1 /* 2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/classLoaderDataGraph.hpp" 27 #include "code/codeCache.hpp" 28 #include "gc/g1/g1BarrierSet.hpp" 29 #include "gc/g1/g1CollectedHeap.inline.hpp" 30 #include "gc/g1/g1CollectorState.hpp" 31 #include "gc/g1/g1ConcurrentMark.inline.hpp" 32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp" 33 #include "gc/g1/g1HeapVerifier.hpp" 34 #include "gc/g1/g1OopClosures.inline.hpp" 35 #include "gc/g1/g1Policy.hpp" 36 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp" 37 #include "gc/g1/g1StringDedup.hpp" 38 #include "gc/g1/g1ThreadLocalData.hpp" 39 #include "gc/g1/heapRegion.inline.hpp" 40 #include "gc/g1/heapRegionRemSet.hpp" 41 #include "gc/g1/heapRegionSet.inline.hpp" 42 #include "gc/shared/adaptiveSizePolicy.hpp" 43 #include "gc/shared/gcId.hpp" 44 #include "gc/shared/gcTimer.hpp" 45 #include "gc/shared/gcTrace.hpp" 46 #include "gc/shared/gcTraceTime.inline.hpp" 47 #include "gc/shared/genOopClosures.inline.hpp" 48 #include "gc/shared/referencePolicy.hpp" 49 #include "gc/shared/strongRootsScope.hpp" 50 #include "gc/shared/suspendibleThreadSet.hpp" 51 #include "gc/shared/taskqueue.inline.hpp" 52 #include "gc/shared/vmGCOperations.hpp" 53 #include "gc/shared/weakProcessor.inline.hpp" 54 #include "include/jvm.h" 55 #include "logging/log.hpp" 56 #include "memory/allocation.hpp" 57 #include "memory/resourceArea.hpp" 58 #include "oops/access.inline.hpp" 59 #include "oops/oop.inline.hpp" 60 #include "runtime/atomic.hpp" 61 #include "runtime/handles.inline.hpp" 62 #include "runtime/java.hpp" 63 #include "runtime/prefetch.inline.hpp" 64 #include "services/memTracker.hpp" 65 #include "utilities/align.hpp" 66 #include "utilities/growableArray.hpp" 67 68 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) { 69 assert(addr < _cm->finger(), "invariant"); 70 assert(addr >= _task->finger(), "invariant"); 71 72 // We move that task's local finger along. 73 _task->move_finger_to(addr); 74 75 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr))); 76 // we only partially drain the local queue and global stack 77 _task->drain_local_queue(true); 78 _task->drain_global_stack(true); 79 80 // if the has_aborted flag has been raised, we need to bail out of 81 // the iteration 82 return !_task->has_aborted(); 83 } 84 85 G1CMMarkStack::G1CMMarkStack() : 86 _max_chunk_capacity(0), 87 _base(NULL), 88 _chunk_capacity(0) { 89 set_empty(); 90 } 91 92 bool G1CMMarkStack::resize(size_t new_capacity) { 93 assert(is_empty(), "Only resize when stack is empty."); 94 assert(new_capacity <= _max_chunk_capacity, 95 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity); 96 97 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC); 98 99 if (new_base == NULL) { 100 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)); 101 return false; 102 } 103 // Release old mapping. 104 if (_base != NULL) { 105 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 106 } 107 108 _base = new_base; 109 _chunk_capacity = new_capacity; 110 set_empty(); 111 112 return true; 113 } 114 115 size_t G1CMMarkStack::capacity_alignment() { 116 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry); 117 } 118 119 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) { 120 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized."); 121 122 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry); 123 124 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 125 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 126 127 guarantee(initial_chunk_capacity <= _max_chunk_capacity, 128 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT, 129 _max_chunk_capacity, 130 initial_chunk_capacity); 131 132 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT, 133 initial_chunk_capacity, _max_chunk_capacity); 134 135 return resize(initial_chunk_capacity); 136 } 137 138 void G1CMMarkStack::expand() { 139 if (_chunk_capacity == _max_chunk_capacity) { 140 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity); 141 return; 142 } 143 size_t old_capacity = _chunk_capacity; 144 // Double capacity if possible 145 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity); 146 147 if (resize(new_capacity)) { 148 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 149 old_capacity, new_capacity); 150 } else { 151 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 152 old_capacity, new_capacity); 153 } 154 } 155 156 G1CMMarkStack::~G1CMMarkStack() { 157 if (_base != NULL) { 158 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 159 } 160 } 161 162 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) { 163 elem->next = *list; 164 *list = elem; 165 } 166 167 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) { 168 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 169 add_chunk_to_list(&_chunk_list, elem); 170 _chunks_in_chunk_list++; 171 } 172 173 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) { 174 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 175 add_chunk_to_list(&_free_list, elem); 176 } 177 178 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) { 179 TaskQueueEntryChunk* result = *list; 180 if (result != NULL) { 181 *list = (*list)->next; 182 } 183 return result; 184 } 185 186 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() { 187 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 188 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list); 189 if (result != NULL) { 190 _chunks_in_chunk_list--; 191 } 192 return result; 193 } 194 195 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() { 196 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 197 return remove_chunk_from_list(&_free_list); 198 } 199 200 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() { 201 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code. 202 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding 203 // wraparound of _hwm. 204 if (_hwm >= _chunk_capacity) { 205 return NULL; 206 } 207 208 size_t cur_idx = Atomic::add(1u, &_hwm) - 1; 209 if (cur_idx >= _chunk_capacity) { 210 return NULL; 211 } 212 213 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk; 214 result->next = NULL; 215 return result; 216 } 217 218 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) { 219 // Get a new chunk. 220 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list(); 221 222 if (new_chunk == NULL) { 223 // Did not get a chunk from the free list. Allocate from backing memory. 224 new_chunk = allocate_new_chunk(); 225 226 if (new_chunk == NULL) { 227 return false; 228 } 229 } 230 231 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 232 233 add_chunk_to_chunk_list(new_chunk); 234 235 return true; 236 } 237 238 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) { 239 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list(); 240 241 if (cur == NULL) { 242 return false; 243 } 244 245 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 246 247 add_chunk_to_free_list(cur); 248 return true; 249 } 250 251 void G1CMMarkStack::set_empty() { 252 _chunks_in_chunk_list = 0; 253 _hwm = 0; 254 _chunk_list = NULL; 255 _free_list = NULL; 256 } 257 258 G1CMRootRegions::G1CMRootRegions() : 259 _survivors(NULL), _cm(NULL), _scan_in_progress(false), 260 _should_abort(false), _claimed_survivor_index(0) { } 261 262 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) { 263 _survivors = survivors; 264 _cm = cm; 265 } 266 267 void G1CMRootRegions::prepare_for_scan() { 268 assert(!scan_in_progress(), "pre-condition"); 269 270 // Currently, only survivors can be root regions. 271 _claimed_survivor_index = 0; 272 _scan_in_progress = _survivors->regions()->is_nonempty(); 273 _should_abort = false; 274 } 275 276 HeapRegion* G1CMRootRegions::claim_next() { 277 if (_should_abort) { 278 // If someone has set the should_abort flag, we return NULL to 279 // force the caller to bail out of their loop. 280 return NULL; 281 } 282 283 // Currently, only survivors can be root regions. 284 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions(); 285 286 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1; 287 if (claimed_index < survivor_regions->length()) { 288 return survivor_regions->at(claimed_index); 289 } 290 return NULL; 291 } 292 293 uint G1CMRootRegions::num_root_regions() const { 294 return (uint)_survivors->regions()->length(); 295 } 296 297 void G1CMRootRegions::notify_scan_done() { 298 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 299 _scan_in_progress = false; 300 RootRegionScan_lock->notify_all(); 301 } 302 303 void G1CMRootRegions::cancel_scan() { 304 notify_scan_done(); 305 } 306 307 void G1CMRootRegions::scan_finished() { 308 assert(scan_in_progress(), "pre-condition"); 309 310 // Currently, only survivors can be root regions. 311 if (!_should_abort) { 312 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index); 313 assert((uint)_claimed_survivor_index >= _survivors->length(), 314 "we should have claimed all survivors, claimed index = %u, length = %u", 315 (uint)_claimed_survivor_index, _survivors->length()); 316 } 317 318 notify_scan_done(); 319 } 320 321 bool G1CMRootRegions::wait_until_scan_finished() { 322 if (!scan_in_progress()) { 323 return false; 324 } 325 326 { 327 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 328 while (scan_in_progress()) { 329 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag); 330 } 331 } 332 return true; 333 } 334 335 // Returns the maximum number of workers to be used in a concurrent 336 // phase based on the number of GC workers being used in a STW 337 // phase. 338 static uint scale_concurrent_worker_threads(uint num_gc_workers) { 339 return MAX2((num_gc_workers + 2) / 4, 1U); 340 } 341 342 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, 343 G1RegionToSpaceMapper* prev_bitmap_storage, 344 G1RegionToSpaceMapper* next_bitmap_storage) : 345 // _cm_thread set inside the constructor 346 _g1h(g1h), 347 _completed_initialization(false), 348 349 _mark_bitmap_1(), 350 _mark_bitmap_2(), 351 _prev_mark_bitmap(&_mark_bitmap_1), 352 _next_mark_bitmap(&_mark_bitmap_2), 353 354 _heap(_g1h->reserved_region()), 355 356 _root_regions(), 357 358 _global_mark_stack(), 359 360 // _finger set in set_non_marking_state 361 362 _worker_id_offset(DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads), 363 _max_num_tasks(ParallelGCThreads), 364 // _num_active_tasks set in set_non_marking_state() 365 // _tasks set inside the constructor 366 367 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)), 368 _terminator(ParallelTaskTerminator((int) _max_num_tasks, _task_queues)), 369 370 _first_overflow_barrier_sync(), 371 _second_overflow_barrier_sync(), 372 373 _has_overflown(false), 374 _concurrent(false), 375 _has_aborted(false), 376 _restart_for_overflow(false), 377 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 378 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()), 379 380 // _verbose_level set below 381 382 _init_times(), 383 _remark_times(), 384 _remark_mark_times(), 385 _remark_weak_ref_times(), 386 _cleanup_times(), 387 _total_cleanup_time(0.0), 388 389 _accum_task_vtime(NULL), 390 391 _concurrent_workers(NULL), 392 _num_concurrent_workers(0), 393 _max_concurrent_workers(0), 394 395 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)), 396 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC)) 397 { 398 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage); 399 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage); 400 401 // Create & start ConcurrentMark thread. 402 _cm_thread = new G1ConcurrentMarkThread(this); 403 if (_cm_thread->osthread() == NULL) { 404 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 405 } 406 407 assert(CGC_lock != NULL, "CGC_lock must be initialized"); 408 409 SATBMarkQueueSet& satb_qs = G1BarrierSet::satb_mark_queue_set(); 410 satb_qs.set_buffer_size(G1SATBBufferSize); 411 412 _root_regions.init(_g1h->survivor(), this); 413 414 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) { 415 // Calculate the number of concurrent worker threads by scaling 416 // the number of parallel GC threads. 417 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads); 418 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num); 419 } 420 421 assert(ConcGCThreads > 0, "ConcGCThreads have been set."); 422 if (ConcGCThreads > ParallelGCThreads) { 423 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).", 424 ConcGCThreads, ParallelGCThreads); 425 return; 426 } 427 428 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset); 429 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads); 430 431 _num_concurrent_workers = ConcGCThreads; 432 _max_concurrent_workers = _num_concurrent_workers; 433 434 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true); 435 _concurrent_workers->initialize_workers(); 436 437 if (FLAG_IS_DEFAULT(MarkStackSize)) { 438 size_t mark_stack_size = 439 MIN2(MarkStackSizeMax, 440 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE))); 441 // Verify that the calculated value for MarkStackSize is in range. 442 // It would be nice to use the private utility routine from Arguments. 443 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 444 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 445 "must be between 1 and " SIZE_FORMAT, 446 mark_stack_size, MarkStackSizeMax); 447 return; 448 } 449 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size); 450 } else { 451 // Verify MarkStackSize is in range. 