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/g1BarrierSet.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1CollectorState.hpp"
32 #include "gc/g1/g1ConcurrentMark.inline.hpp"
33 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/g1ThreadLocalData.hpp"
40 #include "gc/g1/heapRegion.inline.hpp"
41 #include "gc/g1/heapRegionRemSet.hpp"
42 #include "gc/g1/heapRegionSet.inline.hpp"
43 #include "gc/shared/adaptiveSizePolicy.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTrace.hpp"
47 #include "gc/shared/gcTraceTime.inline.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/suspendibleThreadSet.hpp"
52 #include "gc/shared/taskqueue.inline.hpp"
53 #include "gc/shared/vmGCOperations.hpp"
54 #include "gc/shared/weakProcessor.hpp"
55 #include "include/jvm.h"
56 #include "logging/log.hpp"
57 #include "memory/allocation.hpp"
58 #include "memory/resourceArea.hpp"
59 #include "oops/access.inline.hpp"
60 #include "oops/oop.inline.hpp"
61 #include "runtime/atomic.hpp"
62 #include "runtime/handles.inline.hpp"
63 #include "runtime/java.hpp"
64 #include "runtime/prefetch.inline.hpp"
65 #include "services/memTracker.hpp"
66 #include "utilities/align.hpp"
67 #include "utilities/growableArray.hpp"
68
69 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
70 assert(addr < _cm->finger(), "invariant");
71 assert(addr >= _task->finger(), "invariant");
72
73 // We move that task's local finger along.
74 _task->move_finger_to(addr);
75
76 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
77 // we only partially drain the local queue and global stack
78 _task->drain_local_queue(true);
79 _task->drain_global_stack(true);
80
81 // if the has_aborted flag has been raised, we need to bail out of
82 // the iteration
83 return !_task->has_aborted();
84 }
85
86 G1CMMarkStack::G1CMMarkStack() :
87 _max_chunk_capacity(0),
88 _base(NULL),
89 _chunk_capacity(0) {
90 set_empty();
91 }
92
93 bool G1CMMarkStack::resize(size_t new_capacity) {
94 assert(is_empty(), "Only resize when stack is empty.");
95 assert(new_capacity <= _max_chunk_capacity,
96 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
97
98 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
99
100 if (new_base == NULL) {
101 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));
102 return false;
103 }
104 // Release old mapping.
105 if (_base != NULL) {
106 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
107 }
108
109 _base = new_base;
110 _chunk_capacity = new_capacity;
111 set_empty();
112
113 return true;
114 }
115
116 size_t G1CMMarkStack::capacity_alignment() {
117 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
118 }
119
120 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
121 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
122
123 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
124
125 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
126 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
127
128 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
129 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
130 _max_chunk_capacity,
131 initial_chunk_capacity);
132
133 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
134 initial_chunk_capacity, _max_chunk_capacity);
135
136 return resize(initial_chunk_capacity);
137 }
138
139 void G1CMMarkStack::expand() {
140 if (_chunk_capacity == _max_chunk_capacity) {
141 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
142 return;
143 }
144 size_t old_capacity = _chunk_capacity;
145 // Double capacity if possible
146 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
147
148 if (resize(new_capacity)) {
149 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
150 old_capacity, new_capacity);
151 } else {
152 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
153 old_capacity, new_capacity);
154 }
155 }
156
157 G1CMMarkStack::~G1CMMarkStack() {
158 if (_base != NULL) {
159 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
160 }
161 }
162
163 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
164 elem->next = *list;
165 *list = elem;
166 }
167
168 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
169 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
170 add_chunk_to_list(&_chunk_list, elem);
171 _chunks_in_chunk_list++;
172 }
173
174 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
175 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
176 add_chunk_to_list(&_free_list, elem);
177 }
178
179 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
180 TaskQueueEntryChunk* result = *list;
181 if (result != NULL) {
182 *list = (*list)->next;
183 }
184 return result;
185 }
186
187 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
188 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
189 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
190 if (result != NULL) {
191 _chunks_in_chunk_list--;
192 }
193 return result;
194 }
195
196 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
197 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
198 return remove_chunk_from_list(&_free_list);
199 }
200
201 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
202 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
203 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
204 // wraparound of _hwm.
205 if (_hwm >= _chunk_capacity) {
206 return NULL;
207 }
208
209 size_t cur_idx = Atomic::add(1u, &_hwm) - 1;
210 if (cur_idx >= _chunk_capacity) {
211 return NULL;
212 }
213
214 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
215 result->next = NULL;
216 return result;
217 }
218
219 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
220 // Get a new chunk.
221 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
222
223 if (new_chunk == NULL) {
224 // Did not get a chunk from the free list. Allocate from backing memory.
225 new_chunk = allocate_new_chunk();
226
227 if (new_chunk == NULL) {
228 return false;
229 }
230 }
231
232 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
233
234 add_chunk_to_chunk_list(new_chunk);
235
236 return true;
237 }
238
239 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
240 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
241
242 if (cur == NULL) {
243 return false;
244 }
245
246 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
247
248 add_chunk_to_free_list(cur);
249 return true;
250 }
251
252 void G1CMMarkStack::set_empty() {
253 _chunks_in_chunk_list = 0;
254 _hwm = 0;
255 _chunk_list = NULL;
256 _free_list = NULL;
257 }
258
259 G1CMRootRegions::G1CMRootRegions() :
260 _survivors(NULL), _cm(NULL), _scan_in_progress(false),
261 _should_abort(false), _claimed_survivor_index(0) { }
262
263 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) {
264 _survivors = survivors;
265 _cm = cm;
266 }
267
268 void G1CMRootRegions::prepare_for_scan() {
269 assert(!scan_in_progress(), "pre-condition");
270
271 // Currently, only survivors can be root regions.
272 _claimed_survivor_index = 0;
273 _scan_in_progress = _survivors->regions()->is_nonempty();
274 _should_abort = false;
275 }
276
277 HeapRegion* G1CMRootRegions::claim_next() {
278 if (_should_abort) {
279 // If someone has set the should_abort flag, we return NULL to
280 // force the caller to bail out of their loop.
281 return NULL;
282 }
283
284 // Currently, only survivors can be root regions.
