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/heapRegion.inline.hpp"
41 #include "gc/g1/heapRegionRemSet.hpp"
42 #include "gc/g1/heapRegionSet.inline.hpp"
43 #include "gc/shared/gcId.hpp"
44 #include "gc/shared/gcTimer.hpp"
45 #include "gc/shared/gcTrace.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/resourceArea.hpp"
59 #include "oops/access.inline.hpp"
60 #include "oops/oop.inline.hpp"
61 #include "runtime/atomic.hpp"
62 #include "runtime/handles.inline.hpp"
63 #include "runtime/java.hpp"
64 #include "runtime/prefetch.inline.hpp"
65 #include "services/memTracker.hpp"
66 #include "utilities/align.hpp"
67 #include "utilities/growableArray.hpp"
68
69 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
70 assert(addr < _cm->finger(), "invariant");
71 assert(addr >= _task->finger(), "invariant");
72
73 // We move that task's local finger along.
74 _task->move_finger_to(addr);
75
76 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
77 // we only partially drain the local queue and global stack
78 _task->drain_local_queue(true);
79 _task->drain_global_stack(true);
80
81 // if the has_aborted flag has been raised, we need to bail out of
82 // the iteration
83 return !_task->has_aborted();
84 }
85
86 G1CMMarkStack::G1CMMarkStack() :
87 _max_chunk_capacity(0),
88 _base(NULL),
89 _chunk_capacity(0) {
90 set_empty();
91 }
92
93 bool G1CMMarkStack::resize(size_t new_capacity) {
94 assert(is_empty(), "Only resize when stack is empty.");
95 assert(new_capacity <= _max_chunk_capacity,
96 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
97
98 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
99
100 if (new_base == NULL) {
101 log_warning(gc)("Failed to reserve memory for new overflow mark stack with " SIZE_FORMAT " chunks and size " SIZE_FORMAT "B.", new_capacity, new_capacity * sizeof(TaskQueueEntryChunk));
102 return false;
103 }
104 // Release old mapping.
105 if (_base != NULL) {
106 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
107 }
108
109 _base = new_base;
110 _chunk_capacity = new_capacity;
111 set_empty();
112
113 return true;
114 }
115
116 size_t G1CMMarkStack::capacity_alignment() {
117 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
118 }
119
120 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
121 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
122
123 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
124
125 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
126 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
127
128 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
129 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
130 _max_chunk_capacity,
131 initial_chunk_capacity);
132
133 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
134 initial_chunk_capacity, _max_chunk_capacity);
135
136 return resize(initial_chunk_capacity);
137 }
138
139 void G1CMMarkStack::expand() {
140 if (_chunk_capacity == _max_chunk_capacity) {
141 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
142 return;
143 }
144 size_t old_capacity = _chunk_capacity;
145 // Double capacity if possible
146 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
147
148 if (resize(new_capacity)) {
149 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
150 old_capacity, new_capacity);
151 } else {
152 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
153 old_capacity, new_capacity);
154 }
155 }
156
157 G1CMMarkStack::~G1CMMarkStack() {
158 if (_base != NULL) {
159 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
160 }
161 }
162
163 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
164 elem->next = *list;
165 *list = elem;
166 }
167
168 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
169 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
170 add_chunk_to_list(&_chunk_list, elem);
171 _chunks_in_chunk_list++;
172 }
173
174 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
175 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
176 add_chunk_to_list(&_free_list, elem);
177 }
178
179 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
180 TaskQueueEntryChunk* result = *list;
181 if (result != NULL) {
182 *list = (*list)->next;
183 }
184 return result;
185 }
186
187 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
188 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
189 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
190 if (result != NULL) {
191 _chunks_in_chunk_list--;
192 }
193 return result;
194 }
195
196 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
197 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
198 return remove_chunk_from_list(&_free_list);
199 }
200
201 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
202 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
203 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
204 // wraparound of _hwm.
205 if (_hwm >= _chunk_capacity) {
206 return NULL;
207 }
208
209 size_t cur_idx = Atomic::add(1u, &_hwm) - 1;
210 if (cur_idx >= _chunk_capacity) {
211 return NULL;
212 }
213
214 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
215 result->next = NULL;
216 return result;
217 }
218
219 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
220 // Get a new chunk.
221 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
222
223 if (new_chunk == NULL) {
224 // Did not get a chunk from the free list. Allocate from backing memory.
225 new_chunk = allocate_new_chunk();
226
227 if (new_chunk == NULL) {
228 return false;
229 }
230 }
231
232 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
233
234 add_chunk_to_chunk_list(new_chunk);
235
236 return true;
237 }
238
239 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
240 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
241
242 if (cur == NULL) {
243 return false;
244 }
245
246 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
247
248 add_chunk_to_free_list(cur);
249 return true;
250 }
251
252 void G1CMMarkStack::set_empty() {
253 _chunks_in_chunk_list = 0;
254 _hwm = 0;
255 _chunk_list = NULL;
256 _free_list = NULL;
257 }
258
259 G1CMRootRegions::G1CMRootRegions(uint const max_regions) :
260 _root_regions(NEW_C_HEAP_ARRAY(HeapRegion*, max_regions, mtGC)),
261 _max_regions(max_regions),
262 _num_root_regions(0),
263 _claimed_root_regions(0),
264 _scan_in_progress(false),
265 _should_abort(false) { }
266
267 G1CMRootRegions::~G1CMRootRegions() {
268 FREE_C_HEAP_ARRAY(HeapRegion*, _max_regions);
269 }
270
271 void G1CMRootRegions::reset() {
272 _num_root_regions = 0;
273 }
274
275 void G1CMRootRegions::add(HeapRegion* hr) {
276 assert_at_safepoint();
277 size_t idx = Atomic::add((size_t)1, &_num_root_regions) - 1;
278 assert(idx < _max_regions, "Trying to add more root regions than there is space " SIZE_FORMAT, _max_regions);
279 _root_regions[idx] = hr;
280 }
281
282 void G1CMRootRegions::prepare_for_scan() {
283 assert(!scan_in_progress(), "pre-condition");
284
285 _scan_in_progress = _num_root_regions > 0;
286
287 _claimed_root_regions = 0;
288 _should_abort = false;
289 }
290
291 HeapRegion* G1CMRootRegions::claim_next() {
292 if (_should_abort) {
293 // If someone has set the should_abort flag, we return NULL to
294 // force the caller to bail out of their loop.
295 return NULL;
296 }
297
298 if (_claimed_root_regions >= _num_root_regions) {
299 return NULL;
300 }
301
302 size_t claimed_index = Atomic::add((size_t)1, &_claimed_root_regions) - 1;
303 if (claimed_index < _num_root_regions) {
304 return _root_regions[claimed_index];
305 }
306 return NULL;
307 }
308
309 uint G1CMRootRegions::num_root_regions() const {
310 return (uint)_num_root_regions;
311 }
312
313 void G1CMRootRegions::notify_scan_done() {
314 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
315 _scan_in_progress = false;
316 RootRegionScan_lock->notify_all();
317 }
318
319 void G1CMRootRegions::cancel_scan() {
320 notify_scan_done();
321 }
322
323 void G1CMRootRegions::scan_finished() {
324 assert(scan_in_progress(), "pre-condition");
325
326 if (!_should_abort) {
327 assert(_claimed_root_regions >= num_root_regions(),
328 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u",
329 _claimed_root_regions, num_root_regions());
330 }
331
332 notify_scan_done();
333 }
334
335 bool G1CMRootRegions::wait_until_scan_finished() {
336 if (!scan_in_progress()) {
337 return false;
338 }
339
340 {
341 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
342 while (scan_in_progress()) {
343 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
344 }
345 }
346 return true;
347 }
348
349 // Returns the maximum number of workers to be used in a concurrent
350 // phase based on the number of GC workers being used in a STW
351 // phase.
352 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
353 return MAX2((num_gc_workers + 2) / 4, 1U);
354 }
355
356 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
357 G1RegionToSpaceMapper* prev_bitmap_storage,
358 G1RegionToSpaceMapper* next_bitmap_storage) :
359 // _cm_thread set inside the constructor
360 _g1h(g1h),
361 _completed_initialization(false),
362
363 _mark_bitmap_1(),
364 _mark_bitmap_2(),
365 _prev_mark_bitmap(&_mark_bitmap_1),
366 _next_mark_bitmap(&_mark_bitmap_2),
367
368 _heap(_g1h->reserved_region()),
369
370 _root_regions(_g1h->max_regions()),
371
372 _global_mark_stack(),
373
374 // _finger set in set_non_marking_state
375
376 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
377 _max_num_tasks(ParallelGCThreads),
378 // _num_active_tasks set in set_non_marking_state()
379 // _tasks set inside the constructor
380
381 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
382 _terminator((int) _max_num_tasks, _task_queues),
383
384 _first_overflow_barrier_sync(),
385 _second_overflow_barrier_sync(),
386
387 _has_overflown(false),
388 _concurrent(false),
389 _has_aborted(false),
390 _restart_for_overflow(false),
391 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
392 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
393
394 // _verbose_level set below
395
396 _init_times(),
397 _remark_times(),
398 _remark_mark_times(),
399 _remark_weak_ref_times(),
400 _cleanup_times(),
401 _total_cleanup_time(0.0),
402
403 _accum_task_vtime(NULL),
404
405 _concurrent_workers(NULL),
406 _num_concurrent_workers(0),
407 _max_concurrent_workers(0),
408
409 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
410 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
411 {
412 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
413 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
414
415 // Create & start ConcurrentMark thread.
416 _cm_thread = new G1ConcurrentMarkThread(this);
417 if (_cm_thread->osthread() == NULL) {
418 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
419 }
420
421 assert(CGC_lock != NULL, "CGC_lock must be initialized");
422
423 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
424 // Calculate the number of concurrent worker threads by scaling
425 // the number of parallel GC threads.
426 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
427 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
428 }
429
430 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
431 if (ConcGCThreads > ParallelGCThreads) {
432 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
433 ConcGCThreads, ParallelGCThreads);
434 return;
435 }
436
437 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
438 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
439
440 _num_concurrent_workers = ConcGCThreads;
441 _max_concurrent_workers = _num_concurrent_workers;
442
443 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
444 _concurrent_workers->initialize_workers();
445
446 if (FLAG_IS_DEFAULT(MarkStackSize)) {
447 size_t mark_stack_size =
448 MIN2(MarkStackSizeMax,
449 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
450 // Verify that the calculated value for MarkStackSize is in range.
451 // It would be nice to use the private utility routine from Arguments.
452 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
453 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
454 "must be between 1 and " SIZE_FORMAT,
455 mark_stack_size, MarkStackSizeMax);
456 return;
457 }
458 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
459 } else {
460 // Verify MarkStackSize is in range.
461 if (FLAG_IS_CMDLINE(MarkStackSize)) {
462 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
463 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
464 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
465 "must be between 1 and " SIZE_FORMAT,
466 MarkStackSize, MarkStackSizeMax);
467 return;
468 }
469 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
470 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
471 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
472 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
473 MarkStackSize, MarkStackSizeMax);
474 return;
475 }
476 }
477 }
478 }
479
480 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
481 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
482 }
483
484 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
485 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
486
487 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
488 _num_active_tasks = _max_num_tasks;
489
490 for (uint i = 0; i < _max_num_tasks; ++i) {
491 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
492 task_queue->initialize();
493 _task_queues->register_queue(i, task_queue);
494
495 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
496
497 _accum_task_vtime[i] = 0.0;
498 }
499
500 reset_at_marking_complete();
501 _completed_initialization = true;
502 }
503
504 void G1ConcurrentMark::reset() {
505 _has_aborted = false;
506
507 reset_marking_for_restart();
508
509 // Reset all tasks, since different phases will use different number of active
510 // threads. So, it's easiest to have all of them ready.
