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 (ConcGCThreads > 0) {
575 // notice that ConcGCThreads overwrites G1MarkingOverheadPercent
576 // if both are set
577
578 _parallel_marking_threads = (uint) ConcGCThreads;
579 _max_parallel_marking_threads = _parallel_marking_threads;
580 _sleep_factor = 0.0;
581 _marking_task_overhead = 1.0;
582 } else if (G1MarkingOverheadPercent > 0) {
583 // we will calculate the number of parallel marking threads
584 // based on a target overhead with respect to the soft real-time
585 // goal
586
587 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
588 double overall_cm_overhead =
589 (double) MaxGCPauseMillis * marking_overhead /
590 (double) GCPauseIntervalMillis;
591 double cpu_ratio = 1.0 / (double) os::processor_count();
592 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
593 double marking_task_overhead =
594 overall_cm_overhead / marking_thread_num *
595 (double) os::processor_count();
596 double sleep_factor =
597 (1.0 - marking_task_overhead) / marking_task_overhead;
598
599 _parallel_marking_threads = (uint) marking_thread_num;
600 _max_parallel_marking_threads = _parallel_marking_threads;
601 _sleep_factor = sleep_factor;
602 _marking_task_overhead = marking_task_overhead;
603 } else {
604 _parallel_marking_threads = scale_parallel_threads((uint)ParallelGCThreads);
605 _max_parallel_marking_threads = _parallel_marking_threads;
606 _sleep_factor = 0.0;
607 _marking_task_overhead = 1.0;
608 }
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 (parallel_marking_threads() > 0) {
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 (parallel_marking_threads() > 0) {
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 g1h->check_bitmaps("Remark Start");
1264
1265 G1CollectorPolicy* g1p = g1h->g1_policy();
1266 g1p->record_concurrent_mark_remark_start();
1267
1268 double start = os::elapsedTime();
1269
1270 checkpointRootsFinalWork();
1271
1272 double mark_work_end = os::elapsedTime();
1273
1274 weakRefsWork(clear_all_soft_refs);
1275
1276 if (has_overflown()) {
1277 // Oops. We overflowed. Restart concurrent marking.
1278 _restart_for_overflow = true;
1279 // Clear the marking state because we will be restarting
1280 // marking due to overflowing the global mark stack.
1281 reset_marking_state();
1282 if (G1TraceMarkStackOverflow) {
1283 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1284 }
1285 } else {
1286 // Aggregate the per-task counting data that we have accumulated
1287 // while marking.
1288 aggregate_count_data();
1289
1290 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1291 // We're done with marking.
1292 // This is the end of the marking cycle, we're expected all
1293 // threads to have SATB queues with active set to true.
1294 satb_mq_set.set_active_all_threads(false, /* new active value */
1295 true /* expected_active */);
1296
1297 if (VerifyDuringGC) {
1298 HandleMark hm; // handle scope
1299 gclog_or_tty->print(" VerifyDuringGC:(after)");
1300 Universe::heap()->prepare_for_verify();
1301 Universe::verify(/* silent */ false,
1302 /* option */ VerifyOption_G1UseNextMarking);
1303 }
1304 g1h->check_bitmaps("Remark End");
1305 assert(!restart_for_overflow(), "sanity");
1306 // Completely reset the marking state since marking completed
1307 set_non_marking_state();
1308 }
1309
1310 // Expand the marking stack, if we have to and if we can.
1311 if (_markStack.should_expand()) {
1312 _markStack.expand();
1313 }
1314
1315 #if VERIFY_OBJS_PROCESSED
1316 _scan_obj_cl.objs_processed = 0;
1317 ThreadLocalObjQueue::objs_enqueued = 0;
1318 #endif
1319
1320 // Statistics
1321 double now = os::elapsedTime();
1322 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1323 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1324 _remark_times.add((now - start) * 1000.0);
1325
1326 g1p->record_concurrent_mark_remark_end();
1327 }
1328
1329 // Base class of the closures that finalize and verify the
1330 // liveness counting data.
1331 class CMCountDataClosureBase: public HeapRegionClosure {
1332 protected:
1333 G1CollectedHeap* _g1h;
1334 ConcurrentMark* _cm;
1335 CardTableModRefBS* _ct_bs;
1336
1337 BitMap* _region_bm;
1338 BitMap* _card_bm;
1339
1340 // Takes a region that's not empty (i.e., it has at least one
1341 // live object in it and sets its corresponding bit on the region
1342 // bitmap to 1. If the region is "starts humongous" it will also set
1343 // to 1 the bits on the region bitmap that correspond to its
1344 // associated "continues humongous" regions.
1345 void set_bit_for_region(HeapRegion* hr) {
1346 assert(!hr->continuesHumongous(), "should have filtered those out");
1347
1348 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1349 if (!hr->startsHumongous()) {
1350 // Normal (non-humongous) case: just set the bit.
1351 _region_bm->par_at_put(index, true);
1352 } else {
1353 // Starts humongous case: calculate how many regions are part of
1354 // this humongous region and then set the bit range.
1355 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1356 _region_bm->par_at_put_range(index, end_index, true);
1357 }
1358 }
1359
1360 public:
1361 CMCountDataClosureBase(G1CollectedHeap* g1h,
1362 BitMap* region_bm, BitMap* card_bm):
1363 _g1h(g1h), _cm(g1h->concurrent_mark()),
1364 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
1365 _region_bm(region_bm), _card_bm(card_bm) { }
1366 };
1367
1368 // Closure that calculates the # live objects per region. Used
1369 // for verification purposes during the cleanup pause.
1370 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1371 CMBitMapRO* _bm;
1372 size_t _region_marked_bytes;
1373
1374 public:
1375 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1376 BitMap* region_bm, BitMap* card_bm) :
1377 CMCountDataClosureBase(g1h, region_bm, card_bm),
1378 _bm(bm), _region_marked_bytes(0) { }
1379
1380 bool doHeapRegion(HeapRegion* hr) {
1381
1382 if (hr->continuesHumongous()) {
1383 // We will ignore these here and process them when their
1384 // associated "starts humongous" region is processed (see
1385 // set_bit_for_heap_region()). Note that we cannot rely on their
1386 // associated "starts humongous" region to have their bit set to
1387 // 1 since, due to the region chunking in the parallel region
1388 // iteration, a "continues humongous" region might be visited
1389 // before its associated "starts humongous".
1390 return false;
1391 }
1392
1393 HeapWord* ntams = hr->next_top_at_mark_start();
1394 HeapWord* start = hr->bottom();
1395
1396 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1397 err_msg("Preconditions not met - "
1398 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1399 start, ntams, hr->end()));
1400
1401 // Find the first marked object at or after "start".
1402 start = _bm->getNextMarkedWordAddress(start, ntams);
1403
1404 size_t marked_bytes = 0;
1405
1406 while (start < ntams) {
1407 oop obj = oop(start);
1408 int obj_sz = obj->size();
1409 HeapWord* obj_end = start + obj_sz;
1410
1411 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1412 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1413
1414 // Note: if we're looking at the last region in heap - obj_end
1415 // could be actually just beyond the end of the heap; end_idx
1416 // will then correspond to a (non-existent) card that is also
1417 // just beyond the heap.
1418 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1419 // end of object is not card aligned - increment to cover
1420 // all the cards spanned by the object
1421 end_idx += 1;
1422 }
1423
1424 // Set the bits in the card BM for the cards spanned by this object.
1425 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1426
1427 // Add the size of this object to the number of marked bytes.
1428 marked_bytes += (size_t)obj_sz * HeapWordSize;
1429
1430 // Find the next marked object after this one.
1431 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1432 }
1433
1434 // Mark the allocated-since-marking portion...
1435 HeapWord* top = hr->top();
1436 if (ntams < top) {
1437 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1438 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1439
1440 // Note: if we're looking at the last region in heap - top
1441 // could be actually just beyond the end of the heap; end_idx
1442 // will then correspond to a (non-existent) card that is also
1443 // just beyond the heap.
1444 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1445 // end of object is not card aligned - increment to cover
1446 // all the cards spanned by the object
1447 end_idx += 1;
1448 }
1449 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1450
1451 // This definitely means the region has live objects.
1452 set_bit_for_region(hr);
1453 }
1454
1455 // Update the live region bitmap.
1456 if (marked_bytes > 0) {
1457 set_bit_for_region(hr);
1458 }
1459
1460 // Set the marked bytes for the current region so that
1461 // it can be queried by a calling verificiation routine
1462 _region_marked_bytes = marked_bytes;
1463
1464 return false;
1465 }
1466
1467 size_t region_marked_bytes() const { return _region_marked_bytes; }
1468 };
1469
1470 // Heap region closure used for verifying the counting data
1471 // that was accumulated concurrently and aggregated during
1472 // the remark pause. This closure is applied to the heap
1473 // regions during the STW cleanup pause.
1474
1475 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1476 G1CollectedHeap* _g1h;
1477 ConcurrentMark* _cm;
1478 CalcLiveObjectsClosure _calc_cl;
1479 BitMap* _region_bm; // Region BM to be verified
1480 BitMap* _card_bm; // Card BM to be verified
1481 bool _verbose; // verbose output?
1482
1483 BitMap* _exp_region_bm; // Expected Region BM values
1484 BitMap* _exp_card_bm; // Expected card BM values
1485
1486 int _failures;
1487
1488 public:
1489 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1490 BitMap* region_bm,
1491 BitMap* card_bm,
1492 BitMap* exp_region_bm,
1493 BitMap* exp_card_bm,
1494 bool verbose) :
1495 _g1h(g1h), _cm(g1h->concurrent_mark()),
1496 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1497 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1498 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1499 _failures(0) { }
1500
1501 int failures() const { return _failures; }
1502
1503 bool doHeapRegion(HeapRegion* hr) {
1504 if (hr->continuesHumongous()) {
1505 // We will ignore these here and process them when their
1506 // associated "starts humongous" region is processed (see
1507 // set_bit_for_heap_region()). Note that we cannot rely on their
1508 // associated "starts humongous" region to have their bit set to
1509 // 1 since, due to the region chunking in the parallel region
1510 // iteration, a "continues humongous" region might be visited
1511 // before its associated "starts humongous".
1512 return false;
1513 }
1514
1515 int failures = 0;
1516
1517 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1518 // this region and set the corresponding bits in the expected region
1519 // and card bitmaps.
1520 bool res = _calc_cl.doHeapRegion(hr);
1521 assert(res == false, "should be continuing");
1522
1523 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1524 Mutex::_no_safepoint_check_flag);
1525
1526 // Verify the marked bytes for this region.
1527 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1528 size_t act_marked_bytes = hr->next_marked_bytes();
1529
1530 // We're not OK if expected marked bytes > actual marked bytes. It means
1531 // we have missed accounting some objects during the actual marking.
1532 if (exp_marked_bytes > act_marked_bytes) {
1533 if (_verbose) {
1534 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1535 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1536 hr->hrs_index(), exp_marked_bytes, act_marked_bytes);
1537 }
1538 failures += 1;
1539 }
1540
1541 // Verify the bit, for this region, in the actual and expected
1542 // (which was just calculated) region bit maps.
1543 // We're not OK if the bit in the calculated expected region
1544 // bitmap is set and the bit in the actual region bitmap is not.
1545 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1546
1547 bool expected = _exp_region_bm->at(index);
1548 bool actual = _region_bm->at(index);
1549 if (expected && !actual) {
1550 if (_verbose) {
1551 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1552 "expected: %s, actual: %s",
1553 hr->hrs_index(),
1554 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1555 }
1556 failures += 1;
1557 }
1558
1559 // Verify that the card bit maps for the cards spanned by the current
1560 // region match. We have an error if we have a set bit in the expected
1561 // bit map and the corresponding bit in the actual bitmap is not set.
1562
1563 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1564 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1565
1566 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1567 expected = _exp_card_bm->at(i);
1568 actual = _card_bm->at(i);
1569
1570 if (expected && !actual) {
1571 if (_verbose) {
1572 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1573 "expected: %s, actual: %s",
1574 hr->hrs_index(), i,
1575 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1576 }
1577 failures += 1;
1578 }
1579 }
1580
1581 if (failures > 0 && _verbose) {
1582 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1583 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1584 HR_FORMAT_PARAMS(hr), hr->next_top_at_mark_start(),
1585 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1586 }
1587
1588 _failures += failures;
1589
1590 // We could stop iteration over the heap when we
1591 // find the first violating region by returning true.
