1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc/g1/concurrentMark.inline.hpp"
30 #include "gc/g1/concurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1CollectedHeap.inline.hpp"
32 #include "gc/g1/g1CollectorPolicy.hpp"
33 #include "gc/g1/g1ErgoVerbose.hpp"
34 #include "gc/g1/g1Log.hpp"
35 #include "gc/g1/g1OopClosures.inline.hpp"
36 #include "gc/g1/g1RemSet.hpp"
37 #include "gc/g1/g1StringDedup.hpp"
38 #include "gc/g1/heapRegion.inline.hpp"
39 #include "gc/g1/heapRegionManager.inline.hpp"
40 #include "gc/g1/heapRegionRemSet.hpp"
41 #include "gc/g1/heapRegionSet.inline.hpp"
42 #include "gc/shared/gcTimer.hpp"
43 #include "gc/shared/gcTrace.hpp"
44 #include "gc/shared/gcTraceTime.hpp"
45 #include "gc/shared/genOopClosures.inline.hpp"
46 #include "gc/shared/referencePolicy.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/taskqueue.inline.hpp"
49 #include "gc/shared/vmGCOperations.hpp"
50 #include "memory/allocation.hpp"
51 #include "memory/resourceArea.hpp"
52 #include "oops/oop.inline.hpp"
53 #include "runtime/atomic.inline.hpp"
54 #include "runtime/handles.inline.hpp"
55 #include "runtime/java.hpp"
56 #include "runtime/prefetch.inline.hpp"
57 #include "services/memTracker.hpp"
58
59 // Concurrent marking bit map wrapper
60
61 CMBitMapRO::CMBitMapRO(int shifter) :
62 _bm(),
63 _shifter(shifter) {
64 _bmStartWord = 0;
65 _bmWordSize = 0;
66 }
67
68 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
69 const HeapWord* limit) const {
70 // First we must round addr *up* to a possible object boundary.
71 addr = (HeapWord*)align_size_up((intptr_t)addr,
72 HeapWordSize << _shifter);
73 size_t addrOffset = heapWordToOffset(addr);
74 if (limit == NULL) {
75 limit = _bmStartWord + _bmWordSize;
76 }
77 size_t limitOffset = heapWordToOffset(limit);
78 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
79 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
80 assert(nextAddr >= addr, "get_next_one postcondition");
81 assert(nextAddr == limit || isMarked(nextAddr),
82 "get_next_one postcondition");
83 return nextAddr;
84 }
85
86 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr,
87 const HeapWord* limit) const {
88 size_t addrOffset = heapWordToOffset(addr);
89 if (limit == NULL) {
90 limit = _bmStartWord + _bmWordSize;
91 }
92 size_t limitOffset = heapWordToOffset(limit);
93 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
94 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
95 assert(nextAddr >= addr, "get_next_one postcondition");
96 assert(nextAddr == limit || !isMarked(nextAddr),
97 "get_next_one postcondition");
98 return nextAddr;
99 }
100
101 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
102 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
103 return (int) (diff >> _shifter);
104 }
105
106 #ifndef PRODUCT
107 bool CMBitMapRO::covers(MemRegion heap_rs) const {
108 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
109 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
110 "size inconsistency");
111 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
112 _bmWordSize == heap_rs.word_size();
113 }
114 #endif
115
116 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
117 _bm.print_on_error(st, prefix);
118 }
119
120 size_t CMBitMap::compute_size(size_t heap_size) {
121 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
122 }
123
124 size_t CMBitMap::mark_distance() {
125 return MinObjAlignmentInBytes * BitsPerByte;
126 }
127
128 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
129 _bmStartWord = heap.start();
130 _bmWordSize = heap.word_size();
131
132 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
133 _bm.set_size(_bmWordSize >> _shifter);
134
135 storage->set_mapping_changed_listener(&_listener);
136 }
137
138 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
139 if (zero_filled) {
140 return;
141 }
142 // We need to clear the bitmap on commit, removing any existing information.
143 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
144 _bm->clearRange(mr);
145 }
146
147 // Closure used for clearing the given mark bitmap.
148 class ClearBitmapHRClosure : public HeapRegionClosure {
149 private:
150 ConcurrentMark* _cm;
151 CMBitMap* _bitmap;
152 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration.
153 public:
154 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) {
155 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield.");
156 }
157
158 virtual bool doHeapRegion(HeapRegion* r) {
159 size_t const chunk_size_in_words = M / HeapWordSize;
160
161 HeapWord* cur = r->bottom();
162 HeapWord* const end = r->end();
163
164 while (cur < end) {
165 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
166 _bitmap->clearRange(mr);
167
168 cur += chunk_size_in_words;
169
170 // Abort iteration if after yielding the marking has been aborted.
171 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) {
172 return true;
173 }
174 // Repeat the asserts from before the start of the closure. We will do them
175 // as asserts here to minimize their overhead on the product. However, we
176 // will have them as guarantees at the beginning / end of the bitmap
177 // clearing to get some checking in the product.
178 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant");
179 assert(!_may_yield || !G1CollectedHeap::heap()->mark_in_progress(), "invariant");
180 }
181
182 return false;
183 }
184 };
185
186 class ParClearNextMarkBitmapTask : public AbstractGangTask {
187 ClearBitmapHRClosure* _cl;
188 HeapRegionClaimer _hrclaimer;
189 bool _suspendible; // If the task is suspendible, workers must join the STS.
190
191 public:
192 ParClearNextMarkBitmapTask(ClearBitmapHRClosure *cl, uint n_workers, bool suspendible) :
193 _cl(cl), _suspendible(suspendible), AbstractGangTask("Parallel Clear Bitmap Task"), _hrclaimer(n_workers) {}
194
195 void work(uint worker_id) {
196 SuspendibleThreadSetJoiner sts_join(_suspendible);
197 G1CollectedHeap::heap()->heap_region_par_iterate(_cl, worker_id, &_hrclaimer, true);
198 }
199 };
200
201 void CMBitMap::clearAll() {
202 G1CollectedHeap* g1h = G1CollectedHeap::heap();
203 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */);
204 uint n_workers = g1h->workers()->active_workers();
205 ParClearNextMarkBitmapTask task(&cl, n_workers, false);
206 g1h->workers()->run_task(&task);
207 guarantee(cl.complete(), "Must have completed iteration.");
208 return;
209 }
210
211 void CMBitMap::markRange(MemRegion mr) {
212 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
213 assert(!mr.is_empty(), "unexpected empty region");
214 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
215 ((HeapWord *) mr.end())),
216 "markRange memory region end is not card aligned");
217 // convert address range into offset range
218 _bm.at_put_range(heapWordToOffset(mr.start()),
219 heapWordToOffset(mr.end()), true);
220 }
221
222 void CMBitMap::clearRange(MemRegion mr) {
223 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
224 assert(!mr.is_empty(), "unexpected empty region");
225 // convert address range into offset range
226 _bm.at_put_range(heapWordToOffset(mr.start()),
227 heapWordToOffset(mr.end()), false);
228 }
229
230 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
231 HeapWord* end_addr) {
232 HeapWord* start = getNextMarkedWordAddress(addr);
233 start = MIN2(start, end_addr);
234 HeapWord* end = getNextUnmarkedWordAddress(start);
235 end = MIN2(end, end_addr);
236 assert(start <= end, "Consistency check");
237 MemRegion mr(start, end);
238 if (!mr.is_empty()) {
239 clearRange(mr);
240 }
241 return mr;
242 }
243
244 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
245 _base(NULL), _cm(cm)
246 #ifdef ASSERT
247 , _drain_in_progress(false)
248 , _drain_in_progress_yields(false)
249 #endif
250 {}
251
252 bool CMMarkStack::allocate(size_t capacity) {
253 // allocate a stack of the requisite depth
254 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
255 if (!rs.is_reserved()) {
256 warning("ConcurrentMark MarkStack allocation failure");
257 return false;
258 }
259 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
260 if (!_virtual_space.initialize(rs, rs.size())) {
261 warning("ConcurrentMark MarkStack backing store failure");
262 // Release the virtual memory reserved for the marking stack
263 rs.release();
264 return false;
265 }
266 assert(_virtual_space.committed_size() == rs.size(),
267 "Didn't reserve backing store for all of ConcurrentMark stack?");
268 _base = (oop*) _virtual_space.low();
269 setEmpty();
270 _capacity = (jint) capacity;
271 _saved_index = -1;
272 _should_expand = false;
273 return true;
274 }
275
276 void CMMarkStack::expand() {
277 // Called, during remark, if we've overflown the marking stack during marking.
278 assert(isEmpty(), "stack should been emptied while handling overflow");
279 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
280 // Clear expansion flag
281 _should_expand = false;
282 if (_capacity == (jint) MarkStackSizeMax) {
283 if (PrintGCDetails && Verbose) {
284 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
285 }
286 return;
287 }
288 // Double capacity if possible
289 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
290 // Do not give up existing stack until we have managed to
291 // get the double capacity that we desired.
292 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
293 sizeof(oop)));
294 if (rs.is_reserved()) {
295 // Release the backing store associated with old stack
296 _virtual_space.release();
297 // Reinitialize virtual space for new stack
298 if (!_virtual_space.initialize(rs, rs.size())) {
299 fatal("Not enough swap for expanded marking stack capacity");
300 }
301 _base = (oop*)(_virtual_space.low());
302 _index = 0;
303 _capacity = new_capacity;
304 } else {
305 if (PrintGCDetails && Verbose) {
306 // Failed to double capacity, continue;
307 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
308 SIZE_FORMAT"K to " SIZE_FORMAT"K",
309 _capacity / K, new_capacity / K);
310 }
311 }
312 }
313
314 void CMMarkStack::set_should_expand() {
315 // If we're resetting the marking state because of an
316 // marking stack overflow, record that we should, if
317 // possible, expand the stack.
318 _should_expand = _cm->has_overflown();
319 }
320
321 CMMarkStack::~CMMarkStack() {
322 if (_base != NULL) {
323 _base = NULL;
324 _virtual_space.release();
325 }
326 }
327
328 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
329 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
330 jint start = _index;
331 jint next_index = start + n;
332 if (next_index > _capacity) {
333 _overflow = true;
334 return;
335 }
336 // Otherwise.
337 _index = next_index;
338 for (int i = 0; i < n; i++) {
339 int ind = start + i;
340 assert(ind < _capacity, "By overflow test above.");
341 _base[ind] = ptr_arr[i];
342 }
343 }
344
345 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
346 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
347 jint index = _index;
348 if (index == 0) {
349 *n = 0;
350 return false;
351 } else {
352 int k = MIN2(max, index);
353 jint new_ind = index - k;
354 for (int j = 0; j < k; j++) {
355 ptr_arr[j] = _base[new_ind + j];
356 }
357 _index = new_ind;
358 *n = k;
359 return true;
360 }
361 }
362
363 template<class OopClosureClass>
364 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
365 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
366 || SafepointSynchronize::is_at_safepoint(),
367 "Drain recursion must be yield-safe.");
368 bool res = true;
369 debug_only(_drain_in_progress = true);
370 debug_only(_drain_in_progress_yields = yield_after);
371 while (!isEmpty()) {
372 oop newOop = pop();
373 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
374 assert(newOop->is_oop(), "Expected an oop");
375 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
376 "only grey objects on this stack");
377 newOop->oop_iterate(cl);
378 if (yield_after && _cm->do_yield_check()) {
379 res = false;
380 break;
381 }
382 }
383 debug_only(_drain_in_progress = false);
384 return res;
385 }
386
387 void CMMarkStack::note_start_of_gc() {
388 assert(_saved_index == -1,
389 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
390 _saved_index = _index;
391 }
392
393 void CMMarkStack::note_end_of_gc() {
394 // This is intentionally a guarantee, instead of an assert. If we
395 // accidentally add something to the mark stack during GC, it
396 // will be a correctness issue so it's better if we crash. we'll
397 // only check this once per GC anyway, so it won't be a performance
398 // issue in any way.
399 guarantee(_saved_index == _index,
400 err_msg("saved index: %d index: %d", _saved_index, _index));
401 _saved_index = -1;
402 }
403
404 void CMMarkStack::oops_do(OopClosure* f) {
405 assert(_saved_index == _index,
406 err_msg("saved index: %d index: %d", _saved_index, _index));
407 for (int i = 0; i < _index; i += 1) {
408 f->do_oop(&_base[i]);
409 }
410 }
411
412 CMRootRegions::CMRootRegions() :
413 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
414 _should_abort(false), _next_survivor(NULL) { }
415
416 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
417 _young_list = g1h->young_list();
418 _cm = cm;
419 }
420
421 void CMRootRegions::prepare_for_scan() {
422 assert(!scan_in_progress(), "pre-condition");
423
424 // Currently, only survivors can be root regions.
425 assert(_next_survivor == NULL, "pre-condition");
426 _next_survivor = _young_list->first_survivor_region();
427 _scan_in_progress = (_next_survivor != NULL);
428 _should_abort = false;
429 }
430
431 HeapRegion* CMRootRegions::claim_next() {
432 if (_should_abort) {
433 // If someone has set the should_abort flag, we return NULL to
434 // force the caller to bail out of their loop.
435 return NULL;
436 }
437
438 // Currently, only survivors can be root regions.
439 HeapRegion* res = _next_survivor;
440 if (res != NULL) {
441 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
442 // Read it again in case it changed while we were waiting for the lock.
443 res = _next_survivor;
444 if (res != NULL) {
445 if (res == _young_list->last_survivor_region()) {
446 // We just claimed the last survivor so store NULL to indicate
447 // that we're done.
448 _next_survivor = NULL;
449 } else {
450 _next_survivor = res->get_next_young_region();
451 }
452 } else {
453 // Someone else claimed the last survivor while we were trying
454 // to take the lock so nothing else to do.
455 }
456 }
457 assert(res == NULL || res->is_survivor(), "post-condition");
458
459 return res;
460 }
461
462 void CMRootRegions::scan_finished() {
463 assert(scan_in_progress(), "pre-condition");
464
465 // Currently, only survivors can be root regions.
466 if (!_should_abort) {
467 assert(_next_survivor == NULL, "we should have claimed all survivors");
468 }
469 _next_survivor = NULL;
470
471 {
472 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
473 _scan_in_progress = false;
474 RootRegionScan_lock->notify_all();
475 }
476 }
477
478 bool CMRootRegions::wait_until_scan_finished() {
479 if (!scan_in_progress()) return false;
480
481 {
482 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
483 while (scan_in_progress()) {
484 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
485 }
486 }
487 return true;
488 }
489
490 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
491 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
492 #endif // _MSC_VER
493
494 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
495 return MAX2((n_par_threads + 2) / 4, 1U);
496 }
497
498 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
499 _g1h(g1h),
500 _markBitMap1(),
501 _markBitMap2(),
502 _parallel_marking_threads(0),
503 _max_parallel_marking_threads(0),
504 _sleep_factor(0.0),
505 _marking_task_overhead(1.0),
506 _cleanup_sleep_factor(0.0),
507 _cleanup_task_overhead(1.0),
508 _cleanup_list("Cleanup List"),
509 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
510 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >>
511 CardTableModRefBS::card_shift,
512 false /* in_resource_area*/),
513
514 _prevMarkBitMap(&_markBitMap1),
515 _nextMarkBitMap(&_markBitMap2),
516
517 _markStack(this),
518 // _finger set in set_non_marking_state
519
520 _max_worker_id(MAX2((uint)ParallelGCThreads, 1U)),
521 // _active_tasks set in set_non_marking_state
522 // _tasks set inside the constructor
523 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
524 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
525
526 _has_overflown(false),
527 _concurrent(false),
528 _has_aborted(false),
529 _aborted_gc_id(GCId::undefined()),
530 _restart_for_overflow(false),
531 _concurrent_marking_in_progress(false),
532
533 // _verbose_level set below
534
535 _init_times(),
536 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
537 _cleanup_times(),
538 _total_counting_time(0.0),
539 _total_rs_scrub_time(0.0),
540
541 _parallel_workers(NULL),
542
543 _count_card_bitmaps(NULL),
544 _count_marked_bytes(NULL),
545 _completed_initialization(false) {
546 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
547 if (verbose_level < no_verbose) {
548 verbose_level = no_verbose;
549 }
550 if (verbose_level > high_verbose) {
551 verbose_level = high_verbose;
552 }
553 _verbose_level = verbose_level;
554
555 if (verbose_low()) {
556 gclog_or_tty->print_cr("[global] init, heap start = "PTR_FORMAT", "
557 "heap end = " PTR_FORMAT, p2i(_heap_start), p2i(_heap_end));
558 }
559
560 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
561 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
562
563 // Create & start a ConcurrentMark thread.
564 _cmThread = new ConcurrentMarkThread(this);
565 assert(cmThread() != NULL, "CM Thread should have been created");
566 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
567 if (_cmThread->osthread() == NULL) {
568 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
569 }
570
571 assert(CGC_lock != NULL, "Where's the CGC_lock?");
572 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
573 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
574
575 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
576 satb_qs.set_buffer_size(G1SATBBufferSize);
577
578 _root_regions.init(_g1h, this);
579
580 if (ConcGCThreads > ParallelGCThreads) {
581 warning("Can't have more ConcGCThreads (" UINTX_FORMAT ") "
582 "than ParallelGCThreads (" UINTX_FORMAT ").",
583 ConcGCThreads, ParallelGCThreads);
584 return;
585 }
586 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
587 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
588 // if both are set
589 _sleep_factor = 0.0;
590 _marking_task_overhead = 1.0;
591 } else if (G1MarkingOverheadPercent > 0) {
592 // We will calculate the number of parallel marking threads based
593 // on a target overhead with respect to the soft real-time goal
594 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
595 double overall_cm_overhead =
596 (double) MaxGCPauseMillis * marking_overhead /
597 (double) GCPauseIntervalMillis;
598 double cpu_ratio = 1.0 / (double) os::processor_count();
599 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
600 double marking_task_overhead =
601 overall_cm_overhead / marking_thread_num *
602 (double) os::processor_count();
603 double sleep_factor =
604 (1.0 - marking_task_overhead) / marking_task_overhead;
605
606 FLAG_SET_ERGO(uintx, ConcGCThreads, (uint) marking_thread_num);
607 _sleep_factor = sleep_factor;
608 _marking_task_overhead = marking_task_overhead;
609 } else {
610 // Calculate the number of parallel marking threads by scaling
611 // the number of parallel GC threads.
