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