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/g1CollectorState.hpp"
34 #include "gc/g1/g1ErgoVerbose.hpp"
35 #include "gc/g1/g1Log.hpp"
36 #include "gc/g1/g1OopClosures.inline.hpp"
37 #include "gc/g1/g1RemSet.hpp"
38 #include "gc/g1/g1StringDedup.hpp"
39 #include "gc/g1/heapRegion.inline.hpp"
40 #include "gc/g1/heapRegionManager.inline.hpp"
41 #include "gc/g1/heapRegionRemSet.hpp"
42 #include "gc/g1/heapRegionSet.inline.hpp"
43 #include "gc/g1/suspendibleThreadSet.hpp"
44 #include "gc/shared/gcId.hpp"
45 #include "gc/shared/gcTimer.hpp"
46 #include "gc/shared/gcTrace.hpp"
47 #include "gc/shared/gcTraceTime.hpp"
48 #include "gc/shared/genOopClosures.inline.hpp"
49 #include "gc/shared/referencePolicy.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/taskqueue.inline.hpp"
52 #include "gc/shared/vmGCOperations.hpp"
53 #include "memory/allocation.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "runtime/atomic.inline.hpp"
57 #include "runtime/handles.inline.hpp"
58 #include "runtime/java.hpp"
59 #include "runtime/prefetch.inline.hpp"
60 #include "services/memTracker.hpp"
61
62 // Concurrent marking bit map wrapper
63
64 CMBitMapRO::CMBitMapRO(int shifter) :
65 _bm(),
66 _shifter(shifter) {
67 _bmStartWord = 0;
68 _bmWordSize = 0;
69 }
70
71 HeapWord* CMBitMapRO::getNextMarkedWordAddress(const HeapWord* addr,
72 const HeapWord* limit) const {
73 // First we must round addr *up* to a possible object boundary.
74 addr = (HeapWord*)align_size_up((intptr_t)addr,
75 HeapWordSize << _shifter);
76 size_t addrOffset = heapWordToOffset(addr);
77 if (limit == NULL) {
78 limit = _bmStartWord + _bmWordSize;
79 }
80 size_t limitOffset = heapWordToOffset(limit);
81 size_t nextOffset = _bm.get_next_one_offset(addrOffset, limitOffset);
82 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
83 assert(nextAddr >= addr, "get_next_one postcondition");
84 assert(nextAddr == limit || isMarked(nextAddr),
85 "get_next_one postcondition");
86 return nextAddr;
87 }
88
89 HeapWord* CMBitMapRO::getNextUnmarkedWordAddress(const HeapWord* addr,
90 const HeapWord* limit) const {
91 size_t addrOffset = heapWordToOffset(addr);
92 if (limit == NULL) {
93 limit = _bmStartWord + _bmWordSize;
94 }
95 size_t limitOffset = heapWordToOffset(limit);
96 size_t nextOffset = _bm.get_next_zero_offset(addrOffset, limitOffset);
97 HeapWord* nextAddr = offsetToHeapWord(nextOffset);
98 assert(nextAddr >= addr, "get_next_one postcondition");
99 assert(nextAddr == limit || !isMarked(nextAddr),
100 "get_next_one postcondition");
101 return nextAddr;
102 }
103
104 int CMBitMapRO::heapWordDiffToOffsetDiff(size_t diff) const {
105 assert((diff & ((1 << _shifter) - 1)) == 0, "argument check");
106 return (int) (diff >> _shifter);
107 }
108
109 #ifndef PRODUCT
110 bool CMBitMapRO::covers(MemRegion heap_rs) const {
111 // assert(_bm.map() == _virtual_space.low(), "map inconsistency");
112 assert(((size_t)_bm.size() * ((size_t)1 << _shifter)) == _bmWordSize,
113 "size inconsistency");
114 return _bmStartWord == (HeapWord*)(heap_rs.start()) &&
115 _bmWordSize == heap_rs.word_size();
116 }
117 #endif
118
119 void CMBitMapRO::print_on_error(outputStream* st, const char* prefix) const {
120 _bm.print_on_error(st, prefix);
121 }
122
123 size_t CMBitMap::compute_size(size_t heap_size) {
124 return ReservedSpace::allocation_align_size_up(heap_size / mark_distance());
125 }
126
127 size_t CMBitMap::mark_distance() {
128 return MinObjAlignmentInBytes * BitsPerByte;
129 }
130
131 void CMBitMap::initialize(MemRegion heap, G1RegionToSpaceMapper* storage) {
132 _bmStartWord = heap.start();
133 _bmWordSize = heap.word_size();
134
135 _bm.set_map((BitMap::bm_word_t*) storage->reserved().start());
136 _bm.set_size(_bmWordSize >> _shifter);
137
138 storage->set_mapping_changed_listener(&_listener);
139 }
140
141 void CMBitMapMappingChangedListener::on_commit(uint start_region, size_t num_regions, bool zero_filled) {
142 if (zero_filled) {
143 return;
144 }
145 // We need to clear the bitmap on commit, removing any existing information.
146 MemRegion mr(G1CollectedHeap::heap()->bottom_addr_for_region(start_region), num_regions * HeapRegion::GrainWords);
147 _bm->clearRange(mr);
148 }
149
150 // Closure used for clearing the given mark bitmap.
151 class ClearBitmapHRClosure : public HeapRegionClosure {
152 private:
153 ConcurrentMark* _cm;
154 CMBitMap* _bitmap;
155 bool _may_yield; // The closure may yield during iteration. If yielded, abort the iteration.
156 public:
157 ClearBitmapHRClosure(ConcurrentMark* cm, CMBitMap* bitmap, bool may_yield) : HeapRegionClosure(), _cm(cm), _bitmap(bitmap), _may_yield(may_yield) {
158 assert(!may_yield || cm != NULL, "CM must be non-NULL if this closure is expected to yield.");
159 }
160
161 virtual bool doHeapRegion(HeapRegion* r) {
162 size_t const chunk_size_in_words = M / HeapWordSize;
163
164 HeapWord* cur = r->bottom();
165 HeapWord* const end = r->end();
166
167 while (cur < end) {
168 MemRegion mr(cur, MIN2(cur + chunk_size_in_words, end));
169 _bitmap->clearRange(mr);
170
171 cur += chunk_size_in_words;
172
173 // Abort iteration if after yielding the marking has been aborted.
174 if (_may_yield && _cm->do_yield_check() && _cm->has_aborted()) {
175 return true;
176 }
177 // Repeat the asserts from before the start of the closure. We will do them
178 // as asserts here to minimize their overhead on the product. However, we
179 // will have them as guarantees at the beginning / end of the bitmap
180 // clearing to get some checking in the product.
181 assert(!_may_yield || _cm->cmThread()->during_cycle(), "invariant");
182 assert(!_may_yield || !G1CollectedHeap::heap()->collector_state()->mark_in_progress(), "invariant");
183 }
184
185 return false;
186 }
187 };
188
189 class ParClearNextMarkBitmapTask : public AbstractGangTask {
190 ClearBitmapHRClosure* _cl;
191 HeapRegionClaimer _hrclaimer;
192 bool _suspendible; // If the task is suspendible, workers must join the STS.
193
194 public:
195 ParClearNextMarkBitmapTask(ClearBitmapHRClosure *cl, uint n_workers, bool suspendible) :
196 _cl(cl), _suspendible(suspendible), AbstractGangTask("Parallel Clear Bitmap Task"), _hrclaimer(n_workers) {}
197
198 void work(uint worker_id) {
199 SuspendibleThreadSetJoiner sts_join(_suspendible);
200 G1CollectedHeap::heap()->heap_region_par_iterate(_cl, worker_id, &_hrclaimer, true);
201 }
202 };
203
204 void CMBitMap::clearAll() {
205 G1CollectedHeap* g1h = G1CollectedHeap::heap();
206 ClearBitmapHRClosure cl(NULL, this, false /* may_yield */);
207 uint n_workers = g1h->workers()->active_workers();
208 ParClearNextMarkBitmapTask task(&cl, n_workers, false);
209 g1h->workers()->run_task(&task);
210 guarantee(cl.complete(), "Must have completed iteration.");
211 return;
212 }
213
214 void CMBitMap::markRange(MemRegion mr) {
215 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
216 assert(!mr.is_empty(), "unexpected empty region");
217 assert((offsetToHeapWord(heapWordToOffset(mr.end())) ==
218 ((HeapWord *) mr.end())),
219 "markRange memory region end is not card aligned");
220 // convert address range into offset range
221 _bm.at_put_range(heapWordToOffset(mr.start()),
222 heapWordToOffset(mr.end()), true);
223 }
224
225 void CMBitMap::clearRange(MemRegion mr) {
226 mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
227 assert(!mr.is_empty(), "unexpected empty region");
228 // convert address range into offset range
229 _bm.at_put_range(heapWordToOffset(mr.start()),
230 heapWordToOffset(mr.end()), false);
231 }
232
233 MemRegion CMBitMap::getAndClearMarkedRegion(HeapWord* addr,
234 HeapWord* end_addr) {
235 HeapWord* start = getNextMarkedWordAddress(addr);
236 start = MIN2(start, end_addr);
237 HeapWord* end = getNextUnmarkedWordAddress(start);
238 end = MIN2(end, end_addr);
239 assert(start <= end, "Consistency check");
240 MemRegion mr(start, end);
241 if (!mr.is_empty()) {
242 clearRange(mr);
243 }
244 return mr;
245 }
246
247 CMMarkStack::CMMarkStack(ConcurrentMark* cm) :
248 _base(NULL), _cm(cm)
249 #ifdef ASSERT
250 , _drain_in_progress(false)
251 , _drain_in_progress_yields(false)
252 #endif
253 {}
254
255 bool CMMarkStack::allocate(size_t capacity) {
256 // allocate a stack of the requisite depth
257 ReservedSpace rs(ReservedSpace::allocation_align_size_up(capacity * sizeof(oop)));
258 if (!rs.is_reserved()) {
259 warning("ConcurrentMark MarkStack allocation failure");
260 return false;
261 }
262 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
263 if (!_virtual_space.initialize(rs, rs.size())) {
264 warning("ConcurrentMark MarkStack backing store failure");
265 // Release the virtual memory reserved for the marking stack
266 rs.release();
267 return false;
268 }
269 assert(_virtual_space.committed_size() == rs.size(),
270 "Didn't reserve backing store for all of ConcurrentMark stack?");
271 _base = (oop*) _virtual_space.low();
272 setEmpty();
273 _capacity = (jint) capacity;
274 _saved_index = -1;
275 _should_expand = false;
276 return true;
277 }
278
279 void CMMarkStack::expand() {
280 // Called, during remark, if we've overflown the marking stack during marking.
281 assert(isEmpty(), "stack should been emptied while handling overflow");
282 assert(_capacity <= (jint) MarkStackSizeMax, "stack bigger than permitted");
283 // Clear expansion flag
284 _should_expand = false;
285 if (_capacity == (jint) MarkStackSizeMax) {
286 if (PrintGCDetails && Verbose) {
287 gclog_or_tty->print_cr(" (benign) Can't expand marking stack capacity, at max size limit");
288 }
289 return;
290 }
291 // Double capacity if possible
292 jint new_capacity = MIN2(_capacity*2, (jint) MarkStackSizeMax);
293 // Do not give up existing stack until we have managed to
294 // get the double capacity that we desired.
295 ReservedSpace rs(ReservedSpace::allocation_align_size_up(new_capacity *
296 sizeof(oop)));
297 if (rs.is_reserved()) {
298 // Release the backing store associated with old stack
299 _virtual_space.release();
300 // Reinitialize virtual space for new stack
301 if (!_virtual_space.initialize(rs, rs.size())) {
302 fatal("Not enough swap for expanded marking stack capacity");
303 }
304 _base = (oop*)(_virtual_space.low());
305 _index = 0;
306 _capacity = new_capacity;
307 } else {
308 if (PrintGCDetails && Verbose) {
309 // Failed to double capacity, continue;
310 gclog_or_tty->print(" (benign) Failed to expand marking stack capacity from "
311 SIZE_FORMAT "K to " SIZE_FORMAT "K",
312 _capacity / K, new_capacity / K);
313 }
314 }
315 }
316
317 void CMMarkStack::set_should_expand() {
318 // If we're resetting the marking state because of an
319 // marking stack overflow, record that we should, if
320 // possible, expand the stack.
321 _should_expand = _cm->has_overflown();
322 }
323
324 CMMarkStack::~CMMarkStack() {
325 if (_base != NULL) {
326 _base = NULL;
327 _virtual_space.release();
328 }
329 }
330
331 void CMMarkStack::par_push_arr(oop* ptr_arr, int n) {
332 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
333 jint start = _index;
334 jint next_index = start + n;
335 if (next_index > _capacity) {
336 _overflow = true;
337 return;
338 }
339 // Otherwise.
340 _index = next_index;
341 for (int i = 0; i < n; i++) {
342 int ind = start + i;
343 assert(ind < _capacity, "By overflow test above.");
344 _base[ind] = ptr_arr[i];
345 }
346 }
347
348 bool CMMarkStack::par_pop_arr(oop* ptr_arr, int max, int* n) {
349 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
350 jint index = _index;
351 if (index == 0) {
352 *n = 0;
353 return false;
354 } else {
355 int k = MIN2(max, index);
356 jint new_ind = index - k;
357 for (int j = 0; j < k; j++) {
358 ptr_arr[j] = _base[new_ind + j];
359 }
360 _index = new_ind;
361 *n = k;
362 return true;
363 }
364 }
365
366 template<class OopClosureClass>
367 bool CMMarkStack::drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after) {
368 assert(!_drain_in_progress || !_drain_in_progress_yields || yield_after
369 || SafepointSynchronize::is_at_safepoint(),
370 "Drain recursion must be yield-safe.");
371 bool res = true;
372 debug_only(_drain_in_progress = true);
373 debug_only(_drain_in_progress_yields = yield_after);
374 while (!isEmpty()) {
375 oop newOop = pop();
376 assert(G1CollectedHeap::heap()->is_in_reserved(newOop), "Bad pop");
377 assert(newOop->is_oop(), "Expected an oop");
378 assert(bm == NULL || bm->isMarked((HeapWord*)newOop),
379 "only grey objects on this stack");
380 newOop->oop_iterate(cl);
381 if (yield_after && _cm->do_yield_check()) {
382 res = false;
383 break;
384 }
385 }
386 debug_only(_drain_in_progress = false);
387 return res;
388 }
389
390 void CMMarkStack::note_start_of_gc() {
391 assert(_saved_index == -1,
392 "note_start_of_gc()/end_of_gc() bracketed incorrectly");
393 _saved_index = _index;
394 }
395
396 void CMMarkStack::note_end_of_gc() {
397 // This is intentionally a guarantee, instead of an assert. If we
398 // accidentally add something to the mark stack during GC, it
399 // will be a correctness issue so it's better if we crash. we'll
400 // only check this once per GC anyway, so it won't be a performance
401 // issue in any way.
402 guarantee(_saved_index == _index,
403 err_msg("saved index: %d index: %d", _saved_index, _index));
404 _saved_index = -1;
405 }
406
407 CMRootRegions::CMRootRegions() :
408 _young_list(NULL), _cm(NULL), _scan_in_progress(false),
409 _should_abort(false), _next_survivor(NULL) { }
410
411 void CMRootRegions::init(G1CollectedHeap* g1h, ConcurrentMark* cm) {
412 _young_list = g1h->young_list();
413 _cm = cm;
414 }
415
416 void CMRootRegions::prepare_for_scan() {
417 assert(!scan_in_progress(), "pre-condition");
418
419 // Currently, only survivors can be root regions.
420 assert(_next_survivor == NULL, "pre-condition");
421 _next_survivor = _young_list->first_survivor_region();
422 _scan_in_progress = (_next_survivor != NULL);
423 _should_abort = false;
424 }
425
426 HeapRegion* CMRootRegions::claim_next() {
427 if (_should_abort) {
428 // If someone has set the should_abort flag, we return NULL to
429 // force the caller to bail out of their loop.
430 return NULL;
431 }
432
433 // Currently, only survivors can be root regions.
434 HeapRegion* res = _next_survivor;
435 if (res != NULL) {
436 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
437 // Read it again in case it changed while we were waiting for the lock.
438 res = _next_survivor;
439 if (res != NULL) {
440 if (res == _young_list->last_survivor_region()) {
441 // We just claimed the last survivor so store NULL to indicate
442 // that we're done.
443 _next_survivor = NULL;
444 } else {
445 _next_survivor = res->get_next_young_region();
446 }
447 } else {
448 // Someone else claimed the last survivor while we were trying
449 // to take the lock so nothing else to do.
450 }
451 }
452 assert(res == NULL || res->is_survivor(), "post-condition");
453
454 return res;
455 }
456
457 void CMRootRegions::scan_finished() {
458 assert(scan_in_progress(), "pre-condition");
459
460 // Currently, only survivors can be root regions.
461 if (!_should_abort) {
462 assert(_next_survivor == NULL, "we should have claimed all survivors");
463 }
464 _next_survivor = NULL;
465
466 {
467 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
468 _scan_in_progress = false;
469 RootRegionScan_lock->notify_all();
470 }
471 }
472
473 bool CMRootRegions::wait_until_scan_finished() {
474 if (!scan_in_progress()) return false;
475
476 {
477 MutexLockerEx x(RootRegionScan_lock, Mutex::_no_safepoint_check_flag);
478 while (scan_in_progress()) {
479 RootRegionScan_lock->wait(Mutex::_no_safepoint_check_flag);
480 }
481 }
482 return true;
483 }
484
485 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
486 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
487 #endif // _MSC_VER
488
489 uint ConcurrentMark::scale_parallel_threads(uint n_par_threads) {
490 return MAX2((n_par_threads + 2) / 4, 1U);
491 }
492
493 ConcurrentMark::ConcurrentMark(G1CollectedHeap* g1h, G1RegionToSpaceMapper* prev_bitmap_storage, G1RegionToSpaceMapper* next_bitmap_storage) :
494 _g1h(g1h),
495 _markBitMap1(),
496 _markBitMap2(),
497 _parallel_marking_threads(0),
498 _max_parallel_marking_threads(0),
499 _sleep_factor(0.0),
500 _marking_task_overhead(1.0),
501 _cleanup_sleep_factor(0.0),
502 _cleanup_task_overhead(1.0),
503 _cleanup_list("Cleanup List"),
504 _region_bm((BitMap::idx_t)(g1h->max_regions()), false /* in_resource_area*/),
505 _card_bm((g1h->reserved_region().byte_size() + CardTableModRefBS::card_size - 1) >>
506 CardTableModRefBS::card_shift,
507 false /* in_resource_area*/),
508
509 _prevMarkBitMap(&_markBitMap1),
510 _nextMarkBitMap(&_markBitMap2),
511
512 _markStack(this),
513 // _finger set in set_non_marking_state
514
515 _max_worker_id(ParallelGCThreads),
516 // _active_tasks set in set_non_marking_state
517 // _tasks set inside the constructor
518 _task_queues(new CMTaskQueueSet((int) _max_worker_id)),
519 _terminator(ParallelTaskTerminator((int) _max_worker_id, _task_queues)),
520
521 _has_overflown(false),
522 _concurrent(false),
523 _has_aborted(false),
524 _restart_for_overflow(false),
525 _concurrent_marking_in_progress(false),
526
527 // _verbose_level set below
528
529 _init_times(),
530 _remark_times(), _remark_mark_times(), _remark_weak_ref_times(),
531 _cleanup_times(),
532 _total_counting_time(0.0),
533 _total_rs_scrub_time(0.0),
534
535 _parallel_workers(NULL),
536
537 _count_card_bitmaps(NULL),
538 _count_marked_bytes(NULL),
539 _completed_initialization(false) {
540 CMVerboseLevel verbose_level = (CMVerboseLevel) G1MarkingVerboseLevel;
541 if (verbose_level < no_verbose) {
542 verbose_level = no_verbose;
543 }
544 if (verbose_level > high_verbose) {
545 verbose_level = high_verbose;
546 }
547 _verbose_level = verbose_level;
548
549 if (verbose_low()) {
550 gclog_or_tty->print_cr("[global] init, heap start = " PTR_FORMAT ", "
551 "heap end = " PTR_FORMAT, p2i(_heap_start), p2i(_heap_end));
552 }
553
554 _markBitMap1.initialize(g1h->reserved_region(), prev_bitmap_storage);
555 _markBitMap2.initialize(g1h->reserved_region(), next_bitmap_storage);
556
557 // Create & start a ConcurrentMark thread.
558 _cmThread = new ConcurrentMarkThread(this);
559 assert(cmThread() != NULL, "CM Thread should have been created");
560 assert(cmThread()->cm() != NULL, "CM Thread should refer to this cm");
561 if (_cmThread->osthread() == NULL) {
562 vm_shutdown_during_initialization("Could not create ConcurrentMarkThread");
563 }
564
565 assert(CGC_lock != NULL, "Where's the CGC_lock?");
566 assert(_markBitMap1.covers(g1h->reserved_region()), "_markBitMap1 inconsistency");
567 assert(_markBitMap2.covers(g1h->reserved_region()), "_markBitMap2 inconsistency");
568
569 SATBMarkQueueSet& satb_qs = JavaThread::satb_mark_queue_set();
570 satb_qs.set_buffer_size(G1SATBBufferSize);
571
572 _root_regions.init(_g1h, this);
573
574 if (ConcGCThreads > ParallelGCThreads) {
575 warning("Can't have more ConcGCThreads (%u) "
576 "than ParallelGCThreads (%u).",
577 ConcGCThreads, ParallelGCThreads);
578 return;
579 }
580 if (!FLAG_IS_DEFAULT(ConcGCThreads) && ConcGCThreads > 0) {
581 // Note: ConcGCThreads has precedence over G1MarkingOverheadPercent
582 // if both are set
583 _sleep_factor = 0.0;
584 _marking_task_overhead = 1.0;
585 } else if (G1MarkingOverheadPercent > 0) {
586 // We will calculate the number of parallel marking threads based
587 // on a target overhead with respect to the soft real-time goal
588 double marking_overhead = (double) G1MarkingOverheadPercent / 100.0;
589 double overall_cm_overhead =
590 (double) MaxGCPauseMillis * marking_overhead /
591 (double) GCPauseIntervalMillis;
592 double cpu_ratio = 1.0 / (double) os::processor_count();
593 double marking_thread_num = ceil(overall_cm_overhead / cpu_ratio);
594 double marking_task_overhead =
595 overall_cm_overhead / marking_thread_num *
596 (double) os::processor_count();
597 double sleep_factor =
598 (1.0 - marking_task_overhead) / marking_task_overhead;
599
600 FLAG_SET_ERGO(uint, ConcGCThreads, (uint) marking_thread_num);
601 _sleep_factor = sleep_factor;
602 _marking_task_overhead = marking_task_overhead;
603 } else {
604 // Calculate the number of parallel marking threads by scaling
605 // the number of parallel GC threads.
