all_fine_prts, _last_all_fine_prts);
 581     memset(_fine_grain_regions, 0, _max_fine_entries * sizeof(_fine_grain_regions[0]));
 582   } else {
 583     guarantee(_first_all_fine_prts == NULL && _last_all_fine_prts == NULL, "just checking");
 584   }
 585 
 586   _first_all_fine_prts = _last_all_fine_prts = NULL;
 587   _sparse_table.clear();
 588   if (_n_coarse_entries > 0) {
 589     _coarse_map.clear();
 590   }
 591   _n_fine_entries = 0;
 592   _n_coarse_entries = 0;
 593 
 594   clear_fcc();
 595 }
 596 
 597 bool OtherRegionsTable::contains_reference(OopOrNarrowOopStar from) const {
 598   // Cast away const in this case.
 599   MutexLockerEx x((Mutex*)_m, Mutex::_no_safepoint_check_flag);
 600   return contains_reference_locked(from);
 601 }
 602 
 603 bool OtherRegionsTable::contains_reference_locked(OopOrNarrowOopStar from) const {
 604   HeapRegion* hr = _g1h->heap_region_containing(from);
 605   RegionIdx_t hr_ind = (RegionIdx_t) hr->hrm_index();
 606   // Is this region in the coarse map?
 607   if (_coarse_map.at(hr_ind)) return true;
 608 
 609   PerRegionTable* prt = find_region_table(hr_ind & _mod_max_fine_entries_mask,
 610                                           hr);
 611   if (prt != NULL) {
 612     return prt->contains_reference(from);
 613 
 614   } else {
 615     CardIdx_t card_index = card_within_region(from, hr);
 616     return _sparse_table.contains_card(hr_ind, card_index);
 617   }
 618 }
 619 
 620 void
 621 OtherRegionsTable::do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task) {
 622   _sparse_table.do_cleanup_work(hrrs_cleanup_task);
 623 }
 624 
 625 HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetTable* bot,
 626                                    HeapRegion* hr)
 627   : _bot(bot),
 628     _code_roots(),
 629     _m(Mutex::leaf, FormatBuffer<128>("HeapRegionRemSet lock #%u", hr->hrm_index()), true, Monitor::_safepoint_check_never),
 630     _other_regions(hr, &_m),
 631     _state(Untracked)
 632 {
 633 }
 634 
 635 void HeapRegionRemSet::setup_remset_size() {
 636   // Setup sparse and fine-grain tables sizes.
 637   // table_size = base * (log(region_size / 1M) + 1)
 638   const int LOG_M = 20;
 639   int region_size_log_mb = MAX2(HeapRegion::LogOfHRGrainBytes - LOG_M, 0);
 640   if (FLAG_IS_DEFAULT(G1RSetSparseRegionEntries)) {
 641     G1RSetSparseRegionEntries = G1RSetSparseRegionEntriesBase * (region_size_log_mb + 1);
 642   }
 643   if (FLAG_IS_DEFAULT(G1RSetRegionEntries)) {
 644     G1RSetRegionEntries = G1RSetRegionEntriesBase * (region_size_log_mb + 1);
 645   }
 646   guarantee(G1RSetSparseRegionEntries > 0 && G1RSetRegionEntries > 0 , "Sanity");
 647 }
 648 
 649 void HeapRegionRemSet::cleanup() {
 650   SparsePRT::cleanup_all();
 651 }
 652 
 653 void HeapRegionRemSet::clear(bool only_cardset) {
 654   MutexLockerEx x(&_m, Mutex::_no_safepoint_check_flag);
 655   clear_locked(only_cardset);
 656 }
 657 
 658 void HeapRegionRemSet::clear_locked(bool only_cardset) {
 659   if (!only_cardset) {
 660     _code_roots.clear();
 661   }
 662   _other_regions.clear();
 663   set_state_empty();
 664   assert(occupied_locked() == 0, "Should be clear.");
 665 }
 666 
 667 // Code roots support
 668 //
 669 // The code root set is protected by two separate locking schemes
 670 // When at safepoint the per-hrrs lock must be held during modifications
 671 // except when doing a full gc.