511 for (uint i = 0; i < _max_num_tasks; ++i) {
512 _tasks[i]->reset(_next_mark_bitmap);
513 }
514
515 uint max_regions = _g1h->max_regions();
516 for (uint i = 0; i < max_regions; i++) {
517 _top_at_rebuild_starts[i] = NULL;
518 _region_mark_stats[i].clear();
519 }
520 }
521
522 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
523 for (uint j = 0; j < _max_num_tasks; ++j) {
524 _tasks[j]->clear_mark_stats_cache(region_idx);
525 }
526 _top_at_rebuild_starts[region_idx] = NULL;
527 _region_mark_stats[region_idx].clear();
528 }
529
530 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
531 uint const region_idx = r->hrm_index();
532 if (r->is_humongous()) {
533 assert(r->is_starts_humongous(), "Got humongous continues region here");
534 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
535 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
536 clear_statistics_in_region(j);
537 }
538 } else {
539 clear_statistics_in_region(region_idx);
540 }
541 }
542
543 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
544 if (bitmap->is_marked(addr)) {
545 bitmap->clear(addr);
546 }
547 }
548
549 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
550 assert_at_safepoint_on_vm_thread();
551
552 // Need to clear all mark bits of the humongous object.
553 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
554 clear_mark_if_set(_next_mark_bitmap, r->bottom());
555
556 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
557 return;
558 }
559
560 // Clear any statistics about the region gathered so far.
561 clear_statistics(r);
562 }
563
564 void G1ConcurrentMark::reset_marking_for_restart() {
565 _global_mark_stack.set_empty();
566
567 // Expand the marking stack, if we have to and if we can.
568 if (has_overflown()) {
569 _global_mark_stack.expand();
570
571 uint max_regions = _g1h->max_regions();
572 for (uint i = 0; i < max_regions; i++) {
573 _region_mark_stats[i].clear_during_overflow();
574 }
575 }
576
577 clear_has_overflown();
578 _finger = _heap.start();
579
580 for (uint i = 0; i < _max_num_tasks; ++i) {
581 G1CMTaskQueue* queue = _task_queues->queue(i);
582 queue->set_empty();
583 }
584 }
585
586 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
587 assert(active_tasks <= _max_num_tasks, "we should not have more");
588
589 _num_active_tasks = active_tasks;
590 // Need to update the three data structures below according to the
591 // number of active threads for this phase.
592 _terminator.terminator()->reset_for_reuse((int) active_tasks);
593 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
594 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
595 }
596
597 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
598 set_concurrency(active_tasks);
599
600 _concurrent = concurrent;
601
602 if (!concurrent) {
603 // At this point we should be in a STW phase, and completed marking.
604 assert_at_safepoint_on_vm_thread();
605 assert(out_of_regions(),
606 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
607 p2i(_finger), p2i(_heap.end()));
608 }
609 }
610
611 void G1ConcurrentMark::reset_at_marking_complete() {
612 // We set the global marking state to some default values when we're
613 // not doing marking.
614 reset_marking_for_restart();
615 _num_active_tasks = 0;
616 }
617
618 G1ConcurrentMark::~G1ConcurrentMark() {
619 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
620 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
621 // The G1ConcurrentMark instance is never freed.
622 ShouldNotReachHere();
623 }
624
625 class G1ClearBitMapTask : public AbstractGangTask {
626 public:
627 static size_t chunk_size() { return M; }
628
629 private:
630 // Heap region closure used for clearing the given mark bitmap.
631 class G1ClearBitmapHRClosure : public HeapRegionClosure {
632 private:
633 G1CMBitMap* _bitmap;
634 G1ConcurrentMark* _cm;
635 public:
636 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) {
637 }
638
639 virtual bool do_heap_region(HeapRegion* r) {
640 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
641
642 HeapWord* cur = r->bottom();
643 HeapWord* const end = r->end();
644
645 while (cur < end) {
646 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
647 _bitmap->clear_range(mr);
648
649 cur += chunk_size_in_words;
650
651 // Abort iteration if after yielding the marking has been aborted.
652 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
653 return true;
654 }
655 // Repeat the asserts from before the start of the closure. We will do them
656 // as asserts here to minimize their overhead on the product. However, we
657 // will have them as guarantees at the beginning / end of the bitmap
658 // clearing to get some checking in the product.
659 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
660 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
661 }
662 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
663
664 return false;
665 }
666 };
667
668 G1ClearBitmapHRClosure _cl;
669 HeapRegionClaimer _hr_claimer;
670 bool _suspendible; // If the task is suspendible, workers must join the STS.
671
672 public:
673 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
674 AbstractGangTask("G1 Clear Bitmap"),
675 _cl(bitmap, suspendible ? cm : NULL),
676 _hr_claimer(n_workers),
677 _suspendible(suspendible)
678 { }
679
680 void work(uint worker_id) {
681 SuspendibleThreadSetJoiner sts_join(_suspendible);
682 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
683 }
684
685 bool is_complete() {
686 return _cl.is_complete();
687 }
688 };
689
690 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
691 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
692
693 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
694 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
695
696 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
697
698 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
699
700 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
701 workers->run_task(&cl, num_workers);
702 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
703 }
704
705 void G1ConcurrentMark::cleanup_for_next_mark() {
706 // Make sure that the concurrent mark thread looks to still be in
707 // the current cycle.
708 guarantee(cm_thread()->during_cycle(), "invariant");
709
710 // We are finishing up the current cycle by clearing the next
711 // marking bitmap and getting it ready for the next cycle. During
712 // this time no other cycle can start. So, let's make sure that this
713 // is the case.
714 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
715
716 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
717
718 // Repeat the asserts from above.
719 guarantee(cm_thread()->during_cycle(), "invariant");
720 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
721 }
722
723 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
724 assert_at_safepoint_on_vm_thread();
725 clear_bitmap(_prev_mark_bitmap, workers, false);
726 }
727
728 class NoteStartOfMarkHRClosure : public HeapRegionClosure {
729 public:
730 bool do_heap_region(HeapRegion* r) {
731 r->note_start_of_marking();
732 return false;
733 }
734 };
735
736 void G1ConcurrentMark::pre_initial_mark() {
737 assert_at_safepoint_on_vm_thread();
738
739 // Reset marking state.
740 reset();
741
742 // For each region note start of marking.
743 NoteStartOfMarkHRClosure startcl;
744 _g1h->heap_region_iterate(&startcl);
745
746 _root_regions.reset();
747 }
748
749
750 void G1ConcurrentMark::post_initial_mark() {
751 // Start Concurrent Marking weak-reference discovery.
752 ReferenceProcessor* rp = _g1h->ref_processor_cm();
753 // enable ("weak") refs discovery
754 rp->enable_discovery();
755 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
756
757 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
758 // This is the start of the marking cycle, we're expected all
759 // threads to have SATB queues with active set to false.
760 satb_mq_set.set_active_all_threads(true, /* new active value */
761 false /* expected_active */);
762
763 _root_regions.prepare_for_scan();
764
765 // update_g1_committed() will be called at the end of an evac pause
766 // when marking is on. So, it's also called at the end of the
767 // initial-mark pause to update the heap end, if the heap expands
768 // during it. No need to call it here.
769 }
770
771 /*
772 * Notice that in the next two methods, we actually leave the STS
773 * during the barrier sync and join it immediately afterwards. If we
774 * do not do this, the following deadlock can occur: one thread could
775 * be in the barrier sync code, waiting for the other thread to also
776 * sync up, whereas another one could be trying to yield, while also
777 * waiting for the other threads to sync up too.
778 *
779 * Note, however, that this code is also used during remark and in
780 * this case we should not attempt to leave / enter the STS, otherwise
781 * we'll either hit an assert (debug / fastdebug) or deadlock
782 * (product). So we should only leave / enter the STS if we are
783 * operating concurrently.
784 *
785 * Because the thread that does the sync barrier has left the STS, it
786 * is possible to be suspended for a Full GC or an evacuation pause
787 * could occur. This is actually safe, since the entering the sync
788 * barrier is one of the last things do_marking_step() does, and it
789 * doesn't manipulate any data structures afterwards.
790 */
791
792 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
793 bool barrier_aborted;
794 {
795 SuspendibleThreadSetLeaver sts_leave(concurrent());
796 barrier_aborted = !_first_overflow_barrier_sync.enter();
797 }
798
799 // at this point everyone should have synced up and not be doing any
800 // more work
801
802 if (barrier_aborted) {
803 // If the barrier aborted we ignore the overflow condition and
804 // just abort the whole marking phase as quickly as possible.
805 return;
806 }
807 }
808
809 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
810 SuspendibleThreadSetLeaver sts_leave(concurrent());
811 _second_overflow_barrier_sync.enter();
812
813 // at this point everything should be re-initialized and ready to go
814 }
815
816 class G1CMConcurrentMarkingTask : public AbstractGangTask {
817 G1ConcurrentMark* _cm;
818
819 public:
820 void work(uint worker_id) {
821 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
822 ResourceMark rm;
823
824 double start_vtime = os::elapsedVTime();
825
826 {
827 SuspendibleThreadSetJoiner sts_join;
828
829 assert(worker_id < _cm->active_tasks(), "invariant");
830
831 G1CMTask* task = _cm->task(worker_id);
832 task->record_start_time();
833 if (!_cm->has_aborted()) {
834 do {
835 task->do_marking_step(G1ConcMarkStepDurationMillis,
836 true /* do_termination */,
837 false /* is_serial*/);
838
839 _cm->do_yield_check();
840 } while (!_cm->has_aborted() && task->has_aborted());
841 }
842 task->record_end_time();
843 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
844 }
845
846 double end_vtime = os::elapsedVTime();
847 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
848 }
849
850 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
851 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
852
853 ~G1CMConcurrentMarkingTask() { }
854 };
855
856 uint G1ConcurrentMark::calc_active_marking_workers() {
857 uint result = 0;
858 if (!UseDynamicNumberOfGCThreads ||
859 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
860 !ForceDynamicNumberOfGCThreads)) {
861 result = _max_concurrent_workers;
862 } else {
863 result =
864 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers,
865 1, /* Minimum workers */
866 _num_concurrent_workers,
867 Threads::number_of_non_daemon_threads());
868 // Don't scale the result down by scale_concurrent_workers() because
869 // that scaling has already gone into "_max_concurrent_workers".
870 }
871 assert(result > 0 && result <= _max_concurrent_workers,
872 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
873 _max_concurrent_workers, result);
874 return result;
875 }
876
877 void G1ConcurrentMark::scan_root_region(HeapRegion* hr, uint worker_id) {
878 assert(hr->is_old() || (hr->is_survivor() && hr->next_top_at_mark_start() == hr->bottom()),
879 "Root regions must be old or survivor but region %u is %s", hr->hrm_index(), hr->get_type_str());
880 G1RootRegionScanClosure cl(_g1h, this, worker_id);
881
882 const uintx interval = PrefetchScanIntervalInBytes;
883 HeapWord* curr = hr->next_top_at_mark_start();
884 const HeapWord* end = hr->top();
885 while (curr < end) {
886 Prefetch::read(curr, interval);
887 oop obj = oop(curr);
888 int size = obj->oop_iterate_size(&cl);
889 assert(size == obj->size(), "sanity");
890 curr += size;
891 }
892 }
893
894 class G1CMRootRegionScanTask : public AbstractGangTask {
895 G1ConcurrentMark* _cm;
896 public:
897 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
898 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
899
900 void work(uint worker_id) {
901 assert(Thread::current()->is_ConcurrentGC_thread(),
902 "this should only be done by a conc GC thread");
903
904 G1CMRootRegions* root_regions = _cm->root_regions();
905 HeapRegion* hr = root_regions->claim_next();
906 while (hr != NULL) {
907 _cm->scan_root_region(hr, worker_id);
908 hr = root_regions->claim_next();
909 }
910 }
911 };
912
913 void G1ConcurrentMark::scan_root_regions() {
914 // scan_in_progress() will have been set to true only if there was
915 // at least one root region to scan. So, if it's false, we
916 // should not attempt to do any further work.
917 if (root_regions()->scan_in_progress()) {
918 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
919
920 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
921 // We distribute work on a per-region basis, so starting
922 // more threads than that is useless.
923 root_regions()->num_root_regions());
924 assert(_num_concurrent_workers <= _max_concurrent_workers,
925 "Maximum number of marking threads exceeded");
926
927 G1CMRootRegionScanTask task(this);
928 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
929 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
930 _concurrent_workers->run_task(&task, _num_concurrent_workers);
931
932 // It's possible that has_aborted() is true here without actually
933 // aborting the survivor scan earlier. This is OK as it's
934 // mainly used for sanity checking.
