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
1264 G1CollectorPolicy* g1p = g1h->g1_policy();
1265 g1p->record_concurrent_mark_remark_start();
1266
1267 double start = os::elapsedTime();
1268
1269 checkpointRootsFinalWork();
1270
1271 double mark_work_end = os::elapsedTime();
1272
1273 weakRefsWork(clear_all_soft_refs);
1274
1275 if (has_overflown()) {
1276 // Oops. We overflowed. Restart concurrent marking.
1277 _restart_for_overflow = true;
1278 // Clear the marking state because we will be restarting
1279 // marking due to overflowing the global mark stack.
1280 reset_marking_state();
1281 if (G1TraceMarkStackOverflow) {
1282 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1283 }
1284 } else {
1285 // Aggregate the per-task counting data that we have accumulated
1286 // while marking.
1287 aggregate_count_data();
1288
1289 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1290 // We're done with marking.
1291 // This is the end of the marking cycle, we're expected all
1292 // threads to have SATB queues with active set to true.
1293 satb_mq_set.set_active_all_threads(false, /* new active value */
1294 true /* expected_active */);
1295
1296 if (VerifyDuringGC) {
1297 HandleMark hm; // handle scope
1298 gclog_or_tty->print(" VerifyDuringGC:(after)");
1299 Universe::heap()->prepare_for_verify();
1300 Universe::verify(/* silent */ false,
1301 /* option */ VerifyOption_G1UseNextMarking);
1302 }
1303 assert(!restart_for_overflow(), "sanity");
1304 // Completely reset the marking state since marking completed
1305 set_non_marking_state();
1306 }
1307
1308 // Expand the marking stack, if we have to and if we can.
1309 if (_markStack.should_expand()) {
1310 _markStack.expand();
1311 }
1312
1313 #if VERIFY_OBJS_PROCESSED
1314 _scan_obj_cl.objs_processed = 0;
1315 ThreadLocalObjQueue::objs_enqueued = 0;
1316 #endif
1317
1318 // Statistics
1319 double now = os::elapsedTime();
1320 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1321 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1322 _remark_times.add((now - start) * 1000.0);
1323
1324 g1p->record_concurrent_mark_remark_end();
1325 }
1326
1327 // Base class of the closures that finalize and verify the
1328 // liveness counting data.
1329 class CMCountDataClosureBase: public HeapRegionClosure {
1330 protected:
1331 G1CollectedHeap* _g1h;
1332 ConcurrentMark* _cm;
1333 CardTableModRefBS* _ct_bs;
1334
1335 BitMap* _region_bm;
1336 BitMap* _card_bm;
1337
1338 // Takes a region that's not empty (i.e., it has at least one
1339 // live object in it and sets its corresponding bit on the region
1340 // bitmap to 1. If the region is "starts humongous" it will also set
1341 // to 1 the bits on the region bitmap that correspond to its
1342 // associated "continues humongous" regions.
1343 void set_bit_for_region(HeapRegion* hr) {
1344 assert(!hr->continuesHumongous(), "should have filtered those out");
1345
1346 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1347 if (!hr->startsHumongous()) {
1348 // Normal (non-humongous) case: just set the bit.
1349 _region_bm->par_at_put(index, true);
1350 } else {
1351 // Starts humongous case: calculate how many regions are part of
1352 // this humongous region and then set the bit range.
1353 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1354 _region_bm->par_at_put_range(index, end_index, true);
1355 }
1356 }
1357
1358 public:
1359 CMCountDataClosureBase(G1CollectedHeap* g1h,
1360 BitMap* region_bm, BitMap* card_bm):
1361 _g1h(g1h), _cm(g1h->concurrent_mark()),
1362 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
1363 _region_bm(region_bm), _card_bm(card_bm) { }
1364 };
1365
1366 // Closure that calculates the # live objects per region. Used
1367 // for verification purposes during the cleanup pause.
1368 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1369 CMBitMapRO* _bm;
1370 size_t _region_marked_bytes;
1371
1372 public:
1373 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1374 BitMap* region_bm, BitMap* card_bm) :
1375 CMCountDataClosureBase(g1h, region_bm, card_bm),
1376 _bm(bm), _region_marked_bytes(0) { }
1377
1378 bool doHeapRegion(HeapRegion* hr) {
1379
1380 if (hr->continuesHumongous()) {
1381 // We will ignore these here and process them when their
1382 // associated "starts humongous" region is processed (see
1383 // set_bit_for_heap_region()). Note that we cannot rely on their
1384 // associated "starts humongous" region to have their bit set to
1385 // 1 since, due to the region chunking in the parallel region
1386 // iteration, a "continues humongous" region might be visited
1387 // before its associated "starts humongous".
1388 return false;
1389 }
1390
1391 HeapWord* ntams = hr->next_top_at_mark_start();
1392 HeapWord* start = hr->bottom();
1393
1394 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1395 err_msg("Preconditions not met - "
1396 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1397 start, ntams, hr->end()));
1398
1399 // Find the first marked object at or after "start".
1400 start = _bm->getNextMarkedWordAddress(start, ntams);
1401
1402 size_t marked_bytes = 0;
1403
1404 while (start < ntams) {
1405 oop obj = oop(start);
1406 int obj_sz = obj->size();
1407 HeapWord* obj_end = start + obj_sz;
1408
1409 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1410 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1411
1412 // Note: if we're looking at the last region in heap - obj_end
1413 // could be actually just beyond the end of the heap; end_idx
1414 // will then correspond to a (non-existent) card that is also
1415 // just beyond the heap.
1416 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1417 // end of object is not card aligned - increment to cover
1418 // all the cards spanned by the object
1419 end_idx += 1;
1420 }
1421
1422 // Set the bits in the card BM for the cards spanned by this object.
1423 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1424
1425 // Add the size of this object to the number of marked bytes.
1426 marked_bytes += (size_t)obj_sz * HeapWordSize;
1427
1428 // Find the next marked object after this one.
1429 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1430 }
1431
1432 // Mark the allocated-since-marking portion...
1433 HeapWord* top = hr->top();
1434 if (ntams < top) {
1435 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1436 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1437
1438 // Note: if we're looking at the last region in heap - top
1439 // could be actually just beyond the end of the heap; end_idx
1440 // will then correspond to a (non-existent) card that is also
1441 // just beyond the heap.
1442 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1443 // end of object is not card aligned - increment to cover
1444 // all the cards spanned by the object
1445 end_idx += 1;
1446 }
1447 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1448
1449 // This definitely means the region has live objects.
1450 set_bit_for_region(hr);
1451 }
1452
1453 // Update the live region bitmap.
1454 if (marked_bytes > 0) {
1455 set_bit_for_region(hr);
1456 }
1457
1458 // Set the marked bytes for the current region so that
1459 // it can be queried by a calling verificiation routine
1460 _region_marked_bytes = marked_bytes;
1461
1462 return false;
1463 }
1464
1465 size_t region_marked_bytes() const { return _region_marked_bytes; }
1466 };
1467
1468 // Heap region closure used for verifying the counting data
1469 // that was accumulated concurrently and aggregated during
1470 // the remark pause. This closure is applied to the heap
1471 // regions during the STW cleanup pause.
1472
1473 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1474 G1CollectedHeap* _g1h;
1475 ConcurrentMark* _cm;
1476 CalcLiveObjectsClosure _calc_cl;
1477 BitMap* _region_bm; // Region BM to be verified
1478 BitMap* _card_bm; // Card BM to be verified
1479 bool _verbose; // verbose output?
1480
1481 BitMap* _exp_region_bm; // Expected Region BM values
1482 BitMap* _exp_card_bm; // Expected card BM values
1483
1484 int _failures;
1485
1486 public:
1487 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1488 BitMap* region_bm,
1489 BitMap* card_bm,
1490 BitMap* exp_region_bm,
1491 BitMap* exp_card_bm,
1492 bool verbose) :
1493 _g1h(g1h), _cm(g1h->concurrent_mark()),
1494 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1495 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1496 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1497 _failures(0) { }
1498
1499 int failures() const { return _failures; }
1500
1501 bool doHeapRegion(HeapRegion* hr) {
1502 if (hr->continuesHumongous()) {
1503 // We will ignore these here and process them when their
1504 // associated "starts humongous" region is processed (see
1505 // set_bit_for_heap_region()). Note that we cannot rely on their
1506 // associated "starts humongous" region to have their bit set to
1507 // 1 since, due to the region chunking in the parallel region
1508 // iteration, a "continues humongous" region might be visited
1509 // before its associated "starts humongous".
1510 return false;
1511 }
1512
1513 int failures = 0;
1514
1515 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1516 // this region and set the corresponding bits in the expected region
1517 // and card bitmaps.
1518 bool res = _calc_cl.doHeapRegion(hr);
1519 assert(res == false, "should be continuing");
1520
1521 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1522 Mutex::_no_safepoint_check_flag);
1523
1524 // Verify the marked bytes for this region.
1525 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1526 size_t act_marked_bytes = hr->next_marked_bytes();
1527
1528 // We're not OK if expected marked bytes > actual marked bytes. It means
1529 // we have missed accounting some objects during the actual marking.
1530 if (exp_marked_bytes > act_marked_bytes) {
1531 if (_verbose) {
1532 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1533 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1534 hr->hrs_index(), exp_marked_bytes, act_marked_bytes);
1535 }
1536 failures += 1;
1537 }
1538
1539 // Verify the bit, for this region, in the actual and expected
1540 // (which was just calculated) region bit maps.
1541 // We're not OK if the bit in the calculated expected region
1542 // bitmap is set and the bit in the actual region bitmap is not.
1543 BitMap::idx_t index = (BitMap::idx_t) hr->hrs_index();
1544
1545 bool expected = _exp_region_bm->at(index);
1546 bool actual = _region_bm->at(index);
1547 if (expected && !actual) {
1548 if (_verbose) {
1549 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1550 "expected: %s, actual: %s",
1551 hr->hrs_index(),
1552 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1553 }
1554 failures += 1;
1555 }
1556
1557 // Verify that the card bit maps for the cards spanned by the current
1558 // region match. We have an error if we have a set bit in the expected
1559 // bit map and the corresponding bit in the actual bitmap is not set.
1560
1561 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1562 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1563
1564 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1565 expected = _exp_card_bm->at(i);
1566 actual = _card_bm->at(i);
1567
1568 if (expected && !actual) {
1569 if (_verbose) {
1570 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1571 "expected: %s, actual: %s",
1572 hr->hrs_index(), i,
1573 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1574 }
1575 failures += 1;
1576 }
1577 }
1578
1579 if (failures > 0 && _verbose) {
1580 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1581 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1582 HR_FORMAT_PARAMS(hr), hr->next_top_at_mark_start(),
1583 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1584 }
1585
1586 _failures += failures;
1587
1588 // We could stop iteration over the heap when we
1589 // find the first violating region by returning true.
1590 return false;
1591 }
1592 };
1593
1594
1595 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1596 protected:
1597 G1CollectedHeap* _g1h;
1598 ConcurrentMark* _cm;
1599 BitMap* _actual_region_bm;
1600 BitMap* _actual_card_bm;
1601
1602 uint _n_workers;
1603
1604 BitMap* _expected_region_bm;
1605 BitMap* _expected_card_bm;
1606
1607 int _failures;
1608 bool _verbose;
1609
1610 public:
1611 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1612 BitMap* region_bm, BitMap* card_bm,
1613 BitMap* expected_region_bm, BitMap* expected_card_bm)
1614 : AbstractGangTask("G1 verify final counting"),
1615 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1616 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1617 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1618 _failures(0), _verbose(false),
1619 _n_workers(0) {
1620 assert(VerifyDuringGC, "don't call this otherwise");
1621
1622 // Use the value already set as the number of active threads
1623 // in the call to run_task().
1624 if (G1CollectedHeap::use_parallel_gc_threads()) {
1625 assert( _g1h->workers()->active_workers() > 0,
1626 "Should have been previously set");
1627 _n_workers = _g1h->workers()->active_workers();
1628 } else {
1629 _n_workers = 1;
1630 }
1631
1632 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1633 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1634
1635 _verbose = _cm->verbose_medium();
1636 }
1637
1638 void work(uint worker_id) {
1639 assert(worker_id < _n_workers, "invariant");
1640
1641 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1642 _actual_region_bm, _actual_card_bm,
1643 _expected_region_bm,
1644 _expected_card_bm,
1645 _verbose);
1646
1647 if (G1CollectedHeap::use_parallel_gc_threads()) {
1648 _g1h->heap_region_par_iterate_chunked(&verify_cl,
1649 worker_id,
1650 _n_workers,
1651 HeapRegion::VerifyCountClaimValue);
1652 } else {
1653 _g1h->heap_region_iterate(&verify_cl);
1654 }
1655
1656 Atomic::add(verify_cl.failures(), &_failures);
1657 }
1658
1659 int failures() const { return _failures; }
1660 };
1661
1662 // Closure that finalizes the liveness counting data.
1663 // Used during the cleanup pause.
1664 // Sets the bits corresponding to the interval [NTAMS, top]
1665 // (which contains the implicitly live objects) in the
1666 // card liveness bitmap. Also sets the bit for each region,
1667 // containing live data, in the region liveness bitmap.
1668
1669 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1670 public:
1671 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1672 BitMap* region_bm,
1673 BitMap* card_bm) :
1674 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1675
1676 bool doHeapRegion(HeapRegion* hr) {
1677
1678 if (hr->continuesHumongous()) {
1679 // We will ignore these here and process them when their
1680 // associated "starts humongous" region is processed (see
1681 // set_bit_for_heap_region()). Note that we cannot rely on their
1682 // associated "starts humongous" region to have their bit set to
1683 // 1 since, due to the region chunking in the parallel region
1684 // iteration, a "continues humongous" region might be visited
1685 // before its associated "starts humongous".
1686 return false;
1687 }
1688
1689 HeapWord* ntams = hr->next_top_at_mark_start();
1690 HeapWord* top = hr->top();
1691
1692 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1693
1694 // Mark the allocated-since-marking portion...
1695 if (ntams < top) {
1696 // This definitely means the region has live objects.
1697 set_bit_for_region(hr);
1698
1699 // Now set the bits in the card bitmap for [ntams, top)
1700 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1701 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1702
1703 // Note: if we're looking at the last region in heap - top
1704 // could be actually just beyond the end of the heap; end_idx
1705 // will then correspond to a (non-existent) card that is also
1706 // just beyond the heap.
