1 /* 2 * Copyright (c) 2001, 2016, 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 "classfile/metadataOnStackMark.hpp" 27 #include "classfile/symbolTable.hpp" 28 #include "code/codeCache.hpp" 29 #include "gc/g1/concurrentMarkThread.inline.hpp" 30 #include "gc/g1/g1CollectedHeap.inline.hpp" 31 #include "gc/g1/g1CollectorState.hpp" 32 #include "gc/g1/g1ConcurrentMark.inline.hpp" 33 #include "gc/g1/g1HeapVerifier.hpp" 34 #include "gc/g1/g1OopClosures.inline.hpp" 35 #include "gc/g1/g1CardLiveData.inline.hpp" 36 #include "gc/g1/g1Policy.hpp" 37 #include "gc/g1/g1StringDedup.hpp" 38 #include "gc/g1/heapRegion.inline.hpp" 39 #include "gc/g1/heapRegionRemSet.hpp" 40 #include "gc/g1/heapRegionSet.inline.hpp" 41 #include "gc/g1/suspendibleThreadSet.hpp" 42 #include "gc/shared/gcId.hpp" 43 #include "gc/shared/gcTimer.hpp" 44 #include "gc/shared/gcTrace.hpp" 45 #include "gc/shared/gcTraceTime.inline.hpp" 46 #include "gc/shared/genOopClosures.inline.hpp" 47 #include "gc/shared/referencePolicy.hpp" 48 #include "gc/shared/strongRootsScope.hpp" 49 #include "gc/shared/taskqueue.inline.hpp" 50 #include "gc/shared/vmGCOperations.hpp" 51 #include "logging/log.hpp" 52 #include "memory/allocation.hpp" 53 #include "memory/resourceArea.hpp" 54 #include "oops/oop.inline.hpp" 55 #include "runtime/atomic.hpp" 56 #include "runtime/handles.inline.hpp" 57 #include "runtime/java.hpp" 58 #include "runtime/prefetch.inline.hpp" 59 #include "services/memTracker.hpp" 60 #include "utilities/growableArray.hpp" 61 62 // Concurrent marking bit map wrapper 63 64 G1CMBitMapRO::G1CMBitMapRO(int shifter) : 65 _bm(), 66 _shifter(shifter) { 67 _bmStartWord = 0; 68 _bmWordSize = 0; 69 } 70 71 HeapWord* G1CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr, 72 const HeapWord* limit) const { 73 // First we must round addr *up* to a possible object boundary. 74 addr = (HeapWord*)align_size_up((intptr_t)addr, 75 HeapWordSize << _shifter); 76 size_t addrOffset = heapWordToOffset(addr); 77 assert(limit != NULL, "limit must not be NULL"); 78 size_t limitOffset = heapWordToOffset(limit); 79 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset); 80 HeapWord* nextAddr = offsetToHeapWord(nextOffset); 81 assert(nextAddr >= addr, "get_next_one postcondition"); 82 assert(nextAddr == limit || isMarked(nextAddr), 83 "get_next_one postcondition"); 84 return nextAddr; 85 } 86 87 #ifndef PRODUCT 88 bool G1CMBitMapRO::covers(MemRegion heap_rs) const { 89 // assert(_bm.map() == _virtual_space.low(), "map inconsistency"); 90 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize, 91 "size inconsistency"); 92 return _bmStartWord == (HeapWord*)(heap_rs.start()) && 93 _bmWordSize == heap_rs.word_size(); 94 } 95 #endif 96 97 void G1CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const { 98 _bm.print_on_error(st, prefix); 99 } 100 101 size_t G1CMBitMap::compute_size(size_t heap_size) { 102 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance()); 103 } 104 105 size_t G1CMBitMap::mark_distance() { 106 return MinObjAlignmentInBytes * BitsPerByte; 107 } 108 109 void G1CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) { 110 _bmStartWord = heap.start(); 111 _bmWordSize = heap.word_size(); 112 113 _bm = BitMapView((BitMap::bm_word_t*) storage->reserved().start(), _bmWordSize >> _shifter); 114 115 storage->set_mapping_changed_listener(&_listener); 116 } 117 118 void G1CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) { 119 if (zero_filled) { 120 return; 121 } 122 // We need to clear the bitmap on commit, removing any existing information. 123 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords); 124 _bm->clear_range(mr); 125 } 126 127 void G1CMBitMap::clear_range(MemRegion mr) { 128 mr.intersection(MemRegion(_bmStartWord, _bmWordSize)); 129 assert(!mr.is_empty(), "unexpected empty region"); 130 // convert address range into offset range 131 _bm.at_put_range(heapWordToOffset(mr.start()), 132 heapWordToOffset(mr.end()), false); 133 } 134 135 G1CMMarkStack::G1CMMarkStack() : 136 _max_chunk_capacity(0), 137 _base(NULL), 138 _chunk_capacity(0), 139 _out_of_memory(false), 140 _should_expand(false) { 141 set_empty(); 142 } 143 144 bool G1CMMarkStack::resize(size_t new_capacity) { 145 assert(is_empty(), "Only resize when stack is empty."); 146 assert(new_capacity <= _max_chunk_capacity, 147 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity); 148 149 OopChunk* new_base = MmapArrayAllocator<OopChunk, mtGC>::allocate_or_null(new_capacity); 150 151 if (new_base == NULL) { 152 log_warning(gc)("Failed to reserve memory for new overflow mark stack with " SIZE_FORMAT " chunks and size " SIZE_FORMAT "B.", new_capacity, new_capacity * sizeof(OopChunk)); 153 return false; 154 } 155 // Release old mapping. 156 if (_base != NULL) { 157 MmapArrayAllocator<OopChunk, mtGC>::free(_base, _chunk_capacity); 158 } 159 160 _base = new_base; 161 _chunk_capacity = new_capacity; 162 set_empty(); 163 _should_expand = false; 164 165 return true; 166 } 167 168 size_t G1CMMarkStack::capacity_alignment() { 169 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(OopChunk)) / sizeof(void*); 170 } 171 172 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) { 173 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized."); 174 175 size_t const OopChunkSizeInVoidStar = sizeof(OopChunk) / sizeof(void*); 176 177 _max_chunk_capacity = (size_t)align_size_up(max_capacity, capacity_alignment()) / OopChunkSizeInVoidStar; 178 size_t initial_chunk_capacity = (size_t)align_size_up(initial_capacity, capacity_alignment()) / OopChunkSizeInVoidStar; 179 180 guarantee(initial_chunk_capacity <= _max_chunk_capacity, 181 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT, 182 _max_chunk_capacity, 183 initial_chunk_capacity); 184 185 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT, 186 initial_chunk_capacity, _max_chunk_capacity); 187 188 return resize(initial_chunk_capacity); 189 } 190 191 void G1CMMarkStack::expand() { 192 // Clear expansion flag 193 _should_expand = false; 194 195 if (_chunk_capacity == _max_chunk_capacity) { 196 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity); 197 return; 198 } 199 size_t old_capacity = _chunk_capacity; 200 // Double capacity if possible 201 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity); 202 203 if (resize(new_capacity)) { 204 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 205 old_capacity, new_capacity); 206 } else { 207 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 208 old_capacity, new_capacity); 209 } 210 } 211 212 G1CMMarkStack::~G1CMMarkStack() { 213 if (_base != NULL) { 214 MmapArrayAllocator<OopChunk, mtGC>::free(_base, _chunk_capacity); 215 } 216 } 217 218 void G1CMMarkStack::add_chunk_to_list(OopChunk* volatile* list, OopChunk* elem) { 219 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 220 elem->next = *list; 221 *list = elem; 222 } 223 224 G1CMMarkStack::OopChunk* G1CMMarkStack::remove_chunk_from_list(OopChunk* volatile* list) { 225 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 226 227 OopChunk* result = *list; 228 if (result != NULL) { 229 *list = (*list)->next; 230 } 231 return result; 232 } 233 234 G1CMMarkStack::OopChunk* G1CMMarkStack::allocate_new_chunk() { 235 // This dirty read is okay because we only ever increase the _hwm in parallel code. 236 if (_hwm >= _chunk_capacity) { 237 return NULL; 238 } 239 240 size_t cur_idx = Atomic::add(1, &_hwm) - 1; 241 if (cur_idx >= _chunk_capacity) { 242 return NULL; 243 } 244 245 OopChunk* result = ::new (&_base[cur_idx]) OopChunk; 246 result->next = NULL; 247 return result; 248 } 249 250 void G1CMMarkStack::par_push_chunk(oop* ptr_arr) { 251 // Get a new chunk. 252 OopChunk* new_chunk = remove_chunk_from_list(&_free_list); 253 254 if (new_chunk == NULL) { 255 // Did not get a chunk from the free list. Allocate from backing memory. 256 new_chunk = allocate_new_chunk(); 257 } 258 259 if (new_chunk == NULL) { 260 _out_of_memory = true; 261 return; 262 } 263 264 for (size_t i = 0; i < OopsPerChunk; i++) { 265 new_chunk->data[i] = ptr_arr[i]; 266 } 267 268 add_chunk_to_list(&_chunk_list, new_chunk); 269 Atomic::inc(&_chunks_in_chunk_list); 270 } 271 272 bool G1CMMarkStack::par_pop_chunk(oop* ptr_arr) { 273 OopChunk* cur = remove_chunk_from_list(&_chunk_list); 274 275 if (cur == NULL) { 276 return false; 277 } 278 279 Atomic::dec(&_chunks_in_chunk_list); 280 281 for (size_t i = 0; i < OopsPerChunk; i++) { 282 ptr_arr[i] = (oop)cur->data[i]; 283 } 284 285 add_chunk_to_list(&_free_list, cur); 286 return true; 287 } 288 289 void G1CMMarkStack::set_empty() { 290 _chunks_in_chunk_list = 0; 291 _hwm = 0; 292 clear_out_of_memory(); 293 _chunk_list = NULL; 294 _free_list = NULL; 295 } 296 297 G1CMRootRegions::G1CMRootRegions() : 298 _cm(NULL), _scan_in_progress(false), 299 _should_abort(false), _claimed_survivor_index(0) { } 300 301 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) { 302 _survivors = survivors; 303 _cm = cm; 304 } 305 306 void G1CMRootRegions::prepare_for_scan() { 307 assert(!scan_in_progress(), "pre-condition"); 308 309 // Currently, only survivors can be root regions. 310 _claimed_survivor_index = 0; 311 _scan_in_progress = _survivors->regions()->is_nonempty(); 312 _should_abort = false; 313 } 314 315 HeapRegion* G1CMRootRegions::claim_next() { 316 if (_should_abort) { 317 // If someone has set the should_abort flag, we return NULL to 318 // force the caller to bail out of their loop. 319 return NULL; 320 } 321 322 // Currently, only survivors can be root regions. 323 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions(); 324 325 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1; 326 if (claimed_index < survivor_regions->length()) { 327 return survivor_regions->at(claimed_index); 328 } 329 return NULL; 330 } 331 332 uint G1CMRootRegions::num_root_regions() const { 333 return (uint)_survivors->regions()->length(); 334 } 335 336 void G1CMRootRegions::notify_scan_done() { 337 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 338 _scan_in_progress = false; 339 RootRegionScan_lock->notify_all(); 340 } 341 342 void G1CMRootRegions::cancel_scan() { 343 notify_scan_done(); 344 } 345 346 void G1CMRootRegions::scan_finished() { 347 assert(scan_in_progress(), "pre-condition"); 348 349 // Currently, only survivors can be root regions. 350 if (!_should_abort) { 351 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index); 352 assert((uint)_claimed_survivor_index >= _survivors->length(), 353 "we should have claimed all survivors, claimed index = %u, length = %u", 354 (uint)_claimed_survivor_index, _survivors->length()); 355 } 356 357 notify_scan_done(); 358 } 359 360 bool G1CMRootRegions::wait_until_scan_finished() { 361 if (!scan_in_progress()) return false; 362 363 { 364 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 365 while (scan_in_progress()) { 366 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag); 367 } 368 } 369 return true; 370 } 371 372 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) { 373 return MAX2((n_par_threads + 2) / 4, 1U); 374 } 375 376 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) : 377 _g1h(g1h), 378 _markBitMap1(), 379 _markBitMap2(), 380 _parallel_marking_threads(0), 381 _max_parallel_marking_threads(0), 382 _sleep_factor(0.0), 383 _marking_task_overhead(1.0), 384 _cleanup_list("Cleanup List"), 385 386 _prevMarkBitMap(&_markBitMap1), 387 _nextMarkBitMap(&_markBitMap2), 388 389 _global_mark_stack(), 390 // _finger set in set_non_marking_state 391 392 _max_worker_id(ParallelGCThreads), 393 // _active_tasks set in set_non_marking_state 394 // _tasks set inside the constructor 395 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)), 396 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)), 397 398 _has_overflown(false), 399 _concurrent(false), 400 _has_aborted(false), 401 _restart_for_overflow(false), 402 _concurrent_marking_in_progress(false), 403 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 404 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()), 405 406 // _verbose_level set below 407 408 _init_times(), 409 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(), 410 _cleanup_times(), 411 _total_counting_time(0.0), 412 _total_rs_scrub_time(0.0), 413 414 _parallel_workers(NULL), 415 416 _completed_initialization(false) { 417 418 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage); 419 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage); 420 421 // Create & start a ConcurrentMark thread. 422 _cmThread = new ConcurrentMarkThread(this); 423 assert(cmThread() != NULL, "CM Thread should have been created"); 424 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm"); 425 if (_cmThread->osthread() == NULL) { 426 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 427 } 428 429 assert(CGC_lock != NULL, "Where's the CGC_lock?"); 430 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency"); 431 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency"); 432 433 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set(); 434 satb_qs.set_buffer_size(G1SATBBufferSize); 435 436 _root_regions.init(_g1h->survivor(), this); 437 438 if (ConcGCThreads > ParallelGCThreads) { 439 log_warning(gc)("Can't have more ConcGCThreads (%u) than ParallelGCThreads (%u).", 440 ConcGCThreads, ParallelGCThreads); 441 return; 442 } 443 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) { 444 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent 445 // if both are set 446 _sleep_factor = 0.0; 447 _marking_task_overhead = 1.0; 448 } else if (G1MarkingOverheadPercent > 0) { 449 // We will calculate the number of parallel marking threads based 450 // on a target overhead with respect to the soft real-time goal 451 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0; 452 double overall_cm_overhead = 453 (double) MaxGCPauseMillis * marking_overhead / 454 (double) GCPauseIntervalMillis; 455 double cpu_ratio = 1.0 / os::initial_active_processor_count(); 456 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio); 457 double marking_task_overhead = 458 overall_cm_overhead / marking_thread_num * os::initial_active_processor_count(); 459 double sleep_factor = 460 (1.0 - marking_task_overhead) / marking_task_overhead; 461 462 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num); 463 _sleep_factor = sleep_factor; 464 _marking_task_overhead = marking_task_overhead; 465 } else { 466 // Calculate the number of parallel marking threads by scaling 467 // the number of parallel GC threads. 