935 root_regions()->scan_finished();
936 }
937 }
938
939 void G1ConcurrentMark::concurrent_cycle_start() {
940 _gc_timer_cm->register_gc_start();
941
942 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
943
944 _g1h->trace_heap_before_gc(_gc_tracer_cm);
945 }
946
947 void G1ConcurrentMark::concurrent_cycle_end() {
948 _g1h->collector_state()->set_clearing_next_bitmap(false);
949
950 _g1h->trace_heap_after_gc(_gc_tracer_cm);
951
952 if (has_aborted()) {
953 log_info(gc, marking)("Concurrent Mark Abort");
954 _gc_tracer_cm->report_concurrent_mode_failure();
955 }
956
957 _gc_timer_cm->register_gc_end();
958
959 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
960 }
961
962 void G1ConcurrentMark::mark_from_roots() {
963 _restart_for_overflow = false;
964
965 _num_concurrent_workers = calc_active_marking_workers();
966
967 uint active_workers = MAX2(1U, _num_concurrent_workers);
968
969 // Setting active workers is not guaranteed since fewer
970 // worker threads may currently exist and more may not be
971 // available.
972 active_workers = _concurrent_workers->update_active_workers(active_workers);
973 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
974
975 // Parallel task terminator is set in "set_concurrency_and_phase()"
976 set_concurrency_and_phase(active_workers, true /* concurrent */);
977
978 G1CMConcurrentMarkingTask marking_task(this);
979 _concurrent_workers->run_task(&marking_task);
980 print_stats();
981 }
982
983 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
984 G1HeapVerifier* verifier = _g1h->verifier();
985
986 verifier->verify_region_sets_optional();
987
988 if (VerifyDuringGC) {
989 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm);
990
991 size_t const BufLen = 512;
992 char buffer[BufLen];
993
994 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
995 verifier->verify(type, vo, buffer);
996 }
997
998 verifier->check_bitmaps(caller);
999 }
1000
1001 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1002 G1CollectedHeap* _g1h;
1003 G1ConcurrentMark* _cm;
1004 HeapRegionClaimer _hrclaimer;
1005 uint volatile _total_selected_for_rebuild;
1006
1007 G1PrintRegionLivenessInfoClosure _cl;
1008
1009 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1010 G1CollectedHeap* _g1h;
1011 G1ConcurrentMark* _cm;
1012
1013 G1PrintRegionLivenessInfoClosure* _cl;
1014
1015 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1016
1017 void update_remset_before_rebuild(HeapRegion* hr) {
1018 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker();
1019
1020 bool selected_for_rebuild;
1021 if (hr->is_humongous()) {
1022 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0;
1023 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live);
1024 } else {
1025 size_t const live_bytes = _cm->liveness(hr->hrm_index());
1026 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1027 }
1028 if (selected_for_rebuild) {
1029 _num_regions_selected_for_rebuild++;
1030 }
1031 _cm->update_top_at_rebuild_start(hr);
1032 }
1033
1034 // Distribute the given words across the humongous object starting with hr and
1035 // note end of marking.
1036 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1037 uint const region_idx = hr->hrm_index();
1038 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1039 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1040
1041 // "Distributing" zero words means that we only note end of marking for these
1042 // regions.
1043 assert(marked_words == 0 || obj_size_in_words == marked_words,
1044 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1045 obj_size_in_words, marked_words);
1046
1047 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1048 HeapRegion* const r = _g1h->region_at(i);
1049 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1050
1051 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1052 words_to_add, i, r->get_type_str());
1053 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1054 marked_words -= words_to_add;
1055 }
1056 assert(marked_words == 0,
1057 SIZE_FORMAT " words left after distributing space across %u regions",
1058 marked_words, num_regions_in_humongous);
1059 }
1060
1061 void update_marked_bytes(HeapRegion* hr) {
1062 uint const region_idx = hr->hrm_index();
1063 size_t const marked_words = _cm->liveness(region_idx);
1064 // The marking attributes the object's size completely to the humongous starts
1065 // region. We need to distribute this value across the entire set of regions a
1066 // humongous object spans.
1067 if (hr->is_humongous()) {
1068 assert(hr->is_starts_humongous() || marked_words == 0,
1069 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1070 marked_words, region_idx, hr->get_type_str());
1071 if (hr->is_starts_humongous()) {
1072 distribute_marked_bytes(hr, marked_words);
1073 }
1074 } else {
1075 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1076 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1077 }
1078 }
1079
1080 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1081 hr->add_to_marked_bytes(marked_bytes);
1082 _cl->do_heap_region(hr);
1083 hr->note_end_of_marking();
1084 }
1085
1086 public:
1087 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1088 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { }
1089
1090 virtual bool do_heap_region(HeapRegion* r) {
1091 update_remset_before_rebuild(r);
1092 update_marked_bytes(r);
1093
1094 return false;
1095 }
1096
1097 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1098 };
1099
1100 public:
1101 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1102 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1103 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { }
1104
1105 virtual void work(uint worker_id) {
1106 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl);
1107 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id);
1108 Atomic::add(update_cl.num_selected_for_rebuild(), &_total_selected_for_rebuild);
1109 }
1110
1111 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; }
1112
1113 // Number of regions for which roughly one thread should be spawned for this work.
1114 static const uint RegionsPerThread = 384;
1115 };
1116
1117 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1118 G1CollectedHeap* _g1h;
1119 public:
1120 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1121
1122 virtual bool do_heap_region(HeapRegion* r) {
1123 _g1h->policy()->remset_tracker()->update_after_rebuild(r);
1124 return false;
1125 }
1126 };
1127
1128 void G1ConcurrentMark::remark() {
1129 assert_at_safepoint_on_vm_thread();
1130
1131 // If a full collection has happened, we should not continue. However we might
1132 // have ended up here as the Remark VM operation has been scheduled already.
1133 if (has_aborted()) {
1134 return;
1135 }
1136
1137 G1Policy* policy = _g1h->policy();
1138 policy->record_concurrent_mark_remark_start();
1139
1140 double start = os::elapsedTime();
1141
1142 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1143
1144 {
1145 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm);
1146 finalize_marking();
1147 }
1148
1149 double mark_work_end = os::elapsedTime();
1150
1151 bool const mark_finished = !has_overflown();
1152 if (mark_finished) {
1153 weak_refs_work(false /* clear_all_soft_refs */);
1154
1155 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1156 // We're done with marking.
1157 // This is the end of the marking cycle, we're expected all
1158 // threads to have SATB queues with active set to true.
1159 satb_mq_set.set_active_all_threads(false, /* new active value */
1160 true /* expected_active */);
1161
1162 {
1163 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm);
1164 flush_all_task_caches();
1165 }
1166
1167 // Install newly created mark bitmap as "prev".
1168 swap_mark_bitmaps();
1169 {
1170 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1171
1172 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1173 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1174 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1175
1176 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1177 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1178 _g1h->workers()->run_task(&cl, num_workers);
1179
1180 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1181 _g1h->num_regions(), cl.total_selected_for_rebuild());
1182 }
1183 {
1184 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm);
1185 reclaim_empty_regions();
1186 }
1187
1188 // Clean out dead classes
1189 if (ClassUnloadingWithConcurrentMark) {
1190 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm);
1191 ClassLoaderDataGraph::purge();
1192 }
1193
1194 _g1h->resize_heap_if_necessary();
1195
1196 compute_new_sizes();
1197
1198 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1199
1200 assert(!restart_for_overflow(), "sanity");
1201 // Completely reset the marking state since marking completed
1202 reset_at_marking_complete();
1203 } else {
1204 // We overflowed. Restart concurrent marking.
1205 _restart_for_overflow = true;
1206
1207 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1208
1209 // Clear the marking state because we will be restarting
1210 // marking due to overflowing the global mark stack.
1211 reset_marking_for_restart();
1212 }
1213
1214 {
1215 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm);
1216 report_object_count(mark_finished);
1217 }
1218
1219 // Statistics
1220 double now = os::elapsedTime();
1221 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1222 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1223 _remark_times.add((now - start) * 1000.0);
1224
1225 policy->record_concurrent_mark_remark_end();
1226 }
1227
1228 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1229 // Per-region work during the Cleanup pause.
1230 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1231 G1CollectedHeap* _g1h;
1232 size_t _freed_bytes;
1233 FreeRegionList* _local_cleanup_list;
1234 uint _old_regions_removed;
1235 uint _humongous_regions_removed;
1236
1237 public:
1238 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1239 FreeRegionList* local_cleanup_list) :
1240 _g1h(g1h),
1241 _freed_bytes(0),
1242 _local_cleanup_list(local_cleanup_list),
1243 _old_regions_removed(0),
1244 _humongous_regions_removed(0) { }
1245
1246 size_t freed_bytes() { return _freed_bytes; }
1247 const uint old_regions_removed() { return _old_regions_removed; }
1248 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1249
1250 bool do_heap_region(HeapRegion *hr) {
1251 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1252 _freed_bytes += hr->used();
1253 hr->set_containing_set(NULL);
1254 if (hr->is_humongous()) {
1255 _humongous_regions_removed++;
1256 _g1h->free_humongous_region(hr, _local_cleanup_list);
1257 } else {
1258 _old_regions_removed++;
1259 _g1h->free_region(hr, _local_cleanup_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
1260 }
1261 hr->clear_cardtable();
1262 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1263 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1264 }
1265
1266 return false;
1267 }
1268 };
1269
1270 G1CollectedHeap* _g1h;
1271 FreeRegionList* _cleanup_list;
1272 HeapRegionClaimer _hrclaimer;
1273
1274 public:
1275 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1276 AbstractGangTask("G1 Cleanup"),
1277 _g1h(g1h),
1278 _cleanup_list(cleanup_list),
1279 _hrclaimer(n_workers) {
1280 }
1281
1282 void work(uint worker_id) {
1283 FreeRegionList local_cleanup_list("Local Cleanup List");
1284 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list);
1285 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1286 assert(cl.is_complete(), "Shouldn't have aborted!");
1287
1288 // Now update the old/humongous region sets
1289 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1290 {
1291 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1292 _g1h->decrement_summary_bytes(cl.freed_bytes());
1293
1294 _cleanup_list->add_ordered(&local_cleanup_list);
1295 assert(local_cleanup_list.is_empty(), "post-condition");
1296 }
1297 }
1298 };
1299
1300 void G1ConcurrentMark::reclaim_empty_regions() {
1301 WorkGang* workers = _g1h->workers();
1302 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1303
1304 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1305 workers->run_task(&cl);
1306
1307 if (!empty_regions_list.is_empty()) {
1308 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1309 // Now print the empty regions list.
1310 G1HRPrinter* hrp = _g1h->hr_printer();
1311 if (hrp->is_active()) {
1312 FreeRegionListIterator iter(&empty_regions_list);
1313 while (iter.more_available()) {
1314 HeapRegion* hr = iter.get_next();
1315 hrp->cleanup(hr);
1316 }
1317 }
1318 // And actually make them available.
1319 _g1h->prepend_to_freelist(&empty_regions_list);
1320 }
1321 }
1322
1323 void G1ConcurrentMark::compute_new_sizes() {
1324 MetaspaceGC::compute_new_size();
1325
1326 // Cleanup will have freed any regions completely full of garbage.
1327 // Update the soft reference policy with the new heap occupancy.
1328 Universe::update_heap_info_at_gc();
1329
1330 // We reclaimed old regions so we should calculate the sizes to make
1331 // sure we update the old gen/space data.
1332 _g1h->g1mm()->update_sizes();
1333 }
1334
1335 void G1ConcurrentMark::cleanup() {
1336 assert_at_safepoint_on_vm_thread();
1337
1338 // If a full collection has happened, we shouldn't do this.