1707 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1708 // end of object is not card aligned - increment to cover
1709 // all the cards spanned by the object
1710 end_idx += 1;
1711 }
1712
1713 assert(end_idx <= _card_bm->size(),
1714 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1715 end_idx, _card_bm->size()));
1716 assert(start_idx < _card_bm->size(),
1717 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1718 start_idx, _card_bm->size()));
1719
1720 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1721 }
1722
1723 // Set the bit for the region if it contains live data
1724 if (hr->next_marked_bytes() > 0) {
1725 set_bit_for_region(hr);
1726 }
1727
1728 return false;
1729 }
1730 };
1731
1732 class G1ParFinalCountTask: public AbstractGangTask {
1733 protected:
1734 G1CollectedHeap* _g1h;
1735 ConcurrentMark* _cm;
1736 BitMap* _actual_region_bm;
1737 BitMap* _actual_card_bm;
1738
1739 uint _n_workers;
1740
1741 public:
1742 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1743 : AbstractGangTask("G1 final counting"),
1744 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1745 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1746 _n_workers(0) {
1747 // Use the value already set as the number of active threads
1748 // in the call to run_task().
1749 if (G1CollectedHeap::use_parallel_gc_threads()) {
1750 assert( _g1h->workers()->active_workers() > 0,
1751 "Should have been previously set");
1752 _n_workers = _g1h->workers()->active_workers();
1753 } else {
1754 _n_workers = 1;
1755 }
1756 }
1757
1758 void work(uint worker_id) {
1759 assert(worker_id < _n_workers, "invariant");
1760
1761 FinalCountDataUpdateClosure final_update_cl(_g1h,
1762 _actual_region_bm,
1763 _actual_card_bm);
1764
1765 if (G1CollectedHeap::use_parallel_gc_threads()) {
1766 _g1h->heap_region_par_iterate_chunked(&final_update_cl,
1767 worker_id,
1768 _n_workers,
1769 HeapRegion::FinalCountClaimValue);
1770 } else {
1771 _g1h->heap_region_iterate(&final_update_cl);
1772 }
1773 }
1774 };
1775
1776 class G1ParNoteEndTask;
1777
1778 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1779 G1CollectedHeap* _g1;
1780 int _worker_num;
1781 size_t _max_live_bytes;
1782 uint _regions_claimed;
1783 size_t _freed_bytes;
1784 FreeRegionList* _local_cleanup_list;
1785 OldRegionSet* _old_proxy_set;
1786 HumongousRegionSet* _humongous_proxy_set;
1787 HRRSCleanupTask* _hrrs_cleanup_task;
1788 double _claimed_region_time;
1789 double _max_region_time;
1790
1791 public:
1792 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1793 int worker_num,
1794 FreeRegionList* local_cleanup_list,
1795 OldRegionSet* old_proxy_set,
1796 HumongousRegionSet* humongous_proxy_set,
1797 HRRSCleanupTask* hrrs_cleanup_task) :
1798 _g1(g1), _worker_num(worker_num),
1799 _max_live_bytes(0), _regions_claimed(0),
1800 _freed_bytes(0),
1801 _claimed_region_time(0.0), _max_region_time(0.0),
1802 _local_cleanup_list(local_cleanup_list),
1803 _old_proxy_set(old_proxy_set),
1804 _humongous_proxy_set(humongous_proxy_set),
1805 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1806
1807 size_t freed_bytes() { return _freed_bytes; }
1808
1809 bool doHeapRegion(HeapRegion *hr) {
1810 if (hr->continuesHumongous()) {
1811 return false;
1812 }
1813 // We use a claim value of zero here because all regions
1814 // were claimed with value 1 in the FinalCount task.
1815 _g1->reset_gc_time_stamps(hr);
1816 double start = os::elapsedTime();
1817 _regions_claimed++;
1818 hr->note_end_of_marking();
1819 _max_live_bytes += hr->max_live_bytes();
1820 _g1->free_region_if_empty(hr,
1821 &_freed_bytes,
1822 _local_cleanup_list,
1823 _old_proxy_set,
1824 _humongous_proxy_set,
1825 _hrrs_cleanup_task,
1826 true /* par */);
1827 double region_time = (os::elapsedTime() - start);
1828 _claimed_region_time += region_time;
1829 if (region_time > _max_region_time) {
1830 _max_region_time = region_time;
1831 }
1832 return false;
1833 }
1834
1835 size_t max_live_bytes() { return _max_live_bytes; }
1836 uint regions_claimed() { return _regions_claimed; }
1837 double claimed_region_time_sec() { return _claimed_region_time; }
1838 double max_region_time_sec() { return _max_region_time; }
1839 };
1840
1841 class G1ParNoteEndTask: public AbstractGangTask {
1842 friend class G1NoteEndOfConcMarkClosure;
1843
1844 protected:
1845 G1CollectedHeap* _g1h;
1846 size_t _max_live_bytes;
1847 size_t _freed_bytes;
1848 FreeRegionList* _cleanup_list;
1849
1850 public:
1851 G1ParNoteEndTask(G1CollectedHeap* g1h,
1852 FreeRegionList* cleanup_list) :
1853 AbstractGangTask("G1 note end"), _g1h(g1h),
1854 _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list) { }
1855
1856 void work(uint worker_id) {
1857 double start = os::elapsedTime();
1858 FreeRegionList local_cleanup_list("Local Cleanup List");
1859 OldRegionSet old_proxy_set("Local Cleanup Old Proxy Set");
1860 HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
1861 HRRSCleanupTask hrrs_cleanup_task;
1862 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, worker_id, &local_cleanup_list,
1863 &old_proxy_set,
1864 &humongous_proxy_set,
1865 &hrrs_cleanup_task);
1866 if (G1CollectedHeap::use_parallel_gc_threads()) {
1867 _g1h->heap_region_par_iterate_chunked(&g1_note_end, worker_id,
1868 _g1h->workers()->active_workers(),
1869 HeapRegion::NoteEndClaimValue);
1870 } else {
1871 _g1h->heap_region_iterate(&g1_note_end);
1872 }
1873 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1874
1875 // Now update the lists
1876 _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
1877 NULL /* free_list */,
1878 &old_proxy_set,
1879 &humongous_proxy_set,
1880 true /* par */);
1881 {
1882 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1883 _max_live_bytes += g1_note_end.max_live_bytes();
1884 _freed_bytes += g1_note_end.freed_bytes();
1885
1886 // If we iterate over the global cleanup list at the end of
1887 // cleanup to do this printing we will not guarantee to only
1888 // generate output for the newly-reclaimed regions (the list
1889 // might not be empty at the beginning of cleanup; we might
1890 // still be working on its previous contents). So we do the
1891 // printing here, before we append the new regions to the global
1892 // cleanup list.
1893
1894 G1HRPrinter* hr_printer = _g1h->hr_printer();
1895 if (hr_printer->is_active()) {
1896 HeapRegionLinkedListIterator iter(&local_cleanup_list);
1897 while (iter.more_available()) {
1898 HeapRegion* hr = iter.get_next();
1899 hr_printer->cleanup(hr);
1900 }
1901 }
1902
1903 _cleanup_list->add_as_tail(&local_cleanup_list);
1904 assert(local_cleanup_list.is_empty(), "post-condition");
1905
1906 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1907 }
1908 }
1909 size_t max_live_bytes() { return _max_live_bytes; }
1910 size_t freed_bytes() { return _freed_bytes; }
1911 };
1912
1913 class G1ParScrubRemSetTask: public AbstractGangTask {
1914 protected:
1915 G1RemSet* _g1rs;
1916 BitMap* _region_bm;
1917 BitMap* _card_bm;
1918 public:
1919 G1ParScrubRemSetTask(G1CollectedHeap* g1h,
1920 BitMap* region_bm, BitMap* card_bm) :
1921 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()),
1922 _region_bm(region_bm), _card_bm(card_bm) { }
1923
1924 void work(uint worker_id) {
1925 if (G1CollectedHeap::use_parallel_gc_threads()) {
1926 _g1rs->scrub_par(_region_bm, _card_bm, worker_id,
1927 HeapRegion::ScrubRemSetClaimValue);
1928 } else {
1929 _g1rs->scrub(_region_bm, _card_bm);
1930 }
1931 }
1932
1933 };
1934
1935 void ConcurrentMark::cleanup() {
1936 // world is stopped at this checkpoint
1937 assert(SafepointSynchronize::is_at_safepoint(),
1938 "world should be stopped");
1939 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1940
1941 // If a full collection has happened, we shouldn't do this.
1942 if (has_aborted()) {
1943 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1944 return;
1945 }
1946
1947 HRSPhaseSetter x(HRSPhaseCleanup);
1948 g1h->verify_region_sets_optional();
1949
1950 if (VerifyDuringGC) {
1951 HandleMark hm; // handle scope
1952 gclog_or_tty->print(" VerifyDuringGC:(before)");
1953 Universe::heap()->prepare_for_verify();
1954 Universe::verify(/* silent */ false,
1955 /* option */ VerifyOption_G1UsePrevMarking);
1956 }
1957
1958 G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();
1959 g1p->record_concurrent_mark_cleanup_start();
1960
1961 double start = os::elapsedTime();
1962
1963 HeapRegionRemSet::reset_for_cleanup_tasks();
1964
1965 uint n_workers;
1966
1967 // Do counting once more with the world stopped for good measure.
1968 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1969
1970 if (G1CollectedHeap::use_parallel_gc_threads()) {
1971 assert(g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
1972 "sanity check");
1973
1974 g1h->set_par_threads();
1975 n_workers = g1h->n_par_threads();
1976 assert(g1h->n_par_threads() == n_workers,
1977 "Should not have been reset");
1978 g1h->workers()->run_task(&g1_par_count_task);
1979 // Done with the parallel phase so reset to 0.
1980 g1h->set_par_threads(0);
1981
1982 assert(g1h->check_heap_region_claim_values(HeapRegion::FinalCountClaimValue),
1983 "sanity check");
1984 } else {
1985 n_workers = 1;
1986 g1_par_count_task.work(0);
1987 }
1988
1989 if (VerifyDuringGC) {
1990 // Verify that the counting data accumulated during marking matches
1991 // that calculated by walking the marking bitmap.
1992
1993 // Bitmaps to hold expected values
1994 BitMap expected_region_bm(_region_bm.size(), false);
1995 BitMap expected_card_bm(_card_bm.size(), false);
1996
1997 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1998 &_region_bm,
1999 &_card_bm,
2000 &expected_region_bm,
2001 &expected_card_bm);
2002
2003 if (G1CollectedHeap::use_parallel_gc_threads()) {
2004 g1h->set_par_threads((int)n_workers);
2005 g1h->workers()->run_task(&g1_par_verify_task);
2006 // Done with the parallel phase so reset to 0.
2007 g1h->set_par_threads(0);
2008
2009 assert(g1h->check_heap_region_claim_values(HeapRegion::VerifyCountClaimValue),
2010 "sanity check");
2011 } else {
2012 g1_par_verify_task.work(0);
2013 }
2014
2015 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
2016 }
2017
2018 size_t start_used_bytes = g1h->used();
2019 g1h->set_marking_complete();
2020
2021 double count_end = os::elapsedTime();
2022 double this_final_counting_time = (count_end - start);
2023 _total_counting_time += this_final_counting_time;
2024
2025 if (G1PrintRegionLivenessInfo) {
2026 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
2027 _g1h->heap_region_iterate(&cl);
2028 }
2029
2030 // Install newly created mark bitMap as "prev".
2031 swapMarkBitMaps();
2032
2033 g1h->reset_gc_time_stamp();
2034
2035 // Note end of marking in all heap regions.
2036 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list);
2037 if (G1CollectedHeap::use_parallel_gc_threads()) {
2038 g1h->set_par_threads((int)n_workers);
2039 g1h->workers()->run_task(&g1_par_note_end_task);
2040 g1h->set_par_threads(0);
2041
2042 assert(g1h->check_heap_region_claim_values(HeapRegion::NoteEndClaimValue),
2043 "sanity check");
2044 } else {
2045 g1_par_note_end_task.work(0);
2046 }
2047 g1h->check_gc_time_stamps();
2048
2049 if (!cleanup_list_is_empty()) {
2050 // The cleanup list is not empty, so we'll have to process it
2051 // concurrently. Notify anyone else that might be wanting free
2052 // regions that there will be more free regions coming soon.
2053 g1h->set_free_regions_coming();
2054 }
2055
2056 // call below, since it affects the metric by which we sort the heap
2057 // regions.
2058 if (G1ScrubRemSets) {
2059 double rs_scrub_start = os::elapsedTime();
2060 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm);
2061 if (G1CollectedHeap::use_parallel_gc_threads()) {
2062 g1h->set_par_threads((int)n_workers);
2063 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2064 g1h->set_par_threads(0);
2065
2066 assert(g1h->check_heap_region_claim_values(
2067 HeapRegion::ScrubRemSetClaimValue),
2068 "sanity check");
2069 } else {
2070 g1_par_scrub_rs_task.work(0);
2071 }
2072
2073 double rs_scrub_end = os::elapsedTime();
2074 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2075 _total_rs_scrub_time += this_rs_scrub_time;
2076 }
2077
2078 // this will also free any regions totally full of garbage objects,
2079 // and sort the regions.
2080 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2081
2082 // Statistics.
2083 double end = os::elapsedTime();
2084 _cleanup_times.add((end - start) * 1000.0);
2085
2086 if (G1Log::fine()) {
2087 g1h->print_size_transition(gclog_or_tty,
2088 start_used_bytes,
2089 g1h->used(),
2090 g1h->capacity());
2091 }
2092
2093 // Clean up will have freed any regions completely full of garbage.
2094 // Update the soft reference policy with the new heap occupancy.
2095 Universe::update_heap_info_at_gc();
2096
2097 // We need to make this be a "collection" so any collection pause that
2098 // races with it goes around and waits for completeCleanup to finish.
2099 g1h->increment_total_collections();
2100
2101 // We reclaimed old regions so we should calculate the sizes to make
2102 // sure we update the old gen/space data.