1592 return false;
1593 }
1594 };
1595
1596
1597 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1598 protected:
1599 G1CollectedHeap* _g1h;
1600 ConcurrentMark* _cm;
1601 BitMap* _actual_region_bm;
1602 BitMap* _actual_card_bm;
1603
1604 uint _n_workers;
1605
1606 BitMap* _expected_region_bm;
1607 BitMap* _expected_card_bm;
1608
1609 int _failures;
1610 bool _verbose;
1611
1612 public:
1613 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1614 BitMap* region_bm, BitMap* card_bm,
1615 BitMap* expected_region_bm, BitMap* expected_card_bm)
1616 : AbstractGangTask("G1 verify final counting"),
1617 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1618 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1619 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1620 _failures(0), _verbose(false),
1621 _n_workers(0) {
1622 assert(VerifyDuringGC, "don't call this otherwise");
1623
1624 // Use the value already set as the number of active threads
1625 // in the call to run_task().
1626 if (G1CollectedHeap::use_parallel_gc_threads()) {
1627 assert( _g1h->workers()->active_workers() > 0,
1628 "Should have been previously set");
1629 _n_workers = _g1h->workers()->active_workers();
1630 } else {
1631 _n_workers = 1;
1632 }
1633
1634 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1635 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1636
1637 _verbose = _cm->verbose_medium();
1638 }
1639
1640 void work(uint worker_id) {
1641 assert(worker_id < _n_workers, "invariant");
1642
1643 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1644 _actual_region_bm, _actual_card_bm,
1645 _expected_region_bm,
1646 _expected_card_bm,
1647 _verbose);
1648
1649 if (G1CollectedHeap::use_parallel_gc_threads()) {
1650 _g1h->heap_region_par_iterate_chunked(&verify_cl,
1651 worker_id,
1652 _n_workers,
1653 HeapRegion::VerifyCountClaimValue);
1654 } else {
1655 _g1h->heap_region_iterate(&verify_cl);
1656 }
1657
1658 Atomic::add(verify_cl.failures(), &_failures);
1659 }
1660
1661 int failures() const { return _failures; }
1662 };
1663
1664 // Closure that finalizes the liveness counting data.
1665 // Used during the cleanup pause.
1666 // Sets the bits corresponding to the interval [NTAMS, top]
1667 // (which contains the implicitly live objects) in the
1668 // card liveness bitmap. Also sets the bit for each region,
1669 // containing live data, in the region liveness bitmap.
1670
1671 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1672 public:
1673 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1674 BitMap* region_bm,
1675 BitMap* card_bm) :
1676 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1677
1678 bool doHeapRegion(HeapRegion* hr) {
1679
1680 if (hr->continuesHumongous()) {
1681 // We will ignore these here and process them when their
1682 // associated "starts humongous" region is processed (see
1683 // set_bit_for_heap_region()). Note that we cannot rely on their
1684 // associated "starts humongous" region to have their bit set to
1685 // 1 since, due to the region chunking in the parallel region
1686 // iteration, a "continues humongous" region might be visited
1687 // before its associated "starts humongous".
1688 return false;
1689 }
1690
1691 HeapWord* ntams = hr->next_top_at_mark_start();
1692 HeapWord* top = hr->top();
1693
1694 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1695
1696 // Mark the allocated-since-marking portion...
1697 if (ntams < top) {
1698 // This definitely means the region has live objects.
1699 set_bit_for_region(hr);
1700
1701 // Now set the bits in the card bitmap for [ntams, top)
1702 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1703 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1704
1705 // Note: if we're looking at the last region in heap - top
1706 // could be actually just beyond the end of the heap; end_idx
1707 // will then correspond to a (non-existent) card that is also
1708 // just beyond the heap.
1709 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1710 // end of object is not card aligned - increment to cover
1711 // all the cards spanned by the object
1712 end_idx += 1;
1713 }
1714
1715 assert(end_idx <= _card_bm->size(),
1716 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1717 end_idx, _card_bm->size()));
1718 assert(start_idx < _card_bm->size(),
1719 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1720 start_idx, _card_bm->size()));
1721
1722 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1723 }
1724
1725 // Set the bit for the region if it contains live data
1726 if (hr->next_marked_bytes() > 0) {
1727 set_bit_for_region(hr);
1728 }
1729
1730 return false;
1731 }
1732 };
1733
1734 class G1ParFinalCountTask: public AbstractGangTask {
1735 protected:
1736 G1CollectedHeap* _g1h;
1737 ConcurrentMark* _cm;
1738 BitMap* _actual_region_bm;
1739 BitMap* _actual_card_bm;
1740
1741 uint _n_workers;
1742
1743 public:
1744 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1745 : AbstractGangTask("G1 final counting"),
1746 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1747 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1748 _n_workers(0) {
1749 // Use the value already set as the number of active threads
1750 // in the call to run_task().
1751 if (G1CollectedHeap::use_parallel_gc_threads()) {
1752 assert( _g1h->workers()->active_workers() > 0,
1753 "Should have been previously set");
1754 _n_workers = _g1h->workers()->active_workers();
1755 } else {
1756 _n_workers = 1;
1757 }
1758 }
1759
1760 void work(uint worker_id) {
1761 assert(worker_id < _n_workers, "invariant");
1762
1763 FinalCountDataUpdateClosure final_update_cl(_g1h,
1764 _actual_region_bm,
1765 _actual_card_bm);
1766
1767 if (G1CollectedHeap::use_parallel_gc_threads()) {
1768 _g1h->heap_region_par_iterate_chunked(&final_update_cl,
1769 worker_id,
1770 _n_workers,
1771 HeapRegion::FinalCountClaimValue);
1772 } else {
1773 _g1h->heap_region_iterate(&final_update_cl);
1774 }
1775 }
1776 };
1777
1778 class G1ParNoteEndTask;
1779
1780 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1781 G1CollectedHeap* _g1;
1782 int _worker_num;
1783 size_t _max_live_bytes;
1784 uint _regions_claimed;
1785 size_t _freed_bytes;
1786 FreeRegionList* _local_cleanup_list;
1787 OldRegionSet* _old_proxy_set;
1788 HumongousRegionSet* _humongous_proxy_set;
1789 HRRSCleanupTask* _hrrs_cleanup_task;
1790 double _claimed_region_time;
1791 double _max_region_time;
1792
1793 public:
1794 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1795 int worker_num,
1796 FreeRegionList* local_cleanup_list,
1797 OldRegionSet* old_proxy_set,
1798 HumongousRegionSet* humongous_proxy_set,
1799 HRRSCleanupTask* hrrs_cleanup_task) :
1800 _g1(g1), _worker_num(worker_num),
1801 _max_live_bytes(0), _regions_claimed(0),
1802 _freed_bytes(0),
1803 _claimed_region_time(0.0), _max_region_time(0.0),
1804 _local_cleanup_list(local_cleanup_list),
1805 _old_proxy_set(old_proxy_set),
1806 _humongous_proxy_set(humongous_proxy_set),
1807 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1808
1809 size_t freed_bytes() { return _freed_bytes; }
1810
1811 bool doHeapRegion(HeapRegion *hr) {
1812 if (hr->continuesHumongous()) {
1813 return false;
1814 }
1815 // We use a claim value of zero here because all regions
1816 // were claimed with value 1 in the FinalCount task.
1817 _g1->reset_gc_time_stamps(hr);
1818 double start = os::elapsedTime();
1819 _regions_claimed++;
1820 hr->note_end_of_marking();
1821 _max_live_bytes += hr->max_live_bytes();
1822 _g1->free_region_if_empty(hr,
1823 &_freed_bytes,
1824 _local_cleanup_list,
1825 _old_proxy_set,
1826 _humongous_proxy_set,
1827 _hrrs_cleanup_task,
1828 true /* par */);
1829 double region_time = (os::elapsedTime() - start);
1830 _claimed_region_time += region_time;
1831 if (region_time > _max_region_time) {
1832 _max_region_time = region_time;
1833 }
1834 return false;
1835 }
1836
1837 size_t max_live_bytes() { return _max_live_bytes; }
1838 uint regions_claimed() { return _regions_claimed; }
1839 double claimed_region_time_sec() { return _claimed_region_time; }
1840 double max_region_time_sec() { return _max_region_time; }
1841 };
1842
1843 class G1ParNoteEndTask: public AbstractGangTask {
1844 friend class G1NoteEndOfConcMarkClosure;
1845
1846 protected:
1847 G1CollectedHeap* _g1h;
1848 size_t _max_live_bytes;
1849 size_t _freed_bytes;
1850 FreeRegionList* _cleanup_list;
1851
1852 public:
1853 G1ParNoteEndTask(G1CollectedHeap* g1h,
1854 FreeRegionList* cleanup_list) :
1855 AbstractGangTask("G1 note end"), _g1h(g1h),
1856 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1857
1858 void work(uint worker_id) {
1859 double start = os::elapsedTime();
1860 FreeRegionList local_cleanup_list("Local Cleanup List");
1861 OldRegionSet old_proxy_set("Local Cleanup Old Proxy Set");
1862 HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
1863 HRRSCleanupTask hrrs_cleanup_task;
1864 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, worker_id, &local_cleanup_list,
1865 &old_proxy_set,
1866 &humongous_proxy_set,
1867 &hrrs_cleanup_task);
1868 if (G1CollectedHeap::use_parallel_gc_threads()) {
1869 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id,
1870 _g1h->workers()->active_workers(),
1871 HeapRegion::NoteEndClaimValue);
1872 } else {
1873 _g1h->heap_region_iterate(&g1_note_end);
1874 }
1875 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1876
1877 // Now update the lists
1878 _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
1879 NULL /* free_list */,
1880 &old_proxy_set,
1881 &humongous_proxy_set,
1882 true /* par */);
1883 {
1884 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1885 _max_live_bytes += g1_note_end.max_live_bytes();
1886 _freed_bytes += g1_note_end.freed_bytes();
1887
1888 // If we iterate over the global cleanup list at the end of
1889 // cleanup to do this printing we will not guarantee to only
1890 // generate output for the newly-reclaimed regions (the list
1891 // might not be empty at the beginning of cleanup; we might
1892 // still be working on its previous contents). So we do the
1893 // printing here, before we append the new regions to the global
1894 // cleanup list.
1895
1896 G1HRPrinter* hr_printer = _g1h->hr_printer();
1897 if (hr_printer->is_active()) {
1898 HeapRegionLinkedListIterator iter(&local_cleanup_list);
1899 while (iter.more_available()) {
1900 HeapRegion* hr = iter.get_next();
1901 hr_printer->cleanup(hr);
1902 }
1903 }
1904
1905 _cleanup_list->add_as_tail(&local_cleanup_list);
1906 assert(local_cleanup_list.is_empty(), "post-condition");
1907
1908 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1909 }
1910 }
1911 size_t max_live_bytes() { return _max_live_bytes; }
1912 size_t freed_bytes() { return _freed_bytes; }
1913 };
1914
1915 class G1ParScrubRemSetTask: public AbstractGangTask {
1916 protected:
1917 G1RemSet* _g1rs;
1918 BitMap* _region_bm;
1919 BitMap* _card_bm;
1920 public:
1921 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1922 BitMap* region_bm, BitMap* card_bm) :
1923 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1924 _region_bm(region_bm), _card_bm(card_bm) { }
1925
1926 void work(uint worker_id) {
1927 if (G1CollectedHeap::use_parallel_gc_threads()) {
1928 _g1rs->scrub_par(_region_bm, _card_bm, worker_id,
1929 HeapRegion::ScrubRemSetClaimValue);
1930 } else {
1931 _g1rs->scrub(_region_bm, _card_bm);
1932 }
1933 }
1934
1935 };
1936
1937 void ConcurrentMark::cleanup() {
1938 // world is stopped at this checkpoint
1939 assert(SafepointSynchronize::is_at_safepoint(),
1940 "world should be stopped");
1941 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1942
1943 // If a full collection has happened, we shouldn't do this.
