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/g1BarrierSet.hpp" 27 #include "gc/g1/g1BlockOffsetTable.inline.hpp" 28 #include "gc/g1/g1CardTable.inline.hpp" 29 #include "gc/g1/g1CardTableEntryClosure.hpp" 30 #include "gc/g1/g1CollectedHeap.inline.hpp" 31 #include "gc/g1/g1ConcurrentRefine.hpp" 32 #include "gc/g1/g1DirtyCardQueue.hpp" 33 #include "gc/g1/g1FromCardCache.hpp" 34 #include "gc/g1/g1GCPhaseTimes.hpp" 35 #include "gc/g1/g1HotCardCache.hpp" 36 #include "gc/g1/g1OopClosures.inline.hpp" 37 #include "gc/g1/g1RootClosures.hpp" 38 #include "gc/g1/g1RemSet.hpp" 39 #include "gc/g1/g1SharedDirtyCardQueue.hpp" 40 #include "gc/g1/heapRegion.inline.hpp" 41 #include "gc/g1/heapRegionManager.inline.hpp" 42 #include "gc/g1/heapRegionRemSet.inline.hpp" 43 #include "gc/g1/sparsePRT.hpp" 44 #include "gc/shared/gcTraceTime.inline.hpp" 45 #include "gc/shared/ptrQueue.hpp" 46 #include "gc/shared/suspendibleThreadSet.hpp" 47 #include "jfr/jfrEvents.hpp" 48 #include "memory/iterator.hpp" 49 #include "memory/resourceArea.hpp" 50 #include "oops/access.inline.hpp" 51 #include "oops/oop.inline.hpp" 52 #include "runtime/os.hpp" 53 #include "utilities/align.hpp" 54 #include "utilities/globalDefinitions.hpp" 55 #include "utilities/stack.inline.hpp" 56 #include "utilities/ticks.hpp" 57 58 // Collects information about the overall heap root scan progress during an evacuation. 59 // 60 // Scanning the remembered sets works by first merging all sources of cards to be 61 // scanned (log buffers, hcc, remembered sets) into a single data structure to remove 62 // duplicates and simplify work distribution. 63 // 64 // During the following card scanning we not only scan this combined set of cards, but 65 // also remember that these were completely scanned. The following evacuation passes 66 // do not scan these cards again, and so need to be preserved across increments. 67 // 68 // The representation for all the cards to scan is the card table: cards can have 69 // one of three states during GC: 70 // - clean: these cards will not be scanned in this pass 71 // - dirty: these cards will be scanned in this pass 72 // - scanned: these cards have already been scanned in a previous pass 73 // 74 // After all evacuation is done, we reset the card table to clean. 75 // 76 // Work distribution occurs on "chunk" basis, i.e. contiguous ranges of cards. As an 77 // additional optimization, during card merging we remember which regions and which 78 // chunks actually contain cards to be scanned. Threads iterate only across these 79 // regions, and only compete for chunks containing any cards. 80 // 81 // Within these chunks, a worker scans the card table on "blocks" of cards, i.e. 82 // contiguous ranges of dirty cards to be scanned. These blocks are converted to actual 83 // memory ranges and then passed on to actual scanning. 84 class G1RemSetScanState : public CHeapObj<mtGC> { 85 class G1DirtyRegions; 86 87 size_t _max_regions; 88 89 // Has this region that is part of the regions in the collection set been processed yet. 90 typedef bool G1RemsetIterState; 91 92 G1RemsetIterState volatile* _collection_set_iter_state; 93 94 // Card table iteration claim for each heap region, from 0 (completely unscanned) 95 // to (>=) HeapRegion::CardsPerRegion (completely scanned). 96 uint volatile* _card_table_scan_state; 97 98 // Return "optimal" number of chunks per region we want to use for claiming areas 99 // within a region to claim. Dependent on the region size as proxy for the heap 100 // size, we limit the total number of chunks to limit memory usage and maintenance 101 // effort of that table vs. granularity of distributing scanning work. 102 // Testing showed that 8 for 1M/2M region, 16 for 4M/8M regions, 32 for 16/32M regions 103 // seems to be such a good trade-off. 104 static uint get_chunks_per_region(uint log_region_size) { 105 // Limit the expected input values to current known possible values of the 106 // (log) region size. Adjust as necessary after testing if changing the permissible 107 // values for region size. 108 assert(log_region_size >= 20 && log_region_size <= 25, 109 "expected value in [20,25], but got %u", log_region_size); 110 return 1u << (log_region_size / 2 - 7); 111 } 112 113 uint _scan_chunks_per_region; // Number of chunks per region. 114 uint8_t _log_scan_chunks_per_region; // Log of number of chunks per region. 115 bool* _region_scan_chunks; 116 size_t _num_total_scan_chunks; // Total number of elements in _region_scan_chunks. 117 uint8_t _scan_chunks_shift; // For conversion between card index and chunk index. 118 public: 119 uint scan_chunk_size() const { return (uint)1 << _scan_chunks_shift; } 120 121 // Returns whether the chunk corresponding to the given region/card in region contain a 122 // dirty card, i.e. actually needs scanning. 123 bool chunk_needs_scan(uint const region_idx, uint const card_in_region) const { 124 size_t const idx = ((size_t)region_idx << _log_scan_chunks_per_region) + (card_in_region >> _scan_chunks_shift); 125 assert(idx < _num_total_scan_chunks, "Index " SIZE_FORMAT " out of bounds " SIZE_FORMAT, 126 idx, _num_total_scan_chunks); 127 return _region_scan_chunks[idx]; 128 } 129 130 private: 131 // The complete set of regions which card table needs to be cleared at the end of GC because 132 // we scribbled all over them. 133 G1DirtyRegions* _all_dirty_regions; 134 // The set of regions which card table needs to be scanned for new dirty cards 135 // in the current evacuation pass. 136 G1DirtyRegions* _next_dirty_regions; 137 138 // Set of (unique) regions that can be added to concurrently. 139 class G1DirtyRegions : public CHeapObj<mtGC> { 140 uint* _buffer; 141 uint _cur_idx; 142 size_t _max_regions; 143 144 bool* _contains; 145 146 public: 147 G1DirtyRegions(size_t max_regions) : 148 _buffer(NEW_C_HEAP_ARRAY(uint, max_regions, mtGC)), 149 _cur_idx(0), 150 _max_regions(max_regions), 151 _contains(NEW_C_HEAP_ARRAY(bool, max_regions, mtGC)) { 152 153 reset(); 154 } 155 156 static size_t chunk_size() { return M; } 157 158 ~G1DirtyRegions() { 159 FREE_C_HEAP_ARRAY(uint, _buffer); 160 FREE_C_HEAP_ARRAY(bool, _contains); 161 } 162 163 void reset() { 164 _cur_idx = 0; 165 ::memset(_contains, false, _max_regions * sizeof(bool)); 166 } 167 168 uint size() const { return _cur_idx; } 169 170 uint at(uint idx) const { 171 assert(idx < _cur_idx, "Index %u beyond valid regions", idx); 172 return _buffer[idx]; 173 } 174 175 void add_dirty_region(uint region) { 176 if (_contains[region]) { 177 return; 178 } 179 180 bool marked_as_dirty = Atomic::cmpxchg(true, &_contains[region], false) == false; 181 if (marked_as_dirty) { 182 uint allocated = Atomic::add(1u, &_cur_idx) - 1; 183 _buffer[allocated] = region; 184 } 185 } 186 187 // Creates the union of this and the other G1DirtyRegions. 188 void merge(const G1DirtyRegions* other) { 189 for (uint i = 0; i < other->size(); i++) { 190 uint region = other->at(i); 191 if (!_contains[region]) { 192 _buffer[_cur_idx++] = region; 193 _contains[region] = true; 194 } 195 } 196 } 197 }; 198 199 // For each region, contains the maximum top() value to be used during this garbage 200 // collection. Subsumes common checks like filtering out everything but old and 201 // humongous regions outside the collection set. 202 // This is valid because we are not interested in scanning stray remembered set 203 // entries from free or archive regions. 