1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorState.hpp"
31 #include "gc/g1/g1ConcurrentMark.inline.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1HeapVerifier.hpp"
34 #include "gc/g1/g1OopClosures.inline.hpp"
35 #include "gc/g1/g1Policy.hpp"
36 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
37 #include "gc/g1/g1StringDedup.hpp"
38 #include "gc/g1/heapRegion.inline.hpp"
39 #include "gc/g1/heapRegionRemSet.hpp"
40 #include "gc/g1/heapRegionSet.inline.hpp"
41 #include "gc/shared/adaptiveSizePolicy.hpp"
42 #include "gc/shared/gcId.hpp"
43 #include "gc/shared/gcTimer.hpp"
44 #include "gc/shared/gcTrace.hpp"
45 #include "gc/shared/gcTraceTime.inline.hpp"
46 #include "gc/shared/genOopClosures.inline.hpp"
47 #include "gc/shared/referencePolicy.hpp"
48 #include "gc/shared/strongRootsScope.hpp"
49 #include "gc/shared/suspendibleThreadSet.hpp"
50 #include "gc/shared/taskqueue.inline.hpp"
51 #include "gc/shared/vmGCOperations.hpp"
52 #include "gc/shared/weakProcessor.hpp"
53 #include "include/jvm.h"
54 #include "logging/log.hpp"
55 #include "memory/allocation.hpp"
56 #include "memory/resourceArea.hpp"
57 #include "oops/access.inline.hpp"
58 #include "oops/oop.inline.hpp"
59 #include "runtime/atomic.hpp"
60 #include "runtime/handles.inline.hpp"
61 #include "runtime/java.hpp"
62 #include "runtime/prefetch.inline.hpp"
63 #include "services/memTracker.hpp"
64 #include "utilities/align.hpp"
65 #include "utilities/growableArray.hpp"
66
67 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
68 assert(addr < _cm->finger(), "invariant");
69 assert(addr >= _task->finger(), "invariant");
70
71 // We move that task's local finger along.
72 _task->move_finger_to(addr);
73
74 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
75 // we only partially drain the local queue and global stack
76 _task->drain_local_queue(true);
77 _task->drain_global_stack(true);
78
79 // if the has_aborted flag has been raised, we need to bail out of
80 // the iteration
81 return !_task->has_aborted();
82 }
83
84 G1CMMarkStack::G1CMMarkStack() :
85 _max_chunk_capacity(0),
86 _base(NULL),
87 _chunk_capacity(0) {
88 set_empty();
89 }
90
91 bool G1CMMarkStack::resize(size_t new_capacity) {
92 assert(is_empty(), "Only resize when stack is empty.");
93 assert(new_capacity <= _max_chunk_capacity,
94 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
95
96 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
97
98 if (new_base == NULL) {
99 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));
100 return false;
101 }
102 // Release old mapping.
103 if (_base != NULL) {
104 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
105 }
106
107 _base = new_base;
108 _chunk_capacity = new_capacity;
109 set_empty();
110
111 return true;
112 }
113
114 size_t G1CMMarkStack::capacity_alignment() {
115 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
116 }
117
118 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
119 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
120
121 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
122
123 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
124 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
125
126 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
127 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
128 _max_chunk_capacity,
129 initial_chunk_capacity);
130
131 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
132 initial_chunk_capacity, _max_chunk_capacity);
133
134 return resize(initial_chunk_capacity);
135 }
136
137 void G1CMMarkStack::expand() {
138 if (_chunk_capacity == _max_chunk_capacity) {
139 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
140 return;
141 }
142 size_t old_capacity = _chunk_capacity;
143 // Double capacity if possible
144 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
145
146 if (resize(new_capacity)) {
147 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
148 old_capacity, new_capacity);
149 } else {
150 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
151 old_capacity, new_capacity);
152 }
153 }
154
155 G1CMMarkStack::~G1CMMarkStack() {
156 if (_base != NULL) {
157 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
158 }
159 }
160
161 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
162 elem->next = *list;
163 *list = elem;
164 }
165
166 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
167 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
168 add_chunk_to_list(&_chunk_list, elem);
169 _chunks_in_chunk_list++;
170 }
171
172 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
173 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
174 add_chunk_to_list(&_free_list, elem);
175 }
176
177 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
178 TaskQueueEntryChunk* result = *list;
179 if (result != NULL) {
180 *list = (*list)->next;
181 }
182 return result;
183 }
184
185 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
186 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
187 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
188 if (result != NULL) {
189 _chunks_in_chunk_list--;
190 }
191 return result;
192 }
193
194 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
195 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
196 return remove_chunk_from_list(&_free_list);
197 }
198
199 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
200 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
201 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
202 // wraparound of _hwm.
203 if (_hwm >= _chunk_capacity) {
204 return NULL;
205 }
206
207 size_t cur_idx = Atomic::add(1u, &_hwm) - 1;
208 if (cur_idx >= _chunk_capacity) {
209 return NULL;
210 }
211
212 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
213 result->next = NULL;
214 return result;
215 }
216
217 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
218 // Get a new chunk.
219 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
220
221 if (new_chunk == NULL) {
222 // Did not get a chunk from the free list. Allocate from backing memory.
223 new_chunk = allocate_new_chunk();
224
225 if (new_chunk == NULL) {
226 return false;
227 }
228 }
229
230 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
231
232 add_chunk_to_chunk_list(new_chunk);
233
234 return true;
235 }
236
237 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
238 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
239
240 if (cur == NULL) {
241 return false;
242 }
243
244 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
245
246 add_chunk_to_free_list(cur);
247 return true;
248 }
249
250 void G1CMMarkStack::set_empty() {
251 _chunks_in_chunk_list = 0;
252 _hwm = 0;
253 _chunk_list = NULL;
254 _free_list = NULL;
255 }
256
257 G1CMRootRegions::G1CMRootRegions() :
258 _survivors(NULL), _cm(NULL), _scan_in_progress(false),
259 _should_abort(false), _claimed_survivor_index(0) { }
260
261 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) {
262 _survivors = survivors;
263 _cm = cm;
264 }
265
266 void G1CMRootRegions::prepare_for_scan() {
267 assert(!scan_in_progress(), "pre-condition");
268
269 // Currently, only survivors can be root regions.
270 _claimed_survivor_index = 0;
271 _scan_in_progress = _survivors->regions()->is_nonempty();
272 _should_abort = false;
273 }
274
275 HeapRegion* G1CMRootRegions::claim_next() {
276 if (_should_abort) {
277 // If someone has set the should_abort flag, we return NULL to
278 // force the caller to bail out of their loop.
279 return NULL;
280 }
281
282 // Currently, only survivors can be root regions.
283 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions();
284
285 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1;
286 if (claimed_index < survivor_regions->length()) {
287 return survivor_regions->at(claimed_index);
288 }
289 return NULL;
290 }
291
292 uint G1CMRootRegions::num_root_regions() const {
293 return (uint)_survivors->regions()->length();
294 }
295
296 void G1CMRootRegions::notify_scan_done() {
297 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
298 _scan_in_progress = false;
299 RootRegionScan_lock->notify_all();
300 }
301
302 void G1CMRootRegions::cancel_scan() {
303 notify_scan_done();
304 }
305
306 void G1CMRootRegions::scan_finished() {
307 assert(scan_in_progress(), "pre-condition");
308
309 // Currently, only survivors can be root regions.
310 if (!_should_abort) {
311 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index);
312 assert((uint)_claimed_survivor_index >= _survivors->length(),
313 "we should have claimed all survivors, claimed index = %u, length = %u",
314 (uint)_claimed_survivor_index, _survivors->length());
315 }
316
317 notify_scan_done();
318 }
319
320 bool G1CMRootRegions::wait_until_scan_finished() {
321 if (!scan_in_progress()) {
322 return false;
323 }
324
325 {
326 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
327 while (scan_in_progress()) {
328 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
329 }
330 }
331 return true;
332 }
333
334 // Returns the maximum number of workers to be used in a concurrent
335 // phase based on the number of GC workers being used in a STW
336 // phase.
337 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
338 return MAX2((num_gc_workers + 2) / 4, 1U);
339 }
340
341 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
342 G1RegionToSpaceMapper* prev_bitmap_storage,
343 G1RegionToSpaceMapper* next_bitmap_storage) :
344 // _cm_thread set inside the constructor
345 _g1h(g1h),
346 _completed_initialization(false),
347
348 _mark_bitmap_1(),
349 _mark_bitmap_2(),
350 _prev_mark_bitmap(&_mark_bitmap_1),
351 _next_mark_bitmap(&_mark_bitmap_2),
352
353 _heap(_g1h->reserved_region()),
354
355 _root_regions(),
356
357 _global_mark_stack(),
358
359 // _finger set in set_non_marking_state
360
361 _worker_id_offset(DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
362 _max_num_tasks(ParallelGCThreads),
363 // _num_active_tasks set in set_non_marking_state()
364 // _tasks set inside the constructor
365
366 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
367 _terminator(ParallelTaskTerminator((int) _max_num_tasks, _task_queues)),
368
369 _first_overflow_barrier_sync(),
370 _second_overflow_barrier_sync(),
371
372 _has_overflown(false),
373 _concurrent(false),
374 _has_aborted(false),
375 _restart_for_overflow(false),
376 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
377 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
378
379 // _verbose_level set below
380
381 _init_times(),
382 _remark_times(),
383 _remark_mark_times(),
384 _remark_weak_ref_times(),
385 _cleanup_times(),
386 _total_cleanup_time(0.0),
387
388 _accum_task_vtime(NULL),
389
390 _concurrent_workers(NULL),
391 _num_concurrent_workers(0),
392 _max_concurrent_workers(0),
393
394 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
395 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
396 {
397 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
398 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
399
400 // Create & start ConcurrentMark thread.
401 _cm_thread = new G1ConcurrentMarkThread(this);
402 if (_cm_thread->osthread() == NULL) {
403 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
404 }
405
406 assert(CGC_lock != NULL, "CGC_lock must be initialized");
407
408 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
409 satb_qs.set_buffer_size(G1SATBBufferSize);
410
411 _root_regions.init(_g1h->survivor(), this);
412
413 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
414 // Calculate the number of concurrent worker threads by scaling
415 // the number of parallel GC threads.
416 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
417 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
418 }
419
420 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
421 if (ConcGCThreads > ParallelGCThreads) {
422 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
423 ConcGCThreads, ParallelGCThreads);
424 return;
425 }
426
427 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
428 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
429
430 _num_concurrent_workers = ConcGCThreads;
431 _max_concurrent_workers = _num_concurrent_workers;
432
433 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
434 _concurrent_workers->initialize_workers();
435
436 if (FLAG_IS_DEFAULT(MarkStackSize)) {
437 size_t mark_stack_size =
438 MIN2(MarkStackSizeMax,
439 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
440 // Verify that the calculated value for MarkStackSize is in range.
