1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc/g1/concurrentMarkThread.inline.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1CollectorState.hpp"
32 #include "gc/g1/g1ConcurrentMark.inline.hpp"
33 #include "gc/g1/g1HeapVerifier.hpp"
34 #include "gc/g1/g1OopClosures.inline.hpp"
35 #include "gc/g1/g1CardLiveData.inline.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1StringDedup.hpp"
38 #include "gc/g1/heapRegion.inline.hpp"
39 #include "gc/g1/heapRegionRemSet.hpp"
40 #include "gc/g1/heapRegionSet.inline.hpp"
41 #include "gc/g1/suspendibleThreadSet.hpp"
42 #include "gc/shared/gcId.hpp"
43 #include "gc/shared/gcTimer.hpp"
44 #include "gc/shared/gcTrace.hpp"
45 #include "gc/shared/gcTraceTime.inline.hpp"
46 #include "gc/shared/genOopClosures.inline.hpp"
47 #include "gc/shared/referencePolicy.hpp"
48 #include "gc/shared/strongRootsScope.hpp"
49 #include "gc/shared/taskqueue.inline.hpp"
50 #include "gc/shared/vmGCOperations.hpp"
51 #include "logging/log.hpp"
52 #include "memory/allocation.hpp"
53 #include "memory/resourceArea.hpp"
54 #include "oops/oop.inline.hpp"
55 #include "runtime/atomic.hpp"
56 #include "runtime/handles.inline.hpp"
57 #include "runtime/java.hpp"
58 #include "runtime/prefetch.inline.hpp"
59 #include "services/memTracker.hpp"
60 #include "utilities/growableArray.hpp"
61
62 // Concurrent marking bit map wrapper
63
64 G1CMBitMapRO::G1CMBitMapRO(int shifter) :
65 _bm(),
66 _shifter(shifter) {
67 _bmStartWord = 0;
68 _bmWordSize = 0;
69 }
70
71 HeapWord* G1CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
72 const HeapWord* limit) const {
73 // First we must round addr *up* to a possible object boundary.
74 addr = (HeapWord*)align_size_up((intptr_t)addr,
75 HeapWordSize << _shifter);
76 size_t addrOffset = heapWordToOffset(addr);
77 assert(limit != NULL, "limit must not be NULL");
78 size_t limitOffset = heapWordToOffset(limit);
79 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
80 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
81 assert(nextAddr >= addr, "get_next_one postcondition");
82 assert(nextAddr == limit || isMarked(nextAddr),
83 "get_next_one postcondition");
84 return nextAddr;
85 }
86
87 #ifndef PRODUCT
88 bool G1CMBitMapRO::covers(MemRegion heap_rs) const {
89 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
90 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
91 "size inconsistency");
92 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
93 _bmWordSize == heap_rs.word_size();
94 }
95 #endif
96
97 void G1CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
98 _bm.print_on_error(st, prefix);
99 }
100
101 size_t G1CMBitMap::compute_size(size_t heap_size) {
102 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
103 }
104
105 size_t G1CMBitMap::mark_distance() {
106 return MinObjAlignmentInBytes * BitsPerByte;
107 }
108
109 void G1CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
110 _bmStartWord = heap.start();
111 _bmWordSize = heap.word_size();
112
113 _bm = BitMapView((BitMap::bm_word_t*) storage->reserved().start(), _bmWordSize >> _shifter);
114
115 storage->set_mapping_changed_listener(&_listener);
116 }
117
118 void G1CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
119 if (zero_filled) {
120 return;
121 }
122 // We need to clear the bitmap on commit, removing any existing information.
123 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
124 _bm->clear_range(mr);
125 }
126
127 void G1CMBitMap::clear_range(MemRegion mr) {
128 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
129 assert(!mr.is_empty(), "unexpected empty region");
130 // convert address range into offset range
131 _bm.at_put_range(heapWordToOffset(mr.start()),
132 heapWordToOffset(mr.end()), false);
133 }
134
135 G1CMMarkStack::G1CMMarkStack() :
136 _max_chunk_capacity(0),
137 _base(NULL),
138 _chunk_capacity(0),
139 _should_expand(false) {
140 set_empty();
141 }
142
143 bool G1CMMarkStack::resize(size_t new_capacity) {
144 assert(is_empty(), "Only resize when stack is empty.");
145 assert(new_capacity <= _max_chunk_capacity,
146 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
147
148 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk, mtGC>::allocate_or_null(new_capacity);
149
150 if (new_base == NULL) {
151 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));
152 return false;
153 }
154 // Release old mapping.
155 if (_base != NULL) {
156 MmapArrayAllocator<TaskQueueEntryChunk, mtGC>::free(_base, _chunk_capacity);
157 }
158
159 _base = new_base;
160 _chunk_capacity = new_capacity;
161 set_empty();
162 _should_expand = false;
163
164 return true;
165 }
166
167 size_t G1CMMarkStack::capacity_alignment() {
168 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
169 }
170
171 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
172 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
173
174 size_t const TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
175
176 _max_chunk_capacity = (size_t)align_size_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
177 size_t initial_chunk_capacity = (size_t)align_size_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
178
179 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
180 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
181 _max_chunk_capacity,
182 initial_chunk_capacity);
183
184 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
185 initial_chunk_capacity, _max_chunk_capacity);
186
187 return resize(initial_chunk_capacity);
188 }
189
190 void G1CMMarkStack::expand() {
191 // Clear expansion flag
192 _should_expand = false;
193
194 if (_chunk_capacity == _max_chunk_capacity) {
195 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
196 return;
197 }
198 size_t old_capacity = _chunk_capacity;
199 // Double capacity if possible
200 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
201
202 if (resize(new_capacity)) {
203 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
204 old_capacity, new_capacity);
205 } else {
206 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
207 old_capacity, new_capacity);
208 }
209 }
210
211 G1CMMarkStack::~G1CMMarkStack() {
212 if (_base != NULL) {
213 MmapArrayAllocator<TaskQueueEntryChunk, mtGC>::free(_base, _chunk_capacity);
214 }
215 }
216
217 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
218 elem->next = *list;
219 *list = elem;
220 }
221
222 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
223 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
224 add_chunk_to_list(&_chunk_list, elem);
225 _chunks_in_chunk_list++;
226 }
227
228 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
229 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
230 add_chunk_to_list(&_free_list, elem);
231 }
232
233 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
234 TaskQueueEntryChunk* result = *list;
235 if (result != NULL) {
236 *list = (*list)->next;
237 }
238 return result;
239 }
240
241 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
242 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
243 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
244 if (result != NULL) {
245 _chunks_in_chunk_list--;
246 }
247 return result;
248 }
249
250 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
251 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
252 return remove_chunk_from_list(&_free_list);
253 }
254
255 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
256 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
257 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
258 // wraparound of _hwm.
259 if (_hwm >= _chunk_capacity) {
260 return NULL;
261 }
262
263 size_t cur_idx = Atomic::add(1, &_hwm) - 1;
264 if (cur_idx >= _chunk_capacity) {
265 return NULL;
266 }
267
268 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
269 result->next = NULL;
270 return result;
271 }
272
273 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
274 // Get a new chunk.
275 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
276
277 if (new_chunk == NULL) {
278 // Did not get a chunk from the free list. Allocate from backing memory.
279 new_chunk = allocate_new_chunk();
280
281 if (new_chunk == NULL) {
282 return false;
283 }
284 }
285
286 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
287
288 add_chunk_to_chunk_list(new_chunk);
289
290 return true;
291 }
292
293 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
294 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
295
296 if (cur == NULL) {
297 return false;
298 }
299
300 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
301
302 add_chunk_to_free_list(cur);
303 return true;
304 }
305
306 void G1CMMarkStack::set_empty() {
307 _chunks_in_chunk_list = 0;
308 _hwm = 0;
309 _chunk_list = NULL;
310 _free_list = NULL;
311 }
312
313 G1CMRootRegions::G1CMRootRegions() :
314 _cm(NULL), _scan_in_progress(false),
315 _should_abort(false), _claimed_survivor_index(0) { }
316
317 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) {
318 _survivors = survivors;
319 _cm = cm;
320 }
321
322 void G1CMRootRegions::prepare_for_scan() {
323 assert(!scan_in_progress(), "pre-condition");
324
325 // Currently, only survivors can be root regions.
326 _claimed_survivor_index = 0;
327 _scan_in_progress = _survivors->regions()->is_nonempty();
328 _should_abort = false;
329 }
330
331 HeapRegion* G1CMRootRegions::claim_next() {
332 if (_should_abort) {
333 // If someone has set the should_abort flag, we return NULL to
334 // force the caller to bail out of their loop.
335 return NULL;
336 }
337
338 // Currently, only survivors can be root regions.
339 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions();
340
341 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1;
342 if (claimed_index < survivor_regions->length()) {
343 return survivor_regions->at(claimed_index);
344 }
345 return NULL;
346 }
347
348 uint G1CMRootRegions::num_root_regions() const {
349 return (uint)_survivors->regions()->length();
350 }
351
352 void G1CMRootRegions::notify_scan_done() {
353 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
354 _scan_in_progress = false;
355 RootRegionScan_lock->notify_all();
356 }
357
358 void G1CMRootRegions::cancel_scan() {
359 notify_scan_done();
360 }
361
362 void G1CMRootRegions::scan_finished() {
363 assert(scan_in_progress(), "pre-condition");
364
365 // Currently, only survivors can be root regions.
366 if (!_should_abort) {
367 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index);
368 assert((uint)_claimed_survivor_index >= _survivors->length(),
369 "we should have claimed all survivors, claimed index = %u, length = %u",
370 (uint)_claimed_survivor_index, _survivors->length());
371 }
372
373 notify_scan_done();
374 }
375
376 bool G1CMRootRegions::wait_until_scan_finished() {
377 if (!scan_in_progress()) return false;
378
379 {
380 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
381 while (scan_in_progress()) {
382 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
383 }
384 }
385 return true;
386 }
387
388 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
389 return MAX2((n_par_threads + 2) / 4, 1U);
390 }
391
392 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
393 _g1h(g1h),
394 _markBitMap1(),
395 _markBitMap2(),
396 _parallel_marking_threads(0),
397 _max_parallel_marking_threads(0),
398 _sleep_factor(0.0),
399 _marking_task_overhead(1.0),
400 _cleanup_list("Cleanup List"),
401
402 _prevMarkBitMap(&_markBitMap1),
403 _nextMarkBitMap(&_markBitMap2),
404
405 _global_mark_stack(),
406 // _finger set in set_non_marking_state
407
408 _max_worker_id(ParallelGCThreads),
409 // _active_tasks set in set_non_marking_state
410 // _tasks set inside the constructor
411 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)),
412 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
413
414 _has_overflown(false),
415 _concurrent(false),
416 _has_aborted(false),
417 _restart_for_overflow(false),
418 _concurrent_marking_in_progress(false),
419 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
420 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
421
422 // _verbose_level set below
423
424 _init_times(),
425 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
426 _cleanup_times(),
427 _total_counting_time(0.0),
428 _total_rs_scrub_time(0.0),
429
430 _parallel_workers(NULL),
431
432 _completed_initialization(false) {
433
434 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
435 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
436
437 // Create & start a ConcurrentMark thread.
438 _cmThread = new ConcurrentMarkThread(this);
439 assert(cmThread() != NULL, "CM Thread should have been created");
440 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
441 if (_cmThread->osthread() == NULL) {
442 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
443 }
444
445 assert(CGC_lock != NULL, "Where's the CGC_lock?");
446 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
447 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
448
449 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
450 satb_qs.set_buffer_size(G1SATBBufferSize);
451
452 _root_regions.init(_g1h->survivor(), this);
453
454 if (ConcGCThreads > ParallelGCThreads) {
455 log_warning(gc)("Can't have more ConcGCThreads (%u) than ParallelGCThreads (%u).",
456 ConcGCThreads, ParallelGCThreads);
457 return;
458 }
459 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
460 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
461 // if both are set
462 _sleep_factor = 0.0;
463 _marking_task_overhead = 1.0;
464 } else if (G1MarkingOverheadPercent > 0) {
465 // We will calculate the number of parallel marking threads based
466 // on a target overhead with respect to the soft real-time goal
467 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
468 double overall_cm_overhead =
469 (double) MaxGCPauseMillis * marking_overhead /
470 (double) GCPauseIntervalMillis;
471 double cpu_ratio = 1.0 / os::initial_active_processor_count();
472 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
473 double marking_task_overhead =
474 overall_cm_overhead / marking_thread_num * os::initial_active_processor_count();
475 double sleep_factor =
476 (1.0 - marking_task_overhead) / marking_task_overhead;
477
478 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
479 _sleep_factor = sleep_factor;
480 _marking_task_overhead = marking_task_overhead;
481 } else {
482 // Calculate the number of parallel marking threads by scaling
483 // the number of parallel GC threads.