2103 g1h->g1mm()->update_sizes();
2104
2105 if (VerifyDuringGC) {
2106 HandleMark hm; // handle scope
2107 gclog_or_tty->print(" VerifyDuringGC:(after)");
2108 Universe::heap()->prepare_for_verify();
2109 Universe::verify(/* silent */ false,
2110 /* option */ VerifyOption_G1UsePrevMarking);
2111 }
2112
2113 g1h->verify_region_sets_optional();
2114 }
2115
2116 void ConcurrentMark::completeCleanup() {
2117 if (has_aborted()) return;
2118
2119 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2120
2121 _cleanup_list.verify_optional();
2122 FreeRegionList tmp_free_list("Tmp Free List");
2123
2124 if (G1ConcRegionFreeingVerbose) {
2125 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2126 "cleanup list has %u entries",
2127 _cleanup_list.length());
2128 }
2129
2130 // Noone else should be accessing the _cleanup_list at this point,
2131 // so it's not necessary to take any locks
2132 while (!_cleanup_list.is_empty()) {
2133 HeapRegion* hr = _cleanup_list.remove_head();
2134 assert(hr != NULL, "the list was not empty");
2135 hr->par_clear();
2136 tmp_free_list.add_as_tail(hr);
2137
2138 // Instead of adding one region at a time to the secondary_free_list,
2139 // we accumulate them in the local list and move them a few at a
2140 // time. This also cuts down on the number of notify_all() calls
2141 // we do during this process. We'll also append the local list when
2142 // _cleanup_list is empty (which means we just removed the last
2143 // region from the _cleanup_list).
2144 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2145 _cleanup_list.is_empty()) {
2146 if (G1ConcRegionFreeingVerbose) {
2147 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2148 "appending %u entries to the secondary_free_list, "
2149 "cleanup list still has %u entries",
2150 tmp_free_list.length(),
2151 _cleanup_list.length());
2152 }
2153
2154 {
2155 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2156 g1h->secondary_free_list_add_as_tail(&tmp_free_list);
2157 SecondaryFreeList_lock->notify_all();
2158 }
2159
2160 if (G1StressConcRegionFreeing) {
2161 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2162 os::sleep(Thread::current(), (jlong) 1, false);
2163 }
2164 }
2165 }
2166 }
2167 assert(tmp_free_list.is_empty(), "post-condition");
2168 }
2169
2170 // Support closures for reference procssing in G1
2171
2172 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2173 HeapWord* addr = (HeapWord*)obj;
2174 return addr != NULL &&
2175 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2176 }
2177
2178 class G1CMKeepAliveClosure: public ExtendedOopClosure {
2179 G1CollectedHeap* _g1;
2180 ConcurrentMark* _cm;
2181 public:
2182 G1CMKeepAliveClosure(G1CollectedHeap* g1, ConcurrentMark* cm) :
2183 _g1(g1), _cm(cm) {
2184 assert(Thread::current()->is_VM_thread(), "otherwise fix worker id");
2185 }
2186
2187 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2188 virtual void do_oop( oop* p) { do_oop_work(p); }
2189
2190 template <class T> void do_oop_work(T* p) {
2191 oop obj = oopDesc::load_decode_heap_oop(p);
2192 HeapWord* addr = (HeapWord*)obj;
2193
2194 if (_cm->verbose_high()) {
2195 gclog_or_tty->print_cr("\t[0] we're looking at location "
2196 "*"PTR_FORMAT" = "PTR_FORMAT,
2197 p, (void*) obj);
2198 }
2199
2200 if (_g1->is_in_g1_reserved(addr) && _g1->is_obj_ill(obj)) {
2201 _cm->mark_and_count(obj);
2202 _cm->mark_stack_push(obj);
2203 }
2204 }
2205 };
2206
2207 class G1CMDrainMarkingStackClosure: public VoidClosure {
2208 ConcurrentMark* _cm;
2209 CMMarkStack* _markStack;
2210 G1CMKeepAliveClosure* _oopClosure;
2211 public:
2212 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMMarkStack* markStack,
2213 G1CMKeepAliveClosure* oopClosure) :
2214 _cm(cm),
2215 _markStack(markStack),
2216 _oopClosure(oopClosure) { }
2217
2218 void do_void() {
2219 _markStack->drain(_oopClosure, _cm->nextMarkBitMap(), false);
2220 }
2221 };
2222
2223 // 'Keep Alive' closure used by parallel reference processing.
2224 // An instance of this closure is used in the parallel reference processing
2225 // code rather than an instance of G1CMKeepAliveClosure. We could have used
2226 // the G1CMKeepAliveClosure as it is MT-safe. Also reference objects are
2227 // placed on to discovered ref lists once so we can mark and push with no
2228 // need to check whether the object has already been marked. Using the
2229 // G1CMKeepAliveClosure would mean, however, having all the worker threads
2230 // operating on the global mark stack. This means that an individual
2231 // worker would be doing lock-free pushes while it processes its own
2232 // discovered ref list followed by drain call. If the discovered ref lists
2233 // are unbalanced then this could cause interference with the other
2234 // workers. Using a CMTask (and its embedded local data structures)
2235 // avoids that potential interference.
2236 class G1CMParKeepAliveAndDrainClosure: public OopClosure {
2237 ConcurrentMark* _cm;
2238 CMTask* _task;
2239 int _ref_counter_limit;
2240 int _ref_counter;
2241 public:
2242 G1CMParKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task) :
2243 _cm(cm), _task(task),
2244 _ref_counter_limit(G1RefProcDrainInterval) {
2245 assert(_ref_counter_limit > 0, "sanity");
2246 _ref_counter = _ref_counter_limit;
2247 }
2248
2249 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2250 virtual void do_oop( oop* p) { do_oop_work(p); }
2251
2252 template <class T> void do_oop_work(T* p) {
2253 if (!_cm->has_overflown()) {
2254 oop obj = oopDesc::load_decode_heap_oop(p);
2255 if (_cm->verbose_high()) {
2256 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2257 "*"PTR_FORMAT" = "PTR_FORMAT,
2258 _task->worker_id(), p, (void*) obj);
2259 }
2260
2261 _task->deal_with_reference(obj);
2262 _ref_counter--;
2263
2264 if (_ref_counter == 0) {
2265 // We have dealt with _ref_counter_limit references, pushing them and objects
2266 // reachable from them on to the local stack (and possibly the global stack).
2267 // Call do_marking_step() to process these entries. We call the routine in a
2268 // loop, which we'll exit if there's nothing more to do (i.e. we're done
2269 // with the entries that we've pushed as a result of the deal_with_reference
2270 // calls above) or we overflow.
2271 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2272 // while there may still be some work to do. (See the comment at the
2273 // beginning of CMTask::do_marking_step() for those conditions - one of which
2274 // is reaching the specified time target.) It is only when
2275 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2276 // that the marking has completed.
2277 do {
2278 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2279 _task->do_marking_step(mark_step_duration_ms,
2280 false /* do_stealing */,
2281 false /* do_termination */);
2282 } while (_task->has_aborted() && !_cm->has_overflown());
2283 _ref_counter = _ref_counter_limit;
2284 }
2285 } else {
2286 if (_cm->verbose_high()) {
2287 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2288 }
2289 }
2290 }
2291 };
2292
2293 class G1CMParDrainMarkingStackClosure: public VoidClosure {
2294 ConcurrentMark* _cm;
2295 CMTask* _task;
2296 public:
2297 G1CMParDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task) :
2298 _cm(cm), _task(task) { }
2299
2300 void do_void() {
2301 do {
2302 if (_cm->verbose_high()) {
2303 gclog_or_tty->print_cr("\t[%u] Drain: Calling do marking_step",
2304 _task->worker_id());
2305 }
2306
2307 // We call CMTask::do_marking_step() to completely drain the local and
2308 // global marking stacks. The routine is called in a loop, which we'll
2309 // exit if there's nothing more to do (i.e. we'completely drained the
2310 // entries that were pushed as a result of applying the
2311 // G1CMParKeepAliveAndDrainClosure to the entries on the discovered ref
2312 // lists above) or we overflow the global marking stack.
2313 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted() flag
2314 // while there may still be some work to do. (See the comment at the
2315 // beginning of CMTask::do_marking_step() for those conditions - one of which
2316 // is reaching the specified time target.) It is only when
2317 // CMTask::do_marking_step() returns without setting the has_aborted() flag
2318 // that the marking has completed.
2319
2320 _task->do_marking_step(1000000000.0 /* something very large */,
2321 true /* do_stealing */,
2322 true /* do_termination */);
2323 } while (_task->has_aborted() && !_cm->has_overflown());
2324 }
2325 };
2326
2327 // Implementation of AbstractRefProcTaskExecutor for parallel
2328 // reference processing at the end of G1 concurrent marking
2329
2330 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2331 private:
2332 G1CollectedHeap* _g1h;
2333 ConcurrentMark* _cm;
2334 WorkGang* _workers;
2335 int _active_workers;
2336
2337 public:
2338 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2339 ConcurrentMark* cm,
2340 WorkGang* workers,
2341 int n_workers) :
2342 _g1h(g1h), _cm(cm),
2343 _workers(workers), _active_workers(n_workers) { }
2344
2345 // Executes the given task using concurrent marking worker threads.
2346 virtual void execute(ProcessTask& task);
2347 virtual void execute(EnqueueTask& task);
2348 };
2349
2350 class G1CMRefProcTaskProxy: public AbstractGangTask {
2351 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2352 ProcessTask& _proc_task;
2353 G1CollectedHeap* _g1h;
2354 ConcurrentMark* _cm;
2355
2356 public:
2357 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2358 G1CollectedHeap* g1h,
2359 ConcurrentMark* cm) :
2360 AbstractGangTask("Process reference objects in parallel"),
2361 _proc_task(proc_task), _g1h(g1h), _cm(cm) { }
2362
2363 virtual void work(uint worker_id) {
2364 CMTask* marking_task = _cm->task(worker_id);
2365 G1CMIsAliveClosure g1_is_alive(_g1h);
2366 G1CMParKeepAliveAndDrainClosure g1_par_keep_alive(_cm, marking_task);
2367 G1CMParDrainMarkingStackClosure g1_par_drain(_cm, marking_task);
2368
2369 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2370 }
2371 };
2372
2373 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2374 assert(_workers != NULL, "Need parallel worker threads.");
2375
2376 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2377
2378 // We need to reset the phase for each task execution so that
2379 // the termination protocol of CMTask::do_marking_step works.
2380 _cm->set_phase(_active_workers, false /* concurrent */);
2381 _g1h->set_par_threads(_active_workers);
2382 _workers->run_task(&proc_task_proxy);
2383 _g1h->set_par_threads(0);
2384 }
2385
2386 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2387 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2388 EnqueueTask& _enq_task;
2389
2390 public:
2391 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2392 AbstractGangTask("Enqueue reference objects in parallel"),
2393 _enq_task(enq_task) { }
2394
2395 virtual void work(uint worker_id) {
2396 _enq_task.work(worker_id);
2397 }
2398 };
2399
2400 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2401 assert(_workers != NULL, "Need parallel worker threads.");
2402
2403 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2404
2405 _g1h->set_par_threads(_active_workers);
2406 _workers->run_task(&enq_task_proxy);
2407 _g1h->set_par_threads(0);
2408 }
2409
2410 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2411 ResourceMark rm;
2412 HandleMark hm;
2413
2414 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2415
2416 // Is alive closure.
2417 G1CMIsAliveClosure g1_is_alive(g1h);
2418
2419 // Inner scope to exclude the cleaning of the string and symbol
2420 // tables from the displayed time.
2421 {
2422 if (G1Log::finer()) {
2423 gclog_or_tty->put(' ');
2424 }
2425 TraceTime t("GC ref-proc", G1Log::finer(), false, gclog_or_tty);
2426
2427 ReferenceProcessor* rp = g1h->ref_processor_cm();
2428
2429 // See the comment in G1CollectedHeap::ref_processing_init()
2430 // about how reference processing currently works in G1.
2431
2432 // Process weak references.
2433 rp->setup_policy(clear_all_soft_refs);
2434 assert(_markStack.isEmpty(), "mark stack should be empty");
2435
2436 G1CMKeepAliveClosure g1_keep_alive(g1h, this);
2437 G1CMDrainMarkingStackClosure
2438 g1_drain_mark_stack(this, &_markStack, &g1_keep_alive);
2439
2440 // We use the work gang from the G1CollectedHeap and we utilize all
2441 // the worker threads.
2442 uint active_workers = g1h->workers() ? g1h->workers()->active_workers() : 1U;
2443 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2444
2445 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2446 g1h->workers(), active_workers);
2447
2448 if (rp->processing_is_mt()) {
2449 // Set the degree of MT here. If the discovery is done MT, there
2450 // may have been a different number of threads doing the discovery
2451 // and a different number of discovered lists may have Ref objects.
2452 // That is OK as long as the Reference lists are balanced (see
2453 // balance_all_queues() and balance_queues()).
2454 rp->set_active_mt_degree(active_workers);
2455
2456 rp->process_discovered_references(&g1_is_alive,
2457 &g1_keep_alive,
2458 &g1_drain_mark_stack,
2459 &par_task_executor);
2460
2461 // The work routines of the parallel keep_alive and drain_marking_stack
2462 // will set the has_overflown flag if we overflow the global marking
2463 // stack.
2464 } else {
2465 rp->process_discovered_references(&g1_is_alive,
2466 &g1_keep_alive,
2467 &g1_drain_mark_stack,
2468 NULL);
2469 }
2470
2471 assert(_markStack.overflow() || _markStack.isEmpty(),
2472 "mark stack should be empty (unless it overflowed)");
2473 if (_markStack.overflow()) {
2474 // Should have been done already when we tried to push an
2475 // entry on to the global mark stack. But let's do it again.
2476 set_has_overflown();
2477 }
2478
2479 if (rp->processing_is_mt()) {
2480 assert(rp->num_q() == active_workers, "why not");
2481 rp->enqueue_discovered_references(&par_task_executor);
2482 } else {
2483 rp->enqueue_discovered_references();
2484 }
2485
2486 rp->verify_no_references_recorded();
2487 assert(!rp->discovery_enabled(), "Post condition");
2488 }
2489
2490 // Now clean up stale oops in StringTable
2491 StringTable::unlink(&g1_is_alive);
2492 // Clean up unreferenced symbols in symbol table.
2493 SymbolTable::unlink();
2494 }
2495
2496 void ConcurrentMark::swapMarkBitMaps() {
2497 CMBitMapRO* temp = _prevMarkBitMap;
2498 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2499 _nextMarkBitMap = (CMBitMap*) temp;
2500 }
2501
2502 class CMRemarkTask: public AbstractGangTask {
2503 private:
2504 ConcurrentMark *_cm;
2505
2506 public:
2507 void work(uint worker_id) {
2508 // Since all available tasks are actually started, we should
2509 // only proceed if we're supposed to be actived.
2510 if (worker_id < _cm->active_tasks()) {
2511 CMTask* task = _cm->task(worker_id);
2512 task->record_start_time();
2513 do {
2514 task->do_marking_step(1000000000.0 /* something very large */,
2515 true /* do_stealing */,
2516 true /* do_termination */);
2517 } while (task->has_aborted() && !_cm->has_overflown());
2518 // If we overflow, then we do not want to restart. We instead
2519 // want to abort remark and do concurrent marking again.
