1 /*
2 * Copyright (c) 2001, 2014, 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 #if !defined(__clang_major__) && defined(__GNUC__)
26 // FIXME, formats have issues. Disable this macro definition, compile, and study warnings for more information.
27 #define ATTRIBUTE_PRINTF(x,y)
28 #endif
29
30 #include "precompiled.hpp"
31 #include "classfile/stringTable.hpp"
32 #include "code/codeCache.hpp"
33 #include "code/icBuffer.hpp"
34 #include "gc_implementation/g1/bufferingOopClosure.hpp"
35 #include "gc_implementation/g1/concurrentG1Refine.hpp"
36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
40 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
41 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
42 #include "gc_implementation/g1/g1EvacFailure.hpp"
43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
44 #include "gc_implementation/g1/g1Log.hpp"
45 #include "gc_implementation/g1/g1MarkSweep.hpp"
46 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
47 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
48 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
49 #include "gc_implementation/g1/g1RemSet.inline.hpp"
50 #include "gc_implementation/g1/g1StringDedup.hpp"
51 #include "gc_implementation/g1/g1YCTypes.hpp"
52 #include "gc_implementation/g1/heapRegion.inline.hpp"
53 #include "gc_implementation/g1/heapRegionRemSet.hpp"
54 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
55 #include "gc_implementation/g1/vm_operations_g1.hpp"
56 #include "gc_implementation/shared/gcHeapSummary.hpp"
57 #include "gc_implementation/shared/gcTimer.hpp"
58 #include "gc_implementation/shared/gcTrace.hpp"
59 #include "gc_implementation/shared/gcTraceTime.hpp"
60 #include "gc_implementation/shared/isGCActiveMark.hpp"
61 #include "memory/allocation.hpp"
62 #include "memory/gcLocker.inline.hpp"
63 #include "memory/generationSpec.hpp"
64 #include "memory/iterator.hpp"
65 #include "memory/referenceProcessor.hpp"
66 #include "oops/oop.inline.hpp"
67 #include "oops/oop.pcgc.inline.hpp"
68 #include "runtime/atomic.inline.hpp"
69 #include "runtime/orderAccess.inline.hpp"
70 #include "runtime/vmThread.hpp"
71 #include "utilities/globalDefinitions.hpp"
72
73 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
74
75 // turn it on so that the contents of the young list (scan-only /
76 // to-be-collected) are printed at "strategic" points before / during
77 // / after the collection --- this is useful for debugging
78 #define YOUNG_LIST_VERBOSE 0
79 // CURRENT STATUS
80 // This file is under construction. Search for "FIXME".
81
82 // INVARIANTS/NOTES
83 //
84 // All allocation activity covered by the G1CollectedHeap interface is
85 // serialized by acquiring the HeapLock. This happens in mem_allocate
86 // and allocate_new_tlab, which are the "entry" points to the
87 // allocation code from the rest of the JVM. (Note that this does not
88 // apply to TLAB allocation, which is not part of this interface: it
89 // is done by clients of this interface.)
90
91 // Notes on implementation of parallelism in different tasks.
92 //
93 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
94 // The number of GC workers is passed to heap_region_par_iterate_chunked().
95 // It does use run_task() which sets _n_workers in the task.
96 // G1ParTask executes g1_process_roots() ->
97 // SharedHeap::process_roots() which calls eventually to
98 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
99 // SequentialSubTasksDone. SharedHeap::process_roots() also
100 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
101 //
102
103 // Local to this file.
104
105 class RefineCardTableEntryClosure: public CardTableEntryClosure {
106 bool _concurrent;
107 public:
108 RefineCardTableEntryClosure() : _concurrent(true) { }
109
110 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
111 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
112 // This path is executed by the concurrent refine or mutator threads,
113 // concurrently, and so we do not care if card_ptr contains references
114 // that point into the collection set.
115 assert(!oops_into_cset, "should be");
116
117 if (_concurrent && SuspendibleThreadSet::should_yield()) {
118 // Caller will actually yield.
119 return false;
120 }
121 // Otherwise, we finished successfully; return true.
122 return true;
123 }
124
125 void set_concurrent(bool b) { _concurrent = b; }
126 };
127
128
129 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
130 size_t _num_processed;
131 CardTableModRefBS* _ctbs;
132 int _histo[256];
133
134 public:
135 ClearLoggedCardTableEntryClosure() :
136 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
137 {
138 for (int i = 0; i < 256; i++) _histo[i] = 0;
139 }
140
141 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
142 unsigned char* ujb = (unsigned char*)card_ptr;
143 int ind = (int)(*ujb);
144 _histo[ind]++;
145
146 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
147 _num_processed++;
148
149 return true;
150 }
151
152 size_t num_processed() { return _num_processed; }
153
154 void print_histo() {
155 gclog_or_tty->print_cr("Card table value histogram:");
156 for (int i = 0; i < 256; i++) {
157 if (_histo[i] != 0) {
158 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
159 }
160 }
161 }
162 };
163
164 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
165 private:
166 size_t _num_processed;
167
168 public:
169 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
170
171 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
172 *card_ptr = CardTableModRefBS::dirty_card_val();
173 _num_processed++;
174 return true;
175 }
176
177 size_t num_processed() const { return _num_processed; }
178 };
179
180 YoungList::YoungList(G1CollectedHeap* g1h) :
181 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
182 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
183 guarantee(check_list_empty(false), "just making sure...");
184 }
185
186 void YoungList::push_region(HeapRegion *hr) {
187 assert(!hr->is_young(), "should not already be young");
188 assert(hr->get_next_young_region() == NULL, "cause it should!");
189
190 hr->set_next_young_region(_head);
191 _head = hr;
192
193 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
194 ++_length;
195 }
196
197 void YoungList::add_survivor_region(HeapRegion* hr) {
198 assert(hr->is_survivor(), "should be flagged as survivor region");
199 assert(hr->get_next_young_region() == NULL, "cause it should!");
200
201 hr->set_next_young_region(_survivor_head);
202 if (_survivor_head == NULL) {
203 _survivor_tail = hr;
204 }
205 _survivor_head = hr;
206 ++_survivor_length;
207 }
208
209 void YoungList::empty_list(HeapRegion* list) {
210 while (list != NULL) {
211 HeapRegion* next = list->get_next_young_region();
212 list->set_next_young_region(NULL);
213 list->uninstall_surv_rate_group();
214 list->set_not_young();
215 list = next;
216 }
217 }
218
219 void YoungList::empty_list() {
220 assert(check_list_well_formed(), "young list should be well formed");
221
222 empty_list(_head);
223 _head = NULL;
224 _length = 0;
225
226 empty_list(_survivor_head);
227 _survivor_head = NULL;
228 _survivor_tail = NULL;
229 _survivor_length = 0;
230
231 _last_sampled_rs_lengths = 0;
232
233 assert(check_list_empty(false), "just making sure...");
234 }
235
236 bool YoungList::check_list_well_formed() {
237 bool ret = true;
238
239 uint length = 0;
240 HeapRegion* curr = _head;
241 HeapRegion* last = NULL;
242 while (curr != NULL) {
243 if (!curr->is_young()) {
244 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
245 "incorrectly tagged (y: %d, surv: %d)",
246 curr->bottom(), curr->end(),
247 curr->is_young(), curr->is_survivor());
248 ret = false;
249 }
250 ++length;
251 last = curr;
252 curr = curr->get_next_young_region();
253 }
254 ret = ret && (length == _length);
255
256 if (!ret) {
257 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
258 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
259 length, _length);
260 }
261
262 return ret;
263 }
264
265 bool YoungList::check_list_empty(bool check_sample) {
266 bool ret = true;
267
268 if (_length != 0) {
269 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
270 _length);
271 ret = false;
272 }
273 if (check_sample && _last_sampled_rs_lengths != 0) {
274 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
275 ret = false;
276 }
277 if (_head != NULL) {
278 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
279 ret = false;
280 }
281 if (!ret) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
283 }
284
285 return ret;
286 }
287
288 void
289 YoungList::rs_length_sampling_init() {
290 _sampled_rs_lengths = 0;
291 _curr = _head;
292 }
293
294 bool
295 YoungList::rs_length_sampling_more() {
296 return _curr != NULL;
297 }
298
299 void
300 YoungList::rs_length_sampling_next() {
301 assert( _curr != NULL, "invariant" );
302 size_t rs_length = _curr->rem_set()->occupied();
303
304 _sampled_rs_lengths += rs_length;
305
306 // The current region may not yet have been added to the
307 // incremental collection set (it gets added when it is
308 // retired as the current allocation region).
309 if (_curr->in_collection_set()) {
310 // Update the collection set policy information for this region
311 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
312 }
313
314 _curr = _curr->get_next_young_region();
315 if (_curr == NULL) {
316 _last_sampled_rs_lengths = _sampled_rs_lengths;
317 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
318 }
319 }
320
321 void
322 YoungList::reset_auxilary_lists() {
323 guarantee( is_empty(), "young list should be empty" );
324 assert(check_list_well_formed(), "young list should be well formed");
325
326 // Add survivor regions to SurvRateGroup.
327 _g1h->g1_policy()->note_start_adding_survivor_regions();
328 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
329
330 int young_index_in_cset = 0;
331 for (HeapRegion* curr = _survivor_head;
332 curr != NULL;
333 curr = curr->get_next_young_region()) {
334 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
335
336 // The region is a non-empty survivor so let's add it to
337 // the incremental collection set for the next evacuation
338 // pause.
339 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
340 young_index_in_cset += 1;
341 }
342 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
343 _g1h->g1_policy()->note_stop_adding_survivor_regions();
344
345 _head = _survivor_head;
346 _length = _survivor_length;
347 if (_survivor_head != NULL) {
348 assert(_survivor_tail != NULL, "cause it shouldn't be");
349 assert(_survivor_length > 0, "invariant");
350 _survivor_tail->set_next_young_region(NULL);
351 }
352
353 // Don't clear the survivor list handles until the start of
354 // the next evacuation pause - we need it in order to re-tag
355 // the survivor regions from this evacuation pause as 'young'
356 // at the start of the next.
357
358 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
359
360 assert(check_list_well_formed(), "young list should be well formed");
361 }
362
363 void YoungList::print() {
364 HeapRegion* lists[] = {_head, _survivor_head};
365 const char* names[] = {"YOUNG", "SURVIVOR"};
366
367 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
368 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
369 HeapRegion *curr = lists[list];
370 if (curr == NULL)
371 gclog_or_tty->print_cr(" empty");
372 while (curr != NULL) {
373 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
374 HR_FORMAT_PARAMS(curr),
375 curr->prev_top_at_mark_start(),
376 curr->next_top_at_mark_start(),
377 curr->age_in_surv_rate_group_cond());
378 curr = curr->get_next_young_region();
379 }
380 }
381
382 gclog_or_tty->cr();
383 }
384
385 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
386 OtherRegionsTable::invalidate(start_idx, num_regions);
387 }
388
389 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
390 reset_from_card_cache(start_idx, num_regions);
391 }
392
393 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
394 {
395 // Claim the right to put the region on the dirty cards region list
396 // by installing a self pointer.
397 HeapRegion* next = hr->get_next_dirty_cards_region();
398 if (next == NULL) {
399 HeapRegion* res = (HeapRegion*)
400 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
401 NULL);
402 if (res == NULL) {
403 HeapRegion* head;
404 do {
405 // Put the region to the dirty cards region list.
406 head = _dirty_cards_region_list;
407 next = (HeapRegion*)
408 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
409 if (next == head) {
410 assert(hr->get_next_dirty_cards_region() == hr,
411 "hr->get_next_dirty_cards_region() != hr");
412 if (next == NULL) {
413 // The last region in the list points to itself.
414 hr->set_next_dirty_cards_region(hr);
415 } else {
416 hr->set_next_dirty_cards_region(next);
417 }
418 }
419 } while (next != head);
420 }
421 }
422 }
423
424 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
425 {
426 HeapRegion* head;
427 HeapRegion* hr;
428 do {
429 head = _dirty_cards_region_list;
430 if (head == NULL) {
431 return NULL;
432 }
433 HeapRegion* new_head = head->get_next_dirty_cards_region();
434 if (head == new_head) {
435 // The last region.
436 new_head = NULL;
437 }
438 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
439 head);
440 } while (hr != head);
441 assert(hr != NULL, "invariant");
442 hr->set_next_dirty_cards_region(NULL);
443 return hr;
444 }
445
446 #ifdef ASSERT
447 // A region is added to the collection set as it is retired
448 // so an address p can point to a region which will be in the
449 // collection set but has not yet been retired. This method
450 // therefore is only accurate during a GC pause after all
451 // regions have been retired. It is used for debugging
452 // to check if an nmethod has references to objects that can
453 // be move during a partial collection. Though it can be
454 // inaccurate, it is sufficient for G1 because the conservative
455 // implementation of is_scavengable() for G1 will indicate that
456 // all nmethods must be scanned during a partial collection.
457 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
458 if (p == NULL) {
459 return false;
460 }
461 return heap_region_containing(p)->in_collection_set();
462 }
463 #endif
464
465 // Returns true if the reference points to an object that
466 // can move in an incremental collection.
467 bool G1CollectedHeap::is_scavengable(const void* p) {
468 HeapRegion* hr = heap_region_containing(p);
469 return !hr->isHumongous();
470 }
471
472 void G1CollectedHeap::check_ct_logs_at_safepoint() {
473 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
474 CardTableModRefBS* ct_bs = g1_barrier_set();
475
476 // Count the dirty cards at the start.
477 CountNonCleanMemRegionClosure count1(this);
478 ct_bs->mod_card_iterate(&count1);
479 int orig_count = count1.n();
480
481 // First clear the logged cards.
482 ClearLoggedCardTableEntryClosure clear;
483 dcqs.apply_closure_to_all_completed_buffers(&clear);
484 dcqs.iterate_closure_all_threads(&clear, false);
485 clear.print_histo();
486
487 // Now ensure that there's no dirty cards.
488 CountNonCleanMemRegionClosure count2(this);
489 ct_bs->mod_card_iterate(&count2);
490 if (count2.n() != 0) {
491 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
492 count2.n(), orig_count);
493 }
494 guarantee(count2.n() == 0, "Card table should be clean.");
495
496 RedirtyLoggedCardTableEntryClosure redirty;
497 dcqs.apply_closure_to_all_completed_buffers(&redirty);
498 dcqs.iterate_closure_all_threads(&redirty, false);
499 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
500 clear.num_processed(), orig_count);
501 guarantee(redirty.num_processed() == clear.num_processed(),
502 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
503 redirty.num_processed(), clear.num_processed()));
504
505 CountNonCleanMemRegionClosure count3(this);
506 ct_bs->mod_card_iterate(&count3);
507 if (count3.n() != orig_count) {
508 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
509 orig_count, count3.n());
510 guarantee(count3.n() >= orig_count, "Should have restored them all.");
511 }
512 }
513
514 // Private class members.
515
516 G1CollectedHeap* G1CollectedHeap::_g1h;
517
518 // Private methods.
519
520 HeapRegion*
521 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
522 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
523 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
524 if (!_secondary_free_list.is_empty()) {
525 if (G1ConcRegionFreeingVerbose) {
526 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
527 "secondary_free_list has %u entries",
528 _secondary_free_list.length());
529 }
530 // It looks as if there are free regions available on the
531 // secondary_free_list. Let's move them to the free_list and try
532 // again to allocate from it.
533 append_secondary_free_list();
534
535 assert(_hrs.num_free_regions() > 0, "if the secondary_free_list was not "
536 "empty we should have moved at least one entry to the free_list");
537 HeapRegion* res = _hrs.allocate_free_region(is_old);
538 if (G1ConcRegionFreeingVerbose) {
539 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
540 "allocated "HR_FORMAT" from secondary_free_list",
541 HR_FORMAT_PARAMS(res));
542 }
543 return res;
544 }
545
546 // Wait here until we get notified either when (a) there are no
547 // more free regions coming or (b) some regions have been moved on
548 // the secondary_free_list.
549 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
550 }
551
552 if (G1ConcRegionFreeingVerbose) {
553 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
554 "could not allocate from secondary_free_list");
555 }
556 return NULL;
557 }
558
559 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
560 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
561 "the only time we use this to allocate a humongous region is "
562 "when we are allocating a single humongous region");
563
564 HeapRegion* res;
565 if (G1StressConcRegionFreeing) {
566 if (!_secondary_free_list.is_empty()) {
567 if (G1ConcRegionFreeingVerbose) {
568 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
569 "forced to look at the secondary_free_list");
570 }
571 res = new_region_try_secondary_free_list(is_old);
572 if (res != NULL) {
573 return res;
574 }
575 }
576 }
577
578 res = _hrs.allocate_free_region(is_old);
579
580 if (res == NULL) {
581 if (G1ConcRegionFreeingVerbose) {
582 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
583 "res == NULL, trying the secondary_free_list");
584 }
585 res = new_region_try_secondary_free_list(is_old);
586 }
587 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
588 // Currently, only attempts to allocate GC alloc regions set
589 // do_expand to true. So, we should only reach here during a
590 // safepoint. If this assumption changes we might have to
591 // reconsider the use of _expand_heap_after_alloc_failure.
592 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
593
594 ergo_verbose1(ErgoHeapSizing,
595 "attempt heap expansion",
596 ergo_format_reason("region allocation request failed")
597 ergo_format_byte("allocation request"),
598 word_size * HeapWordSize);
599 if (expand(word_size * HeapWordSize)) {
600 // Given that expand() succeeded in expanding the heap, and we
601 // always expand the heap by an amount aligned to the heap
602 // region size, the free list should in theory not be empty.
603 // In either case allocate_free_region() will check for NULL.
604 res = _hrs.allocate_free_region(is_old);
605 } else {
606 _expand_heap_after_alloc_failure = false;
607 }
608 }
609 return res;
610 }
611
612 HeapWord*
613 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
614 uint num_regions,
615 size_t word_size) {
616 assert(first != G1_NO_HRS_INDEX, "pre-condition");
617 assert(isHumongous(word_size), "word_size should be humongous");
618 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
619
620 // Index of last region in the series + 1.
621 uint last = first + num_regions;
622
623 // We need to initialize the region(s) we just discovered. This is
624 // a bit tricky given that it can happen concurrently with
625 // refinement threads refining cards on these regions and
626 // potentially wanting to refine the BOT as they are scanning
627 // those cards (this can happen shortly after a cleanup; see CR
628 // 6991377). So we have to set up the region(s) carefully and in
629 // a specific order.
630
631 // The word size sum of all the regions we will allocate.
632 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
633 assert(word_size <= word_size_sum, "sanity");
634
635 // This will be the "starts humongous" region.
636 HeapRegion* first_hr = region_at(first);
637 // The header of the new object will be placed at the bottom of
638 // the first region.
639 HeapWord* new_obj = first_hr->bottom();
640 // This will be the new end of the first region in the series that
641 // should also match the end of the last region in the series.
642 HeapWord* new_end = new_obj + word_size_sum;
643 // This will be the new top of the first region that will reflect
644 // this allocation.
645 HeapWord* new_top = new_obj + word_size;
646
647 // First, we need to zero the header of the space that we will be
648 // allocating. When we update top further down, some refinement
649 // threads might try to scan the region. By zeroing the header we
650 // ensure that any thread that will try to scan the region will
651 // come across the zero klass word and bail out.
652 //
653 // NOTE: It would not have been correct to have used
654 // CollectedHeap::fill_with_object() and make the space look like
655 // an int array. The thread that is doing the allocation will
656 // later update the object header to a potentially different array
657 // type and, for a very short period of time, the klass and length
658 // fields will be inconsistent. This could cause a refinement
659 // thread to calculate the object size incorrectly.
660 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
661
662 // We will set up the first region as "starts humongous". This
663 // will also update the BOT covering all the regions to reflect
664 // that there is a single object that starts at the bottom of the
665 // first region.
666 first_hr->set_startsHumongous(new_top, new_end);
667
668 // Then, if there are any, we will set up the "continues
669 // humongous" regions.
670 HeapRegion* hr = NULL;
671 for (uint i = first + 1; i < last; ++i) {
672 hr = region_at(i);
673 hr->set_continuesHumongous(first_hr);
674 }
675 // If we have "continues humongous" regions (hr != NULL), then the
676 // end of the last one should match new_end.
677 assert(hr == NULL || hr->end() == new_end, "sanity");
678
679 // Up to this point no concurrent thread would have been able to
680 // do any scanning on any region in this series. All the top
681 // fields still point to bottom, so the intersection between
682 // [bottom,top] and [card_start,card_end] will be empty. Before we
683 // update the top fields, we'll do a storestore to make sure that
684 // no thread sees the update to top before the zeroing of the
685 // object header and the BOT initialization.
686 OrderAccess::storestore();
687
688 // Now that the BOT and the object header have been initialized,
689 // we can update top of the "starts humongous" region.
690 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
691 "new_top should be in this region");
692 first_hr->set_top(new_top);
693 if (_hr_printer.is_active()) {
694 HeapWord* bottom = first_hr->bottom();
695 HeapWord* end = first_hr->orig_end();
696 if ((first + 1) == last) {
697 // the series has a single humongous region
698 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
699 } else {
700 // the series has more than one humongous regions
701 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
702 }
703 }
704
705 // Now, we will update the top fields of the "continues humongous"
706 // regions. The reason we need to do this is that, otherwise,
707 // these regions would look empty and this will confuse parts of
708 // G1. For example, the code that looks for a consecutive number
709 // of empty regions will consider them empty and try to
710 // re-allocate them. We can extend is_empty() to also include
711 // !continuesHumongous(), but it is easier to just update the top
712 // fields here. The way we set top for all regions (i.e., top ==
713 // end for all regions but the last one, top == new_top for the
714 // last one) is actually used when we will free up the humongous
715 // region in free_humongous_region().
716 hr = NULL;
717 for (uint i = first + 1; i < last; ++i) {
718 hr = region_at(i);
719 if ((i + 1) == last) {
720 // last continues humongous region
721 assert(hr->bottom() < new_top && new_top <= hr->end(),
722 "new_top should fall on this region");
723 hr->set_top(new_top);
724 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
725 } else {
726 // not last one
727 assert(new_top > hr->end(), "new_top should be above this region");
728 hr->set_top(hr->end());
729 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
730 }
731 }
732 // If we have continues humongous regions (hr != NULL), then the
733 // end of the last one should match new_end and its top should
734 // match new_top.
735 assert(hr == NULL ||
736 (hr->end() == new_end && hr->top() == new_top), "sanity");
737 check_bitmaps("Humongous Region Allocation", first_hr);
738
739 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
740 _summary_bytes_used += first_hr->used();
741 _humongous_set.add(first_hr);
742
743 return new_obj;
744 }
745
746 // If could fit into free regions w/o expansion, try.
747 // Otherwise, if can expand, do so.
748 // Otherwise, if using ex regions might help, try with ex given back.
749 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
750 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
751
752 verify_region_sets_optional();
753
754 uint first = G1_NO_HRS_INDEX;
755 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
756
757 if (obj_regions == 1) {
758 // Only one region to allocate, try to use a fast path by directly allocating
759 // from the free lists. Do not try to expand here, we will potentially do that
760 // later.
761 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
762 if (hr != NULL) {
763 first = hr->hrs_index();
764 }
765 } else {
766 // We can't allocate humongous regions spanning more than one region while
767 // cleanupComplete() is running, since some of the regions we find to be
768 // empty might not yet be added to the free list. It is not straightforward
769 // to know in which list they are on so that we can remove them. We only
770 // need to do this if we need to allocate more than one region to satisfy the
771 // current humongous allocation request. If we are only allocating one region
772 // we use the one-region region allocation code (see above), that already
773 // potentially waits for regions from the secondary free list.
774 wait_while_free_regions_coming();
775 append_secondary_free_list_if_not_empty_with_lock();
776
777 // Policy: Try only empty regions (i.e. already committed first). Maybe we
778 // are lucky enough to find some.
779 first = _hrs.find_contiguous_only_empty(obj_regions);
780 if (first != G1_NO_HRS_INDEX) {
781 _hrs.allocate_free_regions_starting_at(first, obj_regions);
782 }
783 }
784
785 if (first == G1_NO_HRS_INDEX) {
786 // Policy: We could not find enough regions for the humongous object in the
787 // free list. Look through the heap to find a mix of free and uncommitted regions.
788 // If so, try expansion.
789 first = _hrs.find_contiguous_empty_or_unavailable(obj_regions);
790 if (first != G1_NO_HRS_INDEX) {
791 // We found something. Make sure these regions are committed, i.e. expand
792 // the heap. Alternatively we could do a defragmentation GC.
793 ergo_verbose1(ErgoHeapSizing,
794 "attempt heap expansion",
795 ergo_format_reason("humongous allocation request failed")
796 ergo_format_byte("allocation request"),
797 word_size * HeapWordSize);
798
799 _hrs.expand_at(first, obj_regions);
800 g1_policy()->record_new_heap_size(num_regions());
801
802 #ifdef ASSERT
803 for (uint i = first; i < first + obj_regions; ++i) {
804 HeapRegion* hr = region_at(i);
805 assert(hr->is_empty(), "sanity");
806 assert(is_on_master_free_list(hr), "sanity");
807 }
808 #endif
809 _hrs.allocate_free_regions_starting_at(first, obj_regions);
810 } else {
811 // Policy: Potentially trigger a defragmentation GC.
812 }
813 }
814
815 HeapWord* result = NULL;
816 if (first != G1_NO_HRS_INDEX) {
817 result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
818 assert(result != NULL, "it should always return a valid result");
819
820 // A successful humongous object allocation changes the used space
821 // information of the old generation so we need to recalculate the
822 // sizes and update the jstat counters here.
823 g1mm()->update_sizes();
824 }
825
826 verify_region_sets_optional();
827
828 return result;
829 }
830
831 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
832 assert_heap_not_locked_and_not_at_safepoint();
833 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
834
835 unsigned int dummy_gc_count_before;
836 int dummy_gclocker_retry_count = 0;
837 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
838 }
839
840 HeapWord*
841 G1CollectedHeap::mem_allocate(size_t word_size,
842 bool* gc_overhead_limit_was_exceeded) {
843 assert_heap_not_locked_and_not_at_safepoint();
844
845 // Loop until the allocation is satisfied, or unsatisfied after GC.
846 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
847 unsigned int gc_count_before;
848
849 HeapWord* result = NULL;
850 if (!isHumongous(word_size)) {
851 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
852 } else {
853 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
854 }
855 if (result != NULL) {
856 return result;
857 }
858
859 // Create the garbage collection operation...
860 VM_G1CollectForAllocation op(gc_count_before, word_size);
861 // ...and get the VM thread to execute it.
862 VMThread::execute(&op);
863
864 if (op.prologue_succeeded() && op.pause_succeeded()) {
865 // If the operation was successful we'll return the result even
866 // if it is NULL. If the allocation attempt failed immediately
867 // after a Full GC, it's unlikely we'll be able to allocate now.
868 HeapWord* result = op.result();
869 if (result != NULL && !isHumongous(word_size)) {
870 // Allocations that take place on VM operations do not do any
871 // card dirtying and we have to do it here. We only have to do
872 // this for non-humongous allocations, though.
873 dirty_young_block(result, word_size);
874 }
875 return result;
876 } else {
877 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
878 return NULL;
879 }
880 assert(op.result() == NULL,
881 "the result should be NULL if the VM op did not succeed");
882 }
883
884 // Give a warning if we seem to be looping forever.
885 if ((QueuedAllocationWarningCount > 0) &&
886 (try_count % QueuedAllocationWarningCount == 0)) {
887 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
888 }
889 }
890
891 ShouldNotReachHere();
892 return NULL;
893 }
894
895 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
896 unsigned int *gc_count_before_ret,
897 int* gclocker_retry_count_ret) {
898 // Make sure you read the note in attempt_allocation_humongous().
