1 /*
2 * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc/g1/g1BarrierSet.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorState.hpp"
31 #include "gc/g1/g1ConcurrentMark.inline.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1DirtyCardQueue.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/g1ThreadLocalData.hpp"
40 #include "gc/g1/g1Trace.hpp"
41 #include "gc/g1/heapRegion.inline.hpp"
42 #include "gc/g1/heapRegionRemSet.hpp"
43 #include "gc/g1/heapRegionSet.inline.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "gc/shared/gcVMOperations.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/owstTaskTerminator.hpp"
50 #include "gc/shared/referencePolicy.hpp"
51 #include "gc/shared/strongRootsScope.hpp"
52 #include "gc/shared/suspendibleThreadSet.hpp"
53 #include "gc/shared/taskqueue.inline.hpp"
54 #include "gc/shared/weakProcessor.inline.hpp"
55 #include "gc/shared/workerPolicy.hpp"
56 #include "include/jvm.h"
57 #include "logging/log.hpp"
58 #include "memory/allocation.hpp"
59 #include "memory/iterator.hpp"
60 #include "memory/resourceArea.hpp"
61 #include "memory/universe.hpp"
62 #include "oops/access.inline.hpp"
63 #include "oops/oop.inline.hpp"
64 #include "runtime/atomic.hpp"
65 #include "runtime/handles.inline.hpp"
66 #include "runtime/java.hpp"
67 #include "runtime/orderAccess.hpp"
68 #include "runtime/prefetch.inline.hpp"
69 #include "services/memTracker.hpp"
70 #include "utilities/align.hpp"
71 #include "utilities/growableArray.hpp"
72
73 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
74 assert(addr < _cm->finger(), "invariant");
75 assert(addr >= _task->finger(), "invariant");
76
77 // We move that task's local finger along.
78 _task->move_finger_to(addr);
79
80 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
81 // we only partially drain the local queue and global stack
82 _task->drain_local_queue(true);
83 _task->drain_global_stack(true);
84
85 // if the has_aborted flag has been raised, we need to bail out of
86 // the iteration
87 return !_task->has_aborted();
88 }
89
90 G1CMMarkStack::G1CMMarkStack() :
91 _max_chunk_capacity(0),
92 _base(NULL),
93 _chunk_capacity(0) {
94 set_empty();
95 }
96
97 bool G1CMMarkStack::resize(size_t new_capacity) {
98 assert(is_empty(), "Only resize when stack is empty.");
99 assert(new_capacity <= _max_chunk_capacity,
100 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
101
102 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
103
104 if (new_base == NULL) {
105 log_warning(gc)("Failed to reserve memory for new overflow mark stack with " SIZE_FORMAT " chunks and size " SIZE_FORMAT "B.", new_capacity, new_capacity * sizeof(TaskQueueEntryChunk));
106 return false;
107 }
108 // Release old mapping.
109 if (_base != NULL) {
110 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
111 }
112
113 _base = new_base;
114 _chunk_capacity = new_capacity;
115 set_empty();
116
117 return true;
118 }
119
120 size_t G1CMMarkStack::capacity_alignment() {
121 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
122 }
123
124 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
125 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
126
127 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
128
129 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
130 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
131
132 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
133 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
134 _max_chunk_capacity,
135 initial_chunk_capacity);
136
137 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
138 initial_chunk_capacity, _max_chunk_capacity);
139
140 return resize(initial_chunk_capacity);
141 }
142
143 void G1CMMarkStack::expand() {
144 if (_chunk_capacity == _max_chunk_capacity) {
145 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
146 return;
147 }
148 size_t old_capacity = _chunk_capacity;
149 // Double capacity if possible
150 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
151
152 if (resize(new_capacity)) {
153 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
154 old_capacity, new_capacity);
155 } else {
156 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
157 old_capacity, new_capacity);
158 }
159 }
160
161 G1CMMarkStack::~G1CMMarkStack() {
162 if (_base != NULL) {
163 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
164 }
165 }
166
167 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
168 elem->next = *list;
169 *list = elem;
170 }
171
172 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
173 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
174 add_chunk_to_list(&_chunk_list, elem);
175 _chunks_in_chunk_list++;
176 }
177
178 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
179 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
180 add_chunk_to_list(&_free_list, elem);
181 }
182
183 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
184 TaskQueueEntryChunk* result = *list;
185 if (result != NULL) {
186 *list = (*list)->next;
187 }
188 return result;
189 }
190
191 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
192 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
193 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
194 if (result != NULL) {
195 _chunks_in_chunk_list--;
196 }
197 return result;
198 }
199
200 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
201 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
202 return remove_chunk_from_list(&_free_list);
203 }
204
205 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
206 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
207 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
208 // wraparound of _hwm.
209 if (_hwm >= _chunk_capacity) {
210 return NULL;
211 }
212
213 size_t cur_idx = Atomic::fetch_and_add(&_hwm, 1u);
214 if (cur_idx >= _chunk_capacity) {
215 return NULL;
216 }
217
218 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
219 result->next = NULL;
220 return result;
221 }
222
223 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
224 // Get a new chunk.
225 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
226
227 if (new_chunk == NULL) {
228 // Did not get a chunk from the free list. Allocate from backing memory.
229 new_chunk = allocate_new_chunk();
230
231 if (new_chunk == NULL) {
232 return false;
233 }
234 }
235
236 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
237
238 add_chunk_to_chunk_list(new_chunk);
239
240 return true;
241 }
242
243 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
244 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
245
246 if (cur == NULL) {
247 return false;
248 }
249
250 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
251
252 add_chunk_to_free_list(cur);
253 return true;
254 }
255
256 void G1CMMarkStack::set_empty() {
257 _chunks_in_chunk_list = 0;
258 _hwm = 0;
259 _chunk_list = NULL;
260 _free_list = NULL;
261 }
262
263 G1CMRootMemRegions::G1CMRootMemRegions(uint const max_regions) :
264 _root_regions(NULL),
265 _max_regions(max_regions),
266 _num_root_regions(0),
267 _claimed_root_regions(0),
268 _scan_in_progress(false),
269 _should_abort(false) {
270 _root_regions = new MemRegion[_max_regions];
271 if (_root_regions == NULL) {
272 vm_exit_during_initialization("Could not allocate root MemRegion set.");
273 }
274 }
275
276 G1CMRootMemRegions::~G1CMRootMemRegions() {
277 delete[] _root_regions;
278 }
279
280 void G1CMRootMemRegions::reset() {
281 _num_root_regions = 0;
282 }
283
284 void G1CMRootMemRegions::add(HeapWord* start, HeapWord* end) {
285 assert_at_safepoint();
286 size_t idx = Atomic::fetch_and_add(&_num_root_regions, 1u);
287 assert(idx < _max_regions, "Trying to add more root MemRegions than there is space " SIZE_FORMAT, _max_regions);
288 assert(start != NULL && end != NULL && start <= end, "Start (" PTR_FORMAT ") should be less or equal to "
289 "end (" PTR_FORMAT ")", p2i(start), p2i(end));
290 _root_regions[idx].set_start(start);
291 _root_regions[idx].set_end(end);
292 }
293
294 void G1CMRootMemRegions::prepare_for_scan() {
295 assert(!scan_in_progress(), "pre-condition");
296
297 _scan_in_progress = _num_root_regions > 0;
298
299 _claimed_root_regions = 0;
300 _should_abort = false;
301 }
302
303 const MemRegion* G1CMRootMemRegions::claim_next() {
304 if (_should_abort) {
305 // If someone has set the should_abort flag, we return NULL to
306 // force the caller to bail out of their loop.
307 return NULL;
308 }
309
310 if (_claimed_root_regions >= _num_root_regions) {
311 return NULL;
312 }
313
314 size_t claimed_index = Atomic::fetch_and_add(&_claimed_root_regions, 1u);
315 if (claimed_index < _num_root_regions) {
316 return &_root_regions[claimed_index];
317 }
318 return NULL;
319 }
320
321 uint G1CMRootMemRegions::num_root_regions() const {
322 return (uint)_num_root_regions;
323 }
324
325 void G1CMRootMemRegions::notify_scan_done() {
326 MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
327 _scan_in_progress = false;
328 RootRegionScan_lock->notify_all();
329 }
330
331 void G1CMRootMemRegions::cancel_scan() {
332 notify_scan_done();
333 }
334
335 void G1CMRootMemRegions::scan_finished() {
336 assert(scan_in_progress(), "pre-condition");
337
338 if (!_should_abort) {
339 assert(_claimed_root_regions >= num_root_regions(),
340 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u",
341 _claimed_root_regions, num_root_regions());
342 }
343
344 notify_scan_done();
345 }
346
347 bool G1CMRootMemRegions::wait_until_scan_finished() {
348 if (!scan_in_progress()) {
349 return false;
350 }
351
352 {
353 MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
354 while (scan_in_progress()) {
355 ml.wait();
356 }
357 }
358 return true;
359 }
360
361 // Returns the maximum number of workers to be used in a concurrent
362 // phase based on the number of GC workers being used in a STW
363 // phase.
364 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
365 return MAX2((num_gc_workers + 2) / 4, 1U);
366 }
367
368 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
369 G1RegionToSpaceMapper* prev_bitmap_storage,
370 G1RegionToSpaceMapper* next_bitmap_storage) :
371 // _cm_thread set inside the constructor
372 _g1h(g1h),
373 _completed_initialization(false),
374
375 _mark_bitmap_1(),
376 _mark_bitmap_2(),
377 _prev_mark_bitmap(&_mark_bitmap_1),
378 _next_mark_bitmap(&_mark_bitmap_2),
379
380 _heap(_g1h->reserved_region()),
381
382 _root_regions(_g1h->max_regions()),
383
384 _global_mark_stack(),
385
386 // _finger set in set_non_marking_state
387
388 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
389 _max_num_tasks(ParallelGCThreads),
390 // _num_active_tasks set in set_non_marking_state()
391 // _tasks set inside the constructor
392
393 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
394 _terminator((int) _max_num_tasks, _task_queues),
395
396 _first_overflow_barrier_sync(),
397 _second_overflow_barrier_sync(),
398
399 _has_overflown(false),
400 _concurrent(false),
401 _has_aborted(false),
402 _restart_for_overflow(false),
403 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
404 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
405
406 // _verbose_level set below
407
408 _init_times(),
409 _remark_times(),
410 _remark_mark_times(),
411 _remark_weak_ref_times(),
412 _cleanup_times(),
413 _total_cleanup_time(0.0),
414
415 _accum_task_vtime(NULL),
416
417 _concurrent_workers(NULL),
418 _num_concurrent_workers(0),
419 _max_concurrent_workers(0),
420
421 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
422 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
423 {
424 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
425 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
426
427 // Create & start ConcurrentMark thread.
428 _cm_thread = new G1ConcurrentMarkThread(this);
429 if (_cm_thread->osthread() == NULL) {
430 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
431 }
432
433 assert(CGC_lock != NULL, "CGC_lock must be initialized");
434
435 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
436 // Calculate the number of concurrent worker threads by scaling
437 // the number of parallel GC threads.
438 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
439 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
440 }
441
442 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
443 if (ConcGCThreads > ParallelGCThreads) {
444 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
445 ConcGCThreads, ParallelGCThreads);
446 return;
447 }
448
449 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
450 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
451
452 _num_concurrent_workers = ConcGCThreads;
453 _max_concurrent_workers = _num_concurrent_workers;
454
455 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
456 _concurrent_workers->initialize_workers();
457
458 if (FLAG_IS_DEFAULT(MarkStackSize)) {
459 size_t mark_stack_size =
460 MIN2(MarkStackSizeMax,
461 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
462 // Verify that the calculated value for MarkStackSize is in range.
463 // It would be nice to use the private utility routine from Arguments.
464 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
465 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
466 "must be between 1 and " SIZE_FORMAT,
467 mark_stack_size, MarkStackSizeMax);
468 return;
469 }
470 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
471 } else {
472 // Verify MarkStackSize is in range.
