1 /*
2 * Copyright (c) 2001, 2015, 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/concurrentMark.inline.hpp"
30 #include "gc/g1/concurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1CollectedHeap.inline.hpp"
32 #include "gc/g1/g1CollectorPolicy.hpp"
33 #include "gc/g1/g1CollectorState.hpp"
34 #include "gc/g1/g1ErgoVerbose.hpp"
35 #include "gc/g1/g1Log.hpp"
36 #include "gc/g1/g1OopClosures.inline.hpp"
37 #include "gc/g1/g1RemSet.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/heapRegion.inline.hpp"
40 #include "gc/g1/heapRegionManager.inline.hpp"
41 #include "gc/g1/heapRegionRemSet.hpp"
42 #include "gc/g1/heapRegionSet.inline.hpp"
43 #include "gc/g1/suspendibleThreadSet.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTrace.hpp"
47 #include "gc/shared/gcTraceTime.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/taskqueue.inline.hpp"
52 #include "gc/shared/vmGCOperations.hpp"
53 #include "memory/allocation.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "runtime/atomic.inline.hpp"
57 #include "runtime/handles.inline.hpp"
58 #include "runtime/java.hpp"
59 #include "runtime/prefetch.inline.hpp"
60 #include "services/memTracker.hpp"
61
62 // Concurrent marking bit map wrapper
63
64 CMBitMapRO::CMBitMapRO(int shifter) :
65 _bm(),
66 _shifter(shifter) {
67 _bmStartWord = 0;
68 _bmWordSize = 0;
69 }
70
71 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
72 const HeapWord* limit) const {
73 // First we must round addr *up* to a possible object boundary.
74 addr = (HeapWord*)align_size_up((intptr_t)addr,
75 HeapWordSize << _shifter);
76 size_t addrOffset = heapWordToOffset(addr);
77 if (limit == NULL) {
78 limit = _bmStartWord + _bmWordSize;
79 }
80 size_t limitOffset = heapWordToOffset(limit);
81 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
82 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
83 assert(nextAddr >= addr, "get_next_one postcondition");
84 assert(nextAddr == limit || isMarked(nextAddr),
85 "get_next_one postcondition");
86 return nextAddr;
87 }
88
89 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr,
90 const HeapWord* limit) const {
91 size_t addrOffset = heapWordToOffset(addr);
92 if (limit == NULL) {
93 limit = _bmStartWord + _bmWordSize;
94 }
95 size_t limitOffset = heapWordToOffset(limit);
96 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
97 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
98 assert(nextAddr >= addr, "get_next_one postcondition");
99 assert(nextAddr == limit || !isMarked(nextAddr),
100 "get_next_one postcondition");
101 return nextAddr;
102 }
103
104 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
105 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
106 return (int) (diff >> _shifter);
107 }
108
109 #ifndef PRODUCT
110 bool CMBitMapRO::covers(MemRegion heap_rs) const {
111 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
112 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
113 "size inconsistency");
114 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
115 _bmWordSize == heap_rs.word_size();
116 }
117 #endif
118
119 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
120 _bm.print_on_error(st, prefix);
121 }
122
123 size_t CMBitMap::compute_size(size_t heap_size) {
124 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
125 }
126
127 size_t CMBitMap::mark_distance() {
128 return MinObjAlignmentInBytes * BitsPerByte;
129 }
130
131 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
132 _bmStartWord = heap.start();
133 _bmWordSize = heap.word_size();
134
135 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
136 _bm.set_size(_bmWordSize >> _shifter);
137
138 storage->set_mapping_changed_listener(&_listener);
139 }
140
141 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
142 if (zero_filled) {
143 return;
144 }
145 // We need to clear the bitmap on commit, removing any existing information.
146 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
147 _bm->clearRange(mr);
148 }
149
150 // Closure used for clearing the given mark bitmap.
151 class ClearBitmapHRClosure : public HeapRegionClosure {
152 private:
153 ConcurrentMark* _cm;
154 CMBitMap* _bitmap;
155 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration.
156 public:
157 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) {
158 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield.");
159 }
160
161 virtual bool doHeapRegion(HeapRegion* r) {
162 size_t const chunk_size_in_words = M / HeapWordSize;
163
164 HeapWord* cur = r->bottom();
165 HeapWord* const end = r->end();
166
167 while (cur < end) {
168 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
169 _bitmap->clearRange(mr);
170
171 cur += chunk_size_in_words;
172
173 // Abort iteration if after yielding the marking has been aborted.
174 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) {
175 return true;
176 }
177 // Repeat the asserts from before the start of the closure. We will do them
178 // as asserts here to minimize their overhead on the product. However, we
179 // will have them as guarantees at the beginning / end of the bitmap
180 // clearing to get some checking in the product.
181 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant");
182 assert(!_may_yield || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
183 }
184
185 return false;
186 }
187 };
188
189 class ParClearNextMarkBitmapTask : public AbstractGangTask {
190 ClearBitmapHRClosure* _cl;
191 HeapRegionClaimer _hrclaimer;
192 bool _suspendible; // If the task is suspendible, workers must join the STS.
193
194 public:
195 ParClearNextMarkBitmapTask(ClearBitmapHRClosure *cl, uint n_workers, bool suspendible) :
196 _cl(cl), _suspendible(suspendible), AbstractGangTask("Parallel Clear Bitmap Task"), _hrclaimer(n_workers) {}
197
198 void work(uint worker_id) {
199 SuspendibleThreadSetJoiner sts_join(_suspendible);
200 G1CollectedHeap::heap()->heap_region_par_iterate(_cl, worker_id, &_hrclaimer, true);
201 }
202 };
203
204 void CMBitMap::clearAll() {
205 G1CollectedHeap* g1h = G1CollectedHeap::heap();
206 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */);
207 uint n_workers = g1h->workers()->active_workers();
208 ParClearNextMarkBitmapTask task(&cl, n_workers, false);
209 g1h->workers()->run_task(&task);
210 guarantee(cl.complete(), "Must have completed iteration.");
211 return;
212 }
213
214 void CMBitMap::markRange(MemRegion mr) {
215 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
216 assert(!mr.is_empty(), "unexpected empty region");
217 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
218 ((HeapWord *) mr.end())),
219 "markRange memory region end is not card aligned");
220 // convert address range into offset range
221 _bm.at_put_range(heapWordToOffset(mr.start()),
222 heapWordToOffset(mr.end()), true);
223 }
224
225 void CMBitMap::clearRange(MemRegion mr) {
226 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
227 assert(!mr.is_empty(), "unexpected empty region");
228 // convert address range into offset range
229 _bm.at_put_range(heapWordToOffset(mr.start()),
230 heapWordToOffset(mr.end()), false);
231 }
232
233 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
234 HeapWord* end_addr) {
235 HeapWord* start = getNextMarkedWordAddress(addr);
236 start = MIN2(start, end_addr);
237 HeapWord* end = getNextUnmarkedWordAddress(start);
238 end = MIN2(end, end_addr);
239 assert(start <= end, "Consistency check");
240 MemRegion mr(start, end);
241 if (!mr.is_empty()) {
242 clearRange(mr);
243 }
244 return mr;
245 }
246
247 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
248 _base(NULL), _cm(cm)
249 #ifdef ASSERT
250 , _drain_in_progress(false)
251 , _drain_in_progress_yields(false)
252 #endif
253 {}
254
255 bool CMMarkStack::allocate(size_t capacity) {
256 // allocate a stack of the requisite depth
257 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
258 if (!rs.is_reserved()) {
259 warning("ConcurrentMark MarkStack allocation failure");
260 return false;
261 }
262 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
263 if (!_virtual_space.initialize(rs, rs.size())) {
264 warning("ConcurrentMark MarkStack backing store failure");
265 // Release the virtual memory reserved for the marking stack
266 rs.release();
267 return false;
268 }
269 assert(_virtual_space.committed_size() == rs.size(),
270 "Didn't reserve backing store for all of ConcurrentMark stack?");
271 _base = (oop*) _virtual_space.low();
272 setEmpty();
273 _capacity = (jint) capacity;
274 _saved_index = -1;
275 _should_expand = false;
276 return true;
277 }
278
279 void CMMarkStack::expand() {
280 // Called, during remark, if we've overflown the marking stack during marking.
281 assert(isEmpty(), "stack should been emptied while handling overflow");
282 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
283 // Clear expansion flag
284 _should_expand = false;
285 if (_capacity == (jint) MarkStackSizeMax) {
286 if (PrintGCDetails && Verbose) {
287 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
288 }
289 return;
290 }
291 // Double capacity if possible
292 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
293 // Do not give up existing stack until we have managed to
294 // get the double capacity that we desired.
295 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
296 sizeof(oop)));
297 if (rs.is_reserved()) {
298 // Release the backing store associated with old stack
299 _virtual_space.release();
300 // Reinitialize virtual space for new stack
301 if (!_virtual_space.initialize(rs, rs.size())) {
302 fatal("Not enough swap for expanded marking stack capacity");
303 }
304 _base = (oop*)(_virtual_space.low());
305 _index = 0;
306 _capacity = new_capacity;
307 } else {
308 if (PrintGCDetails && Verbose) {
309 // Failed to double capacity, continue;
310 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
311 SIZE_FORMAT "K to " SIZE_FORMAT "K",
312 _capacity / K, new_capacity / K);
313 }
314 }
315 }
316
317 void CMMarkStack::set_should_expand() {
318 // If we're resetting the marking state because of an
319 // marking stack overflow, record that we should, if
320 // possible, expand the stack.
321 _should_expand = _cm->has_overflown();
322 }
323
324 CMMarkStack::~CMMarkStack() {
325 if (_base != NULL) {
326 _base = NULL;
327 _virtual_space.release();
328 }
329 }
330
331 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
332 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
333 jint start = _index;
334 jint next_index = start + n;
335 if (next_index > _capacity) {
336 _overflow = true;
337 return;
338 }
339 // Otherwise.
340 _index = next_index;
341 for (int i = 0; i < n; i++) {
342 int ind = start + i;
343 assert(ind < _capacity, "By overflow test above.");
344 _base[ind] = ptr_arr[i];
345 }
346 }
347
348 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
349 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
350 jint index = _index;
351 if (index == 0) {
352 *n = 0;
353 return false;
354 } else {
355 int k = MIN2(max, index);
356 jint new_ind = index - k;
357 for (int j = 0; j < k; j++) {
358 ptr_arr[j] = _base[new_ind + j];
359 }
360 _index = new_ind;
361 *n = k;
362 return true;
363 }
364 }
365
366 template<class OopClosureClass>
367 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
368 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
369 || SafepointSynchronize::is_at_safepoint(),
370 "Drain recursion must be yield-safe.");
371 bool res = true;
372 debug_only(_drain_in_progress = true);
373 debug_only(_drain_in_progress_yields = yield_after);
374 while (!isEmpty()) {
375 oop newOop = pop();
376 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
377 assert(newOop->is_oop(), "Expected an oop");
378 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
379 "only grey objects on this stack");
380 newOop->oop_iterate(cl);
381 if (yield_after && _cm->do_yield_check()) {
382 res = false;
383 break;
384 }
385 }
386 debug_only(_drain_in_progress = false);
387 return res;
388 }
389
390 void CMMarkStack::note_start_of_gc() {
391 assert(_saved_index == -1,
392 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
393 _saved_index = _index;
394 }
395
396 void CMMarkStack::note_end_of_gc() {
397 // This is intentionally a guarantee, instead of an assert. If we
398 // accidentally add something to the mark stack during GC, it
399 // will be a correctness issue so it's better if we crash. we'll
400 // only check this once per GC anyway, so it won't be a performance
401 // issue in any way.
402 guarantee(_saved_index == _index,
403 err_msg("saved index: %d index: %d", _saved_index, _index));
404 _saved_index = -1;
405 }
406
407 CMRootRegions::CMRootRegions() :
408 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
409 _should_abort(false), _next_survivor(NULL) { }
410
411 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
412 _young_list = g1h->young_list();
413 _cm = cm;
414 }
415
416 void CMRootRegions::prepare_for_scan() {
417 assert(!scan_in_progress(), "pre-condition");
418
419 // Currently, only survivors can be root regions.
420 assert(_next_survivor == NULL, "pre-condition");
421 _next_survivor = _young_list->first_survivor_region();
422 _scan_in_progress = (_next_survivor != NULL);
423 _should_abort = false;
424 }
425
426 HeapRegion* CMRootRegions::claim_next() {
427 if (_should_abort) {
428 // If someone has set the should_abort flag, we return NULL to
429 // force the caller to bail out of their loop.
430 return NULL;
431 }
432
433 // Currently, only survivors can be root regions.
434 HeapRegion* res = _next_survivor;
435 if (res != NULL) {
436 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
437 // Read it again in case it changed while we were waiting for the lock.
438 res = _next_survivor;
439 if (res != NULL) {
440 if (res == _young_list->last_survivor_region()) {
441 // We just claimed the last survivor so store NULL to indicate
442 // that we're done.
443 _next_survivor = NULL;
444 } else {
445 _next_survivor = res->get_next_young_region();
446 }
447 } else {
448 // Someone else claimed the last survivor while we were trying
449 // to take the lock so nothing else to do.
450 }
451 }
452 assert(res == NULL || res->is_survivor(), "post-condition");
453
454 return res;
455 }
456
457 void CMRootRegions::scan_finished() {
458 assert(scan_in_progress(), "pre-condition");
459
460 // Currently, only survivors can be root regions.
461 if (!_should_abort) {
462 assert(_next_survivor == NULL, "we should have claimed all survivors");
463 }
464 _next_survivor = NULL;
465
466 {
467 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
468 _scan_in_progress = false;
469 RootRegionScan_lock->notify_all();
470 }
471 }
472
473 bool CMRootRegions::wait_until_scan_finished() {
474 if (!scan_in_progress()) return false;
475
476 {
477 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
478 while (scan_in_progress()) {
479 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
480 }
481 }
482 return true;
483 }
484
485 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
486 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
487 #endif // _MSC_VER
488
489 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
490 return MAX2((n_par_threads + 2) / 4, 1U);
491 }
492
493 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
494 _g1h(g1h),
495 _markBitMap1(),
496 _markBitMap2(),
497 _parallel_marking_threads(0),
498 _max_parallel_marking_threads(0),
499 _sleep_factor(0.0),
500 _marking_task_overhead(1.0),
501 _cleanup_sleep_factor(0.0),
502 _cleanup_task_overhead(1.0),
503 _cleanup_list("Cleanup List"),
504 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
505 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >>
506 CardTableModRefBS::card_shift,
507 false /* in_resource_area*/),
508
509 _prevMarkBitMap(&_markBitMap1),
510 _nextMarkBitMap(&_markBitMap2),
511
512 _markStack(this),
513 // _finger set in set_non_marking_state
514
515 _max_worker_id(ParallelGCThreads),
516 // _active_tasks set in set_non_marking_state
517 // _tasks set inside the constructor
518 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
519 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
520
521 _has_overflown(false),
522 _concurrent(false),
523 _has_aborted(false),
524 _restart_for_overflow(false),
525 _concurrent_marking_in_progress(false),
526
527 // _verbose_level set below
528
529 _init_times(),
530 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
531 _cleanup_times(),
532 _total_counting_time(0.0),
533 _total_rs_scrub_time(0.0),
534
535 _parallel_workers(NULL),
536
537 _count_card_bitmaps(NULL),
538 _count_marked_bytes(NULL),
539 _completed_initialization(false) {
540 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
541 if (verbose_level < no_verbose) {
542 verbose_level = no_verbose;
543 }
544 if (verbose_level > high_verbose) {
545 verbose_level = high_verbose;
546 }
547 _verbose_level = verbose_level;
548
549 if (verbose_low()) {
550 gclog_or_tty->print_cr("[global] init, heap start = " PTR_FORMAT ", "
551 "heap end = " PTR_FORMAT, p2i(_heap_start), p2i(_heap_end));
552 }
553
554 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
555 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
556
557 // Create & start a ConcurrentMark thread.
558 _cmThread = new ConcurrentMarkThread(this);
559 assert(cmThread() != NULL, "CM Thread should have been created");
560 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
561 if (_cmThread->osthread() == NULL) {
562 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
563 }
564
565 assert(CGC_lock != NULL, "Where's the CGC_lock?");
566 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
567 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
568
569 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
570 satb_qs.set_buffer_size(G1SATBBufferSize);
571
572 _root_regions.init(_g1h, this);
573
574 if (ConcGCThreads > ParallelGCThreads) {
575 warning("Can't have more ConcGCThreads (%u) "
576 "than ParallelGCThreads (%u).",
577 ConcGCThreads, ParallelGCThreads);
578 return;
579 }
580 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
581 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
582 // if both are set
583 _sleep_factor = 0.0;
584 _marking_task_overhead = 1.0;
585 } else if (G1MarkingOverheadPercent > 0) {
586 // We will calculate the number of parallel marking threads based
587 // on a target overhead with respect to the soft real-time goal
588 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
589 double overall_cm_overhead =
590 (double) MaxGCPauseMillis * marking_overhead /
591 (double) GCPauseIntervalMillis;
592 double cpu_ratio = 1.0 / (double) os::processor_count();
593 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
594 double marking_task_overhead =
595 overall_cm_overhead / marking_thread_num *
596 (double) os::processor_count();
597 double sleep_factor =
598 (1.0 - marking_task_overhead) / marking_task_overhead;
599
600 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
601 _sleep_factor = sleep_factor;
602 _marking_task_overhead = marking_task_overhead;
603 } else {
604 // Calculate the number of parallel marking threads by scaling
605 // the number of parallel GC threads.
