1 /*
2 * Copyright (c) 2001, 2019, 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 "gc/g1/g1BarrierSet.hpp"
27 #include "gc/g1/g1BlockOffsetTable.inline.hpp"
28 #include "gc/g1/g1CardTable.inline.hpp"
29 #include "gc/g1/g1CardTableEntryClosure.hpp"
30 #include "gc/g1/g1CollectedHeap.inline.hpp"
31 #include "gc/g1/g1ConcurrentRefine.hpp"
32 #include "gc/g1/g1DirtyCardQueue.hpp"
33 #include "gc/g1/g1FromCardCache.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1HotCardCache.hpp"
36 #include "gc/g1/g1OopClosures.inline.hpp"
37 #include "gc/g1/g1RootClosures.hpp"
38 #include "gc/g1/g1RemSet.hpp"
39 #include "gc/g1/g1SharedDirtyCardQueue.hpp"
40 #include "gc/g1/heapRegion.inline.hpp"
41 #include "gc/g1/heapRegionManager.inline.hpp"
42 #include "gc/g1/heapRegionRemSet.inline.hpp"
43 #include "gc/g1/sparsePRT.hpp"
44 #include "gc/shared/gcTraceTime.inline.hpp"
45 #include "gc/shared/ptrQueue.hpp"
46 #include "gc/shared/suspendibleThreadSet.hpp"
47 #include "jfr/jfrEvents.hpp"
48 #include "memory/iterator.hpp"
49 #include "memory/resourceArea.hpp"
50 #include "oops/access.inline.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "runtime/atomic.hpp"
53 #include "runtime/os.hpp"
54 #include "utilities/align.hpp"
55 #include "utilities/globalDefinitions.hpp"
56 #include "utilities/stack.inline.hpp"
57 #include "utilities/ticks.hpp"
58
59 // Collects information about the overall heap root scan progress during an evacuation.
60 //
61 // Scanning the remembered sets works by first merging all sources of cards to be
62 // scanned (log buffers, hcc, remembered sets) into a single data structure to remove
63 // duplicates and simplify work distribution.
64 //
65 // During the following card scanning we not only scan this combined set of cards, but
66 // also remember that these were completely scanned. The following evacuation passes
67 // do not scan these cards again, and so need to be preserved across increments.
68 //
69 // The representation for all the cards to scan is the card table: cards can have
70 // one of three states during GC:
71 // - clean: these cards will not be scanned in this pass
72 // - dirty: these cards will be scanned in this pass
73 // - scanned: these cards have already been scanned in a previous pass
74 //
75 // After all evacuation is done, we reset the card table to clean.
76 //
77 // Work distribution occurs on "chunk" basis, i.e. contiguous ranges of cards. As an
78 // additional optimization, during card merging we remember which regions and which
79 // chunks actually contain cards to be scanned. Threads iterate only across these
80 // regions, and only compete for chunks containing any cards.
81 //
82 // Within these chunks, a worker scans the card table on "blocks" of cards, i.e.
83 // contiguous ranges of dirty cards to be scanned. These blocks are converted to actual
84 // memory ranges and then passed on to actual scanning.
85 class G1RemSetScanState : public CHeapObj<mtGC> {
86 class G1DirtyRegions;
87
88 size_t _max_regions;
89
90 // Has this region that is part of the regions in the collection set been processed yet.
91 typedef bool G1RemsetIterState;
92
93 G1RemsetIterState volatile* _collection_set_iter_state;
94
95 // Card table iteration claim for each heap region, from 0 (completely unscanned)
96 // to (>=) HeapRegion::CardsPerRegion (completely scanned).
97 uint volatile* _card_table_scan_state;
98
99 // Return "optimal" number of chunks per region we want to use for claiming areas
100 // within a region to claim. Dependent on the region size as proxy for the heap
101 // size, we limit the total number of chunks to limit memory usage and maintenance
102 // effort of that table vs. granularity of distributing scanning work.
103 // Testing showed that 8 for 1M/2M region, 16 for 4M/8M regions, 32 for 16/32M regions
104 // seems to be such a good trade-off.
105 static uint get_chunks_per_region(uint log_region_size) {
106 // Limit the expected input values to current known possible values of the
107 // (log) region size. Adjust as necessary after testing if changing the permissible
108 // values for region size.
109 assert(log_region_size >= 20 && log_region_size <= 25,
110 "expected value in [20,25], but got %u", log_region_size);
111 return 1u << (log_region_size / 2 - 7);
112 }
113
114 uint _scan_chunks_per_region; // Number of chunks per region.
115 uint8_t _log_scan_chunks_per_region; // Log of number of chunks per region.
116 bool* _region_scan_chunks;
117 size_t _num_total_scan_chunks; // Total number of elements in _region_scan_chunks.
118 uint8_t _scan_chunks_shift; // For conversion between card index and chunk index.
119 public:
120 uint scan_chunk_size() const { return (uint)1 << _scan_chunks_shift; }
121
122 // Returns whether the chunk corresponding to the given region/card in region contain a
123 // dirty card, i.e. actually needs scanning.
124 bool chunk_needs_scan(uint const region_idx, uint const card_in_region) const {
125 size_t const idx = ((size_t)region_idx << _log_scan_chunks_per_region) + (card_in_region >> _scan_chunks_shift);
126 assert(idx < _num_total_scan_chunks, "Index " SIZE_FORMAT " out of bounds " SIZE_FORMAT,
127 idx, _num_total_scan_chunks);
128 return _region_scan_chunks[idx];
129 }
130
131 private:
132 // The complete set of regions which card table needs to be cleared at the end of GC because
133 // we scribbled all over them.
134 G1DirtyRegions* _all_dirty_regions;
135 // The set of regions which card table needs to be scanned for new dirty cards
136 // in the current evacuation pass.
137 G1DirtyRegions* _next_dirty_regions;
138
139 // Set of (unique) regions that can be added to concurrently.
140 class G1DirtyRegions : public CHeapObj<mtGC> {
141 uint* _buffer;
142 uint _cur_idx;
143 size_t _max_regions;
144
145 bool* _contains;
146
147 public:
148 G1DirtyRegions(size_t max_regions) :
149 _buffer(NEW_C_HEAP_ARRAY(uint, max_regions, mtGC)),
150 _cur_idx(0),
151 _max_regions(max_regions),
152 _contains(NEW_C_HEAP_ARRAY(bool, max_regions, mtGC)) {
153
154 reset();
155 }
156
157 static size_t chunk_size() { return M; }
158
159 ~G1DirtyRegions() {
160 FREE_C_HEAP_ARRAY(uint, _buffer);
161 FREE_C_HEAP_ARRAY(bool, _contains);
162 }
163
164 void reset() {
165 _cur_idx = 0;
166 ::memset(_contains, false, _max_regions * sizeof(bool));
167 }
168
169 uint size() const { return _cur_idx; }
170
171 uint at(uint idx) const {
172 assert(idx < _cur_idx, "Index %u beyond valid regions", idx);
173 return _buffer[idx];
174 }
175
176 void add_dirty_region(uint region) {
177 if (_contains[region]) {
178 return;
179 }
180
181 bool marked_as_dirty = Atomic::cmpxchg(&_contains[region], false, true) == false;
182 if (marked_as_dirty) {
183 uint allocated = Atomic::add(&_cur_idx, 1u) - 1;
184 _buffer[allocated] = region;
185 }
186 }
187
188 // Creates the union of this and the other G1DirtyRegions.
189 void merge(const G1DirtyRegions* other) {
190 for (uint i = 0; i < other->size(); i++) {
191 uint region = other->at(i);
192 if (!_contains[region]) {
193 _buffer[_cur_idx++] = region;
194 _contains[region] = true;
195 }
196 }
197 }
198 };
199
200 // Creates a snapshot of the current _top values at the start of collection to
201 // filter out card marks that we do not want to scan.
202 class G1ResetScanTopClosure : public HeapRegionClosure {
203 G1RemSetScanState* _scan_state;
204
205 public:
206 G1ResetScanTopClosure(G1RemSetScanState* scan_state) : _scan_state(scan_state) { }
207
208 virtual bool do_heap_region(HeapRegion* r) {
209 uint hrm_index = r->hrm_index();
210 if (r->in_collection_set()) {
211 // Young regions had their card table marked as young at their allocation;
212 // we need to make sure that these marks are cleared at the end of GC, *but*
213 // they should not be scanned for cards.
214 // So directly add them to the "all_dirty_regions".
215 // Same for regions in the (initial) collection set: they may contain cards from
216 // the log buffers, make sure they are cleaned.
217 _scan_state->add_all_dirty_region(hrm_index);
218 } else if (r->is_old_or_humongous_or_archive()) {
219 _scan_state->set_scan_top(hrm_index, r->top());
220 }
221 return false;
222 }
223 };
224 // For each region, contains the maximum top() value to be used during this garbage
225 // collection. Subsumes common checks like filtering out everything but old and
226 // humongous regions outside the collection set.