 672 // When not at safepoint the CodeCache_lock must be held during modifications.
 673 // When concurrent readers access the contains() function
 674 // (during the evacuation phase) no removals are allowed.
 675 
 676 void HeapRegionRemSet::add_strong_code_root(nmethod* nm) {
 677   assert(nm != NULL, "sanity");
 678   assert((!CodeCache_lock->owned_by_self() || SafepointSynchronize::is_at_safepoint()),
 679           "should call add_strong_code_root_locked instead. CodeCache_lock->owned_by_self(): %s, is_at_safepoint(): %s",
 680           BOOL_TO_STR(CodeCache_lock->owned_by_self()), BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()));
 681   // Optimistic unlocked contains-check
 682   if (!_code_roots.contains(nm)) {
 683     MutexLockerEx ml(&_m, Mutex::_no_safepoint_check_flag);
 684     add_strong_code_root_locked(nm);
 685   }
 686 }
 687 
 688 void HeapRegionRemSet::add_strong_code_root_locked(nmethod* nm) {
 689   assert(nm != NULL, "sanity");
 690   assert((CodeCache_lock->owned_by_self() ||
 691          (SafepointSynchronize::is_at_safepoint() &&
 692           (_m.owned_by_self() || Thread::current()->is_VM_thread()))),
 693           "not safely locked. CodeCache_lock->owned_by_self(): %s, is_at_safepoint(): %s, _m.owned_by_self(): %s, Thread::current()->is_VM_thread(): %s",
 694           BOOL_TO_STR(CodeCache_lock->owned_by_self()), BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),
 695           BOOL_TO_STR(_m.owned_by_self()), BOOL_TO_STR(Thread::current()->is_VM_thread()));
 696   _code_roots.add(nm);
 697 }
 698 
 699 void HeapRegionRemSet::remove_strong_code_root(nmethod* nm) {
 700   assert(nm != NULL, "sanity");
 701   assert_locked_or_safepoint(CodeCache_lock);
 702 
 703   MutexLockerEx ml(CodeCache_lock->owned_by_self() ? NULL : &_m, Mutex::_no_safepoint_check_flag);
 704   _code_roots.remove(nm);
 705 
 706   // Check that there were no duplicates
 707   guarantee(!_code_roots.contains(nm), "duplicate entry found");
 708 }
 709 
 710 void HeapRegionRemSet::strong_code_roots_do(CodeBlobClosure* blk) const {
 711   _code_roots.nmethods_do(blk);
 712 }
 713 
 714 void HeapRegionRemSet::clean_strong_code_roots(HeapRegion* hr) {
 715   _code_roots.clean(hr);
 716 }
 717 
 718 size_t HeapRegionRemSet::strong_code_roots_mem_size() {
 719   return _code_roots.mem_size();
 720 }
 721 
 722 HeapRegionRemSetIterator:: HeapRegionRemSetIterator(HeapRegionRemSet* hrrs) :
 723   _hrrs(hrrs),
 724   _coarse_map(&hrrs->_other_regions._coarse_map),
 725   _bot(hrrs->_bot),
 726   _g1h(G1CollectedHeap::heap()),
 727   _n_yielded_fine(0),
 728   _n_yielded_coarse(0),
 729   _n_yielded_sparse(0),
 730   _is(Sparse),
 731   _cur_region_card_offset(0),
 732   // Set these values so that we increment to the first region.
 733   _coarse_cur_region_index(-1),
 734   _coarse_cur_region_cur_card(HeapRegion::CardsPerRegion-1),
 735   _fine_cur_prt(NULL),
 736   _cur_card_in_prt(HeapRegion::CardsPerRegion),
 737   _sparse_iter(&hrrs->_other_regions._sparse_table) {}
 738 
 739 bool HeapRegionRemSetIterator::coarse_has_next(size_t& card_index) {
 740   if (_hrrs->_other_regions._n_coarse_entries == 0) return false;
 741   // Go to the next card.
