1 /* 2 * Copyright (c) 2001, 2017, 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 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk, 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(TaskQueueEntryChunk)); 153 return false; 154 } 155 // Release old mapping. 156 if (_base != NULL) { 157 MmapArrayAllocator<TaskQueueEntryChunk, 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(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry); 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 TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry); 176 177 _max_chunk_capacity = (size_t)align_size_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 178 size_t initial_chunk_capacity = (size_t)align_size_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 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<TaskQueueEntryChunk, mtGC>::free(_base, _chunk_capacity); 215 } 216 } 217 218 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) { 219 elem->next = *list; 220 *list = elem; 221 } 222 223 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) { 224 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 225 add_chunk_to_list(&_chunk_list, elem); 226 _chunks_in_chunk_list++; 227 } 228 229 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) { 230 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 231 add_chunk_to_list(&_free_list, elem); 232 } 233 234 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) { 235 TaskQueueEntryChunk* result = *list; 236 if (result != NULL) { 237 *list = (*list)->next; 238 } 239 return result; 240 } 241 242 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() { 243 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 244 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list); 245 if (result != NULL) { 246 _chunks_in_chunk_list--; 247 } 248 return result; 249 } 250 251 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() { 252 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 253 return remove_chunk_from_list(&_free_list); 254 } 255 256 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() { 257 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code. 258 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding 259 // wraparound of _hwm. 260 if (_hwm >= _chunk_capacity) { 261 return NULL; 262 } 263 264 size_t cur_idx = Atomic::add(1, &_hwm) - 1; 265 if (cur_idx >= _chunk_capacity) { 266 return NULL; 267 } 268 269 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk; 270 result->next = NULL; 271 return result; 272 } 273 274 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) { 275 // Get a new chunk. 276 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list(); 277 278 if (new_chunk == NULL) { 279 // Did not get a chunk from the free list. Allocate from backing memory. 280 new_chunk = allocate_new_chunk(); 281 } 282 283 if (new_chunk == NULL) { 284 _out_of_memory = true; 285 return false; 286 } 287 288 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 289 290 add_chunk_to_chunk_list(new_chunk); 291 292 return true; 293 } 294 295 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) { 296 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list(); 297 298 if (cur == NULL) { 299 return false; 300 } 301 302 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 303 304 add_chunk_to_free_list(cur); 305 return true; 306 } 307 308 void G1CMMarkStack::set_empty() { 309 _chunks_in_chunk_list = 0; 310 _hwm = 0; 311 clear_out_of_memory(); 312 _chunk_list = NULL; 313 _free_list = NULL; 314 } 315 316 G1CMRootRegions::G1CMRootRegions() : 317 _cm(NULL), _scan_in_progress(false), 318 _should_abort(false), _claimed_survivor_index(0) { } 319 320 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) { 321 _survivors = survivors; 322 _cm = cm; 323 } 324 325 void G1CMRootRegions::prepare_for_scan() { 326 assert(!scan_in_progress(), "pre-condition"); 327 328 // Currently, only survivors can be root regions. 329 _claimed_survivor_index = 0; 330 _scan_in_progress = _survivors->regions()->is_nonempty(); 331 _should_abort = false; 332 } 333 334 HeapRegion* G1CMRootRegions::claim_next() { 335 if (_should_abort) { 336 // If someone has set the should_abort flag, we return NULL to 337 // force the caller to bail out of their loop. 338 return NULL; 339 } 340 341 // Currently, only survivors can be root regions. 342 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions(); 343 344 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1; 345 if (claimed_index < survivor_regions->length()) { 346 return survivor_regions->at(claimed_index); 347 } 348 return NULL; 349 } 350 351 uint G1CMRootRegions::num_root_regions() const { 352 return (uint)_survivors->regions()->length(); 353 } 354 355 void G1CMRootRegions::notify_scan_done() { 356 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 357 _scan_in_progress = false; 358 RootRegionScan_lock->notify_all(); 359 } 360 361 void G1CMRootRegions::cancel_scan() { 362 notify_scan_done(); 363 } 364 365 void G1CMRootRegions::scan_finished() { 366 assert(scan_in_progress(), "pre-condition"); 367 368 // Currently, only survivors can be root regions. 369 if (!_should_abort) { 370 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index); 371 assert((uint)_claimed_survivor_index >= _survivors->length(), 372 "we should have claimed all survivors, claimed index = %u, length = %u", 373 (uint)_claimed_survivor_index, _survivors->length()); 374 } 375 376 notify_scan_done(); 377 } 378 379 bool G1CMRootRegions::wait_until_scan_finished() { 380 if (!scan_in_progress()) return false; 381 382 { 383 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 384 while (scan_in_progress()) { 385 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag); 386 } 387 } 388 return true; 389 } 390 391 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) { 392 return MAX2((n_par_threads + 2) / 4, 1U); 393 } 394 395 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) : 396 _g1h(g1h), 397 _markBitMap1(), 398 _markBitMap2(), 399 _parallel_marking_threads(0), 400 _max_parallel_marking_threads(0), 401 _sleep_factor(0.0), 402 _marking_task_overhead(1.0), 403 _cleanup_list("Cleanup List"), 404 405 _prevMarkBitMap(&_markBitMap1), 406 _nextMarkBitMap(&_markBitMap2), 407 408 _global_mark_stack(), 409 // _finger set in set_non_marking_state 410 411 _max_worker_id(ParallelGCThreads), 412 // _active_tasks set in set_non_marking_state 413 // _tasks set inside the constructor 414 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)), 415 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)), 416 417 _has_overflown(false), 418 _concurrent(false), 419 _has_aborted(false), 420 _restart_for_overflow(false), 421 _concurrent_marking_in_progress(false), 422 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 423 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()), 424 425 // _verbose_level set below 426 427 _init_times(), 428 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(), 429 _cleanup_times(), 430 _total_counting_time(0.0), 431 _total_rs_scrub_time(0.0), 432 433 _parallel_workers(NULL), 434 435 _completed_initialization(false) { 436 437 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage); 438 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage); 439 440 // Create & start a ConcurrentMark thread. 441 _cmThread = new ConcurrentMarkThread(this); 442 assert(cmThread() != NULL, "CM Thread should have been created"); 443 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm"); 444 if (_cmThread->osthread() == NULL) { 445 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 446 } 447 448 assert(CGC_lock != NULL, "Where's the CGC_lock?"); 449 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency"); 450 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency"); 451 452 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set(); 453 satb_qs.set_buffer_size(G1SATBBufferSize); 454 455 _root_regions.init(_g1h->survivor(), this); 456 457 if (ConcGCThreads > ParallelGCThreads) { 458 log_warning(gc)("Can't have more ConcGCThreads (%u) than ParallelGCThreads (%u).", 459 ConcGCThreads, ParallelGCThreads); 460 return; 461 } 462 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) { 463 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent 464 // if both are set 465 _sleep_factor = 0.0; 466 _marking_task_overhead = 1.0; 467 } else if (G1MarkingOverheadPercent > 0) { 468 // We will calculate the number of parallel marking threads based 469 // on a target overhead with respect to the soft real-time goal 470 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0; 471 double overall_cm_overhead = 472 (double) MaxGCPauseMillis * marking_overhead / 473 (double) GCPauseIntervalMillis; 474 double cpu_ratio = 1.0 / os::initial_active_processor_count(); 475 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio); 476 double marking_task_overhead = 477 overall_cm_overhead / marking_thread_num * os::initial_active_processor_count(); 478 double sleep_factor = 479 (1.0 - marking_task_overhead) / marking_task_overhead; 480 481 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num); 482 _sleep_factor = sleep_factor; 483 _marking_task_overhead = marking_task_overhead; 484 } else { 485 // Calculate the number of parallel marking threads by scaling 486 // the number of parallel GC threads. 487 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads); 488 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num); 489 _sleep_factor = 0.0; 490 _marking_task_overhead = 1.0; 491 } 492 493 assert(ConcGCThreads > 0, "Should have been set"); 494 log_debug(gc)("ConcGCThreads: %u", ConcGCThreads); 495 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads); 496 _parallel_marking_threads = ConcGCThreads; 497 _max_parallel_marking_threads = _parallel_marking_threads; 498 499 _parallel_workers = new WorkGang("G1 Marker", 500 _max_parallel_marking_threads, false, true); 501 if (_parallel_workers == NULL) { 502 vm_exit_during_initialization("Failed necessary allocation."); 503 } else { 504 _parallel_workers->initialize_workers(); 505 } 506 507 if (FLAG_IS_DEFAULT(MarkStackSize)) { 508 size_t mark_stack_size = 509 MIN2(MarkStackSizeMax, 510 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE))); 511 // Verify that the calculated value for MarkStackSize is in range. 512 // It would be nice to use the private utility routine from Arguments. 513 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 514 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 515 "must be between 1 and " SIZE_FORMAT, 516 mark_stack_size, MarkStackSizeMax); 517 return; 518 } 519 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size); 520 } else { 521 // Verify MarkStackSize is in range. 522 if (FLAG_IS_CMDLINE(MarkStackSize)) { 523 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 524 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 525 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 526 "must be between 1 and " SIZE_FORMAT, 527 MarkStackSize, MarkStackSizeMax); 528 return; 529 } 530 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 531 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 532 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 533 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 534 MarkStackSize, MarkStackSizeMax); 535 return; 536 } 537 } 538 } 539 } 540 541 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) { 542 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack."); 543 } 544 545 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC); 546 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC); 547 548 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 549 _active_tasks = _max_worker_id; 550 551 for (uint i = 0; i < _max_worker_id; ++i) { 552 G1CMTaskQueue* task_queue = new G1CMTaskQueue(); 553 task_queue->initialize(); 554 _task_queues->register_queue(i, task_queue); 555 556 _tasks[i] = new G1CMTask(i, this, task_queue, _task_queues); 557 558 _accum_task_vtime[i] = 0.0; 559 } 560 561 // so that the call below can read a sensible value 562 _heap_start = g1h->reserved_region().start(); 563 set_non_marking_state(); 564 _completed_initialization = true; 565 } 566 567 void G1ConcurrentMark::reset() { 568 // Starting values for these two. This should be called in a STW 569 // phase. 570 MemRegion reserved = _g1h->g1_reserved(); 571 _heap_start = reserved.start(); 572 _heap_end = reserved.end(); 573 574 // Separated the asserts so that we know which one fires. 575 assert(_heap_start != NULL, "heap bounds should look ok"); 576 assert(_heap_end != NULL, "heap bounds should look ok"); 577 assert(_heap_start < _heap_end, "heap bounds should look ok"); 578 579 // Reset all the marking data structures and any necessary flags 580 reset_marking_state(); 581 582 // We do reset all of them, since different phases will use 583 // different number of active threads. So, it's easiest to have all 584 // of them ready. 585 for (uint i = 0; i < _max_worker_id; ++i) { 586 _tasks[i]->reset(_nextMarkBitMap); 587 } 588 589 // we need this to make sure that the flag is on during the evac 590 // pause with initial mark piggy-backed 591 set_concurrent_marking_in_progress(); 592 } 593 594 595 void G1ConcurrentMark::reset_marking_state(bool clear_overflow) { 596 _global_mark_stack.set_should_expand(has_overflown()); 597 _global_mark_stack.set_empty(); // Also clears the overflow stack's overflow flag 598 if (clear_overflow) { 599 clear_has_overflown(); 600 } else { 601 assert(has_overflown(), "pre-condition"); 602 } 603 _finger = _heap_start; 604 605 for (uint i = 0; i < _max_worker_id; ++i) { 606 G1CMTaskQueue* queue = _task_queues->queue(i); 607 queue->set_empty(); 608 } 609 } 610 611 void G1ConcurrentMark::set_concurrency(uint active_tasks) { 612 assert(active_tasks <= _max_worker_id, "we should not have more"); 613 614 _active_tasks = active_tasks; 615 // Need to update the three data structures below according to the 616 // number of active threads for this phase. 