204 HeapWord** _scan_top; 205 206 class G1ClearCardTableTask : public AbstractGangTask { 207 G1CollectedHeap* _g1h; 208 G1DirtyRegions* _regions; 209 uint _chunk_length; 210 211 uint volatile _cur_dirty_regions; 212 213 G1RemSetScanState* _scan_state; 214 215 public: 216 G1ClearCardTableTask(G1CollectedHeap* g1h, 217 G1DirtyRegions* regions, 218 uint chunk_length, 219 G1RemSetScanState* scan_state) : 220 AbstractGangTask("G1 Clear Card Table Task"), 221 _g1h(g1h), 222 _regions(regions), 223 _chunk_length(chunk_length), 224 _cur_dirty_regions(0), 225 _scan_state(scan_state) { 226 227 assert(chunk_length > 0, "must be"); 228 } 229 230 static uint chunk_size() { return M; } 231 232 void work(uint worker_id) { 233 while (_cur_dirty_regions < _regions->size()) { 234 uint next = Atomic::add(_chunk_length, &_cur_dirty_regions) - _chunk_length; 235 uint max = MIN2(next + _chunk_length, _regions->size()); 236 237 for (uint i = next; i < max; i++) { 238 HeapRegion* r = _g1h->region_at(_regions->at(i)); 239 if (!r->is_survivor()) { 240 r->clear_cardtable(); 241 } 242 } 243 } 244 } 245 }; 246 247 // Clear the card table of "dirty" regions. 248 void clear_card_table(WorkGang* workers) { 249 uint num_regions = _all_dirty_regions->size(); 250 251 if (num_regions == 0) { 252 return; 253 } 254 255 uint const num_chunks = (uint)(align_up((size_t)num_regions << HeapRegion::LogCardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size()); 256 uint const num_workers = MIN2(num_chunks, workers->active_workers()); 257 uint const chunk_length = G1ClearCardTableTask::chunk_size() / (uint)HeapRegion::CardsPerRegion; 258 259 // Iterate over the dirty cards region list. 260 G1ClearCardTableTask cl(G1CollectedHeap::heap(), _all_dirty_regions, chunk_length, this); 261 262 log_debug(gc, ergo)("Running %s using %u workers for %u " 263 "units of work for %u regions.", 264 cl.name(), num_workers, num_chunks, num_regions); 265 workers->run_task(&cl, num_workers); 266 267 #ifndef PRODUCT 268 G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup(); 269 #endif 270 } 271 272 public: 273 G1RemSetScanState() : 274 _max_regions(0), 275 _collection_set_iter_state(NULL), 276 _card_table_scan_state(NULL), 277 _scan_chunks_per_region(get_chunks_per_region(HeapRegion::LogOfHRGrainBytes)), 278 _log_scan_chunks_per_region(log2_uint(_scan_chunks_per_region)), 279 _region_scan_chunks(NULL), 280 _num_total_scan_chunks(0), 281 _scan_chunks_shift(0), 282 _all_dirty_regions(NULL), 283 _next_dirty_regions(NULL), 284 _scan_top(NULL) { 285 } 286 287 ~G1RemSetScanState() { 288 FREE_C_HEAP_ARRAY(G1RemsetIterState, _collection_set_iter_state); 289 FREE_C_HEAP_ARRAY(uint, _card_table_scan_state); 290 FREE_C_HEAP_ARRAY(bool, _region_scan_chunks); 291 FREE_C_HEAP_ARRAY(HeapWord*, _scan_top); 292 } 293 294 void initialize(size_t max_regions) { 295 assert(_collection_set_iter_state == NULL, "Must not be initialized twice"); 296 _max_regions = max_regions; 297 _collection_set_iter_state = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC); 298 _card_table_scan_state = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC); 299 _num_total_scan_chunks = max_regions * _scan_chunks_per_region; 300 _region_scan_chunks = NEW_C_HEAP_ARRAY(bool, _num_total_scan_chunks, mtGC); 301 302 _scan_chunks_shift = (uint8_t)log2_intptr(HeapRegion::CardsPerRegion / _scan_chunks_per_region); 303 _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC); 304 } 305 306 void prepare() { 307 _all_dirty_regions = new G1DirtyRegions(_max_regions); 308 _next_dirty_regions = new G1DirtyRegions(_max_regions); 309 } 310 311 void prepare_for_merge_heap_roots() { 312 _all_dirty_regions->merge(_next_dirty_regions); 313 314 _next_dirty_regions->reset(); 315 for (size_t i = 0; i < _max_regions; i++) { 316 _card_table_scan_state[i] = 0; 317 } 318 319 ::memset(_region_scan_chunks, false, _num_total_scan_chunks * sizeof(*_region_scan_chunks)); 320 } 321 322 // Returns whether the given region contains cards we need to scan. The remembered 323 // set and other sources may contain cards that 324 // - are in uncommitted regions 325 // - are located in the collection set 326 // - are located in free regions 327 // as we do not clean up remembered sets before merging heap roots. 328 bool contains_cards_to_process(uint const region_idx) const { 329 HeapRegion* hr = G1CollectedHeap::heap()->region_at_or_null(region_idx); 330 return (hr != NULL && !hr->in_collection_set() && hr->is_old_or_humongous_or_archive()); 331 } 332 333 size_t num_visited_cards() const { 334 size_t result = 0; 335 for (uint i = 0; i < _num_total_scan_chunks; i++) { 336 if (_region_scan_chunks[i]) { 337 result++; 338 } 339 } 340 return result * (HeapRegion::CardsPerRegion / _scan_chunks_per_region); 341 } 342 343 size_t num_cards_in_dirty_regions() const { 344 return _next_dirty_regions->size() * HeapRegion::CardsPerRegion; 345 } 346 347 void set_chunk_region_dirty(size_t const region_card_idx) { 348 size_t chunk_idx = region_card_idx >> _scan_chunks_shift; 349 for (uint i = 0; i < _scan_chunks_per_region; i++) { 350 _region_scan_chunks[chunk_idx++] = true; 351 } 352 } 353 354 void set_chunk_dirty(size_t const card_idx) { 355 assert((card_idx >> _scan_chunks_shift) < _num_total_scan_chunks, 356 "Trying to access index " SIZE_FORMAT " out of bounds " SIZE_FORMAT, 357 card_idx >> _scan_chunks_shift, _num_total_scan_chunks); 358 size_t const chunk_idx = card_idx >> _scan_chunks_shift; 359 if (!_region_scan_chunks[chunk_idx]) { 360 _region_scan_chunks[chunk_idx] = true; 361 } 362 } 363 364 void cleanup(WorkGang* workers) { 365 _all_dirty_regions->merge(_next_dirty_regions); 366 367 clear_card_table(workers); 368 369 delete _all_dirty_regions; 370 _all_dirty_regions = NULL; 371 372 delete _next_dirty_regions; 373 _next_dirty_regions = NULL; 374 } 375 376 void iterate_dirty_regions_from(HeapRegionClosure* cl, uint worker_id) { 377 uint num_regions = _next_dirty_regions->size(); 378 379 if (num_regions == 0) { 380 return; 381 } 382 383 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 384 385 WorkGang* workers = g1h->workers(); 386 uint const max_workers = workers->active_workers(); 387 388 uint const start_pos = num_regions * worker_id / max_workers; 389 uint cur = start_pos; 390 391 do { 392 bool result = cl->do_heap_region(g1h->region_at(_next_dirty_regions->at(cur))); 393 guarantee(!result, "Not allowed to ask for early termination."); 394 cur++; 395 if (cur == _next_dirty_regions->size()) { 396 cur = 0; 397 } 398 } while (cur != start_pos); 399 } 400 401 void reset_region_claim(uint region_idx) { 402 _collection_set_iter_state[region_idx] = false; 403 } 404 405 // Attempt to claim the given region in the collection set for iteration. Returns true 406 // if this call caused the transition from Unclaimed to Claimed. 407 inline bool claim_collection_set_region(uint region) { 408 assert(region < _max_regions, "Tried to access invalid region %u", region); 409 if (_collection_set_iter_state[region]) { 410 return false; 411 } 412 return !Atomic::cmpxchg(true, &_collection_set_iter_state[region], false); 413 } 414 415 bool has_cards_to_scan(uint region) { 416 assert(region < _max_regions, "Tried to access invalid region %u", region); 417 return _card_table_scan_state[region] < HeapRegion::CardsPerRegion; 418 } 419 420 uint claim_cards_to_scan(uint region, uint increment) { 421 assert(region < _max_regions, "Tried to access invalid region %u", region); 422 return Atomic::add(increment, &_card_table_scan_state[region]) - increment; 423 } 424 425 void add_dirty_region(uint const region) { 426 #ifdef ASSERT 427 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region); 428 assert(!hr->in_collection_set() && hr->is_old_or_humongous_or_archive(), 429 "Region %u is not suitable for scanning, is %sin collection set or %s", 430 hr->hrm_index(), hr->in_collection_set() ? "" : "not ", hr->get_short_type_str()); 431 #endif 432 _next_dirty_regions->add_dirty_region(region); 433 } 434 435 void add_all_dirty_region(uint region) { 436 #ifdef ASSERT 437 