441 // It would be nice to use the private utility routine from Arguments.
442 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
443 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
444 "must be between 1 and " SIZE_FORMAT,
445 mark_stack_size, MarkStackSizeMax);
446 return;
447 }
448 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
449 } else {
450 // Verify MarkStackSize is in range.
451 if (FLAG_IS_CMDLINE(MarkStackSize)) {
452 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
453 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
454 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
455 "must be between 1 and " SIZE_FORMAT,
456 MarkStackSize, MarkStackSizeMax);
457 return;
458 }
459 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
460 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
461 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
462 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
463 MarkStackSize, MarkStackSizeMax);
464 return;
465 }
466 }
467 }
468 }
469
470 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
471 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
472 }
473
474 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
475 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
476
477 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
478 _num_active_tasks = _max_num_tasks;
479
480 for (uint i = 0; i < _max_num_tasks; ++i) {
481 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
482 task_queue->initialize();
483 _task_queues->register_queue(i, task_queue);
484
485 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
486
487 _accum_task_vtime[i] = 0.0;
488 }
489
490 reset_at_marking_complete();
491 _completed_initialization = true;
492 }
493
494 void G1ConcurrentMark::reset() {
495 _has_aborted = false;
496
497 reset_marking_for_restart();
498
499 // Reset all tasks, since different phases will use different number of active
500 // threads. So, it's easiest to have all of them ready.
501 for (uint i = 0; i < _max_num_tasks; ++i) {
502 _tasks[i]->reset(_next_mark_bitmap);
503 }
504
505 uint max_regions = _g1h->max_regions();
506 for (uint i = 0; i < max_regions; i++) {
507 _top_at_rebuild_starts[i] = NULL;
508 _region_mark_stats[i].clear();
509 }
510 }
511
512 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
513 for (uint j = 0; j < _max_num_tasks; ++j) {
514 _tasks[j]->clear_mark_stats_cache(region_idx);
515 }
516 _top_at_rebuild_starts[region_idx] = NULL;
517 _region_mark_stats[region_idx].clear();
518 }
519
520 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
521 uint const region_idx = r->hrm_index();
522 if (r->is_humongous()) {
523 assert(r->is_starts_humongous(), "Got humongous continues region here");
524 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
525 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
526 clear_statistics_in_region(j);
527 }
528 } else {
529 clear_statistics_in_region(region_idx);
530 }
531 }
532
533 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
534 if (bitmap->is_marked(addr)) {
535 bitmap->clear(addr);
536 }
537 }
538
539 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
540 assert_at_safepoint_on_vm_thread();
541
542 // Need to clear all mark bits of the humongous object.
543 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
544 clear_mark_if_set(_next_mark_bitmap, r->bottom());
545
546 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
547 return;
548 }
549
550 // Clear any statistics about the region gathered so far.
551 clear_statistics(r);
552 }
553
554 void G1ConcurrentMark::reset_marking_for_restart() {
555 _global_mark_stack.set_empty();
556
557 // Expand the marking stack, if we have to and if we can.
558 if (has_overflown()) {
559 _global_mark_stack.expand();
560
561 uint max_regions = _g1h->max_regions();
562 for (uint i = 0; i < max_regions; i++) {
563 _region_mark_stats[i].clear_during_overflow();
564 }
565 }
566
567 clear_has_overflown();
568 _finger = _heap.start();
569
570 for (uint i = 0; i < _max_num_tasks; ++i) {
571 G1CMTaskQueue* queue = _task_queues->queue(i);
572 queue->set_empty();
573 }
574 }
575
576 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
577 assert(active_tasks <= _max_num_tasks, "we should not have more");
578
579 _num_active_tasks = active_tasks;
580 // Need to update the three data structures below according to the
581 // number of active threads for this phase.
582 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
583 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
584 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
585 }
586
587 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
588 set_concurrency(active_tasks);
589
590 _concurrent = concurrent;
591
592 if (!concurrent) {
593 // At this point we should be in a STW phase, and completed marking.
594 assert_at_safepoint_on_vm_thread();
595 assert(out_of_regions(),
596 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
597 p2i(_finger), p2i(_heap.end()));
598 }
599 }
600
601 void G1ConcurrentMark::reset_at_marking_complete() {
602 // We set the global marking state to some default values when we're
603 // not doing marking.
604 reset_marking_for_restart();
605 _num_active_tasks = 0;
606 }
607
608 G1ConcurrentMark::~G1ConcurrentMark() {
609 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
610 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
611 // The G1ConcurrentMark instance is never freed.
612 ShouldNotReachHere();
613 }
614
615 class G1ClearBitMapTask : public AbstractGangTask {
616 public:
617 static size_t chunk_size() { return M; }
618
619 private:
620 // Heap region closure used for clearing the given mark bitmap.
621 class G1ClearBitmapHRClosure : public HeapRegionClosure {
622 private:
623 G1CMBitMap* _bitmap;
624 G1ConcurrentMark* _cm;
625 public:
626 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
627 }
628
629 virtual bool do_heap_region(HeapRegion* r) {
630 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
631
632 HeapWord* cur = r->bottom();
633 HeapWord* const end = r->end();
634
635 while (cur < end) {
636 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
637 _bitmap->clear_range(mr);
638
639 cur += chunk_size_in_words;
640
641 // Abort iteration if after yielding the marking has been aborted.
642 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
643 return true;
644 }
645 // Repeat the asserts from before the start of the closure. We will do them
646 // as asserts here to minimize their overhead on the product. However, we
647 // will have them as guarantees at the beginning / end of the bitmap
648 // clearing to get some checking in the product.
649 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
650 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
651 }
652 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
653
654 return false;
655 }
656 };
657
658 G1ClearBitmapHRClosure _cl;
659 HeapRegionClaimer _hr_claimer;
660 bool _suspendible; // If the task is suspendible, workers must join the STS.
661
662 public:
663 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
664 AbstractGangTask("G1 Clear Bitmap"),
665 _cl(bitmap, suspendible ? cm : NULL),
666 _hr_claimer(n_workers),
667 _suspendible(suspendible)
668 { }
669
670 void work(uint worker_id) {
671 SuspendibleThreadSetJoiner sts_join(_suspendible);
672 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
673 }
674
675 bool is_complete() {
676 return _cl.is_complete();
677 }
678 };
679
680 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
681 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
682
683 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
684 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
685
686 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
687
688 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
689
690 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
691 workers->run_task(&cl, num_workers);
692 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
693 }
694
695 void G1ConcurrentMark::cleanup_for_next_mark() {
696 // Make sure that the concurrent mark thread looks to still be in
697 // the current cycle.
698 guarantee(cm_thread()->during_cycle(), "invariant");
699
700 // We are finishing up the current cycle by clearing the next
701 // marking bitmap and getting it ready for the next cycle. During
702 // this time no other cycle can start. So, let's make sure that this
703 // is the case.
704 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
705
706 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
707
708 // Repeat the asserts from above.
709 guarantee(cm_thread()->during_cycle(), "invariant");
710 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
711 }
712
713 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
714 assert_at_safepoint_on_vm_thread();
715 clear_bitmap(_prev_mark_bitmap, workers, false);
716 }
717
718 class CheckBitmapClearHRClosure : public HeapRegionClosure {
719 G1CMBitMap* _bitmap;
720 public:
721 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
722 }
723
724 virtual bool do_heap_region(HeapRegion* r) {
725 // This closure can be called concurrently to the mutator, so we must make sure
726 // that the result of the getNextMarkedWordAddress() call is compared to the
727 // value passed to it as limit to detect any found bits.
728 // end never changes in G1.
729 HeapWord* end = r->end();
730 return _bitmap->get_next_marked_addr(r->bottom(), end) != end;
731 }
732 };
733
734 bool G1ConcurrentMark::next_mark_bitmap_is_clear() {
735 CheckBitmapClearHRClosure cl(_next_mark_bitmap);
736 _g1h->heap_region_iterate(&cl);
737 return cl.is_complete();
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 // Initialize marking structures. This has to be done in a STW phase.
750 reset();
751
752 // For each region note start of marking.
753 NoteStartOfMarkHRClosure startcl;
754 _g1h->heap_region_iterate(&startcl);
755 }
756
757
758 void G1ConcurrentMark::post_initial_mark() {
759 // Start Concurrent Marking weak-reference discovery.
760 ReferenceProcessor* rp = _g1h->ref_processor_cm();
761 // enable ("weak") refs discovery
762 rp->enable_discovery();
763 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
764
765 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
766 // This is the start of the marking cycle, we're expected all
767 // threads to have SATB queues with active set to false.
768 satb_mq_set.set_active_all_threads(true, /* new active value */
769 false /* expected_active */);
770
771 _root_regions.prepare_for_scan();
772
773 // update_g1_committed() will be called at the end of an evac pause
774 // when marking is on. So, it's also called at the end of the
775 // initial-mark pause to update the heap end, if the heap expands
776 // during it. No need to call it here.
777 }
778
779 /*
780 * Notice that in the next two methods, we actually leave the STS
781 * during the barrier sync and join it immediately afterwards. If we
782 * do not do this, the following deadlock can occur: one thread could
783 * be in the barrier sync code, waiting for the other thread to also
784 * sync up, whereas another one could be trying to yield, while also
785 * waiting for the other threads to sync up too.
786 *
787 * Note, however, that this code is also used during remark and in
788 * this case we should not attempt to leave / enter the STS, otherwise
789 * we'll either hit an assert (debug / fastdebug) or deadlock
790 * (product). So we should only leave / enter the STS if we are
791 * operating concurrently.
792 *
793 * Because the thread that does the sync barrier has left the STS, it
794 * is possible to be suspended for a Full GC or an evacuation pause
795 * could occur. This is actually safe, since the entering the sync
796 * barrier is one of the last things do_marking_step() does, and it
797 * doesn't manipulate any data structures afterwards.
798 */
799
800 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
801 bool barrier_aborted;
802 {
803 SuspendibleThreadSetLeaver sts_leave(concurrent());
804 barrier_aborted = !_first_overflow_barrier_sync.enter();
805 }
806
807 // at this point everyone should have synced up and not be doing any
808 // more work
809
810 if (barrier_aborted) {
811 // If the barrier aborted we ignore the overflow condition and
812 // just abort the whole marking phase as quickly as possible.
