1 /* 2 * Copyright (c) 2001, 2020, 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/g1DirtyCardQueue.hpp" 34 #include "gc/g1/g1HeapVerifier.hpp" 35 #include "gc/g1/g1OopClosures.inline.hpp" 36 #include "gc/g1/g1Policy.hpp" 37 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp" 38 #include "gc/g1/g1StringDedup.hpp" 39 #include "gc/g1/g1ThreadLocalData.hpp" 40 #include "gc/g1/g1Trace.hpp" 41 #include "gc/g1/heapRegion.inline.hpp" 42 #include "gc/g1/heapRegionRemSet.hpp" 43 #include "gc/g1/heapRegionSet.inline.hpp" 44 #include "gc/shared/gcId.hpp" 45 #include "gc/shared/gcTimer.hpp" 46 #include "gc/shared/gcTraceTime.inline.hpp" 47 #include "gc/shared/gcVMOperations.hpp" 48 #include "gc/shared/genOopClosures.inline.hpp" 49 #include "gc/shared/referencePolicy.hpp" 50 #include "gc/shared/strongRootsScope.hpp" 51 #include "gc/shared/suspendibleThreadSet.hpp" 52 #include "gc/shared/taskTerminator.hpp" 53 #include "gc/shared/taskqueue.inline.hpp" 54 #include "gc/shared/weakProcessor.inline.hpp" 55 #include "gc/shared/workerPolicy.hpp" 56 #include "include/jvm.h" 57 #include "logging/log.hpp" 58 #include "memory/allocation.hpp" 59 #include "memory/iterator.hpp" 60 #include "memory/resourceArea.hpp" 61 #include "memory/universe.hpp" 62 #include "oops/access.inline.hpp" 63 #include "oops/oop.inline.hpp" 64 #include "runtime/atomic.hpp" 65 #include "runtime/handles.inline.hpp" 66 #include "runtime/java.hpp" 67 #include "runtime/orderAccess.hpp" 68 #include "runtime/prefetch.inline.hpp" 69 #include "services/memTracker.hpp" 70 #include "utilities/align.hpp" 71 #include "utilities/growableArray.hpp" 72 73 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) { 74 assert(addr < _cm->finger(), "invariant"); 75 assert(addr >= _task->finger(), "invariant"); 76 77 // We move that task's local finger along. 78 _task->move_finger_to(addr); 79 80 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr))); 81 // we only partially drain the local queue and global stack 82 _task->drain_local_queue(true); 83 _task->drain_global_stack(true); 84 85 // if the has_aborted flag has been raised, we need to bail out of 86 // the iteration 87 return !_task->has_aborted(); 88 } 89 90 G1CMMarkStack::G1CMMarkStack() : 91 _max_chunk_capacity(0), 92 _base(NULL), 93 _chunk_capacity(0) { 94 set_empty(); 95 } 96 97 bool G1CMMarkStack::resize(size_t new_capacity) { 98 assert(is_empty(), "Only resize when stack is empty."); 99 assert(new_capacity <= _max_chunk_capacity, 100 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity); 101 102 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC); 103 104 if (new_base == NULL) { 105 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)); 106 return false; 107 } 108 // Release old mapping. 109 if (_base != NULL) { 110 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 111 } 112 113 _base = new_base; 114 _chunk_capacity = new_capacity; 115 set_empty(); 116 117 return true; 118 } 119 120 size_t G1CMMarkStack::capacity_alignment() { 121 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry); 122 } 123 124 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) { 125 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized."); 126 127 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry); 128 129 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 130 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 131 132 guarantee(initial_chunk_capacity <= _max_chunk_capacity, 133 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT, 134 _max_chunk_capacity, 135 initial_chunk_capacity); 136 137 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT, 138 initial_chunk_capacity, _max_chunk_capacity); 139 140 return resize(initial_chunk_capacity); 141 } 142 143 void G1CMMarkStack::expand() { 144 if (_chunk_capacity == _max_chunk_capacity) { 145 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity); 146 return; 147 } 148 size_t old_capacity = _chunk_capacity; 149 // Double capacity if possible 150 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity); 151 152 if (resize(new_capacity)) { 153 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 154 old_capacity, new_capacity); 155 } else { 156 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 157 old_capacity, new_capacity); 158 } 159 } 160 161 G1CMMarkStack::~G1CMMarkStack() { 162 if (_base != NULL) { 163 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 164 } 165 } 166 167 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) { 168 elem->next = *list; 169 *list = elem; 170 } 171 172 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) { 173 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 174 add_chunk_to_list(&_chunk_list, elem); 175 _chunks_in_chunk_list++; 176 } 177 178 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) { 179 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 180 add_chunk_to_list(&_free_list, elem); 181 } 182 183 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) { 184 TaskQueueEntryChunk* result = *list; 185 if (result != NULL) { 186 *list = (*list)->next; 187 } 188 return result; 189 } 190 191 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() { 192 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 193 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list); 194 if (result != NULL) { 195 _chunks_in_chunk_list--; 196 } 197 return result; 198 } 199 200 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() { 201 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 202 return remove_chunk_from_list(&_free_list); 203 } 204 205 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() { 206 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code. 207 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding 208 // wraparound of _hwm. 209 if (_hwm >= _chunk_capacity) { 210 return NULL; 211 } 212 213 size_t cur_idx = Atomic::fetch_and_add(&_hwm, 1u); 214 if (cur_idx >= _chunk_capacity) { 215 return NULL; 216 } 217 218 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk; 219 result->next = NULL; 220 return result; 221 } 222 223 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) { 224 // Get a new chunk. 225 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list(); 226 227 if (new_chunk == NULL) { 228 // Did not get a chunk from the free list. Allocate from backing memory. 229 new_chunk = allocate_new_chunk(); 230 231 if (new_chunk == NULL) { 232 return false; 233 } 234 } 235 236 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 237 238 add_chunk_to_chunk_list(new_chunk); 239 240 return true; 241 } 242 243 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) { 244 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list(); 245 246 if (cur == NULL) { 247 return false; 248 } 249 250 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 251 252 add_chunk_to_free_list(cur); 253 return true; 254 } 255 256 void G1CMMarkStack::set_empty() { 257 _chunks_in_chunk_list = 0; 258 _hwm = 0; 259 _chunk_list = NULL; 260 _free_list = NULL; 261 } 262 263 G1CMRootMemRegions::G1CMRootMemRegions(uint const max_regions) : 264 _root_regions(NULL), 265 _max_regions(max_regions), 266 _num_root_regions(0), 267 _claimed_root_regions(0), 268 _scan_in_progress(false), 269 _should_abort(false) { 270 _root_regions = new MemRegion[_max_regions]; 271 if (_root_regions == NULL) { 272 vm_exit_during_initialization("Could not allocate root MemRegion set."); 273 } 274 } 275 276 G1CMRootMemRegions::~G1CMRootMemRegions() { 277 delete[] _root_regions; 278 } 279 280 void G1CMRootMemRegions::reset() { 281 _num_root_regions = 0; 282 } 283 284 void G1CMRootMemRegions::add(HeapWord* start, HeapWord* end) { 285 assert_at_safepoint(); 286 size_t idx = Atomic::fetch_and_add(&_num_root_regions, 1u); 287 assert(idx < _max_regions, "Trying to add more root MemRegions than there is space " SIZE_FORMAT, _max_regions); 288 assert(start != NULL && end != NULL && start <= end, "Start (" PTR_FORMAT ") should be less or equal to " 289 "end (" PTR_FORMAT ")", p2i(start), p2i(end)); 290 _root_regions[idx].set_start(start); 291 _root_regions[idx].set_end(end); 292 } 293 294 void G1CMRootMemRegions::prepare_for_scan() { 295 assert(!scan_in_progress(), "pre-condition"); 296 297 _scan_in_progress = _num_root_regions > 0; 298 299 _claimed_root_regions = 0; 300 _should_abort = false; 301 } 302 303 const MemRegion* G1CMRootMemRegions::claim_next() { 304 if (_should_abort) { 305 // If someone has set the should_abort flag, we return NULL to 306 // force the caller to bail out of their loop. 307 return NULL; 308 } 309 310 if (_claimed_root_regions >= _num_root_regions) { 311 return NULL; 312 } 313 314 size_t claimed_index = Atomic::fetch_and_add(&_claimed_root_regions, 1u); 315 if (claimed_index < _num_root_regions) { 316 return &_root_regions[claimed_index]; 317 } 318 return NULL; 319 } 320 321 uint G1CMRootMemRegions::num_root_regions() const { 322 return (uint)_num_root_regions; 323 } 324 325 void G1CMRootMemRegions::notify_scan_done() { 326 MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 327 _scan_in_progress = false; 328 RootRegionScan_lock->notify_all(); 329 } 330 331 void G1CMRootMemRegions::cancel_scan() { 332 notify_scan_done(); 333 } 334 335 void G1CMRootMemRegions::scan_finished() { 336 assert(scan_in_progress(), "pre-condition"); 337 338 if (!_should_abort) { 339 assert(_claimed_root_regions >= num_root_regions(), 340 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u", 341 _claimed_root_regions, num_root_regions()); 342 } 343 344 notify_scan_done(); 345 } 346 347 bool G1CMRootMemRegions::wait_until_scan_finished() { 348 if (!scan_in_progress()) { 349 return false; 350 } 351 352 { 353 MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 354 while (scan_in_progress()) { 355 ml.wait(); 356 } 357 } 358 return true; 359 } 360 361 // Returns the maximum number of workers to be used in a concurrent 362 // phase based on the number of GC workers being used in a STW 363 // phase. 364 static uint scale_concurrent_worker_threads(uint num_gc_workers) { 365 return MAX2((num_gc_workers + 2) / 4, 1U); 366 } 367 368 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, 369 G1RegionToSpaceMapper* prev_bitmap_storage, 370 G1RegionToSpaceMapper* next_bitmap_storage) : 371 // _cm_thread set inside the constructor 372 _g1h(g1h), 373 _completed_initialization(false), 374 375 _mark_bitmap_1(), 376 _mark_bitmap_2(), 377 _prev_mark_bitmap(&_mark_bitmap_1), 378 _next_mark_bitmap(&_mark_bitmap_2), 379 380 _heap(_g1h->reserved_region()), 381 382 _root_regions(_g1h->max_regions()), 383 384 _global_mark_stack(), 385 386 // _finger set in set_non_marking_state 387 388 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads), 389 _max_num_tasks(ParallelGCThreads), 390 // _num_active_tasks set in set_non_marking_state() 391 // _tasks set inside the constructor 392 393 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)), 394 _terminator((int) _max_num_tasks, _task_queues), 395 396 _first_overflow_barrier_sync(), 397 _second_overflow_barrier_sync(), 398 399 _has_overflown(false), 400 _concurrent(false), 401 _has_aborted(false), 402 _restart_for_overflow(false), 403 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 404 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()), 405 406 // _verbose_level set below 407 408 _init_times(), 409 _remark_times(), 410 _remark_mark_times(), 411 _remark_weak_ref_times(), 412 _cleanup_times(), 413 _total_cleanup_time(0.0), 414 415 _accum_task_vtime(NULL), 416 417 _concurrent_workers(NULL), 418 _num_concurrent_workers(0), 419 _max_concurrent_workers(0), 420 421 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)), 422 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC)) 423 { 424 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage); 425 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage); 426 427 // Create & start ConcurrentMark thread. 428 _cm_thread = new G1ConcurrentMarkThread(this); 429 if (_cm_thread->osthread() == NULL) { 430 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 431 } 432 433 assert(CGC_lock != NULL, "CGC_lock must be initialized"); 434 435 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) { 436 // Calculate the number of concurrent worker threads by scaling 437 // the number of parallel GC threads. 438 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads); 439 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num); 440 } 441 442 assert(ConcGCThreads > 0, "ConcGCThreads have been set."); 443 if (ConcGCThreads > ParallelGCThreads) { 444 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).", 445 ConcGCThreads, ParallelGCThreads); 446 return; 447 } 448 449 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset); 450 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads); 451 452 _num_concurrent_workers = ConcGCThreads; 453 _max_concurrent_workers = _num_concurrent_workers; 454 455 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true); 456 _concurrent_workers->initialize_workers(); 457 458 if (FLAG_IS_DEFAULT(MarkStackSize)) { 459 size_t mark_stack_size = 460 MIN2(MarkStackSizeMax, 461 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE))); 462 // Verify that the calculated value for MarkStackSize is in range. 463 // It would be nice to use the private utility routine from Arguments. 464 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 465 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 466 "must be between 1 and " SIZE_FORMAT, 467 mark_stack_size, MarkStackSizeMax); 468 return; 469 } 470 FLAG_SET_ERGO(MarkStackSize, mark_stack_size); 471 } else { 472 // Verify MarkStackSize is in range. 