473 if (FLAG_IS_CMDLINE(MarkStackSize)) {
474 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
475 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
476 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
477 "must be between 1 and " SIZE_FORMAT,
478 MarkStackSize, MarkStackSizeMax);
479 return;
480 }
481 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
482 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
483 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
484 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
485 MarkStackSize, MarkStackSizeMax);
486 return;
487 }
488 }
489 }
490 }
491
492 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
493 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
494 }
495
496 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
497 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
498
499 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
500 _num_active_tasks = _max_num_tasks;
501
502 for (uint i = 0; i < _max_num_tasks; ++i) {
503 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
504 task_queue->initialize();
505 _task_queues->register_queue(i, task_queue);
506
507 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
508
509 _accum_task_vtime[i] = 0.0;
510 }
511
512 reset_at_marking_complete();
513 _completed_initialization = true;
514 }
515
516 void G1ConcurrentMark::reset() {
517 _has_aborted = false;
518
519 reset_marking_for_restart();
520
521 // Reset all tasks, since different phases will use different number of active
522 // threads. So, it's easiest to have all of them ready.
523 for (uint i = 0; i < _max_num_tasks; ++i) {
524 _tasks[i]->reset(_next_mark_bitmap);
525 }
526
527 uint max_regions = _g1h->max_regions();
528 for (uint i = 0; i < max_regions; i++) {
529 _top_at_rebuild_starts[i] = NULL;
530 _region_mark_stats[i].clear();
531 }
532 }
533
534 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
535 for (uint j = 0; j < _max_num_tasks; ++j) {
536 _tasks[j]->clear_mark_stats_cache(region_idx);
537 }
538 _top_at_rebuild_starts[region_idx] = NULL;
539 _region_mark_stats[region_idx].clear();
540 }
541
542 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
543 uint const region_idx = r->hrm_index();
544 if (r->is_humongous()) {
545 assert(r->is_starts_humongous(), "Got humongous continues region here");
546 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
547 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
548 clear_statistics_in_region(j);
549 }
550 } else {
551 clear_statistics_in_region(region_idx);
552 }
553 }
554
555 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
556 if (bitmap->is_marked(addr)) {
557 bitmap->clear(addr);
558 }
559 }
560
561 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
562 assert_at_safepoint_on_vm_thread();
563
564 // Need to clear all mark bits of the humongous object.
565 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
566 clear_mark_if_set(_next_mark_bitmap, r->bottom());
567
568 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
569 return;
570 }
571
572 // Clear any statistics about the region gathered so far.
573 clear_statistics(r);
574 }
575
576 void G1ConcurrentMark::reset_marking_for_restart() {
577 _global_mark_stack.set_empty();
578
579 // Expand the marking stack, if we have to and if we can.
580 if (has_overflown()) {
581 _global_mark_stack.expand();
582
583 uint max_regions = _g1h->max_regions();
584 for (uint i = 0; i < max_regions; i++) {
585 _region_mark_stats[i].clear_during_overflow();
586 }
587 }
588
589 clear_has_overflown();
590 _finger = _heap.start();
591
592 for (uint i = 0; i < _max_num_tasks; ++i) {
593 G1CMTaskQueue* queue = _task_queues->queue(i);
594 queue->set_empty();
595 }
596 }
597
598 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
599 assert(active_tasks <= _max_num_tasks, "we should not have more");
600
601 _num_active_tasks = active_tasks;
602 // Need to update the three data structures below according to the
603 // number of active threads for this phase.
604 _terminator.reset_for_reuse(active_tasks);
605 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
606 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
607 }
608
609 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
610 set_concurrency(active_tasks);
611
612 _concurrent = concurrent;
613
614 if (!concurrent) {
615 // At this point we should be in a STW phase, and completed marking.
616 assert_at_safepoint_on_vm_thread();
617 assert(out_of_regions(),
618 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
619 p2i(_finger), p2i(_heap.end()));
620 }
621 }
622
623 void G1ConcurrentMark::reset_at_marking_complete() {
624 // We set the global marking state to some default values when we're
625 // not doing marking.
626 reset_marking_for_restart();
627 _num_active_tasks = 0;
628 }
629
630 G1ConcurrentMark::~G1ConcurrentMark() {
631 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
632 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
633 // The G1ConcurrentMark instance is never freed.
634 ShouldNotReachHere();
635 }
636
637 class G1ClearBitMapTask : public AbstractGangTask {
638 public:
639 static size_t chunk_size() { return M; }
640
641 private:
642 // Heap region closure used for clearing the given mark bitmap.
643 class G1ClearBitmapHRClosure : public HeapRegionClosure {
644 private:
645 G1CMBitMap* _bitmap;
646 G1ConcurrentMark* _cm;
647 public:
648 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) {
649 }
650
651 virtual bool do_heap_region(HeapRegion* r) {
652 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
653
654 HeapWord* cur = r->bottom();
655 HeapWord* const end = r->end();
656
657 while (cur < end) {
658 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
659 _bitmap->clear_range(mr);
660
661 cur += chunk_size_in_words;
662
663 // Abort iteration if after yielding the marking has been aborted.
664 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
665 return true;
666 }
667 // Repeat the asserts from before the start of the closure. We will do them
668 // as asserts here to minimize their overhead on the product. However, we
669 // will have them as guarantees at the beginning / end of the bitmap
670 // clearing to get some checking in the product.
671 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
672 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
673 }
674 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
675
676 return false;
677 }
678 };
679
680 G1ClearBitmapHRClosure _cl;
681 HeapRegionClaimer _hr_claimer;
682 bool _suspendible; // If the task is suspendible, workers must join the STS.
683
684 public:
685 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
686 AbstractGangTask("G1 Clear Bitmap"),
687 _cl(bitmap, suspendible ? cm : NULL),
688 _hr_claimer(n_workers),
689 _suspendible(suspendible)
690 { }
691
692 void work(uint worker_id) {
693 SuspendibleThreadSetJoiner sts_join(_suspendible);
694 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
695 }
696
697 bool is_complete() {
698 return _cl.is_complete();
699 }
700 };
701
702 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
703 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
704
705 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
706 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
707
708 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
709
710 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
711
712 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
713 workers->run_task(&cl, num_workers);
714 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
715 }
716
717 void G1ConcurrentMark::cleanup_for_next_mark() {
718 // Make sure that the concurrent mark thread looks to still be in
719 // the current cycle.
720 guarantee(cm_thread()->during_cycle(), "invariant");
721
722 // We are finishing up the current cycle by clearing the next
723 // marking bitmap and getting it ready for the next cycle. During
724 // this time no other cycle can start. So, let's make sure that this
725 // is the case.
726 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
727
728 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
729
730 // Repeat the asserts from above.
731 guarantee(cm_thread()->during_cycle(), "invariant");
732 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
733 }
734
735 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
736 assert_at_safepoint_on_vm_thread();
737 clear_bitmap(_prev_mark_bitmap, workers, false);
738 }
739
740 class NoteStartOfMarkHRClosure : public HeapRegionClosure {
741 public:
742 bool do_heap_region(HeapRegion* r) {
743 r->note_start_of_marking();
744 return false;
745 }
746 };
747
748 void G1ConcurrentMark::pre_initial_mark() {
749 assert_at_safepoint_on_vm_thread();
750
751 // Reset marking state.
752 reset();
753
754 // For each region note start of marking.
755 NoteStartOfMarkHRClosure startcl;
756 _g1h->heap_region_iterate(&startcl);
757
758 _root_regions.reset();
759 }
760
761
762 void G1ConcurrentMark::post_initial_mark() {
763 // Start Concurrent Marking weak-reference discovery.
764 ReferenceProcessor* rp = _g1h->ref_processor_cm();
765 // enable ("weak") refs discovery
766 rp->enable_discovery();
767 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
768
769 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
770 // This is the start of the marking cycle, we're expected all
771 // threads to have SATB queues with active set to false.
772 satb_mq_set.set_active_all_threads(true, /* new active value */
773 false /* expected_active */);
774
775 _root_regions.prepare_for_scan();
776
777 // update_g1_committed() will be called at the end of an evac pause
778 // when marking is on. So, it's also called at the end of the
779 // initial-mark pause to update the heap end, if the heap expands
780 // during it. No need to call it here.
781 }
782
783 /*
784 * Notice that in the next two methods, we actually leave the STS
785 * during the barrier sync and join it immediately afterwards. If we
786 * do not do this, the following deadlock can occur: one thread could
787 * be in the barrier sync code, waiting for the other thread to also
788 * sync up, whereas another one could be trying to yield, while also
789 * waiting for the other threads to sync up too.
790 *
791 * Note, however, that this code is also used during remark and in
792 * this case we should not attempt to leave / enter the STS, otherwise
793 * we'll either hit an assert (debug / fastdebug) or deadlock
794 * (product). So we should only leave / enter the STS if we are
795 * operating concurrently.
796 *
797 * Because the thread that does the sync barrier has left the STS, it
798 * is possible to be suspended for a Full GC or an evacuation pause
799 * could occur. This is actually safe, since the entering the sync
800 * barrier is one of the last things do_marking_step() does, and it
801 * doesn't manipulate any data structures afterwards.
802 */
803
804 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
805 bool barrier_aborted;
806 {
807 SuspendibleThreadSetLeaver sts_leave(concurrent());
808 barrier_aborted = !_first_overflow_barrier_sync.enter();
809 }
810
811 // at this point everyone should have synced up and not be doing any
812 // more work
813
814 if (barrier_aborted) {
815 // If the barrier aborted we ignore the overflow condition and
816 // just abort the whole marking phase as quickly as possible.
817 return;
818 }
819 }
820
821 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
822 SuspendibleThreadSetLeaver sts_leave(concurrent());
823 _second_overflow_barrier_sync.enter();
824
825 // at this point everything should be re-initialized and ready to go
826 }
827
828 class G1CMConcurrentMarkingTask : public AbstractGangTask {
829 G1ConcurrentMark* _cm;
830
831 public:
832 void work(uint worker_id) {
833 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
834 ResourceMark rm;
835
836 double start_vtime = os::elapsedVTime();
837
838 {
839 SuspendibleThreadSetJoiner sts_join;
840
841 assert(worker_id < _cm->active_tasks(), "invariant");
842
843 G1CMTask* task = _cm->task(worker_id);
844 task->record_start_time();
845 if (!_cm->has_aborted()) {
846 do {
847 task->do_marking_step(G1ConcMarkStepDurationMillis,
848 true /* do_termination */,
849 false /* is_serial*/);
850
851 _cm->do_yield_check();
852 } while (!_cm->has_aborted() && task->has_aborted());
853 }
854 task->record_end_time();
855 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
856 }
857
858 double end_vtime = os::elapsedVTime();
859 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
860 }
861
862 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
863 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
864
865 ~G1CMConcurrentMarkingTask() { }
866 };
867
868 uint G1ConcurrentMark::calc_active_marking_workers() {
869 uint result = 0;
870 if (!UseDynamicNumberOfGCThreads ||
871 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
872 !ForceDynamicNumberOfGCThreads)) {
873 result = _max_concurrent_workers;
874 } else {
875 result =
876 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers,
877 1, /* Minimum workers */
878 _num_concurrent_workers,
879 Threads::number_of_non_daemon_threads());
880 // Don't scale the result down by scale_concurrent_workers() because
881 // that scaling has already gone into "_max_concurrent_workers".
882 }
883 assert(result > 0 && result <= _max_concurrent_workers,
884 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
885 _max_concurrent_workers, result);
886 return result;
887 }
888
889 void G1ConcurrentMark::scan_root_region(const MemRegion* region, uint worker_id) {
890 #ifdef ASSERT
891 HeapWord* last = region->last();
892 HeapRegion* hr = _g1h->heap_region_containing(last);
893 assert(hr->is_old() || hr->next_top_at_mark_start() == hr->bottom(),
894 "Root regions must be old or survivor/eden but region %u is %s", hr->hrm_index(), hr->get_type_str());
895 assert(hr->next_top_at_mark_start() == region->start(),
896 "MemRegion start should be equal to nTAMS");
897 #endif
898
899 G1RootRegionScanClosure cl(_g1h, this, worker_id);
900
901 const uintx interval = PrefetchScanIntervalInBytes;
902 HeapWord* curr = region->start();
903 const HeapWord* end = region->end();
904 while (curr < end) {
905 Prefetch::read(curr, interval);
906 oop obj = oop(curr);
907 int size = obj->oop_iterate_size(&cl);
908 assert(size == obj->size(), "sanity");
909 curr += size;
910 }
911 }
912
913 class G1CMRootRegionScanTask : public AbstractGangTask {
914 G1ConcurrentMark* _cm;
915 public:
916 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
917 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
918
919 void work(uint worker_id) {
920 assert(Thread::current()->is_ConcurrentGC_thread(),
921 "this should only be done by a conc GC thread");
922
923 G1CMRootMemRegions* root_regions = _cm->root_regions();
924 const MemRegion* region = root_regions->claim_next();
925 while (region != NULL) {
926 _cm->scan_root_region(region, worker_id);
927 region = root_regions->claim_next();
928 }
929 }
930 };
931
932 void G1ConcurrentMark::scan_root_regions() {
933 // scan_in_progress() will have been set to true only if there was
934 // at least one root region to scan. So, if it's false, we
935 // should not attempt to do any further work.