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region); 438 assert(hr->in_collection_set(), 439 "Only add young regions to all dirty regions directly but %u is %s", 440 hr->hrm_index(), hr->get_short_type_str()); 441 #endif 442 _all_dirty_regions->add_dirty_region(region); 443 } 444 445 void set_scan_top(uint region_idx, HeapWord* value) { 446 _scan_top[region_idx] = value; 447 } 448 449 HeapWord* scan_top(uint region_idx) const { 450 return _scan_top[region_idx]; 451 } 452 453 void clear_scan_top(uint region_idx) { 454 set_scan_top(region_idx, NULL); 455 } 456 }; 457 458 G1RemSet::G1RemSet(G1CollectedHeap* g1h, 459 G1CardTable* ct, 460 G1HotCardCache* hot_card_cache) : 461 _scan_state(new G1RemSetScanState()), 462 _prev_period_summary(false), 463 _g1h(g1h), 464 _ct(ct), 465 _g1p(_g1h->policy()), 466 _hot_card_cache(hot_card_cache) { 467 } 468 469 G1RemSet::~G1RemSet() { 470 delete _scan_state; 471 } 472 473 uint G1RemSet::num_par_rem_sets() { 474 return G1DirtyCardQueueSet::num_par_ids() + G1ConcurrentRefine::max_num_threads() + MAX2(ConcGCThreads, ParallelGCThreads); 475 } 476 477 void G1RemSet::initialize(size_t capacity, uint max_regions) { 478 G1FromCardCache::initialize(num_par_rem_sets(), max_regions); 479 _scan_state->initialize(max_regions); 480 } 481 482 // Helper class to scan and detect ranges of cards that need to be scanned on the 483 // card table. 484 class G1CardTableScanner : public StackObj { 485 public: 486 typedef CardTable::CardValue CardValue; 487 488 private: 489 CardValue* const _base_addr; 490 491 CardValue* _cur_addr; 492 CardValue* const _end_addr; 493 494 static const size_t ToScanMask = G1CardTable::g1_card_already_scanned; 495 static const size_t ExpandedToScanMask = G1CardTable::WordAlreadyScanned; 496 497 bool cur_addr_aligned() const { 498 return ((uintptr_t)_cur_addr) % sizeof(size_t) == 0; 499 } 500 501 bool cur_card_is_dirty() const { 502 CardValue value = *_cur_addr; 503 return (value & ToScanMask) == 0; 504 } 505 506 bool cur_word_of_cards_contains_any_dirty_card() const { 507 assert(cur_addr_aligned(), "Current address should be aligned"); 508 size_t const value = *(size_t*)_cur_addr; 509 return (~value & ExpandedToScanMask) != 0; 510 } 511 512 bool cur_word_of_cards_all_dirty_cards() const { 513 size_t const value = *(size_t*)_cur_addr; 514 return value == G1CardTable::WordAllDirty; 515 } 516 517 size_t get_and_advance_pos() { 518 _cur_addr++; 519 return pointer_delta(_cur_addr, _base_addr, sizeof(CardValue)) - 1; 520 } 521 522 public: 523 G1CardTableScanner(CardValue* start_card, size_t size) : 524 _base_addr(start_card), 525 _cur_addr(start_card), 526 _end_addr(start_card + size) { 527 528 assert(is_aligned(start_card, sizeof(size_t)), "Unaligned start addr " PTR_FORMAT, p2i(start_card)); 529 assert(is_aligned(size, sizeof(size_t)), "Unaligned size " SIZE_FORMAT, size); 530 } 531 532 size_t find_next_dirty() { 533 while (!cur_addr_aligned()) { 534 if (cur_card_is_dirty()) { 535 return get_and_advance_pos(); 536 } 537 _cur_addr++; 538 } 539 540 assert(cur_addr_aligned(), "Current address should be aligned now."); 541 while (_cur_addr != _end_addr) { 542 if (cur_word_of_cards_contains_any_dirty_card()) { 543 for (size_t i = 0; i < sizeof(size_t); i++) { 544 if (cur_card_is_dirty()) { 545 return get_and_advance_pos(); 546 } 547 _cur_addr++; 548 } 549 assert(false, "Should not reach here given we detected a dirty card in the word."); 550 } 551 _cur_addr += sizeof(size_t); 552 } 553 return get_and_advance_pos(); 554 } 555 556 size_t find_next_non_dirty() { 557 assert(_cur_addr <= _end_addr, "Not allowed to search for marks after area."); 558 559 while (!cur_addr_aligned()) { 560 if (!cur_card_is_dirty()) { 561 return get_and_advance_pos(); 562 } 563 _cur_addr++; 564 } 565 566 assert(cur_addr_aligned(), "Current address should be aligned now."); 567 while (_cur_addr != _end_addr) { 568 if (!cur_word_of_cards_all_dirty_cards()) { 569 for (size_t i = 0; i < sizeof(size_t); i++) { 570 if (!cur_card_is_dirty()) { 571 return get_and_advance_pos(); 572 } 573 _cur_addr++; 574 } 575 assert(false, "Should not reach here given we detected a non-dirty card in the word."); 576 } 577 _cur_addr += sizeof(size_t); 578 } 579 return get_and_advance_pos(); 580 } 581 }; 582 583 // Helper class to claim dirty chunks within the card table. 584 class G1CardTableChunkClaimer { 585 G1RemSetScanState* _scan_state; 586 uint _region_idx; 587 uint _cur_claim; 588 589 public: 590 G1CardTableChunkClaimer(G1RemSetScanState* scan_state, uint region_idx) : 591 _scan_state(scan_state), 592 _region_idx(region_idx), 593 _cur_claim(0) { 594 guarantee(size() <= HeapRegion::CardsPerRegion, "Should not claim more space than possible."); 595 } 596 597 bool has_next() { 598 while (true) { 599 _cur_claim = _scan_state->claim_cards_to_scan(_region_idx, size()); 600 if (_cur_claim >= HeapRegion::CardsPerRegion) { 601 return false; 602 } 603 if (_scan_state->chunk_needs_scan(_region_idx, _cur_claim)) { 604 return true; 605 } 606 } 607 } 608 609 uint value() const { return _cur_claim; } 610 uint size() const { return _scan_state->scan_chunk_size(); } 611 }; 612 613 // Scans a heap region for dirty cards. 614 class G1ScanHRForRegionClosure : public HeapRegionClosure { 615 G1CollectedHeap* _g1h; 616 G1CardTable* _ct; 617 G1BlockOffsetTable* _bot; 618 619 G1ParScanThreadState* _pss; 620 621 G1RemSetScanState* _scan_state; 622 623 G1GCPhaseTimes::GCParPhases _phase; 624 625 uint _worker_id; 626 627 size_t _cards_scanned; 628 size_t _blocks_scanned; 629 size_t _chunks_claimed; 630 631 Tickspan _rem_set_root_scan_time; 632 Tickspan _rem_set_trim_partially_time; 633 634 // The address to which this thread already scanned (walked the heap) up to during 635 // card scanning (exclusive). 636 HeapWord* _scanned_to; 637 638 HeapWord* scan_memregion(uint region_idx_for_card, MemRegion mr) { 639 HeapRegion* const card_region = _g1h->region_at(region_idx_for_card); 640 G1ScanCardClosure card_cl(_g1h, _pss); 641 642 HeapWord* const scanned_to = card_region->oops_on_memregion_seq_iterate_careful<true>(mr, &card_cl); 643 assert(scanned_to != NULL, "Should be able to scan range"); 644 assert(scanned_to >= mr.end(), "Scanned to " PTR_FORMAT " less than range " PTR_FORMAT, p2i(scanned_to), p2i(mr.end())); 645 646 _pss->trim_queue_partially(); 647 return scanned_to; 648 } 649 650 void do_claimed_block(uint const region_idx_for_card, size_t const first_card, size_t const num_cards) { 651 HeapWord* const card_start = _bot->address_for_index_raw(first_card); 652 #ifdef ASSERT 653 HeapRegion* hr = _g1h->region_at_or_null(region_idx_for_card); 654 assert(hr == NULL || hr->is_in_reserved(card_start), 655 "Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index()); 656 #endif 657 HeapWord* const top = _scan_state->scan_top(region_idx_for_card); 658 if (card_start >= top) { 659 return; 660 } 661 662 HeapWord* scan_end = MIN2(card_start + (num_cards << BOTConstants::LogN_words), top); 663 if (_scanned_to >= scan_end) { 664 return; 665 } 666 MemRegion mr(MAX2(card_start, _scanned_to), scan_end); 667 _scanned_to = scan_memregion(region_idx_for_card, mr); 668 669 _cards_scanned += num_cards; 670 } 671 672 ALWAYSINLINE void do_card_block(uint const region_idx, size_t const first_card, size_t const num_cards) { 673 _ct->mark_as_scanned(first_card, num_cards); 674 do_claimed_block(region_idx, first_card, num_cards); 675 _blocks_scanned++; 676 } 677 678 void scan_heap_roots(HeapRegion* r) { 679 EventGCPhaseParallel event; 680 uint const region_idx = r->hrm_index(); 681 682 ResourceMark rm; 683 684 G1CardTableChunkClaimer claim(_scan_state, region_idx); 685 686 // Set the current scan "finger" to NULL for every heap region to scan. Since 687 // the claim value is monotonically increasing, the check to not scan below this 688 // will filter out objects spanning chunks within the region too then, as opposed 689 // to resetting this value for every claim. 