1 /*
2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "code/codeCache.hpp"
28 #include "gc/g1/g1BarrierSet.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorState.hpp"
31 #include "gc/g1/g1ConcurrentMark.inline.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1DirtyCardQueue.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1RegionMarkStatsCache.inline.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/g1ThreadLocalData.hpp"
40 #include "gc/g1/g1Trace.hpp"
41 #include "gc/g1/heapRegion.inline.hpp"
42 #include "gc/g1/heapRegionRemSet.hpp"
43 #include "gc/g1/heapRegionSet.inline.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "gc/shared/gcVMOperations.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/suspendibleThreadSet.hpp"
52 #include "gc/shared/taskqueue.inline.hpp"
53 #include "gc/shared/weakProcessor.inline.hpp"
54 #include "gc/shared/workerPolicy.hpp"
55 #include "include/jvm.h"
56 #include "logging/log.hpp"
57 #include "memory/allocation.hpp"
58 #include "memory/iterator.hpp"
59 #include "memory/resourceArea.hpp"
60 #include "memory/universe.hpp"
61 #include "oops/access.inline.hpp"
62 #include "oops/oop.inline.hpp"
63 #include "runtime/atomic.hpp"
64 #include "runtime/handles.inline.hpp"
65 #include "runtime/java.hpp"
66 #include "runtime/orderAccess.hpp"
67 #include "runtime/prefetch.inline.hpp"
68 #include "services/memTracker.hpp"
69 #include "utilities/align.hpp"
70 #include "utilities/growableArray.hpp"
71
72 bool G1CMBitMapClosure::do_addr(HeapWord* const addr) {
73 assert(addr < _cm->finger(), "invariant");
74 assert(addr >= _task->finger(), "invariant");
75
76 // We move that task's local finger along.
77 _task->move_finger_to(addr);
78
79 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
80 // we only partially drain the local queue and global stack
81 _task->drain_local_queue(true);
82 _task->drain_global_stack(true);
83
84 // if the has_aborted flag has been raised, we need to bail out of
85 // the iteration
86 return !_task->has_aborted();
87 }
88
89 G1CMMarkStack::G1CMMarkStack() :
90 _max_chunk_capacity(0),
91 _base(NULL),
92 _chunk_capacity(0) {
93 set_empty();
94 }
95
96 bool G1CMMarkStack::resize(size_t new_capacity) {
97 assert(is_empty(), "Only resize when stack is empty.");
98 assert(new_capacity <= _max_chunk_capacity,
99 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
100
101 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk>::allocate_or_null(new_capacity, mtGC);
102
103 if (new_base == NULL) {
104 log_warning(gc)("Failed to reserve memory for new overflow mark stack with " SIZE_FORMAT " chunks and size " SIZE_FORMAT "B.", new_capacity, new_capacity * sizeof(TaskQueueEntryChunk));
105 return false;
106 }
107 // Release old mapping.
108 if (_base != NULL) {
109 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
110 }
111
112 _base = new_base;
113 _chunk_capacity = new_capacity;
114 set_empty();
115
116 return true;
117 }
118
119 size_t G1CMMarkStack::capacity_alignment() {
120 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
121 }
122
123 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
124 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
125
126 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
127
128 _max_chunk_capacity = align_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
129 size_t initial_chunk_capacity = align_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
130
131 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
132 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
133 _max_chunk_capacity,
134 initial_chunk_capacity);
135
136 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
137 initial_chunk_capacity, _max_chunk_capacity);
138
139 return resize(initial_chunk_capacity);
140 }
141
142 void G1CMMarkStack::expand() {
143 if (_chunk_capacity == _max_chunk_capacity) {
144 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
145 return;
146 }
147 size_t old_capacity = _chunk_capacity;
148 // Double capacity if possible
149 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
150
151 if (resize(new_capacity)) {
152 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
153 old_capacity, new_capacity);
154 } else {
155 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
156 old_capacity, new_capacity);
157 }
158 }
159
160 G1CMMarkStack::~G1CMMarkStack() {
161 if (_base != NULL) {
162 MmapArrayAllocator<TaskQueueEntryChunk>::free(_base, _chunk_capacity);
163 }
164 }
165
166 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
167 elem->next = *list;
168 *list = elem;
169 }
170
171 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
172 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
173 add_chunk_to_list(&_chunk_list, elem);
174 _chunks_in_chunk_list++;
175 }
176
177 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
178 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
179 add_chunk_to_list(&_free_list, elem);
180 }
181
182 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
183 TaskQueueEntryChunk* result = *list;
184 if (result != NULL) {
185 *list = (*list)->next;
186 }
187 return result;
188 }
189
190 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
191 MutexLocker x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
192 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
193 if (result != NULL) {
194 _chunks_in_chunk_list--;
195 }
196 return result;
197 }
198
199 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
200 MutexLocker x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
201 return remove_chunk_from_list(&_free_list);
202 }
203
204 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
205 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
206 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
207 // wraparound of _hwm.
208 if (_hwm >= _chunk_capacity) {
209 return NULL;
210 }
211
212 size_t cur_idx = Atomic::add(&_hwm, 1u) - 1;
213 if (cur_idx >= _chunk_capacity) {
214 return NULL;
215 }
216
217 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
218 result->next = NULL;
219 return result;
220 }
221
222 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
223 // Get a new chunk.
224 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
225
226 if (new_chunk == NULL) {
227 // Did not get a chunk from the free list. Allocate from backing memory.
228 new_chunk = allocate_new_chunk();
229
230 if (new_chunk == NULL) {
231 return false;
232 }
233 }
234
235 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
236
237 add_chunk_to_chunk_list(new_chunk);
238
239 return true;
240 }
241
242 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
243 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
244
245 if (cur == NULL) {
246 return false;
247 }
248
249 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
250
251 add_chunk_to_free_list(cur);
252 return true;
253 }
254
255 void G1CMMarkStack::set_empty() {
256 _chunks_in_chunk_list = 0;
257 _hwm = 0;
258 _chunk_list = NULL;
259 _free_list = NULL;
260 }
261
262 G1CMRootMemRegions::G1CMRootMemRegions(uint const max_regions) :
263 _root_regions(NULL),
264 _max_regions(max_regions),
265 _num_root_regions(0),
266 _claimed_root_regions(0),
267 _scan_in_progress(false),
268 _should_abort(false) {
269 _root_regions = new MemRegion[_max_regions];
270 if (_root_regions == NULL) {
271 vm_exit_during_initialization("Could not allocate root MemRegion set.");
272 }
273 }
274
275 G1CMRootMemRegions::~G1CMRootMemRegions() {
276 delete[] _root_regions;
277 }
278
279 void G1CMRootMemRegions::reset() {
280 _num_root_regions = 0;
281 }
282
283 void G1CMRootMemRegions::add(HeapWord* start, HeapWord* end) {
284 assert_at_safepoint();
285 size_t idx = Atomic::add(&_num_root_regions, (size_t)1) - 1;
286 assert(idx < _max_regions, "Trying to add more root MemRegions than there is space " SIZE_FORMAT, _max_regions);
287 assert(start != NULL && end != NULL && start <= end, "Start (" PTR_FORMAT ") should be less or equal to "
288 "end (" PTR_FORMAT ")", p2i(start), p2i(end));
289 _root_regions[idx].set_start(start);
290 _root_regions[idx].set_end(end);
291 }
292
293 void G1CMRootMemRegions::prepare_for_scan() {
294 assert(!scan_in_progress(), "pre-condition");
295
296 _scan_in_progress = _num_root_regions > 0;
297
298 _claimed_root_regions = 0;
299 _should_abort = false;
300 }
301
302 const MemRegion* G1CMRootMemRegions::claim_next() {
303 if (_should_abort) {
304 // If someone has set the should_abort flag, we return NULL to
305 // force the caller to bail out of their loop.
306 return NULL;
307 }
308
309 if (_claimed_root_regions >= _num_root_regions) {
310 return NULL;
311 }
312
313 size_t claimed_index = Atomic::add(&_claimed_root_regions, (size_t)1) - 1;
314 if (claimed_index < _num_root_regions) {
315 return &_root_regions[claimed_index];
316 }
317 return NULL;
318 }
319
320 uint G1CMRootMemRegions::num_root_regions() const {
321 return (uint)_num_root_regions;
322 }
323
324 void G1CMRootMemRegions::notify_scan_done() {
325 MutexLocker x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
326 _scan_in_progress = false;
327 RootRegionScan_lock->notify_all();
328 }
329
330 void G1CMRootMemRegions::cancel_scan() {
331 notify_scan_done();
332 }
333
334 void G1CMRootMemRegions::scan_finished() {
335 assert(scan_in_progress(), "pre-condition");
336
337 if (!_should_abort) {
338 assert(_claimed_root_regions >= num_root_regions(),
339 "we should have claimed all root regions, claimed " SIZE_FORMAT ", length = %u",
340 _claimed_root_regions, num_root_regions());
341 }
342
343 notify_scan_done();
344 }
345
346 bool G1CMRootMemRegions::wait_until_scan_finished() {
347 if (!scan_in_progress()) {
348 return false;
349 }
350
351 {
352 MonitorLocker ml(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
353 while (scan_in_progress()) {
354 ml.wait();
355 }
356 }
357 return true;
358 }
359
360 // Returns the maximum number of workers to be used in a concurrent
361 // phase based on the number of GC workers being used in a STW
362 // phase.
363 static uint scale_concurrent_worker_threads(uint num_gc_workers) {
364 return MAX2((num_gc_workers + 2) / 4, 1U);
365 }
366
367 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h,
368 G1RegionToSpaceMapper* prev_bitmap_storage,
369 G1RegionToSpaceMapper* next_bitmap_storage) :
370 // _cm_thread set inside the constructor
371 _g1h(g1h),
372 _completed_initialization(false),
373
374 _mark_bitmap_1(),
375 _mark_bitmap_2(),
376 _prev_mark_bitmap(&_mark_bitmap_1),
377 _next_mark_bitmap(&_mark_bitmap_2),
378
379 _heap(_g1h->reserved_region()),
380
381 _root_regions(_g1h->max_regions()),
382
383 _global_mark_stack(),
384
385 // _finger set in set_non_marking_state
386
387 _worker_id_offset(G1DirtyCardQueueSet::num_par_ids() + G1ConcRefinementThreads),
388 _max_num_tasks(ParallelGCThreads),
389 // _num_active_tasks set in set_non_marking_state()
390 // _tasks set inside the constructor
391
392 _task_queues(new G1CMTaskQueueSet((int) _max_num_tasks)),
393 _terminator((int) _max_num_tasks, _task_queues),
394
395 _first_overflow_barrier_sync(),
396 _second_overflow_barrier_sync(),
397
398 _has_overflown(false),
399 _concurrent(false),
400 _has_aborted(false),
401 _restart_for_overflow(false),
402 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
403 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
404
405 // _verbose_level set below
406
407 _init_times(),
408 _remark_times(),
409 _remark_mark_times(),
410 _remark_weak_ref_times(),
411 _cleanup_times(),
412 _total_cleanup_time(0.0),
413
414 _accum_task_vtime(NULL),
415
416 _concurrent_workers(NULL),
417 _num_concurrent_workers(0),
418 _max_concurrent_workers(0),
419
420 _region_mark_stats(NEW_C_HEAP_ARRAY(G1RegionMarkStats, _g1h->max_regions(), mtGC)),
421 _top_at_rebuild_starts(NEW_C_HEAP_ARRAY(HeapWord*, _g1h->max_regions(), mtGC))
422 {
423 _mark_bitmap_1.initialize(g1h->reserved_region(), prev_bitmap_storage);
424 _mark_bitmap_2.initialize(g1h->reserved_region(), next_bitmap_storage);
425
426 // Create & start ConcurrentMark thread.
427 _cm_thread = new G1ConcurrentMarkThread(this);
428 if (_cm_thread->osthread() == NULL) {
429 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
430 }
431
432 assert(CGC_lock != NULL, "CGC_lock must be initialized");
433
434 if (FLAG_IS_DEFAULT(ConcGCThreads) || ConcGCThreads == 0) {
435 // Calculate the number of concurrent worker threads by scaling
436 // the number of parallel GC threads.
437 uint marking_thread_num = scale_concurrent_worker_threads(ParallelGCThreads);
438 FLAG_SET_ERGO(ConcGCThreads, marking_thread_num);
439 }
440
441 assert(ConcGCThreads > 0, "ConcGCThreads have been set.");
442 if (ConcGCThreads > ParallelGCThreads) {
443 log_warning(gc)("More ConcGCThreads (%u) than ParallelGCThreads (%u).",
444 ConcGCThreads, ParallelGCThreads);
445 return;
446 }
447
448 log_debug(gc)("ConcGCThreads: %u offset %u", ConcGCThreads, _worker_id_offset);
449 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
450
451 _num_concurrent_workers = ConcGCThreads;
452 _max_concurrent_workers = _num_concurrent_workers;
453
454 _concurrent_workers = new WorkGang("G1 Conc", _max_concurrent_workers, false, true);
455 _concurrent_workers->initialize_workers();
456
457 if (FLAG_IS_DEFAULT(MarkStackSize)) {
458 size_t mark_stack_size =
459 MIN2(MarkStackSizeMax,
460 MAX2(MarkStackSize, (size_t) (_max_concurrent_workers * TASKQUEUE_SIZE)));
461 // Verify that the calculated value for MarkStackSize is in range.
462 // It would be nice to use the private utility routine from Arguments.
463 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
464 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
465 "must be between 1 and " SIZE_FORMAT,
466 mark_stack_size, MarkStackSizeMax);
467 return;
468 }
469 FLAG_SET_ERGO(MarkStackSize, mark_stack_size);
470 } else {
471 // Verify MarkStackSize is in range.
