1 /* 2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "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/taskqueue.inline.hpp" 53 #include "gc/shared/weakProcessor.inline.hpp" 54 #include "gc/shared/workerPolicy.hpp" 55 #include "include/jvm.h" 56 #include "logging/log.hpp" 57 #include "memory/allocation.hpp" 58 #include "memory/iterator.hpp" 59 #include "memory/resourceArea.hpp" 60 #include "memory/universe.hpp" 61 #include "oops/access.inline.hpp" 62 #include "oops/oop.inline.hpp" 63 #include "runtime/atomic.hpp" 64 #include "runtime/handles.inline.hpp" 65 #include "runtime/java.hpp" 66 #include "runtime/orderAccess.hpp" 67 #include "runtime/prefetch.inline.hpp" 68 #include "services/memTracker.hpp" 69 #include "utilities/align.hpp" 70 #include "utilities/growableArray.hpp" 71 72 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) { 73 assert(addr < _cm->finger(), "invariant"); 74 assert(addr >= _task->finger(), "invariant"); 75 76 // We move that task's local finger along. 77 _task->move_finger_to(addr); 78 79 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr))); 80 // we only partially drain the local queue and global stack 81 _task->drain_local_queue(true); 82 _task->drain_global_stack(true); 83 84 // if the has_aborted flag has been raised, we need to bail out of 85 // the iteration 86 return !_task->has_aborted(); 87 } 88 89 G1CMMarkStack::G1CMMarkStack() : 90 _max_chunk_capacity(0), 91 _base(NULL), 92 _chunk_capacity(0) { 93 set_empty(); 94 } 95 96 bool G1CMMarkStack::resize(size_t new_capacity) { 97 assert(is_empty(), "Only resize when stack is empty."); 98 assert(new_capacity <= _max_chunk_capacity, 99 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity); 100 101 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC); 102 103 if (new_base == NULL) { 104 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)); 105 return false; 106 } 107 // Release old mapping. 108 if (_base != NULL) { 109 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 110 } 111 112 _base = new_base; 113 _chunk_capacity = new_capacity; 114 set_empty(); 115 116 return true; 117 } 118 119 size_t G1CMMarkStack::capacity_alignment() { 120 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry); 121 } 122 123 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) { 124 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized."); 125 126 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry); 127 128 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 129 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar; 130 131 guarantee(initial_chunk_capacity <= _max_chunk_capacity, 132 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT, 133 _max_chunk_capacity, 134 initial_chunk_capacity); 135 136 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT, 137 initial_chunk_capacity, _max_chunk_capacity); 138 139 return resize(initial_chunk_capacity); 140 } 141 142 void G1CMMarkStack::expand() { 143 if (_chunk_capacity == _max_chunk_capacity) { 144 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity); 145 return; 146 } 147 size_t old_capacity = _chunk_capacity; 148 // Double capacity if possible 149 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity); 150 151 if (resize(new_capacity)) { 152 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 153 old_capacity, new_capacity); 154 } else { 155 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks", 156 old_capacity, new_capacity); 157 } 158 } 159 160 G1CMMarkStack::~G1CMMarkStack() { 161 if (_base != NULL) { 162 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity); 163 } 164 } 165 166 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) { 167 elem->next = *list; 168 *list = elem; 169 } 170 171 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) { 172 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 173 add_chunk_to_list(&_chunk_list, elem); 174 _chunks_in_chunk_list++; 175 } 176 177 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) { 178 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 179 add_chunk_to_list(&_free_list, elem); 180 } 181 182 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) { 183 TaskQueueEntryChunk* result = *list; 184 if (result != NULL) { 185 *list = (*list)->next; 186 } 187 return result; 188 } 189 190 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() { 191 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag); 192 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list); 193 if (result != NULL) { 194 _chunks_in_chunk_list--; 195 } 196 return result; 197 } 198 199 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() { 200 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag); 201 return remove_chunk_from_list(&_free_list); 202 } 203 204 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() { 205 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code. 206 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding 207 // wraparound of _hwm. 208 if (_hwm >= _chunk_capacity) { 209 return NULL; 210 } 211 212 size_t cur_idx = Atomic::add(&_hwm, 1u) - 1; 213 if (cur_idx >= _chunk_capacity) { 214 return NULL; 215 } 216 217 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk; 218 result->next = NULL; 219 return result; 220 } 221 222 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) { 223 // Get a new chunk. 224 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list(); 225 226 if (new_chunk == NULL) { 227 // Did not get a chunk from the free list. Allocate from backing memory. 228 new_chunk = allocate_new_chunk(); 229 230 if (new_chunk == NULL) { 231 return false; 232 } 233 } 234 235 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 236 237 add_chunk_to_chunk_list(new_chunk); 238 239 return true; 240 } 241 242 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) { 243 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list(); 244 245 if (cur == NULL) { 246 return false; 247 } 248 249 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry)); 250 251 add_chunk_to_free_list(cur); 252 return true; 253 } 254 255 void G1CMMarkStack::set_empty() { 256 _chunks_in_chunk_list = 0; 257 _hwm = 0; 258 _chunk_list = NULL; 259 _free_list = NULL; 260 } 261 262 G1CMRootMemRegions::G1CMRootMemRegions(uint const max_regions) : 263 _root_regions(NULL), 264 _max_regions(max_regions), 265 _num_root_regions(0), 266 _claimed_root_regions(0), 267 _scan_in_progress(false), 268 _should_abort(false) { 269 _root_regions = new MemRegion[_max_regions]; 270 if (_root_regions == NULL) { 271 vm_exit_during_initialization("Could not allocate root MemRegion set."); 272 } 273 } 274 275 G1CMRootMemRegions::~G1CMRootMemRegions() { 276 delete[] _root_regions; 277 } 278 279 void G1CMRootMemRegions::reset() { 280 _num_root_regions = 0; 281 } 282 283 void G1CMRootMemRegions::add(HeapWord* start, HeapWord* end) { 284 assert_at_safepoint(); 285 size_t idx = Atomic::add(&_num_root_regions, (size_t)1) - 1; 286 assert(idx < _max_regions, "Trying to add more root MemRegions than there is space " SIZE_FORMAT, _max_regions); 287 assert(start != NULL && end != NULL && start <= end, "Start (" PTR_FORMAT ") should be less or equal to " 288 "end (" PTR_FORMAT ")", p2i(start), p2i(end)); 289 _root_regions[idx].set_start(start); 290 _root_regions[idx].set_end(end); 291 } 292 293 void G1CMRootMemRegions::prepare_for_scan() { 294 assert(!scan_in_progress(), "pre-condition"); 295 296 _scan_in_progress = _num_root_regions > 0; 297 298 _claimed_root_regions = 0; 299 _should_abort = false; 300 } 301 302 const MemRegion* G1CMRootMemRegions::claim_next() { 303 if (_should_abort) { 304 // If someone has set the should_abort flag, we return NULL to 305 // force the caller to bail out of their loop. 306 return NULL; 307 } 308 309 if (_claimed_root_regions >= _num_root_regions) { 310 return NULL; 311 } 312 313 size_t claimed_index = Atomic::add(&_claimed_root_regions, (size_t)1) - 1; 314 if (claimed_index < _num_root_regions) { 315 return &_root_regions[claimed_index]; 316 } 317 return NULL; 318 } 319 320 uint G1CMRootMemRegions::num_root_regions() const { 321 return (uint)_num_root_regions; 322 } 323 324 void G1CMRootMemRegions::notify_scan_done() { 325 MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 326 _scan_in_progress = false; 327 RootRegionScan_lock->notify_all(); 328 } 329 330 void G1CMRootMemRegions::cancel_scan() { 331 notify_scan_done(); 332 } 333 334 void G1CMRootMemRegions::scan_finished() { 335 assert(scan_in_progress(), "pre-condition"); 336 337 if (!_should_abort) { 338 assert(_claimed_root_regions >= num_root_regions(), 339 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u", 340 _claimed_root_regions, num_root_regions()); 341 } 342 343 notify_scan_done(); 344 } 345 346 bool G1CMRootMemRegions::wait_until_scan_finished() { 347 if (!scan_in_progress()) { 348 return false; 349 } 350 351 { 352 MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag); 353 while (scan_in_progress()) { 354 ml.wait(); 355 } 356 } 357 return true; 358 } 359 360 // Returns the maximum number of workers to be used in a concurrent 361 // phase based on the number of GC workers being used in a STW 362 // phase. 363 static uint scale_concurrent_worker_threads(uint num_gc_workers) { 364 return MAX2((num_gc_workers + 2) / 4, 1U); 365 } 366 367 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, 368 G1RegionToSpaceMapper* prev_bitmap_storage, 369 G1RegionToSpaceMapper* next_bitmap_storage) : 370 // _cm_thread set inside the constructor 371 _g1h(g1h), 372 _completed_initialization(false), 373 374 _mark_bitmap_1(), 375 _mark_bitmap_2(), 376 _prev_mark_bitmap(&_mark_bitmap_1), 377 _next_mark_bitmap(&_mark_bitmap_2), 378 379 _heap(_g1h->reserved_region()), 380 381 _root_regions(_g1h->max_regions()), 382 383 _global_mark_stack(), 384 385 // _finger set in set_non_marking_state 386 387 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads), 388 _max_num_tasks(ParallelGCThreads), 389 // _num_active_tasks set in set_non_marking_state() 390 // _tasks set inside the constructor 391 392 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)), 393 _terminator((int) _max_num_tasks, _task_queues), 394 395 _first_overflow_barrier_sync(), 396 _second_overflow_barrier_sync(), 397 398 _has_overflown(false), 399 _concurrent(false), 400 _has_aborted(false), 401 _restart_for_overflow(false), 402 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()), 403 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()), 404 405 // _verbose_level set below 406 407 _init_times(), 408 _remark_times(), 409 _remark_mark_times(), 410 _remark_weak_ref_times(), 411 _cleanup_times(), 412 _total_cleanup_time(0.0), 413 414 _accum_task_vtime(NULL), 415 416 _concurrent_workers(NULL), 417 _num_concurrent_workers(0), 418 _max_concurrent_workers(0), 419 420 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)), 421 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC)) 422 { 423 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage); 424 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage); 425 426 // Create & start ConcurrentMark thread. 427 _cm_thread = new G1ConcurrentMarkThread(this); 428 if (_cm_thread->osthread() == NULL) { 429 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread"); 430 } 431 432 assert(CGC_lock != NULL, "CGC_lock must be initialized"); 433 434 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) { 435 // Calculate the number of concurrent worker threads by scaling 436 // the number of parallel GC threads. 437 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads); 438 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num); 439 } 440 441 assert(ConcGCThreads > 0, "ConcGCThreads have been set."); 442 if (ConcGCThreads > ParallelGCThreads) { 443 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).", 444 ConcGCThreads, ParallelGCThreads); 445 return; 446 } 447 448 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset); 449 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads); 450 451 _num_concurrent_workers = ConcGCThreads; 452 _max_concurrent_workers = _num_concurrent_workers; 453 454 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true); 455 _concurrent_workers->initialize_workers(); 456 457 if (FLAG_IS_DEFAULT(MarkStackSize)) { 458 size_t mark_stack_size = 459 MIN2(MarkStackSizeMax, 460 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE))); 461 // Verify that the calculated value for MarkStackSize is in range. 462 // It would be nice to use the private utility routine from Arguments. 463 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) { 464 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): " 465 "must be between 1 and " SIZE_FORMAT, 466 mark_stack_size, MarkStackSizeMax); 467 return; 468 } 469 FLAG_SET_ERGO(MarkStackSize, mark_stack_size); 470 } else { 471 // Verify MarkStackSize is in range. 472 if (FLAG_IS_CMDLINE(MarkStackSize)) { 473 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) { 474 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 475 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): " 476 "must be between 1 and " SIZE_FORMAT, 477 MarkStackSize, MarkStackSizeMax); 478 return; 479 } 480 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) { 481 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) { 482 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")" 483 " or for MarkStackSizeMax (" SIZE_FORMAT ")", 484 MarkStackSize, MarkStackSizeMax); 485 return; 486 } 487 } 488 } 489 } 490 491 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) { 492 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack."); 493 } 494 495 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC); 496 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC); 497 498 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail 499 _num_active_tasks = _max_num_tasks; 500 501 for (uint i = 0; i < _max_num_tasks; ++i) { 502 G1CMTaskQueue* task_queue = new G1CMTaskQueue(); 503 task_queue->initialize(); 504 _task_queues->register_queue(i, task_queue); 505 506 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions()); 507 508 _accum_task_vtime[i] = 0.0; 509 } 510 511 reset_at_marking_complete(); 512 _completed_initialization = true; 513 } 514 515 void G1ConcurrentMark::reset() { 516 _has_aborted = false; 517 518 reset_marking_for_restart(); 519 520 // Reset all tasks, since different phases will use different number of active 521 // threads. So, it's easiest to have all of them ready. 