1 /*
2 * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc/g1/concurrentMarkThread.inline.hpp"
30 #include "gc/g1/g1BarrierSet.hpp"
31 #include "gc/g1/g1CollectedHeap.inline.hpp"
32 #include "gc/g1/g1CollectorState.hpp"
33 #include "gc/g1/g1ConcurrentMark.inline.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1CardLiveData.inline.hpp"
37 #include "gc/g1/g1Policy.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/heapRegion.inline.hpp"
40 #include "gc/g1/heapRegionRemSet.hpp"
41 #include "gc/g1/heapRegionSet.inline.hpp"
42 #include "gc/g1/suspendibleThreadSet.hpp"
43 #include "gc/shared/gcId.hpp"
44 #include "gc/shared/gcTimer.hpp"
45 #include "gc/shared/gcTrace.hpp"
46 #include "gc/shared/gcTraceTime.inline.hpp"
47 #include "gc/shared/genOopClosures.inline.hpp"
48 #include "gc/shared/referencePolicy.hpp"
49 #include "gc/shared/strongRootsScope.hpp"
50 #include "gc/shared/taskqueue.inline.hpp"
51 #include "gc/shared/vmGCOperations.hpp"
52 #include "logging/log.hpp"
53 #include "memory/allocation.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "runtime/atomic.hpp"
57 #include "runtime/handles.inline.hpp"
58 #include "runtime/java.hpp"
59 #include "runtime/prefetch.inline.hpp"
60 #include "services/memTracker.hpp"
61 #include "utilities/growableArray.hpp"
62
63 // Concurrent marking bit map wrapper
64
65 G1CMBitMapRO::G1CMBitMapRO(int shifter) :
66 _bm(),
67 _shifter(shifter) {
68 _bmStartWord = 0;
69 _bmWordSize = 0;
70 }
71
72 HeapWord* G1CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
73 const HeapWord* limit) const {
74 // First we must round addr *up* to a possible object boundary.
75 addr = (HeapWord*)align_size_up((intptr_t)addr,
76 HeapWordSize << _shifter);
77 size_t addrOffset = heapWordToOffset(addr);
78 assert(limit != NULL, "limit must not be NULL");
79 size_t limitOffset = heapWordToOffset(limit);
80 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
81 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
82 assert(nextAddr >= addr, "get_next_one postcondition");
83 assert(nextAddr == limit || isMarked(nextAddr),
84 "get_next_one postcondition");
85 return nextAddr;
86 }
87
88 #ifndef PRODUCT
89 bool G1CMBitMapRO::covers(MemRegion heap_rs) const {
90 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
91 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
92 "size inconsistency");
93 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
94 _bmWordSize == heap_rs.word_size();
95 }
96 #endif
97
98 void G1CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
99 _bm.print_on_error(st, prefix);
100 }
101
102 size_t G1CMBitMap::compute_size(size_t heap_size) {
103 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
104 }
105
106 size_t G1CMBitMap::mark_distance() {
107 return MinObjAlignmentInBytes * BitsPerByte;
108 }
109
110 void G1CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
111 _bmStartWord = heap.start();
112 _bmWordSize = heap.word_size();
113
114 _bm = BitMapView((BitMap::bm_word_t*) storage->reserved().start(), _bmWordSize >> _shifter);
115
116 storage->set_mapping_changed_listener(&_listener);
117 }
118
119 void G1CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
120 if (zero_filled) {
121 return;
122 }
123 // We need to clear the bitmap on commit, removing any existing information.
124 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
125 _bm->clear_range(mr);
126 }
127
128 void G1CMBitMap::clear_range(MemRegion mr) {
129 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
130 assert(!mr.is_empty(), "unexpected empty region");
131 // convert address range into offset range
132 _bm.at_put_range(heapWordToOffset(mr.start()),
133 heapWordToOffset(mr.end()), false);
134 }
135
136 G1CMMarkStack::G1CMMarkStack() :
137 _max_chunk_capacity(0),
138 _base(NULL),
139 _chunk_capacity(0),
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 TaskQueueEntryChunk* new_base = MmapArrayAllocator<TaskQueueEntryChunk, 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(TaskQueueEntryChunk));
153 return false;
154 }
155 // Release old mapping.
156 if (_base != NULL) {
157 MmapArrayAllocator<TaskQueueEntryChunk, 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(TaskQueueEntryChunk)) / sizeof(G1TaskQueueEntry);
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 TaskEntryChunkSizeInVoidStar = sizeof(TaskQueueEntryChunk) / sizeof(G1TaskQueueEntry);
176
177 _max_chunk_capacity = (size_t)align_size_up(max_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
178 size_t initial_chunk_capacity = (size_t)align_size_up(initial_capacity, capacity_alignment()) / TaskEntryChunkSizeInVoidStar;
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<TaskQueueEntryChunk, mtGC>::free(_base, _chunk_capacity);
215 }
216 }
217
218 void G1CMMarkStack::add_chunk_to_list(TaskQueueEntryChunk* volatile* list, TaskQueueEntryChunk* elem) {
219 elem->next = *list;
220 *list = elem;
221 }
222
223 void G1CMMarkStack::add_chunk_to_chunk_list(TaskQueueEntryChunk* elem) {
224 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
225 add_chunk_to_list(&_chunk_list, elem);
226 _chunks_in_chunk_list++;
227 }
228
229 void G1CMMarkStack::add_chunk_to_free_list(TaskQueueEntryChunk* elem) {
230 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
231 add_chunk_to_list(&_free_list, elem);
232 }
233
234 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_list(TaskQueueEntryChunk* volatile* list) {
235 TaskQueueEntryChunk* result = *list;
236 if (result != NULL) {
237 *list = (*list)->next;
238 }
239 return result;
240 }
241
242 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_chunk_list() {
243 MutexLockerEx x(MarkStackChunkList_lock, Mutex::_no_safepoint_check_flag);
244 TaskQueueEntryChunk* result = remove_chunk_from_list(&_chunk_list);
245 if (result != NULL) {
246 _chunks_in_chunk_list--;
247 }
248 return result;
249 }
250
251 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::remove_chunk_from_free_list() {
252 MutexLockerEx x(MarkStackFreeList_lock, Mutex::_no_safepoint_check_flag);
253 return remove_chunk_from_list(&_free_list);
254 }
255
256 G1CMMarkStack::TaskQueueEntryChunk* G1CMMarkStack::allocate_new_chunk() {
257 // This dirty read of _hwm is okay because we only ever increase the _hwm in parallel code.
258 // Further this limits _hwm to a value of _chunk_capacity + #threads, avoiding
259 // wraparound of _hwm.
260 if (_hwm >= _chunk_capacity) {
261 return NULL;
262 }
263
264 size_t cur_idx = Atomic::add(1, &_hwm) - 1;
265 if (cur_idx >= _chunk_capacity) {
266 return NULL;
267 }
268
269 TaskQueueEntryChunk* result = ::new (&_base[cur_idx]) TaskQueueEntryChunk;
270 result->next = NULL;
271 return result;
272 }
273
274 bool G1CMMarkStack::par_push_chunk(G1TaskQueueEntry* ptr_arr) {
275 // Get a new chunk.
276 TaskQueueEntryChunk* new_chunk = remove_chunk_from_free_list();
277
278 if (new_chunk == NULL) {
279 // Did not get a chunk from the free list. Allocate from backing memory.
280 new_chunk = allocate_new_chunk();
281
282 if (new_chunk == NULL) {
283 return false;
284 }
285 }
286
287 Copy::conjoint_memory_atomic(ptr_arr, new_chunk->data, EntriesPerChunk * sizeof(G1TaskQueueEntry));
288
289 add_chunk_to_chunk_list(new_chunk);
290
291 return true;
292 }
293
294 bool G1CMMarkStack::par_pop_chunk(G1TaskQueueEntry* ptr_arr) {
295 TaskQueueEntryChunk* cur = remove_chunk_from_chunk_list();
296
297 if (cur == NULL) {
298 return false;
299 }
300
301 Copy::conjoint_memory_atomic(cur->data, ptr_arr, EntriesPerChunk * sizeof(G1TaskQueueEntry));
302
303 add_chunk_to_free_list(cur);
304 return true;
305 }
306
307 void G1CMMarkStack::set_empty() {
308 _chunks_in_chunk_list = 0;
309 _hwm = 0;
310 _chunk_list = NULL;
311 _free_list = NULL;
312 }
313
314 G1CMRootRegions::G1CMRootRegions() :
315 _cm(NULL), _scan_in_progress(false),
316 _should_abort(false), _claimed_survivor_index(0) { }
317
318 void G1CMRootRegions::init(const G1SurvivorRegions* survivors, G1ConcurrentMark* cm) {
319 _survivors = survivors;
320 _cm = cm;
321 }
322
323 void G1CMRootRegions::prepare_for_scan() {
324 assert(!scan_in_progress(), "pre-condition");
325
326 // Currently, only survivors can be root regions.
327 _claimed_survivor_index = 0;
328 _scan_in_progress = _survivors->regions()->is_nonempty();
329 _should_abort = false;
330 }
331
332 HeapRegion* G1CMRootRegions::claim_next() {
333 if (_should_abort) {
334 // If someone has set the should_abort flag, we return NULL to
335 // force the caller to bail out of their loop.
336 return NULL;
337 }
338
339 // Currently, only survivors can be root regions.
340 const GrowableArray<HeapRegion*>* survivor_regions = _survivors->regions();
341
342 int claimed_index = Atomic::add(1, &_claimed_survivor_index) - 1;
343 if (claimed_index < survivor_regions->length()) {
344 return survivor_regions->at(claimed_index);
345 }
346 return NULL;
347 }
348
349 uint G1CMRootRegions::num_root_regions() const {
350 return (uint)_survivors->regions()->length();
351 }
352
353 void G1CMRootRegions::notify_scan_done() {
354 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
355 _scan_in_progress = false;
356 RootRegionScan_lock->notify_all();
357 }
358
359 void G1CMRootRegions::cancel_scan() {
360 notify_scan_done();
361 }
362
363 void G1CMRootRegions::scan_finished() {
364 assert(scan_in_progress(), "pre-condition");
365
366 // Currently, only survivors can be root regions.
367 if (!_should_abort) {
368 assert(_claimed_survivor_index >= 0, "otherwise comparison is invalid: %d", _claimed_survivor_index);
369 assert((uint)_claimed_survivor_index >= _survivors->length(),
370 "we should have claimed all survivors, claimed index = %u, length = %u",
371 (uint)_claimed_survivor_index, _survivors->length());
372 }
373
374 notify_scan_done();
375 }
376
377 bool G1CMRootRegions::wait_until_scan_finished() {
378 if (!scan_in_progress()) return false;
379
380 {
381 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
382 while (scan_in_progress()) {
383 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
384 }
385 }
386 return true;
387 }
388
389 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
390 return MAX2((n_par_threads + 2) / 4, 1U);
391 }
392
393 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
394 _g1h(g1h),
395 _markBitMap1(),
396 _markBitMap2(),
397 _parallel_marking_threads(0),
398 _max_parallel_marking_threads(0),
399 _sleep_factor(0.0),
400 _marking_task_overhead(1.0),
401 _cleanup_list("Cleanup List"),
402
403 _prevMarkBitMap(&_markBitMap1),
404 _nextMarkBitMap(&_markBitMap2),
405
406 _global_mark_stack(),
407 // _finger set in set_non_marking_state
408
409 _max_worker_id(ParallelGCThreads),
410 // _active_tasks set in set_non_marking_state
411 // _tasks set inside the constructor
412 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)),
413 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
414
415 _has_overflown(false),
416 _concurrent(false),
417 _has_aborted(false),
418 _restart_for_overflow(false),
419 _concurrent_marking_in_progress(false),
420 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
421 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()),
422
423 // _verbose_level set below
424
425 _init_times(),
426 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
427 _cleanup_times(),
428 _total_counting_time(0.0),
429 _total_rs_scrub_time(0.0),
430
431 _parallel_workers(NULL),
432
433 _completed_initialization(false) {
434
435 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
436 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
437
438 // Create & start a ConcurrentMark thread.
