1 /*
2 * Copyright (c) 2001, 2016, 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 _out_of_memory(false),
140 _should_expand(false) {
141 set_empty();
142 }
143
144 bool G1CMMarkStack::resize(size_t new_capacity) {
145 assert(is_empty(), "Only resize when stack is empty.");
146 assert(new_capacity <= _max_chunk_capacity,
147 "Trying to resize stack to " SIZE_FORMAT " chunks when the maximum is " SIZE_FORMAT, new_capacity, _max_chunk_capacity);
148
149 OopChunk* new_base = MmapArrayAllocator<OopChunk, mtGC>::allocate_or_null(new_capacity);
150
151 if (new_base == NULL) {
152 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(OopChunk));
153 return false;
154 }
155 // Release old mapping.
156 if (_base != NULL) {
157 MmapArrayAllocator<OopChunk, mtGC>::free(_base, _chunk_capacity);
158 }
159
160 _base = new_base;
161 _chunk_capacity = new_capacity;
162 set_empty();
163 _should_expand = false;
164
165 return true;
166 }
167
168 size_t G1CMMarkStack::capacity_alignment() {
169 return (size_t)lcm(os::vm_allocation_granularity(), sizeof(OopChunk)) / sizeof(void*);
170 }
171
172 bool G1CMMarkStack::initialize(size_t initial_capacity, size_t max_capacity) {
173 guarantee(_max_chunk_capacity == 0, "G1CMMarkStack already initialized.");
174
175 size_t const OopChunkSizeInVoidStar = sizeof(OopChunk) / sizeof(void*);
176
177 _max_chunk_capacity = (size_t)align_size_up(max_capacity, capacity_alignment()) / OopChunkSizeInVoidStar;
178 size_t initial_chunk_capacity = (size_t)align_size_up(initial_capacity, capacity_alignment()) / OopChunkSizeInVoidStar;
179
180 guarantee(initial_chunk_capacity <= _max_chunk_capacity,
181 "Maximum chunk capacity " SIZE_FORMAT " smaller than initial capacity " SIZE_FORMAT,
182 _max_chunk_capacity,
183 initial_chunk_capacity);
184
185 log_debug(gc)("Initialize mark stack with " SIZE_FORMAT " chunks, maximum " SIZE_FORMAT,
186 initial_chunk_capacity, _max_chunk_capacity);
187
188 return resize(initial_chunk_capacity);
189 }
190
191 void G1CMMarkStack::expand() {
192 // Clear expansion flag
193 _should_expand = false;
194
195 if (_chunk_capacity == _max_chunk_capacity) {
196 log_debug(gc)("Can not expand overflow mark stack further, already at maximum capacity of " SIZE_FORMAT " chunks.", _chunk_capacity);
197 return;
198 }
199 size_t old_capacity = _chunk_capacity;
200 // Double capacity if possible
201 size_t new_capacity = MIN2(old_capacity * 2, _max_chunk_capacity);
202
203 if (resize(new_capacity)) {
204 log_debug(gc)("Expanded mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
205 old_capacity, new_capacity);
206 } else {
207 log_warning(gc)("Failed to expand mark stack capacity from " SIZE_FORMAT " to " SIZE_FORMAT " chunks",
208 old_capacity, new_capacity);
209 }
210 }
211
212 G1CMMarkStack::~G1CMMarkStack() {
213 if (_base != NULL) {
214 MmapArrayAllocator<OopChunk, mtGC>::free(_base, _chunk_capacity);
215 }
216 }
217
218 void G1CMMarkStack::add_chunk_to_list(OopChunk* volatile* list, OopChunk* elem) {
219 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
220 elem->next = *list;
221 *list = elem;
222 }
223
224 G1CMMarkStack::OopChunk* G1CMMarkStack::remove_chunk_from_list(OopChunk* volatile* list) {
225 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
226
227 OopChunk* result = *list;
228 if (result != NULL) {
229 *list = (*list)->next;
230 }
231 return result;
232 }
233
234 G1CMMarkStack::OopChunk* G1CMMarkStack::allocate_new_chunk() {
235 // This dirty read is okay because we only ever increase the _hwm in parallel code.
236 if (_hwm >= _chunk_capacity) {
237 return NULL;
238 }
239
240 size_t cur_idx = Atomic::add(1, &_hwm) - 1;
241 if (cur_idx >= _chunk_capacity) {
242 return NULL;
243 }
244
245 OopChunk* result = ::new (&_base[cur_idx]) OopChunk;
246 result->next = NULL;
247 return result;
248 }
249
250 void G1CMMarkStack::par_push_chunk(oop* ptr_arr) {
251 // Get a new chunk.
252 OopChunk* new_chunk = remove_chunk_from_list(&_free_list);
253
254 if (new_chunk == NULL) {
255 // Did not get a chunk from the free list. Allocate from backing memory.
256 new_chunk = allocate_new_chunk();
257 }
258
259 if (new_chunk == NULL) {
260 _out_of_memory = true;
261 return;
262 }
263
264 for (size_t i = 0; i < OopsPerChunk; i++) {
265 new_chunk->data[i] = ptr_arr[i];
266 }
267
268 add_chunk_to_list(&_chunk_list, new_chunk);
269 Atomic::inc(&_chunks_in_chunk_list);
270 }
271
272 bool G1CMMarkStack::par_pop_chunk(oop* ptr_arr) {
273 OopChunk* cur = remove_chunk_from_list(&_chunk_list);
274
275 if (cur == NULL) {
276 return false;
277 }
278
279 Atomic::dec(&_chunks_in_chunk_list);
280
281 for (size_t i = 0; i < OopsPerChunk; i++) {
282 ptr_arr[i] = (oop)cur->data[i];
283 }
284
285 add_chunk_to_list(&_free_list, cur);
286 return true;
287 }
288
289 void G1CMMarkStack::set_empty() {
290 _chunks_in_chunk_list = 0;
291 _hwm = 0;
292 clear_out_of_memory();
293 _chunk_list = NULL;
294 _free_list = NULL;
295 }
296
297 G1CMRootRegions::G1CMRootRegions() :
298 _cm(NULL), _scan_in_progress(false),
299 _should_abort(false), _claimed_survivor_index(0) { }
300
301 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) {
302 _survivors = survivors;
303 _cm = cm;
304 }
305
306 void G1CMRootRegions::prepare_for_scan() {
307 assert(!scan_in_progress(), "pre-condition");
308
309 // Currently, only survivors can be root regions.
310 _claimed_survivor_index = 0;
311 _scan_in_progress = _survivors->regions()->is_nonempty();
312 _should_abort = false;
313 }
314
315 HeapRegion* G1CMRootRegions::claim_next() {
316 if (_should_abort) {
317 // If someone has set the should_abort flag, we return NULL to
318 // force the caller to bail out of their loop.
319 return NULL;
320 }
321
322 // Currently, only survivors can be root regions.
323 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions();
324
325 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1;
326 if (claimed_index < survivor_regions->length()) {
327 return survivor_regions->at(claimed_index);
328 }
329 return NULL;
330 }
331
332 uint G1CMRootRegions::num_root_regions() const {
333 return (uint)_survivors->regions()->length();
334 }
335
336 void G1CMRootRegions::notify_scan_done() {
337 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
338 _scan_in_progress = false;
339 RootRegionScan_lock->notify_all();
340 }
341
342 void G1CMRootRegions::cancel_scan() {
343 notify_scan_done();
344 }
345
346 void G1CMRootRegions::scan_finished() {
347 assert(scan_in_progress(), "pre-condition");
348
349 // Currently, only survivors can be root regions.
350 if (!_should_abort) {
351 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index);
352 assert((uint)_claimed_survivor_index >= _survivors->length(),
353 "we should have claimed all survivors, claimed index = %u, length = %u",
354 (uint)_claimed_survivor_index, _survivors->length());
355 }
356
357 notify_scan_done();
358 }
359
360 bool G1CMRootRegions::wait_until_scan_finished() {
361 if (!scan_in_progress()) return false;
362
363 {
364 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
365 while (scan_in_progress()) {
366 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
367 }
368 }
369 return true;
370 }
371
372 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
373 return MAX2((n_par_threads + 2) / 4, 1U);
374 }
375
376 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
377 _g1h(g1h),
378 _markBitMap1(),
379 _markBitMap2(),
380 _parallel_marking_threads(0),
381 _max_parallel_marking_threads(0),
382 _sleep_factor(0.0),
383 _marking_task_overhead(1.0),
384 _cleanup_list("Cleanup List"),
385
386 _prevMarkBitMap(&_markBitMap1),
387 _nextMarkBitMap(&_markBitMap2),
388
389 _global_mark_stack(),
390 // _finger set in set_non_marking_state
391
392 _max_worker_id(ParallelGCThreads),
393 // _active_tasks set in set_non_marking_state
394 // _tasks set inside the constructor
395 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)),
396 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
397
398 _has_overflown(false),
399 _concurrent(false),
400 _has_aborted(false),
401 _restart_for_overflow(false),
402 _concurrent_marking_in_progress(false),
403 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
404 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
405
406 // _verbose_level set below
407
408 _init_times(),
409 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
410 _cleanup_times(),
411 _total_counting_time(0.0),
412 _total_rs_scrub_time(0.0),
413
414 _parallel_workers(NULL),
415
416 _completed_initialization(false) {
417
418 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
419 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
420
421 // Create & start a ConcurrentMark thread.
422 _cmThread = new ConcurrentMarkThread(this);
423 assert(cmThread() != NULL, "CM Thread should have been created");
424 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
425 if (_cmThread->osthread() == NULL) {
426 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
427 }
428
429 assert(CGC_lock != NULL, "Where's the CGC_lock?");
430 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
431 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
432
433 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
434 satb_qs.set_buffer_size(G1SATBBufferSize);
435
436 _root_regions.init(_g1h->survivor(), this);
437
438 if (ConcGCThreads > ParallelGCThreads) {
439 log_warning(gc)("Can't have more ConcGCThreads (%u) than ParallelGCThreads (%u).",
440 ConcGCThreads, ParallelGCThreads);
441 return;
442 }
443 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
444 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
445 // if both are set
446 _sleep_factor = 0.0;
447 _marking_task_overhead = 1.0;
448 } else if (G1MarkingOverheadPercent > 0) {
449 // We will calculate the number of parallel marking threads based
450 // on a target overhead with respect to the soft real-time goal
451 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
452 double overall_cm_overhead =
453 (double) MaxGCPauseMillis * marking_overhead /
454 (double) GCPauseIntervalMillis;
455 double cpu_ratio = 1.0 / os::initial_active_processor_count();
456 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
457 double marking_task_overhead =
458 overall_cm_overhead / marking_thread_num * os::initial_active_processor_count();
459 double sleep_factor =
460 (1.0 - marking_task_overhead) / marking_task_overhead;
461
462 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
463 _sleep_factor = sleep_factor;
464 _marking_task_overhead = marking_task_overhead;
465 } else {
466 // Calculate the number of parallel marking threads by scaling
467 // the number of parallel GC threads.
468 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
469 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
470 _sleep_factor = 0.0;
471 _marking_task_overhead = 1.0;
472 }
473
474 assert(ConcGCThreads > 0, "Should have been set");
475 log_debug(gc)("ConcGCThreads: %u", ConcGCThreads);
476 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
477 _parallel_marking_threads = ConcGCThreads;
478 _max_parallel_marking_threads = _parallel_marking_threads;
479
480 _parallel_workers = new WorkGang("G1 Marker",
481 _max_parallel_marking_threads, false, true);
482 if (_parallel_workers == NULL) {
483 vm_exit_during_initialization("Failed necessary allocation.");
484 } else {
485 _parallel_workers->initialize_workers();
486 }
487
488 if (FLAG_IS_DEFAULT(MarkStackSize)) {
489 size_t mark_stack_size =
490 MIN2(MarkStackSizeMax,
491 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
492 // Verify that the calculated value for MarkStackSize is in range.
493 // It would be nice to use the private utility routine from Arguments.
494 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
495 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
496 "must be between 1 and " SIZE_FORMAT,
497 mark_stack_size, MarkStackSizeMax);
498 return;
499 }
500 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
501 } else {
502 // Verify MarkStackSize is in range.
