1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc/g1/concurrentMarkThread.inline.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1CollectorPolicy.hpp"
32 #include "gc/g1/g1CollectorState.hpp"
33 #include "gc/g1/g1ConcurrentMark.inline.hpp"
34 #include "gc/g1/g1HeapVerifier.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1StringDedup.hpp"
37 #include "gc/g1/heapRegion.inline.hpp"
38 #include "gc/g1/heapRegionRemSet.hpp"
39 #include "gc/g1/heapRegionSet.inline.hpp"
40 #include "gc/g1/suspendibleThreadSet.hpp"
41 #include "gc/shared/gcId.hpp"
42 #include "gc/shared/gcTimer.hpp"
43 #include "gc/shared/gcTrace.hpp"
44 #include "gc/shared/gcTraceTime.inline.hpp"
45 #include "gc/shared/genOopClosures.inline.hpp"
46 #include "gc/shared/referencePolicy.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/taskqueue.inline.hpp"
49 #include "gc/shared/vmGCOperations.hpp"
50 #include "logging/log.hpp"
51 #include "memory/allocation.hpp"
52 #include "memory/resourceArea.hpp"
53 #include "oops/oop.inline.hpp"
54 #include "runtime/atomic.inline.hpp"
55 #include "runtime/handles.inline.hpp"
56 #include "runtime/java.hpp"
57 #include "runtime/prefetch.inline.hpp"
58 #include "services/memTracker.hpp"
59
60 // Concurrent marking bit map wrapper
61
62 G1CMBitMapRO::G1CMBitMapRO(int shifter) :
63 _bm(),
64 _shifter(shifter) {
65 _bmStartWord = 0;
66 _bmWordSize = 0;
67 }
68
69 HeapWord* G1CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
70 const HeapWord* limit) const {
71 // First we must round addr *up* to a possible object boundary.
72 addr = (HeapWord*)align_size_up((intptr_t)addr,
73 HeapWordSize << _shifter);
74 size_t addrOffset = heapWordToOffset(addr);
75 assert(limit != NULL, "limit must not be NULL");
76 size_t limitOffset = heapWordToOffset(limit);
77 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
78 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
79 assert(nextAddr >= addr, "get_next_one postcondition");
80 assert(nextAddr == limit || isMarked(nextAddr),
81 "get_next_one postcondition");
82 return nextAddr;
83 }
84
85 #ifndef PRODUCT
86 bool G1CMBitMapRO::covers(MemRegion heap_rs) const {
87 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
88 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
89 "size inconsistency");
90 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
91 _bmWordSize == heap_rs.word_size();
92 }
93 #endif
94
95 void G1CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
96 _bm.print_on_error(st, prefix);
97 }
98
99 size_t G1CMBitMap::compute_size(size_t heap_size) {
100 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
101 }
102
103 size_t G1CMBitMap::mark_distance() {
104 return MinObjAlignmentInBytes * BitsPerByte;
105 }
106
107 void G1CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
108 _bmStartWord = heap.start();
109 _bmWordSize = heap.word_size();
110
111 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
112 _bm.set_size(_bmWordSize >> _shifter);
113
114 storage->set_mapping_changed_listener(&_listener);
115 }
116
117 void G1CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
118 if (zero_filled) {
119 return;
120 }
121 // We need to clear the bitmap on commit, removing any existing information.
122 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
123 _bm->clear_range(mr);
124 }
125
126 void G1CMBitMap::clear_range(MemRegion mr) {
127 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
128 assert(!mr.is_empty(), "unexpected empty region");
129 // convert address range into offset range
130 _bm.at_put_range(heapWordToOffset(mr.start()),
131 heapWordToOffset(mr.end()), false);
132 }
133
134 G1CMMarkStack::G1CMMarkStack(G1ConcurrentMark* cm) :
135 _base(NULL), _cm(cm)
136 {}
137
138 bool G1CMMarkStack::allocate(size_t capacity) {
139 // allocate a stack of the requisite depth
140 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
141 if (!rs.is_reserved()) {
142 warning("ConcurrentMark MarkStack allocation failure");
143 return false;
144 }
145 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
146 if (!_virtual_space.initialize(rs, rs.size())) {
147 warning("ConcurrentMark MarkStack backing store failure");
148 // Release the virtual memory reserved for the marking stack
149 rs.release();
150 return false;
151 }
152 assert(_virtual_space.committed_size() == rs.size(),
153 "Didn't reserve backing store for all of G1ConcurrentMark stack?");
154 _base = (oop*) _virtual_space.low();
155 setEmpty();
156 _capacity = (jint) capacity;
157 _saved_index = -1;
158 _should_expand = false;
159 return true;
160 }
161
162 void G1CMMarkStack::expand() {
163 // Called, during remark, if we've overflown the marking stack during marking.
164 assert(isEmpty(), "stack should been emptied while handling overflow");
165 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
166 // Clear expansion flag
167 _should_expand = false;
168 if (_capacity == (jint) MarkStackSizeMax) {
169 log_trace(gc)("(benign) Can't expand marking stack capacity, at max size limit");
170 return;
171 }
172 // Double capacity if possible
173 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
174 // Do not give up existing stack until we have managed to
175 // get the double capacity that we desired.
176 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
177 sizeof(oop)));
178 if (rs.is_reserved()) {
179 // Release the backing store associated with old stack
180 _virtual_space.release();
181 // Reinitialize virtual space for new stack
182 if (!_virtual_space.initialize(rs, rs.size())) {
183 fatal("Not enough swap for expanded marking stack capacity");
184 }
185 _base = (oop*)(_virtual_space.low());
186 _index = 0;
187 _capacity = new_capacity;
188 } else {
189 // Failed to double capacity, continue;
190 log_trace(gc)("(benign) Failed to expand marking stack capacity from " SIZE_FORMAT "K to " SIZE_FORMAT "K",
191 _capacity / K, new_capacity / K);
192 }
193 }
194
195 void G1CMMarkStack::set_should_expand() {
196 // If we're resetting the marking state because of an
197 // marking stack overflow, record that we should, if
198 // possible, expand the stack.
199 _should_expand = _cm->has_overflown();
200 }
201
202 G1CMMarkStack::~G1CMMarkStack() {
203 if (_base != NULL) {
204 _base = NULL;
205 _virtual_space.release();
206 }
207 }
208
209 void G1CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
210 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
211 jint start = _index;
212 jint next_index = start + n;
213 if (next_index > _capacity) {
214 _overflow = true;
215 return;
216 }
217 // Otherwise.
218 _index = next_index;
219 for (int i = 0; i < n; i++) {
220 int ind = start + i;
221 assert(ind < _capacity, "By overflow test above.");
222 _base[ind] = ptr_arr[i];
223 }
224 }
225
226 bool G1CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
227 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
228 jint index = _index;
229 if (index == 0) {
230 *n = 0;
231 return false;
232 } else {
233 int k = MIN2(max, index);
234 jint new_ind = index - k;
235 for (int j = 0; j < k; j++) {
236 ptr_arr[j] = _base[new_ind + j];
237 }
238 _index = new_ind;
239 *n = k;
240 return true;
241 }
242 }
243
244 void G1CMMarkStack::note_start_of_gc() {
245 assert(_saved_index == -1,
246 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
247 _saved_index = _index;
248 }
249
250 void G1CMMarkStack::note_end_of_gc() {
251 // This is intentionally a guarantee, instead of an assert. If we
252 // accidentally add something to the mark stack during GC, it
253 // will be a correctness issue so it's better if we crash. we'll
254 // only check this once per GC anyway, so it won't be a performance
255 // issue in any way.
256 guarantee(_saved_index == _index,
257 "saved index: %d index: %d", _saved_index, _index);
258 _saved_index = -1;
259 }
260
261 G1CMRootRegions::G1CMRootRegions() :
262 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
263 _should_abort(false), _next_survivor(NULL) { }
264
265 void G1CMRootRegions::init(G1CollectedHeap* g1h, G1ConcurrentMark* cm) {
266 _young_list = g1h->young_list();
267 _cm = cm;
268 }
269
270 void G1CMRootRegions::prepare_for_scan() {
271 assert(!scan_in_progress(), "pre-condition");
272
273 // Currently, only survivors can be root regions.
274 assert(_next_survivor == NULL, "pre-condition");
275 _next_survivor = _young_list->first_survivor_region();
276 _scan_in_progress = (_next_survivor != NULL);
277 _should_abort = false;
278 }
279
280 HeapRegion* G1CMRootRegions::claim_next() {
281 if (_should_abort) {
282 // If someone has set the should_abort flag, we return NULL to
283 // force the caller to bail out of their loop.
284 return NULL;
285 }
286
287 // Currently, only survivors can be root regions.
288 HeapRegion* res = _next_survivor;
289 if (res != NULL) {
290 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
291 // Read it again in case it changed while we were waiting for the lock.
292 res = _next_survivor;
293 if (res != NULL) {
294 if (res == _young_list->last_survivor_region()) {
295 // We just claimed the last survivor so store NULL to indicate
296 // that we're done.
297 _next_survivor = NULL;
298 } else {
299 _next_survivor = res->get_next_young_region();
300 }
301 } else {
302 // Someone else claimed the last survivor while we were trying
303 // to take the lock so nothing else to do.
304 }
305 }
306 assert(res == NULL || res->is_survivor(), "post-condition");
307
308 return res;
309 }
310
311 void G1CMRootRegions::notify_scan_done() {
312 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
313 _scan_in_progress = false;
314 RootRegionScan_lock->notify_all();
315 }
316
317 void G1CMRootRegions::cancel_scan() {
318 notify_scan_done();
319 }
320
321 void G1CMRootRegions::scan_finished() {
322 assert(scan_in_progress(), "pre-condition");
323
324 // Currently, only survivors can be root regions.
325 if (!_should_abort) {
326 assert(_next_survivor == NULL, "we should have claimed all survivors");
327 }
328 _next_survivor = NULL;
329
330 notify_scan_done();
331 }
332
333 bool G1CMRootRegions::wait_until_scan_finished() {
334 if (!scan_in_progress()) return false;
335
336 {
337 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
338 while (scan_in_progress()) {
339 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
340 }
341 }
342 return true;
343 }
344
345 uint G1ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
346 return MAX2((n_par_threads + 2) / 4, 1U);
347 }
348
349 G1ConcurrentMark::G1ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
350 _g1h(g1h),
351 _markBitMap1(),
352 _markBitMap2(),
353 _parallel_marking_threads(0),
354 _max_parallel_marking_threads(0),
355 _sleep_factor(0.0),
356 _marking_task_overhead(1.0),
357 _cleanup_list("Cleanup List"),
358 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
359 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >>
360 CardTableModRefBS::card_shift,
361 false /* in_resource_area*/),
362
363 _prevMarkBitMap(&_markBitMap1),
364 _nextMarkBitMap(&_markBitMap2),
365
366 _markStack(this),
367 // _finger set in set_non_marking_state
368
369 _max_worker_id(ParallelGCThreads),
370 // _active_tasks set in set_non_marking_state
371 // _tasks set inside the constructor
372 _task_queues(new G1CMTaskQueueSet((int) _max_worker_id)),
373 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
374
375 _has_overflown(false),
376 _concurrent(false),
377 _has_aborted(false),
378 _restart_for_overflow(false),
379 _concurrent_marking_in_progress(false),
380 _concurrent_phase_status(ConcPhaseNotStarted),
381
382 // _verbose_level set below
383
384 _init_times(),
385 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
386 _cleanup_times(),
387 _total_counting_time(0.0),
388 _total_rs_scrub_time(0.0),
389
390 _parallel_workers(NULL),
391
392 _count_card_bitmaps(NULL),
393 _count_marked_bytes(NULL),
394 _completed_initialization(false) {
395
396 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
397 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
398
399 // Create & start a ConcurrentMark thread.
400 _cmThread = new ConcurrentMarkThread(this);
401 assert(cmThread() != NULL, "CM Thread should have been created");
402 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
403 if (_cmThread->osthread() == NULL) {
404 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
405 }
406
407 assert(CGC_lock != NULL, "Where's the CGC_lock?");
408 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
409 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
410
411 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
412 satb_qs.set_buffer_size(G1SATBBufferSize);
413
414 _root_regions.init(_g1h, this);
415
416 if (ConcGCThreads > ParallelGCThreads) {
417 warning("Can't have more ConcGCThreads (%u) "
418 "than ParallelGCThreads (%u).",
419 ConcGCThreads, ParallelGCThreads);
420 return;
421 }
422 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
423 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
424 // if both are set
425 _sleep_factor = 0.0;
426 _marking_task_overhead = 1.0;
427 } else if (G1MarkingOverheadPercent > 0) {
428 // We will calculate the number of parallel marking threads based
429 // on a target overhead with respect to the soft real-time goal
430 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
431 double overall_cm_overhead =
432 (double) MaxGCPauseMillis * marking_overhead /
433 (double) GCPauseIntervalMillis;
434 double cpu_ratio = 1.0 / (double) os::processor_count();
435 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
436 double marking_task_overhead =
437 overall_cm_overhead / marking_thread_num *
438 (double) os::processor_count();
439 double sleep_factor =
440 (1.0 - marking_task_overhead) / marking_task_overhead;
441
442 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
443 _sleep_factor = sleep_factor;
444 _marking_task_overhead = marking_task_overhead;
445 } else {
446 // Calculate the number of parallel marking threads by scaling
447 // the number of parallel GC threads.
448 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
449 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
450 _sleep_factor = 0.0;
451 _marking_task_overhead = 1.0;
452 }
453
454 assert(ConcGCThreads > 0, "Should have been set");
455 _parallel_marking_threads = ConcGCThreads;
456 _max_parallel_marking_threads = _parallel_marking_threads;
457
458 _parallel_workers = new WorkGang("G1 Marker",
459 _max_parallel_marking_threads, false, true);
460 if (_parallel_workers == NULL) {
461 vm_exit_during_initialization("Failed necessary allocation.");
462 } else {
463 _parallel_workers->initialize_workers();
464 }
465
466 if (FLAG_IS_DEFAULT(MarkStackSize)) {
467 size_t mark_stack_size =
468 MIN2(MarkStackSizeMax,
469 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
470 // Verify that the calculated value for MarkStackSize is in range.
471 // It would be nice to use the private utility routine from Arguments.
472 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
473 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
474 "must be between 1 and " SIZE_FORMAT,
475 mark_stack_size, MarkStackSizeMax);
476 return;
477 }
478 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
479 } else {
480 // Verify MarkStackSize is in range.
481 if (FLAG_IS_CMDLINE(MarkStackSize)) {
482 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
483 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
484 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
485 "must be between 1 and " SIZE_FORMAT,
486 MarkStackSize, MarkStackSizeMax);
487 return;
488 }
489 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
490 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
491 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
492 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
493 MarkStackSize, MarkStackSizeMax);
494 return;
495 }
496 }
497 }
498 }
499
500 if (!_markStack.allocate(MarkStackSize)) {
501 warning("Failed to allocate CM marking stack");
502 return;
503 }
504
505 _tasks = NEW_C_HEAP_ARRAY(G1CMTask*, _max_worker_id, mtGC);
506 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
507
508 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
509 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
510
511 BitMap::idx_t card_bm_size = _card_bm.size();
512
513 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
514 _active_tasks = _max_worker_id;
515
516 uint max_regions = _g1h->max_regions();
517 for (uint i = 0; i < _max_worker_id; ++i) {
518 G1CMTaskQueue* task_queue = new G1CMTaskQueue();
519 task_queue->initialize();
520 _task_queues->register_queue(i, task_queue);
521
522 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
523 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
524
525 _tasks[i] = new G1CMTask(i, this,
526 _count_marked_bytes[i],
527 &_count_card_bitmaps[i],
528 task_queue, _task_queues);
529
530 _accum_task_vtime[i] = 0.0;
531 }
532
533 // Calculate the card number for the bottom of the heap. Used
534 // in biasing indexes into the accounting card bitmaps.
535 _heap_bottom_card_num =
536 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
537 CardTableModRefBS::card_shift);
538
539 // Clear all the liveness counting data
540 clear_all_count_data();
541
542 // so that the call below can read a sensible value
543 _heap_start = g1h->reserved_region().start();
544 set_non_marking_state();
545 _completed_initialization = true;
546 }
547
548 void G1ConcurrentMark::reset() {
549 // Starting values for these two. This should be called in a STW
550 // phase.