472 if (FLAG_IS_CMDLINE(MarkStackSize)) {
473 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
474 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
475 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
476 "must be between 1 and " SIZE_FORMAT,
477 MarkStackSize, MarkStackSizeMax);
478 return;
479 }
480 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
481 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
482 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
483 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
484 MarkStackSize, MarkStackSizeMax);
485 return;
486 }
487 }
488 }
489 }
490
491 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
492 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
493 }
494
495 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_num_tasks, mtGC);
496 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_num_tasks, mtGC);
497
498 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
499 _num_active_tasks = _max_num_tasks;
500
501 for (uint i = 0; i < _max_num_tasks; ++i) {
502 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
503 task_queue->initialize();
504 _task_queues->register_queue(i, task_queue);
505
506 _tasks[i] = new G1CMTask(i, this, task_queue, _region_mark_stats, _g1h->max_regions());
507
508 _accum_task_vtime[i] = 0.0;
509 }
510
511 reset_at_marking_complete();
512 _completed_initialization = true;
513 }
514
515 void G1ConcurrentMark::reset() {
516 _has_aborted = false;
517
518 reset_marking_for_restart();
519
520 // Reset all tasks, since different phases will use different number of active
521 // threads. So, it's easiest to have all of them ready.
522 for (uint i = 0; i < _max_num_tasks; ++i) {
523 _tasks[i]->reset(_next_mark_bitmap);
524 }
525
526 uint max_regions = _g1h->max_regions();
527 for (uint i = 0; i < max_regions; i++) {
528 _top_at_rebuild_starts[i] = NULL;
529 _region_mark_stats[i].clear();
530 }
531 }
532
533 void G1ConcurrentMark::clear_statistics_in_region(uint region_idx) {
534 for (uint j = 0; j < _max_num_tasks; ++j) {
535 _tasks[j]->clear_mark_stats_cache(region_idx);
536 }
537 _top_at_rebuild_starts[region_idx] = NULL;
538 _region_mark_stats[region_idx].clear();
539 }
540
541 void G1ConcurrentMark::clear_statistics(HeapRegion* r) {
542 uint const region_idx = r->hrm_index();
543 if (r->is_humongous()) {
544 assert(r->is_starts_humongous(), "Got humongous continues region here");
545 uint const size_in_regions = (uint)_g1h->humongous_obj_size_in_regions(oop(r->humongous_start_region()->bottom())->size());
546 for (uint j = region_idx; j < (region_idx + size_in_regions); j++) {
547 clear_statistics_in_region(j);
548 }
549 } else {
550 clear_statistics_in_region(region_idx);
551 }
552 }
553
554 static void clear_mark_if_set(G1CMBitMap* bitmap, HeapWord* addr) {
555 if (bitmap->is_marked(addr)) {
556 bitmap->clear(addr);
557 }
558 }
559
560 void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
561 assert_at_safepoint_on_vm_thread();
562
563 // Need to clear all mark bits of the humongous object.
564 clear_mark_if_set(_prev_mark_bitmap, r->bottom());
565 clear_mark_if_set(_next_mark_bitmap, r->bottom());
566
567 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
568 return;
569 }
570
571 // Clear any statistics about the region gathered so far.
572 clear_statistics(r);
573 }
574
575 void G1ConcurrentMark::reset_marking_for_restart() {
576 _global_mark_stack.set_empty();
577
578 // Expand the marking stack, if we have to and if we can.
579 if (has_overflown()) {
580 _global_mark_stack.expand();
581
582 uint max_regions = _g1h->max_regions();
583 for (uint i = 0; i < max_regions; i++) {
584 _region_mark_stats[i].clear_during_overflow();
585 }
586 }
587
588 clear_has_overflown();
589 _finger = _heap.start();
590
591 for (uint i = 0; i < _max_num_tasks; ++i) {
592 G1CMTaskQueue* queue = _task_queues->queue(i);
593 queue->set_empty();
594 }
595 }
596
597 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
598 assert(active_tasks <= _max_num_tasks, "we should not have more");
599
600 _num_active_tasks = active_tasks;
601 // Need to update the three data structures below according to the
602 // number of active threads for this phase.
603 _terminator.terminator()->reset_for_reuse((int) active_tasks);
604 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
605 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
606 }
607
608 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
609 set_concurrency(active_tasks);
610
611 _concurrent = concurrent;
612
613 if (!concurrent) {
614 // At this point we should be in a STW phase, and completed marking.
615 assert_at_safepoint_on_vm_thread();
616 assert(out_of_regions(),
617 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
618 p2i(_finger), p2i(_heap.end()));
619 }
620 }
621
622 void G1ConcurrentMark::reset_at_marking_complete() {
623 // We set the global marking state to some default values when we're
624 // not doing marking.
625 reset_marking_for_restart();
626 _num_active_tasks = 0;
627 }
628
629 G1ConcurrentMark::~G1ConcurrentMark() {
630 FREE_C_HEAP_ARRAY(HeapWord*, _top_at_rebuild_starts);
631 FREE_C_HEAP_ARRAY(G1RegionMarkStats, _region_mark_stats);
632 // The G1ConcurrentMark instance is never freed.
633 ShouldNotReachHere();
634 }
635
636 class G1ClearBitMapTask : public AbstractGangTask {
637 public:
638 static size_t chunk_size() { return M; }
639
640 private:
641 // Heap region closure used for clearing the given mark bitmap.
642 class G1ClearBitmapHRClosure : public HeapRegionClosure {
643 private:
644 G1CMBitMap* _bitmap;
645 G1ConcurrentMark* _cm;
646 public:
647 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _bitmap(bitmap), _cm(cm) {
648 }
649
650 virtual bool do_heap_region(HeapRegion* r) {
651 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
652
653 HeapWord* cur = r->bottom();
654 HeapWord* const end = r->end();
655
656 while (cur < end) {
657 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
658 _bitmap->clear_range(mr);
659
660 cur += chunk_size_in_words;
661
662 // Abort iteration if after yielding the marking has been aborted.
663 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
664 return true;
665 }
666 // Repeat the asserts from before the start of the closure. We will do them
667 // as asserts here to minimize their overhead on the product. However, we
668 // will have them as guarantees at the beginning / end of the bitmap
669 // clearing to get some checking in the product.
670 assert(_cm == NULL || _cm->cm_thread()->during_cycle(), "invariant");
671 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_or_rebuild_in_progress(), "invariant");
672 }
673 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
674
675 return false;
676 }
677 };
678
679 G1ClearBitmapHRClosure _cl;
680 HeapRegionClaimer _hr_claimer;
681 bool _suspendible; // If the task is suspendible, workers must join the STS.
682
683 public:
684 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
685 AbstractGangTask("G1 Clear Bitmap"),
686 _cl(bitmap, suspendible ? cm : NULL),
687 _hr_claimer(n_workers),
688 _suspendible(suspendible)
689 { }
690
691 void work(uint worker_id) {
692 SuspendibleThreadSetJoiner sts_join(_suspendible);
693 G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hr_claimer, worker_id);
694 }
695
696 bool is_complete() {
697 return _cl.is_complete();
698 }
699 };
700
701 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
702 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
703
704 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
705 size_t const num_chunks = align_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
706
707 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
708
709 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
710
711 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
712 workers->run_task(&cl, num_workers);
713 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
714 }
715
716 void G1ConcurrentMark::cleanup_for_next_mark() {
717 // Make sure that the concurrent mark thread looks to still be in
718 // the current cycle.
719 guarantee(cm_thread()->during_cycle(), "invariant");
720
721 // We are finishing up the current cycle by clearing the next
722 // marking bitmap and getting it ready for the next cycle. During
723 // this time no other cycle can start. So, let's make sure that this
724 // is the case.
725 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
726
727 clear_bitmap(_next_mark_bitmap, _concurrent_workers, true);
728
729 // Repeat the asserts from above.
730 guarantee(cm_thread()->during_cycle(), "invariant");
731 guarantee(!_g1h->collector_state()->mark_or_rebuild_in_progress(), "invariant");
732 }
733
734 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
735 assert_at_safepoint_on_vm_thread();
736 clear_bitmap(_prev_mark_bitmap, workers, false);
737 }
738
739 class NoteStartOfMarkHRClosure : public HeapRegionClosure {
740 public:
741 bool do_heap_region(HeapRegion* r) {
742 r->note_start_of_marking();
743 return false;
744 }
745 };
746
747 void G1ConcurrentMark::pre_initial_mark() {
748 assert_at_safepoint_on_vm_thread();
749
750 // Reset marking state.
751 reset();
752
753 // For each region note start of marking.
754 NoteStartOfMarkHRClosure startcl;
755 _g1h->heap_region_iterate(&startcl);
756
757 _root_regions.reset();
758 }
759
760
761 void G1ConcurrentMark::post_initial_mark() {
762 // Start Concurrent Marking weak-reference discovery.
763 ReferenceProcessor* rp = _g1h->ref_processor_cm();
764 // enable ("weak") refs discovery
765 rp->enable_discovery();
766 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
767
768 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
769 // This is the start of the marking cycle, we're expected all
770 // threads to have SATB queues with active set to false.
771 satb_mq_set.set_active_all_threads(true, /* new active value */
772 false /* expected_active */);
773
774 _root_regions.prepare_for_scan();
775
776 // update_g1_committed() will be called at the end of an evac pause
777 // when marking is on. So, it's also called at the end of the
778 // initial-mark pause to update the heap end, if the heap expands
779 // during it. No need to call it here.
780 }
781
782 /*
783 * Notice that in the next two methods, we actually leave the STS
784 * during the barrier sync and join it immediately afterwards. If we
785 * do not do this, the following deadlock can occur: one thread could
786 * be in the barrier sync code, waiting for the other thread to also
787 * sync up, whereas another one could be trying to yield, while also
788 * waiting for the other threads to sync up too.
789 *
790 * Note, however, that this code is also used during remark and in
791 * this case we should not attempt to leave / enter the STS, otherwise
792 * we'll either hit an assert (debug / fastdebug) or deadlock
793 * (product). So we should only leave / enter the STS if we are
794 * operating concurrently.
795 *
796 * Because the thread that does the sync barrier has left the STS, it
797 * is possible to be suspended for a Full GC or an evacuation pause
798 * could occur. This is actually safe, since the entering the sync
799 * barrier is one of the last things do_marking_step() does, and it
800 * doesn't manipulate any data structures afterwards.
801 */
802
803 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
804 bool barrier_aborted;
805 {
806 SuspendibleThreadSetLeaver sts_leave(concurrent());
807 barrier_aborted = !_first_overflow_barrier_sync.enter();
808 }
809
810 // at this point everyone should have synced up and not be doing any
811 // more work
812
813 if (barrier_aborted) {
814 // If the barrier aborted we ignore the overflow condition and
815 // just abort the whole marking phase as quickly as possible.
816 return;
817 }
818 }
819
820 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
821 SuspendibleThreadSetLeaver sts_leave(concurrent());
822 _second_overflow_barrier_sync.enter();
823
824 // at this point everything should be re-initialized and ready to go
825 }
826
827 class G1CMConcurrentMarkingTask : public AbstractGangTask {
828 G1ConcurrentMark* _cm;
829
830 public:
831 void work(uint worker_id) {
832 assert(Thread::current()->is_ConcurrentGC_thread(), "Not a concurrent GC thread");
833 ResourceMark rm;
834
835 double start_vtime = os::elapsedVTime();
836
837 {
838 SuspendibleThreadSetJoiner sts_join;
839
840 assert(worker_id < _cm->active_tasks(), "invariant");
841
842 G1CMTask* task = _cm->task(worker_id);
843 task->record_start_time();
844 if (!_cm->has_aborted()) {
845 do {
846 task->do_marking_step(G1ConcMarkStepDurationMillis,
847 true /* do_termination */,
848 false /* is_serial*/);
849
850 _cm->do_yield_check();
851 } while (!_cm->has_aborted() && task->has_aborted());
852 }
853 task->record_end_time();
854 guarantee(!task->has_aborted() || _cm->has_aborted(), "invariant");
855 }
856
857 double end_vtime = os::elapsedVTime();
858 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
859 }
860
861 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm) :
862 AbstractGangTask("Concurrent Mark"), _cm(cm) { }
863
864 ~G1CMConcurrentMarkingTask() { }
865 };
866
867 uint G1ConcurrentMark::calc_active_marking_workers() {
868 uint result = 0;
869 if (!UseDynamicNumberOfGCThreads ||
870 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
871 !ForceDynamicNumberOfGCThreads)) {
872 result = _max_concurrent_workers;
873 } else {
874 result =
875 WorkerPolicy::calc_default_active_workers(_max_concurrent_workers,
876 1, /* Minimum workers */
877 _num_concurrent_workers,
878 Threads::number_of_non_daemon_threads());
879 // Don't scale the result down by scale_concurrent_workers() because
880 // that scaling has already gone into "_max_concurrent_workers".
881 }
882 assert(result > 0 && result <= _max_concurrent_workers,
883 "Calculated number of marking workers must be larger than zero and at most the maximum %u, but is %u",
884 _max_concurrent_workers, result);
885 return result;
886 }
887
888 void G1ConcurrentMark::scan_root_region(const MemRegion* region, uint worker_id) {
889 #ifdef ASSERT
890 HeapWord* last = region->last();
891 HeapRegion* hr = _g1h->heap_region_containing(last);
892 assert(hr->is_old() || hr->next_top_at_mark_start() == hr->bottom(),
893 "Root regions must be old or survivor/eden but region %u is %s", hr->hrm_index(), hr->get_type_str());
894 assert(hr->next_top_at_mark_start() == region->start(),
895 "MemRegion start should be equal to nTAMS");
896 #endif
897
898 G1RootRegionScanClosure cl(_g1h, this, worker_id);
899
900 const uintx interval = PrefetchScanIntervalInBytes;
901 HeapWord* curr = region->start();
902 const HeapWord* end = region->end();
903 while (curr < end) {
904 Prefetch::read(curr, interval);
905 oop obj = oop(curr);
906 int size = obj->oop_iterate_size(&cl);
907 assert(size == obj->size(), "sanity");
908 curr += size;
909 }
910 }
911
912 class G1CMRootRegionScanTask : public AbstractGangTask {
913 G1ConcurrentMark* _cm;
914 public:
915 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
916 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
917
918 void work(uint worker_id) {
919 assert(Thread::current()->is_ConcurrentGC_thread(),
920 "this should only be done by a conc GC thread");
921
922 G1CMRootMemRegions* root_regions = _cm->root_regions();
923 const MemRegion* region = root_regions->claim_next();
924 while (region != NULL) {
925 _cm->scan_root_region(region, worker_id);
926 region = root_regions->claim_next();
927 }
928 }
929 };
930
931 void G1ConcurrentMark::scan_root_regions() {
932 // scan_in_progress() will have been set to true only if there was
933 // at least one root region to scan. So, if it's false, we
934 // should not attempt to do any further work.