484 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
485 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
486 _sleep_factor = 0.0;
487 _marking_task_overhead = 1.0;
488 }
489
490 assert(ConcGCThreads > 0, "Should have been set");
491 log_debug(gc)("ConcGCThreads: %u", ConcGCThreads);
492 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
493 _parallel_marking_threads = ConcGCThreads;
494 _max_parallel_marking_threads = _parallel_marking_threads;
495
496 _parallel_workers = new WorkGang("G1 Marker",
497 _max_parallel_marking_threads, false, true);
498 if (_parallel_workers == NULL) {
499 vm_exit_during_initialization("Failed necessary allocation.");
500 } else {
501 _parallel_workers->initialize_workers();
502 }
503
504 if (FLAG_IS_DEFAULT(MarkStackSize)) {
505 size_t mark_stack_size =
506 MIN2(MarkStackSizeMax,
507 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
508 // Verify that the calculated value for MarkStackSize is in range.
509 // It would be nice to use the private utility routine from Arguments.
510 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
511 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
512 "must be between 1 and " SIZE_FORMAT,
513 mark_stack_size, MarkStackSizeMax);
514 return;
515 }
516 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
517 } else {
518 // Verify MarkStackSize is in range.
519 if (FLAG_IS_CMDLINE(MarkStackSize)) {
520 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
521 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
522 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
523 "must be between 1 and " SIZE_FORMAT,
524 MarkStackSize, MarkStackSizeMax);
525 return;
526 }
527 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
528 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
529 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
530 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
531 MarkStackSize, MarkStackSizeMax);
532 return;
533 }
534 }
535 }
536 }
537
538 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
539 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
540 }
541
542 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC);
543 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
544
545 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
546 _active_tasks = _max_worker_id;
547
548 for (uint i = 0; i < _max_worker_id; ++i) {
549 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
550 task_queue->initialize();
551 _task_queues->register_queue(i, task_queue);
552
553 _tasks[i] = new G1CMTask(i, this, task_queue, _task_queues);
554
555 _accum_task_vtime[i] = 0.0;
556 }
557
558 // so that the call below can read a sensible value
559 _heap_start = g1h->reserved_region().start();
560 set_non_marking_state();
561 _completed_initialization = true;
562 }
563
564 void G1ConcurrentMark::reset() {
565 // Starting values for these two. This should be called in a STW
566 // phase.
567 MemRegion reserved = _g1h->g1_reserved();
568 _heap_start = reserved.start();
569 _heap_end = reserved.end();
570
571 // Separated the asserts so that we know which one fires.
572 assert(_heap_start != NULL, "heap bounds should look ok");
573 assert(_heap_end != NULL, "heap bounds should look ok");
574 assert(_heap_start < _heap_end, "heap bounds should look ok");
575
576 // Reset all the marking data structures and any necessary flags
577 reset_marking_state();
578
579 // We do reset all of them, since different phases will use
580 // different number of active threads. So, it's easiest to have all
581 // of them ready.
582 for (uint i = 0; i < _max_worker_id; ++i) {
583 _tasks[i]->reset(_nextMarkBitMap);
584 }
585
586 // we need this to make sure that the flag is on during the evac
587 // pause with initial mark piggy-backed
588 set_concurrent_marking_in_progress();
589 }
590
591
592 void G1ConcurrentMark::reset_marking_state() {
593 _global_mark_stack.set_should_expand(has_overflown());
594 _global_mark_stack.set_empty();
595 clear_has_overflown();
596 _finger = _heap_start;
597
598 for (uint i = 0; i < _max_worker_id; ++i) {
599 G1CMTaskQueue* queue = _task_queues->queue(i);
600 queue->set_empty();
601 }
602 }
603
604 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
605 assert(active_tasks <= _max_worker_id, "we should not have more");
606
607 _active_tasks = active_tasks;
608 // Need to update the three data structures below according to the
609 // number of active threads for this phase.
610 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
611 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
612 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
613 }
614
615 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
616 set_concurrency(active_tasks);
617
618 _concurrent = concurrent;
619 // We propagate this to all tasks, not just the active ones.
620 for (uint i = 0; i < _max_worker_id; ++i)
621 _tasks[i]->set_concurrent(concurrent);
622
623 if (concurrent) {
624 set_concurrent_marking_in_progress();
625 } else {
626 // We currently assume that the concurrent flag has been set to
627 // false before we start remark. At this point we should also be
628 // in a STW phase.
629 assert(!concurrent_marking_in_progress(), "invariant");
630 assert(out_of_regions(),
631 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
632 p2i(_finger), p2i(_heap_end));
633 }
634 }
635
636 void G1ConcurrentMark::set_non_marking_state() {
637 // We set the global marking state to some default values when we're
638 // not doing marking.
639 reset_marking_state();
640 _active_tasks = 0;
641 clear_concurrent_marking_in_progress();
642 }
643
644 G1ConcurrentMark::~G1ConcurrentMark() {
645 // The G1ConcurrentMark instance is never freed.
646 ShouldNotReachHere();
647 }
648
649 class G1ClearBitMapTask : public AbstractGangTask {
650 public:
651 static size_t chunk_size() { return M; }
652
653 private:
654 // Heap region closure used for clearing the given mark bitmap.
655 class G1ClearBitmapHRClosure : public HeapRegionClosure {
656 private:
657 G1CMBitMap* _bitmap;
658 G1ConcurrentMark* _cm;
659 public:
660 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
661 }
662
663 virtual bool doHeapRegion(HeapRegion* r) {
664 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
665
666 HeapWord* cur = r->bottom();
667 HeapWord* const end = r->end();
668
669 while (cur < end) {
670 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
671 _bitmap->clear_range(mr);
672
673 cur += chunk_size_in_words;
674
675 // Abort iteration if after yielding the marking has been aborted.
676 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
677 return true;
678 }
679 // Repeat the asserts from before the start of the closure. We will do them
680 // as asserts here to minimize their overhead on the product. However, we
681 // will have them as guarantees at the beginning / end of the bitmap
682 // clearing to get some checking in the product.
683 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant");
684 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
685 }
686 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
687
688 return false;
689 }
690 };
691
692 G1ClearBitmapHRClosure _cl;
693 HeapRegionClaimer _hr_claimer;
694 bool _suspendible; // If the task is suspendible, workers must join the STS.
695
696 public:
697 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
698 AbstractGangTask("G1 Clear Bitmap"),
699 _cl(bitmap, suspendible ? cm : NULL),
700 _hr_claimer(n_workers),
701 _suspendible(suspendible)
702 { }
703
704 void work(uint worker_id) {
705 SuspendibleThreadSetJoiner sts_join(_suspendible);
706 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true);
707 }
708
709 bool is_complete() {
710 return _cl.complete();
711 }
712 };
713
714 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
715 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
716
717 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
718 size_t const num_chunks = align_size_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
719
720 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
721
722 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
723
724 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
725 workers->run_task(&cl, num_workers);
726 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
727 }
728
729 void G1ConcurrentMark::cleanup_for_next_mark() {
730 // Make sure that the concurrent mark thread looks to still be in
731 // the current cycle.
732 guarantee(cmThread()->during_cycle(), "invariant");
733
734 // We are finishing up the current cycle by clearing the next
735 // marking bitmap and getting it ready for the next cycle. During
736 // this time no other cycle can start. So, let's make sure that this
737 // is the case.
738 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
739
740 clear_bitmap(_nextMarkBitMap, _parallel_workers, true);
741
742 // Clear the live count data. If the marking has been aborted, the abort()
743 // call already did that.
744 if (!has_aborted()) {
745 clear_live_data(_parallel_workers);
746 DEBUG_ONLY(verify_live_data_clear());
747 }
748
749 // Repeat the asserts from above.
750 guarantee(cmThread()->during_cycle(), "invariant");
751 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
752 }
753
754 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
755 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint.");
756 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false);
757 }
758
759 class CheckBitmapClearHRClosure : public HeapRegionClosure {
760 G1CMBitMap* _bitmap;
761 bool _error;
762 public:
763 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
764 }
765
766 virtual bool doHeapRegion(HeapRegion* r) {
767 // This closure can be called concurrently to the mutator, so we must make sure
768 // that the result of the getNextMarkedWordAddress() call is compared to the
769 // value passed to it as limit to detect any found bits.
770 // end never changes in G1.
771 HeapWord* end = r->end();
772 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
773 }
774 };
775
776 bool G1ConcurrentMark::nextMarkBitmapIsClear() {
777 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
778 _g1h->heap_region_iterate(&cl);
779 return cl.complete();
780 }
781
782 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
783 public:
784 bool doHeapRegion(HeapRegion* r) {
785 r->note_start_of_marking();
786 return false;
787 }
788 };
789
790 void G1ConcurrentMark::checkpointRootsInitialPre() {
791 G1CollectedHeap* g1h = G1CollectedHeap::heap();
792 G1Policy* g1p = g1h->g1_policy();
793
794 _has_aborted = false;
795
796 // Initialize marking structures. This has to be done in a STW phase.
797 reset();
798
799 // For each region note start of marking.
800 NoteStartOfMarkHRClosure startcl;
801 g1h->heap_region_iterate(&startcl);
802 }
803
804
805 void G1ConcurrentMark::checkpointRootsInitialPost() {
806 G1CollectedHeap* g1h = G1CollectedHeap::heap();
807
808 // Start Concurrent Marking weak-reference discovery.
809 ReferenceProcessor* rp = g1h->ref_processor_cm();
810 // enable ("weak") refs discovery
811 rp->enable_discovery();
812 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
813
814 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
815 // This is the start of the marking cycle, we're expected all
816 // threads to have SATB queues with active set to false.
817 satb_mq_set.set_active_all_threads(true, /* new active value */
818 false /* expected_active */);
819
820 _root_regions.prepare_for_scan();
821
822 // update_g1_committed() will be called at the end of an evac pause
823 // when marking is on. So, it's also called at the end of the
824 // initial-mark pause to update the heap end, if the heap expands
825 // during it. No need to call it here.
826 }
827
828 /*
829 * Notice that in the next two methods, we actually leave the STS
830 * during the barrier sync and join it immediately afterwards. If we
831 * do not do this, the following deadlock can occur: one thread could
832 * be in the barrier sync code, waiting for the other thread to also
833 * sync up, whereas another one could be trying to yield, while also
834 * waiting for the other threads to sync up too.
835 *
836 * Note, however, that this code is also used during remark and in
837 * this case we should not attempt to leave / enter the STS, otherwise
838 * we'll either hit an assert (debug / fastdebug) or deadlock
839 * (product). So we should only leave / enter the STS if we are
840 * operating concurrently.
841 *
842 * Because the thread that does the sync barrier has left the STS, it
843 * is possible to be suspended for a Full GC or an evacuation pause
844 * could occur. This is actually safe, since the entering the sync
845 * barrier is one of the last things do_marking_step() does, and it
846 * doesn't manipulate any data structures afterwards.
847 */
848
849 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
850 bool barrier_aborted;
851 {
852 SuspendibleThreadSetLeaver sts_leave(concurrent());
853 barrier_aborted = !_first_overflow_barrier_sync.enter();
854 }
855
856 // at this point everyone should have synced up and not be doing any
857 // more work
858
859 if (barrier_aborted) {
860 // If the barrier aborted we ignore the overflow condition and
861 // just abort the whole marking phase as quickly as possible.
862 return;
863 }
864
865 // If we're executing the concurrent phase of marking, reset the marking
866 // state; otherwise the marking state is reset after reference processing,
867 // during the remark pause.
868 // If we reset here as a result of an overflow during the remark we will
869 // see assertion failures from any subsequent set_concurrency_and_phase()
870 // calls.
871 if (concurrent()) {
872 // let the task associated with with worker 0 do this
873 if (worker_id == 0) {
874 // task 0 is responsible for clearing the global data structures
875 // We should be here because of an overflow. During STW we should
876 // not clear the overflow flag since we rely on it being true when
877 // we exit this method to abort the pause and restart concurrent
878 // marking.
