1 /*
2 * Copyright (c) 2001, 2013, 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/g1Log.hpp"
33 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
34 #include "gc_implementation/g1/g1RemSet.hpp"
35 #include "gc_implementation/g1/heapRegion.inline.hpp"
36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
37 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
38 #include "gc_implementation/shared/vmGCOperations.hpp"
39 #include "memory/genOopClosures.inline.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "runtime/handles.inline.hpp"
44 #include "runtime/java.hpp"
45 #include "services/memTracker.hpp"
46
47 // Concurrent marking bit map wrapper
48
49 CMBitMapRO::CMBitMapRO(int shifter) :
50 _bm(),
51 _shifter(shifter) {
52 _bmStartWord = 0;
53 _bmWordSize = 0;
54 }
55
56 HeapWord* CMBitMapRO::getNextMarkedWordAddress(HeapWord* addr,
57 HeapWord* limit) const {
58 // First we must round addr *up* to a possible object boundary.
59 addr = (HeapWord*)align_size_up((intptr_t)addr,
60 HeapWordSize << _shifter);
61 size_t addrOffset = heapWordToOffset(addr);
62 if (limit == NULL) {
63 limit = _bmStartWord + _bmWordSize;
64 }
65 size_t limitOffset = heapWordToOffset(limit);
66 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
67 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
68 assert(nextAddr >= addr, "get_next_one postcondition");
69 assert(nextAddr == limit || isMarked(nextAddr),
70 "get_next_one postcondition");
71 return nextAddr;
72 }
73
74 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(HeapWord* addr,
75 HeapWord* limit) const {
76 size_t addrOffset = heapWordToOffset(addr);
77 if (limit == NULL) {
78 limit = _bmStartWord + _bmWordSize;
79 }
80 size_t limitOffset = heapWordToOffset(limit);
81 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
82 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
83 assert(nextAddr >= addr, "get_next_one postcondition");
84 assert(nextAddr == limit || !isMarked(nextAddr),
85 "get_next_one postcondition");
86 return nextAddr;
87 }
88
89 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
90 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
91 return (int) (diff >> _shifter);
92 }
93
94 #ifndef PRODUCT
95 bool CMBitMapRO::covers(ReservedSpace heap_rs) const {
96 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
97 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
98 "size inconsistency");
99 return _bmStartWord == (HeapWord*)(heap_rs.base()) &&
100 _bmWordSize == heap_rs.size()>>LogHeapWordSize;
101 }
102 #endif
103
104 bool CMBitMap::allocate(ReservedSpace heap_rs) {
105 _bmStartWord = (HeapWord*)(heap_rs.base());
106 _bmWordSize = heap_rs.size()/HeapWordSize; // heap_rs.size() is in bytes
107 ReservedSpace brs(ReservedSpace::allocation_align_size_up(
108 (_bmWordSize >> (_shifter + LogBitsPerByte)) + 1));
109 if (!brs.is_reserved()) {
110 warning("ConcurrentMark marking bit map allocation failure");
111 return false;
112 }
113 MemTracker::record_virtual_memory_type((address)brs.base(), mtGC);
114 // For now we'll just commit all of the bit map up front.
115 // Later on we'll try to be more parsimonious with swap.
116 if (!_virtual_space.initialize(brs, brs.size())) {
117 warning("ConcurrentMark marking bit map backing store failure");
118 return false;
119 }
120 assert(_virtual_space.committed_size() == brs.size(),
121 "didn't reserve backing store for all of concurrent marking bit map?");
122 _bm.set_map((uintptr_t*)_virtual_space.low());
123 assert(_virtual_space.committed_size() << (_shifter + LogBitsPerByte) >=
124 _bmWordSize, "inconsistency in bit map sizing");
125 _bm.set_size(_bmWordSize >> _shifter);
126 return true;
127 }
128
129 void CMBitMap::clearAll() {
130 _bm.clear();
131 return;
132 }
133
134 void CMBitMap::markRange(MemRegion mr) {
135 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
136 assert(!mr.is_empty(), "unexpected empty region");
137 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
138 ((HeapWord *) mr.end())),
139 "markRange memory region end is not card aligned");
140 // convert address range into offset range
141 _bm.at_put_range(heapWordToOffset(mr.start()),
142 heapWordToOffset(mr.end()), true);
143 }
144
145 void CMBitMap::clearRange(MemRegion mr) {
146 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
147 assert(!mr.is_empty(), "unexpected empty region");
148 // convert address range into offset range
149 _bm.at_put_range(heapWordToOffset(mr.start()),
150 heapWordToOffset(mr.end()), false);
151 }
152
153 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
154 HeapWord* end_addr) {
155 HeapWord* start = getNextMarkedWordAddress(addr);
156 start = MIN2(start, end_addr);
157 HeapWord* end = getNextUnmarkedWordAddress(start);
158 end = MIN2(end, end_addr);
159 assert(start <= end, "Consistency check");
160 MemRegion mr(start, end);
161 if (!mr.is_empty()) {
162 clearRange(mr);
163 }
164 return mr;
165 }
166
167 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
168 _base(NULL), _cm(cm)
169 #ifdef ASSERT
170 , _drain_in_progress(false)
171 , _drain_in_progress_yields(false)
172 #endif
173 {}
174
175 bool CMMarkStack::allocate(size_t capacity) {
176 // allocate a stack of the requisite depth
177 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
178 if (!rs.is_reserved()) {
179 warning("ConcurrentMark MarkStack allocation failure");
180 return false;
181 }
182 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
183 if (!_virtual_space.initialize(rs, rs.size())) {
184 warning("ConcurrentMark MarkStack backing store failure");
185 // Release the virtual memory reserved for the marking stack
186 rs.release();
187 return false;
188 }
189 assert(_virtual_space.committed_size() == rs.size(),
190 "Didn't reserve backing store for all of ConcurrentMark stack?");
191 _base = (oop*) _virtual_space.low();
192 setEmpty();
193 _capacity = (jint) capacity;
194 _saved_index = -1;
195 _should_expand = false;
196 NOT_PRODUCT(_max_depth = 0);
197 return true;
198 }
199
200 void CMMarkStack::expand() {
201 // Called, during remark, if we've overflown the marking stack during marking.
202 assert(isEmpty(), "stack should been emptied while handling overflow");
203 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
204 // Clear expansion flag
205 _should_expand = false;
206 if (_capacity == (jint) MarkStackSizeMax) {
207 if (PrintGCDetails && Verbose) {
208 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
209 }
210 return;
211 }
212 // Double capacity if possible
213 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
214 // Do not give up existing stack until we have managed to
215 // get the double capacity that we desired.
216 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
217 sizeof(oop)));
218 if (rs.is_reserved()) {
219 // Release the backing store associated with old stack
220 _virtual_space.release();
221 // Reinitialize virtual space for new stack
222 if (!_virtual_space.initialize(rs, rs.size())) {
223 fatal("Not enough swap for expanded marking stack capacity");
224 }
225 _base = (oop*)(_virtual_space.low());
226 _index = 0;
227 _capacity = new_capacity;
228 } else {
229 if (PrintGCDetails && Verbose) {
230 // Failed to double capacity, continue;
231 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
232 SIZE_FORMAT"K to " SIZE_FORMAT"K",
233 _capacity / K, new_capacity / K);
234 }
235 }
236 }
237
238 void CMMarkStack::set_should_expand() {
239 // If we're resetting the marking state because of an
240 // marking stack overflow, record that we should, if
241 // possible, expand the stack.
242 _should_expand = _cm->has_overflown();
243 }
244
245 CMMarkStack::~CMMarkStack() {
246 if (_base != NULL) {
247 _base = NULL;
248 _virtual_space.release();
249 }
250 }
251
252 void CMMarkStack::par_push(oop ptr) {
253 while (true) {
254 if (isFull()) {
255 _overflow = true;
256 return;
257 }
258 // Otherwise...
259 jint index = _index;
260 jint next_index = index+1;
261 jint res = Atomic::cmpxchg(next_index, &_index, index);
262 if (res == index) {
263 _base[index] = ptr;
264 // Note that we don't maintain this atomically. We could, but it
265 // doesn't seem necessary.
266 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
267 return;
268 }
269 // Otherwise, we need to try again.
270 }
271 }
272
273 void CMMarkStack::par_adjoin_arr(oop* ptr_arr, int n) {
274 while (true) {
275 if (isFull()) {
276 _overflow = true;
277 return;
278 }
279 // Otherwise...
280 jint index = _index;
281 jint next_index = index + n;
282 if (next_index > _capacity) {
283 _overflow = true;
284 return;
285 }
286 jint res = Atomic::cmpxchg(next_index, &_index, index);
287 if (res == index) {
288 for (int i = 0; i < n; i++) {
289 int ind = index + i;
290 assert(ind < _capacity, "By overflow test above.");
291 _base[ind] = ptr_arr[i];
292 }
293 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
294 return;
295 }
296 // Otherwise, we need to try again.
297 }
298 }
299
300 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
301 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
302 jint start = _index;
303 jint next_index = start + n;
304 if (next_index > _capacity) {
305 _overflow = true;
306 return;
307 }
308 // Otherwise.
309 _index = next_index;
310 for (int i = 0; i < n; i++) {
311 int ind = start + i;
312 assert(ind < _capacity, "By overflow test above.");
313 _base[ind] = ptr_arr[i];
314 }
315 NOT_PRODUCT(_max_depth = MAX2(_max_depth, next_index));
316 }
317
318 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
319 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
320 jint index = _index;
321 if (index == 0) {
322 *n = 0;
323 return false;
324 } else {
325 int k = MIN2(max, index);
326 jint new_ind = index - k;
327 for (int j = 0; j < k; j++) {
328 ptr_arr[j] = _base[new_ind + j];
329 }
330 _index = new_ind;
331 *n = k;
332 return true;
333 }
334 }
335
336 template<class OopClosureClass>
337 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
338 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
339 || SafepointSynchronize::is_at_safepoint(),
340 "Drain recursion must be yield-safe.");
341 bool res = true;
342 debug_only(_drain_in_progress = true);
343 debug_only(_drain_in_progress_yields = yield_after);
344 while (!isEmpty()) {
345 oop newOop = pop();
346 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
347 assert(newOop->is_oop(), "Expected an oop");
348 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
349 "only grey objects on this stack");
350 newOop->oop_iterate(cl);
351 if (yield_after && _cm->do_yield_check()) {
352 res = false;
353 break;
354 }
355 }
356 debug_only(_drain_in_progress = false);
357 return res;
358 }
359
360 void CMMarkStack::note_start_of_gc() {
361 assert(_saved_index == -1,
362 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
363 _saved_index = _index;
364 }
365
366 void CMMarkStack::note_end_of_gc() {
367 // This is intentionally a guarantee, instead of an assert. If we
368 // accidentally add something to the mark stack during GC, it
369 // will be a correctness issue so it's better if we crash. we'll
370 // only check this once per GC anyway, so it won't be a performance
371 // issue in any way.
372 guarantee(_saved_index == _index,
373 err_msg("saved index: %d index: %d", _saved_index, _index));
374 _saved_index = -1;
375 }
376
377 void CMMarkStack::oops_do(OopClosure* f) {
378 assert(_saved_index == _index,
379 err_msg("saved index: %d index: %d", _saved_index, _index));
380 for (int i = 0; i < _index; i += 1) {
381 f->do_oop(&_base[i]);
382 }
383 }
384
385 bool ConcurrentMark::not_yet_marked(oop obj) const {
386 return _g1h->is_obj_ill(obj);
387 }
388
389 CMRootRegions::CMRootRegions() :
390 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
391 _should_abort(false), _next_survivor(NULL) { }
392
393 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
394 _young_list = g1h->young_list();
395 _cm = cm;
396 }
397
398 void CMRootRegions::prepare_for_scan() {
399 assert(!scan_in_progress(), "pre-condition");
400
401 // Currently, only survivors can be root regions.
402 assert(_next_survivor == NULL, "pre-condition");
403 _next_survivor = _young_list->first_survivor_region();
404 _scan_in_progress = (_next_survivor != NULL);
405 _should_abort = false;
406 }
407
408 HeapRegion* CMRootRegions::claim_next() {
409 if (_should_abort) {
410 // If someone has set the should_abort flag, we return NULL to
411 // force the caller to bail out of their loop.
412 return NULL;
413 }
414
415 // Currently, only survivors can be root regions.
416 HeapRegion* res = _next_survivor;
417 if (res != NULL) {
418 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
419 // Read it again in case it changed while we were waiting for the lock.
420 res = _next_survivor;
421 if (res != NULL) {
422 if (res == _young_list->last_survivor_region()) {
423 // We just claimed the last survivor so store NULL to indicate
424 // that we're done.
425 _next_survivor = NULL;
426 } else {
427 _next_survivor = res->get_next_young_region();
428 }
429 } else {
430 // Someone else claimed the last survivor while we were trying
431 // to take the lock so nothing else to do.
432 }
433 }
434 assert(res == NULL || res->is_survivor(), "post-condition");
435
436 return res;
437 }
438
439 void CMRootRegions::scan_finished() {
440 assert(scan_in_progress(), "pre-condition");
441
442 // Currently, only survivors can be root regions.
443 if (!_should_abort) {
444 assert(_next_survivor == NULL, "we should have claimed all survivors");
445 }
446 _next_survivor = NULL;
447
448 {
449 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
450 _scan_in_progress = false;
451 RootRegionScan_lock->notify_all();
452 }
453 }
454
455 bool CMRootRegions::wait_until_scan_finished() {
456 if (!scan_in_progress()) return false;
457
458 {
459 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
460 while (scan_in_progress()) {
461 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
462 }
463 }
464 return true;
465 }
466
467 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
468 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
469 #endif // _MSC_VER
470
471 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
472 return MAX2((n_par_threads + 2) / 4, 1U);
473 }
474
475 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, ReservedSpace heap_rs) :
476 _g1h(g1h),
477 _markBitMap1(MinObjAlignment - 1),
478 _markBitMap2(MinObjAlignment - 1),
479
480 _parallel_marking_threads(0),
481 _max_parallel_marking_threads(0),
482 _sleep_factor(0.0),
483 _marking_task_overhead(1.0),
484 _cleanup_sleep_factor(0.0),
485 _cleanup_task_overhead(1.0),
486 _cleanup_list("Cleanup List"),
487 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
488 _card_bm((heap_rs.size() + CardTableModRefBS::card_size - 1) >>
489 CardTableModRefBS::card_shift,
490 false /* in_resource_area*/),
491
492 _prevMarkBitMap(&_markBitMap1),
493 _nextMarkBitMap(&_markBitMap2),
494
495 _markStack(this),
496 // _finger set in set_non_marking_state
497
498 _max_worker_id(MAX2((uint)ParallelGCThreads, 1U)),
499 // _active_tasks set in set_non_marking_state
500 // _tasks set inside the constructor
501 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
502 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
503
504 _has_overflown(false),
505 _concurrent(false),
506 _has_aborted(false),
507 _restart_for_overflow(false),
508 _concurrent_marking_in_progress(false),
509
510 // _verbose_level set below
511
512 _init_times(),
513 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
514 _cleanup_times(),
515 _total_counting_time(0.0),
516 _total_rs_scrub_time(0.0),
517
518 _parallel_workers(NULL),
519
520 _count_card_bitmaps(NULL),
521 _count_marked_bytes(NULL),
522 _completed_initialization(false) {
523 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
524 if (verbose_level < no_verbose) {
525 verbose_level = no_verbose;
526 }
527 if (verbose_level > high_verbose) {
528 verbose_level = high_verbose;
529 }
530 _verbose_level = verbose_level;
531
532 if (verbose_low()) {
533 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
534 "heap end = "PTR_FORMAT, _heap_start, _heap_end);
535 }
536
537 if (!_markBitMap1.allocate(heap_rs)) {
538 warning("Failed to allocate first CM bit map");
539 return;
540 }
541 if (!_markBitMap2.allocate(heap_rs)) {
542 warning("Failed to allocate second CM bit map");
543 return;
544 }
545
546 // Create & start a ConcurrentMark thread.
547 _cmThread = new ConcurrentMarkThread(this);
548 assert(cmThread() != NULL, "CM Thread should have been created");
549 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
550
551 assert(CGC_lock != NULL, "Where's the CGC_lock?");
552 assert(_markBitMap1.covers(heap_rs), "_markBitMap1 inconsistency");
553 assert(_markBitMap2.covers(heap_rs), "_markBitMap2 inconsistency");
554
555 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
556 satb_qs.set_buffer_size(G1SATBBufferSize);
557
558 _root_regions.init(_g1h, this);
559
560 if (ConcGCThreads > ParallelGCThreads) {
561 warning("Can't have more ConcGCThreads (" UINT32_FORMAT ") "
562 "than ParallelGCThreads (" UINT32_FORMAT ").",
563 ConcGCThreads, ParallelGCThreads);
564 return;
565 }
566 if (ParallelGCThreads == 0) {
567 // if we are not running with any parallel GC threads we will not
568 // spawn any marking threads either
569 _parallel_marking_threads = 0;
570 _max_parallel_marking_threads = 0;
571 _sleep_factor = 0.0;
572 _marking_task_overhead = 1.0;
573 } else {
574 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
575 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
576 // if both are set
577 _sleep_factor = 0.0;
578 _marking_task_overhead = 1.0;
579 } else if (G1MarkingOverheadPercent > 0) {
580 // We will calculate the number of parallel marking threads based
581 // on a target overhead with respect to the soft real-time goal
582 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
583 double overall_cm_overhead =
584 (double) MaxGCPauseMillis * marking_overhead /
585 (double) GCPauseIntervalMillis;
586 double cpu_ratio = 1.0 / (double) os::processor_count();
587 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
588 double marking_task_overhead =
589 overall_cm_overhead / marking_thread_num *
590 (double) os::processor_count();
591 double sleep_factor =
592 (1.0 - marking_task_overhead) / marking_task_overhead;
593
594 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num);
595 _sleep_factor = sleep_factor;
596 _marking_task_overhead = marking_task_overhead;
597 } else {
598 // Calculate the number of parallel marking threads by scaling
599 // the number of parallel GC threads.
600 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads);
601 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num);
602 _sleep_factor = 0.0;
603 _marking_task_overhead = 1.0;
604 }
605
606 assert(ConcGCThreads > 0, "Should have been set");
607 _parallel_marking_threads = (uint) ConcGCThreads;
608 _max_parallel_marking_threads = _parallel_marking_threads;
609
610 if (parallel_marking_threads() > 1) {
611 _cleanup_task_overhead = 1.0;
612 } else {
613 _cleanup_task_overhead = marking_task_overhead();
614 }
615 _cleanup_sleep_factor =
616 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
617
618 #if 0
619 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
620 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
621 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
622 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
623 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
624 #endif
625
626 guarantee(parallel_marking_threads() > 0, "peace of mind");
627 _parallel_workers = new FlexibleWorkGang("G1 Parallel Marking Threads",
628 _max_parallel_marking_threads, false, true);
629 if (_parallel_workers == NULL) {
630 vm_exit_during_initialization("Failed necessary allocation.");
631 } else {
632 _parallel_workers->initialize_workers();
633 }
634 }
635
636 if (FLAG_IS_DEFAULT(MarkStackSize)) {
637 uintx mark_stack_size =
638 MIN2(MarkStackSizeMax,
639 MAX2(MarkStackSize, (uintx) (parallel_marking_threads() * TASKQUEUE_SIZE)));
640 // Verify that the calculated value for MarkStackSize is in range.