1339 if (has_aborted()) {
1340 return;
1341 }
1342
1343 G1Policy* policy = _g1h->policy();
1344 policy->record_concurrent_mark_cleanup_start();
1345
1346 double start = os::elapsedTime();
1347
1348 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1349
1350 {
1351 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1352 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1353 _g1h->heap_region_iterate(&cl);
1354 }
1355
1356 if (log_is_enabled(Trace, gc, liveness)) {
1357 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1358 _g1h->heap_region_iterate(&cl);
1359 }
1360
1361 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1362
1363 // We need to make this be a "collection" so any collection pause that
1364 // races with it goes around and waits for Cleanup to finish.
1365 _g1h->increment_total_collections();
1366
1367 // Local statistics
1368 double recent_cleanup_time = (os::elapsedTime() - start);
1369 _total_cleanup_time += recent_cleanup_time;
1370 _cleanup_times.add(recent_cleanup_time);
1371
1372 {
1373 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1374 policy->record_concurrent_mark_cleanup_end();
1375 }
1376 }
1377
1378 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1379 // Uses the G1CMTask associated with a worker thread (for serial reference
1380 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1381 // trace referent objects.
1382 //
1383 // Using the G1CMTask and embedded local queues avoids having the worker
1384 // threads operating on the global mark stack. This reduces the risk
1385 // of overflowing the stack - which we would rather avoid at this late
1386 // state. Also using the tasks' local queues removes the potential
1387 // of the workers interfering with each other that could occur if
1388 // operating on the global stack.
1389
1390 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1391 G1ConcurrentMark* _cm;
1392 G1CMTask* _task;
1393 uint _ref_counter_limit;
1394 uint _ref_counter;
1395 bool _is_serial;
1396 public:
1397 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1398 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval),
1399 _ref_counter(_ref_counter_limit), _is_serial(is_serial) {
1400 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1401 }
1402
1403 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1404 virtual void do_oop( oop* p) { do_oop_work(p); }
1405
1406 template <class T> void do_oop_work(T* p) {
1407 if (_cm->has_overflown()) {
1408 return;
1409 }
1410 if (!_task->deal_with_reference(p)) {
1411 // We did not add anything to the mark bitmap (or mark stack), so there is
1412 // no point trying to drain it.
1413 return;
1414 }
1415 _ref_counter--;
1416
1417 if (_ref_counter == 0) {
1418 // We have dealt with _ref_counter_limit references, pushing them
1419 // and objects reachable from them on to the local stack (and
1420 // possibly the global stack). Call G1CMTask::do_marking_step() to
1421 // process these entries.
1422 //
1423 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1424 // there's nothing more to do (i.e. we're done with the entries that
1425 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1426 // above) or we overflow.
1427 //
1428 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1429 // flag while there may still be some work to do. (See the comment at
1430 // the beginning of G1CMTask::do_marking_step() for those conditions -
1431 // one of which is reaching the specified time target.) It is only
1432 // when G1CMTask::do_marking_step() returns without setting the
1433 // has_aborted() flag that the marking step has completed.
1434 do {
1435 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1436 _task->do_marking_step(mark_step_duration_ms,
1437 false /* do_termination */,
1438 _is_serial);
1439 } while (_task->has_aborted() && !_cm->has_overflown());
1440 _ref_counter = _ref_counter_limit;
1441 }
1442 }
1443 };
1444
1445 // 'Drain' oop closure used by both serial and parallel reference processing.
1446 // Uses the G1CMTask associated with a given worker thread (for serial
1447 // reference processing the G1CMtask for worker 0 is used). Calls the
1448 // do_marking_step routine, with an unbelievably large timeout value,
1449 // to drain the marking data structures of the remaining entries
1450 // added by the 'keep alive' oop closure above.
1451
1452 class G1CMDrainMarkingStackClosure : public VoidClosure {
1453 G1ConcurrentMark* _cm;
1454 G1CMTask* _task;
1455 bool _is_serial;
1456 public:
1457 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1458 _cm(cm), _task(task), _is_serial(is_serial) {
1459 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1460 }
1461
1462 void do_void() {
1463 do {
1464 // We call G1CMTask::do_marking_step() to completely drain the local
1465 // and global marking stacks of entries pushed by the 'keep alive'
1466 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1467 //
1468 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1469 // if there's nothing more to do (i.e. we've completely drained the
1470 // entries that were pushed as a a result of applying the 'keep alive'
1471 // closure to the entries on the discovered ref lists) or we overflow
1472 // the global marking stack.
1473 //
1474 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1475 // flag while there may still be some work to do. (See the comment at
1476 // the beginning of G1CMTask::do_marking_step() for those conditions -
1477 // one of which is reaching the specified time target.) It is only
1478 // when G1CMTask::do_marking_step() returns without setting the
1479 // has_aborted() flag that the marking step has completed.
1480
1481 _task->do_marking_step(1000000000.0 /* something very large */,
1482 true /* do_termination */,
1483 _is_serial);
1484 } while (_task->has_aborted() && !_cm->has_overflown());
1485 }
1486 };
1487
1488 // Implementation of AbstractRefProcTaskExecutor for parallel
1489 // reference processing at the end of G1 concurrent marking
1490
1491 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1492 private:
1493 G1CollectedHeap* _g1h;
1494 G1ConcurrentMark* _cm;
1495 WorkGang* _workers;
1496 uint _active_workers;
1497
1498 public:
1499 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1500 G1ConcurrentMark* cm,
1501 WorkGang* workers,
1502 uint n_workers) :
1503 _g1h(g1h), _cm(cm),
1504 _workers(workers), _active_workers(n_workers) { }
1505
1506 virtual void execute(ProcessTask& task, uint ergo_workers);
1507 };
1508
1509 class G1CMRefProcTaskProxy : public AbstractGangTask {
1510 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1511 ProcessTask& _proc_task;
1512 G1CollectedHeap* _g1h;
1513 G1ConcurrentMark* _cm;
1514
1515 public:
1516 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1517 G1CollectedHeap* g1h,
1518 G1ConcurrentMark* cm) :
1519 AbstractGangTask("Process reference objects in parallel"),
1520 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1521 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1522 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1523 }
1524
1525 virtual void work(uint worker_id) {
1526 ResourceMark rm;
1527 HandleMark hm;
1528 G1CMTask* task = _cm->task(worker_id);
1529 G1CMIsAliveClosure g1_is_alive(_g1h);
1530 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1531 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1532
1533 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1534 }
1535 };
1536
1537 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
1538 assert(_workers != NULL, "Need parallel worker threads.");
1539 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1540 assert(_workers->active_workers() >= ergo_workers,
1541 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)",
1542 ergo_workers, _workers->active_workers());
1543
1544 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1545
1546 // We need to reset the concurrency level before each
1547 // proxy task execution, so that the termination protocol
1548 // and overflow handling in G1CMTask::do_marking_step() knows
1549 // how many workers to wait for.
1550 _cm->set_concurrency(ergo_workers);
1551 _workers->run_task(&proc_task_proxy, ergo_workers);
1552 }
1553
1554 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1555 ResourceMark rm;
1556 HandleMark hm;
1557
1558 // Is alive closure.
1559 G1CMIsAliveClosure g1_is_alive(_g1h);
1560
1561 // Inner scope to exclude the cleaning of the string table
1562 // from the displayed time.
1563 {
1564 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm);
1565
1566 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1567
1568 // See the comment in G1CollectedHeap::ref_processing_init()
1569 // about how reference processing currently works in G1.
1570
1571 // Set the soft reference policy
1572 rp->setup_policy(clear_all_soft_refs);
1573 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1574
1575 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1576 // in serial reference processing. Note these closures are also
1577 // used for serially processing (by the the current thread) the
1578 // JNI references during parallel reference processing.
1579 //
1580 // These closures do not need to synchronize with the worker
1581 // threads involved in parallel reference processing as these
1582 // instances are executed serially by the current thread (e.g.
1583 // reference processing is not multi-threaded and is thus
1584 // performed by the current thread instead of a gang worker).
1585 //
1586 // The gang tasks involved in parallel reference processing create
1587 // their own instances of these closures, which do their own
1588 // synchronization among themselves.
1589 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1590 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1591
1592 // We need at least one active thread. If reference processing
1593 // is not multi-threaded we use the current (VMThread) thread,
1594 // otherwise we use the work gang from the G1CollectedHeap and
1595 // we utilize all the worker threads we can.
1596 bool processing_is_mt = rp->processing_is_mt();
1597 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1598 active_workers = MAX2(MIN2(active_workers, _max_num_tasks), 1U);
1599
1600 // Parallel processing task executor.
1601 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1602 _g1h->workers(), active_workers);
1603 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1604
1605 // Set the concurrency level. The phase was already set prior to
1606 // executing the remark task.
1607 set_concurrency(active_workers);
1608
1609 // Set the degree of MT processing here. If the discovery was done MT,
1610 // the number of threads involved during discovery could differ from
1611 // the number of active workers. This is OK as long as the discovered
1612 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1613 rp->set_active_mt_degree(active_workers);
1614
1615 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues());
1616
1617 // Process the weak references.
1618 const ReferenceProcessorStats& stats =
1619 rp->process_discovered_references(&g1_is_alive,
1620 &g1_keep_alive,
1621 &g1_drain_mark_stack,
1622 executor,
1623 &pt);
1624 _gc_tracer_cm->report_gc_reference_stats(stats);
1625 pt.print_all_references();
1626
1627 // The do_oop work routines of the keep_alive and drain_marking_stack
1628 // oop closures will set the has_overflown flag if we overflow the
1629 // global marking stack.
1630
1631 assert(has_overflown() || _global_mark_stack.is_empty(),
1632 "Mark stack should be empty (unless it has overflown)");
1633
1634 assert(rp->num_queues() == active_workers, "why not");
1635
1636 rp->verify_no_references_recorded();
1637 assert(!rp->discovery_enabled(), "Post condition");
1638 }
1639
1640 if (has_overflown()) {
1641 // We can not trust g1_is_alive and the contents of the heap if the marking stack
1642 // overflowed while processing references. Exit the VM.
1643 fatal("Overflow during reference processing, can not continue. Please "
1644 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
1645 "restart.", MarkStackSizeMax);
1646 return;
1647 }
1648
1649 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1650
1651 {
1652 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1653 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1);
1654 }
1655
1656 // Unload Klasses, String, Code Cache, etc.
1657 if (ClassUnloadingWithConcurrentMark) {
1658 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1659 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm);
1660 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1661 } else if (StringDedup::is_enabled()) {
1662 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm);
1663 _g1h->string_dedup_cleaning(&g1_is_alive, NULL);
1664 }
1665 }
1666
1667 class G1PrecleanYieldClosure : public YieldClosure {
1668 G1ConcurrentMark* _cm;
1669
1670 public:
1671 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { }
1672
1673 virtual bool should_return() {
1674 return _cm->has_aborted();
1675 }
1676
1677 virtual bool should_return_fine_grain() {
1678 _cm->do_yield_check();
1679 return _cm->has_aborted();
1680 }
1681 };
1682
1683 void G1ConcurrentMark::preclean() {
1684 assert(G1UseReferencePrecleaning, "Precleaning must be enabled.");
1685
1686 SuspendibleThreadSetJoiner joiner;
1687
1688 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */);
1689 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */);
1690
1691 set_concurrency_and_phase(1, true);
1692
1693 G1PrecleanYieldClosure yield_cl(this);
1694
1695 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1696 // Precleaning is single threaded. Temporarily disable MT discovery.
1697 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false);
1698 rp->preclean_discovered_references(rp->is_alive_non_header(),
1699 &keep_alive,
1700 &drain_mark_stack,
1701 &yield_cl,
1702 _gc_timer_cm);
1703 }
1704
1705 // When sampling object counts, we already swapped the mark bitmaps, so we need to use
1706 // the prev bitmap determining liveness.
1707 class G1ObjectCountIsAliveClosure: public BoolObjectClosure {
1708 G1CollectedHeap* _g1h;
1709 public:
1710 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
1711
1712 bool do_object_b(oop obj) {
1713 HeapWord* addr = (HeapWord*)obj;
1714 return addr != NULL &&
1715 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_dead(obj));
1716 }
1717 };
1718
1719 void G1ConcurrentMark::report_object_count(bool mark_completed) {
1720 // Depending on the completion of the marking liveness needs to be determined
1721 // using either the next or prev bitmap.