1944 if (has_aborted()) {
1945 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1946 return;
1947 }
1948
1949 HRSPhaseSetter x(HRSPhaseCleanup);
1950 g1h->verify_region_sets_optional();
1951
1952 if (VerifyDuringGC) {
1953 HandleMark hm; // handle scope
1954 gclog_or_tty->print(" VerifyDuringGC:(before)");
1955 Universe::heap()->prepare_for_verify();
1956 Universe::verify(/* silent */ false,
1957 /* option */ VerifyOption_G1UsePrevMarking);
1958 }
1959 g1h->check_bitmaps("Cleanup Start");
1960
1961 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1962 g1p->record_concurrent_mark_cleanup_start();
1963
1964 double start = os::elapsedTime();
1965
1966 HeapRegionRemSet::reset_for_cleanup_tasks();
1967
1968 uint n_workers;
1969
1970 // Do counting once more with the world stopped for good measure.
1971 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1972
1973 if (G1CollectedHeap::use_parallel_gc_threads()) {
1974 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
1975 "sanity check");
1976
1977 g1h->set_par_threads();
1978 n_workers = g1h->n_par_threads();
1979 assert(g1h->n_par_threads() == n_workers,
1980 "Should not have been reset");
1981 g1h->workers()->run_task(&g1_par_count_task);
1982 // Done with the parallel phase so reset to 0.
1983 g1h->set_par_threads(0);
1984
1985 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue),
1986 "sanity check");
1987 } else {
1988 n_workers = 1;
1989 g1_par_count_task.work(0);
1990 }
1991
1992 if (VerifyDuringGC) {
1993 // Verify that the counting data accumulated during marking matches
1994 // that calculated by walking the marking bitmap.
1995
1996 // Bitmaps to hold expected values
1997 BitMap expected_region_bm(_region_bm.size(), false);
1998 BitMap expected_card_bm(_card_bm.size(), false);
1999
2000 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
2001 &_region_bm,
2002 &_card_bm,
2003 &expected_region_bm,
2004 &expected_card_bm);
2005
2006 if (G1CollectedHeap::use_parallel_gc_threads()) {
2007 g1h->set_par_threads((int)n_workers);
2008 g1h->workers()->run_task(&g1_par_verify_task);
2009 // Done with the parallel phase so reset to 0.
2010 g1h->set_par_threads(0);
2011
2012 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue),
2013 "sanity check");
2014 } else {
2015 g1_par_verify_task.work(0);
2016 }
2017
2018 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2019 }
2020
2021 size_t start_used_bytes = g1h->used();
2022 g1h->set_marking_complete();
2023
2024 double count_end = os::elapsedTime();
2025 double this_final_counting_time = (count_end - start);
2026 _total_counting_time += this_final_counting_time;
2027
2028 if (G1PrintRegionLivenessInfo) {
2029 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2030 _g1h->heap_region_iterate(&cl);
2031 }
2032
2033 // Install newly created mark bitMap as "prev".
2034 swapMarkBitMaps();
2035
2036 g1h->reset_gc_time_stamp();
2037
2038 // Note end of marking in all heap regions.
2039 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
2040 if (G1CollectedHeap::use_parallel_gc_threads()) {
2041 g1h->set_par_threads((int)n_workers);
2042 g1h->workers()->run_task(&g1_par_note_end_task);
2043 g1h->set_par_threads(0);
2044
2045 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
2046 "sanity check");
2047 } else {
2048 g1_par_note_end_task.work(0);
2049 }
2050 g1h->check_gc_time_stamps();
2051
2052 if (!cleanup_list_is_empty()) {
2053 // The cleanup list is not empty, so we'll have to process it
2054 // concurrently. Notify anyone else that might be wanting free
2055 // regions that there will be more free regions coming soon.
2056 g1h->set_free_regions_coming();
2057 }
2058
2059 // call below, since it affects the metric by which we sort the heap
2060 // regions.
2061 if (G1ScrubRemSets) {
2062 double rs_scrub_start = os::elapsedTime();
2063 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
2064 if (G1CollectedHeap::use_parallel_gc_threads()) {
2065 g1h->set_par_threads((int)n_workers);
2066 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2067 g1h->set_par_threads(0);
2068
2069 assert(g1h->check_heap_region_claim_values(
2070 HeapRegion::ScrubRemSetClaimValue),
2071 "sanity check");
2072 } else {
2073 g1_par_scrub_rs_task.work(0);
2074 }
2075
2076 double rs_scrub_end = os::elapsedTime();
2077 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2078 _total_rs_scrub_time += this_rs_scrub_time;
2079 }
2080
2081 // this will also free any regions totally full of garbage objects,
2082 // and sort the regions.
2083 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2084
2085 // Statistics.
2086 double end = os::elapsedTime();
2087 _cleanup_times.add((end - start) * 1000.0);
2088
2089 if (G1Log::fine()) {
2090 g1h->print_size_transition(gclog_or_tty,
2091 start_used_bytes,
2092 g1h->used(),
2093 g1h->capacity());
2094 }
2095
2096 // Clean up will have freed any regions completely full of garbage.
2097 // Update the soft reference policy with the new heap occupancy.
2098 Universe::update_heap_info_at_gc();
2099
2100 // We need to make this be a "collection" so any collection pause that
2101 // races with it goes around and waits for completeCleanup to finish.
2102 g1h->increment_total_collections();
2103
2104 // We reclaimed old regions so we should calculate the sizes to make
2105 // sure we update the old gen/space data.
2106 g1h->g1mm()->update_sizes();
2107
2108 if (VerifyDuringGC) {
2109 HandleMark hm; // handle scope
2110 gclog_or_tty->print(" VerifyDuringGC:(after)");
2111 Universe::heap()->prepare_for_verify();
2112 Universe::verify(/* silent */ false,
2113 /* option */ VerifyOption_G1UsePrevMarking);
2114 }
2115 g1h->check_bitmaps("Cleanup End");
2116
2117 g1h->verify_region_sets_optional();
2118 }
2119
2120 void ConcurrentMark::completeCleanup() {
2121 if (has_aborted()) return;
2122
2123 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2124
2125 _cleanup_list.verify_optional();
2126 FreeRegionList tmp_free_list("Tmp Free List");
2127
2128 if (G1ConcRegionFreeingVerbose) {
2129 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2130 "cleanup list has %u entries",
2131 _cleanup_list.length());
2132 }
2133
2134 // Noone else should be accessing the _cleanup_list at this point,
2135 // so it's not necessary to take any locks
2136 while (!_cleanup_list.is_empty()) {
2137 HeapRegion* hr = _cleanup_list.remove_head();
2138 assert(hr != NULL, "the list was not empty");
2139 hr->par_clear();
2140 tmp_free_list.add_as_tail(hr);
2141
2142 // Instead of adding one region at a time to the secondary_free_list,
2143 // we accumulate them in the local list and move them a few at a
2144 // time. This also cuts down on the number of notify_all() calls
2145 // we do during this process. We'll also append the local list when
2146 // _cleanup_list is empty (which means we just removed the last
2147 // region from the _cleanup_list).
2148 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2149 _cleanup_list.is_empty()) {
2150 if (G1ConcRegionFreeingVerbose) {
2151 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2152 "appending %u entries to the secondary_free_list, "
2153 "cleanup list still has %u entries",
2154 tmp_free_list.length(),
2155 _cleanup_list.length());
2156 }
2157
2158 {
2159 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2160 g1h->secondary_free_list_add_as_tail(&tmp_free_list);
2161 SecondaryFreeList_lock->notify_all();
2162 }
2163
2164 if (G1StressConcRegionFreeing) {
2165 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2166 os::sleep(Thread::current(), (jlong) 1, false);
2167 }
2168 }
2169 }
2170 }
2171 assert(tmp_free_list.is_empty(), "post-condition");
2172 }
2173
2174 // Support closures for reference procssing in G1
2175
2176 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2177 HeapWord* addr = (HeapWord*)obj;
2178 return addr != NULL &&
2179 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2180 }
2181
2182 class G1CMKeepAliveClosure: public ExtendedOopClosure {
2183 G1CollectedHeap* _g1;
2184 ConcurrentMark* _cm;
2185 public:
2186 G1CMKeepAliveClosure(G1CollectedHeap* g1, ConcurrentMark* cm) :
2187 _g1(g1), _cm(cm) {
2188 assert(Thread::current()->is_VM_thread(), "otherwise fix worker id");
2189 }
2190
2191 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2192 virtual void do_oop( oop* p) { do_oop_work(p); }
2193
2194 template <class T> void do_oop_work(T* p) {
2195 oop obj = oopDesc::load_decode_heap_oop(p);
2196 HeapWord* addr = (HeapWord*)obj;
2197
2198 if (_cm->verbose_high()) {
2199 gclog_or_tty->print_cr("\t[0] we're looking at location "
2200 "*"PTR_FORMAT" = "PTR_FORMAT,
2201 p, (void*) obj);
2202 }
2203
2204 if (_g1->is_in_g1_reserved(addr) && _g1->is_obj_ill(obj)) {
2205 _cm->mark_and_count(obj);
2206 _cm->mark_stack_push(obj);
2207 }
2208 }
2209 };
2210
2211 class G1CMDrainMarkingStackClosure: public VoidClosure {
2212 ConcurrentMark* _cm;
2213 CMMarkStack* _markStack;
2214 G1CMKeepAliveClosure* _oopClosure;
2215 public:
2216 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMMarkStack* markStack,
2217 G1CMKeepAliveClosure* oopClosure) :
2218 _cm(cm),
2219 _markStack(markStack),
2220 _oopClosure(oopClosure) { }
2221
2222 void do_void() {
2223 _markStack->drain(_oopClosure, _cm->nextMarkBitMap(), false);
2224 }
2225 };
2226
2227 // 'Keep Alive' closure used by parallel reference processing.
2228 // An instance of this closure is used in the parallel reference processing
2229 // code rather than an instance of G1CMKeepAliveClosure. We could have used
2230 // the G1CMKeepAliveClosure as it is MT-safe. Also reference objects are
2231 // placed on to discovered ref lists once so we can mark and push with no
2232 // need to check whether the object has already been marked. Using the
2233 // G1CMKeepAliveClosure would mean, however, having all the worker threads
2234 // operating on the global mark stack. This means that an individual
2235 // worker would be doing lock-free pushes while it processes its own
2236 // discovered ref list followed by drain call. If the discovered ref lists
2237 // are unbalanced then this could cause interference with the other
2238 // workers. Using a CMTask (and its embedded local data structures)
2239 // avoids that potential interference.
2240 class G1CMParKeepAliveAndDrainClosure: public OopClosure {
2241 ConcurrentMark* _cm;
2242 CMTask* _task;
2243 int _ref_counter_limit;
2244 int _ref_counter;
2245 public:
2246 G1CMParKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task) :
2247 _cm(cm), _task(task),
2248 _ref_counter_limit(G1RefProcDrainInterval) {
2249 assert(_ref_counter_limit > 0, "sanity");
2250 _ref_counter = _ref_counter_limit;
2251 }
2252
2253 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2254 virtual void do_oop( oop* p) { do_oop_work(p); }
2255
2256 template <class T> void do_oop_work(T* p) {
2257 if (!_cm->has_overflown()) {
2258 oop obj = oopDesc::load_decode_heap_oop(p);
2259 if (_cm->verbose_high()) {
2260 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2261 "*"PTR_FORMAT" = "PTR_FORMAT,
2262 _task->worker_id(), p, (void*) obj);
2263 }
2264
2265 _task->deal_with_reference(obj);
2266 _ref_counter--;
2267
2268 if (_ref_counter == 0) {
2269 // We have dealt with _ref_counter_limit references, pushing them and objects
2270 // reachable from them on to the local stack (and possibly the global stack).
2271 // Call do_marking_step() to process these entries. We call the routine in a
2272 // loop, which we'll exit if there's nothing more to do (i.e. we're done
2273 // with the entries that we've pushed as a result of the deal_with_reference
2274 // calls above) or we overflow.
2275 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2276 // while there may still be some work to do. (See the comment at the
2277 // beginning of CMTask::do_marking_step() for those conditions - one of which
2278 // is reaching the specified time target.) It is only when
2279 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2280 // that the marking has completed.
