1 /*
2 * Copyright (c) 2001, 2011, 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/symbolTable.hpp"
27 #include "gc_implementation/g1/concurrentMark.inline.hpp"
28 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
29 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
30 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
31 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
32 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
33 #include "gc_implementation/g1/g1RemSet.hpp"
34 #include "gc_implementation/g1/heapRegionRemSet.hpp"
35 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
36 #include "gc_implementation/shared/vmGCOperations.hpp"
37 #include "memory/genOopClosures.inline.hpp"
38 #include "memory/referencePolicy.hpp"
39 #include "memory/resourceArea.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/handles.inline.hpp"
42 #include "runtime/java.hpp"
43
44 //
45 // CMS Bit Map Wrapper
46
47 CMBitMapRO::CMBitMapRO(ReservedSpace rs, int shifter):
48 _bm((uintptr_t*)NULL,0),
49 _shifter(shifter) {
50 _bmStartWord = (HeapWord*)(rs.base());
51 _bmWordSize = rs.size()/HeapWordSize; // rs.size() is in bytes
52 ReservedSpace brs(ReservedSpace::allocation_align_size_up(
53 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
54
55 guarantee(brs.is_reserved(), "couldn't allocate CMS bit map");
56 // For now we'll just commit all of the bit map up fromt.
57 // Later on we'll try to be more parsimonious with swap.
58 guarantee(_virtual_space.initialize(brs, brs.size()),
59 "couldn't reseve backing store for CMS bit map");
60 assert(_virtual_space.committed_size() == brs.size(),
61 "didn't reserve backing store for all of CMS bit map?");
62 _bm.set_map((uintptr_t*)_virtual_space.low());
63 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
64 _bmWordSize, "inconsistency in bit map sizing");
65 _bm.set_size(_bmWordSize >> _shifter);
66 }
67
68 HeapWord* CMBitMapRO::getNextMarkedWordAddress(HeapWord* addr,
69 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(HeapWord* addr,
87 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 bool CMBitMapRO::iterate(BitMapClosure* cl, MemRegion mr) {
107 HeapWord* left = MAX2(_bmStartWord, mr.start());
108 HeapWord* right = MIN2(_bmStartWord + _bmWordSize, mr.end());
109 if (right > left) {
110 // Right-open interval [leftOffset, rightOffset).
111 return _bm.iterate(cl, heapWordToOffset(left), heapWordToOffset(right));
112 } else {
113 return true;
114 }
115 }
116
117 void CMBitMapRO::mostly_disjoint_range_union(BitMap* from_bitmap,
118 size_t from_start_index,
119 HeapWord* to_start_word,
120 size_t word_num) {
121 _bm.mostly_disjoint_range_union(from_bitmap,
122 from_start_index,
123 heapWordToOffset(to_start_word),
124 word_num);
125 }
126
127 #ifndef PRODUCT
128 bool CMBitMapRO::covers(ReservedSpace rs) const {
129 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
130 assert(((size_t)_bm.size() * (size_t)(1 << _shifter)) == _bmWordSize,
131 "size inconsistency");
132 return _bmStartWord == (HeapWord*)(rs.base()) &&
133 _bmWordSize == rs.size()>>LogHeapWordSize;
134 }
135 #endif
136
137 void CMBitMap::clearAll() {
138 _bm.clear();
139 return;
140 }
141
142 void CMBitMap::markRange(MemRegion mr) {
143 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
144 assert(!mr.is_empty(), "unexpected empty region");
145 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
146 ((HeapWord *) mr.end())),
147 "markRange memory region end is not card aligned");
148 // convert address range into offset range
149 _bm.at_put_range(heapWordToOffset(mr.start()),
150 heapWordToOffset(mr.end()), true);
151 }
152
153 void CMBitMap::clearRange(MemRegion mr) {
154 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
155 assert(!mr.is_empty(), "unexpected empty region");
156 // convert address range into offset range
157 _bm.at_put_range(heapWordToOffset(mr.start()),
158 heapWordToOffset(mr.end()), false);
159 }
160
161 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
162 HeapWord* end_addr) {
163 HeapWord* start = getNextMarkedWordAddress(addr);
164 start = MIN2(start, end_addr);
165 HeapWord* end = getNextUnmarkedWordAddress(start);
166 end = MIN2(end, end_addr);
167 assert(start <= end, "Consistency check");
168 MemRegion mr(start, end);
169 if (!mr.is_empty()) {
170 clearRange(mr);
171 }
172 return mr;
173 }
174
175 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
176 _base(NULL), _cm(cm)
177 #ifdef ASSERT
178 , _drain_in_progress(false)
179 , _drain_in_progress_yields(false)
180 #endif
181 {}
182
183 void CMMarkStack::allocate(size_t size) {
184 _base = NEW_C_HEAP_ARRAY(oop, size);
185 if (_base == NULL) {
186 vm_exit_during_initialization("Failed to allocate "
187 "CM region mark stack");
188 }
189 _index = 0;
190 _capacity = (jint) size;
191 _oops_do_bound = -1;
192 NOT_PRODUCT(_max_depth = 0);
193 }
194
195 CMMarkStack::~CMMarkStack() {
196 if (_base != NULL) {
197 FREE_C_HEAP_ARRAY(oop, _base);
198 }
199 }
200
201 void CMMarkStack::par_push(oop ptr) {
202 while (true) {
203 if (isFull()) {
204 _overflow = true;
205 return;
206 }
207 // Otherwise...
208 jint index = _index;
209 jint next_index = index+1;
210 jint res = Atomic::cmpxchg(next_index, &_index, index);
211 if (res == index) {
212 _base[index] = ptr;
213 // Note that we don't maintain this atomically. We could, but it
214 // doesn't seem necessary.
215 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
216 return;
217 }
218 // Otherwise, we need to try again.
219 }
220 }
221
222 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) {
223 while (true) {
224 if (isFull()) {
225 _overflow = true;
226 return;
227 }
228 // Otherwise...
229 jint index = _index;
230 jint next_index = index + n;
231 if (next_index > _capacity) {
232 _overflow = true;
233 return;
234 }
235 jint res = Atomic::cmpxchg(next_index, &_index, index);
236 if (res == index) {
237 for (int i = 0; i < n; i++) {
238 int ind = index + i;
239 assert(ind < _capacity, "By overflow test above.");
240 _base[ind] = ptr_arr[i];
241 }
242 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
243 return;
244 }
245 // Otherwise, we need to try again.
246 }
247 }
248
249
250 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
251 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
252 jint start = _index;
253 jint next_index = start + n;
254 if (next_index > _capacity) {
255 _overflow = true;
256 return;
257 }
258 // Otherwise.
259 _index = next_index;
260 for (int i = 0; i < n; i++) {
261 int ind = start + i;
262 assert(ind < _capacity, "By overflow test above.");
263 _base[ind] = ptr_arr[i];
264 }
265 }
266
267
268 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
269 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
270 jint index = _index;
271 if (index == 0) {
272 *n = 0;
273 return false;
274 } else {
275 int k = MIN2(max, index);
276 jint new_ind = index - k;
277 for (int j = 0; j < k; j++) {
278 ptr_arr[j] = _base[new_ind + j];
279 }
280 _index = new_ind;
281 *n = k;
282 return true;
283 }
284 }
285
286
287 CMRegionStack::CMRegionStack() : _base(NULL) {}
288
289 void CMRegionStack::allocate(size_t size) {
290 _base = NEW_C_HEAP_ARRAY(MemRegion, size);
291 if (_base == NULL) {
292 vm_exit_during_initialization("Failed to allocate CM region mark stack");
293 }
294 _index = 0;
295 _capacity = (jint) size;
296 }
297
298 CMRegionStack::~CMRegionStack() {
299 if (_base != NULL) {
300 FREE_C_HEAP_ARRAY(oop, _base);
301 }
302 }
303
304 void CMRegionStack::push_lock_free(MemRegion mr) {
305 assert(mr.word_size() > 0, "Precondition");
306 while (true) {
307 jint index = _index;
308
309 if (index >= _capacity) {
310 _overflow = true;
311 return;
312 }
313 // Otherwise...
314 jint next_index = index+1;
315 jint res = Atomic::cmpxchg(next_index, &_index, index);
316 if (res == index) {
317 _base[index] = mr;
318 return;
319 }
320 // Otherwise, we need to try again.
321 }
322 }
323
324 // Lock-free pop of the region stack. Called during the concurrent
325 // marking / remark phases. Should only be called in tandem with
326 // other lock-free pops.
327 MemRegion CMRegionStack::pop_lock_free() {
328 while (true) {
329 jint index = _index;
330
331 if (index == 0) {
332 return MemRegion();
333 }
334 // Otherwise...
335 jint next_index = index-1;
336 jint res = Atomic::cmpxchg(next_index, &_index, index);
337 if (res == index) {
338 MemRegion mr = _base[next_index];
339 if (mr.start() != NULL) {
340 assert(mr.end() != NULL, "invariant");
341 assert(mr.word_size() > 0, "invariant");
342 return mr;
343 } else {
344 // that entry was invalidated... let's skip it
345 assert(mr.end() == NULL, "invariant");
346 }
347 }
348 // Otherwise, we need to try again.
349 }
350 }
351
352 #if 0
353 // The routines that manipulate the region stack with a lock are
354 // not currently used. They should be retained, however, as a
355 // diagnostic aid.
356
357 void CMRegionStack::push_with_lock(MemRegion mr) {
358 assert(mr.word_size() > 0, "Precondition");
359 MutexLockerEx x(CMRegionStack_lock, Mutex::_no_safepoint_check_flag);
360
361 if (isFull()) {
362 _overflow = true;
363 return;
364 }
365
366 _base[_index] = mr;
367 _index += 1;
368 }
369
370 MemRegion CMRegionStack::pop_with_lock() {
371 MutexLockerEx x(CMRegionStack_lock, Mutex::_no_safepoint_check_flag);
372
373 while (true) {
374 if (_index == 0) {
375 return MemRegion();
376 }
377 _index -= 1;
378
379 MemRegion mr = _base[_index];
380 if (mr.start() != NULL) {
381 assert(mr.end() != NULL, "invariant");
382 assert(mr.word_size() > 0, "invariant");
383 return mr;
384 } else {
385 // that entry was invalidated... let's skip it
386 assert(mr.end() == NULL, "invariant");
387 }
388 }
389 }
390 #endif
391
392 bool CMRegionStack::invalidate_entries_into_cset() {
393 bool result = false;
394 G1CollectedHeap* g1h = G1CollectedHeap::heap();
395 for (int i = 0; i < _oops_do_bound; ++i) {
396 MemRegion mr = _base[i];
397 if (mr.start() != NULL) {
398 assert(mr.end() != NULL, "invariant");
399 assert(mr.word_size() > 0, "invariant");
400 HeapRegion* hr = g1h->heap_region_containing(mr.start());
401 assert(hr != NULL, "invariant");
402 if (hr->in_collection_set()) {
403 // The region points into the collection set
404 _base[i] = MemRegion();
405 result = true;
406 }
407 } else {
408 // that entry was invalidated... let's skip it
409 assert(mr.end() == NULL, "invariant");
410 }
411 }
412 return result;
413 }
414
415 template<class OopClosureClass>
416 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
417 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
418 || SafepointSynchronize::is_at_safepoint(),
419 "Drain recursion must be yield-safe.");
420 bool res = true;
421 debug_only(_drain_in_progress = true);
422 debug_only(_drain_in_progress_yields = yield_after);
423 while (!isEmpty()) {
424 oop newOop = pop();
425 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
426 assert(newOop->is_oop(), "Expected an oop");
427 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
428 "only grey objects on this stack");
429 // iterate over the oops in this oop, marking and pushing
430 // the ones in CMS generation.
431 newOop->oop_iterate(cl);
432 if (yield_after && _cm->do_yield_check()) {
433 res = false;
434 break;
435 }
436 }
437 debug_only(_drain_in_progress = false);
438 return res;
439 }
440
441 void CMMarkStack::oops_do(OopClosure* f) {
442 if (_index == 0) return;
443 assert(_oops_do_bound != -1 && _oops_do_bound <= _index,
444 "Bound must be set.");
445 for (int i = 0; i < _oops_do_bound; i++) {
446 f->do_oop(&_base[i]);
447 }
448 _oops_do_bound = -1;
449 }
450
451 bool ConcurrentMark::not_yet_marked(oop obj) const {
452 return (_g1h->is_obj_ill(obj)
453 || (_g1h->is_in_permanent(obj)
454 && !nextMarkBitMap()->isMarked((HeapWord*)obj)));
455 }
456
457 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
458 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
459 #endif // _MSC_VER
460
461 ConcurrentMark::ConcurrentMark(ReservedSpace rs,
462 int max_regions) :
463 _markBitMap1(rs, MinObjAlignment - 1),
464 _markBitMap2(rs, MinObjAlignment - 1),
465
466 _parallel_marking_threads(0),
467 _sleep_factor(0.0),
468 _marking_task_overhead(1.0),
469 _cleanup_sleep_factor(0.0),
470 _cleanup_task_overhead(1.0),
471 _cleanup_list("Cleanup List"),
472 _region_bm(max_regions, false /* in_resource_area*/),
473 _card_bm((rs.size() + CardTableModRefBS::card_size - 1) >>
474 CardTableModRefBS::card_shift,
475 false /* in_resource_area*/),
476 _prevMarkBitMap(&_markBitMap1),
477 _nextMarkBitMap(&_markBitMap2),
478 _at_least_one_mark_complete(false),
479
480 _markStack(this),
481 _regionStack(),
482 // _finger set in set_non_marking_state
483
484 _max_task_num(MAX2(ParallelGCThreads, (size_t)1)),
485 // _active_tasks set in set_non_marking_state
486 // _tasks set inside the constructor
487 _task_queues(new CMTaskQueueSet((int) _max_task_num)),
488 _terminator(ParallelTaskTerminator((int) _max_task_num, _task_queues)),
489
490 _has_overflown(false),
491 _concurrent(false),
492 _has_aborted(false),
493 _restart_for_overflow(false),
494 _concurrent_marking_in_progress(false),
495 _should_gray_objects(false),
496
497 // _verbose_level set below
498
499 _init_times(),
500 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
501 _cleanup_times(),
502 _total_counting_time(0.0),
503 _total_rs_scrub_time(0.0),
504
505 _parallel_workers(NULL) {
506 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
507 if (verbose_level < no_verbose) {
508 verbose_level = no_verbose;
509 }
510 if (verbose_level > high_verbose) {
511 verbose_level = high_verbose;
512 }
513 _verbose_level = verbose_level;
514
515 if (verbose_low()) {
516 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
517 "heap end = "PTR_FORMAT, _heap_start, _heap_end);
518 }
519
520 _markStack.allocate(MarkStackSize);
521 _regionStack.allocate(G1MarkRegionStackSize);
522
523 // Create & start a ConcurrentMark thread.
524 _cmThread = new ConcurrentMarkThread(this);
525 assert(cmThread() != NULL, "CM Thread should have been created");
526 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
527
528 _g1h = G1CollectedHeap::heap();
529 assert(CGC_lock != NULL, "Where's the CGC_lock?");
530 assert(_markBitMap1.covers(rs), "_markBitMap1 inconsistency");
531 assert(_markBitMap2.covers(rs), "_markBitMap2 inconsistency");
532
533 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
534 satb_qs.set_buffer_size(G1SATBBufferSize);
535
536 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_task_num);
537 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_task_num);
538
539 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
540 _active_tasks = _max_task_num;
541 for (int i = 0; i < (int) _max_task_num; ++i) {
542 CMTaskQueue* task_queue = new CMTaskQueue();
543 task_queue->initialize();
544 _task_queues->register_queue(i, task_queue);
545
546 _tasks[i] = new CMTask(i, this, task_queue, _task_queues);
547 _accum_task_vtime[i] = 0.0;
548 }
549
550 if (ConcGCThreads > ParallelGCThreads) {
551 vm_exit_during_initialization("Can't have more ConcGCThreads "
552 "than ParallelGCThreads.");
553 }
554 if (ParallelGCThreads == 0) {
555 // if we are not running with any parallel GC threads we will not
556 // spawn any marking threads either
557 _parallel_marking_threads = 0;
558 _sleep_factor = 0.0;
559 _marking_task_overhead = 1.0;
560 } else {
561 if (ConcGCThreads > 0) {
562 // notice that ConcGCThreads overwrites G1MarkingOverheadPercent
563 // if both are set
564
565 _parallel_marking_threads = ConcGCThreads;
566 _sleep_factor = 0.0;
567 _marking_task_overhead = 1.0;
568 } else if (G1MarkingOverheadPercent > 0) {
569 // we will calculate the number of parallel marking threads
570 // based on a target overhead with respect to the soft real-time
571 // goal
572
573 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
574 double overall_cm_overhead =
575 (double) MaxGCPauseMillis * marking_overhead /
576 (double) GCPauseIntervalMillis;
577 double cpu_ratio = 1.0 / (double) os::processor_count();
578 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
579 double marking_task_overhead =
580 overall_cm_overhead / marking_thread_num *
581 (double) os::processor_count();
582 double sleep_factor =
583 (1.0 - marking_task_overhead) / marking_task_overhead;
584
585 _parallel_marking_threads = (size_t) marking_thread_num;
586 _sleep_factor = sleep_factor;
587 _marking_task_overhead = marking_task_overhead;
588 } else {
589 _parallel_marking_threads = MAX2((ParallelGCThreads + 2) / 4, (size_t)1);
590 _sleep_factor = 0.0;
591 _marking_task_overhead = 1.0;
592 }
593
594 if (parallel_marking_threads() > 1) {
595 _cleanup_task_overhead = 1.0;
596 } else {
597 _cleanup_task_overhead = marking_task_overhead();
598 }
599 _cleanup_sleep_factor =
600 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
601
602 #if 0
603 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
604 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
605 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
606 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
607 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
608 #endif
609
610 guarantee(parallel_marking_threads() > 0, "peace of mind");
611 _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
612 (int) _parallel_marking_threads, false, true);
613 if (_parallel_workers == NULL) {
614 vm_exit_during_initialization("Failed necessary allocation.");
615 } else {
616 _parallel_workers->initialize_workers();
617 }
618 }
619
620 // so that the call below can read a sensible value
621 _heap_start = (HeapWord*) rs.base();
622 set_non_marking_state();
623 }
624
625 void ConcurrentMark::update_g1_committed(bool force) {
626 // If concurrent marking is not in progress, then we do not need to
627 // update _heap_end. This has a subtle and important
628 // side-effect. Imagine that two evacuation pauses happen between
629 // marking completion and remark. The first one can grow the
630 // heap (hence now the finger is below the heap end). Then, the
631 // second one could unnecessarily push regions on the region
632 // stack. This causes the invariant that the region stack is empty
633 // at the beginning of remark to be false. By ensuring that we do
634 // not observe heap expansions after marking is complete, then we do
635 // not have this problem.
636 if (!concurrent_marking_in_progress() && !force) return;
637
638 MemRegion committed = _g1h->g1_committed();
639 assert(committed.start() == _heap_start, "start shouldn't change");
640 HeapWord* new_end = committed.end();
641 if (new_end > _heap_end) {
642 // The heap has been expanded.
643
644 _heap_end = new_end;
645 }
646 // Notice that the heap can also shrink. However, this only happens
647 // during a Full GC (at least currently) and the entire marking
648 // phase will bail out and the task will not be restarted. So, let's
649 // do nothing.
650 }
651
652 void ConcurrentMark::reset() {
653 // Starting values for these two. This should be called in a STW
654 // phase. CM will be notified of any future g1_committed expansions
655 // will be at the end of evacuation pauses, when tasks are
656 // inactive.
657 MemRegion committed = _g1h->g1_committed();
658 _heap_start = committed.start();
659 _heap_end = committed.end();
660
661 // Separated the asserts so that we know which one fires.
662 assert(_heap_start != NULL, "heap bounds should look ok");
663 assert(_heap_end != NULL, "heap bounds should look ok");
664 assert(_heap_start < _heap_end, "heap bounds should look ok");
665
666 // reset all the marking data structures and any necessary flags
667 clear_marking_state();
668
669 if (verbose_low()) {
670 gclog_or_tty->print_cr("[global] resetting");
671 }
672
673 // We do reset all of them, since different phases will use
674 // different number of active threads. So, it's easiest to have all
675 // of them ready.
676 for (int i = 0; i < (int) _max_task_num; ++i) {
677 _tasks[i]->reset(_nextMarkBitMap);
678 }
679
680 // we need this to make sure that the flag is on during the evac
681 // pause with initial mark piggy-backed
682 set_concurrent_marking_in_progress();
683 }
684
685 void ConcurrentMark::set_phase(size_t active_tasks, bool concurrent) {
686 assert(active_tasks <= _max_task_num, "we should not have more");
687
688 _active_tasks = active_tasks;
689 // Need to update the three data structures below according to the
690 // number of active threads for this phase.
691 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
692 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
693 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
694
695 _concurrent = concurrent;
696 // We propagate this to all tasks, not just the active ones.
697 for (int i = 0; i < (int) _max_task_num; ++i)
698 _tasks[i]->set_concurrent(concurrent);
699
700 if (concurrent) {
701 set_concurrent_marking_in_progress();
702 } else {
703 // We currently assume that the concurrent flag has been set to
704 // false before we start remark. At this point we should also be
705 // in a STW phase.