690 _scanned_to = NULL; 691 692 while (claim.has_next()) { 693 size_t const region_card_base_idx = ((size_t)region_idx << HeapRegion::LogCardsPerRegion) + claim.value(); 694 CardTable::CardValue* const base_addr = _ct->byte_for_index(region_card_base_idx); 695 696 G1CardTableScanner scan(base_addr, claim.size()); 697 698 size_t first_scan_idx = scan.find_next_dirty(); 699 while (first_scan_idx != claim.size()) { 700 assert(*_ct->byte_for_index(region_card_base_idx + first_scan_idx) <= 0x1, "is %d at region %u idx " SIZE_FORMAT, *_ct->byte_for_index(region_card_base_idx + first_scan_idx), region_idx, first_scan_idx); 701 702 size_t const last_scan_idx = scan.find_next_non_dirty(); 703 size_t const len = last_scan_idx - first_scan_idx; 704 705 do_card_block(region_idx, region_card_base_idx + first_scan_idx, len); 706 707 if (last_scan_idx == claim.size()) { 708 break; 709 } 710 711 first_scan_idx = scan.find_next_dirty(); 712 } 713 _chunks_claimed++; 714 } 715 716 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ScanHR)); 717 } 718 719 public: 720 G1ScanHRForRegionClosure(G1RemSetScanState* scan_state, 721 G1ParScanThreadState* pss, 722 uint worker_id, 723 G1GCPhaseTimes::GCParPhases phase) : 724 _g1h(G1CollectedHeap::heap()), 725 _ct(_g1h->card_table()), 726 _bot(_g1h->bot()), 727 _pss(pss), 728 _scan_state(scan_state), 729 _phase(phase), 730 _worker_id(worker_id), 731 _cards_scanned(0), 732 _blocks_scanned(0), 733 _chunks_claimed(0), 734 _rem_set_root_scan_time(), 735 _rem_set_trim_partially_time(), 736 _scanned_to(NULL) { 737 } 738 739 bool do_heap_region(HeapRegion* r) { 740 assert(!r->in_collection_set() && r->is_old_or_humongous_or_archive(), 741 "Should only be called on old gen non-collection set regions but region %u is not.", 742 r->hrm_index()); 743 uint const region_idx = r->hrm_index(); 744 745 if (_scan_state->has_cards_to_scan(region_idx)) { 746 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_root_scan_time, _rem_set_trim_partially_time); 747 scan_heap_roots(r); 748 } 749 return false; 750 } 751 752 Tickspan rem_set_root_scan_time() const { return _rem_set_root_scan_time; } 753 Tickspan rem_set_trim_partially_time() const { return _rem_set_trim_partially_time; } 754 755 size_t cards_scanned() const { return _cards_scanned; } 756 size_t blocks_scanned() const { return _blocks_scanned; } 757 size_t chunks_claimed() const { return _chunks_claimed; } 758 }; 759 760 void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss, 761 uint worker_id, 762 G1GCPhaseTimes::GCParPhases scan_phase, 763 G1GCPhaseTimes::GCParPhases objcopy_phase) { 764 G1ScanHRForRegionClosure cl(_scan_state, pss, worker_id, scan_phase); 765 _scan_state->iterate_dirty_regions_from(&cl, worker_id); 766 767 G1GCPhaseTimes* p = _g1p->phase_times(); 768 769 p->record_or_add_time_secs(objcopy_phase, worker_id, cl.rem_set_trim_partially_time().seconds()); 770 771 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_root_scan_time().seconds()); 772 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned(), G1GCPhaseTimes::ScanHRScannedCards); 773 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.blocks_scanned(), G1GCPhaseTimes::ScanHRScannedBlocks); 774 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.chunks_claimed(), G1GCPhaseTimes::ScanHRClaimedChunks); 775 } 776 777 // Heap region closure to be applied to all regions in the current collection set 778 // increment to fix up non-card related roots. 779 class G1ScanCollectionSetRegionClosure : public HeapRegionClosure { 780 G1ParScanThreadState* _pss; 781 G1RemSetScanState* _scan_state; 782 783 G1GCPhaseTimes::GCParPhases _scan_phase; 784 G1GCPhaseTimes::GCParPhases _code_roots_phase; 785 786 uint _worker_id; 787 788 size_t _opt_refs_scanned; 789 size_t _opt_refs_memory_used; 790 791 Tickspan _strong_code_root_scan_time; 792 Tickspan _strong_code_trim_partially_time; 793 794 Tickspan _rem_set_opt_root_scan_time; 795 Tickspan _rem_set_opt_trim_partially_time; 796 797 void scan_opt_rem_set_roots(HeapRegion* r) { 798 EventGCPhaseParallel event; 799 800 G1OopStarChunkedList* opt_rem_set_list = _pss->oops_into_optional_region(r); 801 802 G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss); 803 G1ScanRSForOptionalClosure cl(G1CollectedHeap::heap(), &scan_cl); 804 _opt_refs_scanned += opt_rem_set_list->oops_do(&cl, _pss->closures()->strong_oops()); 805 _opt_refs_memory_used += opt_rem_set_list->used_memory(); 806 807 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_scan_phase)); 808 } 809 810 public: 811 G1ScanCollectionSetRegionClosure(G1RemSetScanState* scan_state, 812 G1ParScanThreadState* pss, 813 uint worker_id, 814 G1GCPhaseTimes::GCParPhases scan_phase, 815 G1GCPhaseTimes::GCParPhases code_roots_phase) : 816 _pss(pss), 817 _scan_state(scan_state), 818 _scan_phase(scan_phase), 819 _code_roots_phase(code_roots_phase), 820 _worker_id(worker_id), 821 _opt_refs_scanned(0), 822 _opt_refs_memory_used(0), 823 _strong_code_root_scan_time(), 824 _strong_code_trim_partially_time(), 825 _rem_set_opt_root_scan_time(), 826 _rem_set_opt_trim_partially_time() { } 827 828 bool do_heap_region(HeapRegion* r) { 829 uint const region_idx = r->hrm_index(); 830 831 // The individual references for the optional remembered set are per-worker, so we 832 // always need to scan them. 833 if (r->has_index_in_opt_cset()) { 834 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_opt_root_scan_time, _rem_set_opt_trim_partially_time); 835 scan_opt_rem_set_roots(r); 836 } 837 838 if (_scan_state->claim_collection_set_region(region_idx)) { 839 EventGCPhaseParallel event; 840 841 G1EvacPhaseWithTrimTimeTracker timer(_pss, _strong_code_root_scan_time, _strong_code_trim_partially_time); 842 // Scan the strong code root list attached to the current region 843 r->strong_code_roots_do(_pss->closures()->weak_codeblobs()); 844 845 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_code_roots_phase)); 846 } 847 848 return false; 849 } 850 851 Tickspan strong_code_root_scan_time() const { return _strong_code_root_scan_time; } 852 Tickspan strong_code_root_trim_partially_time() const { return _strong_code_trim_partially_time; } 853 854 Tickspan rem_set_opt_root_scan_time() const { return _rem_set_opt_root_scan_time; } 855 Tickspan rem_set_opt_trim_partially_time() const { return _rem_set_opt_trim_partially_time; } 856 857 size_t opt_refs_scanned() const { return _opt_refs_scanned; } 858 size_t opt_refs_memory_used() const { return _opt_refs_memory_used; } 859 }; 860 861 void G1RemSet::scan_collection_set_regions(G1ParScanThreadState* pss, 862 uint worker_id, 863 G1GCPhaseTimes::GCParPhases scan_phase, 864 G1GCPhaseTimes::GCParPhases coderoots_phase, 865 G1GCPhaseTimes::GCParPhases objcopy_phase) { 866 G1ScanCollectionSetRegionClosure cl(_scan_state, pss, worker_id, scan_phase, coderoots_phase); 867 _g1h->collection_set_iterate_increment_from(&cl, worker_id); 868 869 G1GCPhaseTimes* p = _g1h->phase_times(); 870 871 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_root_scan_time().seconds()); 872 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_trim_partially_time().seconds()); 873 874 p->record_or_add_time_secs(coderoots_phase, worker_id, cl.strong_code_root_scan_time().seconds()); 875 p->add_time_secs(objcopy_phase, worker_id, cl.strong_code_root_trim_partially_time().seconds()); 876 877 // At this time we record some metrics only for the evacuations after the initial one. 878 if (scan_phase == G1GCPhaseTimes::OptScanHR) { 879 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs); 880 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory); 881 } 882 } 883 884 void G1RemSet::prepare_region_for_scan(HeapRegion* region) { 885 uint hrm_index = region->hrm_index(); 886 887 _scan_state->reset_region_claim(hrm_index); 888 if (region->in_collection_set()) { 889 // Young regions had their card table marked as young at their allocation; 890 // we need to make sure that these marks are cleared at the end of GC, *but* 891 // they should not be scanned for cards. 