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_implementation/g1/concurrentMark.inline.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
32 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
33 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
34 #include "gc_implementation/g1/g1Log.hpp"
35 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
36 #include "gc_implementation/g1/g1RemSet.hpp"
37 #include "gc_implementation/g1/g1StringDedup.hpp"
38 #include "gc_implementation/g1/heapRegion.inline.hpp"
39 #include "gc_implementation/g1/heapRegionManager.inline.hpp"
40 #include "gc_implementation/g1/heapRegionRemSet.hpp"
41 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
42 #include "gc_implementation/shared/vmGCOperations.hpp"
43 #include "gc_implementation/shared/gcTimer.hpp"
44 #include "gc_implementation/shared/gcTrace.hpp"
45 #include "gc_implementation/shared/gcTraceTime.hpp"
46 #include "memory/allocation.hpp"
47 #include "memory/genOopClosures.inline.hpp"
48 #include "memory/referencePolicy.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "memory/strongRootsScope.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "runtime/handles.inline.hpp"
53 #include "runtime/java.hpp"
54 #include "runtime/atomic.inline.hpp"
55 #include "runtime/prefetch.inline.hpp"
56 #include "services/memTracker.hpp"
57 #include "utilities/taskqueue.inline.hpp"
58
59 // Concurrent marking bit map wrapper
60
61 CMBitMapRO::CMBitMapRO(int shifter) :
62 _bm(),
63 _shifter(shifter) {
64 _bmStartWord = 0;
65 _bmWordSize = 0;
66 }
67
68 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
69 const HeapWord* limit) const {
70 // First we must round addr *up* to a possible object boundary.
71 addr = (HeapWord*)align_size_up((intptr_t)addr,
72 HeapWordSize << _shifter);
73 size_t addrOffset = heapWordToOffset(addr);
74 if (limit == NULL) {
75 limit = _bmStartWord + _bmWordSize;
76 }
77 size_t limitOffset = heapWordToOffset(limit);
78 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
79 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
80 assert(nextAddr >= addr, "get_next_one postcondition");
81 assert(nextAddr == limit || isMarked(nextAddr),
82 "get_next_one postcondition");
83 return nextAddr;
84 }
85
86 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr,
87 const HeapWord* limit) const {
88 size_t addrOffset = heapWordToOffset(addr);
89 if (limit == NULL) {
90 limit = _bmStartWord + _bmWordSize;
91 }
92 size_t limitOffset = heapWordToOffset(limit);
93 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
94 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
95 assert(nextAddr >= addr, "get_next_one postcondition");
96 assert(nextAddr == limit || !isMarked(nextAddr),
97 "get_next_one postcondition");
98 return nextAddr;
99 }
100
101 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
102 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
103 return (int) (diff >> _shifter);
104 }
105
106 #ifndef PRODUCT
107 bool CMBitMapRO::covers(MemRegion heap_rs) const {
108 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
109 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
110 "size inconsistency");
111 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
112 _bmWordSize == heap_rs.word_size();
113 }
114 #endif
115
116 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
117 _bm.print_on_error(st, prefix);
118 }
119
120 size_t CMBitMap::compute_size(size_t heap_size) {
121 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
122 }
123
124 size_t CMBitMap::mark_distance() {
125 return MinObjAlignmentInBytes * BitsPerByte;
126 }
127
128 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
129 _bmStartWord = heap.start();
130 _bmWordSize = heap.word_size();
131
132 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
133 _bm.set_size(_bmWordSize >> _shifter);
134
135 storage->set_mapping_changed_listener(&_listener);
136 }
137
138 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
139 if (zero_filled) {
140 return;
141 }
142 // We need to clear the bitmap on commit, removing any existing information.
143 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
144 _bm->clearRange(mr);
145 }
146
147 // Closure used for clearing the given mark bitmap.
148 class ClearBitmapHRClosure : public HeapRegionClosure {
149 private:
150 ConcurrentMark* _cm;
151 CMBitMap* _bitmap;
152 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration.
153 public:
154 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) {
155 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield.");
156 }
157
158 virtual bool doHeapRegion(HeapRegion* r) {
159 size_t const chunk_size_in_words = M / HeapWordSize;
160
161 HeapWord* cur = r->bottom();
162 HeapWord* const end = r->end();
163
164 while (cur < end) {
165 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
166 _bitmap->clearRange(mr);
167
168 cur += chunk_size_in_words;
169
170 // Abort iteration if after yielding the marking has been aborted.
171 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) {
172 return true;
173 }
174 // Repeat the asserts from before the start of the closure. We will do them
175 // as asserts here to minimize their overhead on the product. However, we
176 // will have them as guarantees at the beginning / end of the bitmap
177 // clearing to get some checking in the product.
178 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant");
179 assert(!_may_yield || !G1CollectedHeap::heap()->mark_in_progress(), "invariant");
180 }
181
182 return false;
183 }
184 };
185
186 class ParClearNextMarkBitmapTask : public AbstractGangTask {
187 ClearBitmapHRClosure* _cl;
188 HeapRegionClaimer _hrclaimer;
189 bool _suspendible; // If the task is suspendible, workers must join the STS.
190
191 public:
192 ParClearNextMarkBitmapTask(ClearBitmapHRClosure *cl, uint n_workers, bool suspendible) :
193 _cl(cl), _suspendible(suspendible), AbstractGangTask("Parallel Clear Bitmap Task"), _hrclaimer(n_workers) {}
194
195 void work(uint worker_id) {
196 if (_suspendible) {
197 SuspendibleThreadSet::join();
198 }
199 G1CollectedHeap::heap()->heap_region_par_iterate(_cl, worker_id, &_hrclaimer, true);
200 if (_suspendible) {
201 SuspendibleThreadSet::leave();
202 }
203 }
204 };
205
206 void CMBitMap::clearAll() {
207 G1CollectedHeap* g1h = G1CollectedHeap::heap();
208 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */);
209 uint n_workers = g1h->workers()->active_workers();
210 ParClearNextMarkBitmapTask task(&cl, n_workers, false);
211 g1h->workers()->run_task(&task);
212 guarantee(cl.complete(), "Must have completed iteration.");
213 return;
214 }
215
216 void CMBitMap::markRange(MemRegion mr) {
217 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
218 assert(!mr.is_empty(), "unexpected empty region");
219 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
220 ((HeapWord *) mr.end())),
221 "markRange memory region end is not card aligned");
222 // convert address range into offset range
223 _bm.at_put_range(heapWordToOffset(mr.start()),
224 heapWordToOffset(mr.end()), true);
225 }
226
227 void CMBitMap::clearRange(MemRegion mr) {
228 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
229 assert(!mr.is_empty(), "unexpected empty region");
230 // convert address range into offset range
231 _bm.at_put_range(heapWordToOffset(mr.start()),
232 heapWordToOffset(mr.end()), false);
233 }
234
235 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
236 HeapWord* end_addr) {
237 HeapWord* start = getNextMarkedWordAddress(addr);
238 start = MIN2(start, end_addr);
239 HeapWord* end = getNextUnmarkedWordAddress(start);
240 end = MIN2(end, end_addr);
241 assert(start <= end, "Consistency check");
242 MemRegion mr(start, end);
243 if (!mr.is_empty()) {
244 clearRange(mr);
245 }
246 return mr;
247 }
248
249 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
250 _base(NULL), _cm(cm)
251 #ifdef ASSERT
252 , _drain_in_progress(false)
253 , _drain_in_progress_yields(false)
254 #endif
255 {}
256
257 bool CMMarkStack::allocate(size_t capacity) {
258 // allocate a stack of the requisite depth
259 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
260 if (!rs.is_reserved()) {
261 warning("ConcurrentMark MarkStack allocation failure");
262 return false;
263 }
264 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
265 if (!_virtual_space.initialize(rs, rs.size())) {
266 warning("ConcurrentMark MarkStack backing store failure");
267 // Release the virtual memory reserved for the marking stack
268 rs.release();
269 return false;
270 }
271 assert(_virtual_space.committed_size() == rs.size(),
272 "Didn't reserve backing store for all of ConcurrentMark stack?");
273 _base = (oop*) _virtual_space.low();
274 setEmpty();
275 _capacity = (jint) capacity;
276 _saved_index = -1;
277 _should_expand = false;
278 NOT_PRODUCT(_max_depth = 0);
279 return true;
280 }
281
282 void CMMarkStack::expand() {
283 // Called, during remark, if we've overflown the marking stack during marking.
284 assert(isEmpty(), "stack should been emptied while handling overflow");
285 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
286 // Clear expansion flag
287 _should_expand = false;
288 if (_capacity == (jint) MarkStackSizeMax) {
289 if (PrintGCDetails && Verbose) {
290 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
291 }
292 return;
293 }
294 // Double capacity if possible
295 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
296 // Do not give up existing stack until we have managed to
297 // get the double capacity that we desired.
298 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
299 sizeof(oop)));
300 if (rs.is_reserved()) {
301 // Release the backing store associated with old stack
302 _virtual_space.release();
303 // Reinitialize virtual space for new stack
304 if (!_virtual_space.initialize(rs, rs.size())) {
305 fatal("Not enough swap for expanded marking stack capacity");
306 }
307 _base = (oop*)(_virtual_space.low());
308 _index = 0;
309 _capacity = new_capacity;
310 } else {
311 if (PrintGCDetails && Verbose) {
312 // Failed to double capacity, continue;
313 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
314 SIZE_FORMAT"K to " SIZE_FORMAT"K",
315 _capacity / K, new_capacity / K);
316 }
317 }
318 }
319
320 void CMMarkStack::set_should_expand() {
321 // If we're resetting the marking state because of an
322 // marking stack overflow, record that we should, if
323 // possible, expand the stack.
324 _should_expand = _cm->has_overflown();
325 }
326
327 CMMarkStack::~CMMarkStack() {
328 if (_base != NULL) {
329 _base = NULL;
330 _virtual_space.release();
331 }
332 }
333
334 void CMMarkStack::par_push(oop ptr) {
335 while (true) {
336 if (isFull()) {
337 _overflow = true;
338 return;
339 }
340 // Otherwise...
341 jint index = _index;
342 jint next_index = index+1;
343 jint res = Atomic::cmpxchg(next_index, &_index, index);
344 if (res == index) {
345 _base[index] = ptr;
346 // Note that we don't maintain this atomically. We could, but it
347 // doesn't seem necessary.
348 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
349 return;
350 }
351 // Otherwise, we need to try again.
352 }
353 }
354
355 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) {
356 while (true) {
357 if (isFull()) {
358 _overflow = true;
359 return;
360 }
361 // Otherwise...
362 jint index = _index;
363 jint next_index = index + n;
364 if (next_index > _capacity) {
365 _overflow = true;
366 return;
367 }
368 jint res = Atomic::cmpxchg(next_index, &_index, index);
369 if (res == index) {
370 for (int i = 0; i < n; i++) {
371 int ind = index + i;
372 assert(ind < _capacity, "By overflow test above.");
373 _base[ind] = ptr_arr[i];
374 }
375 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
376 return;
377 }
378 // Otherwise, we need to try again.
379 }
380 }
381
382 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
383 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
384 jint start = _index;
385 jint next_index = start + n;
386 if (next_index > _capacity) {
387 _overflow = true;
388 return;
389 }
390 // Otherwise.
391 _index = next_index;
392 for (int i = 0; i < n; i++) {
393 int ind = start + i;
394 assert(ind < _capacity, "By overflow test above.");
395 _base[ind] = ptr_arr[i];
396 }
397 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
398 }
399
400 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
401 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
402 jint index = _index;
403 if (index == 0) {
404 *n = 0;
405 return false;
406 } else {
407 int k = MIN2(max, index);
408 jint new_ind = index - k;
409 for (int j = 0; j < k; j++) {
410 ptr_arr[j] = _base[new_ind + j];
411 }
412 _index = new_ind;
413 *n = k;
414 return true;
415 }
416 }
417
418 template<class OopClosureClass>
419 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
420 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
421 || SafepointSynchronize::is_at_safepoint(),
422 "Drain recursion must be yield-safe.");
423 bool res = true;
424 debug_only(_drain_in_progress = true);
425 debug_only(_drain_in_progress_yields = yield_after);
426 while (!isEmpty()) {
427 oop newOop = pop();
428 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
429 assert(newOop->is_oop(), "Expected an oop");
430 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
431 "only grey objects on this stack");
432 newOop->oop_iterate(cl);
433 if (yield_after && _cm->do_yield_check()) {
434 res = false;
435 break;
436 }
437 }
438 debug_only(_drain_in_progress = false);
439 return res;
440 }
441
442 void CMMarkStack::note_start_of_gc() {
443 assert(_saved_index == -1,
444 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
445 _saved_index = _index;
446 }
447
448 void CMMarkStack::note_end_of_gc() {
449 // This is intentionally a guarantee, instead of an assert. If we
450 // accidentally add something to the mark stack during GC, it
451 // will be a correctness issue so it's better if we crash. we'll
452 // only check this once per GC anyway, so it won't be a performance
453 // issue in any way.
454 guarantee(_saved_index == _index,
455 err_msg("saved index: %d index: %d", _saved_index, _index));
456 _saved_index = -1;
457 }
458
459 void CMMarkStack::oops_do(OopClosure* f) {
460 assert(_saved_index == _index,
461 err_msg("saved index: %d index: %d", _saved_index, _index));
462 for (int i = 0; i < _index; i += 1) {
463 f->do_oop(&_base[i]);
464 }
465 }
466
467 CMRootRegions::CMRootRegions() :
468 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
469 _should_abort(false), _next_survivor(NULL) { }
470
471 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
472 _young_list = g1h->young_list();
473 _cm = cm;
474 }
475
476 void CMRootRegions::prepare_for_scan() {
477 assert(!scan_in_progress(), "pre-condition");
478
479 // Currently, only survivors can be root regions.
480 assert(_next_survivor == NULL, "pre-condition");
481 _next_survivor = _young_list->first_survivor_region();
482 _scan_in_progress = (_next_survivor != NULL);
483 _should_abort = false;
484 }
485
486 HeapRegion* CMRootRegions::claim_next() {
487 if (_should_abort) {
488 // If someone has set the should_abort flag, we return NULL to
489 // force the caller to bail out of their loop.
490 return NULL;
491 }
492
493 // Currently, only survivors can be root regions.
494 HeapRegion* res = _next_survivor;
495 if (res != NULL) {
496 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
497 // Read it again in case it changed while we were waiting for the lock.
498 res = _next_survivor;
499 if (res != NULL) {
500 if (res == _young_list->last_survivor_region()) {
501 // We just claimed the last survivor so store NULL to indicate
502 // that we're done.
503 _next_survivor = NULL;
504 } else {
505 _next_survivor = res->get_next_young_region();
506 }
507 } else {
508 // Someone else claimed the last survivor while we were trying
509 // to take the lock so nothing else to do.
510 }
511 }
512 assert(res == NULL || res->is_survivor(), "post-condition");
513
514 return res;
515 }
516
517 void CMRootRegions::scan_finished() {
518 assert(scan_in_progress(), "pre-condition");
519
520 // Currently, only survivors can be root regions.
521 if (!_should_abort) {
522 assert(_next_survivor == NULL, "we should have claimed all survivors");
523 }
524 _next_survivor = NULL;
525
526 {
527 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
528 _scan_in_progress = false;
529 RootRegionScan_lock->notify_all();
530 }
531 }
532
533 bool CMRootRegions::wait_until_scan_finished() {
534 if (!scan_in_progress()) return false;
535
536 {
537 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
538 while (scan_in_progress()) {
539 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
540 }
541 }
542 return true;
543 }
544
545 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
546 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
547 #endif // _MSC_VER
548
549 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
550 return MAX2((n_par_threads + 2) / 4, 1U);
551 }
552
553 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
554 _g1h(g1h),
555 _markBitMap1(),
556 _markBitMap2(),
557 _parallel_marking_threads(0),
558 _max_parallel_marking_threads(0),
559 _sleep_factor(0.0),
560 _marking_task_overhead(1.0),
561 _cleanup_sleep_factor(0.0),
562 _cleanup_task_overhead(1.0),
563 _cleanup_list("Cleanup List"),
564 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
565 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >>
566 CardTableModRefBS::card_shift,
567 false /* in_resource_area*/),
568
569 _prevMarkBitMap(&_markBitMap1),
570 _nextMarkBitMap(&_markBitMap2),
571
572 _markStack(this),
573 // _finger set in set_non_marking_state
574
575 _max_worker_id(MAX2((uint)ParallelGCThreads, 1U)),
576 // _active_tasks set in set_non_marking_state
577 // _tasks set inside the constructor
578 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
579 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
580
581 _has_overflown(false),
582 _concurrent(false),
583 _has_aborted(false),
584 _aborted_gc_id(GCId::undefined()),
585 _restart_for_overflow(false),
586 _concurrent_marking_in_progress(false),
587
588 // _verbose_level set below
589
590 _init_times(),
591 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
592 _cleanup_times(),
593 _total_counting_time(0.0),
594 _total_rs_scrub_time(0.0),
595
596 _parallel_workers(NULL),
597
598 _count_card_bitmaps(NULL),
599 _count_marked_bytes(NULL),
600 _completed_initialization(false) {
601 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
602 if (verbose_level < no_verbose) {
603 verbose_level = no_verbose;
604 }
605 if (verbose_level > high_verbose) {
606 verbose_level = high_verbose;
607 }
608 _verbose_level = verbose_level;
609
610 if (verbose_low()) {
611 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
612 "heap end = " PTR_FORMAT, p2i(_heap_start), p2i(_heap_end));
613 }
614
615 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
616 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
617
618 // Create & start a ConcurrentMark thread.
619 _cmThread = new ConcurrentMarkThread(this);
620 assert(cmThread() != NULL, "CM Thread should have been created");
621 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
622 if (_cmThread->osthread() == NULL) {
623 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
624 }
625
626 assert(CGC_lock != NULL, "Where's the CGC_lock?");
627 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
628 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
629
630 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
631 satb_qs.set_buffer_size(G1SATBBufferSize);
632
633 _root_regions.init(_g1h, this);
634
635 if (ConcGCThreads > ParallelGCThreads) {
636 warning("Can't have more ConcGCThreads (" UINTX_FORMAT ") "
637 "than ParallelGCThreads (" UINTX_FORMAT ").",
638 ConcGCThreads, ParallelGCThreads);
639 return;
640 }
641 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
642 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
643 // if both are set
644 _sleep_factor = 0.0;
645 _marking_task_overhead = 1.0;
646 } else if (G1MarkingOverheadPercent > 0) {
647 // We will calculate the number of parallel marking threads based
648 // on a target overhead with respect to the soft real-time goal
649 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
650 double overall_cm_overhead =
651 (double) MaxGCPauseMillis * marking_overhead /
652 (double) GCPauseIntervalMillis;
653 double cpu_ratio = 1.0 / (double) os::processor_count();
654 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
655 double marking_task_overhead =
656 overall_cm_overhead / marking_thread_num *
657 (double) os::processor_count();
658 double sleep_factor =
659 (1.0 - marking_task_overhead) / marking_task_overhead;
660
661 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num);
662 _sleep_factor = sleep_factor;
663 _marking_task_overhead = marking_task_overhead;
664 } else {
665 // Calculate the number of parallel marking threads by scaling
666 // the number of parallel GC threads.