706 assert(!concurrent_marking_in_progress(), "invariant");
707 assert(_finger == _heap_end, "only way to get here");
708 update_g1_committed(true);
709 }
710 }
711
712 void ConcurrentMark::set_non_marking_state() {
713 // We set the global marking state to some default values when we're
714 // not doing marking.
715 clear_marking_state();
716 _active_tasks = 0;
717 clear_concurrent_marking_in_progress();
718 }
719
720 ConcurrentMark::~ConcurrentMark() {
721 for (int i = 0; i < (int) _max_task_num; ++i) {
722 delete _task_queues->queue(i);
723 delete _tasks[i];
724 }
725 delete _task_queues;
726 FREE_C_HEAP_ARRAY(CMTask*, _max_task_num);
727 }
728
729 // This closure is used to mark refs into the g1 generation
730 // from external roots in the CMS bit map.
731 // Called at the first checkpoint.
732 //
733
734 void ConcurrentMark::clearNextBitmap() {
735 G1CollectedHeap* g1h = G1CollectedHeap::heap();
736 G1CollectorPolicy* g1p = g1h->g1_policy();
737
738 // Make sure that the concurrent mark thread looks to still be in
739 // the current cycle.
740 guarantee(cmThread()->during_cycle(), "invariant");
741
742 // We are finishing up the current cycle by clearing the next
743 // marking bitmap and getting it ready for the next cycle. During
744 // this time no other cycle can start. So, let's make sure that this
745 // is the case.
746 guarantee(!g1h->mark_in_progress(), "invariant");
747
748 // clear the mark bitmap (no grey objects to start with).
749 // We need to do this in chunks and offer to yield in between
750 // each chunk.
751 HeapWord* start = _nextMarkBitMap->startWord();
752 HeapWord* end = _nextMarkBitMap->endWord();
753 HeapWord* cur = start;
754 size_t chunkSize = M;
755 while (cur < end) {
756 HeapWord* next = cur + chunkSize;
757 if (next > end) {
758 next = end;
759 }
760 MemRegion mr(cur,next);
761 _nextMarkBitMap->clearRange(mr);
762 cur = next;
763 do_yield_check();
764
765 // Repeat the asserts from above. We'll do them as asserts here to
766 // minimize their overhead on the product. However, we'll have
767 // them as guarantees at the beginning / end of the bitmap
768 // clearing to get some checking in the product.
769 assert(cmThread()->during_cycle(), "invariant");
770 assert(!g1h->mark_in_progress(), "invariant");
771 }
772
773 // Repeat the asserts from above.
774 guarantee(cmThread()->during_cycle(), "invariant");
775 guarantee(!g1h->mark_in_progress(), "invariant");
776 }
777
778 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
779 public:
780 bool doHeapRegion(HeapRegion* r) {
781 if (!r->continuesHumongous()) {
782 r->note_start_of_marking(true);
783 }
784 return false;
785 }
786 };
787
788 void ConcurrentMark::checkpointRootsInitialPre() {
789 G1CollectedHeap* g1h = G1CollectedHeap::heap();
790 G1CollectorPolicy* g1p = g1h->g1_policy();
791
792 _has_aborted = false;
793
794 #ifndef PRODUCT
795 if (G1PrintReachableAtInitialMark) {
796 print_reachable("at-cycle-start",
797 VerifyOption_G1UsePrevMarking, true /* all */);
798 }
799 #endif
800
801 // Initialise marking structures. This has to be done in a STW phase.
802 reset();
803 }
804
805
806 void ConcurrentMark::checkpointRootsInitialPost() {
807 G1CollectedHeap* g1h = G1CollectedHeap::heap();
808
809 // If we force an overflow during remark, the remark operation will
810 // actually abort and we'll restart concurrent marking. If we always
811 // force an oveflow during remark we'll never actually complete the
812 // marking phase. So, we initilize this here, at the start of the
813 // cycle, so that at the remaining overflow number will decrease at
814 // every remark and we'll eventually not need to cause one.
815 force_overflow_stw()->init();
816
817 // For each region note start of marking.
818 NoteStartOfMarkHRClosure startcl;
819 g1h->heap_region_iterate(&startcl);
820
821 // Start Concurrent Marking weak-reference discovery.
822 ReferenceProcessor* rp = g1h->ref_processor_cm();
823 // enable ("weak") refs discovery
824 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
825 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
826
827 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
828 // This is the start of the marking cycle, we're expected all
829 // threads to have SATB queues with active set to false.
830 satb_mq_set.set_active_all_threads(true, /* new active value */
831 false /* expected_active */);
832
833 // update_g1_committed() will be called at the end of an evac pause
834 // when marking is on. So, it's also called at the end of the
835 // initial-mark pause to update the heap end, if the heap expands
836 // during it. No need to call it here.
837 }
838
839 /*
840 * Notice that in the next two methods, we actually leave the STS
841 * during the barrier sync and join it immediately afterwards. If we
842 * do not do this, the following deadlock can occur: one thread could
843 * be in the barrier sync code, waiting for the other thread to also
844 * sync up, whereas another one could be trying to yield, while also
845 * waiting for the other threads to sync up too.
846 *
847 * Note, however, that this code is also used during remark and in
848 * this case we should not attempt to leave / enter the STS, otherwise
849 * we'll either hit an asseert (debug / fastdebug) or deadlock
850 * (product). So we should only leave / enter the STS if we are
851 * operating concurrently.
852 *
853 * Because the thread that does the sync barrier has left the STS, it
854 * is possible to be suspended for a Full GC or an evacuation pause
855 * could occur. This is actually safe, since the entering the sync
856 * barrier is one of the last things do_marking_step() does, and it
857 * doesn't manipulate any data structures afterwards.
858 */
859
860 void ConcurrentMark::enter_first_sync_barrier(int task_num) {
861 if (verbose_low()) {
862 gclog_or_tty->print_cr("[%d] entering first barrier", task_num);
863 }
864
865 if (concurrent()) {
866 ConcurrentGCThread::stsLeave();
867 }
868 _first_overflow_barrier_sync.enter();
869 if (concurrent()) {
870 ConcurrentGCThread::stsJoin();
871 }
872 // at this point everyone should have synced up and not be doing any
873 // more work
874
875 if (verbose_low()) {
876 gclog_or_tty->print_cr("[%d] leaving first barrier", task_num);
877 }
878
879 // let task 0 do this
880 if (task_num == 0) {
881 // task 0 is responsible for clearing the global data structures
882 // We should be here because of an overflow. During STW we should
883 // not clear the overflow flag since we rely on it being true when
884 // we exit this method to abort the pause and restart concurent
885 // marking.
886 clear_marking_state(concurrent() /* clear_overflow */);
887 force_overflow()->update();
888
889 if (PrintGC) {
890 gclog_or_tty->date_stamp(PrintGCDateStamps);
891 gclog_or_tty->stamp(PrintGCTimeStamps);
892 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
893 }
894 }
895
896 // after this, each task should reset its own data structures then
897 // then go into the second barrier
898 }
899
900 void ConcurrentMark::enter_second_sync_barrier(int task_num) {
901 if (verbose_low()) {
902 gclog_or_tty->print_cr("[%d] entering second barrier", task_num);
903 }
904
905 if (concurrent()) {
906 ConcurrentGCThread::stsLeave();
907 }
908 _second_overflow_barrier_sync.enter();
909 if (concurrent()) {
910 ConcurrentGCThread::stsJoin();
911 }
912 // at this point everything should be re-initialised and ready to go
913
914 if (verbose_low()) {
915 gclog_or_tty->print_cr("[%d] leaving second barrier", task_num);
916 }
917 }
918
919 #ifndef PRODUCT
920 void ForceOverflowSettings::init() {
921 _num_remaining = G1ConcMarkForceOverflow;
922 _force = false;
923 update();
924 }
925
926 void ForceOverflowSettings::update() {
927 if (_num_remaining > 0) {
928 _num_remaining -= 1;
929 _force = true;
930 } else {
931 _force = false;
932 }
933 }
934
935 bool ForceOverflowSettings::should_force() {
936 if (_force) {
937 _force = false;
938 return true;
939 } else {
940 return false;
941 }
942 }
943 #endif // !PRODUCT
944
945 void ConcurrentMark::grayRoot(oop p) {
946 HeapWord* addr = (HeapWord*) p;
947 // We can't really check against _heap_start and _heap_end, since it
948 // is possible during an evacuation pause with piggy-backed
949 // initial-mark that the committed space is expanded during the
950 // pause without CM observing this change. So the assertions below
951 // is a bit conservative; but better than nothing.
952 assert(_g1h->g1_committed().contains(addr),
953 "address should be within the heap bounds");
954
955 if (!_nextMarkBitMap->isMarked(addr)) {
956 _nextMarkBitMap->parMark(addr);
957 }
958 }
959
960 void ConcurrentMark::grayRegionIfNecessary(MemRegion mr) {
961 // The objects on the region have already been marked "in bulk" by
962 // the caller. We only need to decide whether to push the region on
963 // the region stack or not.
964
965 if (!concurrent_marking_in_progress() || !_should_gray_objects) {
966 // We're done with marking and waiting for remark. We do not need to
967 // push anything else on the region stack.
968 return;
969 }
970
971 HeapWord* finger = _finger;
972
973 if (verbose_low()) {
974 gclog_or_tty->print_cr("[global] attempting to push "
975 "region ["PTR_FORMAT", "PTR_FORMAT"), finger is at "
976 PTR_FORMAT, mr.start(), mr.end(), finger);
977 }
978
979 if (mr.start() < finger) {
980 // The finger is always heap region aligned and it is not possible
981 // for mr to span heap regions.
982 assert(mr.end() <= finger, "invariant");
983
984 // Separated the asserts so that we know which one fires.
985 assert(mr.start() <= mr.end(),
986 "region boundaries should fall within the committed space");
987 assert(_heap_start <= mr.start(),
988 "region boundaries should fall within the committed space");
989 assert(mr.end() <= _heap_end,
990 "region boundaries should fall within the committed space");
991 if (verbose_low()) {
992 gclog_or_tty->print_cr("[global] region ["PTR_FORMAT", "PTR_FORMAT") "
993 "below the finger, pushing it",
994 mr.start(), mr.end());
995 }
996
997 if (!region_stack_push_lock_free(mr)) {
998 if (verbose_low()) {
999 gclog_or_tty->print_cr("[global] region stack has overflown.");
1000 }
1001 }
1002 }
1003 }
1004
1005 void ConcurrentMark::markAndGrayObjectIfNecessary(oop p) {
1006 // The object is not marked by the caller. We need to at least mark
1007 // it and maybe push in on the stack.
1008
1009 HeapWord* addr = (HeapWord*)p;
1010 if (!_nextMarkBitMap->isMarked(addr)) {
1011 // We definitely need to mark it, irrespective whether we bail out
1012 // because we're done with marking.
1013 if (_nextMarkBitMap->parMark(addr)) {
1014 if (!concurrent_marking_in_progress() || !_should_gray_objects) {
1015 // If we're done with concurrent marking and we're waiting for
1016 // remark, then we're not pushing anything on the stack.
1017 return;
1018 }
1019
1020 // No OrderAccess:store_load() is needed. It is implicit in the
1021 // CAS done in parMark(addr) above
1022 HeapWord* finger = _finger;
1023
1024 if (addr < finger) {
1025 if (!mark_stack_push(oop(addr))) {
1026 if (verbose_low()) {
1027 gclog_or_tty->print_cr("[global] global stack overflow "
1028 "during parMark");
1029 }
1030 }
1031 }
1032 }
1033 }
1034 }
1035
1036 class CMConcurrentMarkingTask: public AbstractGangTask {
1037 private:
1038 ConcurrentMark* _cm;
1039 ConcurrentMarkThread* _cmt;
1040
1041 public:
1042 void work(int worker_i) {
1043 assert(Thread::current()->is_ConcurrentGC_thread(),
1044 "this should only be done by a conc GC thread");
1045 ResourceMark rm;
1046
1047 double start_vtime = os::elapsedVTime();
1048
1049 ConcurrentGCThread::stsJoin();
1050
1051 assert((size_t) worker_i < _cm->active_tasks(), "invariant");
1052 CMTask* the_task = _cm->task(worker_i);
1053 the_task->record_start_time();
1054 if (!_cm->has_aborted()) {
1055 do {
1056 double start_vtime_sec = os::elapsedVTime();
1057 double start_time_sec = os::elapsedTime();
1058 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1059
1060 the_task->do_marking_step(mark_step_duration_ms,
1061 true /* do_stealing */,
1062 true /* do_termination */);
1063
1064 double end_time_sec = os::elapsedTime();
1065 double end_vtime_sec = os::elapsedVTime();
1066 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1067 double elapsed_time_sec = end_time_sec - start_time_sec;
1068 _cm->clear_has_overflown();
1069
1070 bool ret = _cm->do_yield_check(worker_i);
1071
1072 jlong sleep_time_ms;
1073 if (!_cm->has_aborted() && the_task->has_aborted()) {
1074 sleep_time_ms =
1075 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1076 ConcurrentGCThread::stsLeave();
1077 os::sleep(Thread::current(), sleep_time_ms, false);
1078 ConcurrentGCThread::stsJoin();
1079 }
1080 double end_time2_sec = os::elapsedTime();
1081 double elapsed_time2_sec = end_time2_sec - start_time_sec;
1082
1083 #if 0
1084 gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, "
1085 "overhead %1.4lf",
1086 elapsed_vtime_sec * 1000.0, (double) sleep_time_ms,
1087 the_task->conc_overhead(os::elapsedTime()) * 8.0);
1088 gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms",
1089 elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0);
1090 #endif
1091 } while (!_cm->has_aborted() && the_task->has_aborted());
1092 }
1093 the_task->record_end_time();
1094 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1095
1096 ConcurrentGCThread::stsLeave();
1097
1098 double end_vtime = os::elapsedVTime();
1099 _cm->update_accum_task_vtime(worker_i, end_vtime - start_vtime);
1100 }
1101
1102 CMConcurrentMarkingTask(ConcurrentMark* cm,
1103 ConcurrentMarkThread* cmt) :
1104 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1105
1106 ~CMConcurrentMarkingTask() { }
1107 };
1108
1109 void ConcurrentMark::markFromRoots() {
1110 // we might be tempted to assert that:
1111 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1112 // "inconsistent argument?");
1113 // However that wouldn't be right, because it's possible that
1114 // a safepoint is indeed in progress as a younger generation
1115 // stop-the-world GC happens even as we mark in this generation.
1116
1117 _restart_for_overflow = false;
1118
1119 size_t active_workers = MAX2((size_t) 1, parallel_marking_threads());
1120 force_overflow_conc()->init();
1121 set_phase(active_workers, true /* concurrent */);
1122
1123 CMConcurrentMarkingTask markingTask(this, cmThread());
1124 if (parallel_marking_threads() > 0) {
1125 _parallel_workers->run_task(&markingTask);
1126 } else {
1127 markingTask.work(0);
1128 }
1129 print_stats();
1130 }
1131
1132 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1133 // world is stopped at this checkpoint
1134 assert(SafepointSynchronize::is_at_safepoint(),
1135 "world should be stopped");
1136
1137 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1138
1139 // If a full collection has happened, we shouldn't do this.
1140 if (has_aborted()) {
1141 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1142 return;
1143 }
1144
1145 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1146
1147 if (VerifyDuringGC) {
1148 HandleMark hm; // handle scope
1149 gclog_or_tty->print(" VerifyDuringGC:(before)");
1150 Universe::heap()->prepare_for_verify();
1151 Universe::verify(/* allow dirty */ true,
1152 /* silent */ false,
1153 /* option */ VerifyOption_G1UsePrevMarking);
1154 }
1155
1156 G1CollectorPolicy* g1p = g1h->g1_policy();
1157 g1p->record_concurrent_mark_remark_start();
1158
1159 double start = os::elapsedTime();
1160
1161 checkpointRootsFinalWork();
1162
1163 double mark_work_end = os::elapsedTime();
1164
1165 weakRefsWork(clear_all_soft_refs);
1166
1167 if (has_overflown()) {
1168 // Oops. We overflowed. Restart concurrent marking.
1169 _restart_for_overflow = true;
1170 // Clear the flag. We do not need it any more.
1171 clear_has_overflown();
1172 if (G1TraceMarkStackOverflow) {
1173 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1174 }
1175 } else {
1176 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1177 // We're done with marking.
1178 // This is the end of the marking cycle, we're expected all
1179 // threads to have SATB queues with active set to true.
1180 satb_mq_set.set_active_all_threads(false, /* new active value */
1181 true /* expected_active */);
1182
1183 if (VerifyDuringGC) {
1184 HandleMark hm; // handle scope
1185 gclog_or_tty->print(" VerifyDuringGC:(after)");
1186 Universe::heap()->prepare_for_verify();
1187 Universe::verify(/* allow dirty */ true,
1188 /* silent */ false,
1189 /* option */ VerifyOption_G1UseNextMarking);
1190 }
1191 assert(!restart_for_overflow(), "sanity");
1192 }
1193
1194 // Reset the marking state if marking completed
1195 if (!restart_for_overflow()) {
1196 set_non_marking_state();
1197 }
1198
1199 #if VERIFY_OBJS_PROCESSED
1200 _scan_obj_cl.objs_processed = 0;
1201 ThreadLocalObjQueue::objs_enqueued = 0;
1202 #endif
1203
1204 // Statistics
1205 double now = os::elapsedTime();
1206 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1207 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1208 _remark_times.add((now - start) * 1000.0);
1209
1210 g1p->record_concurrent_mark_remark_end();
1211 }
1212
1213 #define CARD_BM_TEST_MODE 0
1214
1215 class CalcLiveObjectsClosure: public HeapRegionClosure {
1216
1217 CMBitMapRO* _bm;
1218 ConcurrentMark* _cm;
1219 bool _changed;
1220 bool _yield;
1221 size_t _words_done;
1222 size_t _tot_live;
1223 size_t _tot_used;
1224 size_t _regions_done;
1225 double _start_vtime_sec;
1226
1227 BitMap* _region_bm;
1228 BitMap* _card_bm;
1229 intptr_t _bottom_card_num;
1230 bool _final;
1231
1232 void mark_card_num_range(intptr_t start_card_num, intptr_t last_card_num) {
1233 for (intptr_t i = start_card_num; i <= last_card_num; i++) {
1234 #if CARD_BM_TEST_MODE
1235 guarantee(_card_bm->at(i - _bottom_card_num), "Should already be set.");
1236 #else
1237 _card_bm->par_at_put(i - _bottom_card_num, 1);
1238 #endif
1239 }
1240 }
1241
1242 public:
1243 CalcLiveObjectsClosure(bool final,
1244 CMBitMapRO *bm, ConcurrentMark *cm,
1245 BitMap* region_bm, BitMap* card_bm) :
1246 _bm(bm), _cm(cm), _changed(false), _yield(true),
1247 _words_done(0), _tot_live(0), _tot_used(0),
1248 _region_bm(region_bm), _card_bm(card_bm),_final(final),
1249 _regions_done(0), _start_vtime_sec(0.0)
1250 {
1251 _bottom_card_num =
1252 intptr_t(uintptr_t(G1CollectedHeap::heap()->reserved_region().start()) >>
1253 CardTableModRefBS::card_shift);
1254 }
1255
1256 // It takes a region that's not empty (i.e., it has at least one
1257 // live object in it and sets its corresponding bit on the region
1258 // bitmap to 1. If the region is "starts humongous" it will also set
1259 // to 1 the bits on the region bitmap that correspond to its
1260 // associated "continues humongous" regions.
1261 void set_bit_for_region(HeapRegion* hr) {
1262 assert(!hr->continuesHumongous(), "should have filtered those out");
1263
1264 size_t index = hr->hrs_index();
1265 if (!hr->startsHumongous()) {
1266 // Normal (non-humongous) case: just set the bit.
1267 _region_bm->par_at_put((BitMap::idx_t) index, true);
1268 } else {
1269 // Starts humongous case: calculate how many regions are part of
1270 // this humongous region and then set the bit range. It might
1271 // have been a bit more efficient to look at the object that
1272 // spans these humongous regions to calculate their number from
1273 // the object's size. However, it's a good idea to calculate
1274 // this based on the metadata itself, and not the region
1275 // contents, so that this code is not aware of what goes into
1276 // the humongous regions (in case this changes in the future).
1277 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1278 size_t end_index = index + 1;
1279 while (end_index < g1h->n_regions()) {
1280 HeapRegion* chr = g1h->region_at(end_index);
1281 if (!chr->continuesHumongous()) break;
1282 end_index += 1;
1283 }
1284 _region_bm->par_at_put_range((BitMap::idx_t) index,
1285 (BitMap::idx_t) end_index, true);
1286 }
1287 }
1288
1289 bool doHeapRegion(HeapRegion* hr) {
1290 if (!_final && _regions_done == 0) {
1291 _start_vtime_sec = os::elapsedVTime();
1292 }
1293
1294 if (hr->continuesHumongous()) {
1295 // We will ignore these here and process them when their
1296 // associated "starts humongous" region is processed (see
1297 // set_bit_for_heap_region()). Note that we cannot rely on their
1298 // associated "starts humongous" region to have their bit set to
1299 // 1 since, due to the region chunking in the parallel region
1300 // iteration, a "continues humongous" region might be visited
1301 // before its associated "starts humongous".