551 MemRegion reserved = _g1h->g1_reserved();
552 _heap_start = reserved.start();
553 _heap_end = reserved.end();
554
555 // Separated the asserts so that we know which one fires.
556 assert(_heap_start != NULL, "heap bounds should look ok");
557 assert(_heap_end != NULL, "heap bounds should look ok");
558 assert(_heap_start < _heap_end, "heap bounds should look ok");
559
560 // Reset all the marking data structures and any necessary flags
561 reset_marking_state();
562
563 // We do reset all of them, since different phases will use
564 // different number of active threads. So, it's easiest to have all
565 // of them ready.
566 for (uint i = 0; i < _max_worker_id; ++i) {
567 _tasks[i]->reset(_nextMarkBitMap);
568 }
569
570 // we need this to make sure that the flag is on during the evac
571 // pause with initial mark piggy-backed
572 set_concurrent_marking_in_progress();
573 }
574
575
576 void G1ConcurrentMark::reset_marking_state(bool clear_overflow) {
577 _markStack.set_should_expand();
578 _markStack.setEmpty(); // Also clears the _markStack overflow flag
579 if (clear_overflow) {
580 clear_has_overflown();
581 } else {
582 assert(has_overflown(), "pre-condition");
583 }
584 _finger = _heap_start;
585
586 for (uint i = 0; i < _max_worker_id; ++i) {
587 G1CMTaskQueue* queue = _task_queues->queue(i);
588 queue->set_empty();
589 }
590 }
591
592 void G1ConcurrentMark::set_concurrency(uint active_tasks) {
593 assert(active_tasks <= _max_worker_id, "we should not have more");
594
595 _active_tasks = active_tasks;
596 // Need to update the three data structures below according to the
597 // number of active threads for this phase.
598 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
599 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
600 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
601 }
602
603 void G1ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
604 set_concurrency(active_tasks);
605
606 _concurrent = concurrent;
607 // We propagate this to all tasks, not just the active ones.
608 for (uint i = 0; i < _max_worker_id; ++i)
609 _tasks[i]->set_concurrent(concurrent);
610
611 if (concurrent) {
612 set_concurrent_marking_in_progress();
613 } else {
614 // We currently assume that the concurrent flag has been set to
615 // false before we start remark. At this point we should also be
616 // in a STW phase.
617 assert(!concurrent_marking_in_progress(), "invariant");
618 assert(out_of_regions(),
619 "only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
620 p2i(_finger), p2i(_heap_end));
621 }
622 }
623
624 void G1ConcurrentMark::set_non_marking_state() {
625 // We set the global marking state to some default values when we're
626 // not doing marking.
627 reset_marking_state();
628 _active_tasks = 0;
629 clear_concurrent_marking_in_progress();
630 }
631
632 G1ConcurrentMark::~G1ConcurrentMark() {
633 // The G1ConcurrentMark instance is never freed.
634 ShouldNotReachHere();
635 }
636
637 class G1ClearBitMapTask : public AbstractGangTask {
638 // Heap region closure used for clearing the given mark bitmap.
639 class G1ClearBitmapHRClosure : public HeapRegionClosure {
640 private:
641 G1CMBitMap* _bitmap;
642 G1ConcurrentMark* _cm;
643 public:
644 G1ClearBitmapHRClosure(G1CMBitMap* bitmap, G1ConcurrentMark* cm) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap) {
645 }
646
647 virtual bool doHeapRegion(HeapRegion* r) {
648 size_t const chunk_size_in_words = M / HeapWordSize;
649
650 HeapWord* cur = r->bottom();
651 HeapWord* const end = r->end();
652
653 while (cur < end) {
654 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
655 _bitmap->clear_range(mr);
656
657 cur += chunk_size_in_words;
658
659 // Abort iteration if after yielding the marking has been aborted.
660 if (_cm != NULL && _cm->do_yield_check() && _cm->has_aborted()) {
661 return true;
662 }
663 // Repeat the asserts from before the start of the closure. We will do them
664 // as asserts here to minimize their overhead on the product. However, we
665 // will have them as guarantees at the beginning / end of the bitmap
666 // clearing to get some checking in the product.
667 assert(_cm == NULL || _cm->cmThread()->during_cycle(), "invariant");
668 assert(_cm == NULL || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
669 }
670 assert(cur == end, "Must have completed iteration over the bitmap for region %u.", r->hrm_index());
671
672 return false;
673 }
674 };
675
676 G1ClearBitmapHRClosure _cl;
677 HeapRegionClaimer _hr_claimer;
678 bool _suspendible; // If the task is suspendible, workers must join the STS.
679
680 public:
681 G1ClearBitMapTask(G1CMBitMap* bitmap, G1ConcurrentMark* cm, uint n_workers, bool suspendible) :
682 AbstractGangTask("Parallel Clear Bitmap Task"),
683 _cl(bitmap, suspendible ? cm : NULL),
684 _hr_claimer(n_workers),
685 _suspendible(suspendible)
686 { }
687
688 void work(uint worker_id) {
689 SuspendibleThreadSetJoiner sts_join(_suspendible);
690 G1CollectedHeap::heap()->heap_region_par_iterate(&_cl, worker_id, &_hr_claimer, true);
691 }
692
693 bool is_complete() {
694 return _cl.complete();
695 }
696 };
697
698 void G1ConcurrentMark::clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield) {
699 G1ClearBitMapTask task(bitmap, this, workers->active_workers(), may_yield);
700 workers->run_task(&task);
701 guarantee(!may_yield || task.is_complete(), "Must have completed iteration when not yielding.");
702 }
703
704 void G1ConcurrentMark::cleanup_for_next_mark() {
705 // Make sure that the concurrent mark thread looks to still be in
706 // the current cycle.
707 guarantee(cmThread()->during_cycle(), "invariant");
708
709 // We are finishing up the current cycle by clearing the next
710 // marking bitmap and getting it ready for the next cycle. During
711 // this time no other cycle can start. So, let's make sure that this
712 // is the case.
713 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
714
715 clear_bitmap(_nextMarkBitMap, _parallel_workers, true);
716
717 // Clear the liveness counting data. If the marking has been aborted, the abort()
718 // call already did that.
719 if (!has_aborted()) {
720 clear_all_count_data();
721 }
722
723 // Repeat the asserts from above.
724 guarantee(cmThread()->during_cycle(), "invariant");
725 guarantee(!_g1h->collector_state()->mark_in_progress(), "invariant");
726 }
727
728 void G1ConcurrentMark::clear_prev_bitmap(WorkGang* workers) {
729 assert(SafepointSynchronize::is_at_safepoint(), "Should only clear the entire prev bitmap at a safepoint.");
730 clear_bitmap((G1CMBitMap*)_prevMarkBitMap, workers, false);
731 }
732
733 class CheckBitmapClearHRClosure : public HeapRegionClosure {
734 G1CMBitMap* _bitmap;
735 bool _error;
736 public:
737 CheckBitmapClearHRClosure(G1CMBitMap* bitmap) : _bitmap(bitmap) {
738 }
739
740 virtual bool doHeapRegion(HeapRegion* r) {
741 // This closure can be called concurrently to the mutator, so we must make sure
742 // that the result of the getNextMarkedWordAddress() call is compared to the
743 // value passed to it as limit to detect any found bits.
744 // end never changes in G1.
745 HeapWord* end = r->end();
746 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
747 }
748 };
749
750 bool G1ConcurrentMark::nextMarkBitmapIsClear() {
751 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
752 _g1h->heap_region_iterate(&cl);
753 return cl.complete();
754 }
755
756 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
757 public:
758 bool doHeapRegion(HeapRegion* r) {
759 r->note_start_of_marking();
760 return false;
761 }
762 };
763
764 void G1ConcurrentMark::checkpointRootsInitialPre() {
765 G1CollectedHeap* g1h = G1CollectedHeap::heap();
766 G1CollectorPolicy* g1p = g1h->g1_policy();
767
768 _has_aborted = false;
769
770 // Initialize marking structures. This has to be done in a STW phase.
771 reset();
772
773 // For each region note start of marking.
774 NoteStartOfMarkHRClosure startcl;
775 g1h->heap_region_iterate(&startcl);
776 }
777
778
779 void G1ConcurrentMark::checkpointRootsInitialPost() {
780 G1CollectedHeap* g1h = G1CollectedHeap::heap();
781
782 // Start Concurrent Marking weak-reference discovery.
783 ReferenceProcessor* rp = g1h->ref_processor_cm();
784 // enable ("weak") refs discovery
785 rp->enable_discovery();
786 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
787
788 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
789 // This is the start of the marking cycle, we're expected all
790 // threads to have SATB queues with active set to false.
791 satb_mq_set.set_active_all_threads(true, /* new active value */
792 false /* expected_active */);
793
794 _root_regions.prepare_for_scan();
795
796 // update_g1_committed() will be called at the end of an evac pause
797 // when marking is on. So, it's also called at the end of the
798 // initial-mark pause to update the heap end, if the heap expands
799 // during it. No need to call it here.
800 }
801
802 /*
803 * Notice that in the next two methods, we actually leave the STS
804 * during the barrier sync and join it immediately afterwards. If we
805 * do not do this, the following deadlock can occur: one thread could
806 * be in the barrier sync code, waiting for the other thread to also
807 * sync up, whereas another one could be trying to yield, while also
808 * waiting for the other threads to sync up too.
809 *
810 * Note, however, that this code is also used during remark and in
811 * this case we should not attempt to leave / enter the STS, otherwise
812 * we'll either hit an assert (debug / fastdebug) or deadlock
813 * (product). So we should only leave / enter the STS if we are
814 * operating concurrently.
815 *
816 * Because the thread that does the sync barrier has left the STS, it
817 * is possible to be suspended for a Full GC or an evacuation pause
818 * could occur. This is actually safe, since the entering the sync
819 * barrier is one of the last things do_marking_step() does, and it
820 * doesn't manipulate any data structures afterwards.
821 */
822
823 void G1ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
824 bool barrier_aborted;
825 {
826 SuspendibleThreadSetLeaver sts_leave(concurrent());
827 barrier_aborted = !_first_overflow_barrier_sync.enter();
828 }
829
830 // at this point everyone should have synced up and not be doing any
831 // more work
832
833 if (barrier_aborted) {
834 // If the barrier aborted we ignore the overflow condition and
835 // just abort the whole marking phase as quickly as possible.
836 return;
837 }
838
839 // If we're executing the concurrent phase of marking, reset the marking
840 // state; otherwise the marking state is reset after reference processing,
841 // during the remark pause.
842 // If we reset here as a result of an overflow during the remark we will
843 // see assertion failures from any subsequent set_concurrency_and_phase()
844 // calls.
845 if (concurrent()) {
846 // let the task associated with with worker 0 do this
847 if (worker_id == 0) {
848 // task 0 is responsible for clearing the global data structures
849 // We should be here because of an overflow. During STW we should
850 // not clear the overflow flag since we rely on it being true when
851 // we exit this method to abort the pause and restart concurrent
852 // marking.
853 reset_marking_state(true /* clear_overflow */);
854
855 log_info(gc)("Concurrent Mark reset for overflow");
856 }
857 }
858
859 // after this, each task should reset its own data structures then
860 // then go into the second barrier
861 }
862
863 void G1ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
864 SuspendibleThreadSetLeaver sts_leave(concurrent());
865 _second_overflow_barrier_sync.enter();
866
867 // at this point everything should be re-initialized and ready to go
868 }
869
870 class G1CMConcurrentMarkingTask: public AbstractGangTask {
871 private:
872 G1ConcurrentMark* _cm;
873 ConcurrentMarkThread* _cmt;
874
875 public:
876 void work(uint worker_id) {
877 assert(Thread::current()->is_ConcurrentGC_thread(),
878 "this should only be done by a conc GC thread");
879 ResourceMark rm;
880
881 double start_vtime = os::elapsedVTime();
882
883 {
884 SuspendibleThreadSetJoiner sts_join;
885
886 assert(worker_id < _cm->active_tasks(), "invariant");
887 G1CMTask* the_task = _cm->task(worker_id);
888 the_task->record_start_time();
889 if (!_cm->has_aborted()) {
890 do {
891 double start_vtime_sec = os::elapsedVTime();
892 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
893
894 the_task->do_marking_step(mark_step_duration_ms,
895 true /* do_termination */,
896 false /* is_serial*/);
897
898 double end_vtime_sec = os::elapsedVTime();
899 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
900 _cm->clear_has_overflown();
901
902 _cm->do_yield_check(worker_id);
903
904 jlong sleep_time_ms;
905 if (!_cm->has_aborted() && the_task->has_aborted()) {
906 sleep_time_ms =
907 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
908 {
909 SuspendibleThreadSetLeaver sts_leave;
910 os::sleep(Thread::current(), sleep_time_ms, false);
911 }
912 }
913 } while (!_cm->has_aborted() && the_task->has_aborted());
914 }
915 the_task->record_end_time();
916 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
917 }
918
919 double end_vtime = os::elapsedVTime();
920 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
921 }
922
923 G1CMConcurrentMarkingTask(G1ConcurrentMark* cm,
924 ConcurrentMarkThread* cmt) :
925 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
926
927 ~G1CMConcurrentMarkingTask() { }
928 };
929
930 // Calculates the number of active workers for a concurrent
931 // phase.
932 uint G1ConcurrentMark::calc_parallel_marking_threads() {
933 uint n_conc_workers = 0;
934 if (!UseDynamicNumberOfGCThreads ||
935 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
936 !ForceDynamicNumberOfGCThreads)) {
937 n_conc_workers = max_parallel_marking_threads();
938 } else {
939 n_conc_workers =
940 AdaptiveSizePolicy::calc_default_active_workers(
941 max_parallel_marking_threads(),
942 1, /* Minimum workers */
943 parallel_marking_threads(),
944 Threads::number_of_non_daemon_threads());
945 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
946 // that scaling has already gone into "_max_parallel_marking_threads".
947 }
948 assert(n_conc_workers > 0, "Always need at least 1");
949 return n_conc_workers;
950 }
951
952 void G1ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
953 // Currently, only survivors can be root regions.
954 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
955 G1RootRegionScanClosure cl(_g1h, this, worker_id);
956
957 const uintx interval = PrefetchScanIntervalInBytes;
958 HeapWord* curr = hr->bottom();
959 const HeapWord* end = hr->top();
960 while (curr < end) {
961 Prefetch::read(curr, interval);
962 oop obj = oop(curr);
963 int size = obj->oop_iterate_size(&cl);
964 assert(size == obj->size(), "sanity");
965 curr += size;
966 }
967 }
968
969 class G1CMRootRegionScanTask : public AbstractGangTask {
970 private:
971 G1ConcurrentMark* _cm;
972
973 public:
974 G1CMRootRegionScanTask(G1ConcurrentMark* cm) :
975 AbstractGangTask("Root Region Scan"), _cm(cm) { }
976
977 void work(uint worker_id) {
978 assert(Thread::current()->is_ConcurrentGC_thread(),
979 "this should only be done by a conc GC thread");
980
981 G1CMRootRegions* root_regions = _cm->root_regions();
982 HeapRegion* hr = root_regions->claim_next();
983 while (hr != NULL) {
984 _cm->scanRootRegion(hr, worker_id);
985 hr = root_regions->claim_next();
986 }
987 }
988 };
989
990 void G1ConcurrentMark::scanRootRegions() {
991 // scan_in_progress() will have been set to true only if there was
992 // at least one root region to scan. So, if it's false, we
993 // should not attempt to do any further work.
994 if (root_regions()->scan_in_progress()) {
995 assert(!has_aborted(), "Aborting before root region scanning is finished not supported.");
996 GCTraceConcTime(Info, gc) tt("Concurrent Root Region Scan");
997
998 _parallel_marking_threads = calc_parallel_marking_threads();
999 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1000 "Maximum number of marking threads exceeded");
1001 uint active_workers = MAX2(1U, parallel_marking_threads());
1002
1003 G1CMRootRegionScanTask task(this);
1004 _parallel_workers->set_active_workers(active_workers);
1005 _parallel_workers->run_task(&task);
1006
1007 // It's possible that has_aborted() is true here without actually
1008 // aborting the survivor scan earlier. This is OK as it's
1009 // mainly used for sanity checking.