667 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads);
668 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num);
669 _sleep_factor = 0.0;
670 _marking_task_overhead = 1.0;
671 }
672
673 assert(ConcGCThreads > 0, "Should have been set");
674 _parallel_marking_threads = (uint) ConcGCThreads;
675 _max_parallel_marking_threads = _parallel_marking_threads;
676
677 if (parallel_marking_threads() > 1) {
678 _cleanup_task_overhead = 1.0;
679 } else {
680 _cleanup_task_overhead = marking_task_overhead();
681 }
682 _cleanup_sleep_factor =
683 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
684
685 #if 0
686 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
687 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
688 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
689 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
690 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
691 #endif
692
693 _parallel_workers = new FlexibleWorkGang("G1 Marker",
694 _max_parallel_marking_threads, false, true);
695 if (_parallel_workers == NULL) {
696 vm_exit_during_initialization("Failed necessary allocation.");
697 } else {
698 _parallel_workers->initialize_workers();
699 }
700
701 if (FLAG_IS_DEFAULT(MarkStackSize)) {
702 size_t mark_stack_size =
703 MIN2(MarkStackSizeMax,
704 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
705 // Verify that the calculated value for MarkStackSize is in range.
706 // It would be nice to use the private utility routine from Arguments.
707 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
708 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
709 "must be between 1 and " SIZE_FORMAT,
710 mark_stack_size, MarkStackSizeMax);
711 return;
712 }
713 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
714 } else {
715 // Verify MarkStackSize is in range.
716 if (FLAG_IS_CMDLINE(MarkStackSize)) {
717 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
718 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
719 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
720 "must be between 1 and " SIZE_FORMAT,
721 MarkStackSize, MarkStackSizeMax);
722 return;
723 }
724 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
725 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
726 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
727 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
728 MarkStackSize, MarkStackSizeMax);
729 return;
730 }
731 }
732 }
733 }
734
735 if (!_markStack.allocate(MarkStackSize)) {
736 warning("Failed to allocate CM marking stack");
737 return;
738 }
739
740 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
741 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
742
743 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
744 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
745
746 BitMap::idx_t card_bm_size = _card_bm.size();
747
748 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
749 _active_tasks = _max_worker_id;
750
751 uint max_regions = _g1h->max_regions();
752 for (uint i = 0; i < _max_worker_id; ++i) {
753 CMTaskQueue* task_queue = new CMTaskQueue();
754 task_queue->initialize();
755 _task_queues->register_queue(i, task_queue);
756
757 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
758 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
759
760 _tasks[i] = new CMTask(i, this,
761 _count_marked_bytes[i],
762 &_count_card_bitmaps[i],
763 task_queue, _task_queues);
764
765 _accum_task_vtime[i] = 0.0;
766 }
767
768 // Calculate the card number for the bottom of the heap. Used
769 // in biasing indexes into the accounting card bitmaps.
770 _heap_bottom_card_num =
771 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
772 CardTableModRefBS::card_shift);
773
774 // Clear all the liveness counting data
775 clear_all_count_data();
776
777 // so that the call below can read a sensible value
778 _heap_start = g1h->reserved_region().start();
779 set_non_marking_state();
780 _completed_initialization = true;
781 }
782
783 void ConcurrentMark::reset() {
784 // Starting values for these two. This should be called in a STW
785 // phase.
786 MemRegion reserved = _g1h->g1_reserved();
787 _heap_start = reserved.start();
788 _heap_end = reserved.end();
789
790 // Separated the asserts so that we know which one fires.
791 assert(_heap_start != NULL, "heap bounds should look ok");
792 assert(_heap_end != NULL, "heap bounds should look ok");
793 assert(_heap_start < _heap_end, "heap bounds should look ok");
794
795 // Reset all the marking data structures and any necessary flags
796 reset_marking_state();
797
798 if (verbose_low()) {
799 gclog_or_tty->print_cr("[global] resetting");
800 }
801
802 // We do reset all of them, since different phases will use
803 // different number of active threads. So, it's easiest to have all
804 // of them ready.
805 for (uint i = 0; i < _max_worker_id; ++i) {
806 _tasks[i]->reset(_nextMarkBitMap);
807 }
808
809 // we need this to make sure that the flag is on during the evac
810 // pause with initial mark piggy-backed
811 set_concurrent_marking_in_progress();
812 }
813
814
815 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
816 _markStack.set_should_expand();
817 _markStack.setEmpty(); // Also clears the _markStack overflow flag
818 if (clear_overflow) {
819 clear_has_overflown();
820 } else {
821 assert(has_overflown(), "pre-condition");
822 }
823 _finger = _heap_start;
824
825 for (uint i = 0; i < _max_worker_id; ++i) {
826 CMTaskQueue* queue = _task_queues->queue(i);
827 queue->set_empty();
828 }
829 }
830
831 void ConcurrentMark::set_concurrency(uint active_tasks) {
832 assert(active_tasks <= _max_worker_id, "we should not have more");
833
834 _active_tasks = active_tasks;
835 // Need to update the three data structures below according to the
836 // number of active threads for this phase.
837 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
838 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
839 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
840 }
841
842 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
843 set_concurrency(active_tasks);
844
845 _concurrent = concurrent;
846 // We propagate this to all tasks, not just the active ones.
847 for (uint i = 0; i < _max_worker_id; ++i)
848 _tasks[i]->set_concurrent(concurrent);
849
850 if (concurrent) {
851 set_concurrent_marking_in_progress();
852 } else {
853 // We currently assume that the concurrent flag has been set to
854 // false before we start remark. At this point we should also be
855 // in a STW phase.
856 assert(!concurrent_marking_in_progress(), "invariant");
857 assert(out_of_regions(),
858 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT,
859 p2i(_finger), p2i(_heap_end)));
860 }
861 }
862
863 void ConcurrentMark::set_non_marking_state() {
864 // We set the global marking state to some default values when we're
865 // not doing marking.
866 reset_marking_state();
867 _active_tasks = 0;
868 clear_concurrent_marking_in_progress();
869 }
870
871 ConcurrentMark::~ConcurrentMark() {
872 // The ConcurrentMark instance is never freed.
873 ShouldNotReachHere();
874 }
875
876 void ConcurrentMark::clearNextBitmap() {
877 G1CollectedHeap* g1h = G1CollectedHeap::heap();
878
879 // Make sure that the concurrent mark thread looks to still be in
880 // the current cycle.
881 guarantee(cmThread()->during_cycle(), "invariant");
882
883 // We are finishing up the current cycle by clearing the next
884 // marking bitmap and getting it ready for the next cycle. During
885 // this time no other cycle can start. So, let's make sure that this
886 // is the case.
887 guarantee(!g1h->mark_in_progress(), "invariant");
888
889 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */);
890 ParClearNextMarkBitmapTask task(&cl, parallel_marking_threads(), true);
891 _parallel_workers->run_task(&task);
892
893 // Clear the liveness counting data. If the marking has been aborted, the abort()
894 // call already did that.
895 if (cl.complete()) {
896 clear_all_count_data();
897 }
898
899 // Repeat the asserts from above.
900 guarantee(cmThread()->during_cycle(), "invariant");
901 guarantee(!g1h->mark_in_progress(), "invariant");
902 }
903
904 class CheckBitmapClearHRClosure : public HeapRegionClosure {
905 CMBitMap* _bitmap;
906 bool _error;
907 public:
908 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) {
909 }
910
911 virtual bool doHeapRegion(HeapRegion* r) {
912 // This closure can be called concurrently to the mutator, so we must make sure
913 // that the result of the getNextMarkedWordAddress() call is compared to the
914 // value passed to it as limit to detect any found bits.
915 // We can use the region's orig_end() for the limit and the comparison value
916 // as it always contains the "real" end of the region that never changes and
917 // has no side effects.
918 // Due to the latter, there can also be no problem with the compiler generating
919 // reloads of the orig_end() call.
920 HeapWord* end = r->orig_end();
921 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
922 }
923 };
924
925 bool ConcurrentMark::nextMarkBitmapIsClear() {
926 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
927 _g1h->heap_region_iterate(&cl);
928 return cl.complete();
929 }
930
931 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
932 public:
933 bool doHeapRegion(HeapRegion* r) {
934 if (!r->is_continues_humongous()) {
935 r->note_start_of_marking();
936 }
937 return false;
938 }
939 };
940
941 void ConcurrentMark::checkpointRootsInitialPre() {
942 G1CollectedHeap* g1h = G1CollectedHeap::heap();
943 G1CollectorPolicy* g1p = g1h->g1_policy();
944
945 _has_aborted = false;
946
947 // Initialize marking structures. This has to be done in a STW phase.
948 reset();
949
950 // For each region note start of marking.
951 NoteStartOfMarkHRClosure startcl;
952 g1h->heap_region_iterate(&startcl);
953 }
954
955
956 void ConcurrentMark::checkpointRootsInitialPost() {
957 G1CollectedHeap* g1h = G1CollectedHeap::heap();
958
959 // If we force an overflow during remark, the remark operation will
960 // actually abort and we'll restart concurrent marking. If we always
961 // force an overflow during remark we'll never actually complete the
962 // marking phase. So, we initialize this here, at the start of the
963 // cycle, so that at the remaining overflow number will decrease at
964 // every remark and we'll eventually not need to cause one.
965 force_overflow_stw()->init();
966
967 // Start Concurrent Marking weak-reference discovery.
968 ReferenceProcessor* rp = g1h->ref_processor_cm();
969 // enable ("weak") refs discovery
970 rp->enable_discovery();
971 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
972
973 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
974 // This is the start of the marking cycle, we're expected all
975 // threads to have SATB queues with active set to false.
976 satb_mq_set.set_active_all_threads(true, /* new active value */
977 false /* expected_active */);
978
979 _root_regions.prepare_for_scan();
980
981 // update_g1_committed() will be called at the end of an evac pause
982 // when marking is on. So, it's also called at the end of the
983 // initial-mark pause to update the heap end, if the heap expands
984 // during it. No need to call it here.
985 }
986
987 /*
988 * Notice that in the next two methods, we actually leave the STS
989 * during the barrier sync and join it immediately afterwards. If we
990 * do not do this, the following deadlock can occur: one thread could
991 * be in the barrier sync code, waiting for the other thread to also
992 * sync up, whereas another one could be trying to yield, while also
993 * waiting for the other threads to sync up too.
994 *
995 * Note, however, that this code is also used during remark and in
996 * this case we should not attempt to leave / enter the STS, otherwise
997 * we'll either hit an assert (debug / fastdebug) or deadlock
998 * (product). So we should only leave / enter the STS if we are
999 * operating concurrently.
1000 *
1001 * Because the thread that does the sync barrier has left the STS, it
1002 * is possible to be suspended for a Full GC or an evacuation pause
1003 * could occur. This is actually safe, since the entering the sync
1004 * barrier is one of the last things do_marking_step() does, and it
1005 * doesn't manipulate any data structures afterwards.
1006 */
1007
1008 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
1009 if (verbose_low()) {
1010 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
1011 }
1012
1013 if (concurrent()) {
1014 SuspendibleThreadSet::leave();
1015 }
1016
1017 bool barrier_aborted = !_first_overflow_barrier_sync.enter();
1018
1019 if (concurrent()) {
1020 SuspendibleThreadSet::join();
1021 }
1022 // at this point everyone should have synced up and not be doing any
1023 // more work
1024
1025 if (verbose_low()) {
1026 if (barrier_aborted) {
1027 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id);
1028 } else {
1029 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
1030 }
1031 }
1032
1033 if (barrier_aborted) {
1034 // If the barrier aborted we ignore the overflow condition and
1035 // just abort the whole marking phase as quickly as possible.
1036 return;
1037 }
1038
1039 // If we're executing the concurrent phase of marking, reset the marking
1040 // state; otherwise the marking state is reset after reference processing,
1041 // during the remark pause.
1042 // If we reset here as a result of an overflow during the remark we will
1043 // see assertion failures from any subsequent set_concurrency_and_phase()
1044 // calls.
1045 if (concurrent()) {
1046 // let the task associated with with worker 0 do this
1047 if (worker_id == 0) {
1048 // task 0 is responsible for clearing the global data structures
1049 // We should be here because of an overflow. During STW we should
1050 // not clear the overflow flag since we rely on it being true when
1051 // we exit this method to abort the pause and restart concurrent
1052 // marking.
1053 reset_marking_state(true /* clear_overflow */);
1054 force_overflow()->update();
1055
1056 if (G1Log::fine()) {
1057 gclog_or_tty->gclog_stamp(concurrent_gc_id());
1058 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
1059 }
1060 }
1061 }
1062
1063 // after this, each task should reset its own data structures then
1064 // then go into the second barrier
1065 }
1066
1067 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1068 if (verbose_low()) {
1069 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1070 }
1071
1072 if (concurrent()) {
1073 SuspendibleThreadSet::leave();
1074 }
1075
1076 bool barrier_aborted = !_second_overflow_barrier_sync.enter();
1077
1078 if (concurrent()) {
1079 SuspendibleThreadSet::join();
1080 }
1081 // at this point everything should be re-initialized and ready to go
1082
1083 if (verbose_low()) {
1084 if (barrier_aborted) {
1085 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id);
1086 } else {
1087 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1088 }
1089 }
1090 }
1091
1092 #ifndef PRODUCT
1093 void ForceOverflowSettings::init() {
1094 _num_remaining = G1ConcMarkForceOverflow;
1095 _force = false;
1096 update();
1097 }
1098
1099 void ForceOverflowSettings::update() {
1100 if (_num_remaining > 0) {
1101 _num_remaining -= 1;
1102 _force = true;
1103 } else {
1104 _force = false;
1105 }
1106 }
1107
1108 bool ForceOverflowSettings::should_force() {
1109 if (_force) {
1110 _force = false;
1111 return true;
1112 } else {
1113 return false;
1114 }
1115 }
1116 #endif // !PRODUCT
1117
1118 class CMConcurrentMarkingTask: public AbstractGangTask {
1119 private:
1120 ConcurrentMark* _cm;
1121 ConcurrentMarkThread* _cmt;
1122
1123 public:
1124 void work(uint worker_id) {
1125 assert(Thread::current()->is_ConcurrentGC_thread(),
1126 "this should only be done by a conc GC thread");
1127 ResourceMark rm;
1128
1129 double start_vtime = os::elapsedVTime();
1130
1131 SuspendibleThreadSet::join();
1132
1133 assert(worker_id < _cm->active_tasks(), "invariant");
1134 CMTask* the_task = _cm->task(worker_id);
1135 the_task->record_start_time();
1136 if (!_cm->has_aborted()) {
1137 do {
1138 double start_vtime_sec = os::elapsedVTime();
1139 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1140
1141 the_task->do_marking_step(mark_step_duration_ms,
1142 true /* do_termination */,
1143 false /* is_serial*/);
1144
1145 double end_vtime_sec = os::elapsedVTime();
1146 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1147 _cm->clear_has_overflown();
1148
1149 _cm->do_yield_check(worker_id);
1150
1151 jlong sleep_time_ms;
1152 if (!_cm->has_aborted() && the_task->has_aborted()) {
1153 sleep_time_ms =
1154 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1155 SuspendibleThreadSet::leave();
1156 os::sleep(Thread::current(), sleep_time_ms, false);
1157 SuspendibleThreadSet::join();
1158 }
1159 } while (!_cm->has_aborted() && the_task->has_aborted());
1160 }
1161 the_task->record_end_time();
1162 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1163
1164 SuspendibleThreadSet::leave();
1165
1166 double end_vtime = os::elapsedVTime();
1167 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1168 }
1169
1170 CMConcurrentMarkingTask(ConcurrentMark* cm,
1171 ConcurrentMarkThread* cmt) :
1172 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1173
1174 ~CMConcurrentMarkingTask() { }
1175 };
1176
1177 // Calculates the number of active workers for a concurrent
1178 // phase.
1179 uint ConcurrentMark::calc_parallel_marking_threads() {
1180 uint n_conc_workers = 0;
1181 if (!UseDynamicNumberOfGCThreads ||
1182 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1183 !ForceDynamicNumberOfGCThreads)) {
1184 n_conc_workers = max_parallel_marking_threads();
1185 } else {
1186 n_conc_workers =
1187 AdaptiveSizePolicy::calc_default_active_workers(
1188 max_parallel_marking_threads(),
1189 1, /* Minimum workers */
1190 parallel_marking_threads(),
1191 Threads::number_of_non_daemon_threads());
1192 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1193 // that scaling has already gone into "_max_parallel_marking_threads".
1194 }
1195 assert(n_conc_workers > 0, "Always need at least 1");
1196 return n_conc_workers;
1197 }
1198
1199 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1200 // Currently, only survivors can be root regions.
1201 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1202 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1203
1204 const uintx interval = PrefetchScanIntervalInBytes;
1205 HeapWord* curr = hr->bottom();
1206 const HeapWord* end = hr->top();
1207 while (curr < end) {
1208 Prefetch::read(curr, interval);
1209 oop obj = oop(curr);
1210 int size = obj->oop_iterate(&cl);
1211 assert(size == obj->size(), "sanity");
1212 curr += size;
1213 }
1214 }
1215
1216 class CMRootRegionScanTask : public AbstractGangTask {
1217 private:
1218 ConcurrentMark* _cm;
1219
1220 public:
1221 CMRootRegionScanTask(ConcurrentMark* cm) :
1222 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1223
1224 void work(uint worker_id) {
1225 assert(Thread::current()->is_ConcurrentGC_thread(),
1226 "this should only be done by a conc GC thread");
1227
1228 CMRootRegions* root_regions = _cm->root_regions();
1229 HeapRegion* hr = root_regions->claim_next();
1230 while (hr != NULL) {
1231 _cm->scanRootRegion(hr, worker_id);
1232 hr = root_regions->claim_next();
1233 }
1234 }
1235 };
1236
1237 void ConcurrentMark::scanRootRegions() {
1238 // Start of concurrent marking.
1239 ClassLoaderDataGraph::clear_claimed_marks();
1240
1241 // scan_in_progress() will have been set to true only if there was
1242 // at least one root region to scan. So, if it's false, we
1243 // should not attempt to do any further work.