879 reset_marking_state();
880
881 log_info(gc, marking)("Concurrent Mark reset for overflow");
882 }
883 }
884
885 // after this, each task should reset its own data structures then
886 // then go into the second barrier
887 }
888
889 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
890 SuspendibleThreadSetLeaver sts_leave(concurrent());
891 _second_overflow_barrier_sync.enter();
892
893 // at this point everything should be re-initialized and ready to go
894 }
895
896 class G1CMConcurrentMarkingTask: public AbstractGangTask {
897 private:
898 G1ConcurrentMark* _cm;
899 ConcurrentMarkThread* _cmt;
900
901 public:
902 void work(uint worker_id) {
903 assert(Thread::current()->is_ConcurrentGC_thread(),
904 "this should only be done by a conc GC thread");
905 ResourceMark rm;
906
907 double start_vtime = os::elapsedVTime();
908
909 {
910 SuspendibleThreadSetJoiner sts_join;
911
912 assert(worker_id < _cm->active_tasks(), "invariant");
913 G1CMTask* the_task = _cm->task(worker_id);
914 the_task->record_start_time();
915 if (!_cm->has_aborted()) {
916 do {
917 double start_vtime_sec = os::elapsedVTime();
918 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
919
920 the_task->do_marking_step(mark_step_duration_ms,
921 true /* do_termination */,
922 false /* is_serial*/);
923
924 double end_vtime_sec = os::elapsedVTime();
925 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
926 _cm->clear_has_overflown();
927
928 _cm->do_yield_check();
929
930 jlong sleep_time_ms;
931 if (!_cm->has_aborted() && the_task->has_aborted()) {
932 sleep_time_ms =
933 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
934 {
935 SuspendibleThreadSetLeaver sts_leave;
936 os::sleep(Thread::current(), sleep_time_ms, false);
937 }
938 }
939 } while (!_cm->has_aborted() && the_task->has_aborted());
940 }
941 the_task->record_end_time();
942 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
943 }
944
945 double end_vtime = os::elapsedVTime();
946 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
947 }
948
949 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm,
950 ConcurrentMarkThread* cmt) :
951 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
952
953 ~G1CMConcurrentMarkingTask() { }
954 };
955
956 // Calculates the number of active workers for a concurrent
957 // phase.
958 uint G1ConcurrentMark::calc_parallel_marking_threads() {
959 uint n_conc_workers = 0;
960 if (!UseDynamicNumberOfGCThreads ||
961 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
962 !ForceDynamicNumberOfGCThreads)) {
963 n_conc_workers = max_parallel_marking_threads();
964 } else {
965 n_conc_workers =
966 AdaptiveSizePolicy::calc_default_active_workers(max_parallel_marking_threads(),
967 1, /* Minimum workers */
968 parallel_marking_threads(),
969 Threads::number_of_non_daemon_threads());
970 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
971 // that scaling has already gone into "_max_parallel_marking_threads".
972 }
973 assert(n_conc_workers > 0 && n_conc_workers <= max_parallel_marking_threads(),
974 "Calculated number of workers must be larger than zero and at most the maximum %u, but is %u",
975 max_parallel_marking_threads(), n_conc_workers);
976 return n_conc_workers;
977 }
978
979 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr) {
980 // Currently, only survivors can be root regions.
981 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
982 G1RootRegionScanClosure cl(_g1h, this);
983
984 const uintx interval = PrefetchScanIntervalInBytes;
985 HeapWord* curr = hr->bottom();
986 const HeapWord* end = hr->top();
987 while (curr < end) {
988 Prefetch::read(curr, interval);
989 oop obj = oop(curr);
990 int size = obj->oop_iterate_size(&cl);
991 assert(size == obj->size(), "sanity");
992 curr += size;
993 }
994 }
995
996 class G1CMRootRegionScanTask : public AbstractGangTask {
997 private:
998 G1ConcurrentMark* _cm;
999
1000 public:
1001 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
1002 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
1003
1004 void work(uint worker_id) {
1005 assert(Thread::current()->is_ConcurrentGC_thread(),
1006 "this should only be done by a conc GC thread");
1007
1008 G1CMRootRegions* root_regions = _cm->root_regions();
1009 HeapRegion* hr = root_regions->claim_next();
1010 while (hr != NULL) {
1011 _cm->scanRootRegion(hr);
1012 hr = root_regions->claim_next();
1013 }
1014 }
1015 };
1016
1017 void G1ConcurrentMark::scan_root_regions() {
1018 // scan_in_progress() will have been set to true only if there was
1019 // at least one root region to scan. So, if it's false, we
1020 // should not attempt to do any further work.
1021 if (root_regions()->scan_in_progress()) {
1022 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
1023
1024 _parallel_marking_threads = MIN2(calc_parallel_marking_threads(),
1025 // We distribute work on a per-region basis, so starting
1026 // more threads than that is useless.
1027 root_regions()->num_root_regions());
1028 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1029 "Maximum number of marking threads exceeded");
1030
1031 G1CMRootRegionScanTask task(this);
1032 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
1033 task.name(), _parallel_marking_threads, root_regions()->num_root_regions());
1034 _parallel_workers->run_task(&task, _parallel_marking_threads);
1035
1036 // It's possible that has_aborted() is true here without actually
1037 // aborting the survivor scan earlier. This is OK as it's
1038 // mainly used for sanity checking.
1039 root_regions()->scan_finished();
1040 }
1041 }
1042
1043 void G1ConcurrentMark::concurrent_cycle_start() {
1044 _gc_timer_cm->register_gc_start();
1045
1046 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
1047
1048 _g1h->trace_heap_before_gc(_gc_tracer_cm);
1049 }
1050
1051 void G1ConcurrentMark::concurrent_cycle_end() {
1052 _g1h->trace_heap_after_gc(_gc_tracer_cm);
1053
1054 if (has_aborted()) {
1055 _gc_tracer_cm->report_concurrent_mode_failure();
1056 }
1057
1058 _gc_timer_cm->register_gc_end();
1059
1060 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
1061 }
1062
1063 void G1ConcurrentMark::mark_from_roots() {
1064 // we might be tempted to assert that:
1065 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1066 // "inconsistent argument?");
1067 // However that wouldn't be right, because it's possible that
1068 // a safepoint is indeed in progress as a younger generation
1069 // stop-the-world GC happens even as we mark in this generation.
1070
1071 _restart_for_overflow = false;
1072
1073 // _g1h has _n_par_threads
1074 _parallel_marking_threads = calc_parallel_marking_threads();
1075 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1076 "Maximum number of marking threads exceeded");
1077
1078 uint active_workers = MAX2(1U, parallel_marking_threads());
1079 assert(active_workers > 0, "Should have been set");
1080
1081 // Setting active workers is not guaranteed since fewer
1082 // worker threads may currently exist and more may not be
1083 // available.
1084 active_workers = _parallel_workers->update_active_workers(active_workers);
1085 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _parallel_workers->total_workers());
1086
1087 // Parallel task terminator is set in "set_concurrency_and_phase()"
1088 set_concurrency_and_phase(active_workers, true /* concurrent */);
1089
1090 G1CMConcurrentMarkingTask markingTask(this, cmThread());
1091 _parallel_workers->run_task(&markingTask);
1092 print_stats();
1093 }
1094
1095 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1096 // world is stopped at this checkpoint
1097 assert(SafepointSynchronize::is_at_safepoint(),
1098 "world should be stopped");
1099
1100 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1101
1102 // If a full collection has happened, we shouldn't do this.
1103 if (has_aborted()) {
1104 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1105 return;
1106 }
1107
1108 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1109
1110 if (VerifyDuringGC) {
1111 HandleMark hm; // handle scope
1112 g1h->prepare_for_verify();
1113 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1114 }
1115 g1h->verifier()->check_bitmaps("Remark Start");
1116
1117 G1Policy* g1p = g1h->g1_policy();
1118 g1p->record_concurrent_mark_remark_start();
1119
1120 double start = os::elapsedTime();
1121
1122 checkpointRootsFinalWork();
1123
1124 double mark_work_end = os::elapsedTime();
1125
1126 weakRefsWork(clear_all_soft_refs);
1127
1128 if (has_overflown()) {
1129 // We overflowed. Restart concurrent marking.
1130 _restart_for_overflow = true;
1131
1132 // Verify the heap w.r.t. the previous marking bitmap.
1133 if (VerifyDuringGC) {
1134 HandleMark hm; // handle scope
1135 g1h->prepare_for_verify();
1136 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)");
1137 }
1138
1139 // Clear the marking state because we will be restarting
1140 // marking due to overflowing the global mark stack.
1141 reset_marking_state();
1142 } else {
1143 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1144 // We're done with marking.
1145 // This is the end of the marking cycle, we're expected all
1146 // threads to have SATB queues with active set to true.
1147 satb_mq_set.set_active_all_threads(false, /* new active value */
1148 true /* expected_active */);
1149
1150 if (VerifyDuringGC) {
1151 HandleMark hm; // handle scope
1152 g1h->prepare_for_verify();
1153 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)");
1154 }
1155 g1h->verifier()->check_bitmaps("Remark End");
1156 assert(!restart_for_overflow(), "sanity");
1157 // Completely reset the marking state since marking completed
1158 set_non_marking_state();
1159 }
1160
1161 // Expand the marking stack, if we have to and if we can.
1162 if (_global_mark_stack.should_expand()) {
1163 _global_mark_stack.expand();
1164 }
1165
1166 // Statistics
1167 double now = os::elapsedTime();
1168 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1169 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1170 _remark_times.add((now - start) * 1000.0);
1171
1172 g1p->record_concurrent_mark_remark_end();
1173
1174 G1CMIsAliveClosure is_alive(g1h);
1175 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1176 }
1177
1178 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1179 G1CollectedHeap* _g1;
1180 size_t _freed_bytes;
1181 FreeRegionList* _local_cleanup_list;
1182 uint _old_regions_removed;
1183 uint _humongous_regions_removed;
1184 HRRSCleanupTask* _hrrs_cleanup_task;
1185
1186 public:
1187 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1188 FreeRegionList* local_cleanup_list,
1189 HRRSCleanupTask* hrrs_cleanup_task) :
1190 _g1(g1),
1191 _freed_bytes(0),
1192 _local_cleanup_list(local_cleanup_list),
1193 _old_regions_removed(0),
1194 _humongous_regions_removed(0),
1195 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1196
1197 size_t freed_bytes() { return _freed_bytes; }
1198 const uint old_regions_removed() { return _old_regions_removed; }
1199 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1200
1201 bool doHeapRegion(HeapRegion *hr) {
1202 if (hr->is_archive()) {
1203 return false;
1204 }
1205 _g1->reset_gc_time_stamps(hr);
1206 hr->note_end_of_marking();
1207
1208 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1209 _freed_bytes += hr->used();
1210 hr->set_containing_set(NULL);
1211 if (hr->is_humongous()) {
1212 _humongous_regions_removed++;
1213 _g1->free_humongous_region(hr, _local_cleanup_list, true /* skip_remset */);
1214 } else {
1215 _old_regions_removed++;
1216 _g1->free_region(hr, _local_cleanup_list, true /* skip_remset */);
1217 }
1218 } else {
1219 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1220 }
1221
1222 return false;
1223 }
1224 };
1225
1226 class G1ParNoteEndTask: public AbstractGangTask {
1227 friend class G1NoteEndOfConcMarkClosure;
1228
1229 protected:
1230 G1CollectedHeap* _g1h;
1231 FreeRegionList* _cleanup_list;
1232 HeapRegionClaimer _hrclaimer;
1233
1234 public:
1235 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1236 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1237 }
1238
1239 void work(uint worker_id) {
1240 FreeRegionList local_cleanup_list("Local Cleanup List");
1241 HRRSCleanupTask hrrs_cleanup_task;
1242 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1243 &hrrs_cleanup_task);
1244 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1245 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1246
1247 // Now update the lists
1248 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1249 {
1250 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1251 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1252
1253 // If we iterate over the global cleanup list at the end of
1254 // cleanup to do this printing we will not guarantee to only
1255 // generate output for the newly-reclaimed regions (the list
1256 // might not be empty at the beginning of cleanup; we might
1257 // still be working on its previous contents). So we do the
1258 // printing here, before we append the new regions to the global
1259 // cleanup list.
1260
1261 G1HRPrinter* hr_printer = _g1h->hr_printer();
1262 if (hr_printer->is_active()) {
1263 FreeRegionListIterator iter(&local_cleanup_list);
1264 while (iter.more_available()) {
1265 HeapRegion* hr = iter.get_next();
1266 hr_printer->cleanup(hr);
1267 }
1268 }
1269
1270 _cleanup_list->add_ordered(&local_cleanup_list);
1271 assert(local_cleanup_list.is_empty(), "post-condition");
1272
1273 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1274 }
1275 }
1276 };
1277
1278 void G1ConcurrentMark::cleanup() {
1279 // world is stopped at this checkpoint
1280 assert(SafepointSynchronize::is_at_safepoint(),
1281 "world should be stopped");
1282 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1283
1284 // If a full collection has happened, we shouldn't do this.
1285 if (has_aborted()) {
1286 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1287 return;
1288 }
1289
1290 g1h->verifier()->verify_region_sets_optional();
1291
1292 if (VerifyDuringGC) {
1293 HandleMark hm; // handle scope
1294 g1h->prepare_for_verify();
1295 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1296 }
1297 g1h->verifier()->check_bitmaps("Cleanup Start");
1298
1299 G1Policy* g1p = g1h->g1_policy();
1300 g1p->record_concurrent_mark_cleanup_start();
1301
1302 double start = os::elapsedTime();
1303
1304 HeapRegionRemSet::reset_for_cleanup_tasks();
1305
1306 {
1307 GCTraceTime(Debug, gc)("Finalize Live Data");
1308 finalize_live_data();
1309 }
1310
1311 if (VerifyDuringGC) {
1312 GCTraceTime(Debug, gc)("Verify Live Data");
1313 verify_live_data();
1314 }
1315
1316 g1h->collector_state()->set_mark_in_progress(false);
1317
1318 double count_end = os::elapsedTime();
1319 double this_final_counting_time = (count_end - start);
1320 _total_counting_time += this_final_counting_time;
1321
1322 if (log_is_enabled(Trace, gc, liveness)) {
1323 G1PrintRegionLivenessInfoClosure cl("Post-Marking");
1324 _g1h->heap_region_iterate(&cl);
1325 }
1326
1327 // Install newly created mark bitMap as "prev".