612 uint marking_thread_num = scale_parallel_threads((uint) ParallelGCThreads);
613 FLAG_SET_ERGO(uintx, ConcGCThreads, marking_thread_num);
614 _sleep_factor = 0.0;
615 _marking_task_overhead = 1.0;
616 }
617
618 assert(ConcGCThreads > 0, "Should have been set");
619 _parallel_marking_threads = (uint) ConcGCThreads;
620 _max_parallel_marking_threads = _parallel_marking_threads;
621
622 if (parallel_marking_threads() > 1) {
623 _cleanup_task_overhead = 1.0;
624 } else {
625 _cleanup_task_overhead = marking_task_overhead();
626 }
627 _cleanup_sleep_factor =
628 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
629
630 #if 0
631 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
632 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
633 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
634 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
635 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
636 #endif
637
638 _parallel_workers = new FlexibleWorkGang("G1 Marker",
639 _max_parallel_marking_threads, false, true);
640 if (_parallel_workers == NULL) {
641 vm_exit_during_initialization("Failed necessary allocation.");
642 } else {
643 _parallel_workers->initialize_workers();
644 }
645
646 if (FLAG_IS_DEFAULT(MarkStackSize)) {
647 size_t mark_stack_size =
648 MIN2(MarkStackSizeMax,
649 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
650 // Verify that the calculated value for MarkStackSize is in range.
651 // It would be nice to use the private utility routine from Arguments.
652 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
653 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
654 "must be between 1 and " SIZE_FORMAT,
655 mark_stack_size, MarkStackSizeMax);
656 return;
657 }
658 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
659 } else {
660 // Verify MarkStackSize is in range.
661 if (FLAG_IS_CMDLINE(MarkStackSize)) {
662 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
663 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
664 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
665 "must be between 1 and " SIZE_FORMAT,
666 MarkStackSize, MarkStackSizeMax);
667 return;
668 }
669 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
670 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
671 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
672 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
673 MarkStackSize, MarkStackSizeMax);
674 return;
675 }
676 }
677 }
678 }
679
680 if (!_markStack.allocate(MarkStackSize)) {
681 warning("Failed to allocate CM marking stack");
682 return;
683 }
684
685 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
686 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
687
688 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
689 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
690
691 BitMap::idx_t card_bm_size = _card_bm.size();
692
693 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
694 _active_tasks = _max_worker_id;
695
696 uint max_regions = _g1h->max_regions();
697 for (uint i = 0; i < _max_worker_id; ++i) {
698 CMTaskQueue* task_queue = new CMTaskQueue();
699 task_queue->initialize();
700 _task_queues->register_queue(i, task_queue);
701
702 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
703 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
704
705 _tasks[i] = new CMTask(i, this,
706 _count_marked_bytes[i],
707 &_count_card_bitmaps[i],
708 task_queue, _task_queues);
709
710 _accum_task_vtime[i] = 0.0;
711 }
712
713 // Calculate the card number for the bottom of the heap. Used
714 // in biasing indexes into the accounting card bitmaps.
715 _heap_bottom_card_num =
716 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
717 CardTableModRefBS::card_shift);
718
719 // Clear all the liveness counting data
720 clear_all_count_data();
721
722 // so that the call below can read a sensible value
723 _heap_start = g1h->reserved_region().start();
724 set_non_marking_state();
725 _completed_initialization = true;
726 }
727
728 void ConcurrentMark::reset() {
729 // Starting values for these two. This should be called in a STW
730 // phase.
731 MemRegion reserved = _g1h->g1_reserved();
732 _heap_start = reserved.start();
733 _heap_end = reserved.end();
734
735 // Separated the asserts so that we know which one fires.
736 assert(_heap_start != NULL, "heap bounds should look ok");
737 assert(_heap_end != NULL, "heap bounds should look ok");
738 assert(_heap_start < _heap_end, "heap bounds should look ok");
739
740 // Reset all the marking data structures and any necessary flags
741 reset_marking_state();
742
743 if (verbose_low()) {
744 gclog_or_tty->print_cr("[global] resetting");
745 }
746
747 // We do reset all of them, since different phases will use
748 // different number of active threads. So, it's easiest to have all
749 // of them ready.
750 for (uint i = 0; i < _max_worker_id; ++i) {
751 _tasks[i]->reset(_nextMarkBitMap);
752 }
753
754 // we need this to make sure that the flag is on during the evac
755 // pause with initial mark piggy-backed
756 set_concurrent_marking_in_progress();
757 }
758
759
760 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
761 _markStack.set_should_expand();
762 _markStack.setEmpty(); // Also clears the _markStack overflow flag
763 if (clear_overflow) {
764 clear_has_overflown();
765 } else {
766 assert(has_overflown(), "pre-condition");
767 }
768 _finger = _heap_start;
769
770 for (uint i = 0; i < _max_worker_id; ++i) {
771 CMTaskQueue* queue = _task_queues->queue(i);
772 queue->set_empty();
773 }
774 }
775
776 void ConcurrentMark::set_concurrency(uint active_tasks) {
777 assert(active_tasks <= _max_worker_id, "we should not have more");
778
779 _active_tasks = active_tasks;
780 // Need to update the three data structures below according to the
781 // number of active threads for this phase.
782 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
783 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
784 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
785 }
786
787 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
788 set_concurrency(active_tasks);
789
790 _concurrent = concurrent;
791 // We propagate this to all tasks, not just the active ones.
792 for (uint i = 0; i < _max_worker_id; ++i)
793 _tasks[i]->set_concurrent(concurrent);
794
795 if (concurrent) {
796 set_concurrent_marking_in_progress();
797 } else {
798 // We currently assume that the concurrent flag has been set to
799 // false before we start remark. At this point we should also be
800 // in a STW phase.
801 assert(!concurrent_marking_in_progress(), "invariant");
802 assert(out_of_regions(),
803 err_msg("only way to get here: _finger: "PTR_FORMAT", _heap_end: "PTR_FORMAT,
804 p2i(_finger), p2i(_heap_end)));
805 }
806 }
807
808 void ConcurrentMark::set_non_marking_state() {
809 // We set the global marking state to some default values when we're
810 // not doing marking.
811 reset_marking_state();
812 _active_tasks = 0;
813 clear_concurrent_marking_in_progress();
814 }
815
816 ConcurrentMark::~ConcurrentMark() {
817 // The ConcurrentMark instance is never freed.
818 ShouldNotReachHere();
819 }
820
821 void ConcurrentMark::clearNextBitmap() {
822 G1CollectedHeap* g1h = G1CollectedHeap::heap();
823
824 // Make sure that the concurrent mark thread looks to still be in
825 // the current cycle.
826 guarantee(cmThread()->during_cycle(), "invariant");
827
828 // We are finishing up the current cycle by clearing the next
829 // marking bitmap and getting it ready for the next cycle. During
830 // this time no other cycle can start. So, let's make sure that this
831 // is the case.
832 guarantee(!g1h->mark_in_progress(), "invariant");
833
834 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */);
835 ParClearNextMarkBitmapTask task(&cl, parallel_marking_threads(), true);
836 _parallel_workers->run_task(&task);
837
838 // Clear the liveness counting data. If the marking has been aborted, the abort()
839 // call already did that.
840 if (cl.complete()) {
841 clear_all_count_data();
842 }
843
844 // Repeat the asserts from above.
845 guarantee(cmThread()->during_cycle(), "invariant");
846 guarantee(!g1h->mark_in_progress(), "invariant");
847 }
848
849 class CheckBitmapClearHRClosure : public HeapRegionClosure {
850 CMBitMap* _bitmap;
851 bool _error;
852 public:
853 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) {
854 }
855
856 virtual bool doHeapRegion(HeapRegion* r) {
857 // This closure can be called concurrently to the mutator, so we must make sure
858 // that the result of the getNextMarkedWordAddress() call is compared to the
859 // value passed to it as limit to detect any found bits.
860 // We can use the region's orig_end() for the limit and the comparison value
861 // as it always contains the "real" end of the region that never changes and
862 // has no side effects.
863 // Due to the latter, there can also be no problem with the compiler generating
864 // reloads of the orig_end() call.
865 HeapWord* end = r->orig_end();
866 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
867 }
868 };
869
870 bool ConcurrentMark::nextMarkBitmapIsClear() {
871 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
872 _g1h->heap_region_iterate(&cl);
873 return cl.complete();
874 }
875
876 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
877 public:
878 bool doHeapRegion(HeapRegion* r) {
879 if (!r->is_continues_humongous()) {
880 r->note_start_of_marking();
881 }
882 return false;
883 }
884 };
885
886 void ConcurrentMark::checkpointRootsInitialPre() {
887 G1CollectedHeap* g1h = G1CollectedHeap::heap();
888 G1CollectorPolicy* g1p = g1h->g1_policy();
889
890 _has_aborted = false;
891
892 // Initialize marking structures. This has to be done in a STW phase.
893 reset();
894
895 // For each region note start of marking.
896 NoteStartOfMarkHRClosure startcl;
897 g1h->heap_region_iterate(&startcl);
898 }
899
900
901 void ConcurrentMark::checkpointRootsInitialPost() {
902 G1CollectedHeap* g1h = G1CollectedHeap::heap();
903
904 // If we force an overflow during remark, the remark operation will
905 // actually abort and we'll restart concurrent marking. If we always
906 // force an overflow during remark we'll never actually complete the
907 // marking phase. So, we initialize this here, at the start of the
908 // cycle, so that at the remaining overflow number will decrease at
909 // every remark and we'll eventually not need to cause one.
910 force_overflow_stw()->init();
911
912 // Start Concurrent Marking weak-reference discovery.
913 ReferenceProcessor* rp = g1h->ref_processor_cm();
914 // enable ("weak") refs discovery
915 rp->enable_discovery();
916 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
917
918 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
919 // This is the start of the marking cycle, we're expected all
920 // threads to have SATB queues with active set to false.
921 satb_mq_set.set_active_all_threads(true, /* new active value */
922 false /* expected_active */);
923
924 _root_regions.prepare_for_scan();
925
926 // update_g1_committed() will be called at the end of an evac pause
927 // when marking is on. So, it's also called at the end of the
928 // initial-mark pause to update the heap end, if the heap expands
929 // during it. No need to call it here.
930 }
931
932 /*
933 * Notice that in the next two methods, we actually leave the STS
934 * during the barrier sync and join it immediately afterwards. If we
935 * do not do this, the following deadlock can occur: one thread could
936 * be in the barrier sync code, waiting for the other thread to also
937 * sync up, whereas another one could be trying to yield, while also
938 * waiting for the other threads to sync up too.
939 *
940 * Note, however, that this code is also used during remark and in
941 * this case we should not attempt to leave / enter the STS, otherwise
942 * we'll either hit an assert (debug / fastdebug) or deadlock
943 * (product). So we should only leave / enter the STS if we are
944 * operating concurrently.
945 *
946 * Because the thread that does the sync barrier has left the STS, it
947 * is possible to be suspended for a Full GC or an evacuation pause
948 * could occur. This is actually safe, since the entering the sync
949 * barrier is one of the last things do_marking_step() does, and it
950 * doesn't manipulate any data structures afterwards.
951 */
952
953 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
954 bool barrier_aborted;
955
956 if (verbose_low()) {
957 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
958 }
959
960 {
961 SuspendibleThreadSetLeaver sts_leave(concurrent());
962 barrier_aborted = !_first_overflow_barrier_sync.enter();
963 }
964
965 // at this point everyone should have synced up and not be doing any
966 // more work
967
968 if (verbose_low()) {
969 if (barrier_aborted) {
970 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id);
971 } else {
972 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
973 }
974 }
975
976 if (barrier_aborted) {
977 // If the barrier aborted we ignore the overflow condition and
978 // just abort the whole marking phase as quickly as possible.
979 return;
980 }
981
982 // If we're executing the concurrent phase of marking, reset the marking
983 // state; otherwise the marking state is reset after reference processing,
984 // during the remark pause.
985 // If we reset here as a result of an overflow during the remark we will
986 // see assertion failures from any subsequent set_concurrency_and_phase()
987 // calls.
988 if (concurrent()) {
989 // let the task associated with with worker 0 do this
990 if (worker_id == 0) {
991 // task 0 is responsible for clearing the global data structures
992 // We should be here because of an overflow. During STW we should
993 // not clear the overflow flag since we rely on it being true when
994 // we exit this method to abort the pause and restart concurrent
995 // marking.
996 reset_marking_state(true /* clear_overflow */);
997 force_overflow()->update();
998
999 if (G1Log::fine()) {
1000 gclog_or_tty->gclog_stamp(concurrent_gc_id());
1001 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
1002 }
1003 }
1004 }
1005
1006 // after this, each task should reset its own data structures then
1007 // then go into the second barrier
1008 }
1009
1010 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1011 bool barrier_aborted;
1012
1013 if (verbose_low()) {
1014 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1015 }
1016
1017 {
1018 SuspendibleThreadSetLeaver sts_leave(concurrent());
1019 barrier_aborted = !_second_overflow_barrier_sync.enter();
1020 }
1021
1022 // at this point everything should be re-initialized and ready to go
1023
1024 if (verbose_low()) {
1025 if (barrier_aborted) {
1026 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id);
1027 } else {
1028 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1029 }
1030 }
1031 }
1032
1033 #ifndef PRODUCT
1034 void ForceOverflowSettings::init() {
1035 _num_remaining = G1ConcMarkForceOverflow;
1036 _force = false;
1037 update();
1038 }
1039
1040 void ForceOverflowSettings::update() {
1041 if (_num_remaining > 0) {
1042 _num_remaining -= 1;
1043 _force = true;
1044 } else {
1045 _force = false;
1046 }
1047 }
1048
1049 bool ForceOverflowSettings::should_force() {
1050 if (_force) {
1051 _force = false;
1052 return true;
1053 } else {
1054 return false;
1055 }
1056 }
1057 #endif // !PRODUCT
1058
1059 class CMConcurrentMarkingTask: public AbstractGangTask {
1060 private:
1061 ConcurrentMark* _cm;
1062 ConcurrentMarkThread* _cmt;
1063
1064 public:
1065 void work(uint worker_id) {
1066 assert(Thread::current()->is_ConcurrentGC_thread(),
1067 "this should only be done by a conc GC thread");
1068 ResourceMark rm;
1069
1070 double start_vtime = os::elapsedVTime();
1071
1072 {
1073 SuspendibleThreadSetJoiner sts_join;
1074
1075 assert(worker_id < _cm->active_tasks(), "invariant");
1076 CMTask* the_task = _cm->task(worker_id);
1077 the_task->record_start_time();
1078 if (!_cm->has_aborted()) {
1079 do {
1080 double start_vtime_sec = os::elapsedVTime();
1081 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1082
1083 the_task->do_marking_step(mark_step_duration_ms,
1084 true /* do_termination */,
1085 false /* is_serial*/);
1086
1087 double end_vtime_sec = os::elapsedVTime();
1088 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1089 _cm->clear_has_overflown();
1090
1091 _cm->do_yield_check(worker_id);
1092
1093 jlong sleep_time_ms;
1094 if (!_cm->has_aborted() && the_task->has_aborted()) {
1095 sleep_time_ms =
1096 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1097 {
1098 SuspendibleThreadSetLeaver sts_leave;
1099 os::sleep(Thread::current(), sleep_time_ms, false);
1100 }
1101 }
1102 } while (!_cm->has_aborted() && the_task->has_aborted());
1103 }
1104 the_task->record_end_time();
1105 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1106 }
1107
1108 double end_vtime = os::elapsedVTime();
1109 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1110 }
1111
1112 CMConcurrentMarkingTask(ConcurrentMark* cm,
1113 ConcurrentMarkThread* cmt) :
1114 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1115
1116 ~CMConcurrentMarkingTask() { }
1117 };
1118
1119 // Calculates the number of active workers for a concurrent
1120 // phase.
1121 uint ConcurrentMark::calc_parallel_marking_threads() {
1122 uint n_conc_workers = 0;
1123 if (!UseDynamicNumberOfGCThreads ||
1124 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1125 !ForceDynamicNumberOfGCThreads)) {
1126 n_conc_workers = max_parallel_marking_threads();
1127 } else {
1128 n_conc_workers =
1129 AdaptiveSizePolicy::calc_default_active_workers(
1130 max_parallel_marking_threads(),
1131 1, /* Minimum workers */
1132 parallel_marking_threads(),
1133 Threads::number_of_non_daemon_threads());
1134 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1135 // that scaling has already gone into "_max_parallel_marking_threads".
1136 }
1137 assert(n_conc_workers > 0, "Always need at least 1");
1138 return n_conc_workers;
1139 }
1140
1141 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1142 // Currently, only survivors can be root regions.
1143 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1144 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1145
1146 const uintx interval = PrefetchScanIntervalInBytes;
1147 HeapWord* curr = hr->bottom();
1148 const HeapWord* end = hr->top();
1149 while (curr < end) {
1150 Prefetch::read(curr, interval);
1151 oop obj = oop(curr);
1152 int size = obj->oop_iterate(&cl);
1153 assert(size == obj->size(), "sanity");
1154 curr += size;
1155 }
1156 }
1157
1158 class CMRootRegionScanTask : public AbstractGangTask {
1159 private:
1160 ConcurrentMark* _cm;
1161
1162 public:
1163 CMRootRegionScanTask(ConcurrentMark* cm) :
1164 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1165
1166 void work(uint worker_id) {
1167 assert(Thread::current()->is_ConcurrentGC_thread(),
1168 "this should only be done by a conc GC thread");
1169
1170 CMRootRegions* root_regions = _cm->root_regions();
1171 HeapRegion* hr = root_regions->claim_next();
1172 while (hr != NULL) {
1173 _cm->scanRootRegion(hr, worker_id);
1174 hr = root_regions->claim_next();
1175 }
1176 }
1177 };
1178
1179 void ConcurrentMark::scanRootRegions() {
1180 // Start of concurrent marking.
1181 ClassLoaderDataGraph::clear_claimed_marks();
1182
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 _parallel_workers->set_active_workers(active_workers);
1194 _parallel_workers->run_task(&task);
1195
1196 // It's possible that has_aborted() is true here without actually
1197 // aborting the survivor scan earlier. This is OK as it's
1198 // mainly used for sanity checking.
1199 root_regions()->scan_finished();
1200 }
1201 }
1202
1203 void ConcurrentMark::markFromRoots() {
1204 // we might be tempted to assert that:
1205 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1206 // "inconsistent argument?");
1207 // However that wouldn't be right, because it's possible that
1208 // a safepoint is indeed in progress as a younger generation
1209 // stop-the-world GC happens even as we mark in this generation.
1210
1211 _restart_for_overflow = false;
1212 force_overflow_conc()->init();
1213
1214 // _g1h has _n_par_threads
1215 _parallel_marking_threads = calc_parallel_marking_threads();
1216 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1217 "Maximum number of marking threads exceeded");
1218
1219 uint active_workers = MAX2(1U, parallel_marking_threads());
1220
1221 // Parallel task terminator is set in "set_concurrency_and_phase()"
1222 set_concurrency_and_phase(active_workers, true /* concurrent */);
1223
1224 CMConcurrentMarkingTask markingTask(this, cmThread());
1225 _parallel_workers->set_active_workers(active_workers);
1226 // Don't set _n_par_threads because it affects MT in process_roots()
1227 // and the decisions on that MT processing is made elsewhere.