1244 if (root_regions()->scan_in_progress()) {
1245 _parallel_marking_threads = calc_parallel_marking_threads();
1246 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1247 "Maximum number of marking threads exceeded");
1248 uint active_workers = MAX2(1U, parallel_marking_threads());
1249
1250 CMRootRegionScanTask task(this);
1251 _parallel_workers->set_active_workers(active_workers);
1252 _parallel_workers->run_task(&task);
1253
1254 // It's possible that has_aborted() is true here without actually
1255 // aborting the survivor scan earlier. This is OK as it's
1256 // mainly used for sanity checking.
1257 root_regions()->scan_finished();
1258 }
1259 }
1260
1261 void ConcurrentMark::markFromRoots() {
1262 // we might be tempted to assert that:
1263 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1264 // "inconsistent argument?");
1265 // However that wouldn't be right, because it's possible that
1266 // a safepoint is indeed in progress as a younger generation
1267 // stop-the-world GC happens even as we mark in this generation.
1268
1269 _restart_for_overflow = false;
1270 force_overflow_conc()->init();
1271
1272 // _g1h has _n_par_threads
1273 _parallel_marking_threads = calc_parallel_marking_threads();
1274 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1275 "Maximum number of marking threads exceeded");
1276
1277 uint active_workers = MAX2(1U, parallel_marking_threads());
1278
1279 // Parallel task terminator is set in "set_concurrency_and_phase()"
1280 set_concurrency_and_phase(active_workers, true /* concurrent */);
1281
1282 CMConcurrentMarkingTask markingTask(this, cmThread());
1283 _parallel_workers->set_active_workers(active_workers);
1284 // Don't set _n_par_threads because it affects MT in process_roots()
1285 // and the decisions on that MT processing is made elsewhere.
1286 assert(_parallel_workers->active_workers() > 0, "Should have been set");
1287 _parallel_workers->run_task(&markingTask);
1288 print_stats();
1289 }
1290
1291 // Helper class to get rid of some boilerplate code.
1292 class G1CMTraceTime : public GCTraceTime {
1293 static bool doit_and_prepend(bool doit) {
1294 if (doit) {
1295 gclog_or_tty->put(' ');
1296 }
1297 return doit;
1298 }
1299
1300 public:
1301 G1CMTraceTime(const char* title, bool doit)
1302 : GCTraceTime(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm(),
1303 G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id()) {
1304 }
1305 };
1306
1307 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1308 // world is stopped at this checkpoint
1309 assert(SafepointSynchronize::is_at_safepoint(),
1310 "world should be stopped");
1311
1312 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1313
1314 // If a full collection has happened, we shouldn't do this.
1315 if (has_aborted()) {
1316 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1317 return;
1318 }
1319
1320 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1321
1322 if (VerifyDuringGC) {
1323 HandleMark hm; // handle scope
1324 g1h->prepare_for_verify();
1325 Universe::verify(VerifyOption_G1UsePrevMarking,
1326 " VerifyDuringGC:(before)");
1327 }
1328 g1h->check_bitmaps("Remark Start");
1329
1330 G1CollectorPolicy* g1p = g1h->g1_policy();
1331 g1p->record_concurrent_mark_remark_start();
1332
1333 double start = os::elapsedTime();
1334
1335 checkpointRootsFinalWork();
1336
1337 double mark_work_end = os::elapsedTime();
1338
1339 weakRefsWork(clear_all_soft_refs);
1340
1341 if (has_overflown()) {
1342 // Oops. We overflowed. Restart concurrent marking.
1343 _restart_for_overflow = true;
1344 if (G1TraceMarkStackOverflow) {
1345 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1346 }
1347
1348 // Verify the heap w.r.t. the previous marking bitmap.
1349 if (VerifyDuringGC) {
1350 HandleMark hm; // handle scope
1351 g1h->prepare_for_verify();
1352 Universe::verify(VerifyOption_G1UsePrevMarking,
1353 " VerifyDuringGC:(overflow)");
1354 }
1355
1356 // Clear the marking state because we will be restarting
1357 // marking due to overflowing the global mark stack.
1358 reset_marking_state();
1359 } else {
1360 {
1361 G1CMTraceTime trace("GC aggregate-data", G1Log::finer());
1362
1363 // Aggregate the per-task counting data that we have accumulated
1364 // while marking.
1365 aggregate_count_data();
1366 }
1367
1368 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1369 // We're done with marking.
1370 // This is the end of the marking cycle, we're expected all
1371 // threads to have SATB queues with active set to true.
1372 satb_mq_set.set_active_all_threads(false, /* new active value */
1373 true /* expected_active */);
1374
1375 if (VerifyDuringGC) {
1376 HandleMark hm; // handle scope
1377 g1h->prepare_for_verify();
1378 Universe::verify(VerifyOption_G1UseNextMarking,
1379 " VerifyDuringGC:(after)");
1380 }
1381 g1h->check_bitmaps("Remark End");
1382 assert(!restart_for_overflow(), "sanity");
1383 // Completely reset the marking state since marking completed
1384 set_non_marking_state();
1385 }
1386
1387 // Expand the marking stack, if we have to and if we can.
1388 if (_markStack.should_expand()) {
1389 _markStack.expand();
1390 }
1391
1392 // Statistics
1393 double now = os::elapsedTime();
1394 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1395 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1396 _remark_times.add((now - start) * 1000.0);
1397
1398 g1p->record_concurrent_mark_remark_end();
1399
1400 G1CMIsAliveClosure is_alive(g1h);
1401 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1402 }
1403
1404 // Base class of the closures that finalize and verify the
1405 // liveness counting data.
1406 class CMCountDataClosureBase: public HeapRegionClosure {
1407 protected:
1408 G1CollectedHeap* _g1h;
1409 ConcurrentMark* _cm;
1410 CardTableModRefBS* _ct_bs;
1411
1412 BitMap* _region_bm;
1413 BitMap* _card_bm;
1414
1415 // Takes a region that's not empty (i.e., it has at least one
1416 // live object in it and sets its corresponding bit on the region
1417 // bitmap to 1. If the region is "starts humongous" it will also set
1418 // to 1 the bits on the region bitmap that correspond to its
1419 // associated "continues humongous" regions.
1420 void set_bit_for_region(HeapRegion* hr) {
1421 assert(!hr->is_continues_humongous(), "should have filtered those out");
1422
1423 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1424 if (!hr->is_starts_humongous()) {
1425 // Normal (non-humongous) case: just set the bit.
1426 _region_bm->par_at_put(index, true);
1427 } else {
1428 // Starts humongous case: calculate how many regions are part of
1429 // this humongous region and then set the bit range.
1430 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1431 _region_bm->par_at_put_range(index, end_index, true);
1432 }
1433 }
1434
1435 public:
1436 CMCountDataClosureBase(G1CollectedHeap* g1h,
1437 BitMap* region_bm, BitMap* card_bm):
1438 _g1h(g1h), _cm(g1h->concurrent_mark()),
1439 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
1440 _region_bm(region_bm), _card_bm(card_bm) { }
1441 };
1442
1443 // Closure that calculates the # live objects per region. Used
1444 // for verification purposes during the cleanup pause.
1445 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1446 CMBitMapRO* _bm;
1447 size_t _region_marked_bytes;
1448
1449 public:
1450 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1451 BitMap* region_bm, BitMap* card_bm) :
1452 CMCountDataClosureBase(g1h, region_bm, card_bm),
1453 _bm(bm), _region_marked_bytes(0) { }
1454
1455 bool doHeapRegion(HeapRegion* hr) {
1456
1457 if (hr->is_continues_humongous()) {
1458 // We will ignore these here and process them when their
1459 // associated "starts humongous" region is processed (see
1460 // set_bit_for_heap_region()). Note that we cannot rely on their
1461 // associated "starts humongous" region to have their bit set to
1462 // 1 since, due to the region chunking in the parallel region
1463 // iteration, a "continues humongous" region might be visited
1464 // before its associated "starts humongous".
1465 return false;
1466 }
1467
1468 HeapWord* ntams = hr->next_top_at_mark_start();
1469 HeapWord* start = hr->bottom();
1470
1471 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1472 err_msg("Preconditions not met - "
1473 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1474 p2i(start), p2i(ntams), p2i(hr->end())));
1475
1476 // Find the first marked object at or after "start".
1477 start = _bm->getNextMarkedWordAddress(start, ntams);
1478
1479 size_t marked_bytes = 0;
1480
1481 while (start < ntams) {
1482 oop obj = oop(start);
1483 int obj_sz = obj->size();
1484 HeapWord* obj_end = start + obj_sz;
1485
1486 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1487 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1488
1489 // Note: if we're looking at the last region in heap - obj_end
1490 // could be actually just beyond the end of the heap; end_idx
1491 // will then correspond to a (non-existent) card that is also
1492 // just beyond the heap.
1493 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1494 // end of object is not card aligned - increment to cover
1495 // all the cards spanned by the object
1496 end_idx += 1;
1497 }
1498
1499 // Set the bits in the card BM for the cards spanned by this object.
1500 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1501
1502 // Add the size of this object to the number of marked bytes.
1503 marked_bytes += (size_t)obj_sz * HeapWordSize;
1504
1505 // Find the next marked object after this one.
1506 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1507 }
1508
1509 // Mark the allocated-since-marking portion...
1510 HeapWord* top = hr->top();
1511 if (ntams < top) {
1512 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1513 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1514
1515 // Note: if we're looking at the last region in heap - top
1516 // could be actually just beyond the end of the heap; end_idx
1517 // will then correspond to a (non-existent) card that is also
1518 // just beyond the heap.
1519 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1520 // end of object is not card aligned - increment to cover
1521 // all the cards spanned by the object
1522 end_idx += 1;
1523 }
1524 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1525
1526 // This definitely means the region has live objects.
1527 set_bit_for_region(hr);
1528 }
1529
1530 // Update the live region bitmap.
1531 if (marked_bytes > 0) {
1532 set_bit_for_region(hr);
1533 }
1534
1535 // Set the marked bytes for the current region so that
1536 // it can be queried by a calling verification routine
1537 _region_marked_bytes = marked_bytes;
1538
1539 return false;
1540 }
1541
1542 size_t region_marked_bytes() const { return _region_marked_bytes; }
1543 };
1544
1545 // Heap region closure used for verifying the counting data
1546 // that was accumulated concurrently and aggregated during
1547 // the remark pause. This closure is applied to the heap
1548 // regions during the STW cleanup pause.
1549
1550 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1551 G1CollectedHeap* _g1h;
1552 ConcurrentMark* _cm;
1553 CalcLiveObjectsClosure _calc_cl;
1554 BitMap* _region_bm; // Region BM to be verified
1555 BitMap* _card_bm; // Card BM to be verified
1556 bool _verbose; // verbose output?
1557
1558 BitMap* _exp_region_bm; // Expected Region BM values
1559 BitMap* _exp_card_bm; // Expected card BM values
1560
1561 int _failures;
1562
1563 public:
1564 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1565 BitMap* region_bm,
1566 BitMap* card_bm,
1567 BitMap* exp_region_bm,
1568 BitMap* exp_card_bm,
1569 bool verbose) :
1570 _g1h(g1h), _cm(g1h->concurrent_mark()),
1571 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1572 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1573 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1574 _failures(0) { }
1575
1576 int failures() const { return _failures; }
1577
1578 bool doHeapRegion(HeapRegion* hr) {
1579 if (hr->is_continues_humongous()) {
1580 // We will ignore these here and process them when their
1581 // associated "starts humongous" region is processed (see
1582 // set_bit_for_heap_region()). Note that we cannot rely on their
1583 // associated "starts humongous" region to have their bit set to
1584 // 1 since, due to the region chunking in the parallel region
1585 // iteration, a "continues humongous" region might be visited
1586 // before its associated "starts humongous".
1587 return false;
1588 }
1589
1590 int failures = 0;
1591
1592 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1593 // this region and set the corresponding bits in the expected region
1594 // and card bitmaps.
1595 bool res = _calc_cl.doHeapRegion(hr);
1596 assert(res == false, "should be continuing");
1597
1598 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1599 Mutex::_no_safepoint_check_flag);
1600
1601 // Verify the marked bytes for this region.
1602 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1603 size_t act_marked_bytes = hr->next_marked_bytes();
1604
1605 // We're not OK if expected marked bytes > actual marked bytes. It means
1606 // we have missed accounting some objects during the actual marking.
1607 if (exp_marked_bytes > act_marked_bytes) {
1608 if (_verbose) {
1609 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1610 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1611 hr->hrm_index(), exp_marked_bytes, act_marked_bytes);
1612 }
1613 failures += 1;
1614 }
1615
1616 // Verify the bit, for this region, in the actual and expected
1617 // (which was just calculated) region bit maps.
1618 // We're not OK if the bit in the calculated expected region
1619 // bitmap is set and the bit in the actual region bitmap is not.
1620 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1621
1622 bool expected = _exp_region_bm->at(index);
1623 bool actual = _region_bm->at(index);
1624 if (expected && !actual) {
1625 if (_verbose) {
1626 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1627 "expected: %s, actual: %s",
1628 hr->hrm_index(),
1629 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1630 }
1631 failures += 1;
1632 }
1633
1634 // Verify that the card bit maps for the cards spanned by the current
1635 // region match. We have an error if we have a set bit in the expected
1636 // bit map and the corresponding bit in the actual bitmap is not set.
1637
1638 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1639 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1640
1641 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1642 expected = _exp_card_bm->at(i);
1643 actual = _card_bm->at(i);
1644
1645 if (expected && !actual) {
1646 if (_verbose) {
1647 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1648 "expected: %s, actual: %s",
1649 hr->hrm_index(), i,
1650 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1651 }
1652 failures += 1;
1653 }
1654 }
1655
1656 if (failures > 0 && _verbose) {
1657 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1658 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1659 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()),
1660 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1661 }
1662
1663 _failures += failures;
1664
1665 // We could stop iteration over the heap when we
1666 // find the first violating region by returning true.
1667 return false;
1668 }
1669 };
1670
1671 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1672 protected:
1673 G1CollectedHeap* _g1h;
1674 ConcurrentMark* _cm;
1675 BitMap* _actual_region_bm;
1676 BitMap* _actual_card_bm;
1677
1678 uint _n_workers;
1679
1680 BitMap* _expected_region_bm;
1681 BitMap* _expected_card_bm;
1682
1683 int _failures;
1684 bool _verbose;
1685
1686 HeapRegionClaimer _hrclaimer;
1687
1688 public:
1689 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1690 BitMap* region_bm, BitMap* card_bm,
1691 BitMap* expected_region_bm, BitMap* expected_card_bm)
1692 : AbstractGangTask("G1 verify final counting"),
1693 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1694 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1695 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1696 _failures(0), _verbose(false),
1697 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1698 assert(VerifyDuringGC, "don't call this otherwise");
1699 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1700 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1701
1702 _verbose = _cm->verbose_medium();
1703 }
1704
1705 void work(uint worker_id) {
1706 assert(worker_id < _n_workers, "invariant");
1707
1708 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1709 _actual_region_bm, _actual_card_bm,
1710 _expected_region_bm,
1711 _expected_card_bm,
1712 _verbose);
1713
1714 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer);
1715
1716 Atomic::add(verify_cl.failures(), &_failures);
1717 }
1718
1719 int failures() const { return _failures; }
1720 };
1721
1722 // Closure that finalizes the liveness counting data.
1723 // Used during the cleanup pause.
1724 // Sets the bits corresponding to the interval [NTAMS, top]
1725 // (which contains the implicitly live objects) in the
1726 // card liveness bitmap. Also sets the bit for each region,
1727 // containing live data, in the region liveness bitmap.
1728
1729 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1730 public:
1731 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1732 BitMap* region_bm,
1733 BitMap* card_bm) :
1734 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1735
1736 bool doHeapRegion(HeapRegion* hr) {
1737
1738 if (hr->is_continues_humongous()) {
1739 // We will ignore these here and process them when their
1740 // associated "starts humongous" region is processed (see
1741 // set_bit_for_heap_region()). Note that we cannot rely on their
1742 // associated "starts humongous" region to have their bit set to
1743 // 1 since, due to the region chunking in the parallel region
1744 // iteration, a "continues humongous" region might be visited
1745 // before its associated "starts humongous".
1746 return false;
1747 }
1748
1749 HeapWord* ntams = hr->next_top_at_mark_start();
1750 HeapWord* top = hr->top();
1751
1752 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1753
1754 // Mark the allocated-since-marking portion...
1755 if (ntams < top) {
1756 // This definitely means the region has live objects.
1757 set_bit_for_region(hr);
1758
1759 // Now set the bits in the card bitmap for [ntams, top)
1760 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1761 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1762
1763 // Note: if we're looking at the last region in heap - top
1764 // could be actually just beyond the end of the heap; end_idx
1765 // will then correspond to a (non-existent) card that is also
1766 // just beyond the heap.
1767 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1768 // end of object is not card aligned - increment to cover
1769 // all the cards spanned by the object
1770 end_idx += 1;
1771 }
1772
1773 assert(end_idx <= _card_bm->size(),
1774 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1775 end_idx, _card_bm->size()));
1776 assert(start_idx < _card_bm->size(),
1777 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1778 start_idx, _card_bm->size()));
1779
1780 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1781 }
1782
1783 // Set the bit for the region if it contains live data
1784 if (hr->next_marked_bytes() > 0) {
1785 set_bit_for_region(hr);
1786 }
1787
1788 return false;
1789 }
1790 };
1791
1792 class G1ParFinalCountTask: public AbstractGangTask {
1793 protected:
1794 G1CollectedHeap* _g1h;
1795 ConcurrentMark* _cm;
1796 BitMap* _actual_region_bm;
1797 BitMap* _actual_card_bm;
1798
1799 uint _n_workers;
1800 HeapRegionClaimer _hrclaimer;
1801
1802 public:
1803 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1804 : AbstractGangTask("G1 final counting"),
1805 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1806 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1807 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1808 }
1809
1810 void work(uint worker_id) {
1811 assert(worker_id < _n_workers, "invariant");
1812
1813 FinalCountDataUpdateClosure final_update_cl(_g1h,
1814 _actual_region_bm,
1815 _actual_card_bm);
1816
1817 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer);
1818 }
1819 };
1820
1821 class G1ParNoteEndTask;
1822
1823 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1824 G1CollectedHeap* _g1;
1825 size_t _max_live_bytes;
1826 uint _regions_claimed;
1827 size_t _freed_bytes;
1828 FreeRegionList* _local_cleanup_list;
1829 HeapRegionSetCount _old_regions_removed;
1830 HeapRegionSetCount _humongous_regions_removed;
1831 HRRSCleanupTask* _hrrs_cleanup_task;
1832 double _claimed_region_time;
1833 double _max_region_time;
1834
1835 public:
1836 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1837 FreeRegionList* local_cleanup_list,
1838 HRRSCleanupTask* hrrs_cleanup_task) :
1839 _g1(g1),
1840 _max_live_bytes(0), _regions_claimed(0),
1841 _freed_bytes(0),
1842 _claimed_region_time(0.0), _max_region_time(0.0),
1843 _local_cleanup_list(local_cleanup_list),
1844 _old_regions_removed(),
1845 _humongous_regions_removed(),
1846 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1847
1848 size_t freed_bytes() { return _freed_bytes; }
1849 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; }
1850 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; }
1851
1852 bool doHeapRegion(HeapRegion *hr) {
1853 if (hr->is_continues_humongous()) {
1854 return false;
1855 }
1856 // We use a claim value of zero here because all regions
1857 // were claimed with value 1 in the FinalCount task.