936 if (root_regions()->scan_in_progress()) {
937 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
938
939 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
940 // We distribute work on a per-region basis, so starting
941 // more threads than that is useless.
942 root_regions()->num_root_regions());
943 assert(_num_concurrent_workers <= _max_concurrent_workers,
944 "Maximum number of marking threads exceeded");
945
946 G1CMRootRegionScanTask task(this);
947 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
948 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
949 _concurrent_workers->run_task(&task, _num_concurrent_workers);
950
951 // It's possible that has_aborted() is true here without actually
952 // aborting the survivor scan earlier. This is OK as it's
953 // mainly used for sanity checking.
954 root_regions()->scan_finished();
955 }
956 }
957
958 void G1ConcurrentMark::concurrent_cycle_start() {
959 _gc_timer_cm->register_gc_start();
960
961 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
962
963 _g1h->trace_heap_before_gc(_gc_tracer_cm);
964 }
965
966 void G1ConcurrentMark::concurrent_cycle_end() {
967 _g1h->collector_state()->set_clearing_next_bitmap(false);
968
969 _g1h->trace_heap_after_gc(_gc_tracer_cm);
970
971 if (has_aborted()) {
972 log_info(gc, marking)("Concurrent Mark Abort");
973 _gc_tracer_cm->report_concurrent_mode_failure();
974 }
975
976 _gc_timer_cm->register_gc_end();
977
978 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
979 }
980
981 void G1ConcurrentMark::mark_from_roots() {
982 _restart_for_overflow = false;
983
984 _num_concurrent_workers = calc_active_marking_workers();
985
986 uint active_workers = MAX2(1U, _num_concurrent_workers);
987
988 // Setting active workers is not guaranteed since fewer
989 // worker threads may currently exist and more may not be
990 // available.
991 active_workers = _concurrent_workers->update_active_workers(active_workers);
992 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
993
994 // Parallel task terminator is set in "set_concurrency_and_phase()"
995 set_concurrency_and_phase(active_workers, true /* concurrent */);
996
997 G1CMConcurrentMarkingTask marking_task(this);
998 _concurrent_workers->run_task(&marking_task);
999 print_stats();
1000 }
1001
1002 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
1003 G1HeapVerifier* verifier = _g1h->verifier();
1004
1005 verifier->verify_region_sets_optional();
1006
1007 if (VerifyDuringGC) {
1008 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm);
1009
1010 size_t const BufLen = 512;
1011 char buffer[BufLen];
1012
1013 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
1014 verifier->verify(type, vo, buffer);
1015 }
1016
1017 verifier->check_bitmaps(caller);
1018 }
1019
1020 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1021 G1CollectedHeap* _g1h;
1022 G1ConcurrentMark* _cm;
1023 HeapRegionClaimer _hrclaimer;
1024 uint volatile _total_selected_for_rebuild;
1025
1026 G1PrintRegionLivenessInfoClosure _cl;
1027
1028 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1029 G1CollectedHeap* _g1h;
1030 G1ConcurrentMark* _cm;
1031
1032 G1PrintRegionLivenessInfoClosure* _cl;
1033
1034 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1035
1036 void update_remset_before_rebuild(HeapRegion* hr) {
1037 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker();
1038
1039 bool selected_for_rebuild;
1040 if (hr->is_humongous()) {
1041 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0;
1042 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live);
1043 } else {
1044 size_t const live_bytes = _cm->liveness(hr->hrm_index());
1045 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1046 }
1047 if (selected_for_rebuild) {
1048 _num_regions_selected_for_rebuild++;
1049 }
1050 _cm->update_top_at_rebuild_start(hr);
1051 }
1052
1053 // Distribute the given words across the humongous object starting with hr and
1054 // note end of marking.
1055 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1056 uint const region_idx = hr->hrm_index();
1057 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1058 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1059
1060 // "Distributing" zero words means that we only note end of marking for these
1061 // regions.
1062 assert(marked_words == 0 || obj_size_in_words == marked_words,
1063 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1064 obj_size_in_words, marked_words);
1065
1066 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1067 HeapRegion* const r = _g1h->region_at(i);
1068 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1069
1070 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1071 words_to_add, i, r->get_type_str());
1072 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1073 marked_words -= words_to_add;
1074 }
1075 assert(marked_words == 0,
1076 SIZE_FORMAT " words left after distributing space across %u regions",
1077 marked_words, num_regions_in_humongous);
1078 }
1079
1080 void update_marked_bytes(HeapRegion* hr) {
1081 uint const region_idx = hr->hrm_index();
1082 size_t const marked_words = _cm->liveness(region_idx);
1083 // The marking attributes the object's size completely to the humongous starts
1084 // region. We need to distribute this value across the entire set of regions a
1085 // humongous object spans.
1086 if (hr->is_humongous()) {
1087 assert(hr->is_starts_humongous() || marked_words == 0,
1088 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1089 marked_words, region_idx, hr->get_type_str());
1090 if (hr->is_starts_humongous()) {
1091 distribute_marked_bytes(hr, marked_words);
1092 }
1093 } else {
1094 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1095 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1096 }
1097 }
1098
1099 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1100 hr->add_to_marked_bytes(marked_bytes);
1101 _cl->do_heap_region(hr);
1102 hr->note_end_of_marking();
1103 }
1104
1105 public:
1106 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1107 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { }
1108
1109 virtual bool do_heap_region(HeapRegion* r) {
1110 update_remset_before_rebuild(r);
1111 update_marked_bytes(r);
1112
1113 return false;
1114 }
1115
1116 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1117 };
1118
1119 public:
1120 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1121 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1122 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { }
1123
1124 virtual void work(uint worker_id) {
1125 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl);
1126 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id);
1127 Atomic::add(&_total_selected_for_rebuild, update_cl.num_selected_for_rebuild());
1128 }
1129
1130 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; }
1131
1132 // Number of regions for which roughly one thread should be spawned for this work.
1133 static const uint RegionsPerThread = 384;
1134 };
1135
1136 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1137 G1CollectedHeap* _g1h;
1138 public:
1139 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1140
1141 virtual bool do_heap_region(HeapRegion* r) {
1142 _g1h->policy()->remset_tracker()->update_after_rebuild(r);
1143 return false;
1144 }
1145 };
1146
1147 void G1ConcurrentMark::remark() {
1148 assert_at_safepoint_on_vm_thread();
1149
1150 // If a full collection has happened, we should not continue. However we might
1151 // have ended up here as the Remark VM operation has been scheduled already.
1152 if (has_aborted()) {
1153 return;
1154 }
1155
1156 G1Policy* policy = _g1h->policy();
1157 policy->record_concurrent_mark_remark_start();
1158
1159 double start = os::elapsedTime();
1160
1161 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1162
1163 {
1164 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm);
1165 finalize_marking();
1166 }
1167
1168 double mark_work_end = os::elapsedTime();
1169
1170 bool const mark_finished = !has_overflown();
1171 if (mark_finished) {
1172 weak_refs_work(false /* clear_all_soft_refs */);
1173
1174 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1175 // We're done with marking.
1176 // This is the end of the marking cycle, we're expected all
1177 // threads to have SATB queues with active set to true.
1178 satb_mq_set.set_active_all_threads(false, /* new active value */
1179 true /* expected_active */);
1180
1181 {
1182 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm);
1183 flush_all_task_caches();
1184 }
1185
1186 // Install newly created mark bitmap as "prev".
1187 swap_mark_bitmaps();
1188 {
1189 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1190
1191 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1192 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1193 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1194
1195 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1196 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1197 _g1h->workers()->run_task(&cl, num_workers);
1198
1199 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1200 _g1h->num_regions(), cl.total_selected_for_rebuild());
1201 }
1202 {
1203 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm);
1204 reclaim_empty_regions();
1205 }
1206
1207 // Clean out dead classes
1208 if (ClassUnloadingWithConcurrentMark) {
1209 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm);
1210 ClassLoaderDataGraph::purge();
1211 }
1212
1213 _g1h->resize_heap_if_necessary();
1214
1215 compute_new_sizes();
1216
1217 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1218
1219 assert(!restart_for_overflow(), "sanity");
1220 // Completely reset the marking state since marking completed
1221 reset_at_marking_complete();
1222 } else {
1223 // We overflowed. Restart concurrent marking.
1224 _restart_for_overflow = true;
1225
1226 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1227
1228 // Clear the marking state because we will be restarting
1229 // marking due to overflowing the global mark stack.
1230 reset_marking_for_restart();
1231 }
1232
1233 {
1234 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm);
1235 report_object_count(mark_finished);
1236 }
1237
1238 // Statistics
1239 double now = os::elapsedTime();
1240 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1241 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1242 _remark_times.add((now - start) * 1000.0);
1243
1244 policy->record_concurrent_mark_remark_end();
1245 }
1246
1247 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1248 // Per-region work during the Cleanup pause.
1249 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1250 G1CollectedHeap* _g1h;
1251 size_t _freed_bytes;
1252 FreeRegionList* _local_cleanup_list;
1253 uint _old_regions_removed;
1254 uint _humongous_regions_removed;
1255
1256 public:
1257 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1258 FreeRegionList* local_cleanup_list) :
1259 _g1h(g1h),
1260 _freed_bytes(0),
1261 _local_cleanup_list(local_cleanup_list),
1262 _old_regions_removed(0),
1263 _humongous_regions_removed(0) { }
1264
1265 size_t freed_bytes() { return _freed_bytes; }
1266 const uint old_regions_removed() { return _old_regions_removed; }
1267 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1268
1269 bool do_heap_region(HeapRegion *hr) {
1270 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1271 _freed_bytes += hr->used();
1272 hr->set_containing_set(NULL);
1273 if (hr->is_humongous()) {
1274 _humongous_regions_removed++;
1275 _g1h->free_humongous_region(hr, _local_cleanup_list);
1276 } else {
1277 _old_regions_removed++;
1278 _g1h->free_region(hr, _local_cleanup_list);
1279 }
1280 hr->clear_cardtable();
1281 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1282 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1283 }
1284
1285 return false;
1286 }
1287 };
1288
1289 G1CollectedHeap* _g1h;
1290 FreeRegionList* _cleanup_list;
1291 HeapRegionClaimer _hrclaimer;
1292
1293 public:
1294 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1295 AbstractGangTask("G1 Cleanup"),
1296 _g1h(g1h),
1297 _cleanup_list(cleanup_list),
1298 _hrclaimer(n_workers) {
1299 }
1300
1301 void work(uint worker_id) {
1302 FreeRegionList local_cleanup_list("Local Cleanup List");
1303 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list);
1304 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1305 assert(cl.is_complete(), "Shouldn't have aborted!");
1306
1307 // Now update the old/humongous region sets
1308 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1309 {
1310 MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1311 _g1h->decrement_summary_bytes(cl.freed_bytes());
1312
1313 _cleanup_list->add_ordered(&local_cleanup_list);
1314 assert(local_cleanup_list.is_empty(), "post-condition");
1315 }
1316 }
1317 };
1318
1319 void G1ConcurrentMark::reclaim_empty_regions() {
1320 WorkGang* workers = _g1h->workers();
1321 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1322
1323 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1324 workers->run_task(&cl);
1325
1326 if (!empty_regions_list.is_empty()) {
1327 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1328 // Now print the empty regions list.
1329 G1HRPrinter* hrp = _g1h->hr_printer();
1330 if (hrp->is_active()) {
1331 FreeRegionListIterator iter(&empty_regions_list);
1332 while (iter.more_available()) {
1333 HeapRegion* hr = iter.get_next();
1334 hrp->cleanup(hr);
1335 }
1336 }
1337 // And actually make them available.
1338 _g1h->prepend_to_freelist(&empty_regions_list);
1339 }
1340 }
1341
1342 void G1ConcurrentMark::compute_new_sizes() {
1343 MetaspaceGC::compute_new_size();
1344
1345 // Cleanup will have freed any regions completely full of garbage.