1328 swapMarkBitMaps();
1329
1330 g1h->reset_gc_time_stamp();
1331
1332 uint n_workers = _g1h->workers()->active_workers();
1333
1334 // Note end of marking in all heap regions.
1335 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1336 g1h->workers()->run_task(&g1_par_note_end_task);
1337 g1h->check_gc_time_stamps();
1338
1339 if (!cleanup_list_is_empty()) {
1340 // The cleanup list is not empty, so we'll have to process it
1341 // concurrently. Notify anyone else that might be wanting free
1342 // regions that there will be more free regions coming soon.
1343 g1h->set_free_regions_coming();
1344 }
1345
1346 // call below, since it affects the metric by which we sort the heap
1347 // regions.
1348 if (G1ScrubRemSets) {
1349 double rs_scrub_start = os::elapsedTime();
1350 g1h->scrub_rem_set();
1351 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start);
1352 }
1353
1354 // this will also free any regions totally full of garbage objects,
1355 // and sort the regions.
1356 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1357
1358 // Statistics.
1359 double end = os::elapsedTime();
1360 _cleanup_times.add((end - start) * 1000.0);
1361
1362 // Clean up will have freed any regions completely full of garbage.
1363 // Update the soft reference policy with the new heap occupancy.
1364 Universe::update_heap_info_at_gc();
1365
1366 if (VerifyDuringGC) {
1367 HandleMark hm; // handle scope
1368 g1h->prepare_for_verify();
1369 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)");
1370 }
1371
1372 g1h->verifier()->check_bitmaps("Cleanup End");
1373
1374 g1h->verifier()->verify_region_sets_optional();
1375
1376 // We need to make this be a "collection" so any collection pause that
1377 // races with it goes around and waits for completeCleanup to finish.
1378 g1h->increment_total_collections();
1379
1380 // Clean out dead classes and update Metaspace sizes.
1381 if (ClassUnloadingWithConcurrentMark) {
1382 ClassLoaderDataGraph::purge();
1383 }
1384 MetaspaceGC::compute_new_size();
1385
1386 // We reclaimed old regions so we should calculate the sizes to make
1387 // sure we update the old gen/space data.
1388 g1h->g1mm()->update_sizes();
1389 g1h->allocation_context_stats().update_after_mark();
1390 }
1391
1392 void G1ConcurrentMark::complete_cleanup() {
1393 if (has_aborted()) return;
1394
1395 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1396
1397 _cleanup_list.verify_optional();
1398 FreeRegionList tmp_free_list("Tmp Free List");
1399
1400 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1401 "cleanup list has %u entries",
1402 _cleanup_list.length());
1403
1404 // No one else should be accessing the _cleanup_list at this point,
1405 // so it is not necessary to take any locks
1406 while (!_cleanup_list.is_empty()) {
1407 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
1408 assert(hr != NULL, "Got NULL from a non-empty list");
1409 hr->par_clear();
1410 tmp_free_list.add_ordered(hr);
1411
1412 // Instead of adding one region at a time to the secondary_free_list,
1413 // we accumulate them in the local list and move them a few at a
1414 // time. This also cuts down on the number of notify_all() calls
1415 // we do during this process. We'll also append the local list when
1416 // _cleanup_list is empty (which means we just removed the last
1417 // region from the _cleanup_list).
1418 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
1419 _cleanup_list.is_empty()) {
1420 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1421 "appending %u entries to the secondary_free_list, "
1422 "cleanup list still has %u entries",
1423 tmp_free_list.length(),
1424 _cleanup_list.length());
1425
1426 {
1427 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1428 g1h->secondary_free_list_add(&tmp_free_list);
1429 SecondaryFreeList_lock->notify_all();
1430 }
1431 #ifndef PRODUCT
1432 if (G1StressConcRegionFreeing) {
1433 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
1434 os::sleep(Thread::current(), (jlong) 1, false);
1435 }
1436 }
1437 #endif
1438 }
1439 }
1440 assert(tmp_free_list.is_empty(), "post-condition");
1441 }
1442
1443 // Supporting Object and Oop closures for reference discovery
1444 // and processing in during marking
1445
1446 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1447 HeapWord* addr = (HeapWord*)obj;
1448 return addr != NULL &&
1449 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1450 }
1451
1452 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1453 // Uses the G1CMTask associated with a worker thread (for serial reference
1454 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1455 // trace referent objects.
1456 //
1457 // Using the G1CMTask and embedded local queues avoids having the worker
1458 // threads operating on the global mark stack. This reduces the risk
1459 // of overflowing the stack - which we would rather avoid at this late
1460 // state. Also using the tasks' local queues removes the potential
1461 // of the workers interfering with each other that could occur if
1462 // operating on the global stack.
1463
1464 class G1CMKeepAliveAndDrainClosure: public OopClosure {
1465 G1ConcurrentMark* _cm;
1466 G1CMTask* _task;
1467 int _ref_counter_limit;
1468 int _ref_counter;
1469 bool _is_serial;
1470 public:
1471 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1472 _cm(cm), _task(task), _is_serial(is_serial),
1473 _ref_counter_limit(G1RefProcDrainInterval) {
1474 assert(_ref_counter_limit > 0, "sanity");
1475 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1476 _ref_counter = _ref_counter_limit;
1477 }
1478
1479 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1480 virtual void do_oop( oop* p) { do_oop_work(p); }
1481
1482 template <class T> void do_oop_work(T* p) {
1483 if (!_cm->has_overflown()) {
1484 oop obj = oopDesc::load_decode_heap_oop(p);
1485 _task->deal_with_reference(obj);
1486 _ref_counter--;
1487
1488 if (_ref_counter == 0) {
1489 // We have dealt with _ref_counter_limit references, pushing them
1490 // and objects reachable from them on to the local stack (and
1491 // possibly the global stack). Call G1CMTask::do_marking_step() to
1492 // process these entries.
1493 //
1494 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1495 // there's nothing more to do (i.e. we're done with the entries that
1496 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1497 // above) or we overflow.
1498 //
1499 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1500 // flag while there may still be some work to do. (See the comment at
1501 // the beginning of G1CMTask::do_marking_step() for those conditions -
1502 // one of which is reaching the specified time target.) It is only
1503 // when G1CMTask::do_marking_step() returns without setting the
1504 // has_aborted() flag that the marking step has completed.
1505 do {
1506 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1507 _task->do_marking_step(mark_step_duration_ms,
1508 false /* do_termination */,
1509 _is_serial);
1510 } while (_task->has_aborted() && !_cm->has_overflown());
1511 _ref_counter = _ref_counter_limit;
1512 }
1513 }
1514 }
1515 };
1516
1517 // 'Drain' oop closure used by both serial and parallel reference processing.
1518 // Uses the G1CMTask associated with a given worker thread (for serial
1519 // reference processing the G1CMtask for worker 0 is used). Calls the
1520 // do_marking_step routine, with an unbelievably large timeout value,
1521 // to drain the marking data structures of the remaining entries
1522 // added by the 'keep alive' oop closure above.
1523
1524 class G1CMDrainMarkingStackClosure: public VoidClosure {
1525 G1ConcurrentMark* _cm;
1526 G1CMTask* _task;
1527 bool _is_serial;
1528 public:
1529 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1530 _cm(cm), _task(task), _is_serial(is_serial) {
1531 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1532 }
1533
1534 void do_void() {
1535 do {
1536 // We call G1CMTask::do_marking_step() to completely drain the local
1537 // and global marking stacks of entries pushed by the 'keep alive'
1538 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1539 //
1540 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1541 // if there's nothing more to do (i.e. we've completely drained the
1542 // entries that were pushed as a a result of applying the 'keep alive'
1543 // closure to the entries on the discovered ref lists) or we overflow
1544 // the global marking stack.
1545 //
1546 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1547 // flag while there may still be some work to do. (See the comment at
1548 // the beginning of G1CMTask::do_marking_step() for those conditions -
1549 // one of which is reaching the specified time target.) It is only
1550 // when G1CMTask::do_marking_step() returns without setting the
1551 // has_aborted() flag that the marking step has completed.
1552
1553 _task->do_marking_step(1000000000.0 /* something very large */,
1554 true /* do_termination */,
1555 _is_serial);
1556 } while (_task->has_aborted() && !_cm->has_overflown());
1557 }
1558 };
1559
1560 // Implementation of AbstractRefProcTaskExecutor for parallel
1561 // reference processing at the end of G1 concurrent marking
1562
1563 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
1564 private:
1565 G1CollectedHeap* _g1h;
1566 G1ConcurrentMark* _cm;
1567 WorkGang* _workers;
1568 uint _active_workers;
1569
1570 public:
1571 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1572 G1ConcurrentMark* cm,
1573 WorkGang* workers,
1574 uint n_workers) :
1575 _g1h(g1h), _cm(cm),
1576 _workers(workers), _active_workers(n_workers) { }
1577
1578 // Executes the given task using concurrent marking worker threads.
1579 virtual void execute(ProcessTask& task);
1580 virtual void execute(EnqueueTask& task);
1581 };
1582
1583 class G1CMRefProcTaskProxy: public AbstractGangTask {
1584 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1585 ProcessTask& _proc_task;
1586 G1CollectedHeap* _g1h;
1587 G1ConcurrentMark* _cm;
1588
1589 public:
1590 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1591 G1CollectedHeap* g1h,
1592 G1ConcurrentMark* cm) :
1593 AbstractGangTask("Process reference objects in parallel"),
1594 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1595 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1596 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1597 }
1598
1599 virtual void work(uint worker_id) {
1600 ResourceMark rm;
1601 HandleMark hm;
1602 G1CMTask* task = _cm->task(worker_id);
1603 G1CMIsAliveClosure g1_is_alive(_g1h);
1604 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1605 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1606
1607 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1608 }
1609 };
1610
1611 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1612 assert(_workers != NULL, "Need parallel worker threads.");
1613 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1614
1615 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1616
1617 // We need to reset the concurrency level before each
1618 // proxy task execution, so that the termination protocol
1619 // and overflow handling in G1CMTask::do_marking_step() knows
1620 // how many workers to wait for.
1621 _cm->set_concurrency(_active_workers);
1622 _workers->run_task(&proc_task_proxy);
1623 }
1624
1625 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
1626 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
1627 EnqueueTask& _enq_task;
1628
1629 public:
1630 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
1631 AbstractGangTask("Enqueue reference objects in parallel"),
1632 _enq_task(enq_task) { }
1633
1634 virtual void work(uint worker_id) {
1635 _enq_task.work(worker_id);
1636 }
1637 };
1638
1639 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
1640 assert(_workers != NULL, "Need parallel worker threads.");
1641 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1642
1643 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
1644
1645 // Not strictly necessary but...
1646 //
1647 // We need to reset the concurrency level before each
1648 // proxy task execution, so that the termination protocol
1649 // and overflow handling in G1CMTask::do_marking_step() knows
1650 // how many workers to wait for.
1651 _cm->set_concurrency(_active_workers);
1652 _workers->run_task(&enq_task_proxy);
1653 }
1654
1655 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
1656 if (has_overflown()) {
1657 // Skip processing the discovered references if we have
1658 // overflown the global marking stack. Reference objects
1659 // only get discovered once so it is OK to not
1660 // de-populate the discovered reference lists. We could have,
1661 // but the only benefit would be that, when marking restarts,
1662 // less reference objects are discovered.
1663 return;
1664 }
1665
1666 ResourceMark rm;
1667 HandleMark hm;
1668
1669 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1670
1671 // Is alive closure.
1672 G1CMIsAliveClosure g1_is_alive(g1h);
1673
1674 // Inner scope to exclude the cleaning of the string and symbol
1675 // tables from the displayed time.
1676 {
1677 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm);
1678
1679 ReferenceProcessor* rp = g1h->ref_processor_cm();
1680
1681 // See the comment in G1CollectedHeap::ref_processing_init()
1682 // about how reference processing currently works in G1.
1683
1684 // Set the soft reference policy
1685 rp->setup_policy(clear_all_soft_refs);
1686 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1687
1688 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1689 // in serial reference processing. Note these closures are also
1690 // used for serially processing (by the the current thread) the
1691 // JNI references during parallel reference processing.
1692 //
1693 // These closures do not need to synchronize with the worker
1694 // threads involved in parallel reference processing as these
1695 // instances are executed serially by the current thread (e.g.
1696 // reference processing is not multi-threaded and is thus
1697 // performed by the current thread instead of a gang worker).