641 // It would be nice to use the private utility routine from Arguments.
642 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
643 warning("Invalid value calculated for MarkStackSize (" UINTX_FORMAT "): "
644 "must be between " UINTX_FORMAT " and " UINTX_FORMAT,
645 mark_stack_size, 1, MarkStackSizeMax);
646 return;
647 }
648 FLAG_SET_ERGO(uintx, MarkStackSize, mark_stack_size);
649 } else {
650 // Verify MarkStackSize is in range.
651 if (FLAG_IS_CMDLINE(MarkStackSize)) {
652 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
653 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
654 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT "): "
655 "must be between " UINTX_FORMAT " and " UINTX_FORMAT,
656 MarkStackSize, 1, MarkStackSizeMax);
657 return;
658 }
659 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
660 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
661 warning("Invalid value specified for MarkStackSize (" UINTX_FORMAT ")"
662 " or for MarkStackSizeMax (" UINTX_FORMAT ")",
663 MarkStackSize, MarkStackSizeMax);
664 return;
665 }
666 }
667 }
668 }
669
670 if (!_markStack.allocate(MarkStackSize)) {
671 warning("Failed to allocate CM marking stack");
672 return;
673 }
674
675 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
676 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
677
678 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
679 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
680
681 BitMap::idx_t card_bm_size = _card_bm.size();
682
683 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
684 _active_tasks = _max_worker_id;
685
686 size_t max_regions = (size_t) _g1h->max_regions();
687 for (uint i = 0; i < _max_worker_id; ++i) {
688 CMTaskQueue* task_queue = new CMTaskQueue();
689 task_queue->initialize();
690 _task_queues->register_queue(i, task_queue);
691
692 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
693 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
694
695 _tasks[i] = new CMTask(i, this,
696 _count_marked_bytes[i],
697 &_count_card_bitmaps[i],
698 task_queue, _task_queues);
699
700 _accum_task_vtime[i] = 0.0;
701 }
702
703 // Calculate the card number for the bottom of the heap. Used
704 // in biasing indexes into the accounting card bitmaps.
705 _heap_bottom_card_num =
706 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
707 CardTableModRefBS::card_shift);
708
709 // Clear all the liveness counting data
710 clear_all_count_data();
711
712 // so that the call below can read a sensible value
713 _heap_start = (HeapWord*) heap_rs.base();
714 set_non_marking_state();
715 _completed_initialization = true;
716 }
717
718 void ConcurrentMark::update_g1_committed(bool force) {
719 // If concurrent marking is not in progress, then we do not need to
720 // update _heap_end.
721 if (!concurrent_marking_in_progress() && !force) return;
722
723 MemRegion committed = _g1h->g1_committed();
724 assert(committed.start() == _heap_start, "start shouldn't change");
725 HeapWord* new_end = committed.end();
726 if (new_end > _heap_end) {
727 // The heap has been expanded.
728
729 _heap_end = new_end;
730 }
731 // Notice that the heap can also shrink. However, this only happens
732 // during a Full GC (at least currently) and the entire marking
733 // phase will bail out and the task will not be restarted. So, let's
734 // do nothing.
735 }
736
737 void ConcurrentMark::reset() {
738 // Starting values for these two. This should be called in a STW
739 // phase. CM will be notified of any future g1_committed expansions
740 // will be at the end of evacuation pauses, when tasks are
741 // inactive.
742 MemRegion committed = _g1h->g1_committed();
743 _heap_start = committed.start();
744 _heap_end = committed.end();
745
746 // Separated the asserts so that we know which one fires.
747 assert(_heap_start != NULL, "heap bounds should look ok");
748 assert(_heap_end != NULL, "heap bounds should look ok");
749 assert(_heap_start < _heap_end, "heap bounds should look ok");
750
751 // Reset all the marking data structures and any necessary flags
752 reset_marking_state();
753
754 if (verbose_low()) {
755 gclog_or_tty->print_cr("[global] resetting");
756 }
757
758 // We do reset all of them, since different phases will use
759 // different number of active threads. So, it's easiest to have all
760 // of them ready.
761 for (uint i = 0; i < _max_worker_id; ++i) {
762 _tasks[i]->reset(_nextMarkBitMap);
763 }
764
765 // we need this to make sure that the flag is on during the evac
766 // pause with initial mark piggy-backed
767 set_concurrent_marking_in_progress();
768 }
769
770
771 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
772 _markStack.set_should_expand();
773 _markStack.setEmpty(); // Also clears the _markStack overflow flag
774 if (clear_overflow) {
775 clear_has_overflown();
776 } else {
777 assert(has_overflown(), "pre-condition");
778 }
779 _finger = _heap_start;
780
781 for (uint i = 0; i < _max_worker_id; ++i) {
782 CMTaskQueue* queue = _task_queues->queue(i);
783 queue->set_empty();
784 }
785 }
786
787 void ConcurrentMark::set_phase(uint active_tasks, bool concurrent) {
788 assert(active_tasks <= _max_worker_id, "we should not have more");
789
790 _active_tasks = active_tasks;
791 // Need to update the three data structures below according to the
792 // number of active threads for this phase.
793 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
794 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
795 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
796
797 _concurrent = concurrent;
798 // We propagate this to all tasks, not just the active ones.
799 for (uint i = 0; i < _max_worker_id; ++i)
800 _tasks[i]->set_concurrent(concurrent);
801
802 if (concurrent) {
803 set_concurrent_marking_in_progress();
804 } else {
805 // We currently assume that the concurrent flag has been set to
806 // false before we start remark. At this point we should also be
807 // in a STW phase.
808 assert(!concurrent_marking_in_progress(), "invariant");
809 assert(_finger == _heap_end, "only way to get here");
810 update_g1_committed(true);
811 }
812 }
813
814 void ConcurrentMark::set_non_marking_state() {
815 // We set the global marking state to some default values when we're
816 // not doing marking.
817 reset_marking_state();
818 _active_tasks = 0;
819 clear_concurrent_marking_in_progress();
820 }
821
822 ConcurrentMark::~ConcurrentMark() {
823 // The ConcurrentMark instance is never freed.
824 ShouldNotReachHere();
825 }
826
827 void ConcurrentMark::clearNextBitmap() {
828 G1CollectedHeap* g1h = G1CollectedHeap::heap();
829 G1CollectorPolicy* g1p = g1h->g1_policy();
830
831 // Make sure that the concurrent mark thread looks to still be in
832 // the current cycle.
833 guarantee(cmThread()->during_cycle(), "invariant");
834
835 // We are finishing up the current cycle by clearing the next
836 // marking bitmap and getting it ready for the next cycle. During
837 // this time no other cycle can start. So, let's make sure that this
838 // is the case.
839 guarantee(!g1h->mark_in_progress(), "invariant");
840
841 // clear the mark bitmap (no grey objects to start with).
842 // We need to do this in chunks and offer to yield in between
843 // each chunk.
844 HeapWord* start = _nextMarkBitMap->startWord();
845 HeapWord* end = _nextMarkBitMap->endWord();
846 HeapWord* cur = start;
847 size_t chunkSize = M;
848 while (cur < end) {
849 HeapWord* next = cur + chunkSize;
850 if (next > end) {
851 next = end;
852 }
853 MemRegion mr(cur,next);
854 _nextMarkBitMap->clearRange(mr);
855 cur = next;
856 do_yield_check();
857
858 // Repeat the asserts from above. We'll do them as asserts here to
859 // minimize their overhead on the product. However, we'll have
860 // them as guarantees at the beginning / end of the bitmap
861 // clearing to get some checking in the product.
862 assert(cmThread()->during_cycle(), "invariant");
863 assert(!g1h->mark_in_progress(), "invariant");
864 }
865
866 // Clear the liveness counting data
867 clear_all_count_data();
868
869 // Repeat the asserts from above.
870 guarantee(cmThread()->during_cycle(), "invariant");
871 guarantee(!g1h->mark_in_progress(), "invariant");
872 }
873
874 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
875 public:
876 bool doHeapRegion(HeapRegion* r) {
877 if (!r->continuesHumongous()) {
878 r->note_start_of_marking();
879 }
880 return false;
881 }
882 };
883
884 void ConcurrentMark::checkpointRootsInitialPre() {
885 G1CollectedHeap* g1h = G1CollectedHeap::heap();
886 G1CollectorPolicy* g1p = g1h->g1_policy();
887
888 _has_aborted = false;
889
890 #ifndef PRODUCT
891 if (G1PrintReachableAtInitialMark) {
892 print_reachable("at-cycle-start",
893 VerifyOption_G1UsePrevMarking, true /* all */);
894 }
895 #endif
896
897 // Initialise marking structures. This has to be done in a STW phase.
898 reset();
899
900 // For each region note start of marking.
901 NoteStartOfMarkHRClosure startcl;
902 g1h->heap_region_iterate(&startcl);
903 }
904
905
906 void ConcurrentMark::checkpointRootsInitialPost() {
907 G1CollectedHeap* g1h = G1CollectedHeap::heap();
908
909 // If we force an overflow during remark, the remark operation will
910 // actually abort and we'll restart concurrent marking. If we always
911 // force an oveflow during remark we'll never actually complete the
912 // marking phase. So, we initilize this here, at the start of the
913 // cycle, so that at the remaining overflow number will decrease at
914 // every remark and we'll eventually not need to cause one.
915 force_overflow_stw()->init();
916
917 // Start Concurrent Marking weak-reference discovery.
918 ReferenceProcessor* rp = g1h->ref_processor_cm();
919 // enable ("weak") refs discovery
920 rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
921 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
922
923 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
924 // This is the start of the marking cycle, we're expected all
925 // threads to have SATB queues with active set to false.
926 satb_mq_set.set_active_all_threads(true, /* new active value */
927 false /* expected_active */);
928
929 _root_regions.prepare_for_scan();
930
931 // update_g1_committed() will be called at the end of an evac pause
932 // when marking is on. So, it's also called at the end of the
933 // initial-mark pause to update the heap end, if the heap expands
934 // during it. No need to call it here.
935 }
936
937 /*
938 * Notice that in the next two methods, we actually leave the STS
939 * during the barrier sync and join it immediately afterwards. If we
940 * do not do this, the following deadlock can occur: one thread could
941 * be in the barrier sync code, waiting for the other thread to also
942 * sync up, whereas another one could be trying to yield, while also
943 * waiting for the other threads to sync up too.
944 *
945 * Note, however, that this code is also used during remark and in
946 * this case we should not attempt to leave / enter the STS, otherwise
947 * we'll either hit an asseert (debug / fastdebug) or deadlock
948 * (product). So we should only leave / enter the STS if we are
949 * operating concurrently.
950 *
951 * Because the thread that does the sync barrier has left the STS, it
952 * is possible to be suspended for a Full GC or an evacuation pause
953 * could occur. This is actually safe, since the entering the sync
954 * barrier is one of the last things do_marking_step() does, and it
955 * doesn't manipulate any data structures afterwards.
956 */
957
958 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
959 if (verbose_low()) {
960 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
961 }
962
963 if (concurrent()) {
964 ConcurrentGCThread::stsLeave();
965 }
966 _first_overflow_barrier_sync.enter();
967 if (concurrent()) {
968 ConcurrentGCThread::stsJoin();
969 }
970 // at this point everyone should have synced up and not be doing any
971 // more work
972
973 if (verbose_low()) {
974 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
975 }
976
977 // let the task associated with with worker 0 do this
978 if (worker_id == 0) {
979 // task 0 is responsible for clearing the global data structures
980 // We should be here because of an overflow. During STW we should
981 // not clear the overflow flag since we rely on it being true when
982 // we exit this method to abort the pause and restart concurent
983 // marking.
984 reset_marking_state(concurrent() /* clear_overflow */);
985 force_overflow()->update();
986
987 if (G1Log::fine()) {
988 gclog_or_tty->date_stamp(PrintGCDateStamps);
989 gclog_or_tty->stamp(PrintGCTimeStamps);
990 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
991 }
992 }
993
994 // after this, each task should reset its own data structures then
995 // then go into the second barrier
996 }
997
998 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
999 if (verbose_low()) {
1000 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1001 }
1002
1003 if (concurrent()) {
1004 ConcurrentGCThread::stsLeave();
1005 }
1006 _second_overflow_barrier_sync.enter();
1007 if (concurrent()) {
1008 ConcurrentGCThread::stsJoin();
1009 }
1010 // at this point everything should be re-initialised and ready to go
1011
1012 if (verbose_low()) {
1013 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1014 }
1015 }
1016
1017 #ifndef PRODUCT
1018 void ForceOverflowSettings::init() {
1019 _num_remaining = G1ConcMarkForceOverflow;
1020 _force = false;
1021 update();
1022 }
1023
1024 void ForceOverflowSettings::update() {
1025 if (_num_remaining > 0) {
1026 _num_remaining -= 1;
1027 _force = true;
1028 } else {
1029 _force = false;
1030 }
1031 }
1032
1033 bool ForceOverflowSettings::should_force() {
1034 if (_force) {
1035 _force = false;
1036 return true;
1037 } else {
1038 return false;
1039 }
1040 }
1041 #endif // !PRODUCT
1042
1043 class CMConcurrentMarkingTask: public AbstractGangTask {
1044 private:
1045 ConcurrentMark* _cm;
1046 ConcurrentMarkThread* _cmt;
1047
1048 public:
1049 void work(uint worker_id) {
1050 assert(Thread::current()->is_ConcurrentGC_thread(),
1051 "this should only be done by a conc GC thread");
1052 ResourceMark rm;
1053
1054 double start_vtime = os::elapsedVTime();
1055
1056 ConcurrentGCThread::stsJoin();
1057
1058 assert(worker_id < _cm->active_tasks(), "invariant");
1059 CMTask* the_task = _cm->task(worker_id);
1060 the_task->record_start_time();
1061 if (!_cm->has_aborted()) {
1062 do {
1063 double start_vtime_sec = os::elapsedVTime();
1064 double start_time_sec = os::elapsedTime();
1065 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1066
1067 the_task->do_marking_step(mark_step_duration_ms,
1068 true /* do_stealing */,
1069 true /* do_termination */);
1070
1071 double end_time_sec = os::elapsedTime();
1072 double end_vtime_sec = os::elapsedVTime();
1073 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1074 double elapsed_time_sec = end_time_sec - start_time_sec;
1075 _cm->clear_has_overflown();
1076
1077 bool ret = _cm->do_yield_check(worker_id);
1078
1079 jlong sleep_time_ms;
1080 if (!_cm->has_aborted() && the_task->has_aborted()) {
1081 sleep_time_ms =
1082 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1083 ConcurrentGCThread::stsLeave();
1084 os::sleep(Thread::current(), sleep_time_ms, false);
1085 ConcurrentGCThread::stsJoin();
1086 }
1087 double end_time2_sec = os::elapsedTime();
1088 double elapsed_time2_sec = end_time2_sec - start_time_sec;
1089
1090 #if 0
1091 gclog_or_tty->print_cr("CM: elapsed %1.4lf ms, sleep %1.4lf ms, "
1092 "overhead %1.4lf",
1093 elapsed_vtime_sec * 1000.0, (double) sleep_time_ms,
1094 the_task->conc_overhead(os::elapsedTime()) * 8.0);
1095 gclog_or_tty->print_cr("elapsed time %1.4lf ms, time 2: %1.4lf ms",
1096 elapsed_time_sec * 1000.0, elapsed_time2_sec * 1000.0);
1097 #endif
1098 } while (!_cm->has_aborted() && the_task->has_aborted());
1099 }
1100 the_task->record_end_time();
1101 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1102
1103 ConcurrentGCThread::stsLeave();
1104
1105 double end_vtime = os::elapsedVTime();
1106 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1107 }
1108
1109 CMConcurrentMarkingTask(ConcurrentMark* cm,
1110 ConcurrentMarkThread* cmt) :
1111 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1112
1113 ~CMConcurrentMarkingTask() { }
1114 };
1115
1116 // Calculates the number of active workers for a concurrent
1117 // phase.
1118 uint ConcurrentMark::calc_parallel_marking_threads() {
1119 if (G1CollectedHeap::use_parallel_gc_threads()) {
1120 uint n_conc_workers = 0;
1121 if (!UseDynamicNumberOfGCThreads ||
1122 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1123 !ForceDynamicNumberOfGCThreads)) {
1124 n_conc_workers = max_parallel_marking_threads();
1125 } else {
1126 n_conc_workers =
1127 AdaptiveSizePolicy::calc_default_active_workers(
1128 max_parallel_marking_threads(),
1129 1, /* Minimum workers */
1130 parallel_marking_threads(),
1131 Threads::number_of_non_daemon_threads());
1132 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1133 // that scaling has already gone into "_max_parallel_marking_threads".
1134 }
1135 assert(n_conc_workers > 0, "Always need at least 1");
1136 return n_conc_workers;
1137 }
1138 // If we are not running with any parallel GC threads we will not
1139 // have spawned any marking threads either. Hence the number of
1140 // concurrent workers should be 0.
1141 return 0;
1142 }
1143
1144 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1145 // Currently, only survivors can be root regions.
1146 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1147 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1148
1149 const uintx interval = PrefetchScanIntervalInBytes;
1150 HeapWord* curr = hr->bottom();
1151 const HeapWord* end = hr->top();
1152 while (curr < end) {
1153 Prefetch::read(curr, interval);
1154 oop obj = oop(curr);
1155 int size = obj->oop_iterate(&cl);
1156 assert(size == obj->size(), "sanity");
1157 curr += size;
1158 }
1159 }
1160
1161 class CMRootRegionScanTask : public AbstractGangTask {
1162 private:
1163 ConcurrentMark* _cm;
1164
1165 public:
1166 CMRootRegionScanTask(ConcurrentMark* cm) :
1167 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1168
1169 void work(uint worker_id) {
1170 assert(Thread::current()->is_ConcurrentGC_thread(),
1171 "this should only be done by a conc GC thread");
1172
1173 CMRootRegions* root_regions = _cm->root_regions();
1174 HeapRegion* hr = root_regions->claim_next();
1175 while (hr != NULL) {
1176 _cm->scanRootRegion(hr, worker_id);
1177 hr = root_regions->claim_next();
1178 }
1179 }
1180 };
1181
1182 void ConcurrentMark::scanRootRegions() {
1183 // scan_in_progress() will have been set to true only if there was
1184 // at least one root region to scan. So, if it's false, we
1185 // should not attempt to do any further work.
1186 if (root_regions()->scan_in_progress()) {
1187 _parallel_marking_threads = calc_parallel_marking_threads();
1188 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1189 "Maximum number of marking threads exceeded");
1190 uint active_workers = MAX2(1U, parallel_marking_threads());
1191
1192 CMRootRegionScanTask task(this);
1193 if (use_parallel_marking_threads()) {
1194 _parallel_workers->set_active_workers((int) active_workers);
1195 _parallel_workers->run_task(&task);
1196 } else {
1197 task.work(0);
1198 }
1199
1200 // It's possible that has_aborted() is true here without actually
1201 // aborting the survivor scan earlier. This is OK as it's
1202 // mainly used for sanity checking.