617 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); 618 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 619 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 620 } 621 622 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 623 set_concurrency(active_tasks); 624 625 _concurrent = concurrent; 626 // We propagate this to all tasks, not just the active ones. 627 for (uint i = 0; i < _max_worker_id; ++i) 628 _tasks[i]->set_concurrent(concurrent); 629 630 if (concurrent) { 631 set_concurrent_marking_in_progress(); 632 } else { 633 // We currently assume that the concurrent flag has been set to 634 // false before we start remark. At this point we should also be 635 // in a STW phase. 636 assert(!concurrent_marking_in_progress(), "invariant"); 637 assert(out_of_regions(), 638 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT, 639 p2i(_finger), p2i(_heap_end)); 640 } 641 } 642 643 void G1ConcurrentMark::set_non_marking_state() { 644 // We set the global marking state to some default values when we're 645 // not doing marking. 646 reset_marking_state(); 647 _active_tasks = 0; 648 clear_concurrent_marking_in_progress(); 649 } 650 651 G1ConcurrentMark::~G1ConcurrentMark() { 652 // The G1ConcurrentMark instance is never freed. 653 ShouldNotReachHere(); 654 } 655 656 class G1ClearBitMapTask : public AbstractGangTask { 657 public: 658 static size_t chunk_size() { return M; } 659 660 private: 661 // Heap region closure used for clearing the given mark bitmap. 662 class G1ClearBitmapHRClosure : public HeapRegionClosure { 663 private: 664 G1CMBitMap* _bitmap; 665 G1ConcurrentMark* _cm; 666 public: 667 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) { 668 } 669 670 virtual bool doHeapRegion(HeapRegion* r) { 671 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize; 672 673 HeapWord* cur = r->bottom(); 674 HeapWord* const end = r->end(); 675 676 while (cur < end) { 677 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 678 _bitmap->clear_range(mr); 679 680 cur += chunk_size_in_words; 681 682 // Abort iteration if after yielding the marking has been aborted. 683 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) { 684 return true; 685 } 686 // Repeat the asserts from before the start of the closure. We will do them 687 // as asserts here to minimize their overhead on the product. However, we 688 // will have them as guarantees at the beginning / end of the bitmap 689 // clearing to get some checking in the product. 690 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant"); 691 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant"); 692 } 693 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index()); 694 695 return false; 696 } 697 }; 698 699 G1ClearBitmapHRClosure _cl; 700 HeapRegionClaimer _hr_claimer; 701 bool _suspendible; // If the task is suspendible, workers must join the STS. 702 703 public: 704 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) : 705 AbstractGangTask("G1 Clear Bitmap"), 706 _cl(bitmap, suspendible ? cm : NULL), 707 _hr_claimer(n_workers), 708 _suspendible(suspendible) 709 { } 710 711 void work(uint worker_id) { 712 SuspendibleThreadSetJoiner sts_join(_suspendible); 713 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true); 714 } 715 716 bool is_complete() { 717 return _cl.complete(); 718 } 719 }; 720 721 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) { 722 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint."); 723 724 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor(); 725 size_t const num_chunks = align_size_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size(); 726 727 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); 728 729 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield); 730 731 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks); 732 workers->run_task(&cl, num_workers); 733 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding."); 734 } 735 736 void G1ConcurrentMark::cleanup_for_next_mark() { 737 // Make sure that the concurrent mark thread looks to still be in 738 // the current cycle. 739 guarantee(cmThread()->during_cycle(), "invariant"); 740 741 // We are finishing up the current cycle by clearing the next 742 // marking bitmap and getting it ready for the next cycle. During 743 // this time no other cycle can start. So, let's make sure that this 744 // is the case. 745 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant"); 746 747 clear_bitmap(_nextMarkBitMap, _parallel_workers, true); 748 749 // Clear the live count data. If the marking has been aborted, the abort() 750 // call already did that. 751 if (!has_aborted()) { 752 clear_live_data(_parallel_workers); 753 DEBUG_ONLY(verify_live_data_clear()); 754 } 755 756 // Repeat the asserts from above. 757 guarantee(cmThread()->during_cycle(), "invariant"); 758 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant"); 759 } 760 761 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) { 762 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint."); 763 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false); 764 } 765 766 class CheckBitmapClearHRClosure : public HeapRegionClosure { 767 G1CMBitMap* _bitmap; 768 bool _error; 769 public: 770 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) { 771 } 772 773 virtual bool doHeapRegion(HeapRegion* r) { 774 // This closure can be called concurrently to the mutator, so we must make sure 775 // that the result of the getNextMarkedWordAddress() call is compared to the 776 // value passed to it as limit to detect any found bits. 777 // end never changes in G1. 778 HeapWord* end = r->end(); 779 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end; 780 } 781 }; 782 783 bool G1ConcurrentMark::nextMarkBitmapIsClear() { 784 CheckBitmapClearHRClosure cl(_nextMarkBitMap); 785 _g1h->heap_region_iterate(&cl); 786 return cl.complete(); 787 } 788 789 class NoteStartOfMarkHRClosure: public HeapRegionClosure { 790 public: 791 bool doHeapRegion(HeapRegion* r) { 792 r->note_start_of_marking(); 793 return false; 794 } 795 }; 796 797 void G1ConcurrentMark::checkpointRootsInitialPre() { 798 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 799 G1Policy* g1p = g1h->g1_policy(); 800 801 _has_aborted = false; 802 803 // Initialize marking structures. This has to be done in a STW phase. 804 reset(); 805 806 // For each region note start of marking. 807 NoteStartOfMarkHRClosure startcl; 808 g1h->heap_region_iterate(&startcl); 809 } 810 811 812 void G1ConcurrentMark::checkpointRootsInitialPost() { 813 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 814 815 // Start Concurrent Marking weak-reference discovery. 816 ReferenceProcessor* rp = g1h->ref_processor_cm(); 817 // enable ("weak") refs discovery 818 rp->enable_discovery(); 819 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 820 821 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 822 // This is the start of the marking cycle, we're expected all 823 // threads to have SATB queues with active set to false. 824 satb_mq_set.set_active_all_threads(true, /* new active value */ 825 false /* expected_active */); 826 827 _root_regions.prepare_for_scan(); 828 829 // update_g1_committed() will be called at the end of an evac pause 830 // when marking is on. So, it's also called at the end of the 831 // initial-mark pause to update the heap end, if the heap expands 832 // during it. No need to call it here. 833 } 834 835 /* 836 * Notice that in the next two methods, we actually leave the STS 837 * during the barrier sync and join it immediately afterwards. If we 838 * do not do this, the following deadlock can occur: one thread could 839 * be in the barrier sync code, waiting for the other thread to also 840 * sync up, whereas another one could be trying to yield, while also 841 * waiting for the other threads to sync up too. 842 * 843 * Note, however, that this code is also used during remark and in 844 * this case we should not attempt to leave / enter the STS, otherwise 845 * we'll either hit an assert (debug / fastdebug) or deadlock 846 * (product). So we should only leave / enter the STS if we are 847 * operating concurrently. 848 * 849 * Because the thread that does the sync barrier has left the STS, it 850 * is possible to be suspended for a Full GC or an evacuation pause 851 * could occur. This is actually safe, since the entering the sync 852 * barrier is one of the last things do_marking_step() does, and it 853 * doesn't manipulate any data structures afterwards. 854 */ 855 856 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 857 bool barrier_aborted; 858 { 859 SuspendibleThreadSetLeaver sts_leave(concurrent()); 860 barrier_aborted = !_first_overflow_barrier_sync.enter(); 861 } 862 863 // at this point everyone should have synced up and not be doing any 864 // more work 865 866 if (barrier_aborted) { 867 // If the barrier aborted we ignore the overflow condition and 868 // just abort the whole marking phase as quickly as possible. 869 return; 870 } 871 872 // If we're executing the concurrent phase of marking, reset the marking 873 // state; otherwise the marking state is reset after reference processing, 874 // during the remark pause. 875 // If we reset here as a result of an overflow during the remark we will 876 // see assertion failures from any subsequent set_concurrency_and_phase() 877 // calls. 878 if (concurrent()) { 879 // let the task associated with with worker 0 do this 880 if (worker_id == 0) { 881 // task 0 is responsible for clearing the global data structures 882 // We should be here because of an overflow. During STW we should 883 // not clear the overflow flag since we rely on it being true when 884 // we exit this method to abort the pause and restart concurrent 885 // marking. 886 reset_marking_state(true /* clear_overflow */); 887 888 log_info(gc, marking)("Concurrent Mark reset for overflow"); 889 } 890 } 891 892 // after this, each task should reset its own data structures then 893 // then go into the second barrier 894 } 895 896 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 897 SuspendibleThreadSetLeaver sts_leave(concurrent()); 898 _second_overflow_barrier_sync.enter(); 899 900 // at this point everything should be re-initialized and ready to go 901 } 902 903 class G1CMConcurrentMarkingTask: public AbstractGangTask { 904 private: 905 G1ConcurrentMark* _cm; 906 ConcurrentMarkThread* _cmt; 907 908 public: 909 void work(uint worker_id) { 910 assert(Thread::current()->is_ConcurrentGC_thread(), 911 "this should only be done by a conc GC thread"); 912 ResourceMark rm; 913 914 double start_vtime = os::elapsedVTime(); 915 916 { 917 SuspendibleThreadSetJoiner sts_join; 918 919 assert(worker_id < _cm->active_tasks(), "invariant"); 920 G1CMTask* the_task = _cm->task(worker_id); 921 the_task->record_start_time(); 922 if (!_cm->has_aborted()) { 923 do { 924 double start_vtime_sec = os::elapsedVTime(); 925 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 926 927 the_task->do_marking_step(mark_step_duration_ms, 928 true /* do_termination */, 929 false /* is_serial*/); 930 931 double end_vtime_sec = os::elapsedVTime(); 932 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec; 933 _cm->clear_has_overflown(); 934 935 _cm->do_yield_check(); 936 937 jlong sleep_time_ms; 938 if (!_cm->has_aborted() && the_task->has_aborted()) { 939 sleep_time_ms = 940 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0); 941 { 942 SuspendibleThreadSetLeaver sts_leave; 943 os::sleep(Thread::current(), sleep_time_ms, false); 944 } 945 } 946 } while (!_cm->has_aborted() && the_task->has_aborted()); 947 } 948 the_task->record_end_time(); 949 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant"); 950 } 951 952 double end_vtime = os::elapsedVTime(); 953 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 954 } 955 956 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm, 957 ConcurrentMarkThread* cmt) : 958 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { } 959 960 ~G1CMConcurrentMarkingTask() { } 961 }; 962 963 // Calculates the number of active workers for a concurrent 964 // phase. 965 uint G1ConcurrentMark::calc_parallel_marking_threads() { 966 uint n_conc_workers = 0; 967 if (!UseDynamicNumberOfGCThreads || 968 (!FLAG_IS_DEFAULT(ConcGCThreads) && 969 !ForceDynamicNumberOfGCThreads)) { 970 n_conc_workers = max_parallel_marking_threads(); 971 } else { 972 n_conc_workers = 973 AdaptiveSizePolicy::calc_default_active_workers(max_parallel_marking_threads(), 974 1, /* Minimum workers */ 975 parallel_marking_threads(), 976 Threads::number_of_non_daemon_threads()); 977 // Don't scale down "n_conc_workers" by scale_parallel_threads() because 978 // that scaling has already gone into "_max_parallel_marking_threads". 979 } 980 assert(n_conc_workers > 0 && n_conc_workers <= max_parallel_marking_threads(), 981 "Calculated number of workers must be larger than zero and at most the maximum %u, but is %u", 982 max_parallel_marking_threads(), n_conc_workers); 983 return n_conc_workers; 984 } 985 986 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr) { 987 // Currently, only survivors can be root regions. 