1858 _g1->reset_gc_time_stamps(hr);
1859 double start = os::elapsedTime();
1860 _regions_claimed++;
1861 hr->note_end_of_marking();
1862 _max_live_bytes += hr->max_live_bytes();
1863
1864 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1865 _freed_bytes += hr->used();
1866 hr->set_containing_set(NULL);
1867 if (hr->is_humongous()) {
1868 assert(hr->is_starts_humongous(), "we should only see starts humongous");
1869 _humongous_regions_removed.increment(1u, hr->capacity());
1870 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1871 } else {
1872 _old_regions_removed.increment(1u, hr->capacity());
1873 _g1->free_region(hr, _local_cleanup_list, true);
1874 }
1875 } else {
1876 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1877 }
1878
1879 double region_time = (os::elapsedTime() - start);
1880 _claimed_region_time += region_time;
1881 if (region_time > _max_region_time) {
1882 _max_region_time = region_time;
1883 }
1884 return false;
1885 }
1886
1887 size_t max_live_bytes() { return _max_live_bytes; }
1888 uint regions_claimed() { return _regions_claimed; }
1889 double claimed_region_time_sec() { return _claimed_region_time; }
1890 double max_region_time_sec() { return _max_region_time; }
1891 };
1892
1893 class G1ParNoteEndTask: public AbstractGangTask {
1894 friend class G1NoteEndOfConcMarkClosure;
1895
1896 protected:
1897 G1CollectedHeap* _g1h;
1898 size_t _max_live_bytes;
1899 size_t _freed_bytes;
1900 FreeRegionList* _cleanup_list;
1901 HeapRegionClaimer _hrclaimer;
1902
1903 public:
1904 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1905 AbstractGangTask("G1 note end"), _g1h(g1h), _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1906 }
1907
1908 void work(uint worker_id) {
1909 FreeRegionList local_cleanup_list("Local Cleanup List");
1910 HRRSCleanupTask hrrs_cleanup_task;
1911 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1912 &hrrs_cleanup_task);
1913 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1914 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1915
1916 // Now update the lists
1917 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1918 {
1919 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1920 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1921 _max_live_bytes += g1_note_end.max_live_bytes();
1922 _freed_bytes += g1_note_end.freed_bytes();
1923
1924 // If we iterate over the global cleanup list at the end of
1925 // cleanup to do this printing we will not guarantee to only
1926 // generate output for the newly-reclaimed regions (the list
1927 // might not be empty at the beginning of cleanup; we might
1928 // still be working on its previous contents). So we do the
1929 // printing here, before we append the new regions to the global
1930 // cleanup list.
1931
1932 G1HRPrinter* hr_printer = _g1h->hr_printer();
1933 if (hr_printer->is_active()) {
1934 FreeRegionListIterator iter(&local_cleanup_list);
1935 while (iter.more_available()) {
1936 HeapRegion* hr = iter.get_next();
1937 hr_printer->cleanup(hr);
1938 }
1939 }
1940
1941 _cleanup_list->add_ordered(&local_cleanup_list);
1942 assert(local_cleanup_list.is_empty(), "post-condition");
1943
1944 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1945 }
1946 }
1947 size_t max_live_bytes() { return _max_live_bytes; }
1948 size_t freed_bytes() { return _freed_bytes; }
1949 };
1950
1951 class G1ParScrubRemSetTask: public AbstractGangTask {
1952 protected:
1953 G1RemSet* _g1rs;
1954 BitMap* _region_bm;
1955 BitMap* _card_bm;
1956 HeapRegionClaimer _hrclaimer;
1957
1958 public:
1959 G1ParScrubRemSetTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm, uint n_workers) :
1960 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), _region_bm(region_bm), _card_bm(card_bm), _hrclaimer(n_workers) {
1961 }
1962
1963 void work(uint worker_id) {
1964 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
1965 }
1966
1967 };
1968
1969 void ConcurrentMark::cleanup() {
1970 // world is stopped at this checkpoint
1971 assert(SafepointSynchronize::is_at_safepoint(),
1972 "world should be stopped");
1973 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1974
1975 // If a full collection has happened, we shouldn't do this.
1976 if (has_aborted()) {
1977 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1978 return;
1979 }
1980
1981 g1h->verify_region_sets_optional();
1982
1983 if (VerifyDuringGC) {
1984 HandleMark hm; // handle scope
1985 g1h->prepare_for_verify();
1986 Universe::verify(VerifyOption_G1UsePrevMarking,
1987 " VerifyDuringGC:(before)");
1988 }
1989 g1h->check_bitmaps("Cleanup Start");
1990
1991 G1CollectorPolicy* g1p = g1h->g1_policy();
1992 g1p->record_concurrent_mark_cleanup_start();
1993
1994 double start = os::elapsedTime();
1995
1996 HeapRegionRemSet::reset_for_cleanup_tasks();
1997
1998 uint n_workers;
1999
2000 // Do counting once more with the world stopped for good measure.
2001 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
2002
2003 g1h->set_par_threads();
2004 n_workers = g1h->n_par_threads();
2005 assert(g1h->n_par_threads() == n_workers,
2006 "Should not have been reset");
2007 g1h->workers()->run_task(&g1_par_count_task);
2008 // Done with the parallel phase so reset to 0.
2009 g1h->set_par_threads(0);
2010
2011 if (VerifyDuringGC) {
2012 // Verify that the counting data accumulated during marking matches
2013 // that calculated by walking the marking bitmap.
2014
2015 // Bitmaps to hold expected values
2016 BitMap expected_region_bm(_region_bm.size(), true);
2017 BitMap expected_card_bm(_card_bm.size(), true);
2018
2019 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
2020 &_region_bm,
2021 &_card_bm,
2022 &expected_region_bm,
2023 &expected_card_bm);
2024
2025 g1h->set_par_threads((int)n_workers);
2026 g1h->workers()->run_task(&g1_par_verify_task);
2027 // Done with the parallel phase so reset to 0.
2028 g1h->set_par_threads(0);
2029
2030 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2031 }
2032
2033 size_t start_used_bytes = g1h->used();
2034 g1h->set_marking_complete();
2035
2036 double count_end = os::elapsedTime();
2037 double this_final_counting_time = (count_end - start);
2038 _total_counting_time += this_final_counting_time;
2039
2040 if (G1PrintRegionLivenessInfo) {
2041 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2042 _g1h->heap_region_iterate(&cl);
2043 }
2044
2045 // Install newly created mark bitMap as "prev".
2046 swapMarkBitMaps();
2047
2048 g1h->reset_gc_time_stamp();
2049
2050 // Note end of marking in all heap regions.
2051 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
2052 g1h->set_par_threads((int)n_workers);
2053 g1h->workers()->run_task(&g1_par_note_end_task);
2054 g1h->set_par_threads(0);
2055 g1h->check_gc_time_stamps();
2056
2057 if (!cleanup_list_is_empty()) {
2058 // The cleanup list is not empty, so we'll have to process it
2059 // concurrently. Notify anyone else that might be wanting free
2060 // regions that there will be more free regions coming soon.
2061 g1h->set_free_regions_coming();
2062 }
2063
2064 // call below, since it affects the metric by which we sort the heap
2065 // regions.
2066 if (G1ScrubRemSets) {
2067 double rs_scrub_start = os::elapsedTime();
2068 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers);
2069 g1h->set_par_threads((int)n_workers);
2070 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2071 g1h->set_par_threads(0);
2072
2073 double rs_scrub_end = os::elapsedTime();
2074 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2075 _total_rs_scrub_time += this_rs_scrub_time;
2076 }
2077
2078 // this will also free any regions totally full of garbage objects,
2079 // and sort the regions.
2080 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2081
2082 // Statistics.
2083 double end = os::elapsedTime();
2084 _cleanup_times.add((end - start) * 1000.0);
2085
2086 if (G1Log::fine()) {
2087 g1h->g1_policy()->print_heap_transition(start_used_bytes);
2088 }
2089
2090 // Clean up will have freed any regions completely full of garbage.
2091 // Update the soft reference policy with the new heap occupancy.
2092 Universe::update_heap_info_at_gc();
2093
2094 if (VerifyDuringGC) {
2095 HandleMark hm; // handle scope
2096 g1h->prepare_for_verify();
2097 Universe::verify(VerifyOption_G1UsePrevMarking,
2098 " VerifyDuringGC:(after)");
2099 }
2100
2101 g1h->check_bitmaps("Cleanup End");
2102
2103 g1h->verify_region_sets_optional();
2104
2105 // We need to make this be a "collection" so any collection pause that
2106 // races with it goes around and waits for completeCleanup to finish.
2107 g1h->increment_total_collections();
2108
2109 // Clean out dead classes and update Metaspace sizes.
2110 if (ClassUnloadingWithConcurrentMark) {
2111 ClassLoaderDataGraph::purge();
2112 }
2113 MetaspaceGC::compute_new_size();
2114
2115 // We reclaimed old regions so we should calculate the sizes to make
2116 // sure we update the old gen/space data.
2117 g1h->g1mm()->update_sizes();
2118 g1h->allocation_context_stats().update_after_mark();
2119
2120 g1h->trace_heap_after_concurrent_cycle();
2121 }
2122
2123 void ConcurrentMark::completeCleanup() {
2124 if (has_aborted()) return;
2125
2126 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2127
2128 _cleanup_list.verify_optional();
2129 FreeRegionList tmp_free_list("Tmp Free List");
2130
2131 if (G1ConcRegionFreeingVerbose) {
2132 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2133 "cleanup list has %u entries",
2134 _cleanup_list.length());
2135 }
2136
2137 // No one else should be accessing the _cleanup_list at this point,
2138 // so it is not necessary to take any locks
2139 while (!_cleanup_list.is_empty()) {
2140 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
2141 assert(hr != NULL, "Got NULL from a non-empty list");
2142 hr->par_clear();
2143 tmp_free_list.add_ordered(hr);
2144
2145 // Instead of adding one region at a time to the secondary_free_list,
2146 // we accumulate them in the local list and move them a few at a
2147 // time. This also cuts down on the number of notify_all() calls
2148 // we do during this process. We'll also append the local list when
2149 // _cleanup_list is empty (which means we just removed the last
2150 // region from the _cleanup_list).
2151 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2152 _cleanup_list.is_empty()) {
2153 if (G1ConcRegionFreeingVerbose) {
2154 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2155 "appending %u entries to the secondary_free_list, "
2156 "cleanup list still has %u entries",
2157 tmp_free_list.length(),
2158 _cleanup_list.length());
2159 }
2160
2161 {
2162 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2163 g1h->secondary_free_list_add(&tmp_free_list);
2164 SecondaryFreeList_lock->notify_all();
2165 }
2166 #ifndef PRODUCT
2167 if (G1StressConcRegionFreeing) {
2168 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2169 os::sleep(Thread::current(), (jlong) 1, false);
2170 }
2171 }
2172 #endif
2173 }
2174 }
2175 assert(tmp_free_list.is_empty(), "post-condition");
2176 }
2177
2178 // Supporting Object and Oop closures for reference discovery
2179 // and processing in during marking
2180
2181 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2182 HeapWord* addr = (HeapWord*)obj;
2183 return addr != NULL &&
2184 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2185 }
2186
2187 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2188 // Uses the CMTask associated with a worker thread (for serial reference
2189 // processing the CMTask for worker 0 is used) to preserve (mark) and
2190 // trace referent objects.
2191 //
2192 // Using the CMTask and embedded local queues avoids having the worker
2193 // threads operating on the global mark stack. This reduces the risk
2194 // of overflowing the stack - which we would rather avoid at this late
2195 // state. Also using the tasks' local queues removes the potential
2196 // of the workers interfering with each other that could occur if
2197 // operating on the global stack.
2198
2199 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2200 ConcurrentMark* _cm;
2201 CMTask* _task;
2202 int _ref_counter_limit;
2203 int _ref_counter;
2204 bool _is_serial;
2205 public:
2206 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2207 _cm(cm), _task(task), _is_serial(is_serial),
2208 _ref_counter_limit(G1RefProcDrainInterval) {
2209 assert(_ref_counter_limit > 0, "sanity");
2210 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2211 _ref_counter = _ref_counter_limit;
2212 }
2213
2214 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2215 virtual void do_oop( oop* p) { do_oop_work(p); }
2216
2217 template <class T> void do_oop_work(T* p) {
2218 if (!_cm->has_overflown()) {
2219 oop obj = oopDesc::load_decode_heap_oop(p);
2220 if (_cm->verbose_high()) {
2221 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2222 "*"PTR_FORMAT" = "PTR_FORMAT,
2223 _task->worker_id(), p2i(p), p2i((void*) obj));
2224 }
2225
2226 _task->deal_with_reference(obj);
2227 _ref_counter--;
2228
2229 if (_ref_counter == 0) {
2230 // We have dealt with _ref_counter_limit references, pushing them
2231 // and objects reachable from them on to the local stack (and
2232 // possibly the global stack). Call CMTask::do_marking_step() to
2233 // process these entries.
2234 //
2235 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2236 // there's nothing more to do (i.e. we're done with the entries that
2237 // were pushed as a result of the CMTask::deal_with_reference() calls
2238 // above) or we overflow.
2239 //
2240 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2241 // flag while there may still be some work to do. (See the comment at
2242 // the beginning of CMTask::do_marking_step() for those conditions -
2243 // one of which is reaching the specified time target.) It is only
2244 // when CMTask::do_marking_step() returns without setting the
2245 // has_aborted() flag that the marking step has completed.
2246 do {
2247 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2248 _task->do_marking_step(mark_step_duration_ms,
2249 false /* do_termination */,
2250 _is_serial);
2251 } while (_task->has_aborted() && !_cm->has_overflown());
2252 _ref_counter = _ref_counter_limit;
2253 }
2254 } else {
2255 if (_cm->verbose_high()) {
2256 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2257 }
2258 }
2259 }
2260 };
2261
2262 // 'Drain' oop closure used by both serial and parallel reference processing.
2263 // Uses the CMTask associated with a given worker thread (for serial
2264 // reference processing the CMtask for worker 0 is used). Calls the
2265 // do_marking_step routine, with an unbelievably large timeout value,
2266 // to drain the marking data structures of the remaining entries
2267 // added by the 'keep alive' oop closure above.
2268
2269 class G1CMDrainMarkingStackClosure: public VoidClosure {
2270 ConcurrentMark* _cm;
2271 CMTask* _task;
2272 bool _is_serial;
2273 public:
2274 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2275 _cm(cm), _task(task), _is_serial(is_serial) {
2276 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2277 }
2278
2279 void do_void() {
2280 do {
2281 if (_cm->verbose_high()) {
2282 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2283 _task->worker_id(), BOOL_TO_STR(_is_serial));
2284 }
2285
2286 // We call CMTask::do_marking_step() to completely drain the local
2287 // and global marking stacks of entries pushed by the 'keep alive'
2288 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2289 //
2290 // CMTask::do_marking_step() is called in a loop, which we'll exit
2291 // if there's nothing more to do (i.e. we've completely drained the
2292 // entries that were pushed as a a result of applying the 'keep alive'
2293 // closure to the entries on the discovered ref lists) or we overflow
2294 // the global marking stack.
2295 //
2296 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2297 // flag while there may still be some work to do. (See the comment at
2298 // the beginning of CMTask::do_marking_step() for those conditions -
2299 // one of which is reaching the specified time target.) It is only
2300 // when CMTask::do_marking_step() returns without setting the
2301 // has_aborted() flag that the marking step has completed.
2302
2303 _task->do_marking_step(1000000000.0 /* something very large */,
2304 true /* do_termination */,
2305 _is_serial);
2306 } while (_task->has_aborted() && !_cm->has_overflown());
2307 }
2308 };
2309
2310 // Implementation of AbstractRefProcTaskExecutor for parallel
2311 // reference processing at the end of G1 concurrent marking
2312
2313 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2314 private:
2315 G1CollectedHeap* _g1h;
2316 ConcurrentMark* _cm;
2317 WorkGang* _workers;
2318 int _active_workers;
2319
2320 public:
2321 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2322 ConcurrentMark* cm,
2323 WorkGang* workers,
2324 int n_workers) :
2325 _g1h(g1h), _cm(cm),
2326 _workers(workers), _active_workers(n_workers) { }
2327
2328 // Executes the given task using concurrent marking worker threads.
2329 virtual void execute(ProcessTask& task);
2330 virtual void execute(EnqueueTask& task);
2331 };
2332
2333 class G1CMRefProcTaskProxy: public AbstractGangTask {
2334 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2335 ProcessTask& _proc_task;
2336 G1CollectedHeap* _g1h;
2337 ConcurrentMark* _cm;
2338
2339 public:
2340 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2341 G1CollectedHeap* g1h,
2342 ConcurrentMark* cm) :
2343 AbstractGangTask("Process reference objects in parallel"),
2344 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2345 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2346 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2347 }
2348
2349 virtual void work(uint worker_id) {
2350 ResourceMark rm;
2351 HandleMark hm;
2352 CMTask* task = _cm->task(worker_id);
2353 G1CMIsAliveClosure g1_is_alive(_g1h);
2354 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2355 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2356
2357 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2358 }
2359 };
2360
2361 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2362 assert(_workers != NULL, "Need parallel worker threads.");
2363 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2364
2365 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2366
2367 // We need to reset the concurrency level before each
2368 // proxy task execution, so that the termination protocol
2369 // and overflow handling in CMTask::do_marking_step() knows
2370 // how many workers to wait for.
2371 _cm->set_concurrency(_active_workers);
2372 _g1h->set_par_threads(_active_workers);
2373 _workers->run_task(&proc_task_proxy);
2374 _g1h->set_par_threads(0);
2375 }
2376
2377 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2378 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2379 EnqueueTask& _enq_task;
2380
2381 public:
2382 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2383 AbstractGangTask("Enqueue reference objects in parallel"),
2384 _enq_task(enq_task) { }
2385
2386 virtual void work(uint worker_id) {
2387 _enq_task.work(worker_id);
2388 }
2389 };
2390
2391 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2392 assert(_workers != NULL, "Need parallel worker threads.");
2393 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2394
2395 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2396
2397 // Not strictly necessary but...