892 // So directly add them to the "all_dirty_regions". 893 // Same for regions in the (initial) collection set: they may contain cards from 894 // the log buffers, make sure they are cleaned. 895 _scan_state->clear_scan_top(hrm_index); 896 _scan_state->add_all_dirty_region(hrm_index); 897 } else { 898 assert(region->is_old_or_humongous_or_archive(), "All other regions should be in the collection set"); 899 _scan_state->set_scan_top(hrm_index, region->top()); 900 } 901 } 902 903 void G1RemSet::prepare_for_scan_heap_roots() { 904 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 905 dcqs.concatenate_logs(); 906 907 _scan_state->prepare(); 908 } 909 910 class G1MergeHeapRootsTask : public AbstractGangTask { 911 912 // Visitor for remembered sets, dropping entries onto the card table. 913 class G1MergeCardSetClosure : public HeapRegionClosure { 914 G1RemSetScanState* _scan_state; 915 G1CardTable* _ct; 916 917 uint _merged_sparse; 918 uint _merged_fine; 919 uint _merged_coarse; 920 921 // Returns if the region contains cards we need to scan. If so, remember that 922 // region in the current set of dirty regions. 923 bool remember_if_interesting(uint const region_idx) { 924 if (!_scan_state->contains_cards_to_process(region_idx)) { 925 return false; 926 } 927 _scan_state->add_dirty_region(region_idx); 928 return true; 929 } 930 public: 931 G1MergeCardSetClosure(G1RemSetScanState* scan_state) : 932 _scan_state(scan_state), 933 _ct(G1CollectedHeap::heap()->card_table()), 934 _merged_sparse(0), 935 _merged_fine(0), 936 _merged_coarse(0) { } 937 938 void next_coarse_prt(uint const region_idx) { 939 if (!remember_if_interesting(region_idx)) { 940 return; 941 } 942 943 _merged_coarse++; 944 945 size_t region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion; 946 _ct->mark_region_dirty(region_base_idx, HeapRegion::CardsPerRegion); 947 _scan_state->set_chunk_region_dirty(region_base_idx); 948 } 949 950 void next_fine_prt(uint const region_idx, BitMap* bm) { 951 if (!remember_if_interesting(region_idx)) { 952 return; 953 } 954 955 _merged_fine++; 956 957 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion; 958 BitMap::idx_t cur = bm->get_next_one_offset(0); 959 while (cur != bm->size()) { 960 _ct->mark_clean_as_dirty(region_base_idx + cur); 961 _scan_state->set_chunk_dirty(region_base_idx + cur); 962 cur = bm->get_next_one_offset(cur + 1); 963 } 964 } 965 966 void next_sparse_prt(uint const region_idx, SparsePRTEntry::card_elem_t* cards, uint const num_cards) { 967 if (!remember_if_interesting(region_idx)) { 968 return; 969 } 970 971 _merged_sparse++; 972 973 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion; 974 for (uint i = 0; i < num_cards; i++) { 975 size_t card_idx = region_base_idx + cards[i]; 976 _ct->mark_clean_as_dirty(card_idx); 977 _scan_state->set_chunk_dirty(card_idx); 978 } 979 } 980 981 virtual bool do_heap_region(HeapRegion* r) { 982 assert(r->in_collection_set() || r->is_starts_humongous(), "must be"); 983 984 HeapRegionRemSet* rem_set = r->rem_set(); 985 if (!rem_set->is_empty()) { 986 rem_set->iterate_prts(*this); 987 } 988 989 return false; 990 } 991 992 size_t merged_sparse() const { return _merged_sparse; } 993 size_t merged_fine() const { return _merged_fine; } 994 size_t merged_coarse() const { return _merged_coarse; } 995 }; 996 997 // Visitor for the remembered sets of humongous candidate regions to merge their 998 // remembered set into the card table. 999 class G1FlushHumongousCandidateRemSets : public HeapRegionClosure { 1000 G1MergeCardSetClosure _cl; 1001 1002 public: 1003 G1FlushHumongousCandidateRemSets(G1RemSetScanState* scan_state) : _cl(scan_state) { } 1004 1005 virtual bool do_heap_region(HeapRegion* r) { 1006 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1007 1008 if (!r->is_starts_humongous() || 1009 !g1h->region_attr(r->hrm_index()).is_humongous() || 1010 r->rem_set()->is_empty()) { 1011 return false; 1012 } 1013 1014 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries), 1015 "Found a not-small remembered set here. This is inconsistent with previous assumptions."); 1016 1017 _cl.do_heap_region(r); 1018 1019 // We should only clear the card based remembered set here as we will not 1020 // implicitly rebuild anything else during eager reclaim. Note that at the moment 1021 // (and probably never) we do not enter this path if there are other kind of 1022 // remembered sets for this region. 1023 r->rem_set()->clear_locked(true /* only_cardset */); 1024 // Clear_locked() above sets the state to Empty. However we want to continue 1025 // collecting remembered set entries for humongous regions that were not 1026 // reclaimed. 1027 r->rem_set()->set_state_complete(); 1028 #ifdef ASSERT 1029 G1HeapRegionAttr region_attr = g1h->region_attr(r->hrm_index()); 1030 assert(region_attr.needs_remset_update(), "must be"); 1031 #endif 1032 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty."); 1033 1034 return false; 1035 } 1036 1037 size_t merged_sparse() const { return _cl.merged_sparse(); } 1038 size_t merged_fine() const { return _cl.merged_fine(); } 1039 size_t merged_coarse() const { return _cl.merged_coarse(); } 1040 }; 1041 1042 // Visitor for the log buffer entries to merge them into the card table. 1043 class G1MergeLogBufferCardsClosure : public G1CardTableEntryClosure { 1044 G1RemSetScanState* _scan_state; 1045 G1CardTable* _ct; 1046 1047 size_t _cards_dirty; 1048 size_t _cards_skipped; 1049 public: 1050 G1MergeLogBufferCardsClosure(G1CollectedHeap* g1h, G1RemSetScanState* scan_state) : 1051 _scan_state(scan_state), _ct(g1h->card_table()), _cards_dirty(0), _cards_skipped(0) 1052 {} 1053 1054 void do_card_ptr(CardValue* card_ptr, uint worker_id) { 1055 // The only time we care about recording cards that 1056 // contain references that point into the collection set 1057 // is during RSet updating within an evacuation pause. 1058 // In this case worker_id should be the id of a GC worker thread. 1059 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 1060 1061 uint const region_idx = _ct->region_idx_for(card_ptr); 1062 1063 // The second clause must come after - the log buffers might contain cards to uncommited 1064 // regions. 1065 // This code may count duplicate entries in the log buffers (even if rare) multiple 1066 // times. 1067 if (_scan_state->contains_cards_to_process(region_idx) && (*card_ptr == G1CardTable::dirty_card_val())) { 1068 _scan_state->add_dirty_region(region_idx); 1069 _scan_state->set_chunk_dirty(_ct->index_for_cardvalue(card_ptr)); 1070 _cards_dirty++; 1071 } else { 1072 // We may have had dirty cards in the (initial) collection set (or the 1073 // young regions which are always in the initial collection set). We do 1074 // not fix their cards here: we already added these regions to the set of 1075 // regions to clear the card table at the end during the prepare() phase. 