1010 root_regions()->scan_finished();
1011 }
1012 }
1013
1014 void G1ConcurrentMark::register_concurrent_phase_start(const char* title) {
1015 uint old_val = 0;
1016 do {
1017 old_val = Atomic::cmpxchg(ConcPhaseStarted, &_concurrent_phase_status, ConcPhaseNotStarted);
1018 } while (old_val != ConcPhaseNotStarted);
1019 _g1h->gc_timer_cm()->register_gc_concurrent_start(title);
1020 }
1021
1022 void G1ConcurrentMark::register_concurrent_phase_end_common(bool end_timer) {
1023 if (_concurrent_phase_status == ConcPhaseNotStarted) {
1024 return;
1025 }
1026
1027 uint old_val = Atomic::cmpxchg(ConcPhaseStopping, &_concurrent_phase_status, ConcPhaseStarted);
1028 if (old_val == ConcPhaseStarted) {
1029 _g1h->gc_timer_cm()->register_gc_concurrent_end();
1030 // If 'end_timer' is true, we came here to end timer which needs concurrent phase ended.
1031 // We need to end it before changing the status to 'ConcPhaseNotStarted' to prevent
1032 // starting a new concurrent phase by 'ConcurrentMarkThread'.
1033 if (end_timer) {
1034 _g1h->gc_timer_cm()->register_gc_end();
1035 }
1036 old_val = Atomic::cmpxchg(ConcPhaseNotStarted, &_concurrent_phase_status, ConcPhaseStopping);
1037 assert(old_val == ConcPhaseStopping, "Should not have changed since we entered this scope.");
1038 } else {
1039 do {
1040 // Let other thread finish changing '_concurrent_phase_status' to 'ConcPhaseNotStarted'.
1041 os::naked_short_sleep(1);
1042 } while (_concurrent_phase_status != ConcPhaseNotStarted);
1043 }
1044 }
1045
1046 void G1ConcurrentMark::register_concurrent_phase_end() {
1047 register_concurrent_phase_end_common(false);
1048 }
1049
1050 void G1ConcurrentMark::register_concurrent_gc_end_and_stop_timer() {
1051 register_concurrent_phase_end_common(true);
1052 }
1053
1054 void G1ConcurrentMark::markFromRoots() {
1055 // we might be tempted to assert that:
1056 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1057 // "inconsistent argument?");
1058 // However that wouldn't be right, because it's possible that
1059 // a safepoint is indeed in progress as a younger generation
1060 // stop-the-world GC happens even as we mark in this generation.
1061
1062 _restart_for_overflow = false;
1063
1064 // _g1h has _n_par_threads
1065 _parallel_marking_threads = calc_parallel_marking_threads();
1066 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1067 "Maximum number of marking threads exceeded");
1068
1069 uint active_workers = MAX2(1U, parallel_marking_threads());
1070 assert(active_workers > 0, "Should have been set");
1071
1072 // Parallel task terminator is set in "set_concurrency_and_phase()"
1073 set_concurrency_and_phase(active_workers, true /* concurrent */);
1074
1075 G1CMConcurrentMarkingTask markingTask(this, cmThread());
1076 _parallel_workers->set_active_workers(active_workers);
1077 _parallel_workers->run_task(&markingTask);
1078 print_stats();
1079 }
1080
1081 void G1ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1082 // world is stopped at this checkpoint
1083 assert(SafepointSynchronize::is_at_safepoint(),
1084 "world should be stopped");
1085
1086 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1087
1088 // If a full collection has happened, we shouldn't do this.
1089 if (has_aborted()) {
1090 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1091 return;
1092 }
1093
1094 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1095
1096 if (VerifyDuringGC) {
1097 HandleMark hm; // handle scope
1098 g1h->prepare_for_verify();
1099 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1100 }
1101 g1h->verifier()->check_bitmaps("Remark Start");
1102
1103 G1CollectorPolicy* g1p = g1h->g1_policy();
1104 g1p->record_concurrent_mark_remark_start();
1105
1106 double start = os::elapsedTime();
1107
1108 checkpointRootsFinalWork();
1109
1110 double mark_work_end = os::elapsedTime();
1111
1112 weakRefsWork(clear_all_soft_refs);
1113
1114 if (has_overflown()) {
1115 // Oops. We overflowed. Restart concurrent marking.
1116 _restart_for_overflow = true;
1117 log_develop_trace(gc)("Remark led to restart for overflow.");
1118
1119 // Verify the heap w.r.t. the previous marking bitmap.
1120 if (VerifyDuringGC) {
1121 HandleMark hm; // handle scope
1122 g1h->prepare_for_verify();
1123 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (overflow)");
1124 }
1125
1126 // Clear the marking state because we will be restarting
1127 // marking due to overflowing the global mark stack.
1128 reset_marking_state();
1129 } else {
1130 {
1131 GCTraceTime(Debug, gc) trace("Aggregate Data", g1h->gc_timer_cm());
1132
1133 // Aggregate the per-task counting data that we have accumulated
1134 // while marking.
1135 aggregate_count_data();
1136 }
1137
1138 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1139 // We're done with marking.
1140 // This is the end of the marking cycle, we're expected all
1141 // threads to have SATB queues with active set to true.
1142 satb_mq_set.set_active_all_threads(false, /* new active value */
1143 true /* expected_active */);
1144
1145 if (VerifyDuringGC) {
1146 HandleMark hm; // handle scope
1147 g1h->prepare_for_verify();
1148 Universe::verify(VerifyOption_G1UseNextMarking, "During GC (after)");
1149 }
1150 g1h->verifier()->check_bitmaps("Remark End");
1151 assert(!restart_for_overflow(), "sanity");
1152 // Completely reset the marking state since marking completed
1153 set_non_marking_state();
1154 }
1155
1156 // Expand the marking stack, if we have to and if we can.
1157 if (_markStack.should_expand()) {
1158 _markStack.expand();
1159 }
1160
1161 // Statistics
1162 double now = os::elapsedTime();
1163 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1164 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1165 _remark_times.add((now - start) * 1000.0);
1166
1167 g1p->record_concurrent_mark_remark_end();
1168
1169 G1CMIsAliveClosure is_alive(g1h);
1170 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1171 }
1172
1173 // Base class of the closures that finalize and verify the
1174 // liveness counting data.
1175 class G1CMCountDataClosureBase: public HeapRegionClosure {
1176 protected:
1177 G1CollectedHeap* _g1h;
1178 G1ConcurrentMark* _cm;
1179 CardTableModRefBS* _ct_bs;
1180
1181 BitMap* _region_bm;
1182 BitMap* _card_bm;
1183
1184 // Takes a region that's not empty (i.e., it has at least one
1185 // live object in it and sets its corresponding bit on the region
1186 // bitmap to 1.
1187 void set_bit_for_region(HeapRegion* hr) {
1188 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1189 _region_bm->par_at_put(index, true);
1190 }
1191
1192 public:
1193 G1CMCountDataClosureBase(G1CollectedHeap* g1h,
1194 BitMap* region_bm, BitMap* card_bm):
1195 _g1h(g1h), _cm(g1h->concurrent_mark()),
1196 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
1197 _region_bm(region_bm), _card_bm(card_bm) { }
1198 };
1199
1200 // Closure that calculates the # live objects per region. Used
1201 // for verification purposes during the cleanup pause.
1202 class CalcLiveObjectsClosure: public G1CMCountDataClosureBase {
1203 G1CMBitMapRO* _bm;
1204 size_t _region_marked_bytes;
1205
1206 public:
1207 CalcLiveObjectsClosure(G1CMBitMapRO *bm, G1CollectedHeap* g1h,
1208 BitMap* region_bm, BitMap* card_bm) :
1209 G1CMCountDataClosureBase(g1h, region_bm, card_bm),
1210 _bm(bm), _region_marked_bytes(0) { }
1211
1212 bool doHeapRegion(HeapRegion* hr) {
1213 HeapWord* ntams = hr->next_top_at_mark_start();
1214 HeapWord* start = hr->bottom();
1215
1216 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1217 "Preconditions not met - "
1218 "start: " PTR_FORMAT ", ntams: " PTR_FORMAT ", end: " PTR_FORMAT,
1219 p2i(start), p2i(ntams), p2i(hr->end()));
1220
1221 // Find the first marked object at or after "start".
1222 start = _bm->getNextMarkedWordAddress(start, ntams);
1223
1224 size_t marked_bytes = 0;
1225
1226 while (start < ntams) {
1227 oop obj = oop(start);
1228 int obj_sz = obj->size();
1229 HeapWord* obj_end = start + obj_sz;
1230
1231 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1232 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1233
1234 // Note: if we're looking at the last region in heap - obj_end
1235 // could be actually just beyond the end of the heap; end_idx
1236 // will then correspond to a (non-existent) card that is also
1237 // just beyond the heap.
1238 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1239 // end of object is not card aligned - increment to cover
1240 // all the cards spanned by the object
1241 end_idx += 1;
1242 }
1243
1244 // Set the bits in the card BM for the cards spanned by this object.
1245 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1246
1247 // Add the size of this object to the number of marked bytes.
1248 marked_bytes += (size_t)obj_sz * HeapWordSize;
1249
1250 // This will happen if we are handling a humongous object that spans
1251 // several heap regions.
1252 if (obj_end > hr->end()) {
1253 break;
1254 }
1255 // Find the next marked object after this one.
1256 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1257 }
1258
1259 // Mark the allocated-since-marking portion...
1260 HeapWord* top = hr->top();
1261 if (ntams < top) {
1262 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1263 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1264
1265 // Note: if we're looking at the last region in heap - top
1266 // could be actually just beyond the end of the heap; end_idx
1267 // will then correspond to a (non-existent) card that is also
1268 // just beyond the heap.
1269 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1270 // end of object is not card aligned - increment to cover
1271 // all the cards spanned by the object
1272 end_idx += 1;
1273 }
1274 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1275
1276 // This definitely means the region has live objects.
1277 set_bit_for_region(hr);
1278 }
1279
1280 // Update the live region bitmap.
1281 if (marked_bytes > 0) {
1282 set_bit_for_region(hr);
1283 }
1284
1285 // Set the marked bytes for the current region so that
1286 // it can be queried by a calling verification routine
1287 _region_marked_bytes = marked_bytes;
1288
1289 return false;
1290 }
1291
1292 size_t region_marked_bytes() const { return _region_marked_bytes; }
1293 };
1294
1295 // Heap region closure used for verifying the counting data
1296 // that was accumulated concurrently and aggregated during
1297 // the remark pause. This closure is applied to the heap
1298 // regions during the STW cleanup pause.
1299
1300 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1301 G1CollectedHeap* _g1h;
1302 G1ConcurrentMark* _cm;
1303 CalcLiveObjectsClosure _calc_cl;
1304 BitMap* _region_bm; // Region BM to be verified
1305 BitMap* _card_bm; // Card BM to be verified
1306
1307 BitMap* _exp_region_bm; // Expected Region BM values
1308 BitMap* _exp_card_bm; // Expected card BM values
1309
1310 int _failures;
1311
1312 public:
1313 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1314 BitMap* region_bm,
1315 BitMap* card_bm,
1316 BitMap* exp_region_bm,
1317 BitMap* exp_card_bm) :
1318 _g1h(g1h), _cm(g1h->concurrent_mark()),
1319 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1320 _region_bm(region_bm), _card_bm(card_bm),
1321 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1322 _failures(0) { }
1323
1324 int failures() const { return _failures; }
1325
1326 bool doHeapRegion(HeapRegion* hr) {
1327 int failures = 0;
1328
1329 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1330 // this region and set the corresponding bits in the expected region
1331 // and card bitmaps.
1332 bool res = _calc_cl.doHeapRegion(hr);
1333 assert(res == false, "should be continuing");
1334
1335 // Verify the marked bytes for this region.
1336 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1337 size_t act_marked_bytes = hr->next_marked_bytes();
1338
1339 if (exp_marked_bytes > act_marked_bytes) {
1340 if (hr->is_starts_humongous()) {
1341 // For start_humongous regions, the size of the whole object will be
1342 // in exp_marked_bytes.
1343 HeapRegion* region = hr;
1344 int num_regions;
1345 for (num_regions = 0; region != NULL; num_regions++) {
1346 region = _g1h->next_region_in_humongous(region);
1347 }
1348 if ((num_regions-1) * HeapRegion::GrainBytes >= exp_marked_bytes) {
1349 failures += 1;
1350 } else if (num_regions * HeapRegion::GrainBytes < exp_marked_bytes) {
1351 failures += 1;
1352 }
1353 } else {
1354 // We're not OK if expected marked bytes > actual marked bytes. It means
1355 // we have missed accounting some objects during the actual marking.
1356 failures += 1;
1357 }
1358 }
1359
1360 // Verify the bit, for this region, in the actual and expected
1361 // (which was just calculated) region bit maps.
1362 // We're not OK if the bit in the calculated expected region
1363 // bitmap is set and the bit in the actual region bitmap is not.
1364 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1365
1366 bool expected = _exp_region_bm->at(index);
1367 bool actual = _region_bm->at(index);
1368 if (expected && !actual) {
1369 failures += 1;
1370 }
1371
1372 // Verify that the card bit maps for the cards spanned by the current
1373 // region match. We have an error if we have a set bit in the expected
1374 // bit map and the corresponding bit in the actual bitmap is not set.
1375
1376 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1377 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1378
1379 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1380 expected = _exp_card_bm->at(i);
1381 actual = _card_bm->at(i);
1382
1383 if (expected && !actual) {
1384 failures += 1;
1385 }
1386 }
1387
1388 _failures += failures;
1389
1390 // We could stop iteration over the heap when we
1391 // find the first violating region by returning true.
1392 return false;
1393 }
1394 };
1395
1396 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1397 protected:
1398 G1CollectedHeap* _g1h;
1399 G1ConcurrentMark* _cm;
1400 BitMap* _actual_region_bm;
1401 BitMap* _actual_card_bm;
1402
1403 uint _n_workers;
1404
1405 BitMap* _expected_region_bm;
1406 BitMap* _expected_card_bm;
1407
1408 int _failures;
1409
1410 HeapRegionClaimer _hrclaimer;
1411
1412 public:
1413 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1414 BitMap* region_bm, BitMap* card_bm,
1415 BitMap* expected_region_bm, BitMap* expected_card_bm)
1416 : AbstractGangTask("G1 verify final counting"),
1417 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1418 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1419 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1420 _failures(0),
1421 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1422 assert(VerifyDuringGC, "don't call this otherwise");
1423 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1424 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1425 }
1426
1427 void work(uint worker_id) {
1428 assert(worker_id < _n_workers, "invariant");
1429
1430 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1431 _actual_region_bm, _actual_card_bm,
1432 _expected_region_bm,
1433 _expected_card_bm);
1434
1435 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer);
1436
1437 Atomic::add(verify_cl.failures(), &_failures);
1438 }
1439
1440 int failures() const { return _failures; }
1441 };
1442
1443 // Closure that finalizes the liveness counting data.
1444 // Used during the cleanup pause.
1445 // Sets the bits corresponding to the interval [NTAMS, top]
1446 // (which contains the implicitly live objects) in the
1447 // card liveness bitmap. Also sets the bit for each region,
1448 // containing live data, in the region liveness bitmap.
1449
1450 class FinalCountDataUpdateClosure: public G1CMCountDataClosureBase {
1451 public:
1452 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1453 BitMap* region_bm,
1454 BitMap* card_bm) :
1455 G1CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1456
1457 bool doHeapRegion(HeapRegion* hr) {
1458 HeapWord* ntams = hr->next_top_at_mark_start();
1459 HeapWord* top = hr->top();
1460
1461 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1462
1463 // Mark the allocated-since-marking portion...
1464 if (ntams < top) {
1465 // This definitely means the region has live objects.
1466 set_bit_for_region(hr);
1467
1468 // Now set the bits in the card bitmap for [ntams, top)
1469 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1470 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1471
1472 // Note: if we're looking at the last region in heap - top
1473 // could be actually just beyond the end of the heap; end_idx
1474 // will then correspond to a (non-existent) card that is also
1475 // just beyond the heap.