1228 assert(_parallel_workers->active_workers() > 0, "Should have been set");
1229 _parallel_workers->run_task(&markingTask);
1230 print_stats();
1231 }
1232
1233 // Helper class to get rid of some boilerplate code.
1234 class G1CMTraceTime : public GCTraceTime {
1235 static bool doit_and_prepend(bool doit) {
1236 if (doit) {
1237 gclog_or_tty->put(' ');
1238 }
1239 return doit;
1240 }
1241
1242 public:
1243 G1CMTraceTime(const char* title, bool doit)
1244 : GCTraceTime(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm(),
1245 G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id()) {
1246 }
1247 };
1248
1249 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1250 // world is stopped at this checkpoint
1251 assert(SafepointSynchronize::is_at_safepoint(),
1252 "world should be stopped");
1253
1254 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1255
1256 // If a full collection has happened, we shouldn't do this.
1257 if (has_aborted()) {
1258 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1259 return;
1260 }
1261
1262 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1263
1264 if (VerifyDuringGC) {
1265 HandleMark hm; // handle scope
1266 g1h->prepare_for_verify();
1267 Universe::verify(VerifyOption_G1UsePrevMarking,
1268 " VerifyDuringGC:(before)");
1269 }
1270 g1h->check_bitmaps("Remark Start");
1271
1272 G1CollectorPolicy* g1p = g1h->g1_policy();
1273 g1p->record_concurrent_mark_remark_start();
1274
1275 double start = os::elapsedTime();
1276
1277 checkpointRootsFinalWork();
1278
1279 double mark_work_end = os::elapsedTime();
1280
1281 weakRefsWork(clear_all_soft_refs);
1282
1283 if (has_overflown()) {
1284 // Oops. We overflowed. Restart concurrent marking.
1285 _restart_for_overflow = true;
1286 if (G1TraceMarkStackOverflow) {
1287 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1288 }
1289
1290 // Verify the heap w.r.t. the previous marking bitmap.
1291 if (VerifyDuringGC) {
1292 HandleMark hm; // handle scope
1293 g1h->prepare_for_verify();
1294 Universe::verify(VerifyOption_G1UsePrevMarking,
1295 " VerifyDuringGC:(overflow)");
1296 }
1297
1298 // Clear the marking state because we will be restarting
1299 // marking due to overflowing the global mark stack.
1300 reset_marking_state();
1301 } else {
1302 {
1303 G1CMTraceTime trace("GC aggregate-data", G1Log::finer());
1304
1305 // Aggregate the per-task counting data that we have accumulated
1306 // while marking.
1307 aggregate_count_data();
1308 }
1309
1310 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1311 // We're done with marking.
1312 // This is the end of the marking cycle, we're expected all
1313 // threads to have SATB queues with active set to true.
1314 satb_mq_set.set_active_all_threads(false, /* new active value */
1315 true /* expected_active */);
1316
1317 if (VerifyDuringGC) {
1318 HandleMark hm; // handle scope
1319 g1h->prepare_for_verify();
1320 Universe::verify(VerifyOption_G1UseNextMarking,
1321 " VerifyDuringGC:(after)");
1322 }
1323 g1h->check_bitmaps("Remark End");
1324 assert(!restart_for_overflow(), "sanity");
1325 // Completely reset the marking state since marking completed
1326 set_non_marking_state();
1327 }
1328
1329 // Expand the marking stack, if we have to and if we can.
1330 if (_markStack.should_expand()) {
1331 _markStack.expand();
1332 }
1333
1334 // Statistics
1335 double now = os::elapsedTime();
1336 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1337 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1338 _remark_times.add((now - start) * 1000.0);
1339
1340 g1p->record_concurrent_mark_remark_end();
1341
1342 G1CMIsAliveClosure is_alive(g1h);
1343 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1344 }
1345
1346 // Base class of the closures that finalize and verify the
1347 // liveness counting data.
1348 class CMCountDataClosureBase: public HeapRegionClosure {
1349 protected:
1350 G1CollectedHeap* _g1h;
1351 ConcurrentMark* _cm;
1352 CardTableModRefBS* _ct_bs;
1353
1354 BitMap* _region_bm;
1355 BitMap* _card_bm;
1356
1357 // Takes a region that's not empty (i.e., it has at least one
1358 // live object in it and sets its corresponding bit on the region
1359 // bitmap to 1. If the region is "starts humongous" it will also set
1360 // to 1 the bits on the region bitmap that correspond to its
1361 // associated "continues humongous" regions.
1362 void set_bit_for_region(HeapRegion* hr) {
1363 assert(!hr->is_continues_humongous(), "should have filtered those out");
1364
1365 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1366 if (!hr->is_starts_humongous()) {
1367 // Normal (non-humongous) case: just set the bit.
1368 _region_bm->par_at_put(index, true);
1369 } else {
1370 // Starts humongous case: calculate how many regions are part of
1371 // this humongous region and then set the bit range.
1372 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1373 _region_bm->par_at_put_range(index, end_index, true);
1374 }
1375 }
1376
1377 public:
1378 CMCountDataClosureBase(G1CollectedHeap* g1h,
1379 BitMap* region_bm, BitMap* card_bm):
1380 _g1h(g1h), _cm(g1h->concurrent_mark()),
1381 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
1382 _region_bm(region_bm), _card_bm(card_bm) { }
1383 };
1384
1385 // Closure that calculates the # live objects per region. Used
1386 // for verification purposes during the cleanup pause.
1387 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1388 CMBitMapRO* _bm;
1389 size_t _region_marked_bytes;
1390
1391 public:
1392 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1393 BitMap* region_bm, BitMap* card_bm) :
1394 CMCountDataClosureBase(g1h, region_bm, card_bm),
1395 _bm(bm), _region_marked_bytes(0) { }
1396
1397 bool doHeapRegion(HeapRegion* hr) {
1398
1399 if (hr->is_continues_humongous()) {
1400 // We will ignore these here and process them when their
1401 // associated "starts humongous" region is processed (see
1402 // set_bit_for_heap_region()). Note that we cannot rely on their
1403 // associated "starts humongous" region to have their bit set to
1404 // 1 since, due to the region chunking in the parallel region
1405 // iteration, a "continues humongous" region might be visited
1406 // before its associated "starts humongous".
1407 return false;
1408 }
1409
1410 HeapWord* ntams = hr->next_top_at_mark_start();
1411 HeapWord* start = hr->bottom();
1412
1413 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1414 err_msg("Preconditions not met - "
1415 "start: "PTR_FORMAT", ntams: "PTR_FORMAT", end: "PTR_FORMAT,
1416 p2i(start), p2i(ntams), p2i(hr->end())));
1417
1418 // Find the first marked object at or after "start".
1419 start = _bm->getNextMarkedWordAddress(start, ntams);
1420
1421 size_t marked_bytes = 0;
1422
1423 while (start < ntams) {
1424 oop obj = oop(start);
1425 int obj_sz = obj->size();
1426 HeapWord* obj_end = start + obj_sz;
1427
1428 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1429 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1430
1431 // Note: if we're looking at the last region in heap - obj_end
1432 // could be actually just beyond the end of the heap; end_idx
1433 // will then correspond to a (non-existent) card that is also
1434 // just beyond the heap.
1435 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1436 // end of object is not card aligned - increment to cover
1437 // all the cards spanned by the object
1438 end_idx += 1;
1439 }
1440
1441 // Set the bits in the card BM for the cards spanned by this object.
1442 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1443
1444 // Add the size of this object to the number of marked bytes.
1445 marked_bytes += (size_t)obj_sz * HeapWordSize;
1446
1447 // Find the next marked object after this one.
1448 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1449 }
1450
1451 // Mark the allocated-since-marking portion...
1452 HeapWord* top = hr->top();
1453 if (ntams < top) {
1454 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1455 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1456
1457 // Note: if we're looking at the last region in heap - top
1458 // could be actually just beyond the end of the heap; end_idx
1459 // will then correspond to a (non-existent) card that is also
1460 // just beyond the heap.
1461 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1462 // end of object is not card aligned - increment to cover
1463 // all the cards spanned by the object
1464 end_idx += 1;
1465 }
1466 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1467
1468 // This definitely means the region has live objects.
1469 set_bit_for_region(hr);
1470 }
1471
1472 // Update the live region bitmap.
1473 if (marked_bytes > 0) {
1474 set_bit_for_region(hr);
1475 }
1476
1477 // Set the marked bytes for the current region so that
1478 // it can be queried by a calling verification routine
1479 _region_marked_bytes = marked_bytes;
1480
1481 return false;
1482 }
1483
1484 size_t region_marked_bytes() const { return _region_marked_bytes; }
1485 };
1486
1487 // Heap region closure used for verifying the counting data
1488 // that was accumulated concurrently and aggregated during
1489 // the remark pause. This closure is applied to the heap
1490 // regions during the STW cleanup pause.
1491
1492 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1493 G1CollectedHeap* _g1h;
1494 ConcurrentMark* _cm;
1495 CalcLiveObjectsClosure _calc_cl;
1496 BitMap* _region_bm; // Region BM to be verified
1497 BitMap* _card_bm; // Card BM to be verified
1498 bool _verbose; // verbose output?
1499
1500 BitMap* _exp_region_bm; // Expected Region BM values
1501 BitMap* _exp_card_bm; // Expected card BM values
1502
1503 int _failures;
1504
1505 public:
1506 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1507 BitMap* region_bm,
1508 BitMap* card_bm,
1509 BitMap* exp_region_bm,
1510 BitMap* exp_card_bm,
1511 bool verbose) :
1512 _g1h(g1h), _cm(g1h->concurrent_mark()),
1513 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1514 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1515 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1516 _failures(0) { }
1517
1518 int failures() const { return _failures; }
1519
1520 bool doHeapRegion(HeapRegion* hr) {
1521 if (hr->is_continues_humongous()) {
1522 // We will ignore these here and process them when their
1523 // associated "starts humongous" region is processed (see
1524 // set_bit_for_heap_region()). Note that we cannot rely on their
1525 // associated "starts humongous" region to have their bit set to
1526 // 1 since, due to the region chunking in the parallel region
1527 // iteration, a "continues humongous" region might be visited
1528 // before its associated "starts humongous".
1529 return false;
1530 }
1531
1532 int failures = 0;
1533
1534 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1535 // this region and set the corresponding bits in the expected region
1536 // and card bitmaps.
1537 bool res = _calc_cl.doHeapRegion(hr);
1538 assert(res == false, "should be continuing");
1539
1540 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1541 Mutex::_no_safepoint_check_flag);
1542
1543 // Verify the marked bytes for this region.
1544 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1545 size_t act_marked_bytes = hr->next_marked_bytes();
1546
1547 // We're not OK if expected marked bytes > actual marked bytes. It means
1548 // we have missed accounting some objects during the actual marking.
1549 if (exp_marked_bytes > act_marked_bytes) {
1550 if (_verbose) {
1551 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1552 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1553 hr->hrm_index(), exp_marked_bytes, act_marked_bytes);
1554 }
1555 failures += 1;
1556 }
1557
1558 // Verify the bit, for this region, in the actual and expected
1559 // (which was just calculated) region bit maps.
1560 // We're not OK if the bit in the calculated expected region
1561 // bitmap is set and the bit in the actual region bitmap is not.
1562 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1563
1564 bool expected = _exp_region_bm->at(index);
1565 bool actual = _region_bm->at(index);
1566 if (expected && !actual) {
1567 if (_verbose) {
1568 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1569 "expected: %s, actual: %s",
1570 hr->hrm_index(),
1571 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1572 }
1573 failures += 1;
1574 }
1575
1576 // Verify that the card bit maps for the cards spanned by the current
1577 // region match. We have an error if we have a set bit in the expected
1578 // bit map and the corresponding bit in the actual bitmap is not set.
1579
1580 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1581 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1582
1583 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1584 expected = _exp_card_bm->at(i);
1585 actual = _card_bm->at(i);
1586
1587 if (expected && !actual) {
1588 if (_verbose) {
1589 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1590 "expected: %s, actual: %s",
1591 hr->hrm_index(), i,
1592 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1593 }
1594 failures += 1;
1595 }
1596 }
1597
1598 if (failures > 0 && _verbose) {
1599 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1600 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1601 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()),
1602 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1603 }
1604
1605 _failures += failures;
1606
1607 // We could stop iteration over the heap when we
1608 // find the first violating region by returning true.
1609 return false;
1610 }
1611 };
1612
1613 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1614 protected:
1615 G1CollectedHeap* _g1h;
1616 ConcurrentMark* _cm;
1617 BitMap* _actual_region_bm;
1618 BitMap* _actual_card_bm;
1619
1620 uint _n_workers;
1621
1622 BitMap* _expected_region_bm;
1623 BitMap* _expected_card_bm;
1624
1625 int _failures;
1626 bool _verbose;
1627
1628 HeapRegionClaimer _hrclaimer;
1629
1630 public:
1631 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1632 BitMap* region_bm, BitMap* card_bm,
1633 BitMap* expected_region_bm, BitMap* expected_card_bm)
1634 : AbstractGangTask("G1 verify final counting"),
1635 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1636 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1637 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1638 _failures(0), _verbose(false),
1639 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1640 assert(VerifyDuringGC, "don't call this otherwise");
1641 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1642 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1643
1644 _verbose = _cm->verbose_medium();
1645 }
1646
1647 void work(uint worker_id) {
1648 assert(worker_id < _n_workers, "invariant");
1649
1650 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1651 _actual_region_bm, _actual_card_bm,
1652 _expected_region_bm,
1653 _expected_card_bm,
1654 _verbose);
1655
1656 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer);
1657
1658 Atomic::add(verify_cl.failures(), &_failures);
1659 }
1660
1661 int failures() const { return _failures; }
1662 };
1663
1664 // Closure that finalizes the liveness counting data.
1665 // Used during the cleanup pause.
1666 // Sets the bits corresponding to the interval [NTAMS, top]
1667 // (which contains the implicitly live objects) in the
1668 // card liveness bitmap. Also sets the bit for each region,
1669 // containing live data, in the region liveness bitmap.
1670
1671 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1672 public:
1673 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1674 BitMap* region_bm,
1675 BitMap* card_bm) :
1676 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1677
1678 bool doHeapRegion(HeapRegion* hr) {
1679
1680 if (hr->is_continues_humongous()) {
1681 // We will ignore these here and process them when their
1682 // associated "starts humongous" region is processed (see
1683 // set_bit_for_heap_region()). Note that we cannot rely on their
1684 // associated "starts humongous" region to have their bit set to
1685 // 1 since, due to the region chunking in the parallel region
1686 // iteration, a "continues humongous" region might be visited
1687 // before its associated "starts humongous".
1688 return false;
1689 }
1690
1691 HeapWord* ntams = hr->next_top_at_mark_start();
1692 HeapWord* top = hr->top();
1693
1694 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1695
1696 // Mark the allocated-since-marking portion...
1697 if (ntams < top) {
1698 // This definitely means the region has live objects.
1699 set_bit_for_region(hr);
1700
1701 // Now set the bits in the card bitmap for [ntams, top)
1702 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1703 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1704
1705 // Note: if we're looking at the last region in heap - top
1706 // could be actually just beyond the end of the heap; end_idx
1707 // will then correspond to a (non-existent) card that is also
1708 // just beyond the heap.
1709 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1710 // end of object is not card aligned - increment to cover
1711 // all the cards spanned by the object
1712 end_idx += 1;
1713 }
1714
1715 assert(end_idx <= _card_bm->size(),
1716 err_msg("oob: end_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1717 end_idx, _card_bm->size()));
1718 assert(start_idx < _card_bm->size(),
1719 err_msg("oob: start_idx= "SIZE_FORMAT", bitmap size= "SIZE_FORMAT,
1720 start_idx, _card_bm->size()));
1721
1722 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1723 }
1724
1725 // Set the bit for the region if it contains live data
1726 if (hr->next_marked_bytes() > 0) {
1727 set_bit_for_region(hr);
1728 }
1729
1730 return false;
1731 }
1732 };
1733
1734 class G1ParFinalCountTask: public AbstractGangTask {
1735 protected:
1736 G1CollectedHeap* _g1h;
1737 ConcurrentMark* _cm;
1738 BitMap* _actual_region_bm;
1739 BitMap* _actual_card_bm;
1740
1741 uint _n_workers;
1742 HeapRegionClaimer _hrclaimer;
1743
1744 public:
1745 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1746 : AbstractGangTask("G1 final counting"),
1747 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1748 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1749 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1750 }
1751
1752 void work(uint worker_id) {
1753 assert(worker_id < _n_workers, "invariant");
1754
1755 FinalCountDataUpdateClosure final_update_cl(_g1h,
1756 _actual_region_bm,
1757 _actual_card_bm);
1758
1759 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer);
1760 }
1761 };
1762
1763 class G1ParNoteEndTask;
1764
1765 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1766 G1CollectedHeap* _g1;
1767 size_t _max_live_bytes;
1768 uint _regions_claimed;
1769 size_t _freed_bytes;
1770 FreeRegionList* _local_cleanup_list;
1771 HeapRegionSetCount _old_regions_removed;
1772 HeapRegionSetCount _humongous_regions_removed;
1773 HRRSCleanupTask* _hrrs_cleanup_task;
1774 double _claimed_region_time;
1775 double _max_region_time;
1776
1777 public:
1778 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1779 FreeRegionList* local_cleanup_list,
1780 HRRSCleanupTask* hrrs_cleanup_task) :
1781 _g1(g1),
1782 _max_live_bytes(0), _regions_claimed(0),
1783 _freed_bytes(0),
1784 _claimed_region_time(0.0), _max_region_time(0.0),
1785 _local_cleanup_list(local_cleanup_list),
1786 _old_regions_removed(),
1787 _humongous_regions_removed(),
1788 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1789
1790 size_t freed_bytes() { return _freed_bytes; }
1791 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; }
1792 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; }
1793
1794 bool doHeapRegion(HeapRegion *hr) {
1795 if (hr->is_continues_humongous()) {
1796 return false;
1797 }
1798 // We use a claim value of zero here because all regions
1799 // were claimed with value 1 in the FinalCount task.