439 _cmThread = new ConcurrentMarkThread(this);
440 assert(cmThread() != NULL, "CM Thread should have been created");
441 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
442 if (_cmThread->osthread() == NULL) {
443 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
444 }
445
446 assert(CGC_lock != NULL, "Where's the CGC_lock?");
447 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
448 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
449
450 SATBMarkQueueSet& satb_qs = G1BarrierSet::satb_mark_queue_set();
451 satb_qs.set_buffer_size(G1SATBBufferSize);
452
453 _root_regions.init(_g1h->survivor(), this);
454
455 if (ConcGCThreads > ParallelGCThreads) {
456 log_warning(gc)("Can't have more ConcGCThreads (%u) than ParallelGCThreads (%u).",
457 ConcGCThreads, ParallelGCThreads);
458 return;
459 }
460 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
461 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
462 // if both are set
463 _sleep_factor = 0.0;
464 _marking_task_overhead = 1.0;
465 } else if (G1MarkingOverheadPercent > 0) {
466 // We will calculate the number of parallel marking threads based
467 // on a target overhead with respect to the soft real-time goal
468 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
469 double overall_cm_overhead =
470 (double) MaxGCPauseMillis * marking_overhead /
471 (double) GCPauseIntervalMillis;
472 double cpu_ratio = 1.0 / os::initial_active_processor_count();
473 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
474 double marking_task_overhead =
475 overall_cm_overhead / marking_thread_num * os::initial_active_processor_count();
476 double sleep_factor =
477 (1.0 - marking_task_overhead) / marking_task_overhead;
478
479 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
480 _sleep_factor = sleep_factor;
481 _marking_task_overhead = marking_task_overhead;
482 } else {
483 // Calculate the number of parallel marking threads by scaling
484 // the number of parallel GC threads.
485 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
486 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
487 _sleep_factor = 0.0;
488 _marking_task_overhead = 1.0;
489 }
490
491 assert(ConcGCThreads > 0, "Should have been set");
492 log_debug(gc)("ConcGCThreads: %u", ConcGCThreads);
493 log_debug(gc)("ParallelGCThreads: %u", ParallelGCThreads);
494 _parallel_marking_threads = ConcGCThreads;
495 _max_parallel_marking_threads = _parallel_marking_threads;
496
497 _parallel_workers = new WorkGang("G1 Marker",
498 _max_parallel_marking_threads, false, true);
499 if (_parallel_workers == NULL) {
500 vm_exit_during_initialization("Failed necessary allocation.");
501 } else {
502 _parallel_workers->initialize_workers();
503 }
504
505 if (FLAG_IS_DEFAULT(MarkStackSize)) {
506 size_t mark_stack_size =
507 MIN2(MarkStackSizeMax,
508 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
509 // Verify that the calculated value for MarkStackSize is in range.
510 // It would be nice to use the private utility routine from Arguments.
511 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
512 log_warning(gc)("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
513 "must be between 1 and " SIZE_FORMAT,
514 mark_stack_size, MarkStackSizeMax);
515 return;
516 }
517 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
518 } else {
519 // Verify MarkStackSize is in range.
520 if (FLAG_IS_CMDLINE(MarkStackSize)) {
521 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
522 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
523 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
524 "must be between 1 and " SIZE_FORMAT,
525 MarkStackSize, MarkStackSizeMax);
526 return;
527 }
528 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
529 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
530 log_warning(gc)("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
531 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
532 MarkStackSize, MarkStackSizeMax);
533 return;
534 }
535 }
536 }
537 }
538
539 if (!_global_mark_stack.initialize(MarkStackSize, MarkStackSizeMax)) {
540 vm_exit_during_initialization("Failed to allocate initial concurrent mark overflow mark stack.");
541 }
542
543 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC);
544 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
545
546 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
547 _active_tasks = _max_worker_id;
548
549 for (uint i = 0; i < _max_worker_id; ++i) {
550 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
551 task_queue->initialize();
552 _task_queues->register_queue(i, task_queue);
553
554 _tasks[i] = new G1CMTask(i, this, task_queue, _task_queues);
555
556 _accum_task_vtime[i] = 0.0;
557 }
558
559 // so that the call below can read a sensible value
560 _heap_start = g1h->reserved_region().start();
561 set_non_marking_state();
562 _completed_initialization = true;
563 }
564
565 void G1ConcurrentMark::reset() {
566 // Starting values for these two. This should be called in a STW
567 // phase.
568 MemRegion reserved = _g1h->g1_reserved();
569 _heap_start = reserved.start();
570 _heap_end = reserved.end();
571
572 // Separated the asserts so that we know which one fires.
573 assert(_heap_start != NULL, "heap bounds should look ok");
574 assert(_heap_end != NULL, "heap bounds should look ok");
575 assert(_heap_start < _heap_end, "heap bounds should look ok");
576
577 // Reset all the marking data structures and any necessary flags
578 reset_marking_state();
579
580 // We do reset all of them, since different phases will use
581 // different number of active threads. So, it's easiest to have all
582 // of them ready.
583 for (uint i = 0; i < _max_worker_id; ++i) {
584 _tasks[i]->reset(_nextMarkBitMap);
585 }
586
587 // we need this to make sure that the flag is on during the evac
588 // pause with initial mark piggy-backed
589 set_concurrent_marking_in_progress();
590 }
591
592
593 void G1ConcurrentMark::reset_marking_state() {
594 _global_mark_stack.set_should_expand(has_overflown());
595 _global_mark_stack.set_empty();
596 clear_has_overflown();
597 _finger = _heap_start;
598
599 for (uint i = 0; i < _max_worker_id; ++i) {
600 G1CMTaskQueue* queue = _task_queues->queue(i);
601 queue->set_empty();
602 }
603 }
604
605 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
606 assert(active_tasks <= _max_worker_id, "we should not have more");
607
608 _active_tasks = active_tasks;
609 // Need to update the three data structures below according to the
610 // number of active threads for this phase.
611 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
612 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
613 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
614 }
615
616 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
617 set_concurrency(active_tasks);
618
619 _concurrent = concurrent;
620 // We propagate this to all tasks, not just the active ones.
621 for (uint i = 0; i < _max_worker_id; ++i)
622 _tasks[i]->set_concurrent(concurrent);
623
624 if (concurrent) {
625 set_concurrent_marking_in_progress();
626 } else {
627 // We currently assume that the concurrent flag has been set to
628 // false before we start remark. At this point we should also be
629 // in a STW phase.
630 assert(!concurrent_marking_in_progress(), "invariant");
631 assert(out_of_regions(),
632 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
633 p2i(_finger), p2i(_heap_end));
634 }
635 }
636
637 void G1ConcurrentMark::set_non_marking_state() {
638 // We set the global marking state to some default values when we're
639 // not doing marking.
640 reset_marking_state();
641 _active_tasks = 0;
642 clear_concurrent_marking_in_progress();
643 }
644
645 G1ConcurrentMark::~G1ConcurrentMark() {
646 // The G1ConcurrentMark instance is never freed.
647 ShouldNotReachHere();
648 }
649
650 class G1ClearBitMapTask : public AbstractGangTask {
651 public:
652 static size_t chunk_size() { return M; }
653
654 private:
655 // Heap region closure used for clearing the given mark bitmap.
656 class G1ClearBitmapHRClosure : public HeapRegionClosure {
657 private:
658 G1CMBitMap* _bitmap;
659 G1ConcurrentMark* _cm;
660 public:
661 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
662 }
663
664 virtual bool doHeapRegion(HeapRegion* r) {
665 size_t const chunk_size_in_words = G1ClearBitMapTask::chunk_size() / HeapWordSize;
666
667 HeapWord* cur = r->bottom();
668 HeapWord* const end = r->end();
669
670 while (cur < end) {
671 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
672 _bitmap->clear_range(mr);
673
674 cur += chunk_size_in_words;
675
676 // Abort iteration if after yielding the marking has been aborted.
677 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
678 return true;
679 }
680 // Repeat the asserts from before the start of the closure. We will do them
681 // as asserts here to minimize their overhead on the product. However, we
682 // will have them as guarantees at the beginning / end of the bitmap
683 // clearing to get some checking in the product.
684 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant");
685 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
686 }
687 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
688
689 return false;
690 }
691 };
692
693 G1ClearBitmapHRClosure _cl;
694 HeapRegionClaimer _hr_claimer;
695 bool _suspendible; // If the task is suspendible, workers must join the STS.
696
697 public:
698 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
699 AbstractGangTask("G1 Clear Bitmap"),
700 _cl(bitmap, suspendible ? cm : NULL),
701 _hr_claimer(n_workers),
702 _suspendible(suspendible)
703 { }
704
705 void work(uint worker_id) {
706 SuspendibleThreadSetJoiner sts_join(_suspendible);
707 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true);
708 }
709
710 bool is_complete() {
711 return _cl.complete();
712 }
713 };
714
715 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
716 assert(may_yield || SafepointSynchronize::is_at_safepoint(), "Non-yielding bitmap clear only allowed at safepoint.");
717
718 size_t const num_bytes_to_clear = (HeapRegion::GrainBytes * _g1h->num_regions()) / G1CMBitMap::heap_map_factor();
719 size_t const num_chunks = align_size_up(num_bytes_to_clear, G1ClearBitMapTask::chunk_size()) / G1ClearBitMapTask::chunk_size();
720
721 uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
722
723 G1ClearBitMapTask cl(bitmap, this, num_workers, may_yield);
724
725 log_debug(gc, ergo)("Running %s with %u workers for " SIZE_FORMAT " work units.", cl.name(), num_workers, num_chunks);
726 workers->run_task(&cl, num_workers);
727 guarantee(!may_yield || cl.is_complete(), "Must have completed iteration when not yielding.");
728 }
729
730 void G1ConcurrentMark::cleanup_for_next_mark() {
731 // Make sure that the concurrent mark thread looks to still be in
732 // the current cycle.
733 guarantee(cmThread()->during_cycle(), "invariant");
734
735 // We are finishing up the current cycle by clearing the next
736 // marking bitmap and getting it ready for the next cycle. During
737 // this time no other cycle can start. So, let's make sure that this
738 // is the case.
739 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
740
741 clear_bitmap(_nextMarkBitMap, _parallel_workers, true);
742
743 // Clear the live count data. If the marking has been aborted, the abort()
744 // call already did that.
745 if (!has_aborted()) {
746 clear_live_data(_parallel_workers);
747 DEBUG_ONLY(verify_live_data_clear());
748 }
749
750 // Repeat the asserts from above.
751 guarantee(cmThread()->during_cycle(), "invariant");
752 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
753 }
754
755 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
756 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint.");
757 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false);
758 }
759
760 class CheckBitmapClearHRClosure : public HeapRegionClosure {
761 G1CMBitMap* _bitmap;
762 bool _error;
763 public:
764 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
765 }
766
767 virtual bool doHeapRegion(HeapRegion* r) {
768 // This closure can be called concurrently to the mutator, so we must make sure
769 // that the result of the getNextMarkedWordAddress() call is compared to the
770 // value passed to it as limit to detect any found bits.
771 // end never changes in G1.
