1 /*
   2  * Copyright (c) 2001, 2019, 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.inline.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 PerRegionTable* PerRegionTable::alloc(HeapRegion* hr) {
  46   PerRegionTable* fl = _free_list;
  47   while (fl != NULL) {
  48     PerRegionTable* nxt = fl->next();
  49     PerRegionTable* res = Atomic::cmpxchg(nxt, &_free_list, fl);
  50     if (res == fl) {
  51       fl->init(hr, true);
  52       return fl;
  53     } else {
  54       fl = _free_list;
  55     }
  56   }
  57   assert(fl == NULL, "Loop condition.");
  58   return new PerRegionTable(hr);
  59 }
  60 
  61 PerRegionTable* volatile PerRegionTable::_free_list = NULL;
  62 
  63 size_t OtherRegionsTable::_max_fine_entries = 0;
  64 size_t OtherRegionsTable::_mod_max_fine_entries_mask = 0;
  65 size_t OtherRegionsTable::_fine_eviction_stride = 0;
  66 size_t OtherRegionsTable::_fine_eviction_sample_size = 0;
  67 
  68 OtherRegionsTable::OtherRegionsTable(Mutex* m) :
  69   _g1h(G1CollectedHeap::heap()),
  70   _m(m),
  71   _coarse_map(G1CollectedHeap::heap()->max_regions(), mtGC),
  72   _n_coarse_entries(0),
  73   _fine_grain_regions(NULL),
  74   _n_fine_entries(0),
  75   _first_all_fine_prts(NULL),
  76   _last_all_fine_prts(NULL),
  77   _fine_eviction_start(0),
  78   _sparse_table()
  79 {
  80   typedef PerRegionTable* PerRegionTablePtr;
  81 
  82   if (_max_fine_entries == 0) {
  83     assert(_mod_max_fine_entries_mask == 0, "Both or none.");
  84     size_t max_entries_log = (size_t)log2_long((jlong)G1RSetRegionEntries);
  85     _max_fine_entries = (size_t)1 << max_entries_log;
  86     _mod_max_fine_entries_mask = _max_fine_entries - 1;
  87 
  88     assert(_fine_eviction_sample_size == 0
  89            && _fine_eviction_stride == 0, "All init at same time.");
  90     _fine_eviction_sample_size = MAX2((size_t)4, max_entries_log);
  91     _fine_eviction_stride = _max_fine_entries / _fine_eviction_sample_size;
  92   }
  93 
  94   _fine_grain_regions = NEW_C_HEAP_ARRAY3(PerRegionTablePtr, _max_fine_entries,
  95                         mtGC, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
  96 
  97   if (_fine_grain_regions == NULL) {
  98     vm_exit_out_of_memory(sizeof(void*)*_max_fine_entries, OOM_MALLOC_ERROR,
  99                           "Failed to allocate _fine_grain_entries.");
 100   }
 101 
 102   for (size_t i = 0; i < _max_fine_entries; i++) {
 103     _fine_grain_regions[i] = NULL;
 104   }
 105 }
 106 
 107 void OtherRegionsTable::link_to_all(PerRegionTable* prt) {
 108   // We always append to the beginning of the list for convenience;
 109   // the order of entries in this list does not matter.
 110   if (_first_all_fine_prts != NULL) {
 111     assert(_first_all_fine_prts->prev() == NULL, "invariant");
 112     _first_all_fine_prts->set_prev(prt);
 113     prt->set_next(_first_all_fine_prts);
 114   } else {
 115     // this is the first element we insert. Adjust the "last" pointer
 116     _last_all_fine_prts = prt;
 117     assert(prt->next() == NULL, "just checking");
 118   }
 119   // the new element is always the first element without a predecessor
 120   prt->set_prev(NULL);
 121   _first_all_fine_prts = prt;
 122 
 123   assert(prt->prev() == NULL, "just checking");
 124   assert(_first_all_fine_prts == prt, "just checking");
 125   assert((_first_all_fine_prts == NULL && _last_all_fine_prts == NULL) ||
 126          (_first_all_fine_prts != NULL && _last_all_fine_prts != NULL),
 127          "just checking");
 128   assert(_last_all_fine_prts == NULL || _last_all_fine_prts->next() == NULL,
 129          "just checking");
 130   assert(_first_all_fine_prts == NULL || _first_all_fine_prts->prev() == NULL,
 131          "just checking");
 132 }
 133 
 134 void OtherRegionsTable::unlink_from_all(PerRegionTable* prt) {
 135   if (prt->prev() != NULL) {
 136     assert(_first_all_fine_prts != prt, "just checking");
 137     prt->prev()->set_next(prt->next());
 138     // removing the last element in the list?