227 // This is valid because we are not interested in scanning stray remembered set
228 // entries from free or archive regions.
229 HeapWord** _scan_top;
230
231 class G1ClearCardTableTask : public AbstractGangTask {
232 G1CollectedHeap* _g1h;
233 G1DirtyRegions* _regions;
234 uint _chunk_length;
235
236 uint volatile _cur_dirty_regions;
237
238 G1RemSetScanState* _scan_state;
239
240 public:
241 G1ClearCardTableTask(G1CollectedHeap* g1h,
242 G1DirtyRegions* regions,
243 uint chunk_length,
244 G1RemSetScanState* scan_state) :
245 AbstractGangTask("G1 Clear Card Table Task"),
246 _g1h(g1h),
247 _regions(regions),
248 _chunk_length(chunk_length),
249 _cur_dirty_regions(0),
250 _scan_state(scan_state) {
251
252 assert(chunk_length > 0, "must be");
253 }
254
255 static uint chunk_size() { return M; }
256
257 void work(uint worker_id) {
258 while (_cur_dirty_regions < _regions->size()) {
259 uint next = Atomic::add(&_cur_dirty_regions, _chunk_length) - _chunk_length;
260 uint max = MIN2(next + _chunk_length, _regions->size());
261
262 for (uint i = next; i < max; i++) {
263 HeapRegion* r = _g1h->region_at(_regions->at(i));
264 if (!r->is_survivor()) {
265 r->clear_cardtable();
266 }
267 }
268 }
269 }
270 };
271
272 // Clear the card table of "dirty" regions.
273 void clear_card_table(WorkGang* workers) {
274 uint num_regions = _all_dirty_regions->size();
275
276 if (num_regions == 0) {
277 return;
278 }
279
280 uint const num_chunks = (uint)(align_up((size_t)num_regions << HeapRegion::LogCardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size());
281 uint const num_workers = MIN2(num_chunks, workers->active_workers());
282 uint const chunk_length = G1ClearCardTableTask::chunk_size() / (uint)HeapRegion::CardsPerRegion;
283
284 // Iterate over the dirty cards region list.
285 G1ClearCardTableTask cl(G1CollectedHeap::heap(), _all_dirty_regions, chunk_length, this);
286
287 log_debug(gc, ergo)("Running %s using %u workers for %u "
288 "units of work for %u regions.",
289 cl.name(), num_workers, num_chunks, num_regions);
290 workers->run_task(&cl, num_workers);
291
292 #ifndef PRODUCT
293 G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
294 #endif
295 }
296
297 public:
298 G1RemSetScanState() :
299 _max_regions(0),
300 _collection_set_iter_state(NULL),
301 _card_table_scan_state(NULL),
302 _scan_chunks_per_region(get_chunks_per_region(HeapRegion::LogOfHRGrainBytes)),
303 _log_scan_chunks_per_region(log2_uint(_scan_chunks_per_region)),
304 _region_scan_chunks(NULL),
305 _num_total_scan_chunks(0),
306 _scan_chunks_shift(0),
307 _all_dirty_regions(NULL),
308 _next_dirty_regions(NULL),
309 _scan_top(NULL) {
310 }
311
312 ~G1RemSetScanState() {
313 FREE_C_HEAP_ARRAY(G1RemsetIterState, _collection_set_iter_state);
314 FREE_C_HEAP_ARRAY(uint, _card_table_scan_state);
315 FREE_C_HEAP_ARRAY(bool, _region_scan_chunks);
316 FREE_C_HEAP_ARRAY(HeapWord*, _scan_top);
317 }
318
319 void initialize(size_t max_regions) {
320 assert(_collection_set_iter_state == NULL, "Must not be initialized twice");
321 _max_regions = max_regions;
322 _collection_set_iter_state = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC);
323 _card_table_scan_state = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC);
324 _num_total_scan_chunks = max_regions * _scan_chunks_per_region;
325 _region_scan_chunks = NEW_C_HEAP_ARRAY(bool, _num_total_scan_chunks, mtGC);
326
327 _scan_chunks_shift = (uint8_t)log2_intptr(HeapRegion::CardsPerRegion / _scan_chunks_per_region);
328 _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC);
329 }
330
331 void prepare() {
332 for (size_t i = 0; i < _max_regions; i++) {
333 _collection_set_iter_state[i] = false;
334 clear_scan_top((uint)i);
335 }
336
337 _all_dirty_regions = new G1DirtyRegions(_max_regions);
338 _next_dirty_regions = new G1DirtyRegions(_max_regions);
339
340 G1ResetScanTopClosure cl(this);
341 G1CollectedHeap::heap()->heap_region_iterate(&cl);
342 }
343
344 void prepare_for_merge_heap_roots() {
345 _all_dirty_regions->merge(_next_dirty_regions);
346
347 _next_dirty_regions->reset();
348 for (size_t i = 0; i < _max_regions; i++) {
349 _card_table_scan_state[i] = 0;
350 }
351
352 ::memset(_region_scan_chunks, false, _num_total_scan_chunks * sizeof(*_region_scan_chunks));
353 }
354
355 // Returns whether the given region contains cards we need to scan. The remembered
356 // set and other sources may contain cards that
357 // - are in uncommitted regions
358 // - are located in the collection set
359 // - are located in free regions
360 // as we do not clean up remembered sets before merging heap roots.
361 bool contains_cards_to_process(uint const region_idx) const {
362 HeapRegion* hr = G1CollectedHeap::heap()->region_at_or_null(region_idx);
363 return (hr != NULL && !hr->in_collection_set() && hr->is_old_or_humongous_or_archive());
364 }
365
366 size_t num_visited_cards() const {
367 size_t result = 0;
368 for (uint i = 0; i < _num_total_scan_chunks; i++) {
369 if (_region_scan_chunks[i]) {
370 result++;
371 }
372 }
373 return result * (HeapRegion::CardsPerRegion / _scan_chunks_per_region);
374 }
375
376 size_t num_cards_in_dirty_regions() const {
377 return _next_dirty_regions->size() * HeapRegion::CardsPerRegion;
378 }
379
380 void set_chunk_region_dirty(size_t const region_card_idx) {
381 size_t chunk_idx = region_card_idx >> _scan_chunks_shift;
382 for (uint i = 0; i < _scan_chunks_per_region; i++) {
383 _region_scan_chunks[chunk_idx++] = true;
384 }
385 }
386
387 void set_chunk_dirty(size_t const card_idx) {
388 assert((card_idx >> _scan_chunks_shift) < _num_total_scan_chunks,
389 "Trying to access index " SIZE_FORMAT " out of bounds " SIZE_FORMAT,
390 card_idx >> _scan_chunks_shift, _num_total_scan_chunks);
391 size_t const chunk_idx = card_idx >> _scan_chunks_shift;
392 if (!_region_scan_chunks[chunk_idx]) {
393 _region_scan_chunks[chunk_idx] = true;
394 }
395 }
396
397 void cleanup(WorkGang* workers) {
398 _all_dirty_regions->merge(_next_dirty_regions);
399
400 clear_card_table(workers);
401
402 delete _all_dirty_regions;
403 _all_dirty_regions = NULL;
404
405 delete _next_dirty_regions;
406 _next_dirty_regions = NULL;
407 }
408
409 void iterate_dirty_regions_from(HeapRegionClosure* cl, uint worker_id) {
410 uint num_regions = _next_dirty_regions->size();
411
412 if (num_regions == 0) {
413 return;
414 }
415
416 G1CollectedHeap* g1h = G1CollectedHeap::heap();
417
418 WorkGang* workers = g1h->workers();
419 uint const max_workers = workers->active_workers();
420
421 uint const start_pos = num_regions * worker_id / max_workers;
422 uint cur = start_pos;
423
424 do {
425 bool result = cl->do_heap_region(g1h->region_at(_next_dirty_regions->at(cur)));
426 guarantee(!result, "Not allowed to ask for early termination.");
427 cur++;
428 if (cur == _next_dirty_regions->size()) {
429 cur = 0;
430 }
431 } while (cur != start_pos);
432 }
433
434 // Attempt to claim the given region in the collection set for iteration. Returns true
435 // if this call caused the transition from Unclaimed to Claimed.