2520 task->record_end_time();
2521 }
2522 }
2523
2524 CMRemarkTask(ConcurrentMark* cm, int active_workers) :
2525 AbstractGangTask("Par Remark"), _cm(cm) {
2526 _cm->terminator()->reset_for_reuse(active_workers);
2527 }
2528 };
2529
2530 void ConcurrentMark::checkpointRootsFinalWork() {
2531 ResourceMark rm;
2532 HandleMark hm;
2533 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2534
2535 g1h->ensure_parsability(false);
2536
2537 if (G1CollectedHeap::use_parallel_gc_threads()) {
2538 G1CollectedHeap::StrongRootsScope srs(g1h);
2539 // this is remark, so we'll use up all active threads
2540 uint active_workers = g1h->workers()->active_workers();
2541 if (active_workers == 0) {
2542 assert(active_workers > 0, "Should have been set earlier");
2543 active_workers = (uint) ParallelGCThreads;
2544 g1h->workers()->set_active_workers(active_workers);
2545 }
2546 set_phase(active_workers, false /* concurrent */);
2547 // Leave _parallel_marking_threads at it's
2548 // value originally calculated in the ConcurrentMark
2549 // constructor and pass values of the active workers
2550 // through the gang in the task.
2551
2552 CMRemarkTask remarkTask(this, active_workers);
2553 g1h->set_par_threads(active_workers);
2554 g1h->workers()->run_task(&remarkTask);
2555 g1h->set_par_threads(0);
2556 } else {
2557 G1CollectedHeap::StrongRootsScope srs(g1h);
2558 // this is remark, so we'll use up all available threads
2559 uint active_workers = 1;
2560 set_phase(active_workers, false /* concurrent */);
2561
2562 CMRemarkTask remarkTask(this, active_workers);
2563 // We will start all available threads, even if we decide that the
2564 // active_workers will be fewer. The extra ones will just bail out
2565 // immediately.
2566 remarkTask.work(0);
2567 }
2568 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2569 guarantee(satb_mq_set.completed_buffers_num() == 0, "invariant");
2570
2571 print_stats();
2572
2573 #if VERIFY_OBJS_PROCESSED
2574 if (_scan_obj_cl.objs_processed != ThreadLocalObjQueue::objs_enqueued) {
2575 gclog_or_tty->print_cr("Processed = %d, enqueued = %d.",
2576 _scan_obj_cl.objs_processed,
2577 ThreadLocalObjQueue::objs_enqueued);
2578 guarantee(_scan_obj_cl.objs_processed ==
2579 ThreadLocalObjQueue::objs_enqueued,
2580 "Different number of objs processed and enqueued.");
2581 }
2582 #endif
2583 }
2584
2585 #ifndef PRODUCT
2586
2587 class PrintReachableOopClosure: public OopClosure {
2588 private:
2589 G1CollectedHeap* _g1h;
2590 outputStream* _out;
2591 VerifyOption _vo;
2592 bool _all;
2593
2594 public:
2595 PrintReachableOopClosure(outputStream* out,
2596 VerifyOption vo,
2597 bool all) :
2598 _g1h(G1CollectedHeap::heap()),
2599 _out(out), _vo(vo), _all(all) { }
2600
2601 void do_oop(narrowOop* p) { do_oop_work(p); }
2602 void do_oop( oop* p) { do_oop_work(p); }
2603
2604 template <class T> void do_oop_work(T* p) {
2605 oop obj = oopDesc::load_decode_heap_oop(p);
2606 const char* str = NULL;
2607 const char* str2 = "";
2608
2609 if (obj == NULL) {
2610 str = "";
2611 } else if (!_g1h->is_in_g1_reserved(obj)) {
2612 str = " O";
2613 } else {
2614 HeapRegion* hr = _g1h->heap_region_containing(obj);
2615 guarantee(hr != NULL, "invariant");
2616 bool over_tams = _g1h->allocated_since_marking(obj, hr, _vo);
2617 bool marked = _g1h->is_marked(obj, _vo);
2618
2619 if (over_tams) {
2620 str = " >";
2621 if (marked) {
2622 str2 = " AND MARKED";
2623 }
2624 } else if (marked) {
2625 str = " M";
2626 } else {
2627 str = " NOT";
2628 }
2629 }
2630
2631 _out->print_cr(" "PTR_FORMAT": "PTR_FORMAT"%s%s",
2632 p, (void*) obj, str, str2);
2633 }
2634 };
2635
2636 class PrintReachableObjectClosure : public ObjectClosure {
2637 private:
2638 G1CollectedHeap* _g1h;
2639 outputStream* _out;
2640 VerifyOption _vo;
2641 bool _all;
2642 HeapRegion* _hr;
2643
2644 public:
2645 PrintReachableObjectClosure(outputStream* out,
2646 VerifyOption vo,
2647 bool all,
2648 HeapRegion* hr) :
2649 _g1h(G1CollectedHeap::heap()),
2650 _out(out), _vo(vo), _all(all), _hr(hr) { }
2651
2652 void do_object(oop o) {
2653 bool over_tams = _g1h->allocated_since_marking(o, _hr, _vo);
2654 bool marked = _g1h->is_marked(o, _vo);
2655 bool print_it = _all || over_tams || marked;
2656
2657 if (print_it) {
2658 _out->print_cr(" "PTR_FORMAT"%s",
2659 o, (over_tams) ? " >" : (marked) ? " M" : "");
2660 PrintReachableOopClosure oopCl(_out, _vo, _all);
2661 o->oop_iterate_no_header(&oopCl);
2662 }
2663 }
2664 };
2665
2666 class PrintReachableRegionClosure : public HeapRegionClosure {
2667 private:
2668 G1CollectedHeap* _g1h;
2669 outputStream* _out;
2670 VerifyOption _vo;
2671 bool _all;
2672
2673 public:
2674 bool doHeapRegion(HeapRegion* hr) {
2675 HeapWord* b = hr->bottom();
2676 HeapWord* e = hr->end();
2677 HeapWord* t = hr->top();
2678 HeapWord* p = _g1h->top_at_mark_start(hr, _vo);
2679 _out->print_cr("** ["PTR_FORMAT", "PTR_FORMAT"] top: "PTR_FORMAT" "
2680 "TAMS: "PTR_FORMAT, b, e, t, p);
2681 _out->cr();
2682
2683 HeapWord* from = b;
2684 HeapWord* to = t;
2685
2686 if (to > from) {
2687 _out->print_cr("Objects in ["PTR_FORMAT", "PTR_FORMAT"]", from, to);
2688 _out->cr();
2689 PrintReachableObjectClosure ocl(_out, _vo, _all, hr);
2690 hr->object_iterate_mem_careful(MemRegion(from, to), &ocl);
2691 _out->cr();
2692 }
2693
2694 return false;
2695 }
2696
2697 PrintReachableRegionClosure(outputStream* out,
2698 VerifyOption vo,
2699 bool all) :
2700 _g1h(G1CollectedHeap::heap()), _out(out), _vo(vo), _all(all) { }
2701 };
2702
2703 void ConcurrentMark::print_reachable(const char* str,
2704 VerifyOption vo,
2705 bool all) {
2706 gclog_or_tty->cr();
2707 gclog_or_tty->print_cr("== Doing heap dump... ");
2708
2709 if (G1PrintReachableBaseFile == NULL) {
2710 gclog_or_tty->print_cr(" #### error: no base file defined");
2711 return;
2712 }
2713
2714 if (strlen(G1PrintReachableBaseFile) + 1 + strlen(str) >
2715 (JVM_MAXPATHLEN - 1)) {
2716 gclog_or_tty->print_cr(" #### error: file name too long");
2717 return;
2718 }
2719
2720 char file_name[JVM_MAXPATHLEN];
2721 sprintf(file_name, "%s.%s", G1PrintReachableBaseFile, str);
2722 gclog_or_tty->print_cr(" dumping to file %s", file_name);
2723
2724 fileStream fout(file_name);
2725 if (!fout.is_open()) {
2726 gclog_or_tty->print_cr(" #### error: could not open file");
2727 return;
2728 }
2729
2730 outputStream* out = &fout;
2731 out->print_cr("-- USING %s", _g1h->top_at_mark_start_str(vo));
2732 out->cr();
2733
2734 out->print_cr("--- ITERATING OVER REGIONS");
2735 out->cr();
2736 PrintReachableRegionClosure rcl(out, vo, all);
2737 _g1h->heap_region_iterate(&rcl);
2738 out->cr();
2739
2740 gclog_or_tty->print_cr(" done");
2741 gclog_or_tty->flush();
2742 }
2743
2744 #endif // PRODUCT
2745
2746 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2747 // Note we are overriding the read-only view of the prev map here, via
2748 // the cast.
2749 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2750 }
2751
2752 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2753 _nextMarkBitMap->clearRange(mr);
2754 }
2755
2756 void ConcurrentMark::clearRangeBothBitmaps(MemRegion mr) {
2757 clearRangePrevBitmap(mr);
2758 clearRangeNextBitmap(mr);
2759 }
2760
2761 HeapRegion*
2762 ConcurrentMark::claim_region(uint worker_id) {
2763 // "checkpoint" the finger
2764 HeapWord* finger = _finger;
2765
2766 // _heap_end will not change underneath our feet; it only changes at
2767 // yield points.
2768 while (finger < _heap_end) {
2769 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2770
2771 // Note on how this code handles humongous regions. In the
2772 // normal case the finger will reach the start of a "starts
2773 // humongous" (SH) region. Its end will either be the end of the
2774 // last "continues humongous" (CH) region in the sequence, or the
2775 // standard end of the SH region (if the SH is the only region in
2776 // the sequence). That way claim_region() will skip over the CH
2777 // regions. However, there is a subtle race between a CM thread
2778 // executing this method and a mutator thread doing a humongous
2779 // object allocation. The two are not mutually exclusive as the CM
2780 // thread does not need to hold the Heap_lock when it gets
2781 // here. So there is a chance that claim_region() will come across
2782 // a free region that's in the progress of becoming a SH or a CH
2783 // region. In the former case, it will either
2784 // a) Miss the update to the region's end, in which case it will
2785 // visit every subsequent CH region, will find their bitmaps
2786 // empty, and do nothing, or
2787 // b) Will observe the update of the region's end (in which case
2788 // it will skip the subsequent CH regions).
2789 // If it comes across a region that suddenly becomes CH, the
2790 // scenario will be similar to b). So, the race between
2791 // claim_region() and a humongous object allocation might force us
2792 // to do a bit of unnecessary work (due to some unnecessary bitmap
2793 // iterations) but it should not introduce and correctness issues.
2794 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2795 HeapWord* bottom = curr_region->bottom();
2796 HeapWord* end = curr_region->end();
2797 HeapWord* limit = curr_region->next_top_at_mark_start();
2798
2799 if (verbose_low()) {
2800 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2801 "["PTR_FORMAT", "PTR_FORMAT"), "
2802 "limit = "PTR_FORMAT,
2803 worker_id, curr_region, bottom, end, limit);
2804 }
2805
2806 // Is the gap between reading the finger and doing the CAS too long?
2807 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2808 if (res == finger) {
2809 // we succeeded
2810
2811 // notice that _finger == end cannot be guaranteed here since,
2812 // someone else might have moved the finger even further
2813 assert(_finger >= end, "the finger should have moved forward");
2814
2815 if (verbose_low()) {
2816 gclog_or_tty->print_cr("[%u] we were successful with region = "
2817 PTR_FORMAT, worker_id, curr_region);
2818 }
2819
2820 if (limit > bottom) {
2821 if (verbose_low()) {
2822 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2823 "returning it ", worker_id, curr_region);
2824 }
2825 return curr_region;
2826 } else {
2827 assert(limit == bottom,
2828 "the region limit should be at bottom");
2829 if (verbose_low()) {
2830 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2831 "returning NULL", worker_id, curr_region);
2832 }
2833 // we return NULL and the caller should try calling
2834 // claim_region() again.
2835 return NULL;
2836 }
2837 } else {
2838 assert(_finger > finger, "the finger should have moved forward");
2839 if (verbose_low()) {
2840 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2841 "global finger = "PTR_FORMAT", "
2842 "our finger = "PTR_FORMAT,
2843 worker_id, _finger, finger);
2844 }
2845
2846 // read it again
2847 finger = _finger;
2848 }
2849 }
2850
2851 return NULL;
2852 }
2853
2854 #ifndef PRODUCT
2855 enum VerifyNoCSetOopsPhase {
2856 VerifyNoCSetOopsStack,
2857 VerifyNoCSetOopsQueues,
2858 VerifyNoCSetOopsSATBCompleted,
2859 VerifyNoCSetOopsSATBThread
2860 };
2861
2862 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2863 private:
2864 G1CollectedHeap* _g1h;
2865 VerifyNoCSetOopsPhase _phase;
2866 int _info;
2867
2868 const char* phase_str() {
2869 switch (_phase) {
2870 case VerifyNoCSetOopsStack: return "Stack";
2871 case VerifyNoCSetOopsQueues: return "Queue";
2872 case VerifyNoCSetOopsSATBCompleted: return "Completed SATB Buffers";
2873 case VerifyNoCSetOopsSATBThread: return "Thread SATB Buffers";
2874 default: ShouldNotReachHere();
2875 }
2876 return NULL;
2877 }
2878
2879 void do_object_work(oop obj) {
2880 guarantee(!_g1h->obj_in_cs(obj),
2881 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2882 (void*) obj, phase_str(), _info));
2883 }
2884
2885 public:
2886 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2887
2888 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2889 _phase = phase;
2890 _info = info;
2891 }
2892
2893 virtual void do_oop(oop* p) {
2894 oop obj = oopDesc::load_decode_heap_oop(p);
2895 do_object_work(obj);
2896 }
2897
2898 virtual void do_oop(narrowOop* p) {
2899 // We should not come across narrow oops while scanning marking
2900 // stacks and SATB buffers.