452 if (FLAG_IS_CMDLINE(MarkStackSize)) { 453 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 454 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 455 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 456 "must be between 1 and " SIZE_FORMAT, 457 MarkStackSize, MarkStackSizeMax); 458 return; 459 } 460 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 461 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 462 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 463 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 464 MarkStackSize, MarkStackSizeMax); 465 return; 466 } 467 } 468 } 469 } 470 471 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) { 472 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack."); 473 } 474 475 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC); 476 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC); 477 478 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 479 _num_active_tasks = _max_num_tasks; 480 481 for (uint i = 0; i < _max_num_tasks; ++i) { 482 G1CMTaskQueue* task_queue = new G1CMTaskQueue(); 483 task_queue->initialize(); 484 _task_queues->register_queue(i, task_queue); 485 486 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions()); 487 488 _accum_task_vtime[i] = 0.0; 489 } 490 491 reset_at_marking_complete(); 492 _completed_initialization = true; 493 } 494 495 void G1ConcurrentMark::reset() { 496 _has_aborted = false; 497 498 reset_marking_for_restart(); 499 500 // Reset all tasks, since different phases will use different number of active 501 // threads. So, it's easiest to have all of them ready. 502 for (uint i = 0; i < _max_num_tasks; ++i) { 503 _tasks[i]->reset(_next_mark_bitmap); 504 } 505 506 uint max_regions = _g1h->max_regions(); 507 for (uint i = 0; i < max_regions; i++) { 508 _top_at_rebuild_starts[i] = NULL; 509 _region_mark_stats[i].clear(); 510 } 511 } 512 513 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) { 514 for (uint j = 0; j < _max_num_tasks; ++j) { 515 _tasks[j]->clear_mark_stats_cache(region_idx); 516 } 517 _top_at_rebuild_starts[region_idx] = NULL; 518 _region_mark_stats[region_idx].clear(); 519 } 520 521 void G1ConcurrentMark::clear_statistics(HeapRegion* r) { 522 uint const region_idx = r->hrm_index(); 523 if (r->is_humongous()) { 524 assert(r->is_starts_humongous(), "Got humongous continues region here"); 525 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size()); 526 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) { 527 clear_statistics_in_region(j); 528 } 529 } else { 530 clear_statistics_in_region(region_idx); 531 } 532 } 533 534 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) { 535 if (bitmap->is_marked(addr)) { 536 bitmap->clear(addr); 537 } 538 } 539 540 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) { 541 assert_at_safepoint_on_vm_thread(); 542 543 // Need to clear all mark bits of the humongous object. 544 clear_mark_if_set(_prev_mark_bitmap, r->bottom()); 545 clear_mark_if_set(_next_mark_bitmap, r->bottom()); 546 547 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) { 548 return; 549 } 550 551 // Clear any statistics about the region gathered so far. 552 clear_statistics(r); 553 } 554 555 void G1ConcurrentMark::reset_marking_for_restart() { 556 _global_mark_stack.set_empty(); 557 558 // Expand the marking stack, if we have to and if we can. 559 if (has_overflown()) { 560 _global_mark_stack.expand(); 561 562 uint max_regions = _g1h->max_regions(); 563 for (uint i = 0; i < max_regions; i++) { 564 _region_mark_stats[i].clear_during_overflow(); 565 } 566 } 567 568 clear_has_overflown(); 569 _finger = _heap.start(); 570 571 for (uint i = 0; i < _max_num_tasks; ++i) { 572 G1CMTaskQueue* queue = _task_queues->queue(i); 573 queue->set_empty(); 574 } 575 } 576 577 void G1ConcurrentMark::set_concurrency(uint active_tasks) { 578 assert(active_tasks <= _max_num_tasks, "we should not have more"); 579 580 _num_active_tasks = active_tasks; 581 // Need to update the three data structures below according to the 582 // number of active threads for this phase. 583 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues); 584 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 585 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 586 } 587 588 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 589 set_concurrency(active_tasks); 590 591 _concurrent = concurrent; 592 593 if (!concurrent) { 594 // At this point we should be in a STW phase, and completed marking. 595 assert_at_safepoint_on_vm_thread(); 596 assert(out_of_regions(), 597 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT, 598 p2i(_finger), p2i(_heap.end())); 599 } 600 } 601 602 void G1ConcurrentMark::reset_at_marking_complete() { 603 // We set the global marking state to some default values when we're 604 // not doing marking. 605 reset_marking_for_restart(); 606 _num_active_tasks = 0; 607 } 608 609 G1ConcurrentMark::~G1ConcurrentMark() { 610 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts); 611 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats); 612 // The G1ConcurrentMark instance is never freed. 613 ShouldNotReachHere(); 614 } 615 616 class G1ClearBitMapTask : public AbstractGangTask { 617 public: 618 static size_t chunk_size() { return M; } 619 620 private: 621 // Heap region closure used for clearing the given mark bitmap. 622 class G1ClearBitmapHRClosure : public HeapRegionClosure { 623 private: 624 G1CMBitMap* _bitmap; 625 G1ConcurrentMark* _cm; 626 public: 627 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) { 628 } 629 630 virtual bool do_heap_region(HeapRegion* r) { 631 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize; 632 633 HeapWord* cur = r->bottom(); 634 HeapWord* const end = r->end(); 635 636 while (cur < end) { 637 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 638 _bitmap->clear_range(mr); 639 640 cur += chunk_size_in_words; 641 642 // Abort iteration if after yielding the marking has been aborted. 643 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) { 644 return true; 645 } 646 // Repeat the asserts from before the start of the closure. We will do them 647 // as asserts here to minimize their overhead on the product. However, we 648 // will have them as guarantees at the beginning / end of the bitmap 649 // clearing to get some checking in the product. 650 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant"); 651 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 652 } 653 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index()); 654 655 return false; 656 } 657 }; 658 659 G1ClearBitmapHRClosure _cl; 660 HeapRegionClaimer _hr_claimer; 661 bool _suspendible; // If the task is suspendible, workers must join the STS. 662 663 public: 664 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) : 665 AbstractGangTask("G1 Clear Bitmap"), 666 _cl(bitmap, suspendible ? cm : NULL), 667 _hr_claimer(n_workers), 668 _suspendible(suspendible) 669 { } 670 671 void work(uint worker_id) { 672 SuspendibleThreadSetJoiner sts_join(_suspendible); 673 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id); 674 } 675 676 bool is_complete() { 677 return _cl.is_complete(); 678 } 679 }; 680 681 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) { 682 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint."); 683 684 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor(); 685 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size(); 686 687 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); 688 689 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield); 690 691 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks); 692 workers->run_task(&cl, num_workers); 693 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding."); 694 } 695 696 void G1ConcurrentMark::cleanup_for_next_mark() { 697 // Make sure that the concurrent mark thread looks to still be in 698 // the current cycle. 699 guarantee(cm_thread()->during_cycle(), "invariant"); 700 701 // We are finishing up the current cycle by clearing the next 702 // marking bitmap and getting it ready for the next cycle. During 703 // this time no other cycle can start. So, let's make sure that this 704 // is the case. 705 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 706 707 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true); 708 709 // Repeat the asserts from above. 710 guarantee(cm_thread()->during_cycle(), "invariant"); 711 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 712 } 713 714 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) { 715 assert_at_safepoint_on_vm_thread(); 716 clear_bitmap(_prev_mark_bitmap, workers, false); 717 } 718 719 class NoteStartOfMarkHRClosure : public HeapRegionClosure { 720 public: 721 bool do_heap_region(HeapRegion* r) { 722 r->note_start_of_marking(); 723 return false; 724 } 725 }; 726 727 void G1ConcurrentMark::pre_initial_mark() { 728 // Initialize marking structures. This has to be done in a STW phase. 729 reset(); 730 731 // For each region note start of marking. 732 NoteStartOfMarkHRClosure startcl; 733 _g1h->heap_region_iterate(&startcl); 734 } 735 736 737 void G1ConcurrentMark::post_initial_mark() { 738 // Start Concurrent Marking weak-reference discovery. 739 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 740 // enable ("weak") refs discovery 741 rp->enable_discovery(); 742 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 743 744 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 745 // This is the start of the marking cycle, we're expected all 746 // threads to have SATB queues with active set to false. 747 satb_mq_set.set_active_all_threads(true, /* new active value */ 748 false /* expected_active */); 749 750 _root_regions.prepare_for_scan(); 751 752 // update_g1_committed() will be called at the end of an evac pause 753 // when marking is on. So, it's also called at the end of the 754 // initial-mark pause to update the heap end, if the heap expands 755 // during it. No need to call it here. 756 } 757 758 /* 759 * Notice that in the next two methods, we actually leave the STS 760 * during the barrier sync and join it immediately afterwards. If we 761 * do not do this, the following deadlock can occur: one thread could 762 * be in the barrier sync code, waiting for the other thread to also 763 * sync up, whereas another one could be trying to yield, while also 764 * waiting for the other threads to sync up too. 765 * 766 * Note, however, that this code is also used during remark and in 767 * this case we should not attempt to leave / enter the STS, otherwise 768 * we'll either hit an assert (debug / fastdebug) or deadlock 769 * (product). So we should only leave / enter the STS if we are 770 * operating concurrently. 771 * 772 * Because the thread that does the sync barrier has left the STS, it 773 * is possible to be suspended for a Full GC or an evacuation pause 774 * could occur. This is actually safe, since the entering the sync 775 * barrier is one of the last things do_marking_step() does, and it 776 * doesn't manipulate any data structures afterwards. 777 */ 778 779 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 780 bool barrier_aborted; 781 { 782 SuspendibleThreadSetLeaver sts_leave(concurrent()); 783 barrier_aborted = !_first_overflow_barrier_sync.enter(); 784 } 785 786 // at this point everyone should have synced up and not be doing any 787 // more work 788 789 if (barrier_aborted) { 790 // If the barrier aborted we ignore the overflow condition and 791 // just abort the whole marking phase as quickly as possible. 792 return; 793 } 794 } 795 796 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 797 SuspendibleThreadSetLeaver sts_leave(concurrent()); 798 _second_overflow_barrier_sync.enter(); 799 800 // at this point everything should be re-initialized and ready to go 801 } 802 803 class G1CMConcurrentMarkingTask : public AbstractGangTask { 804 G1ConcurrentMark* _cm; 805 806 public: 807 void work(uint worker_id) { 808 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread"); 809 ResourceMark rm; 810 811 double start_vtime = os::elapsedVTime(); 812 813 { 814 SuspendibleThreadSetJoiner sts_join; 815 816 assert(worker_id < _cm->active_tasks(), "invariant"); 817 818 G1CMTask* task = _cm->task(worker_id); 819 task->record_start_time(); 820 if (!_cm->has_aborted()) { 821 do { 822 task->do_marking_step(G1ConcMarkStepDurationMillis, 823 true /* do_termination */, 824 false /* is_serial*/); 825 826 _cm->do_yield_check(); 827 } while (!_cm->has_aborted() && task->has_aborted()); 828 } 829 task->record_end_time(); 830 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant"); 831 } 832 833 double end_vtime = os::elapsedVTime(); 834 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 835 } 836 837 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) : 838 AbstractGangTask("Concurrent Mark"), _cm(cm) { } 839 840 ~G1CMConcurrentMarkingTask() { } 841 }; 842 843 uint G1ConcurrentMark::calc_active_marking_workers() { 844 uint result = 0; 845 if (!UseDynamicNumberOfGCThreads || 846 (!FLAG_IS_DEFAULT(ConcGCThreads) && 847 !ForceDynamicNumberOfGCThreads)) { 848 result = _max_concurrent_workers; 849 } else { 850 result = 851 AdaptiveSizePolicy::calc_default_active_workers(_max_concurrent_workers, 852 1, /* Minimum workers */ 853 _num_concurrent_workers, 854 Threads::number_of_non_daemon_threads()); 855 // Don't scale the result down by scale_concurrent_workers() because 856 // that scaling has already gone into "_max_concurrent_workers". 857 } 858 assert(result > 0 && result <= _max_concurrent_workers, 859 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u", 860 _max_concurrent_workers, result); 861 return result; 862 } 863 864 void G1ConcurrentMark::scan_root_region(HeapRegion* hr, uint worker_id) { 865 // Currently, only survivors can be root regions. 