285 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions();
286
287 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1;
288 if (claimed_index < survivor_regions->length()) {
289 return survivor_regions->at(claimed_index);
290 }
291 return NULL;
292 }
293
294 uint G1CMRootRegions::num_root_regions() const {
295 return (uint)_survivors->regions()->length();
296 }
297
298 void G1CMRootRegions::notify_scan_done() {
299 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
300 _scan_in_progress = false;
301 RootRegionScan_lock->notify_all();
302 }
303
304 void G1CMRootRegions::cancel_scan() {
305 notify_scan_done();
306 }
307
308 void G1CMRootRegions::scan_finished() {
309 assert(scan_in_progress(), "pre-condition");
310
311 // Currently, only survivors can be root regions.
312 if (!_should_abort) {
313 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index);
314 assert((uint)_claimed_survivor_index >= _survivors->length(),
315 "we should have claimed all survivors, claimed index = %u, length = %u",
316 (uint)_claimed_survivor_index, _survivors->length());
317 }
318
319 notify_scan_done();
320 }
321
322 bool G1CMRootRegions::wait_until_scan_finished() {
323 if (!scan_in_progress()) {
324 return false;
325 }
326
327 {
328 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
329 while (scan_in_progress()) {
330 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
331 }
332 }
333 return true;
334 }
335
336 // Returns the maximum number of workers to be used in a concurrent
337 // phase based on the number of GC workers being used in a STW
338 // phase.
339 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
340 return MAX2((num_gc_workers + 2) / 4, 1U);
341 }
342
343 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
344 G1RegionToSpaceMapper* prev_bitmap_storage,
345 G1RegionToSpaceMapper* next_bitmap_storage) :
346 // _cm_thread set inside the constructor
347 _g1h(g1h),
348 _completed_initialization(false),
349
350 _mark_bitmap_1(),
351 _mark_bitmap_2(),
352 _prev_mark_bitmap(&_mark_bitmap_1),
353 _next_mark_bitmap(&_mark_bitmap_2),
354
355 _heap(_g1h->reserved_region()),
356
357 _root_regions(),
358
359 _global_mark_stack(),
360
361 // _finger set in set_non_marking_state
362
363 _worker_id_offset(DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
364 _max_num_tasks(ParallelGCThreads),
365 // _num_active_tasks set in set_non_marking_state()
366 // _tasks set inside the constructor
367
368 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
369 _terminator(ParallelTaskTerminator((int) _max_num_tasks, _task_queues)),
370
371 _first_overflow_barrier_sync(),
372 _second_overflow_barrier_sync(),
373
374 _has_overflown(false),
375 _concurrent(false),
376 _has_aborted(false),
377 _restart_for_overflow(false),
378 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
379 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
380
381 // _verbose_level set below
382
383 _init_times(),
384 _remark_times(),
385 _remark_mark_times(),
386 _remark_weak_ref_times(),
387 _cleanup_times(),
388 _total_cleanup_time(0.0),
389
390 _accum_task_vtime(NULL),
391
392 _concurrent_workers(NULL),
393 _num_concurrent_workers(0),
394 _max_concurrent_workers(0),
395
396 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
397 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
398 {
399 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
400 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
401
402 // Create & start ConcurrentMark thread.
403 _cm_thread = new G1ConcurrentMarkThread(this);
404 if (_cm_thread->osthread() == NULL) {
405 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
406 }
407
408 assert(CGC_lock != NULL, "CGC_lock must be initialized");
409
410 SATBMarkQueueSet& satb_qs = G1BarrierSet::satb_mark_queue_set();
411 satb_qs.set_buffer_size(G1SATBBufferSize);
412
413 _root_regions.init(_g1h->survivor(), this);
414
415 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
416 // Calculate the number of concurrent worker threads by scaling
417 // the number of parallel GC threads.
418 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
419 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
420 }
421
422 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
423 if (ConcGCThreads > ParallelGCThreads) {
424 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
425 ConcGCThreads, ParallelGCThreads);
426 return;
427 }
428
429 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
430 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
431
432 _num_concurrent_workers = ConcGCThreads;
433 _max_concurrent_workers = _num_concurrent_workers;
434
435 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
436 _concurrent_workers->initialize_workers();
437
438 if (FLAG_IS_DEFAULT(MarkStackSize)) {
439 size_t mark_stack_size =
440 MIN2(MarkStackSizeMax,
441 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
442 // Verify that the calculated value for MarkStackSize is in range.
443 // It would be nice to use the private utility routine from Arguments.
444 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
445 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
446 "must be between 1 and " SIZE_FORMAT,
447 mark_stack_size, MarkStackSizeMax);
448 return;
449 }
450 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
451 } else {
452 // Verify MarkStackSize is in range.
453 if (FLAG_IS_CMDLINE(MarkStackSize)) {
454 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
455 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
456 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
457 "must be between 1 and " SIZE_FORMAT,
458 MarkStackSize, MarkStackSizeMax);
459 return;
460 }
461 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
462 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
463 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
464 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
465 MarkStackSize, MarkStackSizeMax);
466 return;
467 }
468 }
469 }
470 }
471
472 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
473 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
474 }
475
476 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
477 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
478
479 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
480 _num_active_tasks = _max_num_tasks;
481
482 for (uint i = 0; i < _max_num_tasks; ++i) {
483 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
484 task_queue->initialize();
485 _task_queues->register_queue(i, task_queue);
486
487 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
488
489 _accum_task_vtime[i] = 0.0;
490 }
491
492 reset_at_marking_complete();
493 _completed_initialization = true;
494 }
495
496 void G1ConcurrentMark::reset() {
497 _has_aborted = false;
498
499 reset_marking_for_restart();
500
501 // Reset all tasks, since different phases will use different number of active
502 // threads. So, it's easiest to have all of them ready.