1076 _cards_skipped++; 1077 } 1078 } 1079 1080 size_t cards_dirty() const { return _cards_dirty; } 1081 size_t cards_skipped() const { return _cards_skipped; } 1082 }; 1083 1084 HeapRegionClaimer _hr_claimer; 1085 G1RemSetScanState* _scan_state; 1086 BufferNode::Stack _dirty_card_buffers; 1087 bool _initial_evacuation; 1088 1089 volatile bool _fast_reclaim_handled; 1090 1091 void apply_closure_to_dirty_card_buffers(G1MergeLogBufferCardsClosure* cl, uint worker_id) { 1092 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1093 size_t buffer_size = dcqs.buffer_size(); 1094 while (BufferNode* node = _dirty_card_buffers.pop()) { 1095 cl->apply_to_buffer(node, buffer_size, worker_id); 1096 dcqs.deallocate_buffer(node); 1097 } 1098 } 1099 1100 public: 1101 G1MergeHeapRootsTask(G1RemSetScanState* scan_state, uint num_workers, bool initial_evacuation) : 1102 AbstractGangTask("G1 Merge Heap Roots"), 1103 _hr_claimer(num_workers), 1104 _scan_state(scan_state), 1105 _dirty_card_buffers(), 1106 _initial_evacuation(initial_evacuation), 1107 _fast_reclaim_handled(false) 1108 { 1109 if (initial_evacuation) { 1110 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); 1111 G1BufferNodeList buffers = dcqs.take_all_completed_buffers(); 1112 if (buffers._entry_count != 0) { 1113 _dirty_card_buffers.prepend(*buffers._head, *buffers._tail); 1114 } 1115 } 1116 } 1117 1118 virtual void work(uint worker_id) { 1119 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1120 G1GCPhaseTimes* p = g1h->phase_times(); 1121 1122 G1GCPhaseTimes::GCParPhases merge_remset_phase = _initial_evacuation ? 1123 G1GCPhaseTimes::MergeRS : 1124 G1GCPhaseTimes::OptMergeRS; 1125 1126 // We schedule flushing the remembered sets of humongous fast reclaim candidates 1127 // onto the card table first to allow the remaining parallelized tasks hide it. 1128 if (_initial_evacuation && 1129 p->fast_reclaim_humongous_candidates() > 0 && 1130 !_fast_reclaim_handled && 1131 !Atomic::cmpxchg(true, &_fast_reclaim_handled, false)) { 1132 1133 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeER, worker_id); 1134 1135 G1FlushHumongousCandidateRemSets cl(_scan_state); 1136 g1h->heap_region_iterate(&cl); 1137 1138 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse); 1139 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine); 1140 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse); 1141 } 1142 1143 // Merge remembered sets of current candidates. 1144 { 1145 G1GCParPhaseTimesTracker x(p, merge_remset_phase, worker_id, _initial_evacuation /* must_record */); 1146 G1MergeCardSetClosure cl(_scan_state); 1147 g1h->collection_set_iterate_increment_from(&cl, &_hr_claimer, worker_id); 1148 1149 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse); 1150 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine); 1151 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse); 1152 } 1153 1154 // Apply closure to log entries in the HCC. 1155 if (_initial_evacuation && G1HotCardCache::default_use_cache()) { 1156 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase"); 1157 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeHCC, worker_id); 1158 G1MergeLogBufferCardsClosure cl(g1h, _scan_state); 1159 g1h->iterate_hcc_closure(&cl, worker_id); 1160 1161 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeHCCDirtyCards); 1162 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeHCCSkippedCards); 1163 } 1164 1165 // Now apply the closure to all remaining log entries. 1166 if (_initial_evacuation) { 1167 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase"); 1168 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeLB, worker_id); 1169 1170 G1MergeLogBufferCardsClosure cl(g1h, _scan_state); 1171 apply_closure_to_dirty_card_buffers(&cl, worker_id); 1172 1173 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeLBDirtyCards); 1174 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeLBSkippedCards); 1175 } 1176 } 1177 }; 1178 1179 void G1RemSet::print_merge_heap_roots_stats() { 1180 size_t num_visited_cards = _scan_state->num_visited_cards(); 1181 1182 size_t total_dirty_region_cards = _scan_state->num_cards_in_dirty_regions(); 1183 1184 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1185 size_t total_old_region_cards = 1186 (g1h->num_regions() - (g1h->num_free_regions() - g1h->collection_set()->cur_length())) * HeapRegion::CardsPerRegion; 1187 1188 log_debug(gc,remset)("Visited cards " SIZE_FORMAT " Total dirty " SIZE_FORMAT " (%.2lf%%) Total old " SIZE_FORMAT " (%.2lf%%)", 1189 num_visited_cards, 1190 total_dirty_region_cards, 1191 percent_of(num_visited_cards, total_dirty_region_cards), 1192 total_old_region_cards, 1193 percent_of(num_visited_cards, total_old_region_cards)); 1194 } 1195 1196 void G1RemSet::merge_heap_roots(bool initial_evacuation) { 1197 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1198 1199 { 1200 Ticks start = Ticks::now(); 1201 1202 _scan_state->prepare_for_merge_heap_roots(); 1203 1204 Tickspan total = Ticks::now() - start; 1205 if (initial_evacuation) { 1206 g1h->phase_times()->record_prepare_merge_heap_roots_time(total.seconds() * 1000.0); 1207 } else { 1208 g1h->phase_times()->record_or_add_optional_prepare_merge_heap_roots_time(total.seconds() * 1000.0); 1209 } 1210 } 1211 1212 WorkGang* workers = g1h->workers(); 1213 size_t const increment_length = g1h->collection_set()->increment_length(); 1214 1215 uint const num_workers = initial_evacuation ? workers->active_workers() : 1216 MIN2(workers->active_workers(), (uint)increment_length); 1217 1218 { 1219 G1MergeHeapRootsTask cl(_scan_state, num_workers, initial_evacuation); 1220 log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " regions", 1221 cl.name(), num_workers, increment_length); 1222 workers->run_task(&cl, num_workers); 1223 } 1224 1225 if (log_is_enabled(Debug, gc, remset)) { 1226 print_merge_heap_roots_stats(); 1227 } 1228 } 1229 1230 void G1RemSet::prepare_for_scan_heap_roots(uint region_idx) { 1231 _scan_state->clear_scan_top(region_idx); 1232 } 1233 1234 void G1RemSet::cleanup_after_scan_heap_roots() { 1235 G1GCPhaseTimes* phase_times = _g1h->phase_times(); 1236 1237 // Set all cards back to clean. 1238 double start = os::elapsedTime(); 1239 _scan_state->cleanup(_g1h->workers()); 1240 phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0); 1241 } 1242 1243 inline void check_card_ptr(CardTable::CardValue* card_ptr, G1CardTable* ct) { 1244 #ifdef ASSERT 1245 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1246 assert(g1h->is_in_exact(ct->addr_for(card_ptr)), 1247 "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap", 1248 p2i(card_ptr), 1249 ct->index_for(ct->addr_for(card_ptr)), 1250 p2i(ct->addr_for(card_ptr)), 1251 g1h->addr_to_region(ct->addr_for(card_ptr))); 1252 #endif 1253 } 1254 1255 void G1RemSet::refine_card_concurrently(CardValue* card_ptr, 1256 uint worker_id) { 1257 assert(!_g1h->is_gc_active(), "Only call concurrently"); 1258 1259 // Construct the region representing the card. 1260 HeapWord* start = _ct->addr_for(card_ptr); 1261 // And find the region containing it. 1262 HeapRegion* r = _g1h->heap_region_containing_or_null(start); 1263 1264 // If this is a (stale) card into an uncommitted region, exit. 1265 if (r == NULL) { 1266 return; 1267 } 1268 1269 check_card_ptr(card_ptr, _ct); 1270 1271 // If the card is no longer dirty, nothing to do. 1272 if (*card_ptr != G1CardTable::dirty_card_val()) { 1273 return; 1274 } 1275 1276 // This check is needed for some uncommon cases where we should 1277 // ignore the card. 1278 // 1279 // The region could be young. Cards for young regions are 1280 // distinctly marked (set to g1_young_gen), so the post-barrier will 1281 // filter them out. However, that marking is performed 1282 // concurrently. A write to a young object could occur before the 1283 // card has been marked young, slipping past the filter. 1284 // 1285 // The card could be stale, because the region has been freed since 1286 // the card was recorded. In this case the region type could be 1287 // anything. If (still) free or (reallocated) young, just ignore 1288 // it. If (reallocated) old or humongous, the later card trimming 1289 // and additional checks in iteration may detect staleness. At 1290 // worst, we end up processing a stale card unnecessarily. 