436 inline bool claim_collection_set_region(uint region) {
437 assert(region < _max_regions, "Tried to access invalid region %u", region);
438 if (_collection_set_iter_state[region]) {
439 return false;
440 }
441 return !Atomic::cmpxchg(&_collection_set_iter_state[region], false, true);
442 }
443
444 bool has_cards_to_scan(uint region) {
445 assert(region < _max_regions, "Tried to access invalid region %u", region);
446 return _card_table_scan_state[region] < HeapRegion::CardsPerRegion;
447 }
448
449 uint claim_cards_to_scan(uint region, uint increment) {
450 assert(region < _max_regions, "Tried to access invalid region %u", region);
451 return Atomic::add(&_card_table_scan_state[region], increment) - increment;
452 }
453
454 void add_dirty_region(uint const region) {
455 #ifdef ASSERT
456 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
457 assert(!hr->in_collection_set() && hr->is_old_or_humongous_or_archive(),
458 "Region %u is not suitable for scanning, is %sin collection set or %s",
459 hr->hrm_index(), hr->in_collection_set() ? "" : "not ", hr->get_short_type_str());
460 #endif
461 _next_dirty_regions->add_dirty_region(region);
462 }
463
464 void add_all_dirty_region(uint region) {
465 #ifdef ASSERT
466 HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
467 assert(hr->in_collection_set(),
468 "Only add young regions to all dirty regions directly but %u is %s",
469 hr->hrm_index(), hr->get_short_type_str());
470 #endif
471 _all_dirty_regions->add_dirty_region(region);
472 }
473
474 void set_scan_top(uint region_idx, HeapWord* value) {
475 _scan_top[region_idx] = value;
476 }
477
478 HeapWord* scan_top(uint region_idx) const {
479 return _scan_top[region_idx];
480 }
481
482 void clear_scan_top(uint region_idx) {
483 set_scan_top(region_idx, NULL);
484 }
485 };
486
487 G1RemSet::G1RemSet(G1CollectedHeap* g1h,
488 G1CardTable* ct,
489 G1HotCardCache* hot_card_cache) :
490 _scan_state(new G1RemSetScanState()),
491 _prev_period_summary(false),
492 _g1h(g1h),
493 _ct(ct),
494 _g1p(_g1h->policy()),
495 _hot_card_cache(hot_card_cache) {
496 }
497
498 G1RemSet::~G1RemSet() {
499 delete _scan_state;
500 }
501
502 uint G1RemSet::num_par_rem_sets() {
503 return G1DirtyCardQueueSet::num_par_ids() + G1ConcurrentRefine::max_num_threads() + MAX2(ConcGCThreads, ParallelGCThreads);
504 }
505
506 void G1RemSet::initialize(size_t capacity, uint max_regions) {
507 G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
508 _scan_state->initialize(max_regions);
509 }
510
511 // Helper class to scan and detect ranges of cards that need to be scanned on the
512 // card table.
513 class G1CardTableScanner : public StackObj {
514 public:
515 typedef CardTable::CardValue CardValue;
516
517 private:
518 CardValue* const _base_addr;
519
520 CardValue* _cur_addr;
521 CardValue* const _end_addr;
522
523 static const size_t ToScanMask = G1CardTable::g1_card_already_scanned;
524 static const size_t ExpandedToScanMask = G1CardTable::WordAlreadyScanned;
525
526 bool cur_addr_aligned() const {
527 return ((uintptr_t)_cur_addr) % sizeof(size_t) == 0;
528 }
529
530 bool cur_card_is_dirty() const {
531 CardValue value = *_cur_addr;
532 return (value & ToScanMask) == 0;
533 }
534
535 bool cur_word_of_cards_contains_any_dirty_card() const {
536 assert(cur_addr_aligned(), "Current address should be aligned");
537 size_t const value = *(size_t*)_cur_addr;
538 return (~value & ExpandedToScanMask) != 0;
539 }
540
541 bool cur_word_of_cards_all_dirty_cards() const {
542 size_t const value = *(size_t*)_cur_addr;
543 return value == G1CardTable::WordAllDirty;
544 }
545
546 size_t get_and_advance_pos() {
547 _cur_addr++;
548 return pointer_delta(_cur_addr, _base_addr, sizeof(CardValue)) - 1;
549 }
550
551 public:
552 G1CardTableScanner(CardValue* start_card, size_t size) :
553 _base_addr(start_card),
554 _cur_addr(start_card),
555 _end_addr(start_card + size) {
556
557 assert(is_aligned(start_card, sizeof(size_t)), "Unaligned start addr " PTR_FORMAT, p2i(start_card));
558 assert(is_aligned(size, sizeof(size_t)), "Unaligned size " SIZE_FORMAT, size);
559 }
560
561 size_t find_next_dirty() {
562 while (!cur_addr_aligned()) {
563 if (cur_card_is_dirty()) {
564 return get_and_advance_pos();
565 }
566 _cur_addr++;
567 }
568
569 assert(cur_addr_aligned(), "Current address should be aligned now.");
570 while (_cur_addr != _end_addr) {
571 if (cur_word_of_cards_contains_any_dirty_card()) {
572 for (size_t i = 0; i < sizeof(size_t); i++) {
573 if (cur_card_is_dirty()) {
574 return get_and_advance_pos();
575 }
576 _cur_addr++;
577 }
578 assert(false, "Should not reach here given we detected a dirty card in the word.");
579 }
580 _cur_addr += sizeof(size_t);
581 }
582 return get_and_advance_pos();
583 }
584
585 size_t find_next_non_dirty() {
586 assert(_cur_addr <= _end_addr, "Not allowed to search for marks after area.");
587
588 while (!cur_addr_aligned()) {
589 if (!cur_card_is_dirty()) {
590 return get_and_advance_pos();
591 }
592 _cur_addr++;
593 }
594
595 assert(cur_addr_aligned(), "Current address should be aligned now.");
596 while (_cur_addr != _end_addr) {
597 if (!cur_word_of_cards_all_dirty_cards()) {
598 for (size_t i = 0; i < sizeof(size_t); i++) {
599 if (!cur_card_is_dirty()) {
600 return get_and_advance_pos();
601 }
602 _cur_addr++;
603 }
604 assert(false, "Should not reach here given we detected a non-dirty card in the word.");
605 }
606 _cur_addr += sizeof(size_t);
607 }
608 return get_and_advance_pos();
609 }
610 };
611
612 // Helper class to claim dirty chunks within the card table.
613 class G1CardTableChunkClaimer {
614 G1RemSetScanState* _scan_state;
615 uint _region_idx;
616 uint _cur_claim;
617
618 public:
619 G1CardTableChunkClaimer(G1RemSetScanState* scan_state, uint region_idx) :
620 _scan_state(scan_state),
621 _region_idx(region_idx),
622 _cur_claim(0) {
623 guarantee(size() <= HeapRegion::CardsPerRegion, "Should not claim more space than possible.");
624 }
625
626 bool has_next() {
627 while (true) {
628 _cur_claim = _scan_state->claim_cards_to_scan(_region_idx, size());
629 if (_cur_claim >= HeapRegion::CardsPerRegion) {
630 return false;
631 }
632 if (_scan_state->chunk_needs_scan(_region_idx, _cur_claim)) {
633 return true;
634 }
635 }
636 }
637
638 uint value() const { return _cur_claim; }
639 uint size() const { return _scan_state->scan_chunk_size(); }
640 };
641
642 // Scans a heap region for dirty cards.
643 class G1ScanHRForRegionClosure : public HeapRegionClosure {
644 G1CollectedHeap* _g1h;
645 G1CardTable* _ct;
646 G1BlockOffsetTable* _bot;
647
648 G1ParScanThreadState* _pss;
649
650 G1RemSetScanState* _scan_state;
651
652 G1GCPhaseTimes::GCParPhases _phase;
653
654 uint _worker_id;
655
656 size_t _cards_scanned;
657 size_t _blocks_scanned;
658 size_t _chunks_claimed;
659
660 Tickspan _rem_set_root_scan_time;
661 Tickspan _rem_set_trim_partially_time;
662
663 // The address to which this thread already scanned (walked the heap) up to during
664 // card scanning (exclusive).
665 HeapWord* _scanned_to;
666
667 HeapWord* scan_memregion(uint region_idx_for_card, MemRegion mr) {
668 HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
669 G1ScanCardClosure card_cl(_g1h, _pss);
670
671 HeapWord* const scanned_to = card_region->oops_on_memregion_seq_iterate_careful<true>(mr, &card_cl);
672 assert(scanned_to != NULL, "Should be able to scan range");
673 assert(scanned_to >= mr.end(), "Scanned to " PTR_FORMAT " less than range " PTR_FORMAT, p2i(scanned_to), p2i(mr.end()));
674
675 _pss->trim_queue_partially();
676 return scanned_to;
677 }
678
679 void do_claimed_block(uint const region_idx_for_card, size_t const first_card, size_t const num_cards) {
680 HeapWord* const card_start = _bot->address_for_index_raw(first_card);
681 #ifdef ASSERT
682 HeapRegion* hr = _g1h->region_at_or_null(region_idx_for_card);
683 assert(hr == NULL || hr->is_in_reserved(card_start),
684 "Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index());
685 #endif
686 HeapWord* const top = _scan_state->scan_top(region_idx_for_card);
687 if (card_start >= top) {
688 return;
689 }
690
691 HeapWord* scan_end = MIN2(card_start + (num_cards << BOTConstants::LogN_words), top);
692 if (_scanned_to >= scan_end) {
693 return;
694 }
695 MemRegion mr(MAX2(card_start, _scanned_to), scan_end);
696 _scanned_to = scan_memregion(region_idx_for_card, mr);
697
698 _cards_scanned += num_cards;
699 }
700
701 ALWAYSINLINE void do_card_block(uint const region_idx, size_t const first_card, size_t const num_cards) {
702 _ct->mark_as_scanned(first_card, num_cards);
703 do_claimed_block(region_idx, first_card, num_cards);
704 _blocks_scanned++;
705 }
706
707 void scan_heap_roots(HeapRegion* r) {
708 EventGCPhaseParallel event;
709 uint const region_idx = r->hrm_index();
710
711 ResourceMark rm;
712
713 G1CardTableChunkClaimer claim(_scan_state, region_idx);
714
715 // Set the current scan "finger" to NULL for every heap region to scan. Since
716 // the claim value is monotonically increasing, the check to not scan below this
717 // will filter out objects spanning chunks within the region too then, as opposed
718 // to resetting this value for every claim.