1722 if (mark_completed) {
1723 G1ObjectCountIsAliveClosure is_alive(_g1h);
1724 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1725 } else {
1726 G1CMIsAliveClosure is_alive(_g1h);
1727 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1728 }
1729 }
1730
1731
1732 void G1ConcurrentMark::swap_mark_bitmaps() {
1733 G1CMBitMap* temp = _prev_mark_bitmap;
1734 _prev_mark_bitmap = _next_mark_bitmap;
1735 _next_mark_bitmap = temp;
1736 _g1h->collector_state()->set_clearing_next_bitmap(true);
1737 }
1738
1739 // Closure for marking entries in SATB buffers.
1740 class G1CMSATBBufferClosure : public SATBBufferClosure {
1741 private:
1742 G1CMTask* _task;
1743 G1CollectedHeap* _g1h;
1744
1745 // This is very similar to G1CMTask::deal_with_reference, but with
1746 // more relaxed requirements for the argument, so this must be more
1747 // circumspect about treating the argument as an object.
1748 void do_entry(void* entry) const {
1749 _task->increment_refs_reached();
1750 oop const obj = static_cast<oop>(entry);
1751 _task->make_reference_grey(obj);
1752 }
1753
1754 public:
1755 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1756 : _task(task), _g1h(g1h) { }
1757
1758 virtual void do_buffer(void** buffer, size_t size) {
1759 for (size_t i = 0; i < size; ++i) {
1760 do_entry(buffer[i]);
1761 }
1762 }
1763 };
1764
1765 class G1RemarkThreadsClosure : public ThreadClosure {
1766 G1CMSATBBufferClosure _cm_satb_cl;
1767 G1CMOopClosure _cm_cl;
1768 MarkingCodeBlobClosure _code_cl;
1769 int _thread_parity;
1770
1771 public:
1772 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1773 _cm_satb_cl(task, g1h),
1774 _cm_cl(g1h, task),
1775 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1776 _thread_parity(Threads::thread_claim_parity()) {}
1777
1778 void do_thread(Thread* thread) {
1779 if (thread->claim_oops_do(true, _thread_parity)) {
1780 SATBMarkQueue& queue = G1ThreadLocalData::satb_mark_queue(thread);
1781 queue.apply_closure_and_empty(&_cm_satb_cl);
1782 if (thread->is_Java_thread()) {
1783 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1784 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1785 // * Alive if on the stack of an executing method
1786 // * Weakly reachable otherwise
1787 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1788 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1789 JavaThread* jt = (JavaThread*)thread;
1790 jt->nmethods_do(&_code_cl);
1791 }
1792 }
1793 }
1794 };
1795
1796 class G1CMRemarkTask : public AbstractGangTask {
1797 G1ConcurrentMark* _cm;
1798 public:
1799 void work(uint worker_id) {
1800 G1CMTask* task = _cm->task(worker_id);
1801 task->record_start_time();
1802 {
1803 ResourceMark rm;
1804 HandleMark hm;
1805
1806 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1807 Threads::threads_do(&threads_f);
1808 }
1809
1810 do {
1811 task->do_marking_step(1000000000.0 /* something very large */,
1812 true /* do_termination */,
1813 false /* is_serial */);
1814 } while (task->has_aborted() && !_cm->has_overflown());
1815 // If we overflow, then we do not want to restart. We instead
1816 // want to abort remark and do concurrent marking again.
1817 task->record_end_time();
1818 }
1819
1820 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1821 AbstractGangTask("Par Remark"), _cm(cm) {
1822 _cm->terminator()->reset_for_reuse(active_workers);
1823 }
1824 };
1825
1826 void G1ConcurrentMark::finalize_marking() {
1827 ResourceMark rm;
1828 HandleMark hm;
1829
1830 _g1h->ensure_parsability(false);
1831
1832 // this is remark, so we'll use up all active threads
1833 uint active_workers = _g1h->workers()->active_workers();
1834 set_concurrency_and_phase(active_workers, false /* concurrent */);
1835 // Leave _parallel_marking_threads at it's
1836 // value originally calculated in the G1ConcurrentMark
1837 // constructor and pass values of the active workers
1838 // through the gang in the task.
1839
1840 {
1841 StrongRootsScope srs(active_workers);
1842
1843 G1CMRemarkTask remarkTask(this, active_workers);
1844 // We will start all available threads, even if we decide that the
1845 // active_workers will be fewer. The extra ones will just bail out
1846 // immediately.
1847 _g1h->workers()->run_task(&remarkTask);
1848 }
1849
1850 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1851 guarantee(has_overflown() ||
1852 satb_mq_set.completed_buffers_num() == 0,
1853 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1854 BOOL_TO_STR(has_overflown()),
1855 satb_mq_set.completed_buffers_num());
1856
1857 print_stats();
1858 }
1859
1860 void G1ConcurrentMark::flush_all_task_caches() {
1861 size_t hits = 0;
1862 size_t misses = 0;
1863 for (uint i = 0; i < _max_num_tasks; i++) {
1864 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache();
1865 hits += stats.first;
1866 misses += stats.second;
1867 }
1868 size_t sum = hits + misses;
1869 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf",
1870 hits, misses, percent_of(hits, sum));
1871 }
1872
1873 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) {
1874 _prev_mark_bitmap->clear_range(mr);
1875 }
1876
1877 HeapRegion*
1878 G1ConcurrentMark::claim_region(uint worker_id) {
1879 // "checkpoint" the finger
1880 HeapWord* finger = _finger;
1881
1882 while (finger < _heap.end()) {
1883 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1884
1885 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1886 // Make sure that the reads below do not float before loading curr_region.
1887 OrderAccess::loadload();
1888 // Above heap_region_containing may return NULL as we always scan claim
1889 // until the end of the heap. In this case, just jump to the next region.
1890 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1891
1892 // Is the gap between reading the finger and doing the CAS too long?
1893 HeapWord* res = Atomic::cmpxchg(end, &_finger, finger);
1894 if (res == finger && curr_region != NULL) {
1895 // we succeeded
1896 HeapWord* bottom = curr_region->bottom();
1897 HeapWord* limit = curr_region->next_top_at_mark_start();
1898
1899 // notice that _finger == end cannot be guaranteed here since,
1900 // someone else might have moved the finger even further
1901 assert(_finger >= end, "the finger should have moved forward");
1902
1903 if (limit > bottom) {
1904 return curr_region;
1905 } else {
1906 assert(limit == bottom,
1907 "the region limit should be at bottom");
1908 // we return NULL and the caller should try calling
1909 // claim_region() again.
1910 return NULL;
1911 }
1912 } else {
1913 assert(_finger > finger, "the finger should have moved forward");
1914 // read it again
1915 finger = _finger;
1916 }
1917 }
1918
1919 return NULL;
1920 }
1921
1922 #ifndef PRODUCT
1923 class VerifyNoCSetOops {
1924 G1CollectedHeap* _g1h;
1925 const char* _phase;
1926 int _info;
1927
1928 public:
1929 VerifyNoCSetOops(const char* phase, int info = -1) :
1930 _g1h(G1CollectedHeap::heap()),
1931 _phase(phase),
1932 _info(info)
1933 { }
1934
1935 void operator()(G1TaskQueueEntry task_entry) const {
1936 if (task_entry.is_array_slice()) {
1937 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1938 return;
1939 }
1940 guarantee(oopDesc::is_oop(task_entry.obj()),
1941 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1942 p2i(task_entry.obj()), _phase, _info);
1943 guarantee(!_g1h->is_in_cset(task_entry.obj()),
1944 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
1945 p2i(task_entry.obj()), _phase, _info);
1946 }
1947 };
1948
1949 void G1ConcurrentMark::verify_no_collection_set_oops_in_stacks() {
1950 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1951 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
1952 return;
1953 }
1954
1955 // Verify entries on the global mark stack
1956 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
1957
1958 // Verify entries on the task queues
1959 for (uint i = 0; i < _max_num_tasks; ++i) {
1960 G1CMTaskQueue* queue = _task_queues->queue(i);
1961 queue->iterate(VerifyNoCSetOops("Queue", i));
1962 }
1963
1964 // Verify the global finger
1965 HeapWord* global_finger = finger();
1966 if (global_finger != NULL && global_finger < _heap.end()) {
1967 // Since we always iterate over all regions, we might get a NULL HeapRegion
1968 // here.
1969 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
1970 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
1971 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
1972 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
1973 }
1974
1975 // Verify the task fingers
1976 assert(_num_concurrent_workers <= _max_num_tasks, "sanity");
1977 for (uint i = 0; i < _num_concurrent_workers; ++i) {
1978 G1CMTask* task = _tasks[i];
1979 HeapWord* task_finger = task->finger();
1980 if (task_finger != NULL && task_finger < _heap.end()) {
1981 // See above note on the global finger verification.
1982 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger);
1983 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
1984 !task_hr->in_collection_set(),
1985 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
1986 p2i(task_finger), HR_FORMAT_PARAMS(task_hr));
1987 }
1988 }
1989 }
1990 #endif // PRODUCT
1991
1992 void G1ConcurrentMark::rebuild_rem_set_concurrently() {
1993 _g1h->rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset);
1994 }
1995
1996 void G1ConcurrentMark::print_stats() {
1997 if (!log_is_enabled(Debug, gc, stats)) {
1998 return;
1999 }
2000 log_debug(gc, stats)("---------------------------------------------------------------------");
2001 for (size_t i = 0; i < _num_active_tasks; ++i) {
2002 _tasks[i]->print_stats();
2003 log_debug(gc, stats)("---------------------------------------------------------------------");
2004 }
2005 }
2006
2007 void G1ConcurrentMark::concurrent_cycle_abort() {
2008 if (!cm_thread()->during_cycle() || _has_aborted) {
2009 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2010 return;
2011 }
2012
2013 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2014 // concurrent bitmap clearing.
2015 {
2016 GCTraceTime(Debug, gc) debug("Clear Next Bitmap");
2017 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false);
2018 }
2019 // Note we cannot clear the previous marking bitmap here
2020 // since VerifyDuringGC verifies the objects marked during
2021 // a full GC against the previous bitmap.
2022
2023 // Empty mark stack
2024 reset_marking_for_restart();
2025 for (uint i = 0; i < _max_num_tasks; ++i) {
2026 _tasks[i]->clear_region_fields();
2027 }
2028 _first_overflow_barrier_sync.abort();
2029 _second_overflow_barrier_sync.abort();
2030 _has_aborted = true;
2031
2032 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2033 satb_mq_set.abandon_partial_marking();
2034 // This can be called either during or outside marking, we'll read
2035 // the expected_active value from the SATB queue set.
2036 satb_mq_set.set_active_all_threads(
2037 false, /* new active value */
2038 satb_mq_set.is_active() /* expected_active */);
2039 }
2040
2041 static void print_ms_time_info(const char* prefix, const char* name,
2042 NumberSeq& ns) {
2043 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2044 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2045 if (ns.num() > 0) {
2046 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2047 prefix, ns.sd(), ns.maximum());
2048 }
2049 }
2050
2051 void G1ConcurrentMark::print_summary_info() {
2052 Log(gc, marking) log;
2053 if (!log.is_trace()) {
2054 return;
2055 }
2056
2057 log.trace(" Concurrent marking:");
2058 print_ms_time_info(" ", "init marks", _init_times);
2059 print_ms_time_info(" ", "remarks", _remark_times);
2060 {
2061 print_ms_time_info(" ", "final marks", _remark_mark_times);
2062 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2063
2064 }
2065 print_ms_time_info(" ", "cleanups", _cleanup_times);
2066 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2067 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2068 log.trace(" Total stop_world time = %8.2f s.",
2069 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2070 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2071 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum());
2072 }
2073
2074 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2075 _concurrent_workers->print_worker_threads_on(st);
2076 }
2077
2078 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2079 _concurrent_workers->threads_do(tc);
2080 }
2081
2082 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2083 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2084 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap));
2085 _prev_mark_bitmap->print_on_error(st, " Prev Bits: ");
2086 _next_mark_bitmap->print_on_error(st, " Next Bits: ");
2087 }
2088
2089 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2090 ReferenceProcessor* result = g1h->ref_processor_cm();
2091 assert(result != NULL, "CM reference processor should not be NULL");
2092 return result;
2093 }
2094
2095 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2096 G1CMTask* task)
2097 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)),
2098 _g1h(g1h), _task(task)
2099 { }
2100
2101 void G1CMTask::setup_for_region(HeapRegion* hr) {
2102 assert(hr != NULL,
2103 "claim_region() should have filtered out NULL regions");
2104 _curr_region = hr;
2105 _finger = hr->bottom();
2106 update_region_limit();
2107 }
2108
2109 void G1CMTask::update_region_limit() {
2110 HeapRegion* hr = _curr_region;
2111 HeapWord* bottom = hr->bottom();
2112 HeapWord* limit = hr->next_top_at_mark_start();
2113
2114 if (limit == bottom) {
2115 // The region was collected underneath our feet.