 139     if (_last_all_fine_prts == prt) {
 140       _last_all_fine_prts = prt->prev();
 141     }
 142   } else {
 143     assert(_first_all_fine_prts == prt, "just checking");
 144     _first_all_fine_prts = prt->next();
 145     // list is empty now?
 146     if (_first_all_fine_prts == NULL) {
 147       _last_all_fine_prts = NULL;
 148     }
 149   }
 150 
 151   if (prt->next() != NULL) {
 152     prt->next()->set_prev(prt->prev());
 153   }
 154 
 155   prt->set_next(NULL);
 156   prt->set_prev(NULL);
 157 
 158   assert((_first_all_fine_prts == NULL && _last_all_fine_prts == NULL) ||
 159          (_first_all_fine_prts != NULL && _last_all_fine_prts != NULL),
 160          "just checking");
 161   assert(_last_all_fine_prts == NULL || _last_all_fine_prts->next() == NULL,
 162          "just checking");
 163   assert(_first_all_fine_prts == NULL || _first_all_fine_prts->prev() == NULL,
 164          "just checking");
 165 }
 166 
 167 CardIdx_t OtherRegionsTable::card_within_region(OopOrNarrowOopStar within_region, HeapRegion* hr) {
 168   assert(hr->is_in_reserved(within_region),
 169          "HeapWord " PTR_FORMAT " is outside of region %u [" PTR_FORMAT ", " PTR_FORMAT ")",
 170          p2i(within_region), hr->hrm_index(), p2i(hr->bottom()), p2i(hr->end()));
 171   CardIdx_t result = (CardIdx_t)(pointer_delta((HeapWord*)within_region, hr->bottom()) >> (CardTable::card_shift - LogHeapWordSize));
 172   return result;
 173 }
 174 
 175 void OtherRegionsTable::add_reference(OopOrNarrowOopStar from, uint tid) {
 176   // Note that this may be a continued H region.
 177   HeapRegion* from_hr = _g1h->heap_region_containing(from);
 178   RegionIdx_t from_hrm_ind = (RegionIdx_t) from_hr->hrm_index();
 179 
 180   // If the region is already coarsened, return.
 181   if (_coarse_map.at(from_hrm_ind)) {
 182     assert(contains_reference(from), "We just found " PTR_FORMAT " in the Coarse table", p2i(from));
 183     return;
 184   }
 185 
 186   // Otherwise find a per-region table to add it to.
 187   size_t ind = from_hrm_ind & _mod_max_fine_entries_mask;
 188   PerRegionTable* prt = find_region_table(ind, from_hr);
 189   if (prt == NULL) {
 190     MutexLocker x(_m, Mutex::_no_safepoint_check_flag);
 191     // Confirm that it's really not there...
 192     prt = find_region_table(ind, from_hr);
 193     if (prt == NULL) {
 194 
 195       CardIdx_t card_index = card_within_region(from, from_hr);
 196 
 197       if (_sparse_table.add_card(from_hrm_ind, card_index)) {
 198         assert(contains_reference_locked(from), "We just added " PTR_FORMAT " to the Sparse table", p2i(from));
 199         return;
 200       }
 201 
 202       if (_n_fine_entries == _max_fine_entries) {
 203         prt = delete_region_table();
 204         // There is no need to clear the links to the 'all' list here:
 205         // prt will be reused immediately, i.e. remain in the 'all' list.
 206         prt->init(from_hr, false /* clear_links_to_all_list */);
 207       } else {
 208         prt = PerRegionTable::alloc(from_hr);
 209         link_to_all(prt);
 210       }
 211 
 212       PerRegionTable* first_prt = _fine_grain_regions[ind];
 213       prt->set_collision_list_next(first_prt);
 214       // The assignment into _fine_grain_regions allows the prt to
 215       // start being used concurrently. In addition to
 216       // collision_list_next which must be visible (else concurrent
 217       // parsing of the list, if any, may fail to see other entries),
 218       // the content of the prt must be visible (else for instance
 219       // some mark bits may not yet seem cleared or a 'later' update
 220       // performed by a concurrent thread could be undone when the
 221       // zeroing becomes visible). This requires store ordering.
 222       Atomic::release_store(&_fine_grain_regions[ind], prt);
 223       _n_fine_entries++;
 224 
 225       // Transfer from sparse to fine-grain.