1302 return false;
1303 }
1304
1305 HeapWord* nextTop = hr->next_top_at_mark_start();
1306 HeapWord* start = hr->top_at_conc_mark_count();
1307 assert(hr->bottom() <= start && start <= hr->end() &&
1308 hr->bottom() <= nextTop && nextTop <= hr->end() &&
1309 start <= nextTop,
1310 "Preconditions.");
1311 // Otherwise, record the number of word's we'll examine.
1312 size_t words_done = (nextTop - start);
1313 // Find the first marked object at or after "start".
1314 start = _bm->getNextMarkedWordAddress(start, nextTop);
1315 size_t marked_bytes = 0;
1316
1317 // Below, the term "card num" means the result of shifting an address
1318 // by the card shift -- address 0 corresponds to card number 0. One
1319 // must subtract the card num of the bottom of the heap to obtain a
1320 // card table index.
1321 // The first card num of the sequence of live cards currently being
1322 // constructed. -1 ==> no sequence.
1323 intptr_t start_card_num = -1;
1324 // The last card num of the sequence of live cards currently being
1325 // constructed. -1 ==> no sequence.
1326 intptr_t last_card_num = -1;
1327
1328 while (start < nextTop) {
1329 if (_yield && _cm->do_yield_check()) {
1330 // We yielded. It might be for a full collection, in which case
1331 // all bets are off; terminate the traversal.
1332 if (_cm->has_aborted()) {
1333 _changed = false;
1334 return true;
1335 } else {
1336 // Otherwise, it might be a collection pause, and the region
1337 // we're looking at might be in the collection set. We'll
1338 // abandon this region.
1339 return false;
1340 }
1341 }
1342 oop obj = oop(start);
1343 int obj_sz = obj->size();
1344 // The card num of the start of the current object.
1345 intptr_t obj_card_num =
1346 intptr_t(uintptr_t(start) >> CardTableModRefBS::card_shift);
1347
1348 HeapWord* obj_last = start + obj_sz - 1;
1349 intptr_t obj_last_card_num =
1350 intptr_t(uintptr_t(obj_last) >> CardTableModRefBS::card_shift);
1351
1352 if (obj_card_num != last_card_num) {
1353 if (start_card_num == -1) {
1354 assert(last_card_num == -1, "Both or neither.");
1355 start_card_num = obj_card_num;
1356 } else {
1357 assert(last_card_num != -1, "Both or neither.");
1358 assert(obj_card_num >= last_card_num, "Inv");
1359 if ((obj_card_num - last_card_num) > 1) {
1360 // Mark the last run, and start a new one.
1361 mark_card_num_range(start_card_num, last_card_num);
1362 start_card_num = obj_card_num;
1363 }
1364 }
1365 #if CARD_BM_TEST_MODE
1366 /*
1367 gclog_or_tty->print_cr("Setting bits from %d/%d.",
1368 obj_card_num - _bottom_card_num,
1369 obj_last_card_num - _bottom_card_num);
1370 */
1371 for (intptr_t j = obj_card_num; j <= obj_last_card_num; j++) {
1372 _card_bm->par_at_put(j - _bottom_card_num, 1);
1373 }
1374 #endif
1375 }
1376 // In any case, we set the last card num.
1377 last_card_num = obj_last_card_num;
1378
1379 marked_bytes += (size_t)obj_sz * HeapWordSize;
1380 // Find the next marked object after this one.
1381 start = _bm->getNextMarkedWordAddress(start + 1, nextTop);
1382 _changed = true;
1383 }
1384 // Handle the last range, if any.
1385 if (start_card_num != -1) {
1386 mark_card_num_range(start_card_num, last_card_num);
1387 }
1388 if (_final) {
1389 // Mark the allocated-since-marking portion...
1390 HeapWord* tp = hr->top();
1391 if (nextTop < tp) {
1392 start_card_num =
1393 intptr_t(uintptr_t(nextTop) >> CardTableModRefBS::card_shift);
1394 last_card_num =
1395 intptr_t(uintptr_t(tp) >> CardTableModRefBS::card_shift);
1396 mark_card_num_range(start_card_num, last_card_num);
1397 // This definitely means the region has live objects.
1398 set_bit_for_region(hr);
1399 }
1400 }
1401
1402 hr->add_to_marked_bytes(marked_bytes);
1403 // Update the live region bitmap.
1404 if (marked_bytes > 0) {
1405 set_bit_for_region(hr);
1406 }
1407 hr->set_top_at_conc_mark_count(nextTop);
1408 _tot_live += hr->next_live_bytes();
1409 _tot_used += hr->used();
1410 _words_done = words_done;
1411
1412 if (!_final) {
1413 ++_regions_done;
1414 if (_regions_done % 10 == 0) {
1415 double end_vtime_sec = os::elapsedVTime();
1416 double elapsed_vtime_sec = end_vtime_sec - _start_vtime_sec;
1417 if (elapsed_vtime_sec > (10.0 / 1000.0)) {
1418 jlong sleep_time_ms =
1419 (jlong) (elapsed_vtime_sec * _cm->cleanup_sleep_factor() * 1000.0);
1420 os::sleep(Thread::current(), sleep_time_ms, false);
1421 _start_vtime_sec = end_vtime_sec;
1422 }
1423 }
1424 }
1425
1426 return false;
1427 }
1428
1429 bool changed() { return _changed; }
1430 void reset() { _changed = false; _words_done = 0; }
1431 void no_yield() { _yield = false; }
1432 size_t words_done() { return _words_done; }
1433 size_t tot_live() { return _tot_live; }
1434 size_t tot_used() { return _tot_used; }
1435 };
1436
1437
1438 void ConcurrentMark::calcDesiredRegions() {
1439 _region_bm.clear();
1440 _card_bm.clear();
1441 CalcLiveObjectsClosure calccl(false /*final*/,
1442 nextMarkBitMap(), this,
1443 &_region_bm, &_card_bm);
1444 G1CollectedHeap *g1h = G1CollectedHeap::heap();
1445 g1h->heap_region_iterate(&calccl);
1446
1447 do {
1448 calccl.reset();
1449 g1h->heap_region_iterate(&calccl);
1450 } while (calccl.changed());
1451 }
1452
1453 class G1ParFinalCountTask: public AbstractGangTask {
1454 protected:
1455 G1CollectedHeap* _g1h;
1456 CMBitMap* _bm;
1457 size_t _n_workers;
1458 size_t *_live_bytes;
1459 size_t *_used_bytes;
1460 BitMap* _region_bm;
1461 BitMap* _card_bm;
1462 public:
1463 G1ParFinalCountTask(G1CollectedHeap* g1h, CMBitMap* bm,
1464 BitMap* region_bm, BitMap* card_bm)
1465 : AbstractGangTask("G1 final counting"), _g1h(g1h),
1466 _bm(bm), _region_bm(region_bm), _card_bm(card_bm) {
1467 if (ParallelGCThreads > 0) {
1468 _n_workers = _g1h->workers()->total_workers();
1469 } else {
1470 _n_workers = 1;
1471 }
1472 _live_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers);
1473 _used_bytes = NEW_C_HEAP_ARRAY(size_t, _n_workers);
1474 }
1475
1476 ~G1ParFinalCountTask() {
1477 FREE_C_HEAP_ARRAY(size_t, _live_bytes);
1478 FREE_C_HEAP_ARRAY(size_t, _used_bytes);
1479 }
1480
1481 void work(int i) {
1482 CalcLiveObjectsClosure calccl(true /*final*/,
1483 _bm, _g1h->concurrent_mark(),
1484 _region_bm, _card_bm);
1485 calccl.no_yield();
1486 if (G1CollectedHeap::use_parallel_gc_threads()) {
1487 _g1h->heap_region_par_iterate_chunked(&calccl, i,
1488 HeapRegion::FinalCountClaimValue);
1489 } else {
1490 _g1h->heap_region_iterate(&calccl);
1491 }
1492 assert(calccl.complete(), "Shouldn't have yielded!");
1493
1494 assert((size_t) i < _n_workers, "invariant");
1495 _live_bytes[i] = calccl.tot_live();
1496 _used_bytes[i] = calccl.tot_used();
1497 }
1498 size_t live_bytes() {
1499 size_t live_bytes = 0;
1500 for (size_t i = 0; i < _n_workers; ++i)
1501 live_bytes += _live_bytes[i];
1502 return live_bytes;
1503 }
1504 size_t used_bytes() {
1505 size_t used_bytes = 0;
1506 for (size_t i = 0; i < _n_workers; ++i)
1507 used_bytes += _used_bytes[i];
1508 return used_bytes;
1509 }
1510 };
1511
1512 class G1ParNoteEndTask;
1513
1514 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1515 G1CollectedHeap* _g1;
1516 int _worker_num;
1517 size_t _max_live_bytes;
1518 size_t _regions_claimed;
1519 size_t _freed_bytes;
1520 FreeRegionList* _local_cleanup_list;
1521 HumongousRegionSet* _humongous_proxy_set;
1522 HRRSCleanupTask* _hrrs_cleanup_task;
1523 double _claimed_region_time;
1524 double _max_region_time;
1525
1526 public:
1527 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1528 int worker_num,
1529 FreeRegionList* local_cleanup_list,
1530 HumongousRegionSet* humongous_proxy_set,
1531 HRRSCleanupTask* hrrs_cleanup_task);
1532 size_t freed_bytes() { return _freed_bytes; }
1533
1534 bool doHeapRegion(HeapRegion *r);
1535
1536 size_t max_live_bytes() { return _max_live_bytes; }
1537 size_t regions_claimed() { return _regions_claimed; }
1538 double claimed_region_time_sec() { return _claimed_region_time; }
1539 double max_region_time_sec() { return _max_region_time; }
1540 };
1541
1542 class G1ParNoteEndTask: public AbstractGangTask {
1543 friend class G1NoteEndOfConcMarkClosure;
1544
1545 protected:
1546 G1CollectedHeap* _g1h;
1547 size_t _max_live_bytes;
1548 size_t _freed_bytes;
1549 FreeRegionList* _cleanup_list;
1550
1551 public:
1552 G1ParNoteEndTask(G1CollectedHeap* g1h,
1553 FreeRegionList* cleanup_list) :
1554 AbstractGangTask("G1 note end"), _g1h(g1h),
1555 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1556
1557 void work(int i) {
1558 double start = os::elapsedTime();
1559 FreeRegionList local_cleanup_list("Local Cleanup List");
1560 HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
1561 HRRSCleanupTask hrrs_cleanup_task;
1562 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, i, &local_cleanup_list,
1563 &humongous_proxy_set,
1564 &hrrs_cleanup_task);
1565 if (G1CollectedHeap::use_parallel_gc_threads()) {
1566 _g1h->heap_region_par_iterate_chunked(&g1_note_end, i,
1567 HeapRegion::NoteEndClaimValue);
1568 } else {
1569 _g1h->heap_region_iterate(&g1_note_end);
1570 }
1571 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1572
1573 // Now update the lists
1574 _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
1575 NULL /* free_list */,
1576 &humongous_proxy_set,
1577 true /* par */);
1578 {
1579 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1580 _max_live_bytes += g1_note_end.max_live_bytes();
1581 _freed_bytes += g1_note_end.freed_bytes();
1582
1583 // If we iterate over the global cleanup list at the end of
1584 // cleanup to do this printing we will not guarantee to only
1585 // generate output for the newly-reclaimed regions (the list
1586 // might not be empty at the beginning of cleanup; we might
1587 // still be working on its previous contents). So we do the
1588 // printing here, before we append the new regions to the global
1589 // cleanup list.
1590
1591 G1HRPrinter* hr_printer = _g1h->hr_printer();
1592 if (hr_printer->is_active()) {
1593 HeapRegionLinkedListIterator iter(&local_cleanup_list);
1594 while (iter.more_available()) {
1595 HeapRegion* hr = iter.get_next();
1596 hr_printer->cleanup(hr);
1597 }
1598 }
1599
1600 _cleanup_list->add_as_tail(&local_cleanup_list);
1601 assert(local_cleanup_list.is_empty(), "post-condition");
1602
1603 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1604 }
1605 double end = os::elapsedTime();
1606 if (G1PrintParCleanupStats) {
1607 gclog_or_tty->print(" Worker thread %d [%8.3f..%8.3f = %8.3f ms] "
1608 "claimed %d regions (tot = %8.3f ms, max = %8.3f ms).\n",
1609 i, start, end, (end-start)*1000.0,
1610 g1_note_end.regions_claimed(),
1611 g1_note_end.claimed_region_time_sec()*1000.0,
1612 g1_note_end.max_region_time_sec()*1000.0);
1613 }
1614 }
1615 size_t max_live_bytes() { return _max_live_bytes; }
1616 size_t freed_bytes() { return _freed_bytes; }
1617 };
1618
1619 class G1ParScrubRemSetTask: public AbstractGangTask {
1620 protected:
1621 G1RemSet* _g1rs;
1622 BitMap* _region_bm;
1623 BitMap* _card_bm;
1624 public:
1625 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1626 BitMap* region_bm, BitMap* card_bm) :
1627 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1628 _region_bm(region_bm), _card_bm(card_bm)
1629 {}
1630
1631 void work(int i) {
1632 if (G1CollectedHeap::use_parallel_gc_threads()) {
1633 _g1rs->scrub_par(_region_bm, _card_bm, i,
1634 HeapRegion::ScrubRemSetClaimValue);
1635 } else {
1636 _g1rs->scrub(_region_bm, _card_bm);
1637 }
1638 }
1639
1640 };
1641
1642 G1NoteEndOfConcMarkClosure::
1643 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1644 int worker_num,
1645 FreeRegionList* local_cleanup_list,
1646 HumongousRegionSet* humongous_proxy_set,
1647 HRRSCleanupTask* hrrs_cleanup_task)
1648 : _g1(g1), _worker_num(worker_num),
1649 _max_live_bytes(0), _regions_claimed(0),
1650 _freed_bytes(0),
1651 _claimed_region_time(0.0), _max_region_time(0.0),
1652 _local_cleanup_list(local_cleanup_list),
1653 _humongous_proxy_set(humongous_proxy_set),
1654 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1655
1656 bool G1NoteEndOfConcMarkClosure::doHeapRegion(HeapRegion *hr) {
1657 // We use a claim value of zero here because all regions
1658 // were claimed with value 1 in the FinalCount task.
1659 hr->reset_gc_time_stamp();
1660 if (!hr->continuesHumongous()) {
1661 double start = os::elapsedTime();
1662 _regions_claimed++;
1663 hr->note_end_of_marking();
1664 _max_live_bytes += hr->max_live_bytes();
1665 _g1->free_region_if_empty(hr,
1666 &_freed_bytes,
1667 _local_cleanup_list,
1668 _humongous_proxy_set,
1669 _hrrs_cleanup_task,
1670 true /* par */);
1671 double region_time = (os::elapsedTime() - start);
1672 _claimed_region_time += region_time;
1673 if (region_time > _max_region_time) {
1674 _max_region_time = region_time;
1675 }
1676 }
1677 return false;
1678 }
1679
1680 void ConcurrentMark::cleanup() {
1681 // world is stopped at this checkpoint
1682 assert(SafepointSynchronize::is_at_safepoint(),
1683 "world should be stopped");
1684 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1685
1686 // If a full collection has happened, we shouldn't do this.
1687 if (has_aborted()) {
1688 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1689 return;
1690 }
1691
1692 g1h->verify_region_sets_optional();
1693
1694 if (VerifyDuringGC) {
1695 HandleMark hm; // handle scope
1696 gclog_or_tty->print(" VerifyDuringGC:(before)");
1697 Universe::heap()->prepare_for_verify();
1698 Universe::verify(/* allow dirty */ true,
1699 /* silent */ false,
1700 /* option */ VerifyOption_G1UsePrevMarking);
1701 }
1702
1703 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1704 g1p->record_concurrent_mark_cleanup_start();
1705
1706 double start = os::elapsedTime();
1707
1708 HeapRegionRemSet::reset_for_cleanup_tasks();
1709
1710 // Do counting once more with the world stopped for good measure.
1711 G1ParFinalCountTask g1_par_count_task(g1h, nextMarkBitMap(),
1712 &_region_bm, &_card_bm);
1713 if (G1CollectedHeap::use_parallel_gc_threads()) {
1714 assert(g1h->check_heap_region_claim_values(
1715 HeapRegion::InitialClaimValue),
1716 "sanity check");
1717
1718 int n_workers = g1h->workers()->total_workers();
1719 g1h->set_par_threads(n_workers);
1720 g1h->workers()->run_task(&g1_par_count_task);
1721 g1h->set_par_threads(0);
1722
1723 assert(g1h->check_heap_region_claim_values(
1724 HeapRegion::FinalCountClaimValue),
1725 "sanity check");
1726 } else {
1727 g1_par_count_task.work(0);
1728 }
1729
1730 size_t known_garbage_bytes =
1731 g1_par_count_task.used_bytes() - g1_par_count_task.live_bytes();
1732 g1p->set_known_garbage_bytes(known_garbage_bytes);
1733
1734 size_t start_used_bytes = g1h->used();
1735 _at_least_one_mark_complete = true;
1736 g1h->set_marking_complete();
1737
1738 ergo_verbose4(ErgoConcCycles,
1739 "finish cleanup",
1740 ergo_format_byte("occupancy")
1741 ergo_format_byte("capacity")
1742 ergo_format_byte_perc("known garbage"),
1743 start_used_bytes, g1h->capacity(),
1744 known_garbage_bytes,
1745 ((double) known_garbage_bytes / (double) g1h->capacity()) * 100.0);
1746
1747 double count_end = os::elapsedTime();
1748 double this_final_counting_time = (count_end - start);
1749 if (G1PrintParCleanupStats) {
1750 gclog_or_tty->print_cr("Cleanup:");
1751 gclog_or_tty->print_cr(" Finalize counting: %8.3f ms",
1752 this_final_counting_time*1000.0);
1753 }
1754 _total_counting_time += this_final_counting_time;
1755
1756 if (G1PrintRegionLivenessInfo) {
1757 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
1758 _g1h->heap_region_iterate(&cl);
1759 }
1760
1761 // Install newly created mark bitMap as "prev".
1762 swapMarkBitMaps();
1763
1764 g1h->reset_gc_time_stamp();
1765
1766 // Note end of marking in all heap regions.
1767 double note_end_start = os::elapsedTime();
1768 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
1769 if (G1CollectedHeap::use_parallel_gc_threads()) {
1770 int n_workers = g1h->workers()->total_workers();
1771 g1h->set_par_threads(n_workers);
1772 g1h->workers()->run_task(&g1_par_note_end_task);
1773 g1h->set_par_threads(0);
1774
1775 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
1776 "sanity check");
1777 } else {
1778 g1_par_note_end_task.work(0);
1779 }
1780
1781 if (!cleanup_list_is_empty()) {
1782 // The cleanup list is not empty, so we'll have to process it
1783 // concurrently. Notify anyone else that might be wanting free
1784 // regions that there will be more free regions coming soon.
1785 g1h->set_free_regions_coming();
1786 }
1787 double note_end_end = os::elapsedTime();
1788 if (G1PrintParCleanupStats) {
1789 gclog_or_tty->print_cr(" note end of marking: %8.3f ms.",
1790 (note_end_end - note_end_start)*1000.0);
1791 }
1792
1793
1794 // call below, since it affects the metric by which we sort the heap
1795 // regions.
1796 if (G1ScrubRemSets) {
1797 double rs_scrub_start = os::elapsedTime();
1798 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
1799 if (G1CollectedHeap::use_parallel_gc_threads()) {
1800 int n_workers = g1h->workers()->total_workers();
1801 g1h->set_par_threads(n_workers);
1802 g1h->workers()->run_task(&g1_par_scrub_rs_task);
1803 g1h->set_par_threads(0);
1804
1805 assert(g1h->check_heap_region_claim_values(
1806 HeapRegion::ScrubRemSetClaimValue),
1807 "sanity check");
1808 } else {
1809 g1_par_scrub_rs_task.work(0);
1810 }
1811
1812 double rs_scrub_end = os::elapsedTime();
1813 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
1814 _total_rs_scrub_time += this_rs_scrub_time;
1815 }
1816
1817 // this will also free any regions totally full of garbage objects,
1818 // and sort the regions.
1819 g1h->g1_policy()->record_concurrent_mark_cleanup_end(
1820 g1_par_note_end_task.freed_bytes(),
1821 g1_par_note_end_task.max_live_bytes());
1822
1823 // Statistics.
1824 double end = os::elapsedTime();
1825 _cleanup_times.add((end - start) * 1000.0);
1826
1827 // G1CollectedHeap::heap()->print();
1828 // gclog_or_tty->print_cr("HEAP GC TIME STAMP : %d",
1829 // G1CollectedHeap::heap()->get_gc_time_stamp());
1830
1831 if (PrintGC || PrintGCDetails) {
1832 g1h->print_size_transition(gclog_or_tty,
1833 start_used_bytes,
1834 g1h->used(),
1835 g1h->capacity());
1836 }
1837
1838 size_t cleaned_up_bytes = start_used_bytes - g1h->used();
1839 g1p->decrease_known_garbage_bytes(cleaned_up_bytes);
1840
1841 // Clean up will have freed any regions completely full of garbage.