2116 // We set the finger to bottom to ensure that the bitmap
2117 // iteration that will follow this will not do anything.
2118 // (this is not a condition that holds when we set the region up,
2119 // as the region is not supposed to be empty in the first place)
2120 _finger = bottom;
2121 } else if (limit >= _region_limit) {
2122 assert(limit >= _finger, "peace of mind");
2123 } else {
2124 assert(limit < _region_limit, "only way to get here");
2125 // This can happen under some pretty unusual circumstances. An
2126 // evacuation pause empties the region underneath our feet (NTAMS
2127 // at bottom). We then do some allocation in the region (NTAMS
2128 // stays at bottom), followed by the region being used as a GC
2129 // alloc region (NTAMS will move to top() and the objects
2130 // originally below it will be grayed). All objects now marked in
2131 // the region are explicitly grayed, if below the global finger,
2132 // and we do not need in fact to scan anything else. So, we simply
2133 // set _finger to be limit to ensure that the bitmap iteration
2134 // doesn't do anything.
2135 _finger = limit;
2136 }
2137
2138 _region_limit = limit;
2139 }
2140
2141 void G1CMTask::giveup_current_region() {
2142 assert(_curr_region != NULL, "invariant");
2143 clear_region_fields();
2144 }
2145
2146 void G1CMTask::clear_region_fields() {
2147 // Values for these three fields that indicate that we're not
2148 // holding on to a region.
2149 _curr_region = NULL;
2150 _finger = NULL;
2151 _region_limit = NULL;
2152 }
2153
2154 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2155 if (cm_oop_closure == NULL) {
2156 assert(_cm_oop_closure != NULL, "invariant");
2157 } else {
2158 assert(_cm_oop_closure == NULL, "invariant");
2159 }
2160 _cm_oop_closure = cm_oop_closure;
2161 }
2162
2163 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
2164 guarantee(next_mark_bitmap != NULL, "invariant");
2165 _next_mark_bitmap = next_mark_bitmap;
2166 clear_region_fields();
2167
2168 _calls = 0;
2169 _elapsed_time_ms = 0.0;
2170 _termination_time_ms = 0.0;
2171 _termination_start_time_ms = 0.0;
2172
2173 _mark_stats_cache.reset();
2174 }
2175
2176 bool G1CMTask::should_exit_termination() {
2177 if (!regular_clock_call()) {
2178 return true;
2179 }
2180
2181 // This is called when we are in the termination protocol. We should
2182 // quit if, for some reason, this task wants to abort or the global
2183 // stack is not empty (this means that we can get work from it).
2184 return !_cm->mark_stack_empty() || has_aborted();
2185 }
2186
2187 void G1CMTask::reached_limit() {
2188 assert(_words_scanned >= _words_scanned_limit ||
2189 _refs_reached >= _refs_reached_limit ,
2190 "shouldn't have been called otherwise");
2191 abort_marking_if_regular_check_fail();
2192 }
2193
2194 bool G1CMTask::regular_clock_call() {
2195 if (has_aborted()) {
2196 return false;
2197 }
2198
2199 // First, we need to recalculate the words scanned and refs reached
2200 // limits for the next clock call.
2201 recalculate_limits();
2202
2203 // During the regular clock call we do the following
2204
2205 // (1) If an overflow has been flagged, then we abort.
2206 if (_cm->has_overflown()) {
2207 return false;
2208 }
2209
2210 // If we are not concurrent (i.e. we're doing remark) we don't need
2211 // to check anything else. The other steps are only needed during
2212 // the concurrent marking phase.
2213 if (!_cm->concurrent()) {
2214 return true;
2215 }
2216
2217 // (2) If marking has been aborted for Full GC, then we also abort.
2218 if (_cm->has_aborted()) {
2219 return false;
2220 }
2221
2222 double curr_time_ms = os::elapsedVTime() * 1000.0;
2223
2224 // (4) We check whether we should yield. If we have to, then we abort.
2225 if (SuspendibleThreadSet::should_yield()) {
2226 // We should yield. To do this we abort the task. The caller is
2227 // responsible for yielding.
2228 return false;
2229 }
2230
2231 // (5) We check whether we've reached our time quota. If we have,
2232 // then we abort.
2233 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2234 if (elapsed_time_ms > _time_target_ms) {
2235 _has_timed_out = true;
2236 return false;
2237 }
2238
2239 // (6) Finally, we check whether there are enough completed STAB
2240 // buffers available for processing. If there are, we abort.
2241 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2242 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2243 // we do need to process SATB buffers, we'll abort and restart
2244 // the marking task to do so
2245 return false;
2246 }
2247 return true;
2248 }
2249
2250 void G1CMTask::recalculate_limits() {
2251 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2252 _words_scanned_limit = _real_words_scanned_limit;
2253
2254 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2255 _refs_reached_limit = _real_refs_reached_limit;
2256 }
2257
2258 void G1CMTask::decrease_limits() {
2259 // This is called when we believe that we're going to do an infrequent
2260 // operation which will increase the per byte scanned cost (i.e. move
2261 // entries to/from the global stack). It basically tries to decrease the
2262 // scanning limit so that the clock is called earlier.
2263
2264 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4;
2265 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4;
2266 }
2267
2268 void G1CMTask::move_entries_to_global_stack() {
2269 // Local array where we'll store the entries that will be popped
2270 // from the local queue.
2271 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2272
2273 size_t n = 0;
2274 G1TaskQueueEntry task_entry;
2275 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2276 buffer[n] = task_entry;
2277 ++n;
2278 }
2279 if (n < G1CMMarkStack::EntriesPerChunk) {
2280 buffer[n] = G1TaskQueueEntry();
2281 }
2282
2283 if (n > 0) {
2284 if (!_cm->mark_stack_push(buffer)) {
2285 set_has_aborted();
2286 }
2287 }
2288
2289 // This operation was quite expensive, so decrease the limits.
2290 decrease_limits();
2291 }
2292
2293 bool G1CMTask::get_entries_from_global_stack() {
2294 // Local array where we'll store the entries that will be popped
2295 // from the global stack.
2296 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2297
2298 if (!_cm->mark_stack_pop(buffer)) {
2299 return false;
2300 }
2301
2302 // We did actually pop at least one entry.
2303 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2304 G1TaskQueueEntry task_entry = buffer[i];
2305 if (task_entry.is_null()) {
2306 break;
2307 }
2308 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()));
2309 bool success = _task_queue->push(task_entry);
2310 // We only call this when the local queue is empty or under a
2311 // given target limit. So, we do not expect this push to fail.
2312 assert(success, "invariant");
2313 }
2314
2315 // This operation was quite expensive, so decrease the limits
2316 decrease_limits();
2317 return true;
2318 }
2319
2320 void G1CMTask::drain_local_queue(bool partially) {
2321 if (has_aborted()) {
2322 return;
2323 }
2324
2325 // Decide what the target size is, depending whether we're going to
2326 // drain it partially (so that other tasks can steal if they run out
2327 // of things to do) or totally (at the very end).
2328 size_t target_size;
2329 if (partially) {
2330 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize);
2331 } else {
2332 target_size = 0;
2333 }
2334
2335 if (_task_queue->size() > target_size) {
2336 G1TaskQueueEntry entry;
2337 bool ret = _task_queue->pop_local(entry);
2338 while (ret) {
2339 scan_task_entry(entry);
2340 if (_task_queue->size() <= target_size || has_aborted()) {
2341 ret = false;
2342 } else {
2343 ret = _task_queue->pop_local(entry);
2344 }
2345 }
2346 }
2347 }
2348
2349 void G1CMTask::drain_global_stack(bool partially) {
2350 if (has_aborted()) {
2351 return;
2352 }
2353
2354 // We have a policy to drain the local queue before we attempt to
2355 // drain the global stack.
2356 assert(partially || _task_queue->size() == 0, "invariant");
2357
2358 // Decide what the target size is, depending whether we're going to
2359 // drain it partially (so that other tasks can steal if they run out
2360 // of things to do) or totally (at the very end).
2361 // Notice that when draining the global mark stack partially, due to the racyness
2362 // of the mark stack size update we might in fact drop below the target. But,
2363 // this is not a problem.
2364 // In case of total draining, we simply process until the global mark stack is
2365 // totally empty, disregarding the size counter.
2366 if (partially) {
2367 size_t const target_size = _cm->partial_mark_stack_size_target();
2368 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2369 if (get_entries_from_global_stack()) {
2370 drain_local_queue(partially);
2371 }
2372 }
2373 } else {
2374 while (!has_aborted() && get_entries_from_global_stack()) {
2375 drain_local_queue(partially);
2376 }
2377 }
2378 }
2379
2380 // SATB Queue has several assumptions on whether to call the par or
2381 // non-par versions of the methods. this is why some of the code is
2382 // replicated. We should really get rid of the single-threaded version
2383 // of the code to simplify things.
2384 void G1CMTask::drain_satb_buffers() {
2385 if (has_aborted()) {
2386 return;
2387 }
2388
2389 // We set this so that the regular clock knows that we're in the
2390 // middle of draining buffers and doesn't set the abort flag when it
2391 // notices that SATB buffers are available for draining. It'd be
2392 // very counter productive if it did that. :-)
2393 _draining_satb_buffers = true;
2394
2395 G1CMSATBBufferClosure satb_cl(this, _g1h);
2396 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2397
2398 // This keeps claiming and applying the closure to completed buffers
2399 // until we run out of buffers or we need to abort.
2400 while (!has_aborted() &&
2401 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2402 abort_marking_if_regular_check_fail();
2403 }
2404
2405 _draining_satb_buffers = false;
2406
2407 assert(has_aborted() ||
2408 _cm->concurrent() ||
2409 satb_mq_set.completed_buffers_num() == 0, "invariant");
2410
2411 // again, this was a potentially expensive operation, decrease the
2412 // limits to get the regular clock call early
2413 decrease_limits();
2414 }
2415
2416 void G1CMTask::clear_mark_stats_cache(uint region_idx) {
2417 _mark_stats_cache.reset(region_idx);
2418 }
2419
2420 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() {
2421 return _mark_stats_cache.evict_all();
2422 }
2423
2424 void G1CMTask::print_stats() {
2425 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls);
2426 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2427 _elapsed_time_ms, _termination_time_ms);
2428 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms",
2429 _step_times_ms.num(),
2430 _step_times_ms.avg(),
2431 _step_times_ms.sd(),
2432 _step_times_ms.maximum(),
2433 _step_times_ms.sum());
2434 size_t const hits = _mark_stats_cache.hits();
2435 size_t const misses = _mark_stats_cache.misses();
2436 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f",
2437 hits, misses, percent_of(hits, hits + misses));
2438 }
2439
2440 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) {
2441 return _task_queues->steal(worker_id, task_entry);
2442 }
2443
2444 /*****************************************************************************
2445
2446 The do_marking_step(time_target_ms, ...) method is the building
2447 block of the parallel marking framework. It can be called in parallel
2448 with other invocations of do_marking_step() on different tasks
2449 (but only one per task, obviously) and concurrently with the
2450 mutator threads, or during remark, hence it eliminates the need
2451 for two versions of the code. When called during remark, it will
2452 pick up from where the task left off during the concurrent marking
2453 phase. Interestingly, tasks are also claimable during evacuation
2454 pauses too, since do_marking_step() ensures that it aborts before
2455 it needs to yield.