2398 //
2399 // We need to reset the concurrency level before each
2400 // proxy task execution, so that the termination protocol
2401 // and overflow handling in CMTask::do_marking_step() knows
2402 // how many workers to wait for.
2403 _cm->set_concurrency(_active_workers);
2404 _g1h->set_par_threads(_active_workers);
2405 _workers->run_task(&enq_task_proxy);
2406 _g1h->set_par_threads(0);
2407 }
2408
2409 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
2410 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
2411 }
2412
2413 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2414 if (has_overflown()) {
2415 // Skip processing the discovered references if we have
2416 // overflown the global marking stack. Reference objects
2417 // only get discovered once so it is OK to not
2418 // de-populate the discovered reference lists. We could have,
2419 // but the only benefit would be that, when marking restarts,
2420 // less reference objects are discovered.
2421 return;
2422 }
2423
2424 ResourceMark rm;
2425 HandleMark hm;
2426
2427 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2428
2429 // Is alive closure.
2430 G1CMIsAliveClosure g1_is_alive(g1h);
2431
2432 // Inner scope to exclude the cleaning of the string and symbol
2433 // tables from the displayed time.
2434 {
2435 G1CMTraceTime t("GC ref-proc", G1Log::finer());
2436
2437 ReferenceProcessor* rp = g1h->ref_processor_cm();
2438
2439 // See the comment in G1CollectedHeap::ref_processing_init()
2440 // about how reference processing currently works in G1.
2441
2442 // Set the soft reference policy
2443 rp->setup_policy(clear_all_soft_refs);
2444 assert(_markStack.isEmpty(), "mark stack should be empty");
2445
2446 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2447 // in serial reference processing. Note these closures are also
2448 // used for serially processing (by the the current thread) the
2449 // JNI references during parallel reference processing.
2450 //
2451 // These closures do not need to synchronize with the worker
2452 // threads involved in parallel reference processing as these
2453 // instances are executed serially by the current thread (e.g.
2454 // reference processing is not multi-threaded and is thus
2455 // performed by the current thread instead of a gang worker).
2456 //
2457 // The gang tasks involved in parallel reference processing create
2458 // their own instances of these closures, which do their own
2459 // synchronization among themselves.
2460 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2461 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2462
2463 // We need at least one active thread. If reference processing
2464 // is not multi-threaded we use the current (VMThread) thread,
2465 // otherwise we use the work gang from the G1CollectedHeap and
2466 // we utilize all the worker threads we can.
2467 bool processing_is_mt = rp->processing_is_mt();
2468 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2469 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2470
2471 // Parallel processing task executor.
2472 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2473 g1h->workers(), active_workers);
2474 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2475
2476 // Set the concurrency level. The phase was already set prior to
2477 // executing the remark task.
2478 set_concurrency(active_workers);
2479
2480 // Set the degree of MT processing here. If the discovery was done MT,
2481 // the number of threads involved during discovery could differ from
2482 // the number of active workers. This is OK as long as the discovered
2483 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2484 rp->set_active_mt_degree(active_workers);
2485
2486 // Process the weak references.
2487 const ReferenceProcessorStats& stats =
2488 rp->process_discovered_references(&g1_is_alive,
2489 &g1_keep_alive,
2490 &g1_drain_mark_stack,
2491 executor,
2492 g1h->gc_timer_cm(),
2493 concurrent_gc_id());
2494 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2495
2496 // The do_oop work routines of the keep_alive and drain_marking_stack
2497 // oop closures will set the has_overflown flag if we overflow the
2498 // global marking stack.
2499
2500 assert(_markStack.overflow() || _markStack.isEmpty(),
2501 "mark stack should be empty (unless it overflowed)");
2502
2503 if (_markStack.overflow()) {
2504 // This should have been done already when we tried to push an
2505 // entry on to the global mark stack. But let's do it again.
2506 set_has_overflown();
2507 }
2508
2509 assert(rp->num_q() == active_workers, "why not");
2510
2511 rp->enqueue_discovered_references(executor);
2512
2513 rp->verify_no_references_recorded();
2514 assert(!rp->discovery_enabled(), "Post condition");
2515 }
2516
2517 if (has_overflown()) {
2518 // We can not trust g1_is_alive if the marking stack overflowed
2519 return;
2520 }
2521
2522 assert(_markStack.isEmpty(), "Marking should have completed");
2523
2524 // Unload Klasses, String, Symbols, Code Cache, etc.
2525 {
2526 G1CMTraceTime trace("Unloading", G1Log::finer());
2527
2528 if (ClassUnloadingWithConcurrentMark) {
2529 bool purged_classes;
2530
2531 {
2532 G1CMTraceTime trace("System Dictionary Unloading", G1Log::finest());
2533 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
2534 }
2535
2536 {
2537 G1CMTraceTime trace("Parallel Unloading", G1Log::finest());
2538 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
2539 }
2540 }
2541
2542 if (G1StringDedup::is_enabled()) {
2543 G1CMTraceTime trace("String Deduplication Unlink", G1Log::finest());
2544 G1StringDedup::unlink(&g1_is_alive);
2545 }
2546 }
2547 }
2548
2549 void ConcurrentMark::swapMarkBitMaps() {
2550 CMBitMapRO* temp = _prevMarkBitMap;
2551 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2552 _nextMarkBitMap = (CMBitMap*) temp;
2553 }
2554
2555 class CMObjectClosure;
2556
2557 // Closure for iterating over objects, currently only used for
2558 // processing SATB buffers.
2559 class CMObjectClosure : public ObjectClosure {
2560 private:
2561 CMTask* _task;
2562
2563 public:
2564 void do_object(oop obj) {
2565 _task->deal_with_reference(obj);
2566 }
2567
2568 CMObjectClosure(CMTask* task) : _task(task) { }
2569 };
2570
2571 class G1RemarkThreadsClosure : public ThreadClosure {
2572 CMObjectClosure _cm_obj;
2573 G1CMOopClosure _cm_cl;
2574 MarkingCodeBlobClosure _code_cl;
2575 int _thread_parity;
2576
2577 public:
2578 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task) :
2579 _cm_obj(task), _cm_cl(g1h, g1h->concurrent_mark(), task), _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
2580 _thread_parity(Threads::thread_claim_parity()) {}
2581
2582 void do_thread(Thread* thread) {
2583 if (thread->is_Java_thread()) {
2584 if (thread->claim_oops_do(true, _thread_parity)) {
2585 JavaThread* jt = (JavaThread*)thread;
2586
2587 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
2588 // however the liveness of oops reachable from nmethods have very complex lifecycles:
2589 // * Alive if on the stack of an executing method
2590 // * Weakly reachable otherwise
2591 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
2592 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
2593 jt->nmethods_do(&_code_cl);
2594
2595 jt->satb_mark_queue().apply_closure_and_empty(&_cm_obj);
2596 }
2597 } else if (thread->is_VM_thread()) {
2598 if (thread->claim_oops_do(true, _thread_parity)) {
2599 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_obj);
2600 }
2601 }
2602 }
2603 };
2604
2605 class CMRemarkTask: public AbstractGangTask {
2606 private:
2607 ConcurrentMark* _cm;
2608 public:
2609 void work(uint worker_id) {
2610 // Since all available tasks are actually started, we should
2611 // only proceed if we're supposed to be active.
2612 if (worker_id < _cm->active_tasks()) {
2613 CMTask* task = _cm->task(worker_id);
2614 task->record_start_time();
2615 {
2616 ResourceMark rm;
2617 HandleMark hm;
2618
2619 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
2620 Threads::threads_do(&threads_f);
2621 }
2622
2623 do {
2624 task->do_marking_step(1000000000.0 /* something very large */,
2625 true /* do_termination */,
2626 false /* is_serial */);
2627 } while (task->has_aborted() && !_cm->has_overflown());
2628 // If we overflow, then we do not want to restart. We instead
2629 // want to abort remark and do concurrent marking again.
2630 task->record_end_time();
2631 }
2632 }
2633
2634 CMRemarkTask(ConcurrentMark* cm, int active_workers) :
2635 AbstractGangTask("Par Remark"), _cm(cm) {
2636 _cm->terminator()->reset_for_reuse(active_workers);
2637 }
2638 };
2639
2640 void ConcurrentMark::checkpointRootsFinalWork() {
2641 ResourceMark rm;
2642 HandleMark hm;
2643 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2644
2645 G1CMTraceTime trace("Finalize Marking", G1Log::finer());
2646
2647 g1h->ensure_parsability(false);
2648
2649 StrongRootsScope srs;
2650 // this is remark, so we'll use up all active threads
2651 uint active_workers = g1h->workers()->active_workers();
2652 if (active_workers == 0) {
2653 assert(active_workers > 0, "Should have been set earlier");
2654 active_workers = (uint) ParallelGCThreads;
2655 g1h->workers()->set_active_workers(active_workers);
2656 }
2657 set_concurrency_and_phase(active_workers, false /* concurrent */);
2658 // Leave _parallel_marking_threads at it's
2659 // value originally calculated in the ConcurrentMark
2660 // constructor and pass values of the active workers
2661 // through the gang in the task.
2662
2663 CMRemarkTask remarkTask(this, active_workers);
2664 // We will start all available threads, even if we decide that the
2665 // active_workers will be fewer. The extra ones will just bail out
2666 // immediately.
2667 g1h->set_par_threads(active_workers);
2668 g1h->workers()->run_task(&remarkTask);
2669 g1h->set_par_threads(0);
2670
2671 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2672 guarantee(has_overflown() ||
2673 satb_mq_set.completed_buffers_num() == 0,
2674 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2675 BOOL_TO_STR(has_overflown()),
2676 satb_mq_set.completed_buffers_num()));
2677
2678 print_stats();
2679 }
2680
2681 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2682 // Note we are overriding the read-only view of the prev map here, via
2683 // the cast.
2684 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2685 }
2686
2687 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2688 _nextMarkBitMap->clearRange(mr);
2689 }
2690
2691 HeapRegion*
2692 ConcurrentMark::claim_region(uint worker_id) {
2693 // "checkpoint" the finger
2694 HeapWord* finger = _finger;
2695
2696 // _heap_end will not change underneath our feet; it only changes at
2697 // yield points.
2698 while (finger < _heap_end) {
2699 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2700
2701 // Note on how this code handles humongous regions. In the
2702 // normal case the finger will reach the start of a "starts
2703 // humongous" (SH) region. Its end will either be the end of the
2704 // last "continues humongous" (CH) region in the sequence, or the
2705 // standard end of the SH region (if the SH is the only region in
2706 // the sequence). That way claim_region() will skip over the CH
2707 // regions. However, there is a subtle race between a CM thread
2708 // executing this method and a mutator thread doing a humongous
2709 // object allocation. The two are not mutually exclusive as the CM
2710 // thread does not need to hold the Heap_lock when it gets
2711 // here. So there is a chance that claim_region() will come across
2712 // a free region that's in the progress of becoming a SH or a CH
2713 // region. In the former case, it will either
2714 // a) Miss the update to the region's end, in which case it will
2715 // visit every subsequent CH region, will find their bitmaps
2716 // empty, and do nothing, or
2717 // b) Will observe the update of the region's end (in which case
2718 // it will skip the subsequent CH regions).
2719 // If it comes across a region that suddenly becomes CH, the
2720 // scenario will be similar to b). So, the race between
2721 // claim_region() and a humongous object allocation might force us
2722 // to do a bit of unnecessary work (due to some unnecessary bitmap
2723 // iterations) but it should not introduce and correctness issues.
2724 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2725
2726 // Above heap_region_containing_raw may return NULL as we always scan claim
2727 // until the end of the heap. In this case, just jump to the next region.
2728 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
2729
2730 // Is the gap between reading the finger and doing the CAS too long?
2731 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2732 if (res == finger && curr_region != NULL) {
2733 // we succeeded
2734 HeapWord* bottom = curr_region->bottom();
2735 HeapWord* limit = curr_region->next_top_at_mark_start();
2736
2737 if (verbose_low()) {
2738 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2739 "["PTR_FORMAT", "PTR_FORMAT"), "
2740 "limit = "PTR_FORMAT,
2741 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit));
2742 }
2743
2744 // notice that _finger == end cannot be guaranteed here since,
2745 // someone else might have moved the finger even further
2746 assert(_finger >= end, "the finger should have moved forward");
2747
2748 if (verbose_low()) {
2749 gclog_or_tty->print_cr("[%u] we were successful with region = "
2750 PTR_FORMAT, worker_id, p2i(curr_region));
2751 }
2752
2753 if (limit > bottom) {
2754 if (verbose_low()) {
2755 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2756 "returning it ", worker_id, p2i(curr_region));
2757 }
2758 return curr_region;
2759 } else {
2760 assert(limit == bottom,
2761 "the region limit should be at bottom");
2762 if (verbose_low()) {
2763 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2764 "returning NULL", worker_id, p2i(curr_region));
2765 }
2766 // we return NULL and the caller should try calling
2767 // claim_region() again.
2768 return NULL;
2769 }
2770 } else {
2771 assert(_finger > finger, "the finger should have moved forward");
2772 if (verbose_low()) {
2773 if (curr_region == NULL) {
2774 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, "
2775 "global finger = "PTR_FORMAT", "
2776 "our finger = "PTR_FORMAT,
2777 worker_id, p2i(_finger), p2i(finger));
2778 } else {
2779 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2780 "global finger = "PTR_FORMAT", "
2781 "our finger = "PTR_FORMAT,
2782 worker_id, p2i(_finger), p2i(finger));
2783 }
2784 }
2785
2786 // read it again
2787 finger = _finger;
2788 }
2789 }
2790
2791 return NULL;
2792 }
2793
2794 #ifndef PRODUCT
2795 enum VerifyNoCSetOopsPhase {
2796 VerifyNoCSetOopsStack,
2797 VerifyNoCSetOopsQueues,
2798 VerifyNoCSetOopsSATBCompleted,
2799 VerifyNoCSetOopsSATBThread
2800 };
2801
2802 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2803 private:
2804 G1CollectedHeap* _g1h;
2805 VerifyNoCSetOopsPhase _phase;
2806 int _info;
2807
2808 const char* phase_str() {
2809 switch (_phase) {
2810 case VerifyNoCSetOopsStack: return "Stack";
2811 case VerifyNoCSetOopsQueues: return "Queue";
2812 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2813 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2814 default: ShouldNotReachHere();
2815 }
2816 return NULL;
2817 }
2818
2819 void do_object_work(oop obj) {
2820 guarantee(!_g1h->obj_in_cs(obj),
2821 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2822 p2i((void*) obj), phase_str(), _info));
2823 }
2824
2825 public:
2826 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2827
2828 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2829 _phase = phase;
2830 _info = info;
2831 }
2832
2833 virtual void do_oop(oop* p) {
2834 oop obj = oopDesc::load_decode_heap_oop(p);
2835 do_object_work(obj);
2836 }
2837
2838 virtual void do_oop(narrowOop* p) {
2839 // We should not come across narrow oops while scanning marking
2840 // stacks and SATB buffers.
2841 ShouldNotReachHere();
2842 }
2843
2844 virtual void do_object(oop obj) {
2845 do_object_work(obj);
2846 }
2847 };
2848
2849 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2850 bool verify_enqueued_buffers,
2851 bool verify_thread_buffers,
2852 bool verify_fingers) {
2853 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2854 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2855 return;
2856 }
2857
2858 VerifyNoCSetOopsClosure cl;
2859
2860 if (verify_stacks) {
2861 // Verify entries on the global mark stack
2862 cl.set_phase(VerifyNoCSetOopsStack);
2863 _markStack.oops_do(&cl);
2864
2865 // Verify entries on the task queues
2866 for (uint i = 0; i < _max_worker_id; i += 1) {
2867 cl.set_phase(VerifyNoCSetOopsQueues, i);
2868 CMTaskQueue* queue = _task_queues->queue(i);
2869 queue->oops_do(&cl);
2870 }
2871 }
2872
2873 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2874
2875 // Verify entries on the enqueued SATB buffers
2876 if (verify_enqueued_buffers) {
2877 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2878 satb_qs.iterate_completed_buffers_read_only(&cl);
2879 }
2880
2881 // Verify entries on the per-thread SATB buffers
2882 if (verify_thread_buffers) {
2883 cl.set_phase(VerifyNoCSetOopsSATBThread);
2884 satb_qs.iterate_thread_buffers_read_only(&cl);
2885 }
2886
2887 if (verify_fingers) {
2888 // Verify the global finger
2889 HeapWord* global_finger = finger();
2890 if (global_finger != NULL && global_finger < _heap_end) {
2891 // The global finger always points to a heap region boundary. We
2892 // use heap_region_containing_raw() to get the containing region
2893 // given that the global finger could be pointing to a free region
2894 // which subsequently becomes continues humongous. If that
2895 // happens, heap_region_containing() will return the bottom of the
2896 // corresponding starts humongous region and the check below will
2897 // not hold any more.
2898 // Since we always iterate over all regions, we might get a NULL HeapRegion
2899 // here.
2900 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2901 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2902 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2903 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)));
2904 }
2905
2906 // Verify the task fingers
2907 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2908 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
2909 CMTask* task = _tasks[i];
2910 HeapWord* task_finger = task->finger();
2911 if (task_finger != NULL && task_finger < _heap_end) {
2912 // See above note on the global finger verification.
2913 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2914 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2915 !task_hr->in_collection_set(),
2916 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
2917 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)));
2918 }
2919 }
2920 }
2921 }
2922 #endif // PRODUCT
2923
2924 // Aggregate the counting data that was constructed concurrently
2925 // with marking.
2926 class AggregateCountDataHRClosure: public HeapRegionClosure {
2927 G1CollectedHeap* _g1h;
2928 ConcurrentMark* _cm;
2929 CardTableModRefBS* _ct_bs;
2930 BitMap* _cm_card_bm;
2931 uint _max_worker_id;
2932
2933 public:
2934 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2935 BitMap* cm_card_bm,
2936 uint max_worker_id) :
2937 _g1h(g1h), _cm(g1h->concurrent_mark()),
2938 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
2939 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2940
2941 bool doHeapRegion(HeapRegion* hr) {
2942 if (hr->is_continues_humongous()) {
2943 // We will ignore these here and process them when their
2944 // associated "starts humongous" region is processed.
2945 // Note that we cannot rely on their associated
2946 // "starts humongous" region to have their bit set to 1
2947 // since, due to the region chunking in the parallel region
2948 // iteration, a "continues humongous" region might be visited
2949 // before its associated "starts humongous".