935 if (root_regions()->scan_in_progress()) {
936 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
937
938 _num_concurrent_workers = MIN2(calc_active_marking_workers(),
939 // We distribute work on a per-region basis, so starting
940 // more threads than that is useless.
941 root_regions()->num_root_regions());
942 assert(_num_concurrent_workers <= _max_concurrent_workers,
943 "Maximum number of marking threads exceeded");
944
945 G1CMRootRegionScanTask task(this);
946 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
947 task.name(), _num_concurrent_workers, root_regions()->num_root_regions());
948 _concurrent_workers->run_task(&task, _num_concurrent_workers);
949
950 // It's possible that has_aborted() is true here without actually
951 // aborting the survivor scan earlier. This is OK as it's
952 // mainly used for sanity checking.
953 root_regions()->scan_finished();
954 }
955 }
956
957 void G1ConcurrentMark::concurrent_cycle_start() {
958 _gc_timer_cm->register_gc_start();
959
960 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
961
962 _g1h->trace_heap_before_gc(_gc_tracer_cm);
963 }
964
965 void G1ConcurrentMark::concurrent_cycle_end() {
966 _g1h->collector_state()->set_clearing_next_bitmap(false);
967
968 _g1h->trace_heap_after_gc(_gc_tracer_cm);
969
970 if (has_aborted()) {
971 log_info(gc, marking)("Concurrent Mark Abort");
972 _gc_tracer_cm->report_concurrent_mode_failure();
973 }
974
975 _gc_timer_cm->register_gc_end();
976
977 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
978 }
979
980 void G1ConcurrentMark::mark_from_roots() {
981 _restart_for_overflow = false;
982
983 _num_concurrent_workers = calc_active_marking_workers();
984
985 uint active_workers = MAX2(1U, _num_concurrent_workers);
986
987 // Setting active workers is not guaranteed since fewer
988 // worker threads may currently exist and more may not be
989 // available.
990 active_workers = _concurrent_workers->update_active_workers(active_workers);
991 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _concurrent_workers->total_workers());
992
993 // Parallel task terminator is set in "set_concurrency_and_phase()"
994 set_concurrency_and_phase(active_workers, true /* concurrent */);
995
996 G1CMConcurrentMarkingTask marking_task(this);
997 _concurrent_workers->run_task(&marking_task);
998 print_stats();
999 }
1000
1001 void G1ConcurrentMark::verify_during_pause(G1HeapVerifier::G1VerifyType type, VerifyOption vo, const char* caller) {
1002 G1HeapVerifier* verifier = _g1h->verifier();
1003
1004 verifier->verify_region_sets_optional();
1005
1006 if (VerifyDuringGC) {
1007 GCTraceTime(Debug, gc, phases) debug(caller, _gc_timer_cm);
1008
1009 size_t const BufLen = 512;
1010 char buffer[BufLen];
1011
1012 jio_snprintf(buffer, BufLen, "During GC (%s)", caller);
1013 verifier->verify(type, vo, buffer);
1014 }
1015
1016 verifier->check_bitmaps(caller);
1017 }
1018
1019 class G1UpdateRemSetTrackingBeforeRebuildTask : public AbstractGangTask {
1020 G1CollectedHeap* _g1h;
1021 G1ConcurrentMark* _cm;
1022 HeapRegionClaimer _hrclaimer;
1023 uint volatile _total_selected_for_rebuild;
1024
1025 G1PrintRegionLivenessInfoClosure _cl;
1026
1027 class G1UpdateRemSetTrackingBeforeRebuild : public HeapRegionClosure {
1028 G1CollectedHeap* _g1h;
1029 G1ConcurrentMark* _cm;
1030
1031 G1PrintRegionLivenessInfoClosure* _cl;
1032
1033 uint _num_regions_selected_for_rebuild; // The number of regions actually selected for rebuild.
1034
1035 void update_remset_before_rebuild(HeapRegion* hr) {
1036 G1RemSetTrackingPolicy* tracking_policy = _g1h->policy()->remset_tracker();
1037
1038 bool selected_for_rebuild;
1039 if (hr->is_humongous()) {
1040 bool const is_live = _cm->liveness(hr->humongous_start_region()->hrm_index()) > 0;
1041 selected_for_rebuild = tracking_policy->update_humongous_before_rebuild(hr, is_live);
1042 } else {
1043 size_t const live_bytes = _cm->liveness(hr->hrm_index());
1044 selected_for_rebuild = tracking_policy->update_before_rebuild(hr, live_bytes);
1045 }
1046 if (selected_for_rebuild) {
1047 _num_regions_selected_for_rebuild++;
1048 }
1049 _cm->update_top_at_rebuild_start(hr);
1050 }
1051
1052 // Distribute the given words across the humongous object starting with hr and
1053 // note end of marking.
1054 void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
1055 uint const region_idx = hr->hrm_index();
1056 size_t const obj_size_in_words = (size_t)oop(hr->bottom())->size();
1057 uint const num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(obj_size_in_words);
1058
1059 // "Distributing" zero words means that we only note end of marking for these
1060 // regions.
1061 assert(marked_words == 0 || obj_size_in_words == marked_words,
1062 "Marked words should either be 0 or the same as humongous object (" SIZE_FORMAT ") but is " SIZE_FORMAT,
1063 obj_size_in_words, marked_words);
1064
1065 for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
1066 HeapRegion* const r = _g1h->region_at(i);
1067 size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
1068
1069 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous region %u (%s)",
1070 words_to_add, i, r->get_type_str());
1071 add_marked_bytes_and_note_end(r, words_to_add * HeapWordSize);
1072 marked_words -= words_to_add;
1073 }
1074 assert(marked_words == 0,
1075 SIZE_FORMAT " words left after distributing space across %u regions",
1076 marked_words, num_regions_in_humongous);
1077 }
1078
1079 void update_marked_bytes(HeapRegion* hr) {
1080 uint const region_idx = hr->hrm_index();
1081 size_t const marked_words = _cm->liveness(region_idx);
1082 // The marking attributes the object's size completely to the humongous starts
1083 // region. We need to distribute this value across the entire set of regions a
1084 // humongous object spans.
1085 if (hr->is_humongous()) {
1086 assert(hr->is_starts_humongous() || marked_words == 0,
1087 "Should not have marked words " SIZE_FORMAT " in non-starts humongous region %u (%s)",
1088 marked_words, region_idx, hr->get_type_str());
1089 if (hr->is_starts_humongous()) {
1090 distribute_marked_bytes(hr, marked_words);
1091 }
1092 } else {
1093 log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
1094 add_marked_bytes_and_note_end(hr, marked_words * HeapWordSize);
1095 }
1096 }
1097
1098 void add_marked_bytes_and_note_end(HeapRegion* hr, size_t marked_bytes) {
1099 hr->add_to_marked_bytes(marked_bytes);
1100 _cl->do_heap_region(hr);
1101 hr->note_end_of_marking();
1102 }
1103
1104 public:
1105 G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm, G1PrintRegionLivenessInfoClosure* cl) :
1106 _g1h(g1h), _cm(cm), _cl(cl), _num_regions_selected_for_rebuild(0) { }
1107
1108 virtual bool do_heap_region(HeapRegion* r) {
1109 update_remset_before_rebuild(r);
1110 update_marked_bytes(r);
1111
1112 return false;
1113 }
1114
1115 uint num_selected_for_rebuild() const { return _num_regions_selected_for_rebuild; }
1116 };
1117
1118 public:
1119 G1UpdateRemSetTrackingBeforeRebuildTask(G1CollectedHeap* g1h, G1ConcurrentMark* cm, uint num_workers) :
1120 AbstractGangTask("G1 Update RemSet Tracking Before Rebuild"),
1121 _g1h(g1h), _cm(cm), _hrclaimer(num_workers), _total_selected_for_rebuild(0), _cl("Post-Marking") { }
1122
1123 virtual void work(uint worker_id) {
1124 G1UpdateRemSetTrackingBeforeRebuild update_cl(_g1h, _cm, &_cl);
1125 _g1h->heap_region_par_iterate_from_worker_offset(&update_cl, &_hrclaimer, worker_id);
1126 Atomic::add(&_total_selected_for_rebuild, update_cl.num_selected_for_rebuild());
1127 }
1128
1129 uint total_selected_for_rebuild() const { return _total_selected_for_rebuild; }
1130
1131 // Number of regions for which roughly one thread should be spawned for this work.
1132 static const uint RegionsPerThread = 384;
1133 };
1134
1135 class G1UpdateRemSetTrackingAfterRebuild : public HeapRegionClosure {
1136 G1CollectedHeap* _g1h;
1137 public:
1138 G1UpdateRemSetTrackingAfterRebuild(G1CollectedHeap* g1h) : _g1h(g1h) { }
1139
1140 virtual bool do_heap_region(HeapRegion* r) {
1141 _g1h->policy()->remset_tracker()->update_after_rebuild(r);
1142 return false;
1143 }
1144 };
1145
1146 void G1ConcurrentMark::remark() {
1147 assert_at_safepoint_on_vm_thread();
1148
1149 // If a full collection has happened, we should not continue. However we might
1150 // have ended up here as the Remark VM operation has been scheduled already.
1151 if (has_aborted()) {
1152 return;
1153 }
1154
1155 G1Policy* policy = _g1h->policy();
1156 policy->record_concurrent_mark_remark_start();
1157
1158 double start = os::elapsedTime();
1159
1160 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark before");
1161
1162 {
1163 GCTraceTime(Debug, gc, phases) debug("Finalize Marking", _gc_timer_cm);
1164 finalize_marking();
1165 }
1166
1167 double mark_work_end = os::elapsedTime();
1168
1169 bool const mark_finished = !has_overflown();
1170 if (mark_finished) {
1171 weak_refs_work(false /* clear_all_soft_refs */);
1172
1173 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1174 // We're done with marking.
1175 // This is the end of the marking cycle, we're expected all
1176 // threads to have SATB queues with active set to true.
1177 satb_mq_set.set_active_all_threads(false, /* new active value */
1178 true /* expected_active */);
1179
1180 {
1181 GCTraceTime(Debug, gc, phases) debug("Flush Task Caches", _gc_timer_cm);
1182 flush_all_task_caches();
1183 }
1184
1185 // Install newly created mark bitmap as "prev".
1186 swap_mark_bitmaps();
1187 {
1188 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking Before Rebuild", _gc_timer_cm);
1189
1190 uint const workers_by_capacity = (_g1h->num_regions() + G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread - 1) /
1191 G1UpdateRemSetTrackingBeforeRebuildTask::RegionsPerThread;
1192 uint const num_workers = MIN2(_g1h->workers()->active_workers(), workers_by_capacity);
1193
1194 G1UpdateRemSetTrackingBeforeRebuildTask cl(_g1h, this, num_workers);
1195 log_debug(gc,ergo)("Running %s using %u workers for %u regions in heap", cl.name(), num_workers, _g1h->num_regions());
1196 _g1h->workers()->run_task(&cl, num_workers);
1197
1198 log_debug(gc, remset, tracking)("Remembered Set Tracking update regions total %u, selected %u",
1199 _g1h->num_regions(), cl.total_selected_for_rebuild());
1200 }
1201 {
1202 GCTraceTime(Debug, gc, phases) debug("Reclaim Empty Regions", _gc_timer_cm);
1203 reclaim_empty_regions();
1204 }
1205
1206 // Clean out dead classes
1207 if (ClassUnloadingWithConcurrentMark) {
1208 GCTraceTime(Debug, gc, phases) debug("Purge Metaspace", _gc_timer_cm);
1209 ClassLoaderDataGraph::purge();
1210 }
1211
1212 compute_new_sizes();
1213
1214 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark after");
1215
1216 assert(!restart_for_overflow(), "sanity");
1217 // Completely reset the marking state since marking completed
1218 reset_at_marking_complete();
1219 } else {
1220 // We overflowed. Restart concurrent marking.
1221 _restart_for_overflow = true;
1222
1223 verify_during_pause(G1HeapVerifier::G1VerifyRemark, VerifyOption_G1UsePrevMarking, "Remark overflow");
1224
1225 // Clear the marking state because we will be restarting
1226 // marking due to overflowing the global mark stack.
1227 reset_marking_for_restart();
1228 }
1229
1230 {
1231 GCTraceTime(Debug, gc, phases) debug("Report Object Count", _gc_timer_cm);
1232 report_object_count(mark_finished);
1233 }
1234
1235 // Statistics
1236 double now = os::elapsedTime();
1237 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1238 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1239 _remark_times.add((now - start) * 1000.0);
1240
1241 policy->record_concurrent_mark_remark_end();
1242 }
1243
1244 class G1ReclaimEmptyRegionsTask : public AbstractGangTask {
1245 // Per-region work during the Cleanup pause.