719 _scanned_to = NULL;
720
721 while (claim.has_next()) {
722 size_t const region_card_base_idx = ((size_t)region_idx << HeapRegion::LogCardsPerRegion) + claim.value();
723 CardTable::CardValue* const base_addr = _ct->byte_for_index(region_card_base_idx);
724
725 G1CardTableScanner scan(base_addr, claim.size());
726
727 size_t first_scan_idx = scan.find_next_dirty();
728 while (first_scan_idx != claim.size()) {
729 assert(*_ct->byte_for_index(region_card_base_idx + first_scan_idx) <= 0x1, "is %d at region %u idx " SIZE_FORMAT, *_ct->byte_for_index(region_card_base_idx + first_scan_idx), region_idx, first_scan_idx);
730
731 size_t const last_scan_idx = scan.find_next_non_dirty();
732 size_t const len = last_scan_idx - first_scan_idx;
733
734 do_card_block(region_idx, region_card_base_idx + first_scan_idx, len);
735
736 if (last_scan_idx == claim.size()) {
737 break;
738 }
739
740 first_scan_idx = scan.find_next_dirty();
741 }
742 _chunks_claimed++;
743 }
744
745 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ScanHR));
746 }
747
748 public:
749 G1ScanHRForRegionClosure(G1RemSetScanState* scan_state,
750 G1ParScanThreadState* pss,
751 uint worker_id,
752 G1GCPhaseTimes::GCParPhases phase) :
753 _g1h(G1CollectedHeap::heap()),
754 _ct(_g1h->card_table()),
755 _bot(_g1h->bot()),
756 _pss(pss),
757 _scan_state(scan_state),
758 _phase(phase),
759 _worker_id(worker_id),
760 _cards_scanned(0),
761 _blocks_scanned(0),
762 _chunks_claimed(0),
763 _rem_set_root_scan_time(),
764 _rem_set_trim_partially_time(),
765 _scanned_to(NULL) {
766 }
767
768 bool do_heap_region(HeapRegion* r) {
769 assert(!r->in_collection_set() && r->is_old_or_humongous_or_archive(),
770 "Should only be called on old gen non-collection set regions but region %u is not.",
771 r->hrm_index());
772 uint const region_idx = r->hrm_index();
773
774 if (_scan_state->has_cards_to_scan(region_idx)) {
775 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_root_scan_time, _rem_set_trim_partially_time);
776 scan_heap_roots(r);
777 }
778 return false;
779 }
780
781 Tickspan rem_set_root_scan_time() const { return _rem_set_root_scan_time; }
782 Tickspan rem_set_trim_partially_time() const { return _rem_set_trim_partially_time; }
783
784 size_t cards_scanned() const { return _cards_scanned; }
785 size_t blocks_scanned() const { return _blocks_scanned; }
786 size_t chunks_claimed() const { return _chunks_claimed; }
787 };
788
789 void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss,
790 uint worker_id,
791 G1GCPhaseTimes::GCParPhases scan_phase,
792 G1GCPhaseTimes::GCParPhases objcopy_phase) {
793 G1ScanHRForRegionClosure cl(_scan_state, pss, worker_id, scan_phase);
794 _scan_state->iterate_dirty_regions_from(&cl, worker_id);
795
796 G1GCPhaseTimes* p = _g1p->phase_times();
797
798 p->record_or_add_time_secs(objcopy_phase, worker_id, cl.rem_set_trim_partially_time().seconds());
799
800 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_root_scan_time().seconds());
801 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned(), G1GCPhaseTimes::ScanHRScannedCards);
802 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.blocks_scanned(), G1GCPhaseTimes::ScanHRScannedBlocks);
803 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.chunks_claimed(), G1GCPhaseTimes::ScanHRClaimedChunks);
804 }
805
806 // Heap region closure to be applied to all regions in the current collection set
807 // increment to fix up non-card related roots.
808 class G1ScanCollectionSetRegionClosure : public HeapRegionClosure {
809 G1ParScanThreadState* _pss;
810 G1RemSetScanState* _scan_state;
811
812 G1GCPhaseTimes::GCParPhases _scan_phase;
813 G1GCPhaseTimes::GCParPhases _code_roots_phase;
814
815 uint _worker_id;
816
817 size_t _opt_refs_scanned;
818 size_t _opt_refs_memory_used;
819
820 Tickspan _strong_code_root_scan_time;
821 Tickspan _strong_code_trim_partially_time;
822
823 Tickspan _rem_set_opt_root_scan_time;
824 Tickspan _rem_set_opt_trim_partially_time;
825
826 void scan_opt_rem_set_roots(HeapRegion* r) {
827 EventGCPhaseParallel event;
828
829 G1OopStarChunkedList* opt_rem_set_list = _pss->oops_into_optional_region(r);
830
831 G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss);
832 G1ScanRSForOptionalClosure cl(G1CollectedHeap::heap(), &scan_cl);
833 _opt_refs_scanned += opt_rem_set_list->oops_do(&cl, _pss->closures()->strong_oops());
834 _opt_refs_memory_used += opt_rem_set_list->used_memory();
835
836 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_scan_phase));
837 }
838
839 public:
840 G1ScanCollectionSetRegionClosure(G1RemSetScanState* scan_state,
841 G1ParScanThreadState* pss,
842 uint worker_id,
843 G1GCPhaseTimes::GCParPhases scan_phase,
844 G1GCPhaseTimes::GCParPhases code_roots_phase) :
845 _pss(pss),
846 _scan_state(scan_state),
847 _scan_phase(scan_phase),
848 _code_roots_phase(code_roots_phase),
849 _worker_id(worker_id),
850 _opt_refs_scanned(0),
851 _opt_refs_memory_used(0),
852 _strong_code_root_scan_time(),
853 _strong_code_trim_partially_time(),
854 _rem_set_opt_root_scan_time(),
855 _rem_set_opt_trim_partially_time() { }
856
857 bool do_heap_region(HeapRegion* r) {
858 uint const region_idx = r->hrm_index();
859
860 // The individual references for the optional remembered set are per-worker, so we
861 // always need to scan them.
862 if (r->has_index_in_opt_cset()) {
863 G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_opt_root_scan_time, _rem_set_opt_trim_partially_time);
864 scan_opt_rem_set_roots(r);
865 }
866
867 if (_scan_state->claim_collection_set_region(region_idx)) {
868 EventGCPhaseParallel event;
869
870 G1EvacPhaseWithTrimTimeTracker timer(_pss, _strong_code_root_scan_time, _strong_code_trim_partially_time);
871 // Scan the strong code root list attached to the current region
872 r->strong_code_roots_do(_pss->closures()->weak_codeblobs());
873
874 event.commit(GCId::current(), _worker_id, G1GCPhaseTimes::phase_name(_code_roots_phase));
875 }
876
877 return false;
878 }
879
880 Tickspan strong_code_root_scan_time() const { return _strong_code_root_scan_time; }
881 Tickspan strong_code_root_trim_partially_time() const { return _strong_code_trim_partially_time; }
882
883 Tickspan rem_set_opt_root_scan_time() const { return _rem_set_opt_root_scan_time; }
884 Tickspan rem_set_opt_trim_partially_time() const { return _rem_set_opt_trim_partially_time; }
885
886 size_t opt_refs_scanned() const { return _opt_refs_scanned; }
887 size_t opt_refs_memory_used() const { return _opt_refs_memory_used; }
888 };
889
890 void G1RemSet::scan_collection_set_regions(G1ParScanThreadState* pss,
891 uint worker_id,
892 G1GCPhaseTimes::GCParPhases scan_phase,
893 G1GCPhaseTimes::GCParPhases coderoots_phase,
894 G1GCPhaseTimes::GCParPhases objcopy_phase) {
895 G1ScanCollectionSetRegionClosure cl(_scan_state, pss, worker_id, scan_phase, coderoots_phase);
896 _g1h->collection_set_iterate_increment_from(&cl, worker_id);
897
898 G1GCPhaseTimes* p = _g1h->phase_times();
899
900 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_root_scan_time().seconds());
901 p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_opt_trim_partially_time().seconds());
902
903 p->record_or_add_time_secs(coderoots_phase, worker_id, cl.strong_code_root_scan_time().seconds());
904 p->add_time_secs(objcopy_phase, worker_id, cl.strong_code_root_trim_partially_time().seconds());
905
906 // At this time we record some metrics only for the evacuations after the initial one.