473 if (FLAG_IS_CMDLINE(MarkStackSize)) { 474 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 475 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 476 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 477 "must be between 1 and " SIZE_FORMAT, 478 MarkStackSize, MarkStackSizeMax); 479 return; 480 } 481 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 482 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 483 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 484 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 485 MarkStackSize, MarkStackSizeMax); 486 return; 487 } 488 } 489 } 490 } 491 492 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) { 493 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack."); 494 } 495 496 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC); 497 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC); 498 499 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 500 _num_active_tasks = _max_num_tasks; 501 502 for (uint i = 0; i < _max_num_tasks; ++i) { 503 G1CMTaskQueue* task_queue = new G1CMTaskQueue(); 504 task_queue->initialize(); 505 _task_queues->register_queue(i, task_queue); 506 507 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions()); 508 509 _accum_task_vtime[i] = 0.0; 510 } 511 512 reset_at_marking_complete(); 513 _completed_initialization = true; 514 } 515 516 void G1ConcurrentMark::reset() { 517 _has_aborted = false; 518 519 reset_marking_for_restart(); 520 521 // Reset all tasks, since different phases will use different number of active 522 // threads. So, it's easiest to have all of them ready. 523 for (uint i = 0; i < _max_num_tasks; ++i) { 524 _tasks[i]->reset(_next_mark_bitmap); 525 } 526 527 uint max_regions = _g1h->max_regions(); 528 for (uint i = 0; i < max_regions; i++) { 529 _top_at_rebuild_starts[i] = NULL; 530 _region_mark_stats[i].clear(); 531 } 532 } 533 534 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) { 535 for (uint j = 0; j < _max_num_tasks; ++j) { 536 _tasks[j]->clear_mark_stats_cache(region_idx); 537 } 538 _top_at_rebuild_starts[region_idx] = NULL; 539 _region_mark_stats[region_idx].clear(); 540 } 541 542 void G1ConcurrentMark::clear_statistics(HeapRegion* r) { 543 uint const region_idx = r->hrm_index(); 544 if (r->is_humongous()) { 545 assert(r->is_starts_humongous(), "Got humongous continues region here"); 546 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size()); 547 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) { 548 clear_statistics_in_region(j); 549 } 550 } else { 551 clear_statistics_in_region(region_idx); 552 } 553 } 554 555 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) { 556 if (bitmap->is_marked(addr)) { 557 bitmap->clear(addr); 558 } 559 } 560 561 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) { 562 assert_at_safepoint_on_vm_thread(); 563 564 // Need to clear all mark bits of the humongous object. 565 clear_mark_if_set(_prev_mark_bitmap, r->bottom()); 566 clear_mark_if_set(_next_mark_bitmap, r->bottom()); 567 568 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) { 569 return; 570 } 571 572 // Clear any statistics about the region gathered so far. 573 clear_statistics(r); 574 } 575 576 void G1ConcurrentMark::reset_marking_for_restart() { 577 _global_mark_stack.set_empty(); 578 579 // Expand the marking stack, if we have to and if we can. 580 if (has_overflown()) { 581 _global_mark_stack.expand(); 582 583 uint max_regions = _g1h->max_regions(); 584 for (uint i = 0; i < max_regions; i++) { 585 _region_mark_stats[i].clear_during_overflow(); 586 } 587 } 588 589 clear_has_overflown(); 590 _finger = _heap.start(); 591 592 for (uint i = 0; i < _max_num_tasks; ++i) { 593 G1CMTaskQueue* queue = _task_queues->queue(i); 594 queue->set_empty(); 595 } 596 } 597 598 void G1ConcurrentMark::set_concurrency(uint active_tasks) { 599 assert(active_tasks <= _max_num_tasks, "we should not have more"); 600 601 _num_active_tasks = active_tasks; 602 // Need to update the three data structures below according to the 603 // number of active threads for this phase. 604 _terminator.reset_for_reuse(active_tasks); 605 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 606 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 607 } 608 609 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 610 set_concurrency(active_tasks); 611 612 _concurrent = concurrent; 613 614 if (!concurrent) { 615 // At this point we should be in a STW phase, and completed marking. 616 assert_at_safepoint_on_vm_thread(); 617 assert(out_of_regions(), 618 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT, 619 p2i(_finger), p2i(_heap.end())); 620 } 621 } 622 623 void G1ConcurrentMark::reset_at_marking_complete() { 624 // We set the global marking state to some default values when we're 625 // not doing marking. 626 reset_marking_for_restart(); 627 _num_active_tasks = 0; 628 } 629 630 G1ConcurrentMark::~G1ConcurrentMark() { 631 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts); 632 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats); 633 // The G1ConcurrentMark instance is never freed. 634 ShouldNotReachHere(); 635 } 636 637 class G1ClearBitMapTask : public AbstractGangTask { 638 public: 639 static size_t chunk_size() { return M; } 640 641 private: 642 // Heap region closure used for clearing the given mark bitmap. 643 class G1ClearBitmapHRClosure : public HeapRegionClosure { 644 private: 645 G1CMBitMap* _bitmap; 646 G1ConcurrentMark* _cm; 647 public: 648 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) { 649 } 650 651 virtual bool do_heap_region(HeapRegion* r) { 652 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize; 653 654 HeapWord* cur = r->bottom(); 655 HeapWord* const end = r->end(); 656 657 while (cur < end) { 658 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 659 _bitmap->clear_range(mr); 660 661 cur += chunk_size_in_words; 662 663 // Abort iteration if after yielding the marking has been aborted. 664 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) { 665 return true; 666 } 667 // Repeat the asserts from before the start of the closure. We will do them 668 // as asserts here to minimize their overhead on the product. However, we 669 // will have them as guarantees at the beginning / end of the bitmap 670 // clearing to get some checking in the product. 671 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant"); 672 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 673 } 674 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index()); 675 676 return false; 677 } 678 }; 679 680 G1ClearBitmapHRClosure _cl; 681 HeapRegionClaimer _hr_claimer; 682 bool _suspendible; // If the task is suspendible, workers must join the STS. 683 684 public: 685 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) : 686 AbstractGangTask("G1 Clear Bitmap"), 687 _cl(bitmap, suspendible ? cm : NULL), 688 _hr_claimer(n_workers), 689 _suspendible(suspendible) 690 { } 691 692 void work(uint worker_id) { 693 SuspendibleThreadSetJoiner sts_join(_suspendible); 694 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id); 695 } 696 697 bool is_complete() { 698 return _cl.is_complete(); 699 } 700 }; 701 702 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) { 703 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint."); 704 705 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor(); 706 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size(); 707 708 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); 709 710 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield); 711 712 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks); 713 workers->run_task(&cl, num_workers); 714 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding."); 715 } 716 717 void G1ConcurrentMark::cleanup_for_next_mark() { 718 // Make sure that the concurrent mark thread looks to still be in 719 // the current cycle. 720 guarantee(cm_thread()->during_cycle(), "invariant"); 721 722 // We are finishing up the current cycle by clearing the next 723 // marking bitmap and getting it ready for the next cycle. During 724 // this time no other cycle can start. So, let's make sure that this 725 // is the case. 726 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 727 728 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true); 729 730 // Repeat the asserts from above. 731 guarantee(cm_thread()->during_cycle(), "invariant"); 732 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 733 } 734 735 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) { 736 assert_at_safepoint_on_vm_thread(); 737 clear_bitmap(_prev_mark_bitmap, workers, false); 738 } 739 740 class NoteStartOfMarkHRClosure : public HeapRegionClosure { 741 public: 742 bool do_heap_region(HeapRegion* r) { 743 r->note_start_of_marking(); 744 return false; 745 } 746 }; 747 748 void G1ConcurrentMark::pre_initial_mark() { 749 assert_at_safepoint_on_vm_thread(); 750 751 // Reset marking state. 752 reset(); 753 754 // For each region note start of marking. 755 NoteStartOfMarkHRClosure startcl; 756 _g1h->heap_region_iterate(&startcl); 757 758 _root_regions.reset(); 759 } 760 761 762 void G1ConcurrentMark::post_initial_mark() { 763 // Start Concurrent Marking weak-reference discovery. 764 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 765 // enable ("weak") refs discovery 766 rp->enable_discovery(); 767 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 768 769 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 770 // This is the start of the marking cycle, we're expected all 771 // threads to have SATB queues with active set to false. 772 satb_mq_set.set_active_all_threads(true, /* new active value */ 773 false /* expected_active */); 774 775 _root_regions.prepare_for_scan(); 776 777 // update_g1_committed() will be called at the end of an evac pause 778 // when marking is on. So, it's also called at the end of the 779 // initial-mark pause to update the heap end, if the heap expands 780 // during it. No need to call it here. 781 } 782 783 /* 784 * Notice that in the next two methods, we actually leave the STS 785 * during the barrier sync and join it immediately afterwards. If we 786 * do not do this, the following deadlock can occur: one thread could 787 * be in the barrier sync code, waiting for the other thread to also 788 * sync up, whereas another one could be trying to yield, while also 789 * waiting for the other threads to sync up too. 790 * 791 * Note, however, that this code is also used during remark and in 792 * this case we should not attempt to leave / enter the STS, otherwise 793 * we'll either hit an assert (debug / fastdebug) or deadlock 794 * (product). So we should only leave / enter the STS if we are 795 * operating concurrently. 796 * 797 * Because the thread that does the sync barrier has left the STS, it 798 * is possible to be suspended for a Full GC or an evacuation pause 799 * could occur. This is actually safe, since the entering the sync 800 * barrier is one of the last things do_marking_step() does, and it 801 * doesn't manipulate any data structures afterwards. 802 */ 803 804 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 805 bool barrier_aborted; 806 { 807 SuspendibleThreadSetLeaver sts_leave(concurrent()); 808 barrier_aborted = !_first_overflow_barrier_sync.enter(); 809 } 810 811 // at this point everyone should have synced up and not be doing any 812 // more work 813 814 if (barrier_aborted) { 815 // If the barrier aborted we ignore the overflow condition and 816 // just abort the whole marking phase as quickly as possible. 817 return; 818 } 819 } 820 821 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 822 SuspendibleThreadSetLeaver sts_leave(concurrent()); 823 _second_overflow_barrier_sync.enter(); 824 825 // at this point everything should be re-initialized and ready to go 826 } 827 828 class G1CMConcurrentMarkingTask : public AbstractGangTask { 829 G1ConcurrentMark* _cm; 830 831 public: 832 void work(uint worker_id) { 833 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread"); 834 ResourceMark rm; 835 836 double start_vtime = os::elapsedVTime(); 837 838 { 839 SuspendibleThreadSetJoiner sts_join; 840 841 assert(worker_id < _cm->active_tasks(), "invariant"); 842 843 G1CMTask* task = _cm->task(worker_id); 844 task->record_start_time(); 845 if (!_cm->has_aborted()) { 846 do { 847 task->do_marking_step(G1ConcMarkStepDurationMillis, 848 true /* do_termination */, 849 false /* is_serial*/); 850 851 _cm->do_yield_check(); 852 } while (!_cm->has_aborted() && task->has_aborted()); 853 } 854 task->record_end_time(); 855 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant"); 856 } 857 858 double end_vtime = os::elapsedVTime(); 859 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 860 } 861 862 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) : 863 AbstractGangTask("Concurrent Mark"), _cm(cm) { } 864 865 ~G1CMConcurrentMarkingTask() { } 866 }; 867 868 uint G1ConcurrentMark::calc_active_marking_workers() { 869 uint result = 0; 870 if (!UseDynamicNumberOfGCThreads || 871 (!FLAG_IS_DEFAULT(ConcGCThreads) && 872 !ForceDynamicNumberOfGCThreads)) { 873 result = _max_concurrent_workers; 874 } else { 875 result = 876 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers, 877 1, /* Minimum workers */ 878 _num_concurrent_workers, 879 Threads::number_of_non_daemon_threads()); 880 // Don't scale the result down by scale_concurrent_workers() because 881 // that scaling has already gone into "_max_concurrent_workers". 