468 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads); 469 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num); 470 _sleep_factor = 0.0; 471 _marking_task_overhead = 1.0; 472 } 473 474 assert(ConcGCThreads > 0, "Should have been set"); 475 log_debug(gc)("ConcGCThreads: %u", ConcGCThreads); 476 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads); 477 _parallel_marking_threads = ConcGCThreads; 478 _max_parallel_marking_threads = _parallel_marking_threads; 479 480 _parallel_workers = new WorkGang("G1 Marker", 481 _max_parallel_marking_threads, false, true); 482 if (_parallel_workers == NULL) { 483 vm_exit_during_initialization("Failed necessary allocation."); 484 } else { 485 _parallel_workers->initialize_workers(); 486 } 487 488 if (FLAG_IS_DEFAULT(MarkStackSize)) { 489 size_t mark_stack_size = 490 MIN2(MarkStackSizeMax, 491 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE))); 492 // Verify that the calculated value for MarkStackSize is in range. 493 // It would be nice to use the private utility routine from Arguments. 494 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 495 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 496 "must be between 1 and " SIZE_FORMAT, 497 mark_stack_size, MarkStackSizeMax); 498 return; 499 } 500 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size); 501 } else { 502 // Verify MarkStackSize is in range. 503 if (FLAG_IS_CMDLINE(MarkStackSize)) { 504 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 505 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 506 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 507 "must be between 1 and " SIZE_FORMAT, 508 MarkStackSize, MarkStackSizeMax); 509 return; 510 } 511 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 512 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 513 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 514 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 515 MarkStackSize, MarkStackSizeMax); 516 return; 517 } 518 } 519 } 520 } 521 522 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) { 523 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack."); 524 } 525 526 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC); 527 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC); 528 529 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 530 _active_tasks = _max_worker_id; 531 532 for (uint i = 0; i < _max_worker_id; ++i) { 533 G1CMTaskQueue* task_queue = new G1CMTaskQueue(); 534 task_queue->initialize(); 535 _task_queues->register_queue(i, task_queue); 536 537 _tasks[i] = new G1CMTask(i, this, task_queue, _task_queues); 538 539 _accum_task_vtime[i] = 0.0; 540 } 541 542 // so that the call below can read a sensible value 543 _heap_start = g1h->reserved_region().start(); 544 set_non_marking_state(); 545 _completed_initialization = true; 546 } 547 548 void G1ConcurrentMark::reset() { 549 // Starting values for these two. This should be called in a STW 550 // phase. 551 MemRegion reserved = _g1h->g1_reserved(); 552 _heap_start = reserved.start(); 553 _heap_end = reserved.end(); 554 555 // Separated the asserts so that we know which one fires. 556 assert(_heap_start != NULL, "heap bounds should look ok"); 557 assert(_heap_end != NULL, "heap bounds should look ok"); 558 assert(_heap_start < _heap_end, "heap bounds should look ok"); 559 560 // Reset all the marking data structures and any necessary flags 561 reset_marking_state(); 562 563 // We do reset all of them, since different phases will use 564 // different number of active threads. So, it's easiest to have all 565 // of them ready. 566 for (uint i = 0; i < _max_worker_id; ++i) { 567 _tasks[i]->reset(_nextMarkBitMap); 568 } 569 570 // we need this to make sure that the flag is on during the evac 571 // pause with initial mark piggy-backed 572 set_concurrent_marking_in_progress(); 573 } 574 575 576 void G1ConcurrentMark::reset_marking_state(bool clear_overflow) { 577 _global_mark_stack.set_should_expand(has_overflown()); 578 _global_mark_stack.set_empty(); // Also clears the overflow stack's overflow flag 579 if (clear_overflow) { 580 clear_has_overflown(); 581 } else { 582 assert(has_overflown(), "pre-condition"); 583 } 584 _finger = _heap_start; 585 586 for (uint i = 0; i < _max_worker_id; ++i) { 587 G1CMTaskQueue* queue = _task_queues->queue(i); 588 queue->set_empty(); 589 } 590 } 591 592 void G1ConcurrentMark::set_concurrency(uint active_tasks) { 593 assert(active_tasks <= _max_worker_id, "we should not have more"); 594 595 _active_tasks = active_tasks; 596 // Need to update the three data structures below according to the 597 // number of active threads for this phase. 598 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); 599 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 600 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 601 } 602 603 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 604 set_concurrency(active_tasks); 605 606 _concurrent = concurrent; 607 // We propagate this to all tasks, not just the active ones. 608 for (uint i = 0; i < _max_worker_id; ++i) 609 _tasks[i]->set_concurrent(concurrent); 610 611 if (concurrent) { 612 set_concurrent_marking_in_progress(); 613 } else { 614 // We currently assume that the concurrent flag has been set to 615 // false before we start remark. At this point we should also be 616 // in a STW phase. 617 assert(!concurrent_marking_in_progress(), "invariant"); 618 assert(out_of_regions(), 619 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT, 620 p2i(_finger), p2i(_heap_end)); 621 } 622 } 623 624 void G1ConcurrentMark::set_non_marking_state() { 625 // We set the global marking state to some default values when we're 626 // not doing marking. 627 reset_marking_state(); 628 _active_tasks = 0; 629 clear_concurrent_marking_in_progress(); 630 } 631 632 G1ConcurrentMark::~G1ConcurrentMark() { 633 // The G1ConcurrentMark instance is never freed. 634 ShouldNotReachHere(); 635 } 636 637 class G1ClearBitMapTask : public AbstractGangTask { 638 public: 639 static size_t chunk_size() { return M; } 640 641 private: 642 // Heap region closure used for clearing the given mark bitmap. 643 class G1ClearBitmapHRClosure : public HeapRegionClosure { 644 private: 645 G1CMBitMap* _bitmap; 646 G1ConcurrentMark* _cm; 647 public: 648 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) { 649 } 650 651 virtual bool doHeapRegion(HeapRegion* r) { 652 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize; 653 654 HeapWord* cur = r->bottom(); 655 HeapWord* const end = r->end(); 656 657 while (cur < end) { 658 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 659 _bitmap->clear_range(mr); 660 661 cur += chunk_size_in_words; 662 663 // Abort iteration if after yielding the marking has been aborted. 664 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) { 665 return true; 666 } 667 // Repeat the asserts from before the start of the closure. We will do them 668 // as asserts here to minimize their overhead on the product. However, we 669 // will have them as guarantees at the beginning / end of the bitmap 670 // clearing to get some checking in the product. 671 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant"); 672 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant"); 673 } 674 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index()); 675 676 return false; 677 } 678 }; 679 680 G1ClearBitmapHRClosure _cl; 681 HeapRegionClaimer _hr_claimer; 682 bool _suspendible; // If the task is suspendible, workers must join the STS. 683 684 public: 685 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) : 686 AbstractGangTask("G1 Clear Bitmap"), 687 _cl(bitmap, suspendible ? cm : NULL), 688 _hr_claimer(n_workers), 689 _suspendible(suspendible) 690 { } 691 692 void work(uint worker_id) { 693 SuspendibleThreadSetJoiner sts_join(_suspendible); 694 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true); 695 } 696 697 bool is_complete() { 698 return _cl.complete(); 699 } 700 }; 701 702 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) { 703 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint."); 704 705 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor(); 706 size_t const num_chunks = align_size_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size(); 707 708 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); 709 710 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield); 711 712 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks); 713 workers->run_task(&cl, num_workers); 714 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding."); 715 } 716 717 void G1ConcurrentMark::cleanup_for_next_mark() { 718 // Make sure that the concurrent mark thread looks to still be in 719 // the current cycle. 720 guarantee(cmThread()->during_cycle(), "invariant"); 721 722 // We are finishing up the current cycle by clearing the next 723 // marking bitmap and getting it ready for the next cycle. During 724 // this time no other cycle can start. So, let's make sure that this 725 // is the case. 726 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant"); 727 728 clear_bitmap(_nextMarkBitMap, _parallel_workers, true); 729 730 // Clear the live count data. If the marking has been aborted, the abort() 731 // call already did that. 732 if (!has_aborted()) { 733 clear_live_data(_parallel_workers); 734 DEBUG_ONLY(verify_live_data_clear()); 735 } 736 737 // Repeat the asserts from above. 738 guarantee(cmThread()->during_cycle(), "invariant"); 739 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant"); 740 } 741 742 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) { 743 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint."); 744 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false); 745 } 746 747 class CheckBitmapClearHRClosure : public HeapRegionClosure { 748 G1CMBitMap* _bitmap; 749 bool _error; 750 public: 751 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) { 752 } 753 754 virtual bool doHeapRegion(HeapRegion* r) { 755 // This closure can be called concurrently to the mutator, so we must make sure 756 // that the result of the getNextMarkedWordAddress() call is compared to the 757 // value passed to it as limit to detect any found bits. 758 // end never changes in G1. 759 HeapWord* end = r->end(); 760 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end; 761 } 762 }; 763 764 bool G1ConcurrentMark::nextMarkBitmapIsClear() { 765 CheckBitmapClearHRClosure cl(_nextMarkBitMap); 766 _g1h->heap_region_iterate(&cl); 767 return cl.complete(); 768 } 769 770 class NoteStartOfMarkHRClosure: public HeapRegionClosure { 771 public: 772 bool doHeapRegion(HeapRegion* r) { 773 r->note_start_of_marking(); 774 return false; 775 } 776 }; 777 778 void G1ConcurrentMark::checkpointRootsInitialPre() { 779 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 780 G1Policy* g1p = g1h->g1_policy(); 781 782 _has_aborted = false; 783 784 // Initialize marking structures. This has to be done in a STW phase. 785 reset(); 786 787 // For each region note start of marking. 788 NoteStartOfMarkHRClosure startcl; 789 g1h->heap_region_iterate(&startcl); 790 } 791 792 793 void G1ConcurrentMark::checkpointRootsInitialPost() { 794 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 795 796 // Start Concurrent Marking weak-reference discovery. 797 ReferenceProcessor* rp = g1h->ref_processor_cm(); 798 // enable ("weak") refs discovery 799 rp->enable_discovery(); 800 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 801 802 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 803 // This is the start of the marking cycle, we're expected all 804 // threads to have SATB queues with active set to false. 805 satb_mq_set.set_active_all_threads(true, /* new active value */ 806 false /* expected_active */); 807 808 _root_regions.prepare_for_scan(); 809 810 // update_g1_committed() will be called at the end of an evac pause 811 // when marking is on. So, it's also called at the end of the 812 // initial-mark pause to update the heap end, if the heap expands 813 // during it. No need to call it here. 814 } 815 816 /* 817 * Notice that in the next two methods, we actually leave the STS 818 * during the barrier sync and join it immediately afterwards. If we 819 * do not do this, the following deadlock can occur: one thread could 820 * be in the barrier sync code, waiting for the other thread to also 821 * sync up, whereas another one could be trying to yield, while also 822 * waiting for the other threads to sync up too. 823 * 824 * Note, however, that this code is also used during remark and in 825 * this case we should not attempt to leave / enter the STS, otherwise 826 * we'll either hit an assert (debug / fastdebug) or deadlock 827 * (product). So we should only leave / enter the STS if we are 828 * operating concurrently. 829 * 830 * Because the thread that does the sync barrier has left the STS, it 831 * is possible to be suspended for a Full GC or an evacuation pause 832 * could occur. This is actually safe, since the entering the sync 833 * barrier is one of the last things do_marking_step() does, and it 834 * doesn't manipulate any data structures afterwards. 835 */ 836 837 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 838 bool barrier_aborted; 839 { 840 SuspendibleThreadSetLeaver sts_leave(concurrent()); 841 barrier_aborted = !_first_overflow_barrier_sync.enter(); 842 } 843 844 // at this point everyone should have synced up and not be doing any 845 // more work 846 847 if (barrier_aborted) { 848 // If the barrier aborted we ignore the overflow condition and 849 // just abort the whole marking phase as quickly as possible. 850 return; 851 } 852 853 // If we're executing the concurrent phase of marking, reset the marking 854 // state; otherwise the marking state is reset after reference processing, 855 // during the remark pause. 856 // If we reset here as a result of an overflow during the remark we will 857 // see assertion failures from any subsequent set_concurrency_and_phase() 858 // calls. 