1800 _g1->reset_gc_time_stamps(hr);
1801 double start = os::elapsedTime();
1802 _regions_claimed++;
1803 hr->note_end_of_marking();
1804 _max_live_bytes += hr->max_live_bytes();
1805
1806 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1807 _freed_bytes += hr->used();
1808 hr->set_containing_set(NULL);
1809 if (hr->is_humongous()) {
1810 assert(hr->is_starts_humongous(), "we should only see starts humongous");
1811 _humongous_regions_removed.increment(1u, hr->capacity());
1812 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1813 } else {
1814 _old_regions_removed.increment(1u, hr->capacity());
1815 _g1->free_region(hr, _local_cleanup_list, true);
1816 }
1817 } else {
1818 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1819 }
1820
1821 double region_time = (os::elapsedTime() - start);
1822 _claimed_region_time += region_time;
1823 if (region_time > _max_region_time) {
1824 _max_region_time = region_time;
1825 }
1826 return false;
1827 }
1828
1829 size_t max_live_bytes() { return _max_live_bytes; }
1830 uint regions_claimed() { return _regions_claimed; }
1831 double claimed_region_time_sec() { return _claimed_region_time; }
1832 double max_region_time_sec() { return _max_region_time; }
1833 };
1834
1835 class G1ParNoteEndTask: public AbstractGangTask {
1836 friend class G1NoteEndOfConcMarkClosure;
1837
1838 protected:
1839 G1CollectedHeap* _g1h;
1840 size_t _max_live_bytes;
1841 size_t _freed_bytes;
1842 FreeRegionList* _cleanup_list;
1843 HeapRegionClaimer _hrclaimer;
1844
1845 public:
1846 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1847 AbstractGangTask("G1 note end"), _g1h(g1h), _max_live_bytes(0), _freed_bytes(0), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1848 }
1849
1850 void work(uint worker_id) {
1851 FreeRegionList local_cleanup_list("Local Cleanup List");
1852 HRRSCleanupTask hrrs_cleanup_task;
1853 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1854 &hrrs_cleanup_task);
1855 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1856 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1857
1858 // Now update the lists
1859 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1860 {
1861 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1862 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1863 _max_live_bytes += g1_note_end.max_live_bytes();
1864 _freed_bytes += g1_note_end.freed_bytes();
1865
1866 // If we iterate over the global cleanup list at the end of
1867 // cleanup to do this printing we will not guarantee to only
1868 // generate output for the newly-reclaimed regions (the list
1869 // might not be empty at the beginning of cleanup; we might
1870 // still be working on its previous contents). So we do the
1871 // printing here, before we append the new regions to the global
1872 // cleanup list.
1873
1874 G1HRPrinter* hr_printer = _g1h->hr_printer();
1875 if (hr_printer->is_active()) {
1876 FreeRegionListIterator iter(&local_cleanup_list);
1877 while (iter.more_available()) {
1878 HeapRegion* hr = iter.get_next();
1879 hr_printer->cleanup(hr);
1880 }
1881 }
1882
1883 _cleanup_list->add_ordered(&local_cleanup_list);
1884 assert(local_cleanup_list.is_empty(), "post-condition");
1885
1886 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1887 }
1888 }
1889 size_t max_live_bytes() { return _max_live_bytes; }
1890 size_t freed_bytes() { return _freed_bytes; }
1891 };
1892
1893 class G1ParScrubRemSetTask: public AbstractGangTask {
1894 protected:
1895 G1RemSet* _g1rs;
1896 BitMap* _region_bm;
1897 BitMap* _card_bm;
1898 HeapRegionClaimer _hrclaimer;
1899
1900 public:
1901 G1ParScrubRemSetTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm, uint n_workers) :
1902 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), _region_bm(region_bm), _card_bm(card_bm), _hrclaimer(n_workers) {
1903 }
1904
1905 void work(uint worker_id) {
1906 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
1907 }
1908
1909 };
1910
1911 void ConcurrentMark::cleanup() {
1912 // world is stopped at this checkpoint
1913 assert(SafepointSynchronize::is_at_safepoint(),
1914 "world should be stopped");
1915 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1916
1917 // If a full collection has happened, we shouldn't do this.
1918 if (has_aborted()) {
1919 g1h->set_marking_complete(); // So bitmap clearing isn't confused
1920 return;
1921 }
1922
1923 g1h->verify_region_sets_optional();
1924
1925 if (VerifyDuringGC) {
1926 HandleMark hm; // handle scope
1927 g1h->prepare_for_verify();
1928 Universe::verify(VerifyOption_G1UsePrevMarking,
1929 " VerifyDuringGC:(before)");
1930 }
1931 g1h->check_bitmaps("Cleanup Start");
1932
1933 G1CollectorPolicy* g1p = g1h->g1_policy();
1934 g1p->record_concurrent_mark_cleanup_start();
1935
1936 double start = os::elapsedTime();
1937
1938 HeapRegionRemSet::reset_for_cleanup_tasks();
1939
1940 // Do counting once more with the world stopped for good measure.
1941 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1942
1943 g1h->set_par_threads();
1944 uint n_workers = _g1h->workers()->active_workers();
1945 g1h->workers()->run_task(&g1_par_count_task);
1946 // Done with the parallel phase so reset to 0.
1947 g1h->set_par_threads(0);
1948
1949 if (VerifyDuringGC) {
1950 // Verify that the counting data accumulated during marking matches
1951 // that calculated by walking the marking bitmap.
1952
1953 // Bitmaps to hold expected values
1954 BitMap expected_region_bm(_region_bm.size(), true);
1955 BitMap expected_card_bm(_card_bm.size(), true);
1956
1957 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1958 &_region_bm,
1959 &_card_bm,
1960 &expected_region_bm,
1961 &expected_card_bm);
1962
1963 g1h->set_par_threads((int)n_workers);
1964 g1h->workers()->run_task(&g1_par_verify_task);
1965 // Done with the parallel phase so reset to 0.
1966 g1h->set_par_threads(0);
1967
1968 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
1969 }
1970
1971 size_t start_used_bytes = g1h->used();
1972 g1h->set_marking_complete();
1973
1974 double count_end = os::elapsedTime();
1975 double this_final_counting_time = (count_end - start);
1976 _total_counting_time += this_final_counting_time;
1977
1978 if (G1PrintRegionLivenessInfo) {
1979 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
1980 _g1h->heap_region_iterate(&cl);
1981 }
1982
1983 // Install newly created mark bitMap as "prev".
1984 swapMarkBitMaps();
1985
1986 g1h->reset_gc_time_stamp();
1987
1988 // Note end of marking in all heap regions.
1989 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1990 g1h->set_par_threads((int)n_workers);
1991 g1h->workers()->run_task(&g1_par_note_end_task);
1992 g1h->set_par_threads(0);
1993 g1h->check_gc_time_stamps();
1994
1995 if (!cleanup_list_is_empty()) {
1996 // The cleanup list is not empty, so we'll have to process it
1997 // concurrently. Notify anyone else that might be wanting free
1998 // regions that there will be more free regions coming soon.
1999 g1h->set_free_regions_coming();
2000 }
2001
2002 // call below, since it affects the metric by which we sort the heap
2003 // regions.
2004 if (G1ScrubRemSets) {
2005 double rs_scrub_start = os::elapsedTime();
2006 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers);
2007 g1h->set_par_threads((int)n_workers);
2008 g1h->workers()->run_task(&g1_par_scrub_rs_task);
2009 g1h->set_par_threads(0);
2010
2011 double rs_scrub_end = os::elapsedTime();
2012 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
2013 _total_rs_scrub_time += this_rs_scrub_time;
2014 }
2015
2016 // this will also free any regions totally full of garbage objects,
2017 // and sort the regions.
2018 g1h->g1_policy()->record_concurrent_mark_cleanup_end((int)n_workers);
2019
2020 // Statistics.
2021 double end = os::elapsedTime();
2022 _cleanup_times.add((end - start) * 1000.0);
2023
2024 if (G1Log::fine()) {
2025 g1h->g1_policy()->print_heap_transition(start_used_bytes);
2026 }
2027
2028 // Clean up will have freed any regions completely full of garbage.
2029 // Update the soft reference policy with the new heap occupancy.
2030 Universe::update_heap_info_at_gc();
2031
2032 if (VerifyDuringGC) {
2033 HandleMark hm; // handle scope
2034 g1h->prepare_for_verify();
2035 Universe::verify(VerifyOption_G1UsePrevMarking,
2036 " VerifyDuringGC:(after)");
2037 }
2038
2039 g1h->check_bitmaps("Cleanup End");
2040
2041 g1h->verify_region_sets_optional();
2042
2043 // We need to make this be a "collection" so any collection pause that
2044 // races with it goes around and waits for completeCleanup to finish.
2045 g1h->increment_total_collections();
2046
2047 // Clean out dead classes and update Metaspace sizes.
2048 if (ClassUnloadingWithConcurrentMark) {
2049 ClassLoaderDataGraph::purge();
2050 }
2051 MetaspaceGC::compute_new_size();
2052
2053 // We reclaimed old regions so we should calculate the sizes to make
2054 // sure we update the old gen/space data.
2055 g1h->g1mm()->update_sizes();
2056 g1h->allocation_context_stats().update_after_mark();
2057
2058 g1h->trace_heap_after_concurrent_cycle();
2059 }
2060
2061 void ConcurrentMark::completeCleanup() {
2062 if (has_aborted()) return;
2063
2064 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2065
2066 _cleanup_list.verify_optional();
2067 FreeRegionList tmp_free_list("Tmp Free List");
2068
2069 if (G1ConcRegionFreeingVerbose) {
2070 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2071 "cleanup list has %u entries",
2072 _cleanup_list.length());
2073 }
2074
2075 // No one else should be accessing the _cleanup_list at this point,
2076 // so it is not necessary to take any locks
2077 while (!_cleanup_list.is_empty()) {
2078 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
2079 assert(hr != NULL, "Got NULL from a non-empty list");
2080 hr->par_clear();
2081 tmp_free_list.add_ordered(hr);
2082
2083 // Instead of adding one region at a time to the secondary_free_list,
2084 // we accumulate them in the local list and move them a few at a
2085 // time. This also cuts down on the number of notify_all() calls
2086 // we do during this process. We'll also append the local list when
2087 // _cleanup_list is empty (which means we just removed the last
2088 // region from the _cleanup_list).
2089 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2090 _cleanup_list.is_empty()) {
2091 if (G1ConcRegionFreeingVerbose) {
2092 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2093 "appending %u entries to the secondary_free_list, "
2094 "cleanup list still has %u entries",
2095 tmp_free_list.length(),
2096 _cleanup_list.length());
2097 }
2098
2099 {
2100 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2101 g1h->secondary_free_list_add(&tmp_free_list);
2102 SecondaryFreeList_lock->notify_all();
2103 }
2104 #ifndef PRODUCT
2105 if (G1StressConcRegionFreeing) {
2106 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2107 os::sleep(Thread::current(), (jlong) 1, false);
2108 }
2109 }
2110 #endif
2111 }
2112 }
2113 assert(tmp_free_list.is_empty(), "post-condition");
2114 }
2115
2116 // Supporting Object and Oop closures for reference discovery
2117 // and processing in during marking
2118
2119 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2120 HeapWord* addr = (HeapWord*)obj;
2121 return addr != NULL &&
2122 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2123 }
2124
2125 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2126 // Uses the CMTask associated with a worker thread (for serial reference
2127 // processing the CMTask for worker 0 is used) to preserve (mark) and
2128 // trace referent objects.
2129 //
2130 // Using the CMTask and embedded local queues avoids having the worker
2131 // threads operating on the global mark stack. This reduces the risk
2132 // of overflowing the stack - which we would rather avoid at this late
2133 // state. Also using the tasks' local queues removes the potential
2134 // of the workers interfering with each other that could occur if
2135 // operating on the global stack.
2136
2137 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2138 ConcurrentMark* _cm;
2139 CMTask* _task;
2140 int _ref_counter_limit;
2141 int _ref_counter;
2142 bool _is_serial;
2143 public:
2144 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2145 _cm(cm), _task(task), _is_serial(is_serial),
2146 _ref_counter_limit(G1RefProcDrainInterval) {
2147 assert(_ref_counter_limit > 0, "sanity");
2148 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2149 _ref_counter = _ref_counter_limit;
2150 }
2151
2152 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2153 virtual void do_oop( oop* p) { do_oop_work(p); }
2154
2155 template <class T> void do_oop_work(T* p) {
2156 if (!_cm->has_overflown()) {
2157 oop obj = oopDesc::load_decode_heap_oop(p);
2158 if (_cm->verbose_high()) {
2159 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2160 "*"PTR_FORMAT" = "PTR_FORMAT,
2161 _task->worker_id(), p2i(p), p2i((void*) obj));
2162 }
2163
2164 _task->deal_with_reference(obj);
2165 _ref_counter--;
2166
2167 if (_ref_counter == 0) {
2168 // We have dealt with _ref_counter_limit references, pushing them
2169 // and objects reachable from them on to the local stack (and
2170 // possibly the global stack). Call CMTask::do_marking_step() to
2171 // process these entries.
2172 //
2173 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2174 // there's nothing more to do (i.e. we're done with the entries that
2175 // were pushed as a result of the CMTask::deal_with_reference() calls
2176 // above) or we overflow.
2177 //
2178 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2179 // flag while there may still be some work to do. (See the comment at
2180 // the beginning of CMTask::do_marking_step() for those conditions -
2181 // one of which is reaching the specified time target.) It is only
2182 // when CMTask::do_marking_step() returns without setting the
2183 // has_aborted() flag that the marking step has completed.
2184 do {
2185 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2186 _task->do_marking_step(mark_step_duration_ms,
2187 false /* do_termination */,
2188 _is_serial);
2189 } while (_task->has_aborted() && !_cm->has_overflown());
2190 _ref_counter = _ref_counter_limit;
2191 }
2192 } else {
2193 if (_cm->verbose_high()) {
2194 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2195 }
2196 }
2197 }
2198 };
2199
2200 // 'Drain' oop closure used by both serial and parallel reference processing.
2201 // Uses the CMTask associated with a given worker thread (for serial
2202 // reference processing the CMtask for worker 0 is used). Calls the
2203 // do_marking_step routine, with an unbelievably large timeout value,
2204 // to drain the marking data structures of the remaining entries
2205 // added by the 'keep alive' oop closure above.
2206
2207 class G1CMDrainMarkingStackClosure: public VoidClosure {
2208 ConcurrentMark* _cm;
2209 CMTask* _task;
2210 bool _is_serial;
2211 public:
2212 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2213 _cm(cm), _task(task), _is_serial(is_serial) {
2214 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2215 }
2216
2217 void do_void() {
2218 do {
2219 if (_cm->verbose_high()) {
2220 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2221 _task->worker_id(), BOOL_TO_STR(_is_serial));
2222 }
2223
2224 // We call CMTask::do_marking_step() to completely drain the local
2225 // and global marking stacks of entries pushed by the 'keep alive'
2226 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2227 //
2228 // CMTask::do_marking_step() is called in a loop, which we'll exit
2229 // if there's nothing more to do (i.e. we've completely drained the
2230 // entries that were pushed as a a result of applying the 'keep alive'
2231 // closure to the entries on the discovered ref lists) or we overflow
2232 // the global marking stack.
2233 //
2234 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2235 // flag while there may still be some work to do. (See the comment at
2236 // the beginning of CMTask::do_marking_step() for those conditions -
2237 // one of which is reaching the specified time target.) It is only
2238 // when CMTask::do_marking_step() returns without setting the
2239 // has_aborted() flag that the marking step has completed.
2240
2241 _task->do_marking_step(1000000000.0 /* something very large */,
2242 true /* do_termination */,
2243 _is_serial);
2244 } while (_task->has_aborted() && !_cm->has_overflown());
2245 }
2246 };
2247
2248 // Implementation of AbstractRefProcTaskExecutor for parallel
2249 // reference processing at the end of G1 concurrent marking
2250
2251 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2252 private:
2253 G1CollectedHeap* _g1h;
2254 ConcurrentMark* _cm;
2255 WorkGang* _workers;
2256 uint _active_workers;
2257
2258 public:
2259 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2260 ConcurrentMark* cm,
2261 WorkGang* workers,
2262 uint n_workers) :
2263 _g1h(g1h), _cm(cm),
2264 _workers(workers), _active_workers(n_workers) { }
2265
2266 // Executes the given task using concurrent marking worker threads.
2267 virtual void execute(ProcessTask& task);
2268 virtual void execute(EnqueueTask& task);
2269 };
2270
2271 class G1CMRefProcTaskProxy: public AbstractGangTask {
2272 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2273 ProcessTask& _proc_task;
2274 G1CollectedHeap* _g1h;
2275 ConcurrentMark* _cm;
2276
2277 public:
2278 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2279 G1CollectedHeap* g1h,
2280 ConcurrentMark* cm) :
2281 AbstractGangTask("Process reference objects in parallel"),
2282 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2283 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2284 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2285 }
2286
2287 virtual void work(uint worker_id) {
2288 ResourceMark rm;
2289 HandleMark hm;
2290 CMTask* task = _cm->task(worker_id);
2291 G1CMIsAliveClosure g1_is_alive(_g1h);
2292 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2293 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2294
2295 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2296 }
2297 };
2298
2299 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2300 assert(_workers != NULL, "Need parallel worker threads.");
2301 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2302
2303 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2304
2305 // We need to reset the concurrency level before each
2306 // proxy task execution, so that the termination protocol
2307 // and overflow handling in CMTask::do_marking_step() knows
2308 // how many workers to wait for.
2309 _cm->set_concurrency(_active_workers);
2310 _g1h->set_par_threads(_active_workers);
2311 _workers->run_task(&proc_task_proxy);
2312 _g1h->set_par_threads(0);
2313 }
2314
2315 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2316 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2317 EnqueueTask& _enq_task;
2318
2319 public:
2320 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2321 AbstractGangTask("Enqueue reference objects in parallel"),
2322 _enq_task(enq_task) { }
2323
2324 virtual void work(uint worker_id) {
2325 _enq_task.work(worker_id);
2326 }
2327 };
2328
2329 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2330 assert(_workers != NULL, "Need parallel worker threads.");
2331 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2332
2333 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2334
2335 // Not strictly necessary but...
2336 //
2337 // We need to reset the concurrency level before each
2338 // proxy task execution, so that the termination protocol
2339 // and overflow handling in CMTask::do_marking_step() knows
2340 // how many workers to wait for.
2341 _cm->set_concurrency(_active_workers);
2342 _g1h->set_par_threads(_active_workers);
2343 _workers->run_task(&enq_task_proxy);
2344 _g1h->set_par_threads(0);
2345 }
2346
2347 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
2348 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
2349 }
2350
2351 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2352 if (has_overflown()) {
2353 // Skip processing the discovered references if we have
2354 // overflown the global marking stack. Reference objects
2355 // only get discovered once so it is OK to not
2356 // de-populate the discovered reference lists. We could have,
2357 // but the only benefit would be that, when marking restarts,
2358 // less reference objects are discovered.
2359 return;
2360 }
2361
2362 ResourceMark rm;
2363 HandleMark hm;
2364
2365 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2366
2367 // Is alive closure.
2368 G1CMIsAliveClosure g1_is_alive(g1h);
2369
2370 // Inner scope to exclude the cleaning of the string and symbol
2371 // tables from the displayed time.
2372 {
2373 G1CMTraceTime t("GC ref-proc", G1Log::finer());
2374
2375 ReferenceProcessor* rp = g1h->ref_processor_cm();
2376
2377 // See the comment in G1CollectedHeap::ref_processing_init()
2378 // about how reference processing currently works in G1.