606 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
607 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
608 _sleep_factor = 0.0;
609 _marking_task_overhead = 1.0;
610 }
611
612 assert(ConcGCThreads > 0, "Should have been set");
613 _parallel_marking_threads = ConcGCThreads;
614 _max_parallel_marking_threads = _parallel_marking_threads;
615
616 if (parallel_marking_threads() > 1) {
617 _cleanup_task_overhead = 1.0;
618 } else {
619 _cleanup_task_overhead = marking_task_overhead();
620 }
621 _cleanup_sleep_factor =
622 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
623
624 #if 0
625 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
626 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
627 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
628 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
629 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
630 #endif
631
632 _parallel_workers = new WorkGang("G1 Marker",
633 _max_parallel_marking_threads, false, true);
634 if (_parallel_workers == NULL) {
635 vm_exit_during_initialization("Failed necessary allocation.");
636 } else {
637 _parallel_workers->initialize_workers();
638 }
639
640 if (FLAG_IS_DEFAULT(MarkStackSize)) {
641 size_t mark_stack_size =
642 MIN2(MarkStackSizeMax,
643 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
644 // Verify that the calculated value for MarkStackSize is in range.
645 // It would be nice to use the private utility routine from Arguments.
646 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
647 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
648 "must be between 1 and " SIZE_FORMAT,
649 mark_stack_size, MarkStackSizeMax);
650 return;
651 }
652 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
653 } else {
654 // Verify MarkStackSize is in range.
655 if (FLAG_IS_CMDLINE(MarkStackSize)) {
656 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
657 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
658 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
659 "must be between 1 and " SIZE_FORMAT,
660 MarkStackSize, MarkStackSizeMax);
661 return;
662 }
663 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
664 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
665 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
666 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
667 MarkStackSize, MarkStackSizeMax);
668 return;
669 }
670 }
671 }
672 }
673
674 if (!_markStack.allocate(MarkStackSize)) {
675 warning("Failed to allocate CM marking stack");
676 return;
677 }
678
679 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
680 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
681
682 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
683 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
684
685 BitMap::idx_t card_bm_size = _card_bm.size();
686
687 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
688 _active_tasks = _max_worker_id;
689
690 uint max_regions = _g1h->max_regions();
691 for (uint i = 0; i < _max_worker_id; ++i) {
692 CMTaskQueue* task_queue = new CMTaskQueue();
693 task_queue->initialize();
694 _task_queues->register_queue(i, task_queue);
695
696 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
697 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
698
699 _tasks[i] = new CMTask(i, this,
700 _count_marked_bytes[i],
701 &_count_card_bitmaps[i],
702 task_queue, _task_queues);
703
704 _accum_task_vtime[i] = 0.0;
705 }
706
707 // Calculate the card number for the bottom of the heap. Used
708 // in biasing indexes into the accounting card bitmaps.
709 _heap_bottom_card_num =
710 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
711 CardTableModRefBS::card_shift);
712
713 // Clear all the liveness counting data
714 clear_all_count_data();
715
716 // so that the call below can read a sensible value
717 _heap_start = g1h->reserved_region().start();
718 set_non_marking_state();
719 _completed_initialization = true;
720 }
721
722 void ConcurrentMark::reset() {
723 // Starting values for these two. This should be called in a STW
724 // phase.
725 MemRegion reserved = _g1h->g1_reserved();
726 _heap_start = reserved.start();
727 _heap_end = reserved.end();
728
729 // Separated the asserts so that we know which one fires.
730 assert(_heap_start != NULL, "heap bounds should look ok");
731 assert(_heap_end != NULL, "heap bounds should look ok");
732 assert(_heap_start < _heap_end, "heap bounds should look ok");
733
734 // Reset all the marking data structures and any necessary flags
735 reset_marking_state();
736
737 if (verbose_low()) {
738 gclog_or_tty->print_cr("[global] resetting");
739 }
740
741 // We do reset all of them, since different phases will use
742 // different number of active threads. So, it's easiest to have all
743 // of them ready.
744 for (uint i = 0; i < _max_worker_id; ++i) {
745 _tasks[i]->reset(_nextMarkBitMap);
746 }
747
748 // we need this to make sure that the flag is on during the evac
749 // pause with initial mark piggy-backed
750 set_concurrent_marking_in_progress();
751 }
752
753
754 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
755 _markStack.set_should_expand();
756 _markStack.setEmpty(); // Also clears the _markStack overflow flag
757 if (clear_overflow) {
758 clear_has_overflown();
759 } else {
760 assert(has_overflown(), "pre-condition");
761 }
762 _finger = _heap_start;
763
764 for (uint i = 0; i < _max_worker_id; ++i) {
765 CMTaskQueue* queue = _task_queues->queue(i);
766 queue->set_empty();
767 }
768 }
769
770 void ConcurrentMark::set_concurrency(uint active_tasks) {
771 assert(active_tasks <= _max_worker_id, "we should not have more");
772
773 _active_tasks = active_tasks;
774 // Need to update the three data structures below according to the
775 // number of active threads for this phase.
776 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
777 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
778 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
779 }
780
781 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
782 set_concurrency(active_tasks);
783
784 _concurrent = concurrent;
785 // We propagate this to all tasks, not just the active ones.
786 for (uint i = 0; i < _max_worker_id; ++i)
787 _tasks[i]->set_concurrent(concurrent);
788
789 if (concurrent) {
790 set_concurrent_marking_in_progress();
791 } else {
792 // We currently assume that the concurrent flag has been set to
793 // false before we start remark. At this point we should also be
794 // in a STW phase.
795 assert(!concurrent_marking_in_progress(), "invariant");
796 assert(out_of_regions(),
797 err_msg("only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
798 p2i(_finger), p2i(_heap_end)));
799 }
800 }
801
802 void ConcurrentMark::set_non_marking_state() {
803 // We set the global marking state to some default values when we're
804 // not doing marking.
805 reset_marking_state();
806 _active_tasks = 0;
807 clear_concurrent_marking_in_progress();
808 }
809
810 ConcurrentMark::~ConcurrentMark() {
811 // The ConcurrentMark instance is never freed.
812 ShouldNotReachHere();
813 }
814
815 void ConcurrentMark::clearNextBitmap() {
816 G1CollectedHeap* g1h = G1CollectedHeap::heap();
817
818 // Make sure that the concurrent mark thread looks to still be in
819 // the current cycle.
820 guarantee(cmThread()->during_cycle(), "invariant");
821
822 // We are finishing up the current cycle by clearing the next
823 // marking bitmap and getting it ready for the next cycle. During
824 // this time no other cycle can start. So, let's make sure that this
825 // is the case.
826 guarantee(!g1h->collector_state()->mark_in_progress(), "invariant");
827
828 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */);
829 ParClearNextMarkBitmapTask task(&cl, parallel_marking_threads(), true);
830 _parallel_workers->run_task(&task);
831
832 // Clear the liveness counting data. If the marking has been aborted, the abort()
833 // call already did that.
834 if (cl.complete()) {
835 clear_all_count_data();
836 }
837
838 // Repeat the asserts from above.
839 guarantee(cmThread()->during_cycle(), "invariant");
840 guarantee(!g1h->collector_state()->mark_in_progress(), "invariant");
841 }
842
843 class CheckBitmapClearHRClosure : public HeapRegionClosure {
844 CMBitMap* _bitmap;
845 bool _error;
846 public:
847 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) {
848 }
849
850 virtual bool doHeapRegion(HeapRegion* r) {
851 // This closure can be called concurrently to the mutator, so we must make sure
852 // that the result of the getNextMarkedWordAddress() call is compared to the
853 // value passed to it as limit to detect any found bits.
854 // We can use the region's orig_end() for the limit and the comparison value
855 // as it always contains the "real" end of the region that never changes and
856 // has no side effects.
857 // Due to the latter, there can also be no problem with the compiler generating
858 // reloads of the orig_end() call.
859 HeapWord* end = r->orig_end();
860 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
861 }
862 };
863
864 bool ConcurrentMark::nextMarkBitmapIsClear() {
865 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
866 _g1h->heap_region_iterate(&cl);
867 return cl.complete();
868 }
869
870 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
871 public:
872 bool doHeapRegion(HeapRegion* r) {
873 if (!r->is_continues_humongous()) {
874 r->note_start_of_marking();
875 }
876 return false;
877 }
878 };
879
880 void ConcurrentMark::checkpointRootsInitialPre() {
881 G1CollectedHeap* g1h = G1CollectedHeap::heap();
882 G1CollectorPolicy* g1p = g1h->g1_policy();
883
884 _has_aborted = false;
885
886 // Initialize marking structures. This has to be done in a STW phase.
887 reset();
888
889 // For each region note start of marking.
890 NoteStartOfMarkHRClosure startcl;
891 g1h->heap_region_iterate(&startcl);
892 }
893
894
895 void ConcurrentMark::checkpointRootsInitialPost() {
896 G1CollectedHeap* g1h = G1CollectedHeap::heap();
897
898 // If we force an overflow during remark, the remark operation will
899 // actually abort and we'll restart concurrent marking. If we always
900 // force an overflow during remark we'll never actually complete the
901 // marking phase. So, we initialize this here, at the start of the
902 // cycle, so that at the remaining overflow number will decrease at
903 // every remark and we'll eventually not need to cause one.
904 force_overflow_stw()->init();
905
906 // Start Concurrent Marking weak-reference discovery.
907 ReferenceProcessor* rp = g1h->ref_processor_cm();
908 // enable ("weak") refs discovery
909 rp->enable_discovery();
910 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
911
912 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
913 // This is the start of the marking cycle, we're expected all
914 // threads to have SATB queues with active set to false.
915 satb_mq_set.set_active_all_threads(true, /* new active value */
916 false /* expected_active */);
917
918 _root_regions.prepare_for_scan();
919
920 // update_g1_committed() will be called at the end of an evac pause
921 // when marking is on. So, it's also called at the end of the
922 // initial-mark pause to update the heap end, if the heap expands
923 // during it. No need to call it here.
924 }
925
926 /*
927 * Notice that in the next two methods, we actually leave the STS
928 * during the barrier sync and join it immediately afterwards. If we
929 * do not do this, the following deadlock can occur: one thread could
930 * be in the barrier sync code, waiting for the other thread to also
931 * sync up, whereas another one could be trying to yield, while also
932 * waiting for the other threads to sync up too.
933 *
934 * Note, however, that this code is also used during remark and in
935 * this case we should not attempt to leave / enter the STS, otherwise
936 * we'll either hit an assert (debug / fastdebug) or deadlock
937 * (product). So we should only leave / enter the STS if we are
938 * operating concurrently.
939 *
940 * Because the thread that does the sync barrier has left the STS, it
941 * is possible to be suspended for a Full GC or an evacuation pause
942 * could occur. This is actually safe, since the entering the sync
943 * barrier is one of the last things do_marking_step() does, and it
944 * doesn't manipulate any data structures afterwards.
945 */
946
947 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
948 bool barrier_aborted;
949
950 if (verbose_low()) {
951 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
952 }
953
954 {
955 SuspendibleThreadSetLeaver sts_leave(concurrent());
956 barrier_aborted = !_first_overflow_barrier_sync.enter();
957 }
958
959 // at this point everyone should have synced up and not be doing any
960 // more work
961
962 if (verbose_low()) {
963 if (barrier_aborted) {
964 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id);
965 } else {
966 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
967 }
968 }
969
970 if (barrier_aborted) {
971 // If the barrier aborted we ignore the overflow condition and
972 // just abort the whole marking phase as quickly as possible.
973 return;
974 }
975
976 // If we're executing the concurrent phase of marking, reset the marking
977 // state; otherwise the marking state is reset after reference processing,
978 // during the remark pause.
979 // If we reset here as a result of an overflow during the remark we will
980 // see assertion failures from any subsequent set_concurrency_and_phase()
981 // calls.
982 if (concurrent()) {
983 // let the task associated with with worker 0 do this
984 if (worker_id == 0) {
985 // task 0 is responsible for clearing the global data structures
986 // We should be here because of an overflow. During STW we should
987 // not clear the overflow flag since we rely on it being true when
988 // we exit this method to abort the pause and restart concurrent
989 // marking.
990 reset_marking_state(true /* clear_overflow */);
991 force_overflow()->update();
992
993 if (G1Log::fine()) {
994 gclog_or_tty->gclog_stamp();
995 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
996 }
997 }
998 }
999
1000 // after this, each task should reset its own data structures then
1001 // then go into the second barrier
1002 }
1003
1004 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1005 bool barrier_aborted;
1006
1007 if (verbose_low()) {
1008 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1009 }
1010
1011 {
1012 SuspendibleThreadSetLeaver sts_leave(concurrent());
1013 barrier_aborted = !_second_overflow_barrier_sync.enter();
1014 }
1015
1016 // at this point everything should be re-initialized and ready to go
1017
1018 if (verbose_low()) {
1019 if (barrier_aborted) {
1020 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id);
1021 } else {
1022 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1023 }
1024 }
1025 }
1026
1027 #ifndef PRODUCT
1028 void ForceOverflowSettings::init() {
1029 _num_remaining = G1ConcMarkForceOverflow;
1030 _force = false;
1031 update();
1032 }
1033
1034 void ForceOverflowSettings::update() {
1035 if (_num_remaining > 0) {
1036 _num_remaining -= 1;
1037 _force = true;
1038 } else {
1039 _force = false;
1040 }
1041 }
1042
1043 bool ForceOverflowSettings::should_force() {
1044 if (_force) {
1045 _force = false;
1046 return true;
1047 } else {
1048 return false;
1049 }
1050 }
1051 #endif // !PRODUCT
1052
1053 class CMConcurrentMarkingTask: public AbstractGangTask {
1054 private:
1055 ConcurrentMark* _cm;
1056 ConcurrentMarkThread* _cmt;
1057
1058 public:
1059 void work(uint worker_id) {
1060 assert(Thread::current()->is_ConcurrentGC_thread(),
1061 "this should only be done by a conc GC thread");
1062 ResourceMark rm;
1063
1064 double start_vtime = os::elapsedVTime();
1065
1066 {
1067 SuspendibleThreadSetJoiner sts_join;
1068
1069 assert(worker_id < _cm->active_tasks(), "invariant");
1070 CMTask* the_task = _cm->task(worker_id);
1071 the_task->record_start_time();
1072 if (!_cm->has_aborted()) {
1073 do {
1074 double start_vtime_sec = os::elapsedVTime();
1075 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1076
1077 the_task->do_marking_step(mark_step_duration_ms,
1078 true /* do_termination */,
1079 false /* is_serial*/);
1080
1081 double end_vtime_sec = os::elapsedVTime();
1082 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1083 _cm->clear_has_overflown();
1084
1085 _cm->do_yield_check(worker_id);
1086
1087 jlong sleep_time_ms;
1088 if (!_cm->has_aborted() && the_task->has_aborted()) {
1089 sleep_time_ms =
1090 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1091 {
1092 SuspendibleThreadSetLeaver sts_leave;
1093 os::sleep(Thread::current(), sleep_time_ms, false);
1094 }
1095 }
1096 } while (!_cm->has_aborted() && the_task->has_aborted());
1097 }
1098 the_task->record_end_time();
1099 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1100 }
1101
1102 double end_vtime = os::elapsedVTime();
1103 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1104 }
1105
1106 CMConcurrentMarkingTask(ConcurrentMark* cm,
1107 ConcurrentMarkThread* cmt) :
1108 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1109
1110 ~CMConcurrentMarkingTask() { }
1111 };
1112
1113 // Calculates the number of active workers for a concurrent
1114 // phase.
1115 uint ConcurrentMark::calc_parallel_marking_threads() {
1116 uint n_conc_workers = 0;
1117 if (!UseDynamicNumberOfGCThreads ||
1118 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1119 !ForceDynamicNumberOfGCThreads)) {
1120 n_conc_workers = max_parallel_marking_threads();
1121 } else {
1122 n_conc_workers =
1123 AdaptiveSizePolicy::calc_default_active_workers(
1124 max_parallel_marking_threads(),
1125 1, /* Minimum workers */
1126 parallel_marking_threads(),
1127 Threads::number_of_non_daemon_threads());
1128 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1129 // that scaling has already gone into "_max_parallel_marking_threads".
1130 }
1131 assert(n_conc_workers > 0, "Always need at least 1");
1132 return n_conc_workers;
1133 }
1134
1135 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1136 // Currently, only survivors can be root regions.
1137 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1138 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1139
1140 const uintx interval = PrefetchScanIntervalInBytes;
1141 HeapWord* curr = hr->bottom();
1142 const HeapWord* end = hr->top();
1143 while (curr < end) {
1144 Prefetch::read(curr, interval);
1145 oop obj = oop(curr);
1146 int size = obj->oop_iterate_size(&cl);
1147 assert(size == obj->size(), "sanity");
1148 curr += size;
1149 }
1150 }
1151
1152 class CMRootRegionScanTask : public AbstractGangTask {
1153 private:
1154 ConcurrentMark* _cm;
1155
1156 public:
1157 CMRootRegionScanTask(ConcurrentMark* cm) :
1158 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1159
1160 void work(uint worker_id) {
1161 assert(Thread::current()->is_ConcurrentGC_thread(),
1162 "this should only be done by a conc GC thread");
1163
1164 CMRootRegions* root_regions = _cm->root_regions();
1165 HeapRegion* hr = root_regions->claim_next();
1166 while (hr != NULL) {
1167 _cm->scanRootRegion(hr, worker_id);
1168 hr = root_regions->claim_next();
1169 }
1170 }
1171 };
1172
1173 void ConcurrentMark::scanRootRegions() {
1174 double scan_start = os::elapsedTime();
1175
1176 // Start of concurrent marking.
1177 ClassLoaderDataGraph::clear_claimed_marks();
1178
1179 // scan_in_progress() will have been set to true only if there was
1180 // at least one root region to scan. So, if it's false, we
1181 // should not attempt to do any further work.
1182 if (root_regions()->scan_in_progress()) {
1183 if (G1Log::fine()) {
1184 gclog_or_tty->gclog_stamp();
1185 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]");
1186 }
1187
1188 _parallel_marking_threads = calc_parallel_marking_threads();
1189 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1190 "Maximum number of marking threads exceeded");
1191 uint active_workers = MAX2(1U, parallel_marking_threads());
1192
1193 CMRootRegionScanTask task(this);
1194 _parallel_workers->set_active_workers(active_workers);
1195 _parallel_workers->run_task(&task);
1196
1197 if (G1Log::fine()) {
1198 gclog_or_tty->gclog_stamp();
1199 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]", os::elapsedTime() - scan_start);
1200 }
1201
1202 // It's possible that has_aborted() is true here without actually
1203 // aborting the survivor scan earlier. This is OK as it's
1204 // mainly used for sanity checking.