 742   _coarse_cur_region_cur_card++;
 743   // Was the last the last card in the current region?
 744   if (_coarse_cur_region_cur_card == HeapRegion::CardsPerRegion) {
 745     // Yes: find the next region.  This may leave _coarse_cur_region_index
 746     // Set to the last index, in which case there are no more coarse
 747     // regions.
 748     _coarse_cur_region_index =
 749       (int) _coarse_map->get_next_one_offset(_coarse_cur_region_index + 1);
 750     if ((size_t)_coarse_cur_region_index < _coarse_map->size()) {
 751       _coarse_cur_region_cur_card = 0;
 752       HeapWord* r_bot =
 753         _g1h->region_at((uint) _coarse_cur_region_index)->bottom();
 754       _cur_region_card_offset = _bot->index_for_raw(r_bot);
 755     } else {
 756       return false;
 757     }
 758   }
 759   // If we didn't return false above, then we can yield a card.
 760   card_index = _cur_region_card_offset + _coarse_cur_region_cur_card;
 761   return true;
 762 }
 763 
 764 bool HeapRegionRemSetIterator::fine_has_next(size_t& card_index) {
 765   if (fine_has_next()) {
 766     _cur_card_in_prt =
 767       _fine_cur_prt->_bm.get_next_one_offset(_cur_card_in_prt + 1);
 768   }
 769   if (_cur_card_in_prt == HeapRegion::CardsPerRegion) {
 770     // _fine_cur_prt may still be NULL in case if there are not PRTs at all for
 771     // the remembered set.
 772     if (_fine_cur_prt == NULL || _fine_cur_prt->next() == NULL) {
 773       return false;
 774     }
 775     PerRegionTable* next_prt = _fine_cur_prt->next();
 776     switch_to_prt(next_prt);
 777     _cur_card_in_prt = _fine_cur_prt->_bm.get_next_one_offset(_cur_card_in_prt + 1);
 778   }
 779 
 780   card_index = _cur_region_card_offset + _cur_card_in_prt;
 781   guarantee(_cur_card_in_prt < HeapRegion::CardsPerRegion,
 782             "Card index " SIZE_FORMAT " must be within the region", _cur_card_in_prt);
 783   return true;
 784 }
 785 
 786 bool HeapRegionRemSetIterator::fine_has_next() {
 787   return _cur_card_in_prt != HeapRegion::CardsPerRegion;
 788 }
 789 
 790 void HeapRegionRemSetIterator::switch_to_prt(PerRegionTable* prt) {
 791   assert(prt != NULL, "Cannot switch to NULL prt");
 792   _fine_cur_prt = prt;
 793 
 794   HeapWord* r_bot = _fine_cur_prt->hr()->bottom();
 795   _cur_region_card_offset = _bot->index_for_raw(r_bot);
 796 
 797   // The bitmap scan for the PRT always scans from _cur_region_cur_card + 1.
 798   // To avoid special-casing this start case, and not miss the first bitmap
 799   // entry, initialize _cur_region_cur_card with -1 instead of 0.
 800   _cur_card_in_prt = (size_t)-1;
 801 }
 802 
 803 bool HeapRegionRemSetIterator::has_next(size_t& card_index) {
 804   switch (_is) {
 805   case Sparse: {
 806     if (_sparse_iter.has_next(card_index)) {
 807       _n_yielded_sparse++;
 808       return true;
 809     }
 810     // Otherwise, deliberate fall-through
 811     _is = Fine;
 812     PerRegionTable* initial_fine_prt = _hrrs->_other_regions._first_all_fine_prts;
 813     if (initial_fine_prt != NULL) {
 814       switch_to_prt(_hrrs->_other_regions._first_all_fine_prts);
 815     }
 816   }
 817   case Fine:
 818     if (fine_has_next(card_index)) {
 819       _n_yielded_fine++;
 820       return true;
 821     }
 822     // Otherwise, deliberate fall-through
 823     _is = Coarse;
 824   case Coarse:
 825     if (coarse_has_next(card_index)) {
 826       _n_yielded_coarse++;
 827       return true;
 828     }
 829     // Otherwise...