2379
2380 // Set the soft reference policy
2381 rp->setup_policy(clear_all_soft_refs);
2382 assert(_markStack.isEmpty(), "mark stack should be empty");
2383
2384 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2385 // in serial reference processing. Note these closures are also
2386 // used for serially processing (by the the current thread) the
2387 // JNI references during parallel reference processing.
2388 //
2389 // These closures do not need to synchronize with the worker
2390 // threads involved in parallel reference processing as these
2391 // instances are executed serially by the current thread (e.g.
2392 // reference processing is not multi-threaded and is thus
2393 // performed by the current thread instead of a gang worker).
2394 //
2395 // The gang tasks involved in parallel reference processing create
2396 // their own instances of these closures, which do their own
2397 // synchronization among themselves.
2398 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2399 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2400
2401 // We need at least one active thread. If reference processing
2402 // is not multi-threaded we use the current (VMThread) thread,
2403 // otherwise we use the work gang from the G1CollectedHeap and
2404 // we utilize all the worker threads we can.
2405 bool processing_is_mt = rp->processing_is_mt();
2406 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2407 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2408
2409 // Parallel processing task executor.
2410 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2411 g1h->workers(), active_workers);
2412 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2413
2414 // Set the concurrency level. The phase was already set prior to
2415 // executing the remark task.
2416 set_concurrency(active_workers);
2417
2418 // Set the degree of MT processing here. If the discovery was done MT,
2419 // the number of threads involved during discovery could differ from
2420 // the number of active workers. This is OK as long as the discovered
2421 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2422 rp->set_active_mt_degree(active_workers);
2423
2424 // Process the weak references.
2425 const ReferenceProcessorStats& stats =
2426 rp->process_discovered_references(&g1_is_alive,
2427 &g1_keep_alive,
2428 &g1_drain_mark_stack,
2429 executor,
2430 g1h->gc_timer_cm(),
2431 concurrent_gc_id());
2432 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2433
2434 // The do_oop work routines of the keep_alive and drain_marking_stack
2435 // oop closures will set the has_overflown flag if we overflow the
2436 // global marking stack.
2437
2438 assert(_markStack.overflow() || _markStack.isEmpty(),
2439 "mark stack should be empty (unless it overflowed)");
2440
2441 if (_markStack.overflow()) {
2442 // This should have been done already when we tried to push an
2443 // entry on to the global mark stack. But let's do it again.
2444 set_has_overflown();
2445 }
2446
2447 assert(rp->num_q() == active_workers, "why not");
2448
2449 rp->enqueue_discovered_references(executor);
2450
2451 rp->verify_no_references_recorded();
2452 assert(!rp->discovery_enabled(), "Post condition");
2453 }
2454
2455 if (has_overflown()) {
2456 // We can not trust g1_is_alive if the marking stack overflowed
2457 return;
2458 }
2459
2460 assert(_markStack.isEmpty(), "Marking should have completed");
2461
2462 // Unload Klasses, String, Symbols, Code Cache, etc.
2463 {
2464 G1CMTraceTime trace("Unloading", G1Log::finer());
2465
2466 if (ClassUnloadingWithConcurrentMark) {
2467 bool purged_classes;
2468
2469 {
2470 G1CMTraceTime trace("System Dictionary Unloading", G1Log::finest());
2471 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
2472 }
2473
2474 {
2475 G1CMTraceTime trace("Parallel Unloading", G1Log::finest());
2476 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
2477 }
2478 }
2479
2480 if (G1StringDedup::is_enabled()) {
2481 G1CMTraceTime trace("String Deduplication Unlink", G1Log::finest());
2482 G1StringDedup::unlink(&g1_is_alive);
2483 }
2484 }
2485 }
2486
2487 void ConcurrentMark::swapMarkBitMaps() {
2488 CMBitMapRO* temp = _prevMarkBitMap;
2489 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2490 _nextMarkBitMap = (CMBitMap*) temp;
2491 }
2492
2493 // Closure for marking entries in SATB buffers.
2494 class CMSATBBufferClosure : public SATBBufferClosure {
2495 private:
2496 CMTask* _task;
2497 G1CollectedHeap* _g1h;
2498
2499 // This is very similar to CMTask::deal_with_reference, but with
2500 // more relaxed requirements for the argument, so this must be more
2501 // circumspect about treating the argument as an object.
2502 void do_entry(void* entry) const {
2503 _task->increment_refs_reached();
2504 HeapRegion* hr = _g1h->heap_region_containing_raw(entry);
2505 if (entry < hr->next_top_at_mark_start()) {
2506 // Until we get here, we don't know whether entry refers to a valid
2507 // object; it could instead have been a stale reference.
2508 oop obj = static_cast<oop>(entry);
2509 assert(obj->is_oop(true /* ignore mark word */),
2510 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj)));
2511 _task->make_reference_grey(obj, hr);
2512 }
2513 }
2514
2515 public:
2516 CMSATBBufferClosure(CMTask* task, G1CollectedHeap* g1h)
2517 : _task(task), _g1h(g1h) { }
2518
2519 virtual void do_buffer(void** buffer, size_t size) {
2520 for (size_t i = 0; i < size; ++i) {
2521 do_entry(buffer[i]);
2522 }
2523 }
2524 };
2525
2526 class G1RemarkThreadsClosure : public ThreadClosure {
2527 CMSATBBufferClosure _cm_satb_cl;
2528 G1CMOopClosure _cm_cl;
2529 MarkingCodeBlobClosure _code_cl;
2530 int _thread_parity;
2531
2532 public:
2533 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task) :
2534 _cm_satb_cl(task, g1h),
2535 _cm_cl(g1h, g1h->concurrent_mark(), task),
2536 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
2537 _thread_parity(Threads::thread_claim_parity()) {}
2538
2539 void do_thread(Thread* thread) {
2540 if (thread->is_Java_thread()) {
2541 if (thread->claim_oops_do(true, _thread_parity)) {
2542 JavaThread* jt = (JavaThread*)thread;
2543
2544 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
2545 // however the liveness of oops reachable from nmethods have very complex lifecycles:
2546 // * Alive if on the stack of an executing method
2547 // * Weakly reachable otherwise
2548 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
2549 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
2550 jt->nmethods_do(&_code_cl);
2551
2552 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
2553 }
2554 } else if (thread->is_VM_thread()) {
2555 if (thread->claim_oops_do(true, _thread_parity)) {
2556 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
2557 }
2558 }
2559 }
2560 };
2561
2562 class CMRemarkTask: public AbstractGangTask {
2563 private:
2564 ConcurrentMark* _cm;
2565 public:
2566 void work(uint worker_id) {
2567 // Since all available tasks are actually started, we should
2568 // only proceed if we're supposed to be active.
2569 if (worker_id < _cm->active_tasks()) {
2570 CMTask* task = _cm->task(worker_id);
2571 task->record_start_time();
2572 {
2573 ResourceMark rm;
2574 HandleMark hm;
2575
2576 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
2577 Threads::threads_do(&threads_f);
2578 }
2579
2580 do {
2581 task->do_marking_step(1000000000.0 /* something very large */,
2582 true /* do_termination */,
2583 false /* is_serial */);
2584 } while (task->has_aborted() && !_cm->has_overflown());
2585 // If we overflow, then we do not want to restart. We instead
2586 // want to abort remark and do concurrent marking again.
2587 task->record_end_time();
2588 }
2589 }
2590
2591 CMRemarkTask(ConcurrentMark* cm, uint active_workers) :
2592 AbstractGangTask("Par Remark"), _cm(cm) {
2593 _cm->terminator()->reset_for_reuse(active_workers);
2594 }
2595 };
2596
2597 void ConcurrentMark::checkpointRootsFinalWork() {
2598 ResourceMark rm;
2599 HandleMark hm;
2600 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2601
2602 G1CMTraceTime trace("Finalize Marking", G1Log::finer());
2603
2604 g1h->ensure_parsability(false);
2605
2606 // this is remark, so we'll use up all active threads
2607 uint active_workers = g1h->workers()->active_workers();
2608 if (active_workers == 0) {
2609 assert(active_workers > 0, "Should have been set earlier");
2610 active_workers = (uint) ParallelGCThreads;
2611 g1h->workers()->set_active_workers(active_workers);
2612 }
2613 set_concurrency_and_phase(active_workers, false /* concurrent */);
2614 // Leave _parallel_marking_threads at it's
2615 // value originally calculated in the ConcurrentMark
2616 // constructor and pass values of the active workers
2617 // through the gang in the task.
2618
2619 {
2620 StrongRootsScope srs(active_workers);
2621
2622 CMRemarkTask remarkTask(this, active_workers);
2623 // We will start all available threads, even if we decide that the
2624 // active_workers will be fewer. The extra ones will just bail out
2625 // immediately.
2626 g1h->set_par_threads(active_workers);
2627 g1h->workers()->run_task(&remarkTask);
2628 g1h->set_par_threads(0);
2629 }
2630
2631 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2632 guarantee(has_overflown() ||
2633 satb_mq_set.completed_buffers_num() == 0,
2634 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2635 BOOL_TO_STR(has_overflown()),
2636 satb_mq_set.completed_buffers_num()));
2637
2638 print_stats();
2639 }
2640
2641 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2642 // Note we are overriding the read-only view of the prev map here, via
2643 // the cast.
2644 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2645 }
2646
2647 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2648 _nextMarkBitMap->clearRange(mr);
2649 }
2650
2651 HeapRegion*
2652 ConcurrentMark::claim_region(uint worker_id) {
2653 // "checkpoint" the finger
2654 HeapWord* finger = _finger;
2655
2656 // _heap_end will not change underneath our feet; it only changes at
2657 // yield points.
2658 while (finger < _heap_end) {
2659 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2660
2661 // Note on how this code handles humongous regions. In the
2662 // normal case the finger will reach the start of a "starts
2663 // humongous" (SH) region. Its end will either be the end of the
2664 // last "continues humongous" (CH) region in the sequence, or the
2665 // standard end of the SH region (if the SH is the only region in
2666 // the sequence). That way claim_region() will skip over the CH
2667 // regions. However, there is a subtle race between a CM thread
2668 // executing this method and a mutator thread doing a humongous
2669 // object allocation. The two are not mutually exclusive as the CM
2670 // thread does not need to hold the Heap_lock when it gets
2671 // here. So there is a chance that claim_region() will come across
2672 // a free region that's in the progress of becoming a SH or a CH
2673 // region. In the former case, it will either
2674 // a) Miss the update to the region's end, in which case it will
2675 // visit every subsequent CH region, will find their bitmaps
2676 // empty, and do nothing, or
2677 // b) Will observe the update of the region's end (in which case
2678 // it will skip the subsequent CH regions).
2679 // If it comes across a region that suddenly becomes CH, the
2680 // scenario will be similar to b). So, the race between
2681 // claim_region() and a humongous object allocation might force us
2682 // to do a bit of unnecessary work (due to some unnecessary bitmap
2683 // iterations) but it should not introduce and correctness issues.
2684 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2685
2686 // Above heap_region_containing_raw may return NULL as we always scan claim
2687 // until the end of the heap. In this case, just jump to the next region.
2688 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
2689
2690 // Is the gap between reading the finger and doing the CAS too long?
2691 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2692 if (res == finger && curr_region != NULL) {
2693 // we succeeded
2694 HeapWord* bottom = curr_region->bottom();
2695 HeapWord* limit = curr_region->next_top_at_mark_start();
2696
2697 if (verbose_low()) {
2698 gclog_or_tty->print_cr("[%u] curr_region = "PTR_FORMAT" "
2699 "["PTR_FORMAT", "PTR_FORMAT"), "
2700 "limit = "PTR_FORMAT,
2701 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit));
2702 }
2703
2704 // notice that _finger == end cannot be guaranteed here since,
2705 // someone else might have moved the finger even further
2706 assert(_finger >= end, "the finger should have moved forward");
2707
2708 if (verbose_low()) {
2709 gclog_or_tty->print_cr("[%u] we were successful with region = "
2710 PTR_FORMAT, worker_id, p2i(curr_region));
2711 }
2712
2713 if (limit > bottom) {
2714 if (verbose_low()) {
2715 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is not empty, "
2716 "returning it ", worker_id, p2i(curr_region));
2717 }
2718 return curr_region;
2719 } else {
2720 assert(limit == bottom,
2721 "the region limit should be at bottom");
2722 if (verbose_low()) {
2723 gclog_or_tty->print_cr("[%u] region "PTR_FORMAT" is empty, "
2724 "returning NULL", worker_id, p2i(curr_region));
2725 }
2726 // we return NULL and the caller should try calling
2727 // claim_region() again.
2728 return NULL;
2729 }
2730 } else {
2731 assert(_finger > finger, "the finger should have moved forward");
2732 if (verbose_low()) {
2733 if (curr_region == NULL) {
2734 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, "
2735 "global finger = "PTR_FORMAT", "
2736 "our finger = "PTR_FORMAT,
2737 worker_id, p2i(_finger), p2i(finger));
2738 } else {
2739 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2740 "global finger = "PTR_FORMAT", "
2741 "our finger = "PTR_FORMAT,
2742 worker_id, p2i(_finger), p2i(finger));
2743 }
2744 }
2745
2746 // read it again
2747 finger = _finger;
2748 }
2749 }
2750
2751 return NULL;
2752 }
2753
2754 #ifndef PRODUCT
2755 enum VerifyNoCSetOopsPhase {
2756 VerifyNoCSetOopsStack,
2757 VerifyNoCSetOopsQueues
2758 };
2759
2760 class VerifyNoCSetOopsClosure : public OopClosure, public ObjectClosure {
2761 private:
2762 G1CollectedHeap* _g1h;
2763 VerifyNoCSetOopsPhase _phase;
2764 int _info;
2765
2766 const char* phase_str() {
2767 switch (_phase) {
2768 case VerifyNoCSetOopsStack: return "Stack";
2769 case VerifyNoCSetOopsQueues: return "Queue";
2770 default: ShouldNotReachHere();
2771 }
2772 return NULL;
2773 }
2774
2775 void do_object_work(oop obj) {
2776 guarantee(!_g1h->obj_in_cs(obj),
2777 err_msg("obj: "PTR_FORMAT" in CSet, phase: %s, info: %d",
2778 p2i((void*) obj), phase_str(), _info));
2779 }
2780
2781 public:
2782 VerifyNoCSetOopsClosure() : _g1h(G1CollectedHeap::heap()) { }
2783
2784 void set_phase(VerifyNoCSetOopsPhase phase, int info = -1) {
2785 _phase = phase;
2786 _info = info;
2787 }
2788
2789 virtual void do_oop(oop* p) {
2790 oop obj = oopDesc::load_decode_heap_oop(p);
2791 do_object_work(obj);
2792 }
2793
2794 virtual void do_oop(narrowOop* p) {
2795 // We should not come across narrow oops while scanning marking
2796 // stacks
2797 ShouldNotReachHere();
2798 }
2799
2800 virtual void do_object(oop obj) {
2801 do_object_work(obj);
2802 }
2803 };
2804
2805 void ConcurrentMark::verify_no_cset_oops() {
2806 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2807 if (!G1CollectedHeap::heap()->mark_in_progress()) {
2808 return;
2809 }
2810
2811 VerifyNoCSetOopsClosure cl;
2812
2813 // Verify entries on the global mark stack
2814 cl.set_phase(VerifyNoCSetOopsStack);
2815 _markStack.oops_do(&cl);
2816
2817 // Verify entries on the task queues
2818 for (uint i = 0; i < _max_worker_id; i += 1) {
2819 cl.set_phase(VerifyNoCSetOopsQueues, i);
2820 CMTaskQueue* queue = _task_queues->queue(i);
2821 queue->oops_do(&cl);
2822 }
2823
2824 // Verify the global finger
2825 HeapWord* global_finger = finger();
2826 if (global_finger != NULL && global_finger < _heap_end) {
2827 // The global finger always points to a heap region boundary. We
2828 // use heap_region_containing_raw() to get the containing region
2829 // given that the global finger could be pointing to a free region
2830 // which subsequently becomes continues humongous. If that
2831 // happens, heap_region_containing() will return the bottom of the
2832 // corresponding starts humongous region and the check below will
2833 // not hold any more.
2834 // Since we always iterate over all regions, we might get a NULL HeapRegion
2835 // here.
2836 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2837 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2838 err_msg("global finger: "PTR_FORMAT" region: "HR_FORMAT,
2839 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)));
2840 }
2841
2842 // Verify the task fingers
2843 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2844 for (int i = 0; i < (int) parallel_marking_threads(); i += 1) {
2845 CMTask* task = _tasks[i];
2846 HeapWord* task_finger = task->finger();
2847 if (task_finger != NULL && task_finger < _heap_end) {
2848 // See above note on the global finger verification.
2849 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2850 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2851 !task_hr->in_collection_set(),
2852 err_msg("task finger: "PTR_FORMAT" region: "HR_FORMAT,
2853 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)));
2854 }
2855 }
2856 }
2857 #endif // PRODUCT
2858
2859 // Aggregate the counting data that was constructed concurrently
2860 // with marking.
2861 class AggregateCountDataHRClosure: public HeapRegionClosure {
2862 G1CollectedHeap* _g1h;
2863 ConcurrentMark* _cm;
2864 CardTableModRefBS* _ct_bs;
2865 BitMap* _cm_card_bm;
2866 uint _max_worker_id;
2867
2868 public:
2869 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2870 BitMap* cm_card_bm,
2871 uint max_worker_id) :
2872 _g1h(g1h), _cm(g1h->concurrent_mark()),
2873 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
2874 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2875
2876 bool doHeapRegion(HeapRegion* hr) {
2877 if (hr->is_continues_humongous()) {
2878 // We will ignore these here and process them when their
2879 // associated "starts humongous" region is processed.
2880 // Note that we cannot rely on their associated
2881 // "starts humongous" region to have their bit set to 1
2882 // since, due to the region chunking in the parallel region
2883 // iteration, a "continues humongous" region might be visited
2884 // before its associated "starts humongous".
2885 return false;
2886 }
2887
2888 HeapWord* start = hr->bottom();
2889 HeapWord* limit = hr->next_top_at_mark_start();
2890 HeapWord* end = hr->end();
2891
2892 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
2893 err_msg("Preconditions not met - "
2894 "start: "PTR_FORMAT", limit: "PTR_FORMAT", "
2895 "top: "PTR_FORMAT", end: "PTR_FORMAT,
2896 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end())));
2897
2898 assert(hr->next_marked_bytes() == 0, "Precondition");
2899
2900 if (start == limit) {
2901 // NTAMS of this region has not been set so nothing to do.
2902 return false;
2903 }
2904
2905 // 'start' should be in the heap.
2906 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
2907 // 'end' *may* be just beyond the end of the heap (if hr is the last region)
2908 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
2909
2910 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
2911 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
2912 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
2913
2914 // If ntams is not card aligned then we bump card bitmap index
2915 // for limit so that we get the all the cards spanned by
2916 // the object ending at ntams.