1205 root_regions()->scan_finished();
1206 }
1207 }
1208
1209 void ConcurrentMark::markFromRoots() {
1210 // we might be tempted to assert that:
1211 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1212 // "inconsistent argument?");
1213 // However that wouldn't be right, because it's possible that
1214 // a safepoint is indeed in progress as a younger generation
1215 // stop-the-world GC happens even as we mark in this generation.
1216
1217 _restart_for_overflow = false;
1218 force_overflow_conc()->init();
1219
1220 // _g1h has _n_par_threads
1221 _parallel_marking_threads = calc_parallel_marking_threads();
1222 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1223 "Maximum number of marking threads exceeded");
1224
1225 uint active_workers = MAX2(1U, parallel_marking_threads());
1226 assert(active_workers > 0, "Should have been set");
1227
1228 // Parallel task terminator is set in "set_concurrency_and_phase()"
1229 set_concurrency_and_phase(active_workers, true /* concurrent */);
1230
1231 CMConcurrentMarkingTask markingTask(this, cmThread());
1232 _parallel_workers->set_active_workers(active_workers);
1233 _parallel_workers->run_task(&markingTask);
1234 print_stats();
1235 }
1236
1237 // Helper class to get rid of some boilerplate code.
1238 class G1CMTraceTime : public StackObj {
1239 GCTraceTimeImpl _gc_trace_time;
1240 static bool doit_and_prepend(bool doit) {
1241 if (doit) {
1242 gclog_or_tty->put(' ');
1243 }
1244 return doit;
1245 }
1246
1247 public:
1248 G1CMTraceTime(const char* title, bool doit)
1249 : _gc_trace_time(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm()) {
1250 }
1251 };
1252
1253 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1254 // world is stopped at this checkpoint
1255 assert(SafepointSynchronize::is_at_safepoint(),
1256 "world should be stopped");
1257
1258 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1259
1260 // If a full collection has happened, we shouldn't do this.
1261 if (has_aborted()) {
1262 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1263 return;
1264 }
1265
1266 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1267
1268 if (VerifyDuringGC) {
1269 HandleMark hm; // handle scope
1270 g1h->prepare_for_verify();
1271 Universe::verify(VerifyOption_G1UsePrevMarking,
1272 " VerifyDuringGC:(before)");
1273 }
1274 g1h->check_bitmaps("Remark Start");
1275
1276 G1CollectorPolicy* g1p = g1h->g1_policy();
1277 g1p->record_concurrent_mark_remark_start();
1278
1279 double start = os::elapsedTime();
1280
1281 checkpointRootsFinalWork();
1282
1283 double mark_work_end = os::elapsedTime();
1284
1285 weakRefsWork(clear_all_soft_refs);
1286
1287 if (has_overflown()) {
1288 // Oops. We overflowed. Restart concurrent marking.
1289 _restart_for_overflow = true;
1290 if (G1TraceMarkStackOverflow) {
1291 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1292 }
1293
1294 // Verify the heap w.r.t. the previous marking bitmap.
1295 if (VerifyDuringGC) {
1296 HandleMark hm; // handle scope
1297 g1h->prepare_for_verify();
1298 Universe::verify(VerifyOption_G1UsePrevMarking,
1299 " VerifyDuringGC:(overflow)");
1300 }
1301
1302 // Clear the marking state because we will be restarting
1303 // marking due to overflowing the global mark stack.
1304 reset_marking_state();
1305 } else {
1306 {
1307 G1CMTraceTime trace("GC aggregate-data", G1Log::finer());
1308
1309 // Aggregate the per-task counting data that we have accumulated
1310 // while marking.
1311 aggregate_count_data();
1312 }
1313
1314 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1315 // We're done with marking.
1316 // This is the end of the marking cycle, we're expected all
1317 // threads to have SATB queues with active set to true.
1318 satb_mq_set.set_active_all_threads(false, /* new active value */
1319 true /* expected_active */);
1320
1321 if (VerifyDuringGC) {
1322 HandleMark hm; // handle scope
1323 g1h->prepare_for_verify();
1324 Universe::verify(VerifyOption_G1UseNextMarking,
1325 " VerifyDuringGC:(after)");
1326 }
1327 g1h->check_bitmaps("Remark End");
1328 assert(!restart_for_overflow(), "sanity");
1329 // Completely reset the marking state since marking completed
1330 set_non_marking_state();
1331 }
1332
1333 // Expand the marking stack, if we have to and if we can.
1334 if (_markStack.should_expand()) {
1335 _markStack.expand();
1336 }
1337
1338 // Statistics
1339 double now = os::elapsedTime();
1340 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1341 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1342 _remark_times.add((now - start) * 1000.0);
1343
1344 g1p->record_concurrent_mark_remark_end();
1345
1346 G1CMIsAliveClosure is_alive(g1h);
1347 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1348 }
1349
1350 // Base class of the closures that finalize and verify the
1351 // liveness counting data.
1352 class CMCountDataClosureBase: public HeapRegionClosure {
1353 protected:
1354 G1CollectedHeap* _g1h;
1355 ConcurrentMark* _cm;
1356 CardTableModRefBS* _ct_bs;
1357
1358 BitMap* _region_bm;
1359 BitMap* _card_bm;
1360
1361 // Takes a region that's not empty (i.e., it has at least one
1362 // live object in it and sets its corresponding bit on the region
1363 // bitmap to 1. If the region is "starts humongous" it will also set
1364 // to 1 the bits on the region bitmap that correspond to its
1365 // associated "continues humongous" regions.
1366 void set_bit_for_region(HeapRegion* hr) {
1367 assert(!hr->is_continues_humongous(), "should have filtered those out");
1368
1369 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1370 if (!hr->is_starts_humongous()) {
1371 // Normal (non-humongous) case: just set the bit.
1372 _region_bm->par_at_put(index, true);
1373 } else {
1374 // Starts humongous case: calculate how many regions are part of
1375 // this humongous region and then set the bit range.
1376 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1377 _region_bm->par_at_put_range(index, end_index, true);
1378 }
1379 }
1380
1381 public:
1382 CMCountDataClosureBase(G1CollectedHeap* g1h,
1383 BitMap* region_bm, BitMap* card_bm):
1384 _g1h(g1h), _cm(g1h->concurrent_mark()),
1385 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
1386 _region_bm(region_bm), _card_bm(card_bm) { }
1387 };
1388
1389 // Closure that calculates the # live objects per region. Used
1390 // for verification purposes during the cleanup pause.
1391 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1392 CMBitMapRO* _bm;
1393 size_t _region_marked_bytes;
1394
1395 public:
1396 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1397 BitMap* region_bm, BitMap* card_bm) :
1398 CMCountDataClosureBase(g1h, region_bm, card_bm),
1399 _bm(bm), _region_marked_bytes(0) { }
1400
1401 bool doHeapRegion(HeapRegion* hr) {
1402
1403 if (hr->is_continues_humongous()) {
1404 // We will ignore these here and process them when their
1405 // associated "starts humongous" region is processed (see
1406 // set_bit_for_heap_region()). Note that we cannot rely on their
1407 // associated "starts humongous" region to have their bit set to
1408 // 1 since, due to the region chunking in the parallel region
1409 // iteration, a "continues humongous" region might be visited
1410 // before its associated "starts humongous".
1411 return false;
1412 }
1413
1414 HeapWord* ntams = hr->next_top_at_mark_start();
1415 HeapWord* start = hr->bottom();
1416
1417 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1418 err_msg("Preconditions not met - "
1419 "start: " PTR_FORMAT ", ntams: " PTR_FORMAT ", end: " PTR_FORMAT,
1420 p2i(start), p2i(ntams), p2i(hr->end())));
1421
1422 // Find the first marked object at or after "start".
1423 start = _bm->getNextMarkedWordAddress(start, ntams);
1424
1425 size_t marked_bytes = 0;
1426
1427 while (start < ntams) {
1428 oop obj = oop(start);
1429 int obj_sz = obj->size();
1430 HeapWord* obj_end = start + obj_sz;
1431
1432 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1433 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1434
1435 // Note: if we're looking at the last region in heap - obj_end
1436 // could be actually just beyond the end of the heap; end_idx
1437 // will then correspond to a (non-existent) card that is also
1438 // just beyond the heap.
1439 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1440 // end of object is not card aligned - increment to cover
1441 // all the cards spanned by the object
1442 end_idx += 1;
1443 }
1444
1445 // Set the bits in the card BM for the cards spanned by this object.
1446 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1447
1448 // Add the size of this object to the number of marked bytes.
1449 marked_bytes += (size_t)obj_sz * HeapWordSize;
1450
1451 // Find the next marked object after this one.
1452 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1453 }
1454
1455 // Mark the allocated-since-marking portion...
1456 HeapWord* top = hr->top();
1457 if (ntams < top) {
1458 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1459 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1460
1461 // Note: if we're looking at the last region in heap - top
1462 // could be actually just beyond the end of the heap; end_idx
1463 // will then correspond to a (non-existent) card that is also
1464 // just beyond the heap.
1465 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1466 // end of object is not card aligned - increment to cover
1467 // all the cards spanned by the object
1468 end_idx += 1;
1469 }
1470 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1471
1472 // This definitely means the region has live objects.
1473 set_bit_for_region(hr);
1474 }
1475
1476 // Update the live region bitmap.
1477 if (marked_bytes > 0) {
1478 set_bit_for_region(hr);
1479 }
1480
1481 // Set the marked bytes for the current region so that
1482 // it can be queried by a calling verification routine
1483 _region_marked_bytes = marked_bytes;
1484
1485 return false;
1486 }
1487
1488 size_t region_marked_bytes() const { return _region_marked_bytes; }
1489 };
1490
1491 // Heap region closure used for verifying the counting data
1492 // that was accumulated concurrently and aggregated during
1493 // the remark pause. This closure is applied to the heap
1494 // regions during the STW cleanup pause.
1495
1496 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1497 G1CollectedHeap* _g1h;
1498 ConcurrentMark* _cm;
1499 CalcLiveObjectsClosure _calc_cl;
1500 BitMap* _region_bm; // Region BM to be verified
1501 BitMap* _card_bm; // Card BM to be verified
1502 bool _verbose; // verbose output?
1503
1504 BitMap* _exp_region_bm; // Expected Region BM values
1505 BitMap* _exp_card_bm; // Expected card BM values
1506
1507 int _failures;
1508
1509 public:
1510 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1511 BitMap* region_bm,
1512 BitMap* card_bm,
1513 BitMap* exp_region_bm,
1514 BitMap* exp_card_bm,
1515 bool verbose) :
1516 _g1h(g1h), _cm(g1h->concurrent_mark()),
1517 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1518 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1519 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1520 _failures(0) { }
1521
1522 int failures() const { return _failures; }
1523
1524 bool doHeapRegion(HeapRegion* hr) {
1525 if (hr->is_continues_humongous()) {
1526 // We will ignore these here and process them when their
1527 // associated "starts humongous" region is processed (see
1528 // set_bit_for_heap_region()). Note that we cannot rely on their
1529 // associated "starts humongous" region to have their bit set to
1530 // 1 since, due to the region chunking in the parallel region
1531 // iteration, a "continues humongous" region might be visited
1532 // before its associated "starts humongous".
1533 return false;
1534 }
1535
1536 int failures = 0;
1537
1538 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1539 // this region and set the corresponding bits in the expected region
1540 // and card bitmaps.
1541 bool res = _calc_cl.doHeapRegion(hr);
1542 assert(res == false, "should be continuing");
1543
1544 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1545 Mutex::_no_safepoint_check_flag);
1546
1547 // Verify the marked bytes for this region.
1548 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1549 size_t act_marked_bytes = hr->next_marked_bytes();
1550
1551 // We're not OK if expected marked bytes > actual marked bytes. It means
1552 // we have missed accounting some objects during the actual marking.
1553 if (exp_marked_bytes > act_marked_bytes) {
1554 if (_verbose) {
1555 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1556 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1557 hr->hrm_index(), exp_marked_bytes, act_marked_bytes);
1558 }
1559 failures += 1;
1560 }
1561
1562 // Verify the bit, for this region, in the actual and expected
1563 // (which was just calculated) region bit maps.
1564 // We're not OK if the bit in the calculated expected region
1565 // bitmap is set and the bit in the actual region bitmap is not.
1566 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1567
1568 bool expected = _exp_region_bm->at(index);
1569 bool actual = _region_bm->at(index);
1570 if (expected && !actual) {
1571 if (_verbose) {
1572 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1573 "expected: %s, actual: %s",
1574 hr->hrm_index(),
1575 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1576 }
1577 failures += 1;
1578 }
1579
1580 // Verify that the card bit maps for the cards spanned by the current
1581 // region match. We have an error if we have a set bit in the expected
1582 // bit map and the corresponding bit in the actual bitmap is not set.
1583
1584 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1585 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1586
1587 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1588 expected = _exp_card_bm->at(i);
1589 actual = _card_bm->at(i);
1590
1591 if (expected && !actual) {
1592 if (_verbose) {
1593 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1594 "expected: %s, actual: %s",
1595 hr->hrm_index(), i,
1596 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1597 }
1598 failures += 1;
1599 }
1600 }
1601
1602 if (failures > 0 && _verbose) {
1603 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1604 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1605 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()),
1606 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1607 }
1608
1609 _failures += failures;
1610
1611 // We could stop iteration over the heap when we
1612 // find the first violating region by returning true.
1613 return false;
1614 }
1615 };
1616
1617 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1618 protected:
1619 G1CollectedHeap* _g1h;
1620 ConcurrentMark* _cm;
1621 BitMap* _actual_region_bm;
1622 BitMap* _actual_card_bm;
1623
1624 uint _n_workers;
1625
1626 BitMap* _expected_region_bm;
1627 BitMap* _expected_card_bm;
1628
1629 int _failures;
1630 bool _verbose;
1631
1632 HeapRegionClaimer _hrclaimer;
1633
1634 public:
1635 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1636 BitMap* region_bm, BitMap* card_bm,
1637 BitMap* expected_region_bm, BitMap* expected_card_bm)
1638 : AbstractGangTask("G1 verify final counting"),
1639 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1640 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1641 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1642 _failures(0), _verbose(false),
1643 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1644 assert(VerifyDuringGC, "don't call this otherwise");
1645 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1646 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1647
1648 _verbose = _cm->verbose_medium();
1649 }
1650
1651 void work(uint worker_id) {
1652 assert(worker_id < _n_workers, "invariant");
1653
1654 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1655 _actual_region_bm, _actual_card_bm,
1656 _expected_region_bm,
1657 _expected_card_bm,
1658 _verbose);
1659
1660 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer);
1661
1662 Atomic::add(verify_cl.failures(), &_failures);
1663 }
1664
1665 int failures() const { return _failures; }
1666 };
1667
1668 // Closure that finalizes the liveness counting data.
1669 // Used during the cleanup pause.
1670 // Sets the bits corresponding to the interval [NTAMS, top]
1671 // (which contains the implicitly live objects) in the
1672 // card liveness bitmap. Also sets the bit for each region,
1673 // containing live data, in the region liveness bitmap.
1674
1675 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1676 public:
1677 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1678 BitMap* region_bm,
1679 BitMap* card_bm) :
1680 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1681
1682 bool doHeapRegion(HeapRegion* hr) {
1683
1684 if (hr->is_continues_humongous()) {
1685 // We will ignore these here and process them when their
1686 // associated "starts humongous" region is processed (see
1687 // set_bit_for_heap_region()). Note that we cannot rely on their
1688 // associated "starts humongous" region to have their bit set to
1689 // 1 since, due to the region chunking in the parallel region
1690 // iteration, a "continues humongous" region might be visited
1691 // before its associated "starts humongous".
1692 return false;
1693 }
1694
1695 HeapWord* ntams = hr->next_top_at_mark_start();
1696 HeapWord* top = hr->top();
1697
1698 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1699
1700 // Mark the allocated-since-marking portion...
1701 if (ntams < top) {
1702 // This definitely means the region has live objects.
1703 set_bit_for_region(hr);
1704
1705 // Now set the bits in the card bitmap for [ntams, top)
1706 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1707 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1708
1709 // Note: if we're looking at the last region in heap - top
1710 // could be actually just beyond the end of the heap; end_idx
1711 // will then correspond to a (non-existent) card that is also
1712 // just beyond the heap.
1713 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1714 // end of object is not card aligned - increment to cover
1715 // all the cards spanned by the object
1716 end_idx += 1;
1717 }
1718
1719 assert(end_idx <= _card_bm->size(),
1720 err_msg("oob: end_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1721 end_idx, _card_bm->size()));
1722 assert(start_idx < _card_bm->size(),
1723 err_msg("oob: start_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1724 start_idx, _card_bm->size()));
1725
1726 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1727 }
1728
1729 // Set the bit for the region if it contains live data
1730 if (hr->next_marked_bytes() > 0) {
1731 set_bit_for_region(hr);
1732 }
1733
1734 return false;
1735 }
1736 };
1737
1738 class G1ParFinalCountTask: public AbstractGangTask {
1739 protected:
1740 G1CollectedHeap* _g1h;
1741 ConcurrentMark* _cm;
1742 BitMap* _actual_region_bm;
1743 BitMap* _actual_card_bm;
1744
1745 uint _n_workers;
1746 HeapRegionClaimer _hrclaimer;
1747
1748 public:
1749 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1750 : AbstractGangTask("G1 final counting"),
1751 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1752 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1753 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1754 }
1755
1756 void work(uint worker_id) {
1757 assert(worker_id < _n_workers, "invariant");
1758
1759 FinalCountDataUpdateClosure final_update_cl(_g1h,
1760 _actual_region_bm,
1761 _actual_card_bm);
1762
1763 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer);
1764 }
1765 };
1766
1767 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1768 G1CollectedHeap* _g1;
1769 size_t _freed_bytes;
1770 FreeRegionList* _local_cleanup_list;
1771 HeapRegionSetCount _old_regions_removed;
1772 HeapRegionSetCount _humongous_regions_removed;
1773 HRRSCleanupTask* _hrrs_cleanup_task;
1774
1775 public:
1776 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1777 FreeRegionList* local_cleanup_list,
1778 HRRSCleanupTask* hrrs_cleanup_task) :
1779 _g1(g1),
1780 _freed_bytes(0),
1781 _local_cleanup_list(local_cleanup_list),
1782 _old_regions_removed(),
1783 _humongous_regions_removed(),
1784 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1785
1786 size_t freed_bytes() { return _freed_bytes; }
1787 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; }
1788 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; }
1789
1790 bool doHeapRegion(HeapRegion *hr) {
1791 if (hr->is_continues_humongous() || hr->is_archive()) {
1792 return false;
1793 }
1794 // We use a claim value of zero here because all regions
1795 // were claimed with value 1 in the FinalCount task.