503 for (uint i = 0; i < _max_num_tasks; ++i) {
504 _tasks[i]->reset(_next_mark_bitmap);
505 }
506
507 uint max_regions = _g1h->max_regions();
508 for (uint i = 0; i < max_regions; i++) {
509 _top_at_rebuild_starts[i] = NULL;
510 _region_mark_stats[i].clear();
511 }
512 }
513
514 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
515 for (uint j = 0; j < _max_num_tasks; ++j) {
516 _tasks[j]->clear_mark_stats_cache(region_idx);
517 }
518 _top_at_rebuild_starts[region_idx] = NULL;
519 _region_mark_stats[region_idx].clear();
520 }
521
522 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
523 uint const region_idx = r->hrm_index();
524 if (r->is_humongous()) {
525 assert(r->is_starts_humongous(), "Got humongous continues region here");
526 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
527 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
528 clear_statistics_in_region(j);
529 }
530 } else {
531 clear_statistics_in_region(region_idx);
532 }
533 }
534
535 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
536 if (bitmap->is_marked(addr)) {
537 bitmap->clear(addr);
538 }
539 }
540
541 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
542 assert_at_safepoint_on_vm_thread();
543
544 // Need to clear all mark bits of the humongous object.
545 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
546 clear_mark_if_set(_next_mark_bitmap, r->bottom());
547
548 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
549 return;
550 }
551
552 // Clear any statistics about the region gathered so far.
553 clear_statistics(r);
554 }
555
556 void G1ConcurrentMark::reset_marking_for_restart() {
557 _global_mark_stack.set_empty();
558
559 // Expand the marking stack, if we have to and if we can.
560 if (has_overflown()) {
561 _global_mark_stack.expand();
562
563 uint max_regions = _g1h->max_regions();
564 for (uint i = 0; i < max_regions; i++) {
565 _region_mark_stats[i].clear_during_overflow();
566 }
567 }
568
569 clear_has_overflown();
570 _finger = _heap.start();
571
572 for (uint i = 0; i < _max_num_tasks; ++i) {
573 G1CMTaskQueue* queue = _task_queues->queue(i);
574 queue->set_empty();
575 }
576 }
577
578 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
579 assert(active_tasks <= _max_num_tasks, "we should not have more");
580
581 _num_active_tasks = active_tasks;
582 // Need to update the three data structures below according to the
583 // number of active threads for this phase.
584 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
585 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
586 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
587 }
588
589 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
590 set_concurrency(active_tasks);
591
592 _concurrent = concurrent;
593
594 if (!concurrent) {
595 // At this point we should be in a STW phase, and completed marking.
596 assert_at_safepoint_on_vm_thread();
597 assert(out_of_regions(),
598 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
599 p2i(_finger), p2i(_heap.end()));
600 }
601 }
602
603 void G1ConcurrentMark::reset_at_marking_complete() {
604 // We set the global marking state to some default values when we're
605 // not doing marking.
606 reset_marking_for_restart();
607 _num_active_tasks = 0;
608 }
609
610 G1ConcurrentMark::~G1ConcurrentMark() {
611 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
612 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
613 // The G1ConcurrentMark instance is never freed.
614 ShouldNotReachHere();
615 }
616
617 class G1ClearBitMapTask : public AbstractGangTask {
618 public:
619 static size_t chunk_size() { return M; }
620
621 private:
622 // Heap region closure used for clearing the given mark bitmap.
623 class G1ClearBitmapHRClosure : public HeapRegionClosure {
624 private:
625 G1CMBitMap* _bitmap;
626 G1ConcurrentMark* _cm;
627 public:
628 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
629 }
630
631 virtual bool do_heap_region(HeapRegion* r) {
632 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
633
634 HeapWord* cur = r->bottom();
635 HeapWord* const end = r->end();
636
637 while (cur < end) {
638 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
639 _bitmap->clear_range(mr);
640
641 cur += chunk_size_in_words;
642
643 // Abort iteration if after yielding the marking has been aborted.
644 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
645 return true;
646 }
647 // Repeat the asserts from before the start of the closure. We will do them
648 // as asserts here to minimize their overhead on the product. However, we
649 // will have them as guarantees at the beginning / end of the bitmap
650 // clearing to get some checking in the product.
651 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
652 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
653 }
654 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
655
656 return false;
657 }
658 };
659
660 G1ClearBitmapHRClosure _cl;
661 HeapRegionClaimer _hr_claimer;
662 bool _suspendible; // If the task is suspendible, workers must join the STS.
663
664 public:
665 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
666 AbstractGangTask("G1 Clear Bitmap"),
667 _cl(bitmap, suspendible ? cm : NULL),
668 _hr_claimer(n_workers),
669 _suspendible(suspendible)
670 { }
671
672 void work(uint worker_id) {
673 SuspendibleThreadSetJoiner sts_join(_suspendible);
674 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
675 }
676
677 bool is_complete() {
678 return _cl.is_complete();
679 }
680 };
681
682 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
683 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
684
685 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
686 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
687
688 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
689
690 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
691
692 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
693 workers->run_task(&cl, num_workers);
694 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
695 }
696
697 void G1ConcurrentMark::cleanup_for_next_mark() {
698 // Make sure that the concurrent mark thread looks to still be in
699 // the current cycle.
700 guarantee(cm_thread()->during_cycle(), "invariant");
701
702 // We are finishing up the current cycle by clearing the next
703 // marking bitmap and getting it ready for the next cycle. During
704 // this time no other cycle can start. So, let's make sure that this
705 // is the case.
706 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
707
708 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
709
710 // Repeat the asserts from above.
711 guarantee(cm_thread()->during_cycle(), "invariant");
712 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
713 }
714
715 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
716 assert_at_safepoint_on_vm_thread();
717 clear_bitmap(_prev_mark_bitmap, workers, false);
718 }
719
720 class CheckBitmapClearHRClosure : public HeapRegionClosure {
721 G1CMBitMap* _bitmap;
722 public:
723 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
724 }
725
726 virtual bool do_heap_region(HeapRegion* r) {
727 // This closure can be called concurrently to the mutator, so we must make sure
728 // that the result of the getNextMarkedWordAddress() call is compared to the
729 // value passed to it as limit to detect any found bits.
730 // end never changes in G1.
731 HeapWord* end = r->end();
732 return _bitmap->get_next_marked_addr(r->bottom(), end) != end;
733 }
734 };
735
736 bool G1ConcurrentMark::next_mark_bitmap_is_clear() {
737 CheckBitmapClearHRClosure cl(_next_mark_bitmap);
738 _g1h->heap_region_iterate(&cl);
739 return cl.is_complete();
740 }
741
742 class NoteStartOfMarkHRClosure : public HeapRegionClosure {
743 public:
744 bool do_heap_region(HeapRegion* r) {
745 r->note_start_of_marking();
746 return false;
747 }
748 };
749
750 void G1ConcurrentMark::pre_initial_mark() {
751 // Initialize marking structures. This has to be done in a STW phase.