772 HeapWord* end = r->end();
773 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
774 }
775 };
776
777 bool G1ConcurrentMark::nextMarkBitmapIsClear() {
778 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
779 _g1h->heap_region_iterate(&cl);
780 return cl.complete();
781 }
782
783 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
784 public:
785 bool doHeapRegion(HeapRegion* r) {
786 r->note_start_of_marking();
787 return false;
788 }
789 };
790
791 void G1ConcurrentMark::checkpointRootsInitialPre() {
792 G1CollectedHeap* g1h = G1CollectedHeap::heap();
793 G1Policy* g1p = g1h->g1_policy();
794
795 _has_aborted = false;
796
797 // Initialize marking structures. This has to be done in a STW phase.
798 reset();
799
800 // For each region note start of marking.
801 NoteStartOfMarkHRClosure startcl;
802 g1h->heap_region_iterate(&startcl);
803 }
804
805
806 void G1ConcurrentMark::checkpointRootsInitialPost() {
807 G1CollectedHeap* g1h = G1CollectedHeap::heap();
808
809 // Start Concurrent Marking weak-reference discovery.
810 ReferenceProcessor* rp = g1h->ref_processor_cm();
811 // enable ("weak") refs discovery
812 rp->enable_discovery();
813 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
814
815 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
816 // This is the start of the marking cycle, we're expected all
817 // threads to have SATB queues with active set to false.
818 satb_mq_set.set_active_all_threads(true, /* new active value */
819 false /* expected_active */);
820
821 _root_regions.prepare_for_scan();
822
823 // update_g1_committed() will be called at the end of an evac pause
824 // when marking is on. So, it's also called at the end of the
825 // initial-mark pause to update the heap end, if the heap expands
826 // during it. No need to call it here.
827 }
828
829 /*
830 * Notice that in the next two methods, we actually leave the STS
831 * during the barrier sync and join it immediately afterwards. If we
832 * do not do this, the following deadlock can occur: one thread could
833 * be in the barrier sync code, waiting for the other thread to also
834 * sync up, whereas another one could be trying to yield, while also
835 * waiting for the other threads to sync up too.
836 *
837 * Note, however, that this code is also used during remark and in
838 * this case we should not attempt to leave / enter the STS, otherwise
839 * we'll either hit an assert (debug / fastdebug) or deadlock
840 * (product). So we should only leave / enter the STS if we are
841 * operating concurrently.
842 *
843 * Because the thread that does the sync barrier has left the STS, it
844 * is possible to be suspended for a Full GC or an evacuation pause
845 * could occur. This is actually safe, since the entering the sync
846 * barrier is one of the last things do_marking_step() does, and it
847 * doesn't manipulate any data structures afterwards.
848 */
849
850 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
851 bool barrier_aborted;
852 {
853 SuspendibleThreadSetLeaver sts_leave(concurrent());
854 barrier_aborted = !_first_overflow_barrier_sync.enter();
855 }
856
857 // at this point everyone should have synced up and not be doing any
858 // more work
859
860 if (barrier_aborted) {
861 // If the barrier aborted we ignore the overflow condition and
862 // just abort the whole marking phase as quickly as possible.
863 return;
864 }
865
866 // If we're executing the concurrent phase of marking, reset the marking
867 // state; otherwise the marking state is reset after reference processing,
868 // during the remark pause.
869 // If we reset here as a result of an overflow during the remark we will
870 // see assertion failures from any subsequent set_concurrency_and_phase()
871 // calls.
872 if (concurrent()) {
873 // let the task associated with with worker 0 do this
874 if (worker_id == 0) {
875 // task 0 is responsible for clearing the global data structures
876 // We should be here because of an overflow. During STW we should
877 // not clear the overflow flag since we rely on it being true when
878 // we exit this method to abort the pause and restart concurrent
879 // marking.
880 reset_marking_state();
881
882 log_info(gc, marking)("Concurrent Mark reset for overflow");
883 }
884 }
885
886 // after this, each task should reset its own data structures then
887 // then go into the second barrier
888 }
889
890 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
891 SuspendibleThreadSetLeaver sts_leave(concurrent());
892 _second_overflow_barrier_sync.enter();
893
894 // at this point everything should be re-initialized and ready to go
895 }
896
897 class G1CMConcurrentMarkingTask: public AbstractGangTask {
898 private:
899 G1ConcurrentMark* _cm;
900 ConcurrentMarkThread* _cmt;
901
902 public:
903 void work(uint worker_id) {
904 assert(Thread::current()->is_ConcurrentGC_thread(),
905 "this should only be done by a conc GC thread");
906 ResourceMark rm;
907
908 double start_vtime = os::elapsedVTime();
909
910 {
911 SuspendibleThreadSetJoiner sts_join;
912
913 assert(worker_id < _cm->active_tasks(), "invariant");
914 G1CMTask* the_task = _cm->task(worker_id);
915 the_task->record_start_time();
916 if (!_cm->has_aborted()) {
917 do {
918 double start_vtime_sec = os::elapsedVTime();
919 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
920
921 the_task->do_marking_step(mark_step_duration_ms,
922 true /* do_termination */,
923 false /* is_serial*/);
924
925 double end_vtime_sec = os::elapsedVTime();
926 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
927 _cm->clear_has_overflown();
928
929 _cm->do_yield_check();
930
931 jlong sleep_time_ms;
932 if (!_cm->has_aborted() && the_task->has_aborted()) {
933 sleep_time_ms =
934 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
935 {
936 SuspendibleThreadSetLeaver sts_leave;
937 os::sleep(Thread::current(), sleep_time_ms, false);
938 }
939 }
940 } while (!_cm->has_aborted() && the_task->has_aborted());
941 }
942 the_task->record_end_time();
943 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
944 }
945
946 double end_vtime = os::elapsedVTime();
947 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
948 }
949
950 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm,
951 ConcurrentMarkThread* cmt) :
952 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
953
954 ~G1CMConcurrentMarkingTask() { }
955 };
956
957 // Calculates the number of active workers for a concurrent
958 // phase.
959 uint G1ConcurrentMark::calc_parallel_marking_threads() {
960 uint n_conc_workers = 0;
961 if (!UseDynamicNumberOfGCThreads ||
962 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
963 !ForceDynamicNumberOfGCThreads)) {
964 n_conc_workers = max_parallel_marking_threads();
965 } else {
966 n_conc_workers =
967 AdaptiveSizePolicy::calc_default_active_workers(max_parallel_marking_threads(),
968 1, /* Minimum workers */
969 parallel_marking_threads(),
970 Threads::number_of_non_daemon_threads());
971 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
972 // that scaling has already gone into "_max_parallel_marking_threads".
973 }
974 assert(n_conc_workers > 0 && n_conc_workers <= max_parallel_marking_threads(),
975 "Calculated number of workers must be larger than zero and at most the maximum %u, but is %u",
976 max_parallel_marking_threads(), n_conc_workers);
977 return n_conc_workers;
978 }
979
980 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr) {
981 // Currently, only survivors can be root regions.
982 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
983 G1RootRegionScanClosure cl(_g1h, this);
984
985 const uintx interval = PrefetchScanIntervalInBytes;
986 HeapWord* curr = hr->bottom();
987 const HeapWord* end = hr->top();
988 while (curr < end) {
989 Prefetch::read(curr, interval);
990 oop obj = oop(curr);
991 int size = obj->oop_iterate_size(&cl);
992 assert(size == obj->size(), "sanity");
993 curr += size;
994 }
995 }
996
997 class G1CMRootRegionScanTask : public AbstractGangTask {
998 private:
999 G1ConcurrentMark* _cm;
1000
1001 public:
1002 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
1003 AbstractGangTask("G1 Root Region Scan"), _cm(cm) { }
1004
1005 void work(uint worker_id) {
1006 assert(Thread::current()->is_ConcurrentGC_thread(),
1007 "this should only be done by a conc GC thread");
1008
1009 G1CMRootRegions* root_regions = _cm->root_regions();
1010 HeapRegion* hr = root_regions->claim_next();
1011 while (hr != NULL) {
1012 _cm->scanRootRegion(hr);
1013 hr = root_regions->claim_next();
1014 }
1015 }
1016 };
1017
1018 void G1ConcurrentMark::scan_root_regions() {
1019 // scan_in_progress() will have been set to true only if there was
1020 // at least one root region to scan. So, if it's false, we
1021 // should not attempt to do any further work.
1022 if (root_regions()->scan_in_progress()) {
1023 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
1024
1025 _parallel_marking_threads = MIN2(calc_parallel_marking_threads(),
1026 // We distribute work on a per-region basis, so starting
1027 // more threads than that is useless.
1028 root_regions()->num_root_regions());
1029 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1030 "Maximum number of marking threads exceeded");
1031
1032 G1CMRootRegionScanTask task(this);
1033 log_debug(gc, ergo)("Running %s using %u workers for %u work units.",
1034 task.name(), _parallel_marking_threads, root_regions()->num_root_regions());
1035 _parallel_workers->run_task(&task, _parallel_marking_threads);
1036
1037 // It's possible that has_aborted() is true here without actually
1038 // aborting the survivor scan earlier. This is OK as it's
1039 // mainly used for sanity checking.
1040 root_regions()->scan_finished();
1041 }
1042 }
1043
1044 void G1ConcurrentMark::concurrent_cycle_start() {
1045 _gc_timer_cm->register_gc_start();
1046
1047 _gc_tracer_cm->report_gc_start(GCCause::_no_gc /* first parameter is not used */, _gc_timer_cm->gc_start());
1048
1049 _g1h->trace_heap_before_gc(_gc_tracer_cm);
1050 }
1051
1052 void G1ConcurrentMark::concurrent_cycle_end() {
1053 _g1h->trace_heap_after_gc(_gc_tracer_cm);
1054
1055 if (has_aborted()) {
1056 _gc_tracer_cm->report_concurrent_mode_failure();
1057 }
1058
1059 _gc_timer_cm->register_gc_end();
1060
1061 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
1062 }
1063
1064 void G1ConcurrentMark::mark_from_roots() {
1065 // we might be tempted to assert that:
1066 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1067 // "inconsistent argument?");
1068 // However that wouldn't be right, because it's possible that
1069 // a safepoint is indeed in progress as a younger generation
1070 // stop-the-world GC happens even as we mark in this generation.
1071
1072 _restart_for_overflow = false;
1073
1074 // _g1h has _n_par_threads
1075 _parallel_marking_threads = calc_parallel_marking_threads();
1076 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1077 "Maximum number of marking threads exceeded");
1078
1079 uint active_workers = MAX2(1U, parallel_marking_threads());
1080 assert(active_workers > 0, "Should have been set");
1081
1082 // Setting active workers is not guaranteed since fewer
1083 // worker threads may currently exist and more may not be
1084 // available.
1085 active_workers = _parallel_workers->update_active_workers(active_workers);
1086 log_info(gc, task)("Using %u workers of %u for marking", active_workers, _parallel_workers->total_workers());
1087
1088 // Parallel task terminator is set in "set_concurrency_and_phase()"
1089 set_concurrency_and_phase(active_workers, true /* concurrent */);
1090
1091 G1CMConcurrentMarkingTask markingTask(this, cmThread());
1092 _parallel_workers->run_task(&markingTask);
1093 print_stats();
1094 }
1095
1096 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1097 // world is stopped at this checkpoint
1098 assert(SafepointSynchronize::is_at_safepoint(),
1099 "world should be stopped");
1100
1101 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1102
1103 // If a full collection has happened, we shouldn't do this.
1104 if (has_aborted()) {
1105 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1106 return;
1107 }
1108
1109 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1110
1111 if (VerifyDuringGC) {
1112 HandleMark hm; // handle scope
1113 g1h->prepare_for_verify();
1114 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1115 }
1116 g1h->verifier()->check_bitmaps("Remark Start");
1117
1118 G1Policy* g1p = g1h->g1_policy();
1119 g1p->record_concurrent_mark_remark_start();
1120
1121 double start = os::elapsedTime();
1122
1123 checkpointRootsFinalWork();
1124
1125 double mark_work_end = os::elapsedTime();
1126
1127 weakRefsWork(clear_all_soft_refs);
1128
1129 if (has_overflown()) {
1130 // We overflowed. Restart concurrent marking.