1203 root_regions()->scan_finished();
1204 }
1205 }
1206
1207 void ConcurrentMark::markFromRoots() {
1208 // we might be tempted to assert that:
1209 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1210 // "inconsistent argument?");
1211 // However that wouldn't be right, because it's possible that
1212 // a safepoint is indeed in progress as a younger generation
1213 // stop-the-world GC happens even as we mark in this generation.
1214
1215 _restart_for_overflow = false;
1216 force_overflow_conc()->init();
1217
1218 // _g1h has _n_par_threads
1219 _parallel_marking_threads = calc_parallel_marking_threads();
1220 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1221 "Maximum number of marking threads exceeded");
1222
1223 uint active_workers = MAX2(1U, parallel_marking_threads());
1224
1225 // Parallel task terminator is set in "set_phase()"
1226 set_phase(active_workers, true /* concurrent */);
1227
1228 CMConcurrentMarkingTask markingTask(this, cmThread());
1229 if (use_parallel_marking_threads()) {
1230 _parallel_workers->set_active_workers((int)active_workers);
1231 // Don't set _n_par_threads because it affects MT in proceess_strong_roots()
1232 // and the decisions on that MT processing is made elsewhere.
1233 assert(_parallel_workers->active_workers() > 0, "Should have been set");
1234 _parallel_workers->run_task(&markingTask);
1235 } else {
1236 markingTask.work(0);
1237 }
1238 print_stats();
1239 }
1240
1241 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1242 // world is stopped at this checkpoint
1243 assert(SafepointSynchronize::is_at_safepoint(),
1244 "world should be stopped");
1245
1246 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1247
1248 // If a full collection has happened, we shouldn't do this.
1249 if (has_aborted()) {
1250 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1251 return;
1252 }
1253
1254 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1255
1256 if (VerifyDuringGC) {
1257 HandleMark hm; // handle scope
1258 gclog_or_tty->print(" VerifyDuringGC:(before)");
1259 Universe::heap()->prepare_for_verify();
1260 Universe::verify(/* silent */ false,
1261 /* option */ VerifyOption_G1UsePrevMarking);
1262 }
1263
1264 G1CollectorPolicy* g1p = g1h->g1_policy();
1265 g1p->record_concurrent_mark_remark_start();
1266
1267 double start = os::elapsedTime();
1268
1269 checkpointRootsFinalWork();
1270
1271 double mark_work_end = os::elapsedTime();
1272
1273 weakRefsWork(clear_all_soft_refs);
1274
1275 if (has_overflown()) {
1276 // Oops. We overflowed. Restart concurrent marking.
1277 _restart_for_overflow = true;
1278 // Clear the marking state because we will be restarting
1279 // marking due to overflowing the global mark stack.
1280 reset_marking_state();
1281 if (G1TraceMarkStackOverflow) {
1282 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1283 }
1284 } else {
1285 // Aggregate the per-task counting data that we have accumulated
1286 // while marking.
1287 aggregate_count_data();
1288
1289 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1290 // We're done with marking.
1291 // This is the end of the marking cycle, we're expected all
1292 // threads to have SATB queues with active set to true.
1293 satb_mq_set.set_active_all_threads(false, /* new active value */
1294 true /* expected_active */);
1295
1296 if (VerifyDuringGC) {
1297 HandleMark hm; // handle scope
1298 gclog_or_tty->print(" VerifyDuringGC:(after)");
1299 Universe::heap()->prepare_for_verify();
1300 Universe::verify(/* silent */ false,
1301 /* option */ VerifyOption_G1UseNextMarking);
1302 }
1303 assert(!restart_for_overflow(), "sanity");
1304 // Completely reset the marking state since marking completed
1305 set_non_marking_state();
1306 }
1307
1308 // Expand the marking stack, if we have to and if we can.
1309 if (_markStack.should_expand()) {
1310 _markStack.expand();
1311 }
1312
1313 #if VERIFY_OBJS_PROCESSED
1314 _scan_obj_cl.objs_processed = 0;
1315 ThreadLocalObjQueue::objs_enqueued = 0;
1316 #endif
1317
1318 // Statistics
1319 double now = os::elapsedTime();
1320 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1321 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1322 _remark_times.add((now - start) * 1000.0);
1323
1324 g1p->record_concurrent_mark_remark_end();
1325 }
1326
1327 // Base class of the closures that finalize and verify the
1328 // liveness counting data.
1329 class CMCountDataClosureBase: public HeapRegionClosure {
1330 protected:
1331 G1CollectedHeap* _g1h;
1332 ConcurrentMark* _cm;
1333 CardTableModRefBS* _ct_bs;
1334
1335 BitMap* _region_bm;
1336 BitMap* _card_bm;
1337
1338 // Takes a region that's not empty (i.e., it has at least one
1339 // live object in it and sets its corresponding bit on the region
1340 // bitmap to 1. If the region is "starts humongous" it will also set
1341 // to 1 the bits on the region bitmap that correspond to its
1342 // associated "continues humongous" regions.
1343 void set_bit_for_region(HeapRegion* hr) {
1344 assert(!hr->continuesHumongous(), "should have filtered those out");
1345
1346 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1347 if (!hr->startsHumongous()) {
1348 // Normal (non-humongous) case: just set the bit.
1349 _region_bm->par_at_put(index, true);
1350 } else {
1351 // Starts humongous case: calculate how many regions are part of
1352 // this humongous region and then set the bit range.
1353 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1354 _region_bm->par_at_put_range(index, end_index, true);
1355 }
1356 }
1357
1358 public:
1359 CMCountDataClosureBase(G1CollectedHeap* g1h,
1360 BitMap* region_bm, BitMap* card_bm):
1361 _g1h(g1h), _cm(g1h->concurrent_mark()),
1362 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
1363 _region_bm(region_bm), _card_bm(card_bm) { }
1364 };
1365
1366 // Closure that calculates the # live objects per region. Used
1367 // for verification purposes during the cleanup pause.
1368 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1369 CMBitMapRO* _bm;
1370 size_t _region_marked_bytes;
1371
1372 public:
1373 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1374 BitMap* region_bm, BitMap* card_bm) :
1375 CMCountDataClosureBase(g1h, region_bm, card_bm),
1376 _bm(bm), _region_marked_bytes(0) { }
1377
1378 bool doHeapRegion(HeapRegion* hr) {
1379
1380 if (hr->continuesHumongous()) {
1381 // We will ignore these here and process them when their
1382 // associated "starts humongous" region is processed (see
1383 // set_bit_for_heap_region()). Note that we cannot rely on their
1384 // associated "starts humongous" region to have their bit set to
1385 // 1 since, due to the region chunking in the parallel region
1386 // iteration, a "continues humongous" region might be visited
1387 // before its associated "starts humongous".
1388 return false;
1389 }
1390
1391 HeapWord* ntams = hr->next_top_at_mark_start();
1392 HeapWord* start = hr->bottom();
1393
1394 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1395 err_msg("Preconditions not met - "
1396 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1397 start, ntams, hr->end()));
1398
1399 // Find the first marked object at or after "start".
1400 start = _bm->getNextMarkedWordAddress(start, ntams);
1401
1402 size_t marked_bytes = 0;
1403
1404 while (start < ntams) {
1405 oop obj = oop(start);
1406 int obj_sz = obj->size();
1407 HeapWord* obj_end = start + obj_sz;
1408
1409 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1410 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1411
1412 // Note: if we're looking at the last region in heap - obj_end
1413 // could be actually just beyond the end of the heap; end_idx
1414 // will then correspond to a (non-existent) card that is also
1415 // just beyond the heap.
1416 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1417 // end of object is not card aligned - increment to cover
1418 // all the cards spanned by the object
1419 end_idx += 1;
1420 }
1421
1422 // Set the bits in the card BM for the cards spanned by this object.
1423 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1424
1425 // Add the size of this object to the number of marked bytes.
1426 marked_bytes += (size_t)obj_sz * HeapWordSize;
1427
1428 // Find the next marked object after this one.
1429 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1430 }
1431
1432 // Mark the allocated-since-marking portion...
1433 HeapWord* top = hr->top();
1434 if (ntams < top) {
1435 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1436 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1437
1438 // Note: if we're looking at the last region in heap - top
1439 // could be actually just beyond the end of the heap; end_idx
1440 // will then correspond to a (non-existent) card that is also
1441 // just beyond the heap.
1442 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1443 // end of object is not card aligned - increment to cover
1444 // all the cards spanned by the object
1445 end_idx += 1;
1446 }
1447 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1448
1449 // This definitely means the region has live objects.
1450 set_bit_for_region(hr);
1451 }
1452
1453 // Update the live region bitmap.
1454 if (marked_bytes > 0) {
1455 set_bit_for_region(hr);
1456 }
1457
1458 // Set the marked bytes for the current region so that
1459 // it can be queried by a calling verificiation routine
1460 _region_marked_bytes = marked_bytes;
1461
1462 return false;
1463 }
1464
1465 size_t region_marked_bytes() const { return _region_marked_bytes; }
1466 };
1467
1468 // Heap region closure used for verifying the counting data
1469 // that was accumulated concurrently and aggregated during
1470 // the remark pause. This closure is applied to the heap
1471 // regions during the STW cleanup pause.
1472
1473 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1474 G1CollectedHeap* _g1h;
1475 ConcurrentMark* _cm;
1476 CalcLiveObjectsClosure _calc_cl;
1477 BitMap* _region_bm; // Region BM to be verified
1478 BitMap* _card_bm; // Card BM to be verified
1479 bool _verbose; // verbose output?
1480
1481 BitMap* _exp_region_bm; // Expected Region BM values
1482 BitMap* _exp_card_bm; // Expected card BM values
1483
1484 int _failures;
1485
1486 public:
1487 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1488 BitMap* region_bm,
1489 BitMap* card_bm,
1490 BitMap* exp_region_bm,
1491 BitMap* exp_card_bm,
1492 bool verbose) :
1493 _g1h(g1h), _cm(g1h->concurrent_mark()),
1494 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1495 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1496 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1497 _failures(0) { }
1498
1499 int failures() const { return _failures; }
1500
1501 bool doHeapRegion(HeapRegion* hr) {
1502 if (hr->continuesHumongous()) {
1503 // We will ignore these here and process them when their
1504 // associated "starts humongous" region is processed (see
1505 // set_bit_for_heap_region()). Note that we cannot rely on their
1506 // associated "starts humongous" region to have their bit set to
1507 // 1 since, due to the region chunking in the parallel region
1508 // iteration, a "continues humongous" region might be visited
1509 // before its associated "starts humongous".
1510 return false;
1511 }
1512
1513 int failures = 0;
1514
1515 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1516 // this region and set the corresponding bits in the expected region
1517 // and card bitmaps.
1518 bool res = _calc_cl.doHeapRegion(hr);
1519 assert(res == false, "should be continuing");
1520
1521 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1522 Mutex::_no_safepoint_check_flag);
1523
1524 // Verify the marked bytes for this region.
1525 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1526 size_t act_marked_bytes = hr->next_marked_bytes();
1527
1528 // We're not OK if expected marked bytes > actual marked bytes. It means
1529 // we have missed accounting some objects during the actual marking.
1530 if (exp_marked_bytes > act_marked_bytes) {
1531 if (_verbose) {
1532 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1533 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1534 hr->hrs_index(), exp_marked_bytes, act_marked_bytes);
1535 }
1536 failures += 1;
1537 }
1538
1539 // Verify the bit, for this region, in the actual and expected
1540 // (which was just calculated) region bit maps.
1541 // We're not OK if the bit in the calculated expected region
1542 // bitmap is set and the bit in the actual region bitmap is not.
1543 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1544
1545 bool expected = _exp_region_bm->at(index);
1546 bool actual = _region_bm->at(index);
1547 if (expected && !actual) {
1548 if (_verbose) {
1549 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1550 "expected: %s, actual: %s",
1551 hr->hrs_index(),
1552 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1553 }
1554 failures += 1;
1555 }
1556
1557 // Verify that the card bit maps for the cards spanned by the current
1558 // region match. We have an error if we have a set bit in the expected
1559 // bit map and the corresponding bit in the actual bitmap is not set.
1560
1561 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1562 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1563
1564 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1565 expected = _exp_card_bm->at(i);
1566 actual = _card_bm->at(i);
1567
1568 if (expected && !actual) {
1569 if (_verbose) {
1570 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1571 "expected: %s, actual: %s",
1572 hr->hrs_index(), i,
1573 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1574 }
1575 failures += 1;
1576 }
1577 }
1578
1579 if (failures > 0 && _verbose) {
1580 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1581 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1582 HR_FORMAT_PARAMS(hr), hr->next_top_at_mark_start(),
1583 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1584 }
1585
1586 _failures += failures;
1587
1588 // We could stop iteration over the heap when we
1589 // find the first violating region by returning true.
1590 return false;
1591 }
1592 };
1593
1594
1595 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1596 protected:
1597 G1CollectedHeap* _g1h;
1598 ConcurrentMark* _cm;
1599 BitMap* _actual_region_bm;
1600 BitMap* _actual_card_bm;
1601
1602 uint _n_workers;
1603
1604 BitMap* _expected_region_bm;
1605 BitMap* _expected_card_bm;
1606
1607 int _failures;
1608 bool _verbose;
1609
1610 public:
1611 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1612 BitMap* region_bm, BitMap* card_bm,
1613 BitMap* expected_region_bm, BitMap* expected_card_bm)
1614 : AbstractGangTask("G1 verify final counting"),
1615 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1616 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1617 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1618 _failures(0), _verbose(false),
1619 _n_workers(0) {
1620 assert(VerifyDuringGC, "don't call this otherwise");
1621
1622 // Use the value already set as the number of active threads
1623 // in the call to run_task().
1624 if (G1CollectedHeap::use_parallel_gc_threads()) {
1625 assert( _g1h->workers()->active_workers() > 0,
1626 "Should have been previously set");
1627 _n_workers = _g1h->workers()->active_workers();
1628 } else {
1629 _n_workers = 1;
1630 }
1631
1632 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1633 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1634
1635 _verbose = _cm->verbose_medium();
1636 }
1637
1638 void work(uint worker_id) {
1639 assert(worker_id < _n_workers, "invariant");
1640
1641 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1642 _actual_region_bm, _actual_card_bm,
1643 _expected_region_bm,
1644 _expected_card_bm,
1645 _verbose);
1646
1647 if (G1CollectedHeap::use_parallel_gc_threads()) {
1648 _g1h->heap_region_par_iterate_chunked(&verify_cl,
1649 worker_id,
1650 _n_workers,
1651 HeapRegion::VerifyCountClaimValue);
1652 } else {
1653 _g1h->heap_region_iterate(&verify_cl);
1654 }
1655
1656 Atomic::add(verify_cl.failures(), &_failures);
1657 }
1658
1659 int failures() const { return _failures; }
1660 };
1661
1662 // Closure that finalizes the liveness counting data.
1663 // Used during the cleanup pause.
1664 // Sets the bits corresponding to the interval [NTAMS, top]
1665 // (which contains the implicitly live objects) in the
1666 // card liveness bitmap. Also sets the bit for each region,
1667 // containing live data, in the region liveness bitmap.
1668
1669 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1670 public:
1671 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1672 BitMap* region_bm,
1673 BitMap* card_bm) :
1674 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1675
1676 bool doHeapRegion(HeapRegion* hr) {
1677
1678 if (hr->continuesHumongous()) {
1679 // We will ignore these here and process them when their
1680 // associated "starts humongous" region is processed (see
1681 // set_bit_for_heap_region()). Note that we cannot rely on their
1682 // associated "starts humongous" region to have their bit set to
1683 // 1 since, due to the region chunking in the parallel region
1684 // iteration, a "continues humongous" region might be visited
1685 // before its associated "starts humongous".
1686 return false;
1687 }
1688
1689 HeapWord* ntams = hr->next_top_at_mark_start();
1690 HeapWord* top = hr->top();
1691
1692 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1693
1694 // Mark the allocated-since-marking portion...
1695 if (ntams < top) {
1696 // This definitely means the region has live objects.
1697 set_bit_for_region(hr);
1698
1699 // Now set the bits in the card bitmap for [ntams, top)
1700 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1701 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1702
1703 // Note: if we're looking at the last region in heap - top
1704 // could be actually just beyond the end of the heap; end_idx
1705 // will then correspond to a (non-existent) card that is also
1706 // just beyond the heap.
1707 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1708 // end of object is not card aligned - increment to cover
1709 // all the cards spanned by the object
1710 end_idx += 1;
1711 }
1712
1713 assert(end_idx <= _card_bm->size(),
1714 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1715 end_idx, _card_bm->size()));
1716 assert(start_idx < _card_bm->size(),
1717 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1718 start_idx, _card_bm->size()));
1719
1720 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1721 }
1722
1723 // Set the bit for the region if it contains live data
1724 if (hr->next_marked_bytes() > 0) {
1725 set_bit_for_region(hr);
1726 }
1727
1728 return false;
1729 }
1730 };
1731
1732 class G1ParFinalCountTask: public AbstractGangTask {
1733 protected:
1734 G1CollectedHeap* _g1h;
1735 ConcurrentMark* _cm;
1736 BitMap* _actual_region_bm;
1737 BitMap* _actual_card_bm;
1738
1739 uint _n_workers;
1740
1741 public:
1742 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1743 : AbstractGangTask("G1 final counting"),
1744 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1745 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1746 _n_workers(0) {
1747 // Use the value already set as the number of active threads
1748 // in the call to run_task().
1749 if (G1CollectedHeap::use_parallel_gc_threads()) {
1750 assert( _g1h->workers()->active_workers() > 0,
1751 "Should have been previously set");
1752 _n_workers = _g1h->workers()->active_workers();
1753 } else {
1754 _n_workers = 1;
1755 }
1756 }
1757
1758 void work(uint worker_id) {
1759 assert(worker_id < _n_workers, "invariant");
1760
1761 FinalCountDataUpdateClosure final_update_cl(_g1h,
1762 _actual_region_bm,
1763 _actual_card_bm);
1764
1765 if (G1CollectedHeap::use_parallel_gc_threads()) {
1766 _g1h->heap_region_par_iterate_chunked(&final_update_cl,
1767 worker_id,
1768 _n_workers,
1769 HeapRegion::FinalCountClaimValue);
1770 } else {
1771 _g1h->heap_region_iterate(&final_update_cl);
1772 }
1773 }
1774 };
1775
1776 class G1ParNoteEndTask;
1777
1778 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1779 G1CollectedHeap* _g1;
1780 int _worker_num;
1781 size_t _max_live_bytes;
1782 uint _regions_claimed;
1783 size_t _freed_bytes;
1784 FreeRegionList* _local_cleanup_list;
1785 OldRegionSet* _old_proxy_set;
1786 HumongousRegionSet* _humongous_proxy_set;
1787 HRRSCleanupTask* _hrrs_cleanup_task;
1788 double _claimed_region_time;
1789 double _max_region_time;
1790
1791 public:
1792 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1793 int worker_num,
1794 FreeRegionList* local_cleanup_list,
1795 OldRegionSet* old_proxy_set,
1796 HumongousRegionSet* humongous_proxy_set,
1797 HRRSCleanupTask* hrrs_cleanup_task) :
1798 _g1(g1), _worker_num(worker_num),
1799 _max_live_bytes(0), _regions_claimed(0),
1800 _freed_bytes(0),
1801 _claimed_region_time(0.0), _max_region_time(0.0),
1802 _local_cleanup_list(local_cleanup_list),
1803 _old_proxy_set(old_proxy_set),
1804 _humongous_proxy_set(humongous_proxy_set),
1805 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1806
1807 size_t freed_bytes() { return _freed_bytes; }
1808
1809 bool doHeapRegion(HeapRegion *hr) {
1810 if (hr->continuesHumongous()) {
1811 return false;
1812 }
1813 // We use a claim value of zero here because all regions
1814 // were claimed with value 1 in the FinalCount task.