752 reset();
753
754 // For each region note start of marking.
755 NoteStartOfMarkHRClosure startcl;
756 _g1h->heap_region_iterate(&startcl);
757 }
758
759
760 void G1ConcurrentMark::post_initial_mark() {
761 // Start Concurrent Marking weak-reference discovery.
762 ReferenceProcessor* rp = _g1h->ref_processor_cm();
763 // enable ("weak") refs discovery
764 rp->enable_discovery();
765 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
766
767 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
768 // This is the start of the marking cycle, we're expected all
769 // threads to have SATB queues with active set to false.
770 satb_mq_set.set_active_all_threads(true, /* new active value */
771 false /* expected_active */);
772
773 _root_regions.prepare_for_scan();
774
775 // update_g1_committed() will be called at the end of an evac pause
776 // when marking is on. So, it's also called at the end of the
777 // initial-mark pause to update the heap end, if the heap expands
778 // during it. No need to call it here.
779 }
780
781 /*
782 * Notice that in the next two methods, we actually leave the STS
783 * during the barrier sync and join it immediately afterwards. If we
784 * do not do this, the following deadlock can occur: one thread could
785 * be in the barrier sync code, waiting for the other thread to also
786 * sync up, whereas another one could be trying to yield, while also
787 * waiting for the other threads to sync up too.
788 *
789 * Note, however, that this code is also used during remark and in
790 * this case we should not attempt to leave / enter the STS, otherwise
791 * we'll either hit an assert (debug / fastdebug) or deadlock
792 * (product). So we should only leave / enter the STS if we are
793 * operating concurrently.
794 *
795 * Because the thread that does the sync barrier has left the STS, it
796 * is possible to be suspended for a Full GC or an evacuation pause
797 * could occur. This is actually safe, since the entering the sync
798 * barrier is one of the last things do_marking_step() does, and it
799 * doesn't manipulate any data structures afterwards.
800 */
801
802 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
803 bool barrier_aborted;
804 {
805 SuspendibleThreadSetLeaver sts_leave(concurrent());
806 barrier_aborted = !_first_overflow_barrier_sync.enter();
807 }
808
809 // at this point everyone should have synced up and not be doing any
810 // more work
811
812 if (barrier_aborted) {
813 // If the barrier aborted we ignore the overflow condition and
814 // just abort the whole marking phase as quickly as possible.
815 return;
816 }
817 }
818
819 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
820 SuspendibleThreadSetLeaver sts_leave(concurrent());
821 _second_overflow_barrier_sync.enter();
822
823 // at this point everything should be re-initialized and ready to go
824 }
825
826 class G1CMConcurrentMarkingTask : public AbstractGangTask {
827 G1ConcurrentMark* _cm;
828
829 public:
830 void work(uint worker_id) {
831 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
832 ResourceMark rm;
833
834 double start_vtime = os::elapsedVTime();
835
836 {
837 SuspendibleThreadSetJoiner sts_join;
838
839 assert(worker_id < _cm->active_tasks(), "invariant");
840
841 G1CMTask* task = _cm->task(worker_id);
842 task->record_start_time();
843 if (!_cm->has_aborted()) {
844 do {
845 task->do_marking_step(G1ConcMarkStepDurationMillis,
846 true /* do_termination */,
847 false /* is_serial*/);
848
849 _cm->do_yield_check();
850 } while (!_cm->has_aborted() && task->has_aborted());
851 }
852 task->record_end_time();
853 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
854 }
855
856 double end_vtime = os::elapsedVTime();
857 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
858 }
859
860 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
861 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
862
863 ~G1CMConcurrentMarkingTask() { }
864 };
865
866 uint G1ConcurrentMark::calc_active_marking_workers() {
867 uint result = 0;
868 if (!UseDynamicNumberOfGCThreads ||
869 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
870 !ForceDynamicNumberOfGCThreads)) {
871 result = _max_concurrent_workers;
872 } else {
873 result =
874 AdaptiveSizePolicy::calc_default_active_workers(_max_concurrent_workers,
875 1, /* Minimum workers */
876 _num_concurrent_workers,
877 Threads::number_of_non_daemon_threads());
878 // Don't scale the result down by scale_concurrent_workers() because
879 // that scaling has already gone into "_max_concurrent_workers".
880 }
881 assert(result > 0 && result <= _max_concurrent_workers,
882 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
883 _max_concurrent_workers, result);
884 return result;
885 }
886
887 void G1ConcurrentMark::scan_root_region(HeapRegion* hr, uint worker_id) {
888 // Currently, only survivors can be root regions.
889 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
890 G1RootRegionScanClosure cl(_g1h, this, worker_id);
891
892 const uintx interval = PrefetchScanIntervalInBytes;
893 HeapWord* curr = hr->bottom();
894 const HeapWord* end = hr->top();
895 while (curr < end) {
896 Prefetch::read(curr, interval);
897 oop obj = oop(curr);
898 int size = obj->oop_iterate_size(&cl);
899 assert(size == obj->size(), "sanity");
900 curr += size;
901 }
902 }
903
904 class G1CMRootRegionScanTask : public AbstractGangTask {
905 G1ConcurrentMark* _cm;
906 public:
907 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
908 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
909
910 void work(uint worker_id) {
911 assert(Thread::current()->is_ConcurrentGC_thread(),
912 "this should only be done by a conc GC thread");
913
914 G1CMRootRegions* root_regions = _cm->root_regions();
915 HeapRegion* hr = root_regions->claim_next();
916 while (hr != NULL) {
917 _cm->scan_root_region(hr, worker_id);
918 hr = root_regions->claim_next();
919 }
920 }
921 };
922
923 void G1ConcurrentMark::scan_root_regions() {
924 // scan_in_progress() will have been set to true only if there was
925 // at least one root region to scan. So, if it's false, we
926 // should not attempt to do any further work.
927 if (root_regions()->scan_in_progress()) {
928 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
929
930 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
931 // We distribute work on a per-region basis, so starting
932 // more threads than that is useless.