503 if (FLAG_IS_CMDLINE(MarkStackSize)) {
504 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
505 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
506 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
507 "must be between 1 and " SIZE_FORMAT,
508 MarkStackSize, MarkStackSizeMax);
509 return;
510 }
511 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
512 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
513 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
514 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
515 MarkStackSize, MarkStackSizeMax);
516 return;
517 }
518 }
519 }
520 }
521
522 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
523 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
524 }
525
526 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC);
527 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
528
529 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
530 _active_tasks = _max_worker_id;
531
532 for (uint i = 0; i < _max_worker_id; ++i) {
533 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
534 task_queue->initialize();
535 _task_queues->register_queue(i, task_queue);
536
537 _tasks[i] = new G1CMTask(i, this, task_queue, _task_queues);
538
539 _accum_task_vtime[i] = 0.0;
540 }
541
542 // so that the call below can read a sensible value
543 _heap_start = g1h->reserved_region().start();
544 set_non_marking_state();
545 _completed_initialization = true;
546 }
547
548 void G1ConcurrentMark::reset() {
549 // Starting values for these two. This should be called in a STW
550 // phase.
551 MemRegion reserved = _g1h->g1_reserved();
552 _heap_start = reserved.start();
553 _heap_end = reserved.end();
554
555 // Separated the asserts so that we know which one fires.
556 assert(_heap_start != NULL, "heap bounds should look ok");
557 assert(_heap_end != NULL, "heap bounds should look ok");
558 assert(_heap_start < _heap_end, "heap bounds should look ok");
559
560 // Reset all the marking data structures and any necessary flags
561 reset_marking_state();
562
563 // We do reset all of them, since different phases will use
564 // different number of active threads. So, it's easiest to have all
565 // of them ready.
566 for (uint i = 0; i < _max_worker_id; ++i) {
567 _tasks[i]->reset(_nextMarkBitMap);
568 }
569
570 // we need this to make sure that the flag is on during the evac
571 // pause with initial mark piggy-backed
572 set_concurrent_marking_in_progress();
573 }
574
575
576 void G1ConcurrentMark::reset_marking_state(bool clear_overflow) {
577 _global_mark_stack.set_should_expand(has_overflown());
578 _global_mark_stack.set_empty(); // Also clears the overflow stack's overflow flag
579 if (clear_overflow) {
580 clear_has_overflown();
581 } else {
582 assert(has_overflown(), "pre-condition");
583 }
584 _finger = _heap_start;
585
586 for (uint i = 0; i < _max_worker_id; ++i) {
587 G1CMTaskQueue* queue = _task_queues->queue(i);
588 queue->set_empty();
589 }
590 }
591
592 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
593 assert(active_tasks <= _max_worker_id, "we should not have more");
594
595 _active_tasks = active_tasks;
596 // Need to update the three data structures below according to the
597 // number of active threads for this phase.
598 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
599 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
600 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
601 }
602
603 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
604 set_concurrency(active_tasks);
605
606 _concurrent = concurrent;
607 // We propagate this to all tasks, not just the active ones.
608 for (uint i = 0; i < _max_worker_id; ++i)
609 _tasks[i]->set_concurrent(concurrent);
610
611 if (concurrent) {
612 set_concurrent_marking_in_progress();
613 } else {
614 // We currently assume that the concurrent flag has been set to
615 // false before we start remark. At this point we should also be
616 // in a STW phase.
617 assert(!concurrent_marking_in_progress(), "invariant");
618 assert(out_of_regions(),
619 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
620 p2i(_finger), p2i(_heap_end));
621 }
622 }
623
624 void G1ConcurrentMark::set_non_marking_state() {
625 // We set the global marking state to some default values when we're
626 // not doing marking.
627 reset_marking_state();
628 _active_tasks = 0;
629 clear_concurrent_marking_in_progress();
630 }
631
632 G1ConcurrentMark::~G1ConcurrentMark() {
633 // The G1ConcurrentMark instance is never freed.
634 ShouldNotReachHere();
635 }
636
637 class G1ClearBitMapTask : public AbstractGangTask {
638 public:
639 static size_t chunk_size() { return M; }
640
641 private:
642 // Heap region closure used for clearing the given mark bitmap.
643 class G1ClearBitmapHRClosure : public HeapRegionClosure {
644 private:
645 G1CMBitMap* _bitmap;
646 G1ConcurrentMark* _cm;
647 public:
648 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
649 }
650
651 virtual bool doHeapRegion(HeapRegion* r) {
652 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
653
654 HeapWord* cur = r->bottom();
655 HeapWord* const end = r->end();
656
657 while (cur < end) {
658 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
659 _bitmap->clear_range(mr);
660
661 cur += chunk_size_in_words;
662
663 // Abort iteration if after yielding the marking has been aborted.
664 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
665 return true;
666 }
667 // Repeat the asserts from before the start of the closure. We will do them
668 // as asserts here to minimize their overhead on the product. However, we
669 // will have them as guarantees at the beginning / end of the bitmap
670 // clearing to get some checking in the product.
671 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant");
672 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
673 }
674 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
675
676 return false;
677 }
678 };
679
680 G1ClearBitmapHRClosure _cl;
681 HeapRegionClaimer _hr_claimer;
682 bool _suspendible; // If the task is suspendible, workers must join the STS.
683
684 public:
685 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
686 AbstractGangTask("G1 Clear Bitmap"),
687 _cl(bitmap, suspendible ? cm : NULL),
688 _hr_claimer(n_workers),
689 _suspendible(suspendible)
690 { }
691
692 void work(uint worker_id) {
693 SuspendibleThreadSetJoiner sts_join(_suspendible);
694 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true);
695 }
696
697 bool is_complete() {
698 return _cl.complete();
699 }
700 };
701
702 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
703 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
704
705 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
706 size_t const num_chunks = align_size_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
707
708 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
709
710 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
711
712 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
713 workers->run_task(&cl, num_workers);
714 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
715 }
716
717 void G1ConcurrentMark::cleanup_for_next_mark() {
718 // Make sure that the concurrent mark thread looks to still be in
719 // the current cycle.
720 guarantee(cmThread()->during_cycle(), "invariant");
721
722 // We are finishing up the current cycle by clearing the next
723 // marking bitmap and getting it ready for the next cycle. During
724 // this time no other cycle can start. So, let's make sure that this
725 // is the case.
726 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
727
728 clear_bitmap(_nextMarkBitMap, _parallel_workers, true);
729
730 // Clear the live count data. If the marking has been aborted, the abort()
731 // call already did that.
732 if (!has_aborted()) {
733 clear_live_data(_parallel_workers);
734 DEBUG_ONLY(verify_live_data_clear());
735 }
736
737 // Repeat the asserts from above.
738 guarantee(cmThread()->during_cycle(), "invariant");
739 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
740 }
741
742 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
743 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint.");
744 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false);
745 }
746
747 class CheckBitmapClearHRClosure : public HeapRegionClosure {
748 G1CMBitMap* _bitmap;
749 bool _error;
750 public:
751 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
752 }
753
754 virtual bool doHeapRegion(HeapRegion* r) {
755 // This closure can be called concurrently to the mutator, so we must make sure
756 // that the result of the getNextMarkedWordAddress() call is compared to the
757 // value passed to it as limit to detect any found bits.
758 // end never changes in G1.
759 HeapWord* end = r->end();
760 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
761 }
762 };
763
764 bool G1ConcurrentMark::nextMarkBitmapIsClear() {
765 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
766 _g1h->heap_region_iterate(&cl);
767 return cl.complete();
768 }
769
770 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
771 public:
772 bool doHeapRegion(HeapRegion* r) {
773 r->note_start_of_marking();
774 return false;
775 }
776 };
777
778 void G1ConcurrentMark::checkpointRootsInitialPre() {
779 G1CollectedHeap* g1h = G1CollectedHeap::heap();
780 G1Policy* g1p = g1h->g1_policy();
781
782 _has_aborted = false;
783
784 // Initialize marking structures. This has to be done in a STW phase.
785 reset();
786
787 // For each region note start of marking.
788 NoteStartOfMarkHRClosure startcl;
789 g1h->heap_region_iterate(&startcl);
790 }
791
792
793 void G1ConcurrentMark::checkpointRootsInitialPost() {
794 G1CollectedHeap* g1h = G1CollectedHeap::heap();
795
796 // Start Concurrent Marking weak-reference discovery.
797 ReferenceProcessor* rp = g1h->ref_processor_cm();
798 // enable ("weak") refs discovery
799 rp->enable_discovery();
800 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
801
802 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
803 // This is the start of the marking cycle, we're expected all
804 // threads to have SATB queues with active set to false.
805 satb_mq_set.set_active_all_threads(true, /* new active value */
806 false /* expected_active */);
807
808 _root_regions.prepare_for_scan();
809
810 // update_g1_committed() will be called at the end of an evac pause
811 // when marking is on. So, it's also called at the end of the
812 // initial-mark pause to update the heap end, if the heap expands
813 // during it. No need to call it here.
814 }
815
816 /*
817 * Notice that in the next two methods, we actually leave the STS
818 * during the barrier sync and join it immediately afterwards. If we
819 * do not do this, the following deadlock can occur: one thread could
820 * be in the barrier sync code, waiting for the other thread to also
821 * sync up, whereas another one could be trying to yield, while also
822 * waiting for the other threads to sync up too.
823 *
824 * Note, however, that this code is also used during remark and in
825 * this case we should not attempt to leave / enter the STS, otherwise
826 * we'll either hit an assert (debug / fastdebug) or deadlock
827 * (product). So we should only leave / enter the STS if we are
828 * operating concurrently.
829 *
830 * Because the thread that does the sync barrier has left the STS, it
831 * is possible to be suspended for a Full GC or an evacuation pause
832 * could occur. This is actually safe, since the entering the sync
833 * barrier is one of the last things do_marking_step() does, and it
834 * doesn't manipulate any data structures afterwards.
835 */
836
837 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
838 bool barrier_aborted;
839 {
840 SuspendibleThreadSetLeaver sts_leave(concurrent());
841 barrier_aborted = !_first_overflow_barrier_sync.enter();
842 }
843
844 // at this point everyone should have synced up and not be doing any
845 // more work
846
847 if (barrier_aborted) {
848 // If the barrier aborted we ignore the overflow condition and
849 // just abort the whole marking phase as quickly as possible.
850 return;
851 }
852
853 // If we're executing the concurrent phase of marking, reset the marking
854 // state; otherwise the marking state is reset after reference processing,
855 // during the remark pause.
856 // If we reset here as a result of an overflow during the remark we will
857 // see assertion failures from any subsequent set_concurrency_and_phase()
858 // calls.
859 if (concurrent()) {
860 // let the task associated with with worker 0 do this
861 if (worker_id == 0) {
862 // task 0 is responsible for clearing the global data structures
863 // We should be here because of an overflow. During STW we should
864 // not clear the overflow flag since we rely on it being true when
865 // we exit this method to abort the pause and restart concurrent
866 // marking.
867 reset_marking_state(true /* clear_overflow */);
868
869 log_info(gc, marking)("Concurrent Mark reset for overflow");
870 }
871 }
872
873 // after this, each task should reset its own data structures then
874 // then go into the second barrier
875 }
876
877 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
878 SuspendibleThreadSetLeaver sts_leave(concurrent());
879 _second_overflow_barrier_sync.enter();
880
881 // at this point everything should be re-initialized and ready to go
882 }
883
884 class G1CMConcurrentMarkingTask: public AbstractGangTask {
885 private:
886 G1ConcurrentMark* _cm;
887 ConcurrentMarkThread* _cmt;
888
889 public:
890 void work(uint worker_id) {
891 assert(Thread::current()->is_ConcurrentGC_thread(),
892 "this should only be done by a conc GC thread");
893 ResourceMark rm;
894
895 double start_vtime = os::elapsedVTime();
896
897 {
898 SuspendibleThreadSetJoiner sts_join;
899
900 assert(worker_id < _cm->active_tasks(), "invariant");
901 G1CMTask* the_task = _cm->task(worker_id);
902 the_task->record_start_time();
903 if (!_cm->has_aborted()) {
904 do {
905 double start_vtime_sec = os::elapsedVTime();
906 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
907
908 the_task->do_marking_step(mark_step_duration_ms,
909 true /* do_termination */,
910 false /* is_serial*/);
911
912 double end_vtime_sec = os::elapsedVTime();
913 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
914 _cm->clear_has_overflown();
915
916 _cm->do_yield_check();
917
918 jlong sleep_time_ms;
919 if (!_cm->has_aborted() && the_task->has_aborted()) {
920 sleep_time_ms =
921 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
922 {
923 SuspendibleThreadSetLeaver sts_leave;
924 os::sleep(Thread::current(), sleep_time_ms, false);
925 }
926 }
927 } while (!_cm->has_aborted() && the_task->has_aborted());
928 }
929 the_task->record_end_time();
930 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
931 }
932
933 double end_vtime = os::elapsedVTime();
934 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
935 }
936
937 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm,
938 ConcurrentMarkThread* cmt) :
939 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
940
941 ~G1CMConcurrentMarkingTask() { }
942 };
943
944 // Calculates the number of active workers for a concurrent
945 // phase.