899
900 assert_heap_not_locked_and_not_at_safepoint();
901 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
902 "be called for humongous allocation requests");
903
904 // We should only get here after the first-level allocation attempt
905 // (attempt_allocation()) failed to allocate.
906
907 // We will loop until a) we manage to successfully perform the
908 // allocation or b) we successfully schedule a collection which
909 // fails to perform the allocation. b) is the only case when we'll
910 // return NULL.
911 HeapWord* result = NULL;
912 for (int try_count = 1; /* we'll return */; try_count += 1) {
913 bool should_try_gc;
914 unsigned int gc_count_before;
915
916 {
917 MutexLockerEx x(Heap_lock);
918
919 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
920 false /* bot_updates */);
921 if (result != NULL) {
922 return result;
923 }
924
925 // If we reach here, attempt_allocation_locked() above failed to
926 // allocate a new region. So the mutator alloc region should be NULL.
927 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
928
929 if (GC_locker::is_active_and_needs_gc()) {
930 if (g1_policy()->can_expand_young_list()) {
931 // No need for an ergo verbose message here,
932 // can_expand_young_list() does this when it returns true.
933 result = _mutator_alloc_region.attempt_allocation_force(word_size,
934 false /* bot_updates */);
935 if (result != NULL) {
936 return result;
937 }
938 }
939 should_try_gc = false;
940 } else {
941 // The GCLocker may not be active but the GCLocker initiated
942 // GC may not yet have been performed (GCLocker::needs_gc()
943 // returns true). In this case we do not try this GC and
944 // wait until the GCLocker initiated GC is performed, and
945 // then retry the allocation.
946 if (GC_locker::needs_gc()) {
947 should_try_gc = false;
948 } else {
949 // Read the GC count while still holding the Heap_lock.
950 gc_count_before = total_collections();
951 should_try_gc = true;
952 }
953 }
954 }
955
956 if (should_try_gc) {
957 bool succeeded;
958 result = do_collection_pause(word_size, gc_count_before, &succeeded,
959 GCCause::_g1_inc_collection_pause);
960 if (result != NULL) {
961 assert(succeeded, "only way to get back a non-NULL result");
962 return result;
963 }
964
965 if (succeeded) {
966 // If we get here we successfully scheduled a collection which
967 // failed to allocate. No point in trying to allocate
968 // further. We'll just return NULL.
969 MutexLockerEx x(Heap_lock);
970 *gc_count_before_ret = total_collections();
971 return NULL;
972 }
973 } else {
974 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
975 MutexLockerEx x(Heap_lock);
976 *gc_count_before_ret = total_collections();
977 return NULL;
978 }
979 // The GCLocker is either active or the GCLocker initiated
980 // GC has not yet been performed. Stall until it is and
981 // then retry the allocation.
982 GC_locker::stall_until_clear();
983 (*gclocker_retry_count_ret) += 1;
984 }
985
986 // We can reach here if we were unsuccessful in scheduling a
987 // collection (because another thread beat us to it) or if we were
988 // stalled due to the GC locker. In either can we should retry the
989 // allocation attempt in case another thread successfully
990 // performed a collection and reclaimed enough space. We do the
991 // first attempt (without holding the Heap_lock) here and the
992 // follow-on attempt will be at the start of the next loop
993 // iteration (after taking the Heap_lock).
994 result = _mutator_alloc_region.attempt_allocation(word_size,
995 false /* bot_updates */);
996 if (result != NULL) {
997 return result;
998 }
999
1000 // Give a warning if we seem to be looping forever.
1001 if ((QueuedAllocationWarningCount > 0) &&
1002 (try_count % QueuedAllocationWarningCount == 0)) {
1003 warning("G1CollectedHeap::attempt_allocation_slow() "
1004 "retries %d times", try_count);
1005 }
1006 }
1007
1008 ShouldNotReachHere();
1009 return NULL;
1010 }
1011
1012 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1013 unsigned int * gc_count_before_ret,
1014 int* gclocker_retry_count_ret) {
1015 // The structure of this method has a lot of similarities to
1016 // attempt_allocation_slow(). The reason these two were not merged
1017 // into a single one is that such a method would require several "if
1018 // allocation is not humongous do this, otherwise do that"
1019 // conditional paths which would obscure its flow. In fact, an early
1020 // version of this code did use a unified method which was harder to
1021 // follow and, as a result, it had subtle bugs that were hard to
1022 // track down. So keeping these two methods separate allows each to
1023 // be more readable. It will be good to keep these two in sync as
1024 // much as possible.
1025
1026 assert_heap_not_locked_and_not_at_safepoint();
1027 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1028 "should only be called for humongous allocations");
1029
1030 // Humongous objects can exhaust the heap quickly, so we should check if we
1031 // need to start a marking cycle at each humongous object allocation. We do
1032 // the check before we do the actual allocation. The reason for doing it
1033 // before the allocation is that we avoid having to keep track of the newly
1034 // allocated memory while we do a GC.
1035 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1036 word_size)) {
1037 collect(GCCause::_g1_humongous_allocation);
1038 }
1039
1040 // We will loop until a) we manage to successfully perform the
1041 // allocation or b) we successfully schedule a collection which
1042 // fails to perform the allocation. b) is the only case when we'll
1043 // return NULL.
1044 HeapWord* result = NULL;
1045 for (int try_count = 1; /* we'll return */; try_count += 1) {
1046 bool should_try_gc;
1047 unsigned int gc_count_before;
1048
1049 {
1050 MutexLockerEx x(Heap_lock);
1051
1052 // Given that humongous objects are not allocated in young
1053 // regions, we'll first try to do the allocation without doing a
1054 // collection hoping that there's enough space in the heap.
1055 result = humongous_obj_allocate(word_size);
1056 if (result != NULL) {
1057 return result;
1058 }
1059
1060 if (GC_locker::is_active_and_needs_gc()) {
1061 should_try_gc = false;
1062 } else {
1063 // The GCLocker may not be active but the GCLocker initiated
1064 // GC may not yet have been performed (GCLocker::needs_gc()
1065 // returns true). In this case we do not try this GC and
1066 // wait until the GCLocker initiated GC is performed, and
1067 // then retry the allocation.
1068 if (GC_locker::needs_gc()) {
1069 should_try_gc = false;
1070 } else {
1071 // Read the GC count while still holding the Heap_lock.
1072 gc_count_before = total_collections();
1073 should_try_gc = true;
1074 }
1075 }
1076 }
1077
1078 if (should_try_gc) {
1079 // If we failed to allocate the humongous object, we should try to
1080 // do a collection pause (if we're allowed) in case it reclaims
1081 // enough space for the allocation to succeed after the pause.
1082
1083 bool succeeded;
1084 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1085 GCCause::_g1_humongous_allocation);
1086 if (result != NULL) {
1087 assert(succeeded, "only way to get back a non-NULL result");
1088 return result;
1089 }
1090
1091 if (succeeded) {
1092 // If we get here we successfully scheduled a collection which
1093 // failed to allocate. No point in trying to allocate
1094 // further. We'll just return NULL.
1095 MutexLockerEx x(Heap_lock);
1096 *gc_count_before_ret = total_collections();
1097 return NULL;
1098 }
1099 } else {
1100 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 // The GCLocker is either active or the GCLocker initiated
1106 // GC has not yet been performed. Stall until it is and
1107 // then retry the allocation.
1108 GC_locker::stall_until_clear();
1109 (*gclocker_retry_count_ret) += 1;
1110 }
1111
1112 // We can reach here if we were unsuccessful in scheduling a
1113 // collection (because another thread beat us to it) or if we were
1114 // stalled due to the GC locker. In either can we should retry the
1115 // allocation attempt in case another thread successfully
1116 // performed a collection and reclaimed enough space. Give a
1117 // warning if we seem to be looping forever.
1118
1119 if ((QueuedAllocationWarningCount > 0) &&
1120 (try_count % QueuedAllocationWarningCount == 0)) {
1121 warning("G1CollectedHeap::attempt_allocation_humongous() "
1122 "retries %d times", try_count);
1123 }
1124 }
1125
1126 ShouldNotReachHere();
1127 return NULL;
1128 }
1129
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131 bool expect_null_mutator_alloc_region) {
1132 assert_at_safepoint(true /* should_be_vm_thread */);
1133 assert(_mutator_alloc_region.get() == NULL ||
1134 !expect_null_mutator_alloc_region,
1135 "the current alloc region was unexpectedly found to be non-NULL");
1136
1137 if (!isHumongous(word_size)) {
1138 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139 false /* bot_updates */);
1140 } else {
1141 HeapWord* result = humongous_obj_allocate(word_size);
1142 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143 g1_policy()->set_initiate_conc_mark_if_possible();
1144 }
1145 return result;
1146 }
1147
1148 ShouldNotReachHere();
1149 }
1150
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152 G1CollectedHeap* _g1h;
1153 ModRefBarrierSet* _mr_bs;
1154 public:
1155 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1156 _g1h(g1h), _mr_bs(mr_bs) {}
1157
1158 bool doHeapRegion(HeapRegion* r) {
1159 HeapRegionRemSet* hrrs = r->rem_set();
1160
1161 if (r->continuesHumongous()) {
1162 // We'll assert that the strong code root list and RSet is empty
1163 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1164 assert(hrrs->occupied() == 0, "RSet should be empty");
1165 return false;
1166 }
1167
1168 _g1h->reset_gc_time_stamps(r);
1169 hrrs->clear();
1170 // You might think here that we could clear just the cards
1171 // corresponding to the used region. But no: if we leave a dirty card
1172 // in a region we might allocate into, then it would prevent that card
1173 // from being enqueued, and cause it to be missed.
1174 // Re: the performance cost: we shouldn't be doing full GC anyway!
1175 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1176
1177 return false;
1178 }
1179 };
1180
1181 void G1CollectedHeap::clear_rsets_post_compaction() {
1182 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1183 heap_region_iterate(&rs_clear);
1184 }
1185
1186 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1187 G1CollectedHeap* _g1h;
1188 UpdateRSOopClosure _cl;
1189 int _worker_i;
1190 public:
1191 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1192 _cl(g1->g1_rem_set(), worker_i),
1193 _worker_i(worker_i),
1194 _g1h(g1)
1195 { }
1196
1197 bool doHeapRegion(HeapRegion* r) {
1198 if (!r->continuesHumongous()) {
1199 _cl.set_from(r);
1200 r->oop_iterate(&_cl);
1201 }
1202 return false;
1203 }
1204 };
1205
1206 class ParRebuildRSTask: public AbstractGangTask {
1207 G1CollectedHeap* _g1;
1208 public:
1209 ParRebuildRSTask(G1CollectedHeap* g1)
1210 : AbstractGangTask("ParRebuildRSTask"),
1211 _g1(g1)
1212 { }
1213
1214 void work(uint worker_id) {
1215 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1216 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1217 _g1->workers()->active_workers(),
1218 HeapRegion::RebuildRSClaimValue);
1219 }
1220 };
1221
1222 class PostCompactionPrinterClosure: public HeapRegionClosure {
1223 private:
1224 G1HRPrinter* _hr_printer;
1225 public:
1226 bool doHeapRegion(HeapRegion* hr) {
1227 assert(!hr->is_young(), "not expecting to find young regions");
1228 // We only generate output for non-empty regions.
1229 if (!hr->is_empty()) {
1230 if (!hr->isHumongous()) {
1231 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1232 } else if (hr->startsHumongous()) {
1233 if (hr->region_num() == 1) {
1234 // single humongous region
1235 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1236 } else {
1237 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1238 }
1239 } else {
1240 assert(hr->continuesHumongous(), "only way to get here");
1241 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1242 }
1243 }
1244 return false;
1245 }
1246
1247 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1248 : _hr_printer(hr_printer) { }
1249 };
1250
1251 void G1CollectedHeap::print_hrs_post_compaction() {
1252 PostCompactionPrinterClosure cl(hr_printer());
1253 heap_region_iterate(&cl);
1254 }
1255
1256 bool G1CollectedHeap::do_collection(bool explicit_gc,
1257 bool clear_all_soft_refs,
1258 size_t word_size) {
1259 assert_at_safepoint(true /* should_be_vm_thread */);
1260
1261 if (GC_locker::check_active_before_gc()) {
1262 return false;
1263 }
1264
1265 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1266 gc_timer->register_gc_start();
1267
1268 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1269 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1270
1271 SvcGCMarker sgcm(SvcGCMarker::FULL);
1272 ResourceMark rm;
1273
1274 print_heap_before_gc();
1275 trace_heap_before_gc(gc_tracer);
1276
1277 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1278
1279 verify_region_sets_optional();
1280
1281 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1282 collector_policy()->should_clear_all_soft_refs();
1283
1284 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1285
1286 {
1287 IsGCActiveMark x;
1288
1289 // Timing
1290 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1291 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1292 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1293
1294 {
1295 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1296 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1297 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1298
1299 double start = os::elapsedTime();
1300 g1_policy()->record_full_collection_start();
1301
1302 // Note: When we have a more flexible GC logging framework that
1303 // allows us to add optional attributes to a GC log record we
1304 // could consider timing and reporting how long we wait in the
1305 // following two methods.
1306 wait_while_free_regions_coming();
1307 // If we start the compaction before the CM threads finish
1308 // scanning the root regions we might trip them over as we'll
1309 // be moving objects / updating references. So let's wait until
1310 // they are done. By telling them to abort, they should complete
1311 // early.
1312 _cm->root_regions()->abort();
1313 _cm->root_regions()->wait_until_scan_finished();
1314 append_secondary_free_list_if_not_empty_with_lock();
1315
1316 gc_prologue(true);
1317 increment_total_collections(true /* full gc */);
1318 increment_old_marking_cycles_started();
1319
1320 assert(used() == recalculate_used(), "Should be equal");
1321
1322 verify_before_gc();
1323
1324 check_bitmaps("Full GC Start");
1325 pre_full_gc_dump(gc_timer);
1326
1327 COMPILER2_PRESENT(DerivedPointerTable::clear());
1328
1329 // Disable discovery and empty the discovered lists
1330 // for the CM ref processor.
1331 ref_processor_cm()->disable_discovery();
1332 ref_processor_cm()->abandon_partial_discovery();
1333 ref_processor_cm()->verify_no_references_recorded();
1334
1335 // Abandon current iterations of concurrent marking and concurrent
1336 // refinement, if any are in progress. We have to do this before
1337 // wait_until_scan_finished() below.
1338 concurrent_mark()->abort();
1339
1340 // Make sure we'll choose a new allocation region afterwards.
1341 release_mutator_alloc_region();
1342 abandon_gc_alloc_regions();
1343 g1_rem_set()->cleanupHRRS();
1344
1345 // We should call this after we retire any currently active alloc
1346 // regions so that all the ALLOC / RETIRE events are generated
1347 // before the start GC event.
1348 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1349
1350 // We may have added regions to the current incremental collection
1351 // set between the last GC or pause and now. We need to clear the
1352 // incremental collection set and then start rebuilding it afresh
1353 // after this full GC.
1354 abandon_collection_set(g1_policy()->inc_cset_head());
1355 g1_policy()->clear_incremental_cset();
1356 g1_policy()->stop_incremental_cset_building();
1357
1358 tear_down_region_sets(false /* free_list_only */);
1359 g1_policy()->set_gcs_are_young(true);
1360
1361 // See the comments in g1CollectedHeap.hpp and
1362 // G1CollectedHeap::ref_processing_init() about
1363 // how reference processing currently works in G1.
1364
1365 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1366 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1367
1368 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1369 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1370
1371 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1372 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1373
1374 // Do collection work
1375 {
1376 HandleMark hm; // Discard invalid handles created during gc
1377 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1378 }
1379
1380 assert(num_free_regions() == 0, "we should not have added any free regions");
1381 rebuild_region_sets(false /* free_list_only */);
1382
1383 // Enqueue any discovered reference objects that have
1384 // not been removed from the discovered lists.
1385 ref_processor_stw()->enqueue_discovered_references();
1386
1387 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1388
1389 MemoryService::track_memory_usage();
1390
1391 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1392 ref_processor_stw()->verify_no_references_recorded();
1393
1394 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1395 ClassLoaderDataGraph::purge();
1396 MetaspaceAux::verify_metrics();
1397
1398 // Note: since we've just done a full GC, concurrent
1399 // marking is no longer active. Therefore we need not
1400 // re-enable reference discovery for the CM ref processor.
1401 // That will be done at the start of the next marking cycle.
1402 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1403 ref_processor_cm()->verify_no_references_recorded();
1404
1405 reset_gc_time_stamp();
1406 // Since everything potentially moved, we will clear all remembered
1407 // sets, and clear all cards. Later we will rebuild remembered
1408 // sets. We will also reset the GC time stamps of the regions.
1409 clear_rsets_post_compaction();
1410 check_gc_time_stamps();
1411
1412 // Resize the heap if necessary.
1413 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1414
1415 if (_hr_printer.is_active()) {
1416 // We should do this after we potentially resize the heap so
1417 // that all the COMMIT / UNCOMMIT events are generated before
1418 // the end GC event.
1419
1420 print_hrs_post_compaction();
1421 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1422 }
1423
1424 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1425 if (hot_card_cache->use_cache()) {
1426 hot_card_cache->reset_card_counts();
1427 hot_card_cache->reset_hot_cache();
1428 }
1429
1430 // Rebuild remembered sets of all regions.
1431 if (G1CollectedHeap::use_parallel_gc_threads()) {
1432 uint n_workers =
1433 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1434 workers()->active_workers(),
1435 Threads::number_of_non_daemon_threads());
1436 assert(UseDynamicNumberOfGCThreads ||
1437 n_workers == workers()->total_workers(),
1438 "If not dynamic should be using all the workers");
1439 workers()->set_active_workers(n_workers);
1440 // Set parallel threads in the heap (_n_par_threads) only
1441 // before a parallel phase and always reset it to 0 after
1442 // the phase so that the number of parallel threads does
1443 // no get carried forward to a serial phase where there
1444 // may be code that is "possibly_parallel".
1445 set_par_threads(n_workers);
1446
1447 ParRebuildRSTask rebuild_rs_task(this);
1448 assert(check_heap_region_claim_values(
1449 HeapRegion::InitialClaimValue), "sanity check");
1450 assert(UseDynamicNumberOfGCThreads ||
1451 workers()->active_workers() == workers()->total_workers(),
1452 "Unless dynamic should use total workers");
1453 // Use the most recent number of active workers
1454 assert(workers()->active_workers() > 0,
1455 "Active workers not properly set");
1456 set_par_threads(workers()->active_workers());
1457 workers()->run_task(&rebuild_rs_task);
1458 set_par_threads(0);
1459 assert(check_heap_region_claim_values(
1460 HeapRegion::RebuildRSClaimValue), "sanity check");
1461 reset_heap_region_claim_values();
1462 } else {
1463 RebuildRSOutOfRegionClosure rebuild_rs(this);
1464 heap_region_iterate(&rebuild_rs);
1465 }
1466
1467 // Rebuild the strong code root lists for each region
1468 rebuild_strong_code_roots();
1469
1470 if (true) { // FIXME
1471 MetaspaceGC::compute_new_size();
1472 }
1473
1474 #ifdef TRACESPINNING
1475 ParallelTaskTerminator::print_termination_counts();
1476 #endif
1477
1478 // Discard all rset updates
1479 JavaThread::dirty_card_queue_set().abandon_logs();
1480 assert(!G1DeferredRSUpdate
1481 || (G1DeferredRSUpdate &&
1482 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1483
1484 _young_list->reset_sampled_info();
1485 // At this point there should be no regions in the
1486 // entire heap tagged as young.
1487 assert(check_young_list_empty(true /* check_heap */),
1488 "young list should be empty at this point");
1489
1490 // Update the number of full collections that have been completed.
1491 increment_old_marking_cycles_completed(false /* concurrent */);
1492
1493 _hrs.verify_optional();
1494 verify_region_sets_optional();
1495
1496 verify_after_gc();
1497
1498 // Clear the previous marking bitmap, if needed for bitmap verification.
1499 // Note we cannot do this when we clear the next marking bitmap in
1500 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1501 // objects marked during a full GC against the previous bitmap.
1502 // But we need to clear it before calling check_bitmaps below since
1503 // the full GC has compacted objects and updated TAMS but not updated
1504 // the prev bitmap.
1505 if (G1VerifyBitmaps) {
1506 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1507 }
1508 check_bitmaps("Full GC End");
1509
1510 // Start a new incremental collection set for the next pause
1511 assert(g1_policy()->collection_set() == NULL, "must be");
1512 g1_policy()->start_incremental_cset_building();
1513
1514 clear_cset_fast_test();
1515
1516 init_mutator_alloc_region();
1517
1518 double end = os::elapsedTime();
1519 g1_policy()->record_full_collection_end();
1520
1521 if (G1Log::fine()) {
1522 g1_policy()->print_heap_transition();
1523 }
1524
1525 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1526 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1527 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1528 // before any GC notifications are raised.
1529 g1mm()->update_sizes();
1530
1531 gc_epilogue(true);
1532 }
1533
1534 if (G1Log::finer()) {
1535 g1_policy()->print_detailed_heap_transition(true /* full */);
1536 }
1537
1538 print_heap_after_gc();
1539 trace_heap_after_gc(gc_tracer);
1540
1541 post_full_gc_dump(gc_timer);
1542
1543 gc_timer->register_gc_end();
1544 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1545 }
1546
1547 return true;
1548 }
1549
1550 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1551 // do_collection() will return whether it succeeded in performing
1552 // the GC. Currently, there is no facility on the
1553 // do_full_collection() API to notify the caller than the collection
1554 // did not succeed (e.g., because it was locked out by the GC
1555 // locker). So, right now, we'll ignore the return value.
1556 bool dummy = do_collection(true, /* explicit_gc */
1557 clear_all_soft_refs,
1558 0 /* word_size */);
1559 }
1560
1561 // This code is mostly copied from TenuredGeneration.
1562 void
1563 G1CollectedHeap::
1564 resize_if_necessary_after_full_collection(size_t word_size) {
1565 // Include the current allocation, if any, and bytes that will be
1566 // pre-allocated to support collections, as "used".
1567 const size_t used_after_gc = used();
1568 const size_t capacity_after_gc = capacity();
1569 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1570
1571 // This is enforced in arguments.cpp.
1572 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1573 "otherwise the code below doesn't make sense");
1574
1575 // We don't have floating point command-line arguments
1576 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1577 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1578 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1579 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1580
1581 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1582 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1583
1584 // We have to be careful here as these two calculations can overflow
1585 // 32-bit size_t's.
1586 double used_after_gc_d = (double) used_after_gc;
1587 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1588 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1589
1590 // Let's make sure that they are both under the max heap size, which
1591 // by default will make them fit into a size_t.
1592 double desired_capacity_upper_bound = (double) max_heap_size;
1593 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1594 desired_capacity_upper_bound);
1595 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1596 desired_capacity_upper_bound);
1597
1598 // We can now safely turn them into size_t's.
1599 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1600 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1601
1602 // This assert only makes sense here, before we adjust them
1603 // with respect to the min and max heap size.
1604 assert(minimum_desired_capacity <= maximum_desired_capacity,
1605 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1606 "maximum_desired_capacity = "SIZE_FORMAT,
1607 minimum_desired_capacity, maximum_desired_capacity));
1608
1609 // Should not be greater than the heap max size. No need to adjust
1610 // it with respect to the heap min size as it's a lower bound (i.e.,
1611 // we'll try to make the capacity larger than it, not smaller).
1612 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1613 // Should not be less than the heap min size. No need to adjust it
1614 // with respect to the heap max size as it's an upper bound (i.e.,
1615 // we'll try to make the capacity smaller than it, not greater).
1616 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1617
1618 if (capacity_after_gc < minimum_desired_capacity) {
1619 // Don't expand unless it's significant
1620 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1621 ergo_verbose4(ErgoHeapSizing,
1622 "attempt heap expansion",
1623 ergo_format_reason("capacity lower than "
1624 "min desired capacity after Full GC")
1625 ergo_format_byte("capacity")
1626 ergo_format_byte("occupancy")
1627 ergo_format_byte_perc("min desired capacity"),
1628 capacity_after_gc, used_after_gc,
1629 minimum_desired_capacity, (double) MinHeapFreeRatio);
1630 expand(expand_bytes);
1631
1632 // No expansion, now see if we want to shrink
1633 } else if (capacity_after_gc > maximum_desired_capacity) {
1634 // Capacity too large, compute shrinking size
1635 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1636 ergo_verbose4(ErgoHeapSizing,
1637 "attempt heap shrinking",
1638 ergo_format_reason("capacity higher than "
1639 "max desired capacity after Full GC")
1640 ergo_format_byte("capacity")
1641 ergo_format_byte("occupancy")
1642 ergo_format_byte_perc("max desired capacity"),
1643 capacity_after_gc, used_after_gc,
1644 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1645 shrink(shrink_bytes);
1646 }
1647 }
1648
1649
1650 HeapWord*
1651 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1652 bool* succeeded) {
1653 assert_at_safepoint(true /* should_be_vm_thread */);
1654
1655 *succeeded = true;
1656 // Let's attempt the allocation first.
1657 HeapWord* result =
1658 attempt_allocation_at_safepoint(word_size,
1659 false /* expect_null_mutator_alloc_region */);
1660 if (result != NULL) {
1661 assert(*succeeded, "sanity");
1662 return result;
1663 }
1664
1665 // In a G1 heap, we're supposed to keep allocation from failing by
1666 // incremental pauses. Therefore, at least for now, we'll favor
1667 // expansion over collection. (This might change in the future if we can
1668 // do something smarter than full collection to satisfy a failed alloc.)
1669 result = expand_and_allocate(word_size);
1670 if (result != NULL) {
1671 assert(*succeeded, "sanity");
1672 return result;
1673 }
1674
1675 // Expansion didn't work, we'll try to do a Full GC.
1676 bool gc_succeeded = do_collection(false, /* explicit_gc */
1677 false, /* clear_all_soft_refs */
1678 word_size);
1679 if (!gc_succeeded) {
1680 *succeeded = false;
1681 return NULL;
1682 }
1683
1684 // Retry the allocation
1685 result = attempt_allocation_at_safepoint(word_size,
1686 true /* expect_null_mutator_alloc_region */);
1687 if (result != NULL) {
1688 assert(*succeeded, "sanity");
1689 return result;
1690 }
1691
1692 // Then, try a Full GC that will collect all soft references.
1693 gc_succeeded = do_collection(false, /* explicit_gc */
1694 true, /* clear_all_soft_refs */
1695 word_size);
1696 if (!gc_succeeded) {
1697 *succeeded = false;
1698 return NULL;
1699 }
1700
1701 // Retry the allocation once more
1702 result = attempt_allocation_at_safepoint(word_size,
1703 true /* expect_null_mutator_alloc_region */);
1704 if (result != NULL) {
1705 assert(*succeeded, "sanity");
1706 return result;
1707 }
1708
1709 assert(!collector_policy()->should_clear_all_soft_refs(),
1710 "Flag should have been handled and cleared prior to this point");
1711
1712 // What else? We might try synchronous finalization later. If the total
1713 // space available is large enough for the allocation, then a more
1714 // complete compaction phase than we've tried so far might be
1715 // appropriate.
1716 assert(*succeeded, "sanity");
1717 return NULL;
1718 }
1719
1720 // Attempting to expand the heap sufficiently
1721 // to support an allocation of the given "word_size". If
1722 // successful, perform the allocation and return the address of the
1723 // allocated block, or else "NULL".