522 for (uint i = 0; i < _max_num_tasks; ++i) { 523 _tasks[i]->reset(_next_mark_bitmap); 524 } 525 526 uint max_regions = _g1h->max_regions(); 527 for (uint i = 0; i < max_regions; i++) { 528 _top_at_rebuild_starts[i] = NULL; 529 _region_mark_stats[i].clear(); 530 } 531 } 532 533 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) { 534 for (uint j = 0; j < _max_num_tasks; ++j) { 535 _tasks[j]->clear_mark_stats_cache(region_idx); 536 } 537 _top_at_rebuild_starts[region_idx] = NULL; 538 _region_mark_stats[region_idx].clear(); 539 } 540 541 void G1ConcurrentMark::clear_statistics(HeapRegion* r) { 542 uint const region_idx = r->hrm_index(); 543 if (r->is_humongous()) { 544 assert(r->is_starts_humongous(), "Got humongous continues region here"); 545 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size()); 546 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) { 547 clear_statistics_in_region(j); 548 } 549 } else { 550 clear_statistics_in_region(region_idx); 551 } 552 } 553 554 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) { 555 if (bitmap->is_marked(addr)) { 556 bitmap->clear(addr); 557 } 558 } 559 560 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) { 561 assert_at_safepoint_on_vm_thread(); 562 563 // Need to clear all mark bits of the humongous object. 564 clear_mark_if_set(_prev_mark_bitmap, r->bottom()); 565 clear_mark_if_set(_next_mark_bitmap, r->bottom()); 566 567 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) { 568 return; 569 } 570 571 // Clear any statistics about the region gathered so far. 572 clear_statistics(r); 573 } 574 575 void G1ConcurrentMark::reset_marking_for_restart() { 576 _global_mark_stack.set_empty(); 577 578 // Expand the marking stack, if we have to and if we can. 579 if (has_overflown()) { 580 _global_mark_stack.expand(); 581 582 uint max_regions = _g1h->max_regions(); 583 for (uint i = 0; i < max_regions; i++) { 584 _region_mark_stats[i].clear_during_overflow(); 585 } 586 } 587 588 clear_has_overflown(); 589 _finger = _heap.start(); 590 591 for (uint i = 0; i < _max_num_tasks; ++i) { 592 G1CMTaskQueue* queue = _task_queues->queue(i); 593 queue->set_empty(); 594 } 595 } 596 597 void G1ConcurrentMark::set_concurrency(uint active_tasks) { 598 assert(active_tasks <= _max_num_tasks, "we should not have more"); 599 600 _num_active_tasks = active_tasks; 601 // Need to update the three data structures below according to the 602 // number of active threads for this phase. 603 _terminator.terminator()->reset_for_reuse((int) active_tasks); 604 _first_overflow_barrier_sync.set_n_workers((int) active_tasks); 605 _second_overflow_barrier_sync.set_n_workers((int) active_tasks); 606 } 607 608 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) { 609 set_concurrency(active_tasks); 610 611 _concurrent = concurrent; 612 613 if (!concurrent) { 614 // At this point we should be in a STW phase, and completed marking. 615 assert_at_safepoint_on_vm_thread(); 616 assert(out_of_regions(), 617 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT, 618 p2i(_finger), p2i(_heap.end())); 619 } 620 } 621 622 void G1ConcurrentMark::reset_at_marking_complete() { 623 // We set the global marking state to some default values when we're 624 // not doing marking. 625 reset_marking_for_restart(); 626 _num_active_tasks = 0; 627 } 628 629 G1ConcurrentMark::~G1ConcurrentMark() { 630 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts); 631 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats); 632 // The G1ConcurrentMark instance is never freed. 633 ShouldNotReachHere(); 634 } 635 636 class G1ClearBitMapTask : public AbstractGangTask { 637 public: 638 static size_t chunk_size() { return M; } 639 640 private: 641 // Heap region closure used for clearing the given mark bitmap. 642 class G1ClearBitmapHRClosure : public HeapRegionClosure { 643 private: 644 G1CMBitMap* _bitmap; 645 G1ConcurrentMark* _cm; 646 public: 647 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) { 648 } 649 650 virtual bool do_heap_region(HeapRegion* r) { 651 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize; 652 653 HeapWord* cur = r->bottom(); 654 HeapWord* const end = r->end(); 655 656 while (cur < end) { 657 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end)); 658 _bitmap->clear_range(mr); 659 660 cur += chunk_size_in_words; 661 662 // Abort iteration if after yielding the marking has been aborted. 663 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) { 664 return true; 665 } 666 // Repeat the asserts from before the start of the closure. We will do them 667 // as asserts here to minimize their overhead on the product. However, we 668 // will have them as guarantees at the beginning / end of the bitmap 669 // clearing to get some checking in the product. 670 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant"); 671 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 672 } 673 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index()); 674 675 return false; 676 } 677 }; 678 679 G1ClearBitmapHRClosure _cl; 680 HeapRegionClaimer _hr_claimer; 681 bool _suspendible; // If the task is suspendible, workers must join the STS. 682 683 public: 684 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) : 685 AbstractGangTask("G1 Clear Bitmap"), 686 _cl(bitmap, suspendible ? cm : NULL), 687 _hr_claimer(n_workers), 688 _suspendible(suspendible) 689 { } 690 691 void work(uint worker_id) { 692 SuspendibleThreadSetJoiner sts_join(_suspendible); 693 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id); 694 } 695 696 bool is_complete() { 697 return _cl.is_complete(); 698 } 699 }; 700 701 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) { 702 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint."); 703 704 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor(); 705 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size(); 706 707 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); 708 709 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield); 710 711 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks); 712 workers->run_task(&cl, num_workers); 713 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding."); 714 } 715 716 void G1ConcurrentMark::cleanup_for_next_mark() { 717 // Make sure that the concurrent mark thread looks to still be in 718 // the current cycle. 719 guarantee(cm_thread()->during_cycle(), "invariant"); 720 721 // We are finishing up the current cycle by clearing the next 722 // marking bitmap and getting it ready for the next cycle. During 723 // this time no other cycle can start. So, let's make sure that this 724 // is the case. 725 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 726 727 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true); 728 729 // Repeat the asserts from above. 730 guarantee(cm_thread()->during_cycle(), "invariant"); 731 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant"); 732 } 733 734 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) { 735 assert_at_safepoint_on_vm_thread(); 736 clear_bitmap(_prev_mark_bitmap, workers, false); 737 } 738 739 class NoteStartOfMarkHRClosure : public HeapRegionClosure { 740 public: 741 bool do_heap_region(HeapRegion* r) { 742 r->note_start_of_marking(); 743 return false; 744 } 745 }; 746 747 void G1ConcurrentMark::pre_initial_mark() { 748 assert_at_safepoint_on_vm_thread(); 749 750 // Reset marking state. 