1815 _g1->reset_gc_time_stamps(hr);
1816 double start = os::elapsedTime();
1817 _regions_claimed++;
1818 hr->note_end_of_marking();
1819 _max_live_bytes += hr->max_live_bytes();
1820 _g1->free_region_if_empty(hr,
1821 &_freed_bytes,
1822 _local_cleanup_list,
1823 _old_proxy_set,
1824 _humongous_proxy_set,
1825 _hrrs_cleanup_task,
1826 true /* par */);
1827 double region_time = (os::elapsedTime() - start);
1828 _claimed_region_time += region_time;
1829 if (region_time > _max_region_time) {
1830 _max_region_time = region_time;
1831 }
1832 return false;
1833 }
1834
1835 size_t max_live_bytes() { return _max_live_bytes; }
1836 uint regions_claimed() { return _regions_claimed; }
1837 double claimed_region_time_sec() { return _claimed_region_time; }
1838 double max_region_time_sec() { return _max_region_time; }
1839 };
1840
1841 class G1ParNoteEndTask: public AbstractGangTask {
1842 friend class G1NoteEndOfConcMarkClosure;
1843
1844 protected:
1845 G1CollectedHeap* _g1h;
1846 size_t _max_live_bytes;
1847 size_t _freed_bytes;
1848 FreeRegionList* _cleanup_list;
1849
1850 public:
1851 G1ParNoteEndTask(G1CollectedHeap* g1h,
1852 FreeRegionList* cleanup_list) :
1853 AbstractGangTask("G1 note end"), _g1h(g1h),
1854 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1855
1856 void work(uint worker_id) {
1857 double start = os::elapsedTime();
1858 FreeRegionList local_cleanup_list("Local Cleanup List");
1859 OldRegionSet old_proxy_set("Local Cleanup Old Proxy Set");
1860 HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
1861 HRRSCleanupTask hrrs_cleanup_task;
1862 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, worker_id, &local_cleanup_list,
1863 &old_proxy_set,
1864 &humongous_proxy_set,
1865 &hrrs_cleanup_task);
1866 if (G1CollectedHeap::use_parallel_gc_threads()) {
1867 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id,
1868 _g1h->workers()->active_workers(),
1869 HeapRegion::NoteEndClaimValue);
1870 } else {
1871 _g1h->heap_region_iterate(&g1_note_end);
1872 }
1873 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1874
1875 // Now update the lists
1876 _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
1877 NULL /* free_list */,
1878 &old_proxy_set,
1879 &humongous_proxy_set,
1880 true /* par */);
1881 {
1882 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1883 _max_live_bytes += g1_note_end.max_live_bytes();
1884 _freed_bytes += g1_note_end.freed_bytes();
1885
1886 // If we iterate over the global cleanup list at the end of
1887 // cleanup to do this printing we will not guarantee to only
1888 // generate output for the newly-reclaimed regions (the list
1889 // might not be empty at the beginning of cleanup; we might
1890 // still be working on its previous contents). So we do the
1891 // printing here, before we append the new regions to the global
1892 // cleanup list.
1893
1894 G1HRPrinter* hr_printer = _g1h->hr_printer();
1895 if (hr_printer->is_active()) {
1896 HeapRegionLinkedListIterator iter(&local_cleanup_list);
1897 while (iter.more_available()) {
1898 HeapRegion* hr = iter.get_next();
1899 hr_printer->cleanup(hr);
1900 }
1901 }
1902
1903 _cleanup_list->add_as_tail(&local_cleanup_list);
1904 assert(local_cleanup_list.is_empty(), "post-condition");
1905
1906 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1907 }
1908 }
1909 size_t max_live_bytes() { return _max_live_bytes; }
1910 size_t freed_bytes() { return _freed_bytes; }
1911 };
1912
1913 class G1ParScrubRemSetTask: public AbstractGangTask {
1914 protected:
1915 G1RemSet* _g1rs;
1916 BitMap* _region_bm;
1917 BitMap* _card_bm;
1918 public:
1919 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1920 BitMap* region_bm, BitMap* card_bm) :
1921 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1922 _region_bm(region_bm), _card_bm(card_bm) { }
1923
1924 void work(uint worker_id) {
1925 if (G1CollectedHeap::use_parallel_gc_threads()) {
1926 _g1rs->scrub_par(_region_bm, _card_bm, worker_id,
1927 HeapRegion::ScrubRemSetClaimValue);
1928 } else {
1929 _g1rs->scrub(_region_bm, _card_bm);
1930 }
1931 }
1932
1933 };
1934
1935 void ConcurrentMark::cleanup() {
1936 // world is stopped at this checkpoint
1937 assert(SafepointSynchronize::is_at_safepoint(),
1938 "world should be stopped");
1939 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1940
1941 // If a full collection has happened, we shouldn't do this.
1942 if (has_aborted()) {
1943 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1944 return;
1945 }
1946
1947 HRSPhaseSetter x(HRSPhaseCleanup);
1948 g1h->verify_region_sets_optional();
1949
1950 if (VerifyDuringGC) {
1951 HandleMark hm; // handle scope
1952 gclog_or_tty->print(" VerifyDuringGC:(before)");
1953 Universe::heap()->prepare_for_verify();
1954 Universe::verify(/* silent */ false,
1955 /* option */ VerifyOption_G1UsePrevMarking);
1956 }
1957
1958 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1959 g1p->record_concurrent_mark_cleanup_start();
1960
1961 double start = os::elapsedTime();
1962
1963 HeapRegionRemSet::reset_for_cleanup_tasks();
1964
1965 uint n_workers;
1966
1967 // Do counting once more with the world stopped for good measure.
1968 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1969
1970 if (G1CollectedHeap::use_parallel_gc_threads()) {
1971 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
1972 "sanity check");
1973
1974 g1h->set_par_threads();
1975 n_workers = g1h->n_par_threads();
1976 assert(g1h->n_par_threads() == n_workers,
1977 "Should not have been reset");
1978 g1h->workers()->run_task(&g1_par_count_task);
1979 // Done with the parallel phase so reset to 0.
1980 g1h->set_par_threads(0);
1981
1982 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue),
1983 "sanity check");
1984 } else {
1985 n_workers = 1;
1986 g1_par_count_task.work(0);
1987 }
1988
1989 if (VerifyDuringGC) {
1990 // Verify that the counting data accumulated during marking matches
1991 // that calculated by walking the marking bitmap.
1992
1993 // Bitmaps to hold expected values
1994 BitMap expected_region_bm(_region_bm.size(), false);
1995 BitMap expected_card_bm(_card_bm.size(), false);
1996
1997 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1998 &_region_bm,
1999 &_card_bm,
2000 &expected_region_bm,
2001 &expected_card_bm);
2002
2003 if (G1CollectedHeap::use_parallel_gc_threads()) {
2004 g1h->set_par_threads((int)n_workers);
2005 g1h->workers()->run_task(&g1_par_verify_task);
2006 // Done with the parallel phase so reset to 0.
2007 g1h->set_par_threads(0);
2008
2009 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue),
2010 "sanity check");
2011 } else {
2012 g1_par_verify_task.work(0);
2013 }
2014
2015 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2016 }
2017
2018 size_t start_used_bytes = g1h->used();
2019 g1h->set_marking_complete();
2020
2021 double count_end = os::elapsedTime();
2022 double this_final_counting_time = (count_end - start);
2023 _total_counting_time += this_final_counting_time;
2024
2025 if (G1PrintRegionLivenessInfo) {
2026 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2027 _g1h->heap_region_iterate(&cl);
2028 }
2029
2030 // Install newly created mark bitMap as "prev".
2031 swapMarkBitMaps();
2032
2033 g1h->reset_gc_time_stamp();
2034
2035 // Note end of marking in all heap regions.
2036 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
2037 if (G1CollectedHeap::use_parallel_gc_threads()) {
2038 g1h->set_par_threads((int)n_workers);
2039 g1h->workers()->run_task(&g1_par_note_end_task);
2040 g1h->set_par_threads(0);
2041
2042 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
2043 "sanity check");
2044 } else {
2045 g1_par_note_end_task.work(0);
2046 }
2047 g1h->check_gc_time_stamps();
2048
2049 if (!cleanup_list_is_empty()) {
2050 // The cleanup list is not empty, so we'll have to process it
2051 // concurrently. Notify anyone else that might be wanting free
2052 // regions that there will be more free regions coming soon.
2053 g1h->set_free_regions_coming();
2054 }
2055
2056 // call below, since it affects the metric by which we sort the heap
2057 // regions.
2058 if (G1ScrubRemSets) {
2059 double rs_scrub_start = os::elapsedTime();
2060 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
2061 if (G1CollectedHeap::use_parallel_gc_threads()) {
2062 g1h->set_par_threads((int)n_workers);
2063 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2064 g1h->set_par_threads(0);
2065
2066 assert(g1h->check_heap_region_claim_values(
2067 HeapRegion::ScrubRemSetClaimValue),
2068 "sanity check");
2069 } else {
2070 g1_par_scrub_rs_task.work(0);
2071 }
2072
2073 double rs_scrub_end = os::elapsedTime();
2074 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2075 _total_rs_scrub_time += this_rs_scrub_time;
2076 }
2077
2078 // this will also free any regions totally full of garbage objects,
2079 // and sort the regions.
2080 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2081
2082 // Statistics.
2083 double end = os::elapsedTime();
2084 _cleanup_times.add((end - start) * 1000.0);
2085
2086 if (G1Log::fine()) {
2087 g1h->print_size_transition(gclog_or_tty,
2088 start_used_bytes,
2089 g1h->used(),
2090 g1h->capacity());
2091 }
2092
2093 // Clean up will have freed any regions completely full of garbage.
2094 // Update the soft reference policy with the new heap occupancy.
2095 Universe::update_heap_info_at_gc();
2096
2097 // We need to make this be a "collection" so any collection pause that
2098 // races with it goes around and waits for completeCleanup to finish.
2099 g1h->increment_total_collections();
2100
2101 // We reclaimed old regions so we should calculate the sizes to make
2102 // sure we update the old gen/space data.
2103 g1h->g1mm()->update_sizes();
2104
2105 if (VerifyDuringGC) {
2106 HandleMark hm; // handle scope
2107 gclog_or_tty->print(" VerifyDuringGC:(after)");
2108 Universe::heap()->prepare_for_verify();
2109 Universe::verify(/* silent */ false,
2110 /* option */ VerifyOption_G1UsePrevMarking);
2111 }
2112
2113 g1h->verify_region_sets_optional();
2114 }
2115
2116 void ConcurrentMark::completeCleanup() {
2117 if (has_aborted()) return;
2118
2119 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2120
2121 _cleanup_list.verify_optional();
2122 FreeRegionList tmp_free_list("Tmp Free List");
2123
2124 if (G1ConcRegionFreeingVerbose) {
2125 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2126 "cleanup list has %u entries",
2127 _cleanup_list.length());
2128 }
2129
2130 // Noone else should be accessing the _cleanup_list at this point,
2131 // so it's not necessary to take any locks
2132 while (!_cleanup_list.is_empty()) {
2133 HeapRegion* hr = _cleanup_list.remove_head();
2134 assert(hr != NULL, "the list was not empty");
2135 hr->par_clear();
2136 tmp_free_list.add_as_tail(hr);
2137
2138 // Instead of adding one region at a time to the secondary_free_list,
2139 // we accumulate them in the local list and move them a few at a
2140 // time. This also cuts down on the number of notify_all() calls
2141 // we do during this process. We'll also append the local list when
2142 // _cleanup_list is empty (which means we just removed the last
2143 // region from the _cleanup_list).
2144 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2145 _cleanup_list.is_empty()) {
2146 if (G1ConcRegionFreeingVerbose) {
2147 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2148 "appending %u entries to the secondary_free_list, "
2149 "cleanup list still has %u entries",
2150 tmp_free_list.length(),
2151 _cleanup_list.length());
2152 }
2153
2154 {
2155 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2156 g1h->secondary_free_list_add_as_tail(&tmp_free_list);
2157 SecondaryFreeList_lock->notify_all();
2158 }
2159
2160 if (G1StressConcRegionFreeing) {
2161 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2162 os::sleep(Thread::current(), (jlong) 1, false);
2163 }
2164 }
2165 }
2166 }
2167 assert(tmp_free_list.is_empty(), "post-condition");
2168 }
2169
2170 // Supporting Object and Oop closures for reference discovery
2171 // and processing in during marking
2172
2173 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2174 HeapWord* addr = (HeapWord*)obj;
2175 return addr != NULL &&
2176 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2177 }
2178
2179 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2180 // Uses the CMTask associated with a worker thread (for serial reference
2181 // processing the CMTask for worker 0 is used) to preserve (mark) and
2182 // trace referent objects.
2183 //
2184 // Using the CMTask and embedded local queues avoids having the worker
2185 // threads operating on the global mark stack. This reduces the risk
2186 // of overflowing the stack - which we would rather avoid at this late
2187 // state. Also using the tasks' local queues removes the potential
2188 // of the workers interfering with each other that could occur if
2189 // operating on the global stack.
2190
2191 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2192 ConcurrentMark* _cm;
2193 CMTask* _task;
2194 int _ref_counter_limit;
2195 int _ref_counter;
2196 public:
2197 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task) :
2198 _cm(cm), _task(task), _ref_counter_limit(G1RefProcDrainInterval) {
2199 assert(_ref_counter_limit > 0, "sanity");
2200 _ref_counter = _ref_counter_limit;
2201 }
2202
2203 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2204 virtual void do_oop( oop* p) { do_oop_work(p); }
2205
2206 template <class T> void do_oop_work(T* p) {
2207 if (!_cm->has_overflown()) {
2208 oop obj = oopDesc::load_decode_heap_oop(p);
2209 if (_cm->verbose_high()) {
2210 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2211 "*"PTR_FORMAT" = "PTR_FORMAT,
2212 _task->worker_id(), p, (void*) obj);
2213 }
2214
2215 _task->deal_with_reference(obj);
2216 _ref_counter--;
2217
2218 if (_ref_counter == 0) {
2219 // We have dealt with _ref_counter_limit references, pushing them
2220 // and objects reachable from them on to the local stack (and
2221 // possibly the global stack). Call CMTask::do_marking_step() to
2222 // process these entries.
2223 //
2224 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2225 // there's nothing more to do (i.e. we're done with the entries that
2226 // were pushed as a result of the CMTask::deal_with_reference() calls
2227 // above) or we overflow.
2228 //
2229 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2230 // flag while there may still be some work to do. (See the comment at
2231 // the beginning of CMTask::do_marking_step() for those conditions -
2232 // one of which is reaching the specified time target.) It is only
2233 // when CMTask::do_marking_step() returns without setting the
2234 // has_aborted() flag that the marking step has completed.
2235 do {
2236 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2237 _task->do_marking_step(mark_step_duration_ms,
2238 false /* do_stealing */,
2239 false /* do_termination */);
2240 } while (_task->has_aborted() && !_cm->has_overflown());
2241 _ref_counter = _ref_counter_limit;
2242 }
2243 } else {
2244 if (_cm->verbose_high()) {
2245 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2246 }
2247 }
2248 }
2249 };
2250
2251 // 'Drain' oop closure used by both serial and parallel reference processing.
2252 // Uses the CMTask associated with a given worker thread (for serial
2253 // reference processing the CMtask for worker 0 is used). Calls the
2254 // do_marking_step routine, with an unbelievably large timeout value,
2255 // to drain the marking data structures of the remaining entries
2256 // added by the 'keep alive' oop closure above.
2257
2258 class G1CMDrainMarkingStackClosure: public VoidClosure {
2259 ConcurrentMark* _cm;
2260 CMTask* _task;
2261 bool _do_stealing;
2262 bool _do_termination;
2263 public:
2264 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_par) :
2265 _cm(cm), _task(task) {
2266 assert(is_par || _task->worker_id() == 0,
2267 "Only task for worker 0 should be used if ref processing is single threaded");
2268 // We only allow stealing and only enter the termination protocol
2269 // in CMTask::do_marking_step() if this closure is being instantiated
2270 // for parallel reference processing.
2271 _do_stealing = _do_termination = is_par;
2272 }
2273
2274 void do_void() {
2275 do {
2276 if (_cm->verbose_high()) {
2277 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - "
2278 "stealing: %s, termination: %s",
2279 _task->worker_id(),
2280 BOOL_TO_STR(_do_stealing),
2281 BOOL_TO_STR(_do_termination));
2282 }
2283
2284 // We call CMTask::do_marking_step() to completely drain the local
2285 // and global marking stacks of entries pushed by the 'keep alive'
2286 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2287 //
2288 // CMTask::do_marking_step() is called in a loop, which we'll exit
2289 // if there's nothing more to do (i.e. we'completely drained the
2290 // entries that were pushed as a a result of applying the 'keep alive'
2291 // closure to the entries on the discovered ref lists) or we overflow
2292 // the global marking stack.
2293 //
2294 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2295 // flag while there may still be some work to do. (See the comment at
2296 // the beginning of CMTask::do_marking_step() for those conditions -
2297 // one of which is reaching the specified time target.) It is only
2298 // when CMTask::do_marking_step() returns without setting the
2299 // has_aborted() flag that the marking step has completed.
2300
2301 _task->do_marking_step(1000000000.0 /* something very large */,
2302 _do_stealing,
2303 _do_termination);
2304 } while (_task->has_aborted() && !_cm->has_overflown());
2305 }
2306 };
2307
2308 // Implementation of AbstractRefProcTaskExecutor for parallel
2309 // reference processing at the end of G1 concurrent marking
2310
2311 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2312 private:
2313 G1CollectedHeap* _g1h;
2314 ConcurrentMark* _cm;
2315 WorkGang* _workers;
2316 int _active_workers;
2317
2318 public:
2319 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2320 ConcurrentMark* cm,
2321 WorkGang* workers,
2322 int n_workers) :
2323 _g1h(g1h), _cm(cm),
2324 _workers(workers), _active_workers(n_workers) { }
2325
2326 // Executes the given task using concurrent marking worker threads.