2901 ShouldNotReachHere();
2902 }
2903
2904 virtual void do_object(oop obj) {
2905 do_object_work(obj);
2906 }
2907 };
2908
2909 void ConcurrentMark::verify_no_cset_oops(bool verify_stacks,
2910 bool verify_enqueued_buffers,
2911 bool verify_thread_buffers,
2912 bool verify_fingers) {
2913 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2914 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2915 return;
2916 }
2917
2918 VerifyNoCSetOopsClosure cl;
2919
2920 if (verify_stacks) {
2921 // Verify entries on the global mark stack
2922 cl.set_phase(VerifyNoCSetOopsStack);
2923 _markStack.oops_do(&cl);
2924
2925 // Verify entries on the task queues
2926 for (uint i = 0; i < _max_worker_id; i += 1) {
2927 cl.set_phase(VerifyNoCSetOopsQueues, i);
2928 CMTaskQueue* queue = _task_queues->queue(i);
2929 queue->oops_do(&cl);
2930 }
2931 }
2932
2933 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
2934
2935 // Verify entries on the enqueued SATB buffers
2936 if (verify_enqueued_buffers) {
2937 cl.set_phase(VerifyNoCSetOopsSATBCompleted);
2938 satb_qs.iterate_completed_buffers_read_only(&cl);
2939 }
2940
2941 // Verify entries on the per-thread SATB buffers
2942 if (verify_thread_buffers) {
2943 cl.set_phase(VerifyNoCSetOopsSATBThread);
2944 satb_qs.iterate_thread_buffers_read_only(&cl);
2945 }
2946
2947 if (verify_fingers) {
2948 // Verify the global finger
2949 HeapWord* global_finger = finger();
2950 if (global_finger != NULL && global_finger < _heap_end) {
2951 // The global finger always points to a heap region boundary. We
2952 // use heap_region_containing_raw() to get the containing region
2953 // given that the global finger could be pointing to a free region
2954 // which subsequently becomes continues humongous. If that
2955 // happens, heap_region_containing() will return the bottom of the
2956 // corresponding starts humongous region and the check below will
2957 // not hold any more.
2958 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2959 guarantee(global_finger == global_hr->bottom(),
2960 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2961 global_finger, HR_FORMAT_PARAMS(global_hr)));
2962 }
2963
2964 // Verify the task fingers
2965 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2966 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
2967 CMTask* task = _tasks[i];
2968 HeapWord* task_finger = task->finger();
2969 if (task_finger != NULL && task_finger < _heap_end) {
2970 // See above note on the global finger verification.
2971 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2972 guarantee(task_finger == task_hr->bottom() ||
2973 !task_hr->in_collection_set(),
2974 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
2975 task_finger, HR_FORMAT_PARAMS(task_hr)));
2976 }
2977 }
2978 }
2979 }
2980 #endif // PRODUCT
2981
2982 // Aggregate the counting data that was constructed concurrently
2983 // with marking.
2984 class AggregateCountDataHRClosure: public HeapRegionClosure {
2985 G1CollectedHeap* _g1h;
2986 ConcurrentMark* _cm;
2987 CardTableModRefBS* _ct_bs;
2988 BitMap* _cm_card_bm;
2989 uint _max_worker_id;
2990
2991 public:
2992 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2993 BitMap* cm_card_bm,
2994 uint max_worker_id) :
2995 _g1h(g1h), _cm(g1h->concurrent_mark()),
2996 _ct_bs((CardTableModRefBS*) (g1h->barrier_set())),
2997 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2998
2999 bool doHeapRegion(HeapRegion* hr) {
3000 if (hr->continuesHumongous()) {
3001 // We will ignore these here and process them when their
3002 // associated "starts humongous" region is processed.
3003 // Note that we cannot rely on their associated
3004 // "starts humongous" region to have their bit set to 1
3005 // since, due to the region chunking in the parallel region
3006 // iteration, a "continues humongous" region might be visited
3007 // before its associated "starts humongous".
3008 return false;
3009 }
3010
3011 HeapWord* start = hr->bottom();
3012 HeapWord* limit = hr->next_top_at_mark_start();
3013 HeapWord* end = hr->end();
3014
3015 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
3016 err_msg("Preconditions not met - "
3017 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
3018 "top: "PTR_FORMAT", end: "PTR_FORMAT,
3019 start, limit, hr->top(), hr->end()));
3020
3021 assert(hr->next_marked_bytes() == 0, "Precondition");
3022
3023 if (start == limit) {
3024 // NTAMS of this region has not been set so nothing to do.
3025 return false;
3026 }
3027
3028 // 'start' should be in the heap.
3029 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
3030 // 'end' *may* be just beyone the end of the heap (if hr is the last region)
3031 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
3032
3033 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
3034 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
3035 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
3036
3037 // If ntams is not card aligned then we bump card bitmap index
3038 // for limit so that we get the all the cards spanned by
3039 // the object ending at ntams.
3040 // Note: if this is the last region in the heap then ntams
3041 // could be actually just beyond the end of the the heap;
3042 // limit_idx will then correspond to a (non-existent) card
3043 // that is also outside the heap.
3044 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
3045 limit_idx += 1;
3046 }
3047
3048 assert(limit_idx <= end_idx, "or else use atomics");
3049
3050 // Aggregate the "stripe" in the count data associated with hr.
3051 uint hrs_index = hr->hrs_index();
3052 size_t marked_bytes = 0;
3053
3054 for (uint i = 0; i < _max_worker_id; i += 1) {
3055 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
3056 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
3057
3058 // Fetch the marked_bytes in this region for task i and
3059 // add it to the running total for this region.
3060 marked_bytes += marked_bytes_array[hrs_index];
3061
3062 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
3063 // into the global card bitmap.
3064 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
3065
3066 while (scan_idx < limit_idx) {
3067 assert(task_card_bm->at(scan_idx) == true, "should be");
3068 _cm_card_bm->set_bit(scan_idx);
3069 assert(_cm_card_bm->at(scan_idx) == true, "should be");
3070
3071 // BitMap::get_next_one_offset() can handle the case when
3072 // its left_offset parameter is greater than its right_offset
3073 // parameter. It does, however, have an early exit if
3074 // left_offset == right_offset. So let's limit the value
3075 // passed in for left offset here.
3076 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
3077 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
3078 }
3079 }
3080
3081 // Update the marked bytes for this region.
3082 hr->add_to_marked_bytes(marked_bytes);
3083
3084 // Next heap region
3085 return false;
3086 }
3087 };
3088
3089 class G1AggregateCountDataTask: public AbstractGangTask {
3090 protected:
3091 G1CollectedHeap* _g1h;
3092 ConcurrentMark* _cm;
3093 BitMap* _cm_card_bm;
3094 uint _max_worker_id;
3095 int _active_workers;
3096
3097 public:
3098 G1AggregateCountDataTask(G1CollectedHeap* g1h,
3099 ConcurrentMark* cm,
3100 BitMap* cm_card_bm,
3101 uint max_worker_id,
3102 int n_workers) :
3103 AbstractGangTask("Count Aggregation"),
3104 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
3105 _max_worker_id(max_worker_id),
3106 _active_workers(n_workers) { }
3107
3108 void work(uint worker_id) {
3109 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
3110
3111 if (G1CollectedHeap::use_parallel_gc_threads()) {
3112 _g1h->heap_region_par_iterate_chunked(&cl, worker_id,
3113 _active_workers,
3114 HeapRegion::AggregateCountClaimValue);
3115 } else {
3116 _g1h->heap_region_iterate(&cl);
3117 }
3118 }
3119 };
3120
3121
3122 void ConcurrentMark::aggregate_count_data() {
3123 int n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3124 _g1h->workers()->active_workers() :
3125 1);
3126
3127 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3128 _max_worker_id, n_workers);
3129
3130 if (G1CollectedHeap::use_parallel_gc_threads()) {
3131 assert(_g1h->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3132 "sanity check");
3133 _g1h->set_par_threads(n_workers);
3134 _g1h->workers()->run_task(&g1_par_agg_task);
3135 _g1h->set_par_threads(0);
3136
3137 assert(_g1h->check_heap_region_claim_values(HeapRegion::AggregateCountClaimValue),
3138 "sanity check");
3139 _g1h->reset_heap_region_claim_values();
3140 } else {
3141 g1_par_agg_task.work(0);
3142 }
3143 }
3144
3145 // Clear the per-worker arrays used to store the per-region counting data
3146 void ConcurrentMark::clear_all_count_data() {
3147 // Clear the global card bitmap - it will be filled during
3148 // liveness count aggregation (during remark) and the
3149 // final counting task.
3150 _card_bm.clear();
3151
3152 // Clear the global region bitmap - it will be filled as part
3153 // of the final counting task.
3154 _region_bm.clear();
3155
3156 uint max_regions = _g1h->max_regions();
3157 assert(_max_worker_id > 0, "uninitialized");
3158
3159 for (uint i = 0; i < _max_worker_id; i += 1) {
3160 BitMap* task_card_bm = count_card_bitmap_for(i);
3161 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3162
3163 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3164 assert(marked_bytes_array != NULL, "uninitialized");
3165
3166 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3167 task_card_bm->clear();
3168 }
3169 }
3170
3171 void ConcurrentMark::print_stats() {
3172 if (verbose_stats()) {
3173 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3174 for (size_t i = 0; i < _active_tasks; ++i) {
3175 _tasks[i]->print_stats();
3176 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3177 }
3178 }
3179 }
3180
3181 // abandon current marking iteration due to a Full GC
3182 void ConcurrentMark::abort() {
3183 // Clear all marks to force marking thread to do nothing
3184 _nextMarkBitMap->clearAll();
3185 // Clear the liveness counting data
3186 clear_all_count_data();
3187 // Empty mark stack
3188 reset_marking_state();
3189 for (uint i = 0; i < _max_worker_id; ++i) {
3190 _tasks[i]->clear_region_fields();
3191 }
3192 _has_aborted = true;
3193
3194 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3195 satb_mq_set.abandon_partial_marking();
3196 // This can be called either during or outside marking, we'll read
3197 // the expected_active value from the SATB queue set.
3198 satb_mq_set.set_active_all_threads(
3199 false, /* new active value */
3200 satb_mq_set.is_active() /* expected_active */);
3201 }
3202
3203 static void print_ms_time_info(const char* prefix, const char* name,
3204 NumberSeq& ns) {
3205 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3206 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3207 if (ns.num() > 0) {
3208 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3209 prefix, ns.sd(), ns.maximum());
3210 }
3211 }
3212
3213 void ConcurrentMark::print_summary_info() {
3214 gclog_or_tty->print_cr(" Concurrent marking:");
3215 print_ms_time_info(" ", "init marks", _init_times);
3216 print_ms_time_info(" ", "remarks", _remark_times);
3217 {
3218 print_ms_time_info(" ", "final marks", _remark_mark_times);
3219 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3220
3221 }
3222 print_ms_time_info(" ", "cleanups", _cleanup_times);
3223 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3224 _total_counting_time,
3225 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3226 (double)_cleanup_times.num()
3227 : 0.0));
3228 if (G1ScrubRemSets) {
3229 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3230 _total_rs_scrub_time,
3231 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3232 (double)_cleanup_times.num()
3233 : 0.0));
3234 }
3235 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3236 (_init_times.sum() + _remark_times.sum() +
3237 _cleanup_times.sum())/1000.0);
3238 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3239 "(%8.2f s marking).",
3240 cmThread()->vtime_accum(),
3241 cmThread()->vtime_mark_accum());
3242 }
3243
3244 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3245 _parallel_workers->print_worker_threads_on(st);
3246 }
3247
3248 // We take a break if someone is trying to stop the world.
3249 bool ConcurrentMark::do_yield_check(uint worker_id) {
3250 if (should_yield()) {
3251 if (worker_id == 0) {
3252 _g1h->g1_policy()->record_concurrent_pause();
3253 }
3254 cmThread()->yield();
3255 return true;
3256 } else {
3257 return false;
3258 }
3259 }
3260
3261 bool ConcurrentMark::should_yield() {
3262 return cmThread()->should_yield();
3263 }
3264
3265 bool ConcurrentMark::containing_card_is_marked(void* p) {
3266 size_t offset = pointer_delta(p, _g1h->reserved_region().start(), 1);
3267 return _card_bm.at(offset >> CardTableModRefBS::card_shift);
3268 }
3269
3270 bool ConcurrentMark::containing_cards_are_marked(void* start,
3271 void* last) {
3272 return containing_card_is_marked(start) &&
3273 containing_card_is_marked(last);
3274 }
3275
3276 #ifndef PRODUCT
3277 // for debugging purposes
3278 void ConcurrentMark::print_finger() {
3279 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3280 _heap_start, _heap_end, _finger);
3281 for (uint i = 0; i < _max_worker_id; ++i) {
3282 gclog_or_tty->print(" %u: "PTR_FORMAT, i, _tasks[i]->finger());
3283 }
3284 gclog_or_tty->print_cr("");
3285 }
3286 #endif
3287
3288 void CMTask::scan_object(oop obj) {
3289 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3290
3291 if (_cm->verbose_high()) {
3292 gclog_or_tty->print_cr("[%u] we're scanning object "PTR_FORMAT,
3293 _worker_id, (void*) obj);
3294 }
3295
3296 size_t obj_size = obj->size();
3297 _words_scanned += obj_size;
3298
3299 obj->oop_iterate(_cm_oop_closure);
3300 statsOnly( ++_objs_scanned );
3301 check_limits();
3302 }
3303
3304 // Closure for iteration over bitmaps
3305 class CMBitMapClosure : public BitMapClosure {
3306 private:
3307 // the bitmap that is being iterated over
3308 CMBitMap* _nextMarkBitMap;
3309 ConcurrentMark* _cm;
3310 CMTask* _task;
3311
3312 public:
3313 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3314 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3315
3316 bool do_bit(size_t offset) {
3317 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3318 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3319 assert( addr < _cm->finger(), "invariant");
3320
3321 statsOnly( _task->increase_objs_found_on_bitmap() );
3322 assert(addr >= _task->finger(), "invariant");
3323
3324 // We move that task's local finger along.
3325 _task->move_finger_to(addr);
3326
3327 _task->scan_object(oop(addr));
3328 // we only partially drain the local queue and global stack
3329 _task->drain_local_queue(true);
3330 _task->drain_global_stack(true);
3331
3332 // if the has_aborted flag has been raised, we need to bail out of
3333 // the iteration
3334 return !_task->has_aborted();
3335 }
3336 };
3337
3338 // Closure for iterating over objects, currently only used for
3339 // processing SATB buffers.
3340 class CMObjectClosure : public ObjectClosure {
3341 private:
3342 CMTask* _task;
3343
3344 public:
3345 void do_object(oop obj) {
3346 _task->deal_with_reference(obj);
3347 }
3348
3349 CMObjectClosure(CMTask* task) : _task(task) { }
3350 };
3351
3352 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3353 ConcurrentMark* cm,
3354 CMTask* task)
3355 : _g1h(g1h), _cm(cm), _task(task) {
3356 assert(_ref_processor == NULL, "should be initialized to NULL");
3357
3358 if (G1UseConcMarkReferenceProcessing) {
3359 _ref_processor = g1h->ref_processor_cm();
3360 assert(_ref_processor != NULL, "should not be NULL");
3361 }
3362 }
3363
3364 void CMTask::setup_for_region(HeapRegion* hr) {
3365 // Separated the asserts so that we know which one fires.