859 if (concurrent()) { 860 // let the task associated with with worker 0 do this 861 if (worker_id == 0) { 862 // task 0 is responsible for clearing the global data structures 863 // We should be here because of an overflow. During STW we should 864 // not clear the overflow flag since we rely on it being true when 865 // we exit this method to abort the pause and restart concurrent 866 // marking. 867 reset_marking_state(true /* clear_overflow */); 868 869 log_info(gc, marking)("Concurrent Mark reset for overflow"); 870 } 871 } 872 873 // after this, each task should reset its own data structures then 874 // then go into the second barrier 875 } 876 877 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 878 SuspendibleThreadSetLeaver sts_leave(concurrent()); 879 _second_overflow_barrier_sync.enter(); 880 881 // at this point everything should be re-initialized and ready to go 882 } 883 884 class G1CMConcurrentMarkingTask: public AbstractGangTask { 885 private: 886 G1ConcurrentMark* _cm; 887 ConcurrentMarkThread* _cmt; 888 889 public: 890 void work(uint worker_id) { 891 assert(Thread::current()->is_ConcurrentGC_thread(), 892 "this should only be done by a conc GC thread"); 893 ResourceMark rm; 894 895 double start_vtime = os::elapsedVTime(); 896 897 { 898 SuspendibleThreadSetJoiner sts_join; 899 900 assert(worker_id < _cm->active_tasks(), "invariant"); 901 G1CMTask* the_task = _cm->task(worker_id); 902 the_task->record_start_time(); 903 if (!_cm->has_aborted()) { 904 do { 905 double start_vtime_sec = os::elapsedVTime(); 906 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 907 908 the_task->do_marking_step(mark_step_duration_ms, 909 true /* do_termination */, 910 false /* is_serial*/); 911 912 double end_vtime_sec = os::elapsedVTime(); 913 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec; 914 _cm->clear_has_overflown(); 915 916 _cm->do_yield_check(); 917 918 jlong sleep_time_ms; 919 if (!_cm->has_aborted() && the_task->has_aborted()) { 920 sleep_time_ms = 921 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0); 922 { 923 SuspendibleThreadSetLeaver sts_leave; 924 os::sleep(Thread::current(), sleep_time_ms, false); 925 } 926 } 927 } while (!_cm->has_aborted() && the_task->has_aborted()); 928 } 929 the_task->record_end_time(); 930 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant"); 931 } 932 933 double end_vtime = os::elapsedVTime(); 934 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 935 } 936 937 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm, 938 ConcurrentMarkThread* cmt) : 939 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { } 940 941 ~G1CMConcurrentMarkingTask() { } 942 }; 943 944 // Calculates the number of active workers for a concurrent 945 // phase. 946 uint G1ConcurrentMark::calc_parallel_marking_threads() { 947 uint n_conc_workers = 0; 948 if (!UseDynamicNumberOfGCThreads || 949 (!FLAG_IS_DEFAULT(ConcGCThreads) && 950 !ForceDynamicNumberOfGCThreads)) { 951 n_conc_workers = max_parallel_marking_threads(); 952 } else { 953 n_conc_workers = 954 AdaptiveSizePolicy::calc_default_active_workers(max_parallel_marking_threads(), 955 1, /* Minimum workers */ 956 parallel_marking_threads(), 957 Threads::number_of_non_daemon_threads()); 958 // Don't scale down "n_conc_workers" by scale_parallel_threads() because 959 // that scaling has already gone into "_max_parallel_marking_threads". 960 } 961 assert(n_conc_workers > 0 && n_conc_workers <= max_parallel_marking_threads(), 962 "Calculated number of workers must be larger than zero and at most the maximum %u, but is %u", 963 max_parallel_marking_threads(), n_conc_workers); 964 return n_conc_workers; 965 } 966 967 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr) { 968 // Currently, only survivors can be root regions. 969 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant"); 970 G1RootRegionScanClosure cl(_g1h, this); 971 972 const uintx interval = PrefetchScanIntervalInBytes; 973 HeapWord* curr = hr->bottom(); 974 const HeapWord* end = hr->top(); 975 while (curr < end) { 976 Prefetch::read(curr, interval); 977 oop obj = oop(curr); 978 int size = obj->oop_iterate_size(&cl); 979 assert(size == obj->size(), "sanity"); 980 curr += size; 981 } 982 } 983 984 class G1CMRootRegionScanTask : public AbstractGangTask { 985 private: 986 G1ConcurrentMark* _cm; 987 988 public: 989 G1CMRootRegionScanTask(G1ConcurrentMark* cm) : 990 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { } 991 992 void work(uint worker_id) { 993 assert(Thread::current()->is_ConcurrentGC_thread(), 994 "this should only be done by a conc GC thread"); 995 996 G1CMRootRegions* root_regions = _cm->root_regions(); 997 HeapRegion* hr = root_regions->claim_next(); 998 while (hr != NULL) { 999 _cm->scanRootRegion(hr); 1000 hr = root_regions->claim_next(); 1001 } 1002 } 1003 }; 1004 1005 void G1ConcurrentMark::scan_root_regions() { 1006 // scan_in_progress() will have been set to true only if there was 1007 // at least one root region to scan. So, if it's false, we 1008 // should not attempt to do any further work. 1009 if (root_regions()->scan_in_progress()) { 1010 assert(!has_aborted(), "Aborting before root region scanning is finished not supported."); 1011 1012 _parallel_marking_threads = MIN2(calc_parallel_marking_threads(), 1013 // We distribute work on a per-region basis, so starting 1014 // more threads than that is useless. 1015 root_regions()->num_root_regions()); 1016 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1017 "Maximum number of marking threads exceeded"); 1018 1019 G1CMRootRegionScanTask task(this); 1020 log_debug(gc, ergo)("Running %s using %u workers for %u work units.", 1021 task.name(), _parallel_marking_threads, root_regions()->num_root_regions()); 1022 _parallel_workers->run_task(&task, _parallel_marking_threads); 1023 1024 // It's possible that has_aborted() is true here without actually 1025 // aborting the survivor scan earlier. This is OK as it's 1026 // mainly used for sanity checking. 1027 root_regions()->scan_finished(); 1028 } 1029 } 1030 1031 void G1ConcurrentMark::concurrent_cycle_start() { 1032 _gc_timer_cm->register_gc_start(); 1033 1034 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start()); 1035 1036 _g1h->trace_heap_before_gc(_gc_tracer_cm); 1037 } 1038 1039 void G1ConcurrentMark::concurrent_cycle_end() { 1040 _g1h->trace_heap_after_gc(_gc_tracer_cm); 1041 1042 if (has_aborted()) { 1043 _gc_tracer_cm->report_concurrent_mode_failure(); 1044 } 1045 1046 _gc_timer_cm->register_gc_end(); 1047 1048 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 1049 } 1050 1051 void G1ConcurrentMark::mark_from_roots() { 1052 // we might be tempted to assert that: 1053 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), 1054 // "inconsistent argument?"); 1055 // However that wouldn't be right, because it's possible that 1056 // a safepoint is indeed in progress as a younger generation 1057 // stop-the-world GC happens even as we mark in this generation. 1058 1059 _restart_for_overflow = false; 1060 1061 // _g1h has _n_par_threads 1062 _parallel_marking_threads = calc_parallel_marking_threads(); 1063 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1064 "Maximum number of marking threads exceeded"); 1065 1066 uint active_workers = MAX2(1U, parallel_marking_threads()); 1067 assert(active_workers > 0, "Should have been set"); 1068 1069 // Setting active workers is not guaranteed since fewer 1070 // worker threads may currently exist and more may not be 1071 // available. 1072 active_workers = _parallel_workers->update_active_workers(active_workers); 1073 // Parallel task terminator is set in "set_concurrency_and_phase()" 1074 set_concurrency_and_phase(active_workers, true /* concurrent */); 1075 1076 G1CMConcurrentMarkingTask markingTask(this, cmThread()); 1077 _parallel_workers->run_task(&markingTask); 1078 print_stats(); 1079 } 1080 1081 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) { 1082 // world is stopped at this checkpoint 1083 assert(SafepointSynchronize::is_at_safepoint(), 1084 "world should be stopped"); 1085 1086 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1087 1088 // If a full collection has happened, we shouldn't do this. 1089 if (has_aborted()) { 1090 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused 1091 return; 1092 } 1093 1094 SvcGCMarker sgcm(SvcGCMarker::OTHER); 1095 1096 if (VerifyDuringGC) { 1097 HandleMark hm; // handle scope 1098 g1h->prepare_for_verify(); 1099 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)"); 1100 } 1101 g1h->verifier()->check_bitmaps("Remark Start"); 1102 1103 G1Policy* g1p = g1h->g1_policy(); 1104 g1p->record_concurrent_mark_remark_start(); 1105 1106 double start = os::elapsedTime(); 1107 1108 checkpointRootsFinalWork(); 1109 1110 double mark_work_end = os::elapsedTime(); 1111 1112 weakRefsWork(clear_all_soft_refs); 1113 1114 if (has_overflown()) { 1115 // We overflowed. Restart concurrent marking. 1116 _restart_for_overflow = true; 1117 1118 // Verify the heap w.r.t. the previous marking bitmap. 1119 if (VerifyDuringGC) { 1120 HandleMark hm; // handle scope 1121 g1h->prepare_for_verify(); 1122 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)"); 1123 } 1124 1125 // Clear the marking state because we will be restarting 1126 // marking due to overflowing the global mark stack. 1127 reset_marking_state(); 1128 } else { 1129 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1130 // We're done with marking. 1131 // This is the end of the marking cycle, we're expected all 1132 // threads to have SATB queues with active set to true. 1133 satb_mq_set.set_active_all_threads(false, /* new active value */ 1134 true /* expected_active */); 1135 1136 if (VerifyDuringGC) { 1137 HandleMark hm; // handle scope 1138 g1h->prepare_for_verify(); 1139 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)"); 1140 } 1141 g1h->verifier()->check_bitmaps("Remark End"); 1142 assert(!restart_for_overflow(), "sanity"); 1143 // Completely reset the marking state since marking completed 1144 set_non_marking_state(); 1145 } 1146 1147 // Expand the marking stack, if we have to and if we can. 1148 if (_global_mark_stack.should_expand()) { 1149 _global_mark_stack.expand(); 1150 } 1151 1152 // Statistics 1153 double now = os::elapsedTime(); 1154 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1155 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1156 _remark_times.add((now - start) * 1000.0); 1157 1158 g1p->record_concurrent_mark_remark_end(); 1159 1160 G1CMIsAliveClosure is_alive(g1h); 1161 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1162 } 1163 1164 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure { 1165 G1CollectedHeap* _g1; 1166 size_t _freed_bytes; 1167 FreeRegionList* _local_cleanup_list; 1168 uint _old_regions_removed; 1169 uint _humongous_regions_removed; 1170 HRRSCleanupTask* _hrrs_cleanup_task; 1171 1172 public: 1173 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, 1174 FreeRegionList* local_cleanup_list, 1175 HRRSCleanupTask* hrrs_cleanup_task) : 1176 _g1(g1), 1177 _freed_bytes(0), 1178 _local_cleanup_list(local_cleanup_list), 1179 _old_regions_removed(0), 1180 _humongous_regions_removed(0), 1181 _hrrs_cleanup_task(hrrs_cleanup_task) { } 1182 1183 size_t freed_bytes() { return _freed_bytes; } 1184 const uint old_regions_removed() { return _old_regions_removed; } 1185 const uint humongous_regions_removed() { return _humongous_regions_removed; } 1186 1187 bool doHeapRegion(HeapRegion *hr) { 1188 if (hr->is_archive()) { 1189 return false; 1190 } 1191 _g1->reset_gc_time_stamps(hr); 1192 hr->note_end_of_marking(); 1193 1194 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 1195 _freed_bytes += hr->used(); 1196 hr->set_containing_set(NULL); 1197 if (hr->is_humongous()) { 1198 _humongous_regions_removed++; 1199 _g1->free_humongous_region(hr, _local_cleanup_list, true /* skip_remset */); 1200 } else { 1201 _old_regions_removed++; 1202 _g1->free_region(hr, _local_cleanup_list, true /* skip_remset */); 1203 } 1204 } else { 1205 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task); 1206 } 1207 1208 return false; 1209 } 1210 }; 1211 1212 class G1ParNoteEndTask: public AbstractGangTask { 1213 friend class G1NoteEndOfConcMarkClosure; 1214 1215 protected: 1216 G1CollectedHeap* _g1h; 1217 FreeRegionList* _cleanup_list; 1218 HeapRegionClaimer _hrclaimer; 1219 1220 public: 1221 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1222 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) { 1223 } 1224 1225 void work(uint worker_id) { 1226 FreeRegionList local_cleanup_list("Local Cleanup List"); 1227 HRRSCleanupTask hrrs_cleanup_task; 1228 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list, 1229 &hrrs_cleanup_task); 1230 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer); 1231 assert(g1_note_end.complete(), "Shouldn't have yielded!"); 1232 1233 // Now update the lists 1234 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed()); 1235 { 1236 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1237 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes()); 1238 1239 // If we iterate over the global cleanup list at the end of 1240 // cleanup to do this printing we will not guarantee to only 1241 // generate output for the newly-reclaimed regions (the list 1242 // might not be empty at the beginning of cleanup; we might 1243 // still be working on its previous contents). So we do the 1244 // printing here, before we append the new regions to the global 1245 // cleanup list. 1246 1247 G1HRPrinter* hr_printer = _g1h->hr_printer(); 1248 if (hr_printer->is_active()) { 1249 FreeRegionListIterator iter(&local_cleanup_list); 1250 while (iter.more_available()) { 1251 HeapRegion* hr = iter.get_next(); 1252 hr_printer->cleanup(hr); 1253 } 1254 } 1255 1256 _cleanup_list->add_ordered(&local_cleanup_list); 1257 assert(local_cleanup_list.is_empty(), "post-condition"); 1258 1259 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task); 1260 } 1261 } 1262 }; 1263 1264 void G1ConcurrentMark::cleanup() { 1265 // world is stopped at this checkpoint 1266 assert(SafepointSynchronize::is_at_safepoint(), 1267 "world should be stopped"); 1268 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1269 1270 // If a full collection has happened, we shouldn't do this. 1271 if (has_aborted()) { 1272 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused 1273 return; 1274 } 1275 1276 g1h->verifier()->verify_region_sets_optional(); 1277 1278 if (VerifyDuringGC) { 1279 HandleMark hm; // handle scope 1280 g1h->prepare_for_verify(); 1281 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)"); 1282 } 1283 g1h->verifier()->check_bitmaps("Cleanup Start"); 1284 1285 G1Policy* g1p = g1h->g1_policy(); 1286 g1p->record_concurrent_mark_cleanup_start(); 1287 1288 double start = os::elapsedTime(); 1289 1290 HeapRegionRemSet::reset_for_cleanup_tasks(); 1291 1292 { 1293 GCTraceTime(Debug, gc)("Finalize Live Data"); 1294 finalize_live_data(); 1295 } 1296 1297 if (VerifyDuringGC) { 1298 GCTraceTime(Debug, gc)("Verify Live Data"); 1299 verify_live_data(); 1300 } 1301 1302 g1h->collector_state()->set_mark_in_progress(false); 1303 1304 double count_end = os::elapsedTime(); 1305 double this_final_counting_time = (count_end - start); 1306 _total_counting_time += this_final_counting_time; 1307 1308 if (log_is_enabled(Trace, gc, liveness)) { 1309 G1PrintRegionLivenessInfoClosure cl("Post-Marking"); 1310 _g1h->heap_region_iterate(&cl); 1311 } 1312 1313 // Install newly created mark bitMap as "prev". 