946 uint G1ConcurrentMark::calc_parallel_marking_threads() {
947 uint n_conc_workers = 0;
948 if (!UseDynamicNumberOfGCThreads ||
949 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
950 !ForceDynamicNumberOfGCThreads)) {
951 n_conc_workers = max_parallel_marking_threads();
952 } else {
953 n_conc_workers =
954 AdaptiveSizePolicy::calc_default_active_workers(max_parallel_marking_threads(),
955 1, /* Minimum workers */
956 parallel_marking_threads(),
957 Threads::number_of_non_daemon_threads());
958 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
959 // that scaling has already gone into "_max_parallel_marking_threads".
960 }
961 assert(n_conc_workers > 0 && n_conc_workers <= max_parallel_marking_threads(),
962 "Calculated number of workers must be larger than zero and at most the maximum %u, but is %u",
963 max_parallel_marking_threads(), n_conc_workers);
964 return n_conc_workers;
965 }
966
967 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr) {
968 // Currently, only survivors can be root regions.
969 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
970 G1RootRegionScanClosure cl(_g1h, this);
971
972 const uintx interval = PrefetchScanIntervalInBytes;
973 HeapWord* curr = hr->bottom();
974 const HeapWord* end = hr->top();
975 while (curr < end) {
976 Prefetch::read(curr, interval);
977 oop obj = oop(curr);
978 int size = obj->oop_iterate_size(&cl);
979 assert(size == obj->size(), "sanity");
980 curr += size;
981 }
982 }
983
984 class G1CMRootRegionScanTask : public AbstractGangTask {
985 private:
986 G1ConcurrentMark* _cm;
987
988 public:
989 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
990 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
991
992 void work(uint worker_id) {
993 assert(Thread::current()->is_ConcurrentGC_thread(),
994 "this should only be done by a conc GC thread");
995
996 G1CMRootRegions* root_regions = _cm->root_regions();
997 HeapRegion* hr = root_regions->claim_next();
998 while (hr != NULL) {
999 _cm->scanRootRegion(hr);
1000 hr = root_regions->claim_next();
1001 }
1002 }
1003 };
1004
1005 void G1ConcurrentMark::scan_root_regions() {
1006 // scan_in_progress() will have been set to true only if there was
1007 // at least one root region to scan. So, if it's false, we
1008 // should not attempt to do any further work.
1009 if (root_regions()->scan_in_progress()) {
1010 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
1011
1012 _parallel_marking_threads = MIN2(calc_parallel_marking_threads(),
1013 // We distribute work on a per-region basis, so starting
1014 // more threads than that is useless.
1015 root_regions()->num_root_regions());
1016 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1017 "Maximum number of marking threads exceeded");
1018
1019 G1CMRootRegionScanTask task(this);
1020 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
1021 task.name(), _parallel_marking_threads, root_regions()->num_root_regions());
1022 _parallel_workers->run_task(&task, _parallel_marking_threads);
1023
1024 // It's possible that has_aborted() is true here without actually
1025 // aborting the survivor scan earlier. This is OK as it's
1026 // mainly used for sanity checking.
1027 root_regions()->scan_finished();
1028 }
1029 }
1030
1031 void G1ConcurrentMark::concurrent_cycle_start() {
1032 _gc_timer_cm->register_gc_start();
1033
1034 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
1035
1036 _g1h->trace_heap_before_gc(_gc_tracer_cm);
1037 }
1038
1039 void G1ConcurrentMark::concurrent_cycle_end() {
1040 _g1h->trace_heap_after_gc(_gc_tracer_cm);
1041
1042 if (has_aborted()) {
1043 _gc_tracer_cm->report_concurrent_mode_failure();
1044 }
1045
1046 _gc_timer_cm->register_gc_end();
1047
1048 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
1049 }
1050
1051 void G1ConcurrentMark::mark_from_roots() {
1052 // we might be tempted to assert that:
1053 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1054 // "inconsistent argument?");
1055 // However that wouldn't be right, because it's possible that
1056 // a safepoint is indeed in progress as a younger generation
1057 // stop-the-world GC happens even as we mark in this generation.
1058
1059 _restart_for_overflow = false;
1060
1061 // _g1h has _n_par_threads
1062 _parallel_marking_threads = calc_parallel_marking_threads();
1063 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1064 "Maximum number of marking threads exceeded");
1065
1066 uint active_workers = MAX2(1U, parallel_marking_threads());
1067 assert(active_workers > 0, "Should have been set");
1068
1069 // Setting active workers is not guaranteed since fewer
1070 // worker threads may currently exist and more may not be
1071 // available.
1072 active_workers = _parallel_workers->update_active_workers(active_workers);
1073 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _parallel_workers->total_workers());
1074
1075 // Parallel task terminator is set in "set_concurrency_and_phase()"
1076 set_concurrency_and_phase(active_workers, true /* concurrent */);
1077
1078 G1CMConcurrentMarkingTask markingTask(this, cmThread());
1079 _parallel_workers->run_task(&markingTask);
1080 print_stats();
1081 }
1082
1083 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1084 // world is stopped at this checkpoint
1085 assert(SafepointSynchronize::is_at_safepoint(),
1086 "world should be stopped");
1087
1088 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1089
1090 // If a full collection has happened, we shouldn't do this.
1091 if (has_aborted()) {
1092 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1093 return;
1094 }
1095
1096 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1097
1098 if (VerifyDuringGC) {
1099 HandleMark hm; // handle scope
1100 g1h->prepare_for_verify();
1101 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1102 }
1103 g1h->verifier()->check_bitmaps("Remark Start");
1104
1105 G1Policy* g1p = g1h->g1_policy();
1106 g1p->record_concurrent_mark_remark_start();
1107
1108 double start = os::elapsedTime();
1109
1110 checkpointRootsFinalWork();
1111
1112 double mark_work_end = os::elapsedTime();
1113
1114 weakRefsWork(clear_all_soft_refs);
1115
1116 if (has_overflown()) {
1117 // We overflowed. Restart concurrent marking.
1118 _restart_for_overflow = true;
1119
1120 // Verify the heap w.r.t. the previous marking bitmap.
1121 if (VerifyDuringGC) {
1122 HandleMark hm; // handle scope
1123 g1h->prepare_for_verify();
1124 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)");
1125 }
1126
1127 // Clear the marking state because we will be restarting
1128 // marking due to overflowing the global mark stack.
1129 reset_marking_state();
1130 } else {
1131 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1132 // We're done with marking.
1133 // This is the end of the marking cycle, we're expected all
1134 // threads to have SATB queues with active set to true.
1135 satb_mq_set.set_active_all_threads(false, /* new active value */
1136 true /* expected_active */);
1137
1138 if (VerifyDuringGC) {
1139 HandleMark hm; // handle scope
1140 g1h->prepare_for_verify();
1141 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)");
1142 }
1143 g1h->verifier()->check_bitmaps("Remark End");
1144 assert(!restart_for_overflow(), "sanity");
1145 // Completely reset the marking state since marking completed
1146 set_non_marking_state();
1147 }
1148
1149 // Expand the marking stack, if we have to and if we can.
1150 if (_global_mark_stack.should_expand()) {
1151 _global_mark_stack.expand();
1152 }
1153
1154 // Statistics
1155 double now = os::elapsedTime();
1156 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1157 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1158 _remark_times.add((now - start) * 1000.0);
1159
1160 g1p->record_concurrent_mark_remark_end();
1161
1162 G1CMIsAliveClosure is_alive(g1h);
1163 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1164 }
1165
1166 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1167 G1CollectedHeap* _g1;
1168 size_t _freed_bytes;
1169 FreeRegionList* _local_cleanup_list;
1170 uint _old_regions_removed;
1171 uint _humongous_regions_removed;
1172 HRRSCleanupTask* _hrrs_cleanup_task;
1173
1174 public:
1175 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1176 FreeRegionList* local_cleanup_list,
1177 HRRSCleanupTask* hrrs_cleanup_task) :
1178 _g1(g1),
1179 _freed_bytes(0),
1180 _local_cleanup_list(local_cleanup_list),
1181 _old_regions_removed(0),
1182 _humongous_regions_removed(0),
1183 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1184
1185 size_t freed_bytes() { return _freed_bytes; }
1186 const uint old_regions_removed() { return _old_regions_removed; }
1187 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1188
1189 bool doHeapRegion(HeapRegion *hr) {
1190 if (hr->is_archive()) {
1191 return false;
1192 }
1193 _g1->reset_gc_time_stamps(hr);
1194 hr->note_end_of_marking();
1195
1196 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1197 _freed_bytes += hr->used();
1198 hr->set_containing_set(NULL);
1199 if (hr->is_humongous()) {
1200 _humongous_regions_removed++;
1201 _g1->free_humongous_region(hr, _local_cleanup_list, true /* skip_remset */);
1202 } else {
1203 _old_regions_removed++;
1204 _g1->free_region(hr, _local_cleanup_list, true /* skip_remset */);
1205 }
1206 } else {
1207 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1208 }
1209
1210 return false;
1211 }
1212 };
1213
1214 class G1ParNoteEndTask: public AbstractGangTask {
1215 friend class G1NoteEndOfConcMarkClosure;
1216
1217 protected:
1218 G1CollectedHeap* _g1h;
1219 FreeRegionList* _cleanup_list;
1220 HeapRegionClaimer _hrclaimer;
1221
1222 public:
1223 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1224 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1225 }
1226
1227 void work(uint worker_id) {
1228 FreeRegionList local_cleanup_list("Local Cleanup List");
1229 HRRSCleanupTask hrrs_cleanup_task;
1230 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1231 &hrrs_cleanup_task);
1232 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1233 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1234
1235 // Now update the lists
1236 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1237 {
1238 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1239 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1240
1241 // If we iterate over the global cleanup list at the end of
1242 // cleanup to do this printing we will not guarantee to only
1243 // generate output for the newly-reclaimed regions (the list
1244 // might not be empty at the beginning of cleanup; we might
1245 // still be working on its previous contents). So we do the
1246 // printing here, before we append the new regions to the global
1247 // cleanup list.
1248
1249 G1HRPrinter* hr_printer = _g1h->hr_printer();
1250 if (hr_printer->is_active()) {
1251 FreeRegionListIterator iter(&local_cleanup_list);
1252 while (iter.more_available()) {
1253 HeapRegion* hr = iter.get_next();
1254 hr_printer->cleanup(hr);
1255 }
1256 }
1257
1258 _cleanup_list->add_ordered(&local_cleanup_list);
1259 assert(local_cleanup_list.is_empty(), "post-condition");
1260
1261 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1262 }
1263 }
1264 };
1265
1266 void G1ConcurrentMark::cleanup() {
1267 // world is stopped at this checkpoint
1268 assert(SafepointSynchronize::is_at_safepoint(),
1269 "world should be stopped");
1270 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1271
1272 // If a full collection has happened, we shouldn't do this.
1273 if (has_aborted()) {
1274 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1275 return;
1276 }
1277
1278 g1h->verifier()->verify_region_sets_optional();
1279
1280 if (VerifyDuringGC) {
1281 HandleMark hm; // handle scope
1282 g1h->prepare_for_verify();
1283 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1284 }
1285 g1h->verifier()->check_bitmaps("Cleanup Start");
1286
1287 G1Policy* g1p = g1h->g1_policy();
1288 g1p->record_concurrent_mark_cleanup_start();
1289
1290 double start = os::elapsedTime();
1291
1292 HeapRegionRemSet::reset_for_cleanup_tasks();
1293
1294 {
1295 GCTraceTime(Debug, gc)("Finalize Live Data");
1296 finalize_live_data();
1297 }
1298
1299 if (VerifyDuringGC) {
1300 GCTraceTime(Debug, gc)("Verify Live Data");
1301 verify_live_data();
1302 }
1303
1304 g1h->collector_state()->set_mark_in_progress(false);
1305
1306 double count_end = os::elapsedTime();
1307 double this_final_counting_time = (count_end - start);
1308 _total_counting_time += this_final_counting_time;
1309
1310 if (log_is_enabled(Trace, gc, liveness)) {
1311 G1PrintRegionLivenessInfoClosure cl("Post-Marking");
1312 _g1h->heap_region_iterate(&cl);
1313 }
1314
1315 // Install newly created mark bitMap as "prev".
1316 swapMarkBitMaps();
1317
1318 g1h->reset_gc_time_stamp();
1319
1320 uint n_workers = _g1h->workers()->active_workers();
1321
1322 // Note end of marking in all heap regions.
1323 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1324 g1h->workers()->run_task(&g1_par_note_end_task);
1325 g1h->check_gc_time_stamps();
1326
1327 if (!cleanup_list_is_empty()) {
1328 // The cleanup list is not empty, so we'll have to process it
1329 // concurrently. Notify anyone else that might be wanting free
1330 // regions that there will be more free regions coming soon.