882 } 883 assert(result > 0 && result <= _max_concurrent_workers, 884 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u", 885 _max_concurrent_workers, result); 886 return result; 887 } 888 889 void G1ConcurrentMark::scan_root_region(const MemRegion* region, uint worker_id) { 890 #ifdef ASSERT 891 HeapWord* last = region->last(); 892 HeapRegion* hr = _g1h->heap_region_containing(last); 893 assert(hr->is_old() || hr->next_top_at_mark_start() == hr->bottom(), 894 "Root regions must be old or survivor/eden but region %u is %s", hr->hrm_index(), hr->get_type_str()); 895 assert(hr->next_top_at_mark_start() == region->start(), 896 "MemRegion start should be equal to nTAMS"); 897 #endif 898 899 G1RootRegionScanClosure cl(_g1h, this, worker_id); 900 901 const uintx interval = PrefetchScanIntervalInBytes; 902 HeapWord* curr = region->start(); 903 const HeapWord* end = region->end(); 904 while (curr < end) { 905 Prefetch::read(curr, interval); 906 oop obj = oop(curr); 907 int size = obj->oop_iterate_size(&cl); 908 assert(size == obj->size(), "sanity"); 909 curr += size; 910 } 911 } 912 913 class G1CMRootRegionScanTask : public AbstractGangTask { 914 G1ConcurrentMark* _cm; 915 public: 916 G1CMRootRegionScanTask(G1ConcurrentMark* cm) : 917 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { } 918 919 void work(uint worker_id) { 920 assert(Thread::current()->is_ConcurrentGC_thread(), 921 "this should only be done by a conc GC thread"); 922 923 G1CMRootMemRegions* root_regions = _cm->root_regions(); 924 const MemRegion* region = root_regions->claim_next(); 925 while (region != NULL) { 926 _cm->scan_root_region(region, worker_id); 927 region = root_regions->claim_next(); 928 } 929 } 930 }; 931 932 void G1ConcurrentMark::scan_root_regions() { 933 // scan_in_progress() will have been set to true only if there was 934 // at least one root region to scan. So, if it's false, we 935 // should not attempt to do any further work. 936 if (root_regions()->scan_in_progress()) { 937 assert(!has_aborted(), "Aborting before root region scanning is finished not supported."); 938 939 _num_concurrent_workers = MIN2(calc_active_marking_workers(), 940 // We distribute work on a per-region basis, so starting 941 // more threads than that is useless. 942 root_regions()->num_root_regions()); 943 assert(_num_concurrent_workers <= _max_concurrent_workers, 944 "Maximum number of marking threads exceeded"); 945 946 G1CMRootRegionScanTask task(this); 947 log_debug(gc, ergo)("Running %s using %u workers for %u work units.", 948 task.name(), _num_concurrent_workers, root_regions()->num_root_regions()); 949 _concurrent_workers->run_task(&task, _num_concurrent_workers); 950 951 // It's possible that has_aborted() is true here without actually 952 // aborting the survivor scan earlier. This is OK as it's 953 // mainly used for sanity checking. 954 root_regions()->scan_finished(); 955 } 956 } 957 958 void G1ConcurrentMark::concurrent_cycle_start() { 959 _gc_timer_cm->register_gc_start(); 960 961 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start()); 962 963 _g1h->trace_heap_before_gc(_gc_tracer_cm); 964 } 965 966 void G1ConcurrentMark::concurrent_cycle_end() { 967 _g1h->collector_state()->set_clearing_next_bitmap(false); 968 969 _g1h->trace_heap_after_gc(_gc_tracer_cm); 970 971 if (has_aborted()) { 972 log_info(gc, marking)("Concurrent Mark Abort"); 973 _gc_tracer_cm->report_concurrent_mode_failure(); 974 } 975 976 _gc_timer_cm->register_gc_end(); 977 978 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 979 } 980 981 void G1ConcurrentMark::mark_from_roots() { 982 _restart_for_overflow = false; 983 984 _num_concurrent_workers = calc_active_marking_workers(); 985 986 uint active_workers = MAX2(1U, _num_concurrent_workers); 987 988 // Setting active workers is not guaranteed since fewer 989 // worker threads may currently exist and more may not be 990 // available. 991 active_workers = _concurrent_workers->update_active_workers(active_workers); 992 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers()); 993 994 // Parallel task terminator is set in "set_concurrency_and_phase()" 995 set_concurrency_and_phase(active_workers, true /* concurrent */); 996 997 G1CMConcurrentMarkingTask marking_task(this); 998 _concurrent_workers->run_task(&marking_task); 999 print_stats(); 1000 } 1001 1002 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) { 1003 G1HeapVerifier* verifier = _g1h->verifier(); 1004 1005 verifier->verify_region_sets_optional(); 1006 1007 if (VerifyDuringGC) { 1008 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm); 1009 1010 size_t const BufLen = 512; 1011 char buffer[BufLen]; 1012 1013 jio_snprintf(buffer, BufLen, "During GC (%s)", caller); 1014 verifier->verify(type, vo, buffer); 1015 } 1016 1017 verifier->check_bitmaps(caller); 1018 } 1019 1020 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask { 1021 G1CollectedHeap* _g1h; 1022 G1ConcurrentMark* _cm; 1023 HeapRegionClaimer _hrclaimer; 1024 uint volatile _total_selected_for_rebuild; 1025 1026 G1PrintRegionLivenessInfoClosure _cl; 1027 1028 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure { 1029 G1CollectedHeap* _g1h; 1030 G1ConcurrentMark* _cm; 1031 1032 G1PrintRegionLivenessInfoClosure* _cl; 1033 1034 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild. 1035 1036 void update_remset_before_rebuild(HeapRegion* hr) { 1037 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker(); 1038 1039 bool selected_for_rebuild; 1040 if (hr->is_humongous()) { 1041 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0; 1042 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live); 1043 } else { 1044 size_t const live_bytes = _cm->liveness(hr->hrm_index()); 1045 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes); 1046 } 1047 if (selected_for_rebuild) { 1048 _num_regions_selected_for_rebuild++; 1049 } 1050 _cm->update_top_at_rebuild_start(hr); 1051 } 1052 1053 // Distribute the given words across the humongous object starting with hr and 1054 // note end of marking. 1055 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) { 1056 uint const region_idx = hr->hrm_index(); 1057 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size(); 1058 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words); 1059 1060 // "Distributing" zero words means that we only note end of marking for these 1061 // regions. 1062 assert(marked_words == 0 || obj_size_in_words == marked_words, 1063 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT, 1064 obj_size_in_words, marked_words); 1065 1066 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) { 1067 HeapRegion* const r = _g1h->region_at(i); 1068 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words); 1069 1070 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)", 1071 words_to_add, i, r->get_type_str()); 1072 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize); 1073 marked_words -= words_to_add; 1074 } 1075 assert(marked_words == 0, 1076 SIZE_FORMAT " words left after distributing space across %u regions", 1077 marked_words, num_regions_in_humongous); 1078 } 1079 1080 void update_marked_bytes(HeapRegion* hr) { 1081 uint const region_idx = hr->hrm_index(); 1082 size_t const marked_words = _cm->liveness(region_idx); 1083 // The marking attributes the object's size completely to the humongous starts 1084 // region. We need to distribute this value across the entire set of regions a 1085 // humongous object spans. 1086 if (hr->is_humongous()) { 1087 assert(hr->is_starts_humongous() || marked_words == 0, 1088 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)", 1089 marked_words, region_idx, hr->get_type_str()); 1090 if (hr->is_starts_humongous()) { 1091 distribute_marked_bytes(hr, marked_words); 1092 } 1093 } else { 1094 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str()); 1095 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize); 1096 } 1097 } 1098 1099 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) { 1100 hr->add_to_marked_bytes(marked_bytes); 1101 _cl->do_heap_region(hr); 1102 hr->note_end_of_marking(); 1103 } 1104 1105 public: 1106 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) : 1107 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { } 1108 1109 virtual bool do_heap_region(HeapRegion* r) { 1110 update_remset_before_rebuild(r); 1111 update_marked_bytes(r); 1112 1113 return false; 1114 } 1115 1116 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; } 1117 }; 1118 1119 public: 1120 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) : 1121 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"), 1122 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { } 1123 1124 virtual void work(uint worker_id) { 1125 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl); 1126 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id); 1127 Atomic::add(&_total_selected_for_rebuild, update_cl.num_selected_for_rebuild()); 1128 } 1129 1130 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; } 1131 1132 // Number of regions for which roughly one thread should be spawned for this work. 1133 static const uint RegionsPerThread = 384; 1134 }; 1135 1136 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure { 1137 G1CollectedHeap* _g1h; 1138 public: 1139 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { } 1140 1141 virtual bool do_heap_region(HeapRegion* r) { 1142 _g1h->policy()->remset_tracker()->update_after_rebuild(r); 1143 return false; 1144 } 1145 }; 1146 1147 void G1ConcurrentMark::remark() { 1148 assert_at_safepoint_on_vm_thread(); 1149 1150 // If a full collection has happened, we should not continue. However we might 1151 // have ended up here as the Remark VM operation has been scheduled already. 1152 if (has_aborted()) { 1153 return; 1154 } 1155 1156 G1Policy* policy = _g1h->policy(); 1157 policy->record_concurrent_mark_remark_start(); 1158 1159 double start = os::elapsedTime(); 1160 1161 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before"); 1162 1163 { 1164 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm); 1165 finalize_marking(); 1166 } 1167 1168 double mark_work_end = os::elapsedTime(); 1169 1170 bool const mark_finished = !has_overflown(); 1171 if (mark_finished) { 1172 weak_refs_work(false /* clear_all_soft_refs */); 1173 1174 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 1175 // We're done with marking. 1176 // This is the end of the marking cycle, we're expected all 1177 // threads to have SATB queues with active set to true. 1178 satb_mq_set.set_active_all_threads(false, /* new active value */ 1179 true /* expected_active */); 1180 1181 { 1182 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm); 1183 flush_all_task_caches(); 1184 } 1185 1186 // Install newly created mark bitmap as "prev". 1187 swap_mark_bitmaps(); 1188 { 1189 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm); 1190 1191 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) / 1192 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread; 1193 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity); 1194 1195 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers); 1196 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions()); 1197 _g1h->workers()->run_task(&cl, num_workers); 1198 1199 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u", 1200 _g1h->num_regions(), cl.total_selected_for_rebuild()); 1201 } 1202 { 1203 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm); 1204 reclaim_empty_regions(); 1205 } 1206 1207 // Clean out dead classes 1208 if (ClassUnloadingWithConcurrentMark) { 1209 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm); 1210 ClassLoaderDataGraph::purge(); 1211 } 1212 1213 _g1h->resize_heap_if_necessary(); 1214 1215 compute_new_sizes(); 1216 1217 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after"); 1218 1219 assert(!restart_for_overflow(), "sanity"); 1220 // Completely reset the marking state since marking completed 1221 reset_at_marking_complete(); 1222 } else { 1223 // We overflowed. Restart concurrent marking. 1224 _restart_for_overflow = true; 1225 1226 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow"); 1227 1228 // Clear the marking state because we will be restarting 1229 // marking due to overflowing the global mark stack. 1230 reset_marking_for_restart(); 1231 } 1232 1233 { 1234 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm); 1235 report_object_count(mark_finished); 1236 } 1237 1238 // Statistics 1239 double now = os::elapsedTime(); 1240 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1241 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1242 _remark_times.add((now - start) * 1000.0); 1243 1244 policy->record_concurrent_mark_remark_end(); 1245 } 1246 1247 class G1ReclaimEmptyRegionsTask : public AbstractGangTask { 1248 // Per-region work during the Cleanup pause. 