2456
2457 The data structures that it uses to do marking work are the
2458 following:
2459
2460 (1) Marking Bitmap. If there are gray objects that appear only
2461 on the bitmap (this happens either when dealing with an overflow
2462 or when the initial marking phase has simply marked the roots
2463 and didn't push them on the stack), then tasks claim heap
2464 regions whose bitmap they then scan to find gray objects. A
2465 global finger indicates where the end of the last claimed region
2466 is. A local finger indicates how far into the region a task has
2467 scanned. The two fingers are used to determine how to gray an
2468 object (i.e. whether simply marking it is OK, as it will be
2469 visited by a task in the future, or whether it needs to be also
2470 pushed on a stack).
2471
2472 (2) Local Queue. The local queue of the task which is accessed
2473 reasonably efficiently by the task. Other tasks can steal from
2474 it when they run out of work. Throughout the marking phase, a
2475 task attempts to keep its local queue short but not totally
2476 empty, so that entries are available for stealing by other
2477 tasks. Only when there is no more work, a task will totally
2478 drain its local queue.
2479
2480 (3) Global Mark Stack. This handles local queue overflow. During
2481 marking only sets of entries are moved between it and the local
2482 queues, as access to it requires a mutex and more fine-grain
2483 interaction with it which might cause contention. If it
2484 overflows, then the marking phase should restart and iterate
2485 over the bitmap to identify gray objects. Throughout the marking
2486 phase, tasks attempt to keep the global mark stack at a small
2487 length but not totally empty, so that entries are available for
2488 popping by other tasks. Only when there is no more work, tasks
2489 will totally drain the global mark stack.
2490
2491 (4) SATB Buffer Queue. This is where completed SATB buffers are
2492 made available. Buffers are regularly removed from this queue
2493 and scanned for roots, so that the queue doesn't get too
2494 long. During remark, all completed buffers are processed, as
2495 well as the filled in parts of any uncompleted buffers.
2496
2497 The do_marking_step() method tries to abort when the time target
2498 has been reached. There are a few other cases when the
2499 do_marking_step() method also aborts:
2500
2501 (1) When the marking phase has been aborted (after a Full GC).
2502
2503 (2) When a global overflow (on the global stack) has been
2504 triggered. Before the task aborts, it will actually sync up with
2505 the other tasks to ensure that all the marking data structures
2506 (local queues, stacks, fingers etc.) are re-initialized so that
2507 when do_marking_step() completes, the marking phase can
2508 immediately restart.
2509
2510 (3) When enough completed SATB buffers are available. The
2511 do_marking_step() method only tries to drain SATB buffers right
2512 at the beginning. So, if enough buffers are available, the
2513 marking step aborts and the SATB buffers are processed at
2514 the beginning of the next invocation.
2515
2516 (4) To yield. when we have to yield then we abort and yield
2517 right at the end of do_marking_step(). This saves us from a lot
2518 of hassle as, by yielding we might allow a Full GC. If this
2519 happens then objects will be compacted underneath our feet, the
2520 heap might shrink, etc. We save checking for this by just
2521 aborting and doing the yield right at the end.
2522
2523 From the above it follows that the do_marking_step() method should
2524 be called in a loop (or, otherwise, regularly) until it completes.
2525
2526 If a marking step completes without its has_aborted() flag being
2527 true, it means it has completed the current marking phase (and
2528 also all other marking tasks have done so and have all synced up).
2529
2530 A method called regular_clock_call() is invoked "regularly" (in
2531 sub ms intervals) throughout marking. It is this clock method that
2532 checks all the abort conditions which were mentioned above and
2533 decides when the task should abort. A work-based scheme is used to
2534 trigger this clock method: when the number of object words the
2535 marking phase has scanned or the number of references the marking
2536 phase has visited reach a given limit. Additional invocations to
2537 the method clock have been planted in a few other strategic places
2538 too. The initial reason for the clock method was to avoid calling
2539 vtime too regularly, as it is quite expensive. So, once it was in
2540 place, it was natural to piggy-back all the other conditions on it
2541 too and not constantly check them throughout the code.
2542
2543 If do_termination is true then do_marking_step will enter its
2544 termination protocol.
2545
2546 The value of is_serial must be true when do_marking_step is being
2547 called serially (i.e. by the VMThread) and do_marking_step should
2548 skip any synchronization in the termination and overflow code.
2549 Examples include the serial remark code and the serial reference
2550 processing closures.
2551
2552 The value of is_serial must be false when do_marking_step is
2553 being called by any of the worker threads in a work gang.
2554 Examples include the concurrent marking code (CMMarkingTask),
2555 the MT remark code, and the MT reference processing closures.
2556
2557 *****************************************************************************/
2558
2559 void G1CMTask::do_marking_step(double time_target_ms,
2560 bool do_termination,
2561 bool is_serial) {
2562 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2563
2564 _start_time_ms = os::elapsedVTime() * 1000.0;
2565
2566 // If do_stealing is true then do_marking_step will attempt to
2567 // steal work from the other G1CMTasks. It only makes sense to
2568 // enable stealing when the termination protocol is enabled
2569 // and do_marking_step() is not being called serially.
2570 bool do_stealing = do_termination && !is_serial;
2571
2572 double diff_prediction_ms = _g1h->policy()->predictor().get_new_prediction(&_marking_step_diffs_ms);
2573 _time_target_ms = time_target_ms - diff_prediction_ms;
2574
2575 // set up the variables that are used in the work-based scheme to
2576 // call the regular clock method
2577 _words_scanned = 0;
2578 _refs_reached = 0;
2579 recalculate_limits();
2580
2581 // clear all flags
2582 clear_has_aborted();
2583 _has_timed_out = false;
2584 _draining_satb_buffers = false;
2585
2586 ++_calls;
2587
2588 // Set up the bitmap and oop closures. Anything that uses them is
2589 // eventually called from this method, so it is OK to allocate these
2590 // statically.
2591 G1CMBitMapClosure bitmap_closure(this, _cm);
2592 G1CMOopClosure cm_oop_closure(_g1h, this);
2593 set_cm_oop_closure(&cm_oop_closure);
2594
2595 if (_cm->has_overflown()) {
2596 // This can happen if the mark stack overflows during a GC pause
2597 // and this task, after a yield point, restarts. We have to abort
2598 // as we need to get into the overflow protocol which happens
2599 // right at the end of this task.
2600 set_has_aborted();
2601 }
2602
2603 // First drain any available SATB buffers. After this, we will not
2604 // look at SATB buffers before the next invocation of this method.
2605 // If enough completed SATB buffers are queued up, the regular clock
2606 // will abort this task so that it restarts.
2607 drain_satb_buffers();
2608 // ...then partially drain the local queue and the global stack
2609 drain_local_queue(true);
2610 drain_global_stack(true);
2611
2612 do {
2613 if (!has_aborted() && _curr_region != NULL) {
2614 // This means that we're already holding on to a region.
2615 assert(_finger != NULL, "if region is not NULL, then the finger "
2616 "should not be NULL either");
2617
2618 // We might have restarted this task after an evacuation pause
2619 // which might have evacuated the region we're holding on to
2620 // underneath our feet. Let's read its limit again to make sure
2621 // that we do not iterate over a region of the heap that
2622 // contains garbage (update_region_limit() will also move
2623 // _finger to the start of the region if it is found empty).
2624 update_region_limit();
2625 // We will start from _finger not from the start of the region,
2626 // as we might be restarting this task after aborting half-way
2627 // through scanning this region. In this case, _finger points to
2628 // the address where we last found a marked object. If this is a
2629 // fresh region, _finger points to start().
2630 MemRegion mr = MemRegion(_finger, _region_limit);
2631
2632 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2633 "humongous regions should go around loop once only");
2634
2635 // Some special cases:
2636 // If the memory region is empty, we can just give up the region.
2637 // If the current region is humongous then we only need to check
2638 // the bitmap for the bit associated with the start of the object,
2639 // scan the object if it's live, and give up the region.
2640 // Otherwise, let's iterate over the bitmap of the part of the region
2641 // that is left.
2642 // If the iteration is successful, give up the region.
2643 if (mr.is_empty()) {
2644 giveup_current_region();
2645 abort_marking_if_regular_check_fail();
2646 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2647 if (_next_mark_bitmap->is_marked(mr.start())) {
2648 // The object is marked - apply the closure
2649 bitmap_closure.do_addr(mr.start());
2650 }
2651 // Even if this task aborted while scanning the humongous object
2652 // we can (and should) give up the current region.
2653 giveup_current_region();
2654 abort_marking_if_regular_check_fail();
2655 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
2656 giveup_current_region();
2657 abort_marking_if_regular_check_fail();
2658 } else {
2659 assert(has_aborted(), "currently the only way to do so");
2660 // The only way to abort the bitmap iteration is to return
2661 // false from the do_bit() method. However, inside the
2662 // do_bit() method we move the _finger to point to the
2663 // object currently being looked at. So, if we bail out, we
2664 // have definitely set _finger to something non-null.
2665 assert(_finger != NULL, "invariant");
2666
2667 // Region iteration was actually aborted. So now _finger
2668 // points to the address of the object we last scanned. If we
2669 // leave it there, when we restart this task, we will rescan
2670 // the object. It is easy to avoid this. We move the finger by
2671 // enough to point to the next possible object header.
2672 assert(_finger < _region_limit, "invariant");
2673 HeapWord* const new_finger = _finger + ((oop)_finger)->size();
2674 // Check if bitmap iteration was aborted while scanning the last object
2675 if (new_finger >= _region_limit) {
2676 giveup_current_region();
2677 } else {
2678 move_finger_to(new_finger);
2679 }
2680 }
2681 }
2682 // At this point we have either completed iterating over the
2683 // region we were holding on to, or we have aborted.
2684
2685 // We then partially drain the local queue and the global stack.
2686 // (Do we really need this?)
2687 drain_local_queue(true);
2688 drain_global_stack(true);
2689
2690 // Read the note on the claim_region() method on why it might
2691 // return NULL with potentially more regions available for
2692 // claiming and why we have to check out_of_regions() to determine
2693 // whether we're done or not.
2694 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2695 // We are going to try to claim a new region. We should have
2696 // given up on the previous one.
2697 // Separated the asserts so that we know which one fires.
2698 assert(_curr_region == NULL, "invariant");
2699 assert(_finger == NULL, "invariant");
2700 assert(_region_limit == NULL, "invariant");
2701 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2702 if (claimed_region != NULL) {
2703 // Yes, we managed to claim one
2704 setup_for_region(claimed_region);
2705 assert(_curr_region == claimed_region, "invariant");
2706 }
2707 // It is important to call the regular clock here. It might take
2708 // a while to claim a region if, for example, we hit a large
2709 // block of empty regions. So we need to call the regular clock
2710 // method once round the loop to make sure it's called
2711 // frequently enough.
2712 abort_marking_if_regular_check_fail();
2713 }
2714
2715 if (!has_aborted() && _curr_region == NULL) {
2716 assert(_cm->out_of_regions(),
2717 "at this point we should be out of regions");
2718 }
2719 } while ( _curr_region != NULL && !has_aborted());
2720
2721 if (!has_aborted()) {
2722 // We cannot check whether the global stack is empty, since other
2723 // tasks might be pushing objects to it concurrently.
2724 assert(_cm->out_of_regions(),
2725 "at this point we should be out of regions");
2726 // Try to reduce the number of available SATB buffers so that
2727 // remark has less work to do.
2728 drain_satb_buffers();
2729 }
2730
2731 // Since we've done everything else, we can now totally drain the
2732 // local queue and global stack.
2733 drain_local_queue(false);
2734 drain_global_stack(false);
2735
2736 // Attempt at work stealing from other task's queues.
2737 if (do_stealing && !has_aborted()) {
2738 // We have not aborted. This means that we have finished all that
2739 // we could. Let's try to do some stealing...
2740
2741 // We cannot check whether the global stack is empty, since other
2742 // tasks might be pushing objects to it concurrently.