813 return;
814 }
815 }
816
817 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
818 SuspendibleThreadSetLeaver sts_leave(concurrent());
819 _second_overflow_barrier_sync.enter();
820
821 // at this point everything should be re-initialized and ready to go
822 }
823
824 class G1CMConcurrentMarkingTask : public AbstractGangTask {
825 G1ConcurrentMark* _cm;
826
827 public:
828 void work(uint worker_id) {
829 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
830 ResourceMark rm;
831
832 double start_vtime = os::elapsedVTime();
833
834 {
835 SuspendibleThreadSetJoiner sts_join;
836
837 assert(worker_id < _cm->active_tasks(), "invariant");
838
839 G1CMTask* task = _cm->task(worker_id);
840 task->record_start_time();
841 if (!_cm->has_aborted()) {
842 do {
843 task->do_marking_step(G1ConcMarkStepDurationMillis,
844 true /* do_termination */,
845 false /* is_serial*/);
846
847 _cm->do_yield_check();
848 } while (!_cm->has_aborted() && task->has_aborted());
849 }
850 task->record_end_time();
851 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
852 }
853
854 double end_vtime = os::elapsedVTime();
855 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
856 }
857
858 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
859 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
860
861 ~G1CMConcurrentMarkingTask() { }
862 };
863
864 uint G1ConcurrentMark::calc_active_marking_workers() {
865 uint result = 0;
866 if (!UseDynamicNumberOfGCThreads ||
867 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
868 !ForceDynamicNumberOfGCThreads)) {
869 result = _max_concurrent_workers;
870 } else {
871 result =
872 AdaptiveSizePolicy::calc_default_active_workers(_max_concurrent_workers,
873 1, /* Minimum workers */
874 _num_concurrent_workers,
875 Threads::number_of_non_daemon_threads());
876 // Don't scale the result down by scale_concurrent_workers() because
877 // that scaling has already gone into "_max_concurrent_workers".
878 }
879 assert(result > 0 && result <= _max_concurrent_workers,
880 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
881 _max_concurrent_workers, result);
882 return result;
883 }
884
885 void G1ConcurrentMark::scan_root_region(HeapRegion* hr, uint worker_id) {
886 // Currently, only survivors can be root regions.
887 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
888 G1RootRegionScanClosure cl(_g1h, this, worker_id);
889
890 const uintx interval = PrefetchScanIntervalInBytes;
891 HeapWord* curr = hr->bottom();
892 const HeapWord* end = hr->top();
893 while (curr < end) {
894 Prefetch::read(curr, interval);
895 oop obj = oop(curr);
896 int size = obj->oop_iterate_size(&cl);
897 assert(size == obj->size(), "sanity");
898 curr += size;
899 }
900 }
901
902 class G1CMRootRegionScanTask : public AbstractGangTask {
903 G1ConcurrentMark* _cm;
904 public:
905 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
906 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
907
908 void work(uint worker_id) {
909 assert(Thread::current()->is_ConcurrentGC_thread(),
910 "this should only be done by a conc GC thread");
911
912 G1CMRootRegions* root_regions = _cm->root_regions();
913 HeapRegion* hr = root_regions->claim_next();
914 while (hr != NULL) {
915 _cm->scan_root_region(hr, worker_id);
916 hr = root_regions->claim_next();
917 }
918 }
919 };
920
921 void G1ConcurrentMark::scan_root_regions() {
922 // scan_in_progress() will have been set to true only if there was
923 // at least one root region to scan. So, if it's false, we
924 // should not attempt to do any further work.
925 if (root_regions()->scan_in_progress()) {
926 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
927
928 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
929 // We distribute work on a per-region basis, so starting
930 // more threads than that is useless.
931 root_regions()->num_root_regions());
932 assert(_num_concurrent_workers <= _max_concurrent_workers,
933 "Maximum number of marking threads exceeded");
934
935 G1CMRootRegionScanTask task(this);
936 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
937 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
938 _concurrent_workers->run_task(&task, _num_concurrent_workers);
939
940 // It's possible that has_aborted() is true here without actually
941 // aborting the survivor scan earlier. This is OK as it's
942 // mainly used for sanity checking.
943 root_regions()->scan_finished();
944 }
945 }
946
947 void G1ConcurrentMark::concurrent_cycle_start() {
948 _gc_timer_cm->register_gc_start();
949
950 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
951
952 _g1h->trace_heap_before_gc(_gc_tracer_cm);
953 }
954
955 void G1ConcurrentMark::concurrent_cycle_end() {
956 _g1h->collector_state()->set_clearing_next_bitmap(false);
957
958 _g1h->trace_heap_after_gc(_gc_tracer_cm);
959
960 if (has_aborted()) {
961 log_info(gc, marking)("Concurrent Mark Abort");
962 _gc_tracer_cm->report_concurrent_mode_failure();
963 }
964
965 _gc_timer_cm->register_gc_end();
966
967 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
968 }
969
970 void G1ConcurrentMark::mark_from_roots() {
971 _restart_for_overflow = false;
972
973 _num_concurrent_workers = calc_active_marking_workers();
974
975 uint active_workers = MAX2(1U, _num_concurrent_workers);
976
977 // Setting active workers is not guaranteed since fewer
978 // worker threads may currently exist and more may not be
979 // available.
980 active_workers = _concurrent_workers->update_active_workers(active_workers);
981 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
982
983 // Parallel task terminator is set in "set_concurrency_and_phase()"
984 set_concurrency_and_phase(active_workers, true /* concurrent */);
985
986 G1CMConcurrentMarkingTask marking_task(this);
987 _concurrent_workers->run_task(&marking_task);
988 print_stats();
989 }
990
991 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
992 G1HeapVerifier* verifier = _g1h->verifier();
993
994 verifier->verify_region_sets_optional();
995
996 if (VerifyDuringGC) {
997 GCTraceTime(Debug, gc, phases) trace(caller, _gc_timer_cm);
998
999 size_t const BufLen = 512;
1000 char buffer[BufLen];
1001
1002 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
1003 verifier->verify(type, vo, buffer);
1004 }
1005
1006 verifier->check_bitmaps(caller);
1007 }
1008
1009 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1010 G1CollectedHeap* _g1h;
1011 G1ConcurrentMark* _cm;
1012 HeapRegionClaimer _hrclaimer;
1013 uint _num_selected_for_rebuild;
1014
1015 G1PrintRegionLivenessInfoClosure _cl;
1016
1017 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1018 G1CollectedHeap* _g1h;
1019 G1ConcurrentMark* _cm;
1020
1021 G1PrintRegionLivenessInfoClosure* _cl;
1022
1023 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1024
1025 void update_remset_before_rebuild(HeapRegion * hr) {
1026 G1RemSetTrackingPolicy* tracking_policy = _g1h->g1_policy()->remset_tracker();
1027
1028 size_t const live_bytes = _cm->liveness(hr->hrm_index()) * HeapWordSize;
1029 bool selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1030 if (selected_for_rebuild) {
1031 _num_regions_selected_for_rebuild++;
1032 }
1033 _cm->update_top_at_rebuild_start(hr);
1034 }
1035
1036 // Distribute the given words across the humongous object starting with hr and
1037 // note end of marking.
1038 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1039 uint const region_idx = hr->hrm_index();
1040 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1041 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1042
1043 // "Distributing" zero words means that we only note end of marking for these
1044 // regions.
1045 assert(marked_words == 0 || obj_size_in_words == marked_words,
1046 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1047 obj_size_in_words, marked_words);
1048
1049 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1050 HeapRegion* const r = _g1h->region_at(i);
1051 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1052
1053 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1054 words_to_add, i, r->get_type_str());
1055 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1056 marked_words -= words_to_add;
1057 }
1058 assert(marked_words == 0,
1059 SIZE_FORMAT " words left after distributing space across %u regions",
1060 marked_words, num_regions_in_humongous);
1061 }
1062
1063 void update_marked_bytes(HeapRegion* hr) {
1064 uint const region_idx = hr->hrm_index();
1065 size_t const marked_words = _cm->liveness(region_idx);
1066 // The marking attributes the object's size completely to the humongous starts
1067 // region. We need to distribute this value across the entire set of regions a
1068 // humongous object spans.
1069 if (hr->is_humongous()) {
1070 assert(hr->is_starts_humongous() || marked_words == 0,
1071 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1072 marked_words, region_idx, hr->get_type_str());
1073 if (hr->is_starts_humongous()) {
1074 distribute_marked_bytes(hr, marked_words);
1075 }
1076 } else {
1077 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1078 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1079 }
1080 }
1081
1082 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1083 hr->add_to_marked_bytes(marked_bytes);
1084 _cl->do_heap_region(hr);
1085 hr->note_end_of_marking();
1086 }
1087
1088 public:
1089 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1090 _g1h(g1h), _cm(cm), _num_regions_selected_for_rebuild(0), _cl(cl) { }
1091
1092 virtual bool do_heap_region(HeapRegion* r) {
1093 update_remset_before_rebuild(r);
1094 update_marked_bytes(r);
1095
1096 return false;
1097 }
1098
1099 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1100 };
1101
1102 public:
1103 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1104 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1105 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _num_selected_for_rebuild(0), _cl("Post-Marking") { }
1106
1107 virtual void work(uint worker_id) {
1108 G1UpdateRemSetTrackingBeforeRebuild cl(_g1h, _cm, &_cl);
1109 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1110 Atomic::add(cl.num_selected_for_rebuild(), &_num_selected_for_rebuild);
1111 }
1112
1113 uint num_selected_for_rebuild() const { return _num_selected_for_rebuild; }
1114
1115 // Number of regions for which roughly one thread should be spawned for this work.
1116 static const uint RegionsPerThread = 512;
1117 };
1118
1119 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1120 G1CollectedHeap* _g1h;
1121 public:
1122 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1123
1124 virtual bool do_heap_region(HeapRegion* r) {
1125 _g1h->g1_policy()->remset_tracker()->update_after_rebuild(r);
1126 return false;
1127 }
1128 };
1129
1130 void G1ConcurrentMark::remark() {
1131 assert_at_safepoint_on_vm_thread();
1132
1133 // If a full collection has happened, we should not continue. However we might
1134 // have ended up here as the Remark VM operation has been scheduled already.
1135 if (has_aborted()) {
1136 return;
1137 }
1138
1139 G1Policy* g1p = _g1h->g1_policy();
1140 g1p->record_concurrent_mark_remark_start();
1141
1142 double start = os::elapsedTime();
1143
1144 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1145
1146 {
1147 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm);
1148 finalize_marking();
1149 }
1150
1151 double mark_work_end = os::elapsedTime();
1152
1153 bool const mark_finished = !has_overflown();
1154 if (mark_finished) {
1155 weak_refs_work(false /* clear_all_soft_refs */);
1156
1157 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1158 // We're done with marking.