2281 do {
2282 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2283 _task->do_marking_step(mark_step_duration_ms,
2284 false /* do_stealing */,
2285 false /* do_termination */);
2286 } while (_task->has_aborted() && !_cm->has_overflown());
2287 _ref_counter = _ref_counter_limit;
2288 }
2289 } else {
2290 if (_cm->verbose_high()) {
2291 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2292 }
2293 }
2294 }
2295 };
2296
2297 class G1CMParDrainMarkingStackClosure: public VoidClosure {
2298 ConcurrentMark* _cm;
2299 CMTask* _task;
2300 public:
2301 G1CMParDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task) :
2302 _cm(cm), _task(task) { }
2303
2304 void do_void() {
2305 do {
2306 if (_cm->verbose_high()) {
2307 gclog_or_tty->print_cr("\t[%u] Drain: Calling do marking_step",
2308 _task->worker_id());
2309 }
2310
2311 // We call CMTask::do_marking_step() to completely drain the local and
2312 // global marking stacks. The routine is called in a loop, which we'll
2313 // exit if there's nothing more to do (i.e. we'completely drained the
2314 // entries that were pushed as a result of applying the
2315 // G1CMParKeepAliveAndDrainClosure to the entries on the discovered ref
2316 // lists above) or we overflow the global marking stack.
2317 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2318 // while there may still be some work to do. (See the comment at the
2319 // beginning of CMTask::do_marking_step() for those conditions - one of which
2320 // is reaching the specified time target.) It is only when
2321 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2322 // that the marking has completed.
2323
2324 _task->do_marking_step(1000000000.0 /* something very large */,
2325 true /* do_stealing */,
2326 true /* do_termination */);
2327 } while (_task->has_aborted() && !_cm->has_overflown());
2328 }
2329 };
2330
2331 // Implementation of AbstractRefProcTaskExecutor for parallel
2332 // reference processing at the end of G1 concurrent marking
2333
2334 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2335 private:
2336 G1CollectedHeap* _g1h;
2337 ConcurrentMark* _cm;
2338 WorkGang* _workers;
2339 int _active_workers;
2340
2341 public:
2342 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2343 ConcurrentMark* cm,
2344 WorkGang* workers,
2345 int n_workers) :
2346 _g1h(g1h), _cm(cm),
2347 _workers(workers), _active_workers(n_workers) { }
2348
2349 // Executes the given task using concurrent marking worker threads.
2350 virtual void execute(ProcessTask& task);
2351 virtual void execute(EnqueueTask& task);
2352 };
2353
2354 class G1CMRefProcTaskProxy: public AbstractGangTask {
2355 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2356 ProcessTask& _proc_task;
2357 G1CollectedHeap* _g1h;
2358 ConcurrentMark* _cm;
2359
2360 public:
2361 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2362 G1CollectedHeap* g1h,
2363 ConcurrentMark* cm) :
2364 AbstractGangTask("Process reference objects in parallel"),
2365 _proc_task(proc_task), _g1h(g1h), _cm(cm) { }
2366
2367 virtual void work(uint worker_id) {
2368 CMTask* marking_task = _cm->task(worker_id);
2369 G1CMIsAliveClosure g1_is_alive(_g1h);
2370 G1CMParKeepAliveAndDrainClosure g1_par_keep_alive(_cm, marking_task);
2371 G1CMParDrainMarkingStackClosure g1_par_drain(_cm, marking_task);
2372
2373 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2374 }
2375 };
2376
2377 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2378 assert(_workers != NULL, "Need parallel worker threads.");
2379
2380 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2381
2382 // We need to reset the phase for each task execution so that
2383 // the termination protocol of CMTask::do_marking_step works.
2384 _cm->set_phase(_active_workers, false /* concurrent */);
2385 _g1h->set_par_threads(_active_workers);
2386 _workers->run_task(&proc_task_proxy);
2387 _g1h->set_par_threads(0);
2388 }
2389
2390 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2391 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2392 EnqueueTask& _enq_task;
2393
2394 public:
2395 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2396 AbstractGangTask("Enqueue reference objects in parallel"),
2397 _enq_task(enq_task) { }
2398
2399 virtual void work(uint worker_id) {
2400 _enq_task.work(worker_id);
2401 }
2402 };
2403
2404 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2405 assert(_workers != NULL, "Need parallel worker threads.");
2406
2407 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2408
2409 _g1h->set_par_threads(_active_workers);
2410 _workers->run_task(&enq_task_proxy);
2411 _g1h->set_par_threads(0);
2412 }
2413
2414 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2415 ResourceMark rm;
2416 HandleMark hm;
2417
2418 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2419
2420 // Is alive closure.
2421 G1CMIsAliveClosure g1_is_alive(g1h);
2422
2423 // Inner scope to exclude the cleaning of the string and symbol
2424 // tables from the displayed time.
2425 {
2426 if (G1Log::finer()) {
2427 gclog_or_tty->put(' ');
2428 }
2429 TraceTime t("GC ref-proc", G1Log::finer(), false, gclog_or_tty);
2430
2431 ReferenceProcessor* rp = g1h->ref_processor_cm();
2432
2433 // See the comment in G1CollectedHeap::ref_processing_init()
2434 // about how reference processing currently works in G1.
2435
2436 // Process weak references.
2437 rp->setup_policy(clear_all_soft_refs);
2438 assert(_markStack.isEmpty(), "mark stack should be empty");
2439
2440 G1CMKeepAliveClosure g1_keep_alive(g1h, this);
2441 G1CMDrainMarkingStackClosure
2442 g1_drain_mark_stack(this, &_markStack, &g1_keep_alive);
2443
2444 // We use the work gang from the G1CollectedHeap and we utilize all
2445 // the worker threads.
2446 uint active_workers = g1h->workers() ? g1h->workers()->active_workers() : 1U;
2447 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2448
2449 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2450 g1h->workers(), active_workers);
2451
2452 if (rp->processing_is_mt()) {
2453 // Set the degree of MT here. If the discovery is done MT, there
2454 // may have been a different number of threads doing the discovery
2455 // and a different number of discovered lists may have Ref objects.
2456 // That is OK as long as the Reference lists are balanced (see
2457 // balance_all_queues() and balance_queues()).
2458 rp->set_active_mt_degree(active_workers);
2459
2460 rp->process_discovered_references(&g1_is_alive,
2461 &g1_keep_alive,
2462 &g1_drain_mark_stack,
2463 &par_task_executor);
2464
2465 // The work routines of the parallel keep_alive and drain_marking_stack
2466 // will set the has_overflown flag if we overflow the global marking
2467 // stack.
2468 } else {
2469 rp->process_discovered_references(&g1_is_alive,
2470 &g1_keep_alive,
2471 &g1_drain_mark_stack,
2472 NULL);
2473 }
2474
2475 assert(_markStack.overflow() || _markStack.isEmpty(),
2476 "mark stack should be empty (unless it overflowed)");
2477 if (_markStack.overflow()) {
2478 // Should have been done already when we tried to push an
2479 // entry on to the global mark stack. But let's do it again.
2480 set_has_overflown();
2481 }
2482
2483 if (rp->processing_is_mt()) {
2484 assert(rp->num_q() == active_workers, "why not");
2485 rp->enqueue_discovered_references(&par_task_executor);
2486 } else {
2487 rp->enqueue_discovered_references();
2488 }
2489
2490 rp->verify_no_references_recorded();
2491 assert(!rp->discovery_enabled(), "Post condition");
2492 }
2493
2494 // Now clean up stale oops in StringTable
2495 StringTable::unlink(&g1_is_alive);
2496 // Clean up unreferenced symbols in symbol table.
2497 SymbolTable::unlink();
2498 }
2499
2500 void ConcurrentMark::swapMarkBitMaps() {
2501 CMBitMapRO* temp = _prevMarkBitMap;
2502 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2503 _nextMarkBitMap = (CMBitMap*) temp;
2504 }
2505
2506 class CMRemarkTask: public AbstractGangTask {
2507 private:
2508 ConcurrentMark *_cm;
2509
2510 public:
2511 void work(uint worker_id) {
2512 // Since all available tasks are actually started, we should
2513 // only proceed if we're supposed to be actived.
2514 if (worker_id < _cm->active_tasks()) {
2515 CMTask* task = _cm->task(worker_id);
2516 task->record_start_time();
2517 do {
2518 task->do_marking_step(1000000000.0 /* something very large */,
2519 true /* do_stealing */,
2520 true /* do_termination */);
2521 } while (task->has_aborted() && !_cm->has_overflown());
2522 // If we overflow, then we do not want to restart. We instead
2523 // want to abort remark and do concurrent marking again.
2524 task->record_end_time();
2525 }
2526 }
2527
2528 CMRemarkTask(ConcurrentMark* cm, int active_workers) :
2529 AbstractGangTask("Par Remark"), _cm(cm) {
2530 _cm->terminator()->reset_for_reuse(active_workers);
2531 }
2532 };
2533
2534 void ConcurrentMark::checkpointRootsFinalWork() {
2535 ResourceMark rm;
2536 HandleMark hm;
2537 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2538
2539 g1h->ensure_parsability(false);
2540
2541 if (G1CollectedHeap::use_parallel_gc_threads()) {
2542 G1CollectedHeap::StrongRootsScope srs(g1h);
2543 // this is remark, so we'll use up all active threads
2544 uint active_workers = g1h->workers()->active_workers();
2545 if (active_workers == 0) {
2546 assert(active_workers > 0, "Should have been set earlier");
2547 active_workers = (uint) ParallelGCThreads;
2548 g1h->workers()->set_active_workers(active_workers);
2549 }
2550 set_phase(active_workers, false /* concurrent */);
2551 // Leave _parallel_marking_threads at it's
2552 // value originally calculated in the ConcurrentMark
2553 // constructor and pass values of the active workers
2554 // through the gang in the task.
2555
2556 CMRemarkTask remarkTask(this, active_workers);
2557 g1h->set_par_threads(active_workers);
2558 g1h->workers()->run_task(&remarkTask);
2559 g1h->set_par_threads(0);
2560 } else {
2561 G1CollectedHeap::StrongRootsScope srs(g1h);
2562 // this is remark, so we'll use up all available threads
2563 uint active_workers = 1;
2564 set_phase(active_workers, false /* concurrent */);
2565
2566 CMRemarkTask remarkTask(this, active_workers);
2567 // We will start all available threads, even if we decide that the
2568 // active_workers will be fewer. The extra ones will just bail out
2569 // immediately.