1724
1725 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1726 assert_at_safepoint(true /* should_be_vm_thread */);
1727
1728 verify_region_sets_optional();
1729
1730 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1731 ergo_verbose1(ErgoHeapSizing,
1732 "attempt heap expansion",
1733 ergo_format_reason("allocation request failed")
1734 ergo_format_byte("allocation request"),
1735 word_size * HeapWordSize);
1736 if (expand(expand_bytes)) {
1737 _hrs.verify_optional();
1738 verify_region_sets_optional();
1739 return attempt_allocation_at_safepoint(word_size,
1740 false /* expect_null_mutator_alloc_region */);
1741 }
1742 return NULL;
1743 }
1744
1745 bool G1CollectedHeap::expand(size_t expand_bytes) {
1746 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1747 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1748 HeapRegion::GrainBytes);
1749 ergo_verbose2(ErgoHeapSizing,
1750 "expand the heap",
1751 ergo_format_byte("requested expansion amount")
1752 ergo_format_byte("attempted expansion amount"),
1753 expand_bytes, aligned_expand_bytes);
1754
1755 if (is_maximal_no_gc()) {
1756 ergo_verbose0(ErgoHeapSizing,
1757 "did not expand the heap",
1758 ergo_format_reason("heap already fully expanded"));
1759 return false;
1760 }
1761
1762 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1763 assert(regions_to_expand > 0, "Must expand by at least one region");
1764
1765 uint expanded_by = _hrs.expand_by(regions_to_expand);
1766
1767 if (expanded_by > 0) {
1768 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1769 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1770 g1_policy()->record_new_heap_size(num_regions());
1771 } else {
1772 ergo_verbose0(ErgoHeapSizing,
1773 "did not expand the heap",
1774 ergo_format_reason("heap expansion operation failed"));
1775 // The expansion of the virtual storage space was unsuccessful.
1776 // Let's see if it was because we ran out of swap.
1777 if (G1ExitOnExpansionFailure &&
1778 _hrs.available() >= regions_to_expand) {
1779 // We had head room...
1780 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1781 }
1782 }
1783 return regions_to_expand > 0;
1784 }
1785
1786 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1787 size_t aligned_shrink_bytes =
1788 ReservedSpace::page_align_size_down(shrink_bytes);
1789 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1790 HeapRegion::GrainBytes);
1791 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1792
1793 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1794 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1795
1796 ergo_verbose3(ErgoHeapSizing,
1797 "shrink the heap",
1798 ergo_format_byte("requested shrinking amount")
1799 ergo_format_byte("aligned shrinking amount")
1800 ergo_format_byte("attempted shrinking amount"),
1801 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1802 if (num_regions_removed > 0) {
1803 g1_policy()->record_new_heap_size(num_regions());
1804 } else {
1805 ergo_verbose0(ErgoHeapSizing,
1806 "did not shrink the heap",
1807 ergo_format_reason("heap shrinking operation failed"));
1808 }
1809 }
1810
1811 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1812 verify_region_sets_optional();
1813
1814 // We should only reach here at the end of a Full GC which means we
1815 // should not not be holding to any GC alloc regions. The method
1816 // below will make sure of that and do any remaining clean up.
1817 abandon_gc_alloc_regions();
1818
1819 // Instead of tearing down / rebuilding the free lists here, we
1820 // could instead use the remove_all_pending() method on free_list to
1821 // remove only the ones that we need to remove.
1822 tear_down_region_sets(true /* free_list_only */);
1823 shrink_helper(shrink_bytes);
1824 rebuild_region_sets(true /* free_list_only */);
1825
1826 _hrs.verify_optional();
1827 verify_region_sets_optional();
1828 }
1829
1830 // Public methods.
1831
1832 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1833 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1834 #endif // _MSC_VER
1835
1836
1837 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1838 SharedHeap(policy_),
1839 _g1_policy(policy_),
1840 _dirty_card_queue_set(false),
1841 _into_cset_dirty_card_queue_set(false),
1842 _is_alive_closure_cm(this),
1843 _is_alive_closure_stw(this),
1844 _ref_processor_cm(NULL),
1845 _ref_processor_stw(NULL),
1846 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1847 _bot_shared(NULL),
1848 _evac_failure_scan_stack(NULL),
1849 _mark_in_progress(false),
1850 _cg1r(NULL), _summary_bytes_used(0),
1851 _g1mm(NULL),
1852 _refine_cte_cl(NULL),
1853 _full_collection(false),
1854 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1855 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1856 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1857 _humongous_is_live(),
1858 _has_humongous_reclaim_candidates(false),
1859 _free_regions_coming(false),
1860 _young_list(new YoungList(this)),
1861 _gc_time_stamp(0),
1862 _retained_old_gc_alloc_region(NULL),
1863 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1864 _old_plab_stats(OldPLABSize, PLABWeight),
1865 _expand_heap_after_alloc_failure(true),
1866 _surviving_young_words(NULL),
1867 _old_marking_cycles_started(0),
1868 _old_marking_cycles_completed(0),
1869 _concurrent_cycle_started(false),
1870 _in_cset_fast_test(),
1871 _dirty_cards_region_list(NULL),
1872 _worker_cset_start_region(NULL),
1873 _worker_cset_start_region_time_stamp(NULL),
1874 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1875 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1876 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1877 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1878
1879 _g1h = this;
1880 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1881 vm_exit_during_initialization("Failed necessary allocation.");
1882 }
1883
1884 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1885
1886 int n_queues = MAX2((int)ParallelGCThreads, 1);
1887 _task_queues = new RefToScanQueueSet(n_queues);
1888
1889 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1890 assert(n_rem_sets > 0, "Invariant.");
1891
1892 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1893 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1894 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1895
1896 for (int i = 0; i < n_queues; i++) {
1897 RefToScanQueue* q = new RefToScanQueue();
1898 q->initialize();
1899 _task_queues->register_queue(i, q);
1900 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1901 }
1902 clear_cset_start_regions();
1903
1904 // Initialize the G1EvacuationFailureALot counters and flags.
1905 NOT_PRODUCT(reset_evacuation_should_fail();)
1906
1907 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1908 }
1909
1910 jint G1CollectedHeap::initialize() {
1911 CollectedHeap::pre_initialize();
1912 os::enable_vtime();
1913
1914 G1Log::init();
1915
1916 // Necessary to satisfy locking discipline assertions.
1917
1918 MutexLocker x(Heap_lock);
1919
1920 // We have to initialize the printer before committing the heap, as
1921 // it will be used then.
1922 _hr_printer.set_active(G1PrintHeapRegions);
1923
1924 // While there are no constraints in the GC code that HeapWordSize
1925 // be any particular value, there are multiple other areas in the
1926 // system which believe this to be true (e.g. oop->object_size in some
1927 // cases incorrectly returns the size in wordSize units rather than
1928 // HeapWordSize).
1929 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1930
1931 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1932 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1933 size_t heap_alignment = collector_policy()->heap_alignment();
1934
1935 // Ensure that the sizes are properly aligned.
1936 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1937 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1938 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1939
1940 _refine_cte_cl = new RefineCardTableEntryClosure();
1941
1942 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1943
1944 // Reserve the maximum.
1945
1946 // When compressed oops are enabled, the preferred heap base
1947 // is calculated by subtracting the requested size from the
1948 // 32Gb boundary and using the result as the base address for
1949 // heap reservation. If the requested size is not aligned to
1950 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1951 // into the ReservedHeapSpace constructor) then the actual
1952 // base of the reserved heap may end up differing from the
1953 // address that was requested (i.e. the preferred heap base).
1954 // If this happens then we could end up using a non-optimal
1955 // compressed oops mode.
1956
1957 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1958 heap_alignment);
1959
1960 // It is important to do this in a way such that concurrent readers can't
1961 // temporarily think something is in the heap. (I've actually seen this
1962 // happen in asserts: DLD.)
1963 _reserved.set_word_size(0);
1964 _reserved.set_start((HeapWord*)heap_rs.base());
1965 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1966
1967 // Create the gen rem set (and barrier set) for the entire reserved region.
1968 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1969 set_barrier_set(rem_set()->bs());
1970 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1971 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1972 return JNI_ENOMEM;
1973 }
1974
1975 // Also create a G1 rem set.
1976 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1977
1978 // Carve out the G1 part of the heap.
1979
1980 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1981 G1RegionToSpaceMapper* heap_storage =
1982 G1RegionToSpaceMapper::create_mapper(g1_rs,
1983 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1984 HeapRegion::GrainBytes,
1985 1,
1986 mtJavaHeap);
1987 heap_storage->set_mapping_changed_listener(&_listener);
1988
1989 // Reserve space for the block offset table. We do not support automatic uncommit
1990 // for the card table at this time. BOT only.
1991 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1992 G1RegionToSpaceMapper* bot_storage =
1993 G1RegionToSpaceMapper::create_mapper(bot_rs,
1994 os::vm_page_size(),
1995 HeapRegion::GrainBytes,
1996 G1BlockOffsetSharedArray::N_bytes,
1997 mtGC);
1998
1999 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2000 G1RegionToSpaceMapper* cardtable_storage =
2001 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2002 os::vm_page_size(),
2003 HeapRegion::GrainBytes,
2004 G1BlockOffsetSharedArray::N_bytes,
2005 mtGC);
2006 g1_barrier_set()->initialize(cardtable_storage);
2007
2008 // Reserve space for the card counts table.
2009 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2010 G1RegionToSpaceMapper* card_counts_storage =
2011 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2012 os::vm_page_size(),
2013 HeapRegion::GrainBytes,
2014 G1BlockOffsetSharedArray::N_bytes,
2015 mtGC);
2016
2017 // Reserve space for prev and next bitmap.
2018 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2019
2020 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2021 G1RegionToSpaceMapper* prev_bitmap_storage =
2022 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2023 os::vm_page_size(),
2024 HeapRegion::GrainBytes,
2025 CMBitMap::mark_distance(),
2026 mtGC);
2027
2028 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2029 G1RegionToSpaceMapper* next_bitmap_storage =
2030 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2031 os::vm_page_size(),
2032 HeapRegion::GrainBytes,
2033 CMBitMap::mark_distance(),
2034 mtGC);
2035
2036 _hrs.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2037
2038 // Do later initialization work for concurrent refinement.
2039 _cg1r->init(card_counts_storage);
2040
2041 // 6843694 - ensure that the maximum region index can fit
2042 // in the remembered set structures.
2043 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2044 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2045
2046 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2047 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2048 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2049 "too many cards per region");
2050
2051 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2052
2053 _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2054
2055 _g1h = this;
2056
2057 _in_cset_fast_test.initialize(_hrs.reserved().start(), _hrs.reserved().end(), HeapRegion::GrainBytes);
2058 _humongous_is_live.initialize(_hrs.reserved().start(), _hrs.reserved().end(), HeapRegion::GrainBytes);
2059
2060 // Create the ConcurrentMark data structure and thread.
2061 // (Must do this late, so that "max_regions" is defined.)
2062 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2063 if (_cm == NULL || !_cm->completed_initialization()) {
2064 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2065 return JNI_ENOMEM;
2066 }
2067 _cmThread = _cm->cmThread();
2068
2069 // Initialize the from_card cache structure of HeapRegionRemSet.
2070 HeapRegionRemSet::init_heap(max_regions());
2071
2072 // Now expand into the initial heap size.
2073 if (!expand(init_byte_size)) {
2074 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2075 return JNI_ENOMEM;
2076 }
2077
2078 // Perform any initialization actions delegated to the policy.
2079 g1_policy()->init();
2080
2081 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2082 SATB_Q_FL_lock,
2083 G1SATBProcessCompletedThreshold,
2084 Shared_SATB_Q_lock);
2085
2086 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2087 DirtyCardQ_CBL_mon,
2088 DirtyCardQ_FL_lock,
2089 concurrent_g1_refine()->yellow_zone(),
2090 concurrent_g1_refine()->red_zone(),
2091 Shared_DirtyCardQ_lock);
2092
2093 if (G1DeferredRSUpdate) {
2094 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2095 DirtyCardQ_CBL_mon,
2096 DirtyCardQ_FL_lock,
2097 -1, // never trigger processing
2098 -1, // no limit on length
2099 Shared_DirtyCardQ_lock,
2100 &JavaThread::dirty_card_queue_set());
2101 }
2102
2103 // Initialize the card queue set used to hold cards containing
2104 // references into the collection set.
2105 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2106 DirtyCardQ_CBL_mon,
2107 DirtyCardQ_FL_lock,
2108 -1, // never trigger processing
2109 -1, // no limit on length
2110 Shared_DirtyCardQ_lock,
2111 &JavaThread::dirty_card_queue_set());
2112
2113 // In case we're keeping closure specialization stats, initialize those
2114 // counts and that mechanism.
2115 SpecializationStats::clear();
2116
2117 // Here we allocate the dummy HeapRegion that is required by the
2118 // G1AllocRegion class.
2119 HeapRegion* dummy_region = _hrs.get_dummy_region();
2120
2121 // We'll re-use the same region whether the alloc region will
2122 // require BOT updates or not and, if it doesn't, then a non-young
2123 // region will complain that it cannot support allocations without
2124 // BOT updates. So we'll tag the dummy region as young to avoid that.
2125 dummy_region->set_young();
2126 // Make sure it's full.
2127 dummy_region->set_top(dummy_region->end());
2128 G1AllocRegion::setup(this, dummy_region);
2129
2130 init_mutator_alloc_region();
2131
2132 // Do create of the monitoring and management support so that
2133 // values in the heap have been properly initialized.
2134 _g1mm = new G1MonitoringSupport(this);
2135
2136 G1StringDedup::initialize();
2137
2138 return JNI_OK;
2139 }
2140
2141 void G1CollectedHeap::stop() {
2142 // Stop all concurrent threads. We do this to make sure these threads
2143 // do not continue to execute and access resources (e.g. gclog_or_tty)
2144 // that are destroyed during shutdown.
2145 _cg1r->stop();
2146 _cmThread->stop();
2147 if (G1StringDedup::is_enabled()) {
2148 G1StringDedup::stop();
2149 }
2150 }
2151
2152 void G1CollectedHeap::clear_humongous_is_live_table() {
2153 guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2154 _humongous_is_live.clear();
2155 }
2156
2157 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2158 return HeapRegion::max_region_size();
2159 }
2160
2161 void G1CollectedHeap::ref_processing_init() {
2162 // Reference processing in G1 currently works as follows:
2163 //
2164 // * There are two reference processor instances. One is
2165 // used to record and process discovered references
2166 // during concurrent marking; the other is used to
2167 // record and process references during STW pauses
2168 // (both full and incremental).
2169 // * Both ref processors need to 'span' the entire heap as
2170 // the regions in the collection set may be dotted around.
2171 //
2172 // * For the concurrent marking ref processor:
2173 // * Reference discovery is enabled at initial marking.
2174 // * Reference discovery is disabled and the discovered
2175 // references processed etc during remarking.
2176 // * Reference discovery is MT (see below).
2177 // * Reference discovery requires a barrier (see below).
2178 // * Reference processing may or may not be MT
2179 // (depending on the value of ParallelRefProcEnabled
2180 // and ParallelGCThreads).
2181 // * A full GC disables reference discovery by the CM
2182 // ref processor and abandons any entries on it's
2183 // discovered lists.
2184 //
2185 // * For the STW processor:
2186 // * Non MT discovery is enabled at the start of a full GC.
2187 // * Processing and enqueueing during a full GC is non-MT.
2188 // * During a full GC, references are processed after marking.
2189 //
2190 // * Discovery (may or may not be MT) is enabled at the start
2191 // of an incremental evacuation pause.
2192 // * References are processed near the end of a STW evacuation pause.
2193 // * For both types of GC:
2194 // * Discovery is atomic - i.e. not concurrent.
2195 // * Reference discovery will not need a barrier.
2196
2197 SharedHeap::ref_processing_init();
2198 MemRegion mr = reserved_region();
2199
2200 // Concurrent Mark ref processor
2201 _ref_processor_cm =
2202 new ReferenceProcessor(mr, // span
2203 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2204 // mt processing
2205 (int) ParallelGCThreads,
2206 // degree of mt processing
2207 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2208 // mt discovery
2209 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2210 // degree of mt discovery
2211 false,
2212 // Reference discovery is not atomic
2213 &_is_alive_closure_cm);
2214 // is alive closure
2215 // (for efficiency/performance)
2216
2217 // STW ref processor
2218 _ref_processor_stw =
2219 new ReferenceProcessor(mr, // span
2220 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2221 // mt processing
2222 MAX2((int)ParallelGCThreads, 1),
2223 // degree of mt processing
2224 (ParallelGCThreads > 1),
2225 // mt discovery
2226 MAX2((int)ParallelGCThreads, 1),
2227 // degree of mt discovery
2228 true,
2229 // Reference discovery is atomic
2230 &_is_alive_closure_stw);
2231 // is alive closure
2232 // (for efficiency/performance)
2233 }
2234
2235 size_t G1CollectedHeap::capacity() const {
2236 return _hrs.length() * HeapRegion::GrainBytes;
2237 }
2238
2239 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2240 assert(!hr->continuesHumongous(), "pre-condition");
2241 hr->reset_gc_time_stamp();
2242 if (hr->startsHumongous()) {
2243 uint first_index = hr->hrs_index() + 1;
2244 uint last_index = hr->last_hc_index();
2245 for (uint i = first_index; i < last_index; i += 1) {
2246 HeapRegion* chr = region_at(i);
2247 assert(chr->continuesHumongous(), "sanity");
2248 chr->reset_gc_time_stamp();
2249 }
2250 }
2251 }
2252
2253 #ifndef PRODUCT
2254 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2255 private:
2256 unsigned _gc_time_stamp;
2257 bool _failures;
2258
2259 public:
2260 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2261 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2262
2263 virtual bool doHeapRegion(HeapRegion* hr) {
2264 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2265 if (_gc_time_stamp != region_gc_time_stamp) {
2266 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2267 "expected %d", HR_FORMAT_PARAMS(hr),
2268 region_gc_time_stamp, _gc_time_stamp);
2269 _failures = true;
2270 }
2271 return false;
2272 }
2273
2274 bool failures() { return _failures; }
2275 };
2276
2277 void G1CollectedHeap::check_gc_time_stamps() {
2278 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2279 heap_region_iterate(&cl);
2280 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2281 }
2282 #endif // PRODUCT
2283
2284 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2285 DirtyCardQueue* into_cset_dcq,
2286 bool concurrent,
2287 uint worker_i) {
2288 // Clean cards in the hot card cache
2289 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2290 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2291
2292 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2293 int n_completed_buffers = 0;
2294 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2295 n_completed_buffers++;
2296 }
2297 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2298 dcqs.clear_n_completed_buffers();
2299 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2300 }
2301
2302
2303 // Computes the sum of the storage used by the various regions.
2304
2305 size_t G1CollectedHeap::used() const {
2306 assert(Heap_lock->owner() != NULL,
2307 "Should be owned on this thread's behalf.");
2308 size_t result = _summary_bytes_used;
2309 // Read only once in case it is set to NULL concurrently
2310 HeapRegion* hr = _mutator_alloc_region.get();
2311 if (hr != NULL)
2312 result += hr->used();
2313 return result;
2314 }
2315
2316 size_t G1CollectedHeap::used_unlocked() const {
2317 size_t result = _summary_bytes_used;
2318 return result;
2319 }
2320
2321 class SumUsedClosure: public HeapRegionClosure {
2322 size_t _used;
2323 public:
2324 SumUsedClosure() : _used(0) {}
2325 bool doHeapRegion(HeapRegion* r) {
2326 if (!r->continuesHumongous()) {
2327 _used += r->used();
2328 }
2329 return false;
2330 }
2331 size_t result() { return _used; }
2332 };
2333
2334 size_t G1CollectedHeap::recalculate_used() const {
2335 double recalculate_used_start = os::elapsedTime();
2336
2337 SumUsedClosure blk;
2338 heap_region_iterate(&blk);
2339
2340 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2341 return blk.result();
2342 }
2343
2344 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2345 switch (cause) {
2346 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2347 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2348 case GCCause::_g1_humongous_allocation: return true;
2349 default: return false;
2350 }
2351 }
2352
2353 #ifndef PRODUCT
2354 void G1CollectedHeap::allocate_dummy_regions() {
2355 // Let's fill up most of the region
2356 size_t word_size = HeapRegion::GrainWords - 1024;
2357 // And as a result the region we'll allocate will be humongous.
2358 guarantee(isHumongous(word_size), "sanity");
2359
2360 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2361 // Let's use the existing mechanism for the allocation
2362 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2363 if (dummy_obj != NULL) {
2364 MemRegion mr(dummy_obj, word_size);
2365 CollectedHeap::fill_with_object(mr);
2366 } else {
2367 // If we can't allocate once, we probably cannot allocate
2368 // again. Let's get out of the loop.
2369 break;
2370 }
2371 }
2372 }
2373 #endif // !PRODUCT
2374
2375 void G1CollectedHeap::increment_old_marking_cycles_started() {
2376 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2377 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2378 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2379 _old_marking_cycles_started, _old_marking_cycles_completed));
2380
2381 _old_marking_cycles_started++;
2382 }
2383
2384 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2385 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2386
2387 // We assume that if concurrent == true, then the caller is a
2388 // concurrent thread that was joined the Suspendible Thread
2389 // Set. If there's ever a cheap way to check this, we should add an
2390 // assert here.
2391
2392 // Given that this method is called at the end of a Full GC or of a
2393 // concurrent cycle, and those can be nested (i.e., a Full GC can
2394 // interrupt a concurrent cycle), the number of full collections
2395 // completed should be either one (in the case where there was no
2396 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2397 // behind the number of full collections started.
2398
2399 // This is the case for the inner caller, i.e. a Full GC.
2400 assert(concurrent ||
2401 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2402 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2403 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2404 "is inconsistent with _old_marking_cycles_completed = %u",
2405 _old_marking_cycles_started, _old_marking_cycles_completed));
2406
2407 // This is the case for the outer caller, i.e. the concurrent cycle.
2408 assert(!concurrent ||
2409 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2410 err_msg("for outer caller (concurrent cycle): "
2411 "_old_marking_cycles_started = %u "
2412 "is inconsistent with _old_marking_cycles_completed = %u",
2413 _old_marking_cycles_started, _old_marking_cycles_completed));
2414
2415 _old_marking_cycles_completed += 1;
2416
2417 // We need to clear the "in_progress" flag in the CM thread before
2418 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2419 // is set) so that if a waiter requests another System.gc() it doesn't
2420 // incorrectly see that a marking cycle is still in progress.
2421 if (concurrent) {
2422 _cmThread->clear_in_progress();
2423 }
2424
2425 // This notify_all() will ensure that a thread that called
2426 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2427 // and it's waiting for a full GC to finish will be woken up. It is
2428 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2429 FullGCCount_lock->notify_all();
2430 }
2431
2432 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2433 _concurrent_cycle_started = true;
2434 _gc_timer_cm->register_gc_start(start_time);
2435
2436 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2437 trace_heap_before_gc(_gc_tracer_cm);
2438 }
2439
2440 void G1CollectedHeap::register_concurrent_cycle_end() {
2441 if (_concurrent_cycle_started) {
2442 if (_cm->has_aborted()) {
2443 _gc_tracer_cm->report_concurrent_mode_failure();
2444 }
2445
2446 _gc_timer_cm->register_gc_end();
2447 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2448
2449 _concurrent_cycle_started = false;
2450 }
2451 }
2452
2453 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2454 if (_concurrent_cycle_started) {
2455 trace_heap_after_gc(_gc_tracer_cm);
2456 }
2457 }
2458
2459 G1YCType G1CollectedHeap::yc_type() {
2460 bool is_young = g1_policy()->gcs_are_young();
2461 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2462 bool is_during_mark = mark_in_progress();
2463
2464 if (is_initial_mark) {
2465 return InitialMark;
2466 } else if (is_during_mark) {
2467 return DuringMark;
2468 } else if (is_young) {
2469 return Normal;
2470 } else {
2471 return Mixed;
2472 }
2473 }
2474
2475 void G1CollectedHeap::collect(GCCause::Cause cause) {
2476 assert_heap_not_locked();
2477
2478 unsigned int gc_count_before;
2479 unsigned int old_marking_count_before;
2480 bool retry_gc;
2481
2482 do {
2483 retry_gc = false;
2484
2485 {
2486 MutexLocker ml(Heap_lock);
2487
2488 // Read the GC count while holding the Heap_lock
2489 gc_count_before = total_collections();
2490 old_marking_count_before = _old_marking_cycles_started;
2491 }
2492
2493 if (should_do_concurrent_full_gc(cause)) {
2494 // Schedule an initial-mark evacuation pause that will start a
2495 // concurrent cycle. We're setting word_size to 0 which means that
2496 // we are not requesting a post-GC allocation.
2497 VM_G1IncCollectionPause op(gc_count_before,
2498 0, /* word_size */
2499 true, /* should_initiate_conc_mark */
2500 g1_policy()->max_pause_time_ms(),
2501 cause);
2502
2503 VMThread::execute(&op);
2504 if (!op.pause_succeeded()) {
2505 if (old_marking_count_before == _old_marking_cycles_started) {
2506 retry_gc = op.should_retry_gc();
2507 } else {
2508 // A Full GC happened while we were trying to schedule the
2509 // initial-mark GC. No point in starting a new cycle given
2510 // that the whole heap was collected anyway.
2511 }
2512
2513 if (retry_gc) {
2514 if (GC_locker::is_active_and_needs_gc()) {
2515 GC_locker::stall_until_clear();
2516 }
2517 }
2518 }
2519 } else {
2520 if (cause == GCCause::_gc_locker
2521 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2522
2523 // Schedule a standard evacuation pause. We're setting word_size
2524 // to 0 which means that we are not requesting a post-GC allocation.
2525 VM_G1IncCollectionPause op(gc_count_before,
2526 0, /* word_size */
2527 false, /* should_initiate_conc_mark */
2528 g1_policy()->max_pause_time_ms(),
2529 cause);
2530 VMThread::execute(&op);
2531 } else {
2532 // Schedule a Full GC.
2533 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2534 VMThread::execute(&op);
2535 }
2536 }
2537 } while (retry_gc);
2538 }
2539
2540 bool G1CollectedHeap::is_in(const void* p) const {
2541 if (_hrs.reserved().contains(p)) {
2542 // Given that we know that p is in the reserved space,
2543 // heap_region_containing_raw() should successfully
2544 // return the containing region.
2545 HeapRegion* hr = heap_region_containing_raw(p);
2546 return hr->is_in(p);
2547 } else {
2548 return false;
2549 }
2550 }
2551
2552 #ifdef ASSERT
2553 bool G1CollectedHeap::is_in_exact(const void* p) const {
2554 bool contains = reserved_region().contains(p);
2555 bool available = _hrs.is_available(addr_to_region((HeapWord*)p));
2556 if (contains && available) {
2557 return true;
2558 } else {
2559 return false;
2560 }
2561 }
2562 #endif
2563
2564 // Iteration functions.
2565
2566 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2567
2568 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2569 ExtendedOopClosure* _cl;
2570 public:
2571 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2572 bool doHeapRegion(HeapRegion* r) {
2573 if (!r->continuesHumongous()) {
2574 r->oop_iterate(_cl);
2575 }
2576 return false;
2577 }
2578 };
2579
2580 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2581 IterateOopClosureRegionClosure blk(cl);
2582 heap_region_iterate(&blk);
2583 }
2584
2585 // Iterates an ObjectClosure over all objects within a HeapRegion.