1314 swapMarkBitMaps(); 1315 1316 g1h->reset_gc_time_stamp(); 1317 1318 uint n_workers = _g1h->workers()->active_workers(); 1319 1320 // Note end of marking in all heap regions. 1321 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers); 1322 g1h->workers()->run_task(&g1_par_note_end_task); 1323 g1h->check_gc_time_stamps(); 1324 1325 if (!cleanup_list_is_empty()) { 1326 // The cleanup list is not empty, so we'll have to process it 1327 // concurrently. Notify anyone else that might be wanting free 1328 // regions that there will be more free regions coming soon. 1329 g1h->set_free_regions_coming(); 1330 } 1331 1332 // call below, since it affects the metric by which we sort the heap 1333 // regions. 1334 if (G1ScrubRemSets) { 1335 double rs_scrub_start = os::elapsedTime(); 1336 g1h->scrub_rem_set(); 1337 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start); 1338 } 1339 1340 // this will also free any regions totally full of garbage objects, 1341 // and sort the regions. 1342 g1h->g1_policy()->record_concurrent_mark_cleanup_end(); 1343 1344 // Statistics. 1345 double end = os::elapsedTime(); 1346 _cleanup_times.add((end - start) * 1000.0); 1347 1348 // Clean up will have freed any regions completely full of garbage. 1349 // Update the soft reference policy with the new heap occupancy. 1350 Universe::update_heap_info_at_gc(); 1351 1352 if (VerifyDuringGC) { 1353 HandleMark hm; // handle scope 1354 g1h->prepare_for_verify(); 1355 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)"); 1356 } 1357 1358 g1h->verifier()->check_bitmaps("Cleanup End"); 1359 1360 g1h->verifier()->verify_region_sets_optional(); 1361 1362 // We need to make this be a "collection" so any collection pause that 1363 // races with it goes around and waits for completeCleanup to finish. 1364 g1h->increment_total_collections(); 1365 1366 // Clean out dead classes and update Metaspace sizes. 1367 if (ClassUnloadingWithConcurrentMark) { 1368 ClassLoaderDataGraph::purge(); 1369 } 1370 MetaspaceGC::compute_new_size(); 1371 1372 // We reclaimed old regions so we should calculate the sizes to make 1373 // sure we update the old gen/space data. 1374 g1h->g1mm()->update_sizes(); 1375 g1h->allocation_context_stats().update_after_mark(); 1376 } 1377 1378 void G1ConcurrentMark::complete_cleanup() { 1379 if (has_aborted()) return; 1380 1381 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1382 1383 _cleanup_list.verify_optional(); 1384 FreeRegionList tmp_free_list("Tmp Free List"); 1385 1386 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : " 1387 "cleanup list has %u entries", 1388 _cleanup_list.length()); 1389 1390 // No one else should be accessing the _cleanup_list at this point, 1391 // so it is not necessary to take any locks 1392 while (!_cleanup_list.is_empty()) { 1393 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */); 1394 assert(hr != NULL, "Got NULL from a non-empty list"); 1395 hr->par_clear(); 1396 tmp_free_list.add_ordered(hr); 1397 1398 // Instead of adding one region at a time to the secondary_free_list, 1399 // we accumulate them in the local list and move them a few at a 1400 // time. This also cuts down on the number of notify_all() calls 1401 // we do during this process. We'll also append the local list when 1402 // _cleanup_list is empty (which means we just removed the last 1403 // region from the _cleanup_list). 1404 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) || 1405 _cleanup_list.is_empty()) { 1406 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : " 1407 "appending %u entries to the secondary_free_list, " 1408 "cleanup list still has %u entries", 1409 tmp_free_list.length(), 1410 _cleanup_list.length()); 1411 1412 { 1413 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1414 g1h->secondary_free_list_add(&tmp_free_list); 1415 SecondaryFreeList_lock->notify_all(); 1416 } 1417 #ifndef PRODUCT 1418 if (G1StressConcRegionFreeing) { 1419 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) { 1420 os::sleep(Thread::current(), (jlong) 1, false); 1421 } 1422 } 1423 #endif 1424 } 1425 } 1426 assert(tmp_free_list.is_empty(), "post-condition"); 1427 } 1428 1429 // Supporting Object and Oop closures for reference discovery 1430 // and processing in during marking 1431 1432 bool G1CMIsAliveClosure::do_object_b(oop obj) { 1433 HeapWord* addr = (HeapWord*)obj; 1434 return addr != NULL && 1435 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj)); 1436 } 1437 1438 // 'Keep Alive' oop closure used by both serial parallel reference processing. 1439 // Uses the G1CMTask associated with a worker thread (for serial reference 1440 // processing the G1CMTask for worker 0 is used) to preserve (mark) and 1441 // trace referent objects. 1442 // 1443 // Using the G1CMTask and embedded local queues avoids having the worker 1444 // threads operating on the global mark stack. This reduces the risk 1445 // of overflowing the stack - which we would rather avoid at this late 1446 // state. Also using the tasks' local queues removes the potential 1447 // of the workers interfering with each other that could occur if 1448 // operating on the global stack. 1449 1450 class G1CMKeepAliveAndDrainClosure: public OopClosure { 1451 G1ConcurrentMark* _cm; 1452 G1CMTask* _task; 1453 int _ref_counter_limit; 1454 int _ref_counter; 1455 bool _is_serial; 1456 public: 1457 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1458 _cm(cm), _task(task), _is_serial(is_serial), 1459 _ref_counter_limit(G1RefProcDrainInterval) { 1460 assert(_ref_counter_limit > 0, "sanity"); 1461 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1462 _ref_counter = _ref_counter_limit; 1463 } 1464 1465 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 1466 virtual void do_oop( oop* p) { do_oop_work(p); } 1467 1468 template <class T> void do_oop_work(T* p) { 1469 if (!_cm->has_overflown()) { 1470 oop obj = oopDesc::load_decode_heap_oop(p); 1471 _task->deal_with_reference(obj); 1472 _ref_counter--; 1473 1474 if (_ref_counter == 0) { 1475 // We have dealt with _ref_counter_limit references, pushing them 1476 // and objects reachable from them on to the local stack (and 1477 // possibly the global stack). Call G1CMTask::do_marking_step() to 1478 // process these entries. 1479 // 1480 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if 1481 // there's nothing more to do (i.e. we're done with the entries that 1482 // were pushed as a result of the G1CMTask::deal_with_reference() calls 1483 // above) or we overflow. 1484 // 1485 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1486 // flag while there may still be some work to do. (See the comment at 1487 // the beginning of G1CMTask::do_marking_step() for those conditions - 1488 // one of which is reaching the specified time target.) It is only 1489 // when G1CMTask::do_marking_step() returns without setting the 1490 // has_aborted() flag that the marking step has completed. 1491 do { 1492 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1493 _task->do_marking_step(mark_step_duration_ms, 1494 false /* do_termination */, 1495 _is_serial); 1496 } while (_task->has_aborted() && !_cm->has_overflown()); 1497 _ref_counter = _ref_counter_limit; 1498 } 1499 } 1500 } 1501 }; 1502 1503 // 'Drain' oop closure used by both serial and parallel reference processing. 1504 // Uses the G1CMTask associated with a given worker thread (for serial 1505 // reference processing the G1CMtask for worker 0 is used). Calls the 1506 // do_marking_step routine, with an unbelievably large timeout value, 1507 // to drain the marking data structures of the remaining entries 1508 // added by the 'keep alive' oop closure above. 1509 1510 class G1CMDrainMarkingStackClosure: public VoidClosure { 1511 G1ConcurrentMark* _cm; 1512 G1CMTask* _task; 1513 bool _is_serial; 1514 public: 1515 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1516 _cm(cm), _task(task), _is_serial(is_serial) { 1517 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1518 } 1519 1520 void do_void() { 1521 do { 1522 // We call G1CMTask::do_marking_step() to completely drain the local 1523 // and global marking stacks of entries pushed by the 'keep alive' 1524 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 1525 // 1526 // G1CMTask::do_marking_step() is called in a loop, which we'll exit 1527 // if there's nothing more to do (i.e. we've completely drained the 1528 // entries that were pushed as a a result of applying the 'keep alive' 1529 // closure to the entries on the discovered ref lists) or we overflow 1530 // the global marking stack. 1531 // 1532 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1533 // flag while there may still be some work to do. (See the comment at 1534 // the beginning of G1CMTask::do_marking_step() for those conditions - 1535 // one of which is reaching the specified time target.) It is only 1536 // when G1CMTask::do_marking_step() returns without setting the 1537 // has_aborted() flag that the marking step has completed. 1538 1539 _task->do_marking_step(1000000000.0 /* something very large */, 1540 true /* do_termination */, 1541 _is_serial); 1542 } while (_task->has_aborted() && !_cm->has_overflown()); 1543 } 1544 }; 1545 1546 // Implementation of AbstractRefProcTaskExecutor for parallel 1547 // reference processing at the end of G1 concurrent marking 1548 1549 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 1550 private: 1551 G1CollectedHeap* _g1h; 1552 G1ConcurrentMark* _cm; 1553 WorkGang* _workers; 1554 uint _active_workers; 1555 1556 public: 1557 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 1558 G1ConcurrentMark* cm, 1559 WorkGang* workers, 1560 uint n_workers) : 1561 _g1h(g1h), _cm(cm), 1562 _workers(workers), _active_workers(n_workers) { } 1563 1564 // Executes the given task using concurrent marking worker threads. 1565 virtual void execute(ProcessTask& task); 1566 virtual void execute(EnqueueTask& task); 1567 }; 1568 1569 class G1CMRefProcTaskProxy: public AbstractGangTask { 1570 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 1571 ProcessTask& _proc_task; 1572 G1CollectedHeap* _g1h; 1573 G1ConcurrentMark* _cm; 1574 1575 public: 1576 G1CMRefProcTaskProxy(ProcessTask& proc_task, 1577 G1CollectedHeap* g1h, 1578 G1ConcurrentMark* cm) : 1579 AbstractGangTask("Process reference objects in parallel"), 1580 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 1581 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1582 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 1583 } 1584 1585 virtual void work(uint worker_id) { 1586 ResourceMark rm; 1587 HandleMark hm; 1588 G1CMTask* task = _cm->task(worker_id); 1589 G1CMIsAliveClosure g1_is_alive(_g1h); 1590 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 1591 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 1592 1593 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 1594 } 1595 }; 1596 1597 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) { 1598 assert(_workers != NULL, "Need parallel worker threads."); 1599 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1600 1601 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 1602 1603 // We need to reset the concurrency level before each 1604 // proxy task execution, so that the termination protocol 1605 // and overflow handling in G1CMTask::do_marking_step() knows 1606 // how many workers to wait for. 1607 _cm->set_concurrency(_active_workers); 1608 _workers->run_task(&proc_task_proxy); 1609 } 1610 1611 class G1CMRefEnqueueTaskProxy: public AbstractGangTask { 1612 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 1613 EnqueueTask& _enq_task; 1614 1615 public: 1616 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) : 1617 AbstractGangTask("Enqueue reference objects in parallel"), 1618 _enq_task(enq_task) { } 1619 1620 virtual void work(uint worker_id) { 1621 _enq_task.work(worker_id); 1622 } 1623 }; 1624 1625 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 1626 assert(_workers != NULL, "Need parallel worker threads."); 1627 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1628 1629 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task); 1630 1631 // Not strictly necessary but... 1632 // 1633 // We need to reset the concurrency level before each 1634 // proxy task execution, so that the termination protocol 1635 // and overflow handling in G1CMTask::do_marking_step() knows 1636 // how many workers to wait for. 1637 _cm->set_concurrency(_active_workers); 1638 _workers->run_task(&enq_task_proxy); 1639 } 1640 1641 void G1ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) { 1642 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes); 1643 } 1644 1645 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) { 1646 if (has_overflown()) { 1647 // Skip processing the discovered references if we have 1648 // overflown the global marking stack. Reference objects 1649 // only get discovered once so it is OK to not 1650 // de-populate the discovered reference lists. We could have, 1651 // but the only benefit would be that, when marking restarts, 1652 // less reference objects are discovered. 