1159 // This is the end of the marking cycle, we're expected all
1160 // threads to have SATB queues with active set to true.
1161 satb_mq_set.set_active_all_threads(false, /* new active value */
1162 true /* expected_active */);
1163
1164 {
1165 GCTraceTime(Debug, gc, phases) trace("Flush Task Caches", _gc_timer_cm);
1166 flush_all_task_caches();
1167 }
1168
1169 // Install newly created mark bitmap as "prev".
1170 swap_mark_bitmaps();
1171 {
1172 GCTraceTime(Debug, gc, phases) trace("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1173
1174 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1175 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1176 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1177
1178 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1179 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1180 _g1h->workers()->run_task(&cl, num_workers);
1181
1182 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1183 _g1h->num_regions(), cl.num_selected_for_rebuild());
1184 }
1185 {
1186 GCTraceTime(Debug, gc, phases) trace("Reclaim Empty Regions", _gc_timer_cm);
1187 reclaim_empty_regions();
1188 }
1189
1190 // Clean out dead classes
1191 if (ClassUnloadingWithConcurrentMark) {
1192 GCTraceTime(Debug, gc, phases) trace("Purge Metaspace", _gc_timer_cm);
1193 ClassLoaderDataGraph::purge();
1194 }
1195
1196 compute_new_sizes();
1197
1198 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1199
1200 assert(!restart_for_overflow(), "sanity");
1201 // Completely reset the marking state since marking completed
1202 reset_at_marking_complete();
1203 } else {
1204 // We overflowed. Restart concurrent marking.
1205 _restart_for_overflow = true;
1206
1207 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1208
1209 // Clear the marking state because we will be restarting
1210 // marking due to overflowing the global mark stack.
1211 reset_marking_for_restart();
1212 }
1213
1214 {
1215 GCTraceTime(Debug, gc, phases) trace("Report Object Count", _gc_timer_cm);
1216 report_object_count(mark_finished);
1217 }
1218
1219 // Statistics
1220 double now = os::elapsedTime();
1221 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1222 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1223 _remark_times.add((now - start) * 1000.0);
1224
1225 g1p->record_concurrent_mark_remark_end();
1226 }
1227
1228 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1229 // Per-region work during the Cleanup pause.
1230 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1231 G1CollectedHeap* _g1h;
1232 size_t _freed_bytes;
1233 FreeRegionList* _local_cleanup_list;
1234 uint _old_regions_removed;
1235 uint _humongous_regions_removed;
1236 HRRSCleanupTask* _hrrs_cleanup_task;
1237
1238 public:
1239 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1240 FreeRegionList* local_cleanup_list,
1241 HRRSCleanupTask* hrrs_cleanup_task) :
1242 _g1h(g1h),
1243 _freed_bytes(0),
1244 _local_cleanup_list(local_cleanup_list),
1245 _old_regions_removed(0),
1246 _humongous_regions_removed(0),
1247 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1248
1249 size_t freed_bytes() { return _freed_bytes; }
1250 const uint old_regions_removed() { return _old_regions_removed; }
1251 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1252
1253 bool do_heap_region(HeapRegion *hr) {
1254 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1255 _freed_bytes += hr->used();
1256 hr->set_containing_set(NULL);
1257 if (hr->is_humongous()) {
1258 _humongous_regions_removed++;
1259 _g1h->free_humongous_region(hr, _local_cleanup_list);
1260 } else {
1261 _old_regions_removed++;
1262 _g1h->free_region(hr, _local_cleanup_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
1263 }
1264 hr->clear_cardtable();
1265 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1266 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1267 } else {
1268 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1269 }
1270
1271 return false;
1272 }
1273 };
1274
1275 G1CollectedHeap* _g1h;
1276 FreeRegionList* _cleanup_list;
1277 HeapRegionClaimer _hrclaimer;
1278
1279 public:
1280 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1281 AbstractGangTask("G1 Cleanup"),
1282 _g1h(g1h),
1283 _cleanup_list(cleanup_list),
1284 _hrclaimer(n_workers) {
1285
1286 HeapRegionRemSet::reset_for_cleanup_tasks();
1287 }
1288
1289 void work(uint worker_id) {
1290 FreeRegionList local_cleanup_list("Local Cleanup List");
1291 HRRSCleanupTask hrrs_cleanup_task;
1292 G1ReclaimEmptyRegionsClosure cl(_g1h,
1293 &local_cleanup_list,
1294 &hrrs_cleanup_task);
1295 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1296 assert(cl.is_complete(), "Shouldn't have aborted!");
1297
1298 // Now update the old/humongous region sets
1299 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1300 {
1301 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1302 _g1h->decrement_summary_bytes(cl.freed_bytes());
1303
1304 _cleanup_list->add_ordered(&local_cleanup_list);
1305 assert(local_cleanup_list.is_empty(), "post-condition");
1306
1307 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1308 }
1309 }
1310 };
1311
1312 void G1ConcurrentMark::reclaim_empty_regions() {
1313 WorkGang* workers = _g1h->workers();
1314 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1315
1316 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1317 workers->run_task(&cl);
1318
1319 if (!empty_regions_list.is_empty()) {
1320 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1321 // Now print the empty regions list.
1322 G1HRPrinter* hrp = _g1h->hr_printer();
1323 if (hrp->is_active()) {
1324 FreeRegionListIterator iter(&empty_regions_list);
1325 while (iter.more_available()) {
1326 HeapRegion* hr = iter.get_next();
1327 hrp->cleanup(hr);
1328 }
1329 }
1330 // And actually make them available.
1331 _g1h->prepend_to_freelist(&empty_regions_list);
1332 }
1333 }
1334
1335 void G1ConcurrentMark::compute_new_sizes() {
1336 MetaspaceGC::compute_new_size();
1337
1338 // Cleanup will have freed any regions completely full of garbage.
1339 // Update the soft reference policy with the new heap occupancy.
1340 Universe::update_heap_info_at_gc();
1341
1342 // We reclaimed old regions so we should calculate the sizes to make
1343 // sure we update the old gen/space data.
1344 _g1h->g1mm()->update_sizes();
1345 }
1346
1347 void G1ConcurrentMark::cleanup() {
1348 assert_at_safepoint_on_vm_thread();
1349
1350 // If a full collection has happened, we shouldn't do this.
1351 if (has_aborted()) {
1352 return;
1353 }
1354
1355 G1Policy* g1p = _g1h->g1_policy();
1356 g1p->record_concurrent_mark_cleanup_start();
1357
1358 double start = os::elapsedTime();
1359
1360 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1361
1362 {
1363 GCTraceTime(Debug, gc, phases) trace("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1364 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1365 _g1h->heap_region_iterate(&cl);
1366 }
1367
1368 if (log_is_enabled(Trace, gc, liveness)) {
1369 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1370 _g1h->heap_region_iterate(&cl);
1371 }
1372
1373 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1374
1375 // We need to make this be a "collection" so any collection pause that
1376 // races with it goes around and waits for Cleanup to finish.
1377 _g1h->increment_total_collections();
1378
1379 // Local statistics
1380 double recent_cleanup_time = (os::elapsedTime() - start);
1381 _total_cleanup_time += recent_cleanup_time;
1382 _cleanup_times.add(recent_cleanup_time);
1383
1384 {
1385 GCTraceTime(Debug, gc, phases) trace("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1386 _g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1387 }
1388 }
1389
1390 // Supporting Object and Oop closures for reference discovery
1391 // and processing in during marking
1392
1393 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1394 HeapWord* addr = (HeapWord*)obj;
1395 return addr != NULL &&
1396 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_ill(obj));
1397 }
1398
1399 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1400 // Uses the G1CMTask associated with a worker thread (for serial reference
1401 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1402 // trace referent objects.
1403 //
1404 // Using the G1CMTask and embedded local queues avoids having the worker
1405 // threads operating on the global mark stack. This reduces the risk
1406 // of overflowing the stack - which we would rather avoid at this late
1407 // state. Also using the tasks' local queues removes the potential
1408 // of the workers interfering with each other that could occur if
1409 // operating on the global stack.
1410
1411 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1412 G1ConcurrentMark* _cm;
1413 G1CMTask* _task;
1414 int _ref_counter_limit;
1415 int _ref_counter;
1416 bool _is_serial;
1417 public:
1418 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1419 _cm(cm), _task(task), _is_serial(is_serial),
1420 _ref_counter_limit(G1RefProcDrainInterval) {
1421 assert(_ref_counter_limit > 0, "sanity");
1422 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1423 _ref_counter = _ref_counter_limit;
1424 }
1425
1426 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1427 virtual void do_oop( oop* p) { do_oop_work(p); }
1428
1429 template <class T> void do_oop_work(T* p) {
1430 if (!_cm->has_overflown()) {
1431 _task->deal_with_reference(p);
1432 _ref_counter--;
1433
1434 if (_ref_counter == 0) {
1435 // We have dealt with _ref_counter_limit references, pushing them
1436 // and objects reachable from them on to the local stack (and
1437 // possibly the global stack). Call G1CMTask::do_marking_step() to
1438 // process these entries.
1439 //
1440 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1441 // there's nothing more to do (i.e. we're done with the entries that
1442 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1443 // above) or we overflow.
1444 //
1445 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1446 // flag while there may still be some work to do. (See the comment at
1447 // the beginning of G1CMTask::do_marking_step() for those conditions -
1448 // one of which is reaching the specified time target.) It is only
1449 // when G1CMTask::do_marking_step() returns without setting the
1450 // has_aborted() flag that the marking step has completed.
1451 do {
1452 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1453 _task->do_marking_step(mark_step_duration_ms,
1454 false /* do_termination */,
1455 _is_serial);
1456 } while (_task->has_aborted() && !_cm->has_overflown());
1457 _ref_counter = _ref_counter_limit;
1458 }
1459 }
1460 }
1461 };
1462
1463 // 'Drain' oop closure used by both serial and parallel reference processing.
1464 // Uses the G1CMTask associated with a given worker thread (for serial
1465 // reference processing the G1CMtask for worker 0 is used). Calls the
1466 // do_marking_step routine, with an unbelievably large timeout value,
1467 // to drain the marking data structures of the remaining entries
1468 // added by the 'keep alive' oop closure above.