1842 // Update the soft reference policy with the new heap occupancy.
1843 Universe::update_heap_info_at_gc();
1844
1845 // We need to make this be a "collection" so any collection pause that
1846 // races with it goes around and waits for completeCleanup to finish.
1847 g1h->increment_total_collections();
1848
1849 if (VerifyDuringGC) {
1850 HandleMark hm; // handle scope
1851 gclog_or_tty->print(" VerifyDuringGC:(after)");
1852 Universe::heap()->prepare_for_verify();
1853 Universe::verify(/* allow dirty */ true,
1854 /* silent */ false,
1855 /* option */ VerifyOption_G1UsePrevMarking);
1856 }
1857
1858 g1h->verify_region_sets_optional();
1859 }
1860
1861 void ConcurrentMark::completeCleanup() {
1862 if (has_aborted()) return;
1863
1864 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1865
1866 _cleanup_list.verify_optional();
1867 FreeRegionList tmp_free_list("Tmp Free List");
1868
1869 if (G1ConcRegionFreeingVerbose) {
1870 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
1871 "cleanup list has "SIZE_FORMAT" entries",
1872 _cleanup_list.length());
1873 }
1874
1875 // Noone else should be accessing the _cleanup_list at this point,
1876 // so it's not necessary to take any locks
1877 while (!_cleanup_list.is_empty()) {
1878 HeapRegion* hr = _cleanup_list.remove_head();
1879 assert(hr != NULL, "the list was not empty");
1880 hr->par_clear();
1881 tmp_free_list.add_as_tail(hr);
1882
1883 // Instead of adding one region at a time to the secondary_free_list,
1884 // we accumulate them in the local list and move them a few at a
1885 // time. This also cuts down on the number of notify_all() calls
1886 // we do during this process. We'll also append the local list when
1887 // _cleanup_list is empty (which means we just removed the last
1888 // region from the _cleanup_list).
1889 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
1890 _cleanup_list.is_empty()) {
1891 if (G1ConcRegionFreeingVerbose) {
1892 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
1893 "appending "SIZE_FORMAT" entries to the "
1894 "secondary_free_list, clean list still has "
1895 SIZE_FORMAT" entries",
1896 tmp_free_list.length(),
1897 _cleanup_list.length());
1898 }
1899
1900 {
1901 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1902 g1h->secondary_free_list_add_as_tail(&tmp_free_list);
1903 SecondaryFreeList_lock->notify_all();
1904 }
1905
1906 if (G1StressConcRegionFreeing) {
1907 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
1908 os::sleep(Thread::current(), (jlong) 1, false);
1909 }
1910 }
1911 }
1912 }
1913 assert(tmp_free_list.is_empty(), "post-condition");
1914 }
1915
1916 // Support closures for reference procssing in G1
1917
1918 bool G1CMIsAliveClosure::do_object_b(oop obj) {
1919 HeapWord* addr = (HeapWord*)obj;
1920 return addr != NULL &&
1921 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
1922 }
1923
1924 class G1CMKeepAliveClosure: public OopClosure {
1925 G1CollectedHeap* _g1;
1926 ConcurrentMark* _cm;
1927 CMBitMap* _bitMap;
1928 public:
1929 G1CMKeepAliveClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
1930 CMBitMap* bitMap) :
1931 _g1(g1), _cm(cm),
1932 _bitMap(bitMap) {}
1933
1934 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
1935 virtual void do_oop( oop* p) { do_oop_work(p); }
1936
1937 template <class T> void do_oop_work(T* p) {
1938 oop obj = oopDesc::load_decode_heap_oop(p);
1939 HeapWord* addr = (HeapWord*)obj;
1940
1941 if (_cm->verbose_high()) {
1942 gclog_or_tty->print_cr("\t[0] we're looking at location "
1943 "*"PTR_FORMAT" = "PTR_FORMAT,
1944 p, (void*) obj);
1945 }
1946
1947 if (_g1->is_in_g1_reserved(addr) && _g1->is_obj_ill(obj)) {
1948 _bitMap->mark(addr);
1949 _cm->mark_stack_push(obj);
1950 }
1951 }
1952 };
1953
1954 class G1CMDrainMarkingStackClosure: public VoidClosure {
1955 CMMarkStack* _markStack;
1956 CMBitMap* _bitMap;
1957 G1CMKeepAliveClosure* _oopClosure;
1958 public:
1959 G1CMDrainMarkingStackClosure(CMBitMap* bitMap, CMMarkStack* markStack,
1960 G1CMKeepAliveClosure* oopClosure) :
1961 _bitMap(bitMap),
1962 _markStack(markStack),
1963 _oopClosure(oopClosure)
1964 {}
1965
1966 void do_void() {
1967 _markStack->drain((OopClosure*)_oopClosure, _bitMap, false);
1968 }
1969 };
1970
1971 // 'Keep Alive' closure used by parallel reference processing.
1972 // An instance of this closure is used in the parallel reference processing
1973 // code rather than an instance of G1CMKeepAliveClosure. We could have used
1974 // the G1CMKeepAliveClosure as it is MT-safe. Also reference objects are
1975 // placed on to discovered ref lists once so we can mark and push with no
1976 // need to check whether the object has already been marked. Using the
1977 // G1CMKeepAliveClosure would mean, however, having all the worker threads
1978 // operating on the global mark stack. This means that an individual
1979 // worker would be doing lock-free pushes while it processes its own
1980 // discovered ref list followed by drain call. If the discovered ref lists
1981 // are unbalanced then this could cause interference with the other
1982 // workers. Using a CMTask (and its embedded local data structures)
1983 // avoids that potential interference.
1984 class G1CMParKeepAliveAndDrainClosure: public OopClosure {
1985 ConcurrentMark* _cm;
1986 CMTask* _task;
1987 CMBitMap* _bitMap;
1988 int _ref_counter_limit;
1989 int _ref_counter;
1990 public:
1991 G1CMParKeepAliveAndDrainClosure(ConcurrentMark* cm,
1992 CMTask* task,
1993 CMBitMap* bitMap) :
1994 _cm(cm), _task(task), _bitMap(bitMap),
1995 _ref_counter_limit(G1RefProcDrainInterval)
1996 {
1997 assert(_ref_counter_limit > 0, "sanity");
1998 _ref_counter = _ref_counter_limit;
1999 }
2000
2001 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2002 virtual void do_oop( oop* p) { do_oop_work(p); }
2003
2004 template <class T> void do_oop_work(T* p) {
2005 if (!_cm->has_overflown()) {
2006 oop obj = oopDesc::load_decode_heap_oop(p);
2007 if (_cm->verbose_high()) {
2008 gclog_or_tty->print_cr("\t[%d] we're looking at location "
2009 "*"PTR_FORMAT" = "PTR_FORMAT,
2010 _task->task_id(), p, (void*) obj);
2011 }
2012
2013 _task->deal_with_reference(obj);
2014 _ref_counter--;
2015
2016 if (_ref_counter == 0) {
2017 // We have dealt with _ref_counter_limit references, pushing them and objects
2018 // reachable from them on to the local stack (and possibly the global stack).
2019 // Call do_marking_step() to process these entries. We call the routine in a
2020 // loop, which we'll exit if there's nothing more to do (i.e. we're done
2021 // with the entries that we've pushed as a result of the deal_with_reference
2022 // calls above) or we overflow.
2023 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2024 // while there may still be some work to do. (See the comment at the
2025 // beginning of CMTask::do_marking_step() for those conditions - one of which
2026 // is reaching the specified time target.) It is only when
2027 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2028 // that the marking has completed.
2029 do {
2030 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2031 _task->do_marking_step(mark_step_duration_ms,
2032 false /* do_stealing */,
2033 false /* do_termination */);
2034 } while (_task->has_aborted() && !_cm->has_overflown());
2035 _ref_counter = _ref_counter_limit;
2036 }
2037 } else {
2038 if (_cm->verbose_high()) {
2039 gclog_or_tty->print_cr("\t[%d] CM Overflow", _task->task_id());
2040 }
2041 }
2042 }
2043 };
2044
2045 class G1CMParDrainMarkingStackClosure: public VoidClosure {
2046 ConcurrentMark* _cm;
2047 CMTask* _task;
2048 public:
2049 G1CMParDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task) :
2050 _cm(cm), _task(task)
2051 {}
2052
2053 void do_void() {
2054 do {
2055 if (_cm->verbose_high()) {
2056 gclog_or_tty->print_cr("\t[%d] Drain: Calling do marking_step",
2057 _task->task_id());
2058 }
2059
2060 // We call CMTask::do_marking_step() to completely drain the local and
2061 // global marking stacks. The routine is called in a loop, which we'll
2062 // exit if there's nothing more to do (i.e. we'completely drained the
2063 // entries that were pushed as a result of applying the
2064 // G1CMParKeepAliveAndDrainClosure to the entries on the discovered ref
2065 // lists above) or we overflow the global marking stack.
2066 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2067 // while there may still be some work to do. (See the comment at the
2068 // beginning of CMTask::do_marking_step() for those conditions - one of which
2069 // is reaching the specified time target.) It is only when
2070 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2071 // that the marking has completed.
2072
2073 _task->do_marking_step(1000000000.0 /* something very large */,
2074 true /* do_stealing */,
2075 true /* do_termination */);
2076 } while (_task->has_aborted() && !_cm->has_overflown());
2077 }
2078 };
2079
2080 // Implementation of AbstractRefProcTaskExecutor for parallel
2081 // reference processing at the end of G1 concurrent marking
2082
2083 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2084 private:
2085 G1CollectedHeap* _g1h;
2086 ConcurrentMark* _cm;
2087 CMBitMap* _bitmap;
2088 WorkGang* _workers;
2089 int _active_workers;
2090
2091 public:
2092 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2093 ConcurrentMark* cm,
2094 CMBitMap* bitmap,
2095 WorkGang* workers,
2096 int n_workers) :
2097 _g1h(g1h), _cm(cm), _bitmap(bitmap),
2098 _workers(workers), _active_workers(n_workers)
2099 { }
2100
2101 // Executes the given task using concurrent marking worker threads.
2102 virtual void execute(ProcessTask& task);
2103 virtual void execute(EnqueueTask& task);
2104 };
2105
2106 class G1CMRefProcTaskProxy: public AbstractGangTask {
2107 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2108 ProcessTask& _proc_task;
2109 G1CollectedHeap* _g1h;
2110 ConcurrentMark* _cm;
2111 CMBitMap* _bitmap;
2112
2113 public:
2114 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2115 G1CollectedHeap* g1h,
2116 ConcurrentMark* cm,
2117 CMBitMap* bitmap) :
2118 AbstractGangTask("Process reference objects in parallel"),
2119 _proc_task(proc_task), _g1h(g1h), _cm(cm), _bitmap(bitmap)
2120 {}
2121
2122 virtual void work(int i) {
2123 CMTask* marking_task = _cm->task(i);
2124 G1CMIsAliveClosure g1_is_alive(_g1h);
2125 G1CMParKeepAliveAndDrainClosure g1_par_keep_alive(_cm, marking_task, _bitmap);
2126 G1CMParDrainMarkingStackClosure g1_par_drain(_cm, marking_task);
2127
2128 _proc_task.work(i, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2129 }
2130 };
2131
2132 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2133 assert(_workers != NULL, "Need parallel worker threads.");
2134
2135 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm, _bitmap);
2136
2137 // We need to reset the phase for each task execution so that
2138 // the termination protocol of CMTask::do_marking_step works.
2139 _cm->set_phase(_active_workers, false /* concurrent */);
2140 _g1h->set_par_threads(_active_workers);
2141 _workers->run_task(&proc_task_proxy);
2142 _g1h->set_par_threads(0);
2143 }
2144
2145 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2146 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2147 EnqueueTask& _enq_task;
2148
2149 public:
2150 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2151 AbstractGangTask("Enqueue reference objects in parallel"),
2152 _enq_task(enq_task)
2153 { }
2154
2155 virtual void work(int i) {
2156 _enq_task.work(i);
2157 }
2158 };
2159
2160 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2161 assert(_workers != NULL, "Need parallel worker threads.");
2162
2163 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2164
2165 _g1h->set_par_threads(_active_workers);
2166 _workers->run_task(&enq_task_proxy);
2167 _g1h->set_par_threads(0);
2168 }
2169
2170 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2171 ResourceMark rm;
2172 HandleMark hm;
2173
2174 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2175
2176 // Is alive closure.
2177 G1CMIsAliveClosure g1_is_alive(g1h);
2178
2179 // Inner scope to exclude the cleaning of the string and symbol
2180 // tables from the displayed time.
2181 {
2182 bool verbose = PrintGC && PrintGCDetails;
2183 if (verbose) {
2184 gclog_or_tty->put(' ');
2185 }
2186 TraceTime t("GC ref-proc", verbose, false, gclog_or_tty);
2187
2188 ReferenceProcessor* rp = g1h->ref_processor_cm();
2189
2190 // See the comment in G1CollectedHeap::ref_processing_init()
2191 // about how reference processing currently works in G1.
2192
2193 // Process weak references.
2194 rp->setup_policy(clear_all_soft_refs);
2195 assert(_markStack.isEmpty(), "mark stack should be empty");
2196
2197 G1CMKeepAliveClosure g1_keep_alive(g1h, this, nextMarkBitMap());
2198 G1CMDrainMarkingStackClosure
2199 g1_drain_mark_stack(nextMarkBitMap(), &_markStack, &g1_keep_alive);
2200
2201 // We use the work gang from the G1CollectedHeap and we utilize all
2202 // the worker threads.
2203 int active_workers = g1h->workers() ? g1h->workers()->total_workers() : 1;
2204 active_workers = MAX2(MIN2(active_workers, (int)_max_task_num), 1);
2205
2206 G1CMRefProcTaskExecutor par_task_executor(g1h, this, nextMarkBitMap(),
2207 g1h->workers(), active_workers);
2208
2209 if (rp->processing_is_mt()) {
2210 // Set the degree of MT here. If the discovery is done MT, there
2211 // may have been a different number of threads doing the discovery
2212 // and a different number of discovered lists may have Ref objects.
2213 // That is OK as long as the Reference lists are balanced (see
2214 // balance_all_queues() and balance_queues()).
2215 rp->set_active_mt_degree(active_workers);
2216
2217 rp->process_discovered_references(&g1_is_alive,
2218 &g1_keep_alive,
2219 &g1_drain_mark_stack,
2220 &par_task_executor);
2221
2222 // The work routines of the parallel keep_alive and drain_marking_stack
2223 // will set the has_overflown flag if we overflow the global marking
2224 // stack.
2225 } else {
2226 rp->process_discovered_references(&g1_is_alive,
2227 &g1_keep_alive,
2228 &g1_drain_mark_stack,
2229 NULL);
2230 }
2231
2232 assert(_markStack.overflow() || _markStack.isEmpty(),
2233 "mark stack should be empty (unless it overflowed)");
2234 if (_markStack.overflow()) {
2235 // Should have been done already when we tried to push an
2236 // entry on to the global mark stack. But let's do it again.
2237 set_has_overflown();
2238 }
2239
2240 if (rp->processing_is_mt()) {
2241 assert(rp->num_q() == active_workers, "why not");
2242 rp->enqueue_discovered_references(&par_task_executor);
2243 } else {
2244 rp->enqueue_discovered_references();
2245 }
2246
2247 rp->verify_no_references_recorded();
2248 assert(!rp->discovery_enabled(), "Post condition");
2249 }
2250
2251 // Now clean up stale oops in StringTable
2252 StringTable::unlink(&g1_is_alive);
2253 // Clean up unreferenced symbols in symbol table.
2254 SymbolTable::unlink();
2255 }
2256
2257 void ConcurrentMark::swapMarkBitMaps() {
2258 CMBitMapRO* temp = _prevMarkBitMap;
2259 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2260 _nextMarkBitMap = (CMBitMap*) temp;
2261 }
2262
2263 class CMRemarkTask: public AbstractGangTask {
2264 private:
2265 ConcurrentMark *_cm;
2266
2267 public:
2268 void work(int worker_i) {
2269 // Since all available tasks are actually started, we should
2270 // only proceed if we're supposed to be actived.
2271 if ((size_t)worker_i < _cm->active_tasks()) {
2272 CMTask* task = _cm->task(worker_i);
2273 task->record_start_time();
2274 do {
2275 task->do_marking_step(1000000000.0 /* something very large */,
2276 true /* do_stealing */,
2277 true /* do_termination */);
2278 } while (task->has_aborted() && !_cm->has_overflown());
2279 // If we overflow, then we do not want to restart. We instead
2280 // want to abort remark and do concurrent marking again.
2281 task->record_end_time();
2282 }
2283 }
2284
2285 CMRemarkTask(ConcurrentMark* cm) :
2286 AbstractGangTask("Par Remark"), _cm(cm) { }
2287 };
2288
2289 void ConcurrentMark::checkpointRootsFinalWork() {
2290 ResourceMark rm;
2291 HandleMark hm;
2292 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2293
2294 g1h->ensure_parsability(false);
2295
2296 if (G1CollectedHeap::use_parallel_gc_threads()) {
2297 G1CollectedHeap::StrongRootsScope srs(g1h);
2298 // this is remark, so we'll use up all available threads
2299 int active_workers = ParallelGCThreads;
2300 set_phase(active_workers, false /* concurrent */);
2301
2302 CMRemarkTask remarkTask(this);
2303 // We will start all available threads, even if we decide that the
2304 // active_workers will be fewer. The extra ones will just bail out
2305 // immediately.
2306 int n_workers = g1h->workers()->total_workers();
2307 g1h->set_par_threads(n_workers);
2308 g1h->workers()->run_task(&remarkTask);
2309 g1h->set_par_threads(0);
2310 } else {
2311 G1CollectedHeap::StrongRootsScope srs(g1h);
2312 // this is remark, so we'll use up all available threads
2313 int active_workers = 1;
2314 set_phase(active_workers, false /* concurrent */);
2315
2316 CMRemarkTask remarkTask(this);
2317 // We will start all available threads, even if we decide that the
2318 // active_workers will be fewer. The extra ones will just bail out
2319 // immediately.
2320 remarkTask.work(0);
2321 }
2322 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2323 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
2324
2325 print_stats();
2326
2327 #if VERIFY_OBJS_PROCESSED
2328 if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) {
2329 gclog_or_tty->print_cr("Processed = %d, enqueued = %d.",
2330 _scan_obj_cl.objs_processed,
2331 ThreadLocalObjQueue::objs_enqueued);
2332 guarantee(_scan_obj_cl.objs_processed ==
2333 ThreadLocalObjQueue::objs_enqueued,
2334 "Different number of objs processed and enqueued.");
2335 }
2336 #endif
2337 }
2338
2339 #ifndef PRODUCT
2340
2341 class PrintReachableOopClosure: public OopClosure {
2342 private:
2343 G1CollectedHeap* _g1h;
2344 outputStream* _out;
2345 VerifyOption _vo;
2346 bool _all;
2347
2348 public:
2349 PrintReachableOopClosure(outputStream* out,
2350 VerifyOption vo,
2351 bool all) :
2352 _g1h(G1CollectedHeap::heap()),
2353 _out(out), _vo(vo), _all(all) { }
2354
2355 void do_oop(narrowOop* p) { do_oop_work(p); }
2356 void do_oop( oop* p) { do_oop_work(p); }
2357
2358 template <class T> void do_oop_work(T* p) {
2359 oop obj = oopDesc::load_decode_heap_oop(p);
2360 const char* str = NULL;
2361 const char* str2 = "";
2362
2363 if (obj == NULL) {
2364 str = "";
2365 } else if (!_g1h->is_in_g1_reserved(obj)) {
2366 str = " O";
2367 } else {
2368 HeapRegion* hr = _g1h->heap_region_containing(obj);
2369 guarantee(hr != NULL, "invariant");
2370 bool over_tams = false;
2371 bool marked = false;
2372
2373 switch (_vo) {
2374 case VerifyOption_G1UsePrevMarking:
2375 over_tams = hr->obj_allocated_since_prev_marking(obj);
2376 marked = _g1h->isMarkedPrev(obj);
2377 break;
2378 case VerifyOption_G1UseNextMarking:
2379 over_tams = hr->obj_allocated_since_next_marking(obj);
2380 marked = _g1h->isMarkedNext(obj);
2381 break;
2382 case VerifyOption_G1UseMarkWord:
2383 marked = obj->is_gc_marked();
2384 break;
2385 default:
2386 ShouldNotReachHere();
2387 }
2388
2389 if (over_tams) {
2390 str = " >";
2391 if (marked) {
2392 str2 = " AND MARKED";
2393 }
2394 } else if (marked) {
2395 str = " M";
2396 } else {
2397 str = " NOT";
2398 }
2399 }
2400
2401 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2402 p, (void*) obj, str, str2);
2403 }
2404 };
2405
2406 class PrintReachableObjectClosure : public ObjectClosure {
2407 private:
2408 G1CollectedHeap* _g1h;
2409 outputStream* _out;
2410 VerifyOption _vo;
2411 bool _all;
2412 HeapRegion* _hr;
2413
2414 public:
2415 PrintReachableObjectClosure(outputStream* out,
2416 VerifyOption vo,
2417 bool all,
2418 HeapRegion* hr) :
2419 _g1h(G1CollectedHeap::heap()),
2420 _out(out), _vo(vo), _all(all), _hr(hr) { }
2421
2422 void do_object(oop o) {
2423 bool over_tams = false;
2424 bool marked = false;
2425
2426 switch (_vo) {
2427 case VerifyOption_G1UsePrevMarking:
2428 over_tams = _hr->obj_allocated_since_prev_marking(o);
2429 marked = _g1h->isMarkedPrev(o);
2430 break;
2431 case VerifyOption_G1UseNextMarking:
2432 over_tams = _hr->obj_allocated_since_next_marking(o);
2433 marked = _g1h->isMarkedNext(o);
2434 break;
2435 case VerifyOption_G1UseMarkWord:
2436 marked = o->is_gc_marked();
2437 break;
2438 default:
2439 ShouldNotReachHere();
2440 }
2441 bool print_it = _all || over_tams || marked;
2442
2443 if (print_it) {
2444 _out->print_cr(" "PTR_FORMAT"%s",
2445 o, (over_tams) ? " >" : (marked) ? " M" : "");
2446 PrintReachableOopClosure oopCl(_out, _vo, _all);
2447 o->oop_iterate(&oopCl);
2448 }
2449 }
2450 };
2451
2452 class PrintReachableRegionClosure : public HeapRegionClosure {
2453 private:
2454 outputStream* _out;
2455 VerifyOption _vo;
2456 bool _all;
2457
2458 public:
2459 bool doHeapRegion(HeapRegion* hr) {
2460 HeapWord* b = hr->bottom();
2461 HeapWord* e = hr->end();
2462 HeapWord* t = hr->top();
2463 HeapWord* p = NULL;
2464
2465 switch (_vo) {
2466 case VerifyOption_G1UsePrevMarking:
2467 p = hr->prev_top_at_mark_start();
2468 break;
2469 case VerifyOption_G1UseNextMarking:
2470 p = hr->next_top_at_mark_start();
2471 break;
2472 case VerifyOption_G1UseMarkWord:
2473 // When we are verifying marking using the mark word
2474 // TAMS has no relevance.