1249 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure { 1250 G1CollectedHeap* _g1h; 1251 size_t _freed_bytes; 1252 FreeRegionList* _local_cleanup_list; 1253 uint _old_regions_removed; 1254 uint _humongous_regions_removed; 1255 1256 public: 1257 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h, 1258 FreeRegionList* local_cleanup_list) : 1259 _g1h(g1h), 1260 _freed_bytes(0), 1261 _local_cleanup_list(local_cleanup_list), 1262 _old_regions_removed(0), 1263 _humongous_regions_removed(0) { } 1264 1265 size_t freed_bytes() { return _freed_bytes; } 1266 const uint old_regions_removed() { return _old_regions_removed; } 1267 const uint humongous_regions_removed() { return _humongous_regions_removed; } 1268 1269 bool do_heap_region(HeapRegion *hr) { 1270 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) { 1271 _freed_bytes += hr->used(); 1272 hr->set_containing_set(NULL); 1273 if (hr->is_humongous()) { 1274 _humongous_regions_removed++; 1275 _g1h->free_humongous_region(hr, _local_cleanup_list); 1276 } else { 1277 _old_regions_removed++; 1278 _g1h->free_region(hr, _local_cleanup_list); 1279 } 1280 hr->clear_cardtable(); 1281 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index()); 1282 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom())); 1283 } 1284 1285 return false; 1286 } 1287 }; 1288 1289 G1CollectedHeap* _g1h; 1290 FreeRegionList* _cleanup_list; 1291 HeapRegionClaimer _hrclaimer; 1292 1293 public: 1294 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1295 AbstractGangTask("G1 Cleanup"), 1296 _g1h(g1h), 1297 _cleanup_list(cleanup_list), 1298 _hrclaimer(n_workers) { 1299 } 1300 1301 void work(uint worker_id) { 1302 FreeRegionList local_cleanup_list("Local Cleanup List"); 1303 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list); 1304 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id); 1305 assert(cl.is_complete(), "Shouldn't have aborted!"); 1306 1307 // Now update the old/humongous region sets 1308 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed()); 1309 { 1310 MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1311 _g1h->decrement_summary_bytes(cl.freed_bytes()); 1312 1313 _cleanup_list->add_ordered(&local_cleanup_list); 1314 assert(local_cleanup_list.is_empty(), "post-condition"); 1315 } 1316 } 1317 }; 1318 1319 void G1ConcurrentMark::reclaim_empty_regions() { 1320 WorkGang* workers = _g1h->workers(); 1321 FreeRegionList empty_regions_list("Empty Regions After Mark List"); 1322 1323 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers()); 1324 workers->run_task(&cl); 1325 1326 if (!empty_regions_list.is_empty()) { 1327 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length()); 1328 // Now print the empty regions list. 1329 G1HRPrinter* hrp = _g1h->hr_printer(); 1330 if (hrp->is_active()) { 1331 FreeRegionListIterator iter(&empty_regions_list); 1332 while (iter.more_available()) { 1333 HeapRegion* hr = iter.get_next(); 1334 hrp->cleanup(hr); 1335 } 1336 } 1337 // And actually make them available. 1338 _g1h->prepend_to_freelist(&empty_regions_list); 1339 } 1340 } 1341 1342 void G1ConcurrentMark::compute_new_sizes() { 1343 MetaspaceGC::compute_new_size(); 1344 1345 // Cleanup will have freed any regions completely full of garbage. 1346 // Update the soft reference policy with the new heap occupancy. 1347 Universe::update_heap_info_at_gc(); 1348 1349 // We reclaimed old regions so we should calculate the sizes to make 1350 // sure we update the old gen/space data. 1351 _g1h->g1mm()->update_sizes(); 1352 } 1353 1354 void G1ConcurrentMark::cleanup() { 1355 assert_at_safepoint_on_vm_thread(); 1356 1357 // If a full collection has happened, we shouldn't do this. 1358 if (has_aborted()) { 1359 return; 1360 } 1361 1362 G1Policy* policy = _g1h->policy(); 1363 policy->record_concurrent_mark_cleanup_start(); 1364 1365 double start = os::elapsedTime(); 1366 1367 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before"); 1368 1369 { 1370 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm); 1371 G1UpdateRemSetTrackingAfterRebuild cl(_g1h); 1372 _g1h->heap_region_iterate(&cl); 1373 } 1374 1375 if (log_is_enabled(Trace, gc, liveness)) { 1376 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup"); 1377 _g1h->heap_region_iterate(&cl); 1378 } 1379 1380 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after"); 1381 1382 // We need to make this be a "collection" so any collection pause that 1383 // races with it goes around and waits for Cleanup to finish. 1384 _g1h->increment_total_collections(); 1385 1386 // Local statistics 1387 double recent_cleanup_time = (os::elapsedTime() - start); 1388 _total_cleanup_time += recent_cleanup_time; 1389 _cleanup_times.add(recent_cleanup_time); 1390 1391 { 1392 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm); 1393 policy->record_concurrent_mark_cleanup_end(); 1394 } 1395 } 1396 1397 // 'Keep Alive' oop closure used by both serial parallel reference processing. 1398 // Uses the G1CMTask associated with a worker thread (for serial reference 1399 // processing the G1CMTask for worker 0 is used) to preserve (mark) and 1400 // trace referent objects. 1401 // 1402 // Using the G1CMTask and embedded local queues avoids having the worker 1403 // threads operating on the global mark stack. This reduces the risk 1404 // of overflowing the stack - which we would rather avoid at this late 1405 // state. Also using the tasks' local queues removes the potential 1406 // of the workers interfering with each other that could occur if 1407 // operating on the global stack. 1408 1409 class G1CMKeepAliveAndDrainClosure : public OopClosure { 1410 G1ConcurrentMark* _cm; 1411 G1CMTask* _task; 1412 uint _ref_counter_limit; 1413 uint _ref_counter; 1414 bool _is_serial; 1415 public: 1416 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1417 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval), 1418 _ref_counter(_ref_counter_limit), _is_serial(is_serial) { 1419 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1420 } 1421 1422 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 1423 virtual void do_oop( oop* p) { do_oop_work(p); } 1424 1425 template <class T> void do_oop_work(T* p) { 1426 if (_cm->has_overflown()) { 1427 return; 1428 } 1429 if (!_task->deal_with_reference(p)) { 1430 // We did not add anything to the mark bitmap (or mark stack), so there is 1431 // no point trying to drain it. 1432 return; 1433 } 1434 _ref_counter--; 1435 1436 if (_ref_counter == 0) { 1437 // We have dealt with _ref_counter_limit references, pushing them 1438 // and objects reachable from them on to the local stack (and 1439 // possibly the global stack). Call G1CMTask::do_marking_step() to 1440 // process these entries. 1441 // 1442 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if 1443 // there's nothing more to do (i.e. we're done with the entries that 1444 // were pushed as a result of the G1CMTask::deal_with_reference() calls 1445 // above) or we overflow. 1446 // 1447 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1448 // flag while there may still be some work to do. (See the comment at 1449 // the beginning of G1CMTask::do_marking_step() for those conditions - 1450 // one of which is reaching the specified time target.) It is only 1451 // when G1CMTask::do_marking_step() returns without setting the 1452 // has_aborted() flag that the marking step has completed. 1453 do { 1454 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1455 _task->do_marking_step(mark_step_duration_ms, 1456 false /* do_termination */, 1457 _is_serial); 1458 } while (_task->has_aborted() && !_cm->has_overflown()); 1459 _ref_counter = _ref_counter_limit; 1460 } 1461 } 1462 }; 1463 1464 // 'Drain' oop closure used by both serial and parallel reference processing. 1465 // Uses the G1CMTask associated with a given worker thread (for serial 1466 // reference processing the G1CMtask for worker 0 is used). Calls the 1467 // do_marking_step routine, with an unbelievably large timeout value, 1468 // to drain the marking data structures of the remaining entries 1469 // added by the 'keep alive' oop closure above. 1470 1471 class G1CMDrainMarkingStackClosure : public VoidClosure { 1472 G1ConcurrentMark* _cm; 1473 G1CMTask* _task; 1474 bool _is_serial; 1475 public: 1476 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1477 _cm(cm), _task(task), _is_serial(is_serial) { 1478 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1479 } 1480 1481 void do_void() { 1482 do { 1483 // We call G1CMTask::do_marking_step() to completely drain the local 1484 // and global marking stacks of entries pushed by the 'keep alive' 1485 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 1486 // 1487 // G1CMTask::do_marking_step() is called in a loop, which we'll exit 1488 // if there's nothing more to do (i.e. we've completely drained the 1489 // entries that were pushed as a a result of applying the 'keep alive' 1490 // closure to the entries on the discovered ref lists) or we overflow 1491 // the global marking stack. 1492 // 1493 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1494 // flag while there may still be some work to do. (See the comment at 1495 // the beginning of G1CMTask::do_marking_step() for those conditions - 1496 // one of which is reaching the specified time target.) It is only 1497 // when G1CMTask::do_marking_step() returns without setting the 1498 // has_aborted() flag that the marking step has completed. 1499 1500 _task->do_marking_step(1000000000.0 /* something very large */, 1501 true /* do_termination */, 1502 _is_serial); 1503 } while (_task->has_aborted() && !_cm->has_overflown()); 1504 } 1505 }; 1506 1507 // Implementation of AbstractRefProcTaskExecutor for parallel 1508 // reference processing at the end of G1 concurrent marking 1509 1510 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 1511 private: 1512 G1CollectedHeap* _g1h; 1513 G1ConcurrentMark* _cm; 1514 WorkGang* _workers; 1515 uint _active_workers; 1516 1517 public: 1518 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 1519 G1ConcurrentMark* cm, 1520 WorkGang* workers, 1521 uint n_workers) : 1522 _g1h(g1h), _cm(cm), 1523 _workers(workers), _active_workers(n_workers) { } 1524 1525 virtual void execute(ProcessTask& task, uint ergo_workers); 1526 }; 1527 1528 class G1CMRefProcTaskProxy : public AbstractGangTask { 1529 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 1530 ProcessTask& _proc_task; 1531 G1CollectedHeap* _g1h; 1532 G1ConcurrentMark* _cm; 1533 1534 public: 1535 G1CMRefProcTaskProxy(ProcessTask& proc_task, 1536 G1CollectedHeap* g1h, 1537 G1ConcurrentMark* cm) : 1538 AbstractGangTask("Process reference objects in parallel"), 1539 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 1540 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1541 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 1542 } 1543 1544 virtual void work(uint worker_id) { 1545 ResourceMark rm; 1546 HandleMark hm; 1547 G1CMTask* task = _cm->task(worker_id); 1548 G1CMIsAliveClosure g1_is_alive(_g1h); 1549 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 1550 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 1551 1552 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 1553 } 1554 }; 1555 1556 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 1557 assert(_workers != NULL, "Need parallel worker threads."); 1558 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1559 assert(_workers->active_workers() >= ergo_workers, 1560 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)", 1561 ergo_workers, _workers->active_workers()); 1562 1563 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 1564 1565 // We need to reset the concurrency level before each 1566 // proxy task execution, so that the termination protocol 1567 // and overflow handling in G1CMTask::do_marking_step() knows 1568 // how many workers to wait for. 1569 _cm->set_concurrency(ergo_workers); 1570 _workers->run_task(&proc_task_proxy, ergo_workers); 1571 } 1572 1573 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) { 1574 ResourceMark rm; 1575 HandleMark hm; 1576 1577 // Is alive closure. 1578 G1CMIsAliveClosure g1_is_alive(_g1h); 1579 1580 // Inner scope to exclude the cleaning of the string table 1581 // from the displayed time. 1582 { 1583 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm); 1584 1585 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1586 1587 // See the comment in G1CollectedHeap::ref_processing_init() 1588 // about how reference processing currently works in G1. 1589 1590 // Set the soft reference policy 1591 rp->setup_policy(clear_all_soft_refs); 1592 assert(_global_mark_stack.is_empty(), "mark stack should be empty"); 1593 1594 // Instances of the 'Keep Alive' and 'Complete GC' closures used 1595 // in serial reference processing. Note these closures are also 1596 // used for serially processing (by the the current thread) the 1597 // JNI references during parallel reference processing. 1598 // 1599 // These closures do not need to synchronize with the worker 1600 // threads involved in parallel reference processing as these 1601 // instances are executed serially by the current thread (e.g. 1602 // reference processing is not multi-threaded and is thus 1603 // performed by the current thread instead of a gang worker). 1604 // 1605 // The gang tasks involved in parallel reference processing create 1606 // their own instances of these closures, which do their own 1607 // synchronization among themselves. 1608 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 1609 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 1610 1611 // We need at least one active thread. If reference processing 1612 // is not multi-threaded we use the current (VMThread) thread, 1613 // otherwise we use the work gang from the G1CollectedHeap and 1614 // we utilize all the worker threads we can. 1615 bool processing_is_mt = rp->processing_is_mt(); 1616 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U); 1617 active_workers = clamp(active_workers, 1u, _max_num_tasks); 1618 1619 // Parallel processing task executor. 1620 G1CMRefProcTaskExecutor par_task_executor(_g1h, this, 1621 _g1h->workers(), active_workers); 1622 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 1623 1624 // Set the concurrency level. The phase was already set prior to 1625 // executing the remark task. 1626 set_concurrency(active_workers); 1627 1628 // Set the degree of MT processing here. If the discovery was done MT, 1629 // the number of threads involved during discovery could differ from 1630 // the number of active workers. This is OK as long as the discovered 1631 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 1632 rp->set_active_mt_degree(active_workers); 1633 1634 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues()); 1635 1636 // Process the weak references. 1637 const ReferenceProcessorStats& stats = 1638 rp->process_discovered_references(&g1_is_alive, 1639 &g1_keep_alive, 1640 &g1_drain_mark_stack, 1641 executor, 1642 &pt); 1643 _gc_tracer_cm->report_gc_reference_stats(stats); 1644 pt.print_all_references(); 1645 1646 // The do_oop work routines of the keep_alive and drain_marking_stack 1647 // oop closures will set the has_overflown flag if we overflow the 1648 // global marking stack. 