1469
1470 class G1CMDrainMarkingStackClosure : public VoidClosure {
1471 G1ConcurrentMark* _cm;
1472 G1CMTask* _task;
1473 bool _is_serial;
1474 public:
1475 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1476 _cm(cm), _task(task), _is_serial(is_serial) {
1477 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1478 }
1479
1480 void do_void() {
1481 do {
1482 // We call G1CMTask::do_marking_step() to completely drain the local
1483 // and global marking stacks of entries pushed by the 'keep alive'
1484 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1485 //
1486 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1487 // if there's nothing more to do (i.e. we've completely drained the
1488 // entries that were pushed as a a result of applying the 'keep alive'
1489 // closure to the entries on the discovered ref lists) or we overflow
1490 // the global marking stack.
1491 //
1492 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1493 // flag while there may still be some work to do. (See the comment at
1494 // the beginning of G1CMTask::do_marking_step() for those conditions -
1495 // one of which is reaching the specified time target.) It is only
1496 // when G1CMTask::do_marking_step() returns without setting the
1497 // has_aborted() flag that the marking step has completed.
1498
1499 _task->do_marking_step(1000000000.0 /* something very large */,
1500 true /* do_termination */,
1501 _is_serial);
1502 } while (_task->has_aborted() && !_cm->has_overflown());
1503 }
1504 };
1505
1506 // Implementation of AbstractRefProcTaskExecutor for parallel
1507 // reference processing at the end of G1 concurrent marking
1508
1509 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1510 private:
1511 G1CollectedHeap* _g1h;
1512 G1ConcurrentMark* _cm;
1513 WorkGang* _workers;
1514 uint _active_workers;
1515
1516 public:
1517 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1518 G1ConcurrentMark* cm,
1519 WorkGang* workers,
1520 uint n_workers) :
1521 _g1h(g1h), _cm(cm),
1522 _workers(workers), _active_workers(n_workers) { }
1523
1524 // Executes the given task using concurrent marking worker threads.
1525 virtual void execute(ProcessTask& task);
1526 virtual void execute(EnqueueTask& task);
1527 };
1528
1529 class G1CMRefProcTaskProxy : public AbstractGangTask {
1530 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1531 ProcessTask& _proc_task;
1532 G1CollectedHeap* _g1h;
1533 G1ConcurrentMark* _cm;
1534
1535 public:
1536 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1537 G1CollectedHeap* g1h,
1538 G1ConcurrentMark* cm) :
1539 AbstractGangTask("Process reference objects in parallel"),
1540 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1541 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1542 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1543 }
1544
1545 virtual void work(uint worker_id) {
1546 ResourceMark rm;
1547 HandleMark hm;
1548 G1CMTask* task = _cm->task(worker_id);
1549 G1CMIsAliveClosure g1_is_alive(_g1h);
1550 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1551 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1552
1553 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1554 }
1555 };
1556
1557 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1558 assert(_workers != NULL, "Need parallel worker threads.");
1559 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1560
1561 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1562
1563 // We need to reset the concurrency level before each
1564 // proxy task execution, so that the termination protocol
1565 // and overflow handling in G1CMTask::do_marking_step() knows
1566 // how many workers to wait for.
1567 _cm->set_concurrency(_active_workers);
1568 _workers->run_task(&proc_task_proxy);
1569 }
1570
1571 class G1CMRefEnqueueTaskProxy : public AbstractGangTask {
1572 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
1573 EnqueueTask& _enq_task;
1574
1575 public:
1576 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
1577 AbstractGangTask("Enqueue reference objects in parallel"),
1578 _enq_task(enq_task) { }
1579
1580 virtual void work(uint worker_id) {
1581 _enq_task.work(worker_id);
1582 }
1583 };
1584
1585 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
1586 assert(_workers != NULL, "Need parallel worker threads.");
1587 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1588
1589 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
1590
1591 // Not strictly necessary but...
1592 //
1593 // We need to reset the concurrency level before each
1594 // proxy task execution, so that the termination protocol
1595 // and overflow handling in G1CMTask::do_marking_step() knows
1596 // how many workers to wait for.
1597 _cm->set_concurrency(_active_workers);
1598 _workers->run_task(&enq_task_proxy);
1599 }
1600
1601 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1602 ResourceMark rm;
1603 HandleMark hm;
1604
1605 // Is alive closure.
1606 G1CMIsAliveClosure g1_is_alive(_g1h);
1607
1608 // Inner scope to exclude the cleaning of the string and symbol
1609 // tables from the displayed time.
1610 {
1611 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm);
1612
1613 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1614
1615 // See the comment in G1CollectedHeap::ref_processing_init()
1616 // about how reference processing currently works in G1.
1617
1618 // Set the soft reference policy
1619 rp->setup_policy(clear_all_soft_refs);
1620 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1621
1622 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1623 // in serial reference processing. Note these closures are also
1624 // used for serially processing (by the the current thread) the
1625 // JNI references during parallel reference processing.
1626 //
1627 // These closures do not need to synchronize with the worker
1628 // threads involved in parallel reference processing as these
1629 // instances are executed serially by the current thread (e.g.
1630 // reference processing is not multi-threaded and is thus
1631 // performed by the current thread instead of a gang worker).
1632 //
1633 // The gang tasks involved in parallel reference processing create
1634 // their own instances of these closures, which do their own
1635 // synchronization among themselves.
1636 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1637 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1638
1639 // We need at least one active thread. If reference processing
1640 // is not multi-threaded we use the current (VMThread) thread,
1641 // otherwise we use the work gang from the G1CollectedHeap and
1642 // we utilize all the worker threads we can.
1643 bool processing_is_mt = rp->processing_is_mt();
1644 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1645 active_workers = MAX2(MIN2(active_workers, _max_num_tasks), 1U);
1646
1647 // Parallel processing task executor.
1648 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1649 _g1h->workers(), active_workers);
1650 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1651
1652 // Set the concurrency level. The phase was already set prior to
1653 // executing the remark task.
1654 set_concurrency(active_workers);
1655
1656 // Set the degree of MT processing here. If the discovery was done MT,
1657 // the number of threads involved during discovery could differ from
1658 // the number of active workers. This is OK as long as the discovered
1659 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1660 rp->set_active_mt_degree(active_workers);
1661
1662 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->num_q());
1663
1664 // Process the weak references.
1665 const ReferenceProcessorStats& stats =
1666 rp->process_discovered_references(&g1_is_alive,
1667 &g1_keep_alive,
1668 &g1_drain_mark_stack,
1669 executor,
1670 &pt);
1671 _gc_tracer_cm->report_gc_reference_stats(stats);
1672 pt.print_all_references();
1673
1674 // The do_oop work routines of the keep_alive and drain_marking_stack
1675 // oop closures will set the has_overflown flag if we overflow the
1676 // global marking stack.
1677
1678 assert(has_overflown() || _global_mark_stack.is_empty(),
1679 "Mark stack should be empty (unless it has overflown)");
1680
1681 assert(rp->num_q() == active_workers, "why not");
1682
1683 rp->enqueue_discovered_references(executor, &pt);
1684
1685 rp->verify_no_references_recorded();
1686
1687 pt.print_enqueue_phase();
1688
1689 assert(!rp->discovery_enabled(), "Post condition");
1690 }
1691
1692 assert(has_overflown() || _global_mark_stack.is_empty(),
1693 "Mark stack should be empty (unless it has overflown)");
1694
1695 {
1696 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1697 WeakProcessor::weak_oops_do(&g1_is_alive, &do_nothing_cl);
1698 }
1699
1700 if (has_overflown()) {
1701 // We can not trust g1_is_alive if the marking stack overflowed
1702 return;
1703 }
1704
1705 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1706
1707 // Unload Klasses, String, Symbols, Code Cache, etc.
1708 if (ClassUnloadingWithConcurrentMark) {
1709 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1710 bool purged_classes = SystemDictionary::do_unloading(&g1_is_alive, _gc_timer_cm, false /* Defer cleaning */);
1711 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1712 } else {
1713 GCTraceTime(Debug, gc, phases) debug("Cleanup", _gc_timer_cm);
1714 // No need to clean string table and symbol table as they are treated as strong roots when
1715 // class unloading is disabled.
1716 _g1h->partial_cleaning(&g1_is_alive, false, false, G1StringDedup::is_enabled());
1717 }
1718 }
1719
1720 // When sampling object counts, we already swapped the mark bitmaps, so we need to use
1721 // the prev bitmap determining liveness.
1722 class G1ObjectCountIsAliveClosure: public BoolObjectClosure {
1723 G1CollectedHeap* _g1h;
1724 public:
1725 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
1726
1727 bool do_object_b(oop obj) {
1728 HeapWord* addr = (HeapWord*)obj;
1729 return addr != NULL &&
1730 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_dead(obj));
1731 }
1732 };
1733
1734 void G1ConcurrentMark::report_object_count(bool mark_completed) {
1735 // Depending on the completion of the marking liveness needs to be determined
1736 // using either the next or prev bitmap.
1737 if (mark_completed) {
1738 G1ObjectCountIsAliveClosure is_alive(_g1h);
1739 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1740 } else {
1741 G1CMIsAliveClosure is_alive(_g1h);
1742 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1743 }
1744 }
1745
1746
1747 void G1ConcurrentMark::swap_mark_bitmaps() {
1748 G1CMBitMap* temp = _prev_mark_bitmap;
1749 _prev_mark_bitmap = _next_mark_bitmap;
1750 _next_mark_bitmap = temp;
1751 _g1h->collector_state()->set_clearing_next_bitmap(true);
1752 }
1753
1754 // Closure for marking entries in SATB buffers.
1755 class G1CMSATBBufferClosure : public SATBBufferClosure {
1756 private:
1757 G1CMTask* _task;
1758 G1CollectedHeap* _g1h;
1759
1760 // This is very similar to G1CMTask::deal_with_reference, but with
1761 // more relaxed requirements for the argument, so this must be more
1762 // circumspect about treating the argument as an object.