 226       SparsePRTEntry *sprt_entry = _sparse_table.get_entry(from_hrm_ind);
 227       assert(sprt_entry != NULL, "There should have been an entry");
 228       for (int i = 0; i < sprt_entry->num_valid_cards(); i++) {
 229         CardIdx_t c = sprt_entry->card(i);
 230         prt->add_card(c);
 231       }
 232       // Now we can delete the sparse entry.
 233       bool res = _sparse_table.delete_entry(from_hrm_ind);
 234       assert(res, "It should have been there.");
 235     }
 236     assert(prt != NULL && prt->hr() == from_hr, "consequence");
 237   }
 238   // Note that we can't assert "prt->hr() == from_hr", because of the
 239   // possibility of concurrent reuse.  But see head comment of
 240   // OtherRegionsTable for why this is OK.
 241   assert(prt != NULL, "Inv");
 242 
 243   prt->add_reference(from);
 244   assert(contains_reference(from), "We just added " PTR_FORMAT " to the PRT (%d)", p2i(from), prt->contains_reference(from));
 245 }
 246 
 247 PerRegionTable*
 248 OtherRegionsTable::find_region_table(size_t ind, HeapRegion* hr) const {
 249   assert(ind < _max_fine_entries, "Preconditions.");
 250   PerRegionTable* prt = _fine_grain_regions[ind];
 251   while (prt != NULL && prt->hr() != hr) {
 252     prt = prt->collision_list_next();
 253   }
 254   // Loop postcondition is the method postcondition.
 255   return prt;
 256 }
 257 
 258 jint OtherRegionsTable::_n_coarsenings = 0;
 259 
 260 PerRegionTable* OtherRegionsTable::delete_region_table() {
 261   assert(_m->owned_by_self(), "Precondition");
 262   assert(_n_fine_entries == _max_fine_entries, "Precondition");
 263   PerRegionTable* max = NULL;
 264   jint max_occ = 0;
 265   PerRegionTable** max_prev = NULL;
 266   size_t max_ind;
 267 
 268   size_t i = _fine_eviction_start;
 269   for (size_t k = 0; k < _fine_eviction_sample_size; k++) {
 270     size_t ii = i;
 271     // Make sure we get a non-NULL sample.
 272     while (_fine_grain_regions[ii] == NULL) {
 273       ii++;
 274       if (ii == _max_fine_entries) ii = 0;
 275       guarantee(ii != i, "We must find one.");
 276     }
 277     PerRegionTable** prev = &_fine_grain_regions[ii];
 278     PerRegionTable* cur = *prev;
 279     while (cur != NULL) {
 280       jint cur_occ = cur->occupied();
 281       if (max == NULL || cur_occ > max_occ) {
 282         max = cur;
 283         max_prev = prev;
 284         max_ind = i;
 285         max_occ = cur_occ;
 286       }
 287       prev = cur->collision_list_next_addr();
 288       cur = cur->collision_list_next();
 289     }
 290     i = i + _fine_eviction_stride;
 291     if (i >= _n_fine_entries) i = i - _n_fine_entries;
 292   }
 293 
 294   _fine_eviction_start++;
 295 
 296   if (_fine_eviction_start >= _n_fine_entries) {
 297     _fine_eviction_start -= _n_fine_entries;
 298   }
 299 
 300   guarantee(max != NULL, "Since _n_fine_entries > 0");
 301   guarantee(max_prev != NULL, "Since max != NULL.");
 302 
 303   // Set the corresponding coarse bit.
 304   size_t max_hrm_index = (size_t) max->hr()->hrm_index();
 305   if (!_coarse_map.at(max_hrm_index)) {
 306     _coarse_map.at_put(max_hrm_index, true);
 307     _n_coarse_entries++;
 308   }
 309 
 310   // Unsplice.
 311   *max_prev = max->collision_list_next();
 312   Atomic::inc(&_n_coarsenings);
 313   _n_fine_entries--;
 314   return max;
 315 }
 316 
 317 bool OtherRegionsTable::occupancy_less_or_equal_than(size_t limit) const {
 318   if (limit <= (size_t)G1RSetSparseRegionEntries) {
 319     return occ_coarse() == 0 && _first_all_fine_prts == NULL && occ_sparse() <= limit;
 320   } else {
 321     // Current uses of this method may only use values less than G1RSetSparseRegionEntries
 322     // for the limit. The solution, comparing against occupied() would be too slow
 323     // at this time.