2917 // Note: if this is the last region in the heap then ntams
2918 // could be actually just beyond the end of the the heap;
2919 // limit_idx will then correspond to a (non-existent) card
2920 // that is also outside the heap.
2921 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
2922 limit_idx += 1;
2923 }
2924
2925 assert(limit_idx <= end_idx, "or else use atomics");
2926
2927 // Aggregate the "stripe" in the count data associated with hr.
2928 uint hrm_index = hr->hrm_index();
2929 size_t marked_bytes = 0;
2930
2931 for (uint i = 0; i < _max_worker_id; i += 1) {
2932 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
2933 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
2934
2935 // Fetch the marked_bytes in this region for task i and
2936 // add it to the running total for this region.
2937 marked_bytes += marked_bytes_array[hrm_index];
2938
2939 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
2940 // into the global card bitmap.
2941 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
2942
2943 while (scan_idx < limit_idx) {
2944 assert(task_card_bm->at(scan_idx) == true, "should be");
2945 _cm_card_bm->set_bit(scan_idx);
2946 assert(_cm_card_bm->at(scan_idx) == true, "should be");
2947
2948 // BitMap::get_next_one_offset() can handle the case when
2949 // its left_offset parameter is greater than its right_offset
2950 // parameter. It does, however, have an early exit if
2951 // left_offset == right_offset. So let's limit the value
2952 // passed in for left offset here.
2953 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
2954 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
2955 }
2956 }
2957
2958 // Update the marked bytes for this region.
2959 hr->add_to_marked_bytes(marked_bytes);
2960
2961 // Next heap region
2962 return false;
2963 }
2964 };
2965
2966 class G1AggregateCountDataTask: public AbstractGangTask {
2967 protected:
2968 G1CollectedHeap* _g1h;
2969 ConcurrentMark* _cm;
2970 BitMap* _cm_card_bm;
2971 uint _max_worker_id;
2972 uint _active_workers;
2973 HeapRegionClaimer _hrclaimer;
2974
2975 public:
2976 G1AggregateCountDataTask(G1CollectedHeap* g1h,
2977 ConcurrentMark* cm,
2978 BitMap* cm_card_bm,
2979 uint max_worker_id,
2980 uint n_workers) :
2981 AbstractGangTask("Count Aggregation"),
2982 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
2983 _max_worker_id(max_worker_id),
2984 _active_workers(n_workers),
2985 _hrclaimer(_active_workers) {
2986 }
2987
2988 void work(uint worker_id) {
2989 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
2990
2991 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer);
2992 }
2993 };
2994
2995
2996 void ConcurrentMark::aggregate_count_data() {
2997 uint n_workers = _g1h->workers()->active_workers();
2998
2999 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
3000 _max_worker_id, n_workers);
3001
3002 _g1h->set_par_threads(n_workers);
3003 _g1h->workers()->run_task(&g1_par_agg_task);
3004 _g1h->set_par_threads(0);
3005 }
3006
3007 // Clear the per-worker arrays used to store the per-region counting data
3008 void ConcurrentMark::clear_all_count_data() {
3009 // Clear the global card bitmap - it will be filled during
3010 // liveness count aggregation (during remark) and the
3011 // final counting task.
3012 _card_bm.clear();
3013
3014 // Clear the global region bitmap - it will be filled as part
3015 // of the final counting task.
3016 _region_bm.clear();
3017
3018 uint max_regions = _g1h->max_regions();
3019 assert(_max_worker_id > 0, "uninitialized");
3020
3021 for (uint i = 0; i < _max_worker_id; i += 1) {
3022 BitMap* task_card_bm = count_card_bitmap_for(i);
3023 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
3024
3025 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
3026 assert(marked_bytes_array != NULL, "uninitialized");
3027
3028 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
3029 task_card_bm->clear();
3030 }
3031 }
3032
3033 void ConcurrentMark::print_stats() {
3034 if (verbose_stats()) {
3035 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3036 for (size_t i = 0; i < _active_tasks; ++i) {
3037 _tasks[i]->print_stats();
3038 gclog_or_tty->print_cr("---------------------------------------------------------------------");
3039 }
3040 }
3041 }
3042
3043 // abandon current marking iteration due to a Full GC
3044 void ConcurrentMark::abort() {
3045 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
3046 // concurrent bitmap clearing.
3047 _nextMarkBitMap->clearAll();
3048
3049 // Note we cannot clear the previous marking bitmap here
3050 // since VerifyDuringGC verifies the objects marked during
3051 // a full GC against the previous bitmap.
3052
3053 // Clear the liveness counting data
3054 clear_all_count_data();
3055 // Empty mark stack
3056 reset_marking_state();
3057 for (uint i = 0; i < _max_worker_id; ++i) {
3058 _tasks[i]->clear_region_fields();
3059 }
3060 _first_overflow_barrier_sync.abort();
3061 _second_overflow_barrier_sync.abort();
3062 const GCId& gc_id = _g1h->gc_tracer_cm()->gc_id();
3063 if (!gc_id.is_undefined()) {
3064 // We can do multiple full GCs before ConcurrentMarkThread::run() gets a chance
3065 // to detect that it was aborted. Only keep track of the first GC id that we aborted.
3066 _aborted_gc_id = gc_id;
3067 }
3068 _has_aborted = true;
3069
3070 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3071 satb_mq_set.abandon_partial_marking();
3072 // This can be called either during or outside marking, we'll read
3073 // the expected_active value from the SATB queue set.
3074 satb_mq_set.set_active_all_threads(
3075 false, /* new active value */
3076 satb_mq_set.is_active() /* expected_active */);
3077
3078 _g1h->trace_heap_after_concurrent_cycle();
3079 _g1h->register_concurrent_cycle_end();
3080 }
3081
3082 const GCId& ConcurrentMark::concurrent_gc_id() {
3083 if (has_aborted()) {
3084 return _aborted_gc_id;
3085 }
3086 return _g1h->gc_tracer_cm()->gc_id();
3087 }
3088
3089 static void print_ms_time_info(const char* prefix, const char* name,
3090 NumberSeq& ns) {
3091 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3092 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3093 if (ns.num() > 0) {
3094 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3095 prefix, ns.sd(), ns.maximum());
3096 }
3097 }
3098
3099 void ConcurrentMark::print_summary_info() {
3100 gclog_or_tty->print_cr(" Concurrent marking:");
3101 print_ms_time_info(" ", "init marks", _init_times);
3102 print_ms_time_info(" ", "remarks", _remark_times);
3103 {
3104 print_ms_time_info(" ", "final marks", _remark_mark_times);
3105 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3106
3107 }
3108 print_ms_time_info(" ", "cleanups", _cleanup_times);
3109 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3110 _total_counting_time,
3111 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3112 (double)_cleanup_times.num()
3113 : 0.0));
3114 if (G1ScrubRemSets) {
3115 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3116 _total_rs_scrub_time,
3117 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3118 (double)_cleanup_times.num()
3119 : 0.0));
3120 }
3121 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3122 (_init_times.sum() + _remark_times.sum() +
3123 _cleanup_times.sum())/1000.0);
3124 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3125 "(%8.2f s marking).",
3126 cmThread()->vtime_accum(),
3127 cmThread()->vtime_mark_accum());
3128 }
3129
3130 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3131 _parallel_workers->print_worker_threads_on(st);
3132 }
3133
3134 void ConcurrentMark::print_on_error(outputStream* st) const {
3135 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3136 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
3137 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3138 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3139 }
3140
3141 // We take a break if someone is trying to stop the world.
3142 bool ConcurrentMark::do_yield_check(uint worker_id) {
3143 if (SuspendibleThreadSet::should_yield()) {
3144 if (worker_id == 0) {
3145 _g1h->g1_policy()->record_concurrent_pause();
3146 }
3147 SuspendibleThreadSet::yield();
3148 return true;
3149 } else {
3150 return false;
3151 }
3152 }
3153
3154 #ifndef PRODUCT
3155 // for debugging purposes
3156 void ConcurrentMark::print_finger() {
3157 gclog_or_tty->print_cr("heap ["PTR_FORMAT", "PTR_FORMAT"), global finger = "PTR_FORMAT,
3158 p2i(_heap_start), p2i(_heap_end), p2i(_finger));
3159 for (uint i = 0; i < _max_worker_id; ++i) {
3160 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger()));
3161 }
3162 gclog_or_tty->cr();
3163 }
3164 #endif
3165
3166 template<bool scan>
3167 inline void CMTask::process_grey_object(oop obj) {
3168 assert(scan || obj->is_typeArray(), "Skipping scan of grey non-typeArray");
3169 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
3170
3171 if (_cm->verbose_high()) {
3172 gclog_or_tty->print_cr("[%u] processing grey object " PTR_FORMAT,
3173 _worker_id, p2i((void*) obj));
3174 }
3175
3176 size_t obj_size = obj->size();
3177 _words_scanned += obj_size;
3178
3179 if (scan) {
3180 obj->oop_iterate(_cm_oop_closure);
3181 }
3182 statsOnly( ++_objs_scanned );
3183 check_limits();
3184 }
3185
3186 template void CMTask::process_grey_object<true>(oop);
3187 template void CMTask::process_grey_object<false>(oop);
3188
3189 // Closure for iteration over bitmaps
3190 class CMBitMapClosure : public BitMapClosure {
3191 private:
3192 // the bitmap that is being iterated over
3193 CMBitMap* _nextMarkBitMap;
3194 ConcurrentMark* _cm;
3195 CMTask* _task;
3196
3197 public:
3198 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3199 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3200
3201 bool do_bit(size_t offset) {
3202 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3203 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3204 assert( addr < _cm->finger(), "invariant");
3205
3206 statsOnly( _task->increase_objs_found_on_bitmap() );
3207 assert(addr >= _task->finger(), "invariant");
3208
3209 // We move that task's local finger along.
3210 _task->move_finger_to(addr);
3211
3212 _task->scan_object(oop(addr));
3213 // we only partially drain the local queue and global stack
3214 _task->drain_local_queue(true);
3215 _task->drain_global_stack(true);
3216
3217 // if the has_aborted flag has been raised, we need to bail out of
3218 // the iteration
3219 return !_task->has_aborted();
3220 }
3221 };
3222
3223 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3224 ConcurrentMark* cm,
3225 CMTask* task)
3226 : _g1h(g1h), _cm(cm), _task(task) {
3227 assert(_ref_processor == NULL, "should be initialized to NULL");
3228
3229 if (G1UseConcMarkReferenceProcessing) {
3230 _ref_processor = g1h->ref_processor_cm();
3231 assert(_ref_processor != NULL, "should not be NULL");
3232 }
3233 }
3234
3235 void CMTask::setup_for_region(HeapRegion* hr) {
3236 assert(hr != NULL,
3237 "claim_region() should have filtered out NULL regions");
3238 assert(!hr->is_continues_humongous(),
3239 "claim_region() should have filtered out continues humongous regions");
3240
3241 if (_cm->verbose_low()) {
3242 gclog_or_tty->print_cr("[%u] setting up for region "PTR_FORMAT,
3243 _worker_id, p2i(hr));
3244 }
3245
3246 _curr_region = hr;
3247 _finger = hr->bottom();
3248 update_region_limit();
3249 }
3250
3251 void CMTask::update_region_limit() {
3252 HeapRegion* hr = _curr_region;
3253 HeapWord* bottom = hr->bottom();
3254 HeapWord* limit = hr->next_top_at_mark_start();
3255
3256 if (limit == bottom) {
3257 if (_cm->verbose_low()) {
3258 gclog_or_tty->print_cr("[%u] found an empty region "
3259 "["PTR_FORMAT", "PTR_FORMAT")",
3260 _worker_id, p2i(bottom), p2i(limit));
3261 }
3262 // The region was collected underneath our feet.
3263 // We set the finger to bottom to ensure that the bitmap
3264 // iteration that will follow this will not do anything.
3265 // (this is not a condition that holds when we set the region up,
3266 // as the region is not supposed to be empty in the first place)
3267 _finger = bottom;
3268 } else if (limit >= _region_limit) {
3269 assert(limit >= _finger, "peace of mind");
3270 } else {
3271 assert(limit < _region_limit, "only way to get here");
3272 // This can happen under some pretty unusual circumstances. An
3273 // evacuation pause empties the region underneath our feet (NTAMS
3274 // at bottom). We then do some allocation in the region (NTAMS
3275 // stays at bottom), followed by the region being used as a GC
3276 // alloc region (NTAMS will move to top() and the objects
3277 // originally below it will be grayed). All objects now marked in
3278 // the region are explicitly grayed, if below the global finger,
3279 // and we do not need in fact to scan anything else. So, we simply
3280 // set _finger to be limit to ensure that the bitmap iteration
3281 // doesn't do anything.
3282 _finger = limit;
3283 }
3284
3285 _region_limit = limit;
3286 }
3287
3288 void CMTask::giveup_current_region() {
3289 assert(_curr_region != NULL, "invariant");
3290 if (_cm->verbose_low()) {
3291 gclog_or_tty->print_cr("[%u] giving up region "PTR_FORMAT,
3292 _worker_id, p2i(_curr_region));
3293 }
3294 clear_region_fields();
3295 }
3296
3297 void CMTask::clear_region_fields() {
3298 // Values for these three fields that indicate that we're not
3299 // holding on to a region.
3300 _curr_region = NULL;
3301 _finger = NULL;
3302 _region_limit = NULL;
3303 }
3304
3305 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3306 if (cm_oop_closure == NULL) {
3307 assert(_cm_oop_closure != NULL, "invariant");
3308 } else {
3309 assert(_cm_oop_closure == NULL, "invariant");
3310 }
3311 _cm_oop_closure = cm_oop_closure;
3312 }
3313
3314 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3315 guarantee(nextMarkBitMap != NULL, "invariant");
3316
3317 if (_cm->verbose_low()) {
3318 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3319 }
3320
3321 _nextMarkBitMap = nextMarkBitMap;
3322 clear_region_fields();
3323
3324 _calls = 0;
3325 _elapsed_time_ms = 0.0;
3326 _termination_time_ms = 0.0;
3327 _termination_start_time_ms = 0.0;
3328
3329 #if _MARKING_STATS_
3330 _aborted = 0;
3331 _aborted_overflow = 0;
3332 _aborted_cm_aborted = 0;
3333 _aborted_yield = 0;
3334 _aborted_timed_out = 0;
3335 _aborted_satb = 0;
3336 _aborted_termination = 0;
3337 _steal_attempts = 0;
3338 _steals = 0;
3339 _local_pushes = 0;
3340 _local_pops = 0;
3341 _local_max_size = 0;
3342 _objs_scanned = 0;
3343 _global_pushes = 0;
3344 _global_pops = 0;
3345 _global_max_size = 0;
3346 _global_transfers_to = 0;
3347 _global_transfers_from = 0;
3348 _regions_claimed = 0;
3349 _objs_found_on_bitmap = 0;
3350 _satb_buffers_processed = 0;
3351 #endif // _MARKING_STATS_
3352 }
3353
3354 bool CMTask::should_exit_termination() {
3355 regular_clock_call();
3356 // This is called when we are in the termination protocol. We should
3357 // quit if, for some reason, this task wants to abort or the global
3358 // stack is not empty (this means that we can get work from it).
3359 return !_cm->mark_stack_empty() || has_aborted();
3360 }
3361
3362 void CMTask::reached_limit() {
3363 assert(_words_scanned >= _words_scanned_limit ||
3364 _refs_reached >= _refs_reached_limit ,
3365 "shouldn't have been called otherwise");
3366 regular_clock_call();
3367 }
3368
3369 void CMTask::regular_clock_call() {
3370 if (has_aborted()) return;
3371
3372 // First, we need to recalculate the words scanned and refs reached
3373 // limits for the next clock call.
3374 recalculate_limits();
3375
3376 // During the regular clock call we do the following
3377
3378 // (1) If an overflow has been flagged, then we abort.
3379 if (_cm->has_overflown()) {
3380 set_has_aborted();
3381 return;
3382 }
3383
3384 // If we are not concurrent (i.e. we're doing remark) we don't need
3385 // to check anything else. The other steps are only needed during
3386 // the concurrent marking phase.
3387 if (!concurrent()) return;
3388
3389 // (2) If marking has been aborted for Full GC, then we also abort.
3390 if (_cm->has_aborted()) {
3391 set_has_aborted();
3392 statsOnly( ++_aborted_cm_aborted );
3393 return;
3394 }
3395
3396 double curr_time_ms = os::elapsedVTime() * 1000.0;
3397
3398 // (3) If marking stats are enabled, then we update the step history.
3399 #if _MARKING_STATS_
3400 if (_words_scanned >= _words_scanned_limit) {
3401 ++_clock_due_to_scanning;
3402 }
3403 if (_refs_reached >= _refs_reached_limit) {
3404 ++_clock_due_to_marking;
3405 }
3406
3407 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3408 _interval_start_time_ms = curr_time_ms;
3409 _all_clock_intervals_ms.add(last_interval_ms);
3410
3411 if (_cm->verbose_medium()) {
3412 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3413 "scanned = "SIZE_FORMAT"%s, refs reached = "SIZE_FORMAT"%s",
3414 _worker_id, last_interval_ms,
3415 _words_scanned,
3416 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3417 _refs_reached,
3418 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3419 }
3420 #endif // _MARKING_STATS_
3421
3422 // (4) We check whether we should yield. If we have to, then we abort.
3423 if (SuspendibleThreadSet::should_yield()) {
3424 // We should yield. To do this we abort the task. The caller is
3425 // responsible for yielding.
3426 set_has_aborted();
3427 statsOnly( ++_aborted_yield );
3428 return;
3429 }
3430
3431 // (5) We check whether we've reached our time quota. If we have,
3432 // then we abort.
3433 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3434 if (elapsed_time_ms > _time_target_ms) {
3435 set_has_aborted();
3436 _has_timed_out = true;
3437 statsOnly( ++_aborted_timed_out );
3438 return;
3439 }
3440
3441 // (6) Finally, we check whether there are enough completed STAB
3442 // buffers available for processing. If there are, we abort.
3443 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3444 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3445 if (_cm->verbose_low()) {
3446 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3447 _worker_id);
3448 }
3449 // we do need to process SATB buffers, we'll abort and restart
3450 // the marking task to do so
3451 set_has_aborted();
3452 statsOnly( ++_aborted_satb );
3453 return;
3454 }
3455 }
3456
3457 void CMTask::recalculate_limits() {
3458 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3459 _words_scanned_limit = _real_words_scanned_limit;
3460
3461 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3462 _refs_reached_limit = _real_refs_reached_limit;
3463 }
3464
3465 void CMTask::decrease_limits() {
3466 // This is called when we believe that we're going to do an infrequent
3467 // operation which will increase the per byte scanned cost (i.e. move
3468 // entries to/from the global stack). It basically tries to decrease the
3469 // scanning limit so that the clock is called earlier.