1763 void do_entry(void* entry) const {
1764 _task->increment_refs_reached();
1765 oop const obj = static_cast<oop>(entry);
1766 _task->make_reference_grey(obj);
1767 }
1768
1769 public:
1770 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1771 : _task(task), _g1h(g1h) { }
1772
1773 virtual void do_buffer(void** buffer, size_t size) {
1774 for (size_t i = 0; i < size; ++i) {
1775 do_entry(buffer[i]);
1776 }
1777 }
1778 };
1779
1780 class G1RemarkThreadsClosure : public ThreadClosure {
1781 G1CMSATBBufferClosure _cm_satb_cl;
1782 G1CMOopClosure _cm_cl;
1783 MarkingCodeBlobClosure _code_cl;
1784 int _thread_parity;
1785
1786 public:
1787 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1788 _cm_satb_cl(task, g1h),
1789 _cm_cl(g1h, task),
1790 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1791 _thread_parity(Threads::thread_claim_parity()) {}
1792
1793 void do_thread(Thread* thread) {
1794 if (thread->is_Java_thread()) {
1795 if (thread->claim_oops_do(true, _thread_parity)) {
1796 JavaThread* jt = (JavaThread*)thread;
1797
1798 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1799 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1800 // * Alive if on the stack of an executing method
1801 // * Weakly reachable otherwise
1802 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1803 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1804 jt->nmethods_do(&_code_cl);
1805
1806 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
1807 }
1808 } else if (thread->is_VM_thread()) {
1809 if (thread->claim_oops_do(true, _thread_parity)) {
1810 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
1811 }
1812 }
1813 }
1814 };
1815
1816 class G1CMRemarkTask : public AbstractGangTask {
1817 G1ConcurrentMark* _cm;
1818 public:
1819 void work(uint worker_id) {
1820 G1CMTask* task = _cm->task(worker_id);
1821 task->record_start_time();
1822 {
1823 ResourceMark rm;
1824 HandleMark hm;
1825
1826 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1827 Threads::threads_do(&threads_f);
1828 }
1829
1830 do {
1831 task->do_marking_step(1000000000.0 /* something very large */,
1832 true /* do_termination */,
1833 false /* is_serial */);
1834 } while (task->has_aborted() && !_cm->has_overflown());
1835 // If we overflow, then we do not want to restart. We instead
1836 // want to abort remark and do concurrent marking again.
1837 task->record_end_time();
1838 }
1839
1840 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1841 AbstractGangTask("Par Remark"), _cm(cm) {
1842 _cm->terminator()->reset_for_reuse(active_workers);
1843 }
1844 };
1845
1846 void G1ConcurrentMark::finalize_marking() {
1847 ResourceMark rm;
1848 HandleMark hm;
1849
1850 _g1h->ensure_parsability(false);
1851
1852 // this is remark, so we'll use up all active threads
1853 uint active_workers = _g1h->workers()->active_workers();
1854 set_concurrency_and_phase(active_workers, false /* concurrent */);
1855 // Leave _parallel_marking_threads at it's
1856 // value originally calculated in the G1ConcurrentMark
1857 // constructor and pass values of the active workers
1858 // through the gang in the task.
1859
1860 {
1861 StrongRootsScope srs(active_workers);
1862
1863 G1CMRemarkTask remarkTask(this, active_workers);
1864 // We will start all available threads, even if we decide that the
1865 // active_workers will be fewer. The extra ones will just bail out
1866 // immediately.
1867 _g1h->workers()->run_task(&remarkTask);
1868 }
1869
1870 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1871 guarantee(has_overflown() ||
1872 satb_mq_set.completed_buffers_num() == 0,
1873 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1874 BOOL_TO_STR(has_overflown()),
1875 satb_mq_set.completed_buffers_num());
1876
1877 print_stats();
1878 }
1879
1880 void G1ConcurrentMark::flush_all_task_caches() {
1881 size_t hits = 0;
1882 size_t misses = 0;
1883 for (uint i = 0; i < _max_num_tasks; i++) {
1884 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache();
1885 hits += stats.first;
1886 misses += stats.second;
1887 }
1888 size_t sum = hits + misses;
1889 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf",
1890 hits, misses, percent_of(hits, sum));
1891 }
1892
1893 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) {
1894 _prev_mark_bitmap->clear_range(mr);
1895 }
1896
1897 HeapRegion*
1898 G1ConcurrentMark::claim_region(uint worker_id) {
1899 // "checkpoint" the finger
1900 HeapWord* finger = _finger;
1901
1902 while (finger < _heap.end()) {
1903 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1904
1905 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1906 // Make sure that the reads below do not float before loading curr_region.
1907 OrderAccess::loadload();
1908 // Above heap_region_containing may return NULL as we always scan claim
1909 // until the end of the heap. In this case, just jump to the next region.
1910 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1911
1912 // Is the gap between reading the finger and doing the CAS too long?
1913 HeapWord* res = Atomic::cmpxchg(end, &_finger, finger);
1914 if (res == finger && curr_region != NULL) {
1915 // we succeeded
1916 HeapWord* bottom = curr_region->bottom();
1917 HeapWord* limit = curr_region->next_top_at_mark_start();
1918
1919 // notice that _finger == end cannot be guaranteed here since,
1920 // someone else might have moved the finger even further
1921 assert(_finger >= end, "the finger should have moved forward");
1922
1923 if (limit > bottom) {
1924 return curr_region;
1925 } else {
1926 assert(limit == bottom,
1927 "the region limit should be at bottom");
1928 // we return NULL and the caller should try calling
1929 // claim_region() again.
1930 return NULL;
1931 }
1932 } else {
1933 assert(_finger > finger, "the finger should have moved forward");
1934 // read it again
1935 finger = _finger;
1936 }
1937 }
1938
1939 return NULL;
1940 }
1941
1942 #ifndef PRODUCT
1943 class VerifyNoCSetOops {
1944 G1CollectedHeap* _g1h;
1945 const char* _phase;
1946 int _info;
1947
1948 public:
1949 VerifyNoCSetOops(const char* phase, int info = -1) :
1950 _g1h(G1CollectedHeap::heap()),
1951 _phase(phase),
1952 _info(info)
1953 { }
1954
1955 void operator()(G1TaskQueueEntry task_entry) const {
1956 if (task_entry.is_array_slice()) {
1957 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1958 return;
1959 }
1960 guarantee(oopDesc::is_oop(task_entry.obj()),
1961 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1962 p2i(task_entry.obj()), _phase, _info);
1963 guarantee(!_g1h->is_in_cset(task_entry.obj()),
1964 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
1965 p2i(task_entry.obj()), _phase, _info);
1966 }
1967 };
1968
1969 void G1ConcurrentMark::verify_no_cset_oops() {
1970 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1971 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
1972 return;
1973 }
1974
1975 // Verify entries on the global mark stack
1976 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
1977
1978 // Verify entries on the task queues
1979 for (uint i = 0; i < _max_num_tasks; ++i) {
1980 G1CMTaskQueue* queue = _task_queues->queue(i);
1981 queue->iterate(VerifyNoCSetOops("Queue", i));
1982 }
1983
1984 // Verify the global finger
1985 HeapWord* global_finger = finger();
1986 if (global_finger != NULL && global_finger < _heap.end()) {
1987 // Since we always iterate over all regions, we might get a NULL HeapRegion
1988 // here.
1989 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
1990 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
1991 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
1992 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
1993 }
1994
1995 // Verify the task fingers
1996 assert(_num_concurrent_workers <= _max_num_tasks, "sanity");
1997 for (uint i = 0; i < _num_concurrent_workers; ++i) {
1998 G1CMTask* task = _tasks[i];
1999 HeapWord* task_finger = task->finger();
2000 if (task_finger != NULL && task_finger < _heap.end()) {
2001 // See above note on the global finger verification.
2002 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger);
2003 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2004 !task_hr->in_collection_set(),
2005 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2006 p2i(task_finger), HR_FORMAT_PARAMS(task_hr));
2007 }
2008 }
2009 }
2010 #endif // PRODUCT
2011
2012 void G1ConcurrentMark::rebuild_rem_set_concurrently() {
2013 _g1h->g1_rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset);
2014 }
2015
2016 void G1ConcurrentMark::print_stats() {
2017 if (!log_is_enabled(Debug, gc, stats)) {
2018 return;
2019 }
2020 log_debug(gc, stats)("---------------------------------------------------------------------");
2021 for (size_t i = 0; i < _num_active_tasks; ++i) {
2022 _tasks[i]->print_stats();
2023 log_debug(gc, stats)("---------------------------------------------------------------------");
2024 }
2025 }
2026
2027 void G1ConcurrentMark::concurrent_cycle_abort() {
2028 if (!cm_thread()->during_cycle() || _has_aborted) {
2029 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2030 return;
2031 }
2032
2033 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2034 // concurrent bitmap clearing.
2035 {
2036 GCTraceTime(Debug, gc)("Clear Next Bitmap");
2037 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false);
2038 }
2039 // Note we cannot clear the previous marking bitmap here
2040 // since VerifyDuringGC verifies the objects marked during
2041 // a full GC against the previous bitmap.
2042
2043 // Empty mark stack
2044 reset_marking_for_restart();
2045 for (uint i = 0; i < _max_num_tasks; ++i) {
2046 _tasks[i]->clear_region_fields();
2047 }
2048 _first_overflow_barrier_sync.abort();
2049 _second_overflow_barrier_sync.abort();
2050 _has_aborted = true;
2051
2052 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2053 satb_mq_set.abandon_partial_marking();
2054 // This can be called either during or outside marking, we'll read
2055 // the expected_active value from the SATB queue set.
2056 satb_mq_set.set_active_all_threads(
2057 false, /* new active value */
2058 satb_mq_set.is_active() /* expected_active */);
2059 }
2060
2061 static void print_ms_time_info(const char* prefix, const char* name,
2062 NumberSeq& ns) {
2063 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2064 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2065 if (ns.num() > 0) {
2066 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2067 prefix, ns.sd(), ns.maximum());
2068 }
2069 }
2070
2071 void G1ConcurrentMark::print_summary_info() {
2072 Log(gc, marking) log;
2073 if (!log.is_trace()) {
2074 return;
2075 }
2076
2077 log.trace(" Concurrent marking:");
2078 print_ms_time_info(" ", "init marks", _init_times);
2079 print_ms_time_info(" ", "remarks", _remark_times);
2080 {
2081 print_ms_time_info(" ", "final marks", _remark_mark_times);
2082 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2083
2084 }
2085 print_ms_time_info(" ", "cleanups", _cleanup_times);
2086 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2087 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2088 log.trace(" Total stop_world time = %8.2f s.",
2089 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2090 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2091 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum());
2092 }
2093
2094 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2095 _concurrent_workers->print_worker_threads_on(st);
2096 }
2097
2098 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2099 _concurrent_workers->threads_do(tc);
2100 }
2101
2102 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2103 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2104 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap));
2105 _prev_mark_bitmap->print_on_error(st, " Prev Bits: ");
2106 _next_mark_bitmap->print_on_error(st, " Next Bits: ");
2107 }
2108
2109 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2110 ReferenceProcessor* result = g1h->ref_processor_cm();
2111 assert(result != NULL, "CM reference processor should not be NULL");
2112 return result;
2113 }
2114
2115 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2116 G1CMTask* task)
2117 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)),
2118 _g1h(g1h), _task(task)
2119 { }
2120
2121 void G1CMTask::setup_for_region(HeapRegion* hr) {
2122 assert(hr != NULL,
2123 "claim_region() should have filtered out NULL regions");
2124 _curr_region = hr;
2125 _finger = hr->bottom();
2126 update_region_limit();
2127 }
2128
2129 void G1CMTask::update_region_limit() {
2130 HeapRegion* hr = _curr_region;
2131 HeapWord* bottom = hr->bottom();
2132 HeapWord* limit = hr->next_top_at_mark_start();
2133
2134 if (limit == bottom) {
2135 // The region was collected underneath our feet.