988 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant"); 989 G1RootRegionScanClosure cl(_g1h, this); 990 991 const uintx interval = PrefetchScanIntervalInBytes; 992 HeapWord* curr = hr->bottom(); 993 const HeapWord* end = hr->top(); 994 while (curr < end) { 995 Prefetch::read(curr, interval); 996 oop obj = oop(curr); 997 int size = obj->oop_iterate_size(&cl); 998 assert(size == obj->size(), "sanity"); 999 curr += size; 1000 } 1001 } 1002 1003 class G1CMRootRegionScanTask : public AbstractGangTask { 1004 private: 1005 G1ConcurrentMark* _cm; 1006 1007 public: 1008 G1CMRootRegionScanTask(G1ConcurrentMark* cm) : 1009 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { } 1010 1011 void work(uint worker_id) { 1012 assert(Thread::current()->is_ConcurrentGC_thread(), 1013 "this should only be done by a conc GC thread"); 1014 1015 G1CMRootRegions* root_regions = _cm->root_regions(); 1016 HeapRegion* hr = root_regions->claim_next(); 1017 while (hr != NULL) { 1018 _cm->scanRootRegion(hr); 1019 hr = root_regions->claim_next(); 1020 } 1021 } 1022 }; 1023 1024 void G1ConcurrentMark::scan_root_regions() { 1025 // scan_in_progress() will have been set to true only if there was 1026 // at least one root region to scan. So, if it's false, we 1027 // should not attempt to do any further work. 1028 if (root_regions()->scan_in_progress()) { 1029 assert(!has_aborted(), "Aborting before root region scanning is finished not supported."); 1030 1031 _parallel_marking_threads = MIN2(calc_parallel_marking_threads(), 1032 // We distribute work on a per-region basis, so starting 1033 // more threads than that is useless. 1034 root_regions()->num_root_regions()); 1035 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1036 "Maximum number of marking threads exceeded"); 1037 1038 G1CMRootRegionScanTask task(this); 1039 log_debug(gc, ergo)("Running %s using %u workers for %u work units.", 1040 task.name(), _parallel_marking_threads, root_regions()->num_root_regions()); 1041 _parallel_workers->run_task(&task, _parallel_marking_threads); 1042 1043 // It's possible that has_aborted() is true here without actually 1044 // aborting the survivor scan earlier. This is OK as it's 1045 // mainly used for sanity checking. 1046 root_regions()->scan_finished(); 1047 } 1048 } 1049 1050 void G1ConcurrentMark::concurrent_cycle_start() { 1051 _gc_timer_cm->register_gc_start(); 1052 1053 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start()); 1054 1055 _g1h->trace_heap_before_gc(_gc_tracer_cm); 1056 } 1057 1058 void G1ConcurrentMark::concurrent_cycle_end() { 1059 _g1h->trace_heap_after_gc(_gc_tracer_cm); 1060 1061 if (has_aborted()) { 1062 _gc_tracer_cm->report_concurrent_mode_failure(); 1063 } 1064 1065 _gc_timer_cm->register_gc_end(); 1066 1067 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 1068 } 1069 1070 void G1ConcurrentMark::mark_from_roots() { 1071 // we might be tempted to assert that: 1072 // assert(asynch == !SafepointSynchronize::is_at_safepoint(), 1073 // "inconsistent argument?"); 1074 // However that wouldn't be right, because it's possible that 1075 // a safepoint is indeed in progress as a younger generation 1076 // stop-the-world GC happens even as we mark in this generation. 1077 1078 _restart_for_overflow = false; 1079 1080 // _g1h has _n_par_threads 1081 _parallel_marking_threads = calc_parallel_marking_threads(); 1082 assert(parallel_marking_threads() <= max_parallel_marking_threads(), 1083 "Maximum number of marking threads exceeded"); 1084 1085 uint active_workers = MAX2(1U, parallel_marking_threads()); 1086 assert(active_workers > 0, "Should have been set"); 1087 1088 // Setting active workers is not guaranteed since fewer 1089 // worker threads may currently exist and more may not be 1090 // available. 1091 active_workers = _parallel_workers->update_active_workers(active_workers); 1092 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _parallel_workers->total_workers()); 1093 1094 // Parallel task terminator is set in "set_concurrency_and_phase()" 1095 set_concurrency_and_phase(active_workers, true /* concurrent */); 1096 1097 G1CMConcurrentMarkingTask markingTask(this, cmThread()); 1098 _parallel_workers->run_task(&markingTask); 1099 print_stats(); 1100 } 1101 1102 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) { 1103 // world is stopped at this checkpoint 1104 assert(SafepointSynchronize::is_at_safepoint(), 1105 "world should be stopped"); 1106 1107 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1108 1109 // If a full collection has happened, we shouldn't do this. 1110 if (has_aborted()) { 1111 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused 1112 return; 1113 } 1114 1115 SvcGCMarker sgcm(SvcGCMarker::OTHER); 1116 1117 if (VerifyDuringGC) { 1118 HandleMark hm; // handle scope 1119 g1h->prepare_for_verify(); 1120 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)"); 1121 } 1122 g1h->verifier()->check_bitmaps("Remark Start"); 1123 1124 G1Policy* g1p = g1h->g1_policy(); 1125 g1p->record_concurrent_mark_remark_start(); 1126 1127 double start = os::elapsedTime(); 1128 1129 checkpointRootsFinalWork(); 1130 1131 double mark_work_end = os::elapsedTime(); 1132 1133 weakRefsWork(clear_all_soft_refs); 1134 1135 if (has_overflown()) { 1136 // We overflowed. Restart concurrent marking. 1137 _restart_for_overflow = true; 1138 1139 // Verify the heap w.r.t. the previous marking bitmap. 1140 if (VerifyDuringGC) { 1141 HandleMark hm; // handle scope 1142 g1h->prepare_for_verify(); 1143 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)"); 1144 } 1145 1146 // Clear the marking state because we will be restarting 1147 // marking due to overflowing the global mark stack. 1148 reset_marking_state(); 1149 } else { 1150 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1151 // We're done with marking. 1152 // This is the end of the marking cycle, we're expected all 1153 // threads to have SATB queues with active set to true. 1154 satb_mq_set.set_active_all_threads(false, /* new active value */ 1155 true /* expected_active */); 1156 1157 if (VerifyDuringGC) { 1158 HandleMark hm; // handle scope 1159 g1h->prepare_for_verify(); 1160 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)"); 1161 } 1162 g1h->verifier()->check_bitmaps("Remark End"); 1163 assert(!restart_for_overflow(), "sanity"); 1164 // Completely reset the marking state since marking completed 1165 set_non_marking_state(); 1166 } 1167 1168 // Expand the marking stack, if we have to and if we can. 1169 if (_global_mark_stack.should_expand()) { 1170 _global_mark_stack.expand(); 1171 } 1172 1173 // Statistics 1174 double now = os::elapsedTime(); 1175 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1176 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1177 _remark_times.add((now - start) * 1000.0); 1178 1179 g1p->record_concurrent_mark_remark_end(); 1180 1181 G1CMIsAliveClosure is_alive(g1h); 1182 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1183 } 1184 1185 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure { 1186 G1CollectedHeap* _g1; 1187 size_t _freed_bytes; 1188 FreeRegionList* _local_cleanup_list; 1189 uint _old_regions_removed; 1190 uint _humongous_regions_removed; 1191 HRRSCleanupTask* _hrrs_cleanup_task; 1192 1193 public: 1194 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1, 1195 FreeRegionList* local_cleanup_list, 1196 HRRSCleanupTask* hrrs_cleanup_task) : 1197 _g1(g1), 1198 _freed_bytes(0), 1199 _local_cleanup_list(local_cleanup_list), 1200 _old_regions_removed(0), 1201 _humongous_regions_removed(0), 1202 _hrrs_cleanup_task(hrrs_cleanup_task) { } 1203 1204 size_t freed_bytes() { return _freed_bytes; } 1205 const uint old_regions_removed() { return _old_regions_removed; } 1206 const uint humongous_regions_removed() { return _humongous_regions_removed; } 1207 1208 bool doHeapRegion(HeapRegion *hr) { 1209 if (hr->is_archive()) { 1210 return false; 1211 } 1212 _g1->reset_gc_time_stamps(hr); 1213 hr->note_end_of_marking(); 1214 1215 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) { 1216 _freed_bytes += hr->used(); 1217 hr->set_containing_set(NULL); 1218 if (hr->is_humongous()) { 1219 _humongous_regions_removed++; 1220 _g1->free_humongous_region(hr, _local_cleanup_list, true /* skip_remset */); 1221 } else { 1222 _old_regions_removed++; 1223 _g1->free_region(hr, _local_cleanup_list, true /* skip_remset */); 1224 } 1225 } else { 1226 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task); 1227 } 1228 1229 return false; 1230 } 1231 }; 1232 1233 class G1ParNoteEndTask: public AbstractGangTask { 1234 friend class G1NoteEndOfConcMarkClosure; 1235 1236 protected: 1237 G1CollectedHeap* _g1h; 1238 FreeRegionList* _cleanup_list; 1239 HeapRegionClaimer _hrclaimer; 1240 1241 public: 1242 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1243 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) { 1244 } 1245 1246 void work(uint worker_id) { 1247 FreeRegionList local_cleanup_list("Local Cleanup List"); 1248 HRRSCleanupTask hrrs_cleanup_task; 1249 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list, 1250 &hrrs_cleanup_task); 1251 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer); 1252 assert(g1_note_end.complete(), "Shouldn't have yielded!"); 1253 1254 // Now update the lists 1255 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed()); 1256 { 1257 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1258 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes()); 1259 1260 // If we iterate over the global cleanup list at the end of 1261 // cleanup to do this printing we will not guarantee to only 1262 // generate output for the newly-reclaimed regions (the list 1263 // might not be empty at the beginning of cleanup; we might 1264 // still be working on its previous contents). So we do the 1265 // printing here, before we append the new regions to the global 1266 // cleanup list. 1267 1268 G1HRPrinter* hr_printer = _g1h->hr_printer(); 1269 if (hr_printer->is_active()) { 1270 FreeRegionListIterator iter(&local_cleanup_list); 1271 while (iter.more_available()) { 1272 HeapRegion* hr = iter.get_next(); 1273 hr_printer->cleanup(hr); 1274 } 1275 } 1276 1277 _cleanup_list->add_ordered(&local_cleanup_list); 1278 assert(local_cleanup_list.is_empty(), "post-condition"); 1279 1280 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task); 1281 } 1282 } 1283 }; 1284 1285 void G1ConcurrentMark::cleanup() { 1286 // world is stopped at this checkpoint 1287 assert(SafepointSynchronize::is_at_safepoint(), 1288 "world should be stopped"); 1289 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1290 1291 // If a full collection has happened, we shouldn't do this. 1292 if (has_aborted()) { 1293 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused 1294 return; 1295 } 1296 1297 g1h->verifier()->verify_region_sets_optional(); 1298 1299 if (VerifyDuringGC) { 1300 HandleMark hm; // handle scope 1301 g1h->prepare_for_verify(); 1302 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)"); 1303 } 1304 g1h->verifier()->check_bitmaps("Cleanup Start"); 1305 1306 G1Policy* g1p = g1h->g1_policy(); 1307 g1p->record_concurrent_mark_cleanup_start(); 1308 1309 double start = os::elapsedTime(); 1310 1311 HeapRegionRemSet::reset_for_cleanup_tasks(); 1312 1313 { 1314 GCTraceTime(Debug, gc)("Finalize Live Data"); 1315 finalize_live_data(); 1316 } 1317 1318 if (VerifyDuringGC) { 1319 GCTraceTime(Debug, gc)("Verify Live Data"); 1320 verify_live_data(); 1321 } 1322 1323 g1h->collector_state()->set_mark_in_progress(false); 1324 1325 double count_end = os::elapsedTime(); 1326 double this_final_counting_time = (count_end - start); 1327 _total_counting_time += this_final_counting_time; 1328 1329 if (log_is_enabled(Trace, gc, liveness)) { 1330 G1PrintRegionLivenessInfoClosure cl("Post-Marking"); 1331 _g1h->heap_region_iterate(&cl); 1332 } 1333 1334 // Install newly created mark bitMap as "prev". 1335 swapMarkBitMaps(); 1336 1337 g1h->reset_gc_time_stamp(); 1338 1339 uint n_workers = _g1h->workers()->active_workers(); 1340 1341 // Note end of marking in all heap regions. 1342 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers); 1343 g1h->workers()->run_task(&g1_par_note_end_task); 1344 g1h->check_gc_time_stamps(); 1345 1346 if (!cleanup_list_is_empty()) { 1347 // The cleanup list is not empty, so we'll have to process it 1348 // concurrently. Notify anyone else that might be wanting free 1349 // regions that there will be more free regions coming soon. 1350 g1h->set_free_regions_coming(); 1351 } 1352 1353 // call below, since it affects the metric by which we sort the heap 1354 // regions. 1355 if (G1ScrubRemSets) { 1356 double rs_scrub_start = os::elapsedTime(); 1357 g1h->scrub_rem_set(); 1358 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start); 1359 } 1360 1361 // this will also free any regions totally full of garbage objects, 1362 // and sort the regions. 1363 g1h->g1_policy()->record_concurrent_mark_cleanup_end(); 1364 1365 // Statistics. 1366 double end = os::elapsedTime(); 1367 _cleanup_times.add((end - start) * 1000.0); 1368 1369 // Clean up will have freed any regions completely full of garbage. 1370 // Update the soft reference policy with the new heap occupancy. 1371 Universe::update_heap_info_at_gc(); 1372 1373 if (VerifyDuringGC) { 1374 HandleMark hm; // handle scope 1375 g1h->prepare_for_verify(); 1376 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)"); 1377 } 1378 1379 g1h->verifier()->check_bitmaps("Cleanup End"); 1380 1381 g1h->verifier()->verify_region_sets_optional(); 1382 1383 // We need to make this be a "collection" so any collection pause that 1384 // races with it goes around and waits for completeCleanup to finish. 1385 g1h->increment_total_collections(); 1386 1387 // Clean out dead classes and update Metaspace sizes. 