1698 //
1699 // The gang tasks involved in parallel reference processing create
1700 // their own instances of these closures, which do their own
1701 // synchronization among themselves.
1702 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1703 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1704
1705 // We need at least one active thread. If reference processing
1706 // is not multi-threaded we use the current (VMThread) thread,
1707 // otherwise we use the work gang from the G1CollectedHeap and
1708 // we utilize all the worker threads we can.
1709 bool processing_is_mt = rp->processing_is_mt();
1710 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
1711 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
1712
1713 // Parallel processing task executor.
1714 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
1715 g1h->workers(), active_workers);
1716 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1717
1718 // Set the concurrency level. The phase was already set prior to
1719 // executing the remark task.
1720 set_concurrency(active_workers);
1721
1722 // Set the degree of MT processing here. If the discovery was done MT,
1723 // the number of threads involved during discovery could differ from
1724 // the number of active workers. This is OK as long as the discovered
1725 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1726 rp->set_active_mt_degree(active_workers);
1727
1728 // Process the weak references.
1729 const ReferenceProcessorStats& stats =
1730 rp->process_discovered_references(&g1_is_alive,
1731 &g1_keep_alive,
1732 &g1_drain_mark_stack,
1733 executor,
1734 _gc_timer_cm);
1735 _gc_tracer_cm->report_gc_reference_stats(stats);
1736
1737 // The do_oop work routines of the keep_alive and drain_marking_stack
1738 // oop closures will set the has_overflown flag if we overflow the
1739 // global marking stack.
1740
1741 assert(has_overflown() || _global_mark_stack.is_empty(),
1742 "Mark stack should be empty (unless it has overflown)");
1743
1744 assert(rp->num_q() == active_workers, "why not");
1745
1746 rp->enqueue_discovered_references(executor);
1747
1748 rp->verify_no_references_recorded();
1749 assert(!rp->discovery_enabled(), "Post condition");
1750 }
1751
1752 if (has_overflown()) {
1753 // We can not trust g1_is_alive if the marking stack overflowed
1754 return;
1755 }
1756
1757 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1758
1759 // Unload Klasses, String, Symbols, Code Cache, etc.
1760 if (ClassUnloadingWithConcurrentMark) {
1761 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1762 bool purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
1763 g1h->complete_cleaning(&g1_is_alive, purged_classes);
1764 } else {
1765 GCTraceTime(Debug, gc, phases) debug("Cleanup", _gc_timer_cm);
1766 // No need to clean string table and symbol table as they are treated as strong roots when
1767 // class unloading is disabled.
1768 g1h->partial_cleaning(&g1_is_alive, false, false, G1StringDedup::is_enabled());
1769
1770 }
1771 }
1772
1773 void G1ConcurrentMark::swapMarkBitMaps() {
1774 G1CMBitMapRO* temp = _prevMarkBitMap;
1775 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap;
1776 _nextMarkBitMap = (G1CMBitMap*) temp;
1777 }
1778
1779 // Closure for marking entries in SATB buffers.
1780 class G1CMSATBBufferClosure : public SATBBufferClosure {
1781 private:
1782 G1CMTask* _task;
1783 G1CollectedHeap* _g1h;
1784
1785 // This is very similar to G1CMTask::deal_with_reference, but with
1786 // more relaxed requirements for the argument, so this must be more
1787 // circumspect about treating the argument as an object.
1788 void do_entry(void* entry) const {
1789 _task->increment_refs_reached();
1790 HeapRegion* hr = _g1h->heap_region_containing(entry);
1791 if (entry < hr->next_top_at_mark_start()) {
1792 // Until we get here, we don't know whether entry refers to a valid
1793 // object; it could instead have been a stale reference.
1794 oop obj = static_cast<oop>(entry);
1795 assert(obj->is_oop(true /* ignore mark word */),
1796 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj));
1797 _task->make_reference_grey(obj);
1798 }
1799 }
1800
1801 public:
1802 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1803 : _task(task), _g1h(g1h) { }
1804
1805 virtual void do_buffer(void** buffer, size_t size) {
1806 for (size_t i = 0; i < size; ++i) {
1807 do_entry(buffer[i]);
1808 }
1809 }
1810 };
1811
1812 class G1RemarkThreadsClosure : public ThreadClosure {
1813 G1CMSATBBufferClosure _cm_satb_cl;
1814 G1CMOopClosure _cm_cl;
1815 MarkingCodeBlobClosure _code_cl;
1816 int _thread_parity;
1817
1818 public:
1819 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1820 _cm_satb_cl(task, g1h),
1821 _cm_cl(g1h, g1h->concurrent_mark(), task),
1822 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1823 _thread_parity(Threads::thread_claim_parity()) {}
1824
1825 void do_thread(Thread* thread) {
1826 if (thread->is_Java_thread()) {
1827 if (thread->claim_oops_do(true, _thread_parity)) {
1828 JavaThread* jt = (JavaThread*)thread;
1829
1830 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1831 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1832 // * Alive if on the stack of an executing method
1833 // * Weakly reachable otherwise
1834 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1835 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1836 jt->nmethods_do(&_code_cl);
1837
1838 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
1839 }
1840 } else if (thread->is_VM_thread()) {
1841 if (thread->claim_oops_do(true, _thread_parity)) {
1842 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
1843 }
1844 }
1845 }
1846 };
1847
1848 class G1CMRemarkTask: public AbstractGangTask {
1849 private:
1850 G1ConcurrentMark* _cm;
1851 public:
1852 void work(uint worker_id) {
1853 // Since all available tasks are actually started, we should
1854 // only proceed if we're supposed to be active.
1855 if (worker_id < _cm->active_tasks()) {
1856 G1CMTask* task = _cm->task(worker_id);
1857 task->record_start_time();
1858 {
1859 ResourceMark rm;
1860 HandleMark hm;
1861
1862 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1863 Threads::threads_do(&threads_f);
1864 }
1865
1866 do {
1867 task->do_marking_step(1000000000.0 /* something very large */,
1868 true /* do_termination */,
1869 false /* is_serial */);
1870 } while (task->has_aborted() && !_cm->has_overflown());
1871 // If we overflow, then we do not want to restart. We instead
1872 // want to abort remark and do concurrent marking again.
1873 task->record_end_time();
1874 }
1875 }
1876
1877 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1878 AbstractGangTask("Par Remark"), _cm(cm) {
1879 _cm->terminator()->reset_for_reuse(active_workers);
1880 }
1881 };
1882
1883 void G1ConcurrentMark::checkpointRootsFinalWork() {
1884 ResourceMark rm;
1885 HandleMark hm;
1886 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1887
1888 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm);
1889
1890 g1h->ensure_parsability(false);
1891
1892 // this is remark, so we'll use up all active threads
1893 uint active_workers = g1h->workers()->active_workers();
1894 set_concurrency_and_phase(active_workers, false /* concurrent */);
1895 // Leave _parallel_marking_threads at it's
1896 // value originally calculated in the G1ConcurrentMark
1897 // constructor and pass values of the active workers
1898 // through the gang in the task.
1899
1900 {
1901 StrongRootsScope srs(active_workers);
1902
1903 G1CMRemarkTask remarkTask(this, active_workers);
1904 // We will start all available threads, even if we decide that the
1905 // active_workers will be fewer. The extra ones will just bail out
1906 // immediately.
1907 g1h->workers()->run_task(&remarkTask);
1908 }
1909
1910 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1911 guarantee(has_overflown() ||
1912 satb_mq_set.completed_buffers_num() == 0,
1913 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1914 BOOL_TO_STR(has_overflown()),
1915 satb_mq_set.completed_buffers_num());
1916
1917 print_stats();
1918 }
1919
1920 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
1921 // Note we are overriding the read-only view of the prev map here, via
1922 // the cast.
1923 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr);
1924 }
1925
1926 HeapRegion*
1927 G1ConcurrentMark::claim_region(uint worker_id) {
1928 // "checkpoint" the finger
1929 HeapWord* finger = _finger;
1930
1931 // _heap_end will not change underneath our feet; it only changes at
1932 // yield points.
1933 while (finger < _heap_end) {
1934 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1935
1936 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1937 // Make sure that the reads below do not float before loading curr_region.
1938 OrderAccess::loadload();
1939 // Above heap_region_containing may return NULL as we always scan claim
1940 // until the end of the heap. In this case, just jump to the next region.
1941 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1942
1943 // Is the gap between reading the finger and doing the CAS too long?
1944 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
1945 if (res == finger && curr_region != NULL) {
1946 // we succeeded
1947 HeapWord* bottom = curr_region->bottom();
1948 HeapWord* limit = curr_region->next_top_at_mark_start();
1949
1950 // notice that _finger == end cannot be guaranteed here since,
1951 // someone else might have moved the finger even further
1952 assert(_finger >= end, "the finger should have moved forward");
1953
1954 if (limit > bottom) {
1955 return curr_region;
1956 } else {
1957 assert(limit == bottom,
1958 "the region limit should be at bottom");
1959 // we return NULL and the caller should try calling
1960 // claim_region() again.
1961 return NULL;
1962 }
1963 } else {
1964 assert(_finger > finger, "the finger should have moved forward");
1965 // read it again
1966 finger = _finger;
1967 }
1968 }
1969
1970 return NULL;
1971 }
1972
1973 #ifndef PRODUCT
1974 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
1975 private:
1976 G1CollectedHeap* _g1h;
1977 const char* _phase;
1978 int _info;
1979
1980 public:
1981 VerifyNoCSetOops(const char* phase, int info = -1) :
1982 _g1h(G1CollectedHeap::heap()),
1983 _phase(phase),
1984 _info(info)
1985 { }
1986
1987 void operator()(G1TaskQueueEntry task_entry) const {
1988 if (task_entry.is_array_slice()) {
1989 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1990 return;
1991 }
1992 guarantee(task_entry.obj()->is_oop(),
1993 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1994 p2i(task_entry.obj()), _phase, _info);
1995 guarantee(!_g1h->is_in_cset(task_entry.obj()),
1996 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
1997 p2i(task_entry.obj()), _phase, _info);
1998 }
1999 };
2000
2001 void G1ConcurrentMark::verify_no_cset_oops() {
2002 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2003 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) {
2004 return;
2005 }
2006
2007 // Verify entries on the global mark stack
2008 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
2009
2010 // Verify entries on the task queues
2011 for (uint i = 0; i < _max_worker_id; ++i) {
2012 G1CMTaskQueue* queue = _task_queues->queue(i);
2013 queue->iterate(VerifyNoCSetOops("Queue", i));
2014 }
2015
2016 // Verify the global finger
2017 HeapWord* global_finger = finger();
2018 if (global_finger != NULL && global_finger < _heap_end) {
2019 // Since we always iterate over all regions, we might get a NULL HeapRegion
2020 // here.
2021 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
2022 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2023 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
2024 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
2025 }
2026
2027 // Verify the task fingers
2028 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2029 for (uint i = 0; i < parallel_marking_threads(); ++i) {
2030 G1CMTask* task = _tasks[i];
2031 HeapWord* task_finger = task->finger();
2032 if (task_finger != NULL && task_finger < _heap_end) {
2033 // See above note on the global finger verification.
2034 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger);
2035 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2036 !task_hr->in_collection_set(),
2037 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2038 p2i(task_finger), HR_FORMAT_PARAMS(task_hr));
2039 }
2040 }
2041 }
2042 #endif // PRODUCT
2043 void G1ConcurrentMark::create_live_data() {
2044 _g1h->g1_rem_set()->create_card_live_data(_parallel_workers, _nextMarkBitMap);
2045 }
2046
2047 void G1ConcurrentMark::finalize_live_data() {
2048 _g1h->g1_rem_set()->finalize_card_live_data(_g1h->workers(), _nextMarkBitMap);
2049 }
2050
2051 void G1ConcurrentMark::verify_live_data() {
2052 _g1h->g1_rem_set()->verify_card_live_data(_g1h->workers(), _nextMarkBitMap);
2053 }
2054
2055 void G1ConcurrentMark::clear_live_data(WorkGang* workers) {
2056 _g1h->g1_rem_set()->clear_card_live_data(workers);
2057 }
2058
2059 #ifdef ASSERT
2060 void G1ConcurrentMark::verify_live_data_clear() {
2061 _g1h->g1_rem_set()->verify_card_live_data_is_clear();
2062 }
2063 #endif
2064
2065 void G1ConcurrentMark::print_stats() {
2066 if (!log_is_enabled(Debug, gc, stats)) {
2067 return;
2068 }
2069 log_debug(gc, stats)("---------------------------------------------------------------------");
2070 for (size_t i = 0; i < _active_tasks; ++i) {
2071 _tasks[i]->print_stats();
2072 log_debug(gc, stats)("---------------------------------------------------------------------");
2073 }
2074 }
2075
2076 void G1ConcurrentMark::abort() {
2077 if (!cmThread()->during_cycle() || _has_aborted) {
2078 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2079 return;
2080 }
2081
2082 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2083 // concurrent bitmap clearing.