3366 assert(hr != NULL,
3367 "claim_region() should have filtered out continues humongous regions");
3368 assert(!hr->continuesHumongous(),
3369 "claim_region() should have filtered out continues humongous regions");
3370
3371 if (_cm->verbose_low()) {
3372 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3373 _worker_id, hr);
3374 }
3375
3376 _curr_region = hr;
3377 _finger = hr->bottom();
3378 update_region_limit();
3379 }
3380
3381 void CMTask::update_region_limit() {
3382 HeapRegion* hr = _curr_region;
3383 HeapWord* bottom = hr->bottom();
3384 HeapWord* limit = hr->next_top_at_mark_start();
3385
3386 if (limit == bottom) {
3387 if (_cm->verbose_low()) {
3388 gclog_or_tty->print_cr("[%u] found an empty region "
3389 "["PTR_FORMAT", "PTR_FORMAT")",
3390 _worker_id, bottom, limit);
3391 }
3392 // The region was collected underneath our feet.
3393 // We set the finger to bottom to ensure that the bitmap
3394 // iteration that will follow this will not do anything.
3395 // (this is not a condition that holds when we set the region up,
3396 // as the region is not supposed to be empty in the first place)
3397 _finger = bottom;
3398 } else if (limit >= _region_limit) {
3399 assert(limit >= _finger, "peace of mind");
3400 } else {
3401 assert(limit < _region_limit, "only way to get here");
3402 // This can happen under some pretty unusual circumstances. An
3403 // evacuation pause empties the region underneath our feet (NTAMS
3404 // at bottom). We then do some allocation in the region (NTAMS
3405 // stays at bottom), followed by the region being used as a GC
3406 // alloc region (NTAMS will move to top() and the objects
3407 // originally below it will be grayed). All objects now marked in
3408 // the region are explicitly grayed, if below the global finger,
3409 // and we do not need in fact to scan anything else. So, we simply
3410 // set _finger to be limit to ensure that the bitmap iteration
3411 // doesn't do anything.
3412 _finger = limit;
3413 }
3414
3415 _region_limit = limit;
3416 }
3417
3418 void CMTask::giveup_current_region() {
3419 assert(_curr_region != NULL, "invariant");
3420 if (_cm->verbose_low()) {
3421 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3422 _worker_id, _curr_region);
3423 }
3424 clear_region_fields();
3425 }
3426
3427 void CMTask::clear_region_fields() {
3428 // Values for these three fields that indicate that we're not
3429 // holding on to a region.
3430 _curr_region = NULL;
3431 _finger = NULL;
3432 _region_limit = NULL;
3433 }
3434
3435 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3436 if (cm_oop_closure == NULL) {
3437 assert(_cm_oop_closure != NULL, "invariant");
3438 } else {
3439 assert(_cm_oop_closure == NULL, "invariant");
3440 }
3441 _cm_oop_closure = cm_oop_closure;
3442 }
3443
3444 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3445 guarantee(nextMarkBitMap != NULL, "invariant");
3446
3447 if (_cm->verbose_low()) {
3448 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3449 }
3450
3451 _nextMarkBitMap = nextMarkBitMap;
3452 clear_region_fields();
3453
3454 _calls = 0;
3455 _elapsed_time_ms = 0.0;
3456 _termination_time_ms = 0.0;
3457 _termination_start_time_ms = 0.0;
3458
3459 #if _MARKING_STATS_
3460 _local_pushes = 0;
3461 _local_pops = 0;
3462 _local_max_size = 0;
3463 _objs_scanned = 0;
3464 _global_pushes = 0;
3465 _global_pops = 0;
3466 _global_max_size = 0;
3467 _global_transfers_to = 0;
3468 _global_transfers_from = 0;
3469 _regions_claimed = 0;
3470 _objs_found_on_bitmap = 0;
3471 _satb_buffers_processed = 0;
3472 _steal_attempts = 0;
3473 _steals = 0;
3474 _aborted = 0;
3475 _aborted_overflow = 0;
3476 _aborted_cm_aborted = 0;
3477 _aborted_yield = 0;
3478 _aborted_timed_out = 0;
3479 _aborted_satb = 0;
3480 _aborted_termination = 0;
3481 #endif // _MARKING_STATS_
3482 }
3483
3484 bool CMTask::should_exit_termination() {
3485 regular_clock_call();
3486 // This is called when we are in the termination protocol. We should
3487 // quit if, for some reason, this task wants to abort or the global
3488 // stack is not empty (this means that we can get work from it).
3489 return !_cm->mark_stack_empty() || has_aborted();
3490 }
3491
3492 void CMTask::reached_limit() {
3493 assert(_words_scanned >= _words_scanned_limit ||
3494 _refs_reached >= _refs_reached_limit ,
3495 "shouldn't have been called otherwise");
3496 regular_clock_call();
3497 }
3498
3499 void CMTask::regular_clock_call() {
3500 if (has_aborted()) return;
3501
3502 // First, we need to recalculate the words scanned and refs reached
3503 // limits for the next clock call.
3504 recalculate_limits();
3505
3506 // During the regular clock call we do the following
3507
3508 // (1) If an overflow has been flagged, then we abort.
3509 if (_cm->has_overflown()) {
3510 set_has_aborted();
3511 return;
3512 }
3513
3514 // If we are not concurrent (i.e. we're doing remark) we don't need
3515 // to check anything else. The other steps are only needed during
3516 // the concurrent marking phase.
3517 if (!concurrent()) return;
3518
3519 // (2) If marking has been aborted for Full GC, then we also abort.
3520 if (_cm->has_aborted()) {
3521 set_has_aborted();
3522 statsOnly( ++_aborted_cm_aborted );
3523 return;
3524 }
3525
3526 double curr_time_ms = os::elapsedVTime() * 1000.0;
3527
3528 // (3) If marking stats are enabled, then we update the step history.
3529 #if _MARKING_STATS_
3530 if (_words_scanned >= _words_scanned_limit) {
3531 ++_clock_due_to_scanning;
3532 }
3533 if (_refs_reached >= _refs_reached_limit) {
3534 ++_clock_due_to_marking;
3535 }
3536
3537 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3538 _interval_start_time_ms = curr_time_ms;
3539 _all_clock_intervals_ms.add(last_interval_ms);
3540
3541 if (_cm->verbose_medium()) {
3542 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3543 "scanned = %d%s, refs reached = %d%s",
3544 _worker_id, last_interval_ms,
3545 _words_scanned,
3546 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3547 _refs_reached,
3548 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3549 }
3550 #endif // _MARKING_STATS_
3551
3552 // (4) We check whether we should yield. If we have to, then we abort.
3553 if (_cm->should_yield()) {
3554 // We should yield. To do this we abort the task. The caller is
3555 // responsible for yielding.
3556 set_has_aborted();
3557 statsOnly( ++_aborted_yield );
3558 return;
3559 }
3560
3561 // (5) We check whether we've reached our time quota. If we have,
3562 // then we abort.
3563 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3564 if (elapsed_time_ms > _time_target_ms) {
3565 set_has_aborted();
3566 _has_timed_out = true;
3567 statsOnly( ++_aborted_timed_out );
3568 return;
3569 }
3570
3571 // (6) Finally, we check whether there are enough completed STAB
3572 // buffers available for processing. If there are, we abort.
3573 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3574 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3575 if (_cm->verbose_low()) {
3576 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3577 _worker_id);
3578 }
3579 // we do need to process SATB buffers, we'll abort and restart
3580 // the marking task to do so
3581 set_has_aborted();
3582 statsOnly( ++_aborted_satb );
3583 return;
3584 }
3585 }
3586
3587 void CMTask::recalculate_limits() {
3588 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3589 _words_scanned_limit = _real_words_scanned_limit;
3590
3591 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3592 _refs_reached_limit = _real_refs_reached_limit;
3593 }
3594
3595 void CMTask::decrease_limits() {
3596 // This is called when we believe that we're going to do an infrequent
3597 // operation which will increase the per byte scanned cost (i.e. move
3598 // entries to/from the global stack). It basically tries to decrease the
3599 // scanning limit so that the clock is called earlier.
3600
3601 if (_cm->verbose_medium()) {
3602 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3603 }
3604
3605 _words_scanned_limit = _real_words_scanned_limit -
3606 3 * words_scanned_period / 4;
3607 _refs_reached_limit = _real_refs_reached_limit -
3608 3 * refs_reached_period / 4;
3609 }
3610
3611 void CMTask::move_entries_to_global_stack() {
3612 // local array where we'll store the entries that will be popped
3613 // from the local queue
3614 oop buffer[global_stack_transfer_size];
3615
3616 int n = 0;
3617 oop obj;
3618 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3619 buffer[n] = obj;
3620 ++n;
3621 }
3622
3623 if (n > 0) {
3624 // we popped at least one entry from the local queue
3625
3626 statsOnly( ++_global_transfers_to; _local_pops += n );
3627
3628 if (!_cm->mark_stack_push(buffer, n)) {
3629 if (_cm->verbose_low()) {
3630 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3631 _worker_id);
3632 }
3633 set_has_aborted();
3634 } else {
3635 // the transfer was successful
3636
3637 if (_cm->verbose_medium()) {
3638 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3639 _worker_id, n);
3640 }
3641 statsOnly( int tmp_size = _cm->mark_stack_size();
3642 if (tmp_size > _global_max_size) {
3643 _global_max_size = tmp_size;
3644 }
3645 _global_pushes += n );
3646 }
3647 }
3648
3649 // this operation was quite expensive, so decrease the limits
3650 decrease_limits();
3651 }
3652
3653 void CMTask::get_entries_from_global_stack() {
3654 // local array where we'll store the entries that will be popped
3655 // from the global stack.
3656 oop buffer[global_stack_transfer_size];
3657 int n;
3658 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3659 assert(n <= global_stack_transfer_size,
3660 "we should not pop more than the given limit");
3661 if (n > 0) {
3662 // yes, we did actually pop at least one entry
3663
3664 statsOnly( ++_global_transfers_from; _global_pops += n );
3665 if (_cm->verbose_medium()) {
3666 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3667 _worker_id, n);
3668 }
3669 for (int i = 0; i < n; ++i) {
3670 bool success = _task_queue->push(buffer[i]);
3671 // We only call this when the local queue is empty or under a
3672 // given target limit. So, we do not expect this push to fail.
3673 assert(success, "invariant");
3674 }
3675
3676 statsOnly( int tmp_size = _task_queue->size();
3677 if (tmp_size > _local_max_size) {
3678 _local_max_size = tmp_size;
3679 }
3680 _local_pushes += n );
3681 }
3682
3683 // this operation was quite expensive, so decrease the limits
3684 decrease_limits();
3685 }
3686
3687 void CMTask::drain_local_queue(bool partially) {
3688 if (has_aborted()) return;
3689
3690 // Decide what the target size is, depending whether we're going to
3691 // drain it partially (so that other tasks can steal if they run out
3692 // of things to do) or totally (at the very end).
3693 size_t target_size;
3694 if (partially) {
3695 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3696 } else {
3697 target_size = 0;
3698 }
3699
3700 if (_task_queue->size() > target_size) {
3701 if (_cm->verbose_high()) {
3702 gclog_or_tty->print_cr("[%u] draining local queue, target size = %d",
3703 _worker_id, target_size);
3704 }
3705
3706 oop obj;
3707 bool ret = _task_queue->pop_local(obj);
3708 while (ret) {
3709 statsOnly( ++_local_pops );
3710
3711 if (_cm->verbose_high()) {
3712 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3713 (void*) obj);
3714 }
3715
3716 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3717 assert(!_g1h->is_on_master_free_list(
3718 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3719
3720 scan_object(obj);
3721
3722 if (_task_queue->size() <= target_size || has_aborted()) {
3723 ret = false;
3724 } else {
3725 ret = _task_queue->pop_local(obj);
3726 }
3727 }
3728
3729 if (_cm->verbose_high()) {
3730 gclog_or_tty->print_cr("[%u] drained local queue, size = %d",
3731 _worker_id, _task_queue->size());
3732 }
3733 }
3734 }
3735
3736 void CMTask::drain_global_stack(bool partially) {
3737 if (has_aborted()) return;
3738
3739 // We have a policy to drain the local queue before we attempt to
3740 // drain the global stack.
3741 assert(partially || _task_queue->size() == 0, "invariant");
3742
3743 // Decide what the target size is, depending whether we're going to
3744 // drain it partially (so that other tasks can steal if they run out
3745 // of things to do) or totally (at the very end). Notice that,
3746 // because we move entries from the global stack in chunks or
3747 // because another task might be doing the same, we might in fact
3748 // drop below the target. But, this is not a problem.
3749 size_t target_size;
3750 if (partially) {
3751 target_size = _cm->partial_mark_stack_size_target();
3752 } else {
3753 target_size = 0;
3754 }
3755
3756 if (_cm->mark_stack_size() > target_size) {
3757 if (_cm->verbose_low()) {
3758 gclog_or_tty->print_cr("[%u] draining global_stack, target size %d",
3759 _worker_id, target_size);
3760 }
3761
3762 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3763 get_entries_from_global_stack();
3764 drain_local_queue(partially);
3765 }
3766
3767 if (_cm->verbose_low()) {
3768 gclog_or_tty->print_cr("[%u] drained global stack, size = %d",
3769 _worker_id, _cm->mark_stack_size());
3770 }
3771 }
3772 }
3773
3774 // SATB Queue has several assumptions on whether to call the par or
3775 // non-par versions of the methods. this is why some of the code is
3776 // replicated. We should really get rid of the single-threaded version
3777 // of the code to simplify things.
3778 void CMTask::drain_satb_buffers() {
3779 if (has_aborted()) return;
3780
3781 // We set this so that the regular clock knows that we're in the
3782 // middle of draining buffers and doesn't set the abort flag when it
3783 // notices that SATB buffers are available for draining. It'd be
3784 // very counter productive if it did that. :-)
3785 _draining_satb_buffers = true;
3786
3787 CMObjectClosure oc(this);
3788 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3789 if (G1CollectedHeap::use_parallel_gc_threads()) {
3790 satb_mq_set.set_par_closure(_worker_id, &oc);
3791 } else {
3792 satb_mq_set.set_closure(&oc);
3793 }
3794
3795 // This keeps claiming and applying the closure to completed buffers
3796 // until we run out of buffers or we need to abort.