1388 if (ClassUnloadingWithConcurrentMark) { 1389 ClassLoaderDataGraph::purge(); 1390 } 1391 MetaspaceGC::compute_new_size(); 1392 1393 // We reclaimed old regions so we should calculate the sizes to make 1394 // sure we update the old gen/space data. 1395 g1h->g1mm()->update_sizes(); 1396 g1h->allocation_context_stats().update_after_mark(); 1397 } 1398 1399 void G1ConcurrentMark::complete_cleanup() { 1400 if (has_aborted()) return; 1401 1402 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1403 1404 _cleanup_list.verify_optional(); 1405 FreeRegionList tmp_free_list("Tmp Free List"); 1406 1407 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : " 1408 "cleanup list has %u entries", 1409 _cleanup_list.length()); 1410 1411 // No one else should be accessing the _cleanup_list at this point, 1412 // so it is not necessary to take any locks 1413 while (!_cleanup_list.is_empty()) { 1414 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */); 1415 assert(hr != NULL, "Got NULL from a non-empty list"); 1416 hr->par_clear(); 1417 tmp_free_list.add_ordered(hr); 1418 1419 // Instead of adding one region at a time to the secondary_free_list, 1420 // we accumulate them in the local list and move them a few at a 1421 // time. This also cuts down on the number of notify_all() calls 1422 // we do during this process. We'll also append the local list when 1423 // _cleanup_list is empty (which means we just removed the last 1424 // region from the _cleanup_list). 1425 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) || 1426 _cleanup_list.is_empty()) { 1427 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : " 1428 "appending %u entries to the secondary_free_list, " 1429 "cleanup list still has %u entries", 1430 tmp_free_list.length(), 1431 _cleanup_list.length()); 1432 1433 { 1434 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag); 1435 g1h->secondary_free_list_add(&tmp_free_list); 1436 SecondaryFreeList_lock->notify_all(); 1437 } 1438 #ifndef PRODUCT 1439 if (G1StressConcRegionFreeing) { 1440 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) { 1441 os::sleep(Thread::current(), (jlong) 1, false); 1442 } 1443 } 1444 #endif 1445 } 1446 } 1447 assert(tmp_free_list.is_empty(), "post-condition"); 1448 } 1449 1450 // Supporting Object and Oop closures for reference discovery 1451 // and processing in during marking 1452 1453 bool G1CMIsAliveClosure::do_object_b(oop obj) { 1454 HeapWord* addr = (HeapWord*)obj; 1455 return addr != NULL && 1456 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj)); 1457 } 1458 1459 // 'Keep Alive' oop closure used by both serial parallel reference processing. 1460 // Uses the G1CMTask associated with a worker thread (for serial reference 1461 // processing the G1CMTask for worker 0 is used) to preserve (mark) and 1462 // trace referent objects. 1463 // 1464 // Using the G1CMTask and embedded local queues avoids having the worker 1465 // threads operating on the global mark stack. This reduces the risk 1466 // of overflowing the stack - which we would rather avoid at this late 1467 // state. Also using the tasks' local queues removes the potential 1468 // of the workers interfering with each other that could occur if 1469 // operating on the global stack. 1470 1471 class G1CMKeepAliveAndDrainClosure: public OopClosure { 1472 G1ConcurrentMark* _cm; 1473 G1CMTask* _task; 1474 int _ref_counter_limit; 1475 int _ref_counter; 1476 bool _is_serial; 1477 public: 1478 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1479 _cm(cm), _task(task), _is_serial(is_serial), 1480 _ref_counter_limit(G1RefProcDrainInterval) { 1481 assert(_ref_counter_limit > 0, "sanity"); 1482 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1483 _ref_counter = _ref_counter_limit; 1484 } 1485 1486 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 1487 virtual void do_oop( oop* p) { do_oop_work(p); } 1488 1489 template <class T> void do_oop_work(T* p) { 1490 if (!_cm->has_overflown()) { 1491 oop obj = oopDesc::load_decode_heap_oop(p); 1492 _task->deal_with_reference(obj); 1493 _ref_counter--; 1494 1495 if (_ref_counter == 0) { 1496 // We have dealt with _ref_counter_limit references, pushing them 1497 // and objects reachable from them on to the local stack (and 1498 // possibly the global stack). Call G1CMTask::do_marking_step() to 1499 // process these entries. 1500 // 1501 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if 1502 // there's nothing more to do (i.e. we're done with the entries that 1503 // were pushed as a result of the G1CMTask::deal_with_reference() calls 1504 // above) or we overflow. 1505 // 1506 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1507 // flag while there may still be some work to do. (See the comment at 1508 // the beginning of G1CMTask::do_marking_step() for those conditions - 1509 // one of which is reaching the specified time target.) It is only 1510 // when G1CMTask::do_marking_step() returns without setting the 1511 // has_aborted() flag that the marking step has completed. 1512 do { 1513 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1514 _task->do_marking_step(mark_step_duration_ms, 1515 false /* do_termination */, 1516 _is_serial); 1517 } while (_task->has_aborted() && !_cm->has_overflown()); 1518 _ref_counter = _ref_counter_limit; 1519 } 1520 } 1521 } 1522 }; 1523 1524 // 'Drain' oop closure used by both serial and parallel reference processing. 1525 // Uses the G1CMTask associated with a given worker thread (for serial 1526 // reference processing the G1CMtask for worker 0 is used). Calls the 1527 // do_marking_step routine, with an unbelievably large timeout value, 1528 // to drain the marking data structures of the remaining entries 1529 // added by the 'keep alive' oop closure above. 1530 1531 class G1CMDrainMarkingStackClosure: public VoidClosure { 1532 G1ConcurrentMark* _cm; 1533 G1CMTask* _task; 1534 bool _is_serial; 1535 public: 1536 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1537 _cm(cm), _task(task), _is_serial(is_serial) { 1538 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1539 } 1540 1541 void do_void() { 1542 do { 1543 // We call G1CMTask::do_marking_step() to completely drain the local 1544 // and global marking stacks of entries pushed by the 'keep alive' 1545 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 1546 // 1547 // G1CMTask::do_marking_step() is called in a loop, which we'll exit 1548 // if there's nothing more to do (i.e. we've completely drained the 1549 // entries that were pushed as a a result of applying the 'keep alive' 1550 // closure to the entries on the discovered ref lists) or we overflow 1551 // the global marking stack. 1552 // 1553 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1554 // flag while there may still be some work to do. (See the comment at 1555 // the beginning of G1CMTask::do_marking_step() for those conditions - 1556 // one of which is reaching the specified time target.) It is only 1557 // when G1CMTask::do_marking_step() returns without setting the 1558 // has_aborted() flag that the marking step has completed. 1559 1560 _task->do_marking_step(1000000000.0 /* something very large */, 1561 true /* do_termination */, 1562 _is_serial); 1563 } while (_task->has_aborted() && !_cm->has_overflown()); 1564 } 1565 }; 1566 1567 // Implementation of AbstractRefProcTaskExecutor for parallel 1568 // reference processing at the end of G1 concurrent marking 1569 1570 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor { 1571 private: 1572 G1CollectedHeap* _g1h; 1573 G1ConcurrentMark* _cm; 1574 WorkGang* _workers; 1575 uint _active_workers; 1576 1577 public: 1578 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 1579 G1ConcurrentMark* cm, 1580 WorkGang* workers, 1581 uint n_workers) : 1582 _g1h(g1h), _cm(cm), 1583 _workers(workers), _active_workers(n_workers) { } 1584 1585 // Executes the given task using concurrent marking worker threads. 1586 virtual void execute(ProcessTask& task); 1587 virtual void execute(EnqueueTask& task); 1588 }; 1589 1590 class G1CMRefProcTaskProxy: public AbstractGangTask { 1591 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 1592 ProcessTask& _proc_task; 1593 G1CollectedHeap* _g1h; 1594 G1ConcurrentMark* _cm; 1595 1596 public: 1597 G1CMRefProcTaskProxy(ProcessTask& proc_task, 1598 G1CollectedHeap* g1h, 1599 G1ConcurrentMark* cm) : 1600 AbstractGangTask("Process reference objects in parallel"), 1601 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 1602 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1603 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 1604 } 1605 1606 virtual void work(uint worker_id) { 1607 ResourceMark rm; 1608 HandleMark hm; 1609 G1CMTask* task = _cm->task(worker_id); 1610 G1CMIsAliveClosure g1_is_alive(_g1h); 1611 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 1612 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 1613 1614 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 1615 } 1616 }; 1617 1618 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) { 1619 assert(_workers != NULL, "Need parallel worker threads."); 1620 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1621 1622 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 1623 1624 // We need to reset the concurrency level before each 1625 // proxy task execution, so that the termination protocol 1626 // and overflow handling in G1CMTask::do_marking_step() knows 1627 // how many workers to wait for. 1628 _cm->set_concurrency(_active_workers); 1629 _workers->run_task(&proc_task_proxy); 1630 } 1631 1632 class G1CMRefEnqueueTaskProxy: public AbstractGangTask { 1633 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; 1634 EnqueueTask& _enq_task; 1635 1636 public: 1637 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) : 1638 AbstractGangTask("Enqueue reference objects in parallel"), 1639 _enq_task(enq_task) { } 1640 1641 virtual void work(uint worker_id) { 1642 _enq_task.work(worker_id); 1643 } 1644 }; 1645 1646 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) { 1647 assert(_workers != NULL, "Need parallel worker threads."); 1648 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1649 1650 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task); 1651 1652 // Not strictly necessary but... 1653 // 1654 // We need to reset the concurrency level before each 1655 // proxy task execution, so that the termination protocol 1656 // and overflow handling in G1CMTask::do_marking_step() knows 1657 // how many workers to wait for. 1658 _cm->set_concurrency(_active_workers); 1659 _workers->run_task(&enq_task_proxy); 1660 } 1661 1662 void G1ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) { 1663 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes); 1664 } 1665 1666 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) { 1667 if (has_overflown()) { 1668 // Skip processing the discovered references if we have 1669 // overflown the global marking stack. Reference objects 1670 // only get discovered once so it is OK to not 1671 // de-populate the discovered reference lists. We could have, 1672 // but the only benefit would be that, when marking restarts, 1673 // less reference objects are discovered. 1674 return; 1675 } 1676 1677 ResourceMark rm; 1678 HandleMark hm; 1679 1680 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1681 1682 // Is alive closure. 1683 G1CMIsAliveClosure g1_is_alive(g1h); 1684 1685 // Inner scope to exclude the cleaning of the string and symbol 1686 // tables from the displayed time. 1687 { 1688 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm); 1689 1690 ReferenceProcessor* rp = g1h->ref_processor_cm(); 1691 1692 // See the comment in G1CollectedHeap::ref_processing_init() 1693 // about how reference processing currently works in G1. 1694 1695 // Set the soft reference policy 1696 rp->setup_policy(clear_all_soft_refs); 1697 assert(_global_mark_stack.is_empty(), "mark stack should be empty"); 1698 1699 // Instances of the 'Keep Alive' and 'Complete GC' closures used 1700 // in serial reference processing. Note these closures are also 1701 // used for serially processing (by the the current thread) the 1702 // JNI references during parallel reference processing. 1703 // 1704 // These closures do not need to synchronize with the worker 1705 // threads involved in parallel reference processing as these 1706 // instances are executed serially by the current thread (e.g. 1707 // reference processing is not multi-threaded and is thus 1708 // performed by the current thread instead of a gang worker). 1709 // 1710 // The gang tasks involved in parallel reference processing create 1711 // their own instances of these closures, which do their own 1712 // synchronization among themselves. 1713 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 1714 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 1715 1716 // We need at least one active thread. If reference processing 1717 // is not multi-threaded we use the current (VMThread) thread, 1718 // otherwise we use the work gang from the G1CollectedHeap and 1719 // we utilize all the worker threads we can. 1720 bool processing_is_mt = rp->processing_is_mt(); 1721 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U); 1722 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U); 1723 1724 // Parallel processing task executor. 1725 G1CMRefProcTaskExecutor par_task_executor(g1h, this, 1726 g1h->workers(), active_workers); 1727 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 1728 1729 // Set the concurrency level. The phase was already set prior to 1730 // executing the remark task. 1731 set_concurrency(active_workers); 1732 1733 // Set the degree of MT processing here. If the discovery was done MT, 1734 // the number of threads involved during discovery could differ from 1735 // the number of active workers. This is OK as long as the discovered 1736 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 1737 rp->set_active_mt_degree(active_workers); 1738 1739 // Process the weak references. 