751 reset(); 752 753 // For each region note start of marking. 754 NoteStartOfMarkHRClosure startcl; 755 _g1h->heap_region_iterate(&startcl); 756 757 _root_regions.reset(); 758 } 759 760 761 void G1ConcurrentMark::post_initial_mark() { 762 // Start Concurrent Marking weak-reference discovery. 763 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 764 // enable ("weak") refs discovery 765 rp->enable_discovery(); 766 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle 767 768 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 769 // This is the start of the marking cycle, we're expected all 770 // threads to have SATB queues with active set to false. 771 satb_mq_set.set_active_all_threads(true, /* new active value */ 772 false /* expected_active */); 773 774 _root_regions.prepare_for_scan(); 775 776 // update_g1_committed() will be called at the end of an evac pause 777 // when marking is on. So, it's also called at the end of the 778 // initial-mark pause to update the heap end, if the heap expands 779 // during it. No need to call it here. 780 } 781 782 /* 783 * Notice that in the next two methods, we actually leave the STS 784 * during the barrier sync and join it immediately afterwards. If we 785 * do not do this, the following deadlock can occur: one thread could 786 * be in the barrier sync code, waiting for the other thread to also 787 * sync up, whereas another one could be trying to yield, while also 788 * waiting for the other threads to sync up too. 789 * 790 * Note, however, that this code is also used during remark and in 791 * this case we should not attempt to leave / enter the STS, otherwise 792 * we'll either hit an assert (debug / fastdebug) or deadlock 793 * (product). So we should only leave / enter the STS if we are 794 * operating concurrently. 795 * 796 * Because the thread that does the sync barrier has left the STS, it 797 * is possible to be suspended for a Full GC or an evacuation pause 798 * could occur. This is actually safe, since the entering the sync 799 * barrier is one of the last things do_marking_step() does, and it 800 * doesn't manipulate any data structures afterwards. 801 */ 802 803 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) { 804 bool barrier_aborted; 805 { 806 SuspendibleThreadSetLeaver sts_leave(concurrent()); 807 barrier_aborted = !_first_overflow_barrier_sync.enter(); 808 } 809 810 // at this point everyone should have synced up and not be doing any 811 // more work 812 813 if (barrier_aborted) { 814 // If the barrier aborted we ignore the overflow condition and 815 // just abort the whole marking phase as quickly as possible. 816 return; 817 } 818 } 819 820 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) { 821 SuspendibleThreadSetLeaver sts_leave(concurrent()); 822 _second_overflow_barrier_sync.enter(); 823 824 // at this point everything should be re-initialized and ready to go 825 } 826 827 class G1CMConcurrentMarkingTask : public AbstractGangTask { 828 G1ConcurrentMark* _cm; 829 830 public: 831 void work(uint worker_id) { 832 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread"); 833 ResourceMark rm; 834 835 double start_vtime = os::elapsedVTime(); 836 837 { 838 SuspendibleThreadSetJoiner sts_join; 839 840 assert(worker_id < _cm->active_tasks(), "invariant"); 841 842 G1CMTask* task = _cm->task(worker_id); 843 task->record_start_time(); 844 if (!_cm->has_aborted()) { 845 do { 846 task->do_marking_step(G1ConcMarkStepDurationMillis, 847 true /* do_termination */, 848 false /* is_serial*/); 849 850 _cm->do_yield_check(); 851 } while (!_cm->has_aborted() && task->has_aborted()); 852 } 853 task->record_end_time(); 854 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant"); 855 } 856 857 double end_vtime = os::elapsedVTime(); 858 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime); 859 } 860 861 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) : 862 AbstractGangTask("Concurrent Mark"), _cm(cm) { } 863 864 ~G1CMConcurrentMarkingTask() { } 865 }; 866 867 uint G1ConcurrentMark::calc_active_marking_workers() { 868 uint result = 0; 869 if (!UseDynamicNumberOfGCThreads || 870 (!FLAG_IS_DEFAULT(ConcGCThreads) && 871 !ForceDynamicNumberOfGCThreads)) { 872 result = _max_concurrent_workers; 873 } else { 874 result = 875 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers, 876 1, /* Minimum workers */ 877 _num_concurrent_workers, 878 Threads::number_of_non_daemon_threads()); 879 // Don't scale the result down by scale_concurrent_workers() because 880 // that scaling has already gone into "_max_concurrent_workers". 881 } 882 assert(result > 0 && result <= _max_concurrent_workers, 883 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u", 884 _max_concurrent_workers, result); 885 return result; 886 } 887 888 void G1ConcurrentMark::scan_root_region(const MemRegion* region, uint worker_id) { 889 #ifdef ASSERT 890 HeapWord* last = region->last(); 891 HeapRegion* hr = _g1h->heap_region_containing(last); 892 assert(hr->is_old() || hr->next_top_at_mark_start() == hr->bottom(), 893 "Root regions must be old or survivor/eden but region %u is %s", hr->hrm_index(), hr->get_type_str()); 894 assert(hr->next_top_at_mark_start() == region->start(), 895 "MemRegion start should be equal to nTAMS"); 896 #endif 897 898 G1RootRegionScanClosure cl(_g1h, this, worker_id); 899 900 const uintx interval = PrefetchScanIntervalInBytes; 901 HeapWord* curr = region->start(); 902 const HeapWord* end = region->end(); 903 while (curr < end) { 904 Prefetch::read(curr, interval); 905 oop obj = oop(curr); 906 int size = obj->oop_iterate_size(&cl); 907 assert(size == obj->size(), "sanity"); 908 curr += size; 909 } 910 } 911 912 class G1CMRootRegionScanTask : public AbstractGangTask { 913 G1ConcurrentMark* _cm; 914 public: 915 G1CMRootRegionScanTask(G1ConcurrentMark* cm) : 916 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { } 917 918 void work(uint worker_id) { 919 assert(Thread::current()->is_ConcurrentGC_thread(), 920 "this should only be done by a conc GC thread"); 921 922 G1CMRootMemRegions* root_regions = _cm->root_regions(); 923 const MemRegion* region = root_regions->claim_next(); 924 while (region != NULL) { 925 _cm->scan_root_region(region, worker_id); 926 region = root_regions->claim_next(); 927 } 928 } 929 }; 930 931 void G1ConcurrentMark::scan_root_regions() { 932 // scan_in_progress() will have been set to true only if there was 933 // at least one root region to scan. So, if it's false, we 934 // should not attempt to do any further work. 935 if (root_regions()->scan_in_progress()) { 936 assert(!has_aborted(), "Aborting before root region scanning is finished not supported."); 937 938 _num_concurrent_workers = MIN2(calc_active_marking_workers(), 939 // We distribute work on a per-region basis, so starting 940 // more threads than that is useless. 