2475 assert(p == NULL, "post-condition");
2476 break;
2477 default:
2478 ShouldNotReachHere();
2479 }
2480 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2481 "TAMS: "PTR_FORMAT, b, e, t, p);
2482 _out->cr();
2483
2484 HeapWord* from = b;
2485 HeapWord* to = t;
2486
2487 if (to > from) {
2488 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2489 _out->cr();
2490 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2491 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2492 _out->cr();
2493 }
2494
2495 return false;
2496 }
2497
2498 PrintReachableRegionClosure(outputStream* out,
2499 VerifyOption vo,
2500 bool all) :
2501 _out(out), _vo(vo), _all(all) { }
2502 };
2503
2504 static const char* verify_option_to_tams(VerifyOption vo) {
2505 switch (vo) {
2506 case VerifyOption_G1UsePrevMarking:
2507 return "PTAMS";
2508 case VerifyOption_G1UseNextMarking:
2509 return "NTAMS";
2510 default:
2511 return "NONE";
2512 }
2513 }
2514
2515 void ConcurrentMark::print_reachable(const char* str,
2516 VerifyOption vo,
2517 bool all) {
2518 gclog_or_tty->cr();
2519 gclog_or_tty->print_cr("== Doing heap dump... ");
2520
2521 if (G1PrintReachableBaseFile == NULL) {
2522 gclog_or_tty->print_cr(" #### error: no base file defined");
2523 return;
2524 }
2525
2526 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2527 (JVM_MAXPATHLEN - 1)) {
2528 gclog_or_tty->print_cr(" #### error: file name too long");
2529 return;
2530 }
2531
2532 char file_name[JVM_MAXPATHLEN];
2533 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2534 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2535
2536 fileStream fout(file_name);
2537 if (!fout.is_open()) {
2538 gclog_or_tty->print_cr(" #### error: could not open file");
2539 return;
2540 }
2541
2542 outputStream* out = &fout;
2543 out->print_cr("-- USING %s", verify_option_to_tams(vo));
2544 out->cr();
2545
2546 out->print_cr("--- ITERATING OVER REGIONS");
2547 out->cr();
2548 PrintReachableRegionClosure rcl(out, vo, all);
2549 _g1h->heap_region_iterate(&rcl);
2550 out->cr();
2551
2552 gclog_or_tty->print_cr(" done");
2553 gclog_or_tty->flush();
2554 }
2555
2556 #endif // PRODUCT
2557
2558 // This note is for drainAllSATBBuffers and the code in between.
2559 // In the future we could reuse a task to do this work during an
2560 // evacuation pause (since now tasks are not active and can be claimed
2561 // during an evacuation pause). This was a late change to the code and
2562 // is currently not being taken advantage of.
2563
2564 class CMGlobalObjectClosure : public ObjectClosure {
2565 private:
2566 ConcurrentMark* _cm;
2567
2568 public:
2569 void do_object(oop obj) {
2570 _cm->deal_with_reference(obj);
2571 }
2572
2573 CMGlobalObjectClosure(ConcurrentMark* cm) : _cm(cm) { }
2574 };
2575
2576 void ConcurrentMark::deal_with_reference(oop obj) {
2577 if (verbose_high()) {
2578 gclog_or_tty->print_cr("[global] we're dealing with reference "PTR_FORMAT,
2579 (void*) obj);
2580 }
2581
2582 HeapWord* objAddr = (HeapWord*) obj;
2583 assert(obj->is_oop_or_null(true /* ignore mark word */), "Error");
2584 if (_g1h->is_in_g1_reserved(objAddr)) {
2585 assert(obj != NULL, "null check is implicit");
2586 if (!_nextMarkBitMap->isMarked(objAddr)) {
2587 // Only get the containing region if the object is not marked on the
2588 // bitmap (otherwise, it's a waste of time since we won't do
2589 // anything with it).
2590 HeapRegion* hr = _g1h->heap_region_containing_raw(obj);
2591 if (!hr->obj_allocated_since_next_marking(obj)) {
2592 if (verbose_high()) {
2593 gclog_or_tty->print_cr("[global] "PTR_FORMAT" is not considered "
2594 "marked", (void*) obj);
2595 }
2596
2597 // we need to mark it first
2598 if (_nextMarkBitMap->parMark(objAddr)) {
2599 // No OrderAccess:store_load() is needed. It is implicit in the
2600 // CAS done in parMark(objAddr) above
2601 HeapWord* finger = _finger;
2602 if (objAddr < finger) {
2603 if (verbose_high()) {
2604 gclog_or_tty->print_cr("[global] below the global finger "
2605 "("PTR_FORMAT"), pushing it", finger);
2606 }
2607 if (!mark_stack_push(obj)) {
2608 if (verbose_low()) {
2609 gclog_or_tty->print_cr("[global] global stack overflow during "
2610 "deal_with_reference");
2611 }
2612 }
2613 }
2614 }
2615 }
2616 }
2617 }
2618 }
2619
2620 void ConcurrentMark::drainAllSATBBuffers() {
2621 CMGlobalObjectClosure oc(this);
2622 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2623 satb_mq_set.set_closure(&oc);
2624
2625 while (satb_mq_set.apply_closure_to_completed_buffer()) {
2626 if (verbose_medium()) {
2627 gclog_or_tty->print_cr("[global] processed an SATB buffer");
2628 }
2629 }
2630
2631 // no need to check whether we should do this, as this is only
2632 // called during an evacuation pause
2633 satb_mq_set.iterate_closure_all_threads();
2634
2635 satb_mq_set.set_closure(NULL);
2636 assert(satb_mq_set.completed_buffers_num() == 0, "invariant");
2637 }
2638
2639 void ConcurrentMark::markPrev(oop p) {
2640 // Note we are overriding the read-only view of the prev map here, via
2641 // the cast.
2642 ((CMBitMap*)_prevMarkBitMap)->mark((HeapWord*)p);
2643 }
2644
2645 void ConcurrentMark::clear(oop p) {
2646 assert(p != NULL && p->is_oop(), "expected an oop");
2647 HeapWord* addr = (HeapWord*)p;
2648 assert(addr >= _nextMarkBitMap->startWord() ||
2649 addr < _nextMarkBitMap->endWord(), "in a region");
2650
2651 _nextMarkBitMap->clear(addr);
2652 }
2653
2654 void ConcurrentMark::clearRangeBothMaps(MemRegion mr) {
2655 // Note we are overriding the read-only view of the prev map here, via
2656 // the cast.
2657 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2658 _nextMarkBitMap->clearRange(mr);
2659 }
2660
2661 HeapRegion*
2662 ConcurrentMark::claim_region(int task_num) {
2663 // "checkpoint" the finger
2664 HeapWord* finger = _finger;
2665
2666 // _heap_end will not change underneath our feet; it only changes at
2667 // yield points.
2668 while (finger < _heap_end) {
2669 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2670
2671 // Note on how this code handles humongous regions. In the
2672 // normal case the finger will reach the start of a "starts
2673 // humongous" (SH) region. Its end will either be the end of the
2674 // last "continues humongous" (CH) region in the sequence, or the
2675 // standard end of the SH region (if the SH is the only region in
2676 // the sequence). That way claim_region() will skip over the CH
2677 // regions. However, there is a subtle race between a CM thread
2678 // executing this method and a mutator thread doing a humongous
2679 // object allocation. The two are not mutually exclusive as the CM
2680 // thread does not need to hold the Heap_lock when it gets
2681 // here. So there is a chance that claim_region() will come across
2682 // a free region that's in the progress of becoming a SH or a CH
2683 // region. In the former case, it will either
2684 // a) Miss the update to the region's end, in which case it will
2685 // visit every subsequent CH region, will find their bitmaps
2686 // empty, and do nothing, or
2687 // b) Will observe the update of the region's end (in which case
2688 // it will skip the subsequent CH regions).
2689 // If it comes across a region that suddenly becomes CH, the
2690 // scenario will be similar to b). So, the race between
2691 // claim_region() and a humongous object allocation might force us
2692 // to do a bit of unnecessary work (due to some unnecessary bitmap
2693 // iterations) but it should not introduce and correctness issues.
2694 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2695 HeapWord* bottom = curr_region->bottom();
2696 HeapWord* end = curr_region->end();
2697 HeapWord* limit = curr_region->next_top_at_mark_start();
2698
2699 if (verbose_low()) {
2700 gclog_or_tty->print_cr("[%d] curr_region = "PTR_FORMAT" "
2701 "["PTR_FORMAT", "PTR_FORMAT"), "
2702 "limit = "PTR_FORMAT,
2703 task_num, curr_region, bottom, end, limit);
2704 }
2705
2706 // Is the gap between reading the finger and doing the CAS too long?
2707 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2708 if (res == finger) {
2709 // we succeeded
2710
2711 // notice that _finger == end cannot be guaranteed here since,
2712 // someone else might have moved the finger even further
2713 assert(_finger >= end, "the finger should have moved forward");
2714
2715 if (verbose_low()) {
2716 gclog_or_tty->print_cr("[%d] we were successful with region = "
2717 PTR_FORMAT, task_num, curr_region);
2718 }
2719
2720 if (limit > bottom) {
2721 if (verbose_low()) {
2722 gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is not empty, "
2723 "returning it ", task_num, curr_region);
2724 }
2725 return curr_region;
2726 } else {
2727 assert(limit == bottom,
2728 "the region limit should be at bottom");
2729 if (verbose_low()) {
2730 gclog_or_tty->print_cr("[%d] region "PTR_FORMAT" is empty, "
2731 "returning NULL", task_num, curr_region);
2732 }
2733 // we return NULL and the caller should try calling
2734 // claim_region() again.
2735 return NULL;
2736 }
2737 } else {
2738 assert(_finger > finger, "the finger should have moved forward");
2739 if (verbose_low()) {
2740 gclog_or_tty->print_cr("[%d] somebody else moved the finger, "
2741 "global finger = "PTR_FORMAT", "
2742 "our finger = "PTR_FORMAT,
2743 task_num, _finger, finger);
2744 }
2745
2746 // read it again
2747 finger = _finger;
2748 }
2749 }
2750
2751 return NULL;
2752 }
2753
2754 bool ConcurrentMark::invalidate_aborted_regions_in_cset() {
2755 bool result = false;
2756 for (int i = 0; i < (int)_max_task_num; ++i) {
2757 CMTask* the_task = _tasks[i];
2758 MemRegion mr = the_task->aborted_region();
2759 if (mr.start() != NULL) {
2760 assert(mr.end() != NULL, "invariant");
2761 assert(mr.word_size() > 0, "invariant");
2762 HeapRegion* hr = _g1h->heap_region_containing(mr.start());
2763 assert(hr != NULL, "invariant");
2764 if (hr->in_collection_set()) {
2765 // The region points into the collection set
2766 the_task->set_aborted_region(MemRegion());
2767 result = true;
2768 }
2769 }
2770 }
2771 return result;
2772 }
2773
2774 bool ConcurrentMark::has_aborted_regions() {
2775 for (int i = 0; i < (int)_max_task_num; ++i) {
2776 CMTask* the_task = _tasks[i];
2777 MemRegion mr = the_task->aborted_region();
2778 if (mr.start() != NULL) {
2779 assert(mr.end() != NULL, "invariant");
2780 assert(mr.word_size() > 0, "invariant");
2781 return true;
2782 }
2783 }
2784 return false;
2785 }
2786
2787 void ConcurrentMark::oops_do(OopClosure* cl) {
2788 if (_markStack.size() > 0 && verbose_low()) {
2789 gclog_or_tty->print_cr("[global] scanning the global marking stack, "
2790 "size = %d", _markStack.size());
2791 }
2792 // we first iterate over the contents of the mark stack...
2793 _markStack.oops_do(cl);
2794
2795 for (int i = 0; i < (int)_max_task_num; ++i) {
2796 OopTaskQueue* queue = _task_queues->queue((int)i);
2797
2798 if (queue->size() > 0 && verbose_low()) {
2799 gclog_or_tty->print_cr("[global] scanning task queue of task %d, "
2800 "size = %d", i, queue->size());
2801 }
2802
2803 // ...then over the contents of the all the task queues.
2804 queue->oops_do(cl);
2805 }
2806
2807 // Invalidate any entries, that are in the region stack, that
2808 // point into the collection set
2809 if (_regionStack.invalidate_entries_into_cset()) {
2810 // otherwise, any gray objects copied during the evacuation pause
2811 // might not be visited.
2812 assert(_should_gray_objects, "invariant");
2813 }
2814
2815 // Invalidate any aborted regions, recorded in the individual CM
2816 // tasks, that point into the collection set.
2817 if (invalidate_aborted_regions_in_cset()) {
2818 // otherwise, any gray objects copied during the evacuation pause
2819 // might not be visited.
2820 assert(_should_gray_objects, "invariant");
2821 }
2822
2823 }
2824
2825 void ConcurrentMark::clear_marking_state(bool clear_overflow) {
2826 _markStack.setEmpty();
2827 _markStack.clear_overflow();
2828 _regionStack.setEmpty();
2829 _regionStack.clear_overflow();
2830 if (clear_overflow) {
2831 clear_has_overflown();
2832 } else {
2833 assert(has_overflown(), "pre-condition");
2834 }
2835 _finger = _heap_start;
2836
2837 for (int i = 0; i < (int)_max_task_num; ++i) {
2838 OopTaskQueue* queue = _task_queues->queue(i);
2839 queue->set_empty();
2840 // Clear any partial regions from the CMTasks
2841 _tasks[i]->clear_aborted_region();
2842 }
2843 }
2844
2845 void ConcurrentMark::print_stats() {
2846 if (verbose_stats()) {
2847 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2848 for (size_t i = 0; i < _active_tasks; ++i) {
2849 _tasks[i]->print_stats();
2850 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2851 }
2852 }
2853 }
2854
2855 class CSMarkOopClosure: public OopClosure {
2856 friend class CSMarkBitMapClosure;
2857
2858 G1CollectedHeap* _g1h;
2859 CMBitMap* _bm;
2860 ConcurrentMark* _cm;
2861 oop* _ms;
2862 jint* _array_ind_stack;
2863 int _ms_size;
2864 int _ms_ind;
2865 int _array_increment;
2866
2867 bool push(oop obj, int arr_ind = 0) {
2868 if (_ms_ind == _ms_size) {
2869 gclog_or_tty->print_cr("Mark stack is full.");
2870 return false;
2871 }
2872 _ms[_ms_ind] = obj;
2873 if (obj->is_objArray()) {
2874 _array_ind_stack[_ms_ind] = arr_ind;
2875 }
2876 _ms_ind++;
2877 return true;
2878 }
2879
2880 oop pop() {
2881 if (_ms_ind == 0) {
2882 return NULL;
2883 } else {
2884 _ms_ind--;
2885 return _ms[_ms_ind];
2886 }
2887 }
2888
2889 template <class T> bool drain() {
2890 while (_ms_ind > 0) {
2891 oop obj = pop();
2892 assert(obj != NULL, "Since index was non-zero.");
2893 if (obj->is_objArray()) {
2894 jint arr_ind = _array_ind_stack[_ms_ind];
2895 objArrayOop aobj = objArrayOop(obj);
2896 jint len = aobj->length();
2897 jint next_arr_ind = arr_ind + _array_increment;
2898 if (next_arr_ind < len) {
2899 push(obj, next_arr_ind);
2900 }
2901 // Now process this portion of this one.
2902 int lim = MIN2(next_arr_ind, len);
2903 for (int j = arr_ind; j < lim; j++) {
2904 do_oop(aobj->objArrayOopDesc::obj_at_addr<T>(j));
2905 }
2906
2907 } else {
2908 obj->oop_iterate(this);
2909 }
2910 if (abort()) return false;
2911 }
2912 return true;
2913 }
2914
2915 public:
2916 CSMarkOopClosure(ConcurrentMark* cm, int ms_size) :
2917 _g1h(G1CollectedHeap::heap()),
2918 _cm(cm),
2919 _bm(cm->nextMarkBitMap()),
2920 _ms_size(ms_size), _ms_ind(0),
2921 _ms(NEW_C_HEAP_ARRAY(oop, ms_size)),
2922 _array_ind_stack(NEW_C_HEAP_ARRAY(jint, ms_size)),
2923 _array_increment(MAX2(ms_size/8, 16))
2924 {}
2925
2926 ~CSMarkOopClosure() {
2927 FREE_C_HEAP_ARRAY(oop, _ms);
2928 FREE_C_HEAP_ARRAY(jint, _array_ind_stack);
2929 }
2930
2931 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2932 virtual void do_oop( oop* p) { do_oop_work(p); }
2933
2934 template <class T> void do_oop_work(T* p) {
2935 T heap_oop = oopDesc::load_heap_oop(p);
2936 if (oopDesc::is_null(heap_oop)) return;
2937 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2938 if (obj->is_forwarded()) {
2939 // If the object has already been forwarded, we have to make sure
2940 // that it's marked. So follow the forwarding pointer. Note that
2941 // this does the right thing for self-forwarding pointers in the
2942 // evacuation failure case.
2943 obj = obj->forwardee();
2944 }
2945 HeapRegion* hr = _g1h->heap_region_containing(obj);
2946 if (hr != NULL) {
2947 if (hr->in_collection_set()) {
2948 if (_g1h->is_obj_ill(obj)) {
2949 _bm->mark((HeapWord*)obj);
2950 if (!push(obj)) {
2951 gclog_or_tty->print_cr("Setting abort in CSMarkOopClosure because push failed.");
2952 set_abort();
2953 }
2954 }
2955 } else {
2956 // Outside the collection set; we need to gray it
2957 _cm->deal_with_reference(obj);
2958 }
2959 }
2960 }
2961 };
2962
2963 class CSMarkBitMapClosure: public BitMapClosure {
2964 G1CollectedHeap* _g1h;
2965 CMBitMap* _bitMap;
2966 ConcurrentMark* _cm;
2967 CSMarkOopClosure _oop_cl;
2968 public:
2969 CSMarkBitMapClosure(ConcurrentMark* cm, int ms_size) :
2970 _g1h(G1CollectedHeap::heap()),
2971 _bitMap(cm->nextMarkBitMap()),
2972 _oop_cl(cm, ms_size)
2973 {}
2974
2975 ~CSMarkBitMapClosure() {}
2976
2977 bool do_bit(size_t offset) {
2978 // convert offset into a HeapWord*
2979 HeapWord* addr = _bitMap->offsetToHeapWord(offset);
2980 assert(_bitMap->endWord() && addr < _bitMap->endWord(),
2981 "address out of range");
2982 assert(_bitMap->isMarked(addr), "tautology");
2983 oop obj = oop(addr);
2984 if (!obj->is_forwarded()) {
2985 if (!_oop_cl.push(obj)) return false;
2986 if (UseCompressedOops) {
2987 if (!_oop_cl.drain<narrowOop>()) return false;
2988 } else {
2989 if (!_oop_cl.drain<oop>()) return false;
2990 }
2991 }
2992 // Otherwise...