2084 {
2085 GCTraceTime(Debug, gc)("Clear Next Bitmap");
2086 clear_bitmap(_nextMarkBitMap, _g1h->workers(), false);
2087 }
2088 // Note we cannot clear the previous marking bitmap here
2089 // since VerifyDuringGC verifies the objects marked during
2090 // a full GC against the previous bitmap.
2091
2092 {
2093 GCTraceTime(Debug, gc)("Clear Live Data");
2094 clear_live_data(_g1h->workers());
2095 }
2096 DEBUG_ONLY({
2097 GCTraceTime(Debug, gc)("Verify Live Data Clear");
2098 verify_live_data_clear();
2099 })
2100 // Empty mark stack
2101 reset_marking_state();
2102 for (uint i = 0; i < _max_worker_id; ++i) {
2103 _tasks[i]->clear_region_fields();
2104 }
2105 _first_overflow_barrier_sync.abort();
2106 _second_overflow_barrier_sync.abort();
2107 _has_aborted = true;
2108
2109 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2110 satb_mq_set.abandon_partial_marking();
2111 // This can be called either during or outside marking, we'll read
2112 // the expected_active value from the SATB queue set.
2113 satb_mq_set.set_active_all_threads(
2114 false, /* new active value */
2115 satb_mq_set.is_active() /* expected_active */);
2116 }
2117
2118 static void print_ms_time_info(const char* prefix, const char* name,
2119 NumberSeq& ns) {
2120 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2121 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2122 if (ns.num() > 0) {
2123 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2124 prefix, ns.sd(), ns.maximum());
2125 }
2126 }
2127
2128 void G1ConcurrentMark::print_summary_info() {
2129 Log(gc, marking) log;
2130 if (!log.is_trace()) {
2131 return;
2132 }
2133
2134 log.trace(" Concurrent marking:");
2135 print_ms_time_info(" ", "init marks", _init_times);
2136 print_ms_time_info(" ", "remarks", _remark_times);
2137 {
2138 print_ms_time_info(" ", "final marks", _remark_mark_times);
2139 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2140
2141 }
2142 print_ms_time_info(" ", "cleanups", _cleanup_times);
2143 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2144 _total_counting_time, (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2145 if (G1ScrubRemSets) {
2146 log.trace(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
2147 _total_rs_scrub_time, (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2148 }
2149 log.trace(" Total stop_world time = %8.2f s.",
2150 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2151 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2152 cmThread()->vtime_accum(), cmThread()->vtime_mark_accum());
2153 }
2154
2155 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2156 _parallel_workers->print_worker_threads_on(st);
2157 }
2158
2159 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2160 _parallel_workers->threads_do(tc);
2161 }
2162
2163 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2164 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2165 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
2166 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
2167 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
2168 }
2169
2170 // Closure for iteration over bitmaps
2171 class G1CMBitMapClosure : public BitMapClosure {
2172 private:
2173 // the bitmap that is being iterated over
2174 G1CMBitMap* _nextMarkBitMap;
2175 G1ConcurrentMark* _cm;
2176 G1CMTask* _task;
2177
2178 public:
2179 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm, G1CMBitMap* nextMarkBitMap) :
2180 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
2181
2182 bool do_bit(size_t offset) {
2183 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
2184 assert(_nextMarkBitMap->isMarked(addr), "invariant");
2185 assert( addr < _cm->finger(), "invariant");
2186 assert(addr >= _task->finger(), "invariant");
2187
2188 // We move that task's local finger along.
2189 _task->move_finger_to(addr);
2190
2191 _task->scan_task_entry(G1TaskQueueEntry::from_oop(oop(addr)));
2192 // we only partially drain the local queue and global stack
2193 _task->drain_local_queue(true);
2194 _task->drain_global_stack(true);
2195
2196 // if the has_aborted flag has been raised, we need to bail out of
2197 // the iteration
2198 return !_task->has_aborted();
2199 }
2200 };
2201
2202 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2203 ReferenceProcessor* result = g1h->ref_processor_cm();
2204 assert(result != NULL, "CM reference processor should not be NULL");
2205 return result;
2206 }
2207
2208 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2209 G1ConcurrentMark* cm,
2210 G1CMTask* task)
2211 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)),
2212 _g1h(g1h), _cm(cm), _task(task)
2213 { }
2214
2215 void G1CMTask::setup_for_region(HeapRegion* hr) {
2216 assert(hr != NULL,
2217 "claim_region() should have filtered out NULL regions");
2218 _curr_region = hr;
2219 _finger = hr->bottom();
2220 update_region_limit();
2221 }
2222
2223 void G1CMTask::update_region_limit() {
2224 HeapRegion* hr = _curr_region;
2225 HeapWord* bottom = hr->bottom();
2226 HeapWord* limit = hr->next_top_at_mark_start();
2227
2228 if (limit == bottom) {
2229 // The region was collected underneath our feet.
2230 // We set the finger to bottom to ensure that the bitmap
2231 // iteration that will follow this will not do anything.
2232 // (this is not a condition that holds when we set the region up,
2233 // as the region is not supposed to be empty in the first place)
2234 _finger = bottom;
2235 } else if (limit >= _region_limit) {
2236 assert(limit >= _finger, "peace of mind");
2237 } else {
2238 assert(limit < _region_limit, "only way to get here");
2239 // This can happen under some pretty unusual circumstances. An
2240 // evacuation pause empties the region underneath our feet (NTAMS
2241 // at bottom). We then do some allocation in the region (NTAMS
2242 // stays at bottom), followed by the region being used as a GC
2243 // alloc region (NTAMS will move to top() and the objects
2244 // originally below it will be grayed). All objects now marked in
2245 // the region are explicitly grayed, if below the global finger,
2246 // and we do not need in fact to scan anything else. So, we simply
2247 // set _finger to be limit to ensure that the bitmap iteration
2248 // doesn't do anything.
2249 _finger = limit;
2250 }
2251
2252 _region_limit = limit;
2253 }
2254
2255 void G1CMTask::giveup_current_region() {
2256 assert(_curr_region != NULL, "invariant");
2257 clear_region_fields();
2258 }
2259
2260 void G1CMTask::clear_region_fields() {
2261 // Values for these three fields that indicate that we're not
2262 // holding on to a region.
2263 _curr_region = NULL;
2264 _finger = NULL;
2265 _region_limit = NULL;
2266 }
2267
2268 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2269 if (cm_oop_closure == NULL) {
2270 assert(_cm_oop_closure != NULL, "invariant");
2271 } else {
2272 assert(_cm_oop_closure == NULL, "invariant");
2273 }
2274 _cm_oop_closure = cm_oop_closure;
2275 }
2276
2277 void G1CMTask::reset(G1CMBitMap* nextMarkBitMap) {
2278 guarantee(nextMarkBitMap != NULL, "invariant");
2279 _nextMarkBitMap = nextMarkBitMap;
2280 clear_region_fields();
2281
2282 _calls = 0;
2283 _elapsed_time_ms = 0.0;
2284 _termination_time_ms = 0.0;
2285 _termination_start_time_ms = 0.0;
2286 }
2287
2288 bool G1CMTask::should_exit_termination() {
2289 regular_clock_call();
2290 // This is called when we are in the termination protocol. We should
2291 // quit if, for some reason, this task wants to abort or the global
2292 // stack is not empty (this means that we can get work from it).
2293 return !_cm->mark_stack_empty() || has_aborted();
2294 }
2295
2296 void G1CMTask::reached_limit() {
2297 assert(_words_scanned >= _words_scanned_limit ||
2298 _refs_reached >= _refs_reached_limit ,
2299 "shouldn't have been called otherwise");
2300 regular_clock_call();
2301 }
2302
2303 void G1CMTask::regular_clock_call() {
2304 if (has_aborted()) return;
2305
2306 // First, we need to recalculate the words scanned and refs reached
2307 // limits for the next clock call.
2308 recalculate_limits();
2309
2310 // During the regular clock call we do the following
2311
2312 // (1) If an overflow has been flagged, then we abort.
2313 if (_cm->has_overflown()) {
2314 set_has_aborted();
2315 return;
2316 }
2317
2318 // If we are not concurrent (i.e. we're doing remark) we don't need
2319 // to check anything else. The other steps are only needed during
2320 // the concurrent marking phase.
2321 if (!concurrent()) return;
2322
2323 // (2) If marking has been aborted for Full GC, then we also abort.
2324 if (_cm->has_aborted()) {
2325 set_has_aborted();
2326 return;
2327 }
2328
2329 double curr_time_ms = os::elapsedVTime() * 1000.0;
2330
2331 // (4) We check whether we should yield. If we have to, then we abort.
2332 if (SuspendibleThreadSet::should_yield()) {
2333 // We should yield. To do this we abort the task. The caller is
2334 // responsible for yielding.
2335 set_has_aborted();
2336 return;
2337 }
2338
2339 // (5) We check whether we've reached our time quota. If we have,
2340 // then we abort.
2341 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2342 if (elapsed_time_ms > _time_target_ms) {
2343 set_has_aborted();
2344 _has_timed_out = true;
2345 return;
2346 }
2347
2348 // (6) Finally, we check whether there are enough completed STAB
2349 // buffers available for processing. If there are, we abort.
2350 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2351 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2352 // we do need to process SATB buffers, we'll abort and restart
2353 // the marking task to do so
2354 set_has_aborted();
2355 return;
2356 }
2357 }
2358
2359 void G1CMTask::recalculate_limits() {
2360 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2361 _words_scanned_limit = _real_words_scanned_limit;
2362
2363 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2364 _refs_reached_limit = _real_refs_reached_limit;
2365 }
2366
2367 void G1CMTask::decrease_limits() {
2368 // This is called when we believe that we're going to do an infrequent
2369 // operation which will increase the per byte scanned cost (i.e. move
2370 // entries to/from the global stack). It basically tries to decrease the
2371 // scanning limit so that the clock is called earlier.
2372
2373 _words_scanned_limit = _real_words_scanned_limit -
2374 3 * words_scanned_period / 4;
2375 _refs_reached_limit = _real_refs_reached_limit -
2376 3 * refs_reached_period / 4;
2377 }
2378
2379 void G1CMTask::move_entries_to_global_stack() {
2380 // Local array where we'll store the entries that will be popped
2381 // from the local queue.
2382 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2383
2384 size_t n = 0;
2385 G1TaskQueueEntry task_entry;
2386 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2387 buffer[n] = task_entry;
2388 ++n;
2389 }
2390 if (n < G1CMMarkStack::EntriesPerChunk) {
2391 buffer[n] = G1TaskQueueEntry();
2392 }
2393
2394 if (n > 0) {
2395 if (!_cm->mark_stack_push(buffer)) {
2396 set_has_aborted();
2397 }
2398 }
2399
2400 // This operation was quite expensive, so decrease the limits.
2401 decrease_limits();
2402 }
2403
2404 bool G1CMTask::get_entries_from_global_stack() {
2405 // Local array where we'll store the entries that will be popped
2406 // from the global stack.
2407 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2408
2409 if (!_cm->mark_stack_pop(buffer)) {
2410 return false;
2411 }
2412
2413 // We did actually pop at least one entry.
2414 for (size_t i = 0; i < G1CMMarkStack::EntriesPerChunk; ++i) {
2415 G1TaskQueueEntry task_entry = buffer[i];
2416 if (task_entry.is_null()) {
2417 break;
2418 }
2419 assert(task_entry.is_array_slice() || task_entry.obj()->is_oop(), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj()));
2420 bool success = _task_queue->push(task_entry);
2421 // We only call this when the local queue is empty or under a
2422 // given target limit. So, we do not expect this push to fail.
2423 assert(success, "invariant");
2424 }
2425
2426 // This operation was quite expensive, so decrease the limits
2427 decrease_limits();
2428 return true;
2429 }
2430
2431 void G1CMTask::drain_local_queue(bool partially) {
2432 if (has_aborted()) {
2433 return;
2434 }
2435
2436 // Decide what the target size is, depending whether we're going to
2437 // drain it partially (so that other tasks can steal if they run out
2438 // of things to do) or totally (at the very end).
2439 size_t target_size;
2440 if (partially) {
2441 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
2442 } else {
2443 target_size = 0;
2444 }
2445
2446 if (_task_queue->size() > target_size) {
2447 G1TaskQueueEntry entry;
2448 bool ret = _task_queue->pop_local(entry);
2449 while (ret) {
2450 scan_task_entry(entry);
2451 if (_task_queue->size() <= target_size || has_aborted()) {
2452 ret = false;
2453 } else {
2454 ret = _task_queue->pop_local(entry);
2455 }
2456 }
2457 }
2458 }
2459
2460 void G1CMTask::drain_global_stack(bool partially) {
2461 if (has_aborted()) return;
2462
2463 // We have a policy to drain the local queue before we attempt to
2464 // drain the global stack.