941 root_regions()->num_root_regions()); 942 assert(_num_concurrent_workers <= _max_concurrent_workers, 943 "Maximum number of marking threads exceeded"); 944 945 G1CMRootRegionScanTask task(this); 946 log_debug(gc, ergo)("Running %s using %u workers for %u work units.", 947 task.name(), _num_concurrent_workers, root_regions()->num_root_regions()); 948 _concurrent_workers->run_task(&task, _num_concurrent_workers); 949 950 // It's possible that has_aborted() is true here without actually 951 // aborting the survivor scan earlier. This is OK as it's 952 // mainly used for sanity checking. 953 root_regions()->scan_finished(); 954 } 955 } 956 957 void G1ConcurrentMark::concurrent_cycle_start() { 958 _gc_timer_cm->register_gc_start(); 959 960 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start()); 961 962 _g1h->trace_heap_before_gc(_gc_tracer_cm); 963 } 964 965 void G1ConcurrentMark::concurrent_cycle_end() { 966 _g1h->collector_state()->set_clearing_next_bitmap(false); 967 968 _g1h->trace_heap_after_gc(_gc_tracer_cm); 969 970 if (has_aborted()) { 971 log_info(gc, marking)("Concurrent Mark Abort"); 972 _gc_tracer_cm->report_concurrent_mode_failure(); 973 } 974 975 _gc_timer_cm->register_gc_end(); 976 977 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions()); 978 } 979 980 void G1ConcurrentMark::mark_from_roots() { 981 _restart_for_overflow = false; 982 983 _num_concurrent_workers = calc_active_marking_workers(); 984 985 uint active_workers = MAX2(1U, _num_concurrent_workers); 986 987 // Setting active workers is not guaranteed since fewer 988 // worker threads may currently exist and more may not be 989 // available. 990 active_workers = _concurrent_workers->update_active_workers(active_workers); 991 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers()); 992 993 // Parallel task terminator is set in "set_concurrency_and_phase()" 994 set_concurrency_and_phase(active_workers, true /* concurrent */); 995 996 G1CMConcurrentMarkingTask marking_task(this); 997 _concurrent_workers->run_task(&marking_task); 998 print_stats(); 999 } 1000 1001 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) { 1002 G1HeapVerifier* verifier = _g1h->verifier(); 1003 1004 verifier->verify_region_sets_optional(); 1005 1006 if (VerifyDuringGC) { 1007 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm); 1008 1009 size_t const BufLen = 512; 1010 char buffer[BufLen]; 1011 1012 jio_snprintf(buffer, BufLen, "During GC (%s)", caller); 1013 verifier->verify(type, vo, buffer); 1014 } 1015 1016 verifier->check_bitmaps(caller); 1017 } 1018 1019 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask { 1020 G1CollectedHeap* _g1h; 1021 G1ConcurrentMark* _cm; 1022 HeapRegionClaimer _hrclaimer; 1023 uint volatile _total_selected_for_rebuild; 1024 1025 G1PrintRegionLivenessInfoClosure _cl; 1026 1027 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure { 1028 G1CollectedHeap* _g1h; 1029 G1ConcurrentMark* _cm; 1030 1031 G1PrintRegionLivenessInfoClosure* _cl; 1032 1033 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild. 1034 1035 void update_remset_before_rebuild(HeapRegion* hr) { 1036 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker(); 1037 1038 bool selected_for_rebuild; 1039 if (hr->is_humongous()) { 1040 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0; 1041 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live); 1042 } else { 1043 size_t const live_bytes = _cm->liveness(hr->hrm_index()); 1044 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes); 1045 } 1046 if (selected_for_rebuild) { 1047 _num_regions_selected_for_rebuild++; 1048 } 1049 _cm->update_top_at_rebuild_start(hr); 1050 } 1051 1052 // Distribute the given words across the humongous object starting with hr and 1053 // note end of marking. 1054 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) { 1055 uint const region_idx = hr->hrm_index(); 1056 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size(); 1057 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words); 1058 1059 // "Distributing" zero words means that we only note end of marking for these 1060 // regions. 1061 assert(marked_words == 0 || obj_size_in_words == marked_words, 1062 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT, 1063 obj_size_in_words, marked_words); 1064 1065 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) { 1066 HeapRegion* const r = _g1h->region_at(i); 1067 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words); 1068 1069 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)", 1070 words_to_add, i, r->get_type_str()); 1071 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize); 1072 marked_words -= words_to_add; 1073 } 1074 assert(marked_words == 0, 1075 SIZE_FORMAT " words left after distributing space across %u regions", 1076 marked_words, num_regions_in_humongous); 1077 } 1078 1079 void update_marked_bytes(HeapRegion* hr) { 1080 uint const region_idx = hr->hrm_index(); 1081 size_t const marked_words = _cm->liveness(region_idx); 1082 // The marking attributes the object's size completely to the humongous starts 1083 // region. We need to distribute this value across the entire set of regions a 1084 // humongous object spans. 1085 if (hr->is_humongous()) { 1086 assert(hr->is_starts_humongous() || marked_words == 0, 1087 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)", 1088 marked_words, region_idx, hr->get_type_str()); 1089 if (hr->is_starts_humongous()) { 1090 distribute_marked_bytes(hr, marked_words); 1091 } 1092 } else { 1093 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str()); 1094 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize); 1095 } 1096 } 1097 1098 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) { 1099 hr->add_to_marked_bytes(marked_bytes); 1100 _cl->do_heap_region(hr); 1101 hr->note_end_of_marking(); 1102 } 1103 1104 public: 1105 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) : 1106 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { } 1107 1108 virtual bool do_heap_region(HeapRegion* r) { 1109 update_remset_before_rebuild(r); 1110 update_marked_bytes(r); 1111 1112 return false; 1113 } 1114 1115 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; } 1116 }; 1117 1118 public: 1119 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) : 1120 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"), 1121 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { } 1122 1123 virtual void work(uint worker_id) { 1124 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl); 1125 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id); 1126 Atomic::add(&_total_selected_for_rebuild, update_cl.num_selected_for_rebuild()); 1127 } 1128 1129 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; } 1130 1131 // Number of regions for which roughly one thread should be spawned for this work. 1132 static const uint RegionsPerThread = 384; 1133 }; 1134 1135 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure { 1136 G1CollectedHeap* _g1h; 1137 public: 1138 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { } 1139 1140 virtual bool do_heap_region(HeapRegion* r) { 1141 _g1h->policy()->remset_tracker()->update_after_rebuild(r); 1142 return false; 1143 } 1144 }; 1145 1146 void G1ConcurrentMark::remark() { 1147 assert_at_safepoint_on_vm_thread(); 1148 1149 // If a full collection has happened, we should not continue. However we might 1150 // have ended up here as the Remark VM operation has been scheduled already. 