1246 class G1ReclaimEmptyRegionsClosure : public HeapRegionClosure {
1247 G1CollectedHeap* _g1h;
1248 size_t _freed_bytes;
1249 FreeRegionList* _local_cleanup_list;
1250 uint _old_regions_removed;
1251 uint _humongous_regions_removed;
1252
1253 public:
1254 G1ReclaimEmptyRegionsClosure(G1CollectedHeap* g1h,
1255 FreeRegionList* local_cleanup_list) :
1256 _g1h(g1h),
1257 _freed_bytes(0),
1258 _local_cleanup_list(local_cleanup_list),
1259 _old_regions_removed(0),
1260 _humongous_regions_removed(0) { }
1261
1262 size_t freed_bytes() { return _freed_bytes; }
1263 const uint old_regions_removed() { return _old_regions_removed; }
1264 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1265
1266 bool do_heap_region(HeapRegion *hr) {
1267 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young() && !hr->is_archive()) {
1268 _freed_bytes += hr->used();
1269 hr->set_containing_set(NULL);
1270 if (hr->is_humongous()) {
1271 _humongous_regions_removed++;
1272 _g1h->free_humongous_region(hr, _local_cleanup_list);
1273 } else {
1274 _old_regions_removed++;
1275 _g1h->free_region(hr, _local_cleanup_list);
1276 }
1277 hr->clear_cardtable();
1278 _g1h->concurrent_mark()->clear_statistics_in_region(hr->hrm_index());
1279 log_trace(gc)("Reclaimed empty region %u (%s) bot " PTR_FORMAT, hr->hrm_index(), hr->get_short_type_str(), p2i(hr->bottom()));
1280 }
1281
1282 return false;
1283 }
1284 };
1285
1286 G1CollectedHeap* _g1h;
1287 FreeRegionList* _cleanup_list;
1288 HeapRegionClaimer _hrclaimer;
1289
1290 public:
1291 G1ReclaimEmptyRegionsTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1292 AbstractGangTask("G1 Cleanup"),
1293 _g1h(g1h),
1294 _cleanup_list(cleanup_list),
1295 _hrclaimer(n_workers) {
1296 }
1297
1298 void work(uint worker_id) {
1299 FreeRegionList local_cleanup_list("Local Cleanup List");
1300 G1ReclaimEmptyRegionsClosure cl(_g1h, &local_cleanup_list);
1301 _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hrclaimer, worker_id);
1302 assert(cl.is_complete(), "Shouldn't have aborted!");
1303
1304 // Now update the old/humongous region sets
1305 _g1h->remove_from_old_sets(cl.old_regions_removed(), cl.humongous_regions_removed());
1306 {
1307 MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1308 _g1h->decrement_summary_bytes(cl.freed_bytes());
1309
1310 _cleanup_list->add_ordered(&local_cleanup_list);
1311 assert(local_cleanup_list.is_empty(), "post-condition");
1312 }
1313 }
1314 };
1315
1316 void G1ConcurrentMark::reclaim_empty_regions() {
1317 WorkGang* workers = _g1h->workers();
1318 FreeRegionList empty_regions_list("Empty Regions After Mark List");
1319
1320 G1ReclaimEmptyRegionsTask cl(_g1h, &empty_regions_list, workers->active_workers());
1321 workers->run_task(&cl);
1322
1323 if (!empty_regions_list.is_empty()) {
1324 log_debug(gc)("Reclaimed %u empty regions", empty_regions_list.length());
1325 // Now print the empty regions list.
1326 G1HRPrinter* hrp = _g1h->hr_printer();
1327 if (hrp->is_active()) {
1328 FreeRegionListIterator iter(&empty_regions_list);
1329 while (iter.more_available()) {
1330 HeapRegion* hr = iter.get_next();
1331 hrp->cleanup(hr);
1332 }
1333 }
1334 // And actually make them available.
1335 _g1h->prepend_to_freelist(&empty_regions_list);
1336 }
1337 }
1338
1339 void G1ConcurrentMark::compute_new_sizes() {
1340 MetaspaceGC::compute_new_size();
1341
1342 // Cleanup will have freed any regions completely full of garbage.
1343 // Update the soft reference policy with the new heap occupancy.
1344 Universe::update_heap_info_at_gc();
1345
1346 // We reclaimed old regions so we should calculate the sizes to make
1347 // sure we update the old gen/space data.
1348 _g1h->g1mm()->update_sizes();
1349 }
1350
1351 void G1ConcurrentMark::cleanup() {
1352 assert_at_safepoint_on_vm_thread();
1353
1354 // If a full collection has happened, we shouldn't do this.
1355 if (has_aborted()) {
1356 return;
1357 }
1358
1359 G1Policy* policy = _g1h->policy();
1360 policy->record_concurrent_mark_cleanup_start();
1361
1362 double start = os::elapsedTime();
1363
1364 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup before");
1365
1366 {
1367 GCTraceTime(Debug, gc, phases) debug("Update Remembered Set Tracking After Rebuild", _gc_timer_cm);
1368 G1UpdateRemSetTrackingAfterRebuild cl(_g1h);
1369 _g1h->heap_region_iterate(&cl);
1370 }
1371
1372 if (log_is_enabled(Trace, gc, liveness)) {
1373 G1PrintRegionLivenessInfoClosure cl("Post-Cleanup");
1374 _g1h->heap_region_iterate(&cl);
1375 }
1376
1377 verify_during_pause(G1HeapVerifier::G1VerifyCleanup, VerifyOption_G1UsePrevMarking, "Cleanup after");
1378
1379 // We need to make this be a "collection" so any collection pause that
1380 // races with it goes around and waits for Cleanup to finish.
1381 _g1h->increment_total_collections();
1382
1383 {
1384 GCTraceTime(Debug, gc, phases) debug("Expand heap after concurrent mark", _gc_timer_cm);
1385 _g1h->expand_heap_after_concurrent_mark();
1386 }
1387
1388 // Local statistics
1389 double recent_cleanup_time = (os::elapsedTime() - start);
1390 _total_cleanup_time += recent_cleanup_time;
1391 _cleanup_times.add(recent_cleanup_time);
1392
1393 {
1394 GCTraceTime(Debug, gc, phases) debug("Finalize Concurrent Mark Cleanup", _gc_timer_cm);
1395 policy->record_concurrent_mark_cleanup_end();
1396 }
1397 }
1398
1399 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1400 // Uses the G1CMTask associated with a worker thread (for serial reference
1401 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1402 // trace referent objects.
1403 //
1404 // Using the G1CMTask and embedded local queues avoids having the worker
1405 // threads operating on the global mark stack. This reduces the risk
1406 // of overflowing the stack - which we would rather avoid at this late
1407 // state. Also using the tasks' local queues removes the potential
1408 // of the workers interfering with each other that could occur if
1409 // operating on the global stack.
1410
1411 class G1CMKeepAliveAndDrainClosure : public OopClosure {
1412 G1ConcurrentMark* _cm;
1413 G1CMTask* _task;
1414 uint _ref_counter_limit;
1415 uint _ref_counter;
1416 bool _is_serial;
1417 public:
1418 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1419 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval),
1420 _ref_counter(_ref_counter_limit), _is_serial(is_serial) {
1421 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1422 }
1423
1424 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1425 virtual void do_oop( oop* p) { do_oop_work(p); }
1426
1427 template <class T> void do_oop_work(T* p) {
1428 if (_cm->has_overflown()) {
1429 return;
1430 }
1431 if (!_task->deal_with_reference(p)) {
1432 // We did not add anything to the mark bitmap (or mark stack), so there is
1433 // no point trying to drain it.
1434 return;
1435 }
1436 _ref_counter--;
1437
1438 if (_ref_counter == 0) {
1439 // We have dealt with _ref_counter_limit references, pushing them
1440 // and objects reachable from them on to the local stack (and
1441 // possibly the global stack). Call G1CMTask::do_marking_step() to
1442 // process these entries.
1443 //
1444 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1445 // there's nothing more to do (i.e. we're done with the entries that
1446 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1447 // above) or we overflow.
1448 //
1449 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1450 // flag while there may still be some work to do. (See the comment at
1451 // the beginning of G1CMTask::do_marking_step() for those conditions -
1452 // one of which is reaching the specified time target.) It is only
1453 // when G1CMTask::do_marking_step() returns without setting the
1454 // has_aborted() flag that the marking step has completed.
1455 do {
1456 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1457 _task->do_marking_step(mark_step_duration_ms,
1458 false /* do_termination */,
1459 _is_serial);
1460 } while (_task->has_aborted() && !_cm->has_overflown());
1461 _ref_counter = _ref_counter_limit;
1462 }
1463 }
1464 };
1465
1466 // 'Drain' oop closure used by both serial and parallel reference processing.
1467 // Uses the G1CMTask associated with a given worker thread (for serial
1468 // reference processing the G1CMtask for worker 0 is used). Calls the
1469 // do_marking_step routine, with an unbelievably large timeout value,
1470 // to drain the marking data structures of the remaining entries
1471 // added by the 'keep alive' oop closure above.
1472
1473 class G1CMDrainMarkingStackClosure : public VoidClosure {
1474 G1ConcurrentMark* _cm;
1475 G1CMTask* _task;
1476 bool _is_serial;
1477 public:
1478 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1479 _cm(cm), _task(task), _is_serial(is_serial) {
1480 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1481 }
1482
1483 void do_void() {
1484 do {
1485 // We call G1CMTask::do_marking_step() to completely drain the local
1486 // and global marking stacks of entries pushed by the 'keep alive'
1487 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1488 //
1489 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1490 // if there's nothing more to do (i.e. we've completely drained the
1491 // entries that were pushed as a a result of applying the 'keep alive'
1492 // closure to the entries on the discovered ref lists) or we overflow
1493 // the global marking stack.
1494 //
1495 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1496 // flag while there may still be some work to do. (See the comment at
1497 // the beginning of G1CMTask::do_marking_step() for those conditions -
1498 // one of which is reaching the specified time target.) It is only
1499 // when G1CMTask::do_marking_step() returns without setting the
1500 // has_aborted() flag that the marking step has completed.
1501
1502 _task->do_marking_step(1000000000.0 /* something very large */,
1503 true /* do_termination */,
1504 _is_serial);
1505 } while (_task->has_aborted() && !_cm->has_overflown());
1506 }
1507 };
1508
1509 // Implementation of AbstractRefProcTaskExecutor for parallel
1510 // reference processing at the end of G1 concurrent marking
1511
1512 class G1CMRefProcTaskExecutor : public AbstractRefProcTaskExecutor {
1513 private:
1514 G1CollectedHeap* _g1h;
1515 G1ConcurrentMark* _cm;
1516 WorkGang* _workers;
1517 uint _active_workers;
1518
1519 public:
1520 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1521 G1ConcurrentMark* cm,
1522 WorkGang* workers,
1523 uint n_workers) :
1524 _g1h(g1h), _cm(cm),
1525 _workers(workers), _active_workers(n_workers) { }
1526
1527 virtual void execute(ProcessTask& task, uint ergo_workers);
1528 };
1529
1530 class G1CMRefProcTaskProxy : public AbstractGangTask {
1531 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1532 ProcessTask& _proc_task;
1533 G1CollectedHeap* _g1h;
1534 G1ConcurrentMark* _cm;
1535
1536 public:
1537 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1538 G1CollectedHeap* g1h,
1539 G1ConcurrentMark* cm) :
1540 AbstractGangTask("Process reference objects in parallel"),
1541 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1542 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1543 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1544 }
1545
1546 virtual void work(uint worker_id) {
1547 ResourceMark rm;
1548 HandleMark hm;
1549 G1CMTask* task = _cm->task(worker_id);
1550 G1CMIsAliveClosure g1_is_alive(_g1h);
1551 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1552 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1553
1554 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1555 }
1556 };
1557
1558 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
1559 assert(_workers != NULL, "Need parallel worker threads.");
1560 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1561 assert(_workers->active_workers() >= ergo_workers,
1562 "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)",
1563 ergo_workers, _workers->active_workers());
1564
1565 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1566
1567 // We need to reset the concurrency level before each
1568 // proxy task execution, so that the termination protocol
1569 // and overflow handling in G1CMTask::do_marking_step() knows
1570 // how many workers to wait for.
1571 _cm->set_concurrency(ergo_workers);
1572 _workers->run_task(&proc_task_proxy, ergo_workers);
1573 }
1574
1575 void G1ConcurrentMark::weak_refs_work(bool clear_all_soft_refs) {
1576 ResourceMark rm;
1577 HandleMark hm;
1578
1579 // Is alive closure.
1580 G1CMIsAliveClosure g1_is_alive(_g1h);
1581
1582 // Inner scope to exclude the cleaning of the string table
1583 // from the displayed time.
1584 {
1585 GCTraceTime(Debug, gc, phases) debug("Reference Processing", _gc_timer_cm);
1586
1587 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1588
1589 // See the comment in G1CollectedHeap::ref_processing_init()
1590 // about how reference processing currently works in G1.
1591
1592 // Set the soft reference policy
1593 rp->setup_policy(clear_all_soft_refs);
1594 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1595
1596 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1597 // in serial reference processing. Note these closures are also
1598 // used for serially processing (by the the current thread) the
1599 // JNI references during parallel reference processing.
1600 //
1601 // These closures do not need to synchronize with the worker
1602 // threads involved in parallel reference processing as these
1603 // instances are executed serially by the current thread (e.g.
1604 // reference processing is not multi-threaded and is thus
1605 // performed by the current thread instead of a gang worker).
1606 //
1607 // The gang tasks involved in parallel reference processing create
1608 // their own instances of these closures, which do their own
1609 // synchronization among themselves.
1610 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1611 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1612
1613 // We need at least one active thread. If reference processing
1614 // is not multi-threaded we use the current (VMThread) thread,
1615 // otherwise we use the work gang from the G1CollectedHeap and
1616 // we utilize all the worker threads we can.
1617 bool processing_is_mt = rp->processing_is_mt();
1618 uint active_workers = (processing_is_mt ? _g1h->workers()->active_workers() : 1U);
1619 active_workers = clamp(active_workers, 1u, _max_num_tasks);
1620
1621 // Parallel processing task executor.