2950 return false;
2951 }
2952
2953 HeapWord* start = hr->bottom();
2954 HeapWord* limit = hr->next_top_at_mark_start();
2955 HeapWord* end = hr->end();
2956
2957 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
2958 err_msg("Preconditions not met - "
2959 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
2960 "top: "PTR_FORMAT", end: "PTR_FORMAT,
2961 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end())));
2962
2963 assert(hr->next_marked_bytes() == 0, "Precondition");
2964
2965 if (start == limit) {
2966 // NTAMS of this region has not been set so nothing to do.
2967 return false;
2968 }
2969
2970 // 'start' should be in the heap.
2971 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
2972 // 'end' *may* be just beyond the end of the heap (if hr is the last region)
2973 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
2974
2975 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
2976 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
2977 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
2978
2979 // If ntams is not card aligned then we bump card bitmap index
2980 // for limit so that we get the all the cards spanned by
2981 // the object ending at ntams.
2982 // Note: if this is the last region in the heap then ntams
2983 // could be actually just beyond the end of the the heap;
2984 // limit_idx will then correspond to a (non-existent) card
2985 // that is also outside the heap.
2986 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
2987 limit_idx += 1;
2988 }
2989
2990 assert(limit_idx <= end_idx, "or else use atomics");
2991
2992 // Aggregate the "stripe" in the count data associated with hr.
2993 uint hrm_index = hr->hrm_index();
2994 size_t marked_bytes = 0;
2995
2996 for (uint i = 0; i < _max_worker_id; i += 1) {
2997 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
2998 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
2999
3000 // Fetch the marked_bytes in this region for task i and
3001 // add it to the running total for this region.
3002 marked_bytes += marked_bytes_array[hrm_index];
3003
3004 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3005 // into the global card bitmap.
3006 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3007
3008 while (scan_idx < limit_idx) {
3009 assert(task_card_bm->at(scan_idx) == true, "should be");
3010 _cm_card_bm->set_bit(scan_idx);
3011 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3012
3013 // BitMap::get_next_one_offset() can handle the case when
3014 // its left_offset parameter is greater than its right_offset
3015 // parameter. It does, however, have an early exit if
3016 // left_offset == right_offset. So let's limit the value
3017 // passed in for left offset here.
3018 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3019 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3020 }
3021 }
3022
3023 // Update the marked bytes for this region.
3024 hr->add_to_marked_bytes(marked_bytes);
3025
3026 // Next heap region
3027 return false;
3028 }
3029 };
3030
3031 class G1AggregateCountDataTask: public AbstractGangTask {
3032 protected:
3033 G1CollectedHeap* _g1h;
3034 ConcurrentMark* _cm;
3035 BitMap* _cm_card_bm;
3036 uint _max_worker_id;
3037 int _active_workers;
3038 HeapRegionClaimer _hrclaimer;
3039
3040 public:
3041 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3042 ConcurrentMark* cm,
3043 BitMap* cm_card_bm,
3044 uint max_worker_id,
3045 int n_workers) :
3046 AbstractGangTask("Count Aggregation"),
3047 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3048 _max_worker_id(max_worker_id),
3049 _active_workers(n_workers),
3050 _hrclaimer(_active_workers) {
3051 }
3052
3053 void work(uint worker_id) {
3054 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3055
3056 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer);
3057 }
3058 };
3059
3060
3061 void ConcurrentMark::aggregate_count_data() {
3062 int n_workers = _g1h->workers()->active_workers();
3063
3064 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3065 _max_worker_id, n_workers);
3066
3067 _g1h->set_par_threads(n_workers);
3068 _g1h->workers()->run_task(&g1_par_agg_task);
3069 _g1h->set_par_threads(0);
3070 }
3071
3072 // Clear the per-worker arrays used to store the per-region counting data
3073 void ConcurrentMark::clear_all_count_data() {
3074 // Clear the global card bitmap - it will be filled during
3075 // liveness count aggregation (during remark) and the
3076 // final counting task.
3077 _card_bm.clear();
3078
3079 // Clear the global region bitmap - it will be filled as part
3080 // of the final counting task.
3081 _region_bm.clear();
3082
3083 uint max_regions = _g1h->max_regions();
3084 assert(_max_worker_id > 0, "uninitialized");
3085
3086 for (uint i = 0; i < _max_worker_id; i += 1) {
3087 BitMap* task_card_bm = count_card_bitmap_for(i);
3088 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3089
3090 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3091 assert(marked_bytes_array != NULL, "uninitialized");
3092
3093 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3094 task_card_bm->clear();
3095 }
3096 }
3097
3098 void ConcurrentMark::print_stats() {
3099 if (verbose_stats()) {
3100 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3101 for (size_t i = 0; i < _active_tasks; ++i) {
3102 _tasks[i]->print_stats();
3103 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3104 }
3105 }
3106 }
3107
3108 // abandon current marking iteration due to a Full GC
3109 void ConcurrentMark::abort() {
3110 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
3111 // concurrent bitmap clearing.
3112 _nextMarkBitMap->clearAll();
3113
3114 // Note we cannot clear the previous marking bitmap here
3115 // since VerifyDuringGC verifies the objects marked during
3116 // a full GC against the previous bitmap.
3117
3118 // Clear the liveness counting data
3119 clear_all_count_data();
3120 // Empty mark stack
3121 reset_marking_state();
3122 for (uint i = 0; i < _max_worker_id; ++i) {
3123 _tasks[i]->clear_region_fields();
3124 }
3125 _first_overflow_barrier_sync.abort();
3126 _second_overflow_barrier_sync.abort();
3127 const GCId& gc_id = _g1h->gc_tracer_cm()->gc_id();
3128 if (!gc_id.is_undefined()) {
3129 // We can do multiple full GCs before ConcurrentMarkThread::run() gets a chance
3130 // to detect that it was aborted. Only keep track of the first GC id that we aborted.
3131 _aborted_gc_id = gc_id;
3132 }
3133 _has_aborted = true;
3134
3135 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3136 satb_mq_set.abandon_partial_marking();
3137 // This can be called either during or outside marking, we'll read
3138 // the expected_active value from the SATB queue set.
3139 satb_mq_set.set_active_all_threads(
3140 false, /* new active value */
3141 satb_mq_set.is_active() /* expected_active */);
3142
3143 _g1h->trace_heap_after_concurrent_cycle();
3144 _g1h->register_concurrent_cycle_end();
3145 }
3146
3147 const GCId& ConcurrentMark::concurrent_gc_id() {
3148 if (has_aborted()) {
3149 return _aborted_gc_id;
3150 }
3151 return _g1h->gc_tracer_cm()->gc_id();
3152 }
3153
3154 static void print_ms_time_info(const char* prefix, const char* name,
3155 NumberSeq& ns) {
3156 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3157 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3158 if (ns.num() > 0) {
3159 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3160 prefix, ns.sd(), ns.maximum());
3161 }
3162 }
3163
3164 void ConcurrentMark::print_summary_info() {
3165 gclog_or_tty->print_cr(" Concurrent marking:");
3166 print_ms_time_info(" ", "init marks", _init_times);
3167 print_ms_time_info(" ", "remarks", _remark_times);
3168 {
3169 print_ms_time_info(" ", "final marks", _remark_mark_times);
3170 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3171
3172 }
3173 print_ms_time_info(" ", "cleanups", _cleanup_times);
3174 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3175 _total_counting_time,
3176 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3177 (double)_cleanup_times.num()
3178 : 0.0));
3179 if (G1ScrubRemSets) {
3180 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3181 _total_rs_scrub_time,
3182 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3183 (double)_cleanup_times.num()
3184 : 0.0));
3185 }
3186 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3187 (_init_times.sum() + _remark_times.sum() +
3188 _cleanup_times.sum())/1000.0);
3189 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3190 "(%8.2f s marking).",
3191 cmThread()->vtime_accum(),
3192 cmThread()->vtime_mark_accum());
3193 }
3194
3195 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3196 _parallel_workers->print_worker_threads_on(st);
3197 }
3198
3199 void ConcurrentMark::print_on_error(outputStream* st) const {
3200 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3201 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
3202 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3203 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3204 }
3205
3206 // We take a break if someone is trying to stop the world.
3207 bool ConcurrentMark::do_yield_check(uint worker_id) {
3208 if (SuspendibleThreadSet::should_yield()) {
3209 if (worker_id == 0) {
3210 _g1h->g1_policy()->record_concurrent_pause();
3211 }
3212 SuspendibleThreadSet::yield();
3213 return true;
3214 } else {
3215 return false;
3216 }
3217 }
3218
3219 #ifndef PRODUCT
3220 // for debugging purposes
3221 void ConcurrentMark::print_finger() {
3222 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3223 p2i(_heap_start), p2i(_heap_end), p2i(_finger));
3224 for (uint i = 0; i < _max_worker_id; ++i) {
3225 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger()));
3226 }
3227 gclog_or_tty->cr();
3228 }
3229 #endif
3230
3231 template<bool scan>
3232 inline void CMTask::process_grey_object(oop obj) {
3233 assert(scan || obj->is_typeArray(), "Skipping scan of grey non-typeArray");
3234 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3235
3236 if (_cm->verbose_high()) {
3237 gclog_or_tty->print_cr("[%u] processing grey object " PTR_FORMAT,
3238 _worker_id, p2i((void*) obj));
3239 }
3240
3241 size_t obj_size = obj->size();
3242 _words_scanned += obj_size;
3243
3244 if (scan) {
3245 obj->oop_iterate(_cm_oop_closure);
3246 }
3247 statsOnly( ++_objs_scanned );
3248 check_limits();
3249 }
3250
3251 template void CMTask::process_grey_object<true>(oop);
3252 template void CMTask::process_grey_object<false>(oop);
3253
3254 // Closure for iteration over bitmaps
3255 class CMBitMapClosure : public BitMapClosure {
3256 private:
3257 // the bitmap that is being iterated over
3258 CMBitMap* _nextMarkBitMap;
3259 ConcurrentMark* _cm;
3260 CMTask* _task;
3261
3262 public:
3263 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3264 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3265
3266 bool do_bit(size_t offset) {
3267 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3268 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3269 assert( addr < _cm->finger(), "invariant");
3270
3271 statsOnly( _task->increase_objs_found_on_bitmap() );
3272 assert(addr >= _task->finger(), "invariant");
3273
3274 // We move that task's local finger along.
3275 _task->move_finger_to(addr);
3276
3277 _task->scan_object(oop(addr));
3278 // we only partially drain the local queue and global stack
3279 _task->drain_local_queue(true);
3280 _task->drain_global_stack(true);
3281
3282 // if the has_aborted flag has been raised, we need to bail out of
3283 // the iteration
3284 return !_task->has_aborted();
3285 }
3286 };
3287
3288 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3289 ConcurrentMark* cm,
3290 CMTask* task)
3291 : _g1h(g1h), _cm(cm), _task(task) {
3292 assert(_ref_processor == NULL, "should be initialized to NULL");
3293
3294 if (G1UseConcMarkReferenceProcessing) {
3295 _ref_processor = g1h->ref_processor_cm();
3296 assert(_ref_processor != NULL, "should not be NULL");
3297 }
3298 }
3299
3300 void CMTask::setup_for_region(HeapRegion* hr) {
3301 assert(hr != NULL,
3302 "claim_region() should have filtered out NULL regions");
3303 assert(!hr->is_continues_humongous(),
3304 "claim_region() should have filtered out continues humongous regions");
3305
3306 if (_cm->verbose_low()) {
3307 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3308 _worker_id, p2i(hr));
3309 }
3310
3311 _curr_region = hr;
3312 _finger = hr->bottom();
3313 update_region_limit();
3314 }
3315
3316 void CMTask::update_region_limit() {
3317 HeapRegion* hr = _curr_region;
3318 HeapWord* bottom = hr->bottom();
3319 HeapWord* limit = hr->next_top_at_mark_start();
3320
3321 if (limit == bottom) {
3322 if (_cm->verbose_low()) {
3323 gclog_or_tty->print_cr("[%u] found an empty region "
3324 "["PTR_FORMAT", "PTR_FORMAT")",
3325 _worker_id, p2i(bottom), p2i(limit));
3326 }
3327 // The region was collected underneath our feet.
3328 // We set the finger to bottom to ensure that the bitmap
3329 // iteration that will follow this will not do anything.
3330 // (this is not a condition that holds when we set the region up,
3331 // as the region is not supposed to be empty in the first place)
3332 _finger = bottom;
3333 } else if (limit >= _region_limit) {
3334 assert(limit >= _finger, "peace of mind");
3335 } else {
3336 assert(limit < _region_limit, "only way to get here");
3337 // This can happen under some pretty unusual circumstances. An
3338 // evacuation pause empties the region underneath our feet (NTAMS
3339 // at bottom). We then do some allocation in the region (NTAMS
3340 // stays at bottom), followed by the region being used as a GC
3341 // alloc region (NTAMS will move to top() and the objects
3342 // originally below it will be grayed). All objects now marked in
3343 // the region are explicitly grayed, if below the global finger,
3344 // and we do not need in fact to scan anything else. So, we simply
3345 // set _finger to be limit to ensure that the bitmap iteration
3346 // doesn't do anything.
3347 _finger = limit;
3348 }
3349
3350 _region_limit = limit;
3351 }
3352
3353 void CMTask::giveup_current_region() {
3354 assert(_curr_region != NULL, "invariant");
3355 if (_cm->verbose_low()) {
3356 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3357 _worker_id, p2i(_curr_region));
3358 }
3359 clear_region_fields();
3360 }
3361
3362 void CMTask::clear_region_fields() {
3363 // Values for these three fields that indicate that we're not
3364 // holding on to a region.
3365 _curr_region = NULL;
3366 _finger = NULL;
3367 _region_limit = NULL;
3368 }
3369
3370 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3371 if (cm_oop_closure == NULL) {
3372 assert(_cm_oop_closure != NULL, "invariant");
3373 } else {
3374 assert(_cm_oop_closure == NULL, "invariant");
3375 }
3376 _cm_oop_closure = cm_oop_closure;
3377 }
3378
3379 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3380 guarantee(nextMarkBitMap != NULL, "invariant");
3381
3382 if (_cm->verbose_low()) {
3383 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3384 }
3385
3386 _nextMarkBitMap = nextMarkBitMap;
3387 clear_region_fields();
3388
3389 _calls = 0;
3390 _elapsed_time_ms = 0.0;
3391 _termination_time_ms = 0.0;
3392 _termination_start_time_ms = 0.0;
3393
3394 #if _MARKING_STATS_
3395 _aborted = 0;
3396 _aborted_overflow = 0;
3397 _aborted_cm_aborted = 0;
3398 _aborted_yield = 0;
3399 _aborted_timed_out = 0;
3400 _aborted_satb = 0;
3401 _aborted_termination = 0;
3402 _steal_attempts = 0;
3403 _steals = 0;
3404 _local_pushes = 0;
3405 _local_pops = 0;
3406 _local_max_size = 0;
3407 _objs_scanned = 0;
3408 _global_pushes = 0;
3409 _global_pops = 0;
3410 _global_max_size = 0;
3411 _global_transfers_to = 0;
3412 _global_transfers_from = 0;
3413 _regions_claimed = 0;
3414 _objs_found_on_bitmap = 0;
3415 _satb_buffers_processed = 0;
3416 #endif // _MARKING_STATS_
3417 }
3418
3419 bool CMTask::should_exit_termination() {
3420 regular_clock_call();
3421 // This is called when we are in the termination protocol. We should
3422 // quit if, for some reason, this task wants to abort or the global
3423 // stack is not empty (this means that we can get work from it).
3424 return !_cm->mark_stack_empty() || has_aborted();
3425 }
3426
3427 void CMTask::reached_limit() {
3428 assert(_words_scanned >= _words_scanned_limit ||
3429 _refs_reached >= _refs_reached_limit ,
3430 "shouldn't have been called otherwise");
3431 regular_clock_call();
3432 }
3433
3434 void CMTask::regular_clock_call() {
3435 if (has_aborted()) return;
3436
3437 // First, we need to recalculate the words scanned and refs reached
3438 // limits for the next clock call.
3439 recalculate_limits();
3440
3441 // During the regular clock call we do the following
3442
3443 // (1) If an overflow has been flagged, then we abort.
3444 if (_cm->has_overflown()) {
3445 set_has_aborted();
3446 return;
3447 }
3448
3449 // If we are not concurrent (i.e. we're doing remark) we don't need
3450 // to check anything else. The other steps are only needed during
3451 // the concurrent marking phase.
3452 if (!concurrent()) return;
3453
3454 // (2) If marking has been aborted for Full GC, then we also abort.
3455 if (_cm->has_aborted()) {
3456 set_has_aborted();
3457 statsOnly( ++_aborted_cm_aborted );
3458 return;
3459 }
3460
3461 double curr_time_ms = os::elapsedVTime() * 1000.0;
3462
3463 // (3) If marking stats are enabled, then we update the step history.
3464 #if _MARKING_STATS_
3465 if (_words_scanned >= _words_scanned_limit) {
3466 ++_clock_due_to_scanning;
3467 }
3468 if (_refs_reached >= _refs_reached_limit) {
3469 ++_clock_due_to_marking;
3470 }
3471
3472 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3473 _interval_start_time_ms = curr_time_ms;
3474 _all_clock_intervals_ms.add(last_interval_ms);
3475
3476 if (_cm->verbose_medium()) {
3477 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3478 "scanned = "SIZE_FORMAT"%s, refs reached = "SIZE_FORMAT"%s",
3479 _worker_id, last_interval_ms,
3480 _words_scanned,
3481 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3482 _refs_reached,
3483 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3484 }
3485 #endif // _MARKING_STATS_
3486
3487 // (4) We check whether we should yield. If we have to, then we abort.
3488 if (SuspendibleThreadSet::should_yield()) {
3489 // We should yield. To do this we abort the task. The caller is
3490 // responsible for yielding.
3491 set_has_aborted();
3492 statsOnly( ++_aborted_yield );
3493 return;
3494 }
3495
3496 // (5) We check whether we've reached our time quota. If we have,
3497 // then we abort.
3498 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3499 if (elapsed_time_ms > _time_target_ms) {
3500 set_has_aborted();
3501 _has_timed_out = true;
3502 statsOnly( ++_aborted_timed_out );
3503 return;
3504 }
3505
3506 // (6) Finally, we check whether there are enough completed STAB
3507 // buffers available for processing. If there are, we abort.