866 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant"); 867 G1RootRegionScanClosure cl(_g1h, this, worker_id); 868 869 const uintx interval = PrefetchScanIntervalInBytes; 870 HeapWord* curr = hr->bottom(); 871 const HeapWord* end = hr->top(); 872 while (curr < end) { 873 Prefetch::read(curr, interval); 874 oop obj = oop(curr); 875 int size = obj->oop_iterate_size(&cl); 876 assert(size == obj->size(), "sanity"); 877 curr += size; 878 } 879 } 880 881 class G1CMRootRegionScanTask : public AbstractGangTask { 882 G1ConcurrentMark* _cm; 883 public: 884 G1CMRootRegionScanTask(G1ConcurrentMark* cm) : 885 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { } 886 887 void work(uint worker_id) { 888 assert(Thread::current()->is_ConcurrentGC_thread(), 889 "this should only be done by a conc GC thread"); 890 891 G1CMRootRegions* root_regions = _cm->root_regions(); 892 HeapRegion* hr = root_regions->claim_next(); 893 while (hr != NULL) { 894 _cm->scan_root_region(hr, worker_id); 895 hr = root_regions->claim_next(); 896 } 897 } 898 }; 899 900 void G1ConcurrentMark::scan_root_regions() { 901 // scan_in_progress() will have been set to true only if there was 902 // at least one root region to scan. So, if it's false, we 903 // should not attempt to do any further work. 904 if (root_regions()->scan_in_progress()) { 905 assert(!has_aborted(), "Aborting before root region scanning is finished not supported."); 906 907 _num_concurrent_workers = MIN2(calc_active_marking_workers(), 908 // We distribute work on a per-region basis, so starting 909 // more threads than that is useless. 910 root_regions()->num_root_regions()); 911 assert(_num_concurrent_workers <= _max_concurrent_workers, 912 "Maximum number of marking threads exceeded"); 913 914 G1CMRootRegionScanTask task(this); 915 log_debug(gc, ergo)("Running %s using %u workers for %u work units.", 916 task.name(), _num_concurrent_workers, root_regions()->num_root_regions()); 917 _concurrent_workers->run_task(&task, _num_concurrent_workers); 918 919 // It's possible that has_aborted() is true here without actually 920 // aborting the survivor scan earlier. This is OK as it's 921 // mainly used for sanity checking. 922 root_regions()->scan_finished(); 923 } 924 } 925 926 void G1ConcurrentMark::concurrent_cycle_start() { 927 _gc_timer_cm->register_gc_start(); 928 929 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start()); 930 931 _g1h->trace_heap_before_gc(_gc_tracer_cm); 932 } 933 934 void G1ConcurrentMark::concurrent_cycle_end() { 935 _g1h->collector_state()->set_clearing_next_bitmap(false); 936 937 _g1h->trace_heap_after_gc(_gc_tracer_cm); 938 939 if (has_aborted()) { 940 log_info(gc, marking)("Concurrent Mark Abort"); 941 _gc_tracer_cm->report_concurrent_mode_failure(); 942 } 943 944 _gc_timer_cm->register_gc_end(); 945 946 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 947 } 948 949 void G1ConcurrentMark::mark_from_roots() { 950 _restart_for_overflow = false; 951 952 _num_concurrent_workers = calc_active_marking_workers(); 953 954 uint active_workers = MAX2(1U, _num_concurrent_workers); 955 956 // Setting active workers is not guaranteed since fewer 957 // worker threads may currently exist and more may not be 958 // available. 959 active_workers = _concurrent_workers->update_active_workers(active_workers); 960 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers()); 961 962 // Parallel task terminator is set in "set_concurrency_and_phase()" 963 set_concurrency_and_phase(active_workers, true /* concurrent */); 964 965 G1CMConcurrentMarkingTask marking_task(this); 966 _concurrent_workers->run_task(&marking_task); 967 print_stats(); 968 } 969 970 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) { 971 G1HeapVerifier* verifier = _g1h->verifier(); 972 973 verifier->verify_region_sets_optional(); 974 975 if (VerifyDuringGC) { 976 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm); 977 978 size_t const BufLen = 512; 979 char buffer[BufLen]; 980 981 jio_snprintf(buffer, BufLen, "During GC (%s)", caller); 982 verifier->verify(type, vo, buffer); 983 } 984 985 verifier->check_bitmaps(caller); 986 } 987 988 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask { 989 G1CollectedHeap* _g1h; 990 G1ConcurrentMark* _cm; 991 HeapRegionClaimer _hrclaimer; 992 uint volatile _total_selected_for_rebuild; 993 994 G1PrintRegionLivenessInfoClosure _cl; 995 996 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure { 997 G1CollectedHeap* _g1h; 998 G1ConcurrentMark* _cm; 999 1000 G1PrintRegionLivenessInfoClosure* _cl; 1001 1002 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild. 1003 1004 void update_remset_before_rebuild(HeapRegion* hr) { 1005 G1RemSetTrackingPolicy* tracking_policy = _g1h->g1_policy()->remset_tracker(); 1006 1007 bool selected_for_rebuild; 1008 if (hr->is_humongous()) { 1009 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0; 1010 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live); 1011 } else { 1012 size_t const live_bytes = _cm->liveness(hr->hrm_index()); 1013 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes); 1014 } 1015 if (selected_for_rebuild) { 1016 _num_regions_selected_for_rebuild++; 1017 } 1018 _cm->update_top_at_rebuild_start(hr); 1019 } 1020 1021 // Distribute the given words across the humongous object starting with hr and 1022 // note end of marking. 1023 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) { 1024 uint const region_idx = hr->hrm_index(); 1025 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size(); 1026 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words); 1027 1028 // "Distributing" zero words means that we only note end of marking for these 1029 // regions. 1030 assert(marked_words == 0 || obj_size_in_words == marked_words, 1031 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT, 1032 obj_size_in_words, marked_words); 1033 1034 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) { 1035 HeapRegion* const r = _g1h->region_at(i); 1036 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words); 1037 1038 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)", 1039 words_to_add, i, r->get_type_str()); 1040 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize); 1041 marked_words -= words_to_add; 1042 } 1043 assert(marked_words == 0, 1044 SIZE_FORMAT " words left after distributing space across %u regions", 1045 marked_words, num_regions_in_humongous); 1046 } 1047 1048 void update_marked_bytes(HeapRegion* hr) { 1049 uint const region_idx = hr->hrm_index(); 1050 size_t const marked_words = _cm->liveness(region_idx); 1051 // The marking attributes the object's size completely to the humongous starts 1052 // region. We need to distribute this value across the entire set of regions a 1053 // humongous object spans. 1054 if (hr->is_humongous()) { 1055 assert(hr->is_starts_humongous() || marked_words == 0, 1056 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)", 1057 marked_words, region_idx, hr->get_type_str()); 1058 if (hr->is_starts_humongous()) { 1059 distribute_marked_bytes(hr, marked_words); 1060 } 1061 } else { 1062 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str()); 1063 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize); 1064 } 1065 } 1066 1067 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) { 1068 hr->add_to_marked_bytes(marked_bytes); 1069 _cl->do_heap_region(hr); 1070 hr->note_end_of_marking(); 1071 } 1072 1073 public: 1074 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) : 1075 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { } 1076 1077 virtual bool do_heap_region(HeapRegion* r) { 1078 update_remset_before_rebuild(r); 1079 update_marked_bytes(r); 1080 1081 return false; 1082 } 1083 1084 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; } 1085 }; 1086 1087 public: 1088 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) : 1089 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"), 1090 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { } 1091 1092 virtual void work(uint worker_id) { 1093 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl); 1094 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id); 1095 Atomic::add(update_cl.num_selected_for_rebuild(), &_total_selected_for_rebuild); 1096 } 1097 1098 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; } 1099 1100 // Number of regions for which roughly one thread should be spawned for this work. 1101 static const uint RegionsPerThread = 384; 1102 }; 1103 1104 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure { 1105 G1CollectedHeap* _g1h; 1106 public: 1107 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { } 1108 1109 virtual bool do_heap_region(HeapRegion* r) { 1110 _g1h->g1_policy()->remset_tracker()->update_after_rebuild(r); 1111 return false; 1112 } 1113 }; 1114 1115 void G1ConcurrentMark::remark() { 1116 assert_at_safepoint_on_vm_thread(); 1117 1118 // If a full collection has happened, we should not continue. However we might 1119 // have ended up here as the Remark VM operation has been scheduled already. 1120 if (has_aborted()) { 1121 return; 1122 } 1123 1124 G1Policy* g1p = _g1h->g1_policy(); 1125 g1p->record_concurrent_mark_remark_start(); 1126 1127 double start = os::elapsedTime(); 1128 1129 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before"); 1130 1131 { 1132 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm); 1133 finalize_marking(); 1134 } 1135 1136 double mark_work_end = os::elapsedTime(); 1137 1138 bool const mark_finished = !has_overflown(); 1139 if (mark_finished) { 1140 weak_refs_work(false /* clear_all_soft_refs */); 1141 1142 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 1143 // We're done with marking. 1144 // This is the end of the marking cycle, we're expected all 1145 // threads to have SATB queues with active set to true. 1146 satb_mq_set.set_active_all_threads(false, /* new active value */ 1147 true /* expected_active */); 1148 1149 { 1150 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm); 1151 flush_all_task_caches(); 1152 } 1153 1154 // Install newly created mark bitmap as "prev". 1155 swap_mark_bitmaps(); 1156 { 1157 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm); 1158 1159 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) / 1160 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread; 1161 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity); 1162 1163 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers); 1164 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions()); 1165 _g1h->workers()->run_task(&cl, num_workers); 1166 1167 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u", 1168 _g1h->num_regions(), cl.total_selected_for_rebuild()); 1169 } 1170 { 1171 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm); 1172 reclaim_empty_regions(); 1173 } 1174 1175 // Clean out dead classes 1176 if (ClassUnloadingWithConcurrentMark) { 1177 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm); 1178 ClassLoaderDataGraph::purge(); 1179 } 1180 1181 _g1h->resize_heap_if_necessary(); 1182 1183 compute_new_sizes(); 1184 1185 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after"); 1186 1187 assert(!restart_for_overflow(), "sanity"); 1188 // Completely reset the marking state since marking completed 1189 reset_at_marking_complete(); 1190 } else { 1191 // We overflowed. Restart concurrent marking. 1192 _restart_for_overflow = true; 1193 1194 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow"); 1195 1196 // Clear the marking state because we will be restarting 1197 // marking due to overflowing the global mark stack. 1198 reset_marking_for_restart(); 1199 } 1200 1201 { 1202 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm); 1203 report_object_count(mark_finished); 1204 } 1205 1206 // Statistics 1207 double now = os::elapsedTime(); 1208 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1209 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1210 _remark_times.add((now - start) * 1000.0); 1211 1212 g1p->record_concurrent_mark_remark_end(); 1213 } 1214 1215 class G1ReclaimEmptyRegionsTask : public AbstractGangTask { 1216 // Per-region work during the Cleanup pause. 1217 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure { 1218 G1CollectedHeap* _g1h; 1219 size_t _freed_bytes; 1220 FreeRegionList* _local_cleanup_list; 1221 uint _old_regions_removed; 1222 uint _humongous_regions_removed; 1223 HRRSCleanupTask* _hrrs_cleanup_task; 1224 1225 public: 1226 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h, 1227 FreeRegionList* local_cleanup_list, 1228 HRRSCleanupTask* hrrs_cleanup_task) : 1229 _g1h(g1h), 1230 _freed_bytes(0), 1231 _local_cleanup_list(local_cleanup_list), 1232 _old_regions_removed(0), 1233 _humongous_regions_removed(0), 1234 _hrrs_cleanup_task(hrrs_cleanup_task) { } 1235 1236 size_t freed_bytes() { return _freed_bytes; } 1237 const uint old_regions_removed() { return _old_regions_removed; } 1238 const uint humongous_regions_removed() { return _humongous_regions_removed; } 1239 1240 bool do_heap_region(HeapRegion *hr) { 1241 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) { 1242 _freed_bytes += hr->used(); 1243 hr->set_containing_set(NULL); 1244 if (hr->is_humongous()) { 1245 _humongous_regions_removed++; 1246 _g1h->free_humongous_region(hr, _local_cleanup_list); 1247 } else { 1248 _old_regions_removed++; 1249 _g1h->free_region(hr, _local_cleanup_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */); 1250 } 1251 hr->clear_cardtable(); 1252 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index()); 1253 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom())); 1254 } else { 1255 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task); 1256 } 1257 1258 return false; 1259 } 1260 }; 1261 1262 G1CollectedHeap* _g1h; 1263 FreeRegionList* _cleanup_list; 1264 HeapRegionClaimer _hrclaimer; 1265 1266 public: 1267 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1268 AbstractGangTask("G1 Cleanup"), 1269 _g1h(g1h), 1270 _cleanup_list(cleanup_list), 1271 _hrclaimer(n_workers) { 1272 1273 HeapRegionRemSet::reset_for_cleanup_tasks(); 1274 } 1275 1276 void work(uint worker_id) { 1277 FreeRegionList local_cleanup_list("Local Cleanup List"); 1278 HRRSCleanupTask hrrs_cleanup_task; 1279 G1ReclaimEmptyRegionsClosure cl(_g1h, 1280 &local_cleanup_list, 1281 &hrrs_cleanup_task); 1282 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id); 1283 assert(cl.is_complete(), "Shouldn't have aborted!"); 1284 1285 // Now update the old/humongous region sets 1286 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed()); 1287 { 1288 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1289 _g1h->decrement_summary_bytes(cl.freed_bytes()); 1290 1291 _cleanup_list->add_ordered(&local_cleanup_list); 1292 assert(local_cleanup_list.is_empty(), "post-condition"); 1293 1294 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task); 1295 } 1296 } 1297 }; 1298 1299 void G1ConcurrentMark::reclaim_empty_regions() { 1300 WorkGang* workers = _g1h->workers(); 1301 FreeRegionList empty_regions_list("Empty Regions After Mark List"); 1302 1303 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers()); 1304 workers->run_task(&cl); 1305 1306 if (!empty_regions_list.is_empty()) { 1307 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length()); 1308 // Now print the empty regions list. 1309 G1HRPrinter* hrp = _g1h->hr_printer(); 1310 if (hrp->is_active()) { 1311 FreeRegionListIterator iter(&empty_regions_list); 1312 while (iter.more_available()) { 1313 HeapRegion* hr = iter.get_next(); 1314 hrp->cleanup(hr); 1315 } 1316 } 1317 // And actually make them available. 