3797 if (G1CollectedHeap::use_parallel_gc_threads()) {
3798 while (!has_aborted() &&
3799 satb_mq_set.par_apply_closure_to_completed_buffer(_worker_id)) {
3800 if (_cm->verbose_medium()) {
3801 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3802 }
3803 statsOnly( ++_satb_buffers_processed );
3804 regular_clock_call();
3805 }
3806 } else {
3807 while (!has_aborted() &&
3808 satb_mq_set.apply_closure_to_completed_buffer()) {
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 }
3816
3817 if (!concurrent() && !has_aborted()) {
3818 // We should only do this during remark.
3819 if (G1CollectedHeap::use_parallel_gc_threads()) {
3820 satb_mq_set.par_iterate_closure_all_threads(_worker_id);
3821 } else {
3822 satb_mq_set.iterate_closure_all_threads();
3823 }
3824 }
3825
3826 _draining_satb_buffers = false;
3827
3828 assert(has_aborted() ||
3829 concurrent() ||
3830 satb_mq_set.completed_buffers_num() == 0, "invariant");
3831
3832 if (G1CollectedHeap::use_parallel_gc_threads()) {
3833 satb_mq_set.set_par_closure(_worker_id, NULL);
3834 } else {
3835 satb_mq_set.set_closure(NULL);
3836 }
3837
3838 // again, this was a potentially expensive operation, decrease the
3839 // limits to get the regular clock call early
3840 decrease_limits();
3841 }
3842
3843 void CMTask::print_stats() {
3844 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3845 _worker_id, _calls);
3846 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3847 _elapsed_time_ms, _termination_time_ms);
3848 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3849 _step_times_ms.num(), _step_times_ms.avg(),
3850 _step_times_ms.sd());
3851 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3852 _step_times_ms.maximum(), _step_times_ms.sum());
3853
3854 #if _MARKING_STATS_
3855 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3856 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3857 _all_clock_intervals_ms.sd());
3858 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3859 _all_clock_intervals_ms.maximum(),
3860 _all_clock_intervals_ms.sum());
3861 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = %d, marking = %d",
3862 _clock_due_to_scanning, _clock_due_to_marking);
3863 gclog_or_tty->print_cr(" Objects: scanned = %d, found on the bitmap = %d",
3864 _objs_scanned, _objs_found_on_bitmap);
3865 gclog_or_tty->print_cr(" Local Queue: pushes = %d, pops = %d, max size = %d",
3866 _local_pushes, _local_pops, _local_max_size);
3867 gclog_or_tty->print_cr(" Global Stack: pushes = %d, pops = %d, max size = %d",
3868 _global_pushes, _global_pops, _global_max_size);
3869 gclog_or_tty->print_cr(" transfers to = %d, transfers from = %d",
3870 _global_transfers_to,_global_transfers_from);
3871 gclog_or_tty->print_cr(" Regions: claimed = %d", _regions_claimed);
3872 gclog_or_tty->print_cr(" SATB buffers: processed = %d", _satb_buffers_processed);
3873 gclog_or_tty->print_cr(" Steals: attempts = %d, successes = %d",
3874 _steal_attempts, _steals);
3875 gclog_or_tty->print_cr(" Aborted: %d, due to", _aborted);
3876 gclog_or_tty->print_cr(" overflow: %d, global abort: %d, yield: %d",
3877 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3878 gclog_or_tty->print_cr(" time out: %d, SATB: %d, termination: %d",
3879 _aborted_timed_out, _aborted_satb, _aborted_termination);
3880 #endif // _MARKING_STATS_
3881 }
3882
3883 /*****************************************************************************
3884
3885 The do_marking_step(time_target_ms) method is the building block
3886 of the parallel marking framework. It can be called in parallel
3887 with other invocations of do_marking_step() on different tasks
3888 (but only one per task, obviously) and concurrently with the
3889 mutator threads, or during remark, hence it eliminates the need
3890 for two versions of the code. When called during remark, it will
3891 pick up from where the task left off during the concurrent marking
3892 phase. Interestingly, tasks are also claimable during evacuation
3893 pauses too, since do_marking_step() ensures that it aborts before
3894 it needs to yield.
3895
3896 The data structures that is uses to do marking work are the
3897 following:
3898
3899 (1) Marking Bitmap. If there are gray objects that appear only
3900 on the bitmap (this happens either when dealing with an overflow
3901 or when the initial marking phase has simply marked the roots
3902 and didn't push them on the stack), then tasks claim heap
3903 regions whose bitmap they then scan to find gray objects. A
3904 global finger indicates where the end of the last claimed region
3905 is. A local finger indicates how far into the region a task has
3906 scanned. The two fingers are used to determine how to gray an
3907 object (i.e. whether simply marking it is OK, as it will be
3908 visited by a task in the future, or whether it needs to be also
3909 pushed on a stack).
3910
3911 (2) Local Queue. The local queue of the task which is accessed
3912 reasonably efficiently by the task. Other tasks can steal from
3913 it when they run out of work. Throughout the marking phase, a
3914 task attempts to keep its local queue short but not totally
3915 empty, so that entries are available for stealing by other
3916 tasks. Only when there is no more work, a task will totally
3917 drain its local queue.
3918
3919 (3) Global Mark Stack. This handles local queue overflow. During
3920 marking only sets of entries are moved between it and the local
3921 queues, as access to it requires a mutex and more fine-grain
3922 interaction with it which might cause contention. If it
3923 overflows, then the marking phase should restart and iterate
3924 over the bitmap to identify gray objects. Throughout the marking
3925 phase, tasks attempt to keep the global mark stack at a small
3926 length but not totally empty, so that entries are available for
3927 popping by other tasks. Only when there is no more work, tasks
3928 will totally drain the global mark stack.
3929
3930 (4) SATB Buffer Queue. This is where completed SATB buffers are
3931 made available. Buffers are regularly removed from this queue
3932 and scanned for roots, so that the queue doesn't get too
3933 long. During remark, all completed buffers are processed, as
3934 well as the filled in parts of any uncompleted buffers.
3935
3936 The do_marking_step() method tries to abort when the time target
3937 has been reached. There are a few other cases when the
3938 do_marking_step() method also aborts:
3939
3940 (1) When the marking phase has been aborted (after a Full GC).
3941
3942 (2) When a global overflow (on the global stack) has been
3943 triggered. Before the task aborts, it will actually sync up with
3944 the other tasks to ensure that all the marking data structures
3945 (local queues, stacks, fingers etc.) are re-initialised so that
3946 when do_marking_step() completes, the marking phase can
3947 immediately restart.
3948
3949 (3) When enough completed SATB buffers are available. The
3950 do_marking_step() method only tries to drain SATB buffers right
3951 at the beginning. So, if enough buffers are available, the
3952 marking step aborts and the SATB buffers are processed at
3953 the beginning of the next invocation.
3954
3955 (4) To yield. when we have to yield then we abort and yield
3956 right at the end of do_marking_step(). This saves us from a lot
3957 of hassle as, by yielding we might allow a Full GC. If this
3958 happens then objects will be compacted underneath our feet, the
3959 heap might shrink, etc. We save checking for this by just
3960 aborting and doing the yield right at the end.
3961
3962 From the above it follows that the do_marking_step() method should
3963 be called in a loop (or, otherwise, regularly) until it completes.
3964
3965 If a marking step completes without its has_aborted() flag being
3966 true, it means it has completed the current marking phase (and
3967 also all other marking tasks have done so and have all synced up).
3968
3969 A method called regular_clock_call() is invoked "regularly" (in
3970 sub ms intervals) throughout marking. It is this clock method that
3971 checks all the abort conditions which were mentioned above and
3972 decides when the task should abort. A work-based scheme is used to
3973 trigger this clock method: when the number of object words the
3974 marking phase has scanned or the number of references the marking
3975 phase has visited reach a given limit. Additional invocations to
3976 the method clock have been planted in a few other strategic places
3977 too. The initial reason for the clock method was to avoid calling
3978 vtime too regularly, as it is quite expensive. So, once it was in
3979 place, it was natural to piggy-back all the other conditions on it
3980 too and not constantly check them throughout the code.
3981
3982 *****************************************************************************/
3983
3984 void CMTask::do_marking_step(double time_target_ms,
3985 bool do_stealing,
3986 bool do_termination) {
3987 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3988 assert(concurrent() == _cm->concurrent(), "they should be the same");
3989
3990 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3991 assert(_task_queues != NULL, "invariant");
3992 assert(_task_queue != NULL, "invariant");
3993 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3994
3995 assert(!_claimed,
3996 "only one thread should claim this task at any one time");
3997
3998 // OK, this doesn't safeguard again all possible scenarios, as it is
3999 // possible for two threads to set the _claimed flag at the same
4000 // time. But it is only for debugging purposes anyway and it will
4001 // catch most problems.
4002 _claimed = true;
4003
4004 _start_time_ms = os::elapsedVTime() * 1000.0;
4005 statsOnly( _interval_start_time_ms = _start_time_ms );
4006
4007 double diff_prediction_ms =
4008 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
4009 _time_target_ms = time_target_ms - diff_prediction_ms;
4010
4011 // set up the variables that are used in the work-based scheme to
4012 // call the regular clock method
4013 _words_scanned = 0;
4014 _refs_reached = 0;
4015 recalculate_limits();
4016
4017 // clear all flags
4018 clear_has_aborted();
4019 _has_timed_out = false;
4020 _draining_satb_buffers = false;
4021
4022 ++_calls;
4023
4024 if (_cm->verbose_low()) {
4025 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
4026 "target = %1.2lfms >>>>>>>>>>",
4027 _worker_id, _calls, _time_target_ms);
4028 }
4029
4030 // Set up the bitmap and oop closures. Anything that uses them is
4031 // eventually called from this method, so it is OK to allocate these
4032 // statically.
4033 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
4034 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
4035 set_cm_oop_closure(&cm_oop_closure);
4036
4037 if (_cm->has_overflown()) {
4038 // This can happen if the mark stack overflows during a GC pause
4039 // and this task, after a yield point, restarts. We have to abort
4040 // as we need to get into the overflow protocol which happens
4041 // right at the end of this task.
4042 set_has_aborted();
4043 }
4044
4045 // First drain any available SATB buffers. After this, we will not
4046 // look at SATB buffers before the next invocation of this method.
4047 // If enough completed SATB buffers are queued up, the regular clock
4048 // will abort this task so that it restarts.
4049 drain_satb_buffers();
4050 // ...then partially drain the local queue and the global stack
4051 drain_local_queue(true);
4052 drain_global_stack(true);
4053
4054 do {
4055 if (!has_aborted() && _curr_region != NULL) {
4056 // This means that we're already holding on to a region.
4057 assert(_finger != NULL, "if region is not NULL, then the finger "
4058 "should not be NULL either");
4059
4060 // We might have restarted this task after an evacuation pause
4061 // which might have evacuated the region we're holding on to
4062 // underneath our feet. Let's read its limit again to make sure
4063 // that we do not iterate over a region of the heap that
4064 // contains garbage (update_region_limit() will also move
4065 // _finger to the start of the region if it is found empty).
4066 update_region_limit();
4067 // We will start from _finger not from the start of the region,
4068 // as we might be restarting this task after aborting half-way
4069 // through scanning this region. In this case, _finger points to
4070 // the address where we last found a marked object. If this is a
4071 // fresh region, _finger points to start().
4072 MemRegion mr = MemRegion(_finger, _region_limit);
4073
4074 if (_cm->verbose_low()) {
4075 gclog_or_tty->print_cr("[%u] we're scanning part "
4076 "["PTR_FORMAT", "PTR_FORMAT") "
4077 "of region "PTR_FORMAT,
4078 _worker_id, _finger, _region_limit, _curr_region);
4079 }
4080
4081 // Let's iterate over the bitmap of the part of the
4082 // region that is left.
4083 if (mr.is_empty() || _nextMarkBitMap->iterate(&bitmap_closure, mr)) {
4084 // We successfully completed iterating over the region. Now,
4085 // let's give up the region.
4086 giveup_current_region();
4087 regular_clock_call();
4088 } else {
4089 assert(has_aborted(), "currently the only way to do so");
4090 // The only way to abort the bitmap iteration is to return
4091 // false from the do_bit() method. However, inside the
4092 // do_bit() method we move the _finger to point to the
4093 // object currently being looked at. So, if we bail out, we
4094 // have definitely set _finger to something non-null.
4095 assert(_finger != NULL, "invariant");
4096
4097 // Region iteration was actually aborted. So now _finger
4098 // points to the address of the object we last scanned. If we
4099 // leave it there, when we restart this task, we will rescan
4100 // the object. It is easy to avoid this. We move the finger by
4101 // enough to point to the next possible object header (the
4102 // bitmap knows by how much we need to move it as it knows its
4103 // granularity).
4104 assert(_finger < _region_limit, "invariant");
4105 HeapWord* new_finger = _nextMarkBitMap->nextWord(_finger);
4106 // Check if bitmap iteration was aborted while scanning the last object
4107 if (new_finger >= _region_limit) {
4108 giveup_current_region();
4109 } else {
4110 move_finger_to(new_finger);
4111 }
4112 }
4113 }
4114 // At this point we have either completed iterating over the
4115 // region we were holding on to, or we have aborted.
4116
4117 // We then partially drain the local queue and the global stack.
4118 // (Do we really need this?)
4119 drain_local_queue(true);
4120 drain_global_stack(true);
4121
4122 // Read the note on the claim_region() method on why it might
4123 // return NULL with potentially more regions available for
4124 // claiming and why we have to check out_of_regions() to determine
4125 // whether we're done or not.
4126 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4127 // We are going to try to claim a new region. We should have
4128 // given up on the previous one.
4129 // Separated the asserts so that we know which one fires.
4130 assert(_curr_region == NULL, "invariant");
4131 assert(_finger == NULL, "invariant");
4132 assert(_region_limit == NULL, "invariant");
4133 if (_cm->verbose_low()) {
4134 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4135 }
4136 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4137 if (claimed_region != NULL) {
4138 // Yes, we managed to claim one
4139 statsOnly( ++_regions_claimed );
4140
4141 if (_cm->verbose_low()) {
4142 gclog_or_tty->print_cr("[%u] we successfully claimed "
4143 "region "PTR_FORMAT,
4144 _worker_id, claimed_region);
4145 }
4146
4147 setup_for_region(claimed_region);
4148 assert(_curr_region == claimed_region, "invariant");
4149 }
4150 // It is important to call the regular clock here. It might take
4151 // a while to claim a region if, for example, we hit a large
4152 // block of empty regions. So we need to call the regular clock
4153 // method once round the loop to make sure it's called
4154 // frequently enough.