1740 const ReferenceProcessorStats& stats = 1741 rp->process_discovered_references(&g1_is_alive, 1742 &g1_keep_alive, 1743 &g1_drain_mark_stack, 1744 executor, 1745 _gc_timer_cm); 1746 _gc_tracer_cm->report_gc_reference_stats(stats); 1747 1748 // The do_oop work routines of the keep_alive and drain_marking_stack 1749 // oop closures will set the has_overflown flag if we overflow the 1750 // global marking stack. 1751 1752 assert(_global_mark_stack.is_out_of_memory() || _global_mark_stack.is_empty(), 1753 "Mark stack should be empty (unless it is out of memory)"); 1754 1755 if (_global_mark_stack.is_out_of_memory()) { 1756 // This should have been done already when we tried to push an 1757 // entry on to the global mark stack. But let's do it again. 1758 set_has_overflown(); 1759 } 1760 1761 assert(rp->num_q() == active_workers, "why not"); 1762 1763 rp->enqueue_discovered_references(executor); 1764 1765 rp->verify_no_references_recorded(); 1766 assert(!rp->discovery_enabled(), "Post condition"); 1767 } 1768 1769 if (has_overflown()) { 1770 // We can not trust g1_is_alive if the marking stack overflowed 1771 return; 1772 } 1773 1774 assert(_global_mark_stack.is_empty(), "Marking should have completed"); 1775 1776 // Unload Klasses, String, Symbols, Code Cache, etc. 1777 if (ClassUnloadingWithConcurrentMark) { 1778 bool purged_classes; 1779 1780 { 1781 GCTraceTime(Debug, gc, phases) trace("System Dictionary Unloading", _gc_timer_cm); 1782 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */); 1783 } 1784 1785 { 1786 GCTraceTime(Debug, gc, phases) trace("Parallel Unloading", _gc_timer_cm); 1787 weakRefsWorkParallelPart(&g1_is_alive, purged_classes); 1788 } 1789 } 1790 1791 if (G1StringDedup::is_enabled()) { 1792 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", _gc_timer_cm); 1793 G1StringDedup::unlink(&g1_is_alive); 1794 } 1795 } 1796 1797 void G1ConcurrentMark::swapMarkBitMaps() { 1798 G1CMBitMapRO* temp = _prevMarkBitMap; 1799 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap; 1800 _nextMarkBitMap = (G1CMBitMap*) temp; 1801 } 1802 1803 // Closure for marking entries in SATB buffers. 1804 class G1CMSATBBufferClosure : public SATBBufferClosure { 1805 private: 1806 G1CMTask* _task; 1807 G1CollectedHeap* _g1h; 1808 1809 // This is very similar to G1CMTask::deal_with_reference, but with 1810 // more relaxed requirements for the argument, so this must be more 1811 // circumspect about treating the argument as an object. 1812 void do_entry(void* entry) const { 1813 _task->increment_refs_reached(); 1814 HeapRegion* hr = _g1h->heap_region_containing(entry); 1815 if (entry < hr->next_top_at_mark_start()) { 1816 // Until we get here, we don't know whether entry refers to a valid 1817 // object; it could instead have been a stale reference. 1818 oop obj = static_cast<oop>(entry); 1819 assert(obj->is_oop(true /* ignore mark word */), 1820 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj)); 1821 _task->make_reference_grey(obj); 1822 } 1823 } 1824 1825 public: 1826 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h) 1827 : _task(task), _g1h(g1h) { } 1828 1829 virtual void do_buffer(void** buffer, size_t size) { 1830 for (size_t i = 0; i < size; ++i) { 1831 do_entry(buffer[i]); 1832 } 1833 } 1834 }; 1835 1836 class G1RemarkThreadsClosure : public ThreadClosure { 1837 G1CMSATBBufferClosure _cm_satb_cl; 1838 G1CMOopClosure _cm_cl; 1839 MarkingCodeBlobClosure _code_cl; 1840 int _thread_parity; 1841 1842 public: 1843 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) : 1844 _cm_satb_cl(task, g1h), 1845 _cm_cl(g1h, g1h->concurrent_mark(), task), 1846 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 1847 _thread_parity(Threads::thread_claim_parity()) {} 1848 1849 void do_thread(Thread* thread) { 1850 if (thread->is_Java_thread()) { 1851 if (thread->claim_oops_do(true, _thread_parity)) { 1852 JavaThread* jt = (JavaThread*)thread; 1853 1854 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 1855 // however the liveness of oops reachable from nmethods have very complex lifecycles: 1856 // * Alive if on the stack of an executing method 1857 // * Weakly reachable otherwise 1858 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 1859 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 1860 jt->nmethods_do(&_code_cl); 1861 1862 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl); 1863 } 1864 } else if (thread->is_VM_thread()) { 1865 if (thread->claim_oops_do(true, _thread_parity)) { 1866 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl); 1867 } 1868 } 1869 } 1870 }; 1871 1872 class G1CMRemarkTask: public AbstractGangTask { 1873 private: 1874 G1ConcurrentMark* _cm; 1875 public: 1876 void work(uint worker_id) { 1877 // Since all available tasks are actually started, we should 1878 // only proceed if we're supposed to be active. 1879 if (worker_id < _cm->active_tasks()) { 1880 G1CMTask* task = _cm->task(worker_id); 1881 task->record_start_time(); 1882 { 1883 ResourceMark rm; 1884 HandleMark hm; 1885 1886 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task); 1887 Threads::threads_do(&threads_f); 1888 } 1889 1890 do { 1891 task->do_marking_step(1000000000.0 /* something very large */, 1892 true /* do_termination */, 1893 false /* is_serial */); 1894 } while (task->has_aborted() && !_cm->has_overflown()); 1895 // If we overflow, then we do not want to restart. We instead 1896 // want to abort remark and do concurrent marking again. 1897 task->record_end_time(); 1898 } 1899 } 1900 1901 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) : 1902 AbstractGangTask("Par Remark"), _cm(cm) { 1903 _cm->terminator()->reset_for_reuse(active_workers); 1904 } 1905 }; 1906 1907 void G1ConcurrentMark::checkpointRootsFinalWork() { 1908 ResourceMark rm; 1909 HandleMark hm; 1910 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 1911 1912 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm); 1913 1914 g1h->ensure_parsability(false); 1915 1916 // this is remark, so we'll use up all active threads 1917 uint active_workers = g1h->workers()->active_workers(); 1918 set_concurrency_and_phase(active_workers, false /* concurrent */); 1919 // Leave _parallel_marking_threads at it's 1920 // value originally calculated in the G1ConcurrentMark 1921 // constructor and pass values of the active workers 1922 // through the gang in the task. 1923 1924 { 1925 StrongRootsScope srs(active_workers); 1926 1927 G1CMRemarkTask remarkTask(this, active_workers); 1928 // We will start all available threads, even if we decide that the 1929 // active_workers will be fewer. The extra ones will just bail out 1930 // immediately. 1931 g1h->workers()->run_task(&remarkTask); 1932 } 1933 1934 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 1935 guarantee(has_overflown() || 1936 satb_mq_set.completed_buffers_num() == 0, 1937 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT, 1938 BOOL_TO_STR(has_overflown()), 1939 satb_mq_set.completed_buffers_num()); 1940 1941 print_stats(); 1942 } 1943 1944 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) { 1945 // Note we are overriding the read-only view of the prev map here, via 1946 // the cast. 1947 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr); 1948 } 1949 1950 HeapRegion* 1951 G1ConcurrentMark::claim_region(uint worker_id) { 1952 // "checkpoint" the finger 1953 HeapWord* finger = _finger; 1954 1955 // _heap_end will not change underneath our feet; it only changes at 1956 // yield points. 1957 while (finger < _heap_end) { 1958 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 1959 1960 HeapRegion* curr_region = _g1h->heap_region_containing(finger); 1961 // Make sure that the reads below do not float before loading curr_region. 1962 OrderAccess::loadload(); 1963 // Above heap_region_containing may return NULL as we always scan claim 1964 // until the end of the heap. In this case, just jump to the next region. 1965 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 1966 1967 // Is the gap between reading the finger and doing the CAS too long? 1968 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger); 1969 if (res == finger && curr_region != NULL) { 1970 // we succeeded 1971 HeapWord* bottom = curr_region->bottom(); 1972 HeapWord* limit = curr_region->next_top_at_mark_start(); 1973 1974 // notice that _finger == end cannot be guaranteed here since, 1975 // someone else might have moved the finger even further 1976 assert(_finger >= end, "the finger should have moved forward"); 1977 1978 if (limit > bottom) { 1979 return curr_region; 1980 } else { 1981 assert(limit == bottom, 1982 "the region limit should be at bottom"); 1983 // we return NULL and the caller should try calling 1984 // claim_region() again. 1985 return NULL; 1986 } 1987 } else { 1988 assert(_finger > finger, "the finger should have moved forward"); 1989 // read it again 1990 finger = _finger; 1991 } 1992 } 1993 1994 return NULL; 1995 } 1996 1997 #ifndef PRODUCT 1998 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC { 1999 private: 2000 G1CollectedHeap* _g1h; 2001 const char* _phase; 2002 int _info; 2003 2004 public: 2005 VerifyNoCSetOops(const char* phase, int info = -1) : 2006 _g1h(G1CollectedHeap::heap()), 2007 _phase(phase), 2008 _info(info) 2009 { } 2010 2011 void operator()(G1TaskQueueEntry task_entry) const { 2012 if (task_entry.is_array_slice()) { 2013 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice())); 2014 return; 2015 } 2016 guarantee(task_entry.obj()->is_oop(), 2017 "Non-oop " PTR_FORMAT ", phase: %s, info: %d", 2018 p2i(task_entry.obj()), _phase, _info); 2019 guarantee(!_g1h->is_in_cset(task_entry.obj()), 2020 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d", 2021 p2i(task_entry.obj()), _phase, _info); 2022 } 2023 }; 2024 2025 void G1ConcurrentMark::verify_no_cset_oops() { 2026 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 2027 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) { 2028 return; 2029 } 2030 2031 // Verify entries on the global mark stack 2032 _global_mark_stack.iterate(VerifyNoCSetOops("Stack")); 2033 2034 // Verify entries on the task queues 2035 for (uint i = 0; i < _max_worker_id; ++i) { 2036 G1CMTaskQueue* queue = _task_queues->queue(i); 2037 queue->iterate(VerifyNoCSetOops("Queue", i)); 2038 } 2039 2040 // Verify the global finger 2041 HeapWord* global_finger = finger(); 2042 if (global_finger != NULL && global_finger < _heap_end) { 2043 // Since we always iterate over all regions, we might get a NULL HeapRegion 2044 // here. 2045 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger); 2046 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 2047 "global finger: " PTR_FORMAT " region: " HR_FORMAT, 2048 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)); 2049 } 2050 2051 // Verify the task fingers 2052 assert(parallel_marking_threads() <= _max_worker_id, "sanity"); 2053 for (uint i = 0; i < parallel_marking_threads(); ++i) { 2054 G1CMTask* task = _tasks[i]; 2055 HeapWord* task_finger = task->finger(); 2056 if (task_finger != NULL && task_finger < _heap_end) { 2057 // See above note on the global finger verification. 2058 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger); 2059 guarantee(task_hr == NULL || task_finger == task_hr->bottom() || 2060 !task_hr->in_collection_set(), 2061 "task finger: " PTR_FORMAT " region: " HR_FORMAT, 2062 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)); 2063 } 2064 } 2065 } 2066 #endif // PRODUCT 2067 void G1ConcurrentMark::create_live_data() { 2068 _g1h->g1_rem_set()->create_card_live_data(_parallel_workers, _nextMarkBitMap); 2069 } 2070 2071 void G1ConcurrentMark::finalize_live_data() { 2072 _g1h->g1_rem_set()->finalize_card_live_data(_g1h->workers(), _nextMarkBitMap); 2073 } 2074 2075 void G1ConcurrentMark::verify_live_data() { 2076 _g1h->g1_rem_set()->verify_card_live_data(_g1h->workers(), _nextMarkBitMap); 2077 } 2078 2079 void G1ConcurrentMark::clear_live_data(WorkGang* workers) { 2080 _g1h->g1_rem_set()->clear_card_live_data(workers); 2081 } 2082 2083 #ifdef ASSERT 2084 void G1ConcurrentMark::verify_live_data_clear() { 2085 _g1h->g1_rem_set()->verify_card_live_data_is_clear(); 2086 } 2087 #endif 2088 2089 void G1ConcurrentMark::print_stats() { 2090 if (!log_is_enabled(Debug, gc, stats)) { 2091 return; 2092 } 2093 log_debug(gc, stats)("---------------------------------------------------------------------"); 2094 for (size_t i = 0; i < _active_tasks; ++i) { 2095 _tasks[i]->print_stats(); 2096 log_debug(gc, stats)("---------------------------------------------------------------------"); 2097 } 2098 } 2099 2100 void G1ConcurrentMark::abort() { 2101 if (!cmThread()->during_cycle() || _has_aborted) { 2102 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything. 2103 return; 2104 } 2105 2106 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 2107 // concurrent bitmap clearing. 2108 { 2109 GCTraceTime(Debug, gc)("Clear Next Bitmap"); 2110 clear_bitmap(_nextMarkBitMap, _g1h->workers(), false); 2111 } 2112 // Note we cannot clear the previous marking bitmap here 2113 // since VerifyDuringGC verifies the objects marked during 2114 // a full GC against the previous bitmap. 