606 uint marking_thread_num = scale_parallel_threads(ParallelGCThreads);
607 FLAG_SET_ERGO(uint, ConcGCThreads, marking_thread_num);
608 _sleep_factor = 0.0;
609 _marking_task_overhead = 1.0;
610 }
611
612 assert(ConcGCThreads > 0, "Should have been set");
613 _parallel_marking_threads = ConcGCThreads;
614 _max_parallel_marking_threads = _parallel_marking_threads;
615
616 if (parallel_marking_threads() > 1) {
617 _cleanup_task_overhead = 1.0;
618 } else {
619 _cleanup_task_overhead = marking_task_overhead();
620 }
621 _cleanup_sleep_factor =
622 (1.0 - cleanup_task_overhead()) / cleanup_task_overhead();
623
624 #if 0
625 gclog_or_tty->print_cr("Marking Threads %d", parallel_marking_threads());
626 gclog_or_tty->print_cr("CM Marking Task Overhead %1.4lf", marking_task_overhead());
627 gclog_or_tty->print_cr("CM Sleep Factor %1.4lf", sleep_factor());
628 gclog_or_tty->print_cr("CL Marking Task Overhead %1.4lf", cleanup_task_overhead());
629 gclog_or_tty->print_cr("CL Sleep Factor %1.4lf", cleanup_sleep_factor());
630 #endif
631
632 _parallel_workers = new WorkGang("G1 Marker",
633 _max_parallel_marking_threads, false, true);
634 if (_parallel_workers == NULL) {
635 vm_exit_during_initialization("Failed necessary allocation.");
636 } else {
637 _parallel_workers->initialize_workers();
638 }
639
640 if (FLAG_IS_DEFAULT(MarkStackSize)) {
641 size_t mark_stack_size =
642 MIN2(MarkStackSizeMax,
643 MAX2(MarkStackSize, (size_t) (parallel_marking_threads() * TASKQUEUE_SIZE)));
644 // Verify that the calculated value for MarkStackSize is in range.
645 // It would be nice to use the private utility routine from Arguments.
646 if (!(mark_stack_size >= 1 && mark_stack_size <= MarkStackSizeMax)) {
647 warning("Invalid value calculated for MarkStackSize (" SIZE_FORMAT "): "
648 "must be between 1 and " SIZE_FORMAT,
649 mark_stack_size, MarkStackSizeMax);
650 return;
651 }
652 FLAG_SET_ERGO(size_t, MarkStackSize, mark_stack_size);
653 } else {
654 // Verify MarkStackSize is in range.
655 if (FLAG_IS_CMDLINE(MarkStackSize)) {
656 if (FLAG_IS_DEFAULT(MarkStackSizeMax)) {
657 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
658 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT "): "
659 "must be between 1 and " SIZE_FORMAT,
660 MarkStackSize, MarkStackSizeMax);
661 return;
662 }
663 } else if (FLAG_IS_CMDLINE(MarkStackSizeMax)) {
664 if (!(MarkStackSize >= 1 && MarkStackSize <= MarkStackSizeMax)) {
665 warning("Invalid value specified for MarkStackSize (" SIZE_FORMAT ")"
666 " or for MarkStackSizeMax (" SIZE_FORMAT ")",
667 MarkStackSize, MarkStackSizeMax);
668 return;
669 }
670 }
671 }
672 }
673
674 if (!_markStack.allocate(MarkStackSize)) {
675 warning("Failed to allocate CM marking stack");
676 return;
677 }
678
679 _tasks = NEW_C_HEAP_ARRAY(CMTask*, _max_worker_id, mtGC);
680 _accum_task_vtime = NEW_C_HEAP_ARRAY(double, _max_worker_id, mtGC);
681
682 _count_card_bitmaps = NEW_C_HEAP_ARRAY(BitMap, _max_worker_id, mtGC);
683 _count_marked_bytes = NEW_C_HEAP_ARRAY(size_t*, _max_worker_id, mtGC);
684
685 BitMap::idx_t card_bm_size = _card_bm.size();
686
687 // so that the assertion in MarkingTaskQueue::task_queue doesn't fail
688 _active_tasks = _max_worker_id;
689
690 uint max_regions = _g1h->max_regions();
691 for (uint i = 0; i < _max_worker_id; ++i) {
692 CMTaskQueue* task_queue = new CMTaskQueue();
693 task_queue->initialize();
694 _task_queues->register_queue(i, task_queue);
695
696 _count_card_bitmaps[i] = BitMap(card_bm_size, false);
697 _count_marked_bytes[i] = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
698
699 _tasks[i] = new CMTask(i, this,
700 _count_marked_bytes[i],
701 &_count_card_bitmaps[i],
702 task_queue, _task_queues);
703
704 _accum_task_vtime[i] = 0.0;
705 }
706
707 // Calculate the card number for the bottom of the heap. Used
708 // in biasing indexes into the accounting card bitmaps.
709 _heap_bottom_card_num =
710 intptr_t(uintptr_t(_g1h->reserved_region().start()) >>
711 CardTableModRefBS::card_shift);
712
713 // Clear all the liveness counting data
714 clear_all_count_data();
715
716 // so that the call below can read a sensible value
717 _heap_start = g1h->reserved_region().start();
718 set_non_marking_state();
719 _completed_initialization = true;
720 }
721
722 void ConcurrentMark::reset() {
723 // Starting values for these two. This should be called in a STW
724 // phase.
725 MemRegion reserved = _g1h->g1_reserved();
726 _heap_start = reserved.start();
727 _heap_end = reserved.end();
728
729 // Separated the asserts so that we know which one fires.
730 assert(_heap_start != NULL, "heap bounds should look ok");
731 assert(_heap_end != NULL, "heap bounds should look ok");
732 assert(_heap_start < _heap_end, "heap bounds should look ok");
733
734 // Reset all the marking data structures and any necessary flags
735 reset_marking_state();
736
737 if (verbose_low()) {
738 gclog_or_tty->print_cr("[global] resetting");
739 }
740
741 // We do reset all of them, since different phases will use
742 // different number of active threads. So, it's easiest to have all
743 // of them ready.
744 for (uint i = 0; i < _max_worker_id; ++i) {
745 _tasks[i]->reset(_nextMarkBitMap);
746 }
747
748 // we need this to make sure that the flag is on during the evac
749 // pause with initial mark piggy-backed
750 set_concurrent_marking_in_progress();
751 }
752
753
754 void ConcurrentMark::reset_marking_state(bool clear_overflow) {
755 _markStack.set_should_expand();
756 _markStack.setEmpty(); // Also clears the _markStack overflow flag
757 if (clear_overflow) {
758 clear_has_overflown();
759 } else {
760 assert(has_overflown(), "pre-condition");
761 }
762 _finger = _heap_start;
763
764 for (uint i = 0; i < _max_worker_id; ++i) {
765 CMTaskQueue* queue = _task_queues->queue(i);
766 queue->set_empty();
767 }
768 }
769
770 void ConcurrentMark::set_concurrency(uint active_tasks) {
771 assert(active_tasks <= _max_worker_id, "we should not have more");
772
773 _active_tasks = active_tasks;
774 // Need to update the three data structures below according to the
775 // number of active threads for this phase.
776 _terminator = ParallelTaskTerminator((int) active_tasks, _task_queues);
777 _first_overflow_barrier_sync.set_n_workers((int) active_tasks);
778 _second_overflow_barrier_sync.set_n_workers((int) active_tasks);
779 }
780
781 void ConcurrentMark::set_concurrency_and_phase(uint active_tasks, bool concurrent) {
782 set_concurrency(active_tasks);
783
784 _concurrent = concurrent;
785 // We propagate this to all tasks, not just the active ones.
786 for (uint i = 0; i < _max_worker_id; ++i)
787 _tasks[i]->set_concurrent(concurrent);
788
789 if (concurrent) {
790 set_concurrent_marking_in_progress();
791 } else {
792 // We currently assume that the concurrent flag has been set to
793 // false before we start remark. At this point we should also be
794 // in a STW phase.
795 assert(!concurrent_marking_in_progress(), "invariant");
796 assert(out_of_regions(),
797 err_msg("only way to get here: _finger: " PTR_FORMAT ", _heap_end: " PTR_FORMAT,
798 p2i(_finger), p2i(_heap_end)));
799 }
800 }
801
802 void ConcurrentMark::set_non_marking_state() {
803 // We set the global marking state to some default values when we're
804 // not doing marking.
805 reset_marking_state();
806 _active_tasks = 0;
807 clear_concurrent_marking_in_progress();
808 }
809
810 ConcurrentMark::~ConcurrentMark() {
811 // The ConcurrentMark instance is never freed.
812 ShouldNotReachHere();
813 }
814
815 void ConcurrentMark::clearNextBitmap() {
816 G1CollectedHeap* g1h = G1CollectedHeap::heap();
817
818 // Make sure that the concurrent mark thread looks to still be in
819 // the current cycle.
820 guarantee(cmThread()->during_cycle(), "invariant");
821
822 // We are finishing up the current cycle by clearing the next
823 // marking bitmap and getting it ready for the next cycle. During
824 // this time no other cycle can start. So, let's make sure that this
825 // is the case.
826 guarantee(!g1h->collector_state()->mark_in_progress(), "invariant");
827
828 ClearBitmapHRClosure cl(this, _nextMarkBitMap, true /* may_yield */);
829 ParClearNextMarkBitmapTask task(&cl, parallel_marking_threads(), true);
830 _parallel_workers->run_task(&task);
831
832 // Clear the liveness counting data. If the marking has been aborted, the abort()
833 // call already did that.
834 if (cl.complete()) {
835 clear_all_count_data();
836 }
837
838 // Repeat the asserts from above.
839 guarantee(cmThread()->during_cycle(), "invariant");
840 guarantee(!g1h->collector_state()->mark_in_progress(), "invariant");
841 }
842
843 class CheckBitmapClearHRClosure : public HeapRegionClosure {
844 CMBitMap* _bitmap;
845 bool _error;
846 public:
847 CheckBitmapClearHRClosure(CMBitMap* bitmap) : _bitmap(bitmap) {
848 }
849
850 virtual bool doHeapRegion(HeapRegion* r) {
851 // This closure can be called concurrently to the mutator, so we must make sure
852 // that the result of the getNextMarkedWordAddress() call is compared to the
853 // value passed to it as limit to detect any found bits.
854 // We can use the region's orig_end() for the limit and the comparison value
855 // as it always contains the "real" end of the region that never changes and
856 // has no side effects.
857 // Due to the latter, there can also be no problem with the compiler generating
858 // reloads of the orig_end() call.
859 HeapWord* end = r->orig_end();
860 return _bitmap->getNextMarkedWordAddress(r->bottom(), end) != end;
861 }
862 };
863
864 bool ConcurrentMark::nextMarkBitmapIsClear() {
865 CheckBitmapClearHRClosure cl(_nextMarkBitMap);
866 _g1h->heap_region_iterate(&cl);
867 return cl.complete();
868 }
869
870 class NoteStartOfMarkHRClosure: public HeapRegionClosure {
871 public:
872 bool doHeapRegion(HeapRegion* r) {
873 if (!r->is_continues_humongous()) {
874 r->note_start_of_marking();
875 }
876 return false;
877 }
878 };
879
880 void ConcurrentMark::checkpointRootsInitialPre() {
881 G1CollectedHeap* g1h = G1CollectedHeap::heap();
882 G1CollectorPolicy* g1p = g1h->g1_policy();
883
884 _has_aborted = false;
885
886 // Initialize marking structures. This has to be done in a STW phase.
887 reset();
888
889 // For each region note start of marking.
890 NoteStartOfMarkHRClosure startcl;
891 g1h->heap_region_iterate(&startcl);
892 }
893
894
895 void ConcurrentMark::checkpointRootsInitialPost() {
896 G1CollectedHeap* g1h = G1CollectedHeap::heap();
897
898 // If we force an overflow during remark, the remark operation will
899 // actually abort and we'll restart concurrent marking. If we always
900 // force an overflow during remark we'll never actually complete the
901 // marking phase. So, we initialize this here, at the start of the
902 // cycle, so that at the remaining overflow number will decrease at
903 // every remark and we'll eventually not need to cause one.
904 force_overflow_stw()->init();
905
906 // Start Concurrent Marking weak-reference discovery.
907 ReferenceProcessor* rp = g1h->ref_processor_cm();
908 // enable ("weak") refs discovery
909 rp->enable_discovery();
910 rp->setup_policy(false); // snapshot the soft ref policy to be used in this cycle
911
912 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
913 // This is the start of the marking cycle, we're expected all
914 // threads to have SATB queues with active set to false.
915 satb_mq_set.set_active_all_threads(true, /* new active value */
916 false /* expected_active */);
917
918 _root_regions.prepare_for_scan();
919
920 // update_g1_committed() will be called at the end of an evac pause
921 // when marking is on. So, it's also called at the end of the
922 // initial-mark pause to update the heap end, if the heap expands
923 // during it. No need to call it here.
924 }
925
926 /*
927 * Notice that in the next two methods, we actually leave the STS
928 * during the barrier sync and join it immediately afterwards. If we
929 * do not do this, the following deadlock can occur: one thread could
930 * be in the barrier sync code, waiting for the other thread to also
931 * sync up, whereas another one could be trying to yield, while also
932 * waiting for the other threads to sync up too.
933 *
934 * Note, however, that this code is also used during remark and in
935 * this case we should not attempt to leave / enter the STS, otherwise
936 * we'll either hit an assert (debug / fastdebug) or deadlock
937 * (product). So we should only leave / enter the STS if we are
938 * operating concurrently.
939 *
940 * Because the thread that does the sync barrier has left the STS, it
941 * is possible to be suspended for a Full GC or an evacuation pause
942 * could occur. This is actually safe, since the entering the sync
943 * barrier is one of the last things do_marking_step() does, and it
944 * doesn't manipulate any data structures afterwards.
945 */
946
947 void ConcurrentMark::enter_first_sync_barrier(uint worker_id) {
948 bool barrier_aborted;
949
950 if (verbose_low()) {
951 gclog_or_tty->print_cr("[%u] entering first barrier", worker_id);
952 }
953
954 {
955 SuspendibleThreadSetLeaver sts_leave(concurrent());
956 barrier_aborted = !_first_overflow_barrier_sync.enter();
957 }
958
959 // at this point everyone should have synced up and not be doing any
960 // more work
961
962 if (verbose_low()) {
963 if (barrier_aborted) {
964 gclog_or_tty->print_cr("[%u] aborted first barrier", worker_id);
965 } else {
966 gclog_or_tty->print_cr("[%u] leaving first barrier", worker_id);
967 }
968 }
969
970 if (barrier_aborted) {
971 // If the barrier aborted we ignore the overflow condition and
972 // just abort the whole marking phase as quickly as possible.
973 return;
974 }
975
976 // If we're executing the concurrent phase of marking, reset the marking
977 // state; otherwise the marking state is reset after reference processing,
978 // during the remark pause.
979 // If we reset here as a result of an overflow during the remark we will
980 // see assertion failures from any subsequent set_concurrency_and_phase()
981 // calls.
982 if (concurrent()) {
983 // let the task associated with with worker 0 do this
984 if (worker_id == 0) {
985 // task 0 is responsible for clearing the global data structures
986 // We should be here because of an overflow. During STW we should
987 // not clear the overflow flag since we rely on it being true when
988 // we exit this method to abort the pause and restart concurrent
989 // marking.
990 reset_marking_state(true /* clear_overflow */);
991 force_overflow()->update();
992
993 if (G1Log::fine()) {
994 gclog_or_tty->gclog_stamp();
995 gclog_or_tty->print_cr("[GC concurrent-mark-reset-for-overflow]");
996 }
997 }
998 }
999
1000 // after this, each task should reset its own data structures then
1001 // then go into the second barrier
1002 }
1003
1004 void ConcurrentMark::enter_second_sync_barrier(uint worker_id) {
1005 bool barrier_aborted;
1006
1007 if (verbose_low()) {
1008 gclog_or_tty->print_cr("[%u] entering second barrier", worker_id);
1009 }
1010
1011 {
1012 SuspendibleThreadSetLeaver sts_leave(concurrent());
1013 barrier_aborted = !_second_overflow_barrier_sync.enter();
1014 }
1015
1016 // at this point everything should be re-initialized and ready to go
1017
1018 if (verbose_low()) {
1019 if (barrier_aborted) {
1020 gclog_or_tty->print_cr("[%u] aborted second barrier", worker_id);
1021 } else {
1022 gclog_or_tty->print_cr("[%u] leaving second barrier", worker_id);
1023 }
1024 }
1025 }
1026
1027 #ifndef PRODUCT
1028 void ForceOverflowSettings::init() {
1029 _num_remaining = G1ConcMarkForceOverflow;
1030 _force = false;
1031 update();
1032 }
1033
1034 void ForceOverflowSettings::update() {
1035 if (_num_remaining > 0) {
1036 _num_remaining -= 1;
1037 _force = true;
1038 } else {
1039 _force = false;
1040 }
1041 }
1042
1043 bool ForceOverflowSettings::should_force() {
1044 if (_force) {
1045 _force = false;
1046 return true;
1047 } else {
1048 return false;
1049 }
1050 }
1051 #endif // !PRODUCT
1052
1053 class CMConcurrentMarkingTask: public AbstractGangTask {
1054 private:
1055 ConcurrentMark* _cm;
1056 ConcurrentMarkThread* _cmt;
1057
1058 public:
1059 void work(uint worker_id) {
1060 assert(Thread::current()->is_ConcurrentGC_thread(),
1061 "this should only be done by a conc GC thread");
1062 ResourceMark rm;
1063
1064 double start_vtime = os::elapsedVTime();
1065
1066 {
1067 SuspendibleThreadSetJoiner sts_join;
1068
1069 assert(worker_id < _cm->active_tasks(), "invariant");
1070 CMTask* the_task = _cm->task(worker_id);
1071 the_task->record_start_time();
1072 if (!_cm->has_aborted()) {
1073 do {
1074 double start_vtime_sec = os::elapsedVTime();
1075 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
1076
1077 the_task->do_marking_step(mark_step_duration_ms,
1078 true /* do_termination */,
1079 false /* is_serial*/);
1080
1081 double end_vtime_sec = os::elapsedVTime();
1082 double elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;
1083 _cm->clear_has_overflown();
1084
1085 _cm->do_yield_check(worker_id);
1086
1087 jlong sleep_time_ms;
1088 if (!_cm->has_aborted() && the_task->has_aborted()) {
1089 sleep_time_ms =
1090 (jlong) (elapsed_vtime_sec * _cm->sleep_factor() * 1000.0);
1091 {
1092 SuspendibleThreadSetLeaver sts_leave;
1093 os::sleep(Thread::current(), sleep_time_ms, false);
1094 }
1095 }
1096 } while (!_cm->has_aborted() && the_task->has_aborted());
1097 }
1098 the_task->record_end_time();
1099 guarantee(!the_task->has_aborted() || _cm->has_aborted(), "invariant");
1100 }
1101
1102 double end_vtime = os::elapsedVTime();
1103 _cm->update_accum_task_vtime(worker_id, end_vtime - start_vtime);
1104 }
1105
1106 CMConcurrentMarkingTask(ConcurrentMark* cm,
1107 ConcurrentMarkThread* cmt) :
1108 AbstractGangTask("Concurrent Mark"), _cm(cm), _cmt(cmt) { }
1109
1110 ~CMConcurrentMarkingTask() { }
1111 };
1112
1113 // Calculates the number of active workers for a concurrent
1114 // phase.
1115 uint ConcurrentMark::calc_parallel_marking_threads() {
1116 uint n_conc_workers = 0;
1117 if (!UseDynamicNumberOfGCThreads ||
1118 (!FLAG_IS_DEFAULT(ConcGCThreads) &&
1119 !ForceDynamicNumberOfGCThreads)) {
1120 n_conc_workers = max_parallel_marking_threads();
1121 } else {
1122 n_conc_workers =
1123 AdaptiveSizePolicy::calc_default_active_workers(
1124 max_parallel_marking_threads(),
1125 1, /* Minimum workers */
1126 parallel_marking_threads(),
1127 Threads::number_of_non_daemon_threads());
1128 // Don't scale down "n_conc_workers" by scale_parallel_threads() because
1129 // that scaling has already gone into "_max_parallel_marking_threads".
1130 }
1131 assert(n_conc_workers > 0, "Always need at least 1");
1132 return n_conc_workers;
1133 }
1134
1135 void ConcurrentMark::scanRootRegion(HeapRegion* hr, uint worker_id) {
1136 // Currently, only survivors can be root regions.
1137 assert(hr->next_top_at_mark_start() == hr->bottom(), "invariant");
1138 G1RootRegionScanClosure cl(_g1h, this, worker_id);
1139
1140 const uintx interval = PrefetchScanIntervalInBytes;
1141 HeapWord* curr = hr->bottom();
1142 const HeapWord* end = hr->top();
1143 while (curr < end) {
1144 Prefetch::read(curr, interval);
1145 oop obj = oop(curr);
1146 int size = obj->oop_iterate_size(&cl);
1147 assert(size == obj->size(), "sanity");
1148 curr += size;
1149 }
1150 }
1151
1152 class CMRootRegionScanTask : public AbstractGangTask {
1153 private:
1154 ConcurrentMark* _cm;
1155
1156 public:
1157 CMRootRegionScanTask(ConcurrentMark* cm) :
1158 AbstractGangTask("Root Region Scan"), _cm(cm) { }
1159
1160 void work(uint worker_id) {
1161 assert(Thread::current()->is_ConcurrentGC_thread(),
1162 "this should only be done by a conc GC thread");
1163
1164 CMRootRegions* root_regions = _cm->root_regions();
1165 HeapRegion* hr = root_regions->claim_next();
1166 while (hr != NULL) {
1167 _cm->scanRootRegion(hr, worker_id);
1168 hr = root_regions->claim_next();
1169 }
1170 }
1171 };
1172
1173 void ConcurrentMark::scanRootRegions() {
1174 double scan_start = os::elapsedTime();
1175
1176 // Start of concurrent marking.