2327 virtual void execute(ProcessTask& task);
2328 virtual void execute(EnqueueTask& task);
2329 };
2330
2331 class G1CMRefProcTaskProxy: public AbstractGangTask {
2332 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2333 ProcessTask& _proc_task;
2334 G1CollectedHeap* _g1h;
2335 ConcurrentMark* _cm;
2336 bool _processing_is_mt;
2337
2338 public:
2339 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2340 G1CollectedHeap* g1h,
2341 ConcurrentMark* cm) :
2342 AbstractGangTask("Process reference objects in parallel"),
2343 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2344 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2345 _processing_is_mt = rp->processing_is_mt();
2346 }
2347
2348 virtual void work(uint worker_id) {
2349 CMTask* marking_task = _cm->task(worker_id);
2350 G1CMIsAliveClosure g1_is_alive(_g1h);
2351 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, marking_task);
2352 G1CMDrainMarkingStackClosure g1_par_drain(_cm, marking_task, _processing_is_mt);
2353
2354 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2355 }
2356 };
2357
2358 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2359 assert(_workers != NULL, "Need parallel worker threads.");
2360 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2361
2362 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2363
2364 // We need to reset the phase for each task execution so that
2365 // the termination protocol of CMTask::do_marking_step works.
2366 _cm->set_phase(_active_workers, false /* concurrent */);
2367 _g1h->set_par_threads(_active_workers);
2368 _workers->run_task(&proc_task_proxy);
2369 _g1h->set_par_threads(0);
2370 }
2371
2372 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2373 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2374 EnqueueTask& _enq_task;
2375
2376 public:
2377 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2378 AbstractGangTask("Enqueue reference objects in parallel"),
2379 _enq_task(enq_task) { }
2380
2381 virtual void work(uint worker_id) {
2382 _enq_task.work(worker_id);
2383 }
2384 };
2385
2386 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2387 assert(_workers != NULL, "Need parallel worker threads.");
2388 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2389
2390 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2391
2392 _g1h->set_par_threads(_active_workers);
2393 _workers->run_task(&enq_task_proxy);
2394 _g1h->set_par_threads(0);
2395 }
2396
2397 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2398 ResourceMark rm;
2399 HandleMark hm;
2400
2401 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2402
2403 // Is alive closure.
2404 G1CMIsAliveClosure g1_is_alive(g1h);
2405
2406 // Inner scope to exclude the cleaning of the string and symbol
2407 // tables from the displayed time.
2408 {
2409 if (G1Log::finer()) {
2410 gclog_or_tty->put(' ');
2411 }
2412 TraceTime t("GC ref-proc", G1Log::finer(), false, gclog_or_tty);
2413
2414 ReferenceProcessor* rp = g1h->ref_processor_cm();
2415
2416 // See the comment in G1CollectedHeap::ref_processing_init()
2417 // about how reference processing currently works in G1.
2418
2419 // Set the soft reference policy
2420 rp->setup_policy(clear_all_soft_refs);
2421 assert(_markStack.isEmpty(), "mark stack should be empty");
2422
2423 // Non-MT instances 'Keep Alive' and 'Complete GC' oop closures.
2424 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0));
2425 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), false);
2426
2427 // We need at least one active thread. If reference processing is
2428 // not multi-threaded we use the current (ConcurrentMarkThread) thread,
2429 // otherwise we use the work gang from the G1CollectedHeap and we
2430 // utilize all the worker threads we can.
2431 uint active_workers = (rp->processing_is_mt() && g1h->workers() != NULL
2432 ? g1h->workers()->active_workers()
2433 : 1U);
2434
2435 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2436
2437 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2438 g1h->workers(), active_workers);
2439
2440 AbstractRefProcTaskExecutor* executor = (rp->processing_is_mt()
2441 ? &par_task_executor
2442 : NULL);
2443
2444 // Set the degree of MT processing here. If the discovery was done MT,
2445 // the number of threads involved during discovery could differ from
2446 // the number of active workers. This is OK as long as the discovered
2447 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2448 rp->set_active_mt_degree(active_workers);
2449
2450 // Process the weak references.
2451 rp->process_discovered_references(&g1_is_alive,
2452 &g1_keep_alive,
2453 &g1_drain_mark_stack,
2454 executor);
2455
2456 // The do_oop work routines of the keep_alive and drain_marking_stack
2457 // oop closures will set the has_overflown flag if we overflow the
2458 // global marking stack.
2459
2460 assert(_markStack.overflow() || _markStack.isEmpty(),
2461 "mark stack should be empty (unless it overflowed)");
2462 if (_markStack.overflow()) {
2463 // This should have been done already when we tried to push an
2464 // entry on to the global mark stack. But let's do it again.
2465 set_has_overflown();
2466 }
2467
2468 assert(rp->num_q() == active_workers, "why not");
2469
2470 rp->enqueue_discovered_references(executor);
2471
2472 rp->verify_no_references_recorded();
2473 assert(!rp->discovery_enabled(), "Post condition");
2474 }
2475
2476 // Now clean up stale oops in StringTable
2477 StringTable::unlink(&g1_is_alive);
2478 // Clean up unreferenced symbols in symbol table.
2479 SymbolTable::unlink();
2480 }
2481
2482 void ConcurrentMark::swapMarkBitMaps() {
2483 CMBitMapRO* temp = _prevMarkBitMap;
2484 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2485 _nextMarkBitMap = (CMBitMap*) temp;
2486 }
2487
2488 class CMRemarkTask: public AbstractGangTask {
2489 private:
2490 ConcurrentMark *_cm;
2491
2492 public:
2493 void work(uint worker_id) {
2494 // Since all available tasks are actually started, we should
2495 // only proceed if we're supposed to be actived.
2496 if (worker_id < _cm->active_tasks()) {
2497 CMTask* task = _cm->task(worker_id);
2498 task->record_start_time();
2499 do {
2500 task->do_marking_step(1000000000.0 /* something very large */,
2501 true /* do_stealing */,
2502 true /* do_termination */);
2503 } while (task->has_aborted() && !_cm->has_overflown());
2504 // If we overflow, then we do not want to restart. We instead
2505 // want to abort remark and do concurrent marking again.
2506 task->record_end_time();
2507 }
2508 }
2509
2510 CMRemarkTask(ConcurrentMark* cm, int active_workers) :
2511 AbstractGangTask("Par Remark"), _cm(cm) {
2512 _cm->terminator()->reset_for_reuse(active_workers);
2513 }
2514 };
2515
2516 void ConcurrentMark::checkpointRootsFinalWork() {
2517 ResourceMark rm;
2518 HandleMark hm;
2519 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2520
2521 g1h->ensure_parsability(false);
2522
2523 if (G1CollectedHeap::use_parallel_gc_threads()) {
2524 G1CollectedHeap::StrongRootsScope srs(g1h);
2525 // this is remark, so we'll use up all active threads
2526 uint active_workers = g1h->workers()->active_workers();
2527 if (active_workers == 0) {
2528 assert(active_workers > 0, "Should have been set earlier");
2529 active_workers = (uint) ParallelGCThreads;
2530 g1h->workers()->set_active_workers(active_workers);
2531 }
2532 set_phase(active_workers, false /* concurrent */);
2533 // Leave _parallel_marking_threads at it's
2534 // value originally calculated in the ConcurrentMark
2535 // constructor and pass values of the active workers
2536 // through the gang in the task.
2537
2538 CMRemarkTask remarkTask(this, active_workers);
2539 g1h->set_par_threads(active_workers);
2540 g1h->workers()->run_task(&remarkTask);
2541 g1h->set_par_threads(0);
2542 } else {
2543 G1CollectedHeap::StrongRootsScope srs(g1h);
2544 // this is remark, so we'll use up all available threads
2545 uint active_workers = 1;
2546 set_phase(active_workers, false /* concurrent */);
2547
2548 CMRemarkTask remarkTask(this, active_workers);
2549 // We will start all available threads, even if we decide that the
2550 // active_workers will be fewer. The extra ones will just bail out
2551 // immediately.
2552 remarkTask.work(0);
2553 }
2554 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2555 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
2556
2557 print_stats();
2558
2559 #if VERIFY_OBJS_PROCESSED
2560 if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) {
2561 gclog_or_tty->print_cr("Processed = %d, enqueued = %d.",
2562 _scan_obj_cl.objs_processed,
2563 ThreadLocalObjQueue::objs_enqueued);
2564 guarantee(_scan_obj_cl.objs_processed ==
2565 ThreadLocalObjQueue::objs_enqueued,
2566 "Different number of objs processed and enqueued.");
2567 }
2568 #endif
2569 }
2570
2571 #ifndef PRODUCT
2572
2573 class PrintReachableOopClosure: public OopClosure {
2574 private:
2575 G1CollectedHeap* _g1h;
2576 outputStream* _out;
2577 VerifyOption _vo;
2578 bool _all;
2579
2580 public:
2581 PrintReachableOopClosure(outputStream* out,
2582 VerifyOption vo,
2583 bool all) :
2584 _g1h(G1CollectedHeap::heap()),
2585 _out(out), _vo(vo), _all(all) { }
2586
2587 void do_oop(narrowOop* p) { do_oop_work(p); }
2588 void do_oop( oop* p) { do_oop_work(p); }
2589
2590 template <class T> void do_oop_work(T* p) {
2591 oop obj = oopDesc::load_decode_heap_oop(p);
2592 const char* str = NULL;
2593 const char* str2 = "";
2594
2595 if (obj == NULL) {
2596 str = "";
2597 } else if (!_g1h->is_in_g1_reserved(obj)) {
2598 str = " O";
2599 } else {
2600 HeapRegion* hr = _g1h->heap_region_containing(obj);
2601 guarantee(hr != NULL, "invariant");
2602 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo);
2603 bool marked = _g1h->is_marked(obj, _vo);
2604
2605 if (over_tams) {
2606 str = " >";
2607 if (marked) {
2608 str2 = " AND MARKED";
2609 }
2610 } else if (marked) {
2611 str = " M";
2612 } else {
2613 str = " NOT";
2614 }
2615 }
2616
2617 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2618 p, (void*) obj, str, str2);
2619 }
2620 };
2621
2622 class PrintReachableObjectClosure : public ObjectClosure {
2623 private:
2624 G1CollectedHeap* _g1h;
2625 outputStream* _out;
2626 VerifyOption _vo;
2627 bool _all;
2628 HeapRegion* _hr;
2629
2630 public:
2631 PrintReachableObjectClosure(outputStream* out,
2632 VerifyOption vo,
2633 bool all,
2634 HeapRegion* hr) :
2635 _g1h(G1CollectedHeap::heap()),
2636 _out(out), _vo(vo), _all(all), _hr(hr) { }
2637
2638 void do_object(oop o) {
2639 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo);
2640 bool marked = _g1h->is_marked(o, _vo);
2641 bool print_it = _all || over_tams || marked;
2642
2643 if (print_it) {
2644 _out->print_cr(" "PTR_FORMAT"%s",
2645 o, (over_tams) ? " >" : (marked) ? " M" : "");
2646 PrintReachableOopClosure oopCl(_out, _vo, _all);
2647 o->oop_iterate_no_header(&oopCl);
2648 }
2649 }
2650 };
2651
2652 class PrintReachableRegionClosure : public HeapRegionClosure {
2653 private:
2654 G1CollectedHeap* _g1h;
2655 outputStream* _out;
2656 VerifyOption _vo;
2657 bool _all;
2658
2659 public:
2660 bool doHeapRegion(HeapRegion* hr) {
2661 HeapWord* b = hr->bottom();
2662 HeapWord* e = hr->end();
2663 HeapWord* t = hr->top();
2664 HeapWord* p = _g1h->top_at_mark_start(hr, _vo);
2665 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2666 "TAMS: "PTR_FORMAT, b, e, t, p);
2667 _out->cr();
2668
2669 HeapWord* from = b;
2670 HeapWord* to = t;
2671
2672 if (to > from) {
2673 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2674 _out->cr();
2675 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2676 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2677 _out->cr();
2678 }
2679
2680 return false;
2681 }
2682
2683 PrintReachableRegionClosure(outputStream* out,
2684 VerifyOption vo,
2685 bool all) :
2686 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { }
2687 };
2688
2689 void ConcurrentMark::print_reachable(const char* str,
2690 VerifyOption vo,
2691 bool all) {
2692 gclog_or_tty->cr();
2693 gclog_or_tty->print_cr("== Doing heap dump... ");
2694
2695 if (G1PrintReachableBaseFile == NULL) {
2696 gclog_or_tty->print_cr(" #### error: no base file defined");
2697 return;
2698 }
2699
2700 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2701 (JVM_MAXPATHLEN - 1)) {
2702 gclog_or_tty->print_cr(" #### error: file name too long");
2703 return;
2704 }
2705
2706 char file_name[JVM_MAXPATHLEN];
2707 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2708 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2709
2710 fileStream fout(file_name);
2711 if (!fout.is_open()) {
2712 gclog_or_tty->print_cr(" #### error: could not open file");
2713 return;
2714 }
2715
2716 outputStream* out = &fout;
2717 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo));
2718 out->cr();
2719
2720 out->print_cr("--- ITERATING OVER REGIONS");
2721 out->cr();
2722 PrintReachableRegionClosure rcl(out, vo, all);
2723 _g1h->heap_region_iterate(&rcl);
2724 out->cr();
2725
2726 gclog_or_tty->print_cr(" done");
2727 gclog_or_tty->flush();
2728 }
2729
2730 #endif // PRODUCT
2731
2732 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2733 // Note we are overriding the read-only view of the prev map here, via
2734 // the cast.
2735 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2736 }
2737
2738 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2739 _nextMarkBitMap->clearRange(mr);
2740 }
2741
2742 void ConcurrentMark::clearRangeBothBitmaps(MemRegion mr) {
2743 clearRangePrevBitmap(mr);
2744 clearRangeNextBitmap(mr);
2745 }
2746
2747 HeapRegion*
2748 ConcurrentMark::claim_region(uint worker_id) {
2749 // "checkpoint" the finger
2750 HeapWord* finger = _finger;
2751
2752 // _heap_end will not change underneath our feet; it only changes at
2753 // yield points.
2754 while (finger < _heap_end) {
2755 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2756
2757 // Note on how this code handles humongous regions. In the
2758 // normal case the finger will reach the start of a "starts
2759 // humongous" (SH) region. Its end will either be the end of the
2760 // last "continues humongous" (CH) region in the sequence, or the
2761 // standard end of the SH region (if the SH is the only region in
2762 // the sequence). That way claim_region() will skip over the CH
2763 // regions. However, there is a subtle race between a CM thread
2764 // executing this method and a mutator thread doing a humongous
2765 // object allocation. The two are not mutually exclusive as the CM
2766 // thread does not need to hold the Heap_lock when it gets
2767 // here. So there is a chance that claim_region() will come across
2768 // a free region that's in the progress of becoming a SH or a CH
2769 // region. In the former case, it will either
2770 // a) Miss the update to the region's end, in which case it will
2771 // visit every subsequent CH region, will find their bitmaps
2772 // empty, and do nothing, or
2773 // b) Will observe the update of the region's end (in which case
2774 // it will skip the subsequent CH regions).
2775 // If it comes across a region that suddenly becomes CH, the
2776 // scenario will be similar to b). So, the race between
2777 // claim_region() and a humongous object allocation might force us
2778 // to do a bit of unnecessary work (due to some unnecessary bitmap
2779 // iterations) but it should not introduce and correctness issues.
2780 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2781 HeapWord* bottom = curr_region->bottom();
2782 HeapWord* end = curr_region->end();
2783 HeapWord* limit = curr_region->next_top_at_mark_start();
2784
2785 if (verbose_low()) {
2786 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2787 "["PTR_FORMAT", "PTR_FORMAT"), "
2788 "limit = "PTR_FORMAT,
2789 worker_id, curr_region, bottom, end, limit);
2790 }
2791
2792 // Is the gap between reading the finger and doing the CAS too long?
2793 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2794 if (res == finger) {
2795 // we succeeded
2796
2797 // notice that _finger == end cannot be guaranteed here since,
2798 // someone else might have moved the finger even further
2799 assert(_finger >= end, "the finger should have moved forward");
2800
2801 if (verbose_low()) {
2802 gclog_or_tty->print_cr("[%u] we were successful with region = "
2803 PTR_FORMAT, worker_id, curr_region);
2804 }
2805
2806 if (limit > bottom) {
2807 if (verbose_low()) {
2808 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2809 "returning it ", worker_id, curr_region);
2810 }
2811 return curr_region;
2812 } else {
2813 assert(limit == bottom,
2814 "the region limit should be at bottom");
2815 if (verbose_low()) {
2816 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2817 "returning NULL", worker_id, curr_region);
2818 }
2819 // we return NULL and the caller should try calling
2820 // claim_region() again.
2821 return NULL;
2822 }
2823 } else {
2824 assert(_finger > finger, "the finger should have moved forward");
2825 if (verbose_low()) {
2826 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2827 "global finger = "PTR_FORMAT", "
2828 "our finger = "PTR_FORMAT,
2829 worker_id, _finger, finger);
2830 }
2831
2832 // read it again
2833 finger = _finger;
2834 }
2835 }
2836
2837 return NULL;
2838 }
2839
2840 #ifndef PRODUCT
2841 enum VerifyNoCSetOopsPhase {
2842 VerifyNoCSetOopsStack,
2843 VerifyNoCSetOopsQueues,
2844 VerifyNoCSetOopsSATBCompleted,
2845 VerifyNoCSetOopsSATBThread
2846 };
2847
2848 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2849 private:
2850 G1CollectedHeap* _g1h;
2851 VerifyNoCSetOopsPhase _phase;
2852 int _info;
2853
2854 const char* phase_str() {
2855 switch (_phase) {
2856 case VerifyNoCSetOopsStack: return "Stack";
2857 case VerifyNoCSetOopsQueues: return "Queue";
2858 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2859 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2860 default: ShouldNotReachHere();
2861 }
2862 return NULL;
2863 }
2864
2865 void do_object_work(oop obj) {
2866 guarantee(!_g1h->obj_in_cs(obj),
2867 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2868 (void*) obj, phase_str(), _info));
2869 }
2870
2871 public:
2872 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2873
2874 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2875 _phase = phase;
2876 _info = info;
2877 }
2878
2879 virtual void do_oop(oop* p) {
2880 oop obj = oopDesc::load_decode_heap_oop(p);
2881 do_object_work(obj);
2882 }
2883
2884 virtual void do_oop(narrowOop* p) {
2885 // We should not come across narrow oops while scanning marking
2886 // stacks and SATB buffers.
2887 ShouldNotReachHere();
2888 }
2889
2890 virtual void do_object(oop obj) {
2891 do_object_work(obj);
2892 }
2893 };
2894
2895 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2896 bool verify_enqueued_buffers,
2897 bool verify_thread_buffers,
2898 bool verify_fingers) {
2899 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2900 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2901 return;
2902 }
2903
2904 VerifyNoCSetOopsClosure cl;
2905
2906 if (verify_stacks) {
2907 // Verify entries on the global mark stack
2908 cl.set_phase(VerifyNoCSetOopsStack);
2909 _markStack.oops_do(&cl);
2910
2911 // Verify entries on the task queues
2912 for (uint i = 0; i < _max_worker_id; i += 1) {
2913 cl.set_phase(VerifyNoCSetOopsQueues, i);
2914 CMTaskQueue* queue = _task_queues->queue(i);
2915 queue->oops_do(&cl);
2916 }
2917 }
2918
2919 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2920
2921 // Verify entries on the enqueued SATB buffers
2922 if (verify_enqueued_buffers) {
2923 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2924 satb_qs.iterate_completed_buffers_read_only(&cl);
2925 }
2926
2927 // Verify entries on the per-thread SATB buffers
2928 if (verify_thread_buffers) {
2929 cl.set_phase(VerifyNoCSetOopsSATBThread);
2930 satb_qs.iterate_thread_buffers_read_only(&cl);
2931 }
2932
2933 if (verify_fingers) {
2934 // Verify the global finger
2935 HeapWord* global_finger = finger();
2936 if (global_finger != NULL && global_finger < _heap_end) {
2937 // The global finger always points to a heap region boundary. We
2938 // use heap_region_containing_raw() to get the containing region
2939 // given that the global finger could be pointing to a free region
2940 // which subsequently becomes continues humongous. If that
2941 // happens, heap_region_containing() will return the bottom of the
2942 // corresponding starts humongous region and the check below will
2943 // not hold any more.