1131 _restart_for_overflow = true;
1132
1133 // Verify the heap w.r.t. the previous marking bitmap.
1134 if (VerifyDuringGC) {
1135 HandleMark hm; // handle scope
1136 g1h->prepare_for_verify();
1137 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)");
1138 }
1139
1140 // Clear the marking state because we will be restarting
1141 // marking due to overflowing the global mark stack.
1142 reset_marking_state();
1143 } else {
1144 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1145 // We're done with marking.
1146 // This is the end of the marking cycle, we're expected all
1147 // threads to have SATB queues with active set to true.
1148 satb_mq_set.set_active_all_threads(false, /* new active value */
1149 true /* expected_active */);
1150
1151 if (VerifyDuringGC) {
1152 HandleMark hm; // handle scope
1153 g1h->prepare_for_verify();
1154 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)");
1155 }
1156 g1h->verifier()->check_bitmaps("Remark End");
1157 assert(!restart_for_overflow(), "sanity");
1158 // Completely reset the marking state since marking completed
1159 set_non_marking_state();
1160 }
1161
1162 // Expand the marking stack, if we have to and if we can.
1163 if (_global_mark_stack.should_expand()) {
1164 _global_mark_stack.expand();
1165 }
1166
1167 // Statistics
1168 double now = os::elapsedTime();
1169 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1170 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1171 _remark_times.add((now - start) * 1000.0);
1172
1173 g1p->record_concurrent_mark_remark_end();
1174
1175 G1CMIsAliveClosure is_alive(g1h);
1176 _gc_tracer_cm->report_object_count_after_gc(&is_alive);
1177 }
1178
1179 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1180 G1CollectedHeap* _g1;
1181 size_t _freed_bytes;
1182 FreeRegionList* _local_cleanup_list;
1183 uint _old_regions_removed;
1184 uint _humongous_regions_removed;
1185 HRRSCleanupTask* _hrrs_cleanup_task;
1186
1187 public:
1188 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1189 FreeRegionList* local_cleanup_list,
1190 HRRSCleanupTask* hrrs_cleanup_task) :
1191 _g1(g1),
1192 _freed_bytes(0),
1193 _local_cleanup_list(local_cleanup_list),
1194 _old_regions_removed(0),
1195 _humongous_regions_removed(0),
1196 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1197
1198 size_t freed_bytes() { return _freed_bytes; }
1199 const uint old_regions_removed() { return _old_regions_removed; }
1200 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1201
1202 bool doHeapRegion(HeapRegion *hr) {
1203 if (hr->is_archive()) {
1204 return false;
1205 }
1206 _g1->reset_gc_time_stamps(hr);
1207 hr->note_end_of_marking();
1208
1209 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1210 _freed_bytes += hr->used();
1211 hr->set_containing_set(NULL);
1212 if (hr->is_humongous()) {
1213 _humongous_regions_removed++;
1214 _g1->free_humongous_region(hr, _local_cleanup_list, true /* skip_remset */);
1215 } else {
1216 _old_regions_removed++;
1217 _g1->free_region(hr, _local_cleanup_list, true /* skip_remset */);
1218 }
1219 } else {
1220 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1221 }
1222
1223 return false;
1224 }
1225 };
1226
1227 class G1ParNoteEndTask: public AbstractGangTask {
1228 friend class G1NoteEndOfConcMarkClosure;
1229
1230 protected:
1231 G1CollectedHeap* _g1h;
1232 FreeRegionList* _cleanup_list;
1233 HeapRegionClaimer _hrclaimer;
1234
1235 public:
1236 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1237 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1238 }
1239
1240 void work(uint worker_id) {
1241 FreeRegionList local_cleanup_list("Local Cleanup List");
1242 HRRSCleanupTask hrrs_cleanup_task;
1243 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1244 &hrrs_cleanup_task);
1245 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1246 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1247
1248 // Now update the lists
1249 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1250 {
1251 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1252 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1253
1254 // If we iterate over the global cleanup list at the end of
1255 // cleanup to do this printing we will not guarantee to only
1256 // generate output for the newly-reclaimed regions (the list
1257 // might not be empty at the beginning of cleanup; we might
1258 // still be working on its previous contents). So we do the
1259 // printing here, before we append the new regions to the global
1260 // cleanup list.
1261
1262 G1HRPrinter* hr_printer = _g1h->hr_printer();
1263 if (hr_printer->is_active()) {
1264 FreeRegionListIterator iter(&local_cleanup_list);
1265 while (iter.more_available()) {
1266 HeapRegion* hr = iter.get_next();
1267 hr_printer->cleanup(hr);
1268 }
1269 }
1270
1271 _cleanup_list->add_ordered(&local_cleanup_list);
1272 assert(local_cleanup_list.is_empty(), "post-condition");
1273
1274 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1275 }
1276 }
1277 };
1278
1279 void G1ConcurrentMark::cleanup() {
1280 // world is stopped at this checkpoint
1281 assert(SafepointSynchronize::is_at_safepoint(),
1282 "world should be stopped");
1283 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1284
1285 // If a full collection has happened, we shouldn't do this.
1286 if (has_aborted()) {
1287 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1288 return;
1289 }
1290
1291 g1h->verifier()->verify_region_sets_optional();
1292
1293 if (VerifyDuringGC) {
1294 HandleMark hm; // handle scope
1295 g1h->prepare_for_verify();
1296 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1297 }
1298 g1h->verifier()->check_bitmaps("Cleanup Start");
1299
1300 G1Policy* g1p = g1h->g1_policy();
1301 g1p->record_concurrent_mark_cleanup_start();
1302
1303 double start = os::elapsedTime();
1304
1305 HeapRegionRemSet::reset_for_cleanup_tasks();
1306
1307 {
1308 GCTraceTime(Debug, gc)("Finalize Live Data");
1309 finalize_live_data();
1310 }
1311
1312 if (VerifyDuringGC) {
1313 GCTraceTime(Debug, gc)("Verify Live Data");
1314 verify_live_data();
1315 }
1316
1317 g1h->collector_state()->set_mark_in_progress(false);
1318
1319 double count_end = os::elapsedTime();
1320 double this_final_counting_time = (count_end - start);
1321 _total_counting_time += this_final_counting_time;
1322
1323 if (log_is_enabled(Trace, gc, liveness)) {
1324 G1PrintRegionLivenessInfoClosure cl("Post-Marking");
1325 _g1h->heap_region_iterate(&cl);
1326 }
1327
1328 // Install newly created mark bitMap as "prev".
1329 swapMarkBitMaps();
1330
1331 g1h->reset_gc_time_stamp();
1332
1333 uint n_workers = _g1h->workers()->active_workers();
1334
1335 // Note end of marking in all heap regions.
1336 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1337 g1h->workers()->run_task(&g1_par_note_end_task);
1338 g1h->check_gc_time_stamps();
1339
1340 if (!cleanup_list_is_empty()) {
1341 // The cleanup list is not empty, so we'll have to process it
1342 // concurrently. Notify anyone else that might be wanting free
1343 // regions that there will be more free regions coming soon.
1344 g1h->set_free_regions_coming();
1345 }
1346
1347 // call below, since it affects the metric by which we sort the heap
1348 // regions.
1349 if (G1ScrubRemSets) {
1350 double rs_scrub_start = os::elapsedTime();
1351 g1h->scrub_rem_set();
1352 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start);
1353 }
1354
1355 // this will also free any regions totally full of garbage objects,
1356 // and sort the regions.
1357 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1358
1359 // Statistics.
1360 double end = os::elapsedTime();
1361 _cleanup_times.add((end - start) * 1000.0);
1362
1363 // Clean up will have freed any regions completely full of garbage.
1364 // Update the soft reference policy with the new heap occupancy.
1365 Universe::update_heap_info_at_gc();
1366
1367 if (VerifyDuringGC) {
1368 HandleMark hm; // handle scope
1369 g1h->prepare_for_verify();
1370 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)");
1371 }
1372
1373 g1h->verifier()->check_bitmaps("Cleanup End");
1374
1375 g1h->verifier()->verify_region_sets_optional();
1376
1377 // We need to make this be a "collection" so any collection pause that
1378 // races with it goes around and waits for completeCleanup to finish.
1379 g1h->increment_total_collections();
1380
1381 // Clean out dead classes and update Metaspace sizes.
1382 if (ClassUnloadingWithConcurrentMark) {
1383 ClassLoaderDataGraph::purge();
1384 }
1385 MetaspaceGC::compute_new_size();
1386
1387 // We reclaimed old regions so we should calculate the sizes to make
1388 // sure we update the old gen/space data.
1389 g1h->g1mm()->update_sizes();
1390 g1h->allocation_context_stats().update_after_mark();
1391 }
1392
1393 void G1ConcurrentMark::complete_cleanup() {
1394 if (has_aborted()) return;
1395
1396 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1397
1398 _cleanup_list.verify_optional();
1399 FreeRegionList tmp_free_list("Tmp Free List");
1400
1401 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1402 "cleanup list has %u entries",
1403 _cleanup_list.length());
1404
1405 // No one else should be accessing the _cleanup_list at this point,
1406 // so it is not necessary to take any locks
1407 while (!_cleanup_list.is_empty()) {
1408 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
1409 assert(hr != NULL, "Got NULL from a non-empty list");
1410 hr->par_clear();
1411 tmp_free_list.add_ordered(hr);
1412
1413 // Instead of adding one region at a time to the secondary_free_list,
1414 // we accumulate them in the local list and move them a few at a
1415 // time. This also cuts down on the number of notify_all() calls
1416 // we do during this process. We'll also append the local list when
1417 // _cleanup_list is empty (which means we just removed the last
1418 // region from the _cleanup_list).
1419 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
1420 _cleanup_list.is_empty()) {
1421 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1422 "appending %u entries to the secondary_free_list, "
1423 "cleanup list still has %u entries",
1424 tmp_free_list.length(),
1425 _cleanup_list.length());
1426
1427 {
1428 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1429 g1h->secondary_free_list_add(&tmp_free_list);
1430 SecondaryFreeList_lock->notify_all();
1431 }
1432 #ifndef PRODUCT
1433 if (G1StressConcRegionFreeing) {
1434 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
1435 os::sleep(Thread::current(), (jlong) 1, false);
1436 }
1437 }
1438 #endif
1439 }
1440 }
1441 assert(tmp_free_list.is_empty(), "post-condition");
1442 }
1443
1444 // Supporting Object and Oop closures for reference discovery
1445 // and processing in during marking
1446
1447 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1448 HeapWord* addr = (HeapWord*)obj;
1449 return addr != NULL &&
1450 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1451 }
1452
1453 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1454 // Uses the G1CMTask associated with a worker thread (for serial reference
1455 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1456 // trace referent objects.
1457 //
1458 // Using the G1CMTask and embedded local queues avoids having the worker
1459 // threads operating on the global mark stack. This reduces the risk
1460 // of overflowing the stack - which we would rather avoid at this late
1461 // state. Also using the tasks' local queues removes the potential
1462 // of the workers interfering with each other that could occur if
1463 // operating on the global stack.