2586
2587 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2588 ObjectClosure* _cl;
2589 public:
2590 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2591 bool doHeapRegion(HeapRegion* r) {
2592 if (! r->continuesHumongous()) {
2593 r->object_iterate(_cl);
2594 }
2595 return false;
2596 }
2597 };
2598
2599 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2600 IterateObjectClosureRegionClosure blk(cl);
2601 heap_region_iterate(&blk);
2602 }
2603
2604 // Calls a SpaceClosure on a HeapRegion.
2605
2606 class SpaceClosureRegionClosure: public HeapRegionClosure {
2607 SpaceClosure* _cl;
2608 public:
2609 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2610 bool doHeapRegion(HeapRegion* r) {
2611 _cl->do_space(r);
2612 return false;
2613 }
2614 };
2615
2616 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2617 SpaceClosureRegionClosure blk(cl);
2618 heap_region_iterate(&blk);
2619 }
2620
2621 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2622 _hrs.iterate(cl);
2623 }
2624
2625 void
2626 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2627 uint worker_id,
2628 uint num_workers,
2629 jint claim_value) const {
2630 _hrs.par_iterate(cl, worker_id, num_workers, claim_value);
2631 }
2632
2633 class ResetClaimValuesClosure: public HeapRegionClosure {
2634 public:
2635 bool doHeapRegion(HeapRegion* r) {
2636 r->set_claim_value(HeapRegion::InitialClaimValue);
2637 return false;
2638 }
2639 };
2640
2641 void G1CollectedHeap::reset_heap_region_claim_values() {
2642 ResetClaimValuesClosure blk;
2643 heap_region_iterate(&blk);
2644 }
2645
2646 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2647 ResetClaimValuesClosure blk;
2648 collection_set_iterate(&blk);
2649 }
2650
2651 #ifdef ASSERT
2652 // This checks whether all regions in the heap have the correct claim
2653 // value. I also piggy-backed on this a check to ensure that the
2654 // humongous_start_region() information on "continues humongous"
2655 // regions is correct.
2656
2657 class CheckClaimValuesClosure : public HeapRegionClosure {
2658 private:
2659 jint _claim_value;
2660 uint _failures;
2661 HeapRegion* _sh_region;
2662
2663 public:
2664 CheckClaimValuesClosure(jint claim_value) :
2665 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2666 bool doHeapRegion(HeapRegion* r) {
2667 if (r->claim_value() != _claim_value) {
2668 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2669 "claim value = %d, should be %d",
2670 HR_FORMAT_PARAMS(r),
2671 r->claim_value(), _claim_value);
2672 ++_failures;
2673 }
2674 if (!r->isHumongous()) {
2675 _sh_region = NULL;
2676 } else if (r->startsHumongous()) {
2677 _sh_region = r;
2678 } else if (r->continuesHumongous()) {
2679 if (r->humongous_start_region() != _sh_region) {
2680 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2681 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2682 HR_FORMAT_PARAMS(r),
2683 r->humongous_start_region(),
2684 _sh_region);
2685 ++_failures;
2686 }
2687 }
2688 return false;
2689 }
2690 uint failures() { return _failures; }
2691 };
2692
2693 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2694 CheckClaimValuesClosure cl(claim_value);
2695 heap_region_iterate(&cl);
2696 return cl.failures() == 0;
2697 }
2698
2699 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2700 private:
2701 jint _claim_value;
2702 uint _failures;
2703
2704 public:
2705 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2706 _claim_value(claim_value), _failures(0) { }
2707
2708 uint failures() { return _failures; }
2709
2710 bool doHeapRegion(HeapRegion* hr) {
2711 assert(hr->in_collection_set(), "how?");
2712 assert(!hr->isHumongous(), "H-region in CSet");
2713 if (hr->claim_value() != _claim_value) {
2714 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2715 "claim value = %d, should be %d",
2716 HR_FORMAT_PARAMS(hr),
2717 hr->claim_value(), _claim_value);
2718 _failures += 1;
2719 }
2720 return false;
2721 }
2722 };
2723
2724 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2725 CheckClaimValuesInCSetHRClosure cl(claim_value);
2726 collection_set_iterate(&cl);
2727 return cl.failures() == 0;
2728 }
2729 #endif // ASSERT
2730
2731 // Clear the cached CSet starting regions and (more importantly)
2732 // the time stamps. Called when we reset the GC time stamp.
2733 void G1CollectedHeap::clear_cset_start_regions() {
2734 assert(_worker_cset_start_region != NULL, "sanity");
2735 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2736
2737 int n_queues = MAX2((int)ParallelGCThreads, 1);
2738 for (int i = 0; i < n_queues; i++) {
2739 _worker_cset_start_region[i] = NULL;
2740 _worker_cset_start_region_time_stamp[i] = 0;
2741 }
2742 }
2743
2744 // Given the id of a worker, obtain or calculate a suitable
2745 // starting region for iterating over the current collection set.
2746 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2747 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2748
2749 HeapRegion* result = NULL;
2750 unsigned gc_time_stamp = get_gc_time_stamp();
2751
2752 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2753 // Cached starting region for current worker was set
2754 // during the current pause - so it's valid.
2755 // Note: the cached starting heap region may be NULL
2756 // (when the collection set is empty).
2757 result = _worker_cset_start_region[worker_i];
2758 assert(result == NULL || result->in_collection_set(), "sanity");
2759 return result;
2760 }
2761
2762 // The cached entry was not valid so let's calculate
2763 // a suitable starting heap region for this worker.
2764
2765 // We want the parallel threads to start their collection
2766 // set iteration at different collection set regions to
2767 // avoid contention.
2768 // If we have:
2769 // n collection set regions
2770 // p threads
2771 // Then thread t will start at region floor ((t * n) / p)
2772
2773 result = g1_policy()->collection_set();
2774 if (G1CollectedHeap::use_parallel_gc_threads()) {
2775 uint cs_size = g1_policy()->cset_region_length();
2776 uint active_workers = workers()->active_workers();
2777 assert(UseDynamicNumberOfGCThreads ||
2778 active_workers == workers()->total_workers(),
2779 "Unless dynamic should use total workers");
2780
2781 uint end_ind = (cs_size * worker_i) / active_workers;
2782 uint start_ind = 0;
2783
2784 if (worker_i > 0 &&
2785 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2786 // Previous workers starting region is valid
2787 // so let's iterate from there
2788 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2789 result = _worker_cset_start_region[worker_i - 1];
2790 }
2791
2792 for (uint i = start_ind; i < end_ind; i++) {
2793 result = result->next_in_collection_set();
2794 }
2795 }
2796
2797 // Note: the calculated starting heap region may be NULL
2798 // (when the collection set is empty).
2799 assert(result == NULL || result->in_collection_set(), "sanity");
2800 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2801 "should be updated only once per pause");
2802 _worker_cset_start_region[worker_i] = result;
2803 OrderAccess::storestore();
2804 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2805 return result;
2806 }
2807
2808 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2809 HeapRegion* r = g1_policy()->collection_set();
2810 while (r != NULL) {
2811 HeapRegion* next = r->next_in_collection_set();
2812 if (cl->doHeapRegion(r)) {
2813 cl->incomplete();
2814 return;
2815 }
2816 r = next;
2817 }
2818 }
2819
2820 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2821 HeapRegionClosure *cl) {
2822 if (r == NULL) {
2823 // The CSet is empty so there's nothing to do.
2824 return;
2825 }
2826
2827 assert(r->in_collection_set(),
2828 "Start region must be a member of the collection set.");
2829 HeapRegion* cur = r;
2830 while (cur != NULL) {
2831 HeapRegion* next = cur->next_in_collection_set();
2832 if (cl->doHeapRegion(cur) && false) {
2833 cl->incomplete();
2834 return;
2835 }
2836 cur = next;
2837 }
2838 cur = g1_policy()->collection_set();
2839 while (cur != r) {
2840 HeapRegion* next = cur->next_in_collection_set();
2841 if (cl->doHeapRegion(cur) && false) {
2842 cl->incomplete();
2843 return;
2844 }
2845 cur = next;
2846 }
2847 }
2848
2849 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2850 HeapRegion* result = _hrs.next_region_in_heap(from);
2851 while (result != NULL && result->isHumongous()) {
2852 result = _hrs.next_region_in_heap(result);
2853 }
2854 return result;
2855 }
2856
2857 Space* G1CollectedHeap::space_containing(const void* addr) const {
2858 return heap_region_containing(addr);
2859 }
2860
2861 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2862 Space* sp = space_containing(addr);
2863 return sp->block_start(addr);
2864 }
2865
2866 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2867 Space* sp = space_containing(addr);
2868 return sp->block_size(addr);
2869 }
2870
2871 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2872 Space* sp = space_containing(addr);
2873 return sp->block_is_obj(addr);
2874 }
2875
2876 bool G1CollectedHeap::supports_tlab_allocation() const {
2877 return true;
2878 }
2879
2880 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2881 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2882 }
2883
2884 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2885 return young_list()->eden_used_bytes();
2886 }
2887
2888 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2889 // must be smaller than the humongous object limit.
2890 size_t G1CollectedHeap::max_tlab_size() const {
2891 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2892 }
2893
2894 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2895 // Return the remaining space in the cur alloc region, but not less than
2896 // the min TLAB size.
2897
2898 // Also, this value can be at most the humongous object threshold,
2899 // since we can't allow tlabs to grow big enough to accommodate
2900 // humongous objects.
2901
2902 HeapRegion* hr = _mutator_alloc_region.get();
2903 size_t max_tlab = max_tlab_size() * wordSize;
2904 if (hr == NULL) {
2905 return max_tlab;
2906 } else {
2907 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2908 }
2909 }
2910
2911 size_t G1CollectedHeap::max_capacity() const {
2912 return _hrs.reserved().byte_size();
2913 }
2914
2915 jlong G1CollectedHeap::millis_since_last_gc() {
2916 // assert(false, "NYI");
2917 return 0;
2918 }
2919
2920 void G1CollectedHeap::prepare_for_verify() {
2921 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2922 ensure_parsability(false);
2923 }
2924 g1_rem_set()->prepare_for_verify();
2925 }
2926
2927 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2928 VerifyOption vo) {
2929 switch (vo) {
2930 case VerifyOption_G1UsePrevMarking:
2931 return hr->obj_allocated_since_prev_marking(obj);
2932 case VerifyOption_G1UseNextMarking:
2933 return hr->obj_allocated_since_next_marking(obj);
2934 case VerifyOption_G1UseMarkWord:
2935 return false;
2936 default:
2937 ShouldNotReachHere();
2938 }
2939 return false; // keep some compilers happy
2940 }
2941
2942 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2943 switch (vo) {
2944 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2945 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2946 case VerifyOption_G1UseMarkWord: return NULL;
2947 default: ShouldNotReachHere();
2948 }
2949 return NULL; // keep some compilers happy
2950 }
2951
2952 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2953 switch (vo) {
2954 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2955 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2956 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2957 default: ShouldNotReachHere();
2958 }
2959 return false; // keep some compilers happy
2960 }
2961
2962 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2963 switch (vo) {
2964 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2965 case VerifyOption_G1UseNextMarking: return "NTAMS";
2966 case VerifyOption_G1UseMarkWord: return "NONE";
2967 default: ShouldNotReachHere();
2968 }
2969 return NULL; // keep some compilers happy
2970 }
2971
2972 class VerifyRootsClosure: public OopClosure {
2973 private:
2974 G1CollectedHeap* _g1h;
2975 VerifyOption _vo;
2976 bool _failures;
2977 public:
2978 // _vo == UsePrevMarking -> use "prev" marking information,
2979 // _vo == UseNextMarking -> use "next" marking information,
2980 // _vo == UseMarkWord -> use mark word from object header.
2981 VerifyRootsClosure(VerifyOption vo) :
2982 _g1h(G1CollectedHeap::heap()),
2983 _vo(vo),
2984 _failures(false) { }
2985
2986 bool failures() { return _failures; }
2987
2988 template <class T> void do_oop_nv(T* p) {
2989 T heap_oop = oopDesc::load_heap_oop(p);
2990 if (!oopDesc::is_null(heap_oop)) {
2991 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2992 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2993 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2994 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2995 if (_vo == VerifyOption_G1UseMarkWord) {
2996 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2997 }
2998 obj->print_on(gclog_or_tty);
2999 _failures = true;
3000 }
3001 }
3002 }
3003
3004 void do_oop(oop* p) { do_oop_nv(p); }
3005 void do_oop(narrowOop* p) { do_oop_nv(p); }
3006 };
3007
3008 class G1VerifyCodeRootOopClosure: public OopClosure {
3009 G1CollectedHeap* _g1h;
3010 OopClosure* _root_cl;
3011 nmethod* _nm;
3012 VerifyOption _vo;
3013 bool _failures;
3014
3015 template <class T> void do_oop_work(T* p) {
3016 // First verify that this root is live
3017 _root_cl->do_oop(p);
3018
3019 if (!G1VerifyHeapRegionCodeRoots) {
3020 // We're not verifying the code roots attached to heap region.
3021 return;
3022 }
3023
3024 // Don't check the code roots during marking verification in a full GC
3025 if (_vo == VerifyOption_G1UseMarkWord) {
3026 return;
3027 }
3028
3029 // Now verify that the current nmethod (which contains p) is
3030 // in the code root list of the heap region containing the
3031 // object referenced by p.
3032
3033 T heap_oop = oopDesc::load_heap_oop(p);
3034 if (!oopDesc::is_null(heap_oop)) {
3035 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3036
3037 // Now fetch the region containing the object
3038 HeapRegion* hr = _g1h->heap_region_containing(obj);
3039 HeapRegionRemSet* hrrs = hr->rem_set();
3040 // Verify that the strong code root list for this region
3041 // contains the nmethod
3042 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3043 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3044 "from nmethod "PTR_FORMAT" not in strong "
3045 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3046 p, _nm, hr->bottom(), hr->end());
3047 _failures = true;
3048 }
3049 }
3050 }
3051
3052 public:
3053 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3054 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3055
3056 void do_oop(oop* p) { do_oop_work(p); }
3057 void do_oop(narrowOop* p) { do_oop_work(p); }
3058
3059 void set_nmethod(nmethod* nm) { _nm = nm; }
3060 bool failures() { return _failures; }
3061 };
3062
3063 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3064 G1VerifyCodeRootOopClosure* _oop_cl;
3065
3066 public:
3067 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3068 _oop_cl(oop_cl) {}
3069
3070 void do_code_blob(CodeBlob* cb) {
3071 nmethod* nm = cb->as_nmethod_or_null();
3072 if (nm != NULL) {
3073 _oop_cl->set_nmethod(nm);
3074 nm->oops_do(_oop_cl);
3075 }
3076 }
3077 };
3078
3079 class YoungRefCounterClosure : public OopClosure {
3080 G1CollectedHeap* _g1h;
3081 int _count;
3082 public:
3083 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3084 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3085 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3086
3087 int count() { return _count; }
3088 void reset_count() { _count = 0; };
3089 };
3090
3091 class VerifyKlassClosure: public KlassClosure {
3092 YoungRefCounterClosure _young_ref_counter_closure;
3093 OopClosure *_oop_closure;
3094 public:
3095 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3096 void do_klass(Klass* k) {
3097 k->oops_do(_oop_closure);
3098
3099 _young_ref_counter_closure.reset_count();
3100 k->oops_do(&_young_ref_counter_closure);
3101 if (_young_ref_counter_closure.count() > 0) {
3102 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3103 }
3104 }
3105 };
3106
3107 class VerifyLivenessOopClosure: public OopClosure {
3108 G1CollectedHeap* _g1h;
3109 VerifyOption _vo;
3110 public:
3111 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3112 _g1h(g1h), _vo(vo)
3113 { }
3114 void do_oop(narrowOop *p) { do_oop_work(p); }
3115 void do_oop( oop *p) { do_oop_work(p); }
3116
3117 template <class T> void do_oop_work(T *p) {
3118 oop obj = oopDesc::load_decode_heap_oop(p);
3119 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3120 "Dead object referenced by a not dead object");
3121 }
3122 };
3123
3124 class VerifyObjsInRegionClosure: public ObjectClosure {
3125 private:
3126 G1CollectedHeap* _g1h;
3127 size_t _live_bytes;
3128 HeapRegion *_hr;
3129 VerifyOption _vo;
3130 public:
3131 // _vo == UsePrevMarking -> use "prev" marking information,
3132 // _vo == UseNextMarking -> use "next" marking information,
3133 // _vo == UseMarkWord -> use mark word from object header.
3134 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3135 : _live_bytes(0), _hr(hr), _vo(vo) {
3136 _g1h = G1CollectedHeap::heap();
3137 }
3138 void do_object(oop o) {
3139 VerifyLivenessOopClosure isLive(_g1h, _vo);
3140 assert(o != NULL, "Huh?");
3141 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3142 // If the object is alive according to the mark word,
3143 // then verify that the marking information agrees.
3144 // Note we can't verify the contra-positive of the
3145 // above: if the object is dead (according to the mark
3146 // word), it may not be marked, or may have been marked
3147 // but has since became dead, or may have been allocated
3148 // since the last marking.
3149 if (_vo == VerifyOption_G1UseMarkWord) {
3150 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3151 }
3152
3153 o->oop_iterate_no_header(&isLive);
3154 if (!_hr->obj_allocated_since_prev_marking(o)) {
3155 size_t obj_size = o->size(); // Make sure we don't overflow
3156 _live_bytes += (obj_size * HeapWordSize);
3157 }
3158 }
3159 }
3160 size_t live_bytes() { return _live_bytes; }
3161 };
3162
3163 class PrintObjsInRegionClosure : public ObjectClosure {
3164 HeapRegion *_hr;
3165 G1CollectedHeap *_g1;
3166 public:
3167 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3168 _g1 = G1CollectedHeap::heap();
3169 };
3170
3171 void do_object(oop o) {
3172 if (o != NULL) {
3173 HeapWord *start = (HeapWord *) o;
3174 size_t word_sz = o->size();
3175 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3176 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3177 (void*) o, word_sz,
3178 _g1->isMarkedPrev(o),
3179 _g1->isMarkedNext(o),
3180 _hr->obj_allocated_since_prev_marking(o));
3181 HeapWord *end = start + word_sz;
3182 HeapWord *cur;
3183 int *val;
3184 for (cur = start; cur < end; cur++) {
3185 val = (int *) cur;
3186 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3187 }
3188 }
3189 }
3190 };
3191
3192 class VerifyRegionClosure: public HeapRegionClosure {
3193 private:
3194 bool _par;
3195 VerifyOption _vo;
3196 bool _failures;
3197 public:
3198 // _vo == UsePrevMarking -> use "prev" marking information,
3199 // _vo == UseNextMarking -> use "next" marking information,
3200 // _vo == UseMarkWord -> use mark word from object header.
3201 VerifyRegionClosure(bool par, VerifyOption vo)
3202 : _par(par),
3203 _vo(vo),
3204 _failures(false) {}
3205
3206 bool failures() {
3207 return _failures;
3208 }
3209
3210 bool doHeapRegion(HeapRegion* r) {
3211 if (!r->continuesHumongous()) {
3212 bool failures = false;
3213 r->verify(_vo, &failures);
3214 if (failures) {
3215 _failures = true;
3216 } else {
3217 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3218 r->object_iterate(¬_dead_yet_cl);
3219 if (_vo != VerifyOption_G1UseNextMarking) {
3220 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3221 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3222 "max_live_bytes "SIZE_FORMAT" "
3223 "< calculated "SIZE_FORMAT,
3224 r->bottom(), r->end(),
3225 r->max_live_bytes(),
3226 not_dead_yet_cl.live_bytes());
3227 _failures = true;
3228 }
3229 } else {
3230 // When vo == UseNextMarking we cannot currently do a sanity
3231 // check on the live bytes as the calculation has not been
3232 // finalized yet.
3233 }
3234 }
3235 }
3236 return false; // stop the region iteration if we hit a failure
3237 }
3238 };
3239
3240 // This is the task used for parallel verification of the heap regions
3241
3242 class G1ParVerifyTask: public AbstractGangTask {
3243 private:
3244 G1CollectedHeap* _g1h;
3245 VerifyOption _vo;
3246 bool _failures;
3247
3248 public:
3249 // _vo == UsePrevMarking -> use "prev" marking information,
3250 // _vo == UseNextMarking -> use "next" marking information,
3251 // _vo == UseMarkWord -> use mark word from object header.
3252 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3253 AbstractGangTask("Parallel verify task"),
3254 _g1h(g1h),
3255 _vo(vo),
3256 _failures(false) { }
3257
3258 bool failures() {
3259 return _failures;
3260 }
3261
3262 void work(uint worker_id) {
3263 HandleMark hm;
3264 VerifyRegionClosure blk(true, _vo);
3265 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3266 _g1h->workers()->active_workers(),
3267 HeapRegion::ParVerifyClaimValue);
3268 if (blk.failures()) {
3269 _failures = true;
3270 }
3271 }
3272 };
3273
3274 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3275 if (SafepointSynchronize::is_at_safepoint()) {
3276 assert(Thread::current()->is_VM_thread(),
3277 "Expected to be executed serially by the VM thread at this point");
3278
3279 if (!silent) { gclog_or_tty->print("Roots "); }
3280 VerifyRootsClosure rootsCl(vo);
3281 VerifyKlassClosure klassCl(this, &rootsCl);
3282 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3283
3284 // We apply the relevant closures to all the oops in the
3285 // system dictionary, class loader data graph, the string table
3286 // and the nmethods in the code cache.
3287 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3288 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3289
3290 process_all_roots(true, // activate StrongRootsScope
3291 SO_AllCodeCache, // roots scanning options
3292 &rootsCl,
3293 &cldCl,
3294 &blobsCl);
3295
3296 bool failures = rootsCl.failures() || codeRootsCl.failures();
3297
3298 if (vo != VerifyOption_G1UseMarkWord) {
3299 // If we're verifying during a full GC then the region sets
3300 // will have been torn down at the start of the GC. Therefore
3301 // verifying the region sets will fail. So we only verify
3302 // the region sets when not in a full GC.
3303 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3304 verify_region_sets();
3305 }
3306
3307 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3308 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3309 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3310 "sanity check");
3311
3312 G1ParVerifyTask task(this, vo);
3313 assert(UseDynamicNumberOfGCThreads ||
3314 workers()->active_workers() == workers()->total_workers(),
3315 "If not dynamic should be using all the workers");
3316 int n_workers = workers()->active_workers();
3317 set_par_threads(n_workers);
3318 workers()->run_task(&task);
3319 set_par_threads(0);
3320 if (task.failures()) {
3321 failures = true;
3322 }
3323
3324 // Checks that the expected amount of parallel work was done.
3325 // The implication is that n_workers is > 0.
3326 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3327 "sanity check");
3328
3329 reset_heap_region_claim_values();
3330
3331 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3332 "sanity check");
3333 } else {
3334 VerifyRegionClosure blk(false, vo);
3335 heap_region_iterate(&blk);
3336 if (blk.failures()) {
3337 failures = true;
3338 }
3339 }
3340 if (!silent) gclog_or_tty->print("RemSet ");
3341 rem_set()->verify();
3342
3343 if (G1StringDedup::is_enabled()) {
3344 if (!silent) gclog_or_tty->print("StrDedup ");
3345 G1StringDedup::verify();
3346 }
3347
3348 if (failures) {
3349 gclog_or_tty->print_cr("Heap:");
3350 // It helps to have the per-region information in the output to
3351 // help us track down what went wrong. This is why we call
3352 // print_extended_on() instead of print_on().
3353 print_extended_on(gclog_or_tty);
3354 gclog_or_tty->cr();
3355 #ifndef PRODUCT
3356 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3357 concurrent_mark()->print_reachable("at-verification-failure",
3358 vo, false /* all */);
3359 }
3360 #endif
3361 gclog_or_tty->flush();
3362 }
3363 guarantee(!failures, "there should not have been any failures");
3364 } else {
3365 if (!silent) {
3366 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3367 if (G1StringDedup::is_enabled()) {
3368 gclog_or_tty->print(", StrDedup");
3369 }
3370 gclog_or_tty->print(") ");
3371 }
3372 }
3373 }
3374
3375 void G1CollectedHeap::verify(bool silent) {
3376 verify(silent, VerifyOption_G1UsePrevMarking);
3377 }
3378
3379 double G1CollectedHeap::verify(bool guard, const char* msg) {
3380 double verify_time_ms = 0.0;
3381
3382 if (guard && total_collections() >= VerifyGCStartAt) {
3383 double verify_start = os::elapsedTime();
3384 HandleMark hm; // Discard invalid handles created during verification
3385 prepare_for_verify();
3386 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3387 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3388 }
3389
3390 return verify_time_ms;
3391 }
3392
3393 void G1CollectedHeap::verify_before_gc() {
3394 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3395 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3396 }
3397
3398 void G1CollectedHeap::verify_after_gc() {
3399 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3400 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3401 }
3402
3403 class PrintRegionClosure: public HeapRegionClosure {
3404 outputStream* _st;
3405 public:
3406 PrintRegionClosure(outputStream* st) : _st(st) {}
3407 bool doHeapRegion(HeapRegion* r) {
3408 r->print_on(_st);
3409 return false;
3410 }
3411 };
3412
3413 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3414 const HeapRegion* hr,
3415 const VerifyOption vo) const {
3416 switch (vo) {
3417 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3418 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3419 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3420 default: ShouldNotReachHere();
3421 }
3422 return false; // keep some compilers happy
3423 }
3424
3425 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3426 const VerifyOption vo) const {
3427 switch (vo) {
3428 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3429 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3430 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3431 default: ShouldNotReachHere();
3432 }
3433 return false; // keep some compilers happy
3434 }
3435
3436 void G1CollectedHeap::print_on(outputStream* st) const {
3437 st->print(" %-20s", "garbage-first heap");
3438 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3439 capacity()/K, used_unlocked()/K);
3440 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3441 _hrs.reserved().start(),
3442 _hrs.reserved().start() + _hrs.length() + HeapRegion::GrainWords,
3443 _hrs.reserved().end());
3444 st->cr();
3445 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3446 uint young_regions = _young_list->length();
3447 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3448 (size_t) young_regions * HeapRegion::GrainBytes / K);
3449 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3450 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3451 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3452 st->cr();
3453 MetaspaceAux::print_on(st);
3454 }
3455
3456 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3457 print_on(st);
3458
3459 // Print the per-region information.
3460 st->cr();
3461 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3462 "HS=humongous(starts), HC=humongous(continues), "
3463 "CS=collection set, F=free, TS=gc time stamp, "
3464 "PTAMS=previous top-at-mark-start, "
3465 "NTAMS=next top-at-mark-start)");
3466 PrintRegionClosure blk(st);
3467 heap_region_iterate(&blk);
3468 }
3469
3470 void G1CollectedHeap::print_on_error(outputStream* st) const {
3471 this->CollectedHeap::print_on_error(st);
3472
3473 if (_cm != NULL) {
3474 st->cr();
3475 _cm->print_on_error(st);
3476 }
3477 }
3478
3479 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3480 if (G1CollectedHeap::use_parallel_gc_threads()) {
3481 workers()->print_worker_threads_on(st);
3482 }
3483 _cmThread->print_on(st);
3484 st->cr();
3485 _cm->print_worker_threads_on(st);
3486 _cg1r->print_worker_threads_on(st);
3487 if (G1StringDedup::is_enabled()) {
3488 G1StringDedup::print_worker_threads_on(st);
3489 }
3490 }
3491
3492 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3493 if (G1CollectedHeap::use_parallel_gc_threads()) {
3494 workers()->threads_do(tc);
3495 }
3496 tc->do_thread(_cmThread);
3497 _cg1r->threads_do(tc);
3498 if (G1StringDedup::is_enabled()) {
3499 G1StringDedup::threads_do(tc);
3500 }
3501 }
3502
3503 void G1CollectedHeap::print_tracing_info() const {
3504 // We'll overload this to mean "trace GC pause statistics."