1151 if (has_aborted()) { 1152 return; 1153 } 1154 1155 G1Policy* policy = _g1h->policy(); 1156 policy->record_concurrent_mark_remark_start(); 1157 1158 double start = os::elapsedTime(); 1159 1160 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before"); 1161 1162 { 1163 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm); 1164 finalize_marking(); 1165 } 1166 1167 double mark_work_end = os::elapsedTime(); 1168 1169 bool const mark_finished = !has_overflown(); 1170 if (mark_finished) { 1171 weak_refs_work(false /* clear_all_soft_refs */); 1172 1173 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set(); 1174 // We're done with marking. 1175 // This is the end of the marking cycle, we're expected all 1176 // threads to have SATB queues with active set to true. 1177 satb_mq_set.set_active_all_threads(false, /* new active value */ 1178 true /* expected_active */); 1179 1180 { 1181 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm); 1182 flush_all_task_caches(); 1183 } 1184 1185 // Install newly created mark bitmap as "prev". 1186 swap_mark_bitmaps(); 1187 { 1188 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm); 1189 1190 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) / 1191 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread; 1192 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity); 1193 1194 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers); 1195 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions()); 1196 _g1h->workers()->run_task(&cl, num_workers); 1197 1198 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u", 1199 _g1h->num_regions(), cl.total_selected_for_rebuild()); 1200 } 1201 { 1202 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm); 1203 reclaim_empty_regions(); 1204 } 1205 1206 // Clean out dead classes 1207 if (ClassUnloadingWithConcurrentMark) { 1208 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm); 1209 ClassLoaderDataGraph::purge(); 1210 } 1211 1212 _g1h->shrink_heap_after_concurrent_mark(); 1213 1214 compute_new_sizes(); 1215 1216 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after"); 1217 1218 assert(!restart_for_overflow(), "sanity"); 1219 // Completely reset the marking state since marking completed 1220 reset_at_marking_complete(); 1221 } else { 1222 // We overflowed. Restart concurrent marking. 1223 _restart_for_overflow = true; 1224 1225 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow"); 1226 1227 // Clear the marking state because we will be restarting 1228 // marking due to overflowing the global mark stack. 1229 reset_marking_for_restart(); 1230 } 1231 1232 { 1233 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm); 1234 report_object_count(mark_finished); 1235 } 1236 1237 // Statistics 1238 double now = os::elapsedTime(); 1239 _remark_mark_times.add((mark_work_end - start) * 1000.0); 1240 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0); 1241 _remark_times.add((now - start) * 1000.0); 1242 1243 policy->record_concurrent_mark_remark_end(); 1244 } 1245 1246 class G1ReclaimEmptyRegionsTask : public AbstractGangTask { 1247 // Per-region work during the Cleanup pause. 1248 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure { 1249 G1CollectedHeap* _g1h; 1250 size_t _freed_bytes; 1251 FreeRegionList* _local_cleanup_list; 1252 uint _old_regions_removed; 1253 uint _humongous_regions_removed; 1254 1255 public: 1256 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h, 1257 FreeRegionList* local_cleanup_list) : 1258 _g1h(g1h), 1259 _freed_bytes(0), 1260 _local_cleanup_list(local_cleanup_list), 1261 _old_regions_removed(0), 1262 _humongous_regions_removed(0) { } 1263 1264 size_t freed_bytes() { return _freed_bytes; } 1265 const uint old_regions_removed() { return _old_regions_removed; } 1266 const uint humongous_regions_removed() { return _humongous_regions_removed; } 1267 1268 bool do_heap_region(HeapRegion *hr) { 1269 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) { 1270 _freed_bytes += hr->used(); 1271 hr->set_containing_set(NULL); 1272 if (hr->is_humongous()) { 1273 _humongous_regions_removed++; 1274 _g1h->free_humongous_region(hr, _local_cleanup_list); 1275 } else { 1276 _old_regions_removed++; 1277 _g1h->free_region(hr, _local_cleanup_list); 1278 } 1279 hr->clear_cardtable(); 1280 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index()); 1281 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom())); 1282 } 1283 1284 return false; 1285 } 1286 }; 1287 1288 G1CollectedHeap* _g1h; 1289 FreeRegionList* _cleanup_list; 1290 HeapRegionClaimer _hrclaimer; 1291 1292 public: 1293 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) : 1294 AbstractGangTask("G1 Cleanup"), 1295 _g1h(g1h), 1296 _cleanup_list(cleanup_list), 1297 _hrclaimer(n_workers) { 1298 } 1299 1300 void work(uint worker_id) { 1301 FreeRegionList local_cleanup_list("Local Cleanup List"); 1302 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list); 1303 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id); 1304 assert(cl.is_complete(), "Shouldn't have aborted!"); 1305 1306 // Now update the old/humongous region sets 1307 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed()); 1308 { 1309 MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 1310 _g1h->decrement_summary_bytes(cl.freed_bytes()); 1311 1312 _cleanup_list->add_ordered(&local_cleanup_list); 1313 assert(local_cleanup_list.is_empty(), "post-condition"); 1314 } 1315 } 1316 }; 1317 1318 void G1ConcurrentMark::reclaim_empty_regions() { 1319 WorkGang* workers = _g1h->workers(); 1320 FreeRegionList empty_regions_list("Empty Regions After Mark List"); 1321 1322 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers()); 1323 workers->run_task(&cl); 1324 1325 if (!empty_regions_list.is_empty()) { 1326 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length()); 1327 // Now print the empty regions list. 1328 G1HRPrinter* hrp = _g1h->hr_printer(); 1329 if (hrp->is_active()) { 1330 FreeRegionListIterator iter(&empty_regions_list); 1331 while (iter.more_available()) { 1332 HeapRegion* hr = iter.get_next(); 1333 hrp->cleanup(hr); 1334 } 1335 } 1336 // And actually make them available. 1337 _g1h->prepend_to_freelist(&empty_regions_list); 1338 } 1339 } 1340 1341 void G1ConcurrentMark::compute_new_sizes() { 1342 MetaspaceGC::compute_new_size(); 1343 1344 // Cleanup will have freed any regions completely full of garbage. 1345 // Update the soft reference policy with the new heap occupancy. 1346 Universe::update_heap_info_at_gc(); 1347 1348 // We reclaimed old regions so we should calculate the sizes to make 1349 // sure we update the old gen/space data. 1350 _g1h->g1mm()->update_sizes(); 1351 } 1352 1353 void G1ConcurrentMark::cleanup() { 1354 assert_at_safepoint_on_vm_thread(); 1355 1356 // If a full collection has happened, we shouldn't do this. 1357 if (has_aborted()) { 1358 return; 1359 } 1360 1361 G1Policy* policy = _g1h->policy(); 1362 policy->record_concurrent_mark_cleanup_start(); 1363 1364 double start = os::elapsedTime(); 1365 1366 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before"); 1367 1368 { 1369 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm); 1370 G1UpdateRemSetTrackingAfterRebuild cl(_g1h); 1371 _g1h->heap_region_iterate(&cl); 1372 } 1373 1374 if (log_is_enabled(Trace, gc, liveness)) { 1375 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup"); 1376 _g1h->heap_region_iterate(&cl); 1377 } 1378 1379 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after"); 1380 1381 // We need to make this be a "collection" so any collection pause that 1382 // races with it goes around and waits for Cleanup to finish. 