1622 G1CMRefProcTaskExecutor par_task_executor(_g1h, this,
1623 _g1h->workers(), active_workers);
1624 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1625
1626 // Set the concurrency level. The phase was already set prior to
1627 // executing the remark task.
1628 set_concurrency(active_workers);
1629
1630 // Set the degree of MT processing here. If the discovery was done MT,
1631 // the number of threads involved during discovery could differ from
1632 // the number of active workers. This is OK as long as the discovered
1633 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1634 rp->set_active_mt_degree(active_workers);
1635
1636 ReferenceProcessorPhaseTimes pt(_gc_timer_cm, rp->max_num_queues());
1637
1638 // Process the weak references.
1639 const ReferenceProcessorStats& stats =
1640 rp->process_discovered_references(&g1_is_alive,
1641 &g1_keep_alive,
1642 &g1_drain_mark_stack,
1643 executor,
1644 &pt);
1645 _gc_tracer_cm->report_gc_reference_stats(stats);
1646 pt.print_all_references();
1647
1648 // The do_oop work routines of the keep_alive and drain_marking_stack
1649 // oop closures will set the has_overflown flag if we overflow the
1650 // global marking stack.
1651
1652 assert(has_overflown() || _global_mark_stack.is_empty(),
1653 "Mark stack should be empty (unless it has overflown)");
1654
1655 assert(rp->num_queues() == active_workers, "why not");
1656
1657 rp->verify_no_references_recorded();
1658 assert(!rp->discovery_enabled(), "Post condition");
1659 }
1660
1661 if (has_overflown()) {
1662 // We can not trust g1_is_alive and the contents of the heap if the marking stack
1663 // overflowed while processing references. Exit the VM.
1664 fatal("Overflow during reference processing, can not continue. Please "
1665 "increase MarkStackSizeMax (current value: " SIZE_FORMAT ") and "
1666 "restart.", MarkStackSizeMax);
1667 return;
1668 }
1669
1670 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1671
1672 {
1673 GCTraceTime(Debug, gc, phases) debug("Weak Processing", _gc_timer_cm);
1674 WeakProcessor::weak_oops_do(_g1h->workers(), &g1_is_alive, &do_nothing_cl, 1);
1675 }
1676
1677 // Unload Klasses, String, Code Cache, etc.
1678 if (ClassUnloadingWithConcurrentMark) {
1679 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1680 bool purged_classes = SystemDictionary::do_unloading(_gc_timer_cm);
1681 _g1h->complete_cleaning(&g1_is_alive, purged_classes);
1682 } else if (StringDedup::is_enabled()) {
1683 GCTraceTime(Debug, gc, phases) debug("String Deduplication", _gc_timer_cm);
1684 _g1h->string_dedup_cleaning(&g1_is_alive, NULL);
1685 }
1686 }
1687
1688 class G1PrecleanYieldClosure : public YieldClosure {
1689 G1ConcurrentMark* _cm;
1690
1691 public:
1692 G1PrecleanYieldClosure(G1ConcurrentMark* cm) : _cm(cm) { }
1693
1694 virtual bool should_return() {
1695 return _cm->has_aborted();
1696 }
1697
1698 virtual bool should_return_fine_grain() {
1699 _cm->do_yield_check();
1700 return _cm->has_aborted();
1701 }
1702 };
1703
1704 void G1ConcurrentMark::preclean() {
1705 assert(G1UseReferencePrecleaning, "Precleaning must be enabled.");
1706
1707 SuspendibleThreadSetJoiner joiner;
1708
1709 G1CMKeepAliveAndDrainClosure keep_alive(this, task(0), true /* is_serial */);
1710 G1CMDrainMarkingStackClosure drain_mark_stack(this, task(0), true /* is_serial */);
1711
1712 set_concurrency_and_phase(1, true);
1713
1714 G1PrecleanYieldClosure yield_cl(this);
1715
1716 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1717 // Precleaning is single threaded. Temporarily disable MT discovery.
1718 ReferenceProcessorMTDiscoveryMutator rp_mut_discovery(rp, false);
1719 rp->preclean_discovered_references(rp->is_alive_non_header(),
1720 &keep_alive,
1721 &drain_mark_stack,
1722 &yield_cl,
1723 _gc_timer_cm);
1724 }
1725
1726 // When sampling object counts, we already swapped the mark bitmaps, so we need to use
1727 // the prev bitmap determining liveness.
1728 class G1ObjectCountIsAliveClosure: public BoolObjectClosure {
1729 G1CollectedHeap* _g1h;
1730 public:
1731 G1ObjectCountIsAliveClosure(G1CollectedHeap* g1h) : _g1h(g1h) { }
1732
1733 bool do_object_b(oop obj) {
1734 HeapWord* addr = (HeapWord*)obj;
1735 return addr != NULL &&
1736 (!_g1h->is_in_g1_reserved(addr) || !_g1h->is_obj_dead(obj));
1737 }
1738 };
1739
1740 void G1ConcurrentMark::report_object_count(bool mark_completed) {
1741 // Depending on the completion of the marking liveness needs to be determined
1742 // using either the next or prev bitmap.
1743 if (mark_completed) {
1744 G1ObjectCountIsAliveClosure is_alive(_g1h);
1745 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1746 } else {
1747 G1CMIsAliveClosure is_alive(_g1h);
1748 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1749 }
1750 }
1751
1752
1753 void G1ConcurrentMark::swap_mark_bitmaps() {
1754 G1CMBitMap* temp = _prev_mark_bitmap;
1755 _prev_mark_bitmap = _next_mark_bitmap;
1756 _next_mark_bitmap = temp;
1757 _g1h->collector_state()->set_clearing_next_bitmap(true);
1758 }
1759
1760 // Closure for marking entries in SATB buffers.
1761 class G1CMSATBBufferClosure : public SATBBufferClosure {
1762 private:
1763 G1CMTask* _task;
1764 G1CollectedHeap* _g1h;
1765
1766 // This is very similar to G1CMTask::deal_with_reference, but with
1767 // more relaxed requirements for the argument, so this must be more
1768 // circumspect about treating the argument as an object.
1769 void do_entry(void* entry) const {
1770 _task->increment_refs_reached();
1771 oop const obj = static_cast<oop>(entry);
1772 _task->make_reference_grey(obj);
1773 }
1774
1775 public:
1776 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1777 : _task(task), _g1h(g1h) { }
1778
1779 virtual void do_buffer(void** buffer, size_t size) {
1780 for (size_t i = 0; i < size; ++i) {
1781 do_entry(buffer[i]);
1782 }
1783 }
1784 };
1785
1786 class G1RemarkThreadsClosure : public ThreadClosure {
1787 G1CMSATBBufferClosure _cm_satb_cl;
1788 G1CMOopClosure _cm_cl;
1789 MarkingCodeBlobClosure _code_cl;
1790 uintx _claim_token;
1791
1792 public:
1793 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1794 _cm_satb_cl(task, g1h),
1795 _cm_cl(g1h, task),
1796 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1797 _claim_token(Threads::thread_claim_token()) {}
1798
1799 void do_thread(Thread* thread) {
1800 if (thread->claim_threads_do(true, _claim_token)) {
1801 SATBMarkQueue& queue = G1ThreadLocalData::satb_mark_queue(thread);
1802 queue.apply_closure_and_empty(&_cm_satb_cl);
1803 if (thread->is_Java_thread()) {
1804 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1805 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1806 // * Alive if on the stack of an executing method
1807 // * Weakly reachable otherwise
1808 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1809 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1810 JavaThread* jt = (JavaThread*)thread;
1811 jt->nmethods_do(&_code_cl);
1812 }
1813 }
1814 }
1815 };
1816
1817 class G1CMRemarkTask : public AbstractGangTask {
1818 G1ConcurrentMark* _cm;
1819 public:
1820 void work(uint worker_id) {
1821 G1CMTask* task = _cm->task(worker_id);
1822 task->record_start_time();
1823 {
1824 ResourceMark rm;
1825 HandleMark hm;
1826
1827 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1828 Threads::threads_do(&threads_f);
1829 }
1830
1831 do {
1832 task->do_marking_step(1000000000.0 /* something very large */,
1833 true /* do_termination */,
1834 false /* is_serial */);
1835 } while (task->has_aborted() && !_cm->has_overflown());
1836 // If we overflow, then we do not want to restart. We instead
1837 // want to abort remark and do concurrent marking again.
1838 task->record_end_time();
1839 }
1840
1841 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1842 AbstractGangTask("Par Remark"), _cm(cm) {
1843 _cm->terminator()->reset_for_reuse(active_workers);
1844 }
1845 };
1846
1847 void G1ConcurrentMark::finalize_marking() {
1848 ResourceMark rm;
1849 HandleMark hm;
1850
1851 _g1h->ensure_parsability(false);
1852
1853 // this is remark, so we'll use up all active threads
1854 uint active_workers = _g1h->workers()->active_workers();
1855 set_concurrency_and_phase(active_workers, false /* concurrent */);
1856 // Leave _parallel_marking_threads at it's
1857 // value originally calculated in the G1ConcurrentMark
1858 // constructor and pass values of the active workers
1859 // through the gang in the task.
1860
1861 {
1862 StrongRootsScope srs(active_workers);
1863
1864 G1CMRemarkTask remarkTask(this, active_workers);
1865 // We will start all available threads, even if we decide that the
1866 // active_workers will be fewer. The extra ones will just bail out
1867 // immediately.
1868 _g1h->workers()->run_task(&remarkTask);
1869 }
1870
1871 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1872 guarantee(has_overflown() ||
1873 satb_mq_set.completed_buffers_num() == 0,
1874 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1875 BOOL_TO_STR(has_overflown()),
1876 satb_mq_set.completed_buffers_num());
1877
1878 print_stats();
1879 }
1880
1881 void G1ConcurrentMark::flush_all_task_caches() {
1882 size_t hits = 0;
1883 size_t misses = 0;
1884 for (uint i = 0; i < _max_num_tasks; i++) {
1885 Pair<size_t, size_t> stats = _tasks[i]->flush_mark_stats_cache();
1886 hits += stats.first;
1887 misses += stats.second;
1888 }
1889 size_t sum = hits + misses;
1890 log_debug(gc, stats)("Mark stats cache hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %1.3lf",
1891 hits, misses, percent_of(hits, sum));
1892 }
1893
1894 void G1ConcurrentMark::clear_range_in_prev_bitmap(MemRegion mr) {
1895 _prev_mark_bitmap->clear_range(mr);
1896 }
1897
1898 HeapRegion*
1899 G1ConcurrentMark::claim_region(uint worker_id) {
1900 // "checkpoint" the finger
1901 HeapWord* finger = _finger;
1902
1903 while (finger < _heap.end()) {
1904 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1905
1906 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1907 // Make sure that the reads below do not float before loading curr_region.
1908 OrderAccess::loadload();
1909 // Above heap_region_containing may return NULL as we always scan claim
1910 // until the end of the heap. In this case, just jump to the next region.
1911 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1912
1913 // Is the gap between reading the finger and doing the CAS too long?
1914 HeapWord* res = Atomic::cmpxchg(&_finger, finger, end);
1915 if (res == finger && curr_region != NULL) {
1916 // we succeeded
1917 HeapWord* bottom = curr_region->bottom();
1918 HeapWord* limit = curr_region->next_top_at_mark_start();
1919
1920 // notice that _finger == end cannot be guaranteed here since,
1921 // someone else might have moved the finger even further
1922 assert(_finger >= end, "the finger should have moved forward");
1923
1924 if (limit > bottom) {
1925 return curr_region;
1926 } else {
1927 assert(limit == bottom,
1928 "the region limit should be at bottom");
1929 // we return NULL and the caller should try calling
1930 // claim_region() again.
1931 return NULL;
1932 }
1933 } else {
1934 assert(_finger > finger, "the finger should have moved forward");
1935 // read it again
1936 finger = _finger;
1937 }
1938 }
1939
1940 return NULL;
1941 }
1942
1943 #ifndef PRODUCT
1944 class VerifyNoCSetOops {
1945 G1CollectedHeap* _g1h;
1946 const char* _phase;
1947 int _info;
1948
1949 public:
1950 VerifyNoCSetOops(const char* phase, int info = -1) :
1951 _g1h(G1CollectedHeap::heap()),
1952 _phase(phase),
1953 _info(info)
1954 { }
1955
1956 void operator()(G1TaskQueueEntry task_entry) const {
1957 if (task_entry.is_array_slice()) {
1958 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1959 return;
1960 }
1961 guarantee(oopDesc::is_oop(task_entry.obj()),
1962 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1963 p2i(task_entry.obj()), _phase, _info);
1964 HeapRegion* r = _g1h->heap_region_containing(task_entry.obj());
1965 guarantee(!(r->in_collection_set() || r->has_index_in_opt_cset()),
1966 "obj " PTR_FORMAT " from %s (%d) in region %u in (optional) collection set",
1967 p2i(task_entry.obj()), _phase, _info, r->hrm_index());
1968 }
1969 };
1970
1971 void G1ConcurrentMark::verify_no_collection_set_oops() {
1972 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1973 if (!_g1h->collector_state()->mark_or_rebuild_in_progress()) {
1974 return;
1975 }
1976
1977 // Verify entries on the global mark stack
1978 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
1979
1980 // Verify entries on the task queues
1981 for (uint i = 0; i < _max_num_tasks; ++i) {
1982 G1CMTaskQueue* queue = _task_queues->queue(i);
1983 queue->iterate(VerifyNoCSetOops("Queue", i));
1984 }
1985
1986 // Verify the global finger
1987 HeapWord* global_finger = finger();
1988 if (global_finger != NULL && global_finger < _heap.end()) {
1989 // Since we always iterate over all regions, we might get a NULL HeapRegion
1990 // here.