1177 ClassLoaderDataGraph::clear_claimed_marks();
1178
1179 // scan_in_progress() will have been set to true only if there was
1180 // at least one root region to scan. So, if it's false, we
1181 // should not attempt to do any further work.
1182 if (root_regions()->scan_in_progress()) {
1183 if (G1Log::fine()) {
1184 gclog_or_tty->gclog_stamp();
1185 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]");
1186 }
1187
1188 _parallel_marking_threads = calc_parallel_marking_threads();
1189 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1190 "Maximum number of marking threads exceeded");
1191 uint active_workers = MAX2(1U, parallel_marking_threads());
1192
1193 CMRootRegionScanTask task(this);
1194 _parallel_workers->set_active_workers(active_workers);
1195 _parallel_workers->run_task(&task);
1196
1197 if (G1Log::fine()) {
1198 gclog_or_tty->gclog_stamp();
1199 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]", os::elapsedTime() - scan_start);
1200 }
1201
1202 // It's possible that has_aborted() is true here without actually
1203 // aborting the survivor scan earlier. This is OK as it's
1204 // mainly used for sanity checking.
1205 root_regions()->scan_finished();
1206 }
1207 }
1208
1209 void ConcurrentMark::markFromRoots() {
1210 // we might be tempted to assert that:
1211 // assert(asynch == !SafepointSynchronize::is_at_safepoint(),
1212 // "inconsistent argument?");
1213 // However that wouldn't be right, because it's possible that
1214 // a safepoint is indeed in progress as a younger generation
1215 // stop-the-world GC happens even as we mark in this generation.
1216
1217 _restart_for_overflow = false;
1218 force_overflow_conc()->init();
1219
1220 // _g1h has _n_par_threads
1221 _parallel_marking_threads = calc_parallel_marking_threads();
1222 assert(parallel_marking_threads() <= max_parallel_marking_threads(),
1223 "Maximum number of marking threads exceeded");
1224
1225 uint active_workers = MAX2(1U, parallel_marking_threads());
1226 assert(active_workers > 0, "Should have been set");
1227
1228 // Parallel task terminator is set in "set_concurrency_and_phase()"
1229 set_concurrency_and_phase(active_workers, true /* concurrent */);
1230
1231 CMConcurrentMarkingTask markingTask(this, cmThread());
1232 _parallel_workers->set_active_workers(active_workers);
1233 _parallel_workers->run_task(&markingTask);
1234 print_stats();
1235 }
1236
1237 // Helper class to get rid of some boilerplate code.
1238 class G1CMTraceTime : public GCTraceTime {
1239 static bool doit_and_prepend(bool doit) {
1240 if (doit) {
1241 gclog_or_tty->put(' ');
1242 }
1243 return doit;
1244 }
1245
1246 public:
1247 G1CMTraceTime(const char* title, bool doit)
1248 : GCTraceTime(title, doit_and_prepend(doit), false, G1CollectedHeap::heap()->gc_timer_cm()) {
1249 }
1250 };
1251
1252 void ConcurrentMark::checkpointRootsFinal(bool clear_all_soft_refs) {
1253 // world is stopped at this checkpoint
1254 assert(SafepointSynchronize::is_at_safepoint(),
1255 "world should be stopped");
1256
1257 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1258
1259 // If a full collection has happened, we shouldn't do this.
1260 if (has_aborted()) {
1261 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1262 return;
1263 }
1264
1265 SvcGCMarker sgcm(SvcGCMarker::OTHER);
1266
1267 if (VerifyDuringGC) {
1268 HandleMark hm; // handle scope
1269 g1h->prepare_for_verify();
1270 Universe::verify(VerifyOption_G1UsePrevMarking,
1271 " VerifyDuringGC:(before)");
1272 }
1273 g1h->check_bitmaps("Remark Start");
1274
1275 G1CollectorPolicy* g1p = g1h->g1_policy();
1276 g1p->record_concurrent_mark_remark_start();
1277
1278 double start = os::elapsedTime();
1279
1280 checkpointRootsFinalWork();
1281
1282 double mark_work_end = os::elapsedTime();
1283
1284 weakRefsWork(clear_all_soft_refs);
1285
1286 if (has_overflown()) {
1287 // Oops. We overflowed. Restart concurrent marking.
1288 _restart_for_overflow = true;
1289 if (G1TraceMarkStackOverflow) {
1290 gclog_or_tty->print_cr("\nRemark led to restart for overflow.");
1291 }
1292
1293 // Verify the heap w.r.t. the previous marking bitmap.
1294 if (VerifyDuringGC) {
1295 HandleMark hm; // handle scope
1296 g1h->prepare_for_verify();
1297 Universe::verify(VerifyOption_G1UsePrevMarking,
1298 " VerifyDuringGC:(overflow)");
1299 }
1300
1301 // Clear the marking state because we will be restarting
1302 // marking due to overflowing the global mark stack.
1303 reset_marking_state();
1304 } else {
1305 {
1306 G1CMTraceTime trace("GC aggregate-data", G1Log::finer());
1307
1308 // Aggregate the per-task counting data that we have accumulated
1309 // while marking.
1310 aggregate_count_data();
1311 }
1312
1313 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
1314 // We're done with marking.
1315 // This is the end of the marking cycle, we're expected all
1316 // threads to have SATB queues with active set to true.
1317 satb_mq_set.set_active_all_threads(false, /* new active value */
1318 true /* expected_active */);
1319
1320 if (VerifyDuringGC) {
1321 HandleMark hm; // handle scope
1322 g1h->prepare_for_verify();
1323 Universe::verify(VerifyOption_G1UseNextMarking,
1324 " VerifyDuringGC:(after)");
1325 }
1326 g1h->check_bitmaps("Remark End");
1327 assert(!restart_for_overflow(), "sanity");
1328 // Completely reset the marking state since marking completed
1329 set_non_marking_state();
1330 }
1331
1332 // Expand the marking stack, if we have to and if we can.
1333 if (_markStack.should_expand()) {
1334 _markStack.expand();
1335 }
1336
1337 // Statistics
1338 double now = os::elapsedTime();
1339 _remark_mark_times.add((mark_work_end - start) * 1000.0);
1340 _remark_weak_ref_times.add((now - mark_work_end) * 1000.0);
1341 _remark_times.add((now - start) * 1000.0);
1342
1343 g1p->record_concurrent_mark_remark_end();
1344
1345 G1CMIsAliveClosure is_alive(g1h);
1346 g1h->gc_tracer_cm()->report_object_count_after_gc(&is_alive);
1347 }
1348
1349 // Base class of the closures that finalize and verify the
1350 // liveness counting data.
1351 class CMCountDataClosureBase: public HeapRegionClosure {
1352 protected:
1353 G1CollectedHeap* _g1h;
1354 ConcurrentMark* _cm;
1355 CardTableModRefBS* _ct_bs;
1356
1357 BitMap* _region_bm;
1358 BitMap* _card_bm;
1359
1360 // Takes a region that's not empty (i.e., it has at least one
1361 // live object in it and sets its corresponding bit on the region
1362 // bitmap to 1. If the region is "starts humongous" it will also set
1363 // to 1 the bits on the region bitmap that correspond to its
1364 // associated "continues humongous" regions.
1365 void set_bit_for_region(HeapRegion* hr) {
1366 assert(!hr->is_continues_humongous(), "should have filtered those out");
1367
1368 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1369 if (!hr->is_starts_humongous()) {
1370 // Normal (non-humongous) case: just set the bit.
1371 _region_bm->par_at_put(index, true);
1372 } else {
1373 // Starts humongous case: calculate how many regions are part of
1374 // this humongous region and then set the bit range.
1375 BitMap::idx_t end_index = (BitMap::idx_t) hr->last_hc_index();
1376 _region_bm->par_at_put_range(index, end_index, true);
1377 }
1378 }
1379
1380 public:
1381 CMCountDataClosureBase(G1CollectedHeap* g1h,
1382 BitMap* region_bm, BitMap* card_bm):
1383 _g1h(g1h), _cm(g1h->concurrent_mark()),
1384 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
1385 _region_bm(region_bm), _card_bm(card_bm) { }
1386 };
1387
1388 // Closure that calculates the # live objects per region. Used
1389 // for verification purposes during the cleanup pause.
1390 class CalcLiveObjectsClosure: public CMCountDataClosureBase {
1391 CMBitMapRO* _bm;
1392 size_t _region_marked_bytes;
1393
1394 public:
1395 CalcLiveObjectsClosure(CMBitMapRO *bm, G1CollectedHeap* g1h,
1396 BitMap* region_bm, BitMap* card_bm) :
1397 CMCountDataClosureBase(g1h, region_bm, card_bm),
1398 _bm(bm), _region_marked_bytes(0) { }
1399
1400 bool doHeapRegion(HeapRegion* hr) {
1401
1402 if (hr->is_continues_humongous()) {
1403 // We will ignore these here and process them when their
1404 // associated "starts humongous" region is processed (see
1405 // set_bit_for_heap_region()). Note that we cannot rely on their
1406 // associated "starts humongous" region to have their bit set to
1407 // 1 since, due to the region chunking in the parallel region
1408 // iteration, a "continues humongous" region might be visited
1409 // before its associated "starts humongous".
1410 return false;
1411 }
1412
1413 HeapWord* ntams = hr->next_top_at_mark_start();
1414 HeapWord* start = hr->bottom();
1415
1416 assert(start <= hr->end() && start <= ntams && ntams <= hr->end(),
1417 err_msg("Preconditions not met - "
1418 "start: " PTR_FORMAT ", ntams: " PTR_FORMAT ", end: " PTR_FORMAT,
1419 p2i(start), p2i(ntams), p2i(hr->end())));
1420
1421 // Find the first marked object at or after "start".
1422 start = _bm->getNextMarkedWordAddress(start, ntams);
1423
1424 size_t marked_bytes = 0;
1425
1426 while (start < ntams) {
1427 oop obj = oop(start);
1428 int obj_sz = obj->size();
1429 HeapWord* obj_end = start + obj_sz;
1430
1431 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
1432 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(obj_end);
1433
1434 // Note: if we're looking at the last region in heap - obj_end
1435 // could be actually just beyond the end of the heap; end_idx
1436 // will then correspond to a (non-existent) card that is also
1437 // just beyond the heap.
1438 if (_g1h->is_in_g1_reserved(obj_end) && !_ct_bs->is_card_aligned(obj_end)) {
1439 // end of object is not card aligned - increment to cover
1440 // all the cards spanned by the object
1441 end_idx += 1;
1442 }
1443
1444 // Set the bits in the card BM for the cards spanned by this object.
1445 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1446
1447 // Add the size of this object to the number of marked bytes.
1448 marked_bytes += (size_t)obj_sz * HeapWordSize;
1449
1450 // Find the next marked object after this one.
1451 start = _bm->getNextMarkedWordAddress(obj_end, ntams);
1452 }
1453
1454 // Mark the allocated-since-marking portion...
1455 HeapWord* top = hr->top();
1456 if (ntams < top) {
1457 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1458 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1459
1460 // Note: if we're looking at the last region in heap - top
1461 // could be actually just beyond the end of the heap; end_idx
1462 // will then correspond to a (non-existent) card that is also
1463 // just beyond the heap.
1464 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1465 // end of object is not card aligned - increment to cover
1466 // all the cards spanned by the object
1467 end_idx += 1;
1468 }
1469 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1470
1471 // This definitely means the region has live objects.
1472 set_bit_for_region(hr);
1473 }
1474
1475 // Update the live region bitmap.
1476 if (marked_bytes > 0) {
1477 set_bit_for_region(hr);
1478 }
1479
1480 // Set the marked bytes for the current region so that
1481 // it can be queried by a calling verification routine
1482 _region_marked_bytes = marked_bytes;
1483
1484 return false;
1485 }
1486
1487 size_t region_marked_bytes() const { return _region_marked_bytes; }
1488 };
1489
1490 // Heap region closure used for verifying the counting data
1491 // that was accumulated concurrently and aggregated during
1492 // the remark pause. This closure is applied to the heap
1493 // regions during the STW cleanup pause.
1494
1495 class VerifyLiveObjectDataHRClosure: public HeapRegionClosure {
1496 G1CollectedHeap* _g1h;
1497 ConcurrentMark* _cm;
1498 CalcLiveObjectsClosure _calc_cl;
1499 BitMap* _region_bm; // Region BM to be verified
1500 BitMap* _card_bm; // Card BM to be verified
1501 bool _verbose; // verbose output?
1502
1503 BitMap* _exp_region_bm; // Expected Region BM values
1504 BitMap* _exp_card_bm; // Expected card BM values
1505
1506 int _failures;
1507
1508 public:
1509 VerifyLiveObjectDataHRClosure(G1CollectedHeap* g1h,
1510 BitMap* region_bm,
1511 BitMap* card_bm,
1512 BitMap* exp_region_bm,
1513 BitMap* exp_card_bm,
1514 bool verbose) :
1515 _g1h(g1h), _cm(g1h->concurrent_mark()),
1516 _calc_cl(_cm->nextMarkBitMap(), g1h, exp_region_bm, exp_card_bm),
1517 _region_bm(region_bm), _card_bm(card_bm), _verbose(verbose),
1518 _exp_region_bm(exp_region_bm), _exp_card_bm(exp_card_bm),
1519 _failures(0) { }
1520
1521 int failures() const { return _failures; }
1522
1523 bool doHeapRegion(HeapRegion* hr) {
1524 if (hr->is_continues_humongous()) {
1525 // We will ignore these here and process them when their
1526 // associated "starts humongous" region is processed (see
1527 // set_bit_for_heap_region()). Note that we cannot rely on their
1528 // associated "starts humongous" region to have their bit set to
1529 // 1 since, due to the region chunking in the parallel region
1530 // iteration, a "continues humongous" region might be visited
1531 // before its associated "starts humongous".
1532 return false;
1533 }
1534
1535 int failures = 0;
1536
1537 // Call the CalcLiveObjectsClosure to walk the marking bitmap for
1538 // this region and set the corresponding bits in the expected region
1539 // and card bitmaps.
1540 bool res = _calc_cl.doHeapRegion(hr);
1541 assert(res == false, "should be continuing");
1542
1543 MutexLockerEx x((_verbose ? ParGCRareEvent_lock : NULL),
1544 Mutex::_no_safepoint_check_flag);
1545
1546 // Verify the marked bytes for this region.
1547 size_t exp_marked_bytes = _calc_cl.region_marked_bytes();
1548 size_t act_marked_bytes = hr->next_marked_bytes();
1549
1550 // We're not OK if expected marked bytes > actual marked bytes. It means
1551 // we have missed accounting some objects during the actual marking.
1552 if (exp_marked_bytes > act_marked_bytes) {
1553 if (_verbose) {
1554 gclog_or_tty->print_cr("Region %u: marked bytes mismatch: "
1555 "expected: " SIZE_FORMAT ", actual: " SIZE_FORMAT,
1556 hr->hrm_index(), exp_marked_bytes, act_marked_bytes);
1557 }
1558 failures += 1;
1559 }
1560
1561 // Verify the bit, for this region, in the actual and expected
1562 // (which was just calculated) region bit maps.
1563 // We're not OK if the bit in the calculated expected region
1564 // bitmap is set and the bit in the actual region bitmap is not.
1565 BitMap::idx_t index = (BitMap::idx_t) hr->hrm_index();
1566
1567 bool expected = _exp_region_bm->at(index);
1568 bool actual = _region_bm->at(index);
1569 if (expected && !actual) {
1570 if (_verbose) {
1571 gclog_or_tty->print_cr("Region %u: region bitmap mismatch: "
1572 "expected: %s, actual: %s",
1573 hr->hrm_index(),
1574 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1575 }
1576 failures += 1;
1577 }
1578
1579 // Verify that the card bit maps for the cards spanned by the current
1580 // region match. We have an error if we have a set bit in the expected
1581 // bit map and the corresponding bit in the actual bitmap is not set.
1582
1583 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(hr->bottom());
1584 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(hr->top());
1585
1586 for (BitMap::idx_t i = start_idx; i < end_idx; i+=1) {
1587 expected = _exp_card_bm->at(i);
1588 actual = _card_bm->at(i);
1589
1590 if (expected && !actual) {
1591 if (_verbose) {
1592 gclog_or_tty->print_cr("Region %u: card bitmap mismatch at " SIZE_FORMAT ": "
1593 "expected: %s, actual: %s",
1594 hr->hrm_index(), i,
1595 BOOL_TO_STR(expected), BOOL_TO_STR(actual));
1596 }
1597 failures += 1;
1598 }
1599 }
1600
1601 if (failures > 0 && _verbose) {
1602 gclog_or_tty->print_cr("Region " HR_FORMAT ", ntams: " PTR_FORMAT ", "
1603 "marked_bytes: calc/actual " SIZE_FORMAT "/" SIZE_FORMAT,
1604 HR_FORMAT_PARAMS(hr), p2i(hr->next_top_at_mark_start()),
1605 _calc_cl.region_marked_bytes(), hr->next_marked_bytes());
1606 }
1607
1608 _failures += failures;
1609
1610 // We could stop iteration over the heap when we
1611 // find the first violating region by returning true.
1612 return false;
1613 }
1614 };
1615
1616 class G1ParVerifyFinalCountTask: public AbstractGangTask {
1617 protected:
1618 G1CollectedHeap* _g1h;
1619 ConcurrentMark* _cm;
1620 BitMap* _actual_region_bm;
1621 BitMap* _actual_card_bm;
1622
1623 uint _n_workers;
1624
1625 BitMap* _expected_region_bm;
1626 BitMap* _expected_card_bm;
1627
1628 int _failures;
1629 bool _verbose;
1630
1631 HeapRegionClaimer _hrclaimer;
1632
1633 public:
1634 G1ParVerifyFinalCountTask(G1CollectedHeap* g1h,
1635 BitMap* region_bm, BitMap* card_bm,
1636 BitMap* expected_region_bm, BitMap* expected_card_bm)
1637 : AbstractGangTask("G1 verify final counting"),
1638 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1639 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1640 _expected_region_bm(expected_region_bm), _expected_card_bm(expected_card_bm),
1641 _failures(0), _verbose(false),
1642 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1643 assert(VerifyDuringGC, "don't call this otherwise");
1644 assert(_expected_card_bm->size() == _actual_card_bm->size(), "sanity");
1645 assert(_expected_region_bm->size() == _actual_region_bm->size(), "sanity");
1646
1647 _verbose = _cm->verbose_medium();
1648 }
1649
1650 void work(uint worker_id) {
1651 assert(worker_id < _n_workers, "invariant");
1652
1653 VerifyLiveObjectDataHRClosure verify_cl(_g1h,
1654 _actual_region_bm, _actual_card_bm,
1655 _expected_region_bm,
1656 _expected_card_bm,
1657 _verbose);
1658
1659 _g1h->heap_region_par_iterate(&verify_cl, worker_id, &_hrclaimer);
1660
1661 Atomic::add(verify_cl.failures(), &_failures);
1662 }
1663
1664 int failures() const { return _failures; }
1665 };
1666
1667 // Closure that finalizes the liveness counting data.
1668 // Used during the cleanup pause.
1669 // Sets the bits corresponding to the interval [NTAMS, top]
1670 // (which contains the implicitly live objects) in the
1671 // card liveness bitmap. Also sets the bit for each region,
1672 // containing live data, in the region liveness bitmap.
1673
1674 class FinalCountDataUpdateClosure: public CMCountDataClosureBase {
1675 public:
1676 FinalCountDataUpdateClosure(G1CollectedHeap* g1h,
1677 BitMap* region_bm,
1678 BitMap* card_bm) :
1679 CMCountDataClosureBase(g1h, region_bm, card_bm) { }
1680
1681 bool doHeapRegion(HeapRegion* hr) {
1682
1683 if (hr->is_continues_humongous()) {
1684 // We will ignore these here and process them when their
1685 // associated "starts humongous" region is processed (see
1686 // set_bit_for_heap_region()). Note that we cannot rely on their
1687 // associated "starts humongous" region to have their bit set to
1688 // 1 since, due to the region chunking in the parallel region
1689 // iteration, a "continues humongous" region might be visited
1690 // before its associated "starts humongous".
1691 return false;
1692 }
1693
1694 HeapWord* ntams = hr->next_top_at_mark_start();
1695 HeapWord* top = hr->top();
1696
1697 assert(hr->bottom() <= ntams && ntams <= hr->end(), "Preconditions.");
1698
1699 // Mark the allocated-since-marking portion...
1700 if (ntams < top) {
1701 // This definitely means the region has live objects.
1702 set_bit_for_region(hr);
1703
1704 // Now set the bits in the card bitmap for [ntams, top)
1705 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(ntams);
1706 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(top);
1707
1708 // Note: if we're looking at the last region in heap - top
1709 // could be actually just beyond the end of the heap; end_idx
1710 // will then correspond to a (non-existent) card that is also
1711 // just beyond the heap.