1383 _g1h->increment_total_collections(); 1384 1385 // Local statistics 1386 double recent_cleanup_time = (os::elapsedTime() - start); 1387 _total_cleanup_time += recent_cleanup_time; 1388 _cleanup_times.add(recent_cleanup_time); 1389 1390 { 1391 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm); 1392 policy->record_concurrent_mark_cleanup_end(); 1393 } 1394 } 1395 1396 // 'Keep Alive' oop closure used by both serial parallel reference processing. 1397 // Uses the G1CMTask associated with a worker thread (for serial reference 1398 // processing the G1CMTask for worker 0 is used) to preserve (mark) and 1399 // trace referent objects. 1400 // 1401 // Using the G1CMTask and embedded local queues avoids having the worker 1402 // threads operating on the global mark stack. This reduces the risk 1403 // of overflowing the stack - which we would rather avoid at this late 1404 // state. Also using the tasks' local queues removes the potential 1405 // of the workers interfering with each other that could occur if 1406 // operating on the global stack. 1407 1408 class G1CMKeepAliveAndDrainClosure : public OopClosure { 1409 G1ConcurrentMark* _cm; 1410 G1CMTask* _task; 1411 uint _ref_counter_limit; 1412 uint _ref_counter; 1413 bool _is_serial; 1414 public: 1415 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1416 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval), 1417 _ref_counter(_ref_counter_limit), _is_serial(is_serial) { 1418 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1419 } 1420 1421 virtual void do_oop(narrowOop* p) { do_oop_work(p); } 1422 virtual void do_oop( oop* p) { do_oop_work(p); } 1423 1424 template <class T> void do_oop_work(T* p) { 1425 if (_cm->has_overflown()) { 1426 return; 1427 } 1428 if (!_task->deal_with_reference(p)) { 1429 // We did not add anything to the mark bitmap (or mark stack), so there is 1430 // no point trying to drain it. 1431 return; 1432 } 1433 _ref_counter--; 1434 1435 if (_ref_counter == 0) { 1436 // We have dealt with _ref_counter_limit references, pushing them 1437 // and objects reachable from them on to the local stack (and 1438 // possibly the global stack). Call G1CMTask::do_marking_step() to 1439 // process these entries. 1440 // 1441 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if 1442 // there's nothing more to do (i.e. we're done with the entries that 1443 // were pushed as a result of the G1CMTask::deal_with_reference() calls 1444 // above) or we overflow. 1445 // 1446 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1447 // flag while there may still be some work to do. (See the comment at 1448 // the beginning of G1CMTask::do_marking_step() for those conditions - 1449 // one of which is reaching the specified time target.) It is only 1450 // when G1CMTask::do_marking_step() returns without setting the 1451 // has_aborted() flag that the marking step has completed. 1452 do { 1453 double mark_step_duration_ms = G1ConcMarkStepDurationMillis; 1454 _task->do_marking_step(mark_step_duration_ms, 1455 false /* do_termination */, 1456 _is_serial); 1457 } while (_task->has_aborted() && !_cm->has_overflown()); 1458 _ref_counter = _ref_counter_limit; 1459 } 1460 } 1461 }; 1462 1463 // 'Drain' oop closure used by both serial and parallel reference processing. 1464 // Uses the G1CMTask associated with a given worker thread (for serial 1465 // reference processing the G1CMtask for worker 0 is used). Calls the 1466 // do_marking_step routine, with an unbelievably large timeout value, 1467 // to drain the marking data structures of the remaining entries 1468 // added by the 'keep alive' oop closure above. 1469 1470 class G1CMDrainMarkingStackClosure : public VoidClosure { 1471 G1ConcurrentMark* _cm; 1472 G1CMTask* _task; 1473 bool _is_serial; 1474 public: 1475 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) : 1476 _cm(cm), _task(task), _is_serial(is_serial) { 1477 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code"); 1478 } 1479 1480 void do_void() { 1481 do { 1482 // We call G1CMTask::do_marking_step() to completely drain the local 1483 // and global marking stacks of entries pushed by the 'keep alive' 1484 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above). 1485 // 1486 // G1CMTask::do_marking_step() is called in a loop, which we'll exit 1487 // if there's nothing more to do (i.e. we've completely drained the 1488 // entries that were pushed as a a result of applying the 'keep alive' 1489 // closure to the entries on the discovered ref lists) or we overflow 1490 // the global marking stack. 1491 // 1492 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted() 1493 // flag while there may still be some work to do. (See the comment at 1494 // the beginning of G1CMTask::do_marking_step() for those conditions - 1495 // one of which is reaching the specified time target.) It is only 1496 // when G1CMTask::do_marking_step() returns without setting the 1497 // has_aborted() flag that the marking step has completed. 1498 1499 _task->do_marking_step(1000000000.0 /* something very large */, 1500 true /* do_termination */, 1501 _is_serial); 1502 } while (_task->has_aborted() && !_cm->has_overflown()); 1503 } 1504 }; 1505 1506 // Implementation of AbstractRefProcTaskExecutor for parallel 1507 // reference processing at the end of G1 concurrent marking 1508 1509 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor { 1510 private: 1511 G1CollectedHeap* _g1h; 1512 G1ConcurrentMark* _cm; 1513 WorkGang* _workers; 1514 uint _active_workers; 1515 1516 public: 1517 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h, 1518 G1ConcurrentMark* cm, 1519 WorkGang* workers, 1520 uint n_workers) : 1521 _g1h(g1h), _cm(cm), 1522 _workers(workers), _active_workers(n_workers) { } 1523 1524 virtual void execute(ProcessTask& task, uint ergo_workers); 1525 }; 1526 1527 class G1CMRefProcTaskProxy : public AbstractGangTask { 1528 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; 1529 ProcessTask& _proc_task; 1530 G1CollectedHeap* _g1h; 1531 G1ConcurrentMark* _cm; 1532 1533 public: 1534 G1CMRefProcTaskProxy(ProcessTask& proc_task, 1535 G1CollectedHeap* g1h, 1536 G1ConcurrentMark* cm) : 1537 AbstractGangTask("Process reference objects in parallel"), 1538 _proc_task(proc_task), _g1h(g1h), _cm(cm) { 1539 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1540 assert(rp->processing_is_mt(), "shouldn't be here otherwise"); 1541 } 1542 1543 virtual void work(uint worker_id) { 1544 ResourceMark rm; 1545 HandleMark hm; 1546 G1CMTask* task = _cm->task(worker_id); 1547 G1CMIsAliveClosure g1_is_alive(_g1h); 1548 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */); 1549 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */); 1550 1551 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain); 1552 } 1553 }; 1554 1555 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) { 1556 assert(_workers != NULL, "Need parallel worker threads."); 1557 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT"); 1558 assert(_workers->active_workers() >= ergo_workers, 1559 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)", 1560 ergo_workers, _workers->active_workers()); 1561 1562 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm); 1563 1564 // We need to reset the concurrency level before each 1565 // proxy task execution, so that the termination protocol 1566 // and overflow handling in G1CMTask::do_marking_step() knows 1567 // how many workers to wait for. 1568 _cm->set_concurrency(ergo_workers); 1569 _workers->run_task(&proc_task_proxy, ergo_workers); 1570 } 1571 1572 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) { 1573 ResourceMark rm; 1574 HandleMark hm; 1575 1576 // Is alive closure. 