1476 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1477 // end of object is not card aligned - increment to cover
1478 // all the cards spanned by the object
1479 end_idx += 1;
1480 }
1481
1482 assert(end_idx <= _card_bm->size(),
1483 "oob: end_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1484 end_idx, _card_bm->size());
1485 assert(start_idx < _card_bm->size(),
1486 "oob: start_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1487 start_idx, _card_bm->size());
1488
1489 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1490 }
1491
1492 // Set the bit for the region if it contains live data
1493 if (hr->next_marked_bytes() > 0) {
1494 set_bit_for_region(hr);
1495 }
1496
1497 return false;
1498 }
1499 };
1500
1501 class G1ParFinalCountTask: public AbstractGangTask {
1502 protected:
1503 G1CollectedHeap* _g1h;
1504 G1ConcurrentMark* _cm;
1505 BitMap* _actual_region_bm;
1506 BitMap* _actual_card_bm;
1507
1508 uint _n_workers;
1509 HeapRegionClaimer _hrclaimer;
1510
1511 public:
1512 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1513 : AbstractGangTask("G1 final counting"),
1514 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1515 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1516 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1517 }
1518
1519 void work(uint worker_id) {
1520 assert(worker_id < _n_workers, "invariant");
1521
1522 FinalCountDataUpdateClosure final_update_cl(_g1h,
1523 _actual_region_bm,
1524 _actual_card_bm);
1525
1526 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer);
1527 }
1528 };
1529
1530 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1531 G1CollectedHeap* _g1;
1532 size_t _freed_bytes;
1533 FreeRegionList* _local_cleanup_list;
1534 uint _old_regions_removed;
1535 uint _humongous_regions_removed;
1536 HRRSCleanupTask* _hrrs_cleanup_task;
1537
1538 public:
1539 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1540 FreeRegionList* local_cleanup_list,
1541 HRRSCleanupTask* hrrs_cleanup_task) :
1542 _g1(g1),
1543 _freed_bytes(0),
1544 _local_cleanup_list(local_cleanup_list),
1545 _old_regions_removed(0),
1546 _humongous_regions_removed(0),
1547 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1548
1549 size_t freed_bytes() { return _freed_bytes; }
1550 const uint old_regions_removed() { return _old_regions_removed; }
1551 const uint humongous_regions_removed() { return _humongous_regions_removed; }
1552
1553 bool doHeapRegion(HeapRegion *hr) {
1554 if (hr->is_archive()) {
1555 return false;
1556 }
1557 // We use a claim value of zero here because all regions
1558 // were claimed with value 1 in the FinalCount task.
1559 _g1->reset_gc_time_stamps(hr);
1560 hr->note_end_of_marking();
1561
1562 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1563 _freed_bytes += hr->used();
1564 hr->set_containing_set(NULL);
1565 if (hr->is_humongous()) {
1566 _humongous_regions_removed++;
1567 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1568 } else {
1569 _old_regions_removed++;
1570 _g1->free_region(hr, _local_cleanup_list, true);
1571 }
1572 } else {
1573 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1574 }
1575
1576 return false;
1577 }
1578 };
1579
1580 class G1ParNoteEndTask: public AbstractGangTask {
1581 friend class G1NoteEndOfConcMarkClosure;
1582
1583 protected:
1584 G1CollectedHeap* _g1h;
1585 FreeRegionList* _cleanup_list;
1586 HeapRegionClaimer _hrclaimer;
1587
1588 public:
1589 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1590 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1591 }
1592
1593 void work(uint worker_id) {
1594 FreeRegionList local_cleanup_list("Local Cleanup List");
1595 HRRSCleanupTask hrrs_cleanup_task;
1596 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1597 &hrrs_cleanup_task);
1598 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1599 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1600
1601 // Now update the lists
1602 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1603 {
1604 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1605 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1606
1607 // If we iterate over the global cleanup list at the end of
1608 // cleanup to do this printing we will not guarantee to only
1609 // generate output for the newly-reclaimed regions (the list
1610 // might not be empty at the beginning of cleanup; we might
1611 // still be working on its previous contents). So we do the
1612 // printing here, before we append the new regions to the global
1613 // cleanup list.
1614
1615 G1HRPrinter* hr_printer = _g1h->hr_printer();
1616 if (hr_printer->is_active()) {
1617 FreeRegionListIterator iter(&local_cleanup_list);
1618 while (iter.more_available()) {
1619 HeapRegion* hr = iter.get_next();
1620 hr_printer->cleanup(hr);
1621 }
1622 }
1623
1624 _cleanup_list->add_ordered(&local_cleanup_list);
1625 assert(local_cleanup_list.is_empty(), "post-condition");
1626
1627 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1628 }
1629 }
1630 };
1631
1632 void G1ConcurrentMark::cleanup() {
1633 // world is stopped at this checkpoint
1634 assert(SafepointSynchronize::is_at_safepoint(),
1635 "world should be stopped");
1636 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1637
1638 // If a full collection has happened, we shouldn't do this.
1639 if (has_aborted()) {
1640 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1641 return;
1642 }
1643
1644 g1h->verifier()->verify_region_sets_optional();
1645
1646 if (VerifyDuringGC) {
1647 HandleMark hm; // handle scope
1648 g1h->prepare_for_verify();
1649 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (before)");
1650 }
1651 g1h->verifier()->check_bitmaps("Cleanup Start");
1652
1653 G1CollectorPolicy* g1p = g1h->g1_policy();
1654 g1p->record_concurrent_mark_cleanup_start();
1655
1656 double start = os::elapsedTime();
1657
1658 HeapRegionRemSet::reset_for_cleanup_tasks();
1659
1660 // Do counting once more with the world stopped for good measure.
1661 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1662
1663 g1h->workers()->run_task(&g1_par_count_task);
1664
1665 if (VerifyDuringGC) {
1666 // Verify that the counting data accumulated during marking matches
1667 // that calculated by walking the marking bitmap.
1668
1669 // Bitmaps to hold expected values
1670 BitMap expected_region_bm(_region_bm.size(), true);
1671 BitMap expected_card_bm(_card_bm.size(), true);
1672
1673 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1674 &_region_bm,
1675 &_card_bm,
1676 &expected_region_bm,
1677 &expected_card_bm);
1678
1679 g1h->workers()->run_task(&g1_par_verify_task);
1680
1681 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
1682 }
1683
1684 size_t start_used_bytes = g1h->used();
1685 g1h->collector_state()->set_mark_in_progress(false);
1686
1687 double count_end = os::elapsedTime();
1688 double this_final_counting_time = (count_end - start);
1689 _total_counting_time += this_final_counting_time;
1690
1691 if (log_is_enabled(Trace, gc, liveness)) {
1692 G1PrintRegionLivenessInfoClosure cl("Post-Marking");
1693 _g1h->heap_region_iterate(&cl);
1694 }
1695
1696 // Install newly created mark bitMap as "prev".
1697 swapMarkBitMaps();
1698
1699 g1h->reset_gc_time_stamp();
1700
1701 uint n_workers = _g1h->workers()->active_workers();
1702
1703 // Note end of marking in all heap regions.
1704 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1705 g1h->workers()->run_task(&g1_par_note_end_task);
1706 g1h->check_gc_time_stamps();
1707
1708 if (!cleanup_list_is_empty()) {
1709 // The cleanup list is not empty, so we'll have to process it
1710 // concurrently. Notify anyone else that might be wanting free
1711 // regions that there will be more free regions coming soon.
1712 g1h->set_free_regions_coming();
1713 }
1714
1715 // call below, since it affects the metric by which we sort the heap
1716 // regions.
1717 if (G1ScrubRemSets) {
1718 double rs_scrub_start = os::elapsedTime();
1719 g1h->scrub_rem_set(&_region_bm, &_card_bm);
1720 _total_rs_scrub_time += (os::elapsedTime() - rs_scrub_start);
1721 }
1722
1723 // this will also free any regions totally full of garbage objects,
1724 // and sort the regions.
1725 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1726
1727 // Statistics.
1728 double end = os::elapsedTime();
1729 _cleanup_times.add((end - start) * 1000.0);
1730
1731 // Clean up will have freed any regions completely full of garbage.
1732 // Update the soft reference policy with the new heap occupancy.
1733 Universe::update_heap_info_at_gc();
1734
1735 if (VerifyDuringGC) {
1736 HandleMark hm; // handle scope
1737 g1h->prepare_for_verify();
1738 Universe::verify(VerifyOption_G1UsePrevMarking, "During GC (after)");
1739 }
1740
1741 g1h->verifier()->check_bitmaps("Cleanup End");
1742
1743 g1h->verifier()->verify_region_sets_optional();
1744
1745 // We need to make this be a "collection" so any collection pause that
1746 // races with it goes around and waits for completeCleanup to finish.
1747 g1h->increment_total_collections();
1748
1749 // Clean out dead classes and update Metaspace sizes.
1750 if (ClassUnloadingWithConcurrentMark) {
1751 ClassLoaderDataGraph::purge();
1752 }
1753 MetaspaceGC::compute_new_size();
1754
1755 // We reclaimed old regions so we should calculate the sizes to make
1756 // sure we update the old gen/space data.
1757 g1h->g1mm()->update_sizes();
1758 g1h->allocation_context_stats().update_after_mark();
1759
1760 g1h->trace_heap_after_concurrent_cycle();
1761 }
1762
1763 void G1ConcurrentMark::completeCleanup() {
1764 if (has_aborted()) return;
1765
1766 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1767
1768 _cleanup_list.verify_optional();
1769 FreeRegionList tmp_free_list("Tmp Free List");
1770
1771 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1772 "cleanup list has %u entries",
1773 _cleanup_list.length());
1774
1775 // No one else should be accessing the _cleanup_list at this point,
1776 // so it is not necessary to take any locks
1777 while (!_cleanup_list.is_empty()) {
1778 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
1779 assert(hr != NULL, "Got NULL from a non-empty list");
1780 hr->par_clear();
1781 tmp_free_list.add_ordered(hr);
1782
1783 // Instead of adding one region at a time to the secondary_free_list,
1784 // we accumulate them in the local list and move them a few at a
1785 // time. This also cuts down on the number of notify_all() calls
1786 // we do during this process. We'll also append the local list when
1787 // _cleanup_list is empty (which means we just removed the last
1788 // region from the _cleanup_list).
1789 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
1790 _cleanup_list.is_empty()) {
1791 log_develop_trace(gc, freelist)("G1ConcRegionFreeing [complete cleanup] : "
1792 "appending %u entries to the secondary_free_list, "
1793 "cleanup list still has %u entries",
1794 tmp_free_list.length(),
1795 _cleanup_list.length());
1796
1797 {
1798 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1799 g1h->secondary_free_list_add(&tmp_free_list);
1800 SecondaryFreeList_lock->notify_all();
1801 }
1802 #ifndef PRODUCT
1803 if (G1StressConcRegionFreeing) {
1804 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
1805 os::sleep(Thread::current(), (jlong) 1, false);
1806 }
1807 }
1808 #endif
1809 }
1810 }
1811 assert(tmp_free_list.is_empty(), "post-condition");
1812 }
1813
1814 // Supporting Object and Oop closures for reference discovery
1815 // and processing in during marking
1816
1817 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1818 HeapWord* addr = (HeapWord*)obj;
1819 return addr != NULL &&
1820 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1821 }
1822
1823 // 'Keep Alive' oop closure used by both serial parallel reference processing.
1824 // Uses the G1CMTask associated with a worker thread (for serial reference
1825 // processing the G1CMTask for worker 0 is used) to preserve (mark) and
1826 // trace referent objects.
1827 //
1828 // Using the G1CMTask and embedded local queues avoids having the worker
1829 // threads operating on the global mark stack. This reduces the risk
1830 // of overflowing the stack - which we would rather avoid at this late
1831 // state. Also using the tasks' local queues removes the potential
1832 // of the workers interfering with each other that could occur if
1833 // operating on the global stack.
1834
1835 class G1CMKeepAliveAndDrainClosure: public OopClosure {
1836 G1ConcurrentMark* _cm;
1837 G1CMTask* _task;
1838 int _ref_counter_limit;
1839 int _ref_counter;
1840 bool _is_serial;
1841 public:
1842 G1CMKeepAliveAndDrainClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1843 _cm(cm), _task(task), _is_serial(is_serial),
1844 _ref_counter_limit(G1RefProcDrainInterval) {
1845 assert(_ref_counter_limit > 0, "sanity");
1846 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1847 _ref_counter = _ref_counter_limit;
1848 }
1849
1850 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1851 virtual void do_oop( oop* p) { do_oop_work(p); }
1852
1853 template <class T> void do_oop_work(T* p) {
1854 if (!_cm->has_overflown()) {
1855 oop obj = oopDesc::load_decode_heap_oop(p);
1856 _task->deal_with_reference(obj);
1857 _ref_counter--;
1858
1859 if (_ref_counter == 0) {
1860 // We have dealt with _ref_counter_limit references, pushing them
1861 // and objects reachable from them on to the local stack (and
1862 // possibly the global stack). Call G1CMTask::do_marking_step() to
1863 // process these entries.
1864 //
1865 // We call G1CMTask::do_marking_step() in a loop, which we'll exit if
1866 // there's nothing more to do (i.e. we're done with the entries that
1867 // were pushed as a result of the G1CMTask::deal_with_reference() calls
1868 // above) or we overflow.
1869 //
1870 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1871 // flag while there may still be some work to do. (See the comment at
1872 // the beginning of G1CMTask::do_marking_step() for those conditions -
1873 // one of which is reaching the specified time target.) It is only
1874 // when G1CMTask::do_marking_step() returns without setting the
1875 // has_aborted() flag that the marking step has completed.
1876 do {
1877 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1878 _task->do_marking_step(mark_step_duration_ms,
1879 false /* do_termination */,
1880 _is_serial);
1881 } while (_task->has_aborted() && !_cm->has_overflown());
1882 _ref_counter = _ref_counter_limit;
1883 }
1884 }
1885 }
1886 };
1887
1888 // 'Drain' oop closure used by both serial and parallel reference processing.
1889 // Uses the G1CMTask associated with a given worker thread (for serial
1890 // reference processing the G1CMtask for worker 0 is used). Calls the
1891 // do_marking_step routine, with an unbelievably large timeout value,
1892 // to drain the marking data structures of the remaining entries
1893 // added by the 'keep alive' oop closure above.
1894
1895 class G1CMDrainMarkingStackClosure: public VoidClosure {
1896 G1ConcurrentMark* _cm;
1897 G1CMTask* _task;
1898 bool _is_serial;
1899 public:
1900 G1CMDrainMarkingStackClosure(G1ConcurrentMark* cm, G1CMTask* task, bool is_serial) :
1901 _cm(cm), _task(task), _is_serial(is_serial) {
1902 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
1903 }
1904
1905 void do_void() {
1906 do {
1907 // We call G1CMTask::do_marking_step() to completely drain the local
1908 // and global marking stacks of entries pushed by the 'keep alive'
1909 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
1910 //
1911 // G1CMTask::do_marking_step() is called in a loop, which we'll exit
1912 // if there's nothing more to do (i.e. we've completely drained the
1913 // entries that were pushed as a a result of applying the 'keep alive'
1914 // closure to the entries on the discovered ref lists) or we overflow
1915 // the global marking stack.
1916 //
1917 // Note: G1CMTask::do_marking_step() can set the G1CMTask::has_aborted()
1918 // flag while there may still be some work to do. (See the comment at
1919 // the beginning of G1CMTask::do_marking_step() for those conditions -
1920 // one of which is reaching the specified time target.) It is only
1921 // when G1CMTask::do_marking_step() returns without setting the
1922 // has_aborted() flag that the marking step has completed.
1923
1924 _task->do_marking_step(1000000000.0 /* something very large */,
1925 true /* do_termination */,
1926 _is_serial);
1927 } while (_task->has_aborted() && !_cm->has_overflown());
1928 }
1929 };
1930
1931 // Implementation of AbstractRefProcTaskExecutor for parallel
1932 // reference processing at the end of G1 concurrent marking
1933
1934 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
1935 private:
1936 G1CollectedHeap* _g1h;
1937 G1ConcurrentMark* _cm;
1938 WorkGang* _workers;
1939 uint _active_workers;
1940
1941 public:
1942 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
1943 G1ConcurrentMark* cm,
1944 WorkGang* workers,
1945 uint n_workers) :
1946 _g1h(g1h), _cm(cm),
1947 _workers(workers), _active_workers(n_workers) { }
1948
1949 // Executes the given task using concurrent marking worker threads.