1346 // Update the soft reference policy with the new heap occupancy.
1347 Universe::update_heap_info_at_gc();
1348
1349 // We reclaimed old regions so we should calculate the sizes to make
1350 // sure we update the old gen/space data.
1351 _g1h->g1mm()->update_sizes();
1352 }
1353
1354 void G1ConcurrentMark::cleanup() {
1355 assert_at_safepoint_on_vm_thread();
1356
1357 // If a full collection has happened, we shouldn't do this.
1358 if (has_aborted()) {
1359 return;
1360 }
1361
1362 G1Policy* policy = _g1h->policy();
1363 policy->record_concurrent_mark_cleanup_start();
1364
1365 double start = os::elapsedTime();
1366
1367 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1368
1369 {
1370 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1371 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1372 _g1h->heap_region_iterate(&cl);
1373 }
1374
1375 if (log_is_enabled(Trace, gc, liveness)) {
1376 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1377 _g1h->heap_region_iterate(&cl);
1378 }
1379
1380 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1381
1382 // We need to make this be a "collection" so any collection pause that
1383 // races with it goes around and waits for Cleanup to finish.
1384 _g1h->increment_total_collections();
1385
1386 // Local statistics
1387 double recent_cleanup_time = (os::elapsedTime() - start);
1388 _total_cleanup_time += recent_cleanup_time;
1389 _cleanup_times.add(recent_cleanup_time);
1390
1391 {
1392 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1393 policy->record_concurrent_mark_cleanup_end();
1394 }
1395 }
1396
1397 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1398 // Uses the G1CMTask associated with a worker thread (for serial reference
1399 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1400 // trace referent objects.
1401 //
1402 // Using the G1CMTask and embedded local queues avoids having the worker
1403 // threads operating on the global mark stack. This reduces the risk
1404 // of overflowing the stack - which we would rather avoid at this late
1405 // state. Also using the tasks' local queues removes the potential
1406 // of the workers interfering with each other that could occur if
1407 // operating on the global stack.
1408
1409 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1410 G1ConcurrentMark* _cm;
1411 G1CMTask* _task;
1412 uint _ref_counter_limit;
1413 uint _ref_counter;
1414 bool _is_serial;
1415 public:
1416 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1417 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval),
1418 _ref_counter(_ref_counter_limit), _is_serial(is_serial) {
1419 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1420 }
1421
1422 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1423 virtual void do_oop( oop* p) { do_oop_work(p); }
1424
1425 template <class T> void do_oop_work(T* p) {
1426 if (_cm->has_overflown()) {
1427 return;
1428 }
1429 if (!_task->deal_with_reference(p)) {
1430 // We did not add anything to the mark bitmap (or mark stack), so there is
1431 // no point trying to drain it.
1432 return;
1433 }
1434 _ref_counter--;
1435
1436 if (_ref_counter == 0) {
1437 // We have dealt with _ref_counter_limit references, pushing them
1438 // and objects reachable from them on to the local stack (and
1439 // possibly the global stack). Call G1CMTask::do_marking_step() to
1440 // process these entries.
1441 //
1442 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1443 // there's nothing more to do (i.e. we're done with the entries that
1444 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1445 // above) or we overflow.
1446 //
1447 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1448 // flag while there may still be some work to do. (See the comment at
1449 // the beginning of G1CMTask::do_marking_step() for those conditions -
1450 // one of which is reaching the specified time target.) It is only
1451 // when G1CMTask::do_marking_step() returns without setting the
1452 // has_aborted() flag that the marking step has completed.
1453 do {
1454 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1455 _task->do_marking_step(mark_step_duration_ms,
1456 false /* do_termination */,
1457 _is_serial);
1458 } while (_task->has_aborted() && !_cm->has_overflown());
1459 _ref_counter = _ref_counter_limit;
1460 }
1461 }
1462 };
1463
1464 // 'Drain' oop closure used by both serial and parallel reference processing.
1465 // Uses the G1CMTask associated with a given worker thread (for serial
1466 // reference processing the G1CMtask for worker 0 is used). Calls the
1467 // do_marking_step routine, with an unbelievably large timeout value,
1468 // to drain the marking data structures of the remaining entries
1469 // added by the 'keep alive' oop closure above.
1470
1471 class G1CMDrainMarkingStackClosure : public VoidClosure {
1472 G1ConcurrentMark* _cm;
1473 G1CMTask* _task;
1474 bool _is_serial;
1475 public:
1476 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1477 _cm(cm), _task(task), _is_serial(is_serial) {
1478 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1479 }
1480
1481 void do_void() {
1482 do {
1483 // We call G1CMTask::do_marking_step() to completely drain the local
1484 // and global marking stacks of entries pushed by the 'keep alive'
1485 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1486 //
1487 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1488 // if there's nothing more to do (i.e. we've completely drained the
1489 // entries that were pushed as a a result of applying the 'keep alive'
1490 // closure to the entries on the discovered ref lists) or we overflow
1491 // the global marking stack.
1492 //
1493 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1494 // flag while there may still be some work to do. (See the comment at
1495 // the beginning of G1CMTask::do_marking_step() for those conditions -
1496 // one of which is reaching the specified time target.) It is only
1497 // when G1CMTask::do_marking_step() returns without setting the
1498 // has_aborted() flag that the marking step has completed.
1499
1500 _task->do_marking_step(1000000000.0 /* something very large */,
1501 true /* do_termination */,
1502 _is_serial);
1503 } while (_task->has_aborted() && !_cm->has_overflown());
1504 }
1505 };
1506
1507 // Implementation of AbstractRefProcTaskExecutor for parallel
1508 // reference processing at the end of G1 concurrent marking
1509
1510 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1511 private:
1512 G1CollectedHeap* _g1h;
1513 G1ConcurrentMark* _cm;
1514 WorkGang* _workers;
1515 uint _active_workers;
1516
1517 public:
1518 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1519 G1ConcurrentMark* cm,
1520 WorkGang* workers,
1521 uint n_workers) :
1522 _g1h(g1h), _cm(cm),
1523 _workers(workers), _active_workers(n_workers) { }
1524
1525 virtual void execute(ProcessTask& task, uint ergo_workers);
1526 };
1527
1528 class G1CMRefProcTaskProxy : public AbstractGangTask {
1529 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1530 ProcessTask& _proc_task;
1531 G1CollectedHeap* _g1h;
1532 G1ConcurrentMark* _cm;
1533
1534 public:
1535 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1536 G1CollectedHeap* g1h,
1537 G1ConcurrentMark* cm) :
1538 AbstractGangTask("Process reference objects in parallel"),
1539 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1540 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1541 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1542 }
1543
1544 virtual void work(uint worker_id) {
1545 ResourceMark rm;
1546 HandleMark hm;
1547 G1CMTask* task = _cm->task(worker_id);
1548 G1CMIsAliveClosure g1_is_alive(_g1h);
1549 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1550 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1551
1552 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1553 }
1554 };
1555
1556 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
1557 assert(_workers != NULL, "Need parallel worker threads.");
1558 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1559 assert(_workers->active_workers() >= ergo_workers,
1560 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)",
1561 ergo_workers, _workers->active_workers());
1562
1563 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1564
1565 // We need to reset the concurrency level before each
1566 // proxy task execution, so that the termination protocol
1567 // and overflow handling in G1CMTask::do_marking_step() knows
1568 // how many workers to wait for.
1569 _cm->set_concurrency(ergo_workers);
1570 _workers->run_task(&proc_task_proxy, ergo_workers);
1571 }
1572
1573 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1574 ResourceMark rm;
1575 HandleMark hm;
1576
1577 // Is alive closure.
1578 G1CMIsAliveClosure g1_is_alive(_g1h);
1579
1580 // Inner scope to exclude the cleaning of the string table
1581 // from the displayed time.
1582 {
1583 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm);
1584
1585 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1586
1587 // See the comment in G1CollectedHeap::ref_processing_init()
1588 // about how reference processing currently works in G1.
1589
1590 // Set the soft reference policy
1591 rp->setup_policy(clear_all_soft_refs);
1592 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1593
1594 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1595 // in serial reference processing. Note these closures are also
1596 // used for serially processing (by the the current thread) the
1597 // JNI references during parallel reference processing.
1598 //
1599 // These closures do not need to synchronize with the worker
1600 // threads involved in parallel reference processing as these
1601 // instances are executed serially by the current thread (e.g.
1602 // reference processing is not multi-threaded and is thus
1603 // performed by the current thread instead of a gang worker).
1604 //
1605 // The gang tasks involved in parallel reference processing create
1606 // their own instances of these closures, which do their own
1607 // synchronization among themselves.
1608 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1609 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1610
1611 // We need at least one active thread. If reference processing
1612 // is not multi-threaded we use the current (VMThread) thread,
1613 // otherwise we use the work gang from the G1CollectedHeap and
1614 // we utilize all the worker threads we can.
1615 bool processing_is_mt = rp->processing_is_mt();
1616 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1617 active_workers = clamp(active_workers, 1u, _max_num_tasks);
1618
1619 // Parallel processing task executor.
1620 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1621 _g1h->workers(), active_workers);
1622 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1623
1624 // Set the concurrency level. The phase was already set prior to
1625 // executing the remark task.
1626 set_concurrency(active_workers);
1627
1628 // Set the degree of MT processing here. If the discovery was done MT,
1629 // the number of threads involved during discovery could differ from
1630 // the number of active workers. This is OK as long as the discovered
1631 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1632 rp->set_active_mt_degree(active_workers);
1633
1634 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues());
1635
1636 // Process the weak references.
1637 const ReferenceProcessorStats& stats =
1638 rp->process_discovered_references(&g1_is_alive,
1639 &g1_keep_alive,
1640 &g1_drain_mark_stack,
1641 executor,
1642 &pt);
1643 _gc_tracer_cm->report_gc_reference_stats(stats);
1644 pt.print_all_references();
1645
1646 // The do_oop work routines of the keep_alive and drain_marking_stack
1647 // oop closures will set the has_overflown flag if we overflow the
1648 // global marking stack.
1649
1650 assert(has_overflown() || _global_mark_stack.is_empty(),
1651 "Mark stack should be empty (unless it has overflown)");
1652
1653 assert(rp->num_queues() == active_workers, "why not");
1654
1655 rp->verify_no_references_recorded();
1656 assert(!rp->discovery_enabled(), "Post condition");
1657 }
1658
1659 if (has_overflown()) {
1660 // We can not trust g1_is_alive and the contents of the heap if the marking stack
1661 // overflowed while processing references. Exit the VM.
1662 fatal("Overflow during reference processing, can not continue. Please "
1663 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
1664 "restart.", MarkStackSizeMax);
1665 return;
1666 }
1667
1668 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1669
1670 {
1671 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1672 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1);
1673 }
1674
1675 // Unload Klasses, String, Code Cache, etc.
1676 if (ClassUnloadingWithConcurrentMark) {
1677 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1678 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm);
1679 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1680 } else if (StringDedup::is_enabled()) {
1681 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm);
1682 _g1h->string_dedup_cleaning(&g1_is_alive, NULL);
1683 }
1684 }
1685
1686 class G1PrecleanYieldClosure : public YieldClosure {
1687 G1ConcurrentMark* _cm;
1688
1689 public:
1690 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { }
1691
1692 virtual bool should_return() {
1693 return _cm->has_aborted();
1694 }
1695
1696 virtual bool should_return_fine_grain() {
1697 _cm->do_yield_check();
1698 return _cm->has_aborted();
1699 }
1700 };
1701
1702 void G1ConcurrentMark::preclean() {
1703 assert(G1UseReferencePrecleaning, "Precleaning must be enabled.");
1704
1705 SuspendibleThreadSetJoiner joiner;
1706
1707 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */);
1708 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */);
1709
1710 set_concurrency_and_phase(1, true);
1711
1712 G1PrecleanYieldClosure yield_cl(this);
1713
1714 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1715 // Precleaning is single threaded. Temporarily disable MT discovery.
1716 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false);
1717 rp->preclean_discovered_references(rp->is_alive_non_header(),
1718 &keep_alive,
1719 &drain_mark_stack,
1720 &yield_cl,
1721 _gc_timer_cm);
1722 }
1723
1724 // When sampling object counts, we already swapped the mark bitmaps, so we need to use
1725 // the prev bitmap determining liveness.