1331 g1h->set_free_regions_coming();
1332 }
1333
1334 // call below, since it affects the metric by which we sort the heap
1335 // regions.
1336 if (G1ScrubRemSets) {
1337 double rs_scrub_start = os::elapsedTime();
1338 g1h->scrub_rem_set();
1339 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start);
1340 }
1341
1342 // this will also free any regions totally full of garbage objects,
1343 // and sort the regions.
1344 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1345
1346 // Statistics.
1347 double end = os::elapsedTime();
1348 _cleanup_times.add((end - start) * 1000.0);
1349
1350 // Clean up will have freed any regions completely full of garbage.
1351 // Update the soft reference policy with the new heap occupancy.
1352 Universe::update_heap_info_at_gc();
1353
1354 if (VerifyDuringGC) {
1355 HandleMark hm; // handle scope
1356 g1h->prepare_for_verify();
1357 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)");
1358 }
1359
1360 g1h->verifier()->check_bitmaps("Cleanup End");
1361
1362 g1h->verifier()->verify_region_sets_optional();
1363
1364 // We need to make this be a "collection" so any collection pause that
1365 // races with it goes around and waits for completeCleanup to finish.
1366 g1h->increment_total_collections();
1367
1368 // Clean out dead classes and update Metaspace sizes.
1369 if (ClassUnloadingWithConcurrentMark) {
1370 ClassLoaderDataGraph::purge();
1371 }
1372 MetaspaceGC::compute_new_size();
1373
1374 // We reclaimed old regions so we should calculate the sizes to make
1375 // sure we update the old gen/space data.
1376 g1h->g1mm()->update_sizes();
1377 g1h->allocation_context_stats().update_after_mark();
1378 }
1379
1380 void G1ConcurrentMark::complete_cleanup() {
1381 if (has_aborted()) return;
1382
1383 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1384
1385 _cleanup_list.verify_optional();
1386 FreeRegionList tmp_free_list("Tmp Free List");
1387
1388 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1389 "cleanup list has %u entries",
1390 _cleanup_list.length());
1391
1392 // No one else should be accessing the _cleanup_list at this point,
1393 // so it is not necessary to take any locks
1394 while (!_cleanup_list.is_empty()) {
1395 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
1396 assert(hr != NULL, "Got NULL from a non-empty list");
1397 hr->par_clear();
1398 tmp_free_list.add_ordered(hr);
1399
1400 // Instead of adding one region at a time to the secondary_free_list,
1401 // we accumulate them in the local list and move them a few at a
1402 // time. This also cuts down on the number of notify_all() calls
1403 // we do during this process. We'll also append the local list when
1404 // _cleanup_list is empty (which means we just removed the last
1405 // region from the _cleanup_list).
1406 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
1407 _cleanup_list.is_empty()) {
1408 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1409 "appending %u entries to the secondary_free_list, "
1410 "cleanup list still has %u entries",
1411 tmp_free_list.length(),
1412 _cleanup_list.length());
1413
1414 {
1415 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1416 g1h->secondary_free_list_add(&tmp_free_list);
1417 SecondaryFreeList_lock->notify_all();
1418 }
1419 #ifndef PRODUCT
1420 if (G1StressConcRegionFreeing) {
1421 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
1422 os::sleep(Thread::current(), (jlong) 1, false);
1423 }
1424 }
1425 #endif
1426 }
1427 }
1428 assert(tmp_free_list.is_empty(), "post-condition");
1429 }
1430
1431 // Supporting Object and Oop closures for reference discovery
1432 // and processing in during marking
1433
1434 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1435 HeapWord* addr = (HeapWord*)obj;
1436 return addr != NULL &&
1437 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1438 }
1439
1440 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1441 // Uses the G1CMTask associated with a worker thread (for serial reference
1442 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1443 // trace referent objects.
1444 //
1445 // Using the G1CMTask and embedded local queues avoids having the worker
1446 // threads operating on the global mark stack. This reduces the risk
1447 // of overflowing the stack - which we would rather avoid at this late
1448 // state. Also using the tasks' local queues removes the potential
1449 // of the workers interfering with each other that could occur if
1450 // operating on the global stack.
1451
1452 class G1CMKeepAliveAndDrainClosure: public OopClosure {
1453 G1ConcurrentMark* _cm;
1454 G1CMTask* _task;
1455 int _ref_counter_limit;
1456 int _ref_counter;
1457 bool _is_serial;
1458 public:
1459 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1460 _cm(cm), _task(task), _is_serial(is_serial),
1461 _ref_counter_limit(G1RefProcDrainInterval) {
1462 assert(_ref_counter_limit > 0, "sanity");
1463 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1464 _ref_counter = _ref_counter_limit;
1465 }
1466
1467 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1468 virtual void do_oop( oop* p) { do_oop_work(p); }
1469
1470 template <class T> void do_oop_work(T* p) {
1471 if (!_cm->has_overflown()) {
1472 oop obj = oopDesc::load_decode_heap_oop(p);
1473 _task->deal_with_reference(obj);
1474 _ref_counter--;
1475
1476 if (_ref_counter == 0) {
1477 // We have dealt with _ref_counter_limit references, pushing them
1478 // and objects reachable from them on to the local stack (and
1479 // possibly the global stack). Call G1CMTask::do_marking_step() to
1480 // process these entries.
1481 //
1482 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1483 // there's nothing more to do (i.e. we're done with the entries that
1484 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1485 // above) or we overflow.
1486 //
1487 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1488 // flag while there may still be some work to do. (See the comment at
1489 // the beginning of G1CMTask::do_marking_step() for those conditions -
1490 // one of which is reaching the specified time target.) It is only
1491 // when G1CMTask::do_marking_step() returns without setting the
1492 // has_aborted() flag that the marking step has completed.
1493 do {
1494 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1495 _task->do_marking_step(mark_step_duration_ms,
1496 false /* do_termination */,
1497 _is_serial);
1498 } while (_task->has_aborted() && !_cm->has_overflown());
1499 _ref_counter = _ref_counter_limit;
1500 }
1501 }
1502 }
1503 };
1504
1505 // 'Drain' oop closure used by both serial and parallel reference processing.
1506 // Uses the G1CMTask associated with a given worker thread (for serial
1507 // reference processing the G1CMtask for worker 0 is used). Calls the
1508 // do_marking_step routine, with an unbelievably large timeout value,
1509 // to drain the marking data structures of the remaining entries
1510 // added by the 'keep alive' oop closure above.
1511
1512 class G1CMDrainMarkingStackClosure: public VoidClosure {
1513 G1ConcurrentMark* _cm;
1514 G1CMTask* _task;
1515 bool _is_serial;
1516 public:
1517 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1518 _cm(cm), _task(task), _is_serial(is_serial) {
1519 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1520 }
1521
1522 void do_void() {
1523 do {
1524 // We call G1CMTask::do_marking_step() to completely drain the local
1525 // and global marking stacks of entries pushed by the 'keep alive'
1526 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1527 //
1528 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1529 // if there's nothing more to do (i.e. we've completely drained the
1530 // entries that were pushed as a a result of applying the 'keep alive'
1531 // closure to the entries on the discovered ref lists) or we overflow
1532 // the global marking stack.
1533 //
1534 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1535 // flag while there may still be some work to do. (See the comment at
1536 // the beginning of G1CMTask::do_marking_step() for those conditions -
1537 // one of which is reaching the specified time target.) It is only
1538 // when G1CMTask::do_marking_step() returns without setting the
1539 // has_aborted() flag that the marking step has completed.
1540
1541 _task->do_marking_step(1000000000.0 /* something very large */,
1542 true /* do_termination */,
1543 _is_serial);
1544 } while (_task->has_aborted() && !_cm->has_overflown());
1545 }
1546 };
1547
1548 // Implementation of AbstractRefProcTaskExecutor for parallel
1549 // reference processing at the end of G1 concurrent marking
1550
1551 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
1552 private:
1553 G1CollectedHeap* _g1h;
1554 G1ConcurrentMark* _cm;
1555 WorkGang* _workers;
1556 uint _active_workers;
1557
1558 public:
1559 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1560 G1ConcurrentMark* cm,
1561 WorkGang* workers,
1562 uint n_workers) :
1563 _g1h(g1h), _cm(cm),
1564 _workers(workers), _active_workers(n_workers) { }
1565
1566 // Executes the given task using concurrent marking worker threads.
1567 virtual void execute(ProcessTask& task);
1568 virtual void execute(EnqueueTask& task);
1569 };
1570
1571 class G1CMRefProcTaskProxy: public AbstractGangTask {
1572 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1573 ProcessTask& _proc_task;
1574 G1CollectedHeap* _g1h;
1575 G1ConcurrentMark* _cm;
1576
1577 public:
1578 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1579 G1CollectedHeap* g1h,
1580 G1ConcurrentMark* cm) :
1581 AbstractGangTask("Process reference objects in parallel"),
1582 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1583 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1584 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1585 }
1586
1587 virtual void work(uint worker_id) {
1588 ResourceMark rm;
1589 HandleMark hm;
1590 G1CMTask* task = _cm->task(worker_id);
1591 G1CMIsAliveClosure g1_is_alive(_g1h);
1592 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1593 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1594
1595 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1596 }
1597 };
1598
1599 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1600 assert(_workers != NULL, "Need parallel worker threads.");
1601 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1602
1603 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1604
1605 // We need to reset the concurrency level before each
1606 // proxy task execution, so that the termination protocol
1607 // and overflow handling in G1CMTask::do_marking_step() knows
1608 // how many workers to wait for.
1609 _cm->set_concurrency(_active_workers);
1610 _workers->run_task(&proc_task_proxy);
1611 }
1612
1613 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
1614 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
1615 EnqueueTask& _enq_task;
1616
1617 public:
1618 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
1619 AbstractGangTask("Enqueue reference objects in parallel"),
1620 _enq_task(enq_task) { }
1621
1622 virtual void work(uint worker_id) {
1623 _enq_task.work(worker_id);
1624 }
1625 };
1626
1627 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
1628 assert(_workers != NULL, "Need parallel worker threads.");
1629 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1630
1631 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
1632
1633 // Not strictly necessary but...
1634 //
1635 // We need to reset the concurrency level before each
1636 // proxy task execution, so that the termination protocol
1637 // and overflow handling in G1CMTask::do_marking_step() knows
1638 // how many workers to wait for.
1639 _cm->set_concurrency(_active_workers);
1640 _workers->run_task(&enq_task_proxy);
1641 }
1642
1643 void G1ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
1644 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
1645 }
1646
1647 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
1648 if (has_overflown()) {
1649 // Skip processing the discovered references if we have
1650 // overflown the global marking stack. Reference objects
1651 // only get discovered once so it is OK to not
1652 // de-populate the discovered reference lists. We could have,
1653 // but the only benefit would be that, when marking restarts,
1654 // less reference objects are discovered.
1655 return;
1656 }
1657
1658 ResourceMark rm;
1659 HandleMark hm;
1660
1661 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1662
1663 // Is alive closure.
1664 G1CMIsAliveClosure g1_is_alive(g1h);
1665
1666 // Inner scope to exclude the cleaning of the string and symbol
1667 // tables from the displayed time.
1668 {
1669 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm);
1670
1671 ReferenceProcessor* rp = g1h->ref_processor_cm();
1672
1673 // See the comment in G1CollectedHeap::ref_processing_init()
1674 // about how reference processing currently works in G1.
1675
1676 // Set the soft reference policy
1677 rp->setup_policy(clear_all_soft_refs);
1678 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1679
1680 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1681 // in serial reference processing. Note these closures are also
1682 // used for serially processing (by the the current thread) the
1683 // JNI references during parallel reference processing.
1684 //
1685 // These closures do not need to synchronize with the worker
1686 // threads involved in parallel reference processing as these
1687 // instances are executed serially by the current thread (e.g.
1688 // reference processing is not multi-threaded and is thus
1689 // performed by the current thread instead of a gang worker).
1690 //
1691 // The gang tasks involved in parallel reference processing create
1692 // their own instances of these closures, which do their own
1693 // synchronization among themselves.
1694 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1695 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1696
1697 // We need at least one active thread. If reference processing
1698 // is not multi-threaded we use the current (VMThread) thread,
1699 // otherwise we use the work gang from the G1CollectedHeap and
1700 // we utilize all the worker threads we can.
1701 bool processing_is_mt = rp->processing_is_mt();
1702 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
1703 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
1704
1705 // Parallel processing task executor.
1706 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
1707 g1h->workers(), active_workers);
1708 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1709
1710 // Set the concurrency level. The phase was already set prior to
1711 // executing the remark task.