1464
1465 class G1CMKeepAliveAndDrainClosure: public OopClosure {
1466 G1ConcurrentMark* _cm;
1467 G1CMTask* _task;
1468 int _ref_counter_limit;
1469 int _ref_counter;
1470 bool _is_serial;
1471 public:
1472 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1473 _cm(cm), _task(task), _is_serial(is_serial),
1474 _ref_counter_limit(G1RefProcDrainInterval) {
1475 assert(_ref_counter_limit > 0, "sanity");
1476 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1477 _ref_counter = _ref_counter_limit;
1478 }
1479
1480 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1481 virtual void do_oop( oop* p) { do_oop_work(p); }
1482
1483 template <class T> void do_oop_work(T* p) {
1484 if (!_cm->has_overflown()) {
1485 oop obj = oopDesc::load_decode_heap_oop(p);
1486 _task->deal_with_reference(obj);
1487 _ref_counter--;
1488
1489 if (_ref_counter == 0) {
1490 // We have dealt with _ref_counter_limit references, pushing them
1491 // and objects reachable from them on to the local stack (and
1492 // possibly the global stack). Call G1CMTask::do_marking_step() to
1493 // process these entries.
1494 //
1495 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1496 // there's nothing more to do (i.e. we're done with the entries that
1497 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1498 // above) or we overflow.
1499 //
1500 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1501 // flag while there may still be some work to do. (See the comment at
1502 // the beginning of G1CMTask::do_marking_step() for those conditions -
1503 // one of which is reaching the specified time target.) It is only
1504 // when G1CMTask::do_marking_step() returns without setting the
1505 // has_aborted() flag that the marking step has completed.
1506 do {
1507 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1508 _task->do_marking_step(mark_step_duration_ms,
1509 false /* do_termination */,
1510 _is_serial);
1511 } while (_task->has_aborted() && !_cm->has_overflown());
1512 _ref_counter = _ref_counter_limit;
1513 }
1514 }
1515 }
1516 };
1517
1518 // 'Drain' oop closure used by both serial and parallel reference processing.
1519 // Uses the G1CMTask associated with a given worker thread (for serial
1520 // reference processing the G1CMtask for worker 0 is used). Calls the
1521 // do_marking_step routine, with an unbelievably large timeout value,
1522 // to drain the marking data structures of the remaining entries
1523 // added by the 'keep alive' oop closure above.
1524
1525 class G1CMDrainMarkingStackClosure: public VoidClosure {
1526 G1ConcurrentMark* _cm;
1527 G1CMTask* _task;
1528 bool _is_serial;
1529 public:
1530 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1531 _cm(cm), _task(task), _is_serial(is_serial) {
1532 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1533 }
1534
1535 void do_void() {
1536 do {
1537 // We call G1CMTask::do_marking_step() to completely drain the local
1538 // and global marking stacks of entries pushed by the 'keep alive'
1539 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1540 //
1541 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1542 // if there's nothing more to do (i.e. we've completely drained the
1543 // entries that were pushed as a a result of applying the 'keep alive'
1544 // closure to the entries on the discovered ref lists) or we overflow
1545 // the global marking stack.
1546 //
1547 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1548 // flag while there may still be some work to do. (See the comment at
1549 // the beginning of G1CMTask::do_marking_step() for those conditions -
1550 // one of which is reaching the specified time target.) It is only
1551 // when G1CMTask::do_marking_step() returns without setting the
1552 // has_aborted() flag that the marking step has completed.
1553
1554 _task->do_marking_step(1000000000.0 /* something very large */,
1555 true /* do_termination */,
1556 _is_serial);
1557 } while (_task->has_aborted() && !_cm->has_overflown());
1558 }
1559 };
1560
1561 // Implementation of AbstractRefProcTaskExecutor for parallel
1562 // reference processing at the end of G1 concurrent marking
1563
1564 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
1565 private:
1566 G1CollectedHeap* _g1h;
1567 G1ConcurrentMark* _cm;
1568 WorkGang* _workers;
1569 uint _active_workers;
1570
1571 public:
1572 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1573 G1ConcurrentMark* cm,
1574 WorkGang* workers,
1575 uint n_workers) :
1576 _g1h(g1h), _cm(cm),
1577 _workers(workers), _active_workers(n_workers) { }
1578
1579 // Executes the given task using concurrent marking worker threads.
1580 virtual void execute(ProcessTask& task);
1581 virtual void execute(EnqueueTask& task);
1582 };
1583
1584 class G1CMRefProcTaskProxy: public AbstractGangTask {
1585 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1586 ProcessTask& _proc_task;
1587 G1CollectedHeap* _g1h;
1588 G1ConcurrentMark* _cm;
1589
1590 public:
1591 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1592 G1CollectedHeap* g1h,
1593 G1ConcurrentMark* cm) :
1594 AbstractGangTask("Process reference objects in parallel"),
1595 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1596 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1597 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1598 }
1599
1600 virtual void work(uint worker_id) {
1601 ResourceMark rm;
1602 HandleMark hm;
1603 G1CMTask* task = _cm->task(worker_id);
1604 G1CMIsAliveClosure g1_is_alive(_g1h);
1605 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1606 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1607
1608 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1609 }
1610 };
1611
1612 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1613 assert(_workers != NULL, "Need parallel worker threads.");
1614 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1615
1616 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1617
1618 // We need to reset the concurrency level before each
1619 // proxy task execution, so that the termination protocol
1620 // and overflow handling in G1CMTask::do_marking_step() knows
1621 // how many workers to wait for.
1622 _cm->set_concurrency(_active_workers);
1623 _workers->run_task(&proc_task_proxy);
1624 }
1625
1626 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
1627 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
1628 EnqueueTask& _enq_task;
1629
1630 public:
1631 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
1632 AbstractGangTask("Enqueue reference objects in parallel"),
1633 _enq_task(enq_task) { }
1634
1635 virtual void work(uint worker_id) {
1636 _enq_task.work(worker_id);
1637 }
1638 };
1639
1640 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
1641 assert(_workers != NULL, "Need parallel worker threads.");
1642 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1643
1644 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
1645
1646 // Not strictly necessary but...
1647 //
1648 // We need to reset the concurrency level before each
1649 // proxy task execution, so that the termination protocol
1650 // and overflow handling in G1CMTask::do_marking_step() knows
1651 // how many workers to wait for.
1652 _cm->set_concurrency(_active_workers);
1653 _workers->run_task(&enq_task_proxy);
1654 }
1655
1656 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
1657 if (has_overflown()) {
1658 // Skip processing the discovered references if we have
1659 // overflown the global marking stack. Reference objects
1660 // only get discovered once so it is OK to not
1661 // de-populate the discovered reference lists. We could have,
1662 // but the only benefit would be that, when marking restarts,
1663 // less reference objects are discovered.
1664 return;
1665 }
1666
1667 ResourceMark rm;
1668 HandleMark hm;
1669
1670 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1671
1672 // Is alive closure.
1673 G1CMIsAliveClosure g1_is_alive(g1h);
1674
1675 // Inner scope to exclude the cleaning of the string and symbol
1676 // tables from the displayed time.
1677 {
1678 GCTraceTime(Debug, gc, phases) trace("Reference Processing", _gc_timer_cm);
1679
1680 ReferenceProcessor* rp = g1h->ref_processor_cm();
1681
1682 // See the comment in G1CollectedHeap::ref_processing_init()
1683 // about how reference processing currently works in G1.
1684
1685 // Set the soft reference policy
1686 rp->setup_policy(clear_all_soft_refs);
1687 assert(_global_mark_stack.is_empty(), "mark stack should be empty");
1688
1689 // Instances of the 'Keep Alive' and 'Complete GC' closures used
1690 // in serial reference processing. Note these closures are also
1691 // used for serially processing (by the the current thread) the
1692 // JNI references during parallel reference processing.
1693 //
1694 // These closures do not need to synchronize with the worker
1695 // threads involved in parallel reference processing as these
1696 // instances are executed serially by the current thread (e.g.
1697 // reference processing is not multi-threaded and is thus
1698 // performed by the current thread instead of a gang worker).
1699 //
1700 // The gang tasks involved in parallel reference processing create
1701 // their own instances of these closures, which do their own
1702 // synchronization among themselves.
1703 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
1704 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
1705
1706 // We need at least one active thread. If reference processing
1707 // is not multi-threaded we use the current (VMThread) thread,
1708 // otherwise we use the work gang from the G1CollectedHeap and
1709 // we utilize all the worker threads we can.
1710 bool processing_is_mt = rp->processing_is_mt();
1711 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
1712 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
1713
1714 // Parallel processing task executor.
1715 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
1716 g1h->workers(), active_workers);
1717 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
1718
1719 // Set the concurrency level. The phase was already set prior to
1720 // executing the remark task.
1721 set_concurrency(active_workers);
1722
1723 // Set the degree of MT processing here. If the discovery was done MT,
1724 // the number of threads involved during discovery could differ from
1725 // the number of active workers. This is OK as long as the discovered
1726 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
1727 rp->set_active_mt_degree(active_workers);
1728
1729 // Process the weak references.
1730 const ReferenceProcessorStats& stats =
1731 rp->process_discovered_references(&g1_is_alive,
1732 &g1_keep_alive,
1733 &g1_drain_mark_stack,
1734 executor,
1735 _gc_timer_cm);
1736 _gc_tracer_cm->report_gc_reference_stats(stats);
1737
1738 // The do_oop work routines of the keep_alive and drain_marking_stack
1739 // oop closures will set the has_overflown flag if we overflow the
1740 // global marking stack.
1741
1742 assert(has_overflown() || _global_mark_stack.is_empty(),
1743 "Mark stack should be empty (unless it has overflown)");
1744
1745 assert(rp->num_q() == active_workers, "why not");
1746
1747 rp->enqueue_discovered_references(executor);
1748
1749 rp->verify_no_references_recorded();
1750 assert(!rp->discovery_enabled(), "Post condition");
1751 }
1752
1753 if (has_overflown()) {
1754 // We can not trust g1_is_alive if the marking stack overflowed
1755 return;
1756 }
1757
1758 assert(_global_mark_stack.is_empty(), "Marking should have completed");
1759
1760 // Unload Klasses, String, Symbols, Code Cache, etc.
1761 if (ClassUnloadingWithConcurrentMark) {
1762 GCTraceTime(Debug, gc, phases) debug("Class Unloading", _gc_timer_cm);
1763 bool purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
1764 g1h->complete_cleaning(&g1_is_alive, purged_classes);
1765 } else {
1766 GCTraceTime(Debug, gc, phases) debug("Cleanup", _gc_timer_cm);
1767 // No need to clean string table and symbol table as they are treated as strong roots when
1768 // class unloading is disabled.
1769 g1h->partial_cleaning(&g1_is_alive, false, false, G1StringDedup::is_enabled());
1770
1771 }
1772 }
1773
1774 void G1ConcurrentMark::swapMarkBitMaps() {
1775 G1CMBitMapRO* temp = _prevMarkBitMap;
1776 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap;
1777 _nextMarkBitMap = (G1CMBitMap*) temp;
1778 }
1779
1780 // Closure for marking entries in SATB buffers.
1781 class G1CMSATBBufferClosure : public SATBBufferClosure {
1782 private:
1783 G1CMTask* _task;
1784 G1CollectedHeap* _g1h;
1785
1786 // This is very similar to G1CMTask::deal_with_reference, but with
1787 // more relaxed requirements for the argument, so this must be more
1788 // circumspect about treating the argument as an object.
1789 void do_entry(void* entry) const {
1790 _task->increment_refs_reached();
1791 HeapRegion* hr = _g1h->heap_region_containing(entry);
1792 if (entry < hr->next_top_at_mark_start()) {
1793 // Until we get here, we don't know whether entry refers to a valid
1794 // object; it could instead have been a stale reference.