1649 1650 assert(has_overflown() || _global_mark_stack.is_empty(), 1651 "Mark stack should be empty (unless it has overflown)"); 1652 1653 assert(rp->num_queues() == active_workers, "why not"); 1654 1655 rp->verify_no_references_recorded(); 1656 assert(!rp->discovery_enabled(), "Post condition"); 1657 } 1658 1659 if (has_overflown()) { 1660 // We can not trust g1_is_alive and the contents of the heap if the marking stack 1661 // overflowed while processing references. Exit the VM. 1662 fatal("Overflow during reference processing, can not continue. Please " 1663 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and " 1664 "restart.", MarkStackSizeMax); 1665 return; 1666 } 1667 1668 assert(_global_mark_stack.is_empty(), "Marking should have completed"); 1669 1670 { 1671 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm); 1672 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1); 1673 } 1674 1675 // Unload Klasses, String, Code Cache, etc. 1676 if (ClassUnloadingWithConcurrentMark) { 1677 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm); 1678 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm); 1679 _g1h->complete_cleaning(&g1_is_alive, purged_classes); 1680 } else if (StringDedup::is_enabled()) { 1681 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm); 1682 _g1h->string_dedup_cleaning(&g1_is_alive, NULL); 1683 } 1684 } 1685 1686 class G1PrecleanYieldClosure : public YieldClosure { 1687 G1ConcurrentMark* _cm; 1688 1689 public: 1690 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { } 1691 1692 virtual bool should_return() { 1693 return _cm->has_aborted(); 1694 } 1695 1696 virtual bool should_return_fine_grain() { 1697 _cm->do_yield_check(); 1698 return _cm->has_aborted(); 1699 } 1700 }; 1701 1702 void G1ConcurrentMark::preclean() { 1703 assert(G1UseReferencePrecleaning, "Precleaning must be enabled."); 1704 1705 SuspendibleThreadSetJoiner joiner; 1706 1707 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */); 1708 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */); 1709 1710 set_concurrency_and_phase(1, true); 1711 1712 G1PrecleanYieldClosure yield_cl(this); 1713 1714 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1715 // Precleaning is single threaded. Temporarily disable MT discovery. 1716 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); 1717 rp->preclean_discovered_references(rp->is_alive_non_header(), 1718 &keep_alive, 1719 &drain_mark_stack, 1720 &yield_cl, 1721 _gc_timer_cm); 1722 } 1723 1724 // When sampling object counts, we already swapped the mark bitmaps, so we need to use 1725 // the prev bitmap determining liveness. 1726 class G1ObjectCountIsAliveClosure: public BoolObjectClosure { 1727 G1CollectedHeap* _g1h; 1728 public: 1729 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 1730 1731 bool do_object_b(oop obj) { 1732 return obj != NULL && 1733 (!_g1h->is_in_g1_reserved(obj) || !_g1h->is_obj_dead(obj)); 1734 } 1735 }; 1736 1737 void G1ConcurrentMark::report_object_count(bool mark_completed) { 1738 // Depending on the completion of the marking liveness needs to be determined 1739 // using either the next or prev bitmap. 1740 if (mark_completed) { 1741 G1ObjectCountIsAliveClosure is_alive(_g1h); 1742 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1743 } else { 1744 G1CMIsAliveClosure is_alive(_g1h); 1745 _gc_tracer_cm->report_object_count_after_gc(&is_alive); 1746 } 1747 } 1748 1749 1750 void G1ConcurrentMark::swap_mark_bitmaps() { 1751 G1CMBitMap* temp = _prev_mark_bitmap; 1752 _prev_mark_bitmap = _next_mark_bitmap; 1753 _next_mark_bitmap = temp; 1754 _g1h->collector_state()->set_clearing_next_bitmap(true); 1755 } 1756 1757 // Closure for marking entries in SATB buffers. 1758 class G1CMSATBBufferClosure : public SATBBufferClosure { 1759 private: 1760 G1CMTask* _task; 1761 G1CollectedHeap* _g1h; 1762 1763 // This is very similar to G1CMTask::deal_with_reference, but with 1764 // more relaxed requirements for the argument, so this must be more 1765 // circumspect about treating the argument as an object. 1766 void do_entry(void* entry) const { 1767 _task->increment_refs_reached(); 1768 oop const obj = static_cast<oop>(entry); 1769 _task->make_reference_grey(obj); 1770 } 1771 1772 public: 1773 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h) 1774 : _task(task), _g1h(g1h) { } 1775 1776 virtual void do_buffer(void** buffer, size_t size) { 1777 for (size_t i = 0; i < size; ++i) { 1778 do_entry(buffer[i]); 1779 } 1780 } 1781 }; 1782 1783 class G1RemarkThreadsClosure : public ThreadClosure { 1784 G1CMSATBBufferClosure _cm_satb_cl; 1785 G1CMOopClosure _cm_cl; 1786 MarkingCodeBlobClosure _code_cl; 1787 uintx _claim_token; 1788 1789 public: 1790 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) : 1791 _cm_satb_cl(task, g1h), 1792 _cm_cl(g1h, task), 1793 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations), 1794 _claim_token(Threads::thread_claim_token()) {} 1795 1796 void do_thread(Thread* thread) { 1797 if (thread->claim_threads_do(true, _claim_token)) { 1798 SATBMarkQueue& queue = G1ThreadLocalData::satb_mark_queue(thread); 1799 queue.apply_closure_and_empty(&_cm_satb_cl); 1800 if (thread->is_Java_thread()) { 1801 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking 1802 // however the liveness of oops reachable from nmethods have very complex lifecycles: 1803 // * Alive if on the stack of an executing method 1804 // * Weakly reachable otherwise 1805 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be 1806 // live by the SATB invariant but other oops recorded in nmethods may behave differently. 1807 JavaThread* jt = (JavaThread*)thread; 1808 jt->nmethods_do(&_code_cl); 1809 } 1810 } 1811 } 1812 }; 1813 1814 class G1CMRemarkTask : public AbstractGangTask { 1815 G1ConcurrentMark* _cm; 1816 public: 1817 void work(uint worker_id) { 1818 G1CMTask* task = _cm->task(worker_id); 1819 task->record_start_time(); 1820 { 1821 ResourceMark rm; 1822 HandleMark hm; 1823 1824 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task); 1825 Threads::threads_do(&threads_f); 1826 } 1827 1828 do { 1829 task->do_marking_step(1000000000.0 /* something very large */, 1830 true /* do_termination */, 1831 false /* is_serial */); 1832 } while (task->has_aborted() && !_cm->has_overflown()); 1833 // If we overflow, then we do not want to restart. We instead 1834 // want to abort remark and do concurrent marking again. 1835 task->record_end_time(); 1836 } 1837 1838 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) : 1839 AbstractGangTask("Par Remark"), _cm(cm) { 1840 _cm->terminator()->reset_for_reuse(active_workers); 1841 } 1842 }; 1843 1844 void G1ConcurrentMark::finalize_marking() { 1845 ResourceMark rm; 1846 HandleMark hm; 1847 1848 _g1h->ensure_parsability(false); 1849 1850 // this is remark, so we'll use up all active threads 1851 uint active_workers = _g1h->workers()->active_workers(); 1852 set_concurrency_and_phase(active_workers, false /* concurrent */); 1853 // Leave _parallel_marking_threads at it's 1854 // value originally calculated in the G1ConcurrentMark 1855 // constructor and pass values of the active workers 1856 // through the gang in the task. 1857 1858 { 1859 StrongRootsScope srs(active_workers); 1860 1861 G1CMRemarkTask remarkTask(this, active_workers); 1862 // We will start all available threads, even if we decide that the 1863 // active_workers will be fewer. The extra ones will just bail out 1864 // immediately. 1865 _g1h->workers()->run_task(&remarkTask); 1866 } 1867 1868 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 1869 guarantee(has_overflown() || 1870 satb_mq_set.completed_buffers_num() == 0, 1871 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT, 1872 BOOL_TO_STR(has_overflown()), 1873 satb_mq_set.completed_buffers_num()); 1874 1875 print_stats(); 1876 } 1877 1878 void G1ConcurrentMark::flush_all_task_caches() { 1879 size_t hits = 0; 1880 size_t misses = 0; 1881 for (uint i = 0; i < _max_num_tasks; i++) { 1882 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache(); 1883 hits += stats.first; 1884 misses += stats.second; 1885 } 1886 size_t sum = hits + misses; 1887 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf", 1888 hits, misses, percent_of(hits, sum)); 1889 } 1890 1891 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) { 1892 _prev_mark_bitmap->clear_range(mr); 1893 } 1894 1895 HeapRegion* 1896 G1ConcurrentMark::claim_region(uint worker_id) { 1897 // "checkpoint" the finger 1898 HeapWord* finger = _finger; 1899 1900 while (finger < _heap.end()) { 1901 assert(_g1h->is_in_g1_reserved(finger), "invariant"); 1902 1903 HeapRegion* curr_region = _g1h->heap_region_containing(finger); 1904 // Make sure that the reads below do not float before loading curr_region. 1905 OrderAccess::loadload(); 1906 // Above heap_region_containing may return NULL as we always scan claim 1907 // until the end of the heap. In this case, just jump to the next region. 1908 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords; 1909 1910 // Is the gap between reading the finger and doing the CAS too long? 1911 HeapWord* res = Atomic::cmpxchg(&_finger, finger, end); 1912 if (res == finger && curr_region != NULL) { 1913 // we succeeded 1914 HeapWord* bottom = curr_region->bottom(); 1915 HeapWord* limit = curr_region->next_top_at_mark_start(); 1916 1917 // notice that _finger == end cannot be guaranteed here since, 1918 // someone else might have moved the finger even further 1919 assert(_finger >= end, "the finger should have moved forward"); 1920 1921 if (limit > bottom) { 1922 return curr_region; 1923 } else { 1924 assert(limit == bottom, 1925 "the region limit should be at bottom"); 1926 // we return NULL and the caller should try calling 1927 // claim_region() again. 1928 return NULL; 1929 } 1930 } else { 1931 assert(_finger > finger, "the finger should have moved forward"); 1932 // read it again 1933 finger = _finger; 1934 } 1935 } 1936 1937 return NULL; 1938 } 1939 1940 #ifndef PRODUCT 1941 class VerifyNoCSetOops { 1942 G1CollectedHeap* _g1h; 1943 const char* _phase; 1944 int _info; 1945 1946 public: 1947 VerifyNoCSetOops(const char* phase, int info = -1) : 1948 _g1h(G1CollectedHeap::heap()), 1949 _phase(phase), 1950 _info(info) 1951 { } 1952 1953 void operator()(G1TaskQueueEntry task_entry) const { 1954 if (task_entry.is_array_slice()) { 1955 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice())); 1956 return; 1957 } 1958 guarantee(oopDesc::is_oop(task_entry.obj()), 1959 "Non-oop " PTR_FORMAT ", phase: %s, info: %d", 1960 p2i(task_entry.obj()), _phase, _info); 1961 HeapRegion* r = _g1h->heap_region_containing(task_entry.obj()); 1962 guarantee(!(r->in_collection_set() || r->has_index_in_opt_cset()), 1963 "obj " PTR_FORMAT " from %s (%d) in region %u in (optional) collection set", 1964 p2i(task_entry.obj()), _phase, _info, r->hrm_index()); 1965 } 1966 }; 1967 1968 void G1ConcurrentMark::verify_no_collection_set_oops() { 1969 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); 1970 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) { 1971 return; 1972 } 1973 1974 // Verify entries on the global mark stack 1975 _global_mark_stack.iterate(VerifyNoCSetOops("Stack")); 1976 1977 // Verify entries on the task queues 1978 for (uint i = 0; i < _max_num_tasks; ++i) { 1979 G1CMTaskQueue* queue = _task_queues->queue(i); 1980 queue->iterate(VerifyNoCSetOops("Queue", i)); 1981 } 1982 1983 // Verify the global finger 1984 HeapWord* global_finger = finger(); 1985 if (global_finger != NULL && global_finger < _heap.end()) { 1986 // Since we always iterate over all regions, we might get a NULL HeapRegion 1987 // here. 1988 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger); 1989 guarantee(global_hr == NULL || global_finger == global_hr->bottom(), 1990 "global finger: " PTR_FORMAT " region: " HR_FORMAT, 1991 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)); 1992 } 1993 1994 // Verify the task fingers 1995 assert(_num_concurrent_workers <= _max_num_tasks, "sanity"); 1996 for (uint i = 0; i < _num_concurrent_workers; ++i) { 1997 G1CMTask* task = _tasks[i]; 1998 HeapWord* task_finger = task->finger(); 1999 if (task_finger != NULL && task_finger < _heap.end()) { 2000 // See above note on the global finger verification. 2001 HeapRegion* r = _g1h->heap_region_containing(task_finger); 2002 guarantee(r == NULL || task_finger == r->bottom() || 2003 !r->in_collection_set() || !r->has_index_in_opt_cset(), 2004 "task finger: " PTR_FORMAT " region: " HR_FORMAT, 2005 p2i(task_finger), HR_FORMAT_PARAMS(r)); 2006 } 2007 } 2008 } 2009 #endif // PRODUCT 2010 2011 void G1ConcurrentMark::rebuild_rem_set_concurrently() { 2012 _g1h->rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset); 2013 } 2014 2015 void G1ConcurrentMark::print_stats() { 2016 if (!log_is_enabled(Debug, gc, stats)) { 2017 return; 2018 } 2019 log_debug(gc, stats)("---------------------------------------------------------------------"); 2020 for (size_t i = 0; i < _num_active_tasks; ++i) { 2021 _tasks[i]->print_stats(); 2022 log_debug(gc, stats)("---------------------------------------------------------------------"); 2023 } 2024 } 2025 2026 void G1ConcurrentMark::concurrent_cycle_abort() { 2027 if (!cm_thread()->during_cycle() || _has_aborted) { 2028 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything. 2029 return; 2030 } 2031 2032 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next 2033 // concurrent bitmap clearing. 