2993 return true;
2994 }
2995 };
2996
2997
2998 class CompleteMarkingInCSHRClosure: public HeapRegionClosure {
2999 CMBitMap* _bm;
3000 CSMarkBitMapClosure _bit_cl;
3001 enum SomePrivateConstants {
3002 MSSize = 1000
3003 };
3004 bool _completed;
3005 public:
3006 CompleteMarkingInCSHRClosure(ConcurrentMark* cm) :
3007 _bm(cm->nextMarkBitMap()),
3008 _bit_cl(cm, MSSize),
3009 _completed(true)
3010 {}
3011
3012 ~CompleteMarkingInCSHRClosure() {}
3013
3014 bool doHeapRegion(HeapRegion* r) {
3015 if (!r->evacuation_failed()) {
3016 MemRegion mr = MemRegion(r->bottom(), r->next_top_at_mark_start());
3017 if (!mr.is_empty()) {
3018 if (!_bm->iterate(&_bit_cl, mr)) {
3019 _completed = false;
3020 return true;
3021 }
3022 }
3023 }
3024 return false;
3025 }
3026
3027 bool completed() { return _completed; }
3028 };
3029
3030 class ClearMarksInHRClosure: public HeapRegionClosure {
3031 CMBitMap* _bm;
3032 public:
3033 ClearMarksInHRClosure(CMBitMap* bm): _bm(bm) { }
3034
3035 bool doHeapRegion(HeapRegion* r) {
3036 if (!r->used_region().is_empty() && !r->evacuation_failed()) {
3037 MemRegion usedMR = r->used_region();
3038 _bm->clearRange(r->used_region());
3039 }
3040 return false;
3041 }
3042 };
3043
3044 void ConcurrentMark::complete_marking_in_collection_set() {
3045 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3046
3047 if (!g1h->mark_in_progress()) {
3048 g1h->g1_policy()->record_mark_closure_time(0.0);
3049 return;
3050 }
3051
3052 int i = 1;
3053 double start = os::elapsedTime();
3054 while (true) {
3055 i++;
3056 CompleteMarkingInCSHRClosure cmplt(this);
3057 g1h->collection_set_iterate(&cmplt);
3058 if (cmplt.completed()) break;
3059 }
3060 double end_time = os::elapsedTime();
3061 double elapsed_time_ms = (end_time - start) * 1000.0;
3062 g1h->g1_policy()->record_mark_closure_time(elapsed_time_ms);
3063
3064 ClearMarksInHRClosure clr(nextMarkBitMap());
3065 g1h->collection_set_iterate(&clr);
3066 }
3067
3068 // The next two methods deal with the following optimisation. Some
3069 // objects are gray by being marked and located above the finger. If
3070 // they are copied, during an evacuation pause, below the finger then
3071 // the need to be pushed on the stack. The observation is that, if
3072 // there are no regions in the collection set located above the
3073 // finger, then the above cannot happen, hence we do not need to
3074 // explicitly gray any objects when copying them to below the
3075 // finger. The global stack will be scanned to ensure that, if it
3076 // points to objects being copied, it will update their
3077 // location. There is a tricky situation with the gray objects in
3078 // region stack that are being coped, however. See the comment in
3079 // newCSet().
3080
3081 void ConcurrentMark::newCSet() {
3082 if (!concurrent_marking_in_progress()) {
3083 // nothing to do if marking is not in progress
3084 return;
3085 }
3086
3087 // find what the lowest finger is among the global and local fingers
3088 _min_finger = _finger;
3089 for (int i = 0; i < (int)_max_task_num; ++i) {
3090 CMTask* task = _tasks[i];
3091 HeapWord* task_finger = task->finger();
3092 if (task_finger != NULL && task_finger < _min_finger) {
3093 _min_finger = task_finger;
3094 }
3095 }
3096
3097 _should_gray_objects = false;
3098
3099 // This fixes a very subtle and fustrating bug. It might be the case
3100 // that, during en evacuation pause, heap regions that contain
3101 // objects that are gray (by being in regions contained in the
3102 // region stack) are included in the collection set. Since such gray
3103 // objects will be moved, and because it's not easy to redirect
3104 // region stack entries to point to a new location (because objects
3105 // in one region might be scattered to multiple regions after they
3106 // are copied), one option is to ensure that all marked objects
3107 // copied during a pause are pushed on the stack. Notice, however,
3108 // that this problem can only happen when the region stack is not
3109 // empty during an evacuation pause. So, we make the fix a bit less
3110 // conservative and ensure that regions are pushed on the stack,
3111 // irrespective whether all collection set regions are below the
3112 // finger, if the region stack is not empty. This is expected to be
3113 // a rare case, so I don't think it's necessary to be smarted about it.
3114 if (!region_stack_empty() || has_aborted_regions()) {
3115 _should_gray_objects = true;
3116 }
3117 }
3118
3119 void ConcurrentMark::registerCSetRegion(HeapRegion* hr) {
3120 if (!concurrent_marking_in_progress()) return;
3121
3122 HeapWord* region_end = hr->end();
3123 if (region_end > _min_finger) {
3124 _should_gray_objects = true;
3125 }
3126 }
3127
3128 // Resets the region fields of active CMTasks whose values point
3129 // into the collection set.
3130 void ConcurrentMark::reset_active_task_region_fields_in_cset() {
3131 assert(SafepointSynchronize::is_at_safepoint(), "should be in STW");
3132 assert(parallel_marking_threads() <= _max_task_num, "sanity");
3133
3134 for (int i = 0; i < (int)parallel_marking_threads(); i += 1) {
3135 CMTask* task = _tasks[i];
3136 HeapWord* task_finger = task->finger();
3137 if (task_finger != NULL) {
3138 assert(_g1h->is_in_g1_reserved(task_finger), "not in heap");
3139 HeapRegion* finger_region = _g1h->heap_region_containing(task_finger);
3140 if (finger_region->in_collection_set()) {
3141 // The task's current region is in the collection set.
3142 // This region will be evacuated in the current GC and
3143 // the region fields in the task will be stale.
3144 task->giveup_current_region();
3145 }
3146 }
3147 }
3148 }
3149
3150 // abandon current marking iteration due to a Full GC
3151 void ConcurrentMark::abort() {
3152 // Clear all marks to force marking thread to do nothing
3153 _nextMarkBitMap->clearAll();
3154 // Empty mark stack
3155 clear_marking_state();
3156 for (int i = 0; i < (int)_max_task_num; ++i) {
3157 _tasks[i]->clear_region_fields();
3158 }
3159 _has_aborted = true;
3160
3161 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3162 satb_mq_set.abandon_partial_marking();
3163 // This can be called either during or outside marking, we'll read
3164 // the expected_active value from the SATB queue set.
3165 satb_mq_set.set_active_all_threads(
3166 false, /* new active value */
3167 satb_mq_set.is_active() /* expected_active */);
3168 }
3169
3170 static void print_ms_time_info(const char* prefix, const char* name,
3171 NumberSeq& ns) {
3172 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3173 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3174 if (ns.num() > 0) {
3175 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3176 prefix, ns.sd(), ns.maximum());
3177 }
3178 }
3179
3180 void ConcurrentMark::print_summary_info() {
3181 gclog_or_tty->print_cr(" Concurrent marking:");
3182 print_ms_time_info(" ", "init marks", _init_times);
3183 print_ms_time_info(" ", "remarks", _remark_times);
3184 {
3185 print_ms_time_info(" ", "final marks", _remark_mark_times);
3186 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3187
3188 }
3189 print_ms_time_info(" ", "cleanups", _cleanup_times);
3190 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3191 _total_counting_time,
3192 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3193 (double)_cleanup_times.num()
3194 : 0.0));
3195 if (G1ScrubRemSets) {
3196 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3197 _total_rs_scrub_time,
3198 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3199 (double)_cleanup_times.num()
3200 : 0.0));
3201 }
3202 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3203 (_init_times.sum() + _remark_times.sum() +
3204 _cleanup_times.sum())/1000.0);
3205 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3206 "(%8.2f s marking, %8.2f s counting).",
3207 cmThread()->vtime_accum(),
3208 cmThread()->vtime_mark_accum(),
3209 cmThread()->vtime_count_accum());
3210 }
3211
3212 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3213 _parallel_workers->print_worker_threads_on(st);
3214 }
3215
3216 // Closures
3217 // XXX: there seems to be a lot of code duplication here;
3218 // should refactor and consolidate the shared code.
3219
3220 // This closure is used to mark refs into the CMS generation in
3221 // the CMS bit map. Called at the first checkpoint.
3222
3223 // We take a break if someone is trying to stop the world.
3224 bool ConcurrentMark::do_yield_check(int worker_i) {
3225 if (should_yield()) {
3226 if (worker_i == 0) {
3227 _g1h->g1_policy()->record_concurrent_pause();
3228 }
3229 cmThread()->yield();
3230 if (worker_i == 0) {
3231 _g1h->g1_policy()->record_concurrent_pause_end();
3232 }
3233 return true;
3234 } else {
3235 return false;
3236 }
3237 }
3238
3239 bool ConcurrentMark::should_yield() {
3240 return cmThread()->should_yield();
3241 }
3242
3243 bool ConcurrentMark::containing_card_is_marked(void* p) {
3244 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3245 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3246 }
3247
3248 bool ConcurrentMark::containing_cards_are_marked(void* start,
3249 void* last) {
3250 return containing_card_is_marked(start) &&
3251 containing_card_is_marked(last);
3252 }
3253
3254 #ifndef PRODUCT
3255 // for debugging purposes
3256 void ConcurrentMark::print_finger() {
3257 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3258 _heap_start, _heap_end, _finger);
3259 for (int i = 0; i < (int) _max_task_num; ++i) {
3260 gclog_or_tty->print(" %d: "PTR_FORMAT, i, _tasks[i]->finger());
3261 }
3262 gclog_or_tty->print_cr("");
3263 }
3264 #endif
3265
3266 void CMTask::scan_object(oop obj) {
3267 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3268
3269 if (_cm->verbose_high()) {
3270 gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
3271 _task_id, (void*) obj);
3272 }
3273
3274 size_t obj_size = obj->size();
3275 _words_scanned += obj_size;
3276
3277 obj->oop_iterate(_cm_oop_closure);
3278 statsOnly( ++_objs_scanned );
3279 check_limits();
3280 }
3281
3282 // Closure for iteration over bitmaps
3283 class CMBitMapClosure : public BitMapClosure {
3284 private:
3285 // the bitmap that is being iterated over
3286 CMBitMap* _nextMarkBitMap;
3287 ConcurrentMark* _cm;
3288 CMTask* _task;
3289 // true if we're scanning a heap region claimed by the task (so that
3290 // we move the finger along), false if we're not, i.e. currently when
3291 // scanning a heap region popped from the region stack (so that we
3292 // do not move the task finger along; it'd be a mistake if we did so).
3293 bool _scanning_heap_region;
3294
3295 public:
3296 CMBitMapClosure(CMTask *task,
3297 ConcurrentMark* cm,
3298 CMBitMap* nextMarkBitMap)
3299 : _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3300
3301 void set_scanning_heap_region(bool scanning_heap_region) {
3302 _scanning_heap_region = scanning_heap_region;
3303 }
3304
3305 bool do_bit(size_t offset) {
3306 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3307 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3308 assert( addr < _cm->finger(), "invariant");
3309
3310 if (_scanning_heap_region) {
3311 statsOnly( _task->increase_objs_found_on_bitmap() );
3312 assert(addr >= _task->finger(), "invariant");
3313 // We move that task's local finger along.
3314 _task->move_finger_to(addr);
3315 } else {
3316 // We move the task's region finger along.
3317 _task->move_region_finger_to(addr);
3318 }
3319
3320 _task->scan_object(oop(addr));
3321 // we only partially drain the local queue and global stack
3322 _task->drain_local_queue(true);
3323 _task->drain_global_stack(true);
3324
3325 // if the has_aborted flag has been raised, we need to bail out of
3326 // the iteration
3327 return !_task->has_aborted();
3328 }
3329 };
3330
3331 // Closure for iterating over objects, currently only used for
3332 // processing SATB buffers.
3333 class CMObjectClosure : public ObjectClosure {
3334 private:
3335 CMTask* _task;
3336
3337 public:
3338 void do_object(oop obj) {
3339 _task->deal_with_reference(obj);
3340 }
3341
3342 CMObjectClosure(CMTask* task) : _task(task) { }
3343 };
3344
3345 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3346 ConcurrentMark* cm,
3347 CMTask* task)
3348 : _g1h(g1h), _cm(cm), _task(task) {
3349 assert(_ref_processor == NULL, "should be initialized to NULL");
3350
3351 if (G1UseConcMarkReferenceProcessing) {
3352 _ref_processor = g1h->ref_processor_cm();
3353 assert(_ref_processor != NULL, "should not be NULL");
3354 }
3355 }
3356
3357 void CMTask::setup_for_region(HeapRegion* hr) {
3358 // Separated the asserts so that we know which one fires.
3359 assert(hr != NULL,
3360 "claim_region() should have filtered out continues humongous regions");
3361 assert(!hr->continuesHumongous(),
3362 "claim_region() should have filtered out continues humongous regions");
3363
3364 if (_cm->verbose_low()) {
3365 gclog_or_tty->print_cr("[%d] setting up for region "PTR_FORMAT,
3366 _task_id, hr);
3367 }
3368
3369 _curr_region = hr;
3370 _finger = hr->bottom();
3371 update_region_limit();
3372 }
3373
3374 void CMTask::update_region_limit() {
3375 HeapRegion* hr = _curr_region;
3376 HeapWord* bottom = hr->bottom();
3377 HeapWord* limit = hr->next_top_at_mark_start();
3378
3379 if (limit == bottom) {
3380 if (_cm->verbose_low()) {
3381 gclog_or_tty->print_cr("[%d] found an empty region "
3382 "["PTR_FORMAT", "PTR_FORMAT")",
3383 _task_id, bottom, limit);
3384 }
3385 // The region was collected underneath our feet.
3386 // We set the finger to bottom to ensure that the bitmap
3387 // iteration that will follow this will not do anything.
3388 // (this is not a condition that holds when we set the region up,
3389 // as the region is not supposed to be empty in the first place)
3390 _finger = bottom;
3391 } else if (limit >= _region_limit) {
3392 assert(limit >= _finger, "peace of mind");
3393 } else {
3394 assert(limit < _region_limit, "only way to get here");
3395 // This can happen under some pretty unusual circumstances. An
3396 // evacuation pause empties the region underneath our feet (NTAMS
3397 // at bottom). We then do some allocation in the region (NTAMS
3398 // stays at bottom), followed by the region being used as a GC
3399 // alloc region (NTAMS will move to top() and the objects
3400 // originally below it will be grayed). All objects now marked in
3401 // the region are explicitly grayed, if below the global finger,
3402 // and we do not need in fact to scan anything else. So, we simply
3403 // set _finger to be limit to ensure that the bitmap iteration
3404 // doesn't do anything.
3405 _finger = limit;
3406 }
3407
3408 _region_limit = limit;
3409 }
3410
3411 void CMTask::giveup_current_region() {
3412 assert(_curr_region != NULL, "invariant");
3413 if (_cm->verbose_low()) {
3414 gclog_or_tty->print_cr("[%d] giving up region "PTR_FORMAT,
3415 _task_id, _curr_region);
3416 }
3417 clear_region_fields();
3418 }
3419
3420 void CMTask::clear_region_fields() {
3421 // Values for these three fields that indicate that we're not
3422 // holding on to a region.
3423 _curr_region = NULL;
3424 _finger = NULL;
3425 _region_limit = NULL;
3426
3427 _region_finger = NULL;
3428 }
3429
3430 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3431 if (cm_oop_closure == NULL) {
3432 assert(_cm_oop_closure != NULL, "invariant");
3433 } else {
3434 assert(_cm_oop_closure == NULL, "invariant");
3435 }
3436 _cm_oop_closure = cm_oop_closure;
3437 }
3438
3439 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3440 guarantee(nextMarkBitMap != NULL, "invariant");
3441
3442 if (_cm->verbose_low()) {
3443 gclog_or_tty->print_cr("[%d] resetting", _task_id);
3444 }
3445
3446 _nextMarkBitMap = nextMarkBitMap;
3447 clear_region_fields();
3448 assert(_aborted_region.is_empty(), "should have been cleared");
3449
3450 _calls = 0;
3451 _elapsed_time_ms = 0.0;
3452 _termination_time_ms = 0.0;
3453 _termination_start_time_ms = 0.0;
3454
3455 #if _MARKING_STATS_
3456 _local_pushes = 0;
3457 _local_pops = 0;
3458 _local_max_size = 0;
3459 _objs_scanned = 0;
3460 _global_pushes = 0;
3461 _global_pops = 0;
3462 _global_max_size = 0;
3463 _global_transfers_to = 0;
3464 _global_transfers_from = 0;
3465 _region_stack_pops = 0;
3466 _regions_claimed = 0;
3467 _objs_found_on_bitmap = 0;
3468 _satb_buffers_processed = 0;
3469 _steal_attempts = 0;
3470 _steals = 0;
3471 _aborted = 0;
3472 _aborted_overflow = 0;
3473 _aborted_cm_aborted = 0;
3474 _aborted_yield = 0;
3475 _aborted_timed_out = 0;
3476 _aborted_satb = 0;
3477 _aborted_termination = 0;
3478 #endif // _MARKING_STATS_
3479 }
3480
3481 bool CMTask::should_exit_termination() {
3482 regular_clock_call();
3483 // This is called when we are in the termination protocol. We should
3484 // quit if, for some reason, this task wants to abort or the global
3485 // stack is not empty (this means that we can get work from it).
3486 return !_cm->mark_stack_empty() || has_aborted();
3487 }
3488
3489 void CMTask::reached_limit() {
3490 assert(_words_scanned >= _words_scanned_limit ||
3491 _refs_reached >= _refs_reached_limit ,
3492 "shouldn't have been called otherwise");
3493 regular_clock_call();
3494 }
3495
3496 void CMTask::regular_clock_call() {
3497 if (has_aborted()) return;
3498
3499 // First, we need to recalculate the words scanned and refs reached
3500 // limits for the next clock call.
3501 recalculate_limits();
3502
3503 // During the regular clock call we do the following
3504
3505 // (1) If an overflow has been flagged, then we abort.
3506 if (_cm->has_overflown()) {
3507 set_has_aborted();
3508 return;
3509 }
3510
3511 // If we are not concurrent (i.e. we're doing remark) we don't need
3512 // to check anything else. The other steps are only needed during
3513 // the concurrent marking phase.
3514 if (!concurrent()) return;
3515
3516 // (2) If marking has been aborted for Full GC, then we also abort.
3517 if (_cm->has_aborted()) {
3518 set_has_aborted();
3519 statsOnly( ++_aborted_cm_aborted );
3520 return;
3521 }
3522
3523 double curr_time_ms = os::elapsedVTime() * 1000.0;
3524
3525 // (3) If marking stats are enabled, then we update the step history.
3526 #if _MARKING_STATS_
3527 if (_words_scanned >= _words_scanned_limit) {
3528 ++_clock_due_to_scanning;
3529 }
3530 if (_refs_reached >= _refs_reached_limit) {
3531 ++_clock_due_to_marking;
3532 }
3533
3534 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3535 _interval_start_time_ms = curr_time_ms;
3536 _all_clock_intervals_ms.add(last_interval_ms);
3537
3538 if (_cm->verbose_medium()) {
3539 gclog_or_tty->print_cr("[%d] regular clock, interval = %1.2lfms, "
3540 "scanned = %d%s, refs reached = %d%s",
3541 _task_id, last_interval_ms,
3542 _words_scanned,
3543 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3544 _refs_reached,
3545 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3546 }
3547 #endif // _MARKING_STATS_
3548
3549 // (4) We check whether we should yield. If we have to, then we abort.
3550 if (_cm->should_yield()) {
3551 // We should yield. To do this we abort the task. The caller is
3552 // responsible for yielding.
3553 set_has_aborted();
3554 statsOnly( ++_aborted_yield );
3555 return;
3556 }
3557
3558 // (5) We check whether we've reached our time quota. If we have,
3559 // then we abort.
3560 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3561 if (elapsed_time_ms > _time_target_ms) {
3562 set_has_aborted();
3563 _has_timed_out = true;
3564 statsOnly( ++_aborted_timed_out );
3565 return;
3566 }
3567
3568 // (6) Finally, we check whether there are enough completed STAB
3569 // buffers available for processing. If there are, we abort.
3570 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3571 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3572 if (_cm->verbose_low()) {
3573 gclog_or_tty->print_cr("[%d] aborting to deal with pending SATB buffers",
3574 _task_id);
3575 }
3576 // we do need to process SATB buffers, we'll abort and restart
3577 // the marking task to do so
3578 set_has_aborted();
3579 statsOnly( ++_aborted_satb );
3580 return;
3581 }
3582 }
3583
3584 void CMTask::recalculate_limits() {
3585 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3586 _words_scanned_limit = _real_words_scanned_limit;
3587
3588 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3589 _refs_reached_limit = _real_refs_reached_limit;
3590 }
3591
3592 void CMTask::decrease_limits() {
3593 // This is called when we believe that we're going to do an infrequent
3594 // operation which will increase the per byte scanned cost (i.e. move
3595 // entries to/from the global stack). It basically tries to decrease the
3596 // scanning limit so that the clock is called earlier.