3508 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3509 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3510 if (_cm->verbose_low()) {
3511 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3512 _worker_id);
3513 }
3514 // we do need to process SATB buffers, we'll abort and restart
3515 // the marking task to do so
3516 set_has_aborted();
3517 statsOnly( ++_aborted_satb );
3518 return;
3519 }
3520 }
3521
3522 void CMTask::recalculate_limits() {
3523 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3524 _words_scanned_limit = _real_words_scanned_limit;
3525
3526 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3527 _refs_reached_limit = _real_refs_reached_limit;
3528 }
3529
3530 void CMTask::decrease_limits() {
3531 // This is called when we believe that we're going to do an infrequent
3532 // operation which will increase the per byte scanned cost (i.e. move
3533 // entries to/from the global stack). It basically tries to decrease the
3534 // scanning limit so that the clock is called earlier.
3535
3536 if (_cm->verbose_medium()) {
3537 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3538 }
3539
3540 _words_scanned_limit = _real_words_scanned_limit -
3541 3 * words_scanned_period / 4;
3542 _refs_reached_limit = _real_refs_reached_limit -
3543 3 * refs_reached_period / 4;
3544 }
3545
3546 void CMTask::move_entries_to_global_stack() {
3547 // local array where we'll store the entries that will be popped
3548 // from the local queue
3549 oop buffer[global_stack_transfer_size];
3550
3551 int n = 0;
3552 oop obj;
3553 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3554 buffer[n] = obj;
3555 ++n;
3556 }
3557
3558 if (n > 0) {
3559 // we popped at least one entry from the local queue
3560
3561 statsOnly( ++_global_transfers_to; _local_pops += n );
3562
3563 if (!_cm->mark_stack_push(buffer, n)) {
3564 if (_cm->verbose_low()) {
3565 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3566 _worker_id);
3567 }
3568 set_has_aborted();
3569 } else {
3570 // the transfer was successful
3571
3572 if (_cm->verbose_medium()) {
3573 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3574 _worker_id, n);
3575 }
3576 statsOnly( size_t tmp_size = _cm->mark_stack_size();
3577 if (tmp_size > _global_max_size) {
3578 _global_max_size = tmp_size;
3579 }
3580 _global_pushes += n );
3581 }
3582 }
3583
3584 // this operation was quite expensive, so decrease the limits
3585 decrease_limits();
3586 }
3587
3588 void CMTask::get_entries_from_global_stack() {
3589 // local array where we'll store the entries that will be popped
3590 // from the global stack.
3591 oop buffer[global_stack_transfer_size];
3592 int n;
3593 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3594 assert(n <= global_stack_transfer_size,
3595 "we should not pop more than the given limit");
3596 if (n > 0) {
3597 // yes, we did actually pop at least one entry
3598
3599 statsOnly( ++_global_transfers_from; _global_pops += n );
3600 if (_cm->verbose_medium()) {
3601 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3602 _worker_id, n);
3603 }
3604 for (int i = 0; i < n; ++i) {
3605 bool success = _task_queue->push(buffer[i]);
3606 // We only call this when the local queue is empty or under a
3607 // given target limit. So, we do not expect this push to fail.
3608 assert(success, "invariant");
3609 }
3610
3611 statsOnly( size_t tmp_size = (size_t)_task_queue->size();
3612 if (tmp_size > _local_max_size) {
3613 _local_max_size = tmp_size;
3614 }
3615 _local_pushes += n );
3616 }
3617
3618 // this operation was quite expensive, so decrease the limits
3619 decrease_limits();
3620 }
3621
3622 void CMTask::drain_local_queue(bool partially) {
3623 if (has_aborted()) return;
3624
3625 // Decide what the target size is, depending whether we're going to
3626 // drain it partially (so that other tasks can steal if they run out
3627 // of things to do) or totally (at the very end).
3628 size_t target_size;
3629 if (partially) {
3630 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3631 } else {
3632 target_size = 0;
3633 }
3634
3635 if (_task_queue->size() > target_size) {
3636 if (_cm->verbose_high()) {
3637 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT,
3638 _worker_id, target_size);
3639 }
3640
3641 oop obj;
3642 bool ret = _task_queue->pop_local(obj);
3643 while (ret) {
3644 statsOnly( ++_local_pops );
3645
3646 if (_cm->verbose_high()) {
3647 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3648 p2i((void*) obj));
3649 }
3650
3651 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3652 assert(!_g1h->is_on_master_free_list(
3653 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3654
3655 scan_object(obj);
3656
3657 if (_task_queue->size() <= target_size || has_aborted()) {
3658 ret = false;
3659 } else {
3660 ret = _task_queue->pop_local(obj);
3661 }
3662 }
3663
3664 if (_cm->verbose_high()) {
3665 gclog_or_tty->print_cr("[%u] drained local queue, size = %u",
3666 _worker_id, _task_queue->size());
3667 }
3668 }
3669 }
3670
3671 void CMTask::drain_global_stack(bool partially) {
3672 if (has_aborted()) return;
3673
3674 // We have a policy to drain the local queue before we attempt to
3675 // drain the global stack.
3676 assert(partially || _task_queue->size() == 0, "invariant");
3677
3678 // Decide what the target size is, depending whether we're going to
3679 // drain it partially (so that other tasks can steal if they run out
3680 // of things to do) or totally (at the very end). Notice that,
3681 // because we move entries from the global stack in chunks or
3682 // because another task might be doing the same, we might in fact
3683 // drop below the target. But, this is not a problem.
3684 size_t target_size;
3685 if (partially) {
3686 target_size = _cm->partial_mark_stack_size_target();
3687 } else {
3688 target_size = 0;
3689 }
3690
3691 if (_cm->mark_stack_size() > target_size) {
3692 if (_cm->verbose_low()) {
3693 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT,
3694 _worker_id, target_size);
3695 }
3696
3697 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3698 get_entries_from_global_stack();
3699 drain_local_queue(partially);
3700 }
3701
3702 if (_cm->verbose_low()) {
3703 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT,
3704 _worker_id, _cm->mark_stack_size());
3705 }
3706 }
3707 }
3708
3709 // SATB Queue has several assumptions on whether to call the par or
3710 // non-par versions of the methods. this is why some of the code is
3711 // replicated. We should really get rid of the single-threaded version
3712 // of the code to simplify things.
3713 void CMTask::drain_satb_buffers() {
3714 if (has_aborted()) return;
3715
3716 // We set this so that the regular clock knows that we're in the
3717 // middle of draining buffers and doesn't set the abort flag when it
3718 // notices that SATB buffers are available for draining. It'd be
3719 // very counter productive if it did that. :-)
3720 _draining_satb_buffers = true;
3721
3722 CMObjectClosure oc(this);
3723 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3724
3725 // This keeps claiming and applying the closure to completed buffers
3726 // until we run out of buffers or we need to abort.
3727 while (!has_aborted() &&
3728 satb_mq_set.apply_closure_to_completed_buffer(&oc)) {
3729 if (_cm->verbose_medium()) {
3730 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3731 }
3732 statsOnly( ++_satb_buffers_processed );
3733 regular_clock_call();
3734 }
3735
3736 _draining_satb_buffers = false;
3737
3738 assert(has_aborted() ||
3739 concurrent() ||
3740 satb_mq_set.completed_buffers_num() == 0, "invariant");
3741
3742 // again, this was a potentially expensive operation, decrease the
3743 // limits to get the regular clock call early
3744 decrease_limits();
3745 }
3746
3747 void CMTask::print_stats() {
3748 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3749 _worker_id, _calls);
3750 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3751 _elapsed_time_ms, _termination_time_ms);
3752 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3753 _step_times_ms.num(), _step_times_ms.avg(),
3754 _step_times_ms.sd());
3755 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3756 _step_times_ms.maximum(), _step_times_ms.sum());
3757
3758 #if _MARKING_STATS_
3759 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3760 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3761 _all_clock_intervals_ms.sd());
3762 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3763 _all_clock_intervals_ms.maximum(),
3764 _all_clock_intervals_ms.sum());
3765 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = " SIZE_FORMAT ", marking = " SIZE_FORMAT,
3766 _clock_due_to_scanning, _clock_due_to_marking);
3767 gclog_or_tty->print_cr(" Objects: scanned = " SIZE_FORMAT ", found on the bitmap = " SIZE_FORMAT,
3768 _objs_scanned, _objs_found_on_bitmap);
3769 gclog_or_tty->print_cr(" Local Queue: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3770 _local_pushes, _local_pops, _local_max_size);
3771 gclog_or_tty->print_cr(" Global Stack: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3772 _global_pushes, _global_pops, _global_max_size);
3773 gclog_or_tty->print_cr(" transfers to = " SIZE_FORMAT ", transfers from = " SIZE_FORMAT,
3774 _global_transfers_to,_global_transfers_from);
3775 gclog_or_tty->print_cr(" Regions: claimed = " SIZE_FORMAT, _regions_claimed);
3776 gclog_or_tty->print_cr(" SATB buffers: processed = " SIZE_FORMAT, _satb_buffers_processed);
3777 gclog_or_tty->print_cr(" Steals: attempts = " SIZE_FORMAT ", successes = " SIZE_FORMAT,
3778 _steal_attempts, _steals);
3779 gclog_or_tty->print_cr(" Aborted: " SIZE_FORMAT ", due to", _aborted);
3780 gclog_or_tty->print_cr(" overflow: " SIZE_FORMAT ", global abort: " SIZE_FORMAT ", yield: " SIZE_FORMAT,
3781 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3782 gclog_or_tty->print_cr(" time out: " SIZE_FORMAT ", SATB: " SIZE_FORMAT ", termination: " SIZE_FORMAT,
3783 _aborted_timed_out, _aborted_satb, _aborted_termination);
3784 #endif // _MARKING_STATS_
3785 }
3786
3787 /*****************************************************************************
3788
3789 The do_marking_step(time_target_ms, ...) method is the building
3790 block of the parallel marking framework. It can be called in parallel
3791 with other invocations of do_marking_step() on different tasks
3792 (but only one per task, obviously) and concurrently with the
3793 mutator threads, or during remark, hence it eliminates the need
3794 for two versions of the code. When called during remark, it will
3795 pick up from where the task left off during the concurrent marking
3796 phase. Interestingly, tasks are also claimable during evacuation
3797 pauses too, since do_marking_step() ensures that it aborts before
3798 it needs to yield.
3799
3800 The data structures that it uses to do marking work are the
3801 following:
3802
3803 (1) Marking Bitmap. If there are gray objects that appear only
3804 on the bitmap (this happens either when dealing with an overflow
3805 or when the initial marking phase has simply marked the roots
3806 and didn't push them on the stack), then tasks claim heap
3807 regions whose bitmap they then scan to find gray objects. A
3808 global finger indicates where the end of the last claimed region
3809 is. A local finger indicates how far into the region a task has
3810 scanned. The two fingers are used to determine how to gray an
3811 object (i.e. whether simply marking it is OK, as it will be
3812 visited by a task in the future, or whether it needs to be also
3813 pushed on a stack).
3814
3815 (2) Local Queue. The local queue of the task which is accessed
3816 reasonably efficiently by the task. Other tasks can steal from
3817 it when they run out of work. Throughout the marking phase, a
3818 task attempts to keep its local queue short but not totally
3819 empty, so that entries are available for stealing by other
3820 tasks. Only when there is no more work, a task will totally
3821 drain its local queue.
3822
3823 (3) Global Mark Stack. This handles local queue overflow. During
3824 marking only sets of entries are moved between it and the local
3825 queues, as access to it requires a mutex and more fine-grain
3826 interaction with it which might cause contention. If it
3827 overflows, then the marking phase should restart and iterate
3828 over the bitmap to identify gray objects. Throughout the marking
3829 phase, tasks attempt to keep the global mark stack at a small
3830 length but not totally empty, so that entries are available for
3831 popping by other tasks. Only when there is no more work, tasks
3832 will totally drain the global mark stack.
3833
3834 (4) SATB Buffer Queue. This is where completed SATB buffers are
3835 made available. Buffers are regularly removed from this queue
3836 and scanned for roots, so that the queue doesn't get too
3837 long. During remark, all completed buffers are processed, as
3838 well as the filled in parts of any uncompleted buffers.
3839
3840 The do_marking_step() method tries to abort when the time target
3841 has been reached. There are a few other cases when the
3842 do_marking_step() method also aborts:
3843
3844 (1) When the marking phase has been aborted (after a Full GC).
3845
3846 (2) When a global overflow (on the global stack) has been
3847 triggered. Before the task aborts, it will actually sync up with
3848 the other tasks to ensure that all the marking data structures
3849 (local queues, stacks, fingers etc.) are re-initialized so that
3850 when do_marking_step() completes, the marking phase can
3851 immediately restart.
3852
3853 (3) When enough completed SATB buffers are available. The
3854 do_marking_step() method only tries to drain SATB buffers right
3855 at the beginning. So, if enough buffers are available, the
3856 marking step aborts and the SATB buffers are processed at
3857 the beginning of the next invocation.
3858
3859 (4) To yield. when we have to yield then we abort and yield
3860 right at the end of do_marking_step(). This saves us from a lot
3861 of hassle as, by yielding we might allow a Full GC. If this
3862 happens then objects will be compacted underneath our feet, the
3863 heap might shrink, etc. We save checking for this by just
3864 aborting and doing the yield right at the end.
3865
3866 From the above it follows that the do_marking_step() method should
3867 be called in a loop (or, otherwise, regularly) until it completes.
3868
3869 If a marking step completes without its has_aborted() flag being
3870 true, it means it has completed the current marking phase (and
3871 also all other marking tasks have done so and have all synced up).
3872
3873 A method called regular_clock_call() is invoked "regularly" (in
3874 sub ms intervals) throughout marking. It is this clock method that
3875 checks all the abort conditions which were mentioned above and
3876 decides when the task should abort. A work-based scheme is used to
3877 trigger this clock method: when the number of object words the
3878 marking phase has scanned or the number of references the marking
3879 phase has visited reach a given limit. Additional invocations to
3880 the method clock have been planted in a few other strategic places
3881 too. The initial reason for the clock method was to avoid calling
3882 vtime too regularly, as it is quite expensive. So, once it was in
3883 place, it was natural to piggy-back all the other conditions on it
3884 too and not constantly check them throughout the code.
3885
3886 If do_termination is true then do_marking_step will enter its
3887 termination protocol.
3888
3889 The value of is_serial must be true when do_marking_step is being
3890 called serially (i.e. by the VMThread) and do_marking_step should
3891 skip any synchronization in the termination and overflow code.
3892 Examples include the serial remark code and the serial reference
3893 processing closures.
3894
3895 The value of is_serial must be false when do_marking_step is
3896 being called by any of the worker threads in a work gang.
3897 Examples include the concurrent marking code (CMMarkingTask),
3898 the MT remark code, and the MT reference processing closures.
3899
3900 *****************************************************************************/
3901
3902 void CMTask::do_marking_step(double time_target_ms,
3903 bool do_termination,
3904 bool is_serial) {
3905 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3906 assert(concurrent() == _cm->concurrent(), "they should be the same");
3907
3908 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3909 assert(_task_queues != NULL, "invariant");
3910 assert(_task_queue != NULL, "invariant");
3911 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3912
3913 assert(!_claimed,
3914 "only one thread should claim this task at any one time");
3915
3916 // OK, this doesn't safeguard again all possible scenarios, as it is
3917 // possible for two threads to set the _claimed flag at the same
3918 // time. But it is only for debugging purposes anyway and it will
3919 // catch most problems.
3920 _claimed = true;
3921
3922 _start_time_ms = os::elapsedVTime() * 1000.0;
3923 statsOnly( _interval_start_time_ms = _start_time_ms );
3924
3925 // If do_stealing is true then do_marking_step will attempt to
3926 // steal work from the other CMTasks. It only makes sense to
3927 // enable stealing when the termination protocol is enabled
3928 // and do_marking_step() is not being called serially.
3929 bool do_stealing = do_termination && !is_serial;
3930
3931 double diff_prediction_ms =
3932 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3933 _time_target_ms = time_target_ms - diff_prediction_ms;
3934
3935 // set up the variables that are used in the work-based scheme to
3936 // call the regular clock method
3937 _words_scanned = 0;
3938 _refs_reached = 0;
3939 recalculate_limits();
3940
3941 // clear all flags
3942 clear_has_aborted();
3943 _has_timed_out = false;
3944 _draining_satb_buffers = false;
3945
3946 ++_calls;
3947
3948 if (_cm->verbose_low()) {
3949 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
3950 "target = %1.2lfms >>>>>>>>>>",
3951 _worker_id, _calls, _time_target_ms);
3952 }
3953
3954 // Set up the bitmap and oop closures. Anything that uses them is
3955 // eventually called from this method, so it is OK to allocate these
3956 // statically.
3957 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3958 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
3959 set_cm_oop_closure(&cm_oop_closure);
3960
3961 if (_cm->has_overflown()) {
3962 // This can happen if the mark stack overflows during a GC pause
3963 // and this task, after a yield point, restarts. We have to abort
3964 // as we need to get into the overflow protocol which happens
3965 // right at the end of this task.
3966 set_has_aborted();
3967 }
3968
3969 // First drain any available SATB buffers. After this, we will not
3970 // look at SATB buffers before the next invocation of this method.
3971 // If enough completed SATB buffers are queued up, the regular clock
3972 // will abort this task so that it restarts.
3973 drain_satb_buffers();
3974 // ...then partially drain the local queue and the global stack
3975 drain_local_queue(true);
3976 drain_global_stack(true);
3977
3978 do {
3979 if (!has_aborted() && _curr_region != NULL) {
3980 // This means that we're already holding on to a region.
3981 assert(_finger != NULL, "if region is not NULL, then the finger "
3982 "should not be NULL either");
3983
3984 // We might have restarted this task after an evacuation pause
3985 // which might have evacuated the region we're holding on to
3986 // underneath our feet. Let's read its limit again to make sure
3987 // that we do not iterate over a region of the heap that
3988 // contains garbage (update_region_limit() will also move
3989 // _finger to the start of the region if it is found empty).
3990 update_region_limit();
3991 // We will start from _finger not from the start of the region,
3992 // as we might be restarting this task after aborting half-way
3993 // through scanning this region. In this case, _finger points to
3994 // the address where we last found a marked object. If this is a
3995 // fresh region, _finger points to start().
3996 MemRegion mr = MemRegion(_finger, _region_limit);
3997
3998 if (_cm->verbose_low()) {
3999 gclog_or_tty->print_cr("[%u] we're scanning part "
4000 "["PTR_FORMAT", "PTR_FORMAT") "
4001 "of region "HR_FORMAT,
4002 _worker_id, p2i(_finger), p2i(_region_limit),
4003 HR_FORMAT_PARAMS(_curr_region));
4004 }
4005
4006 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
4007 "humongous regions should go around loop once only");
4008
4009 // Some special cases:
4010 // If the memory region is empty, we can just give up the region.