3505 if (TraceYoungGenTime || TraceOldGenTime) {
3506 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3507 // to that.
3508 g1_policy()->print_tracing_info();
3509 }
3510 if (G1SummarizeRSetStats) {
3511 g1_rem_set()->print_summary_info();
3512 }
3513 if (G1SummarizeConcMark) {
3514 concurrent_mark()->print_summary_info();
3515 }
3516 g1_policy()->print_yg_surv_rate_info();
3517 SpecializationStats::print();
3518 }
3519
3520 #ifndef PRODUCT
3521 // Helpful for debugging RSet issues.
3522
3523 class PrintRSetsClosure : public HeapRegionClosure {
3524 private:
3525 const char* _msg;
3526 size_t _occupied_sum;
3527
3528 public:
3529 bool doHeapRegion(HeapRegion* r) {
3530 HeapRegionRemSet* hrrs = r->rem_set();
3531 size_t occupied = hrrs->occupied();
3532 _occupied_sum += occupied;
3533
3534 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3535 HR_FORMAT_PARAMS(r));
3536 if (occupied == 0) {
3537 gclog_or_tty->print_cr(" RSet is empty");
3538 } else {
3539 hrrs->print();
3540 }
3541 gclog_or_tty->print_cr("----------");
3542 return false;
3543 }
3544
3545 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3546 gclog_or_tty->cr();
3547 gclog_or_tty->print_cr("========================================");
3548 gclog_or_tty->print_cr("%s", msg);
3549 gclog_or_tty->cr();
3550 }
3551
3552 ~PrintRSetsClosure() {
3553 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3554 gclog_or_tty->print_cr("========================================");
3555 gclog_or_tty->cr();
3556 }
3557 };
3558
3559 void G1CollectedHeap::print_cset_rsets() {
3560 PrintRSetsClosure cl("Printing CSet RSets");
3561 collection_set_iterate(&cl);
3562 }
3563
3564 void G1CollectedHeap::print_all_rsets() {
3565 PrintRSetsClosure cl("Printing All RSets");;
3566 heap_region_iterate(&cl);
3567 }
3568 #endif // PRODUCT
3569
3570 G1CollectedHeap* G1CollectedHeap::heap() {
3571 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3572 "not a garbage-first heap");
3573 return _g1h;
3574 }
3575
3576 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3577 // always_do_update_barrier = false;
3578 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3579 // Fill TLAB's and such
3580 accumulate_statistics_all_tlabs();
3581 ensure_parsability(true);
3582
3583 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3584 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3585 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3586 }
3587 }
3588
3589 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3590
3591 if (G1SummarizeRSetStats &&
3592 (G1SummarizeRSetStatsPeriod > 0) &&
3593 // we are at the end of the GC. Total collections has already been increased.
3594 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3595 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3596 }
3597
3598 // FIXME: what is this about?
3599 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3600 // is set.
3601 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3602 "derived pointer present"));
3603 // always_do_update_barrier = true;
3604
3605 resize_all_tlabs();
3606
3607 // We have just completed a GC. Update the soft reference
3608 // policy with the new heap occupancy
3609 Universe::update_heap_info_at_gc();
3610 }
3611
3612 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3613 unsigned int gc_count_before,
3614 bool* succeeded,
3615 GCCause::Cause gc_cause) {
3616 assert_heap_not_locked_and_not_at_safepoint();
3617 g1_policy()->record_stop_world_start();
3618 VM_G1IncCollectionPause op(gc_count_before,
3619 word_size,
3620 false, /* should_initiate_conc_mark */
3621 g1_policy()->max_pause_time_ms(),
3622 gc_cause);
3623 VMThread::execute(&op);
3624
3625 HeapWord* result = op.result();
3626 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3627 assert(result == NULL || ret_succeeded,
3628 "the result should be NULL if the VM did not succeed");
3629 *succeeded = ret_succeeded;
3630
3631 assert_heap_not_locked();
3632 return result;
3633 }
3634
3635 void
3636 G1CollectedHeap::doConcurrentMark() {
3637 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3638 if (!_cmThread->in_progress()) {
3639 _cmThread->set_started();
3640 CGC_lock->notify();
3641 }
3642 }
3643
3644 size_t G1CollectedHeap::pending_card_num() {
3645 size_t extra_cards = 0;
3646 JavaThread *curr = Threads::first();
3647 while (curr != NULL) {
3648 DirtyCardQueue& dcq = curr->dirty_card_queue();
3649 extra_cards += dcq.size();
3650 curr = curr->next();
3651 }
3652 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3653 size_t buffer_size = dcqs.buffer_size();
3654 size_t buffer_num = dcqs.completed_buffers_num();
3655
3656 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3657 // in bytes - not the number of 'entries'. We need to convert
3658 // into a number of cards.
3659 return (buffer_size * buffer_num + extra_cards) / oopSize;
3660 }
3661
3662 size_t G1CollectedHeap::cards_scanned() {
3663 return g1_rem_set()->cardsScanned();
3664 }
3665
3666 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3667 HeapRegion* region = region_at(index);
3668 assert(region->startsHumongous(), "Must start a humongous object");
3669 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3670 }
3671
3672 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3673 private:
3674 size_t _total_humongous;
3675 size_t _candidate_humongous;
3676 public:
3677 RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3678 }
3679
3680 virtual bool doHeapRegion(HeapRegion* r) {
3681 if (!r->startsHumongous()) {
3682 return false;
3683 }
3684 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3685
3686 uint region_idx = r->hrs_index();
3687 bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3688 // Is_candidate already filters out humongous regions with some remembered set.
3689 // This will not lead to humongous object that we mistakenly keep alive because
3690 // during young collection the remembered sets will only be added to.
3691 if (is_candidate) {
3692 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3693 _candidate_humongous++;
3694 }
3695 _total_humongous++;
3696
3697 return false;
3698 }
3699
3700 size_t total_humongous() const { return _total_humongous; }
3701 size_t candidate_humongous() const { return _candidate_humongous; }
3702 };
3703
3704 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3705 if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3706 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3707 return;
3708 }
3709
3710 RegisterHumongousWithInCSetFastTestClosure cl;
3711 heap_region_iterate(&cl);
3712 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3713 cl.candidate_humongous());
3714 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3715
3716 if (_has_humongous_reclaim_candidates) {
3717 clear_humongous_is_live_table();
3718 }
3719 }
3720
3721 void
3722 G1CollectedHeap::setup_surviving_young_words() {
3723 assert(_surviving_young_words == NULL, "pre-condition");
3724 uint array_length = g1_policy()->young_cset_region_length();
3725 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3726 if (_surviving_young_words == NULL) {
3727 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3728 "Not enough space for young surv words summary.");
3729 }
3730 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3731 #ifdef ASSERT
3732 for (uint i = 0; i < array_length; ++i) {
3733 assert( _surviving_young_words[i] == 0, "memset above" );
3734 }
3735 #endif // !ASSERT
3736 }
3737
3738 void
3739 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3740 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3741 uint array_length = g1_policy()->young_cset_region_length();
3742 for (uint i = 0; i < array_length; ++i) {
3743 _surviving_young_words[i] += surv_young_words[i];
3744 }
3745 }
3746
3747 void
3748 G1CollectedHeap::cleanup_surviving_young_words() {
3749 guarantee( _surviving_young_words != NULL, "pre-condition" );
3750 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3751 _surviving_young_words = NULL;
3752 }
3753
3754 #ifdef ASSERT
3755 class VerifyCSetClosure: public HeapRegionClosure {
3756 public:
3757 bool doHeapRegion(HeapRegion* hr) {
3758 // Here we check that the CSet region's RSet is ready for parallel
3759 // iteration. The fields that we'll verify are only manipulated
3760 // when the region is part of a CSet and is collected. Afterwards,
3761 // we reset these fields when we clear the region's RSet (when the
3762 // region is freed) so they are ready when the region is
3763 // re-allocated. The only exception to this is if there's an
3764 // evacuation failure and instead of freeing the region we leave
3765 // it in the heap. In that case, we reset these fields during
3766 // evacuation failure handling.
3767 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3768
3769 // Here's a good place to add any other checks we'd like to
3770 // perform on CSet regions.
3771 return false;
3772 }
3773 };
3774 #endif // ASSERT
3775
3776 #if TASKQUEUE_STATS
3777 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3778 st->print_raw_cr("GC Task Stats");
3779 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3780 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3781 }
3782
3783 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3784 print_taskqueue_stats_hdr(st);
3785
3786 TaskQueueStats totals;
3787 const int n = workers() != NULL ? workers()->total_workers() : 1;
3788 for (int i = 0; i < n; ++i) {
3789 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3790 totals += task_queue(i)->stats;
3791 }
3792 st->print_raw("tot "); totals.print(st); st->cr();
3793
3794 DEBUG_ONLY(totals.verify());
3795 }
3796
3797 void G1CollectedHeap::reset_taskqueue_stats() {
3798 const int n = workers() != NULL ? workers()->total_workers() : 1;
3799 for (int i = 0; i < n; ++i) {
3800 task_queue(i)->stats.reset();
3801 }
3802 }
3803 #endif // TASKQUEUE_STATS
3804
3805 void G1CollectedHeap::log_gc_header() {
3806 if (!G1Log::fine()) {
3807 return;
3808 }
3809
3810 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3811
3812 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3813 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3814 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3815
3816 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3817 }
3818
3819 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3820 if (!G1Log::fine()) {
3821 return;
3822 }
3823
3824 if (G1Log::finer()) {
3825 if (evacuation_failed()) {
3826 gclog_or_tty->print(" (to-space exhausted)");
3827 }
3828 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3829 g1_policy()->phase_times()->note_gc_end();
3830 g1_policy()->phase_times()->print(pause_time_sec);
3831 g1_policy()->print_detailed_heap_transition();
3832 } else {
3833 if (evacuation_failed()) {
3834 gclog_or_tty->print("--");
3835 }
3836 g1_policy()->print_heap_transition();
3837 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3838 }
3839 gclog_or_tty->flush();
3840 }
3841
3842 bool
3843 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3844 assert_at_safepoint(true /* should_be_vm_thread */);
3845 guarantee(!is_gc_active(), "collection is not reentrant");
3846
3847 if (GC_locker::check_active_before_gc()) {
3848 return false;
3849 }
3850
3851 _gc_timer_stw->register_gc_start();
3852
3853 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3854
3855 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3856 ResourceMark rm;
3857
3858 print_heap_before_gc();
3859 trace_heap_before_gc(_gc_tracer_stw);
3860
3861 verify_region_sets_optional();
3862 verify_dirty_young_regions();
3863
3864 // This call will decide whether this pause is an initial-mark
3865 // pause. If it is, during_initial_mark_pause() will return true
3866 // for the duration of this pause.
3867 g1_policy()->decide_on_conc_mark_initiation();
3868
3869 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3870 assert(!g1_policy()->during_initial_mark_pause() ||
3871 g1_policy()->gcs_are_young(), "sanity");
3872
3873 // We also do not allow mixed GCs during marking.
3874 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3875
3876 // Record whether this pause is an initial mark. When the current
3877 // thread has completed its logging output and it's safe to signal
3878 // the CM thread, the flag's value in the policy has been reset.
3879 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3880
3881 // Inner scope for scope based logging, timers, and stats collection
3882 {
3883 EvacuationInfo evacuation_info;
3884
3885 if (g1_policy()->during_initial_mark_pause()) {
3886 // We are about to start a marking cycle, so we increment the
3887 // full collection counter.
3888 increment_old_marking_cycles_started();
3889 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3890 }
3891
3892 _gc_tracer_stw->report_yc_type(yc_type());
3893
3894 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3895
3896 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3897 workers()->active_workers() : 1);
3898 double pause_start_sec = os::elapsedTime();
3899 g1_policy()->phase_times()->note_gc_start(active_workers);
3900 log_gc_header();
3901
3902 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3903 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3904
3905 // If the secondary_free_list is not empty, append it to the
3906 // free_list. No need to wait for the cleanup operation to finish;
3907 // the region allocation code will check the secondary_free_list
3908 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3909 // set, skip this step so that the region allocation code has to
3910 // get entries from the secondary_free_list.
3911 if (!G1StressConcRegionFreeing) {
3912 append_secondary_free_list_if_not_empty_with_lock();
3913 }
3914
3915 assert(check_young_list_well_formed(), "young list should be well formed");
3916 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3917 "sanity check");
3918
3919 // Don't dynamically change the number of GC threads this early. A value of
3920 // 0 is used to indicate serial work. When parallel work is done,
3921 // it will be set.
3922
3923 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3924 IsGCActiveMark x;
3925
3926 gc_prologue(false);
3927 increment_total_collections(false /* full gc */);
3928 increment_gc_time_stamp();
3929
3930 verify_before_gc();
3931
3932 check_bitmaps("GC Start");
3933
3934 COMPILER2_PRESENT(DerivedPointerTable::clear());
3935
3936 // Please see comment in g1CollectedHeap.hpp and
3937 // G1CollectedHeap::ref_processing_init() to see how
3938 // reference processing currently works in G1.
3939
3940 // Enable discovery in the STW reference processor
3941 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3942 true /*verify_no_refs*/);
3943
3944 {
3945 // We want to temporarily turn off discovery by the
3946 // CM ref processor, if necessary, and turn it back on
3947 // on again later if we do. Using a scoped
3948 // NoRefDiscovery object will do this.
3949 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3950
3951 // Forget the current alloc region (we might even choose it to be part
3952 // of the collection set!).
3953 release_mutator_alloc_region();
3954
3955 // We should call this after we retire the mutator alloc
3956 // region(s) so that all the ALLOC / RETIRE events are generated
3957 // before the start GC event.
3958 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3959
3960 // This timing is only used by the ergonomics to handle our pause target.
3961 // It is unclear why this should not include the full pause. We will
3962 // investigate this in CR 7178365.
3963 //
3964 // Preserving the old comment here if that helps the investigation:
3965 //
3966 // The elapsed time induced by the start time below deliberately elides
3967 // the possible verification above.
3968 double sample_start_time_sec = os::elapsedTime();
3969
3970 #if YOUNG_LIST_VERBOSE
3971 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3972 _young_list->print();
3973 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3974 #endif // YOUNG_LIST_VERBOSE
3975
3976 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3977
3978 double scan_wait_start = os::elapsedTime();
3979 // We have to wait until the CM threads finish scanning the
3980 // root regions as it's the only way to ensure that all the
3981 // objects on them have been correctly scanned before we start
3982 // moving them during the GC.
3983 bool waited = _cm->root_regions()->wait_until_scan_finished();
3984 double wait_time_ms = 0.0;
3985 if (waited) {
3986 double scan_wait_end = os::elapsedTime();
3987 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3988 }
3989 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3990
3991 #if YOUNG_LIST_VERBOSE
3992 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3993 _young_list->print();
3994 #endif // YOUNG_LIST_VERBOSE
3995
3996 if (g1_policy()->during_initial_mark_pause()) {
3997 concurrent_mark()->checkpointRootsInitialPre();
3998 }
3999
4000 #if YOUNG_LIST_VERBOSE
4001 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4002 _young_list->print();
4003 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4004 #endif // YOUNG_LIST_VERBOSE
4005
4006 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4007
4008 register_humongous_regions_with_in_cset_fast_test();
4009
4010 _cm->note_start_of_gc();
4011 // We should not verify the per-thread SATB buffers given that
4012 // we have not filtered them yet (we'll do so during the
4013 // GC). We also call this after finalize_cset() to
4014 // ensure that the CSet has been finalized.
4015 _cm->verify_no_cset_oops(true /* verify_stacks */,
4016 true /* verify_enqueued_buffers */,
4017 false /* verify_thread_buffers */,
4018 true /* verify_fingers */);
4019
4020 if (_hr_printer.is_active()) {
4021 HeapRegion* hr = g1_policy()->collection_set();
4022 while (hr != NULL) {
4023 G1HRPrinter::RegionType type;
4024 if (!hr->is_young()) {
4025 type = G1HRPrinter::Old;
4026 } else if (hr->is_survivor()) {
4027 type = G1HRPrinter::Survivor;
4028 } else {
4029 type = G1HRPrinter::Eden;
4030 }
4031 _hr_printer.cset(hr);
4032 hr = hr->next_in_collection_set();
4033 }
4034 }
4035
4036 #ifdef ASSERT
4037 VerifyCSetClosure cl;
4038 collection_set_iterate(&cl);
4039 #endif // ASSERT
4040
4041 setup_surviving_young_words();
4042
4043 // Initialize the GC alloc regions.
4044 init_gc_alloc_regions(evacuation_info);
4045
4046 // Actually do the work...
4047 evacuate_collection_set(evacuation_info);
4048
4049 // We do this to mainly verify the per-thread SATB buffers
4050 // (which have been filtered by now) since we didn't verify
4051 // them earlier. No point in re-checking the stacks / enqueued
4052 // buffers given that the CSet has not changed since last time
4053 // we checked.
4054 _cm->verify_no_cset_oops(false /* verify_stacks */,
4055 false /* verify_enqueued_buffers */,
4056 true /* verify_thread_buffers */,
4057 true /* verify_fingers */);
4058
4059 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4060
4061 eagerly_reclaim_humongous_regions();
4062
4063 g1_policy()->clear_collection_set();
4064
4065 cleanup_surviving_young_words();
4066
4067 // Start a new incremental collection set for the next pause.
4068 g1_policy()->start_incremental_cset_building();
4069
4070 clear_cset_fast_test();
4071
4072 _young_list->reset_sampled_info();
4073
4074 // Don't check the whole heap at this point as the
4075 // GC alloc regions from this pause have been tagged
4076 // as survivors and moved on to the survivor list.
4077 // Survivor regions will fail the !is_young() check.
4078 assert(check_young_list_empty(false /* check_heap */),
4079 "young list should be empty");
4080
4081 #if YOUNG_LIST_VERBOSE
4082 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4083 _young_list->print();
4084 #endif // YOUNG_LIST_VERBOSE
4085
4086 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4087 _young_list->first_survivor_region(),
4088 _young_list->last_survivor_region());
4089
4090 _young_list->reset_auxilary_lists();
4091
4092 if (evacuation_failed()) {
4093 _summary_bytes_used = recalculate_used();
4094 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4095 for (uint i = 0; i < n_queues; i++) {
4096 if (_evacuation_failed_info_array[i].has_failed()) {
4097 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4098 }
4099 }
4100 } else {
4101 // The "used" of the the collection set have already been subtracted
4102 // when they were freed. Add in the bytes evacuated.
4103 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4104 }
4105
4106 if (g1_policy()->during_initial_mark_pause()) {
4107 // We have to do this before we notify the CM threads that
4108 // they can start working to make sure that all the
4109 // appropriate initialization is done on the CM object.
4110 concurrent_mark()->checkpointRootsInitialPost();
4111 set_marking_started();
4112 // Note that we don't actually trigger the CM thread at
4113 // this point. We do that later when we're sure that
4114 // the current thread has completed its logging output.
4115 }
4116
4117 allocate_dummy_regions();
4118
4119 #if YOUNG_LIST_VERBOSE
4120 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4121 _young_list->print();
4122 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4123 #endif // YOUNG_LIST_VERBOSE
4124
4125 init_mutator_alloc_region();
4126
4127 {
4128 size_t expand_bytes = g1_policy()->expansion_amount();
4129 if (expand_bytes > 0) {
4130 size_t bytes_before = capacity();
4131 // No need for an ergo verbose message here,
4132 // expansion_amount() does this when it returns a value > 0.
4133 if (!expand(expand_bytes)) {
4134 // We failed to expand the heap. Cannot do anything about it.
4135 }
4136 }
4137 }
4138
4139 // We redo the verification but now wrt to the new CSet which
4140 // has just got initialized after the previous CSet was freed.
4141 _cm->verify_no_cset_oops(true /* verify_stacks */,
4142 true /* verify_enqueued_buffers */,
4143 true /* verify_thread_buffers */,
4144 true /* verify_fingers */);
4145 _cm->note_end_of_gc();
4146
4147 // This timing is only used by the ergonomics to handle our pause target.
4148 // It is unclear why this should not include the full pause. We will
4149 // investigate this in CR 7178365.
4150 double sample_end_time_sec = os::elapsedTime();
4151 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4152 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4153
4154 MemoryService::track_memory_usage();
4155
4156 // In prepare_for_verify() below we'll need to scan the deferred
4157 // update buffers to bring the RSets up-to-date if
4158 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4159 // the update buffers we'll probably need to scan cards on the
4160 // regions we just allocated to (i.e., the GC alloc
4161 // regions). However, during the last GC we called
4162 // set_saved_mark() on all the GC alloc regions, so card
4163 // scanning might skip the [saved_mark_word()...top()] area of
4164 // those regions (i.e., the area we allocated objects into
4165 // during the last GC). But it shouldn't. Given that
4166 // saved_mark_word() is conditional on whether the GC time stamp
4167 // on the region is current or not, by incrementing the GC time
4168 // stamp here we invalidate all the GC time stamps on all the
4169 // regions and saved_mark_word() will simply return top() for
4170 // all the regions. This is a nicer way of ensuring this rather
4171 // than iterating over the regions and fixing them. In fact, the
4172 // GC time stamp increment here also ensures that
4173 // saved_mark_word() will return top() between pauses, i.e.,
4174 // during concurrent refinement. So we don't need the
4175 // is_gc_active() check to decided which top to use when
4176 // scanning cards (see CR 7039627).
4177 increment_gc_time_stamp();
4178
4179 verify_after_gc();
4180 check_bitmaps("GC End");
4181
4182 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4183 ref_processor_stw()->verify_no_references_recorded();
4184
4185 // CM reference discovery will be re-enabled if necessary.
4186 }
4187
4188 // We should do this after we potentially expand the heap so
4189 // that all the COMMIT events are generated before the end GC
4190 // event, and after we retire the GC alloc regions so that all
4191 // RETIRE events are generated before the end GC event.
4192 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4193
4194 #ifdef TRACESPINNING
4195 ParallelTaskTerminator::print_termination_counts();
4196 #endif
4197
4198 gc_epilogue(false);
4199 }
4200
4201 // Print the remainder of the GC log output.
4202 log_gc_footer(os::elapsedTime() - pause_start_sec);
4203
4204 // It is not yet to safe to tell the concurrent mark to
4205 // start as we have some optional output below. We don't want the
4206 // output from the concurrent mark thread interfering with this
4207 // logging output either.
4208
4209 _hrs.verify_optional();
4210 verify_region_sets_optional();
4211
4212 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4213 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4214
4215 print_heap_after_gc();
4216 trace_heap_after_gc(_gc_tracer_stw);
4217
4218 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4219 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4220 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4221 // before any GC notifications are raised.
4222 g1mm()->update_sizes();
4223
4224 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4225 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4226 _gc_timer_stw->register_gc_end();
4227 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4228 }
4229 // It should now be safe to tell the concurrent mark thread to start
4230 // without its logging output interfering with the logging output
4231 // that came from the pause.
4232
4233 if (should_start_conc_mark) {
4234 // CAUTION: after the doConcurrentMark() call below,
4235 // the concurrent marking thread(s) could be running
4236 // concurrently with us. Make sure that anything after
4237 // this point does not assume that we are the only GC thread
4238 // running. Note: of course, the actual marking work will
4239 // not start until the safepoint itself is released in
4240 // SuspendibleThreadSet::desynchronize().
4241 doConcurrentMark();
4242 }
4243
4244 return true;
4245 }
4246
4247 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4248 {
4249 size_t gclab_word_size;
4250 switch (purpose) {
4251 case GCAllocForSurvived:
4252 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4253 break;
4254 case GCAllocForTenured:
4255 gclab_word_size = _old_plab_stats.desired_plab_sz();
4256 break;
4257 default:
4258 assert(false, "unknown GCAllocPurpose");
4259 gclab_word_size = _old_plab_stats.desired_plab_sz();
4260 break;
4261 }
4262
4263 // Prevent humongous PLAB sizes for two reasons:
4264 // * PLABs are allocated using a similar paths as oops, but should
4265 // never be in a humongous region
4266 // * Allowing humongous PLABs needlessly churns the region free lists
4267 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4268 }
4269
4270 void G1CollectedHeap::init_mutator_alloc_region() {
4271 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4272 _mutator_alloc_region.init();
4273 }
4274
4275 void G1CollectedHeap::release_mutator_alloc_region() {
4276 _mutator_alloc_region.release();
4277 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4278 }
4279
4280 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4281 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4282 _retained_old_gc_alloc_region = NULL;
4283
4284 // We will discard the current GC alloc region if:
4285 // a) it's in the collection set (it can happen!),
4286 // b) it's already full (no point in using it),
4287 // c) it's empty (this means that it was emptied during
4288 // a cleanup and it should be on the free list now), or
4289 // d) it's humongous (this means that it was emptied
4290 // during a cleanup and was added to the free list, but
4291 // has been subsequently used to allocate a humongous
4292 // object that may be less than the region size).
4293 if (retained_region != NULL &&
4294 !retained_region->in_collection_set() &&
4295 !(retained_region->top() == retained_region->end()) &&
4296 !retained_region->is_empty() &&
4297 !retained_region->isHumongous()) {
4298 retained_region->record_top_and_timestamp();
4299 // The retained region was added to the old region set when it was
4300 // retired. We have to remove it now, since we don't allow regions
4301 // we allocate to in the region sets. We'll re-add it later, when
4302 // it's retired again.
4303 _old_set.remove(retained_region);
4304 bool during_im = g1_policy()->during_initial_mark_pause();
4305 retained_region->note_start_of_copying(during_im);
4306 _old_gc_alloc_region.set(retained_region);
4307 _hr_printer.reuse(retained_region);
4308 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4309 }
4310 }
4311
4312 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4313 assert_at_safepoint(true /* should_be_vm_thread */);
4314
4315 _survivor_gc_alloc_region.init();
4316 _old_gc_alloc_region.init();
4317
4318 use_retained_old_gc_alloc_region(evacuation_info);
4319 }
4320
4321 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4322 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4323 _old_gc_alloc_region.count());
4324 _survivor_gc_alloc_region.release();
4325 // If we have an old GC alloc region to release, we'll save it in
4326 // _retained_old_gc_alloc_region. If we don't
4327 // _retained_old_gc_alloc_region will become NULL. This is what we
4328 // want either way so no reason to check explicitly for either
4329 // condition.
4330 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4331
4332 if (ResizePLAB) {
4333 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4334 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4335 }
4336 }
4337
4338 void G1CollectedHeap::abandon_gc_alloc_regions() {
4339 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4340 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4341 _retained_old_gc_alloc_region = NULL;
4342 }
4343
4344 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4345 _drain_in_progress = false;
4346 set_evac_failure_closure(cl);
4347 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4348 }
4349
4350 void G1CollectedHeap::finalize_for_evac_failure() {
4351 assert(_evac_failure_scan_stack != NULL &&
4352 _evac_failure_scan_stack->length() == 0,
4353 "Postcondition");
4354 assert(!_drain_in_progress, "Postcondition");
4355 delete _evac_failure_scan_stack;
4356 _evac_failure_scan_stack = NULL;
4357 }
4358
4359 void G1CollectedHeap::remove_self_forwarding_pointers() {
4360 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4361
4362 double remove_self_forwards_start = os::elapsedTime();
4363
4364 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4365
4366 if (G1CollectedHeap::use_parallel_gc_threads()) {
4367 set_par_threads();
4368 workers()->run_task(&rsfp_task);
4369 set_par_threads(0);
4370 } else {
4371 rsfp_task.work(0);
4372 }
4373
4374 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4375
4376 // Reset the claim values in the regions in the collection set.
4377 reset_cset_heap_region_claim_values();
4378
4379 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4380
4381 // Now restore saved marks, if any.