1712 if (_g1h->is_in_g1_reserved(top) && !_ct_bs->is_card_aligned(top)) {
1713 // end of object is not card aligned - increment to cover
1714 // all the cards spanned by the object
1715 end_idx += 1;
1716 }
1717
1718 assert(end_idx <= _card_bm->size(),
1719 err_msg("oob: end_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1720 end_idx, _card_bm->size()));
1721 assert(start_idx < _card_bm->size(),
1722 err_msg("oob: start_idx= " SIZE_FORMAT ", bitmap size= " SIZE_FORMAT,
1723 start_idx, _card_bm->size()));
1724
1725 _cm->set_card_bitmap_range(_card_bm, start_idx, end_idx, true /* is_par */);
1726 }
1727
1728 // Set the bit for the region if it contains live data
1729 if (hr->next_marked_bytes() > 0) {
1730 set_bit_for_region(hr);
1731 }
1732
1733 return false;
1734 }
1735 };
1736
1737 class G1ParFinalCountTask: public AbstractGangTask {
1738 protected:
1739 G1CollectedHeap* _g1h;
1740 ConcurrentMark* _cm;
1741 BitMap* _actual_region_bm;
1742 BitMap* _actual_card_bm;
1743
1744 uint _n_workers;
1745 HeapRegionClaimer _hrclaimer;
1746
1747 public:
1748 G1ParFinalCountTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm)
1749 : AbstractGangTask("G1 final counting"),
1750 _g1h(g1h), _cm(_g1h->concurrent_mark()),
1751 _actual_region_bm(region_bm), _actual_card_bm(card_bm),
1752 _n_workers(_g1h->workers()->active_workers()), _hrclaimer(_n_workers) {
1753 }
1754
1755 void work(uint worker_id) {
1756 assert(worker_id < _n_workers, "invariant");
1757
1758 FinalCountDataUpdateClosure final_update_cl(_g1h,
1759 _actual_region_bm,
1760 _actual_card_bm);
1761
1762 _g1h->heap_region_par_iterate(&final_update_cl, worker_id, &_hrclaimer);
1763 }
1764 };
1765
1766 class G1NoteEndOfConcMarkClosure : public HeapRegionClosure {
1767 G1CollectedHeap* _g1;
1768 size_t _freed_bytes;
1769 FreeRegionList* _local_cleanup_list;
1770 HeapRegionSetCount _old_regions_removed;
1771 HeapRegionSetCount _humongous_regions_removed;
1772 HRRSCleanupTask* _hrrs_cleanup_task;
1773
1774 public:
1775 G1NoteEndOfConcMarkClosure(G1CollectedHeap* g1,
1776 FreeRegionList* local_cleanup_list,
1777 HRRSCleanupTask* hrrs_cleanup_task) :
1778 _g1(g1),
1779 _freed_bytes(0),
1780 _local_cleanup_list(local_cleanup_list),
1781 _old_regions_removed(),
1782 _humongous_regions_removed(),
1783 _hrrs_cleanup_task(hrrs_cleanup_task) { }
1784
1785 size_t freed_bytes() { return _freed_bytes; }
1786 const HeapRegionSetCount& old_regions_removed() { return _old_regions_removed; }
1787 const HeapRegionSetCount& humongous_regions_removed() { return _humongous_regions_removed; }
1788
1789 bool doHeapRegion(HeapRegion *hr) {
1790 if (hr->is_continues_humongous() || hr->is_archive()) {
1791 return false;
1792 }
1793 // We use a claim value of zero here because all regions
1794 // were claimed with value 1 in the FinalCount task.
1795 _g1->reset_gc_time_stamps(hr);
1796 hr->note_end_of_marking();
1797
1798 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
1799 _freed_bytes += hr->used();
1800 hr->set_containing_set(NULL);
1801 if (hr->is_humongous()) {
1802 assert(hr->is_starts_humongous(), "we should only see starts humongous");
1803 _humongous_regions_removed.increment(1u, hr->capacity());
1804 _g1->free_humongous_region(hr, _local_cleanup_list, true);
1805 } else {
1806 _old_regions_removed.increment(1u, hr->capacity());
1807 _g1->free_region(hr, _local_cleanup_list, true);
1808 }
1809 } else {
1810 hr->rem_set()->do_cleanup_work(_hrrs_cleanup_task);
1811 }
1812
1813 return false;
1814 }
1815 };
1816
1817 class G1ParNoteEndTask: public AbstractGangTask {
1818 friend class G1NoteEndOfConcMarkClosure;
1819
1820 protected:
1821 G1CollectedHeap* _g1h;
1822 FreeRegionList* _cleanup_list;
1823 HeapRegionClaimer _hrclaimer;
1824
1825 public:
1826 G1ParNoteEndTask(G1CollectedHeap* g1h, FreeRegionList* cleanup_list, uint n_workers) :
1827 AbstractGangTask("G1 note end"), _g1h(g1h), _cleanup_list(cleanup_list), _hrclaimer(n_workers) {
1828 }
1829
1830 void work(uint worker_id) {
1831 FreeRegionList local_cleanup_list("Local Cleanup List");
1832 HRRSCleanupTask hrrs_cleanup_task;
1833 G1NoteEndOfConcMarkClosure g1_note_end(_g1h, &local_cleanup_list,
1834 &hrrs_cleanup_task);
1835 _g1h->heap_region_par_iterate(&g1_note_end, worker_id, &_hrclaimer);
1836 assert(g1_note_end.complete(), "Shouldn't have yielded!");
1837
1838 // Now update the lists
1839 _g1h->remove_from_old_sets(g1_note_end.old_regions_removed(), g1_note_end.humongous_regions_removed());
1840 {
1841 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
1842 _g1h->decrement_summary_bytes(g1_note_end.freed_bytes());
1843
1844 // If we iterate over the global cleanup list at the end of
1845 // cleanup to do this printing we will not guarantee to only
1846 // generate output for the newly-reclaimed regions (the list
1847 // might not be empty at the beginning of cleanup; we might
1848 // still be working on its previous contents). So we do the
1849 // printing here, before we append the new regions to the global
1850 // cleanup list.
1851
1852 G1HRPrinter* hr_printer = _g1h->hr_printer();
1853 if (hr_printer->is_active()) {
1854 FreeRegionListIterator iter(&local_cleanup_list);
1855 while (iter.more_available()) {
1856 HeapRegion* hr = iter.get_next();
1857 hr_printer->cleanup(hr);
1858 }
1859 }
1860
1861 _cleanup_list->add_ordered(&local_cleanup_list);
1862 assert(local_cleanup_list.is_empty(), "post-condition");
1863
1864 HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
1865 }
1866 }
1867 };
1868
1869 class G1ParScrubRemSetTask: public AbstractGangTask {
1870 protected:
1871 G1RemSet* _g1rs;
1872 BitMap* _region_bm;
1873 BitMap* _card_bm;
1874 HeapRegionClaimer _hrclaimer;
1875
1876 public:
1877 G1ParScrubRemSetTask(G1CollectedHeap* g1h, BitMap* region_bm, BitMap* card_bm, uint n_workers) :
1878 AbstractGangTask("G1 ScrubRS"), _g1rs(g1h->g1_rem_set()), _region_bm(region_bm), _card_bm(card_bm), _hrclaimer(n_workers) {
1879 }
1880
1881 void work(uint worker_id) {
1882 _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
1883 }
1884
1885 };
1886
1887 void ConcurrentMark::cleanup() {
1888 // world is stopped at this checkpoint
1889 assert(SafepointSynchronize::is_at_safepoint(),
1890 "world should be stopped");
1891 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1892
1893 // If a full collection has happened, we shouldn't do this.
1894 if (has_aborted()) {
1895 g1h->collector_state()->set_mark_in_progress(false); // So bitmap clearing isn't confused
1896 return;
1897 }
1898
1899 g1h->verify_region_sets_optional();
1900
1901 if (VerifyDuringGC) {
1902 HandleMark hm; // handle scope
1903 g1h->prepare_for_verify();
1904 Universe::verify(VerifyOption_G1UsePrevMarking,
1905 " VerifyDuringGC:(before)");
1906 }
1907 g1h->check_bitmaps("Cleanup Start");
1908
1909 G1CollectorPolicy* g1p = g1h->g1_policy();
1910 g1p->record_concurrent_mark_cleanup_start();
1911
1912 double start = os::elapsedTime();
1913
1914 HeapRegionRemSet::reset_for_cleanup_tasks();
1915
1916 // Do counting once more with the world stopped for good measure.
1917 G1ParFinalCountTask g1_par_count_task(g1h, &_region_bm, &_card_bm);
1918
1919 g1h->workers()->run_task(&g1_par_count_task);
1920
1921 if (VerifyDuringGC) {
1922 // Verify that the counting data accumulated during marking matches
1923 // that calculated by walking the marking bitmap.
1924
1925 // Bitmaps to hold expected values
1926 BitMap expected_region_bm(_region_bm.size(), true);
1927 BitMap expected_card_bm(_card_bm.size(), true);
1928
1929 G1ParVerifyFinalCountTask g1_par_verify_task(g1h,
1930 &_region_bm,
1931 &_card_bm,
1932 &expected_region_bm,
1933 &expected_card_bm);
1934
1935 g1h->workers()->run_task(&g1_par_verify_task);
1936
1937 guarantee(g1_par_verify_task.failures() == 0, "Unexpected accounting failures");
1938 }
1939
1940 size_t start_used_bytes = g1h->used();
1941 g1h->collector_state()->set_mark_in_progress(false);
1942
1943 double count_end = os::elapsedTime();
1944 double this_final_counting_time = (count_end - start);
1945 _total_counting_time += this_final_counting_time;
1946
1947 if (G1PrintRegionLivenessInfo) {
1948 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Marking");
1949 _g1h->heap_region_iterate(&cl);
1950 }
1951
1952 // Install newly created mark bitMap as "prev".
1953 swapMarkBitMaps();
1954
1955 g1h->reset_gc_time_stamp();
1956
1957 uint n_workers = _g1h->workers()->active_workers();
1958
1959 // Note end of marking in all heap regions.
1960 G1ParNoteEndTask g1_par_note_end_task(g1h, &_cleanup_list, n_workers);
1961 g1h->workers()->run_task(&g1_par_note_end_task);
1962 g1h->check_gc_time_stamps();
1963
1964 if (!cleanup_list_is_empty()) {
1965 // The cleanup list is not empty, so we'll have to process it
1966 // concurrently. Notify anyone else that might be wanting free
1967 // regions that there will be more free regions coming soon.
1968 g1h->set_free_regions_coming();
1969 }
1970
1971 // call below, since it affects the metric by which we sort the heap
1972 // regions.
1973 if (G1ScrubRemSets) {
1974 double rs_scrub_start = os::elapsedTime();
1975 G1ParScrubRemSetTask g1_par_scrub_rs_task(g1h, &_region_bm, &_card_bm, n_workers);
1976 g1h->workers()->run_task(&g1_par_scrub_rs_task);
1977
1978 double rs_scrub_end = os::elapsedTime();
1979 double this_rs_scrub_time = (rs_scrub_end - rs_scrub_start);
1980 _total_rs_scrub_time += this_rs_scrub_time;
1981 }
1982
1983 // this will also free any regions totally full of garbage objects,
1984 // and sort the regions.
1985 g1h->g1_policy()->record_concurrent_mark_cleanup_end();
1986
1987 // Statistics.
1988 double end = os::elapsedTime();
1989 _cleanup_times.add((end - start) * 1000.0);
1990
1991 if (G1Log::fine()) {
1992 g1h->g1_policy()->print_heap_transition(start_used_bytes);
1993 }
1994
1995 // Clean up will have freed any regions completely full of garbage.
1996 // Update the soft reference policy with the new heap occupancy.
1997 Universe::update_heap_info_at_gc();
1998
1999 if (VerifyDuringGC) {
2000 HandleMark hm; // handle scope
2001 g1h->prepare_for_verify();
2002 Universe::verify(VerifyOption_G1UsePrevMarking,
2003 " VerifyDuringGC:(after)");
2004 }
2005
2006 g1h->check_bitmaps("Cleanup End");
2007
2008 g1h->verify_region_sets_optional();
2009
2010 // We need to make this be a "collection" so any collection pause that
2011 // races with it goes around and waits for completeCleanup to finish.
2012 g1h->increment_total_collections();
2013
2014 // Clean out dead classes and update Metaspace sizes.
2015 if (ClassUnloadingWithConcurrentMark) {
2016 ClassLoaderDataGraph::purge();
2017 }
2018 MetaspaceGC::compute_new_size();
2019
2020 // We reclaimed old regions so we should calculate the sizes to make
2021 // sure we update the old gen/space data.
2022 g1h->g1mm()->update_sizes();
2023 g1h->allocation_context_stats().update_after_mark();
2024
2025 g1h->trace_heap_after_concurrent_cycle();
2026 }
2027
2028 void ConcurrentMark::completeCleanup() {
2029 if (has_aborted()) return;
2030
2031 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2032
2033 _cleanup_list.verify_optional();
2034 FreeRegionList tmp_free_list("Tmp Free List");
2035
2036 if (G1ConcRegionFreeingVerbose) {
2037 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2038 "cleanup list has %u entries",
2039 _cleanup_list.length());
2040 }
2041
2042 // No one else should be accessing the _cleanup_list at this point,
2043 // so it is not necessary to take any locks
2044 while (!_cleanup_list.is_empty()) {
2045 HeapRegion* hr = _cleanup_list.remove_region(true /* from_head */);
2046 assert(hr != NULL, "Got NULL from a non-empty list");
2047 hr->par_clear();
2048 tmp_free_list.add_ordered(hr);
2049
2050 // Instead of adding one region at a time to the secondary_free_list,
2051 // we accumulate them in the local list and move them a few at a
2052 // time. This also cuts down on the number of notify_all() calls
2053 // we do during this process. We'll also append the local list when
2054 // _cleanup_list is empty (which means we just removed the last
2055 // region from the _cleanup_list).
2056 if ((tmp_free_list.length() % G1SecondaryFreeListAppendLength == 0) ||
2057 _cleanup_list.is_empty()) {
2058 if (G1ConcRegionFreeingVerbose) {
2059 gclog_or_tty->print_cr("G1ConcRegionFreeing [complete cleanup] : "
2060 "appending %u entries to the secondary_free_list, "
2061 "cleanup list still has %u entries",
2062 tmp_free_list.length(),
2063 _cleanup_list.length());
2064 }
2065
2066 {
2067 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
2068 g1h->secondary_free_list_add(&tmp_free_list);
2069 SecondaryFreeList_lock->notify_all();
2070 }
2071 #ifndef PRODUCT
2072 if (G1StressConcRegionFreeing) {
2073 for (uintx i = 0; i < G1StressConcRegionFreeingDelayMillis; ++i) {
2074 os::sleep(Thread::current(), (jlong) 1, false);
2075 }
2076 }
2077 #endif
2078 }
2079 }
2080 assert(tmp_free_list.is_empty(), "post-condition");
2081 }
2082
2083 // Supporting Object and Oop closures for reference discovery
2084 // and processing in during marking
2085
2086 bool G1CMIsAliveClosure::do_object_b(oop obj) {
2087 HeapWord* addr = (HeapWord*)obj;
2088 return addr != NULL &&
2089 (!_g1->is_in_g1_reserved(addr) || !_g1->is_obj_ill(obj));
2090 }
2091
2092 // 'Keep Alive' oop closure used by both serial parallel reference processing.
2093 // Uses the CMTask associated with a worker thread (for serial reference
2094 // processing the CMTask for worker 0 is used) to preserve (mark) and
2095 // trace referent objects.
2096 //
2097 // Using the CMTask and embedded local queues avoids having the worker
2098 // threads operating on the global mark stack. This reduces the risk
2099 // of overflowing the stack - which we would rather avoid at this late
2100 // state. Also using the tasks' local queues removes the potential
2101 // of the workers interfering with each other that could occur if
2102 // operating on the global stack.
2103
2104 class G1CMKeepAliveAndDrainClosure: public OopClosure {
2105 ConcurrentMark* _cm;
2106 CMTask* _task;
2107 int _ref_counter_limit;
2108 int _ref_counter;
2109 bool _is_serial;
2110 public:
2111 G1CMKeepAliveAndDrainClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2112 _cm(cm), _task(task), _is_serial(is_serial),
2113 _ref_counter_limit(G1RefProcDrainInterval) {
2114 assert(_ref_counter_limit > 0, "sanity");
2115 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2116 _ref_counter = _ref_counter_limit;
2117 }
2118
2119 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
2120 virtual void do_oop( oop* p) { do_oop_work(p); }
2121
2122 template <class T> void do_oop_work(T* p) {
2123 if (!_cm->has_overflown()) {
2124 oop obj = oopDesc::load_decode_heap_oop(p);
2125 if (_cm->verbose_high()) {
2126 gclog_or_tty->print_cr("\t[%u] we're looking at location "
2127 "*" PTR_FORMAT " = " PTR_FORMAT,
2128 _task->worker_id(), p2i(p), p2i((void*) obj));
2129 }
2130
2131 _task->deal_with_reference(obj);
2132 _ref_counter--;
2133
2134 if (_ref_counter == 0) {
2135 // We have dealt with _ref_counter_limit references, pushing them
2136 // and objects reachable from them on to the local stack (and
2137 // possibly the global stack). Call CMTask::do_marking_step() to
2138 // process these entries.
2139 //
2140 // We call CMTask::do_marking_step() in a loop, which we'll exit if
2141 // there's nothing more to do (i.e. we're done with the entries that
2142 // were pushed as a result of the CMTask::deal_with_reference() calls
2143 // above) or we overflow.
2144 //
2145 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2146 // flag while there may still be some work to do. (See the comment at
2147 // the beginning of CMTask::do_marking_step() for those conditions -
2148 // one of which is reaching the specified time target.) It is only
2149 // when CMTask::do_marking_step() returns without setting the
2150 // has_aborted() flag that the marking step has completed.
2151 do {
2152 double mark_step_duration_ms = G1ConcMarkStepDurationMillis;
2153 _task->do_marking_step(mark_step_duration_ms,
2154 false /* do_termination */,
2155 _is_serial);
2156 } while (_task->has_aborted() && !_cm->has_overflown());
2157 _ref_counter = _ref_counter_limit;
2158 }
2159 } else {
2160 if (_cm->verbose_high()) {
2161 gclog_or_tty->print_cr("\t[%u] CM Overflow", _task->worker_id());
2162 }
2163 }
2164 }
2165 };
2166
2167 // 'Drain' oop closure used by both serial and parallel reference processing.
2168 // Uses the CMTask associated with a given worker thread (for serial
2169 // reference processing the CMtask for worker 0 is used). Calls the
2170 // do_marking_step routine, with an unbelievably large timeout value,
2171 // to drain the marking data structures of the remaining entries
2172 // added by the 'keep alive' oop closure above.
2173
2174 class G1CMDrainMarkingStackClosure: public VoidClosure {
2175 ConcurrentMark* _cm;
2176 CMTask* _task;
2177 bool _is_serial;
2178 public:
2179 G1CMDrainMarkingStackClosure(ConcurrentMark* cm, CMTask* task, bool is_serial) :
2180 _cm(cm), _task(task), _is_serial(is_serial) {
2181 assert(!_is_serial || _task->worker_id() == 0, "only task 0 for serial code");
2182 }
2183
2184 void do_void() {
2185 do {
2186 if (_cm->verbose_high()) {
2187 gclog_or_tty->print_cr("\t[%u] Drain: Calling do_marking_step - serial: %s",
2188 _task->worker_id(), BOOL_TO_STR(_is_serial));
2189 }
2190
2191 // We call CMTask::do_marking_step() to completely drain the local
2192 // and global marking stacks of entries pushed by the 'keep alive'
2193 // oop closure (an instance of G1CMKeepAliveAndDrainClosure above).
2194 //
2195 // CMTask::do_marking_step() is called in a loop, which we'll exit
2196 // if there's nothing more to do (i.e. we've completely drained the
2197 // entries that were pushed as a a result of applying the 'keep alive'
2198 // closure to the entries on the discovered ref lists) or we overflow
2199 // the global marking stack.
2200 //
2201 // Note: CMTask::do_marking_step() can set the CMTask::has_aborted()
2202 // flag while there may still be some work to do. (See the comment at
2203 // the beginning of CMTask::do_marking_step() for those conditions -
2204 // one of which is reaching the specified time target.) It is only
2205 // when CMTask::do_marking_step() returns without setting the
2206 // has_aborted() flag that the marking step has completed.
2207
2208 _task->do_marking_step(1000000000.0 /* something very large */,
2209 true /* do_termination */,
2210 _is_serial);
2211 } while (_task->has_aborted() && !_cm->has_overflown());
2212 }
2213 };
2214
2215 // Implementation of AbstractRefProcTaskExecutor for parallel
2216 // reference processing at the end of G1 concurrent marking
2217
2218 class G1CMRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2219 private:
2220 G1CollectedHeap* _g1h;
2221 ConcurrentMark* _cm;
2222 WorkGang* _workers;
2223 uint _active_workers;
2224
2225 public:
2226 G1CMRefProcTaskExecutor(G1CollectedHeap* g1h,
2227 ConcurrentMark* cm,
2228 WorkGang* workers,
2229 uint n_workers) :
2230 _g1h(g1h), _cm(cm),
2231 _workers(workers), _active_workers(n_workers) { }
2232
2233 // Executes the given task using concurrent marking worker threads.
2234 virtual void execute(ProcessTask& task);
2235 virtual void execute(EnqueueTask& task);
2236 };
2237
2238 class G1CMRefProcTaskProxy: public AbstractGangTask {
2239 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2240 ProcessTask& _proc_task;
2241 G1CollectedHeap* _g1h;
2242 ConcurrentMark* _cm;
2243
2244 public:
2245 G1CMRefProcTaskProxy(ProcessTask& proc_task,
2246 G1CollectedHeap* g1h,
2247 ConcurrentMark* cm) :
2248 AbstractGangTask("Process reference objects in parallel"),
2249 _proc_task(proc_task), _g1h(g1h), _cm(cm) {
2250 ReferenceProcessor* rp = _g1h->ref_processor_cm();
2251 assert(rp->processing_is_mt(), "shouldn't be here otherwise");
2252 }
2253
2254 virtual void work(uint worker_id) {
2255 ResourceMark rm;
2256 HandleMark hm;
2257 CMTask* task = _cm->task(worker_id);
2258 G1CMIsAliveClosure g1_is_alive(_g1h);
2259 G1CMKeepAliveAndDrainClosure g1_par_keep_alive(_cm, task, false /* is_serial */);
2260 G1CMDrainMarkingStackClosure g1_par_drain(_cm, task, false /* is_serial */);
2261
2262 _proc_task.work(worker_id, g1_is_alive, g1_par_keep_alive, g1_par_drain);
2263 }
2264 };
2265
2266 void G1CMRefProcTaskExecutor::execute(ProcessTask& proc_task) {
2267 assert(_workers != NULL, "Need parallel worker threads.");
2268 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2269
2270 G1CMRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _cm);
2271
2272 // We need to reset the concurrency level before each
2273 // proxy task execution, so that the termination protocol
2274 // and overflow handling in CMTask::do_marking_step() knows
2275 // how many workers to wait for.