 324     Unimplemented();
 325     return false;
 326   }
 327 }
 328 
 329 bool OtherRegionsTable::is_empty() const {
 330   return occ_sparse() == 0 && occ_coarse() == 0 && _first_all_fine_prts == NULL;
 331 }
 332 
 333 size_t OtherRegionsTable::occupied() const {
 334   size_t sum = occ_fine();
 335   sum += occ_sparse();
 336   sum += occ_coarse();
 337   return sum;
 338 }
 339 
 340 size_t OtherRegionsTable::occ_fine() const {
 341   size_t sum = 0;
 342 
 343   size_t num = 0;
 344   PerRegionTable * cur = _first_all_fine_prts;
 345   while (cur != NULL) {
 346     sum += cur->occupied();
 347     cur = cur->next();
 348     num++;
 349   }
 350   guarantee(num == _n_fine_entries, "just checking");
 351   return sum;
 352 }
 353 
 354 size_t OtherRegionsTable::occ_coarse() const {
 355   return (_n_coarse_entries * HeapRegion::CardsPerRegion);
 356 }
 357 
 358 size_t OtherRegionsTable::occ_sparse() const {
 359   return _sparse_table.occupied();
 360 }
 361 
 362 size_t OtherRegionsTable::mem_size() const {
 363   size_t sum = 0;
 364   // all PRTs are of the same size so it is sufficient to query only one of them.
 365   if (_first_all_fine_prts != NULL) {
 366     assert(_last_all_fine_prts != NULL &&
 367       _first_all_fine_prts->mem_size() == _last_all_fine_prts->mem_size(), "check that mem_size() is constant");
 368     sum += _first_all_fine_prts->mem_size() * _n_fine_entries;
 369   }
 370   sum += (sizeof(PerRegionTable*) * _max_fine_entries);
 371   sum += (_coarse_map.size_in_words() * HeapWordSize);
 372   sum += (_sparse_table.mem_size());
 373   sum += sizeof(OtherRegionsTable) - sizeof(_sparse_table); // Avoid double counting above.
 374   return sum;
 375 }
 376 
 377 size_t OtherRegionsTable::static_mem_size() {
 378   return G1FromCardCache::static_mem_size();
 379 }
 380 
 381 size_t OtherRegionsTable::fl_mem_size() {
 382   return PerRegionTable::fl_mem_size();
 383 }
 384 
 385 void OtherRegionsTable::clear() {
 386   // if there are no entries, skip this step
 387   if (_first_all_fine_prts != NULL) {
 388     guarantee(_first_all_fine_prts != NULL && _last_all_fine_prts != NULL, "just checking");
 389     PerRegionTable::bulk_free(_first_all_fine_prts, _last_all_fine_prts);
 390     memset(_fine_grain_regions, 0, _max_fine_entries * sizeof(_fine_grain_regions[0]));
 391   } else {
 392     guarantee(_first_all_fine_prts == NULL && _last_all_fine_prts == NULL, "just checking");
 393   }
 394 
 395   _first_all_fine_prts = _last_all_fine_prts = NULL;
 396   _sparse_table.clear();
 397   if (_n_coarse_entries > 0) {
 398     _coarse_map.clear();
 399   }
 400   _n_fine_entries = 0;
 401   _n_coarse_entries = 0;
 402 }
 403 
 404 bool OtherRegionsTable::contains_reference(OopOrNarrowOopStar from) const {
 405   // Cast away const in this case.
 406   MutexLocker x((Mutex*)_m, Mutex::_no_safepoint_check_flag);
 407   return contains_reference_locked(from);
 408 }
 409 
 410 bool OtherRegionsTable::contains_reference_locked(OopOrNarrowOopStar from) const {
 411   HeapRegion* hr = _g1h->heap_region_containing(from);
 412   RegionIdx_t hr_ind = (RegionIdx_t) hr->hrm_index();
 413   // Is this region in the coarse map?