907 if (scan_phase == G1GCPhaseTimes::OptScanHR) {
908 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
909 p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
910 }
911 }
912
913 void G1RemSet::prepare_for_scan_heap_roots() {
914 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
915 dcqs.concatenate_logs();
916
917 _scan_state->prepare();
918 }
919
920 class G1MergeHeapRootsTask : public AbstractGangTask {
921
922 // Visitor for remembered sets, dropping entries onto the card table.
923 class G1MergeCardSetClosure : public HeapRegionClosure {
924 G1RemSetScanState* _scan_state;
925 G1CardTable* _ct;
926
927 uint _merged_sparse;
928 uint _merged_fine;
929 uint _merged_coarse;
930
931 size_t _cards_dirty;
932
933 // Returns if the region contains cards we need to scan. If so, remember that
934 // region in the current set of dirty regions.
935 bool remember_if_interesting(uint const region_idx) {
936 if (!_scan_state->contains_cards_to_process(region_idx)) {
937 return false;
938 }
939 _scan_state->add_dirty_region(region_idx);
940 return true;
941 }
942 public:
943 G1MergeCardSetClosure(G1RemSetScanState* scan_state) :
944 _scan_state(scan_state),
945 _ct(G1CollectedHeap::heap()->card_table()),
946 _merged_sparse(0),
947 _merged_fine(0),
948 _merged_coarse(0),
949 _cards_dirty(0) { }
950
951 void next_coarse_prt(uint const region_idx) {
952 if (!remember_if_interesting(region_idx)) {
953 return;
954 }
955
956 _merged_coarse++;
957
958 size_t region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
959 _cards_dirty += _ct->mark_region_dirty(region_base_idx, HeapRegion::CardsPerRegion);
960 _scan_state->set_chunk_region_dirty(region_base_idx);
961 }
962
963 void next_fine_prt(uint const region_idx, BitMap* bm) {
964 if (!remember_if_interesting(region_idx)) {
965 return;
966 }
967
968 _merged_fine++;
969
970 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
971 BitMap::idx_t cur = bm->get_next_one_offset(0);
972 while (cur != bm->size()) {
973 _cards_dirty += _ct->mark_clean_as_dirty(region_base_idx + cur);
974 _scan_state->set_chunk_dirty(region_base_idx + cur);
975 cur = bm->get_next_one_offset(cur + 1);
976 }
977 }
978
979 void next_sparse_prt(uint const region_idx, SparsePRTEntry::card_elem_t* cards, uint const num_cards) {
980 if (!remember_if_interesting(region_idx)) {
981 return;
982 }
983
984 _merged_sparse++;
985
986 size_t const region_base_idx = (size_t)region_idx << HeapRegion::LogCardsPerRegion;
987 for (uint i = 0; i < num_cards; i++) {
988 size_t card_idx = region_base_idx + cards[i];
989 _cards_dirty += _ct->mark_clean_as_dirty(card_idx);
990 _scan_state->set_chunk_dirty(card_idx);
991 }
992 }
993
994 virtual bool do_heap_region(HeapRegion* r) {
995 assert(r->in_collection_set() || r->is_starts_humongous(), "must be");
996
997 HeapRegionRemSet* rem_set = r->rem_set();
998 if (!rem_set->is_empty()) {
999 rem_set->iterate_prts(*this);
1000 }
1001
1002 return false;
1003 }
1004
1005 size_t merged_sparse() const { return _merged_sparse; }
1006 size_t merged_fine() const { return _merged_fine; }
1007 size_t merged_coarse() const { return _merged_coarse; }
1008
1009 size_t cards_dirty() const { return _cards_dirty; }
1010 };
1011
1012 // Visitor for the remembered sets of humongous candidate regions to merge their
1013 // remembered set into the card table.
1014 class G1FlushHumongousCandidateRemSets : public HeapRegionClosure {
1015 G1MergeCardSetClosure _cl;
1016
1017 public:
1018 G1FlushHumongousCandidateRemSets(G1RemSetScanState* scan_state) : _cl(scan_state) { }
1019
1020 virtual bool do_heap_region(HeapRegion* r) {
1021 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1022
1023 if (!r->is_starts_humongous() ||
1024 !g1h->region_attr(r->hrm_index()).is_humongous() ||
1025 r->rem_set()->is_empty()) {
1026 return false;
1027 }
1028
1029 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
1030 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
1031
1032 _cl.do_heap_region(r);
1033
1034 // We should only clear the card based remembered set here as we will not
1035 // implicitly rebuild anything else during eager reclaim. Note that at the moment
1036 // (and probably never) we do not enter this path if there are other kind of
1037 // remembered sets for this region.
1038 r->rem_set()->clear_locked(true /* only_cardset */);
1039 // Clear_locked() above sets the state to Empty. However we want to continue
1040 // collecting remembered set entries for humongous regions that were not
1041 // reclaimed.
1042 r->rem_set()->set_state_complete();
1043 #ifdef ASSERT
1044 G1HeapRegionAttr region_attr = g1h->region_attr(r->hrm_index());
1045 assert(region_attr.needs_remset_update(), "must be");
1046 #endif
1047 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
1048
1049 return false;
1050 }
1051
1052 size_t merged_sparse() const { return _cl.merged_sparse(); }
1053 size_t merged_fine() const { return _cl.merged_fine(); }
1054 size_t merged_coarse() const { return _cl.merged_coarse(); }
1055
1056 size_t cards_dirty() const { return _cl.cards_dirty(); }
1057 };
1058
1059 // Visitor for the log buffer entries to merge them into the card table.
1060 class G1MergeLogBufferCardsClosure : public G1CardTableEntryClosure {
1061 G1RemSetScanState* _scan_state;
1062 G1CardTable* _ct;
1063
1064 size_t _cards_dirty;
1065 size_t _cards_skipped;
1066 public:
1067 G1MergeLogBufferCardsClosure(G1CollectedHeap* g1h, G1RemSetScanState* scan_state) :
1068 _scan_state(scan_state), _ct(g1h->card_table()), _cards_dirty(0), _cards_skipped(0)
1069 {}
1070
1071 void do_card_ptr(CardValue* card_ptr, uint worker_id) {
1072 // The only time we care about recording cards that
1073 // contain references that point into the collection set
1074 // is during RSet updating within an evacuation pause.
1075 // In this case worker_id should be the id of a GC worker thread.
1076 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
1077
1078 uint const region_idx = _ct->region_idx_for(card_ptr);
1079
1080 // The second clause must come after - the log buffers might contain cards to uncommited
1081 // regions.
1082 // This code may count duplicate entries in the log buffers (even if rare) multiple
1083 // times.
1084 if (_scan_state->contains_cards_to_process(region_idx) && (*card_ptr == G1CardTable::dirty_card_val())) {
1085 _scan_state->add_dirty_region(region_idx);
1086 _scan_state->set_chunk_dirty(_ct->index_for_cardvalue(card_ptr));
1087 _cards_dirty++;
1088 } else {
1089 // We may have had dirty cards in the (initial) collection set (or the
1090 // young regions which are always in the initial collection set). We do
1091 // not fix their cards here: we already added these regions to the set of
1092 // regions to clear the card table at the end during the prepare() phase.