1726 class G1ObjectCountIsAliveClosure: public BoolObjectClosure {
1727 G1CollectedHeap* _g1h;
1728 public:
1729 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
1730
1731 bool do_object_b(oop obj) {
1732 return obj != NULL &&
1733 (!_g1h->is_in_g1_reserved(obj) || !_g1h->is_obj_dead(obj));
1734 }
1735 };
1736
1737 void G1ConcurrentMark::report_object_count(bool mark_completed) {
1738 // Depending on the completion of the marking liveness needs to be determined
1739 // using either the next or prev bitmap.
1740 if (mark_completed) {
1741 G1ObjectCountIsAliveClosure is_alive(_g1h);
1742 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1743 } else {
1744 G1CMIsAliveClosure is_alive(_g1h);
1745 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1746 }
1747 }
1748
1749
1750 void G1ConcurrentMark::swap_mark_bitmaps() {
1751 G1CMBitMap* temp = _prev_mark_bitmap;
1752 _prev_mark_bitmap = _next_mark_bitmap;
1753 _next_mark_bitmap = temp;
1754 _g1h->collector_state()->set_clearing_next_bitmap(true);
1755 }
1756
1757 // Closure for marking entries in SATB buffers.
1758 class G1CMSATBBufferClosure : public SATBBufferClosure {
1759 private:
1760 G1CMTask* _task;
1761 G1CollectedHeap* _g1h;
1762
1763 // This is very similar to G1CMTask::deal_with_reference, but with
1764 // more relaxed requirements for the argument, so this must be more
1765 // circumspect about treating the argument as an object.
1766 void do_entry(void* entry) const {
1767 _task->increment_refs_reached();
1768 oop const obj = static_cast<oop>(entry);
1769 _task->make_reference_grey(obj);
1770 }
1771
1772 public:
1773 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1774 : _task(task), _g1h(g1h) { }
1775
1776 virtual void do_buffer(void** buffer, size_t size) {
1777 for (size_t i = 0; i < size; ++i) {
1778 do_entry(buffer[i]);
1779 }
1780 }
1781 };
1782
1783 class G1RemarkThreadsClosure : public ThreadClosure {
1784 G1CMSATBBufferClosure _cm_satb_cl;
1785 G1CMOopClosure _cm_cl;
1786 MarkingCodeBlobClosure _code_cl;
1787 uintx _claim_token;
1788
1789 public:
1790 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1791 _cm_satb_cl(task, g1h),
1792 _cm_cl(g1h, task),
1793 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1794 _claim_token(Threads::thread_claim_token()) {}
1795
1796 void do_thread(Thread* thread) {
1797 if (thread->claim_threads_do(true, _claim_token)) {
1798 SATBMarkQueue& queue = G1ThreadLocalData::satb_mark_queue(thread);
1799 queue.apply_closure_and_empty(&_cm_satb_cl);
1800 if (thread->is_Java_thread()) {
1801 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1802 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1803 // * Alive if on the stack of an executing method
1804 // * Weakly reachable otherwise
1805 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1806 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1807 JavaThread* jt = (JavaThread*)thread;
1808 jt->nmethods_do(&_code_cl);
1809 }
1810 }
1811 }
1812 };
1813
1814 class G1CMRemarkTask : public AbstractGangTask {
1815 G1ConcurrentMark* _cm;
1816 public:
1817 void work(uint worker_id) {
1818 G1CMTask* task = _cm->task(worker_id);
1819 task->record_start_time();
1820 {
1821 ResourceMark rm;
1822 HandleMark hm;
1823
1824 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1825 Threads::threads_do(&threads_f);
1826 }
1827
1828 do {
1829 task->do_marking_step(1000000000.0 /* something very large */,
1830 true /* do_termination */,
1831 false /* is_serial */);
1832 } while (task->has_aborted() && !_cm->has_overflown());
1833 // If we overflow, then we do not want to restart. We instead
1834 // want to abort remark and do concurrent marking again.
1835 task->record_end_time();
1836 }
1837
1838 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1839 AbstractGangTask("Par Remark"), _cm(cm) {
1840 _cm->terminator()->reset_for_reuse(active_workers);
1841 }
1842 };
1843
1844 void G1ConcurrentMark::finalize_marking() {
1845 ResourceMark rm;
1846 HandleMark hm;
1847
1848 _g1h->ensure_parsability(false);
1849
1850 // this is remark, so we'll use up all active threads
1851 uint active_workers = _g1h->workers()->active_workers();
1852 set_concurrency_and_phase(active_workers, false /* concurrent */);
1853 // Leave _parallel_marking_threads at it's
1854 // value originally calculated in the G1ConcurrentMark
1855 // constructor and pass values of the active workers
1856 // through the gang in the task.
1857
1858 {
1859 StrongRootsScope srs(active_workers);
1860
1861 G1CMRemarkTask remarkTask(this, active_workers);
1862 // We will start all available threads, even if we decide that the
1863 // active_workers will be fewer. The extra ones will just bail out
1864 // immediately.
1865 _g1h->workers()->run_task(&remarkTask);
1866 }
1867
1868 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1869 guarantee(has_overflown() ||
1870 satb_mq_set.completed_buffers_num() == 0,
1871 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1872 BOOL_TO_STR(has_overflown()),
1873 satb_mq_set.completed_buffers_num());
1874
1875 print_stats();
1876 }
1877
1878 void G1ConcurrentMark::flush_all_task_caches() {
1879 size_t hits = 0;
1880 size_t misses = 0;
1881 for (uint i = 0; i < _max_num_tasks; i++) {
1882 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache();
1883 hits += stats.first;
1884 misses += stats.second;
1885 }
1886 size_t sum = hits + misses;
1887 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf",
1888 hits, misses, percent_of(hits, sum));
1889 }
1890
1891 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) {
1892 _prev_mark_bitmap->clear_range(mr);
1893 }
1894
1895 HeapRegion*
1896 G1ConcurrentMark::claim_region(uint worker_id) {
1897 // "checkpoint" the finger
1898 HeapWord* finger = _finger;
1899
1900 while (finger < _heap.end()) {
1901 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1902
1903 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1904 // Make sure that the reads below do not float before loading curr_region.
1905 OrderAccess::loadload();
1906 // Above heap_region_containing may return NULL as we always scan claim
1907 // until the end of the heap. In this case, just jump to the next region.
1908 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1909
1910 // Is the gap between reading the finger and doing the CAS too long?
1911 HeapWord* res = Atomic::cmpxchg(&_finger, finger, end);
1912 if (res == finger && curr_region != NULL) {
1913 // we succeeded
1914 HeapWord* bottom = curr_region->bottom();
1915 HeapWord* limit = curr_region->next_top_at_mark_start();
1916
1917 // notice that _finger == end cannot be guaranteed here since,
1918 // someone else might have moved the finger even further
1919 assert(_finger >= end, "the finger should have moved forward");
1920
1921 if (limit > bottom) {
1922 return curr_region;
1923 } else {
1924 assert(limit == bottom,
1925 "the region limit should be at bottom");
1926 // we return NULL and the caller should try calling
1927 // claim_region() again.
1928 return NULL;
1929 }
1930 } else {
1931 assert(_finger > finger, "the finger should have moved forward");
1932 // read it again
1933 finger = _finger;
1934 }
1935 }
1936
1937 return NULL;
1938 }
1939
1940 #ifndef PRODUCT
1941 class VerifyNoCSetOops {
1942 G1CollectedHeap* _g1h;
1943 const char* _phase;
1944 int _info;
1945
1946 public:
1947 VerifyNoCSetOops(const char* phase, int info = -1) :
1948 _g1h(G1CollectedHeap::heap()),
1949 _phase(phase),
1950 _info(info)
1951 { }
1952
1953 void operator()(G1TaskQueueEntry task_entry) const {
1954 if (task_entry.is_array_slice()) {
1955 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1956 return;
1957 }
1958 guarantee(oopDesc::is_oop(task_entry.obj()),
1959 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1960 p2i(task_entry.obj()), _phase, _info);
1961 HeapRegion* r = _g1h->heap_region_containing(task_entry.obj());
1962 guarantee(!(r->in_collection_set() || r->has_index_in_opt_cset()),
1963 "obj " PTR_FORMAT " from %s (%d) in region %u in (optional) collection set",
1964 p2i(task_entry.obj()), _phase, _info, r->hrm_index());
1965 }
1966 };
1967
1968 void G1ConcurrentMark::verify_no_collection_set_oops() {
1969 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1970 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
1971 return;
1972 }
1973
1974 // Verify entries on the global mark stack
1975 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
1976
1977 // Verify entries on the task queues
1978 for (uint i = 0; i < _max_num_tasks; ++i) {
1979 G1CMTaskQueue* queue = _task_queues->queue(i);
1980 queue->iterate(VerifyNoCSetOops("Queue", i));
1981 }
1982
1983 // Verify the global finger
1984 HeapWord* global_finger = finger();
1985 if (global_finger != NULL && global_finger < _heap.end()) {
1986 // Since we always iterate over all regions, we might get a NULL HeapRegion
1987 // here.
1988 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
1989 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
1990 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
1991 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
1992 }
1993
1994 // Verify the task fingers
1995 assert(_num_concurrent_workers <= _max_num_tasks, "sanity");
1996 for (uint i = 0; i < _num_concurrent_workers; ++i) {
1997 G1CMTask* task = _tasks[i];
1998 HeapWord* task_finger = task->finger();
1999 if (task_finger != NULL && task_finger < _heap.end()) {
2000 // See above note on the global finger verification.
2001 HeapRegion* r = _g1h->heap_region_containing(task_finger);
2002 guarantee(r == NULL || task_finger == r->bottom() ||
2003 !r->in_collection_set() || !r->has_index_in_opt_cset(),
2004 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2005 p2i(task_finger), HR_FORMAT_PARAMS(r));
2006 }
2007 }
2008 }
2009 #endif // PRODUCT
2010
2011 void G1ConcurrentMark::rebuild_rem_set_concurrently() {
2012 _g1h->rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset);
2013 }
2014
2015 void G1ConcurrentMark::print_stats() {
2016 if (!log_is_enabled(Debug, gc, stats)) {
2017 return;
2018 }
2019 log_debug(gc, stats)("---------------------------------------------------------------------");
2020 for (size_t i = 0; i < _num_active_tasks; ++i) {
2021 _tasks[i]->print_stats();
2022 log_debug(gc, stats)("---------------------------------------------------------------------");
2023 }
2024 }
2025
2026 void G1ConcurrentMark::concurrent_cycle_abort() {
2027 if (!cm_thread()->during_cycle() || _has_aborted) {
2028 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2029 return;
2030 }
2031
2032 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2033 // concurrent bitmap clearing.
2034 {
2035 GCTraceTime(Debug, gc) debug("Clear Next Bitmap");
2036 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false);
2037 }
2038 // Note we cannot clear the previous marking bitmap here
2039 // since VerifyDuringGC verifies the objects marked during
2040 // a full GC against the previous bitmap.
2041
2042 // Empty mark stack
2043 reset_marking_for_restart();
2044 for (uint i = 0; i < _max_num_tasks; ++i) {
2045 _tasks[i]->clear_region_fields();
2046 }
2047 _first_overflow_barrier_sync.abort();
2048 _second_overflow_barrier_sync.abort();
2049 _has_aborted = true;
2050
2051 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2052 satb_mq_set.abandon_partial_marking();
2053 // This can be called either during or outside marking, we'll read
2054 // the expected_active value from the SATB queue set.