4382 assert(_objs_with_preserved_marks.size() ==
4383 _preserved_marks_of_objs.size(), "Both or none.");
4384 while (!_objs_with_preserved_marks.is_empty()) {
4385 oop obj = _objs_with_preserved_marks.pop();
4386 markOop m = _preserved_marks_of_objs.pop();
4387 obj->set_mark(m);
4388 }
4389 _objs_with_preserved_marks.clear(true);
4390 _preserved_marks_of_objs.clear(true);
4391
4392 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4393 }
4394
4395 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4396 _evac_failure_scan_stack->push(obj);
4397 }
4398
4399 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4400 assert(_evac_failure_scan_stack != NULL, "precondition");
4401
4402 while (_evac_failure_scan_stack->length() > 0) {
4403 oop obj = _evac_failure_scan_stack->pop();
4404 _evac_failure_closure->set_region(heap_region_containing(obj));
4405 obj->oop_iterate_backwards(_evac_failure_closure);
4406 }
4407 }
4408
4409 oop
4410 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4411 oop old) {
4412 assert(obj_in_cs(old),
4413 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4414 (HeapWord*) old));
4415 markOop m = old->mark();
4416 oop forward_ptr = old->forward_to_atomic(old);
4417 if (forward_ptr == NULL) {
4418 // Forward-to-self succeeded.
4419 assert(_par_scan_state != NULL, "par scan state");
4420 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4421 uint queue_num = _par_scan_state->queue_num();
4422
4423 _evacuation_failed = true;
4424 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4425 if (_evac_failure_closure != cl) {
4426 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4427 assert(!_drain_in_progress,
4428 "Should only be true while someone holds the lock.");
4429 // Set the global evac-failure closure to the current thread's.
4430 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4431 set_evac_failure_closure(cl);
4432 // Now do the common part.
4433 handle_evacuation_failure_common(old, m);
4434 // Reset to NULL.
4435 set_evac_failure_closure(NULL);
4436 } else {
4437 // The lock is already held, and this is recursive.
4438 assert(_drain_in_progress, "This should only be the recursive case.");
4439 handle_evacuation_failure_common(old, m);
4440 }
4441 return old;
4442 } else {
4443 // Forward-to-self failed. Either someone else managed to allocate
4444 // space for this object (old != forward_ptr) or they beat us in
4445 // self-forwarding it (old == forward_ptr).
4446 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4447 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4448 "should not be in the CSet",
4449 (HeapWord*) old, (HeapWord*) forward_ptr));
4450 return forward_ptr;
4451 }
4452 }
4453
4454 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4455 preserve_mark_if_necessary(old, m);
4456
4457 HeapRegion* r = heap_region_containing(old);
4458 if (!r->evacuation_failed()) {
4459 r->set_evacuation_failed(true);
4460 _hr_printer.evac_failure(r);
4461 }
4462
4463 push_on_evac_failure_scan_stack(old);
4464
4465 if (!_drain_in_progress) {
4466 // prevent recursion in copy_to_survivor_space()
4467 _drain_in_progress = true;
4468 drain_evac_failure_scan_stack();
4469 _drain_in_progress = false;
4470 }
4471 }
4472
4473 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4474 assert(evacuation_failed(), "Oversaving!");
4475 // We want to call the "for_promotion_failure" version only in the
4476 // case of a promotion failure.
4477 if (m->must_be_preserved_for_promotion_failure(obj)) {
4478 _objs_with_preserved_marks.push(obj);
4479 _preserved_marks_of_objs.push(m);
4480 }
4481 }
4482
4483 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4484 size_t word_size) {
4485 if (purpose == GCAllocForSurvived) {
4486 HeapWord* result = survivor_attempt_allocation(word_size);
4487 if (result != NULL) {
4488 return result;
4489 } else {
4490 // Let's try to allocate in the old gen in case we can fit the
4491 // object there.
4492 return old_attempt_allocation(word_size);
4493 }
4494 } else {
4495 assert(purpose == GCAllocForTenured, "sanity");
4496 HeapWord* result = old_attempt_allocation(word_size);
4497 if (result != NULL) {
4498 return result;
4499 } else {
4500 // Let's try to allocate in the survivors in case we can fit the
4501 // object there.
4502 return survivor_attempt_allocation(word_size);
4503 }
4504 }
4505
4506 ShouldNotReachHere();
4507 // Trying to keep some compilers happy.
4508 return NULL;
4509 }
4510
4511 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4512 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4513
4514 void G1ParCopyHelper::mark_object(oop obj) {
4515 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4516
4517 // We know that the object is not moving so it's safe to read its size.
4518 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4519 }
4520
4521 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4522 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4523 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4524 assert(from_obj != to_obj, "should not be self-forwarded");
4525
4526 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4527 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4528
4529 // The object might be in the process of being copied by another
4530 // worker so we cannot trust that its to-space image is
4531 // well-formed. So we have to read its size from its from-space
4532 // image which we know should not be changing.
4533 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4534 }
4535
4536 template <class T>
4537 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4538 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4539 _scanned_klass->record_modified_oops();
4540 }
4541 }
4542
4543 template <G1Barrier barrier, G1Mark do_mark_object>
4544 template <class T>
4545 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4546 T heap_oop = oopDesc::load_heap_oop(p);
4547
4548 if (oopDesc::is_null(heap_oop)) {
4549 return;
4550 }
4551
4552 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4553
4554 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4555
4556 G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4557
4558 if (state == G1CollectedHeap::InCSet) {
4559 oop forwardee;
4560 if (obj->is_forwarded()) {
4561 forwardee = obj->forwardee();
4562 } else {
4563 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4564 }
4565 assert(forwardee != NULL, "forwardee should not be NULL");
4566 oopDesc::encode_store_heap_oop(p, forwardee);
4567 if (do_mark_object != G1MarkNone && forwardee != obj) {
4568 // If the object is self-forwarded we don't need to explicitly
4569 // mark it, the evacuation failure protocol will do so.
4570 mark_forwarded_object(obj, forwardee);
4571 }
4572
4573 if (barrier == G1BarrierKlass) {
4574 do_klass_barrier(p, forwardee);
4575 }
4576 } else {
4577 if (state == G1CollectedHeap::IsHumongous) {
4578 _g1->set_humongous_is_live(obj);
4579 }
4580 // The object is not in collection set. If we're a root scanning
4581 // closure during an initial mark pause then attempt to mark the object.
4582 if (do_mark_object == G1MarkFromRoot) {
4583 mark_object(obj);
4584 }
4585 }
4586
4587 if (barrier == G1BarrierEvac) {
4588 _par_scan_state->update_rs(_from, p, _worker_id);
4589 }
4590 }
4591
4592 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4593 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4594
4595 class G1ParEvacuateFollowersClosure : public VoidClosure {
4596 protected:
4597 G1CollectedHeap* _g1h;
4598 G1ParScanThreadState* _par_scan_state;
4599 RefToScanQueueSet* _queues;
4600 ParallelTaskTerminator* _terminator;
4601
4602 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4603 RefToScanQueueSet* queues() { return _queues; }
4604 ParallelTaskTerminator* terminator() { return _terminator; }
4605
4606 public:
4607 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4608 G1ParScanThreadState* par_scan_state,
4609 RefToScanQueueSet* queues,
4610 ParallelTaskTerminator* terminator)
4611 : _g1h(g1h), _par_scan_state(par_scan_state),
4612 _queues(queues), _terminator(terminator) {}
4613
4614 void do_void();
4615
4616 private:
4617 inline bool offer_termination();
4618 };
4619
4620 bool G1ParEvacuateFollowersClosure::offer_termination() {
4621 G1ParScanThreadState* const pss = par_scan_state();
4622 pss->start_term_time();
4623 const bool res = terminator()->offer_termination();
4624 pss->end_term_time();
4625 return res;
4626 }
4627
4628 void G1ParEvacuateFollowersClosure::do_void() {
4629 G1ParScanThreadState* const pss = par_scan_state();
4630 pss->trim_queue();
4631 do {
4632 pss->steal_and_trim_queue(queues());
4633 } while (!offer_termination());
4634 }
4635
4636 class G1KlassScanClosure : public KlassClosure {
4637 G1ParCopyHelper* _closure;
4638 bool _process_only_dirty;
4639 int _count;
4640 public:
4641 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4642 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4643 void do_klass(Klass* klass) {
4644 // If the klass has not been dirtied we know that there's
4645 // no references into the young gen and we can skip it.
4646 if (!_process_only_dirty || klass->has_modified_oops()) {
4647 // Clean the klass since we're going to scavenge all the metadata.
4648 klass->clear_modified_oops();
4649
4650 // Tell the closure that this klass is the Klass to scavenge
4651 // and is the one to dirty if oops are left pointing into the young gen.
4652 _closure->set_scanned_klass(klass);
4653
4654 klass->oops_do(_closure);
4655
4656 _closure->set_scanned_klass(NULL);
4657 }
4658 _count++;
4659 }
4660 };
4661
4662 class G1ParTask : public AbstractGangTask {
4663 protected:
4664 G1CollectedHeap* _g1h;
4665 RefToScanQueueSet *_queues;
4666 ParallelTaskTerminator _terminator;
4667 uint _n_workers;
4668
4669 Mutex _stats_lock;
4670 Mutex* stats_lock() { return &_stats_lock; }
4671
4672 public:
4673 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4674 : AbstractGangTask("G1 collection"),
4675 _g1h(g1h),
4676 _queues(task_queues),
4677 _terminator(0, _queues),
4678 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4679 {}
4680
4681 RefToScanQueueSet* queues() { return _queues; }
4682
4683 RefToScanQueue *work_queue(int i) {
4684 return queues()->queue(i);
4685 }
4686
4687 ParallelTaskTerminator* terminator() { return &_terminator; }
4688
4689 virtual void set_for_termination(int active_workers) {
4690 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4691 // in the young space (_par_seq_tasks) in the G1 heap
4692 // for SequentialSubTasksDone.
4693 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4694 // both of which need setting by set_n_termination().
4695 _g1h->SharedHeap::set_n_termination(active_workers);
4696 _g1h->set_n_termination(active_workers);
4697 terminator()->reset_for_reuse(active_workers);
4698 _n_workers = active_workers;
4699 }
4700
4701 // Helps out with CLD processing.
4702 //
4703 // During InitialMark we need to:
4704 // 1) Scavenge all CLDs for the young GC.
4705 // 2) Mark all objects directly reachable from strong CLDs.
4706 template <G1Mark do_mark_object>
4707 class G1CLDClosure : public CLDClosure {
4708 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4709 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4710 G1KlassScanClosure _klass_in_cld_closure;
4711 bool _claim;
4712
4713 public:
4714 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4715 bool only_young, bool claim)
4716 : _oop_closure(oop_closure),
4717 _oop_in_klass_closure(oop_closure->g1(),
4718 oop_closure->pss(),
4719 oop_closure->rp()),
4720 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4721 _claim(claim) {
4722
4723 }
4724
4725 void do_cld(ClassLoaderData* cld) {
4726 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4727 }
4728 };
4729
4730 class G1CodeBlobClosure: public CodeBlobClosure {
4731 OopClosure* _f;
4732
4733 public:
4734 G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4735 void do_code_blob(CodeBlob* blob) {
4736 nmethod* that = blob->as_nmethod_or_null();
4737 if (that != NULL) {
4738 if (!that->test_set_oops_do_mark()) {
4739 that->oops_do(_f);
4740 that->fix_oop_relocations();
4741 }
4742 }
4743 }
4744 };
4745
4746 void work(uint worker_id) {
4747 if (worker_id >= _n_workers) return; // no work needed this round
4748
4749 double start_time_ms = os::elapsedTime() * 1000.0;
4750 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4751
4752 {
4753 ResourceMark rm;
4754 HandleMark hm;
4755
4756 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4757
4758 G1ParScanThreadState pss(_g1h, worker_id, rp);
4759 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4760
4761 pss.set_evac_failure_closure(&evac_failure_cl);
4762
4763 bool only_young = _g1h->g1_policy()->gcs_are_young();
4764
4765 // Non-IM young GC.
4766 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4767 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4768 only_young, // Only process dirty klasses.
4769 false); // No need to claim CLDs.
4770 // IM young GC.
4771 // Strong roots closures.
4772 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4773 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4774 false, // Process all klasses.
4775 true); // Need to claim CLDs.
4776 // Weak roots closures.
4777 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4778 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4779 false, // Process all klasses.
4780 true); // Need to claim CLDs.
4781
4782 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4783 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4784 // IM Weak code roots are handled later.
4785
4786 OopClosure* strong_root_cl;
4787 OopClosure* weak_root_cl;
4788 CLDClosure* strong_cld_cl;
4789 CLDClosure* weak_cld_cl;
4790 CodeBlobClosure* strong_code_cl;
4791
4792 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4793 // We also need to mark copied objects.
4794 strong_root_cl = &scan_mark_root_cl;
4795 strong_cld_cl = &scan_mark_cld_cl;
4796 strong_code_cl = &scan_mark_code_cl;
4797 if (ClassUnloadingWithConcurrentMark) {
4798 weak_root_cl = &scan_mark_weak_root_cl;
4799 weak_cld_cl = &scan_mark_weak_cld_cl;
4800 } else {
4801 weak_root_cl = &scan_mark_root_cl;
4802 weak_cld_cl = &scan_mark_cld_cl;
4803 }
4804 } else {
4805 strong_root_cl = &scan_only_root_cl;
4806 weak_root_cl = &scan_only_root_cl;
4807 strong_cld_cl = &scan_only_cld_cl;
4808 weak_cld_cl = &scan_only_cld_cl;
4809 strong_code_cl = &scan_only_code_cl;
4810 }
4811
4812
4813 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4814
4815 pss.start_strong_roots();
4816 _g1h->g1_process_roots(strong_root_cl,
4817 weak_root_cl,
4818 &push_heap_rs_cl,
4819 strong_cld_cl,
4820 weak_cld_cl,
4821 strong_code_cl,
4822 worker_id);
4823
4824 pss.end_strong_roots();
4825
4826 {
4827 double start = os::elapsedTime();
4828 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4829 evac.do_void();
4830 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4831 double term_ms = pss.term_time()*1000.0;
4832 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4833 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4834 }
4835 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4836 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4837
4838 if (ParallelGCVerbose) {
4839 MutexLocker x(stats_lock());
4840 pss.print_termination_stats(worker_id);
4841 }
4842
4843 assert(pss.queue_is_empty(), "should be empty");
4844
4845 // Close the inner scope so that the ResourceMark and HandleMark
4846 // destructors are executed here and are included as part of the
4847 // "GC Worker Time".
4848 }
4849
4850 double end_time_ms = os::elapsedTime() * 1000.0;
4851 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4852 }
4853 };
4854
4855 // *** Common G1 Evacuation Stuff
4856
4857 // This method is run in a GC worker.
4858
4859 void
4860 G1CollectedHeap::
4861 g1_process_roots(OopClosure* scan_non_heap_roots,
4862 OopClosure* scan_non_heap_weak_roots,
4863 OopsInHeapRegionClosure* scan_rs,
4864 CLDClosure* scan_strong_clds,
4865 CLDClosure* scan_weak_clds,
4866 CodeBlobClosure* scan_strong_code,
4867 uint worker_i) {
4868
4869 // First scan the shared roots.
4870 double ext_roots_start = os::elapsedTime();
4871 double closure_app_time_sec = 0.0;
4872
4873 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4874 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4875
4876 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4877 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4878
4879 process_roots(false, // no scoping; this is parallel code
4880 SharedHeap::SO_None,
4881 &buf_scan_non_heap_roots,
4882 &buf_scan_non_heap_weak_roots,
4883 scan_strong_clds,
4884 // Unloading Initial Marks handle the weak CLDs separately.
4885 (trace_metadata ? NULL : scan_weak_clds),
4886 scan_strong_code);
4887
4888 // Now the CM ref_processor roots.
4889 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4890 // We need to treat the discovered reference lists of the
4891 // concurrent mark ref processor as roots and keep entries
4892 // (which are added by the marking threads) on them live
4893 // until they can be processed at the end of marking.
4894 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4895 }
4896
4897 if (trace_metadata) {
4898 // Barrier to make sure all workers passed
4899 // the strong CLD and strong nmethods phases.
4900 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4901
4902 // Now take the complement of the strong CLDs.
4903 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4904 }
4905
4906 // Finish up any enqueued closure apps (attributed as object copy time).
4907 buf_scan_non_heap_roots.done();
4908 buf_scan_non_heap_weak_roots.done();
4909
4910 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4911 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4912
4913 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4914
4915 double ext_root_time_ms =
4916 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4917
4918 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4919
4920 // During conc marking we have to filter the per-thread SATB buffers
4921 // to make sure we remove any oops into the CSet (which will show up
4922 // as implicitly live).
4923 double satb_filtering_ms = 0.0;
4924 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4925 if (mark_in_progress()) {
4926 double satb_filter_start = os::elapsedTime();
4927
4928 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4929
4930 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4931 }
4932 }
4933 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4934
4935 // Now scan the complement of the collection set.
4936 MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
4937
4938 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4939
4940 _process_strong_tasks->all_tasks_completed();
4941 }
4942
4943 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4944 private:
4945 BoolObjectClosure* _is_alive;
4946 int _initial_string_table_size;
4947 int _initial_symbol_table_size;
4948
4949 bool _process_strings;
4950 int _strings_processed;
4951 int _strings_removed;
4952
4953 bool _process_symbols;
4954 int _symbols_processed;
4955 int _symbols_removed;
4956
4957 bool _do_in_parallel;
4958 public:
4959 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4960 AbstractGangTask("String/Symbol Unlinking"),
4961 _is_alive(is_alive),
4962 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4963 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4964 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4965
4966 _initial_string_table_size = StringTable::the_table()->table_size();
4967 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4968 if (process_strings) {
4969 StringTable::clear_parallel_claimed_index();
4970 }
4971 if (process_symbols) {
4972 SymbolTable::clear_parallel_claimed_index();
4973 }
4974 }
4975
4976 ~G1StringSymbolTableUnlinkTask() {
4977 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4978 err_msg("claim value %d after unlink less than initial string table size %d",
4979 StringTable::parallel_claimed_index(), _initial_string_table_size));
4980 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4981 err_msg("claim value %d after unlink less than initial symbol table size %d",
4982 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4983
4984 if (G1TraceStringSymbolTableScrubbing) {
4985 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4986 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4987 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4988 strings_processed(), strings_removed(),
4989 symbols_processed(), symbols_removed());
4990 }
4991 }
4992
4993 void work(uint worker_id) {
4994 if (_do_in_parallel) {
4995 int strings_processed = 0;
4996 int strings_removed = 0;
4997 int symbols_processed = 0;
4998 int symbols_removed = 0;
4999 if (_process_strings) {
5000 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5001 Atomic::add(strings_processed, &_strings_processed);
5002 Atomic::add(strings_removed, &_strings_removed);
5003 }
5004 if (_process_symbols) {
5005 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5006 Atomic::add(symbols_processed, &_symbols_processed);
5007 Atomic::add(symbols_removed, &_symbols_removed);
5008 }
5009 } else {
5010 if (_process_strings) {
5011 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5012 }
5013 if (_process_symbols) {
5014 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5015 }
5016 }
5017 }
5018
5019 size_t strings_processed() const { return (size_t)_strings_processed; }
5020 size_t strings_removed() const { return (size_t)_strings_removed; }
5021
5022 size_t symbols_processed() const { return (size_t)_symbols_processed; }
5023 size_t symbols_removed() const { return (size_t)_symbols_removed; }
5024 };
5025
5026 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
5027 private:
5028 static Monitor* _lock;
5029
5030 BoolObjectClosure* const _is_alive;
5031 const bool _unloading_occurred;
5032 const uint _num_workers;
5033
5034 // Variables used to claim nmethods.
5035 nmethod* _first_nmethod;
5036 volatile nmethod* _claimed_nmethod;
5037
5038 // The list of nmethods that need to be processed by the second pass.
5039 volatile nmethod* _postponed_list;
5040 volatile uint _num_entered_barrier;
5041
5042 public:
5043 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5044 _is_alive(is_alive),
5045 _unloading_occurred(unloading_occurred),
5046 _num_workers(num_workers),
5047 _first_nmethod(NULL),
5048 _claimed_nmethod(NULL),
5049 _postponed_list(NULL),
5050 _num_entered_barrier(0)
5051 {
5052 nmethod::increase_unloading_clock();
5053 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5054 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5055 }
5056
5057 ~G1CodeCacheUnloadingTask() {
5058 CodeCache::verify_clean_inline_caches();
5059
5060 CodeCache::set_needs_cache_clean(false);
5061 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5062
5063 CodeCache::verify_icholder_relocations();
5064 }
5065
5066 private:
5067 void add_to_postponed_list(nmethod* nm) {
5068 nmethod* old;
5069 do {
5070 old = (nmethod*)_postponed_list;
5071 nm->set_unloading_next(old);
5072 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5073 }
5074
5075 void clean_nmethod(nmethod* nm) {
5076 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5077
5078 if (postponed) {
5079 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5080 add_to_postponed_list(nm);
5081 }
5082
5083 // Mark that this thread has been cleaned/unloaded.
5084 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5085 nm->set_unloading_clock(nmethod::global_unloading_clock());
5086 }
5087
5088 void clean_nmethod_postponed(nmethod* nm) {
5089 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5090 }
5091
5092 static const int MaxClaimNmethods = 16;
5093
5094 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5095 nmethod* first;
5096 nmethod* last;
5097
5098 do {
5099 *num_claimed_nmethods = 0;
5100
5101 first = last = (nmethod*)_claimed_nmethod;
5102
5103 if (first != NULL) {
5104 for (int i = 0; i < MaxClaimNmethods; i++) {
5105 last = CodeCache::alive_nmethod(CodeCache::next(last));
5106
5107 if (last == NULL) {
5108 break;
5109 }
5110
5111 claimed_nmethods[i] = last;
5112 (*num_claimed_nmethods)++;
5113 }
5114 }
5115
5116 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5117 }
5118
5119 nmethod* claim_postponed_nmethod() {
5120 nmethod* claim;
5121 nmethod* next;
5122
5123 do {
5124 claim = (nmethod*)_postponed_list;
5125 if (claim == NULL) {
5126 return NULL;
5127 }
5128
5129 next = claim->unloading_next();
5130
5131 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5132
5133 return claim;
5134 }
5135
5136 public:
5137 // Mark that we're done with the first pass of nmethod cleaning.
5138 void barrier_mark(uint worker_id) {
5139 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5140 _num_entered_barrier++;
5141 if (_num_entered_barrier == _num_workers) {
5142 ml.notify_all();
5143 }
5144 }
5145
5146 // See if we have to wait for the other workers to
5147 // finish their first-pass nmethod cleaning work.
5148 void barrier_wait(uint worker_id) {
5149 if (_num_entered_barrier < _num_workers) {
5150 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5151 while (_num_entered_barrier < _num_workers) {
5152 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5153 }
5154 }
5155 }
5156
5157 // Cleaning and unloading of nmethods. Some work has to be postponed
5158 // to the second pass, when we know which nmethods survive.
5159 void work_first_pass(uint worker_id) {
5160 // The first nmethods is claimed by the first worker.
5161 if (worker_id == 0 && _first_nmethod != NULL) {
5162 clean_nmethod(_first_nmethod);
5163 _first_nmethod = NULL;
5164 }
5165
5166 int num_claimed_nmethods;
5167 nmethod* claimed_nmethods[MaxClaimNmethods];
5168
5169 while (true) {
5170 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5171
5172 if (num_claimed_nmethods == 0) {
5173 break;
5174 }
5175
5176 for (int i = 0; i < num_claimed_nmethods; i++) {
5177 clean_nmethod(claimed_nmethods[i]);
5178 }
5179 }
5180 }
5181
5182 void work_second_pass(uint worker_id) {
5183 nmethod* nm;
5184 // Take care of postponed nmethods.
5185 while ((nm = claim_postponed_nmethod()) != NULL) {
5186 clean_nmethod_postponed(nm);
5187 }
5188 }
5189 };
5190
5191 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5192
5193 class G1KlassCleaningTask : public StackObj {
5194 BoolObjectClosure* _is_alive;
5195 volatile jint _clean_klass_tree_claimed;
5196 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5197
5198 public:
5199 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5200 _is_alive(is_alive),
5201 _clean_klass_tree_claimed(0),
5202 _klass_iterator() {
5203 }
5204
5205 private:
5206 bool claim_clean_klass_tree_task() {
5207 if (_clean_klass_tree_claimed) {
5208 return false;
5209 }
5210
5211 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5212 }
5213
5214 InstanceKlass* claim_next_klass() {
5215 Klass* klass;
5216 do {
5217 klass =_klass_iterator.next_klass();
5218 } while (klass != NULL && !klass->oop_is_instance());
5219
5220 return (InstanceKlass*)klass;
5221 }
5222
5223 public:
5224
5225 void clean_klass(InstanceKlass* ik) {
5226 ik->clean_implementors_list(_is_alive);
5227 ik->clean_method_data(_is_alive);
5228
5229 // G1 specific cleanup work that has
5230 // been moved here to be done in parallel.
5231 ik->clean_dependent_nmethods();
5232 }
5233
5234 void work() {
5235 ResourceMark rm;
5236
5237 // One worker will clean the subklass/sibling klass tree.
5238 if (claim_clean_klass_tree_task()) {
5239 Klass::clean_subklass_tree(_is_alive);
5240 }
5241
5242 // All workers will help cleaning the classes,
5243 InstanceKlass* klass;
5244 while ((klass = claim_next_klass()) != NULL) {
5245 clean_klass(klass);
5246 }
5247 }
5248 };
5249
5250 // To minimize the remark pause times, the tasks below are done in parallel.
5251 class G1ParallelCleaningTask : public AbstractGangTask {
5252 private:
5253 G1StringSymbolTableUnlinkTask _string_symbol_task;
5254 G1CodeCacheUnloadingTask _code_cache_task;
5255 G1KlassCleaningTask _klass_cleaning_task;
5256
5257 public:
5258 // The constructor is run in the VMThread.
5259 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5260 AbstractGangTask("Parallel Cleaning"),
5261 _string_symbol_task(is_alive, process_strings, process_symbols),
5262 _code_cache_task(num_workers, is_alive, unloading_occurred),
5263 _klass_cleaning_task(is_alive) {
5264 }
5265
5266 // The parallel work done by all worker threads.
5267 void work(uint worker_id) {
5268 // Do first pass of code cache cleaning.
5269 _code_cache_task.work_first_pass(worker_id);
5270
5271 // Let the threads mark that the first pass is done.
5272 _code_cache_task.barrier_mark(worker_id);
5273
5274 // Clean the Strings and Symbols.
5275 _string_symbol_task.work(worker_id);
5276
5277 // Wait for all workers to finish the first code cache cleaning pass.
5278 _code_cache_task.barrier_wait(worker_id);
5279
5280 // Do the second code cache cleaning work, which realize on
5281 // the liveness information gathered during the first pass.
5282 _code_cache_task.work_second_pass(worker_id);
5283
5284 // Clean all klasses that were not unloaded.
