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