2115 2116 { 2117 GCTraceTime(Debug, gc)("Clear Live Data"); 2118 clear_live_data(_g1h->workers()); 2119 } 2120 DEBUG_ONLY({ 2121 GCTraceTime(Debug, gc)("Verify Live Data Clear"); 2122 verify_live_data_clear(); 2123 }) 2124 // Empty mark stack 2125 reset_marking_state(); 2126 for (uint i = 0; i < _max_worker_id; ++i) { 2127 _tasks[i]->clear_region_fields(); 2128 } 2129 _first_overflow_barrier_sync.abort(); 2130 _second_overflow_barrier_sync.abort(); 2131 _has_aborted = true; 2132 2133 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2134 satb_mq_set.abandon_partial_marking(); 2135 // This can be called either during or outside marking, we'll read 2136 // the expected_active value from the SATB queue set. 2137 satb_mq_set.set_active_all_threads( 2138 false, /* new active value */ 2139 satb_mq_set.is_active() /* expected_active */); 2140 } 2141 2142 static void print_ms_time_info(const char* prefix, const char* name, 2143 NumberSeq& ns) { 2144 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 2145 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 2146 if (ns.num() > 0) { 2147 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]", 2148 prefix, ns.sd(), ns.maximum()); 2149 } 2150 } 2151 2152 void G1ConcurrentMark::print_summary_info() { 2153 Log(gc, marking) log; 2154 if (!log.is_trace()) { 2155 return; 2156 } 2157 2158 log.trace(" Concurrent marking:"); 2159 print_ms_time_info(" ", "init marks", _init_times); 2160 print_ms_time_info(" ", "remarks", _remark_times); 2161 { 2162 print_ms_time_info(" ", "final marks", _remark_mark_times); 2163 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 2164 2165 } 2166 print_ms_time_info(" ", "cleanups", _cleanup_times); 2167 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).", 2168 _total_counting_time, (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2169 if (G1ScrubRemSets) { 2170 log.trace(" RS scrub total time = %8.2f s (avg = %8.2f ms).", 2171 _total_rs_scrub_time, (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2172 } 2173 log.trace(" Total stop_world time = %8.2f s.", 2174 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0); 2175 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).", 2176 cmThread()->vtime_accum(), cmThread()->vtime_mark_accum()); 2177 } 2178 2179 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const { 2180 _parallel_workers->print_worker_threads_on(st); 2181 } 2182 2183 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const { 2184 _parallel_workers->threads_do(tc); 2185 } 2186 2187 void G1ConcurrentMark::print_on_error(outputStream* st) const { 2188 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 2189 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap)); 2190 _prevMarkBitMap->print_on_error(st, " Prev Bits: "); 2191 _nextMarkBitMap->print_on_error(st, " Next Bits: "); 2192 } 2193 2194 // Closure for iteration over bitmaps 2195 class G1CMBitMapClosure : public BitMapClosure { 2196 private: 2197 // the bitmap that is being iterated over 2198 G1CMBitMap* _nextMarkBitMap; 2199 G1ConcurrentMark* _cm; 2200 G1CMTask* _task; 2201 2202 public: 2203 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm, G1CMBitMap* nextMarkBitMap) : 2204 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { } 2205 2206 bool do_bit(size_t offset) { 2207 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset); 2208 assert(_nextMarkBitMap->isMarked(addr), "invariant"); 2209 assert( addr < _cm->finger(), "invariant"); 2210 assert(addr >= _task->finger(), "invariant"); 2211 2212 // We move that task's local finger along. 2213 _task->move_finger_to(addr); 2214 2215 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr))); 2216 // we only partially drain the local queue and global stack 2217 _task->drain_local_queue(true); 2218 _task->drain_global_stack(true); 2219 2220 // if the has_aborted flag has been raised, we need to bail out of 2221 // the iteration 2222 return !_task->has_aborted(); 2223 } 2224 }; 2225 2226 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) { 2227 ReferenceProcessor* result = g1h->ref_processor_cm(); 2228 assert(result != NULL, "CM reference processor should not be NULL"); 2229 return result; 2230 } 2231 2232 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 2233 G1ConcurrentMark* cm, 2234 G1CMTask* task) 2235 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)), 2236 _g1h(g1h), _cm(cm), _task(task) 2237 { } 2238 2239 void G1CMTask::setup_for_region(HeapRegion* hr) { 2240 assert(hr != NULL, 2241 "claim_region() should have filtered out NULL regions"); 2242 _curr_region = hr; 2243 _finger = hr->bottom(); 2244 update_region_limit(); 2245 } 2246 2247 void G1CMTask::update_region_limit() { 2248 HeapRegion* hr = _curr_region; 2249 HeapWord* bottom = hr->bottom(); 2250 HeapWord* limit = hr->next_top_at_mark_start(); 2251 2252 if (limit == bottom) { 2253 // The region was collected underneath our feet. 2254 // We set the finger to bottom to ensure that the bitmap 2255 // iteration that will follow this will not do anything. 2256 // (this is not a condition that holds when we set the region up, 2257 // as the region is not supposed to be empty in the first place) 2258 _finger = bottom; 2259 } else if (limit >= _region_limit) { 2260 assert(limit >= _finger, "peace of mind"); 2261 } else { 2262 assert(limit < _region_limit, "only way to get here"); 2263 // This can happen under some pretty unusual circumstances. An 2264 // evacuation pause empties the region underneath our feet (NTAMS 2265 // at bottom). We then do some allocation in the region (NTAMS 2266 // stays at bottom), followed by the region being used as a GC 2267 // alloc region (NTAMS will move to top() and the objects 2268 // originally below it will be grayed). All objects now marked in 2269 // the region are explicitly grayed, if below the global finger, 2270 // and we do not need in fact to scan anything else. So, we simply 2271 // set _finger to be limit to ensure that the bitmap iteration 2272 // doesn't do anything. 2273 _finger = limit; 2274 } 2275 2276 _region_limit = limit; 2277 } 2278 2279 void G1CMTask::giveup_current_region() { 2280 assert(_curr_region != NULL, "invariant"); 2281 clear_region_fields(); 2282 } 2283 2284 void G1CMTask::clear_region_fields() { 2285 // Values for these three fields that indicate that we're not 2286 // holding on to a region. 2287 _curr_region = NULL; 2288 _finger = NULL; 2289 _region_limit = NULL; 2290 } 2291 2292 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 2293 if (cm_oop_closure == NULL) { 2294 assert(_cm_oop_closure != NULL, "invariant"); 2295 } else { 2296 assert(_cm_oop_closure == NULL, "invariant"); 2297 } 2298 _cm_oop_closure = cm_oop_closure; 2299 } 2300 2301 void G1CMTask::reset(G1CMBitMap* nextMarkBitMap) { 2302 guarantee(nextMarkBitMap != NULL, "invariant"); 2303 _nextMarkBitMap = nextMarkBitMap; 2304 clear_region_fields(); 2305 2306 _calls = 0; 2307 _elapsed_time_ms = 0.0; 2308 _termination_time_ms = 0.0; 2309 _termination_start_time_ms = 0.0; 2310 } 2311 2312 bool G1CMTask::should_exit_termination() { 2313 regular_clock_call(); 2314 // This is called when we are in the termination protocol. We should 2315 // quit if, for some reason, this task wants to abort or the global 2316 // stack is not empty (this means that we can get work from it). 2317 return !_cm->mark_stack_empty() || has_aborted(); 2318 } 2319 2320 void G1CMTask::reached_limit() { 2321 assert(_words_scanned >= _words_scanned_limit || 2322 _refs_reached >= _refs_reached_limit , 2323 "shouldn't have been called otherwise"); 2324 regular_clock_call(); 2325 } 2326 2327 void G1CMTask::regular_clock_call() { 2328 if (has_aborted()) return; 2329 2330 // First, we need to recalculate the words scanned and refs reached 2331 // limits for the next clock call. 2332 recalculate_limits(); 2333 2334 // During the regular clock call we do the following 2335 2336 // (1) If an overflow has been flagged, then we abort. 2337 if (_cm->has_overflown()) { 2338 set_has_aborted(); 2339 return; 2340 } 2341 2342 // If we are not concurrent (i.e. we're doing remark) we don't need 2343 // to check anything else. The other steps are only needed during 2344 // the concurrent marking phase. 2345 if (!concurrent()) return; 2346 2347 // (2) If marking has been aborted for Full GC, then we also abort. 2348 if (_cm->has_aborted()) { 2349 set_has_aborted(); 2350 return; 2351 } 2352 2353 double curr_time_ms = os::elapsedVTime() * 1000.0; 2354 2355 // (4) We check whether we should yield. If we have to, then we abort. 2356 if (SuspendibleThreadSet::should_yield()) { 2357 // We should yield. To do this we abort the task. The caller is 2358 // responsible for yielding. 2359 set_has_aborted(); 2360 return; 2361 } 2362 2363 // (5) We check whether we've reached our time quota. If we have, 2364 // then we abort. 2365 double elapsed_time_ms = curr_time_ms - _start_time_ms; 2366 if (elapsed_time_ms > _time_target_ms) { 2367 set_has_aborted(); 2368 _has_timed_out = true; 2369 return; 2370 } 2371 2372 // (6) Finally, we check whether there are enough completed STAB 2373 // buffers available for processing. If there are, we abort. 2374 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2375 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 2376 // we do need to process SATB buffers, we'll abort and restart 2377 // the marking task to do so 2378 set_has_aborted(); 2379 return; 2380 } 2381 } 2382 2383 void G1CMTask::recalculate_limits() { 2384 _real_words_scanned_limit = _words_scanned + words_scanned_period; 2385 _words_scanned_limit = _real_words_scanned_limit; 2386 2387 _real_refs_reached_limit = _refs_reached + refs_reached_period; 2388 _refs_reached_limit = _real_refs_reached_limit; 2389 } 2390 2391 void G1CMTask::decrease_limits() { 2392 // This is called when we believe that we're going to do an infrequent 2393 // operation which will increase the per byte scanned cost (i.e. move 2394 // entries to/from the global stack). It basically tries to decrease the 2395 // scanning limit so that the clock is called earlier. 2396 2397 _words_scanned_limit = _real_words_scanned_limit - 2398 3 * words_scanned_period / 4; 2399 _refs_reached_limit = _real_refs_reached_limit - 2400 3 * refs_reached_period / 4; 2401 } 2402 2403 void G1CMTask::move_entries_to_global_stack() { 2404 // Local array where we'll store the entries that will be popped 2405 // from the local queue. 2406 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2407 2408 size_t n = 0; 2409 G1TaskQueueEntry task_entry; 2410 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) { 2411 buffer[n].assign(task_entry); 2412 ++n; 2413 } 2414 if (n < G1CMMarkStack::EntriesPerChunk) { 2415 buffer[n].assign(G1TaskQueueEntry()); 2416 } 2417 2418 if (n > 0) { 2419 if (!_cm->mark_stack_push(buffer)) { 2420 set_has_aborted(); 2421 } 2422 } 2423 2424 // This operation was quite expensive, so decrease the limits. 2425 decrease_limits(); 2426 } 2427 2428 bool G1CMTask::get_entries_from_global_stack() { 2429 // Local array where we'll store the entries that will be popped 2430 // from the global stack. 2431 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2432 2433 if (!_cm->mark_stack_pop(buffer)) { 2434 return false; 2435 } 2436 2437 // We did actually pop at least one entry. 2438 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) { 2439 G1TaskQueueEntry task_entry = buffer[i]; 2440 if (task_entry.is_null()) { 2441 break; 2442 } 2443 assert(task_entry.is_array_slice() || task_entry.obj()->is_oop(), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj())); 2444 bool success = _task_queue->push(task_entry); 2445 // We only call this when the local queue is empty or under a 2446 // given target limit. So, we do not expect this push to fail. 2447 assert(success, "invariant"); 2448 } 2449 2450 // This operation was quite expensive, so decrease the limits 2451 decrease_limits(); 2452 return true; 2453 } 2454 2455 void G1CMTask::drain_local_queue(bool partially) { 2456 if (has_aborted()) { 2457 return; 2458 } 2459 2460 // Decide what the target size is, depending whether we're going to 2461 // drain it partially (so that other tasks can steal if they run out 2462 // of things to do) or totally (at the very end). 2463 size_t target_size; 2464 if (partially) { 2465 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize); 2466 } else { 2467 target_size = 0; 2468 } 2469 2470 if (_task_queue->size() > target_size) { 2471 G1TaskQueueEntry entry; 2472 bool ret = _task_queue->pop_local(entry); 2473 while (ret) { 2474 scan_task_entry(entry); 2475 if (_task_queue->size() <= target_size || has_aborted()) { 2476 ret = false; 2477 } else { 2478 ret = _task_queue->pop_local(entry); 2479 } 2480 } 2481 } 2482 } 2483 2484 void G1CMTask::drain_global_stack(bool partially) { 2485 if (has_aborted()) return; 2486 2487 // We have a policy to drain the local queue before we attempt to 2488 // drain the global stack. 2489 assert(partially || _task_queue->size() == 0, "invariant"); 2490 2491 // Decide what the target size is, depending whether we're going to 2492 // drain it partially (so that other tasks can steal if they run out 2493 // of things to do) or totally (at the very end). 2494 // Notice that when draining the global mark stack partially, due to the racyness 2495 // of the mark stack size update we might in fact drop below the target. But, 2496 // this is not a problem. 2497 // In case of total draining, we simply process until the global mark stack is 2498 // totally empty, disregarding the size counter. 2499 if (partially) { 2500 size_t const target_size = _cm->partial_mark_stack_size_target(); 2501 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 2502 if (get_entries_from_global_stack()) { 2503 drain_local_queue(partially); 2504 } 2505 } 2506 } else { 2507 while (!has_aborted() && get_entries_from_global_stack()) { 2508 drain_local_queue(partially); 2509 } 2510 } 2511 } 2512 2513 // SATB Queue has several assumptions on whether to call the par or 2514 // non-par versions of the methods. this is why some of the code is 2515 // replicated. We should really get rid of the single-threaded version 2516 // of the code to simplify things. 