5285 _klass_cleaning_task.work();
5286 }
5287 };
5288
5289
5290 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5291 bool process_strings,
5292 bool process_symbols,
5293 bool class_unloading_occurred) {
5294 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5295 workers()->active_workers() : 1);
5296
5297 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5298 n_workers, class_unloading_occurred);
5299 if (G1CollectedHeap::use_parallel_gc_threads()) {
5300 set_par_threads(n_workers);
5301 workers()->run_task(&g1_unlink_task);
5302 set_par_threads(0);
5303 } else {
5304 g1_unlink_task.work(0);
5305 }
5306 }
5307
5308 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5309 bool process_strings, bool process_symbols) {
5310 {
5311 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5312 _g1h->workers()->active_workers() : 1);
5313 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5314 if (G1CollectedHeap::use_parallel_gc_threads()) {
5315 set_par_threads(n_workers);
5316 workers()->run_task(&g1_unlink_task);
5317 set_par_threads(0);
5318 } else {
5319 g1_unlink_task.work(0);
5320 }
5321 }
5322
5323 if (G1StringDedup::is_enabled()) {
5324 G1StringDedup::unlink(is_alive);
5325 }
5326 }
5327
5328 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5329 private:
5330 DirtyCardQueueSet* _queue;
5331 public:
5332 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5333
5334 virtual void work(uint worker_id) {
5335 double start_time = os::elapsedTime();
5336
5337 RedirtyLoggedCardTableEntryClosure cl;
5338 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5339 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5340 } else {
5341 _queue->apply_closure_to_all_completed_buffers(&cl);
5342 }
5343
5344 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5345 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5346 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5347 }
5348 };
5349
5350 void G1CollectedHeap::redirty_logged_cards() {
5351 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5352 double redirty_logged_cards_start = os::elapsedTime();
5353
5354 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5355 _g1h->workers()->active_workers() : 1);
5356
5357 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5358 dirty_card_queue_set().reset_for_par_iteration();
5359 if (use_parallel_gc_threads()) {
5360 set_par_threads(n_workers);
5361 workers()->run_task(&redirty_task);
5362 set_par_threads(0);
5363 } else {
5364 redirty_task.work(0);
5365 }
5366
5367 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5368 dcq.merge_bufferlists(&dirty_card_queue_set());
5369 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5370
5371 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5372 }
5373
5374 // Weak Reference Processing support
5375
5376 // An always "is_alive" closure that is used to preserve referents.
5377 // If the object is non-null then it's alive. Used in the preservation
5378 // of referent objects that are pointed to by reference objects
5379 // discovered by the CM ref processor.
5380 class G1AlwaysAliveClosure: public BoolObjectClosure {
5381 G1CollectedHeap* _g1;
5382 public:
5383 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5384 bool do_object_b(oop p) {
5385 if (p != NULL) {
5386 return true;
5387 }
5388 return false;
5389 }
5390 };
5391
5392 bool G1STWIsAliveClosure::do_object_b(oop p) {
5393 // An object is reachable if it is outside the collection set,
5394 // or is inside and copied.
5395 return !_g1->obj_in_cs(p) || p->is_forwarded();
5396 }
5397
5398 // Non Copying Keep Alive closure
5399 class G1KeepAliveClosure: public OopClosure {
5400 G1CollectedHeap* _g1;
5401 public:
5402 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5403 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5404 void do_oop(oop* p) {
5405 oop obj = *p;
5406
5407 G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5408 if (obj == NULL || cset_state == G1CollectedHeap::InNeither) {
5409 return;
5410 }
5411 if (cset_state == G1CollectedHeap::InCSet) {
5412 assert( obj->is_forwarded(), "invariant" );
5413 *p = obj->forwardee();
5414 } else {
5415 assert(!obj->is_forwarded(), "invariant" );
5416 assert(cset_state == G1CollectedHeap::IsHumongous,
5417 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5418 _g1->set_humongous_is_live(obj);
5419 }
5420 }
5421 };
5422
5423 // Copying Keep Alive closure - can be called from both
5424 // serial and parallel code as long as different worker
5425 // threads utilize different G1ParScanThreadState instances
5426 // and different queues.
5427
5428 class G1CopyingKeepAliveClosure: public OopClosure {
5429 G1CollectedHeap* _g1h;
5430 OopClosure* _copy_non_heap_obj_cl;
5431 G1ParScanThreadState* _par_scan_state;
5432
5433 public:
5434 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5435 OopClosure* non_heap_obj_cl,
5436 G1ParScanThreadState* pss):
5437 _g1h(g1h),
5438 _copy_non_heap_obj_cl(non_heap_obj_cl),
5439 _par_scan_state(pss)
5440 {}
5441
5442 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5443 virtual void do_oop( oop* p) { do_oop_work(p); }
5444
5445 template <class T> void do_oop_work(T* p) {
5446 oop obj = oopDesc::load_decode_heap_oop(p);
5447
5448 if (_g1h->is_in_cset_or_humongous(obj)) {
5449 // If the referent object has been forwarded (either copied
5450 // to a new location or to itself in the event of an
5451 // evacuation failure) then we need to update the reference
5452 // field and, if both reference and referent are in the G1
5453 // heap, update the RSet for the referent.
5454 //
5455 // If the referent has not been forwarded then we have to keep
5456 // it alive by policy. Therefore we have copy the referent.
5457 //
5458 // If the reference field is in the G1 heap then we can push
5459 // on the PSS queue. When the queue is drained (after each
5460 // phase of reference processing) the object and it's followers
5461 // will be copied, the reference field set to point to the
5462 // new location, and the RSet updated. Otherwise we need to
5463 // use the the non-heap or metadata closures directly to copy
5464 // the referent object and update the pointer, while avoiding
5465 // updating the RSet.
5466
5467 if (_g1h->is_in_g1_reserved(p)) {
5468 _par_scan_state->push_on_queue(p);
5469 } else {
5470 assert(!Metaspace::contains((const void*)p),
5471 err_msg("Unexpectedly found a pointer from metadata: "
5472 PTR_FORMAT, p));
5473 _copy_non_heap_obj_cl->do_oop(p);
5474 }
5475 }
5476 }
5477 };
5478
5479 // Serial drain queue closure. Called as the 'complete_gc'
5480 // closure for each discovered list in some of the
5481 // reference processing phases.
5482
5483 class G1STWDrainQueueClosure: public VoidClosure {
5484 protected:
5485 G1CollectedHeap* _g1h;
5486 G1ParScanThreadState* _par_scan_state;
5487
5488 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5489
5490 public:
5491 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5492 _g1h(g1h),
5493 _par_scan_state(pss)
5494 { }
5495
5496 void do_void() {
5497 G1ParScanThreadState* const pss = par_scan_state();
5498 pss->trim_queue();
5499 }
5500 };
5501
5502 // Parallel Reference Processing closures
5503
5504 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5505 // processing during G1 evacuation pauses.
5506
5507 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5508 private:
5509 G1CollectedHeap* _g1h;
5510 RefToScanQueueSet* _queues;
5511 FlexibleWorkGang* _workers;
5512 int _active_workers;
5513
5514 public:
5515 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5516 FlexibleWorkGang* workers,
5517 RefToScanQueueSet *task_queues,
5518 int n_workers) :
5519 _g1h(g1h),
5520 _queues(task_queues),
5521 _workers(workers),
5522 _active_workers(n_workers)
5523 {
5524 assert(n_workers > 0, "shouldn't call this otherwise");
5525 }
5526
5527 // Executes the given task using concurrent marking worker threads.
5528 virtual void execute(ProcessTask& task);
5529 virtual void execute(EnqueueTask& task);
5530 };
5531
5532 // Gang task for possibly parallel reference processing
5533
5534 class G1STWRefProcTaskProxy: public AbstractGangTask {
5535 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5536 ProcessTask& _proc_task;
5537 G1CollectedHeap* _g1h;
5538 RefToScanQueueSet *_task_queues;
5539 ParallelTaskTerminator* _terminator;
5540
5541 public:
5542 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5543 G1CollectedHeap* g1h,
5544 RefToScanQueueSet *task_queues,
5545 ParallelTaskTerminator* terminator) :
5546 AbstractGangTask("Process reference objects in parallel"),
5547 _proc_task(proc_task),
5548 _g1h(g1h),
5549 _task_queues(task_queues),
5550 _terminator(terminator)
5551 {}
5552
5553 virtual void work(uint worker_id) {
5554 // The reference processing task executed by a single worker.
5555 ResourceMark rm;
5556 HandleMark hm;
5557
5558 G1STWIsAliveClosure is_alive(_g1h);
5559
5560 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5561 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5562
5563 pss.set_evac_failure_closure(&evac_failure_cl);
5564
5565 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5566
5567 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5568
5569 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5570
5571 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5572 // We also need to mark copied objects.
5573 copy_non_heap_cl = ©_mark_non_heap_cl;
5574 }
5575
5576 // Keep alive closure.
5577 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5578
5579 // Complete GC closure
5580 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5581
5582 // Call the reference processing task's work routine.
5583 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5584
5585 // Note we cannot assert that the refs array is empty here as not all
5586 // of the processing tasks (specifically phase2 - pp2_work) execute
5587 // the complete_gc closure (which ordinarily would drain the queue) so
5588 // the queue may not be empty.
5589 }
5590 };
5591
5592 // Driver routine for parallel reference processing.
5593 // Creates an instance of the ref processing gang
5594 // task and has the worker threads execute it.
5595 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5596 assert(_workers != NULL, "Need parallel worker threads.");
5597
5598 ParallelTaskTerminator terminator(_active_workers, _queues);
5599 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5600
5601 _g1h->set_par_threads(_active_workers);
5602 _workers->run_task(&proc_task_proxy);
5603 _g1h->set_par_threads(0);
5604 }
5605
5606 // Gang task for parallel reference enqueueing.
5607
5608 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5609 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5610 EnqueueTask& _enq_task;
5611
5612 public:
5613 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5614 AbstractGangTask("Enqueue reference objects in parallel"),
5615 _enq_task(enq_task)
5616 { }
5617
5618 virtual void work(uint worker_id) {
5619 _enq_task.work(worker_id);
5620 }
5621 };
5622
5623 // Driver routine for parallel reference enqueueing.
5624 // Creates an instance of the ref enqueueing gang
5625 // task and has the worker threads execute it.
5626
5627 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5628 assert(_workers != NULL, "Need parallel worker threads.");
5629
5630 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5631
5632 _g1h->set_par_threads(_active_workers);
5633 _workers->run_task(&enq_task_proxy);
5634 _g1h->set_par_threads(0);
5635 }
5636
5637 // End of weak reference support closures
5638
5639 // Abstract task used to preserve (i.e. copy) any referent objects
5640 // that are in the collection set and are pointed to by reference
5641 // objects discovered by the CM ref processor.
5642
5643 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5644 protected:
5645 G1CollectedHeap* _g1h;
5646 RefToScanQueueSet *_queues;
5647 ParallelTaskTerminator _terminator;
5648 uint _n_workers;
5649
5650 public:
5651 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5652 AbstractGangTask("ParPreserveCMReferents"),
5653 _g1h(g1h),
5654 _queues(task_queues),
5655 _terminator(workers, _queues),
5656 _n_workers(workers)
5657 { }
5658
5659 void work(uint worker_id) {
5660 ResourceMark rm;
5661 HandleMark hm;
5662
5663 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5664 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5665
5666 pss.set_evac_failure_closure(&evac_failure_cl);
5667
5668 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5669
5670 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5671
5672 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5673
5674 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5675
5676 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5677 // We also need to mark copied objects.
5678 copy_non_heap_cl = ©_mark_non_heap_cl;
5679 }
5680
5681 // Is alive closure
5682 G1AlwaysAliveClosure always_alive(_g1h);
5683
5684 // Copying keep alive closure. Applied to referent objects that need
5685 // to be copied.
5686 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5687
5688 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5689
5690 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5691 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5692
5693 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5694 // So this must be true - but assert just in case someone decides to
5695 // change the worker ids.
5696 assert(0 <= worker_id && worker_id < limit, "sanity");
5697 assert(!rp->discovery_is_atomic(), "check this code");
5698
5699 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5700 for (uint idx = worker_id; idx < limit; idx += stride) {
5701 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5702
5703 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5704 while (iter.has_next()) {
5705 // Since discovery is not atomic for the CM ref processor, we
5706 // can see some null referent objects.
5707 iter.load_ptrs(DEBUG_ONLY(true));
5708 oop ref = iter.obj();
5709
5710 // This will filter nulls.
5711 if (iter.is_referent_alive()) {
5712 iter.make_referent_alive();
5713 }
5714 iter.move_to_next();
5715 }
5716 }
5717
5718 // Drain the queue - which may cause stealing
5719 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5720 drain_queue.do_void();
5721 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5722 assert(pss.queue_is_empty(), "should be");
5723 }
5724 };
5725
5726 // Weak Reference processing during an evacuation pause (part 1).
5727 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5728 double ref_proc_start = os::elapsedTime();
5729
5730 ReferenceProcessor* rp = _ref_processor_stw;
5731 assert(rp->discovery_enabled(), "should have been enabled");
5732
5733 // Any reference objects, in the collection set, that were 'discovered'
5734 // by the CM ref processor should have already been copied (either by
5735 // applying the external root copy closure to the discovered lists, or
5736 // by following an RSet entry).
5737 //
5738 // But some of the referents, that are in the collection set, that these
5739 // reference objects point to may not have been copied: the STW ref
5740 // processor would have seen that the reference object had already
5741 // been 'discovered' and would have skipped discovering the reference,
5742 // but would not have treated the reference object as a regular oop.
5743 // As a result the copy closure would not have been applied to the
5744 // referent object.
5745 //
5746 // We need to explicitly copy these referent objects - the references
5747 // will be processed at the end of remarking.
5748 //
5749 // We also need to do this copying before we process the reference
5750 // objects discovered by the STW ref processor in case one of these
5751 // referents points to another object which is also referenced by an
5752 // object discovered by the STW ref processor.
5753
5754 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5755 no_of_gc_workers == workers()->active_workers(),
5756 "Need to reset active GC workers");
5757
5758 set_par_threads(no_of_gc_workers);
5759 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5760 no_of_gc_workers,
5761 _task_queues);
5762
5763 if (G1CollectedHeap::use_parallel_gc_threads()) {
5764 workers()->run_task(&keep_cm_referents);
5765 } else {
5766 keep_cm_referents.work(0);
5767 }
5768
5769 set_par_threads(0);
5770
5771 // Closure to test whether a referent is alive.
5772 G1STWIsAliveClosure is_alive(this);
5773
5774 // Even when parallel reference processing is enabled, the processing
5775 // of JNI refs is serial and performed serially by the current thread
5776 // rather than by a worker. The following PSS will be used for processing
5777 // JNI refs.
5778
5779 // Use only a single queue for this PSS.
5780 G1ParScanThreadState pss(this, 0, NULL);
5781
5782 // We do not embed a reference processor in the copying/scanning
5783 // closures while we're actually processing the discovered
5784 // reference objects.
5785 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5786
5787 pss.set_evac_failure_closure(&evac_failure_cl);
5788
5789 assert(pss.queue_is_empty(), "pre-condition");
5790
5791 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5792
5793 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5794
5795 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5796
5797 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5798 // We also need to mark copied objects.
5799 copy_non_heap_cl = ©_mark_non_heap_cl;
5800 }
5801
5802 // Keep alive closure.
5803 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5804
5805 // Serial Complete GC closure
5806 G1STWDrainQueueClosure drain_queue(this, &pss);
5807
5808 // Setup the soft refs policy...
5809 rp->setup_policy(false);
5810
5811 ReferenceProcessorStats stats;
5812 if (!rp->processing_is_mt()) {
5813 // Serial reference processing...
5814 stats = rp->process_discovered_references(&is_alive,
5815 &keep_alive,
5816 &drain_queue,
5817 NULL,
5818 _gc_timer_stw,
5819 _gc_tracer_stw->gc_id());
5820 } else {
5821 // Parallel reference processing
5822 assert(rp->num_q() == no_of_gc_workers, "sanity");
5823 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5824
5825 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5826 stats = rp->process_discovered_references(&is_alive,
5827 &keep_alive,
5828 &drain_queue,
5829 &par_task_executor,
5830 _gc_timer_stw,
5831 _gc_tracer_stw->gc_id());
5832 }
5833
5834 _gc_tracer_stw->report_gc_reference_stats(stats);
5835
5836 // We have completed copying any necessary live referent objects.
5837 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5838
5839 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5840 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5841 }
5842
5843 // Weak Reference processing during an evacuation pause (part 2).
5844 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5845 double ref_enq_start = os::elapsedTime();
5846
5847 ReferenceProcessor* rp = _ref_processor_stw;
5848 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5849
5850 // Now enqueue any remaining on the discovered lists on to
5851 // the pending list.
5852 if (!rp->processing_is_mt()) {
5853 // Serial reference processing...
5854 rp->enqueue_discovered_references();
5855 } else {
5856 // Parallel reference enqueueing
5857
5858 assert(no_of_gc_workers == workers()->active_workers(),
5859 "Need to reset active workers");
5860 assert(rp->num_q() == no_of_gc_workers, "sanity");
5861 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5862
5863 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5864 rp->enqueue_discovered_references(&par_task_executor);
5865 }
5866
5867 rp->verify_no_references_recorded();
5868 assert(!rp->discovery_enabled(), "should have been disabled");
5869
5870 // FIXME
5871 // CM's reference processing also cleans up the string and symbol tables.
5872 // Should we do that here also? We could, but it is a serial operation
5873 // and could significantly increase the pause time.
5874
5875 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5876 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5877 }
5878
5879 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5880 _expand_heap_after_alloc_failure = true;
5881 _evacuation_failed = false;
5882
5883 // Should G1EvacuationFailureALot be in effect for this GC?
5884 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5885
5886 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5887
5888 // Disable the hot card cache.
5889 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5890 hot_card_cache->reset_hot_cache_claimed_index();
5891 hot_card_cache->set_use_cache(false);
5892
5893 uint n_workers;
5894 if (G1CollectedHeap::use_parallel_gc_threads()) {
5895 n_workers =
5896 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5897 workers()->active_workers(),
5898 Threads::number_of_non_daemon_threads());
5899 assert(UseDynamicNumberOfGCThreads ||
5900 n_workers == workers()->total_workers(),
5901 "If not dynamic should be using all the workers");
5902 workers()->set_active_workers(n_workers);
5903 set_par_threads(n_workers);
5904 } else {
5905 assert(n_par_threads() == 0,
5906 "Should be the original non-parallel value");
5907 n_workers = 1;
5908 }
5909
5910 G1ParTask g1_par_task(this, _task_queues);
5911
5912 init_for_evac_failure(NULL);
5913
5914 rem_set()->prepare_for_younger_refs_iterate(true);
5915
5916 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5917 double start_par_time_sec = os::elapsedTime();
5918 double end_par_time_sec;
5919
5920 {
5921 StrongRootsScope srs(this);
5922 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5923 if (g1_policy()->during_initial_mark_pause()) {
5924 ClassLoaderDataGraph::clear_claimed_marks();
5925 }
5926
5927 if (G1CollectedHeap::use_parallel_gc_threads()) {
5928 // The individual threads will set their evac-failure closures.
5929 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5930 // These tasks use ShareHeap::_process_strong_tasks
5931 assert(UseDynamicNumberOfGCThreads ||
5932 workers()->active_workers() == workers()->total_workers(),
5933 "If not dynamic should be using all the workers");
5934 workers()->run_task(&g1_par_task);
5935 } else {
5936 g1_par_task.set_for_termination(n_workers);
5937 g1_par_task.work(0);
5938 }
5939 end_par_time_sec = os::elapsedTime();
5940
5941 // Closing the inner scope will execute the destructor
5942 // for the StrongRootsScope object. We record the current
5943 // elapsed time before closing the scope so that time
5944 // taken for the SRS destructor is NOT included in the
5945 // reported parallel time.
5946 }
5947
5948 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5949 g1_policy()->phase_times()->record_par_time(par_time_ms);
5950
5951 double code_root_fixup_time_ms =
5952 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5953 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5954
5955 set_par_threads(0);
5956
5957 // Process any discovered reference objects - we have
5958 // to do this _before_ we retire the GC alloc regions
5959 // as we may have to copy some 'reachable' referent
5960 // objects (and their reachable sub-graphs) that were
5961 // not copied during the pause.
5962 process_discovered_references(n_workers);
5963
5964 // Weak root processing.
5965 {
5966 G1STWIsAliveClosure is_alive(this);
5967 G1KeepAliveClosure keep_alive(this);
5968 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5969 if (G1StringDedup::is_enabled()) {
5970 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5971 }
5972 }
5973
5974 release_gc_alloc_regions(n_workers, evacuation_info);
5975 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5976
5977 // Reset and re-enable the hot card cache.
5978 // Note the counts for the cards in the regions in the
5979 // collection set are reset when the collection set is freed.
5980 hot_card_cache->reset_hot_cache();
5981 hot_card_cache->set_use_cache(true);
5982
5983 // Migrate the strong code roots attached to each region in
5984 // the collection set. Ideally we would like to do this
5985 // after we have finished the scanning/evacuation of the
5986 // strong code roots for a particular heap region.
5987 migrate_strong_code_roots();
5988
5989 purge_code_root_memory();
5990
5991 if (g1_policy()->during_initial_mark_pause()) {
5992 // Reset the claim values set during marking the strong code roots
5993 reset_heap_region_claim_values();
5994 }
5995
5996 finalize_for_evac_failure();
5997
5998 if (evacuation_failed()) {
5999 remove_self_forwarding_pointers();
6000
6001 // Reset the G1EvacuationFailureALot counters and flags
6002 // Note: the values are reset only when an actual
6003 // evacuation failure occurs.
6004 NOT_PRODUCT(reset_evacuation_should_fail();)
6005 }
6006
6007 // Enqueue any remaining references remaining on the STW
6008 // reference processor's discovered lists. We need to do
6009 // this after the card table is cleaned (and verified) as
6010 // the act of enqueueing entries on to the pending list
6011 // will log these updates (and dirty their associated
6012 // cards). We need these updates logged to update any
6013 // RSets.
6014 enqueue_discovered_references(n_workers);
6015
6016 if (G1DeferredRSUpdate) {
6017 redirty_logged_cards();
6018 }
6019 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
6020 }
6021
6022 void G1CollectedHeap::free_region(HeapRegion* hr,
6023 FreeRegionList* free_list,
6024 bool par,
6025 bool locked) {
6026 assert(!hr->isHumongous(), "this is only for non-humongous regions");
6027 assert(!hr->is_empty(), "the region should not be empty");
6028 assert(_hrs.is_available(hr->hrs_index()), "region should be committed");
6029 assert(free_list != NULL, "pre-condition");
6030
6031 if (G1VerifyBitmaps) {
6032 MemRegion mr(hr->bottom(), hr->end());
6033 concurrent_mark()->clearRangePrevBitmap(mr);
6034 }
6035
6036 // Clear the card counts for this region.
6037 // Note: we only need to do this if the region is not young
6038 // (since we don't refine cards in young regions).
6039 if (!hr->is_young()) {
6040 _cg1r->hot_card_cache()->reset_card_counts(hr);
6041 }
6042 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6043 free_list->add_ordered(hr);
6044 }
6045
6046 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6047 FreeRegionList* free_list,
6048 bool par) {
6049 assert(hr->startsHumongous(), "this is only for starts humongous regions");
6050 assert(free_list != NULL, "pre-condition");
6051
6052 size_t hr_capacity = hr->capacity();
6053 // We need to read this before we make the region non-humongous,
6054 // otherwise the information will be gone.
6055 uint last_index = hr->last_hc_index();
6056 hr->set_notHumongous();
6057 free_region(hr, free_list, par);
6058
6059 uint i = hr->hrs_index() + 1;
6060 while (i < last_index) {
6061 HeapRegion* curr_hr = region_at(i);
6062 assert(curr_hr->continuesHumongous(), "invariant");
6063 curr_hr->set_notHumongous();
6064 free_region(curr_hr, free_list, par);
6065 i += 1;
6066 }
6067 }
6068
6069 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6070 const HeapRegionSetCount& humongous_regions_removed) {
6071 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6072 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6073 _old_set.bulk_remove(old_regions_removed);
6074 _humongous_set.bulk_remove(humongous_regions_removed);
6075 }
6076
6077 }
6078
6079 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6080 assert(list != NULL, "list can't be null");
6081 if (!list->is_empty()) {
6082 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6083 _hrs.insert_list_into_free_list(list);
6084 }
6085 }
6086
6087 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6088 assert(_summary_bytes_used >= bytes,
6089 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6090 _summary_bytes_used, bytes));
6091 _summary_bytes_used -= bytes;
6092 }
6093
6094 class G1ParCleanupCTTask : public AbstractGangTask {
6095 G1SATBCardTableModRefBS* _ct_bs;
6096 G1CollectedHeap* _g1h;
6097 HeapRegion* volatile _su_head;
6098 public:
6099 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6100 G1CollectedHeap* g1h) :
6101 AbstractGangTask("G1 Par Cleanup CT Task"),
6102 _ct_bs(ct_bs), _g1h(g1h) { }
6103
6104 void work(uint worker_id) {
6105 HeapRegion* r;
6106 while (r = _g1h->pop_dirty_cards_region()) {
6107 clear_cards(r);
6108 }
6109 }
6110
6111 void clear_cards(HeapRegion* r) {
6112 // Cards of the survivors should have already been dirtied.
6113 if (!r->is_survivor()) {
6114 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6115 }
6116 }
6117 };
6118
6119 #ifndef PRODUCT
6120 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6121 G1CollectedHeap* _g1h;
6122 G1SATBCardTableModRefBS* _ct_bs;
6123 public:
6124 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6125 : _g1h(g1h), _ct_bs(ct_bs) { }
6126 virtual bool doHeapRegion(HeapRegion* r) {
6127 if (r->is_survivor()) {
6128 _g1h->verify_dirty_region(r);
6129 } else {
6130 _g1h->verify_not_dirty_region(r);
6131 }
6132 return false;
6133 }
6134 };
6135
6136 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6137 // All of the region should be clean.
6138 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6139 MemRegion mr(hr->bottom(), hr->end());
6140 ct_bs->verify_not_dirty_region(mr);
6141 }
6142
6143 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6144 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6145 // dirty allocated blocks as they allocate them. The thread that
6146 // retires each region and replaces it with a new one will do a
6147 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6148 // not dirty that area (one less thing to have to do while holding
6149 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6150 // is dirty.
6151 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6152 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6153 if (hr->is_young()) {
6154 ct_bs->verify_g1_young_region(mr);
6155 } else {
6156 ct_bs->verify_dirty_region(mr);
6157 }
6158 }
6159
6160 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6161 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6162 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6163 verify_dirty_region(hr);
6164 }
6165 }
6166
6167 void G1CollectedHeap::verify_dirty_young_regions() {
6168 verify_dirty_young_list(_young_list->first_region());
6169 }
6170
6171 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6172 HeapWord* tams, HeapWord* end) {
6173 guarantee(tams <= end,
6174 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6175 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6176 if (result < end) {
6177 gclog_or_tty->cr();
6178 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6179 bitmap_name, result);
6180 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6181 bitmap_name, tams, end);
6182 return false;
6183 }
6184 return true;
6185 }
6186
6187 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6188 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6189 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6190
6191 HeapWord* bottom = hr->bottom();
6192 HeapWord* ptams = hr->prev_top_at_mark_start();
6193 HeapWord* ntams = hr->next_top_at_mark_start();
6194 HeapWord* end = hr->end();
6195
6196 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6197
6198 bool res_n = true;
6199 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6200 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6201 // if we happen to be in that state.