933 root_regions()->num_root_regions());
934 assert(_num_concurrent_workers <= _max_concurrent_workers,
935 "Maximum number of marking threads exceeded");
936
937 G1CMRootRegionScanTask task(this);
938 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
939 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
940 _concurrent_workers->run_task(&task, _num_concurrent_workers);
941
942 // It's possible that has_aborted() is true here without actually
943 // aborting the survivor scan earlier. This is OK as it's
944 // mainly used for sanity checking.
945 root_regions()->scan_finished();
946 }
947 }
948
949 void G1ConcurrentMark::concurrent_cycle_start() {
950 _gc_timer_cm->register_gc_start();
951
952 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
953
954 _g1h->trace_heap_before_gc(_gc_tracer_cm);
955 }
956
957 void G1ConcurrentMark::concurrent_cycle_end() {
958 _g1h->collector_state()->set_clearing_next_bitmap(false);
959
960 _g1h->trace_heap_after_gc(_gc_tracer_cm);
961
962 if (has_aborted()) {
963 log_info(gc, marking)("Concurrent Mark Abort");
964 _gc_tracer_cm->report_concurrent_mode_failure();
965 }
966
967 _gc_timer_cm->register_gc_end();
968
969 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
970 }
971
972 void G1ConcurrentMark::mark_from_roots() {
973 _restart_for_overflow = false;
974
975 _num_concurrent_workers = calc_active_marking_workers();
976
977 uint active_workers = MAX2(1U, _num_concurrent_workers);
978
979 // Setting active workers is not guaranteed since fewer
980 // worker threads may currently exist and more may not be
981 // available.
982 active_workers = _concurrent_workers->update_active_workers(active_workers);
983 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
984
985 // Parallel task terminator is set in "set_concurrency_and_phase()"
986 set_concurrency_and_phase(active_workers, true /* concurrent */);
987
988 G1CMConcurrentMarkingTask marking_task(this);
989 _concurrent_workers->run_task(&marking_task);
990 print_stats();
991 }
992
993 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
994 G1HeapVerifier* verifier = _g1h->verifier();
995
996 verifier->verify_region_sets_optional();
997
998 if (VerifyDuringGC) {
999 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm);
1000
1001 size_t const BufLen = 512;
1002 char buffer[BufLen];
1003
1004 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
1005 verifier->verify(type, vo, buffer);
1006 }
1007
1008 verifier->check_bitmaps(caller);
1009 }
1010
1011 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1012 G1CollectedHeap* _g1h;
1013 G1ConcurrentMark* _cm;
1014 HeapRegionClaimer _hrclaimer;
1015 uint volatile _total_selected_for_rebuild;
1016
1017 G1PrintRegionLivenessInfoClosure _cl;
1018
1019 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1020 G1CollectedHeap* _g1h;
1021 G1ConcurrentMark* _cm;
1022
1023 G1PrintRegionLivenessInfoClosure* _cl;
1024
1025 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1026
1027 void update_remset_before_rebuild(HeapRegion * hr) {
1028 G1RemSetTrackingPolicy* tracking_policy = _g1h->g1_policy()->remset_tracker();
1029
1030 size_t const live_bytes = _cm->liveness(hr->hrm_index()) * HeapWordSize;
1031 bool selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1032 if (selected_for_rebuild) {
1033 _num_regions_selected_for_rebuild++;
1034 }
1035 _cm->update_top_at_rebuild_start(hr);
1036 }
1037
1038 // Distribute the given words across the humongous object starting with hr and
1039 // note end of marking.
1040 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1041 uint const region_idx = hr->hrm_index();
1042 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1043 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1044
1045 // "Distributing" zero words means that we only note end of marking for these
1046 // regions.
1047 assert(marked_words == 0 || obj_size_in_words == marked_words,
1048 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1049 obj_size_in_words, marked_words);
1050
1051 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1052 HeapRegion* const r = _g1h->region_at(i);
1053 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1054
1055 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1056 words_to_add, i, r->get_type_str());
1057 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1058 marked_words -= words_to_add;
1059 }
1060 assert(marked_words == 0,
1061 SIZE_FORMAT " words left after distributing space across %u regions",
1062 marked_words, num_regions_in_humongous);
1063 }
1064
1065 void update_marked_bytes(HeapRegion* hr) {
1066 uint const region_idx = hr->hrm_index();
1067 size_t const marked_words = _cm->liveness(region_idx);
1068 // The marking attributes the object's size completely to the humongous starts
1069 // region. We need to distribute this value across the entire set of regions a
1070 // humongous object spans.
1071 if (hr->is_humongous()) {
1072 assert(hr->is_starts_humongous() || marked_words == 0,
1073 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1074 marked_words, region_idx, hr->get_type_str());
1075 if (hr->is_starts_humongous()) {
1076 distribute_marked_bytes(hr, marked_words);
1077 }
1078 } else {
1079 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1080 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1081 }
1082 }
1083
1084 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1085 hr->add_to_marked_bytes(marked_bytes);
1086 _cl->do_heap_region(hr);
1087 hr->note_end_of_marking();
1088 }
1089
1090 public:
1091 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1092 _g1h(g1h), _cm(cm), _num_regions_selected_for_rebuild(0), _cl(cl) { }
1093
1094 virtual bool do_heap_region(HeapRegion* r) {
1095 update_remset_before_rebuild(r);
1096 update_marked_bytes(r);
1097
1098 return false;
1099 }
1100
1101 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1102 };
1103
1104 public:
1105 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1106 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1107 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { }
1108
1109 virtual void work(uint worker_id) {
1110 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl);
1111 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id);
1112 Atomic::add(update_cl.num_selected_for_rebuild(), &_total_selected_for_rebuild);
1113 }
1114
1115 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; }
1116
1117 // Number of regions for which roughly one thread should be spawned for this work.
1118 static const uint RegionsPerThread = 384;
1119 };
1120
1121 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1122 G1CollectedHeap* _g1h;
1123 public:
1124 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1125
1126 virtual bool do_heap_region(HeapRegion* r) {
1127 _g1h->g1_policy()->remset_tracker()->update_after_rebuild(r);
1128 return false;
1129 }
1130 };
1131
1132 void G1ConcurrentMark::remark() {
1133 assert_at_safepoint_on_vm_thread();
1134
1135 // If a full collection has happened, we should not continue. However we might
1136 // have ended up here as the Remark VM operation has been scheduled already.