1795 oop obj = static_cast<oop>(entry);
1796 assert(obj->is_oop(true /* ignore mark word */),
1797 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj));
1798 _task->make_reference_grey(obj);
1799 }
1800 }
1801
1802 public:
1803 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
1804 : _task(task), _g1h(g1h) { }
1805
1806 virtual void do_buffer(void** buffer, size_t size) {
1807 for (size_t i = 0; i < size; ++i) {
1808 do_entry(buffer[i]);
1809 }
1810 }
1811 };
1812
1813 class G1RemarkThreadsClosure : public ThreadClosure {
1814 G1CMSATBBufferClosure _cm_satb_cl;
1815 G1CMOopClosure _cm_cl;
1816 MarkingCodeBlobClosure _code_cl;
1817 int _thread_parity;
1818
1819 public:
1820 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
1821 _cm_satb_cl(task, g1h),
1822 _cm_cl(g1h, g1h->concurrent_mark(), task),
1823 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
1824 _thread_parity(Threads::thread_claim_parity()) {}
1825
1826 void do_thread(Thread* thread) {
1827 if (thread->is_Java_thread()) {
1828 if (thread->claim_oops_do(true, _thread_parity)) {
1829 JavaThread* jt = (JavaThread*)thread;
1830
1831 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
1832 // however the liveness of oops reachable from nmethods have very complex lifecycles:
1833 // * Alive if on the stack of an executing method
1834 // * Weakly reachable otherwise
1835 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
1836 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
1837 jt->nmethods_do(&_code_cl);
1838
1839 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
1840 }
1841 } else if (thread->is_VM_thread()) {
1842 if (thread->claim_oops_do(true, _thread_parity)) {
1843 G1BarrierSet::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
1844 }
1845 }
1846 }
1847 };
1848
1849 class G1CMRemarkTask: public AbstractGangTask {
1850 private:
1851 G1ConcurrentMark* _cm;
1852 public:
1853 void work(uint worker_id) {
1854 // Since all available tasks are actually started, we should
1855 // only proceed if we're supposed to be active.
1856 if (worker_id < _cm->active_tasks()) {
1857 G1CMTask* task = _cm->task(worker_id);
1858 task->record_start_time();
1859 {
1860 ResourceMark rm;
1861 HandleMark hm;
1862
1863 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
1864 Threads::threads_do(&threads_f);
1865 }
1866
1867 do {
1868 task->do_marking_step(1000000000.0 /* something very large */,
1869 true /* do_termination */,
1870 false /* is_serial */);
1871 } while (task->has_aborted() && !_cm->has_overflown());
1872 // If we overflow, then we do not want to restart. We instead
1873 // want to abort remark and do concurrent marking again.
1874 task->record_end_time();
1875 }
1876 }
1877
1878 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
1879 AbstractGangTask("Par Remark"), _cm(cm) {
1880 _cm->terminator()->reset_for_reuse(active_workers);
1881 }
1882 };
1883
1884 void G1ConcurrentMark::checkpointRootsFinalWork() {
1885 ResourceMark rm;
1886 HandleMark hm;
1887 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1888
1889 GCTraceTime(Debug, gc, phases) trace("Finalize Marking", _gc_timer_cm);
1890
1891 g1h->ensure_parsability(false);
1892
1893 // this is remark, so we'll use up all active threads
1894 uint active_workers = g1h->workers()->active_workers();
1895 set_concurrency_and_phase(active_workers, false /* concurrent */);
1896 // Leave _parallel_marking_threads at it's
1897 // value originally calculated in the G1ConcurrentMark
1898 // constructor and pass values of the active workers
1899 // through the gang in the task.
1900
1901 {
1902 StrongRootsScope srs(active_workers);
1903
1904 G1CMRemarkTask remarkTask(this, active_workers);
1905 // We will start all available threads, even if we decide that the
1906 // active_workers will be fewer. The extra ones will just bail out
1907 // immediately.
1908 g1h->workers()->run_task(&remarkTask);
1909 }
1910
1911 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
1912 guarantee(has_overflown() ||
1913 satb_mq_set.completed_buffers_num() == 0,
1914 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
1915 BOOL_TO_STR(has_overflown()),
1916 satb_mq_set.completed_buffers_num());
1917
1918 print_stats();
1919 }
1920
1921 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
1922 // Note we are overriding the read-only view of the prev map here, via
1923 // the cast.
1924 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr);
1925 }
1926
1927 HeapRegion*
1928 G1ConcurrentMark::claim_region(uint worker_id) {
1929 // "checkpoint" the finger
1930 HeapWord* finger = _finger;
1931
1932 // _heap_end will not change underneath our feet; it only changes at
1933 // yield points.
1934 while (finger < _heap_end) {
1935 assert(_g1h->is_in_g1_reserved(finger), "invariant");
1936
1937 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
1938 // Make sure that the reads below do not float before loading curr_region.
1939 OrderAccess::loadload();
1940 // Above heap_region_containing may return NULL as we always scan claim
1941 // until the end of the heap. In this case, just jump to the next region.
1942 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
1943
1944 // Is the gap between reading the finger and doing the CAS too long?
1945 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
1946 if (res == finger && curr_region != NULL) {
1947 // we succeeded
1948 HeapWord* bottom = curr_region->bottom();
1949 HeapWord* limit = curr_region->next_top_at_mark_start();
1950
1951 // notice that _finger == end cannot be guaranteed here since,
1952 // someone else might have moved the finger even further
1953 assert(_finger >= end, "the finger should have moved forward");
1954
1955 if (limit > bottom) {
1956 return curr_region;
1957 } else {
1958 assert(limit == bottom,
1959 "the region limit should be at bottom");
1960 // we return NULL and the caller should try calling
1961 // claim_region() again.
1962 return NULL;
1963 }
1964 } else {
1965 assert(_finger > finger, "the finger should have moved forward");
1966 // read it again
1967 finger = _finger;
1968 }
1969 }
1970
1971 return NULL;
1972 }
1973
1974 #ifndef PRODUCT
1975 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
1976 private:
1977 G1CollectedHeap* _g1h;
1978 const char* _phase;
1979 int _info;
1980
1981 public:
1982 VerifyNoCSetOops(const char* phase, int info = -1) :
1983 _g1h(G1CollectedHeap::heap()),
1984 _phase(phase),
1985 _info(info)
1986 { }
1987
1988 void operator()(G1TaskQueueEntry task_entry) const {
1989 if (task_entry.is_array_slice()) {
1990 guarantee(_g1h->is_in_reserved(task_entry.slice()), "Slice " PTR_FORMAT " must be in heap.", p2i(task_entry.slice()));
1991 return;
1992 }
1993 guarantee(task_entry.obj()->is_oop(),
1994 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
1995 p2i(task_entry.obj()), _phase, _info);
1996 guarantee(!_g1h->is_in_cset(task_entry.obj()),
1997 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
1998 p2i(task_entry.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 = G1BarrierSet::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_task_entry(G1TaskQueueEntry::from_oop(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 = G1BarrierSet::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 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
2384
2385 size_t n = 0;
2386 G1TaskQueueEntry task_entry;
2387 while (n < G1CMMarkStack::EntriesPerChunk && _task_queue->pop_local(task_entry)) {
2388 buffer[n] = task_entry;
2389 ++n;
2390 }
2391 if (n < G1CMMarkStack::EntriesPerChunk) {
2392 buffer[n] = G1TaskQueueEntry();
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 G1TaskQueueEntry buffer[G1CMMarkStack::EntriesPerChunk];
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::EntriesPerChunk; ++i) {
2416 G1TaskQueueEntry task_entry = buffer[i];
2417 if (task_entry.is_null()) {
2418 break;
2419 }
2420 assert(task_entry.is_array_slice() || task_entry.obj()->is_oop(), "Element " PTR_FORMAT " must be an array slice or oop", p2i(task_entry.obj()));
2421 bool success = _task_queue->push(task_entry);
2422 // We only call this when the local queue is empty or under a
2423 // given target limit. So, we do not expect this push to fail.
2424 assert(success, "invariant");
2425 }
2426
2427 // This operation was quite expensive, so decrease the limits
2428 decrease_limits();
2429 return true;
2430 }
2431
2432 void G1CMTask::drain_local_queue(bool partially) {
2433 if (has_aborted()) {
2434 return;
2435 }
2436
2437 // Decide what the target size is, depending whether we're going to
2438 // drain it partially (so that other tasks can steal if they run out
2439 // of things to do) or totally (at the very end).
2440 size_t target_size;
2441 if (partially) {
2442 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
2443 } else {
2444 target_size = 0;
2445 }
2446
2447 if (_task_queue->size() > target_size) {
2448 G1TaskQueueEntry entry;
2449 bool ret = _task_queue->pop_local(entry);
2450 while (ret) {
2451 scan_task_entry(entry);
2452 if (_task_queue->size() <= target_size || has_aborted()) {
2453 ret = false;
2454 } else {
2455 ret = _task_queue->pop_local(entry);
2456 }
2457 }
2458 }
2459 }
2460
2461 void G1CMTask::drain_global_stack(bool partially) {
2462 if (has_aborted()) return;
2463
2464 // We have a policy to drain the local queue before we attempt to
2465 // drain the global stack.
2466 assert(partially || _task_queue->size() == 0, "invariant");
2467
2468 // Decide what the target size is, depending whether we're going to
2469 // drain it partially (so that other tasks can steal if they run out
2470 // of things to do) or totally (at the very end).
2471 // Notice that when draining the global mark stack partially, due to the racyness
2472 // of the mark stack size update we might in fact drop below the target. But,
2473 // this is not a problem.
2474 // In case of total draining, we simply process until the global mark stack is
2475 // totally empty, disregarding the size counter.
2476 if (partially) {
2477 size_t const target_size = _cm->partial_mark_stack_size_target();
2478 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
2479 if (get_entries_from_global_stack()) {
2480 drain_local_queue(partially);
2481 }
2482 }
2483 } else {
2484 while (!has_aborted() && get_entries_from_global_stack()) {
2485 drain_local_queue(partially);
2486 }
2487 }
2488 }
2489
2490 // SATB Queue has several assumptions on whether to call the par or
2491 // non-par versions of the methods. this is why some of the code is
2492 // replicated. We should really get rid of the single-threaded version
2493 // of the code to simplify things.
2494 void G1CMTask::drain_satb_buffers() {
2495 if (has_aborted()) return;
2496
2497 // We set this so that the regular clock knows that we're in the
2498 // middle of draining buffers and doesn't set the abort flag when it
2499 // notices that SATB buffers are available for draining. It'd be
2500 // very counter productive if it did that. :-)
2501 _draining_satb_buffers = true;
2502
2503 G1CMSATBBufferClosure satb_cl(this, _g1h);
2504 SATBMarkQueueSet& satb_mq_set = G1BarrierSet::satb_mark_queue_set();
2505
2506 // This keeps claiming and applying the closure to completed buffers
2507 // until we run out of buffers or we need to abort.
2508 while (!has_aborted() &&
2509 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
2510 regular_clock_call();
2511 }
2512
2513 _draining_satb_buffers = false;
2514
2515 assert(has_aborted() ||
2516 concurrent() ||
2517 satb_mq_set.completed_buffers_num() == 0, "invariant");
2518
2519 // again, this was a potentially expensive operation, decrease the
2520 // limits to get the regular clock call early
2521 decrease_limits();
2522 }
2523
2524 void G1CMTask::print_stats() {
2525 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d",
2526 _worker_id, _calls);
2527 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
2528 _elapsed_time_ms, _termination_time_ms);
2529 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
2530 _step_times_ms.num(), _step_times_ms.avg(),
2531 _step_times_ms.sd());
2532 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms",
2533 _step_times_ms.maximum(), _step_times_ms.sum());
2534 }
2535
2536 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, G1TaskQueueEntry& task_entry) {
2537 return _task_queues->steal(worker_id, hash_seed, task_entry);
2538 }
2539
2540 /*****************************************************************************
2541
2542 The do_marking_step(time_target_ms, ...) method is the building
2543 block of the parallel marking framework. It can be called in parallel
2544 with other invocations of do_marking_step() on different tasks
2545 (but only one per task, obviously) and concurrently with the
2546 mutator threads, or during remark, hence it eliminates the need
2547 for two versions of the code. When called during remark, it will
2548 pick up from where the task left off during the concurrent marking
2549 phase. Interestingly, tasks are also claimable during evacuation
2550 pauses too, since do_marking_step() ensures that it aborts before
2551 it needs to yield.