1950 virtual void execute(ProcessTask& task);
1951 virtual void execute(EnqueueTask& task);
1952 };
1953
1954 class G1CMRefProcTaskProxy: public AbstractGangTask {
1955 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
1956 ProcessTask& _proc_task;
1957 G1CollectedHeap* _g1h;
1958 G1ConcurrentMark* _cm;
1959
1960 public:
1961 G1CMRefProcTaskProxy(ProcessTask& proc_task,
1962 G1CollectedHeap* g1h,
1963 G1ConcurrentMark* cm) :
1964 AbstractGangTask("Process reference objects in parallel"),
1965 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
1966 ReferenceProcessor* rp = _g1h->ref_processor_cm();
1967 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
1968 }
1969
1970 virtual void work(uint worker_id) {
1971 ResourceMark rm;
1972 HandleMark hm;
1973 G1CMTask* task = _cm->task(worker_id);
1974 G1CMIsAliveClosure g1_is_alive(_g1h);
1975 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
1976 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
1977
1978 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
1979 }
1980 };
1981
1982 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
1983 assert(_workers != NULL, "Need parallel worker threads.");
1984 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
1985
1986 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
1987
1988 // We need to reset the concurrency level before each
1989 // proxy task execution, so that the termination protocol
1990 // and overflow handling in G1CMTask::do_marking_step() knows
1991 // how many workers to wait for.
1992 _cm->set_concurrency(_active_workers);
1993 _workers->run_task(&proc_task_proxy);
1994 }
1995
1996 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
1997 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
1998 EnqueueTask& _enq_task;
1999
2000 public:
2001 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2002 AbstractGangTask("Enqueue reference objects in parallel"),
2003 _enq_task(enq_task) { }
2004
2005 virtual void work(uint worker_id) {
2006 _enq_task.work(worker_id);
2007 }
2008 };
2009
2010 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2011 assert(_workers != NULL, "Need parallel worker threads.");
2012 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2013
2014 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2015
2016 // Not strictly necessary but...
2017 //
2018 // We need to reset the concurrency level before each
2019 // proxy task execution, so that the termination protocol
2020 // and overflow handling in G1CMTask::do_marking_step() knows
2021 // how many workers to wait for.
2022 _cm->set_concurrency(_active_workers);
2023 _workers->run_task(&enq_task_proxy);
2024 }
2025
2026 void G1ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
2027 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
2028 }
2029
2030 void G1ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2031 if (has_overflown()) {
2032 // Skip processing the discovered references if we have
2033 // overflown the global marking stack. Reference objects
2034 // only get discovered once so it is OK to not
2035 // de-populate the discovered reference lists. We could have,
2036 // but the only benefit would be that, when marking restarts,
2037 // less reference objects are discovered.
2038 return;
2039 }
2040
2041 ResourceMark rm;
2042 HandleMark hm;
2043
2044 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2045
2046 // Is alive closure.
2047 G1CMIsAliveClosure g1_is_alive(g1h);
2048
2049 // Inner scope to exclude the cleaning of the string and symbol
2050 // tables from the displayed time.
2051 {
2052 GCTraceTime(Debug, gc) trace("Reference Processing", g1h->gc_timer_cm());
2053
2054 ReferenceProcessor* rp = g1h->ref_processor_cm();
2055
2056 // See the comment in G1CollectedHeap::ref_processing_init()
2057 // about how reference processing currently works in G1.
2058
2059 // Set the soft reference policy
2060 rp->setup_policy(clear_all_soft_refs);
2061 assert(_markStack.isEmpty(), "mark stack should be empty");
2062
2063 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2064 // in serial reference processing. Note these closures are also
2065 // used for serially processing (by the the current thread) the
2066 // JNI references during parallel reference processing.
2067 //
2068 // These closures do not need to synchronize with the worker
2069 // threads involved in parallel reference processing as these
2070 // instances are executed serially by the current thread (e.g.
2071 // reference processing is not multi-threaded and is thus
2072 // performed by the current thread instead of a gang worker).
2073 //
2074 // The gang tasks involved in parallel reference processing create
2075 // their own instances of these closures, which do their own
2076 // synchronization among themselves.
2077 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2078 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2079
2080 // We need at least one active thread. If reference processing
2081 // is not multi-threaded we use the current (VMThread) thread,
2082 // otherwise we use the work gang from the G1CollectedHeap and
2083 // we utilize all the worker threads we can.
2084 bool processing_is_mt = rp->processing_is_mt();
2085 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2086 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2087
2088 // Parallel processing task executor.
2089 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2090 g1h->workers(), active_workers);
2091 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2092
2093 // Set the concurrency level. The phase was already set prior to
2094 // executing the remark task.
2095 set_concurrency(active_workers);
2096
2097 // Set the degree of MT processing here. If the discovery was done MT,
2098 // the number of threads involved during discovery could differ from
2099 // the number of active workers. This is OK as long as the discovered
2100 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2101 rp->set_active_mt_degree(active_workers);
2102
2103 // Process the weak references.
2104 const ReferenceProcessorStats& stats =
2105 rp->process_discovered_references(&g1_is_alive,
2106 &g1_keep_alive,
2107 &g1_drain_mark_stack,
2108 executor,
2109 g1h->gc_timer_cm());
2110 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2111
2112 // The do_oop work routines of the keep_alive and drain_marking_stack
2113 // oop closures will set the has_overflown flag if we overflow the
2114 // global marking stack.
2115
2116 assert(_markStack.overflow() || _markStack.isEmpty(),
2117 "mark stack should be empty (unless it overflowed)");
2118
2119 if (_markStack.overflow()) {
2120 // This should have been done already when we tried to push an
2121 // entry on to the global mark stack. But let's do it again.
2122 set_has_overflown();
2123 }
2124
2125 assert(rp->num_q() == active_workers, "why not");
2126
2127 rp->enqueue_discovered_references(executor);
2128
2129 rp->verify_no_references_recorded();
2130 assert(!rp->discovery_enabled(), "Post condition");
2131 }
2132
2133 if (has_overflown()) {
2134 // We can not trust g1_is_alive if the marking stack overflowed
2135 return;
2136 }
2137
2138 assert(_markStack.isEmpty(), "Marking should have completed");
2139
2140 // Unload Klasses, String, Symbols, Code Cache, etc.
2141 {
2142 GCTraceTime(Debug, gc) trace("Unloading", g1h->gc_timer_cm());
2143
2144 if (ClassUnloadingWithConcurrentMark) {
2145 bool purged_classes;
2146
2147 {
2148 GCTraceTime(Trace, gc) trace("System Dictionary Unloading", g1h->gc_timer_cm());
2149 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
2150 }
2151
2152 {
2153 GCTraceTime(Trace, gc) trace("Parallel Unloading", g1h->gc_timer_cm());
2154 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
2155 }
2156 }
2157
2158 if (G1StringDedup::is_enabled()) {
2159 GCTraceTime(Trace, gc) trace("String Deduplication Unlink", g1h->gc_timer_cm());
2160 G1StringDedup::unlink(&g1_is_alive);
2161 }
2162 }
2163 }
2164
2165 void G1ConcurrentMark::swapMarkBitMaps() {
2166 G1CMBitMapRO* temp = _prevMarkBitMap;
2167 _prevMarkBitMap = (G1CMBitMapRO*)_nextMarkBitMap;
2168 _nextMarkBitMap = (G1CMBitMap*) temp;
2169 }
2170
2171 // Closure for marking entries in SATB buffers.
2172 class G1CMSATBBufferClosure : public SATBBufferClosure {
2173 private:
2174 G1CMTask* _task;
2175 G1CollectedHeap* _g1h;
2176
2177 // This is very similar to G1CMTask::deal_with_reference, but with
2178 // more relaxed requirements for the argument, so this must be more
2179 // circumspect about treating the argument as an object.
2180 void do_entry(void* entry) const {
2181 _task->increment_refs_reached();
2182 HeapRegion* hr = _g1h->heap_region_containing(entry);
2183 if (entry < hr->next_top_at_mark_start()) {
2184 // Until we get here, we don't know whether entry refers to a valid
2185 // object; it could instead have been a stale reference.
2186 oop obj = static_cast<oop>(entry);
2187 assert(obj->is_oop(true /* ignore mark word */),
2188 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj));
2189 _task->make_reference_grey(obj, hr);
2190 }
2191 }
2192
2193 public:
2194 G1CMSATBBufferClosure(G1CMTask* task, G1CollectedHeap* g1h)
2195 : _task(task), _g1h(g1h) { }
2196
2197 virtual void do_buffer(void** buffer, size_t size) {
2198 for (size_t i = 0; i < size; ++i) {
2199 do_entry(buffer[i]);
2200 }
2201 }
2202 };
2203
2204 class G1RemarkThreadsClosure : public ThreadClosure {
2205 G1CMSATBBufferClosure _cm_satb_cl;
2206 G1CMOopClosure _cm_cl;
2207 MarkingCodeBlobClosure _code_cl;
2208 int _thread_parity;
2209
2210 public:
2211 G1RemarkThreadsClosure(G1CollectedHeap* g1h, G1CMTask* task) :
2212 _cm_satb_cl(task, g1h),
2213 _cm_cl(g1h, g1h->concurrent_mark(), task),
2214 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
2215 _thread_parity(Threads::thread_claim_parity()) {}
2216
2217 void do_thread(Thread* thread) {
2218 if (thread->is_Java_thread()) {
2219 if (thread->claim_oops_do(true, _thread_parity)) {
2220 JavaThread* jt = (JavaThread*)thread;
2221
2222 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
2223 // however the liveness of oops reachable from nmethods have very complex lifecycles:
2224 // * Alive if on the stack of an executing method
2225 // * Weakly reachable otherwise
2226 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
2227 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
2228 jt->nmethods_do(&_code_cl);
2229
2230 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
2231 }
2232 } else if (thread->is_VM_thread()) {
2233 if (thread->claim_oops_do(true, _thread_parity)) {
2234 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
2235 }
2236 }
2237 }
2238 };
2239
2240 class G1CMRemarkTask: public AbstractGangTask {
2241 private:
2242 G1ConcurrentMark* _cm;
2243 public:
2244 void work(uint worker_id) {
2245 // Since all available tasks are actually started, we should
2246 // only proceed if we're supposed to be active.
2247 if (worker_id < _cm->active_tasks()) {
2248 G1CMTask* task = _cm->task(worker_id);
2249 task->record_start_time();
2250 {
2251 ResourceMark rm;
2252 HandleMark hm;
2253
2254 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
2255 Threads::threads_do(&threads_f);
2256 }
2257
2258 do {
2259 task->do_marking_step(1000000000.0 /* something very large */,
2260 true /* do_termination */,
2261 false /* is_serial */);
2262 } while (task->has_aborted() && !_cm->has_overflown());
2263 // If we overflow, then we do not want to restart. We instead
2264 // want to abort remark and do concurrent marking again.
2265 task->record_end_time();
2266 }
2267 }
2268
2269 G1CMRemarkTask(G1ConcurrentMark* cm, uint active_workers) :
2270 AbstractGangTask("Par Remark"), _cm(cm) {
2271 _cm->terminator()->reset_for_reuse(active_workers);
2272 }
2273 };
2274
2275 void G1ConcurrentMark::checkpointRootsFinalWork() {
2276 ResourceMark rm;
2277 HandleMark hm;
2278 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2279
2280 GCTraceTime(Debug, gc) trace("Finalize Marking", g1h->gc_timer_cm());
2281
2282 g1h->ensure_parsability(false);
2283
2284 // this is remark, so we'll use up all active threads
2285 uint active_workers = g1h->workers()->active_workers();
2286 set_concurrency_and_phase(active_workers, false /* concurrent */);
2287 // Leave _parallel_marking_threads at it's
2288 // value originally calculated in the G1ConcurrentMark
2289 // constructor and pass values of the active workers
2290 // through the gang in the task.
2291
2292 {
2293 StrongRootsScope srs(active_workers);
2294
2295 G1CMRemarkTask remarkTask(this, active_workers);
2296 // We will start all available threads, even if we decide that the
2297 // active_workers will be fewer. The extra ones will just bail out
2298 // immediately.
2299 g1h->workers()->run_task(&remarkTask);
2300 }
2301
2302 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2303 guarantee(has_overflown() ||
2304 satb_mq_set.completed_buffers_num() == 0,
2305 "Invariant: has_overflown = %s, num buffers = " SIZE_FORMAT,
2306 BOOL_TO_STR(has_overflown()),
2307 satb_mq_set.completed_buffers_num());
2308
2309 print_stats();
2310 }
2311
2312 void G1ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2313 // Note we are overriding the read-only view of the prev map here, via
2314 // the cast.
2315 ((G1CMBitMap*)_prevMarkBitMap)->clear_range(mr);
2316 }
2317
2318 HeapRegion*
2319 G1ConcurrentMark::claim_region(uint worker_id) {
2320 // "checkpoint" the finger
2321 HeapWord* finger = _finger;
2322
2323 // _heap_end will not change underneath our feet; it only changes at
2324 // yield points.
2325 while (finger < _heap_end) {
2326 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2327
2328 HeapRegion* curr_region = _g1h->heap_region_containing(finger);
2329
2330 // Above heap_region_containing may return NULL as we always scan claim
2331 // until the end of the heap. In this case, just jump to the next region.
2332 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
2333
2334 // Is the gap between reading the finger and doing the CAS too long?
2335 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2336 if (res == finger && curr_region != NULL) {
2337 // we succeeded
2338 HeapWord* bottom = curr_region->bottom();
2339 HeapWord* limit = curr_region->next_top_at_mark_start();
2340
2341 // notice that _finger == end cannot be guaranteed here since,
2342 // someone else might have moved the finger even further
2343 assert(_finger >= end, "the finger should have moved forward");
2344
2345 if (limit > bottom) {
2346 return curr_region;
2347 } else {
2348 assert(limit == bottom,
2349 "the region limit should be at bottom");
2350 // we return NULL and the caller should try calling
2351 // claim_region() again.
2352 return NULL;
2353 }
2354 } else {
2355 assert(_finger > finger, "the finger should have moved forward");
2356 // read it again
2357 finger = _finger;
2358 }
2359 }
2360
2361 return NULL;
2362 }
2363
2364 #ifndef PRODUCT
2365 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
2366 private:
2367 G1CollectedHeap* _g1h;
2368 const char* _phase;
2369 int _info;
2370
2371 public:
2372 VerifyNoCSetOops(const char* phase, int info = -1) :
2373 _g1h(G1CollectedHeap::heap()),
2374 _phase(phase),
2375 _info(info)
2376 { }
2377
2378 void operator()(oop obj) const {
2379 guarantee(obj->is_oop(),
2380 "Non-oop " PTR_FORMAT ", phase: %s, info: %d",
2381 p2i(obj), _phase, _info);
2382 guarantee(!_g1h->obj_in_cs(obj),
2383 "obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
2384 p2i(obj), _phase, _info);
2385 }
2386 };
2387
2388 void G1ConcurrentMark::verify_no_cset_oops() {
2389 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2390 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) {
2391 return;
2392 }
2393
2394 // Verify entries on the global mark stack
2395 _markStack.iterate(VerifyNoCSetOops("Stack"));
2396
2397 // Verify entries on the task queues
2398 for (uint i = 0; i < _max_worker_id; ++i) {
2399 G1CMTaskQueue* queue = _task_queues->queue(i);
2400 queue->iterate(VerifyNoCSetOops("Queue", i));
2401 }
2402
2403 // Verify the global finger
2404 HeapWord* global_finger = finger();
2405 if (global_finger != NULL && global_finger < _heap_end) {
2406 // Since we always iterate over all regions, we might get a NULL HeapRegion
2407 // here.