2743 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2744 "only way to reach here");
2745 while (!has_aborted()) {
2746 G1TaskQueueEntry entry;
2747 if (_cm->try_stealing(_worker_id, entry)) {
2748 scan_task_entry(entry);
2749
2750 // And since we're towards the end, let's totally drain the
2751 // local queue and global stack.
2752 drain_local_queue(false);
2753 drain_global_stack(false);
2754 } else {
2755 break;
2756 }
2757 }
2758 }
2759
2760 // We still haven't aborted. Now, let's try to get into the
2761 // termination protocol.
2762 if (do_termination && !has_aborted()) {
2763 // We cannot check whether the global stack is empty, since other
2764 // tasks might be concurrently pushing objects on it.
2765 // Separated the asserts so that we know which one fires.
2766 assert(_cm->out_of_regions(), "only way to reach here");
2767 assert(_task_queue->size() == 0, "only way to reach here");
2768 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2769
2770 // The G1CMTask class also extends the TerminatorTerminator class,
2771 // hence its should_exit_termination() method will also decide
2772 // whether to exit the termination protocol or not.
2773 bool finished = (is_serial ||
2774 _cm->terminator()->offer_termination(this));
2775 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2776 _termination_time_ms +=
2777 termination_end_time_ms - _termination_start_time_ms;
2778
2779 if (finished) {
2780 // We're all done.
2781
2782 // We can now guarantee that the global stack is empty, since
2783 // all other tasks have finished. We separated the guarantees so
2784 // that, if a condition is false, we can immediately find out
2785 // which one.
2786 guarantee(_cm->out_of_regions(), "only way to reach here");
2787 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2788 guarantee(_task_queue->size() == 0, "only way to reach here");
2789 guarantee(!_cm->has_overflown(), "only way to reach here");
2790 guarantee(!has_aborted(), "should never happen if termination has completed");
2791 } else {
2792 // Apparently there's more work to do. Let's abort this task. It
2793 // will restart it and we can hopefully find more things to do.
2794 set_has_aborted();
2795 }
2796 }
2797
2798 // Mainly for debugging purposes to make sure that a pointer to the
2799 // closure which was statically allocated in this frame doesn't
2800 // escape it by accident.
2801 set_cm_oop_closure(NULL);
2802 double end_time_ms = os::elapsedVTime() * 1000.0;
2803 double elapsed_time_ms = end_time_ms - _start_time_ms;
2804 // Update the step history.
2805 _step_times_ms.add(elapsed_time_ms);
2806
2807 if (has_aborted()) {
2808 // The task was aborted for some reason.
2809 if (_has_timed_out) {
2810 double diff_ms = elapsed_time_ms - _time_target_ms;
2811 // Keep statistics of how well we did with respect to hitting
2812 // our target only if we actually timed out (if we aborted for
2813 // other reasons, then the results might get skewed).
2814 _marking_step_diffs_ms.add(diff_ms);
2815 }
2816
2817 if (_cm->has_overflown()) {
2818 // This is the interesting one. We aborted because a global
2819 // overflow was raised. This means we have to restart the
2820 // marking phase and start iterating over regions. However, in
2821 // order to do this we have to make sure that all tasks stop
2822 // what they are doing and re-initialize in a safe manner. We
2823 // will achieve this with the use of two barrier sync points.
2824
2825 if (!is_serial) {
2826 // We only need to enter the sync barrier if being called
2827 // from a parallel context
2828 _cm->enter_first_sync_barrier(_worker_id);
2829
2830 // When we exit this sync barrier we know that all tasks have
2831 // stopped doing marking work. So, it's now safe to
2832 // re-initialize our data structures.
2833 }
2834
2835 clear_region_fields();
2836 flush_mark_stats_cache();
2837
2838 if (!is_serial) {
2839 // If we're executing the concurrent phase of marking, reset the marking
2840 // state; otherwise the marking state is reset after reference processing,
2841 // during the remark pause.
2842 // If we reset here as a result of an overflow during the remark we will
2843 // see assertion failures from any subsequent set_concurrency_and_phase()
2844 // calls.
2845 if (_cm->concurrent() && _worker_id == 0) {
2846 // Worker 0 is responsible for clearing the global data structures because
2847 // of an overflow. During STW we should not clear the overflow flag (in
2848 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit
2849 // method to abort the pause and restart concurrent marking.
2850 _cm->reset_marking_for_restart();
2851
2852 log_info(gc, marking)("Concurrent Mark reset for overflow");
2853 }
2854
2855 // ...and enter the second barrier.
2856 _cm->enter_second_sync_barrier(_worker_id);
2857 }
2858 // At this point, if we're during the concurrent phase of
2859 // marking, everything has been re-initialized and we're
2860 // ready to restart.
2861 }
2862 }
2863 }
2864
2865 G1CMTask::G1CMTask(uint worker_id,
2866 G1ConcurrentMark* cm,
2867 G1CMTaskQueue* task_queue,
2868 G1RegionMarkStats* mark_stats,
2869 uint max_regions) :
2870 _objArray_processor(this),
2871 _worker_id(worker_id),
2872 _g1h(G1CollectedHeap::heap()),
2873 _cm(cm),
2874 _next_mark_bitmap(NULL),
2875 _task_queue(task_queue),
2876 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize),
2877 _calls(0),
2878 _time_target_ms(0.0),
2879 _start_time_ms(0.0),
2880 _cm_oop_closure(NULL),
2881 _curr_region(NULL),
2882 _finger(NULL),
2883 _region_limit(NULL),
2884 _words_scanned(0),
2885 _words_scanned_limit(0),
2886 _real_words_scanned_limit(0),
2887 _refs_reached(0),
2888 _refs_reached_limit(0),
2889 _real_refs_reached_limit(0),
2890 _has_aborted(false),
2891 _has_timed_out(false),
2892 _draining_satb_buffers(false),
2893 _step_times_ms(),
2894 _elapsed_time_ms(0.0),
2895 _termination_time_ms(0.0),
2896 _termination_start_time_ms(0.0),
2897 _marking_step_diffs_ms()
2898 {
2899 guarantee(task_queue != NULL, "invariant");
2900
2901 _marking_step_diffs_ms.add(0.5);
2902 }
2903
2904 // These are formatting macros that are used below to ensure
2905 // consistent formatting. The *_H_* versions are used to format the
2906 // header for a particular value and they should be kept consistent
2907 // with the corresponding macro. Also note that most of the macros add
2908 // the necessary white space (as a prefix) which makes them a bit
2909 // easier to compose.
2910
2911 // All the output lines are prefixed with this string to be able to
2912 // identify them easily in a large log file.
2913 #define G1PPRL_LINE_PREFIX "###"
2914
2915 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
2916 #ifdef _LP64
2917 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
2918 #else // _LP64
2919 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
2920 #endif // _LP64
2921
2922 // For per-region info
2923 #define G1PPRL_TYPE_FORMAT " %-4s"
2924 #define G1PPRL_TYPE_H_FORMAT " %4s"
2925 #define G1PPRL_STATE_FORMAT " %-5s"
2926 #define G1PPRL_STATE_H_FORMAT " %5s"
2927 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
2928 #define G1PPRL_BYTE_H_FORMAT " %9s"
2929 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
2930 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
2931
2932 // For summary info
2933 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
2934 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
2935 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
2936 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
2937
2938 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) :
2939 _total_used_bytes(0), _total_capacity_bytes(0),
2940 _total_prev_live_bytes(0), _total_next_live_bytes(0),
2941 _total_remset_bytes(0), _total_strong_code_roots_bytes(0)
2942 {
2943 if (!log_is_enabled(Trace, gc, liveness)) {
2944 return;
2945 }
2946
2947 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2948 MemRegion g1_reserved = g1h->g1_reserved();
2949 double now = os::elapsedTime();
2950
2951 // Print the header of the output.
2952 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
2953 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
2954 G1PPRL_SUM_ADDR_FORMAT("reserved")
2955 G1PPRL_SUM_BYTE_FORMAT("region-size"),
2956 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
2957 HeapRegion::GrainBytes);
2958 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
2959 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2960 G1PPRL_TYPE_H_FORMAT
2961 G1PPRL_ADDR_BASE_H_FORMAT
2962 G1PPRL_BYTE_H_FORMAT
2963 G1PPRL_BYTE_H_FORMAT
2964 G1PPRL_BYTE_H_FORMAT
2965 G1PPRL_DOUBLE_H_FORMAT
2966 G1PPRL_BYTE_H_FORMAT
2967 G1PPRL_STATE_H_FORMAT
2968 G1PPRL_BYTE_H_FORMAT,
2969 "type", "address-range",
2970 "used", "prev-live", "next-live", "gc-eff",
2971 "remset", "state", "code-roots");
2972 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2973 G1PPRL_TYPE_H_FORMAT
2974 G1PPRL_ADDR_BASE_H_FORMAT
2975 G1PPRL_BYTE_H_FORMAT
2976 G1PPRL_BYTE_H_FORMAT
2977 G1PPRL_BYTE_H_FORMAT
2978 G1PPRL_DOUBLE_H_FORMAT
2979 G1PPRL_BYTE_H_FORMAT
2980 G1PPRL_STATE_H_FORMAT
2981 G1PPRL_BYTE_H_FORMAT,
2982 "", "",
2983 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
2984 "(bytes)", "", "(bytes)");
2985 }
2986
2987 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) {
2988 if (!log_is_enabled(Trace, gc, liveness)) {
2989 return false;
2990 }
2991
2992 const char* type = r->get_type_str();
2993 HeapWord* bottom = r->bottom();
2994 HeapWord* end = r->end();
2995 size_t capacity_bytes = r->capacity();
2996 size_t used_bytes = r->used();
2997 size_t prev_live_bytes = r->live_bytes();
2998 size_t next_live_bytes = r->next_live_bytes();
2999 double gc_eff = r->gc_efficiency();
3000 size_t remset_bytes = r->rem_set()->mem_size();
3001 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3002 const char* remset_type = r->rem_set()->get_short_state_str();
3003
3004 _total_used_bytes += used_bytes;
3005 _total_capacity_bytes += capacity_bytes;
3006 _total_prev_live_bytes += prev_live_bytes;
3007 _total_next_live_bytes += next_live_bytes;
3008 _total_remset_bytes += remset_bytes;
3009 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3010
3011 // Print a line for this particular region.
3012 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3013 G1PPRL_TYPE_FORMAT
3014 G1PPRL_ADDR_BASE_FORMAT
3015 G1PPRL_BYTE_FORMAT
3016 G1PPRL_BYTE_FORMAT
3017 G1PPRL_BYTE_FORMAT
3018 G1PPRL_DOUBLE_FORMAT
3019 G1PPRL_BYTE_FORMAT
3020 G1PPRL_STATE_FORMAT
3021 G1PPRL_BYTE_FORMAT,
3022 type, p2i(bottom), p2i(end),
3023 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3024 remset_bytes, remset_type, strong_code_roots_bytes);
3025
3026 return false;
3027 }
3028
3029 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3030 if (!log_is_enabled(Trace, gc, liveness)) {
3031 return;
3032 }
3033
3034 // add static memory usages to remembered set sizes
3035 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3036 // Print the footer of the output.
3037 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3038 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3039 " SUMMARY"
3040 G1PPRL_SUM_MB_FORMAT("capacity")
3041 G1PPRL_SUM_MB_PERC_FORMAT("used")
3042 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3043 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3044 G1PPRL_SUM_MB_FORMAT("remset")
3045 G1PPRL_SUM_MB_FORMAT("code-roots"),
3046 bytes_to_mb(_total_capacity_bytes),
3047 bytes_to_mb(_total_used_bytes),
3048 percent_of(_total_used_bytes, _total_capacity_bytes),
3049 bytes_to_mb(_total_prev_live_bytes),
3050 percent_of(_total_prev_live_bytes, _total_capacity_bytes),
3051 bytes_to_mb(_total_next_live_bytes),
3052 percent_of(_total_next_live_bytes, _total_capacity_bytes),
3053 bytes_to_mb(_total_remset_bytes),
3054 bytes_to_mb(_total_strong_code_roots_bytes));
3055 }