1318 _g1h->prepend_to_freelist(&empty_regions_list); 1319 } 1320 } 1321 1322 void G1ConcurrentMark::compute_new_sizes() { 1323 MetaspaceGC::compute_new_size(); 1324 1325 // Cleanup will have freed any regions completely full of garbage. 1326 // Update the soft reference policy with the new heap occupancy. 1327 Universe::update_heap_info_at_gc(); 1328 1329 // We reclaimed old regions so we should calculate the sizes to make 1330 // sure we update the old gen/space data. 1331 _g1h->g1mm()->update_sizes(); 1332 } 1333 1334 void G1ConcurrentMark::cleanup() { 1335 assert_at_safepoint_on_vm_thread(); 1336 1337 // If a full collection has happened, we shouldn't do this. 1338 if (has_aborted()) { 1339 return; 1340 } 1341 1342 G1Policy* g1p = _g1h->g1_policy(); 1343 g1p->record_concurrent_mark_cleanup_start(); 1344 1345 double start = os::elapsedTime(); 1346 1347 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before"); 1348 1349 { 1350 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm); 1351 G1UpdateRemSetTrackingAfterRebuild cl(_g1h); 1352 _g1h->heap_region_iterate(&cl); 1353 } 1354 1355 if (log_is_enabled(Trace, gc, liveness)) { 1356 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup"); 1357 _g1h->heap_region_iterate(&cl); 1358 } 1359 1360 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after"); 1361 1362 // We need to make this be a "collection" so any collection pause that 1363 // races with it goes around and waits for Cleanup to finish. 1364 _g1h->increment_total_collections(); 1365 1366 // Local statistics 1367 double recent_cleanup_time = (os::elapsedTime() - start); 1368 _total_cleanup_time += recent_cleanup_time; 1369 _cleanup_times.add(recent_cleanup_time); 1370 1371 { 1372 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm); 1373 _g1h->g1_policy()->record_concurrent_mark_cleanup_end(); 1374 } 1375 } 1376 1377 // 'Keep Alive' oop closure used by both serial parallel reference processing. 1378 // Uses the G1CMTask associated with a worker thread (for serial reference 1379 // processing the G1CMTask for worker 0 is used) to preserve (mark) and 1380 // trace referent objects. 1381 // 1382 // Using the G1CMTask and embedded local queues avoids having the worker 1383 // threads operating on the global mark stack. This reduces the risk 1384 // of overflowing the stack - which we would rather avoid at this late 1385 // state. Also using the tasks' local queues removes the potential 1386 // of the workers interfering with each other that could occur if 1387 // operating on the global stack. 1388 1389 class G1CMKeepAliveAndDrainClosure : public OopClosure { 1390 G1ConcurrentMark* _cm; 1391 G1CMTask* _task; 1392 uint _ref_counter_limit; 1393 uint _ref_counter; 1394 bool _is_serial; 1395 public: 1396 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1397 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval), 1398 _ref_counter(_ref_counter_limit), _is_serial(is_serial) { 1399 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1400 } 1401 1402 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 1403 virtual void do_oop( oop* p) { do_oop_work(p); } 1404 1405 template <class T> void do_oop_work(T* p) { 1406 if (_cm->has_overflown()) { 1407 return; 1408 } 1409 if (!_task->deal_with_reference(p)) { 1410 // We did not add anything to the mark bitmap (or mark stack), so there is 1411 // no point trying to drain it. 1412 return; 1413 } 1414 _ref_counter--; 1415 1416 if (_ref_counter == 0) { 1417 // We have dealt with _ref_counter_limit references, pushing them 1418 // and objects reachable from them on to the local stack (and 1419 // possibly the global stack). Call G1CMTask::do_marking_step() to 1420 // process these entries. 1421 // 1422 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if 1423 // there's nothing more to do (i.e. we're done with the entries that 1424 // were pushed as a result of the G1CMTask::deal_with_reference() calls 1425 // above) or we overflow. 1426 // 1427 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1428 // flag while there may still be some work to do. (See the comment at 1429 // the beginning of G1CMTask::do_marking_step() for those conditions - 1430 // one of which is reaching the specified time target.) It is only 1431 // when G1CMTask::do_marking_step() returns without setting the 1432 // has_aborted() flag that the marking step has completed. 1433 do { 1434 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1435 _task->do_marking_step(mark_step_duration_ms, 1436 false /* do_termination */, 1437 _is_serial); 1438 } while (_task->has_aborted() && !_cm->has_overflown()); 1439 _ref_counter = _ref_counter_limit; 1440 } 1441 } 1442 }; 1443 1444 // 'Drain' oop closure used by both serial and parallel reference processing. 1445 // Uses the G1CMTask associated with a given worker thread (for serial 1446 // reference processing the G1CMtask for worker 0 is used). Calls the 1447 // do_marking_step routine, with an unbelievably large timeout value, 1448 // to drain the marking data structures of the remaining entries 1449 // added by the 'keep alive' oop closure above. 1450 1451 class G1CMDrainMarkingStackClosure : public VoidClosure { 1452 G1ConcurrentMark* _cm; 1453 G1CMTask* _task; 1454 bool _is_serial; 1455 public: 1456 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1457 _cm(cm), _task(task), _is_serial(is_serial) { 1458 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1459 } 1460 1461 void do_void() { 1462 do { 1463 // We call G1CMTask::do_marking_step() to completely drain the local 1464 // and global marking stacks of entries pushed by the 'keep alive' 1465 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 1466 // 1467 // G1CMTask::do_marking_step() is called in a loop, which we'll exit 1468 // if there's nothing more to do (i.e. we've completely drained the 1469 // entries that were pushed as a a result of applying the 'keep alive' 1470 // closure to the entries on the discovered ref lists) or we overflow 1471 // the global marking stack. 1472 // 1473 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1474 // flag while there may still be some work to do. (See the comment at 1475 // the beginning of G1CMTask::do_marking_step() for those conditions - 1476 // one of which is reaching the specified time target.) It is only 1477 // when G1CMTask::do_marking_step() returns without setting the 1478 // has_aborted() flag that the marking step has completed. 1479 1480 _task->do_marking_step(1000000000.0 /* something very large */, 1481 true /* do_termination */, 1482 _is_serial); 1483 } while (_task->has_aborted() && !_cm->has_overflown()); 1484 } 1485 }; 1486 1487 // Implementation of AbstractRefProcTaskExecutor for parallel 1488 // reference processing at the end of G1 concurrent marking 1489 1490 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 1491 private: 1492 G1CollectedHeap* _g1h; 1493 G1ConcurrentMark* _cm; 1494 WorkGang* _workers; 1495 uint _active_workers; 1496 1497 public: 1498 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 1499 G1ConcurrentMark* cm, 1500 WorkGang* workers, 1501 uint n_workers) : 1502 _g1h(g1h), _cm(cm), 1503 _workers(workers), _active_workers(n_workers) { } 1504 1505 virtual void execute(ProcessTask& task, uint ergo_workers); 1506 }; 1507 1508 class G1CMRefProcTaskProxy : public AbstractGangTask { 1509 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 1510 ProcessTask& _proc_task; 1511 G1CollectedHeap* _g1h; 1512 G1ConcurrentMark* _cm; 1513 1514 public: 1515 G1CMRefProcTaskProxy(ProcessTask& proc_task, 1516 G1CollectedHeap* g1h, 1517 G1ConcurrentMark* cm) : 1518 AbstractGangTask("Process reference objects in parallel"), 1519 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 1520 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1521 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 1522 } 1523 1524 virtual void work(uint worker_id) { 1525 ResourceMark rm; 1526 HandleMark hm; 1527 G1CMTask* task = _cm->task(worker_id); 1528 G1CMIsAliveClosure g1_is_alive(_g1h); 1529 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 1530 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 1531 1532 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 1533 } 1534 }; 1535 1536 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 1537 assert(_workers != NULL, "Need parallel worker threads."); 1538 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1539 assert(_workers->active_workers() >= ergo_workers, 1540 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)", 1541 ergo_workers, _workers->active_workers()); 1542 1543 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 1544 1545 // We need to reset the concurrency level before each 1546 // proxy task execution, so that the termination protocol 1547 // and overflow handling in G1CMTask::do_marking_step() knows 1548 // how many workers to wait for. 1549 _cm->set_concurrency(ergo_workers); 1550 _workers->run_task(&proc_task_proxy, ergo_workers); 1551 } 1552 1553 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) { 1554 ResourceMark rm; 1555 HandleMark hm; 1556 1557 // Is alive closure. 1558 G1CMIsAliveClosure g1_is_alive(_g1h); 1559 1560 // Inner scope to exclude the cleaning of the string table 1561 // from the displayed time. 1562 { 1563 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm); 1564 1565 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1566 1567 // See the comment in G1CollectedHeap::ref_processing_init() 1568 // about how reference processing currently works in G1. 1569 1570 // Set the soft reference policy 1571 rp->setup_policy(clear_all_soft_refs); 1572 assert(_global_mark_stack.is_empty(), "mark stack should be empty"); 1573 1574 // Instances of the 'Keep Alive' and 'Complete GC' closures used 1575 // in serial reference processing. Note these closures are also 1576 // used for serially processing (by the the current thread) the 1577 // JNI references during parallel reference processing. 1578 // 1579 // These closures do not need to synchronize with the worker 1580 // threads involved in parallel reference processing as these 1581 // instances are executed serially by the current thread (e.g. 1582 // reference processing is not multi-threaded and is thus 1583 // performed by the current thread instead of a gang worker). 1584 // 1585 // The gang tasks involved in parallel reference processing create 1586 // their own instances of these closures, which do their own 1587 // synchronization among themselves. 1588 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 1589 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 1590 1591 // We need at least one active thread. If reference processing 1592 // is not multi-threaded we use the current (VMThread) thread, 1593 // otherwise we use the work gang from the G1CollectedHeap and 1594 // we utilize all the worker threads we can. 1595 bool processing_is_mt = rp->processing_is_mt(); 1596 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U); 1597 active_workers = MAX2(MIN2(active_workers, _max_num_tasks), 1U); 1598 1599 // Parallel processing task executor. 1600 G1CMRefProcTaskExecutor par_task_executor(_g1h, this, 1601 _g1h->workers(), active_workers); 1602 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 1603 1604 // Set the concurrency level. The phase was already set prior to 1605 // executing the remark task. 1606 set_concurrency(active_workers); 1607 1608 // Set the degree of MT processing here. If the discovery was done MT, 1609 // the number of threads involved during discovery could differ from 1610 // the number of active workers. This is OK as long as the discovered 1611 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 1612 rp->set_active_mt_degree(active_workers); 1613 1614 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues()); 1615 1616 // Process the weak references. 