2570 remarkTask.work(0);
2571 }
2572 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2573 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
2574
2575 print_stats();
2576
2577 #if VERIFY_OBJS_PROCESSED
2578 if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) {
2579 gclog_or_tty->print_cr("Processed = %d, enqueued = %d.",
2580 _scan_obj_cl.objs_processed,
2581 ThreadLocalObjQueue::objs_enqueued);
2582 guarantee(_scan_obj_cl.objs_processed ==
2583 ThreadLocalObjQueue::objs_enqueued,
2584 "Different number of objs processed and enqueued.");
2585 }
2586 #endif
2587 }
2588
2589 #ifndef PRODUCT
2590
2591 class PrintReachableOopClosure: public OopClosure {
2592 private:
2593 G1CollectedHeap* _g1h;
2594 outputStream* _out;
2595 VerifyOption _vo;
2596 bool _all;
2597
2598 public:
2599 PrintReachableOopClosure(outputStream* out,
2600 VerifyOption vo,
2601 bool all) :
2602 _g1h(G1CollectedHeap::heap()),
2603 _out(out), _vo(vo), _all(all) { }
2604
2605 void do_oop(narrowOop* p) { do_oop_work(p); }
2606 void do_oop( oop* p) { do_oop_work(p); }
2607
2608 template <class T> void do_oop_work(T* p) {
2609 oop obj = oopDesc::load_decode_heap_oop(p);
2610 const char* str = NULL;
2611 const char* str2 = "";
2612
2613 if (obj == NULL) {
2614 str = "";
2615 } else if (!_g1h->is_in_g1_reserved(obj)) {
2616 str = " O";
2617 } else {
2618 HeapRegion* hr = _g1h->heap_region_containing(obj);
2619 guarantee(hr != NULL, "invariant");
2620 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo);
2621 bool marked = _g1h->is_marked(obj, _vo);
2622
2623 if (over_tams) {
2624 str = " >";
2625 if (marked) {
2626 str2 = " AND MARKED";
2627 }
2628 } else if (marked) {
2629 str = " M";
2630 } else {
2631 str = " NOT";
2632 }
2633 }
2634
2635 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2636 p, (void*) obj, str, str2);
2637 }
2638 };
2639
2640 class PrintReachableObjectClosure : public ObjectClosure {
2641 private:
2642 G1CollectedHeap* _g1h;
2643 outputStream* _out;
2644 VerifyOption _vo;
2645 bool _all;
2646 HeapRegion* _hr;
2647
2648 public:
2649 PrintReachableObjectClosure(outputStream* out,
2650 VerifyOption vo,
2651 bool all,
2652 HeapRegion* hr) :
2653 _g1h(G1CollectedHeap::heap()),
2654 _out(out), _vo(vo), _all(all), _hr(hr) { }
2655
2656 void do_object(oop o) {
2657 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo);
2658 bool marked = _g1h->is_marked(o, _vo);
2659 bool print_it = _all || over_tams || marked;
2660
2661 if (print_it) {
2662 _out->print_cr(" "PTR_FORMAT"%s",
2663 o, (over_tams) ? " >" : (marked) ? " M" : "");
2664 PrintReachableOopClosure oopCl(_out, _vo, _all);
2665 o->oop_iterate_no_header(&oopCl);
2666 }
2667 }
2668 };
2669
2670 class PrintReachableRegionClosure : public HeapRegionClosure {
2671 private:
2672 G1CollectedHeap* _g1h;
2673 outputStream* _out;
2674 VerifyOption _vo;
2675 bool _all;
2676
2677 public:
2678 bool doHeapRegion(HeapRegion* hr) {
2679 HeapWord* b = hr->bottom();
2680 HeapWord* e = hr->end();
2681 HeapWord* t = hr->top();
2682 HeapWord* p = _g1h->top_at_mark_start(hr, _vo);
2683 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2684 "TAMS: "PTR_FORMAT, b, e, t, p);
2685 _out->cr();
2686
2687 HeapWord* from = b;
2688 HeapWord* to = t;
2689
2690 if (to > from) {
2691 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2692 _out->cr();
2693 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2694 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2695 _out->cr();
2696 }
2697
2698 return false;
2699 }
2700
2701 PrintReachableRegionClosure(outputStream* out,
2702 VerifyOption vo,
2703 bool all) :
2704 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { }
2705 };
2706
2707 void ConcurrentMark::print_reachable(const char* str,
2708 VerifyOption vo,
2709 bool all) {
2710 gclog_or_tty->cr();
2711 gclog_or_tty->print_cr("== Doing heap dump... ");
2712
2713 if (G1PrintReachableBaseFile == NULL) {
2714 gclog_or_tty->print_cr(" #### error: no base file defined");
2715 return;
2716 }
2717
2718 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2719 (JVM_MAXPATHLEN - 1)) {
2720 gclog_or_tty->print_cr(" #### error: file name too long");
2721 return;
2722 }
2723
2724 char file_name[JVM_MAXPATHLEN];
2725 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2726 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2727
2728 fileStream fout(file_name);
2729 if (!fout.is_open()) {
2730 gclog_or_tty->print_cr(" #### error: could not open file");
2731 return;
2732 }
2733
2734 outputStream* out = &fout;
2735 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo));
2736 out->cr();
2737
2738 out->print_cr("--- ITERATING OVER REGIONS");
2739 out->cr();
2740 PrintReachableRegionClosure rcl(out, vo, all);
2741 _g1h->heap_region_iterate(&rcl);
2742 out->cr();
2743
2744 gclog_or_tty->print_cr(" done");
2745 gclog_or_tty->flush();
2746 }
2747
2748 #endif // PRODUCT
2749
2750 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2751 // Note we are overriding the read-only view of the prev map here, via
2752 // the cast.
2753 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2754 }
2755
2756 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2757 _nextMarkBitMap->clearRange(mr);
2758 }
2759
2760 void ConcurrentMark::clearRangeBothBitmaps(MemRegion mr) {
2761 clearRangePrevBitmap(mr);
2762 clearRangeNextBitmap(mr);
2763 }
2764
2765 HeapRegion*
2766 ConcurrentMark::claim_region(uint worker_id) {
2767 // "checkpoint" the finger
2768 HeapWord* finger = _finger;
2769
2770 // _heap_end will not change underneath our feet; it only changes at
2771 // yield points.
2772 while (finger < _heap_end) {
2773 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2774
2775 // Note on how this code handles humongous regions. In the
2776 // normal case the finger will reach the start of a "starts
2777 // humongous" (SH) region. Its end will either be the end of the
2778 // last "continues humongous" (CH) region in the sequence, or the
2779 // standard end of the SH region (if the SH is the only region in
2780 // the sequence). That way claim_region() will skip over the CH
2781 // regions. However, there is a subtle race between a CM thread
2782 // executing this method and a mutator thread doing a humongous
2783 // object allocation. The two are not mutually exclusive as the CM
2784 // thread does not need to hold the Heap_lock when it gets
2785 // here. So there is a chance that claim_region() will come across
2786 // a free region that's in the progress of becoming a SH or a CH
2787 // region. In the former case, it will either
2788 // a) Miss the update to the region's end, in which case it will
2789 // visit every subsequent CH region, will find their bitmaps
2790 // empty, and do nothing, or
2791 // b) Will observe the update of the region's end (in which case
2792 // it will skip the subsequent CH regions).
2793 // If it comes across a region that suddenly becomes CH, the
2794 // scenario will be similar to b). So, the race between
2795 // claim_region() and a humongous object allocation might force us
2796 // to do a bit of unnecessary work (due to some unnecessary bitmap
2797 // iterations) but it should not introduce and correctness issues.
2798 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2799 HeapWord* bottom = curr_region->bottom();
2800 HeapWord* end = curr_region->end();
2801 HeapWord* limit = curr_region->next_top_at_mark_start();
2802
2803 if (verbose_low()) {
2804 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2805 "["PTR_FORMAT", "PTR_FORMAT"), "
2806 "limit = "PTR_FORMAT,
2807 worker_id, curr_region, bottom, end, limit);
2808 }
2809
2810 // Is the gap between reading the finger and doing the CAS too long?
2811 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2812 if (res == finger) {
2813 // we succeeded
2814
2815 // notice that _finger == end cannot be guaranteed here since,
2816 // someone else might have moved the finger even further
2817 assert(_finger >= end, "the finger should have moved forward");
2818
2819 if (verbose_low()) {
2820 gclog_or_tty->print_cr("[%u] we were successful with region = "
2821 PTR_FORMAT, worker_id, curr_region);
2822 }
2823
2824 if (limit > bottom) {
2825 if (verbose_low()) {
2826 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2827 "returning it ", worker_id, curr_region);
2828 }
2829 return curr_region;
2830 } else {
2831 assert(limit == bottom,
2832 "the region limit should be at bottom");
2833 if (verbose_low()) {
2834 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2835 "returning NULL", worker_id, curr_region);
2836 }
2837 // we return NULL and the caller should try calling
2838 // claim_region() again.
2839 return NULL;
2840 }
2841 } else {
2842 assert(_finger > finger, "the finger should have moved forward");
2843 if (verbose_low()) {
2844 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2845 "global finger = "PTR_FORMAT", "
2846 "our finger = "PTR_FORMAT,
2847 worker_id, _finger, finger);
2848 }
2849
2850 // read it again
2851 finger = _finger;
2852 }
2853 }
2854
2855 return NULL;
2856 }
2857
2858 #ifndef PRODUCT
2859 enum VerifyNoCSetOopsPhase {
2860 VerifyNoCSetOopsStack,
2861 VerifyNoCSetOopsQueues,
2862 VerifyNoCSetOopsSATBCompleted,
2863 VerifyNoCSetOopsSATBThread
2864 };
2865
2866 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2867 private:
2868 G1CollectedHeap* _g1h;
2869 VerifyNoCSetOopsPhase _phase;
2870 int _info;
2871
2872 const char* phase_str() {
2873 switch (_phase) {
2874 case VerifyNoCSetOopsStack: return "Stack";
2875 case VerifyNoCSetOopsQueues: return "Queue";
2876 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2877 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2878 default: ShouldNotReachHere();
2879 }
2880 return NULL;
2881 }
2882
2883 void do_object_work(oop obj) {
2884 guarantee(!_g1h->obj_in_cs(obj),
2885 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2886 (void*) obj, phase_str(), _info));
2887 }
2888
2889 public:
2890 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2891
2892 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2893 _phase = phase;
2894 _info = info;
2895 }
2896
2897 virtual void do_oop(oop* p) {
2898 oop obj = oopDesc::load_decode_heap_oop(p);
2899 do_object_work(obj);
2900 }
2901
2902 virtual void do_oop(narrowOop* p) {
2903 // We should not come across narrow oops while scanning marking
2904 // stacks and SATB buffers.
2905 ShouldNotReachHere();
2906 }
2907
2908 virtual void do_object(oop obj) {
2909 do_object_work(obj);
2910 }
2911 };
2912
2913 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2914 bool verify_enqueued_buffers,
2915 bool verify_thread_buffers,
2916 bool verify_fingers) {
2917 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2918 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2919 return;
2920 }
2921
2922 VerifyNoCSetOopsClosure cl;
2923
2924 if (verify_stacks) {
2925 // Verify entries on the global mark stack
2926 cl.set_phase(VerifyNoCSetOopsStack);
2927 _markStack.oops_do(&cl);
2928
2929 // Verify entries on the task queues
2930 for (uint i = 0; i < _max_worker_id; i += 1) {
2931 cl.set_phase(VerifyNoCSetOopsQueues, i);
2932 CMTaskQueue* queue = _task_queues->queue(i);
2933 queue->oops_do(&cl);
2934 }
2935 }
2936
2937 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2938
2939 // Verify entries on the enqueued SATB buffers
2940 if (verify_enqueued_buffers) {
2941 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2942 satb_qs.iterate_completed_buffers_read_only(&cl);
2943 }
2944
2945 // Verify entries on the per-thread SATB buffers
2946 if (verify_thread_buffers) {
2947 cl.set_phase(VerifyNoCSetOopsSATBThread);
2948 satb_qs.iterate_thread_buffers_read_only(&cl);
2949 }
2950
2951 if (verify_fingers) {
2952 // Verify the global finger
2953 HeapWord* global_finger = finger();
2954 if (global_finger != NULL && global_finger < _heap_end) {
2955 // The global finger always points to a heap region boundary. We
2956 // use heap_region_containing_raw() to get the containing region
2957 // given that the global finger could be pointing to a free region
2958 // which subsequently becomes continues humongous. If that
2959 // happens, heap_region_containing() will return the bottom of the
2960 // corresponding starts humongous region and the check below will
2961 // not hold any more.
2962 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2963 guarantee(global_finger == global_hr->bottom(),
2964 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2965 global_finger, HR_FORMAT_PARAMS(global_hr)));
2966 }
2967
2968 // Verify the task fingers
2969 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2970 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
2971 CMTask* task = _tasks[i];
2972 HeapWord* task_finger = task->finger();
2973 if (task_finger != NULL && task_finger < _heap_end) {
2974 // See above note on the global finger verification.
2975 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2976 guarantee(task_finger == task_hr->bottom() ||
2977 !task_hr->in_collection_set(),
2978 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
2979 task_finger, HR_FORMAT_PARAMS(task_hr)));
2980 }
2981 }
2982 }
2983 }
2984 #endif // PRODUCT
2985
2986 // Aggregate the counting data that was constructed concurrently
2987 // with marking.
2988 class AggregateCountDataHRClosure: public HeapRegionClosure {
2989 G1CollectedHeap* _g1h;
2990 ConcurrentMark* _cm;
2991 CardTableModRefBS* _ct_bs;
2992 BitMap* _cm_card_bm;
2993 uint _max_worker_id;
2994
2995 public:
2996 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2997 BitMap* cm_card_bm,
2998 uint max_worker_id) :
2999 _g1h(g1h), _cm(g1h->concurrent_mark()),
3000 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
3001 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
3002
3003 bool doHeapRegion(HeapRegion* hr) {
3004 if (hr->continuesHumongous()) {
3005 // We will ignore these here and process them when their
3006 // associated "starts humongous" region is processed.
3007 // Note that we cannot rely on their associated
3008 // "starts humongous" region to have their bit set to 1
3009 // since, due to the region chunking in the parallel region
3010 // iteration, a "continues humongous" region might be visited
3011 // before its associated "starts humongous".