2055 satb_mq_set.set_active_all_threads(
2056 false, /* new active value */
2057 satb_mq_set.is_active() /* expected_active */);
2058 }
2059
2060 static void print_ms_time_info(const char* prefix, const char* name,
2061 NumberSeq& ns) {
2062 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2063 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2064 if (ns.num() > 0) {
2065 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2066 prefix, ns.sd(), ns.maximum());
2067 }
2068 }
2069
2070 void G1ConcurrentMark::print_summary_info() {
2071 Log(gc, marking) log;
2072 if (!log.is_trace()) {
2073 return;
2074 }
2075
2076 log.trace(" Concurrent marking:");
2077 print_ms_time_info(" ", "init marks", _init_times);
2078 print_ms_time_info(" ", "remarks", _remark_times);
2079 {
2080 print_ms_time_info(" ", "final marks", _remark_mark_times);
2081 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2082
2083 }
2084 print_ms_time_info(" ", "cleanups", _cleanup_times);
2085 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2086 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2087 log.trace(" Total stop_world time = %8.2f s.",
2088 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2089 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2090 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum());
2091 }
2092
2093 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2094 _concurrent_workers->print_worker_threads_on(st);
2095 }
2096
2097 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2098 _concurrent_workers->threads_do(tc);
2099 }
2100
2101 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2102 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2103 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap));
2104 _prev_mark_bitmap->print_on_error(st, " Prev Bits: ");
2105 _next_mark_bitmap->print_on_error(st, " Next Bits: ");
2106 }
2107
2108 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2109 ReferenceProcessor* result = g1h->ref_processor_cm();
2110 assert(result != NULL, "CM reference processor should not be NULL");
2111 return result;
2112 }
2113
2114 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2115 G1CMTask* task)
2116 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)),
2117 _g1h(g1h), _task(task)
2118 { }
2119
2120 void G1CMTask::setup_for_region(HeapRegion* hr) {
2121 assert(hr != NULL,
2122 "claim_region() should have filtered out NULL regions");
2123 _curr_region = hr;
2124 _finger = hr->bottom();
2125 update_region_limit();
2126 }
2127
2128 void G1CMTask::update_region_limit() {
2129 HeapRegion* hr = _curr_region;
2130 HeapWord* bottom = hr->bottom();
2131 HeapWord* limit = hr->next_top_at_mark_start();
2132
2133 if (limit == bottom) {
2134 // The region was collected underneath our feet.
2135 // We set the finger to bottom to ensure that the bitmap
2136 // iteration that will follow this will not do anything.
2137 // (this is not a condition that holds when we set the region up,
2138 // as the region is not supposed to be empty in the first place)
2139 _finger = bottom;
2140 } else if (limit >= _region_limit) {
2141 assert(limit >= _finger, "peace of mind");
2142 } else {
2143 assert(limit < _region_limit, "only way to get here");
2144 // This can happen under some pretty unusual circumstances. An
2145 // evacuation pause empties the region underneath our feet (NTAMS
2146 // at bottom). We then do some allocation in the region (NTAMS
2147 // stays at bottom), followed by the region being used as a GC
2148 // alloc region (NTAMS will move to top() and the objects
2149 // originally below it will be grayed). All objects now marked in
2150 // the region are explicitly grayed, if below the global finger,
2151 // and we do not need in fact to scan anything else. So, we simply
2152 // set _finger to be limit to ensure that the bitmap iteration
2153 // doesn't do anything.
2154 _finger = limit;
2155 }
2156
2157 _region_limit = limit;
2158 }
2159
2160 void G1CMTask::giveup_current_region() {
2161 assert(_curr_region != NULL, "invariant");
2162 clear_region_fields();
2163 }
2164
2165 void G1CMTask::clear_region_fields() {
2166 // Values for these three fields that indicate that we're not
2167 // holding on to a region.
2168 _curr_region = NULL;
2169 _finger = NULL;
2170 _region_limit = NULL;
2171 }
2172
2173 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2174 if (cm_oop_closure == NULL) {
2175 assert(_cm_oop_closure != NULL, "invariant");
2176 } else {
2177 assert(_cm_oop_closure == NULL, "invariant");
2178 }
2179 _cm_oop_closure = cm_oop_closure;
2180 }
2181
2182 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
2183 guarantee(next_mark_bitmap != NULL, "invariant");
2184 _next_mark_bitmap = next_mark_bitmap;
2185 clear_region_fields();
2186
2187 _calls = 0;
2188 _elapsed_time_ms = 0.0;
2189 _termination_time_ms = 0.0;
2190 _termination_start_time_ms = 0.0;
2191
2192 _mark_stats_cache.reset();
2193 }
2194
2195 bool G1CMTask::should_exit_termination() {
2196 if (!regular_clock_call()) {
2197 return true;
2198 }
2199
2200 // This is called when we are in the termination protocol. We should
2201 // quit if, for some reason, this task wants to abort or the global
2202 // stack is not empty (this means that we can get work from it).
2203 return !_cm->mark_stack_empty() || has_aborted();
2204 }
2205
2206 void G1CMTask::reached_limit() {
2207 assert(_words_scanned >= _words_scanned_limit ||
2208 _refs_reached >= _refs_reached_limit ,
2209 "shouldn't have been called otherwise");
2210 abort_marking_if_regular_check_fail();
2211 }
2212
2213 bool G1CMTask::regular_clock_call() {
2214 if (has_aborted()) {
2215 return false;
2216 }
2217
2218 // First, we need to recalculate the words scanned and refs reached
2219 // limits for the next clock call.
2220 recalculate_limits();
2221
2222 // During the regular clock call we do the following
2223
2224 // (1) If an overflow has been flagged, then we abort.
2225 if (_cm->has_overflown()) {
2226 return false;
2227 }
2228
2229 // If we are not concurrent (i.e. we're doing remark) we don't need
2230 // to check anything else. The other steps are only needed during
2231 // the concurrent marking phase.
2232 if (!_cm->concurrent()) {
2233 return true;
2234 }
2235
2236 // (2) If marking has been aborted for Full GC, then we also abort.
2237 if (_cm->has_aborted()) {
2238 return false;
2239 }
2240
2241 double curr_time_ms = os::elapsedVTime() * 1000.0;
2242
2243 // (4) We check whether we should yield. If we have to, then we abort.
2244 if (SuspendibleThreadSet::should_yield()) {
2245 // We should yield. To do this we abort the task. The caller is
2246 // responsible for yielding.
2247 return false;
2248 }
2249
2250 // (5) We check whether we've reached our time quota. If we have,
2251 // then we abort.
2252 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2253 if (elapsed_time_ms > _time_target_ms) {
2254 _has_timed_out = true;
2255 return false;
2256 }
2257
2258 // (6) Finally, we check whether there are enough completed STAB
2259 // buffers available for processing. If there are, we abort.
2260 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2261 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2262 // we do need to process SATB buffers, we'll abort and restart
2263 // the marking task to do so
2264 return false;
2265 }
2266 return true;
2267 }
2268
2269 void G1CMTask::recalculate_limits() {
2270 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2271 _words_scanned_limit = _real_words_scanned_limit;
2272
2273 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2274 _refs_reached_limit = _real_refs_reached_limit;
2275 }
2276
2277 void G1CMTask::decrease_limits() {
2278 // This is called when we believe that we're going to do an infrequent
2279 // operation which will increase the per byte scanned cost (i.e. move
2280 // entries to/from the global stack). It basically tries to decrease the
2281 // scanning limit so that the clock is called earlier.
2282
2283 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4;
2284 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4;
2285 }
2286
2287 void G1CMTask::move_entries_to_global_stack() {
2288 // Local array where we'll store the entries that will be popped
2289 // from the local queue.
2290 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2291
2292 size_t n = 0;
2293 G1TaskQueueEntry task_entry;
2294 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2295 buffer[n] = task_entry;
2296 ++n;
2297 }
2298 if (n < G1CMMarkStack::EntriesPerChunk) {
2299 buffer[n] = G1TaskQueueEntry();
2300 }
2301
2302 if (n > 0) {
2303 if (!_cm->mark_stack_push(buffer)) {
2304 set_has_aborted();
2305 }
2306 }
2307
2308 // This operation was quite expensive, so decrease the limits.
2309 decrease_limits();
2310 }
2311
2312 bool G1CMTask::get_entries_from_global_stack() {
2313 // Local array where we'll store the entries that will be popped
2314 // from the global stack.
2315 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2316
2317 if (!_cm->mark_stack_pop(buffer)) {
2318 return false;
2319 }
2320
2321 // We did actually pop at least one entry.
2322 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2323 G1TaskQueueEntry task_entry = buffer[i];
2324 if (task_entry.is_null()) {
2325 break;
2326 }
2327 assert(task_entry.is_array_slice() || oopDesc::is_oop(task_entry.obj()), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj()));
2328 bool success = _task_queue->push(task_entry);
2329 // We only call this when the local queue is empty or under a
2330 // given target limit. So, we do not expect this push to fail.
2331 assert(success, "invariant");
2332 }
2333
2334 // This operation was quite expensive, so decrease the limits
2335 decrease_limits();
2336 return true;
2337 }
2338
2339 void G1CMTask::drain_local_queue(bool partially) {
2340 if (has_aborted()) {
2341 return;
2342 }
2343
2344 // Decide what the target size is, depending whether we're going to
2345 // drain it partially (so that other tasks can steal if they run out
2346 // of things to do) or totally (at the very end).
2347 size_t target_size;
2348 if (partially) {
2349 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize);
2350 } else {
2351 target_size = 0;
2352 }
2353
2354 if (_task_queue->size() > target_size) {
2355 G1TaskQueueEntry entry;
2356 bool ret = _task_queue->pop_local(entry);
2357 while (ret) {
2358 scan_task_entry(entry);
2359 if (_task_queue->size() <= target_size || has_aborted()) {
2360 ret = false;
2361 } else {
2362 ret = _task_queue->pop_local(entry);
2363 }
2364 }
2365 }
2366 }
2367
2368 void G1CMTask::drain_global_stack(bool partially) {
2369 if (has_aborted()) {
2370 return;
2371 }
2372
2373 // We have a policy to drain the local queue before we attempt to
2374 // drain the global stack.
2375 assert(partially || _task_queue->size() == 0, "invariant");
2376
2377 // Decide what the target size is, depending whether we're going to
2378 // drain it partially (so that other tasks can steal if they run out
2379 // of things to do) or totally (at the very end).
2380 // Notice that when draining the global mark stack partially, due to the racyness
2381 // of the mark stack size update we might in fact drop below the target. But,
2382 // this is not a problem.
2383 // In case of total draining, we simply process until the global mark stack is
2384 // totally empty, disregarding the size counter.
2385 if (partially) {
2386 size_t const target_size = _cm->partial_mark_stack_size_target();
2387 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2388 if (get_entries_from_global_stack()) {
2389 drain_local_queue(partially);
2390 }
2391 }
2392 } else {
2393 while (!has_aborted() && get_entries_from_global_stack()) {
2394 drain_local_queue(partially);
2395 }
2396 }
2397 }
2398
2399 // SATB Queue has several assumptions on whether to call the par or
2400 // non-par versions of the methods. this is why some of the code is
2401 // replicated. We should really get rid of the single-threaded version
2402 // of the code to simplify things.
2403 void G1CMTask::drain_satb_buffers() {
2404 if (has_aborted()) {
2405 return;
2406 }
2407
2408 // We set this so that the regular clock knows that we're in the
2409 // middle of draining buffers and doesn't set the abort flag when it
2410 // notices that SATB buffers are available for draining. It'd be
2411 // very counter productive if it did that. :-)
2412 _draining_satb_buffers = true;
2413
2414 G1CMSATBBufferClosure satb_cl(this, _g1h);
2415 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2416
2417 // This keeps claiming and applying the closure to completed buffers
2418 // until we run out of buffers or we need to abort.
2419 while (!has_aborted() &&
2420 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2421 abort_marking_if_regular_check_fail();
2422 }
2423
2424 // Can't assert qset is empty here, even if not aborted. If concurrent,
2425 // some other thread might be adding to the queue. If not concurrent,
2426 // some other thread might have won the race for the last buffer, but
2427 // has not yet decremented the count.
2428
2429 _draining_satb_buffers = false;
2430
2431 // again, this was a potentially expensive operation, decrease the
2432 // limits to get the regular clock call early
2433 decrease_limits();
2434 }
2435
2436 void G1CMTask::clear_mark_stats_cache(uint region_idx) {
2437 _mark_stats_cache.reset(region_idx);
2438 }
2439
2440 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() {
2441 return _mark_stats_cache.evict_all();
2442 }
2443
2444 void G1CMTask::print_stats() {
2445 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls);
2446 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2447 _elapsed_time_ms, _termination_time_ms);
2448 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms",
2449 _step_times_ms.num(),
2450 _step_times_ms.avg(),
2451 _step_times_ms.sd(),
2452 _step_times_ms.maximum(),
2453 _step_times_ms.sum());
2454 size_t const hits = _mark_stats_cache.hits();
2455 size_t const misses = _mark_stats_cache.misses();
2456 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f",
2457 hits, misses, percent_of(hits, hits + misses));
2458 }
2459
2460 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) {
2461 return _task_queues->steal(worker_id, task_entry);
2462 }
2463
2464 /*****************************************************************************
2465
2466 The do_marking_step(time_target_ms, ...) method is the building
2467 block of the parallel marking framework. It can be called in parallel
2468 with other invocations of do_marking_step() on different tasks
2469 (but only one per task, obviously) and concurrently with the
2470 mutator threads, or during remark, hence it eliminates the need
2471 for two versions of the code. When called during remark, it will
2472 pick up from where the task left off during the concurrent marking
2473 phase. Interestingly, tasks are also claimable during evacuation
2474 pauses too, since do_marking_step() ensures that it aborts before
2475 it needs to yield.