2276 _cm->set_concurrency(_active_workers);
2277 _workers->run_task(&proc_task_proxy);
2278 }
2279
2280 class G1CMRefEnqueueTaskProxy: public AbstractGangTask {
2281 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
2282 EnqueueTask& _enq_task;
2283
2284 public:
2285 G1CMRefEnqueueTaskProxy(EnqueueTask& enq_task) :
2286 AbstractGangTask("Enqueue reference objects in parallel"),
2287 _enq_task(enq_task) { }
2288
2289 virtual void work(uint worker_id) {
2290 _enq_task.work(worker_id);
2291 }
2292 };
2293
2294 void G1CMRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
2295 assert(_workers != NULL, "Need parallel worker threads.");
2296 assert(_g1h->ref_processor_cm()->processing_is_mt(), "processing is not MT");
2297
2298 G1CMRefEnqueueTaskProxy enq_task_proxy(enq_task);
2299
2300 // Not strictly necessary but...
2301 //
2302 // We need to reset the concurrency level before each
2303 // proxy task execution, so that the termination protocol
2304 // and overflow handling in CMTask::do_marking_step() knows
2305 // how many workers to wait for.
2306 _cm->set_concurrency(_active_workers);
2307 _workers->run_task(&enq_task_proxy);
2308 }
2309
2310 void ConcurrentMark::weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes) {
2311 G1CollectedHeap::heap()->parallel_cleaning(is_alive, true, true, purged_classes);
2312 }
2313
2314 void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
2315 if (has_overflown()) {
2316 // Skip processing the discovered references if we have
2317 // overflown the global marking stack. Reference objects
2318 // only get discovered once so it is OK to not
2319 // de-populate the discovered reference lists. We could have,
2320 // but the only benefit would be that, when marking restarts,
2321 // less reference objects are discovered.
2322 return;
2323 }
2324
2325 ResourceMark rm;
2326 HandleMark hm;
2327
2328 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2329
2330 // Is alive closure.
2331 G1CMIsAliveClosure g1_is_alive(g1h);
2332
2333 // Inner scope to exclude the cleaning of the string and symbol
2334 // tables from the displayed time.
2335 {
2336 G1CMTraceTime t("GC ref-proc", G1Log::finer());
2337
2338 ReferenceProcessor* rp = g1h->ref_processor_cm();
2339
2340 // See the comment in G1CollectedHeap::ref_processing_init()
2341 // about how reference processing currently works in G1.
2342
2343 // Set the soft reference policy
2344 rp->setup_policy(clear_all_soft_refs);
2345 assert(_markStack.isEmpty(), "mark stack should be empty");
2346
2347 // Instances of the 'Keep Alive' and 'Complete GC' closures used
2348 // in serial reference processing. Note these closures are also
2349 // used for serially processing (by the the current thread) the
2350 // JNI references during parallel reference processing.
2351 //
2352 // These closures do not need to synchronize with the worker
2353 // threads involved in parallel reference processing as these
2354 // instances are executed serially by the current thread (e.g.
2355 // reference processing is not multi-threaded and is thus
2356 // performed by the current thread instead of a gang worker).
2357 //
2358 // The gang tasks involved in parallel reference processing create
2359 // their own instances of these closures, which do their own
2360 // synchronization among themselves.
2361 G1CMKeepAliveAndDrainClosure g1_keep_alive(this, task(0), true /* is_serial */);
2362 G1CMDrainMarkingStackClosure g1_drain_mark_stack(this, task(0), true /* is_serial */);
2363
2364 // We need at least one active thread. If reference processing
2365 // is not multi-threaded we use the current (VMThread) thread,
2366 // otherwise we use the work gang from the G1CollectedHeap and
2367 // we utilize all the worker threads we can.
2368 bool processing_is_mt = rp->processing_is_mt();
2369 uint active_workers = (processing_is_mt ? g1h->workers()->active_workers() : 1U);
2370 active_workers = MAX2(MIN2(active_workers, _max_worker_id), 1U);
2371
2372 // Parallel processing task executor.
2373 G1CMRefProcTaskExecutor par_task_executor(g1h, this,
2374 g1h->workers(), active_workers);
2375 AbstractRefProcTaskExecutor* executor = (processing_is_mt ? &par_task_executor : NULL);
2376
2377 // Set the concurrency level. The phase was already set prior to
2378 // executing the remark task.
2379 set_concurrency(active_workers);
2380
2381 // Set the degree of MT processing here. If the discovery was done MT,
2382 // the number of threads involved during discovery could differ from
2383 // the number of active workers. This is OK as long as the discovered
2384 // Reference lists are balanced (see balance_all_queues() and balance_queues()).
2385 rp->set_active_mt_degree(active_workers);
2386
2387 // Process the weak references.
2388 const ReferenceProcessorStats& stats =
2389 rp->process_discovered_references(&g1_is_alive,
2390 &g1_keep_alive,
2391 &g1_drain_mark_stack,
2392 executor,
2393 g1h->gc_timer_cm());
2394 g1h->gc_tracer_cm()->report_gc_reference_stats(stats);
2395
2396 // The do_oop work routines of the keep_alive and drain_marking_stack
2397 // oop closures will set the has_overflown flag if we overflow the
2398 // global marking stack.
2399
2400 assert(_markStack.overflow() || _markStack.isEmpty(),
2401 "mark stack should be empty (unless it overflowed)");
2402
2403 if (_markStack.overflow()) {
2404 // This should have been done already when we tried to push an
2405 // entry on to the global mark stack. But let's do it again.
2406 set_has_overflown();
2407 }
2408
2409 assert(rp->num_q() == active_workers, "why not");
2410
2411 rp->enqueue_discovered_references(executor);
2412
2413 rp->verify_no_references_recorded();
2414 assert(!rp->discovery_enabled(), "Post condition");
2415 }
2416
2417 if (has_overflown()) {
2418 // We can not trust g1_is_alive if the marking stack overflowed
2419 return;
2420 }
2421
2422 assert(_markStack.isEmpty(), "Marking should have completed");
2423
2424 // Unload Klasses, String, Symbols, Code Cache, etc.
2425 {
2426 G1CMTraceTime trace("Unloading", G1Log::finer());
2427
2428 if (ClassUnloadingWithConcurrentMark) {
2429 bool purged_classes;
2430
2431 {
2432 G1CMTraceTime trace("System Dictionary Unloading", G1Log::finest());
2433 purged_classes = SystemDictionary::do_unloading(&g1_is_alive, false /* Defer klass cleaning */);
2434 }
2435
2436 {
2437 G1CMTraceTime trace("Parallel Unloading", G1Log::finest());
2438 weakRefsWorkParallelPart(&g1_is_alive, purged_classes);
2439 }
2440 }
2441
2442 if (G1StringDedup::is_enabled()) {
2443 G1CMTraceTime trace("String Deduplication Unlink", G1Log::finest());
2444 G1StringDedup::unlink(&g1_is_alive);
2445 }
2446 }
2447 }
2448
2449 void ConcurrentMark::swapMarkBitMaps() {
2450 CMBitMapRO* temp = _prevMarkBitMap;
2451 _prevMarkBitMap = (CMBitMapRO*)_nextMarkBitMap;
2452 _nextMarkBitMap = (CMBitMap*) temp;
2453 }
2454
2455 // Closure for marking entries in SATB buffers.
2456 class CMSATBBufferClosure : public SATBBufferClosure {
2457 private:
2458 CMTask* _task;
2459 G1CollectedHeap* _g1h;
2460
2461 // This is very similar to CMTask::deal_with_reference, but with
2462 // more relaxed requirements for the argument, so this must be more
2463 // circumspect about treating the argument as an object.
2464 void do_entry(void* entry) const {
2465 _task->increment_refs_reached();
2466 HeapRegion* hr = _g1h->heap_region_containing_raw(entry);
2467 if (entry < hr->next_top_at_mark_start()) {
2468 // Until we get here, we don't know whether entry refers to a valid
2469 // object; it could instead have been a stale reference.
2470 oop obj = static_cast<oop>(entry);
2471 assert(obj->is_oop(true /* ignore mark word */),
2472 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(obj)));
2473 _task->make_reference_grey(obj, hr);
2474 }
2475 }
2476
2477 public:
2478 CMSATBBufferClosure(CMTask* task, G1CollectedHeap* g1h)
2479 : _task(task), _g1h(g1h) { }
2480
2481 virtual void do_buffer(void** buffer, size_t size) {
2482 for (size_t i = 0; i < size; ++i) {
2483 do_entry(buffer[i]);
2484 }
2485 }
2486 };
2487
2488 class G1RemarkThreadsClosure : public ThreadClosure {
2489 CMSATBBufferClosure _cm_satb_cl;
2490 G1CMOopClosure _cm_cl;
2491 MarkingCodeBlobClosure _code_cl;
2492 int _thread_parity;
2493
2494 public:
2495 G1RemarkThreadsClosure(G1CollectedHeap* g1h, CMTask* task) :
2496 _cm_satb_cl(task, g1h),
2497 _cm_cl(g1h, g1h->concurrent_mark(), task),
2498 _code_cl(&_cm_cl, !CodeBlobToOopClosure::FixRelocations),
2499 _thread_parity(Threads::thread_claim_parity()) {}
2500
2501 void do_thread(Thread* thread) {
2502 if (thread->is_Java_thread()) {
2503 if (thread->claim_oops_do(true, _thread_parity)) {
2504 JavaThread* jt = (JavaThread*)thread;
2505
2506 // In theory it should not be neccessary to explicitly walk the nmethods to find roots for concurrent marking
2507 // however the liveness of oops reachable from nmethods have very complex lifecycles:
2508 // * Alive if on the stack of an executing method
2509 // * Weakly reachable otherwise
2510 // Some objects reachable from nmethods, such as the class loader (or klass_holder) of the receiver should be
2511 // live by the SATB invariant but other oops recorded in nmethods may behave differently.
2512 jt->nmethods_do(&_code_cl);
2513
2514 jt->satb_mark_queue().apply_closure_and_empty(&_cm_satb_cl);
2515 }
2516 } else if (thread->is_VM_thread()) {
2517 if (thread->claim_oops_do(true, _thread_parity)) {
2518 JavaThread::satb_mark_queue_set().shared_satb_queue()->apply_closure_and_empty(&_cm_satb_cl);
2519 }
2520 }
2521 }
2522 };
2523
2524 class CMRemarkTask: public AbstractGangTask {
2525 private:
2526 ConcurrentMark* _cm;
2527 public:
2528 void work(uint worker_id) {
2529 // Since all available tasks are actually started, we should
2530 // only proceed if we're supposed to be active.
2531 if (worker_id < _cm->active_tasks()) {
2532 CMTask* task = _cm->task(worker_id);
2533 task->record_start_time();
2534 {
2535 ResourceMark rm;
2536 HandleMark hm;
2537
2538 G1RemarkThreadsClosure threads_f(G1CollectedHeap::heap(), task);
2539 Threads::threads_do(&threads_f);
2540 }
2541
2542 do {
2543 task->do_marking_step(1000000000.0 /* something very large */,
2544 true /* do_termination */,
2545 false /* is_serial */);
2546 } while (task->has_aborted() && !_cm->has_overflown());
2547 // If we overflow, then we do not want to restart. We instead
2548 // want to abort remark and do concurrent marking again.
2549 task->record_end_time();
2550 }
2551 }
2552
2553 CMRemarkTask(ConcurrentMark* cm, uint active_workers) :
2554 AbstractGangTask("Par Remark"), _cm(cm) {
2555 _cm->terminator()->reset_for_reuse(active_workers);
2556 }
2557 };
2558
2559 void ConcurrentMark::checkpointRootsFinalWork() {
2560 ResourceMark rm;
2561 HandleMark hm;
2562 G1CollectedHeap* g1h = G1CollectedHeap::heap();
2563
2564 G1CMTraceTime trace("Finalize Marking", G1Log::finer());
2565
2566 g1h->ensure_parsability(false);
2567
2568 // this is remark, so we'll use up all active threads
2569 uint active_workers = g1h->workers()->active_workers();
2570 set_concurrency_and_phase(active_workers, false /* concurrent */);
2571 // Leave _parallel_marking_threads at it's
2572 // value originally calculated in the ConcurrentMark
2573 // constructor and pass values of the active workers
2574 // through the gang in the task.
2575
2576 {
2577 StrongRootsScope srs(active_workers);
2578
2579 CMRemarkTask remarkTask(this, active_workers);
2580 // We will start all available threads, even if we decide that the
2581 // active_workers will be fewer. The extra ones will just bail out
2582 // immediately.
2583 g1h->workers()->run_task(&remarkTask);
2584 }
2585
2586 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2587 guarantee(has_overflown() ||
2588 satb_mq_set.completed_buffers_num() == 0,
2589 err_msg("Invariant: has_overflown = %s, num buffers = %d",
2590 BOOL_TO_STR(has_overflown()),
2591 satb_mq_set.completed_buffers_num()));
2592
2593 print_stats();
2594 }
2595
2596 void ConcurrentMark::clearRangePrevBitmap(MemRegion mr) {
2597 // Note we are overriding the read-only view of the prev map here, via
2598 // the cast.
2599 ((CMBitMap*)_prevMarkBitMap)->clearRange(mr);
2600 }
2601
2602 void ConcurrentMark::clearRangeNextBitmap(MemRegion mr) {
2603 _nextMarkBitMap->clearRange(mr);
2604 }
2605
2606 HeapRegion*
2607 ConcurrentMark::claim_region(uint worker_id) {
2608 // "checkpoint" the finger
2609 HeapWord* finger = _finger;
2610
2611 // _heap_end will not change underneath our feet; it only changes at
2612 // yield points.
2613 while (finger < _heap_end) {
2614 assert(_g1h->is_in_g1_reserved(finger), "invariant");
2615
2616 // Note on how this code handles humongous regions. In the
2617 // normal case the finger will reach the start of a "starts
2618 // humongous" (SH) region. Its end will either be the end of the
2619 // last "continues humongous" (CH) region in the sequence, or the
2620 // standard end of the SH region (if the SH is the only region in
2621 // the sequence). That way claim_region() will skip over the CH
2622 // regions. However, there is a subtle race between a CM thread
2623 // executing this method and a mutator thread doing a humongous
2624 // object allocation. The two are not mutually exclusive as the CM
2625 // thread does not need to hold the Heap_lock when it gets
2626 // here. So there is a chance that claim_region() will come across
2627 // a free region that's in the progress of becoming a SH or a CH
2628 // region. In the former case, it will either
2629 // a) Miss the update to the region's end, in which case it will
2630 // visit every subsequent CH region, will find their bitmaps
2631 // empty, and do nothing, or
2632 // b) Will observe the update of the region's end (in which case
2633 // it will skip the subsequent CH regions).
2634 // If it comes across a region that suddenly becomes CH, the
2635 // scenario will be similar to b). So, the race between
2636 // claim_region() and a humongous object allocation might force us
2637 // to do a bit of unnecessary work (due to some unnecessary bitmap
2638 // iterations) but it should not introduce and correctness issues.
2639 HeapRegion* curr_region = _g1h->heap_region_containing_raw(finger);
2640
2641 // Above heap_region_containing_raw may return NULL as we always scan claim
2642 // until the end of the heap. In this case, just jump to the next region.
2643 HeapWord* end = curr_region != NULL ? curr_region->end() : finger + HeapRegion::GrainWords;
2644
2645 // Is the gap between reading the finger and doing the CAS too long?
2646 HeapWord* res = (HeapWord*) Atomic::cmpxchg_ptr(end, &_finger, finger);
2647 if (res == finger && curr_region != NULL) {
2648 // we succeeded
2649 HeapWord* bottom = curr_region->bottom();
2650 HeapWord* limit = curr_region->next_top_at_mark_start();
2651
2652 if (verbose_low()) {
2653 gclog_or_tty->print_cr("[%u] curr_region = " PTR_FORMAT " "
2654 "[" PTR_FORMAT ", " PTR_FORMAT "), "
2655 "limit = " PTR_FORMAT,
2656 worker_id, p2i(curr_region), p2i(bottom), p2i(end), p2i(limit));
2657 }
2658
2659 // notice that _finger == end cannot be guaranteed here since,
2660 // someone else might have moved the finger even further
2661 assert(_finger >= end, "the finger should have moved forward");
2662
2663 if (verbose_low()) {
2664 gclog_or_tty->print_cr("[%u] we were successful with region = "
2665 PTR_FORMAT, worker_id, p2i(curr_region));
2666 }
2667
2668 if (limit > bottom) {
2669 if (verbose_low()) {
2670 gclog_or_tty->print_cr("[%u] region " PTR_FORMAT " is not empty, "
2671 "returning it ", worker_id, p2i(curr_region));
2672 }
2673 return curr_region;
2674 } else {
2675 assert(limit == bottom,
2676 "the region limit should be at bottom");
2677 if (verbose_low()) {
2678 gclog_or_tty->print_cr("[%u] region " PTR_FORMAT " is empty, "
2679 "returning NULL", worker_id, p2i(curr_region));
2680 }
2681 // we return NULL and the caller should try calling
2682 // claim_region() again.
2683 return NULL;
2684 }
2685 } else {
2686 assert(_finger > finger, "the finger should have moved forward");
2687 if (verbose_low()) {
2688 if (curr_region == NULL) {
2689 gclog_or_tty->print_cr("[%u] found uncommitted region, moving finger, "
2690 "global finger = " PTR_FORMAT ", "
2691 "our finger = " PTR_FORMAT,
2692 worker_id, p2i(_finger), p2i(finger));
2693 } else {
2694 gclog_or_tty->print_cr("[%u] somebody else moved the finger, "
2695 "global finger = " PTR_FORMAT ", "
2696 "our finger = " PTR_FORMAT,
2697 worker_id, p2i(_finger), p2i(finger));
2698 }
2699 }
2700
2701 // read it again
2702 finger = _finger;
2703 }
2704 }
2705
2706 return NULL;
2707 }
2708
2709 #ifndef PRODUCT
2710 class VerifyNoCSetOops VALUE_OBJ_CLASS_SPEC {
2711 private:
2712 G1CollectedHeap* _g1h;
2713 const char* _phase;
2714 int _info;
2715
2716 public:
2717 VerifyNoCSetOops(const char* phase, int info = -1) :
2718 _g1h(G1CollectedHeap::heap()),
2719 _phase(phase),
2720 _info(info)
2721 { }
2722
2723 void operator()(oop obj) const {
2724 guarantee(obj->is_oop(),
2725 err_msg("Non-oop " PTR_FORMAT ", phase: %s, info: %d",
2726 p2i(obj), _phase, _info));
2727 guarantee(!_g1h->obj_in_cs(obj),
2728 err_msg("obj: " PTR_FORMAT " in CSet, phase: %s, info: %d",
2729 p2i(obj), _phase, _info));
2730 }
2731 };
2732
2733 void ConcurrentMark::verify_no_cset_oops() {
2734 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
2735 if (!G1CollectedHeap::heap()->collector_state()->mark_in_progress()) {
2736 return;
2737 }
2738
2739 // Verify entries on the global mark stack
2740 _markStack.iterate(VerifyNoCSetOops("Stack"));
2741
2742 // Verify entries on the task queues
2743 for (uint i = 0; i < _max_worker_id; ++i) {
2744 CMTaskQueue* queue = _task_queues->queue(i);
2745 queue->iterate(VerifyNoCSetOops("Queue", i));
2746 }
2747
2748 // Verify the global finger
2749 HeapWord* global_finger = finger();
2750 if (global_finger != NULL && global_finger < _heap_end) {
2751 // The global finger always points to a heap region boundary. We
2752 // use heap_region_containing_raw() to get the containing region
2753 // given that the global finger could be pointing to a free region
2754 // which subsequently becomes continues humongous. If that
2755 // happens, heap_region_containing() will return the bottom of the
2756 // corresponding starts humongous region and the check below will
2757 // not hold any more.
2758 // Since we always iterate over all regions, we might get a NULL HeapRegion
2759 // here.
2760 HeapRegion* global_hr = _g1h->heap_region_containing_raw(global_finger);
2761 guarantee(global_hr == NULL || global_finger == global_hr->bottom(),
2762 err_msg("global finger: " PTR_FORMAT " region: " HR_FORMAT,
2763 p2i(global_finger), HR_FORMAT_PARAMS(global_hr)));
2764 }
2765
2766 // Verify the task fingers
2767 assert(parallel_marking_threads() <= _max_worker_id, "sanity");
2768 for (uint i = 0; i < parallel_marking_threads(); ++i) {
2769 CMTask* task = _tasks[i];
2770 HeapWord* task_finger = task->finger();
2771 if (task_finger != NULL && task_finger < _heap_end) {
2772 // See above note on the global finger verification.
2773 HeapRegion* task_hr = _g1h->heap_region_containing_raw(task_finger);
2774 guarantee(task_hr == NULL || task_finger == task_hr->bottom() ||
2775 !task_hr->in_collection_set(),
2776 err_msg("task finger: " PTR_FORMAT " region: " HR_FORMAT,
2777 p2i(task_finger), HR_FORMAT_PARAMS(task_hr)));
2778 }
2779 }
2780 }
2781 #endif // PRODUCT
2782
2783 // Aggregate the counting data that was constructed concurrently
2784 // with marking.
2785 class AggregateCountDataHRClosure: public HeapRegionClosure {
2786 G1CollectedHeap* _g1h;
2787 ConcurrentMark* _cm;
2788 CardTableModRefBS* _ct_bs;
2789 BitMap* _cm_card_bm;
2790 uint _max_worker_id;
2791
2792 public:
2793 AggregateCountDataHRClosure(G1CollectedHeap* g1h,
2794 BitMap* cm_card_bm,
2795 uint max_worker_id) :
2796 _g1h(g1h), _cm(g1h->concurrent_mark()),
2797 _ct_bs(barrier_set_cast<CardTableModRefBS>(g1h->barrier_set())),
2798 _cm_card_bm(cm_card_bm), _max_worker_id(max_worker_id) { }
2799
2800 bool doHeapRegion(HeapRegion* hr) {
2801 if (hr->is_continues_humongous()) {
2802 // We will ignore these here and process them when their
2803 // associated "starts humongous" region is processed.
2804 // Note that we cannot rely on their associated
2805 // "starts humongous" region to have their bit set to 1
2806 // since, due to the region chunking in the parallel region
2807 // iteration, a "continues humongous" region might be visited
2808 // before its associated "starts humongous".