2944 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2945 guarantee(global_finger == global_hr->bottom(),
2946 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2947 global_finger, HR_FORMAT_PARAMS(global_hr)));
2948 }
2949
2950 // Verify the task fingers
2951 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2952 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
2953 CMTask* task = _tasks[i];
2954 HeapWord* task_finger = task->finger();
2955 if (task_finger != NULL && task_finger < _heap_end) {
2956 // See above note on the global finger verification.
2957 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2958 guarantee(task_finger == task_hr->bottom() ||
2959 !task_hr->in_collection_set(),
2960 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
2961 task_finger, HR_FORMAT_PARAMS(task_hr)));
2962 }
2963 }
2964 }
2965 }
2966 #endif // PRODUCT
2967
2968 // Aggregate the counting data that was constructed concurrently
2969 // with marking.
2970 class AggregateCountDataHRClosure: public HeapRegionClosure {
2971 G1CollectedHeap* _g1h;
2972 ConcurrentMark* _cm;
2973 CardTableModRefBS* _ct_bs;
2974 BitMap* _cm_card_bm;
2975 uint _max_worker_id;
2976
2977 public:
2978 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2979 BitMap* cm_card_bm,
2980 uint max_worker_id) :
2981 _g1h(g1h), _cm(g1h->concurrent_mark()),
2982 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
2983 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2984
2985 bool doHeapRegion(HeapRegion* hr) {
2986 if (hr->continuesHumongous()) {
2987 // We will ignore these here and process them when their
2988 // associated "starts humongous" region is processed.
2989 // Note that we cannot rely on their associated
2990 // "starts humongous" region to have their bit set to 1
2991 // since, due to the region chunking in the parallel region
2992 // iteration, a "continues humongous" region might be visited
2993 // before its associated "starts humongous".
2994 return false;
2995 }
2996
2997 HeapWord* start = hr->bottom();
2998 HeapWord* limit = hr->next_top_at_mark_start();
2999 HeapWord* end = hr->end();
3000
3001 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
3002 err_msg("Preconditions not met - "
3003 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
3004 "top: "PTR_FORMAT", end: "PTR_FORMAT,
3005 start, limit, hr->top(), hr->end()));
3006
3007 assert(hr->next_marked_bytes() == 0, "Precondition");
3008
3009 if (start == limit) {
3010 // NTAMS of this region has not been set so nothing to do.
3011 return false;
3012 }
3013
3014 // 'start' should be in the heap.
3015 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
3016 // 'end' *may* be just beyone the end of the heap (if hr is the last region)
3017 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
3018
3019 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
3020 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
3021 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
3022
3023 // If ntams is not card aligned then we bump card bitmap index
3024 // for limit so that we get the all the cards spanned by
3025 // the object ending at ntams.
3026 // Note: if this is the last region in the heap then ntams
3027 // could be actually just beyond the end of the the heap;
3028 // limit_idx will then correspond to a (non-existent) card
3029 // that is also outside the heap.
3030 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
3031 limit_idx += 1;
3032 }
3033
3034 assert(limit_idx <= end_idx, "or else use atomics");
3035
3036 // Aggregate the "stripe" in the count data associated with hr.
3037 uint hrs_index = hr->hrs_index();
3038 size_t marked_bytes = 0;
3039
3040 for (uint i = 0; i < _max_worker_id; i += 1) {
3041 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
3042 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
3043
3044 // Fetch the marked_bytes in this region for task i and
3045 // add it to the running total for this region.
3046 marked_bytes += marked_bytes_array[hrs_index];
3047
3048 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3049 // into the global card bitmap.
3050 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3051
3052 while (scan_idx < limit_idx) {
3053 assert(task_card_bm->at(scan_idx) == true, "should be");
3054 _cm_card_bm->set_bit(scan_idx);
3055 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3056
3057 // BitMap::get_next_one_offset() can handle the case when
3058 // its left_offset parameter is greater than its right_offset
3059 // parameter. It does, however, have an early exit if
3060 // left_offset == right_offset. So let's limit the value
3061 // passed in for left offset here.
3062 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3063 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3064 }
3065 }
3066
3067 // Update the marked bytes for this region.
3068 hr->add_to_marked_bytes(marked_bytes);
3069
3070 // Next heap region
3071 return false;
3072 }
3073 };
3074
3075 class G1AggregateCountDataTask: public AbstractGangTask {
3076 protected:
3077 G1CollectedHeap* _g1h;
3078 ConcurrentMark* _cm;
3079 BitMap* _cm_card_bm;
3080 uint _max_worker_id;
3081 int _active_workers;
3082
3083 public:
3084 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3085 ConcurrentMark* cm,
3086 BitMap* cm_card_bm,
3087 uint max_worker_id,
3088 int n_workers) :
3089 AbstractGangTask("Count Aggregation"),
3090 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3091 _max_worker_id(max_worker_id),
3092 _active_workers(n_workers) { }
3093
3094 void work(uint worker_id) {
3095 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3096
3097 if (G1CollectedHeap::use_parallel_gc_threads()) {
3098 _g1h->heap_region_par_iterate_chunked(&cl, worker_id,
3099 _active_workers,
3100 HeapRegion::AggregateCountClaimValue);
3101 } else {
3102 _g1h->heap_region_iterate(&cl);
3103 }
3104 }
3105 };
3106
3107
3108 void ConcurrentMark::aggregate_count_data() {
3109 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3110 _g1h->workers()->active_workers() :
3111 1);
3112
3113 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3114 _max_worker_id, n_workers);
3115
3116 if (G1CollectedHeap::use_parallel_gc_threads()) {
3117 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3118 "sanity check");
3119 _g1h->set_par_threads(n_workers);
3120 _g1h->workers()->run_task(&g1_par_agg_task);
3121 _g1h->set_par_threads(0);
3122
3123 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue),
3124 "sanity check");
3125 _g1h->reset_heap_region_claim_values();
3126 } else {
3127 g1_par_agg_task.work(0);
3128 }
3129 }
3130
3131 // Clear the per-worker arrays used to store the per-region counting data
3132 void ConcurrentMark::clear_all_count_data() {
3133 // Clear the global card bitmap - it will be filled during
3134 // liveness count aggregation (during remark) and the
3135 // final counting task.
3136 _card_bm.clear();
3137
3138 // Clear the global region bitmap - it will be filled as part
3139 // of the final counting task.
3140 _region_bm.clear();
3141
3142 uint max_regions = _g1h->max_regions();
3143 assert(_max_worker_id > 0, "uninitialized");
3144
3145 for (uint i = 0; i < _max_worker_id; i += 1) {
3146 BitMap* task_card_bm = count_card_bitmap_for(i);
3147 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3148
3149 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3150 assert(marked_bytes_array != NULL, "uninitialized");
3151
3152 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3153 task_card_bm->clear();
3154 }
3155 }
3156
3157 void ConcurrentMark::print_stats() {
3158 if (verbose_stats()) {
3159 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3160 for (size_t i = 0; i < _active_tasks; ++i) {
3161 _tasks[i]->print_stats();
3162 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3163 }
3164 }
3165 }
3166
3167 // abandon current marking iteration due to a Full GC
3168 void ConcurrentMark::abort() {
3169 // Clear all marks to force marking thread to do nothing
3170 _nextMarkBitMap->clearAll();
3171 // Clear the liveness counting data
3172 clear_all_count_data();
3173 // Empty mark stack
3174 reset_marking_state();
3175 for (uint i = 0; i < _max_worker_id; ++i) {
3176 _tasks[i]->clear_region_fields();
3177 }
3178 _has_aborted = true;
3179
3180 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3181 satb_mq_set.abandon_partial_marking();
3182 // This can be called either during or outside marking, we'll read
3183 // the expected_active value from the SATB queue set.
3184 satb_mq_set.set_active_all_threads(
3185 false, /* new active value */
3186 satb_mq_set.is_active() /* expected_active */);
3187 }
3188
3189 static void print_ms_time_info(const char* prefix, const char* name,
3190 NumberSeq& ns) {
3191 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3192 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3193 if (ns.num() > 0) {
3194 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3195 prefix, ns.sd(), ns.maximum());
3196 }
3197 }
3198
3199 void ConcurrentMark::print_summary_info() {
3200 gclog_or_tty->print_cr(" Concurrent marking:");
3201 print_ms_time_info(" ", "init marks", _init_times);
3202 print_ms_time_info(" ", "remarks", _remark_times);
3203 {
3204 print_ms_time_info(" ", "final marks", _remark_mark_times);
3205 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3206
3207 }
3208 print_ms_time_info(" ", "cleanups", _cleanup_times);
3209 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3210 _total_counting_time,
3211 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3212 (double)_cleanup_times.num()
3213 : 0.0));
3214 if (G1ScrubRemSets) {
3215 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3216 _total_rs_scrub_time,
3217 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3218 (double)_cleanup_times.num()
3219 : 0.0));
3220 }
3221 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3222 (_init_times.sum() + _remark_times.sum() +
3223 _cleanup_times.sum())/1000.0);
3224 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3225 "(%8.2f s marking).",
3226 cmThread()->vtime_accum(),
3227 cmThread()->vtime_mark_accum());
3228 }
3229
3230 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3231 if (use_parallel_marking_threads()) {
3232 _parallel_workers->print_worker_threads_on(st);
3233 }
3234 }
3235
3236 // We take a break if someone is trying to stop the world.
3237 bool ConcurrentMark::do_yield_check(uint worker_id) {
3238 if (should_yield()) {
3239 if (worker_id == 0) {
3240 _g1h->g1_policy()->record_concurrent_pause();
3241 }
3242 cmThread()->yield();
3243 return true;
3244 } else {
3245 return false;
3246 }
3247 }
3248
3249 bool ConcurrentMark::should_yield() {
3250 return cmThread()->should_yield();
3251 }
3252
3253 bool ConcurrentMark::containing_card_is_marked(void* p) {
3254 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3255 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3256 }
3257
3258 bool ConcurrentMark::containing_cards_are_marked(void* start,
3259 void* last) {
3260 return containing_card_is_marked(start) &&
3261 containing_card_is_marked(last);
3262 }
3263
3264 #ifndef PRODUCT
3265 // for debugging purposes
3266 void ConcurrentMark::print_finger() {
3267 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3268 _heap_start, _heap_end, _finger);
3269 for (uint i = 0; i < _max_worker_id; ++i) {
3270 gclog_or_tty->print(" %u: "PTR_FORMAT, i, _tasks[i]->finger());
3271 }
3272 gclog_or_tty->print_cr("");
3273 }
3274 #endif
3275
3276 void CMTask::scan_object(oop obj) {
3277 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3278
3279 if (_cm->verbose_high()) {
3280 gclog_or_tty->print_cr("[%u] we're scanning object "PTR_FORMAT,
3281 _worker_id, (void*) obj);
3282 }
3283
3284 size_t obj_size = obj->size();
3285 _words_scanned += obj_size;
3286
3287 obj->oop_iterate(_cm_oop_closure);
3288 statsOnly( ++_objs_scanned );
3289 check_limits();
3290 }
3291
3292 // Closure for iteration over bitmaps
3293 class CMBitMapClosure : public BitMapClosure {
3294 private:
3295 // the bitmap that is being iterated over
3296 CMBitMap* _nextMarkBitMap;
3297 ConcurrentMark* _cm;
3298 CMTask* _task;
3299
3300 public:
3301 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3302 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3303
3304 bool do_bit(size_t offset) {
3305 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3306 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3307 assert( addr < _cm->finger(), "invariant");
3308
3309 statsOnly( _task->increase_objs_found_on_bitmap() );
3310 assert(addr >= _task->finger(), "invariant");
3311
3312 // We move that task's local finger along.
3313 _task->move_finger_to(addr);
3314
3315 _task->scan_object(oop(addr));
3316 // we only partially drain the local queue and global stack
3317 _task->drain_local_queue(true);
3318 _task->drain_global_stack(true);
3319
3320 // if the has_aborted flag has been raised, we need to bail out of
3321 // the iteration
3322 return !_task->has_aborted();
3323 }
3324 };
3325
3326 // Closure for iterating over objects, currently only used for
3327 // processing SATB buffers.
3328 class CMObjectClosure : public ObjectClosure {
3329 private:
3330 CMTask* _task;
3331
3332 public:
3333 void do_object(oop obj) {
3334 _task->deal_with_reference(obj);
3335 }
3336
3337 CMObjectClosure(CMTask* task) : _task(task) { }
3338 };
3339
3340 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3341 ConcurrentMark* cm,
3342 CMTask* task)
3343 : _g1h(g1h), _cm(cm), _task(task) {
3344 assert(_ref_processor == NULL, "should be initialized to NULL");
3345
3346 if (G1UseConcMarkReferenceProcessing) {
3347 _ref_processor = g1h->ref_processor_cm();
3348 assert(_ref_processor != NULL, "should not be NULL");
3349 }
3350 }
3351
3352 void CMTask::setup_for_region(HeapRegion* hr) {
3353 // Separated the asserts so that we know which one fires.
3354 assert(hr != NULL,
3355 "claim_region() should have filtered out continues humongous regions");
3356 assert(!hr->continuesHumongous(),
3357 "claim_region() should have filtered out continues humongous regions");
3358
3359 if (_cm->verbose_low()) {
3360 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3361 _worker_id, hr);
3362 }
3363
3364 _curr_region = hr;
3365 _finger = hr->bottom();
3366 update_region_limit();
3367 }
3368
3369 void CMTask::update_region_limit() {
3370 HeapRegion* hr = _curr_region;
3371 HeapWord* bottom = hr->bottom();
3372 HeapWord* limit = hr->next_top_at_mark_start();
3373
3374 if (limit == bottom) {
3375 if (_cm->verbose_low()) {
3376 gclog_or_tty->print_cr("[%u] found an empty region "
3377 "["PTR_FORMAT", "PTR_FORMAT")",
3378 _worker_id, bottom, limit);
3379 }
3380 // The region was collected underneath our feet.
3381 // We set the finger to bottom to ensure that the bitmap
3382 // iteration that will follow this will not do anything.
3383 // (this is not a condition that holds when we set the region up,
3384 // as the region is not supposed to be empty in the first place)
3385 _finger = bottom;
3386 } else if (limit >= _region_limit) {
3387 assert(limit >= _finger, "peace of mind");
3388 } else {
3389 assert(limit < _region_limit, "only way to get here");
3390 // This can happen under some pretty unusual circumstances. An
3391 // evacuation pause empties the region underneath our feet (NTAMS
3392 // at bottom). We then do some allocation in the region (NTAMS
3393 // stays at bottom), followed by the region being used as a GC
3394 // alloc region (NTAMS will move to top() and the objects
3395 // originally below it will be grayed). All objects now marked in
3396 // the region are explicitly grayed, if below the global finger,
3397 // and we do not need in fact to scan anything else. So, we simply
3398 // set _finger to be limit to ensure that the bitmap iteration
3399 // doesn't do anything.
3400 _finger = limit;
3401 }
3402
3403 _region_limit = limit;
3404 }
3405
3406 void CMTask::giveup_current_region() {
3407 assert(_curr_region != NULL, "invariant");
3408 if (_cm->verbose_low()) {
3409 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3410 _worker_id, _curr_region);
3411 }
3412 clear_region_fields();
3413 }
3414
3415 void CMTask::clear_region_fields() {
3416 // Values for these three fields that indicate that we're not
3417 // holding on to a region.
3418 _curr_region = NULL;
3419 _finger = NULL;
3420 _region_limit = NULL;
3421 }
3422
3423 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3424 if (cm_oop_closure == NULL) {
3425 assert(_cm_oop_closure != NULL, "invariant");
3426 } else {
3427 assert(_cm_oop_closure == NULL, "invariant");
3428 }
3429 _cm_oop_closure = cm_oop_closure;
3430 }
3431
3432 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3433 guarantee(nextMarkBitMap != NULL, "invariant");
3434
3435 if (_cm->verbose_low()) {
3436 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3437 }
3438
3439 _nextMarkBitMap = nextMarkBitMap;
3440 clear_region_fields();
3441
3442 _calls = 0;
3443 _elapsed_time_ms = 0.0;
3444 _termination_time_ms = 0.0;
3445 _termination_start_time_ms = 0.0;
3446
3447 #if _MARKING_STATS_
3448 _local_pushes = 0;
3449 _local_pops = 0;
3450 _local_max_size = 0;
3451 _objs_scanned = 0;
3452 _global_pushes = 0;
3453 _global_pops = 0;
3454 _global_max_size = 0;
3455 _global_transfers_to = 0;
3456 _global_transfers_from = 0;
3457 _regions_claimed = 0;
3458 _objs_found_on_bitmap = 0;
3459 _satb_buffers_processed = 0;
3460 _steal_attempts = 0;
3461 _steals = 0;
3462 _aborted = 0;
3463 _aborted_overflow = 0;
3464 _aborted_cm_aborted = 0;
3465 _aborted_yield = 0;
3466 _aborted_timed_out = 0;
3467 _aborted_satb = 0;
3468 _aborted_termination = 0;
3469 #endif // _MARKING_STATS_
3470 }
3471
3472 bool CMTask::should_exit_termination() {
3473 regular_clock_call();
3474 // This is called when we are in the termination protocol. We should
3475 // quit if, for some reason, this task wants to abort or the global
3476 // stack is not empty (this means that we can get work from it).
3477 return !_cm->mark_stack_empty() || has_aborted();
3478 }
3479
3480 void CMTask::reached_limit() {
3481 assert(_words_scanned >= _words_scanned_limit ||
3482 _refs_reached >= _refs_reached_limit ,
3483 "shouldn't have been called otherwise");
3484 regular_clock_call();
3485 }
3486
3487 void CMTask::regular_clock_call() {
3488 if (has_aborted()) return;
3489
3490 // First, we need to recalculate the words scanned and refs reached
3491 // limits for the next clock call.
3492 recalculate_limits();
3493
3494 // During the regular clock call we do the following
3495
3496 // (1) If an overflow has been flagged, then we abort.
3497 if (_cm->has_overflown()) {
3498 set_has_aborted();
3499 return;
3500 }
3501
3502 // If we are not concurrent (i.e. we're doing remark) we don't need
3503 // to check anything else. The other steps are only needed during
3504 // the concurrent marking phase.
3505 if (!concurrent()) return;
3506
3507 // (2) If marking has been aborted for Full GC, then we also abort.