2476
2477 The data structures that it uses to do marking work are the
2478 following:
2479
2480 (1) Marking Bitmap. If there are gray objects that appear only
2481 on the bitmap (this happens either when dealing with an overflow
2482 or when the initial marking phase has simply marked the roots
2483 and didn't push them on the stack), then tasks claim heap
2484 regions whose bitmap they then scan to find gray objects. A
2485 global finger indicates where the end of the last claimed region
2486 is. A local finger indicates how far into the region a task has
2487 scanned. The two fingers are used to determine how to gray an
2488 object (i.e. whether simply marking it is OK, as it will be
2489 visited by a task in the future, or whether it needs to be also
2490 pushed on a stack).
2491
2492 (2) Local Queue. The local queue of the task which is accessed
2493 reasonably efficiently by the task. Other tasks can steal from
2494 it when they run out of work. Throughout the marking phase, a
2495 task attempts to keep its local queue short but not totally
2496 empty, so that entries are available for stealing by other
2497 tasks. Only when there is no more work, a task will totally
2498 drain its local queue.
2499
2500 (3) Global Mark Stack. This handles local queue overflow. During
2501 marking only sets of entries are moved between it and the local
2502 queues, as access to it requires a mutex and more fine-grain
2503 interaction with it which might cause contention. If it
2504 overflows, then the marking phase should restart and iterate
2505 over the bitmap to identify gray objects. Throughout the marking
2506 phase, tasks attempt to keep the global mark stack at a small
2507 length but not totally empty, so that entries are available for
2508 popping by other tasks. Only when there is no more work, tasks
2509 will totally drain the global mark stack.
2510
2511 (4) SATB Buffer Queue. This is where completed SATB buffers are
2512 made available. Buffers are regularly removed from this queue
2513 and scanned for roots, so that the queue doesn't get too
2514 long. During remark, all completed buffers are processed, as
2515 well as the filled in parts of any uncompleted buffers.
2516
2517 The do_marking_step() method tries to abort when the time target
2518 has been reached. There are a few other cases when the
2519 do_marking_step() method also aborts:
2520
2521 (1) When the marking phase has been aborted (after a Full GC).
2522
2523 (2) When a global overflow (on the global stack) has been
2524 triggered. Before the task aborts, it will actually sync up with
2525 the other tasks to ensure that all the marking data structures
2526 (local queues, stacks, fingers etc.) are re-initialized so that
2527 when do_marking_step() completes, the marking phase can
2528 immediately restart.
2529
2530 (3) When enough completed SATB buffers are available. The
2531 do_marking_step() method only tries to drain SATB buffers right
2532 at the beginning. So, if enough buffers are available, the
2533 marking step aborts and the SATB buffers are processed at
2534 the beginning of the next invocation.
2535
2536 (4) To yield. when we have to yield then we abort and yield
2537 right at the end of do_marking_step(). This saves us from a lot
2538 of hassle as, by yielding we might allow a Full GC. If this
2539 happens then objects will be compacted underneath our feet, the
2540 heap might shrink, etc. We save checking for this by just
2541 aborting and doing the yield right at the end.
2542
2543 From the above it follows that the do_marking_step() method should
2544 be called in a loop (or, otherwise, regularly) until it completes.
2545
2546 If a marking step completes without its has_aborted() flag being
2547 true, it means it has completed the current marking phase (and
2548 also all other marking tasks have done so and have all synced up).
2549
2550 A method called regular_clock_call() is invoked "regularly" (in
2551 sub ms intervals) throughout marking. It is this clock method that
2552 checks all the abort conditions which were mentioned above and
2553 decides when the task should abort. A work-based scheme is used to
2554 trigger this clock method: when the number of object words the
2555 marking phase has scanned or the number of references the marking
2556 phase has visited reach a given limit. Additional invocations to
2557 the method clock have been planted in a few other strategic places
2558 too. The initial reason for the clock method was to avoid calling
2559 vtime too regularly, as it is quite expensive. So, once it was in
2560 place, it was natural to piggy-back all the other conditions on it
2561 too and not constantly check them throughout the code.
2562
2563 If do_termination is true then do_marking_step will enter its
2564 termination protocol.
2565
2566 The value of is_serial must be true when do_marking_step is being
2567 called serially (i.e. by the VMThread) and do_marking_step should
2568 skip any synchronization in the termination and overflow code.
2569 Examples include the serial remark code and the serial reference
2570 processing closures.
2571
2572 The value of is_serial must be false when do_marking_step is
2573 being called by any of the worker threads in a work gang.
2574 Examples include the concurrent marking code (CMMarkingTask),
2575 the MT remark code, and the MT reference processing closures.
2576
2577 *****************************************************************************/
2578
2579 void G1CMTask::do_marking_step(double time_target_ms,
2580 bool do_termination,
2581 bool is_serial) {
2582 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2583
2584 _start_time_ms = os::elapsedVTime() * 1000.0;
2585
2586 // If do_stealing is true then do_marking_step will attempt to
2587 // steal work from the other G1CMTasks. It only makes sense to
2588 // enable stealing when the termination protocol is enabled
2589 // and do_marking_step() is not being called serially.
2590 bool do_stealing = do_termination && !is_serial;
2591
2592 G1Predictions const& predictor = _g1h->policy()->predictor();
2593 double diff_prediction_ms = predictor.predict_zero_bounded(&_marking_step_diff_ms);
2594 _time_target_ms = time_target_ms - diff_prediction_ms;
2595
2596 // set up the variables that are used in the work-based scheme to
2597 // call the regular clock method
2598 _words_scanned = 0;
2599 _refs_reached = 0;
2600 recalculate_limits();
2601
2602 // clear all flags
2603 clear_has_aborted();
2604 _has_timed_out = false;
2605 _draining_satb_buffers = false;
2606
2607 ++_calls;
2608
2609 // Set up the bitmap and oop closures. Anything that uses them is
2610 // eventually called from this method, so it is OK to allocate these
2611 // statically.
2612 G1CMBitMapClosure bitmap_closure(this, _cm);
2613 G1CMOopClosure cm_oop_closure(_g1h, this);
2614 set_cm_oop_closure(&cm_oop_closure);
2615
2616 if (_cm->has_overflown()) {
2617 // This can happen if the mark stack overflows during a GC pause
2618 // and this task, after a yield point, restarts. We have to abort
2619 // as we need to get into the overflow protocol which happens
2620 // right at the end of this task.
2621 set_has_aborted();
2622 }
2623
2624 // First drain any available SATB buffers. After this, we will not
2625 // look at SATB buffers before the next invocation of this method.
2626 // If enough completed SATB buffers are queued up, the regular clock
2627 // will abort this task so that it restarts.
2628 drain_satb_buffers();
2629 // ...then partially drain the local queue and the global stack
2630 drain_local_queue(true);
2631 drain_global_stack(true);
2632
2633 do {
2634 if (!has_aborted() && _curr_region != NULL) {
2635 // This means that we're already holding on to a region.
2636 assert(_finger != NULL, "if region is not NULL, then the finger "
2637 "should not be NULL either");
2638
2639 // We might have restarted this task after an evacuation pause
2640 // which might have evacuated the region we're holding on to
2641 // underneath our feet. Let's read its limit again to make sure
2642 // that we do not iterate over a region of the heap that
2643 // contains garbage (update_region_limit() will also move
2644 // _finger to the start of the region if it is found empty).
2645 update_region_limit();
2646 // We will start from _finger not from the start of the region,
2647 // as we might be restarting this task after aborting half-way
2648 // through scanning this region. In this case, _finger points to
2649 // the address where we last found a marked object. If this is a
2650 // fresh region, _finger points to start().
2651 MemRegion mr = MemRegion(_finger, _region_limit);
2652
2653 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2654 "humongous regions should go around loop once only");
2655
2656 // Some special cases:
2657 // If the memory region is empty, we can just give up the region.
2658 // If the current region is humongous then we only need to check
2659 // the bitmap for the bit associated with the start of the object,
2660 // scan the object if it's live, and give up the region.
2661 // Otherwise, let's iterate over the bitmap of the part of the region
2662 // that is left.
2663 // If the iteration is successful, give up the region.
2664 if (mr.is_empty()) {
2665 giveup_current_region();
2666 abort_marking_if_regular_check_fail();
2667 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2668 if (_next_mark_bitmap->is_marked(mr.start())) {
2669 // The object is marked - apply the closure
2670 bitmap_closure.do_addr(mr.start());
2671 }
2672 // Even if this task aborted while scanning the humongous object
2673 // we can (and should) give up the current region.
2674 giveup_current_region();
2675 abort_marking_if_regular_check_fail();
2676 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
2677 giveup_current_region();
2678 abort_marking_if_regular_check_fail();
2679 } else {
2680 assert(has_aborted(), "currently the only way to do so");
2681 // The only way to abort the bitmap iteration is to return
2682 // false from the do_bit() method. However, inside the
2683 // do_bit() method we move the _finger to point to the
2684 // object currently being looked at. So, if we bail out, we
2685 // have definitely set _finger to something non-null.
2686 assert(_finger != NULL, "invariant");
2687
2688 // Region iteration was actually aborted. So now _finger
2689 // points to the address of the object we last scanned. If we
2690 // leave it there, when we restart this task, we will rescan
2691 // the object. It is easy to avoid this. We move the finger by
2692 // enough to point to the next possible object header.
2693 assert(_finger < _region_limit, "invariant");
2694 HeapWord* const new_finger = _finger + ((oop)_finger)->size();
2695 // Check if bitmap iteration was aborted while scanning the last object
2696 if (new_finger >= _region_limit) {
2697 giveup_current_region();
2698 } else {
2699 move_finger_to(new_finger);
2700 }
2701 }
2702 }
2703 // At this point we have either completed iterating over the
2704 // region we were holding on to, or we have aborted.
2705
2706 // We then partially drain the local queue and the global stack.
2707 // (Do we really need this?)
2708 drain_local_queue(true);
2709 drain_global_stack(true);
2710
2711 // Read the note on the claim_region() method on why it might
2712 // return NULL with potentially more regions available for
2713 // claiming and why we have to check out_of_regions() to determine
2714 // whether we're done or not.
2715 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2716 // We are going to try to claim a new region. We should have
2717 // given up on the previous one.
2718 // Separated the asserts so that we know which one fires.
2719 assert(_curr_region == NULL, "invariant");
2720 assert(_finger == NULL, "invariant");
2721 assert(_region_limit == NULL, "invariant");
2722 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2723 if (claimed_region != NULL) {
2724 // Yes, we managed to claim one
2725 setup_for_region(claimed_region);
2726 assert(_curr_region == claimed_region, "invariant");
2727 }
2728 // It is important to call the regular clock here. It might take
2729 // a while to claim a region if, for example, we hit a large
2730 // block of empty regions. So we need to call the regular clock
2731 // method once round the loop to make sure it's called
2732 // frequently enough.
2733 abort_marking_if_regular_check_fail();
2734 }
2735
2736 if (!has_aborted() && _curr_region == NULL) {
2737 assert(_cm->out_of_regions(),
2738 "at this point we should be out of regions");
2739 }
2740 } while ( _curr_region != NULL && !has_aborted());
2741
2742 if (!has_aborted()) {
2743 // We cannot check whether the global stack is empty, since other
2744 // tasks might be pushing objects to it concurrently.
2745 assert(_cm->out_of_regions(),
2746 "at this point we should be out of regions");
2747 // Try to reduce the number of available SATB buffers so that
2748 // remark has less work to do.
2749 drain_satb_buffers();
2750 }
2751
2752 // Since we've done everything else, we can now totally drain the
2753 // local queue and global stack.
2754 drain_local_queue(false);
2755 drain_global_stack(false);
2756
2757 // Attempt at work stealing from other task's queues.