1137 if (has_aborted()) {
1138 return;
1139 }
1140
1141 G1Policy* g1p = _g1h->g1_policy();
1142 g1p->record_concurrent_mark_remark_start();
1143
1144 double start = os::elapsedTime();
1145
1146 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1147
1148 {
1149 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm);
1150 finalize_marking();
1151 }
1152
1153 double mark_work_end = os::elapsedTime();
1154
1155 bool const mark_finished = !has_overflown();
1156 if (mark_finished) {
1157 weak_refs_work(false /* clear_all_soft_refs */);
1158
1159 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1160 // We're done with marking.
1161 // This is the end of the marking cycle, we're expected all
1162 // threads to have SATB queues with active set to true.
1163 satb_mq_set.set_active_all_threads(false, /* new active value */
1164 true /* expected_active */);
1165
1166 {
1167 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm);
1168 flush_all_task_caches();
1169 }
1170
1171 // Install newly created mark bitmap as "prev".
1172 swap_mark_bitmaps();
1173 {
1174 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1175
1176 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1177 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1178 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1179
1180 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1181 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1182 _g1h->workers()->run_task(&cl, num_workers);
1183
1184 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1185 _g1h->num_regions(), cl.total_selected_for_rebuild());
1186 }
1187 {
1188 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm);
1189 reclaim_empty_regions();
1190 }
1191
1192 // Clean out dead classes
1193 if (ClassUnloadingWithConcurrentMark) {
1194 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm);
1195 ClassLoaderDataGraph::purge();
1196 }
1197
1198 compute_new_sizes();
1199
1200 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1201
1202 assert(!restart_for_overflow(), "sanity");
1203 // Completely reset the marking state since marking completed
1204 reset_at_marking_complete();
1205 } else {
1206 // We overflowed. Restart concurrent marking.
1207 _restart_for_overflow = true;
1208
1209 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1210
1211 // Clear the marking state because we will be restarting
1212 // marking due to overflowing the global mark stack.
1213 reset_marking_for_restart();
1214 }
1215
1216 {
1217 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm);
1218 report_object_count(mark_finished);
1219 }
1220
1221 // Statistics
1222 double now = os::elapsedTime();
1223 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1224 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1225 _remark_times.add((now - start) * 1000.0);
1226
1227 g1p->record_concurrent_mark_remark_end();
1228 }
1229
1230 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1231 // Per-region work during the Cleanup pause.
1232 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1233 G1CollectedHeap* _g1h;
1234 size_t _freed_bytes;
1235 FreeRegionList* _local_cleanup_list;
1236 uint _old_regions_removed;
1237 uint _humongous_regions_removed;
1238 HRRSCleanupTask* _hrrs_cleanup_task;
1239
1240 public:
1241 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1242 FreeRegionList* local_cleanup_list,
1243 HRRSCleanupTask* hrrs_cleanup_task) :
1244 _g1h(g1h),
1245 _freed_bytes(0),
1246 _local_cleanup_list(local_cleanup_list),
1247 _old_regions_removed(0),
1248 _humongous_regions_removed(0),
1249 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1250
1251 size_t freed_bytes() { return _freed_bytes; }
1252 const uint old_regions_removed() { return _old_regions_removed; }
1253 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1254
1255 bool do_heap_region(HeapRegion *hr) {
1256 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1257 _freed_bytes += hr->used();
1258 hr->set_containing_set(NULL);
1259 if (hr->is_humongous()) {
1260 _humongous_regions_removed++;
1261 _g1h->free_humongous_region(hr, _local_cleanup_list);
1262 } else {
1263 _old_regions_removed++;
1264 _g1h->free_region(hr, _local_cleanup_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
1265 }
1266 hr->clear_cardtable();
1267 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1268 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1269 } else {
1270 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1271 }
1272
1273 return false;
1274 }
1275 };
1276
1277 G1CollectedHeap* _g1h;
1278 FreeRegionList* _cleanup_list;
1279 HeapRegionClaimer _hrclaimer;
1280
1281 public:
1282 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1283 AbstractGangTask("G1 Cleanup"),
1284 _g1h(g1h),
1285 _cleanup_list(cleanup_list),
1286 _hrclaimer(n_workers) {
1287
1288 HeapRegionRemSet::reset_for_cleanup_tasks();
1289 }
1290
1291 void work(uint worker_id) {
1292 FreeRegionList local_cleanup_list("Local Cleanup List");
1293 HRRSCleanupTask hrrs_cleanup_task;
1294 G1ReclaimEmptyRegionsClosure cl(_g1h,
1295 &local_cleanup_list,
1296 &hrrs_cleanup_task);
1297 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1298 assert(cl.is_complete(), "Shouldn't have aborted!");
1299
1300 // Now update the old/humongous region sets
1301 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1302 {
1303 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1304 _g1h->decrement_summary_bytes(cl.freed_bytes());
1305
1306 _cleanup_list->add_ordered(&local_cleanup_list);
1307 assert(local_cleanup_list.is_empty(), "post-condition");
1308
1309 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1310 }
1311 }
1312 };
1313
1314 void G1ConcurrentMark::reclaim_empty_regions() {
1315 WorkGang* workers = _g1h->workers();
1316 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1317
1318 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1319 workers->run_task(&cl);
1320
1321 if (!empty_regions_list.is_empty()) {
1322 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1323 // Now print the empty regions list.
1324 G1HRPrinter* hrp = _g1h->hr_printer();
1325 if (hrp->is_active()) {
1326 FreeRegionListIterator iter(&empty_regions_list);
1327 while (iter.more_available()) {
1328 HeapRegion* hr = iter.get_next();
1329 hrp->cleanup(hr);
1330 }
1331 }
1332 // And actually make them available.
1333 _g1h->prepend_to_freelist(&empty_regions_list);
1334 }
1335 }
1336
1337 void G1ConcurrentMark::compute_new_sizes() {
1338 MetaspaceGC::compute_new_size();
1339
1340 // Cleanup will have freed any regions completely full of garbage.
1341 // Update the soft reference policy with the new heap occupancy.
1342 Universe::update_heap_info_at_gc();
1343
1344 // We reclaimed old regions so we should calculate the sizes to make
1345 // sure we update the old gen/space data.