1653 return; 1654 } 1655 1656 ResourceMark rm; 1657 HandleMark hm; 1658 1659 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1660 1661 // Is alive closure. 1662 G1CMIsAliveClosure g1_is_alive(g1h); 1663 1664 // Inner scope to exclude the cleaning of the string and symbol 1665 // tables from the displayed time. 1666 { 1667 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm); 1668 1669 ReferenceProcessor* rp = g1h->ref_processor_cm(); 1670 1671 // See the comment in G1CollectedHeap::ref_processing_init() 1672 // about how reference processing currently works in G1. 1673 1674 // Set the soft reference policy 1675 rp->setup_policy(clear_all_soft_refs); 1676 assert(_global_mark_stack.is_empty(), "mark stack should be empty"); 1677 1678 // Instances of the 'Keep Alive' and 'Complete GC' closures used 1679 // in serial reference processing. Note these closures are also 1680 // used for serially processing (by the the current thread) the 1681 // JNI references during parallel reference processing. 1682 // 1683 // These closures do not need to synchronize with the worker 1684 // threads involved in parallel reference processing as these 1685 // instances are executed serially by the current thread (e.g. 1686 // reference processing is not multi-threaded and is thus 1687 // performed by the current thread instead of a gang worker). 1688 // 1689 // The gang tasks involved in parallel reference processing create 1690 // their own instances of these closures, which do their own 1691 // synchronization among themselves. 1692 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 1693 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 1694 1695 // We need at least one active thread. If reference processing 1696 // is not multi-threaded we use the current (VMThread) thread, 1697 // otherwise we use the work gang from the G1CollectedHeap and 1698 // we utilize all the worker threads we can. 1699 bool processing_is_mt = rp->processing_is_mt(); 1700 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U); 1701 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U); 1702 1703 // Parallel processing task executor. 1704 G1CMRefProcTaskExecutor par_task_executor(g1h, this, 1705 g1h->workers(), active_workers); 1706 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 1707 1708 // Set the concurrency level. The phase was already set prior to 1709 // executing the remark task. 1710 set_concurrency(active_workers); 1711 1712 // Set the degree of MT processing here. If the discovery was done MT, 1713 // the number of threads involved during discovery could differ from 1714 // the number of active workers. This is OK as long as the discovered 1715 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 1716 rp->set_active_mt_degree(active_workers); 1717 1718 // Process the weak references. 1719 const ReferenceProcessorStats& stats = 1720 rp->process_discovered_references(&g1_is_alive, 1721 &g1_keep_alive, 1722 &g1_drain_mark_stack, 1723 executor, 1724 _gc_timer_cm); 1725 _gc_tracer_cm->report_gc_reference_stats(stats); 1726 1727 // The do_oop work routines of the keep_alive and drain_marking_stack 1728 // oop closures will set the has_overflown flag if we overflow the 1729 // global marking stack. 1730 1731 assert(_global_mark_stack.is_out_of_memory() || _global_mark_stack.is_empty(), 1732 "mark stack should be empty (unless it overflowed)"); 1733 1734 if (_global_mark_stack.is_out_of_memory()) { 1735 // This should have been done already when we tried to push an 1736 // entry on to the global mark stack. But let's do it again. 1737 set_has_overflown(); 1738 } 1739 1740 assert(rp->num_q() == active_workers, "why not"); 1741 1742 rp->enqueue_discovered_references(executor); 1743 1744 rp->verify_no_references_recorded(); 1745 assert(!rp->discovery_enabled(), "Post condition"); 1746 } 1747 1748 if (has_overflown()) { 1749 // We can not trust g1_is_alive if the marking stack overflowed 1750 return; 1751 } 1752 1753 assert(_global_mark_stack.is_empty(), "Marking should have completed"); 1754 1755 // Unload Klasses, String, Symbols, Code Cache, etc. 1756 if (ClassUnloadingWithConcurrentMark) { 1757 bool purged_classes; 1758 1759 { 1760 GCTraceTime(Debug, gc, phases) trace("System Dictionary Unloading", _gc_timer_cm); 1761 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */); 1762 } 1763 1764 { 1765 GCTraceTime(Debug, gc, phases) trace("Parallel Unloading", _gc_timer_cm); 1766 weakRefsWorkParallelPart(&g1_is_alive, purged_classes); 1767 } 1768 } 1769 1770 if (G1StringDedup::is_enabled()) { 1771 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", _gc_timer_cm); 1772 G1StringDedup::unlink(&g1_is_alive); 1773 } 1774 } 1775 1776 void G1ConcurrentMark::swapMarkBitMaps() { 1777 G1CMBitMapRO* temp = _prevMarkBitMap; 1778 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap; 1779 _nextMarkBitMap = (G1CMBitMap*) temp; 1780 } 1781 1782 // Closure for marking entries in SATB buffers. 1783 class G1CMSATBBufferClosure : public SATBBufferClosure { 1784 private: 1785 G1CMTask* _task; 1786 G1CollectedHeap* _g1h; 1787 1788 // This is very similar to G1CMTask::deal_with_reference, but with 1789 // more relaxed requirements for the argument, so this must be more 1790 // circumspect about treating the argument as an object. 1791 void do_entry(void* entry) const { 1792 _task->increment_refs_reached(); 1793 HeapRegion* hr = _g1h->heap_region_containing(entry); 1794 if (entry < hr->next_top_at_mark_start()) { 1795 // Until we get here, we don't know whether entry refers to a valid 1796 // object; it could instead have been a stale reference. 1797 oop obj = static_cast<oop>(entry); 1798 assert(obj->is_oop(true /* ignore mark word */), 1799 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj)); 1800 _task->make_reference_grey(obj); 1801 } 1802 } 1803 1804 public: 1805 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h) 1806 : _task(task), _g1h(g1h) { } 1807 1808 virtual void do_buffer(void** buffer, size_t size) { 1809 for (size_t i = 0; i < size; ++i) { 1810 do_entry(buffer[i]); 1811 } 1812 } 1813 }; 1814 1815 class G1RemarkThreadsClosure : public ThreadClosure { 1816 G1CMSATBBufferClosure _cm_satb_cl; 1817 G1CMOopClosure _cm_cl; 1818 MarkingCodeBlobClosure _code_cl; 1819 int _thread_parity; 1820 1821 public: 1822 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) : 1823 _cm_satb_cl(task, g1h), 1824 _cm_cl(g1h, g1h->concurrent_mark(), task), 1825 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 1826 _thread_parity(Threads::thread_claim_parity()) {} 1827 1828 void do_thread(Thread* thread) { 1829 if (thread->is_Java_thread()) { 1830 if (thread->claim_oops_do(true, _thread_parity)) { 1831 JavaThread* jt = (JavaThread*)thread; 1832 1833 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 1834 // however the liveness of oops reachable from nmethods have very complex lifecycles: 1835 // * Alive if on the stack of an executing method 1836 // * Weakly reachable otherwise 1837 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 1838 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 1839 jt->nmethods_do(&_code_cl); 1840 1841 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl); 1842 } 1843 } else if (thread->is_VM_thread()) { 1844 if (thread->claim_oops_do(true, _thread_parity)) { 1845 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl); 1846 } 1847 } 1848 } 1849 }; 1850 1851 class G1CMRemarkTask: public AbstractGangTask { 1852 private: 1853 G1ConcurrentMark* _cm; 1854 public: 1855 void work(uint worker_id) { 1856 // Since all available tasks are actually started, we should 1857 // only proceed if we're supposed to be active. 1858 if (worker_id < _cm->active_tasks()) { 1859 G1CMTask* task = _cm->task(worker_id); 1860 task->record_start_time(); 1861 { 1862 ResourceMark rm; 1863 HandleMark hm; 1864 1865 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task); 1866 Threads::threads_do(&threads_f); 1867 } 1868 1869 do { 1870 task->do_marking_step(1000000000.0 /* something very large */, 1871 true /* do_termination */, 1872 false /* is_serial */); 1873 } while (task->has_aborted() && !_cm->has_overflown()); 1874 // If we overflow, then we do not want to restart. We instead 1875 // want to abort remark and do concurrent marking again. 1876 task->record_end_time(); 1877 } 1878 } 1879 1880 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) : 1881 AbstractGangTask("Par Remark"), _cm(cm) { 1882 _cm->terminator()->reset_for_reuse(active_workers); 1883 } 1884 }; 1885 1886 void G1ConcurrentMark::checkpointRootsFinalWork() { 1887 ResourceMark rm; 1888 HandleMark hm; 1889 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1890 1891 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm); 1892 1893 g1h->ensure_parsability(false); 1894 1895 // this is remark, so we'll use up all active threads 1896 uint active_workers = g1h->workers()->active_workers(); 1897 set_concurrency_and_phase(active_workers, false /* concurrent */); 1898 // Leave _parallel_marking_threads at it's 1899 // value originally calculated in the G1ConcurrentMark 1900 // constructor and pass values of the active workers 1901 // through the gang in the task. 1902 1903 { 1904 StrongRootsScope srs(active_workers); 1905 1906 G1CMRemarkTask remarkTask(this, active_workers); 1907 // We will start all available threads, even if we decide that the 1908 // active_workers will be fewer. The extra ones will just bail out 1909 // immediately. 1910 g1h->workers()->run_task(&remarkTask); 1911 } 1912 1913 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1914 guarantee(has_overflown() || 1915 satb_mq_set.completed_buffers_num() == 0, 1916 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT, 1917 BOOL_TO_STR(has_overflown()), 1918 satb_mq_set.completed_buffers_num()); 1919 1920 print_stats(); 1921 } 1922 1923 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) { 1924 // Note we are overriding the read-only view of the prev map here, via 1925 // the cast. 1926 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr); 1927 } 1928 1929 HeapRegion* 1930 G1ConcurrentMark::claim_region(uint worker_id) { 1931 // "checkpoint" the finger 1932 HeapWord* finger = _finger; 1933 1934 // _heap_end will not change underneath our feet; it only changes at 1935 // yield points. 1936 while (finger < _heap_end) { 1937 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 1938 1939 HeapRegion* curr_region = _g1h->heap_region_containing(finger); 1940 1941 // Above heap_region_containing may return NULL as we always scan claim 1942 // until the end of the heap. In this case, just jump to the next region. 1943 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 1944 1945 // Is the gap between reading the finger and doing the CAS too long? 1946 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger); 1947 if (res == finger && curr_region != NULL) { 1948 // we succeeded 1949 HeapWord* bottom = curr_region->bottom(); 1950 HeapWord* limit = curr_region->next_top_at_mark_start(); 1951 1952 // notice that _finger == end cannot be guaranteed here since, 1953 // someone else might have moved the finger even further 1954 assert(_finger >= end, "the finger should have moved forward"); 1955 1956 if (limit > bottom) { 1957 return curr_region; 1958 } else { 1959 assert(limit == bottom, 1960 "the region limit should be at bottom"); 1961 // we return NULL and the caller should try calling 1962 // claim_region() again. 1963 return NULL; 1964 } 1965 } else { 1966 assert(_finger > finger, "the finger should have moved forward"); 1967 // read it again 1968 finger = _finger; 1969 } 1970 } 1971 1972 return NULL; 1973 } 1974 1975 #ifndef PRODUCT 1976 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC { 1977 private: 1978 G1CollectedHeap* _g1h; 1979 const char* _phase; 1980 int _info; 1981 1982 public: 1983 VerifyNoCSetOops(const char* phase, int info = -1) : 1984 _g1h(G1CollectedHeap::heap()), 1985 _phase(phase), 1986 _info(info) 1987 { } 1988 1989 void operator()(oop obj) const { 1990 guarantee(obj->is_oop(), 1991 "Non-oop " PTR_FORMAT ", phase: %s, info: %d", 1992 p2i(obj), _phase, _info); 1993 guarantee(!_g1h->obj_in_cs(obj), 1994 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d", 1995 p2i(obj), _phase, _info); 1996 } 1997 }; 1998 1999 void G1ConcurrentMark::verify_no_cset_oops() { 2000 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 2001 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) { 2002 return; 2003 } 2004 2005 // Verify entries on the global mark stack 2006 _global_mark_stack.iterate(VerifyNoCSetOops("Stack")); 2007 2008 // Verify entries on the task queues 2009 for (uint i = 0; i < _max_worker_id; ++i) { 2010 G1CMTaskQueue* queue = _task_queues->queue(i); 2011 queue->iterate(VerifyNoCSetOops("Queue", i)); 2012 } 2013 2014 // Verify the global finger 2015 HeapWord* global_finger = finger(); 2016 if (global_finger != NULL && global_finger < _heap_end) { 2017 // Since we always iterate over all regions, we might get a NULL HeapRegion 2018 // here. 2019 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger); 2020 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 2021 "global finger: " PTR_FORMAT " region: " HR_FORMAT, 2022 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)); 2023 } 2024 2025 // Verify the task fingers 2026 assert(parallel_marking_threads() <= _max_worker_id, "sanity"); 2027 for (uint i = 0; i < parallel_marking_threads(); ++i) { 2028 G1CMTask* task = _tasks[i]; 2029 HeapWord* task_finger = task->finger(); 2030 if (task_finger != NULL && task_finger < _heap_end) { 2031 // See above note on the global finger verification. 