2758 if (do_stealing && !has_aborted()) {
2759 // We have not aborted. This means that we have finished all that
2760 // we could. Let's try to do some stealing...
2761
2762 // We cannot check whether the global stack is empty, since other
2763 // tasks might be pushing objects to it concurrently.
2764 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2765 "only way to reach here");
2766 while (!has_aborted()) {
2767 G1TaskQueueEntry entry;
2768 if (_cm->try_stealing(_worker_id, entry)) {
2769 scan_task_entry(entry);
2770
2771 // And since we're towards the end, let's totally drain the
2772 // local queue and global stack.
2773 drain_local_queue(false);
2774 drain_global_stack(false);
2775 } else {
2776 break;
2777 }
2778 }
2779 }
2780
2781 // We still haven't aborted. Now, let's try to get into the
2782 // termination protocol.
2783 if (do_termination && !has_aborted()) {
2784 // We cannot check whether the global stack is empty, since other
2785 // tasks might be concurrently pushing objects on it.
2786 // Separated the asserts so that we know which one fires.
2787 assert(_cm->out_of_regions(), "only way to reach here");
2788 assert(_task_queue->size() == 0, "only way to reach here");
2789 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2790
2791 // The G1CMTask class also extends the TerminatorTerminator class,
2792 // hence its should_exit_termination() method will also decide
2793 // whether to exit the termination protocol or not.
2794 bool finished = (is_serial ||
2795 _cm->terminator()->offer_termination(this));
2796 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2797 _termination_time_ms +=
2798 termination_end_time_ms - _termination_start_time_ms;
2799
2800 if (finished) {
2801 // We're all done.
2802
2803 // We can now guarantee that the global stack is empty, since
2804 // all other tasks have finished. We separated the guarantees so
2805 // that, if a condition is false, we can immediately find out
2806 // which one.
2807 guarantee(_cm->out_of_regions(), "only way to reach here");
2808 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2809 guarantee(_task_queue->size() == 0, "only way to reach here");
2810 guarantee(!_cm->has_overflown(), "only way to reach here");
2811 guarantee(!has_aborted(), "should never happen if termination has completed");
2812 } else {
2813 // Apparently there's more work to do. Let's abort this task. It
2814 // will restart it and we can hopefully find more things to do.
2815 set_has_aborted();
2816 }
2817 }
2818
2819 // Mainly for debugging purposes to make sure that a pointer to the
2820 // closure which was statically allocated in this frame doesn't
2821 // escape it by accident.
2822 set_cm_oop_closure(NULL);
2823 double end_time_ms = os::elapsedVTime() * 1000.0;
2824 double elapsed_time_ms = end_time_ms - _start_time_ms;
2825 // Update the step history.
2826 _step_times_ms.add(elapsed_time_ms);
2827
2828 if (has_aborted()) {
2829 // The task was aborted for some reason.
2830 if (_has_timed_out) {
2831 double diff_ms = elapsed_time_ms - _time_target_ms;
2832 // Keep statistics of how well we did with respect to hitting
2833 // our target only if we actually timed out (if we aborted for
2834 // other reasons, then the results might get skewed).
2835 _marking_step_diff_ms.add(diff_ms);
2836 }
2837
2838 if (_cm->has_overflown()) {
2839 // This is the interesting one. We aborted because a global
2840 // overflow was raised. This means we have to restart the
2841 // marking phase and start iterating over regions. However, in
2842 // order to do this we have to make sure that all tasks stop
2843 // what they are doing and re-initialize in a safe manner. We
2844 // will achieve this with the use of two barrier sync points.
2845
2846 if (!is_serial) {
2847 // We only need to enter the sync barrier if being called
2848 // from a parallel context
2849 _cm->enter_first_sync_barrier(_worker_id);
2850
2851 // When we exit this sync barrier we know that all tasks have
2852 // stopped doing marking work. So, it's now safe to
2853 // re-initialize our data structures.
2854 }
2855
2856 clear_region_fields();
2857 flush_mark_stats_cache();
2858
2859 if (!is_serial) {
2860 // If we're executing the concurrent phase of marking, reset the marking
2861 // state; otherwise the marking state is reset after reference processing,
2862 // during the remark pause.
2863 // If we reset here as a result of an overflow during the remark we will
2864 // see assertion failures from any subsequent set_concurrency_and_phase()
2865 // calls.
2866 if (_cm->concurrent() && _worker_id == 0) {
2867 // Worker 0 is responsible for clearing the global data structures because
2868 // of an overflow. During STW we should not clear the overflow flag (in
2869 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit
2870 // method to abort the pause and restart concurrent marking.
2871 _cm->reset_marking_for_restart();
2872
2873 log_info(gc, marking)("Concurrent Mark reset for overflow");
2874 }
2875
2876 // ...and enter the second barrier.
2877 _cm->enter_second_sync_barrier(_worker_id);
2878 }
2879 // At this point, if we're during the concurrent phase of
2880 // marking, everything has been re-initialized and we're
2881 // ready to restart.
2882 }
2883 }
2884 }
2885
2886 G1CMTask::G1CMTask(uint worker_id,
2887 G1ConcurrentMark* cm,
2888 G1CMTaskQueue* task_queue,
2889 G1RegionMarkStats* mark_stats,
2890 uint max_regions) :
2891 _objArray_processor(this),
2892 _worker_id(worker_id),
2893 _g1h(G1CollectedHeap::heap()),
2894 _cm(cm),
2895 _next_mark_bitmap(NULL),
2896 _task_queue(task_queue),
2897 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize),
2898 _calls(0),
2899 _time_target_ms(0.0),
2900 _start_time_ms(0.0),
2901 _cm_oop_closure(NULL),
2902 _curr_region(NULL),
2903 _finger(NULL),
2904 _region_limit(NULL),
2905 _words_scanned(0),
2906 _words_scanned_limit(0),
2907 _real_words_scanned_limit(0),
2908 _refs_reached(0),
2909 _refs_reached_limit(0),
2910 _real_refs_reached_limit(0),
2911 _has_aborted(false),
2912 _has_timed_out(false),
2913 _draining_satb_buffers(false),
2914 _step_times_ms(),
2915 _elapsed_time_ms(0.0),
2916 _termination_time_ms(0.0),
2917 _termination_start_time_ms(0.0),
2918 _marking_step_diff_ms()
2919 {
2920 guarantee(task_queue != NULL, "invariant");
2921
2922 _marking_step_diff_ms.add(0.5);
2923 }
2924
2925 // These are formatting macros that are used below to ensure
2926 // consistent formatting. The *_H_* versions are used to format the
2927 // header for a particular value and they should be kept consistent
2928 // with the corresponding macro. Also note that most of the macros add
2929 // the necessary white space (as a prefix) which makes them a bit
2930 // easier to compose.
2931
2932 // All the output lines are prefixed with this string to be able to
2933 // identify them easily in a large log file.
2934 #define G1PPRL_LINE_PREFIX "###"
2935
2936 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
2937 #ifdef _LP64
2938 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
2939 #else // _LP64
2940 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
2941 #endif // _LP64
2942
2943 // For per-region info
2944 #define G1PPRL_TYPE_FORMAT " %-4s"
2945 #define G1PPRL_TYPE_H_FORMAT " %4s"
2946 #define G1PPRL_STATE_FORMAT " %-5s"
2947 #define G1PPRL_STATE_H_FORMAT " %5s"
2948 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
2949 #define G1PPRL_BYTE_H_FORMAT " %9s"
2950 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
2951 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
2952
2953 // For summary info
2954 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
2955 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
2956 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
2957 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
2958
2959 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) :
2960 _total_used_bytes(0), _total_capacity_bytes(0),
2961 _total_prev_live_bytes(0), _total_next_live_bytes(0),
2962 _total_remset_bytes(0), _total_strong_code_roots_bytes(0)
2963 {
2964 if (!log_is_enabled(Trace, gc, liveness)) {
2965 return;
2966 }
2967
2968 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2969 MemRegion g1_reserved = g1h->g1_reserved();
2970 double now = os::elapsedTime();
2971
2972 // Print the header of the output.
2973 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
2974 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
2975 G1PPRL_SUM_ADDR_FORMAT("reserved")
2976 G1PPRL_SUM_BYTE_FORMAT("region-size"),
2977 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
2978 HeapRegion::GrainBytes);
2979 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
2980 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2981 G1PPRL_TYPE_H_FORMAT
2982 G1PPRL_ADDR_BASE_H_FORMAT
2983 G1PPRL_BYTE_H_FORMAT
2984 G1PPRL_BYTE_H_FORMAT
2985 G1PPRL_BYTE_H_FORMAT
2986 G1PPRL_DOUBLE_H_FORMAT
2987 G1PPRL_BYTE_H_FORMAT
2988 G1PPRL_STATE_H_FORMAT
2989 G1PPRL_BYTE_H_FORMAT,
2990 "type", "address-range",
2991 "used", "prev-live", "next-live", "gc-eff",
2992 "remset", "state", "code-roots");
2993 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2994 G1PPRL_TYPE_H_FORMAT
2995 G1PPRL_ADDR_BASE_H_FORMAT
2996 G1PPRL_BYTE_H_FORMAT
2997 G1PPRL_BYTE_H_FORMAT
2998 G1PPRL_BYTE_H_FORMAT
2999 G1PPRL_DOUBLE_H_FORMAT
3000 G1PPRL_BYTE_H_FORMAT
3001 G1PPRL_STATE_H_FORMAT
3002 G1PPRL_BYTE_H_FORMAT,
3003 "", "",
3004 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3005 "(bytes)", "", "(bytes)");
3006 }
3007
3008 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) {
3009 if (!log_is_enabled(Trace, gc, liveness)) {
3010 return false;
3011 }
3012
3013 const char* type = r->get_type_str();
3014 HeapWord* bottom = r->bottom();
3015 HeapWord* end = r->end();
3016 size_t capacity_bytes = r->capacity();
3017 size_t used_bytes = r->used();
3018 size_t prev_live_bytes = r->live_bytes();
3019 size_t next_live_bytes = r->next_live_bytes();
3020 double gc_eff = r->gc_efficiency();
3021 size_t remset_bytes = r->rem_set()->mem_size();
3022 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3023 const char* remset_type = r->rem_set()->get_short_state_str();
3024
3025 _total_used_bytes += used_bytes;
3026 _total_capacity_bytes += capacity_bytes;
3027 _total_prev_live_bytes += prev_live_bytes;
3028 _total_next_live_bytes += next_live_bytes;
3029 _total_remset_bytes += remset_bytes;
3030 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3031
3032 // Print a line for this particular region.
3033 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3034 G1PPRL_TYPE_FORMAT
3035 G1PPRL_ADDR_BASE_FORMAT
3036 G1PPRL_BYTE_FORMAT
3037 G1PPRL_BYTE_FORMAT
3038 G1PPRL_BYTE_FORMAT
3039 G1PPRL_DOUBLE_FORMAT
3040 G1PPRL_BYTE_FORMAT
3041 G1PPRL_STATE_FORMAT
3042 G1PPRL_BYTE_FORMAT,
3043 type, p2i(bottom), p2i(end),
3044 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3045 remset_bytes, remset_type, strong_code_roots_bytes);
3046
3047 return false;
3048 }
3049
3050 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3051 if (!log_is_enabled(Trace, gc, liveness)) {
3052 return;
3053 }
3054
3055 // add static memory usages to remembered set sizes
3056 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3057 // Print the footer of the output.
3058 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3059 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3060 " SUMMARY"
3061 G1PPRL_SUM_MB_FORMAT("capacity")
3062 G1PPRL_SUM_MB_PERC_FORMAT("used")
3063 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3064 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3065 G1PPRL_SUM_MB_FORMAT("remset")
3066 G1PPRL_SUM_MB_FORMAT("code-roots"),
3067 bytes_to_mb(_total_capacity_bytes),
3068 bytes_to_mb(_total_used_bytes),
3069 percent_of(_total_used_bytes, _total_capacity_bytes),
3070 bytes_to_mb(_total_prev_live_bytes),
3071 percent_of(_total_prev_live_bytes, _total_capacity_bytes),
3072 bytes_to_mb(_total_next_live_bytes),
3073 percent_of(_total_next_live_bytes, _total_capacity_bytes),
3074 bytes_to_mb(_total_remset_bytes),
3075 bytes_to_mb(_total_strong_code_roots_bytes));
3076 }