2465 assert(partially || _task_queue->size() == 0, "invariant");
2466
2467 // Decide what the target size is, depending whether we're going to
2468 // drain it partially (so that other tasks can steal if they run out
2469 // of things to do) or totally (at the very end).
2470 // Notice that when draining the global mark stack partially, due to the racyness
2471 // of the mark stack size update we might in fact drop below the target. But,
2472 // this is not a problem.
2473 // In case of total draining, we simply process until the global mark stack is
2474 // totally empty, disregarding the size counter.
2475 if (partially) {
2476 size_t const target_size = _cm->partial_mark_stack_size_target();
2477 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2478 if (get_entries_from_global_stack()) {
2479 drain_local_queue(partially);
2480 }
2481 }
2482 } else {
2483 while (!has_aborted() && get_entries_from_global_stack()) {
2484 drain_local_queue(partially);
2485 }
2486 }
2487 }
2488
2489 // SATB Queue has several assumptions on whether to call the par or
2490 // non-par versions of the methods. this is why some of the code is
2491 // replicated. We should really get rid of the single-threaded version
2492 // of the code to simplify things.
2493 void G1CMTask::drain_satb_buffers() {
2494 if (has_aborted()) return;
2495
2496 // We set this so that the regular clock knows that we're in the
2497 // middle of draining buffers and doesn't set the abort flag when it
2498 // notices that SATB buffers are available for draining. It'd be
2499 // very counter productive if it did that. :-)
2500 _draining_satb_buffers = true;
2501
2502 G1CMSATBBufferClosure satb_cl(this, _g1h);
2503 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2504
2505 // This keeps claiming and applying the closure to completed buffers
2506 // until we run out of buffers or we need to abort.
2507 while (!has_aborted() &&
2508 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2509 regular_clock_call();
2510 }
2511
2512 _draining_satb_buffers = false;
2513
2514 assert(has_aborted() ||
2515 concurrent() ||
2516 satb_mq_set.completed_buffers_num() == 0, "invariant");
2517
2518 // again, this was a potentially expensive operation, decrease the
2519 // limits to get the regular clock call early
2520 decrease_limits();
2521 }
2522
2523 void G1CMTask::print_stats() {
2524 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d",
2525 _worker_id, _calls);
2526 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2527 _elapsed_time_ms, _termination_time_ms);
2528 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
2529 _step_times_ms.num(), _step_times_ms.avg(),
2530 _step_times_ms.sd());
2531 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms",
2532 _step_times_ms.maximum(), _step_times_ms.sum());
2533 }
2534
2535 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry) {
2536 return _task_queues->steal(worker_id, hash_seed, task_entry);
2537 }
2538
2539 /*****************************************************************************
2540
2541 The do_marking_step(time_target_ms, ...) method is the building
2542 block of the parallel marking framework. It can be called in parallel
2543 with other invocations of do_marking_step() on different tasks
2544 (but only one per task, obviously) and concurrently with the
2545 mutator threads, or during remark, hence it eliminates the need
2546 for two versions of the code. When called during remark, it will
2547 pick up from where the task left off during the concurrent marking
2548 phase. Interestingly, tasks are also claimable during evacuation
2549 pauses too, since do_marking_step() ensures that it aborts before
2550 it needs to yield.
2551
2552 The data structures that it uses to do marking work are the
2553 following:
2554
2555 (1) Marking Bitmap. If there are gray objects that appear only
2556 on the bitmap (this happens either when dealing with an overflow
2557 or when the initial marking phase has simply marked the roots
2558 and didn't push them on the stack), then tasks claim heap
2559 regions whose bitmap they then scan to find gray objects. A
2560 global finger indicates where the end of the last claimed region
2561 is. A local finger indicates how far into the region a task has
2562 scanned. The two fingers are used to determine how to gray an
2563 object (i.e. whether simply marking it is OK, as it will be
2564 visited by a task in the future, or whether it needs to be also
2565 pushed on a stack).
2566
2567 (2) Local Queue. The local queue of the task which is accessed
2568 reasonably efficiently by the task. Other tasks can steal from
2569 it when they run out of work. Throughout the marking phase, a
2570 task attempts to keep its local queue short but not totally
2571 empty, so that entries are available for stealing by other
2572 tasks. Only when there is no more work, a task will totally
2573 drain its local queue.
2574
2575 (3) Global Mark Stack. This handles local queue overflow. During
2576 marking only sets of entries are moved between it and the local
2577 queues, as access to it requires a mutex and more fine-grain
2578 interaction with it which might cause contention. If it
2579 overflows, then the marking phase should restart and iterate
2580 over the bitmap to identify gray objects. Throughout the marking
2581 phase, tasks attempt to keep the global mark stack at a small
2582 length but not totally empty, so that entries are available for
2583 popping by other tasks. Only when there is no more work, tasks
2584 will totally drain the global mark stack.
2585
2586 (4) SATB Buffer Queue. This is where completed SATB buffers are
2587 made available. Buffers are regularly removed from this queue
2588 and scanned for roots, so that the queue doesn't get too
2589 long. During remark, all completed buffers are processed, as
2590 well as the filled in parts of any uncompleted buffers.
2591
2592 The do_marking_step() method tries to abort when the time target
2593 has been reached. There are a few other cases when the
2594 do_marking_step() method also aborts:
2595
2596 (1) When the marking phase has been aborted (after a Full GC).
2597
2598 (2) When a global overflow (on the global stack) has been
2599 triggered. Before the task aborts, it will actually sync up with
2600 the other tasks to ensure that all the marking data structures
2601 (local queues, stacks, fingers etc.) are re-initialized so that
2602 when do_marking_step() completes, the marking phase can
2603 immediately restart.
2604
2605 (3) When enough completed SATB buffers are available. The
2606 do_marking_step() method only tries to drain SATB buffers right
2607 at the beginning. So, if enough buffers are available, the
2608 marking step aborts and the SATB buffers are processed at
2609 the beginning of the next invocation.
2610
2611 (4) To yield. when we have to yield then we abort and yield
2612 right at the end of do_marking_step(). This saves us from a lot
2613 of hassle as, by yielding we might allow a Full GC. If this
2614 happens then objects will be compacted underneath our feet, the
2615 heap might shrink, etc. We save checking for this by just
2616 aborting and doing the yield right at the end.
2617
2618 From the above it follows that the do_marking_step() method should
2619 be called in a loop (or, otherwise, regularly) until it completes.
2620
2621 If a marking step completes without its has_aborted() flag being
2622 true, it means it has completed the current marking phase (and
2623 also all other marking tasks have done so and have all synced up).
2624
2625 A method called regular_clock_call() is invoked "regularly" (in
2626 sub ms intervals) throughout marking. It is this clock method that
2627 checks all the abort conditions which were mentioned above and
2628 decides when the task should abort. A work-based scheme is used to
2629 trigger this clock method: when the number of object words the
2630 marking phase has scanned or the number of references the marking
2631 phase has visited reach a given limit. Additional invocations to
2632 the method clock have been planted in a few other strategic places
2633 too. The initial reason for the clock method was to avoid calling
2634 vtime too regularly, as it is quite expensive. So, once it was in
2635 place, it was natural to piggy-back all the other conditions on it
2636 too and not constantly check them throughout the code.
2637
2638 If do_termination is true then do_marking_step will enter its
2639 termination protocol.
2640
2641 The value of is_serial must be true when do_marking_step is being
2642 called serially (i.e. by the VMThread) and do_marking_step should
2643 skip any synchronization in the termination and overflow code.
2644 Examples include the serial remark code and the serial reference
2645 processing closures.
2646
2647 The value of is_serial must be false when do_marking_step is
2648 being called by any of the worker threads in a work gang.
2649 Examples include the concurrent marking code (CMMarkingTask),
2650 the MT remark code, and the MT reference processing closures.
2651
2652 *****************************************************************************/
2653
2654 void G1CMTask::do_marking_step(double time_target_ms,
2655 bool do_termination,
2656 bool is_serial) {
2657 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2658 assert(concurrent() == _cm->concurrent(), "they should be the same");
2659
2660 G1Policy* g1_policy = _g1h->g1_policy();
2661 assert(_task_queues != NULL, "invariant");
2662 assert(_task_queue != NULL, "invariant");
2663 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
2664
2665 assert(!_claimed,
2666 "only one thread should claim this task at any one time");
2667
2668 // OK, this doesn't safeguard again all possible scenarios, as it is
2669 // possible for two threads to set the _claimed flag at the same
2670 // time. But it is only for debugging purposes anyway and it will
2671 // catch most problems.
2672 _claimed = true;
2673
2674 _start_time_ms = os::elapsedVTime() * 1000.0;
2675
2676 // If do_stealing is true then do_marking_step will attempt to
2677 // steal work from the other G1CMTasks. It only makes sense to
2678 // enable stealing when the termination protocol is enabled
2679 // and do_marking_step() is not being called serially.
2680 bool do_stealing = do_termination && !is_serial;
2681
2682 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms);
2683 _time_target_ms = time_target_ms - diff_prediction_ms;
2684
2685 // set up the variables that are used in the work-based scheme to
2686 // call the regular clock method
2687 _words_scanned = 0;
2688 _refs_reached = 0;
2689 recalculate_limits();
2690
2691 // clear all flags
2692 clear_has_aborted();
2693 _has_timed_out = false;
2694 _draining_satb_buffers = false;
2695
2696 ++_calls;
2697
2698 // Set up the bitmap and oop closures. Anything that uses them is
2699 // eventually called from this method, so it is OK to allocate these
2700 // statically.
2701 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
2702 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
2703 set_cm_oop_closure(&cm_oop_closure);
2704
2705 if (_cm->has_overflown()) {
2706 // This can happen if the mark stack overflows during a GC pause
2707 // and this task, after a yield point, restarts. We have to abort
2708 // as we need to get into the overflow protocol which happens
2709 // right at the end of this task.
2710 set_has_aborted();
2711 }
2712
2713 // First drain any available SATB buffers. After this, we will not
2714 // look at SATB buffers before the next invocation of this method.
2715 // If enough completed SATB buffers are queued up, the regular clock
2716 // will abort this task so that it restarts.
2717 drain_satb_buffers();
2718 // ...then partially drain the local queue and the global stack
2719 drain_local_queue(true);
2720 drain_global_stack(true);
2721
2722 do {
2723 if (!has_aborted() && _curr_region != NULL) {
2724 // This means that we're already holding on to a region.
2725 assert(_finger != NULL, "if region is not NULL, then the finger "
2726 "should not be NULL either");
2727
2728 // We might have restarted this task after an evacuation pause
2729 // which might have evacuated the region we're holding on to
2730 // underneath our feet. Let's read its limit again to make sure
2731 // that we do not iterate over a region of the heap that
2732 // contains garbage (update_region_limit() will also move
2733 // _finger to the start of the region if it is found empty).
2734 update_region_limit();
2735 // We will start from _finger not from the start of the region,
2736 // as we might be restarting this task after aborting half-way
2737 // through scanning this region. In this case, _finger points to
2738 // the address where we last found a marked object. If this is a
2739 // fresh region, _finger points to start().
2740 MemRegion mr = MemRegion(_finger, _region_limit);
2741
2742 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2743 "humongous regions should go around loop once only");
2744
2745 // Some special cases:
2746 // If the memory region is empty, we can just give up the region.
2747 // If the current region is humongous then we only need to check
2748 // the bitmap for the bit associated with the start of the object,
2749 // scan the object if it's live, and give up the region.
2750 // Otherwise, let's iterate over the bitmap of the part of the region
2751 // that is left.
2752 // If the iteration is successful, give up the region.
2753 if (mr.is_empty()) {
2754 giveup_current_region();
2755 regular_clock_call();
2756 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2757 if (_nextMarkBitMap->isMarked(mr.start())) {
2758 // The object is marked - apply the closure
2759 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
2760 bitmap_closure.do_bit(offset);
2761 }
2762 // Even if this task aborted while scanning the humongous object
2763 // we can (and should) give up the current region.
2764 giveup_current_region();
2765 regular_clock_call();
2766 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
2767 giveup_current_region();
2768 regular_clock_call();
2769 } else {
2770 assert(has_aborted(), "currently the only way to do so");
2771 // The only way to abort the bitmap iteration is to return
2772 // false from the do_bit() method. However, inside the
2773 // do_bit() method we move the _finger to point to the
2774 // object currently being looked at. So, if we bail out, we
2775 // have definitely set _finger to something non-null.
2776 assert(_finger != NULL, "invariant");
2777
2778 // Region iteration was actually aborted. So now _finger
2779 // points to the address of the object we last scanned. If we
2780 // leave it there, when we restart this task, we will rescan
2781 // the object. It is easy to avoid this. We move the finger by
2782 // enough to point to the next possible object header (the
2783 // bitmap knows by how much we need to move it as it knows its
2784 // granularity).