 414   if (_coarse_map.at(hr_ind)) return true;
 415 
 416   PerRegionTable* prt = find_region_table(hr_ind & _mod_max_fine_entries_mask,
 417                                           hr);
 418   if (prt != NULL) {
 419     return prt->contains_reference(from);
 420 
 421   } else {
 422     CardIdx_t card_index = card_within_region(from, hr);
 423     return _sparse_table.contains_card(hr_ind, card_index);
 424   }
 425 }
 426 
 427 HeapRegionRemSet::HeapRegionRemSet(G1BlockOffsetTable* bot,
 428                                    HeapRegion* hr)
 429   : _bot(bot),
 430     _code_roots(),
 431     _m(Mutex::leaf, FormatBuffer<128>("HeapRegionRemSet lock #%u", hr->hrm_index()), true, Mutex::_safepoint_check_never),
 432     _other_regions(&_m),
 433     _hr(hr),
 434     _state(Untracked)
 435 {
 436 }
 437 
 438 void HeapRegionRemSet::clear_fcc() {
 439   G1FromCardCache::clear(_hr->hrm_index());
 440 }
 441 
 442 void HeapRegionRemSet::setup_remset_size() {
 443   const int LOG_M = 20;
 444   guarantee(HeapRegion::LogOfHRGrainBytes >= LOG_M, "Code assumes the region size >= 1M, but is " SIZE_FORMAT "B", HeapRegion::GrainBytes);
 445 
 446   int region_size_log_mb = HeapRegion::LogOfHRGrainBytes - LOG_M;
 447   if (FLAG_IS_DEFAULT(G1RSetSparseRegionEntries)) {
 448     G1RSetSparseRegionEntries = G1RSetSparseRegionEntriesBase * ((size_t)1 << (region_size_log_mb + 1));
 449   }
 450   if (FLAG_IS_DEFAULT(G1RSetRegionEntries)) {
 451     G1RSetRegionEntries = G1RSetRegionEntriesBase * (region_size_log_mb + 1);
 452   }
 453   guarantee(G1RSetSparseRegionEntries > 0 && G1RSetRegionEntries > 0 , "Sanity");
 454 }
 455 
 456 void HeapRegionRemSet::clear(bool only_cardset) {
 457   MutexLocker x(&_m, Mutex::_no_safepoint_check_flag);
 458   clear_locked(only_cardset);
 459 }
 460 
 461 void HeapRegionRemSet::clear_locked(bool only_cardset) {
 462   if (!only_cardset) {
 463     _code_roots.clear();
 464   }
 465   clear_fcc();
 466   _other_regions.clear();
 467   set_state_empty();
 468   assert(occupied_locked() == 0, "Should be clear.");
 469 }
 470 
 471 // Code roots support
 472 //
 473 // The code root set is protected by two separate locking schemes
 474 // When at safepoint the per-hrrs lock must be held during modifications
 475 // except when doing a full gc.
 476 // When not at safepoint the CodeCache_lock must be held during modifications.
 477 // When concurrent readers access the contains() function
 478 // (during the evacuation phase) no removals are allowed.
 479 
 480 void HeapRegionRemSet::add_strong_code_root(nmethod* nm) {
 481   assert(nm != NULL, "sanity");
 482   assert((!CodeCache_lock->owned_by_self() || SafepointSynchronize::is_at_safepoint()),
 483           "should call add_strong_code_root_locked instead. CodeCache_lock->owned_by_self(): %s, is_at_safepoint(): %s",
 484           BOOL_TO_STR(CodeCache_lock->owned_by_self()), BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()));
 485   // Optimistic unlocked contains-check
 486   if (!_code_roots.contains(nm)) {
 487     MutexLocker ml(&_m, Mutex::_no_safepoint_check_flag);
 488     add_strong_code_root_locked(nm);
 489   }
 490 }
 491 
 492 void HeapRegionRemSet::add_strong_code_root_locked(nmethod* nm) {
 493   assert(nm != NULL, "sanity");
 494   assert((CodeCache_lock->owned_by_self() ||
 495          (SafepointSynchronize::is_at_safepoint() &&
 496           (_m.owned_by_self() || Thread::current()->is_VM_thread()))),
 497           "not safely locked. CodeCache_lock->owned_by_self(): %s, is_at_safepoint(): %s, _m.owned_by_self(): %s, Thread::current()->is_VM_thread(): %s",
 498           BOOL_TO_STR(CodeCache_lock->owned_by_self()), BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()),
 499           BOOL_TO_STR(_m.owned_by_self()), BOOL_TO_STR(Thread::current()->is_VM_thread()));
 500   _code_roots.add(nm);
 501 }
 502 
 503 void HeapRegionRemSet::remove_strong_code_root(nmethod* nm) {
 504   assert(nm != NULL, "sanity");
 505   assert_locked_or_safepoint(CodeCache_lock);
 506 
 507   MutexLocker ml(CodeCache_lock->owned_by_self() ? NULL : &_m, Mutex::_no_safepoint_check_flag);
 508   _code_roots.remove(nm);
 509 
 510   // Check that there were no duplicates
 511   guarantee(!_code_roots.contains(nm), "duplicate entry found");
 512 }
 513 
 514 void HeapRegionRemSet::strong_code_roots_do(CodeBlobClosure* blk) const {
 515   _code_roots.nmethods_do(blk);
 516 }
 517 
 518 void HeapRegionRemSet::clean_strong_code_roots(HeapRegion* hr) {
 519   _code_roots.clean(hr);
 520 }
 521 
 522 size_t HeapRegionRemSet::strong_code_roots_mem_size() {
 523   return _code_roots.mem_size();
 524 }