1577 G1CMIsAliveClosure g1_is_alive(_g1h); 1578 1579 // Inner scope to exclude the cleaning of the string table 1580 // from the displayed time. 1581 { 1582 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm); 1583 1584 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1585 1586 // See the comment in G1CollectedHeap::ref_processing_init() 1587 // about how reference processing currently works in G1. 1588 1589 // Set the soft reference policy 1590 rp->setup_policy(clear_all_soft_refs); 1591 assert(_global_mark_stack.is_empty(), "mark stack should be empty"); 1592 1593 // Instances of the 'Keep Alive' and 'Complete GC' closures used 1594 // in serial reference processing. Note these closures are also 1595 // used for serially processing (by the the current thread) the 1596 // JNI references during parallel reference processing. 1597 // 1598 // These closures do not need to synchronize with the worker 1599 // threads involved in parallel reference processing as these 1600 // instances are executed serially by the current thread (e.g. 1601 // reference processing is not multi-threaded and is thus 1602 // performed by the current thread instead of a gang worker). 1603 // 1604 // The gang tasks involved in parallel reference processing create 1605 // their own instances of these closures, which do their own 1606 // synchronization among themselves. 1607 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */); 1608 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */); 1609 1610 // We need at least one active thread. If reference processing 1611 // is not multi-threaded we use the current (VMThread) thread, 1612 // otherwise we use the work gang from the G1CollectedHeap and 1613 // we utilize all the worker threads we can. 1614 bool processing_is_mt = rp->processing_is_mt(); 1615 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U); 1616 active_workers = clamp(active_workers, 1u, _max_num_tasks); 1617 1618 // Parallel processing task executor. 1619 G1CMRefProcTaskExecutor par_task_executor(_g1h, this, 1620 _g1h->workers(), active_workers); 1621 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL); 1622 1623 // Set the concurrency level. The phase was already set prior to 1624 // executing the remark task. 1625 set_concurrency(active_workers); 1626 1627 // Set the degree of MT processing here. If the discovery was done MT, 1628 // the number of threads involved during discovery could differ from 1629 // the number of active workers. This is OK as long as the discovered 1630 // Reference lists are balanced (see balance_all_queues() and balance_queues()). 1631 rp->set_active_mt_degree(active_workers); 1632 1633 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues()); 1634 1635 // Process the weak references. 1636 const ReferenceProcessorStats& stats = 1637 rp->process_discovered_references(&g1_is_alive, 1638 &g1_keep_alive, 1639 &g1_drain_mark_stack, 1640 executor, 1641 &pt); 1642 _gc_tracer_cm->report_gc_reference_stats(stats); 1643 pt.print_all_references(); 1644 1645 // The do_oop work routines of the keep_alive and drain_marking_stack 1646 // oop closures will set the has_overflown flag if we overflow the 1647 // global marking stack. 1648 1649 assert(has_overflown() || _global_mark_stack.is_empty(), 1650 "Mark stack should be empty (unless it has overflown)"); 1651 1652 assert(rp->num_queues() == active_workers, "why not"); 1653 1654 rp->verify_no_references_recorded(); 1655 assert(!rp->discovery_enabled(), "Post condition"); 1656 } 1657 1658 if (has_overflown()) { 1659 // We can not trust g1_is_alive and the contents of the heap if the marking stack 1660 // overflowed while processing references. Exit the VM. 1661 fatal("Overflow during reference processing, can not continue. Please " 1662 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and " 1663 "restart.", MarkStackSizeMax); 1664 return; 1665 } 1666 1667 assert(_global_mark_stack.is_empty(), "Marking should have completed"); 1668 1669 { 1670 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm); 1671 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1); 1672 } 1673 1674 // Unload Klasses, String, Code Cache, etc. 1675 if (ClassUnloadingWithConcurrentMark) { 1676 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm); 1677 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm); 1678 _g1h->complete_cleaning(&g1_is_alive, purged_classes); 1679 } else if (StringDedup::is_enabled()) { 1680 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm); 1681 _g1h->string_dedup_cleaning(&g1_is_alive, NULL); 1682 } 1683 } 1684 1685 class G1PrecleanYieldClosure : public YieldClosure { 1686 G1ConcurrentMark* _cm; 1687 1688 public: 1689 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { } 1690 1691 virtual bool should_return() { 1692 return _cm->has_aborted(); 1693 } 1694 1695 virtual bool should_return_fine_grain() { 1696 _cm->do_yield_check(); 1697 return _cm->has_aborted(); 1698 } 1699 }; 1700 1701 void G1ConcurrentMark::preclean() { 1702 assert(G1UseReferencePrecleaning, "Precleaning must be enabled."); 1703 1704 SuspendibleThreadSetJoiner joiner; 1705 1706 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */); 1707 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */); 1708 1709 set_concurrency_and_phase(1, true); 1710 1711 G1PrecleanYieldClosure yield_cl(this); 1712 1713 ReferenceProcessor* rp = _g1h->ref_processor_cm(); 1714 // Precleaning is single threaded. Temporarily disable MT discovery. 1715 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false); 1716 rp->preclean_discovered_references(rp->is_alive_non_header(), 1717 &keep_alive, 1718 &drain_mark_stack, 1719 &yield_cl, 1720 _gc_timer_cm); 1721 } 1722 1723 // When sampling object counts, we already swapped the mark bitmaps, so we need to use 1724 // the prev bitmap determining liveness. 1725 class G1ObjectCountIsAliveClosure: public BoolObjectClosure { 1726 G1CollectedHeap* _g1h; 1727 public: 1728 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { } 1729 1730 bool do_object_b(oop obj) { 1731 HeapWord* addr = (HeapWord*)obj; 1732 return addr != NULL && 1733 (!_g1h->is_in_g1_reserved(addr) || !_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 }