3508 if (_cm->has_aborted()) {
3509 set_has_aborted();
3510 statsOnly( ++_aborted_cm_aborted );
3511 return;
3512 }
3513
3514 double curr_time_ms = os::elapsedVTime() * 1000.0;
3515
3516 // (3) If marking stats are enabled, then we update the step history.
3517 #if _MARKING_STATS_
3518 if (_words_scanned >= _words_scanned_limit) {
3519 ++_clock_due_to_scanning;
3520 }
3521 if (_refs_reached >= _refs_reached_limit) {
3522 ++_clock_due_to_marking;
3523 }
3524
3525 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3526 _interval_start_time_ms = curr_time_ms;
3527 _all_clock_intervals_ms.add(last_interval_ms);
3528
3529 if (_cm->verbose_medium()) {
3530 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3531 "scanned = %d%s, refs reached = %d%s",
3532 _worker_id, last_interval_ms,
3533 _words_scanned,
3534 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3535 _refs_reached,
3536 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3537 }
3538 #endif // _MARKING_STATS_
3539
3540 // (4) We check whether we should yield. If we have to, then we abort.
3541 if (_cm->should_yield()) {
3542 // We should yield. To do this we abort the task. The caller is
3543 // responsible for yielding.
3544 set_has_aborted();
3545 statsOnly( ++_aborted_yield );
3546 return;
3547 }
3548
3549 // (5) We check whether we've reached our time quota. If we have,
3550 // then we abort.
3551 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3552 if (elapsed_time_ms > _time_target_ms) {
3553 set_has_aborted();
3554 _has_timed_out = true;
3555 statsOnly( ++_aborted_timed_out );
3556 return;
3557 }
3558
3559 // (6) Finally, we check whether there are enough completed STAB
3560 // buffers available for processing. If there are, we abort.
3561 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3562 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3563 if (_cm->verbose_low()) {
3564 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3565 _worker_id);
3566 }
3567 // we do need to process SATB buffers, we'll abort and restart
3568 // the marking task to do so
3569 set_has_aborted();
3570 statsOnly( ++_aborted_satb );
3571 return;
3572 }
3573 }
3574
3575 void CMTask::recalculate_limits() {
3576 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3577 _words_scanned_limit = _real_words_scanned_limit;
3578
3579 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3580 _refs_reached_limit = _real_refs_reached_limit;
3581 }
3582
3583 void CMTask::decrease_limits() {
3584 // This is called when we believe that we're going to do an infrequent
3585 // operation which will increase the per byte scanned cost (i.e. move
3586 // entries to/from the global stack). It basically tries to decrease the
3587 // scanning limit so that the clock is called earlier.
3588
3589 if (_cm->verbose_medium()) {
3590 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3591 }
3592
3593 _words_scanned_limit = _real_words_scanned_limit -
3594 3 * words_scanned_period / 4;
3595 _refs_reached_limit = _real_refs_reached_limit -
3596 3 * refs_reached_period / 4;
3597 }
3598
3599 void CMTask::move_entries_to_global_stack() {
3600 // local array where we'll store the entries that will be popped
3601 // from the local queue
3602 oop buffer[global_stack_transfer_size];
3603
3604 int n = 0;
3605 oop obj;
3606 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3607 buffer[n] = obj;
3608 ++n;
3609 }
3610
3611 if (n > 0) {
3612 // we popped at least one entry from the local queue
3613
3614 statsOnly( ++_global_transfers_to; _local_pops += n );
3615
3616 if (!_cm->mark_stack_push(buffer, n)) {
3617 if (_cm->verbose_low()) {
3618 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3619 _worker_id);
3620 }
3621 set_has_aborted();
3622 } else {
3623 // the transfer was successful
3624
3625 if (_cm->verbose_medium()) {
3626 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3627 _worker_id, n);
3628 }
3629 statsOnly( int tmp_size = _cm->mark_stack_size();
3630 if (tmp_size > _global_max_size) {
3631 _global_max_size = tmp_size;
3632 }
3633 _global_pushes += n );
3634 }
3635 }
3636
3637 // this operation was quite expensive, so decrease the limits
3638 decrease_limits();
3639 }
3640
3641 void CMTask::get_entries_from_global_stack() {
3642 // local array where we'll store the entries that will be popped
3643 // from the global stack.
3644 oop buffer[global_stack_transfer_size];
3645 int n;
3646 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3647 assert(n <= global_stack_transfer_size,
3648 "we should not pop more than the given limit");
3649 if (n > 0) {
3650 // yes, we did actually pop at least one entry
3651
3652 statsOnly( ++_global_transfers_from; _global_pops += n );
3653 if (_cm->verbose_medium()) {
3654 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3655 _worker_id, n);
3656 }
3657 for (int i = 0; i < n; ++i) {
3658 bool success = _task_queue->push(buffer[i]);
3659 // We only call this when the local queue is empty or under a
3660 // given target limit. So, we do not expect this push to fail.
3661 assert(success, "invariant");
3662 }
3663
3664 statsOnly( int tmp_size = _task_queue->size();
3665 if (tmp_size > _local_max_size) {
3666 _local_max_size = tmp_size;
3667 }
3668 _local_pushes += n );
3669 }
3670
3671 // this operation was quite expensive, so decrease the limits
3672 decrease_limits();
3673 }
3674
3675 void CMTask::drain_local_queue(bool partially) {
3676 if (has_aborted()) return;
3677
3678 // Decide what the target size is, depending whether we're going to
3679 // drain it partially (so that other tasks can steal if they run out
3680 // of things to do) or totally (at the very end).
3681 size_t target_size;
3682 if (partially) {
3683 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3684 } else {
3685 target_size = 0;
3686 }
3687
3688 if (_task_queue->size() > target_size) {
3689 if (_cm->verbose_high()) {
3690 gclog_or_tty->print_cr("[%u] draining local queue, target size = %d",
3691 _worker_id, target_size);
3692 }
3693
3694 oop obj;
3695 bool ret = _task_queue->pop_local(obj);
3696 while (ret) {
3697 statsOnly( ++_local_pops );
3698
3699 if (_cm->verbose_high()) {
3700 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3701 (void*) obj);
3702 }
3703
3704 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3705 assert(!_g1h->is_on_master_free_list(
3706 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3707
3708 scan_object(obj);
3709
3710 if (_task_queue->size() <= target_size || has_aborted()) {
3711 ret = false;
3712 } else {
3713 ret = _task_queue->pop_local(obj);
3714 }
3715 }
3716
3717 if (_cm->verbose_high()) {
3718 gclog_or_tty->print_cr("[%u] drained local queue, size = %d",
3719 _worker_id, _task_queue->size());
3720 }
3721 }
3722 }
3723
3724 void CMTask::drain_global_stack(bool partially) {
3725 if (has_aborted()) return;
3726
3727 // We have a policy to drain the local queue before we attempt to
3728 // drain the global stack.
3729 assert(partially || _task_queue->size() == 0, "invariant");
3730
3731 // Decide what the target size is, depending whether we're going to
3732 // drain it partially (so that other tasks can steal if they run out
3733 // of things to do) or totally (at the very end). Notice that,
3734 // because we move entries from the global stack in chunks or
3735 // because another task might be doing the same, we might in fact
3736 // drop below the target. But, this is not a problem.
3737 size_t target_size;
3738 if (partially) {
3739 target_size = _cm->partial_mark_stack_size_target();
3740 } else {
3741 target_size = 0;
3742 }
3743
3744 if (_cm->mark_stack_size() > target_size) {
3745 if (_cm->verbose_low()) {
3746 gclog_or_tty->print_cr("[%u] draining global_stack, target size %d",
3747 _worker_id, target_size);
3748 }
3749
3750 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3751 get_entries_from_global_stack();
3752 drain_local_queue(partially);
3753 }
3754
3755 if (_cm->verbose_low()) {
3756 gclog_or_tty->print_cr("[%u] drained global stack, size = %d",
3757 _worker_id, _cm->mark_stack_size());
3758 }
3759 }
3760 }
3761
3762 // SATB Queue has several assumptions on whether to call the par or
3763 // non-par versions of the methods. this is why some of the code is
3764 // replicated. We should really get rid of the single-threaded version
3765 // of the code to simplify things.
3766 void CMTask::drain_satb_buffers() {
3767 if (has_aborted()) return;
3768
3769 // We set this so that the regular clock knows that we're in the
3770 // middle of draining buffers and doesn't set the abort flag when it
3771 // notices that SATB buffers are available for draining. It'd be
3772 // very counter productive if it did that. :-)
3773 _draining_satb_buffers = true;
3774
3775 CMObjectClosure oc(this);
3776 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3777 if (G1CollectedHeap::use_parallel_gc_threads()) {
3778 satb_mq_set.set_par_closure(_worker_id, &oc);
3779 } else {
3780 satb_mq_set.set_closure(&oc);
3781 }
3782
3783 // This keeps claiming and applying the closure to completed buffers
3784 // until we run out of buffers or we need to abort.
3785 if (G1CollectedHeap::use_parallel_gc_threads()) {
3786 while (!has_aborted() &&
3787 satb_mq_set.par_apply_closure_to_completed_buffer(_worker_id)) {
3788 if (_cm->verbose_medium()) {
3789 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3790 }
3791 statsOnly( ++_satb_buffers_processed );
3792 regular_clock_call();
3793 }
3794 } else {
3795 while (!has_aborted() &&
3796 satb_mq_set.apply_closure_to_completed_buffer()) {
3797 if (_cm->verbose_medium()) {
3798 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3799 }
3800 statsOnly( ++_satb_buffers_processed );
3801 regular_clock_call();
3802 }
3803 }
3804
3805 if (!concurrent() && !has_aborted()) {
3806 // We should only do this during remark.
3807 if (G1CollectedHeap::use_parallel_gc_threads()) {
3808 satb_mq_set.par_iterate_closure_all_threads(_worker_id);
3809 } else {
3810 satb_mq_set.iterate_closure_all_threads();
3811 }
3812 }
3813
3814 _draining_satb_buffers = false;
3815
3816 assert(has_aborted() ||
3817 concurrent() ||
3818 satb_mq_set.completed_buffers_num() == 0, "invariant");
3819
3820 if (G1CollectedHeap::use_parallel_gc_threads()) {
3821 satb_mq_set.set_par_closure(_worker_id, NULL);
3822 } else {
3823 satb_mq_set.set_closure(NULL);
3824 }
3825
3826 // again, this was a potentially expensive operation, decrease the
3827 // limits to get the regular clock call early
3828 decrease_limits();
3829 }
3830
3831 void CMTask::print_stats() {
3832 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3833 _worker_id, _calls);
3834 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3835 _elapsed_time_ms, _termination_time_ms);
3836 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3837 _step_times_ms.num(), _step_times_ms.avg(),
3838 _step_times_ms.sd());
3839 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3840 _step_times_ms.maximum(), _step_times_ms.sum());
3841
3842 #if _MARKING_STATS_
3843 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3844 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3845 _all_clock_intervals_ms.sd());
3846 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3847 _all_clock_intervals_ms.maximum(),
3848 _all_clock_intervals_ms.sum());
3849 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3850 _clock_due_to_scanning, _clock_due_to_marking);
3851 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3852 _objs_scanned, _objs_found_on_bitmap);
3853 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3854 _local_pushes, _local_pops, _local_max_size);
3855 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3856 _global_pushes, _global_pops, _global_max_size);
3857 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3858 _global_transfers_to,_global_transfers_from);
3859 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed);
3860 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3861 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3862 _steal_attempts, _steals);
3863 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3864 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3865 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3866 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3867 _aborted_timed_out, _aborted_satb, _aborted_termination);
3868 #endif // _MARKING_STATS_
3869 }
3870
3871 /*****************************************************************************
3872
3873 The do_marking_step(time_target_ms) method is the building block
3874 of the parallel marking framework. It can be called in parallel
3875 with other invocations of do_marking_step() on different tasks
3876 (but only one per task, obviously) and concurrently with the
3877 mutator threads, or during remark, hence it eliminates the need
3878 for two versions of the code. When called during remark, it will
3879 pick up from where the task left off during the concurrent marking
3880 phase. Interestingly, tasks are also claimable during evacuation
3881 pauses too, since do_marking_step() ensures that it aborts before
3882 it needs to yield.
3883
3884 The data structures that is uses to do marking work are the
3885 following:
3886
3887 (1) Marking Bitmap. If there are gray objects that appear only
3888 on the bitmap (this happens either when dealing with an overflow
3889 or when the initial marking phase has simply marked the roots
3890 and didn't push them on the stack), then tasks claim heap
3891 regions whose bitmap they then scan to find gray objects. A
3892 global finger indicates where the end of the last claimed region
3893 is. A local finger indicates how far into the region a task has
3894 scanned. The two fingers are used to determine how to gray an
3895 object (i.e. whether simply marking it is OK, as it will be
3896 visited by a task in the future, or whether it needs to be also
3897 pushed on a stack).
3898
3899 (2) Local Queue. The local queue of the task which is accessed
3900 reasonably efficiently by the task. Other tasks can steal from
3901 it when they run out of work. Throughout the marking phase, a
3902 task attempts to keep its local queue short but not totally
3903 empty, so that entries are available for stealing by other
3904 tasks. Only when there is no more work, a task will totally
3905 drain its local queue.
3906
3907 (3) Global Mark Stack. This handles local queue overflow. During
3908 marking only sets of entries are moved between it and the local
3909 queues, as access to it requires a mutex and more fine-grain
3910 interaction with it which might cause contention. If it
3911 overflows, then the marking phase should restart and iterate
3912 over the bitmap to identify gray objects. Throughout the marking
3913 phase, tasks attempt to keep the global mark stack at a small
3914 length but not totally empty, so that entries are available for
3915 popping by other tasks. Only when there is no more work, tasks
3916 will totally drain the global mark stack.
3917
3918 (4) SATB Buffer Queue. This is where completed SATB buffers are
3919 made available. Buffers are regularly removed from this queue
3920 and scanned for roots, so that the queue doesn't get too
3921 long. During remark, all completed buffers are processed, as
3922 well as the filled in parts of any uncompleted buffers.
3923
3924 The do_marking_step() method tries to abort when the time target
3925 has been reached. There are a few other cases when the
3926 do_marking_step() method also aborts:
3927
3928 (1) When the marking phase has been aborted (after a Full GC).
3929
3930 (2) When a global overflow (on the global stack) has been
3931 triggered. Before the task aborts, it will actually sync up with
3932 the other tasks to ensure that all the marking data structures
3933 (local queues, stacks, fingers etc.) are re-initialised so that
3934 when do_marking_step() completes, the marking phase can
3935 immediately restart.
3936
3937 (3) When enough completed SATB buffers are available. The
3938 do_marking_step() method only tries to drain SATB buffers right
3939 at the beginning. So, if enough buffers are available, the
3940 marking step aborts and the SATB buffers are processed at
3941 the beginning of the next invocation.
3942
3943 (4) To yield. when we have to yield then we abort and yield
3944 right at the end of do_marking_step(). This saves us from a lot
3945 of hassle as, by yielding we might allow a Full GC. If this
3946 happens then objects will be compacted underneath our feet, the
3947 heap might shrink, etc. We save checking for this by just
3948 aborting and doing the yield right at the end.
3949
3950 From the above it follows that the do_marking_step() method should
3951 be called in a loop (or, otherwise, regularly) until it completes.
3952
3953 If a marking step completes without its has_aborted() flag being
3954 true, it means it has completed the current marking phase (and
3955 also all other marking tasks have done so and have all synced up).
3956
3957 A method called regular_clock_call() is invoked "regularly" (in
3958 sub ms intervals) throughout marking. It is this clock method that
3959 checks all the abort conditions which were mentioned above and
3960 decides when the task should abort. A work-based scheme is used to
3961 trigger this clock method: when the number of object words the
3962 marking phase has scanned or the number of references the marking
3963 phase has visited reach a given limit. Additional invocations to
3964 the method clock have been planted in a few other strategic places
3965 too. The initial reason for the clock method was to avoid calling
3966 vtime too regularly, as it is quite expensive. So, once it was in
3967 place, it was natural to piggy-back all the other conditions on it
3968 too and not constantly check them throughout the code.
3969
3970 *****************************************************************************/
3971
3972 void CMTask::do_marking_step(double time_target_ms,
3973 bool do_stealing,
3974 bool do_termination) {
3975 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3976 assert(concurrent() == _cm->concurrent(), "they should be the same");
3977
3978 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3979 assert(_task_queues != NULL, "invariant");
3980 assert(_task_queue != NULL, "invariant");
3981 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3982
3983 assert(!_claimed,
3984 "only one thread should claim this task at any one time");
3985
3986 // OK, this doesn't safeguard again all possible scenarios, as it is
3987 // possible for two threads to set the _claimed flag at the same
3988 // time. But it is only for debugging purposes anyway and it will
3989 // catch most problems.
3990 _claimed = true;
3991
3992 _start_time_ms = os::elapsedVTime() * 1000.0;
3993 statsOnly( _interval_start_time_ms = _start_time_ms );
3994
3995 double diff_prediction_ms =
3996 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3997 _time_target_ms = time_target_ms - diff_prediction_ms;
3998
3999 // set up the variables that are used in the work-based scheme to
4000 // call the regular clock method
4001 _words_scanned = 0;
4002 _refs_reached = 0;
4003 recalculate_limits();
4004
4005 // clear all flags
4006 clear_has_aborted();
4007 _has_timed_out = false;
4008 _draining_satb_buffers = false;
4009
4010 ++_calls;
4011
4012 if (_cm->verbose_low()) {
4013 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
4014 "target = %1.2lfms >>>>>>>>>>",
4015 _worker_id, _calls, _time_target_ms);
4016 }
4017
4018 // Set up the bitmap and oop closures. Anything that uses them is
4019 // eventually called from this method, so it is OK to allocate these
4020 // statically.
4021 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4022 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4023 set_cm_oop_closure(&cm_oop_closure);
4024
4025 if (_cm->has_overflown()) {
4026 // This can happen if the mark stack overflows during a GC pause
4027 // and this task, after a yield point, restarts. We have to abort
4028 // as we need to get into the overflow protocol which happens
4029 // right at the end of this task.
4030 set_has_aborted();
4031 }
4032
4033 // First drain any available SATB buffers. After this, we will not
4034 // look at SATB buffers before the next invocation of this method.
4035 // If enough completed SATB buffers are queued up, the regular clock
4036 // will abort this task so that it restarts.
4037 drain_satb_buffers();
4038 // ...then partially drain the local queue and the global stack
4039 drain_local_queue(true);
4040 drain_global_stack(true);
4041
4042 do {
4043 if (!has_aborted() && _curr_region != NULL) {
4044 // This means that we're already holding on to a region.
4045 assert(_finger != NULL, "if region is not NULL, then the finger "
4046 "should not be NULL either");
4047
4048 // We might have restarted this task after an evacuation pause
4049 // which might have evacuated the region we're holding on to
4050 // underneath our feet. Let's read its limit again to make sure
4051 // that we do not iterate over a region of the heap that
4052 // contains garbage (update_region_limit() will also move
4053 // _finger to the start of the region if it is found empty).