1617 const ReferenceProcessorStats& stats = 1618 rp->process_discovered_references(&g1_is_alive, 1619 &g1_keep_alive, 1620 &g1_drain_mark_stack, 1621 executor, 1622 &pt); 1623 _gc_tracer_cm->report_gc_reference_stats(stats); 1624 pt.print_all_references(); 1625 1626 // The do_oop work routines of the keep_alive and drain_marking_stack 1627 // oop closures will set the has_overflown flag if we overflow the 1628 // global marking stack. 1629 1630 assert(has_overflown() || _global_mark_stack.is_empty(), 1631 "Mark stack should be empty (unless it has overflown)"); 1632 1633 assert(rp->num_queues() == active_workers, "why not"); 1634 1635 rp->verify_no_references_recorded(); 1636 assert(!rp->discovery_enabled(), "Post condition"); 1637 } 1638 1639 if (has_overflown()) { 1640 // We can not trust g1_is_alive and the contents of the heap if the marking stack 1641 // overflowed while processing references. Exit the VM. 1642 fatal("Overflow during reference processing, can not continue. Please " 1643 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and " 1644 "restart.", MarkStackSizeMax); 1645 return; 1646 } 1647 1648 assert(_global_mark_stack.is_empty(), "Marking should have completed"); 1649 1650 { 1651 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm); 1652 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1); 1653 } 1654 1655 // Unload Klasses, String, Code Cache, etc. 1656 if (ClassUnloadingWithConcurrentMark) { 1657 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm); 1658 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm, false /* Defer cleaning */); 1659 _g1h->complete_cleaning(&g1_is_alive, purged_classes); 1660 } else { 1661 GCTraceTime(Debug, gc, phases) debug("Cleanup", _gc_timer_cm); 1662 // No need to clean string table as it is treated as strong roots when 1663 // class unloading is disabled. 1664 _g1h->partial_cleaning(&g1_is_alive, false, G1StringDedup::is_enabled()); 1665 } 1666 } 1667 1668 class G1PrecleanYieldClosure : public YieldClosure { 1669 G1ConcurrentMark* _cm; 1670 1671 public: 1672 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { } 1673 1674 virtual bool should_return() { 1675 return _cm->has_aborted(); 1676 } 1677 1678 virtual bool should_return_fine_grain() { 1679 _cm->do_yield_check(); 1680 return _cm->has_aborted(); 1681 } 1682 }; 1683 1684 void G1ConcurrentMark::preclean() { 1685 assert(G1UseReferencePrecleaning, "Precleaning must be enabled."); 1686 1687 SuspendibleThreadSetJoiner joiner; 1688 1689 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */); 1690 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */); 1691 1692 set_concurrency_and_phase(1, true); 1693 1694 G1PrecleanYieldClosure yield_cl(this); 1695 1696 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1697 // Precleaning is single threaded. Temporarily disable MT discovery. 1698 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); 1699 rp->preclean_discovered_references(rp->is_alive_non_header(), 1700 &keep_alive, 1701 &drain_mark_stack, 1702 &yield_cl, 1703 _gc_timer_cm); 1704 } 1705 1706 // When sampling object counts, we already swapped the mark bitmaps, so we need to use 1707 // the prev bitmap determining liveness. 1708 class G1ObjectCountIsAliveClosure: public BoolObjectClosure { 1709 G1CollectedHeap* _g1h; 1710 public: 1711 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 1712 1713 bool do_object_b(oop obj) { 1714 HeapWord* addr = (HeapWord*)obj; 1715 return addr != NULL && 1716 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_dead(obj)); 1717 } 1718 }; 1719 1720 void G1ConcurrentMark::report_object_count(bool mark_completed) { 1721 // Depending on the completion of the marking liveness needs to be determined 1722 // using either the next or prev bitmap. 1723 if (mark_completed) { 1724 G1ObjectCountIsAliveClosure is_alive(_g1h); 1725 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1726 } else { 1727 G1CMIsAliveClosure is_alive(_g1h); 1728 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1729 } 1730 } 1731 1732 1733 void G1ConcurrentMark::swap_mark_bitmaps() { 1734 G1CMBitMap* temp = _prev_mark_bitmap; 1735 _prev_mark_bitmap = _next_mark_bitmap; 1736 _next_mark_bitmap = temp; 1737 _g1h->collector_state()->set_clearing_next_bitmap(true); 1738 } 1739 1740 // Closure for marking entries in SATB buffers. 1741 class G1CMSATBBufferClosure : public SATBBufferClosure { 1742 private: 1743 G1CMTask* _task; 1744 G1CollectedHeap* _g1h; 1745 1746 // This is very similar to G1CMTask::deal_with_reference, but with 1747 // more relaxed requirements for the argument, so this must be more 1748 // circumspect about treating the argument as an object. 1749 void do_entry(void* entry) const { 1750 _task->increment_refs_reached(); 1751 oop const obj = static_cast<oop>(entry); 1752 _task->make_reference_grey(obj); 1753 } 1754 1755 public: 1756 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h) 1757 : _task(task), _g1h(g1h) { } 1758 1759 virtual void do_buffer(void** buffer, size_t size) { 1760 for (size_t i = 0; i < size; ++i) { 1761 do_entry(buffer[i]); 1762 } 1763 } 1764 }; 1765 1766 class G1RemarkThreadsClosure : public ThreadClosure { 1767 G1CMSATBBufferClosure _cm_satb_cl; 1768 G1CMOopClosure _cm_cl; 1769 MarkingCodeBlobClosure _code_cl; 1770 int _thread_parity; 1771 1772 public: 1773 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) : 1774 _cm_satb_cl(task, g1h), 1775 _cm_cl(g1h, task), 1776 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 1777 _thread_parity(Threads::thread_claim_parity()) {} 1778 1779 void do_thread(Thread* thread) { 1780 if (thread->is_Java_thread()) { 1781 if (thread->claim_oops_do(true, _thread_parity)) { 1782 JavaThread* jt = (JavaThread*)thread; 1783 1784 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 1785 // however the liveness of oops reachable from nmethods have very complex lifecycles: 1786 // * Alive if on the stack of an executing method 1787 // * Weakly reachable otherwise 1788 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 1789 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 1790 jt->nmethods_do(&_code_cl); 1791 1792 G1ThreadLocalData::satb_mark_queue(jt).apply_closure_and_empty(&_cm_satb_cl); 1793 } 1794 } else if (thread->is_VM_thread()) { 1795 if (thread->claim_oops_do(true, _thread_parity)) { 1796 G1BarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl); 1797 } 1798 } 1799 } 1800 }; 1801 1802 class G1CMRemarkTask : public AbstractGangTask { 1803 G1ConcurrentMark* _cm; 1804 public: 1805 void work(uint worker_id) { 1806 G1CMTask* task = _cm->task(worker_id); 1807 task->record_start_time(); 1808 { 1809 ResourceMark rm; 1810 HandleMark hm; 1811 1812 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task); 1813 Threads::threads_do(&threads_f); 1814 } 1815 1816 do { 1817 task->do_marking_step(1000000000.0 /* something very large */, 1818 true /* do_termination */, 1819 false /* is_serial */); 1820 } while (task->has_aborted() && !_cm->has_overflown()); 1821 // If we overflow, then we do not want to restart. We instead 1822 // want to abort remark and do concurrent marking again. 1823 task->record_end_time(); 1824 } 1825 1826 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) : 1827 AbstractGangTask("Par Remark"), _cm(cm) { 1828 _cm->terminator()->reset_for_reuse(active_workers); 1829 } 1830 }; 1831 1832 void G1ConcurrentMark::finalize_marking() { 1833 ResourceMark rm; 1834 HandleMark hm; 1835 1836 _g1h->ensure_parsability(false); 1837 1838 // this is remark, so we'll use up all active threads 1839 uint active_workers = _g1h->workers()->active_workers(); 1840 set_concurrency_and_phase(active_workers, false /* concurrent */); 1841 // Leave _parallel_marking_threads at it's 1842 // value originally calculated in the G1ConcurrentMark 1843 // constructor and pass values of the active workers 1844 // through the gang in the task. 1845 1846 { 1847 StrongRootsScope srs(active_workers); 1848 1849 G1CMRemarkTask remarkTask(this, active_workers); 1850 // We will start all available threads, even if we decide that the 1851 // active_workers will be fewer. The extra ones will just bail out 1852 // immediately. 1853 _g1h->workers()->run_task(&remarkTask); 1854 } 1855 1856 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 1857 guarantee(has_overflown() || 1858 satb_mq_set.completed_buffers_num() == 0, 1859 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT, 1860 BOOL_TO_STR(has_overflown()), 1861 satb_mq_set.completed_buffers_num()); 1862 1863 print_stats(); 1864 } 1865 1866 void G1ConcurrentMark::flush_all_task_caches() { 1867 size_t hits = 0; 1868 size_t misses = 0; 1869 for (uint i = 0; i < _max_num_tasks; i++) { 1870 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache(); 1871 hits += stats.first; 1872 misses += stats.second; 1873 } 1874 size_t sum = hits + misses; 1875 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf", 1876 hits, misses, percent_of(hits, sum)); 1877 } 1878 1879 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) { 1880 _prev_mark_bitmap->clear_range(mr); 1881 } 1882 1883 HeapRegion* 1884 G1ConcurrentMark::claim_region(uint worker_id) { 1885 // "checkpoint" the finger 1886 HeapWord* finger = _finger; 1887 1888 while (finger < _heap.end()) { 1889 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 1890 1891 HeapRegion* curr_region = _g1h->heap_region_containing(finger); 1892 // Make sure that the reads below do not float before loading curr_region. 1893 OrderAccess::loadload(); 1894 // Above heap_region_containing may return NULL as we always scan claim 1895 // until the end of the heap. In this case, just jump to the next region. 1896 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 1897 1898 // Is the gap between reading the finger and doing the CAS too long? 1899 HeapWord* res = Atomic::cmpxchg(end, &_finger, finger); 1900 if (res == finger && curr_region != NULL) { 1901 // we succeeded 1902 HeapWord* bottom = curr_region->bottom(); 1903 HeapWord* limit = curr_region->next_top_at_mark_start(); 1904 1905 // notice that _finger == end cannot be guaranteed here since, 1906 // someone else might have moved the finger even further 1907 assert(_finger >= end, "the finger should have moved forward"); 1908 1909 if (limit > bottom) { 1910 return curr_region; 1911 } else { 1912 assert(limit == bottom, 1913 "the region limit should be at bottom"); 1914 // we return NULL and the caller should try calling 1915 // claim_region() again. 1916 return NULL; 1917 } 1918 } else { 1919 assert(_finger > finger, "the finger should have moved forward"); 1920 // read it again 1921 finger = _finger; 1922 } 1923 } 1924 1925 return NULL; 1926 } 1927 1928 #ifndef PRODUCT 1929 class VerifyNoCSetOops { 1930 G1CollectedHeap* _g1h; 1931 const char* _phase; 1932 int _info; 1933 1934 public: 1935 VerifyNoCSetOops(const char* phase, int info = -1) : 1936 _g1h(G1CollectedHeap::heap()), 1937 _phase(phase), 1938 _info(info) 1939 { } 1940 1941 void operator()(G1TaskQueueEntry task_entry) const { 1942 if (task_entry.is_array_slice()) { 1943 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice())); 1944 return; 1945 } 1946 guarantee(oopDesc::is_oop(task_entry.obj()), 1947 "Non-oop " PTR_FORMAT ", phase: %s, info: %d", 1948 p2i(task_entry.obj()), _phase, _info); 1949 guarantee(!_g1h->is_in_cset(task_entry.obj()), 1950 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d", 1951 p2i(task_entry.obj()), _phase, _info); 1952 } 1953 }; 1954 1955 void G1ConcurrentMark::verify_no_cset_oops() { 1956 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 1957 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) { 1958 return; 1959 } 1960 1961 // Verify entries on the global mark stack 1962 _global_mark_stack.iterate(VerifyNoCSetOops("Stack")); 1963 1964 // Verify entries on the task queues 1965 for (uint i = 0; i < _max_num_tasks; ++i) { 1966 G1CMTaskQueue* queue = _task_queues->queue(i); 1967 queue->iterate(VerifyNoCSetOops("Queue", i)); 1968 } 1969 1970 // Verify the global finger 1971 HeapWord* global_finger = finger(); 1972 if (global_finger != NULL && global_finger < _heap.end()) { 1973 // Since we always iterate over all regions, we might get a NULL HeapRegion 1974 // here. 1975 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger); 1976 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 1977 "global finger: " PTR_FORMAT " region: " HR_FORMAT, 1978 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)); 1979 } 1980 1981 // Verify the task fingers 1982 assert(_num_concurrent_workers <= _max_num_tasks, "sanity"); 1983 for (uint i = 0; i < _num_concurrent_workers; ++i) { 1984 G1CMTask* task = _tasks[i]; 1985 HeapWord* task_finger = task->finger(); 1986 if (task_finger != NULL && task_finger < _heap.end()) { 1987 // See above note on the global finger verification. 1988 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger); 1989 guarantee(task_hr == NULL || task_finger == task_hr->bottom() || 1990 !task_hr->in_collection_set(), 1991 "task finger: " PTR_FORMAT " region: " HR_FORMAT, 1992 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)); 1993 } 1994 } 1995 } 1996 #endif // PRODUCT 1997 1998 void G1ConcurrentMark::rebuild_rem_set_concurrently() { 1999 _g1h->g1_rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset); 2000 } 2001 2002 void G1ConcurrentMark::print_stats() { 2003 if (!log_is_enabled(Debug, gc, stats)) { 2004 return; 2005 } 2006 log_debug(gc, stats)("---------------------------------------------------------------------"); 2007 for (size_t i = 0; i < _num_active_tasks; ++i) { 2008 _tasks[i]->print_stats(); 2009 log_debug(gc, stats)("---------------------------------------------------------------------"); 2010 } 2011 } 2012 2013 void G1ConcurrentMark::concurrent_cycle_abort() { 2014 if (!cm_thread()->during_cycle() || _has_aborted) { 2015 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything. 