3012 return false;
3013 }
3014
3015 HeapWord* start = hr->bottom();
3016 HeapWord* limit = hr->next_top_at_mark_start();
3017 HeapWord* end = hr->end();
3018
3019 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
3020 err_msg("Preconditions not met - "
3021 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
3022 "top: "PTR_FORMAT", end: "PTR_FORMAT,
3023 start, limit, hr->top(), hr->end()));
3024
3025 assert(hr->next_marked_bytes() == 0, "Precondition");
3026
3027 if (start == limit) {
3028 // NTAMS of this region has not been set so nothing to do.
3029 return false;
3030 }
3031
3032 // 'start' should be in the heap.
3033 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
3034 // 'end' *may* be just beyone the end of the heap (if hr is the last region)
3035 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
3036
3037 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
3038 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
3039 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
3040
3041 // If ntams is not card aligned then we bump card bitmap index
3042 // for limit so that we get the all the cards spanned by
3043 // the object ending at ntams.
3044 // Note: if this is the last region in the heap then ntams
3045 // could be actually just beyond the end of the the heap;
3046 // limit_idx will then correspond to a (non-existent) card
3047 // that is also outside the heap.
3048 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
3049 limit_idx += 1;
3050 }
3051
3052 assert(limit_idx <= end_idx, "or else use atomics");
3053
3054 // Aggregate the "stripe" in the count data associated with hr.
3055 uint hrs_index = hr->hrs_index();
3056 size_t marked_bytes = 0;
3057
3058 for (uint i = 0; i < _max_worker_id; i += 1) {
3059 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
3060 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
3061
3062 // Fetch the marked_bytes in this region for task i and
3063 // add it to the running total for this region.
3064 marked_bytes += marked_bytes_array[hrs_index];
3065
3066 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3067 // into the global card bitmap.
3068 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3069
3070 while (scan_idx < limit_idx) {
3071 assert(task_card_bm->at(scan_idx) == true, "should be");
3072 _cm_card_bm->set_bit(scan_idx);
3073 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3074
3075 // BitMap::get_next_one_offset() can handle the case when
3076 // its left_offset parameter is greater than its right_offset
3077 // parameter. It does, however, have an early exit if
3078 // left_offset == right_offset. So let's limit the value
3079 // passed in for left offset here.
3080 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3081 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3082 }
3083 }
3084
3085 // Update the marked bytes for this region.
3086 hr->add_to_marked_bytes(marked_bytes);
3087
3088 // Next heap region
3089 return false;
3090 }
3091 };
3092
3093 class G1AggregateCountDataTask: public AbstractGangTask {
3094 protected:
3095 G1CollectedHeap* _g1h;
3096 ConcurrentMark* _cm;
3097 BitMap* _cm_card_bm;
3098 uint _max_worker_id;
3099 int _active_workers;
3100
3101 public:
3102 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3103 ConcurrentMark* cm,
3104 BitMap* cm_card_bm,
3105 uint max_worker_id,
3106 int n_workers) :
3107 AbstractGangTask("Count Aggregation"),
3108 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3109 _max_worker_id(max_worker_id),
3110 _active_workers(n_workers) { }
3111
3112 void work(uint worker_id) {
3113 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3114
3115 if (G1CollectedHeap::use_parallel_gc_threads()) {
3116 _g1h->heap_region_par_iterate_chunked(&cl, worker_id,
3117 _active_workers,
3118 HeapRegion::AggregateCountClaimValue);
3119 } else {
3120 _g1h->heap_region_iterate(&cl);
3121 }
3122 }
3123 };
3124
3125
3126 void ConcurrentMark::aggregate_count_data() {
3127 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3128 _g1h->workers()->active_workers() :
3129 1);
3130
3131 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3132 _max_worker_id, n_workers);
3133
3134 if (G1CollectedHeap::use_parallel_gc_threads()) {
3135 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3136 "sanity check");
3137 _g1h->set_par_threads(n_workers);
3138 _g1h->workers()->run_task(&g1_par_agg_task);
3139 _g1h->set_par_threads(0);
3140
3141 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue),
3142 "sanity check");
3143 _g1h->reset_heap_region_claim_values();
3144 } else {
3145 g1_par_agg_task.work(0);
3146 }
3147 }
3148
3149 // Clear the per-worker arrays used to store the per-region counting data
3150 void ConcurrentMark::clear_all_count_data() {
3151 // Clear the global card bitmap - it will be filled during
3152 // liveness count aggregation (during remark) and the
3153 // final counting task.
3154 _card_bm.clear();
3155
3156 // Clear the global region bitmap - it will be filled as part
3157 // of the final counting task.
3158 _region_bm.clear();
3159
3160 uint max_regions = _g1h->max_regions();
3161 assert(_max_worker_id > 0, "uninitialized");
3162
3163 for (uint i = 0; i < _max_worker_id; i += 1) {
3164 BitMap* task_card_bm = count_card_bitmap_for(i);
3165 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3166
3167 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3168 assert(marked_bytes_array != NULL, "uninitialized");
3169
3170 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3171 task_card_bm->clear();
3172 }
3173 }
3174
3175 void ConcurrentMark::print_stats() {
3176 if (verbose_stats()) {
3177 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3178 for (size_t i = 0; i < _active_tasks; ++i) {
3179 _tasks[i]->print_stats();
3180 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3181 }
3182 }
3183 }
3184
3185 // abandon current marking iteration due to a Full GC
3186 void ConcurrentMark::abort() {
3187 // Clear all marks to force marking thread to do nothing
3188 _nextMarkBitMap->clearAll();
3189
3190 // Note we cannot clear the previous marking bitmap here
3191 // since VerifyDuringGC verifies the objects marked during
3192 // a full GC against the previous bitmap.
3193
3194 // Clear the liveness counting data
3195 clear_all_count_data();
3196 // Empty mark stack
3197 reset_marking_state();
3198 for (uint i = 0; i < _max_worker_id; ++i) {
3199 _tasks[i]->clear_region_fields();
3200 }
3201 _has_aborted = true;
3202
3203 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3204 satb_mq_set.abandon_partial_marking();
3205 // This can be called either during or outside marking, we'll read
3206 // the expected_active value from the SATB queue set.
3207 satb_mq_set.set_active_all_threads(
3208 false, /* new active value */
3209 satb_mq_set.is_active() /* expected_active */);
3210 }
3211
3212 static void print_ms_time_info(const char* prefix, const char* name,
3213 NumberSeq& ns) {
3214 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3215 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3216 if (ns.num() > 0) {
3217 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3218 prefix, ns.sd(), ns.maximum());
3219 }
3220 }
3221
3222 void ConcurrentMark::print_summary_info() {
3223 gclog_or_tty->print_cr(" Concurrent marking:");
3224 print_ms_time_info(" ", "init marks", _init_times);
3225 print_ms_time_info(" ", "remarks", _remark_times);
3226 {
3227 print_ms_time_info(" ", "final marks", _remark_mark_times);
3228 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3229
3230 }
3231 print_ms_time_info(" ", "cleanups", _cleanup_times);
3232 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3233 _total_counting_time,
3234 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3235 (double)_cleanup_times.num()
3236 : 0.0));
3237 if (G1ScrubRemSets) {
3238 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3239 _total_rs_scrub_time,
3240 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3241 (double)_cleanup_times.num()
3242 : 0.0));
3243 }
3244 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3245 (_init_times.sum() + _remark_times.sum() +
3246 _cleanup_times.sum())/1000.0);
3247 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3248 "(%8.2f s marking).",
3249 cmThread()->vtime_accum(),
3250 cmThread()->vtime_mark_accum());
3251 }
3252
3253 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3254 _parallel_workers->print_worker_threads_on(st);
3255 }
3256
3257 // We take a break if someone is trying to stop the world.
3258 bool ConcurrentMark::do_yield_check(uint worker_id) {
3259 if (should_yield()) {
3260 if (worker_id == 0) {
3261 _g1h->g1_policy()->record_concurrent_pause();
3262 }
3263 cmThread()->yield();
3264 return true;
3265 } else {
3266 return false;
3267 }
3268 }
3269
3270 bool ConcurrentMark::should_yield() {
3271 return cmThread()->should_yield();
3272 }
3273
3274 bool ConcurrentMark::containing_card_is_marked(void* p) {
3275 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3276 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3277 }
3278
3279 bool ConcurrentMark::containing_cards_are_marked(void* start,
3280 void* last) {
3281 return containing_card_is_marked(start) &&
3282 containing_card_is_marked(last);
3283 }
3284
3285 #ifndef PRODUCT
3286 // for debugging purposes
3287 void ConcurrentMark::print_finger() {
3288 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3289 _heap_start, _heap_end, _finger);
3290 for (uint i = 0; i < _max_worker_id; ++i) {
3291 gclog_or_tty->print(" %u: "PTR_FORMAT, i, _tasks[i]->finger());
3292 }
3293 gclog_or_tty->print_cr("");
3294 }
3295 #endif
3296
3297 void CMTask::scan_object(oop obj) {
3298 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3299
3300 if (_cm->verbose_high()) {
3301 gclog_or_tty->print_cr("[%u] we're scanning object "PTR_FORMAT,
3302 _worker_id, (void*) obj);
3303 }
3304
3305 size_t obj_size = obj->size();
3306 _words_scanned += obj_size;
3307
3308 obj->oop_iterate(_cm_oop_closure);
3309 statsOnly( ++_objs_scanned );
3310 check_limits();
3311 }
3312
3313 // Closure for iteration over bitmaps
3314 class CMBitMapClosure : public BitMapClosure {
3315 private:
3316 // the bitmap that is being iterated over
3317 CMBitMap* _nextMarkBitMap;
3318 ConcurrentMark* _cm;
3319 CMTask* _task;
3320
3321 public:
3322 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3323 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3324
3325 bool do_bit(size_t offset) {
3326 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3327 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3328 assert( addr < _cm->finger(), "invariant");
3329
3330 statsOnly( _task->increase_objs_found_on_bitmap() );
3331 assert(addr >= _task->finger(), "invariant");
3332
3333 // We move that task's local finger along.
3334 _task->move_finger_to(addr);
3335
3336 _task->scan_object(oop(addr));
3337 // we only partially drain the local queue and global stack
3338 _task->drain_local_queue(true);
3339 _task->drain_global_stack(true);
3340
3341 // if the has_aborted flag has been raised, we need to bail out of
3342 // the iteration
3343 return !_task->has_aborted();
3344 }
3345 };
3346
3347 // Closure for iterating over objects, currently only used for
3348 // processing SATB buffers.
3349 class CMObjectClosure : public ObjectClosure {
3350 private:
3351 CMTask* _task;
3352
3353 public:
3354 void do_object(oop obj) {
3355 _task->deal_with_reference(obj);
3356 }
3357
3358 CMObjectClosure(CMTask* task) : _task(task) { }
3359 };
3360
3361 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3362 ConcurrentMark* cm,
3363 CMTask* task)
3364 : _g1h(g1h), _cm(cm), _task(task) {
3365 assert(_ref_processor == NULL, "should be initialized to NULL");
3366
3367 if (G1UseConcMarkReferenceProcessing) {
3368 _ref_processor = g1h->ref_processor_cm();
3369 assert(_ref_processor != NULL, "should not be NULL");
3370 }
3371 }
3372
3373 void CMTask::setup_for_region(HeapRegion* hr) {
3374 // Separated the asserts so that we know which one fires.
3375 assert(hr != NULL,
3376 "claim_region() should have filtered out continues humongous regions");
3377 assert(!hr->continuesHumongous(),
3378 "claim_region() should have filtered out continues humongous regions");
3379
3380 if (_cm->verbose_low()) {
3381 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3382 _worker_id, hr);
3383 }
3384
3385 _curr_region = hr;
3386 _finger = hr->bottom();
3387 update_region_limit();
3388 }
3389
3390 void CMTask::update_region_limit() {
3391 HeapRegion* hr = _curr_region;
3392 HeapWord* bottom = hr->bottom();
3393 HeapWord* limit = hr->next_top_at_mark_start();
3394
3395 if (limit == bottom) {
3396 if (_cm->verbose_low()) {
3397 gclog_or_tty->print_cr("[%u] found an empty region "
3398 "["PTR_FORMAT", "PTR_FORMAT")",
3399 _worker_id, bottom, limit);
3400 }
3401 // The region was collected underneath our feet.