1291 // 1292 // In the normal (non-stale) case, the synchronization between the 1293 // enqueueing of the card and processing it here will have ensured 1294 // we see the up-to-date region type here. 1295 if (!r->is_old_or_humongous_or_archive()) { 1296 return; 1297 } 1298 1299 // The result from the hot card cache insert call is either: 1300 // * pointer to the current card 1301 // (implying that the current card is not 'hot'), 1302 // * null 1303 // (meaning we had inserted the card ptr into the "hot" card cache, 1304 // which had some headroom), 1305 // * a pointer to a "hot" card that was evicted from the "hot" cache. 1306 // 1307 1308 if (_hot_card_cache->use_cache()) { 1309 assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); 1310 1311 const CardValue* orig_card_ptr = card_ptr; 1312 card_ptr = _hot_card_cache->insert(card_ptr); 1313 if (card_ptr == NULL) { 1314 // There was no eviction. Nothing to do. 1315 return; 1316 } else if (card_ptr != orig_card_ptr) { 1317 // Original card was inserted and an old card was evicted. 1318 start = _ct->addr_for(card_ptr); 1319 r = _g1h->heap_region_containing(start); 1320 1321 // Check whether the region formerly in the cache should be 1322 // ignored, as discussed earlier for the original card. The 1323 // region could have been freed while in the cache. 1324 if (!r->is_old_or_humongous_or_archive()) { 1325 return; 1326 } 1327 } // Else we still have the original card. 1328 } 1329 1330 // Trim the region designated by the card to what's been allocated 1331 // in the region. The card could be stale, or the card could cover 1332 // (part of) an object at the end of the allocated space and extend 1333 // beyond the end of allocation. 1334 1335 // Non-humongous objects are only allocated in the old-gen during 1336 // GC, so if region is old then top is stable. Humongous object 1337 // allocation sets top last; if top has not yet been set, this is 1338 // a stale card and we'll end up with an empty intersection. If 1339 // this is not a stale card, the synchronization between the 1340 // enqueuing of the card and processing it here will have ensured 1341 // we see the up-to-date top here. 1342 HeapWord* scan_limit = r->top(); 1343 1344 if (scan_limit <= start) { 1345 // If the trimmed region is empty, the card must be stale. 1346 return; 1347 } 1348 1349 // Okay to clean and process the card now. There are still some 1350 // stale card cases that may be detected by iteration and dealt with 1351 // as iteration failure. 1352 *const_cast<volatile CardValue*>(card_ptr) = G1CardTable::clean_card_val(); 1353 1354 // This fence serves two purposes. First, the card must be cleaned 1355 // before processing the contents. Second, we can't proceed with 1356 // processing until after the read of top, for synchronization with 1357 // possibly concurrent humongous object allocation. It's okay that 1358 // reading top and reading type were racy wrto each other. We need 1359 // both set, in any order, to proceed. 1360 OrderAccess::fence(); 1361 1362 // Don't use addr_for(card_ptr + 1) which can ask for 1363 // a card beyond the heap. 1364 HeapWord* end = start + G1CardTable::card_size_in_words; 1365 MemRegion dirty_region(start, MIN2(scan_limit, end)); 1366 assert(!dirty_region.is_empty(), "sanity"); 1367 1368 G1ConcurrentRefineOopClosure conc_refine_cl(_g1h, worker_id); 1369 if (r->oops_on_memregion_seq_iterate_careful<false>(dirty_region, &conc_refine_cl) != NULL) { 1370 return; 1371 } 1372 1373 // If unable to process the card then we encountered an unparsable 1374 // part of the heap (e.g. a partially allocated object, so only 1375 // temporarily a problem) while processing a stale card. Despite 1376 // the card being stale, we can't simply ignore it, because we've 1377 // already marked the card cleaned, so taken responsibility for 1378 // ensuring the card gets scanned. 1379 // 1380 // However, the card might have gotten re-dirtied and re-enqueued 1381 // while we worked. (In fact, it's pretty likely.) 1382 if (*card_ptr == G1CardTable::dirty_card_val()) { 1383 return; 1384 } 1385 1386 // Re-dirty the card and enqueue in the *shared* queue. Can't use 1387 // the thread-local queue, because that might be the queue that is 1388 // being processed by us; we could be a Java thread conscripted to 1389 // perform refinement on our queue's current buffer. 1390 *card_ptr = G1CardTable::dirty_card_val(); 1391 G1BarrierSet::shared_dirty_card_queue().enqueue(card_ptr); 1392 } 1393 1394 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) { 1395 if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) && 1396 (period_count % G1SummarizeRSetStatsPeriod == 0)) { 1397 1398 G1RemSetSummary current; 1399 _prev_period_summary.subtract_from(¤t); 1400 1401 Log(gc, remset) log; 1402 log.trace("%s", header); 1403 ResourceMark rm; 1404 LogStream ls(log.trace()); 1405 _prev_period_summary.print_on(&ls); 1406 1407 _prev_period_summary.set(¤t); 1408 } 1409 } 1410 1411 void G1RemSet::print_summary_info() { 1412 Log(gc, remset, exit) log; 1413 if (log.is_trace()) { 1414 log.trace(" Cumulative RS summary"); 1415 G1RemSetSummary current; 1416 ResourceMark rm; 1417 LogStream ls(log.trace()); 1418 current.print_on(&ls); 1419 } 1420 } 1421 1422 class G1RebuildRemSetTask: public AbstractGangTask { 1423 // Aggregate the counting data that was constructed concurrently 1424 // with marking. 1425 class G1RebuildRemSetHeapRegionClosure : public HeapRegionClosure { 1426 G1ConcurrentMark* _cm; 1427 G1RebuildRemSetClosure _update_cl; 1428 1429 // Applies _update_cl to the references of the given object, limiting objArrays 1430 // to the given MemRegion. Returns the amount of words actually scanned. 1431 size_t scan_for_references(oop const obj, MemRegion mr) { 1432 size_t const obj_size = obj->size(); 1433 // All non-objArrays and objArrays completely within the mr 1434 // can be scanned without passing the mr. 1435 if (!obj->is_objArray() || mr.contains(MemRegion((HeapWord*)obj, obj_size))) { 1436 obj->oop_iterate(&_update_cl); 1437 return obj_size; 1438 } 1439 // This path is for objArrays crossing the given MemRegion. Only scan the 1440 // area within the MemRegion. 1441 obj->oop_iterate(&_update_cl, mr); 1442 return mr.intersection(MemRegion((HeapWord*)obj, obj_size)).word_size(); 1443 } 1444 1445 // A humongous object is live (with respect to the scanning) either 1446 // a) it is marked on the bitmap as such 1447 // b) its TARS is larger than TAMS, i.e. has been allocated during marking. 1448 bool is_humongous_live(oop const humongous_obj, const G1CMBitMap* const bitmap, HeapWord* tams, HeapWord* tars) const { 1449 return bitmap->is_marked(humongous_obj) || (tars > tams); 1450 } 1451 1452 // Iterator over the live objects within the given MemRegion. 1453 class LiveObjIterator : public StackObj { 1454 const G1CMBitMap* const _bitmap; 1455 const HeapWord* _tams; 1456 const MemRegion _mr; 1457 HeapWord* _current; 1458 1459 bool is_below_tams() const { 1460 return _current < _tams; 1461 } 1462 1463 bool is_live(HeapWord* obj) const { 1464 return !is_below_tams() || _bitmap->is_marked(obj); 1465 } 1466 1467 HeapWord* bitmap_limit() const { 1468 return MIN2(const_cast<HeapWord*>(_tams), _mr.end()); 1469 } 1470 1471 void move_if_below_tams() { 1472 if (is_below_tams() && has_next()) { 1473 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit()); 1474 } 1475 } 1476 public: 1477 LiveObjIterator(const G1CMBitMap* const bitmap, const HeapWord* tams, const MemRegion mr, HeapWord* first_oop_into_mr) : 1478 _bitmap(bitmap), 1479 _tams(tams), 1480 _mr(mr), 1481 _current(first_oop_into_mr) { 1482 1483 assert(_current <= _mr.start(), 1484 "First oop " PTR_FORMAT " should extend into mr [" PTR_FORMAT ", " PTR_FORMAT ")", 1485 p2i(first_oop_into_mr), p2i(mr.start()), p2i(mr.end())); 1486 1487 // Step to the next live object within the MemRegion if needed. 