2016 return; 2017 } 2018 2019 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 2020 // concurrent bitmap clearing. 2021 { 2022 GCTraceTime(Debug, gc) debug("Clear Next Bitmap"); 2023 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false); 2024 } 2025 // Note we cannot clear the previous marking bitmap here 2026 // since VerifyDuringGC verifies the objects marked during 2027 // a full GC against the previous bitmap. 2028 2029 // Empty mark stack 2030 reset_marking_for_restart(); 2031 for (uint i = 0; i < _max_num_tasks; ++i) { 2032 _tasks[i]->clear_region_fields(); 2033 } 2034 _first_overflow_barrier_sync.abort(); 2035 _second_overflow_barrier_sync.abort(); 2036 _has_aborted = true; 2037 2038 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2039 satb_mq_set.abandon_partial_marking(); 2040 // This can be called either during or outside marking, we'll read 2041 // the expected_active value from the SATB queue set. 2042 satb_mq_set.set_active_all_threads( 2043 false, /* new active value */ 2044 satb_mq_set.is_active() /* expected_active */); 2045 } 2046 2047 static void print_ms_time_info(const char* prefix, const char* name, 2048 NumberSeq& ns) { 2049 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 2050 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 2051 if (ns.num() > 0) { 2052 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]", 2053 prefix, ns.sd(), ns.maximum()); 2054 } 2055 } 2056 2057 void G1ConcurrentMark::print_summary_info() { 2058 Log(gc, marking) log; 2059 if (!log.is_trace()) { 2060 return; 2061 } 2062 2063 log.trace(" Concurrent marking:"); 2064 print_ms_time_info(" ", "init marks", _init_times); 2065 print_ms_time_info(" ", "remarks", _remark_times); 2066 { 2067 print_ms_time_info(" ", "final marks", _remark_mark_times); 2068 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 2069 2070 } 2071 print_ms_time_info(" ", "cleanups", _cleanup_times); 2072 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).", 2073 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2074 log.trace(" Total stop_world time = %8.2f s.", 2075 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0); 2076 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).", 2077 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum()); 2078 } 2079 2080 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const { 2081 _concurrent_workers->print_worker_threads_on(st); 2082 } 2083 2084 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const { 2085 _concurrent_workers->threads_do(tc); 2086 } 2087 2088 void G1ConcurrentMark::print_on_error(outputStream* st) const { 2089 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 2090 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap)); 2091 _prev_mark_bitmap->print_on_error(st, " Prev Bits: "); 2092 _next_mark_bitmap->print_on_error(st, " Next Bits: "); 2093 } 2094 2095 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) { 2096 ReferenceProcessor* result = g1h->ref_processor_cm(); 2097 assert(result != NULL, "CM reference processor should not be NULL"); 2098 return result; 2099 } 2100 2101 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 2102 G1CMTask* task) 2103 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)), 2104 _g1h(g1h), _task(task) 2105 { } 2106 2107 void G1CMTask::setup_for_region(HeapRegion* hr) { 2108 assert(hr != NULL, 2109 "claim_region() should have filtered out NULL regions"); 2110 _curr_region = hr; 2111 _finger = hr->bottom(); 2112 update_region_limit(); 2113 } 2114 2115 void G1CMTask::update_region_limit() { 2116 HeapRegion* hr = _curr_region; 2117 HeapWord* bottom = hr->bottom(); 2118 HeapWord* limit = hr->next_top_at_mark_start(); 2119 2120 if (limit == bottom) { 2121 // The region was collected underneath our feet. 2122 // We set the finger to bottom to ensure that the bitmap 2123 // iteration that will follow this will not do anything. 2124 // (this is not a condition that holds when we set the region up, 2125 // as the region is not supposed to be empty in the first place) 2126 _finger = bottom; 2127 } else if (limit >= _region_limit) { 2128 assert(limit >= _finger, "peace of mind"); 2129 } else { 2130 assert(limit < _region_limit, "only way to get here"); 2131 // This can happen under some pretty unusual circumstances. An 2132 // evacuation pause empties the region underneath our feet (NTAMS 2133 // at bottom). We then do some allocation in the region (NTAMS 2134 // stays at bottom), followed by the region being used as a GC 2135 // alloc region (NTAMS will move to top() and the objects 2136 // originally below it will be grayed). All objects now marked in 2137 // the region are explicitly grayed, if below the global finger, 2138 // and we do not need in fact to scan anything else. So, we simply 2139 // set _finger to be limit to ensure that the bitmap iteration 2140 // doesn't do anything. 2141 _finger = limit; 2142 } 2143 2144 _region_limit = limit; 2145 } 2146 2147 void G1CMTask::giveup_current_region() { 2148 assert(_curr_region != NULL, "invariant"); 2149 clear_region_fields(); 2150 } 2151 2152 void G1CMTask::clear_region_fields() { 2153 // Values for these three fields that indicate that we're not 2154 // holding on to a region. 2155 _curr_region = NULL; 2156 _finger = NULL; 2157 _region_limit = NULL; 2158 } 2159 2160 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 2161 if (cm_oop_closure == NULL) { 2162 assert(_cm_oop_closure != NULL, "invariant"); 2163 } else { 2164 assert(_cm_oop_closure == NULL, "invariant"); 2165 } 2166 _cm_oop_closure = cm_oop_closure; 2167 } 2168 2169 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) { 2170 guarantee(next_mark_bitmap != NULL, "invariant"); 2171 _next_mark_bitmap = next_mark_bitmap; 2172 clear_region_fields(); 2173 2174 _calls = 0; 2175 _elapsed_time_ms = 0.0; 2176 _termination_time_ms = 0.0; 2177 _termination_start_time_ms = 0.0; 2178 2179 _mark_stats_cache.reset(); 2180 } 2181 2182 bool G1CMTask::should_exit_termination() { 2183 regular_clock_call(); 2184 // This is called when we are in the termination protocol. We should 2185 // quit if, for some reason, this task wants to abort or the global 2186 // stack is not empty (this means that we can get work from it). 2187 return !_cm->mark_stack_empty() || has_aborted(); 2188 } 2189 2190 void G1CMTask::reached_limit() { 2191 assert(_words_scanned >= _words_scanned_limit || 2192 _refs_reached >= _refs_reached_limit , 2193 "shouldn't have been called otherwise"); 2194 regular_clock_call(); 2195 } 2196 2197 void G1CMTask::regular_clock_call() { 2198 if (has_aborted()) { 2199 return; 2200 } 2201 2202 // First, we need to recalculate the words scanned and refs reached 2203 // limits for the next clock call. 2204 recalculate_limits(); 2205 2206 // During the regular clock call we do the following 2207 2208 // (1) If an overflow has been flagged, then we abort. 2209 if (_cm->has_overflown()) { 2210 set_has_aborted(); 2211 return; 2212 } 2213 2214 // If we are not concurrent (i.e. we're doing remark) we don't need 2215 // to check anything else. The other steps are only needed during 2216 // the concurrent marking phase. 2217 if (!_cm->concurrent()) { 2218 return; 2219 } 2220 2221 // (2) If marking has been aborted for Full GC, then we also abort. 2222 if (_cm->has_aborted()) { 2223 set_has_aborted(); 2224 return; 2225 } 2226 2227 double curr_time_ms = os::elapsedVTime() * 1000.0; 2228 2229 // (4) We check whether we should yield. If we have to, then we abort. 2230 if (SuspendibleThreadSet::should_yield()) { 2231 // We should yield. To do this we abort the task. The caller is 2232 // responsible for yielding. 2233 set_has_aborted(); 2234 return; 2235 } 2236 2237 // (5) We check whether we've reached our time quota. If we have, 2238 // then we abort. 2239 double elapsed_time_ms = curr_time_ms - _start_time_ms; 2240 if (elapsed_time_ms > _time_target_ms) { 2241 set_has_aborted(); 2242 _has_timed_out = true; 2243 return; 2244 } 2245 2246 // (6) Finally, we check whether there are enough completed STAB 2247 // buffers available for processing. If there are, we abort. 2248 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2249 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 2250 // we do need to process SATB buffers, we'll abort and restart 2251 // the marking task to do so 2252 set_has_aborted(); 2253 return; 2254 } 2255 } 2256 2257 void G1CMTask::recalculate_limits() { 2258 _real_words_scanned_limit = _words_scanned + words_scanned_period; 2259 _words_scanned_limit = _real_words_scanned_limit; 2260 2261 _real_refs_reached_limit = _refs_reached + refs_reached_period; 2262 _refs_reached_limit = _real_refs_reached_limit; 2263 } 2264 2265 void G1CMTask::decrease_limits() { 2266 // This is called when we believe that we're going to do an infrequent 2267 // operation which will increase the per byte scanned cost (i.e. move 2268 // entries to/from the global stack). It basically tries to decrease the 2269 // scanning limit so that the clock is called earlier. 2270 2271 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4; 2272 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4; 2273 } 2274 2275 void G1CMTask::move_entries_to_global_stack() { 2276 // Local array where we'll store the entries that will be popped 2277 // from the local queue. 2278 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2279 2280 size_t n = 0; 2281 G1TaskQueueEntry task_entry; 2282 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) { 2283 buffer[n] = task_entry; 2284 ++n; 2285 } 2286 if (n < G1CMMarkStack::EntriesPerChunk) { 2287 buffer[n] = G1TaskQueueEntry(); 2288 } 2289 2290 if (n > 0) { 2291 if (!_cm->mark_stack_push(buffer)) { 2292 set_has_aborted(); 2293 } 2294 } 2295 2296 // This operation was quite expensive, so decrease the limits. 2297 decrease_limits(); 2298 } 2299 2300 bool G1CMTask::get_entries_from_global_stack() { 2301 // Local array where we'll store the entries that will be popped 2302 // from the global stack. 2303 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2304 2305 if (!_cm->mark_stack_pop(buffer)) { 2306 return false; 2307 } 2308 2309 // We did actually pop at least one entry. 2310 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) { 2311 G1TaskQueueEntry task_entry = buffer[i]; 2312 if (task_entry.is_null()) { 2313 break; 2314 } 2315 assert(task_entry.is_array_slice() || oopDesc::is_oop(task_entry.obj()), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj())); 2316 bool success = _task_queue->push(task_entry); 2317 // We only call this when the local queue is empty or under a 2318 // given target limit. So, we do not expect this push to fail. 2319 assert(success, "invariant"); 2320 } 2321 2322 // This operation was quite expensive, so decrease the limits 2323 decrease_limits(); 2324 return true; 2325 } 2326 2327 void G1CMTask::drain_local_queue(bool partially) { 2328 if (has_aborted()) { 2329 return; 2330 } 2331 2332 // Decide what the target size is, depending whether we're going to 2333 // drain it partially (so that other tasks can steal if they run out 2334 // of things to do) or totally (at the very end). 2335 size_t target_size; 2336 if (partially) { 2337 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize); 2338 } else { 2339 target_size = 0; 2340 } 2341 2342 if (_task_queue->size() > target_size) { 2343 G1TaskQueueEntry entry; 2344 bool ret = _task_queue->pop_local(entry); 2345 while (ret) { 2346 scan_task_entry(entry); 2347 if (_task_queue->size() <= target_size || has_aborted()) { 2348 ret = false; 2349 } else { 2350 ret = _task_queue->pop_local(entry); 2351 } 2352 } 2353 } 2354 } 2355 2356 void G1CMTask::drain_global_stack(bool partially) { 2357 if (has_aborted()) { 2358 return; 2359 } 2360 2361 // We have a policy to drain the local queue before we attempt to 2362 // drain the global stack. 2363 assert(partially || _task_queue->size() == 0, "invariant"); 2364 2365 // Decide what the target size is, depending whether we're going to 2366 // drain it partially (so that other tasks can steal if they run out 2367 // of things to do) or totally (at the very end). 2368 // Notice that when draining the global mark stack partially, due to the racyness 2369 // of the mark stack size update we might in fact drop below the target. But, 2370 // this is not a problem. 2371 // In case of total draining, we simply process until the global mark stack is 2372 // totally empty, disregarding the size counter. 2373 if (partially) { 2374 size_t const target_size = _cm->partial_mark_stack_size_target(); 2375 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 2376 if (get_entries_from_global_stack()) { 2377 drain_local_queue(partially); 2378 } 2379 } 2380 } else { 2381 while (!has_aborted() && get_entries_from_global_stack()) { 2382 drain_local_queue(partially); 2383 } 2384 } 2385 } 2386 2387 // SATB Queue has several assumptions on whether to call the par or 2388 // non-par versions of the methods. this is why some of the code is 2389 // replicated. We should really get rid of the single-threaded version 2390 // of the code to simplify things. 2391 void G1CMTask::drain_satb_buffers() { 2392 if (has_aborted()) { 2393 return; 2394 } 2395 2396 // We set this so that the regular clock knows that we're in the 2397 // middle of draining buffers and doesn't set the abort flag when it 2398 // notices that SATB buffers are available for draining. It'd be 2399 // very counter productive if it did that. :-) 2400 _draining_satb_buffers = true; 2401 2402 G1CMSATBBufferClosure satb_cl(this, _g1h); 2403 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2404 2405 // This keeps claiming and applying the closure to completed buffers 2406 // until we run out of buffers or we need to abort. 