4155 regular_clock_call();
4156 }
4157
4158 if (!has_aborted() && _curr_region == NULL) {
4159 assert(_cm->out_of_regions(),
4160 "at this point we should be out of regions");
4161 }
4162 } while ( _curr_region != NULL && !has_aborted());
4163
4164 if (!has_aborted()) {
4165 // We cannot check whether the global stack is empty, since other
4166 // tasks might be pushing objects to it concurrently.
4167 assert(_cm->out_of_regions(),
4168 "at this point we should be out of regions");
4169
4170 if (_cm->verbose_low()) {
4171 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4172 }
4173
4174 // Try to reduce the number of available SATB buffers so that
4175 // remark has less work to do.
4176 drain_satb_buffers();
4177 }
4178
4179 // Since we've done everything else, we can now totally drain the
4180 // local queue and global stack.
4181 drain_local_queue(false);
4182 drain_global_stack(false);
4183
4184 // Attempt at work stealing from other task's queues.
4185 if (do_stealing && !has_aborted()) {
4186 // We have not aborted. This means that we have finished all that
4187 // we could. Let's try to do some stealing...
4188
4189 // We cannot check whether the global stack is empty, since other
4190 // tasks might be pushing objects to it concurrently.
4191 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4192 "only way to reach here");
4193
4194 if (_cm->verbose_low()) {
4195 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4196 }
4197
4198 while (!has_aborted()) {
4199 oop obj;
4200 statsOnly( ++_steal_attempts );
4201
4202 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4203 if (_cm->verbose_medium()) {
4204 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4205 _worker_id, (void*) obj);
4206 }
4207
4208 statsOnly( ++_steals );
4209
4210 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4211 "any stolen object should be marked");
4212 scan_object(obj);
4213
4214 // And since we're towards the end, let's totally drain the
4215 // local queue and global stack.
4216 drain_local_queue(false);
4217 drain_global_stack(false);
4218 } else {
4219 break;
4220 }
4221 }
4222 }
4223
4224 // If we are about to wrap up and go into termination, check if we
4225 // should raise the overflow flag.
4226 if (do_termination && !has_aborted()) {
4227 if (_cm->force_overflow()->should_force()) {
4228 _cm->set_has_overflown();
4229 regular_clock_call();
4230 }
4231 }
4232
4233 // We still haven't aborted. Now, let's try to get into the
4234 // termination protocol.
4235 if (do_termination && !has_aborted()) {
4236 // We cannot check whether the global stack is empty, since other
4237 // tasks might be concurrently pushing objects on it.
4238 // Separated the asserts so that we know which one fires.
4239 assert(_cm->out_of_regions(), "only way to reach here");
4240 assert(_task_queue->size() == 0, "only way to reach here");
4241
4242 if (_cm->verbose_low()) {
4243 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4244 }
4245
4246 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4247 // The CMTask class also extends the TerminatorTerminator class,
4248 // hence its should_exit_termination() method will also decide
4249 // whether to exit the termination protocol or not.
4250 bool finished = _cm->terminator()->offer_termination(this);
4251 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4252 _termination_time_ms +=
4253 termination_end_time_ms - _termination_start_time_ms;
4254
4255 if (finished) {
4256 // We're all done.
4257
4258 if (_worker_id == 0) {
4259 // let's allow task 0 to do this
4260 if (concurrent()) {
4261 assert(_cm->concurrent_marking_in_progress(), "invariant");
4262 // we need to set this to false before the next
4263 // safepoint. This way we ensure that the marking phase
4264 // doesn't observe any more heap expansions.
4265 _cm->clear_concurrent_marking_in_progress();
4266 }
4267 }
4268
4269 // We can now guarantee that the global stack is empty, since
4270 // all other tasks have finished. We separated the guarantees so
4271 // that, if a condition is false, we can immediately find out
4272 // which one.
4273 guarantee(_cm->out_of_regions(), "only way to reach here");
4274 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4275 guarantee(_task_queue->size() == 0, "only way to reach here");
4276 guarantee(!_cm->has_overflown(), "only way to reach here");
4277 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4278
4279 if (_cm->verbose_low()) {
4280 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4281 }
4282 } else {
4283 // Apparently there's more work to do. Let's abort this task. It
4284 // will restart it and we can hopefully find more things to do.
4285
4286 if (_cm->verbose_low()) {
4287 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4288 _worker_id);
4289 }
4290
4291 set_has_aborted();
4292 statsOnly( ++_aborted_termination );
4293 }
4294 }
4295
4296 // Mainly for debugging purposes to make sure that a pointer to the
4297 // closure which was statically allocated in this frame doesn't
4298 // escape it by accident.
4299 set_cm_oop_closure(NULL);
4300 double end_time_ms = os::elapsedVTime() * 1000.0;
4301 double elapsed_time_ms = end_time_ms - _start_time_ms;
4302 // Update the step history.
4303 _step_times_ms.add(elapsed_time_ms);
4304
4305 if (has_aborted()) {
4306 // The task was aborted for some reason.
4307
4308 statsOnly( ++_aborted );
4309
4310 if (_has_timed_out) {
4311 double diff_ms = elapsed_time_ms - _time_target_ms;
4312 // Keep statistics of how well we did with respect to hitting
4313 // our target only if we actually timed out (if we aborted for
4314 // other reasons, then the results might get skewed).
4315 _marking_step_diffs_ms.add(diff_ms);
4316 }
4317
4318 if (_cm->has_overflown()) {
4319 // This is the interesting one. We aborted because a global
4320 // overflow was raised. This means we have to restart the
4321 // marking phase and start iterating over regions. However, in
4322 // order to do this we have to make sure that all tasks stop
4323 // what they are doing and re-initialise in a safe manner. We
4324 // will achieve this with the use of two barrier sync points.
4325
4326 if (_cm->verbose_low()) {
4327 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4328 }
4329
4330 _cm->enter_first_sync_barrier(_worker_id);
4331 // When we exit this sync barrier we know that all tasks have
4332 // stopped doing marking work. So, it's now safe to
4333 // re-initialise our data structures. At the end of this method,
4334 // task 0 will clear the global data structures.
4335
4336 statsOnly( ++_aborted_overflow );
4337
4338 // We clear the local state of this task...
4339 clear_region_fields();
4340
4341 // ...and enter the second barrier.
4342 _cm->enter_second_sync_barrier(_worker_id);
4343 // At this point everything has bee re-initialised and we're
4344 // ready to restart.
4345 }
4346
4347 if (_cm->verbose_low()) {
4348 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4349 "elapsed = %1.2lfms <<<<<<<<<<",
4350 _worker_id, _time_target_ms, elapsed_time_ms);
4351 if (_cm->has_aborted()) {
4352 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4353 _worker_id);
4354 }
4355 }
4356 } else {
4357 if (_cm->verbose_low()) {
4358 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4359 "elapsed = %1.2lfms <<<<<<<<<<",
4360 _worker_id, _time_target_ms, elapsed_time_ms);
4361 }
4362 }
4363
4364 _claimed = false;
4365 }
4366
4367 CMTask::CMTask(uint worker_id,
4368 ConcurrentMark* cm,
4369 size_t* marked_bytes,
4370 BitMap* card_bm,
4371 CMTaskQueue* task_queue,
4372 CMTaskQueueSet* task_queues)
4373 : _g1h(G1CollectedHeap::heap()),
4374 _worker_id(worker_id), _cm(cm),
4375 _claimed(false),
4376 _nextMarkBitMap(NULL), _hash_seed(17),
4377 _task_queue(task_queue),
4378 _task_queues(task_queues),
4379 _cm_oop_closure(NULL),
4380 _marked_bytes_array(marked_bytes),
4381 _card_bm(card_bm) {
4382 guarantee(task_queue != NULL, "invariant");
4383 guarantee(task_queues != NULL, "invariant");
4384
4385 statsOnly( _clock_due_to_scanning = 0;
4386 _clock_due_to_marking = 0 );
4387
4388 _marking_step_diffs_ms.add(0.5);
4389 }
4390
4391 // These are formatting macros that are used below to ensure
4392 // consistent formatting. The *_H_* versions are used to format the
4393 // header for a particular value and they should be kept consistent
4394 // with the corresponding macro. Also note that most of the macros add
4395 // the necessary white space (as a prefix) which makes them a bit
4396 // easier to compose.
4397
4398 // All the output lines are prefixed with this string to be able to
4399 // identify them easily in a large log file.
4400 #define G1PPRL_LINE_PREFIX "###"
4401
4402 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4403 #ifdef _LP64
4404 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4405 #else // _LP64
4406 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4407 #endif // _LP64
4408
4409 // For per-region info
4410 #define G1PPRL_TYPE_FORMAT " %-4s"
4411 #define G1PPRL_TYPE_H_FORMAT " %4s"
4412 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4413 #define G1PPRL_BYTE_H_FORMAT " %9s"
4414 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4415 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4416
4417 // For summary info
4418 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4419 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4420 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4421 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4422
4423 G1PrintRegionLivenessInfoClosure::
4424 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4425 : _out(out),
4426 _total_used_bytes(0), _total_capacity_bytes(0),
4427 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4428 _hum_used_bytes(0), _hum_capacity_bytes(0),
4429 _hum_prev_live_bytes(0), _hum_next_live_bytes(0) {
4430 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4431 MemRegion g1_committed = g1h->g1_committed();
4432 MemRegion g1_reserved = g1h->g1_reserved();
4433 double now = os::elapsedTime();
4434
4435 // Print the header of the output.
4436 _out->cr();
4437 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4438 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4439 G1PPRL_SUM_ADDR_FORMAT("committed")
4440 G1PPRL_SUM_ADDR_FORMAT("reserved")
4441 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4442 g1_committed.start(), g1_committed.end(),
4443 g1_reserved.start(), g1_reserved.end(),
4444 HeapRegion::GrainBytes);
4445 _out->print_cr(G1PPRL_LINE_PREFIX);
4446 _out->print_cr(G1PPRL_LINE_PREFIX
4447 G1PPRL_TYPE_H_FORMAT
4448 G1PPRL_ADDR_BASE_H_FORMAT
4449 G1PPRL_BYTE_H_FORMAT
4450 G1PPRL_BYTE_H_FORMAT
4451 G1PPRL_BYTE_H_FORMAT
4452 G1PPRL_DOUBLE_H_FORMAT,
4453 "type", "address-range",
4454 "used", "prev-live", "next-live", "gc-eff");
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 "", "",
4463 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)");
4464 }
4465
4466 // It takes as a parameter a reference to one of the _hum_* fields, it
4467 // deduces the corresponding value for a region in a humongous region
4468 // series (either the region size, or what's left if the _hum_* field
4469 // is < the region size), and updates the _hum_* field accordingly.
4470 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4471 size_t bytes = 0;
4472 // The > 0 check is to deal with the prev and next live bytes which
4473 // could be 0.
4474 if (*hum_bytes > 0) {
4475 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4476 *hum_bytes -= bytes;
4477 }
4478 return bytes;
4479 }
4480
4481 // It deduces the values for a region in a humongous region series
4482 // from the _hum_* fields and updates those accordingly. It assumes
4483 // that that _hum_* fields have already been set up from the "starts
4484 // humongous" region and we visit the regions in address order.
4485 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4486 size_t* capacity_bytes,
4487 size_t* prev_live_bytes,
4488 size_t* next_live_bytes) {
4489 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4490 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4491 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4492 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4493 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4494 }
4495
4496 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4497 const char* type = "";
4498 HeapWord* bottom = r->bottom();
4499 HeapWord* end = r->end();
4500 size_t capacity_bytes = r->capacity();
4501 size_t used_bytes = r->used();
4502 size_t prev_live_bytes = r->live_bytes();
4503 size_t next_live_bytes = r->next_live_bytes();
4504 double gc_eff = r->gc_efficiency();
4505 if (r->used() == 0) {
4506 type = "FREE";
4507 } else if (r->is_survivor()) {
4508 type = "SURV";
4509 } else if (r->is_young()) {
4510 type = "EDEN";
4511 } else if (r->startsHumongous()) {
4512 type = "HUMS";
4513
4514 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4515 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4516 "they should have been zeroed after the last time we used them");
4517 // Set up the _hum_* fields.
4518 _hum_capacity_bytes = capacity_bytes;
4519 _hum_used_bytes = used_bytes;
4520 _hum_prev_live_bytes = prev_live_bytes;
4521 _hum_next_live_bytes = next_live_bytes;
4522 get_hum_bytes(&used_bytes, &capacity_bytes,
4523 &prev_live_bytes, &next_live_bytes);
4524 end = bottom + HeapRegion::GrainWords;
4525 } else if (r->continuesHumongous()) {
4526 type = "HUMC";
4527 get_hum_bytes(&used_bytes, &capacity_bytes,
4528 &prev_live_bytes, &next_live_bytes);
4529 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4530 } else {
4531 type = "OLD";
4532 }
4533
4534 _total_used_bytes += used_bytes;
4535 _total_capacity_bytes += capacity_bytes;
4536 _total_prev_live_bytes += prev_live_bytes;
4537 _total_next_live_bytes += next_live_bytes;
4538
4539 // Print a line for this particular region.
4540 _out->print_cr(G1PPRL_LINE_PREFIX
4541 G1PPRL_TYPE_FORMAT
4542 G1PPRL_ADDR_BASE_FORMAT
4543 G1PPRL_BYTE_FORMAT
4544 G1PPRL_BYTE_FORMAT
4545 G1PPRL_BYTE_FORMAT
4546 G1PPRL_DOUBLE_FORMAT,
4547 type, bottom, end,
4548 used_bytes, prev_live_bytes, next_live_bytes, gc_eff);
4549
4550 return false;
4551 }
4552
4553 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4554 // Print the footer of the output.
4555 _out->print_cr(G1PPRL_LINE_PREFIX);
4556 _out->print_cr(G1PPRL_LINE_PREFIX
4557 " SUMMARY"
4558 G1PPRL_SUM_MB_FORMAT("capacity")
4559 G1PPRL_SUM_MB_PERC_FORMAT("used")
4560 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4561 G1PPRL_SUM_MB_PERC_FORMAT("next-live"),
4562 bytes_to_mb(_total_capacity_bytes),
4563 bytes_to_mb(_total_used_bytes),
4564 perc(_total_used_bytes, _total_capacity_bytes),
4565 bytes_to_mb(_total_prev_live_bytes),
4566 perc(_total_prev_live_bytes, _total_capacity_bytes),
4567 bytes_to_mb(_total_next_live_bytes),
4568 perc(_total_next_live_bytes, _total_capacity_bytes));
4569 _out->cr();
4570 }