6202 if (mark_in_progress() || !_cmThread->in_progress()) {
6203 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6204 }
6205 if (!res_p || !res_n) {
6206 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6207 HR_FORMAT_PARAMS(hr));
6208 gclog_or_tty->print_cr("#### Caller: %s", caller);
6209 return false;
6210 }
6211 return true;
6212 }
6213
6214 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6215 if (!G1VerifyBitmaps) return;
6216
6217 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6218 }
6219
6220 class G1VerifyBitmapClosure : public HeapRegionClosure {
6221 private:
6222 const char* _caller;
6223 G1CollectedHeap* _g1h;
6224 bool _failures;
6225
6226 public:
6227 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6228 _caller(caller), _g1h(g1h), _failures(false) { }
6229
6230 bool failures() { return _failures; }
6231
6232 virtual bool doHeapRegion(HeapRegion* hr) {
6233 if (hr->continuesHumongous()) return false;
6234
6235 bool result = _g1h->verify_bitmaps(_caller, hr);
6236 if (!result) {
6237 _failures = true;
6238 }
6239 return false;
6240 }
6241 };
6242
6243 void G1CollectedHeap::check_bitmaps(const char* caller) {
6244 if (!G1VerifyBitmaps) return;
6245
6246 G1VerifyBitmapClosure cl(caller, this);
6247 heap_region_iterate(&cl);
6248 guarantee(!cl.failures(), "bitmap verification");
6249 }
6250 #endif // PRODUCT
6251
6252 void G1CollectedHeap::cleanUpCardTable() {
6253 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6254 double start = os::elapsedTime();
6255
6256 {
6257 // Iterate over the dirty cards region list.
6258 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6259
6260 if (G1CollectedHeap::use_parallel_gc_threads()) {
6261 set_par_threads();
6262 workers()->run_task(&cleanup_task);
6263 set_par_threads(0);
6264 } else {
6265 while (_dirty_cards_region_list) {
6266 HeapRegion* r = _dirty_cards_region_list;
6267 cleanup_task.clear_cards(r);
6268 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6269 if (_dirty_cards_region_list == r) {
6270 // The last region.
6271 _dirty_cards_region_list = NULL;
6272 }
6273 r->set_next_dirty_cards_region(NULL);
6274 }
6275 }
6276 #ifndef PRODUCT
6277 if (G1VerifyCTCleanup || VerifyAfterGC) {
6278 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6279 heap_region_iterate(&cleanup_verifier);
6280 }
6281 #endif
6282 }
6283
6284 double elapsed = os::elapsedTime() - start;
6285 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6286 }
6287
6288 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6289 size_t pre_used = 0;
6290 FreeRegionList local_free_list("Local List for CSet Freeing");
6291
6292 double young_time_ms = 0.0;
6293 double non_young_time_ms = 0.0;
6294
6295 // Since the collection set is a superset of the the young list,
6296 // all we need to do to clear the young list is clear its
6297 // head and length, and unlink any young regions in the code below
6298 _young_list->clear();
6299
6300 G1CollectorPolicy* policy = g1_policy();
6301
6302 double start_sec = os::elapsedTime();
6303 bool non_young = true;
6304
6305 HeapRegion* cur = cs_head;
6306 int age_bound = -1;
6307 size_t rs_lengths = 0;
6308
6309 while (cur != NULL) {
6310 assert(!is_on_master_free_list(cur), "sanity");
6311 if (non_young) {
6312 if (cur->is_young()) {
6313 double end_sec = os::elapsedTime();
6314 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6315 non_young_time_ms += elapsed_ms;
6316
6317 start_sec = os::elapsedTime();
6318 non_young = false;
6319 }
6320 } else {
6321 if (!cur->is_young()) {
6322 double end_sec = os::elapsedTime();
6323 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6324 young_time_ms += elapsed_ms;
6325
6326 start_sec = os::elapsedTime();
6327 non_young = true;
6328 }
6329 }
6330
6331 rs_lengths += cur->rem_set()->occupied_locked();
6332
6333 HeapRegion* next = cur->next_in_collection_set();
6334 assert(cur->in_collection_set(), "bad CS");
6335 cur->set_next_in_collection_set(NULL);
6336 cur->set_in_collection_set(false);
6337
6338 if (cur->is_young()) {
6339 int index = cur->young_index_in_cset();
6340 assert(index != -1, "invariant");
6341 assert((uint) index < policy->young_cset_region_length(), "invariant");
6342 size_t words_survived = _surviving_young_words[index];
6343 cur->record_surv_words_in_group(words_survived);
6344
6345 // At this point the we have 'popped' cur from the collection set
6346 // (linked via next_in_collection_set()) but it is still in the
6347 // young list (linked via next_young_region()). Clear the
6348 // _next_young_region field.
6349 cur->set_next_young_region(NULL);
6350 } else {
6351 int index = cur->young_index_in_cset();
6352 assert(index == -1, "invariant");
6353 }
6354
6355 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6356 (!cur->is_young() && cur->young_index_in_cset() == -1),
6357 "invariant" );
6358
6359 if (!cur->evacuation_failed()) {
6360 MemRegion used_mr = cur->used_region();
6361
6362 // And the region is empty.
6363 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6364 pre_used += cur->used();
6365 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6366 } else {
6367 cur->uninstall_surv_rate_group();
6368 if (cur->is_young()) {
6369 cur->set_young_index_in_cset(-1);
6370 }
6371 cur->set_not_young();
6372 cur->set_evacuation_failed(false);
6373 // The region is now considered to be old.
6374 _old_set.add(cur);
6375 evacuation_info.increment_collectionset_used_after(cur->used());
6376 }
6377 cur = next;
6378 }
6379
6380 evacuation_info.set_regions_freed(local_free_list.length());
6381 policy->record_max_rs_lengths(rs_lengths);
6382 policy->cset_regions_freed();
6383
6384 double end_sec = os::elapsedTime();
6385 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6386
6387 if (non_young) {
6388 non_young_time_ms += elapsed_ms;
6389 } else {
6390 young_time_ms += elapsed_ms;
6391 }
6392
6393 prepend_to_freelist(&local_free_list);
6394 decrement_summary_bytes(pre_used);
6395 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6396 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6397 }
6398
6399 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6400 private:
6401 FreeRegionList* _free_region_list;
6402 HeapRegionSet* _proxy_set;
6403 HeapRegionSetCount _humongous_regions_removed;
6404 size_t _freed_bytes;
6405 public:
6406
6407 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6408 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6409 }
6410
6411 virtual bool doHeapRegion(HeapRegion* r) {
6412 if (!r->startsHumongous()) {
6413 return false;
6414 }
6415
6416 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6417
6418 oop obj = (oop)r->bottom();
6419 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6420
6421 // The following checks whether the humongous object is live are sufficient.
6422 // The main additional check (in addition to having a reference from the roots
6423 // or the young gen) is whether the humongous object has a remembered set entry.
6424 //
6425 // A humongous object cannot be live if there is no remembered set for it
6426 // because:
6427 // - there can be no references from within humongous starts regions referencing
6428 // the object because we never allocate other objects into them.
6429 // (I.e. there are no intra-region references that may be missed by the
6430 // remembered set)
6431 // - as soon there is a remembered set entry to the humongous starts region
6432 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6433 // until the end of a concurrent mark.
6434 //
6435 // It is not required to check whether the object has been found dead by marking
6436 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6437 // all objects allocated during that time are considered live.
6438 // SATB marking is even more conservative than the remembered set.
6439 // So if at this point in the collection there is no remembered set entry,
6440 // nobody has a reference to it.
6441 // At the start of collection we flush all refinement logs, and remembered sets
6442 // are completely up-to-date wrt to references to the humongous object.
6443 //
6444 // Other implementation considerations:
6445 // - never consider object arrays: while they are a valid target, they have not
6446 // been observed to be used as temporary objects.
6447 // - they would also pose considerable effort for cleaning up the the remembered
6448 // sets.
6449 // While this cleanup is not strictly necessary to be done (or done instantly),
6450 // given that their occurrence is very low, this saves us this additional
6451 // complexity.
6452 uint region_idx = r->hrs_index();
6453 if (g1h->humongous_is_live(region_idx) ||
6454 g1h->humongous_region_is_always_live(region_idx)) {
6455
6456 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6457 gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6458 r->isHumongous(),
6459 region_idx,
6460 r->rem_set()->occupied(),
6461 r->rem_set()->strong_code_roots_list_length(),
6462 next_bitmap->isMarked(r->bottom()),
6463 g1h->humongous_is_live(region_idx),
6464 obj->is_objArray()
6465 );
6466 }
6467
6468 return false;
6469 }
6470
6471 guarantee(!obj->is_objArray(),
6472 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6473 r->bottom()));
6474
6475 if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6476 gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6477 r->isHumongous(),
6478 r->bottom(),
6479 region_idx,
6480 r->region_num(),
6481 r->rem_set()->occupied(),
6482 r->rem_set()->strong_code_roots_list_length(),
6483 next_bitmap->isMarked(r->bottom()),
6484 g1h->humongous_is_live(region_idx),
6485 obj->is_objArray()
6486 );
6487 }
6488 // Need to clear mark bit of the humongous object if already set.
6489 if (next_bitmap->isMarked(r->bottom())) {
6490 next_bitmap->clear(r->bottom());
6491 }
6492 _freed_bytes += r->used();
6493 r->set_containing_set(NULL);
6494 _humongous_regions_removed.increment(1u, r->capacity());
6495 g1h->free_humongous_region(r, _free_region_list, false);
6496
6497 return false;
6498 }
6499
6500 HeapRegionSetCount& humongous_free_count() {
6501 return _humongous_regions_removed;
6502 }
6503
6504 size_t bytes_freed() const {
6505 return _freed_bytes;
6506 }
6507
6508 size_t humongous_reclaimed() const {
6509 return _humongous_regions_removed.length();
6510 }
6511 };
6512
6513 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6514 assert_at_safepoint(true);
6515
6516 if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6517 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6518 return;
6519 }
6520
6521 double start_time = os::elapsedTime();
6522
6523 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6524
6525 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6526 heap_region_iterate(&cl);
6527
6528 HeapRegionSetCount empty_set;
6529 remove_from_old_sets(empty_set, cl.humongous_free_count());
6530
6531 G1HRPrinter* hr_printer = _g1h->hr_printer();
6532 if (hr_printer->is_active()) {
6533 FreeRegionListIterator iter(&local_cleanup_list);
6534 while (iter.more_available()) {
6535 HeapRegion* hr = iter.get_next();
6536 hr_printer->cleanup(hr);
6537 }
6538 }
6539
6540 prepend_to_freelist(&local_cleanup_list);
6541 decrement_summary_bytes(cl.bytes_freed());
6542
6543 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6544 cl.humongous_reclaimed());
6545 }
6546
6547 // This routine is similar to the above but does not record
6548 // any policy statistics or update free lists; we are abandoning
6549 // the current incremental collection set in preparation of a
6550 // full collection. After the full GC we will start to build up
6551 // the incremental collection set again.
6552 // This is only called when we're doing a full collection
6553 // and is immediately followed by the tearing down of the young list.
6554
6555 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6556 HeapRegion* cur = cs_head;
6557
6558 while (cur != NULL) {
6559 HeapRegion* next = cur->next_in_collection_set();
6560 assert(cur->in_collection_set(), "bad CS");
6561 cur->set_next_in_collection_set(NULL);
6562 cur->set_in_collection_set(false);
6563 cur->set_young_index_in_cset(-1);
6564 cur = next;
6565 }
6566 }
6567
6568 void G1CollectedHeap::set_free_regions_coming() {
6569 if (G1ConcRegionFreeingVerbose) {
6570 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6571 "setting free regions coming");
6572 }
6573
6574 assert(!free_regions_coming(), "pre-condition");
6575 _free_regions_coming = true;
6576 }
6577
6578 void G1CollectedHeap::reset_free_regions_coming() {
6579 assert(free_regions_coming(), "pre-condition");
6580
6581 {
6582 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6583 _free_regions_coming = false;
6584 SecondaryFreeList_lock->notify_all();
6585 }
6586
6587 if (G1ConcRegionFreeingVerbose) {
6588 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6589 "reset free regions coming");
6590 }
6591 }
6592
6593 void G1CollectedHeap::wait_while_free_regions_coming() {
6594 // Most of the time we won't have to wait, so let's do a quick test
6595 // first before we take the lock.
6596 if (!free_regions_coming()) {
6597 return;
6598 }
6599
6600 if (G1ConcRegionFreeingVerbose) {
6601 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6602 "waiting for free regions");
6603 }
6604
6605 {
6606 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6607 while (free_regions_coming()) {
6608 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6609 }
6610 }
6611
6612 if (G1ConcRegionFreeingVerbose) {
6613 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6614 "done waiting for free regions");
6615 }
6616 }
6617
6618 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6619 assert(heap_lock_held_for_gc(),
6620 "the heap lock should already be held by or for this thread");
6621 _young_list->push_region(hr);
6622 }
6623
6624 class NoYoungRegionsClosure: public HeapRegionClosure {
6625 private:
6626 bool _success;
6627 public:
6628 NoYoungRegionsClosure() : _success(true) { }
6629 bool doHeapRegion(HeapRegion* r) {
6630 if (r->is_young()) {
6631 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6632 r->bottom(), r->end());
6633 _success = false;
6634 }
6635 return false;
6636 }
6637 bool success() { return _success; }
6638 };
6639
6640 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6641 bool ret = _young_list->check_list_empty(check_sample);
6642
6643 if (check_heap) {
6644 NoYoungRegionsClosure closure;
6645 heap_region_iterate(&closure);
6646 ret = ret && closure.success();
6647 }
6648
6649 return ret;
6650 }
6651
6652 class TearDownRegionSetsClosure : public HeapRegionClosure {
6653 private:
6654 HeapRegionSet *_old_set;
6655
6656 public:
6657 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6658
6659 bool doHeapRegion(HeapRegion* r) {
6660 if (r->is_empty()) {
6661 // We ignore empty regions, we'll empty the free list afterwards
6662 } else if (r->is_young()) {
6663 // We ignore young regions, we'll empty the young list afterwards
6664 } else if (r->isHumongous()) {
6665 // We ignore humongous regions, we're not tearing down the
6666 // humongous region set
6667 } else {
6668 // The rest should be old
6669 _old_set->remove(r);
6670 }
6671 return false;
6672 }
6673
6674 ~TearDownRegionSetsClosure() {
6675 assert(_old_set->is_empty(), "post-condition");
6676 }
6677 };
6678
6679 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6680 assert_at_safepoint(true /* should_be_vm_thread */);
6681
6682 if (!free_list_only) {
6683 TearDownRegionSetsClosure cl(&_old_set);
6684 heap_region_iterate(&cl);
6685
6686 // Note that emptying the _young_list is postponed and instead done as
6687 // the first step when rebuilding the regions sets again. The reason for
6688 // this is that during a full GC string deduplication needs to know if
6689 // a collected region was young or old when the full GC was initiated.
6690 }
6691 _hrs.remove_all_free_regions();
6692 }
6693
6694 class RebuildRegionSetsClosure : public HeapRegionClosure {
6695 private:
6696 bool _free_list_only;
6697 HeapRegionSet* _old_set;
6698 HeapRegionSeq* _hrs;
6699 size_t _total_used;
6700
6701 public:
6702 RebuildRegionSetsClosure(bool free_list_only,
6703 HeapRegionSet* old_set, HeapRegionSeq* hrs) :
6704 _free_list_only(free_list_only),
6705 _old_set(old_set), _hrs(hrs), _total_used(0) {
6706 assert(_hrs->num_free_regions() == 0, "pre-condition");
6707 if (!free_list_only) {
6708 assert(_old_set->is_empty(), "pre-condition");
6709 }
6710 }
6711
6712 bool doHeapRegion(HeapRegion* r) {
6713 if (r->continuesHumongous()) {
6714 return false;
6715 }
6716
6717 if (r->is_empty()) {
6718 // Add free regions to the free list
6719 _hrs->insert_into_free_list(r);
6720 } else if (!_free_list_only) {
6721 assert(!r->is_young(), "we should not come across young regions");
6722
6723 if (r->isHumongous()) {
6724 // We ignore humongous regions, we left the humongous set unchanged
6725 } else {
6726 // The rest should be old, add them to the old set
6727 _old_set->add(r);
6728 }
6729 _total_used += r->used();
6730 }
6731
6732 return false;
6733 }
6734
6735 size_t total_used() {
6736 return _total_used;
6737 }
6738 };
6739
6740 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6741 assert_at_safepoint(true /* should_be_vm_thread */);
6742
6743 if (!free_list_only) {
6744 _young_list->empty_list();
6745 }
6746
6747 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrs);
6748 heap_region_iterate(&cl);
6749
6750 if (!free_list_only) {
6751 _summary_bytes_used = cl.total_used();
6752 }
6753 assert(_summary_bytes_used == recalculate_used(),
6754 err_msg("inconsistent _summary_bytes_used, "
6755 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6756 _summary_bytes_used, recalculate_used()));
6757 }
6758
6759 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6760 _refine_cte_cl->set_concurrent(concurrent);
6761 }
6762
6763 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6764 HeapRegion* hr = heap_region_containing(p);
6765 return hr->is_in(p);
6766 }
6767
6768 // Methods for the mutator alloc region
6769
6770 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6771 bool force) {
6772 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6773 assert(!force || g1_policy()->can_expand_young_list(),
6774 "if force is true we should be able to expand the young list");
6775 bool young_list_full = g1_policy()->is_young_list_full();
6776 if (force || !young_list_full) {
6777 HeapRegion* new_alloc_region = new_region(word_size,
6778 false /* is_old */,
6779 false /* do_expand */);
6780 if (new_alloc_region != NULL) {
6781 set_region_short_lived_locked(new_alloc_region);
6782 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6783 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6784 return new_alloc_region;
6785 }
6786 }
6787 return NULL;
6788 }
6789
6790 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6791 size_t allocated_bytes) {
6792 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6793 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6794
6795 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6796 _summary_bytes_used += allocated_bytes;
6797 _hr_printer.retire(alloc_region);
6798 // We update the eden sizes here, when the region is retired,
6799 // instead of when it's allocated, since this is the point that its
6800 // used space has been recored in _summary_bytes_used.
6801 g1mm()->update_eden_size();
6802 }
6803
6804 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6805 bool force) {
6806 return _g1h->new_mutator_alloc_region(word_size, force);
6807 }
6808
6809 void G1CollectedHeap::set_par_threads() {
6810 // Don't change the number of workers. Use the value previously set
6811 // in the workgroup.
6812 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6813 uint n_workers = workers()->active_workers();
6814 assert(UseDynamicNumberOfGCThreads ||
6815 n_workers == workers()->total_workers(),
6816 "Otherwise should be using the total number of workers");
6817 if (n_workers == 0) {
6818 assert(false, "Should have been set in prior evacuation pause.");
6819 n_workers = ParallelGCThreads;
6820 workers()->set_active_workers(n_workers);
6821 }
6822 set_par_threads(n_workers);
6823 }
6824
6825 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6826 size_t allocated_bytes) {
6827 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6828 }
6829
6830 // Methods for the GC alloc regions
6831
6832 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6833 uint count,
6834 GCAllocPurpose ap) {
6835 assert(FreeList_lock->owned_by_self(), "pre-condition");
6836
6837 if (count < g1_policy()->max_regions(ap)) {
6838 bool survivor = (ap == GCAllocForSurvived);
6839 HeapRegion* new_alloc_region = new_region(word_size,
6840 !survivor,
6841 true /* do_expand */);
6842 if (new_alloc_region != NULL) {
6843 // We really only need to do this for old regions given that we
6844 // should never scan survivors. But it doesn't hurt to do it
6845 // for survivors too.
6846 new_alloc_region->record_top_and_timestamp();
6847 if (survivor) {
6848 new_alloc_region->set_survivor();
6849 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6850 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6851 } else {
6852 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6853 check_bitmaps("Old Region Allocation", new_alloc_region);
6854 }
6855 bool during_im = g1_policy()->during_initial_mark_pause();
6856 new_alloc_region->note_start_of_copying(during_im);
6857 return new_alloc_region;
6858 } else {
6859 g1_policy()->note_alloc_region_limit_reached(ap);
6860 }
6861 }
6862 return NULL;
6863 }
6864
6865 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6866 size_t allocated_bytes,
6867 GCAllocPurpose ap) {
6868 bool during_im = g1_policy()->during_initial_mark_pause();
6869 alloc_region->note_end_of_copying(during_im);
6870 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6871 if (ap == GCAllocForSurvived) {
6872 young_list()->add_survivor_region(alloc_region);
6873 } else {
6874 _old_set.add(alloc_region);
6875 }
6876 _hr_printer.retire(alloc_region);
6877 }
6878
6879 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6880 bool force) {
6881 assert(!force, "not supported for GC alloc regions");
6882 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6883 }
6884
6885 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6886 size_t allocated_bytes) {
6887 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6888 GCAllocForSurvived);
6889 }
6890
6891 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6892 bool force) {
6893 assert(!force, "not supported for GC alloc regions");
6894 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6895 }
6896
6897 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6898 size_t allocated_bytes) {
6899 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6900 GCAllocForTenured);
6901 }
6902 // Heap region set verification
6903
6904 class VerifyRegionListsClosure : public HeapRegionClosure {
6905 private:
6906 HeapRegionSet* _old_set;
6907 HeapRegionSet* _humongous_set;
6908 HeapRegionSeq* _hrs;
6909
6910 public:
6911 HeapRegionSetCount _old_count;
6912 HeapRegionSetCount _humongous_count;
6913 HeapRegionSetCount _free_count;
6914
6915 VerifyRegionListsClosure(HeapRegionSet* old_set,
6916 HeapRegionSet* humongous_set,
6917 HeapRegionSeq* hrs) :
6918 _old_set(old_set), _humongous_set(humongous_set), _hrs(hrs),
6919 _old_count(), _humongous_count(), _free_count(){ }
6920
6921 bool doHeapRegion(HeapRegion* hr) {
6922 if (hr->continuesHumongous()) {
6923 return false;
6924 }
6925
6926 if (hr->is_young()) {
6927 // TODO
6928 } else if (hr->startsHumongous()) {
6929 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
6930 _humongous_count.increment(1u, hr->capacity());
6931 } else if (hr->is_empty()) {
6932 assert(_hrs->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
6933 _free_count.increment(1u, hr->capacity());
6934 } else {
6935 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
6936 _old_count.increment(1u, hr->capacity());
6937 }
6938 return false;
6939 }
6940
6941 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionSeq* free_list) {
6942 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6943 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6944 old_set->total_capacity_bytes(), _old_count.capacity()));
6945
6946 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6947 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6948 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6949
6950 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6951 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6952 free_list->total_capacity_bytes(), _free_count.capacity()));
6953 }
6954 };
6955
6956 void G1CollectedHeap::verify_region_sets() {
6957 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6958
6959 // First, check the explicit lists.
6960 _hrs.verify();
6961 {
6962 // Given that a concurrent operation might be adding regions to
6963 // the secondary free list we have to take the lock before
6964 // verifying it.
6965 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6966 _secondary_free_list.verify_list();
6967 }
6968
6969 // If a concurrent region freeing operation is in progress it will
6970 // be difficult to correctly attributed any free regions we come
6971 // across to the correct free list given that they might belong to
6972 // one of several (free_list, secondary_free_list, any local lists,
6973 // etc.). So, if that's the case we will skip the rest of the
6974 // verification operation. Alternatively, waiting for the concurrent
6975 // operation to complete will have a non-trivial effect on the GC's
6976 // operation (no concurrent operation will last longer than the
6977 // interval between two calls to verification) and it might hide
6978 // any issues that we would like to catch during testing.
6979 if (free_regions_coming()) {
6980 return;
6981 }
6982
6983 // Make sure we append the secondary_free_list on the free_list so
6984 // that all free regions we will come across can be safely
6985 // attributed to the free_list.
6986 append_secondary_free_list_if_not_empty_with_lock();
6987
6988 // Finally, make sure that the region accounting in the lists is
6989 // consistent with what we see in the heap.
6990
6991 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrs);
6992 heap_region_iterate(&cl);
6993 cl.verify_counts(&_old_set, &_humongous_set, &_hrs);
6994 }
6995
6996 // Optimized nmethod scanning
6997
6998 class RegisterNMethodOopClosure: public OopClosure {
6999 G1CollectedHeap* _g1h;
7000 nmethod* _nm;
7001
7002 template <class T> void do_oop_work(T* p) {
7003 T heap_oop = oopDesc::load_heap_oop(p);
7004 if (!oopDesc::is_null(heap_oop)) {
7005 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7006 HeapRegion* hr = _g1h->heap_region_containing(obj);
7007 assert(!hr->continuesHumongous(),
7008 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7009 " starting at "HR_FORMAT,
7010 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7011
7012 // HeapRegion::add_strong_code_root() avoids adding duplicate
7013 // entries but having duplicates is OK since we "mark" nmethods
7014 // as visited when we scan the strong code root lists during the GC.
7015 hr->add_strong_code_root(_nm);
7016 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
7017 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
7018 _nm, HR_FORMAT_PARAMS(hr)));
7019 }
7020 }
7021
7022 public:
7023 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7024 _g1h(g1h), _nm(nm) {}
7025
7026 void do_oop(oop* p) { do_oop_work(p); }
7027 void do_oop(narrowOop* p) { do_oop_work(p); }
7028 };
7029
7030 class UnregisterNMethodOopClosure: public OopClosure {
7031 G1CollectedHeap* _g1h;
7032 nmethod* _nm;
7033
7034 template <class T> void do_oop_work(T* p) {
7035 T heap_oop = oopDesc::load_heap_oop(p);
7036 if (!oopDesc::is_null(heap_oop)) {
7037 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7038 HeapRegion* hr = _g1h->heap_region_containing(obj);
7039 assert(!hr->continuesHumongous(),
7040 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7041 " starting at "HR_FORMAT,
7042 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7043
7044 hr->remove_strong_code_root(_nm);
7045 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
7046 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
7047 _nm, HR_FORMAT_PARAMS(hr)));
7048 }
7049 }
7050
7051 public:
7052 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7053 _g1h(g1h), _nm(nm) {}
7054
7055 void do_oop(oop* p) { do_oop_work(p); }
7056 void do_oop(narrowOop* p) { do_oop_work(p); }
7057 };
7058
7059 void G1CollectedHeap::register_nmethod(nmethod* nm) {
7060 CollectedHeap::register_nmethod(nm);
7061
7062 guarantee(nm != NULL, "sanity");
7063 RegisterNMethodOopClosure reg_cl(this, nm);
7064 nm->oops_do(®_cl);
7065 }
7066
7067 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
7068 CollectedHeap::unregister_nmethod(nm);
7069
7070 guarantee(nm != NULL, "sanity");
7071 UnregisterNMethodOopClosure reg_cl(this, nm);
7072 nm->oops_do(®_cl, true);
7073 }
7074
7075 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
7076 public:
7077 bool doHeapRegion(HeapRegion *hr) {
7078 assert(!hr->isHumongous(),
7079 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
7080 HR_FORMAT_PARAMS(hr)));
7081 hr->migrate_strong_code_roots();
7082 return false;
7083 }
7084 };
7085
7086 void G1CollectedHeap::migrate_strong_code_roots() {
7087 MigrateCodeRootsHeapRegionClosure cl;
7088 double migrate_start = os::elapsedTime();
7089 collection_set_iterate(&cl);
7090 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
7091 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
7092 }
7093
7094 void G1CollectedHeap::purge_code_root_memory() {
7095 double purge_start = os::elapsedTime();
7096 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
7097 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7098 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7099 }
7100
7101 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7102 G1CollectedHeap* _g1h;
7103
7104 public:
7105 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7106 _g1h(g1h) {}
7107
7108 void do_code_blob(CodeBlob* cb) {
7109 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7110 if (nm == NULL) {
7111 return;
7112 }
7113
7114 if (ScavengeRootsInCode) {
7115 _g1h->register_nmethod(nm);
7116 }
7117 }
7118 };
7119
7120 void G1CollectedHeap::rebuild_strong_code_roots() {
7121 RebuildStrongCodeRootClosure blob_cl(this);
7122 CodeCache::blobs_do(&blob_cl);
7123 }