2517 void G1CMTask::drain_satb_buffers() { 2518 if (has_aborted()) return; 2519 2520 // We set this so that the regular clock knows that we're in the 2521 // middle of draining buffers and doesn't set the abort flag when it 2522 // notices that SATB buffers are available for draining. It'd be 2523 // very counter productive if it did that. :-) 2524 _draining_satb_buffers = true; 2525 2526 G1CMSATBBufferClosure satb_cl(this, _g1h); 2527 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set(); 2528 2529 // This keeps claiming and applying the closure to completed buffers 2530 // until we run out of buffers or we need to abort. 2531 while (!has_aborted() && 2532 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 2533 regular_clock_call(); 2534 } 2535 2536 _draining_satb_buffers = false; 2537 2538 assert(has_aborted() || 2539 concurrent() || 2540 satb_mq_set.completed_buffers_num() == 0, "invariant"); 2541 2542 // again, this was a potentially expensive operation, decrease the 2543 // limits to get the regular clock call early 2544 decrease_limits(); 2545 } 2546 2547 void G1CMTask::print_stats() { 2548 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d", 2549 _worker_id, _calls); 2550 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 2551 _elapsed_time_ms, _termination_time_ms); 2552 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms", 2553 _step_times_ms.num(), _step_times_ms.avg(), 2554 _step_times_ms.sd()); 2555 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms", 2556 _step_times_ms.maximum(), _step_times_ms.sum()); 2557 } 2558 2559 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry) { 2560 return _task_queues->steal(worker_id, hash_seed, task_entry); 2561 } 2562 2563 /***************************************************************************** 2564 2565 The do_marking_step(time_target_ms, ...) method is the building 2566 block of the parallel marking framework. It can be called in parallel 2567 with other invocations of do_marking_step() on different tasks 2568 (but only one per task, obviously) and concurrently with the 2569 mutator threads, or during remark, hence it eliminates the need 2570 for two versions of the code. When called during remark, it will 2571 pick up from where the task left off during the concurrent marking 2572 phase. Interestingly, tasks are also claimable during evacuation 2573 pauses too, since do_marking_step() ensures that it aborts before 2574 it needs to yield. 2575 2576 The data structures that it uses to do marking work are the 2577 following: 2578 2579 (1) Marking Bitmap. If there are gray objects that appear only 2580 on the bitmap (this happens either when dealing with an overflow 2581 or when the initial marking phase has simply marked the roots 2582 and didn't push them on the stack), then tasks claim heap 2583 regions whose bitmap they then scan to find gray objects. A 2584 global finger indicates where the end of the last claimed region 2585 is. A local finger indicates how far into the region a task has 2586 scanned. The two fingers are used to determine how to gray an 2587 object (i.e. whether simply marking it is OK, as it will be 2588 visited by a task in the future, or whether it needs to be also 2589 pushed on a stack). 2590 2591 (2) Local Queue. The local queue of the task which is accessed 2592 reasonably efficiently by the task. Other tasks can steal from 2593 it when they run out of work. Throughout the marking phase, a 2594 task attempts to keep its local queue short but not totally 2595 empty, so that entries are available for stealing by other 2596 tasks. Only when there is no more work, a task will totally 2597 drain its local queue. 2598 2599 (3) Global Mark Stack. This handles local queue overflow. During 2600 marking only sets of entries are moved between it and the local 2601 queues, as access to it requires a mutex and more fine-grain 2602 interaction with it which might cause contention. If it 2603 overflows, then the marking phase should restart and iterate 2604 over the bitmap to identify gray objects. Throughout the marking 2605 phase, tasks attempt to keep the global mark stack at a small 2606 length but not totally empty, so that entries are available for 2607 popping by other tasks. Only when there is no more work, tasks 2608 will totally drain the global mark stack. 2609 2610 (4) SATB Buffer Queue. This is where completed SATB buffers are 2611 made available. Buffers are regularly removed from this queue 2612 and scanned for roots, so that the queue doesn't get too 2613 long. During remark, all completed buffers are processed, as 2614 well as the filled in parts of any uncompleted buffers. 2615 2616 The do_marking_step() method tries to abort when the time target 2617 has been reached. There are a few other cases when the 2618 do_marking_step() method also aborts: 2619 2620 (1) When the marking phase has been aborted (after a Full GC). 2621 2622 (2) When a global overflow (on the global stack) has been 2623 triggered. Before the task aborts, it will actually sync up with 2624 the other tasks to ensure that all the marking data structures 2625 (local queues, stacks, fingers etc.) are re-initialized so that 2626 when do_marking_step() completes, the marking phase can 2627 immediately restart. 2628 2629 (3) When enough completed SATB buffers are available. The 2630 do_marking_step() method only tries to drain SATB buffers right 2631 at the beginning. So, if enough buffers are available, the 2632 marking step aborts and the SATB buffers are processed at 2633 the beginning of the next invocation. 2634 2635 (4) To yield. when we have to yield then we abort and yield 2636 right at the end of do_marking_step(). This saves us from a lot 2637 of hassle as, by yielding we might allow a Full GC. If this 2638 happens then objects will be compacted underneath our feet, the 2639 heap might shrink, etc. We save checking for this by just 2640 aborting and doing the yield right at the end. 2641 2642 From the above it follows that the do_marking_step() method should 2643 be called in a loop (or, otherwise, regularly) until it completes. 2644 2645 If a marking step completes without its has_aborted() flag being 2646 true, it means it has completed the current marking phase (and 2647 also all other marking tasks have done so and have all synced up). 2648 2649 A method called regular_clock_call() is invoked "regularly" (in 2650 sub ms intervals) throughout marking. It is this clock method that 2651 checks all the abort conditions which were mentioned above and 2652 decides when the task should abort. A work-based scheme is used to 2653 trigger this clock method: when the number of object words the 2654 marking phase has scanned or the number of references the marking 2655 phase has visited reach a given limit. Additional invocations to 2656 the method clock have been planted in a few other strategic places 2657 too. The initial reason for the clock method was to avoid calling 2658 vtime too regularly, as it is quite expensive. So, once it was in 2659 place, it was natural to piggy-back all the other conditions on it 2660 too and not constantly check them throughout the code. 2661 2662 If do_termination is true then do_marking_step will enter its 2663 termination protocol. 2664 2665 The value of is_serial must be true when do_marking_step is being 2666 called serially (i.e. by the VMThread) and do_marking_step should 2667 skip any synchronization in the termination and overflow code. 2668 Examples include the serial remark code and the serial reference 2669 processing closures. 2670 2671 The value of is_serial must be false when do_marking_step is 2672 being called by any of the worker threads in a work gang. 2673 Examples include the concurrent marking code (CMMarkingTask), 2674 the MT remark code, and the MT reference processing closures. 2675 2676 *****************************************************************************/ 2677 2678 void G1CMTask::do_marking_step(double time_target_ms, 2679 bool do_termination, 2680 bool is_serial) { 2681 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 2682 assert(concurrent() == _cm->concurrent(), "they should be the same"); 2683 2684 G1Policy* g1_policy = _g1h->g1_policy(); 2685 assert(_task_queues != NULL, "invariant"); 2686 assert(_task_queue != NULL, "invariant"); 2687 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant"); 2688 2689 assert(!_claimed, 2690 "only one thread should claim this task at any one time"); 2691 2692 // OK, this doesn't safeguard again all possible scenarios, as it is 2693 // possible for two threads to set the _claimed flag at the same 2694 // time. But it is only for debugging purposes anyway and it will 2695 // catch most problems. 2696 _claimed = true; 2697 2698 _start_time_ms = os::elapsedVTime() * 1000.0; 2699 2700 // If do_stealing is true then do_marking_step will attempt to 2701 // steal work from the other G1CMTasks. It only makes sense to 2702 // enable stealing when the termination protocol is enabled 2703 // and do_marking_step() is not being called serially. 2704 bool do_stealing = do_termination && !is_serial; 2705 2706 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms); 2707 _time_target_ms = time_target_ms - diff_prediction_ms; 2708 2709 // set up the variables that are used in the work-based scheme to 2710 // call the regular clock method 2711 _words_scanned = 0; 2712 _refs_reached = 0; 2713 recalculate_limits(); 2714 2715 // clear all flags 2716 clear_has_aborted(); 2717 _has_timed_out = false; 2718 _draining_satb_buffers = false; 2719 2720 ++_calls; 2721 2722 // Set up the bitmap and oop closures. Anything that uses them is 2723 // eventually called from this method, so it is OK to allocate these 2724 // statically. 2725 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap); 2726 G1CMOopClosure cm_oop_closure(_g1h, _cm, this); 2727 set_cm_oop_closure(&cm_oop_closure); 2728 2729 if (_cm->has_overflown()) { 2730 // This can happen if the mark stack overflows during a GC pause 2731 // and this task, after a yield point, restarts. We have to abort 2732 // as we need to get into the overflow protocol which happens 2733 // right at the end of this task. 2734 set_has_aborted(); 2735 } 2736 2737 // First drain any available SATB buffers. After this, we will not 2738 // look at SATB buffers before the next invocation of this method. 2739 // If enough completed SATB buffers are queued up, the regular clock 2740 // will abort this task so that it restarts. 2741 drain_satb_buffers(); 2742 // ...then partially drain the local queue and the global stack 2743 drain_local_queue(true); 2744 drain_global_stack(true); 2745 2746 do { 2747 if (!has_aborted() && _curr_region != NULL) { 2748 // This means that we're already holding on to a region. 2749 assert(_finger != NULL, "if region is not NULL, then the finger " 2750 "should not be NULL either"); 2751 2752 // We might have restarted this task after an evacuation pause 2753 // which might have evacuated the region we're holding on to 2754 // underneath our feet. Let's read its limit again to make sure 2755 // that we do not iterate over a region of the heap that 2756 // contains garbage (update_region_limit() will also move 2757 // _finger to the start of the region if it is found empty). 2758 update_region_limit(); 2759 // We will start from _finger not from the start of the region, 2760 // as we might be restarting this task after aborting half-way 2761 // through scanning this region. In this case, _finger points to 2762 // the address where we last found a marked object. If this is a 2763 // fresh region, _finger points to start(). 2764 MemRegion mr = MemRegion(_finger, _region_limit); 2765 2766 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(), 2767 "humongous regions should go around loop once only"); 2768 2769 // Some special cases: 2770 // If the memory region is empty, we can just give up the region. 2771 // If the current region is humongous then we only need to check 2772 // the bitmap for the bit associated with the start of the object, 2773 // scan the object if it's live, and give up the region. 2774 // Otherwise, let's iterate over the bitmap of the part of the region 2775 // that is left. 2776 // If the iteration is successful, give up the region. 2777 if (mr.is_empty()) { 2778 giveup_current_region(); 2779 regular_clock_call(); 2780 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) { 2781 if (_nextMarkBitMap->isMarked(mr.start())) { 2782 // The object is marked - apply the closure 2783 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start()); 2784 bitmap_closure.do_bit(offset); 2785 } 2786 // Even if this task aborted while scanning the humongous object 2787 // we can (and should) give up the current region. 2788 giveup_current_region(); 2789 regular_clock_call(); 2790 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) { 2791 giveup_current_region(); 2792 regular_clock_call(); 2793 } else { 2794 assert(has_aborted(), "currently the only way to do so"); 2795 // The only way to abort the bitmap iteration is to return 2796 // false from the do_bit() method. However, inside the 2797 // do_bit() method we move the _finger to point to the 2798 // object currently being looked at. So, if we bail out, we 2799 // have definitely set _finger to something non-null. 2800 assert(_finger != NULL, "invariant"); 2801 2802 // Region iteration was actually aborted. So now _finger 2803 // points to the address of the object we last scanned. If we 2804 // leave it there, when we restart this task, we will rescan 2805 // the object. It is easy to avoid this. We move the finger by 2806 // enough to point to the next possible object header (the 2807 // bitmap knows by how much we need to move it as it knows its 2808 // granularity). 