1796 _g1->reset_gc_time_stamps(hr);
1797 hr->note_end_of_marking();
1798
1799 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1800 _freed_bytes += hr->used();
1801 hr->set_containing_set(NULL);
1802 if (hr->is_humongous()) {
1803 assert(hr->is_starts_humongous(), "we should only see starts humongous");
1804 _humongous_regions_removed.increment(1u, hr->capacity());
1805 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1806 } else {
1807 _old_regions_removed.increment(1u, hr->capacity());
1808 _g1->free_region(hr, _local_cleanup_list, true);
1809 }
1810 } else {
1811 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1812 }
1813
1814 return false;
1815 }
1816 };
1817
1818 class G1ParNoteEndTask: public AbstractGangTask {
1819 friend class G1NoteEndOfConcMarkClosure;
1820
1821 protected:
1822 G1CollectedHeap* _g1h;
1823 FreeRegionList* _cleanup_list;
1824 HeapRegionClaimer _hrclaimer;
1825
1826 public:
1827 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1828 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1829 }
1830
1831 void work(uint worker_id) {
1832 FreeRegionList local_cleanup_list("Local Cleanup List");
1833 HRRSCleanupTask hrrs_cleanup_task;
1834 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1835 &hrrs_cleanup_task);
1836 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1837 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1838
1839 // Now update the lists
1840 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1841 {
1842 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1843 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1844
1845 // If we iterate over the global cleanup list at the end of
1846 // cleanup to do this printing we will not guarantee to only
1847 // generate output for the newly-reclaimed regions (the list
1848 // might not be empty at the beginning of cleanup; we might
1849 // still be working on its previous contents). So we do the
1850 // printing here, before we append the new regions to the global
1851 // cleanup list.
1852
1853 G1HRPrinter* hr_printer = _g1h->hr_printer();
1854 if (hr_printer->is_active()) {
1855 FreeRegionListIterator iter(&local_cleanup_list);
1856 while (iter.more_available()) {
1857 HeapRegion* hr = iter.get_next();
1858 hr_printer->cleanup(hr);
1859 }
1860 }
1861
1862 _cleanup_list->add_ordered(&local_cleanup_list);
1863 assert(local_cleanup_list.is_empty(), "post-condition");
1864
1865 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1866 }
1867 }
1868 };
1869
1870 class G1ParScrubRemSetTask: public AbstractGangTask {
1871 protected:
1872 G1RemSet* _g1rs;
1873 BitMap* _region_bm;
1874 BitMap* _card_bm;
1875 HeapRegionClaimer _hrclaimer;
1876
1877 public:
1878 G1ParScrubRemSetTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm, uint n_workers) :
1879 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), _region_bm(region_bm), _card_bm(card_bm), _hrclaimer(n_workers) {
1880 }
1881
1882 void work(uint worker_id) {
1883 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
1884 }
1885
1886 };
1887
1888 void ConcurrentMark::cleanup() {
1889 // world is stopped at this checkpoint
1890 assert(SafepointSynchronize::is_at_safepoint(),
1891 "world should be stopped");
1892 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1893
1894 // If a full collection has happened, we shouldn't do this.
1895 if (has_aborted()) {
1896 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1897 return;
1898 }
1899
1900 g1h->verify_region_sets_optional();
1901
1902 if (VerifyDuringGC) {
1903 HandleMark hm; // handle scope
1904 g1h->prepare_for_verify();
1905 Universe::verify(VerifyOption_G1UsePrevMarking,
1906 " VerifyDuringGC:(before)");
1907 }
1908 g1h->check_bitmaps("Cleanup Start");
1909
1910 G1CollectorPolicy* g1p = g1h->g1_policy();
1911 g1p->record_concurrent_mark_cleanup_start();
1912
1913 double start = os::elapsedTime();
1914
1915 HeapRegionRemSet::reset_for_cleanup_tasks();
1916
1917 // Do counting once more with the world stopped for good measure.
1918 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1919
1920 g1h->workers()->run_task(&g1_par_count_task);
1921
1922 if (VerifyDuringGC) {
1923 // Verify that the counting data accumulated during marking matches
1924 // that calculated by walking the marking bitmap.
1925
1926 // Bitmaps to hold expected values
1927 BitMap expected_region_bm(_region_bm.size(), true);
1928 BitMap expected_card_bm(_card_bm.size(), true);
1929
1930 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1931 &_region_bm,
1932 &_card_bm,
1933 &expected_region_bm,
1934 &expected_card_bm);
1935
1936 g1h->workers()->run_task(&g1_par_verify_task);
1937
1938 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
1939 }
1940
1941 size_t start_used_bytes = g1h->used();
1942 g1h->collector_state()->set_mark_in_progress(false);
1943
1944 double count_end = os::elapsedTime();
1945 double this_final_counting_time = (count_end - start);
1946 _total_counting_time += this_final_counting_time;
1947
1948 if (G1PrintRegionLivenessInfo) {
1949 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
1950 _g1h->heap_region_iterate(&cl);
1951 }
1952
1953 // Install newly created mark bitMap as "prev".
1954 swapMarkBitMaps();
1955
1956 g1h->reset_gc_time_stamp();
1957
1958 uint n_workers = _g1h->workers()->active_workers();
1959
1960 // Note end of marking in all heap regions.
1961 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1962 g1h->workers()->run_task(&g1_par_note_end_task);
1963 g1h->check_gc_time_stamps();
1964
1965 if (!cleanup_list_is_empty()) {
1966 // The cleanup list is not empty, so we'll have to process it
1967 // concurrently. Notify anyone else that might be wanting free
1968 // regions that there will be more free regions coming soon.
1969 g1h->set_free_regions_coming();
1970 }
1971
1972 // call below, since it affects the metric by which we sort the heap
1973 // regions.
1974 if (G1ScrubRemSets) {
1975 double rs_scrub_start = os::elapsedTime();
1976 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers);
1977 g1h->workers()->run_task(&g1_par_scrub_rs_task);
1978
1979 double rs_scrub_end = os::elapsedTime();
1980 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
1981 _total_rs_scrub_time += this_rs_scrub_time;
1982 }
1983
1984 // this will also free any regions totally full of garbage objects,
1985 // and sort the regions.
1986 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1987
1988 // Statistics.
1989 double end = os::elapsedTime();
1990 _cleanup_times.add((end - start) * 1000.0);
1991
1992 if (G1Log::fine()) {
1993 g1h->g1_policy()->print_heap_transition(start_used_bytes);
1994 }
1995
1996 // Clean up will have freed any regions completely full of garbage.
1997 // Update the soft reference policy with the new heap occupancy.
1998 Universe::update_heap_info_at_gc();
1999
2000 if (VerifyDuringGC) {
2001 HandleMark hm; // handle scope
2002 g1h->prepare_for_verify();
2003 Universe::verify(VerifyOption_G1UsePrevMarking,
2004 " VerifyDuringGC:(after)");
2005 }
2006
2007 g1h->check_bitmaps("Cleanup End");
2008
2009 g1h->verify_region_sets_optional();
2010
2011 // We need to make this be a "collection" so any collection pause that
2012 // races with it goes around and waits for completeCleanup to finish.
2013 g1h->increment_total_collections();
2014
2015 // Clean out dead classes and update Metaspace sizes.
2016 if (ClassUnloadingWithConcurrentMark) {
2017 ClassLoaderDataGraph::purge();
2018 }
2019 MetaspaceGC::compute_new_size();
2020
2021 // We reclaimed old regions so we should calculate the sizes to make
2022 // sure we update the old gen/space data.
2023 g1h->g1mm()->update_sizes();
2024 g1h->allocation_context_stats().update_after_mark();
2025
2026 g1h->trace_heap_after_concurrent_cycle();
2027 }
2028
2029 void ConcurrentMark::completeCleanup() {
2030 if (has_aborted()) return;
2031
2032 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2033
2034 _cleanup_list.verify_optional();
2035 FreeRegionList tmp_free_list("Tmp Free List");
2036
2037 if (G1ConcRegionFreeingVerbose) {
2038 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2039 "cleanup list has %u entries",
2040 _cleanup_list.length());
2041 }
2042
2043 // No one else should be accessing the _cleanup_list at this point,
2044 // so it is not necessary to take any locks
2045 while (!_cleanup_list.is_empty()) {
2046 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
2047 assert(hr != NULL, "Got NULL from a non-empty list");
2048 hr->par_clear();
2049 tmp_free_list.add_ordered(hr);
2050
2051 // Instead of adding one region at a time to the secondary_free_list,
2052 // we accumulate them in the local list and move them a few at a
2053 // time. This also cuts down on the number of notify_all() calls
2054 // we do during this process. We'll also append the local list when
2055 // _cleanup_list is empty (which means we just removed the last
2056 // region from the _cleanup_list).
2057 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2058 _cleanup_list.is_empty()) {
2059 if (G1ConcRegionFreeingVerbose) {
2060 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2061 "appending %u entries to the secondary_free_list, "
2062 "cleanup list still has %u entries",
2063 tmp_free_list.length(),
2064 _cleanup_list.length());
2065 }
2066
2067 {
2068 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2069 g1h->secondary_free_list_add(&tmp_free_list);
2070 SecondaryFreeList_lock->notify_all();
2071 }
2072 #ifndef PRODUCT
2073 if (G1StressConcRegionFreeing) {
2074 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2075 os::sleep(Thread::current(), (jlong) 1, false);
2076 }
2077 }
2078 #endif
2079 }
2080 }
2081 assert(tmp_free_list.is_empty(), "post-condition");
2082 }
2083
2084 // Supporting Object and Oop closures for reference discovery
2085 // and processing in during marking
2086
2087 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2088 HeapWord* addr = (HeapWord*)obj;
2089 return addr != NULL &&
2090 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2091 }
2092
2093 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2094 // Uses the CMTask associated with a worker thread (for serial reference
2095 // processing the CMTask for worker 0 is used) to preserve (mark) and
2096 // trace referent objects.
2097 //
2098 // Using the CMTask and embedded local queues avoids having the worker
2099 // threads operating on the global mark stack. This reduces the risk
2100 // of overflowing the stack - which we would rather avoid at this late
2101 // state. Also using the tasks' local queues removes the potential
2102 // of the workers interfering with each other that could occur if
2103 // operating on the global stack.
2104
2105 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2106 ConcurrentMark* _cm;
2107 CMTask* _task;
2108 int _ref_counter_limit;
2109 int _ref_counter;
2110 bool _is_serial;
2111 public:
2112 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2113 _cm(cm), _task(task), _is_serial(is_serial),
2114 _ref_counter_limit(G1RefProcDrainInterval) {
2115 assert(_ref_counter_limit > 0, "sanity");
2116 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2117 _ref_counter = _ref_counter_limit;
2118 }
2119
2120 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2121 virtual void do_oop( oop* p) { do_oop_work(p); }
2122
2123 template <class T> void do_oop_work(T* p) {
2124 if (!_cm->has_overflown()) {
2125 oop obj = oopDesc::load_decode_heap_oop(p);
2126 if (_cm->verbose_high()) {
2127 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2128 "*" PTR_FORMAT " = " PTR_FORMAT,
2129 _task->worker_id(), p2i(p), p2i((void*) obj));
2130 }
2131
2132 _task->deal_with_reference(obj);
2133 _ref_counter--;
2134
2135 if (_ref_counter == 0) {
2136 // We have dealt with _ref_counter_limit references, pushing them
2137 // and objects reachable from them on to the local stack (and
2138 // possibly the global stack). Call CMTask::do_marking_step() to
2139 // process these entries.
2140 //
2141 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2142 // there's nothing more to do (i.e. we're done with the entries that
2143 // were pushed as a result of the CMTask::deal_with_reference() calls
2144 // above) or we overflow.
2145 //
2146 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2147 // flag while there may still be some work to do. (See the comment at
2148 // the beginning of CMTask::do_marking_step() for those conditions -
2149 // one of which is reaching the specified time target.) It is only
2150 // when CMTask::do_marking_step() returns without setting the
2151 // has_aborted() flag that the marking step has completed.
2152 do {
2153 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2154 _task->do_marking_step(mark_step_duration_ms,
2155 false /* do_termination */,
2156 _is_serial);
2157 } while (_task->has_aborted() && !_cm->has_overflown());
2158 _ref_counter = _ref_counter_limit;
2159 }
2160 } else {
2161 if (_cm->verbose_high()) {
2162 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2163 }
2164 }
2165 }
2166 };
2167
2168 // 'Drain' oop closure used by both serial and parallel reference processing.
2169 // Uses the CMTask associated with a given worker thread (for serial
2170 // reference processing the CMtask for worker 0 is used). Calls the
2171 // do_marking_step routine, with an unbelievably large timeout value,
2172 // to drain the marking data structures of the remaining entries
2173 // added by the 'keep alive' oop closure above.
2174
2175 class G1CMDrainMarkingStackClosure: public VoidClosure {
2176 ConcurrentMark* _cm;
2177 CMTask* _task;
2178 bool _is_serial;
2179 public:
2180 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2181 _cm(cm), _task(task), _is_serial(is_serial) {
2182 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2183 }
2184
2185 void do_void() {
2186 do {
2187 if (_cm->verbose_high()) {
2188 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2189 _task->worker_id(), BOOL_TO_STR(_is_serial));
2190 }
2191
2192 // We call CMTask::do_marking_step() to completely drain the local
2193 // and global marking stacks of entries pushed by the 'keep alive'
2194 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2195 //
2196 // CMTask::do_marking_step() is called in a loop, which we'll exit
2197 // if there's nothing more to do (i.e. we've completely drained the
2198 // entries that were pushed as a a result of applying the 'keep alive'
2199 // closure to the entries on the discovered ref lists) or we overflow
2200 // the global marking stack.
2201 //
2202 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2203 // flag while there may still be some work to do. (See the comment at
2204 // the beginning of CMTask::do_marking_step() for those conditions -
2205 // one of which is reaching the specified time target.) It is only
2206 // when CMTask::do_marking_step() returns without setting the
2207 // has_aborted() flag that the marking step has completed.
2208
2209 _task->do_marking_step(1000000000.0 /* something very large */,
2210 true /* do_termination */,
2211 _is_serial);
2212 } while (_task->has_aborted() && !_cm->has_overflown());
2213 }
2214 };
2215
2216 // Implementation of AbstractRefProcTaskExecutor for parallel
2217 // reference processing at the end of G1 concurrent marking
2218
2219 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2220 private:
2221 G1CollectedHeap* _g1h;
2222 ConcurrentMark* _cm;
2223 WorkGang* _workers;
2224 uint _active_workers;
2225
2226 public:
2227 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2228 ConcurrentMark* cm,
2229 WorkGang* workers,
2230 uint n_workers) :
2231 _g1h(g1h), _cm(cm),
2232 _workers(workers), _active_workers(n_workers) { }
2233
2234 // Executes the given task using concurrent marking worker threads.
2235 virtual void execute(ProcessTask& task);
2236 virtual void execute(EnqueueTask& task);
2237 };
2238
2239 class G1CMRefProcTaskProxy: public AbstractGangTask {
2240 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2241 ProcessTask& _proc_task;
2242 G1CollectedHeap* _g1h;
2243 ConcurrentMark* _cm;
2244
2245 public:
2246 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2247 G1CollectedHeap* g1h,
2248 ConcurrentMark* cm) :
2249 AbstractGangTask("Process reference objects in parallel"),
2250 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2251 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2252 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2253 }
2254
2255 virtual void work(uint worker_id) {
2256 ResourceMark rm;
2257 HandleMark hm;
2258 CMTask* task = _cm->task(worker_id);
2259 G1CMIsAliveClosure g1_is_alive(_g1h);
2260 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2261 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2262
2263 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2264 }
2265 };
2266
2267 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2268 assert(_workers != NULL, "Need parallel worker threads.");
2269 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2270
2271 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2272
2273 // We need to reset the concurrency level before each
2274 // proxy task execution, so that the termination protocol
2275 // and overflow handling in CMTask::do_marking_step() knows
2276 // how many workers to wait for.
2277 _cm->set_concurrency(_active_workers);
2278 _workers->run_task(&proc_task_proxy);
2279 }
2280
2281 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2282 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2283 EnqueueTask& _enq_task;
2284
2285 public:
2286 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2287 AbstractGangTask("Enqueue reference objects in parallel"),
2288 _enq_task(enq_task) { }
2289
2290 virtual void work(uint worker_id) {
2291 _enq_task.work(worker_id);
2292 }
2293 };
2294
2295 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2296 assert(_workers != NULL, "Need parallel worker threads.");
2297 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2298
2299 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2300
2301 // Not strictly necessary but...
2302 //
2303 // We need to reset the concurrency level before each
2304 // proxy task execution, so that the termination protocol
2305 // and overflow handling in CMTask::do_marking_step() knows
2306 // how many workers to wait for.
2307 _cm->set_concurrency(_active_workers);
2308 _workers->run_task(&enq_task_proxy);
2309 }
2310
2311 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
2312 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
2313 }
2314
2315 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2316 if (has_overflown()) {
2317 // Skip processing the discovered references if we have
2318 // overflown the global marking stack. Reference objects
2319 // only get discovered once so it is OK to not
2320 // de-populate the discovered reference lists. We could have,
2321 // but the only benefit would be that, when marking restarts,
2322 // less reference objects are discovered.
2323 return;
2324 }
2325
2326 ResourceMark rm;
2327 HandleMark hm;
2328
2329 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2330
2331 // Is alive closure.