2407 while (!has_aborted() && 2408 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 2409 regular_clock_call(); 2410 } 2411 2412 _draining_satb_buffers = false; 2413 2414 assert(has_aborted() || 2415 _cm->concurrent() || 2416 satb_mq_set.completed_buffers_num() == 0, "invariant"); 2417 2418 // again, this was a potentially expensive operation, decrease the 2419 // limits to get the regular clock call early 2420 decrease_limits(); 2421 } 2422 2423 void G1CMTask::clear_mark_stats_cache(uint region_idx) { 2424 _mark_stats_cache.reset(region_idx); 2425 } 2426 2427 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() { 2428 return _mark_stats_cache.evict_all(); 2429 } 2430 2431 void G1CMTask::print_stats() { 2432 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls); 2433 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 2434 _elapsed_time_ms, _termination_time_ms); 2435 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms", 2436 _step_times_ms.num(), 2437 _step_times_ms.avg(), 2438 _step_times_ms.sd(), 2439 _step_times_ms.maximum(), 2440 _step_times_ms.sum()); 2441 size_t const hits = _mark_stats_cache.hits(); 2442 size_t const misses = _mark_stats_cache.misses(); 2443 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f", 2444 hits, misses, percent_of(hits, hits + misses)); 2445 } 2446 2447 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) { 2448 return _task_queues->steal(worker_id, task_entry); 2449 } 2450 2451 /***************************************************************************** 2452 2453 The do_marking_step(time_target_ms, ...) method is the building 2454 block of the parallel marking framework. It can be called in parallel 2455 with other invocations of do_marking_step() on different tasks 2456 (but only one per task, obviously) and concurrently with the 2457 mutator threads, or during remark, hence it eliminates the need 2458 for two versions of the code. When called during remark, it will 2459 pick up from where the task left off during the concurrent marking 2460 phase. Interestingly, tasks are also claimable during evacuation 2461 pauses too, since do_marking_step() ensures that it aborts before 2462 it needs to yield. 2463 2464 The data structures that it uses to do marking work are the 2465 following: 2466 2467 (1) Marking Bitmap. If there are gray objects that appear only 2468 on the bitmap (this happens either when dealing with an overflow 2469 or when the initial marking phase has simply marked the roots 2470 and didn't push them on the stack), then tasks claim heap 2471 regions whose bitmap they then scan to find gray objects. A 2472 global finger indicates where the end of the last claimed region 2473 is. A local finger indicates how far into the region a task has 2474 scanned. The two fingers are used to determine how to gray an 2475 object (i.e. whether simply marking it is OK, as it will be 2476 visited by a task in the future, or whether it needs to be also 2477 pushed on a stack). 2478 2479 (2) Local Queue. The local queue of the task which is accessed 2480 reasonably efficiently by the task. Other tasks can steal from 2481 it when they run out of work. Throughout the marking phase, a 2482 task attempts to keep its local queue short but not totally 2483 empty, so that entries are available for stealing by other 2484 tasks. Only when there is no more work, a task will totally 2485 drain its local queue. 2486 2487 (3) Global Mark Stack. This handles local queue overflow. During 2488 marking only sets of entries are moved between it and the local 2489 queues, as access to it requires a mutex and more fine-grain 2490 interaction with it which might cause contention. If it 2491 overflows, then the marking phase should restart and iterate 2492 over the bitmap to identify gray objects. Throughout the marking 2493 phase, tasks attempt to keep the global mark stack at a small 2494 length but not totally empty, so that entries are available for 2495 popping by other tasks. Only when there is no more work, tasks 2496 will totally drain the global mark stack. 2497 2498 (4) SATB Buffer Queue. This is where completed SATB buffers are 2499 made available. Buffers are regularly removed from this queue 2500 and scanned for roots, so that the queue doesn't get too 2501 long. During remark, all completed buffers are processed, as 2502 well as the filled in parts of any uncompleted buffers. 2503 2504 The do_marking_step() method tries to abort when the time target 2505 has been reached. There are a few other cases when the 2506 do_marking_step() method also aborts: 2507 2508 (1) When the marking phase has been aborted (after a Full GC). 2509 2510 (2) When a global overflow (on the global stack) has been 2511 triggered. Before the task aborts, it will actually sync up with 2512 the other tasks to ensure that all the marking data structures 2513 (local queues, stacks, fingers etc.) are re-initialized so that 2514 when do_marking_step() completes, the marking phase can 2515 immediately restart. 2516 2517 (3) When enough completed SATB buffers are available. The 2518 do_marking_step() method only tries to drain SATB buffers right 2519 at the beginning. So, if enough buffers are available, the 2520 marking step aborts and the SATB buffers are processed at 2521 the beginning of the next invocation. 2522 2523 (4) To yield. when we have to yield then we abort and yield 2524 right at the end of do_marking_step(). This saves us from a lot 2525 of hassle as, by yielding we might allow a Full GC. If this 2526 happens then objects will be compacted underneath our feet, the 2527 heap might shrink, etc. We save checking for this by just 2528 aborting and doing the yield right at the end. 2529 2530 From the above it follows that the do_marking_step() method should 2531 be called in a loop (or, otherwise, regularly) until it completes. 2532 2533 If a marking step completes without its has_aborted() flag being 2534 true, it means it has completed the current marking phase (and 2535 also all other marking tasks have done so and have all synced up). 2536 2537 A method called regular_clock_call() is invoked "regularly" (in 2538 sub ms intervals) throughout marking. It is this clock method that 2539 checks all the abort conditions which were mentioned above and 2540 decides when the task should abort. A work-based scheme is used to 2541 trigger this clock method: when the number of object words the 2542 marking phase has scanned or the number of references the marking 2543 phase has visited reach a given limit. Additional invocations to 2544 the method clock have been planted in a few other strategic places 2545 too. The initial reason for the clock method was to avoid calling 2546 vtime too regularly, as it is quite expensive. So, once it was in 2547 place, it was natural to piggy-back all the other conditions on it 2548 too and not constantly check them throughout the code. 2549 2550 If do_termination is true then do_marking_step will enter its 2551 termination protocol. 2552 2553 The value of is_serial must be true when do_marking_step is being 2554 called serially (i.e. by the VMThread) and do_marking_step should 2555 skip any synchronization in the termination and overflow code. 2556 Examples include the serial remark code and the serial reference 2557 processing closures. 2558 2559 The value of is_serial must be false when do_marking_step is 2560 being called by any of the worker threads in a work gang. 2561 Examples include the concurrent marking code (CMMarkingTask), 2562 the MT remark code, and the MT reference processing closures. 2563 2564 *****************************************************************************/ 2565 2566 void G1CMTask::do_marking_step(double time_target_ms, 2567 bool do_termination, 2568 bool is_serial) { 2569 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 2570 2571 _start_time_ms = os::elapsedVTime() * 1000.0; 2572 2573 // If do_stealing is true then do_marking_step will attempt to 2574 // steal work from the other G1CMTasks. It only makes sense to 2575 // enable stealing when the termination protocol is enabled 2576 // and do_marking_step() is not being called serially. 2577 bool do_stealing = do_termination && !is_serial; 2578 2579 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms); 2580 _time_target_ms = time_target_ms - diff_prediction_ms; 2581 2582 // set up the variables that are used in the work-based scheme to 2583 // call the regular clock method 2584 _words_scanned = 0; 2585 _refs_reached = 0; 2586 recalculate_limits(); 2587 2588 // clear all flags 2589 clear_has_aborted(); 2590 _has_timed_out = false; 2591 _draining_satb_buffers = false; 2592 2593 ++_calls; 2594 2595 // Set up the bitmap and oop closures. Anything that uses them is 2596 // eventually called from this method, so it is OK to allocate these 2597 // statically. 2598 G1CMBitMapClosure bitmap_closure(this, _cm); 2599 G1CMOopClosure cm_oop_closure(_g1h, this); 2600 set_cm_oop_closure(&cm_oop_closure); 2601 2602 if (_cm->has_overflown()) { 2603 // This can happen if the mark stack overflows during a GC pause 2604 // and this task, after a yield point, restarts. We have to abort 2605 // as we need to get into the overflow protocol which happens 2606 // right at the end of this task. 2607 set_has_aborted(); 2608 } 2609 2610 // First drain any available SATB buffers. After this, we will not 2611 // look at SATB buffers before the next invocation of this method. 2612 // If enough completed SATB buffers are queued up, the regular clock 2613 // will abort this task so that it restarts. 2614 drain_satb_buffers(); 2615 // ...then partially drain the local queue and the global stack 2616 drain_local_queue(true); 2617 drain_global_stack(true); 2618 2619 do { 2620 if (!has_aborted() && _curr_region != NULL) { 2621 // This means that we're already holding on to a region. 2622 assert(_finger != NULL, "if region is not NULL, then the finger " 2623 "should not be NULL either"); 2624 2625 // We might have restarted this task after an evacuation pause 2626 // which might have evacuated the region we're holding on to 2627 // underneath our feet. Let's read its limit again to make sure 2628 // that we do not iterate over a region of the heap that 2629 // contains garbage (update_region_limit() will also move 2630 // _finger to the start of the region if it is found empty). 2631 update_region_limit(); 2632 // We will start from _finger not from the start of the region, 2633 // as we might be restarting this task after aborting half-way 2634 // through scanning this region. In this case, _finger points to 2635 // the address where we last found a marked object. If this is a 2636 // fresh region, _finger points to start(). 2637 MemRegion mr = MemRegion(_finger, _region_limit); 2638 2639 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(), 2640 "humongous regions should go around loop once only"); 2641 2642 // Some special cases: 2643 // If the memory region is empty, we can just give up the region. 2644 // If the current region is humongous then we only need to check 2645 // the bitmap for the bit associated with the start of the object, 2646 // scan the object if it's live, and give up the region. 2647 // Otherwise, let's iterate over the bitmap of the part of the region 2648 // that is left. 2649 // If the iteration is successful, give up the region. 2650 if (mr.is_empty()) { 2651 giveup_current_region(); 2652 regular_clock_call(); 2653 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) { 2654 if (_next_mark_bitmap->is_marked(mr.start())) { 2655 // The object is marked - apply the closure 2656 bitmap_closure.do_addr(mr.start()); 2657 } 2658 // Even if this task aborted while scanning the humongous object 2659 // we can (and should) give up the current region. 2660 giveup_current_region(); 2661 regular_clock_call(); 2662 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) { 2663 giveup_current_region(); 2664 regular_clock_call(); 2665 } else { 2666 assert(has_aborted(), "currently the only way to do so"); 2667 // The only way to abort the bitmap iteration is to return 2668 // false from the do_bit() method. However, inside the 2669 // do_bit() method we move the _finger to point to the 2670 // object currently being looked at. So, if we bail out, we 2671 // have definitely set _finger to something non-null. 2672 assert(_finger != NULL, "invariant"); 2673 2674 // Region iteration was actually aborted. So now _finger 2675 // points to the address of the object we last scanned. If we 2676 // leave it there, when we restart this task, we will rescan 2677 // the object. It is easy to avoid this. We move the finger by 2678 // enough to point to the next possible object header. 2679 assert(_finger < _region_limit, "invariant"); 2680 HeapWord* const new_finger = _finger + ((oop)_finger)->size(); 2681 // Check if bitmap iteration was aborted while scanning the last object 2682 if (new_finger >= _region_limit) { 2683 giveup_current_region(); 2684 } else { 2685 move_finger_to(new_finger); 2686 } 2687 } 2688 } 2689 // At this point we have either completed iterating over the 2690 // region we were holding on to, or we have aborted. 2691 2692 // We then partially drain the local queue and the global stack. 2693 // (Do we really need this?) 2694 drain_local_queue(true); 2695 drain_global_stack(true); 2696 2697 // Read the note on the claim_region() method on why it might 2698 // return NULL with potentially more regions available for 2699 // claiming and why we have to check out_of_regions() to determine 2700 // whether we're done or not. 2701 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 2702 // We are going to try to claim a new region. We should have 2703 // given up on the previous one. 2704 // Separated the asserts so that we know which one fires. 