3597
3598 if (_cm->verbose_medium()) {
3599 gclog_or_tty->print_cr("[%d] decreasing limits", _task_id);
3600 }
3601
3602 _words_scanned_limit = _real_words_scanned_limit -
3603 3 * words_scanned_period / 4;
3604 _refs_reached_limit = _real_refs_reached_limit -
3605 3 * refs_reached_period / 4;
3606 }
3607
3608 void CMTask::move_entries_to_global_stack() {
3609 // local array where we'll store the entries that will be popped
3610 // from the local queue
3611 oop buffer[global_stack_transfer_size];
3612
3613 int n = 0;
3614 oop obj;
3615 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3616 buffer[n] = obj;
3617 ++n;
3618 }
3619
3620 if (n > 0) {
3621 // we popped at least one entry from the local queue
3622
3623 statsOnly( ++_global_transfers_to; _local_pops += n );
3624
3625 if (!_cm->mark_stack_push(buffer, n)) {
3626 if (_cm->verbose_low()) {
3627 gclog_or_tty->print_cr("[%d] aborting due to global stack overflow",
3628 _task_id);
3629 }
3630 set_has_aborted();
3631 } else {
3632 // the transfer was successful
3633
3634 if (_cm->verbose_medium()) {
3635 gclog_or_tty->print_cr("[%d] pushed %d entries to the global stack",
3636 _task_id, n);
3637 }
3638 statsOnly( int tmp_size = _cm->mark_stack_size();
3639 if (tmp_size > _global_max_size) {
3640 _global_max_size = tmp_size;
3641 }
3642 _global_pushes += n );
3643 }
3644 }
3645
3646 // this operation was quite expensive, so decrease the limits
3647 decrease_limits();
3648 }
3649
3650 void CMTask::get_entries_from_global_stack() {
3651 // local array where we'll store the entries that will be popped
3652 // from the global stack.
3653 oop buffer[global_stack_transfer_size];
3654 int n;
3655 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3656 assert(n <= global_stack_transfer_size,
3657 "we should not pop more than the given limit");
3658 if (n > 0) {
3659 // yes, we did actually pop at least one entry
3660
3661 statsOnly( ++_global_transfers_from; _global_pops += n );
3662 if (_cm->verbose_medium()) {
3663 gclog_or_tty->print_cr("[%d] popped %d entries from the global stack",
3664 _task_id, n);
3665 }
3666 for (int i = 0; i < n; ++i) {
3667 bool success = _task_queue->push(buffer[i]);
3668 // We only call this when the local queue is empty or under a
3669 // given target limit. So, we do not expect this push to fail.
3670 assert(success, "invariant");
3671 }
3672
3673 statsOnly( int tmp_size = _task_queue->size();
3674 if (tmp_size > _local_max_size) {
3675 _local_max_size = tmp_size;
3676 }
3677 _local_pushes += n );
3678 }
3679
3680 // this operation was quite expensive, so decrease the limits
3681 decrease_limits();
3682 }
3683
3684 void CMTask::drain_local_queue(bool partially) {
3685 if (has_aborted()) return;
3686
3687 // Decide what the target size is, depending whether we're going to
3688 // drain it partially (so that other tasks can steal if they run out
3689 // of things to do) or totally (at the very end).
3690 size_t target_size;
3691 if (partially) {
3692 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3693 } else {
3694 target_size = 0;
3695 }
3696
3697 if (_task_queue->size() > target_size) {
3698 if (_cm->verbose_high()) {
3699 gclog_or_tty->print_cr("[%d] draining local queue, target size = %d",
3700 _task_id, target_size);
3701 }
3702
3703 oop obj;
3704 bool ret = _task_queue->pop_local(obj);
3705 while (ret) {
3706 statsOnly( ++_local_pops );
3707
3708 if (_cm->verbose_high()) {
3709 gclog_or_tty->print_cr("[%d] popped "PTR_FORMAT, _task_id,
3710 (void*) obj);
3711 }
3712
3713 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3714 assert(!_g1h->is_on_master_free_list(
3715 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3716
3717 scan_object(obj);
3718
3719 if (_task_queue->size() <= target_size || has_aborted()) {
3720 ret = false;
3721 } else {
3722 ret = _task_queue->pop_local(obj);
3723 }
3724 }
3725
3726 if (_cm->verbose_high()) {
3727 gclog_or_tty->print_cr("[%d] drained local queue, size = %d",
3728 _task_id, _task_queue->size());
3729 }
3730 }
3731 }
3732
3733 void CMTask::drain_global_stack(bool partially) {
3734 if (has_aborted()) return;
3735
3736 // We have a policy to drain the local queue before we attempt to
3737 // drain the global stack.
3738 assert(partially || _task_queue->size() == 0, "invariant");
3739
3740 // Decide what the target size is, depending whether we're going to
3741 // drain it partially (so that other tasks can steal if they run out
3742 // of things to do) or totally (at the very end). Notice that,
3743 // because we move entries from the global stack in chunks or
3744 // because another task might be doing the same, we might in fact
3745 // drop below the target. But, this is not a problem.
3746 size_t target_size;
3747 if (partially) {
3748 target_size = _cm->partial_mark_stack_size_target();
3749 } else {
3750 target_size = 0;
3751 }
3752
3753 if (_cm->mark_stack_size() > target_size) {
3754 if (_cm->verbose_low()) {
3755 gclog_or_tty->print_cr("[%d] draining global_stack, target size %d",
3756 _task_id, target_size);
3757 }
3758
3759 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3760 get_entries_from_global_stack();
3761 drain_local_queue(partially);
3762 }
3763
3764 if (_cm->verbose_low()) {
3765 gclog_or_tty->print_cr("[%d] drained global stack, size = %d",
3766 _task_id, _cm->mark_stack_size());
3767 }
3768 }
3769 }
3770
3771 // SATB Queue has several assumptions on whether to call the par or
3772 // non-par versions of the methods. this is why some of the code is
3773 // replicated. We should really get rid of the single-threaded version
3774 // of the code to simplify things.
3775 void CMTask::drain_satb_buffers() {
3776 if (has_aborted()) return;
3777
3778 // We set this so that the regular clock knows that we're in the
3779 // middle of draining buffers and doesn't set the abort flag when it
3780 // notices that SATB buffers are available for draining. It'd be
3781 // very counter productive if it did that. :-)
3782 _draining_satb_buffers = true;
3783
3784 CMObjectClosure oc(this);
3785 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3786 if (G1CollectedHeap::use_parallel_gc_threads()) {
3787 satb_mq_set.set_par_closure(_task_id, &oc);
3788 } else {
3789 satb_mq_set.set_closure(&oc);
3790 }
3791
3792 // This keeps claiming and applying the closure to completed buffers
3793 // until we run out of buffers or we need to abort.
3794 if (G1CollectedHeap::use_parallel_gc_threads()) {
3795 while (!has_aborted() &&
3796 satb_mq_set.par_apply_closure_to_completed_buffer(_task_id)) {
3797 if (_cm->verbose_medium()) {
3798 gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id);
3799 }
3800 statsOnly( ++_satb_buffers_processed );
3801 regular_clock_call();
3802 }
3803 } else {
3804 while (!has_aborted() &&
3805 satb_mq_set.apply_closure_to_completed_buffer()) {
3806 if (_cm->verbose_medium()) {
3807 gclog_or_tty->print_cr("[%d] processed an SATB buffer", _task_id);
3808 }
3809 statsOnly( ++_satb_buffers_processed );
3810 regular_clock_call();
3811 }
3812 }
3813
3814 if (!concurrent() && !has_aborted()) {
3815 // We should only do this during remark.
3816 if (G1CollectedHeap::use_parallel_gc_threads()) {
3817 satb_mq_set.par_iterate_closure_all_threads(_task_id);
3818 } else {
3819 satb_mq_set.iterate_closure_all_threads();
3820 }
3821 }
3822
3823 _draining_satb_buffers = false;
3824
3825 assert(has_aborted() ||
3826 concurrent() ||
3827 satb_mq_set.completed_buffers_num() == 0, "invariant");
3828
3829 if (G1CollectedHeap::use_parallel_gc_threads()) {
3830 satb_mq_set.set_par_closure(_task_id, NULL);
3831 } else {
3832 satb_mq_set.set_closure(NULL);
3833 }
3834
3835 // again, this was a potentially expensive operation, decrease the
3836 // limits to get the regular clock call early
3837 decrease_limits();
3838 }
3839
3840 void CMTask::drain_region_stack(BitMapClosure* bc) {
3841 if (has_aborted()) return;
3842
3843 assert(_region_finger == NULL,
3844 "it should be NULL when we're not scanning a region");
3845
3846 if (!_cm->region_stack_empty() || !_aborted_region.is_empty()) {
3847 if (_cm->verbose_low()) {
3848 gclog_or_tty->print_cr("[%d] draining region stack, size = %d",
3849 _task_id, _cm->region_stack_size());
3850 }
3851
3852 MemRegion mr;
3853
3854 if (!_aborted_region.is_empty()) {
3855 mr = _aborted_region;
3856 _aborted_region = MemRegion();
3857
3858 if (_cm->verbose_low()) {
3859 gclog_or_tty->print_cr("[%d] scanning aborted region "
3860 "[ " PTR_FORMAT ", " PTR_FORMAT " )",
3861 _task_id, mr.start(), mr.end());
3862 }
3863 } else {
3864 mr = _cm->region_stack_pop_lock_free();
3865 // it returns MemRegion() if the pop fails
3866 statsOnly(if (mr.start() != NULL) ++_region_stack_pops );
3867 }
3868
3869 while (mr.start() != NULL) {
3870 if (_cm->verbose_medium()) {
3871 gclog_or_tty->print_cr("[%d] we are scanning region "
3872 "["PTR_FORMAT", "PTR_FORMAT")",
3873 _task_id, mr.start(), mr.end());
3874 }
3875
3876 assert(mr.end() <= _cm->finger(),
3877 "otherwise the region shouldn't be on the stack");
3878 assert(!mr.is_empty(), "Only non-empty regions live on the region stack");
3879 if (_nextMarkBitMap->iterate(bc, mr)) {
3880 assert(!has_aborted(),
3881 "cannot abort the task without aborting the bitmap iteration");
3882
3883 // We finished iterating over the region without aborting.
3884 regular_clock_call();
3885 if (has_aborted()) {
3886 mr = MemRegion();
3887 } else {
3888 mr = _cm->region_stack_pop_lock_free();
3889 // it returns MemRegion() if the pop fails
3890 statsOnly(if (mr.start() != NULL) ++_region_stack_pops );
3891 }
3892 } else {
3893 assert(has_aborted(), "currently the only way to do so");
3894
3895 // The only way to abort the bitmap iteration is to return
3896 // false from the do_bit() method. However, inside the
3897 // do_bit() method we move the _region_finger to point to the
3898 // object currently being looked at. So, if we bail out, we
3899 // have definitely set _region_finger to something non-null.
3900 assert(_region_finger != NULL, "invariant");
3901
3902 // Make sure that any previously aborted region has been
3903 // cleared.
3904 assert(_aborted_region.is_empty(), "aborted region not cleared");
3905
3906 // The iteration was actually aborted. So now _region_finger
3907 // points to the address of the object we last scanned. If we
3908 // leave it there, when we restart this task, we will rescan
3909 // the object. It is easy to avoid this. We move the finger by
3910 // enough to point to the next possible object header (the
3911 // bitmap knows by how much we need to move it as it knows its
3912 // granularity).
3913 MemRegion newRegion =
3914 MemRegion(_nextMarkBitMap->nextWord(_region_finger), mr.end());
3915
3916 if (!newRegion.is_empty()) {
3917 if (_cm->verbose_low()) {
3918 gclog_or_tty->print_cr("[%d] recording unscanned region"
3919 "[" PTR_FORMAT "," PTR_FORMAT ") in CMTask",
3920 _task_id,
3921 newRegion.start(), newRegion.end());
3922 }
3923 // Now record the part of the region we didn't scan to
3924 // make sure this task scans it later.
3925 _aborted_region = newRegion;
3926 }
3927 // break from while
3928 mr = MemRegion();
3929 }
3930 _region_finger = NULL;
3931 }
3932
3933 if (_cm->verbose_low()) {
3934 gclog_or_tty->print_cr("[%d] drained region stack, size = %d",
3935 _task_id, _cm->region_stack_size());
3936 }
3937 }
3938 }
3939
3940 void CMTask::print_stats() {
3941 gclog_or_tty->print_cr("Marking Stats, task = %d, calls = %d",
3942 _task_id, _calls);
3943 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3944 _elapsed_time_ms, _termination_time_ms);
3945 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3946 _step_times_ms.num(), _step_times_ms.avg(),
3947 _step_times_ms.sd());
3948 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3949 _step_times_ms.maximum(), _step_times_ms.sum());
3950
3951 #if _MARKING_STATS_
3952 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3953 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3954 _all_clock_intervals_ms.sd());
3955 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3956 _all_clock_intervals_ms.maximum(),
3957 _all_clock_intervals_ms.sum());
3958 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3959 _clock_due_to_scanning, _clock_due_to_marking);
3960 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3961 _objs_scanned, _objs_found_on_bitmap);
3962 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3963 _local_pushes, _local_pops, _local_max_size);
3964 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3965 _global_pushes, _global_pops, _global_max_size);
3966 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3967 _global_transfers_to,_global_transfers_from);
3968 gclog_or_tty->print_cr(" Regions: claimed = %d, Region Stack: pops = %d",
3969 _regions_claimed, _region_stack_pops);
3970 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3971 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3972 _steal_attempts, _steals);
3973 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3974 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3975 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3976 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3977 _aborted_timed_out, _aborted_satb, _aborted_termination);
3978 #endif // _MARKING_STATS_
3979 }
3980
3981 /*****************************************************************************
3982
3983 The do_marking_step(time_target_ms) method is the building block
3984 of the parallel marking framework. It can be called in parallel
3985 with other invocations of do_marking_step() on different tasks
3986 (but only one per task, obviously) and concurrently with the
3987 mutator threads, or during remark, hence it eliminates the need
3988 for two versions of the code. When called during remark, it will
3989 pick up from where the task left off during the concurrent marking
3990 phase. Interestingly, tasks are also claimable during evacuation
3991 pauses too, since do_marking_step() ensures that it aborts before
3992 it needs to yield.
3993
3994 The data structures that is uses to do marking work are the
3995 following:
3996
3997 (1) Marking Bitmap. If there are gray objects that appear only
3998 on the bitmap (this happens either when dealing with an overflow
3999 or when the initial marking phase has simply marked the roots
4000 and didn't push them on the stack), then tasks claim heap
4001 regions whose bitmap they then scan to find gray objects. A
4002 global finger indicates where the end of the last claimed region
4003 is. A local finger indicates how far into the region a task has
4004 scanned. The two fingers are used to determine how to gray an
4005 object (i.e. whether simply marking it is OK, as it will be
4006 visited by a task in the future, or whether it needs to be also
4007 pushed on a stack).
4008
4009 (2) Local Queue. The local queue of the task which is accessed
4010 reasonably efficiently by the task. Other tasks can steal from
4011 it when they run out of work. Throughout the marking phase, a
4012 task attempts to keep its local queue short but not totally
4013 empty, so that entries are available for stealing by other
4014 tasks. Only when there is no more work, a task will totally
4015 drain its local queue.
4016
4017 (3) Global Mark Stack. This handles local queue overflow. During
4018 marking only sets of entries are moved between it and the local
4019 queues, as access to it requires a mutex and more fine-grain
4020 interaction with it which might cause contention. If it
4021 overflows, then the marking phase should restart and iterate
4022 over the bitmap to identify gray objects. Throughout the marking
4023 phase, tasks attempt to keep the global mark stack at a small
4024 length but not totally empty, so that entries are available for
4025 popping by other tasks. Only when there is no more work, tasks
4026 will totally drain the global mark stack.
4027
4028 (4) Global Region Stack. Entries on it correspond to areas of
4029 the bitmap that need to be scanned since they contain gray
4030 objects. Pushes on the region stack only happen during
4031 evacuation pauses and typically correspond to areas covered by
4032 GC LABS. If it overflows, then the marking phase should restart
4033 and iterate over the bitmap to identify gray objects. Tasks will
4034 try to totally drain the region stack as soon as possible.
4035
4036 (5) SATB Buffer Queue. This is where completed SATB buffers are
4037 made available. Buffers are regularly removed from this queue
4038 and scanned for roots, so that the queue doesn't get too
4039 long. During remark, all completed buffers are processed, as
4040 well as the filled in parts of any uncompleted buffers.
4041
4042 The do_marking_step() method tries to abort when the time target
4043 has been reached. There are a few other cases when the
4044 do_marking_step() method also aborts:
4045
4046 (1) When the marking phase has been aborted (after a Full GC).
4047
4048 (2) When a global overflow (either on the global stack or the
4049 region stack) has been triggered. Before the task aborts, it
4050 will actually sync up with the other tasks to ensure that all
4051 the marking data structures (local queues, stacks, fingers etc.)
4052 are re-initialised so that when do_marking_step() completes,
4053 the marking phase can immediately restart.
4054
4055 (3) When enough completed SATB buffers are available. The
4056 do_marking_step() method only tries to drain SATB buffers right
4057 at the beginning. So, if enough buffers are available, the
4058 marking step aborts and the SATB buffers are processed at
4059 the beginning of the next invocation.
4060
4061 (4) To yield. when we have to yield then we abort and yield
4062 right at the end of do_marking_step(). This saves us from a lot
4063 of hassle as, by yielding we might allow a Full GC. If this
4064 happens then objects will be compacted underneath our feet, the
4065 heap might shrink, etc. We save checking for this by just
4066 aborting and doing the yield right at the end.
4067
4068 From the above it follows that the do_marking_step() method should
4069 be called in a loop (or, otherwise, regularly) until it completes.
4070
4071 If a marking step completes without its has_aborted() flag being
4072 true, it means it has completed the current marking phase (and
4073 also all other marking tasks have done so and have all synced up).
4074
4075 A method called regular_clock_call() is invoked "regularly" (in
4076 sub ms intervals) throughout marking. It is this clock method that
4077 checks all the abort conditions which were mentioned above and
4078 decides when the task should abort. A work-based scheme is used to
4079 trigger this clock method: when the number of object words the
4080 marking phase has scanned or the number of references the marking
4081 phase has visited reach a given limit. Additional invocations to
4082 the method clock have been planted in a few other strategic places
4083 too. The initial reason for the clock method was to avoid calling
4084 vtime too regularly, as it is quite expensive. So, once it was in
4085 place, it was natural to piggy-back all the other conditions on it
4086 too and not constantly check them throughout the code.
4087
4088 *****************************************************************************/
4089
4090 void CMTask::do_marking_step(double time_target_ms,
4091 bool do_stealing,
4092 bool do_termination) {
4093 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
4094 assert(concurrent() == _cm->concurrent(), "they should be the same");
4095
4096 assert(concurrent() || _cm->region_stack_empty(),
4097 "the region stack should have been cleared before remark");
4098 assert(concurrent() || !_cm->has_aborted_regions(),
4099 "aborted regions should have been cleared before remark");
4100 assert(_region_finger == NULL,
4101 "this should be non-null only when a region is being scanned");
4102
4103 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
4104 assert(_task_queues != NULL, "invariant");
4105 assert(_task_queue != NULL, "invariant");
4106 assert(_task_queues->queue(_task_id) == _task_queue, "invariant");
4107
4108 assert(!_claimed,
4109 "only one thread should claim this task at any one time");
4110
4111 // OK, this doesn't safeguard again all possible scenarios, as it is
4112 // possible for two threads to set the _claimed flag at the same
4113 // time. But it is only for debugging purposes anyway and it will
4114 // catch most problems.
4115 _claimed = true;
4116
4117 _start_time_ms = os::elapsedVTime() * 1000.0;
4118 statsOnly( _interval_start_time_ms = _start_time_ms );
4119
4120 double diff_prediction_ms =
4121 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
4122 _time_target_ms = time_target_ms - diff_prediction_ms;
4123
4124 // set up the variables that are used in the work-based scheme to
4125 // call the regular clock method
4126 _words_scanned = 0;
4127 _refs_reached = 0;
4128 recalculate_limits();
4129
4130 // clear all flags
4131 clear_has_aborted();
4132 _has_timed_out = false;
4133 _draining_satb_buffers = false;
4134
4135 ++_calls;
4136
4137 if (_cm->verbose_low()) {
4138 gclog_or_tty->print_cr("[%d] >>>>>>>>>> START, call = %d, "
4139 "target = %1.2lfms >>>>>>>>>>",
4140 _task_id, _calls, _time_target_ms);
4141 }
4142
4143 // Set up the bitmap and oop closures. Anything that uses them is
4144 // eventually called from this method, so it is OK to allocate these
4145 // statically.
4146 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4147 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4148 set_cm_oop_closure(&cm_oop_closure);
4149
4150 if (_cm->has_overflown()) {
4151 // This can happen if the region stack or the mark stack overflows
4152 // during a GC pause and this task, after a yield point,
4153 // restarts. We have to abort as we need to get into the overflow
4154 // protocol which happens right at the end of this task.