1712 set_concurrency(active_workers);
1713
1714 // Set the degree of MT processing here. If the discovery was done MT,
1715 // the number of threads involved during discovery could differ from
1716 // the number of active workers. This is OK as long as the discovered
1717 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1718 rp->set_active_mt_degree(active_workers);
1719
1720 // Process the weak references.
1721 const ReferenceProcessorStats& stats =
1722 rp->process_discovered_references(&g1_is_alive,
1723 &g1_keep_alive,
1724 &g1_drain_mark_stack,
1725 executor,
1726 _gc_timer_cm);
1727 _gc_tracer_cm->report_gc_reference_stats(stats);
1728
1729 // The do_oop work routines of the keep_alive and drain_marking_stack
1730 // oop closures will set the has_overflown flag if we overflow the
1731 // global marking stack.
1732
1733 assert(_global_mark_stack.is_out_of_memory() || _global_mark_stack.is_empty(),
1734 "mark stack should be empty (unless it overflowed)");
1735
1736 if (_global_mark_stack.is_out_of_memory()) {
1737 // This should have been done already when we tried to push an
1738 // entry on to the global mark stack. But let's do it again.
1739 set_has_overflown();
1740 }
1741
1742 assert(rp->num_q() == active_workers, "why not");
1743
1744 rp->enqueue_discovered_references(executor);
1745
1746 rp->verify_no_references_recorded();
1747 assert(!rp->discovery_enabled(), "Post condition");
1748 }
1749
1750 if (has_overflown()) {
1751 // We can not trust g1_is_alive if the marking stack overflowed
1752 return;
1753 }
1754
1755 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1756
1757 // Unload Klasses, String, Symbols, Code Cache, etc.
1758 if (ClassUnloadingWithConcurrentMark) {
1759 bool purged_classes;
1760
1761 {
1762 GCTraceTime(Debug, gc, phases) trace("System Dictionary Unloading", _gc_timer_cm);
1763 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
1764 }
1765
1766 {
1767 GCTraceTime(Debug, gc, phases) trace("Parallel Unloading", _gc_timer_cm);
1768 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
1769 }
1770 }
1771
1772 if (G1StringDedup::is_enabled()) {
1773 GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", _gc_timer_cm);
1774 G1StringDedup::unlink(&g1_is_alive);
1775 }
1776 }
1777
1778 void G1ConcurrentMark::swapMarkBitMaps() {
1779 G1CMBitMapRO* temp = _prevMarkBitMap;
1780 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap;
1781 _nextMarkBitMap = (G1CMBitMap*) temp;
1782 }
1783
1784 // Closure for marking entries in SATB buffers.
1785 class G1CMSATBBufferClosure : public SATBBufferClosure {
1786 private:
1787 G1CMTask* _task;
1788 G1CollectedHeap* _g1h;
1789
1790 // This is very similar to G1CMTask::deal_with_reference, but with
1791 // more relaxed requirements for the argument, so this must be more
1792 // circumspect about treating the argument as an object.
1793 void do_entry(void* entry) const {
1794 _task->increment_refs_reached();
1795 HeapRegion* hr = _g1h->heap_region_containing(entry);
1796 if (entry < hr->next_top_at_mark_start()) {
1797 // Until we get here, we don't know whether entry refers to a valid
1798 // object; it could instead have been a stale reference.
1799 oop obj = static_cast<oop>(entry);
1800 assert(obj->is_oop(true /* ignore mark word */),
1801 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj));
1802 _task->make_reference_grey(obj);
1803 }
1804 }
1805
1806 public:
1807 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1808 : _task(task), _g1h(g1h) { }
1809
1810 virtual void do_buffer(void** buffer, size_t size) {
1811 for (size_t i = 0; i < size; ++i) {
1812 do_entry(buffer[i]);
1813 }
1814 }
1815 };
1816
1817 class G1RemarkThreadsClosure : public ThreadClosure {
1818 G1CMSATBBufferClosure _cm_satb_cl;
1819 G1CMOopClosure _cm_cl;
1820 MarkingCodeBlobClosure _code_cl;
1821 int _thread_parity;
1822
1823 public:
1824 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1825 _cm_satb_cl(task, g1h),
1826 _cm_cl(g1h, g1h->concurrent_mark(), task),
1827 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1828 _thread_parity(Threads::thread_claim_parity()) {}
1829
1830 void do_thread(Thread* thread) {
1831 if (thread->is_Java_thread()) {
1832 if (thread->claim_oops_do(true, _thread_parity)) {
1833 JavaThread* jt = (JavaThread*)thread;
1834
1835 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1836 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1837 // * Alive if on the stack of an executing method
1838 // * Weakly reachable otherwise
1839 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1840 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1841 jt->nmethods_do(&_code_cl);
1842
1843 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
1844 }
1845 } else if (thread->is_VM_thread()) {
1846 if (thread->claim_oops_do(true, _thread_parity)) {
1847 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
1848 }
1849 }
1850 }
1851 };
1852
1853 class G1CMRemarkTask: public AbstractGangTask {
1854 private:
1855 G1ConcurrentMark* _cm;
1856 public:
1857 void work(uint worker_id) {
1858 // Since all available tasks are actually started, we should
1859 // only proceed if we're supposed to be active.
1860 if (worker_id < _cm->active_tasks()) {
1861 G1CMTask* task = _cm->task(worker_id);
1862 task->record_start_time();
1863 {
1864 ResourceMark rm;
1865 HandleMark hm;
1866
1867 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1868 Threads::threads_do(&threads_f);
1869 }
1870
1871 do {
1872 task->do_marking_step(1000000000.0 /* something very large */,
1873 true /* do_termination */,
1874 false /* is_serial */);
1875 } while (task->has_aborted() && !_cm->has_overflown());
1876 // If we overflow, then we do not want to restart. We instead
1877 // want to abort remark and do concurrent marking again.
1878 task->record_end_time();
1879 }
1880 }
1881
1882 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1883 AbstractGangTask("Par Remark"), _cm(cm) {
1884 _cm->terminator()->reset_for_reuse(active_workers);
1885 }
1886 };
1887
1888 void G1ConcurrentMark::checkpointRootsFinalWork() {
1889 ResourceMark rm;
1890 HandleMark hm;
1891 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1892
1893 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm);
1894
1895 g1h->ensure_parsability(false);
1896
1897 // this is remark, so we'll use up all active threads
1898 uint active_workers = g1h->workers()->active_workers();
1899 set_concurrency_and_phase(active_workers, false /* concurrent */);
1900 // Leave _parallel_marking_threads at it's
1901 // value originally calculated in the G1ConcurrentMark
1902 // constructor and pass values of the active workers
1903 // through the gang in the task.
1904
1905 {
1906 StrongRootsScope srs(active_workers);
1907
1908 G1CMRemarkTask remarkTask(this, active_workers);
1909 // We will start all available threads, even if we decide that the
1910 // active_workers will be fewer. The extra ones will just bail out
1911 // immediately.
1912 g1h->workers()->run_task(&remarkTask);
1913 }
1914
1915 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1916 guarantee(has_overflown() ||
1917 satb_mq_set.completed_buffers_num() == 0,
1918 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1919 BOOL_TO_STR(has_overflown()),
1920 satb_mq_set.completed_buffers_num());
1921
1922 print_stats();
1923 }
1924
1925 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
1926 // Note we are overriding the read-only view of the prev map here, via
1927 // the cast.
1928 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr);
1929 }
1930
1931 HeapRegion*
1932 G1ConcurrentMark::claim_region(uint worker_id) {
1933 // "checkpoint" the finger
1934 HeapWord* finger = _finger;
1935
1936 // _heap_end will not change underneath our feet; it only changes at
1937 // yield points.
1938 while (finger < _heap_end) {
1939 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1940
1941 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1942 // Make sure that the reads below do not float before loading curr_region.
1943 OrderAccess::loadload();
1944 // Above heap_region_containing may return NULL as we always scan claim
1945 // until the end of the heap. In this case, just jump to the next region.
1946 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1947
1948 // Is the gap between reading the finger and doing the CAS too long?
1949 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
1950 if (res == finger && curr_region != NULL) {
1951 // we succeeded
1952 HeapWord* bottom = curr_region->bottom();
1953 HeapWord* limit = curr_region->next_top_at_mark_start();
1954
1955 // notice that _finger == end cannot be guaranteed here since,
1956 // someone else might have moved the finger even further
1957 assert(_finger >= end, "the finger should have moved forward");
1958
1959 if (limit > bottom) {
1960 return curr_region;
1961 } else {
1962 assert(limit == bottom,
1963 "the region limit should be at bottom");
1964 // we return NULL and the caller should try calling
1965 // claim_region() again.
1966 return NULL;
1967 }
1968 } else {
1969 assert(_finger > finger, "the finger should have moved forward");
1970 // read it again
1971 finger = _finger;
1972 }
1973 }
1974
1975 return NULL;
1976 }
1977
1978 #ifndef PRODUCT
1979 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
1980 private:
1981 G1CollectedHeap* _g1h;
1982 const char* _phase;
1983 int _info;
1984
1985 public:
1986 VerifyNoCSetOops(const char* phase, int info = -1) :
1987 _g1h(G1CollectedHeap::heap()),
1988 _phase(phase),
1989 _info(info)
1990 { }
1991
1992 void operator()(oop obj) const {
1993 guarantee(obj->is_oop(),
1994 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1995 p2i(obj), _phase, _info);
1996 guarantee(!_g1h->obj_in_cs(obj),
1997 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
1998 p2i(obj), _phase, _info);
1999 }
2000 };
2001
2002 void G1ConcurrentMark::verify_no_cset_oops() {
2003 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2004 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) {
2005 return;
2006 }
2007
2008 // Verify entries on the global mark stack
2009 _global_mark_stack.iterate(VerifyNoCSetOops("Stack"));
2010
2011 // Verify entries on the task queues
2012 for (uint i = 0; i < _max_worker_id; ++i) {
2013 G1CMTaskQueue* queue = _task_queues->queue(i);
2014 queue->iterate(VerifyNoCSetOops("Queue", i));
2015 }
2016
2017 // Verify the global finger
2018 HeapWord* global_finger = finger();
2019 if (global_finger != NULL && global_finger < _heap_end) {
2020 // Since we always iterate over all regions, we might get a NULL HeapRegion
2021 // here.
2022 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
2023 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2024 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
2025 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
2026 }
2027
2028 // Verify the task fingers
2029 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2030 for (uint i = 0; i < parallel_marking_threads(); ++i) {
2031 G1CMTask* task = _tasks[i];
2032 HeapWord* task_finger = task->finger();
2033 if (task_finger != NULL && task_finger < _heap_end) {
2034 // See above note on the global finger verification.
2035 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger);
2036 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2037 !task_hr->in_collection_set(),
2038 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2039 p2i(task_finger), HR_FORMAT_PARAMS(task_hr));
2040 }
2041 }
2042 }
2043 #endif // PRODUCT
2044 void G1ConcurrentMark::create_live_data() {
2045 _g1h->g1_rem_set()->create_card_live_data(_parallel_workers, _nextMarkBitMap);
2046 }
2047
2048 void G1ConcurrentMark::finalize_live_data() {
2049 _g1h->g1_rem_set()->finalize_card_live_data(_g1h->workers(), _nextMarkBitMap);
2050 }
2051
2052 void G1ConcurrentMark::verify_live_data() {
2053 _g1h->g1_rem_set()->verify_card_live_data(_g1h->workers(), _nextMarkBitMap);
2054 }
2055
2056 void G1ConcurrentMark::clear_live_data(WorkGang* workers) {
2057 _g1h->g1_rem_set()->clear_card_live_data(workers);
2058 }
2059
2060 #ifdef ASSERT
2061 void G1ConcurrentMark::verify_live_data_clear() {
2062 _g1h->g1_rem_set()->verify_card_live_data_is_clear();
2063 }
2064 #endif
2065
2066 void G1ConcurrentMark::print_stats() {
2067 if (!log_is_enabled(Debug, gc, stats)) {
2068 return;
2069 }
2070 log_debug(gc, stats)("---------------------------------------------------------------------");
2071 for (size_t i = 0; i < _active_tasks; ++i) {
2072 _tasks[i]->print_stats();
2073 log_debug(gc, stats)("---------------------------------------------------------------------");
2074 }
2075 }
2076
2077 void G1ConcurrentMark::abort() {
2078 if (!cmThread()->during_cycle() || _has_aborted) {
2079 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2080 return;
2081 }
2082
2083 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2084 // concurrent bitmap clearing.
2085 {
2086 GCTraceTime(Debug, gc)("Clear Next Bitmap");
2087 clear_bitmap(_nextMarkBitMap, _g1h->workers(), false);
2088 }
2089 // Note we cannot clear the previous marking bitmap here
2090 // since VerifyDuringGC verifies the objects marked during
2091 // a full GC against the previous bitmap.