2809 return false;
2810 }
2811
2812 HeapWord* start = hr->bottom();
2813 HeapWord* limit = hr->next_top_at_mark_start();
2814 HeapWord* end = hr->end();
2815
2816 assert(start <= limit && limit <= hr->top() && hr->top() <= hr->end(),
2817 err_msg("Preconditions not met - "
2818 "start: " PTR_FORMAT ", limit: " PTR_FORMAT ", "
2819 "top: " PTR_FORMAT ", end: " PTR_FORMAT,
2820 p2i(start), p2i(limit), p2i(hr->top()), p2i(hr->end())));
2821
2822 assert(hr->next_marked_bytes() == 0, "Precondition");
2823
2824 if (start == limit) {
2825 // NTAMS of this region has not been set so nothing to do.
2826 return false;
2827 }
2828
2829 // 'start' should be in the heap.
2830 assert(_g1h->is_in_g1_reserved(start) && _ct_bs->is_card_aligned(start), "sanity");
2831 // 'end' *may* be just beyond the end of the heap (if hr is the last region)
2832 assert(!_g1h->is_in_g1_reserved(end) || _ct_bs->is_card_aligned(end), "sanity");
2833
2834 BitMap::idx_t start_idx = _cm->card_bitmap_index_for(start);
2835 BitMap::idx_t limit_idx = _cm->card_bitmap_index_for(limit);
2836 BitMap::idx_t end_idx = _cm->card_bitmap_index_for(end);
2837
2838 // If ntams is not card aligned then we bump card bitmap index
2839 // for limit so that we get the all the cards spanned by
2840 // the object ending at ntams.
2841 // Note: if this is the last region in the heap then ntams
2842 // could be actually just beyond the end of the the heap;
2843 // limit_idx will then correspond to a (non-existent) card
2844 // that is also outside the heap.
2845 if (_g1h->is_in_g1_reserved(limit) && !_ct_bs->is_card_aligned(limit)) {
2846 limit_idx += 1;
2847 }
2848
2849 assert(limit_idx <= end_idx, "or else use atomics");
2850
2851 // Aggregate the "stripe" in the count data associated with hr.
2852 uint hrm_index = hr->hrm_index();
2853 size_t marked_bytes = 0;
2854
2855 for (uint i = 0; i < _max_worker_id; i += 1) {
2856 size_t* marked_bytes_array = _cm->count_marked_bytes_array_for(i);
2857 BitMap* task_card_bm = _cm->count_card_bitmap_for(i);
2858
2859 // Fetch the marked_bytes in this region for task i and
2860 // add it to the running total for this region.
2861 marked_bytes += marked_bytes_array[hrm_index];
2862
2863 // Now union the bitmaps[0,max_worker_id)[start_idx..limit_idx)
2864 // into the global card bitmap.
2865 BitMap::idx_t scan_idx = task_card_bm->get_next_one_offset(start_idx, limit_idx);
2866
2867 while (scan_idx < limit_idx) {
2868 assert(task_card_bm->at(scan_idx) == true, "should be");
2869 _cm_card_bm->set_bit(scan_idx);
2870 assert(_cm_card_bm->at(scan_idx) == true, "should be");
2871
2872 // BitMap::get_next_one_offset() can handle the case when
2873 // its left_offset parameter is greater than its right_offset
2874 // parameter. It does, however, have an early exit if
2875 // left_offset == right_offset. So let's limit the value
2876 // passed in for left offset here.
2877 BitMap::idx_t next_idx = MIN2(scan_idx + 1, limit_idx);
2878 scan_idx = task_card_bm->get_next_one_offset(next_idx, limit_idx);
2879 }
2880 }
2881
2882 // Update the marked bytes for this region.
2883 hr->add_to_marked_bytes(marked_bytes);
2884
2885 // Next heap region
2886 return false;
2887 }
2888 };
2889
2890 class G1AggregateCountDataTask: public AbstractGangTask {
2891 protected:
2892 G1CollectedHeap* _g1h;
2893 ConcurrentMark* _cm;
2894 BitMap* _cm_card_bm;
2895 uint _max_worker_id;
2896 uint _active_workers;
2897 HeapRegionClaimer _hrclaimer;
2898
2899 public:
2900 G1AggregateCountDataTask(G1CollectedHeap* g1h,
2901 ConcurrentMark* cm,
2902 BitMap* cm_card_bm,
2903 uint max_worker_id,
2904 uint n_workers) :
2905 AbstractGangTask("Count Aggregation"),
2906 _g1h(g1h), _cm(cm), _cm_card_bm(cm_card_bm),
2907 _max_worker_id(max_worker_id),
2908 _active_workers(n_workers),
2909 _hrclaimer(_active_workers) {
2910 }
2911
2912 void work(uint worker_id) {
2913 AggregateCountDataHRClosure cl(_g1h, _cm_card_bm, _max_worker_id);
2914
2915 _g1h->heap_region_par_iterate(&cl, worker_id, &_hrclaimer);
2916 }
2917 };
2918
2919
2920 void ConcurrentMark::aggregate_count_data() {
2921 uint n_workers = _g1h->workers()->active_workers();
2922
2923 G1AggregateCountDataTask g1_par_agg_task(_g1h, this, &_card_bm,
2924 _max_worker_id, n_workers);
2925
2926 _g1h->workers()->run_task(&g1_par_agg_task);
2927 }
2928
2929 // Clear the per-worker arrays used to store the per-region counting data
2930 void ConcurrentMark::clear_all_count_data() {
2931 // Clear the global card bitmap - it will be filled during
2932 // liveness count aggregation (during remark) and the
2933 // final counting task.
2934 _card_bm.clear();
2935
2936 // Clear the global region bitmap - it will be filled as part
2937 // of the final counting task.
2938 _region_bm.clear();
2939
2940 uint max_regions = _g1h->max_regions();
2941 assert(_max_worker_id > 0, "uninitialized");
2942
2943 for (uint i = 0; i < _max_worker_id; i += 1) {
2944 BitMap* task_card_bm = count_card_bitmap_for(i);
2945 size_t* marked_bytes_array = count_marked_bytes_array_for(i);
2946
2947 assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
2948 assert(marked_bytes_array != NULL, "uninitialized");
2949
2950 memset(marked_bytes_array, 0, (size_t) max_regions * sizeof(size_t));
2951 task_card_bm->clear();
2952 }
2953 }
2954
2955 void ConcurrentMark::print_stats() {
2956 if (verbose_stats()) {
2957 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2958 for (size_t i = 0; i < _active_tasks; ++i) {
2959 _tasks[i]->print_stats();
2960 gclog_or_tty->print_cr("---------------------------------------------------------------------");
2961 }
2962 }
2963 }
2964
2965 // abandon current marking iteration due to a Full GC
2966 void ConcurrentMark::abort() {
2967 if (!cmThread()->during_cycle() || _has_aborted) {
2968 // We haven't started a concurrent cycle or we have already aborted it. No need to do anything.
2969 return;
2970 }
2971 // Clear all marks in the next bitmap for the next marking cycle. This will allow us to skip the next
2972 // concurrent bitmap clearing.
2973 _nextMarkBitMap->clearAll();
2974
2975 // Note we cannot clear the previous marking bitmap here
2976 // since VerifyDuringGC verifies the objects marked during
2977 // a full GC against the previous bitmap.
2978
2979 // Clear the liveness counting data
2980 clear_all_count_data();
2981 // Empty mark stack
2982 reset_marking_state();
2983 for (uint i = 0; i < _max_worker_id; ++i) {
2984 _tasks[i]->clear_region_fields();
2985 }
2986 _first_overflow_barrier_sync.abort();
2987 _second_overflow_barrier_sync.abort();
2988 _has_aborted = true;
2989
2990 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
2991 satb_mq_set.abandon_partial_marking();
2992 // This can be called either during or outside marking, we'll read
2993 // the expected_active value from the SATB queue set.
2994 satb_mq_set.set_active_all_threads(
2995 false, /* new active value */
2996 satb_mq_set.is_active() /* expected_active */);
2997
2998 _g1h->trace_heap_after_concurrent_cycle();
2999 _g1h->register_concurrent_cycle_end();
3000 }
3001
3002 static void print_ms_time_info(const char* prefix, const char* name,
3003 NumberSeq& ns) {
3004 gclog_or_tty->print_cr("%s%5d %12s: total time = %8.2f s (avg = %8.2f ms).",
3005 prefix, ns.num(), name, ns.sum()/1000.0, ns.avg());
3006 if (ns.num() > 0) {
3007 gclog_or_tty->print_cr("%s [std. dev = %8.2f ms, max = %8.2f ms]",
3008 prefix, ns.sd(), ns.maximum());
3009 }
3010 }
3011
3012 void ConcurrentMark::print_summary_info() {
3013 gclog_or_tty->print_cr(" Concurrent marking:");
3014 print_ms_time_info(" ", "init marks", _init_times);
3015 print_ms_time_info(" ", "remarks", _remark_times);
3016 {
3017 print_ms_time_info(" ", "final marks", _remark_mark_times);
3018 print_ms_time_info(" ", "weak refs", _remark_weak_ref_times);
3019
3020 }
3021 print_ms_time_info(" ", "cleanups", _cleanup_times);
3022 gclog_or_tty->print_cr(" Final counting total time = %8.2f s (avg = %8.2f ms).",
3023 _total_counting_time,
3024 (_cleanup_times.num() > 0 ? _total_counting_time * 1000.0 /
3025 (double)_cleanup_times.num()
3026 : 0.0));
3027 if (G1ScrubRemSets) {
3028 gclog_or_tty->print_cr(" RS scrub total time = %8.2f s (avg = %8.2f ms).",
3029 _total_rs_scrub_time,
3030 (_cleanup_times.num() > 0 ? _total_rs_scrub_time * 1000.0 /
3031 (double)_cleanup_times.num()
3032 : 0.0));
3033 }
3034 gclog_or_tty->print_cr(" Total stop_world time = %8.2f s.",
3035 (_init_times.sum() + _remark_times.sum() +
3036 _cleanup_times.sum())/1000.0);
3037 gclog_or_tty->print_cr(" Total concurrent time = %8.2f s "
3038 "(%8.2f s marking).",
3039 cmThread()->vtime_accum(),
3040 cmThread()->vtime_mark_accum());
3041 }
3042
3043 void ConcurrentMark::print_worker_threads_on(outputStream* st) const {
3044 _parallel_workers->print_worker_threads_on(st);
3045 }
3046
3047 void ConcurrentMark::print_on_error(outputStream* st) const {
3048 st->print_cr("Marking Bits (Prev, Next): (CMBitMap*) " PTR_FORMAT ", (CMBitMap*) " PTR_FORMAT,
3049 p2i(_prevMarkBitMap), p2i(_nextMarkBitMap));
3050 _prevMarkBitMap->print_on_error(st, " Prev Bits: ");
3051 _nextMarkBitMap->print_on_error(st, " Next Bits: ");
3052 }
3053
3054 // We take a break if someone is trying to stop the world.
3055 bool ConcurrentMark::do_yield_check(uint worker_id) {
3056 if (SuspendibleThreadSet::should_yield()) {
3057 if (worker_id == 0) {
3058 _g1h->g1_policy()->record_concurrent_pause();
3059 }
3060 SuspendibleThreadSet::yield();
3061 return true;
3062 } else {
3063 return false;
3064 }
3065 }
3066
3067 #ifndef PRODUCT
3068 // for debugging purposes
3069 void ConcurrentMark::print_finger() {
3070 gclog_or_tty->print_cr("heap [" PTR_FORMAT ", " PTR_FORMAT "), global finger = " PTR_FORMAT,
3071 p2i(_heap_start), p2i(_heap_end), p2i(_finger));
3072 for (uint i = 0; i < _max_worker_id; ++i) {
3073 gclog_or_tty->print(" %u: " PTR_FORMAT, i, p2i(_tasks[i]->finger()));
3074 }
3075 gclog_or_tty->cr();
3076 }
3077 #endif
3078
3079 // Closure for iteration over bitmaps
3080 class CMBitMapClosure : public BitMapClosure {
3081 private:
3082 // the bitmap that is being iterated over
3083 CMBitMap* _nextMarkBitMap;
3084 ConcurrentMark* _cm;
3085 CMTask* _task;
3086
3087 public:
3088 CMBitMapClosure(CMTask *task, ConcurrentMark* cm, CMBitMap* nextMarkBitMap) :
3089 _task(task), _cm(cm), _nextMarkBitMap(nextMarkBitMap) { }
3090
3091 bool do_bit(size_t offset) {
3092 HeapWord* addr = _nextMarkBitMap->offsetToHeapWord(offset);
3093 assert(_nextMarkBitMap->isMarked(addr), "invariant");
3094 assert( addr < _cm->finger(), "invariant");
3095
3096 statsOnly( _task->increase_objs_found_on_bitmap() );
3097 assert(addr >= _task->finger(), "invariant");
3098
3099 // We move that task's local finger along.
3100 _task->move_finger_to(addr);
3101
3102 _task->scan_object(oop(addr));
3103 // we only partially drain the local queue and global stack
3104 _task->drain_local_queue(true);
3105 _task->drain_global_stack(true);
3106
3107 // if the has_aborted flag has been raised, we need to bail out of
3108 // the iteration
3109 return !_task->has_aborted();
3110 }
3111 };
3112
3113 G1CMOopClosure::G1CMOopClosure(G1CollectedHeap* g1h,
3114 ConcurrentMark* cm,
3115 CMTask* task)
3116 : _g1h(g1h), _cm(cm), _task(task) {
3117 assert(_ref_processor == NULL, "should be initialized to NULL");
3118
3119 if (G1UseConcMarkReferenceProcessing) {
3120 _ref_processor = g1h->ref_processor_cm();
3121 assert(_ref_processor != NULL, "should not be NULL");
3122 }
3123 }
3124
3125 void CMTask::setup_for_region(HeapRegion* hr) {
3126 assert(hr != NULL,
3127 "claim_region() should have filtered out NULL regions");
3128 assert(!hr->is_continues_humongous(),
3129 "claim_region() should have filtered out continues humongous regions");
3130
3131 if (_cm->verbose_low()) {
3132 gclog_or_tty->print_cr("[%u] setting up for region " PTR_FORMAT,
3133 _worker_id, p2i(hr));
3134 }
3135
3136 _curr_region = hr;
3137 _finger = hr->bottom();
3138 update_region_limit();
3139 }
3140
3141 void CMTask::update_region_limit() {
3142 HeapRegion* hr = _curr_region;
3143 HeapWord* bottom = hr->bottom();
3144 HeapWord* limit = hr->next_top_at_mark_start();
3145
3146 if (limit == bottom) {
3147 if (_cm->verbose_low()) {
3148 gclog_or_tty->print_cr("[%u] found an empty region "
3149 "[" PTR_FORMAT ", " PTR_FORMAT ")",
3150 _worker_id, p2i(bottom), p2i(limit));
3151 }
3152 // The region was collected underneath our feet.
3153 // We set the finger to bottom to ensure that the bitmap
3154 // iteration that will follow this will not do anything.
3155 // (this is not a condition that holds when we set the region up,
3156 // as the region is not supposed to be empty in the first place)
3157 _finger = bottom;
3158 } else if (limit >= _region_limit) {
3159 assert(limit >= _finger, "peace of mind");
3160 } else {
3161 assert(limit < _region_limit, "only way to get here");
3162 // This can happen under some pretty unusual circumstances. An
3163 // evacuation pause empties the region underneath our feet (NTAMS
3164 // at bottom). We then do some allocation in the region (NTAMS
3165 // stays at bottom), followed by the region being used as a GC
3166 // alloc region (NTAMS will move to top() and the objects
3167 // originally below it will be grayed). All objects now marked in
3168 // the region are explicitly grayed, if below the global finger,
3169 // and we do not need in fact to scan anything else. So, we simply
3170 // set _finger to be limit to ensure that the bitmap iteration
3171 // doesn't do anything.
3172 _finger = limit;
3173 }
3174
3175 _region_limit = limit;
3176 }
3177
3178 void CMTask::giveup_current_region() {
3179 assert(_curr_region != NULL, "invariant");
3180 if (_cm->verbose_low()) {
3181 gclog_or_tty->print_cr("[%u] giving up region " PTR_FORMAT,
3182 _worker_id, p2i(_curr_region));
3183 }
3184 clear_region_fields();
3185 }
3186
3187 void CMTask::clear_region_fields() {
3188 // Values for these three fields that indicate that we're not
3189 // holding on to a region.
3190 _curr_region = NULL;
3191 _finger = NULL;
3192 _region_limit = NULL;
3193 }
3194
3195 void CMTask::set_cm_oop_closure(G1CMOopClosure* cm_oop_closure) {
3196 if (cm_oop_closure == NULL) {
3197 assert(_cm_oop_closure != NULL, "invariant");
3198 } else {
3199 assert(_cm_oop_closure == NULL, "invariant");
3200 }
3201 _cm_oop_closure = cm_oop_closure;
3202 }
3203
3204 void CMTask::reset(CMBitMap* nextMarkBitMap) {
3205 guarantee(nextMarkBitMap != NULL, "invariant");
3206
3207 if (_cm->verbose_low()) {
3208 gclog_or_tty->print_cr("[%u] resetting", _worker_id);
3209 }
3210
3211 _nextMarkBitMap = nextMarkBitMap;
3212 clear_region_fields();
3213
3214 _calls = 0;
3215 _elapsed_time_ms = 0.0;
3216 _termination_time_ms = 0.0;
3217 _termination_start_time_ms = 0.0;
3218
3219 #if _MARKING_STATS_
3220 _aborted = 0;
3221 _aborted_overflow = 0;
3222 _aborted_cm_aborted = 0;
3223 _aborted_yield = 0;
3224 _aborted_timed_out = 0;
3225 _aborted_satb = 0;
3226 _aborted_termination = 0;
3227 _steal_attempts = 0;
3228 _steals = 0;
3229 _local_pushes = 0;
3230 _local_pops = 0;
3231 _local_max_size = 0;
3232 _objs_scanned = 0;
3233 _global_pushes = 0;
3234 _global_pops = 0;
3235 _global_max_size = 0;
3236 _global_transfers_to = 0;
3237 _global_transfers_from = 0;
3238 _regions_claimed = 0;
3239 _objs_found_on_bitmap = 0;
3240 _satb_buffers_processed = 0;
3241 #endif // _MARKING_STATS_
3242 }
3243
3244 bool CMTask::should_exit_termination() {
3245 regular_clock_call();
3246 // This is called when we are in the termination protocol. We should
3247 // quit if, for some reason, this task wants to abort or the global
3248 // stack is not empty (this means that we can get work from it).
3249 return !_cm->mark_stack_empty() || has_aborted();
3250 }
3251
3252 void CMTask::reached_limit() {
3253 assert(_words_scanned >= _words_scanned_limit ||
3254 _refs_reached >= _refs_reached_limit ,
3255 "shouldn't have been called otherwise");
3256 regular_clock_call();
3257 }
3258
3259 void CMTask::regular_clock_call() {
3260 if (has_aborted()) return;
3261
3262 // First, we need to recalculate the words scanned and refs reached
3263 // limits for the next clock call.
3264 recalculate_limits();
3265
3266 // During the regular clock call we do the following
3267
3268 // (1) If an overflow has been flagged, then we abort.
3269 if (_cm->has_overflown()) {
3270 set_has_aborted();
3271 return;
3272 }
3273
3274 // If we are not concurrent (i.e. we're doing remark) we don't need
3275 // to check anything else. The other steps are only needed during
3276 // the concurrent marking phase.
3277 if (!concurrent()) return;
3278
3279 // (2) If marking has been aborted for Full GC, then we also abort.
3280 if (_cm->has_aborted()) {
3281 set_has_aborted();
3282 statsOnly( ++_aborted_cm_aborted );
3283 return;
3284 }
3285
3286 double curr_time_ms = os::elapsedVTime() * 1000.0;
3287
3288 // (3) If marking stats are enabled, then we update the step history.
3289 #if _MARKING_STATS_
3290 if (_words_scanned >= _words_scanned_limit) {
3291 ++_clock_due_to_scanning;
3292 }
3293 if (_refs_reached >= _refs_reached_limit) {
3294 ++_clock_due_to_marking;
3295 }
3296
3297 double last_interval_ms = curr_time_ms - _interval_start_time_ms;
3298 _interval_start_time_ms = curr_time_ms;
3299 _all_clock_intervals_ms.add(last_interval_ms);
3300
3301 if (_cm->verbose_medium()) {
3302 gclog_or_tty->print_cr("[%u] regular clock, interval = %1.2lfms, "
3303 "scanned = " SIZE_FORMAT "%s, refs reached = " SIZE_FORMAT "%s",
3304 _worker_id, last_interval_ms,
3305 _words_scanned,
3306 (_words_scanned >= _words_scanned_limit) ? " (*)" : "",
3307 _refs_reached,
3308 (_refs_reached >= _refs_reached_limit) ? " (*)" : "");
3309 }
3310 #endif // _MARKING_STATS_
3311
3312 // (4) We check whether we should yield. If we have to, then we abort.
3313 if (SuspendibleThreadSet::should_yield()) {
3314 // We should yield. To do this we abort the task. The caller is
3315 // responsible for yielding.
3316 set_has_aborted();
3317 statsOnly( ++_aborted_yield );
3318 return;
3319 }
3320
3321 // (5) We check whether we've reached our time quota. If we have,
3322 // then we abort.
3323 double elapsed_time_ms = curr_time_ms - _start_time_ms;
3324 if (elapsed_time_ms > _time_target_ms) {
3325 set_has_aborted();
3326 _has_timed_out = true;
3327 statsOnly( ++_aborted_timed_out );
3328 return;
3329 }
3330
3331 // (6) Finally, we check whether there are enough completed STAB
3332 // buffers available for processing. If there are, we abort.
3333 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3334 if (!_draining_satb_buffers && satb_mq_set.process_completed_buffers()) {
3335 if (_cm->verbose_low()) {
3336 gclog_or_tty->print_cr("[%u] aborting to deal with pending SATB buffers",
3337 _worker_id);
3338 }
3339 // we do need to process SATB buffers, we'll abort and restart
3340 // the marking task to do so
3341 set_has_aborted();
3342 statsOnly( ++_aborted_satb );
3343 return;
3344 }
3345 }
3346
3347 void CMTask::recalculate_limits() {
3348 _real_words_scanned_limit = _words_scanned + words_scanned_period;
3349 _words_scanned_limit = _real_words_scanned_limit;
3350
3351 _real_refs_reached_limit = _refs_reached + refs_reached_period;
3352 _refs_reached_limit = _real_refs_reached_limit;
3353 }
3354
3355 void CMTask::decrease_limits() {
3356 // This is called when we believe that we're going to do an infrequent
3357 // operation which will increase the per byte scanned cost (i.e. move
3358 // entries to/from the global stack). It basically tries to decrease the
3359 // scanning limit so that the clock is called earlier.