4155 set_has_aborted();
4156 }
4157
4158 // First drain any available SATB buffers. After this, we will not
4159 // look at SATB buffers before the next invocation of this method.
4160 // If enough completed SATB buffers are queued up, the regular clock
4161 // will abort this task so that it restarts.
4162 drain_satb_buffers();
4163 // ...then partially drain the local queue and the global stack
4164 drain_local_queue(true);
4165 drain_global_stack(true);
4166
4167 // Then totally drain the region stack. We will not look at
4168 // it again before the next invocation of this method. Entries on
4169 // the region stack are only added during evacuation pauses, for
4170 // which we have to yield. When we do, we abort the task anyway so
4171 // it will look at the region stack again when it restarts.
4172 bitmap_closure.set_scanning_heap_region(false);
4173 drain_region_stack(&bitmap_closure);
4174 // ...then partially drain the local queue and the global stack
4175 drain_local_queue(true);
4176 drain_global_stack(true);
4177
4178 do {
4179 if (!has_aborted() && _curr_region != NULL) {
4180 // This means that we're already holding on to a region.
4181 assert(_finger != NULL, "if region is not NULL, then the finger "
4182 "should not be NULL either");
4183
4184 // We might have restarted this task after an evacuation pause
4185 // which might have evacuated the region we're holding on to
4186 // underneath our feet. Let's read its limit again to make sure
4187 // that we do not iterate over a region of the heap that
4188 // contains garbage (update_region_limit() will also move
4189 // _finger to the start of the region if it is found empty).
4190 update_region_limit();
4191 // We will start from _finger not from the start of the region,
4192 // as we might be restarting this task after aborting half-way
4193 // through scanning this region. In this case, _finger points to
4194 // the address where we last found a marked object. If this is a
4195 // fresh region, _finger points to start().
4196 MemRegion mr = MemRegion(_finger, _region_limit);
4197
4198 if (_cm->verbose_low()) {
4199 gclog_or_tty->print_cr("[%d] we're scanning part "
4200 "["PTR_FORMAT", "PTR_FORMAT") "
4201 "of region "PTR_FORMAT,
4202 _task_id, _finger, _region_limit, _curr_region);
4203 }
4204
4205 // Let's iterate over the bitmap of the part of the
4206 // region that is left.
4207 bitmap_closure.set_scanning_heap_region(true);
4208 if (mr.is_empty() ||
4209 _nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4210 // We successfully completed iterating over the region. Now,
4211 // let's give up the region.
4212 giveup_current_region();
4213 regular_clock_call();
4214 } else {
4215 assert(has_aborted(), "currently the only way to do so");
4216 // The only way to abort the bitmap iteration is to return
4217 // false from the do_bit() method. However, inside the
4218 // do_bit() method we move the _finger to point to the
4219 // object currently being looked at. So, if we bail out, we
4220 // have definitely set _finger to something non-null.
4221 assert(_finger != NULL, "invariant");
4222
4223 // Region iteration was actually aborted. So now _finger
4224 // points to the address of the object we last scanned. If we
4225 // leave it there, when we restart this task, we will rescan
4226 // the object. It is easy to avoid this. We move the finger by
4227 // enough to point to the next possible object header (the
4228 // bitmap knows by how much we need to move it as it knows its
4229 // granularity).
4230 assert(_finger < _region_limit, "invariant");
4231 HeapWord* new_finger = _nextMarkBitMap->nextWord(_finger);
4232 // Check if bitmap iteration was aborted while scanning the last object
4233 if (new_finger >= _region_limit) {
4234 giveup_current_region();
4235 } else {
4236 move_finger_to(new_finger);
4237 }
4238 }
4239 }
4240 // At this point we have either completed iterating over the
4241 // region we were holding on to, or we have aborted.
4242
4243 // We then partially drain the local queue and the global stack.
4244 // (Do we really need this?)
4245 drain_local_queue(true);
4246 drain_global_stack(true);
4247
4248 // Read the note on the claim_region() method on why it might
4249 // return NULL with potentially more regions available for
4250 // claiming and why we have to check out_of_regions() to determine
4251 // whether we're done or not.
4252 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4253 // We are going to try to claim a new region. We should have
4254 // given up on the previous one.
4255 // Separated the asserts so that we know which one fires.
4256 assert(_curr_region == NULL, "invariant");
4257 assert(_finger == NULL, "invariant");
4258 assert(_region_limit == NULL, "invariant");
4259 if (_cm->verbose_low()) {
4260 gclog_or_tty->print_cr("[%d] trying to claim a new region", _task_id);
4261 }
4262 HeapRegion* claimed_region = _cm->claim_region(_task_id);
4263 if (claimed_region != NULL) {
4264 // Yes, we managed to claim one
4265 statsOnly( ++_regions_claimed );
4266
4267 if (_cm->verbose_low()) {
4268 gclog_or_tty->print_cr("[%d] we successfully claimed "
4269 "region "PTR_FORMAT,
4270 _task_id, claimed_region);
4271 }
4272
4273 setup_for_region(claimed_region);
4274 assert(_curr_region == claimed_region, "invariant");
4275 }
4276 // It is important to call the regular clock here. It might take
4277 // a while to claim a region if, for example, we hit a large
4278 // block of empty regions. So we need to call the regular clock
4279 // method once round the loop to make sure it's called
4280 // frequently enough.
4281 regular_clock_call();
4282 }
4283
4284 if (!has_aborted() && _curr_region == NULL) {
4285 assert(_cm->out_of_regions(),
4286 "at this point we should be out of regions");
4287 }
4288 } while ( _curr_region != NULL && !has_aborted());
4289
4290 if (!has_aborted()) {
4291 // We cannot check whether the global stack is empty, since other
4292 // tasks might be pushing objects to it concurrently. We also cannot
4293 // check if the region stack is empty because if a thread is aborting
4294 // it can push a partially done region back.
4295 assert(_cm->out_of_regions(),
4296 "at this point we should be out of regions");
4297
4298 if (_cm->verbose_low()) {
4299 gclog_or_tty->print_cr("[%d] all regions claimed", _task_id);
4300 }
4301
4302 // Try to reduce the number of available SATB buffers so that
4303 // remark has less work to do.
4304 drain_satb_buffers();
4305 }
4306
4307 // Since we've done everything else, we can now totally drain the
4308 // local queue and global stack.
4309 drain_local_queue(false);
4310 drain_global_stack(false);
4311
4312 // Attempt at work stealing from other task's queues.
4313 if (do_stealing && !has_aborted()) {
4314 // We have not aborted. This means that we have finished all that
4315 // we could. Let's try to do some stealing...
4316
4317 // We cannot check whether the global stack is empty, since other
4318 // tasks might be pushing objects to it concurrently. We also cannot
4319 // check if the region stack is empty because if a thread is aborting
4320 // it can push a partially done region back.
4321 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4322 "only way to reach here");
4323
4324 if (_cm->verbose_low()) {
4325 gclog_or_tty->print_cr("[%d] starting to steal", _task_id);
4326 }
4327
4328 while (!has_aborted()) {
4329 oop obj;
4330 statsOnly( ++_steal_attempts );
4331
4332 if (_cm->try_stealing(_task_id, &_hash_seed, obj)) {
4333 if (_cm->verbose_medium()) {
4334 gclog_or_tty->print_cr("[%d] stolen "PTR_FORMAT" successfully",
4335 _task_id, (void*) obj);
4336 }
4337
4338 statsOnly( ++_steals );
4339
4340 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4341 "any stolen object should be marked");
4342 scan_object(obj);
4343
4344 // And since we're towards the end, let's totally drain the
4345 // local queue and global stack.
4346 drain_local_queue(false);
4347 drain_global_stack(false);
4348 } else {
4349 break;
4350 }
4351 }
4352 }
4353
4354 // If we are about to wrap up and go into termination, check if we
4355 // should raise the overflow flag.
4356 if (do_termination && !has_aborted()) {
4357 if (_cm->force_overflow()->should_force()) {
4358 _cm->set_has_overflown();
4359 regular_clock_call();
4360 }
4361 }
4362
4363 // We still haven't aborted. Now, let's try to get into the
4364 // termination protocol.
4365 if (do_termination && !has_aborted()) {
4366 // We cannot check whether the global stack is empty, since other
4367 // tasks might be concurrently pushing objects on it. We also cannot
4368 // check if the region stack is empty because if a thread is aborting
4369 // it can push a partially done region back.
4370 // Separated the asserts so that we know which one fires.
4371 assert(_cm->out_of_regions(), "only way to reach here");
4372 assert(_task_queue->size() == 0, "only way to reach here");
4373
4374 if (_cm->verbose_low()) {
4375 gclog_or_tty->print_cr("[%d] starting termination protocol", _task_id);
4376 }
4377
4378 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4379 // The CMTask class also extends the TerminatorTerminator class,
4380 // hence its should_exit_termination() method will also decide
4381 // whether to exit the termination protocol or not.
4382 bool finished = _cm->terminator()->offer_termination(this);
4383 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4384 _termination_time_ms +=
4385 termination_end_time_ms - _termination_start_time_ms;
4386
4387 if (finished) {
4388 // We're all done.
4389
4390 if (_task_id == 0) {
4391 // let's allow task 0 to do this
4392 if (concurrent()) {
4393 assert(_cm->concurrent_marking_in_progress(), "invariant");
4394 // we need to set this to false before the next
4395 // safepoint. This way we ensure that the marking phase
4396 // doesn't observe any more heap expansions.
4397 _cm->clear_concurrent_marking_in_progress();
4398 }
4399 }
4400
4401 // We can now guarantee that the global stack is empty, since
4402 // all other tasks have finished. We separated the guarantees so
4403 // that, if a condition is false, we can immediately find out
4404 // which one.
4405 guarantee(_cm->out_of_regions(), "only way to reach here");
4406 guarantee(_aborted_region.is_empty(), "only way to reach here");
4407 guarantee(_cm->region_stack_empty(), "only way to reach here");
4408 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4409 guarantee(_task_queue->size() == 0, "only way to reach here");
4410 guarantee(!_cm->has_overflown(), "only way to reach here");
4411 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4412 guarantee(!_cm->region_stack_overflow(), "only way to reach here");
4413
4414 if (_cm->verbose_low()) {
4415 gclog_or_tty->print_cr("[%d] all tasks terminated", _task_id);
4416 }
4417 } else {
4418 // Apparently there's more work to do. Let's abort this task. It
4419 // will restart it and we can hopefully find more things to do.
4420
4421 if (_cm->verbose_low()) {
4422 gclog_or_tty->print_cr("[%d] apparently there is more work to do",
4423 _task_id);
4424 }
4425
4426 set_has_aborted();
4427 statsOnly( ++_aborted_termination );
4428 }
4429 }
4430
4431 // Mainly for debugging purposes to make sure that a pointer to the
4432 // closure which was statically allocated in this frame doesn't
4433 // escape it by accident.
4434 set_cm_oop_closure(NULL);
4435 double end_time_ms = os::elapsedVTime() * 1000.0;
4436 double elapsed_time_ms = end_time_ms - _start_time_ms;
4437 // Update the step history.
4438 _step_times_ms.add(elapsed_time_ms);
4439
4440 if (has_aborted()) {
4441 // The task was aborted for some reason.
4442
4443 statsOnly( ++_aborted );
4444
4445 if (_has_timed_out) {
4446 double diff_ms = elapsed_time_ms - _time_target_ms;
4447 // Keep statistics of how well we did with respect to hitting
4448 // our target only if we actually timed out (if we aborted for
4449 // other reasons, then the results might get skewed).
4450 _marking_step_diffs_ms.add(diff_ms);
4451 }
4452
4453 if (_cm->has_overflown()) {
4454 // This is the interesting one. We aborted because a global
4455 // overflow was raised. This means we have to restart the
4456 // marking phase and start iterating over regions. However, in
4457 // order to do this we have to make sure that all tasks stop
4458 // what they are doing and re-initialise in a safe manner. We
4459 // will achieve this with the use of two barrier sync points.
4460
4461 if (_cm->verbose_low()) {
4462 gclog_or_tty->print_cr("[%d] detected overflow", _task_id);
4463 }
4464
4465 _cm->enter_first_sync_barrier(_task_id);
4466 // When we exit this sync barrier we know that all tasks have
4467 // stopped doing marking work. So, it's now safe to
4468 // re-initialise our data structures. At the end of this method,
4469 // task 0 will clear the global data structures.
4470
4471 statsOnly( ++_aborted_overflow );
4472
4473 // We clear the local state of this task...
4474 clear_region_fields();
4475
4476 // ...and enter the second barrier.
4477 _cm->enter_second_sync_barrier(_task_id);
4478 // At this point everything has bee re-initialised and we're
4479 // ready to restart.
4480 }
4481
4482 if (_cm->verbose_low()) {
4483 gclog_or_tty->print_cr("[%d] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4484 "elapsed = %1.2lfms <<<<<<<<<<",
4485 _task_id, _time_target_ms, elapsed_time_ms);
4486 if (_cm->has_aborted()) {
4487 gclog_or_tty->print_cr("[%d] ========== MARKING ABORTED ==========",
4488 _task_id);
4489 }
4490 }
4491 } else {
4492 if (_cm->verbose_low()) {
4493 gclog_or_tty->print_cr("[%d] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4494 "elapsed = %1.2lfms <<<<<<<<<<",
4495 _task_id, _time_target_ms, elapsed_time_ms);
4496 }
4497 }
4498
4499 _claimed = false;
4500 }
4501
4502 CMTask::CMTask(int task_id,
4503 ConcurrentMark* cm,
4504 CMTaskQueue* task_queue,
4505 CMTaskQueueSet* task_queues)
4506 : _g1h(G1CollectedHeap::heap()),
4507 _task_id(task_id), _cm(cm),
4508 _claimed(false),
4509 _nextMarkBitMap(NULL), _hash_seed(17),
4510 _task_queue(task_queue),
4511 _task_queues(task_queues),
4512 _cm_oop_closure(NULL),
4513 _aborted_region(MemRegion()) {
4514 guarantee(task_queue != NULL, "invariant");
4515 guarantee(task_queues != NULL, "invariant");
4516
4517 statsOnly( _clock_due_to_scanning = 0;
4518 _clock_due_to_marking = 0 );
4519
4520 _marking_step_diffs_ms.add(0.5);
4521 }
4522
4523 // These are formatting macros that are used below to ensure
4524 // consistent formatting. The *_H_* versions are used to format the
4525 // header for a particular value and they should be kept consistent
4526 // with the corresponding macro. Also note that most of the macros add
4527 // the necessary white space (as a prefix) which makes them a bit
4528 // easier to compose.
4529
4530 // All the output lines are prefixed with this string to be able to
4531 // identify them easily in a large log file.
4532 #define G1PPRL_LINE_PREFIX "###"
4533
4534 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4535 #ifdef _LP64
4536 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4537 #else // _LP64
4538 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4539 #endif // _LP64
4540
4541 // For per-region info
4542 #define G1PPRL_TYPE_FORMAT " %-4s"
4543 #define G1PPRL_TYPE_H_FORMAT " %4s"
4544 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4545 #define G1PPRL_BYTE_H_FORMAT " %9s"
4546 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4547 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4548
4549 // For summary info
4550 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4551 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4552 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4553 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4554
4555 G1PrintRegionLivenessInfoClosure::
4556 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4557 : _out(out),
4558 _total_used_bytes(0), _total_capacity_bytes(0),
4559 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4560 _hum_used_bytes(0), _hum_capacity_bytes(0),
4561 _hum_prev_live_bytes(0), _hum_next_live_bytes(0) {
4562 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4563 MemRegion g1_committed = g1h->g1_committed();
4564 MemRegion g1_reserved = g1h->g1_reserved();
4565 double now = os::elapsedTime();
4566
4567 // Print the header of the output.
4568 _out->cr();
4569 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4570 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4571 G1PPRL_SUM_ADDR_FORMAT("committed")
4572 G1PPRL_SUM_ADDR_FORMAT("reserved")
4573 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4574 g1_committed.start(), g1_committed.end(),
4575 g1_reserved.start(), g1_reserved.end(),
4576 HeapRegion::GrainBytes);
4577 _out->print_cr(G1PPRL_LINE_PREFIX);
4578 _out->print_cr(G1PPRL_LINE_PREFIX
4579 G1PPRL_TYPE_H_FORMAT
4580 G1PPRL_ADDR_BASE_H_FORMAT
4581 G1PPRL_BYTE_H_FORMAT
4582 G1PPRL_BYTE_H_FORMAT
4583 G1PPRL_BYTE_H_FORMAT
4584 G1PPRL_DOUBLE_H_FORMAT,
4585 "type", "address-range",
4586 "used", "prev-live", "next-live", "gc-eff");
4587 _out->print_cr(G1PPRL_LINE_PREFIX
4588 G1PPRL_TYPE_H_FORMAT
4589 G1PPRL_ADDR_BASE_H_FORMAT
4590 G1PPRL_BYTE_H_FORMAT
4591 G1PPRL_BYTE_H_FORMAT
4592 G1PPRL_BYTE_H_FORMAT
4593 G1PPRL_DOUBLE_H_FORMAT,
4594 "", "",
4595 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)");
4596 }
4597
4598 // It takes as a parameter a reference to one of the _hum_* fields, it
4599 // deduces the corresponding value for a region in a humongous region
4600 // series (either the region size, or what's left if the _hum_* field
4601 // is < the region size), and updates the _hum_* field accordingly.
4602 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4603 size_t bytes = 0;
4604 // The > 0 check is to deal with the prev and next live bytes which
4605 // could be 0.
4606 if (*hum_bytes > 0) {
4607 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4608 *hum_bytes -= bytes;
4609 }
4610 return bytes;
4611 }
4612
4613 // It deduces the values for a region in a humongous region series
4614 // from the _hum_* fields and updates those accordingly. It assumes
4615 // that that _hum_* fields have already been set up from the "starts
4616 // humongous" region and we visit the regions in address order.
4617 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4618 size_t* capacity_bytes,
4619 size_t* prev_live_bytes,
4620 size_t* next_live_bytes) {
4621 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4622 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4623 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4624 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4625 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4626 }
4627
4628 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4629 const char* type = "";
4630 HeapWord* bottom = r->bottom();
4631 HeapWord* end = r->end();
4632 size_t capacity_bytes = r->capacity();
4633 size_t used_bytes = r->used();
4634 size_t prev_live_bytes = r->live_bytes();
4635 size_t next_live_bytes = r->next_live_bytes();
4636 double gc_eff = r->gc_efficiency();
4637 if (r->used() == 0) {
4638 type = "FREE";
4639 } else if (r->is_survivor()) {
4640 type = "SURV";
4641 } else if (r->is_young()) {
4642 type = "EDEN";
4643 } else if (r->startsHumongous()) {
4644 type = "HUMS";
4645
4646 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4647 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4648 "they should have been zeroed after the last time we used them");
4649 // Set up the _hum_* fields.
4650 _hum_capacity_bytes = capacity_bytes;
4651 _hum_used_bytes = used_bytes;
4652 _hum_prev_live_bytes = prev_live_bytes;
4653 _hum_next_live_bytes = next_live_bytes;
4654 get_hum_bytes(&used_bytes, &capacity_bytes,
4655 &prev_live_bytes, &next_live_bytes);
4656 end = bottom + HeapRegion::GrainWords;
4657 } else if (r->continuesHumongous()) {
4658 type = "HUMC";
4659 get_hum_bytes(&used_bytes, &capacity_bytes,
4660 &prev_live_bytes, &next_live_bytes);
4661 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4662 } else {
4663 type = "OLD";
4664 }
4665
4666 _total_used_bytes += used_bytes;
4667 _total_capacity_bytes += capacity_bytes;
4668 _total_prev_live_bytes += prev_live_bytes;
4669 _total_next_live_bytes += next_live_bytes;
4670
4671 // Print a line for this particular region.
4672 _out->print_cr(G1PPRL_LINE_PREFIX
4673 G1PPRL_TYPE_FORMAT
4674 G1PPRL_ADDR_BASE_FORMAT
4675 G1PPRL_BYTE_FORMAT
4676 G1PPRL_BYTE_FORMAT
4677 G1PPRL_BYTE_FORMAT
4678 G1PPRL_DOUBLE_FORMAT,
4679 type, bottom, end,
4680 used_bytes, prev_live_bytes, next_live_bytes, gc_eff);
4681
4682 return false;
4683 }
4684
4685 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4686 // Print the footer of the output.
4687 _out->print_cr(G1PPRL_LINE_PREFIX);
4688 _out->print_cr(G1PPRL_LINE_PREFIX
4689 " SUMMARY"
4690 G1PPRL_SUM_MB_FORMAT("capacity")
4691 G1PPRL_SUM_MB_PERC_FORMAT("used")
4692 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4693 G1PPRL_SUM_MB_PERC_FORMAT("next-live"),
4694 bytes_to_mb(_total_capacity_bytes),
4695 bytes_to_mb(_total_used_bytes),
4696 perc(_total_used_bytes, _total_capacity_bytes),
4697 bytes_to_mb(_total_prev_live_bytes),
4698 perc(_total_prev_live_bytes, _total_capacity_bytes),
4699 bytes_to_mb(_total_next_live_bytes),
4700 perc(_total_next_live_bytes, _total_capacity_bytes));
4701 _out->cr();
4702 }