3402 // We set the finger to bottom to ensure that the bitmap
3403 // iteration that will follow this will not do anything.
3404 // (this is not a condition that holds when we set the region up,
3405 // as the region is not supposed to be empty in the first place)
3406 _finger = bottom;
3407 } else if (limit >= _region_limit) {
3408 assert(limit >= _finger, "peace of mind");
3409 } else {
3410 assert(limit < _region_limit, "only way to get here");
3411 // This can happen under some pretty unusual circumstances. An
3412 // evacuation pause empties the region underneath our feet (NTAMS
3413 // at bottom). We then do some allocation in the region (NTAMS
3414 // stays at bottom), followed by the region being used as a GC
3415 // alloc region (NTAMS will move to top() and the objects
3416 // originally below it will be grayed). All objects now marked in
3417 // the region are explicitly grayed, if below the global finger,
3418 // and we do not need in fact to scan anything else. So, we simply
3419 // set _finger to be limit to ensure that the bitmap iteration
3420 // doesn't do anything.
3421 _finger = limit;
3422 }
3423
3424 _region_limit = limit;
3425 }
3426
3427 void CMTask::giveup_current_region() {
3428 assert(_curr_region != NULL, "invariant");
3429 if (_cm->verbose_low()) {
3430 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3431 _worker_id, _curr_region);
3432 }
3433 clear_region_fields();
3434 }
3435
3436 void CMTask::clear_region_fields() {
3437 // Values for these three fields that indicate that we're not
3438 // holding on to a region.
3439 _curr_region = NULL;
3440 _finger = NULL;
3441 _region_limit = NULL;
3442 }
3443
3444 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3445 if (cm_oop_closure == NULL) {
3446 assert(_cm_oop_closure != NULL, "invariant");
3447 } else {
3448 assert(_cm_oop_closure == NULL, "invariant");
3449 }
3450 _cm_oop_closure = cm_oop_closure;
3451 }
3452
3453 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3454 guarantee(nextMarkBitMap != NULL, "invariant");
3455
3456 if (_cm->verbose_low()) {
3457 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3458 }
3459
3460 _nextMarkBitMap = nextMarkBitMap;
3461 clear_region_fields();
3462
3463 _calls = 0;
3464 _elapsed_time_ms = 0.0;
3465 _termination_time_ms = 0.0;
3466 _termination_start_time_ms = 0.0;
3467
3468 #if _MARKING_STATS_
3469 _local_pushes = 0;
3470 _local_pops = 0;
3471 _local_max_size = 0;
3472 _objs_scanned = 0;
3473 _global_pushes = 0;
3474 _global_pops = 0;
3475 _global_max_size = 0;
3476 _global_transfers_to = 0;
3477 _global_transfers_from = 0;
3478 _regions_claimed = 0;
3479 _objs_found_on_bitmap = 0;
3480 _satb_buffers_processed = 0;
3481 _steal_attempts = 0;
3482 _steals = 0;
3483 _aborted = 0;
3484 _aborted_overflow = 0;
3485 _aborted_cm_aborted = 0;
3486 _aborted_yield = 0;
3487 _aborted_timed_out = 0;
3488 _aborted_satb = 0;
3489 _aborted_termination = 0;
3490 #endif // _MARKING_STATS_
3491 }
3492
3493 bool CMTask::should_exit_termination() {
3494 regular_clock_call();
3495 // This is called when we are in the termination protocol. We should
3496 // quit if, for some reason, this task wants to abort or the global
3497 // stack is not empty (this means that we can get work from it).
3498 return !_cm->mark_stack_empty() || has_aborted();
3499 }
3500
3501 void CMTask::reached_limit() {
3502 assert(_words_scanned >= _words_scanned_limit ||
3503 _refs_reached >= _refs_reached_limit ,
3504 "shouldn't have been called otherwise");
3505 regular_clock_call();
3506 }
3507
3508 void CMTask::regular_clock_call() {
3509 if (has_aborted()) return;
3510
3511 // First, we need to recalculate the words scanned and refs reached
3512 // limits for the next clock call.
3513 recalculate_limits();
3514
3515 // During the regular clock call we do the following
3516
3517 // (1) If an overflow has been flagged, then we abort.
3518 if (_cm->has_overflown()) {
3519 set_has_aborted();
3520 return;
3521 }
3522
3523 // If we are not concurrent (i.e. we're doing remark) we don't need
3524 // to check anything else. The other steps are only needed during
3525 // the concurrent marking phase.
3526 if (!concurrent()) return;
3527
3528 // (2) If marking has been aborted for Full GC, then we also abort.
3529 if (_cm->has_aborted()) {
3530 set_has_aborted();
3531 statsOnly( ++_aborted_cm_aborted );
3532 return;
3533 }
3534
3535 double curr_time_ms = os::elapsedVTime() * 1000.0;
3536
3537 // (3) If marking stats are enabled, then we update the step history.
3538 #if _MARKING_STATS_
3539 if (_words_scanned >= _words_scanned_limit) {
3540 ++_clock_due_to_scanning;
3541 }
3542 if (_refs_reached >= _refs_reached_limit) {
3543 ++_clock_due_to_marking;
3544 }
3545
3546 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3547 _interval_start_time_ms = curr_time_ms;
3548 _all_clock_intervals_ms.add(last_interval_ms);
3549
3550 if (_cm->verbose_medium()) {
3551 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3552 "scanned = %d%s, refs reached = %d%s",
3553 _worker_id, last_interval_ms,
3554 _words_scanned,
3555 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3556 _refs_reached,
3557 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3558 }
3559 #endif // _MARKING_STATS_
3560
3561 // (4) We check whether we should yield. If we have to, then we abort.
3562 if (_cm->should_yield()) {
3563 // We should yield. To do this we abort the task. The caller is
3564 // responsible for yielding.
3565 set_has_aborted();
3566 statsOnly( ++_aborted_yield );
3567 return;
3568 }
3569
3570 // (5) We check whether we've reached our time quota. If we have,
3571 // then we abort.
3572 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3573 if (elapsed_time_ms > _time_target_ms) {
3574 set_has_aborted();
3575 _has_timed_out = true;
3576 statsOnly( ++_aborted_timed_out );
3577 return;
3578 }
3579
3580 // (6) Finally, we check whether there are enough completed STAB
3581 // buffers available for processing. If there are, we abort.
3582 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3583 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3584 if (_cm->verbose_low()) {
3585 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3586 _worker_id);
3587 }
3588 // we do need to process SATB buffers, we'll abort and restart
3589 // the marking task to do so
3590 set_has_aborted();
3591 statsOnly( ++_aborted_satb );
3592 return;
3593 }
3594 }
3595
3596 void CMTask::recalculate_limits() {
3597 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3598 _words_scanned_limit = _real_words_scanned_limit;
3599
3600 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3601 _refs_reached_limit = _real_refs_reached_limit;
3602 }
3603
3604 void CMTask::decrease_limits() {
3605 // This is called when we believe that we're going to do an infrequent
3606 // operation which will increase the per byte scanned cost (i.e. move
3607 // entries to/from the global stack). It basically tries to decrease the
3608 // scanning limit so that the clock is called earlier.
3609
3610 if (_cm->verbose_medium()) {
3611 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3612 }
3613
3614 _words_scanned_limit = _real_words_scanned_limit -
3615 3 * words_scanned_period / 4;
3616 _refs_reached_limit = _real_refs_reached_limit -
3617 3 * refs_reached_period / 4;
3618 }
3619
3620 void CMTask::move_entries_to_global_stack() {
3621 // local array where we'll store the entries that will be popped
3622 // from the local queue
3623 oop buffer[global_stack_transfer_size];
3624
3625 int n = 0;
3626 oop obj;
3627 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3628 buffer[n] = obj;
3629 ++n;
3630 }
3631
3632 if (n > 0) {
3633 // we popped at least one entry from the local queue
3634
3635 statsOnly( ++_global_transfers_to; _local_pops += n );
3636
3637 if (!_cm->mark_stack_push(buffer, n)) {
3638 if (_cm->verbose_low()) {
3639 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3640 _worker_id);
3641 }
3642 set_has_aborted();
3643 } else {
3644 // the transfer was successful
3645
3646 if (_cm->verbose_medium()) {
3647 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3648 _worker_id, n);
3649 }
3650 statsOnly( int tmp_size = _cm->mark_stack_size();
3651 if (tmp_size > _global_max_size) {
3652 _global_max_size = tmp_size;
3653 }
3654 _global_pushes += n );
3655 }
3656 }
3657
3658 // this operation was quite expensive, so decrease the limits
3659 decrease_limits();
3660 }
3661
3662 void CMTask::get_entries_from_global_stack() {
3663 // local array where we'll store the entries that will be popped
3664 // from the global stack.
3665 oop buffer[global_stack_transfer_size];
3666 int n;
3667 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3668 assert(n <= global_stack_transfer_size,
3669 "we should not pop more than the given limit");
3670 if (n > 0) {
3671 // yes, we did actually pop at least one entry
3672
3673 statsOnly( ++_global_transfers_from; _global_pops += n );
3674 if (_cm->verbose_medium()) {
3675 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3676 _worker_id, n);
3677 }
3678 for (int i = 0; i < n; ++i) {
3679 bool success = _task_queue->push(buffer[i]);
3680 // We only call this when the local queue is empty or under a
3681 // given target limit. So, we do not expect this push to fail.
3682 assert(success, "invariant");
3683 }
3684
3685 statsOnly( int tmp_size = _task_queue->size();
3686 if (tmp_size > _local_max_size) {
3687 _local_max_size = tmp_size;
3688 }
3689 _local_pushes += n );
3690 }
3691
3692 // this operation was quite expensive, so decrease the limits
3693 decrease_limits();
3694 }
3695
3696 void CMTask::drain_local_queue(bool partially) {
3697 if (has_aborted()) return;
3698
3699 // Decide what the target size is, depending whether we're going to
3700 // drain it partially (so that other tasks can steal if they run out
3701 // of things to do) or totally (at the very end).
3702 size_t target_size;
3703 if (partially) {
3704 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3705 } else {
3706 target_size = 0;
3707 }
3708
3709 if (_task_queue->size() > target_size) {
3710 if (_cm->verbose_high()) {
3711 gclog_or_tty->print_cr("[%u] draining local queue, target size = %d",
3712 _worker_id, target_size);
3713 }
3714
3715 oop obj;
3716 bool ret = _task_queue->pop_local(obj);
3717 while (ret) {
3718 statsOnly( ++_local_pops );
3719
3720 if (_cm->verbose_high()) {
3721 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3722 (void*) obj);
3723 }
3724
3725 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3726 assert(!_g1h->is_on_master_free_list(
3727 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3728
3729 scan_object(obj);
3730
3731 if (_task_queue->size() <= target_size || has_aborted()) {
3732 ret = false;
3733 } else {
3734 ret = _task_queue->pop_local(obj);
3735 }
3736 }
3737
3738 if (_cm->verbose_high()) {
3739 gclog_or_tty->print_cr("[%u] drained local queue, size = %d",
3740 _worker_id, _task_queue->size());
3741 }
3742 }
3743 }
3744
3745 void CMTask::drain_global_stack(bool partially) {
3746 if (has_aborted()) return;
3747
3748 // We have a policy to drain the local queue before we attempt to
3749 // drain the global stack.
3750 assert(partially || _task_queue->size() == 0, "invariant");
3751
3752 // Decide what the target size is, depending whether we're going to
3753 // drain it partially (so that other tasks can steal if they run out
3754 // of things to do) or totally (at the very end). Notice that,
3755 // because we move entries from the global stack in chunks or
3756 // because another task might be doing the same, we might in fact
3757 // drop below the target. But, this is not a problem.
3758 size_t target_size;
3759 if (partially) {
3760 target_size = _cm->partial_mark_stack_size_target();
3761 } else {
3762 target_size = 0;
3763 }
3764
3765 if (_cm->mark_stack_size() > target_size) {
3766 if (_cm->verbose_low()) {
3767 gclog_or_tty->print_cr("[%u] draining global_stack, target size %d",
3768 _worker_id, target_size);
3769 }
3770
3771 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3772 get_entries_from_global_stack();
3773 drain_local_queue(partially);
3774 }
3775
3776 if (_cm->verbose_low()) {
3777 gclog_or_tty->print_cr("[%u] drained global stack, size = %d",
3778 _worker_id, _cm->mark_stack_size());
3779 }
3780 }
3781 }
3782
3783 // SATB Queue has several assumptions on whether to call the par or
3784 // non-par versions of the methods. this is why some of the code is
3785 // replicated. We should really get rid of the single-threaded version
3786 // of the code to simplify things.