3360
3361 if (_cm->verbose_medium()) {
3362 gclog_or_tty->print_cr("[%u] decreasing limits", _worker_id);
3363 }
3364
3365 _words_scanned_limit = _real_words_scanned_limit -
3366 3 * words_scanned_period / 4;
3367 _refs_reached_limit = _real_refs_reached_limit -
3368 3 * refs_reached_period / 4;
3369 }
3370
3371 void CMTask::move_entries_to_global_stack() {
3372 // local array where we'll store the entries that will be popped
3373 // from the local queue
3374 oop buffer[global_stack_transfer_size];
3375
3376 int n = 0;
3377 oop obj;
3378 while (n < global_stack_transfer_size && _task_queue->pop_local(obj)) {
3379 buffer[n] = obj;
3380 ++n;
3381 }
3382
3383 if (n > 0) {
3384 // we popped at least one entry from the local queue
3385
3386 statsOnly( ++_global_transfers_to; _local_pops += n );
3387
3388 if (!_cm->mark_stack_push(buffer, n)) {
3389 if (_cm->verbose_low()) {
3390 gclog_or_tty->print_cr("[%u] aborting due to global stack overflow",
3391 _worker_id);
3392 }
3393 set_has_aborted();
3394 } else {
3395 // the transfer was successful
3396
3397 if (_cm->verbose_medium()) {
3398 gclog_or_tty->print_cr("[%u] pushed %d entries to the global stack",
3399 _worker_id, n);
3400 }
3401 statsOnly( size_t tmp_size = _cm->mark_stack_size();
3402 if (tmp_size > _global_max_size) {
3403 _global_max_size = tmp_size;
3404 }
3405 _global_pushes += n );
3406 }
3407 }
3408
3409 // this operation was quite expensive, so decrease the limits
3410 decrease_limits();
3411 }
3412
3413 void CMTask::get_entries_from_global_stack() {
3414 // local array where we'll store the entries that will be popped
3415 // from the global stack.
3416 oop buffer[global_stack_transfer_size];
3417 int n;
3418 _cm->mark_stack_pop(buffer, global_stack_transfer_size, &n);
3419 assert(n <= global_stack_transfer_size,
3420 "we should not pop more than the given limit");
3421 if (n > 0) {
3422 // yes, we did actually pop at least one entry
3423
3424 statsOnly( ++_global_transfers_from; _global_pops += n );
3425 if (_cm->verbose_medium()) {
3426 gclog_or_tty->print_cr("[%u] popped %d entries from the global stack",
3427 _worker_id, n);
3428 }
3429 for (int i = 0; i < n; ++i) {
3430 bool success = _task_queue->push(buffer[i]);
3431 // We only call this when the local queue is empty or under a
3432 // given target limit. So, we do not expect this push to fail.
3433 assert(success, "invariant");
3434 }
3435
3436 statsOnly( size_t tmp_size = (size_t)_task_queue->size();
3437 if (tmp_size > _local_max_size) {
3438 _local_max_size = tmp_size;
3439 }
3440 _local_pushes += n );
3441 }
3442
3443 // this operation was quite expensive, so decrease the limits
3444 decrease_limits();
3445 }
3446
3447 void CMTask::drain_local_queue(bool partially) {
3448 if (has_aborted()) return;
3449
3450 // Decide what the target size is, depending whether we're going to
3451 // drain it partially (so that other tasks can steal if they run out
3452 // of things to do) or totally (at the very end).
3453 size_t target_size;
3454 if (partially) {
3455 target_size = MIN2((size_t)_task_queue->max_elems()/3, GCDrainStackTargetSize);
3456 } else {
3457 target_size = 0;
3458 }
3459
3460 if (_task_queue->size() > target_size) {
3461 if (_cm->verbose_high()) {
3462 gclog_or_tty->print_cr("[%u] draining local queue, target size = " SIZE_FORMAT,
3463 _worker_id, target_size);
3464 }
3465
3466 oop obj;
3467 bool ret = _task_queue->pop_local(obj);
3468 while (ret) {
3469 statsOnly( ++_local_pops );
3470
3471 if (_cm->verbose_high()) {
3472 gclog_or_tty->print_cr("[%u] popped " PTR_FORMAT, _worker_id,
3473 p2i((void*) obj));
3474 }
3475
3476 assert(_g1h->is_in_g1_reserved((HeapWord*) obj), "invariant" );
3477 assert(!_g1h->is_on_master_free_list(
3478 _g1h->heap_region_containing((HeapWord*) obj)), "invariant");
3479
3480 scan_object(obj);
3481
3482 if (_task_queue->size() <= target_size || has_aborted()) {
3483 ret = false;
3484 } else {
3485 ret = _task_queue->pop_local(obj);
3486 }
3487 }
3488
3489 if (_cm->verbose_high()) {
3490 gclog_or_tty->print_cr("[%u] drained local queue, size = %u",
3491 _worker_id, _task_queue->size());
3492 }
3493 }
3494 }
3495
3496 void CMTask::drain_global_stack(bool partially) {
3497 if (has_aborted()) return;
3498
3499 // We have a policy to drain the local queue before we attempt to
3500 // drain the global stack.
3501 assert(partially || _task_queue->size() == 0, "invariant");
3502
3503 // Decide what the target size is, depending whether we're going to
3504 // drain it partially (so that other tasks can steal if they run out
3505 // of things to do) or totally (at the very end). Notice that,
3506 // because we move entries from the global stack in chunks or
3507 // because another task might be doing the same, we might in fact
3508 // drop below the target. But, this is not a problem.
3509 size_t target_size;
3510 if (partially) {
3511 target_size = _cm->partial_mark_stack_size_target();
3512 } else {
3513 target_size = 0;
3514 }
3515
3516 if (_cm->mark_stack_size() > target_size) {
3517 if (_cm->verbose_low()) {
3518 gclog_or_tty->print_cr("[%u] draining global_stack, target size " SIZE_FORMAT,
3519 _worker_id, target_size);
3520 }
3521
3522 while (!has_aborted() && _cm->mark_stack_size() > target_size) {
3523 get_entries_from_global_stack();
3524 drain_local_queue(partially);
3525 }
3526
3527 if (_cm->verbose_low()) {
3528 gclog_or_tty->print_cr("[%u] drained global stack, size = " SIZE_FORMAT,
3529 _worker_id, _cm->mark_stack_size());
3530 }
3531 }
3532 }
3533
3534 // SATB Queue has several assumptions on whether to call the par or
3535 // non-par versions of the methods. this is why some of the code is
3536 // replicated. We should really get rid of the single-threaded version
3537 // of the code to simplify things.
3538 void CMTask::drain_satb_buffers() {
3539 if (has_aborted()) return;
3540
3541 // We set this so that the regular clock knows that we're in the
3542 // middle of draining buffers and doesn't set the abort flag when it
3543 // notices that SATB buffers are available for draining. It'd be
3544 // very counter productive if it did that. :-)
3545 _draining_satb_buffers = true;
3546
3547 CMSATBBufferClosure satb_cl(this, _g1h);
3548 SATBMarkQueueSet& satb_mq_set = JavaThread::satb_mark_queue_set();
3549
3550 // This keeps claiming and applying the closure to completed buffers
3551 // until we run out of buffers or we need to abort.
3552 while (!has_aborted() &&
3553 satb_mq_set.apply_closure_to_completed_buffer(&satb_cl)) {
3554 if (_cm->verbose_medium()) {
3555 gclog_or_tty->print_cr("[%u] processed an SATB buffer", _worker_id);
3556 }
3557 statsOnly( ++_satb_buffers_processed );
3558 regular_clock_call();
3559 }
3560
3561 _draining_satb_buffers = false;
3562
3563 assert(has_aborted() ||
3564 concurrent() ||
3565 satb_mq_set.completed_buffers_num() == 0, "invariant");
3566
3567 // again, this was a potentially expensive operation, decrease the
3568 // limits to get the regular clock call early
3569 decrease_limits();
3570 }
3571
3572 void CMTask::print_stats() {
3573 gclog_or_tty->print_cr("Marking Stats, task = %u, calls = %d",
3574 _worker_id, _calls);
3575 gclog_or_tty->print_cr(" Elapsed time = %1.2lfms, Termination time = %1.2lfms",
3576 _elapsed_time_ms, _termination_time_ms);
3577 gclog_or_tty->print_cr(" Step Times (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3578 _step_times_ms.num(), _step_times_ms.avg(),
3579 _step_times_ms.sd());
3580 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3581 _step_times_ms.maximum(), _step_times_ms.sum());
3582
3583 #if _MARKING_STATS_
3584 gclog_or_tty->print_cr(" Clock Intervals (cum): num = %d, avg = %1.2lfms, sd = %1.2lfms",
3585 _all_clock_intervals_ms.num(), _all_clock_intervals_ms.avg(),
3586 _all_clock_intervals_ms.sd());
3587 gclog_or_tty->print_cr(" max = %1.2lfms, total = %1.2lfms",
3588 _all_clock_intervals_ms.maximum(),
3589 _all_clock_intervals_ms.sum());
3590 gclog_or_tty->print_cr(" Clock Causes (cum): scanning = " SIZE_FORMAT ", marking = " SIZE_FORMAT,
3591 _clock_due_to_scanning, _clock_due_to_marking);
3592 gclog_or_tty->print_cr(" Objects: scanned = " SIZE_FORMAT ", found on the bitmap = " SIZE_FORMAT,
3593 _objs_scanned, _objs_found_on_bitmap);
3594 gclog_or_tty->print_cr(" Local Queue: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3595 _local_pushes, _local_pops, _local_max_size);
3596 gclog_or_tty->print_cr(" Global Stack: pushes = " SIZE_FORMAT ", pops = " SIZE_FORMAT ", max size = " SIZE_FORMAT,
3597 _global_pushes, _global_pops, _global_max_size);
3598 gclog_or_tty->print_cr(" transfers to = " SIZE_FORMAT ", transfers from = " SIZE_FORMAT,
3599 _global_transfers_to,_global_transfers_from);
3600 gclog_or_tty->print_cr(" Regions: claimed = " SIZE_FORMAT, _regions_claimed);
3601 gclog_or_tty->print_cr(" SATB buffers: processed = " SIZE_FORMAT, _satb_buffers_processed);
3602 gclog_or_tty->print_cr(" Steals: attempts = " SIZE_FORMAT ", successes = " SIZE_FORMAT,
3603 _steal_attempts, _steals);
3604 gclog_or_tty->print_cr(" Aborted: " SIZE_FORMAT ", due to", _aborted);
3605 gclog_or_tty->print_cr(" overflow: " SIZE_FORMAT ", global abort: " SIZE_FORMAT ", yield: " SIZE_FORMAT,
3606 _aborted_overflow, _aborted_cm_aborted, _aborted_yield);
3607 gclog_or_tty->print_cr(" time out: " SIZE_FORMAT ", SATB: " SIZE_FORMAT ", termination: " SIZE_FORMAT,
3608 _aborted_timed_out, _aborted_satb, _aborted_termination);
3609 #endif // _MARKING_STATS_
3610 }
3611
3612 bool ConcurrentMark::try_stealing(uint worker_id, int* hash_seed, oop& obj) {
3613 return _task_queues->steal(worker_id, hash_seed, obj);
3614 }
3615
3616 /*****************************************************************************
3617
3618 The do_marking_step(time_target_ms, ...) method is the building
3619 block of the parallel marking framework. It can be called in parallel
3620 with other invocations of do_marking_step() on different tasks
3621 (but only one per task, obviously) and concurrently with the
3622 mutator threads, or during remark, hence it eliminates the need
3623 for two versions of the code. When called during remark, it will
3624 pick up from where the task left off during the concurrent marking
3625 phase. Interestingly, tasks are also claimable during evacuation
3626 pauses too, since do_marking_step() ensures that it aborts before
3627 it needs to yield.
3628
3629 The data structures that it uses to do marking work are the
3630 following:
3631
3632 (1) Marking Bitmap. If there are gray objects that appear only
3633 on the bitmap (this happens either when dealing with an overflow
3634 or when the initial marking phase has simply marked the roots
3635 and didn't push them on the stack), then tasks claim heap
3636 regions whose bitmap they then scan to find gray objects. A
3637 global finger indicates where the end of the last claimed region
3638 is. A local finger indicates how far into the region a task has
3639 scanned. The two fingers are used to determine how to gray an
3640 object (i.e. whether simply marking it is OK, as it will be
3641 visited by a task in the future, or whether it needs to be also
3642 pushed on a stack).
3643
3644 (2) Local Queue. The local queue of the task which is accessed
3645 reasonably efficiently by the task. Other tasks can steal from
3646 it when they run out of work. Throughout the marking phase, a
3647 task attempts to keep its local queue short but not totally
3648 empty, so that entries are available for stealing by other
3649 tasks. Only when there is no more work, a task will totally
3650 drain its local queue.
3651
3652 (3) Global Mark Stack. This handles local queue overflow. During
3653 marking only sets of entries are moved between it and the local
3654 queues, as access to it requires a mutex and more fine-grain
3655 interaction with it which might cause contention. If it
3656 overflows, then the marking phase should restart and iterate
3657 over the bitmap to identify gray objects. Throughout the marking
3658 phase, tasks attempt to keep the global mark stack at a small
3659 length but not totally empty, so that entries are available for
3660 popping by other tasks. Only when there is no more work, tasks
3661 will totally drain the global mark stack.
3662
3663 (4) SATB Buffer Queue. This is where completed SATB buffers are
3664 made available. Buffers are regularly removed from this queue
3665 and scanned for roots, so that the queue doesn't get too
3666 long. During remark, all completed buffers are processed, as
3667 well as the filled in parts of any uncompleted buffers.
3668
3669 The do_marking_step() method tries to abort when the time target
3670 has been reached. There are a few other cases when the
3671 do_marking_step() method also aborts:
3672
3673 (1) When the marking phase has been aborted (after a Full GC).
3674
3675 (2) When a global overflow (on the global stack) has been
3676 triggered. Before the task aborts, it will actually sync up with
3677 the other tasks to ensure that all the marking data structures
3678 (local queues, stacks, fingers etc.) are re-initialized so that
3679 when do_marking_step() completes, the marking phase can
3680 immediately restart.
3681
3682 (3) When enough completed SATB buffers are available. The
3683 do_marking_step() method only tries to drain SATB buffers right
3684 at the beginning. So, if enough buffers are available, the
3685 marking step aborts and the SATB buffers are processed at
3686 the beginning of the next invocation.
3687
3688 (4) To yield. when we have to yield then we abort and yield
3689 right at the end of do_marking_step(). This saves us from a lot
3690 of hassle as, by yielding we might allow a Full GC. If this
3691 happens then objects will be compacted underneath our feet, the
3692 heap might shrink, etc. We save checking for this by just
3693 aborting and doing the yield right at the end.
3694
3695 From the above it follows that the do_marking_step() method should
3696 be called in a loop (or, otherwise, regularly) until it completes.
3697
3698 If a marking step completes without its has_aborted() flag being
3699 true, it means it has completed the current marking phase (and
3700 also all other marking tasks have done so and have all synced up).
3701
3702 A method called regular_clock_call() is invoked "regularly" (in
3703 sub ms intervals) throughout marking. It is this clock method that
3704 checks all the abort conditions which were mentioned above and
3705 decides when the task should abort. A work-based scheme is used to
3706 trigger this clock method: when the number of object words the
3707 marking phase has scanned or the number of references the marking
3708 phase has visited reach a given limit. Additional invocations to
3709 the method clock have been planted in a few other strategic places
3710 too. The initial reason for the clock method was to avoid calling
3711 vtime too regularly, as it is quite expensive. So, once it was in
3712 place, it was natural to piggy-back all the other conditions on it
3713 too and not constantly check them throughout the code.
3714
3715 If do_termination is true then do_marking_step will enter its
3716 termination protocol.
3717
3718 The value of is_serial must be true when do_marking_step is being
3719 called serially (i.e. by the VMThread) and do_marking_step should
3720 skip any synchronization in the termination and overflow code.
3721 Examples include the serial remark code and the serial reference
3722 processing closures.
3723
3724 The value of is_serial must be false when do_marking_step is
3725 being called by any of the worker threads in a work gang.
3726 Examples include the concurrent marking code (CMMarkingTask),
3727 the MT remark code, and the MT reference processing closures.
3728
3729 *****************************************************************************/
3730
3731 void CMTask::do_marking_step(double time_target_ms,
3732 bool do_termination,
3733 bool is_serial) {
3734 assert(time_target_ms >= 1.0, "minimum granularity is 1ms");
3735 assert(concurrent() == _cm->concurrent(), "they should be the same");
3736
3737 G1CollectorPolicy* g1_policy = _g1h->g1_policy();
3738 assert(_task_queues != NULL, "invariant");
3739 assert(_task_queue != NULL, "invariant");
3740 assert(_task_queues->queue(_worker_id) == _task_queue, "invariant");
3741
3742 assert(!_claimed,
3743 "only one thread should claim this task at any one time");
3744
3745 // OK, this doesn't safeguard again all possible scenarios, as it is
3746 // possible for two threads to set the _claimed flag at the same
3747 // time. But it is only for debugging purposes anyway and it will
3748 // catch most problems.
3749 _claimed = true;
3750
3751 _start_time_ms = os::elapsedVTime() * 1000.0;
3752 statsOnly( _interval_start_time_ms = _start_time_ms );
3753
3754 // If do_stealing is true then do_marking_step will attempt to
3755 // steal work from the other CMTasks. It only makes sense to
3756 // enable stealing when the termination protocol is enabled
3757 // and do_marking_step() is not being called serially.
3758 bool do_stealing = do_termination && !is_serial;
3759
3760 double diff_prediction_ms =
3761 g1_policy->get_new_prediction(&_marking_step_diffs_ms);
3762 _time_target_ms = time_target_ms - diff_prediction_ms;
3763
3764 // set up the variables that are used in the work-based scheme to
3765 // call the regular clock method
3766 _words_scanned = 0;
3767 _refs_reached = 0;
3768 recalculate_limits();
3769
3770 // clear all flags
3771 clear_has_aborted();
3772 _has_timed_out = false;
3773 _draining_satb_buffers = false;
3774
3775 ++_calls;
3776
3777 if (_cm->verbose_low()) {
3778 gclog_or_tty->print_cr("[%u] >>>>>>>>>> START, call = %d, "
3779 "target = %1.2lfms >>>>>>>>>>",
3780 _worker_id, _calls, _time_target_ms);
3781 }
3782
3783 // Set up the bitmap and oop closures. Anything that uses them is
3784 // eventually called from this method, so it is OK to allocate these
3785 // statically.
3786 CMBitMapClosure bitmap_closure(this, _cm, _nextMarkBitMap);
3787 G1CMOopClosure cm_oop_closure(_g1h, _cm, this);
3788 set_cm_oop_closure(&cm_oop_closure);
3789
3790 if (_cm->has_overflown()) {
3791 // This can happen if the mark stack overflows during a GC pause
3792 // and this task, after a yield point, restarts. We have to abort
3793 // as we need to get into the overflow protocol which happens
3794 // right at the end of this task.
3795 set_has_aborted();
3796 }
3797
3798 // First drain any available SATB buffers. After this, we will not
3799 // look at SATB buffers before the next invocation of this method.
3800 // If enough completed SATB buffers are queued up, the regular clock
3801 // will abort this task so that it restarts.
3802 drain_satb_buffers();
3803 // ...then partially drain the local queue and the global stack
3804 drain_local_queue(true);
3805 drain_global_stack(true);
3806
3807 do {
3808 if (!has_aborted() && _curr_region != NULL) {
3809 // This means that we're already holding on to a region.
3810 assert(_finger != NULL, "if region is not NULL, then the finger "
3811 "should not be NULL either");
3812
3813 // We might have restarted this task after an evacuation pause
3814 // which might have evacuated the region we're holding on to
3815 // underneath our feet. Let's read its limit again to make sure
3816 // that we do not iterate over a region of the heap that
3817 // contains garbage (update_region_limit() will also move
3818 // _finger to the start of the region if it is found empty).
3819 update_region_limit();
3820 // We will start from _finger not from the start of the region,
3821 // as we might be restarting this task after aborting half-way
3822 // through scanning this region. In this case, _finger points to
3823 // the address where we last found a marked object. If this is a
3824 // fresh region, _finger points to start().
3825 MemRegion mr = MemRegion(_finger, _region_limit);
3826
3827 if (_cm->verbose_low()) {
3828 gclog_or_tty->print_cr("[%u] we're scanning part "
3829 "[" PTR_FORMAT ", " PTR_FORMAT ") "
3830 "of region " HR_FORMAT,
3831 _worker_id, p2i(_finger), p2i(_region_limit),
3832 HR_FORMAT_PARAMS(_curr_region));
3833 }
3834
3835 assert(!_curr_region->is_humongous() || mr.start() == _curr_region->bottom(),
3836 "humongous regions should go around loop once only");
3837
3838 // Some special cases:
3839 // If the memory region is empty, we can just give up the region.
3840 // If the current region is humongous then we only need to check
3841 // the bitmap for the bit associated with the start of the object,
3842 // scan the object if it's live, and give up the region.
3843 // Otherwise, let's iterate over the bitmap of the part of the region
3844 // that is left.
3845 // If the iteration is successful, give up the region.
3846 if (mr.is_empty()) {
3847 giveup_current_region();
3848 regular_clock_call();
3849 } else if (_curr_region->is_humongous() && mr.start() == _curr_region->bottom()) {
3850 if (_nextMarkBitMap->isMarked(mr.start())) {
3851 // The object is marked - apply the closure
3852 BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
3853 bitmap_closure.do_bit(offset);
3854 }
3855 // Even if this task aborted while scanning the humongous object
3856 // we can (and should) give up the current region.
3857 giveup_current_region();
3858 regular_clock_call();
3859 } else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
3860 giveup_current_region();
3861 regular_clock_call();
3862 } else {
3863 assert(has_aborted(), "currently the only way to do so");
3864 // The only way to abort the bitmap iteration is to return
3865 // false from the do_bit() method. However, inside the
3866 // do_bit() method we move the _finger to point to the
3867 // object currently being looked at. So, if we bail out, we
3868 // have definitely set _finger to something non-null.