2034 { 2035 GCTraceTime(Debug, gc) debug("Clear Next Bitmap"); 2036 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false); 2037 } 2038 // Note we cannot clear the previous marking bitmap here 2039 // since VerifyDuringGC verifies the objects marked during 2040 // a full GC against the previous bitmap. 2041 2042 // Empty mark stack 2043 reset_marking_for_restart(); 2044 for (uint i = 0; i < _max_num_tasks; ++i) { 2045 _tasks[i]->clear_region_fields(); 2046 } 2047 _first_overflow_barrier_sync.abort(); 2048 _second_overflow_barrier_sync.abort(); 2049 _has_aborted = true; 2050 2051 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2052 satb_mq_set.abandon_partial_marking(); 2053 // This can be called either during or outside marking, we'll read 2054 // the expected_active value from the SATB queue set. 2055 satb_mq_set.set_active_all_threads( 2056 false, /* new active value */ 2057 satb_mq_set.is_active() /* expected_active */); 2058 } 2059 2060 static void print_ms_time_info(const char* prefix, const char* name, 2061 NumberSeq& ns) { 2062 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).", 2063 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg()); 2064 if (ns.num() > 0) { 2065 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]", 2066 prefix, ns.sd(), ns.maximum()); 2067 } 2068 } 2069 2070 void G1ConcurrentMark::print_summary_info() { 2071 Log(gc, marking) log; 2072 if (!log.is_trace()) { 2073 return; 2074 } 2075 2076 log.trace(" Concurrent marking:"); 2077 print_ms_time_info(" ", "init marks", _init_times); 2078 print_ms_time_info(" ", "remarks", _remark_times); 2079 { 2080 print_ms_time_info(" ", "final marks", _remark_mark_times); 2081 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times); 2082 2083 } 2084 print_ms_time_info(" ", "cleanups", _cleanup_times); 2085 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).", 2086 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0)); 2087 log.trace(" Total stop_world time = %8.2f s.", 2088 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0); 2089 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).", 2090 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum()); 2091 } 2092 2093 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const { 2094 _concurrent_workers->print_worker_threads_on(st); 2095 } 2096 2097 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const { 2098 _concurrent_workers->threads_do(tc); 2099 } 2100 2101 void G1ConcurrentMark::print_on_error(outputStream* st) const { 2102 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT, 2103 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap)); 2104 _prev_mark_bitmap->print_on_error(st, " Prev Bits: "); 2105 _next_mark_bitmap->print_on_error(st, " Next Bits: "); 2106 } 2107 2108 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) { 2109 ReferenceProcessor* result = g1h->ref_processor_cm(); 2110 assert(result != NULL, "CM reference processor should not be NULL"); 2111 return result; 2112 } 2113 2114 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h, 2115 G1CMTask* task) 2116 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)), 2117 _g1h(g1h), _task(task) 2118 { } 2119 2120 void G1CMTask::setup_for_region(HeapRegion* hr) { 2121 assert(hr != NULL, 2122 "claim_region() should have filtered out NULL regions"); 2123 _curr_region = hr; 2124 _finger = hr->bottom(); 2125 update_region_limit(); 2126 } 2127 2128 void G1CMTask::update_region_limit() { 2129 HeapRegion* hr = _curr_region; 2130 HeapWord* bottom = hr->bottom(); 2131 HeapWord* limit = hr->next_top_at_mark_start(); 2132 2133 if (limit == bottom) { 2134 // The region was collected underneath our feet. 2135 // We set the finger to bottom to ensure that the bitmap 2136 // iteration that will follow this will not do anything. 2137 // (this is not a condition that holds when we set the region up, 2138 // as the region is not supposed to be empty in the first place) 2139 _finger = bottom; 2140 } else if (limit >= _region_limit) { 2141 assert(limit >= _finger, "peace of mind"); 2142 } else { 2143 assert(limit < _region_limit, "only way to get here"); 2144 // This can happen under some pretty unusual circumstances. An 2145 // evacuation pause empties the region underneath our feet (NTAMS 2146 // at bottom). We then do some allocation in the region (NTAMS 2147 // stays at bottom), followed by the region being used as a GC 2148 // alloc region (NTAMS will move to top() and the objects 2149 // originally below it will be grayed). All objects now marked in 2150 // the region are explicitly grayed, if below the global finger, 2151 // and we do not need in fact to scan anything else. So, we simply 2152 // set _finger to be limit to ensure that the bitmap iteration 2153 // doesn't do anything. 2154 _finger = limit; 2155 } 2156 2157 _region_limit = limit; 2158 } 2159 2160 void G1CMTask::giveup_current_region() { 2161 assert(_curr_region != NULL, "invariant"); 2162 clear_region_fields(); 2163 } 2164 2165 void G1CMTask::clear_region_fields() { 2166 // Values for these three fields that indicate that we're not 2167 // holding on to a region. 2168 _curr_region = NULL; 2169 _finger = NULL; 2170 _region_limit = NULL; 2171 } 2172 2173 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) { 2174 if (cm_oop_closure == NULL) { 2175 assert(_cm_oop_closure != NULL, "invariant"); 2176 } else { 2177 assert(_cm_oop_closure == NULL, "invariant"); 2178 } 2179 _cm_oop_closure = cm_oop_closure; 2180 } 2181 2182 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) { 2183 guarantee(next_mark_bitmap != NULL, "invariant"); 2184 _next_mark_bitmap = next_mark_bitmap; 2185 clear_region_fields(); 2186 2187 _calls = 0; 2188 _elapsed_time_ms = 0.0; 2189 _termination_time_ms = 0.0; 2190 _termination_start_time_ms = 0.0; 2191 2192 _mark_stats_cache.reset(); 2193 } 2194 2195 bool G1CMTask::should_exit_termination() { 2196 if (!regular_clock_call()) { 2197 return true; 2198 } 2199 2200 // This is called when we are in the termination protocol. We should 2201 // quit if, for some reason, this task wants to abort or the global 2202 // stack is not empty (this means that we can get work from it). 2203 return !_cm->mark_stack_empty() || has_aborted(); 2204 } 2205 2206 void G1CMTask::reached_limit() { 2207 assert(_words_scanned >= _words_scanned_limit || 2208 _refs_reached >= _refs_reached_limit , 2209 "shouldn't have been called otherwise"); 2210 abort_marking_if_regular_check_fail(); 2211 } 2212 2213 bool G1CMTask::regular_clock_call() { 2214 if (has_aborted()) { 2215 return false; 2216 } 2217 2218 // First, we need to recalculate the words scanned and refs reached 2219 // limits for the next clock call. 2220 recalculate_limits(); 2221 2222 // During the regular clock call we do the following 2223 2224 // (1) If an overflow has been flagged, then we abort. 2225 if (_cm->has_overflown()) { 2226 return false; 2227 } 2228 2229 // If we are not concurrent (i.e. we're doing remark) we don't need 2230 // to check anything else. The other steps are only needed during 2231 // the concurrent marking phase. 2232 if (!_cm->concurrent()) { 2233 return true; 2234 } 2235 2236 // (2) If marking has been aborted for Full GC, then we also abort. 2237 if (_cm->has_aborted()) { 2238 return false; 2239 } 2240 2241 double curr_time_ms = os::elapsedVTime() * 1000.0; 2242 2243 // (4) We check whether we should yield. If we have to, then we abort. 2244 if (SuspendibleThreadSet::should_yield()) { 2245 // We should yield. To do this we abort the task. The caller is 2246 // responsible for yielding. 2247 return false; 2248 } 2249 2250 // (5) We check whether we've reached our time quota. If we have, 2251 // then we abort. 2252 double elapsed_time_ms = curr_time_ms - _start_time_ms; 2253 if (elapsed_time_ms > _time_target_ms) { 2254 _has_timed_out = true; 2255 return false; 2256 } 2257 2258 // (6) Finally, we check whether there are enough completed STAB 2259 // buffers available for processing. If there are, we abort. 2260 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2261 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) { 2262 // we do need to process SATB buffers, we'll abort and restart 2263 // the marking task to do so 2264 return false; 2265 } 2266 return true; 2267 } 2268 2269 void G1CMTask::recalculate_limits() { 2270 _real_words_scanned_limit = _words_scanned + words_scanned_period; 2271 _words_scanned_limit = _real_words_scanned_limit; 2272 2273 _real_refs_reached_limit = _refs_reached + refs_reached_period; 2274 _refs_reached_limit = _real_refs_reached_limit; 2275 } 2276 2277 void G1CMTask::decrease_limits() { 2278 // This is called when we believe that we're going to do an infrequent 2279 // operation which will increase the per byte scanned cost (i.e. move 2280 // entries to/from the global stack). It basically tries to decrease the 2281 // scanning limit so that the clock is called earlier. 2282 2283 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4; 2284 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4; 2285 } 2286 2287 void G1CMTask::move_entries_to_global_stack() { 2288 // Local array where we'll store the entries that will be popped 2289 // from the local queue. 2290 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2291 2292 size_t n = 0; 2293 G1TaskQueueEntry task_entry; 2294 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) { 2295 buffer[n] = task_entry; 2296 ++n; 2297 } 2298 if (n < G1CMMarkStack::EntriesPerChunk) { 2299 buffer[n] = G1TaskQueueEntry(); 2300 } 2301 2302 if (n > 0) { 2303 if (!_cm->mark_stack_push(buffer)) { 2304 set_has_aborted(); 2305 } 2306 } 2307 2308 // This operation was quite expensive, so decrease the limits. 2309 decrease_limits(); 2310 } 2311 2312 bool G1CMTask::get_entries_from_global_stack() { 2313 // Local array where we'll store the entries that will be popped 2314 // from the global stack. 2315 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk]; 2316 2317 if (!_cm->mark_stack_pop(buffer)) { 2318 return false; 2319 } 2320 2321 // We did actually pop at least one entry. 2322 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) { 2323 G1TaskQueueEntry task_entry = buffer[i]; 2324 if (task_entry.is_null()) { 2325 break; 2326 } 2327 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())); 2328 bool success = _task_queue->push(task_entry); 2329 // We only call this when the local queue is empty or under a 2330 // given target limit. So, we do not expect this push to fail. 2331 assert(success, "invariant"); 2332 } 2333 2334 // This operation was quite expensive, so decrease the limits 2335 decrease_limits(); 2336 return true; 2337 } 2338 2339 void G1CMTask::drain_local_queue(bool partially) { 2340 if (has_aborted()) { 2341 return; 2342 } 2343 2344 // Decide what the target size is, depending whether we're going to 2345 // drain it partially (so that other tasks can steal if they run out 2346 // of things to do) or totally (at the very end). 2347 size_t target_size; 2348 if (partially) { 2349 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize); 2350 } else { 2351 target_size = 0; 2352 } 2353 2354 if (_task_queue->size() > target_size) { 2355 G1TaskQueueEntry entry; 2356 bool ret = _task_queue->pop_local(entry); 2357 while (ret) { 2358 scan_task_entry(entry); 2359 if (_task_queue->size() <= target_size || has_aborted()) { 2360 ret = false; 2361 } else { 2362 ret = _task_queue->pop_local(entry); 2363 } 2364 } 2365 } 2366 } 2367 2368 void G1CMTask::drain_global_stack(bool partially) { 2369 if (has_aborted()) { 2370 return; 2371 } 2372 2373 // We have a policy to drain the local queue before we attempt to 2374 // drain the global stack. 2375 assert(partially || _task_queue->size() == 0, "invariant"); 2376 2377 // Decide what the target size is, depending whether we're going to 2378 // drain it partially (so that other tasks can steal if they run out 2379 // of things to do) or totally (at the very end). 2380 // Notice that when draining the global mark stack partially, due to the racyness 2381 // of the mark stack size update we might in fact drop below the target. But, 2382 // this is not a problem. 2383 // In case of total draining, we simply process until the global mark stack is 2384 // totally empty, disregarding the size counter. 2385 if (partially) { 2386 size_t const target_size = _cm->partial_mark_stack_size_target(); 2387 while (!has_aborted() && _cm->mark_stack_size() > target_size) { 2388 if (get_entries_from_global_stack()) { 2389 drain_local_queue(partially); 2390 } 2391 } 2392 } else { 2393 while (!has_aborted() && get_entries_from_global_stack()) { 2394 drain_local_queue(partially); 2395 } 2396 } 2397 } 2398 2399 // SATB Queue has several assumptions on whether to call the par or 2400 // non-par versions of the methods. this is why some of the code is 2401 // replicated. We should really get rid of the single-threaded version 2402 // of the code to simplify things. 2403 void G1CMTask::drain_satb_buffers() { 2404 if (has_aborted()) { 2405 return; 2406 } 2407 2408 // We set this so that the regular clock knows that we're in the 2409 // middle of draining buffers and doesn't set the abort flag when it 2410 // notices that SATB buffers are available for draining. It'd be 2411 // very counter productive if it did that. :-) 2412 _draining_satb_buffers = true; 2413 2414 G1CMSATBBufferClosure satb_cl(this, _g1h); 2415 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 2416 2417 // This keeps claiming and applying the closure to completed buffers 2418 // until we run out of buffers or we need to abort. 2419 while (!has_aborted() && 2420 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) { 2421 abort_marking_if_regular_check_fail(); 2422 } 2423 2424 // Can't assert qset is empty here, even if not aborted. If concurrent, 2425 // some other thread might be adding to the queue. If not concurrent, 2426 // some other thread might have won the race for the last buffer, but 2427 // has not yet decremented the count. 