2136 // We set the finger to bottom to ensure that the bitmap
2137 // iteration that will follow this will not do anything.
2138 // (this is not a condition that holds when we set the region up,
2139 // as the region is not supposed to be empty in the first place)
2140 _finger = bottom;
2141 } else if (limit >= _region_limit) {
2142 assert(limit >= _finger, "peace of mind");
2143 } else {
2144 assert(limit < _region_limit, "only way to get here");
2145 // This can happen under some pretty unusual circumstances. An
2146 // evacuation pause empties the region underneath our feet (NTAMS
2147 // at bottom). We then do some allocation in the region (NTAMS
2148 // stays at bottom), followed by the region being used as a GC
2149 // alloc region (NTAMS will move to top() and the objects
2150 // originally below it will be grayed). All objects now marked in
2151 // the region are explicitly grayed, if below the global finger,
2152 // and we do not need in fact to scan anything else. So, we simply
2153 // set _finger to be limit to ensure that the bitmap iteration
2154 // doesn't do anything.
2155 _finger = limit;
2156 }
2157
2158 _region_limit = limit;
2159 }
2160
2161 void G1CMTask::giveup_current_region() {
2162 assert(_curr_region != NULL, "invariant");
2163 clear_region_fields();
2164 }
2165
2166 void G1CMTask::clear_region_fields() {
2167 // Values for these three fields that indicate that we're not
2168 // holding on to a region.
2169 _curr_region = NULL;
2170 _finger = NULL;
2171 _region_limit = NULL;
2172 }
2173
2174 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2175 if (cm_oop_closure == NULL) {
2176 assert(_cm_oop_closure != NULL, "invariant");
2177 } else {
2178 assert(_cm_oop_closure == NULL, "invariant");
2179 }
2180 _cm_oop_closure = cm_oop_closure;
2181 }
2182
2183 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
2184 guarantee(next_mark_bitmap != NULL, "invariant");
2185 _next_mark_bitmap = next_mark_bitmap;
2186 clear_region_fields();
2187
2188 _calls = 0;
2189 _elapsed_time_ms = 0.0;
2190 _termination_time_ms = 0.0;
2191 _termination_start_time_ms = 0.0;
2192
2193 _mark_stats_cache.reset();
2194 }
2195
2196 bool G1CMTask::should_exit_termination() {
2197 regular_clock_call();
2198 // This is called when we are in the termination protocol. We should
2199 // quit if, for some reason, this task wants to abort or the global
2200 // stack is not empty (this means that we can get work from it).
2201 return !_cm->mark_stack_empty() || has_aborted();
2202 }
2203
2204 void G1CMTask::reached_limit() {
2205 assert(_words_scanned >= _words_scanned_limit ||
2206 _refs_reached >= _refs_reached_limit ,
2207 "shouldn't have been called otherwise");
2208 regular_clock_call();
2209 }
2210
2211 void G1CMTask::regular_clock_call() {
2212 if (has_aborted()) {
2213 return;
2214 }
2215
2216 // First, we need to recalculate the words scanned and refs reached
2217 // limits for the next clock call.
2218 recalculate_limits();
2219
2220 // During the regular clock call we do the following
2221
2222 // (1) If an overflow has been flagged, then we abort.
2223 if (_cm->has_overflown()) {
2224 set_has_aborted();
2225 return;
2226 }
2227
2228 // If we are not concurrent (i.e. we're doing remark) we don't need
2229 // to check anything else. The other steps are only needed during
2230 // the concurrent marking phase.
2231 if (!_cm->concurrent()) {
2232 return;
2233 }
2234
2235 // (2) If marking has been aborted for Full GC, then we also abort.
2236 if (_cm->has_aborted()) {
2237 set_has_aborted();
2238 return;
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 set_has_aborted();
2248 return;
2249 }
2250
2251 // (5) We check whether we've reached our time quota. If we have,
2252 // then we abort.
2253 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2254 if (elapsed_time_ms > _time_target_ms) {
2255 set_has_aborted();
2256 _has_timed_out = true;
2257 return;
2258 }
2259
2260 // (6) Finally, we check whether there are enough completed STAB
2261 // buffers available for processing. If there are, we abort.
2262 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2263 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2264 // we do need to process SATB buffers, we'll abort and restart
2265 // the marking task to do so
2266 set_has_aborted();
2267 return;
2268 }
2269 }
2270
2271 void G1CMTask::recalculate_limits() {
2272 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2273 _words_scanned_limit = _real_words_scanned_limit;
2274
2275 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2276 _refs_reached_limit = _real_refs_reached_limit;
2277 }
2278
2279 void G1CMTask::decrease_limits() {
2280 // This is called when we believe that we're going to do an infrequent
2281 // operation which will increase the per byte scanned cost (i.e. move
2282 // entries to/from the global stack). It basically tries to decrease the
2283 // scanning limit so that the clock is called earlier.
2284
2285 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4;
2286 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4;
2287 }
2288
2289 void G1CMTask::move_entries_to_global_stack() {
2290 // Local array where we'll store the entries that will be popped
2291 // from the local queue.
2292 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2293
2294 size_t n = 0;
2295 G1TaskQueueEntry task_entry;
2296 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2297 buffer[n] = task_entry;
2298 ++n;
2299 }
2300 if (n < G1CMMarkStack::EntriesPerChunk) {
2301 buffer[n] = G1TaskQueueEntry();
2302 }
2303
2304 if (n > 0) {
2305 if (!_cm->mark_stack_push(buffer)) {
2306 set_has_aborted();
2307 }
2308 }
2309
2310 // This operation was quite expensive, so decrease the limits.
2311 decrease_limits();
2312 }
2313
2314 bool G1CMTask::get_entries_from_global_stack() {
2315 // Local array where we'll store the entries that will be popped
2316 // from the global stack.
2317 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2318
2319 if (!_cm->mark_stack_pop(buffer)) {
2320 return false;
2321 }
2322
2323 // We did actually pop at least one entry.
2324 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2325 G1TaskQueueEntry task_entry = buffer[i];
2326 if (task_entry.is_null()) {
2327 break;
2328 }
2329 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()));
2330 bool success = _task_queue->push(task_entry);
2331 // We only call this when the local queue is empty or under a
2332 // given target limit. So, we do not expect this push to fail.
2333 assert(success, "invariant");
2334 }
2335
2336 // This operation was quite expensive, so decrease the limits
2337 decrease_limits();
2338 return true;
2339 }
2340
2341 void G1CMTask::drain_local_queue(bool partially) {
2342 if (has_aborted()) {
2343 return;
2344 }
2345
2346 // Decide what the target size is, depending whether we're going to
2347 // drain it partially (so that other tasks can steal if they run out
2348 // of things to do) or totally (at the very end).
2349 size_t target_size;
2350 if (partially) {
2351 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
2352 } else {
2353 target_size = 0;
2354 }
2355
2356 if (_task_queue->size() > target_size) {
2357 G1TaskQueueEntry entry;
2358 bool ret = _task_queue->pop_local(entry);
2359 while (ret) {
2360 scan_task_entry(entry);
2361 if (_task_queue->size() <= target_size || has_aborted()) {
2362 ret = false;
2363 } else {
2364 ret = _task_queue->pop_local(entry);
2365 }
2366 }
2367 }
2368 }
2369
2370 void G1CMTask::drain_global_stack(bool partially) {
2371 if (has_aborted()) {
2372 return;
2373 }
2374
2375 // We have a policy to drain the local queue before we attempt to
2376 // drain the global stack.
2377 assert(partially || _task_queue->size() == 0, "invariant");
2378
2379 // Decide what the target size is, depending whether we're going to
2380 // drain it partially (so that other tasks can steal if they run out
2381 // of things to do) or totally (at the very end).
2382 // Notice that when draining the global mark stack partially, due to the racyness
2383 // of the mark stack size update we might in fact drop below the target. But,
2384 // this is not a problem.
2385 // In case of total draining, we simply process until the global mark stack is
2386 // totally empty, disregarding the size counter.
2387 if (partially) {
2388 size_t const target_size = _cm->partial_mark_stack_size_target();
2389 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2390 if (get_entries_from_global_stack()) {
2391 drain_local_queue(partially);
2392 }
2393 }
2394 } else {
2395 while (!has_aborted() && get_entries_from_global_stack()) {
2396 drain_local_queue(partially);
2397 }
2398 }
2399 }
2400
2401 // SATB Queue has several assumptions on whether to call the par or
2402 // non-par versions of the methods. this is why some of the code is
2403 // replicated. We should really get rid of the single-threaded version
2404 // of the code to simplify things.
2405 void G1CMTask::drain_satb_buffers() {
2406 if (has_aborted()) {
2407 return;
2408 }
2409
2410 // We set this so that the regular clock knows that we're in the
2411 // middle of draining buffers and doesn't set the abort flag when it
2412 // notices that SATB buffers are available for draining. It'd be
2413 // very counter productive if it did that. :-)
2414 _draining_satb_buffers = true;
2415
2416 G1CMSATBBufferClosure satb_cl(this, _g1h);
2417 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2418
2419 // This keeps claiming and applying the closure to completed buffers
2420 // until we run out of buffers or we need to abort.