1991 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
1992 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
1993 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
1994 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
1995 }
1996
1997 // Verify the task fingers
1998 assert(_num_concurrent_workers <= _max_num_tasks, "sanity");
1999 for (uint i = 0; i < _num_concurrent_workers; ++i) {
2000 G1CMTask* task = _tasks[i];
2001 HeapWord* task_finger = task->finger();
2002 if (task_finger != NULL && task_finger < _heap.end()) {
2003 // See above note on the global finger verification.
2004 HeapRegion* r = _g1h->heap_region_containing(task_finger);
2005 guarantee(r == NULL || task_finger == r->bottom() ||
2006 !r->in_collection_set() || !r->has_index_in_opt_cset(),
2007 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2008 p2i(task_finger), HR_FORMAT_PARAMS(r));
2009 }
2010 }
2011 }
2012 #endif // PRODUCT
2013
2014 void G1ConcurrentMark::rebuild_rem_set_concurrently() {
2015 _g1h->rem_set()->rebuild_rem_set(this, _concurrent_workers, _worker_id_offset);
2016 }
2017
2018 void G1ConcurrentMark::print_stats() {
2019 if (!log_is_enabled(Debug, gc, stats)) {
2020 return;
2021 }
2022 log_debug(gc, stats)("---------------------------------------------------------------------");
2023 for (size_t i = 0; i < _num_active_tasks; ++i) {
2024 _tasks[i]->print_stats();
2025 log_debug(gc, stats)("---------------------------------------------------------------------");
2026 }
2027 }
2028
2029 void G1ConcurrentMark::concurrent_cycle_abort() {
2030 if (!cm_thread()->during_cycle() || _has_aborted) {
2031 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2032 return;
2033 }
2034
2035 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2036 // concurrent bitmap clearing.
2037 {
2038 GCTraceTime(Debug, gc) debug("Clear Next Bitmap");
2039 clear_bitmap(_next_mark_bitmap, _g1h->workers(), false);
2040 }
2041 // Note we cannot clear the previous marking bitmap here
2042 // since VerifyDuringGC verifies the objects marked during
2043 // a full GC against the previous bitmap.
2044
2045 // Empty mark stack
2046 reset_marking_for_restart();
2047 for (uint i = 0; i < _max_num_tasks; ++i) {
2048 _tasks[i]->clear_region_fields();
2049 }
2050 _first_overflow_barrier_sync.abort();
2051 _second_overflow_barrier_sync.abort();
2052 _has_aborted = true;
2053
2054 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2055 satb_mq_set.abandon_partial_marking();
2056 // This can be called either during or outside marking, we'll read
2057 // the expected_active value from the SATB queue set.
2058 satb_mq_set.set_active_all_threads(
2059 false, /* new active value */
2060 satb_mq_set.is_active() /* expected_active */);
2061 }
2062
2063 static void print_ms_time_info(const char* prefix, const char* name,
2064 NumberSeq& ns) {
2065 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2066 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2067 if (ns.num() > 0) {
2068 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2069 prefix, ns.sd(), ns.maximum());
2070 }
2071 }
2072
2073 void G1ConcurrentMark::print_summary_info() {
2074 Log(gc, marking) log;
2075 if (!log.is_trace()) {
2076 return;
2077 }
2078
2079 log.trace(" Concurrent marking:");
2080 print_ms_time_info(" ", "init marks", _init_times);
2081 print_ms_time_info(" ", "remarks", _remark_times);
2082 {
2083 print_ms_time_info(" ", "final marks", _remark_mark_times);
2084 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2085
2086 }
2087 print_ms_time_info(" ", "cleanups", _cleanup_times);
2088 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2089 _total_cleanup_time, (_cleanup_times.num() > 0 ? _total_cleanup_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2090 log.trace(" Total stop_world time = %8.2f s.",
2091 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2092 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2093 cm_thread()->vtime_accum(), cm_thread()->vtime_mark_accum());
2094 }
2095
2096 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2097 _concurrent_workers->print_worker_threads_on(st);
2098 }
2099
2100 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2101 _concurrent_workers->threads_do(tc);
2102 }
2103
2104 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2105 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2106 p2i(_prev_mark_bitmap), p2i(_next_mark_bitmap));
2107 _prev_mark_bitmap->print_on_error(st, " Prev Bits: ");
2108 _next_mark_bitmap->print_on_error(st, " Next Bits: ");
2109 }
2110
2111 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2112 ReferenceProcessor* result = g1h->ref_processor_cm();
2113 assert(result != NULL, "CM reference processor should not be NULL");
2114 return result;
2115 }
2116
2117 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2118 G1CMTask* task)
2119 : MetadataVisitingOopIterateClosure(get_cm_oop_closure_ref_processor(g1h)),
2120 _g1h(g1h), _task(task)
2121 { }
2122
2123 void G1CMTask::setup_for_region(HeapRegion* hr) {
2124 assert(hr != NULL,
2125 "claim_region() should have filtered out NULL regions");
2126 _curr_region = hr;
2127 _finger = hr->bottom();
2128 update_region_limit();
2129 }
2130
2131 void G1CMTask::update_region_limit() {
2132 HeapRegion* hr = _curr_region;
2133 HeapWord* bottom = hr->bottom();
2134 HeapWord* limit = hr->next_top_at_mark_start();
2135
2136 if (limit == bottom) {
2137 // The region was collected underneath our feet.
2138 // We set the finger to bottom to ensure that the bitmap
2139 // iteration that will follow this will not do anything.
2140 // (this is not a condition that holds when we set the region up,
2141 // as the region is not supposed to be empty in the first place)
2142 _finger = bottom;
2143 } else if (limit >= _region_limit) {
2144 assert(limit >= _finger, "peace of mind");
2145 } else {
2146 assert(limit < _region_limit, "only way to get here");
2147 // This can happen under some pretty unusual circumstances. An
2148 // evacuation pause empties the region underneath our feet (NTAMS
2149 // at bottom). We then do some allocation in the region (NTAMS
2150 // stays at bottom), followed by the region being used as a GC
2151 // alloc region (NTAMS will move to top() and the objects
2152 // originally below it will be grayed). All objects now marked in
2153 // the region are explicitly grayed, if below the global finger,
2154 // and we do not need in fact to scan anything else. So, we simply
2155 // set _finger to be limit to ensure that the bitmap iteration
2156 // doesn't do anything.
2157 _finger = limit;
2158 }
2159
2160 _region_limit = limit;
2161 }
2162
2163 void G1CMTask::giveup_current_region() {
2164 assert(_curr_region != NULL, "invariant");
2165 clear_region_fields();
2166 }
2167
2168 void G1CMTask::clear_region_fields() {
2169 // Values for these three fields that indicate that we're not
2170 // holding on to a region.
2171 _curr_region = NULL;
2172 _finger = NULL;
2173 _region_limit = NULL;
2174 }
2175
2176 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2177 if (cm_oop_closure == NULL) {
2178 assert(_cm_oop_closure != NULL, "invariant");
2179 } else {
2180 assert(_cm_oop_closure == NULL, "invariant");
2181 }
2182 _cm_oop_closure = cm_oop_closure;
2183 }
2184
2185 void G1CMTask::reset(G1CMBitMap* next_mark_bitmap) {
2186 guarantee(next_mark_bitmap != NULL, "invariant");
2187 _next_mark_bitmap = next_mark_bitmap;
2188 clear_region_fields();
2189
2190 _calls = 0;
2191 _elapsed_time_ms = 0.0;
2192 _termination_time_ms = 0.0;
2193 _termination_start_time_ms = 0.0;
2194
2195 _mark_stats_cache.reset();
2196 }
2197
2198 bool G1CMTask::should_exit_termination() {
2199 if (!regular_clock_call()) {
2200 return true;
2201 }
2202
2203 // This is called when we are in the termination protocol. We should
2204 // quit if, for some reason, this task wants to abort or the global
2205 // stack is not empty (this means that we can get work from it).
2206 return !_cm->mark_stack_empty() || has_aborted();
2207 }
2208
2209 void G1CMTask::reached_limit() {
2210 assert(_words_scanned >= _words_scanned_limit ||
2211 _refs_reached >= _refs_reached_limit ,
2212 "shouldn't have been called otherwise");
2213 abort_marking_if_regular_check_fail();
2214 }
2215
2216 bool G1CMTask::regular_clock_call() {
2217 if (has_aborted()) {
2218 return false;
2219 }
2220
2221 // First, we need to recalculate the words scanned and refs reached
2222 // limits for the next clock call.
2223 recalculate_limits();
2224
2225 // During the regular clock call we do the following
2226
2227 // (1) If an overflow has been flagged, then we abort.
2228 if (_cm->has_overflown()) {
2229 return false;
2230 }
2231
2232 // If we are not concurrent (i.e. we're doing remark) we don't need
2233 // to check anything else. The other steps are only needed during
2234 // the concurrent marking phase.
2235 if (!_cm->concurrent()) {
2236 return true;
2237 }
2238
2239 // (2) If marking has been aborted for Full GC, then we also abort.
2240 if (_cm->has_aborted()) {
2241 return false;
2242 }
2243
2244 double curr_time_ms = os::elapsedVTime() * 1000.0;
2245
2246 // (4) We check whether we should yield. If we have to, then we abort.
2247 if (SuspendibleThreadSet::should_yield()) {
2248 // We should yield. To do this we abort the task. The caller is
2249 // responsible for yielding.
2250 return false;
2251 }
2252
2253 // (5) We check whether we've reached our time quota. If we have,
2254 // then we abort.
2255 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2256 if (elapsed_time_ms > _time_target_ms) {
2257 _has_timed_out = true;
2258 return false;
2259 }
2260
2261 // (6) Finally, we check whether there are enough completed STAB
2262 // buffers available for processing. If there are, we abort.
2263 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2264 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2265 // we do need to process SATB buffers, we'll abort and restart
2266 // the marking task to do so
2267 return false;
2268 }
2269 return true;
2270 }
2271
2272 void G1CMTask::recalculate_limits() {
2273 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2274 _words_scanned_limit = _real_words_scanned_limit;
2275
2276 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2277 _refs_reached_limit = _real_refs_reached_limit;
2278 }
2279
2280 void G1CMTask::decrease_limits() {
2281 // This is called when we believe that we're going to do an infrequent
2282 // operation which will increase the per byte scanned cost (i.e. move
2283 // entries to/from the global stack). It basically tries to decrease the
2284 // scanning limit so that the clock is called earlier.
2285
2286 _words_scanned_limit = _real_words_scanned_limit - 3 * words_scanned_period / 4;
2287 _refs_reached_limit = _real_refs_reached_limit - 3 * refs_reached_period / 4;
2288 }
2289
2290 void G1CMTask::move_entries_to_global_stack() {
2291 // Local array where we'll store the entries that will be popped
2292 // from the local queue.
2293 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2294
2295 size_t n = 0;
2296 G1TaskQueueEntry task_entry;
2297 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2298 buffer[n] = task_entry;
2299 ++n;
2300 }
2301 if (n < G1CMMarkStack::EntriesPerChunk) {
2302 buffer[n] = G1TaskQueueEntry();
2303 }
2304
2305 if (n > 0) {
2306 if (!_cm->mark_stack_push(buffer)) {
2307 set_has_aborted();
2308 }
2309 }
2310
2311 // This operation was quite expensive, so decrease the limits.
2312 decrease_limits();
2313 }
2314
2315 bool G1CMTask::get_entries_from_global_stack() {
2316 // Local array where we'll store the entries that will be popped
2317 // from the global stack.
2318 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2319
2320 if (!_cm->mark_stack_pop(buffer)) {
2321 return false;
2322 }
2323
2324 // We did actually pop at least one entry.
2325 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2326 G1TaskQueueEntry task_entry = buffer[i];
2327 if (task_entry.is_null()) {
2328 break;
2329 }
2330 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()));
2331 bool success = _task_queue->push(task_entry);
2332 // We only call this when the local queue is empty or under a
2333 // given target limit. So, we do not expect this push to fail.
2334 assert(success, "invariant");
2335 }
2336
2337 // This operation was quite expensive, so decrease the limits
2338 decrease_limits();
2339 return true;
2340 }
2341
2342 void G1CMTask::drain_local_queue(bool partially) {
2343 if (has_aborted()) {
2344 return;
2345 }
2346
2347 // Decide what the target size is, depending whether we're going to
2348 // drain it partially (so that other tasks can steal if they run out
2349 // of things to do) or totally (at the very end).
2350 size_t target_size;
2351 if (partially) {
2352 target_size = MIN2((size_t)_task_queue->max_elems()/3, (size_t)GCDrainStackTargetSize);
2353 } else {
2354 target_size = 0;
2355 }
2356
2357 if (_task_queue->size() > target_size) {
2358 G1TaskQueueEntry entry;
2359 bool ret = _task_queue->pop_local(entry);
2360 while (ret) {
2361 scan_task_entry(entry);
2362 if (_task_queue->size() <= target_size || has_aborted()) {
2363 ret = false;
2364 } else {
2365 ret = _task_queue->pop_local(entry);
2366 }
2367 }
2368 }
2369 }
2370
2371 void G1CMTask::drain_global_stack(bool partially) {
2372 if (has_aborted()) {
2373 return;
2374 }
2375
2376 // We have a policy to drain the local queue before we attempt to
2377 // drain the global stack.
2378 assert(partially || _task_queue->size() == 0, "invariant");
2379
2380 // Decide what the target size is, depending whether we're going to
2381 // drain it partially (so that other tasks can steal if they run out
2382 // of things to do) or totally (at the very end).
2383 // Notice that when draining the global mark stack partially, due to the racyness
2384 // of the mark stack size update we might in fact drop below the target. But,
2385 // this is not a problem.
2386 // In case of total draining, we simply process until the global mark stack is
2387 // totally empty, disregarding the size counter.
2388 if (partially) {
2389 size_t const target_size = _cm->partial_mark_stack_size_target();
2390 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2391 if (get_entries_from_global_stack()) {
2392 drain_local_queue(partially);
2393 }
2394 }
2395 } else {
2396 while (!has_aborted() && get_entries_from_global_stack()) {
2397 drain_local_queue(partially);
2398 }
2399 }
2400 }
2401
2402 // SATB Queue has several assumptions on whether to call the par or
2403 // non-par versions of the methods. this is why some of the code is
2404 // replicated. We should really get rid of the single-threaded version
2405 // of the code to simplify things.