2428 2429 _draining_satb_buffers = false; 2430 2431 // again, this was a potentially expensive operation, decrease the 2432 // limits to get the regular clock call early 2433 decrease_limits(); 2434 } 2435 2436 void G1CMTask::clear_mark_stats_cache(uint region_idx) { 2437 _mark_stats_cache.reset(region_idx); 2438 } 2439 2440 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() { 2441 return _mark_stats_cache.evict_all(); 2442 } 2443 2444 void G1CMTask::print_stats() { 2445 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls); 2446 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms", 2447 _elapsed_time_ms, _termination_time_ms); 2448 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms", 2449 _step_times_ms.num(), 2450 _step_times_ms.avg(), 2451 _step_times_ms.sd(), 2452 _step_times_ms.maximum(), 2453 _step_times_ms.sum()); 2454 size_t const hits = _mark_stats_cache.hits(); 2455 size_t const misses = _mark_stats_cache.misses(); 2456 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f", 2457 hits, misses, percent_of(hits, hits + misses)); 2458 } 2459 2460 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) { 2461 return _task_queues->steal(worker_id, task_entry); 2462 } 2463 2464 /***************************************************************************** 2465 2466 The do_marking_step(time_target_ms, ...) method is the building 2467 block of the parallel marking framework. It can be called in parallel 2468 with other invocations of do_marking_step() on different tasks 2469 (but only one per task, obviously) and concurrently with the 2470 mutator threads, or during remark, hence it eliminates the need 2471 for two versions of the code. When called during remark, it will 2472 pick up from where the task left off during the concurrent marking 2473 phase. Interestingly, tasks are also claimable during evacuation 2474 pauses too, since do_marking_step() ensures that it aborts before 2475 it needs to yield. 2476 2477 The data structures that it uses to do marking work are the 2478 following: 2479 2480 (1) Marking Bitmap. If there are gray objects that appear only 2481 on the bitmap (this happens either when dealing with an overflow 2482 or when the initial marking phase has simply marked the roots 2483 and didn't push them on the stack), then tasks claim heap 2484 regions whose bitmap they then scan to find gray objects. A 2485 global finger indicates where the end of the last claimed region 2486 is. A local finger indicates how far into the region a task has 2487 scanned. The two fingers are used to determine how to gray an 2488 object (i.e. whether simply marking it is OK, as it will be 2489 visited by a task in the future, or whether it needs to be also 2490 pushed on a stack). 2491 2492 (2) Local Queue. The local queue of the task which is accessed 2493 reasonably efficiently by the task. Other tasks can steal from 2494 it when they run out of work. Throughout the marking phase, a 2495 task attempts to keep its local queue short but not totally 2496 empty, so that entries are available for stealing by other 2497 tasks. Only when there is no more work, a task will totally 2498 drain its local queue. 2499 2500 (3) Global Mark Stack. This handles local queue overflow. During 2501 marking only sets of entries are moved between it and the local 2502 queues, as access to it requires a mutex and more fine-grain 2503 interaction with it which might cause contention. If it 2504 overflows, then the marking phase should restart and iterate 2505 over the bitmap to identify gray objects. Throughout the marking 2506 phase, tasks attempt to keep the global mark stack at a small 2507 length but not totally empty, so that entries are available for 2508 popping by other tasks. Only when there is no more work, tasks 2509 will totally drain the global mark stack. 2510 2511 (4) SATB Buffer Queue. This is where completed SATB buffers are 2512 made available. Buffers are regularly removed from this queue 2513 and scanned for roots, so that the queue doesn't get too 2514 long. During remark, all completed buffers are processed, as 2515 well as the filled in parts of any uncompleted buffers. 2516 2517 The do_marking_step() method tries to abort when the time target 2518 has been reached. There are a few other cases when the 2519 do_marking_step() method also aborts: 2520 2521 (1) When the marking phase has been aborted (after a Full GC). 2522 2523 (2) When a global overflow (on the global stack) has been 2524 triggered. Before the task aborts, it will actually sync up with 2525 the other tasks to ensure that all the marking data structures 2526 (local queues, stacks, fingers etc.) are re-initialized so that 2527 when do_marking_step() completes, the marking phase can 2528 immediately restart. 2529 2530 (3) When enough completed SATB buffers are available. The 2531 do_marking_step() method only tries to drain SATB buffers right 2532 at the beginning. So, if enough buffers are available, the 2533 marking step aborts and the SATB buffers are processed at 2534 the beginning of the next invocation. 2535 2536 (4) To yield. when we have to yield then we abort and yield 2537 right at the end of do_marking_step(). This saves us from a lot 2538 of hassle as, by yielding we might allow a Full GC. If this 2539 happens then objects will be compacted underneath our feet, the 2540 heap might shrink, etc. We save checking for this by just 2541 aborting and doing the yield right at the end. 2542 2543 From the above it follows that the do_marking_step() method should 2544 be called in a loop (or, otherwise, regularly) until it completes. 2545 2546 If a marking step completes without its has_aborted() flag being 2547 true, it means it has completed the current marking phase (and 2548 also all other marking tasks have done so and have all synced up). 2549 2550 A method called regular_clock_call() is invoked "regularly" (in 2551 sub ms intervals) throughout marking. It is this clock method that 2552 checks all the abort conditions which were mentioned above and 2553 decides when the task should abort. A work-based scheme is used to 2554 trigger this clock method: when the number of object words the 2555 marking phase has scanned or the number of references the marking 2556 phase has visited reach a given limit. Additional invocations to 2557 the method clock have been planted in a few other strategic places 2558 too. The initial reason for the clock method was to avoid calling 2559 vtime too regularly, as it is quite expensive. So, once it was in 2560 place, it was natural to piggy-back all the other conditions on it 2561 too and not constantly check them throughout the code. 2562 2563 If do_termination is true then do_marking_step will enter its 2564 termination protocol. 2565 2566 The value of is_serial must be true when do_marking_step is being 2567 called serially (i.e. by the VMThread) and do_marking_step should 2568 skip any synchronization in the termination and overflow code. 2569 Examples include the serial remark code and the serial reference 2570 processing closures. 2571 2572 The value of is_serial must be false when do_marking_step is 2573 being called by any of the worker threads in a work gang. 2574 Examples include the concurrent marking code (CMMarkingTask), 2575 the MT remark code, and the MT reference processing closures. 2576 2577 *****************************************************************************/ 2578 2579 void G1CMTask::do_marking_step(double time_target_ms, 2580 bool do_termination, 2581 bool is_serial) { 2582 assert(time_target_ms >= 1.0, "minimum granularity is 1ms"); 2583 2584 _start_time_ms = os::elapsedVTime() * 1000.0; 2585 2586 // If do_stealing is true then do_marking_step will attempt to 2587 // steal work from the other G1CMTasks. It only makes sense to 2588 // enable stealing when the termination protocol is enabled 2589 // and do_marking_step() is not being called serially. 2590 bool do_stealing = do_termination && !is_serial; 2591 2592 G1Predictions const& predictor = _g1h->policy()->predictor(); 2593 double diff_prediction_ms = predictor.predict_zero_bounded(&_marking_step_diff_ms); 2594 _time_target_ms = time_target_ms - diff_prediction_ms; 2595 2596 // set up the variables that are used in the work-based scheme to 2597 // call the regular clock method 2598 _words_scanned = 0; 2599 _refs_reached = 0; 2600 recalculate_limits(); 2601 2602 // clear all flags 2603 clear_has_aborted(); 2604 _has_timed_out = false; 2605 _draining_satb_buffers = false; 2606 2607 ++_calls; 2608 2609 // Set up the bitmap and oop closures. Anything that uses them is 2610 // eventually called from this method, so it is OK to allocate these 2611 // statically. 2612 G1CMBitMapClosure bitmap_closure(this, _cm); 2613 G1CMOopClosure cm_oop_closure(_g1h, this); 2614 set_cm_oop_closure(&cm_oop_closure); 2615 2616 if (_cm->has_overflown()) { 2617 // This can happen if the mark stack overflows during a GC pause 2618 // and this task, after a yield point, restarts. We have to abort 2619 // as we need to get into the overflow protocol which happens 2620 // right at the end of this task. 2621 set_has_aborted(); 2622 } 2623 2624 // First drain any available SATB buffers. After this, we will not 2625 // look at SATB buffers before the next invocation of this method. 2626 // If enough completed SATB buffers are queued up, the regular clock 2627 // will abort this task so that it restarts. 2628 drain_satb_buffers(); 2629 // ...then partially drain the local queue and the global stack 2630 drain_local_queue(true); 2631 drain_global_stack(true); 2632 2633 do { 2634 if (!has_aborted() && _curr_region != NULL) { 2635 // This means that we're already holding on to a region. 2636 assert(_finger != NULL, "if region is not NULL, then the finger " 2637 "should not be NULL either"); 2638 2639 // We might have restarted this task after an evacuation pause 2640 // which might have evacuated the region we're holding on to 2641 // underneath our feet. Let's read its limit again to make sure 2642 // that we do not iterate over a region of the heap that 2643 // contains garbage (update_region_limit() will also move 2644 // _finger to the start of the region if it is found empty). 2645 update_region_limit(); 2646 // We will start from _finger not from the start of the region, 2647 // as we might be restarting this task after aborting half-way 2648 // through scanning this region. In this case, _finger points to 2649 // the address where we last found a marked object. If this is a 2650 // fresh region, _finger points to start(). 2651 MemRegion mr = MemRegion(_finger, _region_limit); 2652 2653 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(), 2654 "humongous regions should go around loop once only"); 2655 2656 // Some special cases: 2657 // If the memory region is empty, we can just give up the region. 2658 // If the current region is humongous then we only need to check 2659 // the bitmap for the bit associated with the start of the object, 2660 // scan the object if it's live, and give up the region. 2661 // Otherwise, let's iterate over the bitmap of the part of the region 2662 // that is left. 2663 // If the iteration is successful, give up the region. 2664 if (mr.is_empty()) { 2665 giveup_current_region(); 2666 abort_marking_if_regular_check_fail(); 2667 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) { 2668 if (_next_mark_bitmap->is_marked(mr.start())) { 2669 // The object is marked - apply the closure 2670 bitmap_closure.do_addr(mr.start()); 2671 } 2672 // Even if this task aborted while scanning the humongous object 2673 // we can (and should) give up the current region. 2674 giveup_current_region(); 2675 abort_marking_if_regular_check_fail(); 2676 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) { 2677 giveup_current_region(); 2678 abort_marking_if_regular_check_fail(); 2679 } else { 2680 assert(has_aborted(), "currently the only way to do so"); 2681 // The only way to abort the bitmap iteration is to return 2682 // false from the do_bit() method. However, inside the 2683 // do_bit() method we move the _finger to point to the 2684 // object currently being looked at. So, if we bail out, we 2685 // have definitely set _finger to something non-null. 2686 assert(_finger != NULL, "invariant"); 2687 2688 // Region iteration was actually aborted. So now _finger 2689 // points to the address of the object we last scanned. If we 2690 // leave it there, when we restart this task, we will rescan 2691 // the object. It is easy to avoid this. We move the finger by 2692 // enough to point to the next possible object header. 2693 assert(_finger < _region_limit, "invariant"); 2694 HeapWord* const new_finger = _finger + ((oop)_finger)->size(); 2695 // Check if bitmap iteration was aborted while scanning the last object 2696 if (new_finger >= _region_limit) { 2697 giveup_current_region(); 2698 } else { 2699 move_finger_to(new_finger); 2700 } 2701 } 2702 } 2703 // At this point we have either completed iterating over the 2704 // region we were holding on to, or we have aborted. 2705 2706 // We then partially drain the local queue and the global stack. 2707 // (Do we really need this?) 2708 drain_local_queue(true); 2709 drain_global_stack(true); 2710 2711 // Read the note on the claim_region() method on why it might 2712 // return NULL with potentially more regions available for 2713 // claiming and why we have to check out_of_regions() to determine 2714 // whether we're done or not. 2715 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) { 2716 // We are going to try to claim a new region. We should have 2717 // given up on the previous one. 2718 // Separated the asserts so that we know which one fires. 