4011 // If the current region is humongous then we only need to check
4012 // the bitmap for the bit associated with the start of the object,
4013 // scan the object if it's live, and give up the region.
4014 // Otherwise, let's iterate over the bitmap of the part of the region
4015 // that is left.
4016 // If the iteration is successful, give up the region.
4017 if (mr.is_empty()) {
4018 giveup_current_region();
4019 regular_clock_call();
4020 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
4021 if (_nextMarkBitMap->isMarked(mr.start())) {
4022 // The object is marked - apply the closure
4023 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
4024 bitmap_closure.do_bit(offset);
4025 }
4026 // Even if this task aborted while scanning the humongous object
4027 // we can (and should) give up the current region.
4028 giveup_current_region();
4029 regular_clock_call();
4030 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4031 giveup_current_region();
4032 regular_clock_call();
4033 } else {
4034 assert(has_aborted(), "currently the only way to do so");
4035 // The only way to abort the bitmap iteration is to return
4036 // false from the do_bit() method. However, inside the
4037 // do_bit() method we move the _finger to point to the
4038 // object currently being looked at. So, if we bail out, we
4039 // have definitely set _finger to something non-null.
4040 assert(_finger != NULL, "invariant");
4041
4042 // Region iteration was actually aborted. So now _finger
4043 // points to the address of the object we last scanned. If we
4044 // leave it there, when we restart this task, we will rescan
4045 // the object. It is easy to avoid this. We move the finger by
4046 // enough to point to the next possible object header (the
4047 // bitmap knows by how much we need to move it as it knows its
4048 // granularity).
4049 assert(_finger < _region_limit, "invariant");
4050 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
4051 // Check if bitmap iteration was aborted while scanning the last object
4052 if (new_finger >= _region_limit) {
4053 giveup_current_region();
4054 } else {
4055 move_finger_to(new_finger);
4056 }
4057 }
4058 }
4059 // At this point we have either completed iterating over the
4060 // region we were holding on to, or we have aborted.
4061
4062 // We then partially drain the local queue and the global stack.
4063 // (Do we really need this?)
4064 drain_local_queue(true);
4065 drain_global_stack(true);
4066
4067 // Read the note on the claim_region() method on why it might
4068 // return NULL with potentially more regions available for
4069 // claiming and why we have to check out_of_regions() to determine
4070 // whether we're done or not.
4071 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4072 // We are going to try to claim a new region. We should have
4073 // given up on the previous one.
4074 // Separated the asserts so that we know which one fires.
4075 assert(_curr_region == NULL, "invariant");
4076 assert(_finger == NULL, "invariant");
4077 assert(_region_limit == NULL, "invariant");
4078 if (_cm->verbose_low()) {
4079 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4080 }
4081 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4082 if (claimed_region != NULL) {
4083 // Yes, we managed to claim one
4084 statsOnly( ++_regions_claimed );
4085
4086 if (_cm->verbose_low()) {
4087 gclog_or_tty->print_cr("[%u] we successfully claimed "
4088 "region "PTR_FORMAT,
4089 _worker_id, p2i(claimed_region));
4090 }
4091
4092 setup_for_region(claimed_region);
4093 assert(_curr_region == claimed_region, "invariant");
4094 }
4095 // It is important to call the regular clock here. It might take
4096 // a while to claim a region if, for example, we hit a large
4097 // block of empty regions. So we need to call the regular clock
4098 // method once round the loop to make sure it's called
4099 // frequently enough.
4100 regular_clock_call();
4101 }
4102
4103 if (!has_aborted() && _curr_region == NULL) {
4104 assert(_cm->out_of_regions(),
4105 "at this point we should be out of regions");
4106 }
4107 } while ( _curr_region != NULL && !has_aborted());
4108
4109 if (!has_aborted()) {
4110 // We cannot check whether the global stack is empty, since other
4111 // tasks might be pushing objects to it concurrently.
4112 assert(_cm->out_of_regions(),
4113 "at this point we should be out of regions");
4114
4115 if (_cm->verbose_low()) {
4116 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4117 }
4118
4119 // Try to reduce the number of available SATB buffers so that
4120 // remark has less work to do.
4121 drain_satb_buffers();
4122 }
4123
4124 // Since we've done everything else, we can now totally drain the
4125 // local queue and global stack.
4126 drain_local_queue(false);
4127 drain_global_stack(false);
4128
4129 // Attempt at work stealing from other task's queues.
4130 if (do_stealing && !has_aborted()) {
4131 // We have not aborted. This means that we have finished all that
4132 // we could. Let's try to do some stealing...
4133
4134 // We cannot check whether the global stack is empty, since other
4135 // tasks might be pushing objects to it concurrently.
4136 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4137 "only way to reach here");
4138
4139 if (_cm->verbose_low()) {
4140 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4141 }
4142
4143 while (!has_aborted()) {
4144 oop obj;
4145 statsOnly( ++_steal_attempts );
4146
4147 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4148 if (_cm->verbose_medium()) {
4149 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4150 _worker_id, p2i((void*) obj));
4151 }
4152
4153 statsOnly( ++_steals );
4154
4155 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4156 "any stolen object should be marked");
4157 scan_object(obj);
4158
4159 // And since we're towards the end, let's totally drain the
4160 // local queue and global stack.
4161 drain_local_queue(false);
4162 drain_global_stack(false);
4163 } else {
4164 break;
4165 }
4166 }
4167 }
4168
4169 // If we are about to wrap up and go into termination, check if we
4170 // should raise the overflow flag.
4171 if (do_termination && !has_aborted()) {
4172 if (_cm->force_overflow()->should_force()) {
4173 _cm->set_has_overflown();
4174 regular_clock_call();
4175 }
4176 }
4177
4178 // We still haven't aborted. Now, let's try to get into the
4179 // termination protocol.
4180 if (do_termination && !has_aborted()) {
4181 // We cannot check whether the global stack is empty, since other
4182 // tasks might be concurrently pushing objects on it.
4183 // Separated the asserts so that we know which one fires.
4184 assert(_cm->out_of_regions(), "only way to reach here");
4185 assert(_task_queue->size() == 0, "only way to reach here");
4186
4187 if (_cm->verbose_low()) {
4188 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4189 }
4190
4191 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4192
4193 // The CMTask class also extends the TerminatorTerminator class,
4194 // hence its should_exit_termination() method will also decide
4195 // whether to exit the termination protocol or not.
4196 bool finished = (is_serial ||
4197 _cm->terminator()->offer_termination(this));
4198 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4199 _termination_time_ms +=
4200 termination_end_time_ms - _termination_start_time_ms;
4201
4202 if (finished) {
4203 // We're all done.
4204
4205 if (_worker_id == 0) {
4206 // let's allow task 0 to do this
4207 if (concurrent()) {
4208 assert(_cm->concurrent_marking_in_progress(), "invariant");
4209 // we need to set this to false before the next
4210 // safepoint. This way we ensure that the marking phase
4211 // doesn't observe any more heap expansions.
4212 _cm->clear_concurrent_marking_in_progress();
4213 }
4214 }
4215
4216 // We can now guarantee that the global stack is empty, since
4217 // all other tasks have finished. We separated the guarantees so
4218 // that, if a condition is false, we can immediately find out
4219 // which one.
4220 guarantee(_cm->out_of_regions(), "only way to reach here");
4221 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4222 guarantee(_task_queue->size() == 0, "only way to reach here");
4223 guarantee(!_cm->has_overflown(), "only way to reach here");
4224 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4225
4226 if (_cm->verbose_low()) {
4227 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4228 }
4229 } else {
4230 // Apparently there's more work to do. Let's abort this task. It
4231 // will restart it and we can hopefully find more things to do.
4232
4233 if (_cm->verbose_low()) {
4234 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4235 _worker_id);
4236 }
4237
4238 set_has_aborted();
4239 statsOnly( ++_aborted_termination );
4240 }
4241 }
4242
4243 // Mainly for debugging purposes to make sure that a pointer to the
4244 // closure which was statically allocated in this frame doesn't
4245 // escape it by accident.
4246 set_cm_oop_closure(NULL);
4247 double end_time_ms = os::elapsedVTime() * 1000.0;
4248 double elapsed_time_ms = end_time_ms - _start_time_ms;
4249 // Update the step history.
4250 _step_times_ms.add(elapsed_time_ms);
4251
4252 if (has_aborted()) {
4253 // The task was aborted for some reason.
4254
4255 statsOnly( ++_aborted );
4256
4257 if (_has_timed_out) {
4258 double diff_ms = elapsed_time_ms - _time_target_ms;
4259 // Keep statistics of how well we did with respect to hitting
4260 // our target only if we actually timed out (if we aborted for
4261 // other reasons, then the results might get skewed).
4262 _marking_step_diffs_ms.add(diff_ms);
4263 }
4264
4265 if (_cm->has_overflown()) {
4266 // This is the interesting one. We aborted because a global
4267 // overflow was raised. This means we have to restart the
4268 // marking phase and start iterating over regions. However, in
4269 // order to do this we have to make sure that all tasks stop
4270 // what they are doing and re-initialize in a safe manner. We
4271 // will achieve this with the use of two barrier sync points.
4272
4273 if (_cm->verbose_low()) {
4274 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4275 }
4276
4277 if (!is_serial) {
4278 // We only need to enter the sync barrier if being called
4279 // from a parallel context
4280 _cm->enter_first_sync_barrier(_worker_id);
4281
4282 // When we exit this sync barrier we know that all tasks have
4283 // stopped doing marking work. So, it's now safe to
4284 // re-initialize our data structures. At the end of this method,
4285 // task 0 will clear the global data structures.
4286 }
4287
4288 statsOnly( ++_aborted_overflow );
4289
4290 // We clear the local state of this task...
4291 clear_region_fields();
4292
4293 if (!is_serial) {
4294 // ...and enter the second barrier.
4295 _cm->enter_second_sync_barrier(_worker_id);
4296 }
4297 // At this point, if we're during the concurrent phase of
4298 // marking, everything has been re-initialized and we're
4299 // ready to restart.
4300 }
4301
4302 if (_cm->verbose_low()) {
4303 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4304 "elapsed = %1.2lfms <<<<<<<<<<",
4305 _worker_id, _time_target_ms, elapsed_time_ms);
4306 if (_cm->has_aborted()) {
4307 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4308 _worker_id);
4309 }
4310 }
4311 } else {
4312 if (_cm->verbose_low()) {
4313 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4314 "elapsed = %1.2lfms <<<<<<<<<<",
4315 _worker_id, _time_target_ms, elapsed_time_ms);
4316 }
4317 }
4318
4319 _claimed = false;
4320 }
4321
4322 CMTask::CMTask(uint worker_id,
4323 ConcurrentMark* cm,
4324 size_t* marked_bytes,
4325 BitMap* card_bm,
4326 CMTaskQueue* task_queue,
4327 CMTaskQueueSet* task_queues)
4328 : _g1h(G1CollectedHeap::heap()),
4329 _worker_id(worker_id), _cm(cm),
4330 _claimed(false),
4331 _nextMarkBitMap(NULL), _hash_seed(17),
4332 _task_queue(task_queue),
4333 _task_queues(task_queues),
4334 _cm_oop_closure(NULL),
4335 _marked_bytes_array(marked_bytes),
4336 _card_bm(card_bm) {
4337 guarantee(task_queue != NULL, "invariant");
4338 guarantee(task_queues != NULL, "invariant");
4339
4340 statsOnly( _clock_due_to_scanning = 0;
4341 _clock_due_to_marking = 0 );
4342
4343 _marking_step_diffs_ms.add(0.5);
4344 }
4345
4346 // These are formatting macros that are used below to ensure
4347 // consistent formatting. The *_H_* versions are used to format the
4348 // header for a particular value and they should be kept consistent
4349 // with the corresponding macro. Also note that most of the macros add
4350 // the necessary white space (as a prefix) which makes them a bit
4351 // easier to compose.
4352
4353 // All the output lines are prefixed with this string to be able to
4354 // identify them easily in a large log file.
4355 #define G1PPRL_LINE_PREFIX "###"
4356
4357 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4358 #ifdef _LP64
4359 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4360 #else // _LP64
4361 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4362 #endif // _LP64
4363
4364 // For per-region info
4365 #define G1PPRL_TYPE_FORMAT " %-4s"
4366 #define G1PPRL_TYPE_H_FORMAT " %4s"
4367 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4368 #define G1PPRL_BYTE_H_FORMAT " %9s"
4369 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4370 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4371
4372 // For summary info
4373 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4374 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4375 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4376 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4377
4378 G1PrintRegionLivenessInfoClosure::
4379 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4380 : _out(out),
4381 _total_used_bytes(0), _total_capacity_bytes(0),
4382 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4383 _hum_used_bytes(0), _hum_capacity_bytes(0),
4384 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4385 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4386 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4387 MemRegion g1_reserved = g1h->g1_reserved();
4388 double now = os::elapsedTime();
4389
4390 // Print the header of the output.
4391 _out->cr();
4392 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4393 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4394 G1PPRL_SUM_ADDR_FORMAT("reserved")
4395 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4396 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
4397 HeapRegion::GrainBytes);
4398 _out->print_cr(G1PPRL_LINE_PREFIX);
4399 _out->print_cr(G1PPRL_LINE_PREFIX
4400 G1PPRL_TYPE_H_FORMAT
4401 G1PPRL_ADDR_BASE_H_FORMAT
4402 G1PPRL_BYTE_H_FORMAT
4403 G1PPRL_BYTE_H_FORMAT
4404 G1PPRL_BYTE_H_FORMAT
4405 G1PPRL_DOUBLE_H_FORMAT
4406 G1PPRL_BYTE_H_FORMAT
4407 G1PPRL_BYTE_H_FORMAT,
4408 "type", "address-range",
4409 "used", "prev-live", "next-live", "gc-eff",
4410 "remset", "code-roots");
4411 _out->print_cr(G1PPRL_LINE_PREFIX
4412 G1PPRL_TYPE_H_FORMAT
4413 G1PPRL_ADDR_BASE_H_FORMAT
4414 G1PPRL_BYTE_H_FORMAT
4415 G1PPRL_BYTE_H_FORMAT
4416 G1PPRL_BYTE_H_FORMAT
4417 G1PPRL_DOUBLE_H_FORMAT
4418 G1PPRL_BYTE_H_FORMAT
4419 G1PPRL_BYTE_H_FORMAT,
4420 "", "",
4421 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4422 "(bytes)", "(bytes)");
4423 }
4424
4425 // It takes as a parameter a reference to one of the _hum_* fields, it
4426 // deduces the corresponding value for a region in a humongous region
4427 // series (either the region size, or what's left if the _hum_* field
4428 // is < the region size), and updates the _hum_* field accordingly.
4429 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4430 size_t bytes = 0;
4431 // The > 0 check is to deal with the prev and next live bytes which
4432 // could be 0.
4433 if (*hum_bytes > 0) {
4434 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4435 *hum_bytes -= bytes;
4436 }
4437 return bytes;
4438 }
4439
4440 // It deduces the values for a region in a humongous region series
4441 // from the _hum_* fields and updates those accordingly. It assumes
4442 // that that _hum_* fields have already been set up from the "starts
4443 // humongous" region and we visit the regions in address order.
4444 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4445 size_t* capacity_bytes,
4446 size_t* prev_live_bytes,
4447 size_t* next_live_bytes) {
4448 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4449 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4450 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4451 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4452 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4453 }
4454
4455 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4456 const char* type = r->get_type_str();
4457 HeapWord* bottom = r->bottom();
4458 HeapWord* end = r->end();
4459 size_t capacity_bytes = r->capacity();
4460 size_t used_bytes = r->used();
4461 size_t prev_live_bytes = r->live_bytes();
4462 size_t next_live_bytes = r->next_live_bytes();
4463 double gc_eff = r->gc_efficiency();
4464 size_t remset_bytes = r->rem_set()->mem_size();
4465 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4466
4467 if (r->is_starts_humongous()) {
4468 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4469 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4470 "they should have been zeroed after the last time we used them");
4471 // Set up the _hum_* fields.
4472 _hum_capacity_bytes = capacity_bytes;
4473 _hum_used_bytes = used_bytes;
4474 _hum_prev_live_bytes = prev_live_bytes;
4475 _hum_next_live_bytes = next_live_bytes;
4476 get_hum_bytes(&used_bytes, &capacity_bytes,
4477 &prev_live_bytes, &next_live_bytes);
4478 end = bottom + HeapRegion::GrainWords;
4479 } else if (r->is_continues_humongous()) {
4480 get_hum_bytes(&used_bytes, &capacity_bytes,
4481 &prev_live_bytes, &next_live_bytes);
4482 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4483 }
4484
4485 _total_used_bytes += used_bytes;
4486 _total_capacity_bytes += capacity_bytes;
4487 _total_prev_live_bytes += prev_live_bytes;
4488 _total_next_live_bytes += next_live_bytes;
4489 _total_remset_bytes += remset_bytes;
4490 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4491
4492 // Print a line for this particular region.
4493 _out->print_cr(G1PPRL_LINE_PREFIX
4494 G1PPRL_TYPE_FORMAT
4495 G1PPRL_ADDR_BASE_FORMAT
4496 G1PPRL_BYTE_FORMAT
4497 G1PPRL_BYTE_FORMAT
4498 G1PPRL_BYTE_FORMAT
4499 G1PPRL_DOUBLE_FORMAT
4500 G1PPRL_BYTE_FORMAT
4501 G1PPRL_BYTE_FORMAT,
4502 type, p2i(bottom), p2i(end),
4503 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4504 remset_bytes, strong_code_roots_bytes);
4505
4506 return false;
4507 }
4508
4509 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4510 // add static memory usages to remembered set sizes
4511 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4512 // Print the footer of the output.
4513 _out->print_cr(G1PPRL_LINE_PREFIX);
4514 _out->print_cr(G1PPRL_LINE_PREFIX
4515 " SUMMARY"
4516 G1PPRL_SUM_MB_FORMAT("capacity")
4517 G1PPRL_SUM_MB_PERC_FORMAT("used")
4518 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4519 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4520 G1PPRL_SUM_MB_FORMAT("remset")
4521 G1PPRL_SUM_MB_FORMAT("code-roots"),
4522 bytes_to_mb(_total_capacity_bytes),
4523 bytes_to_mb(_total_used_bytes),
4524 perc(_total_used_bytes, _total_capacity_bytes),
4525 bytes_to_mb(_total_prev_live_bytes),
4526 perc(_total_prev_live_bytes, _total_capacity_bytes),
4527 bytes_to_mb(_total_next_live_bytes),
4528 perc(_total_next_live_bytes, _total_capacity_bytes),
4529 bytes_to_mb(_total_remset_bytes),
4530 bytes_to_mb(_total_strong_code_roots_bytes));
4531 _out->cr();
4532 }