3470
3471 if (_cm->verbose_medium()) {
3472 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3473 }
3474
3475 _words_scanned_limit = _real_words_scanned_limit -
3476 3 * words_scanned_period / 4;
3477 _refs_reached_limit = _real_refs_reached_limit -
3478 3 * refs_reached_period / 4;
3479 }
3480
3481 void CMTask::move_entries_to_global_stack() {
3482 // local array where we'll store the entries that will be popped
3483 // from the local queue
3484 oop buffer[global_stack_transfer_size];
3485
3486 int n = 0;
3487 oop obj;
3488 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3489 buffer[n] = obj;
3490 ++n;
3491 }
3492
3493 if (n > 0) {
3494 // we popped at least one entry from the local queue
3495
3496 statsOnly( ++_global_transfers_to; _local_pops += n );
3497
3498 if (!_cm->mark_stack_push(buffer, n)) {
3499 if (_cm->verbose_low()) {
3500 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3501 _worker_id);
3502 }
3503 set_has_aborted();
3504 } else {
3505 // the transfer was successful
3506
3507 if (_cm->verbose_medium()) {
3508 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3509 _worker_id, n);
3510 }
3511 statsOnly( size_t tmp_size = _cm->mark_stack_size();
3512 if (tmp_size > _global_max_size) {
3513 _global_max_size = tmp_size;
3514 }
3515 _global_pushes += n );
3516 }
3517 }
3518
3519 // this operation was quite expensive, so decrease the limits
3520 decrease_limits();
3521 }
3522
3523 void CMTask::get_entries_from_global_stack() {
3524 // local array where we'll store the entries that will be popped
3525 // from the global stack.
3526 oop buffer[global_stack_transfer_size];
3527 int n;
3528 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3529 assert(n <= global_stack_transfer_size,
3530 "we should not pop more than the given limit");
3531 if (n > 0) {
3532 // yes, we did actually pop at least one entry
3533
3534 statsOnly( ++_global_transfers_from; _global_pops += n );
3535 if (_cm->verbose_medium()) {
3536 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3537 _worker_id, n);
3538 }
3539 for (int i = 0; i < n; ++i) {
3540 bool success = _task_queue->push(buffer[i]);
3541 // We only call this when the local queue is empty or under a
3542 // given target limit. So, we do not expect this push to fail.
3543 assert(success, "invariant");
3544 }
3545
3546 statsOnly( size_t tmp_size = (size_t)_task_queue->size();
3547 if (tmp_size > _local_max_size) {
3548 _local_max_size = tmp_size;
3549 }
3550 _local_pushes += n );
3551 }
3552
3553 // this operation was quite expensive, so decrease the limits
3554 decrease_limits();
3555 }
3556
3557 void CMTask::drain_local_queue(bool partially) {
3558 if (has_aborted()) return;
3559
3560 // Decide what the target size is, depending whether we're going to
3561 // drain it partially (so that other tasks can steal if they run out
3562 // of things to do) or totally (at the very end).
3563 size_t target_size;
3564 if (partially) {
3565 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3566 } else {
3567 target_size = 0;
3568 }
3569
3570 if (_task_queue->size() > target_size) {
3571 if (_cm->verbose_high()) {
3572 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT,
3573 _worker_id, target_size);
3574 }
3575
3576 oop obj;
3577 bool ret = _task_queue->pop_local(obj);
3578 while (ret) {
3579 statsOnly( ++_local_pops );
3580
3581 if (_cm->verbose_high()) {
3582 gclog_or_tty->print_cr("[%u] popped "PTR_FORMAT, _worker_id,
3583 p2i((void*) obj));
3584 }
3585
3586 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3587 assert(!_g1h->is_on_master_free_list(
3588 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3589
3590 scan_object(obj);
3591
3592 if (_task_queue->size() <= target_size || has_aborted()) {
3593 ret = false;
3594 } else {
3595 ret = _task_queue->pop_local(obj);
3596 }
3597 }
3598
3599 if (_cm->verbose_high()) {
3600 gclog_or_tty->print_cr("[%u] drained local queue, size = %u",
3601 _worker_id, _task_queue->size());
3602 }
3603 }
3604 }
3605
3606 void CMTask::drain_global_stack(bool partially) {
3607 if (has_aborted()) return;
3608
3609 // We have a policy to drain the local queue before we attempt to
3610 // drain the global stack.
3611 assert(partially || _task_queue->size() == 0, "invariant");
3612
3613 // Decide what the target size is, depending whether we're going to
3614 // drain it partially (so that other tasks can steal if they run out
3615 // of things to do) or totally (at the very end). Notice that,
3616 // because we move entries from the global stack in chunks or
3617 // because another task might be doing the same, we might in fact
3618 // drop below the target. But, this is not a problem.
3619 size_t target_size;
3620 if (partially) {
3621 target_size = _cm->partial_mark_stack_size_target();
3622 } else {
3623 target_size = 0;
3624 }
3625
3626 if (_cm->mark_stack_size() > target_size) {
3627 if (_cm->verbose_low()) {
3628 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT,
3629 _worker_id, target_size);
3630 }
3631
3632 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3633 get_entries_from_global_stack();
3634 drain_local_queue(partially);
3635 }
3636
3637 if (_cm->verbose_low()) {
3638 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT,
3639 _worker_id, _cm->mark_stack_size());
3640 }
3641 }
3642 }
3643
3644 // SATB Queue has several assumptions on whether to call the par or
3645 // non-par versions of the methods. this is why some of the code is
3646 // replicated. We should really get rid of the single-threaded version
3647 // of the code to simplify things.
3648 void CMTask::drain_satb_buffers() {
3649 if (has_aborted()) return;
3650
3651 // We set this so that the regular clock knows that we're in the
3652 // middle of draining buffers and doesn't set the abort flag when it
3653 // notices that SATB buffers are available for draining. It'd be
3654 // very counter productive if it did that. :-)
3655 _draining_satb_buffers = true;
3656
3657 CMSATBBufferClosure satb_cl(this, _g1h);
3658 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3659
3660 // This keeps claiming and applying the closure to completed buffers
3661 // until we run out of buffers or we need to abort.
3662 while (!has_aborted() &&
3663 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
3664 if (_cm->verbose_medium()) {
3665 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3666 }
3667 statsOnly( ++_satb_buffers_processed );
3668 regular_clock_call();
3669 }
3670
3671 _draining_satb_buffers = false;
3672
3673 assert(has_aborted() ||
3674 concurrent() ||
3675 satb_mq_set.completed_buffers_num() == 0, "invariant");
3676
3677 // again, this was a potentially expensive operation, decrease the
3678 // limits to get the regular clock call early
3679 decrease_limits();
3680 }
3681
3682 void CMTask::print_stats() {
3683 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3684 _worker_id, _calls);
3685 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3686 _elapsed_time_ms, _termination_time_ms);
3687 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3688 _step_times_ms.num(), _step_times_ms.avg(),
3689 _step_times_ms.sd());
3690 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3691 _step_times_ms.maximum(), _step_times_ms.sum());
3692
3693 #if _MARKING_STATS_
3694 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3695 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3696 _all_clock_intervals_ms.sd());
3697 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3698 _all_clock_intervals_ms.maximum(),
3699 _all_clock_intervals_ms.sum());
3700 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = " SIZE_FORMAT ", marking = " SIZE_FORMAT,
3701 _clock_due_to_scanning, _clock_due_to_marking);
3702 gclog_or_tty->print_cr(" Objects: scanned = " SIZE_FORMAT ", found on the bitmap = " SIZE_FORMAT,
3703 _objs_scanned, _objs_found_on_bitmap);
3704 gclog_or_tty->print_cr(" Local Queue: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3705 _local_pushes, _local_pops, _local_max_size);
3706 gclog_or_tty->print_cr(" Global Stack: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3707 _global_pushes, _global_pops, _global_max_size);
3708 gclog_or_tty->print_cr(" transfers to = " SIZE_FORMAT ", transfers from = " SIZE_FORMAT,
3709 _global_transfers_to,_global_transfers_from);
3710 gclog_or_tty->print_cr(" Regions: claimed = " SIZE_FORMAT, _regions_claimed);
3711 gclog_or_tty->print_cr(" SATB buffers: processed = " SIZE_FORMAT, _satb_buffers_processed);
3712 gclog_or_tty->print_cr(" Steals: attempts = " SIZE_FORMAT ", successes = " SIZE_FORMAT,
3713 _steal_attempts, _steals);
3714 gclog_or_tty->print_cr(" Aborted: " SIZE_FORMAT ", due to", _aborted);
3715 gclog_or_tty->print_cr(" overflow: " SIZE_FORMAT ", global abort: " SIZE_FORMAT ", yield: " SIZE_FORMAT,
3716 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3717 gclog_or_tty->print_cr(" time out: " SIZE_FORMAT ", SATB: " SIZE_FORMAT ", termination: " SIZE_FORMAT,
3718 _aborted_timed_out, _aborted_satb, _aborted_termination);
3719 #endif // _MARKING_STATS_
3720 }
3721
3722 bool ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) {
3723 return _task_queues->steal(worker_id, hash_seed, obj);
3724 }
3725
3726 /*****************************************************************************
3727
3728 The do_marking_step(time_target_ms, ...) method is the building
3729 block of the parallel marking framework. It can be called in parallel
3730 with other invocations of do_marking_step() on different tasks
3731 (but only one per task, obviously) and concurrently with the
3732 mutator threads, or during remark, hence it eliminates the need
3733 for two versions of the code. When called during remark, it will
3734 pick up from where the task left off during the concurrent marking
3735 phase. Interestingly, tasks are also claimable during evacuation
3736 pauses too, since do_marking_step() ensures that it aborts before
3737 it needs to yield.
3738
3739 The data structures that it uses to do marking work are the
3740 following:
3741
3742 (1) Marking Bitmap. If there are gray objects that appear only
3743 on the bitmap (this happens either when dealing with an overflow
3744 or when the initial marking phase has simply marked the roots
3745 and didn't push them on the stack), then tasks claim heap
3746 regions whose bitmap they then scan to find gray objects. A
3747 global finger indicates where the end of the last claimed region
3748 is. A local finger indicates how far into the region a task has
3749 scanned. The two fingers are used to determine how to gray an
3750 object (i.e. whether simply marking it is OK, as it will be
3751 visited by a task in the future, or whether it needs to be also
3752 pushed on a stack).
3753
3754 (2) Local Queue. The local queue of the task which is accessed
3755 reasonably efficiently by the task. Other tasks can steal from
3756 it when they run out of work. Throughout the marking phase, a
3757 task attempts to keep its local queue short but not totally
3758 empty, so that entries are available for stealing by other
3759 tasks. Only when there is no more work, a task will totally
3760 drain its local queue.
3761
3762 (3) Global Mark Stack. This handles local queue overflow. During
3763 marking only sets of entries are moved between it and the local
3764 queues, as access to it requires a mutex and more fine-grain
3765 interaction with it which might cause contention. If it
3766 overflows, then the marking phase should restart and iterate
3767 over the bitmap to identify gray objects. Throughout the marking
3768 phase, tasks attempt to keep the global mark stack at a small
3769 length but not totally empty, so that entries are available for
3770 popping by other tasks. Only when there is no more work, tasks
3771 will totally drain the global mark stack.
3772
3773 (4) SATB Buffer Queue. This is where completed SATB buffers are
3774 made available. Buffers are regularly removed from this queue
3775 and scanned for roots, so that the queue doesn't get too
3776 long. During remark, all completed buffers are processed, as
3777 well as the filled in parts of any uncompleted buffers.
3778
3779 The do_marking_step() method tries to abort when the time target
3780 has been reached. There are a few other cases when the
3781 do_marking_step() method also aborts:
3782
3783 (1) When the marking phase has been aborted (after a Full GC).
3784
3785 (2) When a global overflow (on the global stack) has been
3786 triggered. Before the task aborts, it will actually sync up with
3787 the other tasks to ensure that all the marking data structures
3788 (local queues, stacks, fingers etc.) are re-initialized so that
3789 when do_marking_step() completes, the marking phase can
3790 immediately restart.
3791
3792 (3) When enough completed SATB buffers are available. The
3793 do_marking_step() method only tries to drain SATB buffers right
3794 at the beginning. So, if enough buffers are available, the
3795 marking step aborts and the SATB buffers are processed at
3796 the beginning of the next invocation.
3797
3798 (4) To yield. when we have to yield then we abort and yield
3799 right at the end of do_marking_step(). This saves us from a lot
3800 of hassle as, by yielding we might allow a Full GC. If this
3801 happens then objects will be compacted underneath our feet, the
3802 heap might shrink, etc. We save checking for this by just
3803 aborting and doing the yield right at the end.
3804
3805 From the above it follows that the do_marking_step() method should
3806 be called in a loop (or, otherwise, regularly) until it completes.
3807
3808 If a marking step completes without its has_aborted() flag being
3809 true, it means it has completed the current marking phase (and
3810 also all other marking tasks have done so and have all synced up).
3811
3812 A method called regular_clock_call() is invoked "regularly" (in
3813 sub ms intervals) throughout marking. It is this clock method that
3814 checks all the abort conditions which were mentioned above and
3815 decides when the task should abort. A work-based scheme is used to
3816 trigger this clock method: when the number of object words the
3817 marking phase has scanned or the number of references the marking
3818 phase has visited reach a given limit. Additional invocations to
3819 the method clock have been planted in a few other strategic places
3820 too. The initial reason for the clock method was to avoid calling
3821 vtime too regularly, as it is quite expensive. So, once it was in
3822 place, it was natural to piggy-back all the other conditions on it
3823 too and not constantly check them throughout the code.
3824
3825 If do_termination is true then do_marking_step will enter its
3826 termination protocol.
3827
3828 The value of is_serial must be true when do_marking_step is being
3829 called serially (i.e. by the VMThread) and do_marking_step should
3830 skip any synchronization in the termination and overflow code.
3831 Examples include the serial remark code and the serial reference
3832 processing closures.
3833
3834 The value of is_serial must be false when do_marking_step is
3835 being called by any of the worker threads in a work gang.
3836 Examples include the concurrent marking code (CMMarkingTask),
3837 the MT remark code, and the MT reference processing closures.
3838
3839 *****************************************************************************/
3840
3841 void CMTask::do_marking_step(double time_target_ms,
3842 bool do_termination,
3843 bool is_serial) {
3844 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3845 assert(concurrent() == _cm->concurrent(), "they should be the same");
3846
3847 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3848 assert(_task_queues != NULL, "invariant");
3849 assert(_task_queue != NULL, "invariant");
3850 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3851
3852 assert(!_claimed,
3853 "only one thread should claim this task at any one time");
3854
3855 // OK, this doesn't safeguard again all possible scenarios, as it is
3856 // possible for two threads to set the _claimed flag at the same
3857 // time. But it is only for debugging purposes anyway and it will
3858 // catch most problems.
3859 _claimed = true;
3860
3861 _start_time_ms = os::elapsedVTime() * 1000.0;
3862 statsOnly( _interval_start_time_ms = _start_time_ms );
3863
3864 // If do_stealing is true then do_marking_step will attempt to
3865 // steal work from the other CMTasks. It only makes sense to
3866 // enable stealing when the termination protocol is enabled
3867 // and do_marking_step() is not being called serially.
3868 bool do_stealing = do_termination && !is_serial;
3869
3870 double diff_prediction_ms =
3871 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3872 _time_target_ms = time_target_ms - diff_prediction_ms;
3873
3874 // set up the variables that are used in the work-based scheme to
3875 // call the regular clock method
3876 _words_scanned = 0;
3877 _refs_reached = 0;
3878 recalculate_limits();
3879
3880 // clear all flags
3881 clear_has_aborted();
3882 _has_timed_out = false;
3883 _draining_satb_buffers = false;
3884
3885 ++_calls;
3886
3887 if (_cm->verbose_low()) {
3888 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
3889 "target = %1.2lfms >>>>>>>>>>",
3890 _worker_id, _calls, _time_target_ms);
3891 }
3892
3893 // Set up the bitmap and oop closures. Anything that uses them is
3894 // eventually called from this method, so it is OK to allocate these
3895 // statically.
3896 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3897 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
3898 set_cm_oop_closure(&cm_oop_closure);
3899
3900 if (_cm->has_overflown()) {
3901 // This can happen if the mark stack overflows during a GC pause
3902 // and this task, after a yield point, restarts. We have to abort
3903 // as we need to get into the overflow protocol which happens
3904 // right at the end of this task.
3905 set_has_aborted();
3906 }
3907
3908 // First drain any available SATB buffers. After this, we will not
3909 // look at SATB buffers before the next invocation of this method.
3910 // If enough completed SATB buffers are queued up, the regular clock
3911 // will abort this task so that it restarts.
3912 drain_satb_buffers();
3913 // ...then partially drain the local queue and the global stack
3914 drain_local_queue(true);
3915 drain_global_stack(true);
3916
3917 do {
3918 if (!has_aborted() && _curr_region != NULL) {
3919 // This means that we're already holding on to a region.
3920 assert(_finger != NULL, "if region is not NULL, then the finger "
3921 "should not be NULL either");
3922
3923 // We might have restarted this task after an evacuation pause
3924 // which might have evacuated the region we're holding on to
3925 // underneath our feet. Let's read its limit again to make sure
3926 // that we do not iterate over a region of the heap that
3927 // contains garbage (update_region_limit() will also move
3928 // _finger to the start of the region if it is found empty).
3929 update_region_limit();
3930 // We will start from _finger not from the start of the region,
3931 // as we might be restarting this task after aborting half-way
3932 // through scanning this region. In this case, _finger points to
3933 // the address where we last found a marked object. If this is a
3934 // fresh region, _finger points to start().
3935 MemRegion mr = MemRegion(_finger, _region_limit);
3936
3937 if (_cm->verbose_low()) {
3938 gclog_or_tty->print_cr("[%u] we're scanning part "
3939 "["PTR_FORMAT", "PTR_FORMAT") "
3940 "of region "HR_FORMAT,
3941 _worker_id, p2i(_finger), p2i(_region_limit),
3942 HR_FORMAT_PARAMS(_curr_region));
3943 }
3944
3945 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
3946 "humongous regions should go around loop once only");
3947
3948 // Some special cases:
3949 // If the memory region is empty, we can just give up the region.
3950 // If the current region is humongous then we only need to check
3951 // the bitmap for the bit associated with the start of the object,
3952 // scan the object if it's live, and give up the region.
3953 // Otherwise, let's iterate over the bitmap of the part of the region
3954 // that is left.
3955 // If the iteration is successful, give up the region.
3956 if (mr.is_empty()) {
3957 giveup_current_region();
3958 regular_clock_call();
3959 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
3960 if (_nextMarkBitMap->isMarked(mr.start())) {
3961 // The object is marked - apply the closure
3962 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
3963 bitmap_closure.do_bit(offset);
3964 }
3965 // Even if this task aborted while scanning the humongous object
3966 // we can (and should) give up the current region.