2408 HeapRegion* global_hr = _g1h->heap_region_containing(global_finger);
2409 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2410 "global finger: " PTR_FORMAT " region: " HR_FORMAT,
2411 p2i(global_finger), HR_FORMAT_PARAMS(global_hr));
2412 }
2413
2414 // Verify the task fingers
2415 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2416 for (uint i = 0; i < parallel_marking_threads(); ++i) {
2417 G1CMTask* task = _tasks[i];
2418 HeapWord* task_finger = task->finger();
2419 if (task_finger != NULL && task_finger < _heap_end) {
2420 // See above note on the global finger verification.
2421 HeapRegion* task_hr = _g1h->heap_region_containing(task_finger);
2422 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2423 !task_hr->in_collection_set(),
2424 "task finger: " PTR_FORMAT " region: " HR_FORMAT,
2425 p2i(task_finger), HR_FORMAT_PARAMS(task_hr));
2426 }
2427 }
2428 }
2429 #endif // PRODUCT
2430
2431 // Aggregate the counting data that was constructed concurrently
2432 // with marking.
2433 class AggregateCountDataHRClosure: public HeapRegionClosure {
2434 G1CollectedHeap* _g1h;
2435 G1ConcurrentMark* _cm;
2436 CardTableModRefBS* _ct_bs;
2437 BitMap* _cm_card_bm;
2438 uint _max_worker_id;
2439
2440 public:
2441 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2442 BitMap* cm_card_bm,
2443 uint max_worker_id) :
2444 _g1h(g1h), _cm(g1h->concurrent_mark()),
2445 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
2446 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2447
2448 bool doHeapRegion(HeapRegion* hr) {
2449 HeapWord* start = hr->bottom();
2450 HeapWord* limit = hr->next_top_at_mark_start();
2451 HeapWord* end = hr->end();
2452
2453 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
2454 "Preconditions not met - "
2455 "start: " PTR_FORMAT ", limit: " PTR_FORMAT ", "
2456 "top: " PTR_FORMAT ", end: " PTR_FORMAT,
2457 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end()));
2458
2459 assert(hr->next_marked_bytes() == 0, "Precondition");
2460
2461 if (start == limit) {
2462 // NTAMS of this region has not been set so nothing to do.
2463 return false;
2464 }
2465
2466 // 'start' should be in the heap.
2467 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
2468 // 'end' *may* be just beyond the end of the heap (if hr is the last region)
2469 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
2470
2471 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
2472 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
2473 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
2474
2475 // If ntams is not card aligned then we bump card bitmap index
2476 // for limit so that we get the all the cards spanned by
2477 // the object ending at ntams.
2478 // Note: if this is the last region in the heap then ntams
2479 // could be actually just beyond the end of the the heap;
2480 // limit_idx will then correspond to a (non-existent) card
2481 // that is also outside the heap.
2482 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
2483 limit_idx += 1;
2484 }
2485
2486 assert(limit_idx <= end_idx, "or else use atomics");
2487
2488 // Aggregate the "stripe" in the count data associated with hr.
2489 uint hrm_index = hr->hrm_index();
2490 size_t marked_bytes = 0;
2491
2492 for (uint i = 0; i < _max_worker_id; i += 1) {
2493 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
2494 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
2495
2496 // Fetch the marked_bytes in this region for task i and
2497 // add it to the running total for this region.
2498 marked_bytes += marked_bytes_array[hrm_index];
2499
2500 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
2501 // into the global card bitmap.
2502 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
2503
2504 while (scan_idx < limit_idx) {
2505 assert(task_card_bm->at(scan_idx) == true, "should be");
2506 _cm_card_bm->set_bit(scan_idx);
2507 assert(_cm_card_bm->at(scan_idx) == true, "should be");
2508
2509 // BitMap::get_next_one_offset() can handle the case when
2510 // its left_offset parameter is greater than its right_offset
2511 // parameter. It does, however, have an early exit if
2512 // left_offset == right_offset. So let's limit the value
2513 // passed in for left offset here.
2514 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
2515 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
2516 }
2517 }
2518
2519 // Update the marked bytes for this region.
2520 hr->add_to_marked_bytes(marked_bytes);
2521
2522 // Next heap region
2523 return false;
2524 }
2525 };
2526
2527 class G1AggregateCountDataTask: public AbstractGangTask {
2528 protected:
2529 G1CollectedHeap* _g1h;
2530 G1ConcurrentMark* _cm;
2531 BitMap* _cm_card_bm;
2532 uint _max_worker_id;
2533 uint _active_workers;
2534 HeapRegionClaimer _hrclaimer;
2535
2536 public:
2537 G1AggregateCountDataTask(G1CollectedHeap* g1h,
2538 G1ConcurrentMark* cm,
2539 BitMap* cm_card_bm,
2540 uint max_worker_id,
2541 uint n_workers) :
2542 AbstractGangTask("Count Aggregation"),
2543 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
2544 _max_worker_id(max_worker_id),
2545 _active_workers(n_workers),
2546 _hrclaimer(_active_workers) {
2547 }
2548
2549 void work(uint worker_id) {
2550 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
2551
2552 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer);
2553 }
2554 };
2555
2556
2557 void G1ConcurrentMark::aggregate_count_data() {
2558 uint n_workers = _g1h->workers()->active_workers();
2559
2560 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
2561 _max_worker_id, n_workers);
2562
2563 _g1h->workers()->run_task(&g1_par_agg_task);
2564 }
2565
2566 // Clear the per-worker arrays used to store the per-region counting data
2567 void G1ConcurrentMark::clear_all_count_data() {
2568 // Clear the global card bitmap - it will be filled during
2569 // liveness count aggregation (during remark) and the
2570 // final counting task.
2571 _card_bm.clear();
2572
2573 // Clear the global region bitmap - it will be filled as part
2574 // of the final counting task.
2575 _region_bm.clear();
2576
2577 uint max_regions = _g1h->max_regions();
2578 assert(_max_worker_id > 0, "uninitialized");
2579
2580 for (uint i = 0; i < _max_worker_id; i += 1) {
2581 BitMap* task_card_bm = count_card_bitmap_for(i);
2582 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
2583
2584 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
2585 assert(marked_bytes_array != NULL, "uninitialized");
2586
2587 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
2588 task_card_bm->clear();
2589 }
2590 }
2591
2592 void G1ConcurrentMark::print_stats() {
2593 if (!log_is_enabled(Debug, gc, stats)) {
2594 return;
2595 }
2596 log_debug(gc, stats)("---------------------------------------------------------------------");
2597 for (size_t i = 0; i < _active_tasks; ++i) {
2598 _tasks[i]->print_stats();
2599 log_debug(gc, stats)("---------------------------------------------------------------------");
2600 }
2601 }
2602
2603 // abandon current marking iteration due to a Full GC
2604 void G1ConcurrentMark::abort() {
2605 if (!cmThread()->during_cycle() || _has_aborted) {
2606 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2607 return;
2608 }
2609
2610 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2611 // concurrent bitmap clearing.
2612 clear_bitmap(_nextMarkBitMap, _g1h->workers(), false);
2613
2614 // Note we cannot clear the previous marking bitmap here
2615 // since VerifyDuringGC verifies the objects marked during
2616 // a full GC against the previous bitmap.
2617
2618 // Clear the liveness counting data
2619 clear_all_count_data();
2620 // Empty mark stack
2621 reset_marking_state();
2622 for (uint i = 0; i < _max_worker_id; ++i) {
2623 _tasks[i]->clear_region_fields();
2624 }
2625 _first_overflow_barrier_sync.abort();
2626 _second_overflow_barrier_sync.abort();
2627 _has_aborted = true;
2628
2629 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2630 satb_mq_set.abandon_partial_marking();
2631 // This can be called either during or outside marking, we'll read
2632 // the expected_active value from the SATB queue set.
2633 satb_mq_set.set_active_all_threads(
2634 false, /* new active value */
2635 satb_mq_set.is_active() /* expected_active */);
2636
2637 _g1h->trace_heap_after_concurrent_cycle();
2638
2639 _g1h->register_concurrent_cycle_end();
2640 }
2641
2642 static void print_ms_time_info(const char* prefix, const char* name,
2643 NumberSeq& ns) {
2644 log_trace(gc, marking)("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
2645 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
2646 if (ns.num() > 0) {
2647 log_trace(gc, marking)("%s [std. dev = %8.2f ms, max = %8.2f ms]",
2648 prefix, ns.sd(), ns.maximum());
2649 }
2650 }
2651
2652 void G1ConcurrentMark::print_summary_info() {
2653 LogHandle(gc, marking) log;
2654 if (!log.is_trace()) {
2655 return;
2656 }
2657
2658 log.trace(" Concurrent marking:");
2659 print_ms_time_info(" ", "init marks", _init_times);
2660 print_ms_time_info(" ", "remarks", _remark_times);
2661 {
2662 print_ms_time_info(" ", "final marks", _remark_mark_times);
2663 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
2664
2665 }
2666 print_ms_time_info(" ", "cleanups", _cleanup_times);
2667 log.trace(" Final counting total time = %8.2f s (avg = %8.2f ms).",
2668 _total_counting_time, (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2669 if (G1ScrubRemSets) {
2670 log.trace(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
2671 _total_rs_scrub_time, (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 / (double)_cleanup_times.num() : 0.0));
2672 }
2673 log.trace(" Total stop_world time = %8.2f s.",
2674 (_init_times.sum() + _remark_times.sum() + _cleanup_times.sum())/1000.0);
2675 log.trace(" Total concurrent time = %8.2f s (%8.2f s marking).",
2676 cmThread()->vtime_accum(), cmThread()->vtime_mark_accum());
2677 }
2678
2679 void G1ConcurrentMark::print_worker_threads_on(outputStream* st) const {
2680 _parallel_workers->print_worker_threads_on(st);
2681 }
2682
2683 void G1ConcurrentMark::print_on_error(outputStream* st) const {
2684 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
2685 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
2686 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
2687 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
2688 }
2689
2690 // We take a break if someone is trying to stop the world.
2691 bool G1ConcurrentMark::do_yield_check(uint worker_id) {
2692 if (SuspendibleThreadSet::should_yield()) {
2693 SuspendibleThreadSet::yield();
2694 return true;
2695 } else {
2696 return false;
2697 }
2698 }
2699
2700 // Closure for iteration over bitmaps
2701 class G1CMBitMapClosure : public BitMapClosure {
2702 private:
2703 // the bitmap that is being iterated over
2704 G1CMBitMap* _nextMarkBitMap;
2705 G1ConcurrentMark* _cm;
2706 G1CMTask* _task;
2707
2708 public:
2709 G1CMBitMapClosure(G1CMTask *task, G1ConcurrentMark* cm, G1CMBitMap* nextMarkBitMap) :
2710 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
2711
2712 bool do_bit(size_t offset) {
2713 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
2714 assert(_nextMarkBitMap->isMarked(addr), "invariant");
2715 assert( addr < _cm->finger(), "invariant");
2716 assert(addr >= _task->finger(), "invariant");
2717
2718 // We move that task's local finger along.
2719 _task->move_finger_to(addr);
2720
2721 _task->scan_object(oop(addr));
2722 // we only partially drain the local queue and global stack
2723 _task->drain_local_queue(true);
2724 _task->drain_global_stack(true);
2725
2726 // if the has_aborted flag has been raised, we need to bail out of
2727 // the iteration
2728 return !_task->has_aborted();
2729 }
2730 };
2731
2732 static ReferenceProcessor* get_cm_oop_closure_ref_processor(G1CollectedHeap* g1h) {
2733 ReferenceProcessor* result = g1h->ref_processor_cm();
2734 assert(result != NULL, "CM reference processor should not be NULL");
2735 return result;
2736 }
2737
2738 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
2739 G1ConcurrentMark* cm,
2740 G1CMTask* task)
2741 : MetadataAwareOopClosure(get_cm_oop_closure_ref_processor(g1h)),
2742 _g1h(g1h), _cm(cm), _task(task)
2743 { }
2744
2745 void G1CMTask::setup_for_region(HeapRegion* hr) {
2746 assert(hr != NULL,
2747 "claim_region() should have filtered out NULL regions");
2748 _curr_region = hr;
2749 _finger = hr->bottom();
2750 update_region_limit();
2751 }
2752
2753 void G1CMTask::update_region_limit() {
2754 HeapRegion* hr = _curr_region;
2755 HeapWord* bottom = hr->bottom();
2756 HeapWord* limit = hr->next_top_at_mark_start();
2757
2758 if (limit == bottom) {
2759 // The region was collected underneath our feet.
2760 // We set the finger to bottom to ensure that the bitmap
2761 // iteration that will follow this will not do anything.
2762 // (this is not a condition that holds when we set the region up,
2763 // as the region is not supposed to be empty in the first place)
2764 _finger = bottom;
2765 } else if (limit >= _region_limit) {
2766 assert(limit >= _finger, "peace of mind");
2767 } else {
2768 assert(limit < _region_limit, "only way to get here");
2769 // This can happen under some pretty unusual circumstances. An
2770 // evacuation pause empties the region underneath our feet (NTAMS
2771 // at bottom). We then do some allocation in the region (NTAMS
2772 // stays at bottom), followed by the region being used as a GC
2773 // alloc region (NTAMS will move to top() and the objects
2774 // originally below it will be grayed). All objects now marked in
2775 // the region are explicitly grayed, if below the global finger,
2776 // and we do not need in fact to scan anything else. So, we simply
2777 // set _finger to be limit to ensure that the bitmap iteration
2778 // doesn't do anything.
2779 _finger = limit;
2780 }
2781
2782 _region_limit = limit;
2783 }
2784
2785 void G1CMTask::giveup_current_region() {
2786 assert(_curr_region != NULL, "invariant");
2787 clear_region_fields();
2788 }
2789
2790 void G1CMTask::clear_region_fields() {
2791 // Values for these three fields that indicate that we're not
2792 // holding on to a region.
2793 _curr_region = NULL;
2794 _finger = NULL;
2795 _region_limit = NULL;
2796 }
2797
2798 void G1CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
2799 if (cm_oop_closure == NULL) {
2800 assert(_cm_oop_closure != NULL, "invariant");
2801 } else {
2802 assert(_cm_oop_closure == NULL, "invariant");
2803 }
2804 _cm_oop_closure = cm_oop_closure;
2805 }
2806
2807 void G1CMTask::reset(G1CMBitMap* nextMarkBitMap) {
2808 guarantee(nextMarkBitMap != NULL, "invariant");
2809 _nextMarkBitMap = nextMarkBitMap;
2810 clear_region_fields();
2811
2812 _calls = 0;
2813 _elapsed_time_ms = 0.0;
2814 _termination_time_ms = 0.0;
2815 _termination_start_time_ms = 0.0;
2816 }
2817
2818 bool G1CMTask::should_exit_termination() {
2819 regular_clock_call();
2820 // This is called when we are in the termination protocol. We should
2821 // quit if, for some reason, this task wants to abort or the global
2822 // stack is not empty (this means that we can get work from it).
2823 return !_cm->mark_stack_empty() || has_aborted();
2824 }
2825
2826 void G1CMTask::reached_limit() {
2827 assert(_words_scanned >= _words_scanned_limit ||
2828 _refs_reached >= _refs_reached_limit ,
2829 "shouldn't have been called otherwise");
2830 regular_clock_call();
2831 }
2832
2833 void G1CMTask::regular_clock_call() {
2834 if (has_aborted()) return;
2835
2836 // First, we need to recalculate the words scanned and refs reached
2837 // limits for the next clock call.
2838 recalculate_limits();
2839
2840 // During the regular clock call we do the following
2841
2842 // (1) If an overflow has been flagged, then we abort.
2843 if (_cm->has_overflown()) {
2844 set_has_aborted();
2845 return;
2846 }
2847
2848 // If we are not concurrent (i.e. we're doing remark) we don't need
2849 // to check anything else. The other steps are only needed during
2850 // the concurrent marking phase.
2851 if (!concurrent()) return;
2852
2853 // (2) If marking has been aborted for Full GC, then we also abort.
2854 if (_cm->has_aborted()) {
2855 set_has_aborted();
2856 return;
2857 }
2858
2859 double curr_time_ms = os::elapsedVTime() * 1000.0;
2860
2861 // (4) We check whether we should yield. If we have to, then we abort.
2862 if (SuspendibleThreadSet::should_yield()) {
2863 // We should yield. To do this we abort the task. The caller is
2864 // responsible for yielding.