2809 assert(_finger < _region_limit, "invariant"); 2810 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger); 2811 // Check if bitmap iteration was aborted while scanning the last object 2812 if (new_finger >= _region_limit) { 2813 giveup_current_region(); 2814 } else { 2815 move_finger_to(new_finger); 2816 } 2817 } 2818 } 2819 // At this point we have either completed iterating over the 2820 // region we were holding on to, or we have aborted. 2821 2822 // We then partially drain the local queue and the global stack. 2823 // (Do we really need this?) 2824 drain_local_queue(true); 2825 drain_global_stack(true); 2826 2827 // Read the note on the claim_region() method on why it might 2828 // return NULL with potentially more regions available for 2829 // claiming and why we have to check out_of_regions() to determine 2830 // whether we're done or not. 2831 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 2832 // We are going to try to claim a new region. We should have 2833 // given up on the previous one. 2834 // Separated the asserts so that we know which one fires. 2835 assert(_curr_region == NULL, "invariant"); 2836 assert(_finger == NULL, "invariant"); 2837 assert(_region_limit == NULL, "invariant"); 2838 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 2839 if (claimed_region != NULL) { 2840 // Yes, we managed to claim one 2841 setup_for_region(claimed_region); 2842 assert(_curr_region == claimed_region, "invariant"); 2843 } 2844 // It is important to call the regular clock here. It might take 2845 // a while to claim a region if, for example, we hit a large 2846 // block of empty regions. So we need to call the regular clock 2847 // method once round the loop to make sure it's called 2848 // frequently enough. 2849 regular_clock_call(); 2850 } 2851 2852 if (!has_aborted() && _curr_region == NULL) { 2853 assert(_cm->out_of_regions(), 2854 "at this point we should be out of regions"); 2855 } 2856 } while ( _curr_region != NULL && !has_aborted()); 2857 2858 if (!has_aborted()) { 2859 // We cannot check whether the global stack is empty, since other 2860 // tasks might be pushing objects to it concurrently. 2861 assert(_cm->out_of_regions(), 2862 "at this point we should be out of regions"); 2863 // Try to reduce the number of available SATB buffers so that 2864 // remark has less work to do. 2865 drain_satb_buffers(); 2866 } 2867 2868 // Since we've done everything else, we can now totally drain the 2869 // local queue and global stack. 2870 drain_local_queue(false); 2871 drain_global_stack(false); 2872 2873 // Attempt at work stealing from other task's queues. 2874 if (do_stealing && !has_aborted()) { 2875 // We have not aborted. This means that we have finished all that 2876 // we could. Let's try to do some stealing... 2877 2878 // We cannot check whether the global stack is empty, since other 2879 // tasks might be pushing objects to it concurrently. 2880 assert(_cm->out_of_regions() && _task_queue->size() == 0, 2881 "only way to reach here"); 2882 while (!has_aborted()) { 2883 G1TaskQueueEntry entry; 2884 if (_cm->try_stealing(_worker_id, &_hash_seed, entry)) { 2885 scan_task_entry(entry); 2886 2887 // And since we're towards the end, let's totally drain the 2888 // local queue and global stack. 2889 drain_local_queue(false); 2890 drain_global_stack(false); 2891 } else { 2892 break; 2893 } 2894 } 2895 } 2896 2897 // We still haven't aborted. Now, let's try to get into the 2898 // termination protocol. 2899 if (do_termination && !has_aborted()) { 2900 // We cannot check whether the global stack is empty, since other 2901 // tasks might be concurrently pushing objects on it. 2902 // Separated the asserts so that we know which one fires. 2903 assert(_cm->out_of_regions(), "only way to reach here"); 2904 assert(_task_queue->size() == 0, "only way to reach here"); 2905 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 2906 2907 // The G1CMTask class also extends the TerminatorTerminator class, 2908 // hence its should_exit_termination() method will also decide 2909 // whether to exit the termination protocol or not. 2910 bool finished = (is_serial || 2911 _cm->terminator()->offer_termination(this)); 2912 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 2913 _termination_time_ms += 2914 termination_end_time_ms - _termination_start_time_ms; 2915 2916 if (finished) { 2917 // We're all done. 2918 2919 if (_worker_id == 0) { 2920 // let's allow task 0 to do this 2921 if (concurrent()) { 2922 assert(_cm->concurrent_marking_in_progress(), "invariant"); 2923 // we need to set this to false before the next 2924 // safepoint. This way we ensure that the marking phase 2925 // doesn't observe any more heap expansions. 2926 _cm->clear_concurrent_marking_in_progress(); 2927 } 2928 } 2929 2930 // We can now guarantee that the global stack is empty, since 2931 // all other tasks have finished. We separated the guarantees so 2932 // that, if a condition is false, we can immediately find out 2933 // which one. 2934 guarantee(_cm->out_of_regions(), "only way to reach here"); 2935 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 2936 guarantee(_task_queue->size() == 0, "only way to reach here"); 2937 guarantee(!_cm->has_overflown(), "only way to reach here"); 2938 guarantee(!_cm->mark_stack_overflow(), "only way to reach here"); 2939 } else { 2940 // Apparently there's more work to do. Let's abort this task. It 2941 // will restart it and we can hopefully find more things to do. 2942 set_has_aborted(); 2943 } 2944 } 2945 2946 // Mainly for debugging purposes to make sure that a pointer to the 2947 // closure which was statically allocated in this frame doesn't 2948 // escape it by accident. 2949 set_cm_oop_closure(NULL); 2950 double end_time_ms = os::elapsedVTime() * 1000.0; 2951 double elapsed_time_ms = end_time_ms - _start_time_ms; 2952 // Update the step history. 2953 _step_times_ms.add(elapsed_time_ms); 2954 2955 if (has_aborted()) { 2956 // The task was aborted for some reason. 2957 if (_has_timed_out) { 2958 double diff_ms = elapsed_time_ms - _time_target_ms; 2959 // Keep statistics of how well we did with respect to hitting 2960 // our target only if we actually timed out (if we aborted for 2961 // other reasons, then the results might get skewed). 2962 _marking_step_diffs_ms.add(diff_ms); 2963 } 2964 2965 if (_cm->has_overflown()) { 2966 // This is the interesting one. We aborted because a global 2967 // overflow was raised. This means we have to restart the 2968 // marking phase and start iterating over regions. However, in 2969 // order to do this we have to make sure that all tasks stop 2970 // what they are doing and re-initialize in a safe manner. We 2971 // will achieve this with the use of two barrier sync points. 2972 2973 if (!is_serial) { 2974 // We only need to enter the sync barrier if being called 2975 // from a parallel context 2976 _cm->enter_first_sync_barrier(_worker_id); 2977 2978 // When we exit this sync barrier we know that all tasks have 2979 // stopped doing marking work. So, it's now safe to 2980 // re-initialize our data structures. At the end of this method, 2981 // task 0 will clear the global data structures. 2982 } 2983 2984 // We clear the local state of this task... 2985 clear_region_fields(); 2986 2987 if (!is_serial) { 2988 // ...and enter the second barrier. 2989 _cm->enter_second_sync_barrier(_worker_id); 2990 } 2991 // At this point, if we're during the concurrent phase of 2992 // marking, everything has been re-initialized and we're 2993 // ready to restart. 2994 } 2995 } 2996 2997 _claimed = false; 2998 } 2999 3000 G1CMTask::G1CMTask(uint worker_id, 3001 G1ConcurrentMark* cm, 3002 G1CMTaskQueue* task_queue, 3003 G1CMTaskQueueSet* task_queues) 3004 : _g1h(G1CollectedHeap::heap()), 3005 _worker_id(worker_id), _cm(cm), 3006 _objArray_processor(this), 3007 _claimed(false), 3008 _nextMarkBitMap(NULL), _hash_seed(17), 3009 _task_queue(task_queue), 3010 _task_queues(task_queues), 3011 _cm_oop_closure(NULL) { 3012 guarantee(task_queue != NULL, "invariant"); 3013 guarantee(task_queues != NULL, "invariant"); 3014 3015 _marking_step_diffs_ms.add(0.5); 3016 } 3017 3018 // These are formatting macros that are used below to ensure 3019 // consistent formatting. The *_H_* versions are used to format the 3020 // header for a particular value and they should be kept consistent 3021 // with the corresponding macro. Also note that most of the macros add 3022 // the necessary white space (as a prefix) which makes them a bit 3023 // easier to compose. 3024 3025 // All the output lines are prefixed with this string to be able to 3026 // identify them easily in a large log file. 3027 #define G1PPRL_LINE_PREFIX "###" 3028 3029 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT 3030 #ifdef _LP64 3031 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 3032 #else // _LP64 3033 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 3034 #endif // _LP64 3035 3036 // For per-region info 3037 #define G1PPRL_TYPE_FORMAT " %-4s" 3038 #define G1PPRL_TYPE_H_FORMAT " %4s" 3039 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9) 3040 #define G1PPRL_BYTE_H_FORMAT " %9s" 3041 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 3042 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 3043 3044 // For summary info 3045 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT 3046 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT 3047 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB" 3048 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%" 3049 3050 G1PrintRegionLivenessInfoClosure:: 3051 G1PrintRegionLivenessInfoClosure(const char* phase_name) 3052 : _total_used_bytes(0), _total_capacity_bytes(0), 3053 _total_prev_live_bytes(0), _total_next_live_bytes(0), 3054 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) { 3055 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 3056 MemRegion g1_reserved = g1h->g1_reserved(); 3057 double now = os::elapsedTime(); 3058 3059 // Print the header of the output. 3060 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 3061 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP" 3062 G1PPRL_SUM_ADDR_FORMAT("reserved") 3063 G1PPRL_SUM_BYTE_FORMAT("region-size"), 3064 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 3065 HeapRegion::GrainBytes); 3066 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3067 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3068 G1PPRL_TYPE_H_FORMAT 3069 G1PPRL_ADDR_BASE_H_FORMAT 3070 G1PPRL_BYTE_H_FORMAT 3071 G1PPRL_BYTE_H_FORMAT 3072 G1PPRL_BYTE_H_FORMAT 3073 G1PPRL_DOUBLE_H_FORMAT 3074 G1PPRL_BYTE_H_FORMAT 3075 G1PPRL_BYTE_H_FORMAT, 3076 "type", "address-range", 3077 "used", "prev-live", "next-live", "gc-eff", 3078 "remset", "code-roots"); 3079 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3080 G1PPRL_TYPE_H_FORMAT 3081 G1PPRL_ADDR_BASE_H_FORMAT 3082 G1PPRL_BYTE_H_FORMAT 3083 G1PPRL_BYTE_H_FORMAT 3084 G1PPRL_BYTE_H_FORMAT 3085 G1PPRL_DOUBLE_H_FORMAT 3086 G1PPRL_BYTE_H_FORMAT 3087 G1PPRL_BYTE_H_FORMAT, 3088 "", "", 3089 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 3090 "(bytes)", "(bytes)"); 3091 } 3092 3093 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) { 3094 const char* type = r->get_type_str(); 3095 HeapWord* bottom = r->bottom(); 3096 HeapWord* end = r->end(); 3097 size_t capacity_bytes = r->capacity(); 3098 size_t used_bytes = r->used(); 3099 size_t prev_live_bytes = r->live_bytes(); 3100 size_t next_live_bytes = r->next_live_bytes(); 3101 double gc_eff = r->gc_efficiency(); 3102 size_t remset_bytes = r->rem_set()->mem_size(); 3103 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 3104 3105 _total_used_bytes += used_bytes; 3106 _total_capacity_bytes += capacity_bytes; 3107 _total_prev_live_bytes += prev_live_bytes; 3108 _total_next_live_bytes += next_live_bytes; 3109 _total_remset_bytes += remset_bytes; 3110 _total_strong_code_roots_bytes += strong_code_roots_bytes; 3111 3112 // Print a line for this particular region. 3113 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3114 G1PPRL_TYPE_FORMAT 3115 G1PPRL_ADDR_BASE_FORMAT 3116 G1PPRL_BYTE_FORMAT 3117 G1PPRL_BYTE_FORMAT 3118 G1PPRL_BYTE_FORMAT 3119 G1PPRL_DOUBLE_FORMAT 3120 G1PPRL_BYTE_FORMAT 3121 G1PPRL_BYTE_FORMAT, 3122 type, p2i(bottom), p2i(end), 3123 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 3124 remset_bytes, strong_code_roots_bytes); 3125 3126 return false; 3127 } 3128 3129 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 3130 // add static memory usages to remembered set sizes 3131 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 3132 // Print the footer of the output. 3133 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3134 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3135 " SUMMARY" 3136 G1PPRL_SUM_MB_FORMAT("capacity") 3137 G1PPRL_SUM_MB_PERC_FORMAT("used") 3138 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 3139 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 3140 G1PPRL_SUM_MB_FORMAT("remset") 3141 G1PPRL_SUM_MB_FORMAT("code-roots"), 3142 bytes_to_mb(_total_capacity_bytes), 3143 bytes_to_mb(_total_used_bytes), 3144 perc(_total_used_bytes, _total_capacity_bytes), 3145 bytes_to_mb(_total_prev_live_bytes), 3146 perc(_total_prev_live_bytes, _total_capacity_bytes), 3147 bytes_to_mb(_total_next_live_bytes), 3148 perc(_total_next_live_bytes, _total_capacity_bytes), 3149 bytes_to_mb(_total_remset_bytes), 3150 bytes_to_mb(_total_strong_code_roots_bytes)); 3151 }