2032 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger); 2033 guarantee(task_hr == NULL || task_finger == task_hr->bottom() || 2034 !task_hr->in_collection_set(), 2035 "task finger: " PTR_FORMAT " region: " HR_FORMAT, 2036 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)); 2037 } 2038 } 2039 } 2040 #endif // PRODUCT 2041 void G1ConcurrentMark::create_live_data() { 2042 _g1h->g1_rem_set()->create_card_live_data(_parallel_workers, _nextMarkBitMap); 2043 } 2044 2045 void G1ConcurrentMark::finalize_live_data() { 2046 _g1h->g1_rem_set()->finalize_card_live_data(_g1h->workers(), _nextMarkBitMap); 2047 } 2048 2049 void G1ConcurrentMark::verify_live_data() { 2050 _g1h->g1_rem_set()->verify_card_live_data(_g1h->workers(), _nextMarkBitMap); 2051 } 2052 2053 void G1ConcurrentMark::clear_live_data(WorkGang* workers) { 2054 _g1h->g1_rem_set()->clear_card_live_data(workers); 2055 } 2056 2057 #ifdef ASSERT 2058 void G1ConcurrentMark::verify_live_data_clear() { 2059 _g1h->g1_rem_set()->verify_card_live_data_is_clear(); 2060 } 2061 #endif 2062 2063 void G1ConcurrentMark::print_stats() { 2064 if (!log_is_enabled(Debug, gc, stats)) { 2065 return; 2066 } 2067 log_debug(gc, stats)("---------------------------------------------------------------------"); 2068 for (size_t i = 0; i < _active_tasks; ++i) { 2069 _tasks[i]->print_stats(); 2070 log_debug(gc, stats)("---------------------------------------------------------------------"); 2071 } 2072 } 2073 2074 void G1ConcurrentMark::abort() { 2075 if (!cmThread()->during_cycle() || _has_aborted) { 2076 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything. 2077 return; 2078 } 2079 2080 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 2081 // concurrent bitmap clearing. 2082 { 2083 GCTraceTime(Debug, gc)("Clear Next Bitmap"); 2084 clear_bitmap(_nextMarkBitMap, _g1h->workers(), false); 2085 } 2086 // Note we cannot clear the previous marking bitmap here 2087 // since VerifyDuringGC verifies the objects marked during 2088 // a full GC against the previous bitmap. 2089 2090 { 2091 GCTraceTime(Debug, gc)("Clear Live Data"); 2092 clear_live_data(_g1h->workers()); 2093 } 2094 DEBUG_ONLY({ 2095 GCTraceTime(Debug, gc)("Verify Live Data Clear"); 2096 verify_live_data_clear(); 2097 }) 2098 // Empty mark stack 2099 reset_marking_state(); 2100 for (uint i = 0; i < _max_worker_id; ++i) { 2101 _tasks[i]->clear_region_fields(); 2102 } 2103 _first_overflow_barrier_sync.abort(); 2104 _second_overflow_barrier_sync.abort(); 2105 _has_aborted = true; 2106 2107 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2108 satb_mq_set.abandon_partial_marking(); 2109 // This can be called either during or outside marking, we'll read 2110 // the expected_active value from the SATB queue set. 2111 satb_mq_set.set_active_all_threads( 2112 false, /* new active value */ 2113 satb_mq_set.is_active() /* expected_active */); 2114 } 2115 2116 static void print_ms_time_info(const char* prefix, const char* name, 2117 NumberSeq& ns) { 2118 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 2119 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 2120 if (ns.num() > 0) { 2121 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]", 2122 prefix, ns.sd(), ns.maximum()); 2123 } 2124 } 2125 2126 void G1ConcurrentMark::print_summary_info() { 2127 Log(gc, marking) log; 2128 if (!log.is_trace()) { 2129 return; 2130 } 2131 2132 log.trace(" Concurrent marking:"); 2133 print_ms_time_info(" ", "init marks", _init_times); 2134 print_ms_time_info(" ", "remarks", _remark_times); 2135 { 2136 print_ms_time_info(" ", "final marks", _remark_mark_times); 2137 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 2138 2139 } 2140 print_ms_time_info(" ", "cleanups", _cleanup_times); 2141 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).", 2142 _total_counting_time, (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2143 if (G1ScrubRemSets) { 2144 log.trace(" RS scrub total time = %8.2f s (avg = %8.2f ms).", 2145 _total_rs_scrub_time, (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2146 } 2147 log.trace(" Total stop_world time = %8.2f s.", 2148 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0); 2149 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).", 2150 cmThread()->vtime_accum(), cmThread()->vtime_mark_accum()); 2151 } 2152 2153 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const { 2154 _parallel_workers->print_worker_threads_on(st); 2155 } 2156 2157 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const { 2158 _parallel_workers->threads_do(tc); 2159 } 2160 2161 void G1ConcurrentMark::print_on_error(outputStream* st) const { 2162 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 2163 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap)); 2164 _prevMarkBitMap->print_on_error(st, " Prev Bits: "); 2165 _nextMarkBitMap->print_on_error(st, " Next Bits: "); 2166 } 2167 2168 // Closure for iteration over bitmaps 2169 class G1CMBitMapClosure : public BitMapClosure { 2170 private: 2171 // the bitmap that is being iterated over 2172 G1CMBitMap* _nextMarkBitMap; 2173 G1ConcurrentMark* _cm; 2174 G1CMTask* _task; 2175 2176 public: 2177 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm, G1CMBitMap* nextMarkBitMap) : 2178 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { } 2179 2180 bool do_bit(size_t offset) { 2181 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset); 2182 assert(_nextMarkBitMap->isMarked(addr), "invariant"); 2183 assert( addr < _cm->finger(), "invariant"); 2184 assert(addr >= _task->finger(), "invariant"); 2185 2186 // We move that task's local finger along. 2187 _task->move_finger_to(addr); 2188 2189 _task->scan_object(oop(addr)); 2190 // we only partially drain the local queue and global stack 2191 _task->drain_local_queue(true); 2192 _task->drain_global_stack(true); 2193 2194 // if the has_aborted flag has been raised, we need to bail out of 2195 // the iteration 2196 return !_task->has_aborted(); 2197 } 2198 }; 2199 2200 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) { 2201 ReferenceProcessor* result = g1h->ref_processor_cm(); 2202 assert(result != NULL, "CM reference processor should not be NULL"); 2203 return result; 2204 } 2205 2206 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 2207 G1ConcurrentMark* cm, 2208 G1CMTask* task) 2209 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)), 2210 _g1h(g1h), _cm(cm), _task(task) 2211 { } 2212 2213 void G1CMTask::setup_for_region(HeapRegion* hr) { 2214 assert(hr != NULL, 2215 "claim_region() should have filtered out NULL regions"); 2216 _curr_region = hr; 2217 _finger = hr->bottom(); 2218 update_region_limit(); 2219 } 2220 2221 void G1CMTask::update_region_limit() { 2222 HeapRegion* hr = _curr_region; 2223 HeapWord* bottom = hr->bottom(); 2224 HeapWord* limit = hr->next_top_at_mark_start(); 2225 2226 if (limit == bottom) { 2227 // The region was collected underneath our feet. 2228 // We set the finger to bottom to ensure that the bitmap 2229 // iteration that will follow this will not do anything. 2230 // (this is not a condition that holds when we set the region up, 2231 // as the region is not supposed to be empty in the first place) 2232 _finger = bottom; 2233 } else if (limit >= _region_limit) { 2234 assert(limit >= _finger, "peace of mind"); 2235 } else { 2236 assert(limit < _region_limit, "only way to get here"); 2237 // This can happen under some pretty unusual circumstances. An 2238 // evacuation pause empties the region underneath our feet (NTAMS 2239 // at bottom). We then do some allocation in the region (NTAMS 2240 // stays at bottom), followed by the region being used as a GC 2241 // alloc region (NTAMS will move to top() and the objects 2242 // originally below it will be grayed). All objects now marked in 2243 // the region are explicitly grayed, if below the global finger, 2244 // and we do not need in fact to scan anything else. So, we simply 2245 // set _finger to be limit to ensure that the bitmap iteration 2246 // doesn't do anything. 2247 _finger = limit; 2248 } 2249 2250 _region_limit = limit; 2251 } 2252 2253 void G1CMTask::giveup_current_region() { 2254 assert(_curr_region != NULL, "invariant"); 2255 clear_region_fields(); 2256 } 2257 2258 void G1CMTask::clear_region_fields() { 2259 // Values for these three fields that indicate that we're not 2260 // holding on to a region. 2261 _curr_region = NULL; 2262 _finger = NULL; 2263 _region_limit = NULL; 2264 } 2265 2266 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 2267 if (cm_oop_closure == NULL) { 2268 assert(_cm_oop_closure != NULL, "invariant"); 2269 } else { 2270 assert(_cm_oop_closure == NULL, "invariant"); 2271 } 2272 _cm_oop_closure = cm_oop_closure; 2273 } 2274 2275 void G1CMTask::reset(G1CMBitMap* nextMarkBitMap) { 2276 guarantee(nextMarkBitMap != NULL, "invariant"); 2277 _nextMarkBitMap = nextMarkBitMap; 2278 clear_region_fields(); 2279 2280 _calls = 0; 2281 _elapsed_time_ms = 0.0; 2282 _termination_time_ms = 0.0; 2283 _termination_start_time_ms = 0.0; 2284 } 2285 2286 bool G1CMTask::should_exit_termination() { 2287 regular_clock_call(); 2288 // This is called when we are in the termination protocol. We should 2289 // quit if, for some reason, this task wants to abort or the global 2290 // stack is not empty (this means that we can get work from it). 2291 return !_cm->mark_stack_empty() || has_aborted(); 2292 } 2293 2294 void G1CMTask::reached_limit() { 2295 assert(_words_scanned >= _words_scanned_limit || 2296 _refs_reached >= _refs_reached_limit , 2297 "shouldn't have been called otherwise"); 2298 regular_clock_call(); 2299 } 2300 2301 void G1CMTask::regular_clock_call() { 2302 if (has_aborted()) return; 2303 2304 // First, we need to recalculate the words scanned and refs reached 2305 // limits for the next clock call. 2306 recalculate_limits(); 2307 2308 // During the regular clock call we do the following 2309 2310 // (1) If an overflow has been flagged, then we abort. 2311 if (_cm->has_overflown()) { 2312 set_has_aborted(); 2313 return; 2314 } 2315 2316 // If we are not concurrent (i.e. we're doing remark) we don't need 2317 // to check anything else. The other steps are only needed during 2318 // the concurrent marking phase. 2319 if (!concurrent()) return; 2320 2321 // (2) If marking has been aborted for Full GC, then we also abort. 2322 if (_cm->has_aborted()) { 2323 set_has_aborted(); 2324 return; 2325 } 2326 2327 double curr_time_ms = os::elapsedVTime() * 1000.0; 2328 2329 // (4) We check whether we should yield. If we have to, then we abort. 2330 if (SuspendibleThreadSet::should_yield()) { 2331 // We should yield. To do this we abort the task. The caller is 2332 // responsible for yielding. 2333 set_has_aborted(); 2334 return; 2335 } 2336 2337 // (5) We check whether we've reached our time quota. If we have, 2338 // then we abort. 2339 double elapsed_time_ms = curr_time_ms - _start_time_ms; 2340 if (elapsed_time_ms > _time_target_ms) { 2341 set_has_aborted(); 2342 _has_timed_out = true; 2343 return; 2344 } 2345 2346 // (6) Finally, we check whether there are enough completed STAB 2347 // buffers available for processing. If there are, we abort. 2348 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2349 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 2350 // we do need to process SATB buffers, we'll abort and restart 2351 // the marking task to do so 2352 set_has_aborted(); 2353 return; 2354 } 2355 } 2356 2357 void G1CMTask::recalculate_limits() { 2358 _real_words_scanned_limit = _words_scanned + words_scanned_period; 2359 _words_scanned_limit = _real_words_scanned_limit; 2360 2361 _real_refs_reached_limit = _refs_reached + refs_reached_period; 2362 _refs_reached_limit = _real_refs_reached_limit; 2363 } 2364 2365 void G1CMTask::decrease_limits() { 2366 // This is called when we believe that we're going to do an infrequent 2367 // operation which will increase the per byte scanned cost (i.e. move 2368 // entries to/from the global stack). It basically tries to decrease the 2369 // scanning limit so that the clock is called earlier. 2370 2371 _words_scanned_limit = _real_words_scanned_limit - 2372 3 * words_scanned_period / 4; 2373 _refs_reached_limit = _real_refs_reached_limit - 2374 3 * refs_reached_period / 4; 2375 } 2376 2377 void G1CMTask::move_entries_to_global_stack() { 2378 // Local array where we'll store the entries that will be popped 2379 // from the local queue. 2380 oop buffer[G1CMMarkStack::OopsPerChunk]; 2381 2382 size_t n = 0; 2383 oop obj; 2384 while (n < G1CMMarkStack::OopsPerChunk && _task_queue->pop_local(obj)) { 2385 buffer[n] = obj; 2386 ++n; 2387 } 2388 if (n < G1CMMarkStack::OopsPerChunk) { 2389 buffer[n] = NULL; 2390 } 2391 2392 if (n > 0) { 2393 if (!_cm->mark_stack_push(buffer)) { 2394 set_has_aborted(); 2395 } 2396 } 2397 2398 // This operation was quite expensive, so decrease the limits. 2399 decrease_limits(); 2400 } 2401 2402 bool G1CMTask::get_entries_from_global_stack() { 2403 // Local array where we'll store the entries that will be popped 2404 // from the global stack. 2405 oop buffer[G1CMMarkStack::OopsPerChunk]; 2406 2407 if (!_cm->mark_stack_pop(buffer)) { 2408 return false; 2409 } 2410 2411 // We did actually pop at least one entry. 2412 for (size_t i = 0; i < G1CMMarkStack::OopsPerChunk; ++i) { 2413 oop elem = buffer[i]; 2414 if (elem == NULL) { 2415 break; 2416 } 2417 bool success = _task_queue->push(elem); 2418 // We only call this when the local queue is empty or under a 2419 // given target limit. So, we do not expect this push to fail. 2420 assert(success, "invariant"); 2421 } 2422 2423 // This operation was quite expensive, so decrease the limits 2424 decrease_limits(); 2425 return true; 2426 } 2427 2428 void G1CMTask::drain_local_queue(bool partially) { 2429 if (has_aborted()) return; 2430 2431 // Decide what the target size is, depending whether we're going to 2432 // drain it partially (so that other tasks can steal if they run out 2433 // of things to do) or totally (at the very end). 2434 size_t target_size; 2435 if (partially) { 2436 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize); 2437 } else { 2438 target_size = 0; 2439 } 2440 2441 if (_task_queue->size() > target_size) { 2442 oop obj; 2443 bool ret = _task_queue->pop_local(obj); 2444 while (ret) { 2445 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" ); 2446 assert(!_g1h->is_on_master_free_list( 2447 _g1h->heap_region_containing((HeapWord*) obj)), "invariant"); 2448 2449 scan_object(obj); 2450 2451 if (_task_queue->size() <= target_size || has_aborted()) { 2452 ret = false; 2453 } else { 2454 ret = _task_queue->pop_local(obj); 2455 } 2456 } 2457 } 2458 } 2459 2460 void G1CMTask::drain_global_stack(bool partially) { 2461 if (has_aborted()) return; 2462 2463 // We have a policy to drain the local queue before we attempt to 2464 // drain the global stack. 