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