1346 _g1h->g1mm()->update_sizes();
1347 }
1348
1349 void G1ConcurrentMark::cleanup() {
1350 assert_at_safepoint_on_vm_thread();
1351
1352 // If a full collection has happened, we shouldn't do this.
1353 if (has_aborted()) {
1354 return;
1355 }
1356
1357 G1Policy* g1p = _g1h->g1_policy();
1358 g1p->record_concurrent_mark_cleanup_start();
1359
1360 double start = os::elapsedTime();
1361
1362 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1363
1364 {
1365 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1366 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1367 _g1h->heap_region_iterate(&cl);
1368 }
1369
1370 if (log_is_enabled(Trace, gc, liveness)) {
1371 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1372 _g1h->heap_region_iterate(&cl);
1373 }
1374
1375 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1376
1377 // We need to make this be a "collection" so any collection pause that
1378 // races with it goes around and waits for Cleanup to finish.
1379 _g1h->increment_total_collections();
1380
1381 // Local statistics
1382 double recent_cleanup_time = (os::elapsedTime() - start);
1383 _total_cleanup_time += recent_cleanup_time;
1384 _cleanup_times.add(recent_cleanup_time);
1385
1386 {
1387 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1388 _g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1389 }
1390 }
1391
1392 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1393 // Uses the G1CMTask associated with a worker thread (for serial reference
1394 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1395 // trace referent objects.
1396 //
1397 // Using the G1CMTask and embedded local queues avoids having the worker
1398 // threads operating on the global mark stack. This reduces the risk
1399 // of overflowing the stack - which we would rather avoid at this late
1400 // state. Also using the tasks' local queues removes the potential
1401 // of the workers interfering with each other that could occur if
1402 // operating on the global stack.
1403
1404 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1405 G1ConcurrentMark* _cm;
1406 G1CMTask* _task;
1407 uint _ref_counter_limit;
1408 uint _ref_counter;
1409 bool _is_serial;
1410 public:
1411 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1412 _cm(cm), _task(task), _is_serial(is_serial),
1413 _ref_counter_limit(G1RefProcDrainInterval) {
1414 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1415 _ref_counter = _ref_counter_limit;
1416 }
1417
1418 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1419 virtual void do_oop( oop* p) { do_oop_work(p); }
1420
1421 template <class T> void do_oop_work(T* p) {
1422 if (_cm->has_overflown()) {
1423 return;
1424 }
1425 if (!_task->deal_with_reference(p)) {
1426 // We did not add anything to the mark bitmap (or mark stack), so there is
1427 // no point trying to drain it.
1428 return;
1429 }
1430 _ref_counter--;
1431
1432 if (_ref_counter == 0) {
1433 // We have dealt with _ref_counter_limit references, pushing them
1434 // and objects reachable from them on to the local stack (and
1435 // possibly the global stack). Call G1CMTask::do_marking_step() to
1436 // process these entries.
1437 //
1438 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1439 // there's nothing more to do (i.e. we're done with the entries that
1440 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1441 // above) or we overflow.
1442 //
1443 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1444 // flag while there may still be some work to do. (See the comment at
1445 // the beginning of G1CMTask::do_marking_step() for those conditions -
1446 // one of which is reaching the specified time target.) It is only
1447 // when G1CMTask::do_marking_step() returns without setting the
1448 // has_aborted() flag that the marking step has completed.
1449 do {
1450 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1451 _task->do_marking_step(mark_step_duration_ms,
1452 false /* do_termination */,
1453 _is_serial);
1454 } while (_task->has_aborted() && !_cm->has_overflown());
1455 _ref_counter = _ref_counter_limit;
1456 }
1457 }
1458 };
1459
1460 // 'Drain' oop closure used by both serial and parallel reference processing.
1461 // Uses the G1CMTask associated with a given worker thread (for serial
1462 // reference processing the G1CMtask for worker 0 is used). Calls the
1463 // do_marking_step routine, with an unbelievably large timeout value,
1464 // to drain the marking data structures of the remaining entries
1465 // added by the 'keep alive' oop closure above.
1466
1467 class G1CMDrainMarkingStackClosure : public VoidClosure {
1468 G1ConcurrentMark* _cm;
1469 G1CMTask* _task;
1470 bool _is_serial;
1471 public:
1472 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1473 _cm(cm), _task(task), _is_serial(is_serial) {
1474 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1475 }
1476
1477 void do_void() {
1478 do {
1479 // We call G1CMTask::do_marking_step() to completely drain the local
1480 // and global marking stacks of entries pushed by the 'keep alive'
1481 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1482 //
1483 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1484 // if there's nothing more to do (i.e. we've completely drained the
1485 // entries that were pushed as a a result of applying the 'keep alive'
1486 // closure to the entries on the discovered ref lists) or we overflow
1487 // the global marking stack.
1488 //
1489 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1490 // flag while there may still be some work to do. (See the comment at
1491 // the beginning of G1CMTask::do_marking_step() for those conditions -
1492 // one of which is reaching the specified time target.) It is only
1493 // when G1CMTask::do_marking_step() returns without setting the
1494 // has_aborted() flag that the marking step has completed.
1495
1496 _task->do_marking_step(1000000000.0 /* something very large */,
1497 true /* do_termination */,
1498 _is_serial);
1499 } while (_task->has_aborted() && !_cm->has_overflown());
1500 }
1501 };
1502
1503 // Implementation of AbstractRefProcTaskExecutor for parallel
1504 // reference processing at the end of G1 concurrent marking
1505
1506 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1507 private:
1508 G1CollectedHeap* _g1h;
1509 G1ConcurrentMark* _cm;
1510 WorkGang* _workers;
1511 uint _active_workers;
1512
1513 public:
1514 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1515 G1ConcurrentMark* cm,
1516 WorkGang* workers,
1517 uint n_workers) :
1518 _g1h(g1h), _cm(cm),
1519 _workers(workers), _active_workers(n_workers) { }
1520
1521 // Executes the given task using concurrent marking worker threads.