3787 void CMTask::drain_satb_buffers() {
3788 if (has_aborted()) return;
3789
3790 // We set this so that the regular clock knows that we're in the
3791 // middle of draining buffers and doesn't set the abort flag when it
3792 // notices that SATB buffers are available for draining. It'd be
3793 // very counter productive if it did that. :-)
3794 _draining_satb_buffers = true;
3795
3796 CMObjectClosure oc(this);
3797 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3798 if (G1CollectedHeap::use_parallel_gc_threads()) {
3799 satb_mq_set.set_par_closure(_worker_id, &oc);
3800 } else {
3801 satb_mq_set.set_closure(&oc);
3802 }
3803
3804 // This keeps claiming and applying the closure to completed buffers
3805 // until we run out of buffers or we need to abort.
3806 if (G1CollectedHeap::use_parallel_gc_threads()) {
3807 while (!has_aborted() &&
3808 satb_mq_set.par_apply_closure_to_completed_buffer(_worker_id)) {
3809 if (_cm->verbose_medium()) {
3810 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3811 }
3812 statsOnly( ++_satb_buffers_processed );
3813 regular_clock_call();
3814 }
3815 } else {
3816 while (!has_aborted() &&
3817 satb_mq_set.apply_closure_to_completed_buffer()) {
3818 if (_cm->verbose_medium()) {
3819 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3820 }
3821 statsOnly( ++_satb_buffers_processed );
3822 regular_clock_call();
3823 }
3824 }
3825
3826 if (!concurrent() && !has_aborted()) {
3827 // We should only do this during remark.
3828 if (G1CollectedHeap::use_parallel_gc_threads()) {
3829 satb_mq_set.par_iterate_closure_all_threads(_worker_id);
3830 } else {
3831 satb_mq_set.iterate_closure_all_threads();
3832 }
3833 }
3834
3835 _draining_satb_buffers = false;
3836
3837 assert(has_aborted() ||
3838 concurrent() ||
3839 satb_mq_set.completed_buffers_num() == 0, "invariant");
3840
3841 if (G1CollectedHeap::use_parallel_gc_threads()) {
3842 satb_mq_set.set_par_closure(_worker_id, NULL);
3843 } else {
3844 satb_mq_set.set_closure(NULL);
3845 }
3846
3847 // again, this was a potentially expensive operation, decrease the
3848 // limits to get the regular clock call early
3849 decrease_limits();
3850 }
3851
3852 void CMTask::print_stats() {
3853 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3854 _worker_id, _calls);
3855 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3856 _elapsed_time_ms, _termination_time_ms);
3857 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3858 _step_times_ms.num(), _step_times_ms.avg(),
3859 _step_times_ms.sd());
3860 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3861 _step_times_ms.maximum(), _step_times_ms.sum());
3862
3863 #if _MARKING_STATS_
3864 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3865 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3866 _all_clock_intervals_ms.sd());
3867 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3868 _all_clock_intervals_ms.maximum(),
3869 _all_clock_intervals_ms.sum());
3870 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3871 _clock_due_to_scanning, _clock_due_to_marking);
3872 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3873 _objs_scanned, _objs_found_on_bitmap);
3874 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3875 _local_pushes, _local_pops, _local_max_size);
3876 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3877 _global_pushes, _global_pops, _global_max_size);
3878 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3879 _global_transfers_to,_global_transfers_from);
3880 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed);
3881 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3882 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3883 _steal_attempts, _steals);
3884 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3885 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3886 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3887 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3888 _aborted_timed_out, _aborted_satb, _aborted_termination);
3889 #endif // _MARKING_STATS_
3890 }
3891
3892 /*****************************************************************************
3893
3894 The do_marking_step(time_target_ms) method is the building block
3895 of the parallel marking framework. It can be called in parallel
3896 with other invocations of do_marking_step() on different tasks
3897 (but only one per task, obviously) and concurrently with the
3898 mutator threads, or during remark, hence it eliminates the need
3899 for two versions of the code. When called during remark, it will
3900 pick up from where the task left off during the concurrent marking
3901 phase. Interestingly, tasks are also claimable during evacuation
3902 pauses too, since do_marking_step() ensures that it aborts before
3903 it needs to yield.
3904
3905 The data structures that is uses to do marking work are the
3906 following:
3907
3908 (1) Marking Bitmap. If there are gray objects that appear only
3909 on the bitmap (this happens either when dealing with an overflow
3910 or when the initial marking phase has simply marked the roots
3911 and didn't push them on the stack), then tasks claim heap
3912 regions whose bitmap they then scan to find gray objects. A
3913 global finger indicates where the end of the last claimed region
3914 is. A local finger indicates how far into the region a task has
3915 scanned. The two fingers are used to determine how to gray an
3916 object (i.e. whether simply marking it is OK, as it will be
3917 visited by a task in the future, or whether it needs to be also
3918 pushed on a stack).
3919
3920 (2) Local Queue. The local queue of the task which is accessed
3921 reasonably efficiently by the task. Other tasks can steal from
3922 it when they run out of work. Throughout the marking phase, a
3923 task attempts to keep its local queue short but not totally
3924 empty, so that entries are available for stealing by other
3925 tasks. Only when there is no more work, a task will totally
3926 drain its local queue.
3927
3928 (3) Global Mark Stack. This handles local queue overflow. During
3929 marking only sets of entries are moved between it and the local
3930 queues, as access to it requires a mutex and more fine-grain
3931 interaction with it which might cause contention. If it
3932 overflows, then the marking phase should restart and iterate
3933 over the bitmap to identify gray objects. Throughout the marking
3934 phase, tasks attempt to keep the global mark stack at a small
3935 length but not totally empty, so that entries are available for
3936 popping by other tasks. Only when there is no more work, tasks
3937 will totally drain the global mark stack.
3938
3939 (4) SATB Buffer Queue. This is where completed SATB buffers are
3940 made available. Buffers are regularly removed from this queue
3941 and scanned for roots, so that the queue doesn't get too
3942 long. During remark, all completed buffers are processed, as
3943 well as the filled in parts of any uncompleted buffers.
3944
3945 The do_marking_step() method tries to abort when the time target
3946 has been reached. There are a few other cases when the
3947 do_marking_step() method also aborts:
3948
3949 (1) When the marking phase has been aborted (after a Full GC).
3950
3951 (2) When a global overflow (on the global stack) has been
3952 triggered. Before the task aborts, it will actually sync up with
3953 the other tasks to ensure that all the marking data structures
3954 (local queues, stacks, fingers etc.) are re-initialised so that
3955 when do_marking_step() completes, the marking phase can
3956 immediately restart.
3957
3958 (3) When enough completed SATB buffers are available. The
3959 do_marking_step() method only tries to drain SATB buffers right
3960 at the beginning. So, if enough buffers are available, the
3961 marking step aborts and the SATB buffers are processed at
3962 the beginning of the next invocation.
3963
3964 (4) To yield. when we have to yield then we abort and yield
3965 right at the end of do_marking_step(). This saves us from a lot
3966 of hassle as, by yielding we might allow a Full GC. If this
3967 happens then objects will be compacted underneath our feet, the
3968 heap might shrink, etc. We save checking for this by just
3969 aborting and doing the yield right at the end.
3970
3971 From the above it follows that the do_marking_step() method should
3972 be called in a loop (or, otherwise, regularly) until it completes.
3973
3974 If a marking step completes without its has_aborted() flag being
3975 true, it means it has completed the current marking phase (and
3976 also all other marking tasks have done so and have all synced up).
3977
3978 A method called regular_clock_call() is invoked "regularly" (in
3979 sub ms intervals) throughout marking. It is this clock method that
3980 checks all the abort conditions which were mentioned above and
3981 decides when the task should abort. A work-based scheme is used to
3982 trigger this clock method: when the number of object words the
3983 marking phase has scanned or the number of references the marking
3984 phase has visited reach a given limit. Additional invocations to
3985 the method clock have been planted in a few other strategic places
3986 too. The initial reason for the clock method was to avoid calling
3987 vtime too regularly, as it is quite expensive. So, once it was in
3988 place, it was natural to piggy-back all the other conditions on it
3989 too and not constantly check them throughout the code.
3990
3991 *****************************************************************************/
3992
3993 void CMTask::do_marking_step(double time_target_ms,
3994 bool do_stealing,
3995 bool do_termination) {
3996 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3997 assert(concurrent() == _cm->concurrent(), "they should be the same");
3998
3999 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
4000 assert(_task_queues != NULL, "invariant");
4001 assert(_task_queue != NULL, "invariant");
4002 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
4003
4004 assert(!_claimed,
4005 "only one thread should claim this task at any one time");
4006
4007 // OK, this doesn't safeguard again all possible scenarios, as it is
4008 // possible for two threads to set the _claimed flag at the same
4009 // time. But it is only for debugging purposes anyway and it will
4010 // catch most problems.
4011 _claimed = true;
4012
4013 _start_time_ms = os::elapsedVTime() * 1000.0;
4014 statsOnly( _interval_start_time_ms = _start_time_ms );
4015
4016 double diff_prediction_ms =
4017 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
4018 _time_target_ms = time_target_ms - diff_prediction_ms;
4019
4020 // set up the variables that are used in the work-based scheme to
4021 // call the regular clock method
4022 _words_scanned = 0;
4023 _refs_reached = 0;
4024 recalculate_limits();
4025
4026 // clear all flags
4027 clear_has_aborted();
4028 _has_timed_out = false;
4029 _draining_satb_buffers = false;
4030
4031 ++_calls;
4032
4033 if (_cm->verbose_low()) {
4034 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
4035 "target = %1.2lfms >>>>>>>>>>",
4036 _worker_id, _calls, _time_target_ms);
4037 }
4038
4039 // Set up the bitmap and oop closures. Anything that uses them is
4040 // eventually called from this method, so it is OK to allocate these
4041 // statically.
4042 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4043 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4044 set_cm_oop_closure(&cm_oop_closure);
4045
4046 if (_cm->has_overflown()) {
4047 // This can happen if the mark stack overflows during a GC pause
4048 // and this task, after a yield point, restarts. We have to abort
4049 // as we need to get into the overflow protocol which happens
4050 // right at the end of this task.
4051 set_has_aborted();
4052 }
4053
4054 // First drain any available SATB buffers. After this, we will not
4055 // look at SATB buffers before the next invocation of this method.
4056 // If enough completed SATB buffers are queued up, the regular clock
4057 // will abort this task so that it restarts.
4058 drain_satb_buffers();
4059 // ...then partially drain the local queue and the global stack
4060 drain_local_queue(true);
4061 drain_global_stack(true);
4062
4063 do {
4064 if (!has_aborted() && _curr_region != NULL) {
4065 // This means that we're already holding on to a region.
4066 assert(_finger != NULL, "if region is not NULL, then the finger "
4067 "should not be NULL either");
4068
4069 // We might have restarted this task after an evacuation pause
4070 // which might have evacuated the region we're holding on to
4071 // underneath our feet. Let's read its limit again to make sure
4072 // that we do not iterate over a region of the heap that
4073 // contains garbage (update_region_limit() will also move
4074 // _finger to the start of the region if it is found empty).
4075 update_region_limit();
4076 // We will start from _finger not from the start of the region,
4077 // as we might be restarting this task after aborting half-way
4078 // through scanning this region. In this case, _finger points to
4079 // the address where we last found a marked object. If this is a
4080 // fresh region, _finger points to start().
4081 MemRegion mr = MemRegion(_finger, _region_limit);
4082
4083 if (_cm->verbose_low()) {
4084 gclog_or_tty->print_cr("[%u] we're scanning part "
4085 "["PTR_FORMAT", "PTR_FORMAT") "
4086 "of region "PTR_FORMAT,
4087 _worker_id, _finger, _region_limit, _curr_region);
4088 }
4089
4090 // Let's iterate over the bitmap of the part of the
4091 // region that is left.
4092 if (mr.is_empty() || _nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4093 // We successfully completed iterating over the region. Now,
4094 // let's give up the region.
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->nextWord(_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 }