3869 assert(_finger != NULL, "invariant");
3870
3871 // Region iteration was actually aborted. So now _finger
3872 // points to the address of the object we last scanned. If we
3873 // leave it there, when we restart this task, we will rescan
3874 // the object. It is easy to avoid this. We move the finger by
3875 // enough to point to the next possible object header (the
3876 // bitmap knows by how much we need to move it as it knows its
3877 // granularity).
3878 assert(_finger < _region_limit, "invariant");
3879 HeapWord* new_finger = _nextMarkBitMap->nextObject(_finger);
3880 // Check if bitmap iteration was aborted while scanning the last object
3881 if (new_finger >= _region_limit) {
3882 giveup_current_region();
3883 } else {
3884 move_finger_to(new_finger);
3885 }
3886 }
3887 }
3888 // At this point we have either completed iterating over the
3889 // region we were holding on to, or we have aborted.
3890
3891 // We then partially drain the local queue and the global stack.
3892 // (Do we really need this?)
3893 drain_local_queue(true);
3894 drain_global_stack(true);
3895
3896 // Read the note on the claim_region() method on why it might
3897 // return NULL with potentially more regions available for
3898 // claiming and why we have to check out_of_regions() to determine
3899 // whether we're done or not.
3900 while (!has_aborted() && _curr_region == NULL && !_cm->out_of_regions()) {
3901 // We are going to try to claim a new region. We should have
3902 // given up on the previous one.
3903 // Separated the asserts so that we know which one fires.
3904 assert(_curr_region == NULL, "invariant");
3905 assert(_finger == NULL, "invariant");
3906 assert(_region_limit == NULL, "invariant");
3907 if (_cm->verbose_low()) {
3908 gclog_or_tty->print_cr("[%u] trying to claim a new region", _worker_id);
3909 }
3910 HeapRegion* claimed_region = _cm->claim_region(_worker_id);
3911 if (claimed_region != NULL) {
3912 // Yes, we managed to claim one
3913 statsOnly( ++_regions_claimed );
3914
3915 if (_cm->verbose_low()) {
3916 gclog_or_tty->print_cr("[%u] we successfully claimed "
3917 "region " PTR_FORMAT,
3918 _worker_id, p2i(claimed_region));
3919 }
3920
3921 setup_for_region(claimed_region);
3922 assert(_curr_region == claimed_region, "invariant");
3923 }
3924 // It is important to call the regular clock here. It might take
3925 // a while to claim a region if, for example, we hit a large
3926 // block of empty regions. So we need to call the regular clock
3927 // method once round the loop to make sure it's called
3928 // frequently enough.
3929 regular_clock_call();
3930 }
3931
3932 if (!has_aborted() && _curr_region == NULL) {
3933 assert(_cm->out_of_regions(),
3934 "at this point we should be out of regions");
3935 }
3936 } while ( _curr_region != NULL && !has_aborted());
3937
3938 if (!has_aborted()) {
3939 // We cannot check whether the global stack is empty, since other
3940 // tasks might be pushing objects to it concurrently.
3941 assert(_cm->out_of_regions(),
3942 "at this point we should be out of regions");
3943
3944 if (_cm->verbose_low()) {
3945 gclog_or_tty->print_cr("[%u] all regions claimed", _worker_id);
3946 }
3947
3948 // Try to reduce the number of available SATB buffers so that
3949 // remark has less work to do.
3950 drain_satb_buffers();
3951 }
3952
3953 // Since we've done everything else, we can now totally drain the
3954 // local queue and global stack.
3955 drain_local_queue(false);
3956 drain_global_stack(false);
3957
3958 // Attempt at work stealing from other task's queues.
3959 if (do_stealing && !has_aborted()) {
3960 // We have not aborted. This means that we have finished all that
3961 // we could. Let's try to do some stealing...
3962
3963 // We cannot check whether the global stack is empty, since other
3964 // tasks might be pushing objects to it concurrently.
3965 assert(_cm->out_of_regions() && _task_queue->size() == 0,
3966 "only way to reach here");
3967
3968 if (_cm->verbose_low()) {
3969 gclog_or_tty->print_cr("[%u] starting to steal", _worker_id);
3970 }
3971
3972 while (!has_aborted()) {
3973 oop obj;
3974 statsOnly( ++_steal_attempts );
3975
3976 if (_cm->try_stealing(_worker_id, &_hash_seed, obj)) {
3977 if (_cm->verbose_medium()) {
3978 gclog_or_tty->print_cr("[%u] stolen " PTR_FORMAT " successfully",
3979 _worker_id, p2i((void*) obj));
3980 }
3981
3982 statsOnly( ++_steals );
3983
3984 assert(_nextMarkBitMap->isMarked((HeapWord*) obj),
3985 "any stolen object should be marked");
3986 scan_object(obj);
3987
3988 // And since we're towards the end, let's totally drain the
3989 // local queue and global stack.
3990 drain_local_queue(false);
3991 drain_global_stack(false);
3992 } else {
3993 break;
3994 }
3995 }
3996 }
3997
3998 // If we are about to wrap up and go into termination, check if we
3999 // should raise the overflow flag.
4000 if (do_termination && !has_aborted()) {
4001 if (_cm->force_overflow()->should_force()) {
4002 _cm->set_has_overflown();
4003 regular_clock_call();
4004 }
4005 }
4006
4007 // We still haven't aborted. Now, let's try to get into the
4008 // termination protocol.
4009 if (do_termination && !has_aborted()) {
4010 // We cannot check whether the global stack is empty, since other
4011 // tasks might be concurrently pushing objects on it.
4012 // Separated the asserts so that we know which one fires.
4013 assert(_cm->out_of_regions(), "only way to reach here");
4014 assert(_task_queue->size() == 0, "only way to reach here");
4015
4016 if (_cm->verbose_low()) {
4017 gclog_or_tty->print_cr("[%u] starting termination protocol", _worker_id);
4018 }
4019
4020 _termination_start_time_ms = os::elapsedVTime() * 1000.0;
4021
4022 // The CMTask class also extends the TerminatorTerminator class,
4023 // hence its should_exit_termination() method will also decide
4024 // whether to exit the termination protocol or not.
4025 bool finished = (is_serial ||
4026 _cm->terminator()->offer_termination(this));
4027 double termination_end_time_ms = os::elapsedVTime() * 1000.0;
4028 _termination_time_ms +=
4029 termination_end_time_ms - _termination_start_time_ms;
4030
4031 if (finished) {
4032 // We're all done.
4033
4034 if (_worker_id == 0) {
4035 // let's allow task 0 to do this
4036 if (concurrent()) {
4037 assert(_cm->concurrent_marking_in_progress(), "invariant");
4038 // we need to set this to false before the next
4039 // safepoint. This way we ensure that the marking phase
4040 // doesn't observe any more heap expansions.
4041 _cm->clear_concurrent_marking_in_progress();
4042 }
4043 }
4044
4045 // We can now guarantee that the global stack is empty, since
4046 // all other tasks have finished. We separated the guarantees so
4047 // that, if a condition is false, we can immediately find out
4048 // which one.
4049 guarantee(_cm->out_of_regions(), "only way to reach here");
4050 guarantee(_cm->mark_stack_empty(), "only way to reach here");
4051 guarantee(_task_queue->size() == 0, "only way to reach here");
4052 guarantee(!_cm->has_overflown(), "only way to reach here");
4053 guarantee(!_cm->mark_stack_overflow(), "only way to reach here");
4054
4055 if (_cm->verbose_low()) {
4056 gclog_or_tty->print_cr("[%u] all tasks terminated", _worker_id);
4057 }
4058 } else {
4059 // Apparently there's more work to do. Let's abort this task. It
4060 // will restart it and we can hopefully find more things to do.
4061
4062 if (_cm->verbose_low()) {
4063 gclog_or_tty->print_cr("[%u] apparently there is more work to do",
4064 _worker_id);
4065 }
4066
4067 set_has_aborted();
4068 statsOnly( ++_aborted_termination );
4069 }
4070 }
4071
4072 // Mainly for debugging purposes to make sure that a pointer to the
4073 // closure which was statically allocated in this frame doesn't
4074 // escape it by accident.
4075 set_cm_oop_closure(NULL);
4076 double end_time_ms = os::elapsedVTime() * 1000.0;
4077 double elapsed_time_ms = end_time_ms - _start_time_ms;
4078 // Update the step history.
4079 _step_times_ms.add(elapsed_time_ms);
4080
4081 if (has_aborted()) {
4082 // The task was aborted for some reason.
4083
4084 statsOnly( ++_aborted );
4085
4086 if (_has_timed_out) {
4087 double diff_ms = elapsed_time_ms - _time_target_ms;
4088 // Keep statistics of how well we did with respect to hitting
4089 // our target only if we actually timed out (if we aborted for
4090 // other reasons, then the results might get skewed).
4091 _marking_step_diffs_ms.add(diff_ms);
4092 }
4093
4094 if (_cm->has_overflown()) {
4095 // This is the interesting one. We aborted because a global
4096 // overflow was raised. This means we have to restart the
4097 // marking phase and start iterating over regions. However, in
4098 // order to do this we have to make sure that all tasks stop
4099 // what they are doing and re-initialize in a safe manner. We
4100 // will achieve this with the use of two barrier sync points.
4101
4102 if (_cm->verbose_low()) {
4103 gclog_or_tty->print_cr("[%u] detected overflow", _worker_id);
4104 }
4105
4106 if (!is_serial) {
4107 // We only need to enter the sync barrier if being called
4108 // from a parallel context
4109 _cm->enter_first_sync_barrier(_worker_id);
4110
4111 // When we exit this sync barrier we know that all tasks have
4112 // stopped doing marking work. So, it's now safe to
4113 // re-initialize our data structures. At the end of this method,
4114 // task 0 will clear the global data structures.
4115 }
4116
4117 statsOnly( ++_aborted_overflow );
4118
4119 // We clear the local state of this task...
4120 clear_region_fields();
4121
4122 if (!is_serial) {
4123 // ...and enter the second barrier.
4124 _cm->enter_second_sync_barrier(_worker_id);
4125 }
4126 // At this point, if we're during the concurrent phase of
4127 // marking, everything has been re-initialized and we're
4128 // ready to restart.
4129 }
4130
4131 if (_cm->verbose_low()) {
4132 gclog_or_tty->print_cr("[%u] <<<<<<<<<< ABORTING, target = %1.2lfms, "
4133 "elapsed = %1.2lfms <<<<<<<<<<",
4134 _worker_id, _time_target_ms, elapsed_time_ms);
4135 if (_cm->has_aborted()) {
4136 gclog_or_tty->print_cr("[%u] ========== MARKING ABORTED ==========",
4137 _worker_id);
4138 }
4139 }
4140 } else {
4141 if (_cm->verbose_low()) {
4142 gclog_or_tty->print_cr("[%u] <<<<<<<<<< FINISHED, target = %1.2lfms, "
4143 "elapsed = %1.2lfms <<<<<<<<<<",
4144 _worker_id, _time_target_ms, elapsed_time_ms);
4145 }
4146 }
4147
4148 _claimed = false;
4149 }
4150
4151 CMTask::CMTask(uint worker_id,
4152 ConcurrentMark* cm,
4153 size_t* marked_bytes,
4154 BitMap* card_bm,
4155 CMTaskQueue* task_queue,
4156 CMTaskQueueSet* task_queues)
4157 : _g1h(G1CollectedHeap::heap()),
4158 _worker_id(worker_id), _cm(cm),
4159 _claimed(false),
4160 _nextMarkBitMap(NULL), _hash_seed(17),
4161 _task_queue(task_queue),
4162 _task_queues(task_queues),
4163 _cm_oop_closure(NULL),
4164 _marked_bytes_array(marked_bytes),
4165 _card_bm(card_bm) {
4166 guarantee(task_queue != NULL, "invariant");
4167 guarantee(task_queues != NULL, "invariant");
4168
4169 statsOnly( _clock_due_to_scanning = 0;
4170 _clock_due_to_marking = 0 );
4171
4172 _marking_step_diffs_ms.add(0.5);
4173 }
4174
4175 // These are formatting macros that are used below to ensure
4176 // consistent formatting. The *_H_* versions are used to format the
4177 // header for a particular value and they should be kept consistent
4178 // with the corresponding macro. Also note that most of the macros add
4179 // the necessary white space (as a prefix) which makes them a bit
4180 // easier to compose.
4181
4182 // All the output lines are prefixed with this string to be able to
4183 // identify them easily in a large log file.
4184 #define G1PPRL_LINE_PREFIX "###"
4185
4186 #define G1PPRL_ADDR_BASE_FORMAT " " PTR_FORMAT "-" PTR_FORMAT
4187 #ifdef _LP64
4188 #define G1PPRL_ADDR_BASE_H_FORMAT " %37s"
4189 #else // _LP64
4190 #define G1PPRL_ADDR_BASE_H_FORMAT " %21s"
4191 #endif // _LP64
4192
4193 // For per-region info
4194 #define G1PPRL_TYPE_FORMAT " %-4s"
4195 #define G1PPRL_TYPE_H_FORMAT " %4s"
4196 #define G1PPRL_BYTE_FORMAT " " SIZE_FORMAT_W(9)
4197 #define G1PPRL_BYTE_H_FORMAT " %9s"
4198 #define G1PPRL_DOUBLE_FORMAT " %14.1f"
4199 #define G1PPRL_DOUBLE_H_FORMAT " %14s"
4200
4201 // For summary info
4202 #define G1PPRL_SUM_ADDR_FORMAT(tag) " " tag ":" G1PPRL_ADDR_BASE_FORMAT
4203 #define G1PPRL_SUM_BYTE_FORMAT(tag) " " tag ": " SIZE_FORMAT
4204 #define G1PPRL_SUM_MB_FORMAT(tag) " " tag ": %1.2f MB"
4205 #define G1PPRL_SUM_MB_PERC_FORMAT(tag) G1PPRL_SUM_MB_FORMAT(tag) " / %1.2f %%"
4206
4207 G1PrintRegionLivenessInfoClosure::
4208 G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name)
4209 : _out(out),
4210 _total_used_bytes(0), _total_capacity_bytes(0),
4211 _total_prev_live_bytes(0), _total_next_live_bytes(0),
4212 _hum_used_bytes(0), _hum_capacity_bytes(0),
4213 _hum_prev_live_bytes(0), _hum_next_live_bytes(0),
4214 _total_remset_bytes(0), _total_strong_code_roots_bytes(0) {
4215 G1CollectedHeap* g1h = G1CollectedHeap::heap();
4216 MemRegion g1_reserved = g1h->g1_reserved();
4217 double now = os::elapsedTime();
4218
4219 // Print the header of the output.
4220 _out->cr();
4221 _out->print_cr(G1PPRL_LINE_PREFIX" PHASE %s @ %1.3f", phase_name, now);
4222 _out->print_cr(G1PPRL_LINE_PREFIX" HEAP"
4223 G1PPRL_SUM_ADDR_FORMAT("reserved")
4224 G1PPRL_SUM_BYTE_FORMAT("region-size"),
4225 p2i(g1_reserved.start()), p2i(g1_reserved.end()),
4226 HeapRegion::GrainBytes);
4227 _out->print_cr(G1PPRL_LINE_PREFIX);
4228 _out->print_cr(G1PPRL_LINE_PREFIX
4229 G1PPRL_TYPE_H_FORMAT
4230 G1PPRL_ADDR_BASE_H_FORMAT
4231 G1PPRL_BYTE_H_FORMAT
4232 G1PPRL_BYTE_H_FORMAT
4233 G1PPRL_BYTE_H_FORMAT
4234 G1PPRL_DOUBLE_H_FORMAT
4235 G1PPRL_BYTE_H_FORMAT
4236 G1PPRL_BYTE_H_FORMAT,
4237 "type", "address-range",
4238 "used", "prev-live", "next-live", "gc-eff",
4239 "remset", "code-roots");
4240 _out->print_cr(G1PPRL_LINE_PREFIX
4241 G1PPRL_TYPE_H_FORMAT
4242 G1PPRL_ADDR_BASE_H_FORMAT
4243 G1PPRL_BYTE_H_FORMAT
4244 G1PPRL_BYTE_H_FORMAT
4245 G1PPRL_BYTE_H_FORMAT
4246 G1PPRL_DOUBLE_H_FORMAT
4247 G1PPRL_BYTE_H_FORMAT
4248 G1PPRL_BYTE_H_FORMAT,
4249 "", "",
4250 "(bytes)", "(bytes)", "(bytes)", "(bytes/ms)",
4251 "(bytes)", "(bytes)");
4252 }
4253
4254 // It takes as a parameter a reference to one of the _hum_* fields, it
4255 // deduces the corresponding value for a region in a humongous region
4256 // series (either the region size, or what's left if the _hum_* field
4257 // is < the region size), and updates the _hum_* field accordingly.
4258 size_t G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* hum_bytes) {
4259 size_t bytes = 0;
4260 // The > 0 check is to deal with the prev and next live bytes which
4261 // could be 0.
4262 if (*hum_bytes > 0) {
4263 bytes = MIN2(HeapRegion::GrainBytes, *hum_bytes);
4264 *hum_bytes -= bytes;
4265 }
4266 return bytes;
4267 }
4268
4269 // It deduces the values for a region in a humongous region series
4270 // from the _hum_* fields and updates those accordingly. It assumes
4271 // that that _hum_* fields have already been set up from the "starts
4272 // humongous" region and we visit the regions in address order.
4273 void G1PrintRegionLivenessInfoClosure::get_hum_bytes(size_t* used_bytes,
4274 size_t* capacity_bytes,
4275 size_t* prev_live_bytes,
4276 size_t* next_live_bytes) {
4277 assert(_hum_used_bytes > 0 && _hum_capacity_bytes > 0, "pre-condition");
4278 *used_bytes = get_hum_bytes(&_hum_used_bytes);
4279 *capacity_bytes = get_hum_bytes(&_hum_capacity_bytes);
4280 *prev_live_bytes = get_hum_bytes(&_hum_prev_live_bytes);
4281 *next_live_bytes = get_hum_bytes(&_hum_next_live_bytes);
4282 }
4283
4284 bool G1PrintRegionLivenessInfoClosure::doHeapRegion(HeapRegion* r) {
4285 const char* type = r->get_type_str();
4286 HeapWord* bottom = r->bottom();
4287 HeapWord* end = r->end();
4288 size_t capacity_bytes = r->capacity();
4289 size_t used_bytes = r->used();
4290 size_t prev_live_bytes = r->live_bytes();
4291 size_t next_live_bytes = r->next_live_bytes();
4292 double gc_eff = r->gc_efficiency();
4293 size_t remset_bytes = r->rem_set()->mem_size();
4294 size_t strong_code_roots_bytes = r->rem_set()->strong_code_roots_mem_size();
4295
4296 if (r->is_starts_humongous()) {
4297 assert(_hum_used_bytes == 0 && _hum_capacity_bytes == 0 &&
4298 _hum_prev_live_bytes == 0 && _hum_next_live_bytes == 0,
4299 "they should have been zeroed after the last time we used them");
4300 // Set up the _hum_* fields.
4301 _hum_capacity_bytes = capacity_bytes;
4302 _hum_used_bytes = used_bytes;
4303 _hum_prev_live_bytes = prev_live_bytes;
4304 _hum_next_live_bytes = next_live_bytes;
4305 get_hum_bytes(&used_bytes, &capacity_bytes,
4306 &prev_live_bytes, &next_live_bytes);
4307 end = bottom + HeapRegion::GrainWords;
4308 } else if (r->is_continues_humongous()) {
4309 get_hum_bytes(&used_bytes, &capacity_bytes,
4310 &prev_live_bytes, &next_live_bytes);
4311 assert(end == bottom + HeapRegion::GrainWords, "invariant");
4312 }
4313
4314 _total_used_bytes += used_bytes;
4315 _total_capacity_bytes += capacity_bytes;
4316 _total_prev_live_bytes += prev_live_bytes;
4317 _total_next_live_bytes += next_live_bytes;
4318 _total_remset_bytes += remset_bytes;
4319 _total_strong_code_roots_bytes += strong_code_roots_bytes;
4320
4321 // Print a line for this particular region.
4322 _out->print_cr(G1PPRL_LINE_PREFIX
4323 G1PPRL_TYPE_FORMAT
4324 G1PPRL_ADDR_BASE_FORMAT
4325 G1PPRL_BYTE_FORMAT
4326 G1PPRL_BYTE_FORMAT
4327 G1PPRL_BYTE_FORMAT
4328 G1PPRL_DOUBLE_FORMAT
4329 G1PPRL_BYTE_FORMAT
4330 G1PPRL_BYTE_FORMAT,
4331 type, p2i(bottom), p2i(end),
4332 used_bytes, prev_live_bytes, next_live_bytes, gc_eff,
4333 remset_bytes, strong_code_roots_bytes);
4334
4335 return false;
4336 }
4337
4338 G1PrintRegionLivenessInfoClosure::~G1PrintRegionLivenessInfoClosure() {
4339 // add static memory usages to remembered set sizes
4340 _total_remset_bytes += HeapRegionRemSet::fl_mem_size() + HeapRegionRemSet::static_mem_size();
4341 // Print the footer of the output.
4342 _out->print_cr(G1PPRL_LINE_PREFIX);
4343 _out->print_cr(G1PPRL_LINE_PREFIX
4344 " SUMMARY"
4345 G1PPRL_SUM_MB_FORMAT("capacity")
4346 G1PPRL_SUM_MB_PERC_FORMAT("used")
4347 G1PPRL_SUM_MB_PERC_FORMAT("prev-live")
4348 G1PPRL_SUM_MB_PERC_FORMAT("next-live")
4349 G1PPRL_SUM_MB_FORMAT("remset")
4350 G1PPRL_SUM_MB_FORMAT("code-roots"),
4351 bytes_to_mb(_total_capacity_bytes),
4352 bytes_to_mb(_total_used_bytes),
4353 perc(_total_used_bytes, _total_capacity_bytes),
4354 bytes_to_mb(_total_prev_live_bytes),
4355 perc(_total_prev_live_bytes, _total_capacity_bytes),
4356 bytes_to_mb(_total_next_live_bytes),
4357 perc(_total_next_live_bytes, _total_capacity_bytes),
4358 bytes_to_mb(_total_remset_bytes),
4359 bytes_to_mb(_total_strong_code_roots_bytes));
4360 _out->cr();
4361 }