1522 virtual void execute(ProcessTask& task);
1523 };
1524
1525 class G1CMRefProcTaskProxy : public AbstractGangTask {
1526 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1527 ProcessTask& _proc_task;
1528 G1CollectedHeap* _g1h;
1529 G1ConcurrentMark* _cm;
1530
1531 public:
1532 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1533 G1CollectedHeap* g1h,
1534 G1ConcurrentMark* cm) :
1535 AbstractGangTask("Process reference objects in parallel"),
1536 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1537 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1538 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1539 }
1540
1541 virtual void work(uint worker_id) {
1542 ResourceMark rm;
1543 HandleMark hm;
1544 G1CMTask* task = _cm->task(worker_id);
1545 G1CMIsAliveClosure g1_is_alive(_g1h);
1546 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1547 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1548
1549 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1550 }
1551 };
1552
1553 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1554 assert(_workers != NULL, "Need parallel worker threads.");
1555 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1556
1557 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1558
1559 // We need to reset the concurrency level before each
1560 // proxy task execution, so that the termination protocol
1561 // and overflow handling in G1CMTask::do_marking_step() knows
1562 // how many workers to wait for.
1563 _cm->set_concurrency(_active_workers);
1564 _workers->run_task(&proc_task_proxy);
1565 }
1566
1567 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1568 ResourceMark rm;
1569 HandleMark hm;
1570
1571 // Is alive closure.
1572 G1CMIsAliveClosure g1_is_alive(_g1h);
1573
1574 // Inner scope to exclude the cleaning of the string and symbol
1575 // tables from the displayed time.
1576 {
1577 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm);
1578
1579 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1580
1581 // See the comment in G1CollectedHeap::ref_processing_init()
1582 // about how reference processing currently works in G1.
1583
1584 // Set the soft reference policy
1585 rp->setup_policy(clear_all_soft_refs);
1586 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1587
1588 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1589 // in serial reference processing. Note these closures are also
1590 // used for serially processing (by the the current thread) the
1591 // JNI references during parallel reference processing.
1592 //
1593 // These closures do not need to synchronize with the worker
1594 // threads involved in parallel reference processing as these
1595 // instances are executed serially by the current thread (e.g.
1596 // reference processing is not multi-threaded and is thus
1597 // performed by the current thread instead of a gang worker).
1598 //
1599 // The gang tasks involved in parallel reference processing create
1600 // their own instances of these closures, which do their own
1601 // synchronization among themselves.
1602 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1603 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1604
1605 // We need at least one active thread. If reference processing
1606 // is not multi-threaded we use the current (VMThread) thread,
1607 // otherwise we use the work gang from the G1CollectedHeap and
1608 // we utilize all the worker threads we can.
1609 bool processing_is_mt = rp->processing_is_mt();
1610 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1611 active_workers = MAX2(MIN2(active_workers, _max_num_tasks), 1U);
1612
1613 // Parallel processing task executor.
1614 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1615 _g1h->workers(), active_workers);
1616 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1617
1618 // Set the concurrency level. The phase was already set prior to
1619 // executing the remark task.
1620 set_concurrency(active_workers);
1621
1622 // Set the degree of MT processing here. If the discovery was done MT,
1623 // the number of threads involved during discovery could differ from
1624 // the number of active workers. This is OK as long as the discovered
1625 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1626 rp->set_active_mt_degree(active_workers);
1627
1628 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues());
1629
1630 // Process the weak references.
1631 const ReferenceProcessorStats& stats =
1632 rp->process_discovered_references(&g1_is_alive,
1633 &g1_keep_alive,
1634 &g1_drain_mark_stack,
1635 executor,
1636 &pt);
1637 _gc_tracer_cm->report_gc_reference_stats(stats);
1638 pt.print_all_references();
1639
1640 // The do_oop work routines of the keep_alive and drain_marking_stack
1641 // oop closures will set the has_overflown flag if we overflow the
1642 // global marking stack.
1643
1644 assert(has_overflown() || _global_mark_stack.is_empty(),
1645 "Mark stack should be empty (unless it has overflown)");
1646
1647 assert(rp->num_queues() == active_workers, "why not");
1648
1649 rp->verify_no_references_recorded();
1650 assert(!rp->discovery_enabled(), "Post condition");
1651 }
1652
1653 if (has_overflown()) {
1654 // We can not trust g1_is_alive and the contents of the heap if the marking stack
1655 // overflowed while processing references. Exit the VM.
1656 fatal("Overflow during reference processing, can not continue. Please "
1657 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
1658 "restart.", MarkStackSizeMax);
1659 return;
1660 }
1661
1662 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1663
1664 {
1665 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1666 WeakProcessor::weak_oops_do(&g1_is_alive, &do_nothing_cl);
1667 }
1668
1669 // Unload Klasses, String, Symbols, Code Cache, etc.
1670 if (ClassUnloadingWithConcurrentMark) {
1671 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1672 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm, false /* Defer cleaning */);
1673 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1674 } else {
1675 GCTraceTime(Debug, gc, phases) debug("Cleanup", _gc_timer_cm);
1676 // No need to clean string table and symbol table as they are treated as strong roots when
1677 // class unloading is disabled.
1678 _g1h->partial_cleaning(&g1_is_alive, false, false, G1StringDedup::is_enabled());
1679 }
1680 }
1681
1682 class G1PrecleanYieldClosure : public YieldClosure {
1683 G1ConcurrentMark* _cm;
1684
1685 public:
1686 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { }
1687
1688 virtual bool should_return() {
1689 return _cm->has_aborted();
1690 }
1691
1692 virtual bool should_return_fine_grain() {
1693 _cm->do_yield_check();
1694 return _cm->has_aborted();
1695 }
1696 };
1697
1698 void G1ConcurrentMark::preclean() {
1699 assert(G1UseReferencePrecleaning, "Precleaning must be enabled.");
1700
1701 SuspendibleThreadSetJoiner joiner;
1702
1703 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */);
1704 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */);
1705
1706 set_concurrency_and_phase(1, true);
1707
1708 G1PrecleanYieldClosure yield_cl(this);
1709
1710 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1711 // Precleaning is single threaded. Temporarily disable MT discovery.
1712 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false);
1713 rp->preclean_discovered_references(rp->is_alive_non_header(),
1714 &keep_alive,
1715 &drain_mark_stack,
1716 &yield_cl,
1717 _gc_timer_cm);
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 G1ThreadLocalData::satb_mark_queue(jt).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 G1BarrierSet::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 = G1BarrierSet::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) debug("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 = G1BarrierSet::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 = G1BarrierSet::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, (size_t)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 = G1BarrierSet::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 }