2092
2093 {
2094 GCTraceTime(Debug, gc)("Clear Live Data");
2095 clear_live_data(_g1h->workers());
2096 }
2097 DEBUG_ONLY({
2098 GCTraceTime(Debug, gc)("Verify Live Data Clear");
2099 verify_live_data_clear();
2100 })
2101 // Empty mark stack
2102 reset_marking_state();
2103 for (uint i = 0; i < _max_worker_id; ++i) {
2104 _tasks[i]->clear_region_fields();
2105 }
2106 _first_overflow_barrier_sync.abort();
2107 _second_overflow_barrier_sync.abort();
2108 _has_aborted = true;
2109
2110 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2111 satb_mq_set.abandon_partial_marking();
2112 // This can be called either during or outside marking, we'll read
2113 // the expected_active value from the SATB queue set.
2114 satb_mq_set.set_active_all_threads(
2115 false, /* new active value */
2116 satb_mq_set.is_active() /* expected_active */);
2117 }
2118
2119 static void print_ms_time_info(const char* prefix, const char* name,
2120 NumberSeq& ns) {
2121 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2122 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2123 if (ns.num() > 0) {
2124 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2125 prefix, ns.sd(), ns.maximum());
2126 }
2127 }
2128
2129 void G1ConcurrentMark::print_summary_info() {
2130 Log(gc, marking) log;
2131 if (!log.is_trace()) {
2132 return;
2133 }
2134
2135 log.trace(" Concurrent marking:");
2136 print_ms_time_info(" ", "init marks", _init_times);
2137 print_ms_time_info(" ", "remarks", _remark_times);
2138 {
2139 print_ms_time_info(" ", "final marks", _remark_mark_times);
2140 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2141
2142 }
2143 print_ms_time_info(" ", "cleanups", _cleanup_times);
2144 log.trace(" Finalize live data total time = %8.2f s (avg = %8.2f ms).",
2145 _total_counting_time, (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2146 if (G1ScrubRemSets) {
2147 log.trace(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
2148 _total_rs_scrub_time, (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2149 }
2150 log.trace(" Total stop_world time = %8.2f s.",
2151 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2152 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2153 cmThread()->vtime_accum(), cmThread()->vtime_mark_accum());
2154 }
2155
2156 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2157 _parallel_workers->print_worker_threads_on(st);
2158 }
2159
2160 void G1ConcurrentMark::threads_do(ThreadClosure* tc) const {
2161 _parallel_workers->threads_do(tc);
2162 }
2163
2164 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2165 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2166 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
2167 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
2168 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
2169 }
2170
2171 // Closure for iteration over bitmaps
2172 class G1CMBitMapClosure : public BitMapClosure {
2173 private:
2174 // the bitmap that is being iterated over
2175 G1CMBitMap* _nextMarkBitMap;
2176 G1ConcurrentMark* _cm;
2177 G1CMTask* _task;
2178
2179 public:
2180 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm, G1CMBitMap* nextMarkBitMap) :
2181 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
2182
2183 bool do_bit(size_t offset) {
2184 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
2185 assert(_nextMarkBitMap->isMarked(addr), "invariant");
2186 assert( addr < _cm->finger(), "invariant");
2187 assert(addr >= _task->finger(), "invariant");
2188
2189 // We move that task's local finger along.
2190 _task->move_finger_to(addr);
2191
2192 _task->scan_object(oop(addr));
2193 // we only partially drain the local queue and global stack
2194 _task->drain_local_queue(true);
2195 _task->drain_global_stack(true);
2196
2197 // if the has_aborted flag has been raised, we need to bail out of
2198 // the iteration
2199 return !_task->has_aborted();
2200 }
2201 };
2202
2203 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2204 ReferenceProcessor* result = g1h->ref_processor_cm();
2205 assert(result != NULL, "CM reference processor should not be NULL");
2206 return result;
2207 }
2208
2209 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2210 G1ConcurrentMark* cm,
2211 G1CMTask* task)
2212 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)),
2213 _g1h(g1h), _cm(cm), _task(task)
2214 { }
2215
2216 void G1CMTask::setup_for_region(HeapRegion* hr) {
2217 assert(hr != NULL,
2218 "claim_region() should have filtered out NULL regions");
2219 _curr_region = hr;
2220 _finger = hr->bottom();
2221 update_region_limit();
2222 }
2223
2224 void G1CMTask::update_region_limit() {
2225 HeapRegion* hr = _curr_region;
2226 HeapWord* bottom = hr->bottom();
2227 HeapWord* limit = hr->next_top_at_mark_start();
2228
2229 if (limit == bottom) {
2230 // The region was collected underneath our feet.
2231 // We set the finger to bottom to ensure that the bitmap
2232 // iteration that will follow this will not do anything.
2233 // (this is not a condition that holds when we set the region up,
2234 // as the region is not supposed to be empty in the first place)
2235 _finger = bottom;
2236 } else if (limit >= _region_limit) {
2237 assert(limit >= _finger, "peace of mind");
2238 } else {
2239 assert(limit < _region_limit, "only way to get here");
2240 // This can happen under some pretty unusual circumstances. An
2241 // evacuation pause empties the region underneath our feet (NTAMS
2242 // at bottom). We then do some allocation in the region (NTAMS
2243 // stays at bottom), followed by the region being used as a GC
2244 // alloc region (NTAMS will move to top() and the objects
2245 // originally below it will be grayed). All objects now marked in
2246 // the region are explicitly grayed, if below the global finger,
2247 // and we do not need in fact to scan anything else. So, we simply
2248 // set _finger to be limit to ensure that the bitmap iteration
2249 // doesn't do anything.
2250 _finger = limit;
2251 }
2252
2253 _region_limit = limit;
2254 }
2255
2256 void G1CMTask::giveup_current_region() {
2257 assert(_curr_region != NULL, "invariant");
2258 clear_region_fields();
2259 }
2260
2261 void G1CMTask::clear_region_fields() {
2262 // Values for these three fields that indicate that we're not
2263 // holding on to a region.
2264 _curr_region = NULL;
2265 _finger = NULL;
2266 _region_limit = NULL;
2267 }
2268
2269 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2270 if (cm_oop_closure == NULL) {
2271 assert(_cm_oop_closure != NULL, "invariant");
2272 } else {
2273 assert(_cm_oop_closure == NULL, "invariant");
2274 }
2275 _cm_oop_closure = cm_oop_closure;
2276 }
2277
2278 void G1CMTask::reset(G1CMBitMap* nextMarkBitMap) {
2279 guarantee(nextMarkBitMap != NULL, "invariant");
2280 _nextMarkBitMap = nextMarkBitMap;
2281 clear_region_fields();
2282
2283 _calls = 0;
2284 _elapsed_time_ms = 0.0;
2285 _termination_time_ms = 0.0;
2286 _termination_start_time_ms = 0.0;
2287 }
2288
2289 bool G1CMTask::should_exit_termination() {
2290 regular_clock_call();
2291 // This is called when we are in the termination protocol. We should
2292 // quit if, for some reason, this task wants to abort or the global
2293 // stack is not empty (this means that we can get work from it).
2294 return !_cm->mark_stack_empty() || has_aborted();
2295 }
2296
2297 void G1CMTask::reached_limit() {
2298 assert(_words_scanned >= _words_scanned_limit ||
2299 _refs_reached >= _refs_reached_limit ,
2300 "shouldn't have been called otherwise");
2301 regular_clock_call();
2302 }
2303
2304 void G1CMTask::regular_clock_call() {
2305 if (has_aborted()) return;
2306
2307 // First, we need to recalculate the words scanned and refs reached
2308 // limits for the next clock call.
2309 recalculate_limits();
2310
2311 // During the regular clock call we do the following
2312
2313 // (1) If an overflow has been flagged, then we abort.
2314 if (_cm->has_overflown()) {
2315 set_has_aborted();
2316 return;
2317 }
2318
2319 // If we are not concurrent (i.e. we're doing remark) we don't need
2320 // to check anything else. The other steps are only needed during
2321 // the concurrent marking phase.
2322 if (!concurrent()) return;
2323
2324 // (2) If marking has been aborted for Full GC, then we also abort.
2325 if (_cm->has_aborted()) {
2326 set_has_aborted();
2327 return;
2328 }
2329
2330 double curr_time_ms = os::elapsedVTime() * 1000.0;
2331
2332 // (4) We check whether we should yield. If we have to, then we abort.
2333 if (SuspendibleThreadSet::should_yield()) {
2334 // We should yield. To do this we abort the task. The caller is
2335 // responsible for yielding.
2336 set_has_aborted();
2337 return;
2338 }
2339
2340 // (5) We check whether we've reached our time quota. If we have,
2341 // then we abort.
2342 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2343 if (elapsed_time_ms > _time_target_ms) {
2344 set_has_aborted();
2345 _has_timed_out = true;
2346 return;
2347 }
2348
2349 // (6) Finally, we check whether there are enough completed STAB
2350 // buffers available for processing. If there are, we abort.
2351 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2352 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2353 // we do need to process SATB buffers, we'll abort and restart
2354 // the marking task to do so
2355 set_has_aborted();
2356 return;
2357 }
2358 }
2359
2360 void G1CMTask::recalculate_limits() {
2361 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2362 _words_scanned_limit = _real_words_scanned_limit;
2363
2364 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2365 _refs_reached_limit = _real_refs_reached_limit;
2366 }
2367
2368 void G1CMTask::decrease_limits() {
2369 // This is called when we believe that we're going to do an infrequent
2370 // operation which will increase the per byte scanned cost (i.e. move
2371 // entries to/from the global stack). It basically tries to decrease the
2372 // scanning limit so that the clock is called earlier.
2373
2374 _words_scanned_limit = _real_words_scanned_limit -
2375 3 * words_scanned_period / 4;
2376 _refs_reached_limit = _real_refs_reached_limit -
2377 3 * refs_reached_period / 4;
2378 }
2379
2380 void G1CMTask::move_entries_to_global_stack() {
2381 // Local array where we'll store the entries that will be popped
2382 // from the local queue.
2383 oop buffer[G1CMMarkStack::OopsPerChunk];
2384
2385 size_t n = 0;
2386 oop obj;
2387 while (n < G1CMMarkStack::OopsPerChunk && _task_queue->pop_local(obj)) {
2388 buffer[n] = obj;
2389 ++n;
2390 }
2391 if (n < G1CMMarkStack::OopsPerChunk) {
2392 buffer[n] = NULL;
2393 }
2394
2395 if (n > 0) {
2396 if (!_cm->mark_stack_push(buffer)) {
2397 set_has_aborted();
2398 }
2399 }
2400
2401 // This operation was quite expensive, so decrease the limits.
2402 decrease_limits();
2403 }
2404
2405 bool G1CMTask::get_entries_from_global_stack() {
2406 // Local array where we'll store the entries that will be popped
2407 // from the global stack.
2408 oop buffer[G1CMMarkStack::OopsPerChunk];
2409
2410 if (!_cm->mark_stack_pop(buffer)) {
2411 return false;
2412 }
2413
2414 // We did actually pop at least one entry.
2415 for (size_t i = 0; i < G1CMMarkStack::OopsPerChunk; ++i) {
2416 oop elem = buffer[i];
2417 if (elem == NULL) {
2418 break;
2419 }
2420 bool success = _task_queue->push(elem);
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()) return;
2433
2434 // Decide what the target size is, depending whether we're going to
2435 // drain it partially (so that other tasks can steal if they run out
2436 // of things to do) or totally (at the very end).
2437 size_t target_size;
2438 if (partially) {
2439 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
2440 } else {
2441 target_size = 0;
2442 }
2443
2444 if (_task_queue->size() > target_size) {
2445 oop obj;
2446 bool ret = _task_queue->pop_local(obj);
2447 while (ret) {
2448 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
2449 assert(!_g1h->is_on_master_free_list(
2450 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
2451
2452 scan_object(obj);
2453
2454 if (_task_queue->size() <= target_size || has_aborted()) {
2455 ret = false;
2456 } else {
2457 ret = _task_queue->pop_local(obj);
2458 }
2459 }
2460 }
2461 }
2462
2463 void G1CMTask::drain_global_stack(bool partially) {
2464 if (has_aborted()) return;
2465
2466 // We have a policy to drain the local queue before we attempt to
2467 // drain the global stack.
2468 assert(partially || _task_queue->size() == 0, "invariant");
2469
2470 // Decide what the target size is, depending whether we're going to
2471 // drain it partially (so that other tasks can steal if they run out
2472 // of things to do) or totally (at the very end).
2473 // Notice that when draining the global mark stack partially, due to the racyness
2474 // of the mark stack size update we might in fact drop below the target. But,
2475 // this is not a problem.