2552
2553 The data structures that it uses to do marking work are the
2554 following:
2555
2556 (1) Marking Bitmap. If there are gray objects that appear only
2557 on the bitmap (this happens either when dealing with an overflow
2558 or when the initial marking phase has simply marked the roots
2559 and didn't push them on the stack), then tasks claim heap
2560 regions whose bitmap they then scan to find gray objects. A
2561 global finger indicates where the end of the last claimed region
2562 is. A local finger indicates how far into the region a task has
2563 scanned. The two fingers are used to determine how to gray an
2564 object (i.e. whether simply marking it is OK, as it will be
2565 visited by a task in the future, or whether it needs to be also
2566 pushed on a stack).
2567
2568 (2) Local Queue. The local queue of the task which is accessed
2569 reasonably efficiently by the task. Other tasks can steal from
2570 it when they run out of work. Throughout the marking phase, a
2571 task attempts to keep its local queue short but not totally
2572 empty, so that entries are available for stealing by other
2573 tasks. Only when there is no more work, a task will totally
2574 drain its local queue.
2575
2576 (3) Global Mark Stack. This handles local queue overflow. During
2577 marking only sets of entries are moved between it and the local
2578 queues, as access to it requires a mutex and more fine-grain
2579 interaction with it which might cause contention. If it
2580 overflows, then the marking phase should restart and iterate
2581 over the bitmap to identify gray objects. Throughout the marking
2582 phase, tasks attempt to keep the global mark stack at a small
2583 length but not totally empty, so that entries are available for
2584 popping by other tasks. Only when there is no more work, tasks
2585 will totally drain the global mark stack.
2586
2587 (4) SATB Buffer Queue. This is where completed SATB buffers are
2588 made available. Buffers are regularly removed from this queue
2589 and scanned for roots, so that the queue doesn't get too
2590 long. During remark, all completed buffers are processed, as
2591 well as the filled in parts of any uncompleted buffers.
2592
2593 The do_marking_step() method tries to abort when the time target
2594 has been reached. There are a few other cases when the
2595 do_marking_step() method also aborts:
2596
2597 (1) When the marking phase has been aborted (after a Full GC).
2598
2599 (2) When a global overflow (on the global stack) has been
2600 triggered. Before the task aborts, it will actually sync up with
2601 the other tasks to ensure that all the marking data structures
2602 (local queues, stacks, fingers etc.) are re-initialized so that
2603 when do_marking_step() completes, the marking phase can
2604 immediately restart.
2605
2606 (3) When enough completed SATB buffers are available. The
2607 do_marking_step() method only tries to drain SATB buffers right
2608 at the beginning. So, if enough buffers are available, the
2609 marking step aborts and the SATB buffers are processed at
2610 the beginning of the next invocation.
2611
2612 (4) To yield. when we have to yield then we abort and yield
2613 right at the end of do_marking_step(). This saves us from a lot
2614 of hassle as, by yielding we might allow a Full GC. If this
2615 happens then objects will be compacted underneath our feet, the
2616 heap might shrink, etc. We save checking for this by just
2617 aborting and doing the yield right at the end.
2618
2619 From the above it follows that the do_marking_step() method should
2620 be called in a loop (or, otherwise, regularly) until it completes.
2621
2622 If a marking step completes without its has_aborted() flag being
2623 true, it means it has completed the current marking phase (and
2624 also all other marking tasks have done so and have all synced up).
2625
2626 A method called regular_clock_call() is invoked "regularly" (in
2627 sub ms intervals) throughout marking. It is this clock method that
2628 checks all the abort conditions which were mentioned above and
2629 decides when the task should abort. A work-based scheme is used to
2630 trigger this clock method: when the number of object words the
2631 marking phase has scanned or the number of references the marking
2632 phase has visited reach a given limit. Additional invocations to
2633 the method clock have been planted in a few other strategic places
2634 too. The initial reason for the clock method was to avoid calling
2635 vtime too regularly, as it is quite expensive. So, once it was in
2636 place, it was natural to piggy-back all the other conditions on it
2637 too and not constantly check them throughout the code.
2638
2639 If do_termination is true then do_marking_step will enter its
2640 termination protocol.
2641
2642 The value of is_serial must be true when do_marking_step is being
2643 called serially (i.e. by the VMThread) and do_marking_step should
2644 skip any synchronization in the termination and overflow code.
2645 Examples include the serial remark code and the serial reference
2646 processing closures.
2647
2648 The value of is_serial must be false when do_marking_step is
2649 being called by any of the worker threads in a work gang.
2650 Examples include the concurrent marking code (CMMarkingTask),
2651 the MT remark code, and the MT reference processing closures.
2652
2653 *****************************************************************************/
2654
2655 void G1CMTask::do_marking_step(double time_target_ms,
2656 bool do_termination,
2657 bool is_serial) {
2658 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
2659 assert(concurrent() == _cm->concurrent(), "they should be the same");
2660
2661 G1Policy* g1_policy = _g1h->g1_policy();
2662 assert(_task_queues != NULL, "invariant");
2663 assert(_task_queue != NULL, "invariant");
2664 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
2665
2666 assert(!_claimed,
2667 "only one thread should claim this task at any one time");
2668
2669 // OK, this doesn't safeguard again all possible scenarios, as it is
2670 // possible for two threads to set the _claimed flag at the same
2671 // time. But it is only for debugging purposes anyway and it will
2672 // catch most problems.
2673 _claimed = true;
2674
2675 _start_time_ms = os::elapsedVTime() * 1000.0;
2676
2677 // If do_stealing is true then do_marking_step will attempt to
2678 // steal work from the other G1CMTasks. It only makes sense to
2679 // enable stealing when the termination protocol is enabled
2680 // and do_marking_step() is not being called serially.
2681 bool do_stealing = do_termination && !is_serial;
2682
2683 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms);
2684 _time_target_ms = time_target_ms - diff_prediction_ms;
2685
2686 // set up the variables that are used in the work-based scheme to
2687 // call the regular clock method
2688 _words_scanned = 0;
2689 _refs_reached = 0;
2690 recalculate_limits();
2691
2692 // clear all flags
2693 clear_has_aborted();
2694 _has_timed_out = false;
2695 _draining_satb_buffers = false;
2696
2697 ++_calls;
2698
2699 // Set up the bitmap and oop closures. Anything that uses them is
2700 // eventually called from this method, so it is OK to allocate these
2701 // statically.
2702 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
2703 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
2704 set_cm_oop_closure(&cm_oop_closure);
2705
2706 if (_cm->has_overflown()) {
2707 // This can happen if the mark stack overflows during a GC pause
2708 // and this task, after a yield point, restarts. We have to abort
2709 // as we need to get into the overflow protocol which happens
2710 // right at the end of this task.
2711 set_has_aborted();
2712 }
2713
2714 // First drain any available SATB buffers. After this, we will not
2715 // look at SATB buffers before the next invocation of this method.
2716 // If enough completed SATB buffers are queued up, the regular clock
2717 // will abort this task so that it restarts.
2718 drain_satb_buffers();
2719 // ...then partially drain the local queue and the global stack
2720 drain_local_queue(true);
2721 drain_global_stack(true);
2722
2723 do {
2724 if (!has_aborted() && _curr_region != NULL) {
2725 // This means that we're already holding on to a region.
2726 assert(_finger != NULL, "if region is not NULL, then the finger "
2727 "should not be NULL either");
2728
2729 // We might have restarted this task after an evacuation pause
2730 // which might have evacuated the region we're holding on to
2731 // underneath our feet. Let's read its limit again to make sure
2732 // that we do not iterate over a region of the heap that
2733 // contains garbage (update_region_limit() will also move
2734 // _finger to the start of the region if it is found empty).
2735 update_region_limit();
2736 // We will start from _finger not from the start of the region,
2737 // as we might be restarting this task after aborting half-way
2738 // through scanning this region. In this case, _finger points to
2739 // the address where we last found a marked object. If this is a
2740 // fresh region, _finger points to start().
2741 MemRegion mr = MemRegion(_finger, _region_limit);
2742
2743 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
2744 "humongous regions should go around loop once only");
2745
2746 // Some special cases:
2747 // If the memory region is empty, we can just give up the region.
2748 // If the current region is humongous then we only need to check
2749 // the bitmap for the bit associated with the start of the object,
2750 // scan the object if it's live, and give up the region.
2751 // Otherwise, let's iterate over the bitmap of the part of the region
2752 // that is left.
2753 // If the iteration is successful, give up the region.
2754 if (mr.is_empty()) {
2755 giveup_current_region();
2756 regular_clock_call();
2757 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
2758 if (_nextMarkBitMap->isMarked(mr.start())) {
2759 // The object is marked - apply the closure
2760 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
2761 bitmap_closure.do_bit(offset);
2762 }
2763 // Even if this task aborted while scanning the humongous object
2764 // we can (and should) give up the current region.
2765 giveup_current_region();
2766 regular_clock_call();
2767 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
2768 giveup_current_region();
2769 regular_clock_call();
2770 } else {
2771 assert(has_aborted(), "currently the only way to do so");
2772 // The only way to abort the bitmap iteration is to return
2773 // false from the do_bit() method. However, inside the
2774 // do_bit() method we move the _finger to point to the
2775 // object currently being looked at. So, if we bail out, we
2776 // have definitely set _finger to something non-null.
2777 assert(_finger != NULL, "invariant");
2778
2779 // Region iteration was actually aborted. So now _finger
2780 // points to the address of the object we last scanned. If we
2781 // leave it there, when we restart this task, we will rescan
2782 // the object. It is easy to avoid this. We move the finger by
2783 // enough to point to the next possible object header (the
2784 // bitmap knows by how much we need to move it as it knows its
2785 // granularity).
2786 assert(_finger < _region_limit, "invariant");
2787 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
2788 // Check if bitmap iteration was aborted while scanning the last object
2789 if (new_finger >= _region_limit) {
2790 giveup_current_region();
2791 } else {
2792 move_finger_to(new_finger);
2793 }
2794 }
2795 }
2796 // At this point we have either completed iterating over the
2797 // region we were holding on to, or we have aborted.
2798
2799 // We then partially drain the local queue and the global stack.
2800 // (Do we really need this?)
2801 drain_local_queue(true);
2802 drain_global_stack(true);
2803
2804 // Read the note on the claim_region() method on why it might
2805 // return NULL with potentially more regions available for
2806 // claiming and why we have to check out_of_regions() to determine
2807 // whether we're done or not.
2808 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
2809 // We are going to try to claim a new region. We should have
2810 // given up on the previous one.
2811 // Separated the asserts so that we know which one fires.
2812 assert(_curr_region == NULL, "invariant");
2813 assert(_finger == NULL, "invariant");
2814 assert(_region_limit == NULL, "invariant");
2815 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
2816 if (claimed_region != NULL) {
2817 // Yes, we managed to claim one
2818 setup_for_region(claimed_region);
2819 assert(_curr_region == claimed_region, "invariant");
2820 }
2821 // It is important to call the regular clock here. It might take
2822 // a while to claim a region if, for example, we hit a large
2823 // block of empty regions. So we need to call the regular clock
2824 // method once round the loop to make sure it's called
2825 // frequently enough.