2785 assert(_finger < _region_limit, "invariant");
2786 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
2787 // Check if bitmap iteration was aborted while scanning the last object
2788 if (new_finger >= _region_limit) {
2789 giveup_current_region();
2790 } else {
2791 move_finger_to(new_finger);
2792 }
2793 }
2794 }
2795 // At this point we have either completed iterating over the
2796 // region we were holding on to, or we have aborted.
2797
2798 // We then partially drain the local queue and the global stack.
2799 // (Do we really need this?)
2800 drain_local_queue(true);
2801 drain_global_stack(true);
2802
2803 // Read the note on the claim_region() method on why it might
2804 // return NULL with potentially more regions available for
2805 // claiming and why we have to check out_of_regions() to determine
2806 // whether we're done or not.
2807 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2808 // We are going to try to claim a new region. We should have
2809 // given up on the previous one.
2810 // Separated the asserts so that we know which one fires.
2811 assert(_curr_region == NULL, "invariant");
2812 assert(_finger == NULL, "invariant");
2813 assert(_region_limit == NULL, "invariant");
2814 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2815 if (claimed_region != NULL) {
2816 // Yes, we managed to claim one
2817 setup_for_region(claimed_region);
2818 assert(_curr_region == claimed_region, "invariant");
2819 }
2820 // It is important to call the regular clock here. It might take
2821 // a while to claim a region if, for example, we hit a large
2822 // block of empty regions. So we need to call the regular clock
2823 // method once round the loop to make sure it's called
2824 // frequently enough.
2825 regular_clock_call();
2826 }
2827
2828 if (!has_aborted() && _curr_region == NULL) {
2829 assert(_cm->out_of_regions(),
2830 "at this point we should be out of regions");
2831 }
2832 } while ( _curr_region != NULL && !has_aborted());
2833
2834 if (!has_aborted()) {
2835 // We cannot check whether the global stack is empty, since other
2836 // tasks might be pushing objects to it concurrently.
2837 assert(_cm->out_of_regions(),
2838 "at this point we should be out of regions");
2839 // Try to reduce the number of available SATB buffers so that
2840 // remark has less work to do.
2841 drain_satb_buffers();
2842 }
2843
2844 // Since we've done everything else, we can now totally drain the
2845 // local queue and global stack.
2846 drain_local_queue(false);
2847 drain_global_stack(false);
2848
2849 // Attempt at work stealing from other task's queues.
2850 if (do_stealing && !has_aborted()) {
2851 // We have not aborted. This means that we have finished all that
2852 // we could. Let's try to do some stealing...
2853
2854 // We cannot check whether the global stack is empty, since other
2855 // tasks might be pushing objects to it concurrently.
2856 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2857 "only way to reach here");
2858 while (!has_aborted()) {
2859 G1TaskQueueEntry entry;
2860 if (_cm->try_stealing(_worker_id, &_hash_seed, entry)) {
2861 scan_task_entry(entry);
2862
2863 // And since we're towards the end, let's totally drain the
2864 // local queue and global stack.
2865 drain_local_queue(false);
2866 drain_global_stack(false);
2867 } else {
2868 break;
2869 }
2870 }
2871 }
2872
2873 // We still haven't aborted. Now, let's try to get into the
2874 // termination protocol.
2875 if (do_termination && !has_aborted()) {
2876 // We cannot check whether the global stack is empty, since other
2877 // tasks might be concurrently pushing objects on it.
2878 // Separated the asserts so that we know which one fires.
2879 assert(_cm->out_of_regions(), "only way to reach here");
2880 assert(_task_queue->size() == 0, "only way to reach here");
2881 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2882
2883 // The G1CMTask class also extends the TerminatorTerminator class,
2884 // hence its should_exit_termination() method will also decide
2885 // whether to exit the termination protocol or not.
2886 bool finished = (is_serial ||
2887 _cm->terminator()->offer_termination(this));
2888 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2889 _termination_time_ms +=
2890 termination_end_time_ms - _termination_start_time_ms;
2891
2892 if (finished) {
2893 // We're all done.
2894
2895 if (_worker_id == 0) {
2896 // let's allow task 0 to do this
2897 if (concurrent()) {
2898 assert(_cm->concurrent_marking_in_progress(), "invariant");
2899 // we need to set this to false before the next
2900 // safepoint. This way we ensure that the marking phase
2901 // doesn't observe any more heap expansions.
2902 _cm->clear_concurrent_marking_in_progress();
2903 }
2904 }
2905
2906 // We can now guarantee that the global stack is empty, since
2907 // all other tasks have finished. We separated the guarantees so
2908 // that, if a condition is false, we can immediately find out
2909 // which one.
2910 guarantee(_cm->out_of_regions(), "only way to reach here");
2911 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2912 guarantee(_task_queue->size() == 0, "only way to reach here");
2913 guarantee(!_cm->has_overflown(), "only way to reach here");
2914 } else {
2915 // Apparently there's more work to do. Let's abort this task. It
2916 // will restart it and we can hopefully find more things to do.
2917 set_has_aborted();
2918 }
2919 }
2920
2921 // Mainly for debugging purposes to make sure that a pointer to the
2922 // closure which was statically allocated in this frame doesn't
2923 // escape it by accident.
2924 set_cm_oop_closure(NULL);
2925 double end_time_ms = os::elapsedVTime() * 1000.0;
2926 double elapsed_time_ms = end_time_ms - _start_time_ms;
2927 // Update the step history.
2928 _step_times_ms.add(elapsed_time_ms);
2929
2930 if (has_aborted()) {
2931 // The task was aborted for some reason.
2932 if (_has_timed_out) {
2933 double diff_ms = elapsed_time_ms - _time_target_ms;
2934 // Keep statistics of how well we did with respect to hitting
2935 // our target only if we actually timed out (if we aborted for
2936 // other reasons, then the results might get skewed).
2937 _marking_step_diffs_ms.add(diff_ms);
2938 }
2939
2940 if (_cm->has_overflown()) {
2941 // This is the interesting one. We aborted because a global
2942 // overflow was raised. This means we have to restart the
2943 // marking phase and start iterating over regions. However, in
2944 // order to do this we have to make sure that all tasks stop
2945 // what they are doing and re-initialize in a safe manner. We
2946 // will achieve this with the use of two barrier sync points.
2947
2948 if (!is_serial) {
2949 // We only need to enter the sync barrier if being called
2950 // from a parallel context
2951 _cm->enter_first_sync_barrier(_worker_id);
2952
2953 // When we exit this sync barrier we know that all tasks have
2954 // stopped doing marking work. So, it's now safe to
2955 // re-initialize our data structures. At the end of this method,
2956 // task 0 will clear the global data structures.
2957 }
2958
2959 // We clear the local state of this task...
2960 clear_region_fields();
2961
2962 if (!is_serial) {
2963 // ...and enter the second barrier.
2964 _cm->enter_second_sync_barrier(_worker_id);
2965 }
2966 // At this point, if we're during the concurrent phase of
2967 // marking, everything has been re-initialized and we're
2968 // ready to restart.
2969 }
2970 }
2971
2972 _claimed = false;
2973 }
2974
2975 G1CMTask::G1CMTask(uint worker_id,
2976 G1ConcurrentMark* cm,
2977 G1CMTaskQueue* task_queue,
2978 G1CMTaskQueueSet* task_queues)
2979 : _g1h(G1CollectedHeap::heap()),
2980 _worker_id(worker_id), _cm(cm),
2981 _objArray_processor(this),
2982 _claimed(false),
2983 _nextMarkBitMap(NULL), _hash_seed(17),
2984 _task_queue(task_queue),
2985 _task_queues(task_queues),
2986 _cm_oop_closure(NULL) {
2987 guarantee(task_queue != NULL, "invariant");
2988 guarantee(task_queues != NULL, "invariant");
2989
2990 _marking_step_diffs_ms.add(0.5);
2991 }
2992
2993 // These are formatting macros that are used below to ensure
2994 // consistent formatting. The *_H_* versions are used to format the
2995 // header for a particular value and they should be kept consistent
2996 // with the corresponding macro. Also note that most of the macros add
2997 // the necessary white space (as a prefix) which makes them a bit
2998 // easier to compose.
2999
3000 // All the output lines are prefixed with this string to be able to
3001 // identify them easily in a large log file.
3002 #define G1PPRL_LINE_PREFIX "###"
3003
3004 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
3005 #ifdef _LP64
3006 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
3007 #else // _LP64
3008 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
3009 #endif // _LP64
3010
3011 // For per-region info
3012 #define G1PPRL_TYPE_FORMAT " %-4s"
3013 #define G1PPRL_TYPE_H_FORMAT " %4s"
3014 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
3015 #define G1PPRL_BYTE_H_FORMAT " %9s"
3016 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
3017 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
3018
3019 // For summary info
3020 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
3021 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
3022 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
3023 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
3024
3025 G1PrintRegionLivenessInfoClosure::
3026 G1PrintRegionLivenessInfoClosure(const char* phase_name)
3027 : _total_used_bytes(0), _total_capacity_bytes(0),
3028 _total_prev_live_bytes(0), _total_next_live_bytes(0),
3029 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
3030 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3031 MemRegion g1_reserved = g1h->g1_reserved();
3032 double now = os::elapsedTime();
3033
3034 // Print the header of the output.
3035 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
3036 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
3037 G1PPRL_SUM_ADDR_FORMAT("reserved")
3038 G1PPRL_SUM_BYTE_FORMAT("region-size"),
3039 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
3040 HeapRegion::GrainBytes);
3041 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3042 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3043 G1PPRL_TYPE_H_FORMAT
3044 G1PPRL_ADDR_BASE_H_FORMAT
3045 G1PPRL_BYTE_H_FORMAT
3046 G1PPRL_BYTE_H_FORMAT
3047 G1PPRL_BYTE_H_FORMAT
3048 G1PPRL_DOUBLE_H_FORMAT
3049 G1PPRL_BYTE_H_FORMAT
3050 G1PPRL_BYTE_H_FORMAT,
3051 "type", "address-range",
3052 "used", "prev-live", "next-live", "gc-eff",
3053 "remset", "code-roots");
3054 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3055 G1PPRL_TYPE_H_FORMAT
3056 G1PPRL_ADDR_BASE_H_FORMAT
3057 G1PPRL_BYTE_H_FORMAT
3058 G1PPRL_BYTE_H_FORMAT
3059 G1PPRL_BYTE_H_FORMAT
3060 G1PPRL_DOUBLE_H_FORMAT
3061 G1PPRL_BYTE_H_FORMAT
3062 G1PPRL_BYTE_H_FORMAT,
3063 "", "",
3064 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3065 "(bytes)", "(bytes)");
3066 }
3067
3068 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
3069 const char* type = r->get_type_str();
3070 HeapWord* bottom = r->bottom();
3071 HeapWord* end = r->end();
3072 size_t capacity_bytes = r->capacity();
3073 size_t used_bytes = r->used();
3074 size_t prev_live_bytes = r->live_bytes();
3075 size_t next_live_bytes = r->next_live_bytes();
3076 double gc_eff = r->gc_efficiency();
3077 size_t remset_bytes = r->rem_set()->mem_size();
3078 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3079
3080 _total_used_bytes += used_bytes;
3081 _total_capacity_bytes += capacity_bytes;
3082 _total_prev_live_bytes += prev_live_bytes;
3083 _total_next_live_bytes += next_live_bytes;
3084 _total_remset_bytes += remset_bytes;
3085 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3086
3087 // Print a line for this particular region.
3088 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3089 G1PPRL_TYPE_FORMAT
3090 G1PPRL_ADDR_BASE_FORMAT
3091 G1PPRL_BYTE_FORMAT
3092 G1PPRL_BYTE_FORMAT
3093 G1PPRL_BYTE_FORMAT
3094 G1PPRL_DOUBLE_FORMAT
3095 G1PPRL_BYTE_FORMAT
3096 G1PPRL_BYTE_FORMAT,
3097 type, p2i(bottom), p2i(end),
3098 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3099 remset_bytes, strong_code_roots_bytes);
3100
3101 return false;
3102 }
3103
3104 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3105 // add static memory usages to remembered set sizes
3106 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3107 // Print the footer of the output.
3108 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3109 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3110 " SUMMARY"
3111 G1PPRL_SUM_MB_FORMAT("capacity")
3112 G1PPRL_SUM_MB_PERC_FORMAT("used")
3113 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3114 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3115 G1PPRL_SUM_MB_FORMAT("remset")
3116 G1PPRL_SUM_MB_FORMAT("code-roots"),
3117 bytes_to_mb(_total_capacity_bytes),
3118 bytes_to_mb(_total_used_bytes),
3119 perc(_total_used_bytes, _total_capacity_bytes),
3120 bytes_to_mb(_total_prev_live_bytes),
3121 perc(_total_prev_live_bytes, _total_capacity_bytes),
3122 bytes_to_mb(_total_next_live_bytes),
3123 perc(_total_next_live_bytes, _total_capacity_bytes),
3124 bytes_to_mb(_total_remset_bytes),
3125 bytes_to_mb(_total_strong_code_roots_bytes));
3126 }