2476 // In case of total draining, we simply process until the global mark stack is
2477 // totally empty, disregarding the size counter.
2478 if (partially) {
2479 size_t const target_size = _cm->partial_mark_stack_size_target();
2480 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2481 if (get_entries_from_global_stack()) {
2482 drain_local_queue(partially);
2483 }
2484 }
2485 } else {
2486 while (!has_aborted() && get_entries_from_global_stack()) {
2487 drain_local_queue(partially);
2488 }
2489 }
2490 }
2491
2492 // SATB Queue has several assumptions on whether to call the par or
2493 // non-par versions of the methods. this is why some of the code is
2494 // replicated. We should really get rid of the single-threaded version
2495 // of the code to simplify things.
2496 void G1CMTask::drain_satb_buffers() {
2497 if (has_aborted()) return;
2498
2499 // We set this so that the regular clock knows that we're in the
2500 // middle of draining buffers and doesn't set the abort flag when it
2501 // notices that SATB buffers are available for draining. It'd be
2502 // very counter productive if it did that. :-)
2503 _draining_satb_buffers = true;
2504
2505 G1CMSATBBufferClosure satb_cl(this, _g1h);
2506 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2507
2508 // This keeps claiming and applying the closure to completed buffers
2509 // until we run out of buffers or we need to abort.
2510 while (!has_aborted() &&
2511 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2512 regular_clock_call();
2513 }
2514
2515 _draining_satb_buffers = false;
2516
2517 assert(has_aborted() ||
2518 concurrent() ||
2519 satb_mq_set.completed_buffers_num() == 0, "invariant");
2520
2521 // again, this was a potentially expensive operation, decrease the
2522 // limits to get the regular clock call early
2523 decrease_limits();
2524 }
2525
2526 void G1CMTask::print_stats() {
2527 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d",
2528 _worker_id, _calls);
2529 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2530 _elapsed_time_ms, _termination_time_ms);
2531 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
2532 _step_times_ms.num(), _step_times_ms.avg(),
2533 _step_times_ms.sd());
2534 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms",
2535 _step_times_ms.maximum(), _step_times_ms.sum());
2536 }
2537
2538 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) {
2539 return _task_queues->steal(worker_id, hash_seed, obj);
2540 }
2541
2542 /*****************************************************************************
2543
2544 The do_marking_step(time_target_ms, ...) method is the building
2545 block of the parallel marking framework. It can be called in parallel
2546 with other invocations of do_marking_step() on different tasks
2547 (but only one per task, obviously) and concurrently with the
2548 mutator threads, or during remark, hence it eliminates the need
2549 for two versions of the code. When called during remark, it will
2550 pick up from where the task left off during the concurrent marking
2551 phase. Interestingly, tasks are also claimable during evacuation
2552 pauses too, since do_marking_step() ensures that it aborts before
2553 it needs to yield.
2554
2555 The data structures that it uses to do marking work are the
2556 following:
2557
2558 (1) Marking Bitmap. If there are gray objects that appear only
2559 on the bitmap (this happens either when dealing with an overflow
2560 or when the initial marking phase has simply marked the roots
2561 and didn't push them on the stack), then tasks claim heap
2562 regions whose bitmap they then scan to find gray objects. A
2563 global finger indicates where the end of the last claimed region
2564 is. A local finger indicates how far into the region a task has
2565 scanned. The two fingers are used to determine how to gray an
2566 object (i.e. whether simply marking it is OK, as it will be
2567 visited by a task in the future, or whether it needs to be also
2568 pushed on a stack).
2569
2570 (2) Local Queue. The local queue of the task which is accessed
2571 reasonably efficiently by the task. Other tasks can steal from
2572 it when they run out of work. Throughout the marking phase, a
2573 task attempts to keep its local queue short but not totally
2574 empty, so that entries are available for stealing by other
2575 tasks. Only when there is no more work, a task will totally
2576 drain its local queue.
2577
2578 (3) Global Mark Stack. This handles local queue overflow. During
2579 marking only sets of entries are moved between it and the local
2580 queues, as access to it requires a mutex and more fine-grain
2581 interaction with it which might cause contention. If it
2582 overflows, then the marking phase should restart and iterate
2583 over the bitmap to identify gray objects. Throughout the marking
2584 phase, tasks attempt to keep the global mark stack at a small
2585 length but not totally empty, so that entries are available for
2586 popping by other tasks. Only when there is no more work, tasks
2587 will totally drain the global mark stack.
2588
2589 (4) SATB Buffer Queue. This is where completed SATB buffers are
2590 made available. Buffers are regularly removed from this queue
2591 and scanned for roots, so that the queue doesn't get too
2592 long. During remark, all completed buffers are processed, as
2593 well as the filled in parts of any uncompleted buffers.
2594
2595 The do_marking_step() method tries to abort when the time target
2596 has been reached. There are a few other cases when the
2597 do_marking_step() method also aborts:
2598
2599 (1) When the marking phase has been aborted (after a Full GC).
2600
2601 (2) When a global overflow (on the global stack) has been
2602 triggered. Before the task aborts, it will actually sync up with
2603 the other tasks to ensure that all the marking data structures
2604 (local queues, stacks, fingers etc.) are re-initialized so that
2605 when do_marking_step() completes, the marking phase can
2606 immediately restart.
2607
2608 (3) When enough completed SATB buffers are available. The
2609 do_marking_step() method only tries to drain SATB buffers right
2610 at the beginning. So, if enough buffers are available, the
2611 marking step aborts and the SATB buffers are processed at
2612 the beginning of the next invocation.
2613
2614 (4) To yield. when we have to yield then we abort and yield
2615 right at the end of do_marking_step(). This saves us from a lot
2616 of hassle as, by yielding we might allow a Full GC. If this
2617 happens then objects will be compacted underneath our feet, the
2618 heap might shrink, etc. We save checking for this by just
2619 aborting and doing the yield right at the end.
2620
2621 From the above it follows that the do_marking_step() method should
2622 be called in a loop (or, otherwise, regularly) until it completes.
2623
2624 If a marking step completes without its has_aborted() flag being
2625 true, it means it has completed the current marking phase (and
2626 also all other marking tasks have done so and have all synced up).
2627
2628 A method called regular_clock_call() is invoked "regularly" (in
2629 sub ms intervals) throughout marking. It is this clock method that
2630 checks all the abort conditions which were mentioned above and
2631 decides when the task should abort. A work-based scheme is used to
2632 trigger this clock method: when the number of object words the
2633 marking phase has scanned or the number of references the marking
2634 phase has visited reach a given limit. Additional invocations to
2635 the method clock have been planted in a few other strategic places
2636 too. The initial reason for the clock method was to avoid calling
2637 vtime too regularly, as it is quite expensive. So, once it was in
2638 place, it was natural to piggy-back all the other conditions on it
2639 too and not constantly check them throughout the code.
2640
2641 If do_termination is true then do_marking_step will enter its
2642 termination protocol.
2643
2644 The value of is_serial must be true when do_marking_step is being
2645 called serially (i.e. by the VMThread) and do_marking_step should
2646 skip any synchronization in the termination and overflow code.
2647 Examples include the serial remark code and the serial reference
2648 processing closures.
2649
2650 The value of is_serial must be false when do_marking_step is
2651 being called by any of the worker threads in a work gang.
2652 Examples include the concurrent marking code (CMMarkingTask),
2653 the MT remark code, and the MT reference processing closures.
2654
2655 *****************************************************************************/
2656
2657 void G1CMTask::do_marking_step(double time_target_ms,
2658 bool do_termination,
2659 bool is_serial) {
2660 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2661 assert(concurrent() == _cm->concurrent(), "they should be the same");
2662
2663 G1Policy* g1_policy = _g1h->g1_policy();
2664 assert(_task_queues != NULL, "invariant");
2665 assert(_task_queue != NULL, "invariant");
2666 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
2667
2668 assert(!_claimed,
2669 "only one thread should claim this task at any one time");
2670
2671 // OK, this doesn't safeguard again all possible scenarios, as it is
2672 // possible for two threads to set the _claimed flag at the same
2673 // time. But it is only for debugging purposes anyway and it will
2674 // catch most problems.
2675 _claimed = true;
2676
2677 _start_time_ms = os::elapsedVTime() * 1000.0;
2678
2679 // If do_stealing is true then do_marking_step will attempt to
2680 // steal work from the other G1CMTasks. It only makes sense to
2681 // enable stealing when the termination protocol is enabled
2682 // and do_marking_step() is not being called serially.
2683 bool do_stealing = do_termination && !is_serial;
2684
2685 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms);
2686 _time_target_ms = time_target_ms - diff_prediction_ms;
2687
2688 // set up the variables that are used in the work-based scheme to
2689 // call the regular clock method
2690 _words_scanned = 0;
2691 _refs_reached = 0;
2692 recalculate_limits();
2693
2694 // clear all flags
2695 clear_has_aborted();
2696 _has_timed_out = false;
2697 _draining_satb_buffers = false;
2698
2699 ++_calls;
2700
2701 // Set up the bitmap and oop closures. Anything that uses them is
2702 // eventually called from this method, so it is OK to allocate these
2703 // statically.
2704 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
2705 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
2706 set_cm_oop_closure(&cm_oop_closure);
2707
2708 if (_cm->has_overflown()) {
2709 // This can happen if the mark stack overflows during a GC pause
2710 // and this task, after a yield point, restarts. We have to abort
2711 // as we need to get into the overflow protocol which happens
2712 // right at the end of this task.
2713 set_has_aborted();
2714 }
2715
2716 // First drain any available SATB buffers. After this, we will not
2717 // look at SATB buffers before the next invocation of this method.
2718 // If enough completed SATB buffers are queued up, the regular clock
2719 // will abort this task so that it restarts.
2720 drain_satb_buffers();
2721 // ...then partially drain the local queue and the global stack
2722 drain_local_queue(true);
2723 drain_global_stack(true);
2724
2725 do {
2726 if (!has_aborted() && _curr_region != NULL) {
2727 // This means that we're already holding on to a region.
2728 assert(_finger != NULL, "if region is not NULL, then the finger "
2729 "should not be NULL either");
2730
2731 // We might have restarted this task after an evacuation pause
2732 // which might have evacuated the region we're holding on to
2733 // underneath our feet. Let's read its limit again to make sure
2734 // that we do not iterate over a region of the heap that
2735 // contains garbage (update_region_limit() will also move
2736 // _finger to the start of the region if it is found empty).
2737 update_region_limit();
2738 // We will start from _finger not from the start of the region,
2739 // as we might be restarting this task after aborting half-way
2740 // through scanning this region. In this case, _finger points to
2741 // the address where we last found a marked object. If this is a
2742 // fresh region, _finger points to start().
2743 MemRegion mr = MemRegion(_finger, _region_limit);
2744
2745 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2746 "humongous regions should go around loop once only");
2747
2748 // Some special cases:
2749 // If the memory region is empty, we can just give up the region.
2750 // If the current region is humongous then we only need to check
2751 // the bitmap for the bit associated with the start of the object,
2752 // scan the object if it's live, and give up the region.
2753 // Otherwise, let's iterate over the bitmap of the part of the region
2754 // that is left.
2755 // If the iteration is successful, give up the region.
2756 if (mr.is_empty()) {
2757 giveup_current_region();
2758 regular_clock_call();
2759 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2760 if (_nextMarkBitMap->isMarked(mr.start())) {
2761 // The object is marked - apply the closure
2762 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
2763 bitmap_closure.do_bit(offset);
2764 }
2765 // Even if this task aborted while scanning the humongous object
2766 // we can (and should) give up the current region.
2767 giveup_current_region();
2768 regular_clock_call();
2769 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
2770 giveup_current_region();
2771 regular_clock_call();
2772 } else {
2773 assert(has_aborted(), "currently the only way to do so");
2774 // The only way to abort the bitmap iteration is to return
2775 // false from the do_bit() method. However, inside the
2776 // do_bit() method we move the _finger to point to the
2777 // object currently being looked at. So, if we bail out, we
2778 // have definitely set _finger to something non-null.
2779 assert(_finger != NULL, "invariant");
2780
2781 // Region iteration was actually aborted. So now _finger
2782 // points to the address of the object we last scanned. If we
2783 // leave it there, when we restart this task, we will rescan
2784 // the object. It is easy to avoid this. We move the finger by
2785 // enough to point to the next possible object header (the
2786 // bitmap knows by how much we need to move it as it knows its
2787 // granularity).
2788 assert(_finger < _region_limit, "invariant");
2789 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
2790 // Check if bitmap iteration was aborted while scanning the last object
2791 if (new_finger >= _region_limit) {
2792 giveup_current_region();
2793 } else {
2794 move_finger_to(new_finger);
2795 }
2796 }
2797 }
2798 // At this point we have either completed iterating over the
2799 // region we were holding on to, or we have aborted.