2465 assert(partially || _task_queue->size() == 0, "invariant"); 2466 2467 // Decide what the target size is, depending whether we're going to 2468 // drain it partially (so that other tasks can steal if they run out 2469 // of things to do) or totally (at the very end). 2470 // Notice that when draining the global mark stack partially, due to the racyness 2471 // of the mark stack size update we might in fact drop below the target. But, 2472 // this is not a problem. 2473 // In case of total draining, we simply process until the global mark stack is 2474 // totally empty, disregarding the size counter. 2475 if (partially) { 2476 size_t const target_size = _cm->partial_mark_stack_size_target(); 2477 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 2478 if (get_entries_from_global_stack()) { 2479 drain_local_queue(partially); 2480 } 2481 } 2482 } else { 2483 while (!has_aborted() && get_entries_from_global_stack()) { 2484 drain_local_queue(partially); 2485 } 2486 } 2487 } 2488 2489 // SATB Queue has several assumptions on whether to call the par or 2490 // non-par versions of the methods. this is why some of the code is 2491 // replicated. We should really get rid of the single-threaded version 2492 // of the code to simplify things. 2493 void G1CMTask::drain_satb_buffers() { 2494 if (has_aborted()) return; 2495 2496 // We set this so that the regular clock knows that we're in the 2497 // middle of draining buffers and doesn't set the abort flag when it 2498 // notices that SATB buffers are available for draining. It'd be 2499 // very counter productive if it did that. :-) 2500 _draining_satb_buffers = true; 2501 2502 G1CMSATBBufferClosure satb_cl(this, _g1h); 2503 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2504 2505 // This keeps claiming and applying the closure to completed buffers 2506 // until we run out of buffers or we need to abort. 2507 while (!has_aborted() && 2508 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 2509 regular_clock_call(); 2510 } 2511 2512 _draining_satb_buffers = false; 2513 2514 assert(has_aborted() || 2515 concurrent() || 2516 satb_mq_set.completed_buffers_num() == 0, "invariant"); 2517 2518 // again, this was a potentially expensive operation, decrease the 2519 // limits to get the regular clock call early 2520 decrease_limits(); 2521 } 2522 2523 void G1CMTask::print_stats() { 2524 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d", 2525 _worker_id, _calls); 2526 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 2527 _elapsed_time_ms, _termination_time_ms); 2528 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 2529 _step_times_ms.num(), _step_times_ms.avg(), 2530 _step_times_ms.sd()); 2531 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms", 2532 _step_times_ms.maximum(), _step_times_ms.sum()); 2533 } 2534 2535 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) { 2536 return _task_queues->steal(worker_id, hash_seed, obj); 2537 } 2538 2539 /***************************************************************************** 2540 2541 The do_marking_step(time_target_ms, ...) method is the building 2542 block of the parallel marking framework. It can be called in parallel 2543 with other invocations of do_marking_step() on different tasks 2544 (but only one per task, obviously) and concurrently with the 2545 mutator threads, or during remark, hence it eliminates the need 2546 for two versions of the code. When called during remark, it will 2547 pick up from where the task left off during the concurrent marking 2548 phase. Interestingly, tasks are also claimable during evacuation 2549 pauses too, since do_marking_step() ensures that it aborts before 2550 it needs to yield. 2551 2552 The data structures that it uses to do marking work are the 2553 following: 2554 2555 (1) Marking Bitmap. If there are gray objects that appear only 2556 on the bitmap (this happens either when dealing with an overflow 2557 or when the initial marking phase has simply marked the roots 2558 and didn't push them on the stack), then tasks claim heap 2559 regions whose bitmap they then scan to find gray objects. A 2560 global finger indicates where the end of the last claimed region 2561 is. A local finger indicates how far into the region a task has 2562 scanned. The two fingers are used to determine how to gray an 2563 object (i.e. whether simply marking it is OK, as it will be 2564 visited by a task in the future, or whether it needs to be also 2565 pushed on a stack). 2566 2567 (2) Local Queue. The local queue of the task which is accessed 2568 reasonably efficiently by the task. Other tasks can steal from 2569 it when they run out of work. Throughout the marking phase, a 2570 task attempts to keep its local queue short but not totally 2571 empty, so that entries are available for stealing by other 2572 tasks. Only when there is no more work, a task will totally 2573 drain its local queue. 2574 2575 (3) Global Mark Stack. This handles local queue overflow. During 2576 marking only sets of entries are moved between it and the local 2577 queues, as access to it requires a mutex and more fine-grain 2578 interaction with it which might cause contention. If it 2579 overflows, then the marking phase should restart and iterate 2580 over the bitmap to identify gray objects. Throughout the marking 2581 phase, tasks attempt to keep the global mark stack at a small 2582 length but not totally empty, so that entries are available for 2583 popping by other tasks. Only when there is no more work, tasks 2584 will totally drain the global mark stack. 2585 2586 (4) SATB Buffer Queue. This is where completed SATB buffers are 2587 made available. Buffers are regularly removed from this queue 2588 and scanned for roots, so that the queue doesn't get too 2589 long. During remark, all completed buffers are processed, as 2590 well as the filled in parts of any uncompleted buffers. 2591 2592 The do_marking_step() method tries to abort when the time target 2593 has been reached. There are a few other cases when the 2594 do_marking_step() method also aborts: 2595 2596 (1) When the marking phase has been aborted (after a Full GC). 2597 2598 (2) When a global overflow (on the global stack) has been 2599 triggered. Before the task aborts, it will actually sync up with 2600 the other tasks to ensure that all the marking data structures 2601 (local queues, stacks, fingers etc.) are re-initialized so that 2602 when do_marking_step() completes, the marking phase can 2603 immediately restart. 2604 2605 (3) When enough completed SATB buffers are available. The 2606 do_marking_step() method only tries to drain SATB buffers right 2607 at the beginning. So, if enough buffers are available, the 2608 marking step aborts and the SATB buffers are processed at 2609 the beginning of the next invocation. 2610 2611 (4) To yield. when we have to yield then we abort and yield 2612 right at the end of do_marking_step(). This saves us from a lot 2613 of hassle as, by yielding we might allow a Full GC. If this 2614 happens then objects will be compacted underneath our feet, the 2615 heap might shrink, etc. We save checking for this by just 2616 aborting and doing the yield right at the end. 2617 2618 From the above it follows that the do_marking_step() method should 2619 be called in a loop (or, otherwise, regularly) until it completes. 2620 2621 If a marking step completes without its has_aborted() flag being 2622 true, it means it has completed the current marking phase (and 2623 also all other marking tasks have done so and have all synced up). 2624 2625 A method called regular_clock_call() is invoked "regularly" (in 2626 sub ms intervals) throughout marking. It is this clock method that 2627 checks all the abort conditions which were mentioned above and 2628 decides when the task should abort. A work-based scheme is used to 2629 trigger this clock method: when the number of object words the 2630 marking phase has scanned or the number of references the marking 2631 phase has visited reach a given limit. Additional invocations to 2632 the method clock have been planted in a few other strategic places 2633 too. The initial reason for the clock method was to avoid calling 2634 vtime too regularly, as it is quite expensive. So, once it was in 2635 place, it was natural to piggy-back all the other conditions on it 2636 too and not constantly check them throughout the code. 2637 2638 If do_termination is true then do_marking_step will enter its 2639 termination protocol. 2640 2641 The value of is_serial must be true when do_marking_step is being 2642 called serially (i.e. by the VMThread) and do_marking_step should 2643 skip any synchronization in the termination and overflow code. 2644 Examples include the serial remark code and the serial reference 2645 processing closures. 2646 2647 The value of is_serial must be false when do_marking_step is 2648 being called by any of the worker threads in a work gang. 2649 Examples include the concurrent marking code (CMMarkingTask), 2650 the MT remark code, and the MT reference processing closures. 2651 2652 *****************************************************************************/ 2653 2654 void G1CMTask::do_marking_step(double time_target_ms, 2655 bool do_termination, 2656 bool is_serial) { 2657 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 2658 assert(concurrent() == _cm->concurrent(), "they should be the same"); 2659 2660 G1Policy* g1_policy = _g1h->g1_policy(); 2661 assert(_task_queues != NULL, "invariant"); 2662 assert(_task_queue != NULL, "invariant"); 2663 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant"); 2664 2665 assert(!_claimed, 2666 "only one thread should claim this task at any one time"); 2667 2668 // OK, this doesn't safeguard again all possible scenarios, as it is 2669 // possible for two threads to set the _claimed flag at the same 2670 // time. But it is only for debugging purposes anyway and it will 2671 // catch most problems. 2672 _claimed = true; 2673 2674 _start_time_ms = os::elapsedVTime() * 1000.0; 2675 2676 // If do_stealing is true then do_marking_step will attempt to 2677 // steal work from the other G1CMTasks. It only makes sense to 2678 // enable stealing when the termination protocol is enabled 2679 // and do_marking_step() is not being called serially. 2680 bool do_stealing = do_termination && !is_serial; 2681 2682 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms); 2683 _time_target_ms = time_target_ms - diff_prediction_ms; 2684 2685 // set up the variables that are used in the work-based scheme to 2686 // call the regular clock method 2687 _words_scanned = 0; 2688 _refs_reached = 0; 2689 recalculate_limits(); 2690 2691 // clear all flags 2692 clear_has_aborted(); 2693 _has_timed_out = false; 2694 _draining_satb_buffers = false; 2695 2696 ++_calls; 2697 2698 // Set up the bitmap and oop closures. Anything that uses them is 2699 // eventually called from this method, so it is OK to allocate these 2700 // statically. 2701 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap); 2702 G1CMOopClosure cm_oop_closure(_g1h, _cm, this); 2703 set_cm_oop_closure(&cm_oop_closure); 2704 2705 if (_cm->has_overflown()) { 2706 // This can happen if the mark stack overflows during a GC pause 2707 // and this task, after a yield point, restarts. We have to abort 2708 // as we need to get into the overflow protocol which happens 2709 // right at the end of this task. 2710 set_has_aborted(); 2711 } 2712 2713 // First drain any available SATB buffers. After this, we will not 2714 // look at SATB buffers before the next invocation of this method. 2715 // If enough completed SATB buffers are queued up, the regular clock 2716 // will abort this task so that it restarts. 2717 drain_satb_buffers(); 2718 // ...then partially drain the local queue and the global stack 2719 drain_local_queue(true); 2720 drain_global_stack(true); 2721 2722 do { 2723 if (!has_aborted() && _curr_region != NULL) { 2724 // This means that we're already holding on to a region. 2725 assert(_finger != NULL, "if region is not NULL, then the finger " 2726 "should not be NULL either"); 2727 2728 // We might have restarted this task after an evacuation pause 2729 // which might have evacuated the region we're holding on to 2730 // underneath our feet. Let's read its limit again to make sure 2731 // that we do not iterate over a region of the heap that 2732 // contains garbage (update_region_limit() will also move 2733 // _finger to the start of the region if it is found empty). 2734 update_region_limit(); 2735 // We will start from _finger not from the start of the region, 2736 // as we might be restarting this task after aborting half-way 2737 // through scanning this region. In this case, _finger points to 2738 // the address where we last found a marked object. If this is a 2739 // fresh region, _finger points to start(). 2740 MemRegion mr = MemRegion(_finger, _region_limit); 2741 2742 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(), 2743 "humongous regions should go around loop once only"); 2744 2745 // Some special cases: 2746 // If the memory region is empty, we can just give up the region. 2747 // If the current region is humongous then we only need to check 2748 // the bitmap for the bit associated with the start of the object, 2749 // scan the object if it's live, and give up the region. 2750 // Otherwise, let's iterate over the bitmap of the part of the region 2751 // that is left. 2752 // If the iteration is successful, give up the region. 2753 if (mr.is_empty()) { 2754 giveup_current_region(); 2755 regular_clock_call(); 2756 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) { 2757 if (_nextMarkBitMap->isMarked(mr.start())) { 2758 // The object is marked - apply the closure 2759 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start()); 2760 bitmap_closure.do_bit(offset); 2761 } 2762 // Even if this task aborted while scanning the humongous object 2763 // we can (and should) give up the current region. 