2406 void G1CMTask::drain_satb_buffers() {
2407 if (has_aborted()) {
2408 return;
2409 }
2410
2411 // We set this so that the regular clock knows that we're in the
2412 // middle of draining buffers and doesn't set the abort flag when it
2413 // notices that SATB buffers are available for draining. It'd be
2414 // very counter productive if it did that. :-)
2415 _draining_satb_buffers = true;
2416
2417 G1CMSATBBufferClosure satb_cl(this, _g1h);
2418 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2419
2420 // This keeps claiming and applying the closure to completed buffers
2421 // until we run out of buffers or we need to abort.
2422 while (!has_aborted() &&
2423 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2424 abort_marking_if_regular_check_fail();
2425 }
2426
2427 // Can't assert qset is empty here, even if not aborted. If concurrent,
2428 // some other thread might be adding to the queue. If not concurrent,
2429 // some other thread might have won the race for the last buffer, but
2430 // has not yet decremented the count.
2431
2432 _draining_satb_buffers = false;
2433
2434 // again, this was a potentially expensive operation, decrease the
2435 // limits to get the regular clock call early
2436 decrease_limits();
2437 }
2438
2439 void G1CMTask::clear_mark_stats_cache(uint region_idx) {
2440 _mark_stats_cache.reset(region_idx);
2441 }
2442
2443 Pair<size_t, size_t> G1CMTask::flush_mark_stats_cache() {
2444 return _mark_stats_cache.evict_all();
2445 }
2446
2447 void G1CMTask::print_stats() {
2448 log_debug(gc, stats)("Marking Stats, task = %u, calls = %u", _worker_id, _calls);
2449 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2450 _elapsed_time_ms, _termination_time_ms);
2451 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms max = %1.2lfms, total = %1.2lfms",
2452 _step_times_ms.num(),
2453 _step_times_ms.avg(),
2454 _step_times_ms.sd(),
2455 _step_times_ms.maximum(),
2456 _step_times_ms.sum());
2457 size_t const hits = _mark_stats_cache.hits();
2458 size_t const misses = _mark_stats_cache.misses();
2459 log_debug(gc, stats)(" Mark Stats Cache: hits " SIZE_FORMAT " misses " SIZE_FORMAT " ratio %.3f",
2460 hits, misses, percent_of(hits, hits + misses));
2461 }
2462
2463 bool G1ConcurrentMark::try_stealing(uint worker_id, G1TaskQueueEntry& task_entry) {
2464 return _task_queues->steal(worker_id, task_entry);
2465 }
2466
2467 /*****************************************************************************
2468
2469 The do_marking_step(time_target_ms, ...) method is the building
2470 block of the parallel marking framework. It can be called in parallel
2471 with other invocations of do_marking_step() on different tasks
2472 (but only one per task, obviously) and concurrently with the
2473 mutator threads, or during remark, hence it eliminates the need
2474 for two versions of the code. When called during remark, it will
2475 pick up from where the task left off during the concurrent marking
2476 phase. Interestingly, tasks are also claimable during evacuation
2477 pauses too, since do_marking_step() ensures that it aborts before
2478 it needs to yield.
2479
2480 The data structures that it uses to do marking work are the
2481 following:
2482
2483 (1) Marking Bitmap. If there are gray objects that appear only
2484 on the bitmap (this happens either when dealing with an overflow
2485 or when the initial marking phase has simply marked the roots
2486 and didn't push them on the stack), then tasks claim heap
2487 regions whose bitmap they then scan to find gray objects. A
2488 global finger indicates where the end of the last claimed region
2489 is. A local finger indicates how far into the region a task has
2490 scanned. The two fingers are used to determine how to gray an
2491 object (i.e. whether simply marking it is OK, as it will be
2492 visited by a task in the future, or whether it needs to be also
2493 pushed on a stack).
2494
2495 (2) Local Queue. The local queue of the task which is accessed
2496 reasonably efficiently by the task. Other tasks can steal from
2497 it when they run out of work. Throughout the marking phase, a
2498 task attempts to keep its local queue short but not totally
2499 empty, so that entries are available for stealing by other
2500 tasks. Only when there is no more work, a task will totally
2501 drain its local queue.
2502
2503 (3) Global Mark Stack. This handles local queue overflow. During
2504 marking only sets of entries are moved between it and the local
2505 queues, as access to it requires a mutex and more fine-grain
2506 interaction with it which might cause contention. If it
2507 overflows, then the marking phase should restart and iterate
2508 over the bitmap to identify gray objects. Throughout the marking
2509 phase, tasks attempt to keep the global mark stack at a small
2510 length but not totally empty, so that entries are available for
2511 popping by other tasks. Only when there is no more work, tasks
2512 will totally drain the global mark stack.
2513
2514 (4) SATB Buffer Queue. This is where completed SATB buffers are
2515 made available. Buffers are regularly removed from this queue
2516 and scanned for roots, so that the queue doesn't get too
2517 long. During remark, all completed buffers are processed, as
2518 well as the filled in parts of any uncompleted buffers.
2519
2520 The do_marking_step() method tries to abort when the time target
2521 has been reached. There are a few other cases when the
2522 do_marking_step() method also aborts:
2523
2524 (1) When the marking phase has been aborted (after a Full GC).
2525
2526 (2) When a global overflow (on the global stack) has been
2527 triggered. Before the task aborts, it will actually sync up with
2528 the other tasks to ensure that all the marking data structures
2529 (local queues, stacks, fingers etc.) are re-initialized so that
2530 when do_marking_step() completes, the marking phase can
2531 immediately restart.
2532
2533 (3) When enough completed SATB buffers are available. The
2534 do_marking_step() method only tries to drain SATB buffers right
2535 at the beginning. So, if enough buffers are available, the
2536 marking step aborts and the SATB buffers are processed at
2537 the beginning of the next invocation.
2538
2539 (4) To yield. when we have to yield then we abort and yield
2540 right at the end of do_marking_step(). This saves us from a lot
2541 of hassle as, by yielding we might allow a Full GC. If this
2542 happens then objects will be compacted underneath our feet, the
2543 heap might shrink, etc. We save checking for this by just
2544 aborting and doing the yield right at the end.
2545
2546 From the above it follows that the do_marking_step() method should
2547 be called in a loop (or, otherwise, regularly) until it completes.
2548
2549 If a marking step completes without its has_aborted() flag being
2550 true, it means it has completed the current marking phase (and
2551 also all other marking tasks have done so and have all synced up).
2552
2553 A method called regular_clock_call() is invoked "regularly" (in
2554 sub ms intervals) throughout marking. It is this clock method that
2555 checks all the abort conditions which were mentioned above and
2556 decides when the task should abort. A work-based scheme is used to
2557 trigger this clock method: when the number of object words the
2558 marking phase has scanned or the number of references the marking
2559 phase has visited reach a given limit. Additional invocations to
2560 the method clock have been planted in a few other strategic places
2561 too. The initial reason for the clock method was to avoid calling
2562 vtime too regularly, as it is quite expensive. So, once it was in
2563 place, it was natural to piggy-back all the other conditions on it
2564 too and not constantly check them throughout the code.
2565
2566 If do_termination is true then do_marking_step will enter its
2567 termination protocol.
2568
2569 The value of is_serial must be true when do_marking_step is being
2570 called serially (i.e. by the VMThread) and do_marking_step should
2571 skip any synchronization in the termination and overflow code.
2572 Examples include the serial remark code and the serial reference
2573 processing closures.
2574
2575 The value of is_serial must be false when do_marking_step is
2576 being called by any of the worker threads in a work gang.
2577 Examples include the concurrent marking code (CMMarkingTask),
2578 the MT remark code, and the MT reference processing closures.
2579
2580 *****************************************************************************/
2581
2582 void G1CMTask::do_marking_step(double time_target_ms,
2583 bool do_termination,
2584 bool is_serial) {
2585 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2586
2587 _start_time_ms = os::elapsedVTime() * 1000.0;
2588
2589 // If do_stealing is true then do_marking_step will attempt to
2590 // steal work from the other G1CMTasks. It only makes sense to
2591 // enable stealing when the termination protocol is enabled
2592 // and do_marking_step() is not being called serially.
2593 bool do_stealing = do_termination && !is_serial;
2594
2595 G1Predictions const& predictor = _g1h->policy()->predictor();
2596 double diff_prediction_ms = predictor.predict_zero_bounded(&_marking_step_diff_ms);
2597 _time_target_ms = time_target_ms - diff_prediction_ms;
2598
2599 // set up the variables that are used in the work-based scheme to
2600 // call the regular clock method
2601 _words_scanned = 0;
2602 _refs_reached = 0;
2603 recalculate_limits();
2604
2605 // clear all flags
2606 clear_has_aborted();
2607 _has_timed_out = false;
2608 _draining_satb_buffers = false;
2609
2610 ++_calls;
2611
2612 // Set up the bitmap and oop closures. Anything that uses them is
2613 // eventually called from this method, so it is OK to allocate these
2614 // statically.
2615 G1CMBitMapClosure bitmap_closure(this, _cm);
2616 G1CMOopClosure cm_oop_closure(_g1h, this);
2617 set_cm_oop_closure(&cm_oop_closure);
2618
2619 if (_cm->has_overflown()) {
2620 // This can happen if the mark stack overflows during a GC pause
2621 // and this task, after a yield point, restarts. We have to abort
2622 // as we need to get into the overflow protocol which happens
2623 // right at the end of this task.
2624 set_has_aborted();
2625 }
2626
2627 // First drain any available SATB buffers. After this, we will not
2628 // look at SATB buffers before the next invocation of this method.
2629 // If enough completed SATB buffers are queued up, the regular clock
2630 // will abort this task so that it restarts.
2631 drain_satb_buffers();
2632 // ...then partially drain the local queue and the global stack
2633 drain_local_queue(true);
2634 drain_global_stack(true);
2635
2636 do {
2637 if (!has_aborted() && _curr_region != NULL) {
2638 // This means that we're already holding on to a region.
2639 assert(_finger != NULL, "if region is not NULL, then the finger "
2640 "should not be NULL either");
2641
2642 // We might have restarted this task after an evacuation pause
2643 // which might have evacuated the region we're holding on to
2644 // underneath our feet. Let's read its limit again to make sure
2645 // that we do not iterate over a region of the heap that
2646 // contains garbage (update_region_limit() will also move
2647 // _finger to the start of the region if it is found empty).
2648 update_region_limit();
2649 // We will start from _finger not from the start of the region,
2650 // as we might be restarting this task after aborting half-way
2651 // through scanning this region. In this case, _finger points to
2652 // the address where we last found a marked object. If this is a
2653 // fresh region, _finger points to start().
2654 MemRegion mr = MemRegion(_finger, _region_limit);
2655
2656 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2657 "humongous regions should go around loop once only");
2658
2659 // Some special cases:
2660 // If the memory region is empty, we can just give up the region.
2661 // If the current region is humongous then we only need to check
2662 // the bitmap for the bit associated with the start of the object,
2663 // scan the object if it's live, and give up the region.
2664 // Otherwise, let's iterate over the bitmap of the part of the region
2665 // that is left.
2666 // If the iteration is successful, give up the region.
2667 if (mr.is_empty()) {
2668 giveup_current_region();
2669 abort_marking_if_regular_check_fail();
2670 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2671 if (_next_mark_bitmap->is_marked(mr.start())) {
2672 // The object is marked - apply the closure
2673 bitmap_closure.do_addr(mr.start());
2674 }
2675 // Even if this task aborted while scanning the humongous object
2676 // we can (and should) give up the current region.
2677 giveup_current_region();
2678 abort_marking_if_regular_check_fail();
2679 } else if (_next_mark_bitmap->iterate(&bitmap_closure, mr)) {
2680 giveup_current_region();
2681 abort_marking_if_regular_check_fail();
2682 } else {
2683 assert(has_aborted(), "currently the only way to do so");
2684 // The only way to abort the bitmap iteration is to return
2685 // false from the do_bit() method. However, inside the
2686 // do_bit() method we move the _finger to point to the
2687 // object currently being looked at. So, if we bail out, we
2688 // have definitely set _finger to something non-null.
2689 assert(_finger != NULL, "invariant");
2690
2691 // Region iteration was actually aborted. So now _finger
2692 // points to the address of the object we last scanned. If we
2693 // leave it there, when we restart this task, we will rescan
2694 // the object. It is easy to avoid this. We move the finger by
2695 // enough to point to the next possible object header.
2696 assert(_finger < _region_limit, "invariant");
2697 HeapWord* const new_finger = _finger + ((oop)_finger)->size();
2698 // Check if bitmap iteration was aborted while scanning the last object
2699 if (new_finger >= _region_limit) {
2700 giveup_current_region();
2701 } else {
2702 move_finger_to(new_finger);
2703 }
2704 }
2705 }
2706 // At this point we have either completed iterating over the
2707 // region we were holding on to, or we have aborted.
2708
2709 // We then partially drain the local queue and the global stack.
2710 // (Do we really need this?)
2711 drain_local_queue(true);
2712 drain_global_stack(true);
2713
2714 // Read the note on the claim_region() method on why it might
2715 // return NULL with potentially more regions available for
2716 // claiming and why we have to check out_of_regions() to determine
2717 // whether we're done or not.
2718 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2719 // We are going to try to claim a new region. We should have
2720 // given up on the previous one.
2721 // Separated the asserts so that we know which one fires.