3967 giveup_current_region();
3968 regular_clock_call();
3969 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
3970 giveup_current_region();
3971 regular_clock_call();
3972 } else {
3973 assert(has_aborted(), "currently the only way to do so");
3974 // The only way to abort the bitmap iteration is to return
3975 // false from the do_bit() method. However, inside the
3976 // do_bit() method we move the _finger to point to the
3977 // object currently being looked at. So, if we bail out, we
3978 // have definitely set _finger to something non-null.
3979 assert(_finger != NULL, "invariant");
3980
3981 // Region iteration was actually aborted. So now _finger
3982 // points to the address of the object we last scanned. If we
3983 // leave it there, when we restart this task, we will rescan
3984 // the object. It is easy to avoid this. We move the finger by
3985 // enough to point to the next possible object header (the
3986 // bitmap knows by how much we need to move it as it knows its
3987 // granularity).
3988 assert(_finger < _region_limit, "invariant");
3989 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
3990 // Check if bitmap iteration was aborted while scanning the last object
3991 if (new_finger >= _region_limit) {
3992 giveup_current_region();
3993 } else {
3994 move_finger_to(new_finger);
3995 }
3996 }
3997 }
3998 // At this point we have either completed iterating over the
3999 // region we were holding on to, or we have aborted.
4000
4001 // We then partially drain the local queue and the global stack.
4002 // (Do we really need this?)
4003 drain_local_queue(true);
4004 drain_global_stack(true);
4005
4006 // Read the note on the claim_region() method on why it might
4007 // return NULL with potentially more regions available for
4008 // claiming and why we have to check out_of_regions() to determine
4009 // whether we're done or not.
4010 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
4011 // We are going to try to claim a new region. We should have
4012 // given up on the previous one.
4013 // Separated the asserts so that we know which one fires.
4014 assert(_curr_region == NULL, "invariant");
4015 assert(_finger == NULL, "invariant");
4016 assert(_region_limit == NULL, "invariant");
4017 if (_cm->verbose_low()) {
4018 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
4019 }
4020 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
4021 if (claimed_region != NULL) {
4022 // Yes, we managed to claim one
4023 statsOnly( ++_regions_claimed );
4024
4025 if (_cm->verbose_low()) {
4026 gclog_or_tty->print_cr("[%u] we successfully claimed "
4027 "region "PTR_FORMAT,
4028 _worker_id, p2i(claimed_region));
4029 }
4030
4031 setup_for_region(claimed_region);
4032 assert(_curr_region == claimed_region, "invariant");
4033 }
4034 // It is important to call the regular clock here. It might take
4035 // a while to claim a region if, for example, we hit a large
4036 // block of empty regions. So we need to call the regular clock
4037 // method once round the loop to make sure it's called
4038 // frequently enough.
4039 regular_clock_call();
4040 }
4041
4042 if (!has_aborted() && _curr_region == NULL) {
4043 assert(_cm->out_of_regions(),
4044 "at this point we should be out of regions");
4045 }
4046 } while ( _curr_region != NULL && !has_aborted());
4047
4048 if (!has_aborted()) {
4049 // We cannot check whether the global stack is empty, since other
4050 // tasks might be pushing objects to it concurrently.
4051 assert(_cm->out_of_regions(),
4052 "at this point we should be out of regions");
4053
4054 if (_cm->verbose_low()) {
4055 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
4056 }
4057
4058 // Try to reduce the number of available SATB buffers so that
4059 // remark has less work to do.
4060 drain_satb_buffers();
4061 }
4062
4063 // Since we've done everything else, we can now totally drain the
4064 // local queue and global stack.
4065 drain_local_queue(false);
4066 drain_global_stack(false);
4067
4068 // Attempt at work stealing from other task's queues.
4069 if (do_stealing && !has_aborted()) {
4070 // We have not aborted. This means that we have finished all that
4071 // we could. Let's try to do some stealing...
4072
4073 // We cannot check whether the global stack is empty, since other
4074 // tasks might be pushing objects to it concurrently.
4075 assert(_cm->out_of_regions() && _task_queue->size() == 0,
4076 "only way to reach here");
4077
4078 if (_cm->verbose_low()) {
4079 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
4080 }
4081
4082 while (!has_aborted()) {
4083 oop obj;
4084 statsOnly( ++_steal_attempts );
4085
4086 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
4087 if (_cm->verbose_medium()) {
4088 gclog_or_tty->print_cr("[%u] stolen "PTR_FORMAT" successfully",
4089 _worker_id, p2i((void*) obj));
4090 }
4091
4092 statsOnly( ++_steals );
4093
4094 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
4095 "any stolen object should be marked");
4096 scan_object(obj);
4097
4098 // And since we're towards the end, let's totally drain the
4099 // local queue and global stack.
4100 drain_local_queue(false);
4101 drain_global_stack(false);
4102 } else {
4103 break;
4104 }
4105 }
4106 }
4107
4108 // If we are about to wrap up and go into termination, check if we
4109 // should raise the overflow flag.
4110 if (do_termination && !has_aborted()) {
4111 if (_cm->force_overflow()->should_force()) {
4112 _cm->set_has_overflown();
4113 regular_clock_call();
4114 }
4115 }
4116
4117 // We still haven't aborted. Now, let's try to get into the
4118 // termination protocol.
4119 if (do_termination && !has_aborted()) {
4120 // We cannot check whether the global stack is empty, since other
4121 // tasks might be concurrently pushing objects on it.
4122 // Separated the asserts so that we know which one fires.
4123 assert(_cm->out_of_regions(), "only way to reach here");
4124 assert(_task_queue->size() == 0, "only way to reach here");
4125
4126 if (_cm->verbose_low()) {
4127 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4128 }
4129
4130 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4131
4132 // The CMTask class also extends the TerminatorTerminator class,
4133 // hence its should_exit_termination() method will also decide
4134 // whether to exit the termination protocol or not.
4135 bool finished = (is_serial ||
4136 _cm->terminator()->offer_termination(this));
4137 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4138 _termination_time_ms +=
4139 termination_end_time_ms - _termination_start_time_ms;
4140
4141 if (finished) {
4142 // We're all done.
4143
4144 if (_worker_id == 0) {
4145 // let's allow task 0 to do this
4146 if (concurrent()) {
4147 assert(_cm->concurrent_marking_in_progress(), "invariant");
4148 // we need to set this to false before the next
4149 // safepoint. This way we ensure that the marking phase
4150 // doesn't observe any more heap expansions.
4151 _cm->clear_concurrent_marking_in_progress();
4152 }
4153 }
4154
4155 // We can now guarantee that the global stack is empty, since
4156 // all other tasks have finished. We separated the guarantees so
4157 // that, if a condition is false, we can immediately find out
4158 // which one.
4159 guarantee(_cm->out_of_regions(), "only way to reach here");
4160 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4161 guarantee(_task_queue->size() == 0, "only way to reach here");
4162 guarantee(!_cm->has_overflown(), "only way to reach here");
4163 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4164
4165 if (_cm->verbose_low()) {
4166 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4167 }
4168 } else {
4169 // Apparently there's more work to do. Let's abort this task. It
4170 // will restart it and we can hopefully find more things to do.
4171
4172 if (_cm->verbose_low()) {
4173 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4174 _worker_id);
4175 }
4176
4177 set_has_aborted();
4178 statsOnly( ++_aborted_termination );
4179 }
4180 }
4181
4182 // Mainly for debugging purposes to make sure that a pointer to the
4183 // closure which was statically allocated in this frame doesn't
4184 // escape it by accident.
4185 set_cm_oop_closure(NULL);
4186 double end_time_ms = os::elapsedVTime() * 1000.0;
4187 double elapsed_time_ms = end_time_ms - _start_time_ms;
4188 // Update the step history.
4189 _step_times_ms.add(elapsed_time_ms);
4190
4191 if (has_aborted()) {
4192 // The task was aborted for some reason.
4193
4194 statsOnly( ++_aborted );
4195
4196 if (_has_timed_out) {
4197 double diff_ms = elapsed_time_ms - _time_target_ms;
4198 // Keep statistics of how well we did with respect to hitting
4199 // our target only if we actually timed out (if we aborted for
4200 // other reasons, then the results might get skewed).
4201 _marking_step_diffs_ms.add(diff_ms);
4202 }
4203
4204 if (_cm->has_overflown()) {
4205 // This is the interesting one. We aborted because a global
4206 // overflow was raised. This means we have to restart the
4207 // marking phase and start iterating over regions. However, in
4208 // order to do this we have to make sure that all tasks stop
4209 // what they are doing and re-initialize in a safe manner. We
4210 // will achieve this with the use of two barrier sync points.
4211
4212 if (_cm->verbose_low()) {
4213 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4214 }
4215
4216 if (!is_serial) {
4217 // We only need to enter the sync barrier if being called
4218 // from a parallel context
4219 _cm->enter_first_sync_barrier(_worker_id);
4220
4221 // When we exit this sync barrier we know that all tasks have
4222 // stopped doing marking work. So, it's now safe to
4223 // re-initialize our data structures. At the end of this method,
4224 // task 0 will clear the global data structures.
4225 }
4226
4227 statsOnly( ++_aborted_overflow );
4228
4229 // We clear the local state of this task...
4230 clear_region_fields();
4231
4232 if (!is_serial) {
4233 // ...and enter the second barrier.
4234 _cm->enter_second_sync_barrier(_worker_id);
4235 }
4236 // At this point, if we're during the concurrent phase of
4237 // marking, everything has been re-initialized and we're
4238 // ready to restart.
4239 }
4240
4241 if (_cm->verbose_low()) {
4242 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4243 "elapsed = %1.2lfms <<<<<<<<<<",
4244 _worker_id, _time_target_ms, elapsed_time_ms);
4245 if (_cm->has_aborted()) {
4246 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4247 _worker_id);
4248 }
4249 }
4250 } else {
4251 if (_cm->verbose_low()) {
4252 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4253 "elapsed = %1.2lfms <<<<<<<<<<",
4254 _worker_id, _time_target_ms, elapsed_time_ms);
4255 }
4256 }
4257
4258 _claimed = false;
4259 }
4260
4261 CMTask::CMTask(uint worker_id,
4262 ConcurrentMark* cm,
4263 size_t* marked_bytes,
4264 BitMap* card_bm,
4265 CMTaskQueue* task_queue,
4266 CMTaskQueueSet* task_queues)
4267 : _g1h(G1CollectedHeap::heap()),
4268 _worker_id(worker_id), _cm(cm),
4269 _claimed(false),
4270 _nextMarkBitMap(NULL), _hash_seed(17),
4271 _task_queue(task_queue),
4272 _task_queues(task_queues),
4273 _cm_oop_closure(NULL),
4274 _marked_bytes_array(marked_bytes),
4275 _card_bm(card_bm) {
4276 guarantee(task_queue != NULL, "invariant");
4277 guarantee(task_queues != NULL, "invariant");
4278
4279 statsOnly( _clock_due_to_scanning = 0;
4280 _clock_due_to_marking = 0 );
4281
4282 _marking_step_diffs_ms.add(0.5);
4283 }
4284
4285 // These are formatting macros that are used below to ensure
4286 // consistent formatting. The *_H_* versions are used to format the
4287 // header for a particular value and they should be kept consistent
4288 // with the corresponding macro. Also note that most of the macros add
4289 // the necessary white space (as a prefix) which makes them a bit
4290 // easier to compose.
4291
4292 // All the output lines are prefixed with this string to be able to
4293 // identify them easily in a large log file.
4294 #define G1PPRL_LINE_PREFIX "###"
4295
4296 #define G1PPRL_ADDR_BASE_FORMAT " "PTR_FORMAT"-"PTR_FORMAT
4297 #ifdef _LP64
4298 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4299 #else // _LP64
4300 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4301 #endif // _LP64
4302
4303 // For per-region info
4304 #define G1PPRL_TYPE_FORMAT " %-4s"
4305 #define G1PPRL_TYPE_H_FORMAT " %4s"
4306 #define G1PPRL_BYTE_FORMAT " "SIZE_FORMAT_W(9)
4307 #define G1PPRL_BYTE_H_FORMAT " %9s"
4308 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4309 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4310
4311 // For summary info
4312 #define G1PPRL_SUM_ADDR_FORMAT(tag) " "tag":"G1PPRL_ADDR_BASE_FORMAT
4313 #define G1PPRL_SUM_BYTE_FORMAT(tag) " "tag": "SIZE_FORMAT
4314 #define G1PPRL_SUM_MB_FORMAT(tag) " "tag": %1.2f MB"
4315 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag)" / %1.2f %%"
4316
4317 G1PrintRegionLivenessInfoClosure::
4318 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4319 : _out(out),
4320 _total_used_bytes(0), _total_capacity_bytes(0),
4321 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4322 _hum_used_bytes(0), _hum_capacity_bytes(0),
4323 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4324 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4325 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4326 MemRegion g1_reserved = g1h->g1_reserved();
4327 double now = os::elapsedTime();
4328
4329 // Print the header of the output.
4330 _out->cr();
4331 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4332 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4333 G1PPRL_SUM_ADDR_FORMAT("reserved")
4334 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4335 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
4336 HeapRegion::GrainBytes);
4337 _out->print_cr(G1PPRL_LINE_PREFIX);
4338 _out->print_cr(G1PPRL_LINE_PREFIX
4339 G1PPRL_TYPE_H_FORMAT
4340 G1PPRL_ADDR_BASE_H_FORMAT
4341 G1PPRL_BYTE_H_FORMAT
4342 G1PPRL_BYTE_H_FORMAT
4343 G1PPRL_BYTE_H_FORMAT
4344 G1PPRL_DOUBLE_H_FORMAT
4345 G1PPRL_BYTE_H_FORMAT
4346 G1PPRL_BYTE_H_FORMAT,
4347 "type", "address-range",
4348 "used", "prev-live", "next-live", "gc-eff",
4349 "remset", "code-roots");
4350 _out->print_cr(G1PPRL_LINE_PREFIX
4351 G1PPRL_TYPE_H_FORMAT
4352 G1PPRL_ADDR_BASE_H_FORMAT
4353 G1PPRL_BYTE_H_FORMAT
4354 G1PPRL_BYTE_H_FORMAT
4355 G1PPRL_BYTE_H_FORMAT
4356 G1PPRL_DOUBLE_H_FORMAT
4357 G1PPRL_BYTE_H_FORMAT
4358 G1PPRL_BYTE_H_FORMAT,
4359 "", "",
4360 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4361 "(bytes)", "(bytes)");
4362 }
4363
4364 // It takes as a parameter a reference to one of the _hum_* fields, it
4365 // deduces the corresponding value for a region in a humongous region
4366 // series (either the region size, or what's left if the _hum_* field
4367 // is < the region size), and updates the _hum_* field accordingly.
4368 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4369 size_t bytes = 0;
4370 // The > 0 check is to deal with the prev and next live bytes which
4371 // could be 0.
4372 if (*hum_bytes > 0) {
4373 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4374 *hum_bytes -= bytes;
4375 }
4376 return bytes;
4377 }
4378
4379 // It deduces the values for a region in a humongous region series
4380 // from the _hum_* fields and updates those accordingly. It assumes
4381 // that that _hum_* fields have already been set up from the "starts
4382 // humongous" region and we visit the regions in address order.
4383 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4384 size_t* capacity_bytes,
4385 size_t* prev_live_bytes,
4386 size_t* next_live_bytes) {
4387 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4388 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4389 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4390 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4391 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4392 }
4393
4394 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4395 const char* type = r->get_type_str();
4396 HeapWord* bottom = r->bottom();
4397 HeapWord* end = r->end();
4398 size_t capacity_bytes = r->capacity();
4399 size_t used_bytes = r->used();
4400 size_t prev_live_bytes = r->live_bytes();
4401 size_t next_live_bytes = r->next_live_bytes();
4402 double gc_eff = r->gc_efficiency();
4403 size_t remset_bytes = r->rem_set()->mem_size();
4404 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4405
4406 if (r->is_starts_humongous()) {
4407 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4408 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4409 "they should have been zeroed after the last time we used them");
4410 // Set up the _hum_* fields.
4411 _hum_capacity_bytes = capacity_bytes;
4412 _hum_used_bytes = used_bytes;
4413 _hum_prev_live_bytes = prev_live_bytes;
4414 _hum_next_live_bytes = next_live_bytes;
4415 get_hum_bytes(&used_bytes, &capacity_bytes,
4416 &prev_live_bytes, &next_live_bytes);
4417 end = bottom + HeapRegion::GrainWords;
4418 } else if (r->is_continues_humongous()) {
4419 get_hum_bytes(&used_bytes, &capacity_bytes,
4420 &prev_live_bytes, &next_live_bytes);
4421 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4422 }
4423
4424 _total_used_bytes += used_bytes;
4425 _total_capacity_bytes += capacity_bytes;
4426 _total_prev_live_bytes += prev_live_bytes;
4427 _total_next_live_bytes += next_live_bytes;
4428 _total_remset_bytes += remset_bytes;
4429 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4430
4431 // Print a line for this particular region.
4432 _out->print_cr(G1PPRL_LINE_PREFIX
4433 G1PPRL_TYPE_FORMAT
4434 G1PPRL_ADDR_BASE_FORMAT
4435 G1PPRL_BYTE_FORMAT
4436 G1PPRL_BYTE_FORMAT
4437 G1PPRL_BYTE_FORMAT
4438 G1PPRL_DOUBLE_FORMAT
4439 G1PPRL_BYTE_FORMAT
4440 G1PPRL_BYTE_FORMAT,
4441 type, p2i(bottom), p2i(end),
4442 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4443 remset_bytes, strong_code_roots_bytes);
4444
4445 return false;
4446 }
4447
4448 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4449 // add static memory usages to remembered set sizes
4450 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4451 // Print the footer of the output.
4452 _out->print_cr(G1PPRL_LINE_PREFIX);
4453 _out->print_cr(G1PPRL_LINE_PREFIX
4454 " SUMMARY"
4455 G1PPRL_SUM_MB_FORMAT("capacity")
4456 G1PPRL_SUM_MB_PERC_FORMAT("used")
4457 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4458 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4459 G1PPRL_SUM_MB_FORMAT("remset")
4460 G1PPRL_SUM_MB_FORMAT("code-roots"),
4461 bytes_to_mb(_total_capacity_bytes),
4462 bytes_to_mb(_total_used_bytes),
4463 perc(_total_used_bytes, _total_capacity_bytes),
4464 bytes_to_mb(_total_prev_live_bytes),
4465 perc(_total_prev_live_bytes, _total_capacity_bytes),
4466 bytes_to_mb(_total_next_live_bytes),
4467 perc(_total_next_live_bytes, _total_capacity_bytes),
4468 bytes_to_mb(_total_remset_bytes),
4469 bytes_to_mb(_total_strong_code_roots_bytes));
4470 _out->cr();
4471 }