4054 update_region_limit();
4055 // We will start from _finger not from the start of the region,
4056 // as we might be restarting this task after aborting half-way
4057 // through scanning this region. In this case, _finger points to
4058 // the address where we last found a marked object. If this is a
4059 // fresh region, _finger points to start().
4060 MemRegion mr = MemRegion(_finger, _region_limit);
4061
4062 if (_cm->verbose_low()) {
4063 gclog_or_tty->print_cr("[%u] we're scanning part "
4064 "["PTR_FORMAT", "PTR_FORMAT") "
4065 "of region "HR_FORMAT,
4066 _worker_id, _finger, _region_limit,
4067 HR_FORMAT_PARAMS(_curr_region));
4068 }
4069
4070 assert(!_curr_region->isHumongous() || mr.start() == _curr_region->bottom(),
4071 "humongous regions should go around loop once only");
4072
4073 // Some special cases:
4074 // If the memory region is empty, we can just give up the region.
4075 // If the current region is humongous then we only need to check
4076 // the bitmap for the bit associated with the start of the object,
4077 // scan the object if it's live, and give up the region.
4078 // Otherwise, let's iterate over the bitmap of the part of the region
4079 // that is left.
4080 // If the iteration is successful, give up the region.
4081 if (mr.is_empty()) {
4082 giveup_current_region();
4083 regular_clock_call();
4084 } else if (_curr_region->isHumongous() && mr.start() == _curr_region->bottom()) {
4085 if (_nextMarkBitMap->isMarked(mr.start())) {
4086 // The object is marked - apply the closure
4087 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
4088 bitmap_closure.do_bit(offset);
4089 }
4090 // Even if this task aborted while scanning the humongous object
4091 // we can (and should) give up the current region.
4092 giveup_current_region();
4093 regular_clock_call();
4094 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4095 giveup_current_region();
4096 regular_clock_call();
4097 } else {
4098 assert(has_aborted(), "currently the only way to do so");
4099 // The only way to abort the bitmap iteration is to return
4100 // false from the do_bit() method. However, inside the
4101 // do_bit() method we move the _finger to point to the
4102 // object currently being looked at. So, if we bail out, we
4103 // have definitely set _finger to something non-null.
4104 assert(_finger != NULL, "invariant");
4105
4106 // Region iteration was actually aborted. So now _finger
4107 // points to the address of the object we last scanned. If we
4108 // leave it there, when we restart this task, we will rescan
4109 // the object. It is easy to avoid this. We move the finger by
4110 // enough to point to the next possible object header (the
4111 // bitmap knows by how much we need to move it as it knows its
4112 // granularity).
4113 assert(_finger < _region_limit, "invariant");
4114 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
4115 // Check if bitmap iteration was aborted while scanning the last object
4116 if (new_finger >= _region_limit) {
4117 giveup_current_region();
4118 } else {
4119 move_finger_to(new_finger);
4120 }
4121 }
4122 }
4123 // At this point we have either completed iterating over the
4124 // region we were holding on to, or we have aborted.
4125
4126 // We then partially drain the local queue and the global stack.
4127 // (Do we really need this?)
4128 drain_local_queue(true);
4129 drain_global_stack(true);
4130
4131 // Read the note on the claim_region() method on why it might
4132 // return NULL with potentially more regions available for
4133 // claiming and why we have to check out_of_regions() to determine
4134 // whether we're done or not.
4135 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4136 // We are going to try to claim a new region. We should have
4137 // given up on the previous one.
4138 // Separated the asserts so that we know which one fires.
4139 assert(_curr_region == NULL, "invariant");
4140 assert(_finger == NULL, "invariant");
4141 assert(_region_limit == NULL, "invariant");
4142 if (_cm->verbose_low()) {
4143 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4144 }
4145 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4146 if (claimed_region != NULL) {
4147 // Yes, we managed to claim one
4148 statsOnly( ++_regions_claimed );
4149
4150 if (_cm->verbose_low()) {
4151 gclog_or_tty->print_cr("[%u] we successfully claimed "
4152 "region "PTR_FORMAT,
4153 _worker_id, claimed_region);
4154 }
4155
4156 setup_for_region(claimed_region);
4157 assert(_curr_region == claimed_region, "invariant");
4158 }
4159 // It is important to call the regular clock here. It might take
4160 // a while to claim a region if, for example, we hit a large
4161 // block of empty regions. So we need to call the regular clock
4162 // method once round the loop to make sure it's called
4163 // frequently enough.
4164 regular_clock_call();
4165 }
4166
4167 if (!has_aborted() && _curr_region == NULL) {
4168 assert(_cm->out_of_regions(),
4169 "at this point we should be out of regions");
4170 }
4171 } while ( _curr_region != NULL && !has_aborted());
4172
4173 if (!has_aborted()) {
4174 // We cannot check whether the global stack is empty, since other
4175 // tasks might be pushing objects to it concurrently.
4176 assert(_cm->out_of_regions(),
4177 "at this point we should be out of regions");
4178
4179 if (_cm->verbose_low()) {
4180 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4181 }
4182
4183 // Try to reduce the number of available SATB buffers so that
4184 // remark has less work to do.
4185 drain_satb_buffers();
4186 }
4187
4188 // Since we've done everything else, we can now totally drain the
4189 // local queue and global stack.
4190 drain_local_queue(false);
4191 drain_global_stack(false);
4192
4193 // Attempt at work stealing from other task's queues.
4194 if (do_stealing && !has_aborted()) {
4195 // We have not aborted. This means that we have finished all that
4196 // we could. Let's try to do some stealing...
4197
4198 // We cannot check whether the global stack is empty, since other
4199 // tasks might be pushing objects to it concurrently.
4200 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4201 "only way to reach here");
4202
4203 if (_cm->verbose_low()) {
4204 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4205 }
4206
4207 while (!has_aborted()) {
4208 oop obj;
4209 statsOnly( ++_steal_attempts );
4210
4211 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4212 if (_cm->verbose_medium()) {
4213 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4214 _worker_id, (void*) obj);
4215 }
4216
4217 statsOnly( ++_steals );
4218
4219 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4220 "any stolen object should be marked");
4221 scan_object(obj);
4222
4223 // And since we're towards the end, let's totally drain the
4224 // local queue and global stack.
4225 drain_local_queue(false);
4226 drain_global_stack(false);
4227 } else {
4228 break;
4229 }
4230 }
4231 }
4232
4233 // If we are about to wrap up and go into termination, check if we
4234 // should raise the overflow flag.
4235 if (do_termination && !has_aborted()) {
4236 if (_cm->force_overflow()->should_force()) {
4237 _cm->set_has_overflown();
4238 regular_clock_call();
4239 }
4240 }
4241
4242 // We still haven't aborted. Now, let's try to get into the
4243 // termination protocol.
4244 if (do_termination && !has_aborted()) {
4245 // We cannot check whether the global stack is empty, since other
4246 // tasks might be concurrently pushing objects on it.
4247 // Separated the asserts so that we know which one fires.
4248 assert(_cm->out_of_regions(), "only way to reach here");
4249 assert(_task_queue->size() == 0, "only way to reach here");
4250
4251 if (_cm->verbose_low()) {
4252 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4253 }
4254
4255 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4256 // The CMTask class also extends the TerminatorTerminator class,
4257 // hence its should_exit_termination() method will also decide
4258 // whether to exit the termination protocol or not.
4259 bool finished = _cm->terminator()->offer_termination(this);
4260 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4261 _termination_time_ms +=
4262 termination_end_time_ms - _termination_start_time_ms;
4263
4264 if (finished) {
4265 // We're all done.
4266
4267 if (_worker_id == 0) {
4268 // let's allow task 0 to do this
4269 if (concurrent()) {
4270 assert(_cm->concurrent_marking_in_progress(), "invariant");
4271 // we need to set this to false before the next
4272 // safepoint. This way we ensure that the marking phase
4273 // doesn't observe any more heap expansions.
4274 _cm->clear_concurrent_marking_in_progress();
4275 }
4276 }
4277
4278 // We can now guarantee that the global stack is empty, since
4279 // all other tasks have finished. We separated the guarantees so
4280 // that, if a condition is false, we can immediately find out
4281 // which one.
4282 guarantee(_cm->out_of_regions(), "only way to reach here");
4283 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4284 guarantee(_task_queue->size() == 0, "only way to reach here");
4285 guarantee(!_cm->has_overflown(), "only way to reach here");
4286 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4287
4288 if (_cm->verbose_low()) {
4289 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4290 }
4291 } else {
4292 // Apparently there's more work to do. Let's abort this task. It
4293 // will restart it and we can hopefully find more things to do.
4294
4295 if (_cm->verbose_low()) {
4296 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4297 _worker_id);
4298 }
4299
4300 set_has_aborted();
4301 statsOnly( ++_aborted_termination );
4302 }
4303 }
4304
4305 // Mainly for debugging purposes to make sure that a pointer to the
4306 // closure which was statically allocated in this frame doesn't
4307 // escape it by accident.
4308 set_cm_oop_closure(NULL);
4309 double end_time_ms = os::elapsedVTime() * 1000.0;
4310 double elapsed_time_ms = end_time_ms - _start_time_ms;
4311 // Update the step history.
4312 _step_times_ms.add(elapsed_time_ms);
4313
4314 if (has_aborted()) {
4315 // The task was aborted for some reason.
4316
4317 statsOnly( ++_aborted );
4318
4319 if (_has_timed_out) {
4320 double diff_ms = elapsed_time_ms - _time_target_ms;
4321 // Keep statistics of how well we did with respect to hitting
4322 // our target only if we actually timed out (if we aborted for
4323 // other reasons, then the results might get skewed).
4324 _marking_step_diffs_ms.add(diff_ms);
4325 }
4326
4327 if (_cm->has_overflown()) {
4328 // This is the interesting one. We aborted because a global
4329 // overflow was raised. This means we have to restart the
4330 // marking phase and start iterating over regions. However, in
4331 // order to do this we have to make sure that all tasks stop
4332 // what they are doing and re-initialise in a safe manner. We
4333 // will achieve this with the use of two barrier sync points.
4334
4335 if (_cm->verbose_low()) {
4336 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4337 }
4338
4339 _cm->enter_first_sync_barrier(_worker_id);
4340 // When we exit this sync barrier we know that all tasks have
4341 // stopped doing marking work. So, it's now safe to
4342 // re-initialise our data structures. At the end of this method,
4343 // task 0 will clear the global data structures.
4344
4345 statsOnly( ++_aborted_overflow );
4346
4347 // We clear the local state of this task...
4348 clear_region_fields();
4349
4350 // ...and enter the second barrier.
4351 _cm->enter_second_sync_barrier(_worker_id);
4352 // At this point everything has bee re-initialised and we're
4353 // ready to restart.
4354 }
4355
4356 if (_cm->verbose_low()) {
4357 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4358 "elapsed = %1.2lfms <<<<<<<<<<",
4359 _worker_id, _time_target_ms, elapsed_time_ms);
4360 if (_cm->has_aborted()) {
4361 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4362 _worker_id);
4363 }
4364 }
4365 } else {
4366 if (_cm->verbose_low()) {
4367 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4368 "elapsed = %1.2lfms <<<<<<<<<<",
4369 _worker_id, _time_target_ms, elapsed_time_ms);
4370 }
4371 }
4372
4373 _claimed = false;
4374 }
4375
4376 CMTask::CMTask(uint worker_id,
4377 ConcurrentMark* cm,
4378 size_t* marked_bytes,
4379 BitMap* card_bm,
4380 CMTaskQueue* task_queue,
4381 CMTaskQueueSet* task_queues)
4382 : _g1h(G1CollectedHeap::heap()),
4383 _worker_id(worker_id), _cm(cm),
4384 _claimed(false),
4385 _nextMarkBitMap(NULL), _hash_seed(17),
4386 _task_queue(task_queue),
4387 _task_queues(task_queues),
4388 _cm_oop_closure(NULL),
4389 _marked_bytes_array(marked_bytes),
4390 _card_bm(card_bm) {
4391 guarantee(task_queue != NULL, "invariant");
4392 guarantee(task_queues != NULL, "invariant");
4393
4394 statsOnly( _clock_due_to_scanning = 0;
4395 _clock_due_to_marking = 0 );
4396
4397 _marking_step_diffs_ms.add(0.5);
4398 }
4399
4400 // These are formatting macros that are used below to ensure
4401 // consistent formatting. The *_H_* versions are used to format the
4402 // header for a particular value and they should be kept consistent
4403 // with the corresponding macro. Also note that most of the macros add
4404 // the necessary white space (as a prefix) which makes them a bit
4405 // easier to compose.
4406
4407 // All the output lines are prefixed with this string to be able to
4408 // identify them easily in a large log file.
4409 #define G1PPRL_LINE_PREFIX "###"
4410
4411 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4412 #ifdef _LP64
4413 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4414 #else // _LP64
4415 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4416 #endif // _LP64
4417
4418 // For per-region info
4419 #define G1PPRL_TYPE_FORMAT " %-4s"
4420 #define G1PPRL_TYPE_H_FORMAT " %4s"
4421 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4422 #define G1PPRL_BYTE_H_FORMAT " %9s"
4423 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4424 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4425
4426 // For summary info
4427 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4428 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4429 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4430 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4431
4432 G1PrintRegionLivenessInfoClosure::
4433 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4434 : _out(out),
4435 _total_used_bytes(0), _total_capacity_bytes(0),
4436 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4437 _hum_used_bytes(0), _hum_capacity_bytes(0),
4438 _hum_prev_live_bytes(0), _hum_next_live_bytes(0) {
4439 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4440 MemRegion g1_committed = g1h->g1_committed();
4441 MemRegion g1_reserved = g1h->g1_reserved();
4442 double now = os::elapsedTime();
4443
4444 // Print the header of the output.
4445 _out->cr();
4446 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4447 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4448 G1PPRL_SUM_ADDR_FORMAT("committed")
4449 G1PPRL_SUM_ADDR_FORMAT("reserved")
4450 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4451 g1_committed.start(), g1_committed.end(),
4452 g1_reserved.start(), g1_reserved.end(),
4453 HeapRegion::GrainBytes);
4454 _out->print_cr(G1PPRL_LINE_PREFIX);
4455 _out->print_cr(G1PPRL_LINE_PREFIX
4456 G1PPRL_TYPE_H_FORMAT
4457 G1PPRL_ADDR_BASE_H_FORMAT
4458 G1PPRL_BYTE_H_FORMAT
4459 G1PPRL_BYTE_H_FORMAT
4460 G1PPRL_BYTE_H_FORMAT
4461 G1PPRL_DOUBLE_H_FORMAT,
4462 "type", "address-range",
4463 "used", "prev-live", "next-live", "gc-eff");
4464 _out->print_cr(G1PPRL_LINE_PREFIX
4465 G1PPRL_TYPE_H_FORMAT
4466 G1PPRL_ADDR_BASE_H_FORMAT
4467 G1PPRL_BYTE_H_FORMAT
4468 G1PPRL_BYTE_H_FORMAT
4469 G1PPRL_BYTE_H_FORMAT
4470 G1PPRL_DOUBLE_H_FORMAT,
4471 "", "",
4472 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)");
4473 }
4474
4475 // It takes as a parameter a reference to one of the _hum_* fields, it
4476 // deduces the corresponding value for a region in a humongous region
4477 // series (either the region size, or what's left if the _hum_* field
4478 // is < the region size), and updates the _hum_* field accordingly.
4479 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4480 size_t bytes = 0;
4481 // The > 0 check is to deal with the prev and next live bytes which
4482 // could be 0.
4483 if (*hum_bytes > 0) {
4484 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4485 *hum_bytes -= bytes;
4486 }
4487 return bytes;
4488 }
4489
4490 // It deduces the values for a region in a humongous region series
4491 // from the _hum_* fields and updates those accordingly. It assumes
4492 // that that _hum_* fields have already been set up from the "starts
4493 // humongous" region and we visit the regions in address order.
4494 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4495 size_t* capacity_bytes,
4496 size_t* prev_live_bytes,
4497 size_t* next_live_bytes) {
4498 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4499 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4500 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4501 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4502 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4503 }
4504
4505 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4506 const char* type = "";
4507 HeapWord* bottom = r->bottom();
4508 HeapWord* end = r->end();
4509 size_t capacity_bytes = r->capacity();
4510 size_t used_bytes = r->used();
4511 size_t prev_live_bytes = r->live_bytes();
4512 size_t next_live_bytes = r->next_live_bytes();
4513 double gc_eff = r->gc_efficiency();
4514 if (r->used() == 0) {
4515 type = "FREE";
4516 } else if (r->is_survivor()) {
4517 type = "SURV";
4518 } else if (r->is_young()) {
4519 type = "EDEN";
4520 } else if (r->startsHumongous()) {
4521 type = "HUMS";
4522
4523 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4524 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4525 "they should have been zeroed after the last time we used them");
4526 // Set up the _hum_* fields.
4527 _hum_capacity_bytes = capacity_bytes;
4528 _hum_used_bytes = used_bytes;
4529 _hum_prev_live_bytes = prev_live_bytes;
4530 _hum_next_live_bytes = next_live_bytes;
4531 get_hum_bytes(&used_bytes, &capacity_bytes,
4532 &prev_live_bytes, &next_live_bytes);
4533 end = bottom + HeapRegion::GrainWords;
4534 } else if (r->continuesHumongous()) {
4535 type = "HUMC";
4536 get_hum_bytes(&used_bytes, &capacity_bytes,
4537 &prev_live_bytes, &next_live_bytes);
4538 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4539 } else {
4540 type = "OLD";
4541 }
4542
4543 _total_used_bytes += used_bytes;
4544 _total_capacity_bytes += capacity_bytes;
4545 _total_prev_live_bytes += prev_live_bytes;
4546 _total_next_live_bytes += next_live_bytes;
4547
4548 // Print a line for this particular region.
4549 _out->print_cr(G1PPRL_LINE_PREFIX
4550 G1PPRL_TYPE_FORMAT
4551 G1PPRL_ADDR_BASE_FORMAT
4552 G1PPRL_BYTE_FORMAT
4553 G1PPRL_BYTE_FORMAT
4554 G1PPRL_BYTE_FORMAT
4555 G1PPRL_DOUBLE_FORMAT,
4556 type, bottom, end,
4557 used_bytes, prev_live_bytes, next_live_bytes, gc_eff);
4558
4559 return false;
4560 }
4561
4562 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4563 // Print the footer of the output.
4564 _out->print_cr(G1PPRL_LINE_PREFIX);
4565 _out->print_cr(G1PPRL_LINE_PREFIX
4566 " SUMMARY"
4567 G1PPRL_SUM_MB_FORMAT("capacity")
4568 G1PPRL_SUM_MB_PERC_FORMAT("used")
4569 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4570 G1PPRL_SUM_MB_PERC_FORMAT("next-live"),
4571 bytes_to_mb(_total_capacity_bytes),
4572 bytes_to_mb(_total_used_bytes),
4573 perc(_total_used_bytes, _total_capacity_bytes),
4574 bytes_to_mb(_total_prev_live_bytes),
4575 perc(_total_prev_live_bytes, _total_capacity_bytes),
4576 bytes_to_mb(_total_next_live_bytes),
4577 perc(_total_next_live_bytes, _total_capacity_bytes));
4578 _out->cr();
4579 }