2865 set_has_aborted();
2866 return;
2867 }
2868
2869 // (5) We check whether we've reached our time quota. If we have,
2870 // then we abort.
2871 double elapsed_time_ms = curr_time_ms - _start_time_ms;
2872 if (elapsed_time_ms > _time_target_ms) {
2873 set_has_aborted();
2874 _has_timed_out = true;
2875 return;
2876 }
2877
2878 // (6) Finally, we check whether there are enough completed STAB
2879 // buffers available for processing. If there are, we abort.
2880 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2881 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
2882 // we do need to process SATB buffers, we'll abort and restart
2883 // the marking task to do so
2884 set_has_aborted();
2885 return;
2886 }
2887 }
2888
2889 void G1CMTask::recalculate_limits() {
2890 _real_words_scanned_limit = _words_scanned + words_scanned_period;
2891 _words_scanned_limit = _real_words_scanned_limit;
2892
2893 _real_refs_reached_limit = _refs_reached + refs_reached_period;
2894 _refs_reached_limit = _real_refs_reached_limit;
2895 }
2896
2897 void G1CMTask::decrease_limits() {
2898 // This is called when we believe that we're going to do an infrequent
2899 // operation which will increase the per byte scanned cost (i.e. move
2900 // entries to/from the global stack). It basically tries to decrease the
2901 // scanning limit so that the clock is called earlier.
2902
2903 _words_scanned_limit = _real_words_scanned_limit -
2904 3 * words_scanned_period / 4;
2905 _refs_reached_limit = _real_refs_reached_limit -
2906 3 * refs_reached_period / 4;
2907 }
2908
2909 void G1CMTask::move_entries_to_global_stack() {
2910 // local array where we'll store the entries that will be popped
2911 // from the local queue
2912 oop buffer[global_stack_transfer_size];
2913
2914 int n = 0;
2915 oop obj;
2916 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
2917 buffer[n] = obj;
2918 ++n;
2919 }
2920
2921 if (n > 0) {
2922 // we popped at least one entry from the local queue
2923
2924 if (!_cm->mark_stack_push(buffer, n)) {
2925 set_has_aborted();
2926 }
2927 }
2928
2929 // this operation was quite expensive, so decrease the limits
2930 decrease_limits();
2931 }
2932
2933 void G1CMTask::get_entries_from_global_stack() {
2934 // local array where we'll store the entries that will be popped
2935 // from the global stack.
2936 oop buffer[global_stack_transfer_size];
2937 int n;
2938 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
2939 assert(n <= global_stack_transfer_size,
2940 "we should not pop more than the given limit");
2941 if (n > 0) {
2942 // yes, we did actually pop at least one entry
2943 for (int i = 0; i < n; ++i) {
2944 bool success = _task_queue->push(buffer[i]);
2945 // We only call this when the local queue is empty or under a
2946 // given target limit. So, we do not expect this push to fail.
2947 assert(success, "invariant");
2948 }
2949 }
2950
2951 // this operation was quite expensive, so decrease the limits
2952 decrease_limits();
2953 }
2954
2955 void G1CMTask::drain_local_queue(bool partially) {
2956 if (has_aborted()) return;
2957
2958 // Decide what the target size is, depending whether we're going to
2959 // drain it partially (so that other tasks can steal if they run out
2960 // of things to do) or totally (at the very end).
2961 size_t target_size;
2962 if (partially) {
2963 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
2964 } else {
2965 target_size = 0;
2966 }
2967
2968 if (_task_queue->size() > target_size) {
2969 oop obj;
2970 bool ret = _task_queue->pop_local(obj);
2971 while (ret) {
2972 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
2973 assert(!_g1h->is_on_master_free_list(
2974 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
2975
2976 scan_object(obj);
2977
2978 if (_task_queue->size() <= target_size || has_aborted()) {
2979 ret = false;
2980 } else {
2981 ret = _task_queue->pop_local(obj);
2982 }
2983 }
2984 }
2985 }
2986
2987 void G1CMTask::drain_global_stack(bool partially) {
2988 if (has_aborted()) return;
2989
2990 // We have a policy to drain the local queue before we attempt to
2991 // drain the global stack.
2992 assert(partially || _task_queue->size() == 0, "invariant");
2993
2994 // Decide what the target size is, depending whether we're going to
2995 // drain it partially (so that other tasks can steal if they run out
2996 // of things to do) or totally (at the very end). Notice that,
2997 // because we move entries from the global stack in chunks or
2998 // because another task might be doing the same, we might in fact
2999 // drop below the target. But, this is not a problem.
3000 size_t target_size;
3001 if (partially) {
3002 target_size = _cm->partial_mark_stack_size_target();
3003 } else {
3004 target_size = 0;
3005 }
3006
3007 if (_cm->mark_stack_size() > target_size) {
3008 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3009 get_entries_from_global_stack();
3010 drain_local_queue(partially);
3011 }
3012 }
3013 }
3014
3015 // SATB Queue has several assumptions on whether to call the par or
3016 // non-par versions of the methods. this is why some of the code is
3017 // replicated. We should really get rid of the single-threaded version
3018 // of the code to simplify things.
3019 void G1CMTask::drain_satb_buffers() {
3020 if (has_aborted()) return;
3021
3022 // We set this so that the regular clock knows that we're in the
3023 // middle of draining buffers and doesn't set the abort flag when it
3024 // notices that SATB buffers are available for draining. It'd be
3025 // very counter productive if it did that. :-)
3026 _draining_satb_buffers = true;
3027
3028 G1CMSATBBufferClosure satb_cl(this, _g1h);
3029 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3030
3031 // This keeps claiming and applying the closure to completed buffers
3032 // until we run out of buffers or we need to abort.
3033 while (!has_aborted() &&
3034 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
3035 regular_clock_call();
3036 }
3037
3038 _draining_satb_buffers = false;
3039
3040 assert(has_aborted() ||
3041 concurrent() ||
3042 satb_mq_set.completed_buffers_num() == 0, "invariant");
3043
3044 // again, this was a potentially expensive operation, decrease the
3045 // limits to get the regular clock call early
3046 decrease_limits();
3047 }
3048
3049 void G1CMTask::print_stats() {
3050 log_debug(gc, stats)("Marking Stats, task = %u, calls = %d",
3051 _worker_id, _calls);
3052 log_debug(gc, stats)(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3053 _elapsed_time_ms, _termination_time_ms);
3054 log_debug(gc, stats)(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3055 _step_times_ms.num(), _step_times_ms.avg(),
3056 _step_times_ms.sd());
3057 log_debug(gc, stats)(" max = %1.2lfms, total = %1.2lfms",
3058 _step_times_ms.maximum(), _step_times_ms.sum());
3059 }
3060
3061 bool G1ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) {
3062 return _task_queues->steal(worker_id, hash_seed, obj);
3063 }
3064
3065 /*****************************************************************************
3066
3067 The do_marking_step(time_target_ms, ...) method is the building
3068 block of the parallel marking framework. It can be called in parallel
3069 with other invocations of do_marking_step() on different tasks
3070 (but only one per task, obviously) and concurrently with the
3071 mutator threads, or during remark, hence it eliminates the need
3072 for two versions of the code. When called during remark, it will
3073 pick up from where the task left off during the concurrent marking
3074 phase. Interestingly, tasks are also claimable during evacuation
3075 pauses too, since do_marking_step() ensures that it aborts before
3076 it needs to yield.
3077
3078 The data structures that it uses to do marking work are the
3079 following:
3080
3081 (1) Marking Bitmap. If there are gray objects that appear only
3082 on the bitmap (this happens either when dealing with an overflow
3083 or when the initial marking phase has simply marked the roots
3084 and didn't push them on the stack), then tasks claim heap
3085 regions whose bitmap they then scan to find gray objects. A
3086 global finger indicates where the end of the last claimed region
3087 is. A local finger indicates how far into the region a task has
3088 scanned. The two fingers are used to determine how to gray an
3089 object (i.e. whether simply marking it is OK, as it will be
3090 visited by a task in the future, or whether it needs to be also
3091 pushed on a stack).
3092
3093 (2) Local Queue. The local queue of the task which is accessed
3094 reasonably efficiently by the task. Other tasks can steal from
3095 it when they run out of work. Throughout the marking phase, a
3096 task attempts to keep its local queue short but not totally
3097 empty, so that entries are available for stealing by other
3098 tasks. Only when there is no more work, a task will totally
3099 drain its local queue.
3100
3101 (3) Global Mark Stack. This handles local queue overflow. During
3102 marking only sets of entries are moved between it and the local
3103 queues, as access to it requires a mutex and more fine-grain
3104 interaction with it which might cause contention. If it
3105 overflows, then the marking phase should restart and iterate
3106 over the bitmap to identify gray objects. Throughout the marking
3107 phase, tasks attempt to keep the global mark stack at a small
3108 length but not totally empty, so that entries are available for
3109 popping by other tasks. Only when there is no more work, tasks
3110 will totally drain the global mark stack.
3111
3112 (4) SATB Buffer Queue. This is where completed SATB buffers are
3113 made available. Buffers are regularly removed from this queue
3114 and scanned for roots, so that the queue doesn't get too
3115 long. During remark, all completed buffers are processed, as
3116 well as the filled in parts of any uncompleted buffers.
3117
3118 The do_marking_step() method tries to abort when the time target
3119 has been reached. There are a few other cases when the
3120 do_marking_step() method also aborts:
3121
3122 (1) When the marking phase has been aborted (after a Full GC).
3123
3124 (2) When a global overflow (on the global stack) has been
3125 triggered. Before the task aborts, it will actually sync up with
3126 the other tasks to ensure that all the marking data structures
3127 (local queues, stacks, fingers etc.) are re-initialized so that
3128 when do_marking_step() completes, the marking phase can
3129 immediately restart.
3130
3131 (3) When enough completed SATB buffers are available. The
3132 do_marking_step() method only tries to drain SATB buffers right
3133 at the beginning. So, if enough buffers are available, the
3134 marking step aborts and the SATB buffers are processed at
3135 the beginning of the next invocation.
3136
3137 (4) To yield. when we have to yield then we abort and yield
3138 right at the end of do_marking_step(). This saves us from a lot
3139 of hassle as, by yielding we might allow a Full GC. If this
3140 happens then objects will be compacted underneath our feet, the
3141 heap might shrink, etc. We save checking for this by just
3142 aborting and doing the yield right at the end.
3143
3144 From the above it follows that the do_marking_step() method should
3145 be called in a loop (or, otherwise, regularly) until it completes.
3146
3147 If a marking step completes without its has_aborted() flag being
3148 true, it means it has completed the current marking phase (and
3149 also all other marking tasks have done so and have all synced up).
3150
3151 A method called regular_clock_call() is invoked "regularly" (in
3152 sub ms intervals) throughout marking. It is this clock method that
3153 checks all the abort conditions which were mentioned above and
3154 decides when the task should abort. A work-based scheme is used to
3155 trigger this clock method: when the number of object words the
3156 marking phase has scanned or the number of references the marking
3157 phase has visited reach a given limit. Additional invocations to
3158 the method clock have been planted in a few other strategic places
3159 too. The initial reason for the clock method was to avoid calling
3160 vtime too regularly, as it is quite expensive. So, once it was in
3161 place, it was natural to piggy-back all the other conditions on it
3162 too and not constantly check them throughout the code.
3163
3164 If do_termination is true then do_marking_step will enter its
3165 termination protocol.
3166
3167 The value of is_serial must be true when do_marking_step is being
3168 called serially (i.e. by the VMThread) and do_marking_step should
3169 skip any synchronization in the termination and overflow code.
3170 Examples include the serial remark code and the serial reference
3171 processing closures.
3172
3173 The value of is_serial must be false when do_marking_step is
3174 being called by any of the worker threads in a work gang.
3175 Examples include the concurrent marking code (CMMarkingTask),
3176 the MT remark code, and the MT reference processing closures.
3177
3178 *****************************************************************************/
3179
3180 void G1CMTask::do_marking_step(double time_target_ms,
3181 bool do_termination,
3182 bool is_serial) {
3183 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3184 assert(concurrent() == _cm->concurrent(), "they should be the same");
3185
3186 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3187 assert(_task_queues != NULL, "invariant");
3188 assert(_task_queue != NULL, "invariant");
3189 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3190
3191 assert(!_claimed,
3192 "only one thread should claim this task at any one time");
3193
3194 // OK, this doesn't safeguard again all possible scenarios, as it is
3195 // possible for two threads to set the _claimed flag at the same
3196 // time. But it is only for debugging purposes anyway and it will
3197 // catch most problems.
3198 _claimed = true;
3199
3200 _start_time_ms = os::elapsedVTime() * 1000.0;
3201
3202 // If do_stealing is true then do_marking_step will attempt to
3203 // steal work from the other G1CMTasks. It only makes sense to
3204 // enable stealing when the termination protocol is enabled
3205 // and do_marking_step() is not being called serially.
3206 bool do_stealing = do_termination && !is_serial;
3207
3208 double diff_prediction_ms = _g1h->g1_policy()->predictor().get_new_prediction(&_marking_step_diffs_ms);
3209 _time_target_ms = time_target_ms - diff_prediction_ms;
3210
3211 // set up the variables that are used in the work-based scheme to
3212 // call the regular clock method
3213 _words_scanned = 0;
3214 _refs_reached = 0;
3215 recalculate_limits();
3216
3217 // clear all flags
3218 clear_has_aborted();
3219 _has_timed_out = false;
3220 _draining_satb_buffers = false;
3221
3222 ++_calls;
3223
3224 // Set up the bitmap and oop closures. Anything that uses them is
3225 // eventually called from this method, so it is OK to allocate these
3226 // statically.
3227 G1CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3228 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
3229 set_cm_oop_closure(&cm_oop_closure);
3230
3231 if (_cm->has_overflown()) {
3232 // This can happen if the mark stack overflows during a GC pause
3233 // and this task, after a yield point, restarts. We have to abort
3234 // as we need to get into the overflow protocol which happens
3235 // right at the end of this task.
3236 set_has_aborted();
3237 }
3238
3239 // First drain any available SATB buffers. After this, we will not
3240 // look at SATB buffers before the next invocation of this method.
3241 // If enough completed SATB buffers are queued up, the regular clock
3242 // will abort this task so that it restarts.
3243 drain_satb_buffers();
3244 // ...then partially drain the local queue and the global stack
3245 drain_local_queue(true);
3246 drain_global_stack(true);
3247
3248 do {
3249 if (!has_aborted() && _curr_region != NULL) {
3250 // This means that we're already holding on to a region.
3251 assert(_finger != NULL, "if region is not NULL, then the finger "
3252 "should not be NULL either");
3253
3254 // We might have restarted this task after an evacuation pause
3255 // which might have evacuated the region we're holding on to
3256 // underneath our feet. Let's read its limit again to make sure
3257 // that we do not iterate over a region of the heap that
3258 // contains garbage (update_region_limit() will also move
3259 // _finger to the start of the region if it is found empty).
3260 update_region_limit();
3261 // We will start from _finger not from the start of the region,
3262 // as we might be restarting this task after aborting half-way
3263 // through scanning this region. In this case, _finger points to
3264 // the address where we last found a marked object. If this is a
3265 // fresh region, _finger points to start().
3266 MemRegion mr = MemRegion(_finger, _region_limit);
3267
3268 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
3269 "humongous regions should go around loop once only");
3270
3271 // Some special cases:
3272 // If the memory region is empty, we can just give up the region.
3273 // If the current region is humongous then we only need to check
3274 // the bitmap for the bit associated with the start of the object,
3275 // scan the object if it's live, and give up the region.
3276 // Otherwise, let's iterate over the bitmap of the part of the region
3277 // that is left.
3278 // If the iteration is successful, give up the region.
3279 if (mr.is_empty()) {
3280 giveup_current_region();
3281 regular_clock_call();
3282 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
3283 if (_nextMarkBitMap->isMarked(mr.start())) {
3284 // The object is marked - apply the closure
3285 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
3286 bitmap_closure.do_bit(offset);
3287 }
3288 // Even if this task aborted while scanning the humongous object
3289 // we can (and should) give up the current region.