1488 if (is_live(_current)) { 1489 // Non-objArrays were scanned by the previous part of that region. 1490 if (_current < mr.start() && !oop(_current)->is_objArray()) { 1491 _current += oop(_current)->size(); 1492 // We might have positioned _current on a non-live object. Reposition to the next 1493 // live one if needed. 1494 move_if_below_tams(); 1495 } 1496 } else { 1497 // The object at _current can only be dead if below TAMS, so we can use the bitmap. 1498 // immediately. 1499 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit()); 1500 assert(_current == _mr.end() || is_live(_current), 1501 "Current " PTR_FORMAT " should be live (%s) or beyond the end of the MemRegion (" PTR_FORMAT ")", 1502 p2i(_current), BOOL_TO_STR(is_live(_current)), p2i(_mr.end())); 1503 } 1504 } 1505 1506 void move_to_next() { 1507 _current += next()->size(); 1508 move_if_below_tams(); 1509 } 1510 1511 oop next() const { 1512 oop result = oop(_current); 1513 assert(is_live(_current), 1514 "Object " PTR_FORMAT " must be live TAMS " PTR_FORMAT " below %d mr " PTR_FORMAT " " PTR_FORMAT " outside %d", 1515 p2i(_current), p2i(_tams), _tams > _current, p2i(_mr.start()), p2i(_mr.end()), _mr.contains(result)); 1516 return result; 1517 } 1518 1519 bool has_next() const { 1520 return _current < _mr.end(); 1521 } 1522 }; 1523 1524 // Rebuild remembered sets in the part of the region specified by mr and hr. 1525 // Objects between the bottom of the region and the TAMS are checked for liveness 1526 // using the given bitmap. Objects between TAMS and TARS are assumed to be live. 1527 // Returns the number of live words between bottom and TAMS. 1528 size_t rebuild_rem_set_in_region(const G1CMBitMap* const bitmap, 1529 HeapWord* const top_at_mark_start, 1530 HeapWord* const top_at_rebuild_start, 1531 HeapRegion* hr, 1532 MemRegion mr) { 1533 size_t marked_words = 0; 1534 1535 if (hr->is_humongous()) { 1536 oop const humongous_obj = oop(hr->humongous_start_region()->bottom()); 1537 if (is_humongous_live(humongous_obj, bitmap, top_at_mark_start, top_at_rebuild_start)) { 1538 // We need to scan both [bottom, TAMS) and [TAMS, top_at_rebuild_start); 1539 // however in case of humongous objects it is sufficient to scan the encompassing 1540 // area (top_at_rebuild_start is always larger or equal to TAMS) as one of the 1541 // two areas will be zero sized. I.e. TAMS is either 1542 // the same as bottom or top(_at_rebuild_start). There is no way TAMS has a different 1543 // value: this would mean that TAMS points somewhere into the object. 1544 assert(hr->top() == top_at_mark_start || hr->top() == top_at_rebuild_start, 1545 "More than one object in the humongous region?"); 1546 humongous_obj->oop_iterate(&_update_cl, mr); 1547 return top_at_mark_start != hr->bottom() ? mr.intersection(MemRegion((HeapWord*)humongous_obj, humongous_obj->size())).byte_size() : 0; 1548 } else { 1549 return 0; 1550 } 1551 } 1552 1553 for (LiveObjIterator it(bitmap, top_at_mark_start, mr, hr->block_start(mr.start())); it.has_next(); it.move_to_next()) { 1554 oop obj = it.next(); 1555 size_t scanned_size = scan_for_references(obj, mr); 1556 if ((HeapWord*)obj < top_at_mark_start) { 1557 marked_words += scanned_size; 1558 } 1559 } 1560 1561 return marked_words * HeapWordSize; 1562 } 1563 public: 1564 G1RebuildRemSetHeapRegionClosure(G1CollectedHeap* g1h, 1565 G1ConcurrentMark* cm, 1566 uint worker_id) : 1567 HeapRegionClosure(), 1568 _cm(cm), 1569 _update_cl(g1h, worker_id) { } 1570 1571 bool do_heap_region(HeapRegion* hr) { 1572 if (_cm->has_aborted()) { 1573 return true; 1574 } 1575 1576 uint const region_idx = hr->hrm_index(); 1577 DEBUG_ONLY(HeapWord* const top_at_rebuild_start_check = _cm->top_at_rebuild_start(region_idx);) 1578 assert(top_at_rebuild_start_check == NULL || 1579 top_at_rebuild_start_check > hr->bottom(), 1580 "A TARS (" PTR_FORMAT ") == bottom() (" PTR_FORMAT ") indicates the old region %u is empty (%s)", 1581 p2i(top_at_rebuild_start_check), p2i(hr->bottom()), region_idx, hr->get_type_str()); 1582 1583 size_t total_marked_bytes = 0; 1584 size_t const chunk_size_in_words = G1RebuildRemSetChunkSize / HeapWordSize; 1585 1586 HeapWord* const top_at_mark_start = hr->prev_top_at_mark_start(); 1587 1588 HeapWord* cur = hr->bottom(); 1589 while (cur < hr->end()) { 1590 // After every iteration (yield point) we need to check whether the region's 1591 // TARS changed due to e.g. eager reclaim. 1592 HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx); 1593 if (top_at_rebuild_start == NULL) { 1594 return false; 1595 } 1596 1597 MemRegion next_chunk = MemRegion(hr->bottom(), top_at_rebuild_start).intersection(MemRegion(cur, chunk_size_in_words)); 1598 if (next_chunk.is_empty()) { 1599 break; 1600 } 1601 1602 const Ticks start = Ticks::now(); 1603 size_t marked_bytes = rebuild_rem_set_in_region(_cm->prev_mark_bitmap(), 1604 top_at_mark_start, 1605 top_at_rebuild_start, 1606 hr, 1607 next_chunk); 1608 Tickspan time = Ticks::now() - start; 1609 1610 log_trace(gc, remset, tracking)("Rebuilt region %u " 1611 "live " SIZE_FORMAT " " 1612 "time %.3fms " 1613 "marked bytes " SIZE_FORMAT " " 1614 "bot " PTR_FORMAT " " 1615 "TAMS " PTR_FORMAT " " 1616 "TARS " PTR_FORMAT, 1617 region_idx, 1618 _cm->liveness(region_idx) * HeapWordSize, 1619 time.seconds() * 1000.0, 1620 marked_bytes, 1621 p2i(hr->bottom()), 1622 p2i(top_at_mark_start), 1623 p2i(top_at_rebuild_start)); 1624 1625 if (marked_bytes > 0) { 1626 total_marked_bytes += marked_bytes; 1627 } 1628 cur += chunk_size_in_words; 1629 1630 _cm->do_yield_check(); 1631 if (_cm->has_aborted()) { 1632 return true; 1633 } 1634 } 1635 // In the final iteration of the loop the region might have been eagerly reclaimed. 1636 // Simply filter out those regions. We can not just use region type because there 1637 // might have already been new allocations into these regions. 1638 DEBUG_ONLY(HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);) 1639 assert(top_at_rebuild_start == NULL || 1640 total_marked_bytes == hr->marked_bytes(), 1641 "Marked bytes " SIZE_FORMAT " for region %u (%s) in [bottom, TAMS) do not match calculated marked bytes " SIZE_FORMAT " " 1642 "(" PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT ")", 1643 total_marked_bytes, hr->hrm_index(), hr->get_type_str(), hr->marked_bytes(), 1644 p2i(hr->bottom()), p2i(top_at_mark_start), p2i(top_at_rebuild_start)); 1645 // Abort state may have changed after the yield check. 1646 return _cm->has_aborted(); 1647 } 1648 }; 1649 1650 HeapRegionClaimer _hr_claimer; 1651 G1ConcurrentMark* _cm; 1652 1653 uint _worker_id_offset; 1654 public: 1655 G1RebuildRemSetTask(G1ConcurrentMark* cm, 1656 uint n_workers, 1657 uint worker_id_offset) : 1658 AbstractGangTask("G1 Rebuild Remembered Set"), 1659 _hr_claimer(n_workers), 1660 _cm(cm), 1661 _worker_id_offset(worker_id_offset) { 1662 } 1663 1664 void work(uint worker_id) { 1665 SuspendibleThreadSetJoiner sts_join; 1666 1667 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1668 1669 G1RebuildRemSetHeapRegionClosure cl(g1h, _cm, _worker_id_offset + worker_id); 1670 g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hr_claimer, worker_id); 1671 } 1672 }; 1673 1674 void G1RemSet::rebuild_rem_set(G1ConcurrentMark* cm, 1675 WorkGang* workers, 1676 uint worker_id_offset) { 1677 uint num_workers = workers->active_workers(); 1678 1679 G1RebuildRemSetTask cl(cm, 1680 num_workers, 1681 worker_id_offset); 1682 workers->run_task(&cl, num_workers); 1683 }