 830     break;
 831   }
 832   return false;
 833 }
 834 
 835 void HeapRegionRemSet::reset_for_cleanup_tasks() {
 836   SparsePRT::reset_for_cleanup_tasks();
 837 }
 838 
 839 void HeapRegionRemSet::do_cleanup_work(HRRSCleanupTask* hrrs_cleanup_task) {
 840   _other_regions.do_cleanup_work(hrrs_cleanup_task);
 841 }
 842 
 843 void HeapRegionRemSet::finish_cleanup_task(HRRSCleanupTask* hrrs_cleanup_task) {
 844   SparsePRT::finish_cleanup_task(hrrs_cleanup_task);
 845 }
 846 
 847 #ifndef PRODUCT
 848 void HeapRegionRemSet::test() {
 849   os::sleep(Thread::current(), (jlong)5000, false);
 850   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 851 
 852   // Run with "-XX:G1LogRSetRegionEntries=2", so that 1 and 5 end up in same
 853   // hash bucket.
 854   HeapRegion* hr0 = g1h->region_at(0);
 855   HeapRegion* hr1 = g1h->region_at(1);
 856   HeapRegion* hr2 = g1h->region_at(5);
 857   HeapRegion* hr3 = g1h->region_at(6);
 858   HeapRegion* hr4 = g1h->region_at(7);
 859   HeapRegion* hr5 = g1h->region_at(8);
 860 
 861   HeapWord* hr1_start = hr1->bottom();
 862   HeapWord* hr1_mid = hr1_start + HeapRegion::GrainWords/2;
 863   HeapWord* hr1_last = hr1->end() - 1;
 864 
 865   HeapWord* hr2_start = hr2->bottom();
 866   HeapWord* hr2_mid = hr2_start + HeapRegion::GrainWords/2;
 867   HeapWord* hr2_last = hr2->end() - 1;
 868 
 869   HeapWord* hr3_start = hr3->bottom();
 870   HeapWord* hr3_mid = hr3_start + HeapRegion::GrainWords/2;
 871   HeapWord* hr3_last = hr3->end() - 1;
 872 
 873   HeapRegionRemSet* hrrs = hr0->rem_set();
 874 
 875   // Make three references from region 0x101...
 876   hrrs->add_reference((OopOrNarrowOopStar)hr1_start);
 877   hrrs->add_reference((OopOrNarrowOopStar)hr1_mid);
 878   hrrs->add_reference((OopOrNarrowOopStar)hr1_last);
 879 
 880   hrrs->add_reference((OopOrNarrowOopStar)hr2_start);
 881   hrrs->add_reference((OopOrNarrowOopStar)hr2_mid);
 882   hrrs->add_reference((OopOrNarrowOopStar)hr2_last);
 883 
 884   hrrs->add_reference((OopOrNarrowOopStar)hr3_start);
 885   hrrs->add_reference((OopOrNarrowOopStar)hr3_mid);
 886   hrrs->add_reference((OopOrNarrowOopStar)hr3_last);
 887 
 888   // Now cause a coarsening.
 889   hrrs->add_reference((OopOrNarrowOopStar)hr4->bottom());
 890   hrrs->add_reference((OopOrNarrowOopStar)hr5->bottom());
 891 
 892   // Now, does iteration yield these three?
 893   HeapRegionRemSetIterator iter(hrrs);
 894   size_t sum = 0;
 895   size_t card_index;
 896   while (iter.has_next(card_index)) {
 897     HeapWord* card_start = g1h->bot()->address_for_index(card_index);
 898     tty->print_cr("  Card " PTR_FORMAT ".", p2i(card_start));
 899     sum++;
 900   }
 901   guarantee(sum == 11 - 3 + 2048, "Failure");
 902   guarantee(sum == hrrs->occupied(), "Failure");
 903 }
 904 #endif