2332 G1CMIsAliveClosure g1_is_alive(g1h);
2333
2334 // Inner scope to exclude the cleaning of the string and symbol
2335 // tables from the displayed time.
2336 {
2337 G1CMTraceTime t("GC ref-proc", G1Log::finer());
2338
2339 ReferenceProcessor* rp = g1h->ref_processor_cm();
2340
2341 // See the comment in G1CollectedHeap::ref_processing_init()
2342 // about how reference processing currently works in G1.
2343
2344 // Set the soft reference policy
2345 rp->setup_policy(clear_all_soft_refs);
2346 assert(_markStack.isEmpty(), "mark stack should be empty");
2347
2348 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2349 // in serial reference processing. Note these closures are also
2350 // used for serially processing (by the the current thread) the
2351 // JNI references during parallel reference processing.
2352 //
2353 // These closures do not need to synchronize with the worker
2354 // threads involved in parallel reference processing as these
2355 // instances are executed serially by the current thread (e.g.
2356 // reference processing is not multi-threaded and is thus
2357 // performed by the current thread instead of a gang worker).
2358 //
2359 // The gang tasks involved in parallel reference processing create
2360 // their own instances of these closures, which do their own
2361 // synchronization among themselves.
2362 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2363 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2364
2365 // We need at least one active thread. If reference processing
2366 // is not multi-threaded we use the current (VMThread) thread,
2367 // otherwise we use the work gang from the G1CollectedHeap and
2368 // we utilize all the worker threads we can.
2369 bool processing_is_mt = rp->processing_is_mt();
2370 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2371 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2372
2373 // Parallel processing task executor.
2374 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2375 g1h->workers(), active_workers);
2376 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2377
2378 // Set the concurrency level. The phase was already set prior to
2379 // executing the remark task.
2380 set_concurrency(active_workers);
2381
2382 // Set the degree of MT processing here. If the discovery was done MT,
2383 // the number of threads involved during discovery could differ from
2384 // the number of active workers. This is OK as long as the discovered
2385 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2386 rp->set_active_mt_degree(active_workers);
2387
2388 // Process the weak references.
2389 const ReferenceProcessorStats& stats =
2390 rp->process_discovered_references(&g1_is_alive,
2391 &g1_keep_alive,
2392 &g1_drain_mark_stack,
2393 executor,
2394 g1h->gc_timer_cm());
2395 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2396
2397 // The do_oop work routines of the keep_alive and drain_marking_stack
2398 // oop closures will set the has_overflown flag if we overflow the
2399 // global marking stack.
2400
2401 assert(_markStack.overflow() || _markStack.isEmpty(),
2402 "mark stack should be empty (unless it overflowed)");
2403
2404 if (_markStack.overflow()) {
2405 // This should have been done already when we tried to push an
2406 // entry on to the global mark stack. But let's do it again.
2407 set_has_overflown();
2408 }
2409
2410 assert(rp->num_q() == active_workers, "why not");
2411
2412 rp->enqueue_discovered_references(executor);
2413
2414 rp->verify_no_references_recorded();
2415 assert(!rp->discovery_enabled(), "Post condition");
2416 }
2417
2418 if (has_overflown()) {
2419 // We can not trust g1_is_alive if the marking stack overflowed
2420 return;
2421 }
2422
2423 assert(_markStack.isEmpty(), "Marking should have completed");
2424
2425 // Unload Klasses, String, Symbols, Code Cache, etc.
2426 {
2427 G1CMTraceTime trace("Unloading", G1Log::finer());
2428
2429 if (ClassUnloadingWithConcurrentMark) {
2430 bool purged_classes;
2431
2432 {
2433 G1CMTraceTime trace("System Dictionary Unloading", G1Log::finest());
2434 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
2435 }
2436
2437 {
2438 G1CMTraceTime trace("Parallel Unloading", G1Log::finest());
2439 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
2440 }
2441 }
2442
2443 if (G1StringDedup::is_enabled()) {
2444 G1CMTraceTime trace("String Deduplication Unlink", G1Log::finest());
2445 G1StringDedup::unlink(&g1_is_alive);
2446 }
2447 }
2448 }
2449
2450 void ConcurrentMark::swapMarkBitMaps() {
2451 CMBitMapRO* temp = _prevMarkBitMap;
2452 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2453 _nextMarkBitMap = (CMBitMap*) temp;
2454 }
2455
2456 // Closure for marking entries in SATB buffers.
2457 class CMSATBBufferClosure : public SATBBufferClosure {
2458 private:
2459 CMTask* _task;
2460 G1CollectedHeap* _g1h;
2461
2462 // This is very similar to CMTask::deal_with_reference, but with
2463 // more relaxed requirements for the argument, so this must be more
2464 // circumspect about treating the argument as an object.
2465 void do_entry(void* entry) const {
2466 _task->increment_refs_reached();
2467 HeapRegion* hr = _g1h->heap_region_containing_raw(entry);
2468 if (entry < hr->next_top_at_mark_start()) {
2469 // Until we get here, we don't know whether entry refers to a valid
2470 // object; it could instead have been a stale reference.
2471 oop obj = static_cast<oop>(entry);
2472 assert(obj->is_oop(true /* ignore mark word */),
2473 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj)));
2474 _task->make_reference_grey(obj, hr);
2475 }
2476 }
2477
2478 public:
2479 CMSATBBufferClosure(CMTask* task, G1CollectedHeap* g1h)
2480 : _task(task), _g1h(g1h) { }
2481
2482 virtual void do_buffer(void** buffer, size_t size) {
2483 for (size_t i = 0; i < size; ++i) {
2484 do_entry(buffer[i]);
2485 }
2486 }
2487 };
2488
2489 class G1RemarkThreadsClosure : public ThreadClosure {
2490 CMSATBBufferClosure _cm_satb_cl;
2491 G1CMOopClosure _cm_cl;
2492 MarkingCodeBlobClosure _code_cl;
2493 int _thread_parity;
2494
2495 public:
2496 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task) :
2497 _cm_satb_cl(task, g1h),
2498 _cm_cl(g1h, g1h->concurrent_mark(), task),
2499 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
2500 _thread_parity(Threads::thread_claim_parity()) {}
2501
2502 void do_thread(Thread* thread) {
2503 if (thread->is_Java_thread()) {
2504 if (thread->claim_oops_do(true, _thread_parity)) {
2505 JavaThread* jt = (JavaThread*)thread;
2506
2507 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
2508 // however the liveness of oops reachable from nmethods have very complex lifecycles:
2509 // * Alive if on the stack of an executing method
2510 // * Weakly reachable otherwise
2511 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
2512 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
2513 jt->nmethods_do(&_code_cl);
2514
2515 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
2516 }
2517 } else if (thread->is_VM_thread()) {
2518 if (thread->claim_oops_do(true, _thread_parity)) {
2519 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
2520 }
2521 }
2522 }
2523 };
2524
2525 class CMRemarkTask: public AbstractGangTask {
2526 private:
2527 ConcurrentMark* _cm;
2528 public:
2529 void work(uint worker_id) {
2530 // Since all available tasks are actually started, we should
2531 // only proceed if we're supposed to be active.
2532 if (worker_id < _cm->active_tasks()) {
2533 CMTask* task = _cm->task(worker_id);
2534 task->record_start_time();
2535 {
2536 ResourceMark rm;
2537 HandleMark hm;
2538
2539 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
2540 Threads::threads_do(&threads_f);
2541 }
2542
2543 do {
2544 task->do_marking_step(1000000000.0 /* something very large */,
2545 true /* do_termination */,
2546 false /* is_serial */);
2547 } while (task->has_aborted() && !_cm->has_overflown());
2548 // If we overflow, then we do not want to restart. We instead
2549 // want to abort remark and do concurrent marking again.
2550 task->record_end_time();
2551 }
2552 }
2553
2554 CMRemarkTask(ConcurrentMark* cm, uint active_workers) :
2555 AbstractGangTask("Par Remark"), _cm(cm) {
2556 _cm->terminator()->reset_for_reuse(active_workers);
2557 }
2558 };
2559
2560 void ConcurrentMark::checkpointRootsFinalWork() {
2561 ResourceMark rm;
2562 HandleMark hm;
2563 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2564
2565 G1CMTraceTime trace("Finalize Marking", G1Log::finer());
2566
2567 g1h->ensure_parsability(false);
2568
2569 // this is remark, so we'll use up all active threads
2570 uint active_workers = g1h->workers()->active_workers();
2571 set_concurrency_and_phase(active_workers, false /* concurrent */);
2572 // Leave _parallel_marking_threads at it's
2573 // value originally calculated in the ConcurrentMark
2574 // constructor and pass values of the active workers
2575 // through the gang in the task.
2576
2577 {
2578 StrongRootsScope srs(active_workers);
2579
2580 CMRemarkTask remarkTask(this, active_workers);
2581 // We will start all available threads, even if we decide that the
2582 // active_workers will be fewer. The extra ones will just bail out
2583 // immediately.
2584 g1h->workers()->run_task(&remarkTask);
2585 }
2586
2587 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2588 guarantee(has_overflown() ||
2589 satb_mq_set.completed_buffers_num() == 0,
2590 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2591 BOOL_TO_STR(has_overflown()),
2592 satb_mq_set.completed_buffers_num()));
2593
2594 print_stats();
2595 }
2596
2597 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2598 // Note we are overriding the read-only view of the prev map here, via
2599 // the cast.
2600 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2601 }
2602
2603 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2604 _nextMarkBitMap->clearRange(mr);
2605 }
2606
2607 HeapRegion*
2608 ConcurrentMark::claim_region(uint worker_id) {
2609 // "checkpoint" the finger
2610 HeapWord* finger = _finger;
2611
2612 // _heap_end will not change underneath our feet; it only changes at
2613 // yield points.
2614 while (finger < _heap_end) {
2615 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2616
2617 // Note on how this code handles humongous regions. In the
2618 // normal case the finger will reach the start of a "starts
2619 // humongous" (SH) region. Its end will either be the end of the
2620 // last "continues humongous" (CH) region in the sequence, or the
2621 // standard end of the SH region (if the SH is the only region in
2622 // the sequence). That way claim_region() will skip over the CH
2623 // regions. However, there is a subtle race between a CM thread
2624 // executing this method and a mutator thread doing a humongous
2625 // object allocation. The two are not mutually exclusive as the CM
2626 // thread does not need to hold the Heap_lock when it gets
2627 // here. So there is a chance that claim_region() will come across
2628 // a free region that's in the progress of becoming a SH or a CH
2629 // region. In the former case, it will either
2630 // a) Miss the update to the region's end, in which case it will
2631 // visit every subsequent CH region, will find their bitmaps
2632 // empty, and do nothing, or
2633 // b) Will observe the update of the region's end (in which case
2634 // it will skip the subsequent CH regions).
2635 // If it comes across a region that suddenly becomes CH, the
2636 // scenario will be similar to b). So, the race between
2637 // claim_region() and a humongous object allocation might force us
2638 // to do a bit of unnecessary work (due to some unnecessary bitmap
2639 // iterations) but it should not introduce and correctness issues.
2640 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2641
2642 // Above heap_region_containing_raw may return NULL as we always scan claim
2643 // until the end of the heap. In this case, just jump to the next region.
2644 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
2645
2646 // Is the gap between reading the finger and doing the CAS too long?
2647 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2648 if (res == finger && curr_region != NULL) {
2649 // we succeeded
2650 HeapWord* bottom = curr_region->bottom();
2651 HeapWord* limit = curr_region->next_top_at_mark_start();
2652
2653 if (verbose_low()) {
2654 gclog_or_tty->print_cr("[%u] curr_region = " PTR_FORMAT " "
2655 "[" PTR_FORMAT ", " PTR_FORMAT "), "
2656 "limit = " PTR_FORMAT,
2657 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit));
2658 }
2659
2660 // notice that _finger == end cannot be guaranteed here since,
2661 // someone else might have moved the finger even further
2662 assert(_finger >= end, "the finger should have moved forward");
2663
2664 if (verbose_low()) {
2665 gclog_or_tty->print_cr("[%u] we were successful with region = "
2666 PTR_FORMAT, worker_id, p2i(curr_region));
2667 }
2668
2669 if (limit > bottom) {
2670 if (verbose_low()) {
2671 gclog_or_tty->print_cr("[%u] region " PTR_FORMAT " is not empty, "
2672 "returning it ", worker_id, p2i(curr_region));
2673 }
2674 return curr_region;
2675 } else {
2676 assert(limit == bottom,
2677 "the region limit should be at bottom");
2678 if (verbose_low()) {
2679 gclog_or_tty->print_cr("[%u] region " PTR_FORMAT " is empty, "
2680 "returning NULL", worker_id, p2i(curr_region));
2681 }
2682 // we return NULL and the caller should try calling
2683 // claim_region() again.
2684 return NULL;
2685 }
2686 } else {
2687 assert(_finger > finger, "the finger should have moved forward");
2688 if (verbose_low()) {
2689 if (curr_region == NULL) {
2690 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, "
2691 "global finger = " PTR_FORMAT ", "
2692 "our finger = " PTR_FORMAT,
2693 worker_id, p2i(_finger), p2i(finger));
2694 } else {
2695 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2696 "global finger = " PTR_FORMAT ", "
2697 "our finger = " PTR_FORMAT,
2698 worker_id, p2i(_finger), p2i(finger));
2699 }
2700 }
2701
2702 // read it again
2703 finger = _finger;
2704 }
2705 }
2706
2707 return NULL;
2708 }
2709
2710 #ifndef PRODUCT
2711 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
2712 private:
2713 G1CollectedHeap* _g1h;
2714 const char* _phase;
2715 int _info;
2716
2717 public:
2718 VerifyNoCSetOops(const char* phase, int info = -1) :
2719 _g1h(G1CollectedHeap::heap()),
2720 _phase(phase),
2721 _info(info)
2722 { }
2723
2724 void operator()(oop obj) const {
2725 guarantee(obj->is_oop(),
2726 err_msg("Non-oop " PTR_FORMAT ", phase: %s, info: %d",
2727 p2i(obj), _phase, _info));
2728 guarantee(!_g1h->obj_in_cs(obj),
2729 err_msg("obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
2730 p2i(obj), _phase, _info));
2731 }
2732 };
2733
2734 void ConcurrentMark::verify_no_cset_oops() {
2735 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2736 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) {
2737 return;
2738 }
2739
2740 // Verify entries on the global mark stack
2741 _markStack.iterate(VerifyNoCSetOops("Stack"));
2742
2743 // Verify entries on the task queues
2744 for (uint i = 0; i < _max_worker_id; ++i) {
2745 CMTaskQueue* queue = _task_queues->queue(i);
2746 queue->iterate(VerifyNoCSetOops("Queue", i));
2747 }
2748
2749 // Verify the global finger
2750 HeapWord* global_finger = finger();
2751 if (global_finger != NULL && global_finger < _heap_end) {
2752 // The global finger always points to a heap region boundary. We
2753 // use heap_region_containing_raw() to get the containing region
2754 // given that the global finger could be pointing to a free region
2755 // which subsequently becomes continues humongous. If that
2756 // happens, heap_region_containing() will return the bottom of the
2757 // corresponding starts humongous region and the check below will
2758 // not hold any more.
2759 // Since we always iterate over all regions, we might get a NULL HeapRegion
2760 // here.
2761 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2762 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2763 err_msg("global finger: " PTR_FORMAT " region: " HR_FORMAT,
2764 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)));
2765 }
2766
2767 // Verify the task fingers
2768 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2769 for (uint i = 0; i < parallel_marking_threads(); ++i) {
2770 CMTask* task = _tasks[i];
2771 HeapWord* task_finger = task->finger();
2772 if (task_finger != NULL && task_finger < _heap_end) {
2773 // See above note on the global finger verification.
2774 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2775 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2776 !task_hr->in_collection_set(),
2777 err_msg("task finger: " PTR_FORMAT " region: " HR_FORMAT,
2778 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)));
2779 }
2780 }
2781 }
2782 #endif // PRODUCT
2783
2784 // Aggregate the counting data that was constructed concurrently
2785 // with marking.
2786 class AggregateCountDataHRClosure: public HeapRegionClosure {
2787 G1CollectedHeap* _g1h;
2788 ConcurrentMark* _cm;
2789 CardTableModRefBS* _ct_bs;
2790 BitMap* _cm_card_bm;
2791 uint _max_worker_id;
2792
2793 public:
2794 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2795 BitMap* cm_card_bm,
2796 uint max_worker_id) :
2797 _g1h(g1h), _cm(g1h->concurrent_mark()),
2798 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
2799 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2800
2801 bool doHeapRegion(HeapRegion* hr) {
2802 if (hr->is_continues_humongous()) {
2803 // We will ignore these here and process them when their
2804 // associated "starts humongous" region is processed.
2805 // Note that we cannot rely on their associated
2806 // "starts humongous" region to have their bit set to 1
2807 // since, due to the region chunking in the parallel region
2808 // iteration, a "continues humongous" region might be visited
2809 // before its associated "starts humongous".
2810 return false;
2811 }
2812
2813 HeapWord* start = hr->bottom();
2814 HeapWord* limit = hr->next_top_at_mark_start();
2815 HeapWord* end = hr->end();
2816
2817 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
2818 err_msg("Preconditions not met - "
2819 "start: " PTR_FORMAT ", limit: " PTR_FORMAT ", "
2820 "top: " PTR_FORMAT ", end: " PTR_FORMAT,
2821 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end())));
2822
2823 assert(hr->next_marked_bytes() == 0, "Precondition");
2824
2825 if (start == limit) {
2826 // NTAMS of this region has not been set so nothing to do.
2827 return false;
2828 }
2829
2830 // 'start' should be in the heap.
2831 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
2832 // 'end' *may* be just beyond the end of the heap (if hr is the last region)
2833 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
2834
2835 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
2836 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
2837 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
2838
2839 // If ntams is not card aligned then we bump card bitmap index
2840 // for limit so that we get the all the cards spanned by
2841 // the object ending at ntams.
2842 // Note: if this is the last region in the heap then ntams
2843 // could be actually just beyond the end of the the heap;
2844 // limit_idx will then correspond to a (non-existent) card
2845 // that is also outside the heap.