3290 giveup_current_region();
3291 regular_clock_call();
3292 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
3293 giveup_current_region();
3294 regular_clock_call();
3295 } else {
3296 assert(has_aborted(), "currently the only way to do so");
3297 // The only way to abort the bitmap iteration is to return
3298 // false from the do_bit() method. However, inside the
3299 // do_bit() method we move the _finger to point to the
3300 // object currently being looked at. So, if we bail out, we
3301 // have definitely set _finger to something non-null.
3302 assert(_finger != NULL, "invariant");
3303
3304 // Region iteration was actually aborted. So now _finger
3305 // points to the address of the object we last scanned. If we
3306 // leave it there, when we restart this task, we will rescan
3307 // the object. It is easy to avoid this. We move the finger by
3308 // enough to point to the next possible object header (the
3309 // bitmap knows by how much we need to move it as it knows its
3310 // granularity).
3311 assert(_finger < _region_limit, "invariant");
3312 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
3313 // Check if bitmap iteration was aborted while scanning the last object
3314 if (new_finger >= _region_limit) {
3315 giveup_current_region();
3316 } else {
3317 move_finger_to(new_finger);
3318 }
3319 }
3320 }
3321 // At this point we have either completed iterating over the
3322 // region we were holding on to, or we have aborted.
3323
3324 // We then partially drain the local queue and the global stack.
3325 // (Do we really need this?)
3326 drain_local_queue(true);
3327 drain_global_stack(true);
3328
3329 // Read the note on the claim_region() method on why it might
3330 // return NULL with potentially more regions available for
3331 // claiming and why we have to check out_of_regions() to determine
3332 // whether we're done or not.
3333 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
3334 // We are going to try to claim a new region. We should have
3335 // given up on the previous one.
3336 // Separated the asserts so that we know which one fires.
3337 assert(_curr_region == NULL, "invariant");
3338 assert(_finger == NULL, "invariant");
3339 assert(_region_limit == NULL, "invariant");
3340 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
3341 if (claimed_region != NULL) {
3342 // Yes, we managed to claim one
3343 setup_for_region(claimed_region);
3344 assert(_curr_region == claimed_region, "invariant");
3345 }
3346 // It is important to call the regular clock here. It might take
3347 // a while to claim a region if, for example, we hit a large
3348 // block of empty regions. So we need to call the regular clock
3349 // method once round the loop to make sure it's called
3350 // frequently enough.
3351 regular_clock_call();
3352 }
3353
3354 if (!has_aborted() && _curr_region == NULL) {
3355 assert(_cm->out_of_regions(),
3356 "at this point we should be out of regions");
3357 }
3358 } while ( _curr_region != NULL && !has_aborted());
3359
3360 if (!has_aborted()) {
3361 // We cannot check whether the global stack is empty, since other
3362 // tasks might be pushing objects to it concurrently.
3363 assert(_cm->out_of_regions(),
3364 "at this point we should be out of regions");
3365 // Try to reduce the number of available SATB buffers so that
3366 // remark has less work to do.
3367 drain_satb_buffers();
3368 }
3369
3370 // Since we've done everything else, we can now totally drain the
3371 // local queue and global stack.
3372 drain_local_queue(false);
3373 drain_global_stack(false);
3374
3375 // Attempt at work stealing from other task's queues.
3376 if (do_stealing && !has_aborted()) {
3377 // We have not aborted. This means that we have finished all that
3378 // we could. Let's try to do some stealing...
3379
3380 // We cannot check whether the global stack is empty, since other
3381 // tasks might be pushing objects to it concurrently.
3382 assert(_cm->out_of_regions() && _task_queue->size() == 0,
3383 "only way to reach here");
3384 while (!has_aborted()) {
3385 oop obj;
3386 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
3387 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
3388 "any stolen object should be marked");
3389 scan_object(obj);
3390
3391 // And since we're towards the end, let's totally drain the
3392 // local queue and global stack.
3393 drain_local_queue(false);
3394 drain_global_stack(false);
3395 } else {
3396 break;
3397 }
3398 }
3399 }
3400
3401 // We still haven't aborted. Now, let's try to get into the
3402 // termination protocol.
3403 if (do_termination && !has_aborted()) {
3404 // We cannot check whether the global stack is empty, since other
3405 // tasks might be concurrently pushing objects on it.
3406 // Separated the asserts so that we know which one fires.
3407 assert(_cm->out_of_regions(), "only way to reach here");
3408 assert(_task_queue->size() == 0, "only way to reach here");
3409 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
3410
3411 // The G1CMTask class also extends the TerminatorTerminator class,
3412 // hence its should_exit_termination() method will also decide
3413 // whether to exit the termination protocol or not.
3414 bool finished = (is_serial ||
3415 _cm->terminator()->offer_termination(this));
3416 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
3417 _termination_time_ms +=
3418 termination_end_time_ms - _termination_start_time_ms;
3419
3420 if (finished) {
3421 // We're all done.
3422
3423 if (_worker_id == 0) {
3424 // let's allow task 0 to do this
3425 if (concurrent()) {
3426 assert(_cm->concurrent_marking_in_progress(), "invariant");
3427 // we need to set this to false before the next
3428 // safepoint. This way we ensure that the marking phase
3429 // doesn't observe any more heap expansions.
3430 _cm->clear_concurrent_marking_in_progress();
3431 }
3432 }
3433
3434 // We can now guarantee that the global stack is empty, since
3435 // all other tasks have finished. We separated the guarantees so
3436 // that, if a condition is false, we can immediately find out
3437 // which one.
3438 guarantee(_cm->out_of_regions(), "only way to reach here");
3439 guarantee(_cm->mark_stack_empty(), "only way to reach here");
3440 guarantee(_task_queue->size() == 0, "only way to reach here");
3441 guarantee(!_cm->has_overflown(), "only way to reach here");
3442 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
3443 } else {
3444 // Apparently there's more work to do. Let's abort this task. It
3445 // will restart it and we can hopefully find more things to do.
3446 set_has_aborted();
3447 }
3448 }
3449
3450 // Mainly for debugging purposes to make sure that a pointer to the
3451 // closure which was statically allocated in this frame doesn't
3452 // escape it by accident.
3453 set_cm_oop_closure(NULL);
3454 double end_time_ms = os::elapsedVTime() * 1000.0;
3455 double elapsed_time_ms = end_time_ms - _start_time_ms;
3456 // Update the step history.
3457 _step_times_ms.add(elapsed_time_ms);
3458
3459 if (has_aborted()) {
3460 // The task was aborted for some reason.
3461 if (_has_timed_out) {
3462 double diff_ms = elapsed_time_ms - _time_target_ms;
3463 // Keep statistics of how well we did with respect to hitting
3464 // our target only if we actually timed out (if we aborted for
3465 // other reasons, then the results might get skewed).
3466 _marking_step_diffs_ms.add(diff_ms);
3467 }
3468
3469 if (_cm->has_overflown()) {
3470 // This is the interesting one. We aborted because a global
3471 // overflow was raised. This means we have to restart the
3472 // marking phase and start iterating over regions. However, in
3473 // order to do this we have to make sure that all tasks stop
3474 // what they are doing and re-initialize in a safe manner. We
3475 // will achieve this with the use of two barrier sync points.
3476
3477 if (!is_serial) {
3478 // We only need to enter the sync barrier if being called
3479 // from a parallel context
3480 _cm->enter_first_sync_barrier(_worker_id);
3481
3482 // When we exit this sync barrier we know that all tasks have
3483 // stopped doing marking work. So, it's now safe to
3484 // re-initialize our data structures. At the end of this method,
3485 // task 0 will clear the global data structures.
3486 }
3487
3488 // We clear the local state of this task...
3489 clear_region_fields();
3490
3491 if (!is_serial) {
3492 // ...and enter the second barrier.
3493 _cm->enter_second_sync_barrier(_worker_id);
3494 }
3495 // At this point, if we're during the concurrent phase of
3496 // marking, everything has been re-initialized and we're
3497 // ready to restart.
3498 }
3499 }
3500
3501 _claimed = false;
3502 }
3503
3504 G1CMTask::G1CMTask(uint worker_id,
3505 G1ConcurrentMark* cm,
3506 size_t* marked_bytes,
3507 BitMap* card_bm,
3508 G1CMTaskQueue* task_queue,
3509 G1CMTaskQueueSet* task_queues)
3510 : _g1h(G1CollectedHeap::heap()),
3511 _worker_id(worker_id), _cm(cm),
3512 _claimed(false),
3513 _nextMarkBitMap(NULL), _hash_seed(17),
3514 _task_queue(task_queue),
3515 _task_queues(task_queues),
3516 _cm_oop_closure(NULL),
3517 _marked_bytes_array(marked_bytes),
3518 _card_bm(card_bm) {
3519 guarantee(task_queue != NULL, "invariant");
3520 guarantee(task_queues != NULL, "invariant");
3521
3522 _marking_step_diffs_ms.add(0.5);
3523 }
3524
3525 // These are formatting macros that are used below to ensure
3526 // consistent formatting. The *_H_* versions are used to format the
3527 // header for a particular value and they should be kept consistent
3528 // with the corresponding macro. Also note that most of the macros add
3529 // the necessary white space (as a prefix) which makes them a bit
3530 // easier to compose.
3531
3532 // All the output lines are prefixed with this string to be able to
3533 // identify them easily in a large log file.
3534 #define G1PPRL_LINE_PREFIX "###"
3535
3536 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
3537 #ifdef _LP64
3538 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
3539 #else // _LP64
3540 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
3541 #endif // _LP64
3542
3543 // For per-region info
3544 #define G1PPRL_TYPE_FORMAT " %-4s"
3545 #define G1PPRL_TYPE_H_FORMAT " %4s"
3546 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
3547 #define G1PPRL_BYTE_H_FORMAT " %9s"
3548 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
3549 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
3550
3551 // For summary info
3552 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
3553 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
3554 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
3555 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
3556
3557 G1PrintRegionLivenessInfoClosure::
3558 G1PrintRegionLivenessInfoClosure(const char* phase_name)
3559 : _total_used_bytes(0), _total_capacity_bytes(0),
3560 _total_prev_live_bytes(0), _total_next_live_bytes(0),
3561 _hum_used_bytes(0), _hum_capacity_bytes(0),
3562 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
3563 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
3564 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3565 MemRegion g1_reserved = g1h->g1_reserved();
3566 double now = os::elapsedTime();
3567
3568 // Print the header of the output.
3569 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
3570 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX" HEAP"
3571 G1PPRL_SUM_ADDR_FORMAT("reserved")
3572 G1PPRL_SUM_BYTE_FORMAT("region-size"),
3573 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
3574 HeapRegion::GrainBytes);
3575 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3576 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3577 G1PPRL_TYPE_H_FORMAT
3578 G1PPRL_ADDR_BASE_H_FORMAT
3579 G1PPRL_BYTE_H_FORMAT
3580 G1PPRL_BYTE_H_FORMAT
3581 G1PPRL_BYTE_H_FORMAT
3582 G1PPRL_DOUBLE_H_FORMAT
3583 G1PPRL_BYTE_H_FORMAT
3584 G1PPRL_BYTE_H_FORMAT,
3585 "type", "address-range",
3586 "used", "prev-live", "next-live", "gc-eff",
3587 "remset", "code-roots");
3588 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3589 G1PPRL_TYPE_H_FORMAT
3590 G1PPRL_ADDR_BASE_H_FORMAT
3591 G1PPRL_BYTE_H_FORMAT
3592 G1PPRL_BYTE_H_FORMAT
3593 G1PPRL_BYTE_H_FORMAT
3594 G1PPRL_DOUBLE_H_FORMAT
3595 G1PPRL_BYTE_H_FORMAT
3596 G1PPRL_BYTE_H_FORMAT,
3597 "", "",
3598 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
3599 "(bytes)", "(bytes)");
3600 }
3601
3602 // It takes as a parameter a reference to one of the _hum_* fields, it
3603 // deduces the corresponding value for a region in a humongous region
3604 // series (either the region size, or what's left if the _hum_* field
3605 // is < the region size), and updates the _hum_* field accordingly.
3606 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
3607 size_t bytes = 0;
3608 // The > 0 check is to deal with the prev and next live bytes which
3609 // could be 0.
3610 if (*hum_bytes > 0) {
3611 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
3612 *hum_bytes -= bytes;
3613 }
3614 return bytes;
3615 }
3616
3617 // It deduces the values for a region in a humongous region series
3618 // from the _hum_* fields and updates those accordingly. It assumes
3619 // that that _hum_* fields have already been set up from the "starts
3620 // humongous" region and we visit the regions in address order.
3621 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
3622 size_t* capacity_bytes,
3623 size_t* prev_live_bytes,
3624 size_t* next_live_bytes) {
3625 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
3626 *used_bytes = get_hum_bytes(&_hum_used_bytes);
3627 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
3628 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
3629 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
3630 }
3631
3632 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
3633 const char* type = r->get_type_str();
3634 HeapWord* bottom = r->bottom();
3635 HeapWord* end = r->end();
3636 size_t capacity_bytes = r->capacity();
3637 size_t used_bytes = r->used();
3638 size_t prev_live_bytes = r->live_bytes();
3639 size_t next_live_bytes = r->next_live_bytes();
3640 double gc_eff = r->gc_efficiency();
3641 size_t remset_bytes = r->rem_set()->mem_size();
3642 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
3643
3644 if (r->is_starts_humongous()) {
3645 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
3646 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
3647 "they should have been zeroed after the last time we used them");
3648 // Set up the _hum_* fields.
3649 _hum_capacity_bytes = capacity_bytes;
3650 _hum_used_bytes = used_bytes;
3651 _hum_prev_live_bytes = prev_live_bytes;
3652 _hum_next_live_bytes = next_live_bytes;
3653 get_hum_bytes(&used_bytes, &capacity_bytes,
3654 &prev_live_bytes, &next_live_bytes);
3655 end = bottom + HeapRegion::GrainWords;
3656 } else if (r->is_continues_humongous()) {
3657 get_hum_bytes(&used_bytes, &capacity_bytes,
3658 &prev_live_bytes, &next_live_bytes);
3659 assert(end == bottom + HeapRegion::GrainWords, "invariant");
3660 }
3661
3662 _total_used_bytes += used_bytes;
3663 _total_capacity_bytes += capacity_bytes;
3664 _total_prev_live_bytes += prev_live_bytes;
3665 _total_next_live_bytes += next_live_bytes;
3666 _total_remset_bytes += remset_bytes;
3667 _total_strong_code_roots_bytes += strong_code_roots_bytes;
3668
3669 // Print a line for this particular region.
3670 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3671 G1PPRL_TYPE_FORMAT
3672 G1PPRL_ADDR_BASE_FORMAT
3673 G1PPRL_BYTE_FORMAT
3674 G1PPRL_BYTE_FORMAT
3675 G1PPRL_BYTE_FORMAT
3676 G1PPRL_DOUBLE_FORMAT
3677 G1PPRL_BYTE_FORMAT
3678 G1PPRL_BYTE_FORMAT,
3679 type, p2i(bottom), p2i(end),
3680 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
3681 remset_bytes, strong_code_roots_bytes);
3682
3683 return false;
3684 }
3685
3686 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
3687 // add static memory usages to remembered set sizes
3688 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
3689 // Print the footer of the output.
3690 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX);
3691 log_trace(gc, liveness)(G1PPRL_LINE_PREFIX
3692 " SUMMARY"
3693 G1PPRL_SUM_MB_FORMAT("capacity")
3694 G1PPRL_SUM_MB_PERC_FORMAT("used")
3695 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
3696 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
3697 G1PPRL_SUM_MB_FORMAT("remset")
3698 G1PPRL_SUM_MB_FORMAT("code-roots"),
3699 bytes_to_mb(_total_capacity_bytes),
3700 bytes_to_mb(_total_used_bytes),
3701 perc(_total_used_bytes, _total_capacity_bytes),
3702 bytes_to_mb(_total_prev_live_bytes),
3703 perc(_total_prev_live_bytes, _total_capacity_bytes),
3704 bytes_to_mb(_total_next_live_bytes),
3705 perc(_total_next_live_bytes, _total_capacity_bytes),
3706 bytes_to_mb(_total_remset_bytes),
3707 bytes_to_mb(_total_strong_code_roots_bytes));
3708 }