2705 assert(_curr_region == NULL, "invariant"); 2706 assert(_finger == NULL, "invariant"); 2707 assert(_region_limit == NULL, "invariant"); 2708 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 2709 if (claimed_region != NULL) { 2710 // Yes, we managed to claim one 2711 setup_for_region(claimed_region); 2712 assert(_curr_region == claimed_region, "invariant"); 2713 } 2714 // It is important to call the regular clock here. It might take 2715 // a while to claim a region if, for example, we hit a large 2716 // block of empty regions. So we need to call the regular clock 2717 // method once round the loop to make sure it's called 2718 // frequently enough. 2719 regular_clock_call(); 2720 } 2721 2722 if (!has_aborted() && _curr_region == NULL) { 2723 assert(_cm->out_of_regions(), 2724 "at this point we should be out of regions"); 2725 } 2726 } while ( _curr_region != NULL && !has_aborted()); 2727 2728 if (!has_aborted()) { 2729 // We cannot check whether the global stack is empty, since other 2730 // tasks might be pushing objects to it concurrently. 2731 assert(_cm->out_of_regions(), 2732 "at this point we should be out of regions"); 2733 // Try to reduce the number of available SATB buffers so that 2734 // remark has less work to do. 2735 drain_satb_buffers(); 2736 } 2737 2738 // Since we've done everything else, we can now totally drain the 2739 // local queue and global stack. 2740 drain_local_queue(false); 2741 drain_global_stack(false); 2742 2743 // Attempt at work stealing from other task's queues. 2744 if (do_stealing && !has_aborted()) { 2745 // We have not aborted. This means that we have finished all that 2746 // we could. Let's try to do some stealing... 2747 2748 // We cannot check whether the global stack is empty, since other 2749 // tasks might be pushing objects to it concurrently. 2750 assert(_cm->out_of_regions() && _task_queue->size() == 0, 2751 "only way to reach here"); 2752 while (!has_aborted()) { 2753 G1TaskQueueEntry entry; 2754 if (_cm->try_stealing(_worker_id, entry)) { 2755 scan_task_entry(entry); 2756 2757 // And since we're towards the end, let's totally drain the 2758 // local queue and global stack. 2759 drain_local_queue(false); 2760 drain_global_stack(false); 2761 } else { 2762 break; 2763 } 2764 } 2765 } 2766 2767 // We still haven't aborted. Now, let's try to get into the 2768 // termination protocol. 2769 if (do_termination && !has_aborted()) { 2770 // We cannot check whether the global stack is empty, since other 2771 // tasks might be concurrently pushing objects on it. 2772 // Separated the asserts so that we know which one fires. 2773 assert(_cm->out_of_regions(), "only way to reach here"); 2774 assert(_task_queue->size() == 0, "only way to reach here"); 2775 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 2776 2777 // The G1CMTask class also extends the TerminatorTerminator class, 2778 // hence its should_exit_termination() method will also decide 2779 // whether to exit the termination protocol or not. 2780 bool finished = (is_serial || 2781 _cm->terminator()->offer_termination(this)); 2782 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 2783 _termination_time_ms += 2784 termination_end_time_ms - _termination_start_time_ms; 2785 2786 if (finished) { 2787 // We're all done. 2788 2789 // We can now guarantee that the global stack is empty, since 2790 // all other tasks have finished. We separated the guarantees so 2791 // that, if a condition is false, we can immediately find out 2792 // which one. 2793 guarantee(_cm->out_of_regions(), "only way to reach here"); 2794 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 2795 guarantee(_task_queue->size() == 0, "only way to reach here"); 2796 guarantee(!_cm->has_overflown(), "only way to reach here"); 2797 } else { 2798 // Apparently there's more work to do. Let's abort this task. It 2799 // will restart it and we can hopefully find more things to do. 2800 set_has_aborted(); 2801 } 2802 } 2803 2804 // Mainly for debugging purposes to make sure that a pointer to the 2805 // closure which was statically allocated in this frame doesn't 2806 // escape it by accident. 2807 set_cm_oop_closure(NULL); 2808 double end_time_ms = os::elapsedVTime() * 1000.0; 2809 double elapsed_time_ms = end_time_ms - _start_time_ms; 2810 // Update the step history. 2811 _step_times_ms.add(elapsed_time_ms); 2812 2813 if (has_aborted()) { 2814 // The task was aborted for some reason. 2815 if (_has_timed_out) { 2816 double diff_ms = elapsed_time_ms - _time_target_ms; 2817 // Keep statistics of how well we did with respect to hitting 2818 // our target only if we actually timed out (if we aborted for 2819 // other reasons, then the results might get skewed). 2820 _marking_step_diffs_ms.add(diff_ms); 2821 } 2822 2823 if (_cm->has_overflown()) { 2824 // This is the interesting one. We aborted because a global 2825 // overflow was raised. This means we have to restart the 2826 // marking phase and start iterating over regions. However, in 2827 // order to do this we have to make sure that all tasks stop 2828 // what they are doing and re-initialize in a safe manner. We 2829 // will achieve this with the use of two barrier sync points. 2830 2831 if (!is_serial) { 2832 // We only need to enter the sync barrier if being called 2833 // from a parallel context 2834 _cm->enter_first_sync_barrier(_worker_id); 2835 2836 // When we exit this sync barrier we know that all tasks have 2837 // stopped doing marking work. So, it's now safe to 2838 // re-initialize our data structures. 2839 } 2840 2841 clear_region_fields(); 2842 flush_mark_stats_cache(); 2843 2844 if (!is_serial) { 2845 // If we're executing the concurrent phase of marking, reset the marking 2846 // state; otherwise the marking state is reset after reference processing, 2847 // during the remark pause. 2848 // If we reset here as a result of an overflow during the remark we will 2849 // see assertion failures from any subsequent set_concurrency_and_phase() 2850 // calls. 2851 if (_cm->concurrent() && _worker_id == 0) { 2852 // Worker 0 is responsible for clearing the global data structures because 2853 // of an overflow. During STW we should not clear the overflow flag (in 2854 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit 2855 // method to abort the pause and restart concurrent marking. 2856 _cm->reset_marking_for_restart(); 2857 2858 log_info(gc, marking)("Concurrent Mark reset for overflow"); 2859 } 2860 2861 // ...and enter the second barrier. 2862 _cm->enter_second_sync_barrier(_worker_id); 2863 } 2864 // At this point, if we're during the concurrent phase of 2865 // marking, everything has been re-initialized and we're 2866 // ready to restart. 2867 } 2868 } 2869 } 2870 2871 G1CMTask::G1CMTask(uint worker_id, 2872 G1ConcurrentMark* cm, 2873 G1CMTaskQueue* task_queue, 2874 G1RegionMarkStats* mark_stats, 2875 uint max_regions) : 2876 _objArray_processor(this), 2877 _worker_id(worker_id), 2878 _g1h(G1CollectedHeap::heap()), 2879 _cm(cm), 2880 _next_mark_bitmap(NULL), 2881 _task_queue(task_queue), 2882 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize), 2883 _calls(0), 2884 _time_target_ms(0.0), 2885 _start_time_ms(0.0), 2886 _cm_oop_closure(NULL), 2887 _curr_region(NULL), 2888 _finger(NULL), 2889 _region_limit(NULL), 2890 _words_scanned(0), 2891 _words_scanned_limit(0), 2892 _real_words_scanned_limit(0), 2893 _refs_reached(0), 2894 _refs_reached_limit(0), 2895 _real_refs_reached_limit(0), 2896 _has_aborted(false), 2897 _has_timed_out(false), 2898 _draining_satb_buffers(false), 2899 _step_times_ms(), 2900 _elapsed_time_ms(0.0), 2901 _termination_time_ms(0.0), 2902 _termination_start_time_ms(0.0), 2903 _marking_step_diffs_ms() 2904 { 2905 guarantee(task_queue != NULL, "invariant"); 2906 2907 _marking_step_diffs_ms.add(0.5); 2908 } 2909 2910 // These are formatting macros that are used below to ensure 2911 // consistent formatting. The *_H_* versions are used to format the 2912 // header for a particular value and they should be kept consistent 2913 // with the corresponding macro. Also note that most of the macros add 2914 // the necessary white space (as a prefix) which makes them a bit 2915 // easier to compose. 2916 2917 // All the output lines are prefixed with this string to be able to 2918 // identify them easily in a large log file. 2919 #define G1PPRL_LINE_PREFIX "###" 2920 2921 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT 2922 #ifdef _LP64 2923 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 2924 #else // _LP64 2925 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 2926 #endif // _LP64 2927 2928 // For per-region info 2929 #define G1PPRL_TYPE_FORMAT " %-4s" 2930 #define G1PPRL_TYPE_H_FORMAT " %4s" 2931 #define G1PPRL_STATE_FORMAT " %-5s" 2932 #define G1PPRL_STATE_H_FORMAT " %5s" 2933 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9) 2934 #define G1PPRL_BYTE_H_FORMAT " %9s" 2935 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 2936 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 2937 2938 // For summary info 2939 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT 2940 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT 2941 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB" 2942 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%" 2943 2944 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) : 2945 _total_used_bytes(0), _total_capacity_bytes(0), 2946 _total_prev_live_bytes(0), _total_next_live_bytes(0), 2947 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) 2948 { 2949 if (!log_is_enabled(Trace, gc, liveness)) { 2950 return; 2951 } 2952 2953 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2954 MemRegion g1_reserved = g1h->g1_reserved(); 2955 double now = os::elapsedTime(); 2956 2957 // Print the header of the output. 2958 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 2959 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP" 2960 G1PPRL_SUM_ADDR_FORMAT("reserved") 2961 G1PPRL_SUM_BYTE_FORMAT("region-size"), 2962 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 2963 HeapRegion::GrainBytes); 2964 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 2965 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 2966 G1PPRL_TYPE_H_FORMAT 2967 G1PPRL_ADDR_BASE_H_FORMAT 2968 G1PPRL_BYTE_H_FORMAT 2969 G1PPRL_BYTE_H_FORMAT 2970 G1PPRL_BYTE_H_FORMAT 2971 G1PPRL_DOUBLE_H_FORMAT 2972 G1PPRL_BYTE_H_FORMAT 2973 G1PPRL_STATE_H_FORMAT 2974 G1PPRL_BYTE_H_FORMAT, 2975 "type", "address-range", 2976 "used", "prev-live", "next-live", "gc-eff", 2977 "remset", "state", "code-roots"); 2978 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 2979 G1PPRL_TYPE_H_FORMAT 2980 G1PPRL_ADDR_BASE_H_FORMAT 2981 G1PPRL_BYTE_H_FORMAT 2982 G1PPRL_BYTE_H_FORMAT 2983 G1PPRL_BYTE_H_FORMAT 2984 G1PPRL_DOUBLE_H_FORMAT 2985 G1PPRL_BYTE_H_FORMAT 2986 G1PPRL_STATE_H_FORMAT 2987 G1PPRL_BYTE_H_FORMAT, 2988 "", "", 2989 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 2990 "(bytes)", "", "(bytes)"); 2991 } 2992 2993 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) { 2994 if (!log_is_enabled(Trace, gc, liveness)) { 2995 return false; 2996 } 2997 2998 const char* type = r->get_type_str(); 2999 HeapWord* bottom = r->bottom(); 3000 HeapWord* end = r->end(); 3001 size_t capacity_bytes = r->capacity(); 3002 size_t used_bytes = r->used(); 3003 size_t prev_live_bytes = r->live_bytes(); 3004 size_t next_live_bytes = r->next_live_bytes(); 3005 double gc_eff = r->gc_efficiency(); 3006 size_t remset_bytes = r->rem_set()->mem_size(); 3007 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 3008 const char* remset_type = r->rem_set()->get_short_state_str(); 3009 3010 _total_used_bytes += used_bytes; 3011 _total_capacity_bytes += capacity_bytes; 3012 _total_prev_live_bytes += prev_live_bytes; 3013 _total_next_live_bytes += next_live_bytes; 3014 _total_remset_bytes += remset_bytes; 3015 _total_strong_code_roots_bytes += strong_code_roots_bytes; 3016 3017 // Print a line for this particular region. 3018 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3019 G1PPRL_TYPE_FORMAT 3020 G1PPRL_ADDR_BASE_FORMAT 3021 G1PPRL_BYTE_FORMAT 3022 G1PPRL_BYTE_FORMAT 3023 G1PPRL_BYTE_FORMAT 3024 G1PPRL_DOUBLE_FORMAT 3025 G1PPRL_BYTE_FORMAT 3026 G1PPRL_STATE_FORMAT 3027 G1PPRL_BYTE_FORMAT, 3028 type, p2i(bottom), p2i(end), 3029 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 3030 remset_bytes, remset_type, strong_code_roots_bytes); 3031 3032 return false; 3033 } 3034 3035 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 3036 if (!log_is_enabled(Trace, gc, liveness)) { 3037 return; 3038 } 3039 3040 // add static memory usages to remembered set sizes 3041 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 3042 // Print the footer of the output. 3043 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3044 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3045 " SUMMARY" 3046 G1PPRL_SUM_MB_FORMAT("capacity") 3047 G1PPRL_SUM_MB_PERC_FORMAT("used") 3048 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 3049 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 3050 G1PPRL_SUM_MB_FORMAT("remset") 3051 G1PPRL_SUM_MB_FORMAT("code-roots"), 3052 bytes_to_mb(_total_capacity_bytes), 3053 bytes_to_mb(_total_used_bytes), 3054 percent_of(_total_used_bytes, _total_capacity_bytes), 3055 bytes_to_mb(_total_prev_live_bytes), 3056 percent_of(_total_prev_live_bytes, _total_capacity_bytes), 3057 bytes_to_mb(_total_next_live_bytes), 3058 percent_of(_total_next_live_bytes, _total_capacity_bytes), 3059 bytes_to_mb(_total_remset_bytes), 3060 bytes_to_mb(_total_strong_code_roots_bytes)); 3061 }