2719 assert(_curr_region == NULL, "invariant"); 2720 assert(_finger == NULL, "invariant"); 2721 assert(_region_limit == NULL, "invariant"); 2722 HeapRegion* claimed_region = _cm->claim_region(_worker_id); 2723 if (claimed_region != NULL) { 2724 // Yes, we managed to claim one 2725 setup_for_region(claimed_region); 2726 assert(_curr_region == claimed_region, "invariant"); 2727 } 2728 // It is important to call the regular clock here. It might take 2729 // a while to claim a region if, for example, we hit a large 2730 // block of empty regions. So we need to call the regular clock 2731 // method once round the loop to make sure it's called 2732 // frequently enough. 2733 abort_marking_if_regular_check_fail(); 2734 } 2735 2736 if (!has_aborted() && _curr_region == NULL) { 2737 assert(_cm->out_of_regions(), 2738 "at this point we should be out of regions"); 2739 } 2740 } while ( _curr_region != NULL && !has_aborted()); 2741 2742 if (!has_aborted()) { 2743 // We cannot check whether the global stack is empty, since other 2744 // tasks might be pushing objects to it concurrently. 2745 assert(_cm->out_of_regions(), 2746 "at this point we should be out of regions"); 2747 // Try to reduce the number of available SATB buffers so that 2748 // remark has less work to do. 2749 drain_satb_buffers(); 2750 } 2751 2752 // Since we've done everything else, we can now totally drain the 2753 // local queue and global stack. 2754 drain_local_queue(false); 2755 drain_global_stack(false); 2756 2757 // Attempt at work stealing from other task's queues. 2758 if (do_stealing && !has_aborted()) { 2759 // We have not aborted. This means that we have finished all that 2760 // we could. Let's try to do some stealing... 2761 2762 // We cannot check whether the global stack is empty, since other 2763 // tasks might be pushing objects to it concurrently. 2764 assert(_cm->out_of_regions() && _task_queue->size() == 0, 2765 "only way to reach here"); 2766 while (!has_aborted()) { 2767 G1TaskQueueEntry entry; 2768 if (_cm->try_stealing(_worker_id, entry)) { 2769 scan_task_entry(entry); 2770 2771 // And since we're towards the end, let's totally drain the 2772 // local queue and global stack. 2773 drain_local_queue(false); 2774 drain_global_stack(false); 2775 } else { 2776 break; 2777 } 2778 } 2779 } 2780 2781 // We still haven't aborted. Now, let's try to get into the 2782 // termination protocol. 2783 if (do_termination && !has_aborted()) { 2784 // We cannot check whether the global stack is empty, since other 2785 // tasks might be concurrently pushing objects on it. 2786 // Separated the asserts so that we know which one fires. 2787 assert(_cm->out_of_regions(), "only way to reach here"); 2788 assert(_task_queue->size() == 0, "only way to reach here"); 2789 _termination_start_time_ms = os::elapsedVTime() * 1000.0; 2790 2791 // The G1CMTask class also extends the TerminatorTerminator class, 2792 // hence its should_exit_termination() method will also decide 2793 // whether to exit the termination protocol or not. 2794 bool finished = (is_serial || 2795 _cm->terminator()->offer_termination(this)); 2796 double termination_end_time_ms = os::elapsedVTime() * 1000.0; 2797 _termination_time_ms += 2798 termination_end_time_ms - _termination_start_time_ms; 2799 2800 if (finished) { 2801 // We're all done. 2802 2803 // We can now guarantee that the global stack is empty, since 2804 // all other tasks have finished. We separated the guarantees so 2805 // that, if a condition is false, we can immediately find out 2806 // which one. 2807 guarantee(_cm->out_of_regions(), "only way to reach here"); 2808 guarantee(_cm->mark_stack_empty(), "only way to reach here"); 2809 guarantee(_task_queue->size() == 0, "only way to reach here"); 2810 guarantee(!_cm->has_overflown(), "only way to reach here"); 2811 guarantee(!has_aborted(), "should never happen if termination has completed"); 2812 } else { 2813 // Apparently there's more work to do. Let's abort this task. It 2814 // will restart it and we can hopefully find more things to do. 2815 set_has_aborted(); 2816 } 2817 } 2818 2819 // Mainly for debugging purposes to make sure that a pointer to the 2820 // closure which was statically allocated in this frame doesn't 2821 // escape it by accident. 2822 set_cm_oop_closure(NULL); 2823 double end_time_ms = os::elapsedVTime() * 1000.0; 2824 double elapsed_time_ms = end_time_ms - _start_time_ms; 2825 // Update the step history. 2826 _step_times_ms.add(elapsed_time_ms); 2827 2828 if (has_aborted()) { 2829 // The task was aborted for some reason. 2830 if (_has_timed_out) { 2831 double diff_ms = elapsed_time_ms - _time_target_ms; 2832 // Keep statistics of how well we did with respect to hitting 2833 // our target only if we actually timed out (if we aborted for 2834 // other reasons, then the results might get skewed). 2835 _marking_step_diff_ms.add(diff_ms); 2836 } 2837 2838 if (_cm->has_overflown()) { 2839 // This is the interesting one. We aborted because a global 2840 // overflow was raised. This means we have to restart the 2841 // marking phase and start iterating over regions. However, in 2842 // order to do this we have to make sure that all tasks stop 2843 // what they are doing and re-initialize in a safe manner. We 2844 // will achieve this with the use of two barrier sync points. 2845 2846 if (!is_serial) { 2847 // We only need to enter the sync barrier if being called 2848 // from a parallel context 2849 _cm->enter_first_sync_barrier(_worker_id); 2850 2851 // When we exit this sync barrier we know that all tasks have 2852 // stopped doing marking work. So, it's now safe to 2853 // re-initialize our data structures. 2854 } 2855 2856 clear_region_fields(); 2857 flush_mark_stats_cache(); 2858 2859 if (!is_serial) { 2860 // If we're executing the concurrent phase of marking, reset the marking 2861 // state; otherwise the marking state is reset after reference processing, 2862 // during the remark pause. 2863 // If we reset here as a result of an overflow during the remark we will 2864 // see assertion failures from any subsequent set_concurrency_and_phase() 2865 // calls. 2866 if (_cm->concurrent() && _worker_id == 0) { 2867 // Worker 0 is responsible for clearing the global data structures because 2868 // of an overflow. During STW we should not clear the overflow flag (in 2869 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit 2870 // method to abort the pause and restart concurrent marking. 2871 _cm->reset_marking_for_restart(); 2872 2873 log_info(gc, marking)("Concurrent Mark reset for overflow"); 2874 } 2875 2876 // ...and enter the second barrier. 2877 _cm->enter_second_sync_barrier(_worker_id); 2878 } 2879 // At this point, if we're during the concurrent phase of 2880 // marking, everything has been re-initialized and we're 2881 // ready to restart. 2882 } 2883 } 2884 } 2885 2886 G1CMTask::G1CMTask(uint worker_id, 2887 G1ConcurrentMark* cm, 2888 G1CMTaskQueue* task_queue, 2889 G1RegionMarkStats* mark_stats, 2890 uint max_regions) : 2891 _objArray_processor(this), 2892 _worker_id(worker_id), 2893 _g1h(G1CollectedHeap::heap()), 2894 _cm(cm), 2895 _next_mark_bitmap(NULL), 2896 _task_queue(task_queue), 2897 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize), 2898 _calls(0), 2899 _time_target_ms(0.0), 2900 _start_time_ms(0.0), 2901 _cm_oop_closure(NULL), 2902 _curr_region(NULL), 2903 _finger(NULL), 2904 _region_limit(NULL), 2905 _words_scanned(0), 2906 _words_scanned_limit(0), 2907 _real_words_scanned_limit(0), 2908 _refs_reached(0), 2909 _refs_reached_limit(0), 2910 _real_refs_reached_limit(0), 2911 _has_aborted(false), 2912 _has_timed_out(false), 2913 _draining_satb_buffers(false), 2914 _step_times_ms(), 2915 _elapsed_time_ms(0.0), 2916 _termination_time_ms(0.0), 2917 _termination_start_time_ms(0.0), 2918 _marking_step_diff_ms() 2919 { 2920 guarantee(task_queue != NULL, "invariant"); 2921 2922 _marking_step_diff_ms.add(0.5); 2923 } 2924 2925 // These are formatting macros that are used below to ensure 2926 // consistent formatting. The *_H_* versions are used to format the 2927 // header for a particular value and they should be kept consistent 2928 // with the corresponding macro. Also note that most of the macros add 2929 // the necessary white space (as a prefix) which makes them a bit 2930 // easier to compose. 2931 2932 // All the output lines are prefixed with this string to be able to 2933 // identify them easily in a large log file. 2934 #define G1PPRL_LINE_PREFIX "###" 2935 2936 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT 2937 #ifdef _LP64 2938 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s" 2939 #else // _LP64 2940 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s" 2941 #endif // _LP64 2942 2943 // For per-region info 2944 #define G1PPRL_TYPE_FORMAT " %-4s" 2945 #define G1PPRL_TYPE_H_FORMAT " %4s" 2946 #define G1PPRL_STATE_FORMAT " %-5s" 2947 #define G1PPRL_STATE_H_FORMAT " %5s" 2948 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9) 2949 #define G1PPRL_BYTE_H_FORMAT " %9s" 2950 #define G1PPRL_DOUBLE_FORMAT " %14.1f" 2951 #define G1PPRL_DOUBLE_H_FORMAT " %14s" 2952 2953 // For summary info 2954 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT 2955 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT 2956 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB" 2957 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%" 2958 2959 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) : 2960 _total_used_bytes(0), _total_capacity_bytes(0), 2961 _total_prev_live_bytes(0), _total_next_live_bytes(0), 2962 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) 2963 { 2964 if (!log_is_enabled(Trace, gc, liveness)) { 2965 return; 2966 } 2967 2968 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 2969 MemRegion g1_reserved = g1h->g1_reserved(); 2970 double now = os::elapsedTime(); 2971 2972 // Print the header of the output. 2973 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now); 2974 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP" 2975 G1PPRL_SUM_ADDR_FORMAT("reserved") 2976 G1PPRL_SUM_BYTE_FORMAT("region-size"), 2977 p2i(g1_reserved.start()), p2i(g1_reserved.end()), 2978 HeapRegion::GrainBytes); 2979 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 2980 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 2981 G1PPRL_TYPE_H_FORMAT 2982 G1PPRL_ADDR_BASE_H_FORMAT 2983 G1PPRL_BYTE_H_FORMAT 2984 G1PPRL_BYTE_H_FORMAT 2985 G1PPRL_BYTE_H_FORMAT 2986 G1PPRL_DOUBLE_H_FORMAT 2987 G1PPRL_BYTE_H_FORMAT 2988 G1PPRL_STATE_H_FORMAT 2989 G1PPRL_BYTE_H_FORMAT, 2990 "type", "address-range", 2991 "used", "prev-live", "next-live", "gc-eff", 2992 "remset", "state", "code-roots"); 2993 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 2994 G1PPRL_TYPE_H_FORMAT 2995 G1PPRL_ADDR_BASE_H_FORMAT 2996 G1PPRL_BYTE_H_FORMAT 2997 G1PPRL_BYTE_H_FORMAT 2998 G1PPRL_BYTE_H_FORMAT 2999 G1PPRL_DOUBLE_H_FORMAT 3000 G1PPRL_BYTE_H_FORMAT 3001 G1PPRL_STATE_H_FORMAT 3002 G1PPRL_BYTE_H_FORMAT, 3003 "", "", 3004 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)", 3005 "(bytes)", "", "(bytes)"); 3006 } 3007 3008 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) { 3009 if (!log_is_enabled(Trace, gc, liveness)) { 3010 return false; 3011 } 3012 3013 const char* type = r->get_type_str(); 3014 HeapWord* bottom = r->bottom(); 3015 HeapWord* end = r->end(); 3016 size_t capacity_bytes = r->capacity(); 3017 size_t used_bytes = r->used(); 3018 size_t prev_live_bytes = r->live_bytes(); 3019 size_t next_live_bytes = r->next_live_bytes(); 3020 double gc_eff = r->gc_efficiency(); 3021 size_t remset_bytes = r->rem_set()->mem_size(); 3022 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size(); 3023 const char* remset_type = r->rem_set()->get_short_state_str(); 3024 3025 _total_used_bytes += used_bytes; 3026 _total_capacity_bytes += capacity_bytes; 3027 _total_prev_live_bytes += prev_live_bytes; 3028 _total_next_live_bytes += next_live_bytes; 3029 _total_remset_bytes += remset_bytes; 3030 _total_strong_code_roots_bytes += strong_code_roots_bytes; 3031 3032 // Print a line for this particular region. 3033 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3034 G1PPRL_TYPE_FORMAT 3035 G1PPRL_ADDR_BASE_FORMAT 3036 G1PPRL_BYTE_FORMAT 3037 G1PPRL_BYTE_FORMAT 3038 G1PPRL_BYTE_FORMAT 3039 G1PPRL_DOUBLE_FORMAT 3040 G1PPRL_BYTE_FORMAT 3041 G1PPRL_STATE_FORMAT 3042 G1PPRL_BYTE_FORMAT, 3043 type, p2i(bottom), p2i(end), 3044 used_bytes, prev_live_bytes, next_live_bytes, gc_eff, 3045 remset_bytes, remset_type, strong_code_roots_bytes); 3046 3047 return false; 3048 } 3049 3050 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() { 3051 if (!log_is_enabled(Trace, gc, liveness)) { 3052 return; 3053 } 3054 3055 // add static memory usages to remembered set sizes 3056 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size(); 3057 // Print the footer of the output. 3058 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX); 3059 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX 3060 " SUMMARY" 3061 G1PPRL_SUM_MB_FORMAT("capacity") 3062 G1PPRL_SUM_MB_PERC_FORMAT("used") 3063 G1PPRL_SUM_MB_PERC_FORMAT("prev-live") 3064 G1PPRL_SUM_MB_PERC_FORMAT("next-live") 3065 G1PPRL_SUM_MB_FORMAT("remset") 3066 G1PPRL_SUM_MB_FORMAT("code-roots"), 3067 bytes_to_mb(_total_capacity_bytes), 3068 bytes_to_mb(_total_used_bytes), 3069 percent_of(_total_used_bytes, _total_capacity_bytes), 3070 bytes_to_mb(_total_prev_live_bytes), 3071 percent_of(_total_prev_live_bytes, _total_capacity_bytes), 3072 bytes_to_mb(_total_next_live_bytes), 3073 percent_of(_total_next_live_bytes, _total_capacity_bytes), 3074 bytes_to_mb(_total_remset_bytes), 3075 bytes_to_mb(_total_strong_code_roots_bytes)); 3076 }