1093 _cards_skipped++;
1094 }
1095 }
1096
1097 size_t cards_dirty() const { return _cards_dirty; }
1098 size_t cards_skipped() const { return _cards_skipped; }
1099 };
1100
1101 HeapRegionClaimer _hr_claimer;
1102 G1RemSetScanState* _scan_state;
1103 BufferNode::Stack _dirty_card_buffers;
1104 bool _initial_evacuation;
1105
1106 volatile bool _fast_reclaim_handled;
1107
1108 void apply_closure_to_dirty_card_buffers(G1MergeLogBufferCardsClosure* cl, uint worker_id) {
1109 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1110 size_t buffer_size = dcqs.buffer_size();
1111 while (BufferNode* node = _dirty_card_buffers.pop()) {
1112 cl->apply_to_buffer(node, buffer_size, worker_id);
1113 dcqs.deallocate_buffer(node);
1114 }
1115 }
1116
1117 public:
1118 G1MergeHeapRootsTask(G1RemSetScanState* scan_state, uint num_workers, bool initial_evacuation) :
1119 AbstractGangTask("G1 Merge Heap Roots"),
1120 _hr_claimer(num_workers),
1121 _scan_state(scan_state),
1122 _dirty_card_buffers(),
1123 _initial_evacuation(initial_evacuation),
1124 _fast_reclaim_handled(false)
1125 {
1126 if (initial_evacuation) {
1127 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1128 G1BufferNodeList buffers = dcqs.take_all_completed_buffers();
1129 if (buffers._entry_count != 0) {
1130 _dirty_card_buffers.prepend(*buffers._head, *buffers._tail);
1131 }
1132 }
1133 }
1134
1135 virtual void work(uint worker_id) {
1136 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1137 G1GCPhaseTimes* p = g1h->phase_times();
1138
1139 G1GCPhaseTimes::GCParPhases merge_remset_phase = _initial_evacuation ?
1140 G1GCPhaseTimes::MergeRS :
1141 G1GCPhaseTimes::OptMergeRS;
1142
1143 // We schedule flushing the remembered sets of humongous fast reclaim candidates
1144 // onto the card table first to allow the remaining parallelized tasks hide it.
1145 if (_initial_evacuation &&
1146 p->fast_reclaim_humongous_candidates() > 0 &&
1147 !_fast_reclaim_handled &&
1148 !Atomic::cmpxchg(&_fast_reclaim_handled, false, true)) {
1149
1150 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeER, worker_id);
1151
1152 G1FlushHumongousCandidateRemSets cl(_scan_state);
1153 g1h->heap_region_iterate(&cl);
1154
1155 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
1156 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
1157 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
1158 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
1159 }
1160
1161 // Merge remembered sets of current candidates.
1162 {
1163 G1GCParPhaseTimesTracker x(p, merge_remset_phase, worker_id, _initial_evacuation /* must_record */);
1164 G1MergeCardSetClosure cl(_scan_state);
1165 g1h->collection_set_iterate_increment_from(&cl, &_hr_claimer, worker_id);
1166
1167 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_sparse(), G1GCPhaseTimes::MergeRSMergedSparse);
1168 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_fine(), G1GCPhaseTimes::MergeRSMergedFine);
1169 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.merged_coarse(), G1GCPhaseTimes::MergeRSMergedCoarse);
1170 p->record_or_add_thread_work_item(merge_remset_phase, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeRSDirtyCards);
1171 }
1172
1173 // Apply closure to log entries in the HCC.
1174 if (_initial_evacuation && G1HotCardCache::default_use_cache()) {
1175 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase");
1176 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeHCC, worker_id);
1177 G1MergeLogBufferCardsClosure cl(g1h, _scan_state);
1178 g1h->iterate_hcc_closure(&cl, worker_id);
1179
1180 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeHCCDirtyCards);
1181 p->record_thread_work_item(G1GCPhaseTimes::MergeHCC, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeHCCSkippedCards);
1182 }
1183
1184 // Now apply the closure to all remaining log entries.
1185 if (_initial_evacuation) {
1186 assert(merge_remset_phase == G1GCPhaseTimes::MergeRS, "Wrong merge phase");
1187 G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::MergeLB, worker_id);
1188
1189 G1MergeLogBufferCardsClosure cl(g1h, _scan_state);
1190 apply_closure_to_dirty_card_buffers(&cl, worker_id);
1191
1192 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_dirty(), G1GCPhaseTimes::MergeLBDirtyCards);
1193 p->record_thread_work_item(G1GCPhaseTimes::MergeLB, worker_id, cl.cards_skipped(), G1GCPhaseTimes::MergeLBSkippedCards);
1194 }
1195 }
1196 };
1197
1198 void G1RemSet::print_merge_heap_roots_stats() {
1199 size_t num_visited_cards = _scan_state->num_visited_cards();
1200
1201 size_t total_dirty_region_cards = _scan_state->num_cards_in_dirty_regions();
1202
1203 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1204 size_t total_old_region_cards =
1205 (g1h->num_regions() - (g1h->num_free_regions() - g1h->collection_set()->cur_length())) * HeapRegion::CardsPerRegion;
1206
1207 log_debug(gc,remset)("Visited cards " SIZE_FORMAT " Total dirty " SIZE_FORMAT " (%.2lf%%) Total old " SIZE_FORMAT " (%.2lf%%)",
1208 num_visited_cards,
1209 total_dirty_region_cards,
1210 percent_of(num_visited_cards, total_dirty_region_cards),
1211 total_old_region_cards,
1212 percent_of(num_visited_cards, total_old_region_cards));
1213 }
1214
1215 void G1RemSet::merge_heap_roots(bool initial_evacuation) {
1216 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1217
1218 {
1219 Ticks start = Ticks::now();
1220
1221 _scan_state->prepare_for_merge_heap_roots();
1222
1223 Tickspan total = Ticks::now() - start;
1224 if (initial_evacuation) {
1225 g1h->phase_times()->record_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
1226 } else {
1227 g1h->phase_times()->record_or_add_optional_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
1228 }
1229 }
1230
1231 WorkGang* workers = g1h->workers();
1232 size_t const increment_length = g1h->collection_set()->increment_length();
1233
1234 uint const num_workers = initial_evacuation ? workers->active_workers() :
1235 MIN2(workers->active_workers(), (uint)increment_length);
1236
1237 {
1238 G1MergeHeapRootsTask cl(_scan_state, num_workers, initial_evacuation);
1239 log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " regions",
1240 cl.name(), num_workers, increment_length);
1241 workers->run_task(&cl, num_workers);
1242 }
1243
1244 if (log_is_enabled(Debug, gc, remset)) {
1245 print_merge_heap_roots_stats();
1246 }
1247 }
1248
1249 void G1RemSet::prepare_for_scan_heap_roots(uint region_idx) {
1250 _scan_state->clear_scan_top(region_idx);
1251 }
1252
1253 void G1RemSet::cleanup_after_scan_heap_roots() {
1254 G1GCPhaseTimes* phase_times = _g1h->phase_times();
1255
1256 // Set all cards back to clean.
1257 double start = os::elapsedTime();
1258 _scan_state->cleanup(_g1h->workers());
1259 phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0);
1260 }
1261
1262 inline void check_card_ptr(CardTable::CardValue* card_ptr, G1CardTable* ct) {
1263 #ifdef ASSERT
1264 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1265 assert(g1h->is_in_exact(ct->addr_for(card_ptr)),
1266 "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",
1267 p2i(card_ptr),
1268 ct->index_for(ct->addr_for(card_ptr)),
1269 p2i(ct->addr_for(card_ptr)),
1270 g1h->addr_to_region(ct->addr_for(card_ptr)));
1271 #endif
1272 }
1273
1274 bool G1RemSet::clean_card_before_refine(CardValue** const card_ptr_addr) {
1275 assert(!_g1h->is_gc_active(), "Only call concurrently");
1276
1277 CardValue* card_ptr = *card_ptr_addr;
1278 // Find the start address represented by the card.
1279 HeapWord* start = _ct->addr_for(card_ptr);
1280 // And find the region containing it.
1281 HeapRegion* r = _g1h->heap_region_containing_or_null(start);
1282
1283 // If this is a (stale) card into an uncommitted region, exit.
1284 if (r == NULL) {
1285 return false;
1286 }
1287
1288 check_card_ptr(card_ptr, _ct);
1289
1290 // If the card is no longer dirty, nothing to do.
1291 // We cannot load the card value before the "r == NULL" check, because G1
1292 // could uncommit parts of the card table covering uncommitted regions.
1293 if (*card_ptr != G1CardTable::dirty_card_val()) {
1294 return false;
1295 }
1296
1297 // This check is needed for some uncommon cases where we should
1298 // ignore the card.
1299 //
1300 // The region could be young. Cards for young regions are
1301 // distinctly marked (set to g1_young_gen), so the post-barrier will
1302 // filter them out. However, that marking is performed
1303 // concurrently. A write to a young object could occur before the
1304 // card has been marked young, slipping past the filter.
1305 //
1306 // The card could be stale, because the region has been freed since
1307 // the card was recorded. In this case the region type could be
1308 // anything. If (still) free or (reallocated) young, just ignore
1309 // it. If (reallocated) old or humongous, the later card trimming
1310 // and additional checks in iteration may detect staleness. At
1311 // worst, we end up processing a stale card unnecessarily.
1312 //
1313 // In the normal (non-stale) case, the synchronization between the
1314 // enqueueing of the card and processing it here will have ensured
1315 // we see the up-to-date region type here.