2846 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
2847 limit_idx += 1;
2848 }
2849
2850 assert(limit_idx <= end_idx, "or else use atomics");
2851
2852 // Aggregate the "stripe" in the count data associated with hr.
2853 uint hrm_index = hr->hrm_index();
2854 size_t marked_bytes = 0;
2855
2856 for (uint i = 0; i < _max_worker_id; i += 1) {
2857 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
2858 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
2859
2860 // Fetch the marked_bytes in this region for task i and
2861 // add it to the running total for this region.
2862 marked_bytes += marked_bytes_array[hrm_index];
2863
2864 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
2865 // into the global card bitmap.
2866 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
2867
2868 while (scan_idx < limit_idx) {
2869 assert(task_card_bm->at(scan_idx) == true, "should be");
2870 _cm_card_bm->set_bit(scan_idx);
2871 assert(_cm_card_bm->at(scan_idx) == true, "should be");
2872
2873 // BitMap::get_next_one_offset() can handle the case when
2874 // its left_offset parameter is greater than its right_offset
2875 // parameter. It does, however, have an early exit if
2876 // left_offset == right_offset. So let's limit the value
2877 // passed in for left offset here.
2878 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
2879 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
2880 }
2881 }
2882
2883 // Update the marked bytes for this region.
2884 hr->add_to_marked_bytes(marked_bytes);
2885
2886 // Next heap region
2887 return false;
2888 }
2889 };
2890
2891 class G1AggregateCountDataTask: public AbstractGangTask {
2892 protected:
2893 G1CollectedHeap* _g1h;
2894 ConcurrentMark* _cm;
2895 BitMap* _cm_card_bm;
2896 uint _max_worker_id;
2897 uint _active_workers;
2898 HeapRegionClaimer _hrclaimer;
2899
2900 public:
2901 G1AggregateCountDataTask(G1CollectedHeap* g1h,
2902 ConcurrentMark* cm,
2903 BitMap* cm_card_bm,
2904 uint max_worker_id,
2905 uint n_workers) :
2906 AbstractGangTask("Count Aggregation"),
2907 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
2908 _max_worker_id(max_worker_id),
2909 _active_workers(n_workers),
2910 _hrclaimer(_active_workers) {
2911 }
2912
2913 void work(uint worker_id) {
2914 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
2915
2916 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer);
2917 }
2918 };
2919
2920
2921 void ConcurrentMark::aggregate_count_data() {
2922 uint n_workers = _g1h->workers()->active_workers();
2923
2924 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
2925 _max_worker_id, n_workers);
2926
2927 _g1h->workers()->run_task(&g1_par_agg_task);
2928 }
2929
2930 // Clear the per-worker arrays used to store the per-region counting data
2931 void ConcurrentMark::clear_all_count_data() {
2932 // Clear the global card bitmap - it will be filled during
2933 // liveness count aggregation (during remark) and the
2934 // final counting task.
2935 _card_bm.clear();
2936
2937 // Clear the global region bitmap - it will be filled as part
2938 // of the final counting task.
2939 _region_bm.clear();
2940
2941 uint max_regions = _g1h->max_regions();
2942 assert(_max_worker_id > 0, "uninitialized");
2943
2944 for (uint i = 0; i < _max_worker_id; i += 1) {
2945 BitMap* task_card_bm = count_card_bitmap_for(i);
2946 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
2947
2948 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
2949 assert(marked_bytes_array != NULL, "uninitialized");
2950
2951 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
2952 task_card_bm->clear();
2953 }
2954 }
2955
2956 void ConcurrentMark::print_stats() {
2957 if (verbose_stats()) {
2958 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2959 for (size_t i = 0; i < _active_tasks; ++i) {
2960 _tasks[i]->print_stats();
2961 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2962 }
2963 }
2964 }
2965
2966 // abandon current marking iteration due to a Full GC
2967 void ConcurrentMark::abort() {
2968 if (!cmThread()->during_cycle() || _has_aborted) {
2969 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2970 return;
2971 }
2972
2973 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2974 // concurrent bitmap clearing.
2975 _nextMarkBitMap->clearAll();
2976
2977 // Note we cannot clear the previous marking bitmap here
2978 // since VerifyDuringGC verifies the objects marked during
2979 // a full GC against the previous bitmap.
2980
2981 // Clear the liveness counting data
2982 clear_all_count_data();
2983 // Empty mark stack
2984 reset_marking_state();
2985 for (uint i = 0; i < _max_worker_id; ++i) {
2986 _tasks[i]->clear_region_fields();
2987 }
2988 _first_overflow_barrier_sync.abort();
2989 _second_overflow_barrier_sync.abort();
2990 _has_aborted = true;
2991
2992 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2993 satb_mq_set.abandon_partial_marking();
2994 // This can be called either during or outside marking, we'll read
2995 // the expected_active value from the SATB queue set.
2996 satb_mq_set.set_active_all_threads(
2997 false, /* new active value */
2998 satb_mq_set.is_active() /* expected_active */);
2999
3000 _g1h->trace_heap_after_concurrent_cycle();
3001 _g1h->register_concurrent_cycle_end();
3002 }
3003
3004 static void print_ms_time_info(const char* prefix, const char* name,
3005 NumberSeq& ns) {
3006 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3007 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3008 if (ns.num() > 0) {
3009 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3010 prefix, ns.sd(), ns.maximum());
3011 }
3012 }
3013
3014 void ConcurrentMark::print_summary_info() {
3015 gclog_or_tty->print_cr(" Concurrent marking:");
3016 print_ms_time_info(" ", "init marks", _init_times);
3017 print_ms_time_info(" ", "remarks", _remark_times);
3018 {
3019 print_ms_time_info(" ", "final marks", _remark_mark_times);
3020 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3021
3022 }
3023 print_ms_time_info(" ", "cleanups", _cleanup_times);
3024 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3025 _total_counting_time,
3026 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3027 (double)_cleanup_times.num()
3028 : 0.0));
3029 if (G1ScrubRemSets) {
3030 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3031 _total_rs_scrub_time,
3032 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3033 (double)_cleanup_times.num()
3034 : 0.0));
3035 }
3036 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3037 (_init_times.sum() + _remark_times.sum() +
3038 _cleanup_times.sum())/1000.0);
3039 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3040 "(%8.2f s marking).",
3041 cmThread()->vtime_accum(),
3042 cmThread()->vtime_mark_accum());
3043 }
3044
3045 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3046 _parallel_workers->print_worker_threads_on(st);
3047 }
3048
3049 void ConcurrentMark::print_on_error(outputStream* st) const {
3050 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3051 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
3052 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3053 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3054 }
3055
3056 // We take a break if someone is trying to stop the world.
3057 bool ConcurrentMark::do_yield_check(uint worker_id) {
3058 if (SuspendibleThreadSet::should_yield()) {
3059 if (worker_id == 0) {
3060 _g1h->g1_policy()->record_concurrent_pause();
3061 }
3062 SuspendibleThreadSet::yield();
3063 return true;
3064 } else {
3065 return false;
3066 }
3067 }
3068
3069 #ifndef PRODUCT
3070 // for debugging purposes
3071 void ConcurrentMark::print_finger() {
3072 gclog_or_tty->print_cr("heap [" PTR_FORMAT ", " PTR_FORMAT "), global finger = " PTR_FORMAT,
3073 p2i(_heap_start), p2i(_heap_end), p2i(_finger));
3074 for (uint i = 0; i < _max_worker_id; ++i) {
3075 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger()));
3076 }
3077 gclog_or_tty->cr();
3078 }
3079 #endif
3080
3081 // Closure for iteration over bitmaps
3082 class CMBitMapClosure : public BitMapClosure {
3083 private:
3084 // the bitmap that is being iterated over
3085 CMBitMap* _nextMarkBitMap;
3086 ConcurrentMark* _cm;
3087 CMTask* _task;
3088
3089 public:
3090 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3091 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3092
3093 bool do_bit(size_t offset) {
3094 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3095 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3096 assert( addr < _cm->finger(), "invariant");
3097
3098 statsOnly( _task->increase_objs_found_on_bitmap() );
3099 assert(addr >= _task->finger(), "invariant");
3100
3101 // We move that task's local finger along.
3102 _task->move_finger_to(addr);
3103
3104 _task->scan_object(oop(addr));
3105 // we only partially drain the local queue and global stack
3106 _task->drain_local_queue(true);
3107 _task->drain_global_stack(true);
3108
3109 // if the has_aborted flag has been raised, we need to bail out of
3110 // the iteration
3111 return !_task->has_aborted();
3112 }
3113 };
3114
3115 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3116 ConcurrentMark* cm,
3117 CMTask* task)
3118 : _g1h(g1h), _cm(cm), _task(task) {
3119 assert(_ref_processor == NULL, "should be initialized to NULL");
3120
3121 if (G1UseConcMarkReferenceProcessing) {
3122 _ref_processor = g1h->ref_processor_cm();
3123 assert(_ref_processor != NULL, "should not be NULL");
3124 }
3125 }
3126
3127 void CMTask::setup_for_region(HeapRegion* hr) {
3128 assert(hr != NULL,
3129 "claim_region() should have filtered out NULL regions");
3130 assert(!hr->is_continues_humongous(),
3131 "claim_region() should have filtered out continues humongous regions");
3132
3133 if (_cm->verbose_low()) {
3134 gclog_or_tty->print_cr("[%u] setting up for region " PTR_FORMAT,
3135 _worker_id, p2i(hr));
3136 }
3137
3138 _curr_region = hr;
3139 _finger = hr->bottom();
3140 update_region_limit();
3141 }
3142
3143 void CMTask::update_region_limit() {
3144 HeapRegion* hr = _curr_region;
3145 HeapWord* bottom = hr->bottom();
3146 HeapWord* limit = hr->next_top_at_mark_start();
3147
3148 if (limit == bottom) {
3149 if (_cm->verbose_low()) {
3150 gclog_or_tty->print_cr("[%u] found an empty region "
3151 "[" PTR_FORMAT ", " PTR_FORMAT ")",
3152 _worker_id, p2i(bottom), p2i(limit));
3153 }
3154 // The region was collected underneath our feet.
3155 // We set the finger to bottom to ensure that the bitmap
3156 // iteration that will follow this will not do anything.
3157 // (this is not a condition that holds when we set the region up,
3158 // as the region is not supposed to be empty in the first place)
3159 _finger = bottom;
3160 } else if (limit >= _region_limit) {
3161 assert(limit >= _finger, "peace of mind");
3162 } else {
3163 assert(limit < _region_limit, "only way to get here");
3164 // This can happen under some pretty unusual circumstances. An
3165 // evacuation pause empties the region underneath our feet (NTAMS
3166 // at bottom). We then do some allocation in the region (NTAMS
3167 // stays at bottom), followed by the region being used as a GC
3168 // alloc region (NTAMS will move to top() and the objects
3169 // originally below it will be grayed). All objects now marked in
3170 // the region are explicitly grayed, if below the global finger,
3171 // and we do not need in fact to scan anything else. So, we simply
3172 // set _finger to be limit to ensure that the bitmap iteration
3173 // doesn't do anything.
3174 _finger = limit;
3175 }
3176
3177 _region_limit = limit;
3178 }
3179
3180 void CMTask::giveup_current_region() {
3181 assert(_curr_region != NULL, "invariant");
3182 if (_cm->verbose_low()) {
3183 gclog_or_tty->print_cr("[%u] giving up region " PTR_FORMAT,
3184 _worker_id, p2i(_curr_region));
3185 }
3186 clear_region_fields();
3187 }
3188
3189 void CMTask::clear_region_fields() {
3190 // Values for these three fields that indicate that we're not
3191 // holding on to a region.
3192 _curr_region = NULL;
3193 _finger = NULL;
3194 _region_limit = NULL;
3195 }
3196
3197 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3198 if (cm_oop_closure == NULL) {
3199 assert(_cm_oop_closure != NULL, "invariant");
3200 } else {
3201 assert(_cm_oop_closure == NULL, "invariant");
3202 }
3203 _cm_oop_closure = cm_oop_closure;
3204 }
3205
3206 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3207 guarantee(nextMarkBitMap != NULL, "invariant");
3208
3209 if (_cm->verbose_low()) {
3210 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3211 }
3212
3213 _nextMarkBitMap = nextMarkBitMap;
3214 clear_region_fields();
3215
3216 _calls = 0;
3217 _elapsed_time_ms = 0.0;
3218 _termination_time_ms = 0.0;
3219 _termination_start_time_ms = 0.0;
3220
3221 #if _MARKING_STATS_
3222 _aborted = 0;
3223 _aborted_overflow = 0;
3224 _aborted_cm_aborted = 0;
3225 _aborted_yield = 0;
3226 _aborted_timed_out = 0;
3227 _aborted_satb = 0;
3228 _aborted_termination = 0;
3229 _steal_attempts = 0;
3230 _steals = 0;
3231 _local_pushes = 0;
3232 _local_pops = 0;
3233 _local_max_size = 0;
3234 _objs_scanned = 0;
3235 _global_pushes = 0;
3236 _global_pops = 0;
3237 _global_max_size = 0;
3238 _global_transfers_to = 0;
3239 _global_transfers_from = 0;
3240 _regions_claimed = 0;
3241 _objs_found_on_bitmap = 0;
3242 _satb_buffers_processed = 0;
3243 #endif // _MARKING_STATS_
3244 }
3245
3246 bool CMTask::should_exit_termination() {
3247 regular_clock_call();
3248 // This is called when we are in the termination protocol. We should
3249 // quit if, for some reason, this task wants to abort or the global
3250 // stack is not empty (this means that we can get work from it).
3251 return !_cm->mark_stack_empty() || has_aborted();
3252 }
3253
3254 void CMTask::reached_limit() {
3255 assert(_words_scanned >= _words_scanned_limit ||
3256 _refs_reached >= _refs_reached_limit ,
3257 "shouldn't have been called otherwise");
3258 regular_clock_call();
3259 }
3260
3261 void CMTask::regular_clock_call() {
3262 if (has_aborted()) return;
3263
3264 // First, we need to recalculate the words scanned and refs reached
3265 // limits for the next clock call.
3266 recalculate_limits();
3267
3268 // During the regular clock call we do the following
3269
3270 // (1) If an overflow has been flagged, then we abort.
3271 if (_cm->has_overflown()) {
3272 set_has_aborted();
3273 return;
3274 }
3275
3276 // If we are not concurrent (i.e. we're doing remark) we don't need
3277 // to check anything else. The other steps are only needed during
3278 // the concurrent marking phase.
3279 if (!concurrent()) return;
3280
3281 // (2) If marking has been aborted for Full GC, then we also abort.
3282 if (_cm->has_aborted()) {
3283 set_has_aborted();
3284 statsOnly( ++_aborted_cm_aborted );
3285 return;
3286 }
3287
3288 double curr_time_ms = os::elapsedVTime() * 1000.0;
3289
3290 // (3) If marking stats are enabled, then we update the step history.
3291 #if _MARKING_STATS_
3292 if (_words_scanned >= _words_scanned_limit) {
3293 ++_clock_due_to_scanning;
3294 }
3295 if (_refs_reached >= _refs_reached_limit) {
3296 ++_clock_due_to_marking;
3297 }
3298
3299 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3300 _interval_start_time_ms = curr_time_ms;
3301 _all_clock_intervals_ms.add(last_interval_ms);
3302
3303 if (_cm->verbose_medium()) {
3304 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3305 "scanned = " SIZE_FORMAT "%s, refs reached = " SIZE_FORMAT "%s",
3306 _worker_id, last_interval_ms,
3307 _words_scanned,
3308 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3309 _refs_reached,
3310 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3311 }
3312 #endif // _MARKING_STATS_
3313
3314 // (4) We check whether we should yield. If we have to, then we abort.
3315 if (SuspendibleThreadSet::should_yield()) {
3316 // We should yield. To do this we abort the task. The caller is
3317 // responsible for yielding.
3318 set_has_aborted();
3319 statsOnly( ++_aborted_yield );
3320 return;
3321 }
3322
3323 // (5) We check whether we've reached our time quota. If we have,
3324 // then we abort.
3325 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3326 if (elapsed_time_ms > _time_target_ms) {
3327 set_has_aborted();
3328 _has_timed_out = true;
3329 statsOnly( ++_aborted_timed_out );
3330 return;
3331 }
3332
3333 // (6) Finally, we check whether there are enough completed STAB
3334 // buffers available for processing. If there are, we abort.
3335 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3336 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3337 if (_cm->verbose_low()) {
3338 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3339 _worker_id);
3340 }
3341 // we do need to process SATB buffers, we'll abort and restart
3342 // the marking task to do so
3343 set_has_aborted();
3344 statsOnly( ++_aborted_satb );
3345 return;
3346 }
3347 }
3348
3349 void CMTask::recalculate_limits() {
3350 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3351 _words_scanned_limit = _real_words_scanned_limit;
3352
3353 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3354 _refs_reached_limit = _real_refs_reached_limit;
3355 }
3356
3357 void CMTask::decrease_limits() {
3358 // This is called when we believe that we're going to do an infrequent
3359 // operation which will increase the per byte scanned cost (i.e. move
3360 // entries to/from the global stack). It basically tries to decrease the
3361 // scanning limit so that the clock is called earlier.
3362
3363 if (_cm->verbose_medium()) {
3364 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3365 }
3366
3367 _words_scanned_limit = _real_words_scanned_limit -
3368 3 * words_scanned_period / 4;
3369 _refs_reached_limit = _real_refs_reached_limit -
3370 3 * refs_reached_period / 4;
3371 }
3372
3373 void CMTask::move_entries_to_global_stack() {
3374 // local array where we'll store the entries that will be popped
3375 // from the local queue
3376 oop buffer[global_stack_transfer_size];
3377
3378 int n = 0;
3379 oop obj;
3380 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3381 buffer[n] = obj;
3382 ++n;
3383 }
3384
3385 if (n > 0) {
3386 // we popped at least one entry from the local queue
3387
3388 statsOnly( ++_global_transfers_to; _local_pops += n );
3389
3390 if (!_cm->mark_stack_push(buffer, n)) {
3391 if (_cm->verbose_low()) {
3392 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3393 _worker_id);
3394 }
3395 set_has_aborted();
3396 } else {
3397 // the transfer was successful
3398
3399 if (_cm->verbose_medium()) {
3400 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3401 _worker_id, n);
3402 }
3403 statsOnly( size_t tmp_size = _cm->mark_stack_size();
3404 if (tmp_size > _global_max_size) {
3405 _global_max_size = tmp_size;
3406 }
3407 _global_pushes += n );
3408 }
3409 }
3410
3411 // this operation was quite expensive, so decrease the limits
3412 decrease_limits();
3413 }
3414
3415 void CMTask::get_entries_from_global_stack() {
3416 // local array where we'll store the entries that will be popped
3417 // from the global stack.