2826 regular_clock_call();
2827 }
2828
2829 if (!has_aborted() && _curr_region == NULL) {
2830 assert(_cm->out_of_regions(),
2831 "at this point we should be out of regions");
2832 }
2833 } while ( _curr_region != NULL && !has_aborted());
2834
2835 if (!has_aborted()) {
2836 // We cannot check whether the global stack is empty, since other
2837 // tasks might be pushing objects to it concurrently.
2838 assert(_cm->out_of_regions(),
2839 "at this point we should be out of regions");
2840 // Try to reduce the number of available SATB buffers so that
2841 // remark has less work to do.
2842 drain_satb_buffers();
2843 }
2844
2845 // Since we've done everything else, we can now totally drain the
2846 // local queue and global stack.
2847 drain_local_queue(false);
2848 drain_global_stack(false);
2849
2850 // Attempt at work stealing from other task's queues.
2851 if (do_stealing && !has_aborted()) {
2852 // We have not aborted. This means that we have finished all that
2853 // we could. Let's try to do some stealing...
2854
2855 // We cannot check whether the global stack is empty, since other
2856 // tasks might be pushing objects to it concurrently.
2857 assert(_cm->out_of_regions() && _task_queue->size() == 0,
2858 "only way to reach here");
2859 while (!has_aborted()) {
2860 G1TaskQueueEntry entry;
2861 if (_cm->try_stealing(_worker_id, &_hash_seed, entry)) {
2862 scan_task_entry(entry);
2863
2864 // And since we're towards the end, let's totally drain the
2865 // local queue and global stack.
2866 drain_local_queue(false);
2867 drain_global_stack(false);
2868 } else {
2869 break;
2870 }
2871 }
2872 }
2873
2874 // We still haven't aborted. Now, let's try to get into the
2875 // termination protocol.
2876 if (do_termination && !has_aborted()) {
2877 // We cannot check whether the global stack is empty, since other
2878 // tasks might be concurrently pushing objects on it.
2879 // Separated the asserts so that we know which one fires.
2880 assert(_cm->out_of_regions(), "only way to reach here");
2881 assert(_task_queue->size() == 0, "only way to reach here");
2882 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
2883
2884 // The G1CMTask class also extends the TerminatorTerminator class,
2885 // hence its should_exit_termination() method will also decide
2886 // whether to exit the termination protocol or not.
2887 bool finished = (is_serial ||
2888 _cm->terminator()->offer_termination(this));
2889 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
2890 _termination_time_ms +=
2891 termination_end_time_ms - _termination_start_time_ms;
2892
2893 if (finished) {
2894 // We're all done.
2895
2896 if (_worker_id == 0) {
2897 // let's allow task 0 to do this
2898 if (concurrent()) {
2899 assert(_cm->concurrent_marking_in_progress(), "invariant");
2900 // we need to set this to false before the next
2901 // safepoint. This way we ensure that the marking phase
2902 // doesn't observe any more heap expansions.
2903 _cm->clear_concurrent_marking_in_progress();
2904 }
2905 }
2906
2907 // We can now guarantee that the global stack is empty, since
2908 // all other tasks have finished. We separated the guarantees so
2909 // that, if a condition is false, we can immediately find out
2910 // which one.
2911 guarantee(_cm->out_of_regions(), "only way to reach here");
2912 guarantee(_cm->mark_stack_empty(), "only way to reach here");
2913 guarantee(_task_queue->size() == 0, "only way to reach here");
2914 guarantee(!_cm->has_overflown(), "only way to reach here");
2915 } else {
2916 // Apparently there's more work to do. Let's abort this task. It
2917 // will restart it and we can hopefully find more things to do.
2918 set_has_aborted();
2919 }
2920 }
2921
2922 // Mainly for debugging purposes to make sure that a pointer to the
2923 // closure which was statically allocated in this frame doesn't
2924 // escape it by accident.
2925 set_cm_oop_closure(NULL);
2926 double end_time_ms = os::elapsedVTime() * 1000.0;
2927 double elapsed_time_ms = end_time_ms - _start_time_ms;
2928 // Update the step history.
2929 _step_times_ms.add(elapsed_time_ms);
2930
2931 if (has_aborted()) {
2932 // The task was aborted for some reason.
2933 if (_has_timed_out) {
2934 double diff_ms = elapsed_time_ms - _time_target_ms;
2935 // Keep statistics of how well we did with respect to hitting
2936 // our target only if we actually timed out (if we aborted for
2937 // other reasons, then the results might get skewed).
2938 _marking_step_diffs_ms.add(diff_ms);
2939 }
2940
2941 if (_cm->has_overflown()) {
2942 // This is the interesting one. We aborted because a global
2943 // overflow was raised. This means we have to restart the
2944 // marking phase and start iterating over regions. However, in
2945 // order to do this we have to make sure that all tasks stop
2946 // what they are doing and re-initialize in a safe manner. We
2947 // will achieve this with the use of two barrier sync points.
2948
2949 if (!is_serial) {
2950 // We only need to enter the sync barrier if being called
2951 // from a parallel context
2952 _cm->enter_first_sync_barrier(_worker_id);
2953
2954 // When we exit this sync barrier we know that all tasks have
2955 // stopped doing marking work. So, it's now safe to
2956 // re-initialize our data structures. At the end of this method,
2957 // task 0 will clear the global data structures.
2958 }
2959
2960 // We clear the local state of this task...
2961 clear_region_fields();
2962
2963 if (!is_serial) {
2964 // ...and enter the second barrier.
2965 _cm->enter_second_sync_barrier(_worker_id);
2966 }
2967 // At this point, if we're during the concurrent phase of
2968 // marking, everything has been re-initialized and we're
2969 // ready to restart.
2970 }
2971 }
2972
2973 _claimed = false;
2974 }
2975
2976 G1CMTask::G1CMTask(uint worker_id,
2977 G1ConcurrentMark* cm,
2978 G1CMTaskQueue* task_queue,
2979 G1CMTaskQueueSet* task_queues)
2980 : _g1h(G1CollectedHeap::heap()),
2981 _worker_id(worker_id), _cm(cm),
2982 _objArray_processor(this),
2983 _claimed(false),
2984 _nextMarkBitMap(NULL), _hash_seed(17),
2985 _task_queue(task_queue),
2986 _task_queues(task_queues),
2987 _cm_oop_closure(NULL) {
2988 guarantee(task_queue != NULL, "invariant");
2989 guarantee(task_queues != NULL, "invariant");
2990
2991 _marking_step_diffs_ms.add(0.5);
2992 }
2993
2994 // These are formatting macros that are used below to ensure
2995 // consistent formatting. The *_H_* versions are used to format the
2996 // header for a particular value and they should be kept consistent
2997 // with the corresponding macro. Also note that most of the macros add
2998 // the necessary white space (as a prefix) which makes them a bit
2999 // easier to compose.
3000
3001 // All the output lines are prefixed with this string to be able to
3002 // identify them easily in a large log file.
3003 #define G1PPRL_LINE_PREFIX "###"
3004
3005 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
3006 #ifdef _LP64
3007 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
3008 #else // _LP64
3009 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
3010 #endif // _LP64
3011
3012 // For per-region info
3013 #define G1PPRL_TYPE_FORMAT " %-4s"
3014 #define G1PPRL_TYPE_H_FORMAT " %4s"
3015 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
3016 #define G1PPRL_BYTE_H_FORMAT " %9s"
3017 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
3018 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
3019
3020 // For summary info
3021 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
3022 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
3023 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
3024 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
3025
3026 G1PrintRegionLivenessInfoClosure::
3027 G1PrintRegionLivenessInfoClosure(const char* phase_name)
3028 : _total_used_bytes(0), _total_capacity_bytes(0),
3029 _total_prev_live_bytes(0), _total_next_live_bytes(0),
3030 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
3031 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3032 MemRegion g1_reserved = g1h->g1_reserved();
3033 double now = os::elapsedTime();
3034
3035 // Print the header of the output.
3036 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
3037 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
3038 G1PPRL_SUM_ADDR_FORMAT("reserved")
3039 G1PPRL_SUM_BYTE_FORMAT("region-size"),
3040 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
3041 HeapRegion::GrainBytes);
3042 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3043 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3044 G1PPRL_TYPE_H_FORMAT
3045 G1PPRL_ADDR_BASE_H_FORMAT
3046 G1PPRL_BYTE_H_FORMAT
3047 G1PPRL_BYTE_H_FORMAT
3048 G1PPRL_BYTE_H_FORMAT
3049 G1PPRL_DOUBLE_H_FORMAT
3050 G1PPRL_BYTE_H_FORMAT
3051 G1PPRL_BYTE_H_FORMAT,
3052 "type", "address-range",
3053 "used", "prev-live", "next-live", "gc-eff",
3054 "remset", "code-roots");
3055 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3056 G1PPRL_TYPE_H_FORMAT
3057 G1PPRL_ADDR_BASE_H_FORMAT
3058 G1PPRL_BYTE_H_FORMAT
3059 G1PPRL_BYTE_H_FORMAT
3060 G1PPRL_BYTE_H_FORMAT
3061 G1PPRL_DOUBLE_H_FORMAT
3062 G1PPRL_BYTE_H_FORMAT
3063 G1PPRL_BYTE_H_FORMAT,
3064 "", "",
3065 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3066 "(bytes)", "(bytes)");
3067 }
3068
3069 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
3070 const char* type = r->get_type_str();
3071 HeapWord* bottom = r->bottom();
3072 HeapWord* end = r->end();
3073 size_t capacity_bytes = r->capacity();
3074 size_t used_bytes = r->used();
3075 size_t prev_live_bytes = r->live_bytes();
3076 size_t next_live_bytes = r->next_live_bytes();
3077 double gc_eff = r->gc_efficiency();
3078 size_t remset_bytes = r->rem_set()->mem_size();
3079 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3080
3081 _total_used_bytes += used_bytes;
3082 _total_capacity_bytes += capacity_bytes;
3083 _total_prev_live_bytes += prev_live_bytes;
3084 _total_next_live_bytes += next_live_bytes;
3085 _total_remset_bytes += remset_bytes;
3086 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3087
3088 // Print a line for this particular region.
3089 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3090 G1PPRL_TYPE_FORMAT
3091 G1PPRL_ADDR_BASE_FORMAT
3092 G1PPRL_BYTE_FORMAT
3093 G1PPRL_BYTE_FORMAT
3094 G1PPRL_BYTE_FORMAT
3095 G1PPRL_DOUBLE_FORMAT
3096 G1PPRL_BYTE_FORMAT
3097 G1PPRL_BYTE_FORMAT,
3098 type, p2i(bottom), p2i(end),
3099 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3100 remset_bytes, strong_code_roots_bytes);
3101
3102 return false;
3103 }
3104
3105 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3106 // add static memory usages to remembered set sizes
3107 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3108 // Print the footer of the output.
3109 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3110 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3111 " SUMMARY"
3112 G1PPRL_SUM_MB_FORMAT("capacity")
3113 G1PPRL_SUM_MB_PERC_FORMAT("used")
3114 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3115 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3116 G1PPRL_SUM_MB_FORMAT("remset")
3117 G1PPRL_SUM_MB_FORMAT("code-roots"),
3118 bytes_to_mb(_total_capacity_bytes),
3119 bytes_to_mb(_total_used_bytes),
3120 perc(_total_used_bytes, _total_capacity_bytes),
3121 bytes_to_mb(_total_prev_live_bytes),
3122 perc(_total_prev_live_bytes, _total_capacity_bytes),
3123 bytes_to_mb(_total_next_live_bytes),
3124 perc(_total_next_live_bytes, _total_capacity_bytes),
3125 bytes_to_mb(_total_remset_bytes),
3126 bytes_to_mb(_total_strong_code_roots_bytes));
3127 }