1316 if (!r->is_old_or_humongous_or_archive()) {
1317 return false;
1318 }
1319
1320 // The result from the hot card cache insert call is either:
1321 // * pointer to the current card
1322 // (implying that the current card is not 'hot'),
1323 // * null
1324 // (meaning we had inserted the card ptr into the "hot" card cache,
1325 // which had some headroom),
1326 // * a pointer to a "hot" card that was evicted from the "hot" cache.
1327 //
1328
1329 if (_hot_card_cache->use_cache()) {
1330 assert(!SafepointSynchronize::is_at_safepoint(), "sanity");
1331
1332 const CardValue* orig_card_ptr = card_ptr;
1333 card_ptr = _hot_card_cache->insert(card_ptr);
1334 if (card_ptr == NULL) {
1335 // There was no eviction. Nothing to do.
1336 return false;
1337 } else if (card_ptr != orig_card_ptr) {
1338 // Original card was inserted and an old card was evicted.
1339 start = _ct->addr_for(card_ptr);
1340 r = _g1h->heap_region_containing(start);
1341
1342 // Check whether the region formerly in the cache should be
1343 // ignored, as discussed earlier for the original card. The
1344 // region could have been freed while in the cache.
1345 if (!r->is_old_or_humongous_or_archive()) {
1346 return false;
1347 }
1348 *card_ptr_addr = card_ptr;
1349 } // Else we still have the original card.
1350 }
1351
1352 // Trim the region designated by the card to what's been allocated
1353 // in the region. The card could be stale, or the card could cover
1354 // (part of) an object at the end of the allocated space and extend
1355 // beyond the end of allocation.
1356
1357 // Non-humongous objects are either allocated in the old regions during GC,
1358 // or mapped in archive regions during startup. So if region is old or
1359 // archive then top is stable.
1360 // Humongous object allocation sets top last; if top has not yet been set,
1361 // this is a stale card and we'll end up with an empty intersection.
1362 // If this is not a stale card, the synchronization between the
1363 // enqueuing of the card and processing it here will have ensured
1364 // we see the up-to-date top here.
1365 HeapWord* scan_limit = r->top();
1366
1367 if (scan_limit <= start) {
1368 // If the trimmed region is empty, the card must be stale.
1369 return false;
1370 }
1371
1372 // Okay to clean and process the card now. There are still some
1373 // stale card cases that may be detected by iteration and dealt with
1374 // as iteration failure.
1375 *const_cast<volatile CardValue*>(card_ptr) = G1CardTable::clean_card_val();
1376
1377 return true;
1378 }
1379
1380 void G1RemSet::refine_card_concurrently(CardValue* const card_ptr,
1381 const uint worker_id) {
1382 assert(!_g1h->is_gc_active(), "Only call concurrently");
1383 check_card_ptr(card_ptr, _ct);
1384
1385 // Construct the MemRegion representing the card.
1386 HeapWord* start = _ct->addr_for(card_ptr);
1387 // And find the region containing it.
1388 HeapRegion* r = _g1h->heap_region_containing(start);
1389 // This reload of the top is safe even though it happens after the full
1390 // fence, because top is stable for old, archive and unfiltered humongous
1391 // regions, so it must return the same value as the previous load when
1392 // cleaning the card. Also cleaning the card and refinement of the card
1393 // cannot span across safepoint, so we don't need to worry about top being
1394 // changed during safepoint.
1395 HeapWord* scan_limit = r->top();
1396 assert(scan_limit > start, "sanity");
1397
1398 // Don't use addr_for(card_ptr + 1) which can ask for
1399 // a card beyond the heap.
1400 HeapWord* end = start + G1CardTable::card_size_in_words;
1401 MemRegion dirty_region(start, MIN2(scan_limit, end));
1402 assert(!dirty_region.is_empty(), "sanity");
1403
1404 G1ConcurrentRefineOopClosure conc_refine_cl(_g1h, worker_id);
1405 if (r->oops_on_memregion_seq_iterate_careful<false>(dirty_region, &conc_refine_cl) != NULL) {
1406 return;
1407 }
1408
1409 // If unable to process the card then we encountered an unparsable
1410 // part of the heap (e.g. a partially allocated object, so only
1411 // temporarily a problem) while processing a stale card. Despite
1412 // the card being stale, we can't simply ignore it, because we've
1413 // already marked the card cleaned, so taken responsibility for
1414 // ensuring the card gets scanned.
1415 //
1416 // However, the card might have gotten re-dirtied and re-enqueued
1417 // while we worked. (In fact, it's pretty likely.)
1418 if (*card_ptr == G1CardTable::dirty_card_val()) {
1419 return;
1420 }
1421
1422 // Re-dirty the card and enqueue in the *shared* queue. Can't use
1423 // the thread-local queue, because that might be the queue that is
1424 // being processed by us; we could be a Java thread conscripted to
1425 // perform refinement on our queue's current buffer.
1426 *card_ptr = G1CardTable::dirty_card_val();
1427 G1BarrierSet::shared_dirty_card_queue().enqueue(card_ptr);
1428 }
1429
1430 void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) {
1431 if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
1432 (period_count % G1SummarizeRSetStatsPeriod == 0)) {
1433
1434 G1RemSetSummary current;
1435 _prev_period_summary.subtract_from(¤t);
1436
1437 Log(gc, remset) log;
1438 log.trace("%s", header);
1439 ResourceMark rm;
1440 LogStream ls(log.trace());
1441 _prev_period_summary.print_on(&ls);
1442
1443 _prev_period_summary.set(¤t);
1444 }
1445 }
1446
1447 void G1RemSet::print_summary_info() {
1448 Log(gc, remset, exit) log;
1449 if (log.is_trace()) {
1450 log.trace(" Cumulative RS summary");
1451 G1RemSetSummary current;
1452 ResourceMark rm;
1453 LogStream ls(log.trace());
1454 current.print_on(&ls);
1455 }
1456 }
1457
1458 class G1RebuildRemSetTask: public AbstractGangTask {
1459 // Aggregate the counting data that was constructed concurrently
1460 // with marking.
1461 class G1RebuildRemSetHeapRegionClosure : public HeapRegionClosure {
1462 G1ConcurrentMark* _cm;
1463 G1RebuildRemSetClosure _update_cl;
1464
1465 // Applies _update_cl to the references of the given object, limiting objArrays
1466 // to the given MemRegion. Returns the amount of words actually scanned.
1467 size_t scan_for_references(oop const obj, MemRegion mr) {
1468 size_t const obj_size = obj->size();
1469 // All non-objArrays and objArrays completely within the mr
1470 // can be scanned without passing the mr.
1471 if (!obj->is_objArray() || mr.contains(MemRegion((HeapWord*)obj, obj_size))) {
1472 obj->oop_iterate(&_update_cl);
1473 return obj_size;
1474 }
1475 // This path is for objArrays crossing the given MemRegion. Only scan the
1476 // area within the MemRegion.
1477 obj->oop_iterate(&_update_cl, mr);
1478 return mr.intersection(MemRegion((HeapWord*)obj, obj_size)).word_size();
1479 }
1480
1481 // A humongous object is live (with respect to the scanning) either
1482 // a) it is marked on the bitmap as such
1483 // b) its TARS is larger than TAMS, i.e. has been allocated during marking.
1484 bool is_humongous_live(oop const humongous_obj, const G1CMBitMap* const bitmap, HeapWord* tams, HeapWord* tars) const {
1485 return bitmap->is_marked(humongous_obj) || (tars > tams);
1486 }
1487
1488 // Iterator over the live objects within the given MemRegion.
1489 class LiveObjIterator : public StackObj {
1490 const G1CMBitMap* const _bitmap;
1491 const HeapWord* _tams;
1492 const MemRegion _mr;
1493 HeapWord* _current;
1494
1495 bool is_below_tams() const {
1496 return _current < _tams;
1497 }
1498
1499 bool is_live(HeapWord* obj) const {
1500 return !is_below_tams() || _bitmap->is_marked(obj);
1501 }
1502
1503 HeapWord* bitmap_limit() const {
1504 return MIN2(const_cast<HeapWord*>(_tams), _mr.end());
1505 }
1506
1507 void move_if_below_tams() {
1508 if (is_below_tams() && has_next()) {
1509 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit());
1510 }
1511 }
1512 public:
1513 LiveObjIterator(const G1CMBitMap* const bitmap, const HeapWord* tams, const MemRegion mr, HeapWord* first_oop_into_mr) :
1514 _bitmap(bitmap),
1515 _tams(tams),
1516 _mr(mr),
1517 _current(first_oop_into_mr) {
1518
1519 assert(_current <= _mr.start(),
1520 "First oop " PTR_FORMAT " should extend into mr [" PTR_FORMAT ", " PTR_FORMAT ")",
1521 p2i(first_oop_into_mr), p2i(mr.start()), p2i(mr.end()));
1522
1523 // Step to the next live object within the MemRegion if needed.
1524 if (is_live(_current)) {
1525 // Non-objArrays were scanned by the previous part of that region.