3418 oop buffer[global_stack_transfer_size];
3419 int n;
3420 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3421 assert(n <= global_stack_transfer_size,
3422 "we should not pop more than the given limit");
3423 if (n > 0) {
3424 // yes, we did actually pop at least one entry
3425
3426 statsOnly( ++_global_transfers_from; _global_pops += n );
3427 if (_cm->verbose_medium()) {
3428 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3429 _worker_id, n);
3430 }
3431 for (int i = 0; i < n; ++i) {
3432 bool success = _task_queue->push(buffer[i]);
3433 // We only call this when the local queue is empty or under a
3434 // given target limit. So, we do not expect this push to fail.
3435 assert(success, "invariant");
3436 }
3437
3438 statsOnly( size_t tmp_size = (size_t)_task_queue->size();
3439 if (tmp_size > _local_max_size) {
3440 _local_max_size = tmp_size;
3441 }
3442 _local_pushes += n );
3443 }
3444
3445 // this operation was quite expensive, so decrease the limits
3446 decrease_limits();
3447 }
3448
3449 void CMTask::drain_local_queue(bool partially) {
3450 if (has_aborted()) return;
3451
3452 // Decide what the target size is, depending whether we're going to
3453 // drain it partially (so that other tasks can steal if they run out
3454 // of things to do) or totally (at the very end).
3455 size_t target_size;
3456 if (partially) {
3457 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3458 } else {
3459 target_size = 0;
3460 }
3461
3462 if (_task_queue->size() > target_size) {
3463 if (_cm->verbose_high()) {
3464 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT,
3465 _worker_id, target_size);
3466 }
3467
3468 oop obj;
3469 bool ret = _task_queue->pop_local(obj);
3470 while (ret) {
3471 statsOnly( ++_local_pops );
3472
3473 if (_cm->verbose_high()) {
3474 gclog_or_tty->print_cr("[%u] popped " PTR_FORMAT, _worker_id,
3475 p2i((void*) obj));
3476 }
3477
3478 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3479 assert(!_g1h->is_on_master_free_list(
3480 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3481
3482 scan_object(obj);
3483
3484 if (_task_queue->size() <= target_size || has_aborted()) {
3485 ret = false;
3486 } else {
3487 ret = _task_queue->pop_local(obj);
3488 }
3489 }
3490
3491 if (_cm->verbose_high()) {
3492 gclog_or_tty->print_cr("[%u] drained local queue, size = %u",
3493 _worker_id, _task_queue->size());
3494 }
3495 }
3496 }
3497
3498 void CMTask::drain_global_stack(bool partially) {
3499 if (has_aborted()) return;
3500
3501 // We have a policy to drain the local queue before we attempt to
3502 // drain the global stack.
3503 assert(partially || _task_queue->size() == 0, "invariant");
3504
3505 // Decide what the target size is, depending whether we're going to
3506 // drain it partially (so that other tasks can steal if they run out
3507 // of things to do) or totally (at the very end). Notice that,
3508 // because we move entries from the global stack in chunks or
3509 // because another task might be doing the same, we might in fact
3510 // drop below the target. But, this is not a problem.
3511 size_t target_size;
3512 if (partially) {
3513 target_size = _cm->partial_mark_stack_size_target();
3514 } else {
3515 target_size = 0;
3516 }
3517
3518 if (_cm->mark_stack_size() > target_size) {
3519 if (_cm->verbose_low()) {
3520 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT,
3521 _worker_id, target_size);
3522 }
3523
3524 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3525 get_entries_from_global_stack();
3526 drain_local_queue(partially);
3527 }
3528
3529 if (_cm->verbose_low()) {
3530 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT,
3531 _worker_id, _cm->mark_stack_size());
3532 }
3533 }
3534 }
3535
3536 // SATB Queue has several assumptions on whether to call the par or
3537 // non-par versions of the methods. this is why some of the code is
3538 // replicated. We should really get rid of the single-threaded version
3539 // of the code to simplify things.
3540 void CMTask::drain_satb_buffers() {
3541 if (has_aborted()) return;
3542
3543 // We set this so that the regular clock knows that we're in the
3544 // middle of draining buffers and doesn't set the abort flag when it
3545 // notices that SATB buffers are available for draining. It'd be
3546 // very counter productive if it did that. :-)
3547 _draining_satb_buffers = true;
3548
3549 CMSATBBufferClosure satb_cl(this, _g1h);
3550 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3551
3552 // This keeps claiming and applying the closure to completed buffers
3553 // until we run out of buffers or we need to abort.
3554 while (!has_aborted() &&
3555 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
3556 if (_cm->verbose_medium()) {
3557 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3558 }
3559 statsOnly( ++_satb_buffers_processed );
3560 regular_clock_call();
3561 }
3562
3563 _draining_satb_buffers = false;
3564
3565 assert(has_aborted() ||
3566 concurrent() ||
3567 satb_mq_set.completed_buffers_num() == 0, "invariant");
3568
3569 // again, this was a potentially expensive operation, decrease the
3570 // limits to get the regular clock call early
3571 decrease_limits();
3572 }
3573
3574 void CMTask::print_stats() {
3575 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3576 _worker_id, _calls);
3577 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3578 _elapsed_time_ms, _termination_time_ms);
3579 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3580 _step_times_ms.num(), _step_times_ms.avg(),
3581 _step_times_ms.sd());
3582 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3583 _step_times_ms.maximum(), _step_times_ms.sum());
3584
3585 #if _MARKING_STATS_
3586 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3587 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3588 _all_clock_intervals_ms.sd());
3589 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3590 _all_clock_intervals_ms.maximum(),
3591 _all_clock_intervals_ms.sum());
3592 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = " SIZE_FORMAT ", marking = " SIZE_FORMAT,
3593 _clock_due_to_scanning, _clock_due_to_marking);
3594 gclog_or_tty->print_cr(" Objects: scanned = " SIZE_FORMAT ", found on the bitmap = " SIZE_FORMAT,
3595 _objs_scanned, _objs_found_on_bitmap);
3596 gclog_or_tty->print_cr(" Local Queue: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3597 _local_pushes, _local_pops, _local_max_size);
3598 gclog_or_tty->print_cr(" Global Stack: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3599 _global_pushes, _global_pops, _global_max_size);
3600 gclog_or_tty->print_cr(" transfers to = " SIZE_FORMAT ", transfers from = " SIZE_FORMAT,
3601 _global_transfers_to,_global_transfers_from);
3602 gclog_or_tty->print_cr(" Regions: claimed = " SIZE_FORMAT, _regions_claimed);
3603 gclog_or_tty->print_cr(" SATB buffers: processed = " SIZE_FORMAT, _satb_buffers_processed);
3604 gclog_or_tty->print_cr(" Steals: attempts = " SIZE_FORMAT ", successes = " SIZE_FORMAT,
3605 _steal_attempts, _steals);
3606 gclog_or_tty->print_cr(" Aborted: " SIZE_FORMAT ", due to", _aborted);
3607 gclog_or_tty->print_cr(" overflow: " SIZE_FORMAT ", global abort: " SIZE_FORMAT ", yield: " SIZE_FORMAT,
3608 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3609 gclog_or_tty->print_cr(" time out: " SIZE_FORMAT ", SATB: " SIZE_FORMAT ", termination: " SIZE_FORMAT,
3610 _aborted_timed_out, _aborted_satb, _aborted_termination);
3611 #endif // _MARKING_STATS_
3612 }
3613
3614 bool ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) {
3615 return _task_queues->steal(worker_id, hash_seed, obj);
3616 }
3617
3618 /*****************************************************************************
3619
3620 The do_marking_step(time_target_ms, ...) method is the building
3621 block of the parallel marking framework. It can be called in parallel
3622 with other invocations of do_marking_step() on different tasks
3623 (but only one per task, obviously) and concurrently with the
3624 mutator threads, or during remark, hence it eliminates the need
3625 for two versions of the code. When called during remark, it will
3626 pick up from where the task left off during the concurrent marking
3627 phase. Interestingly, tasks are also claimable during evacuation
3628 pauses too, since do_marking_step() ensures that it aborts before
3629 it needs to yield.
3630
3631 The data structures that it uses to do marking work are the
3632 following:
3633
3634 (1) Marking Bitmap. If there are gray objects that appear only
3635 on the bitmap (this happens either when dealing with an overflow
3636 or when the initial marking phase has simply marked the roots
3637 and didn't push them on the stack), then tasks claim heap
3638 regions whose bitmap they then scan to find gray objects. A
3639 global finger indicates where the end of the last claimed region
3640 is. A local finger indicates how far into the region a task has
3641 scanned. The two fingers are used to determine how to gray an
3642 object (i.e. whether simply marking it is OK, as it will be
3643 visited by a task in the future, or whether it needs to be also
3644 pushed on a stack).
3645
3646 (2) Local Queue. The local queue of the task which is accessed
3647 reasonably efficiently by the task. Other tasks can steal from
3648 it when they run out of work. Throughout the marking phase, a
3649 task attempts to keep its local queue short but not totally
3650 empty, so that entries are available for stealing by other
3651 tasks. Only when there is no more work, a task will totally
3652 drain its local queue.
3653
3654 (3) Global Mark Stack. This handles local queue overflow. During
3655 marking only sets of entries are moved between it and the local
3656 queues, as access to it requires a mutex and more fine-grain
3657 interaction with it which might cause contention. If it
3658 overflows, then the marking phase should restart and iterate
3659 over the bitmap to identify gray objects. Throughout the marking
3660 phase, tasks attempt to keep the global mark stack at a small
3661 length but not totally empty, so that entries are available for
3662 popping by other tasks. Only when there is no more work, tasks
3663 will totally drain the global mark stack.
3664
3665 (4) SATB Buffer Queue. This is where completed SATB buffers are
3666 made available. Buffers are regularly removed from this queue
3667 and scanned for roots, so that the queue doesn't get too
3668 long. During remark, all completed buffers are processed, as
3669 well as the filled in parts of any uncompleted buffers.
3670
3671 The do_marking_step() method tries to abort when the time target
3672 has been reached. There are a few other cases when the
3673 do_marking_step() method also aborts:
3674
3675 (1) When the marking phase has been aborted (after a Full GC).
3676
3677 (2) When a global overflow (on the global stack) has been
3678 triggered. Before the task aborts, it will actually sync up with
3679 the other tasks to ensure that all the marking data structures
3680 (local queues, stacks, fingers etc.) are re-initialized so that
3681 when do_marking_step() completes, the marking phase can
3682 immediately restart.
3683
3684 (3) When enough completed SATB buffers are available. The
3685 do_marking_step() method only tries to drain SATB buffers right
3686 at the beginning. So, if enough buffers are available, the
3687 marking step aborts and the SATB buffers are processed at
3688 the beginning of the next invocation.
3689
3690 (4) To yield. when we have to yield then we abort and yield
3691 right at the end of do_marking_step(). This saves us from a lot
3692 of hassle as, by yielding we might allow a Full GC. If this
3693 happens then objects will be compacted underneath our feet, the
3694 heap might shrink, etc. We save checking for this by just
3695 aborting and doing the yield right at the end.
3696
3697 From the above it follows that the do_marking_step() method should
3698 be called in a loop (or, otherwise, regularly) until it completes.
3699
3700 If a marking step completes without its has_aborted() flag being
3701 true, it means it has completed the current marking phase (and
3702 also all other marking tasks have done so and have all synced up).
3703
3704 A method called regular_clock_call() is invoked "regularly" (in
3705 sub ms intervals) throughout marking. It is this clock method that
3706 checks all the abort conditions which were mentioned above and
3707 decides when the task should abort. A work-based scheme is used to
3708 trigger this clock method: when the number of object words the
3709 marking phase has scanned or the number of references the marking
3710 phase has visited reach a given limit. Additional invocations to
3711 the method clock have been planted in a few other strategic places
3712 too. The initial reason for the clock method was to avoid calling
3713 vtime too regularly, as it is quite expensive. So, once it was in
3714 place, it was natural to piggy-back all the other conditions on it
3715 too and not constantly check them throughout the code.
3716
3717 If do_termination is true then do_marking_step will enter its
3718 termination protocol.
3719
3720 The value of is_serial must be true when do_marking_step is being
3721 called serially (i.e. by the VMThread) and do_marking_step should
3722 skip any synchronization in the termination and overflow code.
3723 Examples include the serial remark code and the serial reference
3724 processing closures.
3725
3726 The value of is_serial must be false when do_marking_step is
3727 being called by any of the worker threads in a work gang.
3728 Examples include the concurrent marking code (CMMarkingTask),
3729 the MT remark code, and the MT reference processing closures.
3730
3731 *****************************************************************************/
3732
3733 void CMTask::do_marking_step(double time_target_ms,
3734 bool do_termination,
3735 bool is_serial) {
3736 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3737 assert(concurrent() == _cm->concurrent(), "they should be the same");
3738
3739 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3740 assert(_task_queues != NULL, "invariant");
3741 assert(_task_queue != NULL, "invariant");
3742 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3743
3744 assert(!_claimed,
3745 "only one thread should claim this task at any one time");
3746
3747 // OK, this doesn't safeguard again all possible scenarios, as it is
3748 // possible for two threads to set the _claimed flag at the same
3749 // time. But it is only for debugging purposes anyway and it will
3750 // catch most problems.
3751 _claimed = true;
3752
3753 _start_time_ms = os::elapsedVTime() * 1000.0;
3754 statsOnly( _interval_start_time_ms = _start_time_ms );
3755
3756 // If do_stealing is true then do_marking_step will attempt to
3757 // steal work from the other CMTasks. It only makes sense to
3758 // enable stealing when the termination protocol is enabled
3759 // and do_marking_step() is not being called serially.
3760 bool do_stealing = do_termination && !is_serial;
3761
3762 double diff_prediction_ms =
3763 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3764 _time_target_ms = time_target_ms - diff_prediction_ms;
3765
3766 // set up the variables that are used in the work-based scheme to
3767 // call the regular clock method
3768 _words_scanned = 0;
3769 _refs_reached = 0;
3770 recalculate_limits();
3771
3772 // clear all flags
3773 clear_has_aborted();
3774 _has_timed_out = false;
3775 _draining_satb_buffers = false;
3776
3777 ++_calls;
3778
3779 if (_cm->verbose_low()) {
3780 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
3781 "target = %1.2lfms >>>>>>>>>>",
3782 _worker_id, _calls, _time_target_ms);
3783 }
3784
3785 // Set up the bitmap and oop closures. Anything that uses them is
3786 // eventually called from this method, so it is OK to allocate these
3787 // statically.
3788 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3789 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
3790 set_cm_oop_closure(&cm_oop_closure);
3791
3792 if (_cm->has_overflown()) {
3793 // This can happen if the mark stack overflows during a GC pause
3794 // and this task, after a yield point, restarts. We have to abort
3795 // as we need to get into the overflow protocol which happens
3796 // right at the end of this task.
3797 set_has_aborted();
3798 }
3799
3800 // First drain any available SATB buffers. After this, we will not
3801 // look at SATB buffers before the next invocation of this method.
3802 // If enough completed SATB buffers are queued up, the regular clock
3803 // will abort this task so that it restarts.
3804 drain_satb_buffers();
3805 // ...then partially drain the local queue and the global stack
3806 drain_local_queue(true);
3807 drain_global_stack(true);
3808
3809 do {
3810 if (!has_aborted() && _curr_region != NULL) {
3811 // This means that we're already holding on to a region.
3812 assert(_finger != NULL, "if region is not NULL, then the finger "
3813 "should not be NULL either");
3814
3815 // We might have restarted this task after an evacuation pause
3816 // which might have evacuated the region we're holding on to
3817 // underneath our feet. Let's read its limit again to make sure
3818 // that we do not iterate over a region of the heap that
3819 // contains garbage (update_region_limit() will also move
3820 // _finger to the start of the region if it is found empty).
3821 update_region_limit();
3822 // We will start from _finger not from the start of the region,
3823 // as we might be restarting this task after aborting half-way
3824 // through scanning this region. In this case, _finger points to
3825 // the address where we last found a marked object. If this is a
3826 // fresh region, _finger points to start().
3827 MemRegion mr = MemRegion(_finger, _region_limit);
3828
3829 if (_cm->verbose_low()) {
3830 gclog_or_tty->print_cr("[%u] we're scanning part "
3831 "[" PTR_FORMAT ", " PTR_FORMAT ") "
3832 "of region " HR_FORMAT,
3833 _worker_id, p2i(_finger), p2i(_region_limit),
3834 HR_FORMAT_PARAMS(_curr_region));
3835 }
3836
3837 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
3838 "humongous regions should go around loop once only");
3839
3840 // Some special cases:
3841 // If the memory region is empty, we can just give up the region.
3842 // If the current region is humongous then we only need to check
3843 // the bitmap for the bit associated with the start of the object,
3844 // scan the object if it's live, and give up the region.
3845 // Otherwise, let's iterate over the bitmap of the part of the region
3846 // that is left.
3847 // If the iteration is successful, give up the region.
3848 if (mr.is_empty()) {
3849 giveup_current_region();
3850 regular_clock_call();
3851 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
3852 if (_nextMarkBitMap->isMarked(mr.start())) {
3853 // The object is marked - apply the closure
3854 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
3855 bitmap_closure.do_bit(offset);
3856 }
3857 // Even if this task aborted while scanning the humongous object
3858 // we can (and should) give up the current region.