2764 giveup_current_region(); 2765 regular_clock_call(); 2766 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) { 2767 giveup_current_region(); 2768 regular_clock_call(); 2769 } else { 2770 assert(has_aborted(), "currently the only way to do so"); 2771 // The only way to abort the bitmap iteration is to return 2772 // false from the do_bit() method. However, inside the 2773 // do_bit() method we move the _finger to point to the 2774 // object currently being looked at. So, if we bail out, we 2775 // have definitely set _finger to something non-null. 2776 assert(_finger != NULL, "invariant"); 2777 2778 // Region iteration was actually aborted. So now _finger 2779 // points to the address of the object we last scanned. If we 2780 // leave it there, when we restart this task, we will rescan 2781 // the object. It is easy to avoid this. We move the finger by 2782 // enough to point to the next possible object header (the 2783 // bitmap knows by how much we need to move it as it knows its 2784 // granularity). 2785 assert(_finger < _region_limit, "invariant"); 2786 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger); 2787 // Check if bitmap iteration was aborted while scanning the last object 2788 if (new_finger >= _region_limit) { 2789 giveup_current_region(); 2790 } else { 2791 move_finger_to(new_finger); 2792 } 2793 } 2794 } 2795 // At this point we have either completed iterating over the 2796 // region we were holding on to, or we have aborted. 2797 2798 // We then partially drain the local queue and the global stack. 2799 // (Do we really need this?) 2800 drain_local_queue(true); 2801 drain_global_stack(true); 2802 2803 // Read the note on the claim_region() method on why it might 2804 // return NULL with potentially more regions available for 2805 // claiming and why we have to check out_of_regions() to determine 2806 // whether we're done or not. 2807 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 2808 // We are going to try to claim a new region. We should have 2809 // given up on the previous one. 2810 // Separated the asserts so that we know which one fires. 2811 assert(_curr_region == NULL, "invariant"); 2812 assert(_finger == NULL, "invariant"); 2813 assert(_region_limit == NULL, "invariant"); 2814 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 2815 if (claimed_region != NULL) { 2816 // Yes, we managed to claim one 2817 setup_for_region(claimed_region); 2818 assert(_curr_region == claimed_region, "invariant"); 2819 } 2820 // It is important to call the regular clock here. It might take 2821 // a while to claim a region if, for example, we hit a large 2822 // block of empty regions. So we need to call the regular clock 2823 // method once round the loop to make sure it's called 2824 // frequently enough. 2825 regular_clock_call(); 2826 } 2827 2828 if (!has_aborted() && _curr_region == NULL) { 2829 assert(_cm->out_of_regions(), 2830 "at this point we should be out of regions"); 2831 } 2832 } while ( _curr_region != NULL && !has_aborted()); 2833 2834 if (!has_aborted()) { 2835 // We cannot check whether the global stack is empty, since other 2836 // tasks might be pushing objects to it concurrently. 2837 assert(_cm->out_of_regions(), 2838 "at this point we should be out of regions"); 2839 // Try to reduce the number of available SATB buffers so that 2840 // remark has less work to do. 2841 drain_satb_buffers(); 2842 } 2843 2844 // Since we've done everything else, we can now totally drain the 2845 // local queue and global stack. 2846 drain_local_queue(false); 2847 drain_global_stack(false); 2848 2849 // Attempt at work stealing from other task's queues. 2850 if (do_stealing && !has_aborted()) { 2851 // We have not aborted. This means that we have finished all that 2852 // we could. Let's try to do some stealing... 2853 2854 // We cannot check whether the global stack is empty, since other 2855 // tasks might be pushing objects to it concurrently. 2856 assert(_cm->out_of_regions() && _task_queue->size() == 0, 2857 "only way to reach here"); 2858 while (!has_aborted()) { 2859 oop obj; 2860 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) { 2861 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), 2862 "any stolen object should be marked"); 2863 scan_object(obj); 2864 2865 // And since we're towards the end, let's totally drain the 2866 // local queue and global stack. 2867 drain_local_queue(false); 2868 drain_global_stack(false); 2869 } else { 2870 break; 2871 } 2872 } 2873 } 2874 2875 // We still haven't aborted. Now, let's try to get into the 2876 // termination protocol. 2877 if (do_termination && !has_aborted()) { 2878 // We cannot check whether the global stack is empty, since other 2879 // tasks might be concurrently pushing objects on it. 2880 // Separated the asserts so that we know which one fires. 2881 assert(_cm->out_of_regions(), "only way to reach here"); 2882 assert(_task_queue->size() == 0, "only way to reach here"); 2883 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 2884 2885 // The G1CMTask class also extends the TerminatorTerminator class, 2886 // hence its should_exit_termination() method will also decide 2887 // whether to exit the termination protocol or not. 2888 bool finished = (is_serial || 2889 _cm->terminator()->offer_termination(this)); 2890 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 2891 _termination_time_ms += 2892 termination_end_time_ms - _termination_start_time_ms; 2893 2894 if (finished) { 2895 // We're all done. 2896 2897 if (_worker_id == 0) { 2898 // let's allow task 0 to do this 2899 if (concurrent()) { 2900 assert(_cm->concurrent_marking_in_progress(), "invariant"); 2901 // we need to set this to false before the next 2902 // safepoint. This way we ensure that the marking phase 2903 // doesn't observe any more heap expansions. 2904 _cm->clear_concurrent_marking_in_progress(); 2905 } 2906 } 2907 2908 // We can now guarantee that the global stack is empty, since 2909 // all other tasks have finished. We separated the guarantees so 2910 // that, if a condition is false, we can immediately find out 2911 // which one. 2912 guarantee(_cm->out_of_regions(), "only way to reach here"); 2913 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 2914 guarantee(_task_queue->size() == 0, "only way to reach here"); 2915 guarantee(!_cm->has_overflown(), "only way to reach here"); 2916 guarantee(!_cm->mark_stack_overflow(), "only way to reach here"); 2917 } else { 2918 // Apparently there's more work to do. Let's abort this task. It 2919 // will restart it and we can hopefully find more things to do. 2920 set_has_aborted(); 2921 } 2922 } 2923 2924 // Mainly for debugging purposes to make sure that a pointer to the 2925 // closure which was statically allocated in this frame doesn't 2926 // escape it by accident. 2927 set_cm_oop_closure(NULL); 2928 double end_time_ms = os::elapsedVTime() * 1000.0; 2929 double elapsed_time_ms = end_time_ms - _start_time_ms; 2930 // Update the step history. 2931 _step_times_ms.add(elapsed_time_ms); 2932 2933 if (has_aborted()) { 2934 // The task was aborted for some reason. 2935 if (_has_timed_out) { 2936 double diff_ms = elapsed_time_ms - _time_target_ms; 2937 // Keep statistics of how well we did with respect to hitting 2938 // our target only if we actually timed out (if we aborted for 2939 // other reasons, then the results might get skewed). 2940 _marking_step_diffs_ms.add(diff_ms); 2941 } 2942 2943 if (_cm->has_overflown()) { 2944 // This is the interesting one. We aborted because a global 2945 // overflow was raised. This means we have to restart the 2946 // marking phase and start iterating over regions. However, in 2947 // order to do this we have to make sure that all tasks stop 2948 // what they are doing and re-initialize in a safe manner. We 2949 // will achieve this with the use of two barrier sync points. 2950 2951 if (!is_serial) { 2952 // We only need to enter the sync barrier if being called 2953 // from a parallel context 2954 _cm->enter_first_sync_barrier(_worker_id); 2955 2956 // When we exit this sync barrier we know that all tasks have 2957 // stopped doing marking work. So, it's now safe to 2958 // re-initialize our data structures. At the end of this method, 2959 // task 0 will clear the global data structures. 2960 } 2961 2962 // We clear the local state of this task... 2963 clear_region_fields(); 2964 2965 if (!is_serial) { 2966 // ...and enter the second barrier. 2967 _cm->enter_second_sync_barrier(_worker_id); 2968 } 2969 // At this point, if we're during the concurrent phase of 2970 // marking, everything has been re-initialized and we're 2971 // ready to restart. 2972 } 2973 } 2974 2975 _claimed = false; 2976 } 2977 2978 G1CMTask::G1CMTask(uint worker_id, 2979 G1ConcurrentMark* cm, 2980 G1CMTaskQueue* task_queue, 2981 G1CMTaskQueueSet* task_queues) 2982 : _g1h(G1CollectedHeap::heap()), 2983 _worker_id(worker_id), _cm(cm), 2984 _claimed(false), 2985 _nextMarkBitMap(NULL), _hash_seed(17), 2986 _task_queue(task_queue), 2987 _task_queues(task_queues), 2988 _cm_oop_closure(NULL) { 2989 guarantee(task_queue != NULL, "invariant"); 2990 guarantee(task_queues != NULL, "invariant"); 2991 2992 _marking_step_diffs_ms.add(0.5); 2993 } 2994 2995 // These are formatting macros that are used below to ensure 2996 // consistent formatting. The *_H_* versions are used to format the 2997 // header for a particular value and they should be kept consistent 2998 // with the corresponding macro. Also note that most of the macros add 2999 // the necessary white space (as a prefix) which makes them a bit 3000 // easier to compose. 3001 3002 // All the output lines are prefixed with this string to be able to 3003 // identify them easily in a large log file. 3004 #define G1PPRL_LINE_PREFIX "###" 3005 3006 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT 3007 #ifdef _LP64 3008 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 3009 #else // _LP64 3010 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 3011 #endif // _LP64 3012 3013 // For per-region info 3014 #define G1PPRL_TYPE_FORMAT " %-4s" 3015 #define G1PPRL_TYPE_H_FORMAT " %4s" 3016 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9) 3017 #define G1PPRL_BYTE_H_FORMAT " %9s" 3018 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 3019 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 3020 3021 // For summary info 3022 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT 3023 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT 3024 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB" 3025 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%" 3026 3027 G1PrintRegionLivenessInfoClosure:: 3028 G1PrintRegionLivenessInfoClosure(const char* phase_name) 3029 : _total_used_bytes(0), _total_capacity_bytes(0), 3030 _total_prev_live_bytes(0), _total_next_live_bytes(0), 3031 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) { 3032 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3033 MemRegion g1_reserved = g1h->g1_reserved(); 3034 double now = os::elapsedTime(); 3035 3036 // Print the header of the output. 3037 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 3038 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP" 3039 G1PPRL_SUM_ADDR_FORMAT("reserved") 3040 G1PPRL_SUM_BYTE_FORMAT("region-size"), 3041 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 3042 HeapRegion::GrainBytes); 3043 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3044 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3045 G1PPRL_TYPE_H_FORMAT 3046 G1PPRL_ADDR_BASE_H_FORMAT 3047 G1PPRL_BYTE_H_FORMAT 3048 G1PPRL_BYTE_H_FORMAT 3049 G1PPRL_BYTE_H_FORMAT 3050 G1PPRL_DOUBLE_H_FORMAT 3051 G1PPRL_BYTE_H_FORMAT 3052 G1PPRL_BYTE_H_FORMAT, 3053 "type", "address-range", 3054 "used", "prev-live", "next-live", "gc-eff", 3055 "remset", "code-roots"); 3056 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3057 G1PPRL_TYPE_H_FORMAT 3058 G1PPRL_ADDR_BASE_H_FORMAT 3059 G1PPRL_BYTE_H_FORMAT 3060 G1PPRL_BYTE_H_FORMAT 3061 G1PPRL_BYTE_H_FORMAT 3062 G1PPRL_DOUBLE_H_FORMAT 3063 G1PPRL_BYTE_H_FORMAT 3064 G1PPRL_BYTE_H_FORMAT, 3065 "", "", 3066 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 3067 "(bytes)", "(bytes)"); 3068 } 3069 3070 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) { 3071 const char* type = r->get_type_str(); 3072 HeapWord* bottom = r->bottom(); 3073 HeapWord* end = r->end(); 3074 size_t capacity_bytes = r->capacity(); 3075 size_t used_bytes = r->used(); 3076 size_t prev_live_bytes = r->live_bytes(); 3077 size_t next_live_bytes = r->next_live_bytes(); 3078 double gc_eff = r->gc_efficiency(); 3079 size_t remset_bytes = r->rem_set()->mem_size(); 3080 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 3081 3082 _total_used_bytes += used_bytes; 3083 _total_capacity_bytes += capacity_bytes; 3084 _total_prev_live_bytes += prev_live_bytes; 3085 _total_next_live_bytes += next_live_bytes; 3086 _total_remset_bytes += remset_bytes; 3087 _total_strong_code_roots_bytes += strong_code_roots_bytes; 3088 3089 // Print a line for this particular region. 3090 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3091 G1PPRL_TYPE_FORMAT 3092 G1PPRL_ADDR_BASE_FORMAT 3093 G1PPRL_BYTE_FORMAT 3094 G1PPRL_BYTE_FORMAT 3095 G1PPRL_BYTE_FORMAT 3096 G1PPRL_DOUBLE_FORMAT 3097 G1PPRL_BYTE_FORMAT 3098 G1PPRL_BYTE_FORMAT, 3099 type, p2i(bottom), p2i(end), 3100 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 3101 remset_bytes, strong_code_roots_bytes); 3102 3103 return false; 3104 } 3105 3106 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 3107 // add static memory usages to remembered set sizes 3108 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 3109 // Print the footer of the output. 3110 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3111 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3112 " SUMMARY" 3113 G1PPRL_SUM_MB_FORMAT("capacity") 3114 G1PPRL_SUM_MB_PERC_FORMAT("used") 3115 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 3116 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 3117 G1PPRL_SUM_MB_FORMAT("remset") 3118 G1PPRL_SUM_MB_FORMAT("code-roots"), 3119 bytes_to_mb(_total_capacity_bytes), 3120 bytes_to_mb(_total_used_bytes), 3121 perc(_total_used_bytes, _total_capacity_bytes), 3122 bytes_to_mb(_total_prev_live_bytes), 3123 perc(_total_prev_live_bytes, _total_capacity_bytes), 3124 bytes_to_mb(_total_next_live_bytes), 3125 perc(_total_next_live_bytes, _total_capacity_bytes), 3126 bytes_to_mb(_total_remset_bytes), 3127 bytes_to_mb(_total_strong_code_roots_bytes)); 3128 }