2722 assert(_curr_region == NULL, "invariant");
2723 assert(_finger == NULL, "invariant");
2724 assert(_region_limit == NULL, "invariant");
2725 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2726 if (claimed_region != NULL) {
2727 // Yes, we managed to claim one
2728 setup_for_region(claimed_region);
2729 assert(_curr_region == claimed_region, "invariant");
2730 }
2731 // It is important to call the regular clock here. It might take
2732 // a while to claim a region if, for example, we hit a large
2733 // block of empty regions. So we need to call the regular clock
2734 // method once round the loop to make sure it's called
2735 // frequently enough.
2736 abort_marking_if_regular_check_fail();
2737 }
2738
2739 if (!has_aborted() && _curr_region == NULL) {
2740 assert(_cm->out_of_regions(),
2741 "at this point we should be out of regions");
2742 }
2743 } while ( _curr_region != NULL && !has_aborted());
2744
2745 if (!has_aborted()) {
2746 // We cannot check whether the global stack is empty, since other
2747 // tasks might be pushing objects to it concurrently.
2748 assert(_cm->out_of_regions(),
2749 "at this point we should be out of regions");
2750 // Try to reduce the number of available SATB buffers so that
2751 // remark has less work to do.
2752 drain_satb_buffers();
2753 }
2754
2755 // Since we've done everything else, we can now totally drain the
2756 // local queue and global stack.
2757 drain_local_queue(false);
2758 drain_global_stack(false);
2759
2760 // Attempt at work stealing from other task's queues.
2761 if (do_stealing && !has_aborted()) {
2762 // We have not aborted. This means that we have finished all that
2763 // we could. Let's try to do some stealing...
2764
2765 // We cannot check whether the global stack is empty, since other
2766 // tasks might be pushing objects to it concurrently.
2767 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2768 "only way to reach here");
2769 while (!has_aborted()) {
2770 G1TaskQueueEntry entry;
2771 if (_cm->try_stealing(_worker_id, entry)) {
2772 scan_task_entry(entry);
2773
2774 // And since we're towards the end, let's totally drain the
2775 // local queue and global stack.
2776 drain_local_queue(false);
2777 drain_global_stack(false);
2778 } else {
2779 break;
2780 }
2781 }
2782 }
2783
2784 // We still haven't aborted. Now, let's try to get into the
2785 // termination protocol.
2786 if (do_termination && !has_aborted()) {
2787 // We cannot check whether the global stack is empty, since other
2788 // tasks might be concurrently pushing objects on it.
2789 // Separated the asserts so that we know which one fires.
2790 assert(_cm->out_of_regions(), "only way to reach here");
2791 assert(_task_queue->size() == 0, "only way to reach here");
2792 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2793
2794 // The G1CMTask class also extends the TerminatorTerminator class,
2795 // hence its should_exit_termination() method will also decide
2796 // whether to exit the termination protocol or not.
2797 bool finished = (is_serial ||
2798 _cm->terminator()->offer_termination(this));
2799 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2800 _termination_time_ms +=
2801 termination_end_time_ms - _termination_start_time_ms;
2802
2803 if (finished) {
2804 // We're all done.
2805
2806 // We can now guarantee that the global stack is empty, since
2807 // all other tasks have finished. We separated the guarantees so
2808 // that, if a condition is false, we can immediately find out
2809 // which one.
2810 guarantee(_cm->out_of_regions(), "only way to reach here");
2811 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2812 guarantee(_task_queue->size() == 0, "only way to reach here");
2813 guarantee(!_cm->has_overflown(), "only way to reach here");
2814 guarantee(!has_aborted(), "should never happen if termination has completed");
2815 } else {
2816 // Apparently there's more work to do. Let's abort this task. It
2817 // will restart it and we can hopefully find more things to do.
2818 set_has_aborted();
2819 }
2820 }
2821
2822 // Mainly for debugging purposes to make sure that a pointer to the
2823 // closure which was statically allocated in this frame doesn't
2824 // escape it by accident.
2825 set_cm_oop_closure(NULL);
2826 double end_time_ms = os::elapsedVTime() * 1000.0;
2827 double elapsed_time_ms = end_time_ms - _start_time_ms;
2828 // Update the step history.
2829 _step_times_ms.add(elapsed_time_ms);
2830
2831 if (has_aborted()) {
2832 // The task was aborted for some reason.
2833 if (_has_timed_out) {
2834 double diff_ms = elapsed_time_ms - _time_target_ms;
2835 // Keep statistics of how well we did with respect to hitting
2836 // our target only if we actually timed out (if we aborted for
2837 // other reasons, then the results might get skewed).
2838 _marking_step_diff_ms.add(diff_ms);
2839 }
2840
2841 if (_cm->has_overflown()) {
2842 // This is the interesting one. We aborted because a global
2843 // overflow was raised. This means we have to restart the
2844 // marking phase and start iterating over regions. However, in
2845 // order to do this we have to make sure that all tasks stop
2846 // what they are doing and re-initialize in a safe manner. We
2847 // will achieve this with the use of two barrier sync points.
2848
2849 if (!is_serial) {
2850 // We only need to enter the sync barrier if being called
2851 // from a parallel context
2852 _cm->enter_first_sync_barrier(_worker_id);
2853
2854 // When we exit this sync barrier we know that all tasks have
2855 // stopped doing marking work. So, it's now safe to
2856 // re-initialize our data structures.
2857 }
2858
2859 clear_region_fields();
2860 flush_mark_stats_cache();
2861
2862 if (!is_serial) {
2863 // If we're executing the concurrent phase of marking, reset the marking
2864 // state; otherwise the marking state is reset after reference processing,
2865 // during the remark pause.
2866 // If we reset here as a result of an overflow during the remark we will
2867 // see assertion failures from any subsequent set_concurrency_and_phase()
2868 // calls.
2869 if (_cm->concurrent() && _worker_id == 0) {
2870 // Worker 0 is responsible for clearing the global data structures because
2871 // of an overflow. During STW we should not clear the overflow flag (in
2872 // G1ConcurrentMark::reset_marking_state()) since we rely on it being true when we exit
2873 // method to abort the pause and restart concurrent marking.
2874 _cm->reset_marking_for_restart();
2875
2876 log_info(gc, marking)("Concurrent Mark reset for overflow");
2877 }
2878
2879 // ...and enter the second barrier.
2880 _cm->enter_second_sync_barrier(_worker_id);
2881 }
2882 // At this point, if we're during the concurrent phase of
2883 // marking, everything has been re-initialized and we're
2884 // ready to restart.
2885 }
2886 }
2887 }
2888
2889 G1CMTask::G1CMTask(uint worker_id,
2890 G1ConcurrentMark* cm,
2891 G1CMTaskQueue* task_queue,
2892 G1RegionMarkStats* mark_stats,
2893 uint max_regions) :
2894 _objArray_processor(this),
2895 _worker_id(worker_id),
2896 _g1h(G1CollectedHeap::heap()),
2897 _cm(cm),
2898 _next_mark_bitmap(NULL),
2899 _task_queue(task_queue),
2900 _mark_stats_cache(mark_stats, max_regions, RegionMarkStatsCacheSize),
2901 _calls(0),
2902 _time_target_ms(0.0),
2903 _start_time_ms(0.0),
2904 _cm_oop_closure(NULL),
2905 _curr_region(NULL),
2906 _finger(NULL),
2907 _region_limit(NULL),
2908 _words_scanned(0),
2909 _words_scanned_limit(0),
2910 _real_words_scanned_limit(0),
2911 _refs_reached(0),
2912 _refs_reached_limit(0),
2913 _real_refs_reached_limit(0),
2914 _has_aborted(false),
2915 _has_timed_out(false),
2916 _draining_satb_buffers(false),
2917 _step_times_ms(),
2918 _elapsed_time_ms(0.0),
2919 _termination_time_ms(0.0),
2920 _termination_start_time_ms(0.0),
2921 _marking_step_diff_ms()
2922 {
2923 guarantee(task_queue != NULL, "invariant");
2924
2925 _marking_step_diff_ms.add(0.5);
2926 }
2927
2928 // These are formatting macros that are used below to ensure
2929 // consistent formatting. The *_H_* versions are used to format the
2930 // header for a particular value and they should be kept consistent
2931 // with the corresponding macro. Also note that most of the macros add
2932 // the necessary white space (as a prefix) which makes them a bit
2933 // easier to compose.
2934
2935 // All the output lines are prefixed with this string to be able to
2936 // identify them easily in a large log file.
2937 #define G1PPRL_LINE_PREFIX "###"
2938
2939 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
2940 #ifdef _LP64
2941 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
2942 #else // _LP64
2943 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
2944 #endif // _LP64
2945
2946 // For per-region info
2947 #define G1PPRL_TYPE_FORMAT " %-4s"
2948 #define G1PPRL_TYPE_H_FORMAT " %4s"
2949 #define G1PPRL_STATE_FORMAT " %-5s"
2950 #define G1PPRL_STATE_H_FORMAT " %5s"
2951 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
2952 #define G1PPRL_BYTE_H_FORMAT " %9s"
2953 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
2954 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
2955
2956 // For summary info
2957 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
2958 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
2959 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
2960 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
2961
2962 G1PrintRegionLivenessInfoClosure::G1PrintRegionLivenessInfoClosure(const char* phase_name) :
2963 _total_used_bytes(0), _total_capacity_bytes(0),
2964 _total_prev_live_bytes(0), _total_next_live_bytes(0),
2965 _total_remset_bytes(0), _total_strong_code_roots_bytes(0)
2966 {
2967 if (!log_is_enabled(Trace, gc, liveness)) {
2968 return;
2969 }
2970
2971 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2972 MemRegion g1_reserved = g1h->g1_reserved();
2973 double now = os::elapsedTime();
2974
2975 // Print the header of the output.
2976 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
2977 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
2978 G1PPRL_SUM_ADDR_FORMAT("reserved")
2979 G1PPRL_SUM_BYTE_FORMAT("region-size"),
2980 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
2981 HeapRegion::GrainBytes);
2982 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
2983 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2984 G1PPRL_TYPE_H_FORMAT
2985 G1PPRL_ADDR_BASE_H_FORMAT
2986 G1PPRL_BYTE_H_FORMAT
2987 G1PPRL_BYTE_H_FORMAT
2988 G1PPRL_BYTE_H_FORMAT
2989 G1PPRL_DOUBLE_H_FORMAT
2990 G1PPRL_BYTE_H_FORMAT
2991 G1PPRL_STATE_H_FORMAT
2992 G1PPRL_BYTE_H_FORMAT,
2993 "type", "address-range",
2994 "used", "prev-live", "next-live", "gc-eff",
2995 "remset", "state", "code-roots");
2996 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
2997 G1PPRL_TYPE_H_FORMAT
2998 G1PPRL_ADDR_BASE_H_FORMAT
2999 G1PPRL_BYTE_H_FORMAT
3000 G1PPRL_BYTE_H_FORMAT
3001 G1PPRL_BYTE_H_FORMAT
3002 G1PPRL_DOUBLE_H_FORMAT
3003 G1PPRL_BYTE_H_FORMAT
3004 G1PPRL_STATE_H_FORMAT
3005 G1PPRL_BYTE_H_FORMAT,
3006 "", "",
3007 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3008 "(bytes)", "", "(bytes)");
3009 }
3010
3011 bool G1PrintRegionLivenessInfoClosure::do_heap_region(HeapRegion* r) {
3012 if (!log_is_enabled(Trace, gc, liveness)) {
3013 return false;
3014 }
3015
3016 const char* type = r->get_type_str();
3017 HeapWord* bottom = r->bottom();
3018 HeapWord* end = r->end();
3019 size_t capacity_bytes = r->capacity();
3020 size_t used_bytes = r->used();
3021 size_t prev_live_bytes = r->live_bytes();
3022 size_t next_live_bytes = r->next_live_bytes();
3023 double gc_eff = r->gc_efficiency();
3024 size_t remset_bytes = r->rem_set()->mem_size();
3025 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3026 const char* remset_type = r->rem_set()->get_short_state_str();
3027
3028 _total_used_bytes += used_bytes;
3029 _total_capacity_bytes += capacity_bytes;
3030 _total_prev_live_bytes += prev_live_bytes;
3031 _total_next_live_bytes += next_live_bytes;
3032 _total_remset_bytes += remset_bytes;
3033 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3034
3035 // Print a line for this particular region.
3036 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3037 G1PPRL_TYPE_FORMAT
3038 G1PPRL_ADDR_BASE_FORMAT
3039 G1PPRL_BYTE_FORMAT
3040 G1PPRL_BYTE_FORMAT
3041 G1PPRL_BYTE_FORMAT
3042 G1PPRL_DOUBLE_FORMAT
3043 G1PPRL_BYTE_FORMAT
3044 G1PPRL_STATE_FORMAT
3045 G1PPRL_BYTE_FORMAT,
3046 type, p2i(bottom), p2i(end),
3047 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3048 remset_bytes, remset_type, strong_code_roots_bytes);
3049
3050 return false;
3051 }
3052
3053 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3054 if (!log_is_enabled(Trace, gc, liveness)) {
3055 return;
3056 }
3057
3058 // add static memory usages to remembered set sizes
3059 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3060 // Print the footer of the output.
3061 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3062 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3063 " SUMMARY"
3064 G1PPRL_SUM_MB_FORMAT("capacity")
3065 G1PPRL_SUM_MB_PERC_FORMAT("used")
3066 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3067 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3068 G1PPRL_SUM_MB_FORMAT("remset")
3069 G1PPRL_SUM_MB_FORMAT("code-roots"),
3070 bytes_to_mb(_total_capacity_bytes),
3071 bytes_to_mb(_total_used_bytes),
3072 percent_of(_total_used_bytes, _total_capacity_bytes),
3073 bytes_to_mb(_total_prev_live_bytes),
3074 percent_of(_total_prev_live_bytes, _total_capacity_bytes),
3075 bytes_to_mb(_total_next_live_bytes),
3076 percent_of(_total_next_live_bytes, _total_capacity_bytes),
3077 bytes_to_mb(_total_remset_bytes),
3078 bytes_to_mb(_total_strong_code_roots_bytes));
3079 }