3859 giveup_current_region();
3860 regular_clock_call();
3861 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
3862 giveup_current_region();
3863 regular_clock_call();
3864 } else {
3865 assert(has_aborted(), "currently the only way to do so");
3866 // The only way to abort the bitmap iteration is to return
3867 // false from the do_bit() method. However, inside the
3868 // do_bit() method we move the _finger to point to the
3869 // object currently being looked at. So, if we bail out, we
3870 // have definitely set _finger to something non-null.
3871 assert(_finger != NULL, "invariant");
3872
3873 // Region iteration was actually aborted. So now _finger
3874 // points to the address of the object we last scanned. If we
3875 // leave it there, when we restart this task, we will rescan
3876 // the object. It is easy to avoid this. We move the finger by
3877 // enough to point to the next possible object header (the
3878 // bitmap knows by how much we need to move it as it knows its
3879 // granularity).
3880 assert(_finger < _region_limit, "invariant");
3881 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
3882 // Check if bitmap iteration was aborted while scanning the last object
3883 if (new_finger >= _region_limit) {
3884 giveup_current_region();
3885 } else {
3886 move_finger_to(new_finger);
3887 }
3888 }
3889 }
3890 // At this point we have either completed iterating over the
3891 // region we were holding on to, or we have aborted.
3892
3893 // We then partially drain the local queue and the global stack.
3894 // (Do we really need this?)
3895 drain_local_queue(true);
3896 drain_global_stack(true);
3897
3898 // Read the note on the claim_region() method on why it might
3899 // return NULL with potentially more regions available for
3900 // claiming and why we have to check out_of_regions() to determine
3901 // whether we're done or not.
3902 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
3903 // We are going to try to claim a new region. We should have
3904 // given up on the previous one.
3905 // Separated the asserts so that we know which one fires.
3906 assert(_curr_region == NULL, "invariant");
3907 assert(_finger == NULL, "invariant");
3908 assert(_region_limit == NULL, "invariant");
3909 if (_cm->verbose_low()) {
3910 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
3911 }
3912 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
3913 if (claimed_region != NULL) {
3914 // Yes, we managed to claim one
3915 statsOnly( ++_regions_claimed );
3916
3917 if (_cm->verbose_low()) {
3918 gclog_or_tty->print_cr("[%u] we successfully claimed "
3919 "region " PTR_FORMAT,
3920 _worker_id, p2i(claimed_region));
3921 }
3922
3923 setup_for_region(claimed_region);
3924 assert(_curr_region == claimed_region, "invariant");
3925 }
3926 // It is important to call the regular clock here. It might take
3927 // a while to claim a region if, for example, we hit a large
3928 // block of empty regions. So we need to call the regular clock
3929 // method once round the loop to make sure it's called
3930 // frequently enough.
3931 regular_clock_call();
3932 }
3933
3934 if (!has_aborted() && _curr_region == NULL) {
3935 assert(_cm->out_of_regions(),
3936 "at this point we should be out of regions");
3937 }
3938 } while ( _curr_region != NULL && !has_aborted());
3939
3940 if (!has_aborted()) {
3941 // We cannot check whether the global stack is empty, since other
3942 // tasks might be pushing objects to it concurrently.
3943 assert(_cm->out_of_regions(),
3944 "at this point we should be out of regions");
3945
3946 if (_cm->verbose_low()) {
3947 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
3948 }
3949
3950 // Try to reduce the number of available SATB buffers so that
3951 // remark has less work to do.
3952 drain_satb_buffers();
3953 }
3954
3955 // Since we've done everything else, we can now totally drain the
3956 // local queue and global stack.
3957 drain_local_queue(false);
3958 drain_global_stack(false);
3959
3960 // Attempt at work stealing from other task's queues.
3961 if (do_stealing && !has_aborted()) {
3962 // We have not aborted. This means that we have finished all that
3963 // we could. Let's try to do some stealing...
3964
3965 // We cannot check whether the global stack is empty, since other
3966 // tasks might be pushing objects to it concurrently.
3967 assert(_cm->out_of_regions() && _task_queue->size() == 0,
3968 "only way to reach here");
3969
3970 if (_cm->verbose_low()) {
3971 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
3972 }
3973
3974 while (!has_aborted()) {
3975 oop obj;
3976 statsOnly( ++_steal_attempts );
3977
3978 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
3979 if (_cm->verbose_medium()) {
3980 gclog_or_tty->print_cr("[%u] stolen " PTR_FORMAT " successfully",
3981 _worker_id, p2i((void*) obj));
3982 }
3983
3984 statsOnly( ++_steals );
3985
3986 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
3987 "any stolen object should be marked");
3988 scan_object(obj);
3989
3990 // And since we're towards the end, let's totally drain the
3991 // local queue and global stack.
3992 drain_local_queue(false);
3993 drain_global_stack(false);
3994 } else {
3995 break;
3996 }
3997 }
3998 }
3999
4000 // If we are about to wrap up and go into termination, check if we
4001 // should raise the overflow flag.
4002 if (do_termination && !has_aborted()) {
4003 if (_cm->force_overflow()->should_force()) {
4004 _cm->set_has_overflown();
4005 regular_clock_call();
4006 }
4007 }
4008
4009 // We still haven't aborted. Now, let's try to get into the
4010 // termination protocol.
4011 if (do_termination && !has_aborted()) {
4012 // We cannot check whether the global stack is empty, since other
4013 // tasks might be concurrently pushing objects on it.
4014 // Separated the asserts so that we know which one fires.
4015 assert(_cm->out_of_regions(), "only way to reach here");
4016 assert(_task_queue->size() == 0, "only way to reach here");
4017
4018 if (_cm->verbose_low()) {
4019 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4020 }
4021
4022 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4023
4024 // The CMTask class also extends the TerminatorTerminator class,
4025 // hence its should_exit_termination() method will also decide
4026 // whether to exit the termination protocol or not.
4027 bool finished = (is_serial ||
4028 _cm->terminator()->offer_termination(this));
4029 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4030 _termination_time_ms +=
4031 termination_end_time_ms - _termination_start_time_ms;
4032
4033 if (finished) {
4034 // We're all done.
4035
4036 if (_worker_id == 0) {
4037 // let's allow task 0 to do this
4038 if (concurrent()) {
4039 assert(_cm->concurrent_marking_in_progress(), "invariant");
4040 // we need to set this to false before the next
4041 // safepoint. This way we ensure that the marking phase
4042 // doesn't observe any more heap expansions.
4043 _cm->clear_concurrent_marking_in_progress();
4044 }
4045 }
4046
4047 // We can now guarantee that the global stack is empty, since
4048 // all other tasks have finished. We separated the guarantees so
4049 // that, if a condition is false, we can immediately find out
4050 // which one.
4051 guarantee(_cm->out_of_regions(), "only way to reach here");
4052 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4053 guarantee(_task_queue->size() == 0, "only way to reach here");
4054 guarantee(!_cm->has_overflown(), "only way to reach here");
4055 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4056
4057 if (_cm->verbose_low()) {
4058 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4059 }
4060 } else {
4061 // Apparently there's more work to do. Let's abort this task. It
4062 // will restart it and we can hopefully find more things to do.
4063
4064 if (_cm->verbose_low()) {
4065 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4066 _worker_id);
4067 }
4068
4069 set_has_aborted();
4070 statsOnly( ++_aborted_termination );
4071 }
4072 }
4073
4074 // Mainly for debugging purposes to make sure that a pointer to the
4075 // closure which was statically allocated in this frame doesn't
4076 // escape it by accident.
4077 set_cm_oop_closure(NULL);
4078 double end_time_ms = os::elapsedVTime() * 1000.0;
4079 double elapsed_time_ms = end_time_ms - _start_time_ms;
4080 // Update the step history.
4081 _step_times_ms.add(elapsed_time_ms);
4082
4083 if (has_aborted()) {
4084 // The task was aborted for some reason.
4085
4086 statsOnly( ++_aborted );
4087
4088 if (_has_timed_out) {
4089 double diff_ms = elapsed_time_ms - _time_target_ms;
4090 // Keep statistics of how well we did with respect to hitting
4091 // our target only if we actually timed out (if we aborted for
4092 // other reasons, then the results might get skewed).
4093 _marking_step_diffs_ms.add(diff_ms);
4094 }
4095
4096 if (_cm->has_overflown()) {
4097 // This is the interesting one. We aborted because a global
4098 // overflow was raised. This means we have to restart the
4099 // marking phase and start iterating over regions. However, in
4100 // order to do this we have to make sure that all tasks stop
4101 // what they are doing and re-initialize in a safe manner. We
4102 // will achieve this with the use of two barrier sync points.
4103
4104 if (_cm->verbose_low()) {
4105 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4106 }
4107
4108 if (!is_serial) {
4109 // We only need to enter the sync barrier if being called
4110 // from a parallel context
4111 _cm->enter_first_sync_barrier(_worker_id);
4112
4113 // When we exit this sync barrier we know that all tasks have
4114 // stopped doing marking work. So, it's now safe to
4115 // re-initialize our data structures. At the end of this method,
4116 // task 0 will clear the global data structures.
4117 }
4118
4119 statsOnly( ++_aborted_overflow );
4120
4121 // We clear the local state of this task...
4122 clear_region_fields();
4123
4124 if (!is_serial) {
4125 // ...and enter the second barrier.
4126 _cm->enter_second_sync_barrier(_worker_id);
4127 }
4128 // At this point, if we're during the concurrent phase of
4129 // marking, everything has been re-initialized and we're
4130 // ready to restart.
4131 }
4132
4133 if (_cm->verbose_low()) {
4134 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4135 "elapsed = %1.2lfms <<<<<<<<<<",
4136 _worker_id, _time_target_ms, elapsed_time_ms);
4137 if (_cm->has_aborted()) {
4138 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4139 _worker_id);
4140 }
4141 }
4142 } else {
4143 if (_cm->verbose_low()) {
4144 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4145 "elapsed = %1.2lfms <<<<<<<<<<",
4146 _worker_id, _time_target_ms, elapsed_time_ms);
4147 }
4148 }
4149
4150 _claimed = false;
4151 }
4152
4153 CMTask::CMTask(uint worker_id,
4154 ConcurrentMark* cm,
4155 size_t* marked_bytes,
4156 BitMap* card_bm,
4157 CMTaskQueue* task_queue,
4158 CMTaskQueueSet* task_queues)
4159 : _g1h(G1CollectedHeap::heap()),
4160 _worker_id(worker_id), _cm(cm),
4161 _claimed(false),
4162 _nextMarkBitMap(NULL), _hash_seed(17),
4163 _task_queue(task_queue),
4164 _task_queues(task_queues),
4165 _cm_oop_closure(NULL),
4166 _marked_bytes_array(marked_bytes),
4167 _card_bm(card_bm) {
4168 guarantee(task_queue != NULL, "invariant");
4169 guarantee(task_queues != NULL, "invariant");
4170
4171 statsOnly( _clock_due_to_scanning = 0;
4172 _clock_due_to_marking = 0 );
4173
4174 _marking_step_diffs_ms.add(0.5);
4175 }
4176
4177 // These are formatting macros that are used below to ensure
4178 // consistent formatting. The *_H_* versions are used to format the
4179 // header for a particular value and they should be kept consistent
4180 // with the corresponding macro. Also note that most of the macros add
4181 // the necessary white space (as a prefix) which makes them a bit
4182 // easier to compose.
4183
4184 // All the output lines are prefixed with this string to be able to
4185 // identify them easily in a large log file.
4186 #define G1PPRL_LINE_PREFIX "###"
4187
4188 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
4189 #ifdef _LP64
4190 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4191 #else // _LP64
4192 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4193 #endif // _LP64
4194
4195 // For per-region info
4196 #define G1PPRL_TYPE_FORMAT " %-4s"
4197 #define G1PPRL_TYPE_H_FORMAT " %4s"
4198 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
4199 #define G1PPRL_BYTE_H_FORMAT " %9s"
4200 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4201 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4202
4203 // For summary info
4204 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
4205 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
4206 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
4207 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
4208
4209 G1PrintRegionLivenessInfoClosure::
4210 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4211 : _out(out),
4212 _total_used_bytes(0), _total_capacity_bytes(0),
4213 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4214 _hum_used_bytes(0), _hum_capacity_bytes(0),
4215 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4216 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4217 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4218 MemRegion g1_reserved = g1h->g1_reserved();
4219 double now = os::elapsedTime();
4220
4221 // Print the header of the output.
4222 _out->cr();
4223 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4224 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4225 G1PPRL_SUM_ADDR_FORMAT("reserved")
4226 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4227 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
4228 HeapRegion::GrainBytes);
4229 _out->print_cr(G1PPRL_LINE_PREFIX);
4230 _out->print_cr(G1PPRL_LINE_PREFIX
4231 G1PPRL_TYPE_H_FORMAT
4232 G1PPRL_ADDR_BASE_H_FORMAT
4233 G1PPRL_BYTE_H_FORMAT
4234 G1PPRL_BYTE_H_FORMAT
4235 G1PPRL_BYTE_H_FORMAT
4236 G1PPRL_DOUBLE_H_FORMAT
4237 G1PPRL_BYTE_H_FORMAT
4238 G1PPRL_BYTE_H_FORMAT,
4239 "type", "address-range",
4240 "used", "prev-live", "next-live", "gc-eff",
4241 "remset", "code-roots");
4242 _out->print_cr(G1PPRL_LINE_PREFIX
4243 G1PPRL_TYPE_H_FORMAT
4244 G1PPRL_ADDR_BASE_H_FORMAT
4245 G1PPRL_BYTE_H_FORMAT
4246 G1PPRL_BYTE_H_FORMAT
4247 G1PPRL_BYTE_H_FORMAT
4248 G1PPRL_DOUBLE_H_FORMAT
4249 G1PPRL_BYTE_H_FORMAT
4250 G1PPRL_BYTE_H_FORMAT,
4251 "", "",
4252 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4253 "(bytes)", "(bytes)");
4254 }
4255
4256 // It takes as a parameter a reference to one of the _hum_* fields, it
4257 // deduces the corresponding value for a region in a humongous region
4258 // series (either the region size, or what's left if the _hum_* field
4259 // is < the region size), and updates the _hum_* field accordingly.
4260 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4261 size_t bytes = 0;
4262 // The > 0 check is to deal with the prev and next live bytes which
4263 // could be 0.
4264 if (*hum_bytes > 0) {
4265 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4266 *hum_bytes -= bytes;
4267 }
4268 return bytes;
4269 }
4270
4271 // It deduces the values for a region in a humongous region series
4272 // from the _hum_* fields and updates those accordingly. It assumes
4273 // that that _hum_* fields have already been set up from the "starts
4274 // humongous" region and we visit the regions in address order.
4275 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4276 size_t* capacity_bytes,
4277 size_t* prev_live_bytes,
4278 size_t* next_live_bytes) {
4279 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4280 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4281 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4282 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4283 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4284 }
4285
4286 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4287 const char* type = r->get_type_str();
4288 HeapWord* bottom = r->bottom();
4289 HeapWord* end = r->end();
4290 size_t capacity_bytes = r->capacity();
4291 size_t used_bytes = r->used();
4292 size_t prev_live_bytes = r->live_bytes();
4293 size_t next_live_bytes = r->next_live_bytes();
4294 double gc_eff = r->gc_efficiency();
4295 size_t remset_bytes = r->rem_set()->mem_size();
4296 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4297
4298 if (r->is_starts_humongous()) {
4299 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4300 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4301 "they should have been zeroed after the last time we used them");
4302 // Set up the _hum_* fields.
4303 _hum_capacity_bytes = capacity_bytes;
4304 _hum_used_bytes = used_bytes;
4305 _hum_prev_live_bytes = prev_live_bytes;
4306 _hum_next_live_bytes = next_live_bytes;
4307 get_hum_bytes(&used_bytes, &capacity_bytes,
4308 &prev_live_bytes, &next_live_bytes);
4309 end = bottom + HeapRegion::GrainWords;
4310 } else if (r->is_continues_humongous()) {
4311 get_hum_bytes(&used_bytes, &capacity_bytes,
4312 &prev_live_bytes, &next_live_bytes);
4313 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4314 }
4315
4316 _total_used_bytes += used_bytes;
4317 _total_capacity_bytes += capacity_bytes;
4318 _total_prev_live_bytes += prev_live_bytes;
4319 _total_next_live_bytes += next_live_bytes;
4320 _total_remset_bytes += remset_bytes;
4321 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4322
4323 // Print a line for this particular region.
4324 _out->print_cr(G1PPRL_LINE_PREFIX
4325 G1PPRL_TYPE_FORMAT
4326 G1PPRL_ADDR_BASE_FORMAT
4327 G1PPRL_BYTE_FORMAT
4328 G1PPRL_BYTE_FORMAT
4329 G1PPRL_BYTE_FORMAT
4330 G1PPRL_DOUBLE_FORMAT
4331 G1PPRL_BYTE_FORMAT
4332 G1PPRL_BYTE_FORMAT,
4333 type, p2i(bottom), p2i(end),
4334 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4335 remset_bytes, strong_code_roots_bytes);
4336
4337 return false;
4338 }
4339
4340 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4341 // add static memory usages to remembered set sizes
4342 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4343 // Print the footer of the output.
4344 _out->print_cr(G1PPRL_LINE_PREFIX);
4345 _out->print_cr(G1PPRL_LINE_PREFIX
4346 " SUMMARY"
4347 G1PPRL_SUM_MB_FORMAT("capacity")
4348 G1PPRL_SUM_MB_PERC_FORMAT("used")
4349 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4350 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4351 G1PPRL_SUM_MB_FORMAT("remset")
4352 G1PPRL_SUM_MB_FORMAT("code-roots"),
4353 bytes_to_mb(_total_capacity_bytes),
4354 bytes_to_mb(_total_used_bytes),
4355 perc(_total_used_bytes, _total_capacity_bytes),
4356 bytes_to_mb(_total_prev_live_bytes),
4357 perc(_total_prev_live_bytes, _total_capacity_bytes),
4358 bytes_to_mb(_total_next_live_bytes),
4359 perc(_total_next_live_bytes, _total_capacity_bytes),
4360 bytes_to_mb(_total_remset_bytes),
4361 bytes_to_mb(_total_strong_code_roots_bytes));
4362 _out->cr();
4363 }