2800
2801 // We then partially drain the local queue and the global stack.
2802 // (Do we really need this?)
2803 drain_local_queue(true);
2804 drain_global_stack(true);
2805
2806 // Read the note on the claim_region() method on why it might
2807 // return NULL with potentially more regions available for
2808 // claiming and why we have to check out_of_regions() to determine
2809 // whether we're done or not.
2810 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2811 // We are going to try to claim a new region. We should have
2812 // given up on the previous one.
2813 // Separated the asserts so that we know which one fires.
2814 assert(_curr_region == NULL, "invariant");
2815 assert(_finger == NULL, "invariant");
2816 assert(_region_limit == NULL, "invariant");
2817 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2818 if (claimed_region != NULL) {
2819 // Yes, we managed to claim one
2820 setup_for_region(claimed_region);
2821 assert(_curr_region == claimed_region, "invariant");
2822 }
2823 // It is important to call the regular clock here. It might take
2824 // a while to claim a region if, for example, we hit a large
2825 // block of empty regions. So we need to call the regular clock
2826 // method once round the loop to make sure it's called
2827 // frequently enough.
2828 regular_clock_call();
2829 }
2830
2831 if (!has_aborted() && _curr_region == NULL) {
2832 assert(_cm->out_of_regions(),
2833 "at this point we should be out of regions");
2834 }
2835 } while ( _curr_region != NULL && !has_aborted());
2836
2837 if (!has_aborted()) {
2838 // We cannot check whether the global stack is empty, since other
2839 // tasks might be pushing objects to it concurrently.
2840 assert(_cm->out_of_regions(),
2841 "at this point we should be out of regions");
2842 // Try to reduce the number of available SATB buffers so that
2843 // remark has less work to do.
2844 drain_satb_buffers();
2845 }
2846
2847 // Since we've done everything else, we can now totally drain the
2848 // local queue and global stack.
2849 drain_local_queue(false);
2850 drain_global_stack(false);
2851
2852 // Attempt at work stealing from other task's queues.
2853 if (do_stealing && !has_aborted()) {
2854 // We have not aborted. This means that we have finished all that
2855 // we could. Let's try to do some stealing...
2856
2857 // We cannot check whether the global stack is empty, since other
2858 // tasks might be pushing objects to it concurrently.
2859 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2860 "only way to reach here");
2861 while (!has_aborted()) {
2862 oop obj;
2863 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
2864 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
2865 "any stolen object should be marked");
2866 scan_object(obj);
2867
2868 // And since we're towards the end, let's totally drain the
2869 // local queue and global stack.
2870 drain_local_queue(false);
2871 drain_global_stack(false);
2872 } else {
2873 break;
2874 }
2875 }
2876 }
2877
2878 // We still haven't aborted. Now, let's try to get into the
2879 // termination protocol.
2880 if (do_termination && !has_aborted()) {
2881 // We cannot check whether the global stack is empty, since other
2882 // tasks might be concurrently pushing objects on it.
2883 // Separated the asserts so that we know which one fires.
2884 assert(_cm->out_of_regions(), "only way to reach here");
2885 assert(_task_queue->size() == 0, "only way to reach here");
2886 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2887
2888 // The G1CMTask class also extends the TerminatorTerminator class,
2889 // hence its should_exit_termination() method will also decide
2890 // whether to exit the termination protocol or not.
2891 bool finished = (is_serial ||
2892 _cm->terminator()->offer_termination(this));
2893 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2894 _termination_time_ms +=
2895 termination_end_time_ms - _termination_start_time_ms;
2896
2897 if (finished) {
2898 // We're all done.
2899
2900 if (_worker_id == 0) {
2901 // let's allow task 0 to do this
2902 if (concurrent()) {
2903 assert(_cm->concurrent_marking_in_progress(), "invariant");
2904 // we need to set this to false before the next
2905 // safepoint. This way we ensure that the marking phase
2906 // doesn't observe any more heap expansions.
2907 _cm->clear_concurrent_marking_in_progress();
2908 }
2909 }
2910
2911 // We can now guarantee that the global stack is empty, since
2912 // all other tasks have finished. We separated the guarantees so
2913 // that, if a condition is false, we can immediately find out
2914 // which one.
2915 guarantee(_cm->out_of_regions(), "only way to reach here");
2916 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2917 guarantee(_task_queue->size() == 0, "only way to reach here");
2918 guarantee(!_cm->has_overflown(), "only way to reach here");
2919 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
2920 } else {
2921 // Apparently there's more work to do. Let's abort this task. It
2922 // will restart it and we can hopefully find more things to do.
2923 set_has_aborted();
2924 }
2925 }
2926
2927 // Mainly for debugging purposes to make sure that a pointer to the
2928 // closure which was statically allocated in this frame doesn't
2929 // escape it by accident.
2930 set_cm_oop_closure(NULL);
2931 double end_time_ms = os::elapsedVTime() * 1000.0;
2932 double elapsed_time_ms = end_time_ms - _start_time_ms;
2933 // Update the step history.
2934 _step_times_ms.add(elapsed_time_ms);
2935
2936 if (has_aborted()) {
2937 // The task was aborted for some reason.
2938 if (_has_timed_out) {
2939 double diff_ms = elapsed_time_ms - _time_target_ms;
2940 // Keep statistics of how well we did with respect to hitting
2941 // our target only if we actually timed out (if we aborted for
2942 // other reasons, then the results might get skewed).
2943 _marking_step_diffs_ms.add(diff_ms);
2944 }
2945
2946 if (_cm->has_overflown()) {
2947 // This is the interesting one. We aborted because a global
2948 // overflow was raised. This means we have to restart the
2949 // marking phase and start iterating over regions. However, in
2950 // order to do this we have to make sure that all tasks stop
2951 // what they are doing and re-initialize in a safe manner. We
2952 // will achieve this with the use of two barrier sync points.
2953
2954 if (!is_serial) {
2955 // We only need to enter the sync barrier if being called
2956 // from a parallel context
2957 _cm->enter_first_sync_barrier(_worker_id);
2958
2959 // When we exit this sync barrier we know that all tasks have
2960 // stopped doing marking work. So, it's now safe to
2961 // re-initialize our data structures. At the end of this method,
2962 // task 0 will clear the global data structures.
2963 }
2964
2965 // We clear the local state of this task...
2966 clear_region_fields();
2967
2968 if (!is_serial) {
2969 // ...and enter the second barrier.
2970 _cm->enter_second_sync_barrier(_worker_id);
2971 }
2972 // At this point, if we're during the concurrent phase of
2973 // marking, everything has been re-initialized and we're
2974 // ready to restart.
2975 }
2976 }
2977
2978 _claimed = false;
2979 }
2980
2981 G1CMTask::G1CMTask(uint worker_id,
2982 G1ConcurrentMark* cm,
2983 G1CMTaskQueue* task_queue,
2984 G1CMTaskQueueSet* task_queues)
2985 : _g1h(G1CollectedHeap::heap()),
2986 _worker_id(worker_id), _cm(cm),
2987 _claimed(false),
2988 _nextMarkBitMap(NULL), _hash_seed(17),
2989 _task_queue(task_queue),
2990 _task_queues(task_queues),
2991 _cm_oop_closure(NULL) {
2992 guarantee(task_queue != NULL, "invariant");
2993 guarantee(task_queues != NULL, "invariant");
2994
2995 _marking_step_diffs_ms.add(0.5);
2996 }
2997
2998 // These are formatting macros that are used below to ensure
2999 // consistent formatting. The *_H_* versions are used to format the
3000 // header for a particular value and they should be kept consistent
3001 // with the corresponding macro. Also note that most of the macros add
3002 // the necessary white space (as a prefix) which makes them a bit
3003 // easier to compose.
3004
3005 // All the output lines are prefixed with this string to be able to
3006 // identify them easily in a large log file.
3007 #define G1PPRL_LINE_PREFIX "###"
3008
3009 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
3010 #ifdef _LP64
3011 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
3012 #else // _LP64
3013 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
3014 #endif // _LP64
3015
3016 // For per-region info
3017 #define G1PPRL_TYPE_FORMAT " %-4s"
3018 #define G1PPRL_TYPE_H_FORMAT " %4s"
3019 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
3020 #define G1PPRL_BYTE_H_FORMAT " %9s"
3021 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
3022 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
3023
3024 // For summary info
3025 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
3026 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
3027 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
3028 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
3029
3030 G1PrintRegionLivenessInfoClosure::
3031 G1PrintRegionLivenessInfoClosure(const char* phase_name)
3032 : _total_used_bytes(0), _total_capacity_bytes(0),
3033 _total_prev_live_bytes(0), _total_next_live_bytes(0),
3034 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
3035 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3036 MemRegion g1_reserved = g1h->g1_reserved();
3037 double now = os::elapsedTime();
3038
3039 // Print the header of the output.
3040 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
3041 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
3042 G1PPRL_SUM_ADDR_FORMAT("reserved")
3043 G1PPRL_SUM_BYTE_FORMAT("region-size"),
3044 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
3045 HeapRegion::GrainBytes);
3046 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3047 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3048 G1PPRL_TYPE_H_FORMAT
3049 G1PPRL_ADDR_BASE_H_FORMAT
3050 G1PPRL_BYTE_H_FORMAT
3051 G1PPRL_BYTE_H_FORMAT
3052 G1PPRL_BYTE_H_FORMAT
3053 G1PPRL_DOUBLE_H_FORMAT
3054 G1PPRL_BYTE_H_FORMAT
3055 G1PPRL_BYTE_H_FORMAT,
3056 "type", "address-range",
3057 "used", "prev-live", "next-live", "gc-eff",
3058 "remset", "code-roots");
3059 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3060 G1PPRL_TYPE_H_FORMAT
3061 G1PPRL_ADDR_BASE_H_FORMAT
3062 G1PPRL_BYTE_H_FORMAT
3063 G1PPRL_BYTE_H_FORMAT
3064 G1PPRL_BYTE_H_FORMAT
3065 G1PPRL_DOUBLE_H_FORMAT
3066 G1PPRL_BYTE_H_FORMAT
3067 G1PPRL_BYTE_H_FORMAT,
3068 "", "",
3069 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3070 "(bytes)", "(bytes)");
3071 }
3072
3073 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
3074 const char* type = r->get_type_str();
3075 HeapWord* bottom = r->bottom();
3076 HeapWord* end = r->end();
3077 size_t capacity_bytes = r->capacity();
3078 size_t used_bytes = r->used();
3079 size_t prev_live_bytes = r->live_bytes();
3080 size_t next_live_bytes = r->next_live_bytes();
3081 double gc_eff = r->gc_efficiency();
3082 size_t remset_bytes = r->rem_set()->mem_size();
3083 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3084
3085 _total_used_bytes += used_bytes;
3086 _total_capacity_bytes += capacity_bytes;
3087 _total_prev_live_bytes += prev_live_bytes;
3088 _total_next_live_bytes += next_live_bytes;
3089 _total_remset_bytes += remset_bytes;
3090 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3091
3092 // Print a line for this particular region.
3093 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3094 G1PPRL_TYPE_FORMAT
3095 G1PPRL_ADDR_BASE_FORMAT
3096 G1PPRL_BYTE_FORMAT
3097 G1PPRL_BYTE_FORMAT
3098 G1PPRL_BYTE_FORMAT
3099 G1PPRL_DOUBLE_FORMAT
3100 G1PPRL_BYTE_FORMAT
3101 G1PPRL_BYTE_FORMAT,
3102 type, p2i(bottom), p2i(end),
3103 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3104 remset_bytes, strong_code_roots_bytes);
3105
3106 return false;
3107 }
3108
3109 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3110 // add static memory usages to remembered set sizes
3111 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3112 // Print the footer of the output.
3113 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3114 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3115 " SUMMARY"
3116 G1PPRL_SUM_MB_FORMAT("capacity")
3117 G1PPRL_SUM_MB_PERC_FORMAT("used")
3118 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3119 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3120 G1PPRL_SUM_MB_FORMAT("remset")
3121 G1PPRL_SUM_MB_FORMAT("code-roots"),
3122 bytes_to_mb(_total_capacity_bytes),
3123 bytes_to_mb(_total_used_bytes),
3124 perc(_total_used_bytes, _total_capacity_bytes),
3125 bytes_to_mb(_total_prev_live_bytes),
3126 perc(_total_prev_live_bytes, _total_capacity_bytes),
3127 bytes_to_mb(_total_next_live_bytes),
3128 perc(_total_next_live_bytes, _total_capacity_bytes),
3129 bytes_to_mb(_total_remset_bytes),
3130 bytes_to_mb(_total_strong_code_roots_bytes));
3131 }