2421 while (!has_aborted() &&
2422 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2423 regular_clock_call();
2424 }
2425
2426 _draining_satb_buffers = false;
2427
2428 assert(has_aborted() ||
2429 _cm->concurrent() ||
2430 satb_mq_set.completed_buffers_num() == 0, "invariant");
2431
2432 // again, this was a potentially expensive operation, decrease the
2433 // limits to get the regular clock call early
2434 decrease_limits();
2435 }
2436
2437 void G1CMTask::clear_mark_stats_cache(uint region_idx) {
2438 _mark_stats_cache.reset(region_idx);
2439 }
2440
2441 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() {
2442 return _mark_stats_cache.evict_all();
2443 }
2444
2445 void G1CMTask::print_stats() {
2446 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls);
2447 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2448 _elapsed_time_ms, _termination_time_ms);
2449 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms",
2450 _step_times_ms.num(),
2451 _step_times_ms.avg(),
2452 _step_times_ms.sd(),
2453 _step_times_ms.maximum(),
2454 _step_times_ms.sum());
2455 size_t const hits = _mark_stats_cache.hits();
2456 size_t const misses = _mark_stats_cache.misses();
2457 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f",
2458 hits, misses, percent_of(hits, hits + misses));
2459 }
2460
2461 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry) {
2462 return _task_queues->steal(worker_id, hash_seed, task_entry);
2463 }
2464
2465 /*****************************************************************************
2466
2467 The do_marking_step(time_target_ms, ...) method is the building
2468 block of the parallel marking framework. It can be called in parallel
2469 with other invocations of do_marking_step() on different tasks
2470 (but only one per task, obviously) and concurrently with the
2471 mutator threads, or during remark, hence it eliminates the need
2472 for two versions of the code. When called during remark, it will
2473 pick up from where the task left off during the concurrent marking
2474 phase. Interestingly, tasks are also claimable during evacuation
2475 pauses too, since do_marking_step() ensures that it aborts before
2476 it needs to yield.
2477
2478 The data structures that it uses to do marking work are the
2479 following:
2480
2481 (1) Marking Bitmap. If there are gray objects that appear only
2482 on the bitmap (this happens either when dealing with an overflow
2483 or when the initial marking phase has simply marked the roots
2484 and didn't push them on the stack), then tasks claim heap
2485 regions whose bitmap they then scan to find gray objects. A
2486 global finger indicates where the end of the last claimed region
2487 is. A local finger indicates how far into the region a task has
2488 scanned. The two fingers are used to determine how to gray an
2489 object (i.e. whether simply marking it is OK, as it will be
2490 visited by a task in the future, or whether it needs to be also
2491 pushed on a stack).
2492
2493 (2) Local Queue. The local queue of the task which is accessed
2494 reasonably efficiently by the task. Other tasks can steal from
2495 it when they run out of work. Throughout the marking phase, a
2496 task attempts to keep its local queue short but not totally
2497 empty, so that entries are available for stealing by other
2498 tasks. Only when there is no more work, a task will totally
2499 drain its local queue.
2500
2501 (3) Global Mark Stack. This handles local queue overflow. During
2502 marking only sets of entries are moved between it and the local
2503 queues, as access to it requires a mutex and more fine-grain
2504 interaction with it which might cause contention. If it
2505 overflows, then the marking phase should restart and iterate
2506 over the bitmap to identify gray objects. Throughout the marking
2507 phase, tasks attempt to keep the global mark stack at a small
2508 length but not totally empty, so that entries are available for
2509 popping by other tasks. Only when there is no more work, tasks
2510 will totally drain the global mark stack.
2511
2512 (4) SATB Buffer Queue. This is where completed SATB buffers are
2513 made available. Buffers are regularly removed from this queue
2514 and scanned for roots, so that the queue doesn't get too
2515 long. During remark, all completed buffers are processed, as
2516 well as the filled in parts of any uncompleted buffers.
2517
2518 The do_marking_step() method tries to abort when the time target
2519 has been reached. There are a few other cases when the
2520 do_marking_step() method also aborts:
2521
2522 (1) When the marking phase has been aborted (after a Full GC).
2523
2524 (2) When a global overflow (on the global stack) has been
2525 triggered. Before the task aborts, it will actually sync up with
2526 the other tasks to ensure that all the marking data structures
2527 (local queues, stacks, fingers etc.) are re-initialized so that
2528 when do_marking_step() completes, the marking phase can
2529 immediately restart.
2530
2531 (3) When enough completed SATB buffers are available. The
2532 do_marking_step() method only tries to drain SATB buffers right
2533 at the beginning. So, if enough buffers are available, the
2534 marking step aborts and the SATB buffers are processed at
2535 the beginning of the next invocation.
2536
2537 (4) To yield. when we have to yield then we abort and yield
2538 right at the end of do_marking_step(). This saves us from a lot
2539 of hassle as, by yielding we might allow a Full GC. If this
2540 happens then objects will be compacted underneath our feet, the
2541 heap might shrink, etc. We save checking for this by just
2542 aborting and doing the yield right at the end.
2543
2544 From the above it follows that the do_marking_step() method should
2545 be called in a loop (or, otherwise, regularly) until it completes.
2546
2547 If a marking step completes without its has_aborted() flag being
2548 true, it means it has completed the current marking phase (and
2549 also all other marking tasks have done so and have all synced up).
2550
2551 A method called regular_clock_call() is invoked "regularly" (in
2552 sub ms intervals) throughout marking. It is this clock method that
2553 checks all the abort conditions which were mentioned above and
2554 decides when the task should abort. A work-based scheme is used to
2555 trigger this clock method: when the number of object words the
2556 marking phase has scanned or the number of references the marking
2557 phase has visited reach a given limit. Additional invocations to
2558 the method clock have been planted in a few other strategic places
2559 too. The initial reason for the clock method was to avoid calling
2560 vtime too regularly, as it is quite expensive. So, once it was in
2561 place, it was natural to piggy-back all the other conditions on it
2562 too and not constantly check them throughout the code.
2563
2564 If do_termination is true then do_marking_step will enter its
2565 termination protocol.
2566
2567 The value of is_serial must be true when do_marking_step is being
2568 called serially (i.e. by the VMThread) and do_marking_step should
2569 skip any synchronization in the termination and overflow code.
2570 Examples include the serial remark code and the serial reference
2571 processing closures.
2572
2573 The value of is_serial must be false when do_marking_step is
2574 being called by any of the worker threads in a work gang.
2575 Examples include the concurrent marking code (CMMarkingTask),
2576 the MT remark code, and the MT reference processing closures.
2577
2578 *****************************************************************************/
2579
2580 void G1CMTask::do_marking_step(double time_target_ms,
2581 bool do_termination,
2582 bool is_serial) {
2583 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2584
2585 _start_time_ms = os::elapsedVTime() * 1000.0;
2586
2587 // If do_stealing is true then do_marking_step will attempt to
2588 // steal work from the other G1CMTasks. It only makes sense to
2589 // enable stealing when the termination protocol is enabled
2590 // and do_marking_step() is not being called serially.
2591 bool do_stealing = do_termination && !is_serial;
2592
2593 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_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 regular_clock_call();
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 regular_clock_call();
2676 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
2677 giveup_current_region();
2678 regular_clock_call();
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 regular_clock_call();
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, &_hash_seed, 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 } else {
2812 // Apparently there's more work to do. Let's abort this task. It
2813 // will restart it and we can hopefully find more things to do.
2814 set_has_aborted();
2815 }
2816 }
2817
2818 // Mainly for debugging purposes to make sure that a pointer to the
2819 // closure which was statically allocated in this frame doesn't
2820 // escape it by accident.
2821 set_cm_oop_closure(NULL);
2822 double end_time_ms = os::elapsedVTime() * 1000.0;
2823 double elapsed_time_ms = end_time_ms - _start_time_ms;
2824 // Update the step history.
2825 _step_times_ms.add(elapsed_time_ms);
2826
2827 if (has_aborted()) {
2828 // The task was aborted for some reason.
2829 if (_has_timed_out) {
2830 double diff_ms = elapsed_time_ms - _time_target_ms;
2831 // Keep statistics of how well we did with respect to hitting
2832 // our target only if we actually timed out (if we aborted for
2833 // other reasons, then the results might get skewed).
2834 _marking_step_diffs_ms.add(diff_ms);
2835 }
2836
2837 if (_cm->has_overflown()) {
2838 // This is the interesting one. We aborted because a global
2839 // overflow was raised. This means we have to restart the
2840 // marking phase and start iterating over regions. However, in
2841 // order to do this we have to make sure that all tasks stop
2842 // what they are doing and re-initialize in a safe manner. We
2843 // will achieve this with the use of two barrier sync points.
2844
2845 if (!is_serial) {
2846 // We only need to enter the sync barrier if being called
2847 // from a parallel context
2848 _cm->enter_first_sync_barrier(_worker_id);
2849
2850 // When we exit this sync barrier we know that all tasks have
2851 // stopped doing marking work. So, it's now safe to
2852 // re-initialize our data structures.
2853 }
2854
2855 clear_region_fields();
2856 flush_mark_stats_cache();
2857
2858 if (!is_serial) {
2859 // If we're executing the concurrent phase of marking, reset the marking
2860 // state; otherwise the marking state is reset after reference processing,
2861 // during the remark pause.
2862 // If we reset here as a result of an overflow during the remark we will
2863 // see assertion failures from any subsequent set_concurrency_and_phase()
2864 // calls.
2865 if (_cm->concurrent() && _worker_id == 0) {
2866 // Worker 0 is responsible for clearing the global data structures because
2867 // of an overflow. During STW we should not clear the overflow flag (in
2868 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit
2869 // method to abort the pause and restart concurrent marking.
2870 _cm->reset_marking_for_restart();
2871
2872 log_info(gc, marking)("Concurrent Mark reset for overflow");
2873 }
2874
2875 // ...and enter the second barrier.
2876 _cm->enter_second_sync_barrier(_worker_id);
2877 }
2878 // At this point, if we're during the concurrent phase of
2879 // marking, everything has been re-initialized and we're
2880 // ready to restart.
2881 }
2882 }
2883 }
2884
2885 G1CMTask::G1CMTask(uint worker_id,
2886 G1ConcurrentMark* cm,
2887 G1CMTaskQueue* task_queue,
2888 G1RegionMarkStats* mark_stats,
2889 uint max_regions) :
2890 _objArray_processor(this),
2891 _worker_id(worker_id),
2892 _g1h(G1CollectedHeap::heap()),
2893 _cm(cm),
2894 _next_mark_bitmap(NULL),
2895 _task_queue(task_queue),
2896 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize),
2897 _calls(0),
2898 _time_target_ms(0.0),
2899 _start_time_ms(0.0),
2900 _cm_oop_closure(NULL),
2901 _curr_region(NULL),
2902 _finger(NULL),
2903 _region_limit(NULL),
2904 _words_scanned(0),
2905 _words_scanned_limit(0),
2906 _real_words_scanned_limit(0),
2907 _refs_reached(0),
2908 _refs_reached_limit(0),
2909 _real_refs_reached_limit(0),
2910 _hash_seed(17),
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_diffs_ms()
2919 {
2920 guarantee(task_queue != NULL, "invariant");
2921
2922 _marking_step_diffs_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 }