1526 if (_current < mr.start() && !oop(_current)->is_objArray()) {
1527 _current += oop(_current)->size();
1528 // We might have positioned _current on a non-live object. Reposition to the next
1529 // live one if needed.
1530 move_if_below_tams();
1531 }
1532 } else {
1533 // The object at _current can only be dead if below TAMS, so we can use the bitmap.
1534 // immediately.
1535 _current = _bitmap->get_next_marked_addr(_current, bitmap_limit());
1536 assert(_current == _mr.end() || is_live(_current),
1537 "Current " PTR_FORMAT " should be live (%s) or beyond the end of the MemRegion (" PTR_FORMAT ")",
1538 p2i(_current), BOOL_TO_STR(is_live(_current)), p2i(_mr.end()));
1539 }
1540 }
1541
1542 void move_to_next() {
1543 _current += next()->size();
1544 move_if_below_tams();
1545 }
1546
1547 oop next() const {
1548 oop result = oop(_current);
1549 assert(is_live(_current),
1550 "Object " PTR_FORMAT " must be live TAMS " PTR_FORMAT " below %d mr " PTR_FORMAT " " PTR_FORMAT " outside %d",
1551 p2i(_current), p2i(_tams), _tams > _current, p2i(_mr.start()), p2i(_mr.end()), _mr.contains(result));
1552 return result;
1553 }
1554
1555 bool has_next() const {
1556 return _current < _mr.end();
1557 }
1558 };
1559
1560 // Rebuild remembered sets in the part of the region specified by mr and hr.
1561 // Objects between the bottom of the region and the TAMS are checked for liveness
1562 // using the given bitmap. Objects between TAMS and TARS are assumed to be live.
1563 // Returns the number of live words between bottom and TAMS.
1564 size_t rebuild_rem_set_in_region(const G1CMBitMap* const bitmap,
1565 HeapWord* const top_at_mark_start,
1566 HeapWord* const top_at_rebuild_start,
1567 HeapRegion* hr,
1568 MemRegion mr) {
1569 size_t marked_words = 0;
1570
1571 if (hr->is_humongous()) {
1572 oop const humongous_obj = oop(hr->humongous_start_region()->bottom());
1573 if (is_humongous_live(humongous_obj, bitmap, top_at_mark_start, top_at_rebuild_start)) {
1574 // We need to scan both [bottom, TAMS) and [TAMS, top_at_rebuild_start);
1575 // however in case of humongous objects it is sufficient to scan the encompassing
1576 // area (top_at_rebuild_start is always larger or equal to TAMS) as one of the
1577 // two areas will be zero sized. I.e. TAMS is either
1578 // the same as bottom or top(_at_rebuild_start). There is no way TAMS has a different
1579 // value: this would mean that TAMS points somewhere into the object.
1580 assert(hr->top() == top_at_mark_start || hr->top() == top_at_rebuild_start,
1581 "More than one object in the humongous region?");
1582 humongous_obj->oop_iterate(&_update_cl, mr);
1583 return top_at_mark_start != hr->bottom() ? mr.intersection(MemRegion((HeapWord*)humongous_obj, humongous_obj->size())).byte_size() : 0;
1584 } else {
1585 return 0;
1586 }
1587 }
1588
1589 for (LiveObjIterator it(bitmap, top_at_mark_start, mr, hr->block_start(mr.start())); it.has_next(); it.move_to_next()) {
1590 oop obj = it.next();
1591 size_t scanned_size = scan_for_references(obj, mr);
1592 if ((HeapWord*)obj < top_at_mark_start) {
1593 marked_words += scanned_size;
1594 }
1595 }
1596
1597 return marked_words * HeapWordSize;
1598 }
1599 public:
1600 G1RebuildRemSetHeapRegionClosure(G1CollectedHeap* g1h,
1601 G1ConcurrentMark* cm,
1602 uint worker_id) :
1603 HeapRegionClosure(),
1604 _cm(cm),
1605 _update_cl(g1h, worker_id) { }
1606
1607 bool do_heap_region(HeapRegion* hr) {
1608 if (_cm->has_aborted()) {
1609 return true;
1610 }
1611
1612 uint const region_idx = hr->hrm_index();
1613 DEBUG_ONLY(HeapWord* const top_at_rebuild_start_check = _cm->top_at_rebuild_start(region_idx);)
1614 assert(top_at_rebuild_start_check == NULL ||
1615 top_at_rebuild_start_check > hr->bottom(),
1616 "A TARS (" PTR_FORMAT ") == bottom() (" PTR_FORMAT ") indicates the old region %u is empty (%s)",
1617 p2i(top_at_rebuild_start_check), p2i(hr->bottom()), region_idx, hr->get_type_str());
1618
1619 size_t total_marked_bytes = 0;
1620 size_t const chunk_size_in_words = G1RebuildRemSetChunkSize / HeapWordSize;
1621
1622 HeapWord* const top_at_mark_start = hr->prev_top_at_mark_start();
1623
1624 HeapWord* cur = hr->bottom();
1625 while (cur < hr->end()) {
1626 // After every iteration (yield point) we need to check whether the region's
1627 // TARS changed due to e.g. eager reclaim.
1628 HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);
1629 if (top_at_rebuild_start == NULL) {
1630 return false;
1631 }
1632
1633 MemRegion next_chunk = MemRegion(hr->bottom(), top_at_rebuild_start).intersection(MemRegion(cur, chunk_size_in_words));
1634 if (next_chunk.is_empty()) {
1635 break;
1636 }
1637
1638 const Ticks start = Ticks::now();
1639 size_t marked_bytes = rebuild_rem_set_in_region(_cm->prev_mark_bitmap(),
1640 top_at_mark_start,
1641 top_at_rebuild_start,
1642 hr,
1643 next_chunk);
1644 Tickspan time = Ticks::now() - start;
1645
1646 log_trace(gc, remset, tracking)("Rebuilt region %u "
1647 "live " SIZE_FORMAT " "
1648 "time %.3fms "
1649 "marked bytes " SIZE_FORMAT " "
1650 "bot " PTR_FORMAT " "
1651 "TAMS " PTR_FORMAT " "
1652 "TARS " PTR_FORMAT,
1653 region_idx,
1654 _cm->liveness(region_idx) * HeapWordSize,
1655 time.seconds() * 1000.0,
1656 marked_bytes,
1657 p2i(hr->bottom()),
1658 p2i(top_at_mark_start),
1659 p2i(top_at_rebuild_start));
1660
1661 if (marked_bytes > 0) {
1662 total_marked_bytes += marked_bytes;
1663 }
1664 cur += chunk_size_in_words;
1665
1666 _cm->do_yield_check();
1667 if (_cm->has_aborted()) {
1668 return true;
1669 }
1670 }
1671 // In the final iteration of the loop the region might have been eagerly reclaimed.
1672 // Simply filter out those regions. We can not just use region type because there
1673 // might have already been new allocations into these regions.
1674 DEBUG_ONLY(HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);)
1675 assert(top_at_rebuild_start == NULL ||
1676 total_marked_bytes == hr->marked_bytes(),
1677 "Marked bytes " SIZE_FORMAT " for region %u (%s) in [bottom, TAMS) do not match calculated marked bytes " SIZE_FORMAT " "
1678 "(" PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT ")",
1679 total_marked_bytes, hr->hrm_index(), hr->get_type_str(), hr->marked_bytes(),
1680 p2i(hr->bottom()), p2i(top_at_mark_start), p2i(top_at_rebuild_start));
1681 // Abort state may have changed after the yield check.
1682 return _cm->has_aborted();
1683 }
1684 };
1685
1686 HeapRegionClaimer _hr_claimer;
1687 G1ConcurrentMark* _cm;
1688
1689 uint _worker_id_offset;
1690 public:
1691 G1RebuildRemSetTask(G1ConcurrentMark* cm,
1692 uint n_workers,
1693 uint worker_id_offset) :
1694 AbstractGangTask("G1 Rebuild Remembered Set"),
1695 _hr_claimer(n_workers),
1696 _cm(cm),
1697 _worker_id_offset(worker_id_offset) {
1698 }
1699
1700 void work(uint worker_id) {
1701 SuspendibleThreadSetJoiner sts_join;
1702
1703 G1CollectedHeap* g1h = G1CollectedHeap::heap();
1704
1705 G1RebuildRemSetHeapRegionClosure cl(g1h, _cm, _worker_id_offset + worker_id);
1706 g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hr_claimer, worker_id);
1707 }
1708 };
1709
1710 void G1RemSet::rebuild_rem_set(G1ConcurrentMark* cm,
1711 WorkGang* workers,
1712 uint worker_id_offset) {
1713 uint num_workers = workers->active_workers();
1714
1715 G1RebuildRemSetTask cl(cm,
1716 num_workers,
1717 worker_id_offset);
1718 workers->run_task(&cl, num_workers);
1719 }